Thermal alterations of potassium exchangeability in micaceous mineral particles of different size

The exchangeability of interlayer K in micaceous minerals is governed by the conditions imposed by the solution around the particles and the mineral properties themselves. This study focused on the role of mineral properties by relating the K extracted by NaCl-NaTPB solutions to differences in existing and thermally altered properties of selected minerals. The relevance of particle size, mixed layering and dioctahedral structures were emphasized by using size-fractions of ground muscovite, \u3c 2 (mu)m fractions of Tumut and Grundite illites and four trioctahedral mica-vermiculites;When the micaceous minerals were heated, several changes in K exchangeability occurred and the minerals lost weight by dehydration and dehydroxylation. Dehydroxylation enhanced the rate and amount of K release in all the dioctahedral minerals by increasing the interlayer spacing. Mica-vermiculites with mixed layering yielded the same thermal response even though trioctahedral micas behaved otherwise and there was no evidence of dehydroxylation involvement. The minerals varied in their response to temperatures under 400(DEGREES)C, but dehydration was not an obvious factor. These low temperatures reduced layer weathering and thereby provided a means of detecting this mechanism of K release. Layer weathering was a significant factor in ground micas, not in the illites. In the absence of dehydroxylation, reductions in edge weathering also occurred in many heated samples. The thermally induced changes in layer and edge weathering probably stemmed from a reduction in interlayer spacing. If so, a similar explanation should be considered for the limited K release in small particles because the relevance of layer weathering was eliminated by comparisons of heated illites and ground mica. X-ray diffraction studies verified the occurrence of structural alterations but not a measurable decrease in interlayer spacing. However, the small particle effect in illites was circumvented by the expanding effects of dehydroxylation. Mixed layering plays a major role in the thermal responses of mica-vermiculites but has no identifiable effect on K exchange in unheated minerals;The interlayer spacing and condition of the lateral edges of the mineral particles appear to dominate the exchangeability of interlayer K

Robust Affinity Propagation using Preference Estimation

Affinity propagation is a novel unsupervised learning algorithm for exemplar-based clustering without the priori knowledge of the number of clusters (NC). In this article, the influence of the “preference” on the accuracy of AP output is addressed. We present a robust AP clustering method, which estimates what preference value could possibly yield an optimal clustering result. To demonstrate the performance promotion, we apply the robust AP on picture clustering, using local SIFT, global MPEG-7 CLD, and the proposed preference as the input of AP. The experimental results show that over 40% enhancement of ARI accuracy for several image datasets

Ultrasound array photoacoustic microscopy for dynamic in vivo 3D imaging

Using realtime ultrasound array photoacoustic microscopy (UA-PAM), we demonstrated the feasibility of noninvasive in vivo imaging of human pulsatile dynamics, as well as 3-D dynamic imaging of sentinel lymph nodes (SLNs) in a murine model. The system, capable of realtime B-scan imaging at 50 Hz and high-speed 3-D imaging, was validated by imaging the subcutaneous microvasculature in rats and humans. After the validation, a human superficial palmar was imaged, and its pulsatile dynamics monitored, with 20-ms B-scan imaging temporal resolution. In addition, noninvasive photoacoustic sentinel lymph node (SLN) mapping with high spatial resolution has the potential to reduce the false negative rate and eliminate the use of radioactive tracers. Upon intra-dermal injection of Evans blue, the system maps SLNs accurately in mice and rats. Furthermore, the ~6 s 3-D imaging temporal resolution offers the capability to quantitatively and noninvasively monitor the dye dynamics in SLNs in vivo through sequential 3-D imaging. The demonstrated capability suggests that high-speed 3-D photoacoustic imaging should facilitate the understanding of the dynamics of various dyes in SLNs, and potentially help identify SLNs with high accuracy. With the results shown in this study, we believe that UA-PAM can potentially enable many new possibilities for studying functional and physiological dynamics in both preclinical and clinical imaging settings

Adaptive fast block-matching algorithm by switching search patterns for sequences with wide-range motion content

[[abstract]]Content with rapid, moderate, and slow motion is frequently mixed together in real video sequences. Until now, no fast block-matching algorithm (FBMA), including the well-known three-step search (TSS), the block-based gradient descent search (BBGDS), and the diamond search (DS), can efficiently remove the temporal redundancy of sequences with wide range motion content. This paper proposes an adaptive FBMA, called A-TDB, to solve this problem. Based on the characteristics of a proposed predicted profit list, the A-TDB can adaptively switch search patterns among the TSS, DS, and BBGDS, according to the motion content. Experimental results reveal that the A-TDB successfully adopts the search patterns to remove the temporal redundancy of sequences with slow, moderate and rapid motion content.[[fileno]]203021101000

Fast 3-D photoacoustic imaging in vivo with a high frequency ultrasound array toward clinical applications

We present an in vivo reflection-mode photoacoustic microscopy system that performs B-scan imaging at 50 Hz with realtime beamforming and 3-D imaging of 166 B-scan frames at 1 Hz with post-beamforming. To our knowledge, this speed is currently the fastest in high frequency photoacoustic imaging. In addition, with a custom fiber based light delivery system, the imaging device is capable of performing handheld operation. Software for image processing and display with clinically user-friendly graphic user interface (GUI) is developed. The system has axial, lateral, and elevational resolutions of 25, 70, and 200 μm, respectively, and can image 3 mm deep in scattering biological tissue. Volumetric images of subcutaneous vasculature in murine are demonstrated in vivo. The system is anticipated to have potential clinical applications in skin melanoma detection due to its unique ability to image in realtime and to image anatomical sites inaccessible to other imaging systems

Fast 3-D dark-field reflection-mode photoacoustic microscopy in vivo with a 30-MHz ultrasound linear array

We present an in vivo dark-field reflection-mode photoacoustic microscopy system that performs cross-sectional (B-scan) imaging at 50Hz with real-time beamforming and 3-D imaging consisting of 166 B-scan frames at 1Hz with postbeamforming. To our knowledge, this speed is currently the fastest in photoacoustic imaging. A custom-designed light delivery system is integrated with a 30-MHz ultrasound linear array to realize dark-field reflection-mode imaging. Linear mechanical scanning of the array produces 3-D images. The system has axial, lateral, and elevational resolutions of 25, 70, and 200μm, respectively, and can image 3mm deep in scattering biological tissues. Volumetric images of subcutaneous vasculature in rats are demonstrated in vivo. Fast 3-D photoacoustic microscopy is anticipated to facilitate applications of photoacoustic imaging in biomedical studies that involve dynamics and clinical procedures that demand immediate diagnosis

Realtime Photoacoustic Microscopy of Murine Cardiovascular Dynamics

Non-invasive visualization of cardiovascular dynamics in small animals is challenging due to their rapid heart-rates. We present a realtime photoacoustic imaging system consisting of a 30-MHz ultrasound array transducer, receive electronics, a high-repetition-rate laser, and a multicore-computer, and demonstrate its ability to image optically-absorbing structures of the beating hearts of young athymic nude mice at rates of ~50 frames per second with 100 µm×25 µm spatial resolution. To our knowledge this is the first report of realtime photoacoustic imaging of physiological dynamics

A 3-D High-Frequency Array Based 16 Channel Photoacoustic Microscopy System for In Vivo Micro-Vascular Imaging

This paper discusses the design of a novel photoacoustic microscopy imaging system with promise for studying the structure of tissue microvasculature for applications in visualizing angiogenesis. A new 16 channel analog and digital high-frequency array based photoacoustic microscopy system (PAM) was developed using an Nd: YLF pumped tunable dye laser, a 30 MHz piezo composite linear array transducer, and a custom multichannel receiver electronics system. Using offline delay and sum beam- forming and beamsteering, phantom images were obtained from a 6 µm carbon fiber in water at a depth of 8 mm. The measured -6 dB lateral and axial spatial resolution of the system was 100 ± 5 µm and 45 ± 5 µm, respectively. The dynamic focusing capability of the system was demonstrated by imaging a composite carbon fiber matrix through a 12.5 mm imaging depth. Next, 2-D in vivo images were formed of vessels around 100 µm in diameter in the human hand. Three-dimensional in vivo images were also formed of micro-vessels 3 mm below the surface of the skin in two Sprague Dawley rats

Imaging microvascular dynamics noninvasively with realtime photoacoustic microscopy

A realtime photoacoustic microscopy system consisting of a high-repetition rate pulsed laser, high-frequency (30 MHz) ultrasound array transducer, and realtime receiving system was used to visualize microvessels pulsations over a cardiac cycle. The system offers 100 μm lateral spatial resolution, 25 µm axial spatial resolution, and can image at a rate of 83 frames per second. The system shows promise for visualizing time-varying processes in the microvasculature