论亚里士多德的“始点”及其实践意义

在古希腊哲学中,似乎并不缺少对始点的追问和追寻,但只有亚里士多德才把始点问题说得清除。亚里士多德的“始点”概念,是对前人的继承和批判,是对“所以是的是”的追问。亚里士多德认为“始点”是哲学对真理的追求,对“本原”和原因的追问,这是形而上学所必须关注的根本问题之一,只有通过哲学的思考才能获得这一概念。如果说,哲学的思考是哲学家在沉思生活中开展的实践活动,是把始点呈现在表象里、把握在意识中,那么相较于哲学式的沉思生活,政治生活更符合城邦社会中的大多数人,大多数人的实践活动均在城邦制中展开,在此基础上,道德德行的习惯养成得以使“始点”概念在政治生活中实现了其实践意义。因此,对于个体的好生活和城邦的公共生活而言,始点的实践意义大于它在哲学上的理论意义。

GABA transporter 1 transcriptional starting site exhibiting tissue specific difference

GABA transporter 1(GAT1) takes important roles in multiple physiological processes through the uptake and release of GABA, but the regulation of GAT1 gene expression in different tissues is rarely known. To address the question, first, 5’ Rapid amplification of cDNA end (RACE) was used to determine GAT1 transcriptional starting sites in neonatal mouse cerebral cortex and intestine, adult mouse brain and adult rat testis. The products of 5’RACE were confirmed by DNA sequencing. We found that the transcript of GAT1 in neonatal mouse cerebral cortex and adult mouse brain starts at the same site (inside of exon 1), while in mouse intestine, GAT1 starts transcription in intron 1, and in rat testis, the transcript of GAT1 has an additional untranslation exon to the 5’ direction.

Experimental study of the onset of nucleate boiling in vertical helically-coiled tubes

The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet subcooling from 4.7 to 15.0℃, heat flux from 0.11 to 8.9 kW/m2 and mass flux from 218. 2 to 443. 7 kg/（ m2 · s ）. The heat flux, superheat and temperature undershoot at the ONB are analyzed in vertical helically-coiled tubes. Also, the effects of mass flux, system pressure, inlet subcooling and geometric parameters on the ONB are studied. The results demonstrate that the inception heat flux and superheat increase with increasing mass flux and inlet subcooling, but decrease with increasing system pressure and helix diameter. The pitch of the helical coil has a slight effect on the wall superheat and heat flux at the ONB. The correlation of heat flux at the ONB of subcooled flow boiling in helical coil is developed based on the experimental data, and it shows a good agreement with the experimental data.

Snapshots of a Viral RNA Polymerase Switching Gears from Transcription Initiation to Elongation

During transcription initiation,RNA polymerase binds tightly to the promoter DNA defining the start of transcription,transcribes comparatively slowly,and frequently releases short transcripts(3-8 nucleotides)in a process called abortive cycling.Transitioning to elongation,the second phase of transcription,the polymerase dissociates from the promoter while RNA synthesis continues.Elongation is characterized by higher rates of transcription and tight binding to the RNA transcript.The RNA polymerase from enterophage T7 (T7 RNAP) has been used as a model to understand the mechanism of transcription in general,and the transition from initiation to elongation specifically.This single-subunit enzyme undergoes dramatic conformational changes during this transition to support the changing requirements of nucleic acid interactions while continuously maintaining polymerase function.Crystal structures,available of multiple stages of the initiation complex and of the elongation complex,combined with biochemical and biophysical data,offer molecular detail of the transition.Some of the crystal structures contain a variant of T7 RNAP where proline 266 is substituted by leucine.This variant shows less abortive products and altered timing of transition,and is a valuable tool to study these processes.The structural transitions from early to late initiation are well understood and are consistent with solution data.The timing of events and the structural intermediates in the transition from late initiation to elongation are less well understood,but the available data allows one to formulate testable models of the transition to guide further research.

Cell Type Specific Expression of CD80 （B7-1） Gene in Murine

The CD80 （B7-1） costimulatory molecule is expressed on the surface of B cells and its expression is transcriptionally upregulated upon stimuli. To identify the region of murine CD80 promoter that direct cell type specific gene expression, four promoters construct of CD80 gene were generated with DNA fragments fused to the GFP reporter gene. In the present study, significant promoter activity was detected with all four promoter constructs only in the murine B lymphocyte. Further, the CD80 promoter region extending from -3,005 bp to ＋273 bp in relation to the previously reported transcription start site, was identified as tissue specific region. Interestingly, the shortest 700 bp （-427/＋273） of promoter fragment was sufficient to direct the CD80 gene expression. The level of CD80 expression was also found to be modulated by exogenous stimuli in B lymphocyte. Additionally, it was demonstrated that the CD80 gene expression is regulated at the level of transcription where the inducible CD80 gene transcript was detected in B lymphocyte with increasing time.

Discrete Differential Evolution for Mixed Discrete Non-Linear Problems

Differential evolution （DE） is a global optimizer for continuous design variables. To enhance DE, it is necessary to handle discrete design variables. In this paper, a discrete differential evolution （DDE） algorithm is proposed to handle discrete design variables The proposed DDE is based on the DE/l/rand/bin method. In the proposed DDE, the mutation ratio is regarded as the exchange probability, and thus, no modifications of DE/l/rand/bin are required. In addition, in order to maintain diversity through the search process, we initialize all search points. By introducing the initialization of all search points, global or quasi-optimum solution can be found. We validate the proposed DDE by applying it to several benchmark problems.

Bifurcation control of nonlinear oscillator in primary and secondary resonance

A weakly nonlinear oscillator was modeled by a sort of differential equation, a saddle-node bifurcation was found in case of primary and secondary resonance. To control the jumping phenomena and the unstable region of the nonlinear oscillator, feedback controllers were designed. Bifurcation control equations were obtained by using the multiple scales method. And through the numerical analysis, good controller could be obtained by changing the feedback control gain. Then a feasible way of further research of saddle-node bifurcation was provided. Finally, an example shows that the feedback control method applied to the hanging bridge system of gas turbine is doable.

Node scattering manipulation based on trajectory model in wireless sensor network

To deploy sensor nodes over the area of interest,a scheme,named node scattering manipulation,was proposed.It adopted the following method:during node scattering,the initial states of every node,including the velocity and direction,were manipulated so that it would land in a region with a certain probability;every sensor was relocated in order to improve the coverage and connectivity.Simultaneously,to easily analyze the process of scattering sensors,a trajectory model was also proposed.Integrating node scattering manipulation with trajectory model,the node deployment in wireless sensor network was thoroughly renovated,that is,this scheme can scatter sensors.In practice,the scheme was operable compared with the previous achievements.The simulation results demonstrate the superiority and feasibility of the scheme,and also show that the energy consumption for sensors relocation is reduced.

Effects of CO_2 Dilution on Methane Ignition in Moderate or Intense Low-oxygen Dilution(MILD) Combustion:A Numerical Study

Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio（0.2~2）.The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Fur-thermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of tem-perature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex be-haviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as ＂reference time＂,for example,to predict ignition delay time in turbulent reacting flow.

A NEWε-GENERALIZED PROJECTION METHOD OF STRONGLY SUB-FEASIBLE DIRECTIONS FOR INEQUALITY CONSTRAINED OPTIMIZATION

In this paper, the nonlinear optimization problems with inequality constraints are discussed. Combining the ideas of the strongly sub-feasible directions method and the s-generalized projection technique, a new algorithm starting with an arbitrary initial iteration point for the discussed problems is presented. At each iteration, the search direction is generated by a new s-generalized projection explicit formula, and the step length is yielded by a new Armijo line search. Under some necessary assumptions, not only the algorithm possesses global and strong convergence, but also the iterative points always get into the feasible set after finite iterations. Finally, some preliminary numerical results are reported.

Regions of Applicability of Aubry-Mather Theory for Non-convex Hamiltonian

Herman constructed an autonomous system of two degrees of freedom which says that in non-convex situations, oscillations do happen and Aubry-Mather Theory cannot apply (see the results due to W. F. Chen in 1992). In this paper, it is shown that although the orbits could visit a region far away from the initial point in phase space, they can only exist in some fixed regions in I = (I1 , I2 ) plane. Moreover, Aubry-Mather Theory can be applied outside the regions.

Riemann boundary value problems and reflection of shock for the Chaplygin gas

In this paper,we study two-dimensional Riemann boundary value problems of Euler system for the isentropic and irrotational Chaplygin gas with initial data being two constant states given in two sectors respectively,where one sector is a quadrant and the other one has an acute vertex angle.We prove that the Riemann boundary value problem admits a global self-similar solution,if either the initial states are close,or the smaller sector is also near a quadrant.Our result can be applied to solving the problem of shock reflection by a ramp.

Stable tin perovskite solar cells developed via additive engineering

Tin perovskite solar cells(TPSCs)are promising for lead-free perovskite solar cells(PSCs)and have led to extensive research;however,the poor crystallinity and chemical stability of tin perovskites are two issues that prevent stable TPSCs.In this study,we outline a new process that addresses these issues by using tin(II)acetate(Sn(Ac)2)in place of the conventional SnF2 precursor additive.Compared with SnF2,Sn(Ac)2 improves the crystallinity and stability of tin perovskite with fewer defects and better charge extraction.Using this process,we developed a device that has a higher external quantum efficiency for charge extraction compared with the control devices and a power conversion efficiency of 9.93%,which maintained more than 90%of its initial efficiency after 1000 h operation at the maximum power point under standard AM 1.5G solar illumination.

Molecular dynamics reveal a novel kinase-substrate interface that regulates protein translation

A key control point in gene expression is the initiation of protein translation, with a universal stress response being constituted by in- hibitory phosphoryiation of the eukaryotic initiation factor 2α （el F2oL）. In humans, four kinases sense diverse physiological stresses to regulate elF2α to control cell differentiation, adaptation, and survival. Here we develop a computational molecular model of elF2α and one of its kinases, the protein kinase R, to simulate the dynamics of their interaction. Predictions generated by coarse-grained dynamics simulations suggest a novel mode of action. Experimentation substantiates these predictions, identifying a previously unrecognized interface in the protein complex, which is constituted by dynamic residues in both elF2α and its kinases that are crucial to regulate protein translation. These findings call for a reinterpretation of the current mechanism of action of the el F2α kinases and demonstrate the value of conducting computational analysis to evaluate protein function.