Fast Approximate KK-Means via Cluster Closures

$K$-means, a simple and effective clustering algorithm, is one of the most widely used algorithms in multimedia and computer vision community. Traditional $k$-means is an iterative algorithm---in each iteration new cluster centers are computed and each data point is re-assigned to its nearest center. The cluster re-assignment step becomes prohibitively expensive when the number of data points and cluster centers are large. In this paper, we propose a novel approximate $k$-means algorithm to greatly reduce the computational complexity in the assignment step. Our approach is motivated by the observation that most active points changing their cluster assignments at each iteration are located on or near cluster boundaries. The idea is to efficiently identify those active points by pre-assembling the data into groups of neighboring points using multiple random spatial partition trees, and to use the neighborhood information to construct a closure for each cluster, in such a way only a small number of cluster candidates need to be considered when assigning a data point to its nearest cluster. Using complexity analysis, image data clustering, and applications to image retrieval, we show that our approach out-performs state-of-the-art approximate $k$-means algorithms in terms of clustering quality and efficiency

Quad-mode functional and molecular photoacoustic microscopy

A conventional photoacoustic microscopy (PAM) system typically has to make tradeoffs between its spatial resolution and penetration depth, by choosing a fixed configuration of optical excitation and acoustic detection. The single-scale imaging capability of PAM may limit its applications in biomedical studies. Here, we report a quad-mode photoacoustic microscopy (QM-PAM) system with four complementary spatial resolutions and maximum penetration depths. For this we first developed a ring-shaped focused ultrasound transducer that has two independent elements with respective central frequencies at 20 MHz and 40 MHz, providing complementary acoustically-determined spatial resolutions and penetration depths. To accommodate the dual-element ultrasound transducer, we implemented two optical excitation modes to provide tightly-and weakly-focused light illumination. The dual-element acoustic detection combined with the two optical focusing modes can thus provide four imaging scales in a single imaging device, with consistent contrast mechanisms and co-registered field of views. We have demonstrated the multiscale morphological, functional, and molecular imaging capability of QM-PAM in the mouse head, leg and ear in vivo. We expect the high scale flexibility of QM-PAM will enable broad applications in preclinical studies.Peer reviewe

Cross-optical-beam nonlinear photoacoustic microscopy

We present a photoacoustic microscopy (PAM) technique with an optical sectioning capability. By combining crossoptical- beam illumination with nonlinear PAM, an axial resolution of 8.7 μm was measured, demonstrating a fourfold improvement over the acoustically determined value. Compared to methods relying on high-frequency ultrasound transducers to improve the axial resolution, our approach offers a greater working distance and a higher signal-to-noise ratio

Trophic effect of bee pollen on small intestine in broiler chickens

ABSTRACT In this study, the effects of bee pollen on the development of digestive organs were evaluated in broiler chickens. A total of 144 1-day-old AA broiler chickens were randomly and equally divided into two groups, assigned as the control group and the pollen group, respectively. The control group was fed with a basic diet, while the pollen group was fed with a basic diet supplemented with 1.5% bee pollen over a period of 6 weeks. At the end of each week, the digestive organs were obtained for comparison from 12 broilers randomly selected from each group. The results demonstrated that compared to the control group, the small intestine villi from the duodenum, jejunum, and ileum were longer and thicker in the pollen group. This difference was more significant during early development, especially through the first 2 weeks. Bee pollen increased the length of the villi by 37.1% and 29.4% in the duodenum, 28.1% and 33.7% in the jejunum, and 18.6% and 16.2% in the ileum in week 1 and 2, respectively. Furthermore, the small intestinal glands were developed at a higher density in the pollen group, and the depth of the glands was significantly increased by bee pollen in the first 2 weeks. These findings suggest that bee pollen could promote the early development of the digestive system and therefore is a potentially beneficial food supplement for certain conditions, such as short bowel syndrome. KEY WORDS: • bee pollen • duodenum • ileum • jejunum • small intestine gland • small intestine vill

Granulocyte colony-stimulating factor affects the distribution and clonality of TRGV and TRDV repertoire of T cells and graft-versus-host disease

<p>Abstract</p> <p>Background</p> <p>The immune modulatory effect of granulocyte colony-stimulating factor (G-CSF) on T cells resulted in an unexpected low incidence of graft-versus-host disease (GVHD) in allogeneic peripheral blood stem cell transplantation (allo-PBSCT). Recent data indicated that gamma delta⁺T cells might participate in mediating graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effect after allogeneic hematopoietic stem cell transplantation. However, whether G-CSF could influence the T cell receptors (TCR) of gamma delta⁺T cells (<it>TRGV </it>and <it>TRDV </it>repertoire) remains unclear. To further characterize this feature, we compared the distribution and clonality of <it>TRGV </it>and <it>TRDV </it>repertoire of T cells before and after G-CSF mobilization and investigated the association between the changes of TCR repertoire and GVHD in patients undergoing G-CSF mobilized allo-PBSCT.</p> <p>Methods</p> <p>The complementarity-determining region 3 (CDR3) sizes of three <it>TRGV </it>and eight <it>TRDV </it>subfamily genes were analyzed in peripheral blood mononuclear cells (PBMCs) from 20 donors before and after G-CSF mobilization, using RT-PCR and genescan technique. To determine the expression levels of <it>TRGV </it>subfamily genes, we performed quantitative analysis of <it>TRGV</it>I~III subfamilies by real-time PCR.</p> <p>Results</p> <p>The expression levels of three <it>TRGV </it>subfamilies were significantly decreased after G-CSF mobilization (<it>P </it>= 0.015, 0.009 and 0.006, respectively). The pattern of <it>TRGV </it>subfamily expression levels was <it>TRGV</it>II ><it>TRGV </it>I ><it>TRGV </it>III before mobilization, and changed to <it>TRGV </it>I ><it>TRGV </it>II ><it>TRGV </it>III after G-CSF mobilization. The expression frequencies of <it>TRGV </it>and <it>TRDV </it>subfamilies changed at different levels after G-CSF mobilization. Most <it>TRGV </it>and <it>TRDV </it>subfamilies revealed polyclonality from pre-G-CSF-mobilized and G-CSF-mobilized samples. Oligoclonality was detected in <it>TRGV </it>and <it>TRDV </it>subfamilies in 3 donors before mobilization and in another 4 donors after G-CSF mobilization, distributed in <it>TRGV</it>II, <it>TRDV</it>1, <it>TRDV</it>3 and <it>TRDV</it>6, respectively. Significant positive association was observed between the invariable clonality of <it>TRDV</it>1 gene repertoire after G-CSF mobilization and low incidence of GVHD in recipients (<it>P </it>= 0.015, <it>OR </it>= 0.047).</p> <p>Conclusions</p> <p>G-CSF mobilization not only influences the distribution and expression levels of <it>TRGV </it>and <it>TRDV </it>repertoire, but also changes the clonality of gamma delta⁺T cells. This alteration of <it>TRGV </it>and <it>TRDV </it>repertoire might play a role in mediating GVHD in G-CSF mobilized allo-PBSCT.</p

Dual-axis illumination for virtually augmenting the detection view of optical-resolution photoacoustic microscopy

Optical-resolution photoacoustic microscopy (OR-PAM) has demonstrated fast, label-free volumetric imaging of optical-absorption contrast within the quasiballistic regime of photon scattering. However, the limited numerical aperture of the ultrasonic transducer restricts the detectability of the photoacoustic waves, thus resulting in incomplete reconstructed features. To tackle the limited-view problem, we added an oblique illumination beam to the original coaxial optical-acoustic scheme to provide a complementary detection view. The virtual augmentation of the detection view was validated through numerical simulations and tissue-phantom experiments. More importantly, the combination of top and oblique illumination successfully imaged a mouse brain in vivo down to 1 mm in depth, showing detailed brain vasculature. Of special note, it clearly revealed the diving vessels that were long missing in images from original OR-PAM

Monitoring of the central blood pressure waveform via a conformal ultrasonic device.

Continuous monitoring of the central-blood-pressure waveform from deeply embedded vessels, such as the carotid artery and jugular vein, has clinical value for the prediction of all-cause cardiovascular mortality. However, existing non-invasive approaches, including photoplethysmography and tonometry, only enable access to the superficial peripheral vasculature. Although current ultrasonic technologies allow non-invasive deep-tissue observation, unstable coupling with the tissue surface resulting from the bulkiness and rigidity of conventional ultrasound probes introduces usability constraints. Here, we describe the design and operation of an ultrasonic device that is conformal to the skin and capable of capturing blood-pressure waveforms at deeply embedded arterial and venous sites. The wearable device is ultrathin (240 μm) and stretchable (with strains up to 60%), and enables the non-invasive, continuous and accurate monitoring of cardiovascular events from multiple body locations, which should facilitate its use in a variety of clinical environments

Fully motorized optical-resolution photoacoustic microscopy

We have developed fully motorized optical-resolution photoacoustic microscopy (OR-PAM), which integrates five complementary scanning modes and simultaneously provides a high imaging speed and a wide field of view (FOV) with 2.6 μm lateral resolution. With one-dimensional (1D) motion-mode mechanical scanning, we measured the blood flow through a cross section of a blood vessel in vivo. With two-dimensional (2D) optical scanning at a laser repetition rate of 40 kHz, we achieved a 2 kHz B-scan rate over a range of 50 μm with 20 A-lines and 50 Hz volumetric-scan rate over a FOV of 50  μm×50  μm with 400 A-lines, which enabled real-time tracking of cellular dynamics in vivo. With synchronized 1D optical and 2D mechanical hybrid scanning, we imaged a 10  mm×8  mm FOV within three minutes, which is 20 times faster than the conventional mechanical scan in our second-generation OR-PAM. With three-dimensional mechanical contour scanning, we maintained the optimal signal-to-noise ratio and spatial resolution of OR-PAM while imaging objects with uneven surfaces, which is essential for quantitative studies