1,501 research outputs found
SSME lifetime prediction and verification, integrating environments, structures, materials: The challenge
The planned missions for the space shuttle dictated a unique and technology-extending rocket engine. The high specific impulse requirements in conjunction with a 55-mission lifetime, plus volume and weight constraints, produced unique structural design, manufacturing, and verification requirements. Operations from Earth to orbit produce severe dynamic environments, which couple with the extreme pressure and thermal environments associated with the high performance, creating large low cycle loads and high alternating stresses above endurance limit which result in high sensitivity to alternating stresses. Combining all of these effects resulted in the requirements for exotic materials, which are more susceptible to manufacturing problems, and the use of an all-welded structure. The challenge of integrating environments, dynamics, structures, and materials into a verified SSME structure is discussed. The verification program and developmental flight results are included. The first six shuttle flights had engine performance as predicted with no failures. The engine system has met the basic design challenges
Numerical convergence of the block-maxima approach to the Generalized Extreme Value distribution
In this paper we perform an analytical and numerical study of Extreme Value
distributions in discrete dynamical systems. In this setting, recent works have
shown how to get a statistics of extremes in agreement with the classical
Extreme Value Theory. We pursue these investigations by giving analytical
expressions of Extreme Value distribution parameters for maps that have an
absolutely continuous invariant measure. We compare these analytical results
with numerical experiments in which we study the convergence to limiting
distributions using the so called block-maxima approach, pointing out in which
cases we obtain robust estimation of parameters. In regular maps for which
mixing properties do not hold, we show that the fitting procedure to the
classical Extreme Value Distribution fails, as expected. However, we obtain an
empirical distribution that can be explained starting from a different
observable function for which Nicolis et al. [2006] have found analytical
results.Comment: 34 pages, 7 figures; Journal of Statistical Physics 201
Magnet Laboratory Research
Contains reports on five research projects.United States Atomic Energy Commission (Contract AT(30-1)-1283
The Majorana experiment: an ultra-low background search for neutrinoless double-beta decay
The observation of neutrinoless double-beta decay would resolve the Majorana
nature of the neutrino and could provide information on the absolute scale of
the neutrino mass. The initial phase of the Majorana experiment, known as the
Demonstrator, will house 40 kg of Ge in an ultra-low background shielded
environment at the 4850' level of the Sanford Underground Laboratory in Lead,
SD. The objective of the Demonstrator is to determine whether a future 1-tonne
experiment can achieve a background goal of one count per tonne-year in a
narrow region of interest around the 76Ge neutrinoless double-beta decay peak.Comment: Presentation for the Rutherford Centennial Conference on Nuclear
Physic
The MAJORANA DEMONSTRATOR: A Search for Neutrinoless Double-beta Decay of Germanium-76
The observation of neutrinoless double-beta decay would determine whether the
neutrino is a Majorana particle and provide information on the absolute scale
of neutrino mass. The MAJORANA Collaboration is constructing the DEMONSTRATOR,
an array of germanium detectors, to search for neutrinoless double-beta decay
of 76-Ge. The DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be
enriched to 86% in 76-Ge. The DEMONSTRATOR will be deployed deep underground in
an ultra-low-background shielded environment. Operation of the DEMONSTRATOR
aims to determine whether a future tonne-scale germanium experiment can achieve
a background goal of one count per tonne-year in a 4-keV region of interest
around the 76-Ge neutrinoless double-beta decay Q-value of 2039 keV.Comment: Submitted to AIP Conference Proceedings, 19th Particles & Nuclei
International Conference (PANIC 2011), Massachusetts Institute of Technology,
Cambridge, MA, USA, July 24-29, 2011; 3 pages, 1 figur
Galaxy Populations and Evolution in Clusters III. The Origin of Low-Mass Galaxies in Clusters: Constraints from Stellar Populations
Low-mass galaxies in nearby clusters are the most numerous galaxy type in the
universe, yet their origin and properties remain largely unknown. To study
basic questions concerning these galaxies we present the results of a survey
designed to constrain the characteristics and properties of the stellar
populations in a magnitude complete sample of low-mass cluster galaxies (LMCGs)
in the center of the Perseus cluster. Using deep, high-quality WIYN UBR images,
we demonstrate that the 53 LMCGs in our sample have a significant scatter about
the color-magnitude relationship at M_B > -15. By comparing single-burst
stellar population models to our photometry, we argue that stellar populations
in LMCGs all have ages > 1 Gyrs, with redder LMCGs having stellar metallicities
[Fe/H] > -0.5. By assuming that the colors of LMCGs reflect metallicity, and
have co-evolved with the giant ellipticals, we find a wide range of values,
from solar to [Fe/H] ~ -3. We argue from this that LMCGs have multiple origins,
and fundamentally differ from Local Group dwarf spheroidals/ellipticals. The
inferred lower metallicities of the bluer LMCGs implies that these are possibly
primordial galaxies formed through self enrichment and stellar feedback
provided by winds from supernova. We also investigate several other formation
scenarios for these LMCGS, including: self enrichment induced by the
confinement of metals in halos by the intracluster medium, in situ formation
out of intracluster gas, systems with extreme dark halos, and as remnants of
higher mass systems. We conclude that roughly half of all low-mass cluster
galaxies have stellar populations and kinematic properties, discussed in
previous papers in this series, consistent with being the remnants of stripped
galaxies accreted into clusters a few Gyrs ago.Comment: Accepted to the Astronomical Journal, 35 pages. For full resolution
images of the cluster LMCGs and other figures, please download the version at
http://www.astro.caltech.edu/~cc/gpec3.p
14th Annual Conference on Legal Issues For Financial Institutions
Materials from the 14th Annual Conference on Legal Issues For Financial Institutions held by UK/CLE in March 1994
Metaplastic ossification in the cartilage of the bronchus of a patient with chronic multi-drug resistant tuberculosis: a case report
<p>Abstract</p> <p>Introduction</p> <p>Pulmonary ossification has been rarely observed in pulmonary fibrosis and in some chronic respiratory diseases such as chronic obstructive pulmonary disease. We report here a metaplastic ossification in the bronchial cartilage of a patient with multi-drug resistant tuberculosis.</p> <p>Case presentation</p> <p>We report the case of a 41-year-old Asian man from Korea with chronic multi-drug resistant tuberculosis with a rare focus of bone formation from the cartilage of a bronchus subtending an active cavity. The patient had a large multi-lobed, thick-walled cavitary tuberculosis lesion in his left upper lobe. Severe infiltration of his lymphocytes and epithelioid cells, along with some giant cells and neutrophils, was observed in the patient's bronchial wall. Desquamated bronchial epithelium and acid-fast bacilli were found inside his bronchus. A small focus of bony metaplasia was found in the cartilage of his bronchial wall. Histopathological examination confirmed calcification and showed hematopoietic cells forming in his marrow cavity.</p> <p>Conclusions</p> <p>Chronic inflammation in the lungs of our patient, caused by underlying tuberculosis, probably played a role in the development of osseous metaplasia from the associated cartilage of the bronchial wall.</p
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