2,219 research outputs found
The Effect of absorbing sites on the one-dimensional cellular automaton traffic flow with open boundaries
The effect of the absorbing sites with an absorbing rate , in both
one absorbing site (one way out) and two absorbing sites (two ways out) in a
road, on the traffic flow phase transition is investigated using numerical
simulations in the one-dimensional cellular automaton traffic flow model with
open boundaries using parallel dynamics.In the case of one way out, there exist
a critical position of the way out below which the current is
constant for and decreases when increasing
for . When the way out is located at a
position greater than , the current increases with for
and becomes constant for any value of
greater than . While, when the way out is located at any position
between and (), the current increases,
for , with and becomes constant for
and decreases with for
. In the later case the density undergoes two
successive first order transitions; from high density to maximal current phase
at and from intermediate density to the low one at
. In the case of two ways out located respectively
at the positions and , the two successive transitions occur
only when the distance - separating the two ways is smaller than
a critical distance . Phase diagrams in the (),
() and () planes are established. It is found
that the transitions between Free traffic, Congested traffic and maximal
current phase are first order
Mean field theory and Monte Carlo simulation of Phase transitions and Magnetic Properties of a tridimensional Fe7S8 Compound
The structural, electronic and magnetic properties of Fe7S8 material have
been studied within the framework of the ab-initio calculations, the mean field
approximation (MFA) and Monte Carlo simulation (MCS). Our study shows that two
forms of the iron atoms, Fe2+ with spin S=2, and Fe3+ with spin {\sigma}=5/2
are the most probable configurations. A mixed Ising model with ferromagnetic
spin coupling between Fe2+ and Fe3+ ions and between Fe3+ and Fe3+ ions, and
with antiferromagnetic spin coupling between Fe2+ ions of adjacent layers has
been used to study the magnetic properties of this compound. We demonstrated
that the magnetic phase transition can be either of the first or of the second
order, depending on the value of the exchange interaction and crystal field.
The presence of vacancies in every second iron layer leads to incomplete
cancellation of magnetic moments, hence to the emergence of the ferrimagnetism.
Anomalies in the magnetization behavior have been found and compared with the
experimental results.Comment: 18 pages, 14 Figures, 4 Table
Study of Zn O,S Films grown by Aerosol Assisted Chemical Vapour Deposition and their Application as Buffer Layers in Cu In,Ga S,Se 2 Solar Cells
To reduce the use of toxic and expensive elements in chalcopyrite thin film solar cells, materials such as cadmium or indium used in buffer layers need to be substituted. Zn O,S is considered to be a potential buffer layer material when deposited with a fast and inexpensive method. Zn O,S layers have been prepared by aerosol assisted chemical vapour deposition AACVD technique. AACVD technique is a simple non vacuum process where the thin film deposition temperatures do not exceed 250 C. 10 mM spray solution was made by dissolving zinc II acetylacetonate monohydrate in ethanol. The films were grown on Mo substrate at 225 C film growth temperature . The effect of deposition parameters spray solution concentration, N2 flow rate, H2S flow rate on Zn O,S thin film properties were studied with SEM and XRD. Thereupon optimizing the deposition parameters, homogeneous and compact Zn O,S thin films were obtained and the films were employed in the chalcopyrite thin film solar cell structure by growing films on Cu In,Ga S,Se 2 substrates industrially produced by BOSCH Solar CISTech GmbH. The resulting cells were studied using current voltage and quantum efficiency analysis and compared with solar cell references that include In2S3 and CdS as buffer layer deposited by ion layer gas reaction and chemical bath deposition, respectively. The best output of the solar cell containing Zn O,S as buffer layer and without intrinsic ZnO under standard test conditions AM 1.5G, 100 mW cm2, 25 C is Voc 573 mV, Jsc 39.2 mA cm2, FF 68.4 and efficiency of 15.4 being slightly better than the In2S3 or CdS containing solar cell reference
THE USE OF NATURAL MATERIALS FOR THE TREATMENT OF LEACHATES OF THE AGADIR DUMP
Within the perspective of adopting effective solutions to the problems related to the burial of urban waste and its resulting harmful effects on both the environment and the human health, suitable actions should be taken to remedy the shortcomings of this somehow primitive method of waste disposal, namely those of the generated leachates. Because of their high pollutant load, leachates have to undergo a treatment of purification before being discharged into the environment.The focus of our study is to develop a simple technique to reduce the pollutant load of leachates in the technical burying center (TBC) of solid waste in Tamellast, Grand Agadir. This technique is based on the treatment of leachates through aeration followed by a percolation-infiltration on sand. The sand used is raw titaniferous sand (RTS) which is very abundant in the region of Agadir. Young leachate samples issued from fresh urban waste were collected at TBC, Tamellast. The physicochemical analyses of the young leachates show that their pH is very acidic, the values of conductivity are very important and greatly exceed the normal limit value specified for the discharges (2.7 mS / cm). The levels of biodegradable organic matter are important (the COD and BOD5 values are 17800 mg of O2 / L and 9100 mg of O2 / L, respectively). The aeration of leachate by injecting air has increased electrical conductivity due to the different chemical and biological reactions involved in the treatment. However, the values of COD and BOD5 have decreased. This decrease shows the significant effect of aeration on the reduction of polluting organic matter. The ratio BOD5 / COD is greater than 0.5 and shows that the treated leachate is of a very good biodegradability. After aeration, the young leachate was infiltrated by percolation on a sand column. The BOD5 value reached 280 mg of O2 / L (the BOD5 limit value of direct discharge = 300 mg of O2 / L) and the COD value is 540 mg of O2 / L (the limit value of direct release COD = 600 mg of O2 / L). The technique developed in this study led to high abatement rates (96.96% for COD and 97% for BOD5) in organic matter and lower COD and BOD5 values
Weight misperception and psychological symptoms from adolescence to young adulthood: longitudinal study of an ethnically diverse UK cohort.
BACKGROUND: To evaluate the association between weight misperception and psychological symptoms in the Determinants of young Adults Social well-being and Health (DASH) longitudinal study. METHODS: A longitudinal sample of 3227 adolescents, in 49 secondary schools in London, aged 11-16 years participated in 2002/2003 and were followed up in 2005/2006. A sub-sample (N = 595) was followed up again at ages 21-23 years in 2012/2013. An index of weight misperception was derived from weight perception and measured weight. Psychological well- being was measured using the Strengths and Difficulties Questionnaire at 11-16 years and the General Health Questionnaire at 21-23 years. Associations with weight misperception was assessed using regression models, adjusted for socio-economic and lifestyle factors. RESULTS: White British males and females were more likely than ethnic minority peers to report accurate perceptions of measured weight. At 11-13y, 46% females and 38% males did not have an accurate perception of their measured weight. The comparable figures at 14-16y were 42 and 40%. Compared with male adolescents, more females perceived themselves as overweight or were unsure of their weight but measured normal weight, and this was more pronounced among Indians, Pakistanis and Bangladeshis. At 14-16y, more males perceived themselves as underweight but measured normal weight, and this was more pronounced among Indians. Compared with those who had an accurate perception of their normal weight, a higher likelihood of probable clinically-relevant psychological symptoms was observed among those who measured normal weight but perceived themselves to be underweight (females Odds Ratio (OR) = 1.87 95% CI 1.03-3.40; males OR = 2.34 95% CI 1.47-3.71), overweight (females only OR = 2.06 95% CI 1.10-3.87), or unsure of their weight (males only OR = 1.61 95% CI 1.04-2.49). Among females, the association was driven by internalising rather than externalising symptoms. An accurate perception of overweight was associated with higher psychological symptoms in adolescence and early 20s. Ethnic specific effects were not evident. CONCLUSION: Weight misperception may be an important determinant of psychological symptoms in young people, with an accurate perception of normal weight status being protective. Culturally targeted interventions should be considered to promote healthy perceptions of body image
Combined In Silico, In Vivo, and In Vitro Studies Shed Insights into the Acute Inflammatory Response in Middle-Aged Mice
We combined in silico, in vivo, and in vitro studies to gain insights into age-dependent changes in acute inflammation in response to bacterial endotoxin (LPS). Time-course cytokine, chemokine, and NO2-/NO3- data from "middle-aged" (6-8 months old) C57BL/6 mice were used to re-parameterize a mechanistic mathematical model of acute inflammation originally calibrated for "young" (2-3 months old) mice. These studies suggested that macrophages from middle-aged mice are more susceptible to cell death, as well as producing higher levels of pro-inflammatory cytokines, vs. macrophages from young mice. In support of the in silico-derived hypotheses, resident peritoneal cells from endotoxemic middle-aged mice exhibited reduced viability and produced elevated levels of TNF-α, IL-6, IL-10, and KC/CXCL1 as compared to cells from young mice. Our studies demonstrate the utility of a combined in silico, in vivo, and in vitro approach to the study of acute inflammation in shock states, and suggest hypotheses with regard to the changes in the cytokine milieu that accompany aging. © 2013 Namas et al
Emotional persistence in online chatting communities
How do users behave in online chatrooms, where they instantaneously read and
write posts? We analyzed about 2.5 million posts covering various topics in
Internet relay channels, and found that user activity patterns follow known
power-law and stretched exponential distributions, indicating that online chat
activity is not different from other forms of communication. Analysing the
emotional expressions (positive, negative, neutral) of users, we revealed a
remarkable persistence both for individual users and channels. I.e. despite
their anonymity, users tend to follow social norms in repeated interactions in
online chats, which results in a specific emotional "tone" of the channels. We
provide an agent-based model of emotional interaction, which recovers
qualitatively both the activity patterns in chatrooms and the emotional
persistence of users and channels. While our assumptions about agent's
emotional expressions are rooted in psychology, the model allows to test
different hypothesis regarding their emotional impact in online communication.Comment: 34 pages, 4 main and 12 supplementary figure
A hyperbolic slicing condition adapted to Killing fields and densitized lapses
We study the properties of a modified version of the Bona-Masso family of
hyperbolic slicing conditions. This modified slicing condition has two very
important features: In the first place, it guarantees that if a spacetime is
static or stationary, and one starts the evolution in a coordinate system in
which the metric coefficients are already time independent, then they will
remain time independent during the subsequent evolution, {\em i.e.} the lapse
will not evolve and will therefore not drive the time lines away from the
Killing direction. Second, the modified condition is naturally adapted to the
use of a densitized lapse as a fundamental variable, which in turn makes it a
good candidate for a dynamic slicing condition that can be used in conjunction
with some recently proposed hyperbolic reformulations of the Einstein evolution
equations.Comment: 11 page
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