The neutron total cross section measurements on protons and nuclei in the energy range of 28–54 GEV

The results of the total cross section measurements of neutrons on protons, deuterons and nuclei C, O, Al, Cu, Sn, Pb in the energy range of 28–54 GeV are reported.     

Spontaneous processing in vacuum

The theory of spontaneous vacuum explosion gives divergent probability due to Lorentz-invariance of the initial state. Evidently such explosion is strictly forbidden by conservation laws,which implies nonexistence of tachyons.     

Investigation of background sources associated with the production of radioactive isotopes in the DEVIS experiment (double-beta decay)

Measurements performed in searches for the double-beta decay of ¹³⁶Xe showed an excess of events in exposures of a target enriched in the isotope ¹³⁶Xe in relation to exposures of a target depleted in this isotope. The activation of xenon in the detector used under the effect of background neutron and muon radiation and the possible contribution of these processes to the results of relevant measurements are studied.     

Thermomechanical coupling in a cylindrical hybrid-aligned nematic liquid crystal

A solution to the system of equations describing a cylindrical hybrid-aligned nematic liquid crystal is obtained. The rotational flow driven by vertical temperature gradient in such a cell is investigated theoretically. The cell is suggested as a new experimental setup for determining an additional relation required to measure the twelve thermomechanical coefficients. It is shown that the terms in the expressions for thermomechanical stress and heat flux obtained in [8] are equivalent to those originally proposed in [7].     

On the Matter of the Gravitational Waves' Detection

The interaction of a gravitational wave (G.W.) with substances causes periodical changes of their density. These changes may be fixed either by means of piezocrystals (just as in Weber's arrangement [1], for example) or by means of the light scattering on the sound aroused by G.W. It is of great interest the utilization of substances' critical states as a detector; the large compressibility of the former affords the maximum of possible changes of their density in a definite gravitational field. They have discussed one kind of experiment in [4] (denoted here as I) in which the presence of the gravitational flow caused periodical changes of the freguency of the light scattered on the fluctuations of one of the components of the two – component solution in its critical state of stratification.     

Synthesis, characterization, and electrocatalytic activity of PtPb nanoparticles prepared by two synthetic approaches

Intermetallic PtPb nanoparticles have been synthesized by two solution-phase reduction methods. In the first (PtPb-B), Pt and Pb salts were reduced by sodium borohydride in methanol at room temperature. In the second (PtPb-N), metal-organic Pt and Pb precursors were reduced by sodium naphthalide in diglyme at 135 degrees C. Both methods produced small agglomerated nanoparticles of the ordered intermetallic PtPb (mean crystal domain size <15 nm) which were characterized by pXRD, SEM, UHV-STEM, BET, EDX, and electron diffraction. The electrocatalytic activity of PtPb nanoparticles produced by both methods toward formic acid and methanol oxidation was investigated and compared to Pt and PtRu. Both PtPb-B and PtPb-N nanoparticles exhibited enhanced electrocatalytic activity compared to commercially available Pt black and PtRu nanoparticles. For formic acid oxidation, the PtPb nanoparticles exhibited considerably lower onset potentials and higher current densities than Pt or PtRu. For methanol oxidation, the PtPb nanoparticles had onset potentials slightly positive of PtRu but exhibited higher current densities at potentials about 100 mV positive of onset. The general applicability of these methods for the synthesis of nanoparticles of ordered intermetallic phases is discussed.     

Observation of muon pairs in neutrino interactions at Serpukhov 70 GeV accelarator

A search for dimuons produced in a spark chamber experiment in neutrino and antineutrino beams of the Serpukhov accelerator is reported. The clear dimuon signal has been observed in vN interactions. R_v = N(2ω)/N(1ω)? (6.2 ± 1.7) × 10^?3 in the energy interval 7.5 ÷ 30 GeV. From antineutrino data we conclude that in the same energy range $\text{R}{}_{\mathrm{<mtext>v</mtext>}}\text{? 1.1. × 10}{}^{\mathrm{?2}}\text{(90\% C.L.)}$.     

Motion of single long DNA molecules through arrays of magnetic columns

We present a videomicroscopy study of T4 DNA (169 kbp) in microfluidic arrays of posts formed by the self-assembly of magnetic beads. We observe DNA moving through an area of 10 000 microm(2), typically containing 100-600 posts. We determine the distribution of the contact times with the posts and the distribution of passage times across the field of view for hundreds of DNA per experiment. The contact time is well approximated by a Poisson process, scaling like the inverse of the field strength, independent of the density of the array. The distribution of passage times allows us to estimate the mean velocity and dispersivity of the DNA during its motion over distances long compared to our field of view. We compare these values with those computed from a lattice Monte Carlo model and geometration theory. We find reasonable quantitative agreement between the lattice Monte Carlo model and experiment, with the error increasing with increasing post density. The deviation between theory and experiment is attributed to the high mobility of DNA after disengaging from the posts, which leads to a difference between the contact time and the total time lost by colliding. Classical geometration theory furnishes surprisingly good agreement for the dispersivity, while geometration theory with a mean free path significantly overestimates the dispersivity.     

On the concentration of relic magnetic monopoles in the universe

The modern concentration of relic 't Hooft-Polyakov monopoles is shown to amount to ～ 10^?19 cm^?3, being determined by the diffusion annihilation rate at t<10^?5 s. To eliminate the contradiction with experimental upper limits some mechanism similar to quark confinement should forbid free monopole existence.     

Diversity Against Adversity: How Adaptive Immune System Evolves Potent Antibodies

Adaptive immunity is an amazing mechanism, whereby new protein functions—affinity of antibodies (Immunoglobulins) to new antigens—evolve through mutation and selection in a matter of a few days. Despite numerous experimental studies, the fundamental physical principles underlying immune response are still poorly understood. In considerable departure from past approaches, here, we propose a microscopic multiscale model of adaptive immune response, which consists of three essential players: The host cells, viruses, and B-cells in Germinal Centers (GC). Each moiety carries a genome, which encodes proteins whose stability and interactions are determined from their sequences using laws of Statistical Mechanics, providing an exact relationship between genomic sequences and strength of interactions between pathogens and antibodies and antibodies and host proteins (autoimmunity). We find that evolution of potent antibodies (the process known as Affinity Maturation (AM)) is a delicate balancing act, which has to reconcile the conflicting requirements of protein stability, lack of autoimmunity, and high affinity of antibodies to incoming antigens. This becomes possible only when antibody producing B cells elevate their mutation rates (process known as Somatic Hypermutation (SHM)) to fall into a certain range—not too low to find potency increasing mutations but not too high to destroy stable Immunoglobulins and/or already achieved affinity. Potent antibodies develop through clonal expansion of initial B cells expressing marginally potent antibodies followed by their subsequent affinity maturation through mutation and selection. As a result, in each GC the population of mature potent Immunoglobulins is monoclonal being ancestors of a single cell from initial (germline) pool. We developed a simple analytical theory, which provides further rationale to our findings. The model and theory reveal the molecular factors that determine the efficiency of affinity maturation, thereby providing insight into the variability of the immune response to cytopathic viruses (the direct response by germline antibodies) and poorly cytopathic viruses (a crucial role of SHM in the response).