234 research outputs found
Topological properties of punctual Hilbert schemes of almost-complex fourfolds (I)
In this article, we study topological properties of Voisin's punctual Hilbert
schemes of an almost-complex fourfold . In this setting, we compute their
Betti numbers and construct Nakajima operators. We also define tautological
bundles associated with any complex bundle on , which are shown to be
canonical in -theory
Hirzebruch-Milnor classes and Steenbrink spectra of certain projective hypersurfaces
We show that the Hirzebruch-Milnor class of a projective hypersurface, which
gives the difference between the Hirzebruch class and the virtual one, can be
calculated by using the Steenbrink spectra of local defining functions of the
hypersurface if certain good conditions are satisfied, e.g. in the case of
projective hyperplane arrangements, where we can give a more explicit formula.
This is a natural continuation of our previous paper on the Hirzebruch-Milnor
classes of complete intersections.Comment: 15 pages, Introduction is modifie
GALEX J201337.6+092801: The lowest gravity subdwarf B pulsator
We present the recent discovery of a new subdwarf B variable (sdBV), with an
exceptionally low surface gravity. Our spectroscopy of J20136+0928 places it at
Teff = 32100 +/- 500, log(g) = 5.15 +/- 0.10, and log(He/H) = -2.8 +/- 0.1.
With a magnitude of B = 12.0, it is the second brightest V361 Hya star ever
found. Photometry from three different observatories reveals a temporal
spectrum with eleven clearly detected periods in the range 376 to 566 s, and at
least five more close to our detection limit. These periods are unusually long
for the V361 Hya class of short-period sdBV pulsators, but not unreasonable for
p- and g-modes close to the radial fundamental, given its low surface gravity.
Of the ~50 short period sdB pulsators known to date, only a single one has been
found to have comparable spectroscopic parameters to J20136+0928. This is the
enigmatic high-amplitude pulsator V338 Ser, and we conclude that J20136+0928 is
the second example of this rare subclass of sdB pulsators located well above
the canonical extreme horizontal branch in the HR diagram.Comment: 5 pages, accepted for publication in ApJ Letter
Affine and toric hyperplane arrangements
We extend the Billera-Ehrenborg-Readdy map between the intersection lattice
and face lattice of a central hyperplane arrangement to affine and toric
hyperplane arrangements. For arrangements on the torus, we also generalize
Zaslavsky's fundamental results on the number of regions.Comment: 32 pages, 4 figure
Implementacija digitalnog generatora obojenog šuma bez množila
Colored noise can be generated by filtering of the white noise. It is a simple task. However, it becomes challenging if high operating speed of the generator is required. The realization of digital filter generally requires one multiplication per coefficient. Therefore, a high operating speed is achieved only with the cost of several generalpurpose multipliers. In this paper, a multiplierless realization of the colored noise generator is proposed. It is based on the filtering of 1-bit random signal by a finite impulse response filter. The design of the generator is described and its implementation is considered. Furthermore, an application is described in which the proposed generator is used in mitigation of undesired effects caused by nonlinearities in an analog to digital converter.Obojeni šum može se generirati filtriranjem bijelog šuma. To je jednostavan postupak. Međutim, on postaje izazovan ako se od generatora traži velika brzina rada. Realizacija digitalnog filtra u pravilu zahtijeva jedno množenje po koeficijentu. Zato se velika brzina rada može postići samo uz cijenu većeg broja množila opće namjene. U ovom radu predložena je realizacija generatora obojenog šuma koja ne sadrži množila. Ona se temelji se na filtraciji 1-bitnog slučajnog signala pomoću filtra s konačnim impulsnim odzivom. Opisano je projektiranje generatora te je razmotrena njegova implementacija. Nadalje, opisana je primjena u kojoj je predloženi generator iskorišten za smanjivanje utjecaja nelinearnosti u analogno digitalnom pretvorniku
Dirichlet fundamental domains and complex-projective varieties
We prove that for every finitely-presented group G there exists a
2-dimensional irreducible complex-projective variety W with the fundamental
group G, so that all singularities of W are normal crossings and Whitney
umbrellas.Comment: 1 figur
Classification of singular Q-homology planes. I. Structure and singularities
A Q-homology plane is a normal complex algebraic surface having trivial
rational homology. We obtain a structure theorem for Q-homology planes with
smooth locus of non-general type. We show that if a Q-homology plane contains a
non-quotient singularity then it is a quotient of an affine cone over a
projective curve by an action of a finite group respecting the set of lines
through the vertex. In particular, it is contractible, has negative Kodaira
dimension and only one singular point. We describe minimal normal completions
of such planes.Comment: improved results from Ph.D. thesis (University of Warsaw, 2009), 25
pages, to appear in Israel J. Mat
Relative Artin motives and the reductive Borel-Serre compactification of a locally symmetric variety
We introduce the notion of Artin motives and cohomological motives over a scheme X. Given a cohomological motive M over X, we consider the universal Artin motive mapping to M and denote it ω0X(M). We use this to define a motive
Attitudes of Mexican anesthesiologists to indicate preoperative fasting periods: A cross-sectional survey
BACKGROUND: In Mexico, guidelines for fasting periods, or any audits on this topic are unavailable, and therefore the attitudes of anesthesiologists for recommending preoperative fasting periods are unknown. MATERIAL AND METHODS: The study was a cross-sectional survey of anesthesiologists subscribed to the Annual Updated Course, organized by the Sociedad Mexicana de Anestesiologia in 2000. The response rate was 31.4%. RESULTS: Most respondents were general anesthesiologists, with 5 or more years experience in a clinical post, were working in both public and private hospitals, and were performing anesthetic procedures on both pediatric and adult patients and in both ambulatory and hospitalized patients. Approximately 23% of the respondents considered natural fruit juices to be clear liquids. For a pediatric patient ingesting breast milk 1 h before undergoing a surgical procedure, 45% thought that surgery should be delayed for 3h, followed by those delaying the surgical procedure for 6 to 8 h. Our results show that more than 50% of the anesthesiologists had better defined attitudes for fasting milk and clear liquids in patients of 6 month or under than for older children and adults. However, due to the poor definition or pre-operative fasting, using clear liquids, in all other patient groups, several patients are allowed to go without oral clear liquids administration for prolonged periods. CONCLUSION: Preoperative fasting periods recommended by Mexican anesthesiologists differ from international guidelines
Variations of moduli of parabolic bundles
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46243/1/208_2005_Article_BF01446645.pd
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