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991.
992.
Soft robotics for chemists 总被引:3,自引:0,他引:3
Ilievski F Mazzeo AD Shepherd RF Chen X Whitesides GM 《Angewandte Chemie (International ed. in English)》2011,50(8):1890-1895
993.
994.
Birgit Graf‐Zeiler Prof. Dr. Rainer H. Fink Prof. Dr. George Tzvetkov 《Chemphyschem》2011,12(18):3503-3509
Direct, real‐time analytical techniques that provide high‐resolution information on the chemical composition and submicrometer structure of various polymer micro‐ and nanoparticles are in high demand in a range of life science disciplines. Synchrotron‐based scanning transmission X‐ray microspectroscopy (STXM) combines both local‐spot chemical information (assessed via near‐edge X‐ray absorption fine structure spectroscopy) and imaging with resolution of several tens of nanometers, and thus can yield new insights into the nanoscale properties of these materials. Furthermore, this method allows in situ examination of soft‐matter samples in aqueous/gaseous environments and under external stimuli, such as temperature, pressure, ultrasound, and light irradiation. This Minireview highlights some recent progress in the application of the STXM technique to study the temperature‐dependent behavior of polymer core–shell microcapsules and to characterize the physicochemical properties of the supporting shells of gas‐filled microbubbles in their natural hydrated state. 相似文献
995.
Bravo I Díaz-de-Mera Y Aranda A Moreno E Nutt DR Marston G 《Physical chemistry chemical physics : PCCP》2011,13(38):17185-17193
Density Functional Theory (DFT) has been used with an empirically-derived correction for the wavenumbers of vibrational band positions to predict the infrared spectra of several fluorinated esters (FESs). Radiative efficiencies (REs) were then determined using the method of Pinnock et al. and these were used with atmospheric lifetimes from the literature to determine the direct global warming potentials of FESs. FESs, in particular fluoroalkylacetates, alkylfluoroacetates and fluoroalkylformates, are potential greenhouse gases and their likely long atmospheric lifetimes and relatively large REs, compared to their parent HFEs, make them active contributors to global warming. Here, we use the concept of indirect global warming potential (indirect GWP) to assess the contribution to the warming of several commonly used HFEs emitted from the Earth's surface, explicitly taking into account that these HFEs will be converted into the corresponding FESs in the troposphere. The indirect GWP can be calculated using the radiative efficiencies and lifetimes of the HFE and its degradation FES products. We found that the GWPs of those studied HFEs which have the smallest direct GWP can be increased by 100-1600% when taking account of the cumulative effect due to the secondary FESs formed during HFE atmospheric oxidation. This effect may be particularly important for non-segregated HFEs and some segregated HFEs, which may contribute significantly more to global warming than can be concluded from examination of their direct GWPs. 相似文献
996.
This paper describes the development of MEMS force sensors constructed using paper as the structural material. The working principle on which these paper-based sensors are based is the piezoresistive effect generated by conductive materials patterned on a paper substrate. The device is inexpensive (~$0.04 per device for materials), simple to fabricate, lightweight, and disposable. Paper can be readily folded into three-dimensional structures to increase the stiffness of the sensor while keeping it light in weight. The entire fabrication process can be completed within one hour without expensive cleanroom facilities using simple tools (e.g., a paper cutter and a painting knife). We demonstrated that the paper-based sensor can measure forces with moderate performance (i.e., resolution: 120 μN, measurement range: ±16 mN, and sensitivity: 0.84 mV mN(-1)). We applied this sensor to characterizing the mechanical properties of a soft material. Leveraging the same sensing concept, we also developed a paper-based balance with a measurement range of 15 g, and a resolution of 0.39 g. 相似文献
997.
A multi-element analytical method based on inductively coupled plasma atomic emission spectrometry (ICP-AES) was developed
for trace elements in pharmaceutical tablets and cosmetics. Titanium was also included in the analytes since it is widely
used in pharmaceuticals. Critical ICP conditions, like RF incident power, argon gas flow rate and nebulizer sample uptake
flow rate were optimized. The most sensitive spectral line of each analyte was selected as optimum for further study. Detection
limits in the low μg g−1 range were obtained. Prior to chemical analysis, the samples were decomposed by acid digestion, using various mixtures of
HCl, HNO3 and HF. Yttrium was used as a suitable internal standard in order to correct for possible matrix effects. The method was
applied to the analysis of six different pharmaceutical products (anti-biotic, anti-inflammatory, anti-hypertensive) in the
form of tablets with film coating and also three cosmetic products like hair and face masks. 相似文献
998.
Data from an one-dimensional homogeneous sand column, which is utilized to investigate the effect of tides on the concentration
of groundwater contaminants discharging to a surface-water body, demonstrate that the tidal fluctuations in water level elevation
create concentration oscillations upgradient of the groundwater discharge locations and there is a resulting decrease in average
contaminant concentration at the point of groundwater discharge to a surface-water body. The further upgradient an observation
point is located, the smaller the amplitude of the tidally induced concentration oscillations. In addition, an excessive upstream
migration of concentration oscillations is observed although there is a net downgradient flow. As the classical groundwater
flow and transport model could not reproduce this phenomena, a multi-mobility model is proposed with one highly mobile liquid
phase, one less mobile liquid phase and a solid phase. Averaging theory is applied in a first step to develop the macroscopic
mass conservation equation from its microscale counterpart and then, in a second step, averaging is again used to reduce dimensionality
to one-dimensional governing equations defined along the axis of the column. The simulation confirms the existence of an enhanced
tidally induced mixing process and the suitability of our mathematical-physical representation of it. 相似文献
999.
Boundary stabilization of a structural acoustic model comprised of a wave and a Reissner–Mindlin plate is addressed. Both the components of the dynamics are subject to localized nonlinear boundary damping: the acoustic dissipative feedback is restricted to the flexible boundary and only a portion of the rigid wall; the plate is damped only on a segment of its edge.Derivation of stabilization/observability inequalities for a coupled system requires weighted energy multipliers dependent on the geometry of the domain, and special microlocal trace estimates for the Reissner–Mindlin plate. The behavior of the energy at infinity can be quantified by a solution to an explicitly constructed nonlinear ODE. The nonlinearities in the feedbacks may include sub- and superlinear growth at infinity, in which case the decay scheme presents a trade-off between the regularity of trajectories and attainable uniform dissipation rates of the finite energy. 相似文献
1000.
An inductive characterization is given of the subsets of a group that extend to the positive cone of a right order on the group. This characterization is used to relate validity of equations in lattice-ordered groups (?-groups) to subsets of free groups that extend to the positive cone of a right order. As a consequence, new proofs are obtained of the decidability of the word problem for free ?-groups and generation of the variety of ?-groups by the ?-group of automorphisms of the real line. An inductive characterization is also given of the subsets of a group that extend to the positive cone of an order on the group. In this case, the characterization is used to relate validity of equations in varieties of representable ?-groups to subsets of relatively free groups that extend to the positive cone of an order. 相似文献