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101.
Commercial explosives are complex mixtures that contain not only the active explosive agent(s) but also a host of other organic and inorganic compounds. The ultrahigh mass resolving power (m/delta m50% >200,000) and mass accuracy (<1 ppm) of electrospray ionization Fourier transform ion cyclotron resonance (ESI FTICR) mass spectrometry allow for definitive identification of various species in TNT, RDX, and HMX. We are thereby able to correct prior misassignments of the elemental compositions of the most abundant negative ions from electrospray of RDX and HMX. Although the (known) active agents of many explosives may be identified by low-resolution MS or MS/MS, it is the other characteristic components (indigenous or artificial additives) whose presence and elemental composition can potentially identify the source of the product. ESI FTICR mass spectrometry of smokeless powder, TNT, and Powermite resolves and identifies numerous nonactive ingredients, many of which are recovered in a postblast residue. In contrast, the residue recovered from an explosion of military C4 yielded several species derived from RDX but virtually none from other ingredients. 相似文献
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Chen Edith; Hermann Cathy; Rodgers Denise; Oliver-Welker Tina; Strunk Robert C. 《Canadian Metallurgical Quarterly》2006,25(3):389
This study tested the relationship of anxiety and asthma severity to symptom perception. Eighty-six children diagnosed with mild or moderate asthma had symptom perception and pulmonary function measured throughout methacholine challenge (to induce bronchoconstriction). Higher trait anxiety was associated with heightened symptom perception (controlling for pulmonary function) at baseline. Greater asthma severity was associated with blunted symptom perception (controlling for pulmonary function) at the end of methacholine challenge and with a slower rate of increase in symptom perception across methacholine challenge. These results suggest that anxiety plays a role when children's symptoms are mild, whereas medical variables such as severity play a role in perception of changes in asthma symptomatology as bronchoconstriction worsens. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Soil surface-bound polycyclic aromatic hydrocarbons (PAHs) were identified by use of Real-Time Aerosol Mass Spectrometry (RTAMS) in two NIST standard research material (SRM) soils (Montana SRM 2710 and Peruvian SRM 4355) each contaminated separately with three common petroleum hydrocarbons (diesel fuel, gasoline, and kerosene). The described contaminated soil analysis required no sample preparation. Direct laser desorption/ionization mass spectrometric analysis of individual soil particles contaminated with each of the petroleum hydrocarbons at three different contamination levels (0.8, 8, and 80 ppth (wt/wt)) yielded detectable PAH cation distributions that ranged from m/z 128 to 234, depending on the fuel contaminant. The same analysis performed on uncontaminated SRM soils revealed very little (Peruvian) to no (Montana) detectable PAH species. Size analysis showed that most of the individual soil particles analyzed were between 1 and 5 microm in diameter. Tandem mass spectrometry (MS/MS) experiments identified alkyl-substituted two- and three-ringed PAHs in all three petroleum hydrocarbon contaminated soils. However, due to similarities in fragmentation patterns, MS/MS analysis of higher MW species (m/z > 200) was unable to distinguish between the possibility of highly alkyl-substituted three-ringed PAHs and hydrogenated four-ringed PAHs. The described technique offers the direct, rapid determination and characterization of surface-bound PAHs in petroleum-contaminated soils at part-per-million levels without prior extraction, separation, or other sample preparation methods. 相似文献
105.
Knowledge about the sizes of peptides generated by proteasomes during protein degradation is essential to fully understand their degradative mechanisms and the subsequent steps in protein turnover and generation of major histocompatibility complex class I antigenic peptides. We demonstrate here that 26 S and activated 20 S proteasomes from rabbit muscle degrade denatured, nonubiquitinated proteins in a highly processive fashion but generate different patterns of peptides (despite their containing identical proteolytic sites). With both enzymes, products range in length from 3 to 22 residues, and their abundance decreases with increasing length according to a log-normal distribution. Less than 15% of the products are the length of class I presented peptides (8 or 9 residues), and two-thirds are too short to function in antigen presentation. Surprisingly, these mammalian proteasomes, which contain two "chymotryptic," two "tryptic," and two "post-acidic" active sites, generate peptides with a similar size distribution as do archaeal 20 S proteasomes, which have 14 identical sites. Furthermore, inactivation of the "tryptic" sites altered the peptides produced without significantly affecting their size distribution. Therefore, this distribution is not determined by the number, specificity, or arrangement of the active sites (as proposed by the "molecular ruler" model); instead, we propose that proteolysis continues until products are small enough to diffuse out of the proteasomes. 相似文献
106.
In the preliminary phase of this study, a selective isolation medium was developed. Using the new medium, 24 strains of Bacillus Spp. that elevate tomato juice pH were isolated from garden soil or natural vegetative materials. Two jars of home-canned, water-bathed tomatoes contained sporeformers which produced noneffervescent spoilage. All strains were morphologically and physiologically different from 2 flat-sour strains of B. coagulans and B. licheniformis strains, but similar to a previous isolate from home-canned, spoiled green beans that elevated pH. The new medium may have future applications in isolation and enumeration of other acidurics including yeast-like microorganisms. 相似文献
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AL Gerbes V Gülberg T Waggershauser J Holl M Reiser 《Canadian Metallurgical Quarterly》1998,43(11):2463-2469
Nonsurgical reduction of portal hypertension by transjugular intrahepatic portosystemic shunt (TIPS) is widely used for prevention of variceal rebleeding (elective TIPS). Information is limited about the value of emergency TIPS for acute variceal bleeding unresponsive to endoscopic and drug therapy. The aim of the present study was therefore to determine whether the effects and complications differ between emergency and elective TIPS in patients with cirrhosis of the liver. TIPS was performed in 11 patients with acute variceal bleeding unresponsive to endoscopic treatment and 22 patients in stable condition after an episode of variceal bleeding. Clinical examination, blood sampling, Doppler sonography of TIPS flow, and upper gastrointestinal endoscopy were performed at days 1, 7, and 30 and at three-month intervals after TIPS. Mean follow-up was 549 (1-987) days. Bleeding was controlled by emergency TIPS in 10/11 patients. Probability of survival was not different after emergency and elective TIPS (0.73 vs 0.84 at one year). Early rebleeding (< or =2 weeks) occurred more often after emergency TIPS (3/11 vs 0/22 patients; P = 0.03), but there was no significant difference in late rebleeding. Occlusion of TIPS was more frequent after emergency TIPS. Occurrence of TIPS stenoses was identical in both groups (4/11 vs 8/22). De novo or deterioration of preexisting hepatic encephalopathy was similar (18% vs 24%; NS). It is concluded that TIPS is effective for control of acute variceal bleeding unresponsive to endoscopic and drug treatment. Early rebleeding and stent occlusion occurred more often after emergency TIPS. Late rebleeding, complications, and long-term survival did not differ from elective TIPS. 相似文献