Surface Outwards Research Articles

Coulomb’s Law in Electrostatic, Gravitational and Inertial Forces and Emission of Radiation

Electric fields, from charges in bodies, in accordance with Coulomb’s law, occupying a vacuum, constitute an elastic medium called aether. Electrostatic, gravitational, and inertial forces are explained by considering the aether as an electric-field medium, supporting transmission of radiation at the speed of light. A partice of charge Q is supposed to be an impregnable hollow sphere, with radial force pulling the surface outwards, to maintain a stable structure of radius a and mass m, as the smallest quantities. Lines of force from stationary adjacent charges, are curled, in positive potential energy, for repulsion or negative for attraction. A charge Q, moving at constant velocity, carries its straight lines of radial fields, with increase forwards, to account for the kinetic energy. Force of gravity is by virtue of bodies displacing volumes of the aether, one in the shadow of another, to make for a pushings force of attraction, in accordance with Newton’s law. Due to finite speed of light, acceleration of charge Q moving at time t with velocity v, is not simultaneously passed to all the fields, resulting in curling of lateral field lines and creation of reactive field E and inertial force QE = -m(dv/dt), as inertia. Coulomb’s law is modified, with a velocity term, in view of aberration of electric field, for radiation from accelerated charges. Curving of space-time continuum is replaced with curling of electric field lines of force. Materials for teaching electromagnetic fields and radiation, in space, are well provided.

Ostomy Bag and Betel Leaf in Pediatric Stoma Care

Background: Construction of a stoma is a common procedure in pediatric surgical practice. For care of these stomas, commercially available devices such as Ostomy bag, either disposable or of longer duration are usually used. These are expensive, particularly in countries like Bangladesh, and proper-sized ones are not always available. We have found an alternative for stoma care, betel leaf, which is suitable for Bangladeshis. Objective: The main objective of this study was to compare between Ostomy bag and betel leaf in Pediatric stoma care and also comparison of skin excoriation between Ostomy bag and betel leaf using in pediatric stoma care & comparison of cost and care givers satisfaction of the study groups. Materials and Methods: A total of 60 patients having various types of stoma within the age of 12 years were included in the study and randomly assigned to 2 groups – group 1 with Ostomy bag (30 patients) and group 2 with Betel leaf (30 patients). After construction of stoma, at first zinc oxide paste was applied on the Peristomal skin. A betel leaf with shiny, smooth surface outwards & rough surface inwards was put over the stoma with a hole made in the center according to the size of stoma. Another intact leaf covers the stomal opening. When bowel movement occurs, the overlying intact leaf was removed & the faecal matter was washed away from both. The leaves were reused after cleaning. Use of commercially available Ostomy bag (e.g., Convatec ostomy bag) with Adhesive paste (Stomahesive) will be applied on the Peristomal skin. Results: Out of 60 pediatric patients, 20 had pelvic colostomy, 19 had transverse colostomy and 21 had ileostomy. Of 60 patients under stoma care Mild excoriation had seen 21.7% cases of ostomy bag group and 13.3% cases of betel leaf group. Only 5% cases of ostomy bag group had moderate excoriation (P value was 0.116 which was not significant).Out of 40% excoriation, 30% occurred in ileostomy (p value <0.0001, hence significant). .....

Cytochemical and immunocytochemical characterization of wood decayed by the white rot fungus Pycnoporus sanguineus II. Degradation of lignin and non-cellulosic polysaccharides in European ash wood

Degradation of lignin and non-cellulosic polysaccharides (pectins and hemicelluloses) by the white rot fungus Pycnoporus sanguineus were investigated in European ash wood (hardwood) using transmission electron microscopy coupled with immunocytochemistry. Lignin was preferentially removed in secondary cell walls of ash xylem cells including fibers, vessel and (ray/axial) parenchyma cells prior to degradation of hemicelluloses (i.e. selective decay). Concomitantly, degradation of cell walls occurred by progressive thinning from the lumen surface outwards similar to simultaneous decay. Preferential degradation of middle lamellae before complete degradation of secondary cell walls (i.e. a typical feature of selective decay) was only observed in bi-/triseriate rays by initial attack from pit regions. Vessel and parenchyma cells showed greater resistance to decay than fibers with narrower decay zone produced. A comparison of decay between ash and spruce wood (Part I, softwood) demonstrated that P. sanguineus produces selective decay in both hard- and softwoods but more typical micromorphological features of selective decay are produced in spruce tracheids than ash fibers. This study highlights that degradation of lignin proceeds hemicelluloses in wood cell walls attacked by the selective white rot fungus P. sanguineus.

Evaluation of fouling formation and evolution on hollow fibre membrane: Effects of ageing and chemical exposure on biofoulant

Bio-deposition and biofouling, a major challenge for membrane filtration, is still not fully understood due to its complex structure and intricate evolution with time and chemical environment. In this work, diluted sludge from an anaerobic bioreactor with low mixed liquor suspended solid (MLSS) concentration was filtered for 3.5 h to form initial fouling layers which were then exposed to various solution environments for 17 h. Apart from monitoring the hydraulic resistance of membrane fouling, a real time direct observation (DO) technique was applied to monitor the change of thickness in the fouling layer. The cohesion and adhesion of different fouling layer were investigated by monitoring the transmembrane pressure (TMP) and thickness change after applying relaxation (cessation of filtration) and backwash. It was found that TMPs and resistances of the aged fouling layers increased significantly after 17 h filtration. All the aged fouling layers exhibited lower compressibility as a result of more soluble microbial products (SMP) and extracellular polymeric substances (EPS) excretion, biofilm growth. From in situ imaging, the fouling on the membrane surface appeared to be inhomogeneous from the inner (lumen) surface outwards. During long term filtration of fouling layer with Milli-Q water, direct observation (DO) results indicated the reorganization of the fouling layer in terms of peeling, rolling over and re-depositing on the membrane surface, resulting into more compressed fouling layers with higher resistances. Confocal Laser Scanning Microscopy (CLSM) analysis of aged fouling layers also indicated that the dead/total ratio of microorganisms was not uniform and increased gradually from the bottom to the top of the fouling layers.

Influence of the single-particle structure on the nuclear surface and the neutron skin

We analyze the influence of the single-particle structure on the neutron density distribution and the neutron skin in Ca, Ni, Zr, Sn, and Pb isotopes. The nucleon density distributions are calculated in the Hartree-Fock+BCS approach with the SLy4 Skyrme force. A close correlation is found between the quantum numbers of the valence neutrons and the changes in the position and the diffuseness of the nuclear surface, which in turn affect the neutron skin thickness. Neutrons in the valence orbitals with low principal quantum number and high angular momentum mainly displace the position of the neutron surface outwards, while neutrons with high principal quantum number and low angular momentum basically increase the diffuseness of the neutron surface. The impact of the valence shell neutrons on the tail of the neutron density distribution is discussed.

Synthesis of cellulose nanocrystals bearing photocleavable grafts by ATRP

Cellulose nanocrystals (CNC) were grafted with photocleavable polymeric chains using Atom Transfer Radical Polymerisation (ATRP). The nanoparticle synthesis relies on two main steps: first the grafting of a photosensitive moiety bearing an ATRP initiating site onto the surface of CNC, followed by surface initiated ATRP from the modified surface outwards. An original UV-sensitive linker bearing one ATRP initiating site and one anchoring hydroxyl functionality, which was grafted to the CNC surface using a diisocyanate linker, was designed to achieve this goal. Polystyrene (PS) was then polymerized from the modified CNC, resulting in CNC-g-photolinker-PS nanoparticles. The possibility to degraft the PS chains using UV-irradiation was further investigated, and PS grafts with a narrow polydispersity index (1.08) and molecular weights close to those of formed homopolymers through sacrificial initiator addition were obtained. This is the first example where it has been proven that good control of SI-ATRP from CNC can be achieved. It also confirms that homopolymers initiated by sacrificial initiator in the polymerization medium can be an indication of the grafted polymer brush length. These materials further offer potential as smart delivery vehicles and smart materials.

Betel leaf in stoma care

Background/Purpose Construction of a stoma is a common procedure in pediatric surgical practice. For care of these stomas, commercially available devices such as ostomy bag, either disposable or of longer duration are usually used. These are expensive, particularly in countries like Bangladesh, and proper-sized ones are not always available. We have found an alternative for stoma care, betel leaf, which is suitable for Bangladeshis. We report the outcome of its use. Methods After construction of stoma, at first zinc oxide paste was applied on the peristomal skin. A betel leaf with shiny, smooth surface outwards and rough surface inwards was put over the stoma with a hole made in the center according to the size of stoma. Another intact leaf covers the stomal opening. When bowel movement occurs, the overlying intact leaf was removed and the fecal matter was washed away from both. The leaves were reused after cleaning. Leaves were changed every 2 to 3 days. From June 1998 to December 2005, in the department of pediatric surgery, Chittagong Medical College and Hospital, Chittagong, Bangladesh, a total of 623 patients had exteriorization of bowel. Of this total, 495 stomas were cared for with betel leaves and 128 with ostomy bags. Results Of 623 children, 287 had sigmoid colostomy, 211 had transverse colostomy, 105 had ileostomy, and 20 had jejunostomy. Of the 495 children under betel leaf stoma care, 13 patients (2.6%) developed skin excoriation. There were no allergic reactions. Of the 128 patients using ostomy bag, 52 (40.65%) had skin excoriation. Twenty-four (18.75%) children developed some allergic reactions to adhesive. Monthly costs for betel leaves were 15 cents (10 BDT), whereas ostomy bags cost about US$24. Conclusion In the care of stoma, betel leaves are cheap, easy to handle, nonirritant, and nonallergic.

Crop establishment using subsurface drip irrigation: a comparison of point and area sources

One of the greatest challenges faced by irrigators using subsurface drip irrigation (SDI) is crop establishment. Establishment with SDI relies on unsaturated water movement from the buried source to the seed or seedling. Establishment is therefore affected by distance to source, soil texture, structure, and antecedent water content. Two products were compared (drip tape and CRZI – Capillary Root Zone Irrigation) in a field trial designed to address the establishment issue. To measure the widest establishment extent, a crop was sown perpendicular to the drip laterals. The CRZI system comprises a combination of both impermeable and highly conductive materials designed to produce a wider lateral wetting pattern, while reducing drainage and surface tunnelling. The hypothesis being tested was that the CRZI concept would offer some advantage over drip tape for addressing the establishment issue. Results showed that for the soil at the experimental site (Hanwood loam), installation depth of either product should be no greater than 0.2 m. If attempting to establish a broadsown crop such as lucerne or pasture, lateral spacing should be no greater than 1.0 m. With this configuration, an application depth of 120 mm should still be expected for total surface coverage. CRZI did not produce any establishment advantage over drip tape. Two explanations are given for this result. Firstly, the soil in which the trial was performed has excellent capillary properties and has a natural clay pan which would serve to even out results. Secondly, the two products exploited very different wetting methods to produce similar surface wetting efficiency (ratio of surface wetted width to applied irrigation volume). The drip tape quickly saturated the surface and wet outwards through surface flow. As CRZI did not utilise the surface to aid with distribution, it produced a slower, more even, wetting pattern.

Parental Care in Dicellophilus carniolensis (C. L. Koch, 1847): New Behavioural Evidence with Implications for the Higher Phylogeny of Centipedes (Chilopoda)

Parental care in Dicellophilus carniolensis (Chilopoda Geophilomorpha Mecistocephalidae) is described for the first time: the female coils around the brood with the dorsal surface outwards, as do the females of other centipede orders (Craterostigmomorpha and Scolopendromorpha) but at variance with the remaining geophilomorphs, whose brooding females remain coiled with the ventral surface outwards. The available information on this behaviour in centipedes is reviewed and interpreted in the context of the phylogeny of the group, based on morphological and molecular characters, and also in relation to the evolution of the sternal glands, a feature common to most Geophilomorpha. The evolutionary transition from brooding female with dorsal side outwards (plesiomorphic state) to brooding female with ventral side outwards (apomorphic state) was most likely associated with the evolution of defensive glands on the ventral surface of the female. The behaviour observed in D. carniolensis is probably common to the whole of Mecistocephalidae, thus supporting the basal position of this clade within the Geophilomorpha.

Electronic structure of SnO2 (110) surface

The electronic structure of the stoichiometric and reduced SnO2 (110) surfaces is studied with first-principles calculations. Calculations are carried out with two complementary self-consistent ab initio–DFT–GGA methods. Surface relaxation is considered, where the most prominent feature turns out to be the surface layer in-plane oxygen displacement of the reduced surface outwards, about 0.4 Å with respect to the surface layer tin atoms. The electronic structure of the relaxed surfaces is considered in terms of atomic orbitals and rehybridization, and the surface band structure. The bands are flat at the stoichiometric surface, but strong dispersion occurs at the reduced surface. The dispersion results in electronic levels into the band gap, which have also been experimentally observed.

A parabolic equation-based backpropagation algorithm for matched-field processing

In applications of matched-field processing (MFP) to passive sonar, signals measured on a hydrophone array due to a source at some unknown position xs=(rs,zs) are correlated with signals predicted by a propagation model (replicas) due to a source at a given position x=(r,z). This matching is carried out for many assumed x’s within a search region (range, r and depth, z) to form a (normalized) ambiguity surface whose peak value provides an estimate of xs. For an N-element array, reciprocity is invoked to reduce the computational effort to computing N replica fields at each point on the search grid. In this paper, a matched-field processor proposed by Tappert et al. [J. Acoust. Soc. Am. 78, S85 (1985)] is revisited that combines measured data with PE starting fields to effectively backpropagate an (unnormalized) ambiguity surface outwards from the receiving array. This unnormalized processor generates the ambiguity surface N times faster than the normalized one. The effectiveness of the backpropagation algorithm is examined by applying it to some multi-tonal data obtained during the Hudson Canyon experiment. Issues relating to normalization and incoherent/coherent frequency averaging are discussed.

Winds from neutron stars and strong type I X-ray bursts

view Abstract Citations (34) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Winds from Neutron Stars and Strong Type I X-Ray Bursts Nobili, Luciano ; Turolla, Roberto ; Lapidus, Iosif Abstract A model for stationary, radiatively driven winds from X--ray bursting neutron stars is presented. General relativistic hydrodynamical and radiative transfer equations are integrated from the neutron star surface outwards, taking into account for helium nuclear burning in the inner, dense, nearly hydrostatic shells. Radiative processes include both bremsstrahlung emission--absorption and Compton scattering; only the frequency--integrated transport is considered here. It is shown that each solution is characterized by just one parameter: the mass loss rate $\Mdot$, or, equivalently, the envelope mass $\Menv$. We found that, owing to the effects of Comptonization, steady, supersonic winds can exist only for $\Mdot$ larger than a limiting value $\Mdot_{min} \approx\Mdot_{E}$. Several models, covering about two decades in mass loss rate, have been computed for given neutron star parameters. We discuss how the sequence of our solutions with decreasing $\Menv$ can be used to follow the time evolution of a strong X--ray burst during the expansion/contraction phase near to the luminosity maximum. The comparison between our numerical results and the observational data of Haberl {\it et al.\/} (1987) for the bursts in 4U/MXB 1820-30 gives an estimate for both the spectral hardening factor and the accretion rate in this source. Publication: The Astrophysical Journal Pub Date: September 1994 DOI: 10.1086/174643 arXiv: arXiv:astro-ph/9405065 Bibcode: 1994ApJ...433..276N Keywords: Hydrodynamics; Neutron Stars; Radiative Transfer; Stellar Mass; Stellar Models; Stellar Radiation; Stellar Winds; X Rays; Bremsstrahlung; Bursts; Compton Effect; Mathematical Models; Stellar Mass Accretion; Astrophysics; HYDRODYNAMICS; RADIATION MECHANISMS: NONTHERMAL; RADIATIVE TRANSFER; STARS: INDIVIDUAL ALPHANUMERIC: 4U/MXB 1820-30; STARS: MASS LOSS; STARS: NEUTRON; X-RAYS: BURSTS; Astrophysics E-Print: 32 pages (10 postsript figures available on request), PlainTeX full text sources arXiv | ADS | data products SIMBAD (4)

Microstructures and precipitates in laser-ablated YBCO thin films on SrTiO 3 (110)

Thin YBCO films (∼ 100 nm) have been deposited by laser ablation on SrTiO 3 (110) substrates. Microstructural investigations have been performed by scanning tunneling and high-resolution electron microscopy. The results show that the surface corrugation is related to the growth of twisted YBCO domains that nucleate at the film/substrate interface. The twist is characterized by a 90° rotation of YBCO around the [100] and/or [010] axes, which results in {013} and/or {103} planes parallel to the substrate surface. Precipitates belonging to Y 2O 3 are densely distributed on the film surface. No such second phases have been identified inside the YBCO films. The orientational relationship between precipitates and film is such that the lattice mismatch is minimized in the interface planes. A large number of precipitates grow from the film surface outwards. This phenomenon can be explained on the basis of lattice matching arguments and favorable growth kinetics.

Test instructions

Construction of a stoma is a common procedure in pediatric surgical practice. For care of these stomas, commercially available devices such as ostomy bag, either disposable or of longer duration are usually used. These are expensive, particularly in countries like Bangladesh, and proper-sized ones are not always available. We have found an alternative for stoma care, betel leaf, which is suitable for Bangladeshis. We report the outcome of its use.After construction of stoma, at first zinc oxide paste was applied on the peristomal skin. A betel leaf with shiny, smooth surface outwards and rough surface inwards was put over the stoma with a hole made in the center according to the size of stoma. Another intact leaf covers the stomal opening. When bowel movement occurs, the overlying intact leaf was removed and the fecal matter was washed away from both. The leaves were reused after cleaning. Leaves were changed every 2 to 3 days. From June 1998 to December 2005, in the department of pediatric surgery, Chittagong Medical College and Hospital, Chittagong, Bangladesh, a total of 623 patients had exteriorization of bowel. Of this total, 495 stomas were cared for with betel leaves and 128 with ostomy bags.Of 623 children, 287 had sigmoid colostomy, 211 had transverse colostomy, 105 had ileostomy, and 20 had jejunostomy. Of the 495 children under betel leaf stoma care, 13 patients (2.6%) developed skin excoriation. There were no allergic reactions. Of the 128 patients using ostomy bag, 52 (40.65%) had skin excoriation. Twenty-four (18.75%) children developed some allergic reactions to adhesive. Monthly costs for betel leaves were 15 cents (10 BDT), whereas ostomy bags cost about US$24.In the care of stoma, betel leaves are cheap, easy to handle, nonirritant, and nonallergic.

Motor and predatory behavior of Litonotus lamella (Protozoa, Ciliata)

The ethogram of Litonotus lamella is described and discussed. Individuals of the species creep on the substrate at a velocity of 189 ± 40 μm/s, moving toward the right along geometrically perfect arcs with different radii, lengths, and amplitudes. The arcs are connected by four types of reaction: the continuous trajectory change, the smooth trajectory change, the rough trajectory change, and the side-stepping reaction. Litonotus lamella swims along a helicoid, keeping its ciliated surface outwards. Under appropriate conditions, L. lamella kills, engulfs, and eats the ciliate Euplotes crassus. This predatory behavior consists of two different sets of behavioral patterns; the first is part of the normal motor behavior, while the second comprises behavioral patterns performed characteristically and exclusively during the predatory activity.

Europan surface phenomena

The interaction of corotating iogenic plasma with the surface of Europa in light of recent ice sputtering, experimental results, and published Voyager data has been examined. It has been found that the residual atmosphere of Europa is made up of sputtered molecular oxygen and is exospheric from the surface outwards. It was also found that if sputtering, redistribution, and escape are considered and the sulfur dioxide/water mixing ratio is held constant over a UV observing depth, the observed sulfur dioxide density on the trailing hemisphere lends support to the hypothesis that liquid water from the interior of Europa is boiling out and being deposited as a frost layer on the surface at the rate of about 0.04 μm/year.

Three dimensional analysis of the eggshell fromDrosophila melanogaster

Formation of the insect eggshell is being studied as a model case of cell differentiation. Because of the potential for genetic analysis, we are concentrating on the eggshell ofDrosophila melanogaster. Here we summarize our understanding of the wild type structure as determined using a variety of ultrastructural methods. Follicles, eggshells or pure endochorion were prepared as described and studied with a Philips 301 TEM, an AMR 1000 SEM, a JSM-35 SEM, and a JEM-1000 high voltage electron microscope. Glutaraldehyde fixation (Figs. 6, 8, 9) followed by OsO4, (Figs. 1, 3, 4, 7, 10, 11) was used.Thin sections (Fig. 1) of stage 14 follicles reveal the following layers of the mature eggshell from the oocyte surface outwards: vitelline membrane (VM), intermediate chorionic layer (ICL), endochorion (END) and exochorion(EX). The amorphous VM and the loosely fibrous EX appear simple in structure. The ICL has been purified and shown by negative staining to have a prominent crystalline structure (Fig. 2) which has been further investigated by optical diffraction and filtering.

Mastophorus muris (Nematoda: Spirurina): Cuticular Ultrastructure of the Adult and Third Stage Larva

The fine structure of the cuticle of the infective larva and of the adult male and female was studied in Mastophorus muris, a stomach parasite of rats. The infective larva develops in the hemocoel of the insect intermediate host where it lays coiled in a gelatinous cyst with its ventral surface outwards. In transverse sections of uncoiled larvae the cuticle is 2.4 uAm thick and consists of a cortex in which a narrow band of striations is visible, a median layer, and one layer of basal fibers. In coiled specimens the ventral cuticle of the larva is stretched and thin, whereas the dorsal cuticle is thicker, folded, and appears compressed. The cuticle of the adult worms is 17-74 Arm thick and consists of an outer fuzzy coat, an external trilaminar structure, a granular external cortex, and an internal cortex containing striated fibers with a periodicity of 200 nm. The median layer consists of homogeneous, electron-dense material in which less electron-dense material is seen. Three sublayers of fibers comprise the basal layer. The innermost basal lamella consists of striated fibers with a 140-nm period. The ultrastructure of nematode cuticle has been reviewed by Lee (1966b, 1972), Bird and Bird (1969), and Bird (1971). With the exception of several species of filariae, representatives of the suborder Spirurina have been studied only by light microscopy (Bogoyavlenski, 1961). In the present study the cuticular ultrastructure of adult Mastophorus muris, parasitic in the stomach of rats, and of its infective third stage larva, parasitic in the hemocoel of the cockroach, is described. MATERIALS AND METHODS Mastophorus muris, isolated from city rats (Wertheim, 1963), was maintained in the outbred Hebrew University Sabra strain of rats and in Blatella germanica. Roaches, fasted for 48 hr, were infected with larvated eggs mixed with powdered wet oat flakes. The rats, 80-100 g, were infected by gavage with 15 gelatinous cysts containing 3rd stage larvae, dissected from the roaches 4-5 weeks postinfection. For this study adult worms were removed from Received for publication 6 September 1977. * On Fellowship Leave from LaGuardia Community College, City University of New York, Long Island City, New York. the stomach of ether-killed rats, infected 60 days previously. The 3rd stage larvae were freed from the gelatinous cysts by treatment with artificial gastric juice for 10 min at 37 C. Worms were rinsed in saline and cut into appropriately sized cylinders. Tissue was fixed for 1-2 hr in ice-cold 2.5% glutaraldehyde in either phosphate or cacodylate buffer pH 7.4. Worms were then rinsed in 3 changes of cold buffer for 1 hr. Postfixation was carried out for 1 hr with ice-cold 1% osmium tetroxide in one of the above mentioned buffers. The tissue was rinsed in distilled water and in 2% uranyl acetate in distilled water, dehydrated in an ethanol series, transferred to propylene oxide, and left overnight in a 1:1 mixture of propylene oxide-Epon. Following 2 hr in fresh Epon in vacuo (Bird, 1971), the tissue was embed ed in fresh Epon in flat silicone rubber molds, oriented, and polymerized at 60 C for 48 hr. Blocks were sectioned with glass knives on a LKB Ultratome. Thick (0.5-1.0 tum) sections were stained with 1% toluidine blue in 0.5% sodium borate at 60 C. Selected areas were thin sectioned and picked up on naked or formvarcarbon coated grids, stained with uranyl acetate and lead citrate, and examined with a Philips 300 electron microscope at 60 kV. Worms for scanning electron microscopy were prepared according to the method descibed elsewhere (Wertheim and Chabaud, 1977). FIGURES 1, 2. Third stage larva of Mastophorus muris. 1. Electron micrograph of a transverse section from the middle of uncoiled larva. The striated band is visible near the interior border of the cortex. Cortex (C), median (M), and basal (B) layers. X 53,000. 2. Transverse section of the lateral alae of larva. Body wall layers are retained, cortex (C), median (M), and basal (B), and an electron-dense granular deposit (G) is visible between the cortex (C) and median (M) layers. Cyst debris is visible on external surface of the cuticle. X 20,000.

Paper 10: Metallurgical Aspects of Rolling Contact Fatigue

Metallurgical investigations aided by electron microscopy and associated techniques have been carried out on failed test specimens and bearings from service, to obtain information of use in the elucidation of the mechanisms of failure. Investigations have revealed that cracks initiating rolling contact fatigue can start at the surface and spread into the material, or start below the surface and spread outwards, the more dominant mechanism depending upon prevailing circumstances. Metallographic changes in surface material owing to rolling and sliding action, and subsurface microstructural changes at depths associated with the region of maximum Hertzian shearing stress can influence the mechanism of failure. Environment can affect the rate of crack propagation and mode of fracture; hydrogen embrittlement can be a contributory factor in catastrophic fracture, and non-metallic inclusions can have a dominant effect on the incidence of failure.

A Simple Inexpensive Ultracentrifuge

IN designing quantitative ultracentrifuges costing only a few pounds and available for measurements of sedimentation velocity and of sedimentation equilibrium, it is clearly best to adopt the simple modification of the air-driven spinning top of Henriot and Hugenard, in which the essential part of the system is immobilized by mechanical baffles1. This dispenses entirely with an optical system and depends upon direct analysis of the liquid after ultracentrifuging, using any suitable chemical, physical or biological method. Such opaque ultracentrifuges possess the further advantage over any transparent ultracentrifuge that the whole of the column of liquid from its upper surface outwards and from the very beginning of the sedimentation is available, without distortion, for exact measurement.