Optimization of pulsed thermoelectric materials using simulated annealing and non-linear finite elements

[EN] The objective of this work is to determine the optimal shape, gains and duration of an electric pulse applied to a Peltier cell, together with the length of the thermoelectric to maximize cooling while min- imizing electric consumption. For this purpose, a fully coupled, multiphysics, dynamic finite-element model, which solves for the thermal, electric and mechanical fields is used. Because of the demanding computing requirements of the optimization process, a special mesh is designed and a convergence anal- ysis is carried out before using the multiphysics model. The highly non-linear optimization is done by simulated annealing, a heuristic algorithm in the Markov chain Monte-Carlo family. A preliminary para- metric investigation is presented, analyzing the impact of some of the parameters. The results of this pre- liminary analysis help to understand the effect of the different shapes in the evolution of the cold face temperature. Some of these results are expected and have already been discussed elsewhere, but others can only be explained after further analysis and a full system modeling. Pulse optimization is multiobjec- tive and multiparametric, i.e., it can consider several targets such as maximizing the cooling temperature, the cooling duration or others. The trade-offs between the different targets are studied. In all cases, stres- ses inside the thermoelement are examined at all points, and the pulses must meet the restriction that an equivalent stress is not above the allowable value.This research was partially supported by the grants, Haut-de-France Region (CR Picardie, 120-2015-RDISTRUCT-000010), EU funding (FEDER, RDISTRUCT-000010) for Chaire-de-Mecanique, and Spanish Ministry of Economy and Competitiveness grant CGL2014-59841-P. These supports are gratefully acknowledgedMoreno-Navarro, P.; Pérez-Aparicio, JL.; Gómez-Hernández, JJ. (2017). Optimization of pulsed thermoelectric materials using simulated annealing and non-linear finite elements. Applied Thermal Engineering. 120:603-613. https://doi.org/10.1016/j.applthermaleng.2017.04.036S60361312

Weighted sum optimization for combined thermoelectric geometry and electric pulse using finite elements

[EN] Thermoelectric materials assembled in Peltier cells are an increasingly widespread option for generating electricity from residual sources and refrigeration, even at the nanoscale. These cells can cool below the nominal temperatures with an electric pulse, during short periods and for applications such as laser devices or microchips. The present article uses heuristic algorithms to improve the response of a Peltier cell by concurrently optimizing the pulse and geometry of its thermoelements. The study is based on the Finite Element method, handling full coupling and dynamics of the thermal, electric, and mechanical fields and temperature dependency of the material properties. The optimization algorithm is Simulated Annealing, capable of discarding local minima to reach robust results and permitting set limiting factors such as the maximum stress. The main novelty lies in multilayered geometries and pulse shapes that can reproduce any geometry and pulse virtually. First, a complete parametric analysis under constant pulse is presented to understand the complexities of the temperature, electric flux, and stress distributions in these layered geometries. Second, combined optimizations are discussed. The targets are overcooling temperature, time to reach it, overheating minimization, overcooling duration, and combinations. In the best cases, the first target is doubled, the second is reduced to a few milliseconds, the third is null, and the duration can be 95% of the pulse while reducing the stress up to 40%.This work was partly supported by the Generalitat Valenciana re-search programs PROMETEO/2020/016: Applications de Topologic Isolators in Spintronics and Thermoelectricity (TOP-TERM) . Funding for open access charge was from CRUE-Universitat Politecnica de Valencia.Pérez-Aparicio, JL.; Moreno-Navarro, P.; Gómez-Hernández, JJ. (2023). Weighted sum optimization for combined thermoelectric geometry and electric pulse using finite elements. Applied Thermal Engineering. 236. https://doi.org/10.1016/j.applthermaleng.2023.12159923

Analytical and multicoupled methods for optimal steady-state thermoelectric solutions

[EN] Peltier cells have low efficiency, but they are becoming attractive alternatives for affordable and environmentally clean cooling. In this line, the current article develops closed-form and semianalytical solutions to improve the temperature distribution of Bi2Te3 thermoelements. From the distribution, the main objective of the current work-the optimal electric intensity to maximize cooling-is inferred. The general one-dimensional differential coupled equation is integrated for linear and quadratic geometry of thermoelements, under temperature constant properties. For a general shape, a piece-wise solution based on heat flux continuity among virtual layers gives accurate analytical solutions. For variable properties, another piece-wise solution is developed but solved iteratively. Taking advantage of the formulae, the optimal intensity is directly derived with a minimal computational cost; its value will be of utility for more advanced designs. Finally, a parametric study including straight, two linear, barrel, hourglass and vase geometries is presented, drawing conclusions on how the shape of the thermoelement affects the coupled phenomena. A specially developed coupled and non-linear finite element research code is run taking into account all the materials of the cell and using symmetries and repetitions. These accurate results are used to validate the analytical ones.This work was supported by the Generalitat Valenciana research programmes PROMETEO/2020/016: Applications de Topologic Isolators in Spintronics and Thermoelectricity (TOP-TERM) and BEST/2021/079. The support is gratefully acknowledged.Moreno-Navarro, P.; Pérez-Aparicio, JL.; Gómez-Hernández, JJ. (2022). Analytical and multicoupled methods for optimal steady-state thermoelectric solutions. Coupled Systems Mechanics, an international journal. 11(2):151-166. https://doi.org/10.12989/csm.2022.11.2.15115116611

Influence of age, gender and obesity on pressure discomfort threshold of the foot: A cross-sectional study

[EN] Background: Foot pain is a highly prevalent health problem for which measures such as a pattern of Pressure Discomfort Threshold of the foot plantar surface can provide valuable information for orthosis design. This study aimed to describe such pattern as a tool for the assessment of painful conditions of the feet and to analyse how it modifies according to age, gender and obesity. Methods: A cross-sectional study was performed with participants allocated in: Group 1 people aged 20 to 35 years, Group 2 aged 50 to 65 years and Group 3 aged over 65. Pressure Discomfort Threshold on twelve points of the foot plantar surface was measured with an adapted manual dynamometer. Inferential analyses of the data were performed using one-way analysis of variance (ANOVA) considering foot areas, age group, gender and obesity. Findings: 36 participants were analysed. The pattern of Pressure Discomfort Threshold for all individuals showed a significantly higher threshold on the heel and external foot (P < 0.001, eta(2) = 0.124) and was statistical significantly influenced by age (P < 0.001, eta(2) = 0.17), especially in participants aged over 65; by gender, with women having higher values (P < 0.001, eta(2) = 0.13), and by obesity (P < 0.001, eta(2) = 0.19). Interpretation: A Pressure Discomfort Threshold pattern exists in the foot plantar surface. The characteristics of the discomfort pattern of the foot and its association with aging, gender and obesity may have considerable implications for orthosis and footwear design.Dueñas, L.; Arnal-Gómez, A.; Aparicio, I.; Balasch-Bernat, M.; López-Bueno, L.; Gonzalez Garcia, JC.; Solves Camallonga, C.... (2021). Influence of age, gender and obesity on pressure discomfort threshold of the foot: A cross-sectional study. Clinical Biomechanics. 82(105252):1-7. https://doi.org/10.1016/j.clinbiomech.2020.105252S1782105252AKDEMIR, O., BILKAY, U., TIFTIKCIOGLU, Y. O., OZEK, C., YAN, H., ZHANG, F., & AKIN, Y. (2010). New alternative in treatment of callus. The Journal of Dermatology, 38(2), 146-150. doi:10.1111/j.1346-8138.2010.00978.xAnguera, J. A., & Gazzaley, A. (2012). Dissociation of motor and sensory inhibition processes in normal aging. Clinical Neurophysiology, 123(4), 730-740. doi:10.1016/j.clinph.2011.08.024Awale, A., Dufour, A. B., Katz, P., Menz, H. B., & Hannan, M. T. (2016). Link Between Foot Pain Severity and Prevalence of Depressive Symptoms. Arthritis Care & Research, 68(6), 871-876. doi:10.1002/acr.22779Bacarin, T. A., Sacco, I. C. N., & Hennig, E. M. (2009). Plantar pressure distribution patterns during gait in diabetic neuropathy patients with a history of foot ulcers. Clinics, 64(2). doi:10.1590/s1807-59322009000200008Barlow, A., Braid, S., & Jayson, M. (1990). Foot problems in the elderly. Clinical Rehabilitation, 4(3), 217-222. doi:10.1177/026921559000400306Betts, R. P., Franks, C. I., & Duckworth, T. (1980). Analysis of pressure and loads under the foot. II. Quantitation of the dynamic distribution. Clinical Physics and Physiological Measurement, 1(2), 113-124. doi:10.1088/0143-0815/1/2/002Bus, S. A., Ulbrecht, J. S., & Cavanagh, P. R. (2004). Pressure relief and load redistribution by custom-made insoles in diabetic patients with neuropathy and foot deformity. Clinical Biomechanics, 19(6), 629-638. doi:10.1016/j.clinbiomech.2004.02.010Caravaggi, P., Giangrande, A., Lullini, G., Padula, G., Berti, L., & Leardini, A. (2016). In shoe pressure measurements during different motor tasks while wearing safety shoes: The effect of custom made insoles vs. prefabricated and off-the-shelf. Gait & Posture, 50, 232-238. doi:10.1016/j.gaitpost.2016.09.013Duckworth, T., Boulton, A., Betts, R., Franks, C., & Ward, J. (1985). Plantar pressure measurements and the prevention of ulceration in the diabetic foot. The Journal of Bone and Joint Surgery. British volume, 67-B(1), 79-85. doi:10.1302/0301-620x.67b1.3968150Dufour, A. B., Broe, K. E., Nguyen, U.-S. D. T., Gagnon, D. R., Hillstrom, H. J., Walker, A. H., … Hannan, M. T. (2009). Foot pain: Is current or past shoewear a factor? Arthritis & Rheumatism, 61(10), 1352-1358. doi:10.1002/art.24733Von Elm, E., Altman, D. G., Egger, M., Pocock, S. J., Gøtzsche, P. C., & Vandenbroucke, J. P. (2008). The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Journal of Clinical Epidemiology, 61(4), 344-349. doi:10.1016/j.jclinepi.2007.11.008Fillingim, R. B. (2000). Sex, gender, and pain: Women and men really are different. Current Review of Pain, 4(1), 24-30. doi:10.1007/s11916-000-0006-6Gonzalez JC, García AC, Vivas MJ, Ferrús E, Alcántara E, Forner A. A new portable method for the measurement of pressure discomfort threshold on the foot plant. Fourth symposium of the Technical Group on Footwear Biomechanics. 5–7 August 1999. Canmore, Canada. International Society of Biomechanics.Gorter, K., Kuyvenhoven, M., & de Melker, R. (2000). Nontraumatic foot complaints in older people. A population-based survey of risk factors, mobility, and well-being. Journal of the American Podiatric Medical Association, 90(8), 397-402. doi:10.7547/87507315-90-8-397Greenspan, J. D., Craft, R. M., LeResche, L., Arendt-Nielsen, L., Berkley, K. J., Fillingim, R. B., … Traub, R. J. (2007). Studying sex and gender differences in pain and analgesia: A consensus report. Pain, 132(Supplement 1), S26-S45. doi:10.1016/j.pain.2007.10.014Hennig, E. M., & Sterzing, T. (2009). Sensitivity Mapping of the Human Foot: Thresholds at 30 Skin Locations. Foot & Ankle International, 30(10), 986-991. doi:10.3113/fai.2009.0986Hill, C. L., Gill, T. K., Menz, H. B., & Taylor, A. W. (2008). Prevalence and correlates of foot pain in a population-based study: the North West Adelaide health study. Journal of Foot and Ankle Research, 1(1). doi:10.1186/1757-1146-1-2Hills, A., Hennig, E., McDonald, M., & Bar-Or, O. (2001). Plantar pressure differences between obese and non-obese adults: a biomechanical analysis. International Journal of Obesity, 25(11), 1674-1679. doi:10.1038/sj.ijo.0801785Hong, W.-H., Lee, Y.-H., Chen, H.-C., Pei, Y.-C., & Wu, C.-Y. (2005). Influence of Heel Height and Shoe Insert on Comfort Perception and Biomechanical Performance of Young Female Adults During Walking. Foot & Ankle International, 26(12), 1042-1048. doi:10.1177/107110070502601208Le Johansson, L., Kjellberg, A., Kilbom, A., & Hagg, G. M. (1999). Perception of surface pressure applied to the hand. Ergonomics, 42(10), 1274-1282. doi:10.1080/001401399184947Kwan, R. L.-C., Zheng, Y.-P., & Cheing, G. L.-Y. (2010). The effect of aging on the biomechanical properties of plantar soft tissues. Clinical Biomechanics, 25(6), 601-605. doi:10.1016/j.clinbiomech.2010.04.003Machado, Á. S., Bombach, G. D., Duysens, J., & Carpes, F. P. (2016). Differences in foot sensitivity and plantar pressure between young adults and elderly. Archives of Gerontology and Geriatrics, 63, 67-71. doi:10.1016/j.archger.2015.11.005McPoil, T. G., & Cornwall, M. W. (2006). Plantar tactile sensory thresholds in healthy men and women. The Foot, 16(4), 192-197. doi:10.1016/j.foot.2006.07.001Messing, K., & Kilbom, Å. (2001). Standing and very slow walking: foot pain-pressure threshold, subjective pain experience and work activity. Applied Ergonomics, 32(1), 81-90. doi:10.1016/s0003-6870(00)00030-2Mickle, K. J., & Steele, J. R. (2015). Obese older adults suffer foot pain and foot-related functional limitation. Gait & Posture, 42(4), 442-447. doi:10.1016/j.gaitpost.2015.07.013Mickle, K. J., Munro, B. J., Lord, S. R., Menz, H. B., & Steele, J. R. (2010). Foot Pain, Plantar Pressures, and Falls in Older People: A Prospective Study. Journal of the American Geriatrics Society, 58(10), 1936-1940. doi:10.1111/j.1532-5415.2010.03061.xOkifuji, A., Bradshaw, D. H., & Olson, C. (2009). Evaluating obesity in fibromyalgia: neuroendocrine biomarkers, symptoms, and functions. Clinical Rheumatology, 28(4), 475-478. doi:10.1007/s10067-009-1094-2Redmond, A. C., Landorf, K. B., & Keenan, A.-M. (2009). Contoured, prefabricated foot orthoses demonstrate comparable mechanical properties to contoured, customised foot orthoses: a plantar pressure study. Journal of Foot and Ankle Research, 2(1). doi:10.1186/1757-1146-2-20Shrout, P. E., & Fleiss, J. L. (1979). Intraclass correlations: Uses in assessing rater reliability. Psychological Bulletin, 86(2), 420-428. doi:10.1037/0033-2909.86.2.420Veves, A., Murray, H. J., Young, M. J., & Boulton, A. J. M. (1992). The risk of foot ulceration in diabetic patients with high foot pressure: a prospective study. Diabetologia, 35(7), 660-663. doi:10.1007/bf00400259Weerasinghe, T. W., Goonetilleke, R. S., & Reischl, U. (2016). Pressure thresholds and stiffness on the plantar surface of the human foot. Ergonomics, 60(7), 985-996. doi:10.1080/00140139.2016.1229042Xiong, S., Goonetilleke, R. S., Witana, C. P., & Rodrigo, W. D. A. S. (2010). An indentation apparatus for evaluating discomfort and pain thresholds in conjunction with mechanical properties of foot tissue in vivo. The Journal of Rehabilitation Research and Development, 47(7), 629. doi:10.1682/jrrd.2009.09.0152Xiong, S., Goonetilleke, R. S., & Jiang, Z. (2011). Pressure thresholds of the human foot: measurement reliability and effects of stimulus characteristics. Ergonomics, 54(3), 282-293. doi:10.1080/00140139.2011.552736Xu, R., Wang, Z., Ma, T., Ren, Z., & Jin, H. (2019). Effect of 3D Printing Individualized Ankle-Foot Orthosis on Plantar Biomechanics and Pain in Patients with Plantar Fasciitis: A Randomized Controlled Trial. Medical Science Monitor, 25, 1392-1400. doi:10.12659/msm.915045Van der Zwaard, B. C., Elders, P. J., Knol, D. L., Gorter, K. J., Peeraer, L., van der Windt, D. A., & van der Horst, H. E. (2011). Treatment of forefoot problems in older people: study protocol for a randomised clinical trial comparing podiatric treatment to standardised shoe advice. Journal of Foot and Ankle Research, 4(1). doi:10.1186/1757-1146-4-1

Correlation between anthropometric measurements and blood pressure in a population of Palestinian adults.

This manuscript is part of the PhD research developed by Moath Abu Ejheisheh, included in the Official PhD Program of Clinical Medicine and Public Health at the University of Granada, Spain. The authors in this study would like to extend her appreciation to the study participants for their time.Obesity can be a major problem due to its potential to cause a number of health issues, including high blood pressure and diabetes. Many reports have come out of Palestine on overweight and obesity and their direct link to non-communicable diseases, although there is only limited evidence available on the connection between obesity and hypertension in Palestinian adults. We aimed to look at the associations between anthropometric and body composition variables and blood pressure in a large population of Palestinian adults (1337 subjects) and determine which anthropometric indices most strongly correlate with high blood pressure. Anthropometric measurements including height, waist circumference (WC), hip circumference (HC), body mass index (BMI), and total body fat (TBF) were assessed. A body composition analyzer was used to measure body weight, fat mass and fat-free mass. Systolic (SBP) and diastolic (DBP) blood pressure were measured using a Dinamap vital signs monitor. In both males and females, all the anthropometric measurements showed significant strong positive correlations with mean SBP and mean DBP (p < 0.01). SBP correlated the most strongly with waist circumference in all subjects (r = 0.444 in females, r = 0.422 in males), while DBP correlated the most strongly with WC in males (r = 0.386), but with TBF in females (r = 0.256). By controlling fat percentage, WC, HC, and BMI, which are affected by extra weight and lack of exercise, blood pressure levels can be regulated.The author(s) received no financial support for the research, authorship, and/or publication of this article

Fuzzy controller to compensate comunication loads in real-time

[EN] A Fuzzy Resource Manager (RM) to compensate communication loads in real-time systems is presented. The design is based on a new model of a Constant Bandwidth Server (CBS), which is responsible for assigning time slots to tasks with the highest priority when idle time is available. Assuming that each application can be executed at dierent service levels, without being below a minimum limit, a fuzzy approach is introduced that allows to adjust the time resources assigned to each task and to compensate non-linearities in time resources requests. The RM increases or decreases the virtual platform for each application and assigns a maximum process time budget for it, which is gradually used and refilled when depleted, without aecting the other applications. The scheme self-adjusts to sudden changes in applications process time requirements.[ES] Se presenta un administrador de recursos (RM) difuso para compensar las cargas de comunicación en sistemas en tiempo real. El diseño del RM se basa en un nuevo modelo de Servidor de Ancho de Banda Constante (CBS) que se encarga, a través de una plataforma virtual, de asignar tiempo de proceso a las tareas de mayor prioridad cuando existe capacidad disponible. Si se asume que cada aplicación puede ser ejecutada con diferentes niveles de servicio sin que este esté por debajo de un límite mínimo, se propone una aproximación difusa que permite actualizar de manera gradual los tiempos de proceso asignados a cada tarea. Esta aproximación permite compensar el comportamiento no lineal en las solicitudes de tiempo de proceso. El RM aumenta o disminuye la plataforma virtual para cada aplicación y le asigna un presupuesto máximo de tiempo de proceso, mismo que la aplicación usa gradualmente y que se reasigna al agotarse, sin por ello afectar el desempeño del resto de las aplicaciones. El esquema se auto-ajusta cuando ocurren a cambios repentinos en los requerimientos de tiempo de proceso de las aplicaciones.Este trabajo ha sido realizado parcialmente gracias al apoyo del CONACYT BECA 597175, PAPIIT IT100320 y PAPIIT IN104516.Aparicio-Santos, J.; Hermosillo-Gómez, J.; Benítez-Pérez, H.; Álvarez-Icaza, L. (2021). Controlador difuso para compensar cargas de comunicación en sistemas en tiempo real. Revista Iberoamericana de Automática e Informática industrial. 18(3):288-299. https://doi.org/10.4995/riai.2021.14544OJS288299183Abeni, L., Buttazzo, G., Dec 1998. Integrating multimedia applications in hard real-time systems. In: Proceedings 19th IEEE Real-Time Systems Symposium (Cat. No.98CB36279). pp. 4-13. https://doi.org/10.1109/REAL.1998.739726Aparicio, Santos, J. A., 2017. Diseño de un controlador difuso para compensar cargas de comunicación en tiempo real. Master's thesis, Universidad Nacional Autónoma de México, México.Bini, E., Buttazzo, G., Eker, J., Schorr, S., Guerra, R., Fohler, G., Arzen, K. E., Romero, V., Scordino, C., May 2011. Resource management on multicore systems: The actors approach. IEEE Micro 31 (3), 72-81. https://doi.org/10.1109/MM.2011.1Boutalis, Y., Theodoridis, D., Kottas, T., Christodoulou, M. A., 2014. System Identification and Adaptive Control: Theory and Applications of the Neurofuzzy and Fuzzy Cognitive Network Models. Springer.Buttazzo, G. C., 2011. Hard Real-Time Computing Systems: Predictable Scheduling Algorithms and Applications, 3rd Edition. Springer Publishing Company, Incorporated. Byeong Gi, L., Daeyoung, P., Hanbyul, S., 2009. Wireless Communications Resource Managemen. John Wiley and Sons.Byeong Gi, L., Daeyoung, P., Hanbyul, S., 2009. Wireless Communications Resource Managemen. John Wiley and Sons.Chasparis, G., Maggio, M., Arzen, K. E., Bini, E., June 2013. Distributed management of cpu resources for time-sensitive applications. In: 2013 American Control Conference. pp. 5305-5312. https://doi.org/10.1109/ACC.2013.6580666Chasparis, G. C., Maggio, M., Bini, E., Arzen, K.-E., 2016. Desing and implementation of distributed resource management for time-sensitive applications. Automatica 64, 44 - 53. https://doi.org/10.1016/j.automatica.2015.09.015Clark, R. K., 1990. Scheduling dependent real-time activities. Ph.D. thesis, USA, aAI9107552.Ganz, A., Ganz, Z., Wongthavarawat, K., 2003. Multimedia Wireless Networks: Technologies, Standards and QoS. Pearson Education.Horn, W., 1974. Some simple scheduling algorithms. Naval Research Logistics Quarterly 21 (1), 177-185. https://doi.org/10.1002/nav.3800210113IEEE Standard Glossary of Software Engineering Terminology. https://doi.org/10.1109/IEEESTD.1990.101064Litoiu, M., Tadei, R., 2001. Fuzzy scheduling with application to real-time systems. Fuzzy Sets and Systems 121 (3), 523 - 535. https://doi.org/10.1016/S0165-0114(99)00176-1Mahmoud, M., of Engineering, I., Technology, 2013. Distributed Control and Filtering for Industrial Systems. Control, Robotics and Sensors. Institution of Engineering and Technology. URL: https://books.google.com.mx/books?id=qWhWx2hRLYcC https://doi.org/10.1049/PBCE088EMok, A. K., Feng, X., May 2001. Resource partition for real-time systems. In: Proceedings Seventh IEEE Real-Time Technology and Applications Symposium. pp. 75-84. https://doi.org/10.1109/RTTAS.2001.929867Nesbit, K. J., Moreto, M., Cazorla, F. J., Ramirez, A., Valero, M., Smith, J. E., May 2008. Multicore resource management. IEEE Micro 28 (3), 6-16. https://doi.org/10.1109/MM.2008.43Quanser, 2012. USER MANUAL 3 DOF Gyroscope Experiment Set Up and Configuration. Quanser inc.Robert H. Cannon, J., 2003. Dynamics Of Physical Systems. Dover Publications, INC.Stankovic, J. A., 1988. Misconceptions about real-time computing: a serious problem for next-generation systems. Computer 21 (10), 10-19. https://doi.org/10.1109/2.7053Subrata, R., Zomaya, A. Y., Landfeldt, B., Oct 2008. A cooperative game framework for qos guided job allocation schemes in grids. IEEE Transactions on Computers 57 (10), 1413-1422. https://doi.org/10.1109/TC.2008.79Tanaka, K., Ikeda, T., Wang, H. O., May 1998. Fuzzy regulators and fuzzy observers: relaxed stability conditions and lmi-based designs. IEEE Transactions on Fuzzy Systems 6 (2), 250-265. https://doi.org/10.1109/91.66902

Low plasma fibrinogen levels and blood product transfusion in liver transplantation

Aim: Risk of bleeding in liver transplantation is determined by surgical technique, preoperative hemoglobin and antifibrinolitic therapy. We hypothesized that keeping these confounders factors identical, preoperative plasma fibrinogen level of ≤2 g/L influenced on blood product requirements. Methods: Adult patients underwent orthotropic liver transplantation (LT) during the period between January 1998 and December 2009. Cases were selected according to a propensity matching analysis meeting the following criteria: surgical vena cava preservation, tranexamic acid administration and hemoglobin range between 90 to 120 g/L. Intraoperative management was protocolized. The main variable was the percentage of patients that did not require red blood cells (RBC's). Results: Six hundred sixty-four patients with LT, 208 excluded, 266 who cannot be matched, the analysis was performed on 190 patients. Two cohorts: Low fibrinogen (≤2 g/L) (61 cases) and standard fibrinogen (>2 g/L) (129 cases) were analyzed. Preoperative platelet count (73.5±52 vs. 104±65; 103/mm3) was different in contrast to the hemoglobin (104.2±8.6 vs. 105.6±8.3; g/L). Use of RBC's resulted significantly higher in the low fibrinogen group (median, 3 vs. 2). The number of patients with no blood product requirements was fewer in the low fibrinogen group (8 cases, 13% vs. 45 cases, 35%). The critical level of plasma fibrinogen (1 g/L) was reached after graft reperfusion in 7 cases (5.5%) in the standard fibrinogen group vs. 24 cases (39%) in the low fibrinogen group. Conclusion: Our data suggest that preoperative plasma fibrinogen level of ≤2 g/L increases requirements for blood products during the surgical procedure of liver transplantation

Non-linear effects of drought under shade: reconciling physiological and ecological models in plant communities

The combined effects of shade and drought on plant performance and the implications for species interactions are highly debated in plant ecology. Empirical evidence for positive and negative effects of shade on the performance of plants under dry conditions supports two contrasting theoretical models about the role of shade under dry conditions: the trade-off and the facilitation hypotheses. We performed a meta-analysis of field and greenhouse studies evaluating the effects of drought at two or more irradiance levels on nine response variables describing plant physiological condition, growth, and survival. We explored differences in plant response across plant functional types, ecosystem types and methodological approaches. The data were best fit using quadratic models indicating a humped-back shape response to drought along an irradiance gradient for survival, whole plant biomass, maximum photosynthetic capacity, stomatal conductance and maximal photochemical efficiency. Drought effects were ameliorated at intermediate irradiance, becoming more severe at higher or lower light levels. This general pattern was maintained when controlling for potential variations in the strength of the drought treatment among light levels. Our quantitative meta-analysis indicates that dense shade ameliorates drought especially among drought-intolerant and shade-tolerant species. Wet tropical species showed larger negative effects of drought with increasing irradiance than semiarid and cold temperate species. Non-linear responses to irradiance were stronger under field conditions than under controlled greenhouse conditions. Non-linear responses to drought along the irradiance gradient reconciliate opposing views in plant ecology, indicating that facilitation is more likely within certain range of environmental conditions, fading under deep shade, especially for drought-tolerant species

Electronic structure and exotic exchange splitting in spin-density-wave states of BaFe2_2As2_2

The magnetic properties in the parent compounds are often intimately related to the microscopic mechanism of superconductivity. Here we report the first direct measurements on the electronic structure of a parent compound of the newly discovered iron-based superconductor, BaFe$_2$As$_2$, which provides a foundation for further studies. We show that the energy of the spin density wave (SDW) in BaFe$_2$As$_2$ is lowered through exotic exchange splitting of the band structure, rather than Fermi surface nesting of itinerant electrons. This clearly demonstrates that a metallic SDW state could be solely induced by interactions of local magnetic moments, resembling the nature of antiferromagnetic order in cuprate parent compounds.Comment: 5 pages, 4 figure