Cylindrical solutions in braneworld gravity

In this article we investigate exact cylindrically symmetric solutions to the modified Einstein field equations in the brane world gravity scenarios. It is shown that for the special choice of the equation of state $2U+P=0$ for the dark energy and dark pressure, the solutions found could be considered formally as solutions of the Einstein-Maxwell equations in 4-D general relativity.Comment: 12 pages, RevTex format, typos corrected and references added. Accepted for publication in PR

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

Fermat's principle in quantum gravitational optics

Interactions incorporating the vacuum polarization effects in curved backgrounds modify the null cone structure in such a way that the photon trajectories would not be the space-time geodesics anymore. The gravitational birefringence introduced as a direct consequence of these effects, will allow shifts in the photon velocities leading to polarization dependent superluminal propagation. Taking these effects into account we study Fermat's principle in the context of the 1+3 (threading) formulation of the space-time decomposition. We find an expression for the modified spacetime refractive index and show it is proportional to the light cone correction to the first order. Consequences of this modification on polarization sum rules and spatial light paths are considered.Comment: 13 Pages, REVTex format, section on gravitomagnetic monopoles is removed along with its references, new references adde

Effects of intake flow on the spray structure of a multi-hole injector in a DISI engine

The spray characteristics of a 6-hole injector were examined in a single cylinder optical direct injection spark ignition engine. The effects of injection timing, in-cylinder charge motion, fuel injection pressure, and coolant temperature were investigated using the 2-dimensional Mie scattering technique. It was confirmed that the in-cylinder charge motion played a major role in the fuel spray distribution during the induction stroke while injection timing had to be carefully considered at high injection pressures during the compression stroke to prevent spray impingement on the piston

Massive spinor fields in flat spacetimes with non-trivial topology

The vacuum expectation value of the stress-energy tensor is calculated for spin $1\over 2$ massive fields in several multiply connected flat spacetimes. We examine the physical effects of topology on manifolds such as $R^3 \times S^1$, $R^2\times T^2$, $R^1 \times T^3$, the Mobius strip and the Klein bottle. We find that the spinor vacuum stress tensor has the opposite sign to, and twice the magnitude of, the scalar tensor in orientable manifolds. Extending the above considerations to the case of Misner spacetime, we calculate the vacuum expectation value of spinor stress-energy tensor in this space and discuss its implications for the chronology protection conjecture.Comment: 18 pages, Some of the equations in section VI as well as typographical errors corrected, 5 figures, Revtex

A Comparison Between Foley and Nelatone Urinary Catheters in Causing Urinary Tract Infection in Animal Models

Background: Urinary catheterization is one of the main measures used to treat and care for hospitalized patients. Several complications have been attributed to the presence of latex with routine Foley catheters. Therefore, some studies have recommended that Nelatone catheters be substituted for the ordinary Foley catheters to prevent these complications. Objectives: This study aimed to compare the rates of urinary tract infection (UTI) in rabbits catheterized either with Foley or with Nelatone catheters. Materials and Methods: A randomized controlled trial was conducted on 60 rabbits that were randomly assigned to three groups of twenty. The first group was catheterized using Nelatone catheter; the second group was catheterized using Foley catheter and the third group was studied without performing any catheterization. After seven days, urine samples were collected using suprapubic aspiration and were sent to the laboratory for culture. Descriptive statistics were calculated. Moreover, chi-square and Fisher’s exact tests were used for data analysis. Results: At the end of the study, four 4 cases in the Nelatone group and 12 cases in the Foley group presented with UTI (P = 0.01). No positive urine cultures were found in the control group. Conclusions: The Nelatone catheters, compared with the Foley ones, had a lower risk of UTI in the long term use. Verifying this claim by further studies can have an important role in reducing UTIs in patients using urinary catheters

Investigating the Effect of Zinc Chloride to Control External Bleeding in Rats

Background: Despite all progresses in surgical science, bleeding caused by traffic accidents is still a challenge for surgeons to save patients’ lives. Therefore, introducing an effective method to control external bleeding is an important research priority. Objectives: This study aimed to compare haemostatic effect of zinc chloride and simple suturing to control external bleeding. Materials and Methods: In this animal model study, 60 male Wistar rats were used. An incision (two cm in length and half a cm in depth) was made on shaved back of rats. The hemostasis time was measured once using zinc chloride with different concentrations (5%, 10%, 15%, 25%, and 50%) and then using simple suturing. Skin tissue was assessed for pathological changes. Due to abnormal distribution of variables in Kolmogorov-Smirnov test, the data was analyzed using Kruskal-Wallis test Mann-Whitney U tests. Results: In all the groups, complete hemostasis occurred. Hemostasis times of different concentrations of zinc chloride were significantly less than that of the control group (P < 0.001). Conclusions: Zinc chloride was effective to control external bleeding in rats

Gauged motion in general relativity and in Kaluza-Klein theories

In a recent paper [1] a new generalization of the Killing motion, the {\it gauged motion}, has been introduced for stationary spacetimes where it was shown that the physical symmetries of such spacetimes are well described through this new symmetry. In this article after a more detailed study in the stationary case we present the definition of gauged motion for general spacetimes. The definition is based on the gauged Lie derivative induced by a threading family of observers and the relevant reparametrization invariance. We also extend the gauged motion to the case of Kaluza-Klein theories.Comment: 42 pages, revised version, typos correction along with some minor changes, Revtex forma