Lipase production in continuous culture of Candida rugosa

The yeast Candida rugosa produces multiple extracellular lipases. The production of extra‐ and intracellular lipases was investigated in continuous cultures using a sole or different mixtures of carbon sources. Also, the effect of different C:N ratios was tested. Lipase productivity in continuous cultures increased by 50% compared with data obtained from batch fermentations and depended on the dilution rate applied. Maximum yields relative to consumed substrate were obtained with oleic acid at low dilution rate. It was found that during nitrogen limitation, lipase activity was suppressed. All carbon source mixtures tested allowed both cell growth and lipase production, but extra‐ and intracellular lipase activities were affected by the combination of substrates used. Maximum extracellular lipolytic productivity was attained with lactic and oleic acid mixtures, probably due to the non‐repressor effect of these carbon sources. The chemical composition of the biomass also depended on the type of substrate used and was related to the accumulation of lipidic compounds as intracellular inclusions, which were observed when oleic acid was used as the carbon source. The results obtained were compared with previous data from batch and fed‐batch cultures in order to select the best process strategies for the lipase production with C rugosa. The best lipase yields were obtained in fed‐batch fermentations using oleic acid. Copyright © 2003 Society of Chemical Industry     

Centrifuge Modeling of Earthquake Effects on Buried High-Density Polyethylene (HDPE) Pipelines Crossing Fault Zones

Permanent ground deformation is a severe hazard for continuous buried pipelines. This technical paper presents results from four centrifuge tests designed to investigate the influence of pipe-fault orientation on pipe behavior under earthquake faulting. The experimental setup and procedures are described, and the test results are presented. The test results show that, as expected, pipe axial strain is strongly influenced by the pipe-fault orientation angle, whereas the influence of pipe-fault orientation angle on pipe bending strain is minor. The measured pipe strains were shown to follow the trend predicted by the Kennedy model. Also, through a parametric study using the Kennedy model, the experimental data were extrapolated for cases of pipeline with longer unanchored length. By combing the data from strain gauges and tactile pressure sensors, transverse force–deformation relations or p–y relations for the pipe were determined. The data indicates that the underlying p–y relationship varies along the length of the pipe with a stiffer p–y relationship at points closer to the fault and a softer p–y relationship at points farther away. The stiffer p–y relationship, appropriate for locations moderately close to the fault, was compared with the ASCE Guidelines in 1984 and Turner’s recommendation in 2004 for moist sand. It was found that the force level for the plastic p–y behavior in the centrifuge tests compared favorably with that in the ASCE Guidelines (1984).     

Recent advances in scanning x-ray microscopy

A scanning x-ray microscope has been built at the Daresbury synchrotron radiation source and used to obtain images at soft x-ray wavelengths (～2–4 nm). The focusing element of the microscope is a zone plate, fabricated by a contamination writing process developed at King's College. Zone plates with the finest zone widths, and hence theoretical resolutions, below 20 nm have been fabricated in this way. The contamination material is carbon, and as such is unsuitable for high-efficiency focusing. In order to increase the zone plate efficiency, a shadowing pattern transfer process has been developed and used to replicate contamination lines with 25 nm widths into more suitable materials.     

Nondestructive characterization of the mechanical strength of diffusion bonds. II. Application of a quasi-static spring model

It has been shown that the acoustic response of imperfect interfaces may be described by a quasi-static spring model. In the present paper, experimental data on the geometry of the contacts between two diffusion-bonded blocks have been used to determine the spring stiffness of such interfaces which have been correlated with experimentally determined ultrasonic reflection coefficients. The correlation between the theoretical reflection coefficient and the spring stiffness was found to be in excellent agreement with experimentally-observed values, if the disbonds are of infinitesimally small thickness. For disbonds of finite thickness, the agreement is less satisfactory. Reasons for the discrepancy in the latter case are unknown at the present time.     

Collision Detection for Animation using Sphere-Trees

The detection of collisions between moving polyhedral objects is one of the most computationally intensive tasks in the computer animation process. The use of object-oriented techniques to encapsulate data within the objects' structures compounds this problem through the requirement for inter-object message passing in order to obtain geometric information for collision detection. The REALISM system decreases the time for collision detection by using a three stage process. The first stage identifies objects in the same locality using a global bounding volume table. The second stage locates regions of possible collision using a sphere-tree data structure (a hierarchical tree of spheres based on octree-type spatial subdivision). The final stage finds intersections between polygonal faces of the objects that are contained within the intersecting pairs of leaf nodes. Hence the algorithm uses a spherical geometry approximation rapidly to locate regions of potential collisions and then uses a local intersection test with actual object geometry information. The system is therefore fast and accurate. Tests for various geometric objects support this and show performance improvements of jive times over traditional polyhedral intersection tests.     

Review of the Year,Part II: 2001: A game of two halves

In Part 1 of this Review, we got as far as the middle of the year. The economic climate was driving a lot of discussion and technology usage seemed to take second place to what was economically viable. The major event of this year took place in September, but we still have a little way to go before we get there. And, don’t forget to check out our predictions for 2002 as well. But enough of the doom and gloom, let’s kick off Part II by revisiting some moments the world’s largest software firm would rather forget…     

Three-dimensional motion and reconstruction of coronary arteries from biplane cineangiography

A new approach is described for reconstructing coronary arteries from two sequences of projection images. The estimation of motion is performed on three-dimensional line segments (or centrelines), and is based on a ‘predictionprojection-optimization’ loop. The method copes with time varying properties, deformations and superpositions of vessels. Experiments using simulated and real data have been carried out. and the results found to be robust over a full cycle of a human heart. Local and global kinetic features can then be derived to obtain a greater insight on the cardiac functional state     

Morphology of peripheral airways in current smokers and ex-smokers

To investigate the effect of smoking status on pulmonary function and pathologic changes in the peripheral airways, we studied 97 patients who underwent thoracotomy for coin lesions. The patients were divided into 4 groups: nonsmokers (n = 9), current smokers (n = 51), and those who had ceased smoking for less than (n = 18) or more than (n = 19) 2 yr prior to surgery. We found that current smokers had evidence of air-flow obstruction with abnormal lung volumes when compared with nonsmokers. Ex-smokers had lung volumes similar to those of nonsmokers, but showed evidence of obstruction, with the FEV1/FVC between the values found for nonsmokers and current smokers. Examination of the small airways showed that the membranous bronchioles of current smokers and ex-smokers displayed only increased goblet cell metaplasia when compared with those in nonsmokers; the respiratory bronchioles of current and ex-smokers showed increases in intraluminal and airway wall inflammatory cells, wall fibrosis, and pigment deposition. We conclude that patients who currently smoke cigarettes have reduced lung function that is associated with abnormalities of airway structure. Although those who have stopped smoking have function that is closer to the nonsmoking group, there is no apparent difference in structural change between current and ex-smokers.