Twenty-four hour Holter ECG in normocalcemic and hypercalcemic patients with hyperparathyroidism.

PURPOSE: To investigate the occurrence of arrhythmias in patients with normocalcemic (NC) primary hyperparathyroidism (PHPT) compared to both hypercalcemic PHPT patients and control subjects by means of 24-h Holter ECG. METHODS: Thirteen NCPHPT postmenopausal patients were enrolled and age-matched with 13 hypercalcemic PHPT patients and 13 controls. Every subject underwent basal ECG, 24-h Holter ECG and mineral metabolism biochemical evaluation. RESULTS: PHPT patients had higher mean serum calcium levels compared to both NCPHPT and controls; there was no difference in mean serum calcium levels between NCPHPT and controls. Both NCPHPT and PHPT patients had significantly higher mean PTH levels compared with controls. There were no differences in ECG parameters between the three groups, except for QTc interval. PHPT patients had normal QTc interval values, but significantly shorter mean values compared with those of controls and NCPHPT patients. During 24-h Holter ECG recording, 100% of PHPT patients had supraventricular premature beats (SVPBs), compared to 46% of NCPHPT (p = 0.005) and to 53% of controls (p = 0.01). PHPT patients experienced ventricular premature beats (VPBs) (69.2%) vs 15% of NCPHPT patients (p = 0.01) and 23% of controls (p = 0.04). There was no difference between NCPHPT and controls subjects concerning occurrence of both VPBs and SVPBs. CONCLUSIONS: NCPHPT patients did not experience an increased occurrence of arrhythmias compared to controls, while PHPT patients showed an increased occurrence compared to both controls and NCPHPT. Our findings are most probably related to the short QTc interval caused by hypercalcemia observed in PHPT patients, but not in NCPHPT.

Activated sludge treatment for promoting the reuse of a synthetic produced water in irrigation.

Large volumes of produced water are generated as a byproduct in activities of oil and gas exploitation, which can be reused in agriculture after a treatment process. Activated sludge treatment has been successfully used to remove oil from wastewater, but systematic studies on the toxicity of this effluent using this treatment are scarce in the literature. In this study, it was investigated the performance of an activated sludge system in the treatment of a synthetic produced water under different initial conditions in terms of salinity and oil and grease concentration. Furthermore, it was evaluated this effluent phytotoxicity in the germination, and seedling and plant growths of sunflower and corn seeds using untreated and treated synthetic produced water. Results revealed the activated sludge effectiveness in oil and grease and salinity removal from produced water, viz. high removal efficiency of 99.01 ± 0.28 and 91.07 ± 0.39%., respectively. Untreated produced water showed considerable toxic effects on the germination (74.67 ± 2.31% and 82.67 ± 2.31 for sunflower and corn seeds, respectively) and growth stages of sunflower and corn seed plants. The germination percentage was approximately 100% for both types of seed. The seedling and plant growth of the two seeds irrigated with treated produced water had similar performance when used tap water. These results highlighted the potential reuse as an unconventional water resource for plant irrigation of the synthetic produced water treated by an activated sludge process, which technology has showed high removal performance of salinity and oil.

Os fatores associados à asma em crianças e adolescentes são universais? Estudo sistemático multicêntrico brasileiro / Are the factors associated with asthma in children and adolescents universal? A systematic multicenter Brazilian study

Objetivo: Comparar os fatores de risco associados à asma em escolares brasileiros habitantes de diferentes regiões do país. Método: Participaram estudantes (4-8 anos, n = 4.262; 10-14 anos, n = 10.603) matriculados em escolas privadas ou particulares de onze centros de nove cidades brasileiras, utilizando-se o protocolo do International Study of Asthma and Allergy in Childhood (ISAAC). Após a obtenção das taxas de prevalência de asma, foram selecionados de modo aleatório estudantes com asma ativa (resposta afirmativa para "sibilos nos últimos 12 meses") e sem asma (resposta negativa) mantendo-se como base a proporção 1:2. A seguir os responsáveis responderam questionário complementar ISAAC sobre fatores de risco. A análise de regressão logística identificou os fatores associados à expressão da asma nos escolares, em cada centro de origem. Resultados: Na faixa etária mais jovem, ter antecedente de rinite ou eczema atópico, história familiar de doenças alérgicas e ser exposto ao tabaco foram identificados pela maioria dos centros. Entre os adolescentes ocorreu o mesmo: ter rinite alérgica (8/11 centros), ter antecedentes familiares de doenças alérgicas (6/11), ser exposto passivamente ao tabaco (6/11), assim como a animais domésticos, sobretudo gato (5/11), nascer pré-termo, ter baixo consumo de vegetais e suco de frutas foram os fatores identificados. Conclusões: Os fatores associados ao desenvolvimento de asma em escolares brasileiros não foram uniformes. Fatores genéticos, como ter outra doença alérgica, ou familiares com doença alérgica, foram identificados pela maioria dos centros participantes. A exposição ao tabaco, assim como a animais domésticos, também mostrou ser de importância clínica.

Objective: To compare factors associated with the development of asthma in Brazilian schoolchildren residing in different geographical regions. Method: Children and adolescents (4-8 years, n = 4,262; 10-14 years, n = 10,603) enrolled in public or private schools at 11 centers from 9 Brazilian cities were screened using the protocol of the International Study of Asthma and Allergies in Childhood (ISAAC). After obtaining asthma prevalence rates, schoolchildren with active asthma (positive response for wheezing in the past 12 months) and without asthma (negative response) were randomly selected at a ratio of 1:2. Then, their parents or guardians were asked to answer the supplementary ISAAC questionnaire on risk factors. Multivariate logistic regression analysis identified factors associated with the expression of asthma among schoolchildren at each center. Results: Among children, having a history of rhinitis or atopic eczema, having a family history of allergic diseases, and being exposed to tobacco were identified as risk factors at most centers. Among adolescents, similar results were found: having allergic rhinitis (8/11 centers), having a family history of allergic diseases (6/11), being passively exposed to tobacco (6/11), being exposed to domestic animals, especially cat (5/11), having been born preterm, and having a low intake of vegetables and fruit juice were the main factors identified. Conclusion: Risk factors for the development of asthma in Brazilian schoolchildren were not unanimous. Genetic factors, such as having another allergic disease, or having family members with allergic disease, were identified by most of the participating centers. Exposure to tobacco, as well as to domestic animals, also showed to be clinically important.

Simulating structural transitions with kinetic Monte Carlo: The case of epitaxial graphene on SiC.

We have developed a kinetic Monte Carlo numerical scheme, specifically suited to simulate structural transitions in crystalline materials, and implemented it for the case of epitaxial graphene on SiC. In this process, surface Si atoms selectively sublimate, while the residual C atoms rearrange from a position occupied in the SiC hexagonal lattice to the graphene honeycomb structure, modifying their hybridization (from sp(3) to sp(2)) and bond partners (from Si-C to C-C). The model is based on the assumption that the Monte Carlo particles follow the evolution of their reference crystal until they experience a thermally activated reversible transition to another crystal structure. We demonstrate that, in a formulation based on three parallel lattices, the method is able to recover the complex evolution steps of epitaxial graphene on SiC. Moreover, the simulation results are in noteworthy agreement with the overall experimental scenario, both when varying the structural properties of the material (e.g., the initial surface configuration or polarity) as well as the process conditions (e.g., the temperature and pressure).

Combined strategy to realize efficient photoelectrodes for low temperature fabrication of dye solar cells.

We implemented a low-temperature approach to fabricate efficient photoanodes for dye-sensitized solar cells, which combines three different nanoarchitectures, namely, a highly conductive and highly transparent AZO film, a thin TiO2-blocking layer, and a mesoporous TiO2 nanorod-based working electrode. All the components were processed at T≤200°C. Both the AZO and the TiO2 blocking layers were deposited by reactive sputtering, whereas the TiO2 nanorods were synthesized by surfactant-assisted wet-chemical routes and processed into photoelectrodes in which the native geometric features assured uniform mesoporous structure with effective nanocrystal interconnectivity suitable to maximize light harvesting and electron diffusion. Because of the optimized structure of the TiO2-blocking/AZO bilayer, and thanks to the good adhesion of the TiO2 nanorods over it, a significant enhancement of the charge recombination resistance was demonstrated, this laying on the basis of the outstanding power conversion efficiency achievable through the use of this photoanode's architecture: a value of 4.6% (N719) was achieved with a 4-µm-thick electrode processed at T=200°C. This value noticeably overcomes the current literature limit got on AZO-based cells (N719), which instead use Nb-doped and thicker blocking layers, and thicker nanostructured photoanodes, which have been even sintered at higher temperatures (450-500°C).

Interaction between hydrogen flux and carbon monolayer on SiC(0001): graphene formation kinetics.

Manipulation of graphene-based systems is a formidable challenge, since it requires the control of atomic interactions over long timescales. Although the effectiveness of a certain number of processes has been experimentally demonstrated, the underlying atomic mechanisms are often not understood. An import class of techniques relies on the interaction between hydrogen and graphene, which is the focus of this research. In particular, the growth of epitaxial graphene on SiC(0001) is subject to a single-atom-thick interface carbon layer strongly bound to the substrate, which can be detached through hydrogen intercalation. Here we report that a nucleation phenomenon induces the transformation of this buffer layer into graphene. We study the graphenization dynamics by an ab initio based method that permits the simulation of large systems with an atomic resolution, spanning the time scales from nanoseconds to hours. The early evolution stage (∼ms time scale) is characterised by the formation of a metastable H layer deposited on the C surface. H penetration in the interface between the C monolayer and the SiC(0001) surface is a rare event due to the large penetration barrier, which is ∼2 eV. However, at high H densities, energetically favoured Si-H bonding appears on the substrate's surface. The local increase of the H density at the interface due to statistical transitions leads to the graphenization of the overlying C atoms. Thermally activated density fluctuations promote the formation of these graphene-like islands on the buffer layer: this nucleation phenomenon is evidenced by our simulations at a later evolution stage (>10(2) s at 700 °C for ∼3.6 × 10(15) at. cm(-2) s(-1) H flux). Such nuclei grow and quasi-freestanding graphene forms if the exposition to the H flux continues for a sufficiently long time (∼30 min for the same conditions). We have systematically explored this phenomenon by varying the substrate temperature and the H flux, demonstrating that the surface morphology during graphenization and post-graphenization anneals significantly depends on these variables. The computational findings are consistent with the experimental analyses reported so far and could serve as guidelines for future experimental works on graphene manipulation.

Anomalous impurity segregation and local bonding fluctuation in l-Si.

Anomalous impurity redistribution after a laser irradiation process in group-IV elements has been reported in numerous papers. In this Letter, we correlate this still unexplained behavior with the peculiar bonding character of the liquid state of group-IV semiconductors. Analyzing the B-Si system in a wide range of experimental conditions we demonstrate that this phenomenon derives from the non-Fickian diffusion transport of B in l-Si. The proposed diffusion model relies on the balance between two impurity states in different bonding configurations: one migrating at higher diffusivity than the other. This microscopic mechanism explains the anomalous B segregation, whereas accurate comparisons between experimental chemical profiles and simulation results validate the model.

Kinetic Monte Carlo simulations for transient thermal fields: Computational methodology and application to the submicrosecond laser processes in implanted silicon.

Pulsed laser irradiation of damaged solids promotes ultrafast nonequilibrium kinetics, on the submicrosecond scale, leading to microscopic modifications of the material state. Reliable theoretical predictions of this evolution can be achieved only by simulating particle interactions in the presence of large and transient gradients of the thermal field. We propose a kinetic Monte Carlo (KMC) method for the simulation of damaged systems in the extremely far-from-equilibrium conditions caused by the laser irradiation. The reference systems are nonideal crystals containing point defect excesses, an order of magnitude larger than the equilibrium density, due to a preirradiation ion implantation process. The thermal and, eventual, melting problem is solved within the phase-field methodology, and the numerical solutions for the space- and time-dependent thermal field were then dynamically coupled to the KMC code. The formalism, implementation, and related tests of our computational code are discussed in detail. As an application example we analyze the evolution of the defect system caused by P ion implantation in Si under nanosecond pulsed irradiation. The simulation results suggest a significant annihilation of the implantation damage which can be well controlled by the laser fluence.

A multiscale study of electronic structure and quantum transport in C(6n(2))H(6n)-based graphene quantum dots.

We implement a bottom-up multiscale approach for the modeling of defect localization in C(6n(2))H(6n) islands, i.e. graphene quantum dots with a hexagonal symmetry, by means of density functional and semiempirical approaches. Using the ab initio calculations as a reference, we recognize the theoretical framework under which semiempirical methods adequately describe the electronic structure of the studied systems and thereon proceed to the calculation of quantum transport within the nonequilibrium Green function formalism. The computational data reveal an impurity-like behavior of vacancies in these clusters and evidence the role of parameterization even within the same semiempirical context. In terms of conduction, failure to capture the proper chemical aspects in the presence of generic local alterations of the ideal atomic structure results in an improper description of the transport features. As an example, we show wavefunction localization phenomena induced by the presence of vacancies and discuss the importance of their modeling for the conduction characteristics of the studied structures.

Ab Initio Prediction of Boron Compounds Arising from Borozene: Structural and Electronic Properties.

Structure and electronic properties of two unusual boron clusters obtained by fusion of borozene rings have been studied by means of first principles calculations based on the generalized-gradient approximation of the density functional theory. Moreover, a semiempirical tight-binding model has been appropriately calibrated for transport calculations on these clusters. Results show that the pure boron clusters are topologically planar and characterized by (3c-2e) bonds, which can explain, together with the aromaticity (estimated by means of NICS), the remarkable cohesive energy values obtained. Such feature makes these systems competitive with the most stable boron clusters to date. The energy gap values indicate that these clusters possess a semiconducting character, while when the larger system is considered, zero-values of the density of states are found exclusively within the HOMO-LUMO gap. Electron transport calculations within the Landauer formalism confirm these indications, showing semiconductor-like low bias differential conductance for these structures. Differences and similarities with carbon clusters are highlighted in the discussion.