3,810 research outputs found
Intraoperative detection of blood vessels with an imaging needle during neurosurgery in humans
Intracranial hemorrhage can be a devastating complication associated with needle biopsies of the brain. Hemorrhage can occur to vessels located adjacent to the biopsy needle as tissue is aspirated into the needle and removed. No intraoperative technology exists to reliably identify blood vessels that are at risk of damage. To address this problem, we developed an “imaging needle” that can visualize nearby blood vessels in real time. The imaging needle contains a miniaturized optical coherence tomography probe that allows differentiation of blood flow and tissue. In 11 patients, we were able to intraoperatively detect blood vessels (diameter, \u3e500 μm) with a sensitivity of 91.2% and a specificity of 97.7%. This is the first reported use of an optical coherence tomography needle probe in human brain in vivo. These results suggest that imaging needles may serve as a valuable tool in a range of neurosurgical needle interventions
Acid-sensing ion channels (ASICs) as pharmacological targets for neurodegenerative diseases
A significant drop of tissue pH or acidosis is a common feature of acute neurological conditions such as ischemic stroke, brain trauma, and epileptic seizures. Acid-sensing ion channels, or ASICs, are proton-gated cation channels widely expressed in peripheral sensory neurons and in the neurons of the central nervous system. Recent studies have demonstrated that activation of these channels by protons plays an important role in a variety of physiological and pathological processes such as nociception, mechanosensation, synaptic plasticity, and acidosis-mediated neuronal injury. This review provides an overview of the recent advance in electrophysiological, pharmacological characterization of ASICs, and their role in neurological diseases. Therapeutic potential of current available ASIC inhibitors is discussed
The Interplay of Landau Level Broadening and Temperature on Two-Dimensional Electron Systems
This work investigates the influence of low temperature and broadened Landau
levels on the thermodynamic properties of two-dimensional electron systems. The
interplay between these two physical parameters on the magnetic field
dependence of the chemical potential, the specific heat and the magnetization
is calculated. In the absence of a complete theory that explains the Landau
level broadening, experimental and theoretical studies in literature perform
different model calculations of this parameter. Here it is presented that
different broadening parameters of Gaussian-shaped Landau levels cause width
variations in their contributions to interlevel and intralevel excitations.
Below a characteristic temperature, the interlevel excitations become
negligible. Likewise, at this temperature range, the effect of the Landau level
broadening vanishes.Comment: 5 pages, 5 figures, submitted to Solid State Communication
On the lowest eigenvalue of Laplace operators with mixed boundary conditions
In this paper we consider a Robin-type Laplace operator on bounded domains.
We study the dependence of its lowest eigenvalue on the boundary conditions and
its asymptotic behavior in shrinking and expanding domains. For convex domains
we establish two-sided estimates on the lowest eigenvalues in terms of the
inradius and of the boundary conditions
The Large Magellanic Cloud: A power spectral analysis of Spitzer images
We present a power spectral analysis of Spitzer images of the Large
Magellanic Cloud. The power spectra of the FIR emission show two different
power laws. At larger scales (kpc) the slope is ~ -1.6, while at smaller ones
(tens to few hundreds of parsecs) the slope is steeper, with a value ~ -2.9.
The break occurs at a scale around 100-200 pc. We interpret this break as the
scale height of the dust disk of the LMC. We perform high resolution
simulations with and without stellar feedback. Our AMR hydrodynamic simulations
of model galaxies using the LMC mass and rotation curve, confirm that they have
similar two-component power-laws for projected density and that the break does
indeed occur at the disk thickness. Power spectral analysis of velocities
betrays a single power law for in-plane components. The vertical component of
the velocity shows a flat behavior for large structures and a power law similar
to the in-plane velocities at small scales. The motions are highly anisotropic
at large scales, with in-plane velocities being much more important than
vertical ones. In contrast, at small scales, the motions become more isotropic.Comment: 8 pages, 4 figures, talk presented at "Galaxies and their Masks",
celebrating Ken Freeman's 70-th birthday, Sossusvlei, Namibia, April 2010. To
be published by Springer, New York, editors D.L. Block, K.C. Freeman, & I.
Puerar
The impact of analyst sentiment on UK stock recommendations and target prices
© 2015 Taylor & Francis. The aim of this paper is to investigate the relationship between narrative sentiment in analysts' company reports and their recommendation and target price outputs. We study an industry-balanced sample of 275 UK quoted company sell-side analyst reports over the period 2006-2010 using a content analysis methodology to measure net sentiment for a range of themes. We then model analysts' outputs against themed sentiment scores to analyse the impact of the Global Financial Crisis. We find that themed sentiments impact upon analysts' outputs, but their magnitude and direction vary over the pre-crisis, crisis and post-crisis periods. In particular, before the crisis we find a strong negative relationship between the macroeconomic and regulatory environment and report outputs, though this effect diminishes somewhat with the onset of the crisis, to be restored thereafter. Growth sentiment exerts a weak positive impact before the crisis which disappears thereafter. Financial performance sentiment becomes a significant positive driver of outputs following the crisis. There is evidently a "back to basics" approach following the crisis which restores financial fundamentals to the heart of stock analysis. Our findings provide some insight into the thought processes of analysts by identifying the dynamic relation between analysts' outputs and themed sentiments
The evolution of cosmic string loops in Kerr-de Sitter spacetimes
The equation of cosmic string loops in Kerr-de Sitter spacetimes is derived.
Having solved the equation numerically, we find that the loops can expand and
exist except for too small ones.Comment: 8 page
Effect of Boron substitution on the superconductivity of non-oxide perovskite MgCNi3
We report synthesis, structural and magnetic (DC and AC) properties of Boron
substituted MgCNi3 superconductor. A series of polycrystalline bulk samples
Mg1.2C1.6-xBxNi3 (x = 0.0, 0.08 and 0.16) is synthesized through standard
solid-state reaction route, which are found to crystallize in cubic perovskite
structure with space group Pm3m. Rietveld analysis of observed XRD data show
that lattice parameters expand from a = 3.8106 (4) {\AA} for pure, to 3.8164
(2) {\AA} and 3.8173 (5) {\AA} for 5% and 10% Boron substituted samples
respectively. DC magnetization exhibited superconducting transition (Tc) at
around 7.3 K for pure sample, and the same decreases slightly with Boron
substitution. The lower critical field (Hc1) at 2 K is around 150 Oe for pure
sample, which increases slightly with Boron substitution. For pure sample the
upper critical field (Hc2) being determined from AC susceptibility measurements
is 11.6 kOe and 91.70 kOe with 50% and 90% diamagnetism criteria respectively,
which decreases to 5.57 kOe and 42.5 kOe respectively for 10% Boron substituted
sample. 10% Boron substitution at Carbon site has decreased both the Hc2 and
Tc. On the other hand lower critical field (Hc1) at 2 K is slightly increased
from around 150 Oe for pure sample, to 200 Oe for 10% Boron substituted sample.
Seemingly, the Carbon site Boron substitution induced disorder though has
increased slightly the Hc1 but with simultaneous decrease in superconducting
transition temperature (Tc) and upper critical field (Hc2). The high relative
proportion of Ni in studied MgCNi3 suggests that magnetic interactions are
important and non-oxide perovskite structure make it interesting.Comment: 13 Pages Text + Figures: comments/suggestions
([email protected]
Primary Extra-gastrointestinal Stromal Tumor of Retroperitoneum
Background Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. More rarely neoplasms with histology and immunohistochemistry similar to GISTs may occur outside the gastrointestinal tract (omentum, mesentery and retroperitoneum) and are so-called Extra-gastrointestinal Stromal Tumors (EGISTs). EGISTs arising in the retroperitoneum are extremely rare: to date, only 58 cases have been reported in the literature. Case Report We herein report a case of a primary EGIST of the retroperitoneum surgically treated. The pre-operative radiological evaluation showed a retroperitoneal mass, placed in left paravertebral region. Results Morphological and immunohistochemical features led to a diagnosis of extra-gastrointestinal stromal tumor (intermediate-low risk form). Conclusions As a result of the rarity of reports of primary EGISTs of retroperitoneum we need to analyze the data of reported cases in order to gain a better understanding about the pathogenesis, prognosis and optimal treatment of this disease
Curve counting via stable pairs in the derived category
For a nonsingular projective 3-fold , we define integer invariants
virtually enumerating pairs where is an embedded curve and
is a divisor. A virtual class is constructed on the associated
moduli space by viewing a pair as an object in the derived category of . The
resulting invariants are conjecturally equivalent, after universal
transformations, to both the Gromov-Witten and DT theories of . For
Calabi-Yau 3-folds, the latter equivalence should be viewed as a wall-crossing
formula in the derived category.
Several calculations of the new invariants are carried out. In the Fano case,
the local contributions of nonsingular embedded curves are found. In the local
toric Calabi-Yau case, a completely new form of the topological vertex is
described.
The virtual enumeration of pairs is closely related to the geometry
underlying the BPS state counts of Gopakumar and Vafa. We prove that our
integrality predictions for Gromov-Witten invariants agree with the BPS
integrality. Conversely, the BPS geometry imposes strong conditions on the
enumeration of pairs.Comment: Corrected typos and duality error in Proposition 4.6. 47 page
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