Chaotic Electron Motion in Superlattices. Quantum-Classical Correspondence of the Structure of Eigenstates and LDOS

We investigate the classical-quantum correspondence for particle motion in a superlattice in the form of a 2D channel with periodic modulated boundaries. Its classical dynamics undergoes the generic transition to chaos of Hamiltonian systems as the amplitude of the modulation is increased. We show that for strong chaotic motion, the classical counterpart of the structure of eigenstates (SES) in energy space reveals an excellent agreement with the quantum one. This correspondence allows us to understand important features of the SES in terms of classical trajectories. We also show that for typical 2D modulated waveguides there exist, at any energy range, extremely localized eigenstates (in energy) which are practically unperturbed by the modulation. These states contribute to the strong fluctuations around the classical SES. The approach to the classical limit is discussed.Comment: 4 pages, 4 figure

Quantum-classical correspondence for local density of states and eigenfunctions of a chaotic periodic billiard

Classical-quantum correspondence for conservative chaotic Hamiltonians is investigated in terms of the structure of the eigenfunctions and the local density of states, using as a model a 2D rippled billiard in the regime of global chaos. The influence of the observed localized and sparsed states in the quantum-classical correspondence is discussed.Comment: 8 pages, 4 figure

Efetividade da política brasileira de vacinação contra influenza, uma revisão sistemática

Since 1999, Brazil has undertaken annual influenza vaccine campaigns, free of charge, targeting the elderly population, health professionals, and immune-deficient patients. We conducted a systematic review of literature in order to evaluate the effectiveness of the initiative. We used the keywords influenza, vaccine, Brazil and effectiveness to search the main databases. Thirty-one studies matched our inclusion and exclusion criteria. Influenza vaccine coverage among the elderly is high, though not as high as suggested by the official figures. Estimates on effectiveness are scarce. The majority come from ecological studies that show a modest reduction in mortality and hospital admissions due to influenza-related causes. Such reduction is not evident in the North and Northeastern states of Brazil, a finding that is probably related to the different seasonal pattern of influenza in equatorial and tropical regions. Brazilian epidemiologists still owe society better-designed studies addressing the effectiveness of influenza vaccine campaigns.Desde 1999 o Brasil realiza campanhas anuais de vacinação contra influenza. A vacinação é gratuita, e tem como grupos alvo os idosos, os profissionais de saúde e os pacientes com comprometimento imunitário. Nós realizamos uma revisão sistemática da literatura, com o propósito de avaliar a efetividade desta iniciativa. Foram usadas as palavras chave influenza, vacina, Brasil e efetividade, para a busca nas bases de dados mais relevantes. Trinta e um estudos se encaixaram nos nossos critérios de inclusão e exclusão. A cobertura vacinal nos idosos é alta, porém não tão alta como apresentado nos dados oficiais. Estimativas de efetividade são escassas. A maioria delas vem de estudos ecológicos, que demonstram um modesto efeito na redução da mortalidade e internações hospitalares por causas relacionadas à influenza. Esta redução não se evidencia nos estados do Norte e Nordeste do Brasil, achado que provavelmente relaciona-se ao padrão distinto de sazonalidade da influenza nas regiões equatoriais e tropicais. Os epidemiologistas brasileiros ainda devem à sociedade estudos com desenhos mais adequados à análise da efetividade das campanhas de vacinação contra influenza

Ballistic Localization in Quasi-1D Waveguides with Rough Surfaces

Structure of eigenstates in a periodic quasi-1D waveguide with a rough surface is studied both analytically and numerically. We have found a large number of "regular" eigenstates for any high energy. They result in a very slow convergence to the classical limit in which the eigenstates are expected to be completely ergodic. As a consequence, localization properties of eigenstates originated from unperturbed transverse channels with low indexes, are strongly localized (delocalized) in the momentum (coordinate) representation. These eigenstates were found to have a quite unexpeted form that manifests a kind of "repulsion" from the rough surface. Our results indicate that standard statistical approaches for ballistic localization in such waveguides seem to be unappropriate.Comment: 5 pages, 4 figure

The potential demand for an HIV/AIDS vaccine in Brazil

This study assesses the potential demand by the public sector for a preventive HIV/AIDS vaccine in Brazil and the costs of alternative strategies for a vaccination program. Brazil has a mature AIDS epidemic: the percent of the population living with HIV or AIDS (about 0.6 percent of adults) is not as high as in other severely affected developing countries, but infection rates in specific risk groups in the population are very high and HIV has spread beyond these groups into the general population of low-risk individuals. Preventive HIV/AIDS vaccines are still in the testing stage. The characteristics of the first vaccines developed, in terms of their efficacy, duration of effectiveness, ease of administration, and price, are still unknown. But the potential benefits of such a vaccine in Brazil would be high. The study reviews the cost and impact of HIV/AIDS in Brazil, in terms of disease and economic burden, as a proxy for the benefits of an HIV/AIDS vaccine. The epidemiology of AIDS and Brazil's experience with immunization coverage with other vaccines are used to assess the number of vaccines, delivery strategies, and possible costs of an HIV/AIDS immunization program in Brazil, assuming the availability of a 100 percent effective AIDS vaccine that lasts a lifetime under different pricing and dosing assumptions. A low-cost, highly effective vaccine would likely be affordable to an upper-middle-income country like Brazil and yield large benefits from a policy of universal, publicly subsidized immunization. But if prices are higher and the impact less favorable, the costs and effects would have to be compared with other AIDS prevention programs or other health interventions. Both political and economic considerations will likely figure into public policy on HIV/AIDS vaccination, when such a vaccine is developed.Disease Control&Prevention,Early Child and Children's Health,Health Economics&Finance,Public Health Promotion,Health Monitoring&Evaluation,HIV AIDS,Health Monitoring&Evaluation,Health Economics&Finance,Adolescent Health,Health Indicators

COVID-19 post-vaccination in healthcare workers and vaccine effectiveness, Brazil, 2021

Objects: This study aimed to describe COVID-19 cases in healthcare workers at a large tertiary hospital, after a vaccination campaign, to understand the individual characteristics, timeliness, symptomatology, and severity of the conditions. Methods: The COVID-19 reporting files from the hospital's healthcare workers and their records in the vaccine registry were analyzed, regarding vaccination status, symptoms, sociodemographic characteristics, comorbidities, and outcomes. Vaccination descriptive analysis was carried out and the impact and effectiveness of vaccination in relation to symptomatic infection and hospitalization were estimated. Results: In a total of 696 PCR-confirmed COVID-19 patients, vaccination coverage for the 1st and 2nd dose was 92.8% and 85.5%. Patients with complete doses had a mean interval of 96.8 days between vaccination and the onset of symptoms. Of the 664 participants with available clinical data, 165 had at least 1 comorbidity. During the study, 12 patients were hospitalized, 58.3% with a complete vaccination schedule. Three of this group died. The effectiveness of vaccination for symptomatic cases and hospitalization was 22.1% and 69.0%, respectively. The impact of vaccination on symptomatic cases and hospitalization was 81.4% and 89.7%, respectively. Discussion: The majority of COVID-19 cases in the study were classified as mild. The impact of vaccination for confirmed cases was significant, both in reducing the incidence of symptomatic cases and hospitalizations. The presence of comorbidities in approximately ¼ of the patients increased the risk of these individuals. The mean time interval between diagnosis and the 2nd dose of vaccine was longer in the hospitalized group, reinforcing the protective decline over longer periods

Synthesis and Characterization of Nanocrystalline ZnO Doped with Al3+ and Ni2+ by a Sol-Gel Method Coupled with Ultrasound Irradiation

Zinc oxide is one of the most important semiconducting metal oxides and one of the most promising n-type materials, but its practical use is limited because of both its high thermal conductivity and its low electrical conductivity. Numerous studies have shown that doping with metals in ZnO structures leads to the modification of the band gap energy. In this work, Al-doped ZnO, Ni-doped ZnO, and undoped ZnO nanocrystalline powders were prepared by a sol&-gel method coupled with ultrasound irradiation, and the results show the influence of Al3+ and Ni2+ ions in the ZnO network. The doping concentrations in ZnO of 0.99 atom % for ZnO&-Al and 0.80 atom % for ZnO&-Ni were obtained by X-ray Fluorescence (XRF). X-ray Diffraction (XRD) and Raman Spectroscopy showed a decreased intensity and broadening of main peaks, indicating metallic ions. The crystallite size of the sample was decreased from 24.5 nm (ZnO) to 22.0 nm (ZnO&-Al) and 21 nm (ZnO&-Ni). The textural and morphological properties were analyzed via Nitrogen Adsorption (BET method) and Field Emission Scanning Electron Microscopy (FESEM).The authors of this paper wish to thank Advanced Nanostructured Materials and Applications Network for its support via Secretaría de Educación Pública (SEP)

Modeling Optical and Electronic Properties of Silica Nano-Clusters in Silicon Rich Oxide Films

Quantum effects are very important in nano scale systems such as molecules and clusters constituted of particles from a few to hundreds or a few thousands of atoms. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these molecules or clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of the bulk materials. Silica agglomerates expected in Silicon Rich Oxide (SRO) films have optical properties, which depend directly on size, and their rationalization can lead to new applications with a potential impact on many fields of science and technology. On the other hand, the room temperature photoluminescence (PL) of Si : SiO2 or Si : SiOx structures usually found in SRO has recently generated an enormous interest due to their possible applications in optoelectronic devices. However, the understanding of the emission mechanism is still under debate. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6-31 G* to calculate the electronic and optical properties of molecules and clusters of silicon dioxide. With the theoretical calculation of the structural and optical properties of silicon dioxide clusters is possible to evaluate the contribution of silica in the luminescent emission mechanism experimentally found in thin SRO films. It was found that silica contribution to the luminescent phenomenon in SRO thin films is less important than that of the silicon monoxide agglomerates because the number of silica structures, which may show emission in the visible spectrum, is much lower [1], compared to the number of silicon monoxide structures which emit in this region. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3192

Criptococosis meníngea en un paciente inmunocompetente: reporte de un caso y revisión de la literatura

ResumenLa criptococosis meníngea es una infección infrecuente en pacientes inmunocompetentes. Es de vital importancia realizar una adecuada historia clínica y exploración física para hacer un buen diagnóstico e iniciar un tratamiento lo antes posible, para prevenir complicaciones o secuelas de la misma. Nosotros reportamos un caso de un paciente del sexo masculino de 23años de edad que se presenta a consulta de neurología por cefalea intensa de tipo pulsátil holocraneana, acompañada de náuseas, que no cede ante el uso de analgésicos. Conforme progresaba la enfermedad, se añadían síntomas como vómito en proyectil, parestesias, alteraciones auditivas, disminución en la agudeza visual y cuadriparesia. Se hospitalizó para la realización de estudios complementarios, en los que se concluyó el diagnóstico de criptococosis meníngea. Los aspectos referentes a esta enfermedad, como epidemiología, etiología, diagnóstico, tratamiento y complicaciones, se discuten en este reporte de caso.AbstractThe cryptococcal meningitis is an infrequent infection in immunocompetent patients. It is vital to make an adequate history and physical examination to make a proper diagnosis and begin treatment as soon as possible to prevent complications or consequences thereof. We report a case of a male patient of 23years of age presenting to the neurology service because of an intense, throbbing headache accompanied with nausea that does not yield to the use of analgesics. As the disease progressed, other symptoms presented like projectile vomiting, paresthesias, hearing impairment, decreased visual acuity and quadriparesis. He was hospitalized for complementary studies which concluded the diagnosis of meningeal cryptococcosis. The aspects concerning this disease including epidemiology, etiology, diagnosis, treatment and complications are discussed in this case report