Variational problem on minimum drag body with given volume and lateral surface area

1971 ◽  
Vol 3 (1) ◽  
pp. 75-77
Author(s):  
G. I. Bogomolov
Keyword(s):  
Variational Problem ◽  
Surface Area ◽  
Lateral Surface ◽  
Minimum Drag

Methods of analysing morphology of kaolinites: relations between crystallographic and morphological properties

Clay Minerals ◽  
1986 ◽  
Vol 21 (1) ◽  
pp. 55-68 ◽  
Author(s):  
J.M. Cases ◽  
P. Cunin ◽  
Y. Grillett ◽  
C. Poinsignon ◽  
J. Yvon
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Area ◽  
Lateral Surface ◽  
Morphological Properties ◽  
Surfactant Adsorption ◽  
Adsorption Calorimetry ◽  
Crystalline Sample ◽  
Transmission Electron ◽  
Total Specific Surface Area

AbstractA study was made of the extent to which the lateral surfaces contribute to the surface area of five kaolinites of different crystallinities. Methods used included the low-temperature adsorption of N2and Ar as measured by a volumetric technique coupled with microcalorimetry, the interpretation of the adsorption isotherms of alkyldodecylammonium ions, particle-size distribution curves, and shadowed transmission electron microscopy. With the exception of surfactant adsorption and adsorption calorimetry using Ar, these methods gave different and debatable results. For instance, specific lateral surface area values expressed as a percentage of total specific surface area varied from 17·0 to 40·4% for the most crystalline sample and from 12·0 to 54·3% for the least crystalline. It is shown that the decrease in crystallinity of samples is accompanied by a reduction in crystallite size from 0·8 to 0·08 µm and a decrease in lateral surface area from 34·0 to 12·0%.

Evaluation of talc morphology using FTIR and H/D substitution

Clay Minerals ◽  
2003 ◽  
Vol 38 (2) ◽  
pp. 141-150 ◽  
Author(s):  
E. Ferrage ◽  
F. Martin ◽  
S . Petit ◽  
S. Pejo-soucaille ◽  
P. Micoud ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Lateral Surface ◽  
Ftir Spectra ◽  
Hexagonal Ring ◽  
Particle Shapes

AbstractDeuteration (H/D substitution at 200ºC) was performed on powders of two ground talcs of different particle shapes (different basal/lateral surface ratios). Results indicate that the deuteration process is only efficient on lateral talc surfaces, and suggest that the hydrogens located in the hexagonal ring of the talc basal surfaces are not exchanged. The FTIR spectra collected from the two talc samples show that it is possible to discriminate between particles with the same specific surface area but with different basal/lateral surface ratios using the deuteration process.

Influence of distension on absorption and villous structure in rat jejunum

1989 ◽  
Vol 256 (1) ◽  
pp. G188-G197 ◽  
Author(s):  
G. Holzheimer ◽  
D. Winne
Keyword(s):  
Surface Area ◽  
Lateral Surface ◽  
Permeability Coefficient ◽  
Venous Blood ◽  
Intraluminal Pressure ◽  
Simplified Model ◽  
Diffusion Resistance ◽  
Rat Jejunum ◽  
Jejunal Segment ◽  
Mucosal Surface Area

In urethan-anesthetized rats the appearance rates of urea (U), antipyrine (A), and alpha-methyl-D-glucoside (MG) in the venous blood of perfused jejunal segment were measured in the undistended state and after elevation of the intraluminal pressure up to 10 cmH2O. Serosal and inner cylindrical surface area of the jejunal segment were enlarged by maximally 100 and 150%, respectively. The absorption rates, however, increased only by 34 (U), 28 (A), and 26% (MG). The increase of the supravillous diffusion resistance contributed only partially to this effect. The "cylindrical" permeability coefficient (Pcyl, average permeability coefficient related to inner cylindrical area, neglecting villous structure) decreased by 39, 57, and 50%, respectively. Due to circular stretching, broad intervillous spaces were formed that covered finally approximately 40% of the mucosal surface area. The additional intervillous diffusion resistance in these spaces was more effective than the absorption through the lateral surface of the villi. Thus the overall permeability of the mucosa, i.e., Pcyl, was reduced. Calculations based on a simplified model of the mucosa confirmed the experimental results.

Flagellar Attachment in Selected Trypanosomes

1973 ◽  
Vol 31 ◽  
pp. 496-497
Author(s):  
J. J. Paulin
Keyword(s):  
Cell Membrane ◽  
Lateral Surface ◽  
The Body ◽  
Flagellar Pocket ◽  
Integral Component ◽  
Free Flagellum ◽  
Flagellar Axoneme

Movement in epimastigote and trypomastigote stages of trypanosomes is accomplished by planar sinusoidal beating of the anteriorly directed flagellum and associated undulating membrane. The flagellum emerges from a bottle-shaped depression, the flagellar pocket, opening on the lateral surface of the cell. The limiting cell membrane envelopes not only the body of the trypanosome but is continuous with and insheathes the flagellar axoneme forming the undulating membrane. In some species a paraxial rod parallels the axoneme from its point of emergence at the flagellar pocket and is an integral component of the undulating membrane. A portion of the flagellum may extend beyond the anterior apex of the cell as a free flagellum; the length is variable in different species of trypanosomes.

Preparation and characterisation of vanadium pentoxide supported rhodium catalyst

1988 ◽  
Vol 46 ◽  
pp. 946-947
Author(s):  
A. Legrouri
Keyword(s):  
Aqueous Solution ◽  
Thermal Decomposition ◽  
Physicochemical Properties ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
High Purity ◽  
Gas Adsorption ◽  
Rhodium Catalyst ◽  
Optical Methods ◽  
Reducible Oxides

The industrial importance of metal catalysts supported on reducible oxides has stimulated considerable interest during the last few years. This presentation reports on the study of the physicochemical properties of metallic rhodium supported on vanadium pentoxide (Rh/V2O5). Electron optical methods, in conjunction with other techniques, were used to characterise the catalyst before its use in the hydrogenolysis of butane; a reaction for which Rh metal is known to be among the most active catalysts.V2O5 powder was prepared by thermal decomposition of high purity ammonium metavanadate in air at 400 °C for 2 hours. Previous studies of the microstructure of this compound, by HREM, SEM and gas adsorption, showed it to be non— porous with a very low surface area of 6m2/g3. The metal loading of the catalyst used was lwt%Rh on V2Q5. It was prepared by wet impregnating the support with an aqueous solution of RhCI3.3H2O.

Cell morphology, volume, and surface area determinations from multilevel contouring within HVEM micrographs of serial sections and whole-cell mounts

1987 ◽  
Vol 45 ◽  
pp. 588-589
Author(s):  
M. Marko ◽  
A. Leith ◽  
D. Parsons
Keyword(s):  
Surface Area ◽  
Electron Micrographs ◽  
Cell Morphology ◽  
Individual Variation ◽  
Serial Section ◽  
Stereo Pair ◽  
Complex Structures ◽  
Serial Sections ◽  
Surface Areas ◽  
Computer Based

The use of serial sections and computer-based 3-D reconstruction techniques affords an opportunity not only to visualize the shape and distribution of the structures being studied, but also to determine their volumes and surface areas. Up until now, this has been done using serial ultrathin sections.The serial-section approach differs from the stereo logical methods of Weibel in that it is based on the Information from a set of single, complete cells (or organelles) rather than on a random 2-dimensional sampling of a population of cells. Because of this, it can more easily provide absolute values of volume and surface area, especially for highly-complex structures. It also allows study of individual variation among the cells, and study of structures which occur only infrequently.We have developed a system for 3-D reconstruction of objects from stereo-pair electron micrographs of thick specimens.

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