824 research outputs found
Lunar subsurface architecture enhanced by artificial biosphere concepts
The integration of artificial biosphere technology with subselene architecture can create a life-enhancing, productive habitat that is safe from solar radiation and extreme temperature fluctuations while maximizing resources brought from Earth and derived from lunar regolith. In the short term, the resulting biotectural (biosphere and architectural) designs will not only make the structures more habitable, productive, and manageable, but will ultimately provide the self-sufficiency factors necessary for the mature lunar settlement. From a long-term perspective, this biotecture approach to astronautics and extraterrestrial development (1) helps reduce mass lift requirements, (2) contributes to habitat self-sufficiency, and (3) actualizes at least one philosophy of solar system exploration, which is to exploit nonterrestrial resources in an effort to conserve our natural resources on this planet
Formalism for testing theories of gravity using lensing by compact objects. III: Braneworld gravity
Braneworld gravity is a model that endows physical space with an extra
dimension. In the type II Randall-Sundrum braneworld gravity model, the extra
dimension modifies the spacetime geometry around black holes, and changes
predictions for the formation and survival of primordial black holes. We
develop a comprehensive analytical formalism for far-field black hole lensing
in this model, using invariant quantities to compute all geometric optics
lensing observables. We then make the first analysis of wave optics in
braneworld lensing, working in the semi-classical limit. We show that wave
optics offers the only realistic way to observe braneworld effects in black
hole lensing. We point out that if primordial braneworld black holes exist,
have mass M, and contribute a fraction f of the dark matter, then roughly 3e5 x
f (M/1e-18 Msun)^(-1) of them lie within our Solar System. These objects, which
we call "attolenses," would produce interference fringes in the energy spectra
of gamma-ray bursts at energies ~100 (M/1e-18 Msun)^(-1) MeV (which will soon
be accessible with the GLAST satellite). Primordial braneworld black holes
spread throughout the universe could produce similar interference effects; the
probability for "attolensing" may be non-negligible. If interference fringes
were observed, the fringe spacing would yield a simple upper limit on M.
Detection of a primordial black hole with M <~ 1e-19 Msun would challenge
general relativity and favor the braneworld model. Further work on lensing
tests of braneworld gravity must proceed into the physical optics regime, which
awaits a description of the full spacetime geometry around braneworld black
holes.Comment: 13 pages, 3 figures; accepted in PRD; expanded discussion of
prospects for observing attolensing with GLAS
Mesoscopic Effects in Quantum Phases of Ultracold Quantum Gases in Optical Lattices
We present a wide array of quantum measures on numerical solutions of 1D
Bose- and Fermi-Hubbard Hamiltonians for finite-size systems with open boundary
conditions. Finite size effects are highly relevant to ultracold quantum gases
in optical lattices, where an external trap creates smaller effective regions
in the form of the celebrated "wedding cake" structure and the local density
approximation is often not applicable. Specifically, for the Bose-Hubbard
Hamiltonian we calculate number, quantum depletion, local von-Neumann entropy,
generalized entanglement or Q-measure, fidelity, and fidelity susceptibility;
for the Fermi-Hubbard Hamiltonian we also calculate the pairing correlations,
magnetization, charge-density correlations, and antiferromagnetic structure
factor. Our numerical method is imaginary time propagation via time-evolving
block decimation. As part of our study we provide a careful comparison of
canonical vs. grand canonical ensembles and Gutzwiller vs. entangled
simulations. The most striking effect of finite size occurs for bosons: we
observe a strong blurring of the tips of the Mott lobes accompanied by higher
depletion, and show how the location of the first Mott lobe tip approaches the
thermodynamic value as a function of system size.Comment: 13 pages, 10 figure
Extracellular matrix signatures of human primary metastatic colon cancers and their metastases to liver
Background: Colorectal cancer is the third most frequently diagnosed cancer and the third cause of cancer deaths in the United States. Despite the fact that tumor cell-intrinsic mechanisms controlling colorectal carcinogenesis have been identified, novel prognostic and diagnostic tools as well as novel therapeutic strategies are still needed to monitor and target colon cancer progression. We and others have previously shown, using mouse models, that the extracellular matrix (ECM), a major component of the tumor microenvironment, is an important contributor to tumor progression. In order to identify candidate biomarkers, we sought to define ECM signatures of metastatic colorectal cancers and their metastases to the liver. Methods: We have used enrichment of extracellular matrix (ECM) from human patient samples and proteomics to define the ECM composition of primary colon carcinomas and their metastases to liver in comparison with normal colon and liver samples. Results: We show that robust signatures of ECM proteins characteristic of each tissue, normal and malignant, can be defined using relatively small samples from small numbers of patients. Comparisons with gene expression data from larger cohorts of patients confirm the association of subsets of the proteins identified by proteomic analysis with tumor progression and metastasis. Conclusions: The ECM protein signatures of metastatic primary colon carcinomas and metastases to liver defined in this study, offer promise for development of diagnostic and prognostic signatures of metastatic potential of colon tumors. The ECM proteins defined here represent candidate serological or tissue biomarkers and potential targets for imaging of occult metastases and residual or recurrent tumors and conceivably for therapies. Furthermore, the methods described here can be applied to other tumor types and can be used to investigate other questions such as the role of ECM in resistance to therapy
What have we already learned from the CMB?
The COBE satellite, and the DMR experiment in particular, was extraordinarily
successful. However, the DMR results were announced about 7 years ago, during
which time a great deal more has been learned about anisotropies in the Cosmic
Microwave Background (CMB). The CMB experiments currently being designed and
built, including long-duration balloons, interferometers, and two space
missions, promise to address several fundamental cosmological issues. We
present our evaluation of what we already know, what we are beginning to learn
now, and what the future may bring.Comment: 20 pages, 3 figures. Changes to match version accepted by PAS
Stationary solutions of the one-dimensional nonlinear Schroedinger equation: II. Case of attractive nonlinearity
All stationary solutions to the one-dimensional nonlinear Schroedinger
equation under box or periodic boundary conditions are presented in analytic
form for the case of attractive nonlinearity. A companion paper has treated the
repulsive case. Our solutions take the form of bounded, quantized, stationary
trains of bright solitons. Among them are two uniquely nonlinear classes of
nodeless solutions, whose properties and physical meaning are discussed in
detail. The full set of symmetry-breaking stationary states are described by
the character tables from the theory of point groups. We make
experimental predictions for the Bose-Einstein condensate and show that, though
these are the analog of some of the simplest problems in linear quantum
mechanics, nonlinearity introduces new and surprising phenomena.Comment: 11 pages, 9 figures -- revised versio
Reconciling Trends in U.S. Male Earnings Volatility: Results from Survey and Administrative Data
There is a large literature on earnings and income volatility in labor economics, household finance, and macroeconomics. One strand of that literature has studied whether individual earnings volatility has risen or fallen in the U.S. over the last several decades. There are strong disagreements in the empirical literature on this important question, with some studies showing upward trends, some showing downward trends, and some showing no trends. Some studies have suggested that the differences are the result of using flawed survey data instead of more accurate administrative data. This paper summarizes the results of a project attempting to reconcile these findings with four different data sets and six different data series--three survey and three administrative data series, including two which match survey respondent data to their administrative data. Using common specifications, measures of volatility, and other treatments of the data, four of the six data series show a lack of any significant long-term trend in male earnings volatility over the last 20-to-30+ years when differences across the data sets are properly accounted for. A fifth data series (the PSID) shows a positive net trend but small in magnitude. A sixth, administrative, data set, available only since 1998, shows no net trend 1998-2011 and only a small decline thereafter. Many of the remaining differences across data series can be explained by differences in their cross-sectional distribution of earnings, particularly differences in the size of the lower tail. We conclude that the data sets we have analyzed, which include many of the most important available, show little evidence of any significant trend in male earnings volatility since the mid-1980s
Report of the Committee on Resolutions- Declaration
Pamphlet concerning a declaration made by the National Educational Association at the forty-third annual convention
Recommended from our members
The systemic pathology of cerebral malaria in African children
Pediatric cerebral malaria carries a high mortality rate in sub-Saharan Africa. We present our systematic analysis of the descriptive and quantitative histopathology of all organs sampled from a series of 103 autopsies performed between 1996 and 2010 in Blantyre, Malawi on pediatric cerebral malaria patients and control patients (without coma, or without malaria infection) who were clinically well characterized prior to death. We found brain swelling in all cerebral malaria patients and the majority of controls. The histopathology in patients with sequestration of parasites in the brain demonstrated two patterns: (a) the “classic” appearance (i.e., ring hemorrhages, dense sequestration, and extra-erythrocytic pigment) which was associated with evidence of systemic activation of coagulation and (b) the “sequestration only” appearance associated with shorter duration of illness and higher total burden of parasites in all organs including the spleen. Sequestration of parasites was most intense in the gastrointestinal tract in all parasitemic patients (those with cerebral malarial and those without)
Platelet Accumulation in Brain Microvessels in Fatal Pediatric Cerebral Malaria
The pathogenesis of fatal cerebral malaria (CM) is not well understood, in part because data from patients in whom a clinical diagnosis was established prior to death are rare. In a murine CM model, platelets accumulate in brain microvasculature, and antiplatelet therapy can improve outcome. We determined whether platelets are also found in cerebral vessels in human CM, and we performed immunohistopathology for platelet-specific glycoprotein, GPIIb-IIIa, on tissue from multiple brain sites in Malawian children whose fatal illness was severe malarial anemia, CM, or nonmalarial encephalopathy. Platelets were observed in 3 locations within microvessels: between malaria pigment and leukocytes, associated with malaria pigment, or alone. The mean surface area of platelet staining and the proportion of vessels showing platelet accumulation were significantly higher in patients with CM than in those without it. Platelet accumulation occurs in the microvasculature of patients with CM and may play a role in the pathogenesis of the diseas
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