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991.
There is an increasing emphasis on using natural processes, including riparian forest restoration, to enhance the ecological, hydrological and geomorphological functioning of watercourses. However, we have insufficient knowledge on how the supply and retention of in‐channel wood from riparian forest stands changes with age, with inferences typically based on data from terrestrial forests. This presents a challenge in estimating the efficacy and functional lifespan of restoration projects. In this paper, we use a riparian forest growth model to show there is a lag of up to 40–50 years between the start of forest growth and trees delivering wood to the channel that is large enough to resist fluvial transport, anchor logjams and so increase channel complexity and hydraulic resistance. Resource managers need to account for realistic timescales over which changes promoted by riparian woodland restoration will occur and may need to consider using interim engineered logjams as the forest develops. 相似文献
992.
Silicon - Bisfunctional dichlorosilanes were reacted with tetrasilanol of double-decker shaped octaphenylsilsesquioxane (DDSQ) to form fully condensed DDSQ compounds. The crystallographic and... 相似文献
993.
994.
Geoffrey L. Beausoleil II Patrick Price David Thomsen Alex Punnoose Rick Ubic Scott Misture Darryl P. Butt 《Journal of the American Ceramic Society》2014,97(1):228-234
The thermal expansion and magnetic behaviors of divalent, alkaline‐doped lanthanum ferrites (La0.9M0.1FeO3, M=Ca, Sr, Ba) were assessed using a combination of dilatometry, magnetometry, time‐of‐flight neutron diffraction, and high‐temperature X‐ray diffraction. Néel temperatures were determined through vibrating sample magnetometry and correlated well with changes in thermal expansion behavior observed during both dilatometry and X‐ray diffraction. The Néel temperatures observed for pure, Ca‐doped, Sr‐doped, and Ba‐doped lanthanum ferrites were 471°C, 351°C, 465°C, and 466°C, respectively. The effect of divalent substitutions on the magnetic behavior are attributed to charge compensation mechanisms and structural changes in the material. 相似文献
995.
Electrostatically designing materials opens a new avenue for realizing systems with user‐defined electronic properties. Here, an approach is presented for efficiently patterning the electronic structure of layered systems such as graphene by means of collective electrostatic effects. Using density‐functional theory simulations, it is found that lines of polar elements can strongly modify the energy landscape of this prototypical 2D material. This results in a confinement of electronic states in specific regions of the sample and, consequently, in a local energetic shift of the density of states. The latter is also directly reflected in the details of the band structure of the electrostatically patterned sample. Finally, it is shown that the approach can also be successfully applied to other 2D materials such as hexagonal boron nitride, where the effects are predicted to be even more pronounced than in graphene. 相似文献
996.
Joan E. Haysom Omid Jafarieh Hanan Anis Karin Hinzer David Wright 《Progress in Photovoltaics: Research and Applications》2015,23(11):1678-1686
Price declines and volume growth of concentrated photovoltaic (CPV) systems are analysed using the learning curve methodology and compared with other forms of solar electricity generation. Logarithmic regression analysis determines a learning rate of 18% for CPV systems with 90% confidence of that rate being between 14 and 22%, which is higher than the learning rates of other solar generation systems (11% for CSP and 12 to 14% for PV). Current CPV system prices are competitive with PV and CSP, which, when combined with the higher learning rate, indicates that CPV is likely to further improve its marketability. A target price of 1 $/W in 2020 could be achieved with a compound growth rate of 67% for the total deployed volume between 2014 and 2020, which would realize a cumulative deployed volume of 7900 MW. Other projections of deployment volumes from commercial sources are converted using the learning rate into future price scenarios, resulting in predicted prices in the range of 1.1 to 1.3 $/W in 2020. © 2014 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd. 相似文献
997.
Limin Dong David J. T. Hill James H. O'Donnell Peter J. Pomery Koichi Hatada 《应用聚合物科学杂志》1996,59(4):589-597
The γ irradiation of poly(methacrylate)s with various ester groups at room temperature was investigated by gel permeation chromatography and NMR techniques. The G values for scission and crosslinking for each of the polymers were estimated from the changes in the molecular weights and molecular weight distributions. The new structures formed during γ irradiation were examined by 1H-NMR spectroscopy. All of the investigated poly(alkanemethacrylate)s were found to produce the alkane formates during γ irradiation, and for poly(2-methyl heptyl methacrylate) G(S) was less than 4G(X), indicating gel formation in this polymer. In the investigation of poly(benzyl methacrylate), no formate ester was found, but some small molecule compounds formed from the benzyl radical were detected. The benzyl group was also found to stabilize the polymer against radiation damage. © 1996 John Wiley & Sons, Inc. 相似文献
998.
999.
Ewen R Brierley Peter J Wilde Akiko Onishi Paul S Hughes William J Simpson David C Clark 《Journal of the science of food and agriculture》1996,70(4):531-537
The effect of ethanol on the foaming properties of beer protein fractions was studied using a microconductivity method and nitrogen gas to generate the foam. Increasing the ethanol concentration resulted in a decrease in foam stability. Interfacial studies including thin film drainage and dilational elasticity measurements indicated that ethanol reduced the rigidity of the adsorbed protein layer resulting in accelerated drainage from the foam lamellae and increased probability of film rupture. These results conflict with data from the Rudin method (using nitrogen gas to generate the foam) which indicate that, at low concentration, ethanol improves foam stability. These apparently conflicting results may be explained by the foam positive effects of a decline in bubble size and increase in bulk viscosity observed for the Rudin method, contrasted with the negative influence of a reduction in surface viscosity observed for the microconductivity foam assessment method. 相似文献
1000.
Reverse genetics in fission yeast is hindered by the lack of a versatile established plasmid shuffle system. In order to screen efficiently and accurately through plasmid-borne mutations in the essential gene for the RNA component of RNase MRP, mrp1, we have developed a system for plasmid shuffling in fission yeast using counterselection on canavanine. The system takes advantage of the ability of the Saccharomyces cerevisiae CAN1 gene to complement a Schizosaccharomyces pombe can1-1 mutation. Two general use plasmids were constructed that allow directional cloning and initial selection for histidine before counterselection by canavanine. The strain constructed for plasmid shuffling carries auxotrophic markers for ade6, leu1, ura4 and his3 along with the can1-1 mutation. Using this system we examined several partial deletions and point mutations in conserved nucleotides of Schizosaccharomyces pombe RNase MRP RNA for their ability to complement a chromosomal deletion of the mrp1 gene. The degree of background canavanine resistance as well as plasmid–plasmid recombination encountered in these experiments was sufficiently low to suggest that the system we have set up for counterselection by canavanine in fission yeast using multicopy plasmids will be widely useful. 相似文献