Automatic laser welding and milling with in situ inline coherent imaging.

Although new affordable high-power laser technologies enable many processing applications in science and industry, depth control remains a serious technical challenge. In this Letter we show that inline coherent imaging (ICI), with line rates up to 312 kHz and microsecond-duration capture times, is capable of directly measuring laser penetration depth, in a process as violent as kW-class keyhole welding. We exploit ICI's high speed, high dynamic range, and robustness to interference from other optical sources to achieve automatic, adaptive control of laser welding, as well as ablation, achieving 3D micron-scale sculpting in vastly different heterogeneous biological materials.

Loss determination in microsphere resonators by phase-shift cavity ring-down measurements.

The optical loss of whispering gallery modes of resonantly excited microresonator spheres is determined by optical lifetime measurements. The phase-shift cavity ring-down technique is used to extract ring-down times and optical loss from the difference in amplitude modulation phase between the light entering the microresonator and light scattered from the microresonator. In addition, the phase lag of the light exiting the waveguide, which was used to couple light into the resonator, was measured. The intensity and phase measurements were fully described by a model that assumed interference of the cavity modes with the light propagating in the waveguide.

Text or talk? Social anxiety, loneliness, and divergent preferences for cell phone use.

This paper investigates whether social anxiety and loneliness lead to contrasting beliefs and preferences among cell phone users towards texting and talking on their cell phones. Three hypotheses are examined: (1) that social anxiety and loneliness are differentially associated with generalized preferences either for texting or for talking on the cell phone, (2) that these preferences are linked to contrasting beliefs concerning the social functionality of the short message service (SMS), and (3) that these divergent beliefs mediate the effects of social anxiety and loneliness on cell phone users' generalized preferences for texting or talking. Results from an Internet questionnaire (N=158) showed that, whilst lonely participants preferred making voice calls and rated texting as a less intimate method of contact, anxious participants preferred to text, and rated it a superior medium for expressive and intimate contact. These divergent beliefs accounted for 36% and 16% of the variance in preference for texting and voice calls, respectively, and significantly attenuated the influence of loneliness and social anxiety when they were added to the regression equations for these measures. Results are discussed in terms of the hyperpersonal possibilities of mobile communications technologies.

Dissection autoradiography: a screening technique using storage phosphor autoradiography to detect the biodistribution of radiolabelled compounds.

INTRODUCTION: This study reports an alternative, rapid, whole body autoradiography technique which utilises storage-phosphor imaging technology. Conventionally, tissue or whole body sections have been used to examine the distribution of radiolabelled test compounds. However, the information acquired relates only to the sections examined, and the amount of radioactivity within the whole organ cannot be quantified. We have developed a rapid semi-quantitative technique that produces a concise visual representation of the distribution of the isotope throughout the entire animal: dissection autoradiography (DAR). METHODS: By dissecting a mouse which has been administered 14C-labelled methotrexate (MTX) and drying the tissues on a gel dryer, whole organs and aliquots of body fluids can be exposed to a phosphor imaging plate. The data obtained was analysed with the software associated with the phosphor imaging system and, by using 14C standards, the amount of 14C per total organ or tissue was quantified relative to other samples. Another widely used method to detect radiolabelled material in vivo is tissue solubilisation (TS) followed by liquid scintillation counting (LSC). This conventional method was compared with DAR. RESULTS: The new technique described in this communication was found to have a high level of reproducibility (R(2)= 88-95%). Whilst DAR was less sensitive than TS and LSC, trends over time in the biodistribution of 14C-MTX throughout most tissues were consistent between techniques. DISCUSSION: Whilst TS and LSC was a more sensitive technique, it was labour intensive and expensive in terms of consumables and time when compared with DAR. Dissection autoradiography has the potential to be used to screen quickly large numbers of samples in the biodistribution studies of various conjugates, isomers, derivatives or formulations of a parent compound, following a variety of routes of administration.

Generation of high-repetition-rate femtosecond pulses from 8 to 18 microm.

We generated subpicosecond pulses from 8 to 18 mum by difference-frequency mixing in a 1-mm-thick AgGaSe(2) crystal, the 130- and 180-fs output pulses (1.45 < lambda < 1.85 mum) from an 84-MHz-repetition-rate optical parametric oscillator. Numerical simulations show that intrapulse and interpulse group velocity dispersion determine minimum pulse duration above and below 15 mum, respectively. By cross correlation (upconversion) of 10.5-mum pulses with 90-fs, 810-nm pulses in AgGaS(2), the pulse length was measured to be 310 fs in good agreement with simulations.

Rat liver metabolism and toxicity of 2,2,2-trifluoroethanol.

2,2,2-Trifluoroethanol (TFE) is a metabolite of anesthetic agents and chlorofluorocarbon alternatives. Its toxicity in rats is a consequence of its metabolism to 2,2,2-trifluoroacetaldehyde (TFAld) and then to trifluoroacetic acid (TFAA). The enzymes involved in the toxic metabolic pathway have been investigated in this study. For the reaction of TFE to TFAld, the major hepatic metabolism associated with toxicity (as assessed by pyrazole-inhibitability) was NADPH dependent and occurred in the microsomes, whereas for TFAld conversion to TFAA, NADPH-dependent microsomal metabolism was significant, but mitochondrial and cytosolic metabolism in the presence of NADPH were also major contributors. NADPH-dependent hepatic microsomal metabolism of TFE to TFAld and TFAld to TFAA was inhibited by carbon monoxide, 2-allyl-2-isopropylacetamide, SKF-525A, metyrapone, imidazole, and pyrazole, and both reactions were oxygen dependent. The metabolism of TFE to TFAld was inhibited by diethyldithiocarbamate, a specific inhibitor of cytochrome P450E1, and by a monoclonal antibody to P4502E1, whereas the metabolism of TFAld was inhibited by neither. Ethanol pretreatment of rats enhanced the Vmax for hepatic microsomal metabolism of TFE to TFAld from 5.3 to 9.7 nmol/mg protein/min, while for TFAld to TFAA the Vmax was increased from 4.3 to 6.5 and the Km was unaffected for both reactions. Phenobarbital pretreatment of the rats did not affect any of these kinetic parameters. Coadministration of ethanol and a lethal dose of TFE very markedly decreased the lethality. Both the lethality (LD50 0.21 to 0.44 g/kg) and the metabolic kinetic parameters [(Vmax/Km)H(Vmax/Km)D = 4.2] were affected markedly when deuterated TFE replaced TFE. In contrast, deuteration of TFAld did not affect its lethality or rates of metabolism, but did affect its Km. Taken together these results indicate that P4502E1 catalyzed toxicity-associated hepatic metabolism of TFE to TFAld, while TFAld metabolism was catalyzed by a P450 which was not P4502E1. The hepatic metabolism of TFAld was not associated with its toxicity, which has been determined previously to be associated with its intestinal metabolism.

Procedural errors in antibody identification.

In experimental studies of students and line technologists performing antibody identification procedures, both groups made errors. These errors included, at times, either failing to identify an antibody or misidentifying the specficity(ies)A. prospective study was undertaken to identify errors made in a laboratory setting. Errors were classified as 1) failing to follow protocol (procedural error) or 2) arriving at the wrong answer (misidentification error). Over a 1-year period, 1,057 workups were reviewed. There were 41 (3.88%) procedural errors and no misidentification errors. In 25 workups (61% of errors), the selection of cells m rule out underlying alloantibody(ies) was in error. The remaining 16 involved various "slips" (minor mistakes or memory lapses) and clerical errors. Based on an analysis of the probable causes of these errors, potential solutions include 1) developing computer aids to detect "rule-out" errors or missing tests results; 2) providing timely, careful review of workups before transfusion; and 3) designing better panel layout and cell selection.

2,2,2-Trifluoroethanol intestinal and bone marrow toxicity: the role of its metabolism to 2,2,2-trifluoroacetaldehyde and trifluoroacetic acid.

2,2,2-Trifluoroethanol (TFE) produces bone marrow and small intestine toxicity resulting in leukopenia, loss of intestinal dry weight, and consequent lethal septicemia in male Wistar rats. Its metabolic pathway, based on serum and small intestine time courses of substrate and metabolites, was determined to be TFE in equilibrium 2,2,2-trifluoroacetaldehyde (TFAld)----trifluoroacetic acid (TFAA). Administered TFE and TFAld were not toxic per se, since their toxicity and metabolism were inhibited by pyrazole. TFE and TFAld were equipotent at equimolar doses thus precluding the oxidative reaction, TFE to TFAld, from being the toxic step. Since equimolar TFAA exhibited no toxic effects, an oxidative intermediate on the pathway from TFAld to TFAA, most likely F3C-C+(OH)2, must thus be the toxic moiety. The intermediate TFAld is stable in serum, as determined by a novel assay developed for its analysis in biological systems, and can be transported to the target tissues, bone marrow, and small intestine, after formation probably in the liver. On the basis of the more rapid metabolism of TFE to higher levels of TFAld in the small intestine and bone marrow than in the serum, the closer correspondence of bone marrow and small intestine metabolite ratios than serum ratios at high and low doses of TFE to the corresponding ratios of toxicity, and the decreased toxicity of TFAld when administered ig versus ip, the formation of the toxic metabolic intermediate of TFE probably occurs in the target tissues.

New locus for exopolysaccharide overproduction in Escherichia coli K-12.

A new locus for exopolysaccharide overproduction in Escherichia coli K-12 was mapped by insertion mutagenesis. A 66% linkage to serA, which is located at 62 min on the E. coli K-12 linkage map, was shown by P1 transduction. The polysaccharide produced by the mutant was isolated and was shown to be similar to colanic acid.

Metabolism of 2,2,2-trifluoroethanol and its relationship to toxicity.

2,2,2-Trifluoroethanol (TFE), the toxic metabolite of the anesthetic agent fluoroxene, is further metabolized to trifluoroacetic acid, which accumulated to maximum serum concentrations 16 to 24 hr after TFE administration to rats. To determine how the metabolic pathways of TFE are related to its toxicity, male Wistar rats were pretreated with various metabolic inhibitors and inducers of cytochrome P-450 metabolism, and TFE toxicity and metabolism were assessed. Pyrazole, disulfiram, isoniazid, diethyldithiocarbamate, and 2-allyl-2-isopropyl-acetamide pretreatment significantly decreased the in vivo metabolism of TFE by 53-100% and decreased the toxicity (as assessed by mortality and leukocyte count alterations). Ethanol induction of rats increased metabolism of TFE by 65% 24 hr after TFE administration but not the toxicity. We conclude that hepatic ethanol-inducible cytochrome P-450 catalyzes the metabolism of most of the TFE but this metabolism is not associated with TFE toxicity, which probably arises by extrahepatic metabolism of TFE by another cytochrome P-450 form.

2,2,2-Trifluoroethanol-induced enteropathy in rats: chemically or bacterially mediated effects.

The lethal effects of the fluorinated ether anesthetic, fluroxene, in rats are a consequence of its metabolism, which is catalyzed by cytochrome P-450 to the toxic metabolite 2,2,2-trifluoroethanol (TFE). The anesthetic or TFE (0.21 g/kg) caused decreased white blood cell counts, necrosis of bone marrow and lymphocytes, and decreased small intestine dry weight and was associated with septicemia. To elucidate the mechanism of TFE toxicity in rats we undertook histopathologic, ultrastructural and bacteriologic studies. TFE produced severe edema of intestinal lamina propria and submucosae, dilatation of crypts, loss of surface epithelium, vacuolation and necrosis of intestinal epithelial cells, and infiltration of polymorphonuclear leukocytes into the edematous lamina propria. Intestinal epithelial villi lost their cellular tissue integrity. Coccobacillary organisms were numerous in the ulcerated intestine. Hemolytic E. coli were isolated from intestinal tissue at a two-log increase in concentration relative to controls. Hemograms from TFE-treated rats exhibited marked leukopenia and morphologic differences. The platelets lost their discoid shape, extended pseudopods, and centralizing granules. Hemoglobin precipitation as Heinz bodies and crystalloid structures was observed in TFE-treated rats. Together the data suggest that TFE-induced enteropathy was most probably due to E. coli precipitated from TFE-mediated alterations in the population of small intestinal microbes. The antibiotics erythromycin, active against gram-positive bacteria, and streptomycin, active against gram-negative bacteria, and the antiendotoxin, polymyxin B, were administered to rats prior to TFE in an effort to differentiate between these mechanisms by altering the intestinal bacteria populations. The results indicate that the TFE-induced small intestinal lesions are initiated by the direct focal necrotic effect of TFE or its metabolites on the small intestinal epithelium. The focal coagulation necrosis produced by TFE predisposes the animals to lethal enteritis and systemic bacteremia.

Mechanism of toxicity of 2,2,2-trifluoroethanol in rats.

2,2,2-Trifluoroethanol (TFE) is the toxic metabolite of the anesthetic agent fluroxene. TFE treatment (0.21 g/kg, ip) of male Wistar rats significantly reduced peripheral white blood cell count, bone marrow nucleated cellularity, and dry weight of the small intestine. These toxic effects of TFE were first observed at 8 to 16 hr after treatment, persisted for 96 hr, and were accompanied by severe diarrhea and edema of the small intestine. A non-lethal dose of TFE increased the sensitivity of rats to bacterial endotoxin lethality by approximately 1000-fold. Antibiotic and antiendotoxin pretreatment reduced the lethality of TFE from 80 to 20% of the rats, but did not prevent the other toxic effects of TFE. In vitro experiments with serum from TFE-pretreated rats (0.13 g/kg) supported the growth of an average of 65% fewer cultured bone marrow cell colonies compared to the number of colonies produced when serum from control rats was used. This suggests that TFE-induced bone marrow depression and leukopenia are related to a decrease in colony stimulating factor activity. Taken together these results explain the rapid development of lethal bacterial infections in TFE-treated rats. TFE-mediated damage to the small intestine combined with prolonged leukopenia decreases the resistance of the rat to endogenous pathogens leading to systemic bacterial infection. In addition, the increased sensitivity to endotoxin induced by TFE leads to lethal endotoxemia.

In vitro HeLa cell DNA synthesis. II. Partial characterization of soluble factors stimulating nuclear dna synthesis.

When HeLa cells are lysed in hypotonic buffer and the lysate is fractionated by centrifugation into particulate and soluble components, the particulate component (nuclei) is deficient compared to unfractionated lysate in the extent to which it can carry out in vitro DNA synthesis. In addition, rapidly labeled short DNA chains (Okazaki pieces) accumulate in purified nuclei, and are chased into higher molecular weight DNA to a lesser degree than in unfractinated lysate. When purified nuclei were reconstituted with soluble component, the capacity of the nuclei for in vitro DNA synthesis was fully restored, as was the capacity of the nuclei for conversion of Okazaki pieces to higher molecular weight DNA. This suggests that the soluble component contains a factor or factors necessary for normal DNA replication. The major incorporation-stimulating activity was partially characterized and partially purified from the soluble component. It is heat labile, non-dialyzable, partially recoverable in the supernatant after pH 5 precipitation, found mainly in a 55--85% saturated (NH4)2SO4 fraction, and is included on Sephadex G-100. After passage through Sephadex G-100, the activity displays increased instability to storage at either 4 degrees C or --70 degrees C. Part of the activity does not bind to phosphocellulose at pH 7.2 and low salt; no additional activity can be recovered in a 0.5 M KC1 wash of the phosphocellulose column. The Okazaki-piece-joining activity was found, along with the bulk of the incorporation-stimulating activity, in the 55--85% (NH4)2SO4 fraction. These findings provide some of the groundwork for future attempts to completely purify and characterize those activities in the soluble component of cell lysates which are involved in DNA replication.