scholarly journals THE FINE STRUCTURE AND ARRANGEMENT OF MICROCYLINDERS IN THE LUMINA OF FLAGELLAR FIBERS IN CRICKET SPERMATIDS

1970 ◽  
Vol 45 (2) ◽  
pp. 416-430 ◽  
Author(s):  
Jerome S. Kaye
Keyword(s):  
Fine Structure ◽  
Matrix Material ◽  
The Other ◽  
Amorphous Substance ◽  
Mean Diameter ◽  
The Matrix ◽  
Cytoplasmic Microtubules ◽  
The Mean ◽  
Center Distance ◽  
Electron Lucent

Flagellar structure in spermatids of several species of cricket was studied with the electron microscope. The flagella of mid-spermatids contain the usual 9 + 2 set of fibers and a set of nine accessory fibers. At first all are hollow, then the lumina become filled with an electron-opaque matrix material in which narrow electron-lucent microcylinders are embedded. The accessory fibers and one central fiber become filled first, then the B subfibers and the other central fiber, and finally the A subfiber. In all but the B subfibers, microcylinders are arranged in a circular or oval group that lies against the wall of the lumen and encloses one or several additional microcylinders. In accessory fibers there are 9–11 microcylinders in the outer group and 4–5 in the inner group. In the central fibers and the A subfibers there are 7–9 microcylinders that enclose one or two more. In the B subfibers there is a crescentic group of 6–7 microcylinders that partially encloses 2–3 more. Microcylinders become packed as though they are independent units; the matrix appears to be an amorphous substance that fills the spaces around the microcylinders. The mean diameter of the microcylinders is 36 A, and they have a center-to-center distance of 56 A. In both respects they resemble wall subunits of flagellar fibers and microtubules and they may be similar structures but with a different localization. The diameter of accessory fibers is about 350 A, which is 25% greater than that of the other flagellar fibers and of cytoplasmic microtubules. Rotation tests suggest that the accessory fibers have 16 wall-subunits.

scholarly journals Nanometer Scale Tomographic Investigation of Fine Scale Precipitates in a CuFeNi Granular System by Three-Dimensional Field Ion Microscopy

2012 ◽  
Vol 18 (5) ◽  
pp. 1129-1134 ◽  
Author(s):  
Sophie Cazottes ◽  
François Vurpillot ◽  
Abdeslem Fnidiki ◽  
Dany Lemarchand ◽  
Marcello Baricco ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Precise Determination ◽  
Atomic Scale ◽  
Granular System ◽  
Field Ion Microscopy ◽  
Mean Diameter ◽  
The Matrix ◽  
The Mean ◽  
Ion Microscopy

AbstractThe microstructure of Cu80Fe10Ni10 (at. %) granular ribbons was investigated by means of three-dimensional field ion microscopy (3D FIM). This ribbon is composed of magnetic precipitates embedded in a nonmagnetic matrix. The magnetic precipitates have a diameter smaller than 5 nm in the as-spun state and are coherent with the matrix. No accurate characterization of such a microstructure has been performed so far. A tomographic characterization of the microstructure of melt spun and annealed Cu80Fe10Ni10 ribbon was achieved with 3D FIM at the atomic scale. A precise determination of the size distribution, number density, and distance between the precipitates was carried out. The mean diameter for the precipitates is 4 nm in the as-spun state. After 2 h at 350°C, there is an increase of the size of the precipitates, while after 2 h at 400°C the mean diameter of the precipitates decreases. Those data were used as inputs in models that describe the magnetic and magnetoresistive properties of this alloy.

Maturity and Fecundity of Walleyes from the Eastern and Western Basins of Lake Erie

1969 ◽  
Vol 26 (7) ◽  
pp. 1877-1888 ◽  
Author(s):  
David R. Wolfert
Keyword(s):  
Lake Erie ◽  
The Other ◽  
Western Basin ◽  
Eastern Basin ◽  
Total Length ◽  
Younger Age ◽  
Mean Diameter ◽  
The Mean ◽  
Egg Diameter ◽  
Accurate Indicator

Of 2427 walleyes (Stizostedion vitreum vitreum (Mitchill)) examined from Lake Erie in 1964–66, no females were mature at ages below III and all were mature at age V. All male walleyes from the eastern basin were mature at age II, and those from the western basin at age III. Females from the western basin matured at a shorter length and a younger age than those from the eastern basin. Males from the western basin, on the other hand, matured at a longer length and greater age than those from the eastern basin.Egg production, which was estimated for 60 walleyes from the eastern basin and 78 from the western basin, ranged from 48,000 to 614,000. The number of eggs increased rapidly with increase in total length, but the relation between fecundity and weight was almost linear. Walleyes from the western basin were much more fecund for any given length, weight, or age than those from the eastern basin. Weight was the most accurate indicator of fecundity. The mean diameter of eggs from 32 ripe walleyes was 1.72 mm. Little relation existed between egg diameter and length or age of fish.

scholarly journals Fertilization and development of bovine oocytes grown in female SCID mice

Zygote ◽  
2005 ◽  
Vol 13 (4) ◽  
pp. 309-315 ◽  
Author(s):  
Shoichiro Senbon ◽  
Kyosuke Ishii ◽  
Yoshiyuki Fukumi ◽  
Takashi Miyano
Keyword(s):  
Chorionic Gonadotropin ◽  
Blastocyst Stage ◽  
Scid Mice ◽  
The Other ◽  
Cell Stage ◽  
Mean Diameter ◽  
Bovine Spermatozoa ◽  
The Mean ◽  
Equine Chorionic Gonadotropin ◽  
Bovine Oocytes

We previously reported that xenografted bovine secondary follicles developed to the antral stage in severe combined immunodeficient (SCID) mice. In the present study, bovine secondary follicles 100–240 μm in diameter were xenografted under the kidney capsules of female SCID mice for 6 and 8 weeks, and we examined the oocytes' fertilization and developmental abilities. Bovine follicles developed with prolongation of grafting and became significantly larger than those before grafting. Injection of equine chorionic gonadotropin (eCG) into host mice made some surviving follicles develop larger than the other follicles. Furthermore, bovine oocytes grew in the follicles, and the mean diameter of the oocytes was 100 μm or more at 6 and 8 weeks of transplantation. Bovine oocytes that had grown in eCG-stimulated SCID mice 8 weeks after grafting were subjected to maturation culture. Some of the oocytes that had grown to 110 μm or more matured to the second metaphase (7% of oocytes 110–119 μm and 44% of those >120 μm). When the oocytes were inseminated with bovine spermatozoa, 15% (6/39) formed a female and a male pronucleus, and 2 days after insemination 24% (18/75) of oocytes cleaved and 2% (2/75) developed to the 5- to 8-cell stage. However, no embryo reached the blastocyst stage. These results indicate that bovine oocytes grown in SCID mice could be fertilized but acquired insufficient competence for embryonic development in the present conditions.

scholarly journals Friction and Wear Mechanisms of Phenolic-Based Materials on High Speed Tribometer

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Damien Meresse ◽  
Michel Watremez ◽  
Monica Siroux ◽  
Laurent Dubar ◽  
Souad Harmand
Keyword(s):  
Wear Mechanisms ◽  
High Speed ◽  
Friction And Wear ◽  
Matrix Material ◽  
Normal Pressure ◽  
Optical Observations ◽  
Friction And Wear Mechanisms ◽  
The Matrix ◽  
Higher Temperature ◽  
The Mean

This work takes place in the understanding of the friction and wear mechanisms occurring in reinforced phenolic materials, widely used in organic braking pads. As the matrix is filled with a large variety of particles, the phenomena in the contact zone are complex and multiphysic. In a first approach the reinforcement is restricted to spherical steel particles with diameters in the range of the fibbers size. The influence of the sliding speed, the mean normal pressure and the contact temperature are examined and the benefits of using this kind of particle is as well discussed. The tribological tests are performed on a newly developed High Speed Tribometer designed to reproduce braking conditions. The results show that temperature is the most influential parameter, leading to a decrease of the friction coefficient. They further indicate that reinforcement pushes the loss of efficiency to a higher temperature. Optical observations and profilometer analysis show that the wear mechanisms are clearly dependent on friction conditions. These results improve our knowledge of wear debris formation and conditions leading to particle debonding in phenolic matrix material.

scholarly journals AN ELECTRON MICROSCOPE STUDY OF THE FINE STRUCTURE OF FEATHER KERATIN

1962 ◽  
Vol 13 (1) ◽  
pp. 1-12 ◽  
Author(s):  
B. K. Filshie ◽  
G. E. Rogers
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Matrix Material ◽  
X Ray Diffraction ◽  
Thin Sections ◽  
Apparent Lack ◽  
Feather Keratin ◽  
Fibrous Protein ◽  
The Matrix ◽  
Lead Hydroxide

Thin sections of the rachis of regenerating follicles of pigmented fowl feathers and of mature non-pigmented seagull feather rachis, embedded in methacrylate and Araldite respectively, were studied in the electron microscope. The late stages of development of keratin fibrils were examined in OsO4-fixed follicle material, and after poststaining with lead hydroxide the keratin aggregates were found to be composed of fine microfibrils approximately 30 A in diameter apparently embedded in a matrix material which had absorbed the lead stain. The centre-to-centre separation of the microfibrils was of the order of 35 A. After bulk treatment by reduction with thioglycollic acid, OsO4 staining, and poststaining with lead hydroxide, a similar microfibrillar fine structure was observed in mature rachis. Only after lead staining could the microfibrils be delineated, and their diameter and separation were similar to that found in the keratin of the follicle. It is suggested that feather keratin resembles α-keratins in consisting of microfibrils embedded in an amorphous protein matrix. However, in comparison with α-keratins, the microfibrils are much smaller in diameter, their arrangement is less orderly, and on the basis of the reactions towards the electron staining procedures, the cystine content of the matrix appears to be not greatly different from that of the microfibrils. The significance of a microfibrillar constitution of feather keratin is discussed in relation to current structural models for this fibrous protein deduced from x-ray diffraction studies. The boundaries between the component cells of feather rachis are desmosomal in character and similar to those of related keratinous structures and a number of different types of cells; the melanin granules are dissimilar to those of mammalian epidermis in their apparent lack of melanin-protein lamellae.

scholarly journals The intramitochondrial volume measured using sucrose as an extramitochondrial marker overestimates the true matrix volume determined with mannitol

1983 ◽  
Vol 214 (2) ◽  
pp. 387-393 ◽  
Author(s):  
A P Halestrap ◽  
P T Quinlan
Keyword(s):  
Liver Mitochondria ◽  
The Other ◽  
Heart Mitochondria ◽  
Protonmotive Force ◽  
Mitochondrial Matrix ◽  
Matrix Volume ◽  
The Matrix ◽  
The Mean ◽  
Isolated Liver

The matrix volume of isolated liver and heart mitochondria has been estimated at various osmolarities and in various osmotic supports using 36Cl- and [14C]sucrose, D-mannitol, D-3-methoxyglucose and choline as extramitochondrial markers. The use of 3-methoxyglucose was only possible at 0 degree C since it entered mitochondria at physiological temperatures. All extramitochondrial markers used gave linear plots of apparent matrix volume against the reciprocal of the osmolarity, but the slope of this plot was greater when sucrose was used than with the other extramitochondrial markers. When extrapolated to infinite osmolarity the mean matrix volume was zero when mannitol was used, but about 0.6 microliter/mg of protein for sucrose and Cl- and -0.4 microliter/mg of protein when choline was used. At physiological osmolarity (about 330 m-osmol) the mean matrix volume of de-energized liver mitochondria in KCl medium estimated using mannitol was 0.46 microliter/mg of protein, whereas that obtained using sucrose was 1.68 microliters/mg of protein. Values in mannitol, choline and sucrose media were similar when mannitol but not sucrose was used as extramitochondrial marker. It is argued that the 3H2O/[14C]mannitol space more accurately reflects the true mitochondrial matrix volume than does the 3H2O/[14C]sucrose space. The consequences of this for measurements of the protonmotive force and the intramitochondrial concentration of metabolites are discussed.

Normal and Shear Impact of Layered Composite With a Crack: Dynamic Stress Intensification

1980 ◽  
Vol 47 (2) ◽  
pp. 351-358 ◽  
Author(s):  
G. C. Sih ◽  
E. P. Chen
Keyword(s):  
Laplace Transform ◽  
Dynamic Stress ◽  
Matrix Material ◽  
Dynamic Stress Intensity Factor ◽  
Layered Composite ◽  
The Other ◽  
Crack Plane ◽  
Time Inversion ◽  
Dual Integral Equations ◽  
The Matrix

The dynamic response of a layered composite under normal and shear impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. Because of the complexities that arise from the interaction of waves scattered by the crack with those reflected by the interfaces within the composite, dynamic analyses of composites with cracks have been treated only for a few simple cases. One of the objectives of the present work is to develop an effective analytical method for determining dynamic stress solutions. This will not only lead to an in-depth understanding of the failure of composites due to impact but also provide reliable solutions that can guide the development of numerical methods. The analysis method utilizes Fourier transform for the space variable and Laplace transform for the time variable. The time-dependent angle loading is separated into two parts: one being symmetric and the other skew-symmetric with reference to the crack plane. By means of superposition, the transient boundary conditions consist of applying normal and shear tractions to a crack embedded in a layered composite. One phase of the composite could represent the fiber while the other could be the matrix. Mathematically, these conditions reduce the problem to a system of dual integral equations which are solved in the Laplace transform plane for the transform of the dynamic stress-intensity factor. The time inversion is carried out numerically for various combinations of the material properties of the composite and the results are displayed graphically.

Preparation of Biologically Derived Hydroxyapatite and its Dissolution

2007 ◽  
Vol 342-343 ◽  
pp. 657-660 ◽  
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Jong Kook Lee
Keyword(s):  
Tricalcium Phosphate ◽  
The Other ◽  
Distilled Water ◽  
Large Defect ◽  
Human Teeth ◽  
Liquid Environment ◽  
The Matrix ◽  
The Mean ◽  
Lattice Planes ◽  
Mean Time

Hydroxyapatite derived from human teeth was sintered at 1200°C for 2 h. Dissolving behavior of the biologically derived HA (BHA) in distilled water was investigated and compared with an artificial hydroxyapatite (HA) made of synthetic HA powder. All disks were immersed in 40 ml of pH 7.4 distilled water (buffered using 0.05 M Tris.) for 7 and 14 days at 37°C. All detectable peaks in the HA are identical only to HA lattice planes, whereas BHA consisted of a mixture of HA and β-tricalcium phosphate (TCP). In the case of the HA specimen, the surface dissolution was initiated at grain boundaries followed by generated many separated grains and large defect like cavities. On the other hand, biologically derived HA showed that definite grains considered as β-TCP was predominantly dissolved and the grains were separated from the matrix leaving pores. In the mean time, the rest region, mainly consisting of HA, did not show any evidence of dissolution. It seems that BHA is more stable than the artificial HA in liquid environment.

scholarly journals Effect of Processing and Loading Conditions upon the Fatigue Behaviour of a Cf/Epoxy Laminate

2009 ◽  
Vol 18 (3) ◽  
pp. 096369350901800 ◽  
Author(s):  
Christos Koimtzoglou ◽  
Konstantinos G. Dassios ◽  
Costas Galiotis
Keyword(s):  
Fatigue Limit ◽  
Failure Modes ◽  
Matrix Material ◽  
High Stress ◽  
Fatigue Behaviour ◽  
Static Strength ◽  
Testing Conditions ◽  
The Matrix ◽  
The Mean ◽  
Loading Scheme

The current work reports on the tensile and fatigue behaviour of an autoclave-cured unidirectional carbon fibre reinforced epoxy-matrix laminate. The macromechanical properties of the composite are established under interrupted and uninterrupted, static and dynamic conditions at a maximum strain below the critical fatigue limit of the matrix material. The established S-N curve was used to calculate the endurance fatigue limit of the laminate as well as to record an increase in fatigue life of specimens tested at load levels lower than two standard deviations below the mean static strength of the material. The failure modes exhibited by the composite under all testing conditions were recorded and interpreted by means of the damage mechanisms that originate them. The results of interrupted testing showed that the combined effect of fatigue and residence at high stress levels for prolonged periods of time - conditions that simulate a realistic loading scheme- trigger premature fibre failure and thus specimen failure.

Hairiness in wool and a method for selection based on the nature of the fibres and the distribution of halo hairs of the lamb's tail

1957 ◽  
Vol 49 (1) ◽  
pp. 1-18 ◽  
Author(s):  
F. M. Labban
Keyword(s):  
Fibre Diameter ◽  
The Body ◽  
The Other ◽  
Significant Difference ◽  
Mean Diameter ◽  
Wide Variability ◽  
The Mean ◽  
Highly Correlated ◽  
Different Parts

Hairiness in wool of Suffolk sheep as a fault was found to be associated with other defects like coarseness of wool fibres, hairiness of the britch, and the occurrence of pigmented fibres. The presence of these various defects was studied in the lamb's tail at docking time, and subsequently evaluated and correlated with the fleece.The tails were graded according to the nature of the fibres and the spread of halo hairs from the tip to the base into four principal grades which by further subgrading could be made into seven grades. The results were as follows:(1) There was wide variability in grades of tails within each flock.(2) Average grade of tails followed in general the mean quality of the adult fleece.(3) When Border Leicester were crossed with Welsh Mountain the tails of the two reciprocal crosses were found to be of hairy type of tail and nearly like the Welsh Mountain type.(4) The percentage of coloured tails in the least hairy grades was found to be inversely related to the quality of the tail grade and indirectly to the fleece quality.(5) The diameter of the wool fibres on the base of the tail is highly correlated with the diameter of fibres from the britch regions or mean fibre diameter from four regions of the body (mid-shoulder, midside, hip and britch).(6) The mean diameter of the wool fibres obtained from four different parts of the tail was correlated with those of the britch regions only.(7) The diameter and variability of fibres increased from shoulder to britch in the body and from base to tip in the tails.(8) The britch and tails of two groups of sheep, one group characterized by coarse and the other by fine britch and tail wool, were studied histologically. There were significant or highly significant differences in the following characteristics in the britch of the two groups: (a) total number of follicles, (b) primary follicles with no medulla, (c) total number of secondary follicles, (d) secondaries with no medulla, (e) secondaries with large medulla. The only type of follicle where a significant difference was found in the tail was in the number of secondary follicles with no medulla.

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