Mid-infrared spectroscopy of erbium doped chloride laser crystals.

We report on a spectroscopic analysis of ErCl3 and 1% Er 3+:YCl3 to determine their potential as possible laser sources at 3.5 and 4.5 mm. Concentration quenching of the low lying excited states is reported to be surprisingly very weak in this system. Although some shortening of the lifetimes is measured in the fully concentrated system, they retain lifetimes that are of order several milliseconds or more. A Judd-Ofelt analysis is performed and the projected gains for the 3.5 and 4.5 mm transitions are calculated. Successful growth techniques of erbium doped chlorides are also described.

High-average-power operation of a Q-switched diode-pumped holmium laser.

We have investigated high-peak- and high-average-power operation of diode-pumped, thulium-sensitized, holmium 2.1-microm lasers. Free-running laser powers of 14 W at 29 Hz have been demonstrated with 2.6% electrical efficiency. Q-switched operation produced average powers in excess of 11 W in a burst of short pulses. Preliminary optical parametric oscillator frequency conversion of the holmium laser to 4 microm is also reported.

Ar(2) excimer emission from a pulsed-discharge-excited pulsed supersonic gas jet.

We report what is to our knowledge the first observation of argon excimer fluorescence between 115 and 140 nm in a pulsed supersonically cooled gas jet after pulsed-discharge excitation. The emission is observed for measured pressures at the supersonic orifice greater than 3 atm.

Laser beam propagation in turbulent conditions.

Diffraction-limited low power laser beams at 1.06 and 3.8 microm were focused by a 91-cm diam aperture onto a receiver located 10.5 km away on a low slant angle path over a desert basin. The analysis of beam areas and turbulence levels was used to determine a new scaling law for tilt-corrected turbulence-induced beam spread.

Stereochemical effect in the mutagenicity of the aflatoxicols toward Salmonella typhimurium.

The mutagenicities of [1R] and [1S] aflatoxicol were measured using the Salmonella microsome test. In strain TA100 the [1R] form (unnatural aflatoxicol, aflatoxicol B) had a mutagenic potency approximately four times that of the [1S] epimer (natural aflatoxicol, aflatoxicol A, Ro) in the presence of S-9 liver microsomal fraction. The order in mutagenic potency compared to some other toxicologically important aflatoxins was as follows: B1 greater than [1R] approximately equal to G1 much greater than [1S] much much greater than B2. Thus, the trans relationship between the vinyl ether and hydroxyl groups leads to greater mutagenicity than the cis relationship. This may be important in the elucidation of stereochemical structure-activity relationships for the aflatoxins.

The direct mutagenicity of aflatoxin B1 and metabolites to Salmonella typhimurium: structure mutagenicity relationships and mechanisms of action.

The non-microsomal mutagenesis of a series of aflatoxins in Salmonella typhimurium TA100 and TA98 was evaluated. Aflatoxin B1 had the highest direct or non-microsomal potency. However, the order of direct mutagenic activity as compared to indirect or microsomal activity was as follows; aflatoxin Q1 much greater than G1 greater than B1 greater than aflatoxicol. This order was determined using a new plotting strategy for identification of direct contribution to the mutagenesis, an I-D graph (indirect vs. direct activities). It is suggested from our analyses that the fused carbonyl bearing rings in aflatoxins are necessary for direct mutagenesis. This activity is facilitated by oxygen substitution at the terminal carbonyl ring. On the other hand, the cyclopentene structure may either attenuate or amplify the microsome mediated mutagenesis which is assumed to be produced by the vinyl ether portion of the molecule. This was dependent upon substitution at the cyclopentene. Stereo-sensitivity was revealed by the greater mutagenicity of unnatural aflatoxicol over the natural epimer. These observations point to a need for further study of direct binding and transmolecular-structure-activity relationships in order to fully develop the mechanism of aflatoxin mutagenicity.

New low-bleed implant--Silastic II.

A new low-bleed breast implant has been tested both clinically and experimentally. In the guinea pig, two-thirds of the capsules are thin; there is less inflammation and less foreign body reaction than we have seen in previous implants. Evaluations by various investigators show good patient and surgeon acceptance of the new low-bleed implants.

A methodologic framework to study nurse-patient communication.

Communicative interaction patterns among nurses and patients in a complex hospital setting were examined, using the methodologic framework, synchronology. Extensive videotaped time-series data of patient-health care personnel interactions, involving four patients admitted for elective surgery, were collected approximately 16 hours a day from admission to discharge and computerized in both mnemonic word form and numeric files. These interactional data were instrumental in the methodologic development. Communicative interaction is conceptualized as a dynamic, ongoing behavior process which can be studied by identifying the observed effects of presenting behaviors on the participants. The process is complex, contex-related, and multivariate in nature. Synchronology provides a structure for in-context description and analysis of the complex verbal and nonverbal interaction patterns, preservation of multivariate data, and identification of key concepts in human interaction which are of use in education, practice, and research.

Kinetic Mass Spectrometric Investigation of the Ion-Molecule Reactions Occurring in C4 and C5 Alkanes Following Photoionization at 106.7 and 104.8 nm.

The photoionization of C4 and C5 alkanes has been investigated at 106.7 and 104.8 nm in a mass spectrometer specifically designed for the investigation of ion-molecule reactions occurring at thermal kinetic energies. Absolute rate constants are reported for the reactions of various fragment ions with the corresponding parent molecule. The rate constants found for reactions of sec - C 3 H 7 + ions with i-C4H10, n-C4H10, i-C5H12, and n-C5H12 were found to be 3.3, 4.4, 4.7, and 5.2 × 10-10 cm3/molecule-second respectively. The C 4 H 9 + ions were also found to be highly reactive, exhibiting rate constants of 3.6 and 3.8 × 10-10 cm3/molecule-second in reactions with i-C5H12 and n-C5H12. The rate constants for reaction of C 3 H 6 + with i-C4H10, n-C4H10, i-C5H12, and n-C5H12 were found to be 4.9, 4.9, 7.6, and 7.9 × 10-10 cm3/molecule-second, respectively. Butene ions are less reactive by an order of magnitude. The results are compared with complementary data derived from electron impact experiments, and the relationship between the structure and reactivity of the various ions is discussed.