Confinement effects and why carbon nanotube bundles can work as gas sensors

Carbon nanotubes have been at the forefront of nanotechnology, leading not only to a better understanding of the basic properties of charge transport in one dimensional materials, but also to the perspective of a variety of possible applications, including highly sensitive sensors. Practical issues, however, have led to the use of bundles of nanotubes in devices, instead of isolated single nanotubes. From a theoretical perspective, the understanding of charge transport in such bundles, and how it is affected by the adsorption of molecules, has been very limited, one of the reasons being the sheer size of the calculations. A frequent option has been the extrapolation of knowledge gained from single tubes to the properties of bundles. In the present work we show that such procedure is not correct, and that there are qualitative differences in the effects caused by molecules on the charge transport in bundles versus isolated nanotubes. Using a combination of density functional theory and recursive Green's function techniques we show that the adsorption of molecules randomly distributed onto the walls of carbon nanotube bundles leads to changes in the charge density and consequently to significant alterations in the conductance even in pristine tubes. We show that this effect is driven by confinement which is not present in isolated nanotubes. Furthermore, a low concentration of dopants randomly adsorbed along a two-hundred nm long bundle drives a change in the transport regime; from ballistic to diffusive, which can account for the high sensitivity to different molecules.

The use of stable isotopes to investigate the effects of supplemental lysine and methionine on protein turnover and amino acid utilization in pacu, Piaractus mesopotamicus, juveniles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Finite element evaluation of three methods of stable fixation of condyle base fractures

The surgical treatment of mandibular condyle fractures currently offers several possibilities for stable internal fixation. In this study, a finite element model evaluation was performed of three different methods for osteosynthesis of low subcondylar fractures: (1) two four-hole straight plates, (2) one seven-hole lambda plate, and (3) one four-hole trapezoidal plate. The finite element model evaluation considered a load applied to the first molar on the contralateral side to the fracture. Results showed that, although the three methods are capable of withstanding functional loading, the lambda plate displayed a more homogeneous stress distribution for both osteosynthesis material and bone and may be a better method when single-plate fixation is the option.

COINCIDENCES OF FIBREWISE MAPS BETWEEN SPHERE BUNDLES OVER THE CIRCLE

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of Fe uptake and translocation in transgenic and non-transgenic soybean plants using enriched stable Fe-57 as a tracer

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stable and mobile excited two-dimensional dipolar Bose-Einstein condensate solitons

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assessment of low amounts of meat and bone meal in the diet of laying hens by using stable isotopes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Profiles of steroid hormones in canine X-Linked muscular dystrophy via stable isotope dilution LC-MS/MS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hydrochemical and stable isotopes (H, O, S) signatures in deep groundwaters of Parana basin, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Developmental Morphology of a Dimorphic Grass Inflorescence: The Brazilian Bamboo Eremitis (Poaceae)

Premise of research.The highly specialized grass inflorescence varies with respect to phyllotaxis, with the reproductive meristem forming primary lateral branches that are either spirally arranged or distichous. The Brazilian bamboo Eremitis is highly unusual in that it has a dimorphic inflorescence, typically composed of an apical gynecandrous whorl of both male and female spikelets and basal whorls of male spikelets. Although not closely related to them, Eremitis shares some structural similarities with some early-divergent grasses.Methodology.We use SEM and LM to describe the development of the reproductive structures of Eremitis to clarify our understanding of the highly specialized grass inflorescence and flower.Pivotal results.Developmental studies show that the inflorescence of Eremitis is actually partially whorled and partially distichous. The apical whorl is abortive. The female spikelet is not terminal on the axis, in contrast with the majority of grasses. All the male spikelets are distichously attached to the inflorescence axis and separated into groups. There is a hollow style with two vascular bundles.Conclusions.The strong morphological similarities between Eremitis and some early-divergent grasses are here supplemented by several anatomical similarities, perhaps due to a shared pollination syndrome.

Stable retrograde orbits around the triple system 2001 SN263

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Poultry offal meal traceability in meat quail tissues using the technique of stable carbon (13C/12C) and nitrogen (15N/14N) isotopes

Studies on the detection of animal by-products in poultry meat are rare, and non-existent on quail meat. This study aimed at detectiong increasing levels of poultry offal meal (POM) in quail meat, using carbon (13C/12C) and nitrogen (15N/14N) stable isotopes technique. Sixty four on-day-old male quails derived from a commercial farm were randomly distributed into seven different groups, which were fed experimental diets containing 0, 1.5, 3.0, 4.5, 6.0, 7.5, and 15% of POM. Diets were formulated to contain equal energy, protein, and amino acid levels. Four individuals per treatment were sacrificed at 42 days of age for breast muscle (Pectoralis major), keel, and tibia collection, which were subsequently submitted to analyses. Isotopic δ13C and δ15N enrichment was observed in all analyzed tissues, with the lowest detection level of 3% dietary inclusion of poultry offal meal.

Modelling and determination of metabolic pools by stable carbon isotopes in the avian duodenal mucosa and albumen

Stable isotope analyses have helped in assessing dietary switches if the diet undergoes metabolic alteration (isotopic exchange). However, when considering the effects over time of switching from one diet to another, one can assess how quickly the new diet is incorporated into tissues via the isotopic renewal or incorporation rate, or turnover. Turnover is obtained using exponential curves that fit the original data, allowing the determination of practical order parameters such as the half-life (T) and the turnover constant (k). Researchers have found that metabolic incorporation can be fractionated. The resulting fractions, called metabolic pools, are identified using the linearization of the isotopic exchange model and its linear fit. This fractionation methodology is still not well defined. The objective of this study was to assess the behaviour of the metabolic renewal rate (turnover) in fractionated form, explain the theory, and apply it to data from the avian duodenal mucosa and albumen. We concluded that the duodenal mucosa has one metabolic pool, with a half-life of 1.23 days, and that the albumen has two metabolic pools, with half-lives of 1.89 and 6.32 days.

Discrimination of production environments of specialty coffees by means of stable isotopes and discriminant model

The south of Minas Gerais, Brazil stands out among various regions through its capacity for production of specialty coffees. Its potential, manifested through being one of the most award-winning Brazilian regions in recent years, has been recognized by the Cup of Excellence (COE). With the evident relationship between product quality and the environment in mind, the need arises for scientific studies to provide a foundation for discrimination of product origin, creating new methods for combating possible fraud. The aim of this study was to evaluate the use of carbon and nitrogen isotopes in discrimination of production environments of specialty coffees from the Serra da Mantiqueira of Minas Gerais by means of the discriminant model. Coffee samples were composed of ripe yellow and red fruits collected manually at altitudes below 1,000 m, from 1,000 to 1,200 m and above 1,200 m. The yellow and red fruits were subjected to dry processing and wet processing, with five replications. A total of 119 samples were used for discrimination of specialty coffee production environments by means of stable isotopes and statistical modeling. The model generated had an accuracy rate of 89% in discrimination of environments and was composed of the isotope variables of δ15N, δ13C, %C, %N, δD, δ18O (meteoric water) and sensory analysis scores. In addition, for the first time, discrimination of environments on a local geographic scale, within a single municipality, was proposed and successfully concluded. This shows that isotope analysis is an effective method in verifying geographic origin for specialty coffees.

Ecology, stable isotopes, and management of grassland songbirds at National Park Service properties on the Great Plains

Grassland ecosystems have been severely reduced and grassland bird populations have experienced consistent declines. National Park Service (NPS) properties on the Great Plains provide breeding habitat for grassland songbirds, though little is known about the quality of this habitat. A short-term study on songbirds at three NPS properties complemented current monitoring, providing an among park comparison addressing grassland bird productivity and fidelity relative to NPS property size. During 2008-2009, I assessed avian species richness, and estimated bird density and grassland songbird nest success. Bird species richness was greatest at small and medium sites, while number of nesting obligate species was greatest at the large site. Species-specific densities varied among sites, with few grassland obligates occurring at all three sites. Nest success estimates for grassland obligates were highest at the small site and lower at the large site. Another method to quantify habitat quality is assessment of breeding site fidelity. Current extrinsic markers used in monitoring site fidelity are inadequate for small birds; stable isotope analyses provide an alternative. I compared two techniques for assigning stable isotope tissue origin and measured grassland songbird site fidelity. My method of assigning origin provided site-specific variances of expected stable isotope values, an improvement over the most commonly used method. Fidelity tended to be higher at the large site, which may indicate a more robust breeding community of grassland birds. The small size of two of my sites precluded large sample sizes and made strong inferences difficult. To quantify how scientists cope with weak inference, I conducted a literature review. Strong inference was rarely observed, and most authors of weak-inference papers provided specific management recommendations. I suggest that adaptive management is an ideal method to resolve uncertainty from weak inference. Managers should consider my results within the context of regional and global management and the extent to which their unit might aide songbird conservation.