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51.
Hutchins DA McIntosh JS Neild A Billson DR Noble RA 《The Journal of the Acoustical Society of America》2003,114(3):1435-1449
This paper presents a study of the radiated ultrasonic fields of capacitive micromachined ultrasonic transducers (often referred to as cMUTs) in air. These fields were modeled theoretically and then compared to the experimental near-field amplitude variations and directivity patterns of square cMUTs. The good agreement between theory and experiment indicates that the devices can be approximated to plane piston radiators. The fields of multiple elements driven in phase on the same silicon substrate are presented, where again comparison is made to theory. The results indicate that individual elements are unaffected by radiation through the silicon substrate from adjacent devices. It will also be demonstrated that it is possible to use the knowledge of these fields to develop air-coupled ultrasonic surface imaging systems. 相似文献
52.
Medley AP Billson DR Hutchins DA Neild A 《The Journal of the Acoustical Society of America》2007,122(5):2587-2593
A theoretical approach is described which predicts the fields of acoustic radiators with a predefined surface topography. This is achieved by dividing the surface of the source into small elements, each of which is oriented parallel to the tangent to the surface at that point. The result is an improved modeling performance, in that it is more efficient and requires far fewer elements compared to other numerical approaches using parallel elements. Theoretical predictions are compared to experimental results from curved electrostatic radiators, to demonstrate that the approach has promise. 相似文献
53.
The temperature‐composition phase equilibria of the Hg0.8Cd0.2Te‐HgI2 system were investigated between about 100 and 800 °C using Debye‐Scherrer powder X‐ray diffraction techniques, differential thermal analysis, differential scanning calorimetry, and thermochemical and structural calculations. This system is a pseudobinary temperature‐ composition plane in the HgTe‐CdTe‐HgI2 pseudoternary phase diagram. Measurable solid solutions of HgI2 in Hg0.8Cd0.2Te with the cubic zinc blende‐type structure exist between about 290 and 700 °C, with a maximum solubility of 4.9 ± 0.3 mole‐% HgI2 at 363 ± 3 °C. Further addition of HgI2 to HgI2‐saturated Hg0.8Cd0.2Te yields the formation of CdI2, which reduces the mole fraction (x) of CdTe in the Hg1—xCdxTe host lattice. After sufficient HgI2 is added, the host lattice is depleted in CdTe and forms Hg3Te2I2 in addition to CdI2. Phase fields containing the ternary compound Hg3TeI4, which we first observed in the HgTe‐HgI2 system, also exist in the present system. Quaternary analogs of the known ternary compounds Hg3Te2I2 and Hg3TeI4, i.e., Hg3—yCdyTe2I2 and Hg3—yCdyTeI4, were not observed under present experimental conditions. 相似文献
54.
Hutchins BM Kazane SA Staflin K Forsyth JS Felding-Habermann B Smider VV Schultz PG 《Chemistry & biology》2011,18(3):299-303
We report a strategy for the generation of heterodimeric protein conjugates using an unnatural amino acid with orthogonal reactivity. This paper addresses the challenges of site-specificity and homogeneity with respect to the synthesis of bivalent proteins and antibody-drug conjugates. There are numerous antibody-drug conjugates in preclinical and clinical development, yet these are based either on nonspecific lysine coupling chemistry or on disulfide modification made difficult by the large number of cysteines in antibodies. Here, we describe a recombinant approach that can be used to rapidly generate a variety of constructs with defined conjugation sites. Moreover, this methodology results in homogeneous antibody conjugates whose biological, physical, and pharmacological properties can be quantitatively assessed and subsequently optimized. As proof of concept, we have generated anti-Her2 Fab-Saporin conjugates that demonstrate excellent potency in vitro. 相似文献
55.
Transducers based on a capacitive micromachined ultrasonic transducer (CMUT) design have been fabricated using a rapid prototyping technique. This results in a device that is constructed principally from polymers, in a process which is simple and inexpensive. The resultant devices can be attached to the surfaces of solids. Their peak sensitivity is in the 80–100 kHz range, making them ideal for applications such as acoustic emission and structural health monitoring. Good low frequency sensitivity leads to applications in vibration monitoring. 相似文献
56.
Heribert Wiedemeier Mark A. Hutchins Yuri Grin Claus Feldmann Hans Georg von Schnering 《无机化学与普通化学杂志》1997,623(11):1843-1846
The structure of cubic Hg3TeI4 was determined from powder data. The four positions of the cubic closestpacking of the anions are statistically occupied by 0.8 Te-atoms and 3.2 I-atoms. The two types of tetrahedral holes are occupied to the extent of 2/4 and 0.4/4, respectively, by Hg-atoms. With an ordered model of lower symmetry, the stoichiometric composition can be explained and a homogeneous charge distribution can be achieved. The ordered model contains regions of the structure of red HgI2, which are connected by fragments of the SiS2-type. 相似文献
57.
A wide bandwidth 1–3 connectivity piezocomposite air transducer has been used to detect laser-generated ultrasound in a variety of composite materials. Through thickness waveforms in various carbon fibre reinforced polymer (CFRP) composite plates will be presented, as well as a selection of Lamb waves. Signals were also obtained in samples of pultruded glass fibre reinforced composite of different thickness. Using the laser/air-transducer system, images were obtained of machined defects and delaminations by conventional C-scanning methods, and tomographic reconstruction techniques. 相似文献
58.
Kristin M. Hutchins Ryan H. Groeneman Eric W. Reinheimer Dale C. Swenson Leonard R. MacGillivray 《Chemical science》2015,6(8):4717-4722
Thermal expansion involves a response of a material to an external stimulus that typically involves an increase in a crystallographic axis (positive thermal expansion (PTE)), although shrinking with applied heat (negative thermal expansion (NTE)) is known in rarer cases. Here, we demonstrate a means to achieve dynamic molecular motion and thermal expansions in organic solids via co-crystallizations. One co-crystal component is known to exhibit dynamic behaviour in the solid state while the second, when varied systematically, affords co-crystals with linear thermal expansion coefficients that range from colossal to nearly zero. Two co-crystals exhibit rare NTE. We expect the approach to guide the design of molecular solids that enable predesigned motion related to thermal expansion processes. 相似文献
59.
An industrial TEA-CO2 laser, operating at a wavelength of 10.6 μm, has been used to produced broadband ultrasonic pulses in polymers. The generation mechanism falls into three categories. At low power densities ≤ 107 W cm−2 a thermoelastic regime predominates. As the power density is increased in the range (1–5) × 107 W cm−2 ablation of the material surface plays an increasingly important role in the acoustic generation. Thirdly, at greater power densities, plasma breakdown just above the material surface serves as the means of generation. This paper describes the acoustic sources for these types of generation mechanism and presents theoretically calculated acoustic waveforms to match those recorded experimentally. 相似文献
60.
An electrode assembly suitable for voltammetric analysis of very small sample volumes, in vitro or (vivo), has been constructed inside a catheter. Well-defined differential pulse current peaks have been obtained for acetaminophen, chlorpromazine and ascorbic acid at the submillimolar concentration level. Voltamperograms recorded for rhesus monkey blood in vivo and in vitro were similar. 相似文献