Do flares in Sagittarius A* reflect the last stage of tidal capture?

In recent years the case for the presence of 3-4 10^6 M_sun black hole in our Galactic Center has gained strength from results of stellar dynamics observations and from the detection of several rapid X-ray and IR flares observed in the Sagittarius A* from 2000 to 2004. Here we explore the idea that such flares are produced when the central black hole tidally captures and disrupts a small body - e.g. a comet or an asteroid.Comment: 6 pages, 9 figures, acknowledgments added, to appear in the Proceedings of the Albert Einstein's Century International Conference, Paris 200

Evaluation of the nutrient status of wheat plants

The balance of the principal ionic constituents in plants is reviewed in relation to the requirements for each of the elements, and for total accumulation as reflected in the total cation content (C), the inorganic anion conent (A) and the organic anion content (C-A). The balance in young wheat plants is investigated by means of adding various combinations of the principal ions to the soil. A summary of tests on adequacy of supply with the principal nutrient ions and of accumulation of cations, inorganic anions and organic anions, based on critical values. for contents in the plant material, is presented for diagnosing the nutrient status in relation to capacity for maximum growth

Reasoning and Logical-Proofs of the Fundamental Laws: 'No Hope' for the Challengers of the Second Law of Thermodynamics

This comprehensive treatise is written for the special occasion of the author's 70th birthday. It presents his lifelong endeavors and reflections with original reasoning and re-interpretations of the most critical and misleading issues in thermodynamics; since now, we have the advantage to look at the historical developments more comprehensively and objectively than the pioneers. Starting from Carnot (grandfather of thermodynamics-to-be) to Kelvin and Clausius (fathers of thermodynamics), and other followers, the most relevant issues are critically examined and put in historical and contemporary perspective. From original reasoning of energy forcing and displacement to logical proofs of the fundamental laws, to ubiquity of thermal motion and heat, and indestructibility of entropy, including the new concept of "thermal roughness" and the inevitability of dissipative irreversibility, to "dissecting Carnot true reversible-equivalency" and critical concept of "Carnot-Clausius heat-work equivalency (CCHWE)" regarding the interchangeability of heat and work, and to demonstrating "no hope" for the "challengers" of the Second Law of thermodynamics, among others, are offered. It is hoped that the novel contributions presented will enhance comprehension and resolve some of the fundamental issues, as well as promote collaboration and future progress.Comment: This comprehensive treatise is written for the special occasion of the author's 70th birthday, to be submitted for review and publication. It presents his lifelong endeavors and reflections with original reasoning and re-interpretations of the most critical and misleading issues in thermodynamics, and especially the Second Law of thermodynamics and entrop

Bacterial Secondary Metabolites as Biopigments for Textile Dyeing

In the past two decades, a growing body of research regarding the utilization of natural bacterial pigments or dyes for textile dyeing has emerged. Bacterial pigments are bacterial secondary metabolites that usually have bright colors and some special properties (e.g., antimicrobial, antioxidative, UV protective etc.). In addition to their high production yield, these special properties led scientists to research and develop methods for utilizing bacterial pigments in textile dyeing. This study presents the current state this field of research, with a focus on the dyeing potential of bacterial pigments for different types of textile material. The potential future directions of research in this area are also highlighted. In addition to the durable dyeing of textiles, bacterial pigments with special properties, such as antimicrobial activity, can add multifunctionality to dyed materials, thus increasing the value of the final product. This emerging field of research will also have a great impact on sustainability and the environment, contributing to the decreased usage of synthetic dyes in the textile industry.This work was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (contract no. 451-03-68/2022-14/200135)

Data-based design of high-performance motion controllers

This paper presents a data-based design of a linear feedback controller which realizes desired closed-loop sensitivity and complementary sensitivity transfer functions. These transfer functions are specified via a single model-based performance cost. The data-based equivalent of this cost is derived, and its utility for the feedback design is demonstrated. A designer can prescribe the controller structure and complexity. Experimental results obtained in a direct-drive robot motion control problem confirm the effectiveness of the design

ANALYSIS OF ENTHALPY APPROXIMATION FOR COMPRESSED LIQUID WATER

ABSTRACT It is custom to approximate solid and liquid thermodynamic properties as being function of temperature only, since they are virtually incompressible, and Pdv compression work may be neglected. Furthermore, in classical literature, for isothermal compression processes, a general improvement and correction for liquid enthalpy approximation is given by adding the "pumping" work, vdP, to the corresponding saturation value. Analysis of water real properties shows that such a correction is unnecessary for intermediate pressures and temperatures, and it is even erroneous for higher temperatures and pressures, and thus counterproductive and misleading

Sharp Spectral Rates for Koopman Operator Learning

Nonlinear dynamical systems can be handily described by the associated Koopman operator, whose action evolves every observable of the system forward in time.Learning the Koopman operator and its spectral decomposition from data is enabled by a number of algorithms.In this work we present for the first time non-asymptotic learning bounds for the Koopman eigenvalues and eigenfunctions.We focus on time-reversal-invariant stochastic dynamical systems, including the important example of Langevin dynamics.We analyze two popular estimators: Extended Dynamic Mode Decomposition (EDMD) and Reduced Rank Regression (RRR).Our results critically hinge on novel minimax estimation bounds for the operator norm error, that may be of independent interest.Our spectral learning bounds are driven by the simultaneous control of the operator norm error and a novel metric distortion functional of the estimated eigenfunctions.The bounds indicates that both EDMD and RRR have similar variance, but EDMD suffers from a larger bias which might be detrimental to its learning rate.Our results shed new light on the emergence of spurious eigenvalues, an issue which is well known empirically.Numerical experiments illustrate the implications of the bounds in practice

Cross-Border Investment, Conflict of Laws, and the Privatization of Securities Law

The rapid acceleration of transnational investing is occurring in an environment in which emerging markets, and foreign interest in these markets, are exploding. The issues involved with cross-border investment, conflict of laws and the privatization of securities law are examined