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In order to manage Quality of Service (QoS) and energy efficiency in the optical access network, an online Dynamic Bandwidth Allocation (DBA) algorithm with adaptive sleep cycle is presented. This DBA algorithm has the ability to allocate an additional bandwidth to the end user within a single sleep cycle whose duration changes depending on the current buffers occupancy. The purpose of this DBA algorithm is to tune the duration of the sleep cycle depending on the network load in order to provide service to the end user without violating strict QoS requests in all network operating conditions.

This paper analyzes renewal input batch arrival queues with multiple and single working vacation policy. We obtain the steady state system-length distributions at pre-arrival and arbitrary epochs. The Laplace-Stieltjes transforms (LST) of the sojourn time distribution for the first customer and an arbitrary customer in an accepted batch have been derived. Also the probability density function of sojourn time distribution for the first customer in an accepted batch has been obtained. The proposed analysis is based on the roots of the characteristics equations formed using the probability generating functions (p.g.f.) of embedded pre-arrival epoch probabilities. Several performance measures such as the mean system-length and mean sojourn times of first and an arbitrary customer in an accepted batch are presented. The suggested queues have potential application in ethernet passive optical network (EPON).

Human, rat and mouse pituitary tissues have been examined electron microscopically in transmission (TEM), scanning-transmission (STEM) and scanning (SEM) modes for the surface appearance of the secretory granules in tissue sections. Cryofixed and cryosectioned tissue showed only slightly protruding granule profiles which had a smooth surface. Cryofixed, freeze-dried and Epon embedded pituitaries, on the other hand, demonstrated swollen and furrowed surfaces over the granules after contact with water. This topography could also be seen after glutaraldehyde fixation but less after post-fixation in OsO4. The surface alterations in the sections of pituitary secretory granules are thought to be due to differences in the homogeneity of the resin infiltration, leaving resin-free openings where water can enter. It also seems probable that the Epon resin is more influenced by water than has been previously assumed, based on the findings of efficient elimination of osmium from the granules after incubation of tissue sections in water for only 10 min.

Intracellular, extracellular, and bacterial antigens were demonstrated ultrastructurally by means of silver enhanced immunogold marker systems (IGSS method). Mild fixation provided a suitable compromise between the ultrastructural and antigenic preservation. The use of small (5 nm) gold-coupled streptavidin on anti-rabbit IgG markers resulted in high sensitivity, which could be further amplified in the latter case by repeating both incubation steps in a double sandwich. However, without the silver enhancement step, the traditional counterstainings obscured theparticles, and theultrastructure was hardly visible on weak tissue staining. The photographic silver reaction allowed good reaction product visualization. In LR-White sections, a doubled silver reaction time was necessary to attain the same particle size as for those in epoxides. LR-White embedding was found to be at least as good as epoxy embedding in preserving immunoreactivity, and in some cases, more effective.The system described is a s...

A quantitative evaluation of spermatogenesis in the guinea pig was made at the light microscope level following improved methods of fixation and plastic embedding. The pattern of germ cell differentiation was studied by counting the average number of germ cell nuclei per Sertoli cell nucleus during the seminiferous epithelial cycle. Appreciable cell loss occurred during spermatogenesis. As a result, only 20.8% of the theoretically possible number of spermatozoa were produced from each spermatogonium. A slightly better yield of germ cells was obtained from Epon sections in comparison to paraffin sections. Epon sections can be effectively used for quantitative analyses of various cell populations in small biopsy specimens of testis tissue.

The described technique, based upon a one-step Mallory-Heidenhain stain, can be applied as a routine stain for glutaraldehyde or OsO4 fixed, Epon embedded tissues of various organs. The technique consists of a short treatment of the sections with H2O2, a nuclear staining with celestine blue B and a final staining in a modified Cason's solution. The different tissue and cell components are displayed as follows: dark brown nuclei, yellow cytoplasm, red collagen fibers and blue elastic fibers. Intracytoplasmic components as glycogen and mucus are stained respectively blue and violet, whereas other inclusions such as leucocyte granules are colored orange to red.

Four-week-old Holtzman rats were injected intraperitoneally with 20 μCi 125I. Six or eight weeks later, they were killed by intracardiac perfusion with glutaraldehyde; thyroid and adrenal glands were excised, postfixed in osmic acid, and embedded in Epon. Steps in the staining procedure of 0.5-1 μm thick sections are: oxidation in 0.3% potassium permanganate in 0.625% sulfuric acid, 2-5 min at 70 C; brief rinse; bleaching with 2.5% NaHSO3, 4-5 min; brief r-utse; let dry completely; aldehydefuchsm, 15-20 min at 50 C; 95% alcohol; rinse in absolute alcohol; let dry completely. seaions were coated with Kodak NTB2 emulsion and exposed for 3 to 8 weeks. Results indicate that (1) tissues are well stained even after an 8-week exposure, (2) aldehyde-fuchsin pduces no chemographic effect, and (3) structures underneath the emulsion are easily identified.

OsO-fixed, Epon- or Araldite-embedded tissue can be stained by the silver amminocarbonate method of del Rio Hortega. Sections, 0.5–1.5 μ thick, are floated on the silver solution and impregnated for 0.5–2 hr at 60 C. Pyridine, 1–2 drops/10 ml of staining solution, facilitates the staining. Reduction in 1% formalin and fixation by Na2S2O3 are optional. Staining may be influenced by the buffering vehicle in the fixative and appears to be dependent on sites of osmium binding. Cytoplasmic processes and basement membranes are well stained, as are intracytoplasmic organelles. Nuclear and nucleolar staining is variable.

Tissue blocks or sections immunofluorescent stained before embedding, i.g., liver and kidney, can be stored for more than 3 years without demonstrable fluorescence decay. The processing steps, including poststaining dehydration by alcohols and embedding in expoxy resins, seem to stabilize the fluorochromes fluorescein isothiocyanate (FITC) and tetramethylrhodamine isothiocyanate (TRITC) so that they fade less during illumination. This is an advantage of the pre-embedding, immunofluorescent staining technique which is combined with a lack of damage to the antigens by the plastic embedding medium.

A 3-step procedure performed at 85 C was as follows: Sections were treated with 4% aqueous ferric ammonium sulfate for 15-300 sec, washed, placed in ripened, 0.5% hematoxylin for 15-300 sec, washed, and counterstained in 1% Safranin O for 15-90 sec. This procedure produced a durable stain with clear cytoplasmic and nuclear differentiation.

Serial sectioning epoxy embedments by steel knife permits rapid light microscope survey of large tissue volumes, and preselection of areas of interest for electron microscopy. Acetate film (Hollander 1970) and Turtox plastic slides (West 1972) have been suggested as substrates upon which the sections may be “cleared” with an added layer of cured epoxy. In our experience, these substrates are excessively adherent to Epon, and “cleared” sections thinner than 40-50 μm cannot be released from them reliably. The following method is suitable for processing Epon sections 10 or more microns thick.

The paper describes surface treatment methods to improve adhesion between copper and vinyl ester in glass fiber–vinyl ester composites. Surface treatment methods were developed for commercially available copper that was optimized for epoxies and adhesion performance was compared based on 90° peel strength measurements. Four surface treatments for copper were tested: (i) co-cured Epon/vinyl ester; (ii) fully cured Epon; (iii) epoxy film adhesive; and (iv) γ-MPS silane along with two baseline systems: copper/vinyl ester and copper/epoxy. Measured average peel strengths for the surface treatments were 21%, 101%, 110% and 91% of the baseline copper/vinyl ester system, respectively. Compared to the copper/epoxy system, fully cured Epon, epoxy film adhesive and the silane treatment generated comparable adhesion between copper and vinyl ester. For all samples tested, mixed cohesive/adhesive failure modes were observed. Overall, the surface treatment with the silane coupling agent is the most appropriate method f...

In order to gain an insight into the aspects of surface roughness, surface profile, adhesive viscosity, and surface morphology, experiments were conducted using two different steels (1018 cold-rolled and hot-rolled weld steels). Four different surface modifications were performed on these samples by sand-blasting at 552 kPa from a distance of 25.4 mm, and etching for 2 and 10 min with a chemical recipe containing chromic acid. Two different adhesives were used, namely Epon 815 and Epon 830 with viscosities of 5-7 and 170-225 Poise, respectively, to assess the effect of viscosity in bonding to adherends with different surface topographies. Contact angles were measured on all surfaces using the two adhesives. To gain an insight into the effect of surface topography, scanning electron microscopy (SEM) was utilized to observe the modified surfaces at different magnifications. Both average and maximum peak-to-valley height values were measured using a profilometer and surface profiles were also obtained for al...

This paper presents the results of comprehensive testing to characterize the effect of several different surface treatments on shear and tensile bond strength between 7075-T6 aluminum and two epoxy systems: EPON 815/V40 and EPON 828/Z. A rod pull-out test was used to determine interfacial shear strength, modeled after similar tests on reinforced concrete. The tensile bond strength was characterized using a tension test fixture designed in this study. Overall, the interfacial shear strengths were higher than the tension strengths. Surface knurling gave the highest interfacial shear strength, representing a 72% increase over untreated specimens. Phosphoric acid anodization (PAA) was also quite effective in shear. In tension, the highest strength was obtained from specimens treated with the PAA process along with a silane coupling agent. These specimens showed an increase in interfacial tensile strength by a factor of 5.6.

in basidiomycete systematics. Arguments for and against including false truffles in the Agaricales hinge on the interpretation ofthe character suites and the degree of importance given to them in forming phylogenetic hypotheses (e.g., Kuhner, 1980, 1984; Julich, 1981; Singer, 1986). A number of mycologists have postulated a close relationship between the false-truffle genera Hydnangium Wallr. and Podohydnangium Beaton, Pegler, & Young and the mushroom genus Laccaria Berk. & Br. (e.g., Pegler and Young, 1979; Kuhner, 1980, 1984; Julich, 1981; Beaton et al., 1984; Mueller, 1992; Mueller and Ammirati, 1993) based on similar basidiospore or? namentation. There are numerous publications illustrating basidiospore ornamentation as viewed under the scanning electron microscope for one or more of these three genera (e.g., Pegler and Young, 1969, 1971, 1979; Beaton et al., 1984; Castellano et al., 1989; Mueller, 1991, 1992). Kuhner (1980, 1984) reported that the discrete, conical echinulae observed on basidiospores of both Laccaria and Hydnangium have microfibrils that run nearly parallel to the axis of the spine. He used these wall ultrastructure features, along with cytological and ecological characters, to justify placing Hydnangium and Laccaria in the same family Hydnangiaceae in his Tricholomatales (Kuhner, 1980, 1984). Based on unpublished micrographs of Hydnangium, Mueller (1992) and Mueller and Ammirati (1993) argued that this type of basidiospore wall ultrastructure is the one shared derived morphological feature that links these genera. However, while illustra? tions of the basidiospore wall ultrastructure of Laccaria were presented in Besson and Kiihner (1971) and Kiihner (1980), to our knowledge, no transmission electron micrographs showing the basidiospore wall ultrastructure of Hydnangium or Podohydnangium have been published. In this paper, we present micrographs documenting the similarity of wall ultrastructure of Hydnangium and Laccaria and discuss the phylogenetic implications of these data. Scanning electron micrographs were taken at the Field Museum of Natural History following the procedures outlined in Mueller (1991,1992). For examination on the Uppsala University Jeol 100 B transmission electron microscope, small pieces of lamellar tissue from air-dried herbari? um specimens were rehydrated in 3% KOH, fixed in 2.5% glutaraldehyde in 0.1 M phosphate buffer (pH 7.5), and washed in buffer three times. The samples were then postfixed in 2% Os04 in 0.1 M phosphate buffer for 2 h at 4 C, washed in buffer three times, dehydrated in a graded eth? anol series and propylene oxide infiltrated with Epon, and embedded in Epon that was polymerized for 48 h at 60 C. Sections of 50 nm thickness were cut with a Dupont diamond knife

A method is presented for histological examination of undecalcified ground sections of tooth roots affected with periodontal disease. The roots were placed in Karnovsky's fixative overnight, postfixed in 2% buffered osmic acid, and dehydrated in an ascending series of ethanol. The specimens were then infiltrated with propylene-oxide and Epon-Araldite resin, embedded in Epon-Araldite, and sections were prepared using a cutting and grinding system. The resulting ground sections were 8-12 microns thick. The sections were allowed to air dry at room temperature. When thoroughly dried, a coverglass was applied using resinous mounting medium DPX. The specimens were examined by phase-contrast microscopy. The method is useful for simultaneous examination of mineralized dental tissue and bacterial morphotypes covering the root surface of teeth involved with periodontal disease.

Rapid three-dimensional reconstruction of serial sections at the light microscopic and ultrastructural levels was accomplished using a two-step technique. Fixed specimens were embedded in Epon and 1 microns sections were cut and placed on glass slides. One of every four sections was drawn onto transparency film for rapid three-dimensional reconstruction. The semi-thin sections were re-embedded in Epon and sectioned at 90 nm for examination in the electron microscopy.

Intranuclear inclusion bodies in hepatic cells of seven Peach-faced Lovebirds (Agapornis roseicollis), two Black-masked Love birds (A. personata) and two galahs (Cacatua roseicapilla) were examined electron microscopically. Thin sections were prepared from formalin-fixed Epon-embedded tissue or from haematoxylin and eosin stained sections that were subsequently embedded in Epon. Discrete and diffuse eosinophilic inclusions in hepatocytes of eight birds were composed of filaments and virus particles were not demonstrated within them. Virus-like particles of at least three types were found in diffuse, lightly basophilic inclusions of similar appearance in hepatocytes and Kupffer cells or endothelial cells in four birds. Particles, 66 nm in diameter which were probably adenovirus were demonstrated in hepatocytes in one A. roseicollis. Particles 26 nm to 39 nm in diameter which resembled papovaviruses were seen in one A. personata and one C. roseicapilla. Particles of 40 nm to 50 nm in diameter were seen in one A. personata but because of the method of preparation it was not possible to state whether they were adenovirus or papovavirus.

Monolayers of cells grown in ordinary plastic flasks are fixed and embedded “in situ” into Epon. When polymerized at 40 C for 4 days instead of the usual 60 C., the Epon sheet containing the cells is easily detached from the bottom of the plastic container. The Epon sheet is observed by light microscopy as a histological preparation. Ultrathin sectioning of preselected areas can then be carried out in a horizontal plane.

An improved method is described in which tissue areas can be initially identified in thick sections by light microscopy and isolated for subsequent ultrathin sections and observation by electron microscopy. This is achieved by embedding in hard Epon which can be sectioned at 25–150 μm on a sliding microtome after softening the blockface by applying a 60–70 C tacking iron to its surface immediately before each section is taken. The thick sections are then mounted on plastic slides to enable light microscopic selection of areas to be observed by electron microscopy. The selected areas are remounted on faced Epon blanks and resectioned at less than 50 nm. This technique makes it possible to obtain thick sections while maintaining an Epon hard enough for good serial ultrathin sections.

In this article, Bayesian inference for the Offered Optical Network Unit Load (OOL) using non-informative, gamma, power function, and gamma-power function priors is considered. Pareto distributed ON-and OFF-periods generated by the ON/OFF sources at an Optical Network Unit (ONU) in an Ethernet Passive Optical Network (EPON) system are assumed for our implementation in this article. A simulation study and a real-data-based illustrative example are given to demonstrate the advantages of the proposed Bayesian method over the large-sample method.

The development of handheld signal cluster and 40-mm parachute green light–emitting pyrotechnic compositions is described. Of the new compositions evaluated, one was found to exceed the military requirements in burn time, luminous intensity, dominant wavelength, and spectral purity in both the cluster and parachute configurations. The new illuminant composition is not plagued by single-point-of-failure concerns, as the Laminac 4116/Lupersol binder system has been replaced by the widely available Epon 813/Versamid 140 binder system. In addition, the new illuminant composition was found to be insensitive toward impact, friction, and electrostatic discharge and had a high thermal onset temperature.

Latex microspheres used in biological research have been visualized by light microscopy in mounts of cell suspensions, disrupted cells, or cleared tissues (Mishima et al 1987, Koonce et al 1986, LeFevre et al 1978); in unembedded coverslip monolayers (Koerten et al 1980); in fixed (Cornwall and Phillipson 1988) or unfixed (Wells et al 1988) frozen sections; in paraffin sections cleared and deparaffinized with n-butyl alcohol (Callebaut and Meeussen 1989); and in tissues embedded in resins suitable for transmission electron microscopy, such as Spurr's (Hampton et al 1987), Epon (Herzog and Miller 1979), or Ladd Low Viscosity Epon (LeFevre et al 1985). Paraffin embedding, and some plastic embedments, are impractical for demonstration of latex beads because the beads are dissolved by such organic solvents as xylene, dioxane, or chloroform (Van Furth and Diesselhoff-Den Dulk 1980), propylene oxide (Lentzen et al 1984), amyl acetate (Okada et al 1981), or toluene, the solvent in commonly used mounting media su...

An immunoperoxidase cytochemical study of fibronectin localization in the rat corneal stroma and Descemet's membrane was conducted following organ culture to determine whether stromal swelling allowed better primary antibody penetration into the normally tough fibrous corneal stroma.Following 24 h organ culture, corneas were fixed in 4% paraformaldehyde, washed and stained overnight at 4 °C in anti-fibronectin followed by washing and incubation in an appropriate secondary antibody and exposure to protein A-HRP. Cytochemical processing was carried out in a DAB-containing medium followed by dehydration and Epon embedding.Observations of the stromal lamellae revealed the presence of a novel punctate staining pattern along the length of the collagen fibrils that extended around the fibril's circumference. Measurements on the peroxidase reaction product spacing indicated a periodicity of approximately 20.69 ± 3.57 nm along the fibril's length. Light microscopic immunocytochemistry revealed the presence of fibronectin staining occurred within the endothelial cell layer but only along the DM/stromal interface. Electron microscopic observations however, revealed that fibronectin staining occurred in distinct linear patterns along the length of both the endothelial and stromal DM interfaces.Results indicate that organ culture mediated swelling helps facilitate the penetration of primary antibody into the corneal stroma. Observations suggest a novel association exists between fibronectin and stromal collagen fibrils that helps to mediate the arrangement and organization of the stromal extracellular matrix. Results also definitively indicate that fibronectin is deposited along both DM interfaces suggesting that it plays a role in the adhesion of both the endothelial cell layer and stroma to Descemet's membrane to help maintain the tissue architecture within this region of the cornea.

Multiwalled carbon nanotube (MWNT) reinforced epoxy resin composites were fabricated and characterised. Several process variables were investigated using design of experiments. The MWNTs (0·5 wt-%) were dispersed in Epon 862 epoxy resin under various sonication conditions. Young’s modulus, energy to failure, glass transition temperature Tg and storage modulus E′ were assessed. The first three were selected in a design of experiment optimisation study. The results indicated that as the sonication intensity and the duration of sonication were increased, the material response of the MWNT/epoxy composite, specifically Young’s modulus, energy and Tg, was enhanced. The fracture surfaces of the composites were examined using scanning electron microscopy. Improved dispersion was observed in samples fabricated with increased sonication intensities. The Mori–Tanaka model was used to predict the mechanical properties of the MWNT/epoxy composites and was found to be in reasonable agreement with experimental d...

Epoxy/nickel adhesives can be used as integrated circuit (IC) packaging material due to their lower cost than epoxy/silver adhesives with acceptable electrical conductivity. In this work, chemorheological behaviors of Epon 830/Ni/diethylenetriamine (DETA) adhesives were investigated during processing and cure, as a function of shear rate, resin conversion, Ni volume fraction and temperature. A strongly nonlinear characteristic of filled epoxy/Ni systems was revealed, and a steady shear had to be employed for chemorheological analyses. A strongly non-Newtonian flow behavior was observed for epoxy/Ni adhesives also during cure. The power-law model, Castro–Macosko model, Liu model and the Arrhenius model adequately describe, respectively, the effects of shear rate, resin conversion, filler volume fraction and temperature on chemoviscosity. A comprehensive model combining these individual models predicts the isothermal chemoviscosity data well and the nonisothermal data reasonably. A modified comprehensive mo...

Epoxy/nickel adhesives can be used as integrated circuit (IC) packaging materials due to their lower cost than epoxy/silver adhesives with acceptable electrical conductivity. In this study, stable and unstable capillary flows of highly-filled epoxy/Ni suspensions were investigated with and without cure at room temperature, via the capillary rheometry and syringe extrusion. Variations of the bulk electrical conductivity in these processes were discussed as well. Axial filtration of the polymer binder occurs under a static pressure for a cured epoxy/Ni system, Epon 815 C/Ni/diethylenetriamine (DETA) adhesive with 50 wt% of Ni in the syringe, resulting in an unstable flow and a cross-sectional filler concentration or electrical conductivity gradient. In dynamic capillary extrusion, lower resin viscosity and apparent shear rates enhance the flow instability and filtering of polymeric binder for epoxy/Ni suspensions with 75 wt% of Ni, thus facilitating a change in bulk electrical conductivity during processing...

The surface of multi-wall carbon nanotubes (MWNTs) was functionalized by covalent linking of long alkyl chains. Such functionalization led to a much better tube dispersion in organic solvents than pristine nanotubes, favored the formation of homogenous nanocomposite films, and yielded good interfacial bonding between the nanotubes and two polymer matrices: a thermo-set (Epon 828/T-403) and a thermoplastic (PMMA). Tensile tests indicated, however, that the reinforcement was greatly affected by the type of polymer matrix used. Relative to pure PMMA, a 32% improvement in tensile modulus and a 28% increase in tensile strength were observed in PMMA-based nanocomposites using 1.0 wt% nanotube filler. Contrasting with this, no improvement in mechanical properties was observed in epoxy-based nanocomposites. The poorer mechanical performance of the latter system can be explained by a decrease of the crosslinking density of the epoxy matrix in the nanocomposites, relative to pure epoxy. Indeed we demonstrate that t...

Acute rejection is the most important threat to transplanted kidneys in the early phase after transplantation. With the advances in renal transplant surgery and immunosuppressive therapies, one-year graft survival rates reached 90%, but long-term graft survival did not improve to a similar degree. To prevent acute rejection more effectively and decrease the risk of chronic nephropathy development, the pathogenesis and effects of acute rejection on renal grafts should be further explored. This study aimed to examine the glomerular and tubular changes ultrastructurally. Tissues were obtained from 11 renal allografts with acute rejection, fixed in 1% Osmium tetra oxide embedded in Epon. The changes in glomerular basement membrane, podocyte, mesangium, and proximal tubules were examined by electron microscope. Tubular changes such as tubular basement membrane multi-lamellation, MN and PMN cells in peritubular capillaries, tubular vacuolization, mitochondrial changes (increase in number, alterations in cristae organization, or cristae effacement), and infiltration of tubular epithelium by MN cells (mainly lymphocytes) were found statistically significant (p0.01) when compared to those of control group. Some forms of endothelial injury (swelling of endothelial cells or fenestrae loss) were also statistically significant (p0.01). Acute rejection is an important predictor of long-term graft survival, and there may be no clinical clue to make diagnosis easier. Therefore ultrastructural changes may help solve this problem together with molecular studies.

Pigment epithelium-derived factor (PEDF) is a protein shown to have neurotrophic activity. The purpose of this study was to determine whether PEDF is neuroprotective of retinal neurons that are exposed to transient ischemia-reperfusion.Transient retinal ischemia was produced by increasing the intraocular pressure for 45 min in albino rats eyes. Immediately after reperfusion, PEDF was injected intravitreally into the experimental eyes. Injury was evaluated morphologically and by measuring the thickness of the inner retinal layers (IRL) and by counting the number of retinal ganglion cells (RGC) in epon embedded sections.Morphologic and morphometric analysis of the thickness of the IRL and the counting of RGC demonstrated that PEDF injected immediately after reperfusion protected the eyes partially but significantly from the ischemic injury.Intravitreal injection of PEDF even after the ischemia can ameliorate retinal injury. PEDF may be useful in preventing neuronal degeneration in the inner retina resulting from ischemia.

Eighteen screw-shaped extraoral osseointegrated implants retrieved from 10 patients were analysed by microradiography. Retrieved implants were trephined with a border of surrounding bone, fixed, embedded in epon plastic, ground and processed for microradiography. The reasons for retrieval were unexplained pain (n = 4), inability to cope with the implants (n = 2), fracture of central screw (n = 2), skin penetration problems (n = 1) and trauma (n = 1). The study group comprised six males and four females with a mean age of 53.4 years (range: 9-81 years). All implants were clinically stable at the time of removal, and mean osseointegration time was 3 years (range: 1-5 years). Six implants were removed from the temporal bone, five from the frontal bone and seven from the maxilla. Bone metal contact was estimated to vary between 27% and 83%. Bone metal contact was lower in the frontal bone compared to the temporal bone or maxilla, and was further reduced after preoperative irradiation. Longer osseointegration time increased bone metal contact, as did increased age up to 60 years. It is concluded that extraoral osseointegrated implants in humans may integrate morphologically as well as clinically. By microradiography it was possible to define bone metal contact in the region of implant installation.

Cholesteric formulations (coco-cholesteryl esters:E7) were dispersed in commercial polymethylmethacrylate (PMMA) and in laboratory synthesized side-chain polymers (SCP). The side-chain copolymers were obtained via the ring opening reaction of a commercially available epon resin, ethyleneglycol diglycidyl ether, with the nematic 4-(ω -aminohexyloxy)-4′ -cyanobiphenyl and the twisted nematic cholesteryl 4-aminobutyrate. Switching properties of the resulting dispersions were evaluated. Cells using PMMA as matrix exhibited distinguishable droplet with bipolar and twisted radial configuration. A maximum voltage of 60 volts was needed to transform a 70:30 by weight (LC:PMMA) composite into a transparent state. LC formulations dispersed in the SCP bearing cholesteryl and cyanobiphenyl pendant groups were found to exhibit fingerprint texture. Compared to the LC/PMMA composite, the LC/SCP dispersions required lower voltage for switching.

In order to gain insight into the film thickness-dependent conduction behavior of adhesives containing conductive particles of different sizes, shapes, and types, the effect of adhesive film thickness was studied. Epon 830 resin was used as the base resin and 4-7 mu m silver powder was used as the base particle for comparative purposes. Adhesive films of length 2.0 cm and width 0.7 cm were cast subsequent to mixing with conductive particles in the amount of 25% by volume. The conductive particles were 100% Ag or a 50% by weight mixture of Ag with Ni powder, flakes, or filaments. Silver-coated Ni flakes of size 20 mu m were also mixed in 50% proportion with Ag powder to assess the effect of silver coating. Subsequent to cure, the resistance of the filled films was measured by the four-point method and resistivities were calculated based on these measurements. In general, the addition of flake and filament material (Ni) to the conductive mixture in epoxy films resulted in distinct thickness thresholds for transition from three-dimensional to two-dimensional conductivity with a considerable increase in resistivity when the film thicknesses were smaller than these threshold values. This behavior is attributed to the specific geometry of the flake and filament particles which, when added to a thin film resin, are likely to align flat in planar directions: thus reducing the number of three-dimensional conduction paths.

On the basis of the circadian oscillations of the rat’s exocrine pancreatic function and previous reports on concomitant ultrastructural changes in the pancreatic tissue, we analysed stereologically the circadian rhythmicity in the structure of this organ. Twenty-four male Wistar rats, four and a half months old, were singly housed two months before the experiment in a lighting regimen LD=12:12, constant environmental temperature and relative humidity, with food and water ad libitum. The experiment was performed in winter. The rats were randomly divided into 6 balanced groups and killed under ether anesthesia at 6 equidistant time points in 24 hours. The pancreatic tissue was fixed in glutaraldehyde and osmium and embedded in Epon. 1 µm thick sections were examined by light microscopy for the evaluation by stereological methods of: a) volume fractions of the different parenchymal components of the exocrine pancreas; b) surface fractions of acinar cell faces; c) size distribution of acinar cell nuclei, the...

Skin biopsies from 25 patients with fibromyalgia, 5 healthy controls, 8 patients with rheumatoid arthritis, and 9 patients with local chronic pain after whiplash injury, were examined for the occurrence of IgG deposits and collagen types, using direct and indirect immunofluorescence, and for dermal connective tissue mast cells, using semithin Epon sections. Fibromyalgia skin biopsies had significantly higher values of IgG deposits in the dermis and vessel walls and showed a higher reactivity for collagen III. They also had a higher mean number of mast cells. There was a correlation between the percentage of damaged/degranulated mast cells and the individual IgG immunofluorescence scores. These findings support the hypothesis of neurogenic inflammation involvement in fibromyalgia.

The aim of the present study was to describe some histopathologic features of tissues collected from root resorption areas of maxillary canines after transalveolar transplantation surgery. In 8 of 101 transplanted canines, complications including cervical root resorption occurred between 6 and 11 years after treatment. The resorptive processes were located at the supra-alveolar portions of the distal and/or mesial aspects of the teeth and were scheduled for treatment involving surgical exploration. The resorption cavities, which extended from the cementoenamel junction to a position immediately below the bone crest, were filled with a granulation tissue. In four of the diagnosed complication cases, this granulation tissue was carefully excised concomitant with the adjacent gingival tissue after flap elevation and placed in a buffered fixative. After proper soft-tissue healing, the cavities were filled with a glass-ionomer material. The collected biopsy specimens were, after fixation and, in one case, decalcification in ethylenediaminetetraacetic acid, dehydrated and embedded in Epon. Sections 3 microns thick were produced, stained in periodic acid-Schiff and toluidine blue, and used for histometric and morphometric analyses. The histologic analysis showed that the dissected tissue harbored well-encapsulated areas of inflammatory infiltrates. The lesions comprised a relatively low volume of collagen and a large number of inflammatory cells, predominantly lymphocytes.

The ultrastructure of hyaluronic acid (HA) and collagen in the human vitreous was investigated. After fixation with 4% glutaraldehyde and 0.1% cetylpyridinium chloride (CPC), sectioned blocks of retina and attached vitreous body were stained with 500 ppm ruthenium red (RR) in 1.25% glutaraldehyde, postfixed with 500 ppm RR in 2% OsO4, and embedded in Epon 812. In addition, collagen II immunostaining was done. Collagen fibrils were coated with amorphous material believed to be HA. No amorphous material was seen in the fibrils in the cortical areas adjacent to the retina, but the amount of material gradually increased toward the center of the vitreous body. By using anticollagen II antibody, we showed the presence of collagen II, often oriented perpendicular to the surface. The central vitreous demonstrated some dense materials that were collagen fibrils packed into bundles of parallel fibrils. In summary, collagen fibrils contained little HA in the cortical areas adjacent to the retina, but they were packed into bundles of parallel fibrils in the central vitreous.

The effect of external loading of fiber on fiber/resin interfacial adhesion has been studied using the microbond technique. The results show that the applied load on the fiber weakened the fiber/matrix bonding at the interface. The effect of cyclic loading of fiber on fiber/matrix interfacial adhesion was also investigated by loading and unloading the fiber by means of a moving platform oscillating vertically at a specific frequency. After the cyclic loading process, residual bond strengths were measured using the TRI microbond pullout procedure. Fiber/matrix combinations of Kevlar 49®/Epon 828® and Kevlar 49/polycarbonate have been investigated using this technique. Significant bond strength reduction is observed when load is applied and after cyclic loading. In the latter case, most of the loss occurs after relatively few cycles. Possible bond weakening mechanisms are proposed to explain the experimental results.

Two-dimensional Nuclear Magnetic Resonance (NMR) spectroscopy is used to characterize polymer dispersed liquid crystals (PDLCs) in the solid-state. The wideline separation (WISE) pulse sequence is used to correlate structure and mobility in a PDLC. The PDLC is 40% E7 as 0.4 μ droplets in an Epon 828 matrix. The WISE pulse sequence generates 1H wideline spectra in one dimension for each high resolution solid state 13C resonance in the other dimension. For each 13C resonance, the width of the 1H line shape reflects the mobility of the protons in the vicinity of the respective 13C. Spin diffusion is incorporated into the WISE pulse sequence to determine the relative spatial positions of components with different mobilities. The aliphatic portions of E7 exhibit extremely narrow 1H line widths of a few hundred hertz. Therefore, the aliphatic pendant groups of E7 undergo pseudo-random isotropic motions with rates above 1 MHz. The aromatic portions of E7 exhibit pronounced spinning sidebands in the 1H d...

To establish bromodeoxyuridine (BrdUrd)/iododeoxyuridine (IdUrd) double immunostaining for thick sections of epoxy resin-embedded tissues, young hamsters received intra-peritoneal injections of IdUrd and BrdUrd 3 hr and 1 hr before sacrifice, respectively. The intestines were fixed with phosphate-buffered 4% paraformaldehyde and embedded in an Epon-Araldite mixture. The epoxy resin was removed completely by a sodium methoxide/benzene/methanol solution. This epoxy resin removal method was effective for BrdUrd/IdUrd immunostaining using a mono-specific antibody for BrdUrd (Br-3) and a bi-specific antibody for BrdUrd (Br-3) and a bi-specific antibody for BrdUrd and IdUrd (IU-4), followed by the ABC complex method. Epoxy sections stained with these antibodies showed clear localization of nuclei incorporating the two thymidine analogues with precise morphology of labeled cells. Furthermore, ultrastructural observation of thin sections adjacent to thick sections immunostained for BrdUrd/IdUrd confirmed the cell type and ultrastructural features of cells labeled with these thymidine analogues.

The interface between the eighth cranial nerve and acoustic neuroma was investigated by light microscopy and immunohistochemistry in paraffin sections in 13 patients, and in Epon sections in 19 patients. The cochlear nerve was severely invaded by tumor cells in two of six specimens examined, moderately invaded in two specimens, and not invaded in two specimens. Gliosis was frequently found within the cochlear and vestibular nerve. Hemangioma-like tissue was occasionally found attached to the cochlear and vestibular nerve adjacent to the tumor. These findings were considered to be related to difficulty in hearing preservation in some patients although acoustic neuroma surgery was successful.

The diglycidyl ether of bisphenol-A epoxy resin (EPON 828®) was cured with 4,4′-diaminodiphenylsulfone (DDS) and, optionally, an animophenyl functional reactive polyethersulfone (R-PES, ⟨ Mn ⟩=10k) as a co-curing agent. Commercial polysulfone, Udel® P-1700, was also utilized to afford epoxy-Udel® blends (or semi-IPNs). Cured epoxy polymers were subjected to Tg determinations, plane strain fracture toughness (KIC) tests, adhesive bond strength measurements, tensile tests and chemical resistance studies. The morphologies of the fractured samples were studied by SEM and correlated to the property changes. Only the reactive polysulfone modification improved both fracture toughness and adhesive properties without detracting from the good mechanical properties and chemical resistance.

Taurine may act as an antioxidant, preventing development of inflammatory response and morphologic alteration in lungs of hamsters exposed to nitrogen dioxide. It may bind to plasma membrane reactive sites or stabilize specific molecules in cells inhibiting destructive processes. Localization of taurine is necessary in confirming its role. Hamsters were injected intraperitoneally with H3 labeled taurine (0.1 μCi/ml sp act 20 Ci/mmol) and sacrificed 1 hr or 18 hr after injection. Lungs were removed. fixed, and embedded in Epon. Control lungs were preparedto compare in vivo and in vitro labeling. Lung slices from untreated hamsters were incubated for 1 hr in McCoy 5A medium and then in medium containing H3 taurine for 1 hr. Slices were washed in cold taurine for 1 hr, fixed, and embedded. One-μm sections were prepared for autoradiographic analyses. In situ and in vitro labeled tissues showed no differences in taurine distribution. All in vitro cells showed reater amounts of label than observed in th...

A mildly macerated, hydropic fetus was delivered spontaneously at 25 weeks gestation by a multigravidous black mother. At autopsy, gross and microscopic evidence suggested fetal anemia, and excessive extramedullary erythroblastosis was present generally. Erythroid precursor cells in the pulmonary capillary circulation contained eosinophilic nuclear inclusions consistent with human parvovirus B19 infection. Transmission electron microscopy on osmicated Epon lung sections showed lucent, granular chromatin corresponding to the inclusions. In rare foci only these sections contained paracrystalline arrays of 20-nm virions. In the same cells, similar virions were seen within the cytoplasm, both randomly distributed and in paracrystalline aggregates. Postembedding immunoelectron microscopy, done on formalin-fixed lung embedded in a hydrophilic resin, showed positive labelling over the nuclear inclusions, and also localized the viral capsid antigen to cytoplasmic virion aggregates. The nuclear aggregates suggest that the virus would reach the circulation after cell lysis whereas those in cytoplasm suggest that parvovirus also may be excreted from infected cells before they lyse.

Plastination permits the preservation of anatomical specimens in a physical state approaching that of the living condition. We studied the possibility of using silicone plastinated fragments of spleen and pancreas for optical and electron microscopy, and found that with an adequate fixation protocol, plastinated specimens can be used for both light microscopy and ultrastructural studies. Deplastination with sodium methoxide permitted production of clean sections. Artifacts produced by plastination/deplastination could be nearly eliminated by glutaraldehyde/formaldehyde fixation. The (Biodur) silicone S10 polymer is transparent and stable in an electron beam, and plastinated tissues can be contrasted or colored similar to tissues embedded in Epon 812. In addition to being very life-like, plastinated tissues are stable and easy to handle. They can also be used for electron and light microscopic studies. This technique may also allow retrospective epidemiological studies of archived pathology specimens.

Model epoxy resins with controlled crosslinking densities were prepared from a commercially available DGEBA (Epon Resin 825® from Shell Chemical) and α,ω-aliphatic diamines having different lengths of the aliphatic chain. The mixtures were always prepared in stoichiometric ratio. Dumbbell specimens, either with a cylindrical (with thin walls) or a rectangular cross section, have been subjected to combined static tensile strains (applied vertically) and dynamic torsional strains (applied horizontally). The experiments were performed at temperatures encompassing the glassy and the rubbery range of each investigated resin. The apparatus, by which the combined dynamic and static stresses were applied, was equipped with load cells for measurement of stresses developed in the specimens, both in tension and in shear. In this paper, results concerning the effect of the above combinations of stresses on stress relaxation rates in tension are shown. The main conclusion of this study is that combinations of...

The effects of loading rate, fiber sizing, test temperature and global strain level on the adhesion strength between carbon fibers and a thermosetting epoxy (Epon 815) are studied using the single fiber fragmentation test procedure. Analytical methodology describing the viscoelastic behavior observed is also presented. The possibility of rate-temperature-interphase thickness superposition for the interfacial strength function is illustrated based on the analytical models discussed. Experimental data are discussed using Weibull statistics and also presented in the form of percent relative frequency histograms for the fiber fragments in a collective fashion. The use of histograms allows for interpretation of the skewness in the data population.