Enameloid microstructure of some Cretaceous Hexanchiformes and Synechodontiformes (Chondrichthyes,Neoselachii): New structures and systematic implications

Modern neoselachian sharks may be separated from more basal relatives by the presence of tooth enameloid comprising three layers. Although enameloid microstructure studies were mostly used in the aim of differentiating supposed basal neoselachians from hybodonts, differences in the enameloid organization among neoselachians have been recognized suggesting the potential for use of enameloid microstructure as a phylogenetic tool within the neoselachian sharks. The enameloid microstructure of five taxa of neoselachian sharks belonging to two orders, the Hexanchiformes and Synechodontiformes, has been studied. The Hexanchiformes are a monophyletic order with extant representatives, whereas the extinct Synechodontiformes have been considered as monophyletic, paraphyletic, or polyphyletic by different authors. This study has revealed numerous new enameloid microstructures such as amalgamated crystallites in the internal units [parallel‐bundled enameloid (PBE) and tangled‐bundled enameloid], cavities at the shiny‐layered enameloid (SLE)/PBE boundary, radial furrows in the PBE, as well as different original organizations at the base of the crown and in the PBE at the level of the cutting edges. Pachyhexanchus pockrandti (Hexanchiforme) and Welcommia bodeuri have the most of the features in common and they share more characters with those of Paraorthacodus sp. and Sphenodus sp. than with Synechodus sp. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

Microstructure of pharyngeal tooth enameloid in the parrotfish Scarus rivulatus (Pisces: Scaridae)

The microstructure of parrotfish pharyngeal teeth was examined using scanning electron microscopy to infer possible mechanical properties of the dentition with respect to their function. Parrotfish tooth enameloid is formed from fluorapatite crystals grouped into bundles. In the upper and lower pharyngeal jaw, the majority of the crystal bundles are orientated either perpendicularly or vertically to the enameloid surface. The only exception is in the trailing apical enameloid in which the majority of bundles are orientated perpendicularly or horizontally to the trailing surface. A distinct transition occurs through the middle of the apex between the leading and trailing enameloid in teeth of the lower pharyngeal jaw. This transition appears less distinct in the teeth of the upper pharyngeal jaw. Enameloid microstructure indicates that shear forces predominate at the apex of the teeth. In the remainder of the enameloid, the microstructure indicates that wear is predominant, and the shear forces are of less importance.     

Convergence in dental histology between the late Triassic semionotiform Sargodon tomicus (Neopterygii) and a late cretaceous (Turonian) pycnodontid (Neopterygii: Pycnodontiformes) species

Microstructural scanning electron microscope investigation was performed on sectioned and surface‐etched isolated, prehensile teeth of the Late Triassic semionotiform species Sargodon tomicus and Pycnodontidae incertae sedis from the Late Cretaceous. The teeth of both taxa display a system of vascular canals penetrating the dentine and the overlying hypermineralized acrodin cap; small tubules are radiating at an angle to the long axis of the canals, interpreted as residual spaces left by odontoblast cell processes. This is the first detailed account of vascular acrodin encountered in a pycnodont species. New information is revealed also about Sargodon dental histology in the shape of mineralized remnants of the basal lamina at the acrodin–dentine junction. This implies that deposition of the acrodin organic matrix proceeded centrifugally by the cells of the inner dental epithelium, probably with minor collagen contribution from odontoblasts. This is contrary to the more typical centripetal formation (beneath the basal lamina) of the acrodin layer implied for the studied pycnodontid teeth. The rare occurrences of vascular acrodin within Actinopterygii, and the demonstrated differences in its histogenesis, do not suggest the usefulness of the tissue as systematic character but rather point to its adaptive significance. The superficial increase in the order of acrodin bundle orientation, observed in both species, is similarly regarded as convergently acquired mechanical adaptation. The observed uneven shape of crystallite rows and lesser degree of mineralization of the inner collariform ganoin, compared to its outer portion, is indicative of epithelial‐ectomesenchymal interaction and qualifies the tissue as enameloid. Microsc. Res. Tech., 2011. © 2010 Wiley‐Liss, Inc.     

Microscopic characterization of petiole anatomy of Asteraceous taxa of Western Himalaya-Pakistan

Petiole anatomy of 15 species of family Asteraceae was examined which aimed to investigate petiolar anatomical structures for species level identification. Shandon Microtome was used for petiole histological preparations. Both qualitative and quantitative features were studied under microscope which showed significant variation in petiole, collenchyma, parenchyma shape/size, vascular bundles arrangement/size, and vessel elements quantity. Artemisia japonica Thunb., Cirsium vulgare (Savi) Ten., Myriactis nepalensis Less., Seriphidium brevifolium Ling & Y.R.Ling, Taraxacum officinale (L.) Weber ex F.H.Wigg., and Xanthium strumarium L. showed winged petioles. Maximum length and width of upper and lower epidermis was found in Tagetes erecta L. which is 23.05 ± 0.89 μm, 24.9 ± 1.257 μm length and 21.75 ± 1.38067 μm, 22.75 ± 0.467 μm width, respectively. Petioles of Parthenium hysterophorus L. was longest one with 9.85 ± 10.45 μm while A. japonica Thunb. showed highest number of vessel elements. Maximum size of vascular bundles was found in T. erecta L. with 5.05 ± 14.25 μm. Artemisia annua L., C. vulgare (Savi) Ten, Cyanthillium cinereum (L.) H.Rob., Helianthus annus L., M. nepalensis Less., P. hysterophorus L., Senecio chrysanthemoides DC. have trichomes while Tussilago farfara L. has highest number of vascular bundles. All species have angular collenchyma type except M. nepalensis Less., P. hysterophorus L., S. brevifolium Ling & Y.R.Ling, Tagetes minuta L., T. officinale L., S. chrysanthemoides DC., and T. farfara L. Cluster analysis implemented that distinct plant species in cluster. Petiolar anatomical structures and taxonomic key will helpful for distinguishing Asteraceous taxa at genus and species level. This taxonomic significant investigation will also provide baseline to taxonomists for other Asteraceae studies and phylogenetic research.     

Human teeth biobank: Microbiological analysis of the teeth storage solution

The cross‐infections may occur during handling of dental elements, affecting the health of dental practitioners and researchers. This study aimed to analyze the influence of the storage medium temperature on the bacterial contingent of the human teeth used for research purposes. Thirty human teeth were donated to the Human Teeth Biobank immediately after extraction. The teeth were cleaned with tap water and neutral soap. The teeth were randomly distributed according to the temperature of the storage solution (deionized water): at 4 °C (refrigerator) or at ?10 °C (freezer) and were stored individually in sterile vials during 60 days. After this period, a microbiological analysis (CFU/mL) of the storage solutions was performed and teeth were submitted to SEM analysis. Data were analyzed by Kruskal–Wallis test followed by Dunn's post‐test (p ≤ .05). Total aerobic bacteria ranged from 5.8 to 8.4 log₁₀ CFU/mL for refrigerated solution and from 1.9 to 8.5 log₁₀ CFU/mL for frozen solution. No statistical differences were found between the storage solutions (p > .05). The counts of Streptococcus spp., Lactobacillus spp., and Staphylococcus spp. were similar for both storage solutions (p > .05). SEM analysis showed spiral‐ and rod‐shaped bacteria attached on teeth stored under 4 °C, which may suggest the presence of Treponema spp. and Lactobacillus spp. Similar morphological forms were found on teeth stored under ?10 °C. A biofilm organized in honeycomb‐like form was found in the frozen teeth. Cocci were eventually found in all the samples. It was concluded that bacterial growth and survival were not influenced by the temperature of the teeth storage solution.     

Microscopic diagnosis of the leaf and stem of Piper solmsianum C.DC

Piper solmsianum C.DC., which is popularly known as pariparoba, is a shrub that measures 1–3 m in height and it inhabits areas with wet tropical soils. The objective of this study was to analyze the leaf and stem anatomy using light microscopy, scanning electron micrographs, and energy‐dispersive X‐ray spectroscopy in order to provide information for species identification. The anatomical profile showed the following main microscopic markers: hypostomatic leaf; hypodermis layer on both sides; pearl glands; biconvex midrib shape; five collateral vascular bundles in open arc with the central bundle larger than the others; circular stem shape; collateral vascular bundles arranged in two rings; sinuous sclerenchymatic sheath in the pith; secretory idioblasts; and starch grains in the mesophyll, in the ground parenchyma of the midrib, petiole, and in the stem; and six morphotypes of calcium oxalate crystals (styloids, cuneiform, tabular crystal rosettes, cuneiform crystal rosettes, elongated square dipyramids, as well as very elongated square dipyramids).     

Histochemical and structural characterization of egg extra‐cellular matrix in bufonid toads,Bufo bufo and Bufotes balearicus: Molecular diversity versus morphological uniformity

The extra‐cellular matrix of fertilized eggs in the bufonid toads Bufo bufo and Bufotes balearicus was studied to clear the relationships between structural and molecular diversity. Histochemical (PAS, AB pH 2.5 and pH 1.0, Beta‐elimination PAS) and lectin‐histochemical (Con A, WGA, Succinyl‐WGA, PNA, RCA‐1, DBA, SBA, AAA, UEA‐I, LTA) techniques were used and the observations were made under light and electron microscopy. Both species present a fertilization envelope (FE) and two jelly layers (J₁ and J₂). The fibers of J₂ are shared among the eggs of a clutch in a jelly ribbon. The FE of both species presents neutral glycoproteins, mostly N‐linked. In B. bufo there are also residuals of mannose and/or glucose and N‐acetylglucosamine. In the FE fibers run parallel to egg's surface or are in bundles or looser hanks with no clear orientation. The J₁ layer of both species presents sialosulfoglycoproteins, mostly O‐linked, with lactosaminylated, galactosaminylated, glycosaminylated, and fucosylated residuals. A lower amount of galactosaminylated residuals is observed in B. balearicus in respect to B. bufo, whereas the opposite is seen in the amount of fucosylated residuals. The J₂ layer is similar in composition to J₁ but in B. balearicus there are no glucosaminylated residuals. J layers present fibers and granules that reduce towards J₂. Several microorganisms, in particular blue algae, are observed in the J₂ layer of both species. In respect to other species, B. bufo and B. balearicus have a lower number of jelly layers, but a comparable number of glycan types. Microsc. Res. Tech. 77:910–917, 2014. © 2014 Wiley Periodicals, Inc.     

Fast evaluation of cutting forces in milling, applying no approximate models

A new method for fast evaluation of cutting forces in milling is introduced and tested experimentally. Unlike all existing procedures, which include the use of cutting models and approximate assumptions, in this method, the elementary functions of the cutting force are obtained from measured values only.The basic force functions for the whole feed range are acquired from one experiment using a single-tooth full-diameter (slot) milling, applying a specially developed procedure. The milling experiment is conducted under low-impact conditions, enabling accurate measurement and convenient signal processing. The basic force functions are then integrated and superimposed, using known procedures, to combine the total force in any multitooth milling combination. In this work the method is explained and tested experimentally.The suggested method enables a reliable evaluation of the cutting forces, while demanding minimal experimental work, the method applies to cutters having complicated edge geometry, and to high speed milling.Nomenclature a radial depth of cut 0<a<D - feed per tooth ratio 0<1 - d axial depth of cut - D cutter diameter - a/D radial depth ratio - cutter rotation angle - cutter rotation angle [6] - F _x,y,z() instantaneous edge cutting forces in fixture coordinates - F _t,r,z() instantaneous edge cutting forces in tool coordinates - F _x,y,z ^* F_t,r,z tool cutting force components on a multitooth cutter - h instantaneous chip thickness [6] - h* equivalent edge coefficient [6] - r ₁,r ₂ tangential radial ratio coefficient [6] - K _T tangential specific cutting force [4] - K _R radial specific cutting force [4] - N number of teeth - R _r resolution reduction factor - t instantaneous chip thickness - S ₁,S feed per tooth     

Edge micro-creation of Ti(C,N) cermet inserts by micro-abrasive blasting process and its tool performance

Abstract

In this study, the cutting edge passivation by a micro-abrasive blasting method for cermet inserts and its machining performance were investigated. The micro-abrasive blasting parameters for cermet inserts were optimized and the micro-creation of cutting edge was determined with detail. A Back Propagation (BP) neural network prediction model was further established based on our micro-abrasive blasting experiment datum, which can directly evaluate the micro-abrasive blasting ability to generate the specific edge radius. The improvement of cutting performance of micro-abrasive blasted cermet inserts benefits from the strengthening of cutting edge that caused by the obvious elimination of a large number of micro-defects rooted around the edge, and the formation of circular cutting edge is the result of brittle removal and plastic removal. The micro-creation of inserts can acquire a circular cutting edge, and the optimal edge radius is 15?μm under the selected cutting conditions when the tool life was chosen as an optimization target and the surface roughness was simultaneously taken into account. It is found that the blasted cermet inserts can prolong the tool life by at least 86% and the machined-surface quality can be improved by up to 1.65?μm, compared to inserts without micro-abrasive blasting.     

Contribution of specific work of fracture to size effect in microcutting

Specific work of fracture (R) has been widely used to quantify the energy consumed in formation of new surfaces during metal cutting. R becomes a significant portion of total cutting energy in microcutting, thereby influencing the phenomenon of “size effect. ” Therefore, this work presents an evaluation of specific work of fracture for sharp and rounded-edged tools, knowing cutting forces and shear angles from LS-DYNA simulations of orthogonal microcutting of low-carbon AISI 1215 steel. The R was also evaluated as a function of process parameters such as cutting speed, rake angle, tool edge radius, and uncut chip thickness, so as to illustrate the effect of these variables on the magnitude of R and contribution of R to the specific cutting energy or “size effect.” It is observed that R increases with an increase in uncut chip thickness, whereas it decreases with an increase in cutting speed, rake angle, and tool edge radius. U_R defines the contribution of fracture to the specific cutting energy (U) due to specific work of fracture R. At all the parametric conditions, the contribution of fracture is higher at lower uncut chip thickness and it is of 8–36% in microcutting of AISI 1215 steel.     

Microstructure and mineral composition of dental enamel of permanent and deciduous teeth

Purpose: This study evaluated and compared in vitro the microstructure and mineral composition of permanent and deciduous teeth's dental enamel. Methods: Sound third molars (n = 12) and second primary molars (n = 12) were selected and randomly assigned to the following groups, according to the analysis method performed (n = 4): Scanning electron microscopy (SEM), X‐Ray diffraction (XRD) and Energy dispersive X‐ray spectrometer (EDS). Qualitative and quantitative comparisons of the dental enamel were done. The microscopic findings were analyzed statistically by a nonparametric test (Kruskal‐Wallis). The measurements of the prisms number and thickness were done in SEM photomicrographs. The relative amounts of calcium (Ca) and phosphorus (P) were determined by EDS investigation. Chemical phases present in both types of teeth were observed by the XRD analysis. Results: The mean thickness measurements observed in the deciduous teeth enamel was 1.14 mm and in the permanent teeth enamel was 2.58 mm. The mean rod head diameter in deciduous teeth was statistically similar to that of permanent teeth enamel, and a slightly decrease from the outer enamel surface to the region next to the enamel‐dentine junction was assessed. The numerical density of enamel rods was higher in the deciduous teeth, mainly near EDJ, that showed statistically significant difference. The percentage of Ca and P was higher in the permanent teeth enamel. Conclusions: The primary enamel structure showed a lower level of Ca and P, thinner thickness and higher numerical density of rods. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc.     

A Note on Interpreting Tool Temperature Measurements from Thermography

Thermography (thermal imaging) is a well-established experimental method for studying cutting tool temperature distributions. In one form, cutting edge temperatures within the chip / tool contact area are deduced from thermal images of tool faces normal to the cutting edge but offset from the contact region. In general practice, the offset is made as small as possible (<< 1 mm) and it is assumed that the observed temperature is the same as that within the contact. In this short communication an approximate analytical model is developed for the influence of the offset on the observed temperature. The predictions from the model are compared with previously unpublished existing results on the machining of Ti alloys (Ti6Al4V and Ti5Al4V) and on steel (AISI 4140). It is shown that ignoring the offset may introduce underestimates of cutting edge temperature of ≈ 30% or more. This is large compared to the usually considered uncertainties of ± 5% from camera and tool emissivity calibration. There is a need for a dedicated study of this effect.     

Grey-scale conversion X-ray mapping by EDS of multielement and multiphase layered microstructures

A procedure for grey‐scale conversion of energy dispersive spectroscopy X‐ray maps has been developed, which is particularly useful for the plotting of line composition profiles across modified layered engineering surfaces. The method involves (a) the collection of grey‐scale elemental maps, (b) the calculation of mean grey‐scale levels along strips parallel to the layered microstructure and (c) the conversion of grey‐scale line profiles into composition line profiles. As an example of the grey‐scale conversion method and its advantages for multielement and multiphase layered microstructures, the procedure has been applied to a layered microstructure that results from a plasma‐sprayed metallic MCrAlY coating onto a nickel‐superalloy turbine blade. As a further demonstration of the accuracy and amount of compositional data that can be obtained with this procedure, measured compositional profiles have been obtained for several long‐term isothermal heat treatments in which significant interdiffusion has taken place. The resulting composition profiles have greatly improved counting statistics compared to traditional point‐by‐point scans for the same scanning electron microscope time and may be considered as a rapid alternative to energy dispersive spectroscopy spectrum imaging. The composition profiles obtained may be conveniently compared with results of multicomponent thermodynamic modelling of interdiffusion.     

OPTIMIZATION OF THE CUTTING EDGE GEOMETRY OF COATED CARBIDE TOOLS IN DRY TURNING OF STEELS USING A FINITE ELEMENT ANALYSIS

This paper investigates the effects of edge radius of a round-edge coated carbide tool on chip formation, cutting forces, and tool stresses in orthogonal cutting of an alloy steel 42CrMo₄ (AISI 4142H). A comprehensive experimental study by end turning of thin-walled tubes is conducted, using advanced coated tools with well-defined cutting edge radii ranging from 5 to 68 microns. In parallel, 2-D finite element cutting simulations based on Lagrangian thermo-viscoplastic formulation are used to predict the cutting temperatures and tool-stress distributions within the tool coating and substrate. The results obtained from this study provide a fundamental understanding of the cutting mechanics for the coated carbide tool used, and can assist in the optimization of tool edge design for more complex geometries, such as chamfered edge. Specifically, the results obtained from the experiments and simulations of this study demonstrated that finite element analysis can significantly help in optimizing the design of coated cutting tools through the prediction of tool stresses and temperatures, especially within the coating layer.     

基于GSK980TD系统车削梯形螺纹的应用研究

梯形螺纹在数控车床上,尤其是在经济型数控车床上的加工存在扎刀现象,是比较难解决的问题。利用GSK980TD系统提供的宏功能解决了梯形螺纹编程困难的问题,为各种直径和螺距的梯形螺纹加工编制了通用的数控车削程序。在程序中巧妙地结合了普通车床车削梯形螺纹时应用的各种工艺技巧,采用分层切削、螺纹切削粗、精加工分段降低牙侧的表面粗糙度,为数控车削梯形螺纹提供了一个实用合理的加工程序。     

可补偿切削刃磨损的不铲齿成形铣刀的设计与制造

研制了一种可补偿切削刃磨损量的不铲齿成形铣刀 ,介绍了这种刀齿可调的装配式刀具的设计与制造方法。该刀具经反复重磨后 ,仍可保持切削刃的尺寸、形状参数和加工精度不变 ,且刀齿齿背曲线为圆弧过渡 ,不需铲齿。     

Membranes,minerals, and proteins of developing vertebrate enamel

Developing tooth enamel is formed as organized mineral in a specialized protein matrix. In order to analyze patterns of enamel mineralization and enamel protein expression in species representative of the main extant vertebrate lineages, we investigated developing teeth in a chondrichthyan, the horn shark, a teleost, the guppy, a urodele amphibian, the Mexican axolotl, an anuran amphibian, the leopard frog, two lepidosauria, a gecko and an iguana, and two mammals, a marsupial, the South American short-tailed gray opossum, and the house mouse. Electron microscopic analysis documented the presence of a distinct basal lamina in all species investigated. Subsequent stages of enamel biomineralization featured highly organized long and parallel enamel crystals in mammals, lepidosaurians, the frog, and the shark, while amorphous mineral deposits and/or randomly oriented crystals were observed in the guppy and the axolotl. In situ hybridization using a full-length mouse probe for amelogenin mRNA resulted in amelogenin specific signals in mouse, opossum, gecko, frog, axolotl, and shark. Using immunohistochemistry, amelogenin and tuftelin enamel proteins were detected in the enamel organ of many species investigated, but tuftelin epitopes were also found in other tissues. The anti-M179 antibody, however, did not react with the guppy and axolotl enameloid matrix. We conclude that basic features of vertebrate enamel/enameloid formation such as the presence of enamel proteins or the mineral deposition along the dentin-enamel junction were highly conserved in vertebrates. There were also differences in terms of enamel protein distribution and mineral organization between the vertebrates lineages. Our findings indicated a correlation between the presence of amelogenins and the presence of long and parallel hydroxyapatite crystals in tetrapods and shark.     

Morphoanatomical and phytochemical studies of Salvia lachnostachys (Lamiaceae)

Salvia lachnostachys Benth., Lamiaceae, is a endemic species from southern Brazil. The essential oil of its leaves and flowers is mainly constituted by aliphatic compounds, such as dodecanoic acid, with sesquiterpenes as minor constituents. This work evaluated the morphology, anatomy, microchemistry, and phytochemistry of S. lachnostachys to provide advanced knowledge of Brazilian plants with medicinal potential. Light and scanning electron microscopy techniques were used in the anatomical and microchemical studies. Compounds were isolated by chromatographic techniques, identified by analysis of their NMR spectra and compared with published data. S. lachnostachys can be distinguished from other related species mainly by its petiolate leaves, terminal inflorescence, persistent bracts, and villous‐glandular corolla. The stem and leaves of S. lachnostachys display anatomical characteristics common to the family Lamiaceae. However, this species can be distinguished from other family members by the morphology and the presence of eglandular and glandular trichomes, as well as the organization of the vascular bundles of the petiole. The phytochemical results revealed that S. lacnostachys produces oleanolic and ursolic acids in addition to the diterpene fruticuline A, which is a rare compound, previously found only in Salvia fruticulosa Benth. and S. corrugata Vahl. Ursolic and oleanolic acids are bioactive triterpenes that exhibit antiatherosclerotic, anticancer, antihypertensive, antinflammatory, antileukemic, antimutagenic, antioxidant, antiproliferative, and antiviral activities, and fruticuline A has antibacterial activity. Microsc. Res. Tech. © 2012 Wiley Periodicals, Inc.     

Research on grinding staggered teeth on ball-end rotary burr

Staggered teeth type rotary burr is a new cutter with a special rotary surface. Since branch cutting edges are interlaced with main cutting edges on the sphere of the rotary burr and only main cutting edges pass by the zenith of the ball, it greatly widens the chip flutes and improves machining properties of cutter teeth nearby the zenith. The machining properties of staggered teeth type rotary burr are better than general ball-end rotary burr’s. Although it is widely used, the research of rotary burr with staggered teeth is not great. In this paper, firstly the helical cutting edge equations on sphere are built. Then, based on the geometry model of helical cutting edge, a helical stagger teeth design is presented and theory of grinding helical grooves of staggered teeth is studied in detail. The smooth spiral rake surface and flank surface can be formed during one-pass grinding process by this method. At last, the validity of the theory given in the paper is identified by example of grinding.