Optical excitations in organic molecules, clusters and defects studied by first-principles Green's function methods

Spectroscopic and optical properties of nanosystems and point defects are discussed within the framework of Green's function methods. We use an approach based on evaluating the self-energy in the so-called GW approximation and solving the Bethe-Salpeter equation in the space of single-particle transitions. Plasmon-pole models or numerical energy integration, which have been used in most of the previous GW calculations, are not used. Fourier transforms of the dielectric function are also avoided. This approach is applied to benzene, naphthalene, passivated silicon clusters (containing more than one hundred atoms), and the F center in LiCl. In the latter, excitonic effects and the $1s \to 2p$ defect line are identified in the energy-resolved dielectric function. We also compare optical spectra obtained by solving the Bethe-Salpeter equation and by using time-dependent density functional theory in the local, adiabatic approximation. From this comparison, we conclude that both methods give similar predictions for optical excitations in benzene and naphthalene, but they differ in the spectra of small silicon clusters. As cluster size increases, both methods predict very low cross section for photoabsorption in the optical and near ultra-violet ranges. For the larger clusters, the computed cross section shows a slow increase as function of photon frequency. Ionization potentials and electron affinities of molecules and clusters are also calculated.Comment: 9 figures, 5 tables, to appear in Phys. Rev. B, 200

Recovery in Stroke Rehabilitation through the Rotation of Preferred Directions Induced by Bimanual Movements: A Computational Study

Stroke patients recover more effectively when they are rehabilitated with bimanual movement rather than with unimanual movement; however, it remains unclear why bimanual movement is more effective for stroke recovery. Using a computational model of stroke recovery, this study suggests that bimanual movement facilitates the reorganization of a damaged motor cortex because this movement induces rotations in the preferred directions (PDs) of motor cortex neurons. Although the tuning curves of these neurons differ during unimanual and bimanual movement, changes in PD, but not changes in modulation depth, facilitate such reorganization. In addition, this reorganization was facilitated only when encoding PDs are rotated, but decoding PDs are not rotated. Bimanual movement facilitates reorganization because this movement changes neural activities through inter-hemispheric inhibition without changing cortical-spinal-muscle connections. Furthermore, stronger inter-hemispheric inhibition between motor cortices results in more effective reorganization. Thus, this study suggests that bimanual movement is effective for stroke rehabilitation because this movement rotates the encoding PDs of motor cortex neurons

Adult-onset Alexander disease with typical "tadpole" brainstem atrophy and unusual bilateral basal ganglia involvement: a case report and review of the literature

<p>Abstract</p> <p>Background</p> <p>Alexander disease (ALX) is a rare neurological disorder characterized by white matter degeneration and cytoplasmic inclusions in astrocytes called Rosenthal fibers, labeled by antibodies against glial fibrillary acidic protein (GFAP). Three subtypes are distinguished according to age at onset: infantile (under age 2), juvenile (age 2 to 12) and adult (over age 12). Following the identification of heterozygous mutations in <it>GFAP </it>that cause this disease, cases of adult-onset ALX have been increasingly reported.</p> <p>Case Presentation</p> <p>We present a 60-year-old Japanese man with an unremarkable past and no family history of ALX. After head trauma in a traffic accident at the age of 46, his character changed, and dementia and dysarthria developed, but he remained independent. Spastic paresis and dysphagia were observed at age 57 and 59, respectively, and worsened progressively. Neurological examination at the age of 60 revealed dementia, pseudobulbar palsy, left-side predominant spastic tetraparesis, axial rigidity, bradykinesia and gaze-evoked nystagmus. Brain MRI showed tadpole-like atrophy of the brainstem, caused by marked atrophy of the medulla oblongata, cervical spinal cord and midbrain tegmentum, with an intact pontine base. Analysis of the <it>GFAP </it>gene revealed a heterozygous missense mutation, c.827G>T, p.R276L, which was already shown to be pathogenic in a case of pathologically proven hereditary adult-onset ALX.</p> <p>Conclusion</p> <p>The typical tadpole-like appearance of the brainstem is strongly suggestive of adult-onset ALX, and should lead to a genetic investigation of the <it>GFAP </it>gene. The unusual feature of this patient is the symmetrical involvement of the basal ganglia, which is rarely observed in the adult form of the disease. More patients must be examined to confirm, clinically and neuroradiologically, extrapyramidal involvement of the basal ganglia in adult-onset ALX.</p

Microbial−mammalian cometabolites dominate the age-associated urinary metabolic phenotype in Taiwanese and American populations

Understanding the metabolic processes associated with aging is key to developing effective management and treatment strategies for age-related diseases. We investigated the metabolic profiles associated with age in a Taiwanese and an American population. 1H NMR spectral profiles were generated for urine specimens collected from the Taiwanese Social Environment and Biomarkers of Aging Study (SEBAS; n = 857; age 54–91 years) and the Mid-Life in the USA study (MIDUS II; n = 1148; age 35–86 years). Multivariate and univariate linear projection methods revealed some common age-related characteristics in urinary metabolite profiles in the American and Taiwanese populations, as well as some distinctive features. In both cases, two metabolites—4-cresyl sulfate (4CS) and phenylacetylglutamine (PAG)—were positively associated with age. In addition, creatine and β-hydroxy-β-methylbutyrate (HMB) were negatively correlated with age in both populations (p < 4 × 10–6). These age-associated gradients in creatine and HMB reflect decreasing muscle mass with age. The systematic increase in PAG and 4CS was confirmed using ultraperformance liquid chromatography–mass spectrometry (UPLC–MS). Both are products of concerted microbial–mammalian host cometabolism and indicate an age-related association with the balance of host–microbiome metabolism

Inactivation of PNKP by mutant ATXN3 triggers apoptosis by activating the DNA damage-response pathway in SCA3.

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is an untreatable autosomal dominant neurodegenerative disease, and the most common such inherited ataxia worldwide. The mutation in SCA3 is the expansion of a polymorphic CAG tri-nucleotide repeat sequence in the C-terminal coding region of the ATXN3 gene at chromosomal locus 14q32.1. The mutant ATXN3 protein encoding expanded glutamine (polyQ) sequences interacts with multiple proteins in vivo, and is deposited as aggregates in the SCA3 brain. A large body of literature suggests that the loss of function of the native ATNX3-interacting proteins that are deposited in the polyQ aggregates contributes to cellular toxicity, systemic neurodegeneration and the pathogenic mechanism in SCA3. Nonetheless, a significant understanding of the disease etiology of SCA3, the molecular mechanism by which the polyQ expansions in the mutant ATXN3 induce neurodegeneration in SCA3 has remained elusive. In the present study, we show that the essential DNA strand break repair enzyme PNKP (polynucleotide kinase 3'-phosphatase) interacts with, and is inactivated by, the mutant ATXN3, resulting in inefficient DNA repair, persistent accumulation of DNA damage/strand breaks, and subsequent chronic activation of the DNA damage-response ataxia telangiectasia-mutated (ATM) signaling pathway in SCA3. We report that persistent accumulation of DNA damage/strand breaks and chronic activation of the serine/threonine kinase ATM and the downstream p53 and protein kinase C-d pro-apoptotic pathways trigger neuronal dysfunction and eventually neuronal death in SCA3. Either PNKP overexpression or pharmacological inhibition of ATM dramatically blocked mutant ATXN3-mediated cell death. Discovery of the mechanism by which mutant ATXN3 induces DNA damage and amplifies the pro-death signaling pathways provides a molecular basis for neurodegeneration due to PNKP inactivation in SCA3, and for the first time offers a possible approach to treatment.This study was funded by NIH grant NS073976 to TKH and a John Sealy Grant to PSS

Diagnóstico da qualidade da água em áreas utilizadas pela bubalinocultura no Baixo Araguari, Amapá, Brasil.

A bacia do rio Araguari presencia há muitos anos a exploração de búfalos, atividade que pode potencializar o processo de erosão do solo, produzindo modificações das drenagens naturais e alterando o regime hidrodinâmico das bacias secundárias. Este estudo se propôs a avaliar a qualidade da água em duas fazendas com bubalinocultura situadas em canais do rio Araguari, e também no leito do rio Araguari, como ponto controle. As amostragens foram realizadas em dois períodos sazonais, isto é, em diferentes situações de inundação. Em cada ponto de coleta foram efetuadas medições in situ, bem como a coleta de água para determinação em laboratório de fatores físico-químicos (sólidos suspensos, nitrato, nitrito e fósforo total) e bióticos (clorofila-a, coliformes totais, coliformes termotolerantes e densidade do fitoplâncton). Foi possível observar que apenas os parâmetros fósforo, sólidos suspensos e coliformes estiveram acima do permitido na legislação nos pontos mais internos dos canais e no período seco. Portanto, concluímos que a queda na qualidade da água ocorre apenas no período seco, e é agravada pela maior concentração desses animais, especialmente nos canais. Porém, não podemos atribuir aos búfalos a culpa exclusiva pela deterioração do Araguari no período seco, pois esse fenômeno ocorre devido a diminuição da sua vazão e por várias razões como a evolução natural do rio Araguari, o despejo de esgotos das cidades, a construção/operação de hidroelétricas, extração mineral, entre outros, e já foi relatado em estudos anteriores, inclusive em áreas sem bubalinocultura.Made available in DSpace on 2018-09-16T00:35:22Z (GMT). No. of bitstreams: 1 CPAFAP2018Diagnosticodaqualidadedaagua.pdf: 950319 bytes, checksum: a025e658f86b71edb1150114b3736739 (MD5) Previous issue date: 2018-09-14bitstream/item/183016/1/CPAF-AP-2018-Diagnostico-da-qualidade-da-agua.pd

Diagnóstico da qualidade da água em áreas utilizadas pela bubalinocultura no Baixo Araguari, Amapá, Brasil.

A bacia do rio Araguari presencia há muitos anos a exploração de búfalos, atividade que pode potencializar o processo de erosão do solo, produzindo modificações das drenagens naturais e alterando o regime hidrodinâmico das bacias secundárias. Este estudo se propôs a avaliar a qualidade da água em duas fazendas com bubalinocultura situadas em canais do rio Araguari, e também no leito do rio Araguari, como ponto controle. As amostragens foram realizadas em dois períodos sazonais, isto é, em diferentes situações de inundação. Em cada ponto de coleta foram efetuadas medições in situ, bem como a coleta de água para determinação em laboratório de fatores físico-químicos (sólidos suspensos, nitrato, nitrito e fósforo total) e bióticos (clorofila-a, coliformes totais, coliformes termotolerantes e densidade do fitoplâncton). Foi possível observar que apenas os parâmetros fósforo, sólidos suspensos e coliformes estiveram acima do permitido na legislação nos pontos mais internos dos canais e no período seco. Portanto, concluímos que a queda na qualidade da água ocorre apenas no período seco, e é agravada pela maior concentração desses animais, especialmente nos canais. Porém, não podemos atribuir aos búfalos a culpa exclusiva pela deterioração do Araguari no período seco, pois esse fenômeno ocorre devido a diminuição da sua vazão e por várias razões como a evolução natural do rio Araguari, o despejo de esgotos das cidades, a construção/operação de hidroelétricas, extração mineral, entre outros, e já foi relatado em estudos anteriores, inclusive em áreas sem bubalinocultura