Breaking the GaN material limits with nanoscale vertical polarisation super junction structures: A simulation analysis

This is the first report on the numerical analysis of the performance of nanoscale vertical superjunction structures based on impurity doping and an innovative approach that utilizes the polarisation properties inherent in III-V nitride semiconductors. Such nanoscale vertical polarisation super junction structures can be realized by employing a combination of epitaxial growth along the non-polar crystallographic axes of Wurtzite GaN and nanolithography-based processing techniques. Detailed numerical simulations clearly highlight the limitations of a doping based approach and the advantages of the proposed solution for breaking the unipolar one-dimensional material limits of GaN by orders of magnitude

Numerical modeling and experimental validation of passive microfluidic mixer designs for biological applications

The present work reports numerical simulation and experimental validation of novel designs of microfluidic mixers that can be employed for biological mixing applications. Numerical simulations involving various geometrical models were performed for design optimization. The effect of the presence of embedded obstacles was studied in detail, in order to understand the effect of channel occlusion on micromixing. The mixing performance of various channel designs was compared, and crossover in the mixing performance of the designs was observed in response to a change in the flow Reynolds number (Re). The improvement in micromixing efficiency was discussed in connection with the variations in local values of the Reynolds number and Dean number. It was observed that the presence of obstacles contributes to a significant increase in local Re in the vicinity of sharp-edged obstacles, thereby enhancing the efficiency of mixing. In addition, the local Dean number is observed to increase significantly inside spiral microfluidic designs. We validate the optimized microfluidic mixer designs by performing micromixing experiments and image analysis based on regions of interest along the length of the channels. Numerical predictions were observed to be in reasonable agreement with experimental results. Finally, we demonstrated the biological applicability of an optimized micromixer design for on-chip detection of calcium levels in blood serum. The passive mixing designs presented in this work are useful for chip-scale implementations of cell-drug biology, where some of the key cell signaling processes appear at second time scales

Building clinical trials capacity for tuberculosis drugs in high-burden countries

The long duration of TB therapy, the high prevalence of HIV coinfection, and the growing prevalence of drug-resistant TB underscore the urgent need for more effective treatments

Analysis of drain current saturation behaviour in GaN polarisation super junction HFETs

The magnitude of saturation current in a power device significantly impacts its short-circuit capability. In conjunction with the unprecedented miniaturisation that gallium nitride (GaN) offers, there is a compelling rationale to examine this critical parameter in GaN transistors for thermally stable and reliable power converter applications. This study presents a comprehensive analysis of the physical behaviour that yields intrinsically low drain current saturation in GaN polarisation super junction heterojunction field-effect transistors (PSJ HFETs). The analysis in this work has been performed using electrical characterisation data of conventional and PSJ HFETs, supported by physics-based two-dimensional device simulations. Insight is gained on the differing device architecture-dependent mechanisms that determine the magnitude of drain current density in both types of devices when biased in the saturation region

Safety and efficacy of botox injection in alleviating post-operative pain and improving quality of life in lower extremity limb lengthening and deformity correction

<p>Abstract</p> <p>Background</p> <p>Distraction osteogenesis is the standard treatment for the management of lower limb length discrepancy of more than 3 cm and bone loss secondary to congenital anomalies, trauma or infection. This technique consists of an osteotomy of the bone to be lengthened, application of an external fixator, followed by gradual and controlled distraction of the bone ends. Although limb lengthening using the Ilizarov distraction osteogenesis principle yields excellent results in most cases, the technique has numerous problems and is not well tolerated by many children. The objective of the current study is to determine if Botulinum Toxin A (BTX-A), which is known to possess both analgesic and paralytic actions, can be used to alleviate post-operative pain and improve the functional outcome of children undergoing distraction osteogenesis.</p> <p>Methods/Design</p> <p>The study design consists of a multi centre, randomized, double-blinded, placebo-controlled trial. Patients between ages 5–21 years requiring limb lengthening or deformity correction using distraction will be recruited from 6 different sites (Shriners Hospital for Children in Montreal, Honolulu, Philadelphia and Portland as well as DuPont Hospital for Children in Wilmington, Delaware and Hospital for Sick Children in Toronto, Ont). Approximately 150 subjects will be recruited over 2 years and will be randomized to either receive 10 units per Kg of BTX-A or normal saline (control group) intraoperatively following the surgery. Functional outcome effects will be assessed using pain scores, medication dosages, range of motion, flexibility, strength, mobility function and quality of life of the patient. IRB approval was obtained from all sites and adverse reactions will be monitored vigorously and reported to IRB, FDA and Health Canada.</p> <p>Discussion</p> <p>BTX-A injection has been widely used world wide with no major side effects reported. However, to the best of our knowledge, this is the first time BTX-A is being used under the context of limb lengthening and deformity correction.</p> <p>Trial Registration</p> <p>NCT00412035</p

Assessment of foot alignment and function for ambulatory children with cerebral palsy: Results of a modified Delphi technique consensus study

PURPOSE The purpose of this study was to establish consensus for the assessment of foot alignment and function in ambulatory children with cerebral palsy, using expert surgeon's opinion through a modified Delphi technique. METHODS The panel used a five-level Likert-type scale to record agreement or disagreement with 33 statements regarding the assessment of foot alignment and function. Consensus was defined as at least 80% of responses being in the highest or lowest of two of the five Likert-type ratings. General agreement was defined as 60%-79% falling into the highest or lowest two ratings. There was no agreement if neither threshold was reached. RESULTS Consensus was achieved for 25 (76%) statements, general agreement for 4 (12%) statements, and lack of consensus for 4 (12%) of the statements. There was consensus that the functional anatomy of the foot is best understood by dividing the foot into three segments and two columns. Consensus was achieved concerning descriptors of foot segmental alignment for both static and dynamic assessment. There was consensus that radiographs of the foot should be weight-bearing. There was general agreement that foot deformity in children with cerebral palsy can be classified into three levels based on soft tissue imbalance and skeletal malalignment. CONCLUSION The practices identified in this study can be used to establish best care guidelines, and the format used will be a template for future Delphi technique studies on clinical decision-making for the management of specific foot segmental malalignment patterns commonly seen in children with cerebral palsy. LEVEL OF EVIDENCE V

Distal femoral extension osteotomy and patellar tendon advancement or shortening in ambulatory children with cerebral palsy: A modified Delphi consensus study and literature review

PURPOSE In children with cerebral palsy, flexion deformities of the knee can be treated with a distal femoral extension osteotomy combined with either patellar tendon advancement or patellar tendon shortening. The purpose of this study was to establish a consensus through expert orthopedic opinion, using a modified Delphi process to describe the surgical indications for distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening. A literature review was also conducted to summarize the recent literature on distal femoral extension osteotomy and patellar tendon shortening/patellar tendon advancement. METHOD A group of 16 pediatric orthopedic surgeons, with more than 10 years of experience in the surgical management of children with cerebral palsy, was established. The group used a 5-level Likert-type scale to record agreement or disagreement with statements regarding distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening. Consensus for the surgical indications for distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening was achieved through a modified Delphi process. The literature review, summarized studies of clinical outcomes of distal femoral extension osteotomy/patellar tendon shortening/patellar tendon advancement, published between 2008 and 2022. RESULTS There was a high level of agreement with consensus for 31 out of 44 (70%) statements on distal femoral extension osteotomy. Agreement was lower for patellar tendon advancement/patellar tendon shortening with consensus reached for 8 of 21 (38%) of statements. The literature review included 25 studies which revealed variation in operative technique for distal femoral extension osteotomy, patellar tendon advancement, and patellar tendon shortening. Distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening were generally effective in correcting knee flexion deformities and extensor lag, but there was marked variation in outcomes and complication rates. CONCLUSION The results from this study will provide guidelines for surgeons who care for children with cerebral palsy and point to unresolved questions for further research. LEVEL OF EVIDENCE level V

Anterior distal femoral hemiepiphysiodesis in children with cerebral palsy: Establishing surgical indications and techniques using the modified Delphi method and literature review

PURPOSE The purpose of this study was to develop consensus for the surgical indications of anterior distal femur hemiepiphysiodesis in children with cerebral palsy using expert surgeon opinion through a modified Delphi technique. METHODS The panel used a 5-level Likert-type scale to record agreement or disagreement with 27 statements regarding anterior distal femur hemiepiphysiodesis. Consensus was defined as at least 80% of responses being in the highest or lowest 2 of the Likert-type ratings. General agreement was defined as 60%-79% falling into the highest or lowest 2 ratings. RESULTS For anterior distal femur hemiepiphysiodesis, 27 statements were surveyed: consensus or general agreement among the panelists was achieved for 22 of 27 statements (22/27, 82%) and 5 statements had no agreement (5/27, 18%). There was general consensus that anterior distal femur hemiepiphysiodesis is indicated for ambulatory children with cerebral palsy, with at least 2 years growth remaining, and smaller (<30 degrees) knee flexion contractures and for minimally ambulatory children to aid in standing/transfers. Consensus was achieved regarding the importance of close radiographic follow-up after screw insertion to identify or prevent secondary deformity. There was general agreement that percutaneous screws are preferred over anterior plates due to the pain and irritation associated with plates. Finally, it was agreed that anterior distal femur hemiepiphysiodesis was not indicated in the absence of a knee flexion contracture. CONCLUSION Anterior distal femur hemiepiphysiodesis can be used to treat fixed knee flexion contractures in the setting of crouch gait, but other associated lever arm dysfunctions must be addressed by single-event multilevel surgery. LEVEL OF EVIDENCE V

Finding consensus for hamstring surgery in ambulatory children with cerebral palsy using the Delphi method

PURPOSE There is marked variation in indications and techniques for hamstring surgery in children with cerebral palsy. There is particular uncertainty regarding the indications for hamstring transfer compared to traditional hamstring lengthening. The purpose of this study was for an international panel of experts to use the Delphi method to establish consensus indications for hamstring surgery in ambulatory children with cerebral palsy. METHODS The panel used a five-level Likert-type scale to record agreement or disagreement with statements regarding hamstring surgery, including surgical indications and techniques, post-operative care, and outcome measures. Consensus was defined as at least 80% of responses being in the highest or lowest two of the five Likert-type ratings. General agreement was defined as 60%-79% falling into the highest or lowest two ratings. There was no agreement if neither of these thresholds was reached. RESULTS The panel reached consensus or general agreement for 38 (84%) of 45 statements regarding hamstring surgery. The panel noted the importance of assessing pelvic tilt during gait when considering hamstring surgery, and also that lateral hamstring lengthening is rarely needed, particularly at the index surgery. They noted that repeat hamstring lengthening often has poor outcomes. The panel was divided regarding hamstring transfer surgery, with only half performing such surgery. CONCLUSION The results of this study can help pediatric orthopedic surgeons optimize decision-making in their choice and practice of hamstring surgery for ambulatory children with cerebral palsy. This has the potential to reduce practice variation and significantly improve outcomes for ambulatory children with cerebral palsy. LEVEL OF EVIDENCE level V