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101.
Abstract

The use of crustacean shells, in particular crab shells, for the removal of metal ions in solution is described. Research studies found in the literature on the ability of the shells, effect of particle size, pH, competitive studies in mixtures of metals, application to real samples such as acid mine drainage, and use of the shells in a column are presented. The major component of the shells that allows uptake to occur is chitin. Several mechanisms are proposed for uptake. There are conflicting accounts in the literature on such areas as the effect of pH, flow rate, and particle size.  相似文献   
102.
A new mechanism for exciting cavitation has been identified. Surface-reflected shock waves can produced localized spalling in liquids. This spalling mechanism forms cavities which then collapse under the influence of gravity and atmospheric pressure. The form of the closure pulses generated by cavity collapse characterizes this new type of cavitation.  相似文献   
103.
Optics and Spectroscopy - Scattering of light by disordered structures is normally detrimental to their applicability in many optoelectronic devices. However, some micro and nanostructures are...  相似文献   
104.
Near-field optical trapping can be realized with focused evanescent waves that are excited at the water–glass interface due to the total internal reflection, or with focused plasmonic waves excited on the water–gold interface. Herein, the performance of these two kinds of near-field optical trapping techniques is compared using the same optical microscope configuration. Experimental results show that only a single-micron polystyrene bead can be trapped by the focused evanescent waves, whereas many beads are simultaneously attracted to the center of the excited region by focused plasmonic waves. This difference in trapping behavior is analyzed from the electric field intensity distributions of these two kinds of focused surface waves and the difference in trapping behavior is attributed to photothermal effects due to the light absorption by the gold film.  相似文献   
105.
Thirteen patients with biopsy proven hepatic lymphoma (2 Hodgkin, 11 Non-Hodgkin) and a control group of 15 patients with hepatic metastases were analyzed quantitatively and qualitatively by MRI. Focal hepatic lymphoma was most reliably detected (eight of eight patients) and appeared hypointense relative to liver on T1 weighted (CNR − 7.4 ± 2.3) and hyperintense on T2 weighted (CNR + 8.4 ± 2.9) images. The mean T1 and T2 relaxation times of focal hepatic lymphoma (T1 = 832 ± 234 msec, T2 = 84 ± 16 ms) differed significantly from adjacent non-tumorous liver (T1 = 420 ± 121 ms, T2 = 51 ± 9 ms; p < 0.05), however CNR values and relaxation times were similar to those of hepatic metastases. Diffuse hepatic lymphoma (microscopic periportal infiltration) was undetectable by MRI in three patients by either morphologic features or quantitative criteria. A mixed pattern of hepatic lymphoma (focal lesions and diffuse infiltration) showed focal areas of slightly decreased signal intensity on T1 weighted images (CNR = −1.7 ± 0.4) while T2 weighted images revealed multiple regions of focal hyperintensity (CNR = +13.3 ± 8.4) superimposed on a diffusely hyperintense liver. Our experience demonstrates that either T1 or T2 weighted techniques are useful in detecting focal and that T2 weighted techniques are useful in detecting mixed hepatic lymphoma. Conventional image derived relaxation time measurements and quantitative parameters were of no additional diagnostic value.  相似文献   
106.
We discuss quantum insights due to the null-strut formalism. These insights deal primarily with two topics: the formalism of a theory of canonical simplicial quantum gravity based on the geometrodynamic duality of null-strut calculus, and the natural implementation of spinors and spin networks in null-strut calculus.  相似文献   
107.
We report on a comparative study of two methods of chemical shift imaging which can be used to selectively image fat and water in vivo. Both methods require a B0 field sufficiently homogenous to resolve the methylene and water spectral lines. One method, called CHESS, uses a chemically selective pulse to saturate the unwanted spectral line. The other method, called SECSI, achieves chemical selectivity by using a soft 180 degree RF pulse in forming a spin echo image. Both methods require that the strength of the B1 RF field be accurately calibrated and homogenous. We show by theoretical analysis that the suppression of unwanted spectral lines is sensitive to the first power of B1 errors in the CHESS method but to the second power of B1 errors in the SECSI method. Experiments with phantoms confirmed the expected non linearity of the SECSI method, and showed superior water suppression factors in phantoms with it. Experiments with a large phantom and a living rabbit showed superior results using the SECSI method, and the best results were obtained using a combination of the two techniques.  相似文献   
108.
A healthy voice depends upon healthy respiration. An understanding of respiratory function is essential in evaluating disorders that affect the voice. This review addresses the assessment of respiratory complaints by history, physical examination, laboratory testing, and endoscopic procedures. Allergy testing and pulmonary function testing are covered in detail. Special problems that confront the professional voice user, such as the need to optimize respiratory function even in mild disease states, exposure to environmental irritants, and the athletic demands of performance, are related specifically to respiratory function. The discussion of diagnosis and treatment of common ailments such as allergic rhinitis and bronchitis is directed toward treatment of the active singer.  相似文献   
109.
Summary The stick-slip problem for a round jet studied in Part I gives a good approximation for the swell of a low speed jet when the surface tension is large but it fails when the surface tension is small. In this paper a new stick-slip problem (II) is defined and solved using matched eigenfunction expansions. The new problem reduces to that solved in Part I when the surface tension is large and gives good results in the case of zero and small surface tension.With 18 figures  相似文献   
110.
A moiré method for processing optical image-plane holograms of acoustic fields is introduced. Derivatives of acoustic pressure with respect to space, time and other system variables can be obtained by this extension of holographic interferometry methods. The new method is employed to obtain simultaneous, independent measurements of acoustic pressure and particle acceleration. It is also demonstrated that moiré processes can improve the sensitivity of optical, whole field measurements at least 30 times.  相似文献   
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