Physical mapping of cleavage sites recognized by restriction endonucleases on the genome of bacteriophage T5

The DNA of bacteriophage T5 has been treated with restriction endonucleases EcoRI, HindIII, BamI, SmaI, PstI, SalI, KpnI and the electrophoretic pattern obtained in agarose gel has been analyzed in order to localize the specific cleavage sites on the T5 DNA. The localization of cleavage sites has been reduced from the electrophoretic pattern of double and partial digests, the digests of isolated restriction fragments and the digests of deletion mutant T5st(o) DNA. Four BamI cleavage sites have been found and localized on the physical map of T5 DNA at 0.21, 0.225, 0.685 and 0.725 fractional length. Endonuclease SmaI cleaves at 0.39, 0.59 and 0.69 fractional length. Endonuclease PstI cuts T5 DNA at 11 sites: 0.090, 0.210, 0.320, 0.510, 0.635, 0.670, 0.705, 0.770, 0.815, 0.840, 0.875 fractional length. Six KpnI cleavage sites have been mapped at 0.170, 0.215, 0.525, 0.755, 0.830, 0.850 fractional length. A complete cleavage map of the phage genome is presented for seven restriction enzymes.     

Simulation on the thermal cycle of a welding process by space–time convection–diffusion finite element analysis

Welding plays an important role in manufacturing. But difficulties still exist for simulation of the welding process of large welded structures, due to the limitation of computer capacity, mathematical models and software. This paper is devoted to developing an algorithm that tries to simulate the thermal cycle during welding efficiently and accurately. A space–time finite element method (FEM) is proposed to solve the transient convection–diffusion thermal equation. The method has been applied to the steady-state thermal analysis of welds. A moving coordinate frame (Eulerian frame), in which the heat source is stationary, is used to improve the spatial resolution of a numerical analysis for the thermal cycle of welds effectively, as well as to incorporate the addition of the filler metal naturally. This method is suitable for the thermal analysis in the weld pool or/and weld joint region including starting and stopping transients.     

Analysis of predicted residual stress in a weld and comparison with experimental data using regression model

Residual stress in a welded plate is computed in the first part of the paper using a weld analysis software program VrWeld () that computes the 3D transient temperature field, the evolution of micro-structure and the evolution of stress-strain fields. The computed residual stress is compared to the residual stress distribution measured by Paradowska (J Mater Process 164–165:1099–1105, 2005) with a neutron diffraction method to show that the computational model captures the physics well. Two uncertainty analyses are conducted in the second part to investigate the question of how variations in parameters contribute to the result from part one provided that computational model can predict residual stress well resulted in part one. The difference between the two is the number of parameters. The former has only one parameter and we employed the computational model for perturbation analysis in order to find the uncertainty due to perturbation in the parameter. For such a test, the number of test required in sample space to approximate normality by central limit theorem, is feasible considering computational resources although it is not true when we have higher number of interrelated parameters. The latter therefore has 4 highly interrelated parameters to show that an alternative way can be employed instead of using directly computational model for such a case. Uncertainty analyses are based on Monte Carlo method in this paper and the idea is that if numerical modeling is valid and also there is a need for a great number of tests for Monte Carlo analysis that make it unfeasible to run such an analysis directly by computational model then extracting a regression model from the computational model and working with it, is an effective alternative.     

New methods of signal excitation and processing in magneto-inductive testing of structures and alloys

This paper describes some results of applying noise excitation to eddy current testing. Pseudo random binary sequences (PRBS) were used as a noise equivalent. The advantage of this technique compared with conventional methods is mainly the simplicity of the equipment used. It is possible to produce a device using noise excitation on the basis of a microcalculator. Also, this technique gives a direct comparison between the reference object and the object under test as in the well known CS (controlled signals) method. The performance of the PRBS method is compared with a multifrequency eddy current method by solving the problem of separating various grades of steel. Both methods show nearly the same results.     

Sustained net CO2 evolution during photosynthesis by marine microorganisms

BACKGROUND: Many aquatic photosynthetic microorganisms possess an inorganic-carbon-concentrating mechanism that raises the CO2 concentration at the intracellular carboxylation sites, thus compensating for the relatively low affinity of the carboxylating enzyme for its substrate. In cyanobacteria, the concentrating mechanism involves the energy-dependent influx of inorganic carbon, the accumulation of this carbon--largely in the form of HCO3(-)-in the cytoplasm, and the generation of CO2 at carbonic anhydrase sites in close proximity to the carboxylation sites. RESULTS: During measurements of inorganic carbon fluxes associated with the inorganic-carbon-concentrating mechanism, we observed the surprising fact that several marine photosynthetic microorganisms, including significant contributors to oceanic primary productivity, can serve as a source of CO2 rather than a sink during CO2 fixation. The phycoerythrin-possessing cyanobacterium Synechococcus sp. WH7803 evolved CO2 at a rate that increased with light intensity and attained a value approximately five-fold that for photosynthesis. The external CO2 concentration reached was significantly higher than that predicted for chemical equilibrium between HCO3- and CO2, as confirmed by the rapid decline in the CO2 concentration upon the addition of carbonic anhydrase. Measurements of oxygen exchange between water and CO2, by means of stable isotopes, demonstrated that the evolved CO2 originated from HCO3- taken up and converted intracellularly to CO2 in a light-dependent process. CONCLUSIONS: We report net, sustained CO2 evolution during photosynthesis. The results have implications for energy balance and pH regulation of the cells, for carbon cycling between the cells and the marine environment, and for the observed fractionation of stable carbon isotopes.