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Search Results: 1 - 10 of 197854 matches for " N. Bednar "
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Guidelines for Optimization of the Absorber Layer Energy Gap for High Efficiency Cu(In,Ga)Se2 Solar Cells  [PDF]
N. Severino, N. Bednar, N. Adamovic
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.64015
Abstract: This work investigates in-depth the effects of variation of the compositional ratio of the absorber layer in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Electrical simulations were carried out in order to propose the most suitable gallium double-grading profile for the high efficiency devices. To keep the model as close as possible to the real behavior of the thin film solar cell a trap model was implemented to describe the bulk defects in the absorber layer. The performance of a solar cell with a standard CIGS layer thickness (2 μm) exhibits a strong dependence on the front grading height (decreasing band gap toward the middle of the CIGS layer). An absolute gain in the efficiency (higher than 1%) is observed by a front grading height of 0.22. Moreover, simulation results show that the position of the plateau (the region characterized by the minimum band gap) should be accurately positioned at a compositional ratio of 20% Ga and 80% In, which corresponds to the region where a lower bulk defect density is expected. The developed model demonstrates that the length of the plateau is not playing a relevant role, causing just a slight change in the solar cell performances. Devices with different absorber layer thicknesses were simulated. The highest efficiency is obtained for a CIGS thin film with thicknesses between 0.8 and 1.1 μm.
Development of Maps of Simple and Complex Cells in the Primary Visual Cortex
n Antolík,James A. Bednar
Frontiers in Computational Neuroscience , 2011, DOI: 10.3389/fncom.2011.00017
Abstract: Hubel and Wiesel (1962) classified primary visual cortex (V1) neurons as either simple, with responses modulated by the spatial phase of a sine grating, or complex, i.e., largely phase invariant. Much progress has been made in understanding how simple-cells develop, and there are now detailed computational models establishing how they can form topographic maps ordered by orientation preference. There are also models of how complex cells can develop using outputs from simple cells with different phase preferences, but no model of how a topographic orientation map of complex cells could be formed based on the actual connectivity patterns found in V1. Addressing this question is important, because the majority of existing developmental models of simple-cell maps group neurons selective to similar spatial phases together, which is contrary to experimental evidence, and makes it difficult to construct complex cells. Overcoming this limitation is not trivial, because mechanisms responsible for map development drive receptive fields (RF) of nearby neurons to be highly correlated, while co-oriented RFs of opposite phases are anti-correlated. In this work, we model V1 as two topographically organized sheets representing cortical layer 4 and 2/3. Only layer 4 receives direct thalamic input. Both sheets are connected with narrow feed-forward and feedback connectivity. Only layer 2/3 contains strong long-range lateral connectivity, in line with current anatomical findings. Initially all weights in the model are random, and each is modified via a Hebbian learning rule. The model develops smooth, matching, orientation preference maps in both sheets. Layer 4 units become simple cells, with phase preference arranged randomly, while those in layer 2/3 are primarily complex cells. To our knowledge this model is the first explaining how simple cells can develop with random phase preference, and how maps of complex cells can develop, using only realistic patterns of connectivity.
MAREDAT: towards a World Ocean Atlas of MARine Ecosystem DATa
E. T. Buitenhuis,M. Vogt,R. Moriarty,N. Bednar?ek
Earth System Science Data Discussions , 2012, DOI: 10.5194/essdd-5-1077-2012
Abstract: We present a summary of biomass data for 11 Plankton Functional Types (PFTs) plus phytoplankton pigment data, compiled as part of the MARine Ecosystem biomass DATa (MAREDAT) initiative. The goal of the MAREDAT initiative is to provide global gridded data products with coverage of all biological components of the global ocean ecosystem. This special issue is the first step towards achieving this. The PFTs presented here include picophytoplankton, diazotrophs, coccolithophores, Phaeocystis, diatoms, picoheterotrophs, microzooplankton, foraminifers, mesozooplankton, pteropods and macrozooplankton. All variables have been gridded onto a World Ocean Atlas (WOA) grid (1° × 1° × 33 vertical levels × monthly climatologies). The data show that (1) the global total heterotrophic biomass (2.0–6.4 Pg C) is at least as high as the total autotrophic biomass (0.5–2.6 Pg C excluding nanophytoplankton and autotrophic dinoflagellates), (2) the biomass of zooplankton calcifiers (0.9–2.3 Pg C) is substantially higher than that of coccolithophores (0.01–0.14 Pg C), (3) patchiness of biomass distribution increases with organism size, and (4) although zooplankton biomass measurements below 200 m are rare, the limited measurements available suggest that Bacteria and Archaea are not the only heterotrophs in the deep sea. More data will be needed to characterize ocean ecosystem functioning and associated biogeochemistry in the Southern Hemisphere and below 200 m. Microzooplankton database: doi:10.1594/PANGAEA.779970.
The global distribution of pteropods and their contribution to carbonate and carbon biomass in the modern ocean
N. Bednar ek, J. Mo ina, M. Vogt, C. O'Brien,G. A. Tarling
Earth System Science Data (ESSD) & Discussions (ESSDD) , 2012, DOI: 10.5194/essd-4-167-2012
Abstract: Pteropods are a group of holoplanktonic gastropods for which global biomass distribution patterns remain poorly described. The aim of this study was to collect and synthesise existing pteropod (Gymnosomata, Thecosomata and Pseudothecosomata) abundance and biomass data, in order to evaluate the global distribution of pteropod carbon biomass, with a particular emphasis on temporal and spatial patterns. We collected 25 939 data points from several online databases and 41 scientific articles. These data points corresponded to observations from 15 134 stations, where 93% of observations were of shelled pteropods (Thecosomata) and 7% of non-shelled pteropods (Gymnosomata). The biomass data has been gridded onto a 360 × 180° grid, with a vertical resolution of 33 depth levels. Both the raw data file and the gridded data in NetCDF format can be downloaded from PANGAEA, doi:10.1594/PANGAEA.777387. Data were collected between 1950–2010, with sampling depths ranging from 0–2000 m. Pteropod biomass data was either extracted directly or derived through converting abundance to biomass with pteropod-specific length to carbon biomass conversion algorithms. In the Northern Hemisphere (NH), the data were distributed quite evenly throughout the year, whereas sampling in the Southern Hemisphere (SH) was biased towards winter and summer values. 86% of all biomass values were located in the NH, most (37%) within the latitudinal band of 30–60° N. The range of global biomass values spanned over four orders of magnitude, with mean and median (non-zero) biomass values of 4.6 mg C m 3 (SD = 62.5) and 0.015 mg C m 3, respectively. The highest mean biomass was located in the SH within the 70–80° S latitudinal band (39.71 mg C m 3, SD = 93.00), while the highest median biomass was in the NH, between 40–50° S (0.06 mg C m 3, SD = 79.94). Shelled pteropods constituted a mean global carbonate biomass of 23.17 mg CaCO3 m 3 (based on non-zero records). Total biomass values were lowest in the equatorial regions and equally high at both poles. Pteropods were found at least to depths of 1000 m, with the highest biomass values located in the surface layer (0–10 m) and gradually decreasing with depth, with values in excess of 100 mg C m 3 only found above 200 m depth. Tropical species tended to concentrate at greater depths than temperate or high-latitude species. Global biomass levels in the NH were relatively invariant over the seasonal cycle, but more seasonally variable in the SH. The collected database provides a valuable tool for modellers for the study of marine ecosystem processes and global biogeochemical cycles. By extrapolating regional biomass to a global scale, we established global pteropod biomass to add up to 500 Tg C.
Corrigendum to "The global distribution of pteropods and their contribution to carbonate and carbon biomass in the modern ocean" published in Earth Syst. Sci. Data, 4, 167–186, 2012
N. Bednar ek, J. Mo ina, M. Vogt, C. O'Brien,G. A. Tarling
Earth System Science Data (ESSD) & Discussions (ESSDD) , 2013, DOI: 10.5194/essd-5-1-2013
Abstract: No abstract available.
Global distribution of pteropods representing carbonate functional type biomass
N. Bednar?ek,J. Mo?ina,M. Vu?kovi?,M. Vogt
Earth System Science Data Discussions , 2012, DOI: 10.5194/essdd-5-317-2012
Abstract: Pteropods are a group of holoplanktonic gastropods for which global biomass distribution patterns remain poorly resolved. The aim of this study was to collect and synthesize existing pteropod (Gymnosomata, Thecosomata and Pseudothecosomata) abundance and biomass data, in order to evaluate the global distribution of pteropod carbon biomass, with a particular emphasis on its seasonal, temporal and vertical patterns. We collected 25 902 data points from several online databases and a number of scientific articles. The biomass data has been gridded onto a 360 × 180° grid, with a vertical resolution of 33 WOA depth levels. Data has been converted to NetCDF format which can be downloaded from PANGAEA, http://doi.pangaea.de/10.1594/PANGAEA.777387. Data were collected between 1951–2010, with sampling depths ranging from 0–1000 m. Pteropod biomass data was either extracted directly or derived through converting abundance to biomass with pteropod specific length to weight conversions. In the Northern Hemisphere (NH) the data were distributed evenly throughout the year, whereas sampling in the Southern Hemisphere was biased towards the austral summer months. 86% of all biomass values were located in the NH, most (42%) within the latitudinal band of 30–50° N. The range of global biomass values spanned over three orders of magnitude, with a mean and median biomass concentration of 8.2 mg C l 1 (SD = 61.4) and 0.25 mg C l 1, respectively for all data points, and with a mean of 9.1 mg C l 1 (SD = 64.8) and a median of 0.25 mg C l 1 for non-zero biomass values. The highest mean and median biomass concentrations were located in the NH between 40–50° S (mean biomass: 68.8 mg C l 1 (SD × 213.4) median biomass: 2.5 mg C l 1) while, in the SH, they were within the 70–80° S latitudinal band (mean: 10.5 mg C l 1 (SD × 38.8) and median: 0.2 mg C l 1). Biomass values were lowest in the equatorial regions. A broad range of biomass concentrations was observed at all depths, with the biomass peak located in the surface layer (0–25 m) and values generally decreasing with depth. However, biomass peaks were located at different depths in different ocean basins: 0–25 m depth in the N Atlantic, 50–100 m in the Pacific, 100–200 m in the Arctic, 200–500 m in the Brazilian region and >500 m in the Indo-Pacific region. Biomass in the NH was relatively invariant over the seasonal cycle, but more seasonally variable in the SH. The collected database provides a valuable tool for modellers for the study of ecosystem processes and global biogeochemical cycles.
A photometric screening for significant bacteriuria
Bednar M,Nemeckova V
Indian Journal of Medical Microbiology , 2007,
Abstract:
A Contextual Integration of Individual and Organizational Learning Perspectives as Part of IS Analysis
Peter M. Bednar
Informing Science The International Journal of an Emerging Transdiscipline , 2000,
Abstract: The Strategic Systemic Thinking (SST) framework is presented as a stepping stone towards enabling the refocusing of organizational analysis in Information Systems (IS). The paper introduces some of the fundamental assumptions regarding the objectives of the SST framework; such as sense making as learning processes build upon communicative actions. The main concepts of the SST framework are presented, which are focused on developing a learning organization inclusive of having a constructive dialogue mechanism. The SST framework includes constructive dialogue as a means of gaining access to the existing but unreleased individual and group competencies for improved IS analysis.
Metastatic Pancreatic Cancer Is Dependent on Oncogenic Kras in Mice
Meredith A. Collins, Jean-Christophe Brisset, Yaqing Zhang, Filip Bednar, Josette Pierre, Kevin A. Heist, Craig J. Galbán, Stefanie Galbán, Marina Pasca di Magliano
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049707
Abstract: Pancreatic cancer is one of the deadliest human malignancies, and its prognosis has not improved over the past 40 years. Mouse models that spontaneously develop pancreatic adenocarcinoma and mimic the progression of the human disease are emerging as a new tool to investigate the basic biology of this disease and identify potential therapeutic targets. Here, we describe a new model of metastatic pancreatic adenocarcinoma based on pancreas-specific, inducible and reversible expression of an oncogenic form of Kras, together with pancreas-specific expression of a mutant form of the tumor suppressor p53. Using high-resolution magnetic resonance imaging to follow individual animals in longitudinal studies, we show that both primary and metastatic lesions depend on continuous Kras activity for their maintenance. However, re-activation of Kras* following prolonged inactivation leads to rapid tumor relapse, raising the concern that Kras*-resistance might eventually be acquired. Thus, our data identifies Kras* as a key oncogene in pancreatic cancer maintenance, but raises the possibility of acquired resistance should Kras inhibitors become available for use in pancreatic cancer.
An Ink-Jet Printed Eddy Current Position Sensor
Nikola Jeran?e,Nikola Bednar,Goran Stojanovi?
Sensors , 2013, DOI: 10.3390/s130405205
Abstract: An eddy current sensor with an ink-jet printed flexible inductor has been designed and fabricated. The inductor has been designed by means of software developed in-house. It has been fabricated by ink-jet printing with silver ink on a flexible substrate. The inductor is a part of the oscillator circuit whose oscillating frequency is measured by a microcontroller. The sensor characteristics have been analyzed for two types of application. The first considered application is the displacement of a large conductive target in a direction perpendicular to the inductor plane. The second considered application is the displacement of a small steel ball parallel to the inductor plane. Inductance and oscillating frequency have been measured in order to completely characterize the sensor. The obtained results validate the use of the sensor for both considered applications, and are in good agreement with the simulations. The advantages of this type of sensor are low cost, the possibility for the inductor to match any curved surface and flexibility and precision of the inductor design.
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