Mechanism of the Initial Stage of Thermal Decomposition of Nitroguanidine

A theoretical and experimental study of the thermal decomposition of nitroguanidine(NQ) has been carried out. Various thermolysis channels were studied by quantum chemistry methods at the CCSD(or DLPNO-CCSD) level using the aug-cc-pVDZ basis set. It is shown that the lowest activation enthalpies(170-180kJ/mol) are characteristic of the reactions of NO2abstraction from the initial NQ and the reaction channel with the transfer of oxygen from the nitro group to carbon in the limiting stage. Additionally, the thermolysis of NQ was studied experimentally in a nonisothermal mode with heating rates from 1 to 10K/min. In these experiments, the weight loss of the sample, thermal effects, and mass spectra of the products were recorded. An analysis of the experimental data confirmed the results of a theoretical study of the mechanism of thermal decomposition of NQ. The main thermolysis products are N2O, HNCO, NH3, and NO2, which fully corresponds to quantum chemical calculations.

Validity and Systematic Position of Rana altaica(Rana:Ranidae):Results of a Phylogenetic Analysis

In order to evaluate the phylogenetic position and validity of Rana altaica,we investigated the phylogeny of brown frogs in Eurasia by Bayesian Inference and Maximum Parsimony analyses of a fragment from the mitochondrial DNA gene Cytochrome b.Both analyses resolved R.altaica as nesting deeply within R.arvalis.Most samples of the nominal R.altaica from the Altai region and specimens from Central Siberia shared a haplotype with R.arvalis based on the network analysis.The matrilineal relationships suggested that R.altaica should be considered as a junior synonym of R.arvalis.Furthermore,our study suggested that the species group division of Chinese brown frogs should be re-evaluated within a phylogenetic context.

刚性沉水植物影响下波浪传播及泥沙悬浮数值模拟

由于植物引起的紊动作用,含刚性植物床面中悬浮泥沙浓度与无植物裸床相比显著增加,而通过平均流速计算底床切应力的传统泥沙模型无法模拟出该现象。因此,在含植物水流水沙运动物理模型试验的基础上,构建了基于Flow–3D的含刚性沉水植物条件下波浪传播的三维数学模型,模拟了植物影响下波浪动力特征和泥沙悬浮过程,同时从紊动能角度修正希尔兹数,对泥沙模块进行了改进。与实测数据相比,该模型可较精确地模拟出植物引起的整体水流流速减小和局部冠层顶部处的流速增大、水体紊动增强以及紊动能在波周期内出现两个峰值的现象。与原始泥沙模块相比,改进的模型考虑了植物尾流紊动对泥沙运动的影响,可提高含植物床面泥沙悬浮模拟的精度。

添加剂对受石油污染的不同粒径组分的冻土热性能的影响(英文)

The results of studying of thermal properties of oil contaminated disturbed and undisturbed soils, group composition of oil and moisture phase structures contented in these soils are considered in this paper. The thermal properties for oil contaminated soils of undisturbed addition after 6 years of oil transformation and for soils of disturbed addition and artificial pollution are compared. And the influence of addition on thermal properties of soils was revealed.

Mathematical modeling of tornadoes and squall storms

Recent advances in modeling of tornadoes and twisters consist of significant achievements in mathematical calculation of occurrence and evolution of a violent F5-class tornado on the Fujita scale, and four-dimensional mathematical modeling of a tornado with the fourth coordinate time multiplied by its characteristic velocity. Such a tornado can arise in a thunderstorm supercell filled with turbulent whirlwinds. A theory of the squall storms is proposed. The squall storm is modeled by running pertur- bation of the temperature inversion on the lower boundary of cloudiness. This perturbation is induced by the action of strong, hurricane winds in the upper and middle troposphere, and looks like a running solitary wave （soliton）; which is developed also in a field of pressure and velocity of a wind. If a soliton of a squall storm gets into the thunderstorm supercell then this soliton is captured by supercell. It leads to additional pressure fall of air inside a storm supercell and stimulate amplification of wind velocity here. As a result, a cyclostrophic balance inside a storm supercell generates a tornado. Comparison of the radial distribution of wind velocity inside a tornado calculated by using the new formulas and equations with radar observations of the wind velocity inside Texas Tornado Dummit in 1995 and inside the 3 May 1999 Oklahoma City Tornado shows good correspondence.

东欧黄土-古土壤剖面的孢粉和气候地层学记录及其与ESR测年的海相地层对比(英文)

记述东欧平原黄土-古土壤剖面多重年代地层的划分结果,评估黄土地区更新世主要的古地理事件的对比,建立东欧平原黄土-古土壤发育时期的17个期—9个间冰期和8个冰期。间冰期内次一级单元是吸热凉温阶(endothermal coolings)(冷时段,cold spells),干热阶、湿热阶(thermoxerotic and thermohygrotic stages)和间冰期中次级气候韵律,以及冰期内的冰阶(stadials),间冰阶(interstadials),中间阶(interphasials),湿冷阶(cryohygrotic),干冷阶(cryoxerotic stages)和冰期中的次级气候韵律。其中吸热凉温阶占据了间冰期的大部分。 东欧平原黄土-古土壤形成时期的环境和植被演化由以下剖面的孢粉资料构成:上Oka(Likhvin-Chekalin section),上Don(Strelitsa section),中Kuma(Otkaznoe section),中Dniester(Molodova section,Ketrosy section)和中Desna(Arapovichi section)。 根据孢粉-气候地层研究获得的原始资料,本文重建了欧亚大陆北部60万年以来的古气候事件、古基岩沉积、冰川、冰缘、外冰缘带沉积,并进行了周期的确定和远距离对比。在综合年代地层柱上的古环境事件及其相应的带和年代地层的对比,是依据亚化石化的软体动物外壳的电子自旋共振分析结果。已知的间冰期集中在58万年,40万年,31万年,22万年及14.

Discovery of Japalura chapaensis Bourret, 1937 (Reptilia： Squamata： Agamidae) from Southeast Yunnan Province, China

Due to a paucity of surveys in northern Indochina and lack of international collaborations among neighboring countries, recognized distributional ranges for many amphibian and reptile species end at the political borders for some countries, despite seemingly continuous suitable habitat spanning the region. Combining both morphological and genetic data, we report the first discovery of Japalura chapaensis, a rare agamid lizard believed previously to be endemic to northern Vietnam only, along the border region of southeastern Yunnan Province, China. To facilitate future research on the genus Japalura sensu lato in Indochina, we provide detailed descriptions of additional specimens of this rare species, including the first description of coloration in life and an expanded diagnosis, and discuss the species boundary of J. chapaensis with respect to its congeners.

Influence of non-covalent interactions on properties of lanthanide systems with aromatic ligands

Two series of lanthanide compounds, namely, chlorides containing different numbers of both 1,10-phenanthroline （Phen） molecules and chloride anions in the first coordination sphere, and Schiff Bases （SBs） derived from Pyridoxal （PL） and amino acids, were characterized by single crystal X-ray diffraction and luminescence techniques. The combined use of these techniques for the analysis of long-distance europium non-covalent interactions was performed for the first time. As a result, the correlation between supramolecular organization and the features of the Eum electronic transitions was found for the compounds of the first series. Strong non-covalent interactions between pyridoxal tings of SBs （the second series of compotmd） led to the formation of 1：2 species and four-dentate coordination function of these SBs in aqueous solution.

Direct laser interference patterning of nonvolatile magnetic nanostructures in Fe60Al40 alloy via disorder‐induced ferromagnetism

Current magnetic memories are based on writing and reading out the domains with opposite orientation of the magnetization vector.Alternatively,information can be encoded in regions with a different value of the saturation magnetization.The latter approach can be realized in principle with chemical order-disorder transitions in intermetallic alloys.Here,we study such transformations in a thin-film(35 nm)Fe60Al40 alloy and demonstrate the formation of periodic magnetic nanostructures(PMNS)on its surface by direct laser interference patterning(DLIP).These PMNS are nonvolatile and detectable by magnetic force microscopy(MFM)at room temperature after DLIP with a single nanosecond pulse.We provide different arguments that the PMNS we observe originate from increasing magnetization in maxima of the interference pattern because of chemical disordering in the atomic lattice of the alloy at temperatures T higher than the critical temperature Tc for the order(B2)-disorder(A2)transition.Theoretically,our simulations of the temporal evolution of a partially ordered state at T>Tc reveal that the disordering rate is significant even below the melting threshold.Experimentally,we find that the PMNS are erasable with standard thermal annealing at T<Tc.

The characteristic pattern of multiple colored layers in coastal stratified lakes in the process of separation from the White Sea

An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located.

Residues of Logarithmic Differential Forms in Complex Analysis and Geometry

In the article, we discuss basic concepts of the residue theory of logarithmic and multi-logarithmic differential forms, and describe some aspects of the theory, de-veloped by the author in the past few years. In particular, we introduce the notion of logarithmic differential forms with the use of the classical de Rham lemma and give an explicit description of regular meromorphic differential forms in terms of residues of logarithmic or multi-logarithmic differential forms with respect to hypersurfaces, com-plete intersections or pure-dimensional Cohen-Macaulay spaces. Among other things, several useful applications are considered, which are related with the theory of holo-nomic D-modules, the theory of Hodge structures, the theory of residual currents and others.

Carbcations Chemistry： β-Methyl Shift--A New Rearrangement of the Carbcations Bridged Alicyclic Hydrocarbons

Results of researches on study of the kinetics and isomerization mechanism of the alkyladamantanes in the presence of the heterogeneous catalysts of the acid type are considered as detection and experimental proof of a new intramolecular rearrangement of the carbcations bridged alicyclic hydrocarbons--2,4-moving of the methyl groups （β-methyl shift）. The proof of realization of such rearrangement is direct and primary formation 1,4-dimethyladamantane from 1,2-dimethyladamatane, passing a formation stage of the thermodynamic much stable 1,3-dimethyladamantane; direct formation 1,3,6-trimethyladamantane from 1,3,4-trimethyladamantane, excepting a formation stage 1,3.5-trimethyladamantane, and also other isomers which formation is impossible to explain by means of known 1,2-methyl shift （a-methyl shift）.

Ferromagnetic Resonance in Gd/Co Multilayer

Magnetometric and ferromagnetic resonance(MFR)measurements have been performed on the polycrystalline multilayered structure,[Gd(7.5 nm)/Co(3 nm)]20.The temperature dependence of magnetization of the sample suggests a compensation temperature Tcomp in the region of 240 K,implying that the Co and Gd layers are antiferromagnetically aligned.The FMR curves are strongly temperature dependent,particularly in the vicinity of Tcomp.

Fluorescence color diversity of great barrier reef corals

A group of variously colored proteins belonging to the green fAuorescent protein(GFP)family are responsible for coloring coral tissues.Corals of the Great Barrier Reef were studied with the custom-built fiber laser fluorescence spectrometers.Spectral analysis showed that most of the excarmined corals contained multiple fuorescent peaks ranging from 470 to 620nm.This obser-vation was attributed to the presence of multiple genes of GFP-like proteins in a single coral,as well as by the photo-induced post-translational modifcations of certain GFP-like proteins.We isolated a novel photo-convertible fuorescent protein(FP)from one of the tested corals.We:propose that two processes may explain the observed diversity of the fuorescent spectra in corals:(1)dark post-translational modifcation(maturation),and(2)color photo-conversion of certain maturated proteins in response to sunlight.

Nonlinear Magnetoimpedance Effect in FeCoNi Ferromagnetic Tubes

The very high (up to 820% of the magnetoimpedance ratio) and sensitive nonlinear giant magnetoimpedance effect has been studied in the FeCo1Ni magnetic tubes electroplated onto Cu(3%)Be nonmagnetic wirefor frequencies from 1-10MHz. Special annealing was carried out in order to induce the magnetic anisotropy. The high harmonic generation was observed and the harmonics show larger variations with the external magnetic field than the fundamental frequency. The super high sensitivity of the harmonics is promising as regards the increase of the sensitivity of magnetoimpedance sensors.

SiC_(f)/SiC与GH5188钎焊接头的界面产物及机制研究

使用CuTi+NbB_(2)活性钎料成功实现了碳化硅纤维增强碳化硅(SiC_(f)/SiC)复合材料与GH5188钴基高温合金二者的连接,研究了钎焊温度对接头界面微观组织以及力学性能的影响,并对连接机制展开了分析。接头典型的界面结构为GH5188/Cu+(Ni,Co,Cu)3Ti_(2)+(Co,Ni,Cu)Ti_(2)/Cu_(4)Ti/Cu+Cu_(3)Ti_(2)+(Ni,Co)-Si+(Ni,Co,Cu)Ti_(2)/TiC+Cr-C/SiC+Cu/SiC_(f)/SiC。由于NbB2粉末的引入,导致形核点的增加,金属间化合物倾向于以小颗粒相的形态析出并弥散分布在钎缝中。而随着温度的升高,金属的溶解情况以及元素的互扩散以及反应情况均有所加强,但温度的改变基本上不改变各层的占比;同时,陶瓷侧的补充活性元素(Co,Cr,Ni)随着温度而增多,这在一定程度上有利于陶瓷与焊缝之间的连接。因此,在1050℃/10 min的情况下,接头的室温抗剪强度最高达到72 MPa。接头均沿钎缝和SiC_(f)/SiC复合材料的反应界面断裂。

A detailed reconstruction of changes in the factors and parameters of soil erosion over the past 250 years in the forest zone of European Russia(Moscow region)

Accelerated soil erosion is a major threat to soil,and there are great variations in the rate of soil erosion over time due to natural and human-induced factors.The temperate forest zone of Russia is character-ized by complex stages of land-use history(i.e.active urbanization,agricultural development,land abandonment,etc.).We have for the first time estimated the rates of soil erosion by the WaTEM/SEDEM model(rainfall erosion)and by a regional model(snowmelt erosion)over the past 250 years(from 1780 to 2019)for a 100-km2 study site in the Moscow region of Russia.The calculations were made on the basis of a detailed historical reconstruction of the following factors:the location of the arable land,crop rotation,the rain erosivity factor,and the maximum snow water equivalent.The area of arable land has decreased more than 3.5-fold over the past 250 years.At the end of the 20th century,the rates of gross erosion had declined more than 5.5-fold(from 28×10^(3) to 5×10^(3) t·ha^(-1)yr^(-1))in comparison with the end of the 18th century.Changes in the boundaries of arable land and also the relief features had led to a significant intra-slope accumulation of sediments.As a result of sediment redeposition within the arable land,the variation in net soil erosion was significantly lower than the variation in gross soil erosion.The changes in arable land area and in crop composition are the factors that have to the greatest extent determined the changes in soil erosion in this territory.

Adiabatic paths and pseudoholomorphic curves

We consider the (2+1)-dimensional Abelian Higgs model, governed by the Ginzburg-Landau action functional and describe the adiabatic limit construction for this model. Then we switch to the 4-dimensional case and Show that the Taubes correspondence may be considered as a (2+2)-dimensional analogue of the adiabatic limit construction.

The history and assessment of effectiveness of soil erosion control measures deployed in Russia

Research activities aimed at design and application of soil conservation measures for reduction of soil losses from cultivated fields started in Russia in the last quarter of the 19th century.A network of"zonal agrofor-estry melioration experimental stations"was organized in the different landscape zones of Russia in the first half of the 20th century.The main task of the experiments was to develop effective soil conservation measures for Russian climatic,soil and land use conditions.The most widespread and large-scale introduction of coun-termeasures to cope with soil erosion by water and wind into agricultural practice supported by serious governmental investments took place during the Soviet Union period after the Second World War.After the Soviet Union collapse in 1991,general deterioration of the agricultural economy sector and the absence of investments resulted in cessation of organized soil conservation measures application at the nation-wide level.However,some of the long-term erosion control measures such as forest shelter belts,artificial slope terracing,water diversion dams above formerly active gully heads survived until the present.In the case study of sediment redistribution within the small cultivated catchment presented in this paper an attempt was made to evaluate average annual erosion rates on arable slopes with and without soil conservation measures for two time intervals.It has been found that application of conservation measures on cultivated slopes within the experimental part of the case study catchment has led to a decrease of average soil loss rates by at least 2.52.8 times.The figures obtained are in good agreement with previously published results of direct monitoring of snowmelt erosion rates,reporting approximately a 3-fold decrease of average snowmelt erosion rates in the experimental sub-catchment compared to a traditionally cultivated control sub-catchment.A substantial decrease of soil erosion rates on arable slopes has been equally reflected in a corresponding decrease of aggradation rates in the main valley bottom and tributaries.

Chaotic Driven Tunneling in Rectangular Double-Well

We consider a charged particle confined in a one-dimensional rectangular doublewell potential,driven by an external periodic excitation at frequencyΩand with amplitude A.We find that there is the regime of the parametric resonance due to the modulation of the amplitude A at the frequencyωprm,which results in the change in the population dynamics of the energy levels.The analysis relies on the Dirac system of Hamiltonian equations that are equivalent to the Schr¨odinger equation.Considering a finite dimensional approximation to the Dirac system,we construct the foliation of its phase space by subsets F_(ab)given by constraints a≤N_(0)≤b on the occupation probabilities N0 of the ground state,and describe the tunneling by frequenciesνab of the system’s visiting subsets F_(ab).The frequenciesνab determine the probability density and thus the Shannon entropy,which has the maximum value at the resonant frequencyω=ωprm.The reconstruction of the state-space of the system’s dynamics with the help of the Shaw-Takens method indicates that the quasi-periodic motion breaks down at the resonant valueωprm.