Momentum-imaging apparatus for the study of dissociative electron attachment dynamics.

An ion-momentum spectrometer is used to study the dissociative dynamics of electron attachment to molecules. A skimmed, supersonic gas jet is crossed with a pulsed beam of low-energy electrons, and the resulting negative ions are extracted toward a time- and position-sensitive detector. Calculations of the momentum in three dimensions may be used to determine the angular dependence of dissociative attachment as well as the energetics of the reaction.

X-ray Emission Measurements following Charge Exchange Between C6+ and He.

X-ray spectra following charge exchange collisions between C6+ and He are presented for collision energies between 460 eV/u and 32,000 eV/u. Spectra were obtained at the Oak Ridge National Laboratory Multicharged Ion Research Facility using a microcalorimeter X-ray detector capable of fully resolving the C VI Lyman series lines through Ly-γ. These line ratios are sensitive to the initial electron l-distribution and test our understanding of the charge exchange process. In addition, these line ratios are important for identifying charge exchange in astrophysical contexts involving the interaction of solar wind ions with neutrals. Our measurements are performed at collision velocities (300 km/s to 2500 km/s) which overlap most of the solar wind range. Additional data of this type can be combined with computations to provide an extensive set of reliable line ratios and absolute cross sections for the interpretation of a variety of astrophysical situations.

Hot water from cold. The dissociative recombination of water cluster ions.

Dissociative recombination of the Zundel cation D(5)O(2)(+) almost exclusively produces D + 2 D(2)O with a maximum kinetic energy release of 5.1 eV. An imaging technique is used to investigate the distribution of the available reaction energy among these products. Analysis shows that as much as 4 eV can be stored internally by the molecular fragments, with a preference for producing highly excited molecular fragments, and that the deuteron shows a nonrandom distribution of kinetic energies. A possible mechanism and the implications for these observations are addressed.

Heat stability of chaetoglobosins A and C.

Chaetomium globosum is commonly found in water-damaged buildings and produces the mycotoxins chaetoglobosin A and chaetoglobosin C (Ch-A and Ch-C, respectively). While attempting to purify Ch-A and Ch-C, we observed that these mycotoxins were broken down after heating. The objective of this study was to determine the temperature and the amount of time necessary to break down Ch-A and Ch-C. We demonstrated that the amounts of Ch-A were significantly reduced when exposed to 75 degrees C for 24 h and 100 degrees C for 90, 120, or 150 min. Under the same conditions, the levels of Ch-C were also lower (although not significantly). At 175 degrees C, no Ch-A was detected after 15 min and Ch-C was significantly reduced after 30 min. Our findings will aid other researchers who work with these mycotoxins in the future.

Three-body breakup in the dissociative recombination of the covalent triatomic molecular ion O3+.

We report the first observation of almost exclusive three-body breakup in the dissociative recombination of a covalent triatomic molecular ion O3+. The three-body channel, constituting about 94% of the total reactivity, has been investigated in detail. The atomic fragments are formed in only the first two electronic states, 3P and 1D, while formation in the 1S state has not been observed. The breakup predominantly proceeds through dissociative states with linear geometry.

Dielectronic resonance method for measuring isotope shifts.

Long standing problems in the comparison of very accurate hyperfine-shift measurements to theory were partly overcome by precise measurements on few-electron highly charged ions. Still the agreement between theory and experiment is unsatisfactory. In this Letter, we present a radically new way of precisely measuring hyperfine shifts, and demonstrate its effectiveness in the case of the hyperfine shift of 4s1/2 and 4p1/2 in 207Pb53+. It is based on the precise detection of dielectronic resonances that occur in electron-ion recombination at very low energy. This allows us to determine the hyperfine constant to around 0.6 meV accuracy which is on the order of 10%.

An investigation into techniques for cleaning mold-contaminated home contents.

This study examined the efficacy of the following treatments to reduce selected fungal spore and mycotoxin levels on materials commonly found in home contents: (1) gamma irradiation at a 10-13 kiloGray exposure, (2) a detergent/bleach wash, and (3) a steam cleaning technique. A minimum of six replicates were performed per treatment. Paper, cloth, wood, and carpet were inoculated with either fungal spores (Stachybotrys chartarum, Aspergillus niger, Penicillium chrysogenum, or Chaetomium globosum) at 240,000 spores/2.54 cm2 of material or with the mycotoxins roridin A, T-2, and verrucarin A at 10 microg per 2.54 cm2 of material. Treatments were evaluated with an agar plating technique for fungal spores and a yeast toxicity culture assay for mycotoxins. Results showed that gamma irradiation inactivated fungal spores, but the treatment was not successful in inactivating mycotoxins. The washing technique completely inactivated or removed spores on all materials except for C. globosum, which was reduced on all items except paper (p < 0.05). Washing inactivated all mycotoxins on paper and cloth but not on carpet or untreated wood (p < 0.001). The steam cleaning treatment did not completely eliminate any fungal spores; however, it reduced P. chrysogenum numbers on all materials, C. globosum was reduced on wood and carpet, and S. chartarum was reduced on wood (p < 0.05). Steam cleaning was unsuccessful in inactivating any of the tested mycotoxins. These results show that the bleach/detergent washing technique was more effective overall in reducing spore and mycotoxin levels than gamma irradiation or steam cleaning. However, the other examined techniques were successful in varying degrees.

Determination of plasma trace elements in tumor-bearing animals by proton-induced X-ray emission spectroscopy.

Although altered levels of circulating essential trace elements are known to accompany malignant disease, the lack of sensitivity of conventional detection methods has generally limited their study to clinical conditions involving extensive disease (i.e., significant tumor burden). As such, the application of altered trace element levels as potential prognostic guides or as response indicators subsequent to treatment has been of limited use. During this study, proton-induced X-ray emission spectroscopy was evaluated as a tool to determine trace element imbalances in a murine tumor model. Using plasma from C57B1/6 mice bearing the syngeneic Lewis lung carcinoma (LLCa), levels of Fe, Cu, and Zn, as well as changes in the Cu /Zn ratio, were measured in animals carrying an increasing primary tumor burden. The plasma levels of Fe, Cu, and Zn were found to decrease significantly 7 d following implants of LLCa cells with no significant change observed in the Cu/Zn ratio. By d 21, however, an increase in the Cu/Zn ratio was found to accompany increased growth of the LLCa tumor; the plasma levels of Cu had returned to normal levels, whereas both the Fe and Zn plasma levels remained lowered. Collectively, the results suggest that although a net change in individual plasma trace element concentrations might not be accurately associated with tumor growth, a clear relationship was established between the Cu/Zn ratio and tumor size.

Comparison of five measures of motivation to quit smoking among a sample of hospitalized smokers.

OBJECTIVE: To compare the predictive validity of several measures of motivation to quit smoking among inpatients enrolled in a smoking cessation program. METHODS: Data collected during face-to-face counseling sessions included a standard measure of motivation to quit (stage of readiness [Stage]: precontemplation, contemplation, or preparation) and four items with responses grouped in three categories: "How much do you want to quit smoking" (Want), "How likely is it that you will stay off cigarettes after you leave the hospital" (Likely), "Rate your confidence on a scale from 0 to 100 about successfully quitting in the next month" (Confidence), and a counselor assessment in response to the question, "How motivated is this patient to quit?" (Motivation). Patients were classified as nonsmokers if they reported not smoking at both the 6-month and 12-month interviews. All patients lost to follow-up were considered smokers. MAIN RESULTS: At 1 year, the smoking cessation rate was 22. 5%. Each measure of motivation to quit was independently associated with cessation ( p <.001) when added individually to an adjusted model. Likely was most closely associated with cessation and Stage was least. Likely had a sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio of 70.2%, 68.1%, 39.3%, 88.6%, and 2.2, respectively. CONCLUSIONS: The motivation of inpatient smokers to quit may be as easily and as accurately predicted with a single question as with the series of questions that are typically used.

Distal revascularization-interval ligation for limb salvage and maintenance of dialysis access in ischemic steal syndrome.

PURPOSE: Traditional options for treating ischemic steal syndrome related to a functioning dialysis access graft or fistula include banding or ligation. Unfortunately, these techniques usually result in inconsistent limb salvage, loss of a functional access, or both. We report our experience with an alternative method of limb revascularization that eliminates steal while maintaining continuous dialysis access. METHODS: Patients who had critical limb ischemia and functioning arteriovenous fistulae (AVF) underwent color-flow duplex scanning, digital photoplethysmography, and arteriography. Arterial ligation distal to the AVF origin eliminated the steal physiologic mechanism while arterial bypass grafting from above to below the AVF revascularized the extremity (distal revascularization-interval ligation [DRIL] procedure). RESULTS: From March 1994 through December 1996, 21 patients with functioning extremity AVFs presented with critical ischemia and steal syndrome. Eleven patients had chronic ischemia with rest pain, paresthesias, or ulcerations related to nine native fistulae (six brachiocephalic, two basilic vein transpositions, one radiocephalic) and two prosthetic bridge grafts (one upper arm, one lower extremity). Acute ischemia developed in 10 patients related to three native fistulae (two brachiocephalic, one radiocephalic) and seven prosthetic bridge grafts (three forearm, three lower extremity, one upper arm). All 21 patients were treated with the DRIL technique. Three of these patients required treatment for ischemia at the time of AVF construction. Nineteen of 21 bypass procedures were performed with autogenous vein, including nine brachial-brachial, three brachial-radial, two radial-radial, two brachial-ulnar, one popliteal-popliteal, one femoral-popliteal, and one femoral-peroneal. Polytetrafluoroethylene grafts were used for one external iliac-popliteal bypass graft and one axillary-brachial bypass graft. Limb salvage and maintenance of a functional fistula were achieved in 100% and 94%, respectively, at 18 months by life-table analysis. CONCLUSION: The DRIL technique reliably restores antegrade flow to the ischemic limb, eliminates the potential pathway for the steal physiologic mechanism, and maintains continuous dialysis access in these difficult patients.

Rheumatoid arthritis in a United States Public Health Service Hospital in Oklahoma: serologic manifestations in rheumatoid arthritis vary among tribal groups.

OBJECTIVE: To study the serologic manifestations of rheumatoid arthritis (RA) at a United States Public Health Service Hospital that serves numerous tribes in Oklahoma. METHODS: Forty-five patients with RA were identified, and serologic studies for antinuclear antibody (ANA), rheumatoid factor, and antibodies to extractable nuclear antigens were performed. Extraarticular manifestations of RA were also evaluated. RESULTS: Twelve of the 45 patients with RA were Kiowa. These patients were significantly more likely to have a positive ANA (75%) than the other patients with RA (28%). In addition, anti-Ro was significantly more common among Kiowa (33%) than among members of other tribes (3%). There was no difference in the extraarticular manifestations of the Kiowa compared with the other Native American tribes. CONCLUSION: RA can be distinctly characterized by serology among groups of American Indians living in the same geographic area.

A comparison of in situ and reversed saphenous vein grafts for infrainguinal reconstruction.

Despite the recent popularity of the in situ saphenous vein graft for infrainguinal arterial reconstruction, considerable doubt exists as to whether this approach offers any real advantage over conventional reversed vein grafts. Therefore we have reviewed our experience with 675 infrainguinal vein grafts undertaken during the past 10 years. There have been no substantial modifications in the technique used for 535 reversed vein grafts over the 10-year period. During the past 3 years, 140 in situ vein grafts have been carried out with the Leather valvulotome used to incise the venous valves. Life-table analysis of 449 femoropopliteal reversed saphenous vein grafts demonstrated 1- and 3-year cumulative patency rates of 81% and 73%, respectively, and a 5-year patency rate of 63%. Seventy-five femoropopliteal in situ bypasses demonstrated a patency rate of 85% at both 1- and 3-year intervals. Cumulative patency rates for 86 femoroinfrapopliteal reversed saphenous vein grafts were 64% and 62% at 1 and 3 years, respectively. Comparable patency rates for 65 infrapopliteal in situ saphenous vein grafts remained stable at 87% for 3 years. Fifteen of the in situ bypasses were anastomosed to vessels at the ankle or foot level, whereas none of the reversed bypasses was carried that far distally. This experience with both in situ and reversed techniques on one service by the same surgeons demonstrates a clear superiority of the in situ saphenous vein graft for infrapopliteal reconstruction at the 3-year interval.

Detection of cadmium electrode surfaces using cw and pulsed radiation.

Simultaneous in situ photoacoustic, photoconductive, and electrochemical detection of species at the surface of the cadmium electrode has been demonstrated using both cw and pulsed light sources. The advantages of the cw and pulsed photoacoustic techniques were evaluated. Both techniques were applied to study the passivation of the cadmium electrode on high rate discharge. Cadmium oxide was identified on the electrode after passivation.