The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction.

The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subångström length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the subpicosecond timescale.

Imaging Molecular Motion: Femtosecond X-Ray Scattering of an Electrocyclic Chemical Reaction.

Structural rearrangements within single molecules occur on ultrafast time scales. Many aspects of molecular dynamics, such as the energy flow through excited states, have been studied using spectroscopic techniques, yet the goal to watch molecules evolve their geometrical structure in real time remains challenging. By mapping nuclear motions using femtosecond x-ray pulses, we have created real-space representations of the evolving dynamics during a well-known chemical reaction and show a series of time-sorted structural snapshots produced by ultrafast time-resolved hard x-ray scattering. A computational analysis optimally matches the series of scattering patterns produced by the x rays to a multitude of potential reaction paths. In so doing, we have made a critical step toward the goal of viewing chemical reactions on femtosecond time scales, opening a new direction in studies of ultrafast chemical reactions in the gas phase.

Confinement of lactating sows in crates for 4 days after farrowing reduces piglet mortality.

To reduce mortality among suckling piglets, lactating sows are traditionally housed in farrowing crates. Alternatively, lactating sows can be housed in farrowing pens where the sow is loose to ensure more behavioural freedom and consequently a better welfare for the sow, although under commercial conditions, farrowing pens have been associated with increased piglet mortality. Most suckling piglets that die do so within the first week of life, so potentially lactating sows do not have to be restrained during the entire lactation period. Therefore, the aim of the current study was to investigate whether confinement of the sow for a limited number of days after farrowing would affect piglet mortality. A total of 210 sows (Danish Landrace × Danish Yorkshire) were farrowed in specially designed swing-aside combination farrowing pens measuring 2.6 m × 1.8 m (combi-pen), where the sows could be kept loose or in a crate. The sows were either: (a) loose during the entire experimental period, (b) crated from days 0 to 4 postpartum, (c) crated from days 0 to 7 postpartum or (d) crated from introduction to the farrowing pen to day 7 postpartum. The sows and their subsequent litters were studied from introduction to the combi-pen ∼1 week before expected farrowing and until 10 days postpartum. Confinement period of the sow failed to affect the number of stillborn piglets; however, sows that were crated after farrowing had fewer live-born mortality deaths (P < 0.001) compared with the sows that were loose during the experimental period. The increased piglet mortality among the loose sows was because of higher mortality in the first 4 days after farrowing. In conclusion, the current study demonstrated that crating the sow for 4 days postpartum was sufficient to reduce piglet mortality.

Effect of pulse shape on the efficiency of multiphoton processes: implications for biological microscopy.

The effects of spectral shape on two photon fluorescence excitation are investigated experimentally using an acousto-optic pulse shaper to modify femtosecond pulses from a Ti:sapphire laser. By using different spectral window shapes, we find that the measured two photon efficiency can vary by a factor of 2 for differently shaped spectra with the same full width at half maximum. We find that these effects are described well by a simple model assuming transform-limited pulses. The fact that even small changes in the spectral wings can significantly affect the efficiency of nonlinear processes has implications for biological multiphoton imaging, where it may be desirable to minimize sample exposure to radiation and maximize fluorescence or harmonic efficiency. © 1999 Society of Photo-Optical Instrumentation Engineers.

Continuous-wave oscillation of thulium-sensitized holmium-doped silica fiber laser.

We have observed oscillation in a Tm(3+) and Ho(3+) codoped silica fiber from the (5)I(7) ? (5)I(8) transition of Ho(3+) in the 2-microm region, by pumping the fiber laser into a Tm(3+) absorption between 800 and 830 nm. By a change in the cavity length, the laser was tunable between 2.037 and 2.096 microm. When the laser was pumped with a Ti:sapphire laser at 820 nm, an absorbed threshold power extracted power of 214mW, a slope efficiency of 4.2%,and maximum extracted power of 12.5 mW were measured.

Broadband superfluorescent emission of the (3)H(4) ? (3)H(6) transition in a Tm-doped multicomponent silicate fiber.

We report the observation of amplified spontaneous emission in the (3)H(4) ? (3)H(6) transition of Tm(+3) in a Ta(2)O(5)-doped multicomponent silicate fiber. The evolutions of the spectral shape, output power, and center wavelength were measured as a function of fiber length and pump power in the previously unstudied high-power range, where saturation effects dominate. An output power of 1 mW has been achieved at 1.91 microm with a bandwidth of 77 nm.

Indium-111 leukocyte imaging in appendicitis.

Indium-111-labeled leukocyte scintigraphy was applied to the diagnosis of acute appendicitis. Thirty-two patients observed in the hospital for possible appendicitis were prospectively studied. Scanning was done 2 hr after radiopharmaceutical injection. Thirteen scans were positive for acute appendicitis, and all but one were confirmed at laparotomy. In addition, two cases of colitis and two cases of peritonitis were detected. Of 15 negative studies, 11 had a benign course. Four patients with negative studies had laparotomy; two were found to have appendicitis and two had a normal appendix. Of 14 proven cases of appendicitis, 12 scans were positive for appendicitis with one false-positive scan, providing a sensitivity of 86%. Specificity was 93%: all negative cases except one had negative scans. Overall accuracy was 91% (29 of 32), comparing favorably with the accepted false-positive laparotomy rate of 25%. Use of In-111-labeled leukocyte scintigraphy serves to reduce the false-positive laparotomy rate and to shorten the clinical observation time in patients with acute appendicitis.

[Acute mucosal damage of the stomach of the Wistar rat and its prevention with the drug combination droperidol/atropine--an animal experiment study]. / Der akute Schleimhautschaden des Magens der Wistar-Ratte und dessen Prophylaxe mit der Pharmakakombination Droperidol/Atropin - eine tierexperimentelle Untersuchung.

The employment of the alpha receptor blocking Droperidol with and without combination of atropine for prophylaxis of the acute mucosal damage of the stomach was investigated in the experimental animal Wistar rat. The immobilisation stress in the stress roll was chosen as stress model. The animals get an infusion programme by a central venous catheter. The stomachs were searched for macroscopic mucosal changes after an immobilisation period of 6 hours. The results were certained statistically. The acute mucosal damage in the rat stomach could be prevented in 100% (p 0.05) by means of the drug combination Droperidol/atropine (IV).

Diagnosis of acute cholecystitis using hepatobiliary scan with technetium-99m PIPIDA.

Sixty patients were evaluated for acute abdominal pain using technetium-99m PIPIDA hepatobiliary imaging. The sensitivity of the test was 90.6 percent in all patients and the accuracy was 93.3 percent. In the evaluation of acutely ill patients with right upper quadrant pain, fever, nausea and vomiting, hepatobiliary imaging with PIPIDA is the preferred test for diagnosing acute cholecystitis. If the test is positive, disease of the gallbladder and probably acute cholecystitis are present. Early operation can proceed if desirable. If the test is negative and the bilirubin level is less than 5.0 mg/dl, acute cholecystitis is not present. In such cases conservative treatment is appropriate, and follow-up tests should be performed to evaluate the possibility of chronic cholecystitis. When the bilirubin level exceeds 5.0 mg/dl, the test is often indeterminate.

Double-antibody radioimmunoassay of thyroid microsomal antibody in serum.

We describe a double-antibody radioimmunoassay for antimicrosomal antibodies in serum. Antigen in centrifuged pellets of microsome is solubilized by treatment with sodium deoxycholate solution and radiolabeled (125I] by the Chloramine T method. A 10-microL aliquot of human serum or antimicrosomal antibody standard is incubated overnight at room temperature with 125I-labeled microsome. Bound radiolabeled microsome is separated by precipitation with goat antihuman IgG antiserum. The percentage of 125I-labeled microsome bound by each serum is calculated, and its concentration of antimicrosomal antibody interpolated from a standard curve. The prevalence of abnormal antimicrosomal antibody was 16% in a self-referred asymptomatic or not acutely ill group of patients having a periodic multiphasic health examination. Values for patients with certain thyroid diseases generally agreed with other published data. We conclude that our assay is sensitive, precise, and accurate, and is more efficient for routine measurement of antimicrosomal antibody than the currently used solid-phase radioimmunoassay.

Detecting unsuspected thyroid dysfunction by the free thyroxine index.

The free thyroxine index (FTI) was used in 2,704 adults to detect unsuspected thyroid dysfunction. Among 2,581 adults found to be clinically euthyroid without thyroid medication, 2,571 had a truly normal FTI (121 to 360) and ten had a falsely abnormal FTI (seven less than 121, three greater than 360). Among 25 subjects with newly diagnosed thyroid dysfunction, there were eight hyperthyroid (prevalence, 0.31%) and 14 hypothyroid (prevalence, 0.50%) subjects. The sensitivity of the FTI was 1.0, and the specificity was 0.996. The predictive value of an abnormal FTI with a prevalence of 0.81% was 67%. The cost to find a new case averaged $127. The annual incidence of symptomatic hyperthyroidism was 0.05%; of hypothyroidism, about 0.08%. We conclude that the FTI is cost-effective for case finding in thyroid dysfunction.

[Surgical intervention in cases of gastro-duodenal ulcer bleeding (author's transl)]. / Chirurgische Intervention bei Blutungen aus gastroduodenalen Ulzera.

Results in the treatment of the bleeding gastro-duodenal ulcer during a period of 21 years are analysed. The results refer to an early surgery intervention. A bleeding-stop must be tried, particularly in the elderly patient. If possible a causal therapy should be performed.