Formation of Turing structures in catalytic surface reactions: The facetting of Pt(110) in CO+O₂

The Pt(110) surface facets during the catalytic oxidation of CO, if reaction conditions are adjusted such that the CO‐induced 1×1⇄1×2 phase transition can take place simultaneously. A detailed low‐energy electron diffraction beam profile analysis revealed that regularly spaced (430) and (340) facets are formed with a lateral periodicity of ∼70 lattice units along the [11̄0] direction. This result, together with the observation that the facetted surface is only stable under reaction conditions, indicates a dissipative structure of the Turing type. Such structures, which are stationary but exhibit a periodic variation of the concentration variables in space, have so far almost exclusively been discussed theoretically. The interpretation of the facetted surface as a Turing structure could be confirmed by a Monte Carlo simulation based on the Langmuir Hinshelwood mechanism of catalytic CO oxidation and the CO‐induced 1×1⇄1×2 phase transition

Educational profession-oriented propaedeutic Russian language course as a basis of coming of international students of pre-university training stage into the educational medium of the higher medical institution

Цель статьи - рассмотреть некоторые способы и методы (фреймовый подход) формирования лингвокультурологической медицинской компетенции иностранных учащихся предвузовского этапа на занятиях по русскому языку общелитературного стиля в соответствии со спецификой их будущего обучения в русскоязычной среде медицинского вуза. Актуальность исследования заключается в том, что учебный пропедевтический курс русского языка, ориентированный на изучение иностранными учащимися языка медицинской науки, является важнейшим и необходимым условием для их обучения в медицинском университете. Преподавание основывается на использовании общедидактических и методических принципов начального обучения русскому языку будущих студентов- медиков, которые способствуют дальнейшему усвоению и совершенствованию учебно- профессиональных знаний в условиях русской языковой среды медицинского вуза. В процессе исследования были использованы следующие методы: теоретический и практический анализ научной литературы по методике преподавания иностранного языка и русского как иностранного, аудиовизуальное наблюдение, беседы с иностранными студентами, пробное обучение. Результаты. В процессе изучения русского языка иностранные учащиеся приобретают новые знания, расширяется их эрудиция, кругозор. Иностранные учащиеся предвузовского этапа входят в мир языка медицинской науки, знакомясь с элементами её лингвистической, коммуникативной и культурологической базы. Выводы: пропедевтический курс русского языка закладывает основы знаний о специфике изучения медицины на русском языке, которые помогут иностранным учащимся предвузовского этапа подготовки спустя год войти в образовательную среду медицинского университета.The aim of the research is to consider some ways and methods (frame approach) of forming lingual- cultural medical competence of international students of pre-University training stage at the Russian Language classes in accordance with the specifics of their future learning in Russian-speaking medium of higher medical institution. Relevance of the study lies in the fact that educational propaedeutic course of the Russian Language, focused on training foreign students the language of medical science, is the most important and necessary condition for their studying in the medical university. Training is based on the usage of general didactic and methodical principles of elementary level of teaching Russian the future medical students, which promoting further learning and mastering the educational-professional knowledge in the conditions of Russian speaking environment of higher medical institution. The author has used the following methods: theoretical and practical analysis of scientific literature on methods of teaching foreign language and Russian as a foreign language, audio-visual monitoring, interviews with foreign students, experimental teaching. Results. When learning Russian the international students get knowledge, enlarge their erudition, the outlook. International students of pre-University training stage come into the world of the Language of medical science, becoming acquainted with the elements of its linguistic, communicative and cultural base. Conclusion. The propaedeutic course of Russian lays foundations of knowledge of specifics of learning medicine in Russian, which will help international students of pre-university training stage to be admitted to the educational environment of medical University after the first year of studying

A transmission x ray microscopy and NEXAFS approach for studying corroded silicate glasses at the nanometre scale

In this study transmission X ray microscopy TXM was tested as a method to investigate the chemistry and structure of corroded silicate glasses at the nanometer scale. Three different silicate glasses were altered in static corrosion experiments for 1 336 hours at temperatures between 60 C and 85 C using a 25 HCl solution. Thin lamellas were cut perpendicular to the surface of corroded glass monoliths and were analysed with conventional TEM as well as with TXM. By recording optical density profiles at photon energies around the Na and O K edges, the shape of the corrosion rim pristine glass interfaces and the thickness of the corrosion rims has been determined. Na and O near edge X ray absorption fine structure spectra NEXAFS were obtained without inducing irradiation damage and have been used to detect chemical changes in the corrosion rims. Spatially resolved NEXAFS spectra at the O K edge provided insight to structural changes in the corrosion layer on the atomic scale. By comparison to O K edge spectra of silicate minerals and hydrous albite glass as well as to O K edge NEXAFS of model structures simulated with ab initio calculations, evidence is provided that changes of the fine structure at the O K edge are assigned to the formation of siloxane groups in the corrosion ri

Adsorption induced reconstruction of the Cu(110) surface

The formation of the O/Cu(110)-(2 × 1) and H/Cu(110)-(1 × 2) superstructures has been investigated by a LEED beam profile analysis. The oxygen induced reconstruction proceeds at later stages by creation of holes on flat terraces. This could not be observed at the hydrogen induced missing row reconstruction. The formation of the missing row structure proceeds most probably via nucleation at steps and subsequent growth of (1 × 2) islands. The influence of different distributions of steps and islands on beam profiles is discussed

Gate Leakage Reduction by Clocked Power Supply of Adiabatic Logic Circuits

Losses due to gate-leakage-currents become more dominant in new technologies as gate leakage currents increase exponentially with decreasing gate oxide thickness. The most promising Adiabatic Logic (AL) families use a clocked power supply with four states. Hence, the full <i>V</i>_<i>DD</i> voltage drops over an AL gate only for a quarter of the clock cycle, causing a full gate leakage only for a quarter of the clock period. The rising and falling ramps of the clocked power supply lead to an additional energy consumption by gate leakage. This energy is smaller than the fraction caused by the constant <i>V</i>_<i>DD</i> drop, because the gate leakage exponentially depends on the voltage across the oxide. To obtain smaller energy consumption, Improved Adiabatic Logic (IAL) has been introduced. IAL swaps all n- and p-channel transistors. The logic blocks are built of p-channel devices which show gate tunneling currents significantly smaller than in n-channel devices. Using IAL instead of conventional AL allows an additional reduction of the energy consumption caused by gate leakage. Simulations based on a 90nm CMOS process show a lowering in gate leakage energy consumption for AL by a factor of 1.5 compared to static CMOS. For IAL the factor is up to 4. The achievable reduction varies depending on the considered AL family and the complexity of the gate

Determining Distribution and Size of Larval Pacific Geoduck Clams (Panopea Generosa Gould 1850) in Quartermaster Harbor (Washington, USA) Using a Novel Sampling Approach

Realistic species-specific information about larval life history is necessary for effective management of shellfish and parameterization of larval connectivity models. The patchiness of dispersing larvae, and the resources needed for sorting and identifying them, has limited many studies of larval distribution in the field, especially for species that are less common. In particular, little is known about in situ larval distribution of Pacific geoduck clams (Panopea generosa Gould 1850), a commercially important species found in Puget Sound, WA. A novel approach-time-integrating larval tube traps paired with molecular identification and sorting (FISH-CS)-was used to determine the distribution of geoduck larvae over 4 moat 3 stations in Quartermaster Harbor. Larvae were found consistently at the surface and thermocline rather than at the bottom. More and larger larvae were captured in the inside and middle of the harbor than the outer harbor, indicating at least some larval retention. Two pulses of larvae were captured, in March and late May to early June. Size frequency distributions of larvae indicate that these were 2 separate cohorts of larvae, with the possibility of a pulse of larvae from elsewhere toward the end of the season. The only physical parameter associated with relative larval abundance was degree of stratification, although the association was weak. These data represent the first reported study of geoduck larval distribution in the field and the first use of the FISH-CS technique for field collections. In the future, this approach can be used to answer many relevant management questions locally and more broadly, including quantifying larval export from shellfish farms, placement of restoration sites and marine protected areas, and spread of invasive species

Red blood cell invasion by Plasmodium vivax: Structural basis for DBP engagement of DARC

Plasmodium parasites use specialized ligands which bind to red blood cell (RBC) receptors during invasion. Defining the mechanism of receptor recognition is essential for the design of interventions against malaria. Here, we present the structural basis for Duffy antigen (DARC) engagement by P. vivax Duffy binding protein (DBP). We used NMR to map the core region of the DARC ectodomain contacted by the receptor binding domain of DBP (DBP-RII) and solved two distinct crystal structures of DBP-RII bound to this core region of DARC. Isothermal titration calorimetry studies show these structures are part of a multi-step binding pathway, and individual point mutations of residues contacting DARC result in a complete loss of RBC binding by DBP-RII. Two DBP-RII molecules sandwich either one or two DARC ectodomains, creating distinct heterotrimeric and heterotetrameric architectures. The DARC N-terminus forms an amphipathic helix upon DBP-RII binding. The studies reveal a receptor binding pocket in DBP and critical contacts in DARC, reveal novel targets for intervention, and suggest that targeting the critical DARC binding sites will lead to potent disruption of RBC engagement as complex assembly is dependent on DARC binding. These results allow for models to examine inter-species infection barriers, Plasmodium immune evasion mechanisms, P. knowlesi receptor-ligand specificity, and mechanisms of naturally acquired P. vivax immunity. The step-wise binding model identifies a possible mechanism by which signaling pathways could be activated during invasion. It is anticipated that the structural basis of DBP host-cell engagement will enable development of rational therapeutics targeting this interaction

Anomalous thickness dependence of the Hall effect in ultrathin Pb layers on Si(111)

The magnetoconductive properties of ultrathin Pb films deposited on Si(111) are measured and compared with density-functional electronic band-structure calculations on two-dimensional, free-standing, 1 to 8 monolayers thick Pb(111) slabs. A description with free-standing slabs is possible because it turned out that the Hall coefficient is independent of the substrate and of the crystalline order in the film. We show that the oscillations in sign of the Hall coefficient observed as a function of film thickness can be explained directly from the thickness dependent variations of the electronic bandstructure at the Fermi energy.Comment: 4 pages incl. 3 figures, RevTeX, to appear in Phys. Rev.