Evolutionary approach for finding the atomic structure of steps on stable crystal surfaces

The problem addressed here can be concisely formulated as follows: Given a stable surface orientation with a known reconstruction and given a direction in the plane of this surface, find the atomic structure of the steps oriented along that direction. We report a robust and generally applicable variable-number genetic algorithm for determining the atomic configuration of crystallographic steps, and exemplify it by finding structures for several types of monatomic steps on Si(114)-2×1. We show that the location of the step edge with respect to the terrace reconstructions, the step width (number of atoms), and the positions of the atoms in the step region can all be simultaneously determined

The stability of strained H:Si(105) and H:Ge(105) surfaces

We report atomic scale studies of the effect of applied strain and hydrogen environment on the reconstructions of the (105) Si and Ge surfaces. Surface energy calculations for monohydride-terminated (001) and (105) reconstructions reveal that the recently established single-height rebonded model is unstable not only with respect to (001), but also in comparison to other monohydride (105) structures. This finding persists for both Si and Ge, for applied biaxial strains from -4% to 4%, and for nearly the entire relevant domain of the chemical potential of hydrogen, thus providing an explanation for the recently observed H-induced destabilization of the Ge(105) surface

Model reconstructions for the Si(337) orientation

Although unstable, the Si(337) orientation has been known to appear in diverse experimental situations such as the nanoscale faceting of Si(112), or in the case of miscutting a Si(113) surface. Various models for Si(337) have been proposed over time, which motivates a comprehensive study of the structure of this orientation. Such a study is undertaken in this article, where we report the results of a genetic algorithm optimization of the Si(337)-$(2\times 1)$ surface. The algorithm is coupled with a highly optimized empirical potential for silicon, which is used as an efficient way to build a set of possible Si(337) models; these structures are subsequently relaxed at the level of ab initio density functional methods. Using this procedure, we retrieve most of the (337) reconstructions proposed in previous works, as well as a number of novel ones.Comment: 5 figures (low res.); to appear in J. Appl. Phy

Конечные продукты гликирования и эластичность периферических артерий при сердечной недостаточности

Department of Interventional Cardiology, Institute of CardiologyAdvanced glycation and products (AGEs) are modifications of proteins or lipids that become nonenzymatically glycated and oxidized after contact with mono-sugars. Bounding to specific cell receptors they lead to cross-link formation basically of the large matrix proteins such as collagen and elastin resulting in increased stiffness of the vasculature. By this reason we evaluated the AGEs circulating levels and artery elasticity indices in heart failure due to diastolic or systolic dysfunction. In hypertensive patients with diastolic dysfunction AGEs level elevated 2.5 times while elasticity value of large and smooth arteries decreased by 54 and 46% respectively. Systolic dysfunction was associated with AGEs rising 2.9 times and smooths elasticity index diminution by almost 30%. Hence, the AGEs can be vied as a predictor of vascular stiffening and remedies of glycation inhibition may be useful in heart failure treatment.Конечные продукты гликирования (КПГ) представляют собой модифицированные белки или липиды, образующиеся при неферментативной гликации и способствующие формированию связей, в основном, белков интерстиция, коллагена и эластина, что приводит к увеличению ригидности сосудов. В этой связи мы определили уровень КПГ в крови и показатели эластичности периферических артерий при сердечной недостаточности. У гипертензивных больных с диастолической дисфункцией уровень КПГ был повышен в 3,5 раза, в то время как показатели эластичности больших и малых артерий снизились на 54 и 46% соответственно. Систолическая дисфункция сопровождалась увеличением КПГ в 2,9 раза и уменьшением эластичности малых артерий на 30%. КПГ могут быть рассмотрены как предиктор ригидности сосудов, а средства ингибирующие гликирование – как препараты для лечения сердечной недостаточности

Ground states of a mixture of two species of spin-1 Bose gases with interspecies spin exchange in a magnetic field

We consider a mixture of two species of spin-1 atoms with both interspecies and intraspecies spin exchanges in a weak magnetic field. Under the usual single mode approximation, it can be reduced to a model of coupled giant spins. We find most of its ground states. This is a complicated problem of energy minimization, with three quantum variables under constraints, i.e. the total spin of each species and the total spin of the whole mixture, as well as four parameters, including intraspecies and interspecies spin coupling strengths and the magnetic field. The quantum phase diagram is very rich. Compared with the case without a magnetic field, the ground states are modified by a magnetic field, which also modifies the ground state boundaries or introduces new crossover regimes on the phase diagram. Without interspecies spin coupling, the quantum phase transitions existing in absence of a magnetic field disappear when a magnetic field is applied, which leads to crossover regimes in the phase diagram. Under ferromagnetic interspecies spin coupling, the ground states remain disentangled no matter whether there is a magnetic field. For antiferromagnetic interspecies spin coupling, a magnetic field entangles the ground states in some parameter regimes. When the intraspecies spin couplings are both ferromagnetic, the quantum phase transition between antiferromagnetic and zero interspecies spin couplings survives the magnetic field. When the intraspecies spin couplings are both antiferromagnetic, a magnetic field induces new quantum phase transitions between antiferromagnetic and zero interspecies spin couplings.Comment: 17 pages, initially submitted to Phys. Rev. A on September 15 2010, to appear in Int. J. Mod. Phys.

Early and late changes of multi-marker panel in patients with STEMI after angioplasty

Background: Post-infarction remodeling is strongly linked with collagen turnover which is influenced mostly by oxidative stress and inflammation, the last being, according to our previous data, triggered by early infiltrated neutrophils (24–48 h) followed by accumulation of macrophages M1 (72 h) and M2 (7–14 days). Aim: Evaluation of circulating markers of inflammation and oxidative stress in the different periods of 1 year follow up post-infarct evolution: first 2 weeks (each day), 1st month (synthesis of collagen type III), 3rd month (synthesis of collagen type I), 6 and 12 months. Material and methods: Study was performed in 47 patients (age range of 37–68 years) with STEMI exposed to angioplasty (<12 hours). Circulating levels of 28 markers were determined at admission, 1, 2, 3 ... 14 days, 1, 3, 6 and 12 months. Obtained results were compared with control value of markers determined in 17 apparently healthy persons and admission level (before PCI). Results: The earliest (first 24 h) significant change was inherent to MMP-8, whose double elevation (averagely from 3,1 up to 6,4 ng/ml) corresponded to period of neutrophil infiltration (24–48 h). Serum levels of IL-1, IL-6 have raised significantly since 48 h, followed by authentic increase of TNF-alpha, IL-8, CRPhs and phospholipase A2 since 72 h. Up to a period of 7 days these markers remained increased, but toward 14th day fell by 24–46% arguably due to macrophage M2 activation. This is consistent to dynamics of anti-inflammatory markers, IL-4 and IL-10 which decreased till 7th, elevated toward 14th day although remained below control. Inflammation boosting was associated by oxidative stress activation during 1st week manifested by malonic dialdehyde (MAD) rise and total antioxidant activity fall. To be noted that markers improvement till 3rd month was poor and a conspicuous dynamics began since 6th month with nearing to control level toward 12th month. However, at this time following markers significantly differed from control value: TNF-alpha (+29,6%), IL-4 (-31,7%), S-nitrosothiols (-17,8%), CRPhs exceeded 3,0 g/L (4,77±0,38) and MAD (+23,6%). Conclusions: (1). Dynamics of inflammation markers in patients with STEMI during first 14 days after angioplasty conclusive reflect chronologic accumulation of inflammatory cells in necrotic zone. (2). Maximal serum plateau of MMP-8, IL-1, IL-6, IL-6, TNF-alpha and CRPhs goes till 7th day of post-infarct evolution, associated with lowest IL-4 and IL-10. (3). Marker improvements begin since 3rd month with nearing to control toward 12th month, excepting IL-4, TNF-alpha, CRPhs and MAD indicating thus a late statement of inflammation dissemination

Fournier's gangrene: summary of 8 years of clinical experience

Catedra Chirugie nr.1 „N.Anestiadi”, USMF „Nicolae Testemiţanu”, Spitalul „Sf.Arhanghel Mihail”, Chişinau, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Gangrena Fournier este o fasciită necrozantă care implică zona genitală şi perineul, progresează spre coapse şi peretele abdominal prin trabeculele fasciale. Material şi metode: Experienţa noastră include opt pacienţi cu gangrena Fournier, trataţi pe parcursul anilor 2006-2014. Repartizarea după sex a fost: 5 femei şi 3 bărbaţi. În etiologia bolii putem evidenţia calea ano-rectală (2 cazuri), infecţia urogenitală (3 cazuri) şi infecţia pielii (3 cazuri). Diagnosticul a fost stabilit în baza tabloulului clinic şi examenului ultrasonor. Toţi pacienţii au beneficiat de debridare chirurgicală radicală imediată, necrozectomii seriate, antibioticoterapia combinată şi terapie intensivă. Numărul de operaţii seriate a variat de la 4 până la 13. Rezultate: În urma tratamentului efectuat am obţinut stoparea procesului de necroză la 7 pacienţi. Doi pacienţi au evoluat spre septicemie cu hemocultură pozitivă. La un pacient sa dezvoltat şocul toxico-infecţios. Analiza bacteriologică din plagă a determinat: Staphylococcus aureus (2 cazuri), Enterococcus faecium (un caz), Escherichia coli (2 cazuri), floră mixtă (3 cazuri). Mortalitatea a fost de 37,5%. Concluzii: Stabilirea precoce a diagnosticului şi debridarea primară imediată urmată de necrozectomii etapizate stau la baza evoluţiei favorabile a procesului necrotico-septic. Antibioticoterapia efectuată prin asocierea a 3 antibiotice cu diferit spectru de acţiune împiedică răspândirea procesului putrid şi generalizarea infecţiei. Mortalitatea înaltă în gangrena Fournier este dic tată de insuccesele terapiei intensive în stările septice avansate cu comorbidităţi severe, în pofida metodelor contemporane de tratament chirurgical.Introduction: Fournier's gangrene is a necrotizing fasciitis which involves the genitals regions and perineum, spreading to thighs and abdominal wall through fascial trabeculae. Material and methods: Our experience includes eight patients with Fournier's gangrene treated during 2006-2014. Distribution by gender: 5 women and 3 men. In the etiology of the disease we can highlight ano-rectal way (2 cases), urogenital infection (3 cases) and skin infection (3 cases). The diagnosis was based on clinical features and ultrasound exam. All patients underwent immediate radical surgical debridement, serial necrosectomy, combined antibiotic therapy and intensive care. Number of serial operations ranged from 4 to 13. Results: After the provided treatment we were able to stop the process of necrosis in 7 patients. Two patients progressed to sepsis with positive blood test. Toxico-infectious shock was present in one patient. Bacteriological analysis showed: Staphylococcus aureus (2 cases), Enterococcus faecium (one case), Escherichia coli (2 cases), and mixed flora (3 cases). Mortality was 37.5%. Conclusions: Early diagnosis establishment and immediate primary debridement followed by serial necrosectomy is the base of the favourable evolution of the necrotic septic process. Antibacterial therapy carried out by the association with 3 different action spectrum antibiotics prevent the spread of the putrid process and generalized of infection. High mortality in Fournier's gangrene is a consequence of failures in intensive care in advanced sepsis with severe comorbidities, in spite of the contemporary methods of the surgical treatment

Elastic constants of beta-eucryptite: A density functional theory study

The five independent elastic constants of hexagonal $\beta$-eucryptite have been determined using density functional theory (DFT) total energy calculations. The calculated values agree well, to within 15%, with the experimental data. Using the calculated elastic constants, the linear compressibility of $\beta$-eucryptite parallel to the c-axis, $\chi_c$, and perpendicular to it, $\chi_a$, have been evaluated. These values are in close agreement to those obtained from experimentally known elastic constants, but are in contradiction to the direct measurements based on a three-terminal technique. The calculated compressibility parallel to the c-axis was found to positive as opposed to the negative value obtained by direct measurements. We have demonstrated that $\chi_c$ must be positive and discussed the implications of a positive $\chi_c$ in the context of explaining the negative bulk thermal expansion of $\beta$-eucryptite.Comment: 3 eps figures, submitted for publicatio

Topological defects in spinor condensates

We investigate the structure of topological defects in the ground states of spinor Bose-Einstein condensates with spin F=1 or F=2. The type and number of defects are determined by calculating the first and second homotopy groups of the order-parameter space. The order-parameter space is identified with a set of degenerate ground state spinors. Because the structure of the ground state depends on whether or not there is an external magnetic field applied to the system, defects are sensitive to the magnetic field. We study both cases and find that the defects in zero and non-zero field are different.Comment: 10 pages, 1 figure. Published versio