Small Changes In Shape Research Articles

Effects of adrenergic agents and phosphodiesterase inhibitors on outflow facility and cell shape of bovine trabecular meshwork

Changes in the outflow facility of perfused calf eyes and in the shape of cells in cultured trabecular meshwork (TM) have been studied, following exposure to adrenergic agents and phosphodiesterase inhibitors (PDE). Dobutamine caused confluent TM cells to change their usual polygonal shape to a characteristic stellate shape. Salbutamol had no effect, but PDE inhibitors, isobutylmethylxanthine (IBMX), theophylline, and caffeine were very effective in producing this shape change. Epinephrine, isoproterenol, dobutamine, and salbutamol did not increase the outflow facility, either at 22°C or 36°C, while theophylline, caffeine, and IBMX did increase it in a dose-dependent manner. On the other hand, the high concentrations of β-adrenergic agents required to produce even a small change in outflow facility and cell shape argue against the involvement of adrenergic-receptor mediation and may suggest another mechanism; on the other, the enhancement of epinephrine effects by PDE inhibitors and the similar effect produced by cyclic adenosine 3′,5′-cyclic phosphate (cAMP) and purines suggest that changes in the cell shape are produced by β-receptor activation. The β-adrenergic agents were not effective in changing outflow facility, but the PDE inhibitors were remarkably effective both in changing the shape and in increasing facility.

Metric-topological approach to shape representation and recognition

Visual shape can be represented by means of certain integer valued functions of two real variables called size functions. This paper presents the theory of size functions in detail and discusses several useful properties of size functions, like stability to small shape changes and invariance to transformations of increasing generality. Then, a scheme for shape recognition based on size functions is described and tested on a study case. It is concluded that size functions can be very useful for shape representation and recognition.

Comparative studies of structural properties and conformational changes of proteins by analytical ultracentrifugation and other techniques

Analytical ultracentrifugation is a powerful tool for investigating the size of proteins in solution, especially by measuring sedimentation and diffusion coefficients and molar masses. Several further molecular parameters such as frictional ratios, axial ratios of hydrodynamic models, and Stokes radii allow a rough estimate of the protein overall structure. Sedimentation analysis may also be applied efficaciously for monitoring conformational changes of proteins occurring upon ligand binding or denaturation. For the determination of very small changes in shape, however, great care and a series of precautions are required. We investigated the enzymes citrate synthase and malate synthase in the absence and in the presence of ligands, in order to study the structural properties of the proteins and their ligand complexes. We also compared the results of the ultracentrifugal analysis with the results of other solution techniques such as UV absorption, fluorescence spectroscopy, circular dichroism, and small-angle x-ray scattering on the one hand, and the crystallographic 3D structure of citrate synthase on the other. The spectroscopic methods may be used as efficient and rapid tools for screening the occurrence of conformational changes caused by alterations of chromophores and fluorophores. The structural information provided by small-angle scattering (e.g., radii of gyration, maximum particle diameters, vclumes and surface areas) can be used to establish quantitative correlations between solution scattering and hydrodynamic data. In this context, however, knowledge or qualified assumptions of partial specific volumes and hydration are additionally required. Good agreement was reached between small-angle scattering and ultracentrifugal data, and also with crystallographic data if protein hydration was considered properly. The given approaches may be used to predict hydrodynamic properties if x-ray data are available, and for many verifications of other structural data, e.g., Stokes radii, diffusion coefficients, axial and frictional ratios determined by independent methods.

Pathogenesis of acute ischemic mitral regurgitation in three dimensions

Changes in the geometric and intravalvular relationships between subunits of the ovine mitral valve were measured before and after acute posterior wall myocardial infarction in three dimensions by means of sonomicrometry array localization. In 13 sheep, nine sonomicrometer transducers were attached around the mitral anulus and to the tip and base of each papillary muscle. Five additional transducers were placed on the epicardium. Snares were placed around three branches of the circumflex coronary artery. One to 2 weeks later, echocardiograms, dimension measurements, and left ventricular pressures were obtained before and after the coronary arteries were occluded. Data were obtained from seven sheep. Coronary occlusion infarcted 32% of the posterior left ventricle and produced 2 to 3+ mitral regurgitation by Doppler color flow mapping. Multidimensional scaling of dimension measurements obtained from sonomicrometry transducers produced three-dimensional spatial coordinates of each transducer location throughout the cardiac cycle before and after infarction and onset of mitral regurgitation. After posterior infarction, the mitral anulus enlarges asymmetrically along the posterior anulus, and the tip of the posterior papillary muscle moves 1.5 ± 0.3 mm closer to the posterior commissure at end-systole. The posterior papillary muscle also elongates 1.9 ± 0.3 mm at end-systole. The left ventricle enlarges asymmetrically and ventricular torsion along the long axis changes. The development of postinfarction mitral regurgitation appears to be the consequence of multiple small changes in ventricular shape and contractile deformation and in the spatial relationships of mitral valvular subunits. (J T HORAC C ARDIOVASC S URG 1995;109:684-93)

Body image, disfigurement and disability

The body-related attitudes of groups of women suffering from physical conditions that are commonly regarded as being disfiguring and/or disabling were studied by means of the Body Attitudes Questionnaire. Despite their conditions, the women did not necessarily disparage their bodies. They also seemed to worry less about small changes in weight and shape than did comparable women without physical difficulties, and to have an enhanced sense of their own robustness. There was an indication that development of negative body attitudes might be linked to emergence of a chronic physical condition during adolescence, rather than from birth or during adulthood. If our results are confirmed, they point to the need to pay special attention to the psychological needs of women whose bodies become dysfunctional at this sensitive time.

An Experimental Test of the Concept of the Characteristic Drying Curve Using the Thin-Layer Method

ABSTRACT The drying behaviour of paticles ( purolit and silica gel) was studied using the thin-layer method described by Langrish et al ( 1). The experiments covered inlet air temperatures between 100 and 150°C, inlet air humidities from 0.02 to 0.052 kgkg1 superficial air velocities between 3.8 and 10.8 ms-1, with layer thicknem of 2 – 10mm. No constant mle period war observed. Characteristic drying curves were found to fall within a narrow band fur these ranges of process variables, for material of uniform size and shape and with relative moisture content defined in terms of the end of the induction period. Small changes in panicle shape, particle size distribution and uniformity of particle layers had negligible infuence on the drying kinetics. However, reduction in particle size from 5.2mm diameter to 0.86mm had a marked effect: the normalised drying rate at a given relative moisture content became larger as the particle size became smaller. This phenomenon is attributed to an increase in available contact area per unit volume with diminishing particle size. The thin-layer technique thus appears to be a useful and robust way of obtaining a general characteristic drying curve for a given particulate material. A review of various works ( Keey, 2) has shown that the concept ofa characteristic drying curve may be used to describe the drying kinetics of paniculate materials below 20mm in size for modest changes in process variables ( air temperature, humidity and velocity). This concept has found to be very useful to help model drying processes of a wide variety of particulates, cross-circulated slabs, heaped loaw fabric fibres, hygroscopic ceramic cylinders and discrete vermiculite particles. The drying of a single particle has been related lo the drying kinetics of a fluidized bed by the use of this ida. ( Tsotsas, 7). A grater understanding of the properties of the characteristic drying curve will provide a greater confidence in applying thir concept more generally to process design and the analysis of industrial drying equipment. The goal of this study was to examine further the experimental and theoretical foundations of the characteristic drying curve, using thin-layer methods.

Computer simulation study of liquid crystal formation in a semi-flexible system of linked hard spheres

Results are reported for a molecular dynamics simulation study of a flexible model mesogen composed of seven tangential spheres. We follow the ‘rattling spheres’ method by which bonded atoms are constrained to lie within narrow potential wells. The dynamics of the system is that of a hard sphere fluid with added constraints. The phase diagram of our model system is calculated as a function of density and shows the presence of three fluid phases. These are assigned to be isotropic, nematic and smectic-A phases. Results are reported for the orientational order, radial distribution functions, structure factors and single-particle structural data within these phases. A small but significant change in shape is measured as the nematic phase is entered from the isotropic liquid. This is interpreted in terms of a quenching of allowed conformations parallel to the director.

Physical properties of mixtures of low molar mass nematic liquid crystals with photochromic fulgide guest dyes

Abstract This paper considers how a low concentration (> 2 per cent w/w) of a photochrome dissolved in a liquid crystal affects the physical properties of the host mesogen. A novel class of photochromes, the fulgide based dyes, have been used to give a new approach in this area of study. Unlike many other light active dyes, the fulgides exhibit only a relatively small shape change. Because of this, the influence of the changes in the physical properties of the guest (for example, the dipole moment) are readily studied. Both thiophene and furan fulgide doped liquid crystal systems were studied in the irradiated and non-irradiated states and as a function of concentration. The changes in phase transition temperature, refractive index and order parameter for these various states as compared to the pure host liquid crystal have been measured to investigate the way in which the dye alters the mesomorphic properties of the host, on a molecular level.

High temperature properties of ductile CuAlNi shape memory alloys with boron additions

The use of polycrystalline CuAlNi alloys for high temperature applications is restricted to very small shape changes due to their brittle nature. Additions of alloying elements such as manganese and boron have been introduced to improve the ductility of the material. The behaviour of these alloys has been studied in terms of the influence of these elements on the stability of the microstructure after high temperature annealing or after room and high temperature deformation. The results show that the martensitic structure produced by quenching the alloy from the β-temperature has a lower degree of order than that obtained after further annealing at 300°C for up to an hour. Also, the alloys containing higher boron concentrations present a lower degree of order in all cases. Similarly, the ductility has been much influenced by the boron content. The ductility is greater, in particular at high temperatures, in the alloys with lower concentration of boron.

Prediction of wheel profile wear

Prediction techniques have existed for some years to calculate wheel-rail contact patch information and the response of a vehicle to any input from track roughness. More recently, experimental information has become available relating the wear rate of a wheel or rail surface to the energy dissipated within the contact zone. The prediction method described in this paper brings all this information together into a single programme in which each programme loop represents a single-journey calculation. From the time history of the response, the position of the contact on the wheel and the wheel-rail creep forces and creepages are correlated and summed to give a material loss distribution across the wheel profile and hence a small change in profile shape. The contact patch data are recomputed before each journey, which is then repeated as often as required to achieve a desired mileage.

Stiffness and shortening changes in myofilament-extracted rat cardiac myocytes.

Sarcomere lengths, cell widths, volumes, stiffness, and regional striation uniformity were determined from isolated adult cardiac myocytes. Single cells were examined in the control saline solution followed by a sequence of relaxing, membrane skinning, and myofilament extraction solutions. Cell size and shape parameters were determined from freely dispersed myocytes, whereas stiffness was measured from myocytes attached to a perturbator and tension transducer with micropipettes. There were small changes in cell appearance, size, shape, and stiffness in the relaxing and skinning solutions. However, in 0.17-0.56 M KCl myosin extraction media, cell length declined significantly to 1.19 microns, and stiffness fell to 5-10% of control. The rate of cell shortening and stiffness decline was dependent on KCl concentration and pH. Subsequent exposure to higher ionic strength 0.60 M KI thin filament extraction media elicited additional decreases in stiffness (less than 5% of control) and cell length (0.98 micron). Cell shortening and stiffness decline have similar time courses under the same conditions, and they appear to coincide with A-band disassembly as indicated by electron micrographs. These data suggest that cardiac myocyte stiffness, size, and shape are determined in part by a stressed cytoskeleton that is associated with the myofilament apparatus.

ＳＵＳ３０４ステンレス鋼拡散接合部のＨＩＰ処理

To eliminate all voids on diffusion-welded interface, diffusion-welded joints were treated using a hot isostatic pressing equipment without the canning of joints. The material used was SUS304 stainless steel. Results obtained are summarized as follows:1. All voids on diffusion-welded interface, that are shut from the external environment and have not residual gas, are eliminated by the hot isostatic pressing treatment.2. In the case of the welding surface prepared by a lathe, all voids on diffusion-welded joint are shut from the external environment when welded area ratio is above 35%.3. It is difficult to eliminate voids in diffusion-welded joint made under the welding environment of Ar.4. All voids of diffusion-welded joints are eliminated under hot isostatic pressing conditions of 1100°C, 2h and above 50 MPa.5. The joints subjected to hot isostaic pressing treatment after diffusion welding have very small change in specimen shape, and the mechanical properties of the joints is not influenced by the roughness of welding surface.

Control of a Sequential Brakeforming Process

The process of sequential three point bending (or “bumpforming”) is often used to produce smoothly varying simple curvature parts. The process involves bending and incrementing the bend line in sequence to produce the desired curvature profile along the arc length of the part. The actual shape produced represents the integration of small local shape changes, and the opportunity for error is great since knowledge of the bending properties of the material is required to accurately plan and execute the sequence. As a result, the manual process is slow and highly inaccurate. In this paper an in-process control method is presented that performs two functions: 1) sequence planning based upon an optimization between allowable variations about the desired shape and processing time; and 2) closed-loop control of the desired shape to insure accurate parts even when material properties or dimensions change.

Measurements of despin and yawing moments produced by a viscous liquid

The behavior indicated in Figs. 3 and 4 suggests that a small shape change would occur with each pitch oscillation of the vehicle, so that the resulting trim moments would tend to cancel out. If the net trim remained sufficiently small, then the epicyclic motion would persist until it damped out from inherent pitch and normal force damping. Because successive points of minimum ! I and presumed shape change occur on essentially opposite meridians (from the point of view of an observer fixed in space), the lift nonaveraging dispersion associated with equal increments of shape change should be minimal.' It is emphasized that these conclusions are based on the assumption that very small incipient ablation or erosion asymmetries exist which do not influence the motion. A more rigorous treatment of the problem should include the effects of these shape asymmetries on the coupling between the angle of attack and windward-meridian rotation rate.

Lower consolute boundaries of a poly(oxyethylene) surfactant in aqueous solutions of monovalent salts

Lower consolute boundaries up to 50 vol% surfactant have been determined for n-octylpenta(oxyethylene glycol)(C8E5) in the presence of the monovalent salts NaF, LiCl, NaCl, KCl, CsCl, NaBr and NaI. We find that the lower consolute boundaries are shifted, with only small changes in shape, to lower or higher temperatures (salting-out or salting-in, depending on the salt used). The amount and sign of the miscibility shift is determined almost solely by the anion, and the shift is related to the surface charge density of the ion. The shifts in the lower consolute boundary cannot be explained by structural changes in the bulk water structure due to the addition of salts. We have applied the Flory–Huggins lattice theory to relate the shifts of the lower consolute boundaries to changes in micelle–solvent interactions. This analysis shows that small changes in the free energy of interaction between oxyethylene and water can explain the shifts in temperature of the lower consolute boundary. We discuss the use and limitations of the Flory–Huggins theory, as applied to micellar phase separation. The salt effects are explained in terms of salt-deficient or salt-rich regions around the oligo-oxyethylene chains.

A carbon Auger line shape study of nitroaromatic explosives

The C(KVV) Auger line shapes of a series of nitroaromatic explosives have been compared to condensed benzene. Energy shifts of the pi levels in TNB (1,3,5-trinitrobenzene) and TNT (2,4,6-trinitrotoluene) and charge redistribution caused by the resonance electron withdrawing effect of the nitro groups lead to changes in the Auger line shape of transitions involving these levels compared to those of benzene. In MATB (1-amino-2,4,6-trinitrobenzene), DATB (1,3-diamino-2,4,6-trinitrobenzene), and TATB (1,3,5-triamino-2,4,6-trinitrobenzene), the amino groups form resonant structures with the aromatic ring and donate charge density into the ring pi levels. This more than compensates for the charge density withdrawn by the nitro groups. As a result, an amino-carbon pi level is populated which leads to dramatic changes in the energy and intensity of the leading edge of the C(KVV) line shape for these compounds. Hole-hole correlation in the final state causes only small changes in line shape. The relative explosive shock initiation sensitivity of TNB and TNT, where the intermolecular bonding is weak, correlates with the observed Auger line shape changes and reflects the relative ring stability of these aromatic molecules. However, the addition of amino groups in MATB, DATB, and TATB decreases the ring bonding, as reflected in the Auger spectra, in favor of intra- and intermolecular hydrogen bond formation and the initiation sensitivity no longer correlates with ring bonding strength.

Residual α 2-macroglobulin in fetal calf serum and properties of its complex with thrombin

Summary Active α2-macroglobulin (α2M) has been shown to persist in commercial preparations of fetal bovine serum. Reaction with trypsin and the mitogenic protease thrombin leads to cleavage of the polypeptide chain of α2M, with simultaneous conversion to a fast electrophoretic form. The trapped protease is fully active toward low molecular weight synthetic substrates, but reacts slowly if at all with the protein inhibitor hirudin (M.W. 12,200). Addition of methylamine to fetal bovine α2M leads to covalent incorporation of the amine into the protein, but the subsequent and apparently spontaneous conversion from the slow to the fast electrophoretic form seen with human α2M is not observed. Sedimentation velocity studies of intact and modified fetal bovine α2M show that a small shape change results from reaction with proteases but that, in contrast to the human protein, no shape change results from reaction with methylamine.

Left ventricular dynamic geometry in the intact and open chest dog.

No approach to describing the heart's dynamic geometry has been widely adopted, probably because all require questionable assumptions of chamber shape, symmetry, or placement of the measuring devices. In other words, these approaches require assumptions about shape to reach conclusions about shape. We present an analysis that avoids such assumptions and provides an objective description of how the left ventricle deforms and rotates during the cardiac cycle. We only assume that the deformation of the left ventricular cavity is homogeneous, and explicitly validate this assumption. Our analysis yields the following new information about the contracting left ventricle: three principal directions of deformation and the relative length change alone these directions: the axis and angle of rotation, and relative volume. All these changes are referenced to the ventricle's configuration at end-diastole. We instrumented 13 dogs with tantalum screws without opening their chests. During systole, the three principal directions of deformation essentially are aligned along apex-base, anterior-posterior, and septum-free wall directions. There is little length change in the apex-base direction. The anterior and septal principal directions do not remain fixed with respect to the heart's anatomy during systole. During isovolumic relaxation and early filling, systolic shape changes are reversed. During slow filling, only small shape changes occur. Opening the pleura or performing a sternotomy and pericardiectomy makes the heart change orientation within the chest, but does not alter the magnitude of shortening, relative to the left ventricle's end-diastolic configuration.

Neocognitron: a self organizing neural network model for a mechanism of pattern recognition unaffected by shift in position.

A neural network model for a mechanism of visual pattern recognition is proposed in this paper. The network is self-organized by "learning without a teacher", and acquires an ability to recognize stimulus patterns based on the geometrical similarity (Gestalt) of their shapes without affected by their positions. This network is given a nickname "neocognitron". After completion of self-organization, the network has a structure similar to the hierarchy model of the visual nervous system proposed by Hubel and Wiesel. The network consists of an input layer (photoreceptor array) followed by a cascade connection of a number of modular structures, each of which is composed of two layers of cells connected in a cascade. The first layer of each module consists of "S-cells", which show characteristics similar to simple cells or lower order hypercomplex cells, and the second layer consists of "C-cells" similar to complex cells or higher order hypercomplex cells. The afferent synapses to each S-cell have plasticity and are modifiable. The network has an ability of unsupervised learning: We do not need any "teacher" during the process of self-organization, and it is only needed to present a set of stimulus patterns repeatedly to the input layer of the network. The network has been simulated on a digital computer. After repetitive presentation of a set of stimulus patterns, each stimulus pattern has become to elicit an output only from one of the C-cells of the last layer, and conversely, this C-cell has become selectively responsive only to that stimulus pattern. That is, none of the C-cells of the last layer responds to more than one stimulus pattern. The response of the C-cells of the last layer is not affected by the pattern's position at all. Neither is it affected by a small change in shape nor in size of the stimulus pattern.

Discrete internal pattern representations and visual detection of small changes in pattern shape

A scheme is proposed that relates the internal representation of pattern stimuli to visual pattern discrimination performance. The main assumptions of the scheme are: (1) internal representations are assigned to patterns probabilistically; (2) internal representations are discrete; (3) visual discriminability of two patterns is determined by the differences in the assignment probabilities of their internal representations. It is suggested that the internal representations associated with a pattern may be analyzed by measuring the visual detectability of small changes in pattern shape at points along a continuum of shapes. This continuum is generated by a group of transformations smoothly parameterized by a single variable. In two experiments designed to test this approach, subjects discriminated pattern displays containing combinations of three-dot subpatterns. Under the hypothesis that there were just two relevant internal representations, specifying dot collinearity and dot noncollinearity, the qualitative characteristics of the discrimination performance were correctly predicted.