534 research outputs found
Conjunto de Bases Gaussianas Universal para Átomos de K até Kr.
Um Conjunto de Bases Gaussianas Universal de tamanho pequeno para os átomos de K até Kr é apresentado. Esse conjunto foi construído a partir de uma sequência única contendo 20 expoentes gerada através do conjunto de bases DZP [1, 2, 3]. As funções Gaussianas de todas as simetrias de cada átomo são extraídas a partir da sequência única. Essas funções foram escolhidas de acordo com sua inuência na energia Hartree-Fock total. Para cada átomo estudado um esquema de contração segmentado foi proposto e, então, funções de polarização e difusas foram acrescentadas. O conjunto Universal gerado neste trabalho mostrou ser competitivo com outros conjuntos de bases adaptados de tamanho similar nos cálculos de geometria de equilíbrio, momento de dipolo elétrico e polarizabilidade de alguns sistemas moleculares
Re-hierarquização e Extrapolações para o Limite do Conjunto de Base Completo.
Um método sugerido previamente para calcular a energia de correlação no limite do conjunto de base completo pela redesignação dos números hierárquicos, e o uso do esquema de extrapolação unified singlet- and triplet-pair é aplicado a um conjunto de prova de 106 sistemas. A aproximação é utilizada para obter os valores extrapolados para energia de correlação, energia de atomização, anisotropia e polarizabilidade média no limite do conjunto de base completo, através de teoria de perturbação de segunda ordem de Møller-Plesset, método de coupled-cluster com excitações simples e duplas e coupled-cluster com excitações simples e duplas com correções triplas perturbativas.
Uma boa concordância com as melhores estimativas disponíveis é obtida, mesmo quando o par de números hierárquicos (d, t) é usado para realizar a extrapolação. Com isso, é concebível justificar que não há razão física forte para excluir as energias dulpa-zeta em extrapolações, especialmente se a base é calibrada para obedecer ao modelo teórico.
Além disso, um esquema simples de extrapolação unificado de um parâmetro é sugerido para extrapolar a energia de correlação de valência para o conjunto de base completo em espécies formadas por átomos de H até Ne. A performance do novo modelo é avaliada para a energia de correlação com um conjunto de de dados de 106 sistemas e, para polarizabilidade média, em um conjunto de 8 moléculas. Para as energias de correlação, os resultados são excelentes, na maioria das vezes melhores do que quando extrapolado com os mais populares protocolos de dois parâmetros disponíveis na literatura. Para a
polarizabilidade, os resultados mostram uma melhora em relação aos valores ab initio, e uma boa concordância com os dados experimentais
Executive function impairment in early - treated PKU subjects with normal mental development
Executive functions were studied in 14 early and continuously treated PKU subjects (age 10.8 years, range 8-13) in comparison with controls matched for IQ, sex, age and socioeconomic status. Brain MRI examination was normal in all PKU patients. Neuropsychological evaluation included Wisconsin Card Sorting Test, Rey-Osterreith Complex Figure Test, Elithorn's Perceptual Maze Test, Weigl's Sorting Test, Tower of London, Visual Search and Motor Motor Learning Test. Whatever the IQ, PKU subjects performed worse than controls in tests exploring executive functions. Subgrouping the PKU subjects according to the quality of dietary control for the entire follow-up period (using 400 micromol/L as cut-off value for blood phenylalanine (Phe) concentration) showed that patients with worse dietary control performed more poorly than both the PKU group with the best dietary control and the control group. However, a mild impairment of executive functions was still found in PKU patients with a good dietary control (Phe 400 micromol/L) compared to controls. Concerning the PKU group as a whole, no linear correlation was found between neuropsychological performance and historical and concurrent biochemical parameters. We conclude that (a) PKU patients, even when treated early, rigorously and continuously, show an impairment of frontal lobe functions; (b) a protracted exposure to moderately high levels of Phe can affect frontal lobe functions independently of the possible effect of the same exposure on IQ; (c) in order to reduce the risk of frontal lobe dysfunction, the target of dietary therapy should be to maintain blood Phe concentration below 400 micromol/L
Late Epiphrenic-Retroperitoneal Fistula of an Esophageal Diverticulum Ten Years after Surgical Excision: Report of the First Case
Background: Esophageal fistula is a rare complication of an epiphrenic diverticulum and represents a difficult diagnostic challenge. In the majority of cases in the English literature, the fistula is secondary to the spontaneous perforation of the epiphrenic diverticulum and in only one case an esophagobronchial fistula occurs after resection of an epiphrenic diverticulum. No case of esophageal fistula communicating with the retroperitoneum tissues was found. Case Report: We present a case of 84 years old male admitted in 2017 in our Hospital for the appearance of epigastralgia and cough with traces of blood to sputum, asthenia and night sweats. Ten years before he underwent to a hiatal hernia plastic sec. Nissen and subsequently was reoperated for exeresis of diverticulum of the distal third of the esophagus by thoracotomy. In August 2008, because of esophageal substenosis an operation of posterior gastropexy sec. Hill with the demolition of the previous hiatoplasty was performed. In 2017, a computerized tomography shows a voluminous abscess in the right paravertebral region with development along the muscular plane of the ipsilateral psoas and a fistular path of about 4 cm between the posterior wall of the esophagus and the retroperitoneal collection of the abdomen. Conclusions: Esophageal fistula represents a complex problem of epiphrenic diverticulum and rarely a hidden complication of surgery. Surgery is the treatment of choice in suitable patients
Effects of Current and Future Summer Marine Heat Waves on Posidonia oceanica: Plant Origin Matters?
Marine heat waves (MHWs), prolonged discrete anomalously warm water events, have
been increasing significantly in duration, intensity and frequency all over the world,
and have been associated with a variety of impacts including alteration of ecosystem
structure and function. This study assessed the effects of current and futureMHWs on the
Mediterranean seagrass Posidonia oceanica performance, also testing the importance
of the thermal environment where the plant lives. The effects of current MHWs were
studied through a mensurative experiment in a cold and in a warm site (West and
North-West Sardinia, Italy, respectively). Future MHWs effects were tested through a
manipulative experiment using P. oceanica shoots collected fromthe cold and warmsites
and transplanted in a common garden in front of a power plant (North-West Sardinia):
here plants were exposed to heat longer in duration and stronger in intensity than
the natural MHWs of the last 20 years, resembling the future scenario. Morphological
(total # of leaves, maximum leaf length, and percentage of total necrotic leaf length
per shoot) and biochemical variables (leaf proteins, carbohydrates, and lipids) were
considered. Plants had similar sublethal responses in both the experiments for most
of the variables, revealing that current and future MHWs had similar effect types, but
different in magnitude depending on the intensity of the waves: in general, the number
of leaves, the maximum leaf length and lipid content decreased, while the leaf necrosis
and carbohydrates increased. However, also the origin of the plants affected the results,
corroborating the hypothesis that the thermal context the plants live affects their tolerance
to the heat. Overall, this study provided evidence about the importance of biochemical
variations, such as carbohydrate and lipid levels, as potentially good indicators of
seagrass heat stress
EP-1947: Evaluation of dosimetric properties of 3D printed flat bolus for external beam radiotherapy
Silica Meets Tannic Acid: Designing Green Nanoplatforms for Environment Preservation
Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO2 NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solu-tions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-5SiO2 NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu2+ ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO2 NPs exhibited a different adsorption behaviour towards Cu2+, which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu2+ amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution
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