Quantum gravitational optics in the field of a gravitomagnetic monopole

Vacuum polarization in QED in a background gravitational field induces interactions which {\it effectively} modify the classical picture of light rays as the null geodesics of spacetime. After a short introduction on the main aspects of the quantum gravitational optics, as a nontrivial example, we study this effect in the background of NUT space characterizing the spacetime of a spherical mass endowed with a gravitomagnetic monopole charge, the so called NUT factor.Comment: 9 pages, title changed and the text abridged for publication in the Journal of Physics: Conference serie

New bounds on the signed total domination number of graphs

In this paper, we study the signed total domination number in graphs and present new sharp lower and upper bounds for this parameter. For example by making use of the classic theorem of Turan, we present a sharp lower bound on this parameter for graphs with no complete graph of order r+1 as a subgraph. Also, we prove that n-2(s-s') is an upper bound on the signed total domination number of any tree of order n with s support vertices and s' support vertives of degree two. Moreover, we characterize all trees attainig this bound.Comment: This paper contains 11 pages and one figur

Thermodynamics and Phase Transitions of Electrolytes on Lattices with Different Discretization Parameters

Lattice models are crucial for studying thermodynamic properties in many physical, biological and chemical systems. We investigate Lattice Restricted Primitive Model (LRPM) of electrolytes with different discretization parameters in order to understand thermodynamics and the nature of phase transitions in the systems with charged particles. A discretization parameter is defined as a number of lattice sites that can be occupied by each particle, and it allows to study the transition from the discrete picture to the continuum-space description. Explicit analytic and numerical calculations are performed using lattice Debye-H\"{u}ckel approach, which takes into account the formation of dipoles, the dipole-ion interactions and correct lattice Coulomb potentials. The gas-liquid phase separation is found at low densities of charged particles for different types of lattices. The increase in the discretization parameter lowers the critical temperature and the critical density, in agreement with Monte Carlo computer simulations results. In the limit of infinitely large discretization our results approach the predictions from the continuum model of electrolytes. However, for the very fine discretization, where each particle can only occupy one lattice site, the gas-liquid phase transitions are suppressed by order-disorder phase transformations.Comment: Submitted to Molecular Physic

Detecting Singleton Review Spammers Using Semantic Similarity

Online reviews have increasingly become a very important resource for consumers when making purchases. Though it is becoming more and more difficult for people to make well-informed buying decisions without being deceived by fake reviews. Prior works on the opinion spam problem mostly considered classifying fake reviews using behavioral user patterns. They focused on prolific users who write more than a couple of reviews, discarding one-time reviewers. The number of singleton reviewers however is expected to be high for many review websites. While behavioral patterns are effective when dealing with elite users, for one-time reviewers, the review text needs to be exploited. In this paper we tackle the problem of detecting fake reviews written by the same person using multiple names, posting each review under a different name. We propose two methods to detect similar reviews and show the results generally outperform the vectorial similarity measures used in prior works. The first method extends the semantic similarity between words to the reviews level. The second method is based on topic modeling and exploits the similarity of the reviews topic distributions using two models: bag-of-words and bag-of-opinion-phrases. The experiments were conducted on reviews from three different datasets: Yelp (57K reviews), Trustpilot (9K reviews) and Ott dataset (800 reviews).Comment: 6 pages, WWW 201

Comparing the effect of using normal saline, N-acetyl cysteine and not using them in endotracheal tube suction on physiologic parameters and the amount of secretions in intubated patients under mechanical ventilation

Aims: Today a large number of patients hospitalized in Intensive Care Unit need mechanical ventilation via an artificial air way. Since these patients have endotracheal tube, endotracheal suctioning is necessary for increasing oxygenation, cleaning the airway and keeping it open. But this method consists of various side effects such as increased blood pressure and heart rate and respiratory rate, cyanosis, dizziness and increased intracranial pressure and hypoxia. This study aimed at comparing the effect of using normal saline serum, N-acetyl cysteine and not using them in endotracheal suctioning on physiologic parameters and the amount of secretions in intubated patients under mechanical ventilation. Material & Methods: It was a controlled clinical trial study with random allocation that was performed on 54 intubated patients hospitalized in ICU of health educational centers of Babol Medical Sciences University in 2014. Endotracheal tube suctioning was performed for each patient once without saline, the second time with 3 ml of normal saline and the third time with 2 ml of N-acetyl cysteine. Blood pressure, Heart rate, Respiratory rate, Arterial oxygen saturation were measured and recorded before each stage of suctioning and two and five minutes after that. Amount of secretions was measured after each method of suctioning. Data were analyzed by SPSS16 statistical software, variance analysis with repeated measures, ANOVA and paired t statistical tests. Results: Blood pressure, Heart rate and Respiratory rate were increased after suction in all the three groups, but these changes were higher in the group that received normal saline. Mean decrease of Arterial oxygen saturation was more in the method of receiving normal saline (p<0.05). The amount of secretion was more in the method of receiving N-acetyl cysteine (p=0.004). Conclusions: Endotracheal tube suctioning by using normal saline had more adverse effects on post- suction physiological parameters in compare with the other two methods. Therefore, it is recommended to not use normal saline in endotracheal tube suctioning to the possible extent, and if removing secretions is required, endotracheal N_acetyl cysteine should be used according to the patient's condition

Free Vibration Analysis of Gabled Frame Considering Elastic Supports and Semi-Rigid Connections

Free vibration analysis of a gabled frame with elastic support and semi-rigid connections is performed by using a program in OpenSees software. Natural frequencies and mode shape details of frame are obtained for two states, which are semi-rigid connections and elastic supports, separately. The members of this structure are analyzed as a prismatic nonlinear beam-column element in software. The mass of structure is considered as two equal lumped masses at the head of two columns in horizontal and vertical directions. Note that the degree of freedom, allocated to all nodes, is equal to three. Furthermore, the mode shapes of frame are achieved. Conclusively, the effects of connections and supports flexibility on the natural frequencies and mode shapes of structure are investigated

Free Vibration Analysis of Gabled Frame Considering Elastic Supports and Semi-Rigid Connections

Free vibration analysis of a gabled frame with elastic support and semi-rigid connections is performed by using a program in OpenSees software. Natural frequencies and mode shape details of frame are obtained for two states, which are semi-rigid connections and elastic supports, separately. The members of this structure are analyzed as a prismatic nonlinear beam-column element in software. The mass of structure is considered as two equal lumped masses at the head of two columns in horizontal and vertical directions. Note that the degree of freedom, allocated to all nodes, is equal to three. Furthermore, the mode shapes of frame are achieved. Conclusively, the effects of connections and supports flexibility on the natural frequencies and mode shapes of structure are investigated