Acid-growth response and alpha-expansins in suspension cultures of bright yellow 2 tobacco

The possibility that Bright Yellow 2 (BY2) tobacco (Nicotiana tabacum L.) suspension-cultured cells possess an expansin-mediated acid-growth mechanism was examined by multiple approaches. BY2 cells grew three times faster upon treatment with fusicoccin, which induces an acidification of the cell wall. Exogenous expansins likewise stimulated BY2 cell growth 3-fold. Protein extracted from BY2 cell walls possessed the expansin-like ability to induce extension of isolated walls. In western-blot analysis of BY2 wall protein, one band of 29 kD was recognized by anti-expansin antibody. Six different classes of alpha-expansin mRNA were identified in a BY2 cDNA library. Northern-blot analysis indicated moderate to low abundance of multiple alpha-expansin mRNAs in BY2 cells. From these results we conclude that BY2 suspension-cultured cells have the necessary components for expansin-mediated cell wall enlargement.     

Numerical simulation of the flow field in the mixing section of a screw extruder by the lattice Boltzmann model

The single-screw extruder is commonly used in polymer processing where the performance of the mixing section is significant in determining the quality of the final product. It is therefore of great interest to simulate the flow field in a single-screw extruder. In this paper the simulation is performed using the lattice Botlzmann model giving a fast and efficient numerical technique. The solution is compared to a finite difference and lattice gas simulation and found to give more accurate results.     

Three-dimensional echocardiographic planimetry of maximal regurgitant orifice area in myxomatous mitral regurgitation: intraoperative comparison with proximal flow convergence

The purpose of this study was to evaluate the usefulness of multishot echo-planar imaging in detecting liver tumors in comparison with respiratory triggered T2-weighted fast-spin-echo (FSE) imaging. Thirty-two patients with 70 focal liver lesions were imaged using a 1.5-T high speed MR imager. Eight-shot echo-planar images covering the whole liver were acquired during a single breath-hold period. FSE images were acquired with respiratory triggering in approximately 4 minutes. Lesion detectability and image quality of the two pulse sequences were analyzed qualitatively. Quantitative analysis was performed by means of signal-to-noise and tumor-liver contrast-to-noise analysis. Lesion detectability was comparable in both solid (86.3% vs 90.2%: .3 < P < .5) and nonsolid lesions (89.5% vs 100%: .3 < P < .5) between echo-planar and FSE images. Echo-planar imaging provided significantly reduced image artifact, better lesion conspicuity, and anatomic detail compared with FSE imaging. The signal-to-noise and contrast-to-noise ratios of echo-planar images were significantly higher than those of FSE images. Breath-hold eight-shot echo-planar imaging can be an alternative to T2-weighted FSE imaging because it can provide comparable image quality in a substantially decreased acquisition time.     

Trained detection of buried mines in SAR images via the deflection-optimal criterion

In this paper, we apply a deflection-optimal linear-quadratic detector to the detection of buried mines in images formed by a forward-looking ground-penetrating synthetic aperture radar. The detector is a linear-quadratic form that maximizes the output SNR (deflection), and its parameters are estimated from a set of training data. We show that this detector is useful when the signal to be detected is expected to be stochastic, with an unknown distribution, and when only a small set of training data is available to estimate its statistics. The detector structure can be understood in terms of the singular value decomposition; the statistical variations of the target signature are modeled using a compact set of orthogonal "eigenmodes" (or principal components) of the training dataset. Because only the largest eigenvalues and associated eigenvectors contribute, statistical variations that are underrepresented in the training data do not significantly corrupt the detector performance. The resulting detection algorithm is tested on data that are not in the training set, which has been collected at government test sites, and the algorithm performance is reported.     

Optimizing mitral valve exposure with conventional left atriotomy

The standard surgical approach to the mitral valve is accomplished through a longitudinal incision in the left atrium, posterior and parallel to the interatrial groove. Many other surgical approaches have evolved. This report describes a technique of optimizing mitral valve exposure via the standard approach. These modifications are simple, do not lengthen the procedure, and usually obviate the need for more complex maneuvers.     

Evaluation of Dry Powdered Lubricants at 1000 F in a Modified Four-ball Wear Machine

The friction and wear behavior of selected solid lubricants and wear specimens has been studied in a modified four-ball wear machine. Data were obtained at 1000 F for sliding speeds of 120 and 700 ft per min under initial Hertzian contact stresses of about 250,000 psi. Conventional solid lubricant material ssuch as lead oxide (litharge), molybdenum disulfide, and graphite were evaluated. A new dry solid lubricant, metal-free phthalocyanine, was studied and was usually found to have superior lubricating ability. Wear specimens of AISI Type M-1 tool steel and titanium carbide-nickel-molybdenum cermet showed the most promise for high-temperature sliding systems. Initial coefficients of friction less than 0.1 were obtained with combinations of these materials.     

Reviews

VALUED ENVIRONMENTS edited by John R. Gold and Jacquelin Burgess. 203 pages. George Allen and Unwin, 1982. £15.00 (hardback).

HANDBUCH STADTGRUN Landschaftsarchitektur im Stadtischen Freiraum by Gerhard Richter. 319 pages. BLV Verlagsgesellschaft, Munich, 1981. DM 115.

RESEARCH AND PLANNING FOR NATURE CONSERVATION AND AMENITY IN WOODLANDS edited by Katherine Hearn. Recreation Ecology Research Group, 1981.

BROADLEAVES IN BRITAIN edited by D. C. Malcolm, J. Evans and P. N. Edwards. 253 pages. Edinburgh University Press, 1982. £8.00 (hardback).     

Behavioral analysis and nursing interventions for reducing disruptive behaviors of patients with dementia

In this study, two cases were used to examine the potential of behavioral analysis as an intervention to decrease disruptive behaviors of institutionalized individuals with dementia. Behavioral modeling was used to teach the principles of behavioral analysis. The nurses observed a behavior change plan implemented by the investigator, revised the plan based on behavioral analysis techniques, and subsequently implemented the revised behavioral strategies. The patients' disruptive behaviors decreased markedly when the behavioral intervention was implemented. Patients resumed disruptive behaviors when care was provided without the behavioral plan. The findings suggest the need to address interventions in nursing research, education, and practice that use behavioral analysis to reduce disruptive behaviors in individuals with dementia.     

Group I allergens of grass pollen as cell wall-loosening agents

Group I allergens are the major allergens of grass pollen, but their biological function is unknown. These proteins are shown here to be structurally related to expansins, which are able to induce extension (creep) of plant cell walls. Extracts of maize pollen possess potent expansin-like activity, as measured in wall extension and wall stress-relaxation assays. This activity is selective for grass cell walls and is, at least partly, due to the action of maize group I allergens. We propose that group I allergens facilitate invasion of the pollen tube into the maternal tissues by loosening the cell walls of the grass stigma and style. Additionally, the presence of related mRNAs in vegetative tissues of rice, Arabidopsis, and soybean implies that allergen homologs may function to loosen walls in growing vegetative tissues as well.