PTHash: Revisiting FCH Minimal Perfect Hashing

Given a set S of n distinct keys, a function f that bijectively maps the keys of S into the range (0,...,n-1) is called a minimal perfect hash function for S. Algorithms that find such functions when n is large and retain constant evaluation time are of practical interest; for instance, search engines and databases typically use minimal perfect hash functions to quickly assign identifiers to static sets of variable-length keys such as strings. The challenge is to design an algorithm which is efficient in three different aspects: time to find f (construction time), time to evaluate f on a key of S (lookup time), and space of representation for f. Several algorithms have been proposed to trade-off between these aspects. In 1992, Fox, Chen, and Heath (FCH) presented an algorithm at SIGIR providing very fast lookup evaluation. However, the approach received little attention because of its large construction time and higher space consumption compared to other subsequent techniques. Almost thirty years later we revisit their framework and present an improved algorithm that scales well to large sets and reduces space consumption altogether, without compromising the lookup time. We conduct an extensive experimental assessment and show that the algorithm finds functions that are competitive in space with state-of-the art techniques and provide 2-4x better lookup time

Near-surface eddy dynamics in the southern ocean

The Antarctic Circumpolar Current (ACC) is a crucial component of the global ocean conveyor belt, acting as a zonal link among the major ocean basins but, to some extent, limiting meridional exchange and tending to isolate the ocean south of it from momentum and heat income. In this work we investigate one of the most important mechanisms contributing to the poleward transfer of properties in the Southern Ocean, that is the eddy component of the dynamics. For this particular purpose, observations obtained from near-surface drifters have been used: they represent a very useful data set to analyse the eddy field because of their ability to catch a large number of scales of motion while providing a quasi-synoptic coverage of the investigated area. Estimates of the eddy heat and momentum fluxes are carried out using data taken from the Global Drifter Program databank; they refer to Surface Velocity Program drifter trajectories collected in the area south of 35°S between 1995 and 2006. Eddy kinetic energies, variance ellipses, momentum and heat fluxes have been calculated using the pseudo-Eulerian method, showing patterns in good agreement with those present in the literature based on observational and model data, although there are some quantitative differences. The eddy fluxes have been separated into their rotational and divergent portions, the latter being responsible for the meridional transports. The associated zonal and depth-exponentially integrated meridional heat transport exhibits values spanning over a range between -0.4 PW and -1.1 PW in the ACC region, consistent with previous estimates. © 2011 M. Trani et al

Comorbid depressive disorders in ADHD. the role of ADHD severity, subtypes and familial psychiatric disorders

ObjectiveaaTo evaluate the presence of Major Depressive Disorder (MDD) and Dysthymic Disorder (DD) in a sample of Italian children with Attention Deficit Hyperactivity Disorder (ADHD) and to explore specific features of comorbid depressive disorders in ADHD. MethodsaaThree hundred and sixty-six consecutive, drug-naïve Caucasian Italian outpatients with ADHD were recruited and comorbid disorders were evaluated using DSM-IV-TR criteria. To evaluate ADHD severity, parents of all children filled out the ADHD Rating Scale. Thirty-seven children with comorbid MDD or DD were compared with 118 children with comorbid conduct disorder and 122 without comorbidity for age, sex, IQ level, family psychiatric history, and ADHD subtypes and severity. Resultsaa42 of the ADHD children displayed comorbid depressive disorders: 16 exhibited MDD, 21 DD, and 5 both MDD and DD. The frequency of hyperactive-impulsive subtypes was significantly lower in ADHD children with depressive disorders, than in those without any comorbidity. ADHD children with depressive disorders showed a higher number of familial psychiatric disorders and higher score in the Inattentive scale of the ADHD Rating Scale, than children without any comorbidity. No differences were found for age, sex and IQ level between the three groups. Conclusions: Consistent with previous studies in other countries, depressive disorders affect a significant proportion of ADHD children in Italy. Patient assessment and subsequent treatment should take into consideration the possible presence of this comorbidity, which could specifically increase the severity of ADHD attention problems

Screening for developmental disorders in 3- and 4-year-old italian children: a preliminary study

BACKGROUND: The "Osserviamo" project, coordinated by the Municipality of Rome and the Department of Pediatrics and Child Neuropsychiatry of Sapienza University, aimed to validate an Italian version of the Ages and Stages Questionnaire-3 and to collect, for the first time in Italy, data on developmental disorders in a sample of 4,000 children aged 3 and 4 years. The present paper presents the preliminary results of the "Osserviamo" project. METHODS: 600 parents of children between 39 and 50 months of age (divided in two age stages: 42 and 48 months) were contacted from 15 kindergarden schools. RESULTS: 23.35% of the whole sample scored in the risk range of at least one developmental area of the Ages and Stages Questionnaire-3rd Edition (ASQ-3) and 7.78% scored in the clinical range. Specifically, 23.97% of the children in the 42-month age stage scored in the risk range and 5.79% scored in the clinical range. Males scored lower than females in the fine motor skills and personal-social development domains. Moreover, 22.79% of the children in the 48-month age stage scored in the risk range, while 9.55% scored in the clinical range. Males scored lower than females in fine motor skills. CONCLUSION: Italian validation of the ASQ-3 and recruitment of all 4,000 participants will allow these data on the distribution of developmental disorders to be extended to the general Italian pediatric population. One main limitation of the study is the lack of clinical confirmation of the data yielded by the screening programme, which the authors aim to obtain in later stages of the study

Alexithymia and obesity: controversial findings from a multimethod assessment

OBJECTIVE: The aim of the study is to assess alexithymia levels in obese patients using a multimethod measurement (TAS-20 and TSIA) to evaluate both possible differences between the two instruments and their relationship with body weight. PATIENTS AND METHODS: 54 obese patients, seeking surgical treatment, were enrolled. They completed a socio-demographic questionnaire, 20-items Toronto Alexithymia Scale and the Toronto Structured Interview for Alexithymia. RESULTS: Data analysis showed a significant positive association between TAS-20 and TSIA total scores (r=.28, p<.05), but only the TSIA score was positively related to body weight (r=.39; p<.001). Multivariable linear regression models showed the predictive effects of TSIA total score (beta=.41; p<.001) and difficulty in identifying feelings (DIF) (beta=.56; p<.001) respectively on weight. CONCLUSIONS: The findings showed a different association between body weight and alexithymia according to the instrument employed to evaluate alexithymia, supporting the importance of a multimethod assessment in some clinical conditions

Services for Adults with an Autism Spectrum Disorder

Objective: The need for useful evidence about services is increasing as larger numbers of children identified with an autism spectrum disorder age toward adulthood. The objective of this review was to characterize the topical and methodological aspects of research on services for supporting success in work, education, and social participation among adults with an autism spectrum disorder and to propose recommendations for moving this area of research forward. Method: Review of literature published in English from 2000 to 2010.Results: We found that the evidence base about services for adults with an ASD is underdeveloped and can be considered a field of inquiry that is relatively unformed. Extant research does not reflect the demographic or impairment heterogeneity of the population, the range of services that adults with autism require in order to function with purposeful lives in the community, and the need for coordination across service systems and sectors. Conclusions: Future studies must examine issues related to cost and efficiency given the broader sociopolitical and economic context of service provision. Furthermore, future research needs to consider how demographic and impairment heterogeneity have implications for building an evidence base that will have greater external validity

Screening in semiconductor nanocrystals: \textit{Ab initio} results and Thomas-Fermi theory

A first-principles calculation of the impurity screening in Si and Ge nanocrystals is presented. We show that isocoric screening gives results in agreement with both the linear response and the point-charge approximations. Based on the present ab initio results, and by comparison with previous calculations, we propose a physical real-space interpretation of the several contributions to the screening. Combining the Thomas-Fermi theory and simple electrostatics, we show that it is possible to construct a model screening function that has the merit of being of simple physical interpretation. The main point upon which the model is based is that, up to distances of the order of a bond length from the perturbation, the charge response does not depend on the nanocrystal size. We show in a very clear way that the link between the screening at the nanoscale and in the bulk is given by the surface polarization. A detailed discussion is devoted to the importance of local field effects in the screening. Our first-principles calculations and the Thomas-Fermi theory clearly show that in Si and Ge nanocrystals, local field effects are dominated by surface polarization, which causes a reduction of the screening in going from the bulk down to the nanoscale. Finally, the model screening function is compared with recent state-of-the-art ab initio calculations and tested with impurity activation energies

Human and animal integrated influenza surveillance: a novel sampling approach for an additional transmission way in the aquatic bird reservoir.

Background: infectious low pathogenic avian influenza viruses (LPAIVs) have been recently detected on feathers of wild ducks. Laboratory trial results suggested that the preen oil gland secretion, covering waterbirds\u2019 feathers, may attract and concentrate virus particles from AIV-contaminated waters to birds\u2019 bodies. We evaluated whether ducks can become infected by the ingestion of preen oil-associated viral particles, experimentally smeared on their plumage. In addition, we compared virologic and serologic results obtained from mallards whose feathers were experimentally infected, with those from wild mallards naturally carrying AIVs on feathers. Methods: we experimentally coated 7 mallards (Anas plathyrynchos) using preen oil mixed with a LPAIV (H10N7 subtype), and housed them for 45 days with a control, uncoated duck. Cloacal, oropharyngeal and feather swabs were collected from all birds and examined for AIV molecular detection and isolation. Blood samples were also taken to detect influenza specific antibodies. In addition, sera from 10 wild mallards, carrying on feathers infectious LPAIV H10N7, were examined. Results: virologic and serologic results indicated that through self- and allopreening all the birds experimentally coated with the preen oil/AIV mix and the control duck ingested viruses covering feathers and became infected. Virus isolation from feathers was up to 32 days post-coating treatment. One out of 8 wild mallards showing antibodies against type A influenza virus was seropositive for H10 subtype too. Conclusions: our experimental and field results show evidences suggesting that uninfected birds carrying viruses on their feathers, including immune ones, might play an active role in spreading AIV infection in nature. For this reason, routine AIV surveillance programs, aimed at detecting intestinal and/or respiratory viruses, should include the collection of samples, such as feather swabs, enabling the detection of viruses sticky to preened birds\u2019 bodies

Pandemic influenza A/H1N1 virus in a swine farm house in Sicily, Italy

This report describes a pandemic A/H1N1 (H1N1 pdm) virus outbreak occurred in December, 2009 in a swine farm used as research facility (Istituto Mediterraneo Trapianti e Terapie ad Alta Specializzazione) for preclinical studies, located in Sicily, Italy. All the 13 pigs of the farm, showed cough, fever, inappetence and weakness. At the same time, an unvaccinated worker of the stabling showed influenza-like symptoms. RNAv extracted from two swabs collected from infected pigs resulted positive by Real Time RT-PCR for Influenza A virus. Furthermore, after growth on embryonated eggs, viral isolates were identified by Real Time RT-PCR specific for H1N1 pdm virus and characterized antigenically. Sequencing of the whole genome was also performed. All sera taken from animals and from the worker were tested by a competitive Influenza A ELISA and by the haemoagglutination inhibition test. Serological findings confirmed the circulation of influenza virus H1N1 pdm in pigs and the presence of specific antibodies against H1N1 pdm in human serum. The results of this study seem to support a H1N1 pdm transmission from man to animals showing the importance of serological and virological investigation to control the pig farms and the importance of close cooperation between the different authorities like veterinarian and human public. © 2012 Triveni Enterprises

The evolution of kicked stellar-mass black holes in star cluster environments - II. Rotating star clusters

In this paper, we continue our study on the evolution of black holes (BHs) that receive velocity kicks at the origin of their host star cluster potential. We now focus on BHs in rotating clusters that receive a range of kick velocities in different directions with respect to the rotation axis. We perform N-body simulations to calculate the trajectories of the kicked BHs and develop an analytic framework to study their motion as a function of the host cluster and the kick itself. Our simulations indicate that for a BH that is kicked outside of the cluster's core, as its orbit decays in a rotating cluster the BH will quickly gain angular momentum as it interacts with stars with high rotational frequencies. Once the BH decays to the point where its orbital frequency equals that of local stars, its orbit will be circular and dynamical friction becomes ineffective since local stars will have low relative velocities. After circularization, the BH's orbit decays on a longer time-scale than if the host cluster was not rotating. Hence BHs in rotating clusters will have longer orbital decay times. The time-scale for orbit circularization depends strongly on the cluster's rotation rate and the initial kick velocity, with kicked BHs in slowly rotating clusters being able to decay into the core before circularization occurs. The implication of the circularization phase is that the probability of a BH undergoing a tidal capture event increases, possibly aiding in the formation of binaries and high-mass BHs