RESUMEN
The thermal relaxation of macrospins in a strongly interacting thin film of spinel-phase iron oxide nanocrystals (NCs) is probed by vibrating sample magnetometry (VSM). Thin films are fabricated by depositing FeO/Fe(3)O(4) core-shell NCs by electrophoretic deposition (EPD), followed by sintering at 400°C. Sintering transforms the core-shell structure to a uniform spinel phase, which effectively increases the magnetic moment per NC. Atomic force microscopy (AFM) confirms a large packing density and a reduced inter-particle separation in comparison with colloidal assemblies. At an applied field of 25 Oe, the superparamagnetic blocking temperature is T(B) (SP) ≈ 348 K, which is much larger than the Néel-Brown approximation of T(B) (SP) ≈ 210 K. The enhanced value of T(B) (SP) is attributed to strong dipole-dipole interactions and local exchange coupling between NCs. The field dependence of the blocking temperature, T(B) (SP)(H), is characterized by a monotonically decreasing function, which is in agreement with recent theoretical models of interacting macrospins.
RESUMEN
The objective of the study was to determine the clinical and immunologic status of trimellitic anhydride (TMA) workers who have had immunologic lung diseases and who have been moved to lower exposure jobs. Twenty-nine consecutive workers with TMA-induced immunologic lung diseases who had been moved to low exposure jobs for more than 1 yr were studied retrospectively. Pulmonary symptoms were obtained by physician-administered questionnaire. Immunologic studies were performed using radioimmunoassay. Spirometry and chest film were obtained. Workers with late asthma (LA) (n = 3), late respiratory systemic syndrome (LRSS) (n = 8), or both LRSS and asthma rhinitis (A/R) (n = 6) had improved symptoms, improved pulmonary functions, and lower total antibody against TM-HSA. Five of the 12 workers with A/R had improved symptoms, improved pulmonary functions, and lower IgE against TM-HSA, whereas seven continued to have moderate to severe symptoms, abnormal pulmonary functions, and elevated IgE against TM-HSA. There were no chest film findings in any group that were definitely attributed to TMA. Although TMA workers with LA or LRSS improve when moved to lower exposure jobs, only half of workers with A/R improve; elevated IgE against TM-HSA appears to be a marker for the subpopulation of workers with A/R that does not improve.
Asunto(s)
Enfermedades del Sistema Inmune/inducido químicamente , Enfermedades Pulmonares/inducido químicamente , Enfermedades Profesionales/inducido químicamente , Exposición Profesional/efectos adversos , Anhídridos Ftálicos/efectos adversos , Adulto , Asma/inducido químicamente , Asma/diagnóstico , Asma/epidemiología , Femenino , Estudios de Seguimiento , Humanos , Enfermedades del Sistema Inmune/diagnóstico , Enfermedades del Sistema Inmune/epidemiología , Pruebas Inmunológicas , Enfermedades Pulmonares/diagnóstico , Enfermedades Pulmonares/epidemiología , Masculino , Persona de Mediana Edad , Enfermedades Profesionales/diagnóstico , Enfermedades Profesionales/epidemiología , Exposición Profesional/estadística & datos numéricos , Estudios Retrospectivos , Encuestas y CuestionariosRESUMEN
We conducted a 1-year cross-sectional survey of 474 employees of a large chemical manufacturing complex to relate trimellitic anhydride (TMA) exposure to serologic and clinical outcomes. In 1988-1989, employees were evaluated by history and immunologic assay of total (T) and IgE antibody to trimellityl human serum albumin (TM-HSA). All employees were assigned to a TMA exposure class, from 1 (highest) to 5 (lowest), by an industrial hygienist, independent of the clinical and immunological data. Thirty-two (6.8%) of 474 employees had a TMA immunologic syndrome, 31.6% with an irritant response and 61.6% with no symptoms. Twelve had asthma/rhinitis, 10 had the late respiratory systemic syndrome (LRSS), four had late onset asthma, one had late onset arthralgia, and five had a distant history of LRSS. Included in this survey of the entire work force were 321 new enrollees, who had not joined the previous (1976 to 1988) voluntary surveillance program. Only four (1.3%) of the new enrollee group had a TMA immunologic syndrome. Among new enrollees, there were lower mean total and IgE serum antibody levels in lower exposure classes and a higher percentage with elevated antibody levels in high exposure classes (for T, x2 = 17.5, p = .0016; for IgE, x2 = 76.7, p less than .0001). In the new enrollee population, demographic variables of age, sex, date of hire, and smoking status were examined related to antibody levels. Only current or former smoking was related to elevated total antibody levels.