Serologic evidence of human orthopoxvirus infections in Sierra Leone

<p>Abstract</p> <p>Background</p> <p>Orthopoxviruses, including variola virus, vaccinia virus, and monkeypox virus, have previously been documented in humans in West Africa, however, no cases of human orthopoxvirus infection have been reported in the region since 1986. We conducted a serosurvey to determine whether human exposure to orthopoxviruses continues to occur in eastern Sierra Leone.</p> <p>Findings</p> <p>To examine evidence of exposure to orthopoxviruses in the Kenema District of Sierra Leone, we collected and tested sera from 1596 persons by IgG ELISA and a subset of 313 by IgM capture ELISA. Eleven persons born after the cessation of smallpox vaccination had high orthopoxvirus-specific IgG values, and an additional 6 persons had positive IgM responses. No geographic clustering was noted.</p> <p>Conclusions</p> <p>These data suggest that orthopoxviruses continue to circulate in Sierra Leone. Studies aimed at obtaining orthopoxvirus isolates and/or genetic sequences from rodents and symptomatic humans in the area are indicated.</p

CVD growth of boron nitride nanotubes

Multiwalled BN nanotubes are grown from nickel boride catalyst particles by chemical vapor deposition at 1000-1100 degrees C using borazine, B3N3H6, as the precursor. This precursor is generated in situ from molten salt that forms from mixtures of (NH4)(2)SO4, NaBH4, and Co3O4 at 300-400 degrees C. The BN nanotubes have concentric-tube structures, are free of internal closures, have crystalline walls, and exhibit lengths of up to similar to 5 mu m. The nanotubes often possess bulbous, flag-like, or club-like tip closures. A root-growth mechanism is proposed for the catalyzed process

Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load

The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a &quot;nanostressing stage&quot; located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost Layer (&quot;sword-in-sheath&quot; failure), and the tensile strength of this Layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were Loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young&apos;s modulus E of the outermost Layer varied from 270 to 950 gigapascals, Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse