10,918 research outputs found
Driven low density granular mixtures
We study the steady state properties of a 2D granular mixture in the presence
of energy driving by employing simple analytical estimates and Direct
Simulation Monte Carlo. We adopt two different driving mechanisms: a) a
homogeneous heat bath with friction and b) a vibrating boundary (thermal or
harmonic) in the presence of gravity. The main findings are: the appearance of
two different granular temperatures, one for each species; the existence of
overpopulated tails in the velocity distribution functions and of non trivial
spatial correlations indicating the spontaneous formation of cluster
aggregates. In the case of a fluid subject to gravity and to a vibrating
boundary, both densities and temperatures display non uniform profiles along
the direction normal to the wall, in particular the temperature profiles are
different for the two species while the temperature ratio is almost constant
with the height. Finally, we obtained the velocity distributions at different
heights and verified the non gaussianity of the resulting distributions.Comment: 19 pages, 12 figures, submitted for publicatio
Critical properties of Ising model on Sierpinski fractals. A finite size scaling analysis approach
The present paper focuses on the order-disorder transition of an Ising model
on a self-similar lattice. We present a detailed numerical study, based on the
Monte Carlo method in conjunction with the finite size scaling method, of the
critical properties of the Ising model on some two dimensional deterministic
fractal lattices with different Hausdorff dimensions. Those with finite
ramification order do not display ordered phases at any finite temperature,
whereas the lattices with infinite connectivity show genuine critical behavior.
In particular we considered two Sierpinski carpets constructed using different
generators and characterized by Hausdorff dimensions d_H=log 8/log 3 = 1.8927..
and d_H=log 12/log 4 = 1.7924.., respectively.
The data show in a clear way the existence of an order-disorder transition at
finite temperature in both Sierpinski carpets.
By performing several Monte Carlo simulations at different temperatures and
on lattices of increasing size in conjunction with a finite size scaling
analysis, we were able to determine numerically the critical exponents in each
case and to provide an estimate of their errors.
Finally we considered the hyperscaling relation and found indications that it
holds, if one assumes that the relevant dimension in this case is the Hausdorff
dimension of the lattice.Comment: 21 pages, 7 figures; a new section has been added with results for a
second fractal; there are other minor change
AGB and SAGB stars: modelling dust production at solar metallicity
We present dust yields for asymptotic giant branch (AGB) and
super--asymptotic giant branch (SAGB) stars of solar metallicity. Stars with
initial mass reach the carbon
star stage during the AGB phase and produce mainly solid carbon and SiC. The
size and the amount of the carbon particles formed follows a positive trend
with themass of the star; the carbon grains with the largest size (m) are produced by AGB stars with ,
as these stars are those achieving the largest enrichment of carbon in the
surface regions. The size of SiC grains, being sensitive to the surface silicon
abundance, keeps around m. The mass of carbonaceous
dust formed is in the range , whereas the
amount of SiC produced is . Massive
AGB/SAGB stars with experience HBB, that inhibits
formation of carbon stars. The most relevant dust species formed in these stars
are silicates and alumina dust, with grain sizes in the range m and m, respectively. The
mass of silicates produced spans the interval and increases with the initial
mass of the star.Comment: Accepted for publication in MNRA
Pseudo-critical clusterization in nuclear multifragmentation
In this contribution we show that the biggest fragment charge distribution in
central collisions of Xe+Sn leading to multifragmentation is an admixture of
two asymptotic distributions observed for the lowest and highest bombarding
energies. The evolution of the relative weights of the two components with
bombarding energy is shown to be analogous to that observed as a function of
time for the largest cluster produced in irreversible aggregation for a finite
system. We infer that the size distribution of the largest fragment in nuclear
multifragmentation is also characteristic of the time scale of the process,
which is largely determined by the onset of radial expansion in this energy
range.Comment: 4 pages, 3 figures, Contribution to conference proceedings of the
25th International Nuclear Physics Conference (INPC 2013
Oral malodor in Special Care Patients: current knowledge
Epidemiological studies report that about 50% of the population may have oral malodor
with a strong social and psychological impact in their daily life. When intra-oral causes are
excluded, referral to an appropriate medical specialist is paramount for management and
treatment of extra-oral causes. The intra-oral causes of halitosis are highly common, and the
dentist is the central clinician to diagnose and treat them. Pseudohalitosis or halitophobia
may occur and an early identification of these conditions by the dentist is important in order
to avoid unnecessary dental treatments for patients who need psychological or psychiatric
therapy. The organoleptic technique is still considered the most reliable examination method
to diagnose genuine halitosis. Special needs patients are more prone than others to have
oral malodor because of concurrent systemic or metabolic diseases, and medications.
The present report reviews halitosis, its implications, and the management in special care
dentistry
Incidence of the Ventilation Holes and the Mechanical Ventilation Systems of Façade on the Noise Insulation
This study will assess the influence on the acoustic insulation of façade of small elements such as ventilation holes or mechanical ventilation systems. These elements are present to ensure an appropriate air exchange, and they can be with or without heat recovery units. The noise insulation of façade, taking into account such ventilation holes, was evaluated starting from the calculations carried in accordance with the procedures laid down by the standard EN 12354 and performing measurements concerning specific case studies
A Soluble Phase Field Model
The kinetics of an initially undercooled solid-liquid melt is studied by
means of a generalized Phase Field model, which describes the dynamics of an
ordering non-conserved field phi (e.g. solid-liquid order parameter) coupled to
a conserved field (e.g. thermal field). After obtaining the rules governing the
evolution process, by means of analytical arguments, we present a discussion of
the asymptotic time-dependent solutions. The full solutions of the exact
self-consistent equations for the model are also obtained and compared with
computer simulation results. In addition, in order to check the validity of the
present model we confronted its predictions against those of the standard Phase
field model and found reasonable agreement. Interestingly, we find that the
system relaxes towards a mixed phase, depending on the average value of the
conserved field, i.e. on the initial condition. Such a phase is characterized
by large fluctuations of the phi field.Comment: 13 pages, 8 figures, RevTeX 3.1, submitted to Physical Review
Pre-exposure to an electrical stimulus primes associative pairing of audio and electrical stimuli for dairy heifers in a virtual fencing feed attractant trial
This experiment examined whether pre-exposure to an electrical stimulus from electric fencing attenuates associative pairing of audio and electrical stimuli in dairy heifers. Two treatments were applied to 30 weaned heifers naive to electric fencing. Heifers in the ‘electric-fence’ treatment were exposed to an electrified perimeter fence and two periods of strip-grazing using electrified poly-wire. Control heifers remained naïve to electric fencing. The pairing of audio and electrical stimuli was assessed in a feed attractant trial using manually controlled training collars. Heifers received an audio stimulus (2 s; 84 dB) when they breached a virtual fence after which a short electrical stimulus (0.5 s; 120 mW) was administered if they continued to move forward. If the animal stopped moving forward no further stimuli were applied. By the third training session, electric-fence heifers received a lower proportion of electrical stimuli than control heifers (p = 0.03). The more exploratory interactions a heifer had with the electric fence, the lower the proportion of electrical stimuli she received during training (rs = −0.77, p = 0.002). We conclude that experience with electrical fencing enhanced the salience of the electrical stimulus delivered by manual collars used for virtual fence training
Toward a Definition of the Linguistic Profile of Children With Autism Spectrum Disorder
The current investigation assessed linguistic and narrative abilities in a cohort of children with Autism Spectrum Disorder (ASD). The linguistic assessment was performed with both traditional tests and a multilevel procedure for discourse analysis. The results showed difficulties at different stages of message planning, organization, and microlinguistic processing (i.e., lexical selection and grammatical processing). Their macrolinguistic impairments were likely related to more general difficulties in the prelinguistic conceptual phase of message planning and mental model generation. Such weaknesses included a difficulty in the non-verbal conceptualization of the story and the generation of an internal representation of the addressee\u2019s mental model
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