scholarly journals Enzyme activities of rumen particles and feed samples incubatedin situwith differing types of cloth

1998 ◽  
Vol 79 (2) ◽  
pp. 161-168 ◽  
Author(s):  
Pekka Huhtanen ◽  
Aila Vanhatalo ◽  
Tuomo Varvikko
Keyword(s):  
Free Surface ◽  
Pore Size ◽  
Microbial Activity ◽  
Surface Area ◽  
Enzyme Activities ◽  
Xylanase Activity ◽  
General Assumption ◽  
Free Surface Area ◽  
Highly Correlated

Three ruminally cannulated non-lactating dairy cows were used to investigate the effects of six different bag cloth types with pore size (μm): free surface area (%) ratios of 200: 45, 41: 33, 16: 5, 10: 2, 6: 5 and 1: 2 respectively on the disappearance of grass silage DM and neutral-detergent fibre (NDF), and on particle-associated carboxymethylcellulase (EC3.2.1.4; CMCase) and xylanase (EC3.2.1.8) activties extracted from feed residues. Another objective was to compare microbial activity inside the bags and in rumen ingesta. Rumen incubation periods were 3, 6, 12, 24, 48 and 96 h. DM and NDF disappearance and particle-associated enzyme activities were greatly reduced with the smaller pore size and/or open surface area. Re-analysing some of the data as a 2 x 2 factorial (pore size x free surface area) indicated that, generally, free surface area rather than pore size affected the disappearance of feed components and particle-associated enzyme activities. Enzyme activities were highly correlated with NDF disappearance at 6–48 h of incubation. Cumulative area under CMCase and xylanase activity curves explained 0·79 and 0·88 of the variation in NDF disappearance when different cloth type and 6–48 h incubation data were combined. Weighted mean enzyme activities inside the bags were less than 0·35 those in rumen ingesta. The highest activity values inside the bags (24 or 48 h) were less than 0·50 those found in rumen ingesta. The lower microbial activity inside the bags explains the slower rates of NDF digestion reported within situtechniques than with rumen evacuation techniques. The general assumption of similar microbial activity inside the bags and in rumen ingesta is not justified by the present results, and caution must be taken in interpretingin situresults quantitatively for feed evaluation systems.

scholarly journals The effect of differing types of cloth and of contamination by non-feed nitrogen on intestinal digestion estimates using porous synthetic-fibre bags in a cow

1990 ◽  
Vol 63 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Tuomo Varvikko ◽  
Aila Vanhatalo
Keyword(s):  
Free Surface ◽  
Chemical Composition ◽  
Pore Size ◽  
Surface Area ◽  
Dry Matter ◽  
Synthetic Fibre ◽  
Aqueous Suspension ◽  
Barley Straw ◽  
Intestinal Digestion ◽  
Free Surface Area

The influence of free surface area and pore size of a synthetic-fibre bag, and flow of intestinal substances into the bag, on the intestinal digestion estimates by the nylon-bag method of dry matter (DM), neutral detergent fibre (NDF), nitrogen, NDF-N and feed 15N was studied using a non-lactating cow fed on hay supplemented with barley and oats at maintenance level. The bags containing 15N-labelled ground ryegrass (Lolium perenne), barley, barley straw or rapeseed (Brassica napus) straw were introduced into the duodenum through a T-shaped cannula and collected from the faeces. Also, the disappearance of N from the bag was related to the true intestinal N digestion by comparing it with the net loss between duodenum and faeces of 15N in ryegrass introduced into the duodenum in an aqueous suspension. It was noted that the bag cloth often significantly affected both disappearance values and the subsequent chemical composition of the residues. Re-analysing part of the data as a 2x2 factorial (free surface x pore size) suggested that free surface area was often more important than pore size as a determinant of both disappearance values and chemical composition. Lower apparent (Kjeldahl N) than true (15N) feed N disappearance from the bag suggested a notable proportion of non-feed N in the residues, especially with fibrous feeds with low N. With ryegrass, 15N net loss within the intestine was lower than 15N disappearance from the bags. It was concluded that disappearance of Kjeldahl N is an underestimate of feed N disappearance from bags, but may possibly be an overestimate of the true intestinal digestion of feed N.

Improved Methods of Obtaining Clean Larvae of Haemonchus contortus

1963 ◽  
Vol 37 (4) ◽  
pp. 251-254 ◽  
Author(s):  
M. G. Christie ◽  
J. E. Patterson
Keyword(s):  
Free Surface ◽  
Surface Area ◽  
Haemonchus Contortus ◽  
Water Repellent ◽  
Optimum Conditions ◽  
Infective Larvae ◽  
Mucous Coat ◽  
Third Stage ◽  
Free Surface Area ◽  
Improved Methods

A pellet of sheep faeces containing eggs of Haemonchus contortus forms an adequate environment for the development of those eggs to third stage infective larvae, provided that it is kept moist. Observation shows a concentration of developing larvae on the external mucous coat of the pellet. These data suggest that optimum conditions for development would occur when pellets are separated one from another and standing on a water repellent surface, thus presenting the maximum free surface area and minimum opportunity for aggregation and hence of over crowding. The best method of recovering the infective larvae would be one that obtained larvae free from contamination without requiring them to expend energy in separating themselves from the contamination.

Assessment of the free surface area of magnesia-supported magnesium ferrite particles using selective oxygen chemisorption

1992 ◽  
Vol 27 (2) ◽  
pp. 343-350 ◽  
Author(s):  
D. E. Stobbe ◽  
F. R. Van Buren ◽  
A. J. Orbons ◽  
A. J. Van Dillen ◽  
J. W. Geus
Keyword(s):  
Free Surface ◽  
Surface Area ◽  
Magnesium Ferrite ◽  
Oxygen Chemisorption ◽  
Free Surface Area

Late Thrombogenicity of Grafts in the Venous System

1987 ◽  
Vol 2 (1) ◽  
pp. 29-36
Author(s):  
Gunnar Plate ◽  
Larry H. Hollier ◽  
Mrinal K. Dewanjee ◽  
Michael P. Kaye
Keyword(s):  
Free Surface ◽  
Surface Area ◽  
Half Life ◽  
Venous System ◽  
Long Term Results ◽  
Microscopic Appearance ◽  
Endothelial Seeding ◽  
Vein Grafts ◽  
Autogenous Vein ◽  
Free Surface Area

Although some previous experiments have demonstrated encouraging early results with venous vascular prosthesis, the long-term results have not been sufficiently investigated. The late thrombogenicity of 12 autogenous vein grafts and eight polytetrafluoroethylene (PTFE) grafts, three of which had been subjected to endothelial seeding, was evaluated 6 months after implantation in the canine venous system by determination of the survival time of the indium-labelled autogenous platelets and of the light and electron microscopic appearance of the graft-to-blood interface. Twelve dogs receiving autogenous vein grafts had a platelet half-life of 64 ± 13 (mean ± s.d.) hours and a completely thrombus-free internal graft surface covered by a smooth endothelium. The platelet half-life in five dogs with non-seeded PTFE grafts was significantly ( P < 0.01) shorter (44 ± 11h). The PTFE-to-blood interface consisted of a 100- to 170-μm-thick pseudointima with a thrombus-free surface area of 25-90% and substantial endothelial coverage in only two animals. Three dogs receiving endothelial-seeded PTFE grafts had a platelet half-life of 38, 46 and 53h, respectively, a 10- to 80-μm-thick pseudointima covered with typical endothelium, and a thrombus-free surface area of 90-100%. Our results demonstrate that PTFE grafts are still thrombogenic at 6 months following implantation in the canine venous system. Therefore, additional measures are required to maintain graft patency. Our limited experience with endothelial seeding does not allow any definite conclusions, but our findings indicate that this procedure might be beneficial.

An In Situ SEM-FIB-Based Method for Contrast Enhancement and Tomographic Reconstruction for Structural Quantification of Porous Carbon Electrodes

2014 ◽  
Vol 20 (5) ◽  
pp. 1576-1580 ◽  
Author(s):  
Santhana K. Eswara-Moorthy ◽  
Prasanth Balasubramanian ◽  
Willem van Mierlo ◽  
Jörg Bernhard ◽  
Mario Marinaro ◽  
...  
Keyword(s):  
Pore Size ◽  
Surface Area ◽  
Porous Carbon ◽  
Tomographic Reconstruction ◽  
Vacuum Impregnation ◽  
Solid Boundary ◽  
Carbon Electrodes ◽  
Impregnation Method ◽  
Porous Carbon Electrodes

AbstractA new in situ Scanning Electron Microscope-Focused Ion Beam-based method to study porous carbon electrodes involving Pt filling of pores from gaseous precursors has been demonstrated to show drastically improved image contrast between the carbon and porous phases when compared with the Si-resin vacuum-impregnation method. Whereas, the latter method offered up to 20% contrast, the new method offers remarkably higher contrast (42%), which enabled fast semi-automated demarcation of carbon boundaries and subsequent binarization of the images with very high fidelity. Tomographic reconstruction of the porous carbon electrode was then obtained from which several morphological parameters were quantified. The porosity was found to be 72±2%. The axial and radial tortuosites were 1.45±0.04 and 1.43±0.04, respectively. Pore size, which is defined to be the distance from the medial axis of the pore to the nearest solid boundary, was quantified. Average pore size determined from the pore size distribution was 90 nm and the corresponding 1 sigma ranges from 45 to 134 nm. Surface-to-volume ratio of the carbon phase was 46.5 µm−1. The ratio of total surface area to the total volume of electrode including pores (i.e., specific surface area) was 13 µm−1.

scholarly journals Association of Cellulytic Enzyme Activities in Eucalyptus Mulches with Biological Control of Phytophthora cinnamomi

2001 ◽  
Vol 91 (9) ◽  
pp. 847-855 ◽  
Author(s):  
A. J. Downer ◽  
J. A. Menge ◽  
E. Pond
Keyword(s):  
Microbial Activity ◽  
Enzyme Activities ◽  
Phytophthora Cinnamomi ◽  
Soil Depth ◽  
Soil Layers ◽  
Soil P ◽  
Fungal Populations ◽  
Hydrolysis Of ◽  
Vertical Transect

A series of samples were taken from mulched and unmulched trees starting at the surface of mulch or soil to a 15 cm soil depth, forming a vertical transect. Saprophytic fungi isolated from the soil samples on rose bengal medium and surveyed visually were most abundant in mulches and at the interface of mulch and soil (P < 0.05). Microbial activity as assayed by the hydrolysis of fluorescein diacetate was significantly greater in mulch layers than in soils. Cellulase and laminarinase enzyme activities were greatest in upper mulch layers and rapidly decreased in soil layers (P < 0.05). Enzyme activities against Phytophthora cinnamomi cell walls were significantly greater in mulch than in soil layers. When Phytophthora cinnamomi was incubated in situ at the various transect depths, it was most frequently lysed at the interface between soil and mulch (P < 0.001). Roots that grew in mulch layers were significantly less infected with Phytophthora cinnamomi than roots formed in soil layers. In mulched soil, roots were commonly formed at the mulch-soil interface where Phytophthora populations were reduced, whereas roots in unmulched soil were numerous at the 7.5 cm depth where Phytophthora cinnamomi was prevalent. Enzyme activities were significantly and positively correlated with each other, microbial activity, and saprophytic fungal populations, but significantly and negatively correlated with Phytophthora recovery.

scholarly journals SIZING AND EXPERIMENTAL STUDY OF A SOLAR STILL FOR THE PRODUCTIVITY OF WATER DESALINATION IN SOUTH-WEST OF ALGERIA – BECHAR: التصميم والدراسة التجريبية لجهاز التقطير الشمسي لإنتاجية تحلية المياه في جنوب غرب الجزائر – بشار

2020 ◽  
Vol 4 (4) ◽  
Author(s):  
Abdelkarim Maamar Abdelkader, Bounegta Bachir Mohammed
Keyword(s):  
Drinking Water ◽  
Free Surface ◽  
Surface Area ◽  
Evaporation Rate ◽  
Salt Content ◽  
Experimental Studies ◽  
Water Desalination ◽  
Solar Still ◽  
Free Surface Area ◽  
The Third World

Algeria, like many countries belonging mostly to the Third World, has considerable water resources saline (salt content ranging between 1500 and 2000 ppm, exceeding the required standards for drinking water and therefore unfit for consumption). We must therefore think of making use these huge reserves interested in desalination techniques. The stain majored is therefore to achieve a distiller solar plan which meets these needs in drinking water. The absorber surface of the modified solar still is coated with black enamel paint and covered with copper chips. The evaporation rate of the water in the solar still is directly proportional to the exposure area of the water. Thus the productivity of the solar still increases with the free surface area of the water in the basin. The distillate yield was found to have improved considerably, especially when the water depth was high. The study also indicated some design features that would further enhance the improvement in output due to the modification made, the evaporation rate is proportional to the temperature of the free surface area of the water only. A general model based on heat transfer balances in each component of the system was developed to predict the mass of freshwater. The efficiency of this still was about 65% and can produce about 5.13 l/m2 per day, experimental studies and the outcomes are discussed in the article. We propose a new design of the cascading solar desalination still with obstacles and preheating of inlet water.

scholarly journals In-Situ Pore Structure Analysis During Aging and Drying of Gels

1990 ◽  
Vol 180 ◽  
Author(s):  
Douglas M. Smith ◽  
Pamela J. Davis ◽  
C. Jeffrey Brinker
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Surface Area ◽  
Pore Fluid ◽  
Structure Evolution ◽  
High Ph ◽  
Drying Rates

ABSTRACTThe use of NMR relaxation measurements for the in-situ study of pore structure evolution during gel aging and drying is illustrated. The change in the pore size distribution and surface area of both wet and dried gels is examined as a function of aging conditions including temporal aging, thermal aging, changing pH, and changing pore fluid. The effect of pore fluid pH on dissolution/reprecipitation in ordered packings of monodisperse silica spheres is also examined as a model system for particulate gels. As expected, the pore size distribution narrows with increasing time of treatment in high pH pore fluids. Interpretation of high pH results for the wet state is complicated by a microporous layer which forms on colloidal silica resulting in significantly larger wet surface area as compared to the final dried material. Narrowing of the pore size distribution, which is of interest for maximizing drying rates, is maximized in the least time by using either high pH or repeated ethanol washes for the base-catalyzed gel (B2) used.

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