Extremely Metal-Poor Asymptotic Giant Branch Stars

Little is known about the first stars, but hints on this stellar population can be derived from the peculiar chemical composition of the most metal-poor objects in the Milky Way and in resolved stellar populations of nearby galaxies. In this paper, we review the evolution and nucleosynthesis of metal-poor and extremely metal-poor (EMP) stars with low and intermediate masses. In particular, new models of 6 M⊙ with three different levels of metallicity, namely Z=10−4, 10−6 and 10−10, are presented. In addition, we illustrate the results obtained for a 2 M⊙, Z=10−5 model. All these models have been computed by means of the latest version of the FuNS code. We adopted a fully coupled scheme of solutions for the complete set of differential equations describing the evolution of the physical structure and the chemical abundances, as modified by nuclear processes and convective mixing. The scarcity of CNO in the material from which these stars formed significantly affects their evolution, their final fate and their contribution to the chemical pollution of the ISM in primordial galaxies. We show the potential of these models for the interpretation of the composition of EMP stars, with particular emphasis on CEMP stars.

Complete set of quasi-conserved quantities for spinning particles around Kerr

We revisit the conserved quantities of the Mathisson-Papapetrou-Tulczyjew equations describing the motion of spinning particles on a fixed background. Assuming Ricci-flatness and the existence of a Killing-Yano tensor, we demonstrate that besides the two non-trivial quasi-conserved quantities, i.e. conserved at linear order in the spin, found by Rüdiger, non-trivial quasi-conserved quantities are in one-to-one correspondence with non-trivial mixed-symmetry Killing tensors. We prove that no such stationary and axisymmetric mixed-symmetry Killing tensor exists on the Kerr geometry. We discuss the implications for the motion of spinning particles on Kerr spacetime where the quasi-constants of motion are shown not to be in complete involution.

Getting the valuation formulas right when it comes to annuities

PurposeThe purpose of this paper is to establish the flow-to-equity method, the free cash flow (FCF) method, the adjusted present value method and the relationships between these methods when the FCF appears as an annuity. More specifically, we depart from the two most widely used evaluation settings. The first setting is that of Modigliani and Miller who based their analysis on a stationary FCF. The second setting is that of Miles and Ezzell who worked with an FCF that represents an autoregressive possess of first order.Design/methodology/approachInspired by recent observations in the literature concerning cash flows, discount rates and values in discounted cash flow (DCF) methods, we mathematically derive DCF valuation formulas for annuities.FindingsThe following relationships are established: (a) the correct discount rate of the tax shield when the free cash flow takes the form of a first-order autoregressive annuity, (b) the direct valuation of the tax shield from the free cash flow for a first-order autoregressive annuity, (c) the correct translation from the required return on unlevered equity to the levered equity, when the free cash flow is a stationary annuity and (d) direct calculation of the unlevered and levered firm values and the value of the tax shield for a stationary annuity.Originality/valueUntil now the complete set of formulas for the valuation of stochastic annuities by different DCF methods has not been established in the literature. These formulas are developed here. These formulas are important for practitioners and academics when it comes to the valuation of cash flows of finite lifetime.

Challenges and Trends of Agile

Rapidly increasing of requirements of business pushed researchers to define new approaches and methodologies to meet marketing needs. Agile methodology has been created and replaced the traditional-driven development methods that focus on soliciting, documenting a complete set of requirements, and take a long time comparing to market change. On the other hand, customers need to be closer to the development process and collaborate with team development. Despite agile advantages, introducing new tools, coordination, and collaboration concepts, some challenges still need to be discussed and improved. These challenges relate to achieve balanced IT service development process in the organization. As a result, new trends have been created to facilitate new changes in software development. This chapter will study agile methodologies and different challenges with suggested solutions generated from agile philosophy itself.

Prohibited Press in the Central State Bookshop in 1919–1940

This article analyses the issues of collecting and storing illegal publications and those confiscated by censorship authorities in the Central State Bookshop. It describes the structure of the military and other general censorship institutions, which sent the prohibited press to the Central State Bookshop. The aim of the study is to establish the approximate date of commencement of the activities of the department that stored confiscated by censorship or illegally issued publications, and several lists of publications prohibited by censorship and transmitted by the CSB are discussed. It is worth noting that until the 1940s, libraries were also called bookshops. In 1936, after the promulgation of the Law on Public Libraries, the Central State Bookshop became the Central State Library, and its departments became state public libraries. Between 1919–1922, under the management of Eduardas Volteris, the collection and storage of illegal and censored publications at the Central State Bookshop became a matter of interest. The legal deposit was the key and constant source of acquisition of the collections of the Central State Bookshop. In 1919 and 1935, the press laws stipulated how many mandatory copies had to be delivered to county governors or simply to state institutions. However, illegal and confiscated publications were not included in the legal deposit. The main aim of the library was to collect and store all publications published in Lithuania and by Lithuanian publishers abroad. Therefore, it was important for the library to compile a complete set of the current press. To obtain prohibited titles, the library cooperated with the structural units of the Ministry of National Defense and the Ministry of the Interior responsible for the supervision of the press. In various historical periods, unequal attention was paid to the compilation of censorship-restricted press in the Central State Bookshop. Until the 1930s, there was an intensive correspondence between war censors and the Press and Societies Division of the Department of Civil Protection about sending and collecting prohibited press in the Central State Bookstore. During c. 1920–1921, illegal and confiscated publications began to be collected in a separate office called the “secret division”. In the 1940s, censorship institutions sent lists of prohibited press of various volumes to the library. After reviewing the publications on these lists, no signs of censorship could be found. Records of censorship office provenances and censorship officers were found in individual publications that were not included in the lists of prohibited books. Although the publications confiscated by censorship authorities were stored in the library of the University of Lithuania, and in the library of Vytautas Magnus University since 1930, CSB was the only library in the interwar period in which special attention was paid to the issues of collecting prohibited press. Use of the prohibited press was restricted. These titles were not open to general public; only employees of ministries and members of the Seimas could read it. The prohibited press could serve scientific research and press statistics.

Design and Simulation of a Servo-Drive Motor Using ANSYS Electromagnetics

The paper is devoted to determining the output parameters of a servomotor, which belongs to synchronous machines with permanent magnets, in order to further determine the characteristics of transient modes in the software package ANSYS Electromagnetics. RMxprt, part of ANSYS Electromagnetics, allows to determine the parameters of windings, losses, motor performance, but requires filling out a form with a complete set of geometric dimensions and winding data. Of course, such data are not available in the motor data sheet, so the first task solved in the paper is to determine all the necessary and sufficient parameters to perform the calculation in RMxprt. The results of the calculations were compared with the measurements on the experimental servomotor EMG-10APA22. This paper shows how to export a servomotor object from RMxprt to the Simplorer workspace, which is also part of the ANSYS Electromagnetics. According to the simulation results in ANSYS Simplorer, the characteristics of the transient modes of the servomotor powered by a stable three-phase source are obtained. Prospects for further research related to the improvement of the simulation model in ANSYS Simplorer are presented.

Quantum Walks: Schur Functions Meet Symmetry Protected Topological Phases

This paper uncovers and exploits a link between a central object in harmonic analysis, the so-called Schur functions, and the very hot topic of symmetry protected topological phases of quantum matter. This connection is found in the setting of quantum walks, i.e. quantum analogs of classical random walks. We prove that topological indices classifying symmetry protected topological phases of quantum walks are encoded by matrix Schur functions built out of the walk. This main result of the paper reduces the calculation of these topological indices to a linear algebra problem: calculating symmetry indices of finite-dimensional unitaries obtained by evaluating such matrix Schur functions at the symmetry protected points $$\pm 1$$ ± 1 . The Schur representation fully covers the complete set of symmetry indices for 1D quantum walks with a group of symmetries realizing any of the symmetry types of the tenfold way. The main advantage of the Schur approach is its validity in the absence of translation invariance, which allows us to go beyond standard Fourier methods, leading to the complete classification of non-translation invariant phases for typical examples.

On the statements of boundary conditions in models of the woven materials production

В статье обсуждаются проблемы постановка краевых задач при моделировании процессов аддитивного производства 3D материала, при учете наличия в нем дополнительных выделенных направлений (выкладки волокон в тканых материалах, арматуры в бетонных конструкциях, биоволокон в мышечной ткани и т.д.). Выводится общая форма тензорного соотношения на поверхности наращивания, при учете дополнительного выделенного направления. Определяется необходимая система независимых аргументов определяющей тензорной функции на поверхности наращивания в рассматриваемом случае. Определяется полный набор совместных рациональных инвариантов тензора напряжений и характерных директоров. Дается инвариантно-полная формулировка определяющих соотношений на поверхности наращивания. Предложены постановки краевых задач, моделирующих процессы синтеза тканых 3D материалов. Полученные дифференциальные ограничения конкретизируются для ортогональных систем координат, учитывающих геометрию процесса наращивания. The article discusses the problem of boundary value problems in models of the additive production processes of a 3D material, taking into account the presence of additional selected directions in it (laying out fibers in woven materials, reinforcement in concrete structures, biofibers in muscle tissue, etc.). The general form of the tensor relation on the growing surface is shown, taking into account the additional selected direction. The necessary system of independent arguments of the constitutive tensor function on the growing surface in the considered case is determined. A complete set of joint rational invariants of the stress tensor and characteristic directors is determined. An invariant-complete formulation of the constitutive relations on the growing surface is given. The formulation of boundary value problems that simulate the processes of synthesis of woven 3D materials are proposed. The resulting differential constraints are specified for orthogonal coordinate systems taking account of the geometry of the growing process.