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Publikacije (37471)

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P. Lazic, N. Atodiresei, V. Caciuc, R. Brako, B. Gumhalter, S. Blügel

Density functional theory (DFT) has been steadily improving over the past few decades, becoming the standard tool for electronic structure calculations. The early local functionals (LDA) were eventually replaced by more accurate semilocal functionals (GGA) which are in use today. A major persisting drawback is the lack of the nonlocal correlation which is at the core of dispersive (van der Waals) forces, so that a large and important class of systems remains outside the scope of DFT. The vdW-DF correlation functional of Langreth and Lundqvist, published in 2004, was the first nonlocal functional which could be easily implemented. Beyond expectations, the nonlocal functional has brought significant improvement to systems that were believed not to be sensitive to nonlocal correlations. In this paper, we use the example of graphene nanodomes growing on the Ir(111) surface, where with an increase of the size of the graphene islands the character of the bonding changes from strong chemisorption towards almost pure physisorption. We demonstrate how the seamless character of the vdW-DF functionals makes it possible to treat all regimes self-consistently, proving to be a systematic and consistent improvement of DFT regardless of the nature of bonding. We also discuss the typical surface science example of CO adsorption on (111) surfaces of metals, which shows that the nonlocal correlation may also be crucial for strongly chemisorbed systems. We briefly discuss open questions, in particular the choice of the most appropriate exchange part of the functional. As the vdW-DF begins to appear implemented self-consistently in a number of popular DFT codes, with numerical costs close to the GGA calculations, we draw the attention of the DFT community to the advantages and benefits of the adoption of this new class of functionals.

V. Nikolić, T. Jevtović-Stoimenov, R. Veličković-Radovanović, S. Ilić, M. Deljanin-Ilić, D. Marinkovic, S. Apostolovic, D. Stanojević et al.

Dino Kečo, A. Subasi

In this paper we present parallel implementation of genetic algorithm using map/reduce programming paradigm. Hadoop implementation of map/reduce library is used for this purpose. We compare our implementation with implementation presented in [1]. These two implementations are compared in solving One Max (Bit counting) problem. The comparison criteria between implementations are fitness convergence, quality of final solution, algorithm scalability, and cloud resource utilization. Our model for parallelization of genetic algorithm shows better performances and fitness convergence than model presented in [1], but our model has lower quality of solution because of species problem.

F. Nizamic, V. Degeler, R. Groenboom, A. Lazovik

Worldwide accessibility of clouds brings great benefits by providing easy access to resources. However, scheduling cloud resources for utilization among multiple collaborating cloud users is still often executed manually. To address this problem, we developed a scheduling service for cloud middleware that guarantees optimal resource utilization in terms of a total number of used resources in a given interval based on user-defined policies. In the paper, we introduce the scheduling algorithm, describe its supporting system architecture and provide the evaluation that proves the feasibility of the developed solution. The provided scheduling algorithm takes into account dependencies between individual services, and can enforce common use of shared resources that lead to the optimal resource utilization. By assuring continuous schedule optimality, costs caused by unnecessary usage of additional cloud resources are minimized.

S. Janković, Z. Djordjevic

Background. The incidence of ventilator-associated pneumonia (VAP) among patients on mechanical ventilation is from 15% to 25%, and mortality ranges from 33% to 38%. Aim. The aim of our study was to analyze importance of previously un-investigated potential risk factors for death in intensive care unit (ICU) patients with VAP. Methods. A cross-sectional design was chosen for this study. The study population consisted of all patients who developed ventilator associated pneumonia in the central ICU of a tertiary care hospital (n = 65) during the period of 6 months. Cases (n=45) were patients who died during their treatment in the ICU, if their primary cause of death was ventilator associated pneumonia. Controls (n=20) were patients with VAP who survived their treatment in the ICU, and were transferred to other hospital wards. Results.  Significant associations were found between death and age over 65 (OR adjusted 10.66; CI 1.22, 93.12; p = 0.032), death and hospitalization at another hospital ward prior to ICU (OR adjusted 1.25; CI 1.03, 1.52; p = 0.28), death and infection on admission to ICU (OR adjusted 434.39; CI 3.07, 61449.65; p = 0.016), and death and administration of ceftriaxone prior to VAP (OR adjusted 69.32; 1.74, 2768.92; p = 0.024). Synergistic effect on death was found only for age over 65 and infection on admission to ICU.  Conclusions. The ICU patients with VAP have increased mortality if they receive ceftriaxone prophylactically, if they have an infection at admission to ICU and when their age is advanced.

Felix Bauer, L. Bertinetti, A. Masic, T. Scheibel

Silk fibers are well known for their mechanical properties such as strength and toughness and are lightweight, making them an interesting material for a variety of applications. Silk mechanics mainly rely on the secondary structure of the underlying proteins. Lacewing egg stalk silk proteins obtain a cross-β structure with individual β strands aligned perpendicular to the fiber axis. This structure is in contrast with that of silks of spiders or silkworms with β strands parallel to the fiber axis and to that of silks of honeybees with α helices arranged in coiled coils. On the basis of the cross-β structure the mechanical properties of egg stalks are different from those of other silks concerning extensibility, toughness, and bending stiffness. Here we show the influence of relative humidity on the mechanical behavior of lacewing egg stalks and propose a model based on secondary structure changes to explain the differences on a molecular level. At low relative humidity, the stalks rupture at an extension of 3%, whereas at high relative humidity the stalks rupture at 434%. This dramatic increase corresponds to breakage of hydrogen bonds between the β strands and a rearrangement thereof in a parallel-β structure.

Z. Janjuš, A. Petrovic, A. Jovović, R. Prokić-Cvetković, Predrag Ilić

The purpose of this paper is to show polymer waste as a raw material or otherwise usable material derived from a partial separation of communal waste. This paper describes the possibilities of polypropylene re-use through recycling with addition of glass powder, from the point of view of toughness caused by impact load. Standard test specimens, made of basic material – polypropylene, with addition of  0%, 5%, 10%, 15%, 20%, 25% and 30% of glass powder with granulation less than 0,5 mm, have been tested through six processing cycles. The measured values gave a possibility of forming patterns for changes of the observed material with different content of additives, through processing cycles, which can be helpful in further research and analysis.

T. Vukušić Pušić, T. Janjic, I. Dujmović, A. Poljičanin, V. Šoljić, M. Saraga-Babic, K. Vukojević

Jong Seto, B. Busse, H. Gupta, C. Schäfer, S. Krauss, J. Dunlop, A. Masic, M. Kerschnitzki et al.

The plasma protein fetuin-A/alpha2-HS-glycoprotein (genetic symbol Ahsg) is a systemic inhibitor of extraskeletal mineralization, which is best underscored by the excessive mineral deposition found in various tissues of fetuin-A deficient mice on the calcification-prone genetic background DBA/2. Fetuin-A is known to accumulate in the bone matrix thus an effect of fetuin-A on skeletal mineralization is expected. We examined the bones of fetuin-A deficient mice maintained on a C57BL/6 genetic background to avoid bone disease secondary to renal calcification. Here, we show that fetuin-A deficient mice display normal trabecular bone mass in the spine, but increased cortical thickness in the femur. Bone material properties, as well as mineral and collagen characteristics of cortical bone were unaffected by the absence of fetuin-A. In contrast, the long bones especially proximal limb bones were severely stunted in fetuin-A deficient mice compared to wildtype littermates, resulting in increased biomechanical stability of fetuin-A deficient femora in three-point-bending tests. Elevated backscattered electron signal intensities reflected an increased mineral content in the growth plates of fetuin-A deficient long bones, corroborating its physiological role as an inhibitor of excessive mineralization in the growth plate cartilage matrix - a site of vigorous physiological mineralization. We show that in the case of fetuin-A deficiency, active mineralization inhibition is a necessity for proper long bone growth.

Iulia Prodan, Tatsunori Obara, F. Adachi, H. Gačanin

Recently, broadband analog network coding (ANC) has intensively been studied due to its potential to increase the network capacity by exploiting the broadcasting nature of the wireless channel. However, channel state information (CSI) knowledge is required for self-information removal and signal detection. A low-complexity pilot-assisted channel estimation (PACE) scheme has been presented for broadband ANC, where feedback of the CSI estimates from the relay to the users is required. In this study, we propose a PACE scheme without CSI feedback from the relay for broadband ANC using orthogonal frequency-division multiplexing. In the first time slot the users transmit their respective pilots to the relay and in the second time slot the relay simply amplifies and forwards the received pilot signals to both users. Each user can then estimate all the CSI it needs for self-information removal and coherent signal detection, without requiring any feedback of the CSI estimates from the relay. We theoretically analyze the channel estimator’s mean square error (MSE) performance and evaluate the bit error rate (BER) and throughput performance of broadband ANC using the proposed PACE by computer simulation. The results show that the increase in the MSE of the proposed CE scheme causes only a slight BER performance degradation compared to the conventional PACE scheme with ideal feedback. However, the benefit of eliminating the CSI feedback can be seen in the throughput performance.

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