Spin vortices and vacancies: interactions and pinning on a square lattice

The study gives a decisive answer to the recently risen question about the type and origin of interaction between spin vortices and spin vacancies in 2D spin models. The approach is based on the low-temperature approximation of the 2D XY model known as the Villain model and does not involve any additional approximations, thus preserving the lattice structure. The exact form of the Hamiltonian describing a system of topological charges and a vacant site supports the attractive type of interaction between the vacancy and the charges. The quantitative difference between the characteristics of the vortex behavior in the 2D XY and Villain models due to the different energy of the vortex "cores" in the two models is pointed out. This leads to a conclusion that the interaction between a vortex and a spin vacancy and between a vortex and the antivortex differs quantitatively for small separations in the two mentioned models.Comment: 13 pages, 5 figure

The Joint Action of Sesquiterpene Lactones from Leaves as an Explanation for the Activity of Cynara cardunculus

The work described herein is a continuation of a previous study centered on the bioprospect of cardoon (Cynara cardunculus) leaf extracts through the isolation of secondary metabolites with phytotoxic activity. Chromatographic fractionations of the ethyl acetate extract and spectroscopic analysis showed that the majority of the components were sesquiterpene lactones. Of these compounds, aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth. The joint action of binary mixtures of these three active sesquiterpene lactones and one nonactive compound (11,13-dihydroxy-8-desoxygrosheimin) was studied. The activities of fixed-ratio mixtures were assessed on wheat coleoptile. The results can be interpreted with respect to a reference model by considering dose−response analyses and isobolograms with linear regression analyses. A total of 17 binary mixtures at different levels of inhibition (ED25, ED50, and ED75) were studied, and predominantly they responded additively (25). Deviations from additivity included seven synergistic responses and two antagonistic responses. The joint action of major sesquiterpene lactones isolated from C. cardunculus can explain the activities observed in extracts and fractions. The results reported here reiterate the utility of the wheat coleoptile bioassay as a quick tool to detect potential synergistic effects in binary mixtures

Cystic Fibrosis: A New Target for 4-Imidazo[2,1-b]thiazole-1,4-dihydropyridines

The pharmacology of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel has attracted significant interest in recent years with the aim to search for rational new therapies for diseases caused by CFTR malfunction. Mutations that abolish the function of CFTR cause the life-threatening genetic disease cystic fibrosis (CF). The most common cause of CF is the deletion of phenylalanine 508 (ΔF508) in the CFTR chloride channel. Felodipine, nifedipine, and other antihypertensive 1,4-dihydropyridines (1,4-DHPs) that block L-type Ca(2+) channels are also effective potentiators of CFTR gating, able to correct the defective activity of ΔF508 and other CFTR mutants ( Mol. Pharmacol. 2005 , 68 , 1736 ). For this purpose, we evaluated the ability of the previously and newly synthesized 4-imidazo[2,1-b]thiazoles-1,4-dihydropyridines without vascular activity and inotropic and/or chronotropic cardiac effects ( J. Med. Chem. 2008 , 51 , 1592 ) to enhance the activity of ΔF508-CFTR. Our studies indicate compounds 17, 18, 20, 21, 38, and 39 as 1,4-DHPs with an interesting profile of activity

Perifosine as a Potential Novel Anti-Cancer Agent Inhibits EGFR/MET-AKT Axis in Malignant Pleural Mesothelioma

PI3K/AKT signalling pathway is aberrantly active and plays a critical role for cell cycle progression of human malignant pleural mesothelioma (MMe) cells. AKT is one of the important cellular targets of perifosine, a novel bio-available alkylphospholipid that has displayed significant anti-proliferative activity in vitro and in vivo in several human tumour model systems and is currently being tested in clinical trials.We tested Perifosine activity on human mesothelial cells and different mesothelioma cell lines, in order to provide evidence of its efficacy as single agent and combined therapy.We demonstrate here that perifosine, currently being evaluated as an anti-cancer agent in phase 1 and 2 clinical trials, caused a dose-dependent reduction of AKT activation, at concentrations causing MMe cell growth arrest. In this study we firstly describe that MMe cells express aside from AKT1 also AKT3 and that either the myristoylated, constitutively active, forms of the two proteins, abrogated perifosine-mediated cell growth inhibition. Moreover, we describe here a novel mechanism of perifosine that interferes, upstream of AKT, affecting EGFR and MET phosphorylation. Finally, we demonstrate a significant increase in cell toxicity when MMe cells were treated with perifosine in combination with cisplatin.This study provides a novel mechanism of action of perifosine, directly inhibiting EGFR/MET-AKT1/3 axis, providing a rationale for a novel translational approach to the treatment of MMe

Interfacial Chemistry in Al/CuO Reactive Nanomaterial and Its Role in Exothermic Reaction.

Interface layers between reactive and energetic materials in nanolaminates or nanoenergetic materials are believed to play a crucial role in the properties of nanoenergetic systems. Typically, in the case of Metastable Interstitial Composite nanolaminates, the interface layer between the metal and oxide controls the onset reaction temperature, reaction kinetics, and stability at low temperature. So far, the formation of these interfacial layers is not well understood for lack of in situ characterization, leading to a poor control of important properties. We have combined in situ infrared spectroscopy and ex situ X-ray photoelectron spectroscopy, differential scanning calorimetry, and high resolution transmission electron microscopy, in conjunction with firstprinciples calculations to identify the stable configurations that can occur at the interface and determine the kinetic barriers for their formation. We find that (i) an interface layer formed during physical deposition of aluminum is composed of a mixture of Cu, O, and Al through Al penetration into CuO and constitutes a poor diffusion barrier (i.e., with spurious exothermic reactions at lower temperature), and in contrast, (ii) atomic layer deposition (ALD) of alumina layers using trimethylaluminum (TMA)produces a conformal coating that effectively prevents Al diffusion even for ultrathin layer thicknesses (∼0.5 nm), resulting in better stability at low temperature and reduced reactivity. Importantly, the initial reaction of TMA with CuO leads to the extraction of oxygen from CuO to form an amorphous interfacial layer that is an important component for superior protection properties of the interface and is responsible for the high system stability. Thus, while Al e-beam evaporation and ALD growth of an alumina layer on CuO both lead to CuO reduction, the mechanism for oxygen removal is different, directly affecting the resistance to Al diffusion. This work reveals that it is the nature of the monolayer interface between CuO and alumina/Al rather than the thickness of the alumina layer that controls the kinetics of Al diffusion, underscoring the importance of the chemical bonding at the interface in these energetic materials

Water Contamination Reduces the Tolerance of Coral Larvae to Thermal Stress

Coral reefs are highly susceptible to climate change, with elevated sea surface temperatures (SST) posing one of the main threats to coral survival. Successful recruitment of new colonies is important for the recovery of degraded reefs following mortality events. Coral larvae require relatively uncontaminated substratum on which to metamorphose into sessile polyps, and the increasing pollution of coastal waters therefore constitutes an additional threat to reef resilience. Here we develop and analyse a model of larval metamorphosis success for two common coral species to quantify the interactive effects of water pollution (copper contamination) and SST. We identify thresholds of temperature and pollution that prevent larval metamorphosis, and evaluate synergistic interactions between these stressors. Our analyses show that halving the concentration of Cu can protect corals from the negative effects of a 2–3°C increase in SST. These results demonstrate that effective mitigation of local impacts can reduce negative effects of global stressors