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Acoustic Microscopy (acoustic + microscopy)
Selected AbstractsTime-resolved Acoustic MicroscopyIMAGING & MICROSCOPY (ELECTRONIC), Issue 3 2007Dynamical Processes in Cell Biology Recent growth of interest in the mechanical properties of cells demands for the development of new techniques for the assessement of these atributes. Acoustic microscopy equipped with time-resolved signal analysis provides unique possibilities for the determination of dynamical processes in biological cells and allows probing biological specimen with submicrometre resolution. [source] Elastic properties of dry clay mineral aggregates, suspensions and sandstonesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Tiziana Vanorio SUMMARY The presence of clay minerals can alter the elastic behaviour of rocks significantly. Although clay minerals are common in sedimentary formations and seismic measurements are our main tools for studying subsurface lithologies, measurements of elastic properties of clay minerals have proven difficult. Theoretical values for the bulk modulus of clay are reported between 20 and 50 GPa. The only published experimental measurement of Young's modulus in a clay mineral using atomic force acoustic microscopy (AFAM) gave a much lower value of 6.2 GPa. This study has concentrated on using independent experimental methods to measure the elastic moduli of clay minerals as functions of pressure and saturation. First, ultrasonic P - and S -wave velocities were measured as functions of hydrostatic pressure in cold-pressed clay aggregates with porosity and grain density ranging from 4 to 43 per cent and 2.13 to 2.83 g cm,3, respectively. In the second experiment, P - and S -wave velocities in clay powders were measured under uniaxial stresses compaction. In the third experiment, P -wave velocity and attenuation in a kaolinite,water suspension with clay concentrations between 0 and 60 per cent were measured at ambient conditions. Our elastic moduli measurements of kaolinite, montmorillonite and smectite are consistent for all experiments and with reported AFAM measurements on a nanometre scale. The bulk modulus values of the solid clay phase (Ks) lie between 6 and 12 GPa and shear (,s) modulus values vary between 4 and 6 GPa. A comparison is made between the accuracy of velocity prediction in shaley sandstones and clay,water and clay,sand mixtures using the values measured in this study and those from theoretical models. Using Ks= 12 GPa and ,s= 6 GPa from this study, the models give a much better prediction both of experimental velocity reduction due to increase in clay content in sandstones and velocity measurements in a kaolinite,water suspension. [source] Changes of articular cartilage after immobilization in a rat knee contracture modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2009Yoshihiro Hagiwara Abstract The objective was to determine the changes of articular cartilage of the knee joint during immobilization in a rat model. The knee joints of adult male rats were immobilized at 150° of flexion using an internal fixator for 3 days, and 1, 2, 4, 8, and 16 weeks. The articular cartilage from the medial midcondylar region of the knee was obtained, divided into three areas (non-contact area, transitional area, contact area), and in each area, a degree of degeneration was evaluated by gross observation, histomorphometric grading, and measurements of thickness and number of chondrocytes. Elasticity of the articular cartilage was estimated by measuring the sound speed with use of scanning acoustic microscopy. Degeneration of the articular cartilage was mainly observed in the contact and transitional areas. Matrix staining intensity by safranin-O and number of chondrocytes were decreased in these two areas. The thickness of the articular cartilage in the non-contact and contact areas was unchanged, but it was increased in the transitional area. Decrease in sound speed was observed in the transitional area of both the femoral and tibial cartilage, indicating the softening of the articular cartilage. The changes of articular cartilage became obvious as early as 1 week after immobilization. These changes may be due to a lack of mechanical stress or a lack of joint fluid circulation during immobilization. Although we do not know the reversibility of these changes of articular cartilage, early mobilization is preferable to avoid these cartilage changes. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:236,242, 2009 [source] Evaluation by scanning acoustic microscopy (SAM) on glomerular lesion of IgA nephropathyNEPHROLOGY, Issue 2001H Kiyomoto IgA nephropathy (IgAN) is known to commonly cause of end-stage renal failure in Japan. The glomerular lesions of IgAN have histological variations. The determination of prognosis and therapeutic strategy should be carefully done by experts because morphological information from renal biopsies using ordinary optical microscopy is usually qualitative and subjective. Moreover, the histological items for the evaluation of glomerular lesions seems to be unsatisfactory for expression of the disease condition of IgAN. The beneficial properties of scanning acoustic microscopy (SAM) include not only observation of microstructure but also quantitative measurement of acoustic propagation speed (APS), indicating the tissue elasticity. In the present study we compared the APS of glomeruli with the pathological scores that were determined by ordinary light microscopy. We used stocked human renal biopsy specimens diagnosed as IgAN (n = 12) and normal/minimal changes (n = 5). All samples were taken by renal biopsy in Kagawa Medical University Hospital during 1997,2000 under informed consent of the patients. The obtained renal tissue were immersed in 10% formalin and embedded in paraffin. A fixed specimen was consecutively cut into 4 ,m slices. One of the deparaffinized 4 ,m-specimens was directly utilized for SAM without any staining, and the others were stained with haematoxylin-eosin and Masson Trichrome for counting cell number and evaluation of collagen accumulation. For the measurement of glomerular APS, the sample line was set on the equator of the glomerulus and then scanning of the X,Z axis was carried out to obtain the interference fringes that were analysed with a computer imaging software in order to calculate the APS. In light microscopic study, pathological scores were evaluated semiquantitatively by two independent investigators who were unaware of the sample number. Glomerular lesions were scored into five grades and glomerular cell number was also counted in individual glomerulus. The computer-assisted imaging analyser Win ROOF (Mitani, Fukui, Japan) was also used for the determination of glomerular collagen content in specimens stained by Masson Trichrome. A two-dimensional image (C-mode scanning) of SAM enabled imaging of glomerulus in renal biopsy specimen compatible with findings of ordinary light microscopy without staining dye. The glomerular APS in IgAN was significantly higher than in normal/minimal changes. This alteration of glomerular APS in IgAN was positively correlated to both semiquantitative pathological scores and glomerular collagen content determined by light microscopy. However, the cell number of glomelurus did not change between IgAN and normal/minimal change. As a result, we conclude that the glomerular lesion, especially matrix expansion in IgAN, was comparable with the absolute value among specimens. Therefore, it is suggested that SAM method is a novel and useful technique for quantitative evaluation of glomerular lesion in IgAN. [source] | ||||||||||