412 research outputs found
Comparative study of screened inter-layer interactions in the Coulomb drag effect in bilayer electron systems
Coulomb drag experiments in which the inter-layer resistivity is measured are
important as they provide information on the Coulomb interactions in bilayer
systems. When the layer densities are low correlation effects become
significant to account for the quantitative description of experimental
results. We investigate systematically various models of effective inter-layer
interactions in a bilayer system and compare our results with recent
experiments. In the low density regime, the correlation effects are included
via the intra- and inter-layer local-field corrections. We employ several
theoretical approaches to construct static local-field corrections. Our
comparative study demonstrates the importance of including the correlation
effects accurately in the calculation of drag resistivity. Recent experiments
performed at low layer densities are adequately described by effective
inter-layer interactions incorporating static correlations.Comment: Final Version. To appear in Phys. Rev.
Effects of roughness on droplet apparent contact angles on a fiber
This paper reports on our investigation of the effects of surface roughness on the equilibrium shape and apparent contact angles of a droplet deposited on a fiber. In particular, the shape of a droplet on a roughened fiber is studied via the energy minimization method implemented in the surface evolver finite element code. Sinusoidal roughness varying in both the longitudinal and radial directions is considered in the simulations to study the effects of surface roughness on the most stable shape of a droplet on a fiber (corresponding a global minimum energy state). It is found that surface roughness delays droplet shape transition from a symmetric barrel to a clamshell or an asymmetric barrel profile. A phase diagram that includes the effects of fiber roughness on droplet configurations-symmetric barrel, clamshell, and asymmetric barrel-is presented for the first time. It is also found that droplet apparent contact angle tends to decrease on rough fibers. Likewise, roughness tends to increase the force required to detach a droplet from a fiber but the effect diminishes as droplet size increases relative to the size of surface roughness. The results presented in our study have been compared with experimental data or those from prior studies whenever possible, and good agreement has been observed
Restoration of Rotational Symmetry in the Continuum Limit of Lattice Field Theories
We explore how rotational invariance is systematically recovered from
calculations on hyper-cubic lattices through the use of smeared lattice
operators that smoothly evolve into continuum operators with definite angular
momentum as the lattice-spacing is reduced. Perturbative calculations of the
angular momentum violation associated with such operators at tree-level and at
one-loop are presented in phi^4 theory and QCD. Contributions from these
operators that violate rotational invariance occur at tree-level, with
coefficients that are suppressed by O(a^2) in the continuum limit. Quantum
loops do not modify this behavior in phi^4, nor in QCD if the gauge-fields are
smeared over a comparable spatial region. Consequently, the use of this type of
operator should, in principle, allow for Lattice QCD calculations of the higher
moments of the hadron structure functions.Comment: 35 pages, 10 figures; v2: added references and one footnot
Hard-core Yukawa model for two-dimensional charge stabilized colloids
The hyper-netted chain (HNC) and Percus-Yevick (PY) approximations are used
to study the phase diagram of a simple hard-core Yukawa model of
charge-stabilized colloidal particles in a two-dimensional system. We calculate
the static structure factor and the pair distribution function over a wide
range of parameters. Using the statics correlation functions we present an
estimate for the liquid-solid phase diagram for the wide range of the
parameters.Comment: 7 pages, 9figure
Improved battery life for context awareness application in smart-phones
The new smart-phones with new operating system and portable sensors support the basis for context awareness systems and applications for handling user activity and user privacy. Nowadays, individuals need new services and real time information anywhere and anytime. Context awareness is an emerging service, which could be able to improve the user experiences in current situation. Context awareness can be considered as location, calendar, user activity and etc. The review of the literature proves that context awareness in mobile phone can be useful and studied as unavoidable service in next generation of smart-phone applications. In this paper, a short review about context awareness in mobile phone is studied, furthermore, we critically analyzed related works of context awareness in smart-phones. The review shows that the most important context in mobile phone is location, which is mostly obtained by using Global Positioning System (GPS) sensor in mobile phones but GPS can significantly increases battery consumption in mobile phones. In this regard, a framework as Improved Battery life in Context Awareness System (IBCS) is proposed to improve battery life and reduce cost of using GPS in context awareness applications based on smart-phones. The review argues the weakness and strength of these studies, and aims to (a) indicate the most important context in mobile phone, (b) reduce the battery consumption of GPS sensor in mobile phone
Correlation energy of a two-dimensional electron gas from static and dynamic exchange-correlation kernels
We calculate the correlation energy of a two-dimensional homogeneous electron
gas using several available approximations for the exchange-correlation kernel
entering the linear dielectric response of the system.
As in the previous work of Lein {\it et al.} [Phys. Rev. B {\bf 67}, 13431
(2000)] on the three-dimensional electron gas, we give attention to the
relative roles of the wave number and frequency dependence of the kernel and
analyze the correlation energy in terms of contributions from the plane. We find that consistency of the kernel with the electron-pair
distribution function is important and in this case the nonlocality of the
kernel in time is of minor importance, as far as the correlation energy is
concerned. We also show that, and explain why, the popular Adiabatic Local
Density Approximation performs much better in the two-dimensional case than in
the three-dimensional one.Comment: 9 Pages, 4 Figure
Non-relativistic bound states in a finite volume
We derive general results for the mass shift of bound states with angular
momentum l >= 1 in a periodic cubic box in two and three spatial dimensions.
Our results have applications to lattice simulations of hadronic molecules,
halo nuclei, and Feshbach molecules. The sign of the mass shift can be related
to the symmetry properties of the state under consideration. We verify our
analytical results with explicit numerical calculations. Moreover, we comment
on the relations connecting the effective range parameter, the binding momentum
of a given state and the asymptotic normalization coefficient of the
corresponding wave function. We give explicit expressions for this relation in
the shallow binding limit.Comment: 26 pages, 4 figure
Low rank perturbations and the spectral statistics of pseudointegrable billiards
We present an efficient method to solve Schr\"odinger's equation for
perturbations of low rank. In particular, the method allows to calculate the
level counting function with very little numerical effort. To illustrate the
power of the method, we calculate the number variance for two pseudointegrable
quantum billiards: the barrier billiard and the right triangle billiard
(smallest angle ). In this way, we obtain precise estimates for the
level compressibility in the semiclassical (high energy) limit. In both cases,
our results confirm recent theoretical predictions, based on periodic orbit
summation.Comment: 4 page
Evaluation of Chest and Abdominal Injuries in Trauma Patients Hospitalized in the Surgery Ward of Poursina Teaching Hospital, Guilan, Iran
Background: Trauma, especially chest and abdominal trauma are increasing due to the growing number of vehicles on the roads, which leads to an increased incidence of road accidents. Urbanization, industrialization and additional problems are the other associated factors which accelerate this phenomenon. A better understanding of the etiology and pattern of such injuries can help to improve the management and ultimate the outcomes of these patients.
Objectives: This study aimed to evaluate the patients with chest and abdominal trauma hospitalized in the surgery ward of Poursina teaching hospital, Guilan, Iran.
Patients and Methods: In this cross-sectional study, the data of all chest and abdominal trauma patients hospitalized in the surgery ward of Poursina teaching hospital were collected from March 2011 to March 2012. Information about age, gender, injured areas, type of injury (penetrating or blunt), etiology of the injury, accident location (urban or rural) and patients\' discharge outcomes were collected by a questionnaire.
Results: In total, 211 patients with a mean age of 34.1 ± 1.68 years was entered into the study. The most common cause of trauma was traffic accidents (51.7%). Among patients with chest trauma, 45 cases (35.4%) had penetrating injuries and 82 cases (64.6%) blunt lesions. The prevalence of chest injuries was 35.5% and rib fractures 26.5%. In chest injuries, the prevalence of hemothorax was 65.3%, pneumothorax 2.7%, lung contusion 4% and emphysema 1.3%, respectively. There were 24 cases (27.9%) with abdominal trauma which had penetrating lesions and 62 cases (72.1%) with blunt lesions. The most common lesions in patients with penetrating abdominal injuries were spleen (24.2%) and liver (12.1%) lesions. The outcomes of the patients were as follow: 95.7% recovery and 4.3% death. The majority of deaths were observed among road traffic victims (77.7%).
Conclusions: Considering the fact that road-related accidents are quite predictable and controllable; therefore, the quality promotion of traumatic patients\' care, and the road safety should be noted as problems associated with public health
Chlamydia trachomatis in women with full-term deliveries and women with abortion
Problem statement: There are some documents which support the role of some certain infections such as Chlamydia trachomatis in spontaneous abortion. As there were not data about role this bacterium in abortion in this area of IRAN, this study was conducted to evaluate the prevalence of Chlamydia trachomatis in women with abortion and compare it with healthy women with no previous history of abortion. Approach: This case-control study was carried out in Shariatee hospital of Hormozgan University of medical sciences, during 2004-2005. A number of 220 women with definite diagnosis of previous abortion and 200 matched women with normal full term delivery and negative history of miscarriage as controls were studied as case and control groups. All obtained PAP smears from the case and the control groups were then tested using Immunoflourescent method for detection of Chlamydia trachomatis. Data was analyzed, using SPSS software (chi square and t-test). Results: The prevalence of positive direct immunofluorescent test on PAP smears indicating the presence of Chlamydia trachomatis was 56 (25.45) in women with abortion comparing to 13 (5.20) in women in control group, the difference was significant (p = 0.0001). Conclusion: This study showed Chlamydia trachomatis is an important causative agent for abortion in this area of IRAN. © 2010 Science Publications
- …