990 research outputs found
The Performance of Natural Ventilation In A Dance Studio – Lessons From Tracer Gas Measurements And Control Integration
The naturally ventilated, three storey School of Arts Jarman Building provides two dance studios, an exhibition gallery, teaching rooms, video editing suites and offices. The main dance studio is double-height, has underfloor heating and accommodates sixty people. Fresh air enters from low level perimeter louvres and exits at high level through a stack that rises through the third storey to a stack terminal with motorized louvres. Tracer gas (CO2) measurements were used to measure the ventilation rate in conjunction with hot-wire anemometry in the stack tower. The results showed that when all air inlet and exit louvres were set to closed, the residual air flow up the stack was 0.33m3/s representing a potential heat loss of 9kW in winter at 0°C outside. When the louvres were all open, the air flow increased to between 0.49 and 0.62m3/s, a level consistent with the studio’s design occupancy. It was found that the studio’s 4m high perimeter curtains represent a barrier to fresh air entering the main room space and cause the incoming air to migrate upwards towards the stack exit and effectively bypass the central part of the studio. Tracer gas decay rates showed that the main space experienced an air exchange rate 50% less than that for the overall studio. An investigation of the controls also revealed that the underfloor heating system operated independently of the control of the stack ventilation system, leading to simultaneous heating and venting. The research shows the vital importance of prescribing contractually that key controls are integrated, that fresh air dampers are well-sealed when closed, and the importance of designing a fresh air supply that matches the way a space is used
Optimal Moments for the Analysis of Peculiar Velocity Surveys
We present a new method for the analysis of peculiar velocity surveys which
removes contributions to velocities from small scale, nonlinear velocity modes
while retaining information about large scale motions. Our method utilizes
Karhunen--Lo\`eve methods of data compression to construct a set of moments out
of the velocities which are minimally sensitive to small scale power. The set
of moments are then used in a likelihood analysis. We develop criteria for the
selection of moments, as well as a statistic to quantify the overall
sensitivity of a set of moments to small scale power. Although we discuss our
method in the context of peculiar velocity surveys, it may also prove useful in
other situations where data filtering is required.Comment: 25 Pages, 3 figures. Submitted to Ap
Sealing Glasses for Titanium and Titanium Alloys
Glass compositions containing calcium oxide, alumina, boric oxide, strontium oxide and barium oxide in various mole % combinations were studied. These compositions are capable of forming stable glass to metal seals with titanium and titanium alloys for use as seals for battery headers
Bulk Flow and Shear Moments of the SFI++ Survey
We find the nine bulk--flow and shear moments from the SFI++ survey, as well
as for subsamples of group and field galaxies. We constrain the velocity power
spectrum shape parameter in linear theory using these moments. A
likelihood function for was found after marginalizing over the power
spectrum amplitude using constraints obtained from
comparisons between redshift surveys and peculiar velocity data. We have
estimated the velocity noise from the data since without it our
results may be biased. We also performed a statistical analysis of the
difference between the field and group catalogues and found that the results
from each reflect the same underlying large scale flows. We found that we can
constrain the power spectrum shape parameter to be
for the groups catalogue and
for the field galaxy catalogue in fair agreement
with the value from WMAP
Compact High Current Rare-Earth Emitter Hollow Cathode for Hall Effect Thrusters
An apparatus and method for achieving an efficient central cathode in a Hall effect thruster is disclosed. A hollow insert disposed inside the end of a hollow conductive cathode comprises a rare-earth element and energized to emit electrons from an inner surface. The cathode employs an end opening having an area at least as large as the internal cross sectional area of the rare earth insert to enhance throughput from the cathode end. In addition, the cathode employs a high aspect ratio geometry based on the cathode length to width which mitigates heat transfer from the end. A gas flow through the cathode and insert may be impinged by the emitted electrons to yield a plasma. One or more optional auxiliary gas feeds may also be employed between the cathode and keeper wall and external to the keeper near the outlet
A New Approach to Probing Large Scale Power with Peculiar Velocities
We propose a new strategy to probe the power spectrum on large scales using
galaxy peculiar velocities. We explore the properties of surveys that cover
only two small fields in opposing directions on the sky. Surveys of this type
have several advantages over those that attempt to cover the entire sky; in
particular, by concentrating galaxies in narrow cones these surveys are able to
achieve the density needed to measure several moments of the velocity field
with only a modest number of objects, even for surveys designed to probe scales
\gtwid 100\hmpc. We construct mock surveys with this geometry and analyze
them in terms of the three moments to which they are most sensitive. We
calculate window functions for these moments and construct a statistic
which can be used to put constraints on the power spectrum. In order to explore
the sensitivity of these surveys, we calculate the expectation values of the
moments and their associated measurement noise as a function of the survey
parameters such as density and depth and for several popular models of
structure formation. In addition, we have studied how well these kind of
surveys can distinguish between different power spectra and found that, for the
same number of objects, cone surveys are as good or better than full-sky
surveys in distinguishing between popular cosmological models. We find that a
survey with galaxy peculiar velocities with distance errors of 15% in
two cones with opening angle of could put significant
constraints on the power spectrum on scales of \hmpc, where few other
constraints exist.Comment: 15 pages, 3 figures, Some revisions and different figure. Accepted
for publication at ApJ letter
Hubble flow variance and the cosmic rest frame
We characterize the radial and angular variance of the Hubble flow in the
COMPOSITE sample of 4534 galaxies, on scales in which much of the flow is in
the nonlinear regime. With no cosmological assumptions other than the existence
of a suitably averaged linear Hubble law, we find with decisive Bayesian
evidence (ln B >> 5) that the Hubble constant averaged in independent spherical
radial shells is closer to its asymptotic value when referred to the rest frame
of the Local Group, rather than the standard rest frame of the Cosmic Microwave
Background. An exception occurs for radial shells in the range 40/h-60/h Mpc.
Angular averages reveal a dipole structure in the Hubble flow, whose amplitude
changes markedly over the range 32/h-62/h Mpc. Whereas the LG frame dipole is
initially constant and then decreases significantly, the CMB frame dipole
initially decreases but then increases. The map of angular Hubble flow
variation in the LG rest frame is found to coincide with that of the residual
CMB temperature dipole, with correlation coefficient -0.92. These results are
difficult to reconcile with the standard kinematic interpretation of the motion
of the Local Group in response to the clustering dipole, but are consistent
with a foreground non-kinematic anisotropy in the distance-redshift relation of
0.5% on scales up to 65/h Mpc. Effectively, the differential expansion of space
produced by nearby nonlinear structures of local voids and denser walls and
filaments cannot be reduced to a local boost. This hypothesis suggests a
reinterpretation of bulk flows, which may potentially impact on calibration of
supernovae distances, anomalies associated with large angles in the CMB
anisotropy spectrum, and the dark flow inferred from the kinematic
Sunyaev-Zel'dovich effect. It is consistent with recent studies that find
evidence for a non-kinematic dipole in the distribution of distant radio
sources.Comment: 37 pages, 9 tables, 13 figures; v2 adds extensive new analysis
(including additional subsections, tables, figures); v3 adds a Monte Carlo
analysis (with additional table, figure) which further tightens the
statistical robustness of the dipole results; v4 adds further clarifications,
small corrections, references and discussion of Planck satellite results; v5
typos fixed, matches published versio
Current trends in the treatment of pneumonia due to multidrug-resistant Gram-negative bacteria [version 1; referees: 2 approved]
Pneumonia is one of the most common infections worldwide. Morbidity, mortality, and healthcare costs increase substantially when pneumonia is caused by multidrug-resistant Gram-negative bacteria (MDR-GNB). The ongoing spread of antimicrobial resistance has made treating MDR-GNB pneumonia increasingly difficult. Fortunately, there have been some recent additions to our antibiotic armamentarium in the US and Europe for MDR-GNB, along with several agents that are in advanced stages of development. In this article, we review the risk factors for and current management of MDR-GNB pneumonia as well as novel agents with activity against these important and challenging pathogens
Current trends in the treatment of pneumonia due to multidrug-resistant Gram-negative bacteria [version 2; referees: 2 approved]
Pneumonia is one of the most common infections worldwide. Morbidity, mortality, and healthcare costs increase substantially when pneumonia is caused by multidrug-resistant Gram-negative bacteria (MDR-GNB). The ongoing spread of antimicrobial resistance has made treating MDR-GNB pneumonia increasingly difficult. Fortunately, there have been some recent additions to our antibiotic armamentarium in the US and Europe for MDR-GNB, along with several agents that are in advanced stages of development. In this article, we review the risk factors for and current management of MDR-GNB pneumonia as well as novel agents with activity against these important and challenging pathogens
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