Sufficient Water Content Research Articles

Thermal Conductivity Prediction of Soil in Complex Plant Soil System using Artificial Neural Networks

Thermal conductivity is one of thermal properties of soil in seed germination and plants growth. Different soil types have different thermal conductivity. One of soft-computing promising method to predict thermal conductivity of soil types is Artificial Neural Network (ANN). In this study, we estimate the thermal conductivity of soil prediction in a soil-plant complex systems using ANN. With a feed-forward multilayer trained with back-propagation with 4, 10 and 1 on the input, hidden and output layers respectively. Our input are heating time, temperature and thermal resistance with thermal conductivity of soil as a target. ANN prediction demonstrates a good agreement with Mean Squared Error-testing (MSEte) of 9.56 x 10-7 for soils with green beans and those of bare soils is 7.00 × 10-7 respectively Green beans grow only on black-clay soil with a thermal conductivity of 0.7 W/m K with a sufficient water content. Our results demonstrate that temperature, moisture content, colour, texture and structure of soil are greatly affect to the thermal conductivity of soil in seed germination and plant growth. In future, it is potentially applied to estimate more complex compositions of plant-soil systems.

PEG-penetrated chitosan-alginate co-polysaccharide-based partially and fully cross-linked hydrogels as ECM mimic for tissue engineering applications.

The emerging strategy of tissue engineering for the management of end-stage organ failure and associated complications mainly relies on ECM mimicking scaffolds for neo-tissue genesis. In the current study, novel polyethylene glycol interpenetrated cross-linked hydrogel scaffold based on a co-polysaccharide (PIAC) synthesized from two marine heteropolysaccharides, alginate and chitosan, was designed. Partially cross-linked (PIAC-P) and fully cross-linked hydrogels (PIAC-F) were prepared. The physiochemical evaluations of both the hydrogels revealed the presence of alginate fraction and extensive –OH groups on the surface, sufficient water content and water holding capacity. The porosity and bulk density were also appreciable. The scaffolds were hemocompatible and were able to adsorb appreciable plasma proteins on to the surface. MTT assay on hydrogel extracts and direct contact assay showed the nontoxic effects of fibroblast cells upon contact with the hydrogel. Live/dead assay using ethidium bromide/acridine orange cocktail on fibroblast cells grown on the hydrogels after 5 days of initial seeding displayed green nucleus revealing the non-apoptotic cells. PIAC-P hydrogels were superior to certain aspects due to the availability of free functional groups than PIAC-F where most of these groups were utilized for cross-linking. The biological evaluations confirmed the healthy being and 3D growth of fibroblasts on the porous networks of both the hydrogels. The present hydrogel can form an ECM mimic and can form a potent candidate for various tissue engineering applications.

Analysis of icicle growth process of composite insulator under energized condition and its impact factors

Composite insulators are more vulnerable to ice flashover because of the short spacing. This paper was concerned with icicle growth under energized condition. Firstly, icing experiments were carried out to record the icicle length which was classified into three different stages, and show the effect of environmental parameters. Afterward, three characteristic quantities were proposed to reflect the performance of icicle growth, including natural icicle growth rate vNE, dripping frequency f, and critical discharge position function ϕ(L), where vNE determined the steady icing time, f and ϕ(L) determined the steady icicle length. Finally, according to the experimental and theoretical analysis, the relationship between environmental parameters and characteristic quantities were built to illustrate the mechanism of icicle growth. It was found that the applied voltage increase induced the partial discharges ahead of time to change discharge position function ϕ(L). Temperature was in proportion to natural icicle growth rate vNE. Higher rainfall intensity provided sufficient liquid water content to improve dripping frequency f. Applied water conductivity only affected the icing morphology and was irrelevant with the steady icicle length. Pollution improved the electrical thermal effect and suppressed natural icicle growth rate vNE.

施氮对空心莲子草（Alternanthera philoxeroides）和莲子草（Alternanthera sessilis）种间关系的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 施氮对空心莲子草(Alternanthera philoxeroides)和莲子草(Alternanthera sessilis)种间关系的影响 DOI: 10.5846/stxb201405281098 作者: 作者单位: 北京林业大学自然保护区学院,北京林业大学自然保护区学院,北京林业大学自然保护区学院,北京林业大学自然保护区学院,北京林业大学自然保护区学院 作者简介: 通讯作者: 中图分类号: 基金项目: 中央高校基本科研业务费专项资金资助(TD-JC-2013-1);高等学校博士学科点专项科研基金新教师类资助课题(20120014120001);国家自然科学基金项目(31200313,31200314) Effects of nitrogen addition on interspecific competition between Alternanthera philoxeroides and Alternanthera sessilis Author: Affiliation: School of Nature Conservation, Beijing Forestry University,,School of Nature Conservation, Beijing Forestry University,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:自然界的氮素释放总是呈现出空间和时间上的异质性,但关于异质性氮释放对于入侵植物和本地植物种间关系影响的研究相对较少。将入侵植物空心莲子草(Alternanthera philoxeroides)和同属本地植物莲子草(Alternanthera sessilis)分别进行单种种植(12株,无种间竞争)和混种种植(每种6株,有种间竞争),模拟大气氮湿沉降设置由两种不同施氮总量(15g N m-2 a-1和30g N m-2 a-1)和两种不同施氮频率(每5天1次和每15天1次)交叉组成的4种施氮处理,并以不施氮为对照。施氮总量的增加显著促进了两种植物的生长,但对两种植物的种间竞争关系没有显著影响。施氮频率对两种植物的生长以及种间竞争关系都没有显著影响。两种植物在面对竞争时表现出不同的生物量分配策略,空心莲子草将更多的生物量分配到茎,而莲子草将更多的生物量分配到根。在全球变化的背景下,大气氮湿沉降可能会改变两种植物的种群结构和动态,但可能对这两种植物的种间关系影响较小。 Abstract:Nitrogen (N) is one of the most important soil nutrients for plants, and the amount and frequency of N release in soils is heterogeneous. Many studies have focused on the effects of heterogeneous N addition on a single plant species, but little is known about the effects of N amount and short-term N pulse on interspecific competition between invasive and native plant species. A replacement series experiment was conducted under greenhouse conditions to examine the effects of N amount and frequency release on the growth and interspecific competition between an invasive wetland clonal plant, Alternanthera philoxeroides (alligator weed), which is native in South America but highly invasive in China, and its native congener Alternanthera sessilis (sessile joyweed). Plant materials of A. philoxeroides and A. sessilis were collected from five locations in Xixi Wetland Park in Hangzhou, Zhejiang Province, China. Stem fragments of similar length (20 cm), with a stem tip for each species, were grown in monoculture (12 ramets in one container, no interspecific competition) and in mixture (six invasive plants with six native plants, with interspecific competition) in five different N treatments: control (no N added), low amount and high frequency (a total of 15 g N m-2 a-1 added every 5 days), low amount and low frequency (a total of 15 g N m-2 a-1 added every 15 days), high amount and high frequency (a total of 30 g N m-2 a-1 added every 5 days), and high amount and low frequency (a total of 30 g N m-2 a-1 added every 15 days). The results showed that N addition significantly increased the growth of both A. philoxeroides and A. sessilis. No significant difference was observed between the control and treatments for the relative yield (yield of each species in mixture divided by yield in its monoculture) for both species, indicating that N addition did not significantly affect the interspecific competition between the two species. The probable reason is that both species are from the same functional group and may have comparable capacities to compete and utilize the soil nutrients. The N pulse did not significantly modify growth or interspecific competition for either species. The sufficient soil water content and availability of nutrients other than N may explain why there were no effects of a N pulse on competition between the two species. Alternatively, high tolerance of both species to low soil nutrients and water content may lead to weaker responsiveness to a N pulse. With interspecific competition, the invasive species, A. philoxeroides, invested more biomass to stems, i.e., the stem biomass increased by 60%, which significantly decreased the root to shoot ratio. The native species, A. sessilis, allocated more biomass to roots, i.e., the root biomass increased by 250%, which significantly increased the root to shoot ratio. The results indicate that increasing atmospheric N deposition in the context of climate change may change population structure and dynamics of both species, but may not affect the interspecific competition of these plants. 参考文献 相似文献 引证文献

LABORATORY EQUIPMENT FOR AUTOTHERMAL REFORMING OF ORGANIC MATTER IN SUPERCRITICAL WATER

The ability of water to dissolve organic substances is very limited. However, its ability to dissolve them changes if pressure and temperature values reach the so-called critical point (<em>p</em> = 22.06MPa, <em>T</em> = 373.95 °C). Fluid water in this state is called supercritical water (SCW), and values of its physical properties are included among the values of such properties for liquid phase and gaseous phase. Various types of organic matter can be treated in SCW, and it is especially useful for materials that cannot be treated cost-effectively with conventional technologies (incineration, etc.). Suitable input materials are mainly industrial waste or biomass with high water content. Conventional processing of these materials requires energy-intensive drying or densification. Processing the inputs in SCW completely removes these problems, since sufficient water content is a prerequisite for creating a suitable environment for efficient operation of the system. In this paper, glycerol as a by-product of alternative fuel production was chosen for evaluation in the SCW autothermal reforming cycle. The paper analyses the influence of several processing parameters on the operation of model laboratory equipment.

Influence of Glycerol and Clay Contents on Biodegradability of Corn Starch Nanocomposites

In this study, biodegradation of corn starch/glycerol/Na-MMT nanocomposites by soil burial tests were carried out for up to 6 months. Films were prepared by casting method according to central composite design and response surface methodology was applied for analysis of the results. The effects of formulation on the water solubility, contact angle and tensile strength of starch films were investigated. Increasing in Na-MMT content decreased biodegradability; while presence of glycerol, increased it. The effect of nanoparticles content might have been attributed to interactions between starch and Na-MMT that further prevented enzymatic attack on the biopolymer. In addition, the films with higher initial contact angle and lower water solubility revealed slower biodegradation. The effect of glycerol is debated because higher hydrophilicity and weaker mechanical properties enhanced the amylase attack on the samples. Furthermore, weight loss due to soluble matters caused an increase to account of the biodegradability. By increasing in glycerol amount as a water holding agent, the films could store sufficient water content for microbial activities around the buried samples. According to FTIR spectra for partially biodegraded films, the intensity of the peaks at 1150 and 1040 cm -1 associated with starch glycosidic linkages decreased which indicates the action of alpha-amylase produced by soil microorganisms.

Extrusion of xylans extracted from corn cobs into biodegradable polymeric materials

Solvent casting technique, which comprises multiple energy demanding steps including the dissolution of a polymer in a solvent followed by the evaporation of the solvent from the polymer solution, is currently the main technique for the production of xylan based polymeric materials. The present study shows that sufficient water content renders arabinoglucuronoxylan (AGX) polymers extrudable, enabling the production of AGX based polymeric materials in a single step via extrusion, which is economically advantageous to solvent casting process for mass production. AGX polymers with water content of 27% were found to yield extrudates at an extrusion temperature of 90°C. The extruded strips showed very good mechanical properties with an ultimate tensile strength of 76 ± 6 MPa and elongation at break value of 35 ± 8%, which were superior to the mechanical properties of the strips obtained from polylactic acid.

Effect of dune sand mulch on water recharging into root zone using drip lines

Surface drip irrigation has been used for agricultural production for more than three decades. Surface drip irrigation (SDI) can maintain sufficient water content in soil for seed germination and emergence, seedling development and plant growth. Insufficient water content in the root zone may cause crop failure. In this study, the effects of Tottori dune sand mulch on drip lines on water recharging into root zone was examined under drip irrigation. Two irrigation levels of 60 and 100% evapotranspiration, and three dune sand mulches of 0, 2 and 5 cm thickness on the drip lines were used in this experiment. The results indicated that water recharging into the root zone under 5 cm dune sand was highest among the three dune sand mulch treatments. The drip lines under the 2 cm dune sand mulch expanded and contracted resulting in protrusion from the sand mulch. An irrigation level of 100% evapotranspiration under the 5 cm dune sand mulch resulted in increase of dry matter yield of sorghum. From this study, it is concluded that to increase water recharging into the root zone (to the depth of 25 cm), the minimum thickness of dune sand mulch on the drip lines was 5 cm. Key words: Irrigation level, root zone, dune sand, surface drip irrigation, water recharging.

Reduction and immobilization of chromate in chromite ore processing residue with nanoscale zero-valent iron

Chromite ore processing residue (COPR) poses a great environmental and health risk with persistent Cr(VI) leaching. To reduce Cr(VI) and subsequently immobilize in the solid matrix, COPR was incubated with nanoscale zero-valent iron (nZVI) and the Cr(VI) speciation and leachability were studied. Multiple complementary analysis methods including leaching tests, X-ray powder diffraction, X-ray absorption near edge structure (XANES) spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to investigate the immobilization mechanism. Geochemical PHREEQC model calculation agreed well with our acid neutralizing capacity experimental results and confirmed that when pH was lowered from 11.7 to 7.0, leachate Cr(VI) concentrations were in the range 358–445mgL−1 which contributed over 90% of dissolved Cr from COPR. Results of alkaline digestion, XANES, and XPS demonstrated that incubation COPR with nZVI under water content higher than 27% could result in a nearly complete Cr(VI) reduction in solids and less than 0.1mgL−1 Cr(VI) in the TCLP leachate. The results indicated that remediation approaches using nZVI to reduce Cr(VI) in COPR should be successful with sufficient water content to facilitate electron transfer from nZVI to COPR.

Measurement of Water Content in Polymer Electrolyte Membranes Using High Resolution Neutron Imaging

Sufficient water content within a polymer electrolyte membrane (PEM) is necessary for adequate ionic conductivity. Membrane hydration is therefore a fundamental requirement for fuel cell operation. The hydration state of the membrane affects the water transport within, as both the diffusion coefficient and electro-osmotic drag depend on the water content. Membrane's water uptake is conventionally measured ex situ by weighing free-swelling samples equilibrated at controlled water activity. In the present study, water profiles in Nafion® membranes were measured using high-resolution neutron imaging. The state-of-the-art, 13 μm resolution neutron detector is capable of resolving water distributions across N1120, N1110 and N117 membranes. It provides a means to measure the water uptake and transport properties of fuel cell membranes in situ.

Intramolecular Charge Transfer Reaction, Polarity, and Dielectric Relaxation in AOT/Water/Heptane Reverse Micelles: Pool Size Dependence

Intramolecular charge transfer (ICT) reaction in a newly synthesized molecule, of 4-(1-morpholenyl) benzonitrile (M6C), in AOT/water/heptane reverse micelles at different pool sizes has been studied by using steady-state and time-resolved fluorescence emission spectroscopy. The pool size dependences of the reaction equilibrium constant and reaction rate have been explained in terms of the average polarity of the confined solvent pools estimated from the fluorescence emission Stokes shift of a nonreactive probe, coumarin 153, dissolved in these microemulsions. The complex permittivity measurements in the frequency range 0.01<or=nu/GHz<or=2 for these microemulsions at different pool sizes (0<or=w0<or=40) and AOT concentrations (0.1<or=c/M<or=0.5) at 298.15 K have also been performed. At sufficient water content, a large dispersion with a relaxation time of approximately 600 ps has been observed at approximately 300 MHz and attributed to the average reorientation of water molecules residing in the close vicinity of the polar interface of the AOT headgroup and n-heptane. The reorientation of these interfacial water molecules is probably responsible for the nanosecond component observed in numerous polar solvation dynamics experiments in these reverse micelles. Subsequently, the estimated polarity and the measured reorientational time scale have been used to explain the dramatic slowing down of the ICT reaction rate and its dependence on pool size in these confined environments.

Ambient Molecular Imaging and Depth Profiling of Live Tissue by Infrared Laser Ablation Electrospray Ionization Mass Spectrometry

Mass spectrometry in conjunction with atmospheric pressure ionization methods enables the in vivo investigation of biochemical changes with high specificity and sensitivity. Laser ablation electrospray ionization (LAESI) is a recently introduced ambient ionization method suited for the analysis of biological samples with sufficient water content. With LAESI mass spectrometric analysis of chimeric Aphelandra squarrosa leaf tissue, we identify the metabolites characteristic for the green and yellow sectors of variegation. Significant parts of the related biosynthetic pathways (e.g., kaempferol biosynthesis) are ascertained from the detected metabolites and metabolomic databases. Scanning electron microscopy of the ablated areas indicates the feasibility of both two-dimensional imaging and depth profiling with a approximately 350 microm lateral and approximately 50 microm depth resolution. Molecular distributions of some endogenous metabolites show chemical contrast between the sectors of variegation and quantitative changes as the ablation reaches the epidermal and mesophyll layers. Our results demonstrate that LAESI mass spectrometry opens a new way for ambient molecular imaging and depth profiling of metabolites in biological tissues and live organisms.

Significance of Na+ and K+ for Sustained Hydration of Organ Tissues in Ecologically Distinct Halophytes of the Family Chenopodiaceae

The contents of Na+, K+, water, and dry matter were measured in leaves and roots of euhalophytes Salicornia europaea L. and Climacoptera lanata (Pall.) Botsch featuring succulent and xeromorphic cell structures, respectively, as well as in saltbush Atriplex micrantha C.A. Mey, a halophyte having bladder-like salt glands on their leaves. All three species were able to accumulate Na+ in their tissues. The Na+ content in organs increased with elevation of NaCl concentration in the substrate, the concentrations of Na+ being higher in leaves than in roots. When these halophytes were grown on a NaCl-free substrate, a trend toward K+ accumulation was observed and was better pronounced in leaves than in roots. Particularly high K+ concentrations were accumulated in Salicornia leaves. There were no principal differences in the partitioning of Na+ and K+ between organs of three halophyte species representing different ecological groups. At all substrate concentrations of NaCl, the total content of Na+ and K+ in leaves was higher than in roots. This distribution pattern persisted in Atriplex possessing salt glands, as well as in euhalophytes Salicornia and Climacoptera. The physiological significance of such universal pattern of ion accumulation and distribution among organs in halophytes is related to the necessity of water absorption by roots, its transport to shoots, and maintenance of sufficient cell water content in all organs under high soil salinity.

Progressive Soil Drought Promotes the Export Function in the Birch (Betula platyphylla) Leaf

A greenhouse experiment, which imitated a short (4-day-long) and progressive (3-week-long) soil drought, was employed to assess, with an IR gas analyzer, leaf CO2 exchange rate (CER) in intact one-year-old seedlings of Betula platyphylla as related to the flux of photosynthetically active radiation ranging from 0 to 1400 μE/(m2 s). The registered indices comprised leaf temperature, leaf transpiration conductivity, and the average daily increment of the leaf area. Within a week period following the transition from the short severe soil drought (20% H2O per soil weight) to the conditions of sufficient water content (35–40%), the plants completely regained the initial leaf CER. Under the progressive soil drought, leaf CER was reduced by 30–35%, as compared to the conditions of sufficient water content, evidently due to a 3.7-fold drop in the transpiration conductivity as compared to the control plants. The apparent constant of Rubisco carboxylation and leaf respiration in the light were not affected by the drought period. The rate of leaf growth under the progressive drought was reduced by 64% as compared to the sufficient moisture conditions. Thus, under the progressive drought, the diminished stomatal conductivity reduced CO2 concentration inside the leaf and lowered carbon photosynthetic assimilation. Meanwhile, the leaf source activity considerably increased in spite of diminished photosynthesis.

Development of a high-performance PEFC module operated by reformed gas

Improvements in the CO tolerance of the anode has been studied with the objective of developing PEFC modules operated with reformed gas. The CO tolerance of the Pt–Ru alloy anode was improved by reducing its thickness from 40 μm to 20 μm. Maintaining a saturated steam pressure of the fuel cell anode gas outlet is expected to decrease the influence of CO poisoning. When keeping sufficient water content in the feed fuel, it was established that the cell performance was stable over a wide range of air-humidification conditions. Successful operation was achieved with a 1 kW class system utilizing the improved CO-tolerant anode and fuel processor. An output power of 1.1 kW (average cell voltage: 0.62 V) was achieved at the current density of 0.3 A/cm 2.

Early morning photosynthesis of the moss Tortula ruralis following summer dew fall in a Hungarian temperate dry sandy grassland

Air temperature and humidity, moss surface temperature, moss water content, and photosynthetically active radiation were measured through a clear dry night and early morning in July 1998; CO2 gas exchange of the moss was measured by infra-red gas analysis. The measurements showed progressive absorption of water by the moss through much of the night. The moss reached sufficient water content for about 1.5 h of positive net CO2 uptake immediately after dawn. The cumulative net carbon balance on this occasion was negative, but mornings with heavier dew could give a positive daily carbon balance, and short, early morning periods of photosynthesis during prolonged dry weather may mitigate long-term desiccation damage and allow for regular molecular repair.

Stability of beta-galactosidase, a model protein drug, is related to water mobility as measured by 17O nuclear magnetic resonance (NMR).

The inactivation of freeze-dried beta-galactosidase during storage was studied, focusing on the effect of water mobility as measured by the spin-lattice relaxation time, T1, of water using 17O NMR. Inactivation of beta-galactosidase lyophilized from phosphate buffer solution was studied as a function of water content, which in turn affected the T1 of water. An increase in the water content of freeze-dried beta-galactosidase brought about an increase in the T1 of water, as well as a rise in pH. For the freeze-dried enzyme with sufficient water content to be dissolved, the inactivation rate was related to the T1 of water rather than to the pH change. It is suggested that as the water content increases, the mobility of water around the enzyme increases, resulting in enhanced enzyme inactivation. The freeze-dried samples with limited moisture showed inactivation rates faster than those expected from the pH and water mobility, suggesting that the inactivation mechanism is different from that for the freeze-dried enzyme with a larger amount of water. Inactivation of beta-galactosidase in solutions was also studied as a function of phosphate buffer and sodium chloride concentrations, which in turn affected the T1 of water. Because the inactivation rate increased with increasing salt concentrations and the rate extrapolated to zero concentration was negligible, inactivation of the freeze-dried enzyme was apparently induced by the salts used as additives for lyophilization. The enhancing effect of phosphate buffer components, however, was reduced at higher concentrations, an effect related to the decrease in the T1 of water. This result may be ascribed to the decrease in water mobility caused by phosphate buffer components and is consistent with the observation that the inactivation rate of the freeze-dried enzyme with a relatively large amount of water decreased with decreasing T1 of water.

Temperature Regulation in the Incubation Mounds of the Australian Brush-Turkey

The Australian Brush-turkey, Alectura lathami, constructs incubation mounds of decomposing forest litter in which many large eggs are incubated by microbial heat generation. On Kangaroo Island, the average mound is about 12.7 m3 and weighs about 6,800 kg. It maintains an incubation of 330C in an average ambient air of 180C. When eggs are in the mound, the rate of heat production is estimated to be about 100 Watts, a value more than 20 times the heat production of the resting adult. Thus, the mound can incubate many more eggs than would be possible in a normal nest. Core is stable due to mound size and biophysical homeothermy. Mounds tend to reach a stable temperature at which the rate of microbial heat production equals the rate of heat loss to the environment. The bird adjusts equilibrium by adding or removing litter as required. A numerical computer model, incorporating experimental data on mound size, ambient temperature, and the mound material's rate of heat production, water content, dry density, and thermal conductivity, predicts that as little as 1 cm of litter added to the mound will raise core about 1.50C. Experimental manipulation of artificial and natural mounds uphold the model and indicate that functional mounds require (1) a critical mass of fresh litter (ca. 3,000 kg), (2) sufficient water content (>0.2 ml/g dry material), and (3) occasional mixing of the litter. Once constructed and adjusted, natural mounds require little attention, and larger ones can stay warm for several weeks without the bird. The mound characteristics appear to minimize the work required for maintenance. The bird maintains water content of the mound at a level (9 = 0.3 ml/g) that minimizes thermal conductivity and microbial heat production. Therefore, heat is retained in the mound and decomposition occurs slowly, reducing the requirement to collect fresh litter. Kangaroo Island mounds are larger than those in sub-tropical rainforest, probably because rates of decomposition of mound material are lower, not because of differences in either thermal conductivity of the material or ambient temperature.