Numerical Evaluation of the Elastic Moduli of AlN and GaN Nanosheets.

Two-dimensional (2D) nanostructures of aluminum nitride (AlN) and gallium nitride (GaN), called nanosheets, have a graphene-like atomic arrangement and represent novel materials with important upcoming applications in the fields of flexible electronics, optoelectronics, and strain engineering, among others. Knowledge of their mechanical behavior is key to the correct design and enhanced functioning of advanced 2D devices and systems based on aluminum nitride and gallium nitride nanosheets. With this background, the surface Young's and shear moduli of AlN and GaN nanosheets over a wide range of aspect ratios were assessed using the nanoscale continuum model (NCM), also known as the molecular structural mechanics (MSM) approach. The NCM/MSM approach uses elastic beam elements to represent interatomic bonds and allows the elastic moduli of nanosheets to be evaluated in a simple way. The surface Young's and shear moduli calculated in the current study contribute to building a reference for the evaluation of the elastic moduli of AlN and GaN nanosheets using the theoretical method. The results show that an analytical methodology can be used to assess the Young's and shear moduli of aluminum nitride and gallium nitride nanosheets without the need for numerical simulation. An exploratory study was performed to adjust the input parameters of the numerical simulation, which led to good agreement with the results of elastic moduli available in the literature. The limitations of this method are also discussed.

Numerical Simulation Study of the Mechanical Behaviour of 1D and 2D Germanium Carbide and Tin Carbide Nanostructures.

One-dimensional (nanotubes) and two-dimensional (nanosheets) germanium carbide (GeC) and tin carbide (SnC) structures have been predicted and studied only theoretically. Understanding their mechanical behaviour is crucial, considering forthcoming prospects, especially in batteries and fuel cells. Within this framework, the present study aims at the numerical evaluation of the elastic properties, surface Young's and shear moduli and Poisson's ratio, of GeC and SnC nanosheets and nanotubes, using a nanoscale continuum modelling approach. A robust methodology to assess the elastic constants of the GeC and SnC nanotubes without of the need for numerical simulation is proposed. The surface Young's and shear moduli of the GeC and SnC nanotubes and nanosheets are compared with those of their three-dimensional counterparts, to take full advantage of 1D and 2D germanium carbide and tin carbide in novel devices. The obtained outcomes establish a solid basis for future explorations of the mechanical behaviour of 1D and 2D GeC and SnC nanostructures, where the scarcity of studies is evident.

Microstructural Characterization of Al/CNTs Nanocomposites after Cold Rolling.

The deformation behaviour of aluminium reinforced by carbon nanotubes (Al/CNTs) nanocomposites during cold rolling was investigated in this work. Deformation processes after production by conventional powder metallurgy routes may be an efficient approach to improve the microstructure and mechanical properties by decreasing the porosity. Metal matrix nanocomposites have enormous potential to produce advanced components, mainly in the mobility industry, with powder metallurgy being one of the most reported production processes. For this reason, it is increasingly important to study the deformation behaviour of nanocomposites. In this context, nanocomposites were produced via powder metallurgy. Advanced characterization techniques carried out the microstructural characterization of the as-received powders and produced nanocomposites. The microstructural characterization of the as-received powders and produced nanocomposites was carried out through optical microscopy (OM), and scanning and transmission electron microscopy (SEM and TEM), complemented by electron backscattered diffraction (EBSD). The powder metallurgy route followed by cold rolling is reliable for Al/CNTs nanocomposites. The microstructural characterization shows that the nanocomposites exhibit a different crystallographic orientation than the Al matrix. CNTs in the matrix influence grain rotation during sintering and deformation. Mechanical characterization revealed that during deformation, there is an initial decrease in the hardness and tensile strength for the Al/CNTs and Al matrix. The initial decrease was attributed to the Bauschinger effect being more significant for the nanocomposites. The difference in the mechanical properties of the nanocomposites and Al matrix was attributed to distinct texture evolution during cold rolling.

Elastic Properties of Single-Walled Phosphide Nanotubes: Numerical Simulation Study.

After a large-scale investigation into carbon nanotubes, significant research efforts have been devoted to discovering and synthesizing other nanotubes formed by chemical elements other than carbon. Among them, non-carbon nanotubes based on compounds of the elements of the 13th group of the periodic table and phosphorus. These inorganic nanotubes have proved to be more suitable candidates than carbon nanotubes for the construction of novel electronic and optical-electronic nano-devices. For this reason, until recently, mainly the structural and electrical properties of phosphide nanotubes were investigated, and studies to understand their mechanical behavior are infrequent. In the present work, the elastic properties of single-walled boron phosphide, aluminum phosphide, gallium phosphide and indium phosphide nanotubes were numerically evaluated using a nanoscale continuum modelling (also called molecular structural mechanics) approach. The force field constants required to assess the input parameters for numerical simulations were calculated for boron phosphide, aluminum phosphide, gallium phosphide and indium phosphide nanostructures using two different methods. The influence of input parameters on the elastic properties evaluated by numerical simulation was studied. A robust methodology to calculate the surface elastic moduli of phosphide nanotubes is proposed.

On the Determination of Elastic Properties of Single-Walled Boron Nitride Nanotubes by Numerical Simulation.

The elastic properties of chiral and non-chiral single-walled boron nitride nanotubes in a wide range of their chiral indices and diameters were studied. With this aim, a three-dimensional finite element model was used to assess their rigidities and, subsequently, elastic moduli and Poisson's ratio. An extensive study was performed to understand the impact of the input parameters on the results obtained by numerical simulation. For comparison, the elastic properties of single-walled boron nitride nanotubes are shown together with those obtained for single-walled carbon nanotubes.

Identification of promiscuous T cell epitopes on Mayaro virus structural proteins using immunoinformatics, molecular modeling, and QM:MM approaches.

The Mayaro virus (MAYV) belongs to genus Alphavirus (family Togaviridae) and has been reported in several countries, especially in tropical regions of America. Due to its outbreaks and potential lack of medication, an effective vaccine formulation is strongly required. This study aimed to predict promiscuous T cell epitopes from structural polyproteins of MAYV using an immunoinformatics approach. For this purpose, consensus sequences were used to identify short protein sequences capable of binding to MHC class I and class II alleles. Our analysis pointed out 4 MHC-I/TCD8+ and 21 MHC-II/TCD4+ epitopes on capside (1;3), E1 (2;5), E2 (1;10), E3 (0;2), and 6 K (0;1) proteins. These predicted epitopes were characterized by high antigenicity, immunogenicity, conservancy, non-allergenic, non-toxic, and good population coverage rate values for North and South American geographical areas. Afterwards, we used the crystal structure of human toll-like receptor 3 (TLR3) ectodomain as a template to predict, through docking essays, the placement of a vaccine prototype at the TLR3 receptor binding site. Finally, classical and quantum mechanics/molecular mechanics (QM:MM) computations were employed to improve the quality of docking calculations, with the QM part of the simulations being accomplished by using the density functional theory (DFT) formalism. These results provide important insights into the advancement of diagnostic platforms, the development of vaccines, and immunotherapeutic interventions.

Mechanical Characterisation of Single-Walled Carbon Nanotube Heterojunctions: Numerical Simulation Study.

The elastic properties of single-walled carbon nanotube heterojunctions were investigated using conventional tensile, bending and torsion tests. A three-dimensional finite element model was built in order to describe the elastic behaviour of cone heterojunctions (armchair-armchair and zigzag-zigzag). This comprehensive systematic study, to evaluate the tensile, bending and torsional rigidities of heterojunctions, enabled the formulation analytical methods for easy assessment of the elastic properties of heterojunctions using a wide range of their geometrical parameters.

Mechanical Characterization of Multiwalled Carbon Nanotubes: Numerical Simulation Study.

The elastic properties of armchair and zigzag multiwalled carbon nanotubes were investigated under tensile, bending, and torsion loading conditions. A simplified finite element model of the multiwalled carbon nanotubes, without taking into account the van der Waals interactions between layers, was used to assess their tensile, bending, and torsional rigidities and, subsequently, Young's and shear moduli. Relationships between the tensile rigidity and the squares of the diameters of the outer and inner layers in multiwalled carbon nanotubes, and between the bending and torsional rigidities with the fourth powers of the diameters of the outer and inner layers, were established. These relationships result in two consistent methods, one for assessment to the Young's modulus of armchair and zigzag multiwalled carbon nanotubes, based on tensile and bending rigidities, and the other to evaluate shear modulus using tensile, bending, and torsional rigidities. This study provides a benchmark regarding the determination of the mechanical properties of nonchiral multiwalled carbon nanotubes by nanoscale continuum modeling approach.

EBSD Analysis of Metal Matrix Nanocomposite Microstructure Produced by Powder Metallurgy.

The development of metal nanocomposites reinforced by carbon nanotubes (CNTs) remains a focus of the scientific community due to the growing need to produce lightweight advanced materials with unique mechanical properties. However, for the successful production of these nanocomposites, there is a need to consolidate knowledge about how reinforcement influences the matrix microstructure and which are the strengthening mechanisms promoting the best properties. In this context, this investigation focuses on the study of the reinforcement effect on the microstructure of an Ni-CNT nanocomposites produced by powder metallurgy. The microstructural evolution was analysed by electron backscattered diffraction (EBSD). The EBSD results revealed that the dispersion/mixing and pressing processes induce plastic deformation in the as-received powders. The dislocation structures produced in those initial steps are partially eliminated in the sintering process due to the activation of recovery and recrystallization mechanisms. However, the presence of CNTs in the matrix has a significant effect on the dislocation annihilation, thus reducing the recovery of the dislocation structures.

Dengue virus in Aedes aegypti and Aedes albopictus in urban areas in the state of Rio Grande do Norte, Brazil: Importance of virological and entomological surveillance.

BACKGROUND: Vector control remains the sole effective method to prevent dengue virus (DENV) transmission, although a vaccine for dengue has recently become available and testing of its efficacy and coverage is being performed in multiple places. Entomological surveillance is a key factor in alerting authorities to possible outbreaks, but until now natural DENV infection of mosquito populations has been scarcely used as an early warning system to monitor fluctuating prevalence of infected mosquitoes. The purpose of this study was to determine the burden of adult and larval/pupae of Aedes aegypti and Aedes albopictus with DENV in urban areas in the state of Rio Grande do Norte, Brazil. METHODOLOGY/PRINCIPAL FINDINGS: Immature insect forms (larvae and pupae) were collected from April 2011 to March 2012, whereas the collection of adults was conducted along 3 years: May 2011 to April 2014. Total RNAs of the samples were extracted and the nested reverse transcriptase PCR assay for detecting and typing DENV was performed. Of the 1333 immature insects collected during the study period, 1186 (89%) were A. aegypti and 147 (11%) A. albopictus. DENV-4 was identified in pools of A. aegypti larvae. The rate of DENV infection in immature A. aegypti was expressed as MIR = 3.37. DENV wasnot detected in immature A. albopictus. A total of 1360 adult female mosquitoes of the Aedes genus were captured from May 2011 to April 2014. Of this total, 1293 were A. aegypti (95%) and 67 were A. albopictus (5%). From the 130 pools studied, 27 (20.7%) were positive for DENV. DENV-1 was identified in 2/27 (7.4%) pools; 1of A. albopictus and 1 of A. aegypti. DENV-2 was identified in only 1/27 (3.7%) A. aegypti pools. DENV-4 was the most prevalent, identified in 24/27 (88.8%) of the positive pools, with 19 being of A. aegypti and 5 of A. albopictus pools. The minimum infection rate for adults of the Aedes genus was 19.8, considering both A. aegypti and A. albopictus. CONCLUSIONS/SIGNIFICANCE: This work represents the most complete study to date on the interaction between dengue viruses and Aedes mosquitoes in the State of Rio Grande do Norte, and raises important questions about a possible role of A. albopictus in the transmission of dengue virus in Brazil.

Dengue in the State of Rio Grande do Norte, Brazil, 2010-2012.

OBJECTIVE: To present results of virological surveillance and epidemiological aspects of dengue in the State of Rio Grande do Norte, Brazil. METHODS: A total of 1581 cases, reported from 2010 to 2012 at various health centres in the state, were analysed by viral isolation and/or RT-PCR for viral detection and typing. To identify whether different genotypes were circulating in the state during this period, sequencing of the complete E gene for DENV (1485 bp in length) was performed directly from patient serum samples. RESULTS: All four serotypes of dengue virus circulated in Rio Grande do Norte, with the introduction of DENV-4 in the state in 2011. In 2012, DENV-4 represented 100% of positive confirmed cases. 53.97% of cases occurred in Natal. Case numbers peaked in April (21%) and May (23%). Genetic characterisation of circulating strains confirmed the circulation of genotypes V, south-east Asian/American and II, respectively, for DENV-1, DENV-2 and DENV-4. CONCLUSIONS: This work furthers a better understanding of dengue viruses in the State of Rio Grande do Norte. Strengthening control efforts in the region is important considering the impact of dengue.

Herpes simplex virus type 1 is the main cause of genital herpes in women of Natal, Brazil.

OBJECTIVES: The purpose of this study was to assess the prevalence of HSV-1 and HSV-2 in sexually active women who participated in the cervical cancer screening program in Natal, Brazil. STUDY DESIGN: The study included 261 sexually active women resident in the metropolitan area of Natal, Brazil and attending a public clinic for cervical screening. From each participant, a sample of exfoliated uterine cervical cells was collected, using a cytobrush which was conditioned in a tube containing a preserving solution (PBS+vancomycin+nystatin) and sent to a laboratory where it was processed for DNA extraction. The samples were analyzed for the presence of HSV-1 and HSV-2 DNA in separate reactions by PCRs using specific primers. RESULTS: HSV-1 in genital infection is four times more prevalent than HSV-2 in the population analyzed. The highest prevalence rates for both viruses were found in women aged 31-39years. We did not observe any association between the presence of both virus serotypes and socio-demographic characteristics in the population studied, nor with some classical risk factors for sexually transmitted diseases. CONCLUSIONS: HSV-1 was the major cause of genital infection by Herpes simplex virus in the women included in this study. No association was found between HSV infection and the socio-demographic characteristics or some classical risk factors for sexually transmitted diseases.

Prevalence of human papillomavirus in archival samples obtained from patients with cervical pre-malignant and malignant lesions from Northeast Brazil.

BACKGROUND: Human Papillomavirus (HPV) is considered as a necessary, but not sufficient, cause of cervical cancer. In this study, we aimed to assess the prevalence of HPV in a series of pre-malignant and malignant cervical lesion cases, to identify the virus genotypes, and to assess their distribution pattern according to lesion type, age range, and other considered variables. The samples were submitted to histopathological revision examination and analysed by polymerase chain reaction (PCR) for the presence of HPV DNA, followed by HPV typing by dot blot hybridisation. FINDINGS: Of the analysed samples, 53.7% showed pre-malignant cervical lesions, and 46.3% presented with cervical cancer. Most cancer samples (84.1%) were classified as invasive carcinoma. The mean age of these cancer patients was 47.3 years. The overall HPV prevalence was 82.4% in patients with pre-malignant lesions and 92.0% in the cancer patients. HPV 16 was the most prevalent type, followed by HPV 18 and 58, including both single and double infections. Double infection was detected in 11.6% of the samples, and the most common combination was HPV 16+18. CONCLUSIONS: Cervical cancer appears to occur in women in a lower age range in the studied area, compared to the situation in other Brazilian regions. Furthermore, among the patients with CIN 3 and those with cancer, we observed a higher proportion of married women, women with more than one sexual partner, smokers, and individuals with less than an elementary education, relative to their counterparts. FINDINGS: The overall HPV prevalence was 82.4% in patients with pre-malignant lesions and 92.0% in the cervical cancer patients from Northeast Brazil. HPV 16 was the most prevalent type, followed by HPV 18 and 58. The most common double infection was HPV 16+18. Cervical cancer appears to occur in women in a lower age range in the Northeast Brazil. Among the patients with CIN 3 and those with cancer, we observed a higher proportion of married women, women with more than one sexual partner, smokers, and individuals with less than an elementary education, relative to their counterparts.

Detecção de rotavírus nas fezes de crianças com diarréia aguda / Rotavirus detection in feces of children with acute diarrhea

Objetivo: Determinar a prevalência da infecção por rotavírus em um grupo crianças da cidade de Natal-RN, Brasil, que apresentravam diarréia aguda e verificar a existência ou não de distribuição sazonal da infecção por esses patógenes em nosso meio. Métodos: Foram analisados amostras fecais de 1.903 crianças de ambos os sexos, idade variando de 1 mês a 10 anos, residentes na cidade de Natal-RN, que apresentavam episódio de diarréia aguda, no período de janeiro de 1996 a dezembro de 1998. O método utilizado foi a pesquisa de partículas virais diretamente nas fezes, através de uma reação de aglutinação passiva, empregando-se partículas de látex cobertas com anticorpos monoclonais grupo-específico anti-rotavírus. Resultados: Na população estudada, 151 crianças (7,9 por cento) apresentaram reação positiva para a presença de partículas de rotavírus ns fezes. Considerando-se, no entanto, apenas as crianças mais suscetíveis à infecção por esse grupo de vírus, que compreende a faixa etária de 1 a 24 meses de vida, constatou-se que, de um total de 1.065 crianças examinadas, 136 (12,8 por cento) apresentaram reação positiva para rotavírus, sendo que 96,3 por cento tinham entre 6 e 24 meses de vida. A distribuição pelos meses do ano, dos casos de diarréia aguda de crianças que apresentaram rotavírus nas fezes revelou que a incidência da infecção por esses patógenos foi maior nos meses de julho, agosto e setembro, nos três anos estudados. Conclusões: Os resultados indicam que os rotavírus têm participação importante na etiologia da diarréia aguda em nosso meio, e que a maioria dos casos da infecção, por esses patógenos, ocorre durante os dois primeiros anos de vida, atingindo principalmente as crianças na faixa etária de 6 a 24 meses e com uma maior prevalência nos meses de julho, agosto e setembro

Prevalência de marcadores sorológicos do vírus da hepatite B em trabalhadores do serviço hospitalar / Prevalence of serologic markers of the hepatitis B virus in hospital personnel

Determina a prevalência de marcadores sorológicos do vírus da hepatite B (VHB) e identifica fatores de risco, de transmissäo desse vírus, no ambiente hospitalar. Foram examinados 210 indivíduos de diversas profissöes que trabalham em hospital universitário. O método empregado foi o ELISA e utilizou-se, como grupo-controle, 45 doadores voluntários de sangue. Constatou-se que 20,5 por cento dos profissionais que trabalham no hospital apresentavam positividade para, pelo menos, um dos três marcadores dos vírus pesquisados, contra 6,6 por cento do grupo-controle. Nos trabalhadores do hospital, a prevalência de cada marcador isoladamente foi: anti-HBc 8,1 por cento, anti-HBs 5,2 por centoe AgHBs 2,9 por cento, sendo que em 4,3 por cento desses indivíduos foi detectada a presença simultânea dos marcadores anti-HBc e anti-HBs. No grupo-controle, foi detectada apenas a presença dos marcadores anti-HBc e anti-HBs, isoladamente, com prevalências de 4,4 e 2,2 por cento, respectivamente. Os maiores índices de positividade observados foram: pessoal de laboratório, 24,0 por cento; pessoal de enfermagem, 23,6 por cento; médicos, 20,8 por cento; e pessoal da limpeza, 18,2 por cento. Os achados indicam que os profissionais da saúde estäo mais expostos à infecçäo pelo VHB, sugerindo que o contato com pacientes e a manipulaçäo de fluidos corporais säo fatores de risco de transmissäo ocupacional desse vírus, recomendando-se a vacinaçäo desses profissionais contra a hepatite B

Infecção pelo vírus da rubéola em um segmento da população feminina em idade fértil, residentes em Natal - RN / Rubella infections among women at childearing age in Natal, Rio Grande do Norte

Foram examinadas 609 mulheres com idades variando de 21 a 35 anos, média de 28 anos, todas residentes na área urbana de Natal - RN e com suspeita de infecção pelo vírus da rubéola. Coletou-se duas amostras de soro de cada paciente, com intervalo de 15 a 20 dias e estabeleceu-se a análise comparativa dos títulos de anticorpos para o vírus da rubéola nas duas amostras, através de sorologia pareada. A técnica utilizada foi o ensaio imunoenzimático (ELlSA), consideran- do-se como ocorrência da infecção, quando o título de anticorpos da segunda amostra de soro foi, pelo menos, quatro vezes maior que o da primeira. Do total de mulheres examinadas, 452 delas (74%) apresentaram anticorpos para o vírus da rubéola e 157 (26%) não apresentaram qualquer sinal da presença desses anticorpos. Dentre as mulheres que apresentaram reação positiva, 262 (58%), fizeram soro-conversão, indicando que desenvolveram a infecção durante o período em que foram examinadas. As demais mulheres, num total de 190 (42%), não apresentaram diferenças significativas nos títulos de anticorpos das duas amostras de soro, revelando a existência de imu- nidade pregressa para a rubéola .. A infecção pelo vírus da rubéola foi diagnosticada em todos os meses do ano, nos três anos estudados, sendo que a incidência maior se deu no periodo compreendido entre os meses de abril e julho. Os achados indicam a existência de eleva- da proporção de mulheres em idade fértil, ainda susceptíveis ao vírus da rubéola, o que justifica a realização de campanha de vacinação, com forma de prevenção da infecção congênita.

609 women, between 21-35 years, residing in Natal - Rio Grande do Norte with suspected rubella infections were examinated. Observation of a fourfold or greater rise in antibody titers in two serum samples obtained 15 to 21 days apart by ELISA indicated recent infection. 452 women (74%) had positive antibodies for rubella virus, and 157 (26%) had no antibodies. 262 women of 452 (58%) seroconverted. Thus reflects a primary infection occuring whitin the preceding months. The others 190 women (42%) had no differences of the antibodies of two samples. Thus reflected an immune state of rubella.