Determination of relative signs of 13C?13C coupling constants in doubly labelled compounds

Analysis of the noise decoupled ¹³C spectra of doubly ¹³C labelled compounds where the two labelled carbons are identical, makes the determination of reltive signs of ¹³C? ¹³C coupling constants possible in a very simple way. The involved carbon form AA'X or AA'B spin systems.     

SU (2) lattice gauge theory and Monte Carlo calculations

Monte Carlo results for theSU (2) lattice gauge theory in four dimensions are presented. The string tension is measured with high statistics and also the mass of the perimeter term is determined. Wilson loop-plaquette correlations, which are related to roughening, are measured.     

Wine analysis: Study and comparison of techniques developed for the study of volatile constituents

Summary A number of headspace techniques have been compared, using a standard solution containing 12 compounds and a wine sample, viz.: (1) purge and cold trap injection; (2) dynamic headspace combined with liquidliquid extraction; (3) static headspace with and without preconcentration; (4) direct liquid injection. The sensitivity, reproducibility and speed of analysis were determined. Considering the results obtained and dependent on the purpose of the experiments and the number of samples to be examined the appropriate technique can be selected.     

Optimal replacement policies for two-unit machines with increasing running costs 1

A machine consists of two stochastically failing units. Failure of either of the units causes a failure of the machine and the failed unit has to be replaced immediately. Associated with the units are running costs which increase with the age of the unit because of increasing maintenance costs, decreasing output, etc.A preventive replacement policy is proposed under which, at failure points, we also replace the second unit if its age exceeds a predetermined control limit. It is proved that, for two identical units with exponential life-time distributions and linear running costs, this policy is optimal and the optimal control limit is calculated. In an additional model we take into consideration the length of time it takes to replace one unit or both units.The method of solution is a variation of dynamic semi-Markov programming. Analytical results are obtained and the influence of the various parameters on them is investigated. Finally, we study the saving due to our policy in comparison with a policy in which only failed units are replaced.     

Random paths and random surfaces on a digital computer

We describe a local stochastic process that generates statistical ensembles of paths (or surfaces) with a Boltzmann probabilistic weight. The method is expected to be applicable to Monte Carlo simulations of field theories that contain fermions, to the roughening transition and to a reformulation of gauge theories in terms of random surfaces.     

Critical behaviour in baryonic matter

First we consider the phenomenology of deconfinement and chiral symmetry restoration for strongly interacting matter at non-vanishing baryon number density. Subsequently, we present numerical results obtained by a Monte Carlo evaluation of statistical QCD on an 8³×3 lattice, using Wilson fermions withN _f =2, in fourth order hopping parameter expansion, and suppressing the imaginary part of the fermion action. We consider baryonic chemical potentials up to μa=0.6μa=0.6 (μ/Λ _L ?200); in this range, the critical parameters for deconfinement and chiral symmetry restoration are found to coincide.     

Exact finite-range DWBA description of the60Ni(160,12C)64Zn reaction at 60 MeV incident energy

Cross section angular distributions of⁶⁰Ni(¹⁶O,¹²C)⁶⁴Zn reactions leading to three strongly excited states at 60 MeV incident energy and the¹⁶O+⁶⁰Ni and¹²C+⁶⁴Zn elastic scattering at 60 MeV respectively 45 MeV and 54 MeV have been measured using aQ3D magnetic spectrograph. EFR-DWBA calculations assuming the transfer of anα-cluster in its 0s ground state are able to describe the general features of the strongly oscillating experimental angular distributions using a surface transparent optical model potential. The optical model parameters used in the DWBA calculations are obtained from fits of the elastic scattering data of incident and exit channels. The importance of “correct” optical model parameters in the exit channels for relative spectroscopic factors will be discussed and the extracted relative spectroscopic factors will be compared to previous (⁶Li,d) results.     

A rapid and economical method for hybrid purity testing of tomato (Lycopersicon esculentum L.) F1 hybrids using ultrathin-layer isoelectric focusing of alcohol dehydrogenase variants from seeds

In the cultivated tomato (Lycopersicon esculentum L.), two electrophoretic variants of the enzyme alcohol dehydrogenase (ADH) encoded by the alleles Adh-1+ and Adh-1(1) are found. A rapid and economic method for testing the hybrid purity of tomato F1 seeds, based on the expected presence of Adh-1 alleles, was developed. The method is based on the analysis of the ADH variants by ultrathin-layer isoelectric focusing, pH range 3-10, of crude extracts from imbibed seeds, followed by enzyme activity staining. The isoelectric points (pI's) of the ADH variants were estimated to be 5.5 and 5.7 for Adh-1+ and Adh-1(1), respectively. Using the procedure described and a newly developed sample applicator strip, it is possible for one person to routinely analyze 1152 seeds per day using only a single electrophoresis unit. An investigation of a large number of inbred lines, both experimental and commercial hybrids, together with open-pollinated varieties, showed the potential of the method. Among F1 hybrids, a higher frequency of the Adh-1(1) allele was found than among open pollinated varieties, suggesting that F1 hybrid breeding has resulted in a higher frequency of Adh-1(1) alleles by selection of linked genes.     

Comparison between spectrophotometric and chemiluminescence detection in enzyme immunoasays for nortestosterone

Steroid solid-phase immunoassays with peroxidase labels were examined with two detection methods. Immunoassays were applied for 19-nortestosterone (NT) by using a solid phase coated with a second antibody and a solid phase coated directly with NT-antibody. For end-point detection, either an enzyme-enhanced chemiluminescence procedure or spectrophotometry based on tetramethylbenzidine was used. Both methods gave similar calibration graphs. The chemiluminescence procedure, in which a new commercial microtitre-plate luminometer was used, was more sensitive and the second-antibody immunoassays provided lower limits of detection.