Fine elasticity imaging utilizing the iterative RF-echo phase matching method

To non-invasively quantify elasticity of soft tissue, we previously developed the iterative two-dimensional (2-D) rf-echo phase matching method for accurately measuring a 2-D displacement vector field generated in vivo in soft tissue during acquisition of two successive rf-echo data frames. We also developed a stable method for uniquely reconstructing a shear modulus distribution using strains derived from the measurement data. However, as in our measurement method a displacement is determined by using the phase characteristics of the finite local echo data as the index to iteratively search for the corresponding local data, change of the local phase characteristics due to tissue deformation deteriorates the accuracy of the determination. Thus, we improve the previous method such that, in principle, the displacement can be determined using an infinitesimal phase characteristics. That is, we incorporate an effective mechanism into the previous iterative phase matching scheme: the local size is made suitably smaller during the iterative phase matching. The demonstrated ability of measurement and reconstruction in simulation, and experiments on in vitro in pork rib and in vivo in breast tissue, shows this refinement allows not only better spatial resolution of the shear modulus image but also improved accuracy, and indicates that the improved method has a high potential to be applied for various soft tissues.     

Simultaneous measurement of velocity and length of moving surfaces by a speckle velocimeter with two self-mixing laser diodes

A novel laser speckle velocimeter with two self-mixing laser diodes (SM-LD's) for velocity and length measurements of moving surfaces is reported. The mean frequency of the speckle signal obtained in the measurement system depends on the surface path illuminated by the SM-LD. This behavior of the speckle signal in the SM-LD's is exploited to detect the front and the end edges of a target surface by sampling continuously the number of intensity changes in a speckle signal waveform. Once the edges are determined, the velocity and the length of the surface are calculated easily. The error for length and velocity measurements of a target with a homogeneous rough plane surface of 60-mm length, moving at a velocity of 200 mm/s, can be as low as 2.1% and 1.75%, respectively.     

Collaborative capturing, interpreting, and sharing of experiences

This paper proposes a notion of interaction corpus, a captured collection of human behaviors and interactions among humans and artifacts. Digital multimedia and ubiquitous sensor technologies create a venue to capture and store interactions that are automatically annotated. A very large-scale accumulated corpus provides an important infrastructure for a future digital society for both humans and computers to understand verbal/non-verbal mechanisms of human interactions. The interaction corpus can also be used as a well-structured stored experience, which is shared with other people for communication and creation of further experiences. Our approach employs wearable and ubiquitous sensors, such as video cameras, microphones, and tracking tags, to capture all of the events from multiple viewpoints simultaneously. We demonstrate an application of generating a video-based experience summary that is reconfigured automatically from the interaction corpus.

A strategy of automatic hexahedral mesh generation by using an improved whisker-weaving method with a surface mesh modification procedure

One of the demands for three dimensional (3D) finite element analyses is the development of an automatic hexahedral mesh generator. For this problem, several methods have been proposed by many researchers. However, reliable automatic hexahedral mesh generation has not been developed at present. In this paper, a new strategy of fully automatic hexahedral mesh generation is proposed. In this strategy, the prerequisite for generating a hexahedral mesh is a quadrilateral surface mesh. From the given surface mesh, combinatorial dual cycles (sheet loops for the whisker-weaving algorithm) are generated to produce a hexahedral mesh. Since generating a good quality hexahedral mesh does not depend only on the quality of quadrilaterals of the surface mesh but also on the quality of the sheet loops generated from it, a surface mesh modification method to remove self-intersections from sheet loops is developed. Next, an automatic hexahedral mesh generator by the improved whisker-weaving algorithm is developed in this paper. By creating elements and nodes on 3D real space during the weaving process, it becomes possible to generate a hexahedral mesh with fewer bad-quality elements. Several examples will be presented to show the validity of the proposed mesh generation strategy.     

Human Activity Recognition and Pattern Discovery

Activity recognition and activity pattern discovery hold significant promise to enabling many applications in the domain of human behavior monitoring, understanding and alteration. However, concurrent, interleaved and highly similar activities challenge the utility of existing approaches. In this installment of the Standards and Emerging Technologies column we survey the state of the art and point to crucial limitations worthy of additional research and investigations.     

Reliability of power cycling for IGBT power semiconductor modules

Power cycling capability is one of the most important reliability items in the application of power semiconductor modules. This paper describes the failure mechanism of power cycling by analysis of the structure of lead-based solder and joint failure due to solder fatigue. By the application of some additional elements, it has been found that a newly developed tin-silver-based solder shows both excellent mechanical properties and wettability. Further, we have established, both by experiment and computer calculation, that the dependence of the failure mechanism on /spl Delta/Tj is completely different between the new tin-silver-based solder and conventional lead-based solder. According to these evaluations, it has become clear that the power cycling lifetime of the new tin-silver-based solder depends on the solder joint at higher than around 110 K, while it depends on the aluminum wire bonds at lower than around 50 K. As a result, higher power cycling capability can be successfully achieved by using this newly developed solder instead of conventional lead-based solder.     

Chemical and biological degradation of 5-fluorouracil prodrugs having high serum albumin binding potencies

In order to understand the fundamental structural features which yield both high serum albumin binding potency and desired property as a prodrug, the derivatization was performed at N-1 or N-3 position in 5-fluorouracil. The N-3 derivatives were more stable than N-1 derivatives in vitro, whereas they were metabolized quickly in vivo. It is suggested that N-1 position should be blocked to avoid fast metabolism in vivo.     

Similarity graphing and enzyme-reaction database: methods to detect sequence regions of importance for recognition of chemical structures

We developed a new method which searches sequence segments responsiblefor the recognition of a given chemical structure. These segmentsare detected as those locally conserved among a sequence tobe analyzed (target sequence) and a set of sequences (referencesequences). Reference sequences are the sequences of functionallyrelated proteins, ligands of which contain a common chemicalsubstructure in their molecular structures. ‘Similaritygraphing’ cuts target sequences into segments, alignsthem with reference sequence pairwise, calculates the degreeof similarity for each alignment, and shows graphically cumulativesimilarity values on target sequence. Any locally conservedregions, short or long in length and weak or strong in similarity,are detected at their optimal conditions by adjusting threeparameters. The ‘enzyme-reaction database’ containschemical structures and their related enzymes. When a chemicalsubstructure is input into the database, sequences of the enzymesrelated to the input substructure are systematically searchedfrom the NBRF sequence database and output as reference sequences.Examples of analysis using similarity graphing in combinationwith the enzyme-reaction database showed a great potentialityin the systematic analysis of the relationships between sequencesand molecular recognitions for protein engineering.     

A robust numerical solution to reconstruct a globally relativeshear modulus distribution from strain measurements

To noninvasively quantify tissue elasticity for differentiating malignancy of soft tissue, the authors previously proposed a two-dimensional (2-D) mechanical inverse problem in which simultaneous partial differential equations (PDE's) represented the target distribution globally of relative shear moduli with respect to reference shear moduli such that the relative values could be determined from strain distributions obtained by conventional ultrasound (US) or nuclear magnetic resonance (NMR) imaging-based analysis. Here, the authors further consider the analytic solution in the region of interest, subsequently demonstrating that the problem is inevitably ill-conditioned in real-world applications, i.e., noise in measurement data and improper configurations of mechanical sources/reference regions make it impossible to guarantee the existence of a stable and unique target global distribution. Next, based on clarification of the inherent problematic conditions, the authors describe a newly developed numerical-based implicit-integration approach that novelly incorporates a computationally efficient regularization method designed to solve this differential inverse problem using just low-pass filtered spectra derived from strain measurements. To evaluate method effectiveness, reconstructions of the global distribution are carried out using intentionally created ill-conditioned models. The resultant reconstructions indicate the robust solution is highly suitable, while also showing it has high potential to be applied in the development of an effective yet versatile diagnostic tool for quantifying the distribution of elasticity in various soft tissues     

Ubiquitous Experience Media

We exploit recorded activities as a good source of human-human and human-robot communication for sharing experience, memory, and knowledge. In particular, we're interested in audiovisual, ubiquitous, and wearable-experience-capturing technology as interaction-grounded lifelong tools. We've developed several devices - such as a wearable interaction tracker - that facilitate an indexed recording of human experiences