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1.
The aim of this study was to investigate the effect of the thermal modification process by hot-press on the wettability and surface roughness characteristics of the eucalyptus wood boards. The roughness measurements, average roughness (Ra), and maximum roughness (Rmax) were taken both parallel and perpendicular to the grain using a fine stylus tracing technique. Contact angle measurements were obtained using a goniometer system connected to a digital camera and computer system. The results showed that surface roughness values of the modified wood boards using a hot-press significantly decreased with increasing press pressure and with decreasing temperature. The contact angle measurements indicated that the thermal modification had a significant influence on the surface wettability of the wood boards. Statistical analyses showed significant differences in the surface roughness and contact angle values of the wood boards following thermal modification. The results acquired in this work provide important information for future research and utilization of the thermally modified wood boards.  相似文献   

2.
The concept of thermal modification has evolved from a challenging research program to commercial reality in several European countries in recent years. The aim of this study is to determine the change of various physical properties (oven-dry density, air-dry density, weight loss, swelling and anti-swelling efficiency (ASE)), compression strength parallel to grain, colour difference (ΔE), glossiness and surface roughness of narrow-leaved ash (Fraxinus angustifolia Vahl.) and chestnut (Castanea sativa Mill.) woods after heat treatment under different temperatures and durations. For this study two different temperatures (160 °C and 180 °C) and two different durations (2 h and 4 h) were considered. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber. Four main roughness parameters which are mean arithmetic deviation of profile (Ra), mean peak-to-valley height (Rz), root mean square roughness (Rq), and maximum roughness (Ry) obtained from the surface of wood were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. The properties studied were significantly different (p = 0.05) at two temperatures and two durations of heat treatment. Based on the findings of this study, the results showed that oven-dry density, air-dry density, swelling, compression strength parallel to grain and surface roughness decreases with increasing heat treatment temperature and time.  相似文献   

3.
Thermally modified wood is being increasingly offered in Europe as an alternative to preservative-treated timber. The aim of this study is to determine the change of various physical properties (oven-dry density, air-dry density, weight loss, swelling and anti-swelling efficiency (ASE)), compression strength parallel to grain, colour difference (ΔE), glossiness and surface roughness of sapele (Entandrophragma cylindricum), limba (Terminalia superba) and iroko (Chlorophora excelsa) woods after heat treatment under different temperatures and durations. For this study wood specimens were subjected to heat treatment under atmospheric pressure and air at two different temperatures (160 °C and 180 °C) and two different times (2 h and 4 h). Multiple physical properties (oven-dry density, air-dry density, and swelling), compression strength parallel to the grain and surface roughness of the heat-treated wood and control samples were tested. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements using the stylus method were made in the direction perpendicular to the fiber. Four main roughness parameters which are mean arithmetic deviation of profile (Ra), mean peak-tovalley height (Rz), root mean square roughness (Rq), and maximum roughness (Ry) obtained from the surface of wood were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Significant difference was found (P = 0.05) between physical and technological properties, and surface roughness parameters (Ra, Rz, Ry, Rq) at two temperatures and two durations of heat treatment. Based on the findings of this study, the results showed that oven-dry density, air-dry density, swelling, compression strength parallel to grain and surface roughness values decreased with increasing treatment temperature and treatment time. Thus, sapele, iroko, and limba wood can be utilized with proper heat treatment techniques for outdoor and indoor applications.  相似文献   

4.
Non-destructive and quick assessment of leaf nitrogen (N) status is important for dynamic management of nitrogen nutrition and productivity forecast in crop production. This research was undertaken to make a systematic analysis on the quantitative relationship of leaf nitrogen concentrations (LNCs) to different hyperspectral vegetation indices with multiple field experiments under varied nitrogen rates and varied types in rice (Oryza sativa L.). The results showed that some published indices had good relations with LNC such as two-band indices, R750/R710 (ZM), Gitelson and Merzlyak index two (GM-2), R735/R720 (RI-1dB), R738/R720 (RI-2dB) and the normalized difference red edge index (NDRE), three-band indices, adjusted normalized index 705 (mND705), physiological reflectance index c (PRIc), terrestrial chlorophyll index (MTCI), and red edge position derived with four point linear interpolation (REP_LI). Three-band indices performed better than two-band indices, with MTCI exhibiting the best logarithmic relation to LNC in rice. Then, hyper-spectral vegetation indices computed with random two bands (λ1 and λ2) from 400 to 2500 nm range were related to LNC of rice. The results indicated that two-band indices combined with bands of 550–600 nm and 500–550 nm in green region had good relationships with LNC, and simple ratio index SR(533,565) performed the best in all two-band indices, similar to the published three-band indices (mND705, PRIc and MTCI). New three-band indices R434/(R496 + R401) and R705/(R717 + R491) were proposed for prediction of LNC with improved ability over the SR(533,565) and published spectral indices. Moreover, R705/(R717 + R491) performed well in all the data from ground spectra, modeled AVIRIS and Hyperion spectra, and acquired Hyperion image hyperspectra. The R434/(R496 + R401) also exhibited well in both ground and modeled AVIRIS and Hyperion image spectra, but could not be tested with the acquired Hyperion image because of the absence in radiometric calibration of the bands less than 416 nm. Overall, the newly developed three-band spectral index R705/(R717 + R491) should be a good indicator of LNC at ground and space scales in rice. Yet, these new indices still need to be tested with more remote sensors based on ground, airborne and spaceborne, and verified widely in other ecological locations involving different cultivars and production systems.  相似文献   

5.
The objective of this investigation was to evaluate some of the physical and mechanical properties of resin-treated plywood type panels manufactured from bamboo strips (Gigantochloa scortechinii). Experimental plybamboo samples were made from low molecular weight phenol formaldehyde (LMwPF) treated bamboo strips. They were exposed to outdoor condition ranging from 1 to 12 months. Modulus of elasticity (MOE), modulus of rupture (MOR), compression strength, and surface roughness of treated and untreated samples were evaluated. Resin impregnated samples had the highest bending and compression strength properties. While the untreated samples failed after 3-month of outdoor exposure. Treated specimens exposed for 12-month had the MOE, MOR, and compression strength values of 14,253 N/mm2, 101.3 N/mm2, and 34.63 N/mm2, respectively. Surface quality of both treated and untreated samples was adversely influenced as the function of outdoor exposure time, based on numerical values obtained from a stylus type equipment. Overall properties of treated samples tested in work resulted in higher values than those of untreated samples. It appears that resin impregnation could be considered as an alternative method to enhance the characteristics of plybamboo exposed to environmental conditions as can be concluded from the results of this study.  相似文献   

6.
The phase behavior of zein films has been investigated at nano-scale using atomic force microscopy (AFM) and compared to the phase behavior of the bulk using a thermal characterization technique. The local surface properties of the films were evaluated as a function of water activity using AFM. The glass transition temperature (Tg) of zein films decreased with increasing water activity. Adhesion forces measured by the AFM force curves increased with increasing water activity. Topography of zein and zein fractions were evaluated both qualitatively and quantitatively by the use of AFM and dedicated software to calculate the surface roughness. It has been found that processing technologies (solvent casting, drop deposition and spin casting) has influence on the surface structures of films. The films which were formed by the alpha zein rich fraction were found to have highest roughness values. Sectional surface profiles revealed that α-zein films have mean roughness (Ra) of 1.808 nm and root mean square roughness (RMS) of 2.239 nm while β-zein films have mean roughness (Ra) of 1.745 nm and root mean square roughness (RMS) of 3.623 nm. The discussions conducted on the differences/similarities in the observations were based on the hydrophobic/hydrophilic properties and interactions of these zein fractions.  相似文献   

7.
An active crop canopy reflectance sensor could be used to increase N-use efficiency in maize (Zea mays L.), if temporal and spatial variability in soil N availability and plant demand are adequately accounted for with an in-season N application. Our objective was to evaluate the success of using an active canopy sensor for developing maize N recommendations. This study was conducted in 21 farmers’ fields from 2007 to 2009, representing the maize production regions of east central and southeastern Pennsylvania, USA. Four blocks at each site included seven sidedress N rates (0–280 kg N ha−1) and one at-planting N rate of 280 kg N ha−1. Canopy reflectance in the 590 nm and 880 nm wavelengths, soil samples, chlorophyll meter (SPAD) measurements and above-ground biomass were collected at the 6th–7th-leaf growth stage (V6–V7). Relative amber normalized difference vegetative index (ANDVIrelative) and relative SPAD (SPADrelative) were determined based on the relative measurements from the zero sidedress treatment to the 280 kg N ha−1 at-planting treatment. Observations from the current study were compared to relationships between economic optimum N rate (EONR) and ANDVIrelative, presidedress NO3 test (PSNT), or SPADrelative that were developed from a previous study. These comparisons were based on an absolute mean difference (AMD) between observed EONR and the previously determined predicted relationships. The AMD for the relationship between EONR and ANDVIrelative in the current study was 46 kg N ha−1. Neither the PSNT (AMD = 66 kg N ha−1) nor the SPADrelative (AMD = 72 kg N ha−1) provided as good an indicator of EONR. When using all the observations from the two studies for the relationships between EONR and the various measurements, ANDVIrelative (R2 = 0.65) provided a better estimate of EONR than PSNT (R2 = 0.49) or SPADrelative (not significant). Crop reflectance captured similar information as the PSNT and SPADrelative, as reflected in strong relationships (R2 > 0.60) among these variables. Crop canopy reflectance using an active sensor (i.e. ANDVIrelative) provided as good or better an indicator of EONR than PSNT or SPADrelative, and provides an opportunity to easily adjust in-season N applications spatially.  相似文献   

8.
Simple plant-based diagnostic tools can be used to determine crop P status. Our objectives were to establish the relationships between P and N concentrations of the uppermost collared leaf (PL and NL) of spring wheat (Triticum aestivum L.) and maize (Zea mays L.) during the growing season and, in particular, to determine the critical leaf P concentrations required to diagnose P deficiencies. Various N applications were evaluated over six site-years for wheat and eight site-years for maize (2004-2006) with adequate soil P for growth. Phosphorus and N concentrations of the uppermost collared leaf were determined weekly and the relationships between leaf N and P concentrations were established using only the sampling dates from the stem elongation stage for wheat and from the V8 stage of development for maize. Leaf P concentration generally decreased with decreasing N fertilization. Relationships between PL and NL concentrations (mg g−1 DM) using all site-years and sampling dates were described by significant linear-plateau functions in both maize (PL = 0.82 + 0.089 NL if NL ≤ 32.1 and PL = 3.7 if NL > 32.1; R2 = 0.41; P < 0.001) and wheat (PL = 0.02 + 0.106 NL if NL ≤ 33.2 and PL = 3.5 if NL > 33.2; R2 = 0.42; P < 0.001). Variation among sampling dates in the relationships were noted. By restricting the sampling dates [413-496 growing degree days (5 °C basis) in wheat (i.e., stem elongation) and 1494-1579 crop heat units in maize (i.e., silking), relationships for wheat (PL = 0.29 + 0.073 NL, R2 = 0.66; P < 0.001) and maize (PL = 1.04 + 0.084 NL, R2 = 0.66; P < 0.001) were improved. In maize, expressing P and N concentrations on a leaf area basis (PLA and NLA) at silking further improved the relationship (PLA = 0.002 + 0.101 NLA, R2 = 0.80; P < 0.001). Predictive models of critical P concentration as a function of N concentration in the uppermost collared leaf of wheat and maize were established which could be used for diagnostic purposes.  相似文献   

9.
The response of plant development rate (including germination rate) to temperature might be described as a non-linear function. We compared 3 non-linear regression models (Dent-like, segmented and beta) to describe the germination rate-temperature relationships of opium poppy (Papaver somniferum L.) over 6 constant temperatures to find cardinal temperatures and thermal time required to reach different germination percentiles. Two replicated experiments were performed with the same temperatures. An iterative optimization method was used to calibrate the models and different statistical indices (mean absolute error, coefficient of determination (R2), intercept and slope of the regression equation of predicted vs. observed germination rate) were applied to compare their performance. The segmented was found to be the best model to predict germination rate (R2 = 0.92, MAE = 0.0011 and CV of 1.4-3.6%). Estimated cardinal temperatures were similar for different germination percentiles (P < 0.05). Base on the model outputs, the base, the optimum and the maximum temperatures for germination were estimated as 3.02, 27.36 and 36.31 °C. The thermal time required to reach 50 and 95% germination was 57.27 and 87.55 degree-days, respectively. Model predictions of the time required for seed germination agreed reasonably well with the observed times (MAE = 0.56 day, R2 = 0.887). All model parameters may be readily used in crop simulation models.  相似文献   

10.
Soil acidity and Al toxicity are highly extended in agricultural lands of Chile, especially where wheat is widely sown. To evaluate quantitatively the response of wheat biomass and its physiological determinants (intercepted radiation and radiation use efficiency) to Al toxicity, two field experiments were conducted in an Andisol in Valdivia (39°47′S, 73°14′W), Chile, during the 2005–2006 and 2006–2007 growing seasons. Treatments consisted of a factorial arrangement of: (i) two spring wheat cultivars with different sensitivity to Al toxicity (the sensitive cultivar: Domo.INIA and the tolerant cultivar: Dalcahue.INIA) and (ii) five exchangeable Al levels (from 0 to 2.7 cmol(+) kg−1) with three replicates. Crop phenology and intercepted radiation (IR) were registered during the entire crop cycle, while 10 samples of above-ground biomass were taken at different stages between double ridge and maturity. Both biomass and leaf area index (LAI) were recorded in these 10 stages. Radiation use efficiency (RUE) was calculated as the slope of the relationship between accumulated above-ground biomass and accumulated photosynthetically active radiation intercepted by the canopy (IPARa). Crop phenology was little affected by soil Al treatments, showing only up to 17 days delay in the Al-sensitive cultivar under extreme Al treatments. Above-ground biomass at harvest was closely associated (R2 = 0.92) with the crop growth rate but no relationship (R2 = 0.14) was found between the crop cycle length. IPARa explained almost completely (R2 = 0.93) the above-ground biomass reached by the crop at harvest under the wide range of soil Al concentrations explored in both experiments. On the other hand, a weaker relationship was found between above-ground biomass and RUE. The effect of soil Al concentration on IPARa was mainly explained by LAI as a single relationship (R2 = 0.93) between IR (%) and LAI at maximum radiation interception showing a common light attenuation coefficient (k = 0.33).  相似文献   

11.
The impacts of acidic soils and Al toxicity on wheat nutrient economy have been scarcely researched under field conditions even though these soils are widely spread in wheat production areas around the world. The main objective of this study was to quantitatively evaluate the element (N, P, K, Ca and Al) economy of an Al-sensitive and an Al-tolerant wheat cultivar growing under different soil Al concentrations at field conditions. To reach this objective, two field experiments were conducted in an Andisol in Valdivia (39°47′18″S, 73°14′05″W), Chile. Treatments were a factorial arrangement of: (i) two spring wheat cultivars (Al-sensitive, Domo.INIA and Al-tolerant, Dalcahue.INIA) and (ii) five exchangeable Al levels (0-2.7 cmol(+) kg−1) with three replicates. At harvest, plant biomass was sampled and divided into 5 organ categories: ears, grains, blade leaves, stems plus sheath leaves and roots. The element content (N, P, K, Ca and Al) in each organ was measured to quantify element uptake and concentration, nutrient uptake efficiency (UPE) and nutrient utilization efficiency (UTE). Element uptake (N, P, K, Ca, and Al) was negatively affected by the increased soil Al concentration in above-ground and root biomass in both cultivars (R2 = 0.61-0.98, p < 0.01), although clear differences were found between cultivars. On the contrary, the impact of soil exchangeable Al on the plant element concentration was minor, showing weak associations with soil Al levels. However, the Al concentration in above-ground tissues of the Al-sensitive cultivar was an exception because it increased exponentially with the Al soil concentration (R2 = 0.96-0.99, p < 0.001). Nutrient uptake efficiencies, UPEs (N, P, K and Ca), were negatively affected by soil Al concentrations and were well described by linear equations in both cultivars (R2 = 0.58-0.98, p < 0.05), with notable differences between them. Both nutrient uptake (capture) and UPE were the traits that best explained above-ground biomass production (R2 = 0.82-0.99, p < 0.001, n = 20). Nutrient utilization efficiency, UTEs (N, P, K and Ca) responded more conservatively to the soil Al concentration, except for the Al sensitive cultivar under very high soil Al levels.  相似文献   

12.
As a novel renewable resource, Sapindus mukorossi seed oil (SMSO) with an iodine value of 84.86 g/100 g, and containing 51.0 ± 0.9% oleic acid (18:1), 6.6 ± 0.6% linoleic acid (18:2), 1.1 ± 0.3% linolenic acid (18:3), and 23.1 ± 0.9% eicosanoic acid (20:1), was epoxidized using hydrogen peroxide as oxygen donor and stearic acid as active oxygen carrier in the presence of immobilized Candida antarctica lipase B. The effect of the amount of stearic acid on the enzymatic epoxidation was investigated. Response surface methodology (RSM) was used to study and optimize the effects of variables (reaction temperature, enzyme load, mole ratio of H2O2/CC-bonds, and reaction time) on the epoxy oxygen group content (EOC) of epoxidized SMSO. Results showed that stearic acid as active oxygen carrier could enhance the enzymatic epoxidation of SMSO. The variables of reaction temperature and enzyme load were the most significant in the process. A two second-order model was satisfactorily fitted the data (R2 = 0.9723) with non-significant lack of fit. The optimum EOC of epoxidized SMSO was 4.6 ± 0.3% under the conditions of 50.0 °C, 7.0 h, 2.00% (relative to the weight of SMSO) enzyme load, and 4:1 mole ratio of H2O2/CC-bonds.  相似文献   

13.
In Argentina, delayed sowing causes a decrease in seed yield and in radiation use efficiency (RUE) of peanut crops (Arachis hypogaea L.), but it is not known if RUE reduction is mainly due to reduced temperature during late reproductive stages or to a sink limitation promoted by decreased seed number in these conditions. We analyzed seed yield determination and RUE dynamics of two cultivars (Florman and ASEM) in four irrigated field experiments (Expn) grown at three sites and five contrasting sowing dates (between 17 October and 21 December) in three growing seasons. An additional field experiment was performed with widely spaced plants (i.e. with no interference among them) to evaluate the effect of peg removal on RUE and leaf carbon exchange rate (CER). Seasonal dynamics of mean air temperature and irradiance, biomass production (total and pods), and intercepted photosynthetically active radiation (IPAR) were followed. Seed yield and seed yield components (pod number, seeds per pod, seed number and seed weight) were determined at final harvest. Crop growth rate (CGR) and pod growth rate (PGR) were computed for growth phases of interest. RUE values for crops sown until 14 November were 1.89–1.98 g MJ−1 IPAR, within the usual range. RUE decreased significantly for cv. Florman in the late sowing of Exp1 (29 November) and for both cultivars in Exp3 (21 December sowing). Across experiments, seed yield (4.5-fold variation relative to minimum) was strongly associated (r2 = 0.87, P < 0.0001) with variations in seed number (3.5-fold variation relative to minimum), and to a lesser extent (r2 ≤ 0.54, P ≤ 0.001) to variations in seed weight (1.9-fold variation relative to minimum). Seed number was positively related (P < 0.01) to CGR (r2 = 0.66) and to PGR (r2 = 0.72) during the R3–R6.5 phase (seed number determination window), while crop growth during the grain-filling phase (i.e. between R6.5 and final harvest) was positively associated with grain number (r2 = 0.80, P < 0.001). No association was found between RUE and mean air temperature, neither for the whole cycle nor for the phase between R6.5 and final harvest, which showed the largest temperature variation (16.4–22.4 °C) across experiments. Use of mean minimum temperature records (range between 13.8 and 18.5 °C) did no improve the relationship. However, grain-filling phase RUE showed a positive (r2 = 0.69, P = 0.003) linear response to seed number across experiments. This apparent sink limitation of source activity was consistent with the reduced RUE (from 2.73 to 1.42 g MJ−1 IPAR) and reduced leaf CER at high irradiance (from ca. 30 to 15 μmol m−2 s−1) for plants subjected to 75% peg removal.  相似文献   

14.
Livestock producers are interested in growing forage soybean [Glycine max (L.) Merr.] in summer and ensiling alone or in mixtures with corn or sorghum. Four row spacings (20, 40, 60, and 80 cm), four seeding rates (50, 100, 150, and 200 kg seeds per hectare) and four harvesting stages for forage production (V5, R2, R4, and R6) were evaluated under irrigated conditions in a randomized split–split plot design with three replications in three different locations in Turkey with Mediterranean-type climate in 2004 and 2005. Dry matter (DM) yield was significantly reduced with increased row spacings in all locations. There was no significant difference between 20, 40, or 60 cm row spacings while 80 cm provided the lowest yield. Increased seeding rates (50, 100, 150, and 200 kg seeds per hectare) generally increased DM yield, although the most suitable row spacing varied by location. DM yield was significantly affected by harvest maturity increasing with advancing maturity in all locations. DM constituent plant components were generally unaffected by row spacing and seeding rate but harvest maturity did significantly affect DM partitioning. As expected, leaf blade fractions decreased continually as plant maturity increased, while stem and flower plus pod fraction increased from V5 to R6. In general, row spacing and seeding rate did not significantly affect crude protein, degradable protein, and in vitro dry matter digestibility of soybean forage, but all decreased significantly with advancing maturity. These studies demonstrated soybeans managed for forage in a Mediterranean-type environment can average of 9.3 and 11.3 t ha−1 dry matter yield at R4 and R6 stages, respectively, while averaging 13.3% crude protein, 8.2% degradable protein, and 60.6% in vitro dry matter digestibility.  相似文献   

15.
Grain yield of crops can be expressed as a function of the intercepted radiation, the radiation use efficiency and the partitioning of above-ground biomass to grain yield (harvest index). When a wheat crop is grown under P deficiency the grain yield is reduced but it is not clear how these three components are affected. Our aim was (i) to identify which of these components were affected in spring bread wheat under P deficiency at field conditions and (ii) to relate the grain yield responses to processes of grain yield formation during the spike growth period. Three field experiments were conducted in the potentially high wheat yielding environment of southern Chile. All experiments had two levels of P availability: with (155 kg P ha−1) or without P fertilization (average soil P-Olsen concentration of 10 ppm, a medium level of P availability). High wheat grain yields were obtained varying between 815 and 1222 g m−2 with P applications. Experiments showed a grain yield reduction caused by P deficiencies of 35, 16 and 18% in experiments 1, 2 and 3, respectively. This was related (R2 = 0.99, P < 0.01) to a reduction in the total above-ground biomass at harvest and not to the harvest index. Reductions in above-ground biomass were due to a reduction in radiation intercepted under P deficiency without effecting radiation use efficiency. Grain number per square meter was the main yield component (R2 = 0.99, P < 0.01) that explained the grain yield reduction caused by the P deficiency which was due to low spike biomass at anthesis (R2 = 0.96, P < 0.05). The reduction in spike biomass at anthesis was related (R2 = 0.86, P < 0.01) to reductions in crop growth rate during the spike growth period as a consequence of a lower radiation intercepted during this period. This study showed that under high wheat yield conditions the main effect of a P deficiency on grain yield reduction was a negative impact on the total above-ground biomass due to the negative impact on intercepted radiation, particularly during the spike growth period, affecting negatively spike biomass at anthesis and consequently grain number and yield.  相似文献   

16.
Heterogeneous crop stands require locally adapted nitrogen fertilizer application based on rapid and precise measurements of the local crop nitrogen status. In the present study, we validated a promising technique for the latter, namely a tractor-mounted field spectrometer with an oblique quadrilateral-view measuring optic, measuring solar radiation and canopy reflectance in four directions simultaneously. Dry matter yield (kg ha−1), total N content (g N g−1 dry matter) and total aerial N (aboveground N-uptake) (kg N ha−1) in maize were determined in 10 m2 calibration areas in 60 plots differing in their N treatment and seeding density three times in each of three years under field conditions. Results show that the sensor used can reliably determine total aerial N ranging from as little as 5 kg N to 150 kg N ha−1 with R2-values ≥0.81 in 2002 and 2004, and with R2-values ranging from ≥0.57 to 0.84 in 2003. Dry matter yields from as low as 0.3–4.2 t ha−1 could be determined with R2-values ranging from 0.67 to 0.91 in 2002 to 2004. The capacity to ascertain DM yield spectrally was drastically reduced in the higher yield range (>6 t ha−1) probably due to decreased sensitivity of the spectral signal. N-contents were generally not well determined. Taken together there is a good potential to determine reliably differences in total aerial N or DM yield from the five leaf stages unfolded to the five node stage where typically nitrogen applications are carried out.  相似文献   

17.
Cellulase production is one of the most critical steps in the economics of second generation ethanol. Although solid-state fermentation (SSF) is an attractive process for the production of enzymes, SSF is highly limited by the difficulty in controlling the operating variables which affect microbial growth and metabolites production. In this context, this work evaluates the effects of operational conditions on endoglucanase production by a selected strain of Aspergillus niger cultivated under SSF using an instrumented lab-scale bioreactor equipped with an on-line automated monitoring and control system. The effects of air flow rate, inlet air relative humidity and substrate initial moisture on endoglucanase production were evaluated using a statistical design methodology. A correlation coefficient of 0.9106 and a calculated value of F, 5.46 folds higher than the listed value (P-value < 0.05) allowed the modeling of endoglucanase production under different process conditions. Higher endoglucanase production (56.1 U/g) was achieved for a selected condition of substrate initial moisture of 72%, air inlet humidity of 70%, and flow rate of 20 mL/min. A significant increase in endoglucanase production was also found to be achieved under forced aeration conditions (50.2 IU/g) compared to static conditions (29.8 IU/g) after 72 h of cultivation. Besides, respirometric analysis revealed that the total amount of CO2 produced was linearly correlated with enzyme production (R2 of 0.988). The bioreactor system used, as well as the methodology employed herein, was very effective in evaluating the influence of operational variables on enzymes production under SSF.  相似文献   

18.
Vernalization requirement, photoperiod response and earliness per se (EPS) of bread wheat cultivars are often determined using controlled environments. However, use of non-field conditions may reduce the applicability of results for predicting field performance as well as increase the cost of evaluations. This research was undertaken, therefore, to determine whether field experiments could replace controlled environment studies and provide accurate characterization of these three traits among winter wheat cultivars. Twenty-six cultivars were evaluated under field conditions using two natural photoperiod regimes (from different transplanting dates) and vernalization pre-treatments. Relative responses to vernalization (RRVGDD) and photoperiod (RRPGDD) were quantified using the reciprocal of thermal time to end of ear emergence, whereas earliness per se was estimated by calculating thermal time from seedling emergence until end of ear emergence for fully vernalized and lately planted material. An additional index based on final leaf numbers was also calculated to characterize response to vernalization (RRVFLN). To test whether the obtained indices have predictive power, results were compared with cultivar parameters estimated for the CSM-Cropsim-CERES-Wheat model Version 4.0.2.0. For vernalization requirement, RRVGDD was compared with the vernalization parameter P1V, for photoperiod (RRPGDD), with P1D, and for earliness per se, EPS was compared with the sum of the component phase durations. Allowing for variation in EPS in the calibration improved the relation between observed versus simulated data substantially: correlations of RRPGDD with P1D increased from r2 = .34 (p < .01), to .82 (p < .001), and of RRVGDD with P1V, from r2 = .88 (p < .001), to .94 (p < .001). In comparisons of observed versus simulated anthesis dates for independent field experiments, the estimated model coefficients resulted in an r2 of .98 (p < .001) and root mean square error of 1d. Overall, the results indicated that combining planting dates with vernalization pre-treatments can permit reliable, quantitative characterization of vernalization requirement, photoperiod response and EPS of wheat cultivars. Furthermore, emphasize the need for further study to clarify aspects that determine EPS, including whether measured EPS varies with temperature or other factors.  相似文献   

19.
Polyol production from chemical modification of date seeds has been investigated through oxypropylation and liquefaction techniques (using organic solvents in the presence of a catalyst). The obtained products were characterized using infrared spectroscopy analysis, 1H NMR, thermogravimetric analysis and other parameters such as hydroxyl number (IOH) and viscosity. Results showed that 93% of the solid substance was converted into polyol in the oxypropylation reaction at the date seeds/propylene oxide ratio of 0.25 and 10% potassium hydroxide at 160 °C. The oxypropylated product has IOH of 779 mg KOH/g and viscosity of 6.9 Pa s. Regarding the liquefaction technique, results show that a yield of 95% was obtained at the date seeds/liquefying solvent ratio of 0.25 in 60 min of reaction at 160 °C. The liquefied product shows IOH of 336 mg KOH/g and viscosity of 0.9 Pa s.  相似文献   

20.
A novel idea of utilizing a digital torque wrench (DTW) assembled with a common bypass lopper to determine the cutting energy of corn stalks in combination with a modified Warner-Bratzler device attachment on a standard universal testing machine (UTM) was developed. Peak torque, torque per unit area, peak stress, and net and specific cutting energy were determined. The DTW peak torque and UTM standard net cutting energy, and the DTW torque per unit area and UTM specific energy were strongly correlated (r ≥ 0.95; P < 0.0001). Simple linear models (R2 ≥ 0.91; P < 0.0001) of net and specific cutting energy from the DTW readings were developed. The DTW cutting energy measurement method is fast, simple, less expensive, portable, and suitable for on-site measurements.  相似文献   

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