Generalization of the ordinary state-based peridynamic model for isotropic linear viscoelasticity

This paper presents a generalization of the original ordinary state-based peridynamic model for isotropic linear viscoelasticity. The viscoelastic material response is represented using the thermodynamically acceptable Prony series approach. It can feature as many Prony terms as required and accounts for viscoelastic spherical and deviatoric components. The model was derived from an equivalence between peridynamic viscoelastic parameters and those appearing in classical continuum mechanics, by equating the free energy densities expressed in both frameworks. The model was simplified to a uni-dimensional expression and implemented to simulate a creep-recovery test. This implementation was finally validated by comparing peridynamic predictions to those predicted from classical continuum mechanics. An exact correspondence between peridynamics and the classical continuum approach was shown when the peridynamic horizon becomes small, meaning peridynamics tends toward classical continuum mechanics. This work provides a clear and direct means to researchers dealing with viscoelastic phenomena to tackle their problem within the peridynamic framework.     

超空泡水下航行器定深控制研究

极高的航速使得对超空泡水下航行器的控制变得异常复杂. 为了对其深度进行有效控制, 必须对其纵平面运动特性进行研究. 本文首先建立了超空泡水下航行器的纵平面运动模型, 分析了其纵平面运动特性; 然后进行了控制算法的综合; 最后, 仿真及试验结果均验证了所设计的航行器纵平面运动控制算法的有效性. 试验结果表明该控制系统具有较高的控制精度. 本文的研究成果为进一步研究水下超空泡航行器的运动控制提供了必要的理论基础.     

BK Polyomavirus bkv-miR-B1-5p: A Stable Micro-RNA to Monitor Active Viral Replication after Kidney Transplantation

Background: Bkv-miR-B1-5p is a viral micro-RNA (miRNA) specifically produced during BK polyomavirus (BKPyV) replication. Recent studies have suggested using bkv-miR-B1-5p as a biomarker to monitor viral infection and predict complications in kidney transplant patients. To identify the technical limitations of this miRNA quantification in biological samples, knowledge of its stability and distribution in the extracellular compartment is necessary. Moreover, a proof of concept for using bkv-miR-B1-5p as a biomarker of active replication in chronic infection is still missing in the published literature. Methods: The stability of bkv-miR-B1-5p was evaluated in samples derived from cell cultures and in urine from BKPyV-infected kidney transplant recipients. The miRNA was quantified in different fractions of the extracellular compartment, including exosomes, and protein binding was evaluated. Finally, we developed an in vitro model for chronic culture of BKPyV clinical isolates to observe changes in the bkv-miR-B1-5p level during persistent infections. Results: Bkv-miR-B1-5p is a stable biomarker in samples from humans and in vitro experiments. Marginally associated with the exosomes, most of the circulating bkv-miR-B1-5p is bound to proteins, especially Ago2, so the miRNA quantification does not require specific exosome isolation. The bkv-miR-B1-5p level is predictable of viral infectivity, which makes it a potential specific biomarker of active BKPyV replication after kidney transplantation.     

Study on the Signal Control System of Urban Traffic with a Genetic Algorithm

In the paper the aim and meaning of traffic microscopic simulation is discussed first, and then three sub-models of the system are established, e. i. the model for random generation of the vehicles, the model for car-following and lane change influenced by an adjacent vehicle, and the model for control and optimization of intersection with signal. Optimization of the traffic signal timing with a genetic algorithm and a microscopic simulation is carried out. It represents a novel approach to solving optimal signal timing.     

A Single Bout of Ultra-Endurance Exercise Reveals Early Signs of Muscle Aging in Master Athletes

Middle-aged and master endurance athletes exhibit similar physical performance and long-term muscle adaptation to aerobic exercise. Nevertheless, we hypothesized that the short-term plasticity of the skeletal muscle might be distinctly altered for master athletes when they are challenged by a single bout of prolonged moderate-intensity exercise. Six middle-aged (37Y) and five older (50Y) master highly-trained athletes performed a 24-h treadmill run (24TR). Vastus lateralis muscle biopsies were collected before and after the run and assessed for proteomics, fiber morphometry, intramyocellular lipid droplets (LD), mitochondrial oxidative activity, extracellular matrix (ECM), and micro-vascularisation. Before 24TR, muscle fiber type morphometry, intramyocellular LD, oxidative activity, ECM and micro-vascularisation were similar between master and middle-aged runners. For 37Y runners, 24TR was associated with ECM thickening, increased capillary-to-fiber interface, and an 89% depletion of LD in type-I fibers. In contrast, for 50Y runners, 24TR did not alter ECM and capillarization and poorly depleted LDs. Moreover, an impaired succinate dehydrogenase activity and functional class scoring of proteomes suggested reduced oxidative phosphorylation post-24TR exclusively in 50Y muscle. Collectively, our data support that middle-aged and master endurance athletes exhibit distinct transient plasticity in response to a single bout of ultra-endurance exercise, which may constitute early signs of muscle aging for master athletes.     

Identification of ritual blood in African artifacts using TOF-SIMS and synchrotron radiation microspectroscopies

A new protocol is implemented to demonstrate the presence of blood in the patina of African art objects from Mali. Divided into three steps, the protocol first consists in demonstrating the presence of proteins and localizing them in the sample's cross sections using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and synchrotron-based infrared microspectrometry (microFT-IR). In a second time, TOF-SIMS is used to investigate heme, which is a blood marker. If heme is missing, which could mean that it is too degraded to be detected, X-ray microfluorescence (microXRF) and X-ray absorption near-edge microspectroscopy (microXANES) are used to prove the presence of iron in the protein area and to get a fingerprint of its chemical environment. This permits us thus to demonstrate that iron is indeed linked with proteins and not with mineral phases of the sample. Coupled with the ritual context of the objects, this constitutes a proof of the use of blood. Thanks to this protocol, which has the major advantage of avoiding false positive results, the presence of blood has been demonstrated in seven out of the eight studied samples.     

Attentional control in normal aging and Alzheimer's disease.

Objective: Attentional control, the ability to maintain goal-directedness in the face of distraction, has been shown to decline in normal aging (NA) and Alzheimer's disease (AD), yet the nature and extent of deficits is under debate. This study investigated attentional control in NA and AD compared to healthy young adults in several tasks such as setting, suppressing, switching, and preparing attention. Method: Fifty-two participants (17 AD, 17 NA, and 18 young participants) underwent the Tower of London, the Zoo map test, the Stroop test, letter verbal fluency, a computerized version of the Rule shift cards tests, the Trail making test, the Plus-minus test, and a reaction time task with variable preparatory intervals. Results: Analyses of variance showed that NA as compared to young participants were impaired in the Tower of London, the Stroop test, and the Rule shift cards tests. AD as compared to NA participants were impaired in all tests except the Stroop test. Principal component analysis in young adults confirmed the modularity of attentional tasks, which was reduced in NA and AD participants. Principal component analysis in all populations showed a decline of attentional control with NA and AD regardless of the tasks, with an increase in between-participants variability only between young and NA participants. Conclusions: Attentional control dysfunction is different in NA and AD: NA affects suppressing attention, switching attention for unpredictable but not predictable events, and preparing attention for unpredictable events, whereas AD affects setting, suppressing, switching, and preparing attention with less specificity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

On the origin of the blue/green color of blast‐furnace slag‐based materials: Sulfur K‐edge XANES investigation

Slag‐based materials including mortars, concretes, Ca‐geopolymers, etc., are known to display a fascinating blue/green color upon hydration. This specific color is of particular concern in applications where visual esthetics are important. Yet only limited studies have been devoted to this phenomenon so far and its origin remains unexplained. It has sometimes been attributed, without any experimental evidence, to the presence of polysulfur species in the slag. To address the origin of this coloration, sulfur K‐edge X‐ray absorption near edge structure (XANES) spectroscopy was used to investigate the evolution of the speciation of sulfur during slag hydration. Three methods of slag activation were considered: thermal, portland cement, and sodium silicate. The impact of the activation method on the sulfur K‐edge XANES spectrum was examined first. Then, a comparison was made between the XANES of blue and white samples or zones with or without the blue color within the same sample. Independently of the activation route, the blue color was found to be unambiguously related to the presence of a prepeak in the corresponding XANES spectrum. This feature was absent for white samples or white zones. The prepeak, which was located at lower energy than the peak corresponding to the most common reduced sulfur species, was attributed to the presence of the trisulfur radical anion S₃^?. This blue chromophore is known to be at the origin of the deep blue color of the stone lapis lazuli or the ultramarine pigment (derived from lazurite).     

Gelatin supports with immobilized laccase as sustainable biocatalysts for water treatment

Millimeter-size beads of gelatin are manufactured by dripping process to give enzyme supports qualified for micropollutants biodegradation in alternative wastewater treatment. The bead diameter is dependent on the tip diameter, the gelatin solution viscosity and the swelling of polymer chains in the collecting bath. Chemical crosslinking was performed with glutaraldehyde using optimal concentration to give mechanical and thermal properties suitable for application in stirred reactor in aqueous medium. Laccases from Trametes versicolor are grafted on the gelatin beads with glutaraldehyde. Sixty percentage of the initial enzymatic activity, evaluated by the oxidation of 2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) is maintained after 10 successive cycles of reaction. Thermal stability at 60°C of immobilized biocatalysts is improved when compared to free enzymes (45% vs 10% of relative activity after 6 h of incubation). The simplicity of the procedure to form gelatin beads and their properties make them promising bio-based and biodegradable support for enzyme immobilization.     

舰船冷却设备的防腐对策

针对舰船用海水冷却设备的腐蚀情况的调查，提出了 基本的舰用冷却设备的腐蚀控制原则，并论述了电绝缘措施控制电偶腐蚀、非金属复合层保 护、牺牲阳极和外加电流阴极保护等几种防腐方法，实践证明通过对冷却设备采用本文中提 出的防腐措施，可以很好的解决舰船冷却设备的腐蚀防护问题.