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  • 1
    Publication Date: 2016-09-02
    Description: Motivation: Microscopy imaging is an essential tool for medical diagnosis and molecular biology. It is particularly useful for extracting information about disease states, tissue heterogeneity and cell specific parameters such as cell type or cell size from biological specimens. However, the information obtained from the images is likely to be subjected to sampling and observational bias with respect to the underlying cell size/type distributions. Results: We present an algorithm, Estimate Tissue Cell Size/Type Distribution (EstiTiCS), for the adjustment of the underestimation of the number of small cells and the size of measured cells while accounting for the section thickness independent of the tissue type. We introduce the sources of bias under different tissue distributions and their effect on the measured values with simulation experiments. Furthermore, we demonstrate our method on histological sections of paraffin-embedded adipose tissue sample images from 57 people from a dietary intervention study. This data consists of measured cell size and its distribution over the dietary intervention period at four time points. Adjusting for the bias with EstiTiCS results in a closer fit to the true/expected adipocyte size distribution with earlier studies. Therefore, we conclude that our method is suitable as the final step in estimating the tissue wide cell type/size distribution from microscopy imaging pipeline. Availability and Implementation: Source code and its documentation are available at https://github.com/michaelLenz/EstiTiCS . The whole pipeline of our method is implemented in R and makes use of the ‘nloptr’ package. Adipose tissue data used for this study are available on request. Contact: Michael.Lenz@Maastrichtuniversity.nl , Gokhan.Ertaylan@Maastrichtuniversity.nl
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 2
    Publication Date: 2005-07-23
    Description: We observed mixing between two-electron singlet and triplet states in a double quantum dot, caused by interactions with nuclear spins in the host semiconductor. This mixing was suppressed when we applied a small magnetic field or increased the interdot tunnel coupling and thereby the singlet-triplet splitting. Electron transport involving transitions between triplets and singlets in turn polarized the nuclei, resulting in marked bistabilities. We extract from the fluctuating nuclear field a limitation on the time-averaged spin coherence time T2* of 25 nanoseconds. Control of the electron-nuclear interaction will therefore be crucial for the coherent manipulation of individual electron spins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Koppens, F H L -- Folk, J A -- Elzerman, J M -- Hanson, R -- van Beveren, L H Willems -- Vink, I T -- Tranitz, H P -- Wegscheider, W -- Kouwenhoven, L P -- Vandersypen, L M K -- New York, N.Y. -- Science. 2005 Aug 26;309(5739):1346-50. Epub 2005 Jul 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16037418" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2007-09-18
    Description: Antibodies play a central role in immunity by forming an interface with the innate immune system and, typically, mediate proinflammatory activity. We describe a novel posttranslational modification that leads to anti-inflammatory activity of antibodies of immunoglobulin G, isotype 4 (IgG4). IgG4 antibodies are dynamic molecules that exchange Fab arms by swapping a heavy chain and attached light chain (half-molecule) with a heavy-light chain pair from another molecule, which results in bispecific antibodies. Mutagenesis studies revealed that the third constant domain is critical for this activity. The impact of IgG4 Fab arm exchange was confirmed in vivo in a rhesus monkey model with experimental autoimmune myasthenia gravis. IgG4 Fab arm exchange is suggested to be an important biological mechanism that provides the basis for the anti-inflammatory activity attributed to IgG4 antibodies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉van der Neut Kolfschoten, Marijn -- Schuurman, Janine -- Losen, Mario -- Bleeker, Wim K -- Martinez-Martinez, Pilar -- Vermeulen, Ellen -- den Bleker, Tamara H -- Wiegman, Luus -- Vink, Tom -- Aarden, Lucien A -- De Baets, Marc H -- van de Winkel, Jan G J -- Aalberse, Rob C -- Parren, Paul W H I -- New York, N.Y. -- Science. 2007 Sep 14;317(5844):1554-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sanquin Research-AMC Landsteiner Laboratory, Department of Immunopathology, Plesmanlaan 125, 1066 CX Amsterdam, the Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17872445" target="_blank"〉PubMed〈/a〉
    Keywords: Allergens/immunology ; Animals ; Antibodies, Bispecific/immunology ; Antibodies, Monoclonal/immunology ; Antigens, CD20/immunology ; Antigens, Plant ; Autoantibodies/immunology ; Glycoproteins/immunology ; Humans ; Immunoglobulin Constant Regions/chemistry ; Immunoglobulin Fab Fragments/*chemistry/*immunology/metabolism ; Immunoglobulin G/*chemistry/*immunology/metabolism ; Immunoglobulin Heavy Chains ; Macaca mulatta ; Mice ; Mutation ; Myasthenia Gravis, Autoimmune, Experimental/immunology/prevention & control ; Protein Processing, Post-Translational ; Receptor, Epidermal Growth Factor/immunology ; Receptors, Cholinergic/immunology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2018-07-27
    Description: Farr and Mandel reanalyze our data, finding initial mass function slopes for high-mass stars in 30 Doradus that agree with our results. However, their reanalysis appears to underpredict the observed number of massive stars. Their technique results in more precise slopes than in our work, strengthening our conclusion that there is an excess of massive stars (〉30 solar masses) in 30 Doradus.
    Keywords: Astronomy
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2018-01-05
    Description: The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large star-formation events in the distant universe. We determined the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic observations of 247 stars more massive than 15 solar masses ( M ). The main episode of massive star formation began about 8 million years (My) ago, and the star-formation rate seems to have declined in the last 1 My. The IMF is densely sampled up to 200 M and contains 32 ± 12% more stars above 30 M than predicted by a standard Salpeter IMF. In the mass range of 15 to 200 M , the IMF power-law exponent is 1.90–0.26+0.37 , shallower than the Salpeter value of 2.35.
    Keywords: Astronomy
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2572-2580 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the zero-bias barrier heights of hydrogenated amorphous-silicon-based Schottky diodes and the prevailing current transport mechanisms in these structures is made using electrical and electro-optical techniques. Several series of devices were made using Cr, Mo, W, and Pt as Schottky metals. The current-voltage characteristics of the devices were obtained with their temperature dependence. The barrier heights were determined independently using internal photoemission experiments at three temperatures between 270 and 380 K. In devices where the Schottky barrier is deposited on top of the semiconductor material, the saturation current density is found to be most likely determined by combined drift and diffusion of the carriers. In devices where the Schottky barrier is formed at the bottom of the diode, the transport mechanism tends towards thermionic (field) emission, but only slight effects of the prevailing transport mechanism on the electrical performance of these diodes were observed. Also, in these devices a relatively defect-rich a-Si:H layer at the bottom (Schottky) contact could be detected opto-electronically, which prohibited barrier height determination using internal photoemission. For the influence of the metal work function φm on the electron-barrier height φb we obtain φb=(0.10±0.02)φm+(0.48±0.12), which is in good agreement with a previous determination of the dependence of the barrier for holes on φm.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 988-995 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tungsten thin films were deposited on glass substrates by direct-current planar magnetron sputtering. The induced thickness-averaged film stress within the plane of the film was determined with the bending-beam technique and changed from compressive to tensile on increasing working-gas pressure. The microstructure of these films was investigated by cross-sectional transmission electron microscopy. Compressively stressed films consisted of tightly packed columnar grains, whereas in films with a maximum value for the tensile stress the onset of a void network surrounding the columnar grains was observed. High-pressure conditions resulted in dendritic-like film growth, which brought about complete relaxation of internal stresses. The α phase was predominantly found in films under compression, while an increasing amount of β-W coincided with the transition to the tensile stress regime. Special attention was focused on stress-depth dependence and the development of two overlapping line profiles in x-ray diffraction (XRD) diagrams with film thickness as observed in compressively stressed films. Both findings constitute a remarkable result in respect of stress-depth distributions in thin films: the presence of two sublayers in a monophase film, one experiencing tensile and the other compressive stress. The occurrence of a modest tensile stress maximum present in the substrate-adjacent part of the film was explained by an elastically accommodated volume reduction, associated with a phase transformation (β into α) of initially formed β-W. Furthermore, a comparison of bending-beam stresses and XRD lattice strains (utilizing the sin2 ψ method) provided a consistent view of the mechanical behavior of the differently strained sublayers in this monophase (α-W) film.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2581-2589 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The physical mechanisms that determine the current transport in reverse-biased Schottky diodes on undoped "device-grade'' hydrogenated amorphous silicon (a-Si:H) are elucidated. The current-voltage (J-V) curves for several Schottky diodes up to reverse-biases of 40 V have been measured at temperatures between 40 and 180 °C. The reverse currents generally increase approximately exponentially with reverse bias. The decrease of the apparent barrier height as obtained from internal photoemission experiments is in good agreement with the decrease of the thermal activation energy with reverse bias. Extra information on the current transport mechanism can be obtained from the bias dependence of the prefactor in the Arrhenius plot. A theoretical model is presented which gives a semiquantitative fit to all the features observed in the experimental data. The model involves quantum-mechanical tunnelling of a thermal distribution of carriers through an image-force lowered triangular potential shape. At low reverse bias, the apparent barrier height decreases due to image-force lowering alone and the prevailing carrier transport mechanism is drift/diffusion or thermionic emission over the barrier, which can be determined from the bias dependence of the conduction prefactor in the Arrhenius plots. At higher fields, the apparent barrier height decreases faster than the image-force lowering. This is due to tunnelling of carriers through (the top of) the potential barrier and the apparent barrier becomes approximately equal to the mean energy at which the carriers move through the barrier. This energy is lowered with increasing reverse bias. The conduction prefactor from the Arrhenius plot now decreases with increasing applied bias and gives an indication of the effective tunnel probability.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4399-4404 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of hydrogenated amorphous silicon (a-Si:H) surfaces before and after thermal and plasma oxidation treatments was carried out using x-ray photoelectron spectroscopy. The thickness of the surface oxides is correlated with the electrical properties of corresponding Mo Schottky barrier structures. Oxide layers up to 1.5 nm in thickness cause a decrease of the reverse current of nearly two orders in magnitude, while the forward current is hardly affected. For oxide thicknesses above 2.0 nm a large reduction in the forward current is observed. Surprisingly, the associated tunneling probabilities of the oxide interface layers in the a-Si:H Schottky diodes are the same as those previously reported for c-Si-based tunnel diodes. Tunneling in the a-Si:H devices cannot be simply described by the properties of a rectangular barrier, which is adopted most frequently in these studies. A potential form where the barrier height increases quadratically with thickness fits the observed tunneling characteristics more quantitatively, both in absolute magnitude and oxide-thickness dependence of the tunnel current.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7252-7254 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present study, we show that the stoichiometry of sputtered molybdenum oxide films can be changed from oxygen deficient to, more surprisingly, oxygen rich. O/Mo ratios as high as 3.2 were measured, depending on the oxygen partial pressure in the sputtering atmosphere. It is shown that a substantial part of the excess oxygen is physically trapped in the film while the remaining part is chemically bonded in the form of H2O groups. The presence of physically trapped oxygen is demonstrated through a hydration reaction of the film resulting in the controlled detrapping of both excess oxygen and argon. The quantities of released oxygen are electrochemically measured and compared with the elemental composition of the film as determined by means of Rutherford backscattering spectroscopy (Mo, O, and Ar) and elastic recoil detection (H). © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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