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1.
Controlled laboratory and field experiments were performed to determine the developmental response to temperature and moisture of Arundo donax, a riparian invasive grass and potential bioenergy crop. A logistic function was parameterized and used to predict thermal times to sprouting and the nine-leaf stage. Consistent estimates of the base temperature (Tb) and base water potential (ψb) below which development ceases were obtained from various statistical and mathematical analyses. Estimates of Tb and ψb were 12.7 ± 1.7 °C and −1.56 ± 0.43 MPa, respectively, for the median fraction of sprouting rhizomes. Median hydrothermal time to sprouting was 124.1 MPa °Cd under laboratory conditions and median thermal times, or degree-day (°Cd), to sprouting and nine-leaf stage was estimated to be 94 and 129 °Cd under field conditions, respectively. A degree-day is defined as one day (24 h) spent one degree above Tb. Results demonstrated that thermal time alone is sufficient to accurately predict time to sprouting under field conditions. Further, there may be a fixed moisture threshold of about 6% volumetric water content above which sprouting rate was constant. This threshold corresponded very closely to the −1.5 MPa for ψb that was estimated under laboratory conditions for the soil typically infested by A. donax. This information is crucial for assessing risk of invasive spread for A. donax.  相似文献   

2.
In this study, pyrolysis of grape bagasse was investigated with the aim to study the product distribution and their chemical compositions and to identify optimum process conditions for maximizing the bio-oil yield. Particular investigated process variables were temperature (350-600 °C), heating rate (10-50 °C/min) and nitrogen gas flow rate (50-200 cm3/min). The maximum oil yield of 27.60% was obtained at the final pyrolysis temperature of 550 °C, sweeping gas flow rate of 100 cm3/min and heating rate of 50 °C/min in a fixed-bed reactor. The elemental analysis and heating value of the bio-oils were determined, and then the chemical composition of the bio-oil was investigated using chromatographic and spectroscopic techniques such as column chromatography, 1H NMR and FTIR. The fuel properties of the bio-oil such as flash point, viscosity and density were also determined. The bio-oils obtained from grape bagasse were presented as an environmentally friendly feedstock candidate for bio-fuels.  相似文献   

3.
Cellulosic plant and waste materials are potential resources for fermentative hydrogen production. In this study, hydrogen producing, cellulolytic cultures were enriched from compost material at 52, 60 and 70 °C. Highest cellulose degradation and highest H2 yield were 57% and 1.4 mol-H2 mol-hexose−1 (2.4 mol-H2 mol-hexose-degraded−1), respectively, obtained at 52 °C with the heat-treated (80 °C for 20 min) enrichment culture. Heat-treatments as well as the sequential enrichments decreased the diversity of microbial communities. The enrichments contained mainly bacteria from families Thermoanaerobacteriaceae and Clostridiaceae, from which a bacterium closely related to Thermoanaerobium thermosaccharolyticum was mainly responsible for hydrogen production and bacteria closely related to Clostridium cellulosi and Clostridium stercorarium were responsible for cellulose degradation.  相似文献   

4.
Wood from the leguminous tree, Leucaena diversifolia, was subjected to hydrothermal treatment (autohydrolysis) at 160-180 °C for 0-30 min followed by ethanol-soda-anthraquinone delignification. The liquid phase contained 18.65 g of sugars per liter, and the solid phase had a gross heating value of 19.083 MJ/kg, but could also be used as a source of cellulose pulp for the production of paper with tear, burst, and tensile indexes of 2.4 N m2/kg, 2.6 MPa m2/kg and 40.7 kN m/kg, respectively. L. diversifolia lends itself readily to valorization for energy production, and also to integral, fractional exploitation by autohydrolysis and ethanol-soda-anthraquinone delignification, which can additionally bring environmental benefits to cropping zones.  相似文献   

5.
The resting metabolic rate (RMR) of seasonally-acclimated Mabuya brevicollis of various body masses was determined at 20, 25, 30, 35 and 40 °C, using open-flow respirometry. RMR (ml g−1 h−1) decreased with increasing mass at each temperature. RMRs increaProd. Type: FTPsed as temperature increased. The highest and lowest Q10 values were obtained for the temperature ranges 20–25 °C and 30–35 °C for the summer-acclimated lizards. The exponent of mass “b” in the metabolism-body mass relation ranged from 0.41 to 0.61. b values were lower in the autumn and winter-acclimated lizards than in spring and summer-acclimated lizards. Seasonal acclimation effects were evident at all temperatures (20–40 °C) for M. brevicollis. Winter-acclimated skinks had the lowest metabolic rates at different temperatures. The pattern of acclimation exhibited by M. brevicollis may represent a useful adaptation for lizards inhabiting subtropical deserts to promote activity during their active seasons.  相似文献   

6.
The poor and inconsistent physicochemical properties of bio-oil are inhibiting its industrialized production. We investigated the variability in properties of switchgrass bio-oil produced at three pyrolysis temperatures (T = 450, 500, and 550 °C) and three feedstock moisture contents (MC = 5%, 10%, and 15%) in a 3 × 3 factorial experiment in order to exploit opportunities to improve bio-oil properties through optimization of pyrolysis parameters. Results showed that even with the single type of feedstock and pyrolysis system, the two main factors and their interaction caused large variations in bio-oil yield and most of the measured physicochemical properties. Following improvements of bio-oil properties could be individually achieved by selecting an optimal pyrolysis condition (shown in parenthesis) comparing with the worst case: increase of bio-oil yield by more than twofold (MC = 10%, T = 450 °C), increase of pH by 20.4% from 2.74 to 3.3 (MC = 10%, T = 550 °C), increase of higher heating value by 18.1% from 16.6 to 19.6 MJ/kg (MC = 10%, T = 450 °C), decrease of density by 5.9% from 1.18 to 1.11 g/cm3 (MC = 5%, T = 550 °C), decrease of water content by 36% from 31.4 to 20.1 wt.% (MC = 5%, T = 450 °C), decrease of viscosity by 40% from 28.2 to 17 centistokes (MC = 5%, T = 550 °C), decrease of solid content by 57% from 2.86 to 1.23 wt.% (MC = 15%, T = 550 °C), and decrease of ash content by 41.9% from 0.62 to 0.36 wt.% (MC = 15%, T = 550 °C). There is no single, clear-cut optimal condition that can satisfy the criteria for a bio-oil product with all the desired properties. Trade-offs should be balanced according to the usage of the end-products.  相似文献   

7.
Water hyacinth was pretreated, under variable conditions, with NaOH, alkaline H2O2, peracetic acid and sodium chlorite. Combined pretreatments included sodium chlorite with each of NaOH, alkaline H2O2 and peracetic acid. Combined pretreatment with 0.1% NaClO2 for 1 h at 100 °C and peracetic acid at 100 °C for 15 min afforded the most promising sample. The recovered lignin, cellulose and hemicellulose of this sample was 2.56%, 96.69%, and 81.38%, respectively. The same sample, by cellulase hydrolysis showed the highest cellulose conversion (80.8%) and 90% saccharification using 200 FPU/g substrate. Some ambient factors affecting saccharification of pretreated water hyacinth were investigated. Enzymic saccharification after 6 h was about 50% of that at 48 h, indicating a slow hydrolysis rate by time. Addition of 8% glucose at the beginning of the enzymic hydrolysis decreased the saccharification to about its half while addition of 8% ethanol brought about complete inhibition of the enzyme. Addition of cellobiase to the reaction mixture increased cellulose conversion and saccharification by 10%.  相似文献   

8.
The synergistic effect of steam explosion pretreatment and sodium hydroxide post-treatment of Lespedeza stalks (Lespedeza crytobotrya) has been investigated in this study. In this case, Lespedeza stalks were firstly exploded at a fixed steam pressure (22.5 kg/m2) for 2–10 min. Then the steam-exploded Lespedeza stalks was extracted with 1 M NaOH at 50 °C for 3 h with a shrub to water ratio of 1:20 (g/ml), which yielded 57.3%, 53.1%, 55.4%, 52.8%, 53.2%, and 56.4% (% dry weight) cellulose rich fractions, comparing to 68.0% from non-steam-exploded material. The content of glucose in cellulose rich residues increased with increment of the steaming time and reached to 94.10% at the most severity. The similar increasing trend occurred during the dissolution of hemicelluloses. It is evident that at shorter steam explosion time, autohydrolysis mainly occurred on the hemicelluloses and the amorphous area of cellulose. The crystalline region of cellulose was depolymerized under a prolonged incubation time. The characteristics of the cellulose rich fractions in terms of FT-IR and CP/MAS 13C NMR spectroscopy and thermal analysis were discussed, and the surface structure was also investigated by SEM.  相似文献   

9.
This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h−1) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CTmax) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae−1 h−1 in one-day old larvae to 40.1-99.4 nmol h−1 at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q10) on 5 days old larvae (Q10=1.35) was lower when compared with the 1 day old larvae (Q10=1.68). The lower Q10 in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.  相似文献   

10.
The celB gene of Caldicellulosiruptor saccharolyticus was cloned and expressed in Escherichia coli to create a recombinant biocatalyst for hydrolyzing lignocellulosic biomass at high temperature. The GH5 domain of CelB hydrolyzed 4-nitrophenyl-β-d-cellobioside and carboxymethyl cellulose with optimum activity at pH 4.7-5.5 and 80 °C. The recombinant GH5 and CBM3-GH5 constructs were both stable at 80 °C with half-lives of 23 h and 39 h, respectively, and retained >94% activity after 48 h at 70 °C. Enzymatic hydrolysis of corn stover and cellulose pretreated with the ionic liquid 1-ethyl-3-methylimidazolium acetate showed that GH5 and CBM3-GH5 primarily produce cellobiose, with product yields for CBM3-GH5 being 1.2- to 2-fold higher than those for GH5. Confocal microscopy of bound protein on cellulose confirmed tighter binding of CBM3-GH5 to cellulose than GH5, indicating that the enhancement of enzymatic activity on solid substrates may be due to the substrate binding activity of CBM3 domain.  相似文献   

11.
The brackish water copepod Eurytemora affinis is the most abundant copepod species in the low salinity zone (2-15) of the Seine estuary. Despite its ecological importance, little is known about its population dynamics in the Seine. We studied the effects of temperature (10 °C and 15 °C) and salinity (5, 15 and 25) on reproduction under non-limiting food conditions. We used experiments to determine multiple reproductive parameters for E. affinis. In all experiments, we fed E. affinis a mixture of Rhodomonas marina and Isochrysis galbana. Couples of pre-adult females (C5) and adult males were mated until the female extruded a clutch of eggs and then individual females were observed every 6-12 hours until death to determine (a) embryonic development time, (b) inter clutch time and (c) clutch size throughout their adult lifespan. All reproductive parameters were negatively affected by low temperature (10 °C) and by high salinity (25). At 10 °C and a salinity of 25, mortality during the post-embryonic period was extremely high (85%). Differences in all reproductive parameters between salinities 5 and 15 were minimal. From 15 °C to 10 °C mean latency time (time between hatching of eggs and extrusion of new ones) increased from 0.8 to 2.25 days, the mean embryonic development time from 2.2 to 3.2 days and the mean clutch size decreased from 38 to 22 eggs female- 1. The mean clutch size decreased when females reached a critical age. The hatching success was high (near 95%) under all conditions except at high salinity. Egg production rates showed no significant differences between salinities 5 and 15 and were significantly higher at 15 °C (13 eggs female- 1 day- 1 at salinity 5 and 15) than at 10 °C (4 eggs female- 1 day- 1). These values at 15 °C were higher compared to those from other populations of E. affinis in estuaries or lakes. The high reproductive potential of E. affinis from the Seine estuary at 15 °C and low salinities explain its high densities in the low salinity zone during spring and early summer.  相似文献   

12.
Marine brachyuran and anomuran crustaceans are completely absent from the extremely cold (− 1.8 °C) Antarctic continental shelf, but caridean shrimps are abundant. This has at least partly been attributed to low capacities for magnesium excretion in brachyuran and anomuran lithodid crabs ([Mg2+]HL = 20-50 mmol L− 1) compared to caridean shrimp species ([Mg2+]HL = 5-12 mmol L− 1). Magnesium has an anaesthetizing effect and reduces cold tolerance and activity of adult brachyuran crabs. We investigated whether the capacity for magnesium regulation is a factor that influences temperature-dependent activity of early ontogenetic stages of the Sub-Antarctic lithodid crab Paralomis granulosa. Ion composition (Na+, Mg2+, Ca2+, Cl, SO42−) was measured in haemolymph withdrawn from larval stages, the first and second juvenile instars (crabs I and II) and adult males and females. Magnesium excretion improved during ontogeny, but haemolymph sulphate concentration was lowest in the zoeal stages. Neither haemolymph magnesium concentrations nor Ca2+:Mg2+ ratios paralleled activity levels of the life stages. Long-term (3 week) cold exposure of crab I to 1 °C caused a significant rise of haemolymph sulphate concentration and a decrease in magnesium and calcium concentrations compared to control temperature (9 °C). Spontaneous swimming activity of the zoeal stages was determined at 1, 4 and 9 °C in natural sea water (NSW, [Mg2+] = 51 mmol L− 1) and in sea water enriched with magnesium (NSW + Mg2+, [Mg2+] = 97 mmol L− 1). It declined significantly with temperature but only insignificantly with increased magnesium concentration. Spontaneous velocities were low, reflecting the demersal life style of the zoeae. Heart rate, scaphognathite beat rate and forced swimming activity (maxilliped beat rate, zoea I) or antennule beat rate (crab I) were investigated in response to acute temperature change (9, 6, 3, 1, − 1 °C) in NSW or NSW + Mg2+. High magnesium concentration reduced heart rates in both stages. The temperature-frequency curve of the maxilliped beat (maximum: 9.6 beats s− 1 at 6.6 °C in NSW) of zoea I was depressed and shifted towards warmer temperatures by 2 °C in NSW + Mg2+, but antennule beat rate of crab I was not affected. Magnesium may therefore influence cold tolerance of highly active larvae, but it remains questionable whether the slow-moving lithodid crabs with demersal larvae would benefit from an enhanced magnesium excretion in nature.  相似文献   

13.
Regenerated films were successfully prepared from cellulose/NaOH/urea solution by coagulating with water at temperature from 25 to 45 °C. The results of solid 13C NMR, wide angle X-ray diffraction, scanning electron microscopy (SEM) and tensile testing revealed that the cellulose films possessed homogeneous structure and cellulose II crystalline, similar to that prepared previously by coagulating with 5 wt% H2SO4. By changing the coagulation temperature from 25 to 45 °C, tensile strength of the films was in the range of 85-139 MPa. Interestingly, the RC35 film coagulated at 35 °C exhibited the highest tensile strength (σb = 139 MPa). The inclusion complex associated with cellulose, NaOH and urea hydrates in the cellulose solution were broken by adding water (non-solvent), leading to the self-association of cellulose to regenerate through rearrangement of the hydrogen bonds. This work provided low-cost and “green” pathway to prepare cellulose films, which is important in industry.  相似文献   

14.
Germanium tetra(tertiary butoxide), [Ge(OtBu)4], has been prepared by the reaction of GeCl4 with KOBut in benzene. It is a monomeric crystalline solid having a distorted tetrahedral configuration, defined by the coordination of four OBut groups around germanium atom. The TG analysis showed that the compound is thermally stable and volatilizes at around 130 °C. Europium doped and un-doped germanium oxide nanoparticles were prepared based on the urea hydrolysis of Ge(OtBu)4/Eu(OOCCH3)3 in ethylene glycol medium at 150 °C followed by heating the resulting product at 750 °C. The nanoparticles were characterized by XRD, TEM and PL measurements. The europium doped nanoparticles, which were nearly monodispersed (∼30 nm), showed luminescence and the Eu3+ ions were occupying the surface of the GeO2 nanoparticles.  相似文献   

15.
Thermogenic characteristics and evaporative water loss were measured at different temperatures in Tupaia belangeri. The thermal neutral zone (TNZ) of T. belangeri was 30–35 °C. Mean body temperature was 39.76±0.27 °C and mean body mass was 100.86±9.09 g. Basal metabolic rate (BMR) was 1.38±0.03 ml O2/g h. Average minimum thermal conductance (Cm) was 0.13±0.01 ml O2/g h °C. Evaporative water loss in T. belangeri increased when the temperature rose; the maximal evaporative water loss was 3.88±0.41 mg H2O/g h at 37.5 °C. The results may reflect features of small mammals in the sub-tropical plateau region: T. belangeri had high basal metabolic rate and high total thermal conductance, compared with the predicted values based on their body mass whilst their body temperatures are relatively high; T. belangeri has high levels of evaporative water loss and poor water-retention capacity. Evaporative water loss plays an important role in temperature regulation.  相似文献   

16.
To examine the synergism of high temperature and sulfide on two dominant tropical seagrass species, a large-scale mesocosm experiment was conducted in which sulfide accumulation rates (SAR) were increased by adding labile carbon (glucose) to intact seagrass sediment cores across a range of temperatures. During the initial 10 d of the 38 d experiment, porewater SAR in cores increased 2- to 3-fold from 44 and 136 μmol L− 1 d− 1 at 28-29 °C to 80 and 308 μmol L− 1 d− 1 at 34-35 °C in Halodule wrightii and Thalassia testudinum cores, respectively. Labile C additions to the sediment resulted in SAR of 443 and 601 μmol L− 1 d− 1 at 28-29 °C and 758 to 1,557 μmol L− 1 d− 1 at 34-35 °C in H. wrightii and T. testudinum cores, respectively. Both T. testudinum and H. wrightii were highly thermal tolerant, demonstrating their tropical affinities and potential to adapt to high temperatures. While plants survived the 38 d temperature treatments, there was a clear thermal threshold above 33 °C where T. testudinum growth declined and leaf quantum efficiencies (Fv/Fm) fell below 0.7. At this threshold temperature, H. wrightii maintained shoot densities and leaf quantum efficiencies. Although H. wrightii showed a greater tolerance to high temperature, T. testudinum had a greater capacity to sustain biomass and short shoots under thermal stress with labile C enrichment, regardless of the fact that sulfide levels in the T. testudinum cores were 2 times higher than in the H. wrightii cores. Tropical seagrass tolerance to elevated temperatures, predicted in the future with global warming, should be considered in the context of the sediment-plant complex which incorporates the synergism of plant physiological responses and shifts in sulfur biogeochemistry leading to increased plant exposure to sulfides, a known toxin.  相似文献   

17.
Basal metabolic rate (BMR) is thought to be a major hub in the network of physiological mechanisms connecting life history traits. Evaporative water loss (EWL) is a physiological indicator that is widely used to measure water relations in inter- or intraspecific studies of birds in different environments. In this study, we examined the physiological responses of summer-acclimatized Hwamei Garrulax canorus to temperature by measuring their body temperature (Tb), metabolic rate (MR) and EWL at ambient temperatures (Ta) between 5 and 40 °C. Overall, we found that mean body temperature was 42.4 °C and average minimum thermal conductance (C) was 0.15 ml O2 g−1 h−1 °C−1 measured between 5 and 20 °C. The thermal neutral zone (TNZ) was 31.8–35.3 °C and BMR was 181.83 ml O2 h−1. Below the lower critical temperature, MR increased linearly with decreasing Ta according to the relationship: MR (ml O2 h−1)=266.59–2.66 Ta. At Tas above the upper critical temperature, MR increased with Ta according to the relationship: MR (ml O2 h−1)=−271.26+12.85 Ta. EWL increased with Ta according to the relationship: EWL (mg H2O h−1)=−19.16+12.64 Ta and exceeded metabolic water production at Ta>14.0 °C. The high Tb and thermal conductance, low BMR, narrow TNZ, and high evaporative water production/metabolic water production (EWP/MWP) ratio in the Hwamei are consistent with the idea that this species is adapted to warm, mesic climates, where metabolic thermogenesis and water conservation are not strong selective pressures.  相似文献   

18.
Anyphaena accentuata and Philodromus spp. are cold adapted and winter-active spider species. Their predation activity was investigated at constant temperatures between –4 and 30 °C. The lower temperature threshold for Anyphaena was –3.7 °C, while that of Philodromus was –1.2 °C. At 1 °C the latency to capture and prey consumption was significantly shorter in Anyphaena than in Philodromus. The capture rate increased with temperature and was maximal at 15 °C in Anyphaena and at 30 °C in Philodromus. At 30 °C, the latency to the capture was significantly shorter in Philodromus than in Anyphaena whose mortality significantly increased.  相似文献   

19.
Lasia spinosa seeds were not dormant at maturity in early spring. The most favorable temperatures for germination were between 25 and 30 °C, and final percentage and rate of germination decreased with an increase or decrease in temperature. When L. spinosa seeds were transferred to 25 °C, after 60 days at 10 °C (where none of the seeds germinated), final germination increased from 0% to 78%. Seeds germinated to high percentage both in light and in dark, although dark germination took more than twice as long as in the light. During desiccation of seeds at 15 °C and 45% relatively humidity, moisture loss decreased exponentially from 2.02 to 0.13 g H2O g−1 dry wt within 16 days, and only a few seeds (12%) survived 0.13 g H2O g−1 dry wt moisture content. Seeds stored at 0.58 g H2O g−1 dry wt moisture content at four constant temperatures (4, 10, 15, and −18 °C) for up to 6 months exhibited a well-defined trend of decreasing viability with decreasing temperature. Thus, we concluded that freshly harvested L. spinosa seeds are non-dormant and recalcitrant. Also, the seeds with 0.58 g H2O g−1 dry wt moisture content could be effectively stored for a few months between 10 and 15 °C although the most appropriate temperature for wet storage appears to be 10 °C, as it is close to the minimum temperature for germination and so there will be less pre-sprouting compared to 15 °C.  相似文献   

20.
Proper adjustment of thermoregulatory mechanisms ensures the survival of mammals when they are subjected to seasonal changes in their natural environment. To understand the physiological and ecological adaptations of Eothenomys olitor, we measured their metabolic rate, thermal conductance, body temperature (Tb) and evaporative water loss at a temperature range of 5–30 °C in summer. The thermal neutral zone (TNZ) of E. olitor was 20–27.5 °C, and the mean body temperature was 35.81±0.15 °C. Basal metabolic rate (BMR) was 2.81±0.11 ml O2/g h and mean minimum thermal conductance (Cm) was 0.18±0.01 ml O2/g h °C. Evaporative water loss (EWL) in E. olitor increased when the ambient temperature increased. The maximal evaporative water loss was 6.74±0.19 mg H2O/g h at 30 °C. These results indicated that E. olitor have relatively high BMR, low body temperature, low lower critical temperature, and normal thermal conductance. EWL plays an inportant role in temperature regulation. These characteristics are closely related to the living habitat of the species, and represent its adaptive strategy to the climate of the Yunnan-Kweichow Plateau, a low-latitude, high-altitude region where annual temperature fluctuations are small, but daily temperature fluctuations are greater.  相似文献   

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