Search results for "sort"

Unusual Assortment of Segments in 2 Rare Human Rotavirus Genomes

2010

Using full-length genome sequence analysis, we investigated 2 rare G3P[9] human rotavirus strains isolated from children with diarrhea. The genomes were recognized as assortments of genes closely related to rotaviruses originating from cats, ruminants, and humans. Results suggest multiple transmissions of genes from animal to human strains of rotaviruses.

Molecular characterization of rotavirus strains from children with diarrhea in Italy, 2007-2009.

2011

The surveillance network RotaNet-Italia was established in 2007 in order to investigate the diversity of co-circulating rotavirus strains in Italy, and to provide a baseline for future assessment of possible effects of vaccine implementation in selecting novel versus common rotavirus strains. A total of 2,645 rotavirus strains from pediatric patients with acute diarrhea were collected over three consecutive seasons from September 2006 through August 2009, and partially characterized by standardized multiplex RT-PCR. Most of strains (89.1%) belonged to genotypes G1–G4, and G9, associated with either P[8] or P[4], commonly found in humans worldwide. However, in at least 2.0% of cases, viruses…

Spatial Search on Grids with Minimum Memory

2015

We study quantum algorithms for spatial search on finite dimensional grids. Patel et al. and Falk have proposed algorithms based on a quantum walk without a coin, with different operators applied at even and odd steps. Until now, such algorithms have been studied only using numerical simulations. In this paper, we present the first rigorous analysis for an algorithm of this type, showing that the optimal number of steps is $O(\sqrt{N\log N})$ and the success probability is $O(1/\log N)$, where $N$ is the number of vertices. This matches the performance achieved by algorithms that use other forms of quantum walks.

Adjacent Vertices Can Be Hard to Find by Quantum Walks

2017

Quantum walks have been useful for designing quantum algorithms that outperform their classical versions for a variety of search problems. Most of the papers, however, consider a search space containing a single marked element only. We show that if the search space contains more than one marked element, their placement may drastically affect the performance of the search. More specifically, we study search by quantum walks on general graphs and show a wide class of configurations of marked vertices, for which search by quantum walk needs \(\varOmega (N)\) steps, that is, it has no speed-up over the classical exhaustive search. The demonstrated configurations occur for certain placements of …

2014

Is there a general theorem that tells us when we can hope for exponential speedups from quantum algorithms, and when we cannot? In this paper, we make two advances toward such a theorem, in the black-box model where most quantum algorithms operate. First, we show that for any problem that is invariant under permuting inputs and outputs (like the collision or the element distinctness problems), the quantum query complexity is at least the 9 th root of the classical randomized query complexity. This resolves a conjecture of Watrous from 2002. Second, inspired by recent work of O’Donnell et al. and Dinur et al., we conjecture that every bounded low-degree polynomial has a “highly influential” …

Lesion load may predict long-term cognitive dysfunction in multiple sclerosis patients

2015

Background: Magnetic Resonance Imaging (MRI) techniques provided evidences into the understanding of cognitive impairment (CIm) in Multiple Sclerosis (MS). Objectives: To investigate the role of white matter (WM) and gray matter (GM) in predicting long-term CIm in a cohort of MS patients. Methods: 303 out of 597 patients participating in a previous multicenter clinical-MRI study were enrolled (49.4% were lost at follow-up). The following MRI parameters, expressed as fraction (f) of intracranial volume, were evaluated: cerebrospinal fluid (CSF-f), WM-f, GM-f and abnormal WM (AWM-f), a measure of lesion load. Nine years later, cognitive status was assessed in 241 patients using the Symbol Dig…

Coincidental loss of bacterial virulence in multi-enemy microbial communities.

2014

The coincidental virulence evolution hypothesis suggests that outside-host selection, such as predation, parasitism and resource competition can indirectly affect the virulence of environmentally-growing bacterial pathogens. While there are some examples of coincidental environmental selection for virulence, it is also possible that the resource acquisition and enemy defence is selecting against it. To test these ideas we conducted an evolutionary experiment by exposing the opportunistic pathogen bacterium Serratia marcescens to the particle-feeding ciliate Tetrahymena thermophila, the surfacefeeding amoeba Acanthamoeba castellanii, and the lytic bacteriophage Semad11, in all possible combi…

Resistant Microbial Cooccurrence Patterns Inferred by Network Topology

2015

ABSTRACT Although complex cooccurrence patterns have been described for microbes in natural communities, these patterns have scarcely been interpreted in the context of ecosystem functioning and stability. Here we constructed networks from species cooccurrences between pairs of microorganisms which were extracted from five individual aquatic time series, including a dystrophic and a eutrophic lake as well as an open ocean site. The resulting networks exhibited higher clustering coefficients, shorter path lengths, and higher average node degrees and levels of betweenness than those of random networks. Moreover, simulations demonstrated that taxa with a large number of cooccurrences and place…

Crowding-out effect and sorting in competitive labour markets with motivated workers

2018

ABSTRACTThis article makes a contribution to the economics literature by inducing proper self-selection into contracts based on workers’ motivation. The novelty of our results is that it points out the alternative potential role of the crowding-out effect to separate workers based on their motivation.

Job Mobility and Sorting: Theory and Evidence

2019

Abstract Motivated by the canonical (random) on-the-job search model, I measure a person’s ability to sort into higher ranked jobs by the risk ratio of job-to-job transitions to transitions into unemployment. I show that this measure possesses various desirable features. Making use of the Survey of Income and Program Participation (SIPP), I study the relation between human capital and the risk ratio of job-to-job transitions to transitions into unemployment. Formal education tends to be positively associated with this risk ratio. General experience and occupational tenure have a pronounced negative correlation with both job-to-job transitions and transitions into unemployment, leaving the r…