12,883 research outputs found
Model studies of fluctuations in the background for jets in heavy ion collisions
Jets produced in high energy heavy ion collisions are quenched by the
production of the quark gluon plasma. Measurements of these jets are influenced
by the methods used to suppress and subtract the large, fluctuating background
and the assumptions inherent in these methods. We compare the measurements of
the background in Pb+Pb collisions at = 2.76 TeV by the ALICE
collaboration to calculations in TennGen (a data-driven random background
generator) and PYTHIA Angantyr. The standard deviation of the energy in random
cones in TennGen is approximately in agreement with the form predicted in the
ALICE paper, with deviations of 1-6 . The standard deviation of energy in
random cones in Angantyr exceeds the same predictions by approximately 40 .
Deviations in both models can be explained by the assumption that the single
particle is a Gamma distribution in the derivation of the
prediction. This indicates that model comparisons are potentially sensitive to
the treatment of the background
Monte Carlo simulation of HIV-1 evolution in response to selection by antibodies
Held in conjunction with the 16th International Parallel and Distributed Processing Symposium Copyright © 2002 IEEE – All Rights ReservedThe persistence of human immunodeficiency virus type 1 (HIV-1) infection may be in part attributed to its ability to evolve to evade neutralizing antibody (NAb) surveillance. We have tested the prediction that positive selection of V3 is positively correlated with the strength of a patient’s NAb response by analyzing a data set containing both sequences from the principal neutralizing domain of HIV-1 (V3) and measures of the strength of the NAb responses of several patients. Only viral sequences from the patient with the strongest NAb response exhibited evidence of significant positive selection. To investigate the nature of selection by NAbs, we simulated the evolution of V3 at the nucleotide level. Two forms of plausible NAb selection were used: negative frequency-dependent selection and negative viral-age-dependent selection. Assuming negative age-dependent selection rather than negative frequency-dependent selection better simulated the temporal pattern of V3 variation from the patient with the strongest NAb response.Jack da Silva; Austin Hughe
Multiphoton Processes in Driven Mesoscopic Systems
We study the statistics of multi-photon absorption/emission processes in a
mesoscopic ring threaded by an harmonic time-dependent flux . For this
sake, we demonstrate a useful analogy between the Keldysh quantum kinetic
equation for the electrons distribution function and a Continuous Time Random
Walk in energy space with corrections due to interference effects. Studying the
probability to absorb/emit quanta per scattering event, we
explore the crossover between ultra-quantum/low-intensity limit and
quasi-classical/high-intensity regime, and the role of multiphoton processes in
driving it.Comment: 6 pages, 5 figures, extended versio
Genetic analysis of members of the species Oropouche virus and identification of a novel M segment sequence
Oropouche virus (OROV) is a public health threat in South America, and in particular Northern Brazil, causing frequent outbreaks of febrile illness. Using a combination of deep sequencing and Sanger sequencing approaches we have determined complete genome sequences of eight clinical isolates that were obtained from patient sera during an Oropouche fever outbreak in Amapa state, northern Brazil in 2009. We also report complete genome sequences of two OROV reassortants isolated from two marmosets in Minas Gerais state, southeast Brazil in 2012 that contain a novel M genome segment. Interestingly, all ten isolates posses a 947 nucleotide long S segment that lacks 11 residues in the S segment 3' UTR compared to the recently redetermined Brazilian prototype OROV strain BeAn19991. OROV maybe circulating more widely in Brazil and in the non-human primate population than previously appreciated and the identification of yet another reassortant highlights the importance of bunyavirus surveillance in South America
Solution processable multi-channel ZnO nanowire field-effect transistors with organic gate dielectric
The present work focuses on nanowire (NW) applications as semiconducting elements in solution processable field-effect transistors (FETs) targeting large-area low-cost electronics. We address one of the main challenges related to NW deposition and alignment by using dielectrophoresis (DEP) to select multiple ZnO nanowires with the correct length, and to attract, orientate and position them in predefined substrate locations. High-performance top-gate ZnO NW FETs are demonstrated on glass substrates with organic gate dielectric layers and surround source–drain contacts. Such devices are hybrids, in which inorganic multiple single-crystal ZnO NWs and organic gate dielectric are synergic in a single system. Current–voltage (I–V) measurements of a representative hybrid device demonstrate excellent device performance with high on/off ratio of ~107, steep subthreshold swing (s-s) of ~400 mV/dec and high electron mobility of ~35 cm2 V−1 s−1 in N2 ambient. Stable device operation is demonstrated after 3 months of air exposure, where similar device parameters are extracted including on/off ratio of ~4 × 106, s-s ~500 mV/dec and field-effect mobility of ~28 cm2 V−1 s−1. These results demonstrate that DEP can be used to assemble multiples of NWs from solvent formulations to enable low-temperature hybrid transistor fabrication for large-area inexpensive electronics
Prospects for ACT: simulations, power spectrum, and non-Gaussian analysis
A new generation of instruments will reveal the microwave sky at high
resolution. We focus on one of these, the Atacama Cosmology Telescope, which
probes scales 1000<l<10000, where both primary and secondary anisotropies are
important. Including lensing, thermal and kinetic Sunyaev-Zeldovich (SZ)
effects, and extragalactic point sources, we simulate the telescope's
observations of the CMB in three channels, then extract the power spectra of
these components in a multifrequency analysis. We present results for various
cases, differing in assumed knowledge of the contaminating point sources. We
find that both radio and infrared point sources are important, but can be
effectively eliminated from the power spectrum given three (or more) channels
and a good understanding of their frequency dependence. However, improper
treatment of the scatter in the point source frequency dependence relation may
introduce a large systematic bias. Even if all thermal SZ and point source
effects are eliminated, the kinetic SZ effect remains and corrupts measurements
of the primordial slope and amplitude on small scales. We discuss the
non-Gaussianity of the one-point probability distribution function as a way to
constrain the kinetic SZ effect, and we develop a method for distinguishing
this effect from the CMB in a window where they overlap. This method provides
an independent constraint on the variance of the CMB in that window and is
complementary to the power spectrum analysis.Comment: 22 pages, 11 figures. Submitted to New Astronomy. High resolution
figures provided at
http://www.princeton.edu/~khuffenb/pubs/prospects-act.htm
Far infrared and Radio emission in dusty starburst galaxies
We revisit the nature of the FIR/Radio correlation by means of the most
recent models for star forming galaxies. We model the IR emission with our
population synthesis code, GRASIL (Silva et al. 1998). As for the radio
emission, we revisit the simple model of Condon & Yin (1990). We find that a
tightFIR/Radio correlation is natural when the synchrotron mechanism dominates
over the inverse Compton, and the electrons cooling time is shorter than the
fading time of the supernova rate. Observations indicate that both these
conditions are met in star forming galaxies. However since the radio non
thermal emission is delayed, deviations are expected both in the early phases
of a starburst, when the radio thermal component dominates, and in the
post-starburst phase, when the bulk of the NT component originates from less
massive stars. This delay allows the analysis of obscured starbursts with a
time resolution of a few tens of Myrs, unreachable with other star formation
indicators. We suggest to complement the analysis of the deviations from the
FIR/Radio correlation with the radio slope to obtain characteristic parameters
of the burst. The analysis of a sample of compact ULIRGs shows that they are
intense but transient starbursts, to which one should not apply usual SF
indicators devised for constant SF rates. We also discuss the possibility of
using the q- radio slope diagram to asses the presence of obscured AGN. A firm
prediction of the models is an apparent radio excess during the post-starburst
phase, which seems to be typical of a class of star forming galaxies in rich
cluster cores. We discuss how deviations from the correlation, due to the
evolutionary status of the starburst, affect the technique of photometric
redshift determination widely used for high-z sources.Comment: accepted by A&A, 16 page
Urban integration of aeroelastic belt for low-energy wind harvesting
In this modern age low-energy devices are pervasive especially when considering their applications in the built-environment. The multitude of low-energy applications extend from wireless sensors, radio-frequency transceivers, charging devices, cameras and other small-scale electronic devices. The energy consumptions of these devices range in the milliwatt and microwatt scale which is a result of continuous development of these technologies. Thus, renewable wind energy harnessed from the aeroelastic effect can play a pivotal role in providing sufficient power for extended operation with little or no battery replacement. An aeroelastic belt is a simple device composed of a tensioned membrane coupled to electromagnetic coils and power conditioning components. This simplicity of the aeroelastic belt translates to its low cost and overall modularity. The aim of this study is to investigate the potential of integrating the aeroelastic belt into the built environment using Computational Fluid Dynamics (CFD) simulations. The work will investigate the effect of various external conditions (wind speed, wind direction and physical parameters, positioning and sizing) on the performance of the aeroelastic belt. The results from this study can be used for the design and integration of low-energy wind generation technologies into buildings
Recommended from our members
A multi-approach and multi-scale study on water quantity and quality changes in the Tapajós River basin, Amazon
We analyzed changes in water quantity and quality at different spatial scales within the Tapajós River
basin (Amazon) based on experimental fieldwork, hydrological modelling, and statistical time-trend analysis.
At a small scale, we compared the river discharge (Q) and suspended-sediment concentrations (SSC) of two
adjacent micro-catchments ( < 1 km2) with similar characteristics but contrasting land uses (forest vs. pasture)
using empirical data from field measurements. At an intermediary scale, we simulated the hydrological responses
of a sub-basin of the Tapajós (Jamanxim River basin, 37 400 km2), using a hydrological model (SWAT) and
land-use change scenario in order to quantify the changes in the water balance components due to deforestation.
At the Tapajós’ River basin scale, we investigated trends in Q, sediments, hydrochemistry, and geochemistry
in the river using available data from the HYBAM Observation Service. The results in the micro-catchments
showed a higher runoff coefficient in the pasture (0.67) than in the forest catchment (0.28). At this scale, the SSC
were also significantly greater during stormflows in the pasture than in the forest catchment. At the Jamanxim
watershed scale, the hydrological modelling results showed a 2 % increase in Q and a 5 % reduction of baseflow
contribution to total Q after a conversion of 22 % of forest to pasture. In the Tapajós River, however, trend
analysis did not show any significant trend in discharge and sediment concentration. However, we found upward
trends in dissolved organic carbon and NO− 3 over the last 20 years. Although the magnitude of anthropogenic
impact has shown be scale-dependent, we were able to find changes in the Tapajós River basin in streamflow,
sediment concentration, and water quality across all studied scales
- …