Проблемы нуклеосинтеза. Куда исчез литий?

В данной статье рассматриваются проблемы нуклеосинтеза во Вселенной - процесса образованияядер химических элементов тяжелее водорода в ходе реакции ядерного синтеза. В статье анализируютсяактуальные научные работы, выдвигающие или опровергающие различные гипотезы, объясняющиевозможные причины дисбаланса лития во Вселенной. Проведенный анализ и составленный обзор научныхработ позволили сделать общий вывод о современном состоянии и перспективах исследований по проблеметеории большого взрыва.Im vorliegenden Artikel werden die Probleme der Nucleosynthese im Weltall - der Entstehung vonAtomkernen kurz nach dem Urknall - betrachtet. Im Artikel werden auch die neuesten wissenschaftlichen Arbeitenzum Thema "Abgleichfehler von Lithium im Universum", die verschiedene Hypothesen vom angegebenen Probleminterpretieren, analysiert. Aufgrund der durchgefuhrten Analyse wird die allgemeine Schlussfolgerung uber dasProblem von der Urknall-Theorie und die Perspektiven ihrer weiteren Erforschung gemacht

Nonequilibrium functional renormalization group for interacting quantum systems

We propose a nonequilibrium version of functional renormalization within the Keldysh formalism by introducing a complex valued flow parameter in the Fermi or Bose functions of each reservoir. Our cutoff scheme provides a unified approach to equilibrium and nonequilibrium situations. We apply it to nonequilibrium transport through an interacting quantum wire coupled to two reservoirs and show that the nonequilibrium occupation induces new power law exponents for the conductance.Comment: 5 pages, 2 figures; published versio

Bulk Nanocrystalline Thermoelectrics Based on Bi-Sb-Te Solid Solution

A nanopowder from p-Bi-Sb-Te with particles ~ 10 nm were fabricated by the ball milling using different technological modes. Cold and hot pressing at different conditions and also SPS process were used for consolidation of the powder into a bulk nanostructure and nanocomposites. The main factors allowing slowing-down of the growth of nanograins as a result of recrystallization are the reduction of the temperature and of the duration of the pressing, the increase of the pressure, as well as addition of small value additives (like MoS2, thermally expanded graphite or fullerenes). It was reached the thermoelectric figure of merit ZT=1.22 (at 360 K) in the bulk nanostructure Bi0,4Sb1,6Te3 fabricated by SPS method. Some mechanisms of the improvement of the thermoelectric efficiency in bulk nanocrystalline semiconductors based on BixSb2-xTe3 are studied theoretically. The reduction of nanograin size can lead to improvement of the thermoelectric figure of merit. The theoretical dependence of the electric and heat conductivities and the thermoelectric power as the function of nanograins size in BixSb2-xTe3 bulk nanostructure are quite accurately correlates with the experimental data.Comment: 35 pages, 24 figures, 4 tables, 52 reference

Risks and controls in the implementation of ERP systems

The implementation of ERP systems has been problematic for many organizations. Given the many reports of substantial failures, the implementation of packaged ERP software and associated changes in business processes has proved not to be an easy task. As many organizations have discovered, the implementation of ERP systems can be a monumental disaster unless the process is handled carefully. The aim of this study is to identify the risks and controls used in ERP implementations, with the objective to understand the ways in which organizations can minimize the business risks involved. By controlling and minimizing the major business risks in the first instance, the scene can be set for the successful implementation of an ERP system. The study was motivated by the significance, for both the research and practice communities, of understanding the risks and controls critical for the successful implementation of ERP systems. Following the development of a model of risks and controls, a field study of an ERP system implementation project in an organization was conducted to provide a limited test of the model. The results from the field study provided support for risks and controls identified in the literature. The results also identified several controls not mentioned in the reviewed literature. The study lays the foundation for further research into the risk/control framework so important for the success of the implementations of ERP systems.La implementación de los sistemas ERP ha sido problemática para muchas organizaciones. Dada la cantidad de informes sobre fallos considerables, la implementación de los paquetes de software ERP y los cambios asociados en los procesos de negocios han demostrado no ser tarea fácil. Como muchas organizaciones ya han descubierto, la implementación de los sistemas ERP pueden ser un desastre monumental a no ser que el proceso se lleve a cabo cuidadosamente. El objetivo de este estudio es identificar los riesgos y controles usados en las implementaciones de ERP, con el propósito de comprender la forma en que las organizaciones pueden minimizar los riesgos implicados en los negocios. Mediante el control y disminución de los riesgos en primer lugar, se puede preparar el escenario para una implementación exitosa de un sistema de ERP. El estudio fue motivado por la importancia de comprender y controlar los riesgos críticos (tanto para las comunidades de investigación como las que los practican), para la implementación exitosa de los sistemas ERP. Siguiendo el desarrollo de un modelo de riesgos y control, un estudio de campo de un proyecto de implementación de un sistema ERP se llevó a cabo en una organización para proporcionar una pequeña prueba del modelo. Los resultados de este estudio proporcionaron apoyo para los riesgos y controles identificados en la literatura. El estudio pavimenta las bases para ahondar en las investigaciones sobre el ámbito del riesgo/control que es tan importante para una implementación exitosa de los sistemas ERP

Resources-Events-Agents Design Theory: A Revolutionary Approach to Enterprise System Design

Enterprise systems typically include constructs such as ledgers and journals with debit and credit entries as central pillars of the systems’ architecture due in part to accountants and auditors who demand those constructs. At best, structuring systems with such constructs as base objects results in the storing the same data at multiple levels of aggregation, which creates inefficiencies in the database. At worst, basing systems on such constructs destroys details that are unnecessary for accounting but that may facilitate decision making by other enterprise functional areas. McCarthy (1982) proposed the resources-events-agents (REA) framework as an alternative structure for a shared data environment more than thirty years ago, and scholars have further developed it such that it is now a robust design theory. Despite this legacy, the broad IS community has not widely researched REA. In this paper, we discuss REA’s genesis and primary constructs, provide a history of REA research, discuss REA’s impact on practice, and speculate as to what the future may hold for REA-based enterprise systems. We invite IS researchers to consider integrating REA constructs with other theories and various emerging technologies to help advance the future of information systems and business research

Diagrammatic Attention Management and the Effect of Conceptual Model Structure on Cardinality Validation

Diagrams are frequently used to document various components of information systems, from the procedures established for user-system interaction, to the structure of the database at the system’s core. Past research has revealed that diagrams are not always used as effectively as their creators intend. This study proposes a theory of diagrammatic attention management to contribute to the exploration of diagram effectiveness. Based upon diagrammatic attention management, this study demonstrates that the type of diagram most commonly used to represent conceptual models is less effective than three other alternatives for validating the models’ cardinalities. Most conceptual models are documented using entity-relationship diagrams that include a full transaction cycle or module on a single page, i.e., an aggregate diagrammatic format. Participants in this study using three alternative representations (disaggregate diagrammatic, aggregate sentential, and disaggregate sentential) outperformed users of the aggregate diagrammatic format for cardinality validation. Results suggest that to facilitate effective use of aggregate diagrams, users need a mechanism by which to direct their attention while using the diagrams. If such an attention direction mechanism is not inherent in a diagram, it may need to be applied as an external tool, or the diagram may need to be disaggregated to facilitate use