200 research outputs found
Simulation of the transit-time optical stochastic cooling process in the Cornell Electron Storage Ring
In preparation for a demonstration of optical stochastic cooling in the
Cornell Electron Storage Ring (CESR) we have developed a particle tracking
simulation to study the relevant beam dynamics. Optical radiation emitted in
the pickup undulator gives a momentum kick to that same particle in the kicker
undulator. The optics of the electron bypass from pickup to kicker couples
betatron amplitude and momentum offset to path length so that the momentum kick
reduces emittance and momentum spread. Nearby electrons contribute an
incoherent noise. Layout of the bypass line is presented that accommodates
optics with a range of transverse and longitudinal cooling parameters. The
simulation is used to determine cooling rates and their dependence on bunch and
lattice parameters for bypass optics with distinct emittance and momentum
acceptance
Formation of the internal structure of solids under severe action
On the example of a particular problem, the theory of vacancies, a new form
of kinetic equations symmetrically incorporation the internal and free energies
has been derived. The dynamical nature of irreversible phenomena at formation
and motion of defects (dislocations) has been analyzed by a computer
experiment. The obtained particular results are extended into a thermodynamic
identity involving the law of conservation of energy at interaction with an
environment (the 1st law of thermodynamics) and the law of energy
transformation into internal degree of freedom (relaxation). The identity is
compared with the analogous Jarzynski identity. The approach is illustrated by
simulation of processes during severe plastic deformation, the Rybin kinetic
equation for this case has been derived.Comment: 9 pages, 5 figure
Beam-Breakup Instability Theory for Energy Recovery Linacs
Here we will derive the general theory of the beam-breakup instability in
recirculating linear accelerators, in which the bunches do not have to be at
the same RF phase during each recirculation turn. This is important for the
description of energy recovery linacs (ERLs) where bunches are recirculated at
a decelerating phase of the RF wave and for other recirculator arrangements
where different RF phases are of an advantage. Furthermore it can be used for
the analysis of phase errors of recirculated bunches. It is shown how the
threshold current for a given linac can be computed and a remarkable agreement
with tracking data is demonstrated. The general formulas are then analyzed for
several analytically solvable cases, which show: (a) Why different higher order
modes (HOM) in one cavity do not couple so that the most dangerous modes can be
considered individually. (b) How different HOM frequencies have to be in order
to consider them separately. (c) That no optics can cause the HOMs of two
cavities to cancel. (d) How an optics can avoid the addition of the
instabilities of two cavities. (e) How a HOM in a multiple-turn recirculator
interferes with itself. Furthermore, a simple method to compute the orbit
deviations produced by cavity misalignments has also been introduced. It is
shown that the BBU instability always occurs before the orbit excursion becomes
very large.Comment: 12 pages, 6 figure
Spatial problem of water distribution in open channels
The article discusses the spatial problem of cold water movement in an open channel water distribution system through a door in a side wall. The formula for calculating the amount of cold water flowing through the channel is based on the cross-sectional area of the main channel. It is presented in terms of the velocity and depth of the water surface
Phylogenetic analysis of the microbial mat in the hot spring Garga (Baikal rift zone) and the diversity of natural peptidases
Hydrolytic bacteria (in particular, proteolytics) are the primary destructors in hot springs. The proteolytic bacteria are able to secrete enzymes that are active in wide ranges of pH and temperature. The aim of this work was to study the taxonomic composition, the structure of the bacterial microbial mat, and to study the distribution of peptidases in the thermophilic microbial Garga community. For the study, we sampled the microbial mat at a water temperature of 54.2 °C and a pH of 8.3. Hydrochemical analysis of water showed a high content of sulfates, 390 mg/dm3. The microelement composition of water showed that the Garga water had increased concentrations of B, Rb, Li, Ba, Sr. We analyzed the taxonomic diversity of the microbial community in the hot spring Garga at a temperature zone of 54 °C. The structure of the microbial mat is represented by various phylogenetic groups of mesophilic and thermophilic bacteria, with various metabolic and ecological functions. The dominant group in this community was the phylum Firmicutes (64 %). The analysis of the collected metagenomic sequences of the microbial community allowed the detected peptidases in the microbial community in the hot spring Garga to be for the first time systematized and characterized. Comparisons of metagenomic sequences of representative data showed a dominance of serine peptidase class enzymes. Natural peptidases in the investigated microbial community ensure the hydrolysis of biopolymers at the first stages of the destruction of organic matter and may have biotechnological relevance
Notes on the Third Law of Thermodynamics.I
We analyze some aspects of the third law of thermodynamics. We first review
both the entropic version (N) and the unattainability version (U) and the
relation occurring between them. Then, we heuristically interpret (N) as a
continuity boundary condition for thermodynamics at the boundary T=0 of the
thermodynamic domain. On a rigorous mathematical footing, we discuss the third
law both in Carath\'eodory's approach and in Gibbs' one. Carath\'eodory's
approach is fundamental in order to understand the nature of the surface T=0.
In fact, in this approach, under suitable mathematical conditions, T=0 appears
as a leaf of the foliation of the thermodynamic manifold associated with the
non-singular integrable Pfaffian form . Being a leaf, it cannot
intersect any other leaf const. of the foliation. We show that (N) is
equivalent to the requirement that T=0 is a leaf. In Gibbs' approach, the
peculiar nature of T=0 appears to be less evident because the existence of the
entropy is a postulate; nevertheless, it is still possible to conclude that the
lowest value of the entropy has to belong to the boundary of the convex set
where the function is defined.Comment: 29 pages, 2 figures; RevTex fil
The crystal growth and properties of novel magnetic double molybdate RbFe(MoO) with mixed Fe/Festates and 1D negative thermal expansion
Single crystals of new compound RbFe(MoO) were successfully grown by the flux method, and their crystal structure was determined using the X-ray single-crystal diffraction technique. The XRD analysis showed that the compound crystallizes in the monoclinic space group P21/m, with unit cell parameters a = 6.8987(4), b = 21.2912(12) and c = 8.6833(5) Å, β = 102.1896(18)°, V = 1246.66(12) Å, Z (molecule number in the unit cell) = 2, R-factor (reliability factor) = 0.0166, and T = 293(2) K. Raman spectra were collected on the single crystal to show the local symmetry of MoO tetrahedra, after the confirmation of crystal composition using energy dispersive X-ray spectroscopy (EDS). The polycrystalline samples were synthesized by a solid-state reaction in the Ar atmosphere; the particle size and thermal stability were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) analyses. The compound decomposes above 1073 K in an Ar atmosphere with the formation of Fe(III) molybdate. The thermal expansion coefficient along the c direction has the value α = −1.3 ppm K over the temperature range of 298–473 K. Magnetic measurements revealed two maxima in the magnetization below 20 K, and paramagnetic behavior above 50 K with the calculated paramagnetic moment of 12.7 μB per formula unit is in good agreement with the presence of Fe and Fe in the high-spin (HS) state. The electronic structure of RbFe5(MoO4)7 is comparatively evaluated using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations
Identity Leadership, Employee Burnout and the Mediating Role of Team Identification: Evidence from the Global Identity Leadership Development Project
Do leaders who build a sense of shared social identity in their teams thereby protect them from the adverse effects of workplace stress? This is a question that the present paper explores by testing the hypothesis that identity leadership contributes to stronger team identification among employees and, through this, is associated with reduced burnout. We tested this model with unique datasets from the Global Identity Leadership Development (GILD) project with participants from all inhabited continents. We compared two datasets from 2016/2017 (n = 5290; 20 countries) and 2020/2021 (n = 7294; 28 countries) and found very similar levels of identity leadership, team identification and burnout across the five years. An inspection of the 2020/2021 data at the onset of and later in the COVID-19 pandemic showed stable identity leadership levels and slightly higher levels of both burnout and team identification. Supporting our hypotheses, we found almost identical indirect effects (2016/2017, b = −0.132; 2020/2021, b = −0.133) across the five-year span in both datasets. Using a subset of n = 111 German participants surveyed over two waves, we found the indirect effect confirmed over time with identity leadership (at T1) predicting team identification and, in turn, burnout, three months later. Finally, we explored whether there could be a “too-much-of-a-good-thing” effect for identity leadership. Speaking against this, we found a u-shaped quadratic effect whereby ratings of identity leadership at the upper end of the distribution were related to even stronger team identification and a stronger indirect effect on reduced burnout
Political leaders' identity leadership and civic citizenship behavior:The mediating role of trust in fellow citizens and the moderating role of economic inequality
Identity leadership captures leaders efforts to create and promote a sense of shared group membership (i.e., a sense of “we” and of “us”) among followers. The present research report tests this claim by drawing on data from 26 countries that are part of the Global Identity Leadership Development (GILD) project to examine the relationship between political leaders' identity leadership and civic citizenship behavior (N = 6787). It also examines the contributions of trust and economic inequality to this relationship. Political leaders' identity leadership (PLIL) was positively associated with respondents' people-oriented civic citizenship behaviors (CCB-P) in 20 of 26 countries and civic citizenship behaviors aimed at one's country (CCB-C) in 23 of 26 countries. Mediational analyses also confirmed the indirect effects of PLIL via trust in fellow citizens on both CCB-P (in 25 out of 26 countries) and CCB-C (in all 26 countries). Economic inequality moderated these effects such that the main and indirect effects of trust in one's fellow citizens on CCB-C were stronger in countries with higher economic inequality. This interaction effect was not observed for CCB-P. The study highlights the importance of identity leadership and trust in fellow citizens in promoting civic citizenship behavior, especially in the context of economic inequality.</p
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