Differences In Surface Texture Research Articles

Determination of the topography and biometry of chlorosomes by atomic force microscopy.

Isolated chlorosomes of several species of filamentous anoxygenic phototrophic bacteria (FAPB) and green sulfur bacteria (GSB) were examined by atomic force microscopy (AFM) to characterize their topography and biometry. Chlorosomes of Chloroflexus aurantiacus, Chloronema sp., and Chlorobium (Chl.) tepidum exhibited a smooth surface, whereas those of Chl. phaeobacteroides and Chl. vibrioforme showed a rough one. The potential artifactual nature of the two types of surfaces, which may have arisen because of sample manipulation or AFM processing, was ruled out when AFM images and transmission electron micrographs were compared. The difference in surface texture might be associated with the specific lipid and polypeptide composition of the chlorosomal envelope. The study of three-dimensional AFM images also provides information about the size and shape of individual chlorosomes. Chlorosomal volumes ranged from ca. 35 000 nm(3) to 247 000 nm(3) for Chl. vibrioforme and Chl. phaeobacteroides, respectively. The mean height was about 25 nm for all the species studied, except Chl. vibrioforme, which showed a height of only 14 nm, suggesting that GSB have 1-2 layers of bacteriochlorophyll (BChl) rods and GFB have approximately 4. Moreover, the average number of BChl molecules per chlorosome was estimated according to models of BChl rod organisation. These calculations yielded upper limits ranging from 34 000 BChl molecules in Chl. vibrioforme to 240 000 in Chl. phaeobacteroides, values that greatly surpass those conventionally accepted.

Effect of physical conditions on the spatial and temporal dynamics of the soil‐borne fungal pathogen Rhizoctonia solani

The transmission of infection by many soil‐borne fungal parasites of plants depends on the ability of the fungus to grow on or through soil. Progress in analysing the effects of soil physical factors on the temporal and spatial dynamics of fungal growth has been hindered by technical difficulties of quantifying fungal biomass in soil and heterogeneity in soil properties. In this paper we use a combination of a monoclonal antibody‐based immunosorbent assay and microscopy to analyse the effects of soil physical properties on the spatial and temporal dynamics of colonies of the economically important fungus Rhizoctonia solani Kühn growing in two dimensions and three dimensions in a sand. Combinations of different particle‐size distributions and matric potential are used to manipulate the air‐filled pore volume and pore‐size distribution independently of each other. Temporal dynamics are measured by the change in fungal biomass over time whereas spatial dynamics relate to fungal spread and are measured by the colony size, the rate of colony expansion and the biomass distribution within colonies. We show that the fungus spreads more than three times further over surfaces than through sand, even though the same amount of biomass is produced in each case. Pore‐size distribution and air‐filled pore space both affected the extent and rate of fungal spread in three dimensions within sand, with more rapid and extensive spread in a coarse sand compared with a fine sand at identical air‐filled pore volume. The spread of fungal hyphae along surfaces was affected neither by differences in surface texture nor by air‐filled volume, and was substantially more homogeneous than for three‐dimensional spread. We argue that the relative impermeability of sand surfaces to penetration by hyphae might be influenced by the ability of the fungus to branch within a confined space rather than simply to penetrate the pores. The broader epidemiological and ecological consequences of preferential spread by parasitic and saprophytic fungi along surfaces rather than through the dense soil volume are discussed.

Morphogenetic guidance cues can interact synergistically and hierarchically in steering nerve cell growth

Nerve cell growth is influenced by guiding properties of its substratum. Microfabricated cell culture substrata were used to determine whether rat dorsal root ganglia (DRG) nerve cells could detect and integrate simultaneous model adhesive and topographic guidance cues. Interference reflection microscopy demonstrated strips of surface contact under the marginal zone of growth cones on planar surfaces which were coincident with actin immunostaining at the periphery of the C-domain. Clusters of focal contacts below the growth cone C-domain delineated the track edges on adhesive gratings. Neurite extension was guided most effectively by adhesive gratings of 25-μm period where highly aligned cells were typically bipolar. Nanometric steps and differences in surface texture between the adhesive tracks was detected using atomic force microscopy (AFM). Neurites did not align to 12- to 100-μm pitch grooves which were less than 1 μm deep. The proportion of aligned neurites increased with groove depth. Maximum neurite alignment was seen when 6-μm-deep, 25-μm-wide grooves contained superimposed parallel adhesive tracks of matched pitch. Neurites aligned preferentially to adhesive tracks superimposed orthogonally over shallow grooves (1 μm deep). Primary neurites aligned increasingly to grooves with orthogonal adhesive tracks as their depth increased. These neurites frequently had highly branched terminal arbours aligned to the orthogonal adhesive tracks. We conclude that morphogenetic guidance cues can interact synergistically and hierarchically to steer nerve cell growth.

生活歯の漂白 １０％過酸化尿素処理による歯質表層の変化

The interest of patients in vital tooth bleaching has created a demand for aesthetic dental treatment.However, very few studies have determined the effect of vital bleaching upon dental hard tissues and the surrounding tissues.The purpose of this in vitro study was to determine the effects of 10% carbamide peroxide solution, which was the reagent for patient-applied home bleaching, on enamel and root surfaces using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS).Mesial halves or distal halves of extracted teeth were bleached for 7 consecutive days by 10% carbamide peroxide solution in custom-fabricated trays.Other samples were subjected to the same protocol in acidulated (pH 5.0) hydrochloric solutions.The untreated and treated sample halves were examined for differences in surface texture and were compared to enamel etched with 37% phosphoric acid.Significant differences in enamel surface texture were detected between the control and treated enamel surfaces in all groups.Furthermore, the removal of the deposition originated in periodontal membrane was detected in bleached root surfaces.These findings were also verified with EDS spectrum.

Cleanability of stainless steel in relation to chemical modifications due to industrial cleaning procedures used in the dairy industry

The cleanability and surface characterization of 0·8-mm thickness bright annealed finish 304 L stainless steel were assessed by standardized methods. Cleanability was previously compared to surface chemical modifications from industrial cleaning procedures commonly used in dairy industries. Strips were cleaned by four different processes including rinsing phases. The reference treatment is a RBS 35 ® surfactant cleaning. The other cleanings were: NaOH cleaning, HNO 3 cleaning, and a dairy cleaning in place (including HNO 3 and NaOH). The industrial cleaning processes were carried out once to simulate start-up conditions and 10 times to simulate working conditions. No notable differences in surface texture were found between the different cleaned surfaces studied. It was assumed that detergent and cleaning conditions used were not aggressive enough to attack stainless steel surfaces. Cleanability differences observed were due to differences in the chemical compositions used. When cleanability results and surface chemical composition results were compared, it was observed that the greater the degree of oxygen and carbon surface concentrations for the same iron surface composition, the lower were the chances of soiling remaining during the test cleaning. In the same way, it was observed that the greater the degree of the iron surface concentration for the same oxygen and carbon surface compositions, the greater was the change of soiling remaining during the test cleaning. As many differences in surface chemical compositions were observed between all studied surfaces, the difference in cleanability observed could be explained by an ageing phenomenon due to chemical surface composition changes induced by cleaning detergent actions.

A colostrum feeder for newborn lambs

Newborn lambs were studied in a series of experiments to identify simple cues that elicit teat-seeking behaviour, and to incorporate these cues into a device that would guide lambs to find and suck from a colostrum bottle. In six experiments, lambs were removed from the ewe before suckling and were observed for 10 min in a small cubicle where alternative design features were presented in pairs. When presented with a horizontal ledge at head height with a fleecy undersurface wide enough (160 mm) to cover the lamb's muzzle, most lambs performed teat-seeking behaviour, including contacting the fleece repeatedly with the muzzle, opening and closing the mouth on the fleece, and upward butting movements of the head. These activities occurred much less if the fleecy undersurface was replaced by a hard wooden ledge ( P < 0.01), if the fleecy ledge was oriented vertically, or if the ledge width was reduced to cover only the mouth area ( P < 0.01 in most comparisons). Differences in surface texture (fleece vs. cotton-covered fleece), surface temperature (10 vs. 37°C), and use of extra padding beneath the fleece had less marked effects ( P > 0.05 in most comparisons). Reactions of lambs were then tested with a prototype colostrum bottle holder which incorporated soft rubber teats surrounded by a fleecy horizontal undersurface. Of 27 lambs tested with a blind teat, 24 found and sucked the teat without assistance in a median of 2.1 min. In a final test, of 13 lambs offered colostrum from the bottle, ten found the teat and consumed 100 ml of colostrum in a median of 4.9 min. Thus, the prototype makes it easy to bottle-feed a newborn lamb in most cases, but some handling would be needed for certain individuals.

Some tribological observations of sliding tungsten carbide coated steel against aluminum

The wear behavior of tungsten carbide coated steel in contact with aluminum alloys was investigated using a block-on-ring test. The wear surfaces generated were observed using a scanning electron microscope equipped for EDAX analysis. Three wear phenomena occur at the interface: abrasive deformation of the aluminum surface by ploughing, transfer of aluminum back and forth between the carbide and aluminum surfaces, and transfer of carbide particles to the aluminum surface. The differences in wear attributed to coating type correlate with microscopic observations of differences in surface texture for the same initial Ra value. No significant effect of lubricant type was discerned.

Perioral somesthetic sensibility: Do the skin of the lower face and the midface exhibit comparable sensitivity?

Studies of the perioral somatosensory capacities of neurologically normal adults were reviewed to determine whether sensitivities within the mental and infraorbital nerve distributions are comparable. It was found that tactile detection sensitivity, spatial acuity, and sensitivity to warmth are greater on skin sites located on the midface than on the lower face. In contrast, sensitivity to direction of motion and to differences in surface texture may be greater on skin sites located on the lower face. The literature further suggests that sensitivity within the distribution of each nerve varies appreciably. For example, the vermilion of the lips exhibits considerably greater vibrotactile detection sensitivity, spatial acuity, and sensitivity to direction of motion than does the perioral hairy skin. In addition, spatial acuity is notably greater on midline structures. These findings suggest that knowledge of the patterns of spatial variations in perioral tactile sensibilities can be effectively used during neurosensory examination to select control skin sites for comparison with areas of suspected neurosensor` impairment and to distinguish apparent pathological alterations in tactile sensitivity from normal regional differences that characterize the perioral complex.

Morphology of Lignin-Polyurethane Blends

AbstractThe morphology of blended polyurethane (PU) sealants was studied by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The PU was modifided by mechanical mixing with various amounts of Lignin (L) to achieve a homogeneous blend. Specimens were subjected to control (C), accelerated weathering (AW), and natural weathering (NW) conditions. Results obtained from SEM analysis reveal an even distribution of L particles in the PU matrix. Furthermore, the SEM photomicrographs clearly emphasize the differing morphologies of the constituent phases. They also depict the differences in surface texture between control and aged specimens. The DSC analysis shows that the two phases are immiscible which is in agreement with observations by microscopy.

Morphology of Lignin-Polyurethane Blends

AbstractThe morphology of blended polyurethane (PU) sealants was studied by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The PU was modifided by mechanical mixing with various amounts of Lignin (L) to achieve a homogeneous blend. Specimens were subjected to control (C), accelerated weathering (AW), and natural weathering (NW) conditions. Results obtained from SEM analysis reveal an even distribution of L particles in the PU matrix. Furthermore, the SEM photomicrographs clearly emphasize the differing morphologies of the constituent phases. They also depict the differences in surface texture between control and aged specimens. The DSC analysis shows that the two phases are immiscible which is in agreement with observations by microscopy.

An evaluation of finishing instruments for an anterior and a posterior composite

The same finishing instruments and techniques revealed no significant differences in the surface roughness of the anterior and posterior composites. The smoothest surface was achieved with Mylar strips; the smoothest instrumented surface was achieved with a series of abrasive disks, but a fine diamond bur with 25 μm particles produced the roughest surface. However, an x-fine diamond with 15 μm particles produced a surface smoothness superior to that produced with a white stone and similar to the smoothness produced with a carbide bur and rubber point. Diamond finishing with slow speed produced a somewhat smoother finish than with high speed. SEM analysis revealed qualitative differences in surface texture even though the average roughness was not shown to differ.

A Machine that Separates Rough from Smooth Seed

ABSTRACT Anew machine has been developed to separate con-taminants from seed by sensing differences in sur-face textures. A moving friction belt carries the seed mix-ture to intercepting pairs of bars that separate rough from smooth particles. The machine has effectively removed contaminants from 38 seed mixtures including dirt clods from beans, dodder from alfalfa, and inert material from many seeds.

Bacterial sampling techniques on beef, pork, and lamb adipose tissue

Two methods were used to evaluate bacterial recovery from beef, pork, and lamb adipose tissue. Higher counts were obtained with a tissue removal and fluid agitation technique (shaking) than with surface swabbing, but only when bacterial levels were low. Bacterial recovery by both methods was unaffected by specie origin of adipose tissue and differences in surface texture, sample storage time (12 versus 6 days), and duration fluid agitation (5 versus 10 min).

Application of scanning electron microscopy to semen analysis of the sub-fertile man utilising data obtained by transmission electron microscopy as an aid to interpretation

The limitations of semen analysis as routinely practiced by light microscopy are briefly reviewed. The value of using SEM together with information obtained from TEM has been examined in a ‘blind’ study on three men attending a sub-fertility clinic so that clinical details, including sperm concentration, were not known to the investigators until the work was completed; the men had a clinical history of infertility and the sperm concentrations of the samples examined by electron microscopy were 16 × 10 6/ml, 84 × 10 6/ml and 237 × 10 6/ml. For study by SEM the cells were fixed in buffered glutaraldehyde, concentrated by low-speed centrifugation and tried with acetone, collected on a Millipore filter, dried by the critical point method and coated with gold. This method of preparation gave excellent preservation. Micrographs were obtained showing up to 40 spermatozoa per field which were suitable for assessing variations in the general shape and size of the cells and, at high magnification, differences in surface texture. All the samples contained spermatozoa possessing a large mass of extraneous cytoplasm which was readily visible by SEM. When examined by TEM this region possessed features characteristic of the residual cytoplasm (or body) of spermatids. This results, together with others reported in the present paper and data published elsewhere, suggests that sperm dysgenesis may be a relatively common feature of the spermatozoa of sub-fertile men. It is suggested that the degree of differentiation could be used as an objective basis for identifying and hence classifying, cells considered to be abnormal. It is concluded that SEM, together with information obtained by TEM, can make a valuable contribution to semen analysis of sub-fertile men with widely different sperm concentrations.

Experiments on the Flow of Heat across Stacks of Steel Laminations

Further measurements of the thermal conductivities of stacked laminations are reported. Differences in surface textures are important in a normal atmospheric environment, but not in an environment of helium, when the interface gas carries most of the heat flow across adjacent laminations.

Coefficients of Friction

SummaryA summary is presented of information collected on coefficients of friction (rolling and sliding) between rubber tyres and road or runway surfaces. Nearly all the data collected are from tests on automobile tyres and are limited to speeds of about 40 m.p.h. In some cases the primary object of the tests was to distinguish between good and bad roads, and not to determine absolute values of friction coefficients.The reasons for the importance of the information for aircraft design use are discussed and distinctions are made between coefficients measured in different ways.The results show the variation of sliding friction coefficient with various parameters at speeds up to 40 m.p.h. There is a set of American tests at speeds up to 110 m.p.h., and some estimates made by the Dunlop Rubber Company up to 120 m.p.h.It is concluded that for sliding friction coeficients differences in surface texture (as distinct from surface material) are significant, and that information can be given only in the form of limits within which the values can be expected to lie.Few results are available on the variation of rolling resistance coefficient, but it is felt that the approximate values quoted for different types of surface are sufficiently accurate.