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51.
Directional Materials—Nanoporous Organosilica Monoliths with Multiple Gradients Prepared Using Click Chemistry 下载免费PDF全文
Andreas Schachtschneider Martin Wessig Martin Spitzbarth Adrian Donner Christian Fischer Dr. Malte Drescher Prof. Dr. Sebastian Polarz 《Angewandte Chemie (International ed. in English)》2015,54(36):10465-10469
The existence of more than one functional entity is fundamental for materials, which are desired of fulfilling complementary or succeeding tasks. Whereas it is feasible to make materials with a homogeneous distribution of two different, functional groups, cases are extremely rare exhibiting a smooth transition from one property to the next along a defined distance. We present a new approach leading to high‐surface area solids with functional gradients at the microstructural level. Periodically ordered mesoporous organosilicas (PMOs) and aerogel‐like monolithic bodies with a maximum density of azide groups were prepared from a novel sol–gel precursor. The controlled and fast conversion of the azide into numerous functions by click chemistry is the prerequisite for the implementation of manifold gradient profiles. Herein we discuss materials with chemical, optical and structural gradients, which are interesting for all applications requiring directionality, for example, chromatography. 相似文献
52.
We have experimentally investigated the formation of off-diagonal long-range order in a gas of ultracold atoms. A magnetically trapped atomic cloud prepared in a highly nonequilibrium state thermalizes and thereby crosses the Bose-Einstein condensation phase transition. The evolution of phase coherence between different regions of the sample is constantly monitored and information on the spatial first-order correlation function is obtained. We observe the growth of the spatial coherence and the formation of long-range order in real time and compare it to the growth of the atomic density. Moreover, we study the evolution of the momentum distribution during the nonequilibrium formation of the condensate. 相似文献
53.
54.
Statistically distinguishing between phase-coherent and noncoherent chaotic dynamics from time series is a contemporary problem in nonlinear sciences. In this work, we propose different measures based on recurrence properties of recorded trajectories, which characterize the underlying systems from both geometric and dynamic viewpoints. The potentials of the individual measures for discriminating phase-coherent and noncoherent chaotic oscillations are discussed. A detailed numerical analysis is performed for the chaotic Ro?ssler system, which displays both types of chaos as one control parameter is varied, and the Mackey-Glass system as an example of a time-delay system with noncoherent chaos. Our results demonstrate that especially geometric measures from recurrence network analysis are well suited for tracing transitions between spiral- and screw-type chaos, a common route from phase-coherent to noncoherent chaos also found in other nonlinear oscillators. A detailed explanation of the observed behavior in terms of attractor geometry is given. 相似文献
55.
Lombi E de Jonge MD Donner E Ryan CG Paterson D 《Analytical and bioanalytical chemistry》2011,400(6):1637-1644
Environmental samples are extremely diverse but share a tendency for heterogeneity and complexity. This heterogeneity poses
methodological challenges when investigating biogeochemical processes. In recent years, the development of analytical tools
capable of probing element distribution and speciation at the microscale have allowed this challenge to be addressed. Of these
available tools, laterally resolved synchrotron techniques such as X-ray fluorescence mapping are key methods for the in situ
investigation of micronutrients and inorganic contaminants in environmental samples. This article demonstrates how recent
advances in X-ray fluorescence detector technology are bringing new possibilities to environmental research. Fast detectors
are helping to circumvent major issues such as X-ray beam damage of hydrated samples, as dwell times during scanning are reduced.
They are also helping to reduce temporal beamtime requirements, making particularly time-consuming techniques such as micro
X-ray fluorescence (μXRF) tomography increasingly feasible. This article focuses on μXRF mapping of nutrients and metalloids
in environmental samples, and suggests that the current divide between mapping and speciation techniques will be increasingly
blurred by the development of combined approaches. 相似文献
56.
C. Ern W. Donner A. Rühm H. Dosch B.P. Toperverg R.L. Johnson 《Applied Physics A: Materials Science & Processing》1997,64(4):383-390
3 Au(001) surface using Synchrotron radiation and show that the intensity distribution along the specular rod exhibits the same
features as in the case of liquid metals which has been discussed in recent literature. The results are discussed within the
framework of the distorted wave Born approximation which allows a straightforward easy-to-apply scheme to analyze such reflectivity
data in the entire -range including the total external reflection regime. The data analysis gives a direct evidence for an oscillating average
density profile which is analoguous to the socalled surface layering at liquid surfaces. The experimental values for the thermal
roughness indicate that surface roughness is suppressed in the ordered phase and allowed to softly grow with temperature above
the bulk order-disorder phase transition. The presented experimental and theoretical study of X-ray reflectivity from binary
alloys demonstrates the potential of this technique for the study of surface roughening, surface layering and surface segregation
phenomena at solid and liquid surfaces.
Received: 14 August 1996/Accepted: 7 October
1996 相似文献
57.
L. Chekli B. Bayatsarmadi R. Sekine B. Sarkar A. Maoz Shen K.G. Scheckel W. Skinner R. Naidu H.K. Shon E. Lombi E. Donner 《Analytica chimica acta》2016
Zero-valent iron nanoparticles (nZVI) have been widely tested as they are showing significant promise for environmental remediation. However, many recent studies have demonstrated that their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Both the mobility and reactivity of nZVI mainly depends on properties such as particle size, surface chemistry and bulk composition. In order to ensure efficient remediation, it is crucial to accurately assess and understand the implications of these properties before deploying these materials into contaminated environments. Many analytical techniques are now available to determine these parameters and this paper provides a critical review of their usefulness and limitations for nZVI characterisation. These analytical techniques include microscopy and light scattering techniques for the determination of particle size, size distribution and aggregation state, and X-ray techniques for the characterisation of surface chemistry and bulk composition. Example characterisation data derived from commercial nZVI materials is used to further illustrate method strengths and limitations. Finally, some important challenges with respect to the characterisation of nZVI in groundwater samples are discussed. 相似文献
58.
We propose a simple kinetic model in which two types of processes between two reactants occur: diffusional processes for distances greater than , the reaction distance, and static quenching for distances smaller than . This model might be useful in the studies of diffusion in membrane systems.
, , : , , , . .相似文献
59.
Bo Xiao a Qingchun Yuan b a EaStChem School of Chemistry Purdie Building North Haugh University of St. rews Fife St. rews KY ST UK b Institute of Particle Science Engineering School of Processing Environmental & Mineral Engineering University of Leeds Houldworth Building Leeds LS JT UK 《中国颗粒学报》2009,7(2)
Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels.One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems,capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements.Metal organic framework (MOF) is a new type of inorganic and organic hybrid nanoporous particulate materials.Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs.The MOF materials so far developed adsorb hydrogen through weak disperston interactions,which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics.Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions.This review surveys the development of such candidate materials,their performance and future research needs. 相似文献
60.
A methodology is proposed for predicting the effective thermal conductivity of dilute suspensions of nanoparticles (nanofluids) based on rheology.The methodology uses the rheological data to infer microstructures of nanoparticles quantitatively,which is then incorporated into the conventional Hamilton-Crosser equation to predict the effective thermal conductivity of nanofluids.The methodology is experimentally validated using four types of nanofluids made of titania nanoparticles and titanate nanotubes dispersed in water and ethylene glycol.And the modified Hamilton-Crosser equation successfully predicted the effective thermal conductivity of the nanofluids. 相似文献