1,505 research outputs found
Euclidean TSP with few inner points in linear space
Given a set of points in the Euclidean plane, such that just points
are strictly inside the convex hull of the whole set, we want to find the
shortest tour visiting every point. The fastest known algorithm for the version
when is significantly smaller than , i.e., when there are just few inner
points, works in time [Knauer and Spillner,
WG 2006], but also requires space of order . The best
linear space algorithm takes time [Deineko, Hoffmann, Okamoto,
Woeginer, Oper. Res. Lett. 34(1), 106-110]. We construct a linear space
time algorithm. The new insight is extending the
known divide-and-conquer method based on planar separators with a
matching-based argument to shrink the instance in every recursive call. This
argument also shows that the problem admits a quadratic bikernel.Comment: under submissio
Calcitonin receptor-like receptor is expressed on gastrointestinal immune cells
Background/Aims: Pharmacological and morphological studies suggest that the gut mucosal immune system and local neuropeptide-containing neurones interact. We aimed to determine whether gut immune cells are targets for calcitonin gene-related peptide (CGRP), which has potent immune regulatory properties. Methods: Using density gradient centrifugation, rat lamina propria mononuclear cells (LP-MNCs) and intra-epithelial lymphocytes (IELs) were isolated. RT-PCR was employed for the detection of mRNA of rat calcitonin receptor-like receptor (CRLR), which is considered to represent the pharmacologically defined CGRP receptor-1 subtype, as well as mRNA of the receptor activity-modifying proteins, which are essential for CRLR function and determine ligand specificity. A radioreceptor assay was employed for the detection of specific CGRP binding sites. Results: RT-PCR and DNA sequencing showed that LP-MNCs and IELs express CRLR. Incubation of isolated LP-MNCs with radiolabelled alphaCGRP revealed the existence of specific binding sites for CGRP. Conclusion: These novel data indicate that mucosal immune cells of the rat gut are a target for CGRP and provide significant evidence that CGRP functions as an immune regulator in the gut mucosa. Copyright (C) 2002 S. Karger AG, Basel
Discharge chamber studies for mercury bombardment ion thrusters
Discharge chamber performance optimization for mercury bombardment ion thruster
High voltage solar array study Final report
High voltage solar array stud
Competition between Blue Collar Latinos and Blacks in Growing and Declining Industries in North Carolina
Blue collar immigrant Latinos have increasingly gained employment within North Carolina's growing meatpacking industry and declining textile industry from 1980 to 2000. This paper uses three decades of Census data to provide a theoretically descriptive discussion about trends and patterns that have emerged within these industries. Results indicate that in meatpacking, Latinos are being crowded into low wage ghettos, despite cases where they are substituting for exiting white workers or where they have been queued upward into better paying jobs. In textiles, Latinos gained employment because they are inexpensive labor or because they are substituting for whites and slowing growth among blacks. Within narrow occupational categories, interpretations of growing Latino presence were consistent from macro to micro levels while in other cases crowding in meatpacking and wage discrimination in textiles were not foreshadowed. Overall, Latinos appear to be affecting employment rates of whites more than blacks in both industries
A Laboratory Investigation of Supersonic Clumpy Flows: Experimental Design and Theoretical Analysis
We present a design for high energy density laboratory experiments studying
the interaction of hypersonic shocks with a large number of inhomogeneities.
These ``clumpy'' flows are relevant to a wide variety of astrophysical
environments including the evolution of molecular clouds, outflows from young
stars, Planetary Nebulae and Active Galactic Nuclei. The experiment consists of
a strong shock (driven by a pulsed power machine or a high intensity laser)
impinging on a region of randomly placed plastic rods. We discuss the goals of
the specific design and how they are met by specific choices of target
components. An adaptive mesh refinement hydrodynamic code is used to analyze
the design and establish a predictive baseline for the experiments. The
simulations confirm the effectiveness of the design in terms of articulating
the differences between shocks propagating through smooth and clumpy
environments. In particular, we find significant differences between the shock
propagation speeds in a clumpy medium compared to a smooth one with the same
average density. The simulation results are of general interest for foams in
both inertial confinement fusion and laboratory astrophysics studies. Our
results highlight the danger of using average properties of inhomogeneous
astrophysical environments when comparing timescales for critical processes
such as shock crossing and gravitational collapse times.Comment: 7 pages, 6 figures. Submitted to the Astrophysical Journal. For
additional information, including simulation animations and the pdf and ps
files of the paper with embedded high-quality images, see
http://pas.rochester.edu/~wm
Spatial clustering of defect luminescence centers in Si-doped low resistivity Al0.82Ga0.18N
A series of Si-doped AlN-rich AlGaN layers with low resistivities was characterized by a combination of nanoscale imaging techniques. Utilizing the capability of scanning electron microscopy to reliably investigate the same sample area with different techniques, it was possible to determine the effect of doping concentration, defect distribution, and morphology on the luminescence properties of these layers. Cathodoluminescence shows that the dominant defect luminescence depends on the Si-doping concentration. For lower doped samples, the most intense peak was centered between 3.36 eV and 3.39 eV, while an additional, stronger peak appears at 3 eV for the highest doped sample. These peaks were attributed to the (VIII-ON)2− complex and the V3−III vacancy, respectively. Multimode imaging using cathodoluminescence, secondary electrons, electron channeling contrast, and atomic force microscopy demonstrates that the luminescence intensity of these peaks is not homogeneously distributed but shows a strong dependence on the topography and on the distribution of screw dislocations.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeBMBF, 13N12587, Photonische Plattformtechnologie zur ultrasensitiven und hochspezifischen biochemischen Sensorik auf Basis neuartiger UV-LEDs (UltraSens
- …