The purpose of this narrative review was to examine the usability and feasibility of multimedia intervention as a platform to enable patient participation in the context of acute recovery and to discover what outcomes have been measured.A narrative review of primary research articles identified through a search of four electronic databases  identified peer‐reviewed research evidence published in English language with no limitation placed on time period or publication type. Two authors independently assessed articles for inclusion. From the 277 articles identified through the search, 10 papers reporting the outcomes of seven studies were included in this review.Articles were independently assessed for quality and relevance by two authors. The most appropriate method for data synthesis for this review was a narrative synthesis.From the narrative synthesis of study outcomes, two findings emerged as follows: (a) multimedia interventions are feasible and usable in the context of acute care, and (b) multimedia interventions can improve patients’ perception of care‐related knowledge. Identified gaps included a lack of evidence in relation to the effect of interventions on enhancing patients’ ability to participate in their care and the impact on patients’ health‐related outcomes.In conclusion, there is some evidence of the feasibility and usability of multimedia interventions in acute care. That is, patients can use these types of platforms in this context and are satisfied with doing so. Multimedia platforms have a role in the delivery of information for patients during acute recovery; however, the effectiveness of these platforms to engage and enhance patients’ capability to participate in their recovery and the impact on outcomes needs to be rigorously evaluated. For example, use of multimedia platforms to provide patient information and education has increased significantly over the past decade. Multimedia tools have being successfully used in a wide range of health situations including preparing patients for specific procedures or surgery by providing education pre‐operatively or to gain pre‐operative consentThe purpose of this narrative review was to examine the usability and feasibility of multimedia intervention as a platform to enable patient participation in the context of acute recovery, and to discover what outcomes have been measured as a result of using multimedia.multimedia was defined as a tool that uses animation, sound and text,usability was defined as the degree to which a multimedia intervention is easy to use for patients in the acute care context,feasibility was defined as the ease or convenience of applying a multimedia intervention.Acute care was defined as a pattern of health care in which patients are treated for brief but severe episode of illness, for example recovery following accident or trauma or during recovery from surgery.For the purpose of this review, 22.1A specific mnemonic for qualitative systematic reviews (PICO) was used to develop the question for this review.Are multimedia interventions effective in engaging patients in their care in the context of acute recovery? andWhat outcomes have been measured?The research questions were as follows:2.2and acute hospital care and patient participation ; however, there was no difference between groups in terms of correctly naming a nurse (P = .45), or awareness of planned tests (P = .33), procedures (P = .11) or new medications (P = .19) or discontinued medications (P = .58). The patient activation measure (PAM) was used to determine differences in the level of activation between groups, but despite there being a trend towards higher activation in the intervention group, no significant difference between groups was revealed. However, it is possible that the study was not sufficiently powered to detect a statically significant difference between groups, as patient activation was not the primary outcome. These findings support that patients’ desire to participate in their care is an important consideration when evaluating interventions designed to improve outcomes.The majority of reviewed studies were not designed to measure the impact of the intervention on clinical outcomes, and only one study measured patient participation as a function of using multimedia interventions designed to increase patients’ involvement in their care. O'Leary et alons P = . or discoOne indirect measure of patient participation in care and recovery is improvements in clinical outcomes and acute care length of stay.In another related study in 2014, Cook et al3.3All of the studies reviewed reported high patient satisfaction as an outcome of the use of multimedia interventions.4Patients taking an active role in their own health care have known benefits for patients with chronic illness.If we accept that patients do engage with multimedia, what effect does this engagement have on their ability to participate in their care and/or there recovery outcomes? Overall, the studies provide some evidence to suggest that multimedia, as a way to deliver information to patients in the acute care setting, is acceptable to patients and/or caregivers. Further, the time taken to instruct patients to navigate the system, although not always reported, appeared low. Patients showed moderate engagement with the tools; however, the effectiveness of multimedia interventions in increasing patient participation in their care or in improving patient outcomes has not been investigated. In addition, research needs to take into account previous work around patients’ preference for participation,A major limitation of the studies reviewed was the quasi‐experimental, post‐test design and lack of a comparative or control group. One exception was O'LearyThe evidence from this narrative review adds to the growing body of work around the need to engage patients in their own care5There is a worldwide movement to include patients as participants in their own care in the recognition that participation will enhance the quality and safety of the care that patients receive.All authors declare there is no conflict of interest.


Genetic providers face the challenge of having adequate time to conduct a comprehensive evaluation. Hypermobile Ehlers–Danlos (hEDS) syndrome has a complex array of symptoms. An initial visit can involve approximately 60–80 min and an additional 45 min for the check‐in and checkout process. We propose a model to improve clinic flow and patient satisfaction by using: (a) pre‐appointment questionnaire (b) disease information sheet outlining basic management and (c) itinerary detailing the visit.New patients were given a questionnaire, an EDS information sheet, and a visit itinerary. In the end, a patient satisfaction survey was administered containing 18 questions pertaining to their satisfaction with the questionnaire, the information sheet, and their overall visit. Completed surveys were turned in to the front desk to maintain anonymity.Based on the survey results, patient satisfaction toward the implementation of a questionnaire was overwhelmingly positive. Survey responders found that the itinerary was added to their understanding of the appointment process and that the hEDS information sheets were helpful, understandable, and appropriate in length. Respondents said that they strongly agreed or agreed with the following statements: (a) I was satisfied with the visit; (b) I now have a better understanding of my condition; (c) This visit was successful in addressing my most pressing concerns; and (d) I would recommend this clinic to others.Designing a disease‐centered model that implements patient‐centered resources improves patient understanding and satisfaction for new hEDS patient visits. This model can be emulated in diagnosis and management of other complex genetic and nongenetic conditions. Though many genetic conditions are diagnosed in childhood, there are many others that are diagnosed in adulthood and require follow‐up throughout life. As a result, adult genetics clinics are often inundated with patient appointments  Genetics Clinic focusing on new patient appointments for a potential diagnosis of EDS. EDS comprises a spectrum of hereditary connective tissue disorders that involve defects in the synthesis and functioning of collagen. These disorders are fairly common, with an overall prevalence of EDS of 1/5,000, resulting in an increasing demand for genetic evaluation for these conditions  of patients found the questionnaire to be helpful. Ninety percent (n = 65) of patients responded positively toward the questionnaire with regard to its length, and 85% (n = 61) responded positively toward its ability to address the patient's health concerns. Of note, 4% (n = 3) did not believe the questionnaire addressed all of their health concerns  of patients found the EDS information sheets to be helpful and 94% (n = 68) found them understandable. Ninety percent (n = 65) of patients felt that the amount of information presented in the sheets was appropriate. A majority of patients, 86% (n = 62), believed their main priorities were addressed with the information sheets, and 8% (n = 6) patients felt that the sheets did not expound on their main priorities. While 40% (n = 29) of patients responded that they would rather receive the information sheets prior to their appointment, 15% (n = 11) disagreed or strongly disagreed with this statement  of patients found the itinerary to be helpful and 75% (n = 54) of patients found that the itinerary broadened their understanding of the appointment process  of patients responded favorably to the length of the visit and 97% (n = 70) of patients found the visit to be efficient. By the end of the clinic appointment, 99% (n = 71) of patients felt that the physician answered their most pressing concerns. Overall, 99% (n = 71) of patients were satisfied with their visit and 97% (n = 70) of the surveyed patients would recommend the Baylor College of Medicine EDS Genetics Clinic to others based on their experience .4Hypermobile Ehlers–Danlos syndrome (hEDS) continues to be a unique diagnostic challenge for health providers due to its complex array of symptoms such as joint hypermobility, skin hyperelasticity, chronic musculoskeletal pain, and dysautonomia, which are variably expressed among patients and somewhat nonspecific. Also, the underlying genetic etiology of hEDS is still unknown necessitating the diagnosis to be entirely clinical.There is a growing need to focus on patient satisfaction and to ensure that patients’ concerns are heard and addressed in the current medical practice milieu. Several health institutions have implemented Press Ganey surveys for patients to complete after their clinic and hospital experiences, and the data collected from these surveys have ultimately driven quality improvement measures addressing patient satisfaction . Patients felt that the questionnaire was helpful, of an appropriate length, and adequately allowed them to express their health concerns. Because the questionnaire covers the plethora of systems affected by EDS, it relieves patient burden regarding remembering to discuss each aspect of their experience with the disease and can allow for visit time to elaborate on the most pressing concerns. A small percentage (4%) of patients felt that the questionnaire did not fully address their health concerns. Though the questionnaire provides a framework for patients to state their health concerns, any issue that is not listed in the questionnaire can be addressed directly to the physician during the clinic visit. This is evidenced by the data showing that 99% of patients felt that their concerns were ultimately addressed by the conclusion of the visit. Based on the free‐written survey comments concerning the time needed to fill out the questionnaire, perhaps it would be beneficial to remind patients to arrive 15–30 min prior to their appointment in order to have adequate time to fill out the questionnaire in a relaxed manner. Alternatively, patients could be required to submit their completed questionnaire prior to scheduling an appointment. Overall, the questionnaire provides patients a platform to expound on the many symptoms of hEDS and present a clear clinical picture to a geneticist in an organized, thorough manner. Such a questionnaire could be developed for other complex conditions or more broadly for a range of conditions commonly seen in a given specialty clinic. The physician providers using this questionnaire in our clinic found it to be very helpful in coming to a diagnosis as all the information was available in an organized and efficient manner. It also shortened the time of history taking particularly since patients with hEDS tend to have complex and lengthy histories.Moreover, the survey responders found the EDS information sheets to be helpful, understandable, and appropriate in content. A majority of patients found that the information addressed their main priorities concerning their illness. For the 8% of patients who felt that the information sheets did not address their priorities, we argue that the information sheets were meant to provide an outline of the condition and its management but not to replace counseling and physician education for hEDS. Any additional concerns could be brought up directly to the physician. A number of responders (40%) would rather have read this information prior to their clinic appointment. It might be contended that the information and FAQ sheets could be provided prior to the appointment through mail or email, allowing patients to gain knowledge about their potential diagnosis prior to their appointment and prompt more in‐depth questions once they meet with their geneticist. However, there are distinct disadvantages to this approach. It might give the false impression to the patient that they already have a diagnosis of hEDS. It also has the potential to bias patient responses in the pre‐appointment questionnaire.With regard to the visit itinerary, the majority of patients found this helpful. Patients felt that it added to their understanding of the appointment process. Itineraries or preplanned schedules have been traditionally used in other fields, such as the travel industry. Itineraries not only provide an outline on future steps in a process, but also aid in time management. Clinic visits for a new diagnosis can be lengthy and complicated. Providing a clear itinerary allows patients to be more involved and aware of the clinic process, which can ultimately help with the diagnostic evaluation.The survey indicated that patients found their visit to be appropriate in length and efficient. Though the average clinic appointment time was 90 min, we did not document the actual clinic appointment length for patients in relation to their survey responses in order to preserve patient confidentiality. Thus, it is unclear if the patients who responded favorably to the length of the visit had a longer or shorter appointment time. We can conclude, however, that the implementation of our quality improvement measures did not negatively affect patient satisfaction in terms of the length of clinic appointments.As an overall assessment, survey responders found the clinic visit to be successful in addressing their most pressing concerns. The majority of survey responders felt that they left their visit with a better understanding of their condition, were satisfied with their visit, and would recommend this clinic to others. The free‐written comments on the survey illustrate that patients felt that their struggles were heard and understood. Strong patient–physician relationships have been shown to increase patient compliance and improve clinical outcomes. When clinics place emphasis on showing care and concern for a patient's health, it improves patient satisfaction and inspires patients to have greater concern for their own health , not all of the patients who presented for a new EDS clinic visit filled out the survey. Thus, our study might not account for the opinions of all patients who had a new visit in the EDS clinic during the study period.Overall, this study highlights the promising nature of several strategies including a pre‐appointment questionnaire, clinic itinerary, and disease information sheets with management guidelines in improving patient understanding and satisfaction for new EDS patient visits. This systematic and organized approach in addressing the complexity of an hEDS evaluation could potentially be used for the diagnosis of other complex genetic and nongenetic conditions in new patient visits. In terms of future directions, this study focused on whether the process of using a pre‐appointment questionnaire improved patient satisfaction with new hEDS patient clinic visits. It would be vital to also analyze whether this process aids in improving the average time of new patient visits, as increased efficiency allows physicians to diagnose more patients on dedicated new patient visit days and would pose less of a time burden on patients.The other authors declare no conflict of interest.


To evaluate the attitude and training of nurses in Saudi Arabia towards the care of patients with diabetes.A cross‐sectional study.Data were collected in 2016 from 1,695 participants at the King Fahad Medical City using the Diabetes Attitude Scale version 3.Most nurses had not received diabetes training. The agreement score of nurses for the requirement of special training for the management of diabetes is high; the survey found that most nurses were aware of the psychological effect of diabetes. However, the low agreement regarding the perception of the seriousness of diabetes among nurses and the valuing of self‐care attributes such as tight control of glycaemic level in patients with diabetes indicates the need for diabetes training. Clark  has arguHealthcare services are provided by the country's Ministry of Health (MOH) at three levels: primary, secondary and tertiary care. Health systems with strong health care from primary to tertiary care are more likely to give greater attention to the management of diabetes, including specialized diabetes care nurses who share the responsibilities in managing the patients with the physicians' in Saudi Arabia, one of the largest healthcare facilities in the Gulf Region, with a total capacity of 1,200 beds. Based on hospital data, the KFMC employs a total of 3,295 nurses in total who are able to switch between jobs in different departments, including the Specialised Diabetes and Endocrine Centre (SDEC) Diabetes Centre. The population included all nurses in KFMC, from which a sample of 1,695 participants was targeted for recruitment. The inclusion criteria for the participants were as follows: all nurses who are employed as full time, age of participants from 21–60 years of age, has 1 year of work experience and they can read and write in Arabic or English.Data collection continued for a period of five months. It was expected that after five months the researcher would have collected enough data to meet the minimum number of samples required for the study. At the end of the data collection period, the researcher encoded the data in Excel and transferred all the data to SPSS. All statistical calculations were undertaken using the SPSS v. 23 software.During the recruitment phase, nurses who were interested to participate in the study were given a survey package. In the survey package, an informed consent form was provided. The participants were asked to sign the informed consent form prior to responding to the DAS‐3 study instrument. Participants were allowed to respond to the survey questionnaire at their own convenient time and location. Participants were asked to submit the survey package to a box located in the Nursing Department.To achieve the desired 95% confidence level for a 0.05 margin of error, a sample size of 1,695 was required  developed by the Michigan Diabetes Research and Training Centre , and only 3.4% were clinical educators (N = 38). The largest age group represented in the survey is 31–40 years . Most participants were non‐Saudi ; only 4.5% were from the KSA (N = 51).Demographic data collected with the DAS‐3 survey included age group, occupation, gender, nationality, years of experience and diabetes training. The results presented in Table N = 1,062, 94.3%), and 5.7% were male (N = 64). They varied in terms of experience: 1–5 years , 6–10 years , 11–15 years  and >15 years' experience . Most  had not received any prior diabetes training.More than half of the participants were female , specifically nurses, towards diabetes are important as nurses are the first point of contact for patients with diabetes. Several studies have assessed the attitudes of HCPs towards diabetes and how HCPs perceive different aspects of that disease. An examination of the literature identified many studies performed in the United States, Europe, South America and Asia to assess the attitudes of physicians, pharmacists and nurses towards diabetes, as attitudes play an important role in how HCPs communicate with patients to give health care. A few studies have been conducted in Gulf countries (such as the UAE), other Arab countries (such as Yemen) and countries in Africa (including Nigeria and South Africa) Table . The curM = 4.4). This score was the highest in both studies: Bani‐Issa et al. (Most nurses included in the current study (78.4%) had not received diabetes training. The number of nurses who had received diabetes training was less than that reported in the UAE, where more than half of the nurses included in the study by Bani‐Issa, Eldeirawi, and Al Tawil  had recea et al.  found thM = 3.82). This finding suggests that nurses believe that patient with diabetes should participate in formulating their own care plan and contribute to decisions concerned with their self‐management.Comparing other scales of the DAS‐3 between the two studies, several differences were found. The score for patient autonomy in the current study is higher than that reported by Bani‐Issa et al.  (3.8 vs.The main surprise among findings in the current study is the low attitude score for the seriousness of diabetes (mean = 3.02) compared with results from other countries. For example, the study performed in the UAE reported overall mean = 3.8 for HCPs and nurses. This indicates that the attitude towards the seriousness of diabetes is low in the current sample, which may negatively affect how nurses communicate with diabetic patients. This difference with respect to the UAE study may be explained by the fact that 50% of the nurses in the UAE study had received diabetes training and almost 18% had diabetes certification . Nonetheless, there is good agreement between the results of the two studies. For example, the need for special training ranked first in Yemen, with a score of 4.2, which concords with the results here. Moreover, attitudes towards the seriousness of diabetes and the value of tight glycaemic control are similar in the two studies. However, the attitude scores towards the psychological effect of diabetes and patient autonomy are higher in the current study.Comparing the current results with those from a study of Yemen by Babelgaith et al. , an inteM = 3.17) as that reported in the current study (M = 3.0). Likewise, they reported that the attitude score towards the need for special training was high, similar to the current study. This further confirms that nurses are aware of their relative lack of knowledge when it comes to communicating and dealing with diabetic patients   . This finding suggests that nurses believe that patients with diabetes should participate in formulating their own care plan and contribute to decisions concerned with their self‐management. The patients should be properly advised regarding the importance of strict control of their glycaemic levels to prevent severe physiological effects of T2D; this can be achieved if nurses and HCPs are aware of the seriousness of T2D and are trained to teach and recognize the importance of strict glycaemic control. Proper management in terms of diagnosis and treatment is essential with involvement of policymakers in KSA government to relook at current system and should seek to invest in ensuring proper service delivery and better accessibility to programmes and institutions that can help with issues related to diabetes. The involvement of the government in the disease issue will go a long way towards improving the lives of patients with diabetes.6The study findings are significant towards diabetes patient care and nursing education. Nurses in KSA need special training in diabetes to tackle the increasing burden of diabetes among the population. These findings imply that greater concern should be made to address the issue by hospital administrators and nurse managers. Effective strategies are recommended for better quality and service for nursing care in KSA.All authors have read and understood the Nursing Outlook declaration of conflicts of interests. We declare that we have no competing interests in this project.All listed authors meet the authorship criteria, and all authors are in agreement with the content of the manuscript.No additional data are available for sharing.


The paper focuses on surveillance and monitoring using aerial drones. The aim is to estimate the minimal number of drones necessary to monitor a given area of a very uneven terrain. The proposed problem may be viewed as a drone version of the 3D Art Gallery Problem. A computationally simple algorithm to calculate an upper estimate of the minimal number of drones together with their locations is developed. Computer simulations are conducted to demonstrate the effectiveness of the proposed method. Aerial Drones or Unmanned Aerial Vehicles (UAVs), which were initially used in military applications, have now been applied widely in various civilian tasks , such asIn surveillance and monitoring applications, aerial drones are equipped with some specific sensors, such as video cameras. They fly into the sky and monitor ground targets of interest, such as humans, buildings, pipelines, roads, vehicles, landmarks, and animals, for the purpose of surveillance, security, etc. ,21,22,25The remainder of the paper is organized as follows. The model of very uneven terrains and the problem statement are presented in z be the coordinate axis perpendicular to the ground plane. A terrain is a graph of a function Let i and j, and i and the terrain. The following safety constraints should hold:Furthermore, let uld hold:ρij≥c1,ρiP on the terrain is visible from a drone located at the point D if P is inside of the visibility cone of the drone, and there is not any other point of the terrain on the straight line segment Moreover, drones have a given observation angle Definition 1.Deployment of several drones is said to be covering if the constraints , 2) are are2) arTerrain Model: This paper considers the following class of very uneven terrains. First it is assumed that the set n vertices. Furthermore, let Assumption 1.Any point where It is also assumed need the following technical assumptions that usually hold in practice.Assumption 2.The inequality Assumption 3.The altitude of any point the drone version of the 3D Art Gallery Problem can be stated as follows.The problem studied in this paper that may be called Problem Statement: What is the minimum number of aerial drones for which covering deployment exists and where should they be deployed? Moreover, it is preferred not only to deploy the minimum number of drones but also deploy the drones at as low altitudes as possible to make them closer to the observed region of the terrain.k “holes” and The deployment algorithm requires some geometric constructions. Let Step A1: Choose k non-intersecting diagonals of the polygon k diagonals connects either two vertices of k diagonals as two different sides of the polygon Step A2: Make some triangulation Step A3: Build a triangulation i, add all the vertices Step A4: Paint the vertices of the triangulation Step A5: The set of vertices of the triangulation Step A6: Select the altitude of each drone as follows. If the corresponding vertex is not a vertex of any polygons a be the maximum altitude of all the terrain points corresponding to the vertices of the two side quadrilaterals for which this point is a vertex. Furthermore, let b be the maximum altitude of all the terrain points corresponding to the vertices of i, select one vertex that is a vertex of some polygon If the corresponding vertex is a vertex of some polygons For all other selected vertices that are vertices of either polygon Remark 1.It should be pointed out that in the proposed algorithmA1–A6, this approach always considers triangulations on the ground plane Remark 2.In the case when two selected vertices on the triangulation correspond to the same point of the actual terrain, which can happen when either there are two vertices from one which is the end point of a cutting diagonal inA1or a vertex of Remark 3.StepA4of the algorithm is based on the 3-coloring method of .For the main result, the following assumptions are needed.Assumption 4.The drone altitudes fined by –7) sati satizd dAssumption 5.The length d of any side of any triangle of the triangulation x, i.e., the maximal integer i such that The following notation is also needed. For any number Now it is the position to state the main result of the paper.Theorem 1.A number N of drones are deployed by the algorithmA1–A6. Suppose that Assumptions 1–5 hold. This deployment is covering andProof of Theorem 1.N satisfies (It is obvious that the number of vertices in the constructed triangulation atisfies . Now proltitudes –7) and  and T^ iltitudes  and (7) ows from –(7) thatirements –(7) and A2 and A3, the triangulation This section demonstrates how the proposed approach works through a case study using MATLAB. Consider a 20 m by 20 m square area of interest shown in This also shows that the estimate of Theorem 1 is quite close. Finally, the altitudes of the drones are computed by –7), and, and7), A novel aerial drone deployment problem was introduced. In this problem, drones are to be placed over a very uneven terrain with the aim to cover every point of a given terrain area. A computationally simple algorithm was developed to give an upper estimate of the minimal number of drones necessary and calculate their locations. This problem may be viewed as a drone version of the 3D Art Gallery Problem. Simulation results demonstrated the effectiveness of the algorithm. There several possible directions in which this research may be extended. One important question is how to approximate a real uneven terrain by the terrain model proposed in this paper. Another practically important direction is to extend the developed Drone Art Gallery Theorem to the case when the drone placement region does not coincide with the ground surveillance region. Such situations happen when there are some ”no-fly zones” over which aerial drones are not allowed to be deployed for safety reasons. Another direction of future research is to apply the proposed method to surveillance and monitoring problems in which aerial drones are not steady but flying over an uneven terrain region . This wo


EPID images during VMAT treatments.The aim of this study was to develop a model that optimizes the fiducial marker locations in the prostate to increase detectability of the markers in the projected MATLAB . Three unique weighting factors were added to penalize the detectability score. The detectability scores of four different patterns containing 40 combinations of simulated fiducial marker locations were evaluated with 101 previously treated prostate treatment plans . The results were analyzed for each pattern group and each marker separation distance on the transverse plane.The fiducial marker tracking capability for each arc was evaluated through a proposed formula. The output of the formula, a detectability score, was calculated with the in‐house developed software written in The maximum detectability of the markers occurred when they were placed between 10 and 15 mm from the center of the prostate in the transverse plane and 6–13 mm in the superior–inferior direction. The detectability decreased when the markers were placed beyond 20 mm in both directions.MV imaging.The fiducial marker‐based detectability score can be used to predict the real‐time tracking capability. Suggestions for optimal insertion locations were given to improve prostate motion management using  However, there are two major fundamental challenges with MV‐based fiducial marker tracking techniques for VMAT deliveries: (a) frequently blocked radiation fields by the multileaf collimator (MLC) and (b) potential large time intervals between two detections.Thus, in this study, we aim to develop a model based on several simulated fiducial marker locations in the prostate to identify the optimal marker locations for MV EPID‐based tracking during VMAT treatments. In addition, we propose a detectability score to predict the detectability for MV‐based fiducial marker tracking techniques and recommend locations within the prostate to implant the fiducial markers to increase detectability of the prostate during treatments.2The first part of the study focused on developing a model based on several simulated fiducial marker locations. The origin of imaginary fiducial marker locations was positioned in the center of patient prostate, which was at the center of the MLC field. DICOM RT plan files from previously treated patients were used to generate the detectability score as described in the following sections.2.A3, was modeled as a 2 × 2 × 6 mm3 cuboid volume due to the scatter on the CT images. Typically, in our institute, four fiducial markers are inserted into the patient via an ultrasound‐guided needle and a grid template , a tool for pinpointing the prostate location in transverse plane to accurately deposit the marker into the designated spot. Throughout this manuscript, X‐Y defines the plane parallel to the template plane (transverse plane), from left to right (X) and posterior to anterior (Y) directions, accordingly. The inferior–superior direction is indicated by letter Z. In the X‐Y plane, the resolutions of the fiducial marker center locations were generated according to the resolution of grid template, which is 5 mm, while interval along the Z direction was determined by the size of the fiducial markers and the average‐sized prostate.The radiopaque fiducial marker used in our institution, having a size of 0.8 × 0.8 × 5 mm2.BTotal of 101 previously treated prostate VMAT cases, containing 202 arcs were used in this study. All plans were created using Varian Eclipse treatment planning system . The plans were chosen such that the target was limited to the prostate with corresponding PTV margin only.2.CThe projected fiducial marker locations that overlap at a particular EPID projection will reduce the detectability of the prostate at that EPID projection angle, therefore, the overlap ratio was introduced to take into account the reduction of prostate detectability due to overlap of projected fiducial marker locations on the EPID images. The overlapping ratio was defined as the ratio of number of control points having overlap of projected fiducial markers on EPID images to the total control points in an arc.2.D(Auij) is calculated for each fiducial marker i at control point j. The detectability score was calculated as the percentage of the summed unblocked area over the total area (A) for all fiducial markers at control points j.A particular fiducial marker is considered to be detectable if the area comprising a 3 mm radius around the corresponding fiducial marker center was unblocked by the MLC or the jaws. The unblocked area wd) was introduced to penalize the control points that had less than three unblocked fiducial markers detected . The wd weighting factor was set to 1 if three or more markers were visible on a projected EPID image for a particular control point. The factor is set to 2/3 for only two marker detections, 1/3 for only one marker detection, and zero if no markers were detected.The detectability of the prostate location on an EPID image is greatly affected by the number of fiducial markers detected on that image. A detection‐number weighting factor (wo) was incorporated into the detectability score to take into account the overlapped markers on the projected EPID images. This factor is different from the aforementioned overlapping ratio in two aspects: (a) it was applied only for the unblocked markers while the overlapping ratio was calculated for the open field, and (b) for each control point, the total number of overlapped markers are counted and treated differently. The wo weighting factor was set to 1 if there is no overlap between all four fiducial markers, wo was set to 0.5 when two markers overlap, and 1/3 for all other cases.In addition, an overlap weighting factor (wts). wts was given for the entire arc. Each segment of consecutive control points that had no detection was first counted. The threshold of 15 control points was given to sift out the segments that were not deemed as large time interval. One minus the half of summed control points of all remaining segments over the total number of control points was the final wts value.The fiducial markers that were blocked by the MLC or jaws for consecutive control points were additionally penalized in the detectability score with a weighting factor (D) was calculated as:i is the fiducial marker number, j is control point number, n corresponds to the total number of control points for that arc, wd is the weighting factor of detectable number of markers, wo is the overlapping weighting factor, wts is the time span weighing factor, Auij is the unblocked area for ith fiducial marker at control point j, and A is the total area of the four fiducial markers.Thus, the detectability score  value was calculated for each arc of all the prostate plans. The calculation method was based on the equation described by McNiven.3As shown in Fig. The overall detectability scores are shown in Fig. Figure Figure 4As seen from Fig. Figures Meanwhile, placing the fiducial markers closer to the CAX means that the changes limited to the very peripheral region of the prostate would not be detected, especially the rotational changes of the prostate. It is a balance between detecting most of the markers in the projected EPID images to determine the position of the prostate during the entire treatment and accurately determining the rotation of the prostate during treatment. The optimum placement of the markers should be toward the higher limit of the proposed range to maximize the detectability of the markers and to accurately monitor rotational changes in the prostate.In certain clinical environment, one marker is considered sufficient enough to pinpoint the target location at a time. Then, the detection‐number weighting factor would be assigned to 1 for cases that at least one valid detection is observed and 0 for no detection. To take these situations into account, a recalculation of the detectability score with the new detection weighting factor was presented here in Fig. The detectability score would tend to favor the ones scattered more on the X‐Y plane. This is reasonable. Majorly, the MLC openings are around the central region. The MLC will irradiate occasionally around the peripheral area, which, with no detection number penalty, gives a boost to detectability score in the original scores. Compared to the original results, the more peripheral the markers get, the higher the chance will be blocked. Therefore, with the original detect number weighting factor, the patterns with more scattered markers got lower values. Whether to choose the original format and simple detection‐number weighting format is purely depended on how it is going to be implemented in the clinical environment. However, the final results remain the same.The relationship between MCS and detectability indicated that lower complexity of the treatment field would improve the overall performance of the marker tracking technique via MV imager. Future work can be done to maintain the same treatment plan quality while decreasing the complexity of the MLC movements.D designates the interval between each transverse plane 6–13 mm is recommended for ΔD. The color from dark blue to white (transparent) indicated the degree of preference from highly recommended to not‐recommended marker placement. Dark blue indicates the recommended fiducial marker location bands/spots. The rate gradually decreased as the position moves away from the central dark blue region.Figures 5Tracking the movement of the prostate is crucial during treatment to ensure the intended dose is given to the target while minimizing the dose to surrounding healthy organs. From our results, the optimal locations to place the fiducial markers are determined to be 10–15 mm from the center of the prostate in the transverse plane and 6–13 mm in the superior–inferior direction. These fiducial marker locations will enable the best detectability of the prostate to provide better real‐time tracking with the MV imaging technique.The authors have no other relevant conflicts of interest to disclose.


Acoustic source emission rate is generally low at low frequencies. In this work, we propose a simple design of ‘LEGO’-type acoustic metamaterial that can significantly enhance the low frequency emission rate of an acoustic monopole source. Such enhancement is resulted from the coupling between resonances of a cavity and a dual grating comprised of two concentric layers of periodically distributed narrow slits. We develop an effective medium model to characterize the enhancement. Because of its simple structure, the metamaterial is easy to fabricate and thus facilitates the applications in various domains such as oil exploration. D is proportional to (D/λ)2, where λ is the wavelength, and the power decreases proportionally for higher multipoles1. Traditional means to enhance acoustic source emission rate usually include bulky structures, for example, a loudspeaker mouth adapted in a horn shape to improve the emission, and a woofer diaphragm mounted in a speaker cabinet to boost the low-frequency emission3. Very recently, a slab of acoustic metamaterial utilizing Fabry-Perot resonance was proposed to enhance the emission rate of a monopole source, but its planar geometry makes the emission enhancement not omnidirectional4. But such issue has been addressed by using a highly symmetric labyrinthine structure6. It can achieve low frequency enhancement of an acoustic source radiation because the elongated acoustic path effectively reduces the wave velocity along the radial direction. Despite of its good performance in the radiation enhancement, its complex structure adds complexity to the fabrication, which can be achieved only by 3D printing technology.Acoustic source emission rate is generally low at low frequencies because of its small size compared to the wavelength. The power radiated to the far field of an acoustic monopole source with size In this work, we propose a simple ‘LEGO’-type design of an acoustic metamaterial to enhance the low frequency source radiation. The enhancement relies on a new mechanism that couples the resonant modes of a cavity and periodically distributed narrow slits, which is different from the usual Fabry-Perot resonance and the elongated path effect. We find substantial emission enhancement in the low frequency regime, where the wavelength is about three times of the diameter of the metamaterial. Furthermore, our metamaterial has a very simple structure that is easy to fabricate, just like the LEGO toy bricks. Our design thus provides an alternative method for the realization of low frequency acoustic radiation enhancement, which will benefit potential applications in various fields such as oil exploration.t = 3 mm. The inner radii of these two annuli are r1 = 2 mm and r2 = 8 mm, respectively. Thus, the two annuli are separated by a d = 3 mm air spacer and the diameter of the entire enclosure is D = 22 mm. Both annuli have 12 cut-through slits, each of which occupies 3° and is distributed uniformly along the azimuthal direction. An acoustic line source is located at the center of the enclosure, which emits uniformly within the entire 2π radians range of the in-plane angle.The proposed design of the two-dimensional enclosure is schematically illustrated in Fig. We use COMSOL Multiphysics, a commercial software based on the finite-element method, to conduct numerical simulations of wave propagation properties of the described system. Pressure acoustics module in the frequency domain is used in the simulation. The boundary between steel and air background is modulated as a sound hard boundary condition, which is justified by the huge acoustic impedance mismatch between air and steel. Monopole line source is set at the enclosure center, and a cylindrical wave radiation condition is specified at the outer boundary of the simulation domain to absorb the outgoing waves radiated by the line source.Figure 6. In this regard, we use P1 and P0 to denote the integrated wave power measured in the far-field with and without the enclosure, respectively. Then the ratio of P1/P0 is the acoustic Purcell factor. In Fig. λ = 64 mm) and 12300 Hz (λ = 27 mm), respectively, indicating significant enhancement of the acoustic source radiation at these frequencies. It is worth noting that the wavelengths at these two frequencies are both large compared to any characteristic length in the double-layer enclosure. Therefore, the enhanced source emission occurs in the sub-wavelength regime. The respective pressure intensity field distributions in the near-field at these frequencies are plotted in Fig. The ratio of the integrated wave power measured in the far-field with and without the enclosure is defined as acoustic Purcell factorλ = 30 mm) is observed in the acoustic Purcell factor spectrum as shown in the black solid curve in Fig. If we remove the outer annulus and keep the inner one, the enclosure becomes a single layer device as illustrated in Fig. We further rotate the outer annulus by 15° such that the slits in the outer annulus no longer align with those in the inner annulus as illustrated schematically in Fig. 14, we can obtain the following anisotropic effective medium expressions for each annulus:As per discussed earlier, the wavelengths at which the acoustic Purcell factor reaches its peaks are large compared to any characteristic size of the enclosure suggest the enclosure may be described by an effective medium, which is further affirmed by the results shown in Fig. B is the effective bulk modulus, ρr and ρθ are the radial and angular components of the effective mass density, and f = 1/10 denotes the filling ratio of the slit. We would like to point out Eq.  and ρair(Bair) are the mass density (bulk modulus) of air with and without viscothermal effect, respectively. In Eqs ,,3), we hBair and ρair by Bair,v−th and ρair,v−th, respectively and the resulted effective parameters  are complex numbers.We also notice that the effective medium expressions given in Eq.  can be ed vanishes, the two annuli merge into a single one with a thickness of 6 mm and there only exists one peak. It is observed from Fig. d increases, the space of the in-between cavity also increases, offering more space available for the cavity modes, and therefore resulting in more extended cavity modes. From the reciprocal relationship between the spatial coordinate (as measured by the wavelength λ) and frequency, the resonance frequency will be lowered when a more spatially extended mode is obtained8. Figure st resonance frequency changes more rapidly than the 2nd one as d increases, because the 1st resonance depends heavily on the in-between cavity, which is manifested by the field pattern shown in Fig. 6, where the low frequency feature is mainly contributed by the elongated acoustic path in the labyrinthine structure.All of the results presented so far indicate the enhanced acoustic source emission by the double-layer enclosure strongly depends on its geometry. Figure 15, which reveals the resonant frequency of the slab increases as the filling ratio of the holes increases because of the interaction between the holes through the evanescent waves. Indeed, similar mechanism also exists in our proposed structure.We further alter the size of the slits while keeping the thicknesses and radii of the annuli unchanged and studying the influences on the resonant frequencies. The results are plotted in Fig.5. The solution to the acoustic wave equation in an effective medium with parameters given by Eq. (v, respectively, and m is an integer. An th order Bessel function and Hankel function of the first kind survives in the solution, regardless of the value of m, which is attributed to the extremely large angular component of the mass density that forces v to be zero. This feature differs drastically from those common cases with isotropic enclosure and results in the degeneracy of Mie resonances with different orders. The degenerate Mie resonances help enhancing the density of states for both the monopole and multipole sources14.Although we focus on the enhanced emission of the acoustic monopole, the enhancement also occurs for multipoles, which is related to an interesting type of resonances, the so-called degenerate Mie resonance, where the Mie resonant frequencies of different orders overlap. The degenerate Mie resonance is enabled by the super-anisotropic feature of the effective mass densityn by Eq.  can be wIn this work, we propose a simple ‘LEGO’-type design of acoustic metamaterial that comprises a dual grating structure to enhance the acoustic source emission rate at low frequencies. Different from previous work that based on either Fabry-Perot resonance or the reduced effective acoustic speed by elongated acoustic path, our metamaterial attributes its functionality to the coupling between the cavity modes and the resonances of the dual grating. An anisotropic effective medium model is developed to characterize the enhancement, and the dependence of the enhancement on various geometric parameters is explicitly studied. Since our structure is simple to fabricate, we believe it will benefit the communities that desires high acoustic source emission rate.All the numerical simulations presented in this article are performed using COMSOL Multiphysics, a commercial package based on the finite-element method. The pressure field patterns presented in Figs


Pinnipeds like seals and sea lions use their whiskers to hunt their prey in dark and turbid situations. There is currently no theoretical model or hypothesis to explain the interaction between whiskers and hydrodynamic fish trails. The current study, however, provides a theoretical and experimental insight into the mechanism behind the detection of the Strouhal frequency from a Von-Karman vortex street, similar to that of the inverted hydrodynamic fish trail. Herein the flow around a 3D printed sea lion head, with integrated whiskers of comparable geometry and material properties to a real seal lion, is investigated when exposed to vortex streets generated by cylindrical bluff bodies. The whiskers respond to the vortices with a jerky motion, analogous to the stick-slip response of rat whiskers; this motion is found to be the time derivative of the Gaussian function. Compared to the displacement response, the time-derivative of the whisker response decodes the Strouhal frequency of the Von-Karman wake, which improves the sensing efficiency in noisy environments. The study hypothesizes that the time derivative of the whisker bending moment is the best physical variable that can be used as the input to the pinnipeds neural system. Bats, whales, and dolphins use the bio-sonar system to locate the objects and recognize them4. Similarly, land mammals such as rats and squirrels vibrate their whiskers, commonly known as ‘whisking’ to obtain data about their surroundings5. Pinnipeds like Phocidae and Otariidae also have highly sensitive whiskers that function as hydrodynamic receptors, which can detect even minute velocity changes in the water generated by fish.Nature has provided sensing capabilities for different living organisms depending on their living environment and the struggles they encounter in their habitats. For instance, fish use their lateral line system to detect even the slightest movement in the wateret al. demonstrated that Harbor seals respond to dipole stimuli ranging from 10–100 Hz with a minimum perceivable water velocity of 0.25 mm/sec at 50 Hz6. Later, Dehnhardt found that Harbor seals could track hydrodynamic trails generated by a model submarine even after a period of 25 sec, which corresponds to a chase length of 40 m7. However, Gläser et al. performed the same experiment as Dehnhardt with a California sea lion rather than the Harbor seal. They found that the California sea lion can also follow the wake trail, but it could only track the model submarine if the delay time was 7 sec or less8. In dipole experiments, California sea lions are even more sensitive than Harbor seals. They have already responded to sinusoidal water motions with a velocity amplitude of only 0.35 mm/sec in the frequency range 20 to 30 Hz9. The differences in tracking ability between these two species are ascribed to the whisker’s topological variation. Harbor seal whiskers have the form of tapered beams with an undulating elliptic cross-section. This undulating geometry was seen to reduce self-excited vibrations or ‘Vortex Induced Vibrations’ (VIV)10. The VIV phenomenon is induced by alternating shedding of vortices from either side of the whisker cross-section, resulting in a strong periodic force variation in cross-flow direction (see Appendix-1 for comprehensive description). On the other hand, the California sea lion whisker has an elliptical cross-section that tapers towards the tip and has a constant perpendicular orientation over the length11. This geometry was observed to not perform well in reducing VIV. Miersch et al. compared the hydrodynamics over the isolated whiskers of the two species in a rotating flow tank and quantified that Harbor seal whisker’s signal to noise ratio (SNR) is ten times greater than that of the California sea lion whisker. This large difference was attributed to the reduced accuracy in wake tracking ability of the species12 as observed previously by Glaser et al. They added that the sea lion whisker’s self-excited oscillations, linked to VIV, could serve as a carrier signal that can be used to determine the self-swimming velocity. Beem and Triantafyllou studied the flow over model whiskers manufactured of plastic using stereolithography. They described the whisker motion as ‘slaloming’ with the vortices when exposed to vortex streets generated from an upstream cylinder. Compared to the clean flow conditions, the model whisker’s vibration amplitude was very large in the upstream cylinder wake (Referred to Wake-Induced Vibrations (WIV) to differentiate from the self-induced vibrations (VIV)) (Appendix-1). This larger amplitude of the whisker vibration is considered to be the reason for the improved sensitivity of Harbor seals13. Schulte-Pelkum has demonstrated that harbor seals can effectively follow the biogenic trails of the same species. Seal pups could use this tracking ability to follow lactating mother seals during feeding time14. In this study, the trail-following seal trajectory was aligned with the pilot seal path for most trials. In some of the trials, however, the follower crossed the path in a zig-zag way to redefine its course. Additionally, it was inferred that the trail-following seal was able to resolve the wake’s inner flow structure while tracking.Dehnhardt et al. found that the Harbor seal could indicate and follow the direction of a wake trail generated by moving an artificial flexible fin up to a delay of 35 sec15. As such, it was suggested that the seal could have used the information in the high-velocity region between the two counter-rotating vortices and the vortex street structure as a hydrodynamic cue to track the direction. In a successive experiment, Wieskotten et al. found that the Harbor seal could discriminate the size and shape of the objects by tracking their corresponding wakes16. They also concluded, however, that the ability to discriminate in size and shape is based on more than one hydrodynamic parameter. Krüger et al. argued that harbor seals use vortex rings as the primary source of directional discrimination17. By simulating a range of test cases with single vortex rings, it was concluded that the minimum perceivable angle between the anteroposterior axis and the vortex ring path was less than 5.7°, however, the minimum value was not found due to technical limitations. Niesterok et al. experimented with intermittent jets from an underwater surface to imitate artificial flatfish breathing currents on sea lions and found that the seals could detect velocities in the range of 2–2.5 cm/sec18. This value is significantly higher than the value (0.25 mm/sec) obtained from dipole studies6. Due to the movement of the animal, the self-induced velocity variations could be the cause behind this reduced sensitivity. Murphy et al. tagged an accelerometer on a supraorbital whisker of a true Harbor seal and observed that if exposed to an upstream hydrodynamic disturbance, the seal whiskers vibrate over a broad range of frequencies19.Wieskotten et al. tested a 3D printed individual Harbor seal whisker in a towing tank and reported that Harbor seal whisker’s VIV is lower in magnitude compared to cylindrical whisker20. Solomon and Hartmann used multiple tandem whiskers to trace and reconstruct complex surfaces using Euler-Bernoulli beam theory as well as measuring the velocity profile in a free jet flow21. Inspired by the seal’s whisker array, Eberhardt et al. placed eight cylindrical whiskers on a torpedo-shaped body to sense the wake interference from an upstream submarine model22. They concluded that the use of multiple whiskers will assist in accurate object tracking and can be used in surveillance.Sensors based on mammalian whiskers were developed and tested successfully in biomimetic applications. Subramaniam 23. The Strouhal number and the Reynolds number are defined by equations ∞’ is the swimming speed and ‘μ’ are the density and viscosity of the fluid (water).Despite all the earlier studies still some fundamental questions remain unanswered in the study of pinnipeds and their hydrodynamic trail tracking abilities. To list a few, what impact does the animal’s head have in changing the signal strength, do they make use of multiple whiskers and how the arrangement of multiple whiskers interacts with oncoming alternating vortices from wakes generated by fish. Fish swim at cruising conditions within a very narrow Strouhal number band, St mentclass2pt{minim24. The frequency is, therefore, the single most significant characteristic to identify the fish’s swimming speed. The wake behind a 10 cm long swimming goldfish generated a wake path of measurable velocities for at least 30 sec25 and this time-lapse should theoretically scale with the fish’s length. Since Harbor seals feed on fish with an average length of 30 cm26, the information left behind the fish wake is certainly a strong hydrodynamic cue for predators. The crucial question here is, how the neural system of the seal decodes this information in an otherwise noisy environment. From a fluid dynamics perspective, when the seal swims with its whiskers protracted forward, the fluid-induced drag forces induce the whiskers to bend in the mean flow direction and hence the swimming speed is directly proportional to the whisker’s deflection (Appendix-2). Since whiskers have no nerves27, therefore, the nerve endings in the whisker pads read the information about the bending moment at the root of the whiskers. These nerves connects the somatosensory system in the brain of sea lions28. Consequently, a wake trail of a fish swimming upstream should alter the whisker’s bending moment based on the flow-induced force distribution along the whisker and this could be encoded with the neural system. A satisfactory answer to this question is not there in literature for the following reasons: First, it is very difficult to experiment with live seals or sea lions in a regulated environment such as steady swimming speeds without any lateral head motions. Second, it is very challenging to monitor the motion of the whiskers and the vortex convection concurrently in the same experiment when the wake generator is moved upstream. This is the primary objective of this research and it is the first type of experiment on pinniped whisker-like models, which is almost comparable to the realistic scenario.At cruising, as the Strouhal number is a constant, swimming speed is proportional to the tail-beating frequency∞) of 20, 25 and 30 cm/sec, where these parameters were seleted based on previous findings12. The experiments were divided into two phases. The first phase was to monitor the whiskers’ movement, where, as shown in Fig. The experiments were conducted in a return type open surface water tunnel with a velocity range of 10 to 200 cm/sec. Flow straighteners were installed before the convergent section in the settling chamber to maintain uniform flow in the test section. The test section is 40 cm wide × 50 cm depth × 120 cm in length and transparent in all the sides to provide optical access for flow studies. The sea lion model was placed at 70 cm downstream of the inlet and at the centre of the test section as shown in Fig. L2 = 50 mm and all other whiskers were approximately L1,3,4,5,6 = 100 mm in length. The whisker’s tip motion were tracked in a plane parallel to the X-Y plane as shown in Fig. The results of the six indicated whiskers in Fig. 29. When calculating the Strouhal number for this based on the diameter of the whisker (d = 0.75 mm) a value of Std = 0.19 is obtained and the corresponding Reynolds number based on the diameter of the whisker is Red = 225. At the specified Reynolds number, the reported Strouhal frequency is in good agreement with earlier literature for flow around circular cylinders30. It is important to note that the 75 Hz component of the spectrum is the dominant mode of whisker vibration in undisturbed flow (in the absence of any fish wake vortices). When the same whisker experiences a Von-Karman vortex street, generated by placing a 25 mm diameter cylinder upstream of the model, significant changes can be observed in its response. Figure D = 0.2. This corresponds exactly to the value cited in the literature for a cylinder at a Reynolds number of ReD = 750031. An increase in energy at lower frequencies <2 Hz can also be observed, with the appearance of the WIV’s first subharmonic at 1.2 Hz. In addition, noticeable peaks can be observed below 1 Hz, which is believed to result from a low-frequency sloshing motion in the open-surface water tunnel. When looking at the vertical motion . The results are shown in Fig. For the case with a larger cylinder (D = 35 mm) at a flow speed of f). From Eqn. f) is equivalent to (U∞) to obtain the length scale of the vortices34,  at a velocity of 35 in the measured region. These are sometimes difficult to observe due to the presence of the short whiskers and reflected light from the model which affects the image quality. The ‘Q’ criterion is defined as the second invariant of velocity gradient tensor defined by Eqn. The passage of successive vortex cores in the Von-Karman vortex street over the whisker defines the vortex shedding frequency from the upstream cylinder. The experiments were repeated with concurrent PIV flow field measurements and whisker tip recordings to better understand the interaction between vortex core dynamics and the induced whisker motion. In these experiments, the 25 mm cylinder was placed at a lateral offset from the body axis (100 mm offset in the ‘z’ direction) and positioned upstream of the sea lion model such that the vortex street faces the whiskers only on one side of the model; the same side that the LED light-sheet illuminated the flow. The vortex rollers shedding from the upstream cylinder are identified as regions of concentrated Q-values36. This pressure difference is proportional to the Vθ is the circumferential velocity within the vortex core. When a vortex, shed from the cylinder and embedded in the mean flow approaches the whisker, the low-pressure region in the vortex core reduces the drag force on the whisker. This, in turn, decreases the net bending moment on the whisker, which enables them to move towards the vortex. On the other hand, the whisker bending increases again when the vortex crosses the whisker as the low-pressure core pulls the whisker in addition to the mean flow drag. These small-scale motions associated with time are repeated at every instant when a vortex core moves across the whisker, and these occurrences define the frequency of the vortex shedding. Note that the sense of rotation of the vortices does not influence this jerky motion, therefore it does not make a difference if the vortex street is generated by the wake of a body (Von-Karman vortex street) or by the propulsion of a fish (inverted Von-Karman vortex street).In the following figures, a series of images were selected where the location of the shed vortices could be tracked over time while crossing whisker w3. In Fig. U∞ = 10 cm/sec was conducted to generate a Von-Karman vortex street. The turbulence effects are reduced at this low velocity and therefore the vortex cores are better identified with the ‘Q’ criterion mentioned above. Figure A better understanding of the whisker’s interaction with a vortex core is only possible with an isolated whisker facing the vortex street. Using the Euler-Bernoulli beam dynamics, a theoretical model of the whisker dynamics due to a vortex core motion is derived and provided in Appendix-2. It revealed that the vortex only influences the whisker response, when the distance from the whisker to the vortex core is within one diameter of the vortex upstream and downstream. To verify this, a PIV experiment with a 100 mm long single whisker with an upstream D = 25 mm cylinder at a flow velocity of et al.37 showing a videographic trace of whisker movement. Our reconstruction is analogous to this in a fixed coordinate system when the sea lion passes a vortex street. The stick-slip effect is clearly visible from this reconstruction of the whisker motion.The displacement response of whisker w3 for a time frame of 1 second is shown in Fig. 38. However, all whiskers are effective at identifying the Strouhal frequency with variations only in the peak elevation by using the jerk signal. Secondly, whiskers in front of the snout always display a more defined peak in frequency plots compared to whiskers in the aft portion of the head . It is therefore thought that this could be the reason why seals and sea lion to protract their whiskers in the most forward position to minimize body interference. The time series of whisker motion in Fig. J(t) is a time derivative of the Gaussian function given by Eqn. A is the maximum amplitude based on several fluid and structural parameters, ‘R’ is the radius of the vortex core, ‘C’ is a constant depending on the normalised position of the vortex impact on the whisker yc/L and . As shown in Fig. Now let us discuss the similarities between the sensing mechanism between rodents and pinnipeds. Recent research on rat whiskers revealed that the best way for texture coding is through stick-slip motions that are discrete short-lasting kinematic eventsTo summarise, this is the first study to explore the interaction of whiskers installed on a model of sea lion head to vortex streets as they occur in nature. Multiple fibre optic cables with comparable mechanical properties to whiskers were used to monitor the whisker tip motion for various Von-Karman vortex streets generated from upstream objects. The tests were performed without interfering with the flow or by using force transducers which increase the complexity of the experiment. This is because the tip deflection is an immediate indicator of the bending moment at the whisker’s root. Furthermore, the collective response of all whiskers in the field of view can be successfully tracked with the use of the ‘Eye motion’ camera. We have identified that the WIV response in the lower frequency range is at least one order more intense than the whisker’s VIV response. It is claimed here that the use of elliptical cross-section whiskers reduce the VIV response and amplifies the SNR. From the PIV results and the derived theory, it is shown that whiskers slip from the bending direction when they encounter a vortex and stick with a higher rate than the slip phase when the vortex passes over the whiskers. This small jerky movement, which occurs in a shorter time scale, enlarges the time derivative domain , which amplifies the Strouhal frequency peak elevation and increases the SNR by a factor of three.et al.28. The model was 3D printed at City, University of London. Fibre optic cables of 0.75 mm diameter 40 were inserted through the holes from the back end and were cut into the required length of the whiskers which ranges from 5 mm to 115 mm as mentioned by Sawyer et al.28. All the fibres were glued in position at the model surface to provide a fixed cantilever condition. The open ends of the fibres were bunched together and cut to form a flat surface such that they can all be illuminated with a light source outside the water tunnel. Hence, the fibre optic cable acts as a whisker and the movement of the whisker can be tracked with its light at the tip of the fibre. The optical fibres are made of polymethylmethacrylate (PMMA) plastic material which has an elastic modulus value of around 3.5 GPa , and the value of the seal whisker is in the order of 4 GPa as mentioned by Subramaniam et al.20. Since both the geometrical and the mechanical properties of the whiskers are comparable, we expect this model to act as a passive whisker successfully. However, there are some limitations in this study, the fibre is circular in shape when compared to an elliptical section of the sea lion whisker. The diameter is constant for all fibres, and it is constant along the length, however for sea lions the whisker diameter changes throughout the length and the diameter changes for different whiskers.Scanned data of sea lion body was acquired from Museo delle Scienze, Italy. The digitized data was cleaned and converted into a 3D model using CATIA. On the head of the sea lion, 38 holes of 0.8 mm diameter were modelled on either side of the head on six rows as mentioned in Sawyer A high-speed camera (ProcImage 500-Eagle high-speed camera) at a sampling rate of 250 Hz was used to track the motion of the whiskers. It had a pixel size of 1280 × 1024 which relates to a physical dimension of 238 × 190 mm. The built-in function in the camera calculates the centroid of a light spot automatically using the barycentre mode. The camera function is explained in Fig. μm were introduced into the water tunnel and were continually added until a suitable seeding density was observed for the PIV measurements. The images were captured with Phantom Miro M310 camera at a frame rate of 700 Hz, for a flow period of 4 seconds. Due to the curvature and orientation of the whiskers, the PIV was arranged in a plane such that two whiskers were within PIV plane. The post-processing of PIV images was carried out using Dantec Dynamic Studio software with adaptive PIV algorithm to calculate the velocity with a pair of two successive images and the velocity was averaged with the 3x3 filter. The Strouhal frequency of the upstream disturbance is calculated from the cross velocity spectrum of the wake, and the vortex core was visualised with an absolute ‘Q’ criterion method.A 3 mm thick LED light sheet was focused on the region near the long whisker (Whisker 3) portion of the model. Neutrally buoyant particles of 50 Supplementary Information: Appendix 1 and 2


We report extensive numerical simulations of the flow of anisotropic self-propelled particles through a constriction. In particular, we explore the role of the particles’ desired orientation with respect to the moving direction on the system flowability. We observe that when particles propel along the direction of their long axis  the flow-rate notably reduces compared with the case of propulsion along the short axis . And this is so even when the effective section (measured as the number of particles that are necessary to span the whole outlet) is larger for the case of longitudinal propulsion. This counterintuitive result is explained in terms of the formation of clogging structures at the outlet, which are revealed to have higher stability when the particles align along the long axis. This generic result might be applied to many different systems flowing through bottlenecks such as microbial populations or different kind of cells. Indeed, it has already a straightforward connection with recent results of pedestrian  and mice or sheep . Such statistical features agree with a description of the intermittent flow in which the probability of blockage formation is constant over time, whereas the probability of getting the block destroyed depends on time. Interestingly, this behavior seems to hold for systems built of different constituents  as well as for different confining geometries .In some circumstances, the flow of an ensemble of discrete macroscopic particles through a constriction might display intermittencies. These have been generically characterized by an exponential tail of the flowing intervals distribution and a broad tail (some times a power law) of the clogging times distributions17 or the necessity of simulating  exceedingly long times1. Recently, we postulated that introducing an anisotropy in the particles’ shape gave immediately rise to the emergence of robust power law decays of the clogging time distributions18. Indeed, the shape of particles has been demonstrated to have a strong impact on the flow23 and clogging patterns of inert grains when discharged from a silo25. Also, particle elongation has evidenced to cause the emergence of new features for the case of active particles27 (see28 for a review on this field).Curiously, the broad tails in the clogging times distributions are not easily reproduced by means of molecular dynamics simulations of discs or spheres, which have evidenced suspicious features such as the apparition of cut-offs31 but, for different reasons, contacts among the particles were not implemented; therefore the shape role is expected to be less determinant than in a highly packed situation where particles align each other determining the system response. The only exception to this trend is the work of Alonso-Marroquín et al.32 who introduced a novel two dimensional section of a human body to simulate counter flow of dense crowds through narrow corridors. Inspired by this paper, we recently simulated the egress of pedestrians by using spherocylinders that aim to propel transversally; i.e. with their longer axis perpendicular to the trajectory18. Beyond the undeniable role of the particle shape, both the strength of the torque inducing the desired orientation of the individuals and the magnitude of the noise imposed to erase the blocks at the outlet, were proved to strongly influence the flow rate.Surprisingly, the number of works where the effect of particle shape is studied for active particles passing through a constriction is scarce. Some of these simulations are within the field of pedestrian dynamicsIn this manuscript we generalize the results of that previous work and enlarge its scope beyond the field of pedestrian dynamics. To this end, we investigate the role of active desired orientation in the flow of particles through bottlenecks, an issue that -to our knowledge- has been never addressed in the field of active matter. This analysis allows us to discover that the flow dramatically drops when the anisotropic particles propel with the long axis in the displacement direction and suggests that, in order to minimize clogging at confined geometries, a suitable design of artificial active particles might involve self-propulsion without any preferred orientation.18. Therefore, we will only describe here its main characteristics.The contact force model that allows to simulate highly packed ensembles of spherocylinders was already presented ini, the equations of motion for the translation of the center of mass and the rotation around it are given by Eqs mi is the particle’s mass, Ii its moment of inertia, For particle Nc contacting neighbors j on i. These contact forces also produce a torque on the particle i that is given byi to the contact point with particle j. More details about the numerical implementation of contacts among two spherocylinders can be found in18.The contact forces vdei are the actual and desired particle velocities respectively. The normalized vector ei points to the desired target; i.e. towards the exit. Finally, λ = 0.5 s is the characteristic time that a free particle (with no contacts) would need to achieve vd.Focusing now on the self-propulsion terms of Eqs desired torque, τDi, which accounts for the strength with which particles aim to align in a certain orientation. In our case, we define it as:Implementing anisotropic particles provides the opportunity of introducing a desired torque has a linear part proportional to Δθ ∈ , the angular difference between the particle orientation and the desired one  orientation, ne is aligned to the particle’s long axis and has a predefined sense  propulsion is analogous to the propulsion of sheep12 or janus rods28, and transversal propulsion corresponds to the case of humans.Considering the definition of particle orientation introduced above, the desired orientation of each particle coincides with the direction of the target  as can be seen in Fig. 36 related to the system’s initial state and guarantee stationary conditions we have implemented periodic boundary conditions18. In Fig. SD = 0). The simulations were run for Tend = 2000 s for each set of parameters. During this time, the number of circulating particles range from ~1500 to ~7500, depending on the conditions.Initially, the self-propelled particles are homogeneously distributed within the enclosure at the vertices of a 12 × 16 square lattice (16 particles arranged in the direction perpendicular to the door) and randomly oriented. Then, they begin moving towards the exit, in such a way that the direction of the desired velocity W, desired velocity vd, and the angular strength SD. Based on our previous knowledge, the three parameters took values of: W = {0.6, 0.7, 0.8, 0.9, 1} m; vd = {0.5, 1, 1.5, 2, 2.5, 3} m/s; and SD = {0, 2, 5, 10, 15, 20} Nm.The parameters studied were the particle orientation (3 different options), door width We start by presenting the number of particles that flow out of the enclosure versus time, when the different types of particle orientation are implemented keeping constant the rest of parameters Fig. . ClearlyQs) during the whole simulation run which can be computed as Ntot is the total number of pedestrians that cross the door in the time up to Tend = 2000s and the sub-index 150 indicates that we discard the first 150 outgoing particles to avoid the initial transient18.To this end, we look at the global specific flow rate  lead to similar outcomes. This confirms that, despite transversal orientation implies a larger cross section of the particle’s size with respect to the exit, the flow rate is notably larger. Apart from this, we should also stress that the faster-is-slower effect38 is present in all cases, hence demonstrating that this effect is robust and does not depend on the orientation at which particles propel. Finally, note the significant flow rate fluctuations obtained for desired velocities tc) follow a power-law1. For the cases indicated in Fig. et al.39 which are shown in Table Figure W = 0.7 m and vd = 1 m/s versus the directional strength. Again, the transversal orientation reveals higher flow rates than the two longitudinal ones. The later are very similar, hence confirming that the preference of sense has little effect on the flow rate. In addition, we observe that in all cases the flow rate reduces monotonously with SD. This means that the case with no preferred orientation (SD = 0) is the one where the flow rate through bottlenecks is maximized. Importantly, these results contradict the idea suggested in18 where the reduction of flow rate when increasing SD in pedestrian like particles  was attributed to the increase of the cross section in the direction parallel to the outlet. And this is so because the flow rate also reduces when increasing SD in longitudinally oriented particles, which reduce the effective cross section as they become more aligned.In Fig. Finally, we report the outcomes of the flow rate when varying the exit size and keeping the rest of the parameters constant Fig. . Once moParticles with transversal orientation give rise to higher flow rates than longitudinal ones, despite the higher cross section of the former with respect to the exit direction.Particles that move with no preferred orientation reveal the highest flow rates.For large exits, longitudinally propelled particles evidence slightly higher flow rates when they have a predefined sense of movement.Up to now, we have reported several features of the influence of particle orientation with respect to moving direction on the flow rate through bottlenecks that can be summarized as:In what follows we will justify all these features based on a very simple idea: the flow is highly conditioned by the formation of clogs at the outlet. Therefore, the stability of clogging configurations against the perturbations that might destroy them (which come mainly from the noise in the desired torque) is crucial in determining the flow rate. And, clearly, the particles orientation in the ensembles that are clogged must play a role in their stability.2  of the particles.Aiming a better quantification of this behavior, in Fig. θ|〉 as a function of the distance to the door  indicate that the particles take any possible orientation  with the same probability; hence revealing that the actual alignment by shear forces is very weak. When comparing the outcomes for the three different orientations we confirm that the deviation from desired orientation is higher for transversal propulsion. This feature becomes more obvious near the door, where the shearing forces are expected to be higher. The cases of symmetric and non-symmetric longitudinal orientation are indistinguishable.First, we display the average of the absolute value of this difference 〈|Δoor Fig. . Note thNow, in order to look with more detail at the region near the door, we present the distribution of orientation deviations of those particles being at a distance to the exit smaller than 0.75 m in Fig. g(r) and the orientation distribution function Q(r) of the whole ensemble of particles for the different cases  accounts for the probability of finding any two particles whose centers are at a distance r. It evidences peaks at distances that coincide with the particle short (ds) and long diameters and the sum of these; i.e. r/ds = 1, 1.4, 2, 2.8... m. These peaks are a signature of very dense packings. Indeed, the fact that for the particles without any preference of orientation, most of the g(r) structure disappears correlates with the high degree of disorder deduced from the distributions of Fig. g(r) outcomes also support that transversally oriented moving particles lead to higher disorder; as the height of the peaks in this case is distinctly lower than for longitudinally propelled agents. Apart from the ordering, we quantify particle’s alignment by means of the Q(r) which stands for the probability that two particles are aligned to each other, given that their centers are at a distance r. The specific equation for Q(r) can be found in11 but the idea is that when two particles are perfectly aligned Q = 1, whereas when their angles differ in π/2, then Q = −1. The obtained distributions definitively prove that the alignment developed when particles propel longitudinally is much higher than in the transversal case. Also, the values of Q ≈ 0 reached for r/ds > 1.4 for the case of particles without preferred propulsion orientation, confirm the complete absence of order in this case. Incidentally, note that the peaks in the Q(r) appear for values of r/ds slightly smaller than the ones at which were displayed in the g(r); an issue which is attributed to the polydispersity of the particles in terms of the size of their short and long diameters.The SD) implies a reduction of flow rate in all cases. This result is understood if we are aware that the clogging structures that interrupt the flow can be only destroyed by means of the angular noise intrinsic to each particle. As the magnitude of this noise has a constant value, its effect (in terms of ability of breaking arches) reduces when the angular strength increases.In this work we investigate the influence of the orientation at which asymmetric active particles propel on their flow through a constriction. First, we show that all kind of self-orientation mechanisms lead to the well known faster-is-slower effect evidencing its robustness against this property. In a similar way, increasing the angular strength . Clearly, transversally propelled particles give rise to less ordered structures where particles are not well aligned to each other, an effect attributed to shear forces that give rise to torques acting in a different direction than the one desired by the particles.Finally, let us focus on the small effect that the propulsion sense of longitudinally propelled particles has in the outflow. In principle, it sounds reasonable that both symmetric and asymmetric particles give rise to similar outcomes. Certainly, if asymmetric particles point towards the exit with their desired sense, the global configurations reached in both cases are equivalent. The only difference among these two kind of agents might arise if, for some reason, collective forces align an asymmetric particle in the direction of the door, but pointing backwards. In that case, the efforts of such misaligned particle to rotate 180 degrees, will introduce a local disorder in the system that would surely provoke a slight improvement of the flowability. As indicated by Fig. 38; where the variation of flow rates when changing competitiveness were significantly lower for pedestrians (around 7%) than sheep (around 19%).In this manuscript we have examined what it could be considered the simplest example of anisotropic particles that propel along three basic orientations. Despite this simplicity, we believe that our results could set the basis to understand the flow of active particles through constrictions, whether real ones or artificially designed. More importantly, our findings can be straightforwardly connected to recent works about bottleneck flow of pedestrians, sheep or mice. Indeed, the smaller variation of the flow rate with desired velocity observed for transversal orientation than for longitudinal one Fig.  is perfe