Peel Technique Research Articles

Acetate peel technique: a rapid way of preparing sequential surface replicas of dental hard tissues for microscopic examination

In order to study dental structures in three-dimensional views, sequential microscopic sections are needed. Routine thin-sectioning needs equipment, it is time-consuming, expensive and cause sample wastage during sectioning. The acetate peel technique used for microscopic examinations of carbonate rocks and fossils was modified and successfully adapted for teeth. A human tooth was embedded in resin block; the surface to be peeled was ground and polished with carborundum powder on a glass plate using water. The polished surface was etched, washed, and dried. The dry surface was flooded with acetone and a piece of acetate film was placed over it. As the acetone evaporated, the film settled down to take the shape of micro relief produced by etching. The film dried in 10--15 min. It was pulled off the surface and mounted between two glass slides for examination under microscope. This technique enabled making numerous sequential surface replicas (peels) from a tooth, especially from fully mineralised enamel without routine decalcifying, dehydrating, sawing, and mounting processes. The results obtained with the stained peels, showed that this technique is an efficient way to study gross and fine structures of etched dental hard tissues surfaces and restoration-cavity marginal integrity with three-dimensional detail.

Taxodiaceous Pollen Cones from the Early Tertiary of British Columbia, Canada

Two permineralized conifer pollen cones have been identified from the Appian Way locality on the east coast of Vancouver Island, British Columbia. These cones, found in marine calcareous nodules with invertebrates, are Eocene in age and have been studied with the cellulose acetate peel technique. Cones are small, terminal, and globose, with helically arranged subtending leaves, ensheathing leaves, microsporophylls, and pollen sacs with enclosed pollen grains. Peltate microsporophylls have a distal lamina with three abaxial pollen sacs. Pollen grains are small, subspherical, nonsaccate, and papillate, with a distal leptoma and proximal orbicules. Phyllotaxy of subtending leaves and microsporophylls, number of pollen sacs per microsporophyll, and ultrastructure of pollen grains are similar to those of the taxodiaceous Cupressaceae. These cones have closest similarities to Athrotaxis, Cunninghamia, Sequoia, Sequoiadendron, Taiwania, the extinct Sewardiodendron laxum (sensu Yao et al.), and Athrotaxites berryi. However, they have a combination of characters that make these cones unique among taxodiaceous conifers. Therefore, a new genus and species are described as Homalcoia littoralis Hernandez‐Castillo, Stockey et Beard. These cones show a novel combination of characters within the Cupressaceae that extends our understanding of the family and shows the presence of another extinct taxodiaceous genus in the North American Eocene.

Cretaceous and Eocene poroid hymenophores from Vancouver Island, British Columbia

Two fossil poroid hymenophore fragments, one from the Cretaceous Period and the other from the Eocene Epoch, are described. The permineralized specimens were obtained from marine calcareous concretions on Vancouver Island, British Columbia, Canada, and were studied using the cellulose acetate peel technique. Size and distribution of pores in the hymenophores, as well as the hyphal anatomy of the dissepiments and some hymenial elements, were examined. In the Cretaceous specimen, Quatsinoporites cranhamii sp. nov., pores are round to elliptical, three per mm, and 130–540 μm diam. Dissepiments consist of narrow, simple septate, hyphae. Neither basidia nor basidiospores are present, but acuminate hymenial cystidia, up to 54 μm in length, are common. The Eocene specimen, Appianoporites vancouverensis sp. nov., has a pore density of six per mm and pores are 130–163 μm in diam. Dissepiments consist of narrow, simple septate, thin-walled hyphae. Neither basidia nor basidiospores are present, but acuminate, thick-walled hymenial cystidia, up to 32 μm in length, are common. The poroid hymenophore is a characteristic of a number of extant basidiomycete taxa, including the Boletales, Polyporales and Hymenochaetales. It is unlikely that the fleshy, ephemeral, terrestrial basidiomata of the Boletales would be preserved in a marine environment, and thus the specimens are interpreted as belonging to basidiomycete lineages, with persistent, leathery or corky basidiomata. The simple septate hyphae, the minute pores and presence of cystidia most closely resemble taxa of the Hymenochaetales. These fossils unequivocally push back the minimum age of homobasidiomycetes and extend their paleogeographical range.

Vegetative Growth ofDecodon allenbyensis(Lythraceae) from the Middle Eocene Princeton Chert with Anatomical Comparisons toDecodon verticillatus

Large numbers of roots and stems of aquatic Lythraceae have been found in association with fruits and seeds of Decodon allenbyensis Cevallos‐Ferriz et Stockey in the Princeton chert, British Columbia, Canada. The permineralized fossils come from layer 43 in the chert, part of the Middle Eocene, Allenby Formation. Vegetative remains were studied using the cellulose acetate peel technique in an attempt to reconstruct the whole plant of D. allenbyensis. Reconstruction is based on close anatomical comparisons of tissues in the fossil organs to those of extant Decodon verticillatus (L.) Ell. and on attachment of organs and tissue systems. A detailed description of both root and stem wood anatomy is provided for the fossil species. Stem anatomy is revised for extant D. verticillatus, and detailed root anatomy is described for the first time using paraffin sectioning techniques and scanning electron microscopy. Fossil roots and stems show diffuse porous wood with vessels that are solitary or in radial multiples of two to five with numerous tyloses. Heterocellular rays vary from one to at least five cells wide. Secondary phloem with clusters of thick‐walled fibers is preserved in some axes. Most roots and some stems show distinctive concentric layers of thin‐walled lacunate phellem, characteristic of submerged aquatics. This tissue has been described in extant Decodon J.F. Gmelin and other Lythraceae. Anatomy of D. allenbyensis indicates that these plants were growing under submerged conditions with stable water levels at the edge of a quiet body of fresh water.

Permineralized Pine Cones from the Cretaceous of Vancouver Island, British Columbia

Two abraded, cylindrical cone specimens found in calcareous concretions from the Cretaceous Spray Formation (Late Campanian) of Vancouver Island, British Columbia, were sectioned using the cellulose acetate peel technique and characterized anatomically. Their sclerenchymatous pith is surrounded by a ring of separate secondary xylem bundles that lack resin canals. The outer cortical zone is sclerenchymatous and covered in a dense ramentum of trichomes that is also present on ovuliferous scale and bract bases. Vascular traces to the ovuliferous scales and bracts arise independently. The bract, with a terete trace and two lateral resin canals, lacks a distinct abaxial lobe. Ovuliferous scales are sclerotic with resin canals adaxial, abaxial, and between the vascular bundles. The ovuliferous scales have an interseminal ridge that is prominent and thick near the micropylar end of the seed, thins out near the seed chalaza, and attaches to the seed wing tissue. There are two winged seeds per scale, and the edges of the ovuliferous scale turn upward and partly enclose the seeds near the micropylar end. Seeds have a ridged sclerotesta; nucellus, megagametophyte, and embryos with eight cotyledons are preserved. Cone structure most closely resembles fossil Pinaceae of the genus Pityostrobus. These cones have a unique combination of characters that distinguish them from the previously described taxa and are described as Pityostrobus beardii sp. nov. A phylogenetic analysis using morphological data from the ovulate cones of extant and fossil taxa of Pinaceae with Cryptomeria japonica (L. f.) D. Don and Sciadopitys verticillata (Thunb.) Siebold et Zucc. as outgroups was undertaken to assess the phylogenetic position of P. beardii within Pinaceae. Pityostrobus beardii appears to be most closely related to Pityostrobus hokodzensis from the Cretaceous of Russia. These cones provide further evidence that the Pinaceae, like the angiosperms, were undergoing a rapid Cretaceous radiation.

A New Species ofPityostrobusfrom the Lower Cretaceous of California and Its Bearing on the Evolution of Pinaceae

A single cylindrical, abraded cone specimen has been found associated with ammonites of the Lower Cretaceous Budden Canyon Formation near Ono, California. The specimen was embedded in bioplastic and sectioned using the cellulose acetate peel technique. The pith is composed of parenchyma and scattered sclereids and is bounded by a ring of resin canals. The secondary xylem of the cone axis, with a ring of small‐diameter resin canals, is continuous. The cortex is composed primarily of parenchyma with an outer sclerotic zone 10–16 cells thick and has 27–30 dilating resin canals. Vascular traces to the ovuliferous scale and bract diverge separately from the vascular cylinder and are accompanied by a single resin canal from the pith that is positioned between the arms of the horseshoe‐shaped ovuliferous scale trace. The bract trace is terete, accompanied by two lateral resin canals from the cortical axial system, and enters the free part of the bract. The ovuliferous scale is almost completely sclerotic, with r...

Chemical peel of nonfacial skin using glycolic acid gel augmented with TCA and neutralized based on visual staging.

Until recently, standard techniques for laser or chemical peeling have not always provided consistent results when applied to the nonfacial skin. The author describes a more controlled chemical peel technique for nonfacial skin using 70% glycolic acid gel combined with 40% trichloroacetic acid (TCA). The method has given consistently good results on the skin of the neck, chest, arms, hands, back, and other nonfacial skin. More than 3100 patients were given skin peels of the neck, chest, and other areas of the body as indicated. Seventy percent glycolic acid gel was applied to the areas to be peeled, then immediately augmented with 40% TCA. Each area was carefully monitored for the end point and then neutralized with copious amounts of 10% sodium bicarbonate solution. The end point was determined by visual observation using a six-stage classification to determine the degree of peeling. Clinical results were excellent, with smoother skin texture, decreased wrinkling and striae, and fading of lentigines and other pigmentary abnormalities. There was excellent blending into peeled facial skin and into adjacent areas of nonpeeled skin. Complications were minimal. This technique can provide the benefits of skin peeling to nonfacial skin with excellent cosmetic results and minimal complications.

Adjunctive treatment of congenital pigmented nevi with phenol chemical peel.

The purpose of this study was a retrospective evaluation of the treatment of congenital pigmented nevi using the phenol chemical peel technique. Patients were treated with standard Baker formula in the operating room under general anesthesia or intravenous sedation with continuous electrocardiogram monitoring. A total of 20 patients were reviewed (13 girls and 7 boys, mean age 3.8 years). Eight patients had nevi located on the face, five patients had trunk lesions, and three patients had lesions on the thighs. Two patients had nevi located on both the face and the trunk, and two patients had involvement of the face, trunk, and thigh. Three of the above patients had the classic "bathing trunk" distribution of the nevi. A test area was peeled in four patients, and in five patients preoperative biopsies were performed to rule out malignancy before initiation of therapy. An average of 2.6 treatments were performed per patient. Two patients had adjunctive dermabrasion to increase the depth of peel and to contour surface irregularities. The length of follow-up ranged from 6 to 84 months with a mean of 28 months. Healing of the wounds occurred within 2 to 3 weeks postoperatively. Seventy-five percent of patients had satisfactory cosmetic improvement in the appearance of the lesions following treatment. Four patients had recurrence of the pigmentation after an initial lightening response, three of whom had their nevi subsequently excised. There was no incidence of hypertrophic scarring or cardiac and/or renal complications. There was one death from complications of leptomeningeal melanocytosis. Chemical peeling of congenital pigmented nevi is an acceptable alternative method of therapy for those lesions that are too large for excision and primary closure or for lesions in which excision would result in unacceptable scars in areas such as the face.

A New Species of Millerocaulis (Osmundaceae) from the Lower Cretaceous of California.

A small permineralized osmundaceous stem has been collected from marine sediments of the Early Cretaceous (Aptian), Upper Chickabally Member of the Budden Canyon Formation near Ono, California. The specimen, 8.5 cm long and 5.4 cm wide, represents a stem surrounded by a mantle of stipular leaf bases and adventitious roots. A large number of sections were studied through the use of the cellulose acetate peel technique. The stem was erect, 11x13 mm in diameter, with a parenchymatous pith and two-layered cortex. The stele is an ectophloic siphonostele with 65-79 leaf traces in the stem per cross section. Leaf gaps are only produced in 13% of the departing traces. Most leaf traces have "delayed" gaps or completely lack leaf gaps. Leaf traces are C-shaped, endarch, with one protoxylem strand, and have sclerenchyma lining the adaxial concavity. Leaf bases have stipular wings with large patches of heterogeneous sclerenchyma and a few scattered strands outside of the heterogeneous sclerotic ring. Patches of sclerenchyma occur inside the ring and outside of the vascular tissues. Numerous diarch roots arise singly or doubly from the leaf traces as they depart the axis stele. Although the stem compares fairly closely to both Ashicaulis Tidwell and Millerocaulis Erasmus ex Tidwell emend. Tidwell, it is most similar to Millerocaulis. However, the combination of characters observed in our specimen differs from that of the seven known species of Millerocaulis. This stem is described as Millerocaulis embreei sp. nov. and is the youngest known species of the genus and the first to be found in the Northern Hemisphere.

Aculeovinea yunguiensis Gen. et Sp. Nov. (Gigantopteridales), a New Taxon of Gigantopterid Stem from the Upper Permian of Guizhou Province, China

Permineralized gigantopterid stems of Aculeovinea yunguiensis Li et Taylor gen. et sp. nov. were collected from the Upper Permian of western Guizhou, China, and prepared with the cellulose acetate peel technique. The stems are narrow and covered with prickles, and contain a parenchymatous cortex with sparganum‐type fibrous strands, an endodermis‐like layer, variable amounts of secondary xylem, a eustele of mesarch primary vascular bundles, and a parenchymatous pith. The stems are vesselless, and tracheids of the protoxylem have annular, helical, scalariform, or reticulate thickenings, while the metaxylem tracheids have scalariform to transversely elongated bordered pits. The secondary xylem has nearly storied tracheids with bordered pits that are commonly multiseriate, alternately arranged, and more or less transversely elongated but are occasionally uniseriate scalariform. Heteroseriate rays and scattered axial parenchyma in single‐celled columns also are found in the wood. From a different site of weste...

Permineralized fruits of Diplopanax (Cornaceae, Mastixioideae) from the middle Eocene Princeton chert of British Columbia

Over 80 specimens of a permineralized fruit referable to the Cornaceae (Mastixioideae) have been recovered from the middle Eocene Princeton chert (Allenby Formation) of British Columbia, Canada. Specimens were studied using a modified cellulose acetate peel technique using hydrofluoric acid. Diplopanax eydei Stockey, LePage et Pigg sp. nov. has fruits with endocarps up to 11 mm long and 10 mm in diameter that have a smooth stone surface, a single locule that is U-shaped in cross section, and a germination valve that extends nearly the full length of the fruit. An epicarp (exocarp + mesocarp) composed of thin-walled parenchymatous cells, 1.2–1.5 mm thick, is preserved on one specimen. Remnants of an apical disc with possible perianth scars are seen in three specimens. The endocarp is composed of interlocking fibers with scattered resin ducts and vascular tissue that parallels the edges of the valve. Seed integuments consist of a single external layer of large cells with brown contents and an inner zone of two to four thin-walled cells of smaller diameter lacking contents. Numerous septate fungal hyphae are usually present in the integumentary layers. These fruits represent the first reported fossils of the genus Diplopanax Handel-Mazzetti, and the northernmost known mastixioids in North America. The fruits are compared to those of other living and fossil mastixioids including Mastixicarpum Chandler and add to our knowledge of the diversity and distribution of the North American mastixioids during the Tertiary.

A rapid, lightweight sediment peel technique using polyurethane foam

A rapid, lightweight sediment peel technique using polyurethane foam

Polymer/metal Interfaces in Interconnect Structures: Moisture Diffusion and Stress Corrosion Effects

ABSTRACTMoisture can cause a host of reliability problems at interfaces including interface debonding. Two mechanisms can be identified. First, moisture at an interface can reduce the interface bonding strength dramatically by altering the chemical bonds. Second, when an interface with a crack or a crack-like defect is under tensile stresses, stress corrosion may allow crack growth at stresses much lower than critical fracture would require. To avoid wet interfaces, wafers should be briefly baked or exposed to a plasmain situbefore the next film deposition step. However, moisture can also reach interfaces by diffusion along interfaces from unprotected edges during a wet process, such as CMP, or during storage in the ambient. In this work, the effect of moisture induced interface strength reduction was utilized to determine the diffusion distance. By using a mechanical peel technique, the diffusivity of moisture along the interface between Al and a poly(arylene ether) based low-K material (PAE2) was measured to be 4–6 μm2/s. Stress corrosion was studied using a special 4-point bend technique so that both strain energy release rate and crack velocity can be obtained. It was found that the mechanism of stress corrosion at this interface is more complicated compared to that in a bulk material: while the chemical reaction took place at the crack tip, moisture diffusion was also occurring along the interface ahead of the crack tip, preconditioning the interface. There appeared to be a region that kinetics was limited by interfacial moisture diffusion and reaction, from which the reaction time for interface weakening was estimated to be ∼ 10 seconds. It was also found that even for samples saturated with moisture, the relative humidity of the test environment was still very important.

A Rapid, Lightweight Sediment Peel Technique Using Polyurethane Foam

A Rapid, Lightweight Sediment Peel Technique Using Polyurethane Foam

An Experimental Technique for Studying Mixed-Mode Fatigue Crack Growth in Solder Joints

Failures of solder joints often result from development of cracks under complex mixed-mode loading conditions. In this study, a flexural peel technique was developed to investigate the growth of cracks at the interface between solder and Cu substrate. The technique was based on a tri-layer solder/Cu joints, with the solder layer sand-wiched between two Cu layers of desired thicknesses. Finite element analysis was used to calculate the mixed-mode condition at the crack tip as a function of the thicknesses of Cu outerlayers and the solder interlayer. The application of this technique to studying interface crack growth under fatigue loading is demonstrated for eutectic solder joints.

Subcritical crack growth at bimaterial interfaces: Part I. flexural peel technique

A flexural peel (FP) technique was developed to study the crack growth behavior along a bimaterial interface. The technique was based on a sandwich specimen where one arm of the specimen was peeled away from the interface under a combined tensile and shear mode. An approximate linear elastic fracture mechanics solution was derived analytically from theJ integral formulation. The solution was compared to finite element calculations based on the crack closure method and experimental measurements. From the finite element analysis, ratios of the mode-I and mode-II components of the crack tip field were determined for a wide range of modulus and thickness ratios.

Subcritical crack growth at bimaterial interfaces: Part II. microstructural effects on fracture resistance of metal/ceramic interfaces

The flexural peel technique was used to study the fracture resistance of two model A12O3/A1 interfaces. The bimaterial interface was formed by bonding high-purity A12O3 with molten Al-5 pct Cu alloy under pressure. The specimens were then heat treated so that the Al-Cu alloy reached peakaged and extended-overaged conditions. The fracture resistance curve was established for two interfaces with either the peak-aged or overaged Al alloy. The fracture resistance of the interface with the peak-aged Al-Cu alloy was higher in terms of both the initiation and peak toughness. While the peak toughness of the interface scaled with the yield strength of the metal, the initiation toughness differed by a factor of 8. The difference in the initiation toughness is discussed in terms of the disparity in the interfacial microstructure.

Subcritical crack growth at bimaterial interfaces: Part III. shear-enhanced fatigue crack growth resistance at polymer/metal interface

Fatigue crack growth along an Al/epoxy interface was examined under different combinations of mode-I and mode-II loadings using the flexural peel technique. Fatigue crack growth rates were obtained as a function of the total strain energy rate for GII/GI ratios of 0.3 to 1.4, achieved by varying the relative thickness of the outerlayers for the flexural peel specimen. Fatigue crack growth resistance of the interface was found to increase with increasing GII/GI ratio. Such a shear-enhanced crack growth resistance of the interface resulted in a gradual transition of crack growth mechanism from interfacial at the low GII/GI ratio to cohesive at the high GII/GI ratio. Under predominantly mode-I loading, the damage in the polymer took the form of crazing and cavitation. In contrast, laminar shear occurred under highly shear loading, resulting in a larger amount of plastic dissipation at the crack tip and improved fatigue crack growth resistance.

Heterogeneous Spatial Distribution of Periphytic Diatoms on Vertical Artificial Substrata

Traditional techniques for algal enumeration on substrata may ignore variation along microenvironmental gradients. To examine microdistributional patterns of diatoms on such surfaces, topographically simple, nutritionally inert artificial substrata were positioned in a duckweed-covered canal and in the littoral zone of a prairie lake. After a period of colonization, substrata were sampled using a surficial peel technique along a short section suspected to traverse sharp microenvironmental gradients of irradiance and nutrient concentration. At both sites, significant horizontal and vertical microheterogeneity in diatom species abundance was observed on a single substratum. A zonation of diatom species occurred with depth in the duckweed mat; Achnanthes hungarica, an apparently host-specific taxon, was distributed mostly in the leaf zone of the mat. Join-count analysis of a peel sample from the lake demonstrated that the major diatom taxa were significantly more abundant on some parts of the substratum than others. Refined nearest-neighbor analysis of mapped populations of Cocconeis diminute and Epithemia turgida in these peels showed that they were significantly aggregated in the distance range of a few cell lengths, suggesting that their progeny were only weakly motile after cell division. A relatively motile diatom, Achnanthes hungarica, was distributed randomly at low cell density; a more dense A. hungarica population was distributed regularly. These results illustrate the importance of examining microdistributional patterns of diatoms on substrata as the genesis of ultimate community development and macrodistribution.

Blackspot pigment development of resistant and susceptibleSolanum Tuberosum L. genotypes at harvest and during storage measured by three methods of evaluation

Blackspot pigment development was measured by three methods: 1) impact, 2) abrasive peeling, and 3) oxidation of tuber homogenates. Genotypes and storage periods were used as variable treatments. All methods were able to separate genotypes based on blackspot resistance although the abrasive peel and homogenization methods provided more consistent results than the impact bruise method. Bruise resistant genotypes transferred their resistance to progeny in crosses with a susceptible genotype which was correlated with tyrosine content. According to the traditional impact bruise technique, tuber resistance to blackspot increased during the eight-to ninemonth storage at 3 C. In contrast, resistance was found to decrease with the homogenization procedure and did not change with the abrasive peel technique. Free tyrosine was consistently associated with blackspot pigment development but chlorogenic acid and caffeic acid were not.