5,239 research outputs found
A Primer to Relativistic MOND Theory
We first review the nonrelativistic lagrangian theory as a framework for the
MOND equation. Obstructions to a relativistic version of it are discussed
leading up to TeVeS, a relativistic tensor-vector-scalar field theory which
displays both MOND and Newtonian limits. The whys for its particular structure
are discussed and its achievements so far are summarized.Comment: 6 pages, LaTeX, 1 figure, to appear in proceedings of IAP05 in Paris:
Mass Profiles and Shapes of Cosmological Structures, G. Mamon, F. Combes, C.
Deffayet and B. Fort (eds), (EDP-Sciences 2005
Protecting cattle from horse flies (1996)
Horse flies (insect family Tabanidae) are probably the most severe fly pests of cattle on Missouri pasture and range. Only the females 'bite,' but the blood-feeding activities of these large, agile insects can constitute a serious threat to economical cattle performance when populations are large.New June 1996 -- Extension website
Design of a cold neutron source for the MIT reactor
Also issued as a Sc. D. thesis in the Dept. of Nuclear Engineering, MIT, 1970Includes bibliographical references (leaves 211-212
Ischemia and reperfusion injury in kidney transplantation : relevant mechanisms in injury and repair
Ischemia and reperfusion injury (IRI) is a complex pathophysiological phenomenon, inevitable in kidney transplantation and one of the most important mechanisms for non- or delayed function immediately after transplantation. Long term, it is associated with acute rejection and chronic graft dysfunction due to interstitial fibrosis and tubular atrophy. Recently, more insight has been gained in the underlying molecular pathways and signalling cascades involved, which opens the door to new therapeutic opportunities aiming to reduce IRI and improve graft survival. This review systemically discusses the specific molecular pathways involved in the pathophysiology of IRI and highlights new therapeutic strategies targeting these pathways
Association between benzodiazepine use and exacerbations and mortality in patients with asthma: a matched case-control and survival analysis using the United Kingdom Clinical Practice Research Datalink
Purpose: To investigate the association between the GABAergic drugs, benzodiazepines or zopiclone, and the occurrence of asthma exacerbations and subsequent mortality in a cohort of asthma patients.
Methods: 105,747 patients without asthma exacerbation and 25,895 patients with exacerbated asthma were included. A nested case-control study probed the association between benzodiazepines or zopiclone and occurrence of asthma exacerbation (primary outcome) using conditional logistic regression. Cox regression was used to determine the association between the drugs and all-cause mortality in patients with recorded asthma exacerbation. Adjusted matched odds ratios (adj mOR), and adjusted hazard ratios (adj HR) with 95% confidence intervals (CI) are presented.
Results: Current benzodiazepine use was associated with increased occurrence of asthma exacerbation (adj mOR 1.49; 1.15-1.93; P=0.001) as was current zopiclone use (adj mOR 1.59; 95% CI 1.37-1.85; P<0.001). In patients with an asthma exacerbation, current benzodiazepine use was associated with increased all-cause mortality during a median follow-up of 2 years (adj HR 2.78; 95% CI 1.26-6.12; P=0.011), and the association between zopiclone use and all-cause mortality showed borderline statistical significance (adj HR 1.58; 95% CI 0.98-2.54; P=0.058).
Conclusion: Benzodiazepines and zopiclone may increase the likelihood of asthma exacerbation and benzodiazepines may also increase the likelihood of mortality following exacerbation. These data suggest that caution should be exercised when prescribing benzodiazepines to patients with asthma
The onsite manufacture of propellant oxygen from lunar resources
The Aerojet carbothermal process for the manufacture of oxygen from lunar materials has three essential steps: the reduction of silicate with methane to form carbon monoxide and hydrogen; the reduction of carbon monoxide with hydrogen to form methane and water; and the electrolysis of water to form hydrogen and oxygen. The reactions and the overall process are shown. It is shown with laboratory experimentation that the carbothermal process is feasible. Natural silicates can be reduced with carbon or methane. The important products are carbon monoxide, metal, and slag. The carbon monoxide can be completely reduced to form methane and water. The water can be electrolyzed to produce hydrogen and oxygen. A preliminary engineering study shows that the operation of plants using this process for the manufacture of propellant oxygen has a large economic advantage when the cost of the plant and its operation is compared to the cost of delivering oxygen from Earth
Recommended from our members
Modeling information technology impacts in clerical work environments
The industrialization of white collar work via information technology (IT) is a key indicator of the emerging post-industrial economy (Hirschhorn, 1988). A conceptual model linking clerical work environments to effective IT impacts such as IT utilization, IT\u27s perceived ease of use and performance impact was developed and empirically tested. Underlying the model is the premise that clerical job structure is a facilitator of IT impacts (Weber, 1988). The results indicate that clerical job structure factors such as typing, composing or editing, and bookkeeping were significantly related to IT impacts in clerical work settings. A job holder\u27s IT competence and top management commitment to IT were also found to be significantly related to IT impacts in clerical work settings. Antecedent relationships among the IT impacts also contributed to understanding the IT impacts - for example, IT utilization affected perceived ease of use and perceived performance impact, and perceived ease of use affected perceived performance impact
Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars
We present Hubble ACS images of thirteen dust reddened Type-1 quasars
selected from the FIRST/2MASS Red Quasar Survey. These quasars have high
intrinsic luminosities after correction for dust obscuration (-23.5 > M_B >
-26.2 from K-magnitude). The images show strong evidence of recent or ongoing
interaction in eleven of the thirteen cases, even before the quasar nucleus is
subtracted. None of the host galaxies are well fit by a simple elliptical
profile. The fraction of quasars showing interaction is significantly higher
than the 30% seen in samples of host galaxies of normal, unobscured quasars.
There is a weak correlation between the amount of dust reddening and the
magnitude of interaction in the host galaxy, measured using the Gini
coefficient and the Concentration index. Although few host galaxy studies of
normal quasars are matched to ours in intrinsic quasar luminosity, no evidence
has been found for a strong dependence of merger activity on host luminosity in
samples of the host galaxies of normal quasars. We thus believe that the high
merger fraction in our sample is related to their obscured nature, with a
significant amount of reddening occurring in the host galaxy. The red quasar
phenomenon seems to have an evolutionary explanation, with the young quasar
spending the early part of its lifetime enshrouded in an interacting galaxy.
This might be further indication of a link between AGN and starburst galaxies.Comment: 18 pages, 6 low resolution figures, accepted for publication in Ap
Analysis of a distributed fiber-optic temperature sensor using single-photon detectors
We demonstrate a high-accuracy distributed fiber-optic temperature sensor using superconducting nanowire single-photon detectors and single-photon counting techniques. Our demonstration uses inexpensive single-mode fiber at standard telecommunications wavelengths as the sensing fiber, which enables extremely low-loss experiments and compatibility with existing fiber networks. We show that the uncertainty of the temperature measurement decreases with longer integration periods, but is ultimately limited by the calibration uncertainty. Temperature uncertainty on the order of 3 K is possible with spatial resolution of the order of 1 cm and integration period as small as 60 seconds. Also, we show that the measurement is subject to systematic uncertainties, such as polarization fading, which can be reduced with a polarization diversity receiver
- …
