Structural transitions in vertically and horizontally coupled parabolic channels of Wigner crystals

Structural phase transitions in two vertically or horizontally coupled channels of strongly interacting particles are investigated. The particles are free to move in the $x$-direction but are confined by a parabolic potential in the $y$-direction. They interact with each other through a screened power-law potential ($r^{-n}e^{-r/\lambda}$). In vertically coupled systems the channels are stacked above each other in the direction perpendicular to the $(x,y)$-plane, while in horizontally coupled systems both channels are aligned in the confinement direction. Using Monte Carlo (MC) simulations we obtain the ground state configurations and the structural transitions as a function of the linear particle density and the separation between the channels. At zero temperature the vertically coupled system exhibits a rich phase diagram with continuous and discontinuous transitions. On the other hand the vertically coupled system exhibits only a very limited number of phase transitions due to its symmetry. Further we calculated the normal modes for the Wigner crystals in both cases. From MC simulations we found that in the case of vertically coupled systems the zigzag transition is only possible for low densities. A Ginzburg-Landau theory for the zigzag transition is presented, which predicts correctly the behavior of this transition from which we interpret the structural phase transition of the Wigner crystal through the reduction of the Brillouin zone.Comment: 9 pages, 13 figure

ON SOME PHARMACOLOGICAL PROPERТIES OF ТНЕ ALKALOIDS OF VINCA MAJOR

Pharmacological studies of the alkaloids of Vinca minor and Vinca hеrbасеае revealed  that compounds found in these plants аrе highly active pharmacologic agents. Тhеу hаve а sedative effect оn the central nervous system, they considerably lower the blооd pressure, theyblосk some ganglia, belonging to the parasympathetic part of the vegetative nervous system and interrupt the transmission of nervous impulses in the myo-neural synapses, realizing а curare-like effect; they also anesthesize the receptors of the cornea etc. On the basis of these investigations а maгket product was deliveгed under the name of Vincaipan, containing the total alkaloids of Vinca minor, whose previous clinical trial seemed quite encuoraging. All this stimulated the phytochemical and pharmacological elaboration of the third representative of the botanic family Appocynaceae. This plant also belongs to the species Vinca - Vinca major, grown in our country. Mention slhould also bе made of the fact that according to phytochemical investigations of а number of foreign authors Vinca major contains alkaloids with indolic structure, which аrе more or less structurally гelated to гeserpine, whose polypharmacological activity and great therapeutic significance аrе well known.These were the motives fог our systematic pharmaco1logical analysis of the total alkaloids of this plant. obtained at the Chair of Pharmacology at the Higher Medical Institute in Varna.

Meissner phases in spin-triplet ferromagnetic superconductors

We present new results for the properties of phases and phase transitions in spin-triplet ferromagnetic superconductors. The superconductivity of the mixed phase of coexistence of ferromagnetism and unconventional superconductivity is triggered by the presence of spontaneous magnetization. The mixed phase is stable but the other superconducting phases that usually exist in unconventional superconductors are either unstable or for particular values of the parameters of the theory some of them are metastable at relatively low temperatures in a quite narrow domain of the phase diagram. Phase transitions from the normal phase to the phase of coexistence is of first order while the phase transition from the ferromagnetic phase to the coexistence phase can be either of first or second order depending on the concrete substance. Cooper pair and crystal anisotropies determine a more precise outline of the phase diagram shape and reduce the degeneration of ground states of the system but they do not change drastically phase stability domains and thermodynamic properties of the respective phases. The results are discussed in view of application to metallic ferromagnets as UGe2, ZrZn2, URhGe.Comment: 21 pages, 7 figures; Phys. Rev. B (2005) in pres

A comparison of predicted distortion of a manifold fabricated by laser powder bed fusion using solid and shell element-based finite element models

This paper compares the predicted distortion of a manifold geometry fabricated by laser powder bed fusion between an established finite element model using solid elements and a newly developed in this paper finite element model using shell elements. The developed finite element models utilized two methods to induce a strain field (inherent strain and analytical thermal methods). The predicted distortions from these models were also compared with experimentally measured distortions. The results showed that the predicted distortion using solid elements is more suitable to predict the buckling effect on the manifold geometry. Despite that, the model using shell elements showed an accurate prediction of distortion in many areas of the manifold, and it proved to be computationally more efficient (2.4 times faster), this model showed lower accuracy in the prediction of distortion generated by buckling. However, shell elements could be used in other applications where the bucking is not the driving mechanism for the prediction of distortion in laser powder bed fusion or in applications where the accuracy of distortion is not a requirement (e.g., support structures)

Engineering security into distributed systems: a survey of methodologies

Rapid technological advances in recent years have precipitated a general shift towards software distribution as a central computing paradigm. This has been accompanied by a corresponding increase in the dangers of security breaches, often causing security attributes to become an inhibiting factor for use and adoption. Despite the acknowledged importance of security, especially in the context of open and collaborative environments, there is a growing gap in the survey literature relating to systematic approaches (methodologies) for engineering secure distributed systems. In this paper, we attempt to fill the aforementioned gap by surveying and critically analyzing the state-of-the-art in security methodologies based on some form of abstract modeling (i.e. model-based methodologies) for, or applicable to, distributed systems. Our detailed reviews can be seen as a step towards increasing awareness and appreciation of a range of methodologies, allowing researchers and industry stakeholders to gain a comprehensive view of the field and make informed decisions. Following the comprehensive survey we propose a number of criteria reflecting the characteristics security methodologies should possess to be adopted in real-life industry scenarios, and evaluate each methodology accordingly. Our results highlight a number of areas for improvement, help to qualify adoption risks, and indicate future research directions.Anton V. Uzunov, Eduardo B. Fernandez, Katrina Falkne

MANAGEMENT ACTIVITIES EFFECTIVENESS IN MODERN RUSSIAN INSTITUTION IN THE CONTEXT OF HEAD WORKPLACE MODELING

Purpose: The scientific approach to the organization of labor and the workplace of the institution head involves the search for the most optimal model or technique acceptable to the Russian conditions within the current management culture, traditional views on the nature of managerial work, the scale and effectiveness of management activities. Methodology: Methodological guidelines for the study of workplaces’ organization of credit and financial institutions’ heads are based on the provisions of modern ergonomics and the principles of a system-based approach, allowing justifying as a significant one the environment-oriented approach. Result: The obtained results served as the basis for the development of appropriate recommendations to optimize the current situation in the context of eliminating existing gaps and problems in the credit and financial sector of the Russian economy from the standpoint of optimizing the process of organizing working places for managers of institutions in this profile. Applications: This research can be used for universities, teachers, and students. Novelty/Originality: In this research, the model of the Management Activities Effectiveness in Modern Russian Institution in the context of Head Workplace Modeling is presented in a comprehensive and complete manner

Mechanical properties of materials for 3D printed orthodontic retainers

Aim: The purpose of this study was to compare the mechanical properties of materials used for orthodontic retainers made by direct 3D printing and thermoforming. Materials and methods: Twenty-one specimens (n=7) from 3 different materials (Formlabs Dental LT Clear V2 - Formlabs Inc., Somerville, Massachusetts, USA; NextDent Ortho Flex - Vertex-Dental B.V., Soesterberg, The Netherlands, and Erkodent Erkodur - ERKODENT, Germany) were manufactured and their mechanical properties were evaluated. Two of the specimen groups were 3D printed and the other one was fabricated using a material for thermoforming. The statistical methods we applied were descriptive statistics, the Kruskal-Wallis and Dunn’s post-hoc tests. Results: With respect to Young’s modulus (E), the Kruskal-Wallis test (df=2, χ2=17.121, p=0.0002) showed a significant difference between the materials for direct 3D printing of orthodontic retainers (E=2762.4 MPa±115.16 MPa for group 1 and 2393.05 MPa±158.13 MPa for group 2) and thermoforming foils (group 3, E=1939.4 MPa±74.18 MPa). Statistically significant differences were also found between the flexural strength (FS) (Kruskal-Wallis test, df=2, χ2=17.818, p=0.0001) and F(max) (Kruskal-Wallis test, df=2, χ2=17.818, p=0.0001). Conclusions: The materials tested in the current study showed statistically significant differences in their Young’s modulus, flexural strength, and F(max)

Critical Properties of Condensation of Field-Induced Triplet Quasiparticles

A review on the field-induced magnetic ordering is given, together with some results of a quantum Monte Carlo simulation focused on the critical behevior near the quantum critical point.Comment: Proceedings of SPQS, Sendai, 200

Critical behavior in 2+1 dimensional black holes

The critical behavior and phase transition in the 2+1 dimensional Ba\~nados, Teitelboim, and Zanelli (BTZ) black holes are discussed. By calculating the equilibrium thermodynamic fluctuations in the microcanonical ensemble, canonical ensemble, and grand canonical ensemble, respectively, we find that the extremal spinning BTZ black hole is a critical point, some critical exponents satisfy the scaling laws of the ``first kind'', and the scaling laws related to the correlation length suggest that the effective spatial dimension of extremal black holes is one, which is in agreement with the argument that the extremal black holes are the Bogomol'nyi saturated string states. In addition, we find that the massless BTZ black hole is a critical point of spinless BTZ black holes.Comment: RevTex, 9 pages, nofigur