7,783 research outputs found
Can the nuclear symmetry potential at supra-saturation densities be negative?
In the framework of an Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU)
transport model, for the central Au+Au reaction at an incident
beam energy of 400 MeV/nucleon, effect of nuclear symmetry potential at
supra-saturation densities on the pre-equilibrium clusters emission is studied.
It is found that for the positive symmetry potential at supra-saturation
densities the neutron to proton ratio of lighter clusters with mass number
() is larger than that of the weighter clusters with
mass number (), whereas for the negative symmetry potential
at supra-saturation densities the is \emph{smaller} than that
of the . This may be considered as a probe of the negative
symmetry potential at supra-saturation densities.Comment: 5 pages, 3 figures, 1 table, to be publishe
Large QCD at non-zero chemical potential
The general issue of large QCD at nonzero chemical potential is
considered with a focus on understanding the difference between large QCD
with an isospin chemical potential and large QCD with a baryon chemical
potential. A simple diagrammatic analysis analogous to `t Hooft's analysis at
implies that the free energy with a given baryon chemical potential is
equal to the free energy with an isospin chemical potential of the same value
plus corrections. Phenomenologically, these two systems behave quite
differently. A scenario to explain this difference in light of the diagrammatic
analysis is explored. This scenario is based on a phase transition associated
with pion condensation when the isospin chemical potential exceeds ;
associated with this transition there is breakdown of the expansion--in
the pion condensed phase there is a distinct expansion including a
larger set of diagrams. While this scenario is natural, there are a number of
theoretical issues which at least superficially challenge it. Most of these can
be accommodated. However, the behavior of quenched QCD which raises a number of
apparently analogous issues cannot be easily understood completely in terms of
an analogous scenario. Thus, the overall issue remains open
Intranasal Inhalation of Oxytocin Improves Face Processing in Developmental Prosopagnosia
Developmental prosopagnosia (DP) is characterised by a severe, lifelong impairment in face recognition. Little work has attempted to improve face processing in these individuals, but intriguingly, recent evidence suggests oxytocin can improve face processing in both healthy participants and individuals with autism. This study examined whether oxytocin could also improve face processing in individuals with DP. Ten adults with the condition and 10 matched controls were tested using a randomized placebo-controlled double-blind within-subject experimental design (AB-BA). Each participant took part in two testing sessions where they inhaled 24IU of oxytocin or placebo spray and completed two face processing tests: one assessing face memory and the other face perception. Results showed main effects of both participant group and treatment condition in both face processing tests, but the two did not interact. Specifically, the performance of DP participants was significantly lower than control performance under both oxytocin and placebo conditions, but oxytocin improved processing to a similar extent in both groups
The Effect of the Hall Term on the Nonlinear Evolution of the Magnetorotational Instability: I. Local Axisymmetric Simulations
The effect of the Hall term on the evolution of the magnetorotational
instability (MRI) in weakly ionized accretion disks is investigated using local
axisymmetric simulations. First, we show that the Hall term has important
effects on the MRI when the temperature and density in the disk is below a few
thousand K and between 10^13 and 10^18 cm^{-3} respectively. Such conditions
can occur in the quiescent phase of dwarf nova disks, or in the inner part
(inside 10 - 100 AU) of protoplanetary disks. When the Hall term is important,
the properties of the MRI are dependent on the direction of the magnetic field
with respect to the angular velocity vector \Omega. If the disk is threaded by
a uniform vertical field oriented in the same sense as \Omega, the axisymmetric
evolution of the MRI is an exponentially growing two-channel flow without
saturation. When the field is oppositely directed to \Omega, however, small
scale fluctuations prevent the nonlinear growth of the channel flow and the MRI
evolves into MHD turbulence. These results are anticipated from the
characteristics of the linear dispersion relation. In axisymmetry on a field
with zero-net flux, the evolution of the MRI is independent of the size of the
Hall term relative to the inductive term. The evolution in this case is
determined mostly by the effect of ohmic dissipation.Comment: 31 pages, 3 tables, 12 figures, accepted for publication in ApJ,
postscript version also available from
http://www.astro.umd.edu/~sano/publications
External and internal noise surveys of London primary schools
Internal and external noise surveys have been carried out around schools in London, UK, to provide information on typical levels and sources to which children are exposed while at school. Noise levels were measured outside 142 schools, in areas away from flightpaths into major airports. 86% of the schools surveyed were exposed to noise from road traffic, the average external noise level outside a school being 57 dB LAeq. Detailed internal noise surveys have been carried out in 140 classrooms in 16 schools, together with classroom observations. It was found that noise levels inside classrooms depend upon the activities in which the children are engaged, with a difference of 20 dB LAeq between the 'quietest' and 'noisiest' activities. The average background noise level in classrooms exceeds the level recommended in current standards. The number of children in the classroom was found to affect noise levels. External noise influenced internal noise levels only when children were engaged in the quietest classroom activities. The effects of the age of the school buildings and types of window upon internal noise were examined but results were inconclusive
Learning From Early Attempts to Generalize Darwinian Principles to Social Evolution
Copyright University of Hertfordshire & author.Evolutionary psychology places the human psyche in the context of evolution, and addresses the Darwinian processes involved, particularly at the level of genetic evolution. A logically separate and potentially complementary argument is to consider the application of Darwinian principles not only to genes but also to social entities and processes. This idea of extending Darwinian principles was suggested by Darwin himself. Attempts to do this appeared as early as the 1870s and proliferated until the early twentieth century. But such ideas remained dormant in the social sciences from the 1920s until after the Second World War. Some lessons can be learned from this earlier period, particularly concerning the problem of specifying the social units of selection or replication
Connection between inner jet kinematics and broadband flux variability in the BL Lac object S5 0716+714
We present a high-frequency very long baseline interferometry (VLBI)
kinematical study of the BL Lac object S5 0716+714 over the time period of
September 2008 to October 2010. The aim of the study is to investigate the
relation of the jet kinematics to the observed broadband flux variability. We
find significant non-radial motions in the jet outflow of the source. In the
radial direction, the highest measured apparent speed is \sim37 c, which is
exceptionally high, especially for a BL Lac object. Patterns in the jet flow
reveal a roughly stationary feature \sim0.15 mas downstream of the core. The
long-term fits to the component trajectories reveal acceleration in the sub-mas
region of the jet. The measured brightness temperature, T_{B}, follows a
continuous trend of decline with distance, T_B \propto
r_{jet}^{-(2.36\pm0.41)}, which suggests a gradient in Doppler factor along the
jet axis. Our analysis suggest that a moving disturbance (or a shock wave) from
the base of the jet produces the high-energy (optical to \gamma-ray) variations
upstream of the 7 mm core, and then later causes an outburst in the core.
Repetitive optical/\gamma-ray flares and the curved trajectories of the
associated components suggest that the shock front propagates along a bent
trajectory or helical path. Sharper \gamma-ray flares could be related to the
passage of moving disturbances through the stationary feature. Our analysis
suggests that the \gamma-ray and radio emission regions have different Doppler
factors.Comment: 12 pages, 8 figures, accepted for publication in A&
Development of a regional glycerol dialkyl glycerol tetraether (GDGT) temperature calibration for Antarctic and sub-Antarctic lakes
Satisfying due-dates in the presence of sequence dependent family setups with a special comedown structure
Cataloged from PDF version of article.This paper addresses a static, n-job, single-machine scheduling problem with sequence dependent family setups. The
setup matrix follows a special structure where a constant setup is required only if a job from a smaller indexed family
is an immediate successor of one from a larger indexed family. The objective is to minimize the maximum lateness (Lmax).
A two-step neighborhood search procedure and an implicit enumeration scheme are proposed. Both procedures exploit the
problem structure. The enumeration scheme produces optimum solutions to small and medium sized problems in
reasonable computational times, yet it fails to perform efficiently in larger instances. Computational results show that
the heuristic procedure is highly effective, and is efficient even for extremely large problems.
2006 Elsevier Ltd. All rights reserved
- …