10,149 research outputs found
Compositional dependence of the strain-free optical band gap in InxGa1 - xN layers
The effect of strain on the compositional and optical properties of a set of epitaxial single layers of
InxGa12xN was studied. Indium content was measured free from the effects of strain by Rutherford
backscattering spectrometry. Accurate knowledge of the In mole fraction, combined with x-ray
diffraction measurements, allows perpendicular strain (e zz) to be evaluated. Optical band gaps were
determined by absorption spectroscopy and corrected for strain. Following this approach, the strain
free dependence of the optical band gap in InxGa12xN alloys was determined for x<0.25. Our
results indicate an ââanomalous,ââ linear, dependence of the energy gap on the In content, at room
temperature: Eg(x)53.39â 3.57x eV. Extension of this behavior to higher concentrations is
discussed on the basis of reported result
Fullerenes In Asphaltenes And Other Carbonaceous Materials: Natural Constituents Or Laser Artifacts.
The presence of fullerenes as natural constituents of carbonaceous materials or their formation as laser artifacts during laser desorption ionization (LDI) mass spectrometry (MS) analysis is reinvestigated and reviewed. The results using asphaltene samples with varying composition as well as standard polycyclic aromatic hydrocarbons (PAH) and fullerene samples as models have demonstrated that indeed Cn ring fullerenes are not natural constituents but they are formed as common and often as predominant artifacts upon laser radiation, and a series of incorrect assignments based on LDI-MS data of several carbonaceous materials seems unfortunately to have been made. When the present results are evaluated also in the light of the vast literature on LDI-MS of carbonaceous materials, the formation of fullerene artifacts seems particularly common for LDI-MS analysis of asphaltenes and other carbonaceous samples with considerably high levels of PAH and varies according to the type of laser used, and the intensity of the laser beam.14
Research On Zinc Blood Levels And Nutritional Status In Adolescents With Autoimmune Hepatitis.
Zinc deficiency in children and adolescents impairs their growing, development and immune system. To verify the existence of plasma and leukocyte zinc deficiency in adolescents with autoimmune hepatitis. The study comprised 23 patients with autoimmune hepatitis, aged 10-18 years, assisted at the Ambulatory Service of Pediatric Hepatology of the University of Campinas Teaching Hospital, Campinas, SP, Brazil, and adolescents with ages compatible with the patients' ages comprised the control group. Sample of blood in both groups was collected for the analyses of plasma zinc and leukocyte zinc by atomic absorption spectrophotometry, beyond the nutritional status was evaluated in each adolescent. The following statistical tests were used: Mann-Whitney, Spearman's correlation and interclass concordance analysis. The significance level adopted was 5%. The average zinc level in plasma in patients was 71.91 ± 11.79 ”g/dL and, in the control group, it was 80.74 ± 10.92 ”g/dL, showing a significant difference (P = 0.04). The leukocyte zinc level in patients was 222.33 ± 166.13 pmol/10ⶠcells and, in the control group, it was 226.64 ± 217.81 pmol/10ⶠcells; there was no statistical significance between them (P = 0.45). The evaluation of the nutritional status showed that eutrophy is prevalent in patients, and they presented a higher body fat value than the control group, with a significant difference. More research is needed with adolescents with autoimmune hepatitis regarding levels of essential micronutrients, such as zinc, because a good nutritional status can improve the prognostic of liver disease.4862-
The Extraordinary X-ray Light Curve of the Classical Nova V1494 Aquilae (1999 #2) in Outburst: The Discovery of Pulsations and a "Burst"
V1494 Aql (Nova Aql 1999 No. 2) was discovered on 2 December 1999. We
obtained Chandra ACIS-I spectra on 15 April and 7 June 2000 which appear to
show only emission lines. Our third observation, on 6 August, showed that its
spectrum had evolved to that characteristic of a Super Soft X-ray Source. We
then obtained Chandra LETG+HRC-S spectra on 28 September (8 ksec) and 1 October
(17 ksec). We analyzed the X-ray light curve of our grating observations and
found both a short time scale ``burst'' and oscillations. Neither of these
phenomena have previously been seen in the light curve of a nova in outburst.
The ``burst'' was a factor of 10 rise in X-ray counts near the middle of the
second observation, and which lasted about 1000 sec; it exhibited at least two
peaks, in addition to other structure. Our time series analysis of the combined
25 ksec observation shows a peak at 2500 s which is present in independent
analyses of both the zeroth order image and the dispersed spectrum and is not
present in similar analyses of grating data for HZ 43 and Sirius B. Further
analyses of the V1494 Aql data find other periods present which implies that we
are observing non-radial g+ modes from the pulsating, rekindled white dwarf.Comment: ApJ accepte
Central Mediterranean tephrochronology between 313 and 366 ka. New insights from the Fucino paleolake sediment succession
Thirty-two tephra layers were identified in the time-interval 313â366 ka (Marine Isotope Stages 9â10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the OrvietoâBagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfinavolcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion 40Ar/39Ar dating, providing the basis for a Bayesian ageâdepth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework,
which was previously based on limited proximal and distal archives for that time interval
Compostos bioativos e atividade inibitĂłria de alfa-glicosidase em genĂłtipos de butiĂĄ (butia odorata).
Butia Ă© um gĂȘnero de palmeiras da AmĂ©rica do Sul, de ocorrĂȘncia natural no Uruguai, Paraguai, Argentina e Brasil, reconhecido pela produção de frutos que sĂŁo utilizados para fins culinĂĄrios
HEIGHT OF THE Tabebuia avellanedae IN THE CONVENTIONAL HANDLING AND SITE SPECIFIC HANDLING USING THE GEOESTATISTICS ANALYSIS
A silvicultura de precis\ue3o visa aumentar a efici\ueancia da
produ\ue7\ue3o agr\uedcola, fundamentada em manejo diferenciado
de \ue1reas de agricultura. O objetivo deste trabalho foi analisar e
comparar o desenvolvimento do ip\uea-roxo (Tabebuia avellanedae
Lorentz ex Griseb.) sob duas formas de manejo de solo. A an\ue1lise
foi realizada durante o per\uedodo de 01/03/03 a 01/03/04 em uma
\ue1rea no munic\uedpio de Mundo Novo-MS, dividida em dois blocos,
e cada bloco em duas parcelas: uma sob manejo de silvicultura de
precis\ue3o e outra sob manejo convencional. Cada uma das parcelas
recebeu 252 mudas de ip\uea-roxo, totalizando 1008 plantas.
Utilizaram-se t\ue9cnicas geoestat\uedsticas como semivariogramas
para an\ue1lise da estrutura da variabilidade espacial dos dados e a
interpola\ue7\ue3o por krigagem para a constru\ue7\ue3o de
mapas tem\ue1ticos. Dos resultados obtidos, tem-se que os mapas de
necessidade e aplica\ue7\ue3o de nutrientes e os mapas de
incremento na altura das plantas apresentaram estrutura de
variabilidade semelhante para ambos os manejos. Nenhuma diferen\ue7a
expressiva entre os tratamentos foi encontrada.The precision forestry aims to increase the agricultural production
efficiency, based in differentiated handling of agriculture areas. The
objective of this research was to analyze and to compare the
development of the Tabebuia avellanedaeLorentz ex Griseb. in two
different soil handling. This analysis was accomplished during the
period of one year (01/03/03 to 01/03/04) in an area belongs to the
city of Mundo Novo, MS, Brazil. The area was divided in two blocks and
each block in two plots, one with handling Precision Forestry and other
one with conventional handling. Each one of the portions received 252
seedlings, totaling 1008 plants. Geoestatistics was used through the
semivariograms for spatial variability analysis and kriging for
building the thematic maps. The necessity and the applied nutrients
maps and the height increment maps showed similar variability for both
treatments. No expressive difference between the treatments was found
Network Archaeology: Uncovering Ancient Networks from Present-day Interactions
Often questions arise about old or extinct networks. What proteins interacted
in a long-extinct ancestor species of yeast? Who were the central players in
the Last.fm social network 3 years ago? Our ability to answer such questions
has been limited by the unavailability of past versions of networks. To
overcome these limitations, we propose several algorithms for reconstructing a
network's history of growth given only the network as it exists today and a
generative model by which the network is believed to have evolved. Our
likelihood-based method finds a probable previous state of the network by
reversing the forward growth model. This approach retains node identities so
that the history of individual nodes can be tracked. We apply these algorithms
to uncover older, non-extant biological and social networks believed to have
grown via several models, including duplication-mutation with complementarity,
forest fire, and preferential attachment. Through experiments on both synthetic
and real-world data, we find that our algorithms can estimate node arrival
times, identify anchor nodes from which new nodes copy links, and can reveal
significant features of networks that have long since disappeared.Comment: 16 pages, 10 figure
Modulation of auxin signalling through DIAGETROPICA and ENTIRE differentially affects tomato plant growth via changes in photosynthetic and mitochondrial metabolism
Auxin modulates a range of plant developmental processes including embryogenesis, organogenesis, and shoot and root development. Recent studies have shown that plant hormones also strongly influence metabolic networks, which results in altered growth phenotypes. Modulating auxin signalling pathways may therefore provide an opportunity to alter crop performance. Here, we performed a detailed physiological and metabolic characterization of tomato (Solanum lycopersicum) mutants with either increased (entire) or reduced (diageotropicaâdgt) auxin signalling to investigate the consequences of altered auxin signalling on photosynthesis, water use, and primary metabolism. We show that reduced auxin sensitivity in dgt led to anatomical and physiological modifications, including altered stomatal distribution along the leaf blade and reduced stomatal conductance, resulting in clear reductions in both photosynthesis and water loss in detached leaves. By contrast, plants with higher auxin sensitivity (entire) increased the photosynthetic capacity, as deduced by higher Vcmax and Jmax coupled with reduced stomatal limitation. Remarkably, our results demonstrate that auxinâsensitive mutants (dgt) are characterized by impairments in the usage of starch that led to lower growth, most likely associated with decreased respiration. Collectively, our findings suggest that mutations in different components of the auxin signalling pathway specifically modulate photosynthetic and respiratory processes
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