1,222 research outputs found
High-pressure study of X-ray diffuse scattering in ferroelectric perovskites
We present a high-pressure x-ray diffuse scattering study of the ABO
ferroelectric perovskites BaTiO_3 and KNbO_3. The well-known diffuse lines are
observed in all the phases studied. In KNbO_3, we show that the lines are
present up to 21.8 GPa, with constant width and a slightly decreasing
intensity. At variance, the intensity of the diffuse lines observed in the
cubic phase of BaTiO_3 linearly decreases to zero at GPa. These
results are discussed with respect to x-ray absorption measurements, which
leads to the conclusion that the diffuse lines are only observed when the B
atom is off the center of the oxygen tetrahedron. The role of such disorder on
the ferroelectric instability of perovskites is discussed.Comment: 4 pages, Accepted in PR
Performance of various quantum key distribution systems using 1.55 um up-conversion single-photon detectors
We compare the performance of various quantum key distribution (QKD) systems
using a novel single-photon detector, which combines frequency up-conversion in
a periodically poled lithium niobate (PPLN) waveguide and a silicon avalanche
photodiode (APD). The comparison is based on the secure communication rate as a
function of distance for three QKD protocols: the Bennett-Brassard 1984 (BB84),
the Bennett, Brassard, and Mermin 1992 (BBM92), and the coherent differential
phase shift keying (DPSK). We show that the up-conversion detector allows for
higher communication rates and longer communication distances than the commonly
used InGaAs/InP APD for all the three QKD protocols.Comment: 9 pages, 9 figure
Comparison of manual and semi-automated delineation of regions of interest for radioligand PET imaging analysis
BACKGROUND
As imaging centers produce higher resolution research scans, the number of man-hours required to process regional data has become a major concern. Comparison of automated vs. manual methodology has not been reported for functional imaging. We explored validation of using automation to delineate regions of interest on positron emission tomography (PET) scans. The purpose of this study was to ascertain improvements in image processing time and reproducibility of a semi-automated brain region extraction (SABRE) method over manual delineation of regions of interest (ROIs).
METHODS
We compared 2 sets of partial volume corrected serotonin 1a receptor binding potentials (BPs) resulting from manual vs. semi-automated methods. BPs were obtained from subjects meeting consensus criteria for frontotemporal degeneration and from age- and gender-matched healthy controls. Two trained raters provided each set of data to conduct comparisons of inter-rater mean image processing time, rank order of BPs for 9 PET scans, intra- and inter-rater intraclass correlation coefficients (ICC), repeatability coefficients (RC), percentages of the average parameter value (RM%), and effect sizes of either method.
RESULTS
SABRE saved approximately 3 hours of processing time per PET subject over manual delineation (p 0.8) for both methods. RC and RM% were lower for the manual method across all ROIs, indicating less intra-rater variance across PET subjects' BPs.
CONCLUSION
SABRE demonstrated significant time savings and no significant difference in reproducibility over manual methods, justifying the use of SABRE in serotonin 1a receptor radioligand PET imaging analysis. This implies that semi-automated ROI delineation is a valid methodology for future PET imaging analysis
Scaling Relations of Viscous Fingers in Anisotropic Hele-Shaw Cells
Viscous fingers in a channel with surface tension anisotropy are numerically
studied. Scaling relations between the tip velocity v, the tip radius and the
pressure gradient are investigated for two kinds of boundary conditions of
pressure, when v is sufficiently large. The power-law relations for the
anisotropic viscous fingers are compared with two-dimensional dendritic growth.
The exponents of the power-law relations are theoretically evaluated.Comment: 5 pages, 4 figure
Localization, analysis and evolution of transposed human immunoglobulin VK genes
The localization of Vκ gene regions to chromosome 2, on which the κ locus is located, and to other chromosomes is described. The Vκ genes that have been transposed to other chromosomes are called orphons. The finding of two new Vκ genes on chromosome 22 is reported. A Vκ II gene of this region and two Vκ I genes of the Chr 1 and the cos 118 regions were sequenced. The two Vκ I orphon sequences and two others that had been determined previously were 97.5% identical, indicating that they may have evolved from a common ancestor by amplification. A model of the evolution of the human Vκ orphons is discussed.
Author Keywords: Human-rodent cell hybrids; cosmids; restriction maps; ligation artifacts; orphon; recombinant DNA
Abbreviations: aa, amino acid(s); bp, base pair(s); Chr1, Vκ gene-containing regions of chromosomes 1; Chr22, Vκ gene-containing regions of chromosomes 22; FR, framework regions; CDR, complementary determining regions; kb, kilo-base(s) or 1000 bp; L, L′, parts of a leader gene segment; m219-1, the first subclone of the cosmid clone cos 219; orphon, Vκ gene outside the κ locus on chromosome 2pl2; SSC, 0.15 M NaCl, 0.015 M Na3-citrate, pH 7.6; V, variable gene segments; J, joining gene segments; C, constant gene segments; Vκ I to Vκ IV, variable gene segments of immunoglobulin light chains of the κ type belonging to subgroups I to IV; for reasons of simplicity Vκ gene segments are generally called Vκ gene
Comparison of Niskin vs. in situ approaches for analysis of gene expression in deep Mediterranean Sea water samples
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 129 (2016): 213-222, doi:10.1016/j.dsr2.2014.10.020.Obtaining an accurate picture of microbial processes occurring in situ is essential for our
understanding of marine biogeochemical cycles of global importance. Water samples are
typically collected at depth and returned to the sea surface for processing and downstream
experiments. Metatranscriptome analysis is one powerful approach for investigating metabolic
activities of microorganisms in their habitat and which can be informative for determining
responses of microbiota to disturbances such as the Deepwater Horizon oil spill. For studies of
microbial processes occurring in the deep sea, however, sample handling, pressure, and other
changes during sample recovery can subject microorganisms to physiological changes that alter
the expression profile of labile messenger RNA. Here we report a comparison of gene expression
profiles for whole microbial communities in a bathypelagic water column sample collected in the
Eastern Mediterranean Sea using Niskin bottle sample collection and a new water column
sampler for studies of marine microbial ecology, the Microbial Sampler – In Situ Incubation
Device (MS-SID). For some taxa, gene expression profiles from samples collected and preserved
33 in situ were significantly different from potentially more stressful Niskin sampling and
34 preservation on deck. Some categories of transcribed genes also appear to be affected by sample
35 handling more than others. This suggests that for future studies of marine microbial ecology,
36 particularly targeting deep sea samples, an in situ sample collection and preservation approach
37 should be considered.This research was funded by NSF OCE-1061774 to VE and
CT, NSF DBI-0424599 to CT and NSF OCE-0849578 to VE and colleague J. Bernhard. Cruise
participation was partially supported by Deutsche Forschungsgemeinschaft (DFG) grant
STO414/10-1 to T. Stoeck
A New Class of Nonsingular Exact Solutions for Laplacian Pattern Formation
We present a new class of exact solutions for the so-called {\it Laplacian
Growth Equation} describing the zero-surface-tension limit of a variety of 2D
pattern formation problems. Contrary to common belief, we prove that these
solutions are free of finite-time singularities (cusps) for quite general
initial conditions and may well describe real fingering instabilities. At long
times the interface consists of N separated moving Saffman-Taylor fingers, with
``stagnation points'' in between, in agreement with numerous observations. This
evolution resembles the N-soliton solution of classical integrable PDE's.Comment: LaTeX, uuencoded postscript file
Persistent fenestration may be a marker for physiologic intolerance after Fontan completion
BackgroundWe sought to evaluate the medium-term implications of fenestration status.MethodsBetween 1994 and 2012, 326 patients received an extracardiac Fontan (hospital mortality n = 6, 1.8%). A fenestration was routinely created (n = 306, 94%) unless there was technical difficulty. Three hundred patients discharged with an open fenestration were included. The primary end points were death and Fontan failure. Secondary outcomes were Fontan complications such as venovenous collaterals, protein-losing enteropathy, pacemaker requirement, and arrhythmias.ResultsThe fenestration was closed in 260 patients: 185 as a catheter intervention (62%) and 75 (25%) spontaneously. Forty patients (13%) had the fenestration open at a median follow-up period of 5.05 years. Of these patients, catheter-based closure failed in 10 (3%). There was no statistically significant difference in pre-Fontan hemodynamic parameters, such as pulmonary artery pressure and pulmonary vascular resistance between the patients with open fenestration and the ones with closed fenestration. Patients with an open fenestration had significantly more late deaths (P < .001), Fontan failure (P = .021), and Fontan complications (P = .011) compared with those with a closed fenestration. Multivariable Cox regression revealed open fenestration (P < .001) and indeterminate ventricular morphology (P = .002) as risk factors for death/Fontan failure, and ventricular dysfunction (P = .014) and open fenestration (P = .009) as risk factors for Fontan complications.ConclusionsPersistent fenestration was a marker for physiologic intolerance as noted by increased rates of mortality and a higher incidence of Fontan failure/complications. The specificity of pre-Fontan physiologic data for fenestration status may not have the fidelity needed for long-term care and thus, the consequences of decision making regarding fenestration status may not be determined until well after the operation
- …