Optical matrix elements in tight-binding models with overlap

We investigate the effect of orbital overlap on optical matrix elements in empirical tight-binding models. Empirical tight-binding models assume an orthogonal basis of (atomiclike) states and a diagonal coordinate operator which neglects the intra-atomic part. It is shown that, starting with an atomic basis which is not orthogonal, the orthogonalization process induces intra-atomic matrix elements of the coordinate operator and extends the range of the effective Hamiltonian. We analyze simple tight-binding models and show that non-orthogonality plays an important role in optical matrix elements. In addition, the procedure gives formal justification to the nearest-neighbor spin-orbit interaction introduced by Boykin [Phys. Rev \textbf{B} 57, 1620 (1998)] in order to describe the Dresselahaus term which is neglected in empirical tight-binding models.Comment: 16 pages 6 figures, to appear in Phys. Rev.

Electronic and optical properties of beryllium chalcogenides/silicon heterostructures

We have calculated electronic and optical properties of Si/BeSe$_{0.41}$Te$_{0.59}$ heterostructures by a semiempirical $sp^{3}s^{*}$ tight-binding method. Tight-binding parameters and band bowing of BeSe$_{0.41}$Te$_{0.59}$ are considered through a recent model for highly mismatched semiconductor alloys. The band bowing and the measurements of conduction band offset lead to a type II heterostucture for Si/BeSe$_{0.41}$Te$_{0.59}$ with conduction band minimum in the Si layer and valence band maximum in the BeSe$_{0.41}$Te$_{0.59}$ layer. The electronic structure and optical properties of various (Si$_{2})_{n }$/(BeSe$_{0.41}$Te$_{0.59})_{m}$ [001] superlattices have been considered. Two bands of interface states were found within the bandgap of bulk Si. Our calculations indicate that the optical edges are below the fundamental bandgap of bulk Si and the transitions are optically allowed.Comment: 16 pager, 7 figure

Does Insurance Sector Matter for Economic Complexity?

The study examines the impact of the insurance market on economic complexity in 28 OECD nations within a period of 1995–2020. The study also examines whether the impact of life insurance on economic complexity would be different from that of the non-life insurance sector within the insurance market. The results based on pooled mean group (PMG) estimators reveal that the insurance sector influences economic complexity positively. This finding is further substantiated after employing panel co-integrating regression and method of moment quantile regression (MM-QR). The study concludes that the insurance sector is a key instrument in upgrading the economic complexity of an economy. Since the distributional impact of economic complexity also depends on economic and financial risk, the insurance sector can assist in mitigating the risks and uphold the productive knowledge structure needed to enhance national product sophistication

Perlindungan Hukum Bagi Konsumen Air Minum Atas Layanan Pdam Tirta Siak Kota Pekanbaru Ditinjau dari Undang-undang Nomor 8 Tahun 1999 Tentang Perlindungan Konsumen

Among the complaints of the customers are the taps until the water quality is very bad home-home even unfit for consumption as drinking water or for cooking. We each month to pay the bills that do not fit with the water that we use. We hold water and be spilled and dumped because the water is dirty, smelly and sometimes the smell of garbage. From the first, as this issue continues to be present when talking about PDAM Pekanbaru. Customers upset because they feel disadvantaged by poor water quality especially when it rains. But, until now there is no fix for this problem. Even changing penguasapun in Pekanbaru not bring good changes to the quality of service to consumers.This study using sociological juridical approach. Sociological juridical research or empirical research approach is to look at in terms of the fact that occur in the field. While the descriptive nature of the research is aimed at providing a clear picture of the issues examined. Population and sample in this study is a population study in PDAM Tirta Siak Pekanbaru City and sample the Director of PDAM Tirta Siak Pekanbaru and Consumer Services Drinking Water Using Tirta Siak Pekanbaru in Pekanbaru District of the City.The results of this study are: First, the law for the protection of drinking water consumers for services PDAM Tirta Siak Pekanbaru city on water quality is very bad, resulting in non-fulfillment of the rights of consumers, resulting in harm to consumers both Financial and nonfinancial. Second, the recognition of the people who use the water utility PDAM TirtaSiak Pekanbaru, the absence of realized what strived by PDAM TirtaSiak Pekanbaru City until recently, even the water quality is getting worse. If rainy days, the water supplied by PDAM Tirta Siak Pekanbaru City unfit for dikosumsi. Legal efforts are made to consumers who are disadvantaged on layanana drinking water by PDAM Tirta Siak Pekanbaru City may file a lawsuit to the Consumer Dispute Settlement Board (BPSK) which is based on Law No. 8 of 1999 on Consumer Protection

Breakdown of Lindstedt Expansion for Chaotic Maps

In a previous paper of one of us [Europhys. Lett. 59 (2002), 330--336] the validity of Greene's method for determining the critical constant of the standard map (SM) was questioned on the basis of some numerical findings. Here we come back to that analysis and we provide an interpretation of the numerical results by showing that no contradiction is found with respect to Greene's method. We show that the previous results based on the expansion in Lindstedt series do correspond to the transition value but for a different map: the semi-standard map (SSM). Moreover, we study the expansion obtained from the SM and SSM by suppressing the small divisors. The first case turns out to be related to Kepler's equation after a proper transformation of variables. In both cases we give an analytical solution for the radius of convergence, that represents the singularity in the complex plane closest to the origin. Also here, the radius of convergence of the SM's analogue turns out to be lower than the one of the SSM. However, despite the absence of small denominators these two radii are lower than the ones of the true maps for golden mean winding numbers. Finally, the analyticity domain and, in particular, the critical constant for the two maps without small divisors are studied analytically and numerically. The analyticity domain appears to be an perfect circle for the SSM analogue, while it is stretched along the real axis for the SM analogue yielding a critical constant that is larger than its radius of convergence.Comment: 12 pages, 3 figure

NASA Planetary Mission Concept Study: Assessing: Dwarf Planet Ceres' past and Present Habitability Potential

The Dawn mission revolutionized our understanding of Ceres during the same decade that has also witnessed the rise of ocean worlds as a research and exploration focus. We will report progress on the Planetary Mission Concept Study (PMCS) on the future exploration of Ceres under the New Frontiers or Flagship program that was selected for NASA funding in October 2019. At the time this writing, the study was just kicked off, hence this abstract reports the study plan as presented in the proposal

Advancing the Microbiome Research Community

The human microbiome has become a recognized factor in promoting and maintaining health. We outline opportunities in interdisciplinary research, analytical rigor, standardization, and policy development for this relatively new and rapidly developing field. Advances in these aspects of the research community may in turn advance our understanding of human microbiome biology. It is now widely recognized that disturbances in our normal microbial populations may be linked to acute infections such as Clostridium difficile and to chronic diseases such as heart disease, cancer, obesity, and autoimmune disorders (Clemente et al., 2012). This has prompted substantial interest in the microbiome from both basic and clinical perspectives. Although our genome is relatively static throughout life, each of our microbial communities changes profoundly from infancy through adulthood, continuing to adapt through ongoing exposures to diet, drugs and environment. Understanding the microbiome and its dynamic nature may be critical for diagnostics and, eventually, interventions based on the microbiome itself. However, several important challenges limit the ability of researchers to enter the microbiome field and/or conduct research most effectively