582 research outputs found
Existence of positive solutions of a superlinear boundary value problem with indefinite weight
We deal with the existence of positive solutions for a two-point boundary
value problem associated with the nonlinear second order equation
. The weight is allowed to change its sign. We assume
that the function is
continuous, and satisfies suitable growth conditions, so as the case
, with , is covered. In particular we suppose that is
large near infinity, but we do not require that is non-negative in a
neighborhood of zero. Using a topological approach based on the Leray-Schauder
degree we obtain a result of existence of at least a positive solution that
improves previous existence theorems.Comment: 12 pages, 4 PNG figure
PT Symmetric, Hermitian and P-Self-Adjoint Operators Related to Potentials in PT Quantum Mechanics
In the recent years a generalization of the
harmonic oscillator using a complex deformation was investigated, where
\epsilon\ is a real parameter. Here, we will consider the most simple case:
\epsilon even and x real. We will give a complete characterization of three
different classes of operators associated with the differential expression H:
The class of all self-adjoint (Hermitian) operators, the class of all PT
symmetric operators and the class of all P-self-adjoint operators.
Surprisingly, some of the PT symmetric operators associated to this expression
have no resolvent set
High Li+ and Na+ Conductivity in New Hybrid Solid Electrolytes based on the Porous MIL-121 Metal Organic Framework
Solid-state electrolytes (SSEs) can leapfrog the development of all-solid-state batteries (ASSBs), enabling them to power electric vehicles and to store renewable energy from intermittent sources. Here, a new hybrid Li+ and Na+ conducting SSE based on the MIL-121 metal-organic framework (MOF) structure is reported. Following synthesis and activation of the MOF, the free carboxylic units along the 1D pores are functionalized with Li+ or Na+ ions by ion exchange. Ion dynamics are investigated by broadband impedance spectroscopy and by Li-7 and Na-23 NMR spin-lattice relaxation. A crossover at 50 degrees C (Li+) and at 10 degrees C (Na+) from correlated to almost uncorrelated motion at higher temperature is observed, which is in line with Ngai\u27s coupling model. Alternatively, in accordance to the jump relaxation model of Funke, at low temperature only a fraction of the jump processes are successful as lattice rearrangement in the direct vicinity of Li+ (Na+) is slow. H-1 NMR unambiguously shows that Li+ is the main charge carrier. Conductivities reach 0.1 mS cm(-1) (298 K, Na+) while the activation energies are 0.28 eV (Li+) and 0.36 eV (Na+). The findings pave the way towards development of easily tunable and rationally adjustable high-performance MOF-based hybrid SSEs for ASSBs
Density-potential mappings in quantum dynamics
In a recent letter [Europhys. Lett. 95, 13001 (2011)] the question of whether
the density of a time-dependent quantum system determines its external
potential was reformulated as a fixed point problem. This idea was used to
generalize the existence and uniqueness theorems underlying time-dependent
density functional theory. In this work we extend this proof to allow for more
general norms and provide a numerical implementation of the fixed-point
iteration scheme. We focus on the one-dimensional case as it allows for a more
in-depth analysis using singular Sturm-Liouville theory and at the same time
provides an easy visualization of the numerical applications in space and time.
We give an explicit relation between the boundary conditions on the density and
the convergence properties of the fixed-point procedure via the spectral
properties of the associated Sturm-Liouville operator. We show precisely under
which conditions discrete and continuous spectra arise and give explicit
examples. These conditions are then used to show that in the most physically
relevant cases the fixed point procedure converges. This is further
demonstrated with an example.Comment: 20 pages, 8 figures, 3 table
The Cerebrospinal Fluid in Multiple Sclerosis
Investigation of cerebrospinal fluid (CSF) in the diagnostic work-up in suspected multiple sclerosis (MS) patients has regained attention in the latest version of the diagnostic criteria due to its good diagnostic accuracy and increasing issues with misdiagnosis of MS based on over interpretation of neuroimaging results. The hallmark of MS-specific changes in CSF is the detection of oligoclonal bands (OCB) which occur in the vast majority of MS patients. Lack of OCB has a very high negative predictive value indicating a red flag during the diagnostic work-up, and alternative diagnoses should be considered in such patients. Additional molecules of CSF can help to support the diagnosis of MS, improve the differential diagnosis of MS subtypes and predict the course of the disease, thus selecting the optimal therapy for each patient
2-(4-(Biphenyl-4-ylamino)-6-chloropyrimidin-2-ylthio)octanoic acid (HZ52) - a novel type 5-lipoxygenase inhibitor with favorable molecular pharmacology and efficacy in vivo.
BACKGROUND AND PURPOSE:
5-Lipoxygenase (5-LO) is the key enzyme in the biosynthesis of pro-inflammatory leukotrienes (LTs) representing a potential target for pharmacological intervention with inflammation and allergic disorders. Although many LT synthesis inhibitors are effective in simple in vitro test systems, they frequently fail in vivo due to lack of efficacy. Here, we attempted to assess the pharmacological potential of the previously identified 5-LO inhibitor 2-(4-(biphenyl-4-ylamino)-6-chloropyrimidin-2-ylthio)octanoic acid (HZ52).
EXPERIMENTAL APPROACH:
We evaluated the efficacy of HZ52 in vivo using carrageenan-induced pleurisy in rats and platelet-activating factor (PAF)-induced lethal shock in mice. We also characterized 5-LO inhibition by HZ52 at the cellular and molecular level in comparison with other types of 5-LO inhibitor, that is, BWA4C, ZM230487 and hyperforin.
KEY RESULTS:
HZ52, 1.5 mg·kg⁻¹ i.p., prevented carrageenan-induced pleurisy accompanied by reduced LTB(4) levels and protected mice (10 mg·kg⁻¹, i.p.) against PAF-induced shock. Detailed analysis in cell-based and cell-free assays revealed that inhibition of 5-LO by HZ52 (i) does not depend on radical scavenging properties and is reversible; (ii) is not impaired by an increased peroxide tone or by elevated substrate concentrations; and (iii) is little affected by the cell stimulus or by phospholipids, glycerides, membranes or Ca²⁺.
CONCLUSIONS AND IMPLICATIONS:
HZ52 is a promising new type of 5-LO inhibitor with efficacy in vivo and with a favourable pharmacological profile. It possesses a unique 5-LO inhibitory mechanism different from classical 5-LO inhibitors and seemingly lacks the typical disadvantages of former classes of LT synthesis blockers
First-passage and first-exit times of a Bessel-like stochastic process
We study a stochastic process related to the Bessel and the Rayleigh
processes, with various applications in physics, chemistry, biology, economics,
finance and other fields. The stochastic differential equation is , where is the Wiener process. Due to the
singularity of the drift term for , different natures of boundary at
the origin arise depending on the real parameter : entrance, exit, and
regular. For each of them we calculate analytically and numerically the
probability density functions of first-passage times or first-exit times.
Nontrivial behaviour is observed in the case of a regular boundary.Comment: 15 pages, 6 figures, submitted to Physical Review
Effects of Repeated Intrathecal Triamcinolone-Acetonide Application on Cerebrospinal Fluid Biomarkers of Axonal Damage and Glial Activity in Multiple Sclerosis Patients
Multiple sclerosis (MS) is the most common inflammatory disease of the central nervous system in young adults. Over time, the disease progresses and, with accumulating disability, symptoms such as spasticity may occur. Although several treatment options are available, some patients may not respond to first-line therapeutics. However, some of these patients may benefit from intrathecally administered triamcinolone-acetonide (TCA), a derivative of glucocorticosteroids (GCS).GCSmay have neurotoxic effects, and cell apoptosis may occur. The aim of this study was to investigate the effects of TCA on biomarkers in the cerebrospinal fluid (CSF) suggestive of neurodegeneration
Controlled Growth of a Line Defect in Graphene and Implications for Gate-Tunable Valley Filtering
Atomically precise tailoring of graphene can enable unusual transport
pathways and new nanometer-scale functional devices. Here we describe a recipe
for the controlled production of highly regular "5-5-8" line defects in
graphene by means of simultaneous electron irradiation and Joule heating by
applied electric current. High-resolution transmission electron microscopy
reveals individual steps of the growth process. Extending earlier theoretical
work suggesting valley-discriminating capabilities of a graphene 5-5-8 line
defect, we perform first-principles calculations of transport and find a strong
energy dependence of valley polarization of the charge carriers across the
defect. These findings inspire us to propose a compact electrostatically gated
"valley valve" device, a critical component for valleytronics
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