Atomistic simulations of self-trapped exciton formation in silicon nanostructures: The transition from quantum dots to nanowires

Using an approximate time-dependent density functional theory method, we calculate the absorption and luminescence spectra for hydrogen passivated silicon nanoscale structures with large aspect ratio. The effect of electron confinement in axial and radial directions is systematically investigated. Excited state relaxation leads to significant Stokes shifts for short nanorods with lengths less than 2 nm, but has little effect on the luminescence intensity. The formation of self-trapped excitons is likewise observed for short nanostructures only; longer wires exhibit fully delocalized excitons with neglible geometrical distortion at the excited state minimum.Comment: 10 pages, 4 figure

Transcriptome Analysis of Alcohol Drinking in Non-Dependent and Dependent Mice Following Repeated Cycles of Forced Swim Stress Exposure

Chronic stress is a known contributing factor to the development of drug and alcohol addiction. Animal models have previously shown that repeated forced swim stress promotes escalated alcohol consumption in dependent animals. To investigate the underlying molecular adaptations associated with stress and chronic alcohol exposure, RNA-sequencing and bioinformatics analyses were conducted on the prefrontal cortex (CTX) of male C57BL/6J mice that were behaviorally tested for either non-dependent alcohol consumption (CTL), chronic intermittent ethanol (CIE) vapor dependent alcohol consumption, repeated bouts of forced swim stress alone (FSS), and chronic intermittent ethanol with forced swim stress (CIE + FSS). Brain tissue from each group was collected at 0-h, 72-h, and 168-h following the final test to determine long-lasting molecular changes associated with maladaptive behavior. Our results demonstrate unique temporal patterns and persistent changes in coordinately regulated gene expression systems with respect to the tested behavioral group. For example, increased expression of genes involved in “transmitter-gated ion channel activity” was only determined for CIE + FSS. Overall, our results provide a summary of transcriptomic adaptations across time within the CTX that are relevant to understanding the neurobiology of chronic alcohol exposure and stress

Single-Molecule Interactions of a Monoclonal Anti-DNA Antibody with DNA

© 2016, Springer Science+Business Media New York.Interactions of DNA with proteins are essential for key biological processes and have both a fundamental and practical significance. In particular, DNA binding to anti-DNA antibodies is a pathogenic mechanism in autoimmune pathology, such as systemic lupus erythematosus. Here we measured at the single-molecule level binding and forced unbinding of surface-attached DNA and a monoclonal anti-DNA antibody MRL4 from a lupus erythematosus mouse. In optical trap-based force spectroscopy, a microscopic antibody-coated latex bead is trapped by a focused laser beam and repeatedly brought into contact with a DNA-coated surface. After careful discrimination of non-specific interactions, we showed that the DNA-antibody rupture force spectra had two regimes, reflecting formation of weaker (20–40 pN) and stronger (>40 pN) immune complexes that implies the existence of at least two bound states with different mechanical stability. The two-dimensional force-free off-rate for the DNA-antibody complexes was ∼2.2 × 10−3 s−1, the transition state distance was ∼0.94 nm, the apparent on-rate was ∼5.26 s−1, and the stiffness of the DNA-antibody complex was characterized by a spring constant of 0.0021 pN/nm, suggesting that the DNA-antibody complex is a relatively stable, but soft and deformable macromolecular structure. The stretching elasticity of the DNA molecules was characteristic of single-stranded DNA, suggesting preferential binding of the MRL4 antibody to one strand of DNA. Collectively, the results provide fundamental characteristics of formation and forced dissociation of DNA-antibody complexes that help to understand principles of DNA-protein interactions and shed light on the molecular basis of autoimmune diseases accompanied by formation of anti-DNA antibodies

Бактеріологічний контроль молока корів та ефективність протимаститних заходів

Under the current conditions of livestock development, the main task of farms is the systematic bacteriological control of milk and the development of comprehensive programs for the control and prevention of mastitis in cows. These measures will make it possible to establish control over this pathology, reduce veterinary treatment costs, improve milk quality, increase average hopes for lactation, increase the productive use of cows, and more. It was found that among the forms of clinical mastitis in the farm registered catarrhal and purulent-catarrhal (65.0 %), serous (12.0 %), and less often – fibrinous (11.5 %), hemorrhagic (11.0 %), and abscess udder (0.5 %). Bacteriological studies of milk taken from cows proved the presence of Staphylococcus saprophyticus, Escherichia coli, β-hemolytic Streptococcus spp. Microbiological studies showed that the isolated cultures of microorganisms were sensitive to tetracycline, neomycin, and cloxacycline; conditionally sensitive to streptomycin, doxycillin; no sensitivity to amoxicillin + clavulanic acid, norfloxacin and gatifloxacin. A treatment scheme was proposed for patients with purulent-catarrhal mastitis of cows, included intra-tank injections of the drug “Mastidev-Linko,” intramuscular injections of the drug “Tseftiodev 5%” and external application of the ointment “Dibutaliastin.” As a result of studies on the therapeutic efficiency of the proposed veterinary drugs when used in cows of Holstein-Friesian and black-spotted breed, patients with purulent-catarrhal mastitis, 91.6 % therapeutic efficiency of drugs was established. It is recommended that animals infected with infectious agents should be milked last and milking machines thoroughly disinfected; apply the pre- and post-milking treatment of udder teats with disinfectants (dips); periodically check in the laboratory the disinfecting ability of drugs for udder treatment and disinfection of accessories; use only proven tools; control the correct preparation of solutions and treatment of the udder with disinfectants (dips); to reject animals that do not respond to treatment (chronically ill).При нинішніх умовах розвитку тваринництва, основним завданням господарств залишається систематичний бактеріологічний контроль молока та розробка комплексних програм боротьби й профілактики маститу корів. Дані заходи дадуть можливість встановити контроль над цією патологією, зменшити ветеринарні витрати на лікування, покращити якість молока, підвищити середній надій за лактацію, збільшити термін продуктивного використання корів тощо. Встановлено, що серед форм клінічного маститу, у господарстві реєстрували: катаральний і гнійно-катаральний (65,0 %), серозний (12,0 %), рідше – фібринозний (11,5 %), геморагічний (11,0 %) мастит та абсцес вимені (0,5 %). Бактеріологічними дослідженнями молока, відібраного від корів, доведена наявність Staphylococcus saprophyticus, Escherichia coli, β-гемолітичний Streptococcus spp. Мікробіологічними дослідженнями встановлено, що виділені культури мікроорганізмів були чутливими до тетрацикліну, неоміцину і клоксацикліну; умовно чутливими до стрептоміцину, доксициліну; відсутня чутливість до амоксицилін+клавуланової кислоти, норфлоксацину та гатифлоксацину. Запропоновано схему лікування, яка для хворих на гнійно-катаральний мастит корів, передбачала внутрішньоцистернальні введення препарату “Мастидев-Лінко”, внутрішньом’язові ін’єкції лікарського засобу “Цефтіодев 5 %” та зовнішнє застосування мазі “Дібуталястін”. У результаті проведених досліджень терапевтичної ефективності, запропонованих ветеринарних препаратів при застосуванні у корів голштинсько-фризької та чорно-рябої породи, хворих на гнійно-катаральний мастит, встановлено 91,6 % терапевтичну ефективність лікарських засобів. Господарству рекомендовано наступне: тварин, інфікованих заразними збудниками, слід доїти в останню чергу та ретельно дезінфікувати доїльні апарати; застосовувати перед- та післядоїльну обробку дійок вимені дезінфектантами (діпами); періодично перевіряти в лабораторії дезінфікуючу здатність препаратів для обробки вимені та дезінфекції приладдя; використовувати тільки перевірені засоби для дезінфекції; контролювати правильність приготування розчинів та проведення обробки вимені дезінфектантами (діпами); вибраковувати тварин, які не піддаються лікуванню (хронічно хворих)

Simulation of dimensionality effects in thermal transport

The discovery of nanostructures and the development of growth and fabrication techniques of one- and two-dimensional materials provide the possibility to probe experimentally heat transport in low-dimensional systems. Nevertheless measuring the thermal conductivity of these systems is extremely challenging and subject to large uncertainties, thus hindering the chance for a direct comparison between experiments and statistical physics models. Atomistic simulations of realistic nanostructures provide the ideal bridge between abstract models and experiments. After briefly introducing the state of the art of heat transport measurement in nanostructures, and numerical techniques to simulate realistic systems at atomistic level, we review the contribution of lattice dynamics and molecular dynamics simulation to understanding nanoscale thermal transport in systems with reduced dimensionality. We focus on the effect of dimensionality in determining the phononic properties of carbon and semiconducting nanostructures, specifically considering the cases of carbon nanotubes, graphene and of silicon nanowires and ultra-thin membranes, underlying analogies and differences with abstract lattice models.Comment: 30 pages, 21 figures. Review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.

Experimental evidence of the ferroelectric phase transition near the λ−\lambda-point in liquid water

We studied dielectric properties of nano-sized liquid water samples confined in polymerized silicates MCM-41 characterized by the porous sizes \sim 3-10nm. We report the direct measurements of the dielectric constant by the dielectric spectroscopy method at frequencies 25Hz-1MHz and demonstrate clear signatures of the second-order phase transition of ferroelectric nature at temperatures next to the \lambda- point in the bulk supercooled water. The presented results support the previously developed polar liquid phenomenology and hence establish its applicability to model actual phenomena in liquid water.Comment: 4 pages, single figur

Automatic segmentation of cerebral infarcts in follow-up computed tomography images with convolutional neural networks

Background and purpose: Infarct volume is a valuable outcome measure in treatment trials of acute ischemic stroke and is strongly associated with functional outcome. Its manual volumetric assessment is, however, too demanding to be implemented in clinical practice. Objective: To assess the value of convolutional neural networks (CNNs) in the automatic segmentation of infarct volume in follow-up CT images in a large population of patients with acute ischemic stroke. Materials and methods: We included CT images of 1026 patients from a large pooling of patients with acute ischemic stroke. A reference standard for the infarct segmentation was generated by manual delineation. We introduce three CNN models for the segmentati

Methodological advances in imaging intravital axonal transport.

Axonal transport is the active process whereby neurons transport cargoes such as organelles and proteins anterogradely from the cell body to the axon terminal and retrogradely in the opposite direction. Bi-directional transport in axons is absolutely essential for the functioning and survival of neurons and appears to be negatively impacted by both aging and diseases of the nervous system, such as Alzheimer's disease and amyotrophic lateral sclerosis. The movement of individual cargoes along axons has been studied in vitro in live neurons and tissue explants for a number of years; however, it is currently unclear as to whether these systems faithfully and consistently replicate the in vivo situation. A number of intravital techniques originally developed for studying diverse biological events have recently been adapted to monitor axonal transport in real-time in a range of live organisms and are providing novel insight into this dynamic process. Here, we highlight these methodological advances in intravital imaging of axonal transport, outlining key strengths and limitations while discussing findings, possible improvements, and outstanding questions

Phonons in Slow Motion: Dispersion Relations in Ultra-Thin Si Membranes

We report the changes in dispersion relations of hypersonic acoustic phonons in free-standing silicon membranes as thin as \sim 8 nm. We observe a reduction of the phase and group velocities of the fundamental flexural mode by more than one order of magnitude compared to bulk values. The modification of the dispersion relation in nanostructures has important consequences for noise control in nano and micro-electromechanical systems (MEMS/NEMS) as well as opto-mechanical devices.Comment: 5 page