Maximum weight cycle packing in directed graphs, with application to kidney exchange programs

Centralized matching programs have been established in several countries to organize kidney exchanges between incompatible patient-donor pairs. At the heart of these programs are algorithms to solve kidney exchange problems, which can be modelled as cycle packing problems in a directed graph, involving cycles of length 2, 3, or even longer. Usually, the goal is to maximize the number of transplants, but sometimes the total benefit is maximized by considering the differences between suitable kidneys. These problems correspond to computing cycle packings of maximum size or maximum weight in directed graphs. Here we prove the APX-completeness of the problem of finding a maximum size exchange involving only 2-cycles and 3-cycles. We also present an approximation algorithm and an exact algorithm for the problem of finding a maximum weight exchange involving cycles of bounded length. The exact algorithm has been used to provide optimal solutions to real kidney exchange problems arising from the National Matching Scheme for Paired Donation run by NHS Blood and Transplant, and we describe practical experience based on this collaboration

A Holistic Assessment of the Reliability of Machine Learning Systems

As machine learning (ML) systems increasingly permeate high-stakes settings such as healthcare, transportation, military, and national security, concerns regarding their reliability have emerged. Despite notable progress, the performance of these systems can significantly diminish due to adversarial attacks or environmental changes, leading to overconfident predictions, failures to detect input faults, and an inability to generalize in unexpected scenarios. This paper proposes a holistic assessment methodology for the reliability of ML systems. Our framework evaluates five key properties: in-distribution accuracy, distribution-shift robustness, adversarial robustness, calibration, and out-of-distribution detection. A reliability score is also introduced and used to assess the overall system reliability. To provide insights into the performance of different algorithmic approaches, we identify and categorize state-of-the-art techniques, then evaluate a selection on real-world tasks using our proposed reliability metrics and reliability score. Our analysis of over 500 models reveals that designing for one metric does not necessarily constrain others but certain algorithmic techniques can improve reliability across multiple metrics simultaneously. This study contributes to a more comprehensive understanding of ML reliability and provides a roadmap for future research and development

3D Volumetric Modeling and Microvascular Reconstruction of Irradiated Lumbosacral Defects after Oncologic Resection

Background: Locoregional flaps are sufficient in most sacral reconstructions. However, large sacral defects due to malignancy necessitate a different reconstructive approach, with local flaps compromised by radiation and regional flaps inadequate for broad surface areas or substantial volume obliteration. In this report, we present our experience using free muscle transfer for volumetric reconstruction in such cases, and demonstrate 3D haptic models of the sacral defect to aid preoperative planning.Methods: Five consecutive patients with irradiated sacral defects secondary to oncologic resections were included, surface area ranging from 143-600cm2. Latissimus dorsi-based free flap sacral reconstruction was performed in each case, between 2005 and 2011. Where the superior gluteal artery was compromised, the subcostal artery was used as a recipient vessel. Microvascular technique, complications and outcomes are reported. The use of volumetric analysis and 3D printing is also demonstrated, with imaging data converted to 3D images suitable for 3D printing with Osirix software (Pixmeo, Geneva, Switzerland). An office-based, desktop 3D printer was used to print 3D models of sacral defects, used to demonstrate surface area and contour and produce a volumetric print of the dead space needed for flap obliteration. Results: The clinical series of latissimus dorsi free flap reconstructions is presented, with successful transfer in all cases, and adequate soft-tissue cover and volume obliteration achieved. The original use of the subcostal artery as a recipient vessel was successfully achieved. All wounds healed uneventfully. 3D printing is also demonstrated as a useful tool for 3D evaluation of volume and dead-space.Conclusion: Free flaps offer unique benefits in sacral reconstruction where local tissue is compromised by irradiation and tumor recurrence, and dead-space requires accurate volumetric reconstruction. We describe for the first time the use of the subcostal artery as a recipient in free flap sacral reconstruction. 3D printing of haptic bio-models is a rapidly evolving field with a substantial role in preoperative planning

Dynamic padding by retrofit airbags and knee bars. A study of Swedish mail delivery cars

Ostrom, M., Eriksson, A., Thorson, J., Romeo, D.J and Svensson, L., 1992. Dynamic padding by retrofit airbags and knee bars. A study of Swedish mail delivery cars. Safety Science, 15: 147-154.The present study demonstrates the feasibility of a retrofit driver airbag system and knee bars in passenger cars for mail delivery. The system was tested in field experiments, in rough road test, and in low and high speed barrier test. No faults of the system occurred and the crash tests revealed that the energy reducing capacity in frontal collisions was satisfactory. As airbags prevent injuries to non-belt-users, such as certain occupational drivers, we advocate a wider implementation of retrofit airbag systems. We also stress the importance of using seat belts in conjunction with airbags.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29859/1/0000207.pd

¿Se asocia el consumo de refrescos azucarados con la composición corporal? Estudio transversal en adolescentes españoles

Objectives: Published data about the association between the consumption of sweetened soft-drinks (SSD) and obesity in childhood are controversial and still inconsistent. In addition, data are lacking in the Spanish population. The purpose of this study was therefore, to explore the cross-sectional association between body composition- related parameters and SSD consumption in Spanish adolescents. Subjects and methods: A representative sample of 1,523 adolescents (768 boys and 755 girls), with complete dietary data as well as anthropometric measurements, were included in this study. Weight, height, waist circumferences, and 6 skinfolds were measured, and BMI and percentage body fat were calculated. From a 24h dietary recall the subjects were grouped in 3 groups according to their SSD consumption: 1) Non-consumers (0 g of SSD consumption); 2) Moderate consumption (< 336 g/day of SSD, equivalent to the average SSD portion size); and 3) High consumption (> 336 g/day of SSD). Results: 67% males and 75% females did not consume any SSD the day before the dietary recall interview. Males consumed more SSD than females. Regarding the association between SSD consumption and measures of obesity, no difference was observed between the three groups of SSD consumption in any of the anthropometric measurement, BMI or body fat. Conclusion: As no association was present between SSD consumption and obesity in our cross-sectional study we suggest that dietary patterns and habits as well as lifestyle factors such as physical activity should be present when examining cross-sectional or longitudinal relationships with obesity. Multidisciplinary intervention studies are crucial when trying to develop solutions against the increasing obesity epidemic.Objetivos: Los datos publicados sobre la asociación entre el consumo de refrescos azucarados (SSD) y la obesidad en la infancia son controvertidos y todavía inconsistentes. Además, estos datos son muy escasos en la población española. Por ello, el propósito de este estudio ha sido estudiar la asociación entre los parámetros relacionados con la composición corporal y el consumo de SSD en adolescentes españoles. Sujetos y métodos: Se ha realizado el estudio en una muestra de 1.523 adolescentes (768 chicos y 755 chicas) que tenían cumplimentados los datos dietéticos y los parámetros antropométricos (peso, altura, circunferencias de cintura, y 6 pliegues). Se calculó el IMC y el porcentaje de grasa corporal. La dieta ha sido calculada a partir de un recordatorio de 24h. Los sujetos fueron divididos en grupos dependiendo de la cantidad de SSD que consumían: 1) No consumidores (0 g de consumo SSD); 2) Consumo moderado (< 336 g/día de SSD, equivalente a una bebida al día de SSD); y 3) Consumo alto (> 336 g/día de SSD). Resultados: El 67% de los varones y el 75% de las mujeres indican no consumir este tipo de bebidas el día anterior a la encuesta. Los varones en general consumieron más SSD que las mujeres. En cuanto a la asociación entre consumo SSD y medidas antropométricas y de composición corporal, no se encontraron diferencias significativas entre los tres grupos de estudio en los parámetros antropométricos, IMC o grasa corporal. Conclusión: Dado que no se ha encontrado en este estudio ninguna asociación entre el consumo de SSD y la obesidad, sugerimos que los patrones y hábitos dietarios así como los factores del estilo de vida, y la actividad física, deberían tenerse en cuenta al examinar las relaciones transversales o longitudinales con la obesidad, y que los estudios de intervención multidisciplinar son cruciales cuando se trata de desarrollar soluciones contra el incremento de una epidemia como la obesidad.The AVENA study was supported by Spanish Ministry of Health (00/0015) and by grants from the Spanish Higher Sports Council (05/UPB32/01, 09/UPB31/03 and 13/UPB20/04), the Spanish Ministry of Education (AP2003-2128 and AP2004-2745), Coca-Cola, Panrico SA, Madaus SA and Procter & Gamble SA

Synthesis of layered silicon-graphene hetero-structures by wet jet milling for high capacity anodes in Li-ion batteries

While silicon-based negative electrode materials have been extensively studied, to develop high capacity lithium-ion batteries, implementing a large-scale production method that can be easily transferred to industy, has been a crucial challenge. Here, a scalable wet-jet milling method was developed to prepare a silicon-graphene hybrid material to be used as negative electrode in lithium-ion batteries. This synthesized composite, when used as an anode in lithium cells, demonstrated high Li ion storage capacity, long cycling stability and high-rate capability. In particular, the electrode exhibited a reversible discharge capacity exceeding 1763 mAh g-1 after 450 cycles with a capacity retention of 98% and a coulombic efficiency of 99.85% (with a current density of 358 mA g-1). This significantly supersedes the performance of a Si-dominant electrode structures. The capacity fade rate after 450 cycles was only 0.005% per cycle in the 0.05-1 V range. This superior electrochemical performance is ascribed to the highly layered, silicon-graphene porous structure, as investigated via focused ion beam in conjunction with scanning electron microscopy (FIB-SEM) tomography. The hybrid electrode could retain 89% of its porosity (under a current density of 358 mA g-1) after 200 cycles compared with only 35% in a Si-dominant electrode. Moreover, this morphology can not only accommodate the large volume strains from active silicon particles, but also maintains robust electrical connectivity. This confers faster transportation of electrons and ions with significant permeation of electrolyte within the electrode. Physicochemical characterisations were performed to further correlate the electrochemical performance with the microstructural dynamics. The excellent performance of the hybrid material along with the scalability of the synthesizing process is a step forward to realize high capacity/energy density lithium-ion batteries for multiple device applications

ANGPTL4 variants E40K and T266M are associated with lower fasting triglyceride levels in Non-Hispanic White Americans from the Look AHEAD Clinical Trial

<p>Abstract</p> <p>Background</p> <p>Elevated triglyceride levels are a risk factor for cardiovascular disease. Angiopoietin-like protein 4 (Angptl4) is a metabolic factor that raises plasma triglyceride levels by inhibiting lipoprotein lipase (LPL). In non-diabetic individuals, the <it>ANGPTL4 </it>coding variant E40K has been associated with lower plasma triglyceride levels while the T266M variant has been associated with more modest effects on triglyceride metabolism. The objective of this study was to determine whether ANGPTL4 E40K and T266M are associated with triglyceride levels in the setting of obesity and T2D, and whether modification of triglyceride levels by these genetic variants is altered by a lifestyle intervention designed to treat T2D.</p> <p>Methods</p> <p>The association of <it>ANGPTL4 </it>E40K and T266M with fasting triglyceride levels was investigated in 2,601 participants from the Look AHEAD Clinical Trial, all of whom had T2D and were at least overweight. Further, we tested for an interaction between genotype and treatment effects on triglyceride levels.</p> <p>Results</p> <p>Among non-Hispanic White Look AHEAD participants, <it>ANGPTL4 </it>K40 carriers had mean triglyceride levels of 1.61 ± 0.62 mmol/L, 0.33 mmol/L lower than E40 homozygotes (p = 0.001). Individuals homozygous for the minor M266 allele (MAF 30%) had triglyceride levels of 1.75 ± 0.58 mmol/L, 0.24 mmol/L lower than T266 homozygotes (p = 0.002). The association of the M266 with triglycerides remained significant even after removing K40 carriers from the analysis (p = 0.002). There was no interaction between the weight loss intervention and genotype on triglyceride levels.</p> <p>Conclusions</p> <p>This is the first study to demonstrate that the <it>ANGPTL4 </it>E40K and T266M variants are associated with lower triglyceride levels in the setting of T2D. In addition, our findings demonstrate that <it>ANGPTL4 </it>genotype status does not alter triglyceride response to a lifestyle intervention in the Look AHEAD study.</p

The effect of initial local anesthetic dose with continuous interscalene analgesia on postoperative pain and diaphragmatic function in patients undergoing arthroscopic shoulder surgery: a double-blind, randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Interscalene block (ISB) is commonly performed using 20-40 mL of local anesthetic. Spread to adjacent structures and consequent adverse effects including paralysis of the ipsilateral hemidiaphragm are frequent. Pain ratings, analgesic requirements, adverse events, satisfaction, function and diaphragmatic excursion were compared following interscalene block (ISB) with reduced initial bolus volumes.</p> <p>Methods</p> <p>Subjects undergoing arthroscopic rotator cuff repair were randomized to receive 5, 10, or 20 mL ropivacaine 0.75% for ISB in a double-blind fashion (N = 36). Continuous infusion with ropivacaine 0.2% was maintained for 48 h. Pain and diaphragmatic excursion were assessed before block and in the recovery unit.</p> <p>Results</p> <p>Pain ratings in the recovery room were generally less than 4 (0-10 NRS) for all treatment groups, but a statistically significant difference was noted between the 5 and 20 mL groups (NRS: 2.67 vs. 0.62 respectively; p = 0.04). Pain ratings and supplemental analgesic use were similar among the groups at 24 h, 48 h and 12 weeks. There were no differences in the quality of block for surgical anesthesia. Dyspnea was significantly greater in the 20 mL group (p = 0.041). Subjects with dyspnea had significant diaphragmatic impairment more frequently (Relative risk: 2.5; 95%CI: 1.3-4.8; p = 0.042). Increased contralateral diaphragmatic motion was measured in 29 of the 36 subjects. Physical shoulder function at 12 weeks improved over baseline in all groups (baseline mean SST: 6.3, SEM: 0.6; 95%CI: 5.1-7.5; 12 week mean SST: 8.2, SEM: 0.46; 95%CI: 7.3-9.2; p = 0.0035).</p> <p>Conclusions</p> <p>ISB provided reliable surgical analgesia with 5 mL, 10 mL or 20 mL ropivacaine (0.75%). The 20 mL volume was associated with increased complaints of dyspnea. The 5 mL volume was associated with statistically higher pain scores in the immediate postoperative period. Lower volumes resulted in a reduced incidence of dyspnea compared to 20 mL, however diaphragmatic impairment was not eliminated. Compensatory increases in contralateral diaphragmatic movement may explain tolerance for ipsilateral paresis.</p> <p>Trial Registration</p> <p>clinicaltrials.gov. identifier: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00672100">NCT00672100</a></p