17,243 research outputs found
Supernova Resonance--scattering Line Profiles in the Absence of a Photosphere
In supernova spectroscopy relatively little attention has been given to the
properties of optically thick spectral lines in epochs following the
photosphere's recession. Most treatments and analyses of post-photospheric
optical spectra of supernovae assume that forbidden-line emission comprises
most if not all spectral features. However, evidence exists which suggests that
some spectra exhibit line profiles formed via optically thick
resonance-scattering even months or years after the supernova explosion. To
explore this possibility we present a geometrical approach to supernova
spectrum formation based on the "Elementary Supernova" model, wherein we
investigate the characteristics of resonance-scattering in optically thick
lines while replacing the photosphere with a transparent central core emitting
non-blackbody continuum radiation, akin to the optical continuum provided by
decaying 56Co formed during the explosion. We develop the mathematical
framework necessary for solving the radiative transfer equation under these
conditions, and calculate spectra for both isolated and blended lines. Our
comparisons with analogous results from the Elementary Supernova code SYNOW
reveal several marked differences in line formation. Most notably, resonance
lines in these conditions form P Cygni-like profiles, but the emission peaks
and absorption troughs shift redward and blueward, respectively, from the
line's rest wavelength by a significant amount, despite the spherically
symmetric distribution of the line optical depth in the ejecta. These
properties and others that we find in this work could lead to misidentification
of lines or misattribution of properties of line-forming material at
post-photospheric times in supernova optical spectra.Comment: 37 pages, 24 figures; accepted for publication in ApJ Supplement
Serie
Answering Conjunctive Queries under Updates
We consider the task of enumerating and counting answers to -ary
conjunctive queries against relational databases that may be updated by
inserting or deleting tuples. We exhibit a new notion of q-hierarchical
conjunctive queries and show that these can be maintained efficiently in the
following sense. During a linear time preprocessing phase, we can build a data
structure that enables constant delay enumeration of the query results; and
when the database is updated, we can update the data structure and restart the
enumeration phase within constant time. For the special case of self-join free
conjunctive queries we obtain a dichotomy: if a query is not q-hierarchical,
then query enumeration with sublinear delay and sublinear update time
(and arbitrary preprocessing time) is impossible.
For answering Boolean conjunctive queries and for the more general problem of
counting the number of solutions of k-ary queries we obtain complete
dichotomies: if the query's homomorphic core is q-hierarchical, then size of
the the query result can be computed in linear time and maintained with
constant update time. Otherwise, the size of the query result cannot be
maintained with sublinear update time. All our lower bounds rely on the
OMv-conjecture, a conjecture on the hardness of online matrix-vector
multiplication that has recently emerged in the field of fine-grained
complexity to characterise the hardness of dynamic problems. The lower bound
for the counting problem additionally relies on the orthogonal vectors
conjecture, which in turn is implied by the strong exponential time hypothesis.
By sublinear we mean for some
, where is the size of the active domain of the current
database
High frequency dynamics in a monatomic glass
The high frequency dynamics of glassy Selenium has been studied by Inelastic
X-ray Scattering at beamline BL35XU (SPring-8). The high quality of the data
allows one to pinpoint the existence of a dispersing acoustic mode for
wavevectors () of nm, helping to clarify a previous
contradiction between experimental and numerical results. The sound velocity
shows a positive dispersion, exceeding the hydrodynamic value by 10%
at nm. The dependence of the sound attenuation
, reported for other glasses, is found to be the low- limit of a
more general law which applies also to the
higher region, where no longer holds.Comment: Phys. Rev. Lett. (Accepted
Near-infrared line identification in type Ia supernovae during the transitional phase
We present near-infrared synthetic spectra of a delayed-detonation
hydrodynamical model and compare them to observed spectra of four normal type
Ia supernovae ranging from day +56.5 to day +85. This is the epoch during which
supernovae are believed to be undergoing the transition from the photospheric
phase, where spectra are characterized by line scattering above an optically
thick photosphere, to the nebular phase, where spectra consist of optically
thin emission from forbidden lines. We find that most spectral features in the
near-infrared can be accounted for by permitted lines of Fe II and Co II. In
addition, we find that [Ni II] fits the emission feature near 1.98 {\mu}m,
suggesting that a substantial mass of 58Ni exists near the center of the ejecta
in these objects, arising from nuclear burning at high density. A tentative
identification of Mn II at 1.15 {\mu}m may support this conclusion as well.Comment: accepted to Ap
Beyond Worst-Case Analysis for Joins with Minesweeper
We describe a new algorithm, Minesweeper, that is able to satisfy stronger
runtime guarantees than previous join algorithms (colloquially, `beyond
worst-case guarantees') for data in indexed search trees. Our first
contribution is developing a framework to measure this stronger notion of
complexity, which we call {\it certificate complexity}, that extends notions of
Barbay et al. and Demaine et al.; a certificate is a set of propositional
formulae that certifies that the output is correct. This notion captures a
natural class of join algorithms. In addition, the certificate allows us to
define a strictly stronger notion of runtime complexity than traditional
worst-case guarantees. Our second contribution is to develop a dichotomy
theorem for the certificate-based notion of complexity. Roughly, we show that
Minesweeper evaluates -acyclic queries in time linear in the certificate
plus the output size, while for any -cyclic query there is some instance
that takes superlinear time in the certificate (and for which the output is no
larger than the certificate size). We also extend our certificate-complexity
analysis to queries with bounded treewidth and the triangle query.Comment: [This is the full version of our PODS'2014 paper.
A C-Terminal Protease-Resistant Prion Fragment Distinguishes Ovine “CH1641-Like” Scrapie from Bovine Classical and L-Type BSE in Ovine Transgenic Mice
The protease-resistant prion protein (PrPres) of a few natural scrapie isolates identified in sheep, reminiscent of the experimental isolate CH1641 derived from a British natural scrapie case, showed partial molecular similarities to ovine bovine spongiform encephalopathy (BSE). Recent discovery of an atypical form of BSE in cattle, L-type BSE or BASE, suggests that also this form of BSE might have been transmitted to sheep. We studied by Western blot the molecular features of PrPres in four “CH1641-like” natural scrapie isolates after transmission in an ovine transgenic model (TgOvPrP4), to see if “CH1641-like” isolates might be linked to L-type BSE. We found less diglycosylated PrPres than in classical BSE, but similar glycoform proportions and apparent molecular masses of the usual PrPres form (PrPres #1) to L-type BSE. However, the “CH1641-like” isolates differed from both L-type and classical BSE by an abundant, C-terminally cleaved PrPres product (PrPres #2) specifically recognised by a C-terminal antibody (SAF84). Differential immunoprecipitation of PrPres #1 and PrPres #2 resulted in enrichment in PrPres #2, and demonstrated the presence of mono- and diglycosylated PrPres products. PrPres #2 could not be obtained from several experimental scrapie sources (SSBP1, 79A, Chandler, C506M3) in TgOvPrP4 mice, but was identified in the 87V scrapie strain and, in lower and variable proportions, in 5 of 5 natural scrapie isolates with different molecular features to CH1641. PrPres #2 identification provides an additional method for the molecular discrimination of prion strains, and demonstrates differences between “CH1641-like” ovine scrapie and bovine L-type BSE transmitted in an ovine transgenic mouse model
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A behavioral comparison of male and female adults with high functioning autism spectrum conditions
Autism spectrum conditions (ASC) affect more males than females in the general population. However, within ASC it is unclear if there are phenotypic sex differences. Testing for similarities and differences between the sexes is important not only for clinical assessment but also has implications for theories of typical sex differences and of autism. Using cognitive and behavioral measures, we investigated similarities and differences between the sexes in age- and IQ-matched adults with ASC (high-functioning autism or Asperger syndrome). Of the 83 (45 males and 38 females) participants, 62 (33 males and 29 females) met Autism Diagnostic Interview-Revised (ADI-R) cut-off criteria for autism in childhood and were included in all subsequent analyses. The severity of childhood core autism symptoms did not differ between the sexes. Males and females also did not differ in self-reported empathy, systemizing, anxiety, depression, and obsessive-compulsive traits/symptoms or mentalizing performance. However, adult females with ASC showed more lifetime sensory symptoms (p = 0.036), fewer current socio-communication difficulties (p = 0.001), and more self-reported autistic traits (p = 0.012) than males. In addition, females with ASC who also had developmental language delay had lower current performance IQ than those without developmental language delay (p<0.001), a pattern not seen in males. The absence of typical sex differences in empathizing-systemizing profiles within the autism spectrum confirms a prediction from the extreme male brain theory. Behavioral sex differences within ASC may also reflect different developmental mechanisms between males and females with ASC. We discuss the importance of the superficially better socio-communication ability in adult females with ASC in terms of why females with ASC may more often go under-recognized, and receive their diagnosis later, than males
{\eta} and {\eta}' mesons from Nf=2+1+1 twisted mass lattice QCD
We determine mass and mixing angles of eta and eta' states using Nf=2+1+1
Wilson twisted mass lattice QCD. We describe how those flavour singlet states
need to be treated in this lattice formulation. Results are presented for three
values of the lattice spacing, a=0.061 fm, a=0.078 fm and a=0.086 fm, with
light quark masses corresponding to values of the charged pion mass in a range
of 230 to 500 MeV and fixed bare strange and charm quark mass values. We obtain
557(15)(45) MeV for the eta mass (first error statistical, second systematic)
and 44(5) degrees for the mixing angle in the quark flavour basis,
corresponding to -10(5) degrees in the octet-singlet basis.Comment: 28 pages, 9 figures, version to appear in JHEP, extended discussion
of autocorrelation times and comparison to results available in the
literature, added a comment for FS-effects and clarified the description of
our blocking procedur
Social Conformity in Autism
Humans are extremely susceptible to social influence. Here, we examine whether this susceptibility is altered in autism, a condition characterized by social difficulties. Autistic participants (N=22) and neurotypical controls (N=22) completed a memory test of previously seen words and were then exposed to answers supposedly given by four other individuals. Autistic individuals and controls were as likely to alter their judgements to align with inaccurate responses of group members. These changes reflected both temporary judgement changes (public conformity) and long-lasting memory changes (private conformity). Both groups were more susceptible to answers believed to be from other humans than from computer algorithms. Our results suggest that autistic individuals and controls are equally susceptible to social influence when reporting their memories
Colloidal stability of tannins: astringency, wine tasting and beyond
Tannin-tannin and tannin-protein interactions in water-ethanol solvent
mixtures are studied in the context of red wine tasting. While tannin
self-aggregation is relevant for visual aspect of wine tasting (limpidity and
related colloidal phenomena), tannin affinities for salivary proline-rich
proteins is fundamental for a wide spectrum of organoleptic properties related
to astringency. Tannin-tannin interactions are analyzed in water-ethanol
wine-like solvents and the precipitation map is constructed for a typical grape
tannin. The interaction between tannins and human salivary proline-rich
proteins (PRP) are investigated in the framework of the shell model for
micellization, known for describing tannin-induced aggregation of beta-casein.
Tannin-assisted micellization and compaction of proteins observed by SAXS are
described quantitatively and discussed in the case of astringency
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