On the new string theory inspired mechanism of generation of cosmological perturbations

Recently a non-inflationary mechanism of generation of scale-free cosmological perturbations of metric was proposed by Brandenberger, Nayeri, and Vafa in the context of the string gas cosmology. We discuss various problems of their model and argue that the cosmological perturbations of metric produced in this model have blue spectrum with a spectral index n = 5, which strongly disagrees with observations. We conclude that this model in its present form is not a viable alternative to inflationary cosmology.Comment: 11 pages, 1 figur

Observational Constraints on Theories with a Blue Spectrum of Tensor Modes

Motivated by the string gas cosmological model, which predicts a blue tilt of the primordial gravitational wave spectrum, we examine the constraints imposed by current and planned observations on a blue tilted tensor spectrum. Starting from an expression for the primordial gravitational wave spectrum normalized using cosmic microwave background observations, pulsar timing, direct detection and nucleosynthesis bounds are examined. If we assume a tensor to scalar ratio on scales of the CMB which equals the current observational upper bound, we obtain from these current observations constraints on the tensor spectral index of $n_{T} \lesssim 0.79$, $n_{T} \lesssim 0.53$, and $n_{T} \lesssim 0.15$ respectively.Comment: 12 pages, 1 figure, 2 references added, relationship of this work with Ref. 20 adde

Psychometric Properties of the Persian Version of Self-Management Scale for a Sample of Iranian Patients With Epilepsy

Background: Despite the importance of self-management in epileptics, no instrument has been developed or validated in Iran. Since self-management is a multi-dimensional construct, having a valid and reliable instrument for measuring this compound construct is crucial. Objectives: This study aims to validate the Persian version of the self-management scale and provide a valid and reliable tool to measure self-management of patients with epilepsy. Patients and Methods: This is a methodological psychometric study. Construct , face and content validity was calculated on 200 samples after translation. Tool reliability was examined by using two methods: internal consistency and test-retest. Finally, the modified model was presented using exploratory factor analysis for the Iranian version of the tool. Results: The validity of all items was above 0.63 and their content validity indexes (0.81-1) were appropriate. Construct validity, exploratory and confirmatory factor analysis confirmed all the dimensions except for some safety and pharmacotherapy items. The overall tool reliability with internal consistency had alpha of 0.77. Conclusions: Persian version of the self-management scale for patients with epilepsy is valid and reliable to measure the dimensions of self-management in Iranian patients and it can be used to measure epileptics’ self-management. Further research on the safety of this tool is recommended

Analysis of V transmission lines response to external electromagnetic fields

Abstract-In the present paper the response of V transmission line to electromagnetic illumination has been obtained. Also in order to determine the VTL frequency operation band for both TE and TM modes a Gaussian pulse source has been applied to the structure. The VTL structure has received considerable attention in high frequency and microwave IC packaging. The purpose of this study is to determine high frequency design considerations in order to reduce the effects of electromagnetic interference (EMI) on the VTL structure and maintain the desired performance. It was observed that the effect of incident EM waves on the V lines performance is considerably lower than conventional microstrips, however the V lines are more sensitive to sources at close proximity. In addition, although the V lines show lower dispersion at higher frequencies, their frequency operation band is limited by a resonance like behavior which is directly related to the V groove dimensions. The full wave analysis is carried out using the Yee-cell based 2 Dimensional Finite Difference Time Domain method (2D-FDTD), while enforcing a very stable and efficient mesh truncation technique

Effects of a Staff Development Program on Head Nurses' Communication Skills and Job Satisfaction

Background: Communication skills of operational managers such as head nurses greatly influence the performance of nursing personnel and by extension, the quality of the care provided by them. Objectives: This study was conducted to identify the role of a development program on communication skills and job satisfaction in head nurses. Materials and Methods: This research was a non-randomized two-group trial. A random allocation of two hospitals affiliated to Tehran University of Medical Sciences created an intervention and control group. In the intervention group, all head nurses were entered in a two-day communication skills development workshop using adult learning theory. The head nurses of the other hospital were allocated to the control group. Job satisfaction and communication skills of head nurses were investigated prior and 6 weeks following intervention in two groups. The data were analyzed by Chi-square, Fisher exact test, T-test, paired t test and analysis of covariance. Results: Following intervention, the communication skills scores achieved by intervention group were 127.5 ± 7.10 at pretest and increased to 134.11 ± 7.32 after the intervention (P < 0.01). The mean score of the communication skills did not alter significantly in the control group. Moreover, no significant change was observed in the mean scores of job satisfaction of head nurses in the intervention group compared to those of the control group (P = 0.102). Conclusions: The development programs of communication skills resulted in an increased level of communication skills in the head nurses. However, more effective steps have to be taken in professional and organization conditions to enhance head nurses’ job satisfaction level. Keywords: Job Satisfaction; Communication; Nursing, Supervisory; Growth and Developmen

Could Fermion Masses Play a Role in the Stabilization of the Dilaton in Cosmology?

We study the possibility that the Dilaton is stabilized by the contribution of fermion masses to its effective potential. We consider the Dilaton gravity action in four dimensions to which we add a mass term for a Dirac fermion. Such an action describes the interaction of the Dilaton with the fermions in the Yang-Mills sector of the coupled supergravity/super-Yang-Mills action which emerges as the low energy effective action of superstring theory after the extra spatial dimensions have been fixed. The Dilaton couples to the Fermion mass term via the usual exponential factor of this field which multiplies the non-kinetic terms of the matter Lagrangian, if we work in the Einstein frame. In the kinetic part of the Fermion action in the Einstein frame the Dilaton does not enter. Such masses can be generated in several ways: they can arise as a consequence of flux about internal spatial dimensions, they may arise as thermal fermion masses in a quasi-static phase in the early universe, and they will arise after the breaking of supersymmetry at late times. The vacuum contribution to the potential for the Dilaton is evaluated up to two loops. The result shows a minimum which could stabilize the Dilaton for reasonable ranges of parameter values.Comment: 11 pages, 1 figure; shortened versio