376 research outputs found

    Silizium-basierte Lichtemitter : Neue Möglichkeiten für Lab-on-Chip Systeme?

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    Die Realisierung von Lichtemittern in herkömmlicher Siliziumtechnologie ist ein großer Traum der Mikroelektronik. Aufgrund seines indirekten Bandgaps ist Silizium prinzipiell schlecht als Lichtemitter geeignet. Teure und aufwendige andere Verfahren und Werkstoffe (z.B. Verbindungshalbleiter wie GaAs, GaN, SiC usw.) fanden Verwendung für Leuchtdioden und werden heute kommerziell eingesetzt. Diese sind jedoch nicht in herkömmliche Silizium-Chipstrukturen integrierbar. Die Integration in die Silizium – Technologie ist jedoch von eminenter Bedeutung für die kostengünstige Herstellung von Emitterarrays, die neben der Nutzung für integrierte Systeme der Mikrosystemtechnik und der optischen Informationsübertragung auf und zwischen Chips auch zur Lumineszenzanregung von Farbstoffmolekülen in Lab-on-Chip Systemen dienen können. Seit Anfang der 90er Jahre kann durch modifizierte Schichten und Strukturen im Nanometerbereich die bisherige Beschränkung des Siliziums überwunden werden. So können in Siliziumdioxid eingebettete Nanostrukturen aufgrund ihrer speziellen Eigenschaften zur Lumineszenz angeregt werden. In den hier beschriebenen Untersuchungen werden Nanostrukturen durch Ionenimplantation in thermisch auf einen Siliziumwafer (100, n-Typ) aufgewachsene SiO2 – Schichten erzeugt. Im Anschluß an die Ionenimplantation werden durch eine Temperung Strahlenschäden ausgeheilt und die Clusterbildung angeregt. Die so erhaltenen Nanocluster weisen Größen von 4 ... 6 nm auf. Als Frontkontakt der Lumineszenzstrukturen wird eine aufgesputterte transparente Indium-Zinnoxid (ITO) - Schicht lithographisch in kreisrunde Flächen von 0.2mm2 strukturiert. Der Rückseitenkontakt wird durch Al - Beschichtung der Wafersrückseite hergestellt

    Hypercomplex quantum mechanics

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    The fundamental axioms of the quantum theory do not explicitly identify the algebraic structure of the linear space for which orthogonal subspaces correspond to the propositions (equivalence classes of physical questions). The projective geometry of the weakly modular orthocomplemented lattice of propositions may be imbedded in a complex Hilbert space; this is the structure which has traditionally been used. This paper reviews some work which has been devoted to generalizing the target space of this imbedding to Hilbert modules of a more general type. In particular, detailed discussion is given of the simplest generalization of the complex Hilbert space, that of the quaternion Hilbert module.Comment: Plain Tex, 11 page

    Oxidation of Cellular Amino Acid Pools Leads to Cytotoxic Mistranslation of the Genetic Code

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    Aminoacyl-tRNA synthetases use a variety of mechanisms to ensure fidelity of the genetic code and ultimately select the correct amino acids to be used in protein synthesis. The physiological necessity of these quality control mechanisms in different environments remains unclear, as the cost vs benefit of accurate protein synthesis is difficult to predict. We show that in Escherichia coli, a non-coded amino acid produced through oxidative damage is a significant threat to the accuracy of protein synthesis and must be cleared by phenylalanine-tRNA synthetase in order to prevent cellular toxicity caused by mis-synthesized proteins. These findings demonstrate how stress can lead to the accumulation of non-canonical amino acids that must be excluded from the proteome in order to maintain cellular viability

    Angiosarcoma With Malignant Peripheral Nerve Sheath Tumour Developing in a Patient With Klippel–Trénaunay–Weber Syndrome

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    Purpose: We discuss the coexistence of Klippel–Trénaunay–Weber syndrome with various malignancies, the possible histogenetic pathways and therapeutic implications

    Evidence for a Common Mechanism of SIRT1 Regulation by Allosteric Activators

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    A molecule that treats multiple age-related diseases would have a major impact on global health and economics. The SIRT1 deacetylase has drawn attention in this regard as a target for drug design. Yet controversy exists around the mechanism of sirtuin-activating compounds (STACs). We found that specific hydrophobic motifs found in SIRT1 substrates such as PGC-1α and FOXO3a facilitate SIRT1 activation by STACs. A single amino acid in SIRT1, Glu[superscript 230], located in a structured N-terminal domain, was critical for activation by all previously reported STAC scaffolds and a new class of chemically distinct activators. In primary cells reconstituted with activation-defective SIRT1, the metabolic effects of STACs were blocked. Thus, SIRT1 can be directly activated through an allosteric mechanism common to chemically diverse STACs.Glenn Foundation for Medical ResearchEllison Medical FoundationJuvenile Diabetes Research Foundation InternationalUnited Mitochondrial Disease FoundationNational Institutes of Health (U.S.)National Institute of Allergy and Infectious Diseases (U.S.

    The Antioxidant Potential of the Mediterranean Diet in Patients at High Cardiovascular Risk: An In-Depth Review of the PREDIMED

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    Cardiovascular disease (CVD) is the leading global cause of death. Diet is known to be important in the prevention of CVD. The PREDIMED trial tested a relatively low-fat diet versus a high-fat Mediterranean diet (MedDiet) for the primary prevention of CVD. The resulting reduction of the CV composite outcome resulted in a paradigm shift in CV nutrition. Though many dietary factors likely contributed to this effect, this review focuses on the influence of the MedDiet on endogenous antioxidant systems and the effect of dietary polyphenols. Subgroup analysis of the PREDIMED trial revealed increased endogenous antioxidant and decreased pro-oxidant activity in the MedDiet groups. Moreover, higher polyphenol intake was associated with lower incidence of the primary outcome, overall mortality, blood pressure, inflammatory biomarkers, onset of new-onset type 2 diabetes mellitus (T2DM), and obesity. This suggests that polyphenols likely contributed to the lower incidence of the primary event in the MedDiet groups. In this article, we summarize the potential benefits of polyphenols found in the MedDiet, specifically the PREDIMED cohort. We also discuss the need for further research to confirm and expand the findings of the PREDIMED in a non-Mediterranean population and to determine the exact mechanisms of action of polyphenols

    Comparative Long-term Adverse Effects Elicited by Invasive Group B and C Meningococcal Infections

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    No vaccine is universally active against serogroup B meningococci. A theoretical concern that serogroup B capsular polysaccharide may induce autoimmunity hampers vaccine development. We studied long-term complications in 120 survivors of meningococcal disease. No evidence of increased autoimmune, neurological, or psychiatric disease was noted

    Activation of Estrogen Receptor Is Crucial for Resveratrol-Stimulating Muscular Glucose Uptake via Both Insulin-Dependent and -Independent Pathways

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    OBJECTIVE—Estradiol (E2) is known to modulate insulin sensitivity and, consequently, glucose homeostasis. Resveratrol (RSV), an agonist of estrogen receptor (ER), has exerted antihyperglycemic effects in streptozotocin-induced type 1 diabetic rats in our previous study and was also shown to improve insulin resistance in other reports. However, it remains unknown whether activation of ER is involved in the metabolic effects of RSV via insulin-dependent and -independent mechanisms
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