301 research outputs found
Cylindrically symmetric, static strings with a cosmological constant in Brans-Dicke theory
The static, cylindrically symmetric vacuum solutions with a cosmological
constant in the framework of the Brans-Dicke theory are investigated. Some of
these solutions admitting Lorentz boost invariance along the symmetry axis
correspond to local, straight cosmic strings with a cosmological constant. Some
physical properties of such solutions are studied. These strings apply
attractive or repulsive forces on the test particles. A smooth matching is also
performed with a recently introduced interior thick string solution with a
cosmological constant.Comment: 8 pages, Revtex; Published versio
Finite temperature properties of the two-dimensional SU(2) Kondo-necklace
We analyse several thermodynamic properties of the two-dimensional Kondo
necklace using finite-temperature stochastic series expansion. In agreement
with previous zero-temperature findings the model is shown to exhibit a quantum
critical point (QCP), separating an antiferromagnetic from a paramagnetic
dimerized state at a critical Kondo exchange-coupling strength . We evaluate the temperature dependent uniform and staggered structure
factors as well as the uniform and staggered susceptibilities and the local
'impurity' susceptibility close to the QCP as well as in the ordered and
quantum disordered phase. The crossover between the classical, renormalized
classical, and quantum critical regime is analyzed as a function of temperature
and Kondo coupling.Comment: 4.2 pages, 6 figure
Vitamin C in Health and Disease
Vitamin C is a pivotal water soluble electron donor in nature and an essential nutrient in man. Despite its many years as a research focus, new and increasingly regulatory functions of vitamin C in human health are continually being unravelled. This improved mechanistic insight is starting to provide rationales explaining the extensive epidemiological literature that, for decades, has consistently shown strong associations between poor vitamin C status and increased morbidity and mortality. In this Special Issue, we include original research and literature reviews by experts in the field outlining the roles of vitamin C in early, daily and late life, as well as the roles of deficiency in cardiovascular disease, inflammation and cancer
Comparison of Three Sample Preparation Procedures for the Quantification of L-Arginine, Asymmetric Dimethylarginine, and Symmetric Dimethylarginine in Human Plasma Using HPLC-FLD
Increased asymmetric dimethylarginine (ADMA) in human plasma has been associated with reduced generation of nitric oxide, leading to atherosclerotic diseases. ADMA may therefore be an important biomarker for cardiovascular disease. In the present study, three sample preparation techniques were compared regarding the quantification of L-arginine and ADMA in human plasma: (A) protein precipitation (PP) based on aqueous trichloroacetic acid (TCA), (B) PP using a mixture of ammonia and acetonitrile, and (C) solid-phase extraction (SPE). The samples were analysed by using high-performance liquid chromatography with fluorescence detection (HPLC-FLD). The analytical performance of (A) was comparable with that of (C), demonstrating recoveries of >90%, coefficient of variations (CVs, %) of <8, and a resolution (Rs) between ADMA and symmetric dimethylarginine (SDMA) of 1.2. (B) was disregarded due to recoveries below 75%. (A) was validated with good results regarding linearity (>0.994), precision (<5%), and sensitivity (lower limit of quantification (LLOQ)) of 0.14 µM and 12 nM for L-arginine and ADMA, respectively. Due to the simplicity and speed of procedure (A), this approach may serve as preferred sample preparation of human plasma samples before HPLC-FLD in providing important information regarding elevated ADMA concentrations
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