Timely microscopy screening of peripheral blood smears is essential for the diagnosis of acute promyelocytic leukemia (APL) due to the occurrence of early death (ED) before or during the initial therapy. Screening manually is time-consuming and tedious, and may lead to missed diagnosis or misdiagnosis because of subjective bias. To address these problems, we develop a three-step pipeline to help in the early diagnosis of APL from peripheral blood smears. The entire pipeline consists of leukocytes focusing, cell classification and diagnostic opinions. As the key component of the pipeline, a compact classification model based on attention embedded convolutional neural network blocks is proposed to distinguish promyelocytes from normal leukocytes. The compact classification model is validated on both the combination of two public datasets, APL-Cytomorphology_LMU and APL-Cytomorphology_JHH, as well as the clinical dataset, to yield a precision of 96.53% and 99.20%, respectively. The results indicate that our model outperforms the other evaluated popular classification models owing to its better accuracy and smaller size. Furthermore, the entire pipeline is validated on realistic patient data. The proposed method promises to act as an assistant tool for APL diagnosis. Acute promyelocytic leukemia (APL) is one of the sub types of acute myeloid leukemia (AML), namely M3, according to the French–American–British (FAB) classification guidelines of acute leukemia. The incidence of APL is around 0.23 per 100,000 people in China and around 600–800 cases each year in the United States .Early diagnosis plays a dramatically important role in APL treatment selection and is closely bound to its prognosis, since APL benefits most from timely treatment compared with the other subtypes of AML. APL used to be fatal before the specific target therapy with all-trans retinoic acid (ATRA) was adopted. Currently the five-year disease free survival rate has risen from 25% to 95%, and APL has been thought to be almost a curable disease. Despite this, it is still difficult to avoid early death (ED) before or during the initial therapy due to mortal hemorrhagic complications such as disseminated intravascular coagulation (DIC) . TheoretAccording to the morphology screening guidelines for APL proposed by FAB, the microscopic examination should be implemented manually by well-trained hematopathologists, which are scarce in most primary hospitals . BesidesThere have been state-of-the-art achievements in the classification or automatic detection of cell images of acute leukemia, especially for acute lymphoblastic leukemia (ALL) and AML. These methods categorize all the cells and then predict the leukemia based on the existence of abnormal blast cells, some of which segment the individual white blood cells first. The main differences among them are the different classification algorithms employed. Some of them chose the traditional solutions to classification problems, for example, workflow consisting of manually-designed image features and support vector machines as the classifier ,12,13 orIn addition, there are some cell image processing, analysis and segmentation methods based on deep learning proposed for problems other than acute leukemia. By comparing the prediction of two classifiers and selecting the label with the higher confidence value, the overall accuracy of embryo image classification has been further increased . A deep 1.A new compact cell classification model based on the attention embedded convolutional neural network is designed to distinguish promyelocytes from the normal white blood cells. The whole model is tiny and it is easily trained on a small dataset to avoid fine tuning. The experiment’s results demonstrate that it outperforms other popular benchmark classification models.2.To the best of our knowledge, this is the first work to investigate the early diagnosis method of APL on a large dataset consisting of all public accessible datasets and private data. The entire dataset is nearly twice as large as that used in current work and includes multicenter data, which helps with generalization.3.The end-to-end pipeline has been validated on realistic patient data.In this study, we develop a clinically applicable pipeline to help with the early diagnosis of APL. According to the FAB guidelines, the most critical evidence of APL is the discovery of abnormal promyelocytes in peripheral blood through a series of morphological features including kidney-shaped or biloba nuclei, large and/or numerous cytoplasmic granules, and Auer rods . A compaThe remainder of the paper is organized as follows: The proposed artificial intelligence aided pipeline for APL diagnosis works on the microscopy images of peripheral blood smear samples. It consists of three steps, namely leukocyte focusing, cell classification and diagnostic opinions as shown in The input of our system is the microscopy image, which contains numerous blood cells. Since we mainly care about leukocytes in APL diagnosis, the first step is to focus on our target cells. As shown in A compact CNN model with attention mechanism embedding was designed to perform the cell classification. It consists of a group of convolution layers—a channel attention module and two fully-connected layers as shown in A convolution layer is composed of convolution, batch normalization, ReLU activation function and max pooling operation as listed in Equation .(1)F(·)Since the convolution group produced a large number of feature maps, the channel-wise attention module was embedded to highlight the most discriminative feature channels and help them to contribute more to the final prediction. It was implemented through the squeeze-and-excitation (SE) module  as in EqTwo cascaded fully-connected layers were employed to compress the feature maps and to generate the final prediction for cell classification. The details of the architecture are shown in Based on the latest National Comprehensive Cancer Network (NCCN) guidelines, the induction therapy should be started as soon as possible in cases suspected of APL by morphological examination . Thus, wThree datasets were employed to validate the performance of the proposed model. The first was the public dataset AML-Cytomorphology_LMU, which contains more than 10,000 expert-labeled single-cell images taken from peripheral blood smears diagnosis with acute myeloid leukemia at Munich University Hospital . The secTPR and FPR.In order to measure the performance of our method quantitatively, the most commonly used statistics, denoted as the true positives The entire system was implemented through Python and the cell classification framework was based on Pytorch . All expIn the training phase of the cell classification model, the hyper parameters were as follows. The SGD optimizer was applied with momentum = 0.9. The initial learning rate was set as In order to validate the performance of our proposed compact cell classification model, we trained our model on the APL-Cytomorphology_LMU and the APL-Cytomorphology_JHH. The results are listed in p-value = 0.0018, which is smaller than 0.05, to prove that the performance differences of the four models are statistically significant. We then visualized the difference between the average ranks of the four models using the Critical Distance (CD) diagrams made from the results of the post-hoc Nemenyi test  combined with arsenic trioxide, the cure rate of APL has been greatly improved. Therefore, early screening, early diagnosis and timely treatment are particularly important in clinical practice. In the 2019 NCCN clinical guidelines, it recommends that the retinoic acid induction therapy should be applied as soon as possible once APL is suspected based solely on the morphology characteristics, since early clinical intervention is important for decreasing the early bleeding mortality and improving the long-term cure rate. As an important means of initial diagnosis, the morphological analysis of biological smears through microscopy has high technical requirements for hematologists, and faces problems such as long training cycle, poor repeatability, strong subjectivity and high rate of missed detection, especially in primary hospitals. What is worse is that most APL cases have a low white blood cell count, which makes the manual check more difficult. We seek to provide a potential solution to address the mentioned difficulties. There are three components, including the leukocyte, that focus on identifying the white blood cells from the microscopic images: the cell classification to classify the abnormal promyelocytes and the five types of normal leukocytes, as well as the final diagnosis recommendation associated with the risk estimation.The popular classification networks require more computing resources during the training process due to the large number of parameters of these networks. For our task, not only are there the problems of slow training and inferencing, but also the risk of overfitting. Instead of using these networks, a compact convolutional neural network model embedded with the channel-wise attention mechanism was proposed. The model has fewer tunable parameters so that it does not ask for fine-tuning based on the large public dataset and has lower hardware requirements. However, the achieved performance is competitive as shown in Since the two public datasets only provide microscopic images of single cells, we chose to validate our entire workflow on the clinical data and to investigate its capability of auxiliary early diagnosis. This time, we trained the cell classification model for use in the workflow on the clinical dataset from scratch to avoid any domain bias. The classification performance is listed in The limitation of the proposed pipeline is that the overlap of cells occurs frequently in the peripheral blood smears of high-white-blood patients, due to the dense distribution of white blood cells, as shown in In this study, we demonstrated an artificial intelligence aided APL diagnosis pipeline consisting of cell focusing, classification and diagnostic opinions. The cell focusing step helps to find the leukocytes from the microscopic images through automatic segmentation methods. The presented compact convolutional neural network model embedded with an attention mechanism can identify the abnormal promyelocytes directly from microscopy images through cell classification. The model distinguishes the cells based on the automatic learned features, instead of on the manually designed ones. The experiment’s results demonstrate that our model achieves a better performance than the competitive models, such as ResNet-34 and ResNeXt-50, on both public datasets—APL-Cytomorphology_LMU and APL-Cytomorphology_JHH—as well as on the clinical dataset. Our method can be employed in situations with very low white blood cell counts at the early stage of APL to save time when making a diagnosis decision. As an entire workflow, the proposed method shows great potential to act as a tool for the early diagnosis of APL.


The range of diagnostic and therapeutic applications of needle arthroscopy (NA) continue to expand due to advances in image quality and resolution. Minimally invasive techniques can be augmented by the smaller camera size and reduced fluid use made possible by NA. Small-bore arthroscopy presents opportunities for use in smaller joints, such as the elbow, where applications of standard arthroscopic equipment may be limited by small anatomic spaces and fluid extravasation. In this Technical Note, we present our technique for NA-assisted treatment of terrible triad injuries, specifically in the setting of an intact radial head. The technique describes a stepwise approach to arthroscopically aided fixation of the coronoid process, followed by open reconstruction of the lateral collateral ligament complex. Details the described technique in a stepwise approach to arthroscopically aided fixation of the coronoid process, followed by open reconstruction of the lateral collateral ligament complex . Concomitant coronoid, collateral ligament, and radial head injuries in the setting of an elbow instability event traditionally have been considered difficult clinical entities to treat, as evidenced by the name “terrible triad” adopted throughout the literature. Coronoid fractures are especially difficult to address when the radial head component of the injury does not require open treatment, as in nondisplaced fractures or articular injuries involving less and 25% of the articular surface.Although good outcomes with traditional arthroscopy have been described in the treatment of these injuries, the technique is challenging owing to the proximity of neurovascular structures to the surgical field and the small anatomic spaces at play in the elbow. Despite these challenges, arthroscopic assistance can lead to better visualization of the injuries, reduced surgical morbidity, and lower risk of wound-related complications. Needle arthroscopy (NA) has been described in the diagnostic and therapeutic evaluation of the knee, shoulder, and elbow.The surgical technique is demonstrated in A manual examination with the patient under anesthesia can confirm the typical posterolateral instability pattern by recreating an axial load, valgus, and posterior lateral rotatory force. This is critical for distinguishing an isolated coronoid fracture from a true instability pattern if the preoperative imaging and examination are in question. Furthermore, an intact radial head or neck in the setting of lateral ligament disruption and coronoid fracture should alert the treating surgeon to be aware of osteochondral fracture or loose bodies in the joint, as this can occur as the intact radial head and neck dislocate. If present, these injuries can be treated arthroscopically or through an open lateral approach during ligamentous repair.General anesthesia is recommended, as regional anesthesia does not allow postoperative assessment of nerve function and patients may not tolerate the positioning while awake. The patient is positioned in the lateral decubitus position on an inflatable bean bag with the arm over a radiolucent arm board. Fluoroscopy can be positioned from the patient’s head with the c-arm and receiver parallel to the side of the bed to allow for ease of intraoperative imaging on the lateral view. A sterile tourniquet is applied after the limb is prepped and draped in the usual fashion and the relevant anatomic landmarks are marked with a sterile marking pen.The NA system  includes a zero-degree arthroscope with power cord, monitor, and sharp and blunt trocars with corresponding sheaths including inflow portals. Assorted instruments, including a retractable probe and a 2.0-mm shaver, are also available. With the use of a sterile technique, the cords are attached, and the monitor can be relayed to overhead monitors in the operating room via a standard high-definition multimedia interface cable .Fig 1RooThe technique for diagnostic elbow arthroscopy with the NA system has been previously described in detail.After completion of a diagnostic arthroscopy, attention is turned to the arthroscopic fracture reduction. The camera with high flow cannula (Arthrex) is placed in the mPAMP and the 2.0 shaver  is used to debride the fracture bed from the MALP. If the high-flow cannula is not used, inflow from a separate sheath may be provided from the PALP. Use of a small-diameter shaver facilitates fluid management and prevents collapse of the anterior capsule into the field of view by minimizing applied suction . Once adAttention is then turned to the open lateral approach. A standard incision is made from the lateral epicondyle toward the lateral margin of the radial head. Deep dissection typically exploits a traumatic tear in the lateral ligaments; however, if necessary, the Kocher interval between the extensor carpi ulnaris and the anconeus can be used in the rare instance the overlying extensor origin is intact. It is important to remember the proximity of the posterior interosseous nerve and pronate the forearm, which moves the nerve farther from the plane of surgical dissection. In addition, anterior dissection should be performed carefully, as the radial nerve is just anterior to the anterior lateral capsule. Ligamentous tissue most commonly avulses as a sleeve with the common extensor wad. After splitting the interval, the soft tissue is elevated from the lateral epicondyle to provide optimal exposure and a working arthrotomy. A self-retainer is left in place to maintain the open lateral exposure during suture passage and button fixation.Under fluoroscopic guidance, a small longitudinal incision is placed on the dorsal border of the proximal ulna in line with the coronoid fracture bed. A guidewire is introduced that contains a wire loop for suture passage. Under direct visualization and while maintaining the reduction with a dental pick or k-wire, the wire is advanced through the coronoid tip fragment. An arthroscopic grasper is then used to retrieve the wire through the open lateral arthrotomy. Position of the wire and fracture reduction are verified fluoroscopically .Fig 4LatA looped end of a passing suture  is then loaded on the wire loop on the guidewire and retrieved through the lateral portal as the guide wire is removed. This suture is then used to shuttle the 2 tails of a nonabsorbable suture , which are loaded through a 2.6-mm suture button . As the suture tails are placed in traction through the fracture site and exiting on the dorsal aspect of the proximal ulna, the button is drawn against the coronoid tip effectively reducing the fracture. The reduction is confirmed arthroscopically and fluoroscopically.One to two centimeters distal to the exiting suture tails a drill guide is placed and a 2.7-mm guide hole is drilled for a 3.5-mm knotless suture anchor . Suture tails are loaded into the anchor, maximally tensioned, and the anchor is inserted into the bone. Remaining suture tails are cut and discarded. The knotless suture anchor is preferred to a suture button because there is no prominence that may result in irritation on the subcutaneous border of the ulna. The final coronoid reduction is confirmed fluoroscopically.Two suture anchors are then placed on the lateral epicondyle. The first is placed just distal and anterior to the central portion of the anatomic origin of the lateral collateral ligament complex. This is used primarily for fixation of the ligamentous tissue itself. The second is placed more proximally for repair of the common extensor origin that was previously elevated. Repair of the ligaments is performed with horizontal mattress sutures from the anchors which are used to imbricate the anterior flap over the more posterior tissue sleeve. This has the effect of tightening the lateral collateral ligament complex, which often has been attenuated from the initial trauma.At this point, with the elbow in supination and the ligaments provisionally repaired, the radial head should point directly at the capitellum without any posterior subluxation. After imbrication of the ligament complex to the distal anchor, and reattachment of the extensor origins more proximally, the remaining muscular interval may be closed with interrupted absorbable braided sutures to ensure water-tight capsular closure. The elbow is taken through a complete range of motion and stability is confirmed in flexion, extension, pronation, and supination. The final construct may be confirmed fluoroscopically. Standard skin closure is then performed .Fig 5(A)Postoperatively, patients are placed in a posterior slab splint with the forearm in neutral to slight pronation. The splint is removed 10 to 14 days later at the first postoperative visit, and the patient is converted into a removable brace. In the absence of poor wound healing, progressive motion is then initiated under the guidance of an occupational therapist with a goal of full range of motion 8 to 10 weeks postoperatively. Strengthening is initiated at 12 weeks postoperatively, working from flexion and pronation (most stable) to supination and extension (least inherently stable). Full recovery is expected between 4.5 and 6 months from the time of surgery .Table 1PPosterolateral rotatory instability has been described as a spectrum of injury resulting from failure of the soft-tissue and bony stabilizers of the elbow.As arthroscopic technology has continued to improve, an increasing number of patients with posterolateral rotatory instability and terrible triad injuries are being treated, at least in part, using minimally invasive, arthroscopic techniques. A number of studies have shown comparable outcomes with arthroscopic techniques for ligament repair and/or reconstruction, as well as fixation of coronoid fractures, when compared with open techniques.While traditional arthroscopy has been shown to be valuable in the treatment of elbow pathology, proximity of neurovascular structures, small intraarticular working space, and issues with fluid extravasation are problems that can make the procedure technically demanding. The role for small bore needle arthroscopy for both diagnostic and therapeutic applications is becoming clearer in the literature.NA is a useful adjunct to arthroscopic examination, debridement, reduction, and fixation of coronoid tip fractures, particularly in the setting of a largely intact radial head or minimally displaced radial neck fracture.


The task force launched a knowledge translation initiative consisting of a webinar series and online resources to communicate information directly to the IBD community. Taskforce recommendations were posted to CCC’s website and included guidance such as risk stratification, management of immunosuppressant medications, physical distancing, and mental health. A weekly webinar series communicated critical information directly to the IBD community. During the pandemic, traffic to CCC’s website increased with 484,755 unique views of the COVID-19 webpages and 126,187 views of the 23 webinars, including their video clips. CCC’s COVID-19 and IBD Taskforce provided critical guidance to the IBD community as the pandemic emerged, the nation underwent a lockdown, the economy reopened, and the second wave ensued. By integrating public health guidance through the unique prism of a vulnerable population, CCC’s knowledge translation platform informed and protected the IBD community.The prevalence of inflammatory bowel diseases (IBD), Crohn’s disease and ulcerative colitis, in Canada, is over 0.75% in 2021. Many individuals with IBD are immunocompromised. Consequently, the World Health Organization’s declaration of a global pandemic uniquely impacted those with IBD. Crohn’s and Colitis Canada (CCC) formed the COVID-19 and IBD Taskforce to provide evidence-based guidance during the pandemic to individuals with IBD and their families. The Taskforce met regularly through the course of the pandemic, synthesizing available information on the impact of COVID-19 on IBD. At first, the information was extrapolated from expert consensus guidelines, but eventually, recommendations were adapted for an  During the COVID-19 pandemic, one of the most essential health services has been the communication of expert health information and population-level advice; for the IBD population, this was achieved through expert-created online materials and frequent webinars geared towards a public audience.Because the epidemiology of the COVID-19 pandemic differed by region, emphasis is placed on providing the best information possible so that people with IBD can assess their personal risk based on personal health risk factors, ability to stay home, and the state of local outbreaks.In addition to increased web content and topical webinars, one of the most effective tools at communicating expert information to the IBD population were short topical videos spliced from the full webinar series that allowed individuals to search and find answers to specific questions related to their personal risk and/or the COVID-19 pandemic.Roughly 300,000 people are living with inflammatory bowel disease (IBD) in Canada in 2021, and this number is expected to exceed 400,000 by 2030 . The preCrohn’s and Colitis Canada (CCC) instituted a task force to make evidence-based recommendations to people with IBD. In order to deliver expert recommendations and answers to the IBD community, CCC launched a knowledge translation initiative consisting of a webinar series and online resources.The World Health Organization (WHO) declared the novel SARS-CoV-2 outbreak a global pandemic on March 11, 2020 ; this imIn this article, we detail the dynamic and iterative process of the knowledge translation initiatives developed to inform and protect the IBD community during the first year of the pandemic.COVID-19 and IBD Taskforce convened via videoconference with representatives from across Canada, including: adult and pediatric gastroenterologists (GIs), IBD nurses, infectious diseases experts, scientists, public health officials, communications and government relations experts, and patient advisors  and most of the Atlantic region  initially had low to medium case counts, but were able to limit the spread of the virus early on and experienced fewer total cases , experience from prior viral outbreaks, and current public health guidance modified for the needs of the IBD community . RecommeCCC’s website. An explicit statement that the recommendations should supplement, but not replace, the recommendations made by an individual’s physician or local public health authority was included in all communication. Detailed information made available included FAQ sheets and video clips from a weekly webinar series  registry . These webinars were developed as the primary mechanism to communicate critical information directly to the IBD community in a manner that was accessible to a broad audience. The webinars were promoted through email membership and volunteer lists compiled by CCC, as well as CCC’s social media network . As with the topics for Taskforce discussion, content was developed based on questions received directly from the IBD community in a questionnaire filled out during registration for the webinars, from the live chat during the webinar broadcast, or from the post-webinar surveys deployed to all webinar registrants. The direct connection to people with IBD and their families addressed the critical requirement for effective knowledge translation with information directly relevant to the audience  of confirmed Canadian cases of COVID-19 . The ability to select pieces of each video to augment COVID-19 information on the CCC website has proven to be exceptionally impactful with a further 78,862 views of individual clips  registering for more than one COVID19 webinar. Links to the recorded webinars were provided on the CCC website 24 h after the live event and added to the organization’s al clips . As of ACCC was able to quickly assemble the COVID-19 and IBD Taskforce at the outset of the global pandemic. The Taskforce members have met and continue to meet regularly in an effort to ensure that the IBD community has the best available information to support them as they navigate a new reality with COVID-19. Direct communication from the Taskforce and the expert community in Canada to people with IBD and caregivers through a webinar series was an effective and efficient knowledge translation vehicle. The spring webinars ably guided the vulnerable IBD community from a population-wide lockdown in March 2020 through to an understanding of risk and appropriate measures to ensure physical and mental health during the re-opening of the country over the summer and through the second wave of the pandemic. On March 18, 2021, the one-year anniversary of the webinar series, CCC completed the twenty-third webinar that addressed questions by the IBD community on vaccination. As future waves of the pandemic unfold in Canada, the Taskforce is prepared to guide the IBD community.


Increasing the efficiency of the photodynamic action of the dyes used inphotodynamic therapy is crucial in the field of modern biomedicine. There aretwo main approaches used to increase the efficiency of photosensitizers. Thefirst one is targeted delivery to the object of photodynamic action, while thesecond one is increasing the absorption capacity of the molecule. Bothapproaches can be implemented by producing dye–nanoparticle conjugates.In this review, we focus on the features of the latter approach, whennanoparticles act as a light-harvesting agent and nonradiatively transfer theelectronic excitation energy to a photosensitizer molecule. We will considerthe hybrid photosensitizer–quantum dot complexes with energy transferoccurring according to the inductive-resonance mechanism as an example. Theprinciple consisting in optimizing the design of hybrid complexes is proposedafter an analysis of the published data; the parameters affecting theefficiency of energy transfer and the generation of reactive oxygen species insuch systems are described. Theranostics, which combines photodynamic therapy (PDT) and fluorescencediagnostics, is a promising field in modern medicine that uses light to detectand eliminate tumors, other unwanted structures, as well as the foci ofmicrobial and fungal infections of the skin and mucous membrane, 2.PhotOne of the key criteria in choosing dyes for PDT is the significant absorptioncapacity of PS in the red and near-infrared spectral regions, since lightpenetration depth into biological tissues is considered to be the greatest inthis range. Modifying the structure of a PS molecule might be an inefficientway to meet this criterion; therefore, it might be required to use additionallight collectors. Having absorbed light of the required spectral range, thelight collector will transfer energy to the PS and, thereby, enhance itsphotodynamic effect.The main mechanism of energy transfer in such hybrid complexes (HCs) isconsidered to be the nonradiative one .Accordingly, a number of requirements also apply regarding the light collector.In particular, the resonance condition imposes certain restrictions on thespectral characteristics of an energy donor and an energy acceptor. Taking intoaccount the fact that the spectral properties of HC components largely dependon their structural properties, which can change during the complex formation,we obtain a complicated multicomponent system whose design optimization isamong the most consequential issues in applied biophysics.Luminescent nanoparticles (LNPs) are currently the most commonly used as lightcollectors for PS molecules . SuchnaUpconversion , 12,silThis review considers the features of the design of HCs based on QDs and PSswith allowance for the complex formation mechanism, the stoichiometry of thecomplex, the structure of HC components, as well as the influence of theseparameters on the efficiency of energy transfer and ROS generation in thecomplexes. We found out that the photodynamic properties of PS decrease with arising ratio of the components of the PS : LNP complex because of its highlocal concentration on the nanoparticle surface even through energy transferefficiency is enhanced. Enhancement of the luminescent properties of QDs due toprotective shells can reduce the efficiency of energy transfer in HC, as thedistance between the energy donor and the acceptor increases. Based on thecorrelations obtained, a technique allowing one to synthesize highly efficientHCs has been proposed; the aim of this technique is to maximize the generationof reactive oxygen species by the photosensitizer within a HC. The conclusionsdrawn in this review largely apply to HCs based on all other types of LNPs.1.1. Second-generation tetrapyrrolic photosensitizersA photosensitizer that is highly efficient in terms of ROS yield is supposed toboast the following characteristics. First, the energy of its triplet statemust be sufficient to enable a photodynamic reaction with molecular oxygen; theselection is performed to increase the yield of the triplet state and itslifetime. Second, the PS is supposed to exist in a monomeric state, since PSaggregates do not generate ROS as efficiently. Third, the PS should have a highabsorption capacity, preferably within the “optical window” ofbiological tissues.It is obvious that the photodynamic properties depend on the structure of a PSmolecule. We will consider the relationship between the structural andphotophysical properties of PSs using tetrapyrrole dyes, the most commonsecond-generation PSs, as an example.Fig. 1A):Porphin is the simplest dye of the tetrapyrrole series. The absorption spectrumof porphin contains an intense Soret band at the boundary between the UV andvisible regions, as well as four low-intensity narrow bands in the visibleregion . There areseveral main ways to modify the structure of a porphin molecule, making itpossible to obtain PS that exhibit high photodynamic activity((A) sequential hydrogenation of two double bonds, which are not formallyincluded in the conjugated system, shifts the QI band to the long-wavelengthspectral region (a bathochromic shift) and increases its intensity by more thanan order of magnitude. Hydrogenation gives rise to the classes ofdihydroporphyrins (chlorins) and tetrahydroporphyrins (bacteriochlorins);(B) replacement of carbon in the methine CH groups with a nitrogen atom(tetrazaporphyrins) or incorporation of benzene rings in the macrocycle of adye molecule (tetrabenzoporphyrins) increases the intensity of the QI and QIIIbands, as well as causes their bathochromic shift. The strongest effect isobtained when these two approaches are combined, i.e., in the classes oftetrazatetrabenzoporphyrins or phthalocyanines (Pcs); and(C) coordination of various elements by the macrocycle of a porphin moleculedue to the lone electron pairs of the central nitrogen atoms. For porphyrins,complexes with divalent metals are the most typical. Formation of a metalcomplex leads to the degeneration of four absorption bands in the visiblespectral region to leave two bands whose intensity is significantly increased.This situation is typical of all porphyrin dyes containing no hydrogenatedpyrrole rings. When a metal atom is incorporated into the Pc macrocycle,insignificant bathochromic shifts of the QI and QII bands are observed and themagnitude of the bathochromic shift increases as the atomic number of the metalincreases .d-shells of the metal in the conjugation systemmax is determined by the number of charged groups onthe organic shell of QD, as well as the number of charged groups on the PSmolecule. There is ambiguity here: the more charges there are on the PS, thestronger the interaction is, but fewer PS molecules will bind to the QDsurface.The PS : LNP stoichiometric ratio can be increased to a certain limiting valuethat depends on the complexation method. If HC is formed by covalentcrosslinking, then [PS : LNP]maxis determined by the LNP surface area, as well as by thehydrophilic–hydrophobic balance of the PS molecule. For a bulk polymershell of a nanoparticle, [PS : LNP]max will be much higher than thatwhen a monolayer of low-molecular-weight ligands is used. However, additionalPS molecules will be located far enough from the QD center so that theefficiency of energy transfer to these PS molecules should beminimal. Figure 4 showsthe situation where PS is covalently bound to thepolymer shell of QD. One can see that for a total nanoparticle radius of 11.5nm and Forster radius R0 = 5 nm, the efficiency of energy transfer to a givenPS molecule will be no more than 0.7%.If HC is stabilized trough sorption interactions, the [PS : LNP]χ2 describing the mutualorientation of the transition dipole moments of the donor and acceptor canincrease the energy transfer efficiency. The χ2 valuescan vary from 0 to 4. In solutions, χ2 is taken equal to2/3 due to rotational diffusion and random orientation of the molecules. Thisis also used in the case of HCs, since most QDs do not have luminescenceanisotropy. Nevertheless, in the general case, the orientation of transitiondipole moments in the HC can be nonrandom. It is assumed that studies focusingon the anisotropy of the PS and LNPs fluorescence would potentially helpestimate the possible mutual orientations of the transition dipole moments andthereby refine the χ2 value max values are. It is fair to say that the absolute energytransfer efficiency W increases with a rising number of PSmolecules in HC, while the energy transfer efficiency W forevery separate PS molecule decreases.Let us imagine that the number of PS molecules on the LNP surface can increaseinfinitely without an increase in the average PS–LNP distance that isequal to the Forster radius R0. According to Forster’s theory, at PS :LNP = x = 1, the energy transfer efficiency Consequently, the more PS molecules there are in a complex with LNP, the lessadditional energy each of them receives, and, therefore, the enhancement ofphotodynamic properties of PS tends to zero. The photodynamic activity of PS inthe HC at large PS : LNP ratios turns out to be lower than the activity of freePS due to self-quenching effects.Finally, the use of some types of LNP shells can lead to the fact that ROSformed in a reaction between PS and molecular oxygen inside the organic shellof LNP cannot effectively damage the targets in the solution surrounding HC,since diffusion in the LNP shell is hindered. In this case, the most likelytarget of oxidation will be the PS molecule itself. Indeed, inelectrostatically stabilized HCs based on aluminum phthalocyanines and QDscoated with a polymer shell, we observed rapid bleaching of the dye both underselective illumination of Pc and upon excitation of QD, followed by energytransfer . As a reTherefore, the increased energy transfer efficiency in HCs due to a rise in thePS : LNP value contradicts the idea of enhancing the photodynamic activity ofPS.It should be noted that the interaction between PS and LNP can result inelectron transfer. This phenomenon is observed quite rarely and is easilydetected with strong changes in the spectral properties of PS due to theformation of radical anions and other derivatives , 109. InFig. 6. One can seethat all the key characteristics of PS and LNPs are interconnected. Therefore,the full set of parameters optimized so as to ensure the highest ROS yield mustinvolve some degree of compromise.All the mentioned functional relationships between the structural and spectralproperties of PSs and LNPs, which can affect the efficiency of LNP as a lightcollector, and an enhancement of the photodynamic activity of PS in HC can besummarized in a single scheme shownin Fig. 6 can beidentified as quan titative dependences. Since most of these parameters arerelated to each other by the well-known formulas of the FRET theory, thedifficulty arises only at the stage of uncovering the relationship between thestructural and photophysical characteristics of the HC components. First ofall, this concerns LNPs, since the relationship between the structural andspectral properties of tetrapyrrolic PSs has been studied quite thoroughly.Achieving this compromise is the primary task for PDT on its path to creatingthird-generation PSs. However, even though an impressive number of studies havebeen devoted to HCs, the data collected are too fragmentary and heterogeneous,making a global analysis and the selection of the required set of HCcharacteristics impossible. This would be feasible only by using an integratedapproach, when all the connections shownin However, it is not enough to possess information about the properties of eachcomponent to optimize the design of the HC. Phenomena such as PS aggregationand static quenching of the luminescence of LNPs  can be quantitatively studied onlythrough experiments on HC formation. It should also be noted that electrondensity perturbation in a PS molecule during the formation of HC (even in theabsence of the aforementioned aggregation and quenching effects) has someeffect on the photophysical properties of PS and, thus, indirectly affects theenergy transfer efficiency and the enhancement of the ROS yield. Failure totake into account any of the parameters described above leads to the followingfact: even in the presence of PSs and LNPs with spectral characteristicsoptimal for FRET, it might not always be possible to obtain HC where enhancedPS fluorescence or the ROS generation rate is observed , 106. ThFig. 6 should beexpanded with allowance for all the aspects of the functional activity of HC asa third-generation photosensitizer. Building a complete scheme of this kindwill allow one to take the prospects for using HC with energy transfer in PDTto a fundamentally new level and is, therefore, the main objective of modernmedical biophysics.It might be possible to find several variants of complexes significantlydiffering in terms of their set of internal characteristics but havingcomparable ROS yields  by optimizing the HC design. Sincethe enhancement of the photodynamic characteristics of PS can be achieved onlyat low PS : LNP values, when the luminescence of the LNP is not completelyquenched, the LNP luminescence can be used for diagnostic purposes. Such HCscan obviously be used to solve specific problems of PDT and fluorescencediagnostics depending on the properties of the target object. In this regard,it must be said that we have discussed the trends in optimizing the HC designexclusively with a view to enhancing the ROS yield. In fact, the overallphotodynamic activity will depend not only on the absorption capacity of HC andthe ROS yield, but also on the efficiency of interaction between HC and cells,the internalization mechanism, and the stability of HC in the presence of bloodcomponents when an HC-based drug is administered to a living being. It ishighly likely that the approaches to optimizing HC for increasing theefficiency of targeted delivery will significantly affect the final set of HCparameters. Therefore, the scheme shownin


New neurons are continuously generated and functionally integrated into the dentate gyrus (DG) network during the adult lifespan of most mammals. The hippocampus is a crucial structure for spatial learning and memory, and the addition of new neurons into the DG circuitry of rodents seems to be a key element for these processes to occur. The Morris water maze (MWM) and contextual fear conditioning (CFC) are among the most commonly used hippocampus-dependent behavioral tasks to study episodic-like learning and memory in rodents. While the functional contribution of adult hippocampal neurogenesis (AHN) through these paradigms has been widely addressed, results have generated controversial findings. In this review, we analyze and discuss possible factors in the experimental methods that could explain the inconsistent results among AHN studies; moreover, we provide specific suggestions for the design of more sensitive protocols to assess AHN-mediated learning and memory functions. The discovery of neurogenesis in the brain of adult mammals  contradiThe DG is a crucial structure that participates in hippocampus-dependent learning and memory . ThousanThe hippocampus is a key structure in navigation and in spatial learning and memory , while iDifferent behavioral paradigms have been used to study the functional implications of AHN in spatial learning and memory   while otIt is worth noting that during the learning phase of the MWM, rodents develop allocentric and egocentric search strategies to find the hidden platform . When usThe search strategy pattern adopted by the rodent can be classified according to the type of learning taking place from the least precise strategies  to the most precise  . Mice wiRegarding the degree of the hippocampal-dependency of the task, it has been proposed that MWM protocols promoting cognitive flexibility during the learning phase place a substantial demand on both hippocampal and AHN functions . PertineA recent study reported that immature new neurons (DCX + without tertiary dendrites) are more likely implicated in tasks that demand cognitive flexibility than mature new neurons . SeveralSpecifically, it has been shown that after reversal learning, mice with increased AHN display low neuronal activity in the suprapyramidal blade of the DG as well as in the CA3ab region. Thus, this sparsity decreases the overlap in memory representations from both structures . The conIt has been shown that AHN is of particular importance in the performance of tasks that require spatial discrimination, where rodents have to distinguish between two highly similar contexts and learn that they are different from each other . In thisIt has been shown that the saliency of the cues set around the testing room modulates the precision of the searching patterns in MWM task . Some feFinally, the age of animals at the time of AHN reduction is another factor that influences whether alterations in spatial learning are observed after neurogenesis manipulation. The generation of newborn neurons declines with the age of rodents. High rates of AHN are found in juvenile animals, moderate rates in adult, and low rates in old ages . In ratsOverall, the above mentioned works suggest that the decrease in AHN does not affect the general learning phase in the MWM but negatively impacts specific DG functions, such as the selection of precise allocentric spatial research strategies, cognitive flexibility, and spatial discrimination tasks. Moreover, given that the saliency of the visual cues located in the testing room can influence the use of allocentric searching patterns, the features of the visual cues must be carefully considered before the onset of the learning phase and should be described in detail. Finally, the age of rodents at the time of AHN reduction influences whether alterations in spatial learning are observed after neurogenesis manipulation. In the next section, we discuss results related to AHN and the memory phase in the MWM task.Regarding the evaluation of the role of adult-born neurons in memory using the MWM paradigm, there are several differences across studies that complicate their integration. To understand these results, we analyzed them according to the time elapsed between the end of the learning period and the beginning of the memory evaluation phase: short-term (≤24 h) and long-term (≥1 week) retention intervals.Several works have reported impairments in rodents with decreased AHN when memory retrieval was evaluated in retention time intervals ≤ 24 h. However, others have failed to find such impairments. Some possible explanations for the discrepancy among studies may be related, but not limited to the degree of the hippocampal dependency of the protocol employed (see above), the specificity of the methods used to modulate AHN, the age of the newborn neurons affected during testing and the possible stress generated when using intermediate probe tests.In regard to the age of adult born neurons, it has been shown that immature new neurons ∼4–6 weeks old are particularly important for hippocampal memory function . New-borOverall, as discussed in regard to the learning phase, the impact of AHN on memory formation seems to become more evident with protocol configurations that promote cognitive flexibility and spatial discrimination, while it is particularly important to consider the age of the new neurons when being tested.In addition to short-term memory findings, there are other studies involving the MWM that highlight the importance of new neurons in long-term memory. Notably, animals with reduced neurogenesis already before learning, spent less time swimming in the goal quadrant when memory was evaluated 1 or 4 weeks after the end of the learning phase . ConversConcerning long-term memory consolidation, it has been suggested that a given memory is initially dependent on the hippocampal region and that over time, cortical structures end up storing, at least partially, such memories . The mecConsidering all the above, we suggest some specifications that should be considered in the design of a sensitive protocol for the assessment of the functional relevance of AHN through the MWM: (1) precise parameters should be analyzed that reflect the formation of a spatial allocentric cognitive map to the escape platform, such as the searching strategies used by rodents during navigation; (2) cognitive flexibility and spatial discrimination behaviors should be promoted using the reversal learning and visual discrimination in the MWM task; (3) the saliency of the visual cues should be evaluated regarding whether they promote the establishment of hippocampal allocentric searching strategies; (4) the age of rodents at the time of AHN manipulation; and (5) the best time to manipulate AHN during the task should be identified.Contextual fear conditioning is a behavioral procedure in which an animal learns to predict the presence of an aversive stimulus, like a foot-shock, through its association with a specific context (conditioning chamber). The foot-shock represents the unconditioned stimulus (US), and the context represents the conditioned stimulus (CS). The association between the US and the CS drives a classical fear response in rodents characterized by freezing (immobility) . This beSimilar to studies in MWM, inconsistent results have been reported regarding the role of AHN in fear conditioning. However, a common factor among studies reporting alterations when AHN is decreased is that only contextual, but not cued fear memory is affected in rodents with low neurogenesis levels see . This hiBelow, we discuss some factors that differ across the studies and that likely contribute to the discrepant results. Moreover, we briefly analyze other fear-related behaviors that have been associated with the function of AHN, such as fear extinction, spontaneous fear recovery, and fear generalization.During the conditioning phase, animals learn to associate a foot shock with a specific context. Rodents are placed into the context (conditioning chamber), and then single or multiple foot shocks are delivered. Learning performance is evaluated through the progressive increase in a freezing response across the training session . The methodology employed during conditioning varies considerably among AHN studies. These variations may yield discrepancies among the findings. Here, we highlight four factors related to the conditioning protocol that may impact CFC results.This refers to the intensity, duration and the number of foot shocks delivered to rodents during the conditioning phase; these factors determine the time of incubation and the brain areas involved in processing fear-associated memories . TraininThe sensory perception of foot shocks in rodents can modulate their fear response during memory evaluation. Moreover, the sensory perception of a foot shock can result in a decreased conditioned fear or even the lack of a fear response  if the shock is perceived as a low-intensity stimulus. In contrast, the sensory perception of a foot shock can increase animals’ conditioned fear or even result in a maladaptive fear response  if the shock is perceived as a high-intensity stimulus . Thus, tThis refers to the interval between the introduction of the rodent into the context and the delivery of the first foot shock. The preshock time is important for context encoding and memory resolution, as animals need time to form a representation of the context before the shock is presented . If a shThe DG is critical for associating individual items with their context, which comprises the background setting of a spatial environment . The feaOverall, the impact of AHN seems to become more evident when the conditioning phase consists of mild training (single foot shock) and a short preshock interval (180 s). Moreover, the reactivity of the rodent to a foot shock and access to visual cues in the conditioning context are variables that should be considered in the interpretation of the results.During the memory phase, rodents are placed in the context again but do not receive any foot shocks. If they remember the context as an aversive experience, the animals display freezing behavior (immobility). Contextual memory is evaluated through the percentage of time that rodents freeze during memory assessment. While a high percentage of freezing reflects adequate contextual fear memory establishment, lower levels of freezing indicate degraded or impaired contextual fear memory. Interestingly, in the AHN literature, there are several studies showing that newly generated adult neurons are necessary for optimal contextual fear memory function . Here, wN-Methyl-D-aspartate (NMDA) receptor and type T-Ca2++ channels  of these immature neurons (∼4–6 weeks old) has a more disruptive effect on memory resolution than prelearning manipulation . This suIn agreement with MWM results, there are studies using contextual fear memory that support the role of adult neurogenesis in long-term memory . These sRecent studies have stressed the physiological relevance of the activity of memory-engram cells in memory consolidation through the CFC task . Memory-After establishing contextual fear conditioning, it is possible to analyze other DG-mediated cognitive behaviors, such as fear extinction , fear reIn this process, extinction is defined as a decline in the conditioned fear response following repeated exposure to the context in the absence of foot shock . After eAfter fear extinction, the expression of fear often returns as time passes, a phenomenon known as spontaneous fear recovery . It has After associating the aversive presence of a foot shock to a specific context, rodents can show fear responses even in a similar innocuous context, which reflects their inability to make fine spatial discriminations . The uncIn summary, there is high heterogeneity among the protocols used to evaluate the function of neurogenesis through contextual fear. We posit that there are four possible conditioning parameters that may influence behavioral results and that experimenters should carefully consider in their experimental design: (1) the severity of the trial (multiple vs. single shock), (2) the preshock time interval, (3) the context configuration and, (4) the impact of the side effects generated by the ablating methods on mouse nociception. Finally, through pattern separation or by the forgetting of a previously learned memory, AHN may modulate other fear-related cognitive behaviors, such as fear extinction, fear recovery, and fear generalization.Adult neurogenesis occurring in the rodent hippocampus has been widely accepted for a few decades now. Efforts to understand the role of adult-born neurons in behavior started almost hand-in-hand with these observations. The refinement of strategies to analyze, target and manipulate adult-born cells has provided clear evidence of the role of neurogenesis in behavior. Moreover, the dissection of the elements involved in the design of behavioral tasks has shown to be crucial for understanding the subtle roles of new neurons in episodic-like learning and memory. The consideration of each of the discussed elements for the implementation of a task when addressing the role of neurogenesis in behavior may provide a refined framework for discussing the obtained results.KH-M and AZ wrote the manuscript. KH-M prepared the figures. AZ revised the manuscript. Both authors contributed to the article and approved the submitted versionThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Virtual reality (VR) has become a common tool and is often considered for sport-specific purposes. Despite the increased usage, the transfer of VR-adapted skills into the real-world (RW) has not yet been sufficiently studied, and it is still unknown how much of the own body must be visible to complete motoric tasks within VR. In addition, it should be clarified whether older adults also need to perceive their body within VR scenarios to the same extent as younger people extending the usability. Therefore, younger (18–30 years old) and elderly adults (55 years and older) were tested (n = 42) performing a balance-, grasping- and throwing task in VR (HMD based) accompanied with different body visualization types in VR and in the RW having the regular visual input of body’s components. Comparing the performances between the age groups, the time for completion, the number of steps , the subjective estimation of difficulty, the number of errors, and a rating system revealing movements’ quality were considered as examined parameters. A one-way ANOVA/Friedmann with repeated measurements with factor [body visualization] was conducted to test the influence of varying body visualizations during task completion. Comparisons between the conditions  were performed using the t-Tests/Wilcoxon tests, and to compare both age groups , t-Tests for independent samples/Mann-Whitney-U-Test were used. The analyses of the effect of body visualization on performances showed a significant loss in movement’s quality when no body part was visualized (p < .05). This did not occur for the elderly adults, for which no influence of the body visualization on their performance could be proven. Comparing both age groups, the elderly adults performed significantly worse than the young age group in both conditions (p < .05). In VR, both groups showed longer times for completion, a higher rating of tasks’ difficulty in the balance and throwing task, and less performance quality in the grasping task. Overall, the results suggest using VR for the elderly with caution to the task demands, and the visualization of the body seemed less crucial for generating task completion. In summary, the actual task demands in VR could be successfully performed by elderly adults, even once one has to reckon with losses within movement’s quality. Although more different movements should be tested, basic elements are also realizable for elderly adults expanding possible areas of VR applications. Virtual reality (VR) has become a common tool to assess and treat health problems –3 due toNot confirming transfer effects could be caused by differences in visual perception of virtual environments like underestimating distances from egocentric perspectives , or incoConsidering the usage of VR for elderly adults, previous studies showed that they also can (and should) use VR technology for training and clinical applications . In 1515, the mTherefore, the previously conducted study  in whichThe current study has two primary aims: First, the impact of varying visualization types of the own virtual body on the performances between both age groups. It is also examined whether elderly adults need to perceive visually their own body in VR to the same extent as younger ones did and if the performance decreased when no virtual body was visualized as previously proven . Second,The current study is classical structured, in which information of the participants and the procedure, including a description of each task, are presented. Since technical components play a crucial role within VR research, details including soft- and hardware are listed. In data analysis, the parameters for each task were explained being able to compare participants’ performances between both age groups. The statistical methods are also described step by step to ensure tracking of each goal. The results section starts with a short introduction of which graphs are assigned to the specific research goal.The study was designed and conducted in accordance with the declaration of Helsinki. The approval of the Ethics Committee of the Otto-von-Guericke University at the Medical Faculty Hospital Magdeburg was obtained under the number 132/16.Forty-two healthy participants were collected for this study. Twenty-one older-aged participants  formed one group and twenty-one younger-aged participants  the other one. The mean age of the young1 tested in the first study was 21±1.6 years . No significant differences in age between both young groups are obtained (p>.05). The prerequisites for both groups were no or at least corrected visual impairment , no neuronal disorders and no physical impairments which prevent smooth execution of the motoric tasks. The older-aged group stated not having participated in VR experiments, nor did they collect any experiences in computer gaming before. All participants were informed about the aim and procedures and gave their written consent.balance task, followed by the grasping task and the throwing task as the final task  was used considering the scales and the textures of the objects in the real world. For the visualization of the beam, the ball, and the goal, rigged meshes compatible with real size were used and tracked in real-time. The created virtual environments were then imported into Unity3D (version 2019.1), and the SteamVR (version 2.5.0) was used to enable users to interact in the virtual reality. Visual Studio 2017 was used for implementing the C# program for Unity to run the studies.The participants perceived the virtual environment through a head-mounted display . A high-performance desktop equipped with Intel i7 CPU, 16 GB memory, 512 GB SSD, and Nvidia GTX 1080 8GB graphics card was used to ensure the presentation of VR without interruptions. A motion capture system  including 13 cameras with a sampling rate of 200 Hz was used to visualize the own body within the VR. Two computers were connected through a network cable to track participants’ movements simultaneously to visualize those on the virtual avatar provided by Vicon Shogun. In total, 53 markers were placed on the participant’s body indicating the standard Vicon Shogun marker set. The objects which play a role within the different motoric tasks were also marked to ensure high precise position tracking in real-time and generalize haptic feedback.First, a one-way ANOVA with repeated measurements was used to compare between the two young age groups, in which the body visualization types were treated as within subject factor and the group as between subject factor . First, the performances for each task were analyzed  accompanied with the different body visualization types  within each age groups . A detailed description of the chosen parameters is given in . Hereby,The results were divided into three major parts. First, the performances of the two young age groups (young1 and young2) were compared to strengthen the expressiveness of the results from the first conducted study  see Tab. Here, nThe second goal was the investigation of the different body visualization types on both age groups  and the age groups (young2 vs. old) see . TestingTo show the extent of the drop of performance in VR, the percentages of RW related to the values of VR are calculated and visualized see . In the The current article’s aim is to compare the behavior between two different age groups in the real and virtual environment. The behavior was examined by completing tasks requiring motoric skills such as balancing, grasping, and throwing. First, a comparison was made between the first  and the The results indicate that both young age groups similarly performed all examined motoric tasks. Significant differences accompanied by small effect sizes occur for the time for completion in the balance and grasping task. These shifts were also observed by comparing the time duration in RW, in which the second young group also needed less time to complete the task. The quality of movement (determined by the same scoring system except for the grasping task) and the subjective estimation of difficulty do not differ between the groups, which reinforces the feasibility of the tasks.In both groups, the body visualization’s importance turned out, since differences occurred between the performances when different types of body visualization were presented. Since no significant differences within the interactions are found , it is concludable that both age young age groups needed to perceive at least one remaining limb where the body’s position could be adjusted, which is in line with previous findings . This isThe analysis of the impact of the different body visualization types on participants’ performances showed that the younger age group was most affected by the no visualization type see . During For the elderly aged group, there is no difference in performances affecting by the different body visualization, even if no body was visual perceivable. They were not affected by the different visualization types which are consisted of their verbal feedback, since in some cases, participants from this group stated not having realized the missing visualizations. This could be reasoned by the difference in attention on the task demands or on the limited Field of View (FoV), which is also discussed in previous research , 15. In For both age groups, no significant differences were found in the number of errors and the subjective estimation of difficulty. Accordingly, the difficulty of each task did not increase over an increased reduction of body visualization types. The younger adults were more sensitive according to the perception of their own body, since they experienced a strange feeling when no visualization was provided. Previous studies could show that the visualization of a realistic looking avatar lead to better performances and an increased feeling of being present indicated by a more naturalistic interaction, improved spatial perception, more precise distance estimation and less cognitive load –40. If tConsidering the grasping task, a significant difference occurred only within the younger aged group. The best performances mirrored by the shortest duration of grasping the ball and placing it to the target position was observed when no body was visualized. The participants verbalized confusion since the hands of the virtual body were merged sometimes with the mesh of the ball, which could have had an effect of maintaining their sense of presence . This leThe results of the throwing tasks confirmed the previously investigated findings. No quality loss within the performance of the participants was found, which is not in line with previous findings which revealed decreased accuracy in hitting a target by throwing a ball in VR . The youMany of the presented findings coincide with previous results, which show that the visualization of the hands and feet were sufficient to generate a feeling of owning a virtual body . FurtherRegarding the results presented in Further comparisons between the younger and the older-aged group within both environments were made. The differences between the groups are not surprising. It is noticeable that the older- group took longer to master the balancing and the grasping task in both conditions (p < .05). In the balance task, further restrictions such as higher number of foot strikes and errors were identified in the older-aged group under real conditions. In VR, the number of foot strikes did not differ compared to the younger aged group. One main factor that could be responsible for the founded differences between the groups is the familiarity with VR systems, since the participants within the older-aged groups experienced the virtual environment for the first time. Previous studies showed the importance of adjustment phases within virtual environments which could lead to better performances .The study revealed significant worse performances of the elderly compared to the younger aged group in RW as well as in VR. The tasks were obviously more difficult to complete in VR except the throwing task, although it was higher rated in the subjective difficulty in both groups. In addition, the different types of visualization of the body parts had no impact on the performances of the older-aged group. In contrast, the younger aged group seemed to be more sensitive to the visual perception of different body parts, since significant worse performances was observable when the body was not visualized at all. The advantages of the visualization of the own body on acting or performing in VR were crystallized in other examinations , 35, 51.It was further analyzed whether cybersickness symptoms occurred for both age groups to examine the possible use of future VR devices for different aging groups. Interestingly, the older-aged group reached a score under the threshold (20) to a “bad simulator”, whereas the young people suffered more by getting a total score of 24.58. For both groups, the disorientation was worse , whereas the nausea was less problematic . As indicated by , averageTo expand the usage of VR for sports-related purposes, even more, different sport-motoric tasks should be completed, and further analyzes concerning the transfer into the real-world should be done. A further limitation is that no measurements of embodiment were included since it was just focused on the impact of less visual feedback of bodies’ components. However, this could have impacted the sense of body ownership, which is already discussed in .To extend the possible age groups which can train via VR technology in the future, it is essential to check the requirements such technology needs. Overall, the results suggest using virtual reality for older aged people with caution to the task demands. In summary, all tasks could be completed except longer execution times in balancing and grasping (which persist to a maximum delay of two seconds). The balance task was hard to take, even for the younger aged group. Without including the practice trials before starting to balance over the beam, the participants felt insecure and repeatedly stepped down. For grasping and throwing, these problems disappeared. The subjective impressions of task difficulty were rated higher in VR for all tasks in both age groups, which could be reduced by increased participation within virtual environments. According to the participants’ behavior, the motivation, and the enjoyment from participating and completing each task were enormous, and the interest in the usage in the VR system itself increased. Those differences might be minimized when more adjustment of perceiving and acting in virtual environments take place or technical improvement providing more realistic visualization were made. In addition, it is not required to visualize the whole body either for the young or for the older adults. The older age group seemed to pay less attention to this part which positively affects the possible integration of today’s VR technology.S1 Data(ZIP)Click here for additional data file.


In this work, we analyze the effect of the distribution of transparent Fresnel regions over the focusing profile of Soret Zone Plates (SZP) based on binary sequences. It is shown that this effect becomes very significant in those fields where directional transducers are employed, such as microwaves or acoustics. A thorough analysis of both the SZP transmission efficiency and the focusing enhancement factor is presented. Moreover, experimental measurements are also carried out for a particular type of binary sequence, the Cantor ternary set, validating the theoretical model and demonstrating that the distribution of transparent Fresnel regions becomes a critical parameter in applications requiring directional emitters. Acoustic waves are employed in a wide range of fields because they are able to penetrate deep into objects or biological tissues where optical techniques are not feasible due to scattering and absorption. In particular, ultrasound focusing is widely employed in non-destructive testing in industrial scenarios  and biomIn contrast, Fresnel Zone Plates (FZPs) are planar monofocal lenses that can achieve a good focusing performance while maintaining an easy design and manufacturing process. This type of lenses have been widely employed since decades ago in various fields, including microwaves , optics Interestingly, in recent years, novel kinds of lenses based on applying a binary sequence to the different Fresnel regions of a conventional FZP  have beeIt has already been shown that the distribution of the transparent Fresnel regions on a conventional Soret FZP affects both the transmission and the focusing efficiencies of the lens when directional emitters are involved , demonstIn plane wave incidence scenarios, which is usually the case in most optical applications, the difference between Soret FZPs with opaque and transparent central regions is only significant for a small number of Fresnel regions as was previously shown in . When thIn a conventional Soret FZP, the transparent and opaque areas are distributed in a sandwich pattern, with each transparent region located between two opaque regions and vice versa. However, there is still one design decision that becomes very significant: the determination of the central Fresnel region. If the central Fresnel region is opaque (O-FZP), the rest of the Fresnel regions are already determined as well. The even-order Fresnel regions are transparent, whereas the odd-order Fresnel regions are opaque, as is the central one (first Fresnel region). On the contrary, if the central Fresnel region is transparent (T-FZP), the even-order and odd-order regions are then reversely opaque and transparent, respectively. As we stated before, the inner regions are favored in power distribution due to the directivity diagram of the piston transducer. Therefore, common sense indicates that the T-FZP lens will be more efficient than the O-FZP lens. This is very straightforward because the number or transparent and opaque regions in an FZP is basically identical and, moreover, these regions are very evenly distributed. For example, the binary sequence of length However, if a different type of binary sequence is used, for example, a Cantor binary sequence, the number of transparent and opaque regions may not be as evenly distributed as in the conventional FZP case. For instance, if the Cantor ternary set of order d from the lens can be modelled as a point source emitter with a given directivity pattern. In this case, the incident pressure at the lens can be expressed asa is the piston active radius, r is the radial coordinate, k is the wavenumber, and It is well known  that in F is the focal length, d is the distance between the piston transducer and the SZP, N the total number of Fresnel regions of the SZP. This Equation is easily derived from the Fresnel zone construction principle [The incident power ,,ηtx, is quations  and 2),,ηtx, is In order to determine which type of SZP presents a higher transmission efficiency, either the T-SZP or the O-SZP, the Transmission enhancement factor is defined as the ratio between the transmission efficiencies for the T-SZP and O-SZP cases, and is given byTherefore, Not only the transmission efficiency is important in the performance of the SZP. Another critical parameter is the maximum intensity value that the lens is able to achieve at its focus.The acoustic intensity along the z-axis is given by ,(8)I(z)If we particularize Equation  at z=F, Furthermore, combining Equations , 2) and and2) anThe focusing enhancement factor can be found as,Thus, combining Equations  and 11)11), the Thus, Transmission efficiencies and focusing profiles have been calculated in MATLAB  using the analytical model described in the previous section. The parameters used in the simulation have been selected accordingly to the experimental measurements that are shown in the next section to improve the coherence and readability of the paper. Therefore, FZP lenses have been design with a binary sequence length L is increased in the CZP case, the transmission enhancement factor becomes smaller while the focusing enhancement factor increases its value. The explanation of this unexpected behaviour has to be understood from the nature of the different parameters. When dealing with As can be observed from f) or the focal length (F) are also different. All FZPs and CZPs have been manufactured using brass for implementing the opaque Fresnel regions, because this material presents a high acoustic impedance mismatch with water. CZPs have been designed using the binary sequences associated to the Cantor ternary set with Several experimental measurements have been carried out to demonstrate the focusing enhancement achieved combining T-SZPs with directional transducers. The experimental set-up consists of a 3D underwater automated positioning system with a spatial resolution of f is the ultrasound frequency used in each experiment. F represents the experimental focal length and matches perfectly the design parameter. FLHM and FWHM stand for the Full Length Half Maximum and the Full Width Half Maximum, respectively. The FLHM parameter corresponds to the “Length” of the focus in the axial direction, and it is calculated from the difference between the z locations, at opposite sides of the focus central point, at which the normalized intensity is half of its maximum value. Analogously, the FWHM represents the width of the focus along the lateral direction. Both FLHM and FWHM parameters are related to the longitudinal and lateral resolutions, respectively. As the value of any parameter is diminished, the corresponding resolution increases and the focus becomes slimmer. Some of the main parameters of experimental measurements have been summed up in In this work, we have analyzed the impact that the distribution of transparent and opaque Fresnel regions has on the focusing capability of a SZP generated from a binary sequence, when considering directional emitters. An analytical model that introduces two efficiency parameters in order to determine the optimum distribution for the Fresnel regions has been developed. These efficiency parameters are the transmission enhancement factor , the best alternative is always the transparent case (T-SZP), with independence of the transmission efficiency. As an example, we have shown ZPs based on Cantor binary sequences, where a higher transmission efficiency is obtained in the opaque scenario (O-CZP), but the higher focusing peak is achieved again at the T-CZP case, contrary to what initially could be expected. This behaviour is replicated for any other ZP based on a different binary sequence regardless of the transmission enhancement factor. Therefore, the transmission efficiency is not a critical parameter that should be considered for taking the design decision of selecting an opaque or a transparent central Fresnel region in order to improve the ZP focusing profile, and the right choice is always to go with the transparent central area (T-SZP), regardless of the type of ZP lens or its transmission efficiency. This is an important issue that should be widespread, as many researchers still manufacture their ZPs with an opaque central region (O-SZP), reducing the dynamic range of their ZP focusing profiles and applications.