Some comments on the divergence of perturbation series in Quantum Eletrodynamics

It has been argued by Dyson that the perturbation series in coupling constant in QED can not be convergent. We find that similiar albeit slightly different arguments lead to the divergence of the series of $1/N_f$ expansion in QED.Comment: Final Version, To appear in Modern Physics Letters

Studying the Effect of Cutting Conditions in Turning Process on Surface Roughness for Different Materials

Surfaces quality is one of the most specified customer requirements for machine parts. The major indication of surfaces quality on machined parts is surface roughness. The research aim is to study the cutting conditions and their effects on the surface roughness. This research will use regression models and neuro-fuzzy to predict surface roughness over the machining time for variety of cutting conditions in turning. In the experimental part for turning, different types of materials (Aluminum alloy, brass alloy, and low carbon steel) were considered with different cutting speed, and feed rate. A linear regression and neuro-fuzzy model depending on statistical-mathematical method between surface roughness, Ra, and cutting condition will be derived, for the three materials. The effect of cutting parameters on surface roughness is evaluated and the optimum cutting condition for minimizing the surface roughness will be determined. The model will be established between the cutting conditions and surface roughness using regression and neuro-fuzzy model. As the results of this work, the linear regression and neuro-fuzzy model will be used in predicting surface roughness, can be used in manufacturing systems, this modeling helps engineer to reduce the efforts and improve the quality

Are our people health conscious? results of a patients survey in Karachi, Pakistan

BACKGROUND: Life style is known to influence health and may be responsible for certain diseases. There is a need to document the life style on health among the Pakistani population. METHODS: The study was conducted on patients visiting the Family Practice Center, the Aga Khan University, Karachi. A questionnaire was used to collect information on the demographic profile, and the life style on health. The ethical requirements for conducting the study were met. RESULTS: 393 patients were surveyed. The majority were young married men, in either private or government service. Preference for consumption of fats/oils, sweets, spicy foods, salt, fruits/vegetables, tea, coffee, cola drinks and alcohol was found among 103 (26%), 84 (22%), 86 (22%), 110 (28%), 239 (61%), 319 (81%), 117 (30%), 253 (64%) and 13 (03%) respondents respectively. Hand washing after defecation, before eating food and after work was seen among 341 (87%), 296 (75%) and 256 (65%) respondents respectively. Brushing of teeth after eating food, before breakfast and bedtime was seen in 56 (14%), 346 (88%) and 176 (45%) respondents respectively. Preventive dental check-up was practiced by 102 (26%) of the respondents. Sleep of less than 6 hours per day among 74 (19%), water consumption of less than 1 liter daily among 84 (21%) and fish consumption on once a week basis among 173 (44%) respondents was found. Tobacco and betel nuts use was found among 69 (17%) and 79 (20%) respondents. CONCLUSIONS: We have documented a clear need to raise public awareness on the issue of life style on health. There is a need and we strongly recommend debate and further research, along with interventional strategies in line with the available evidence on healthy life style

Non-relativistic limit of Randall-Sundrum model: solutions, applications and constraints

In the Randall-Sundrum model with one brane, we found the approximate and exact solutions for gravitational potentials and accelerations of test bodies in these potentials for different geometrical configurations. We applied these formulas for calculation of the gravitational interaction between two spheres and found the approximate and exact expressions for the relative force corrections to the Newton's gravitational force. We demonstrated that the difference between relative force corrections for the approximate and exact cases increases with the parameter $l$ (for the fixed distance $r$ between centers of the spheres). On the other hand, this difference increases with decreasing of the distance between the centers of the spheres (for the fixed curvature scale parameter $l$). We got the upper limit for the curvature scale parameter $l\lesssim 10\, \mu$m. For these values of $l$, the difference between the approximate and exact solutions is negligible.Comment: LaTex 11 pages, 3 figure

MAJOR DETERMINANTS ON THE PROFITABILITY OF SRI LANKAN LOCAL COMMERCIAL BANKS

The main purpose of this study is to investigate the relationship between bank-specific factors and the profitability of local commercial banks in Sri Lanka. Thus, finding the main internal characteristics for achieving higher profitability. In this research, OLS regression analysis is used to examine the relationship between bank-specific characteristics and bank’s profitability for a sample of 11 major Sri Lankan local banks during 12 years period from 2006 to 2017. The findings reveal that assets base and size of branch network are the main determinants of bank’s profitability, by showing a significant relationship with all measures of profitability. Net profits of banks show a significant relationship with size of branch networks and total assets, but insignificant with deposit interest ratio. However, loan interest ratio and deposit interest ratio together have a significant effect on net interest margin thus leading an impact on banks’ profitability. This study is an extension and a country application to the research carried-out by Kassem N.M. & Sakr A (2018) on Commercial Banks in Egypt. JEL: G20; G21  Article visualizations

AN EXPLORATORY FACTOR ANALYSIS ON VARIABLES AFFECTING THE PROFITABILITY OF SRI LANKAN LOCAL COMMERCIAL BANKS

The main purpose of this study is to investigate the relationship between bank-specific factors and the profitability of local commercial banks in Sri Lanka. Thus, finding the main internal and external characteristics for achieving higher profitability. In this research, Exploratory Factor Analysis (EFA) is used as an alternative approach to examine the relationships between bank-specific characteristics of bank’s profitability for a sample of 11 major Sri Lankan local banks during the 12 years period from 2006 to 2017. The findings reveal that assets base and size of branch network are the main determinants of banks’ profitability, by showing a significant relationship with all measures of profitability. Net profits of banks show a significant relationship with size of branch networks and total assets, but insignificant with deposit interest ratio. However, loan interest ratio and deposit interest ratio together have a significant effect on net interest margin thus leading an impact on banks’ profitability.  Article visualizations

DEVELOPING A FRAMEWORK FOR SCRUTINIZING STRATEGIC GREEN ORIENTATION AND ORGANIZATIONAL PERFORMANCE WITH RELEVANCE TO THE SUSTAINABILITY OF TOURISM INDUSTRY

The purpose of this paper is to review the concept of sustainability, theoretical background and strategic green orientation (SGO) to develop an in-depth understands for the benefit of organizational performance (OP). Theoretical background outlines how triple bottom line and ecological modernization viewpoints relate with SGO and OP towards the sustainability to develop a research framework. The paper discloses a series of gaps in sustainability related theories and empirical research at business organizations and recommends a quantitative research approach and method for an empirical study on SGO of business organizations in tourism industry of Sri Lanka. Proposed study expects that new relationships could be discovered and theorized. This may address identified research gaps and would contribute to the body of knowledge. The findings of proposed research could be useful to future research initiatives on green business modeling for the sustainability in terms of triple bottom line: economic, environmental, and social performance.  Article visualizations

Energy-Momentum Distribution: Some Examples

In this paper, we elaborate the problem of energy-momentum in General Relativity with the help of some well-known solutions. In this connection, we use the prescriptions of Einstein, Landau-Lifshitz, Papapetrou and M\"{o}ller to compute the energy-momentum densities for four exact solutions of the Einstein field equations. We take the gravitational waves, special class of Ferrari-Ibanez degenerate solution, Senovilla-Vera dust solution and Wainwright-Marshman solution. It turns out that these prescriptions do provide consistent results for special class of Ferrari-Ibanez degenerate solution and Wainwright-Marshman solution but inconsistent results for gravitational waves and Senovilla-Vera dust solution.Comment: 20 pages, accepted for publication in Int. J. Mod. Phys.

Precursors, black holes, and a locality bound

We revisit the problem of precursors in the AdS/CFT correspondence. Identification of the precursors is expected to improve our understanding of the tension between holography and bulk locality and of the resolution of the black hole information paradox. Previous arguments that the precursors are large, undecorated Wilson loops are found to be flawed. We argue that the role of precursors should become evident when one saturates a certain locality bound. The spacetime uncertainty principle is a direct consequence of this bound.Comment: 26 pages, 8 figs; reference added, minor clarification in sec. 2; incorrect draft mistakenly used in version