246 research outputs found
Train of high-power femtosecond pulses: Probe wave in a gas of prepared atoms
We present a new method for generating a regular train of ultrashort optical
pulses in a prepared two-level medium. The train develops from incident
monochromatic probe radiation travelling in a medium of atoms, which are in a
quantum mechanical superposition of dressed internal states. In the frame of
used linear theory for the probe radiation, the energy of individual pulses is
an exponentially growing function of atom density and of interaction cross
section. Pulse repetition rate is determined by the generalized Rabi frequency
and can be around 1 THz and greater. We also show that the terms, extra to the
dipole approximation, endow the gas by a new property: non-saturating
dependence of refractive index on the dressing monochromatic field intensity.
Contribution of these nonsaturating terms can be compatible with the main
dipole approximation in the wavelength region of about ten micrometers (the
range of CO_2 laser) or larger
Validating a prediction tool to determine the risk of nosocomial multidrug-resistant Gram-negative bacilli infection in critically ill patients: A retrospective case–control study
BACKGROUND:The Singapore GSDCS score was developed to enable clinicians predict the risk of nosocomial multidrug-resistant Gram-negative bacilli (RGNB) infection in critically ill patients. We aimed to validate this score in a UK setting. METHOD:A retrospective case-control study was conducted including patients who stayed for more than 24h in intensive care units (ICUs) across two tertiary National Health Service hospitals in London, UK (April 2011-April 2016). Cases with RGNB and controls with sensitive Gram-negative bacilli (SGNB) infection were identified. RESULTS:The derived GSDCS score was calculated from when there was a step change in antimicrobial therapy in response to clinical suspicion of infection as follows: prior Gram-negative organism, Surgery, Dialysis with end-stage renal disease, prior Carbapenem use and intensive care Stay of more than 5 days. A total of 110 patients with RGNB infection (cases) were matched 1:1 to 110 geotemporally chosen patients with SGNB infection (controls). The discriminatory ability of the prediction tool by receiver operating characteristic curve analysis in our validation cohort was 0.75 (95% confidence interval 0.65-0.81), which is comparable with the area under the curve of the derivation cohort (0.77). The GSDCS score differentiated between low- (0-1.3), medium- (1.4-2.3) and high-risk (2.4-4.3) patients for RGNB infection (P<0.001) in a UK setting. CONCLUSION:A simple bedside clinical prediction tool may be used to identify and differentiate patients at low, medium and high risk of RGNB infection prior to initiation of prompt empirical antimicrobial therapy in the intensive care setting
Pervasive sensing to model political opinions in face-to-face networks
Exposure and adoption of opinions in social networks are
important questions in education, business, and government. We de-
scribe a novel application of pervasive computing based on using mobile
phone sensors to measure and model the face-to-face interactions and
subsequent opinion changes amongst undergraduates, during the 2008
US presidential election campaign. We nd that self-reported political
discussants have characteristic interaction patterns and can be predicted
from sensor data. Mobile features can be used to estimate unique individ-
ual exposure to di erent opinions, and help discover surprising patterns
of dynamic homophily related to external political events, such as elec-
tion debates and election day. To our knowledge, this is the rst time
such dynamic homophily e ects have been measured. Automatically esti-
mated exposure explains individual opinions on election day. Finally, we
report statistically signi cant di erences in the daily activities of individ-
uals that change political opinions versus those that do not, by modeling
and discovering dominant activities using topic models. We nd people
who decrease their interest in politics are routinely exposed (face-to-face)
to friends with little or no interest in politics.U.S. Army Research Laboratory (Cooperative Agreement No. W911NF-09-2-0053)United States. Air Force Office of Scientific Research (Award No. FA9550-10-1-0122)Swiss National Science Foundatio
Investment Opportunity Set, Product Mix, and the Relationship between Bank CEO Compensation and Risk-Taking
Multi-level evidence of an allelic hierarchy of USH2A variants in hearing, auditory processing and speech/language outcomes.
Language development builds upon a complex network of interacting subservient systems. It therefore follows that variations in, and subclinical disruptions of, these systems may have secondary effects on emergent language. In this paper, we consider the relationship between genetic variants, hearing, auditory processing and language development. We employ whole genome sequencing in a discovery family to target association and gene x environment interaction analyses in two large population cohorts; the Avon Longitudinal Study of Parents and Children (ALSPAC) and UK10K. These investigations indicate that USH2A variants are associated with altered low-frequency sound perception which, in turn, increases the risk of developmental language disorder. We further show that Ush2a heterozygote mice have low-level hearing impairments, persistent higher-order acoustic processing deficits and altered vocalizations. These findings provide new insights into the complexity of genetic mechanisms serving language development and disorders and the relationships between developmental auditory and neural systems
Axelrod’s metanorm games on networks
Metanorms is a mechanism proposed to promote cooperation in social dilemmas. Recent experimental results show that
network structures that underlie social interactions influence the emergence of norms that promote cooperation. We
generalize Axelrod’s analysis of metanorms dynamics to interactions unfolding on networks through simulation and
mathematical modeling. Network topology strongly influences the effectiveness of the metanorms mechanism in
establishing cooperation. In particular, we find that average degree, clustering coefficient and the average number of
triplets per node play key roles in sustaining or collapsing cooperationSpanish MICINN projects CSD2010-00034 (CONSOLIDER-INGENIO 2010) and DPI2010-16920, and by the Junta de Castilla y
Leo´ n, references BU034A08 and GREX251-2009
Will ocean acidification affect marine microbes?
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in The ISME Journal 5 (2011): 1-7, doi:10.1038/ismej.2010.79.The pH of the surface ocean is changing as a result of increases in
atmospheric carbon dioxide (CO2) and there are concerns about potential
impacts of lower pH and associated alterations in seawater carbonate
chemistry on the biogeochemical processes in the ocean. However, it is
important to place these changes within the context of pH in the present day
ocean, which is not constant; it varies systematically with season, depth and
along productivity gradients. Yet this natural variability in pH has rarely been
considered in assessments of the effect of ocean acidification on marine
microbes. Surface pH can change as a consequence of microbial utilisation
and production of carbon dioxide, and to a lesser extent other microbiallymediated
processes such as nitrification. Useful comparisons can be made
with microbes in other aquatic environments that readily accommodate very
large and rapid pH change. For example, in many freshwater lakes, pH changes
that are orders of magnitude greater than those projected for the 22nd century
oceans can occur over periods of hours. Marine and freshwater assemblages
have always experienced variable pH conditions. Therefore, an appropriate null
hypothesis may be, until evidence is obtained to the contrary, that major
biogeochemical processes in the oceans other than calcification will not be
fundamentally different under future higher CO2 / lower pH conditions.Funding from the Gordon and Betty Moore Foundation, and logistical support from
the Plymouth Marine Laboratory and the Center for Microbial Oceanography:
Research and Education (National Science Foundation grant EF-0424599) are
gratefully acknowledged
The impact of the North Atlantic Oscillation on the uptake and accumulation of anthropogenic CO2 by North Atlantic Ocean mode waters
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 25 (2011): GB3022, doi:10.1029/2010GB003892.The North Atlantic Ocean accounts for about 25% of the global oceanic anthropogenic carbon sink. This basin experiences significant interannual variability primarily driven by the North Atlantic Oscillation (NAO). A suite of biogeochemical model simulations is used to analyze the impact of interannual variability on the uptake and storage of contemporary and anthropogenic carbon (Canthro) in the North Atlantic Ocean. Greater winter mixing during positive NAO years results in increased mode water formation and subsequent increases in subtropical and subpolar Canthro inventories. Our analysis suggests that changes in mode water Canthro inventories are primarily due to changes in water mass volumes driven by variations in water mass transformation rates rather than local air-sea CO2 exchange. This suggests that a significant portion of anthropogenic carbon found in the ocean interior may be derived from surface waters advected into water formation regions rather than from local gas exchange. Therefore, changes in climate modes, such as the NAO, may alter the residence time of anthropogenic carbon in the ocean by altering the rate of water mass transformation. In addition, interannual variability in Canthro storage increases the difficulty of Canthro detection and attribution through hydrographic observations, which are limited by sparse sampling of subsurface waters in time and space.We would like to acknowledge funding
from the NOAA Climate Program under the Office of Climate Observations
and Global Carbon Cycle Program (NOAA‐NA07OAR4310098),
NSF (OCE‐0623034), NCAR, the WHOI Ocean Climate Institute, a
National Defense Science and Engineering Graduate Fellowship and an
Environmental Protection Agency STAR graduate fellowship. NCAR is
sponsored by the National Science Foundation
Analysis of the genetic phylogeny of multifocal prostate cancer identifies multiple independent clonal expansions in neoplastic and morphologically normal prostate tissue.
Genome-wide DNA sequencing was used to decrypt the phylogeny of multiple samples from distinct areas of cancer and morphologically normal tissue taken from the prostates of three men. Mutations were present at high levels in morphologically normal tissue distant from the cancer, reflecting clonal expansions, and the underlying mutational processes at work in morphologically normal tissue were also at work in cancer. Our observations demonstrate the existence of ongoing abnormal mutational processes, consistent with field effects, underlying carcinogenesis. This mechanism gives rise to extensive branching evolution and cancer clone mixing, as exemplified by the coexistence of multiple cancer lineages harboring distinct ERG fusions within a single cancer nodule. Subsets of mutations were shared either by morphologically normal and malignant tissues or between different ERG lineages, indicating earlier or separate clonal cell expansions. Our observations inform on the origin of multifocal disease and have implications for prostate cancer therapy in individual cases
How non-native English-speaking staff are evaluated in linguistically diverse organizations: A sociolinguistic perspective
The aim of this paper is to examine the effects of evaluations of non-native speaking staff?s spoken English in international business settings. We adopt a sociolinguistic perspective on power and inequalities in linguistically diverse organizations in an Anglophone environment. The interpretive qualitative study draws on 54 interviews with non-native English-speaking staff in 19 UK business schools. We analyze, along the dimensions of status, solidarity and dynamism, the ways in which non-native speakers, on the basis of their spoken English, are evaluated by themselves and by listeners. We show how such evaluations refer to issues beyond the speaker?s linguistic fluency, and have consequences for her or his actions. The study contributes to the literature on language and power in international business through offering fine-grained insights into and elucidating how the interconnected evaluative processes impact the formation and perpetuation of organizational power relations and inequalities. It also puts forward implications for managing the officially monolingual, yet linguistically diverse organizations
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