scholarly journals Appearance of Purine-Catabolizing Enzymes in Fix+ and Fix− Root Nodules on Soybean and Effect of Oxygen on the Expression of the Enzymes in Callus Tissue

1987 ◽  
Vol 85 (2) ◽  
pp. 452-456 ◽  
Author(s):  
Knud Larsen ◽  
Bjarne U. Jochimsen
Keyword(s):  
Callus Tissue ◽  
Root Nodules ◽  
Effect Of Oxygen

Effect of Oxygen Supply on Nitrogenase Activity of Nitrate- and Dark-Stressed Soybean (Glycine max (L.) Merr.) Plants

1987 ◽  
Vol 14 (6) ◽  
pp. 679 ◽  
Author(s):  
BJ Carroll ◽  
AP Hansen ◽  
DL Mcneil ◽  
PM Gresshoff
Keyword(s):  
Glycine Max ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Short Term ◽  
Glycine Max L ◽  
Autonomous Activity ◽  
Effect Of Oxygen ◽  
Substrate Deprivation ◽  
Dark Stress ◽  
Oxygen Concentrations

Nitrate and dark stress were used to induce decline in nitrogenase activity of root nodules of soybeans (Glycine max (L.) Merr. cv. Bragg). Response to this treatment and to various oxygen concentrations was assessed by short-term acetylene reduction assays. Decreases in oxygen partial pressure reduced nitrogenase activity substantially in unstressed soybean nodules and even further in nodules of nitrate- or dark-stressed plants. Increasing oxygen concentrations from 21 to 60% severely restricted nitrogenase activity in control plants, but stimulated activity in soybeans exposed to 10 mol m-3 nitrate or darkness for 2 days. Less stressed plants (treated with 7.5 mol m-3 nitrate) were stimulated less by high oxygen tension. Soybeans deprived of light for 4 days were symbiotically inactive and did not respond to raised O2 concentrations. Bacteroids isolated from these plants had lost their autonomous activity but recovered in the presence of succinate, indicating substrate deprivation. The data presented suggest that suboptimal oxygen concentration near the bacteroids is an important factor limiting nitrogenase activity in nitrate-or dark-stressed soybeans.

A TEM study of the effect of oxygen on nanocavity formation and precipitation in rapid - solidified Fe-16Ni-9Cr stainless steels

1994 ◽  
Vol 52 ◽  
pp. 700-701
Author(s):  
S. Wisutmethangoon ◽  
T. F. Kelly ◽  
J.E. Flinn
Keyword(s):  
Stainless Steels ◽  
High Mobility ◽  
Hot Extrusion ◽  
Extrusion Ratio ◽  
Gas Atomization ◽  
Cavity Formation ◽  
Nucleation Sites ◽  
Heat Treated ◽  
Different Types ◽  
Effect Of Oxygen

Vacancies are introduced into the crystal phase during quenching of rapid solidified materials. Cavity formation occurs because of the coalescence of the vacancies into a cluster. However, because of the high mobility of vacancies at high temperature, most of them will diffuse back into the liquid phase, and some will be lost to defects such as dislocations. Oxygen is known to stabilize cavities by decreasing the surface energy through a chemisorption process. These stabilized cavities, furthermore, act as effective nucleation sites for precipitates to form during aging. Four different types of powders with different oxygen contents were prepared by gas atomization processing. The atomized powders were then consolidated by hot extrusion at 900 °C with an extrusion ratio 10,5:1. After consolidation, specimens were heat treated at 1000 °C for 1 hr followed by water quenching. Finally, the specimens were aged at 600 °C for about 800 hrs. TEM samples were prepared from the gripends of tensile specimens of both unaged and aged alloys.

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 689-694
Author(s):  
QINGZHI MA ◽  
QI WANG ◽  
CHU WANG ◽  
NIANJIE FENG ◽  
HUAMIN ZHAI
Keyword(s):  
Intrinsic Viscosity ◽  
Chlorine Dioxide ◽  
High Purity ◽  
Kraft Pulp ◽  
Alkaline Media ◽  
Industrial Scale ◽  
Elemental Chlorine ◽  
Effect Of Oxygen ◽  
Alkaline Tolerant ◽  
Ecf Bleaching

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

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