798 research outputs found

    Distribution of streaming rates into high-redshift galaxies

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    We study the accretion along streams from the cosmic web into high-redshift massive galaxies using three sets of AMR hydro-cosmological simulations. We find that the streams keep a roughly constant accretion rate as they penetrate into the halo centre. The mean accretion rate follows the mass and redshift dependence predicted for haloes by the EPS approximation, dM / dt is proportional to Mvir^{1.25} (1 + z)^{2.5}. The distribution of the accretion rates can well be described by a sum of two Gaussians, the primary corresponding to "smooth inflow" and the secondary to "mergers". The same functional form was already found for the distributions of specific star formation rates in observations. The mass fraction in the smooth component is 60 - 90 %, insensitive to redshift or halo mass. The simulations with strong feedback show clear signs of reaccretion due to recycling of galactic winds. The mean accretion rate for the mergers is a factor 2 - 3 larger than that of the smooth component. The standard deviation of the accretion rate is 0.2 - 0.3 dex, showing no trend with mass or redshift. For the smooth component it is 0.12 - 0.24 dex.Comment: 13 pages, 6 figures, 2 tables, final version accepted for publication in MNRA

    Using a Language and Literacy Intervention to Increase Autistic Students\u27 Social Interactions with Peers

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    This paper explores the research looking at an intervention done with four preschool students with autism-like tendencies. Two of the students are on the autism spectrum and two students show autism-like tendencies and deficiencies. All four students struggled in social situations and play with their peers. The intervention provided for all four students was a checklist of skills needed to be successful in a social situation; group games, cooperative play and cleaning up. The article review discusses many supports provided and areas of need for young and adolescent students on the autism spectrum. The results of the intervention showed that three out of the four students did show improved social skills according to the preschool social skills checklist; one student maintained his current social skills

    Tight Thresholds for Cuckoo Hashing via XORSAT

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    We settle the question of tight thresholds for offline cuckoo hashing. The problem can be stated as follows: we have n keys to be hashed into m buckets each capable of holding a single key. Each key has k >= 3 (distinct) associated buckets chosen uniformly at random and independently of the choices of other keys. A hash table can be constructed successfully if each key can be placed into one of its buckets. We seek thresholds alpha_k such that, as n goes to infinity, if n/m <= alpha for some alpha < alpha_k then a hash table can be constructed successfully with high probability, and if n/m >= alpha for some alpha > alpha_k a hash table cannot be constructed successfully with high probability. Here we are considering the offline version of the problem, where all keys and hash values are given, so the problem is equivalent to previous models of multiple-choice hashing. We find the thresholds for all values of k > 2 by showing that they are in fact the same as the previously known thresholds for the random k-XORSAT problem. We then extend these results to the setting where keys can have differing number of choices, and provide evidence in the form of an algorithm for a conjecture extending this result to cuckoo hash tables that store multiple keys in a bucket.Comment: Revision 3 contains missing details of proofs, as appendix

    The Scaling Window of the 2-SAT Transition

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    We consider the random 2-satisfiability problem, in which each instance is a formula that is the conjunction of m clauses of the form (x or y), chosen uniformly at random from among all 2-clauses on n Boolean variables and their negations. As m and n tend to infinity in the ratio m/n --> alpha, the problem is known to have a phase transition at alpha_c = 1, below which the probability that the formula is satisfiable tends to one and above which it tends to zero. We determine the finite-size scaling about this transition, namely the scaling of the maximal window W(n,delta) = (alpha_-(n,delta),alpha_+(n,delta)) such that the probability of satisfiability is greater than 1-delta for alpha < alpha_- and is less than delta for alpha > alpha_+. We show that W(n,delta)=(1-Theta(n^{-1/3}),1+Theta(n^{-1/3})), where the constants implicit in Theta depend on delta. We also determine the rates at which the probability of satisfiability approaches one and zero at the boundaries of the window. Namely, for m=(1+epsilon)n, where epsilon may depend on n as long as |epsilon| is sufficiently small and |epsilon|*n^(1/3) is sufficiently large, we show that the probability of satisfiability decays like exp(-Theta(n*epsilon^3)) above the window, and goes to one like 1-Theta(1/(n*|epsilon|^3)) below the window. We prove these results by defining an order parameter for the transition and establishing its scaling behavior in n both inside and outside the window. Using this order parameter, we prove that the 2-SAT phase transition is continuous with an order parameter critical exponent of 1. We also determine the values of two other critical exponents, showing that the exponents of 2-SAT are identical to those of the random graph.Comment: 57 pages. This version updates some reference

    Human Chitinases and Chitinase-Like Proteins as Indicators for Inflammation and Cancer

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    Human Glyco_18 domain-containing proteins constitute a family of chitinases and chitinase-like proteins. Chitotriosidase and AMCase are true enzymes which hydrolyse chitin and have a C-terminal chitin-binding domain. YKL-40, YKL-39, SI-CLP and murine YM1/2 proteins possess solely Glyco_18 domain and do not have the hydrolytic activity. The major sources of Glyco_18 containing proteins are macrophages, neutrophils, epithelial cells, chondrocytes, synovial cells, and cancer cells. Both macrophages and neutrophils use the regulated secretory mechanism for the release of Glyco_18 containing proteins. Glyco_18 containing proteins are established biomarkers for human diseases. Chitotriosidase is overproduced by lipid-laden macrophages and is a major marker for the inherited lysosomal storage Gaucher disease. AMCase and murine lectin YM1 are upregulated in Th2-environment, and enzymatic activity of AMCase contributes to asthma pathogenesis. YKL proteins act as soluble mediators for the cell proliferation and migration, and are also involved in rheumatoid arthritis, inflammatory bowel disease, hepatic fibrosis and cirrhosis. Chitotriosidase and YKL-40 reflect the macrophage activation in atherosclerotic plaques. Serum level of YKL-40 is a diagnostic and prognostic marker for numerous types of solid tumors. YKL-39 is a marker for the activation of chondrocytes and the progression of the osteoarthritis in human. Recently identified SI-CLP is upregulated by Th2 cytokine IL-4 as well as by glucocorticoids. This unique feature of SI-CLP makes it an attractive candidate for the examination of individual sensitivity of patients to glucocorticoid treatment and prediction of side effects of glucocorticoid therapy. Human chitinases and chitinase-like proteins are found in tissues and circulation, and can be detected by non-invasive technologies

    Strong Refutation Heuristics for Random k-SAT

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    This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A simple first moment argument shows that in a randomly chosen kk-SAT formula with mm clauses over nn boolean variables, the fraction of satisfiable clauses is 12k+o(1)1-2^{-k}+o(1) as m/nm/n\rightarrow\infty almost surely. In this paper, we deal with the corresponding algorithmic strong refutation problem: given a random kk-SAT formula, can we find a certificate that the fraction of satisfiable clauses is 12k+o(1)1-2^{-k}+o(1) in polynomial time? We present heuristics based on spectral techniques that in the case k=3k=3 and mln(n)6n3/2m\geq\ln(n)^6n^{3/2}, and in the case k=4k=4 and mCn2m\geq Cn^2, find such certificates almost surely. In addition, we present heuristics for bounding the independence number (resp. the chromatic number) of random kk-uniform hypergraphs from above (resp. from below) for k=3,4k=3,4.Peer Reviewe

    The Power of Non-Determinism in Higher-Order Implicit Complexity

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    We investigate the power of non-determinism in purely functional programming languages with higher-order types. Specifically, we consider cons-free programs of varying data orders, equipped with explicit non-deterministic choice. Cons-freeness roughly means that data constructors cannot occur in function bodies and all manipulation of storage space thus has to happen indirectly using the call stack. While cons-free programs have previously been used by several authors to characterise complexity classes, the work on non-deterministic programs has almost exclusively considered programs of data order 0. Previous work has shown that adding explicit non-determinism to cons-free programs taking data of order 0 does not increase expressivity; we prove that this - dramatically - is not the case for higher data orders: adding non-determinism to programs with data order at least 1 allows for a characterisation of the entire class of elementary-time decidable sets. Finally we show how, even with non-deterministic choice, the original hierarchy of characterisations is restored by imposing different restrictions.Comment: pre-edition version of a paper accepted for publication at ESOP'1

    Distribution of streaming rates into high-redshift galaxies

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    We study the accretion along streams from the cosmic web into high-redshift massive galaxies using three sets of AMR hydrocosmological simulations. We find that the streams keep a roughly constant accretion rate as they penetrate into the halo centre. The mean accretion rate follows the mass and redshift dependence predicted for haloes by the EPS approximation, M˙Mvir1.25 (1+z)2.5\dot{M} \propto M_{\rm vir}^{1.25} \ (1 + z)^{2.5}. The distribution of the accretion rates can well be described by a sum of two Gaussians, the primary corresponding to ‘smooth inflow' and the secondary to ‘mergers'. The same functional form was already found for the distributions of specific star formation rates in observations. The mass fraction in the smooth component is 60-90 per cent, insensitive to redshift or halo mass. The simulations with strong feedback show clear signs of reaccretion due to recycling of galactic winds. The mean accretion rate for the mergers is a factor 2-3 larger than that of the smooth component. The standard deviation of the merger accretion rate is 0.2-0.3 dex, showing no trend with mass or redshift. For the smooth component it is 0.12-0.24 de
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