Use of plant water relations to assess forage quality and growth for two cultivars of Napier grass (Pennisetum purpureum) subjected to different levels of soil water supply and temperature regimes

2013 ◽  
Vol 64 (10) ◽  
pp. 1008 ◽  
Author(s):  
S. W. Mwendia ◽  
I. A. M. Yunusa ◽  
R. D. B. Whalley ◽  
B. M. Sindel ◽  
D. Kenney ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Water Supply ◽  
Soil Water ◽  
Temperature Regime ◽  
Water Status ◽  
Forage Quality ◽  
Napier Grass ◽  
Pennisetum Purpureum ◽  
High Temperature Regime

Napier grass (Pennisetum purpureum Schumach.) is an important fodder and relatively drought-tolerant crop in tropical and subtropical regions, especially in developing countries. For this and other species, tools are needed for identifying drought-tolerant cultivars to aid selection for semi-arid environments. We determined tissue water status, carbon assimilation, biomass yield and forage quality for Napier grass cvv. Bana and Atherton grown in bins and subjected to three soil-water supply levels (100, 50 or 25% of field capacity) in glasshouses set at either low (15−25°C) or high (25−35°C) temperature regimes, over three growing cycles. Our aim was to explore whether differences in leaf water potential (LWP) and carbon assimilation rates could be reliable indicators of the relative yield potential and forage quality of the two cultivars in environments prone to water and heat stresses. At the low soil-water supply of 25% and low temperature, Bana had lower (more negative) LWP and relative water content (RWC) than Atherton, while at 50% and 100% soil-water supply, Bana had a higher tissue water status. Under the high temperature regime, Bana had consistently more positive LWP and RWC than Atherton, but the differences were not significant. The two cultivars had a similar CO2 assimilation rate (A) and there were no significant differences in the total dry matter yields over the three growing cycles. Water-use efficiency for above-ground biomass (kg ha–1 mm–1) was similar for both cultivars and was 28.5–35.1 under the low temperature regime and 16.9–22.9 under the high temperature regime. Neutral detergent fibre (NDF) was often higher for Bana at low water supply and low temperature than for Atherton, but the trend was reversed under the high temperature regime. Digestibility was generally improved under water-stressed conditions, and there was a positive correlation between NDF and both LWP and RWC measured at midday, but only under the low temperature regime. We conclude that LWP, RWC and A, alone or together, are inadequate for selecting cultivars for dry and hot environments, because cultivars may differ in other mechanistic responses to water stress and high temperatures.

High-Temperature Ignition Kinetics of Gas Turbine Lubricating Oils

2021 ◽  
Author(s):  
Sean P. Cooper ◽  
Eric L. Petersen
Keyword(s):  
Regression Analysis ◽  
High Temperature ◽  
Low Temperature ◽  
Shock Tube ◽  
Gas Turbine ◽  
Temperature Regime ◽  
Ignition Process ◽  
High Temperature Regime ◽  
Second Stage ◽  
Arrhenius Expression

Abstract Lubricant ignition is a highly undesirable event in any mechanical system, and surprisingly minimal work has been conducted to investigate the auto-ignition properties of gas turbine lubricants. To this end, using a recently established spray injection scheme in a shock tube, two gas turbine lubricants (Mobil DTE 732 and Lubricant A from Cooper et al. 2020) were subjected to high-temperature, post-reflected-shock conditions, and OH* chemiluminescence was monitored at the sidewall location of the shock tube to measure ignition delay time (τign). A combination of an extended shock-tube driver and driver-gas tailoring were utilized to observe ignition between 1183 K and 1385 K at near-atmospheric pressures. A clear, two-stage-ignition process was observed for all tests with Mobil DTE 732, and both first and second stage τign are compared. Second stage ignition was found to be more indicative of lubricant ignition and was used to compare τign values with lubricant A. Both lubricants exhibit three ignition regimes: a high-temperature, Arrhenius-like regime (> 1275 K); an intermediate, negative-temperature-coefficient-like regime (1230–1275 K); and a low-temperature ignition regime (< 1230 K). Similar τign behavior in the high-temperature regime was seen for both lubricants, and a regression analysis using τign data from both lubricants in this region produced the Arrhenius expression τign(μs) = 4.4 × 10−14exp(96.7(kcal/mol)/RT). While lubricant A was found to be less reactive in the intermediate-temperature regime, Mobil DTE 732 was less reactive in the low-temperature regime. As the low-temperature regime is more relevant to gas turbine conditions, Mobil DTE 732 is considered more desirable for system implementation. Chemical kinetic modeling was also performed using n-hexadecane models (a lubricant surrogate suggested in the literature). The current models are unable to reproduce the three regimes observed and predict activation energies much lower than those observed in the high-temperature regime, suggesting n-hexadecane is a poor surrogate for lubricant ignition. Additionally, experiments were conducted with Jet-A for temperatures between 1145 and 1419 K around 1 atm. Good agreement is seen with both literature data and model predictions, anchoring the experiment with previously established τign measurement methods and calculations. A linear regression analysis of the Jet-A data produced the Arrhenius expression: τign(μs) = 6.39 × 10−5exp(41.4(kcal/mol)/RT).

Ignition in the supersonic hydrogen/air mixing layer with reduced reaction mechanisms

1996 ◽  
Vol 322 ◽  
pp. 275-296 ◽  
Author(s):  
H. G. Im ◽  
B. T. Helenbrook ◽  
S. R. Lee ◽  
C. K. Law
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Regime ◽  
Characteristic Temperature ◽  
Mixing Layer ◽  
Reaction Rates ◽  
Thermal Runaway ◽  
Ignition Process ◽  
High Temperature Regime ◽  
Air Mixing

Asymptotic analysis of ignition within the supersonic hydrogen/air mixing layer is performed using reduced mechanisms. Two distinct reduced mechanisms for the high-temperature and the low-temperature regimes are used depending on the characteristic temperature of the reaction zone relative to the crossover temperature at which the reaction rates of the H + 02 branching and termination steps are equal. Each regime further requires two distinct analyses for the hot-stream and the viscous-heating cases, depending on the relative dominance of external and internal ignition energy sources. These four cases are analysed separately, and it is shown that the present analysis successfully describes the ignition process by exhibiting turning point or thermal runaway behaviour in the low-temperature regime, and radical branching followed by thermal runaway in the high-temperature regime. Results for the predicted ignition distances are then mapped out over the entire range of the parameters, showing consistent behaviour with the previous one-step model analysis. Furthermore, it is demonstrated that ignition in the low-temperature regime is controlled by a larger activation energy process, so that the ignition distance is more sensitive to its characteristic temperature than that in the high-temperature regime. The ignition distance is also found to vary non-monotonically with the system pressure in the manner of the well-known hydrogen/oxygen explosion limits, thereby further substantiating the importance of chemical chain mechanisms in this class of chemically reacting boundary layer flows.

EFFECT OF Ni SUBSTITUTION FOR Cu IN THE VORTEX STATE OF (Bi,Pb):2223 SUPERCONDUCTOR

1999 ◽  
Vol 13 (21n22) ◽  
pp. 2775-2782 ◽  
Author(s):  
A. V. POP
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Magnetic Fields ◽  
Temperature Regime ◽  
Vortex State ◽  
Partial Substitution ◽  
High Temperature Regime ◽  
Ni Substitution ◽  
Dissipation Processes

The influence of the partial substitution of x=0.02 Ni for Cu on the magnetoresistivity in the (Bi,Pb):2223 superconductor has been investigated. The resistive transitions were studied under magnetic fields up to 0.7 Tesla by using the dρ/dT versus T curves. The Arrhenius plots shows that the dissipation processes are induced by two distinct regimes. In the high temperature regime the activation energy is proportional to ln B and to B-1 in low temperature regime. The main dissipation processes in these regimes are discussed.

Glyphosate Activity in Potato (Solanum tuberosum) Under Different Temperature Regimes and Light Levels

Weed Science ◽  
1988 ◽  
Vol 36 (2) ◽  
pp. 137-140 ◽  
Author(s):  
John B. Masiunas ◽  
Stephen C. Weller
Keyword(s):  
Solanum Tuberosum ◽  
High Temperature ◽  
Low Temperature ◽  
Temperature Regime ◽  
Distribution Patterns ◽  
Light Level ◽  
Fresh Weight ◽  
High Temperature Regime ◽  
Light Levels ◽  
Temperature Regimes

The response of potato (Solanum tuberosumL. 'Superior’) to glyphosate [N-(phosphonomethyl)glycine] at rates between 0.28 and 2.24 kg ae/ha was determined in four environments: 24/13 or 13/4 C temperature regimes with light levels of 650 ± 53 or 320 ± 45 μE · m−2· S−1. Light level did not affect phytotoxicity ratings or shoot fresh weight following glyphosate application. Greater phytotoxicity and reduced fresh weight accumulation were observed from glyphosate at rates above 0.56 kg/ha in a high-temperature regime than for comparable plants grown at low temperature. Studies of14C-glyphosate uptake and translocation indicated that the differences in phytotoxicity were due to less glyphosate absorption at low temperature and not a shift in distribution patterns within the plant.

scholarly journals MAGNETIC INSTABILITY IN A PARITY INVARIANT TWO-DIMENSIONAL FERMION SYSTEM

2000 ◽  
Vol 14 (14) ◽  
pp. 1441-1449 ◽  
Author(s):  
M. ELIASHVILI ◽  
G. TSITSISHVILI
Keyword(s):  
High Temperature ◽  
Temperature Regime ◽  
Ground State ◽  
Finite Temperature ◽  
Two Dimensional ◽  
Fermion System ◽  
Temperature Analysis ◽  
Magnetic Instability ◽  
High Temperature Regime

We consider the parity invariant QED2+1 where the matter is represented as a mixture of fermions with opposite spins. It is argued that the perturbative ground state of the system is unstable with respect to the formation of magnetized ground state. Carrying out the finite temperature analysis we show that the magnetic instability disappears in the high temperature regime.

scholarly journals Stabilization of spin liquid in Kondo lattice: High temperature regime

1997 ◽  
Vol 230-232 ◽  
pp. 490-492 ◽  
Author(s):  
K.A. Kikoin ◽  
M.N. Kiselev ◽  
A.S. Mishchenko
Keyword(s):  
High Temperature ◽  
Temperature Regime ◽  
Kondo Lattice ◽  
Spin Liquid ◽  
High Temperature Regime

The behavior of ZrO 2 /20%Y 2 O 3 and Al 2 O 3 coatings deposited on aluminum alloys at high temperature regime

2015 ◽  
Vol 352 ◽  
pp. 178-183 ◽  
Author(s):  
G.L. Pintilei ◽  
V.I. Crismaru ◽  
M. Abrudeanu ◽  
C. Munteanu ◽  
E.R. Baciu ◽  
...  
Keyword(s):  
High Temperature ◽  
Aluminum Alloys ◽  
Temperature Regime ◽  
High Temperature Regime

scholarly journals Growth, flowering and fruiting in tomatoes in relation to temperature, cycocel and GA.

1970 ◽  
Vol 18 (2) ◽  
pp. 105-110
Author(s):  
A.A. Abdalla ◽  
K. Verkerk
Keyword(s):  
Growth Rate ◽  
High Temperature ◽  
High Temperatures ◽  
Root Development ◽  
Temperature Regime ◽  
Low Temperatures ◽  
Fruit Set ◽  
High Temperature Regime ◽  
Temperature Regimes ◽  
Dark Green

The effects were assessed of CCC and GA on tomatoes grown either under a high temperature regime (35 degrees day and 25 degrees C. night) or at normal temperatures (22 degrees and 18 degrees ). CCC (0.4%) was applied to the soil in the pots either 2 days after transplanting or at the start of flowering; G A was applied by dipping the first truss in GA (50 p.p.m.). CCC greatly retarded the growth rate of the stems of the plants under both temperature regimes; this effect persisted for about 17 and 24 days under the high and normal temperature regimes, respectively. With plants grown at high temperatures CCC applied at the start of flowering greatly reduced flower shedding and slightly increased the fruit set and fruit development of hand-pollinated flowers. With plants grown at normal temperatures, however, the effects of CCC were slight. CCC-treated plants were sturdy with dark-green leaves which remained green longer, especially under the high temperature regime. More N accumulated in the tissues of plants grown at high temperatures than at normal temperatures, and the N content of the latter plants was considerably increased by CCC treatment. The root development of the CCC-treated plants was much more extensive than that of the untreated plants. The numbers of seeds in the hand-pollinated fruit were not affected by CCC, but at high temperatures there were considerably less seeds than at low temperatures. GA enhanced fruit set of the high-temperature plants, but the fruits were small and seedless. GA also accelerated fruit ripening by 2 and 3 weeks in the plants grown at high and normal temperatures, respectively.-Agric. Univ., Wageningen. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Magnetic susceptibility of semimagnetic semiconductors: The high-temperature regime and the role of superexchange

1986 ◽  
Vol 33 (5) ◽  
pp. 3407-3418 ◽  
Author(s):  
J. Spal/ek ◽  
A. Lewicki ◽  
Z. Tarnawski ◽  
J. K. Furdyna ◽  
R. R. Galazka ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
High Temperature ◽  
Temperature Regime ◽  
High Temperature Regime ◽  
Semimagnetic Semiconductors
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