The Multidimensional Study of Viral Campaigns as Branching Processes

Viral campaigns on the Internet may follow variety of models, depending on the content, incentives, personal attitudes of sender and recipient to the content and other factors. Due to the fact that the knowledge of the campaign specifics is essential for the campaign managers, researchers are constantly evaluating models and real-world data. The goal of this article is to present the new knowledge obtained from studying two viral campaigns that took place in a virtual world which followed the branching process. The results show that it is possible to reduce the time needed to estimate the model parameters of the campaign and, moreover, some important aspects of time-generations relationship are presented.Comment: In proceedings of the 4th International Conference on Social Informatics, SocInfo 201

Declining performance of master athletes:silhouettes of the trajectory of healthy human ageing?

Analysis of world record performances by master athletes suggests an essentially linear decline with age until around the eighth decade after which performance decline accelerates. Because these records are obtained from highly trained individuals they can be viewed as being reflective of the diminution of integrative physiological prowess that occurs solely as a result of ageing, unaffected by the confounding effects of inactivity. It can also be argued that these performance profiles mirror and provide an insight into the trajectory of the physiology of the human ageing process. Here we propose a set point theory that hypothesises that a given threshold of physical activity is needed to age optimally and to maximise the ‘healthspan’. Exercising at levels below the set point will result in ageing being contaminated by the unpredictable and pathological effects of inactivity. Exercise above this threshold stimulates adaptations towards maximising athletic performance, but is unlikely to have further beneficial effects on health. Thus the decades-long, controlled diminution in athletic performance, should not be seen as a disease process. The ageing process is separate from, and independent of, exercise-mediated processes that maintain or adapt physiological function. Whether an understanding of these mechanisms will also help uncover mechanisms underpinning the ageing process itself is open to question. However, any model which does not take into account the effects of activity will not adequately describe the inherent ageing process. (Figure presented.).</p

Neutron background in large-scale xenon detectors for dark matter searches

Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (alpha,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of $10^{-9}-10^{-10}$ pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector.Comment: 35 pages, 13 figures, 2 tables, accepted for publication in Astroparticle Physic

Search for electroweak production of single top quarks in ppˉp\bar{p} collisions.

We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb. (arXiv

An fMRI investigation of the relationship between future imagination and cognitive flexibility

While future imagination is largely considered to be a cognitive process grounded in default mode network activity, studies have shown that future imagination recruits regions in both default mode and frontoparietal control networks. In addition, it has recently been shown that the ability to imagine the future is associated with cognitive flexibility, and that tasks requiring cognitive flexibility result in increased coupling of the default mode network with frontoparietal control and salience networks. In the current study, we investigated the neural correlates underlying the association between cognitive flexibility and future imagination in two ways. First, we experimentally varied the degree of cognitive flexibility required during future imagination by manipulating the disparateness of episodic details contributing to imagined events. To this end, participants generated episodic details (persons, locations, objects) within three social spheres; during fMRI scanning they were presented with sets of three episodic details all taken from the same social sphere (Congruent condition) or different social spheres (Incongruent condition) and required to imagine a future event involving the three details. We predicted that, relative to the Congruent condition, future simulation in the Incongruent condition would be associated with increased activity in regions of the default mode, frontoparietal and salience networks. Second, we hypothesized that individual differences in cognitive flexibility, as measured by performance on the Alternate Uses Task, would correspond to individual differences in the brain regions recruited during future imagination. A task partial least squares (PLS) analysis showed that the Incongruent condition resulted in an increase in activity in regions in salience networks (e.g. the insula) but, contrary to our prediction, reduced activity in many regions of the default mode network (including the hippocampus). A subsequent functional connectivity (within-subject seed PLS) analysis showed that the insula exhibited increased coupling with default mode regions during the Incongruent condition. Finally, a behavioral PLS analysis showed that individual differences in cognitive flexibility were associated with differences in activity in a number of regions from frontoparietal, salience and default-mode networks during both future imagination conditions, further highlighting that the cognitive flexibility underlying future imagination is grounded in the complex interaction of regions in these networks

Racial Differences in Physical and Mental Health

This article examines the extent to which racial differences in socio-economic status (SES), social class and acute and chronic indicators of perceived discrimination, as well as general measures of stress can account for black-white differences in self-reported measures of physical and mental health. The observed racial differences in health were markedly reduced when adjusted for education and especially income. However, both perceived discrimination and more traditional measures of stress are related to health and play an incremental role in accounting for differences between the races in health status. These findings underscore the need for research efforts to identify the complex ways in which economic and non-economic forms of discrimination relate to each other and combine with socio-economic position and other risk factors and resources to affect health.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67159/2/10.1177_135910539700200305.pd

CUORE: An experiment to investigate for neutrinoless double beta decay by cooling 750 kg of TeO\u3csub\u3e2\u3c/sub\u3e crystals at 10 mK

CUORE (Cryogenic Underground Observatory for Rare Events) is an experiment proposed to infer the effective Majorana mass of the electron neutrino from measurements on neutrinoless double beta decay (0νDBD). The goal of CUORE is to achieve a background rate in the range 0.001 to 0.01 counts/keV/kg/y at the 0νDBD transition energy of 130Te (2528 keV). The proposed experiment, to be mounted in the underground Gran Sasso INFN National Laboratory, Italy, is realized by cooling about 1000 TeO2 bolometers, of 750 g each, at a temperature of 10mK. We will describe the experiment, to be cooled by an extremely powerful dilution refrigerator, operating with no liquid helium, and the main experimental features designed to assure the predicted sensitivity. We present moreover the last results of a small scale (40.7 kg) 0νDBD experiment carried on in the Gran Sasso Laboratory (CUORICINO)

Radio frequency and DC high voltage breakdown of high pressure helium, argon, and xenon

Motivated by the possibility of guiding daughter ions from double beta decay events to single-ion sensors for barium tagging, the NEXT collaboration is developing a program of R&D to test radio frequency (RF) carpets for ion transport in high pressure xenon gas. This would require carpet functionality in regimes at higher pressures than have been previously reported, implying correspondingly larger electrode voltages than in existing systems. This mode of operation appears plausible for contemporary RF-carpet geometries due to the higher predicted breakdown strength of high pressure xenon relative to low pressure helium, the working medium in most existing RF carpet devices. In this paper we present the first measurements of the high voltage dielectric strength of xenon gas at high pressure and at the relevant RF frequencies for ion transport (in the 10 MHz range), as well as new DC and RF measurements of the dielectric strengths of high pressure argon and helium gases at small gap sizes. We find breakdown voltages that are compatible with stable RF carpet operation given the gas, pressure, voltage, materials and geometry of interest

Status and prospects for CUORE

CUORE is a cryogenic detector consisting of 988 TeO2 crystals, 750 g each, and will be operated at a temperature of ~10 mK, to search for neutrinoless double beta decay (0¿ßß) of 130Te. The detector, in the final stages of construction at the Laboratori Nazionali del Gran Sasso (Italy), will start its operations in 2016. CUORE-0, its pilot experiment, has proven the feasibility of CUORE, demonstrating that the target background of 0.01 counts/keV/kg/y and the energy resolution of 5 keV are within reach. CUORE-0 also made the most precise measurement of the 2¿ßß decay. The expected sensitivity of CUORE to the 0¿ßß 130Te half-life is 9 •1025y, for 5 years of data taking. Here, we report the most recent results of CUORE-0, their implications for CUORE, and the current status of the CUORE experiment