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21.
David P. Cormode Jason J. Davis Paul D. Beer 《Journal of Inorganic and Organometallic Polymers and Materials》2008,18(1):32-40
Disulfide and dithiocarbamate functionalized porphyrins have been synthesized and used as protecting ligands for gold nanoparticle
formation either via ligand substitution reactions or by direct synthesis. These nanoparticles have been shown to recognize
anions via changes in the absorbance spectrum of the surface adsorbed porphyrin moieties. Association constants, derived from
quantitative titrations, indicate a remarkable surface enhancement effect where the surface bound porphyrins bind anions much
more strongly than the free receptor in solution. 相似文献
22.
Alexey B. Nadykto Fangqun Yu Jason Herb 《International journal of molecular sciences》2008,9(11):2184-2193
Hydration directly affects the mobility, thermodynamic properties, lifetime and nucleation rates of atmospheric ions. In the present study, the role of ammonia on the formation of hydrogen bonded complexes of the common atmospheric hydrogensulfate (HSO4−) ion with water has been investigated using the Density Functional Theory (DFT). Our findings rule out the stabilizing effect of ammonia on the formation of negatively charged cluster hydrates and show clearly that the conventional (classical) treatment of ionic clusters as presumably more stable compared to neutrals may not be applicable to pre-nucleation clusters. These considerations lead us to conclude that not only quantitative but also qualitative assessment of the relative thermodynamic stability of atmospheric clusters requires a quantum-chemical treatment. 相似文献
23.
The reduction and subsequent reoxidation of isolated vanadate species supported on silica was investigated using temperature-programmed reduction and oxidation, along with in-situ XANES and Raman spectroscopy. Approximately 70–80% of the vanadium was reduced to V3+ after reduction in H2 at temperatures up to 923 K. Upon reduction, the vanadyl oxygen was removed and the three remaining V–O bonds are lengthened by 0.2 Å. The vanadate species are rapidly reoxidized when exposed to O2, with the amount of oxygen uptake matching well with the amount removed during reduction. In-situ Raman spectroscopy during reoxidation in 18O2 showed that significant scrambling occurs between gas phase oxygen and surface oxygen species during the reoxidation of the vanadate species. 相似文献
24.
Knapp Samuel; Gottlieb Michael; Berman Jason; Handelsman Mitchell M. 《Canadian Metallurgical Quarterly》2007,38(1):54
At times the laws under which psychologists function may appear to contradict generally recognized ethical values and/or good clinical care. When these circumstances arise, psychologists must determine if a conflict really exists and, if so, seek solutions that reconcile respect for the law with their ethical values. At times, psychologists may decide to follow the law despite their ethical concerns. At other times, they may determine that a conscientious objection is warranted. The authors recommend options to consider when these situations arise and offer a decision-making process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
Synthesis and Characterisation of Some New Ferrocenyl- and Ferrocenylalkynyl-[60]Fullerene Compounds
David J. Cardin Trevor Gibson Jason A. Peel 《Fullerenes, Nanotubes and Carbon Nanostructures》1997,5(4):681-694
We report the synthesis and characterisation of a series of ferrocenylfullerene compounds, and some new ferrocene derivatives required as intermediates. The new fullerene species are Fc-[60]fullerene, (8); Fc-C=C-[60]fullerene, (10); Fc-C=C-C=C-[60]fullerene, (12); and (η-C5H4SiBu3)Fe(η-C5H4)-[60]fullerene, (14). 相似文献
26.
Rosalie Bruel J. Ellen Marsden Bernie Pientka Nick Staats Timothy Mihuc Jason D. Stockwell 《Journal of Great Lakes research》2021,47(4):1171-1181
Invasive species can cause major disruptions in native food webs, yet the impact of species introductions and whether they will become invasive appears to be context-dependent. Rainbow smelt and alewife co-exist as invasive species in the Laurentian Great Lakes and as native species on the Atlantic coast of North America, but in Lake Champlain rainbow smelt is the dominant native forage fish and alewife are invasive. Alewife became abundant by 2007, providing an opportunity to explore the dynamics of these two species in a system where only one is invasive. We used data from a 28-year forage fish survey to compare demographics of rainbow smelt populations in three basins of Lake Champlain with different volumes, nutrient levels, and predator abundances. Rainbow smelt catch-per-unit-effort (CPUE) remained constant in the large, deep Main Lake before and after alewife invaded, but decreased in the two smaller basins. Declines were primarily a result of increased age-0 and age-1 mortality. Predation by top piscivores, system productivity, and competition for resources alone could not explain the patterns in CPUE across the basins. The mechanisms that allow alewife and rainbow smelt to co-exist could be related to system volume and oxythermal habitat availability, and may explain why the two species do not negatively affect each other in the Great Lakes. Summer hypoxia in the smaller basins could force individuals into smaller habitat volumes with higher densities of competitors and cannibalistic adult rainbow smelt. Habitat availability may mediate the impact of invasive alewife on native rainbow smelt. 相似文献
27.
One strategy for alleviating excess latency (delay) in the Internet is the caching of web content at multiple locations. This
reduces the number of hops necessary to reach the desired content. This strategy is used for web content such as html pages,
images, streaming video, and Internet radio. The network of servers which store this content, and the collections of objects
stored on each server, is called a content distribution network (CDN). In order to optimally design a CDN, given a network
topology with available server storage capacity at various points in the network, one must decide which object collections
to place on each server in order to achieve performance or cost objectives. The placements must be within the storage limits
of the servers and must reflect the request patterns for each collection of objects to be cached. Researchers have suggested
formulations for the CDN problem which address performance by minimizing latency (the average number of hops is a commonly
accepted measure of latency) from client to content, or formulations that focus on minimizing cost of storage and/or bandwidth.
In this research, we develop a model which allows for the simultaneous treatment of performance and cost, present examples
to illustrate the application of the model and perform a detailed designed experiment to gain insights into cost/hops tradeoff
for a variety of network parameters. 相似文献
28.
Register allocation for write activity minimization on non-volatile main memory for embedded systems
Yazhi Huang Author VitaeTiantian Liu Author Vitae Chun Jason XueAuthor Vitae 《Journal of Systems Architecture》2012,58(1):13-23
Non-volatile memories are good candidates for DRAM replacement as main memory in embedded systems and they have many desirable characteristics. Nevertheless, the disadvantages of non-volatile memory co-exist with its advantages. First, the lifetime of some of the non-volatile memories is limited by the number of erase operations. Second, read and write operations have asymmetric speed or power consumption in non-volatile memory. This paper focuses on the embedded systems using non-volatile memory as main memory. We propose register allocation technique with re-computation to reduce the number of store instructions. When non-volatile memory is applied as the main memory, reducing store instructions will reduce write activities on non-volatile memory. To re-compute the spills effectively during register allocation, a novel potential spill selection strategy is proposed. During this process, live range splitting is utilized to split certain long live ranges such that they are more likely to be assigned into registers. In addition, techniques for re-computation overhead reduction is proposed on systems with multiple functional units. With the proposed approach, the lifetime of non-volatile memory is extended accordingly. The experimental results demonstrate that the proposed technique can efficiently reduce the number of store instructions on systems with non-volatile memory by 33% on average. 相似文献
29.
Haluk Demirkan Sagnika Sen Michael Goul Jason Nichols 《Information Systems Frontiers》2012,14(3):765-788
In the age of Business-to-Business (B2B) collaboration, ensuring reliability of workflows underlying inter-organizational business processes is of significant importance. There are, however, quite a few challenges towards achieving seamless operation. Such challenges arise from heterogeneity in infrastructure and coordination mechanism at participant organizations, as well as time and cost associated with recovery from failure. Our research presents foundations for a reliable scheme for recovery from failure of workflow processes spanning through multiple business entities. First, a system model is adapted from the mobile computing literature that serves to establish the requirements to be enforced by each participating organization. In our model, we adopt the Maximal Sequence Path (MSP) approach from Yoo et al. (Lecture Notes in Artificial Intelligence 2132:222–236, 2001), as a means of decomposing workflows into mobile agent-driven processes that communicate via web services at each organization. This decomposition ensures defining logical points within the dynamics of a workflow instance for locating accurate and consistent states of the system for recovery in case of a failure. Then, a set of algorithms for various business scenarios are developed and presented as practical solutions. These algorithms are shown to create checkpoints such that the system is always in a globally consistent state. As such, these algorithms constitute a set of standards that can be incorporated in business process management suites that support reliable inter-organizational collaboration. 相似文献
30.
Cookies are the primary means for web applications to authenticate HTTP requests and to maintain client states. Many web applications (such as those for electronic commerce) demand a secure cookie scheme. Such a scheme needs to provide the following four services: authentication, confidentiality, integrity, and anti-replay. Several secure cookie schemes have been proposed in previous literature; however, none of them are completely satisfactory. In this paper, we propose a secure cookie scheme that is effective, efficient, and easy to deploy. In terms of effectiveness, our scheme provides all of the above four security services. In terms of efficiency, our scheme does not involve any database lookup or public key cryptography. In terms of deployability, our scheme can be easily deployed on existing web services, and it does not require any change to the Internet cookie specification. We implemented our secure cookie scheme using PHP and conducted experiments. The experimental results show that our scheme is very efficient on both the client side and the server side.A notable adoption of our scheme in industry is that our cookie scheme has been used by Wordpress since version 2.4. Wordpress is a widely used open source content management system. 相似文献