Investigation of the Ga-rich GaAs(001) Surface Reconstructions Stability and Interaction with Halogens

Atomic and electronic structures for a number of GaAs(001) surface geometries were studied within the density functional theory in order to re-examine the energy stability of surface reconstructions in the Ga-rich limit. It was shown that among geometries with (42) symmetry so-called ζ-model is most stable but the energetically favored Ga-rich (24) reconstructions are stabilized by dimerized Ga and As atoms. Our calculations predict the coexistence of (24) and (44) reconstructions on GaAs(001) in the Ga-rich limit. Comparative study of the halogens (F, Cl, I) adsorption on the -GaAs(001)-(42) surface were performed. The energetically preferable positions for all considered halogens are found on-top sites above dimerized and nondimerized Ga atoms. The electronic properties of the semiconductor surface and its change upon halogen adsorption are discussed. It was shown that the interaction of halogen with the Ga dimerized at-oms leads to the weakening of the chemical bonds between surface atoms that determines the initial stage of surface etching. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3531

ENDOVASCULAR OCCLUSION OF THE PATENT FORAMEN OVALE AS PART OF ANTIARRHYTHMIC TREATMENT OF A PATIENT WITH PERSISTENT ATRIAL FIBRILLATION (CASE REPORT)

Below is a case report of treatment of a patient with persistent tachysystolic atrial fibrillation (AF), chronic heart failure (CHF) with a moderately reduced left ventricular ejection fraction (EF) and patent foramen ovale (PFO) with an atrial septal aneurysm. A 58-year-old man (with body mass index of 27.8 kg/m2) with tachysystolic persistent AF (duration 3 months) was hospitalized due to an increase in CHF symptoms (CHF functional class according to NYHA is II-III). The patient had been constantly receiving therapy in accordance with current recommendations (angiotensin receptor blockers, diuretics, beta-blockers, amiodorone and rivaroxaban). Transthoracic echocardiography showed a moderate decrease in ejection fraction (EF) (41%), an increase in the left (47 mm) and right (51x74 mm) atria. The patient underwent AF radiofrequency catheter ablation (RFA) in the left atrium, which identified PFO. The final stage of RFA was performed by external electrical cardioversion with successful restoration of sinus rhythm. Four months after RFA, despite a stable sinus rhythm, the patient maintained a moderately reduced LV EF (44%) and dilatation of the left (44 mm) and right (43x65 mm) atria. Transesophageal echocardiography revealed an aneurysmally altered atrial septum and a positive bubble test with a large number of bubbles. In accordance with current recommendations, the patient had indications for primary prevention of stroke - endovascular occlusion of the PFO, which was performed. Three months after PFO closure, the patient discontinued diuretics, amiodarone, and rivaroxaban. Combined therapy in a patient with persistent AF, with a moderately reduced EF and verified PFO, which included pathogenetic therapy for CHF, prescription of antiarrhythmic drugs, RFA of the AF substrate, and interventional closure of the PFO, made it possible to effectively control sinus rhythm, significantly reduce the manifestations of CHF and provide primary prevention of embolic disorders

ENDOVASCULAR OCCLUSION OF THE PATENT FORAMEN OVALE AS PART OF ANTIARRHYTHMIC TREATMENT OF A PATIENT WITH PERSISTENT ATRIAL FIBRILLATION (CASE REPORT)

Below is a case report of treatment of a patient with persistent tachysystolic atrial fibrillation (AF), chronic heart failure (CHF) with a moderately reduced left ventricular ejection fraction (EF) and patent foramen ovale (PFO) with an atrial septal aneurysm. A 58-year-old man (with body mass index of 27.8 kg/m2) with tachysystolic persistent AF (duration 3 months) was hospitalized due to an increase in CHF symptoms (CHF functional class according to NYHA is II-III). The patient had been constantly receiving therapy in accordance with current recommendations (angiotensin receptor blockers, diuretics, beta-blockers, amiodorone and rivaroxaban). Transthoracic echocardiography showed a moderate decrease in ejection fraction (EF) (41%), an increase in the left (47 mm) and right (51x74 mm) atria. The patient underwent AF radiofrequency catheter ablation (RFA) in the left atrium, which identified PFO. The final stage of RFA was performed by external electrical cardioversion with successful restoration of sinus rhythm. Four months after RFA, despite a stable sinus rhythm, the patient maintained a moderately reduced LV EF (44%) and dilatation of the left (44 mm) and right (43x65 mm) atria. Transesophageal echocardiography revealed an aneurysmally altered atrial septum and a positive bubble test with a large number of bubbles. In accordance with current recommendations, the patient had indications for primary prevention of stroke - endovascular occlusion of the PFO, which was performed. Three months after PFO closure, the patient discontinued diuretics, amiodarone, and rivaroxaban. Combined therapy in a patient with persistent AF, with a moderately reduced EF and verified PFO, which included pathogenetic therapy for CHF, prescription of antiarrhythmic drugs, RFA of the AF substrate, and interventional closure of the PFO, made it possible to effectively control sinus rhythm, significantly reduce the manifestations of CHF and provide primary prevention of embolic disorders

Measurement of xF3xF_3 and F2F_2 Structure Functions in Low Q2Q^2 Region with the IHEP-JINR Neutrino Detector

The isoscalar structure functions $xF_3$ and $F_2$ are measured as functions of $x$ averaged over all $Q^2$ permissible for the range of 6 to 28 GeV of incident neutrino (anti-neutrino) energy at the IHEP-JINR Neutrino Detector. The QCD analysis of $xF_3$ structure function provides $\Lambda_{\bar{MS}}^{(4)} = (411 \pm 200)$ MeV under the assumption of QCD validity in the region of low $Q^2$. The corresponding value of the strong interaction constant $\alpha_S (M_Z) = 0.123^{+0.010}_{-0.013}$ agrees with the recent result of the CCFR collaboration and with the combined LEP/SLC result.Comment: 11 pages, 1 Postscript figure, LaTeX. Talk given at the 7th International Workshop on Deep Inelastic Scattering and QCD (DIS 99), Zeuthen, Germany, 19-23 Apr 199

Determination of the high-twist contribution to the structure function xF3νNxF^{\nu N}_3

We extract the high-twist contribution to the neutrino-nucleon structure function $xF_3^{(\nu+\bar{\nu})N}$ from the analysis of the data collected by the IHEP-JINR Neutrino Detector in the runs with the focused neutrino beams at the IHEP 70 GeV proton synchrotron. The analysis is performed within the infrared renormalon (IRR) model of high twists in order to extract the normalization parameter of the model. From the NLO QCD fit to our data we obtained the value of the IRR model normalization parameter $\Lambda^2_{3}=0.69\pm0.37~({\rm exp})\pm0.16~({\rm theor})~{\rm GeV}^2$. We also obtained $\Lambda^2_{3}=0.36\pm0.22~({\rm exp})\pm0.12~({\rm theor})~{\rm GeV}^2$ from a similar fit to the CCFR data. The average of both results is $\Lambda^2_{3}=0.44\pm0.19~({\rm exp})~{\rm GeV}^2$.Comment: preprint IHEP-01-18, 7 pages, LATEX, 1 figure (EPS

Search for heavy neutrinos mixing with tau neutrinos

We report on a search for heavy neutrinos (\nus) produced in the decay D_s\to \tau \nus at the SPS proton target followed by the decay \nudecay in the NOMAD detector. Both decays are expected to occur if \nus is a component of $\nu_{\tau}$.\ From the analysis of the data collected during the 1996-1998 runs with $4.1\times10^{19}$ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the \nus mass range from 10 to 190 $\rm MeV$. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector.\Comment: 20 pages, 7 figures, a few comments adde

Scintillator ageing of the T2K near detectors from 2010 to 2021

The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradation