829 research outputs found

    Testing strong gravity with gravitational waves and Love numbers

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    The LIGO observation of GW150914 has inaugurated the gravitational-wave astronomy era and the possibility of testing gravity in extreme regimes. While distorted black holes are the most convincing sources of gravitational waves, similar signals might be produced also by other compact objects. In particular, we discuss what the gravitational-wave ringdown could tell us about the nature of the emitting object, and how measurements of the tidal Love numbers could help us in understanding the internal structure of compact dark objects

    Quantum oscillator and Kepler-Coulomb problems in curved spaces: deformed shape invariance, point canonical transformations, and rational extensions

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    The quantum oscillator and Kepler-Coulomb problems in dd-dimensional spaces with constant curvature are analyzed from several viewpoints. In a deformed supersymmetric framework, the corresponding nonlinear potentials are shown to exhibit a deformed shape invariance property. By using the point canonical transformation method, the two deformed Schr\"odinger equations are mapped onto conventional ones corresponding to some shape-invariant potentials, whose rational extensions are well known. The inverse point canonical transformations then provide some rational extensions of the oscillator and Kepler-Coulomb potentials in curved space. The oscillator on the sphere and the Kepler-Coulomb potential in a hyperbolic space are studied in detail and their extensions are proved to be consistent with already known ones in Euclidean space. The partnership between nonextended and extended potentials is interpreted in a deformed supersymmetric framework. Those extended potentials that are isospectral to some nonextended ones are shown to display deformed shape invariance, which in the Kepler-Coulomb case is enlarged by also translating the degree of the polynomial arising in the rational part denominator.Comment: 32 pages, no figure; published versio

    Alterations in heterosis of maize populations derived from single-cross hybrids after reciprocal recurrent selection.

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    One hundred and sixty-nine interpopulational half sib progenies were obtained from maize populations derived from the commercial single-cross hybrids AG9012 (1) and C333 (2) to investigate the efficiency of reciprocal recurrent selection (RRS). Fifteen progenies with highest hulled ear yield were obtained. Two recombination trials were sown with remnant S1 seeds, and the improved CI1 and CI2 populations were simultaneously obtained with their hybrid combination. Yield trials were set up in three sites to assess the efficiency of the RRS. The F1 from single-cross hybrid AG9012 and C333, the double-cross (F1(1)x F1(2) hybrids, the C0 1 and C02 populations, the interpopulational hybrid (C01 x C02), the CI1 and CI2 improved populations, and their hybrid (CI1 x CI2) were compared. A 5.7% progress was obtained in one cycle of RRS for ear yield, mainly attributed to increased heterosis. The yield of the improved hybrid was superior to the F1 from single-cross hybrids AG9012 and C333, demonstrating the potential of the referred hybrid combination. Para verificar a eficiência da seleção recorrente recíproca (SRR) em populações originárias dos híbridos simples comerciais AG9012 (1) e C333 (2) foram obtidas, inicialmente, 169 progênies de meios-irmãos interpopulacionais. As 15 melhores progênies em produção de espigas despalhadas foram identificadas. Utilizando-se sementes S1 remanescentes, semearam-se dois campos de recombinação, sendo simultaneamente obtidas as populações melhoradas C1 1 e C1 2 e a combinação híbrida entre elas. Os experimentos para avaliar a eficiência da SRR foram instalados em três locais. Foram comparados o F1 dos híbridos simples AG9012 e C333, o híbrido duplo F1(1) x F1 (2), entre eles as populações CD1 e CD2, o híbrido interpopulacinal (CD1 e CD2), as populações melhoradas C1 1 e C1 2 e a sua combinação híbrida (C1 1 e C 1 2). O progresso com um ciclo de SRR foi de 5,7% para a produção de espigas e deveu-se , principalmente, ao incremento na heterose. O desempenho do híbrido melhorado superou a geração F1 dos híbridos simples AG9012 e C333, evidenciando o potencial da referida combinação híbrida

    First Diabetic Retinopathy Prevalence Study in Portugal: RETINODIAB Study-Evaluation of the Screening Programme for Lisbon and Tagus Valley Region

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    BACKGROUND/AIMS: In Portugal, so far, there is no study or even accurate data on the prevalence of diabetic retinopathy (DR), based on a large representative sample and on a long-term follow-up. The objective of our study was to determine the prevalence of DR based on a national screening community-based programme. METHODS: A 5-year retrospective analysis of the RETINODIAB screening programme results was implemented in Lisbon and Tagus Valley area between July 2009 and October 2014. We estimated the prevalence of retinopathy for all patients with type 2 diabetes and studied the association between known risk factors and retinopathy emergence at their first screening. RESULTS: Throughout this period, from a total of 103 102 DR readable screening examinations, 52 739 corresponded to patients who attended RETINODIAB screening at entry. Globally, DR was detected in 8584 patients (16.3%). Of these, 5484 patients (10.4%) had mild non-proliferative (NP) DR, 1457 patients (2.8%) had moderate NPDR and 672 (1.3%) had severe NPDR. Finally, 971 patients (1.8%) had proliferative DR requiring urgent referral to an ophthalmologist. The presence of any DR, non-referable DR or referable DR was strongly associated with increasing duration of diabetes and earlier age at diagnosis. CONCLUSIONS: The prevalence rate of DR in our study (16.3%) was slightly lower than other published international data. The RETINODIAB network proved to be an effective screening programme as it improved DR screening in Lisbon and Tagus Valley surrounding are

    First Incidence and Progression Study for Diabetic Retinopathy in Portugal, the RETINODIAB Study: Evaluation of the Screening Program for Lisbon Region

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    PURPOSE: To estimate the 5-year incidence and progression of diabetic retinopathy (DR) among persons with type 2 diabetes mellitus (DM). DESIGN: Population-based, prospective, cohort study. PARTICIPANTS: The RETINODIAB (Study Group for Diabetic Retinopathy Screening) program was implemented in the Lisbon and Tagus Valley area between July 2009 and December 2014. A total of 109 543 readable screening examinations were performed and corresponded to 56 903 patients who attended the screening program at entry. A total of 30 641 patients (53.85%) had at least 1 further screening event within the study period and were included in the analysis. METHODS: Participants underwent two 45° nonstereoscopic retinal digital photographs per eye according to RETINODIAB protocol. All images were graded according to the International Clinical Diabetic Retinopathy Scale. Referable diabetic retinopathy (RDR) was defined for all patients graded as moderate nonproliferative DR (NPDR), severe NPDR, or proliferative DR (PDR), with or without maculopathy or mild NPDR with maculopathy. Nonparametric estimates of the annual and cumulative incidences were obtained by Turnbull's estimator. Associations between the potential risk factors and the time to onset/progression of retinopathy were assessed through a parametric survival analysis for interval-censored data. MAIN OUTCOME MEASURES: The authors estimated the onset and progression incidence rates of DR. RESULTS: Yearly incidence of any DR in patients without retinopathy at baseline was 4.60% (95% confidence interval [CI], 3.96-4.76) in the first year, decreasing to 3.87% (95% CI, 2.57-5.78) in the fifth year. In participants with mild NPDR at baseline, the progression rate to RDR in year 1 was 1.18% (95% CI, 0.96-1.33). Incidence of any DR and RDR and DR progression rate were associated with known duration of diabetes, age at diagnosis, and use of insulin treatment. CONCLUSIONS: This longitudinal epidemiologic study provides the first Portuguese incidence DR data in a large-scale population-based cohort of type 2 diabetes after a 5-year follow-up. Duration of diabetes, age at diagnosis, and insulin treatment were associated with increasing risk of incidence and progression of DR. A personalized schedule distribution of screening intervals according to the individual patient's profile should be implemented, with resulting benefits in terms of health costs.info:eu-repo/semantics/publishedVersio

    5-Arylazo-2,2´-bithiophenes: a novel promising series of NLO chromophores

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    The synthesis of 5-arylazo- substituted bithiophenes and their UV-visible, solvatochromic and nonlinear optical properties (NLO) are described. In agreement with the solvatochromic data and also with the second-order molecular NLO characterization, the new donor-acceptor systems could find application as suitable solvatochromic probes and also as new NLO materials.Fundação para a Ciência e Tecnologia (FCT

    Salicornia as a fermented product: development of an optimised procedure for a controlled process

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    In order to develop a fermented product with young stems of salicornia/pickleweed, an experiment was worked out and the fermentative process was studied. Initial data on the bacterial fauna of the plants revealed the existence of no lactic acid bacteria. Therefore, we chose to use of starting cultures. Sterile “heart cabbage” juice was the base for different fermentative bacteria: Lactobacillus plantarum, Leuconostoc mesenteroides, Pediococcus acidilactici, and pH, titrated acidity and salinity were evaluated. The same experiment was undertaken with and without the glasswort or salicornia. Significant differences were observed only with L. plantarum: pH variation and percentage of lactic acid suffered a significant increase during the fermentative process, specially when salicornia was introduced in the juice. Results obtained for the titrated acidity were also good, since approximately 1% lactic acid was detected, as a result of the fermentative activity in the different starting cultures. Predominant species by the end of the fermentation was L. plantarum, being the one that produced higher quantities of lactic acid

    Functional Amyloid Formation within Mammalian Tissue

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    Amyloid is a generally insoluble, fibrous cross-β sheet protein aggregate. The process of amyloidogenesis is associated with a variety of neurodegenerative diseases including Alzheimer, Parkinson, and Huntington disease. We report the discovery of an unprecedented functional mammalian amyloid structure generated by the protein Pmel17. This discovery demonstrates that amyloid is a fundamental nonpathological protein fold utilized by organisms from bacteria to humans. We have found that Pmel17 amyloid templates and accelerates the covalent polymerization of reactive small molecules into melanin—a critically important biopolymer that protects against a broad range of cytotoxic insults including UV and oxidative damage. Pmel17 amyloid also appears to play a role in mitigating the toxicity associated with melanin formation by sequestering and minimizing diffusion of highly reactive, toxic melanin precursors out of the melanosome. Intracellular Pmel17 amyloidogenesis is carefully orchestrated by the secretory pathway, utilizing membrane sequestration and proteolytic steps to protect the cell from amyloid and amyloidogenic intermediates that can be toxic. While functional and pathological amyloid share similar structural features, critical differences in packaging and kinetics of assembly enable the usage of Pmel17 amyloid for normal function. The discovery of native Pmel17 amyloid in mammals provides key insight into the molecular basis of both melanin formation and amyloid pathology, and demonstrates that native amyloid (amyloidin) may be an ancient, evolutionarily conserved protein quaternary structure underpinning diverse pathways contributing to normal cell and tissue physiology

    Local mean-field study of capillary condensation in silica aerogels

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    We apply local mean-field (i.e. density functional) theory to a lattice model of a fluid in contact with a dilute, disordered gel network. The gel structure is described by a diffusion-limited cluster aggregation model. We focus on the influence of porosity on both the hysteretic and the equilibrium behavior of the fluid as one varies the chemical potential at low temperature. We show that the shape of the hysteresis loop changes from smooth to rectangular as the porosity increases and that this change is associated to disorder-induced out-of-equilibrium phase transitions that differ on adsorption and on desorption. Our results provide insight in the behavior of 4^4He in silica aerogels.Comment: 19 figure
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