As a convenient and natural way of human-computer interaction, gesture recognition technology has broad research and application prospects in many fields, such as intelligent perception and virtual reality. This paper summarized the relevant literature on gesture recognition using Frequency Modulated Continuous Wave (FMCW) millimeter-wave radar from January 2015 to June 2023. In the manuscript, the widely used methods involved in data acquisition, data processing, and classification in gesture recognition were systematically investigated. This paper counts the information related to FMCW millimeter wave radar, gestures, data sets, and the methods and results in feature extraction and classification. Based on the statistical data, we provided analysis and recommendations for other researchers. Key issues in the studies of current gesture recognition, including feature fusion, classification algorithms, and generalization, were summarized and discussed. Finally, this paper discussed the incapability of the current gesture recognition technologies in complex practical scenes and their real-time performance for future development. In recent years, with the continuous development of intelligent perception and human-computer interaction technologies, gesture recognition has received more attention and has been used as a convenient approach to human-computer interaction  in many At present, the studies relating to FMCW mmW radar-based gesture recognition have achieved certain milestones. For example, in 2015, Google’s Soli project implemented proximity micro-motion gesture recognition by end-to-end convolutional recurrent neural networks based on distance Doppler features using a FMCW mmW radar chip at 60 GHz , and thiThis paper summarized the main methods and challenges involved in recent research on FMCW mmW radar-based gesture recognition and discussed the key issues as well as the development of the technology.The remainder of this paper is organized as follows: (1)Web of Science;(2)IEEE Explore Digital Library(3)Association for Computing Machinery;(4)Springer Link;(5)Google Scholar.In this review article, we searched several databases for references and covered the following databases:The searching keyword was a combination of “Gesture recognition”, “Radar”, “Millimeter-wave”, and “FMCW”.(1)Publication date: between January 2015 and January 2023.(2)Searching domain: science, technology, or computer science.(3)Publication types: journals, proceedings, and conferences.(4)Language: English.To screen our initial searches, we applied the following inclusion criteria:(1)Studies that do not include FMCW mmW radar-based gesture recognition.(2)Studies that do not provide details of experiments or experimental designs.(3)Studies that replicate with others.(4)Studies for which the full text of the paper is not available.We applied the following exclusion criteria:In addition, we classified the studies according to their publication date, innovation, accuracy, features, and algorithms in order to compare and summarize the problems, methods, and results involved.In general, FMCW MMW radar-based gesture recognition is divided into three main steps: data acquisition, data processing, and classification. At the beginning of any study, researchers need to select the appropriate FMCW mmW radar and gestures as tools and objects for data acquisition. In this section, we introduced FMCW mmW radar and gestures in gesture recognition.In gesture recognition, the FMCW mmW radar transmits FM continuous waves, whose frequency increases over time, to the hand. The received and transmitted signals are filtered through a mixer and low-pass filter. After ADC sampling, an intermediate frequency (IF) signal is generated. The IF signal allows information such as the distance, speed, and even angle of the gesture to be calculated and the corresponding feature maps to be obtained. These features reflect the motion of the gesture through changes in distance, Doppler frequency, and angle rather than 3D shape, which is one of the differences between dynamic and static gesture recognition. The whole process of data acquisition is shown in The range measurement in FMCW radar is based on the time delay between the transmitted and received signals. The range of the target  is the classical way to describe single frames of signal data from FMCW mmW radar, which can significantly show the clutter distribution, we introduced the method of acquiring RDM and summarized the main methods for removing clutter based on previous studies.In general, the gesture signal needs to be processed into a data matrix, the rows of which represent the sampled values of the chirp signal in the fast-time and slow-time domains, respectively. The popular pre-processing method for the chirp signal is the Fourier transform, such as the fast Fourier transform (FFT)  and the Spurious signals are divided into static and dynamic spurious waves. Static clutter refers to radar signals in the environment that are reflected by static targets. Dynamic interference comes from echoes from other moving parts of the hand. From the perspective of parametric characteristics, static target echoes are quite different from moving target echoes, which tend to exhibit low-frequency characteristics in the Doppler domain and thus can usually be achieved by using high-pass filtering , pulse-tIn the previous section, we introduced RDM, which is also one of the most commonly used gesture features. However, the RDM only contains the position and velocity of the target in a single-frame signal and cannot represent the complete gesture feature over a period of time. Therefore, some features with a time dimension are used to represent the overall gesture. In fact, classical gesture features can be divided into time-frequency maps and spectrum map videos. Time-frequency maps include range-time maps (RTMs), Doppler-time maps (DTMs), and angle-time maps (ATMs). The spectrum map videos consist of the multi-frame accumulation of range-Doppler maps (RDMs), range-angle maps (RAMs), and Doppler-angle maps (DAMs) . These fHowever, it is difficult to achieve high recognition accuracy by relying on a single feature in gesture recognition. In contrast, rich gesture features can improve the accuracy of a recognition system. Therefore, many studies have proposed feature fusion as a way to consider more gesture features in gesture recognition. Since the traditional convolutional neural network structure is limited by a single input data set, some studies have proposed a multi-channel algorithmic model to exploit more gesture features ,65. In aBefore comparing the results of different feature extraction methods, it is necessary to clarify the radars used in these studies and their resolution in different dimensions. In gesture recognition, resolution has the greatest correlation with features. As we mentioned before, the object of gesture recognition is the movement of dynamic gestures that are reflected by features. Higher resolution may allow more gesture motion details to be included in the same feature, which is more important in the detection of micro-gestures. Based on radar parameters, we calculated the range, velocity, and angular resolution of the radars used in the studies according to the formula, as shown in Excluding the effect of resolutions on the results, we are able to directly compare each feature extraction method. First, by comparing the results of applying a single feature, it can be found that the accuracy of the feature in the recognition of different gestures varies greatly, even in the same study. We believe this is because the expressive force of gestures in different dimensions is different. For example, the change of range and Doppler in macro gestures is more prominent, while angle information plays a greater role in the recognition of micro gestures. This confirms, from another perspective, the need to consider multiple characteristics. In addition, by comparing the results of applying a single feature and a fusion feature, it can be found that the application of a fusion feature can increase the accuracy of gesture recognition regardless of the experimental conditions, and the accuracy tends to increase with the increase in feature information. It is worth noting that we also found that there were cases where the feature information increased but the accuracy did not increase or even slightly decreased , althougIn this section, we conducted statistics on the datasets in gesture recognition. Since most studies used self-constructed data sets, we selected some representative self-constructed datasets for summary and analysis, as shown in The self-constructed datasets used in most of the studies differed considerably in terms of features, the number of experimenters, the type of gestures, and the total sample, as shown in In this section, we summarize the classification algorithms in the studies on gesture recognition and count the experimental conditions  and results where the classification algorithms were located, as shown in The widely used machine learning methods in gesture recognition are support vector machine (SVM) ,73, K-neClassification algorithms based on deep learning have been widely used in gesture recognition, which mainly involves two classical deep neural network models: the convolutional neural network (CNN)  and the Generalization is the focus of improving accuracy in gesture recognition, which can make the recognition system perform better in the face of strange people and complex environments. In this part, we summarized the suggestions and methods to improve algorithm generalization in gesture recognition and discussed three aspects.Firstly, abundant samples and sufficient data are important factors in improving the accuracy of gesture recognition. There are some studies that have proposed data augmentation. The purpose is to increase the number of samples and improve the recognition effectiveness of the model. Data augmentation can be broadly classified into two types: generative adversarial networks (GANs) and mixup augmentation (MA). The images generated by the GAN are not derived from the original samples but are mainly trained by the model to obtain the applicable images, thus increasing the number of samples . The MA Secondly, we focused on data dependencies in gesture recognition. Indeed, most gesture recognition methods require a large amount of data for training. Studies generally focus on the classification of the fixed predefined gestures that already exist in the training set, but gesture data in real scenes often contains more variations. In recent years, several studies have proposed the use of meta-learning networks as a solution to the few-shot learning problem for the sample and generalization problems of gesture recognition. Different from conventional machine learning or deep learning models, the proposed model is able to make use of domain knowledge learned from a relatively large number of labeled points to quickly adapt to unseen hand gesture classes with only a few training observations ,83. ThisThirdly, the variability of gestures is also an important direction to take to solve the generalization problem. In practical applications, the recognition of new users is an unavoidable problem for gesture recognition systems. Users with different hand habits and diseases  often pose a great challenge to gesture recognition systems. Zeng et al.  applied The experimental scenario of the existing study is ideal without much interference compared to the actual complex application environment. However, in long-distance or large field-of-view (LD/LFoV) environments, there are not only more interference factors but also problems such as dynamic blurring of target gestures due to small observation angles . AlthougOn the other hand, most studies have used single radar sensors for dynamic gesture recognition. However, in more complex application scenarios, the gesture information obtained by a single radar sensor is not rich and accurate enough. At present, studies have been conducted on incoherent radar sensor networks and joint recognition of radar and other categories of sensors ,85. The At present, gesture recognition tends to achieve high accuracy through a large amount of feature data and complex classification models, which require a large amount of memory and computing resources. However, most commercial embedded systems, such as smartphones and other portable devices, have limited memory and computing power. Complex gesture recognition systems are also unable to meet the requirements of real-time performance, which is not accepted in commercial applications. Therefore, many studies hope to reduce the complexity of gesture recognition systems while ensuring accuracy and put forward some methods from two aspects: data and classification models. The feature cube introduced in The progress of FMCW mmW radar gesture recognition technology opens up a new approach to human-computer interaction. This paper summarized the methods, results, and key issues of gesture recognition based on the main step process of gesture recognition, discussed three aspects of feature fusion, classification algorithms, and generalization, and provided analysis and recommendations for other researchers based on the statistical data. This paper provides a reference for future research on gesture recognition based on FMCW mmW radar and is of great significance in promoting the practice and research of gesture recognition methods.


The comprehension of intricate and interconnected biological processes necessitates the adoption of an integrative systems biology approach. The incorporation of diverse omics data, encompassing genomes, proteomics, transcriptomics, and metabolomics, will yield a comprehensive perspective that elucidates the interplay between different biomolecules and their roles in plant development, resilience, characteristics, and other significant attributes. The integration of multi-omics data has been made possible by recent advancements in analytical capabilities and the processing of massive data sets. As a result, researchers now possess a significantly enhanced understanding of the cell, tissue, organ, or even the entirety of an organism under investigation.The primary objective of this Research Topic is not solely limited to the dissemination of the omics data that is of superior quality and dependability, but also encompasses the broader inquiry into the methods of integrating and establishing correlations amongst diverse data sets derived from numerous omics investigations. The studies included in this topic are focused on the areas of integration of multiple omics data for discovering gene(s) functions in autophagy, circadian clock and its connection with response against herbicides, resistance in plants, advancements in single cell and spatial transcriptomics, study of cultivars based on chemotype, and the interaction of proteins with the metabolites.Chen et al. conducted a comparative analysis of experimental methodologies employed in several plant species, focusing specifically on plant single-cell or spatial transcriptomics. The constraints and difficulties associated with single-cell and spatial transcriptome investigations are readily apparent, including restrictions in terms of application, geographical information, and resolution. The review also proposes additional applications, including the examination of roots at the single-cell level through cross-species analysis and asserts that the integration of single-cell transcriptome analysis with other omics studies is necessary to surpass the capabilities of individual omics analyses.The emergence of single-cell and spatial transcriptomics has shifted the focus of researchers from the study of multicellular systems to the exploration of single-cell phenomena and spatial information. The utilization of single-cell transcriptomes enables the examination of transcriptomic profiles at the individual cell level, facilitating a deeper understanding of cellular heterogeneity. Conversely, spatial transcriptomes have the advantage of preserving and analyzing the spatial organization of gene expression patterns within tissues or organisms. Despite the usefulness and maturity of these two omics methods, additional study is required to assure their broad usage in plant studies. In a comprehensive review, i.e., multi-omics data). Ding et al. analyzed the effects of mutations in two AuTophaGy-related (ATG) genes of Arabidopsis by combining lipidomics, metabolite mass-spectral imaging, and transcriptomics data from leaves and roots. The autophagy process, which is necessary for the degradation and recycling of macromolecules and organelles, is inhibited in the atg7 and atg9 mutants studied here. A prior knowledge of the exact biochemical function of the relevant proteins greatly facilitates the development of a comprehensive physiological model.Discovering gene functions has been argued to be possible through the use of a systems biology technique, which combines molecular data from many levels of genome expression , spearmint (Mentha spicata L.), and horsemint (Mentha longifolia (L.) Huds.), emit volatiles from stems, rhizomes, and roots. The terpenoid volatile composition of these organs differs significantly from leaves, suggesting significant chemical diversity exists. The newly sequenced M. longifolia CMEN 585 genome was used to identify candidate genes for monoterpene synthases (MTSs), which catalyze the first step in the biosynthesis of monoterpenoid volatiles. This was done to investigate the genetic and biochemical basis of chemical diversity. These MTSs can contribute to the production of all main monoterpene skeletons seen in volatiles from various mint organs.Commercial distillation of mint produces essential oils, which are used in many consumer products. Most study on terpenoid oil constituent development has focused on leaves. Liu et al. provide valuable insights into the regulatory networks involved in the interactions between wheat and Puccinia striiformis f. sp. tritici (Pst). These insights have the potential to facilitate the development of durable resistance breeding strategies in wheat, which could contribute to addressing global environmental and food challenges. The findings of the study indicated that the infection caused by Pst led to the upregulation of genes and metabolites associated with the manufacture of phenylpropanoids. The unique resistance exhibited by R88 is controlled by the selective expression of genes that are involved in the precise regulation of interactions between wheat and Pst. In addition, the examination of the metabolome indicated that the accumulation of metabolites associated to lignin production was significantly influenced by Pst.Wheat is well recognized as a prominent staple crop within the global food production system. Nevertheless, the presence of stripe rust fungus has a substantial negative impact on both the productivity and quality of wheat. The findings of a study by Chabi et al. studied genome-wide transcription profiling in bast fiber-bearing tissues of seven flax cultivars and found 1041 differentially expressed genes, with 97 connected to cell wall metabolism. Three distinct clusters were identified based on gene expression levels for 32 proteins, out of which 4 proteins significantly linked with morphometric characteristics. These findings identify molecular players involved in determining in-planta fiber morphometrics and ex-planta fiber mechanical characteristics, which are crucial for determining basic and scutched fiber quality in flax.A major obstacle to widespread use of plant fibers is understanding the molecular components that affect the mechanical properties of both elementary and scutched fibers. Fernandes et al. assessed the phenotypic and chemotype of three high-THCA and one high-CBDA cultivars in their diploid, triploid, and tetraploid states using agronomic and metabolomic methods. This study reports that plant morphology showed a cultivar-dependent increase in height and leaf size with higher ploidy levels. Higher ploidy levels severely impacted cannabinoids, with concentrations of total cannabinoids, THCA, CBDA, and CBGA dropping significantly across all four cultivars. Overall, plant morphology observations match the giga phenotype in other polyploid plant species. This study indicated that tetraploidization can boost Cannabis sativa L. therapeutic potential, although cultivar and genotype-dependently. This effort prepares the breeding, biotechnological, and pharmaceutical industries to improve, evaluate, and use C. sativa chemical diversity.Wolters et al. used in silico analysis, gene overexpression, transcriptomics, and metabolic profiling to study the impact of a homologous protein in the Russian dandelion (Taraxacum koksaghyz) on its rich isoprenoid network. Research suggests that TkPEL-like negatively controls genes involved to photosynthesis and chlorophyll in a light-dependent way, which is conserved across animals. These findings will guide future research on leaf isoprenoid biosynthesis and photomorphogenesis regulation, enabling breeding techniques to improve plant isoprenoid profiles and create plant-based industrial platforms.Chlorophylls and carotenoids, which are generated from isoprenoid precursors, are needed for photosynthesis and plant greening. A study by The Guest Editors would like to express their gratitude to all the authors and reviewers of this Research Topic, and acknowledge their hard work and dedication toward the area of omics and systems biology. The Guest Editors believe that the presented researches will encourage the generation of more knowledge and valuable research in the fields of omics, their integration, and systems biology.KA: Writing – original draft. MG: Writing – review & editing.


AIMS Neuroscience, we would like to provide a thoughtful perspective on the role of neuroinformatics and data analysis in the regulation of stress-related disorders In recent years, stress-related disorders have become a pressing global health concern, affecting millions of individuals worldwide. The profound impact of these disorders on mental well-being and overall quality of life has propelled the scientific community to explore innovative approaches to better understand, diagnose and treat them. In this endeavor, neuroinformatics and data analysis have emerged as powerful tools that hold immense promise in revolutionizing our understanding and regulation of stress-related disorders. Inspired by this special issue of Neuroinformatics, a multidisciplinary field that combines neuroscience, computer science and informatics, has the potential to unlock the secrets of the human brain. By integrating vast amounts of neuroimaging data, genetic information and clinical records, neuroinformatics allows researchers to unravel the complex neurobiological mechanisms underlying stress-related disorders. Neuroimaging techniques such as functional magnetic resonance imaging and positron emission tomography enable researchers to visualize and quantify brain activity and structural changes associated with stress In addition, the availability of vast amounts of data in the digital age has necessitated the development of advanced data analysis techniques. By employing machine learning algorithms and statistical models, researchers can sift through massive data sets to identify meaningful correlations, predict outcomes and develop personalized treatment approaches One of the critical challenges in managing stress-related disorders is the timely identification of individuals at risk or those already experiencing symptoms. Neuroinformatics, coupled with data analysis, offers the potential for earlier detection and diagnosis of stress-related disorders, improving outcomes and reducing the burden on healthcare systems. Integration of multi-omics data in stress-related disorders presents both challenges and opportunities. It allows for a comprehensive analysis of various biological layers, such as genomics, epigenomics, transcriptomics and proteomics, providing a deeper understanding of the molecular mechanisms underlying stress-related disorders. However, the complexity and heterogeneity of multi-omics data pose challenges in data integration, interpretation and validation, requiring advanced computational and analytical approaches to unlock the full potential of this valuable resource. Through the integration of diverse data sources, including neuroimaging, genomic, proteomic and behavioral data, researchers can identify reliable biomarkers associated with stress-related disorders While neuroinformatics and data analysis offer great promise, they also present ethical considerations and challenges. Safeguarding patient privacy, ensuring data security and addressing potential biases in data collection and analysis are crucial aspects that require careful attention AIMS Neuroscience is one of the perfect venues to spark evidence-based discussion on this topic. By harnessing the power of advanced computational tools and the integration of diverse data sources, we can unlock the mysteries of the human brain and develop personalized approaches to prevention, diagnosis and treatment. However, it is imperative that we address ethical considerations and ensure equitable access to these technologies, ensuring that they are used responsibly and for the benefit of all individuals affected by stress-related disorders. By embracing the potential of neuroinformatics and data analysis, we can pave the way for a future where stress-related disorders are effectively regulated, improving the lives of countless individuals around the world.In conclusion, neuroinformatics and data analysis are revolutionizing our understanding and regulation of stress-related disorders. We believe this special issue of


There was a pervasive debate around the risk of transmission to patients and to health care professionals engaged in organ procurement, and on the influence of immunosuppression on the clinical course of COVID-19. Additionally, there was an obvious need to allocate staff and beds in high complexity hospitals to treat a fast-growing number of patients with severe forms of COVID-19. The dilemma was further complicated considering the perspective of overwhelming dialysis units if the number of kidney transplants was reduced drastically, in addition of a significant proportion of patients developing COVID-19 associated acute kidney injury requiring renal replacement therapy.During the early period of the COVID-19 pandemic, most kidney transplant centers hesitated on whether to interrupt transplant procedures, resulting in a significant and universal reduction in the number of kidney transplants, performed before any vaccine was available, analyzed the incidence, lethality and risk factors associated with SARS-CoV-2 in patients receiving hemodialysis, patients on the waiting list for a kidney transplant, and in kidney transplant recipients. In the study period, patients receiving hemodialysis and recipients of kidney transplant presented a high incidence of COVID-19 and high COVID-19-related lethality. The impact on the patients on the transplant waiting list was less pronounced, most likely because they were younger and had fewer limiting comorbidities.The study by Teichmann et al.. While elective living donor kidney transplants were postponed, many transplant centers persisted performing transplants with deceased donor kidneys, depending to the local impact of the pandemic on health care resources, and highly encouraged by frequent videoconferences with experts and transplant physicians promoted by the Associação Brasileira de Transplant de Órgãos (ABTO). Therefore, by the end of 2020, the overall reduction in the number of kidney transplants was only 30%, much lower than that observed in other countries.The reported 9.85% incidence and 14.9% lethality of COVID-19 among kidney transplant recipients is relatively lower compared to other studies in the country, influenced perhaps by the migratory pattern of the disease, clinical surveillance strategies and testing availability.Transplant activity progressively increased with the widespread availability of testing, increased knowledge of the disease and treatment options, availability of vaccines, and the observed reduction in lethality rates in high-risk groups, including the elderly, patients with chronic kidney disease, and recipients of a kidney transplant, further mitigating the burden to dialysis units. After the observation that SARS-CoV-2 could not be transmitted through solid organs, except for the lungs, most centers even began to perform transplantation using organs from individuals who tested positive for SARS-CoV-2 but died for other causes. The situation remained unchanged regardless of virus variant and number or origin of vaccines offered, until the advent of the omicron variant, when the fatality rate among kidney transplant patients was lowered from 25% to 2%.Although large-scale vaccination has reduced the need for, and length of, hospitalization and disease lethality in the general population and dialysis patients, such benefit was not immediately observed among kidney transplant recipients. In this group, the humoral and cellular response to vaccination was low, and lethality was sustained in more than twenty-five percent of infected patients, possibly associated with the chronic use of immunosuppressive drugs. Thus, transplant patients should continue to use face masks in contexts of greater risk, such as when in and around crowds, and be vaccinated whenever recommended.During the pandemic, many chemical or biological drugs were tested to decrease lethality from COVID-19. However, none achieved clinical meaningful results. Antiviral drugs such as paxlovid are available in the public healthcare system for early treatment, but the extent of their benefit both in the general population and transplant recipients has not yet been establishedSistema National de Transplantes (SNT) and ABTO have also been implemented to fully restore and even increase the annual number of kidney transplants, with strategies directed to the four pillars of the national transplant system, namely, reporting hospitals, organ procurement organizations, dialysis clinics, and transplant centers.Finally, initiatives coordinated by the , the decision to maintain and foment the transplant activity, considering the local environment during the evolving phases of the COVID-19 pandemic, in retrospect, appears to have been the right decision.Kidney transplant is a highly complex and integrated procedure that saves lives. Despite the initial hesitance, in view of the findings reported by Teichmann et al.


Human papillomavirus (HPV) is associated with 5% of all cancers globally at a range of body sites, including cervix, anus, penis, vagina, vulva, and oropharynx. These cancers claim > 400,000 lives annually. The persistent infection of HPV and the function of viral oncogenes are the primary causes of HPV-related cancers. However, only some HPV-infected persons or infected lesions will progress to cancer, and the burden of HPV-associated cancer varies widely according to gender and the part of the body infected. The dissimilarity in infection rates at different sites can explain only a small part of the differences observed. Much responsibility likely sits with contributions of specific epithelial cells and the cellular microenvironment at infected sites to the process of malignant transformation, both of which affect the regulation of viral gene expression and the viral life cycle. By understanding the biology of these epithelial sites, better diagnosis/treatment/management of HPV-associated cancer and/or pre-cancer lesions will be provided. Forty yOne of the most distinctive characteristics of HPV is the genotype-specific preference for distinct anatomical sites (tropism) of particular HPV types, where they cause lesions with distinctive clinical pathologies . TheGiven the impact of high-risk HPV as a cancer causative agent, it is reasonable that the study of HPV has been driven by the association of the high-risk Alphapapillomavirus types to anogenital and oropharyngeal cancers . By compSome of the notable functions of the high-risk E6 protein are its interaction with and degradation of TP53 and BAK, which result in the inhibition of growth arrest and apoptosis after DNA damage, as well as an accumulation of mutations , 15. E6 Given the malignant transformation of the infected lesion, which produces no virus progeny, the development of cancer from lesions does not contribute to the virus fitness and is considered to be a collateral consequence of the infection . FurtherAlthough high-risk HPV infections are common, with the majority of people being infected at least once in their lifetime, most will develop only subclinical or transient lesions that spontaneously regress, and invasive cervical cancer will only develop in some persistent infections/lesions. Also, it is now being accepted as the natural history of HPV infection that HPV infection is not always cleared completely but becomes a controlled infection below the limits of detection (latent infection) , 35, whiClinically, HPV infection in the cervix is classified depending on its risk of developing precancer and cancer. For example, a subclinical infection can be HPV-positive, but no cervical abnormalities are detected. Though the detection of high-risk HPV is considered as the risk of developing precancer and cancer, the lack of detectable cervical lesions is considered as there being no immediate risk of cancer. Such subclinical infections have become more common since the HPV test was introduced as part of primary cervical cancer screening. CIN1, which is referred to as the LSIL  designation used in the Bethesda system, also does not show a significantly higher risk of precancer lesions . As therHistopathologically, the classification of CIN1-3 reflects the extent to which basal-like cells (undifferentiated cells with a high nuclear/cytoplasmic ratio and nuclear atypia) have replaced the cervical epithelium. Since the discovery that cervical dysplasia is an HPV-infected lesion, our understanding of cervical dysplasia has become much more advanced. Low-grade lesions (CIN1) typically represent a "productive infection", where the level and pattern of viral gene expression are properly controlled to complete the stages of its viral life cycle and to produce virus progeny. In contrast, high-grade lesions represent "non-productive" or "abortive infection", where the expression of viral genes is dysregulated  and no infectious virus is produced. Virologically, the extent to which basal-like cell replacement has occurred reflects the extent of viral oncogene expression.The deregulated expression of high-risk E6 and E7 proteins is the primary risk of the development of cancer, and it explains the difference in the risk of developing cancer among cervical dysplasia. Deregulation of viral gene expression may be caused by viral genome integration, which is often observed in high-grade premalignant lesions and cancer , 43. Suc(i) Tobacco smoking has shown a significant increase in the development of cervical cancer and its precursor lesions . The mol(ii) The long-term use of oral contraceptives has been hypothesized to be associated with development of precancer and invasive cervical cancer. The regulatory region of HPV genome contains hormone response elements that can be stimulated by estrogen and affect the proliferative capacity of the infected cells. There is also some evidence of cooperation between estrogen and HPV in the development of cervical cancer in humans and in model systems. However, the interpretation of studies of oral contraceptives for risk of cervical cancer has been impeded by limitations in design  confounded by Pap smear history , and the formulation and dose of hormonal contraceptives. In summary, the long-term (5 yeas o more) use of oral contraceptives can increase the risk up to twice as much , with li(iii) The microbial microenvironment in cervical tissue is considered to determine the integrity of homeostasis and protective mucous layer of cervical tissue by maintaining healthy immunity and metabolic signalling. This can affect HPV infection or risk of persistent/dysregulated infection by changing viral gene expression. The role of chronic inflammation is less certain, with very limited data about Chlamydia trachomatis infection . The inf(iv) There have been numerous studies which examined the association between risk for cervical cancer and dietary intake or nutrient concentrations, including vitamin C, folate, β-Carotene, retinoic acid. Most of the studies were small and high rates of spontaneous regression of lesions hampers sufficient power to test the efficacy of the selected agents. In addition, most of these studies have methodological limitations in analysis, lack of adequate consideration of HPV infection, and confounding factors . Due to these limitations in observational studies and supplementation trials, there has been no strong evidence of a role for any one micronutrient in the development of cervical cancer. Limited data, though, suggests that higher folate is possibly protective against the risk of malignant transformation.(v) Familial clustering of cervical cancer has been explored as a potential risk marker of inherited genetic susceptibility for cervical cancer. In general, these studies failed to differentiate sufficiently the effects of genetic susceptibility from those of environmental and behavioural factors, with indications of a familial risk, and requires further investigation. As the control of HPV infection (spontaneous regression of LSILs and even HSILs) is mediated by cellular immune responses against virus-specific antigens, it is reasonable that the polymorphisms of HLA Class I and II genes lead to variations in the antigen recognition site that may confer susceptibility or resistance to HPV infection and malignant transformation. HLA recognition is considered to be HPV type-specific, and HLA polymorphisms can also explain that HPV type-specific prevalence varies according to geographic area and ethnicity. Indeed, epidemiological studies in different populations have found various relationships between risk for malignant transformation and HLA polymorphisms. However, it has not been utilised for diagnosis/treatment/management of cervical pre-cancer lesions.Compared to the infection of carcinogenic high-risk HPV types, non-infectious co-factors play a minor part in cancer development. Many potential co-factors, which may affect the risk of infection or risk of persistent/dysregulated infection, have not been evaluated rigorously enough in epidemiological studies (see ).(i) TobThe primary risk of HPV-associated cancer development is a function of HPV infection. High-risk human papillomaviruses infect a wide range of epithelial sites, however, the frequency of HPV-associated cancer among the sites of bodies shows huge diversity Fig.  due to tThe infection of high-risk HPV types is associated with virtually all (> 99%) cervical cancers. In some developed countries, the number of cases other HPV-associated cancers is increasing. The incidence of HPV-associated head and neck cancer is also increasing and is greater than the incidence of cervical cancer. However, cervical cancer is the most prevalent (> 80%) cancer among all HPV-associated cancers worldwide. While cervical cancer reaches over 600,000 cases per ear worldwide, HPV-associated cancer of the vulva, vagina, and penile cases reaches around 50,000 per year . The cerHead and neck squamous cell carcinoma (HNSCC) develops at different anatomic sites of the upper aerodigestive tract including the nasopharynx, paranasal sinuses, oral cavity, oropharynx, hypopharynx, and larynx. Since HPV was discovered in cervical cancer, HPV has also been recognised as a causative agent for HNSCC, especially for oropharyngeal squamous cell carcinoma (OPSCC). The main difference when compared with cervical cancer is that OPSCC can be observed as two (HPV-negative and HPV-positive) diseases. The socioeconomic status of patients, molecular profiles, clinical characteristics, and especially the prognosis of the tumours, tend to differ between HPV-positive and HPV-negative OPSCC. High-risk HPV-associated OPSCC makes up a substantial proportion of all OPSCC cases and this number is rising, mainly in the Western world. This is most likely due to changes in sexual behaviour , 63. TheHPV infection is also associated with a small number of other HNSCCs, however, the contribution of each site varies hugely  accounts for only 4% of cases, while in contrast, 47% of cases of OPSCC is HPV-associated). HPV-positive OPSCC often arises from the tonsillar crypt epithelium. Interestingly, reticular tonsillar crypt epithelium would provide easier access to HPV than other stratified squamous epithelium, and it suggests that its malignant transformation reflects the different biology of infected tissue at each anatomical site. The tonsillar reticular crypt epithelium might not be permissive for productive HPV infections that support the viral life cycle to generate viral progeny, but may be permissive for abortive/non-productive infection, where viral gene expression is dysregulated and likely to progress to malignant transformation . This is consistent with the observations that large studies on non-malignant tonsil samples have detected no or low HPV prevalence, and LSIL-type productive lesions, which are the most common infected lesion at cervix, have not been identified as a cancer precursor at the tonsillar crypt.High-risk HPV has been detected in 90% of anal cancers with HPV16 detected in 80% of those cases , 65. TheTwo distinct pathways to invasive squamous cell carcinoma (SCC) exist in the vulva with HPV being detected in one-third of vulvar SCC . This diHigh-risk human papillomavirus infection causes HPV-associated cancer, with a great diversity of its incidence among the sites of the body infected. It appears that differences in infection rates at different sites are only a small part of the reason for this. Specific epithelial stem cells and the cellular microenvironment at these sites must be influencing the control of viral gene expression and contributing differently to the process of malignant transformation. In contrast to our understanding of high-risk HPV protein functions, our knowledge of the biology/molecular mechanisms of the different epithelial sites is very limited, and further studies are required to provide better diagnosis/treatment/management of HPV-associated cancer and/or pre-cancer lesions.


A continuous search for bioactive materials capable of supporting the replacementof damaged pulp tissue, with effective sealing potential and biocompatibility,has represented the attention of studies over the last decades. This studyinvolves a narrative review of the literature developed by searchingrepresentative research in PUBMED/MEDLINE and searches in textbooks associatedwith the mechanism of action of bioactive materials , and calcium silicate cements). The reflective analysisof the particularities of the chemical elements of these materials, consideringthe tissue and antibacterial mechanism of action, allows a better understandingof the characteristics and similarities in their tissue responses. Calciumhydroxide paste remains the antibacterial substance of choice as intracanaldressing for the treatment of root canal system infections. Calcium silicatecements, including MTA, show a favorable biological response with thestimulation of mineralized tissue deposition in sealed areas when in contactwith connective tissue. This is due to the similarity between the chemicalelements, especially ionic dissociation, the potential stimulation of enzymes intissues, and the contribution towards an alkaline environment due to the pH ofthese materials. The behavior of bioactive materials, especially MTA and the newcalcium silicate cements in the biological sealing activity, has been shown tobe effective. Contemporary endodontics has access to bioactive materials withsimilar properties, which can stimulate a biological seal in lateral andfurcation root perforations, root-end fillings and root fillings, pulp capping,pulpotomy, apexification, and regenerative endodontic procedures, in addition toother clinical conditions. Root canal treatment (RCT) aims to restore the health of damaged pulp and periapicaltissues, by eliminating the agents responsible for inflammation and infection The endodontic history encompasses the several stages of root canal therapeuticprocedures, characterizing the differences observed over time of various endodonticmaterials proposed. Among the available endodontic materials are included thoseindicated for the treatment of the inflamed dental pulp, root infectionsdecontamination, treatment of the consequences of traumatic dental injuries (rootresorption), apexification, regenerative endodontic procedures, as well as thesealing of root perforations, root-end fillings and root canal filling materials. Inthis sense, a growing search for bioactive materials and for application inendodontics can be observed Among the materials well studied in endodontics clinical practice, calcium hydroxide,mineral trioxide aggregate, and new calcium silicate cement can be highlighted Calcium hydroxide was described for application in dentistry by Hermann in 1920 Mineral trioxide aggregate (MTA), proposed by Torabinejad (Loma LindaUniversity)Based on the premise and function of improving the physical-chemical properties ofthis material, with the addition of plasticizing agents, in the following years,different calcium silicate cements  among others) were introduced on thedental materials market 23,24These materials have been used in various clinical conditions in which one of theexpected intrinsic features has been their bioactive potential. The InternationalOrganization for Standardization (ISO 10993-1:2018) In this sense, the present study reviewed and contextualized some similarities in themechanism of action of these bioactive endodontic materials , as wellThis review of bioactive endodontic materials was structured through previous studiesand reviews in which the focus of attention was a reflective analysis and arelationship of the chemical components and mechanisms of action of all thesesubstances.Calcium hydroxide constitutes a strong base ,which through calcination of calcium carbonate transforms it into calcium oxide. Inturn, calcium hydroxide is obtained through the hydration of calcium oxide and whenit reacts with carbon dioxide it leads to the formation of calcium carbonate The properties of calcium hydroxide derive from its ionic dissociation into calciumions and hydroxyl ions Calcium hydroxide potential to stimulate the formation of mineralized tissue (hardtissue barrier) from its ionic dissociation and the biological mechanism of actionwas described by Holland In addition, calcium ions actively participate in the repair process  According to Holland et al. In addition to the biological mechanism of action of calcium hydroxide in connectivetissue, its antibacterial mechanism of action previously described The mechanism of action of calcium hydroxide is associated with the effect of pH onbacterial cell growth, metabolism, and division The biological effect of pH on bacterial enzyme activity influences cell metabolism,growth, and division. The high pH of calcium hydroxide (12.6), and the release of ahigh amount of hydroxyl ions, alters the integrity of the cytoplasmic membranethrough chemical aggressions to organic components and nutrient transport, orthrough the destruction of phospholipids or unsaturated fatty acids from thecytoplasmic membrane (lipid peroxidation process - saponification reaction) The explanation of the mechanism of action of calcium hydroxide in the control ofbacterial enzymatic activity leads to the hypothesis of an irreversible bacterialenzymatic inactivation , andreversible bacterial enzymatic inactivation; enzymatic action is reestablished ifthe ideal pH returns, with a subsequent return to normal activity In the dentistry market, several pastes containing calcium hydroxide have beencommercialized; however, the pure paste Pro-analysis may be favored by having ahigher ionic concentration of its chemical elements. It is essential to rememberthat this material, when applied as intracanal dressing, should only be deliveredinside the root canal since it constitutes a very strong base, therefore istoxic.Hydraulic cements are materials that depend on water for the occurrence of theirhardening. The first calcium-silicate based hydraulic material that emerged for usein dentistry was Mineral Trioxide Aggregate. Then, new materials using tricalciumand dicalcium silicate emerged. The Mineral trioxide aggregate (MTA) was incorporated into endodontics for differentclinical practice applications 2 (17.7%), Al2O3 (4.5%). Based on thischemical similarity between compositions of mineral trioxide aggregate and Portlandcement, Holland et al. Wucherpfenning & Green The properties of MTA have been extensively studied  using different methodologies, and demonstrating good potential toseal lateral and furcal root perforations, root-end fillings, pulp capping,pulpotomy, apexification and regenerative endodontic procedures, and other clinicalconditions Since MTA is a calcium silicate cement, new materials with similar composition havebeen proposed with additional characteristics that allow an improved clinicalapplication, which facilitate handling and manipulation and minimizes the coronaldiscoloration. To achieve this, the new calcium silicate cements  form a colloidal structure after hydration and sequentially developinto a hard structure The advantages that have been described in the literature of the new calcium silicatecements are related to their physicochemical and biological properties, includingexcellent sealing potential, due to their physicochemical interaction with the localenvironment, and high biocompatibility Tissue reactions against calcium silicate cements begin before the material sets andcontinue until complete tissue repair. The initial reactions are triggered by thehydration of di and tri-calcium silicate During the tissue repair process promoted by calcium silicate cements, as describedpreviously and similarly to the response to calcium hydroxide, it is possible todistinguish 5 different zones: 1. zone of necrosis by coagulation, corresponding tothe area of protein denaturation; 2. superficial granular zone, composed of morerobust granulations of calcium carbonate; 3. deep granular zone, composed ofgranulations of calcium salts and an area of dystrophic calcification; 4. zone ofcell proliferation, composed of young cells in activity; 5. repaired or normaltissue zone.Among the physical properties that a root canal filling and repair materials shouldpresent are setting, solubility, flow and adequate radiopacity Hydraulic cements that have as their main component the di and tri calcium silicatesare available in the ready-to-use form or powder and liquid form. In both forms ofpresentation, water is responsible for providing the setting reaction of thesematerials. In the case of ready-to-use water comes from dentinal tubular fluids andperiapical tissues, while in the powder/liquid form, water is the main component ofthe liquid .About the setting time, some substances can slow down or accelerate the setting timeRegarding solubility, laboratory studies show great variability that may also varyaccording to the solution in which the material was immersed in, distilled water orphosphate buffer solution. But most studies show that solubility values transcendwhat is recommended by the ISO standard that recommends not being greater than 3%In performing endodontic root canal fillings, the flow is a property that willprovide the ability for the material to penetrate areas of morphological complexity.The literature shows that the flow of hydraulic materials is in accordance with theISO standard, and with values higher than epoxy resin materials such as AH PlusRadiopacity is the property that allows the material to be discerned against themineralized structures of the tooth and the jaws. The first hydraulic cements usedbismuth oxide as a radiopacifier agent With regard to the chemical properties of hydraulic cements, their setting reactioninvolves the transformation of di and tricalcium silicates, into hydrated calciumsilicate and produces a component that is the Portlandite, which is nothing morethan calcium hydroxide. Portlandite is the soluble part of the material, as thehydraulic materials are similar in composition to Portland cement, with mostPortland cements producing 13 to 17% calcium hydroxide after setting Considering the physical chemical properties of hydraulic cements overall, perhapsthe high solubility should be considered a limitation. Controlled clinical trialsneed to be conducted to verify the impact of the high solubility demonstrated inlaboratory studies on the clinical performance of these materials The present reflective analysis of the particularities of the chemical elements ofthe bioactive materials discussed in the present review, which considers theirtissue and antibacterial mechanism of action, allows a better understanding of thecharacteristics and similarity in their tissue behavior.Calcium hydroxide paste remains the antibacterial substance of choice as anintracanal dressing for the treatment of root canal system infections. This is dueto the chemical availability of calcium and hydroxyl ions of calcium hydroxide madeavailable for the surrounding tissues, and the bacterial enzymatic inhibition.Calcium silicate cements, including MTA, show a favorable biological responseregarding the stimulation of mineralized tissue deposition in sealed areas when incontact with connective tissue. This is due to the similarity between the chemicalelements, especially to the ionic dissociation, the potential stimulation of tissueenzymes, and the contribution of an alkaline environment due to the pH of thesematerials.Bioactive materials, especially MTA and the new calcium silicate cements areeffective to support a biological seal. Contemporary endodontics practice has accessto bioactive materials with similar properties capable of stimulating biologicalsealing in lateral and furcation root perforations, root-end fillings and rootfillings, pulp capping, pulpotomy, apexification, and regenerative endodonticprocedures, in addition to other clinical conditions. The positive impact of thesebioactive materials used in therapeutic procedures for various conditions inendodontic clinical practice was to induce a healing response in the injured hosttissue and prevent tooth loss and its disastrous consequences.However, even with the knowledge regarding the materials discussed here, it isimportant to say that all new material must be deeply studied. The new materialsmust also undergo long-term clinical tests to verify whether new components added totheir formulas, in an attempt to improve some of their properties, may have harmedanother property. Further studies are recommended to better understand the clinicaltranslation of the increased solubility demonstrated in laboratory studies forcalcium silicate hydraulic cements, as this may compromise their long-term seal,thus potentially increasing the risk of permanence or reoccurrence of apicalperiodontitis.


Extracellular vesicles (EVs) are small biological structures that are released by cells and have important roles in intercellular communication. They are enclosed in a phospholipid bilayer and can contain a variety of biomolecules, including proteins, lipids, and nucleic acids. The term “extracellular vesicle” encompasses various subtypes, including exosomes, microvesicles, and apoptotic bodies, which differ in size, biogenesis, and cargo . EVs havThe transfer of EVs between different kingdoms of life illustrates the intricate connections within biological systems and the potential for developing innovative therapeutic strategies that can harness their unique biological properties. EVs from different kingdoms can impact human cells and tissues through their inherent cargo, as well as their potential to serve as vehicles for delivering drugs. Research has demonstrated that plant-derived EVs have the ability to interact with human or animal cells, and significantly affect physiological processes, such as regulating gut function or treating oncological diseases ,11,12. BThis Special Issue is devoted to the study of “Molecular Mechanisms of the Therapeutic Properties of Extracellular Vesicles”, and aims to explore the diverse roles and functions of EVs in both normal and pathological conditions. The collection of research and review articles provides an insight into the molecular mechanisms that mediate the therapeutic effects of EVs, including targeted delivery of drugs and vaccines, and the modulation of physiological processes. The articles cover a range of topics, from the role of EVs in bacterial evolution to the specific cargo molecules that mediate their therapeutic effects in animals. We hope that the articles in this Special Issue inspire further research to explore the uncharted potential of EVs in the context of medicine and biotechnology.E. coli isolated from the long-term evolution experiment, following 50,000 generations of adaptation to glucose minimal medium [E. coli is a phenotype that alters during bacterial evolution, and the contribution of OMV-mediated interactions in bacterial adaptation is questioned. Another exciting study has been published by Schaack B. et al., who analyzed microbiota-derived EVs in human blood [Two articles describing the role of bacterial EVs are included in the Special Issue. Based on a unique ongoing study, Laurin D. et al. examined the OMVs released by specific clones of l medium . It was an blood . Analysian blood . ResearcA considerable amount of current research has been directed toward exploring the healing potential of EVs obtained from MSCs, which has led to a surge of interest in this field of study. The use of MSC-derived EVs expands on previous stem cell therapies, overcoming many of the challenges related to the limited availability, storage, and transplantation costs of live cells. Sanz-Ros et al. reviewed the potential therapeutic role of EVs in various aging-related diseases . EVs havThe study by Khandagale et al. focused on the miR profile of EVs from the plasma of pulmonary arterial hypertension (PAH) patients and healthy controls . miR proThe ability of EVs to interact with target cells and induce downstream biological effects is determined not only by their cargo, but also by the surface molecules. These molecules play a crucial role in the uptake mechanisms, cargo delivery, and targeting of EVs, and can also serve as biomarkers with potential diagnostic value. Clos-Sansalvador et al. focused on the role of N-glycosylation of MSC-derived EVs in mediating their interaction with endothelial cells . The stuMustajab et al. provided an informative overview of the potential of EVs as tools for the treatment of COVID-19 . The autFurthermore, non-alcoholic steatohepatitis (NASH) is a rising global health concern and the main reason for liver transplantation. Therefore, there is a pressing need to develop more efficacious therapies to manage the pathology of this condition. In recent years, there has been growing interest in the emerging role of EVs and autophagy machinery in the pathogenesis of NASH. Trifylli et al. reviewed the interplay between autophagy and EVs in the development of NASH, and their potential for novel therapeutic strategies, that could improve clinical outcomes for patients with NASH .In conclusion, research on the molecular mechanisms of the therapeutic properties of extracellular vesicles has provided insights into their potential as promising tools for the treatment of various diseases. Notably, there are impressive prospects for the clinical use of EVs from diverse sources, including stem cells, plants, and bacteria. Progress in the identification and isolation of EVs, as well as the development of clinical application protocols, could guide us to the discovery of novel drugs in the near future. However, extended research and clinical trials are still necessary to fully establish their efficacy, safety, and effectiveness in the treatment of different diseases.


In the case of trauma, the presence of free fluid in the abdominal cavity on the focused assessment with sonography for trauma scan usually indicates the possibility of hemoperitoneum caused by injury to the abdominal organs. However, on rare occasions, isolated injuries to gynecologic organs can also result in hemoperitoneum, especially among women of reproductive age. Thus, the rupture of a corpus luteal cyst may be one of the myriad causes of massive hemoperitoneum and carries a risk of misdiagnosis for patients with trauma.In this case report, we highlight the characteristic imaging findings of a case of apoplexy of the corpus luteum cyst that presented to the emergency department as a cause of massive hemoperitoneum after blunt abdominal trauma. Hemoperitoneum can occur in various emergency scenarios. In the case of trauma, the presence of free fluid in the abdominal cavity on the focused assessment with sonography for trauma (FAST) scan usually indicates the possibility of hemoperitoneum due to injury to the abdominal organs. In decreasing order of frequency, the most commonly injured abdominal organs following blunt abdominal trauma are the spleen, liver, kidney, small bowel, and mesentery ,2. On raTherefore, a radiologist should always be alert for common and rare causes of hemoperitoneum. We present a case of blunt abdominal trauma that led to the rupture of an incidental corpus luteal cyst as a culprit of the massive hemoperitoneum. We highlight the salient CT imaging features of a ruptured corpus luteal cyst to enable an efficient diagnosis.A 26-year-old female presented with trauma after an alleged fall from a height that directly impacted her lower abdomen. The primary survey revealed that her vitals were within the normal range, but mild tachycardia was recorded (102 beats/minute). Bruising was conspicuous over the lower abdomen. Per the institutional trauma protocol, the eFAST revealed the presence of free fluid in all four quadrants, including the epigastrium, hepatorenal, perisplenic, and pelvic regions. The patient’s pneumo-scan and urine pregnancy test (UPT) results were negative. Afterward, per our institutional protocol, she underwent a non-contrast CT (NCCT) scan of the head and cervical spine and a contrast-enhanced CT (CECT) scan of the torso with both arterial and venous phases.The CECT of the torso revealed the presence of high-attenuation free fluid (>30 HU) in all four quadrants around the perihepatic, perisplenic, epigastrium, and pelvic regions Figure , Panel aOutcome and follow-upThe patient underwent diagnostic laparoscopy (DL) in view of persistent tachycardia and the presence of gross hemoperitoneum. Intraoperatively, gross hemoperitoneum was observed around the right ovary as well in all four quadrants. Further, a large cyst was confirmed in the right ovary with an irregular crenated surface and a small rent, which was cauterized Figure , Panel eThe corpus luteal cyst is a functional vascular ovarian structure with tiny, fragile vessels in the wall that are prone to rupture, resulting in intracystic hemorrhage, intraperitoneal rupture, and massive hemoperitoneum . Its manThe etiology of the corpus luteal cyst varies from spontaneous rupture to lower abdominal trauma. Its recognized risk factors include anticoagulation therapy, strenuous physical activity, and iatrogenic factors such as uterine examination . As was Imaging is essential in diagnosis and characterization and helps in timely management. Ultrasonography (USG) is an easily accessible, non-invasive, real-time, and radiation-free method. Hence, this method is preferred for the initial evaluation and diagnosis of simple and complicated corpus luteal cysts effectively only in routine or follow-up cases, but in level 1 trauma centers where eFAST is performed as an adjunct to the primary survey to observe the presence of free fluid  in the peritoneal and pleural cavity and not to look actively for pelvic organ. Therefore the major findings of a complicated corpus luteal cyst on USG can be easily missed.MRI is the investigation of choice for better characterization of adnexal lesions in routine or follow-up cases but not in acute trauma settings, where CECT of the torso is the tool of choice to identify the source of hemoperitoneum after a positive FAST status. The most common cause of hemoperitoneum is solid organ injury, followed by bowel and mesenteric injuries and, on rare occasions, gynecologic injuries, as was observed in the present case.On CECT, the corpus luteal cyst appears as a hypodense adnexal cystic structure with a thick, enhancing wall . Direct The differential diagnosis in the case of hemoperitoneum includes ruptured ectopic pregnancy, which a negative pregnancy test and the serum β-HCG level can be used to rule out. Another differential diagnosis is the spontaneous rupture of a corpus luteum cyst, which is more common in the luteal phase of the menstrual cycle during pregnancy or after infertility treatment. The absence of pain in the abdomen before the trauma, a bruise over the lower abdomen on clinical examination, and fresh blood during surgery favor posttraumatic rupture over spontaneous rupture.The management strategy is either conservative or surgical, depending on the clinical and imaging presentation. Unstable vital signs, uncontrolled pain with massive bleeding, and active contrast extravasation on CECT are indications of immediate surgical intervention . In thisCauses of rupture of corpus luteum cysts vary from spontaneous to traumatic. Although traumatic rupture of an incidental corpus luteal cyst is rare, it should always be included in the differential diagnosis of women of childbearing age who present with a large hemoperitoneum after trauma without injury to a solid organ. The plausible mechanism could be a direct impact or deceleration injury in the lower abdomen. Because of the difference in anatomic embryology, the right ovary is more vulnerable than the left. Therefore, CECT of the abdomen is an important tool in the trauma setting for localizing the anatomic site of hemorrhage (sentinel clot sign) and effectively visualizing the direct or indirect signs of a complicated luteal cyst as described with varying sensitivity.


Electromagnetic coils are indispensable components for energy conversion and transformation in various systems across industries. However, electromagnetic coil insulation failure occurs frequently, which can lead to serious consequences. To facilitate predictive maintenance for industrial systems, it is essential to monitor insulation degradation prior to the formation of turn-to-turn shorts. This paper experimentally investigates coil insulation degradation from both macro and micro perspectives. At the macro level, an evaluation index based on a weighted linear combination of trend, monotonicity and robustness is proposed to construct a degradation-sensitive health indicator (DSHI) based on high-frequency electrical response parameters for precise insulation degradation monitoring. While at the micro level, a coil finite element analysis and twisted pair accelerated degradation test are conducted to obtain the actual turn-to-turn insulation status. The correlation analysis between macroscopic and microscopic effects of insulation degradation is used to verify the proposed DSHI-based method. Further, it helps to determine the threshold of DSHI. This breakthrough opens new possibilities for predictive maintenance for industrial equipment that incorporates coils. As an important energy conversion component for most components, such as equipment and large equipment, the performance of electromagnetic coils will inevitably deteriorate during industrial production due to long-term operation in harsh environments, which may cause serious economic losses . TherefoThe existing typical turn-to-turn insulation degradation monitoring methods are summarized as follows. Werynski et al.  and PeriTo address this issue, this paper takes a small commercial transformer as the research object and carries out insulation degradation monitoring research simultaneously at the macro and micro levels. On the one hand, an evaluation index based on a weighted linear combination of trend, monotonicity and robustness is proposed to construct a DSHI based on impedance evolution characteristics for precise insulation degradation monitoring. On the other hand, the transformer temperature field distribution is obtained by FEM under the accelerated test condition, and thus an accelerated aging test on twisted pairs were designed and performed to explore the correlation between the health indicator of the proposed method and actual turn-to-turn insulation health status, which helps to provide engineering guidance for determining the health indicator failure threshold.The organizational structure of this paper is as follows. The methodology framework of coil precise insulation degradation monitoring is shown in High-frequency electrical parameter analysis is an effective method for monitoring the degradation of electromagnetic coils. Impedance, resonant frequency, and parasitic capacitance are common high-frequency electrical response parameters. In general, high-frequency electrical response parameters can be generated through accelerated tests or historical data. During the accelerated test, high-frequency electrical responses collection equipment is used to inject small-amplitude high-frequency signals into the coil to be tested and collect high-frequency electrical response impedance signals. Data set In this paper, root mean square (RMS) and kurtosis (K), which are effective time-domain features in fault diagnosis and health management, are considered. However, in the process of electromagnetic coil insulation degradation, the degradation features are usually nonstationary and nonlinear. For this reason, the time-frequency domain features of fuzzy entropy (FE) and wavelet packet node energy (WPNE) are also extracted. Such physical quantities that characterize equipment degradation are generally referred to as physical health indicators. At the same time, information fusion algorithms, such as Principal Component Analysis (PCA) and Mahalanobis–Taguchi system (MTS) are considered for feature dimension reduction to avoid information redundancy and model training overfitting. PCA  and MTS The above physical health indicators and virtual health indicators are used as preliminary health indicators. The calculation equations of the preliminary health indicators are shown in The determination process of the DSHI based on the above preliminary health indicators Since the coil insulation degradation layer will gradually become thinner during the insulation degradation process, indicating that the insulation degradation is an irreversible process, the health indicator reflecting coil insulation degradation should have monotonic characteristics. With the increase of the aging cycle, the coil insulation degradation will also change, so the health indicator and the aging time should have a certain correlation, which is also called the trend. In addition, the health indicator should have good anti-interference ability for outliers, that is, it has a certain robustness. In this paper, the evaluation indexes, such as trend, monotonicity and robustness based on trend and residual ,25,26 arThe equation is generally taken as The trend, monotonicity and robustness equations  are showThe values for each evaluation index of the health indicator are located at , and the closer to 1, the more sensitive the health indicator is. However, the DSHI cannot be reasonably selected based on a single evaluation index. Therefore, this paper constructs an evaluation index To achieve precise insulation health assessment, this paper constructs a knowledge base to obtain the actual turn-to-turn insulation degradation state. Specifically, the temperature field distribution of the transformer is obtained based on finite element simulation, and then the accelerated aging test of twisted pairs is designed to measure the actual turn-to-turn insulation degradation state index, which is finally used as a benchmark to validate the proposed DSHI-based method. At the same time, the correlation between the DSHI and the actual turn-to-turn insulation state is explored to provide theoretical guidance for determining the DSHI threshold value. The precise insulation degradation monitoring method can provide an early warning of insulation failures and remaining life prediction for coils, which can help reduce the risk of unplanned downtime in industrial systems containing electromagnetic coils.In this section, an experimental scheme is proposed, as depicted in The winding accelerated aging test platform and high-frequency electric response acquisition system for transformers in this section are shown in After cooling, the high-frequency electrical response signals of the transformer primary coil in the frequency range of 20 Hz–1 MHz will be collected by an E4980A impedance analyzer. Based on the reactance data of the whole life cycle of electromagnetic coils, multi-domain features are extracted, and physical health indicators and virtual health indicators are constructed. The physical health indicators include RMS, K, FE and three-layer wavelet packet node energy features (WPNE-01~WPNE-08), as shown in The above physical health indicators and virtual health indicators are used as preliminary health indicators. The monotonicity, trend and robustness of the above preliminary health indicators are evaluated, respectively. The results of each evaluation index of preliminary health indicators are shown in In this section, an evaluation index based on a weighted linear combination of trend, monotonicity and robustness is constructed by (7). According to the importance of the three indexes in the coil insulation degradation process described in Normally, the MTS method requires the data distribution to follow a normal curve. If the data does not have a normal distribution, the calculation results of MTS may be biased. To solve the problem of data distribution, the Box-Cox power transformation ,29 is emThe resonant frequency-based method and Spearman correlation spectrum-based method are two existing classical impedance analysis techniques for insulation degradation monitoring. Therefore, coil impedance data obtained during the accelerating test is also analyzed by these two methods for comparison purpose. Wangkai et al.  found thJameson N J et al.  used theTo find a benchmark that can represent the actual insulation health status of electromagnetic coils, a twisted pair accelerated fatigue test is designed to measure the breakdown voltage, which is a physical indicator that can truly reflect the degradation state of electromagnetic coils. To address the problem that it is difficult to measure the internal temperature of the transformer during the practical industrial applications, the relevant conditions of the accelerated aging test of the transformer are entered into the finite element simulation software for thermal simulation, and the temperature field distribution inside the transformer is obtained in this paper. The highest temperature inside the transformer is selected as the aging temperature of the twisted pair. The twisted pair samples are placed in a constant temperature aging chamber for accelerated fatigue testing, and then the breakdown voltage is measured.Utilizing Catiav5R21, construct the geometric model of the transformer with consideration of its symmetry in the xyz direction. Only one-eighth of the transformer without symmetry is reserved for actual simulation to reduce unnecessary calculations. The geometric model should consist of the core, the core skeleton, the primary and secondary coils, as well as the insulation paper between them.Import the Catia 3D model into the ANSYS ICEM for meshing. Repair the geometric model first, block the components of the model, and then execute the corresponding mapping. Next, divide the model using a hexahedral mesh, and export the mesh file to prepare for the subsequent thermal simulation.Utilizing the Fluent module of Ansys, execute a thermal simulation on the model. Import the mesh file into the Fluent module of Ansys, and employ Fluent’s workflow to establish the physical properties of the material, including the thermal conductivity of each part. Among them, the coil and core are established to be anisotropic, the axis direction of the transformer coil skeleton is defined as Z direction, the thermal conductivity of this direction is 1.15 Analyze the results of the simulation. Based on the temperature distribution cloud of the model, identify the global maximum temperature and its location. The temperature field distribution is depicted in The simulation process is as follows:The twisted pair samples were subjected to thermal aging tests according to the IEC 60851-5 standard , as showTo compare the performance of DSHI-based precise insulation degradation monitoring method and the existing techniques, the breakdown voltage, the DSHI-based method (transformed MTS-based method), Spearman correlation coefficient-based method and resonance frequency-based method are normalized to obtain the degradation process of the whole life cycle of electromagnetic coils in the  interval, as shown in Taking breakdown voltage as a benchmark, the degradation monitoring accuracy of the DSHI-based method, Spearman correlation coefficient-based method and resonant frequency-based method relative to the breakdown voltage is calculated. The calculation results show that the degradation monitoring accuracy of the DSHI-based method is 89.48%, which is 42.84% higher than that of resonant frequency-based method and 39.69% higher than that of Spearman correlation coefficient-based method. Therefore, the DSHI-based precise insulation degradation monitoring method has a higher accuracy than the existing mainstream methods.σ statistical approach is selected to set the threshold. 3Setting the failure threshold properly for a health indicator is of great significance for degradation monitoring and predictive maintenance, because when the health indicator crosses its threshold, the coil should be replaced. Therefore, this section discusses the threshold setting for the DSHI-based precise insulation degradation monitoring method. Considering that MTS is determined as the DSHI in the experiment, the 3Breakdown voltage measurement values during the accelerated test is used to verify the effectiveness of the DSHI threshold setting. Considering that as the breakdown voltage measured gradually approaches the rated voltage, the insulation failure probability increases accordingly, insulation failure probability model is defined as (10).The insulation probability calculation results during the accelerated test are shown in Insulation degradation monitoring plays an important role in avoiding the unexpected shutdown of electrical equipment, especially in safety-critical domains. This paper proposed an insulation degradation monitoring method by exploring the macroscopic and microscopic effects of coil thermal aging. At the macro level, an evaluation index based on a weighted linear combination of trend, monotonicity and robustness is proposed to construct DSHI based on the coil high-frequency response parameters during the whole life cycle. The simultaneous development of coil FEA and twisted pair accelerated tests are performed at the micro level. Comparison analysis of macro and micro results shows that the degradation monitoring accuracy of the DSHI-based method is 89.48%, which is higher than mainstream insulation degradation methods, like the resonant frequency-based method and Spearman correlation coefficient-based method. Further, a breakdown voltage-based insulation failure probability model is defined to verify the threshold setting of the DSHI-based method. The proposed method supports the development of a coil insulation health assessment model that enables electrical equipment condition-based maintenance. Considering that the effect of temperature on high-frequency response parameters measurement is not considered in this paper, in the future research, a high-frequency response parameter mapping model at different measurement temperatures will be developed to improve the robustness of the proposed method.


Cervical cancer is the leading cause of disability and mortality among women in Africa. Despite a significant correlation between HIV/AIDS and cervical cancer, there is unacceptably low coverage of the uptake of cervical cancer screening among human immunodeficiency virus-positive women in Sub-Saharan Africa. Individual primary studies are limited in explaining the patterns of uptake of cervical cancer screening. This review therefore considers the uptake of cervical cancer screening and its barriers among human immunodeficiency virus-positive women in Sub-Saharan Africa.31, 2019, from the PubMed, Cochrane Library, POP LINE, Google Scholar, African Journals Online and JURN databases. The quality of the included articles was assessed by using the Newcastle‒Ottawa Scale, and the coverage of uptake of cervical cancer screening was pooled after checking for heterogeneity and publication bias. The random effect model was used, and subgroup analysis estimates were performed by country.We systematically searched articles published until December 2 = 100%). The main barriers to uptake of cervical screening include poor knowledge about cervical cancer and screening, low risk perception of cervical cancer, fear of test result and fear of screening as painful, lack of access to screening services, high cost of screening service, and poor partner attitude and acceptance of the service. The perception of an additional burden of having a cervical cancer diagnosis was found to be a unique barrier among this population of women.Twenty-one studies comprising 20,672 human immunodeficiency virus-positive women were included. Applying a random effect model, the overall cervical cancer screening uptake among this group of women in Sub-Saharan Africa was estimated to be 30% (95% CI: 19, 41, IThe unacceptably low coverage of uptake of cervical cancer screening would indicate that the need to scale up the opportunities to these groups of women as well. This review revealed that in addition to structural and health care system barriers, sociocultural and personal barriers are powerful barriers in HIV-positive women. For these cohorts of population, a particular obstacle was discovered to be perception of an additional burden of having cervical cancer.The online version contains supplementary material available at 10.1186/s12905-023-02479-w. Cervical cancer was the fourth most common cancer in women, ranking after breast cancer, colorectal Cancer and lung cancer and continues to become a major cause of death in resource limited countries such as Sub Saharan Africa , 2. The As the US Centers for Disease Control and Prevention (CDC) categorized cervical cancer as an acquired immunodeficiency syndrome (AIDS) defining cancer in 1970, the coinfection of the two diseases represents substantial public health impacts in SSA –7. InfecAccording to the recommendation of the CDC, National Institute of Health (NIH), and HIV Medicine Association (HIVMA), HIV-infected women should undergo two Pap tests within the first year after the diagnosis of HIV infection, followed by annual Pap testing irrespective of their age , 15. TheWHO recommends that women living in HIV high prevalence areas and be sexually active; as soon as possible to initiate screening for cervical cancer . AlthougThe incidence of co-infection HIV/AIDS with cervical cancer is high globally and in SSA –24.Although the reasons for not screening for cervical cancer vary from region to region, HIV-positive women have unique challenges that hinder them from utilizing the service. However, in most cases, they share the same barriers with HIV-negative women , 26. ThiAlthough there have been a few systematic review studies addressing the barriers to cervical cancer screening in the whole population in Sub-Saharan Africa (SSA), there is a lack of evidence on the pooled effect  of uptake and barriers to CC  screening among this group of women (HIV-positive women) in SSA. Therefore, this review aimed to describe the ranges of and barriers to cervical cancer screening among HIV-positive women (unique barriers) in SSA. Uptake of cervical cancer screening for this review is defined as those respondents who have been screened for cervical cancer once in their lifetime , 27, 28.st, 2019 were searched systematically and thoroughly in the following databases and search engines: PubMed, Cochrane Library, POPLINE, Google Scholar, African Journals Online (AJOL) and JURN. In addition, a back and forth review of references from eligible included studies was undertaken.This review was written in accordance with the recommendation of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA-P) 2015 statement . Observa“(((((uptake) OR (("Facilities and Services Utilization"[Mesh])))))) AND "Uterine Cervical Neoplasms"[Mesh]) AND ((((("Mass Screening"[Mesh])) AND ("Early Detection of Cancer"[Mesh]) AND "Diagnosis"[Mesh]) AND "diagnosis" [Subheading] ))) AND (("Africa"[Mesh]) OR "Africa South of the Sahara"[Mesh])”.Observational studies that reported uptake of CC screening among HIV-positive women, measured by those respondents who screened for CC at least once in their lifetime, studies conducted in SSA, all published articles in English language, and no restriction in the publication year were included.Excluded studies report populations other than HIV-positive women, unable to access full text, studies did not address the barriers to cervical cancer screening services, and studies published in languages other than English.The primary outcome of this review was to determine a pooled single estimate of the uptake of cervical cancer screening among HIV-positive women in SSA, and the secondary aim was to identify the barriers to CC screening services among HIV-positive women in SSA. For this review, any documented evidence of having screened and become involved in mass/campaign screenings, clinic/facility-based or programmatic screenings at least once in life is considered uptake of CC screening and is similar to the barriers to screening.Initially, an advanced and systematic search was made via the identified databases. In addition, a manual review of references of included studies was conducted to access additional relevant articles. Next, studies published other than in English language, conducted out of SSA; unrelated and irrelevant articles based on their title and abstract were excluded. Then, the remaining articles were imported into Endnote version 7, and duplicate articles were removed. After exact duplicates were removed, two reviewers (MBM and HDH) independently conducted abstract and full text reviews to determine the articles to be included and excluded. In the case of disagreement, divergent views were resolved by consulting a third reviewer TTC. The final articles selected were then reviewed by the two reviewers for data abstraction. Finally, data were extracted from the included studies through a structured data extraction form and presented using tables: name of authors, study period, year of publication, study design, country of the study, residence, type of screening for cervical cancer, total sample size, uptake of cervical cancer screening (proportion), reasons for not being screened, and frequency/number of identified barriers [frequency/number of women who reported barriers among those who did not undergo cervical cancer screening in their lifetime].The quality assessment of cohort and cross-sectional studies was assessed using the Newcastle‒Ottawa Scale (NOS) , 31. The2 statistics were determined and reported. Publication bias was assessed using a visual inspection of funnel plots and Egger’s regression test. During meta-analysis, in the case of a high level of heterogeneity, a random effect model was used, and a subgroup analysis estimate was performed by the countries in which the study was performed.Coverage (proportion) of uptake of cervical cancer screening and estimates of barriers gained from each study were pooled and estimated as a single estimate. The heterogeneity level across the studies was tested using the Higgins test, where the ISensitivity analysis was performed for studies included in the review. The meta-analysis, subgroup analysis, sensitivity analysis and publication biases were carried out with statistical R-software version 3.6.1 and Stata Version 14 for sensitivity analysis. Sixteen variables, name of authors, study period, year of publication, study design, country of the study, residence, type of screening for cervical cancer, total sample size, uptake of cervical cancer screening (proportion), reasons for not being screened, and frequency of identified barriers, were entered into statistical R-software version 3.6.1. to run the meta-analysis. In addition to the use of a random effect model, sensitivity analysis was performed in Stata 14 ‘influence-analysis (metaninf) tests, which indicated that the estimated values of all the included studies were within the CI. Accordingly, we declared that two studies affected the results of the other studies. Nevertheless, they were not as influential and did not significantly affect the result. The protocol of this systematic review is under registration process with the prospective registration number of 167,569 for systematic reviews (PROSPERO acknowledgement of receipt [167569]).The online search yielded 1824 records through database searching. From this search, 1803 retrieved studies were removed through a step-by-step process for the following reasons: 1665 were excluded as irrelevant by title and abstract, 48 were removed as duplicates, 5 full texts were not accessible, 35 reflected different study populations, 37 reflected different outcomes, 3 had unknown study areas, and 10 were out of the study setting. One hundred and six full text articles were assessed for eligibility, and 21 articles were included in the quantitative synthesis   HIV-positive women. The smallest sample size was a study performed in Zimbabwe with 70 participants, , fear of test result as positive 18% , and fear of screening and procedure is painful 11%  (Table Poor knowledge of CC and poor awareness of CC screening were identified as the main reasons for not undertaking screening (barrier) in three studies contributing qualitative results Table . In one Although most HIV-positive women perceived a high risk of getting the disease, some of them would not participate in CC screening because of the perception of “I am not sick or I do not have signs and symptoms of the disease” , 48, 53.Four studies revealed that fear of a positive test result was a potential hindrance for not using the service. Belete N. et al. 2015  reportedIn most SSA countries, there is a male-dominated family model, with the husband deciding every issue of the family as the primary income earner. Hence, the male partner’s reluctance to have their wife undergo CC screening is often related to the belief that this procedure violates the pride and privacy of their partner , 34, 48.Lack of well-equipped health facilities and qualified personnel to carry out the procedure were identified as barriers for accessibility and uptake of CC screening. Trouble in navigating health care facilities and lack of awareness about the location of screening facilities were also reported as barriers , 47, 54.Four studies reported that a lack of financial support and associated costs for screening were barriers to the uptake of CC screening. In areas where poverty is prevalent, payment for nonemergency health services such as CC screening is a challenge. In addition, the cost of transportation contributes to the nonaccessibility and nonuse of the service , 41, 54.Cervical cancer is a major cause of disability and mortality and has a substantial health impact in SSA. The scale up of cervical cancer screening coupled with HPV vaccination can reduces cervical cancer disease and has a potential to make cervical cancer disease no more threat to the coming generation . The covThis systematic review and meta-analysis found that the pooled coverage of uptake of CC screening among HIV-positive women in SSA was 30% . This finding was comparable with findings reported from Tigray, Ethiopia, 19.8% , but lowThe findings from the subanalysis showed that the pooled coverage of uptake of CC screening among HIV-positive women was higher in western Africa and other Eastern parts of African countries other than Ethiopia. The observed differences might be due to the implementation of CC screening programs among HIV-positive women in these regions, sociodemographic differences, and the health care system.Considering this low coverage of cervical cancer screening uptake among HIV-positive women, it would not be erroneous to expect that a significant number of HIV-positive women are suffering from an additional burden of cervical cancer, which impacts their lifespan and quality of life. Recent studies have demonstrated that sexually transmitted diseases such as HIV/AIDS are more likely to be linked to CC than human papilloma virus . Women iWe identified the following barriers that hinder this target group from undertaking the service: Knowledge about cervical cancer and screening, Risk perception of cervical cancer, Fear of test result and fear of screening as painful, Access to screening services, Cost of screening service, and Partner attitude and acceptance of the service.In line with the findings reported by SSA countries on barriers to and facilitators of CC screening among the whole population, we also identified that 49% of HIV-positive women had poor knowledge of cervical cancer and screening. In SSA countries, where there is significant illiteracy, there is a lack of information and knowledge about the high mortality rate from CC and the early control and screening mechanisms of the disease. Fear of test results and screening (18%) and risk of perception of the disease (23%) were the other barriers identified in this review. Poor knowledge more likely intensifies misconceptions about the disease and service, fear and sense of pain and low perceived risk of the disease. Individual challenges stated by HIV-positive women are that they do not want to go screening for the reason of stigma, they do not want to add another stress, and the burden of the disease scares them more than anything else.Poor partner attitude and acceptance of the service were other reasons for not screening for CC among HIV-positive women. This finding is consistent with reports done in Uganda, , Iran, , and BriOur review demonstrated that a lack of access to screening services was a barrier to uptake. Difficulties in navigating health care facilities, lack of awareness about screening locations, and prolonged waiting times are all potential contributors to limited uptake. The other identified barrier was the high cost of the service. This finding is in line with findings reported from the United States , NigeriaThis review adds further evidence of low coverage of cervical cancer screening among women living with HIV/AIDS in SSA countries, despite significant association between HIV/AIDS and cervical cancer. This implies a further need of promotional policies, enhanced nationwide advocacy, strengthening of health education and creation awareness programs through media outlets, integrating of cervical cancer screening to primary health care levels and to routine treatments among these vulnerable and high risk group of women. It also shows that, though this group of women is expected to come into contact with the care system on regular basis, poor medical advice, and poor coordination of cervical cancer screening services to routine treatment contributes to a low level of cervical cancer screening among these groups.This finding should be interpreted considering the limitations of the study. High heterogeneity as a result of differences in health care systems, implementation of services between countries, high discrepancy in uptake of cervical cancer screening, and underrepresentation of countries may affect the generalizability of the review to all Sub-Saharan countries. However, the concern of heterogeneity was addressed using a random effect model for pooling the estimates. As a limitation, all the included articles only measured lifetime receipt of cervical cancer screening; however, it is possible that HIV-positive women may have been screened before they tested positive.Although we included unpublished papers, there might still be unpublished articles concerning this topic.The unacceptably low coverage of uptake of cervical cancer screening would indicate that the need to scale up the opportunities to these groups of women as well. This review revealed that in addition to structural and health care system barriers, sociocultural and personal barriers are powerful barriers in HIV-positive women. For these cohorts of population, a particular obstacle was discovered to be perception of an additional burden of having cervical cancer.Additional file 1: Annex Table S1. Newcastle - Ottawa quality assessment scale for cohort stduy designs.Additional file 2: Annex 2 Table S2. Newcastle - Ottawa quality assessment scale for cross-sectional stduy designs.