Self-expanding metallic stent for refractory pancreatic duct stricture in chronic pancreatitis: A prospective follow-up study.

BACKGROUND AND AIMS: In chronic pancreatitis, fully covered self-expanding metal stents (FCSEMS) are used to treat refractory pancreatic duct strictures. However, the FCSEMS design, effectiveness, safety, optimal stent indwelling time and patient selection remain unclear. This study aimed at evaluating technical success, clinical success and adverse events with FCSEMS in patients with symptomatic pancreatic duct stricture. METHODS: The prospective study was conducted between May 2017 and May 2021 at a tertiary care center for chronic pancreatitis with refractory pancreatic duct stricture using controlled radial expansion (CRE) endoscopic retrograde cholangiopancreatography (ERCP) with FCSEMS (Niti-S, Bumpy stent, Taewoong Medical, Gimpo-Si, South Korea). RESULTS: During the study period, a total of 11 patients underwent ERCP with FCSEMS for refractory pancreatic duct stricture. The mean age (± standard deviation, [SD]) was 32.36 ± 10.98 years and nine patients (81%) were male. Technical and clinical success rates were 100% and 90.9%, respectively. All patients had a history of prior pancreatic endotherapy. The median (inter quartile range, [IQR]) stent indwell time was seven (6-10) months. The median visual analogue scale (VAS) pain score pre and post-FCSEMS was 8 (5-8) and 1 (0-2), respectively (p-value 0.003). Median (IQR) follow-up after stent removal was 48 (40-60) months. One patient (9%) developed de novo main pancreatic duct (MPD) stricture, which was asymptomatic. None of the patients had cholangitis, pancreatitis, perforation, proximal migration or stent fracture. CONCLUSION: The FCSEMS treatment appears to be safe, feasible and possibly an effective option for patients who have not responded to endoscopic plastic stenting.

Toward High Conversion Efficiency of Thermoelectric Modules through Synergistical Optimization of Layered Materials.

Waste-heat electricity generation using high-efficiency solid-state conversion technology can significantly decrease dependence on fossil fuels. Here, a synergistical optimization of layered half-Heusler (hH) materials and module to improve thermoelectric conversion efficiency is reported. This is realized by manufacturing multiple thermoelectric materials with major compositional variations and temperature-gradient-coupled carrier distribution by one-step spark plasma sintering. This strategy provides a solution to overcome the intrinsic concomitants of the conventional segmented architecture that only considers the matching of the figure of merit (zT) with the temperature gradient. The current design is dedicated to temperature-gradient-coupled resistivity and compatibility matching, optimum zT matching, and reducing contact resistance sources. By enhancing the quality factor of the materials by Sb-vapor-pressure-induced annealing, a superior zT of 1.47 at 973 K is achieved for (Nb, Hf)FeSb hH alloys. Along with the low-temperature high-zT hH alloys of (Nb, Ta, Ti, V)FeSb, the single stage layered hH modules are developed with efficiencies of ≈15.2% and ≈13.5% for the single-leg and unicouple thermoelectric modules, respectively, under ΔT of 670 K. Therefore, this work has a transformative impact on the design and development of next-generation thermoelectric generators for any thermoelectric material families.

A Systematic Review of Risk Factors for Hepatitis C Virus Infection Among Low-Risk Population in India.

Background: Identification of risk factors for hepatitis C virus (HCV) transmission will help in targeted screening of people who are at risk for HCV. Method: Indian studies, published between January 1989 and June 2020, were systematically reviewed to identify the relevant studies. We searched electronic databases including PubMed/Medline, Embase, Scopus, and Google scholar to identify the original data published in English language. The full-text studies, published in any form, which reported data on risk factors for HCV transmission among low-risk population were selected. The studies which exclusively included high-risk groups were excluded. Results: Data were extracted from 31,176 participants included in 25 studies (median [range] 40 [7-20,113). The participants were HCV infected patients who visited the hospital (n = 10), community population (n = 6), pregnant women (n = 5), blood donors (n = 2), people with diabetes mellitus (n = 1), army recruits (n = 1), or slum dwellers (n = 1). These studies provided data on blood transfusion, use of unsafe injections, minor or major surgery, unsafe dental procedures, tattooing, body piercing, obstetrical procedures, unsafe shaving, intravenous drug use, and unsafe sexual practices as risk factors for HCV transmission. Conclusion: Unsafe injections, body piercing, unsafe dental procedure, unsafe shaving, and tattooing were identified as major risk factors for reported by HCV population participants.More data are needed to identify the risk factors for HCV in Indian population. Risk-factor-targeted screening may increase the yield and reduce the cost of HCV screening in India.

Serological Immune Response Following ChAdOx1 nCoV-19 Vaccine (Covishield®) in Patients with Liver Cirrhosis.

Introduction: Data are limited on antibody response to the ChAdOx1 nCoV-19 vaccine (AZD1222; Covishield®) in cirrhosis. We studied the antibody response following two doses of the ChAdOx1 vaccine, given 4−12 weeks apart, in cirrhosis. Methods: Prospectively enrolled, 131 participants (71% males; age 50 (43−58); alcohol-related etiology 14, hepatitis B 33, hepatitis C 46, cryptogenic 21, autoimmune 9, others 8; Child−Turcott−Pugh class A/B/C 52/63/16). According to dose intervals, the participants were grouped as ≤6 weeks (group I), 7−12 weeks (group II), and 13−36 weeks (group III). Blood specimens collected at ≥4 weeks after the second dose were tested for anti-spike antibody titre (ASAb; positive ≥ 0.80 U/mL) and neutralizing antibody (NAb; positive ≥20% neutralization) using Elecsys Anti-SARS-CoV-2 S (Roche) and SARS-CoV-2 NAb ELISA Kit (Invitrogen), respectively. Data are expressed as number (proportion) and median (interquartile range) and compared using non-parametric tests. Results: Overall, 99.2% and 84% patients developed ASAb (titre 5440 (1719−9980 U/mL)) and NAb (92 (49.1−97.6%)), respectively. When comparing between the study groups, the ASAb titres were significantly higher in group II than in group I (2613 (310−7518) versus 6365 (2968−9463), p = 0.027) but were comparable between group II and III (6365 (2968−9463) versus 5267 (1739−11,653), p = 0.999). Similarly, NAb was higher in group II than in group I (95.5 (57.6−98.0) versus 45.9 (15.4−92.0); p < 0.001), but not between the groups II and III (95.5 (57.6−98.0) versus 92.4 (73.8−97.5); p = 0.386). Conclusion: Covishield® induces high titres of ASAb and NAb in cirrhosis. A higher titre is achieved if two doses are given at an interval of more than six weeks.

Antibody Response to ChAdOx1 nCoV-19 (AZD1222) Vaccine in Kidney Transplant Recipients.

Kidney transplant recipients (KTRs) are at a much higher risk of complications and death following COVID-19 and are poor vaccine responders. The data are limited on the immune response to Covishield® in KTRs. We prospectively recruited a cohort of 67 KTRs aged >18 between April 2021 and December 2021. Each participant was given two intramuscular doses of Covishield®, each of 0.5 mL, at an interval of 12 weeks. A blood specimen of 5.0 mL was collected from each participant at two points within a few days before administering the first dose of the vaccine and at any time between 4−12 weeks after administering the second dose. The sera were tested for anti-RBD antibody (ARAb) titre and neutralising antibody (NAb). An ACE2 competition assay was used as a proxy for virus neutralization. According to the prior COVID-19 infection, participants were grouped as (i) group A: prior symptomatic COVID-19 infection, (ii) group B: prior asymptomatic COVID-19 infection as evidenced by detectable ARAb in the prevaccination specimen, (iii) Group C: no prior infection with COVID-19, (iv) group D: Unclassified, i.e., participants had no symptoms suggestive of COVID-19, but their prevaccination specimen was not available for ARAb testing before vaccination. Fifty of sixty-seven participants (74.6%) provided paired specimens (group A 14, group B 27, and group C 9) and 17 participants (25.4%) provided only postvaccination specimens (group D). In the overall cohort (n = 67), 91% and 77.6% of participants developed ARAb and NAb, respectively. Their ARAb titre and NAb proportion were 2927 (520−7124) U/mL and 87.9 (24.4−93.2) %, respectively. Their median ARAb titre increased 65.6 folds, from 38.2 U/mL to 3137 U/mL. Similarly, the proportion of participants with NAb increased from 56% to 86%, and the NAb proportion raised 2.7 folds, from 23% to 91%. A comparison of vaccine response between the study groups showed that all those with or without prior COVID-19 infection showed a significant rise in ARAb titre (p < 0.05) and NAb proportion (p < 0.05) after the two doses of vaccine administration. The median value of folds rise in anti-RBD and NAb between groups A and B were comparable. Hence, ARAb is present in more than 3/4th of KTRs before the ChAdOx1 vaccine in India. The titer of ARAb and the proportion of NAb significantly increased after the two doses of the ChAdOx1 vaccine in KTRs.

Vanishing Bile Duct Syndrome Secondary to Hodgkin Lymphoma in a Child.

Vanishing bile duct syndrome (VBDS) is a condition resulting from progressive destruction and loss of intrahepatic bile ducts leading to cholestasis, biliary cirrhosis, and liver failure. It occurs secondary to various pathologic conditions like autoimmune diseases, graft versus host disease, drug reactions, and as a paraneoplastic syndrome in malignancies. We here described a 9-year-old girl who presented with cervical lymphadenopathy and jaundice. This child was diagnosed as a case of Hodgkin lymphoma. All other causes of cholestasis were ruled out by appropriate investigations (particularly autoimmune, metabolic, infections, and drug-induced possibilities). On liver biopsy, her diagnosis was established as VBDS. In view of hepatic dysfunction, alternative chemotherapy with dexamethasone, high-dose cytarabine, and cisplatin (DHAP) was given, and she was started on hepatoprotective measures with ursodeoxycholic acid. Hepatic function gradually improved after the initiation of chemotherapy. VBDS is considered a dismal paraneoplastic syndrome with a high-case fatality. This case report highlights the importance of early recognition and initiation of appropriate full-dose chemotherapy as the only way to achieve complete resolution of VBDS.

Conformal High-Power-Density Half-Heusler Thermoelectric Modules: A Pathway toward Practical Power Generators.

Thermoelectric generators (TEGs) exploiting the Seebeck effect provide a promising solution for waste heat recovery. Among the large number of thermoelectric (TE) materials, half-Heusler (hH) alloys are leading candidates for medium- to high-temperature power generation applications. However, the fundamental challenge in this field has been inhomogeneous material properties at large wafer diameters, insufficient power output from the modules, and rigid form factors of TE modules. This has restricted the transition of TEGs in practical applications for over three decades. Here, we successfully demonstrate large diameter wafers with uniform TE properties, high-power conformal hH TE modules for high-temperature application, and their direct integration on flue gas platforms, such as cylindrical tubes, to form large area flexible TEGs. This new conformal architecture design provides a breakthrough toward medium-/high-temperature TEGs over the conventional BiTe- and polymer-based flexible TEG design. A variable fill factor and greater flexibility due to the conformal design result in higher device performance as compared to conventional rigid TEG devices. Modules with 72-couple hH legs exhibit a device high-power-density of 3.13 W cm-2 and a total output power of 56.6 W under a temperature difference of 570 °C. These results provide a promising pathway toward widespread utilization of thermoelectric technology into the waste heat recovery application and will have a significant impact on the development of practical thermal to electrical converters.

An approach to giant neonatal hydrocolpos with normally sited anus - Diagnosis and management including a novel one stage operation.

INTRODUCTION: Giant non cloacal neonatal hydrocolpos is a rare entity where early recognition of the underlying cause and drainage of the distended vagina is paramount. Conventionally, immediate management has been by abdominal tube vaginostomy or, in urogenital sinus by vaginal clean intermittent catheterisation (CIC). Though effective in providing temporary relief, the abdominal tube vaginostomy is replete with complications, making it imperative to search for alternatives. Here we describe our method of emergent and definitive management of these children, where definitive repair, depending on the aetiology, has been made possible in a single stage. MATERIAL AND METHODS: Seven girls who presented primarily or with history of giant non cloacal neonatal hydrocolpos at two tertiary care centres from January 2013 to March 2021 were studied retrospectively. None had imperforate anus or a bulging hymenal membrane. Four had high vaginal atresia (VA) and three had Urogenital sinus (UGS), one with high confluence. Four girls (2 VA, 2 UGS) presented to us as neonates and were managed by emergency drainage procedures other than tube vaginostomy: CIC in one (low UGS) and a novel abdominoperineal U flap vaginoplasty in three (2 VA, 1 high confluence UGS) which was also the definitive procedure. This procedure involved fashioning an inferiorly based inverted U flap from the posterior wall of distended vagina which is tubularised and flipped down by an abdomino-perineal procedure. The girl with a low UGS later underwent a perineal procedure. Three presented elsewhere as neonates (2 VA, 1 UGS) and had abdominal tube vaginostomy as the emergency drainage procedure. This was complicated by tube dislodgement and pyocolpos till successful reconstruction was performed by us. Successful reconstructions included the abdominoperineal U flap vaginoplasty in one (VA) and a perineal procedure in another (low UGS). One girl with high VA had an inflamed vagina after tube vaginostomy, precluding the U flap vaginoplasty, and underwent abdominal vaginal mobilisation and pull through complicated by partial vaginal necrosis with septic complications. RESULTS: Reconstruction resulted in a patent and a good calibre neo-vagina in all at a mean follow up of 48 months. CONCLUSION: Immediate management of giant non cloacal neonatal hydrocolpos may either be vaginal CIC or a surgical procedure. The abdomino-perineal U flap vaginoplasty is a one stage neonatal procedure that provides effective drainage and forms a definitive neo-vagina. An abdominal tube vaginostomy can be avoided except where neonatal surgical expertise is unavailable.

Real world safety of bevacizumab in cancer patients: A systematic literature review of case reports.

BACKGROUND: Real-world safety of bevacizumab in cancer patients is limited. OBJECTIVE: To review the adverse drug reactions (ADRs) due to bevacizumab in cancer patients, in published case reports. METHODS: PubMed was searched; case reports of patients with any type of cancer, administered with bevacizumab (monotherapy/combination) and reported ADRs were included. Causality of ADRs was presented as reported in individual papers. ADRs were classified using the information in the USFDA-approved prescribing information (PI) of bevacizumab as 'Serious', 'Common', and 'Post-marketing surveillance' ADRs; ADRs not mentioned in the bevacizumab PI were termed as 'Non-label ADRs'. RESULTS: A total of 130 published papers comprising 154 cases from 22 different countries were included. Most papers (102/130; 78.46%) had moderate methodological quality. Age range of patients was 9-77 years. Off-label use of bevacizumab was found in 34/154 cases (22.08%). Ninety-six unique ADRs were found among 154 ADRs; most reported ADRs affected circulatory, digestive, and respiratory systems (33, 32, and 26 cases respectively). Most commonly reported ADRs were posterior leukoencephalopathy, fistulae, and gastrointestinal perforation (17, 17, and 16 cases respectively). Twenty-eight unique non-label ADRs (29.17%) were found. CONCLUSION: Bevacizumab is associated with more ADRs in the real world among cancer patients than those reported during clinical trials.

Management and outcome in dehisced exstrophy with a simplified bladder re-closure and further reconstruction.

INTRODUCTION: The traditionally accepted method of bladder re closure in dehisced exstrophy involves osteotomy assisted pubic bone approximation (PBA). Continent voluntary voiding is achieved in a small proportion of children sometimes after many operative procedures. We propose a simple yet reliable method of repair of the dehisced bladder using Rectus abdominis muscle flap (RAM) instead of PBA to bridge the inter-pubic gap, followed by concomitant or subsequent bladder augmentation (BA). AIM: The aim of this study is to assess the outcome of dehisced exstrophy, using a RAM flap assisted redo closure (without PBA) with concomitant or subsequent further reconstruction. MATERIALS AND METHODS: This is a retrospective analysis of children who presented with dehisced exstrophy after repair in other institutions and who have undergone redo repair using RAM flap in two tertiary care centers from 2001 to 2019. The outcome of the redo closure and subsequent or concomitant further reconstruction as regards dryness, stability of the upper tracts and resolution of vesico ureteric reflux (VUR) was studied. RESULTS: Fifty five children (34 boys) underwent redo exstrophy repair for dehisced exstrophy using the RAM flap. Epispadias repair was performed concomitantly in 31 boys. In 26 children (group1) of mean age 12 months further surgery was deferred while in 29 children (group 2) of mean age 69 months underwent concomitant BA. Nine group 1 children underwent BA subsequently. Ureteric reimplantation was done at the time of BA in 54 ureters, 40 into the bladder plate and rest into the bowel segment of BA. 22 ureters were not reimplanted. Bladder neck surgery including 18 bladder neck closure and Mitrofanoff port for Clean Intermittent catheterization (CIC) were done along with BA. The RAM assisted bladder closure was event free and none needed redo operation. 35/38 augmented children are dry on Mitrofanoff CIC and one unaugmented boy voids normally. The upper tracts remain stable on ultrasound and VUR has resolved in 67/76 ureters. At current follow up, after a mean period of 53 months eGFR was normal in all except 3 who had initially presented with severe hydro uretero nephrosis. CONCLUSION: We present a simple and reliable method of repair of dehisced exstrophy using RAM flap with the feasibility of concomitant BA. Dryness was achieved with stable upper tracts in 36/39 children, 27 of them with a single reconstructive attempt.

3D printed graphene-based self-powered strain sensors for smart tires in autonomous vehicles.

The transition of autonomous vehicles into fleets requires an advanced control system design that relies on continuous feedback from the tires. Smart tires enable continuous monitoring of dynamic parameters by combining strain sensing with traditional tire functions. Here, we provide breakthrough in this direction by demonstrating tire-integrated system that combines direct mask-less 3D printed strain gauges, flexible piezoelectric energy harvester for powering the sensors and secure wireless data transfer electronics, and machine learning for predictive data analysis. Ink of graphene based material was designed to directly print strain sensor for measuring tire-road interactions under varying driving speeds, normal load, and tire pressure. A secure wireless data transfer hardware powered by a piezoelectric patch is implemented to demonstrate self-powered sensing and wireless communication capability. Combined, this study significantly advances the design and fabrication of cost-effective smart tires by demonstrating practical self-powered wireless strain sensing capability.

Urethro vaginal injuries associated with pelvic fracture - A spectrum of clinical presentation and management.

BACKGROUND: Blunt trauma to the paediatric pelvis is associated with urethral rupture, sometimes even without a bony fracture. While such rupture of the male urethra has received considerable mention, female urethral injury is both less common and has received less attention. OBJECTIVE: We describe 4 cases of urethro vaginal injury associated with pelvic fracture, its varied presentations and the modalities employed in its management. PATIENTS AND METHODS: A retrospective study was done to identify 4 patients who presented to our institution between 2007 and 2018. All 4 girls suffered a loss of a urethral segment ranging from the distal urethra (n = 2) to complete urethral loss (n = 2) and rupture of the bladder neck in one. All 4 girls also had associated vaginal injury resulting in varied clinical presentation including total urinary incontinence, urocolpos, vaginal voiding via an acquired hypospadias and urinary retention with late onset haematocolpos. All were managed initially with SPC and three of them underwent urethral substitution with Monti ileal tube in two and vestibular mucosal flap in one. The hypospadiac neo-meatus was continent and was left alone. The ruptured vagina was repaired by rectus muscle interposition, direct suturing, posterior vaginal U flap or colonic patch. An appendicular Mitrofanoff was added for safety in 2 girls. RESULTS: Follow up was done till June 2019 (range 1-12 years). All patients voided satisfactorily and were fully continent. Normal menstrual function was present in the 3 post pubertal children. CONCLUSION: A traumatic force capable of causing urethral injury may often result in associated vaginal injury and should not be overlooked. Thus urinary retention is not the only presentation of urethral injury in girls. Fistulation to the vagina may result in continent or incontinent vaginal voiding if the vagina has not been transected and urocolpos/haematocolpos in those with vaginal transection. Various modalities maybe employed to maintain continuity of the urethra and vagina including use of bowel and local flaps.

High-Performance Thermoelectric Generators for Field Deployments.

Thermoelectric power generation is a reliable energy harvesting technique for directly converting heat into electricity. Recent studies have reported the thermal-to-electrical energy conversion efficiency of thermoelectric generators (TEGs) up to 11% under laboratory settings. However, the practical efficiency of TEGs deployed under real environments is still not more than a few percent. In this study, we provide fundamental insight on the operation of TEGs in realistic environments by illustrating the combinatory effect of thermoelectric material properties, device boundary conditions, and environmental thermal resistivity on TEG performance in conjunction with the module parameters. Using numerical and experimental studies, we demonstrate the existence of a critical heat transfer coefficient that dramatically affects the design and performance of TEGs. Results provide a set of concrete design criteria for developing efficient TEGs that meet the metrics for field deployments. High-performance TEGs demonstrated in this study generated up to 28% higher power and 162% higher power per unit mass of thermoelectric materials as compared to the commercial module deployed for low-grade waste heat recovery. This advancement in understanding the TEG operation will have a transformative impact on the development of scalable thermal energy harvesters and in realizing their practical targets for efficiency, power density, and total output power.

High Power Density Body Heat Energy Harvesting.

Thermoelectric generators (TEGs) can convert body heat into electricity, thereby providing a continuous power source for wearable and implantable devices. For wearables, the low fill factor (area occupied by legs over the TEG base area) TEG modules are relevant as they provide large thermal gradient across the legs and require less material, which reduces the cost and weight. However, TEGs with a fill factor below 15% suffer from reduced mechanical robustness; consequently, commercial modules are usually fabricated with a fill factor in the range of 25-50%. In this study, TEG modules with a low and high fill factor are demonstrated and their performance is compared in harvesting body heat. Fabricated modules demonstrate ∼80% output power enhancement as compared to commercially available designs, resulting in high power density of up to 35 µW/cm2 in a steady state. This enhanced power is achieved by using two-third less thermoelectric materials in comparison to commercial modules. These results will advance the ongoing development of wearable devices by providing a consistent high specific power density source.

Ultra-high performance wearable thermoelectric coolers with less materials.

Thermoelectric coolers are attracting significant attention for replacing age-old cooling and refrigeration devices. Localized cooling by wearable thermoelectric coolers will decrease the usage of traditional systems, thereby reducing global warming and providing savings on energy costs. Since human skin as well as ambient air is a poor conductor of heat, wearable thermoelectric coolers operate under huge thermally resistive environment. The external thermal resistances greatly influence thermoelectric material behavior, device design, and device performance, which presents a fundamental challenge in achieving high efficiency for on-body applications. Here, we examine the combined effect of heat source/sink thermal resistances and thermoelectric material properties on thermoelectric cooler performance. Efficient thermoelectric coolers demonstrated here can cool the human skin up to 8.2 °C below the ambient temperature (170% higher cooling than commercial modules). Cost-benefit analysis shows that cooling over material volume for our optimized thermoelectric cooler is 500% higher than that of the commercial modules.

A Review on Low-Grade Thermal Energy Harvesting: Materials, Methods and Devices.

Combined rejected and naturally available heat constitute an enormous energy resource that remains mostly untapped. Thermal energy harvesting can provide a cost-effective and reliable way to convert available heat into mechanical motion or electricity. This extensive review analyzes the literature covering broad topical areas under solid-state low temperature thermal energy harvesting. These topics include thermoelectricity, pyroelectricity, thermomagneticity, and thermoelasticity. For each topical area, a detailed discussion is provided comprising of basic physics, working principle, performance characteristics, state-of-the-art materials, and current generation devices. Technical advancements reported in the literature are utilized to analyze the performance, identify the challenges, and provide guidance for material and mechanism selection. The review provides a detailed analysis of advantages and disadvantages of each energy harvesting mechanism, which will provide guidance towards designing a hybrid thermal energy harvester that can overcome various limitations of the individual mechanism.

Self-Powered Temperature-Mapping Sensors Based on Thermo-Magneto-Electric Generator.

We demonstrate a thermo-magneto-electric generator (TMEG) based on second-order phase transition of soft magnetic materials that provides a promising pathway for scavenging low-grade heat. It takes advantage of the cyclic magnetic forces of attraction and repulsion arising through ferromagnetic-to-paramagnetic phase transition to create mechanical vibrations that are converted into electricity through piezoelectric benders. To enhance the mechanical vibration frequency and thereby the output power of the TMEG, we utilize the nonlinear behavior of piezoelectric cantilevers and enhanced thermal transport through silver (Ag) nanoparticles (NPs) applied on the surface of a soft magnet. This results in large enhancement of the oscillation frequency reaching up to 9 Hz (300% higher compared with that of the prior literature). Optimization of the piezoelectric beam and Ag NP distribution resulted in the realization of nonlinear TMEGs that can generate a high output power of 80 µW across the load resistance of 0.91 MΩ, which is 2200% higher compared with that of the linear TMEG. Using a nonlinear TMEG, we fabricated and evaluated self-powered temperature-mapping sensors for monitoring the thermal variations across the surface. Combined, our results demonstrate that nonlinear TMEGs can provide additional functionality including temperature monitoring, thermal mapping, and powering sensor nodes.

Laparoscopic cholangiogram in biliary atresia: a refinement in the gallbladder hitch technique.

INTRODUCTION: The study describes a refinement in the gallbladder hitch stitch and assesses the value of the laparoscopic cholangiogram in children with suspected biliary atresia. METHODS: Twenty children with neonatal jaundice and no drainage as shown on the HIDA scan underwent a diagnostic laparoscopy through an umbilical 5 mm port. A 3 mm laparoscopic needle holder inserted through a 3.5 mm port to the left of the umbilicus was used to hitch the gallbladder to the abdominal wall. The stylet of a large bore 16F IV cannula then was used to penetrate the gallbladder to perform the laparoscopic cholangiogram. RESULTS: There was no need for conversion in all 20 children by this technique. Patent biliary anatomy was demonstrated in 11 children (11/20). These children had no further procedures. In 3 (3/20) children, the common bile duct was demonstrated, while the hepatic ducts were not. These children had a laparotomy for Kasai procedure after an open cholangiogram with a vascular bulldog clamp on the CBD confirmed the finding. Six (6/20) had no demonstrable patency; 3 had it confirmed when the abdomen was opened for the Kasai procedure; only those proceeding to Kasai portoenterostomy (3 hepatic duct atresia, 3 complete biliary atresias) had an epidural catheter placed by the anesthetist. The remaining 3 had no further procedure performed due to the advanced nodular liver with ascites and evidence of portal hypertension. CONCLUSION: The findings of laparoscopic cholangiogram were confirmed in all six children who underwent laparotomy for Kasai procedure. The laparoscopic cholangiogram using gallbladder hitch reliably demonstrates a patent biliary system (11/11) and was valuable in avoiding further invasive procedures in 70% (14/20) of babies.

Optimization of segmented thermoelectric generator using Taguchi and ANOVA techniques.

Recent studies have demonstrated that segmented thermoelectric generators (TEGs) can operate over large thermal gradient and thus provide better performance (reported efficiency up to 11%) as compared to traditional TEGs, comprising of single thermoelectric (TE) material. However, segmented TEGs are still in early stages of development due to the inherent complexity in their design optimization and manufacturability. In this study, we demonstrate physics based numerical techniques along with Analysis of variance (ANOVA) and Taguchi optimization method for optimizing the performance of segmented TEGs. We have considered comprehensive set of design parameters, such as geometrical dimensions of p-n legs, height of segmentation, hot-side temperature, and load resistance, in order to optimize output power and efficiency of segmented TEGs. Using the state-of-the-art TE material properties and appropriate statistical tools, we provide near-optimum TEG configuration with only 25 experiments as compared to 3125 experiments needed by the conventional optimization methods. The effect of environmental factors on the optimization of segmented TEGs is also studied. Taguchi results are validated against the results obtained using traditional full factorial optimization technique and a TEG configuration for simultaneous optimization of power and efficiency is obtained.

Thermo-Magneto-Electric Generator Arrays for Active Heat Recovery System.

Continued emphasis on development of thermal cooling systems is being placed that can cycle low grade heat. Examples include solar powered unmanned aerial vehicles (UAVs) and data storage servers. The power efficiency of solar module degrades at elevated temperature, thereby, necessitating the need for heat extraction system. Similarly, data centres in wireless computing system are facing increasing efficiency challenges due to high power consumption associated with managing the waste heat. We provide breakthrough in addressing these problems by developing thermo-magneto-electric generator (TMEG) arrays, composed of soft magnet and piezoelectric polyvinylidene difluoride (PVDF) cantilever. TMEG can serve dual role of extracting the waste heat and converting it into useable electricity. Near room temperature second-order magnetic phase transition in soft magnetic material, gadolinium, was employed to obtain mechanical vibrations on the PVDF cantilever under small thermal gradient. TMEGs were shown to achieve high vibration frequency at small temperature gradients, thereby, demonstrating effective heat transfer.