Some ultrastructural characteristics of mandibular cuticle in an elaterid larva (Coleoptera)

1979 ◽  
Vol 57 (8) ◽  
pp. 1682-1692 ◽  
Author(s):  
R. Y. Zacharuk
Keyword(s):  
Wall Thickness ◽  
Tooth Wear ◽  
Preferred Orientation ◽  
Wall Strength ◽  
Ultrastructural Characteristics ◽  
Mandibular Teeth ◽  
Pore Canals ◽  
Mandibular Base ◽  
Ctenicera Destructor

The cuticular walls of the mandibles of larvae of Ctenicera destructor (Brown) have a layer of nonlamellate procuticle with a preferred orientation of cuticular microfibrils and pore canals. This type of cuticle is characteristic of many pterygote adult cuticles but has not been noted in larval cuticles of other cephalic appendages or body sclerites and membranes. This nonlamellate layer is sandwiched between two layers of lamellate procuticle over most but not all of the mandibular base. There is no outer lamellate layer of procuticle in the walls of the mandibular teeth, but the layer of protein epicuticle is exceptionally thick here, comprising about two-thirds of the total wall thickness. These characteristics of the mandibular cuticle are discussed with respect to wall strength, tooth wear, function of mandibular mechanosensilla, and development.

Biomechanical approaches to eurypterid cuticles and chelicerate exoskeletons

1985 ◽  
Vol 76 (2-3) ◽  
pp. 359-364 ◽  
Author(s):  
John E. Dalingwater
Keyword(s):  
Preferred Orientation ◽  
Limiting Factor ◽  
Critical Factors ◽  
Scaling Exponents ◽  
Pore Canals

ABSTRACTMicrostructural features of eurypterid cuticles are analysed from a biomechanical viewpoint: some fibrous elements are now considered to resemble the macrofibres of extant arthropod cuticles; possible preferred orientation zones in Mycterops are related to directional stresses; pore canals are not viewed as acting as crack-stoppers but laminae (sensu Dennell 1978) may have served this function. Could some eurypterids have walked on land?—this problem is approached by using extant Limulus as a model. It leads on to the use of scaling exponents to determine the limits that possessing an exoskeleton places on the size of land arthropods: moulting may be the limiting factor. Possible critical factors limiting the size of aquatic arthropods are discussed briefly.

scholarly journals Biomechanical rupture risk assessment of abdominal aortic aneurysms based on a novel probabilistic rupture risk index

2015 ◽  
Vol 12 (113) ◽  
pp. 20150852 ◽  
Author(s):  
Stanislav Polzer ◽  
T. Christian Gasser
Keyword(s):  
Risk Assessment ◽  
Wall Thickness ◽  
Risk Index ◽  
Wall Stress ◽  
Aortic Aneurysms ◽  
Rupture Risk ◽  
Discriminative Power ◽  
Wall Strength ◽  
Abdominal Aortic ◽  
Wide Range

A rupture risk assessment is critical to the clinical treatment of abdominal aortic aneurysm (AAA) patients. The biomechanical AAA rupture risk assessment quantitatively integrates many known AAA rupture risk factors but the variability of risk predictions due to model input uncertainties remains a challenging limitation. This study derives a probabilistic rupture risk index (PRRI). Specifically, the uncertainties in AAA wall thickness and wall strength were considered, and wall stress was predicted with a state-of-the-art deterministic biomechanical model. The discriminative power of PRRI was tested in a diameter-matched cohort of ruptured ( n = 7) and intact ( n = 7) AAAs and compared to alternative risk assessment methods. Computed PRRI at 1.5 mean arterial pressure was significantly ( p = 0.041) higher in ruptured AAAs (20.21(s.d. 14.15%)) than in intact AAAs (3.71(s.d. 5.77)%). PRRI showed a high sensitivity and specificity (discriminative power of 0.837) to discriminate between ruptured and intact AAA cases. The underlying statistical representation of stochastic data of wall thickness, wall strength and peak wall stress had only negligible effects on PRRI computations. Uncertainties in AAA wall stress predictions, the wide range of reported wall strength and the stochastic nature of failure motivate a probabilistic rupture risk assessment. Advanced AAA biomechanical modelling paired with a probabilistic rupture index definition as known from engineering risk assessment seems to be superior to a purely deterministic approach.

The Microstructure of Shock-Synthesized Diamond

1967 ◽  
Vol 25 ◽  
pp. 324-325
Author(s):  
Lucien F. Trueb
Keyword(s):  
Single Crystals ◽  
Preferred Orientation ◽  
High Magnification ◽  
Texture Pattern ◽  
Shock Process ◽  
New Type ◽  
Diffraction Diagram

A new type of synthetic industrial diamond formed by an explosive shock process has been recently developed by the Du Pont Company. This material consists of a mixture of two basically different forms, as shown in Figure 1: relatively flat and compact aggregates of acicular crystallites, and single crystals in the form of irregular polyhedra with straight edges.Figure 2 is a high magnification micrograph typical for the fibrous aggregates; it shows that they are composed of bundles of crystallites 0.05-0.3 μ long and 0.02 μ. wide. The selected area diffraction diagram (insert in Figure 2) consists of a weak polycrystalline ring pattern and a strong texture pattern with arc reflections. The latter results from crystals having preferred orientation, which shows that in a given particle most fibrils have a similar orientation.

Existence of Cubic ZrO2 at 300°C on Bulk Zirconium

1969 ◽  
Vol 27 ◽  
pp. 166-167
Author(s):  
R.A. Ploc
Keyword(s):  
Metal Oxide ◽  
Metal Substrate ◽  
Preferred Orientation ◽  
Monoclinic Zirconia ◽  
Epitaxial Relationship

The manner in which ZrO2 forms on zirconium at 300°C in air has been discussed in the first reference. In short, monoclinic zirconia nucleates and grows with a preferred orientation relative to the metal substrate. The mode of growth is not well understood since an epitaxial relationship which gives minimum misfit between the zirconium ions in the metal/oxide combination is not realized. The reason may be associated with a thin cubic or tetragonal layer of ZrO2 between the inner oxygen saturated metal and the outer monoclinic zirconia.

Permeability of the microcirculation in area postrema of rat

1988 ◽  
Vol 46 ◽  
pp. 348-349
Author(s):  
Shams M. Ghoneim ◽  
Frank M. Faraci ◽  
Gary L. Baumbach
Keyword(s):  
Brain Stem ◽  
Area Postrema ◽  
Upper Body ◽  
Sprague Dawley ◽  
Sodium Cacodylate ◽  
Acute Hypertension ◽  
Sprague Dawley Rats ◽  
Ultrastructural Characteristics ◽  
The Brain ◽  
Adjacent Brain

The area postrema is a circumventricular organ in the brain stem and is one of the regions in the brain that lacks a fully functional blood-brain barrier. Recently, we found that disruption of the microcirculation during acute hypertension is greater in area postrema than in the adjacent brain stem. In contrast, hyperosmolar disruption of the microcirculation is greater in brain stem. The objective of this study was to compare ultrastructural characteristics of the microcirculation in area postrema and adjacent brain stem.We studied 5 Sprague-Dawley rats. Horseradish peroxidase was injected intravenously and allowed to circulate for 1, 5 or 15 minutes. Following perfusion of the upper body with 2.25% glutaraldehyde in 0.1 M sodium cacodylate, the brain stem was removed, embedded in agar, and chopped into 50-70 μm sections with a TC-Sorvall tissue chopper. Sections of brain stem were incubated for 1 hour in a solution of 3,3' diaminobenzidine tetrahydrochloride (0.05%) in 0.05M Tris buffer with 1% H2O2.

Human Enamel Replication

1976 ◽  
Vol 34 ◽  
pp. 180-181
Author(s):  
Norman L. Dockum ◽  
John G. Dockum
Keyword(s):  
Organic Matrix ◽  
Human Teeth ◽  
Human Enamel ◽  
Straight Line ◽  
Ultrastructural Characteristics

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.

Ultrastructural Characteristics of Platelets Separated from Plasma by ADP-Induced Aggregation

1976 ◽  
Vol 34 ◽  
pp. 164-165
Author(s):  
B.A. Shinoda ◽  
M.D. Hardison ◽  
S.F. Mohammad ◽  
H.Y.K. Chuang ◽  
R.G. Mason
Keyword(s):  
Blood Platelets ◽  
Gel Filtration ◽  
Differential Centrifugation ◽  
Ultrastructural Characteristics ◽  
Induced Aggregation

The utilization of blood platelets in experimentation frequently requires their separation from blood and subsequent resuspension in media of known composition. Several methods are available for preparation of isolated platelets (1-3) by differential centrifugation or gel filtration, but most methods are tedious and time consuming. Often platelets obtained by use of such methods are in a state different functionally and ultrastructurally from that of platelets in plasma (4).Recently Mohammad, Reddick, and Mason (5) reported a method in which platelets were separated from plasma by ADP-induced aggregation, washed several times, and then incubated in a carefully selected medium that resulted in deaggregation of platelets.

SEM and TEM observations of sperm development in the testis of the freshwater fish Oreochromis mossambicus

1990 ◽  
Vol 48 (3) ◽  
pp. 58-59
Author(s):  
Daryl A. Cornish ◽  
George L. Smit
Keyword(s):  
Morphological Characteristics ◽  
Oreochromis Mossambicus ◽  
Breeding Cycle ◽  
Limited Information ◽  
North West ◽  
The North ◽  
Sem And Tem ◽  
Sperm Development ◽  
Ultrastructural Characteristics ◽  
The University

Oreochromis mossambicus is currently receiving much attention as a candidater species for aquaculture programs within Southern Africa. This has stimulated interest in its breeding cycle as well as the morphological characteristics of the gonads. Limited information is available on SEM and TEM observations of the male gonads. It is known that the testis of O. mossambicus is a paired, intra-abdominal structure of the lobular type, although further details of its characteristics are not known. Current investigations have shown that spermatids reach full maturity some two months after the female becomes gravid. Throughout the year, the testes contain spermatids at various stages of development although spermiogenesis appears to be maximal during November when spawning occurs. This paper describes the morphological and ultrastructural characteristics of the testes and spermatids.Specimens of this fish were collected at Syferkuil Dam, 8 km north- west of the University of the North over a twelve month period, sacrificed and the testes excised.

Ultrastructural Classification of Pituary Adenomas

1990 ◽  
Vol 48 (3) ◽  
pp. 258-258
Author(s):  
S. Arumugam ◽  
Sarasa Bharati Arumugam
Keyword(s):  
Cytoplasmic Organelle ◽  
Null Cell ◽  
Cell Adenoma ◽  
Mixed Cell ◽  
Light Microscope Level ◽  
Null Cell Adenoma ◽  
Growth Hormone Cell ◽  
Ultrastructural Characteristics ◽  
Organelle Morphology

Adenoaas of the pituitary are no longer classified based on their tinctorial affinity to dyes. With the advent of the newer methods of sophisticated technology, it is now possible to classify. These depending upon the type of hormone secreted based either on histochemical techniques or on ultrastructural characteristics. The latter provides an insight into the cytoplasmic organelle morphology which offers a delightful feast to the eye as well.This paper presents the ultrastructural characters of the pituitary adenoma as seen in Madras. 171 adenomas (124 males and 47 females) were seen during 1972-1989, classified at the light microscope level as 159 chromophobe, 2 basophilic, 4 eosinophilic and 6 mixed adenomas.Ultrastructural examination showed that the sparsely granular prolactin cell adenoma is the commonest adenoma to be encountered closely followed by the growth hormone cell adenoma, null cell adenoma, the mixed cell adenoma and others.

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