300 research outputs found
Observation of Josephson coupling through an interlayer of antiferromagnetically ordered chromium
The supercurrent transport in metallic Josephson tunnel junctions with an
additional interlayer made up by chromium, being an itinerant antiferromagnet,
was studied. Uniform Josephson coupling was observed as a function of the
magnetic field. The supercurrent shows a weak dependence on the interlayer
thickness for thin chromium layers and decays exponentially for thicker films.
The diffusion constant and the coherence length in the antiferromagnet were
estimated. The antiferromagnetic state of the barrier was indirectly verified
using reference samples. Our results are compared to macroscopic and
microscopic models.Comment: Phys. Rev. B (2009), in prin
The oxygen-independent metabolism of cyclic monoterpenes in Castellaniella defragrans 65Phen
BACKGROUND: The facultatively anaerobic betaproteobacterium Castellaniella defragrans 65Phen utilizes acyclic, monocyclic and bicyclic monoterpenes as sole carbon source under oxic as well as anoxic conditions. A biotransformation pathway of the acyclic β-myrcene required linalool dehydratase-isomerase as initial enzyme acting on the hydrocarbon. An in-frame deletion mutant did not use myrcene, but was able to grow on monocyclic monoterpenes. The genome sequence and a comparative proteome analysis together with a random transposon mutagenesis were conducted to identify genes involved in the monocyclic monoterpene metabolism. Metabolites accumulating in cultures of transposon and in-frame deletion mutants disclosed the degradation pathway. RESULTS: Castellaniella defragrans 65Phen oxidizes the monocyclic monoterpene limonene at the primary methyl group forming perillyl alcohol. The genome of 3.95 Mb contained a 70 kb genome island coding for over 50 proteins involved in the monoterpene metabolism. This island showed higher homology to genes of another monoterpene-mineralizing betaproteobacterium, Thauera terpenica 58Eu(T), than to genomes of the family Alcaligenaceae, which harbors the genus Castellaniella. A collection of 72 transposon mutants unable to grow on limonene contained 17 inactivated genes, with 46 mutants located in the two genes ctmAB (cyclic terpene metabolism). CtmA and ctmB were annotated as FAD-dependent oxidoreductases and clustered together with ctmE, a 2Fe-2S ferredoxin gene, and ctmF, coding for a NADH:ferredoxin oxidoreductase. Transposon mutants of ctmA, B or E did not grow aerobically or anaerobically on limonene, but on perillyl alcohol. The next steps in the pathway are catalyzed by the geraniol dehydrogenase GeoA and the geranial dehydrogenase GeoB, yielding perillic acid. Two transposon mutants had inactivated genes of the monoterpene ring cleavage (mrc) pathway. 2-Methylcitrate synthase and 2-methylcitrate dehydratase were also essential for the monoterpene metabolism but not for growth on acetate. CONCLUSIONS: The genome of Castellaniella defragrans 65Phen is related to other genomes of Alcaligenaceae, but contains a genomic island with genes of the monoterpene metabolism. Castellaniella defragrans 65Phen degrades limonene via a limonene dehydrogenase and the oxidation of perillyl alcohol. The initial oxidation at the primary methyl group is independent of molecular oxygen
The oxygen-independent metabolism of cyclic monoterpenes in Castellaniella defragrans 65Phen
Background: The facultatively anaerobic betaproteobacterium Castellaniella defragrans 65Phen utilizes acyclic, monocyclic and bicyclic monoterpenes as sole carbon source under oxic as well as anoxic conditions. A biotransformation pathway of the acyclic beta-myrcene required linalool dehydratase-isomerase as initial enzyme acting on the hydrocarbon. An in-frame deletion mutant did not use myrcene, but was able to grow on monocyclic monoterpenes. The genome sequence and a comparative proteome analysis together with a random transposon mutagenesis were conducted to identify genes involved in the monocyclic monoterpene metabolism. Metabolites accumulating in cultures of transposon and in-frame deletion mutants disclosed the degradation pathway. Results: Castellaniella defragrans 65Phen oxidizes the monocyclic monoterpene limonene at the primary methyl group forming perillyl alcohol. The genome of 3.95 Mb contained a 70 kb genome island coding for over 50 proteins involved in the monoterpene metabolism. This island showed higher homology to genes of another monoterpene-mineralizing betaproteobacterium, Thauera terpenica 58Eu(T), than to genomes of the family Alcaligenaceae, which harbors the genus Castellaniella. A collection of 72 transposon mutants unable to grow on limonene contained 17 inactivated genes, with 46 mutants located in the two genes ctmAB (cyclic terpene metabolism). CtmA and ctmB were annotated as FAD-dependent oxidoreductases and clustered together with ctmE, a 2Fe-2S ferredoxin gene, and ctmF, coding for a NADH: ferredoxin oxidoreductase. Transposon mutants of ctmA, B or E did not grow aerobically or anaerobically on limonene, but on perillyl alcohol. The next steps in the pathway are catalyzed by the geraniol dehydrogenase GeoA and the geranial dehydrogenase GeoB, yielding perillic acid. Two transposon mutants had inactivated genes of the monoterpene ring cleavage (mrc) pathway. 2-Methylcitrate synthase and 2-methylcitrate dehydratase were also essential for the monoterpene metabolism but not for growth on acetate. Conclusions: The genome of Castellaniella defragrans 65Phen is related to other genomes of Alcaligenaceae, but contains a genomic island with genes of the monoterpene metabolism. Castellaniella defragrans 65Phen degrades limonene via a limonene dehydrogenase and the oxidation of perillyl alcohol. The initial oxidation at the primary methyl group is independent of molecular oxygen
Size Dependence of Metal-Insulator Transition in Stoichiometric Fe3O4 Nanocrystals
Magnetite (Fe3O4) is one of the most actively studied materials with a famous
metal-insulator transition (MIT), so-called the Verwey transition at around 123
K. Despite the recent progress in synthesis and characterization of Fe3O4
nanocrystals (NCs), it is still an open question how the Verwey transition
changes on a nanometer scale. We herein report the systematic studies on size
dependence of the Verwey transition of stoichiometric Fe3O4 NCs. We have
successfully synthesized stoichiometric and uniform-sized Fe3O4 NCs with sizes
ranging from 5 to 100 nm. These stoichiometric Fe3O4 NCs show the Verwey
transition when they are characterized by conductance, magnetization, cryo-XRD,
and heat capacity measurements. The Verwey transition is weakly size-dependent
and becomes suppressed in NCs smaller than 20 nm before disappearing completely
for less than 6 nm, which is a clear, yet highly interesting indication of a
size effect of this well-known phenomena. Our current work will shed new light
on this ages-old problem of Verwey transition.Comment: 18 pages, 4 figures, Nano Letters (accepted
Evidence for a Common Mechanism of SIRT1 Regulation by Allosteric Activators
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-1Îą 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.
Involvement of Lgl and Mahjong/VprBP in Cell Competition
Mahjong is a novel Lethal giant larvae-binding protein that plays a vital role in cell competition in both flies and mammals
Mucosal Leishmaniasis Caused by Leishmania (Viannia) braziliensis and Leishmania (Viannia) guyanensis in the Brazilian Amazon
Background: Leishmania (Viannia) braziliensis is a parasite recognized as the most important etiologic agent of mucosal leishmaniasis (ML) in the New World. In Amazonia, seven different species of Leishmania, etiologic agents of human Cutaneous Leishmaniasis, have been described. Isolated cases of ML have been described for several different species of Leishmania: L. (V.) panamensis, L. (V.) guyanensis and L. (L.) amazonensis. Methodology: Leishmania species were characterized by polymerase chain reaction (PCR) of tissues taken from mucosal biopsies of Amazonian patients who were diagnosed with ML and treated at the Tropical Medicine Foundation of Amazonas (FMTAM) in Manaus, Amazonas state, Brazil. Samples were obtained retrospectively from the pathology laboratory and prospectively from patients attending the aforementioned tertiary care unit. Results: This study reports 46 cases of ML along with their geographical origin, 30 cases caused by L. (V.) braziliensis and 16 cases by L. (V.) guyanensis. This is the first record of ML cases in 16 different municipalities in the state of Amazonas and of simultaneous detection of both species in 4 municipalities of this state. It is also the first record of ML caused by L. (V.) guyanensis in the states of Para, Acre, and Rondonia and cases of ML caused by L. (V.) braziliensis in the state of Rondonia. Conclusions/Significance: L. (V.) braziliensis is the predominant species that causes ML in the Amazon region. However, contrary to previous studies, L. (V.) guyanensis is also a significant causative agent of ML within the region. The clinical and epidemiological expression of ML in the Manaus region is similar to the rest of the country, although the majority of ML cases are found south of the Amazon River.SUFRAMA[016/2004
Assessment of variation in the alberta context tool: the contribution of unit level contextual factors and specialty in Canadian pediatric acute care settings
Background: There are few validated measures of organizational context and none that we located are
parsimonious and address modifiable characteristics of context. The Alberta Context Tool (ACT) was developed to
meet this need. The instrument assesses 8 dimensions of context, which comprise 10 concepts. The purpose of
this paper is to report evidence to further the validity argument for ACT. The specific objectives of this paper are
to: (1) examine the extent to which the 10 ACT concepts discriminate between patient care units and (2) identify
variables that significantly contribute to between-unit variation for each of the 10 concepts.
Methods: 859 professional nurses (844 valid responses) working in medical, surgical and critical care units of 8
Canadian pediatric hospitals completed the ACT. A random intercept, fixed effects hierarchical linear modeling
(HLM) strategy was used to quantify and explain variance in the 10 ACT concepts to establish the ACTâs ability to
discriminate between units. We ran 40 models (a series of 4 models for each of the 10 concepts) in which we
systematically assessed the unique contribution (i.e., error variance reduction) of different variables to between-unit
variation. First, we constructed a null model in which we quantified the variance overall, in each of the concepts.
Then we controlled for the contribution of individual level variables (Model 1). In Model 2, we assessed the
contribution of practice specialty (medical, surgical, critical care) to variation since it was central to construction of
the sampling frame for the study. Finally, we assessed the contribution of additional unit level variables (Model 3).
Results: The null model (unadjusted baseline HLM model) established that there was significant variation between
units in each of the 10 ACT concepts (i.e., discrimination between units). When we controlled for individual
characteristics, significant variation in the 10 concepts remained. Assessment of the contribution of specialty to
between-unit variation enabled us to explain more variance (1.19% to 16.73%) in 6 of the 10 ACT concepts. Finally,
when we assessed the unique contribution of the unit level variables available to us, we were able to explain
additional variance (15.91% to 73.25%) in 7 of the 10 ACT concepts.
Conclusion: The findings reported here represent the third published argument for validity of the ACT and adds
to the evidence supporting its use to discriminate patient care units by all 10 contextual factors. We found
evidence of relationships between a variety of individual and unit-level variables that explained much of this
between-unit variation for each of the 10 ACT concepts. Future research will include examination of the
relationships between the ACTâs contextual factors and research utilization by nurses and ultimately the
relationships between context, research utilization, and outcomes for patients
The impact of ventilation cooling towers on plus energy houses in southern Europe
This is an Open Access Article. It is published by Taylor and Francis under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/Cooling homes is often important to maintain acceptable internal comfort. This can be achieved by both active and passive solutions. This research focused on passive systems and has examined one hypothesis: that evaporative cooling towers are an important element of plus-energy houses in southern Europe. Refinements to the design of the existing ventilation tower of a Solar Decathlon House developed by the Hochschule fĂźr Technik Stuttgart are proposed and tested in eight locations in Greece, Italy, Portugal and Spain using dynamic thermal and computational fluid dynamics simulations in order to predict energy consumption, mean and peak CO2 levels, temperatures, ventilation rates, cooling potential, fresh air distribution, indoor air quality and water consumption of the evaporative cooling system implemented within the tower. Results show that a 50% reduction of the annual energy demand for space cooling to be satisfied by other systems is achieved without compromising the internal comfort
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