Asparagine requirement in Plasmodium berghei as a target to prevent malaria transmission and liver infections

The proteins of Plasmodium, the malaria parasite, are strikingly rich in asparagine. Plasmodium depends primarily on host haemoglobin degradation for amino acids and has a rudimentary pathway for amino acid biosynthesis, but retains a gene encoding asparagine synthetase (AS). Here we show that deletion of AS in Plasmodium berghei (Pb) delays the asexual-and liver-stage development with substantial reduction in the formation of ookinetes, oocysts and sporozoites in mosquitoes. In the absence of asparagine synthesis, extracellular asparagine supports suboptimal survival of PbAS knockout (KO) parasites. Depletion of blood asparagine levels by treating PbASKO-infected mice with asparaginase completely prevents the development of liver stages, exflagellation of male gametocytes and the subsequent formation of sexual stages. In vivo supplementation of asparagine in mice restores the exflagellation of PbASKO parasites. Thus, the parasite life cycle has an absolute requirement for asparagine, which we propose could be targeted to prevent malaria transmission and liver infections.

Size Effects on Strength in the Transition from Single-to-Polycrystalline Behavior

During the transition from single crystalline to polycrystalline behavior, the available data show the strength increasing or decreasing as the number of grains in a cross section is reduced. Tensile experiments were conducted on polycrystalline Ni with grain sizes (d) between 16 and 140 mu m and varying specimen thickness (t), covering a range of lambda (-t/d) between similar to 0.5 and 20. With a decrease in lambda, the data revealed a consistent trend of strength being independent of lambda at large lambda, an increase in strength, and then a decrease in strength. Microstructural studies revealed that lower constraints enabled easier rotation of the surface grains and texture evolution, independent of the specimen thickness. In specimen interiors, there was a greater ease of rotation in thinner samples. Measurements of misorientation deviations within grains revealed important differences in the specimen interiors. A simple model is developed taking into account the additional geometrically necessary dislocations due to variations in the behavior of surface and interior grains, leading to additional strengthening. A suitable combination of this strengthening and surface weakening can give rise to wide range of possibilities with a decrease in lambda, including weakening, strengthening, and strengthening and weakening.

Microstructural evolution and strength variability in microwires

Tensile experiments on cold-drawn Ni microwires with diameters from similar to 115 to 50 gm revealed high strengths, with significant strength variability for finer wires with diameters less than similar to 50 gm. The wires showed pronounced necking at fracture. The coarser wires with diameters > 50 mu m exhibited conventional ductile cup-cone fracture, with dimples in the central zone and peripheral shear lips, whereas finer wires failed by shear with knife or chisel-edge fractures. Shear bands were observed in all samples. Further, through- section microscopy of selected fractured samples revealed that the shear bands did not go across the enitre specimen for the coarser wires. The shear bands led to grain fragmention, with a reduction in grain aspect ratio as well as rotations away from the initial < 111 > orientations. The strength data were analysed based on a Weibull approach. The data could be rationalized in terms of failure from volume defects in coarser wires, with a high Weibull modulus, and from surface defects in finer wires, with a low Weibull modulus and greater variability. (C) 2015 Elsevier B.V. All rights reserved.

Strength reliability and in vitro degradation of three-dimensional powder printed strontium-substituted magnesium phosphate scaffolds

Strontium ions (Sr2+) are known to prevent osteoporosis and also encourage bone formation. Such twin requirements have motivated researchers to develop Sr-substituted biomaterials for orthopaedic applications. The present study demonstrates a new concept of developing Sr-substituted Mg-3(PO4)(2) - based biodegradable scaffolds. In particular, this work reports the fabrication, mechanical properties with an emphasis on strength reliability as well as in vitro degradation of highly biodegradable strontium-incorporated magnesium phosphate cements. These implantable scaffolds were fabricated using three-dimensional powder printing, followed by high temperature sintering and/or chemical conversion, a technique adaptable to develop patient-specific implants. A moderate combination of strength properties of 36.7 MPa (compression), 242 MPa (bending) and 10.7 MPa (tension) were measured. A reasonably modest Weibull modulus of up to 8.8 was recorded after uniaxial compression or diametral tensile tests on 3D printed scaffolds. A comparison among scaffolds with varying compositions or among sintered or chemically hardened scaffolds reveals that the strength reliability is not compromised in Sr-substituted scaffolds compared to baseline Mg-3(PO4)(2). The micro-computed tomography analysis reveals the presence of highly interconnected porous architecture in three-dimension with lognormal pore size distribution having median in the range of 17.74-26.29 mu m for the investigated scaffolds. The results of extensive in vitro ion release study revealed passive degradation with a reduced Mg2+ release and slow but sustained release of Sr2+ from strontium-substituted magnesium phosphate scaffolds. Taken together, the present study unequivocally illustrates that the newly designed Sr-substituted magnesium phosphate scaffolds with good strength reliability could be used for biomedical applications requiring consistent Sr2+-release, while the scaffold degrades in physiological medium. Statement of significance The study investigates the additive manufacturing of scaffolds based on different strontium-substituted magnesium phosphate bone cements by means of three-dimensional powder printing technique (3DPP). Magnesium phosphates were chosen due to their higher biodegradability compared to calcium phosphates, which is due to both a higher solubility as well as the absence of phase changes (to low soluble hydroxyapatite) in vivo. Since strontium ions are known to promote bone formation by stimulating osteoblast growth, we aimed to establish such a highly degradable magnesium phosphate ceramic with an enhanced bioactivity for new bone ingrowth. After post-processing, mechanical strengths of up to 36.7 MPa (compression), 24.2 MPa (bending) and 10.7 MPa (tension) could be achieved. Simultaneously, the failure reliability of those bioceramic implant materials, measured by Weibull modulus calculations, were in the range of 4.3-8.8. Passive dissolution studies in vitro proved an ion release of Mg2+ and PO43- as well as Sr2+, which is fundamental for in vivo degradation and a bone growth promoting effect. In our opinion, this work broadens the range of bioceramic bone replacement materials suitable for additive manufacturing processing. The high biodegradability of MPC ceramics together with the anticipated promoting effect on osseointegration opens up the way for a patient-specific treatment with the prospect of a fast and complete healing of bone fractures. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Cumulative Impulse Strength for Epoch Extraction

Algorithms for extracting epochs or glottal closure instants (GCIs) from voiced speech typically fall into two categories: i) ones which operate on linear prediction residual (LPR) and ii) those which operate directly on the speech signal. While the former class of algorithms (such as YAGA and DPI) tend to be more accurate, the latter ones (such as ZFR and SEDREAMS) tend to be more noise-robust. In this letter, a temporal measure termed the cumulative impulse strength is proposed for locating the impulses in a quasi-periodic impulse-sequence embedded in noise. Subsequently, it is applied for detecting the GCIs from the inverted integrated LPR using a recursive algorithm. Experiments on two large corpora of speech with simultaneous electroglottographic recordings demonstrate that the proposed method is more robust to additive noise than the state-of-the-art algorithms, despite operating on the LPR.

The impact of latent heating on the location and strength of the tropical easterly jet

The tropical easterly jet (TEJ) is a prominent atmospheric circulation feature observed during the Asian summer monsoon. It is generally assumed that sensible heating over the Tibetan Plateau directly influences the location of the TEJ. However, other studies have suggested the importance of latent heating in determining the jet location. In this paper, the relative importance of latent heating on the maintenance of the TEJ is explored through simulations with a general circulation model. The simulation of the TEJ by the Community Atmosphere Model, version 3.1 is discussed in detail. These simulations showed that the location of the TEJ is well correlated with the location of the precipitation. Significant zonal shifts in the location of the precipitation resulted in similar shifts in the zonal location of the TEJ. These zonal shifts had minimal effect on the large-scale structure of the jet. Further, provided that precipitation patterns were relatively unchanged, orography did not directly impact the location of the TEJ. These changes were robust even with changes in the cumulus parameterization. This suggests the potential important role of latent heating in determining the location and structure of the TEJ. These results were used to explain the significant differences in the zonal location of the TEJ in the years 1988 and 2002. To understand the contribution of the latitudinal location of latent heating on the strength of the TEJ, aqua-planet simulations were carried out. It has been shown that for similar amounts of net latent heating, the jet is stronger when heating is in the higher tropical latitudes. This may partly explain the reason for the jet to be very strong during the JJA monsoon season.

Elasticity, stability, and ideal strength of beta-SiC in plane-wave-based ab initio calculations

On the basis of the pseudopotential plane-wave method and the local-density-functional theory, this paper studies energetics, stress-strain relation, stability, and ideal strength of beta-SiC under various loading modes, where uniform uniaxial extension and tension and biaxial proportional extension are considered along directions [001] and [111]. The lattice constant, elastic constants, and moduli of equilibrium state are calculated and the results agree well with the experimental data. As the four SI-C bonds along directions [111], [(1) over bar 11], [11(1) over bar] and [111] are not the same under the loading along [111], internal relaxation and the corresponding internal displacements must be considered. We find that, at the beginning of loading, the effect of internal displacement through the shuffle and glide plane diminishes the difference among the four Si-C bonds lengths, but will increase the difference at the subsequent loading, which will result in a crack nucleated on the {111} shuffle plane and a subsequently cleavage fracture. Thus the corresponding theoretical strength is 50.8 GPa, which agrees well with the recent experiment value, 53.4 GPa. However, with the loading along [001], internal relaxation is not important for tetragonal symmetry. Elastic constants during the uniaxial tension along [001] are calculated. Based on the stability analysis with stiffness coefficients, we find that the spinodal and Born instabilities are triggered almost at the same strain, which agrees with the previous molecular-dynamics simulation. During biaxial proportional extension, stress and strength vary proportionally with the biaxial loading ratio at the same longitudinal strain.

Experimental Study on Dynamic Properties of High Strength Fiber Clusters

In this paper, the dynamic behaviors of several kinds of high strength fibers, including Kevlar, UHMPE, glass fibers, carbon fibers etc., are investigated experimentally, with a Split Hopkinson Tension Bar (SHTB). The effect of strain rate on the modulus, strength, failure strain and failure characteristics of fibers, under impact loading, is analyzed with the relative stress vs. strain curves. At the same time, the mechanism about the rate dependence of mechanical behaviors of various fibers is discussed based on the understanding on the microstructures and deformation models of materials. Some comments are also presented on the decentralization of experimental results, and a new method called traveling wave method is presented to increase the experimental accuracy. Research results obtained in this paper will benefit to understand the energy absorption and to build up the constitutive law of protective materials reinforced by high strength fibers.

Experimental investigation of the shear strength of a unidirectional carbon/aluminum composite under dynamic torsional loading

In this paper, the dynamic shear strength of a unidirectional C/A356.0 composite and A356.0 alloy, respectively, are measured with a split Hopkinson torsional bar (SHTB) technique. The results indicate that the carbon fibers make very little contribution to the enhancement of the shear strength of the matrix material. The microscopic inspections on the fracture surface of the composite show a multi-scale zigzag feature. This implies that there is a complicated shear failure mechanism in the unidirectional carbon/aluminum composite.

Strength of Offshore Pipelines in Different Operation States and Analyzing Software

在近海管线的铺设、安装、使用过程中有多种作业状态：在位、悬跨、挖沟、提吊、铺管等。各种状态下管线的受力特点不同,加上管线结构、海况和海底土壤等因素又都很复杂,所以近海管线的强度分析难度大、内容多。分别采用解析方法、数值方法（有限元法、打靶法）和二者结合来解决理论上的（如几何非线性、动边界等）、实用性方面的难点。在理论分析的基础上,编制了符合产业部门工程师使用要求的近海管线强度分析软件。介绍了该软件进行力学分析时采用的理论以及软件界面。

Shear Strength Measurements in LY-12 Aluminium Alloy During Shock Loading

Lateral stress of LY-12 alummium alloy under plate impact shock loading was measured. Based on the measured data, the Hugoniot relation and shear strength were obtained. The result has demonstrated that the shear strenath of the tested material increases remarkably with the increasing longitudinal stress. This means that the assumption of constant shear strength usually adopted in shock stress calculation is not suitable for the present material.

A simple approach to the evaluation of fiber/matrix interfacial shear strength and fracture toughness

On the basis of microscopical analyses of the fiber distribution and longitudinal shear deformation in unidirectional fiber composites, a simple approach is presented for characterizing the interfacial sheer strength and fracture toughness.

Effects of Nanostructures on the Fracture Strength of the Interfaces in Nacre

A strengthening mechanism arising from a type of inorganic nanostructure in the organic matrix layers is presented by studying the structural and mechanical properties of the interfaces in nacre. This nanostructural mechanism not only averagely increases the fracture strength of the organic matrix interfaces by about 5 times, but also effectively arrests the cracks in the organic matrix layers and causes the crack deflection in this biomaterial. The present investigation shows that the main mechanism governing the strength of the organic matrix interfaces relies on the inorganic nanostructures rather than the organic matrix. This study provides a guide to the interfacial design of synthetic materials.

Efecto de distintos intervalos de mediciones de leche sobre la estimación de producción de leche total, repetibilidad y la forma de la curva de lactancia en un hato reyna

El presente trabajo se realizó con el objetivo de estudiar el efecto de cuatro intervalos de medición de leche (diario, cada 7, 14 y 28 días) sobre la producción de leche total, la repetibilidad y la forma de la curva de lactancia. Para lo cual se utilizaron los registros productivos y reproductivos del hato criollo Reyna de la Finca San José ubicada en Masatepe, Nicaragua. Se estudiaron 105 lactancia provenientes de 28 vacas durante el periodo de 1982 - 1990. Las características estudiadas fueron PLTOT, repetibilidad y la forma de la curva de lactancia. Todos los análisis estadísticos fueron realizados con el procedimiento de mínimos cuadrados y máxima verosimilitud establecido en el paquete estadístico LSMLMW demás, se utilizaron los modelos y ecuaciones propuestas por de varianza se estudió el efecto de cuatro tratamientos (intervalos de medición) sobre la producción de leche total, obteniéndose las siguientes medias de mínimos cuadrados: 1,655.23±77.79 para el tratamiento 1 <mediciones diarias), 1,655.98±77.79 para el tratamiento 2 <mediciones cada 7 días), 1,644.64±77.79 para el tratamiento 3 (mediciones cada 14 días) y 1,669.21±77.79 para el tratamiento 4 (mediciones cada 28 días). Encontrándose un efecto no significativo de los diferentes intervalos de medición sobre la producción de leche total. Los valores encontrados para los indices de Repetibilidad para cada uno de los tratamientos fueron de: 0.46±0.11, 0.50±0.11, 0.48±0.11 y 0.50±0.11 para los tratamientos 1, 2, 3, 4 respectivamente Los valores para los parámetros y variables estudias en la curva de la lactancia fueron 3.2±2.5, 0.47±0.32, 0.01± 0.06, 51.81±29.10, 9.45±3.49 y 6.97±1.02 para a, b, c, Tp, Rp y S respectivamente Al estudiar el efecto de los tratamiento sobre las variables y parámetros de la curva de lactancia se determino que solamente la variable (S) que determina la persistencia fue afectada significativamente de medición. Analizando el efecto de los intervalos de medición de leche sobre la forma de la curva de lactancia se determinó que dicho efecto es no significativo debido a que la forma de la curva es similar para los cuatro intervalos estudiados.