Long-term decomposition of sugarcane harvest residues in Sao Paulo state, Brazil

Crop residues returned to the soil are important to preserve fertility and sustainability. This research addressed the long-term decomposition of sugarcane post-harvest residues (trash) under reduced tillage, therefore field renewal was performed with herbicide followed by subsoiling and ratoons were deprived of interrow scarification. The trial was conducted in the northern Sao Paulo State, Brazil during four consecutive crops (2005-2008) where litter bags containing N-15-labeled trash were disposed in the field attempting to simulate two distinct situations: the previous crop trash (PCT) or residues incorporated in the field after tillage, and post-harvest trash (PHT) or the remains of plant-cane harvest. Decomposition rates regarding dry matter (DM), carbon (C), root growth, plant nutrients (N, P, K, Ca, Mg and S), lignin (LIG) cellulose (CEL) and hemicellulose (HCEL) contents were assessed for PCT (2005 ndash;2008) and for PHT (2006-2008). There were significant reductions on DM and C:N ratio due to C losses and root growth within the litter bags over time. The DM from PCT and PHT decreased 96% and 73% after four and three crops, respectively, and the higher nutrients release were found for K, Ca and N. The LIG, CEL and HCEL concentrations in PCT decreased 60%, 29%, 70% after four crops and 47%, 35%, 70% from PHT after three crops, respectively. Trash decomposition was driven mainly by residues biochemical composition, root growth within the trash blanket and the climatic conditions during the crop cycles. (C) 2012 Elsevier Ltd. All rights reserved.

Effect of electromagnetic field on bone regeneration around dental implants after immediate placement in the dog mandible: a pilot study

Background: Accelerating bone healing around dental implants can reduce the long-term period between the insertion of implants and functional rehabilitation. Objective: This in vivo study evaluated the effect of a constant electromagnetic field (CEF) on bone healing around dental implants in dogs. Materials and methods: Eight dental implants were placed immediately after extraction of the first premolar and molar teeth on the mandible of two male dogs and divided into experimental (CEF) and control groups. A CEF at magnetic intensity of 0.8 mT with a pulse width of 25 mu s and frequency of 1.5 MHz was applied on the implants for 20 min per day for 2 weeks. Result and conclusion: After qualitative histological analysis, a small quantity of newly formed bone was observed in the gap between the implant surface and alveolar bone in both groups.

Revision of Singlet Quantum Yields in the Catalyzed Decomposition of Cyclic Peroxides

The chemiluminescence of cyclic peroxides activated by oxidizable fluorescent dyes is an example of chemically initiated electron exchange luminescence (CIEEL), which has been used also to explain the efficient bioluminescence of fireflies. Diphenoyl peroxide and dimethyl-1,2-dioxetanone were used as model compounds for the development of this CIEEL mechanism. However, the chemiexcitation efficiency of diphenoyl peroxide was found to be much lower than originally described. In this work, we redetermine the chemiexcitation quantum efficiency of dimethyl-1,2-dioxetanone, a more adequate model for firefly bioluminescence, and found a singlet quantum yield (Phi(s)) of 0.1%, a value at least 2 orders of magnitude lower than previously reported. Furthermore, we synthesized two other 1,2-dioxetanone derivatives and confirm the low chemiexcitation efficiency (Phi(s) < 0.1%) of the intermolecular CIEEL-activated decomposition of this class of cyclic. peroxides. These results are compared with other chemiluminescent reactions, supporting the general trend that intermolecular CIEEL systems are much less efficient in generating singlet excited states than analogous intramolecular processes (Phi(s) approximate to 50%), with the notable exception of the peroxyoxalate reaction (Phi(s) approximate to 60%).

Kinetics of thermal decomposition of niobium hydride

High-purity niobium powders can be obtained from the well-known hydride-dehydride (HDH) process. The aim of this work was the investigation of the structural phase transition of the niobium hydride to niobium metal as function of temperature, heating rate and time. The niobium powder used in this work was obtained by high-temperature hydriding of niobium machining chips followed by conventional ball milling and sieving. X-ray diffraction measurements were carried out in vacuum using a high-temperature chamber coupled to an X-ray diffractometer. During the dehydriding process, it is possible to follow the phase transition from niobium hydride to niobium metal starting at about 380 degrees C for a heating rate of 20 degrees C/min. The heating rate was found to be an important parameter, since complete dehydriding was obtained at 490 degrees C for a heating rate of 20 degrees C/min. The higher dehydriding rate was found at 500 degrees C. Results contribute to a better understanding of the kinetics of thermal decomposition of niobium hydride to niobium metal. (C) 2011 Elsevier Ltd. All rights reserved.

Development of Plurimetallic Electrocatalysts Prepared by Decomposition of Polymeric Precursors for EtOH/O-2 Fuel Cell

This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal: carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L-1 H2SO4), in the absence and presence of ethanol. Addition of Sn to PtRuNi/C catalysts significantly shifted the ethanol and CO onset potentials toward lower values, thus increasing the catalytic activity, especially for the quaternary composition Pt64Sn15Ru13Ni8/C. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed determination of acetaldehyde and acetic acid as the main reaction products. The presence of Ru in alloys promoted formation of acetic acid as the main product of ethanol oxidation. The Pt64Sn15Ru13Ni8/C catalyst displayed the best performance for DEFC.

OXYGEN ABUNDANCES IN LOW- AND HIGH-alpha FIELD HALO STARS AND THE DISCOVERY OF TWO FIELD STARS BORN IN GLOBULAR CLUSTERS

Oxygen abundances of 67 dwarf stars in the metallicity range -1.6 < [Fe/H] < -0.4 are derived from a non-LTE analysis of the 777 nm O I triplet lines. These stars have precise atmospheric parameters measured by Nissen and Schuster, who find that they separate into three groups based on their kinematics and alpha-element (Mg, Si, Ca, Ti) abundances: thick disk, high-alpha halo, and low-alpha halo. We find the oxygen abundance trends of thick-disk and high-alpha halo stars very similar. The low-alpha stars show a larger star-to-star scatter in [O/Fe] at a given [Fe/H] and have systematically lower oxygen abundances compared to the other two groups. Thus, we find the behavior of oxygen abundances in these groups of stars similar to that of the a elements. We use previously published oxygen abundance data of disk and very metal-poor halo stars to present an overall view (-2.3 < [Fe/H] < +0.3) of oxygen abundance trends of stars in the solar neighborhood. Two field halo dwarf stars stand out in their O and Na abundances. Both G53-41 and G150-40 have very low oxygen and very high sodium abundances, which are key signatures of the abundance anomalies observed in globular cluster (GC) stars. Therefore, they are likely field halo stars born in GCs. If true, we estimate that at least 3% +/- 2% of the local field metal-poor star population was born in GCs.

Development of plurimetallic electrocatalysts prepared by decomposition of polymeric precursors for EtOH/O2 fuel cell

This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal:carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L-1 H2SO4), in the absence and presence of ethanol. Addition of Sn to PtRuNi/C catalysts significantly shifted the ethanol and CO onset potentials toward lower values, thus increasing the catalytic activity, especially for the quaternary composition Pt64Sn15Ru13Ni8/C. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed determination of acetaldehyde and acetic acid as the main reaction products. The presence of Ru in alloys promoted formation of acetic acid as the main product of ethanol oxidation. The Pt64Sn15Ru13Ni8/C catalyst displayed the best performance for DEFC.

Testing the influence of far-field topographic forcing on subduction initiation at a passive margin

Despite favourable gravitational instability and ridge-push, elastic and frictional forces prevent subduction initiation fromarising spontaneously at passive margins. Here,we argue that forces arising fromlarge continental topographic gradients are required to initiate subduction at passivemargins. In order to test this hypothesis,we use 2Dnumerical models to assess the influence of the Andean Plateau on stressmagnitudes and deformation patterns at the Brazilian passive margin. The numerical results indicate that “plateau-push” in this region is a necessary additional force to initiate subduction. As the SE Brazilianmargin currently shows no signs of self-sustained subduction, we examined geological and geophysical data to determine if themargin is in the preliminary stages of subduction initiation. The compiled data indicate that the margin is presently undergoing tectonic inversion, which we infer as part of the continental–oceanic overthrusting stage of subduction initiation. We refer to this early subduction stage as the “Brazilian Stage”, which is characterized by N10 kmdeep reverse fault seismicity at themargin, recent topographic uplift on the continental side, thick continental crust at themargin, and bulging on the oceanic side due to loading by the overthrusting continent. The combined results of the numerical simulations and passivemargin analysis indicate that the SE Brazilian margin is a prototype candidate for subduction initiation.

Classifying A-field and B-field configurations in the presence of D-branes. Part II: Stacks of D-branes

In the paper of Bonora et al. (2008) [3] we have shown, in the context of type II superstring theory, the classification of the allowed B-field and A-field configurations in the presence of anomaly-free D-branes, the mathematical framework being provided by the geometry of gerbes. Here we complete the discussion considering in detail the case of a stack of D-branes, carrying a non-abelian gauge theory, which was just sketched in Bonora et al. (2008) [3]. In this case we have to mix the geometry of abelian gerbes, describing the B-field, with the one of higher-rank bundles, ordinary or twisted. We describe in detail the various cases that arise according to such a classification, as we did for a single D-brane, showing under which hypotheses the A-field turns out to be a connection on a canonical gauge bundle. We also generalize to the non-abelian setting the discussion about "gauge bundles with non-integral Chern classes", relating them to twisted bundles with connection. Finally, we analyze the geometrical nature of the Wilson loop for each kind of gauge theory on a D-brane or stack of D-branes.

On the pathogenesis of Plasmodium vivax malaria: Perspectives from the Brazilian field

Life-threatening Plasmodium vivax malaria cases, while uncommon, have been reported since the early 20th century. Unfortunately, the pathogenesis of these severe vivax malaria cases is still poorly understood. In Brazil, the proportion of vivax malaria cases has been steadily increasing, as have the number of cases presenting serious clinical complications. The most frequent syndromes associated with severe vivax malaria in Brazil are severe anaemia and acute respiratory distress. Additionally, P. vivax infection may also result in complications associated with pregnancy. Here, we review the latest findings on severe vivax malaria in Brazil. We also discuss how the development of targeted field research infrastructure in Brazil is providing clinical and ex vivo experimental data that benefits local and international efforts to understand the pathogenesis of P. vivax. (C) 2012 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Characterization of depolymerized residues from extremely low acid hydrolysis (ELA) of sugarcane bagasse cellulose: Effects of degree of polymerization, crystallinity and crystallite size on thermal decomposition

Sugarcane bagasse cellulose was subjected to the extremely low acid (ELA) hydrolysis in 0.07% H2SO4 at 190, 210 and 225 degrees C for various times. The cellulose residues from this process were characterized by TGA, XRD, GPC, FIR and SEM. A kinetic study of thermal decomposition of the residues was also carried out, using the ASTM and Kissinger methods. The thermal studies revealed that residues of cellulose hydrolyzed at 190, 210 and 225 degrees C for 80,40 and 8 min have initial decomposition temperature and activation energy for the main decomposition step similar to those of Avicel PH-101. XRD studies confirmed this finding by showing that these cellulose residues are similar to Avicel in crystallinity index and crystallite size in relation to the 110 and 200 planes. FTIR spectra revealed no significant changes in the cellulose chemical structure and analysis of SEM micrographs demonstrated that the particle size of the cellulose residues hydrolyzed at 190 and 210 degrees C were similar to that of Avicel. (C) 2011 Elsevier B.V. All rights reserved.

Local symmetries in gauge theories in a finite-dimensional setting

It is shown that the correct mathematical implementation of symmetry in the geometric formulation of classical field theory leads naturally beyond the concept of Lie groups and their actions on manifolds, out into the realm of Lie group bundles and, more generally, of Lie groupoids and their actions on fiber bundles. This applies not only to local symmetries, which lie at the heart of gauge theories, but is already true even for global symmetries when one allows for fields that are sections of bundles with (possibly) non-trivial topology or, even when these are topologically trivial, in the absence of a preferred trivialization. (C) 2012 Elsevier B.V. All rights reserved.

Thermal decomposition kinetics of Brazilian limestones: effect of CO2 partial pressure

The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E-alpha) were 197.4 kJ mol(-1) and 188.1 kJ mol(-1) for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E-alpha for 15% CO2 were 378.7 kJ mol(-1) for the CI, and 299.8 kJ mol(-1) (first decomposition) and 453.4 kJ mol(-1) (second decomposition) for the DP, showing that the determination of E-alpha for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations.

Dilute Acid Hydrolysis of Sugar Cane Bagasse at High Temperatures: A Kinetic Study of Cellulose Saccharification and Glucose Decomposition. Part I: Sulfuric Acid as the Catalyst

The kinetics of sugar cane bagasse cellulose saccharification and the decomposition of glucose under extremely low acid (ELA) conditions, (0.07%), 0.14%, and 0.28% H2SO4, and at high temperatures were investigated using batch reactors. The first-order rate constants were obtained by weight loss, remaining glucose, and fitting glucose concentration profiles determined with HPLC using the Saeman model. The maximum glucose yields reached 67.6% (200 degrees C, 0.07% H2SO4, 30 min), 69.8% (210 degrees C, 0.14% H2SO4, 10 min), and 67.3% (210 degrees C, 0.28% H2SO4, 6 min). ELA conditions produced remarkable glucose yields when applied to bagasse cellulose. The first-order rate constants were used to calculate activation energies and extrathermodynamic parameters to elucidate the reaction mechanism under ELA conditions. The effect of acid concentration on cellulose hydrolysis and glucose decomposition was also investigated. The observed activation energies and reaction orders with respect to hydronium ion for cellulose hydrolysis and glucose decomposition were 184.9 and 124.5 kJ/mol and 1.27 and 0.75, respectively.

Rates of Change in the Visual Field and Optic Disc in Patients with Distinct Patterns of Glaucomatous Optic Disc Damage

Purpose: To investigate the rate of visual field and optic disc change in patients with distinct patterns of glaucomatous optic disc damage. Design: Prospective longitudinal study. Participants: A total of 131 patients with open-angle glaucoma with focal (n = 45), diffuse (n = 42), and sclerotic (n = 44) optic disc damage. Methods: Patients were examined every 4 months with standard automated perimetry (SAP, SITA Standard, 24-2 test, Humphrey Field Analyzer, Carl Zeiss Meditec, Dublin, CA) and confocal scanning laser tomography (CSLT, Heidelberg Retina Tomograph, Heidelberg Engineering GmbH, Heidelberg, Germany) for a period of 4 years. During this time, patients were treated according to a predefined protocol to achieve a target intraocular pressure (IOP). Rates of change were estimated by robust linear regression of visual field mean deviation (MD) and global optic disc neuroretinal rim area with follow-up time. Main Outcome Measures: Rates of change in MD and rim area. Results: Rates of visual field change in patients with focal optic disc damage (mean -0.34, standard deviation [SD] 0.69 dB/year) were faster than in patients with sclerotic (mean - 0.14, SD 0.77 dB/year) and diffuse (mean + 0.01, SD 0.37 dB/year) optic disc damage (P = 0.003, Kruskal-Wallis). Rates of optic disc change in patients with focal optic disc damage (mean - 11.70, SD 25.5 x 10(-3) mm(2)/year) were faster than in patients with diffuse (mean -9.16, SD 14.9 x 10(-3) mm(2)/year) and sclerotic (mean -0.45, SD 20.6 x 10(-3) mm(2)/year) optic disc damage, although the differences were not statistically significant (P = 0.11). Absolute IOP reduction from untreated levels was similar among the groups (P = 0.59). Conclusions: Patients with focal optic disc damage had faster rates of visual field change and a tendency toward faster rates of optic disc deterioration when compared with patients with diffuse and sclerotic optic disc damage, despite similar IOP reductions during follow-up. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references. Ophthalmology 2012; 119: 294-303 (C) 2012 by the American Academy of Ophthalmology.