The influence of radiation on the skin and the basis of protection

This paper reviews current ideas concerning the reactions involved in sunburn, suntanning, premature ageing and carcinogenesis due to acute or chronic exposure to sunlight. The physiological mechanisms of protection involving melanin pigmentation, thickening of the epidermal horny layer and urocanic acid are briefly discussed. The importance of wavelengths from 290-315 nm (UV-B) for these reactions is emphasized as is the need to investigate further the involvement of longer wavelength (UV-A, 315-400 nm).
L'influence des radiations sur la peau et les principes de la protection solaire
Cet article passe en revue les données actuelles concernant les réactions impliquées dans les processus de brûlure, bronzage, vieillissement prématuré et carcinogenese dus aux expositions aigues ou chroniques de la peau à la lumière solaire. Les mécanismes physiologiques de protection qui mettent en oeuvre la pigmentation par la mélanine, l'épais-sissement de la couche cornée, et l'acide urocanique sont brièvement discutés. On insiste sur l'importance des UV-B (longueurs d'onde de 290 à 315 nm) dans ces réactions, de même que sur la nécessité d'entreprendre des études plus approfondies sur le rôle des UV-A (315-400 nm).     

CHANGE STIMULUS SEQUENCES FOR DISCRIMINATION TASKS.

SEQUENCES OF POSITIONS FOR THE PLACING OF THE POSITIVE STIMULUS IN A 2-CHOICE VISUAL DISCRIMINATION TASK AS CONSTRUCTED BY GELLERMAN ARE EXAMINED BY MEANS OF A HYPOTHESIS-ANALYSIS TECHNIQUE AND ARE FOUND TO BE UNSATISFACTORY ON 2 COUNTS: (1) THEY FAIL TO ENSURE THAT NO POSITION HYPOTHESIS WILL PRODUCE OTHER THAN CHANCE PERFORMANCE ON THE LEARNING CURVE, AND (2) THEY FAIL TO PREVENT THE DIFFERENTIAL REINFORCEMENT OF POSITION HYPOTHESES. A NEW SET OF SEQUENCES IS PROPOSED WHICH SATISFY THESE CONDITIONS. SUGGESTIONS ARE MADE AS TO THE COMBINATION OF THESE SEQUENCES FOR USE IN RELATIVELY LONG DISCRIMINATION TASKS. (22 REF.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Model‐based approach for microvasculature structure distortion correction in two‐photon fluorescence microscopy images

This paper investigates a postprocessing approach to correct spatial distortion in two‐photon fluorescence microscopy images for vascular network reconstruction. It is aimed at in vivo imaging of large field‐of‐view, deep‐tissue studies of vascular structures. Based on simple geometric modelling of the object‐of‐interest, a distortion function is directly estimated from the image volume by deconvolution analysis. Such distortion function is then applied to subvolumes of the image stack to adaptively adjust for spatially varying distortion and reduce the image blurring through blind deconvolution. The proposed technique was first evaluated in phantom imaging of fluorescent microspheres that are comparable in size to the underlying capillary vascular structures. The effectiveness of restoring three‐dimensional (3D) spherical geometry of the microspheres using the estimated distortion function was compared with empirically measured point‐spread function. Next, the proposed approach was applied to in vivo vascular imaging of mouse skeletal muscle to reduce the image distortion of the capillary structures. We show that the proposed method effectively improve the image quality and reduce spatially varying distortion that occurs in large field‐of‐view deep‐tissue vascular dataset. The proposed method will help in qualitative interpretation and quantitative analysis of vascular structures from fluorescence microscopy images.     

LINEAR PROGRAMMING SOLUTION OF MASONRY ARCH STABILITY

A pier, jack arch, and segmental arch will be analyzed using a minimization of potential energy procedure. The method involves creating an energy equation that describes the structure in terms of local displacements. The energy equation will be set up in a linear form so that it can utilize linear programming methods of minimization. The minimization routine will be subject to a number of constraints used to enforce the end conditions of the arch at the abutments and constraints against interpenetration and sliding of adjacent blocks, and then solved for both the primal and dual solutions.

The normal forces which are necessary to determine the frictional energy dissipated due to a sliding failure will be derived from the slack of the dual solution. The primal solution will result in either an unbounded solution, indicating an unstable structure, or a solution of zero, indicating a stable structure. This information will be used to solve for a critical value of stability for a particular unknown.     

Bioactive peptides and lactic fermentations

Milk proteins contain regions within their primary structures that encrypt for many latent biological activities. The beneficial health effects associated with some fermented dairy products may, in part, be attributed to the release of bioactive peptide sequences during the fermentation process. Peptides displaying opioid, mineral binding, cytomodulatory and hypotensive activities, for example, have been identified in cheese and yogurt. Much effort has to date concentrated on the release of angiotensin-converting enzyme (ACE) inhibitory peptides due to their potential to act as hypotensive agents. Peptide fractions obtained by hydrophobic interaction chromatography of different cheese varieties (Blue, Camembert, Edam, Emmental, Gouda and Havarti) were reported to give systolic blood pressure (SBP) decreases in spontaneously hypertensive rats (SHR) ranging from 7.1 to 29.3 mm mercury (Hg). Skim milks fermented with various strains of Lactobacillus helveticus , and in one case also with Saccharomyces cerevisiae , have been reported to display SBP decreases in mildly hypertensive human volunteers ranging from 4.6 to 14.1 mmHg. These human hypotensive effects have, in part, been attributed to the release of potent casein-derived tripeptide inhibitors of ACE during fermentation. In general, the likelihood of any bioactive peptide released during fermentation mediating a physiological response is dependent on the ability of that peptide to reach an appropriate target site. Therefore, peptides may need to be resistant to further degradation by gastrointestinal and serum proteinases/peptidases following oral ingestion in order to display a functional food effect.     

DISTRIBUTION AND SOME CHARACTERISTICS OF TRIMETHYLAMINE N-OXIDE (TMAO) DEMETHYLASE ACTIVITY OF RED HAKE MUSCLE

It has been suggested by some workers that decomposition of trimethyl N-oxide (TMAO) to dimethylamine (DMA) and formaldehyde in gadoid fishes occurs via enzymic processes while others have suggested a nonenzymic pathway. DMA production in frozen red hake muscle is shown in this study to be enzymic by the necessity of the high molecular weight soluble or insoluble fraction from red hake to convert the low molecular weight components of flounder muscle to DMA. In red hake muscle the TMAO demethylase activity is approximately evenly divided between the high molecular weight soluble and the insoluble fractions: the amount of potential activity in either fraction is 60–100 times that required for the production of DMA that normally occurs during frozen storage of the muscle tissue. The K_m for TMAO of the soluble enzyme was approximately 3 mM; the concentrations of TMAO in red hake muscle range from 60 to 140 mM (calculation based on water content of 80%). Thus, it seems unlikely that TMAO or TMAO demethylase limit the rate of the reaction. On the other hand, the K_m values for flavin mononucleotide and NADH are higher than the concentrations of these components found in the tissue suggesting that the cofactors limit the rate of TMAO breakdown to DMA and formaldehyde in the stored muscle. This supports other studies (Landolt and Hultin 1982; Banda and Hultin 1983) in which the same conclusion is reached based on other considerations.     

PREDICTIVE MODEL FOR THE COMBINED EFFECT OF TEMPERATURE,pH, SODIUM CHLORIDE,AND SODIUM PYROPHOSPHATE ON THE HEAT RESISTANCE OF ESCHERICHIA COLI O157:H71

The effects and interactions of heating temperature (5–62.5C), pH (4 – 8), NaCl (0 – 6%, w/v), and sodium pyrophosphate (0 – 0.3%, w/v) on the heat resistance of a four strain mixture of Escherichia coli O157:H7 in beef gravy were examined. Thermal death times were determined using a submerged coil heating apparatus. The recovery medium was plate count agar supplemented with 1% sodium pyruvate. Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve fitting program. The D-values were analyzed by second order response surface regression for temperature, pH, NaCl and sodium pyrophosphate levels. The four variables interacted to affect the inactivation of the pathogen. Thermal resistance of E. coli O157:H7 can be lowered by combining these intrinsic factors. A mathematical model describing the combined effect of temperature, pH, NaCl and sodium pyrophosphate levels on the thermal inactivation of E. coli O157:H7 was developed. The model can predict D-values for any combinations of temperature, pH, NaCl and sodium pyrophosphate that are within the range of those tested.     

Sintering of PZT Ceramics: I, Atmosphere Control

Methods of PbO atmosphere control during the sintering of PZT ceramics are briefly reviewed. The problem of atmosphere control of PZT compositions containing a PbO excess (PbO/(Zr,Ti)O₂>1) is discussed. Weight-loss experiments were performed to compare with behavior predicted by reference to the PbO-rich part of the ternary PbO-ZrO₂-TiO₂ phase diagram. The results indicated that the PbO activity of a PZT composition is a function of the excess PbO content, contrary to earlier reports. Experimental procedures were established in order to control the PbO content within satisfactory limits. The effects of various packing powders on the PbO content of sintered PZT compacts were evaluated.     

The Automated Underground: Computer-Aided Design of Boston's Central Artery Project

Computer applications related to under-ground construction are described as they are being applied to Boston's Central Artery/Third Harbor Tunnel Project. The project is currently one of the largest highway projects in the country. Computer applications include a geotechnical boring log management system, spreadsheets for tunnel analysis and design, finite-element studies of soil-structure interaction for a construction excavation problem, and software that draws flow nets. Each application is outlined, and problems and future improvements to the methods are discussed.     

Colour Differences in Azo Pigments

Four azo pigments - C.I. Pigment Red 1 and 6, Yellow 1 and Orange 6 - have been prepared using a continuous coupling process under a range of conditions of pH, coupling temperature, concentration and rate of flow. The colour and size distribution of the pigments have been measured, the latter using a modified optical centrifuge for which new conversion factors have been determined. Continuous methods generally give lower particle sizes than comparable batch methods. This is discussed in terms of theories of nucleation and growth, as is the potential industrial application of continuous coupling.