4,141 research outputs found
Community development in rural communities
This report examines provides an overview of the economic conditions in northern New Hampshire, in 1987. (Library-derived description)Bloch, J. (1984). Community development in rural communities. Retrieved from http://academicarchive.snhu.eduMaster of Science (M.S.)School of Community Economic Developmen
Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector
The Phase-II upgrade of the ATLAS detector for the High Luminosity Large
Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector
with an all-silicon tracker consisting of pixel and strip detectors. The
current Phase-II detector layout requires the construction of 20,000 strip
detector modules consisting of sensor, circuit boards and readout chips, which
are connected mechanically using adhesives. The adhesive between readout chips
and circuit board is a silver epoxy glue as was used in the current ATLAS
SemiConductor Tracker (SCT). This glue has several disadvantages, which
motivated the search for an alternative.
This paper presents a study concerning the use of six ultra-violet (UV) cure
glues and a glue pad for use in the assembly of silicon strip detector modules
for the ATLAS upgrade. Trials were carried out to determine the ease of use,
the thermal conduction and shear strength, thermal cycling, radiation hardness,
corrosion resistance and shear strength tests. These investigations led to the
exclusion of three UV cure glues as well as the glue pad.
Three UV cure glues were found to be possible better alternatives. Results
from electrical tests of first prototype modules constructed using these glues
are presented.Comment: 23 pages, to be published in Journal of Instrumentatio
Comparative study of sequence-dependent hybridization kinetics in solution and on microspheres
Hybridization kinetics of DNA sequences with known secondary structures and random sequences designed with similar melting temperatures were studied in solution and when one strand was bound to 5 μm silica microspheres. The rates of hybridization followed second-order kinetics and were measured spectrophotometrically in solution and fluorometrically in the solid phase. In solution, the rate constants for the model sequences varied by almost two orders of magnitude, with a decrease in the rate constant with increasing amounts of secondary structure in the target sequence. The random sequences also showed over an order of magnitude difference in the rate constant. In contrast, the hybridization experiments in the solid phase with the same model sequences showed almost no change in the rate constant. Solid phase rate constants were approximately three orders of magnitude lower compared with the solution phase constants for sequences with little or no single-stranded structure. Sequences with a known secondary structure yielded solution phase rate constants as low as 3 × 10(3) M(−1) s(−1) with solid phase rate constants for the same sequences measured at 2.5 × 10(2) M(−1) s(−1). The results from these experiments indicate that (i) solid phase hybridization occurs three orders of magnitude slower than solution phase, (ii) trends observed in structure-dependent kinetics of solution phase hybridization may not be applicable to solid phase hybridization and (iii) model probes with known secondary structure decrease reaction rates; however, even random sequences with no known internal single-stranded structure can yield a broad range of reaction rates
Dispersive Elastodynamics of 1D Banded Materials and Structures: Design
Within periodic materials and structures, wave scattering and dispersion
occur across constituent material interfaces leading to a banded frequency
response. In an earlier paper, the elastodynamics of one-dimensional periodic
materials and finite structures comprising these materials were examined with
an emphasis on their frequency-dependent characteristics. In this work, a novel
design paradigm is presented whereby periodic unit cells are designed for
desired frequency band properties, and with appropriate scaling, these cells
are used as building blocks for forming fully periodic or partially periodic
structures with related dynamical characteristics. Through this multiscale
dispersive design methodology, which is hierarchical and integrated, structures
can be devised for effective vibration or shock isolation without needing to
employ dissipative damping mechanisms. The speed of energy propagation in a
designed structure can also be dictated through synthesis of the unit cells.
Case studies are presented to demonstrate the effectiveness of the methodology
for several applications. Results are given from sensitivity analyses that
indicate a high level of robustness to geometric variation.Comment: 33 text pages, 27 figure
Vlasov moments, integrable systems and singular solutions
The Vlasov equation for the collisionless evolution of the single-particle
probability distribution function (PDF) is a well-known Lie-Poisson Hamiltonian
system. Remarkably, the operation of taking the moments of the Vlasov PDF
preserves the Lie-Poisson structure. The individual particle motions correspond
to singular solutions of the Vlasov equation. The paper focuses on singular
solutions of the problem of geodesic motion of the Vlasov moments. These
singular solutions recover geodesic motion of the individual particles.Comment: 16 pages, no figures. Submitted to Phys. Lett.
Prompt Optical Observations of Gamma-ray Bursts
The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure
simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs).
A search for optical counterparts to six GRBs with localization errors of 1
square degree or better produced no detections. The earliest limiting
sensitivity is m(ROTSE) > 13.1 at 10.85 seconds (5 second exposure) after the
gamma-ray rise, and the best limit is m(ROTSE) > 16.0 at 62 minutes (897 second
exposure). These are the most stringent limits obtained for GRB optical
counterpart brightness in the first hour after the burst. Consideration of the
gamma-ray fluence and peak flux for these bursts and for GRB990123 indicates
that there is not a strong positive correlation between optical flux and
gamma-ray emission.Comment: 4 pages, 3 figures, submitted to ApJ Letter
The smooth Whitehead spectrum of a point at odd regular primes
Let p be an odd regular prime, and assume that the Lichtenbaum-Quillen
conjecture holds for K(Z[1/p]) at p. Then the p-primary homotopy type of the
smooth Whitehead spectrum Wh(*) is described. A suspended copy of the
cokernel-of-J spectrum splits off, and the torsion homotopy of the remainder
equals the torsion homotopy of the fiber of the restricted S^1-transfer map t:
SigmaCP^infty--> S. The homotopy groups of Wh(*) are determined in a range of
degrees, and the cohomology of Wh(*) is expressed as an A-module in all
degrees, up to an extension. These results have geometric topological
interpretations, in terms of spaces of concordances or diffeomorphisms of
highly connected, high dimensional compact smooth manifolds.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol7/paper4.abs.htm
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