Control of Particle Size and Orientation during in Situ Precipitation of Oxides in Polymers

1992 ◽  
Vol 286 ◽  
Author(s):  
Jeremy Burdon ◽  
Paul Calvert
Keyword(s):  
Particle Size ◽  
Bone Matrix ◽  
Two Phase ◽  
The Matrix ◽  
Hydrolysis Of Metal Alkoxides ◽  
Micron Diameter ◽  
High Level ◽  
Kinetics Of ◽  
Hydrolysis Of

ABSTRACTComposite materials may be prepared by bio-mimetic routes where reinforcing particles are grown by chemical reaction in a polymer matrix, by analogy to the mineralization of collagenous bone matrix by hydroxyapatite. Ideally these resulting composites should resemble bone in having sub-micron, elongated particles packed to high densities in the matrix. The resulting material should have good mechanical properties and may also be fired to a dense ceramic.We have been exploring the control of the precipitation of oxide ceramics, particularly titania, by in situ hydrolysis of metal alkoxides. The size of the precipitate particles can be controlled by variation of the compatibility of polymer and alkoxide. A high level of compatibility leads to particles with sizes below 0.1 microns while less compatible alkoxides give particles up to 1 micron diameter. The kinetics of the hydrolysis also affect the particle size. Elongated and oriented particles can be produced by deformation of the polymer during precipitation. Two-phase polymer blends can be used to provide nanoscale molds within which elongated particles grow. By controlling the scale of phase separation in the blend it is possible to produce rod-shaped particles with diameters in the range from one micron down to a few nanometers.

scholarly journals Kinetic Analysis of the Hydrolysis of Pentose-1-Phosphates Through Apparent Nucleoside Phosphorolysis Equilibrium Shifts

2020 ◽  
Author(s):  
Felix Kaspar ◽  
Peter Neubauer ◽  
Anke Kurreck
Keyword(s):  
Kinetic Analysis ◽  
Hydrolysis Kinetics ◽  
Equilibrium Thermodynamics ◽  
Apparent Increase ◽  
Equilibrium Conversion ◽  
Sugar Phosphates ◽  
Kinetics Of ◽  
Hydrolysis Of

<div>Ask what an equilibrium can do for you:</div><div>Hydrolysis of pentose-1-phosphates leads to an apparent increase of the equilibrium conversion in nucleoside phosphorolysis reactions. This information can be leveraged via equilibrium thermodynamics to determine the hydrolysis kinetics of in situ generated sugar phosphates, which are known to be elusive and difficult to quantify.<br></div>

Ultra-small MnCo2O4 nanocrystals decorated on nitrogen-enriched carbon nanofibers as oxygen cathode for Li-O2 batteries

2020 ◽  
Vol 13 (06) ◽  
pp. 2051035
Author(s):  
Xiaoping Jiang ◽  
Ronghua Wang ◽  
Ning Hu ◽  
Chaohe Xu
Keyword(s):  
Particle Size ◽  
Cathode Materials ◽  
Nitrogen Doping ◽  
Carbon Nanofiber ◽  
Nucleation And Growth ◽  
Ex Situ ◽  
Aprotic Electrolyte ◽  
High Level ◽  
Oxygen Cathode

Ultra-small MnCo2O4 nanocrystals/nitrogen enriched carbon nanofiber composites, with particle size as small as 2–4[Formula: see text]nm and nitrogen content as high as [Formula: see text][Formula: see text]at.%, were designed and used as oxygen cathode materials for Li-O2 batteries, with an aprotic electrolyte. Via an in-situ nucleation and growth, the morphology, size and distribution of MnCo2O4 nanocrystals were well controlled on surface of nanofibers, with strong interfacial interactions between the two components. Benefitting from the unique microstructure and high-level nitrogen doping, the MnCo2O4/NCF composite can deliver discharge and charge capacities of 4147.8 and 3842.8[Formula: see text]mAh/g as oxygen cathode materials, and columbic efficiencies are about 92.6%. More importantly, the discharge products can completely decompose in charging process as evidenced by an ex-situ FESEM investigation, while for pure NCF cathode, particle and plate-like Li2O2 were still observed on its surface, which confirmed that the MnCo2O4/NCF composite has a superior electrocatalytic activity that that of NCF.

Studies on Protein Subunits. V. Specific Interaction between Matrix–Bound Subunits of Aldolase and Soluble Aldolase Subunits

1973 ◽  
Vol 51 (9) ◽  
pp. 1240-1247 ◽  
Author(s):  
W. W.-C. Chan
Keyword(s):  
Specific Interaction ◽  
Saturation Level ◽  
Guanidinium Chloride ◽  
Protein Subunits ◽  
The Matrix ◽  
Tetrameric Structure ◽  
Matrix Bound ◽  
Small Aliquot ◽  
Kinetics Of

A derivative containing matrix-bound (MB) subunits of aldolase was prepared by attaching native tetrameric aldolase to Sepharose to form MB-aldolase followed by dissociation with 6 M guanidinium chloride and renaturation. The interaction between the MB-subunit aldolase derivative so prepared and subunits added in solution was studied. Nascent subunits of aldolase were generated in situ by diluting a small aliquot of guanidinium chloride-denatured aldolase into a much larger volume of buffer containing a suspension of MB-subunit aldolase. This treatment caused a significant increase in the amount of bound activity. The ability of MB-subunit aldolase to pick up activity from solution is highly specific. After repeated treatments with nascent sub-units, the matrix-bound activity reached a saturation level close to four times the activity of MB-subunit aldolase. The product of this treatment is very similar in properties to the original MB-tetrameric aldolase but different from MB-subunit aldolase. These observations suggest that MB-subunit aldolase can associate with nascent subunits generated in solution to form MB-tetrameric aldolase. The results in this paper support the conclusion from the kinetics of renaturation (Chan et al. J. Biol. Chem. 248, 2778 (1973)) that aldolase monomers have the same activity whether they exist singly or as part of a tetrameric structure.

Physically effectiveness of beet pulp in dairy cows 1: physical characteristics, ruminal kinetics of nutrients degradation, hydration, and functional specific gravity

2007 ◽  
Vol 2007 ◽  
pp. 215-215
Author(s):  
Teimouri Yansari Asadollah
Keyword(s):  
Particle Size ◽  
Specific Gravity ◽  
Physical Characteristics ◽  
Particle Size Measurement ◽  
Effective Factor ◽  
Beet Pulp ◽  
Water Holding ◽  
Kinetics Of

Some physical properties including particle size, functional specific gravity (FSG; Teimouri Yansari et al., 2004), hydration rate, water holding capacity (WHC) and ionion-cation exchange (Van Soest, 1994) influenced on physically effective factor (pef), but only particle size measurement is central to all effective fibre systems. The objective of this study was to evaluate the effects of three types of beet pulp (BP) on physical characteristics including bulk density, particle size, kinetics of hydration, FSG, WHC, and intrinsic osmotic pressure that measured usingin vitroandin situmethods.

Atheromatosis of arterial intima

2016 ◽  
Vol 94 (8) ◽  
pp. 582-590
Author(s):  
Vladimir N. Titov ◽  
T. A. Rozhkova ◽  
V. A. Amelyushkina
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Arterial Wall ◽  
Proteolytic Enzymes ◽  
Muscle Cells ◽  
Acid Hydrolases ◽  
The Matrix ◽  
Arterial Intima ◽  
Hydrolysis Of

Phylogenetically late arterial intima of the elastic type contains no proteins for the transfer of ligandless oxidized low density lipoproteins (LDLP) for sedentary macrophages adsorbed on the matrix. Phylogenetically early cells realize the extracellular digestive reaction by releasing proteolytic enzymes (metalloproteinases) into intimal matrix that hydrolize matrix proteoglycans, adsorbed ligandless LDLP, detritus, and complete lysosomal hydrolysis of the most hydrophobic polyenic cholesterol esters (poly-ECS). Smooth muscle cells migrate from the middle muscular layer of the arterial wall, change their contractile phenotype to secretory one, and synthesize in situ de novomatrix proteoglycans. The arterial wall has three layers (monolayer endothelium, intimal media (smooth muscle cells), and adventitia) only in elastic type arteries. It is desirable to elucidate functional differences between phylogenetically early sedentarymacrophages and monocytes-macrophages of later origin and understand whether theydepends on specific features of activity of scavenger eceptors, CD36 translocases, expression of acid hydrolases synthesis for poly-ECS or realization of the extracellular digestion reaction. We believe that formation of atheromatous masses takes place in the matrix of arterial intima rather than in lysosomes taking into account limited possibilities for monocytes-macrophages to realize endocytosis of ligandless LDLP from the matrix. Given that atheromatosis is a syndrome of deficit of essential polyenic fatty acids (PFA) in the cells, intimal atheromatosisshould be regarded only as partial utilization of excess PFA in the matrix of elastic type arteries. At later stages of phylogenesis, intima was formed from media smooth muscle cells.

scholarly journals Effects of lucerne particle size and source of dietary carbohydrates on in situ degradation and ruminal variables in sheep

2009 ◽  
Vol 54 (No. 6) ◽  
pp. 277-285 ◽  
Author(s):  
A. Asadi Alamouti ◽  
G.R. Ghorbani ◽  
M. Alikhani ◽  
H.R. Rahmani ◽  
A. Teimouri Yansari ◽  
...  
Keyword(s):  
Particle Size ◽  
Latin Square ◽  
Dietary Carbohydrates ◽  
Ruminal Fermentation ◽  
Ruminal Ph ◽  
Degradation Rate Constant ◽  
Beet Pulp ◽  
Feeding Diets ◽  
Kinetics Of

The effects of altering forage particle size and source of rapidly degradable carbohydrates on <I>in situ</I> degradation and ruminal variables were studied in four Iranian male sheep. The study was designed as a Latin square with a 2 × 2 factorial arrangement of treatments including two carbohydrate sources (pelleted beet pulp vs. maize- and barley-based concentrate) and two lucerne particle sizes (2.38 vs. 0.94 mm). Kinetics of disappearance of lucerne, concentrates and mixed samples was studied <I>in situ</I>. Among feed samples, the degradation rate constant of lucerne dry matter was higher (<I>P</I> < 0.02) and disappearance of lucerne neutral detergent fibre (NDF) in 4 h of incubation was lower (<I>P</I> = 0.06) in diets with reduced particle size. The rapidly degradable fraction of lucerne samples was also affected by treatments. Other degradability components were not affected. The mean ruminal pH was lower in diets containing short hay than in those containing long hay (5.76 vs. 5.86, <I>P</I> < 0.006) and pH values were consistently lower immediately after feeding diets with short lucerne hay. The form of carbohydrates did not affect ruminal pH, however, altering the source of carbohydrates changed the pattern of pH over time. Total volatile fatty acid (VFA) concentration and proportions of individual VFA were similar but numerical differences indicated a lower acetate to propionate ratio in diets with short hay. Most of the affected variables were influenced by the particle size of forage to a larger extent than by the source of rapidly degradable carbohydrates or the interaction between them. So, when sheep diets contain no more than 250 g/kg starch, the source of dietary carbohydrates may not interact with forage particle size to affect DM degradability and ruminal fermentation.

The Mechanical Properties of Near-equiatomic B2/f.c.c. FeNiMnAl Alloys

2013 ◽  
Vol 1516 ◽  
pp. 249-254 ◽  
Author(s):  
Xiaolan Wu ◽  
Ian Baker ◽  
Hong Wu ◽  
Paul R. Munroe
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Temperature Dependence ◽  
Orientation Relationship ◽  
Annealing Time ◽  
Two Phase ◽  
Chemical Partitioning ◽  
The Matrix ◽  
In Situ Heating

ABSTRACTTwo types of as-cast microstructures have been observed in a series of near-equiatomic FeNiMnAl alloys: 1) an ultrafine microstructure in Fe30Ni20Mn20Al30 [1] and Fe25Ni25Mn20Al30, which consists of (Fe, Mn)-rich B2-ordered (ordered b.c.c.) and (Ni, Al)-rich L21-ordered (Heusler) phases aligned along <100>; and 2) a fine two-phase microstructure in Fe30Ni20Mn30Al20 and Fe25Ni25Mn30Al20, which consists of alternating (Fe, Mn)-rich f.c.c. and (Ni, Al)-rich B2-ordered platelets with an orientation relationship close to f.c.c (002) // B2 (002); f.c.c. [011] // B2 [001] [2]. The phases in Fe25Ni25Mn20Al30 coarsened upon annealing with no significant change in the chemical partitioning. The hardness behavior was studied as a function of the annealing time at 823 K. AnL21-to-B2 transition, which occurred at 573-623K, was observed using in-situ heating in a TEM. After annealing at 973 K for 100 h, needle-shaped clusters of (Fe, Mn)-rich precipitates were observed along the grain boundaries and in the matrix. The temperature dependence of the yield strength of as-cast Fe25Ni25Mn20Al30 was also studied.

Sign in / Sign up

Export Citation Format

Share Document