Detection of quantitative trait loci affecting the milk fatty acid profile on sheep chromosome 22: Role of the stearoyl-CoA desaturase gene in Spanish Churra sheep

Sheep milk fat contains several components that may provide human health benefits, such as monounsaturated fatty acids and conjugated linoleic acid (CLA). Most of the CLA in ruminant milk is synthesized in the mammary gland by the action of the enzyme stearoyl-CoA desaturase (SCD) on circulating vaccenic acid (trans-11 C18:2; VA). Previous studies have found significant associations between polymorphisms in the SCD gene and the fatty acid composition of ruminant products, including sheep milk. Based on this, we performed a quantitative trait loci (QTL) analysis of an ovine chromosome (22) that harbors the SCD gene for effects on milk fatty acid composition traits and classical milk production traits. We identified a suggestive QTL influencing the CLA/VA ratio with the maximum statistic at position 26 cM of the studied chromosome, whereas the SCD gene has been mapped to position 41.6 cM. The individual introduction of 4 SCD single nucleotide polymorphisms in the QTL model did not cause a reduction of the variance explained by the QTL, which suggests that the SCD gene is not directly responsible for the detected effect in the Churra population studied herein. This conclusion was supported by the lack of any significant association identified between the 4 SCD single nucleotide polymorphisms and the CLA/VA ratio. This association analysis suggested a possible effect of the SCD gene on milk fat percentage in Churra sheep. An independent confirmation of these primary results will be required before attempting its practical implementation in selection programs.     

Optimal Control on the Heisenberg Group

Let H denote either the Heisenberg group , or the Cartesian product of n copies of the three-dimensional Heisenberg group . Let {X ₁, Y ₁, ...;, X _n, Y _n} be an independent set of left-invariant vector fields on H. In this paper, we study the left-invariant optimal control problem on H with the dynamics the cost functional with arbitrary positive parameters ₁, ...;, _n , and admissible controls taken from the set of measurable functions The above control system is encoded either in the kernel of a contact 1-form (for ), or in the kernel of a Pfaffian system (for ). In both cases, the action of the semi-direct product of the torus T ⁿ with H describe the symmetries of the problem.The Pontryagin maximum principle provides optimal controls; extremal trajectories are solutions to the Hamiltonian system associated with the problem. Abnormal extremals (which do not depend on the cost functional) yield solutions that are geometrically irrelevant.An explicit integration of the extremal equations provides a tool for studying some aspects of the sub-Riemannian structure defined on H by means of the above optimal control problem.     

Analysis of constant-volume shear tests based on precise measurement of stresses in powder beds

This study demonstrates a new constant-volume shear test configuration to analyze the stresses in powder beds and evaluate powder flowability. A novel cylindrical shear cell geometry and load cell arrangement allowed precise measurement of the normal stress acting on the shear planes of the powder beds. The stress transmission ratio between the top and shear planes decreased with increasing ratio of the powder bed height in the upper section of the shear cell to the shear cell diameter. This was due to friction between the powder bed and the side wall of the upper section of the shear cell. Using the measured values of the normal stress on the shear planes, the effects of the powder bed height and shear cell diameter were eliminated from the data. In addition, to evaluate the shear properties of the powder beds, the powder yield locus, consolidation yield locus, critical state line, shear cohesion, and void fraction were obtained from a single shear test. The powder yield locus data were used to obtain flow functions.     

Shear properties and water connectivity of wet granules at high solid content concentration

The inner liquid distribution in wet granules strongly influences their mechanical properties. In this study, we examined the shear properties (internal friction angle, cohesion, storage modulus and loss modulus) of wet granules composed of graphite particles and water, and determined their inner water connectivity using X-ray refraction contrast imaging computed tomography (CT) to elucidate their correlation. At high solid content concentration (C_SC) region (C_SC = 85 wt.%), internal friction angle of wet granules was slightly lower than that of wet granules with lower C_SC, and their cohesion becomes almost zero. Furthermore, storage modulus of wet granules at C_SC = 85 wt.% was the highest among all wet granules. The X-ray CT and scanning electron microscopy (SEM) observations revealed that the water connectivity in the wet granules was in the pendular state and graphite particles fractured under shear test at C_SC = 85 wt.%. From these results, it can be concluded that lower shear cohesion at C_SC = 85 wt.% is caused by an increase in the number of isolated liquid bridges, and particle fracture results in a decrease in the internal friction angle owing to decreasing roughness of shear plane. Furthermore, the particle fracture also resulted in the higher storage modulus at C_SC = 85 wt.% in rheological measurements.     

Gene Mapping,Cloning and Association Analysis for Salt Tolerance in Rice

Soil salinization caused by the accumulation of sodium can decrease rice yield and quality. Identification of rice salt tolerance genes and their molecular mechanisms could help breeders genetically improve salt tolerance. We studied QTL mapping of populations for rice salt tolerance, period and method of salt tolerance identification, salt tolerance evaluation parameters, identification of salt tolerance QTLs, and fine-mapping and map cloning of salt tolerance QTLs. We discuss our findings as they relate to other genetic studies of salt tolerance association.     

基于分形方法的机载雷达云仿真

为了提高军事仿真训练的逼真程度,根据云的特性以及机载气象雷达上云的成像,提出了一种虚拟云的建模方法,应用分形技术中一种改进的逐次随机增加法进行云数据建模,并且选择适当的控制源曲面,在此控制源曲面基础上与分形生成的曲面进行加权融合,生成具有预定形状的云数据模型。最后将此数据模型按照一定的生成法则在相应点映射成颜色值,建立高度和颜色值的对应关系,可实现机载气象雷达屏幕云的成像仿真。     

融合认知心理学理论的新型教与学优化算法及应用

针对教与学优化算法(teaching-learning-based optimization, TLBO)寻优精度低、易陷入局部最优的问题,提出了一种融合认知心理学理论的新型教与学优化算法(cognitive psychology teaching-learning-based optimization, CPTLBO)。在教阶段融入登门槛效应理论,对于学习有困难的学生设置阶段性学习目标,从而提高学生的整体水平;在学阶段加入老师引导机制,提高算法收敛速度;随后,加入自我调整阶段,学生根据心理控制源理论可被分为内控型和外控型,不同类型的学生对自身成绩采取不同的归因方式并采取相应措施。利用经典的基准测试函数对CPTLBO进行测验,结果表明改进算法在寻优精度和收敛速度方面具有优势。构建CPTLBO-ELM自来水供水量预测模型,采用CPTLBO算法优化极端学习机的输入权值和隐含层阈值参数,以提高模型的预测精度和泛化能力。仿真结果表明:用CPTLBO算法优化后的模型预测结果更准确。     

Stabilizability of two-dimensional linear systems via switched output feedback

The problem of stabilizing a second-order SISO LTI system of the form , y=Cx with feedback of the form u(x)=v(x)Cx is considered, where v(x) is real-valued and has domain which is all of . It is shown that, when stabilization is possible, v(x) can be chosen to take on no more than two values throughout the entire state-space (i.e., v(x){k₁,k₂} for all x and for some k₁,k₂), and an algorithm for finding a specific choice of v(x) is presented. It is also shown that the classical root locus of the corresponding transfer function C(sI-A)^-1B has a strong connection to this stabilization problem, and its utility is demonstrated through examples.     

Fabrication of hybrid micro/nano-textured surfaces using rotary ultrasonic machining with one-point diamond tool

A novel rotary ultrasonic texturing (RUT) technique is proposed to fabricate hybrid periodic micro/nano-textures on flat surfaces. Different from conventional rotary ultrasonic machining, a tailored one-point diamond tool was manufactured and employed for RUT on surfaces of electroless nickel–phosphorus (Ni–P) plating. A one-dimensional longitudinal-vibration mode is used. The combined effect of ultrasonic vibration, rotation and feed motion leads to high-frequency periodic change of cutting edge׳s motion, which is the basic principle for the RUT process. Therefore, to accurately predict and control the texturing process, the cutting locus is firstly mathematically calculated. Hybrid periodic micro/nano-textures comprising linear grooves at the micrometer scale and sinusoidal grooves at the micrometer or nanometer scale were successfully fabricated on machined surfaces, which are in compliance with the results of the mathematical calculations. Different types of surface textures were generated by changing machining conditions. The surface generation mechanism of RUT is illustrated and discussed by analyzing the surface textural features, the cutting locus and the tool tip׳s geometry, including various tool faces, cutting edges, and the cutting corner. The requirements for RUT technique are concluded.     

直齿锥齿轮摆线旋分加工数学模型及参数优化

针对直齿锥齿轮加工方法间歇分度、生产效率低的问题,基于直齿锥齿轮摆线旋分加工方法,采用空间曲线逼近直线的数学方法解释直齿锥齿轮旋分加工原理。在此基础之上,给出摆线旋分加工数学模型,即切削点轨迹的数学模型,并分析影响参数,确定各参数范围及影响规律,进而获得符合加工要求的切削点轨迹。