The effects of lipid A on gamma-irradiated human peripheral blood lymphocytes in vitro

The modulatory effects of lipid A (diphosphoryl lipid A (DLA) and monophosphoryl lipid A (MLA)) on apoptosis induction and DNA structure damage (single and double-strand breaks (SSBs and DSBs, respectively)) in peripheral human blood lymphocytes are studied for ⁶⁰Co gamma-irradiation. It is shown that in the presence of these agents the amount of apoptotic cells increases compared with the irradiated control samples. The effect is most strongly pronounced for DLA. In its presence, a significant increase is observed in the number of radiation-induced DNA SSBs and DSBs. Possible mechanisms are discussed of the modifying influence of the used agents on radiation-induced cell reactions     

Synthesis and characterization of a family of layered trichalcogenides for assisted hydrogen photogeneration

Three layered trisulfides (TiS₃, ZrS₃, HfS₃) have been synthesized by solid–gas reaction between metal and sulfur in a vacuum sealed ampoule at 550 °C during 60 h. The samples used in this work were prepared from a colloidal suspension of powder of each one of the metal trisulfides (MS₃, M = Ti, Zr, Hf) in ethanol and deposited on titanium disks and quartz substrates by ”drop coating” technique. These samples have been characterized by X‐ray diffraction, energy dispersive analysis of X‐ray and scanning electron microscopy. The obtained direct optical band gaps are 1.0 ± 0.1 eV, 2.0 ± 0.1 eV and 2.2 ± 0.1 eV for TiS₃, ZrS₃ and HfS₃, respectively. Photoelectrochemical measurements in 0.5 M Na₂SO₃ have been carried out to characterize the MS₃/electrolyte interface. The flat‐band potentials (V_fb) vs. Ag/AgCl measured by electrochemical impedance spectroscopy (EIS) are –0.84 ± 0.02 V (TiS₃), –0.93 ± 0.02 V (ZrS₃) and –0.92 ± 0.02 V (HfS₃). Hydrogen generation was investigated in a photoelectrochemical cell (PEC) with MS₃ as photoanodes under white light illumination of 200 ± 20 mW/cm² at external bias potentials of 0.3 V vs. Ag/AgCl. Hydrogen evolution flows have been quantified by quadrupole mass spectrometry (QMS) reaching instantaneous values up to 19 ± 2 nmol H₂/min cm² with TiS₃ as photoanode.     

The slowly reacting mode of combustion of gaseous mixtures in spherical vessels. Part 1: Transient analysis and explosion limits

Frank-Kamenetskii's analysis of thermal explosions is revisited, using also a single-reaction model with an Arrhenius rate having a large activation energy, to describe the transient combustion of initially cold gaseous mixtures enclosed in a spherical vessel with a constant wall temperature. The analysis shows two modes of combustion. There is a flameless slowly reacting mode for low wall temperatures or small vessel sizes, when the temperature rise resulting from the heat released by the reaction is kept small by the heat-conduction losses to the wall, so as not to change significantly the order of magnitude of the reaction rate. In the other mode, the slow reaction rates occur only in an initial ignition stage, which ends abruptly when very large reaction rates cause a temperature runaway, or thermal explosion, at a well-defined ignition time and location, thereby triggering a flame that propagates across the vessel to consume the reactant rapidly. Explosion limits are defined, in agreement with Frank-Kamenetskii's analysis, by the limiting conditions for existence of the slowly reacting mode of combustion. In this mode, a quasi-steady temperature distribution is established after a transient reaction stage with small reactant consumption. Most of the reactant is burnt, with nearly uniform mass fraction, in a subsequent long stage during which the temperature follows a quasi-steady balance between the rates of heat conduction to the wall and of chemical heat release. The changes in the explosion limits caused by the enhanced heat-transfer rates associated with buoyant motion are described in an accompanying paper.     

Multi-Center Vector Field Methods for Wave Equations

We develop the method of vector-fields to further study Dispersive Wave Equations. Radial vector fields are used to get a-priori estimates such as the Morawetz estimate on solutions of Dispersive Wave Equations. A key to such estimates is the repulsiveness or nontrapping conditions on the flow corresponding to the wave equation. Thus this method is limited to potential perturbations which are repulsive, that is the radial derivative pointing away from the origin. In this work, we generalize this method to include potentials which are repulsive relative to a line in space (in three or higher dimensions), among other cases. This method is based on constructing multi-centered vector fields as multipliers, cancellation lemmas and energy localization.     

Optimal spin squeezing inequalities detect bound entanglement in spin models

We determine the complete set of generalized spin squeezing inequalities. These are entanglement criteria that can be used for the experimental detection of entanglement in a system of spin-1/2 particles in which the spins cannot be individually addressed. They can also be used to show the presence of bound entanglement in the thermal states of several spin models.     

Pressure-induced two-color photoluminescence in MnF(2) at room temperature

A novel two-color photoluminescence (PL) is found in MnF(2) at room temperature under high pressure. Contrary to low-temperature PL, PL at room temperature is unusual in transition-metal concentrated materials like MnF(2), since the deexcitation process at room temperature is fully governed by energy transfer to nonradiative centers. We show that room-temperature PL in MnF(2) originates from two distinct Mn(2+) emissions in the high-pressure cotunnite phase. The electronic structure and the excited-state dynamics are investigated by time-resolved emission and excitation spectroscopy at high pressure.     

Black hole entropy quantization

Ever since the pioneering works of Bekenstein and Hawking, black hole entropy has been known to have a quantum origin. Furthermore, it has long been argued by Bekenstein that entropy should be quantized in discrete (equidistant) steps given its identification with horizon area in (semi-)classical general relativity and the properties of area as an adiabatic invariant. This lead to the suggestion that the black hole area should also be quantized in equidistant steps to account for the discrete black hole entropy. Here we shall show that loop quantum gravity, in which area is not quantized in equidistant steps, can nevertheless be consistent with Bekenstein's equidistant entropy proposal in a subtle way. For that we perform a detailed analysis of the number of microstates compatible with a given area and show consistency with the Bekenstein framework when an oscillatory behavior in the entropy-area relation is properly interpreted.     

Amplified signal response in scale-free networks by collaborative signaling

Many natural and artificial two-states signaling devices are connected forming networks. The information-processing potential of these systems is usually related to the response to weak external signals. Here, using a network of overdamped bistable elements, we study the effect of a heterogeneous complex topology on the signal response. The analysis of the problem in random scale-free networks, reveals that heterogeneity plays a crucial role in amplifying external signals. We have contrasted numerical simulations with analytical calculations in simplified topologies.     

Magnetic anisotropies of late transition metal atomic clusters

We analyze the impact of the magnetic anisotropy on the geometric structure and magnetic ordering of small atomic clusters of palladium, iridium, platinum, and gold. We have employed a noncollinear implementation of density functional theory where the spin-orbit interaction has been included self-consistently. The size of the clusters ranges from two to five, six, or seven atoms, depending on the element. Our results highlight the relevance of the spin-orbit interaction in the magnetic properties of small atomic clusters made of fourth- and fifth-row elements.     

Observation of resonant behavior in the energy velocity of diffused light

In this Letter we demonstrate Mie resonances mediated transport of light in randomly arranged, monodisperse dielectric spheres packed at high filling fractions. By means of both static and dynamic optical experiments we show resonant behavior in the key transport parameters and, in particular, we find that the energy transport velocity, which is lower than the group velocity, also displays a resonant behavior.