1,131 research outputs found
Kondo resonance in a nanotube quantum dot coupled to a normal and a superconducting lead
We report on electrical transport measurements through a carbon nanotube
quantum dot coupled to a normal and a superconducting lead. The ratio of Kondo
temperature and superconducting gap is identified to govern the
transport properties of the system. In the case of the
conductance resonance splits into two resonances at . For the
opposite scenario the conductance resonance persists, however
the conductance is not enhanced compared to the normal state due to a relative
asymmetry of the lead-dot couplings. Within this limit the data is in agreement
with a simple model of a resonant SN-interface.Comment: 4 pages, 2 figures. submitted to the Proc. Rencontres de Moriond on
Quantum Information and Decoherence in Nanosystems 200
Effects of 9-hour time zone changes on fatigue and circadian rhythms of sleep/wake and core temperature
Physiological and psychological disruptions caused by transmeridian flights may affect the ability of flight crews to meet operational demands. To study these effects, 9 Royal Norwegian Airforces P3-Orion crewmembers flew from Norway to California (-9 hr), and back (+9 hr). Rectal temperature, heart rate and wrist activity were recorded every 2 min, fatigue and mood were rated every 2 hr during the waking day, and logs were kept of sleep times and ratings. Subjects also completed 4 personality inventories. The time-zone shifts produced negative changes in mood which persisted longer after westward flights. Sleep quality (subjective and objective) and duration were slightly disrupted (more after eastward flights). The circadian rhythms of sleep/wake and temperature both completed the 9-hr delay by day 5 in California, although temperature adjusted more slowly. The size of the delay shift was significantly correlated with scores on extraversion and achievement need personality scales. Response to the 9-hr advance were more variable. One subject exhibited a 15-hr delay in his temperature rhythm, and an atypical sleep/nap pattern. On average, the sleep/wake cycle (but not the temperature rhythm), completed the 9-hr advance by the end of the study. Both rhythms adapted more slowly after the eastward flight
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Balancing macronutrient stoichiometry to alleviate eutrophication
Reactive nitrogen (N) and phosphorus (P) inputs to surface waters modify aquatic environments and affect public health and recreation. Until now, source control is the dominating measure of eutrophication management, and biological regulation of nutrients is largely neglected, although aquatic microbial organisms have huge potential to process nutrients. The stoichiometric ratio of organic carbon (OC) to N to P atoms should modulate heterotrophic pathways of aquatic nutrient processing, as high OC availability favours aquatic microbial processing. Such microbial processing removes N by denitrification and captures N and P as organically-complexed, less eutrophying forms. With a global data synthesis, we show that the atomic ratios of bioavailable dissolved OC to either N or P in rivers with urban and agricultural land use are often distant from a ‘microbial optimum’. This OC-deficiency relative to high availabilities of N and P likely overwhelms within-river heterotrophic processing and we propose that the capability of streams and rivers to retain N and P may be improved by active stoichiometric rebalancing. This rebalancing should be done by reconnecting appropriate OC sources such as wetlands and riparian forests, many of which have become disconnected from rivers concurrent to the progress of agriculture and urbanization. However, key knowledge gaps leave questions in the safe implementation of this approach in management: Mechanistic research is required to (i) evaluate system responses to catchment inputs of dissolved OC forms and amounts relative to internal-cycling controls of dissolved OC from aquatic production and particulate OC from aquatic and terrestrial sources and (ii) evaluate risk factors in anoxia-mediated P desorption with elevated OC scenarios. Still, we find this to be an approach with high potential for river management and we recommend to evaluate this stoichiometric approach for alleviating eutrophication, improving water quality and aquatic ecosystem health
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Modeling Progressive Fibrosis with Pluripotent Stem Cells Identifies an Anti-fibrotic Small Molecule.
Progressive organ fibrosis accounts for one-third of all deaths worldwide, yet preclinical models that mimic the complex, progressive nature of the disease are lacking, and hence, there are no curative therapies. Progressive fibrosis across organs shares common cellular and molecular pathways involving chronic injury, inflammation, and aberrant repair resulting in deposition of extracellular matrix, organ remodeling, and ultimately organ failure. We describe the generation and characterization of an in vitro progressive fibrosis model that uses cell types derived from induced pluripotent stem cells. Our model produces endogenous activated transforming growth factor β (TGF-β) and contains activated fibroblastic aggregates that progressively increase in size and stiffness with activation of known fibrotic molecular and cellular changes. We used this model as a phenotypic drug discovery platform for modulators of fibrosis. We validated this platform by identifying a compound that promotes resolution of fibrosis in in vivo and ex vivo models of ocular and lung fibrosis
The ENaC-overexpressing mouse as a model of cystic fibrosis lung disease
AbstractChronic lung disease remains the major cause of morbidity and mortality of cystic fibrosis (CF) patients. Cftr mutant mice developed severe intestinal obstruction, but did not exhibit the characteristic CF ion transport defects (i.e. deficient cAMP-dependent Cl− secretion and increased Na+ absorption) in the lower airways, and failed to develop CF-like lung disease. These observations led to the generation of transgenic mice with airway-specific overexpression of the epithelial Na+ channel (ENaC) as an alternative approach to mimic CF ion transport pathophysiology in the lung. Studies of the phenotype of βENaC-transgenic mice demonstrated that increased airway Na+ absorption causes airway surface liquid (ASL) depletion, reduced mucus transport and a spontaneous CF-like lung disease with airway mucus obstruction and chronic airway inflammation. Here, we summarize approaches that can be applied for studies of the complex in vivo pathogenesis and preclinical evaluation of novel therapeutic strategies in this model of CF lung disease
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