Size effects on atomic collapse in the dice lattice.

We study the role of size effects on atomic collapse of charged impurity in the flat band system. The tight-binding simulations are made for the dice lattice with circular quantum dot shapes. It is shown that the mixing of in-gap edge states with bound states in impurity potential leads to increasing the critical charge value. This effect, together with enhancement of gap due to spatial quantization, makes it more difficult to observe the dive-into-continuum phenomenon in small quantum dots. At the same time, we show that if in-gap states are filled, the resonant tunneling to bound state in the impurity potential might occur at much smaller charge, which demonstrates non-monotonous dependence with the size of sample lattice. In addition, we study the possibility of creating supercritical localized potential well on different sublattices, and show that it is possible only on rim sites, but not on hub site. The predicted effects are expected to naturally occur in artificial flat band lattices.

Time Dependence of the Electron and Positron Components of the Cosmic Radiation Measured by the PAMELA Experiment between July 2006 and December 2015.

Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field.

An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV.

Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium, which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars and microquasars or through dark matter annihilation, which would be 'primary sources'. Previous statistically limited measurements of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.

New measurement of the antiproton-to-proton flux ratio up to 100 GeV in the cosmic radiation.

A new measurement of the cosmic-ray antiproton-to-proton flux ratio between 1 and 100 GeV is presented. The results were obtained with the PAMELA experiment, which was launched into low-Earth orbit on-board the Resurs-DK1 satellite on June 15th 2006. During 500 days of data collection a total of about 1000 antiprotons have been identified, including 100 above an energy of 20 GeV. The high-energy results are a tenfold improvement in statistics with respect to all previously published data. The data follow the trend expected from secondary production calculations and significantly constrain contributions from exotic sources, e.g., dark matter particle annihilations.

Design of a new invertible polymer coating on a solid surface and its effect on dispersion colloidal stability.

This article presents a new approach to building up self-adjustable invertible polymer coatings at solid surfaces. The approach is based on a two-step process. In the first step, the surface of dispersed TiO2 or silicon wafers was functionalized with the aid of a reactive copolymer, viz., poly(styrene-alt-maleic anhydride) (PSM), to which, in the second step, the chains of amphiphilic oligoester have been tethered. The latter contains both hydrophilic poly(ethylene glycol) and hydrophobic aliphatic dibasic acid moieties being alternately distributed along the oligomer chains. It is shown that the titania modified in this way can form stable suspensions in both polar (water) and nonpolar (toluene) media. Moreover, multiple drying/redispersion cycles demonstrate the ability of the modified titania particles, after their removal from one type of dispersion and consequent drying, to be redispersed in dispersing media strongly differing by polarity from that of the previous medium. An environmentally induced switching of the surface properties has been observed via the measurement of the wetting contact angles and scanning force microscopy (SFM) of silicon wafers covered by PSM with tethered oligoester chains. These experiments give strong support for the predicted capability of such polymer coatings to switch their environmental appearance (i.e., to behave as a self-adjustable invertible interface because of the ability of the tethered amphiphilic oligoester chains to change their conformations in response to environmental changes in such a manner so as to adapt and enhance their compatibility with the surrounding media).

[Adequate gas exchange in two-sided and combined surgeries on thoracic and abdominal organs].

Method of combined artificial lung ventilation during simultaneous two-sided operations on the lungs was studied in 60 patients. This method is based on traditional ALV with parameters calculated according to functional state of the patient's respiratory system, and additional high-frequency jet pulmonary ventilation. The developed method was not accompanied by any severe disorders of gas exchange and mechanics of ventilation.

[Surgical approach in bilateral and combined echinococcosis of the lung].

One hundred and two patients aged from 4 to 65 years with echinococcosis were treated. Solitary cysts in both lungs were diagnosed in 69 patients, multiple cysts -- in 33 patients. In 10 cases small and middle cysts were in the upper parts of both lungs. These patients underwent one-stage operation consisting in lateral thoracotomy, removing of the cyst from one lung, incision of retrosternal mediastinal pleura, removing of the cyst from the second lung, drainage of pleural cavity. Fifteen patients with combined echinococcosis of the upper lobe of the right lung and liver were operated with another one-stage surgical method through thoracotomy in the third and sixth or seventh intercostal space. These methods are characterized by low traumaticity, decreased number of postoperative complications and hospital stay.

[Structure-functional features of homologous domains of angiotensin-converting enzyme]. / Strukturno-funktsional'nye osobennosti gomologichnykh domenov angiotenzinprevrashchaiushchego fermenta.

Somatic angiotensin-converting enzyme (ACE) consists of two homologous domains, each of them containing an active site. Differences in substrate specificities and affinity to inhibitors of the active sites of the two domains of bovine ACE are described. The ACE domains demonstrate different thermostability, and the reasons for this difference are analyzed. A structural model of the ACE domains is suggested, which allows us to reveal the structural subdomain important for the protein stability and localize the hydrophobic and the carbohydrate-binding sites.

A hydrophobic site on the surface of the angiotensin-converting enzyme molecule.

Using the hydrophobic fluorescent dye 8-anilino-1-naphthalenesulfonic acid (8-ANS), a hydrophobic site on the surface of the protein globule of angiotensin-converting enzyme (ACE) from bovine lung was found. The dissociation constant of the ACE-8-ANS complex was estimated as 1.5 +/- 0.2 microM. This hydrophobic site is far from the ACE catalytic sites because the binding of the hydrophobic dye does not influence ACE activity. Shielding of the ACE hydrophobic site due to the complex formation with 8-ANS or Triton X-100 resulted in pronounced stabilization of the enzyme against the action of water radiolysis products during gamma-irradiation of dilute solutions of ACE.

Control of laser high-harmonic generation with counterpropagating light.

Relatively weak counterpropagating light is shown to disrupt the emission of laser high-harmonic generation. Harmonic orders ranging from the teens to the low thirties produced by a 30-femtosecond pulse in a narrow argon jet are "shut down" with a contrast as high as 2 orders of magnitude by a chirped 1-picosecond counterpropagating laser pulse (60 times less intense). Alternatively, under poor phase-matching conditions, the counterpropagating light boosts harmonic production by similar contrast through quasiphase matching where out-of-phase emission is suppressed.

Fluorescence polarization studies of different forms of angiotensin-converting enzyme.

The interaction of three forms of bovine angiotensin-converting enzyme (ACE) with the competitive peptide inhibitor lisinopril with a fluorescent label was studied using fluorescence polarization. The dissociation constants Kd of the enzyme-inhibitor complexes in 50 mM Hepes-buffer (pH 7.5) containing 150 mM NaCl and 1 microM ZnCl2 at 37 degrees C were (2.3 +/- 0.4).10(-8), (2.1 +/- 0.3).10(-8), and (2.1 +/- 0.2).10(-8) M for two-domain somatic ACE, single-domain testicular ACE, and for the N-domain of the enzyme, respectively. The interaction of the enzyme with the inhibitor strongly depended on the presence of chloride in the medium, and the apparent dissociation constant of the ACE-chloride complex was (1.3 +/- 0.2).10(-3) M for the somatic enzyme. The dissociation kinetics of the complex of the inhibitor with somatic ACE did not fit the kinetics of a first-order reaction, but it was approximated by a model of simultaneous dissociation of two complexes with the dissociation rate constants (0.13 +/- 0.01) sec(-1) and (0.026 +/- 0.001) sec(-1) that were present at approximately equal initial concentrations. The dissociation kinetics of the single-domain ACE complexes with the inhibitor were apparently first-order, and the dissociation rate constants were similar: (0.055 +/- 0.001) and (0.041 +/- 0.001) sec(-1) for the N-domain and for testicular ACE, respectively.

Dephosphorylation of beta2-syntrophin and Ca2+/mu-calpain-mediated cleavage of ICA512 upon stimulation of insulin secretion.

Islet cell autoantigen (ICA) 512 is a receptor-tyrosine phosphatase-like protein associated with the secretory granules of neuroendocrine cells, including pancreatic beta-cells. Binding of its cytoplasmic tail to beta2-syntrophin suggests that ICA512 connects secretory granules to the utrophin complex and the actin cytoskeleton. Here we show that stimulation of insulin secretion from INS-1 cells triggers the biosynthesis of pro-ICA512 and the degradation of its mature form. Inhibition of calpain, which is activated upon stimulation of insulin secretion, prevents the Ca2+-dependent proteolysis of ICA512. In vitro mu-calpain cleaves ICA512 between a putative PEST domain and the beta2-syntrophin binding site, whereas binding of ICA512 to beta2-syntrophin protects the former from cleavage. beta2-syntrophin and its F-actin-binding protein utrophin are enriched in subcellular fractions containing secretory granules. ICA512 preferentially binds phospho-beta2-syntrophin and stimulation of insulin secretion induces the Ca2+-dependent, okadaic acid-sensitive dephosphorylation of beta2-syntrophin. Similarly to calpeptin, okadaic acid inhibits ICA512 proteolysis and insulin secretion. Thus, stimulation of insulin secretion might promote the mobilization of secretory granules by inducing the dissociation of ICA512 from beta2-syntrophin-utrophin complexes and the cleavage of the ICA512 cytoplasmic tail by mu-calpain.

[Methodologic aspects of body water kinetic dynamic studies]. / Metodologicheskie aspekty dinamicheskikh issledovanii kinetiki vody v organizme.

In studying the level of hydration and liquid phases (LPs) in a space mission there use the stable and/or radioactive isotopes. The investigations are unique, the methods are adequate but not adapted in full measure to the challenges of the problem under study. The methodical approaches to the study of the dynamics of water metabolism are not available. Repeated introduction of the markers for these purposes is not acceptable. Another problem associates with taking the markers orally. In this case, a concentration of the markers will depend on the absorption and excretion processes. Prior to, during and in the readaptation period these functions will be different, making a correlation of the accumulated data difficult. There advances a possible version of solving these problems, namely, to use for the dynamic studies the residual contents of the markers in the LPs after single injection. However, this approach calls for investigating the kinetics of markers in weightlessness or during its ground-based simulation. The kinetics of tritium water has been studied in 6 volunteers under conditions of the 5-day bedrest and in 9 healthy men during free motor activity. There determined the characteristics of marker kinetics in a healthy man during his routine living activities. Under bedrest conditions there have been noted slowing-down of the rate and a decrease in the degree of marker accumulation in the body after its single injection, the shift of a period of relative stabilization of marker content in LP to the more late dates of experiment, slowing-down of the marker excretion rate from the body.

Glycosylation of bovine pulmonary angiotensin-converting enzyme modulates its catalytic properties.

To study the role of the oligosaccharide moiety in the catalytic properties of angiotensin-converting enzyme (ACE), we obtained asialo- and partially deglycosylated ACE by enzymatic treatment of two-domain somatic enzyme from bovine lung. Treated enzymes demonstrated appreciable, but different changes of catalytic properties in the reaction of the hydrolysis of N-substituted tripeptides, C-terminal analogs of angiotensin I and bradykinin among them, compared to those for native enzyme. Deglycosylation also altered the catalytic properties of a single N domain of bovine ACE. So, various patterns of glycosylation modulate substrate specificity of somatic ACE and may be the reason for functional heterogeneity of the enzyme.

Selective zoning of high harmonic emission using counter-propagating light.

High harmonic production can be dramatically increased by utilizing an interaction region much longer than a coherence length. Counter-propagating light pulses can be used to disrupt the out-of-phase harmonic emission from selected zones in the focus so that the remaining emission builds constructively. Counter-propagating light creates a standing field modulation repeating over a half laser wavelength in which phase cancellations for harmonic emission occur. A simple power-law model is used to demonstrate how such pulses can be designed to counteract geometrical phase mismatches and improve emission for individual harmonics by more than two orders of magnitude.

[Structural changes in the endothelium of the major arteries under conditions of longitudinal stretching in vivo (based on scanning electron microscopic data)]. / Izmenenie struktury éndoteliia magistral'nykh arterii v usloviiakh prodol'nogo rastiazheniia in vivo (po dannym skaniruiushchei élektronnoi mikroskopii).

The method of scanning electron microscopy was used for studying three-dimensional organization of the endothelium of major vessels under conditions of distraction in vivo. The distraction resulted in an enlargement of the spaces between endotheliocytes without formation of considerable areas of deendothelialized surface. The main mechanism of induction of flattening and division of endotheliocytes in the zone of distraction seems to be the elimination of the contact inhibition resulting from a mechanical distraction.

[Changes in the spatial organization and structure of the smooth-muscle cells of the tunica media of the major arteries during lengthwise stretching in situ]. / Izmenenie prostranstvennoi organizatsii i struktury gladkomyshechnykh kletok srednei obolochki magistral'nykh arterii v usloviiakh prodol'nogo rastiazheniia in situ.

It has been shown that in vivo stretching of the arterial wall leads to the loss of cell-cell contacts between medial smooth muscle cells (SMC), and to the change in the cell cooperation type. It is accompanied by the increase in SMC proliferative activity, and by changes in their shape and phenotype, from the contractile to the synthetic one. The increase in the number of extracellular connective tissue structures occurs in the intercellular space.

[Changes in the orientation of the smooth-muscle cells of the tunica media from major arteries under constant lengthwise stretching in situ]. / Izmenenie orientatsii gladkomyshechnykh kletok srednei obolochki magistral'nykh arterii v usloviiakh postoiannogo prodol'nogo rastiazheniia in situ.

It has been shown that changes in the orientation of arterial smooth muscle cells during a constant longitudinal stretching of the artery in vivo are not similar in different sections of the stretching zone. Cells in the proximal and distal sections keep their orientation but this orientation differs from that of smooth muscle cells in the control arteries. Cells in the central part of the stretching region lose their definite orientation to settle randomly.

The ionic channels formed by cholera toxin in planar bilayer lipid membranes are entirely attributable to its B-subunit.

The interaction of cholera toxin with planar bilayer lipid membranes (BLM) at low pH results in the formation of ionic channels, the conductance of which can be directly measured in voltage-clamp experiments. It is found that the B-subunit of cholera toxin (CT-B) also is able to induce ionic channels in BLM whereas the A-subunit is not able to do it. The increase of pH inhibited the channel-forming activity of CT-B. The investigation of pH-dependences of both the conductance and the cation-anion selectivity of the CT-B channel allowed us to suggest that the water pore of this channel is confined to the B-subunit of cholera toxin. The effective diameter of the CT-B channels water pores was directly measured in BLM and is equal to 2.1 +/- 0.2 nm. The channels formed by whole toxin and its B-subunit exhibit voltage-dependent activity. We believe these channels are relevant to the mode of action of cholera toxin and especially to the endosomal pathway of the A-subunit into cells.