6,992 research outputs found
Use of the MATRIXx Integrated Toolkit on the Microwave Anisotropy Probe Attitude Control System
Recent advances in analytical software tools allow the analysis, simulation, flight code, and documentation of an algorithm to be generated from a single source, all within one integrated analytical design package. NASA's Microwave Anisotropy Probe project has used one such package, Integrated Systems' MATRIXx suite, in the design of the spacecraft's Attitude Control System. The project's experience with the linear analysis, simulation, code generation, and documentation tools will be presented and compared with more traditional development tools. In particular, the quality of the flight software generated will be examined in detail. Finally, lessons learned on each of the tools will be shared
Membrane amplitude and triaxial stress in twisted bilayer graphene deciphered using first-principles directed elasticity theory and scanning tunneling microscopy
Twisted graphene layers produce a moir\'e pattern (MP) structure with a
predetermined wavelength for given twist angle. However, predicting the
membrane corrugation amplitude for any angle other than pure AB-stacked or
AA-stacked graphene is impossible using first-principles density functional
theory (DFT) due to the large supercell. Here, within elasticity theory we
define the MP structure as the minimum energy configuration, thereby leaving
the height amplitude as the only unknown parameter. The latter is determined
from DFT calculations for AB and AA stacked bilayer graphene in order to
eliminate all fitting parameters. Excellent agreement with scanning tunneling
microscopy (STM) results across multiple substrates is reported as function of
twist angle.Comment: to appear in Phys. Rev.
Gauging N=2 Supersymmetric Non-Linear -Models in the Atiyah-Ward Space-Time
We build up a class of N=2 supersymmetric non-linear -models in an
N=1 superspace based on the Atiyah-Ward space-time of (2+2)-signature metric.
We also discuss the gauging of isometries of the associated hyper-K\"ahlerian
target spaces and present the resulting gauge-covariant supersymmetric action
functional.Comment: 12 pages, latex, no figure
Circulating microRNAs are associated with Paroxysmal or Persistent Atrial Fibrillation
Introduction: Novel methods of identifying individuals at risk for atrial fibrillation (AF) are needed. MicroRNAs (MiRNAs) regulate gene expression in a number of cardiovascular diseases, including AF. It is unknown, however, if key circulating, cardiac-specific miRNAs differ between individuals with paroxysmal or persistent AF and those in sinus rhythm.
Methods: 17 individuals with a history of AF were recruited prior to catheter ablation. 24 hospitalized patients in normal sinus rhythm and no history of AF comprised the control group. 94 plasma miRNAs were selected based on a priori associations with processes implicated in AF for evaluation using the TaqMan miRNA expression profiling system.
Results:We found that miRNA expression differed by at least 2-fold for 14 miRNAs, including several previously implicated in cardiovascular remodeling and disease (Figure 1). Levels of miR-7, miR-208, and miR-302b were statistically significantly up- or down-regulated in AF patients relative to controls (p
Application: Although power was limited by the modest sample size, these data support the rationale for using circulating miRNA as AF biomarkers. Moreover, since miRNA can modulate disease pathways, miRNA-based therapeutics would theoretically enable targeting of novel gene regulatory pathways implicated in AF in a unique and powerful manner.
Next Steps/ Future: Further investigations involving well-characterized, large samples from longitudinal studies with standardized miRNA assessment and evaluation for AF are required to validate the observed associations
Space-Time Supersymmetry of Extended Fermionic Strings in Dimensions
The fermionic string theory is revisited in light of its recently
proposed equivalence to the non-compact fermionic string model. The
issues of space-time Lorentz covariance and supersymmetry for the BRST
quantized strings living in uncompactified dimensions are
discussed. The equivalent local quantum supersymmetric field theory appears to
be the most transparent way to represent the space-time symmetries of the
extended fermionic strings and their interactions. Our considerations support
the Siegel's ideas about the presence of Lorentz symmetry as well as
at least one self-dual space-time supersymmetry in the theory of the
fermionic strings, though we do not have a compelling reason to argue about the
necessity of the {\it maximal} space-time supersymmetry. The world-sheet
arguments about the absence of all string massive modes in the physical
spectrum, and the vanishing of all string-loop amplitudes in the Polyakov
approach, are given on the basis of general consistency of the theory.Comment: 29 pages, LaTeX, ITP-UH-1/9
Regulation of neutrophil senescence by microRNAs
Neutrophils are rapidly recruited to sites of tissue injury or infection, where they protect against invading pathogens. Neutrophil functions are limited by a process of neutrophil senescence, which renders the cells unable to respond to chemoattractants, carry out respiratory burst, or degranulate. In parallel, aged neutrophils also undergo spontaneous apoptosis, which can be delayed by factors such as GMCSF. This is then followed by their subsequent removal by phagocytic cells such as macrophages, thereby preventing unwanted inflammation and tissue damage. Neutrophils translate mRNA to make new proteins that are important in maintaining functional longevity. We therefore hypothesised that neutrophil functions and lifespan might be regulated by microRNAs expressed within human neutrophils. Total RNA from highly purified neutrophils was prepared and subjected to microarray analysis using the Agilent human miRNA microarray V3. We found human neutrophils expressed a selected repertoire of 148 microRNAs and that 6 of these were significantly upregulated after a period of 4 hours in culture, at a time when the contribution of apoptosis is negligible. A list of predicted targets for these 6 microRNAs was generated from http://mirecords.biolead.org and compared to mRNA species downregulated over time, revealing 83 genes targeted by at least 2 out of the 6 regulated microRNAs. Pathway analysis of genes containing binding sites for these microRNAs identified the following pathways: chemokine and cytokine signalling, Ras pathway, and regulation of the actin cytoskeleton. Our data suggest that microRNAs may play a role in the regulation of neutrophil senescence and further suggest that manipulation of microRNAs might represent an area of future therapeutic interest for the treatment of inflammatory disease
Super Multi-Instantons in Conformal Chiral Superspace
We reformulate self-dual supersymmetric theories directly in conformal chiral
superspace, where superconformal invariance is manifest. The superspace can be
interpreted as the generalization of the usual Atiyah-Drinfel'd-Hitchin-Manin
twistors (the quaternionic projective line), the real projective light-cone in
six dimensions, or harmonic superspace, but can be reduced immediately to
four-dimensional chiral superspace. As an example, we give the 't Hooft and
ADHM multi-instanton constructions for self-dual super Yang-Mills theory. In
both cases, all the parameters are represented as a single, irreducible,
constant tensor.Comment: 21 pg., uuencoded compressed postscript file (twist.ps.Z.uu), other
formats (.dvi, .ps, .ps.Z, 8-bit .tex) available at
http://insti.physics.sunysb.edu/~siegel/preprints or at
ftp://max.physics.sunysb.edu/preprints/siege
Patterns of analgesic use, pain and self-efficacy: a cross-sectional study of patients attending a hospital rheumatology clinic
Background: Many people attending rheumatology clinics use analgesics and non-steroidal anti-inflammatories for persistent musculoskeletal pain. Guidelines for pain management recommend regular and pre-emptive use of analgesics to reduce the impact of pain. Clinical experience indicates that analgesics are often not used in this way. Studies exploring use of analgesics in arthritis have historically measured adherence to such medication. Here we examine patterns of analgesic use and their relationships to pain, self-efficacy and demographic factors.
Methods: Consecutive patients were approached in a hospital rheumatology out-patient clinic. Pattern of analgesic use was assessed by response to statements such as 'I always take my tablets every day.' Pain and self-efficacy (SE) were measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Arthritis Self-Efficacy Scale (ASES). Influence of factors on pain level and regularity of analgesic use were investigated using linear regression. Differences in pain between those agreeing and disagreeing with statements regarding analgesic use were assessed using t-tests.
Results: 218 patients (85% of attendees) completed the study. Six (2.8%) patients reported no current pain, 26 (12.3%) slight, 100 (47.4%) moderate, 62 (29.4%) severe and 17 (8.1%) extreme pain. In multiple linear regression self efficacy and regularity of analgesic use were significant (p < 0.01) with lower self efficacy and more regular use of analgesics associated with more pain.
Low SE was associated with greater pain: 40 (41.7%) people with low SE reported severe pain versus 22 (18.3%) people with high SE, p < 0.001. Patients in greater pain were significantly more likely to take analgesics regularly; 13 (77%) of those in extreme pain reported always taking their analgesics every day, versus 9 (35%) in slight pain. Many patients, including 46% of those in severe pain, adjusted analgesic use to current pain level. In simple linear regression, pain was the only variable significantly associated with regularity of analgesic use: higher levels of pain corresponded to more regular analgesic use (p = 0.003).
Conclusion: Our study confirms that there is a strong inverse relationship between self-efficacy and pain severity. Analgesics are often used irregularly by people with arthritis, including some reporting severe pain
Electromagnetic response functions of few-nucleon systems
Inclusive electromagnetic reactions in few-nucleon systems are studied basing
on accurate three- and four-body calculations. The longitudinal 4He(e,e')
response function obtained at q\le 600 MeV/c completely agrees with experiment.
The exact 4He spectral function obtained in a semirealistic potential model is
presented, and the accuracy of the quasielastic response calculated with its
help is assessed, as well as the accuracy of some simpler approximations for
the response. The photodisintegration cross section of 3He obtained with the
realistic AV14 NN force plus UrbanaVIII NNN force agrees with experiment. It is
shown that this cross section is very sensitive to underlying nuclear dynamics
in the E_\gamma\simeq 70-100 MeV region. In particular, the NNN nuclear force
clearly manifests itself in this region.Comment: 10 pages, Latex, style file is included, 7 ps figures, to appear in
Proc. of the 2nd Int. Conf. on Perspectives in Hadronic Physics, ITCP,
Triest, May 1999, World Sci., Singapor
Habitable Zones in the Universe
Habitability varies dramatically with location and time in the universe. This
was recognized centuries ago, but it was only in the last few decades that
astronomers began to systematize the study of habitability. The introduction of
the concept of the habitable zone was key to progress in this area. The
habitable zone concept was first applied to the space around a star, now called
the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable
zones have been proposed. We review the historical development of the concept
of habitable zones and the present state of the research. We also suggest ways
to make progress on each of the habitable zones and to unify them into a single
concept encompassing the entire universe.Comment: 71 pages, 3 figures, 1 table; to be published in Origins of Life and
Evolution of Biospheres; table slightly revise
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