2,264 research outputs found
Topological noetherianity for cubic polynomials
Let be the space of complex cubic polynomials in
infinitely many variables. We show that this space is
-noetherian, meaning that any
-stable Zariski closed subset is cut out by finitely many
orbits of equations. Our method relies on a careful analysis of an invariant of
cubics introduced here called q-rank. This result is motivated by recent work
in representation stability, especially the theory of twisted commutative
algebras. It is also connected to certain stability problems in commutative
algebra, such as Stillman's conjecture.Comment: 13 page
Portable beveling tool
Portable tool was designed to semiautomatically bevel end surfaces of tubular or cylindrical components. Tool may be used for fabrication of elbow assembly which requires mating flange and elbow by fusion butt welding
Radiation effects on silicon second quarterly progress report, sep. 1 - nov. 30, 1964
Electron spin resonance measurements on P-doped silicon - vacancy phosphorus defec
Probing the structure of the cold dark matter halo with ancient mica
Mica can store (for >1 Gy) etchable tracks caused by atoms recoiling from
WIMPs. Ancient mica is a directional detector despite the complex motions it
makes with respect to the WIMP "wind". We can exploit the properties of
directionality and long integration time to probe for structure in the dark
matter halo of our galaxy. We compute a sample of possible signals in mica for
a plausible model of halo structure.Comment: 7 pages, 2 figure
Recommended from our members
Model reduction in mathematical pharmacology: integration, reduction and linking of PBPK and systems biology models
In this paper we present a framework for the reduction and linking of physiologically based pharmacokinetic (PBPK) models with models of systems biology to describe the effects of drug administration across multiple scales. To address the issue of model complexity, we propose the reduction of each type of model separately prior to being linked. We highlight the use of balanced truncation in reducing the linear components of PBPK models, whilst proper lumping is shown to be efficient in reducing typically nonlinear systems biology type models. The overall methodology is demonstrated via two example systems; a model of bacterial chemotactic signalling in Escherichia coli and a model of extracellular regulatory kinase activation mediated via the extracellular growth factor and nerve growth factor receptor pathways. Each system is tested under the simulated administration of three hypothetical compounds; a strong base, a weak base, and an acid, mirroring the parameterisation of pindolol, midazolam, and thiopental, respectively. Our method can produce up to an 80% decrease in simulation time, allowing substantial speed-up for computationally intensive applications including parameter fitting or agent based modelling. The approach provides a straightforward means to construct simplified Quantitative Systems Pharmacology models that still provide significant insight into the mechanisms of drug action. Such a framework can potentially bridge pre-clinical and clinical modelling - providing an intermediate level of model granularity between classical, empirical approaches and mechanistic systems describing the molecular scale
A Suborbital Payload for Soft X-ray Spectroscopy of Extended Sources
We present a suborbital rocket payload capable of performing soft X-ray
spectroscopy on extended sources. The payload can reach resolutions of
~100(lambda/dlambda) over sources as large as 3.25 degrees in diameter in the
17-107 angstrom bandpass. This permits analysis of the overall energy balance
of nearby supernova remnants and the detailed nature of the diffuse soft X-ray
background. The main components of the instrument are: wire grid collimators,
off-plane grating arrays and gaseous electron multiplier detectors. This
payload is adaptable to longer duration orbital rockets given its comparatively
simple pointing and telemetry requirements and an abundance of potential
science targets.Comment: Accepted to Experimental Astronomy, 12 pages plus 1 table and 17
figure
The Supergiant Shell LMC2: II. Physical Properties of the 10^6 K Gas
LMC2 has the highest X-ray surface brightness of all know supergiant shells
in the Large Magellanic Cloud (LMC). The X-ray emission peaks within the
ionized filaments that define the shell boundary, but also extends beyond the
southern border of LMC2 as an X-ray bright spur. ROSAT HRI images reveal the
X-ray emission from LMC2 and the spur to be truly diffuse, indicating a hot
plasma origin. We have obtained ROSAT PSPC and ASCA SIS spectra to study the
physical conditions of the hot gas interior to LMC2 and the spur. Raymond-Smith
thermal plasma model fits to the X-ray spectra, constrained by HI 21-cm
emission-line measurements of the column density, show the plasma temperature
of the hot gas interior of LMC2 to be kT = 0.1 - 0.7 keV and of the spur to be
kT = 0.1 - 0.5 keV. We have compared the physical conditions of the hot gas
interior to LMC2 with those of other supergiant shells, superbubbles, and
supernova remnants (SNRs) in the LMC. We find that our derived electron
densities for the hot gas inside LMC2 is higher than the value determined for
the supergiant shell LMC4, comparable to the value determined for the
superbubble N11, and lower than the values determined for the superbubble N44
and a number of SNRs.Comment: 29 pages, 5 figures, to be published in Ap
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