Search results for " effects"
showing 10 items of 2364 documents
Current‐voltage curves of bipolar membranes
1992
Bipolar membranes consist of a layered ion‐exchange structure composed of a cation selective membrane joined to an anion selective membrane. They are analogous to semiconductor p‐n devices as both of them present current‐voltage curves exhibiting similar rectification properties. In this article, we present some current‐voltage curves obtained for different bipolar membranes at several temperatures. The results can be interpreted in terms of a simple model for ion transport and field‐enhanced water dissociation previously developed. The mechanism responsible for water splitting is assumed to be a catalytic proton transfer reaction between the charged groups and the water at the membrane int…
Domain wall energy in quasi-one-dimensional Fe/W(110) nanostripes
2003
The magnetic susceptibility in Fe/W(110) nanostripes decreases exponentially with increasing temperature according to an Arrhenius law which indicates a quasi-one-dimensional behavior. The interface energy of the Arrhenius law corresponds to the domain wall energy of a domain wall across a single stripe, separating fluctuating regions of homogeneous magnetization. The domain wall energy increases linearly with the width of the stripes, revealing a negative offset which we attribute to boundary effects. Domain wall energies have been determined for Fe/W(110) nanostripes coated with Au and Pd and are compared to values for uncoated Fe/W(110) nanostripes in ultrahigh vacuum.
Temperature dependance of the generation and decay of E’ centers induced in silica by 4.7eV laser radiation
2009
We report a study of the generation of silicon dangling bonds (E' centers) induced in fused silica by 4.7 eV laser irradiation in the 10 200 K the induced defects undergo a post-irradiation decay due to their reaction with mobile H(2). The interplay between generation and annealing gives rise to a bell-shaped temperature dependence of the concentration of induced E' centers, peaking at 250 K
Ligand Design for Heterobimetallic Single-Chain Magnets: Synthesis, Crystal Structures, and Magnetic Properties of MIICuII (M=Mn, Co) Chains with Ste…
2006
Two new series of neutral ox-amato-bridged heterobimetallic chains of general formula [MCu(L x ) 2 ]- m DMSO (m=0-4) (L 1 =N-2-methyl-phenyloxamate, M=Mn (1a) and Co (1 b); L2 = N-2,6-dimethylphenyloxamate, M=Mn (2a) and Co (2b); L 3 = N-2,4,6-trimethylphenyloxamate, M= Mn (3a) and Co (3b)) have been prepared by reaction between the corresponding anionic oxamatocopper(II) complexes [Cu(L x ) 2 ] 2- with Mn 2+ or Co 2+ cations in DMSO. The crystal structures of [CoCu(L 2 ) 2 (H 2 O) 2 ] (2b') and [CoCu(L 3 ) 2 (H 2 O) 2 ]·4H 2 O (3b') have been solved by single-crystal X-ray diffraction methods. Compounds 2b' and 3b' adopt zigzag and linear chain structures, respectively. The intrachain Cu··…
Toxicity of the antimalarial artemisinin and its dervatives.
2010
As long as no effective malaria vaccine is available, chemotherapy belongs to the most important weapons fighting malaria. One of the most promising new drug developments is the sesquiterpene artemisinin (ARS) and its derivatives, e.g., artemether, arteether, and sodium artesunate. Large clinical studies and meta-analyses did not show serious side effects, although proper monitoring of adverse effects in developing countries might not be a trivial task. There is a paucity of large-scale clinical trials suitable to detect rare but significant toxicity. Therefore, a final and definitive statement on the safety of artemisinins still cannot be made. In contrast, animal experiments show consider…
Ionic liquids/[bmim][N3] mixtures: promising media for the synthesis of aryl azides by SNAr
2008
The nucleophilic aromatic substitution of some activated aryl or heteroaryl halides has been performed in ionic liquid solution, using the 1-butyl-3-methylimidazolium azide as a nucleophile. The reaction course was studied varying the structures of both substrates and ionic liquids. In particular, in the latter case, the reaction of 2-bromo-5-nitrothiophene was carried out in five different ionic liquids ([bmim][BF 4], [bmim][PF 6], [bmim][NTf 2], [bm 2im][NTf 2], and [bmpyrr][NTf 2]). Finally, for all the substrates considered, a comparison with data obtained in MeOH solution in the presence of NaN 3 was also performed. Data collected indicate that in some cases it is possible to obtain ar…
Properties of the Binary Neutron Star Merger GW170817
2019
On August 17, 2017, the Advanced LIGO and Advanced Virgo gravitational-wave detectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wave signal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary's properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wave frequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models, which ar…
Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background
2018
The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually-unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generic…
The Effects of Orography on the Extratropical Transition of Tropical Cyclones: A Case Study of Typhoon Sinlaku (2008)
2018
Abstract Extratropical transition (ET) can cause high-impact weather in midlatitude regions and therefore constitutes an ongoing threat at the end of a tropical cyclone’s (TC) life cycle. Most of the ET events occur over the ocean, but some TCs recurve and undergo ET along coastal regions; however, the latter category is less investigated. Typhoon Sinlaku (2008), for example, underwent ET along the southern coast of Japan. It was one of the typhoons that occurred during the T-PARC field campaign, providing unprecedented high-resolution observational data. Sinlaku is therefore an excellent case to investigate the impact of a coastal region, and in particular orography, on the evolution of ET…
Origin of atmospheric aerosols at the Pierre Auger Observatory using studies of air mass trajectories in South America
2014
The Pierre Auger Observatory is making significant contributions towards understanding the nature and origin of ultra-high energy cosmic rays. One of its main challenges is the monitoring of the atmosphere, both in terms of its state variables and its optical properties. The aim of this work is to analyze aerosol optical depth $\tau_{\rm a}(z)$ values measured from 2004 to 2012 at the observatory, which is located in a remote and relatively unstudied area of the Pampa Amarilla, Argentina. The aerosol optical depth is in average quite low - annual mean $\tau_{\rm a}(3.5~{\rm km})\sim 0.04$ - and shows a seasonal trend with a winter minimum - $\tau_{\rm a}(3.5~{\rm km})\sim 0.03$ -, and a sum…