Controlling Molecular Scattering by Laser-Induced Field-Free Alignment

We consider deflection of polarizable molecules by inhomogeneous optical fields, and analyze the role of molecular orientation and rotation in the scattering process. It is shown that molecular rotation induces spectacular rainbow-like features in the distribution of the scattering angle. Moreover, by preshaping molecular angular distribution with the help of short and strong femtosecond laser pulses, one may efficiently control the scattering process, manipulate the average deflection angle and its distribution, and reduce substantially the angular dispersion of the deflected molecules. We provide quantum and classical treatment of the deflection process. The effects of strong deflecting field on the scattering of rotating molecules are considered by the means of the adiabatic invariants formalism. This new control scheme opens new ways for many applications involving molecular focusing, guiding and trapping by optical and static fields

Mapping quantum-classical Liouville equation: projectors and trajectories

The evolution of a mixed quantum-classical system is expressed in the mapping formalism where discrete quantum states are mapped onto oscillator states, resulting in a phase space description of the quantum degrees of freedom. By defining projection operators onto the mapping states corresponding to the physical quantum states, it is shown that the mapping quantum-classical Liouville operator commutes with the projection operator so that the dynamics is confined to the physical space. It is also shown that a trajectory-based solution of this equation can be constructed that requires the simulation of an ensemble of entangled trajectories. An approximation to this evolution equation which retains only the Poisson bracket contribution to the evolution operator does admit a solution in an ensemble of independent trajectories but it is shown that this operator does not commute with the projection operators and the dynamics may take the system outside the physical space. The dynamical instabilities, utility and domain of validity of this approximate dynamics are discussed. The effects are illustrated by simulations on several quantum systems.Comment: 4 figure

An Extension of the Fluctuation Theorem

Heat fluctuations are studied in a dissipative system with both mechanical and stochastic components for a simple model: a Brownian particle dragged through water by a moving potential. An extended stationary state fluctuation theorem is derived. For infinite time, this reduces to the conventional fluctuation theorem only for small fluctuations; for large fluctuations, it gives a much larger ratio of the probabilities of the particle to absorb rather than supply heat. This persists for finite times and should be observable in experiments similar to a recent one of Wang et al.Comment: 12 pages, 1 eps figure in color (though intelligible in black and white

Efficient algorithms for rigid body integration using optimized splitting methods and exact free rotational motion

Hamiltonian splitting methods are an established technique to derive stable and accurate integration schemes in molecular dynamics, in which additional accuracy can be gained using force gradients. For rigid bodies, a tradition exists in the literature to further split up the kinetic part of the Hamiltonian, which lowers the accuracy. The goal of this note is to comment on the best combination of optimized splitting and gradient methods that avoids splitting the kinetic energy. These schemes are generally applicable, but the optimal scheme depends on the desired level of accuracy. For simulations of liquid water it is found that the velocity Verlet scheme is only optimal for crude simulations with accuracies larger than 1.5%, while surprisingly a modified Verlet scheme (HOA) is optimal up to accuracies of 0.4% and a fourth order gradient scheme (GIER4) is optimal for even higher accuracies.Comment: 2 pages, 1 figure. Added clarifying comments. Accepted for publication in the Journal of Chemical Physic

Клінічні ознаки у собак, що позитивно реагують на антиген Yersinia enterocolitica 0:9

Canine yersiniosis is currently a scantily researched disease. Two agents predominately cause yersiniosis: Y. enterocolitica (gut yersiniosis), Y. preudotuberculosis (yersiniosis). There are three clinical forms of the disease: intestinal, generalized and secondary-focal. Current available research states the prevalence of Y. enterocolitica against other biovariants in canine infections. The majority of infected dogs demonstrate both asymptomatic clinical course and unspecific symptoms or serve as a carrier. Meanwhile yersiniosis pose a threat to human health causing a severe complex of symptoms. In some cases the disease can be lethal, thus the disease has both epizootological and epidemiological value. The goal of this paper was to generalize clinical signs in dogs that demonstrated positive reaction to Y. enterocolitica antigen 0:9, which is a dominant causative agent of yersiniosis in the northeastern region of Ukraine. The study was conducted based on clinical data, biochemical and hematological laboratory studies. Contamination of canine subjects with Y. enterocolitica 0:9 was conducted using agglutination reaction using respective antigen. The research showed, that the dominant symptoms in canines, affected by Yersinia serovariant 0:9 were gastrointestinal lesions in 100 % of the cases. The clinical signs included melena or bloody stool, general depression, anorexia, cachexia, more rarely – vomiting, tachypnea and breathing irregularities. The results of biochemical blood assays and CBC were heterogeneous and cannot be used as a specific marker of Yersinia infection. The main method of confirmation for Yersinia infection would be a serological agglutination reaction, which can identify positive diagnostic titers in animal blood samples. Further research is planned to study mono- and concurrent course of Yersiniosis with different infectious diseases.Ієрсиніоз собак досі маловивчене захворювання. Найчастіше його викликають два збудники – Y. enterocolitica (кишковий ієрсиніоз) і Y. pseudotuberculosis (ієрсиніоз). Виділяють три клінічні форми хвороби: кишкову, генералізовану, вторинно-вогнещеву. Відомі дослідження вказують на превалювання Y. enterocolitica над іншими біоварами в інфекційному процесі у собак. У більшості інфікованих собак захворювання перебігає безсимптомно з неспецифічною клінічною картиною або у вигляді бактеріоносійства. Водночас ієрсиніози становляють загрозу здоров’ю людини, проявляючись складним симптомокомплексом, а в окремих випадках закінчуються летально. Тому ієрсиніоз має як епізоотологічне, так і епідеміологічне значення. Мета роботи – узагальнити клінічні ознаки у собак, які в діагностичних титрах реагували на ієрсиніозний антиген Y. enterocolitica 0:9, домінуючий збудник кишкового ієрсиніозу собак в північно-східному регіоні України. У роботі використовували клінічні, гематологічні та біохімічні дослідження. Позитивні реакції на контамінацію організму собак Y. enterocolitica 0:9 визначали в реакції аглютинації з відповідним антигеном. Дослідження показали, що домінуючими симптомами при ураженні собак сероваром 0:9 у 100 % випадків було ураження шлунково-кишкового тракту з діареєю, з домішками крові у фекаліях, на тлі пригнічення, анорексії, кахексії. Рідше хвороба супроводжувалася блюванням і порушенням ритму дихання. Результати гематологічних та біохімічних досліджень у собак з позитивною реакцією на іерсініозной антиген 0:9 характеризувалися різноманітністю і не можуть служити діагностичним маркером ієрсиниозної інфекції. Основною підозрою на захворювання кишковим ієрсинізом може слугувати серологічна реакція аглютинації з виявленням позитивно реагуючих тварин в діагностичних титрах. Подальші дослідження планується спрямувати на вивчення моно- і асоційованого перебігу ієрсиніозу з іншими захворюваннями собак інфекційної природи

Effective pair potentials for spherical nanoparticles

An effective description for spherical nanoparticles in a fluid of point particles is presented. The points inside the nanoparticles and the point particles are assumed to interact via spherically symmetric additive pair potentials, while the distribution of points inside the nanoparticles is taken to be spherically symmetric and smooth. The resulting effective pair interactions between a nanoparticle and a point particle, as well as between two nanoparticles, are then given by spherically symmetric potentials. If overlap between particles is allowed, the effective potential generally has non-analytic points, but for each effective potential the expressions for different overlapping cases can be written in terms of one analytic auxiliary potential. Effective potentials for hollow nanoparticles (appropriate e.g. for buckyballs) are also considered, and shown to be related to those for solid nanoparticles. Finally, explicit expressions are given for the effective potentials derived from basic pair potentials of power law and exponential form, as well as from the commonly used London-Van der Waals, Morse, Buckingham, and Lennard-Jones potential. The applicability of the latter is demonstrated by comparison with an atomic description of nanoparticles with an internal face centered cubic structure.Comment: 27 pages, 12 figures. Unified description of overlapping and nonoverlapping particles added, as well as a comparison with an idealized atomic descriptio

Extended Heat-Fluctuation Theorems for a System with Deterministic and Stochastic Forces

Heat fluctuations over a time \tau in a non-equilibrium stationary state and in a transient state are studied for a simple system with deterministic and stochastic components: a Brownian particle dragged through a fluid by a harmonic potential which is moved with constant velocity. Using a Langevin equation, we find the exact Fourier transform of the distribution of these fluctuations for all \tau. By a saddle-point method we obtain analytical results for the inverse Fourier transform, which, for not too small \tau, agree very well with numerical results from a sampling method as well as from the fast Fourier transform algorithm. Due to the interaction of the deterministic part of the motion of the particle in the mechanical potential with the stochastic part of the motion caused by the fluid, the conventional heat fluctuation theorem is, for infinite and for finite \tau, replaced by an extended fluctuation theorem that differs noticeably and measurably from it. In particular, for large fluctuations, the ratio of the probability for absorption of heat (by the particle from the fluid) to the probability to supply heat (by the particle to the fluid) is much larger here than in the conventional fluctuation theorem.Comment: 23 pages, 6 figures. Figures are now in color, Eq. (67) was corrected and a footnote was added on the d-dimensional cas

Synthesis of Phosphorothioate Oligonucleotides with Stereodefined Phosphorothioate Linkages

A method for solid‐phase synthesis of stereodefined PS‐oligos via an oxathiaphospholane approach using pure P‐diastereomers of nucleoside oxathiaphospholane monomers is described. The oxathiaphospholane monomers are synthesized by phosphitylation of 5′‐O‐DMTr‐N‐protected deoxyribonucleosides with 2‐chloro‐spiro‐4,4‐pentamethylene‐1,3,2‐oxathiaphospholane followed by sulfurization. The procedure is general and may be applied to other analogs, depending on the aldehyde (or mercaptoalcohol) used. Starting from an 18O‐labeled mercaptoalcohol, the corresponding 18O‐labeled phosphitylating reagent and nucleoside monomers can be obtained and used for synthesis of labeled stereodefined PS‐oligos, which are useful for studying mechanisms of enzymatic reactions. Details are provided for chromatographic separation of the 5′‐O‐DMTr‐N‐protected‐deoxyribonucleoside‐3′‐O‐(2‐thio‐spiro‐4,4‐pentamethylene‐1,3,2‐oxathiaphospholane)s into their P‐diastereomers, and for manual solid‐phase synthesis of PS‐oligos. Oxidation of 5′‐O‐DMTr‐N‐protected‐deoxyribonucleoside‐3′‐O‐(2‐thio‐spiro‐4,4‐pentamethylene‐1,3,2‐oxathiaphospholane)s with selenium dioxide yields their 2‐oxo‐analogs, which are suitable either for elongation of stereodefined PS‐oligos with segments consisting of unmodified nucleotide units possessing phosphate internucleotide linkages, or for generating isotopomeric 18O‐labeled PO‐oligos of predetermined P‐chirality.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143684/1/cpnc0417.pd