Small droplets forming twisted radial structures were studied. We obtained two different paths of structural transformations under electric field in such droplets. The choice between these paths has probabilistic nature. The ratio between the two transition types was found to be sensitive to the elastic constants of LC forming the droplet. We suggest the principal approach for  The direct connection between topological defects in particle physics and liquid crystals allows using liquid crystals as convenient systems for studies of several fundamental problems22. Last decade, the most intriguing discoveries shift from nematic to cholesteric liquid crystals (CLC). CLCs demonstrate plenty of various director configurations in confined geometries. For example, twisted bipolar structure23, structures with diametrical 24, uniform helix axis distribution25 and the double twisted the structure26 can be observed, as well as structures with the point defect in the bulk of CLC or at the surface and bipolar distribution of CLC axes28.The study of liquid crystals confined to microscopic cavities demonstrates growing interest for the last decades, both from the fundamental point of view32. In turn, the content of an LC mixture in a PDLC droplet may differ from the original LC mixture due to various adsorption rates to the matrix of different components of a mix. And finally, it will affect the material properties of the LC mixture within the droplet , its optical properties, and response to an electric field34. Thus it is essential to estimate the properties of LC material inside PDLC droplets after film preparation.One of the practically important ways to fabricate, examine and use LCs in confined geometries are polymer-dispersed liquid crystal (PDLC) films. Typically, it is prepared by phase separation methods by mixing the polymer with LC in a homogeneous, single-phase blend. The subsequent phase separation can be induced in several ways. In temperature-induced phase separation (TIPS), a melted mixture of thermoplastic polymer and LC is placed on a substrate and gradually cooled down until polymer solidification induces phase separation Fig. . In the 36. Second, it is possible to measure optical structural features of the end droplets by means of microscopy and estimate material properties from it. This is an empirical approach requiring more complex studies. On the other side, its important benefit is that it can be based on experimental observations or directly compared with it. Recently this problem was addressed37 by simulating polarized microscopy images of a large set of structures for various elastic constants.There are seemingly two ways to solve the problem of estimating an LC mixture content in PDLC droplets. First, one can study adsorption rates and then evaluate the mixture composition. As there are many different LC compounds and polymer matrices, it is typically done theoreticallyin situ estimation of ratios between elastic constants in cholesteric LCs deposited in PDLC material.In this work, we studied the behavior of cholesteric droplets with homeotropic boundary conditions experimentally and by computer simulations. Small droplets forming twisted radial structures were studied. We obtained two different paths of structural transformations under electric fields in such droplets. The choice between these paths has probabilistic nature. The ratio between the two transition types was found to be sensitive to the elastic constants of LC forming the droplet. Thus we suggest the principal method for 38. It is known that twisted radial defect (tR) structure with a single point defect shifted to the droplet edge is formed in the range of d is droplet diameter and 28. At PiBMA polymer assigns the homeotropic anchoring for the E7 nematicmentclass2pt{minimtR structure under the action of an electric field. In both experiment and computer simulations, two possible sequences of structure transformation were obtained. In one case, the droplet remained axially symmetrical all the time; in another, the symmetry broke and was then restored only after transition to toron configuration. Below we depict both cases in detail.We studied the behavior of droplets with c)-(f) for a droplet with tR structure symmetry axis is parallel to the electric field, and point defect shifts close to the border of the droplet. In an intermediate electric field, the point defect slowly shifts toward the center of the droplet. Simultaneously, the twisted cone becomes thinner, which significantly changes its visual appearance in cross-polarized microscopy. Finally, the point defect breaks down into a circular line defect, and the droplet rapidly transforms into the toroidal configuration in a high electric field . However, at an intermediate electric field, the point defect rapidly shifts to the side of the droplet, and the structure loses its symmetry. In further increasing electric field, the point defect approaches the border of the droplet, and the droplet structure undergoes reorientation . We consider the following blueprint of the protocol for such measurements: (1) estimate oblateness of the droplets under study; (2) estimate the possible range of values for the elastic constant ratios; (3) measure symmetric and asymmetric transition probabilities and check reference tables for the specific polymer (these data are to be collected in future studies).The ratio between the two transformation scenarios was shown to be highly sensitive to the LC elastic constants ratio 39 allows one to estimate it in a non-destructive manner. Third, it is unclear how to compare LC droplets in different matrixes. Different polymer materials may lead to varying strengths of surface anchoring, droplet shape, etc. Finally, the resulting numbers will strongly depend on the protocol in both experiments and simulations . The data taken under different protocols can be compared only qualitatively but not quantitatively. An actual protocol can be adjusted to meet the technological requirements. As a primary option for laboratory measurements, we suggest the protocol used in this work. Despite these caveats, we believe the emphasized difficulties are vincible, as it requires more data but does not spoil the found effect. Thus we hope it can be used for in situ estimation of ratios of elastic constants in cholesteric LCs in the future.We understand that the applied measurements require more detailed research and testing. First of all, more extensive studies in a broad range of elastic constant ratios are needed. Ideally, it should be done for pure LCs or LC mixtures with a known matrix absorption ratio. We understand it is very hard to implement for a single matrix type. Thus we suggest composing the complete reference datasets by combining experiments and simulations. Second, the influence of droplet oblateness on the transition probabilities may be also considered. While our approach utilizes small droplets  perpendicular or ii) parallel to the plane of the PDLC film. Two identical ITO coated glass substrates were used to make electro-optical cells of the first type. In electro-optical cell of the second type, two ITO electrodes separated by Experimental studies of the CLC droplet structures reaction were performed using polymer dispersed liquid crystal (PDLC) films. PDLC films were based on poly(isobutyl methacrylate) (PiBMA) (Sigma Aldrich) and the nematic mixture E7 (Merck) doped with cholesteryl acetate (Sigma Aldrich). To study the effect of the electric field on the cholesteric structures, it was used LC with the cholesteryl acetate concentration equal to 1 wt.% corresponding to the intrinsic helix pitch 40 to find the energy-optimal droplet structures. This approach includes the effects of the director field distortion and the formation of defects in the droplet:W is the surface anchoring energy density, 40).We performed simulations of the LC structure within spherical droplets with homeotropic boundaries filled with chiral nematic. The volume was rendered in 40). To take into account potential formation of the disclination lines with core, its linear energy density was set to 28). The relative chiral parameter The initial structures in absence of an electric field, including the director field, the types, positions, and energies of defects were calculated during the Monte-Carlo optimization procedure (see the details in ref.41. This technique supposes direct unidirectional propagation of linearly polarized light through a non-uniform birefringent material. Light diffraction, diffusion, and scattering are not taken into account in the Jones calculus, and thus textures on the peripheral parts of the droplets are roughly estimated. Textures were calculated for ten different wavelengths within the visible spectrum, from 400 nm to 700 nm with the equal step of 33 nm. The values of ordinary and extraordinary reflective indices for E7 cholesteric were set in according to ref.42. Color textures were created by merging the individual wavelength textures with regard to the luminescence spectra of the black body at a temperature We have calculated the POM textures of spherical-cap droplets using the Jones matrix technique, formulated for PDLC materials in ref.Supplementary Information.


Health supply chain is crucial for proper functioning of a health system and advancing national and international health security goals. The Coronavirus 2019 pandemic caused major challenges for health supply chain systems in Uganda and globally.This study involved literature review to examine how the electronic logistics management information system and related digital systems were harnessed be best support public health emergencies.We describe how the health supply chain system leveraged the emergency Electronic Logistic Management Information System developed during the Ebola epidemic in 2019 to support the COVID-19 response in Uganda. The findings are based on the analysis of reports, guidelines, and discussions with stakeholders involved in implementing the electronic Management Information System during the COVID-19 response. Lessons and experiences are shared on how the system supported data visibility, use and health commodity management.A web-based emergency Electronic Management Information System was developed to support the supply chain system during preparedness and response to the Ebola Virus. The system facilitated coordination, information management and provided real-time data for planning, decision making, and distribution of commodities during the COVID-19 response. To address any human resource challenges, 863 staff were trained and mentored in the use of the system. The system enabled the Ministry of Health to track the distribution of Medical Counter Measures through the warehouses, eight regional pre-positioning centers, and over 2000 user units in 136 district vaccine stores. In addition, the system provided quality data for the quantification and monitoring of commodities at all levels of care. Over 1800 bulk orders were processed through the system. Real time stock status reports were transmitted from all national, regional, district and health facility levels. Procurement tracking reports, stock gap analysis and partner contribution were all accessible and visible in the system. This supported the Ministry of Health’s resource mobilization and coordination efforts.Availability of reliable, quality real-time data are essential for effective decision making during public health emergencies. The emergency Electronic Logistic Management Information Systems supported health authorities to mount coordinated and effective responses to ensure timely availability of commodities and supplies to support the COVID-19 pandemic response. Lessons learnt from the Ebola epidemic response were translated into actions that enabled effective preparedness and response to the COVID-19 pandemic. Emerging infectious diseases (EID) have increased over the past decade . ApproxiAnticipating and preparation for prevention, response for epidemics control are essential epidemic management and control . HoweverEffective preparedness and response to pandemics require uninterrupted supply of EMHS . HoweverWe describe the use of an integrated emergency Electronic Logistic Management Information System (eELMIS) to support the supply chain system during the COVID-19 preparedness and response in Uganda. Lessons learnt and experiences are shared on how the eELMIS supported data visibility and use across the supply chain system. The eELMIS includes components of the routine ELMIS and PHE supplies enhancement. The incorporation of PHE epidemic related supplies within the ELMIS facilitated evidence-based decision-making regarding inventory management, resource allocation, and other aspects regarding effective supply chain system performance. An effective eELMIS can enhance availability of and access to information that is critical for decision making during PHE preparedness and response.We reviewed published and unpublished literature regarding the adoption and implementation of an eELMIS during the COVID-19 preparedness and response in Uganda. Documents reviewed included journal articles, reports, and national guidelines. In addition, data were abstracted from the eELMIS database. To supplement the literature review and secondary data, we held interviews and discussions with stakeholders involved in implementing the eELMIS. Furthermore, the authors used observations during the planning, preparedness, and response to the COVID-19 in Uganda (most of whom were actively involved and attended many of the meetings and participated in the epidemic response). The results are structured to capture adoption, implementation, and results of the use of the eELMIS during the COVID-19preparedness and response in Uganda.Uganda’s PHE supply chain system is anchored on a robust electronic information system known as the eELMIS. The eELMIS was established to support the supply chain preparedness and response to the Ebola virus disease (EVD). This system was later adopted to support preparedness and response during the COVID-19 emergency . The eELMIS is a Ministry of Health (MoH) web-based information management system. The eELMIS is a standalone system specifically tailored to support the supply chain system during PHEs. The eELMIS is built with core functionalities of stock ordering, receiving issuing and reporting. These functionalities are available at four levels, i.e., the district, node, partner and national modules , World Food Programme (WFP), United Nations Children’s Fund , the GloThe eELMIS provided real time data on PHE commodities from user units. The data were essential for planning and management of commodities and other supplies. User units, districts, and partners are expected to update and provide weekly stock status using the eELMIS. These data are essential for informing the quantification, forecasting and pipeline monitoring of commodities at all levels of care and decision making. One of the key roles of the logistics sub-committee is to maintain an updated inventory and inform the country of the current situation of logistics and commodities during the COVID-19 response. This role was implemented using of the eELMIS. The eELMIS provides real time back-to-back tracking of logistics activities at every level of the PHE supply chain and facilitates . In addiData provided by the eELMIS supported the logistics sub-committee to prepare reports that were used to update the MoH on a weekly basis. The minister in turn presented the reports to the cabinet to make decisions on resources mobilization for the COVID-19 response and larger strategies during preparedness and response., about 863 staff were trained in use of the eELMIS at the national level, sub-national and health facility levels between 2019 and 2022. Staff trained at the national level consisted of members of the logistics sub-committee, donors, and partners. At the sub-national level, supply chain staff trained included those working at the regional prepositioning centers and district stores, and health facilities (emergency treatment centers). The training content included PHE supply chain management system, application, and use of the eELMIS to support the COVID-19 response. These form the core of the coordination teams at national, regional and the districts  from the warehouses to eight regional pre-positioning centers, and over 2000 user units  in all 136 district medical stores. Through the eELMIS, the logistics sub-committee was able to track and coordinate COVID-19 treatment centers and prepositioning sites for MCM orders. Emergency orders for COVID-19 supplies for all 20 Regional Referral Hospitals (RRH), i.e., Mulago, Butabika, Kawempe, Kiruddu, Lira, Mubende, Mbarara, Hoima, Kabale, Moroto, Soroti, Gulu, Masaka, Jinja, Entebbe, Bombo, Mbale, Naguru, Fort portal, and Arua were processed through the eELMIS, and deliveries made to the respective hospitals. In addition to the RRHs, orders for supplies such as Personal Protective Equipment’s (PPEs) from all public hospitals in 136 districts were served through the eELMIS. Eight prepositioning sites  submitted their orders through the eELMIS to the logistics sub-committee. In addition, 89 quarantine centers and makeshift treatment centers received emergency supplies through the eELMIS. Furthermore, 75 boarders (points of entry) received emergency supplies through the eELMIS Fig. .Fig. 4eEOver 1800 bulk orders for PPEs, medicines, oxygen supplies and other non-medical COVID-19 supplies were served through the eELMIS from March 2020 to November 2022. Furthermore, 96.5% (1745) of the orders that came through the eELMIS have been served since the beginning of the response. In addition, 85.5% overall/aggregate order fulfilment rate was attained. Of all the orders that came through to the logistics sub-committee, 85.5% of the emergency supplies that were requested for were delivered.The eELMIS was critical in ensuring that quality data were used for the quantification and monitoring of commodities across all levels of care. First, the Quantification Procurement and Planning Unit (QPPU) had access to consumption data and orders from all user units. This was important as it minimized shortages of emergency supplies at treatment centers as stock-outs would easily have led to higher morbidities and mortalities and further spread of the COVID-19. Second, the eELMIS supported routine planning, forecasting for future demand. In addition, it facilitated the determination of quantities of COVID-19 MCMs to be procured for both stockpiling during the preparedness and response phase, while considering the country’s supply chain, service, and resource capacities. Third, the eELMIS provided an updated catalogue list of MCMs required and available for COVID-19 response. This enabled the logistics sub-committee to support immediate deployment of COVID-19 supplies to the identified high-risk districts with point of entries, public hospitals and quarantine centers based on the quantified needs raised in the orders submitted through the eELMIS. Fourth, the eELMIS readily provided an MCM gap analysis (stock-on-hand verses outbreak requirement amount) which guided the logistics sub-committee in  resource mobilization from donors and partners .The quantification procurement and planning process was guided by an existing framework for managing MCMs for PHEs in Uganda. This framework provides details of a streamlined quantification methodology to be used during emergency response. This was efficiently referenced and followed by the QPPU which supports the logistics sub-committee. The QPPU provided daily updates to stakeholders in logistics sub-committee meetings. The logistics sub-committee meetings were held every day at the Emergency Operations Center (EOC). Issues discussed include stock-status, quantification, procurement tracking or pipeline stock information of COVID-19 emergency supplies in the country. Throughout these processes, eELMIS served as the reference tool for the QPPU.The eELMIS supported the development of the COVID-19 emergency stock gap report that was shared and utilized to support decision making at various levels of planning and management. A report was compiled for the Commissioner pharmacy department for planning and informing budget allocations. Additionally, report was also prepared and shared with the MoH on a weekly basis by the logistics sub-committee. The minister then presented the findings to the cabinet to give the country direction on the COVID-19 preparedness and response. All this information was generated by the eELMIS as a tool for PHE supply chain during Uganda’s COVID-19 emergency response.Our results demonstrate that the use of eELMIS can influence the adaptiveness of the supply chain system during PHEs. The eELMIS system supported the MoH, central medical stores, health facilities and partners adjust and respond to the increased demand for commodities brought about by the COVID-19 emergency. The use of the eELMIS contributed to the responsiveness and effectiveness of the supply chain system during the COVID-19 emergency. These findings have several implications for understanding the adaptiveness of the supply chain system in a digitally enabled extended environment and design and functionality of the eELMIS.The eELMIS is an important information system to help the supply chain system achieve its objectives of ensuring availability of EMHS across all levels of care during PHEs. It has the potential to contribute to the overall health systems process and data exchanges thus supporting the achievement of greater integration of the supply chain system. Digital health information systems offer an opportunity to integrate entire supply chain process and functions and opening innovative ways of optimizing the logistics process . In addiOur study advances key insights on how the eELMIS can support preparedness and response during PHEs. We show how using the eELMIS, stakeholder resources and technical capacity were amassed and deployed efficiently during the COVID-19 epidemic response. Managers, health workers and partners were able to use the eELMIS to support data-driven decision making. This is key for ensuring that emergency responders and service providers at health facilities across the country have access to critical commodities required to manage disease outbreaks. Our study shows that the use of the eELMIS supports epidemic preparedness and response. The use of the eELMIS can indeed be leveraged to build adaptive supply chain systems in the context of digitally enabled epidemic preparedness and response. As the eELMIS improves with additional capabilities with robust functionalities, to enable new architecture  we anticipate that the use of such systems will further enhance the adaptive capacity of the supply chain system particularly during PHEs.Our findings suggest that the use of eELMIS by the different tiers of the supply chain system enables the different levels to leverage the robust capabilities and functionalities of the system. These qualities combined with a shared understanding created through the eELMIS can lead to a better understanding of the specific information needs of different supply chain stakeholders during a PHE. Similarly, by adopting and using the standard ELMIS, the eELMIS interface can build strong coordination mechanisms between different supply chain stakeholders. The use of the eELMIS enables supply chain stakeholders to know that the system is acting in the best interest of the system and that it is responsive by adopting and using the system. Thus, a standardized (yet flexible) health information systems developed and promoted to support the supply chain system is critical for reconciling both the strengths and weaknesses of existing systems. The use of eELMIS can facilitate connecting various systems without building in a digitally extended supply chain ecosystem. The eELMIS can act as a connecting tool allowing different stakeholders to bring perspectives from different parts of the system that can enhance PHE preparedness and response.Our shows the importance of the eELMS in promoting and nurturing data use to facilitate decision making that is critical for adapting to challenges associated with preparedness and response to PHEs from a supply chain perspective. However, this necessitates investing in building capacity and increasing understanding of how the eELIMS can support different supply chain functions during PHEs. In this regard, strategy and management support are critical in facilitating the adoption, implementation of electronic logistics information systems . As suchThis review had limitations as we selected articles restricted to Uganda over 5-year period which we believe is representative of the use of the electronic Logistics Management Information Systems to respond to public health emergencies in Uganda. While the literature reviewed may not be exhaustive, it is comprehensive, since it covers accessible work in the field. Notwithstanding the above limitation, we suggest future research directions on how to leverage information technology in health supply chain operations and processes to achieve competitive advantage, based on the literature and experience with other stakeholders working in this area. Future studies  could evaluate the effects of digital systems in different contexts  across the supply chain system.The present review showed that the eELMIS can support the supply chain system to better respond to PHEs. By supporting information management, the eELMIS ensures that the MoH and its partners have access to real time information to respond to a PHE including the increased demand for EMHS thereby ensuring responsiveness of the system. Furthermore, the findings show that it is important to build on existing health information systems that are scalable, modular, compatible and can be quickly adapted and reconfigured, thus allowing effective information flow within the supply chain system and the health system in its entirety. Furthermore, an adaptable system enables timely identification and response through its flexibility. This allows the MoH and other supply chain stakeholders to promptly meet the increased demand for commodities. While the current assessment is based on the review of reports and limited number of interviews, the findings show the importance of a cyclical loop between information generation capabilities for a simple and useful health information system that can support effective preparedness and response to PHEs.


Endoscopic endonasal skull base surgery is a promising alternative to transcranial approaches. However, standard instruments lack articulation, and thus, could benefit from robotic technologies. The aim of this study was to develop an ergonomic handle for a handheld robotic instrument intended to enhance this procedure. Two different prototypes were developed based on ergonomic guidelines within the literature. The first is a forearm-mounted handle that maps the surgeon’s wrist degrees-of-freedom to that of the robotic end-effector; the second is a joystick-and-trigger handle with a rotating body that places the joystick to the position most comfortable for the surgeon. These handles were incorporated into a custom-designed surgical virtual simulator and were assessed for their performance and ergonomics when compared with a standard neurosurgical grasper. The virtual task was performed by nine novices with all three devices as part of a randomised crossover user-study. Their performance and ergonomics were evaluated both subjectively by themselves and objectively by a validated observational checklist. Both handles outperformed the standard instrument with the rotating joystick-body handle offering the most substantial improvement in terms of balance between performance and ergonomics. Thus, it is deemed the more suitable device to drive instrumentation for endoscopic endonasal skull base surgery.The online version contains supplementary material available at 10.1007/s10439-022-02942-z. However, some of the main issues associated with CTRs in surgery are their distal-end dexterity and force-delivery capabilities.26 This is why the robotic systems intended for the endonasal approach often employ articulated miniature end-effectors.9 These systems can also be potentially incorporated into magnetic resonance imaging (MRI) machines, so that the robotic platform can be used simultaneously with image acquisition.16The enhancement of the EEEA is a popular research field with clinical translation potential. One of its main research disciplines concerns the development of tele-operated robotic platforms. These platforms often employ concentric tube robots (CTR),33While it is common that the surgical robots developed with the aim to aid surgical approaches, including the EEEA, are tele-operated, they are not the sole robotic device type used in surgery. Another category of surgical robotic devices are handheld surgical robots that can have different advantages when introduced into the operating theatre. These include their smaller footprint and the fact that they can be associated with smaller purchasing and maintenance costs. Additionally, they can be easily integrated into the surgical workflow because they can be interchangeable during the procedure and they often resemble traditional devices which the surgeons already know how to control, reducing, thus, the surgeon’s training period.18 This device controls the robotic end-effector with a trackball and buttons and preliminary experiments and user-studies showcase its promise, without, however, evaluating its procedural ergonomics. A handheld surgical device that controls an articulated end-effector with a more traditional joystick and trigger setup was compared against a conventional, non-articulated surgical tool,25 outperforming the latter in complex surgical training tasks. Despite the improved performance, the majority of the study participants found its design uncomfortable. Alongside these research systems, commercial handheld surgical robots have been introduced into the surgical workflow, such as the Kymerax Precision-Drive Articulating Surgical System , a robotic laparoscopic device that has been used in-human for a total hysterectomy.23Combining the advantages of handheld robotic mechanisms with the increased manipulation of CTRs, the first fully-handheld CTR intended for minimally invasive surgery (MIS) was developed.17 This robotic device was evaluated using a force-sensing test platform and did not demonstrate superiority compared to conventional needle-holders after short-term training. A surgical device similar to this design achieves enhanced manipulability by adopting an isomorphic DoF layout and a stable grip force that was produced with a modelling method for grip force pre-compensation.42 The feasibility of this device was verified during animal trials with an ergonomic analysis intended for future work.Following different design approaches, some handheld surgical devices employ more intuitive control methods. Such an example is a robotised needle-holder with a 7 degrees-of-freedom (DoF) handle that allows for wrist control.2 or finger-operated,8 these devices can offer increased manipulation and dexterity. Despite the extensive workspace when compared to non-articulated tools, these purely mechanical devices lack the advantages that robotic instruments offer such as tremor reduction, robotised guidance and incorporation of imaging and sensing.Alongside robotic surgical devices that achieve enhanced articulation, there are some fully mechanical instruments. Whether they are forearm-mounted,37With the popularity of handheld surgical robotic devices increasing, it is very important that these devices are ergonomically designed since there are significant physical problems related to surgical techniques that could result in discomfort for the surgeon.3 Two of the most common manipulation methods that handheld robotic instruments employ are joystick- and wrist-control. An assessment of both control methods was carried out with 17 clinicians performing a needle-driving task using both actuation means.32 In this particular experiment, the joystick-controlled instrument outperformed the wrist-controlled. Finally, the DEX Robotised Laparoscopic System  was compared with a standard non-articulated needle-holder in a study that involved 6 surgeons.36 Even though using the robotised instrument was more time-consuming, it offered better ergonomics of the surgeon’s hand posture. Based on these literature findings, we can assume that it is difficult to achieve both a substantially improved performance, as well as an improved ergonomic posture, when using a handheld surgical robot.To assess the ergonomic design of various robotic instruments, a number of user-studies have been carried out. The robotic needle-holder Jaimy  was compared with a traditional needle holder and showed statistically improved posture under the Rapid Upper Limb Assessment (RULA) in a study involving 14 clinicians.In this study we present two novel ergonomically designed robotic handles for a handheld surgical robotic device with the aim to increase the efficacy of the EEEA. These prototypes have been developed following different design philosophies that literature suggests could lead to an ergonomically designed device. The first design is based on the suggestion that handheld robotic devices for surgery could benefit from intuitive control methods, while the second is an ergonomically designed alternative to traditional handheld robotic devices. The handle prototypes, as well as a standard, non-articulated neurosurgical tool, were paired with a custom surgical training task virtual simulator and a physical setup that resembled the constrained workspace of the EEEA. To evaluate the performance of the handles, as well as to validate their ergonomic design, we designed and ran a randomised crossover user-study. During this experiment, the participants carried out the same simulated surgical training task with all devices, providing insight on the most suitable robotic handle for endoscopic endonasal skull base surgery.13 The robotic end-effector alongside its coordinate frame system are shown in Fig. The robotic end-effector that both the handle presented in this Section, as well as the handle presented in “14 The handle has maximum dimensions of 42 cm length, 16 cm height, and 431 g weight. It employs a 3-DoF gimbal joystick, with an additional rotating pen-like manipulation DoF for the opening and closing of the gripper. These 4 DoF are directly mapped to the robot-joints pitch, yaw and roll, as well as the gripper DoF to offer easy intuitive control. The handle is forearm-mounted with adjustable straps, in order to alleviate the surgeon from any wrist fatigue and strain.This handle prototype follows the ergonomic suggestion that handheld robotic devices could benefit from intuitive manipulation. Its development, as well as the set of literature suggestions that were followed during its design process, have also been presented in previous work.By mounting the handle on the surgeon’s forearm, the origin of the coordinate axes frame of the joystick coincides with the corresponding origin point on the surgeon’s wrist, creating a stable platform on which the surgeon can easily manipulate the robotic joints. The FMH, alongside the DoF mapping on the robot-joints is depicted in Fig. 14 one single surgeon tested the device and thus, further investigation was needed.The FMH design was preliminarily evaluated and showed substantially improved performance and procedural ergonomics over the standard instrumentation. However, in that initial study14 the second ergonomic handle design follows a different design philosophy. It employs a rotating joystick-body with the joystick controlling the end-effector joint movements and a standard trigger that actuates the gripper.To cater to a larger set of literature suggestions when it comes to ergonomically designed surgical robotic tools than the ones that were previously satisfied,12 However, relevant literature suggests some instructions that could lead to an ergonomic design. One such suggestion is that since each surgeon considers a different handle size optimal, mostly depending on their hand-size, the device should be indifferent to hand-size.20 The preferable handle manipulation type is finger-operated, specifically with the thumb and index finger,43 and it is important that the thumb is employed for controlling the robotic joints for manipulation precision.37 This can be done by a joystick, rotary switch or other device, while the index finger should actuate a round trigger for the opening and closing of the robotic gripper.39When trying to design an ergonomic surgical tool, there is not a universally-accepted consensus on specific components or instructions that make a handle design comfortable to use.21 In the same study it is also stated that the handle with the shaft should maintain a 34 it is suggested that in order for a handle to be comfortable, the instrument at rest should be maintained by a partially open hand, just like the hand is kept at rest.Regarding the geometry of the handle, an improved ergonomic handle shape could include a large palmar grip surface and the combination of precision and turning ability.Following these design specifications, we developed the handle presented in Fig. entclass1pt{minima22All these suggested ergonomic parameters were accounted for with design modifications. The indifference to the surgeon’s hand-size, and designing the handle in a way that the instrument at rest is maintained by a hand that is also kept at rest, were bigger challenges. To solve both problems, we introduced a rotating joystick-body that is modifiable and can be rotated and tight-fitted into seven discrete positions, in order to be placed at the position that each surgeon feels more comfortable with. Fig. The level/resting position of the hand is shown in Figs. If we were to place the joystick at the exact centre of the handle, the thumb would be at an ’adduction’ position and the chance that the surgeon would feel uncomfortable and easily tired could be higher. By placing the joystick on a rotating body, the surgeon can rotate the joystick to the left if they are to use it with their right hand and to the right, if they are to use it with their left hand. The angle of rotation, namely the angle by which the surgeon needs to rotate the joystick body to feel comfortable, depends on the surgeon’s hand-size. In Fig. 14 to evaluate the newly developed RJH, and to investigate if one of the two is superior. To do that, we organised and ran a randomised crossover user-study where a total of nine medical students used the novel handles and a standard neurosurgical instrument carrying out a surgical training task inside a custom virtual simulator. To conduct the study, we sought and obtained ethics approval by the University College London Research Ethics Committee (UCL REC - reference 18035/001).The purpose of this study is to expand on the preliminary findings we obtained for the FMH,14 and extended for the needs of this comparative experiment. The simulated surgical training task is a ’peg-transfer’ task, taken from the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS)11 because it is indicative of surgical skill when carried out in small and constrained spaces, and it is a task that is highly affected by the lack of articulation.29The custom virtual simulator was initially presented in previous work29 While we are focused on the endonasal approach, the operative working space and the region within which instruments must operate during transcranial approaches are similar, despite the different access pathways. The pegs were placed all around this volume with some of them purposefully positioned in coordinates where it would be difficult for the standard instrument to reach them, to highlight the importance of articulation.When designed to adhere to the constrained operative space of the endonasal approach, by manipulating the dimension of the pegs and peg-board, this task can represent the effect that the added articulation can have in keyhole neurosurgery. The peg-board bounding-box dimensions, including the pegs, are To prototype both handles we deployed additive manufacturing techniques, namely 3D printing. All parts of the handles were 3D-printed , using polylactic acid (PLA). For the end-effector shaft, a 3 mm diameter stainless steel rod was used, whereas the end-effector was simulated within the virtual environment. The data from the joystick and rotary potentiometers used in both prototypes were processed using a miniature microcontroller .10 In this study, we decided to replicate the first scenario, with each user-subject of the study manipulating both the prototypes and endoscope, so that they have complete control of the task.Other than the two handle prototypes, additional tools were used for the comparative experiment. These were a 28164TA surgical forceps (Karl Storz SE & Co. KG), and a 3D-printed endoscopic device aimed for camera manipulation by the person carrying out the experiment. During the endonasal approach, a single surgeon can hold the camera in their one hand and the operating instrument in their other hand, a passive endoscope-holder can be used, or an assistant surgeon can hold the endoscope while the operating surgeon is using an instrument in each nostril.All tools used were optically tracked using a motion capture system  and custom marker attachments of negligible weight. The optical markers were placed in positions on the handle body where they would not affect the handling of the instrument. Their physical pose on the handle was transformed in the software environment in relation to the simulated robotic end-effector, and thus the operator manipulation could be realistically replicated inside the simulation environment. To constrain the tools in 3D space, we prototyped a physical constraint which was a model of a cranial CT, modified so that it only includes the areas of interest of the endonasal approach.35 with the same 3D model of the end-effector being used for the two novel handles, while the conventional tool had an end-effector 3D model of the same dimensions, but without the added robotic joint articulation. The experimental setup is shown in Fig. Finally, the custom simulator was developed in the simulation environment CoppeliaSim (formerly V-REP),The performance and ergonomic assessment of the participants using this universal experimental setup could be highly affected by the individual surgeon’s preferred surgical setup. To alleviate this potential bias, we recruited medical students rather than senior trainees or staff neurosurgeons, that did not yet have an operating preference. A total of nine participants were recruited, with two thirds of them covering the six possible combinations between the three devices. The remaining three participants used the devices in random sequence. The device sequence for each participant is depicted in the Online Appendix A.37 to access their initial impressions of the three handles. In order to complete this questionnaire, the participants inspected the different prototypes, and briefly used them inside the virtual simulator to get a feel of their operation and control. The aim of this was to assess the face validity of each handle and explore whether there is a general consensus of subjective opinion about each handle between participants. While it is evident that experts would provide better and more formed insight on the face validity of our designs,4 having this introductory portion in our comparative experiment proved important, because it gave the participants the opportunity to have a brief trial with the prototypes to understand their operation. The questionnaire that the volunteers were asked to fill in is shown in the Online Appendix B.At the start of the experiment the participants were asked to complete an adapted version of an already published questionnaire19Then, the following measurements of participants’ hands were taken: length of the hand, length of the palm, width of the hand at the metacarpal, length of the index finger, width of the index finger-proximal, width of the index finger-distal, and width of the thumb. The purpose of these measurements was to assess if hand-size impacts the performance of each handle.Using each device in random sequence and whilst wearing surgical gloves, the participants carried out the peg-transfer task. They were maintaining a standing pose and looking at a screen at their eye level, where the simulated task was taking place, and their task was to transfer all rings from one set of pegs to the other, with no particular order. With each device, they attempted the task a total of 10 times, with a maximum duration of 2 min for each attempt. No breaks were taken between these individual 2-min attempts to simulate continuous instrument usage, whereas a 5-min break was scheduled between tool changes. For each attempt, the time at which each ring was successfully transferred was manually recorded, something that can give insight on the completion and success rates, as well as the learning curve of the handles.31 When using this score-based system, lower RULA scores for a procedure are associated with better ergonomic postures. The RULA ergonomic scores throughout the experimental procedure with each device were taken at the participant’s worst demonstrated posture.To investigate the procedural ergonomics, the participants were observed and assessed while carrying out the tasks, completing the Rapid Upper Limb Assessment, a validated measure to assess the ergonomics of instruments.41 This questionnaire assesses the mental, physical, and temporal demands of using an instrument, along with situational stress and distractions during the task. Each participant completed this two-part questionnaire for each of the three devices, and based on their answers 6 weighted SURG-TLX dimension scores for each one of them, and for each device are extracted. The aim of this questionnaire is to assess the ergonomics of the handles from the participants perspective, alongside the more objective Rapid Upper Limb Assessment.At the end of the task with each device, the participants were asked to complete the Surgery Task Load Index questionnaire.For the first question of the ’Handle Evaluation’ questionnaire, the participants were asked to rate the two handles on four different categories as shown in the Online Appendix B. Overall, the participants preferred the RJH, which scored mean ratings of 4.1 for intuitiveness, 4 for comfort, 3.8 for precision and 3.8 for stability, with the respective ratings for the FMH being 3.7, 3, 3.6 and 3.8. This preference was also reflected in the ’Handle Preference’ part of the questionnaire, where the majority of the participants agreed that the RJH felt easier to use, was less tiresome, and it employed easier gripper control. To improve the design of the handles, it was suggested that the RJH incorporates a clicking joystick rather than a standard trigger, while the FMH would feel better with an articulated trigger or button controlling the trigger, rather than the pen-like rotating trigger that controls it in this current iteration.22 Thus, the study included five participants with small-sized hands, three with medium-sized hands, and one participant with large-sized hands. Resultantly, the respective angles by which the rotating body on the RJH was rotated based on hand-size category were The hand measurements a.-g. as mentioned in “The completion rate, here defined as the percentage of rings that were successfully transferred from the one set of pegs to the other out of the total of 6 rings, for each of the 9 participants throughout their 10 2-min attempts, and for each of the 3 devices is depicted in Figs. The median of rings transferred between the 9 participants when they were using the standard instrument was 4, whereas for both the RJH and FMH was 6. With the standard instrument, 2 participants did not manage to transfer any rings at all at least once during their 10 attempts. The least amount of rings that were transferred with the RJH during a single attempt were 2, and with the FMH 3, with the exception of participant #2, who asked to end the experiment early due to shoulder discomfort, as discussed in “Overall, the participants showcased significantly improved performances with the robotic handles rather than with the standard instrument, with both the lower and upper quartiles of their box-plots scoring higher for the two novel handles. The mean completion rate, here defined as the arithmetic average percentage of rings that were successfully transferred from the one set of pegs to the other out of the total of 6 rings, between all 9 participants, and for each of the 3 devices is depicted in Fig. To have an understanding of the time-efficiency of each handle, we calculated the mean time it took the participants to transfer each one of the 6 rings. The results are shown in Fig. Finally, in Figs. The RULA survey method posture scores for all 9 participants, and for each individual posture of the upper limbs, neck, trunk, and legs are shown in Figs. The upper arm posture was worst for the FMH, where the participants had to raise their shoulders to translate the simulated robotic end-effector, followed by the standard instrument, and then by the RJH. The lower arm posture was similar for the first two devices with the participants occasionally working across the midline of their bodies, and again best performance occurred with the RJH.As expected, wrist posture was worse with the standard instrument, with extreme angles occurring and participants having to bend their wrist away from the midline. When using the FMH, participants needed to often employ mid-range and extreme angles, while bending their wrist, and when using the RJH they were mostly within a healthy angle range. The final parameter for the RULA posture group A, which includes the arms and wrists, was the wrist-twist, that was almost always near the end of the twisting range for the standard instrument, mainly mid-range for the RJH, and always at the natural wrist twist position for the FMH.As far as the RULA group B is concerned, namely the neck, the trunk and the legs, participants seemed to struggle more to find a comfortable neck position when using the standard instrument, and they would often twist their neck. The corresponding behavior with the two novel robotic handles was similar between each other, and slightly better than with the standard instrument. When using the RJH the participants would mostly maintain a well-supported trunk and would rarely flex forward, twist or bend it. The same cannot be said for the other two devices, where the participants showed similar behavior that included all flexion, twisting and bending. Finally, throughout the experiment the participants’ legs and feet were well supported and in an evenly balanced posture, meaning that no participant scored more than a score of 1.The final measure to assess the participants’ ergonomic behaviour was the SURG-TLX questionnaire, a subjective questionnaire that aims to assess the participants’ mental, physical, and temporal demands while using an instrument, alongside with situational stress and distractions during the task.The mean of the weighted SURG-TLX scores, for each dimension and for each device are shown in Fig. In this study, we presented a novel ergonomically designed surgical robot handle intended for a handheld robotic instrument for endoscopic endonasal skull base surgery, and compared it with a previously developed handle with different design philosophies. The previously developed handle is forearm-mounted with surgeon-wrist to robot-joints movement mapping, and the novel handle employed a rotating joystick-body that can be maintained at the surgeon’s natural resting hand position. To decide which one of the two handle prototypes would be the most suitable to improve the efficacy and human factors of the endonasal approach, we designed and carried out a randomised crossover user study where these robotic handle prototypes were evaluated with a virtual surgical task simulator.In terms of performance and efficacy, the two robotic handles clearly outperformed the standard neurosurgical instrument. Although an expected result, since a tool with added articulation is designed to have a larger workspace than a non-articulated instrument, performance was still an important aspect to investigate. The ergonomic design considerations implemented in the two designs, namely the forearm constraint of the one handle, and the moving joystick-body of the other, could potentially lead to declined performance because of dexterity loss or imprecise control. The fact that both handles outperformed the standard tool suggests otherwise.When comparing the performance of the two novel handles, the two devices had very similar behaviours. The RJH showcased a slight edge in the categories of completion rate per participant and mean successful attempt rate, while the FMH performed slightly better in terms of mean completion rate. These differences, however, are small and thus are not adequate to confidently suggest which one of the two novel devices is the most suitable for the EEEA.Both handles seem to have similar and small learning-curves, with the RJH being associated with a more consistent learning curve, and the participants were able to perform very well or even complete the task very early in their 10 attempts sequence. The one category where one handle clearly outperforms the other is time-efficiency, with participants being able to successfully complete the task using the FMH approximately Much clearer conclusions can be drawn from the ergonomic assessment. The RJH is the safest handle to use for an extended amount of time according to the RULA survey, since it only scored 3 and 4, both scores falling into the ’low risk’ category. On the contrary, the FMH scored both 3 and 4, but also 5 and even 6 once, deeming it low to medium risk. As far as the standard instrument is concerned, and with the exception of one ’low risk’ score and one ’high risk’ score, it was deemed medium risk.Finally, when participants were able to voice their opinion at the start of the experiment, the majority preferred the RJH. This consensus was inverted after the experimental procedure took place with the majority of the participants favoring the FMH in terms of total mental, physical and temporal workload. This preference contradicts the RULA assessment outcomes, with the most probable explanation being that the participants highly valued the intuitiveness of the handle, but only used it for a limited amount of time. Had they used the handle for an extensive period, the RULA assessment suggests that there is a higher likelihood for discomfort.Despite the low mental demands and situational stress associated with the FMH, as well as its time-efficiency, the poor ergonomic results and the similar performance with the RJH, combined with the increased time and effort it would take to switch between instruments during the endonasal approach, indicate that the more favorable handle for the EEEA, amongst the two investigated in this study, is the RJH. The increased time and effort would be evident in instances when non-robotic tools would need deploying for the operation. To un-mount the FMH from the surgeon’s forearm, the operating surgeon would need to leave whatever tool they hold with their other hand to untie the straps, or a second clinician would need to be involved. With the RJH, on the other hand, the operating surgeon would just need to leave the tool on the operating tray and pick-up another tool. We believe that the RJH device offers a more complete solution than the FMH with similar increased joint articulation, while simultaneously maintaining a low ergonomic risk.While these findings showcase potential for improved neurosurgical instrumentation, there are still some aspects of this work that need addressing. During the study design, it was decided that the operator would control both the instruments and endoscopic device. While camera control does not immediately affect the perceived ergonomics of each device, since the mock endoscope and instrument did not collide inside the operative workspace, it could affect the performance of the operator. The more time the operator would spend in manipulating the camera, the better perception of depth inside the simulated environment they would develop. To try and alleviate this risk, we deployed randomized tool sequences between the participants. However, different camera setups could showcase interesting results and their exploration could be scope of future work.Another limitation of our study design, was the decision to not include expert neurosurgeons in the experiment. The reason why we wanted to avoid mixed cohorts for this specific comparative experiment between all three instruments, was that the preferred surgical setup that expert surgeons have developed over the years, would probably lead to a non-representative performance when using the conventional tool, introducing bias to the comparative experiment. However, understanding how helpful the opinion of an expert neurosurgeon cohort would be towards our device development, as part of future work, a human-factors workshop consisting of expert neurosurgeons will be organised, that will validate the performance and ergonomic behavior of our fully-functional handheld prototype.One of the main points of concern was that despite the fact that most participants preferred the FMH during their SURG-TLX evaluation, one participant could not manage to finish the part of the experiment with this handle due to shoulder discomfort. This happened even after the surgical table was lowered as to fit the participants height, and suggests that this forearm-constraint can be affected by the surgical setup, and thus will not always be suitable depending on the surgeon’s preference and also the operating theatre arrangement.The same participant evaluated the RJH an order of magnitude lower than the other participants in the SURG-TLX scale. If we omit this outlier value from the average, the FMH would score significantly lower than the RJH. More specifically, the average total SURG-TLX score for the RJH would be 165.87, while for the FMH would be 135.62. While the difference between the two scores would be much clearer, the outcome of this part of the experiment remains the same, ie the participants preferred the FMH over the RJH. Still, the objective RULA evaluation suggests that the chance of them feeling discomfort would be higher with the FMH than with the RJH were they to use the robotic instrument for an extended amount of time.24 up to more than 10 h for more complex ones.5 A variety of different tools are used for each stage of the procedure, with frequent tool changes.7 While we believe that each 20-min session with each handle would be sufficient to give us representative information on ergonomics about shorter approaches with frequent tool changes, more complex procedures would necessitate more elaborate phantoms, tasks, and also the allocation of time from surgeons.Operative times for endonasasl approaches vary depending on the complexity of each case and the surgeon experience, ranging from one to 2 h for routine cases,As far as the rotating joystick-body handle is concerned, the design presented in this paper will have to be altered to incorporate motor electronics as well as the robotic end-effector. It will, thus, have to be re-validated for its ergonomics, because while the weight distribution of the functional device will be similar to the suggested prototype, the weight itself will increase with the addition of motors and cables, and the geometry will have to be amended.In future work, the superior handle prototype will be paired with the previously developed miniature robotic end-effector in order to form a fully functional surgical robotic instrument. This will require redesign in order to fit electronics and actuation tendons. After the new design will have been validated for its improved ergonomics, it would be beneficial to compare its ergonomic behavior with other handheld surgical robotic systems that are commercially available. We also intend to incorporate sensing and feedback mechanisms such as tactile-feedback or imaging modalities. As a final step in the device development, this robotic prototype will be evaluated through surgical training tasks and phantom trials in order to validate its potential.Supplementary file1 (PDF 1171 kb).Below is the link to the electronic supplementary material.


Blind source separation (BSS) recovers source signals from observations without knowing the mixing process or source signals. Underdetermined blind source separation (UBSS) occurs when there are fewer mixes than source signals. Sparse component analysis (SCA) is a general UBSS solution that benefits from sparse source signals which consists of (1) mixing matrix estimation and (2) source recovery estimation. The first stage of SCA is crucial, as it will have an impact on the recovery of the source. Single-source points (SSPs) were detected and clustered during the process of mixing matrix estimation. Adaptive time–frequency thresholding (ATFT) was introduced to increase the accuracy of the mixing matrix estimations. ATFT only used significant TF coefficients to detect the SSPs. After identifying the SSPs, hierarchical clustering approximates the mixing matrix. The second stage of SCA estimated the source recovery using least squares methods. The mixing matrix and source recovery estimations were evaluated using the error rate and mean squared error (MSE) metrics. The experimental results on four bioacoustics signals using ATFT demonstrated that the proposed technique outperformed the baseline method, Zhen’s method, and three state-of-the-art methods over a wide range of signal-to-noise ratio (SNR) ranges while consuming less time. When the original source signals of interest cannot be recorded directly and only a combination of mixtures is available, a source separation problem will exist. The objective of the source separation problem is to isolate the original signals from a combination of several source signals. Blind source separation (BSS) is a typical method used for source separation in the signal processing research community and it has gained considerable attention ,2,3. RecUBSS has garnered substantial scholarly interest, and numerous solutions to this issue have been offered ,7,8,9,10The authors of  introducThe method in  used a pThe goal of this work was to propose an adaptive approach for selecting meaningful data from TF mixtures that facilitates better identification of SSPs. The study focused on increasing the accuracy and decreasing the time costs of estimating the mixing matrix as well as enhancing the quality of source signal separation. After identifying the SSPs in the TF plane during the estimation of the mixing matrix, these points are clustered by hierarchical clustering to estimate the mixing matrix. The second stage of SCA employed the least squares method to carry out the source recovery estimation.The remainder of this article is organised as follows. The UBSS approach based on SCA is made up of two phases. The initial step of the procedure is to estimate the mixing matrix, followed by estimating the source signal. The procedure starts with mixed signal generation. The flowchart of the entire process is shown in M-many mixed signals received by the sensors at the receiving end, M-many sources, T is the instant time and This study considered an underdetermined instantaneous mixed model where the mixed signal in the time domain can be expressed asThe mixed signals in the time–frequency (TF) domain was used to estimate the mixing matrix. The mixing matrix estimation is an essential procedure in SCA, and it can be improved in two ways: single-source point (SSP) detection and clustering. In this work, an adaptive algorithm was applied before the SSP detection step to increase the accuracy and reduce the complexity. An SSP is a time–frequency point at which the energy of just one source is significant, while the energies of signals from other sources are either zero or very near to zero at that point. By locating the SSPs, the data clustering can be enhanced, allowing clustering algorithms to be able to estimate the mixing matrix more accurately.Through the development of mixing matrix estimation, research has been carried out to find a new way to improve SCA. Estimating an unknown mixing matrix accurately is crucial to provide a sufficient condition for the recoverability of a source vector. Many different SSP detection strategies have been put forth as means of enhancing the accuracy of mixing matrix estimates. By extracting 1D subspaces from the whole collection of TF representation vectors of the observed mixed signals, ref.  providedAccording to Step 1: The normalisation process was executed for each element in the TF vectors of the mixed signals would have a unit norm, using the following operation:Step 2: An adaptive threshold, Let The threshold of ATFT, The threshold values varied for each different mixture and dataset. The selected column must meet the condition.3.According to Equation (5), the thresholding operation is defined asStep 3: From Equation (6), the corresponding column of the TF mixture vectors will be selected as follows:In this study, sparse coding was used to find and extract the SSPs from the ATFT method’s mixture vectors. Sparse coding is a technique for representing an input signal with a limited number of basic functions . Sparse t,f)∀j≠i . Based odated by , if X~u,After obtaining the sparse coding solutions for each TF point, TF points with just one nonzero element were considered in the sparse coding coefficient vector to be SSPs. Following the identification of the SSPs, the next step was to estimate the mixing matrix. The detected SSPs consisted of the set of normalised column vectors of the mixing matrix denoted as Ω, as stated in Equation (13): To aid the clustering analysis, the data must be normalised after the SSP detection process, which entails mapping the data points to the positive half-unit circle. The normalised SSPs then will be clustered by the clustering method. In summary, the proposed ATFT and SSP approaches are described in Algorithm 1.Algorithm 1: Mixing matrix estimation procedure using the proposed ATFT methodInput: The mixed signal, Each element in the mixture vectors, The mean of the unit norm, ELet where The threshold For each The mixture of TF vectors with sparse coding coefficient vectors containing only one nonzero element is added into Ω.The elements are normalised on Ω.Output: Normalised Ω.The hierarchical clustering algorithm  was usedAlgorithm 2: The procedure of mixing matrix estimation using hierarchical clusteringInput: The extracted SSP vectors, The clustering method is applied to the extracted SSPs to group its elements into The centres of these n clusters are calculated as the estimations for the columns of the mixing matrix to produce the estimated mixing matrix.The outliers are removed and The centres of the clusters are calculated as the estimated mixing matrix, Output: The estimated mixing matrix, To construct a sparse TF representation of the recovered sources, a sequence of least square problems was used to recover the source signals, minimising the error function by selecting the optimal Finally, by inverting the STFT, the time domain of the predicted source signals Algorithm 3: Source recovery estimationInput: The mixed signal, All The source of TF representation is estimated for each TF point.Using inverse STFT, the estimated source signals are transformed back into the time domain.Output: The estimated source signals, In this section, numerical results demonstrating the efficiency of the proposed methods are presented. Taking into consideration the fact that bioacoustic source separation is comparatively understudied in comparison with human speech separation , this stabase of  were conIn all experiments, the source signal was synthetically mixed to create the mixtures. Four source signals with 15,000 samples were randomly selected and mixed with different random 3 × 4 mixing matrices for each simulation test to generate the mixed signals. For each of the mixture signals, the proposed algorithm was implemented to separate these bioacoustic source signals. The mixed signals were combined with Gaussian noise, and the noise performance of the algorithm at various signal-to-noise ratios (SNR) ranging from 5 dB to 45 dB was tested. The average of 100 Monte Carlo simulation tests was obtained to evaluate the performance of the proposed method. Natural signals such as bioacoustics signals are not often extremely sparse in the temporal domain. The source signals were made sparser by applying STFT. The performance of the proposed technique was assessed by two categories of assessment metrics.The following performance indicator was used in this work to assess the performance of mixing matrix estimation:The simulation results showed that for each method, the accuracy improved with an increase in the SNR. Furthermore, the tests revealed that the ATFT approach was able to predict the mixing matrix more accurately than the existing method. Because of the adaptive threshold setting process, it was able to automatically adapt to the data and consistently achieved accurate estimations. The proposed technique provides an excellent alternative for mixing matrix estimation over the baseline techniques, thus lowering the errors. To analyse the complexity of the research method, the time cost was used to represent the total time in second (s) taken by the CPU for estimating the mixing matrix. The simulations were performed using MATLAB 2016(a) and tested in the Windows 7 operating system with an Intel Core i7 with a 2.93 GHz CPU and 8 GB of RAM. The results showed that the ATFT method was slightly faster than Zhen’s method for all sets in the bioacoustic database, including the speech signals. Zhen’s technique takes the sparse linear representation of the relationships among all time–frequency (TF) mixing vectors into account to determine the locations of the single sources (SSPs). In contrast, the ATFT method uses only the most significant mixtures. Because of the computational difficulty of the approach, the size of the mixture vectors in the ATFT method were sufficient for obtaining an accurate estimation of the mixing matrix. Therefore, the ATFT method cost less than Zhen’s method, since the number of samples needed to estimate the mixing matrix was smaller than in Zhen’s method. In conclusion, the ATFT method provides a more efficient and lower time cost, and it performs better in real-time applications than Zhen’s method.To further validate the relevance of the ATFT method, additional related techniques were also used to demonstrate the performance of the suggested method. The results of ,34,35 weWhen the SNR was less than 30 dB, the difference in estimation performance between the methods of DUET, TIFROM, Reju, and Zhen, and the ATFT method was rather large. When the SNR exceeded 30 dB, the performance of all estimation methods reduced. Both the ATFT and Zhen’s methods had a more stable and reliable performance. When the error changed to be not more than 0.2 dB, as the SNR decreased from 45 dB to 5 dB, it was observed that the ATFT method still performed the best. In the noisy case, the ATFT method outperformed the methods developed by ,34,35 wiThe performance of the ATFT algorithm was further evaluated by setting different numbers of mixtures When the performance of different settings is compared between s′^i denotes the estimation of the source signals s′i and The performance of the source recovery estimation was examined using the following method to accomplish bioacoustic source recovery:The simulation results of the original sources and the estimated sources are shown in The primary objectives of this work were to develop an adaptive algorithm that selected significant coefficients from time–frequency (TF) mixtures to promote better detection of SSPs for estimating the mixing matrix by using the SCA-based UBSS technique. In comparing the proposed method with the benchmark method and several state-of-the-art methods after 100 Monte Carlo trials, the results revealed that the TF selection factor of the proposed method provided higher accuracy than the others for estimating the mixing matrix under different signal-to-noise ratios (SNR) ranging from 5 to 45 dB. In terms of source recovery at all levels of SNR, the proposed method excelled in comparison with the benchmark method approach because of its the more accurate estimation of the mixing matrix that it provided. The simulation results illustrated that the estimated sources were recovered successfully for bioacoustic signals. In conclusion, a method based on the SCA technique has successfully been developed to estimate the mixing matrix and source recovery, and it can address the problems concerning the accuracy, time costs and separation quality of UBSS.


Automatic speech recognition (ASR) is an essential technique of human–computer interactions; gain control is a commonly used operation in ASR. However, inappropriate gain control strategies can lead to an increase in the word error rate (WER) of ASR. As there is a current lack of sufficient theoretical analyses and proof of the relationship between gain control and WER, various unconstrained gain control strategies have been adopted on realistic ASR systems, and the optimal gain control with respect to the lowest WER, is rarely achieved. A gain control strategy named maximized original signal transmission (MOST) is proposed in this study to minimize the adverse impact of gain control on ASR systems. First, by modeling the gain control strategy, the quantitative relationship between the gain control strategy and the ASR performance was established using the noise figure index. Second, through an analysis of the quantitative relationship, an optimal MOST gain control strategy with minimal performance degradation was theoretically deduced. Finally, comprehensive comparative experiments on a Mandarin dataset show that the proposed MOST gain control strategy can significantly reduce the WER of the experimental ASR system, with a 10% mean absolute WER reduction at −9 dB gain. Automatic speech recognition (ASR) has been widely integrated into human–robot interactions in the form of voice user interfaces (VUIs) ,2,3. VirCurrently, the performance of the ASR system in many human–robot interaction scenarios is unsatisfactory due to robustness limitations, and one of the critical factors is that various practical noises make it more challenging to extract the features, such as Mel-frequency cepstral coefficients (MFCC) ,13,14, lThe function units before the recognition in From the perspective of noise, theories in  show thaThis paper proposes an optimal gain control strategy named the maximized original signal transmission (MOST) to minimize the adverse effect of noises induced by gain control on ASR. The gain control strategy within the ASR system can be optimized, since it has been shown that the performances of similar systems, such as RF systems, can be significantly improved by modifying the gain structures ,29. FirsThe paper is organized as follows: In Currently, most of the research on ASR focus on recognition-related algorithms, and there is insufficient research on gain control strategies that actually have a significant impact on ASR systems. The recognition-related algorithms on ASR include two main categories: the pre-processing algorithms and machine learning (ML)-based ASR algorithms. The pre-processing algorithms, such as dereverberation ,19,20,21In ML-based ASR algorithms, the recognition process works on the extracted features. As shown in the lower part of However, the noises caused by gain controls distort the features, such as Mel-cepstral features  and pitcIn this section, the MOST gain control strategy is first proposed, and then the detailed modeling and analysis for deriving the proposed MOST gain control strategy are demonstrated. For the convenience of the subsequent description, the components or subsystems within the ASR system are classified into three categories: (1) receiving unit, (2) middle unit, and (3) recognition unit. For the ASR system shown in The proposed MOST gain control strategy is a constraint on gain controls: gain control operations are performed as close to the recognition unit as possible. In practice, the constraint as close to the recognition unit as possible must be considered in the following two perspectives. For clarity, assume the ASR system in the listed cases all consist of a receiving unit, three middle units, and a recognition unit.From the perspective of different units, assume that a gain of −3 dB is required in the recognition unit. For the current gain control strategy, the execution position of the gain of −3 dB is unconstrained, and it can be performed at the output of the receiving unit, or −1 dB at each middle unit, etc. On the contrary, the proposed MOST gain control strategy means that the −3 dB gain must be performed at the output of the last middle unit;From the perspective of a specific unit, assume that the middle unit of pre-processing needs a −2 dB gain control. Ensuring the −2 dB gain control is only performed on this middle unit does not satisfy the constraint. Because this middle unit probably consists of many smaller software function units, the gain control also has an execution order among these smaller function units. Thus, the −2 dB gain control should be placed as close to the end of these smaller function units.The name MOST alludes to the optimization effect and the optimization method. The effect of the proposed gain control strategy lies in the maximum preservation of the speech signal features, and the description “maximum original signal transmission” represents the idea of the proposed gain control strategy. The proposed MOST gain control strategy can be implemented in many specific forms in practice, such as presented in Transmission channel for gain control commands represented by the arrow between units, which can be wired or wireless, together or independently;Gain control logic on the right side of the dotted line in each unit. The double pole double throw is critical, because it maps the switch control command into the corresponding gain control logic.The advantage of the form in When different units are connected, the units with the proposed MOST gain control strategy perform two actions before establishing the transmission channel for gain control commands.Wait for a handshake signal at the input. If the handshake signal is received, return the ACK signal to the former unit;Send handshake signals periodically on the output and check for the ACK signal. If received, return the ACK signal to the switch control module.The two actions are used to establish communication between adjacent units. Wait for a handshake signal is attempting to establish communication between the current unit and the former unit. Send handshake signals periodically is attempting to establish communication between the current unit and the latter unit.The modeling and analysis of gain control strategies in ASR systems are achieved by the following two steps. (1) Establish the gain control strategy model by regarding the macroscopic function units in ASR systems as the microscopic components in the RF signal chain; (2) Analyze the gain control strategy model using the noise figure theory.F is defined as  corresponding to the clean test utterances without any attenuation and noise was 8.19%, and the lowest WER in the experiment was around 10%. From the overall trend of WER changes in In detail, the following conclusions can be obtained.The WER result increased with decreasing gains in all 18 sets of comparison test conditions in The proposed MOST gain control strategy showed advantages over the current strategies under the 18 sets of comparison test conditions in For a certain noise type shown in In order to show the degree of improvement of the proposed MOST gain control strategy to the WER, the absolute WER reduction is calculated byFrom The gain control strategy dramatically influences the performance improvement degree of the proposed MOST gain control strategy, and the noise type, signal-to-noise ratio, RT60, and distance factors have a relatively small influence. The average performance improvement of the proposed MOST gain control strategy was around 10% under the −9 dB gain condition, while it was about 2% under −3 dB gain condition;The performance improvement degree of the proposed MOST gain control strategy is rather effective under a lower gain. In the case of −9 dB gain, 8 of the 18 sets of the proposed MOST gain control strategy offered a WER reduction of more than 10%, as shown with the △ symbols in The proposed MOST gain control strategy has a smaller performance improvement if the utterances are less affected by the noises or reverberations. (1) The WER reduction is relatively small for the test utterances with high SNRs, corresponding to the two circle positions in The performance improvement degree of the proposed MOST gain control strategy becomes evident as the reverberation condition becomes severe. The increase in the vertical distance of the circles in The performance improvement degree of the proposed MOST gain control strategy decreases under extremely severe reverberation conditions. When the distance is extremely long (4 m) and RT60 is large (1.0 s) .The experiments were conducted on the Meridian dataset; this is the limitation of this paper. However, the ’improvement’ of this paper involves the speech signal features. The proposed MOST gain control strategy ensures that more features are fed into the recognition algorithm. Thereby, higher recognition accuracy is achieved. Features are the common foundation for the speech recognition of Mandarin and other languages. Thus, the proposed MOST gain control strategy is probably applicable for the other languages. One future work is to prove the effectiveness of the proposed MOST gain control strategy with other languages.Moreover, unlike directly improving the ASR of the algorithm layer, this paper indirectly improves ASR performance by optimizing the noise caused by the gain control in the signal layer. The signal layer is the basis of the algorithm layer, and the influence and processing of the signal layer on the original sound signal take precedence over the algorithm layer. Therefore, in the research of ASR, the importance of the signal layer cannot be ignored. In future work, other aspects of the signal layer that affects the performance of ASR systems should be investigated, such as dynamic range compression at the microphone, which is a variant of gain control.Inappropriate gain control strategies cause an increase in the ASR WER, with respect to a performance degradation of the human–computer interaction system. In this paper, an optimal gain control strategy named MOST was proposed to minimize this adverse impact. Our primary contribution involved modeling the gain control strategy and theoretically prove that unconstrained gain control will cause the performance degradation of the ASR system using the noise figure theory. The second contribution theoretically demonstrates that the proposed MOST gain control strategy is the optimal gain control strategy for the ASR system. Finally, comprehensive comparison experiments under different conditions were conducted on the Mandarin dataset. For a −9 dB gain setting, the proposed MOST gain control strategy improved the WER performance of the experimental ASR system by an average of up to 10%. Such a considerable performance improvement shows that the proposed gain control strategy, as well as its corresponding modeling method, are effective in real ASR systems.


Background and objectiveWe report a novel block technique aimed to provide thoracic analgesia: the serratus posterior superior intercostal plane (SPSIP) block.DesignA cadaveric evaluation along with a retrospective case series evaluating the potential analgesic effect of the SPSIP block. This study included one unembalmed cadaver and five patients.InterventionsBilateral ultrasound-guided SPSIP block was used on cadavers with 30 mL of methylene blue 0.5% on each side; single-injection SPSIP blocks were used in patients. To measure results, dye spread was used in the cadaver, and dermatomal/pain score evaluation was used in patients.Main resultsAnatomical investigation in one unembalmed cadaver shows that its mechanism of action covers the rhomboid major muscle, erector spinae muscle, the deep fascia of the subscapularis/serratus anterior muscles, and intercostal nerves. In our patients, SPSIP resulted in an almost complete sensory block in the back of the neck, shoulder, and hemithorax.ConclusionOur cadaveric study shows extensive dye spread from C7 to T7. Patients who were administrated SPSIP block reported consistent dermatomal blockade from C3 to T10 levels of the hemitorax. The SPSIP block seems to be a safe, simple, and effective technique for thoracic analgesia. Thoracic epidural and paravertebral blocks are regarded as the gold standard in thoracic surgery analgesia; ultrasonography-guided interfascial plane blocks have become increasingly popular owing to their minimal invasiveness and associated low complications . ErectorESPB is a technique that has been the topic of countless publications and can be applied at multiple levels, from the cervical to the sacral vertebrae . HoweverWhen the muscles to the medial of the scapula are examined from cephalad to caudal, the trapezius (TM), RM, and intercostal muscles form the middle and lower muscle groups, while the TM, Rm, and serratus posterior superior muscles (SPSM) lie on the superomedial side, from superficial to deep. The SPSM originates from C7-T2 (sometimes T3) spinous processes, progressing obliquely and inserting on the lateral of the second to fifth ribs' angles. SPSM differs anatomically from the aforementioned muscles in that it is the only muscle that originates from the spinous process and extends deeply into the scapula. Due to this structure, it may theoretically be advantageous for local anesthetic diffusion to dorsal ramus and lateral cutaneous branches of intercostal nerves at C3-T7 levels.On the basis of these anatomical features, a local anesthetic (LA) delivered to the plane between the SPSM and the intercostal muscles would diffuse to a different area from other paraspinal interfascial plane blocks. The aim of this paper was to present the results of the cadaveric evaluation of the serratus posterior superior intercostal plane (SPSIP) block, as well as our clinical applications.MethodCadaveric examination in one cadaver was performed following approval from Istanbul Medipol University Ethics and Research Committee . The same committee also approved  the retrospective evaluation of five patients that underwent SPSIP between 15/04/2022 and 11/05/2022. All patients gave written informed consent for inclusion of their data in this study.Description of SPSIP blockAlthough we prefer the prone position for the block, it can also be performed in the sitting position. To lateralize the scapula, the patient is instructed to grip the opposing shoulder with the hand on the side where the block is to be performed or to put the affected arm into adduction and internal rotation. A high frequency (4-12 MHz) linear transducer  is placed at the spinae scapula level in the transverse plane, and the upper medial border of the scapula, the trapezius muscle, Rm, SPSM and the second and third ribs are visualized. The ultrasound probe is rotated 90 degrees in a parasagittal orientation from the posterior aspect of the supraclavicular fossa to identify the first rib. After its identification, the second and third ribs are confirmed. The linear transducer is then rotated so that an oblique visualization is obtained  with the upper medial border of the scapula in the sonographic view Figure . The neeAnatomic study of the SPSIP blockBilateral SPSIP block was performed to an unembalmed cadaver. There were no surgical incisions or scars in the paraspinal region and thorax/neck/shoulder/upper abdominal regions of the cadaver, nor were there any anatomical deformities on inspection. The cadaver was maintained at room temperature for 12 hours prior to block application. Thirty mL of methylene blue 0.5% was administered to each side using the in-plane technique (ST-HAA). One hour after administration, an experienced anatomist (AF) began dissection. Beginning at C7 and proceeding dorsally to T10, the skin, and fascia were dissected from the midline. Both sides were simultaneously dissected and compared with each other. The trapezius muscle, latissimus dorsi, rhomboids, and erector spinae muscles were dissected and evaluated for the presence of dye. After dissecting the rhomboid muscles away from the midline, the scapula and its superficial and deep muscles were shifted laterally without making a transverse incision in order to analyze the distribution of dye along the intercostal muscles. The intercostal muscles were subsequently dissected in the sagittal plane to assess the presence of dye within the muscles. To evaluate dye distribution, the deep fascia of the trapezius muscle was traced to the scapula. To define the anterior boundary of dye spread, vertical incisions were made at the posterior, middle, and anterior axillary lines.Case seriesConsidering the cadaveric findings, the SPSIP block application was chosen for eligible individuals who were likely to benefit from this new block technique. All of these patients were selected from patients who were diagnosed with myofascial pain syndrome (MPS), which causes complaints in the cervical and interscapular region, according to MPS diagnostic criteria, and who had previously been treated with medications, physiotherapy, and neural therapy for this, but could not provide sufficient pain relief.After informing patients of the risks, benefits, and alternatives of this procedure, all patients provided informed written consent. The block was performed in the prone position under sterile conditions and after administration of 2% lidocaine for local anesthetic infiltration of the skin. Dermatomal evaluation was performed 40 minutes after block administration using the cold test.Anatomic evaluationThere was dye staining between the seventh and 10th intercostal levels along the deep fascia of the trapezius muscle on the left of the cadaver, and no staining was observed in this plane on the right side of the cadaver. Dye was present deep in the trapezius muscle, bilaterally. Dye was present in both the superficial and deep areas of the rhomboid major muscle, while it was observed in only the deep areas of the rhomboid minor muscle. Dye was observed both on the superficial and deep planes of the erector spinae muscles, bilaterally. On the intercostal muscle plane, the dye was evident bilaterally from C7 to T7, spreading to the anterior axillary line on the right and the mid-axillary line on the left. The deep fascia of the subscapularis and serratus anterior muscles were stained bilaterally. A review of dye staining observed from the cadaveric evaluation is shown in Table PatientsSPSIP block was administered to a total of five patients aged between 26 and 64 years. Two of the blocks were bilateral, while the remaining four were unilateral, with a total of eight blocks being performed. Five patients diagnosed with MPS were evaluated. None of the patients had cervical spinal pathology. These patients have received non-pharmacological and pharmacological conservative treatments for MPS, but short-term pain relief was provided. Analgesia management was not achieved in the entire aching area in any of the patients.The demographic and block characteristics of the patients are detailed in Table The cadaveric examination demonstrated that the dye injected between the serratus posterior superior muscle and the intercostal muscles spread from the deep of the subscapularis and serratus anterior muscles to the anterior axillary line and from the first rib to the seventh and eighth ribs in the craniocaudal planeIn our patients, SPSIP resulted in an almost complete sensory block in the back of the neck, shoulder, and hemithorax.Over the past decade, interfacial plane blocks have gained prominence in regional anesthetic practices. Numerous interfascial blocks have been defined in recent years with the intention of providing effective sensory blockage in the target location by blocking the posterior-lateral or anterior branches of the spinal nerves alone or in multiples . It can The injection of local anesthetic into the interfascial plane between the serratus posterior superior muscle and the rhomboid minor muscle was first described by Takete et al.  for the The rhomboid minor muscle attaches to the scapula from the lateral side, and the continuity of the interfascial plane on the superficial serratus posterior to the subscapular region interrupts. These factors would have limited the success of Taketa's technique. However, applying more volume to the fascial planes with transverse and craniocaudal continuity, as we applied between the serratus posterior superior (SPS) muscle and intercostal muscles, provides a more extensive spread of LA and provides sensory blockade in larger areas.Both the demonstration of dye distribution in cadaveric examination and the dermatome analyses in the patients are significantly different and extensive when compared to other interfascial plane blocks applied to anatomically similar locations. The fact that SPSIP leads to an effective cutaneous block in the neck, shoulder, and hemithorax, even when administered alone, could make this new regional anesthetic approach widely utilized. As with ESPB and RIB, directing the needle towards a bone barrier will reduce the rate of needling-related complications such as pneumothorax. However, this region's anatomy should be fully understood to prepare for any potential complications.The area for the SPSIP block contains many anatomical structures that need to be identified for safety. The spinal accessory nerve (SAN) travels between the trapezius and rhomboid minor muscles, and local anesthetic can reach this plane . The SANSimilarly, the dorsal scapular artery (DSA) and the dorsal scapular nerve (DSN) course between the rhomboid minor and SPS muscle. DSN is the motor innervation of the rhomboid muscles, and its blockage may also lead to a winged scapula. Although we did not observe any complications in our patients, it is still theoretically possible.Our study has some limitations. Firstly, we were unable to determine the cephalic extension of the dye, as we did not dissect above the C7 vertebra. Secondarly, we were unable to thoroughly dissect the scapula in the cadaver to determine the subscapular extension of the dye and whether the lateral cutaneous branches or the intercostobrachial nerve was affected. In addition, we did not dissect the supraclavicular fossa and were, therefore, not able to assess the cervical and brachial plexus. Lastly, we did not use SPSIP block for acute postoperative pain or another indication of pain syndromes.Our limited preliminary data has shown that SPSIP, a newly defined interfascial plane block, can be used in acute and chronic pain relief. Further randomized controlled trials are needed to verify the exact role SPSIP may play in regional anesthesia and its comparison with different analgesic modalities in surgeries concerning the breast, thorax, and shoulder.