Binding energy of localized biexcitons in quantum wells

A variational calculation of the ground state energy of a biexciton in a GaAs/AlGaAs quantum well is presented. The well width fluctuations leading to trapping of the biexcitons are modeled by a parabolic potential. The results obtained for different well widths are compared with recent experimental data. Good agreement is obtained both for the biexciton binding energy and for the Haynes factor. We find that the structure of a biexciton is similar to the one of the H_2 molecule.Comment: 9 pages, 4 figure

Electrochemical processes and systems: application for tutors

The features of redox reactions and the principles of their balancing according to the medium composition are considered. The basic representations about electrochemical processes and systems are outlined. The reactions and principles of chemical sources of electric energy and electrolysis systems functioning are analyzed. A general idea is given about the chemical properties of metals, corrosion resistance in environments of various aggressiveness, and the protection principles are given. Multivariate tasks and exercises for students, and PhD student’s classroom and independent work are offered. For teachers, PhD students and students of universities of specialties "Chemical technologies and engineering", "Biotechnologies and bioengineering", "Oil and gas engineering and technologies".Розглянуто особливості окисно-відновних реакцій і принципи їх балансування залежно від складу середовища. Викладено фундаментальні уявлення про електрохімічні процеси і системи. Проаналізовано перебіг реакцій і принципи функціонування хімічних джерел електричної енергії та систем електролізу. Узагальнено уявлення щодо хімічних властивостей металів, корозійної стійкості у середовищах різної агресивності та наведено принципи організації захисту від руйнування. Запропоновано багатоваріантні завдання та вправи для аудиторної та самостійної роботи студентів і аспірантів. Розраховано на викладачів, аспірантів і студентів вищих навчальних закладів спеціальностей "Хімічні технології та інженерія”, "Біотехнології та біоінженерія", "Нафтогазова інженерія та технології"

Membrane-transferring regions of gp41 as targets for HIV-1 fusion inhibition and viral neutralization

12 páginas, 4 figurasThe fusogenic function of HIV-1 gp41 transmembrane Env subunit relies on two different kinds of structural elements: i) a collapsible ectodomain structure (the hairpin or six-helix bundle) that opens and closes, and ii) two membrane- transferring regions (MTRs), the fusion peptide (FP) and the membrane-proximal external region (MPER), which ensure coupling of hairpin closure to apposition and fusion of cell and viral membranes. The isolation of naturally produced short peptides and neutralizing IgG-s, that interact with FP and MPER, respectively, and block viral infection, suggests that these conserved regions might represent useful targets for clinical intervention. Furthermore, MTR-derived peptides have been shown to be membrane-active. Here, it is discussed the potential use of these molecules and how the analysis of their membrane activity in vitro could contribute to the development of HIV fusion inhibitors and effective immunogensThe authors wish to thank financial support obtained from Spanish MICINN (BIO2008- 00772) (JLN) and University of the Basque Country (GIU 06/42 and DIPE08/12) (NH and JLN).Peer reviewe

Structure and properties of powder cathode materials of titanium - titanium carbide system

We discuss structural and electrical properties of AlAsxSb1-x bulk layers and InAs/AlAsxSb1-x heterostructures grown by molecular beam epitaxy over a wide range of composition (0≤x≤0.4). We demonstrate the strong sensitivity of the structural quality and the composition of Al(As,Sb) on growth parameters such as substrate temperature, As : Sb flux ratio, as well as total group-V flux, and discuss the influence of a miscibility gap on the molecular beam epitaxial growth of Al(As,Sb). We also find that both the composition and the growth temperature strongly influence the surface morphology: Al(As,Sb) - especially when grown at low substrate temperature - appears to grow in an island-coalescence mode rather than in a two-dimensional manner as it does for pure AlAs or AlSb. The electrical transport along AlSb/InAs/Al(As,Sb) quantum wells is strongly influenced by the growth temperature of Al(As,Sb) and we observe the formation of additional defects when the top barrier was grown at low substrate temperature. The transport across InAs/Al(As,Sb) heterojunctions was found to depend on both the growth temperature and the arsenic composition. An increase in arsenic composition results in a strongly decreased current across the heterojunction. From ballistic electron emission spectroscopy experiments, we confirm the transition from a staggered band lineup for InAs/AlSb to a straddled band lineup for InAs/AlAsxSb1-x for x=0.16

Study of drinking water activity towards the formation organoferric complexes

The article considers one of the methods of the study of drinking water activity towards the formation of organoferric complexes that helps to solve the problem of asiderotic anemia

Automated control system for a mashing process

The goal of this paper is to describe a system for a mashing process, which is the first part of brewing beer. The mashing is a procedure where the fermentable (and some non-fermentable) sugars are extracted from malts. The program part based on LabVIEW, which is used to control NI CompactRIO. The main target of the project is to reach a predefined levels of the temperatures and maintain it during the pauses. When the necessary break time is ended the system is ready to go to the new value. The precise control of the temperatures during the breaks is one of the critical factors that define the texture and alcohol content of the beer. The system has two tanks with resistors PT100 in both of them, heat exchanger (coil), heater and pump. The first tank has heating element in order to rise the temperature in the other one. This project has practical solution with all explanations and graphs which are proven working ability of this control system