A microscopic study of the proton-neutron symmetry and phonon structure of the low-lying states in 92Zr

We studied in a microscopic multiphonon approach the proton-neutron symmetry and phonon structure of some low-lying states recently discovered in 92Zr. We confirm the breaking of F-spin symmetry, but argue that the breaking mechanism is more complex than the one suggested in the original shell model analysis of the data. We found other new intriguing features of the spectrum, like a pronounced multiphonon fragmentation of the states and a tentative evidence of a three-phonon mixed symmetry state.Comment: 13 pages, to appear in Phys. Rev.

Cell shape recognition by colloidal cell imprints: Energy of the cell-imprint interaction

The results presented in this study are aimed at the theoretical estimate of the interactions between a spherical microbial cell and the colloidal cell imprints in terms of the Derjaguin, Landau, Vervey, and Overbeek (DLVO) surface forces. We adapted the Derjaguin approximation to take into account the geometry factor in the colloidal interaction between a spherical target particle and a hemispherical shell at two different orientations with respect to each other. We took into account only classical DLVO surface forces, i.e., the van der Waals and the electric double layer forces, in the interaction of a spherical target cell and a hemispherical shell as a function of their size ratio, mutual orientation, distance between their surfaces, their respective surface potentials, and the ionic strength of the aqueous solution. We found that the calculated interaction energies are several orders higher when match and recognition between the target cell and the target cell imprint is achieved. Our analysis revealed that the recognition effect of the hemispherical shell towards the target microsphere comes from the greatly increased surface contact area when a full match of their size and shape is produced. When the interaction between the surfaces of the hemishell and the target cell is attractive, the recognition greatly amplifies the attraction and this increases the likelihood of them to bind strongly. However, if the surface interaction between the cell and the imprint is repulsive, the shape and size match makes this interaction even more repulsive and thus decreases the likelihood of binding. These results show that the surface chemistry of the target cells and their colloidal imprints is very important in controlling the outcome of the interaction, while the shape recognition only amplifies the interaction. In the case of nonmonotonous surface-to-surface interaction we discovered some interesting interplay between the effects of shape match and surface chemistry which is discussed in the paper. The results from this study establish the theoretical basis of cell shape recognition by colloidal cell imprints which, combined with cell killing strategies, could lead to an alternative class of cell shape selective antimicrobials, antiviral, and potentially anticancer therapies

SPLEEN LYMPHOCYTE BLAST TRANSFORMATION IN THYMECTOMIZED CHICKENS

No abstrac

Spectral observations of X Persei: Connection between H-alpha and X-ray emission

We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period 1999 - 2018. Using new and published data, we found that during "disc-rise" the expansion velocity of the circumstellar disc is 0.4 - 0.7 km/s. Our results suggest that the disc radius in recent decades show evidence of resonant truncation of the disc by resonances 10:1, 3:1, and 2:1, while the maximum disc size is larger than the Roche lobe of the primary and smaller than the closest approach of the neutron star. We find correlation between equivalent width of H-alpha emission line ($W\alpha$) and the X-ray flux, which is visible when $15 \: \AA \: < W\alpha \le 40 \: \AA$. The correlation is probably due to wind Roche lobe overflow.Comment: Accepted for publication in Astronomy & Astrophysic

Connection between orbital modulation of H-alpha and gamma-rays in the Be/X-ray binary LSI+61303

We studied the average orbital modulation of various parameters (gamma-ray flux, H-alpha emission line, optical V band brightness) of the radio- and gamma-ray emitting Be/X-ray binary LSI+61303. Using the Spearman rank correlation test, we found highly significant correlations between the orbital variability of the equivalent width of the blue hump of the H-alpha and Fermi-LAT flux with a Spearman p-value 2e-5, and the equivalent widths ratio EW_B/EW_R and Fermi-LAT flux with p-value 9e-5. We also found a significant anti-correlation between Fermi-LAT flux and V band magnitude with p-value 7.10^{-4}. All these correlations refer to the average orbital variability, and we conclude that the H-alpha and gamma-ray emission processes in LSI+61303 are connected. The possible physical scenario is briefly discussed.Comment: accepted as a Letter in Astronomy and Astrophysic

An ultra melt-resistant hydrogel from food grade carbohydrates

© 2017 The Royal Society of Chemistry. We report a binary hydrogel system made from two food grade biopolymers, agar and methylcellulose (agar-MC), which does not require addition of salt for gelation to occur and has very unusual rheological and thermal properties. It is found that the storage modulus of the agar-MC hydrogel far exceeds those of hydrogels from the individual components. In addition, the agar-MC hydrogel has enhanced mechanical properties over the temperature range 25-85 °C and a maximum storage modulus at 55 °C when the concentration of methylcellulose was 0.75% w/v or higher. This is explained by a sol-gel phase transition of the methylcellulose upon heating as supported by differential scanning calorimetry (DSC) measurements. Above the melting point of agar, the storage modulus of agar-MC hydrogel decreases but is still an elastic hydrogel with mechanical properties dominated by the MC gelation. By varying the mixing ratio of the two polymers, agar and MC, it was possible to engineer a food grade hydrogel of controlled mechanical properties and thermal response. SEM imaging of flash-frozen and freeze-dried samples revealed that the agar-MC hydrogel contains two different types of heterogeneous regions of distinct microstructures. The latter was also tested for its stability towards heat treatment which showed that upon heating to temperatures above 120 °C its structure was retained without melting. The produced highly thermally stable hydrogel shows melt resistance which may find application in high temperature food processing and materials templating

Correlations for pairs of periodic trajectories for open billiards

In this paper we prove two asymptotic estimates for pairs of closed trajectories for open billiards similar to those established by Pollicott and Sharp for closed geodesics on negatively curved compact surfaces. The first of these estimates holds for general open billiards in any dimension. The more intricate second estimate is established for open billiards satisfying the so called Dolgopyat type estimates. This class of billiards includes all open billiards in the plane and open billiards in $\R^N, N \geq 3$ satisfying some additional conditions

Role of Landau-Rabi quantization of electron motion on the crust of magnetars within the nuclear energy density functional theory

Magnetic fields of order $10^{15}$ G have been measured at the surface of some neutron stars, and much stronger magnetic fields are expected to be present in the solid region beneath the surface. The effects of the magnetic field on the equation of state and on the composition of the crust due to Landau-Rabi quantization of electron motion are studied. Both the outer and inner crustal regions are described in a unified and consistent way within the nuclear-energy density functional theory.Comment: 23 pages, 11 figure

Fabrication of living soft matter by symbiotic growth of unicellular microorganisms

We report the fabrication of living soft matter made as a result of the symbiotic relationship of two unicellular microorganisms. The material is composed of bacterial cellulose produced in situ by acetobacter (Acetobacter aceti NCIMB 8132) in the presence of photosynthetic microalgae (Chlamydomonas reinhardtii cc-124), which integrates into a symbiotic consortium and gets embedded in the produced cellulose composite. The same concept of growing living materials can be applied to other symbiotic microorganism pairs similar to the combination of algae and fungi in lichens, which is widespread in Nature. We demonstrate the in situ growth and immobilisation of the C. reinhardtii cells in the bacterial cellulose matrix produced by the simultaneous growth of acetobacter. The effect of the growth media composition on the produced living materials was investigated. The microstructure and the morphology of the produced living biomaterials were dependent on the shape of the growth culture container and media stirring conditions, which control the access to oxygen. As the photosynthetic C. reinhardtii cells remain viable and produce oxygen as they spontaneously integrate into the matrix of the bacterial cellulose generated by the acetobacter, such living materials have the potential for various applications in bio-hydrogen generation from the immobilised microalgae. The proposed approach for building living soft matter can provide new ways of immobilising other commercially important microorganisms in a bacterial cellulose matrix as a result of symbiosis with acetobacter without the use of synthetic binding agents and in turn increase their production efficiency

Landau quantization and neutron emissions by nuclei in the crust of a magnetar

Magnetars are neutron stars endowed with surface magnetic fields of the order of $10^{14}-10^{15}$~G, and with presumably much stronger fields in their interior. As a result of Landau quantization of electron motion, the neutron-drip transition in the crust of a magnetar is shifted to either higher or lower densities depending on the magnetic field strength. The impact of nuclear uncertainties is explored considering the recent series of Brussels-Montreal microscopic nuclear mass models. All these models are based on the Hartree-Fock-Bogoliubov method with generalized Skyrme functionals. They differ in their predictions for the symmetry energy coefficient at saturation, and for the stiffness of the neutron-matter equation of state. For comparison, we have also considered the very accurate but more phenomenological model of Duflo and Zuker. Although the equilibrium composition of the crust of a magnetar and the onset of neutron emission are found to be model dependent, the quantum oscillations of the threshold density are essentially universal.Comment: 7 pages, 2 figure