Critical assessment of enhancement factor measurements in surface-enhanced raman scattering on different substrates

The SERS enhancement factor (SERS-EF) is one of the most important parameters that characterizes the ability of a given substrate to enhance the Raman signal for SERS applications. The comparison of SERS intensities and SERS-EF values across different substrates is a common practice to unravel the performance of a given substrate. In this study, it is shown that such a comparison may lack significance if we compare substrates of very distinct nature and optical properties. It is specifically shown that the SERS-EF values for static substrates (e.g. immobilized metallic nanostructures) cannot be compared to those of dynamic ones (e.g. colloidal metal nanoparticle solutions), and that the optical properties for the latter show strong dependence on the metal-molecule interaction dynamics. The most representative experimental results concerning the dynamic substrates have been supported by generalized Mie theory simulations, which are tools used to describe the substrate complexity and the microscopic information not usually taken into account17332129421301CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIGFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPES

Use of manganese oxides recovered from spent batteries in electrocatalysis of oxygen reduction reaction in alkaline medium

The oxygen reduction reaction was studied in alkaline media using manganese oxides obtained from spent batteries as electrocatalysts. Three processes were used to recover manganese oxides from spent batteries. The particles obtained were in the range from 8 to 11 nm. The electrochemical experiments indicated a good electrocatalytic activity toward oxygen reduction using the different samples and showing approximately a direct transference of 4 electrons during the process. Even though all the processes were efficient, the best result was observed for the prepared sample using reactants of low cost.FAPESPCNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)UFAB

Comparing parallel algorithms for van der waals energy with cell-list technique for protein structure prediction / Comparando algoritmos paralelos para energia de van der waals com técnica de lista de células para predição de estrutura de proteína

The discovery of the structure of a protein is a difficult and expensive task, because it requires minimizing different energies related to them. The van der Waals energy hás the most expensive evaluation in this context, and computational methods have been developed in this way, such as Genetic Algorithm (GA) and cell-list technique, which reduces its the complexity from O(n2) to O(n). Even with the support of GA and cell lists, the van der Waals energy evaluation still requires a long computing time, even for a small protein. Parallel Computing is capable to reduce the runtime to predict the structure of proteins. Parallel algorithms in such context are usually specific for one programming model and computer architecture, resulting in limited speedups. This paper compares the runtime of three distinct parallel algorithms for the evaluation of an ab initio and full-atom approach based on GA and cell-list technique, in order to minimize the van der Waals energy. The three parallel algorithms are in C and use one of these programming models: MPI, OpenMP or hybrid (MPI+Open MP). Our results show that van der Waals Energy are executed faster and with better speedups when using hybrid and more flexible parallel algorithms to predict the structure of larger proteins. We also show that for small proteins the communication of MPI imposes a high overhead for the parallel execution and, thus the Open MP presents a better relation cost x benefit in such cases

Neurodevelopmental regression, severe generalized dystonia, and metabolic acidosis caused by POLR3A mutations.

OBJECTIVE: To expand the clinical phenotype of POLR3A mutations by assessing the functional consequences of a missense and a splicing acceptor mutation. METHODS: We performed whole-exome sequencing for identification of likely pathogenic mutations in a 9-year-old female patient with severe generalized dystonia, metabolic acidosis, leukocytosis, hypotonia, and dysphagia. Brain MRI showed basal ganglia atrophy and presence of lactate and lipid peaks by [1H]-magnetic resonance spectroscopy. Expression levels of Pol III target genes were measured by quantitative real-time (qRT)-PCR to study the pathogenicity of the biallelic mutations in patient fibroblasts. RESULTS: The patient is a compound heterozygous for a novel missense c.3721G>A (p.Val1241Met) and the splicing region c.1771-6C>G mutation in POLR3A, the gene coding for the catalytic subunit of RNA polymerase III (Pol III). Aberrant splicing was observed for the c.1771-6C>G mutation. Decreased RNA expression levels of Pol III targets (HNRNPH2, ubiquitin B, lactotransferrin, and HSP90AA1) were observed in patient fibroblasts with rescue to normal levels by overexpression of the wild-type protein but not by the p.Val1241Met variant. CONCLUSIONS: Mutations in the POLR3A gene cause POLR3A-related hypomyelinating leukodystrophy with or without oligodontia or hypogonadotropic hypogonadism (HLD7, OMIM: 607694) and neonatal progeroid syndrome (OMIM: 264090), both with high phenotypic variability. We demonstrated the pathogenicity of c.1771-6C>G and c.3721G>A mutations causing an early-onset disorder. The phenotype of our patient expands the clinical presentation of POLR3A-related mutations and suggests a new classification that we propose designating as Neurodevelopmental Disorder with Regression, Abnormal Movements, and Increased Lactate

Structural, morphological, and magnetic characterizations of (FexMn1-x)2O3 nanocrystals: A comprehensive stoichiometric determination

Iron manganese trioxide (FexMn1-x)2O3 nanocrystals were synthesized by the sol-gel method. The 80 K Mossbauer spectrum was well-fitted using two doublets representing the 8b and 24d crystallographic sites of the (FexMn1-x)2O3 phase and two weak extra sextets which were attributed to crystalline and amorphous hematite. Our findings showed formation of a bixbyite primary phase. The Raman spectrum exhibits six Raman active modes, typical of (Fe,Mn)2O3, and two extra Raman modes associated with the secondary hematite phase. X-ray photoelectron spectroscopy analysis confirmed the presence of oxygen vacancy onto the (FexMn1-x)2O3 particle surface, with varying oxidation states. X-band magnetic resonance data revealed a single broad resonance line in the whole temperature range (3.8 K - 300 K). The temperature dependence of both resonance field and resonance linewidth shows a remarkable change in the range of 40 - 50 K, herein credited to surface spin glass behavior. The model picture used assumes (FexMn1-x)2O3 nanoparticles with a core-shell structure. Results indicate that below about 50 K the spin system of shell reveals a paramagnetic to spin glass-like transition upon cooling, with a critical temperature estimated at 43 K. In the higher temperature range, the superparamagnetic hematite (secondary) phase contributes remarkably to the temperature dependence of the resonance linewidth. Zero-field-cooled (ZFC) and fieldcooled (FC) data show strong irreversibility and a peak in the ZFC curve at 33 K, attributed to a paramagnetic-ferrimagnetic transition of the main phase. Hysteresis curve at 5 K shows a low coercive field of 4 kOe, with the magnetization not reaching saturation at 70 kOe, suggesting the occurrence of a ferrimagnetic core with a magnetic disorder at surface, characteristic of core-shell spin-glass-like behavior

Calibração de sensor de capacitância para determinação do teor de água em um latossolo amarelo.

Meta 2007