Three-Dimensional Topological Insulators

Topological insulators in three dimensions are nonmagnetic insulators that possess metallic surface states as a consequence of the nontrivial topology of electronic wavefunctions in the bulk of the material. They are the first known examples of topological order in bulk solids. We review the basic phenomena and experimental history, starting with the observation of topological insulator behavior in Bi$_x$Sb$_{1-x}$ by spin- and angle-resolved photoemission spectroscopy and continuing through measurements on other materials and by other probes. A self-contained introduction to the single-particle theory is then given, followed by the many-particle definition of a topological insulator as a material with quantized magnetoelectric polarizability. The last section reviews recent work on strongly correlated topological insulators and new effects that arise from the proximity effect between a topological insulator and a superconductor. While this article is not intended to be a comprehensive review of what is already a rather large field, we hope that it will serve as a useful introduction, summary of recent progress, and guideline to future directions.Comment: 53 pages, 9 figures, 1 table. Preprint version from June 2010 of invited article for Annual Review of Condensed Matter Physics. Final edited version will be published online c. January 201

Cigarette Smoking Habits Among University Students: Prevalence and Associated Factors

Smoking is the main cause of morbidity and mortality in the world and is estimated to kill 5 million people each year worldwide. If current patterns of tobacco consumption continue, smoking will kill more than 8 million people each year globally by the year 2030, with 80% of these deaths in the developing countries. This study aimed to determine the prevalence and associated factors of cigarette smoking among male university students in Muzaffarabad, Pakistan. A descriptive cross-sectional study was conducted among 542 male students at University of Azad Jammu & Kashmir in Muzaffarabad from July to December 2015. The socio-demographic characteristics and cigarette smoking behavior of the students were measured by using a standardized pre-tested self-administrated validated questionnaire in English. The overall prevalence of cigarette smoking among students was found to be 49.4%. The mean age of starting cigarette smoking was 19.2 2.73 years. Age, marital status and education were found significantly associted with cigarette smoking behavior (p-value<0.05). The most common reason for cigarette smoking was stress alleviation (35.0%) followed by peer pressure (24.5%). As cigarette smoking is considerably higher among students. There is a need to develop effective tobacco control measures among university students in Muzaffarabad

Poverty, Gender, and Primary School Enrolment in Pakistan

Primary education is at the base of the pyramid of education, and is regarded as a fundamental human right today. In addition, it has several tangible social and economic effects. As an essential component of human capital, primary education plays an important role in the economic growth and development of a country.1 Its impact on several other socioeconomic variables has also been documented in the literature. To quote a few examples, Butt (1984) has found that five or more years of a farmer’s education lead to increased farm productivity, reduced use of farm labour, and increased use of yield augmenting inputs. Azhar (1988) also reports a significant relationship between the number of years of schooling and increase in farm output due to increased technical efficiency. Studies of the rates of returns to education attribute a positive value to the rate of returns to primary education.2 This means that by acquiring primary education one can increase one’s earnings. Every policy document prepared by the Government of Pakistan aims at attaining universal primary education. However, it is also true that each of these documents has advanced the date for achieving the target specified in the previous one. The net enrolment rates at the primary level show that we are still far from this target.