扩展键基近场动力学的几何非线性扩展

扩展键基近场动力学模型解决了经典模型中固定泊松比的限制问题,但是仅限应用于小变形情况下的模拟。提出了一种计算键变形的实现方法,利用有限变形理论中的描述使模型能够处理几何非线性问题。通过最小二乘拟合得到物质点的局部位移场,再对位移函数求导得到局部域的变形梯度张量。固体的旋转与拉伸通过对变形梯度张量的极分解分离,从而将扩展键的变形部分从总体位移中提取。随后,通过对变形系统的各个键力进行积分,从而获得系统大变形的正确预测结果。最后,开展了几个基准测试,与非线性有限元结果进行对比并验证了所提出模型的有效性和精确性。

改进的键基正交各向异性近场动力学模型

针对经典的键基近场动力学(bond-based peridynamic,BPD)模型受固定泊松比限制的问题,提出一种改进BPD模型。该模型可解除泊松比限制,并可用于分析正交各向异性单向板的变形和裂纹扩展问题。在改进BPD模型中,每根键受到轴向和横向成对力的作用,额外增加的节点转动可消除由横向力引起的附加弯矩,从而确保该模型满足角动量守恒条件。仿真结果验证所提出的改进BPD模型的精度,并展示其预测碳纤维复合材料变形和裂纹扩展的能力。

Investigation of bioactivity and biodegradability of Mg-bioceramic implants:An in vitro study for biomedical applications

In this study,Mg-based composites,by the addition of ZnO,Ca_(2)ZnSi_(2)O_(7),Ca_(2)MgSi_(2)O_(7),and CaSiO_(3)as bioactive agents,were fabricated using friction stir processing.The microstructure and in vitro assessment of bioactivity,biodegradation rate,and corrosion behavior of the resultant composites were investigated in simulated body fluid(SBF).The results showed that during the immersion of composites in SBF for 28 d,due to the release of Ca^(2+)and PO_(4)^(3-)ions,hydroxyapatite(HA)crystals with cauliflower shaped morphology were deposited on the surface of composites,confirming good bioactivity of composites.In addition,due to the uniform distribution of bioceramic powders throughout Mg matrix,grain refinement of the Mg matrix,and uniform redistribution of secondary phase particles,the polarization resistance increased,and the biodegradation rate of composites significantly reduced compared to monolithic Mg matrix.The polarization corrosion resistance of Mg-ZnO increased from 0.216 to 2.499 kΩ/cm^(2)compared to monolithic Mg alloy.Additionally,Mg-ZnO composite with the weight loss of 0.0217 g after 28 d immersion showed lower weight loss compared to other samples with increasing immersion time.Moreover,Mg-ZnO composite with the biodegradation rate of 37.71 mm/a exhibited lower biodegradation rate compared to other samples with increasing immersion time.

平行双裂纹扩展的单键双参数近场动力学研究

针对键基近场动力学方法存在固定泊松比的限制,本文提出了单键双参数键基近场动力学模型。根据Cauchy-Born准则,在小变形条件下采用均匀应变工况,一次推导出该键基近场动力学的所有模型参数,通过薄板的连续变形和破坏实例验证了它的准确性,进而研究了薄板预制平行双裂纹的受拉破坏现象。结果表明:传统键基近场动力学模型仅适合模拟特定泊松比材料的力学行为,否则材料的位移误差较大,材料的破坏模式也可能失真;在一定条件下,平行双裂纹的纵向间距对薄板整个破坏过程产生一定的影响,随着双裂纹纵向间距的增大,裂纹起裂时刻提前,水平延伸长度逐渐减小,裂纹偏移角度、贯通间距和贯通时刻却随之增大;随机细小裂纹的分布在一定程度上会抑制某一主裂纹在单侧或两侧的扩展,导致薄板的破坏形态发生了显著改变。该模型具有传统单键单参数键基近场动力学模型的简便性,同时拓展了它的泊松比适用范围。

冲击荷载作用下泊松比对脆性材料破坏影响的近场动力学分析

键基近场动力学(Peridynamic,PD)方法已证实能模拟固体材料中裂纹自发地萌生和扩展,但存在特定泊松比的限制。提出了单键双参数键基PD模型,它继承了传统键基PD简单性、稳定性等特点,并拓展了泊松比的适用范围。通过变形的静力定量计算、冲击荷载作用下Kalthoff-Winkler试验等裂纹扩展过程的模拟,验证了该模型。进一步就平行双裂纹薄板的冲击破坏现象,研究了泊松比对其破坏的影响。结果表明:冲击荷载一定时,材料泊松比的增大,会导致薄板起裂提前,其抗冲击破坏能力变弱,同时泊松比改变破坏路径致使薄板贯通延迟,破坏总时间延长,贯通速度降低;冲击荷载较大时,泊松比的变化会对平行双裂纹脆性薄板的裂纹扩展路径产生明显影响。

Theoretical Study of the C-CI Bond Dissociation Enthalpy and Electronic Structure of Substituted Chlorobenzene Compounds

Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3PW91, B3P86） methods together with 6-31G^＊＊ and 6-311G^＊＊ basis sets. The results show that B3P86/6-311G^＊＊ method is the best method to compute the reliable BDEs for substituted chlorobenzene compounds which contain the C-C1 bond. It is found that the C-C1 BDE depends strongly on the computational method and the basis sets used. Substituent effect on the C-C1 BDE of substituted chlorobenzene compounds is further discussed. It is noted that the effects of substitution on the C-C1 BDE of substituted chlorobenzene compounds are very insignificant. The energy gaps between the HOMO and LUMO of studied compounds estimate the relative thermal stability ordering are also investigated and from this data we of substituted chlorobenzene compounds.

Electronic Structures, DNA-binding, SAR, and Spectral Properties of Ruthenium Methylimidazole Complexes [Ru（MeIm）4L]^2＋（L=iip,tip,2ntz）

Theoretical studies on the electronic and geometric structures, the trend in DNA-binding affinities as well as the the structure-activity relationship （SAR） of a series of water-soluble Ru（II） methylimidazole complexes, i.e. [Ru（Mehn）4iip]^2＋ （1） （MeIm=l-methylimidazole, iip=2-（1H-imidazo-4-group）-lH-imidazo[n,5-f][1,10]phenanthroline）, [Ru（MeIm）4tip]^2＋ （2） （tip=2-（thiophene-2-group）-lH-imidazo[4,5-f] [i,10]phenanthroline）, and [Ru（Melm）42ntz]^2＋ （3） （2ntz=2-（2-nitro-l,3-thiazole-5-group）-lH-imidazo[4,5-f][1,10]phenanthroline）, were car- ried out using the density functional theory （DFT）. The electronic structures of these Ru（II） complexes were analyzed on the basis of their geometric structures optimized in aqueous solution, and the trend in the DNA-binding constants （Kb） was reasonably explained. The results show that the replacement of imidazole ligand by thiophene ligand can effectively improve the DNA-binding affinity of the complex. Meanwhile, it was found that introduc- ing the stronger electronegative N atom and NO2 group on terminal loop of intercalative ligand can obviously reduce the complex＇s LUMO and HOMO-LUMO gap energies. Based on these findings, the designed complex [Ru（MeIm）42ntz]^2＋ （3） can be expected to have the greatest Kb value in complexes 1-3. In addition, the structure-activity relationships and antitumor mechanism were also carefully discussed, and the antimetastatic activity of the designed complex 3 was predicted. Finally, the electronic absorption spectra of this series of complexes in aqueous solution were calculated, simulated and assigned using DFT/TDDFT methods as well as conductor-like polarizable continuum model （CPCM）, and were in good agreement with the experimental results.

Improved Keystroke Authentication Accuracy Based on Statistics and Weight

Abstract： In order to improve the recognition accuracy of key stroke authentication, a methodology based on feature extraction of keystroke sequence is presented in this paper. Firstly, the data of the users＇ keystroke feature information that has too much deviation with the mean deviation is filtered out. Secondly, the probability of each input key is calculated and 10 values which do not have the best features are selected. Thirdly, they are weighed and a score evaluating the extent to which the user could be authenticated successfully is calculated. The benefit of using a third-party data set is more objective and comparable. At last,

Halogen Bonding or Hydrogen Bonding between 2,2,6,6-Tetramethyl- piperidine-noxyl Radical and Trihalomethanes CHX3 （X=CI, Br, I）

The halogen and hydrogen bonding complexes and trihalomethanes （CHX3, X=C1, Br, I） are between 2,2,6,6-tetramethylpiperidine-noxyl simulated by computational quantum chem- istry. The molecular electrostatic potentials, geometrical parameters and interaction energy of halogen and hydrogen bonding complexes combined with natural bond orbital analysis are obtained. The results indicate that both halogen and hydrogen bonding interactions obey the order CI〈Br〈I, and hydrogen bonding is stronger than the corresponding halogen bond- ing. So, hydrogen bonding complexes should be dominant in trihalomethanes. However, it is possible that halogen bonding complex is competitive, even preponderant, in triiodomethane due to the similar interaction energy. This work might provide useful information on specific solvent effects as well as for understanding the mechanism of nitroxide radicals as a bioprobe to interact with the halogenated compounds in biological and biochemical fields.

Synthesis of nucleoside-peptide conjugate with disulfide bond as linker at C-5 of uridine

In order to prepare pyrimidine nucleoside-peptide conjugate concisely, we developed a one-pot synthetic strategy. Started from uridine, 5-S-acetyl-thiomethyl-2＇,3 ＇-di-O-isopropylidene-uridine （4） was synthesized as the key intermediate in four steps. Under acidic condition, compound 4 was deprotected and reacted with PySS-R （8, 12, 15, Py = 2-pyridyl, R = amino acid or peptide） in one pot to form uridine conjugates （9, 13, 2） with disulfide bond as linker.

N-Radical enabled cyclization of 1,n-enynes

Compared to the widely used carbon-centered radicals,N-radicals have been relatively unexplored owing to the lack of practical and convenient production methods.Over the past few years,benefitting from the resurgence of reliable and controllable radical chemistry,N-radicals have been produced via thermal decomposition,oxidants,metal salts,or electrocatalysis.Therefore,numerous N-radical enabled cyclization of 1,n-enynes methods have been developed,providing a versatile and concise synthetic platform for the preparation of complex cyclic systems and natural products containing elaborate ring frameworks.In this review,we will summarize recent advances in the promising field of radical chemistry focusing on the production methods of N-radicals and their cyclization patterns,associated mechanisms,unmet challenges,and future opportunities.

Hydroxyl radicals-mediated oxidative cleavage of the glycosidic bond in cellobiose by copper catalysts and its application to low-temperature depolymerization of cellulose

As the most abundant source of biomass in nature for sustainable production of fuels and chemicals,efficient depolymerization of cellulose under mild conditions,due to the difficulty in selective cleavage of itsβ-1,4-glycosidic bonds,still remains challenging.Here,we report a novel method for oxidative cleavage of the glycosidic bonds by free radicals.Probed by the cellobiose reaction,it was found that·OH radicals,generated from the decomposition of H2O2 catalyzed by CuSO4 or CuO/SiO2,were efficient for selective conversion of cellobiose to glucose and gluconic acid at a low temperature of 333 K,and their selectivities reached 30.0%and 34.6%,respectively,at 23.4%cellobiose conversion.Other radicals,such as·SO4?,also exhibited high efficacy in the cellobiose reaction.Mechanistic studies suggest that the oxidative cleavage of theβ-1,4-glycosidic bond by the free radicals involve formation of the carbon radical intermediate via abstraction of the H atom dominantly at the C1 position.Following this oxidative mechanism,treatment of microcrystalline cellulose with·OH by impregnation with H2O2 and CuSO4 catalyst at 343 K led to significant enhancement in its hydrolysis efficiency.These results demonstrate the effectiveness of this new method in the oxidative cleavage of glycosidic bonds,and its viability for the efficient depolymerization of cellulose at low temperatures,which can be further improved,for example,by exploring new free radicals and optimizing their reactivity and selectivity.

Association of triacylglyceride content and transcript abundance of genes involving in lipid synthesis of nitrogen deficient Phaeodactylum tricornutum

Phaeodactylum tricornutum is a diatom that is rich in lipids. Recently, it has received much attention as a feedstock for biodiesel production. Nitrogen deficiency is widely known to increase the content of neutral lipids （mainly triacylglycerides, or TAGs） of microalgae, including P. tricornutum, but the mechanism is unclear. In this study, we deciphered the correlations between TAG content and nine key enzymatic genes involved in lipid synthesis in P. tricornuturn. After being cultured under nitrogen-free conditions for 0, 4, 24, 48, 72, 120, and 168 h, the TAG contents ofP. tricornutum cells were assayed and the transcript abundances of the target genes were monitored by quantitative real-time PCR. The results show that the abundances of four target gene transcripts （LACS3, G3PDH2, G3PDH3, and G3PDH5） were positively correlated with TAG content, indicating that these genes may be involved in TAG synthesis in P. tricornutum. The findings improve our understanding of the metabolic network and regulation of lipid synthesis and will guide the future genetic improvement of the TAG content ofP. tricornutum.

The Connection Between Slavery and Prophecy as It Relates tothe American Nation in the Writings of the Adventist PioneersDuring the Antebellum Period

The period between 1850 and 1865 was a period of major social upheavals in American society; the major issue was the slavery. This period also witnessed the birth and organization of the Sabbatarian Adventism, a pre-millennial Christian movement distinguished by an emphasis on the Seventh-day Sabbath and a special understanding of Bible prophecies. Most Adventist pioneers vehemently opposed slavery, although not always on the same ground as their Christian counterparts. Aided by their peculiar understanding of Bible prophecy, the early Adventists identified America with apocalyptical end-time power, slavery being the key attribute of the ＂beast that looks like a lamb but speaks like a dragon＂ from Revelation 13：11. This article investigates the development of Adventist connection between slavery, America and Bible prophecy.

Isolation and Purification of Carp Mitochondrial DNA and Structural Analysis of Its tRNA^(Cys) Gene and the Light Strand Origin

A new method is presented with which we isolated milochondrial DNA from fresh carp liver usingdifferential centrifugation and DNase treatment that gave high yield of purified product with an easyand economical procedure. Highly distinct bands were displayed in agarose gel electrophoresls ofthe product digested with restrictlon enzymes, which were successfully used in constructingrestriction map and molecular clone of mitochondrial genes. With DNAs thus obtained, we havecloned cysteine tRNA gene (tRNA^(Cys) gene) of carp mitochondria, determined the nucleotide sequenceof it and the light strand origin, and depicted the cloverleaf secondary structure of tDNA^(Cya) and thelight strand origin. Analysis of nucleotide sequences of tRNA^(Cy) genes of 5 vertebrates has revealedunusual features of carp mitochondrial tRNA^(Cy) gene as compared with their cytoplasmic counter-parts, Altogether 36 bases were found in the light strand origin of carp mitochondriaf: 11 pairs in thestem; and 14 bases in the loop. As compared with those of other 11 vertebrate species, the sequenceof the stem is very conservative while both sequence and length of the loop are quite variable. Thestructure of the stem-loop may play an important role in light strand replication.

Photocatalytic C–X borylation of aryl halides by hierarchical SiC nanowire-supported Pd nanoparticles

Hierarchical Si C nanowire-supported Pd nanoparticles showed high photocatalytic activity for the C–X(X = Br, I) borylation of aryl halides at 30 °C. The Si C/Pd Mott-Schottky contact enhances the rapid transfer of the photogenerated electrons from Si C to the Pd nanoparticles. As a result, the concentrated energetic electrons in the Pd nanoparticles can facilitate the cleavage of C–I or C–Br bonds, which normally requires high-temperature thermal processes. We show that the present Pd/Si C photocatalyst is capable of catalyzing the transformation of a large variety of aryl halides to their corresponding boronate esters under visible light irradiation, with excellent yields.

Infrared Photodisssociation Spectroscopy of Boron Carbonyl Cation Complexes

The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly bound complexes involving a B（CO）3＋ core ion, which is predicted to have a planar D3h structure with the central boron retaining the most favorable 8-electron configuration. The B2（C0）4＋ cation is determined to have a planar D2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDA- NOCV method indicates that the OC→B cr donation is stronger than the B-＋CO π back donation in both ions.

Immobilization of Lipase by Covalent Binding on Crosslinked Allyl Dextran

Lipase was immobilized by covalent binding on crosslinked allyl dextranusing SESA as coupling agent. It is shown that this immobilization approach isan efficient one for lipase. The activity of the immobilized lipase can rerch to300 - 450 U/g (dry weight). It exhibits good temperature stability, can retain88% activity after being incubated at 70℃ for 2 h. Special effects will be expected from our immobilized lipase in its applications in organic media due tothe nature Of the support.

Lower baseline ALT cut-off values and HBV DNA levels better differentiate HBeAg(-) chronic hepatitis B patients from inactive chronic carriers

AIM： To determine whether new cut-off values for aianine aminotransferase （ALT） and baseline hepatitis B virus （HBV） DNA levels better differentiate HBeAg（-） chronic hepatitis B （CriB） patients from inactive chronic carriers. METHODS： Ninety-one patients [32 HBeAg（＋） CriB, 19 inactive carriers and 40 HBeAg（-） CriB] were followed up for 2 years and were tested for HBV DNA levels by a PCR-based assay. ALT was tested twice during the last 6 mo using new cut-off values： ULN （upper limit of normal） 30 IU/L for males, 19 IU/L for females. Diagnostic accuracy, sensitivity, specificity, positive and negative predictive values were calculated by discriminant analysis. RESULTS： When using the revised ALT cut-off values, the lowest optimal HBV DNA level that differentiated HBeAg（-） CHB patients from inactive carriers was 50000 copies/mL. The diagnostic accuracy of HBV DNA to determine inactive carriers with a cut-off of 50000 copies/mL was similar to the previously recommended cut-off of 100000 copies/mL （91%）. HBV DNA levels were lower than the cut-off value in 95% of inactive carriers and in 28% of HBeAg（-） CHB patients. With ALT 〈 30 IU/L in men and 〈 19 IU/L in women and HBV DNA levels 〈 100000 copies/mL, the risk of CHB is 5%. On the other hand, if ALT values were 〉 30 IU in men and 〉 19 IU in women and baseline HBV DNA levels were 〉 100000 copies/mL, the risk is 86%. CONCLUSION： New cut-off values for ALT together with HBV DNA levels proposed by AASLD （American Association for the Study of Liver Diseases） and NIH （National Institute of Health） consensus seem appropriate to characterize inactive carriers.

A Simplified Green Chemistry Approach to the Synthesis of Carbon-Carbon Double Bonds Via Knoevenagel Condensation Catalyzed with ZrOCl2.8H2O

A green and simplified room-temperature procedure was reported for the synthesis of carbon-carbon double bonds by Knoevenagel condensation of various aldehydes with malononitrile and ethyl cyanoacetate in the presence of catalytic amount of ZrOCl2·8H2O in aqueous media.