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Search Results: 1 - 10 of 209094 matches for " Silke L. Diedenhofen "
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Broadband and omnidirectional anti-reflection layer for III/V multi-junction solar cells
Silke L. Diedenhofen,Grzegorz Grzela,Erik Haverkamp,Gerard Bauhuis,John Schermer,Jaime Gómez Rivas
Physics , 2012, DOI: 10.1016/j.solmat.2012.02.022
Abstract: We report a novel graded refractive index antireflection coating for III/V quadruple solar cells based on bottom-up grown tapered GaP nanowires. We have calculated the photocurrent density of an InGaP-GaAs-InGaAsP-InGaAs solar cell with a MgF2/ZnS double layer antireflection coating and with a graded refractive index coating. The photocurrent density can be increased by 5.9 % when the solar cell is coated with a graded refractive index layer with a thickness of 1\mu m. We propose to realize such a graded refractive index layer by growing tapered GaP nanowires on III/V solar cells. For a first demonstration of the feasibility of the growth of tapered nanowires on III/V solar cells, we have grown tapered GaP nanowires on AlInP/GaAs substrates. We show experimentally that the reflection from the nanowire coated substrate is reduced and that the transmission into the substrate is increased for a broad spectral and angular range.
Generic nano-imprint process for fabrication of nanowire arrays
Aurelie Pierret,Moira Hocevar,Silke L. Diedenhofen,Rienk E. Algra,E. Vlieg,Eugene C. Timmering,Marc A. Verschuuren,George W. G. Immink,Marcel A. Verheijen,Erik P. A. M. Bakkers
Physics , 2009, DOI: 10.1088/0957-4484/21/6/065305
Abstract: A generic process has been developed to grow nearly defect free arrays of (heterostructured) InP and GaP nanowires. Soft nanoimprint lithography has been used to pattern gold particle arrays on full 2 inch substrates. After lift-off organic residues remain on the surface, which induce the growth of additional undesired nanowires. We show that cleaning of the samples before growth with piranha solution in combination with a thermal anneal at 550 C for InP and 700 C for GaP results in uniform nanowire arrays with 1% variation in nanowire length, and without undesired extra nanowires. Our chemical cleaning procedure is applicable to other lithographic techniques such as e-beam lithography, and therefore represents a generic process.
The Possible Mechanisms Involved in the Protection Strategies against Radiation-Induced Cellular Damage by Carnitines  [PDF]
Ashraf Virmani, Andreas Diedenhofen
International Journal of Clinical Medicine (IJCM) , 2015, DOI: 10.4236/ijcm.2015.62011
There is constant low level background radiation from the cosmos but in certain situation the body may be subjected to increased acute or chronic exposure from other sources. This occurs in situations such as radiation accidents, medical use and could possibly occur in military/terrorist incident. Dependent on the type, strength of the actual source, degree of exposure and type of radiation different strategies may be employed to reduce damage to the body tissues. A number of pharmacological agents such as peroxisome proliferator-activated receptor (PPAR) gamma agonists, diltiazem, amifostine and palifermin as well as antioxidants and metabolic compounds have been shown to be effective in preventing and also in reducing the long-term damage of the exposure of the living cells to radiation. The major drawback of synthetic (pharmacological) compounds has been that they are highly toxic at the optimum protective dose. Studies have shown that various endogenously found compounds such as L-carnitine, and its derivative acetyl-L-carnitine, are able to protect tissues and organs against various forms of toxic insult including radiation damage. The radiation-induced chronic injury may also be counteracted by other metabolic compounds with amine groups and antioxidant properties similar to the carnitines such as cysteine, 3,3’-diindolylmethane (DIM) and N-acetylcysteine. This review discuses the radioprotective compounds as well as the potential mechanism of cellular protection against radiation by carnitines and other compounds.
Increased frequency of CCR4+ and CCR6+ memory T-cells including CCR7+CD45RAmed very early memory cells in granulomatosis with polyangiitis (Wegener's)
Ursula Fagin, Silke Pitann, Wolfgang L Gross, Peter Lamprecht
Arthritis Research & Therapy , 2012, DOI: 10.1186/ar3794
Abstract: Multicolor flow cytometry was used to analyze CCR4, CCR6, and intracellular cytokine expression of T cells from whole blood of GPA-patients (n = 26) and healthy controls (n = 20). CCR7 and CD45RA were included for phenotypic characterization.We found a significant increase in the percentages of circulating CCR4+ and CCR6+ cells within the total CD4+ T cell population in GPA. In contrast, there was no difference in the percentages of CD8+CCR4+ and CD8+CCR6+ T cells between GPA and healthy controls. CCR4 and CCR6 expression was largely confined to central (TCM) and effector memory T cells (TEM, TEMRA). A significant increase in the frequency of CCR4+ and CCR6+ TEMRA and CCR6+ TCM was shown in GPA. Of note, we could dissect CCR4 and CCR6 expressing CCR7+CD45RAmed very early memory T cells (TVEM) from genuine CCR7+CD45RAhigh na?ve T cells lacking CCR4 and CCR6 expression for peripheral tissue-migration within the CCR7+CD45RA+ compartment. The frequencies of CCR4+ and CCR6+ TVEM were also significantly increased in GPA. An increased percentage of IL-17+ and IL-22+ cells was detected in the CCR6+ cell subsets and IL-4+ cells in the CRR4+ cell subset when compared with CD4+ cells lacking CCR4 and CCR6 expression.Increased frequencies of circulating CCR4+ and CCR6+ memory T cell subsets including hitherto unreported TVEM suggest persistent T cell activation with the accumulation of CCR4+ and CCR6+ cells in GPA. CCR4 and CCR6 could be involved in the recruitment of T cells including cytokine-producing subsets to inflamed sites in GPA.T cells display considerable heterogeneity in terms of phenotype, function, and anatomical distribution. Whereas na?ve T cells represent a relatively homogenous population, primed T cells acquire effector functions and differentiate into distinct effector and memory subsets. Whereas na?ve and central memory T cells home to secondary lymphoid organs to mount antigen-driven proliferative responses, effector memory T cells migrate into peripheral t
From single cells to whole organisms
Silke Sperling
Genome Biology , 2006, DOI: 10.1186/gb-2005-6-13-365
Abstract: Functional genomics aims to provide a bridge from the static information in the genome to the related functional properties of the cell, tissue or organism. Data on a genome-wide level are generated using a variety of high-throughput technologies, and are analyzed using bioinformatics and system-level integration. The program of the recent European Science Foundation Conference on functional genomics linked the most promising developments in functional genomics research and technology with their applications and future in biomedicine.Considerable effort is currently being made to reveal the relationship between complex genotypes and phenotype, for example, in looking at the enormous genetic variation that exists in outbred populations such as our own and how it manifests itself in phenotypic variation. One approach to uncovering the molecular basis of common diseases such as cancer and cardiovascular diseases is the correlation of sequence variation among healthy and ill individuals to try and understand how genetic perturbations interact to affect clinical outcome. Analyzing genotype-phenotype relationships in simpler organisms than humans, Charlie Boone (University of Toronto, Canada) and Andrew Fraser (Wellcome Trust Sanger Institute, Cambridge, UK) reported on global genetic-interaction projects in Saccharomyces cerevisiae and Caenorhabditis elegans that aim to identify overlapping functions and compensatory pathways that complicate the phenotype. Using an automated screen for suppressor/enhancer mutations, Boone's group analyzed 250,000 mutants of S. cerevisiae for synthetic genetic sickness or lethal genotypes, which are important for understanding how an organism tolerates random mutation. Interestingly, the genetic-interaction map appears to be four times as complex as the protein-protein interaction map. Genetic interactions do not overlap with physical interactions, but predict functional neighborhoods and clearly identify components of pathways whose orde
Why the way we consider the body matters – Reflections on four bioethical perspectives on the human body
Silke Schicktanz
Philosophy, Ethics, and Humanities in Medicine , 2007, DOI: 10.1186/1747-5341-2-30
Abstract: The author begins by descriptively exploring some main positions in bioethics from which the "body" is conceptualized. Such positions conflict: the body is that which is constitutive of the individual's experience and perception, or it is conceived of materially or mechanistically; or as a constructed locus, always historically and culturally transformed. The author goes on to suggest a methodological approach that dialectically considers embodiment from four different perspectives: as bodily self-determination, as respect for the bodily unavailability of the other, as care for bodily individuality; and lastly, as acknowledgement of bodily-constituted communities. These four perspectives encompass autonomy in two of its main interpretations: as the capability of a person to act independent of external forces, and as the moral ideal of pursuing individual wishes by means of role distance, self-limitation and universalization. Various bioethical cases are utilized to show how the four perspectives on the body can complement one another.The way we consider the body matters. The author's dialectical method allows a premise-critical identification and exploration of bioethical problems concerning the body. The method is potentially applicable to other bioethical problems.During the 1970s, a number of performance artists shocked the public by making their bodies the subject of artistic performances. By being thus displayed, the body itself becomes both the medium of the artistic work and the scene on which it takes place. In the performance Zerrei?probe (1970) the Austrian artist Günter Brus injured himself by cutting his head and thigh with a razor blade. The vulnerability of the flesh was to be shown by means of the extreme display of a body disfigured by pain and by interventions from the outside. Brus' perfomance at the same time was intended to demonstrate limits and extremes. The American Chris Burden had his left arm shot by a friend in the course of the performanc
Notas sobre o CNE e a qualidade do ensino superior
Weber, Silke;
Educa??o & Sociedade , 2002, DOI: 10.1590/S0101-73302002008000006
Abstract: this paper brings forth some notes upon the action of the brazilian council of education (cne), especially at the chamber of higher education, since its creation, in 1996, through law number 9131/1996. the cne is conceived as a social space that establishes direct links between agents of the political society, specifically the government, and segments of the civil society as for issues related to education. its institutional dynamics ? proposals and conflicts aroused ?, as well as some its possible repercussions not only on higher education, more particularly on the increase of offers of graduate and specialization courses, but also on teacher training are briefly highlighted.
Como e onde formar professores: espa?os em confronto
Weber, Silke;
Educa??o & Sociedade , 2000, DOI: 10.1590/S0101-73302000000100008
Abstract: this paper emphasizes the status given to professional teacher-training in educational legislation during the last 40 years, pointing out elements which interfered in law changing its focus: if in the beginning emphasis was put mainly on the indication of the formal patterns required, as time passes by, legislation concentrates more on training itself, which is to be effected through undergraduate studies. the argumentation centers on brazilian society's struggle for the reconstruction of democracy, context in which the debate about the quality of apprenticeship has increased and the professional dimension of teaching has been rescued. at last, the paper focuses on the discussion about the locus of professional teacher-training. this debate expresses once more the historical tensions between the academic and governmental instances.
Profissionaliza??o docente e políticas públicas no Brasil
Weber, Silke;
Educa??o & Sociedade , 2003, DOI: 10.1590/S0101-73302003000400003
Abstract: teachers, beginning in the 80's, became recognized as major agents of change, be it in the quality of education, or in the democratization of brazilian society. their organized actions, however, according to cunha (1991), could be having an "effect of political retro-annulment", favoring the theses of the privatization of public education. the relevance of this interpretation is examined in the perspective of the teacher as a professional who seeks to expand his/her power and to have his/her specialty recognized by the state and the market. stress is given to the movement, shifts of interest and demands promoted by the action of the representative organs of basic education, wherein the data indicate that, different from cunha's (1991) interpretation, the organized action of teachers has favored the delimitation of their specific sphere of action and the range of their political influence.
Avalia??o e regula??o da educa??o superior: conquistas e impasses
Weber, Silke;
Educa??o & Sociedade , 2010, DOI: 10.1590/S0101-73302010000400011
Abstract: this text seeks to retrieve references that have imposed themselves in the brazilian debate and practice of assessment of higher education and underpin a process that, since it necessarily refers to the assessment of merit and value, is far from obtaining the enthusiastic adhesion of institutions and of their main agents. these orienting landmarks, the legislation and its application are conceived of as speeches, texts or utterances, whose meaning is fixed in the context of articulation practices that involve social agents contending for the hegemony of society projects, in given social-political spaces. to the light of the tension between conceptions of assessment and of support to regulation, especially those contained in the sinaes (brazilian system to assess higher education) law, we point out some conquests that have had a positive impact on the quality of the training offered at this level of teaching and the impasses that can lead to the prevalence of a vision of assessment privileging the individual performance of students, courses and institutions. we also list aspects that could help reduce the social differences that characterize brazilian higher education.
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