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81.
By using electron beam lithography, we fabricated pairs of gold nanoparticles with varying interparticle separation. Double-beam femtosecond transient absorption spectroscopy was used to determine the coherent lattice oscillation frequency as a function of the interparticle separation in the presence of the plasmon field excited by the monitoring probe light. We found that the fractional shift in the coherent lattice phonon oscillation frequency follows an exponential decay with respect to the interparticle gap scaled by the disc diameter with the same decay constant as that previously observed for the fractional shift in the surface plasmon electronic oscillation resonance frequency. This strongly suggests that it is the near-field coupling between the particles that shifts both the coherent electronic oscillation (plasmon) frequency and the coherent lattice oscillation (phonon) frequency. The similar trend in the effect of interparticle coupling on the plasmon frequency and the phonon frequency is essentially a reflection of the universal scaling behavior of the distance decay of the interparticle plasmonic near-field. It is shown that the observed decrease in the lattice oscillation frequency with decrease in the interparticle distance is the result of a reduction in the effective free electron density within each nanoparticle pair partner as a result of the polarizing perturbation of the plasmonic field of the other nanoparticle in the pair. 相似文献
82.
Zinian Wang Marilyn L. Kwan Reina Haque Prashant K. Singh Maciej Goniewicz Rachel Pratt Valerie S. Lee Janise M. Roh Isaac J. Ergas Kimberly L. Cannavale Ronald K. Loo David S. Aaronson Charles P. Quesenberry Yuesheng Zhang Christine B. Ambrosone Lawrence H. Kushi Li Tang 《Molecular nutrition & food research》2024,68(8):2400087
83.
A method for noninvasive thickness measurements of dielectric films using fringe-effect (FE) sensors is developed and experimentally validated. The fringing electrical field, created by electrodes microfabricated at the film substrate, depends on the film thickness and dielectric permittivity of the film under test (FUT). The unknown film thickness is estimated by matching the theoretical prediction of thickness-dependent sensor admittance with the measured value. In the case of FE sensors with spatially periodic, interdigitated electrode (IDE) configuration, the admittance prediction is simplified, which allows for the real-time measurements of changing thickness. The developed method can be used to continuously measure the changing dielectric permittivity of the FUT material, which makes it possible to determine the thickness of films of changing dielectric properties, caused by chemical or other transformations. The application of the developed method is demonstrated experimentally by measuring the thickness of silicon nitride film deposited in several increments on the quartz substrate of the IDE sensor. In the expected range of sensor sensitivity, the results show an excellent agreement with the independent thickness measurements. 相似文献
84.
Rigved Epur Madhumati Ramanathan Faith R. Beck Ayyakkannu Manivannan Prashant N. Kumta 《Materials Science and Engineering: B》2012,177(14):1157-1162
Amorphous silicon has been successfully electrodeposited on copper using a SiCl4 based organic electrolyte under galvanostatic conditions. The electrodeposited silicon films were characterized for their composition, morphology and structural characteristics using glancing angle X-ray diffraction (GAXRD), scanning electron microscopy (SEM), and Raman spectroscopy. GAXRD and Raman analyses clearly confirm the amorphous state of the deposited silicon film. The deposited films were tested for possible application as anodes for Li-ion battery. The results indicate that this binder free amorphous silicon anode exhibits a reversible capacity of ∼1300 mAh g−1 with a columbic efficiency of >99.5% up to 100 cycles. Impedance measurements at the end of each charge cycle show a non-variable charge transfer resistance which contributes to the excellent cyclability over 100 cycles observed for the films. This approach of developing thin amorphous silicon films directly on copper eliminates the use of binders and conducting additives, rendering the process simple, facile and easily amenable for large scale manufacturing. 相似文献
85.
86.
Combined Effect of Ultrasound and Mild Temperatures on the Inactivation of E. coli in Fresh Carrot Juice and Changes on its Physicochemical Characteristics
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87.
A design of a parallel flow solar air heater with packed material in its upper channel and capable of providing a higher heat flux compared to the conventional non-porous bed double flow systems is presented. An analytical model describing the various temperatures and heat transfer characteristics of such a parallel flow packed bed solar air heater (PFPBSAH) has been developed and employed to study the effects of the mass flow rate and varying porosities of the packed material on its thermal performance. The model employs an iterative solution procedure to solve the governing energy balance equations describing the complex heat and mass exchanges involved. To validate the proposed analytical model, comparisons between theoretical and experimental results showed that good agreement is achieved with reasonable accuracy. Also, PFPBSAH is found to perform more efficiently than the conventional non-porous double flow solar air heaters with 10–20% increase in its thermal efficiency. Furthermore, the effect of the fraction of mass flow rate in the upper or lower flow channel of PFPBSAH device on its performance, has also investigated theoretically. The fraction of the mass flow rate in the respective channels of the PFPBSAH is shown to be dominant parameter in determining the effective thermal efficiency of the heater. 相似文献
88.
The market for fruits and vegetables has received considerable interest in recent years, with much of its growth attributed to consumer interest in nutrition and health. Quality has been indicated to be the most important factor in produce sales, and appearance is of noted significance with regard to perceived quality. The broad objectives of this research were to identify the impact of simultaneous colour contrast (i.e. the produce viewed through a mesh bag) on (a) attentive behaviours as measured by eye tracking and (b) perceived quality, visual appeal and purchase intention as measured with a Likert scale. To accomplish these objectives, six different types of produce (red apples, oranges, lemons, green apples, purple onions and white onions) were photographed with four differently coloured mesh treatments: the same (as the produce), complementary, complementary‐analogous and analogous. Visual stimuli were then presented during the eye tracking study and in a subsequent questionnaire. Colour contrast was found to have a significant effect on both resultant eye tracking variables [number of visual fixations (p < 0.001) and time spent (p < 0.001)]. Produce shown with mesh of the same, or an analogous colour, induced significantly more visual fixations and more time than those depicted with complementary or complementary‐analogous treatments. Subsequent to the eye tracking study, subjects were shown the stimuli and asked to rate the expected quality, visual appeal and their purchase intention for the 24 photographs (6 types of produce × 4 colour contrasts) by using a Likert scale. Pairwise comparisons suggested that produce packaged in the same or analogous mesh were perceived by subjects to be of higher quality, more visually appealing and evoked a higher level of purchase intention than those packaged in complementary or complementary‐analogous mesh (α = 0.05). Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
89.
Thanh D. Nguyen Sheng Mao Yao‐Wen Yeh Prashant K. Purohit Michael C. McAlpine 《Advanced materials (Deerfield Beach, Fla.)》2013,25(7):946-974
Electromechanical effects are ubiquitous in biological and materials systems. Understanding the fundamentals of these coupling phenomena is critical to devising next‐generation electromechanical transducers. Piezoelectricity has been studied in detail, in both the bulk and at mesoscopic scales. Recently, an increasing amount of attention has been paid to flexoelectricity: electrical polarization induced by a strain gradient. While piezoelectricity requires crystalline structures with no inversion symmetry, flexoelectricity does not carry this requirement, since the effect is caused by inhomogeneous strains. Flexoelectricity explains many interesting electromechanical behaviors in hard crystalline materials and underpins core mechanoelectric transduction phenomena in soft biomaterials. Most excitingly, flexoelectricity is a size‐dependent effect which becomes more significant in nanoscale systems. With increasing interest in nanoscale and nano‐bio hybrid materials, flexoelectricity will continue to gain prominence. This Review summarizes work in this area. First, methods to amplify or manipulate the flexoelectric effect to enhance material properties will be investigated, particularly at nanometer scales. Next, the nature and history of these effects in soft biomaterials will be explored. Finally, some theoretical interpretations for the effect will be presented. Overall, flexoelectricity represents an exciting phenomenon which is expected to become more considerable as materials continue to shrink. 相似文献
90.
Wei Li Zhiying Zhang Erica G. Bithell Andrei S. Batsanov Phillip T. Barton Paul J. Saines Prashant Jain Christopher J. Howard Michael A. Carpenter Anthony K. Cheetham 《Acta Materialia》2013,61(13):4928-4938
A metal–organic framework perovskite, [(CH2)3NH2][Mn(HCOO)3], exhibits a weakly first order ferroelastic phase transition at ~272 K, from orthorhombic Pnma to monoclinic P21/n, and a further transition associated with antiferromagnetic ordering at ~8.5 K. The main structural changes, through the phase transition, are orientational ordering of the azetidium groups and associated changes in hydrogen bonding. In marked contrast to conventional improper ferroelastic oxide perovskites, the driving mechanism is associated with the X-point of the cubic Brillouin zone rather than being driven by R- and M-point octahedral tilting. The total ferroelastic shear strain of up to ~5% is substantially greater than found for typical oxide perovskites, and highlights the potential of the flexible framework to undergo large relaxations in response to local structural changes. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show some of the characteristic features of ferroelastic materials. In particular, acoustic dissipation below the transition point can be understood in terms of mobility of twin walls under the influence of external stress with relaxation times on the order of ~10?7 s. Elastic softening as the transition is approached from above is interpreted in terms of coupling between acoustic modes and dynamic local ordering of the azetidium groups. Subsequent stiffening with further temperature reduction is interpreted in terms of classical strain–order parameter coupling at an improper ferroelastic transition which is close to being tricritical. By way of contrast, there are no overt changes in elastic or anelastic properties near 9 K, implying that any coupling of the antiferromagnetic order parameter with strain is weak or negligible. 相似文献