Periodicities in Cluster Algebras and Cluster Automorphism Groups

We study the relations between two groups related to cluster automorphism groups which are defined by Assem,Schiffler and Shamchenko.We establish the relation-ships among (strict) direct cluster automorphism groups and those groups consisting of periodicities of labeled seeds and exchange matrices,respectively,in the language of short exact sequences.As an application,we characterize automorphism-finite cluster algebras in the cases of bipartite seeds or finite mutation type.Finally,we study the relation between the group Aut(A) for a cluster algebra A and the group AutMn(S) for a mutation group Mn and a labeled mutation class S,and we give a negative answer via counter-examples to King and Pressland's problem.     

水稻压致变异和高压对水稻生长发育的影响

 将高收获指数型优质籼稻（Oryza sativa L.）品种“粤香占”种子在不同条件下进行了3个生长周期的高压种子处理和实验室种植试验。稻种经高压处理后,与对照样品相比,当代种子发芽和秧苗成长较慢且植株个体差异较大;后期生长较快,分蘖数及产量与对照样持平或有所增加。受压样品产生了4种新的植株变异,其中2种为不育植株,另外两种变异植株种植至F2及F3代,变异性状都能稳定遗传。表明高压不仅可以对水稻当代植株生理产生明显的影响,而且可以诱导水稻产生明显和稳定的可遗传变异。     

Cancer-Associated Mutations of the Adenosine A2A Receptor Have Diverse Influences on Ligand Binding and Receptor Functions

The adenosine A_2A receptor (A_2AAR) is a class A G-protein-coupled receptor (GPCR). It is an immune checkpoint in the tumor micro-environment and has become an emerging target for cancer treatment. In this study, we aimed to explore the effects of cancer-patient-derived A_2AAR mutations on ligand binding and receptor functions. The wild-type A_2AAR and 15 mutants identified by Genomic Data Commons (GDC) in human cancers were expressed in HEK293T cells. Firstly, we found that the binding affinity for agonist NECA was decreased in six mutants but increased for the V275A mutant. Mutations A165V and A265V decreased the binding affinity for antagonist ZM241385. Secondly, we found that the potency of NECA (EC₅₀) in an impedance-based cell-morphology assay was mostly correlated with the binding affinity for the different mutants. Moreover, S132L and H278N were found to shift the A_2AAR towards the inactive state. Importantly, we found that ZM241385 could not inhibit the activation of V275A and P285L stimulated by NECA. Taken together, the cancer-associated mutations of A_2AAR modulated ligand binding and receptor functions. This study provides fundamental insights into the structure–activity relationship of the A_2AAR and provides insights for A_2AAR-related personalized treatment in cancer.     

近红外光谱分析原理及其在牧草航天育种的应用前景

近红外光谱(NIRS)的定量分析技术是一项高效、快捷检测样品中某种化学成分的分析新方法,近年来在饲料营养价值评估、土壤养分检测等方面得到了广泛的应用。文章简要介绍了NIRS技术产生和探测的基本原理、方法和技术特点,回顾了航天育种的研究进展及其在草类植物上的应用情况,然后从牧草营养成分分析、次生代谢产物预测、病虫害抗性鉴定、非生物胁迫抗性评估4个方面阐述了NIRS分析技术应用于草类植物航天育种的意义和潜在价值。NIRS技术不仅能提高育种选择效率、加快育种进程,还有助于诱变机理研究的深入,将其应用于草类植物航天育种有着重要的理论和实际意义。     

A Reevaluation of the Critical Membrane Potential of the Effective Refractory Period in Guinea Pig Ventricular Fibres

The traditional critical membrane potential (CMP), -55—-60mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile responses to the stimulus during repolarization of action potential (AP), particularly from+10 to -60 mV, were observed. One third of 35 tested cells displayed testing action potential (TAP) and local response at≥-54 mV when they were stimulated by testing pulses in 37℃ normal Tyrode's solution. Potential level of TAP which occurred earliest was at -30 mV and that of local response which appeared earliest was at 0 mV during repolarization among 95 systematic tests. Most of the TAPs belonged to the slow response potential type. The ratio of TAP evoked at ≥-54 mV initial membrane potential (IMP) was as high as 86% when the experiment was carried out in 37℃ 1.5 mmol KC1/L Tyrode's solution. In view of distribution of IMPs of TAPs, the CMP of ERP in guinea pig ventricular muscle fibres was more     

Improvement of speciation analysis in environmental matrices. Identification of refractory arsenicals—some analytical difficulties

Arsenic species that do not form hydrides have been recently put in evidence in coastal seawater. This paper describes the procedures used in the first attempts to concentrate, purify and identify these forms as well as the difficulties that make this identification problematic. The rationale behind a new scheme under investigation based on solvent extraction/high-performance liquid chromatography/dynamic-flow-fast-atom-bombardment mass spectrometry is presented. Some alternatives that seem promising for the future are indicated.     

Study of energy-band structures,some thermomechanical properties and chemical bonding for a number of refractory metal carbides by the LMTO-ASA method

The energy-band structures of V, Nb, VC, NbC and WC have been calculated with the use of the linearized method of “muffin-tin” orbitals (LMTO-ASA). The calculated band structures are in good agreement with a previous self-consistent APW calculation. The prominent features of the band structures for WC are a particularly wide 5d W, 2p C band, and also the presence of a separate 5d W band below the Fermi level. The values of the lattice constants, bulk moduli, sound velocities, Debye temperatures and melting temperatures have been calculated and are in reasonable agreement with experiment. It is shown that the high values of the bulk moduli of VC and NbC are explained by the hybridization between s- and p-metal states and 2s C, 2p C states, while the extreme value of the modulus for WC is due mainly to the covalency resulting from 5d W, 2s C and 2p C hybridization.     

A NEW SILENT MUTATION FOUND IN THE CHINESE PAH LOCUS AND ITS ROLE IN THE PRENATAL DIAGNOSIS OF PHENYLKETONURIA

A silent mutation or sequence polymorphism, A to T substitution at codon 399 in exon11 of the PAH gene from a Chinese PKU patient, was found by sequence analysis. The fre-quencies of this new mutation in normal and abnormal (PKU) genes were 0.005 and 0.09,respectively, based on the analyses of 100 normal individuals and 39 PKU patients usingDNA amplification with polymerase chain reaction (PCR) and oligonucleotide hybridizationmethods. This silent mutation can be used as a "genetic marker" for PKU prenatal diagno-sis. Recently, a fetus at risk for PKU, who could not be completely predicted by RFLPslinkage analysis, was prenatally diagnosed with this genetic marker.     

Detection of C677T mutation in methylenetetrahydrofolate reductase gene by denaturing high performance liquid chromatography

In this paper, we described an assay for the detection of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene using denaturing high-performance liquid chromatography (DHPLC). The conditions for DHPLC analysis were systematically investigated based on a general HPLC instrument (Prostar VARIAN). A 225 bp DNA fragment covering the 677 site of MTHFR gene was amplified by PCR technology using the purified DNA from whole blood or whole blood as template DNA. PCR products were directly injected without the need for purification. The C677T mutation could be clearly distinguished by DHPLC technology. Our data demonstrated that DHPLC was a powerful and alternative tool for detection of genetic variants and single-nucleotide polymorphisms to electrophoresis technology.     

Transmission and filtering in photonic circuits: effects of absorption and amplification

We study the effect of absorption and amplification on transmission and filtering in one-dimensional dielectric photonic structures made of dangling side branches grafted periodically along an infinite monomode waveguide with defective branches. The loss and gain are introduced by adding an imaginary part ″ to the dielectric constant. We show that for reasonable values of ″, loss and gain affect essentially the transmission at the frequencies of localized modes associated with the defect branch introduced into the periodic structure. The amplitude and the phase of the transmission and reflection coefficients associated with defect modes are discussed as function of ″ and the size of the structure. The properties of the defect modes in presence of loss and gain can be used as an on/off switching device in a demultiplexer made of the above photonic structures.