593 research outputs found
Twitter-based analysis of the dynamics of collective attention to political parties
Large-scale data from social media have a significant potential to describe
complex phenomena in real world and to anticipate collective behaviors such as
information spreading and social trends. One specific case of study is
represented by the collective attention to the action of political parties. Not
surprisingly, researchers and stakeholders tried to correlate parties' presence
on social media with their performances in elections. Despite the many efforts,
results are still inconclusive since this kind of data is often very noisy and
significant signals could be covered by (largely unknown) statistical
fluctuations. In this paper we consider the number of tweets (tweet volume) of
a party as a proxy of collective attention to the party, identify the dynamics
of the volume, and show that this quantity has some information on the
elections outcome. We find that the distribution of the tweet volume for each
party follows a log-normal distribution with a positive autocorrelation of the
volume over short terms, which indicates the volume has large fluctuations of
the log-normal distribution yet with a short-term tendency. Furthermore, by
measuring the ratio of two consecutive daily tweet volumes, we find that the
evolution of the daily volume of a party can be described by means of a
geometric Brownian motion (i.e., the logarithm of the volume moves randomly
with a trend). Finally, we determine the optimal period of averaging tweet
volume for reducing fluctuations and extracting short-term tendencies. We
conclude that the tweet volume is a good indicator of parties' success in the
elections when considered over an optimal time window. Our study identifies the
statistical nature of collective attention to political issues and sheds light
on how to model the dynamics of collective attention in social media.Comment: 16 pages, 7 figures, 3 tables. Published in PLoS ON
A reverse engineering approach to the suppression of citation biases reveals universal properties of citation distributions
The large amount of information contained in bibliographic databases has
recently boosted the use of citations, and other indicators based on citation
numbers, as tools for the quantitative assessment of scientific research.
Citations counts are often interpreted as proxies for the scientific influence
of papers, journals, scholars, and institutions. However, a rigorous and
scientifically grounded methodology for a correct use of citation counts is
still missing. In particular, cross-disciplinary comparisons in terms of raw
citation counts systematically favors scientific disciplines with higher
citation and publication rates. Here we perform an exhaustive study of the
citation patterns of millions of papers, and derive a simple transformation of
citation counts able to suppress the disproportionate citation counts among
scientific domains. We find that the transformation is well described by a
power-law function, and that the parameter values of the transformation are
typical features of each scientific discipline. Universal properties of
citation patterns descend therefore from the fact that citation distributions
for papers in a specific field are all part of the same family of univariate
distributions.Comment: 9 pages, 6 figures. Supporting information files available at
http://filrad.homelinux.or
Universality, limits and predictability of gold-medal performances at the Olympic Games
Inspired by the Games held in ancient Greece, modern Olympics represent the
world's largest pageant of athletic skill and competitive spirit. Performances
of athletes at the Olympic Games mirror, since 1896, human potentialities in
sports, and thus provide an optimal source of information for studying the
evolution of sport achievements and predicting the limits that athletes can
reach. Unfortunately, the models introduced so far for the description of
athlete performances at the Olympics are either sophisticated or unrealistic,
and more importantly, do not provide a unified theory for sport performances.
Here, we address this issue by showing that relative performance improvements
of medal winners at the Olympics are normally distributed, implying that the
evolution of performance values can be described in good approximation as an
exponential approach to an a priori unknown limiting performance value. This
law holds for all specialties in athletics-including running, jumping, and
throwing-and swimming. We present a self-consistent method, based on normality
hypothesis testing, able to predict limiting performance values in all
specialties. We further quantify the most likely years in which athletes will
breach challenging performance walls in running, jumping, throwing, and
swimming events, as well as the probability that new world records will be
established at the next edition of the Olympic Games.Comment: 8 pages, 3 figures, 1 table. Supporting information files and data
are available at filrad.homelinux.or
Behavioural Correlate of Choice Confidence in a Discrete Trial Paradigm
How animals make choices in a changing and often uncertain environment is a central theme in the behavioural sciences. There is a substantial literature on how animals make choices in various experimental paradigms but less is known about the way they assess a choice after it has been made in terms of the expected outcome. Here, we used a discrete trial paradigm to characterise how the reward history shaped the behaviour on a trial by trial basis. Rats initiated each trial which consisted of a choice between two drinking spouts that differed in their probability of delivering a sucrose solution. Critically, sucrose was delivered after a delay from the first lick at the spouts â this allowed us to characterise the behavioural profile during the window between the time of choice and its outcome. Rats' behaviour converged to optimum choice, both during the acquisition phase and after the reversal of contingencies. We monitored the post-choice behaviour at a temporal precision of 1 millisecond; lick-response profiles revealed that rats spent more time at the spout with the higher reward probability and exhibited a sparser lick pattern. This was the case when we exclusively examined the unrewarded trials, where the outcome was identical. The differential licking profiles preceded the differential choice ratios and could thus predict the changes in choice behaviour
Activation of Human T-Helper/Inducer Cell, T-Cytotoxic Cell, B-Cell, and Natural Killer (NK)-Cells and induction of Natural Killer Cell Activity against K562 Chronic Myeloid Leukemia Cells with Modified Citrus Pectin
<p>Abstract</p> <p>Background</p> <p>Modified citrus pectin (MCP) is known for its anti-cancer effects and its ability to be absorbed and circulated in the human body. In this report we tested the ability of MCP to induce the activation of human blood lymphocyte subsets like T, B and NK-cells.</p> <p>Methods</p> <p>MCP treated human blood samples were incubated with specific antibody combinations and analyzed in a flow cytometer using a 3-color protocol. To test functionality of the activated NK-cells, isolated normal lymphocytes were treated with increasing concentrations of MCP. Log-phase PKH26-labeled K562 leukemic cells were added to the lymphocytes and incubated for 4 h. The mixture was stained with FITC-labeled active form of caspase 3 antibody and analyzed by a 2-color flow cytometry protocol. The percentage of K562 cells positive for PKH26 and FITC were calculated as the dead cells induced by NK-cells. Monosaccharide analysis of the MCP was performed by high-performance anion-exchange chromatography with pulse amperometric detection (HPAEC-PAD).</p> <p>Results</p> <p>MCP activated T-cytotoxic cells and B-cell in a dose-dependent manner, and induced significant dose-dependent activation of NK-cells. MCP-activated NK-cells demonstrated functionality in inducing cancer cell death. MCP consisted of oligogalacturonic acids with some containing 4,5-unsaturated non-reducing ends.</p> <p>Conclusions</p> <p>MCP has immunostimulatory properties in human blood samples, including the activation of functional NK cells against K562 leukemic cells in culture. Unsaturated oligogalacturonic acids appear to be the immunostimulatory carbohydrates in MCP.</p
Single-Spin Addressing in an Atomic Mott Insulator
Ultracold atoms in optical lattices are a versatile tool to investigate
fundamental properties of quantum many body systems. In particular, the high
degree of control of experimental parameters has allowed the study of many
interesting phenomena such as quantum phase transitions and quantum spin
dynamics. Here we demonstrate how such control can be extended down to the most
fundamental level of a single spin at a specific site of an optical lattice.
Using a tightly focussed laser beam together with a microwave field, we were
able to flip the spin of individual atoms in a Mott insulator with
sub-diffraction-limited resolution, well below the lattice spacing. The Mott
insulator provided us with a large two-dimensional array of perfectly arranged
atoms, in which we created arbitrary spin patterns by sequentially addressing
selected lattice sites after freezing out the atom distribution. We directly
monitored the tunnelling quantum dynamics of single atoms in the lattice
prepared along a single line and observed that our addressing scheme leaves the
atoms in the motional ground state. Our results open the path to a wide range
of novel applications from quantum dynamics of spin impurities, entropy
transport, implementation of novel cooling schemes, and engineering of quantum
many-body phases to quantum information processing.Comment: 8 pages, 5 figure
The impact of change in a doctor's job position: a five-year cohort study of job satisfaction among Norwegian doctors
<p>Abstract</p> <p>Background</p> <p>Job satisfaction among physicians may be of importance to their individual careers and their work with patients. We lack prospective studies on whether a change in a doctor's job position influences their job satisfaction over a five-year period if we control for other workload factors.</p> <p>Methods</p> <p>A longitudinal national cohort of all physicians who graduated in Norway in 1993 and 1994 was surveyed by postal questionnaire in 2003 (T1) and 2008 (T2). Outcomes were measured with a 10-item job satisfaction scale. Predictor variables in a multiple regression model were: change in job position, reduction in work-home interface stress, reduction in work hours, age, and gender.</p> <p>Results</p> <p>A total of 59% of subjects (306/522) responded at both time points. The mean value of job satisfaction in the total sample increased from 51.6 (SD = 9.0) at T1 to 53.4 (SD = 8.2) at T2 (paired <it>t </it>test, <it>t </it>= 3.8, <it>p </it>< 0.001). The major groups or positions at T1 were senior house officers (45%), chief specialists in hospitals (23%), and general practitioners (17%), and the latter showed the highest levels of job satisfaction. Physicians who changed position during the period (n = 176) experienced an increase in job satisfaction from 49.5 (SD = 8.4) in 2003 to 52.9 (SD = 7.5) in 2008 (paired <it>t </it>test, <it>t </it>= 5.2, <it>p </it>< 0.001). Job satisfaction remained unchanged for physicians who stayed in the same position. There was also an increase in satisfaction among those who changed from positions other than senior house officer at T1 (<it>p </it>< 0.01). The significant adjusted predictor variables in the multiple regression model were the change in position from senior house officer at T1 to any other position (β = 2.83, <it>p </it>< 0.001), any change in job position (from any position except SHO at T1) (β = 4.18, <it>p </it>< 0.01) and reduction in work-home interface stress (β = 1.04, <it>p </it>< 0.001).</p> <p>Conclusions</p> <p>The physicians experienced an increase in job satisfaction over a five-year period, which was predicted by a change in job position and a reduction in work-home stress. This study has implications with respect to career advice for young doctors.</p
A Bayesian approach to modelling heterogeneous calcium responses in cell populations
Calcium responses have been observed as spikes of the whole-cell calcium concentration in numerous cell types and are essential for translating extracellular stimuli into cellular responses. While there are several suggestions for how this encoding is achieved, we still lack a comprehensive theory. To achieve this goal it is necessary to reliably predict the temporal evolution of calcium spike sequences for a given stimulus. Here, we propose a modelling framework that allows us to quantitatively describe the timing of calcium spikes. Using a Bayesian approach, we show that Gaussian processes model calcium spike rates with high fidelity and perform better than standard tools such as peri-stimulus time histograms and kernel smoothing. We employ our modelling concept to analyse calcium spike sequences from dynamically-stimulated HEK293T cells. Under these conditions, different cells often experience diverse stimuli time courses, which is a situation likely to occur in vivo. This single cell variability and the concomitant small number of calcium spikes per cell pose a significant modelling challenge, but we demonstrate that Gaussian processes can successfully describe calcium spike rates in these circumstances. Our results therefore pave the way towards a statistical description of heterogeneous calcium oscillations in a dynamic environmen
Effectiveness of interventions to improve the health and housing status of homeless people: a rapid systematic review
Background: Research on interventions to positively impact health and housing status of people who are homeless has received substantially increased attention over the past 5 years. This rapid review examines recent evidence regarding interventions that have been shown to improve the health of homeless people, with particular
focus on the effect of these interventions on housing status.
Methods: A total of 1,546 articles were identified by a structured search of five electronic databases, a hand search of grey literature and relevant journals, and contact with experts. Two reviewers independently screened the first 10% of titles and abstracts for relevance. Inter-rater reliability was high and as a result only one reviewer screened the remaining titles and abstracts. Articles were included if they were published between January 2004 and December 2009 and examined the effectiveness of an intervention to improve the health or healthcare utilization
of people who were homeless, marginally housed, or at risk of homelessness. Two reviewers independently scored all relevant articles for quality.
Results: Eighty-four relevant studies were identified; none were of strong quality while ten were rated of moderate quality. For homeless people with mental illness, provision of housing upon hospital discharge was effective in improving sustained housing. For homeless people with substance abuse issues or concurrent
disorders, provision of housing was associated with decreased substance use, relapses from periods of substance abstinence, and health services utilization, and increased housing tenure. Abstinent dependent housing was more effective in supporting housing status, substance abstinence, and improved psychiatric outcomes than non-abstinence dependent housing or no housing. Provision of housing also improved health outcomes among homeless populations with HIV. Health promotion programs can decrease risk behaviours among homeless populations.
Conclusions: These studies provide important new evidence regarding interventions to improve health, housing status, and access to healthcare for homeless populations. The additional studies included in this current review provide further support for earlier evidence which found that coordinated treatment programs for homeless
persons with concurrent mental illness and substance misuse issues usually result in better health and access to healthcare than usual care. This review also provides a synthesis of existing evidence regarding interventions that specifically support homeless populations with HIV.Partial funding for this paper was provided to the Effective Public Health Practice Project by the Region of Peel, Canada
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