Cvm study of charge transfer in YBa2Cu3O6+x material

The number of positive holes transferred from the CuOx basal planes to the superconducting CuO2 planes of YBa2Cu3O6+x material was calculated as a function of oxygen content x, by the use of numerical cluster variation method (CVM). The calculations were performed for the set of three different temperatures and for the different values of the parameter ξl which represents the ratio of the number m of divalent oxygen ions in the chain fragment and the total number l of oxygen ions in the chain fragment. The obtained hole count versus x dependence showed no plateau behavior for low temperatures (t=0.25 and t=0.35) while for t=0.45 indication of plateau behavior is present.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Emission Reduction and Economical Optimization of an Urban Microgrid Operation Including Dispatched PV-Based Active Generators

In order to take full advantage of distributed generators, an evolution of the classical power system organization and management is also necessary. An aggregator of a residential urban electrical network can be considered by the distribution system operator as a stakeholder, which is able to control a cluster of local generators and loads with technical constraints for the connection with the remaining distribution grid and commercial contracts with outer electrical producers. This paper is focused on the design of the microgrid central energy management system which relies on a day-ahead operational planning and an online adjustment procedure during the operation. A dynamic programming-based algorithm is derived to solve the unit commitment problem with a multiobjective function in order to reduce the economic cost and CO2 equivalent emissions. The proposed energy management system is implemented into a supervisory control and data acquisition (SCADA) and tested by using a hardware-in-the-loop simulation of the urban network. Economic and environmental gains are evaluated

The dependence of critical temperature on oxygen concentration in YBa2Cu3O6+x in terms of the fragmented chain model

An extended ASYNNNI model, that beside nearest-neighbour and next-nearest neighbour O-O interactions in the basal plane also includes interactions between the three nearest oxygen atoms, is used to describe the statistics of CuO chain fragmentation and to calculate doping and T (c) in YBa2Cu3O6+x . Calculations were made by the Monte Carlo method employing the recently proposed charge transfer model that assumes only chains whose length is equal to, or exceeds, a characteristic (critical) length, l (cr) , can provide holes to the layers and contribute to doping p. The obtained p(x) is then combined with a universal T (c) versus p relation to yield T (c) (x) characteristics that correlate remarkably with those reported in recent experiments. The best coordination between theoretical and experimental T (c) (x) characteristics has been achieved for l (cr) = 2, implying that only isolated basal plane oxygen atoms (trivial chains) do not contribute holes to CuO2 layers

Work with motivated and gifted students in physics in RCT “Mihajlo Pupin” from Pančevo - a review of the last 15 years

Since the very beginning, Regional Center for Talents “Mihajlo Pupin” in Pančevo had a physics group. Over time, the number of classes has grown, but so did the number of students and mentors. Consequently, the achievements on national and even international competitions in physics were growing steadily. After first few years spent in experimenting different possibilities in the field of work with talented students in physics, the standard of classes has been established. Such standard, with the help of motivated students and mentors has produced a successful mechanism for preparing students for various challenges in the field of physics and beyond. This paper presents a model of working in the physics group in Regional Center for Talents “Mihajlo Pupin” in Pančevo, as well as the results our students have achieved on national and international physics and science competitions in the last 15 years of work.BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S14-PEHPP Physics Education, History and Philosophy of Physic

Modulation of γ-Secretase Activity by Multiple Enzyme-Substrate Interactions: Implications in Pathogenesis of Alzheimer's Disease

BACKGROUND: We describe molecular processes that can facilitate pathogenesis of Alzheimer's disease (AD) by analyzing the catalytic cycle of a membrane-imbedded protease γ-secretase, from the initial interaction with its C99 substrate to the final release of toxic Aβ peptides. RESULTS: The C-terminal AICD fragment is cleaved first in a pre-steady-state burst. The lowest Aβ42/Aβ40 ratio is observed in pre-steady-state when Aβ40 is the dominant product. Aβ42 is produced after Aβ40, and therefore Aβ42 is not a precursor for Aβ40. The longer more hydrophobic Aβ products gradually accumulate with multiple catalytic turnovers as a result of interrupted catalytic cycles. Saturation of γ-secretase with its C99 substrate leads to 30% decrease in Aβ40 with concomitant increase in the longer Aβ products and Aβ42/Aβ40 ratio. To different degree the same changes in Aβ products can be observed with two mutations that lead to an early onset of AD, ΔE9 and G384A. Four different lines of evidence show that γ-secretase can bind and cleave multiple substrate molecules in one catalytic turnover. Consequently depending on its concentration, NotchΔE substrate can activate or inhibit γ-secretase activity on C99 substrate. Multiple C99 molecules bound to γ-secretase can affect processive cleavages of the nascent Aβ catalytic intermediates and facilitate their premature release as the toxic membrane-imbedded Aβ-bundles. CONCLUSIONS: Gradual saturation of γ-secretase with its substrate can be the pathogenic process in different alleged causes of AD. Thus, competitive inhibitors of γ-secretase offer the best chance for a successful therapy, while the noncompetitive inhibitors could even facilitate development of the disease by inducing enzyme saturation at otherwise sub-saturating substrate. Membrane-imbedded Aβ-bundles generated by γ-secretase could be neurotoxic and thus crucial for our understanding of the amyloid hypothesis and AD pathogenesis

Energy management and operational planning of a microgrid with a PV-based active generator for Smart Grid Applications

The development of energy management tools for consumers and next generation PV installations, including storage units, provides flexibility to distribution system operators. In this paper the aggregation and implementation of this new energy management method for business customers in a microgrid power system is presented. The proposed energy management system is organized according to different functions and is implemented in two parts: a central energy management of the microgrid and a local power management at the customer side. The central and local management systems exchange data and orders through a communication network. The power planning is designed according to the prediction for PV power production and the load forecasting by taking into account the capabilities of dispatched customers. According to received grid power references, additional functions are also designed to manage locally the power flows between the various sources. Application to the case of a hybrid supercapacitor battery based PV active generator is presented

Geometric distribution of CuO chains in YBa2Cu3O6+x

Statistics of CuO chains in basal planes of YBa2Cu3O6+x high-T-c superconductor has been studied in terms of two dimensional asymmetric next-to-nearest-neighbor Ising (ASYNNNI) model, with accentuation on distribution of CuO, chains per different chain lengths. It has been shown that the fraction p(1) of CuO chains containing l oxygen ions (i.e., having the length equal to l), satisfies so-called law of geometric distribution p(l) = w(1-w)(l-1), where the quantity w is equal to the inverse of average chain length l(av) in the system, for given values of oxygen content x and temperature T. In the case of ortho-II (OII) structural phase, the geometric chain probability distribution is shown to hold separately for each of two different sublattices of oxygen sites, commonly known as alpha(1), and alpha(2), with respectively defined l(av)(alpha 1)(x, T) and l(av)(alpha 2)(x, T). The theoretically derived result of the chain probability distribution p(l) is shown to be in a remarkable agreement with the results obtained out of extensive Monte Carlo calculations that were made within region of stability of orthorhombic structural phases in (x, 7) space. The relevance of chain length distribution for accurate count of the number of transferred electronic holes to superconducting CuO2 layers has been pointed out and expression for hole concentration has been derived. The concept of critical chain length for charge transfer mechanism was briefly discussed. (c) 2006 Elsevier B.V. All rights reserved

Distribution Of CuO Chains In The Oxygen Deficient Planes Of YBa2Cu3O6+2c

The distribution p(l) of CuO chains in YBa2Cu3O6+2c, with respect to different chain lengths l, obeys a simple exponential-low dependence p(l)=A×Bl, where the parameters A and B are functions of oxygen concentration c and temperature T. By the use of Monte Carlo numerical simulation of the ASYNNNI model, we have found that the parameters A and B can be expressed as a functions of a single parameter: average chain length lav. This dependence is established to be valid for a large number of points in the temperature-concentration plain (for the oxygen content in the range c∈(0.39,0.50), and for the temperatures extending from τ =kBT/V1≈ 0.3 to τ ≈1.8).SFKM 2004 : September 20–23, 2004, Sokobanja