Real-time diode laser measurements of vapor-phase benzene.

An absorption spectrometer equipped with a IV-VI semiconductor tunable mid-IR diode laser was used to make sensitive measurements of benzene (C(6)H(6)) gas in the 5.1-microm spectral range. Wavelength modulation coupled with second-harmonic detection achieved accurate real-time quantification of benzene concentrations down to a minimum detection limit of 1 ppmv with an integration time of 4 s. A variety of calibrated benzene-sensing measurements were made, including the determination of the benzene concentrations in vehicle exhaust and headspace vapors from unleaded gasoline and other liquids. Kinetic phenomena, including the monitoring of benzene evaporation and absorption/desorption by granulated activated carbon were observed with the instrument. Measurements were performed that allowed experimental determination of the activation energy for desorption of benzene from activated carbon, which was found to be 198 meV/molecule (19.0 kJ/mol).

Simultaneous NO and CO(2) measurement in human breath with a single IV-VI mid-infrared laser.

A tunable diode laser absorption spectroscopy (TDLAS) system equipped with a IV-VI mid-IR laser operating near 5.2>mu;m was used to measure exhaled nitric oxide (eNO) and carbon dioxide (CO(2)) simultaneously in human breath over a single exhalation. Breath was sampled in real time, and eNO levels were measured from seven volunteers, two steroid-naive asthmatics and five nonasthmatics. Measured CO(2) levels were used as an internal standard to verify correct breath collection and calculate eNO values. Calculated eNO concentrations agreed well with reported values for asthmatic and nonasthmatic individuals.

Host associations of ticks parasitizing rodents at Borrelia burgdorferi enzootic sites in South Carolina.

A total of 237 rodents was collected in 4 regions of South Carolina from July 1994 through December 1995. Eight species were collected, including cotton mouse, hispid cotton rat, eastern woodrat, marsh rice rat, white-footed mouse, eastern harvest mouse, golden mouse, and black rat. Of the 1,514 ticks recovered from these hosts, Ixodes minor Neumann, including larvae, nymphs, and adults, was the most abundant species, representing 54% of the total. Only immature stages of other tick species were found, including larvae and nymphs of Dermacentor variabilis (Say), Amblyomma maculatum Koch, Ixodes affinis Neumann, and Ixodes scapularis Say. All 5 tick species parasitized cotton mice, cotton rats, and woodrats, which were the most important small mammal hosts for ticks at the localities studied. Rice rats were hosts of A. maculatum, D. variabilis, and L. minor. Amblyomma maculatum was more strongly associated with cotton rats than other rodent species. Ixodes scapularis was most strongly associated with cotton mice, and I. minor was more strongly associated with both woodrats and cotton mice than other species of rodents. Ixodes minor parasitized hosts in the Coastal Zone only, where among spirochete-infected hosts, it was present in significantly greater numbers than other ticks. Furthermore, I. minor was the only tick species that showed a statistically significant positive association with spirochetal infection in rodents. More I. affinis parasitized spirochete-infected hosts than I. scapularis, but fewer than I. minor. The findings discussed herein provide evidence that implicates I. minor as the possible primary enzootic vector of the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt and Brenner in the Coastal Zone of South Carolina. They also indicate that the high level of B. burgdorferi infection in rodents from this region may be a function of the combined involvement of I. minor, I. affinis, and I. scapularis in the enzootic transmission of the spirochete.

VOC elimination in a compost biofilter using a previously acclimated bacterial inoculum.

A comparison of biodegradation efficiencies was done for volatile benzene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene elimination in a compost biofilter. The column was first exposed to a synthetic mixture and then a free phase product mixture containing these compounds at increasing pollutant loads. The optimal moisture content of the system was determined, and this was used in the biodegradation experiments. An acclimated culture was used as an inoculum for the biofilter, the matrix of which consisted of composted forestry products, composted sewage sludge, lime, and perlite. Inlet and outlet concentrations were measured, and pollutant loads, elimination capacities, and removal efficiencies were determined for each of the compounds. Optimal moisture content for this system was found to be 40%, and the short lag times (one to five days) in acclimating to the compounds was ascribed to the presence of the well-acclimated inoculum. The compounds in the synthetic mixture had higher removal efficiencies (80-99%) even at the higher pollutant loads experienced, with the exception of o-xylene. Dynamic removal efficiencies and acclimation periods were seen in the free phase product mixture, with a removal efficiency range from 70 to 95%. This was attributed to the presence of chlorinated aliphatics in the free phase product.

Incidence of idiopathic full-thickness macular holes in fellow eyes. A 5-year prospective natural history study.

PURPOSE: This study aimed to determine the incidence of idiopathic full-thickness macular hole (FTMH) in normal fellow eyes and to evaluate the role of electrodiagnostic and psychophysical tests in identifying eyes at risk. PATIENTS AND METHODS: A prospective longitudinal natural history study of a cohort of patients with unilateral holes and normal, asymptomatic fellow eyes without posterior vitreous detachment was conducted. Subjects underwent baseline examination, pattern reversal electroretinography, electro-oculography (EOG), and color contrast sensitivity (CCS) testing for protan, deutan, and tritan thresholds and were recalled for clinical examination at 18 months and 5 years. RESULTS: At baseline, 114 patients were examined. Eighty were available for review at 18 months, of whom 6 had full-thickness macular holes develop in the fellow eye. At 5 years, 67 of the remaining 74 patients who had not developed holes at 18 months were re-examined and a further 5 were found to have holes develop in the fellow eye. A posterior vitreous detachment without hole formation had developed in 20 fellow eyes at 5 years. Although mean pattern reversal electroretinography and EOG responses were within normal limits in affected and fellow eyes at baseline, mean CCS protan, deutan, and tritan thresholds were elevated significantly in affected eyes at baseline (P = 0.0001). Unaffected fellow eyes showed normal mean protan and deutan thresholds, but significantly elevated mean tritan thresholds (P = 0.01) at baseline. Mean tritan CCS loss was, however, similar in fellow eyes in which holes later developed and in fellow eyes in which holes did not. CONCLUSIONS: The Kaplan-Meier estimated risk of fellow eye involvement is 15.6% (range, 8.4%-22.3%; P = 0.05) at 5 years. Although electrodiagnostic and psychophysical testing was not predictive of fellow eye involvement, tritan CCS loss at baseline, in apparently normal fellow eyes, may indicate subclinical foveal dysfunction, the nature of which is unclear.

Predilection of brain metastasis in gray and white matter junction and vascular border zones.

BACKGROUND: The purpose of this study was to asses the importance of the vascular border zone and the gray and white matter junction on the distribution of brain metastases. METHODS: We reviewed the medical records, computed tomography (CT) of magnetic resonance imaging (MRI) of 105 patients with secondary brain tumors. The metastatic lesions noted on CT scans of MRI ere matched with a predetermined standard sheet containing axial images with shading on the border zones. To be included in the border zones, the center on more than 50% of the lesion had to be situated within these zones. RESULTS: Among 100 evaluable patients, there were 302 metastatic brain lesions. Of the 302 lesions, 210 lesions were 2 cm or smaller in greatest dimension and located in the cerebral and cerebellar hemispheres. The major vascular border zones were the site of predilection for 103 lesions (62%) although the border zones constitute only 29% of the area. Gray and white matter junction was the preferred site for 135 lesions (64%). CONCLUSION: The results demonstrated that brain metastasis occurs in the vascular border zone regions and the gray and white matter junction more frequently than previously recognized, and also supported the notion that metastatic emboli tend to lodge in an area of sudden reduction of vascular caliber (gray/white matter junction) and in the area most distal vascular field (border zone).

Arachidonic acid production by Mortierella alpina grown on solid substrates.

Mortierella alpina grown in solid state fermentations on cereal substrates gave up to 16% lipid in the final biomass. Arachidonic was at 50% of total fatty acids, with a yield of 36 mg/g of original substrate. Microbial lipid production was successfully scaled up to use 5-kg dry substrate batches.

Fatty acid alterations in Saccharomyces cerevisiae exposed to ethanol stress.

The influence of ethanol concentration on fatty acid alterations in total phospholipids (PL), phosphatidylcholine (PCH), phosphatidylethanolamine (PE), phosphatidylinositol (PI), sterol esters (ES) and triacylglycerols (TAG) of Saccharomyces cerevisiae was studied. Ethanol induced the elevation of palmitic and oleic acid level in major membrane phospholipids (PCH and PE) and also the palmitoleic acid content in ES and TAG.