bluuebunny/crossref_metadata_2025 huggingface dataset:
Abnormal platelet kinetics are detected before the occurrence of thrombocytopaenia in HBV‐related liver disease
Authors: Wang Xiaoyun , Jiang Wei , Li Feng , Hua Fanli , Zhan Yanxia , Li Yingying , Ji Lili , Zou Shanhua , Min Zhihui , Song Dongli , Cheng Yunfeng
Published: August 2013

Background & Aims

Thrombocytopaenia is a frequent feature in patients with HBV‐related liver disease. Its underlying mechanism is not fully understood. Multiple factors might contribute to the development of thrombocytopaenia. In this study, we investigated the reticulated platelets (RP), glycocalicin (GC), serum thrombopoietin (TPO) and platelet glycoprotein (GP) in different stages of the disease.

Methods

One hundred and fourteen patients with HBV‐related liver disease (30 with chronic hepatitis B (CHB), 20 patients in Child A without thrombocytopaenia, 19 patients in Child A with thrombocytopaenia, 45 in Child B/C with thrombocytopaenia) and 25 normal controls (NC) were enrolled. Liver cirrhosis (LC) was classified according to modified Child‐Turcotte‐Pugh (CTP) score. Serum TPO levels and GC were measured by ELISA. RP and platelet glycoprotein (GP) expression were detected by flow cytometry.

Results

The TPO levels of patients with LC were significantly lower than that of controls, even in patients of Child A without thrombocytopaenia group. Serum TPO level was positively correlated (r = 0.65, p < 0.01) with serum albumin in Child B/C group. Both the RP percentages and the glycocalicin index (GCI) levels were significantly higher in patients groups including CHB and Child A without thrombocytopaenia than that of normal controls. A negative correlation existed in HBV DNA copies and the GPs% in patients with CHB and Child A without thrombocytopaenia.

Conclusion

Abnormal platelet production, destruction and platelet‐specific glycoproteins levels were detected before the occurrence of thrombocytopaenia in HBV‐related liver disease, indicating that multiple mechanisms might play roles in thrombocytopaenia in HBV‐infected patients.
PNPLA3 I148M (rs738409) genetic variant and age at onset of at‐risk alcohol consumption are independent risk factors for alcoholic cirrhosis
Authors: Burza Maria Antonella , Molinaro Antonio , Attilia Maria Luisa , Rotondo Claudia , Attilia Fabio , Ceccanti Mauro , Ferri Flaminia , Maldarelli Federica , Maffongelli Angela , De Santis Adriano , Attili Adolfo Francesco , Romeo Stefano , Ginanni Corradini Stefano
Published: August 2013

Background & Aims

Environmental and genetic factors contribute to alcoholic cirrhosis onset. In particular, age at exposure to liver stressors has been shown to be important in progression to fibrosis in hepatitis C individuals. However, no definite data on the role of age at onset of at‐risk alcohol consumption are available. Moreover, patatin‐like phospholipase domain‐containing protein 3 (PNPLA3) I148M (rs738409) variant has been associated with alcoholic cirrhosis, but only in cross‐sectional studies. The aim of this study was to investigate the role of age at onset of at‐risk alcohol consumption and PNPLA3 I148M variant on alcoholic cirrhosis incidence.

Methods

A total of 384 at‐risk alcohol drinkers were retrospectively examined. The association among age at onset of at‐risk alcohol consumption, PNPLA3 I148M variant and cirrhosis incidence was tested.

Results

A higher incidence of alcoholic cirrhosis was observed in individuals with an older (≥24 years) compared with a younger (<24) age at onset of at‐risk alcohol consumption (P‐value < 0.001). Moreover, PNPLA3 148M allele carriers showed an increased incidence of cirrhosis (P‐value < 0.001). Both age at onset of at‐risk alcohol consumption and PNPLA3 148M allele were independent risk factors for developing cirrhosis (H.R. (95% C.I.): 2.76 (2.18–3.50), P‐value < 0.001; 1.53(1.07–2.19), P‐value = 0.021 respectively). The 148M allele was associated with a two‐fold increased risk of cirrhosis in individuals with a younger compared with an older age at onset of at‐risk alcohol consumption (H.R. (95% C.I.): 3.03(1.53–6.00) vs. 1.61(1.09–2.38).

Conclusions

Age at onset of at‐risk alcohol consumption and PNPLA3 I148M genetic variant are independently associated with alcoholic cirrhosis incidence.
Looking into the black box: simulating the role of self‐fertilization and mortality in the genetic structure of Macrocystis pyrifera
Authors: Johansson Mattias L. , Raimondi Peter T. , Reed Daniel C. , Coelho Nelson C. , Serrão Ester A. , Alberto Filipe A.
Published: August 2013

Patterns of spatial genetic structure (SGS), typically estimated by genotyping adults, integrate migration over multiple generations and measure the effective gene flow of populations. SGS results can be compared with direct ecological studies of dispersal or mating system to gain additional insights. When mismatches occur, simulations can be used to illuminate the causes of these mismatches. Here, we report a SGS and simulation‐based study of self‐fertilization in Macrocystis pyrifera, the giant kelp. We found that SGS is weaker than expected in M. pyrifera and used computer simulations to identify selfing and early mortality rates for which the individual heterozygosity distribution fits that of the observed data. Only one (of three) population showed both elevated kinship in the smallest distance class and a significant negative slope between kinship and geographical distance. All simulations had poor fit to the observed data unless mortality due to inbreeding depression was imposed. This mortality could only be imposed for selfing, as these were the only simulations to show an excess of homozygous individuals relative to the observed data. Thus, the expected data consistently achieved nonsignificant differences from the observed data only under models of selfing with mortality, with best fits between 32% and 42% selfing. Inbreeding depression ranged from 0.70 to 0.73. The results suggest that density‐dependent mortality of early life stages is a significant force in structuring Macrocystis populations, with few highly homozygous individuals surviving. The success of these results should help to validate simulation approaches even in data‐poor systems, as a means to estimate otherwise difficult‐to‐measure life cycle parameters.
Signal peptide etiquette during assembly of a complex respiratory enzyme
Authors: James Martyn J. , Coulthurst Sarah J. , Palmer Tracy , Sargent Frank
Published: August 2013

Salmonella enterica serovar Typhimurium is a Gram‐negative pathogen capable of respiration with a number of terminal electron acceptors. Tetrathionate reductase is important for the infection process and is encoded by the ttrBCA operon where TtrA and TtrB are metallocofactor‐containing proteins targeted to the periplasmic side of the membrane by two different Tat targeting peptides. In this work, the inter‐relationship between these two signal peptides has been explored. Molecular genetics and biochemical approaches reveal that the processing of the TtrB Tat signal peptide is dependent on the successful assembly of its partner protein, TtrA. Inactivation of either the TtrA or the TtrB Tat targeting peptides individually was observed to have limited overall effects on assembly of the enzyme or on cellular tetrathionate reductase activity. However, inactivation of both signal peptides simultaneously was found to completely abolish physiological tetrathionate reductase activity. These data suggest both signals are normally active during assembly of the enzyme, and imply a code of conduct exists between the signal peptides where one can compensate for inactivity in the other. Since it appears likely that tetrathionate reductase presents itself for export as a multi‐signal complex, these observations also have implications for the mechanism of the bacterial Tat translocase.
Surveillance transbronchial biopsies in infant lung and heart–lung transplant recipients
Authors: Hayes Don , Baker Peter B. , Kopp Benjamin T. , Kirkby Stephen , Galantowicz Mark , McConnell Patrick I. , Astor Todd L.
Published: August 2013

There are limited published data on surveillance TBB for the identification of allograft rejection in infants after lung or heart‐lung transplantation. We performed a retrospective review of children under one yr of age who underwent lung or heart–lung transplant at our institution. Since 2005, four infants were transplanted (three heart–lung and one lung). The mean age (±s.d.) at the time of transplant was 5.5 ± 2.4 (range 3–8) months. A total of 16 surveillance TBB procedures were completed in both inpatient and outpatient settings, with a range of 3–7 performed per patient. A minimum of five acceptable tissue pieces with expanded alveoli were obtained in 81% (13/16) of TBB procedures and a minimum of three pieces in 88% (14/16). There was no evidence of acute allograft rejection in 88% (14/16) of TBB procedures. One TBB procedure yielded two tissue specimens demonstrating A2 acute allograft rejection. One TBB procedure failed to yield tissue with sufficient alveoli. Additionally, B‐grade assessment identified B0 in 50% (8/16), B1R in 12% (2/16), and BX (ungradeable or insufficient sample) in 38% (6/16) of biopsy procedures, respectively. In conclusion, TBB may be safely performed as an inpatient and outpatient procedure in infant lung and heart–lung transplant recipients and may provide adequate tissue for detecting acute allograft rejection and small airway inflammation.
Vitamin D deficiency and insufficiency after pediatric liver transplantation
Authors: Legarda Maria , Gordon Graham , Lloyd Carla , Baumann Ulrich , Kelly Deirdre A. , Shaw Nick , McKiernan Patrick
Published: August 2013

Vitamin D deficiency and insufficiency are increasingly recognized in the general population, including healthy children. There is also an increasing emphasis on the importance of vitamin D status following pediatric liver transplantation and specifically its relationship to metabolic bone disease and growth retardation. Vitamin D insufficiency has also been associated with multiple immunological and metabolic disorders in adults. To our knowledge, this has not been systematically evaluated in children undergoing liver transplantation to date. Between October 2004 and August 2008, serum 25‐(OH)‐vitamin D levels were measured in 199 children who had undergone liver transplantation at Birmingham Children's Hospital. Potential factors contributing to vitamin D levels were evaluated. Additionally, we evaluated a possible relationship between vitamin D levels and immunological phenomena and metabolic complications. Median 25‐(OH)‐vitamin D level was 19.5 ng/mL (range: 4.4–71.4 ng/mL). A total of 105 children (53%) had insufficient vitamin D levels and 28 children (14%) showed vitamin D deficiency. The only factors found to be associated with vitamin D deficiency were season of sample, ethnicity, and PTH levels. Vitamin D deficiency was more prevalent during the first year after transplantation. We did not find a significant relationship between vitamin D levels and graft function or any other immunological and metabolic complications. Vitamin D insufficiency and deficiency are common in children after liver transplantation, especially in winter and spring and in non‐white patients. Initial post‐transplant period and high PTH are significantly associated with vitamin D deficiency. Vitamin D status should be monitored following pediatric liver transplantation and vitamin D supplementation provided as required.
Delayed short‐term administration of granulocyte colony‐stimulating factor is a good mobilization strategy for harvesting autologous peripheral blood stem cells in pediatric patients with solid tumors
Authors: Takahashi Hiroyoshi , Kato Motohiro , Kikuchi Akira , Hanada Ryoji , Koh Katsuyoshi
Published: August 2013

PBSCs have become the preferred source of autologous stem cells for supporting high‐dose chemotherapy in childhood solid tumors. The aims of this retrospective study were to examine the optimal timing for administration of G‐CSF after chemotherapy and to identify the patients from whom an optimal dose of PBSCs can be harvested. We evaluated the timing of G‐CSF administration for harvesting PBSCs in patients with childhood solid tumors. G‐CSF was administered immediately after chemotherapy in eight patients (11 harvests, long‐term group) and following recovery from hematological nadirs in 17 patients (21 harvests, short‐term group). The median duration of G‐CSF administration was 22 vs. 5 days, respectively (p < 0.005), and the dose of harvested CD34+ cells (×106/kg) was 1.4 vs. 2.9, respectively (p = 0.023). Our results suggest that short‐term G‐CSF administration is a good strategy for harvesting PBSCs in these patients.
Prospective Study of Maternal Mid‐pregnancy 25‐hydroxyvitamin D Level and Early Childhood Respiratory Disorders
Authors: Magnus Maria C. , Stene Lars C. , Håberg Siri E. , Nafstad Per , Stigum Hein , London Stephanie J. , Nystad Wenche
Published: August 2013

Background

Studies suggest that prenatal vitamin D status may be inversely associated with lower respiratory tract infections (LRTIs) early in life. Studies of prenatal vitamin D status and development of asthma have inconsistent findings.

Methods

We examined the associations of maternal mid‐pregnancy 25‐hydroxyvitamin D [25(OH)D] level with the frequency of LRTIs by 36 months and with current asthma at 36 months using the Norwegian Mother and Child Cohort Study. Maternal plasma 25(OH)D level was measured using liquid chromatography‐tandem mass spectrometry. Respiratory disorders were evaluated by maternal report through questionnaires. LRTIs were analysed in a random sample of 1248 children. Asthma was analysed using a case–control design, including 489 cases and 1183 controls. Multivariable generalised linear models calculated adjusted measures of association.

Results

The median gestational week of sample collection was 18 weeks (range 9, 35). The mean 25(OH)D level was 73.7 nmol/L (standard deviation 23.7). Higher maternal mid‐pregnancy 25(OH)D level was associated with a reduced risk of three or more LRTIs by 36 months vs. none, adjusted risk ratio 0.74 [95% confidence interval (CI): 0.58, 0.93] per 20 nmol/L increase. Associations were similar when examining the frequency of LRTIs by 18 months, and the frequency of LRTIs between 18 and 36 months. Maternal mid‐pregnancy 25(OH)D level was not significantly associated with current asthma at 36 months, adjusted odds ratio 0.91 [95% CI 0.81, 1.02] per 20 nmol/L increase.

Conclusions

Higher maternal mid‐pregnancy 25(OH)D level was associated with a modestly reduced risk of recurrent LRTIs by 36 months, but was not associated with current asthma at 36 months.
The homeodomain‐leucine zipper ATHB23, a phytochrome B‐interacting protein, is important for phytochrome B‐mediated red light signaling
Authors: Choi Hyunmo , Jeong Suyeong , Kim Dong Su , Na Hyung Jin , Ryu Jong Sang , Lee Seung Sik , Nam Hong Gil , Lim Pyung Ok , Woo Hye Ryun
Published: August 2013

Phytochromes are red (R)/far‐red (FR) photoreceptors that are central to the regulation of plant growth and development. Although it is well known that photoactivated phytochromes are translocated into the nucleus where they interact with a variety of nuclear proteins and ultimately regulate genome‐wide transcription, the mechanisms by which these photoreceptors function are not completely understood. In an effort to enhance our understanding of phytochrome‐mediated light signaling networks, we attempted to identify novel proteins interacting with phytochrome B (phyB). Using affinity purification in Arabidopsis phyB overexpressor, coupled with mass spectrometry analysis, 16 proteins that interact with phyB in vivo were identified. Interactions between phyB and six putative phyB‐interacting proteins were confirmed by bimolecular fluorescence complementation (BiFC) analysis. Involvement of these proteins in phyB‐mediated signaling pathways was also revealed by physiological analysis of the mutants defective in each phyB‐interacting protein. We further characterized the athb23 mutant impaired in the homeobox protein 23 (ATHB23) gene. The athb23 mutant displayed altered hypocotyl growth under R light, as well as defects in phyB‐dependent seed germination and phyB‐mediated cotyledon expansion. Taken together, these results suggest that the ATHB23 transcription factor is a novel component of the phyB‐mediated R light signaling pathway.
Genomic Selection: Status in Different Species and Challenges for Breeding
Authors: Stock KF , Reents R
Published: August 2013

Contents

Technical advances and development in the market for genomic tools have facilitated access to whole‐genome data across species. Building‐up on the acquired knowledge of the genome sequences, large‐scale genotyping has been optimized for broad use, so genotype information can be routinely used to predict genetic merit. Genomic selection (GS) refers to the use of aggregates of estimated marker effects as predictors which allow improved individual differentiation at young age. Realizable benefits of GS are influenced by several factors and vary in quantity and quality between species. General characteristics and challenges of GS in implementation and routine application are described, followed by an overview over the current status of its use, prospects and challenges in important animal species. Genetic gain for a particular trait can be enhanced by shortening of the generation interval, increased selection accuracy and increased selection intensity, with species‐ and breed‐specific relevance of the determinants. Reliable predictions based on genetic marker effects require assembly of a reference for linking of phenotype and genotype data to allow estimation and regular re‐estimation. Experiences from dairy breeding have shown that international collaboration can set the course for fast and successful implementation of innovative selection tools, so genomics may significantly impact the structures of future breeding and breeding programmes. Traits of great and increasing importance, which were difficult to improve in the conventional systems, could be emphasized, if continuous availability of high‐quality phenotype data can be assured. Equally elaborate strategies for genotyping and phenotyping will allow tailored approaches to balance efficient animal production, sustainability, animal health and welfare in future.
Growth and Regression in Bovine Corpora Lutea: Regulation by Local Survival and Death Pathways
Authors: Skarzynski DJ , Piotrowska‐Tomala KK , Lukasik K , Galvão A , Farberov S , Zalman Y , Meidan R
Published: August 2013

Contents

The bovine corpus luteum (CL) is a transient gland with a life span of only 18 days in the cyclic cow. Mechanisms controlling CL development and secretory function may involve factors produced both within and outside this gland. Although luteinizing hormone (LH) surge is the main trigger of ovulation and granulosa cells luteinization, many locally produced agents such as arachidonic acid (AA) metabolites, growth factors and cytokines were shown to complement gonadotropins action in the process of CL development. Bovine CL is a highly vascular gland, where the very rapid angiogenesis rate (until Day 5 of the cycle) results in the development of a capillary network, endowing this gland with one of the highest blood flow rate per unit mass in the body. Angiogenesis in the developing CL is later followed by either controlled regression of the microvascular tree in the non‐fertile cycle or maintenance and stabilization of the blood vessels, as seen during pregnancy. Different luteal cell types (both steroidogenic and accessory luteal cells: immune cells, endothelial cells, pericytes and fibroblasts) are involved in the pro‐ and/or anti‐angiogenic responses. The balance between pro‐ and anti‐angiogenic responses to the main luteolysin – prostaglandin F2α (PGF2α) could be decisive in whether or not PGF2α induces CL regression. Fibroblast growth factor‐2 (FGF2) may be one of the factors that modulate the angiogenic response to PGF2α. Manipulation of local production and action of FGF2 will provide new tools for reproductive management of dairy cattle. Luteolysis is characterized by a rapid decrease in progesterone production, followed by structural regression. Factors like endothelin‐1, cytokines (tumour necrosis factorα, interferons) and nitric oxide were all shown to play critical roles in functional and structural regression of the CL by inhibiting steroidogenesis and inducting apoptosis.
Drivers of Post‐partum Uterine Disease in Dairy Cattle
Authors: Williams EJ
Published: August 2013

Contents

Post‐partum uterine disease has a detrimental effect on dairy cow fertility; affected cows require more serves per conception, have reduced conception rates and are more likely to be culled for infertility. Furthermore, the detrimental effects on fertility remain even after clinical resolution of disease. There are many factors that influence a cow's resistance to or development of post‐partum disease, and the key drivers determining disease outcome are uterine microbial load, regulation of inflammation and immune responses peripherally and at a local level, production pressure, and metabolic (energy) status. These factors are intricately interlinked, which makes assessment of their individual effects difficult. It is clear, however, that the period surrounding calving is a key transition phase and events during this time point will influence uterine disease outcome and subsequent fertility. Good peripartum management and accurate diagnosis are critical to facilitate the use of the most effective treatment and limit the negative impact of post‐partum uterine disease on fertility. If we can improve our understanding of the underlying causes of disease, then we can identify ‘at risk’ animals and implement management and breeding strategies to prevent uterine disease or reduce its severity. Thus, this article aims to summarize the key factors that drive uterine disease in the post‐partum dairy cow.
Hypothalamic Integration of Nutrient Status and Reproduction in the Sheep
Authors: Daniel JA , Foradori CD , Whitlock BK , Sartin JL
Published: August 2013

Contents

Nutrient availability is a determinant of reproductive success. It is well known that inadequate nutrition results in reproductive failure due to a number of factors including delay of puberty or anoestrous in post‐pubertal animals. The lack of nutrients is detected primarily by changes in circulating nutrient molecules and hormones and communicated directly or indirectly to the hypothalamus and brain stem for integration. The general effect is that low nutrition leads to increased appetite stimulation and reduced reproductive performance. When nutrition is adequate, the reverse is true. Both aspects will be the focus of this review. One result of the lack of nutrients is a reduction in luteinizing hormone (LH) concentrations and pulse frequency. Nutrient signals, such as glucose availability, hormonal signals, such as insulin and leptin, and neuroendocrine signals, such as neuropeptide Y and corticotropin‐releasing hormone, have been clearly demonstrated to interact to produce changes in LH and reproductive success. Other signals, such as fatty acids, ghrelin, agouti‐related peptide, melanin‐concentrating hormone, orexin, melanocyte‐stimulating hormone, kisspeptin, neurokinin, dynorphin and gonadotropin inhibitory hormone may also play a role in integrating nutrition and reproduction. This review will focus on the major features of the reciprocal control of appetite and reproduction in sheep.
A Model of a High-Temperature Direct Methanol Fuel Cell
Authors: Scott K. , Pilditch S. , Mamlouk M.
Published: August 2013

A steady-state, isothermal, one-dimensional model of a direct methanol proton exchange membrane fuel cell (PEMFC), with a polybenzimidazole (PBI) membrane, was developed. The electrode kinetics were represented by the Butler–Volmer equation, mass transport was described by the multicomponent Stefan–Maxwell equations and Darcy's law, and the ionic and electronic resistances described by Ohm's law. The model incorporated the effects of temperature and pressure on the open circuit potential, the exchange current density, and diffusion coefficients, together with the effect of water transport across the membrane on the conductivity of the PBI membrane. The influence of methanol crossover on the cathode polarization is included in the model. The polarization curves predicted by the model were validated against experimental data for a direct methanol fuel cell (DMFC) operating in the temperature range of 125–175 °C. There was good agreement between experimental and model data for the effect of temperature and oxygen/air pressure on cell performance. The fuel cell performance was relatively poor, at only 16 mW cm−2 peak power density using low concentrations of methanol in the vapor phase.
Optical Parameters in High-Efficiency Optical Receivers With a Parabolic Reflector Before and After Coating With Ag Film
Authors: Jui Lee Chung , Fin Lin Jen
Published: August 2013

High-efficiency optical receivers before and after the coating of Ag film are composed of a parabolic reflector, a solid parabolic second optical element (SOE), and a Fresnel/aspheric concentrating lens. The optical receivers before the Ag-film coating are fabricated on a high-precision machine tool based on an optimum design attained from ray tracing software simulations. The real profiles of the reflector before and after coating the Ag film are found to be the average of the two orthogonal parabolic profiles. They are then compared to the perfect profile (without profile error and surface roughness) in order to investigate the influence of the profile error and the Ag film on optical performances. The optical parameters, including the total flux, the optical efficiency, and the maximum, minimum, and mean irradiances are evaluated for ray projection simulations in the ASTM G173-03 spectrum. Experiments for the same ray source are also carried out to compare with the simulation results. It is determined that Ag-film coating can improve the profile error and surface roughness of the reflector, thus resulting in all optical parameters being either equal to or higher than those of the reflector without Ag coating. The total flux and optical efficiency obtained from the module with the Fresnel lens has values relatively higher than those of the aspheric lens. The irradiance uniformity for the Fresnel lens is also determined to be better than that of the aspheric lens. The irradiance intensity of the reflector after coating the Ag film has a magnitude at various wavelengths higher than that of the reflector without the Ag-film coating. Due to the coating of the Ag film, the optical receiver shows an almost constant rise in optical efficiency for the two types of concentrating lenses. This characteristic is shown to be valid for both the simulation and experimental results.
Large Eddy Simulation of Flame Response to Transverse Acoustic Excitation in a Model Reheat Combustor
Authors: Zellhuber Mathieu , Meraner Christoph , Kulkarni Rohit , Polifke Wolfgang , Schuermans Bruno
Published: August 2013

The response of a perfectly premixed, turbulent jet flame at elevated inflow temperature to high frequency flow perturbations is investigated. A generic reheat burner geometry is considered, where the spatial distribution of heat release is controlled by autoignition in the jet core on the one hand, and kinematic balance between flow and flame propagation in the shear layers between the jet and the external recirculation zones on the other. To model autoignition and heat release in compressible turbulent flow, a progress variable/stochastic fields formulation adapted for the LES context is used. Flow field perturbations corresponding to transverse acoustic modes are imposed by harmonic excitation of velocity at the combustor boundaries. Simulations with single-frequency excitation are carried out in order to study the flame response to transverse fluctuations of velocity. Heat release fluctuations are observed predominantly in the shear layers, where flame propagation is important. The flow-flame coupling in these regions is analyzed in detail with a filter-based postprocessing approach, invoking a local Rayleigh index and providing insight into the interactions of flame wrinkling by vorticity and convection due to mean and fluctuating velocity.
Analysis and Modeling of Entropy Modes in a Realistic Aeronautical Gas Turbine
Authors: Motheau Emmanuel , Mery Yoann , Nicoud Franck , Poinsot Thierry
Published: August 2013

A combustion instability in a combustor typical of aero-engines is analyzed and modeled thanks to a low order Helmholtz solver. A dynamic mode decomposition (DMD) is first applied to the large eddy simulation (LES) database. The mode with the highest amplitude shares the same frequency of oscillation as the experiment (approximately 350 Hz) and it shows the presence of large entropy spots generated within the combustion chamber and convected down to the exit nozzle. With the lowest purely acoustic mode being in the range 650–700 Hz, it is postulated that the instability observed around 350 Hz stems from a mixed entropy/acoustic mode where the acoustic generation associated with the entropy spots being convected throughout the choked nozzle plays a key role. A delayed entropy coupled boundary condition is then derived in order to account for this interaction in the framework of a Helmholtz solver where the baseline flow is assumed to be at rest. When fed with the appropriate transfer functions to model the entropy generation and convection from the flame to the exit, the Helmholtz solver proves able to predict the presence of an unstable mode around 350 Hz, which is in agreement with both the LES and the experiments. This finding supports the idea that the instability observed in the combustor is indeed driven by the entropy/acoustic coupling.
Maximum Power Point Tracking With Reactant Flow Optimization of Proton Exchange Membrane Fuel Cell
Authors: Karami Nabil , Outbib Rachid , Moubayed Nazih
Published: August 2013

In this paper, a fuel cell (FC) maximum power point tracking (MPPT) with fuel flow optimization is presented. The aim of this study is to extract the maximum power from a FC at different fuel flow rates and to protect the FC from over-current and voltage collapse across terminals. The system is composed of a tracker with a buck converter able to change the output impedance of the FC and therefore its power. In order to illustrate our approach, the tracker is simulated by using both static and dynamic FC models to describe the FC response. Simulation results show the behavior of the tracker at different fuel and oxidant flow rates and verify the concept of maximum power tracking.
Effect of Solution Content ZnO Nanoparticles on Thermal Stability of Polyvinyl Chloride
Authors: Farahbod Farshad , Bagheri Narges , Madadpour Fereshteh
Published: August 2013

Today's pipe made of polyvinyl chloride (PVC) is used as basic good in different industries. The thermal stability of the PVC while is filled with ZnO nanoparticles was studied in this paper. This paper show that the stability of the PVC resin mixed with ZnO nanoparticles solution and Sn was better than that of the PVC resin mixed with Sn alone. The UV (ultraviolet)–vis spectra is showed that under certain heat treatment conditions, the PVC samples without ZnO nanoparticles solution embodied relatively high content of the conjugated double bonds with the chain length of about 3–5. However, the content of the conjugated double bond with the chain length of about 6 was greatly increased when the nanoparticles was filled into the PVC resin. This work shows the ZnO nanoparticles could inhibit the thermal degradation process of PVC resin in ionic mechanism.
Performance Entitlement of Supercritical Steam Bottoming Cycle
Authors: Can Gülen S.
Published: August 2013

A supercritical steam bottoming cycle has been proposed as a performance enhancement option for gas turbine combined cycle power plants. The technology has been widely used in coal-fired steam turbine power plants since the 1950s and can be considered a mature technology. Its application to the gas-fired combined cycle systems presents unique design challenges due to the much lower gas temperatures (i.e., 650 °C at the gas turbine exhaust vis-à-vis 2000 °C in fossil fuel-fired steam boilers). Thus, the potential impact of the supercritical steam conditions is hampered to the point of economic infeasibility. This technical brief draws upon the second-law based exergy concept to rigorously quantify the performance entitlement of a supercritical high-pressure boiler section in a heat recovery steam generator utilizing the exhaust of a gas turbine to generate steam for power generation in a steam turbine.
Numerical Investigation of Combustion Instability in a V-Gutter Stabilized Combustor
Authors: Sundaram S. Soma , Babu V.
Published: August 2013

The stability of the combustion process in a V-gutter stabilized combustor is numerically investigated. To this end, 3D compressible turbulent and unsteady reacting flow calculations have been carried out using LES. The time history of the pressure at several locations is used to determine the frequency and amplitude of the oscillations along with the mode shapes. A shift in the dominant mode of the frequency spectra from the acoustic mode to the hydrodynamic mode is observed. A POD analysis of pressure time histories on the symmetry plane also corroborates this trend. The computational domain is divided into several subvolumes in the wake region of the V-gutter and the time histories of pressure, temperature, and heat release are collected in the individual volumes. It is seen that the fluctuation of pressure and heat release tend to oscillate from being in phase to out of phase over a time period. Unstable regions predicted by the Rayleigh index across a plane are shown to be different from those predicted in a volume owing to the three dimensionality of the flame. Quite interestingly, the calculated values of the indices show the combustor to be most unstable for an equivalence ratio of 0.1665 which is not the leanest one considered here. The global Rayleigh index is shown to correlate well with the amplitude of the dominant mode.
Steady Modeling of a Turbocharger Turbine for Automotive Engines
Authors: Bozza Fabio , De Bellis Vincenzo
Published: August 2013

Nowadays the turbocharging technique is playing a fundamental role in improving automotive engine performance and reducing fuel consumption and the exhaust emissions, in spark-ignition and compression ignition engines, as well. To this end, one-dimensional (1D) modeling is usually employed to compute the engine-turbocharger matching, to select the boost level in different operating conditions, and to estimate the low-end torque level and the transient response. However, 1D modeling of a turbocharged engine requires the availability of the turbine and compressor characteristic maps. This leads to some typical drawbacks: (1)Performance maps of the turbocharger device are usually limited to a reduced number of rotational speeds, pressure ratios, and mass flow rates because of turbine/compressor matching limits; (2) as a consequence of previous issue, unphysical extrapolation of maps' data is commonly required; and (3) heat transfer conditions may strongly differ between test bench measurements and actual operation, where turbocharger is coupled to an internal combustion engine. To overcome the above problems, in the present paper a numerical procedure is introduced: It solves 1D steady flow equations inside the turbine components with the aim of accurately reproducing the experimentally derived characteristic maps. The steady procedure describes the main phenomena and losses arising within the stationary and rotating channels constituting the turbine. It is utilized to directly compute the related steady maps, starting from the specification of a reduced set of geometrical data. An optimization process is employed to identify a number of tuning constants included in the various loss correlations. The procedure is applied to the simulation of five different turbines: three waste-gated turbines, a twin-entry turbine, and a variable geometry turbine. The numerical results show good agreement with the experimentally derived maps for all the tested devices. The model is, hence, used to evaluate the turbine performance in the whole operating domain.
Radial differential interior tomography and its image reconstruction with differentiated backprojection and projection onto convex sets
Authors: Tang Shaojie , Tang Xiangyang
Published: August 2013

Purpose:

Interior tomography has been recognized as one of the most effective approaches in computed tomography (CT) to reduce radiation dose rendered to patients. In this work, the authors propose and evaluate an imaging method of radial differential interior tomography.

Methods:

In interior tomography, an x‐ray beam is collimated to only irradiate the region of interest (ROI) with suspected lesions while the surrounding area/volume of normal tissues/organs is spared. In the proposed imaging method of radial differential interior tomography, the outcome is a ROI image that has gone through a radial differential filtering. The image reconstruction algorithm for the radial differential interior tomography is kept in the fashion of differentiated backprojection and projection onto convex sets, but the requireda priori knowledge in a small round area becomes zero and may be more readily available in practice.

Results:

Using the projection data simulated by computer and acquired by CT scanner, the authors evaluate and verify the performance of the proposed radial differential interior tomography method and its associated image reconstruction algorithm. The preliminary results show that the proposed imaging method can generate an image that is the radial differentiation of a conventional tomographic image and is robust over noise that inevitably exist in practice.

Conclusions:

It is believed that the proposed imaging method may find its utility in advanced clinical applications wherein a ROI‐based image processing and analysis is required for lesion visualization, characterization, and diagnosis.
The Tyrosine Kinase Syk Differentially Regulates Toll-like Receptor Signaling Downstream of the Adaptor Molecules TRAF6 and TRAF3
Authors: Lin Ying-Cing , Huang Duen-Yi , Chu Ching-Liang , Lin Yi-Ling , Lin Wan-Wan
Published: August 2013

The kinase Syk maintains a balanced immune response to pathogens detected by the receptor TLR4.
Allergy Induction
Authors: Mueller Kristen
Published: August 2013

Allergic inflammation requires proteinase-dependent cleavage of fibrinogen that activates innate immunity through Toll-like receptor 4.
Food as Reward
Authors: Kiberstis Paula
Published: August 2013

In mice, a high-fat diet functionally disrupts a gut lipid that controls the brain’s perception of the reward value of food.
How to Stop Responding to Stressful Conditions
Authors: Wong Wei
Published: August 2013

Astrin prevents the association of mTOR and raptor to limit mTORC1 activation in response to stress.
Research for Universal Health Coverage
Authors: Dye Christopher , Reeder John C. , Terry Robert F.
Published: August 2013

The 2013 World Health Report argues that universal health coverage cannot be achieved without funding basic and applied health research.
Skinflammation and Drug Toxicity—A Delicate Balance
Authors: Lacouture Mario E. , Rodeck Ulrich
Published: August 2013

Loss of epidermal growth factor receptor function in keratinocytes triggers an acneiform rash through activation of innate and adaptive immune defense mechanisms.
Torted gallbladder causing massive distension and gross necrosis; a rare surgical emergency
Authors: Ball William Robert , Dalmia Sanjay , Rajamanickam Shenbaga Kumar , Khan Mohammed Ayub
Published: August 2013

Gallbladder torsion is rare and is more frequently seen in elderly women. Published case reports comment that diagnosis of this entity can be made preoperatively through imaging with some advocating removal laparoscopically. This case reports an elderly woman who underwent emergency laparotomy for a massively distended gallbladder with suspected cholecystitis. At laparotomy the gallbladder was found to be torted over 360° round its pedicle of the cystic duct and artery. The torsion was so pronounced that the gallbladder was massively distended and grossly necrotic with a high risk of perforation. As the pedicle was long the gallbladder was easily separated form the liver and removed in its entirety. This case presented significant diagnostic and management difficulties. By observing the clinical features in the triad of triads for gallbladder volvulus prompt diagnosis, investigation and treatment can be started for this rare emergency presentation.
Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers
Authors: Hulin Billy T , Gabbett Tim J , Blanch Peter , Chapman Paul , Bailey David , Orchard John W
Published: August 2013

Objective

To determine if the comparison of acute and chronic workload is associated with increased injury risk in elite cricket fast bowlers.

Methods

Data were collected from 28 fast bowlers who completed a total of 43 individual seasons over a 6-year period. Workloads were estimated by summarising the total number of balls bowled per week (external workload), and by multiplying the session rating of perceived exertion by the session duration (internal workload). One-week data (acute workload), together with 4-week rolling average data (chronic workload), were calculated for external and internal workloads. The size of the acute workload in relation to the chronic workload provided either a negative or positive training-stress balance.

Results

A negative training-stress balance was associated with an increased risk of injury in the week after exposure, for internal workload (relative risk (RR)=2.2 (CI 1.91 to 2.53), p=0.009), and external workload (RR=2.1 (CI 1.81 to 2.44), p=0.01). Fast bowlers with an internal workload training-stress balance of greater than 200% had a RR of injury of 4.5 (CI 3.43 to 5.90, p=0.009) compared with those with a training-stress balance between 50% and 99%. Fast bowlers with an external workload training-stress balance of more than 200% had a RR of injury of 3.3 (CI 1.50 to 7.25, p=0.033) in comparison to fast bowlers with an external workload training-stress balance between 50% and 99%.

Conclusions

These findings demonstrate that large increases in acute workload are associated with increased injury risk in elite cricket fast bowlers.
Positive effect of specific low-frequency electrical stimulation during short-term recovery on subsequent high-intensity exercise
Authors: Bieuzen François , Borne Rachel , Toussaint Jean-François , Hausswirth Christophe
Published: August 2013

The objective of this study was to test how low-frequency electrical stimulation (LFES; Veinoplus Sport (AdRem Technology, Paris, France)) of the calf muscles affects recovery indices compared with 2 other commonly used recovery methods (active, ACT; passive, PAS). The tests used assessed predominantly anaerobic performance after short-term (15 min) recovery, and the kinetics of blood markers. Fourteen highly trained female handball players completed 2 Yo-Yo Intermittent Recovery tests (level 2; YYIR2) separated by a 15-min recovery period. During recovery, 1 of 3 recovery methods (ACT, LFES or PAS) was randomly selected. Performance (i.e., distance run) was measured at the end of each YYIR2 test. Blood lactate, pH, bicarbonate concentrations, heart rate, respiratory gas exchange and tissue saturation index for the lateral gastrocnemius were recorded. LFES showed a very likely beneficial effect on performance during the second YYIR2 relative to PAS and a possible beneficial effect relative to ACT (distance Pre vs. Post; LFES: –1.8%; ACT: –7.6%; PAS: –15.9%). Compared with PAS recovery, LFES and ACT recovery clearly showed a faster return to baseline for blood lactate, pH and bicarbonate concentrations during the recovery period. LFES of the calf muscles and, to a lesser extent, ACT recovery appear to effectively improve short-term recovery between 2 bouts of exhausting exercises. These methods could be of benefit if applied during half-time, for sports involving successive rounds, or where only a limited recovery period is available.
Establishing the value of a salt marsh as a potential benchmark: vegetation surveys and paleoecological analyses as assessment tools
Authors: Bourgon Desroches Myosotis , Lavoie Martin , Lavoie Claude
Published: August 2013

Identifying tidal salt marshes as priority sites for conservation or restoration remains a challenge, as several sites are so severely degraded that allocating financial resources for their protection would be questionable. The decision-making process could nevertheless be facilitated by comparing species assemblages and the dynamics and (or) ecological functions of a site with an ecological benchmark, i.e., a tidal marsh that remains free from anthropogenic disturbances. We used plant surveys and plant macrofossil and pollen analyses for evaluating the benchmark potential of the Pointe-aux-Épinettes marsh, a protected salt marsh of the St. Lawrence River estuary (Canada) and one of the last salt marshes that could potentially be a benchmark along the estuary. Historical evidence indicated that the forests surrounding the marsh were converted into agricultural lands circa 1850. Nevertheless, this land-use change had little impact on the marsh. The long-term impacts of trampling and grazing by livestock on the vegetation were negligible. Macrofossil analyses indicated that the plant assemblages were dynamic, but past and current vegetation assemblages are representative of those characterizing an undisturbed salt marsh, with a very high proportion of native wetland species. In a context where truly undisturbed salt marshes are extremely rare ecosystems, our study indicates that the Pointe-aux-Épinettes plant assemblages could be used as benchmarks against which the condition of the vegetation of other salt marshes in northeastern North America could be evaluated.
Early Devonian graptolites and graptolite biostratigraphy, Arctic Islands, Canada
Authors: Lenz Alfred C.
Published: August 2013

The Early Devonian graptolite fauna of the Arctic Islands comprises the highest species content (17 species) in the world. In spite of this richness, no new species have been recognized; instead already-existing species, scattered around the then-known continents, suggest that relatively complete cosmopolitanism held sway for graptolites. Canadian Arctic biozonation is very similar to schemes elsewhere, consisting of the uniformis and hercynicus biozones in the Lochkovian, falcarius in the lower Pragian, and an expanded yukonensis Biozone in the upper Pragian and the lower Emsian. Three genera and 17 species are recognized: “Monograptus” (microdon cf. microdon, microdon curvatus); Neomonograptus (cf. atopus, aequabilis, bardoensis, falcarius, notoaequabilis); and Uncinatograptus (birchensis, craigensis, hercynicus, langgunensis, parangustidens, subhercynicus, telleri, thomasi, uniformis, yukonensis).
Improving forest field inventories by using remote sensing data in novel sampling designs
Authors: Grafström Anton , Ringvall Anna Hedström
Published: August 2013

It is becoming more common that auxiliary information from remote sensing is available at the planning stage of a forest field inventory. Recent developments in sampling theory allows the inclusion of such information in the sampling design to obtain better samples and, hence, improve estimates of common forest attributes. We explain the methodology and evaluate the possibility of including data from airborne laser scanning in the sampling design. The novel designs that we use can select samples that are balanced on a set of auxiliary variables and (or) well spread in a set of auxiliary variables. The results from a simulation study with real data indicate that significant improvement is achieved.