Практико-ориентированная направленность подготовки студентов стоматологического факультета

МЕДИЦИНСКИЕ УЧЕБНЫЕ ЗАВЕДЕНИЯОБРАЗОВАНИЕ МЕДИЦИНСКОЕСТУДЕНТЫ МЕДИЦИНСКИХ УЧЕБНЫХ ЗАВЕДЕНИЙОБРАЗОВАНИЕ СТОМАТОЛОГИЧЕСКОЕПРАКТИКО-ОРИЕНТИРОВАННОЕ ОБРАЗОВАНИ

Energy Balanced Strategies for Maximizing the Lifetime of Sparsely Deployed Underwater Acoustic Sensor Networks

Underwater acoustic sensor networks (UWA-SNs) are envisioned to perform monitoring tasks over the large portion of the world covered by oceans. Due to economics and the large area of the ocean, UWA-SNs are mainly sparsely deployed networks nowadays. The limited battery resources is a big challenge for the deployment of such long-term sensor networks. Unbalanced battery energy consumption will lead to early energy depletion of nodes, which partitions the whole networks and impairs the integrity of the monitoring datasets or even results in the collapse of the entire networks. On the contrary, balanced energy dissipation of nodes can prolong the lifetime of such networks. In this paper, we focus on the energy balance dissipation problem of two types of sparsely deployed UWA-SNs: underwater moored monitoring systems and sparsely deployed two-dimensional UWA-SNs. We first analyze the reasons of unbalanced energy consumption in such networks, then we propose two energy balanced strategies to maximize the lifetime of networks both in shallow and deep water. Finally, we evaluate our methods by simulations and the results show that the two strategies can achieve balanced energy consumption per node while at the same time prolong the networks lifetime

Modelling of Dislocation Bias in FCC Materials

Irradiation induced void swelling is problematic for the application of austenitic steels under high dose irradiation. In this thesis, the swelling is characterized by dislocation bias. The dislocation bias is obtained using the finite element method, accounting for fcc copper and nickel under electron irradiation. The methodology is implemented with the interaction energies between an edge dislocation and point defects. Analytically derived interaction energies, which are based on elasticity theory, are compared with interaction energies obtained from atomistic model using semi-empirical atomic potentials as physics basis. The comparison shows that the description of analytical interaction energies is inaccurate in the dislocation core regions. The bias factor dependence on dislocation density and temperature is presented and discussed. At high temperatures or low dislocation densities, the two approaches tend to converge. However, the dislocation bias based on the interaction energies from the two approaches, reveals larger discrepancy for nickel than for copper. The impact on dislocation bias from the different stacking fault energies of copper and nickel is elaborated. Nickel, which has a larger stacking fault energy, is predicted to have larger swelling rate than copper under the same irradiation conditions.QC 20130530</p

Perspective on CO₂ Hydrogenation for Dimethyl Ether Economy

The CO2 hydrogenation to dimethyl ether (DME) is a potentially promising process for efficiently utilizing CO2 as a renewable and cheap carbon resource. Currently, the one-step heterogeneous catalytic conversion of CO2 to value-added chemicals exhibits higher efficiency than photocatalytic or electrocatalytic routes. However, typical catalysts for the one-step CO2 hydrogenation to DME still suffer from the deficient space–time yield and stability in industrial demonstrations/applications. In this perspective, the recent development of the one-step CO2 hydrogenation to DME is focused on different catalytic systems by examining the reported experimental results and the reaction mechanism including the catalytic nature of active sites, activation modes and of CO2 molecules under relevant conditions; surface intermediates are comparatively analyzed and discussed. In addition to the more traditional Cu-based, Pd-based, and oxide-derived bifunctional catalysts, a further emphasis is given to the characteristics of the recently emerged In2O3-based bifunctional catalysts for the one-step conversion of CO2 to DME. Moreover, GaN itself, as a bifunctional catalyst, shows over 90% DME selectivity and a reasonably high activity for one-step CO2 hydrogenation, and the direct hydrogenation of CO2 via the unique non-methanol intermediate mechanism is highlighted as an important illustration for exploring new catalytic systems. With these analyses and current understandings, the research directions in the aspects of catalysis and DME economy are suggested for the further development of one-step DME synthesis from CO2 hydrogenation

Microbiological characterization of commercially produced mineral water

Ūdens ir dabīgs resurss, kas nodrošina daudzus dzīvības procesus cilvēka organismā. Piesārņots dzeramais ūdens izraisa daudzas saslimšanas, kas noved pie smagām sekām. Ir ļoti svarīgi noteikt un uzturēt kvalitātes standartus gan ūdensvada, gan fasētam ūdenim. Šajā pētījumā tika veikts bakterioloģiskais raksturojums komerciāli pieejamajiem dabīgajiem minerālūdeņiem. Paraugi tika inkubēti uz R2A agara platēm 240 stundas un iegūtie rezultāti salīdzināti ar normatīvajos aktos noteiktajām prasībām. Iegūtais kultivējamo baktēriju skaits būtiski pārsniedza normatīvajos aktos pieļaujamās vērtības. Nosakot baktēriju rezistenci pret ampicilīnu un tetraciklīnu, tika konstatētas baktērijas gan ar dabisku, gan iegūtu rezistenci pret šīm antibiotikām, bet nejutīgo baktēriju skaits bija būtiski zemāks nekā attīrītā Rīgas ūdensvada ūdenī. Identificētās ūdens paraugus raksturojošās sugas bija daļa no dabiskās ūdens mikrobiotas un paraugos netika konstatētas patogēnas sugas vai koliformas.Water is a natural resource that is essential for many life processes in the human body. Contaminated water is responsible for many human diseases that lead to severe consequences for the affected individual. It is very important to set and fulfill quality standards for both tap and bottled water. In this research we assessed the bacteriological quality for commercially available natural mineral water. The samples were incubated on R2A agar for 240 hours and the results compared to standards set in normative acts. Our results were considerably higher than the values set in the law. We determined that these samples contained bacteria with both innate and acquired resistance to ampicillin and tetracycline, but the amounts of resistant bacteria were considerably lower than treated Riga tap water. The identified bacteria from the water samples were a part of the natural water microbiota, and we did not find any pathogens or coliforms

Dislocation bias factors in fcc copper derived from atomistic calculations

Atomistic calculations were employed in order to calculate the interaction energy of an edge dislocation with different point defects. The bias factor was calculated by applying a finite element method on the interaction energy landscapes obtained from the atomistic calculations. A comparison of the calculated bias factor with a model based on elasticity theory reveals around 30% discrepancy under conditions representative for electron irradiation at 600 degrees C. Possible reasons are discussed. The bias factor dependence on dislocation density and ambient temperature is presented and discussed.QC 20130718Generation IV reactor research and development (GENIUS

Multiscale calculation of dislocation bias in fcc Ni and bcc Fe model lattices

In order to gain more insights on void swelling, dislocation bias is studied in this work. Molecular staticsimulations with empirical potentials are applied to map the dislocation–point defects interactionenergies in both fcc Ni and bcc Fe model lattices. The interaction energies are then used to numericallysolve the diffusion equation and obtain the dislocation bias. The importance of the dislocation core regionis studied under a the temperature range 573–1173 K and the dislocation densities 1012—1015 m-2. Theresults show that larger dislocation bias is found in the fcc Ni than in the bcc Fe under differenttemperatures and dislocation densities. The anisotropic interaction energy model is used to obtain thedislocation bias and the result is compared to that obtained using the atomistic interaction model, thecontribution from the core structure is then shown in both the Ni lattice and the Fe lattice.QC 20150331</p

Modeling of the magnetic free energy of self-diusion in bcc Fe

to be submitted to Physical review B. QS 2015</p