280 research outputs found
HerpesvĂrus humano-7 como causa de doença exantemĂĄtica em BelĂ©m, ParĂĄ, Brasil
We screened sera from 370 patients suffering from exanthematous illnesses in BelĂ©m, North Brazil, for the presence of human herpesvirus-7 (HHV-7) IgM and IgG antibodies. Samples were obtained from January 1996 to December 2002 and were processed by a HHV-7-specific indirect immunofluorescence assay (IFA). HHV-7-specific IgM and/or IgG antibodies were found in 190 (51.4%) of these patients, with similar prevalence rates (IgM+ and IgG+ subgroups taken together) for female and male subjects: 52.5% and 50.3%, respectively. Serological status as defined by IgG was identified in 135 (36.5%) patients. In 55 (14.9%) of the patients HHV-7 IgM antibodies were detected. HHV-7 IgM- and- IgG antibody rates were similar (p >; 0.05) when male and female subjects are compared: 14.4% versus 15.3% and 38.1% versus 35.0%, respectively. Statistically significant difference (p = 0.003) was noted when HHV-7-IgM-positive female and male patients aged 5-8 months are compared. Prevalence rates ranging from 4.6% (female, 5-8 months of age) to 93.3% (female, >; 10 years of age) and 12.2% (male, 5-8 months) to 80.0% (male, 8-10 years of age) were noted in the IgG- positive subgroups. A subgroup (n = 131) of patients with IgM or IgG HHV-7 antibodies were examined for the presence of DNA using a polymerase chain reaction/nested PCR. Recent/active HHV-7 infection occurred at a rate of 11.0% (6/55) among patients whose samples presented IgM+ specific antibodies. In a subgroup (n = 76) of patients with high HHV-7-IgG antibody levels (titre >; 1:160) DNA could not be detected in sera examined by PCR/nested PCR. Of the six recent/active infections, four subjects with less than 1 year and two with 3 and 6 years of age, presented typical exanthem subitum (E.S), as defined by higher fever (>; 38.0 ºC) with duration of 24 to 72 hours, followed by a maculopapular skin rash. Our results underscore the need for searching HHV-7 infection in patients with exanthematous diseases, particularly those presenting with typical E.S. HHV-7 appears therefore to emerge as a newly recognized pathogen of exanthem in our region.Examinamos soros de 370 pacientes acometidos de doença exantemĂĄtica, selecionados em BelĂ©m, norte do Brasil, com o propĂłsito de se detectarem anticorpos IgM e IgG para o herpesvĂrus humano-7 (HHV-7). As amostras foram obtidas entre janeiro de 1996 e dezembro de 2002 e, posteriormente, processadas utilizando-se a tĂ©cnica da imunofluorescĂȘncia indireta (IFI). Taxas de anticorpos IgM e/ou IgG foram encontradas em 190 (51,4%) desses pacientes. Observamos taxas de prevalĂȘncia similares para os sexos feminino e masculino com: 52,5% e 50,3%, respectivamente. O "status" sorolĂłgico foi definido pela presença de anticorpos IgG nos espĂ©cimes de 135 (36,5%) pacientes. A par disso, em 55 (14,9%) dos 370 pacientes foram detectados anticorpos IgM para o HHV-7. Taxas de anticorpos IgM e IgG para o HHV-7 foram similares (p >; 0.05) quando comparamos indivĂduos do sexo feminino e masculino: 14,4% versus 15,3% e 38,1% versus 35,0%, respectivamente. Diferença estatisticamente significativa (p = 0,003) foi observada quando comparamos as taxas de anticorpos IgM para o HHV-7 nos indivĂduos do grupo etĂĄrio de 5-8 meses pertencentes ao sexo feminino e masculino. Taxas de prevalĂȘncia variando de 4,6% (masculino, 5-8 meses de idade) a 93,3% (feminino, >; 10 anos de idade) e 12,2% (masculino, 5-8 meses de idade) a 80,0% (masculino, 8-10 anos de idade) foram observadas no subgrupo positivo para IgG. Um subgrupo (n = 131) de pacientes com anticorpos IgM ou IgG foi examinado quanto a presença de DNA para o HHV-7 pela tĂ©cnica da reação em cadeia da polimerase/ "nested" PCR. Infecção recente/ativa para o HHV-7 ocorreu em 11,0% (6/55) dos pacientes cujas amostras apresentaram anticorpos IgM especĂficos para o HHV-7. Em um subgrupo (n = 76) de pacientes com altos nĂveis de anticorpos IgG para o HHV-7 (tĂtulo >; 1: 160) nĂŁo foi detectada a presença de DNA em seus soros pelo PCR/ "nested" PCR. Entre as seis infecçÔes recentes/ativas, quatro indivĂduos com menos de um ano e dois com 3 e 6 anos de idade apresentaram tĂpico exantema sĂșbito (E.S) definido por febre elevada (>; 38,0 ºC) com duração de 24 a 72 horas, acompanhando-se de erupção cutĂąnea maculopapular. Nossos resultados ressaltam a necessidade de procurarmos a infecção pelo HHV-7 em pacientes portadores de doença exantemĂĄtica, particularmente naquelas apresentaçÔes tĂpicas de E.S. O HHV-7 parece emergir como um novo patĂłgeno associado a quadros exantemĂĄticos em nossa regiĂŁo
Diffusion behavior of water confined in deformed carbon nanotubes
We use molecular dynamics simulations to study the diffusion of water inside
deformed carbon nanotubes, with different degrees of eccentricity at 300K. We
found a water structural transition between tubular-like to single-file for the
(7,7) nanotubes associated with a change from a high to low mobility regimes.
The water which in the undeformed (9,9) nanotubes is frozen, becomes liquid for
the distortion above a certain threshold. These water diffusion enhancement
(suppresion) is related to a reduction (increase) in the number of hydrogen
bonds. This suggests that the shape of the nanotube is a particularly important
ingredient when considering the dynamical and structural properties of confined
water.Comment: 16 pages, 9 figure
Iron oxide doped boron nitride nanotubes: structural and magnetic properties
A first-principles formalism is employed to investigate the interaction of
iron oxide (FeO) with a boron nitride (BN) nanotube. The stable structure of
the FeO-nanotube has Fe atoms binding N atoms, with bond length of roughly
2.1 \AA, and binding between O and B atoms, with bond length of 1.55 \AA.
In case of small FeO concentrations, the total magnetic moment is
(4) times the number of Fe atoms in the unit cell and it is
energetically favorable to FeO units to aggregate rather than randomly bind to
the tube. As a larger FeO concentration case, we study a BN nanotube fully
covered by a single layer of FeO. We found that such a structure has square FeO
lattice with Fe-O bond length of 2.11 \AA, similar to that of FeO bulk, and
total magnetic moment of 3.94 per Fe atom. Consistently with
experimental results, the FeO covered nanotube is a semi-half-metal which can
become a half-metal if a small change in the Fermi level is induced. Such a
structure may be important in the spintronics context.Comment: 10 pages, 3 figure
Water diffusion in carbon nanotubes for rigid and flexible models
We compared the diffusion of water confined in armchair and zigzag carbon
nanotubes for rigid and flexible water models. Using one rigid model,
TIP4P/2005, and two flexible models, SPC/Fw and SPC/FH, we found that the
number of the number of hydrogen bonds that water forms depends on the
structure of the nanotube, directly affecting the diffusion of water. The
simulation results reveal that due to the hydrophobic nature of carbon
nanotubes and the degrees of freedom imposed by the water force fields, water
molecules tend to avoid the surface of the carbon nanotube. This junction of
variables plays a central role in the diffusion of water, mainly in narrow
and/or deformed nanotubes, governing the mobility of confined water in a
non-trivial way, where the greater the degree of freedom of the water force
field, the smaller it will be mobility in confinement, as we limit the
competition between area/volume, and it no longer plays the unique role in
changing water diffusivity.Comment: 28 pages, 6 figure
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