The asymptotic expansion of certain canonical integrals

Integrals of the form $\text{I(λ) = ∝}{}_{\mathrm{R}}{}^2\text{?(}\text{x}\text{?}\text{)}\text{exp}\text{{iλφ(}\text{x}\text{?}\text{)} d}\text{x}\text{?}$, common in diffraction theory, are usually evaluated asymptotically for large λ using the stationary phase technique. At caustic points the classical technique is not applicable. A computation-oriented algorithm is developed for determining the asymptotic expansion of such integrals with $\text{φ(}\text{x}\text{)}$ a Thom umbilic, the canonical form appropriate at caustic points for most cases of physical interest.     

The reactions K−p → π∓Σ± at 4.2 GeV/c

We present differential cross sections and the Σ⁺ polarization for the reactions K^?p → π^?Σ^± using data from a high statistics bubble chamber experiment at 4.2 GeV/c incident momentum. The statistical level allows a detailed analysis of these reactions over the whole t range. Several significant structures are observed. Comparisons are made with SU(3)-related reactions; for backward production of π^?Σ⁺ such a comparison shows good evidence for Δ exchange. The exotic forward peak in K^?p → π⁺Σ^? is definitely confirmed.     

Non-strange vector meson production in K−p interactions at 4.2 GeV/c

The vector meson production, hypercharge exchange reactions K^?p → (φ, ω, ?) Λ and (φ, ?) Σ⁰ are studied at 4.2 GeV/c incident momentum. The data come from a high statistics bubble chamber experiment with a sensitivity of ～ 120 events/μb. Total and differential cross sections are presented. The vector meson density matrix elements and hyperon polarization are investigated as functions of momentum transfer. Amplitude analyses are performed for all five reactions. The results are compared with duality and quark model predictions, as well as used to test current ideas in two-body phenomenology.     

Remote electronic acquisition of soil cone index measurement

The cone penetrometer is widely used in tillage and off-road mobility research as an indicator of soil strength and density characteristics. Light-weight, manually operated units are especially useful in recording cone index determinations at remote field locations. Such units permit a single operator to measure and record penetration force vs depth in graphic form. However, the interpretation and analysis of such data has remained a tedious manual operation which has limited the number of determinations which are practical for a given field experiment. The system described in this paper allows one person to determine and electronically record penetration force vs depth relationships using a standard cone penetrometer (ASAE S313.1, 1979). A CMOS (complementary metal oxide semiconductor) microprocessor is utilized to sample and digitize analog signals and to record them on a magnetic tape cassette. An identifying code can be associated with each measurement and the microprocessor is subsequently utilized in interpreting cassette-stored data and transmitting it to a remote computer terminal or minicomputer for processing and analysis. Thus, this relatively low-cost system significantly enhances manual acquisition and interpretation of cone penetrometer measurements.     

Synthesis and cytotoxic activity of a series of diacetylenic compounds related to falcarindiol

The synthesis of a series of diacetylenic compounds related to the natural product falcarindiol has been carried out. Unsymmetrical diacetylenes were prepared by a modification of the Cadiot-Chodkiewicz coupling reaction, while a Glaser coupling was used to prepare symmetrical diacetylenes. These compounds have been tested for in vitro cytotoxic activity against Hep-G2, and H-4-II-E cell lines. Diacetylenes with additional unsaturation at C-1, 2, appended with hydroxyl groups at C-3 and C-8, or with long hydrophobic chains, exhibited IC50 values in the micromolar range.     

How to detect the Chandler and the annual wobble of the Earth with a large ring laser gyroscope

We demonstrate a 16 m(2) helium-neon ring laser gyroscope with sufficient sensitivity and stability to directly detect the Chandler wobble of the rotating Earth. The successful detection of both the Chandler and the annual wobble is verified by comparing the time series of the ring laser measurements against the "C04 series" of Earth rotation data from the International Earth Rotation and Reference System Service.     

Time resolved velocity map imaging of H-atom elimination from photoexcited imidazole and its methyl substituted derivatives

The photoresistive properties of DNA bases, amino acids and corresponding subunits have received considerable attention through spectroscopic studies in recent years. One photoresistive property implicates the participation of (1)πσ* states, allowing electronically excited states to evolve either back to the electronic ground state or undergo direct dissociation along a heteroatom-hydride (X-H) coordinate. To this effect, time-resolved velocity map imaging (TR-VMI) studies of imidazole (a subunit of both adenine and histidine) and methylated derivatives thereof have been undertaken, with the goal of understanding the effects of increasing molecular complexity, through methylation, on the dynamics following photoexcitation at 200 nm. The results of these measurements clearly show that H-atom elimination along the N-H coordinate results in a bimodal distribution in the total kinetic energy release (TKER) spectra in both imidazole and it's methylated derivatives: 2-methyl, 4-methyl and 2,4-dimethylimidazole. The associated time constants for H-atoms eliminated with both high and low kinetic energies are all less than 500 fs. A noticeable increase in the time constants for the methylated derivatives is also observed. This could be attributed to either: ring methylation hindering in-plane and out-of-plane ring distortions which have been implicated as mediating excited state dynamics of these molecules or; an increase in the density of vibrational states at 200 nm causing an increased sampling of orthogonal modes, as opposed to modes which drive any dynamics that cause subsequent H-atom elimination. The results of these findings once again serve to illustrate the seemingly ubiquitous nature of (1)πσ* states in the photoexcited state dynamics of biomolecules and their subunits.