RESUMEN
Electron energy loss spectra collected from fresh and corroded silver nanoparticles are compared with those from a number of reference materials, focusing on the M4,5 edge. Chemical shifts and changes in the energy loss near edge structure (ELNES) are described and found to be sufficient to distinguish metallic silver from chemically oxidised silver. The measurements, in conjunction with electron energy loss spectrum imaging, are used to assess the mechanisms for atmospheric corrosion of silver nanoparticles. We unambiguously assign the corrosion product under atmospheric conditions to be silver sulphide, but show the reaction process to be distinctly inhomogeneous, producing a variety of types of corroded particles. LAY DESCRIPTION: >Here, we use analytical electron microscopy to track the corrosion of silver nanoparticles and present chemical maps of the corrosion products. We show clear spectroscopic differences between metallic and corroded silver using the M4,5 electron energy loss spectral feature, which is not commonly studied. Our study shows that corrosion is due to interactions with sulphur in the atmosphere; and the corrosion is not uniform, but appears to develop from specific points on the surface of the nanoparticles.
RESUMEN
A 37-year-old woman with clinically occult, abscessed uterine myomas presented with fever, anemia, splenomegaly, and viridans streptococcal bacteremia. An initial diagnosis of endocarditis was made, but fever persisted despite appropriate antibiotics. Pelvic pain evolved and laparotomy revealed an infected myoma. Streptococcus milleri was isolated from both the blood and the uterine abscess. Infected uterine myomata may be clinically silent despite producing sustained bacteremia. The occurrence of suppurating myomas and the significance of S milleri isolates are briefly reviewed.
Asunto(s)
Absceso/diagnóstico , Endocarditis Bacteriana/diagnóstico , Leiomioma/complicaciones , Infecciones Estreptocócicas/diagnóstico , Enfermedades Uterinas/diagnóstico , Absceso/etiología , Adulto , Diagnóstico Diferencial , Femenino , Fístula/etiología , Humanos , Sepsis/etiología , Infecciones Estreptocócicas/etiología , Supuración , Enfermedades Uterinas/etiología , Neoplasias Uterinas/complicacionesRESUMEN
A prospective study on 6,125 job applicants for light duty telephone company work is presented, which indicates that a preplacement medical evaluation is not predictive of risks relating to work attendance or job performance in nonhazardous assignments. Results show that between groups of employees, who were medically classified at the time of hire into categories with or without employment risk factors, there was no significant difference relative to sickness, accident or other absence, or to work performance during the first twelve months after hire. A work force loss of 25% is seen during the first year after hire without significant difference between groups for either numbers of employees lost or reason for loss. A cost-benefit analysis based on this study is presented, which demonstrates that the preplacement medical evaluation for light duty assignments is not cost effective. In addition, further unnecessary costs are incurred when job applicants are medically evaluated but not hired, which is shown to occur here for 27.5% of healthy applicants.
Asunto(s)
Medicina del Trabajo , Examen Físico , Absentismo , Análisis Costo-Beneficio , Empleo , Estudios de Evaluación como Asunto , Femenino , Humanos , Masculino , Servicios de Salud del Trabajador , Estudios Prospectivos , Teléfono , Estados UnidosRESUMEN
Viruses were isolated from kidneys of normal and renal tumor-bearing Vermont Rana pipiens after subinoculation into red eft newts (Triturus viridescens). Organs of efts inoculated with viable cell suspensions from four of seven tumor-bearing kidneys yielded virus (LT-1, -2, -3, -4) when inoculated into TH-1 (Terrapene heart) cell culture. One tumor-bearing kidney also yielded virus (L-4) by direct inoculation into TH-1 cells. An additional isolate (L-5) was obtained from 1 of 52 normal Vermont frog kidneys inoculated directly into TH-1 cells. LT-1 was propagated with cytopathic effect (CPE) in each of 38 cell types tested, of fish, amphibian, reptilian, avian, and mammalian origin, at 23 or 30 C. LT-1 through LT-4, L-4 and L-5, and FV-1 through FV-3 each induced similar CPE in all cells tested. LT-2, however, induced CPE that progressed at a slower rate than that caused by the other isolates and produced smaller plaques (<0.8 mm) under starch gel overlay. Each of the viruses replicated to high titer in embryonated eggs incubated at 30 C. The viruses also grew in efts and adult newts, but not in bullfrog (Rana catesbeiana) tadpoles or adult leopard frogs. Tumor induction in adult leopard frogs inoculated with LT-1 was not demonstrated. Electron microscopic observations of LT-1 and LT-2 viruses revealed cytoplasmic particles, hexagonal in cross section, approximately 120 to 140 mmu in diameter, containing a dense nucleoid. LT-1 and LT-2 viruses were indistinguishable from FV-1 and Tipula iridescent virus. LT-1 was presumed to be a deoxyribonucleic acid virus on the basis of 5-bromodeoxyuridine inhibition. The isolates were ether-sensitive. On the basis of biological, physicochemical, and antigenic similarities, LT-1 through LT-4, L-4, L-5, FV-1 through FV-3, and isolates recently recovered from the bullfrog and the newt may represent strains of the same amphibian cytoplasmic virus.