Minimal parameterizations for modified gravity

The increasing precision of cosmological data provides us with an opportunity to test general relativity (GR) on the largest accessible scales. Parameterizing modified gravity models facilitates the systematic testing of the predictions of GR, and gives a framework for detecting possible deviations from it. Several different parameterizations have already been suggested, some linked to classifications of theories, and others more empirically motivated. Here we describe a particular new approach which casts modifications to gravity through two free functions of time and scale, which are directly linked to the field equations, but also easy to confront with observational data. We compare our approach with other existing methods of parameterizing modied gravity, specifically the parameterized post-Friedmann approach and the older method using the parameter set $\{\mu,\gamma\}$. We explain the connection between our parameters and the physics that is most important for generating cosmic microwave background anisotropies. Some qualitative features of this new parameterization, and therefore modifications to the gravitational equations of motion, are illustrated in a toy model, where the two functions are simply assumed to be constant parameters.Comment: 8 pages, 7 figures, 1 tabl

Improving QC Relaxations of OPF Problems via Voltage Magnitude Difference Constraints and Envelopes for Trilinear Monomials

AC optimal power flow (AC~OPF) is a challenging non-convex optimization problem that plays a crucial role in power system operation and control. Recently developed convex relaxation techniques provide new insights regarding the global optimality of AC~OPF solutions. The quadratic convex (QC) relaxation is one promising approach that constructs convex envelopes around the trigonometric and product terms in the polar representation of the power flow equations. This paper proposes two methods for tightening the QC relaxation. The first method introduces new variables that represent the voltage magnitude differences between connected buses. Using "bound tightening" techniques, the bounds on the voltage magnitude difference variables can be significantly smaller than the bounds on the voltage magnitudes themselves, so constraints based on voltage magnitude differences can tighten the relaxation. Second, rather than a potentially weaker "nested McCormick" formulation, this paper applies "Meyer and Floudas" envelopes that yield the convex hull of the trilinear monomials formed by the product of the voltage magnitudes and trignometric terms in the polar form of the power flow equations. Comparison to a state-of-the-art QC implementation demonstrates the advantages of these improvements via smaller optimality gaps.Comment: 8 pages, 1 figur

The Relationship of Alexithymia and Cognitive Failure with Spiritual Health in Male Students of Ardabil Payam-e Noor University

Background & Objectives: Students with a high spiritual health can adapt to the problems in their personal life. The purpose of this study was to investigate the relationship of alexithymia and cognitive failure with spiritual health in male students of Ardabil Payam-e Noor University. Methods: This descriptive-analytic study was performed on 268 male students of Ardabil Payam-e Noor University selected through multistage multi-cluster random sampling. Data collection tools included questionnaires of alexithymia (20 items), cognitive failure (25 items), and spiritual well-being (20 questions). Data were entered into SPSS version 23 and analyzed using inferential statistics tests, Pearson Correlation Coefficient and Multiple Regression tests. Results: There was no statistically significant relationship between demographic variables (age, educational level and field, occupation and marital status) and spiritual health among male students. However, alexithymia and cognitive failure showed significant statistical relationships with spiritual well-being. According to multiple regression results, alexithymia and cognitive failure have the potential for predicting spiritual well-being in male students (P <0.05). Conclusion: Considering the effect of alexithymia and cognitive failure on students’ spiritual health, it is recommended to help students to improve their spiritual health by overcoming alexithymia and cognitive failure. Key¬words: Affective Symptoms, Cognition, Health, Students Citation: Narimani M, Samadifard HR. The Relationship of Alexithymia and Cognitive Failure with Spiritual Health in Male Students of Ardabil Payam-e Noor University. Journal of Health Based Research 2017; 3(2): 163-173

Bacterial Leakage and Microgap along Implant-Abutment Connection in Three Different Implant Systems

A microgap between implant and abutment connection can act as a bacterial source and cause inflammation, even endanger Osseointegration and subsequently change clinical and histological parameters. The goal of this study was to evaluate the microgap and microbial leakage of implant-abutment connection in three different implant systems. In this experimental study, 28 implants in 3 groups (10 Zimmer with conical connection of 8 degrees, 10 Dentium with conical connection of 11 degrees, 8 Test implants with conical connection of 16 degrees) were used. Microleakage of Escherichia coli was assessed at intervals of 5, 24, 48 hours and 2 weeks. Microgap was measured at 4 random points by scanning electron microscope. Data were analysed by Spss version 22 and kruskal-Wallis, Mann-Whitney, Chisquare, Kaplan-Meier tests. (alpha=0.5) Mean microgap was 4.8 mu m (+/- 2.2) in Zimmer group, 3.1 mu m (+/- 1.4) in Implantium group and 16.9 mu m (+/- 8.7) in test group. After 2 weeks from start of the study, 20 percent of Zimmer and Dentium implants and 25 percent of test implant showed microleakage. Microleakage between Zimmer and Dentium implants was not significant; however, there was a significant difference between test implant and other groups. Microbial leakage was observed in all three implant systems. Although; there were differences in microgap between three groups, Microbial leakage was not statistically significant

The role of spiritual well-being and Religious Adherence in predicting marital satisfaction among nurses

زمینه و هدف: رضایت زناشویی از جمله عوامل مرتبط با سلامت روان و استرس شغلی پرستاران است. پژوهش حاضر با هدف تعیین نقش بهزیستی معنوی و پایبندی مذهبی در پیش بینی رضامندی زناشویی پرستاران صورت گرفته است. روش بررسی: در این مطالعه توصیفی تحلیلی، 176 نفر از پرستاران شاغل در بیمارستان های اردبیل در سال 93 به ‌صورت نمونه‌گیری خوشه‌ای چند مرحله ای انتخاب شدند. برای جمع ‌آوری داده‌ها از پرسش‌نامه های بهزیستی معنوی پالوتزیان و الیسون، پایبندی مذهبی و رضامندی زناشویی بر اساس معیارهای اسلامی استفاده شد. داده‌های به‌دست‌آمده با آزمون ضریب همبستگی پیرسون و تحلیل رگرسیون همزمان مورد تجزیه و تحلیل قرار گرفتند. یافته ها: بین پایبندی مذهبی و بهزیستی معنوی با رضامندی زناشویی رابطه مثبت و معناداری وجود داشت. همچنین نتایج تحلیل رگرسیون نشان داد که 3/32 درصد رضامندی زناشویی پرستاران، براساس پایبندی مذهبی و بهزیستی معنوی قابل تبیین است (001/0