Measurement of elastin hydrolysis by reverse-phase HPLC with on-line post-colum derivatization

Summary Excessive breakdown of elastin, a structural protein, may be related to aortic disease and emphysema. Since L-valyl-L-proline occurs in high concentrations in elastin, a rapid and sensitive method using HPLC with post-column on-line derivatization was used to measure the dipeptide from swine aortic tissue, and the amount of elastin present was determined. Elastin was extracted by alkaline hydrolysis. After neutralization and filtration, the sample was injected onto a ODS-2 gel column, and the dipeptide was eluted by a linear gradient of 0 to 10% of 1-propanol in 50 mM heptafluorobutyrate, pH 3, at a flow rate of 1 ml/min. The eluent was reacted with fluorescamine at pH 8.6, and fluorescence was detected at an excitation wavelength of 395 nm and a 455 nm cutoff emission filter.Presented at the 17th International Symposium on Chromatography, September 25–30, 1988, Vienna, Austria.     

Preparation of rhodium–phyllosilicate catalysts without leaching in liquid-phase 1-hexene hydrogenation

Rhodium catalysts have been prepared on palygorskite and montmorillonite (clay) supports by reduction with hydrogen (1 atmosphere) at room temperature of a cationic organometallic rhodium compound anchored to the support. The activity of these catalysts for the hydrogenation of liquid-phase 1-hexene remains constant with increase of prehydrogenation time and with re-use for several runs. No rhodium leaching is observed.     

The auction algorithm for the transportation problem

The auction algorithm is a parallel relaxation method for solving the classical assignment problem. It resembles a competitive bidding process whereby unassigned persons bid simultaneously for objects, thereby raising their prices. Once all bids are in, objects are awarded to the highest bidder. This paper generalizes the auction algorithm to solve linear transportation problems. The idea is to convert the transportation problem into an assignment problem, and then to modify the auction algorithm to exploit the special structure of this problem. Computational results show that this modified version of the auction algorithm is very efficient for certain types of transportation problems.     

Plasma parameters within the cathode spot of the vacuum arc

The composition of the vacuum arc plasma for five elements (Cd, Mg, Al, Ni, and Mo) is calculated by the Saha equation, which assumes local thermodynamic equilibrium conditions within the ionization region of the cathode spot(s). The lowering of the ionization potential due to the high density of charged particles is considered. By matching the computed and the measured plasma ionic composition, the electron density and the temperature are estimated. The experimental plasma compositions can be approximated only at a high electron density (10¹⁹-10 ²¹ cm^-3) and at electron temperatures in the range of a few electronvolts     

The effect of traffic noise on sleep of young adults in their homes

The disturbance of sleep by traffic noise is a major problem area in noise pollution. Extensive laboratory tests using multichannel electroencephalograms (EEG) have been carried out by many workers to determine the general response of people when exposed to noise during sleep. An experimental technique for obtaining results in people's homes has been developed using a simplified one-channel EEG. The responses of six people in the age range 19-24 were measured. A significant correlation was found between sleep disturbance and traffic noise when the noise is expressed in EPNdB. In the home experiments the subjects appeared to be approximately 10 dB less sensitive to noises than laboratory subjects for similar noise exposure. There also appeared to be some adaptation to the noise exposure; however, only one subject was tested for a period of 20 days and was insufficient to give definite results on adaptation.     

Observation of nucleon clusters in the spontaneous decay of234U

The emission of Ne and Mg nuclei was detected in the spontaneous decay of²³⁴U with probabilities of, respectively, (3.9 ±1.0) × 10^?13 and (2.3 ±0.7) × 10^?13 relative toα-decay. The upper limits of this kind of decay for²³⁵U and²³⁶U have been established. Systematics of half-lives for cluster emission are found to be similar to the Geiger-Nuttall dependence forα-decay. Some evidence for the presence of hindrance to cluster emission from the odd-mass nuclei²³³U and²³⁵U is obtained.