The arithmetic of arithmetic Coxeter groups

In the 1990s, J.H. Conway published a combinatorial-geometric method for analyzing integer-valued binary quadratic forms (BQFs). Using a visualization he named the "topograph," Conway revisited the reduction of BQFs and the solution of quadratic Diophantine equations such as Pell's equation. It appears that the crux of his method is the coincidence between the arithmetic group $PGL_2({\mathbb Z})$ and the Coxeter group of type $(3,\infty)$. There are many arithmetic Coxeter groups, and each may have unforeseen applications to arithmetic. We introduce Conway's topograph, and generalizations to other arithmetic Coxeter groups. This includes a study of "arithmetic flags" and variants of binary quadratic forms.Comment: 14 pages, 11 figure

Romania’s Foreign Debt: Trend, Structure, Indicators

The foreign debt is a solution for supplementing the internal savings. The objectives of the article[1] are to analyze the evolution of Romania’s medium and long-term foreign debt and of its components between 2005 and 2013, as well as the structure by creditors of the medium and long term Romanian public foreign debt, to highlight some of the causes that explain its evolution and structure and to show if Romania’s foreign debt is sustainable, using comparative analyses, qualitative and quantitative evaluations, interpretations and correlations. The results of the analysis show that 2009 has represented a turning point in the evolution of the Romanian foreign debt on the medium and long term and its components. Also, although the values of the analyzed external debt indicators still show a good payback and indebtedness capacity of our country, a complex and coherent reimbursement strategy must be developed in agreement with the progress of the economic reform. An indebtedness strategy should also be drawn up, taking into consideration an optimal ratio between the different maturities of foreign debt, in order to avoid payback peaks. [1] The article is based on the chapter "Assessing the balance of payments", from the research project "The financial state of Romania" elaborated in CFMR "Victor Slăvescu" in 2013, under the coordination of Prof. E. Dinga, Ph

Waste as a Social Dilemma. Issues of Social and Environmental Justice and the Role of Residents in Municipal Solid Waste Management, Delhi, India

In Delhi, as in many other large cities in developing countries, the inappropriate management of municipal solid waste is a significant flaw in the quality of life of its residents, and a serious threat to the environment. Taking the integrated approach to solid waste management as its point of departure, this thesis focuses on city residents as waste producers and their role in municipal solid waste management (MSWM). It argues that the waste problem is caused by human behaviour and therefore the solution lies in changing that behaviour. The aim of this project is to identify the city residents’ current attitudes and behaviour related to waste and waste management in Delhi and the factors influencing them. Based on that, the paper proposes several recommendations on the best ways to change behaviours towards more environmental-friendly and socially equitable ones. Methodologically, a triangulation of key informant interviews, statistical analysis based on a survey with 99 city residents, and observations of everyday practice was employed. The findings of this thesis point out that, although garbage is perceived as a big problem in Delhi by the majority of respondents, there is little awareness on the ways one could contribute to solving it. The sense of responsibility for one’s waste was found to be the major factor determining littering and waste separation but waste minimization is mainly associated with income and not perceived as part of the waste problem. As for ways out of the problem, it is suggested that public campaigns should emphasise residents’ responsibility for their waste and the importance of each and every citizen’s cooperation, thus creating a sense of a shared social goal around solving the waste problem. The information and motivation campaign should be supplemented with measures that would facilitate citizen participation

Connections between the Concepts of Equality and Non-Discrimination and Foreign Direct Investments

The purpose of the paper consists in introducing the concepts of equality and discrimination. Also, the author presents the economic implications of these concepts and their interdependencies with foreign direct investments. The research methods used consist in comparative analysis in time and space, qualitative and quantitative evaluations, interpretations and correlations. The analysis shows that women's participation in the economic activity is important not only for reasons of fairness, but also as a strategic element. The undervaluation of the work of women and the improper use of their skills mean an inadequate allocation of resources, a loss of competitivity. Another result refers to the fact that the equal treatment of men and women depends on the mentality, culture and traditions from the host country, but also on those from the country of origin of foreign direct investments companies. Due to the connection between companies and the equal opportunity concept, I consider that finding a solution to the equal opportunity problem should begin at the company level, beginning with the employee selection process to the remuneration, treatment, etc. I consider, that in Romania, one can try to solve the problem of poverty and, implicitly, of the equal opportunity, by drawing foreign direct investments towards the poorly developed regions

Financing the Current Account Deficit through Foreign Direct Investments versus External Loans

The purpose of the article is to compare the financing of the current account deficit by foreign direct investments and by external loans, presenting the advantages and disadvantages of each type of financing. The analysis shows that both foreign direct investments and external loans may have positive and negative effects on the economy of the host country. In addition, some advantages of foreign direct investments have disappeared in recent years (eg stability has been partly replaced by volatility). In the article, the author also presents the characteristics of current account deficit financing in Romania during the period 2006-2018. Concerning the foreign debt, it is noticed that in Romania there has been a replacement of institutional creditors with private creditors, which we consider to be a negative evolution of the situation of the Romanian economy from the point of view of the reimbursement effort and the sustainability. The research methods used consist in comparative analysis in time, qualitative and quantitative evaluations, interpretations and correlations

The Actor in Search of Musical Forms. Case Studies

This article looks at the major differences in the reception of the sounds of a musical fragment, depending on the personal experience of each individual  and his profession. The musicians relate to the sound universe guided by the constituent elements of the scores, and the actors look for connections  between sounds, gestures, words, characters, and stage situations. They can approach music in other ways than musicians and remember the melodic lines  or create accompaniments by making connections with the context in which they find themselves. In some examples that the article offers, the studied  actors demonstrate that sound can become music even in the absence of the vocal or rhythmic qualities of the performers. Other examples refer to the way  in which the personality and creativity of artists have a significant role in creating songs or the sound support they need

A Look at the Trend and Features of the Romanian Current Account over the Past Years

The balance of the current account provides the possibility of assessing the level of economic development of a country, its degree of foreign dependence and the international specialization of each economy. This article[1] aims to analyze the evolution of the Romanian current account balance and of some of its components during the period 2013-2016, showing the determinants and some of the factors influencing Romania's current account. Also, there are analysed the ways of financing the Romanian current account deficit, highlighting the advantages and disadvantages of this financing structure. The research methods used consist in comparative analysis in time, qualitative and quantitative evaluations, interpretations and correlations. The analysis shows that the services sector has developed, which increased the surplus of the services subaccount. Another result highlights that currently, the evolution of the current account deficit is sustainable in Romania. Also, the author concludes that the current account deficit of Romania has been and is still financed mainly from inflows of foreign direct investments. [1] The article is based on the chapter "The assessment of the external equilibrium", from the research project "The financial stance of Romania, edition 2016" elaborated in CFMR "Victor Slăvescu" in 2016, under the coordination of C. Marin, Ph.D

Technology, science, and environtmental impact of a novel Cu-Ag core-shell solderless interconnect system

Tin-based solder is ubiquitous in microelectronics manufacturing and plays a critical role in electronic packaging and attachment. While manufacturers of consumer electronics have made the transition to the use of lead-free solder, there are still a variety of reliability issues associated with these lead-free alternatives, particularly for high performance, high reliability applications. Because of these performance short-comings, researchers are still searching for a material, an alloy, or a unique alternative that can meet the thermal, mechanical, and electrical requirements for conventional reflow solder applications. In an effort to produce a more reliable alternative, Kim et al. proposed the low-temperature (200°C) sintering of copper-silver core-shell particles as a viable solderless interconnect technology. This technology is based on the silver atoms from the shell diffusing by surface diffusion to form sintered necks between copper particles, and therefore dewetting most of the copper surfaces. This study presents a 3-fold, in-depth evaluation of this Cu-Ag core-shell lead-free solderless interconnect technology focusing on solder paste development and prototyping, silver thin film stress relaxation and dewetting kinetics, and the environmental impacts associated with this new technology. ^ First, an evaluation of the starting particle consistency and sintered compact mechanical properties determined that a specific core-shell particle geometry (1µm average core diameter and 10nm shell thickness) outperformed other combinations, exhibiting the highest modulus and yield strengths in sintered compacts, of 620 MPa and 40-60 MPa respectively. In particular, yield strengths for sintered compacts are similar to those reported for Sn-3.5Ag-0.75Cu (a commonly used lead-free solder) for the same strain rate. Following particle evaluations, the development of a functioning flux formulation was a key factor in the creation of a viable drop-in replacement. The processing of the final flux/particle paste combination was optimized at a commercial test facility for printing on test boards containing a wide variety of pad shapes, sizes, and pitches and thus, validated the ability of the Cu-Ag core-shell paste to be a drop-in replacement for traditional solder paste using conventional manufacturing techniques. ^ The second study addresses the fundamental mechanisms behind interconnect formation. An assessment of the kinetics and microstructure evolution during silver thin film dewetting and defect formation provides essential materials science knowledge to understand and control the functionality of the Cu-Ag core-shell system. From an interrupted annealing study used to quantify dewetting kinetics, a range of surface diffusion coefficients were calculated from the experimental results, assuming that surface diffusion controlled dewetting. The two order of magnitude range in calculated diffusion coefficient demonstrates that the diffusion-limited kinetic models traditionally used to quantify hillock and hole growth kinetics during thin film relaxation and dewetting do not apply to the dewetting of Ag films. The presence of interface-limited kinetics was then validated through the non-uniform growth of individual hillocks over time. ^ Lastly, an environmental assessment compares the impacts associated with the manufacturing and materials for the Cu-Ag core-shell particle system and SAC 305, the most commonly used lead-free solder alloy that contains 96.5% tin, 3% silver, and 0.5% copper. By comparing the impacts on global warming, acidification, eutrophication, ozone depletion, ecotoxicity, smog, carcinogenics, non-carcinogenics, and respiratory effects associated with each technology, the environmental advantages and disadvantages of each system are clearly communicated. By utilizing this information and the versatility of the core-shell system, possible methods for reducing impacts of the Cu-Ag core-shell system are addressed in order to reduce its environmental footprint. ^ This multidimensional assessment provides a comprehensive validation in terms of technology, science, and environmental impacts of the Cu-Ag core-shell interconnect technology as a viable drop-in replacement for lead-based and lead-free solders for microelectronic manufacturing

Modeling the Financial Behavior of Population (I) – Conceptual Assignations

The paper shows a few conceptual assignations concerning the financial behavior of the population. Thus, there are defined attached predicates (the inclusion into the economic behavior category, the existence of a monetary factor, the action for goods and non-autonomous flows, as well as for goods and nominal flows), the sources that generate the financial behavior (acquisition of real goods and services, acquisition of financing sources, acquisition of saving sources), the process of non-autonomous financial flow formation and finally, there are identified categories of nominal flows attached to the financial behavior of the population.logic model, financial behavior, sustainability

Neuropathies optiques héréditaires

Les neuropathies optiques héréditaires sont un groupe hétérogène de pathologies affectant les nerfs optiques et qui peuvent se transmettre selon un mode autosomique dominant, autosomique récessif, lié à l’X ou selon une hérédité mitochondriale. Les deux pathologies héréditaires non syndromiques les plus fréquentes (neuropathie optique héréditaire de Leber et l’atrophie optique dominante) ont des manifestations cliniques et des modes de transmission très différents, aboutissant néanmoins à une atrophie optique non spécifique. Au-delà des manifestations purement visuelles, il n’est pas exceptionnel de constater chez des patients atteints, un nombre croissant de manifestations neurologiques associées