429 research outputs found
Supersymmetry with Grand Unification
Supersymmetry (SUSY) has many well known attractions, especially in the
context of Grand Unified Theories (GUTs). SUSY stabilizes scalar mass
corrections (the hierarchy problem), greatly reduces the number of free
parameters, facilitates gauge coupling unification, and provides a plausible
candidate for cosmological dark matter. In this conference report we survey
some recent examples of progress in SUSY-GUT applications.Comment: Talk V. Barger at the Workshop on Physics at Current Accelerators and
the Supercollider, Argonne, June 1993, 15 pages + 12 PS figures included
(uuencoded), (correct author list in header) MAD/PH/78
Features of Blastocystis spp. in xenic culture revealed by deconvolutional microscopy.
Blastocystis spp. are common human enteric parasites with complex morphology and have been reported to cause irritable bowel syndrome (IBS). Deconvolutional microscopy with time-lapse imaging and fluorescent spectroscopy of xenic cultures of Blastocystis spp. from stool samples of IBS patients and from asymptomatic, healthy pigs allowed observations of living organisms in their natural microbial environment. Blastocystis organisms of the vacuolated, granular, amoebic and cystic forms were observed to autofluorescence in the 557/576 emission spectra. Autofluorescence could be distinguished from fluorescein-conjugated Blastocystis-specific antibody labelling in vacuolated and granular forms. This antibody labelled Blastocystis subtypes 1, 3 and 4 but not 5. Surface pores of 1 μm in diameter were observed cyclically opening and closing over 24 h. Vacuolated forms extruded a viscous material from a single surface point with coincident deflation that may demonstrate osmoregulation. Tear-shaped granules were observed exiting from the surface of an amoebic form, but their origin and identity remain unknown
Spin-Polarized STM for a Kondo adatom
We investigate the bias dependence of the tunneling conductance between a
spin-polarized (SP) scanning tunneling microscope (STM) tip and the surface
conduction states of a normal metal with a Kondo adatom. Quantum interference
between tip-host metal and tip-adatom-host metal conduction paths is studied in
the full range of the Fano parameter . The spin-polarized STM gives rise to
a splitting of the Kondo peak and asymmetry in the zero-bias anomaly depending
on the lateral tip-adatom distance. For increasing lateral distances, the Kondo
peak-splitting shows a strong suppression and the spin-polarized conductance
exhibits the standard Fano-Kondo profile.Comment: new version with improved discussion. added one figure. 12 pages
(one-column) + 5 figure
Beyond 'Global Production Networks': Australian Fashion Week's Trans-Sectoral Synergies
When studies of industrial organisation are informed by commodity chain, actor network, or global production network theories and focus on tracing commodity flows, social networks, or a combination of the two, they can easily overlook the less routine trans-sectoral
associations that are crucial to the creation and realisation of value. This paper shifts attention to
identifying the sites at which diverse specialisations meet to concentrate and amplify mutually reinforcing circuits of value. These valorisation processes are demonstrated in the case of Australian Fashion Week, an event in which multiple interests converge to synchronize different expressions
of fashion ideas, actively construct fashion markets and enhance the value of a diverse range of fashionable commodities. Conceptualising these interconnected industries as components of a trans-sectoral fashion complex has implications for understanding regional development, world cities, production location, and the manner in which production systems “touch down” in different
places
Deoxyribonucleic Acid Encoded and Size-Defined π-Stacking of Perylene Diimides
Natural photosystems use protein scaffolds to control intermolecular interactions that enable exciton flow, charge generation, and long-range charge separation. In contrast, there is limited structural control in current organic electronic devices such as OLEDs and solar cells. We report here the DNA-encoded assembly of π-conjugated perylene diimides (PDIs) with deterministic control over the number of electronically coupled molecules. The PDIs are integrated within DNA chains using phosphoramidite coupling chemistry, allowing selection of the DNA sequence to either side, and specification of intermolecular DNA hybridization. In this way, we have developed a “toolbox” for construction of any stacking sequence of these semiconducting molecules. We have discovered that we need to use a full hierarchy of interactions: DNA guides the semiconductors into specified close proximity, hydrophobic–hydrophilic differentiation drives aggregation of the semiconductor moieties, and local geometry and electrostatic interactions define intermolecular positioning. As a result, the PDIs pack to give substantial intermolecular π wave function overlap, leading to an evolution of singlet excited states from localized excitons in the PDI monomer to excimers with wave functions delocalized over all five PDIs in the pentamer. This is accompanied by a change in the dominant triplet forming mechanism from localized spin–orbit charge transfer mediated intersystem crossing for the monomer toward a delocalized excimer process for the pentamer. Our modular DNA-based assembly reveals real opportunities for the rapid development of bespoke semiconductor architectures with molecule-by-molecule precision
The pH of the skin surface and its impact on the barrier function
The `acid mantle' of the stratum corneum seems to be important for both permeability barrier formation and cutaneous antimicrobial defense. However, the origin of the acidic pH, measurable on the skin surface, remains conjectural. Passive and active influencing factors have been proposed, e. g. eccrine and sebaceous secretions as well as proton pumps. In recent years, numerous investigations have been published focusing on the changes in the pH of the deeper layers of the stratum corneum, as well as on the influence of physiological and pathological factors. The pH of the skin follows a sharp gradient across the stratum corneum, which is suspected to be important in controlling enzymatic activities and skin renewal. The skin pH is affected by a great number of endogenous factors, e. g. skin moisture, sweat, sebum, anatomic site, genetic predisposition and age. In addition, exogenous factors like detergents, application of cosmetic products, occlusive dressings as well as topical antibiotics may influence the skin pH. Changes in the pH are reported to play a role in the pathogenesis of skin diseases like irritant contact dermatitis, atopic dermatitis, ichthyosis, acne vulgaris and Candida albicans infections. Therefore, the use of skin cleansing agents, especially synthetic detergents with a pH of about 5.5, may be of relevance in the prevention and treatment of those skin diseases. Copyright (c) 2006 S. Karger AG, Base
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