Fast simulation of the leaky bucket algorithm

We use fast simulation methods, based on importance sampling, to efficiently estimate cell loss probability in queueing models of the Leaky Bucket algorithm. One of these models was introduced by Berger (1991), in which the rare event of a cell loss is related to the rare event of an empty finite buffer in an "overloaded" queue. In particular, we propose a heuristic change of measure for importance sampling to efficiently estimate the probability of the rare empty-buffer event in an asymptotically unstable GI/GI/1/k queue. This change of measure is, in a way, "dual" to that proposed by Parekh and Walrand (1989) to estimate the probability of a rare buffer overflow event. We present empirical results to demonstrate the effectiveness of our fast simulation method. Since we have not yet obtained a mathematical proof, we can only conjecture that our heuristic is asymptotically optimal, as k/spl rarr//spl infin/

The potential role of dietary calcium in obesity

There is substantial evidence from cellular, animal and epidemiological studies in support of a role for calcium, and in particular, dairy foods in the regulation of weight (McCarron, 1983; Davies et al. 2000; Heaney, 2003a; Jacqmain et al. 2003; Parikh & Yanovski, 2003; Soares et al. 2004a; Azadbakht et al. 2005). These studies suggest, but do not provide, a causal link between increased calcium intake and reduced adiposity. In contrast, randomised controlled trails (RCT) are limited and their outcomes, to date, are conflicting in their findings (Zemel et al. 2004b; Harvey-Berino et al. 2005; Thompson et al. 2005; Zemel et al. 2005a; 2005b). The primary mechanism involves the control of intracellular calcium by calcitrophic hormones, vitamin D3 and PTH. It is proposed that a higher calcium intake lowers the calcitrophic hormones, thus reducing intracellular calcium and attenuating lipid storage (Zemel et al. 2000). Other flow through effects may include the greater utilisation of fat as a fuel source, increased thermogenesis, increased fat excretion, improved satiety and reduced food intake. (Melanson et al. 2003; Sun & Zemel, 2004; Boon et al. 2005a; Gunther et al. 2005b; Jacobsen et al. 2005b; Melanson et al. 2006). In this thesis we demonstrate that the acute ingestion of calcium, increased postprandial fat oxidation in overweight and obese humans. The results were consistent between the two sources of calcium tested (dairy and calcium citrate). Circulating levels of non-esterified fatty acids (NEFA) were less suppressed, while glycerol tended to be higher following both high calcium meals (Cummings et al. 2006).There was no evidence of a modulation of subjective feelings of hunger, or satiety, nor immediate food intake (buffet) or 24 hour food intake. A prolongation of the inter-meal interval was however observed in subjects consuming the high calcium meals. A single-blind 12 week RCT, with a 12 week wash out period, compared two energy restricted (ER) diets either high (HC 1200 mg/d) or low in calcium (LD 600 mg/d). Forty overweight/obese male and female subjects were recruited for the study with 29 subjects completing both arms of the study. Anthropometric data and body composition from DEXA were measured before, during and following each diet. There was no difference between the diets in the loss of body weight, total fat mass or trunk fat mass. A greater reduction in waist circumference of 1.23 cm was observed when subjects had consumed the HC diet; this however was just short of significance (P=0.052). There was a smaller reduction of resting energy expenditure on the hypocaloric HC diet with a trend for a greater fat oxidation at week 10 of intervention. No differences were observed between the treatment groups for fasting levels of glucose, insulin, Hba1c, LDL-C, HDL-C or TC. We also found an inverse relationship between resting metabolic rate at the start of ER and body fat lost when subjects consumed the LC diet, but not the HC diet.This is a novel finding in that it would be expected to see an inverse relationship between initial RMR and the amount of fat lost; however, the HC diet seems to achieve the same fat loss as the LC diet by taking away the effect of initial body size/composition. Overall, the ingestion of a single meal containing 500 mg of dietary and elemental calcium has some benefits for the obese individual. Six hours post-prandially fat oxidation is stimulated following the consumption of the dietary and elemental calcium breakfast meals. During a 12-week weight loss period, a higher calcium intake did not result in a greater weight loss compared to a low calcium diet. The HC diet did result in a trend for a greater reduction in waist circumference; however, this did not transcribe into an increased loss of total or regional body fat

Low-resource synchronous coincidence processor for positron emission tomography

We developed a new FPGA-based method for coincidence detection in positronemissiontomography. The method requires low device resources and no specific peripherals in order to resolve coincident digital pulses within a time window of a few nanoseconds. This method has been validated with a low-end Xilinx Spartan-3E and provided coincidence resolutions lower than 6 ns. This resolution depends directly on the signal propagation properties of the target device and the maximum available clock frequency, therefore it is expected to improve considerably on higher-end FPGAs

Faster Prefix-Sorting Algorithms for Deterministic Finite Automata

Sorting is a fundamental algorithmic pre-processing technique which often allows to represent data more compactly and, at the same time, speeds up search queries on it. In this paper, we focus on the well-studied problem of sorting and indexing string sets. Since the introduction of suffix trees in 1973, dozens of suffix sorting algorithms have been described in the literature. In 2017, these techniques were extended to sets of strings described by means of finite automata: the theory of Wheeler graphs [Gagie et al., TCS'17] introduced automata whose states can be totally-sorted according to the co-lexicographic (co-lex in the following) order of the prefixes of words accepted by the automaton. More recently, in [Cotumaccio, Prezza, SODA'21] it was shown how to extend these ideas to arbitrary automata by means of partial co-lex orders. This work showed that a co-lex order of minimum width (thus optimizing search query times) on deterministic finite automata (DFAs) can be computed in O(m² + n^{5/2}) time, m being the number of transitions and n the number of states of the input DFA. In this paper, we exhibit new combinatorial properties of the minimum-width co-lex order of DFAs and exploit them to design faster prefix sorting algorithms. In particular, we describe two algorithms sorting arbitrary DFAs in O(mn) and O(n² log n) time, respectively, and an algorithm sorting acyclic DFAs in O(m log n) time. Within these running times, all algorithms compute also a smallest chain partition of the partial order (required to index the DFA). We present an experiment result to show that an optimized implementation of the O(n² log n)-time algorithm exhibits a nearly-linear behaviour on large deterministic pan-genomic graphs and is thus also of practical interest

Prime saliency in semantic priming with 18-month-olds

This study investigated semantic priming in 18-month-old infants using the inter-modal priming technique, focusing on the effects of prime repetition on saliency. Our findings showed that prime repetition led to longer looking times at target referents for related primes compared to unrelated primes, supporting the existence of a structured semantic system in infants as young as 18 months. The results are consistent with both Spreading Activation and Distributed models of semantic priming. Additionally, our findings highlighted the impact of prime-target stimulus onset asynchronies (SOAs) on priming effects, revealing positive, negative, or no priming effects depending on the chosen SOA. A post-hoc explanation of this finding points to negative priming as a possible mechanism. The study also demonstrated the utility of the inter-modal priming task in studying lexical-semantic structure in younger infants with its diverse measures of infant behaviour

The Spectral and Temporal Properties of Transient Sources in Early-type Galaxies

Copyright 2012 Elsevier B.V., All rights reserved.We report the spectral and temporal variability properties of 18 candidate transient (TC) and potential transient (PTC) sources detected in deep multi-epoch Chandra observation of the nearby elliptical galaxies, NGC3379, NGC4278, and NGC4697. Only one source can be identified with a background counterpart, leaving 17 TCs + PTCs in the galaxies. Of these, 14 are in the galaxy field, supporting the theoretical picture that the majority of field X-ray binaries (XRBs) will exhibit transient accretion for >75% of their lifetime. Three sources are coincident with globular clusters, including two high-luminosity candidate black hole (BH) XRBs, with Lx= 5.4 × 10 erg/s and Lx= 2.8 × 10 erg/s, respectively. The spectra, luminosities, and temporal behavior of these 17 sources suggest that the transient population is heterogeneous, including neutron star (NS) and BH XRBs in both normal and high-rate accretion modes, and super soft sources containing white dwarf binaries. Our TC and PTC detections are noticeably fewer than the number expected from the population synthesis (PS) models of Fragos et al., tailored to our new Chandra pointings of NGC4278. We attribute this discrepancy to the PS assumption that the transient population is composed of NS XRBs, as well as differences between the statistical analysis and error estimates used in the model and our observationsPeer reviewe

Efficient slave-boson approach for multiorbital two-particle response functions and superconductivity

We develop an efficient approach for computing two-particle response functions and interaction vertices for multiorbital strongly correlated systems based on fluctuation around rotationally-invariant slave-boson saddle-point. The method is applied to the degenerate three-orbital Hubbard-Kanamori model for investigating the origin of the s-wave orbital antisymmetric spin-triplet superconductivity in the Hund's metal regime, previously found in the dynamical mean-field theory studies. By computing the pairing interaction considering the particle-particle and the particle-hole scattering channels, we identify the mechanism leading to the pairing instability around Hund's metal crossover arises from the particle-particle channel, containing the local electron pair fluctuation between different particle-number sectors of the atomic Hilbert space. On the other hand, the particle-hole spin fluctuations induce the s-wave pairing instability before entering the Hund's regime. Our approach paves the way for investigating the pairing mechanism in realistic correlated materials

Inadequate heart rate control despite widespread use of beta-blockers in outpatients with stable CAD: findings from the international prospective CLARIFY registry

Background: To use CLARIFY, a prospective registry of patients with stable CAD (45 countries), to explore heart rate (HR) control and beta-blocker use.<p></p> Methods: We analyzed the CLARIFY population according to beta-blocker use via descriptive statistics with Pearson's χ2 test for comparisons, as well as a multivariable stepwise model.<p></p> Results: Data on beta-blocker use was available for 32,914 patients, in whom HR was 68 ± 11 bpm; patients with angina, previous myocardial infarction, and heart failure had HRs of 69 ± 12, 68 ± 11, and 70 ± 12 bpm, respectively. 75% of these patients were receiving beta-blockers. Bisoprolol (34%), metoprolol tartrate (16%) or succinate (13%), atenolol (15%), and carvedilol (12%) were mostly used; mean dosages were 49%, 76%, 35%, 53%, and 45% of maximum doses, respectively. Patients aged < 65 years were more likely to receive beta-blockers than patients ≥ 75 years (P < 0.0001). Gender had no effect. Subjects with HR ≤ 60 bpm were more likely to be on beta-blockers than patients with HR ≥ 70 bpm (P < 0.0001). Patients with angina, previous myocardial infarction, heart failure, and hypertension were more frequently receiving beta-blockers (all P < 0.0001), and those with PAD and asthma/COPD less frequently (both P < 0.0001). Beta-blocker use varied according to geographical region (from 87% to 67%).<p></p> Conclusions: Three-quarters of patients with stable CAD receive beta-blockers. Even so, HR is insufficiently controlled in many patients, despite recent guidelines for the management of CAD. There is still much room for improvement in HR control in the management of stable CAD

Double it up: vocabulary size comparison between UK bilingual and monolingual toddlers

We compared vocabulary sizes in comprehension and production between bilingual toddlers growing up in the United Kingdom (UK) and age-matched UK English monolinguals (12–36 months old) using parent-report vocabulary questionnaires. We found that bilingual toddlers' vocabulary sizes in English were smaller than the vocabulary sizes of their monolingual peers. Notably, this vocabulary gap was not found when groups were compared on conceptual vocabulary in comprehension. Conceptual scoring also reduced the vocabulary gap in production but group differences were still significant. Bilingual toddlers knew more words than monolinguals when words across their two languages were added together, for both comprehension and production. This large total vocabulary size could be attributed to a high proportion of doublets (cross-linguistic word pairs with the same meaning) in bilinguals' vocabularies. These findings are discussed in relation to language exposure, facilitation from cross-linguistic overlap and maturation constraints on vocabulary size