Multiresolution imaging in elastography

The range of strains that can be imaged by any practical elastographic imaging system is inherently limited, and a performance measure is valuable to evaluate these systems from the signal and noise properties of their output images. Such a measure was previously formulated for systems employing cross-correlation based time-delay estimators through the strain filter. While the strain filter predicts the signal-to-noise ratio (SNR(e)) for each tissue strain in the elastogram and provides valuable insights into the nature of image noise, it understated the effects of image resolution (axial resolution, as determined by the cross-correlation window length) on the noise. In this work, the strain filter is modified to study the strain noise at multiple resolutions. The effects of finite window length on signal decorrelation and on the variance of the strain estimator are investigated. Long-duration windows are preferred for improved sensitivity, dynamic range, and SNR(e). However, in this limit the elastogram is degraded due to poor resolution. The results indicate that for nonzero strain, a window length exists at which the variance of strain estimator attains its minima, and consequently the elastographic sensitivity, dynamic range and SNR(e) are strongly affected by the selected window length. Simulation results corroborate the theoretical results, illustrating the presence of a window length where the strain estimation variance is minimized for a given strain value. Multiresolution elastography, where the strain estimate with the highest SNR(e) obtained by processing the pre- and post-compression waveforms at different window lengths is used to generate a composite elastogram and is proposed to improve elastograms. All the objective elastogram parameters (namely: SNR(e), dynamic range, sensitivity and the average elastographic resolution-defined as the cross-correlation window length) are improved with multiresolution elastography when compared to the traditional method of utilizing a single window length to generate the elastogram. Experimental results using a phantom with a hard inclusion illustrates the improvement in elastogram obtained using multiresolution analysis.     

In Vivo Sequestration of Innate Small Molecules to Promote Bone Healing

Approaches that enable innate repair mechanisms hold great potential for tissue repair. Herein, biomaterial-assisted sequestration of small molecules is described to localize pro-regenerative signaling at the injury site. Specifically, a synthetic biomaterial containing boronate molecules is designed to sequester adenosine, a small molecule ubiquitously present in the human body. The biomaterial-assisted sequestration of adenosine leverages the transient surge of extracellular adenosine following injury to prolong local adenosine signaling. It is demonstrated that implantation of the biomaterial patch following injury establishes an in situ stockpile of adenosine, resulting in accelerated healing by promoting both osteoblastogenesis and angiogenesis. The adenosine content within the patch recedes to the physiological level as the tissue regenerates. In addition to sequestering endogenous adenosine, the biomaterial is also able to deliver exogenous adenosine to the site of injury, offering a versatile solution to utilizing adenosine as a potential therapeutic for tissue repair.     

PVDF-SIC Composite Thick Films an Effective ESD Composition for Growing Anti-static Applications

Journal of Electronic Materials - Thin polyvinylidene fluoride-silicon carbide (PVDF-SiC) shielding composite films were prepared by a simple solution casting process. X-ray diffraction (XRD) and...     

Improved Merkle Hash Tree-Based One-Time Signature Scheme for Capability-Enhanced Security Enforcing Architecture for Named Data Networking

The concept of network caching is determined to be the potential requirement of named data networks (NDN) for enhancing the capabilities of the traditional IP networking. It is responsible for location independent data accesses and optimal bandwidth utilization in multi-path data dissemination. However, the network caching process in NDN introduces security challenges such as content cache poisoning, malicious injection or flooding of the packets and violation in accessing content packets. In this paper, an Improved Merkle Hash Tree-based one-time signature scheme for capability-enhanced security enforcing architecture (IMHT-OTSS-CSEA) is proposed for provisioning data authenticity in a distributed manner for leveraging the capabilities to inform the access privileges of the packets during the process of data dissemination. It is proposed for permitting the routers to verify the forwarded packets’ authenticity in NDN. It is capable in handling the issues that emerge from unsolicited packets during a flooding-based denial of service attacks by supporting the indispensable verification process in routers that confirms the timeliness of packets. The simulation experiments conducted using the open source CCNs platform and Planetlab confirmed a significant mean reduction in delay of 14.61%, superior to the benchmarked schemes. It is identified to minimize the delay incurred in generating bit vectors by a average margin of 13.06%, excellent to the baseline approaches. It also confirmed a mean increase in the true positive rate of 5.42%, a mean increase in the precision rate of 6.04%, decrease in false positive rate of 6.82% and increase in F-measure of 5.62% compared to the baseline approaches in the context of detecting content cache pollution attack respectively.

     

Decision Making in the Battlefield-of-Things

Wireless Personal Communications - This paper accentuates the paradigm shift in battlefield-environments. In perspective of a decision-maker to enable shrinking of his decision-cycle, the...     

Gas transport through nano and micro composites of natural rubber (NR) and their blends with carboxylated styrene butadiene rubber (XSBR) latex membranes

The gas permeability coefficient of nano and micro composites of natural rubber, carboxylated styrene butadiene rubber and 70:30 natural rubber/carboxylated styrene butadiene rubber blend membranes has been investigated with special reference to type of filler, gases, filler loading and pressure. The layered silicates such as sodium bentonite and sodium fluorohectorite were the nanofillers used and the conventional micro fillers were clay and silica. Latex nanocomposites were characterized by X-ray diffraction technique. The dispersion of layered silicates in the polymer matrix was analysed using transmission electron microscopy. The fluorohectorite silicate showed excellent dispersion in natural rubber matrix. The effect of free volume on the gas barrier properties was investigated by positron annihilation lifetime spectroscopy. It was observed that due to the platelet like morphology and high aspect ratio of layered silicates, the gas barrier properties of nano filled latex membranes were very high. The crosslink density values and extent of reinforcement were estimated in order to correlate with the gas barrier properties. The oxygen/nitrogen selectivity of these membranes were investigated. The diffusion of gas molecules through the polymer was determined by time-lag method and diffusion selectivity of the membranes was computed.     

Vertically aligned single crystal TiO2 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis details and applications

Single-crystal one-dimensional (1D) semiconductor architectures are important in materials-based applications requiring a large surface area, morphological control, and superior charge transport. Titania has widespread utility in applications including photocatalysis, photochromism, photovoltaics, and gas sensors. While considerable efforts have focused on the preparation of 1D TiO2, no methods have been available to grow crystalline nanowire arrays directly onto transparent conducting oxide (TCO) substrates, greatly limiting the performance of TiO2 photoelectrochemical devices. Herein, we present a straightforward low temperature method to prepare single crystal rutile TiO2 nanowire arrays up to 5 microm long on TCO glass via a non-polar solvent/hydrophilic substrate interfacial reaction under mild hydrothermal conditions. The as-prepared densely packed nanowires grow vertically oriented from the TCO glass substrate along the (110) crystal plane with a preferred (001) orientation. In a dye sensitized solar cell, N719 dye, using TiO2 nanowire arrays 2-3 microm long we achieve an AM 1.5 photoconversion efficiency of 5.02%.     

Finite element analysis of tissue deformation with a radiofrequency ablation electrode for strain imaging

Recent studies have shown that radiofrequency (RF) electrode displacement or deformation-based strain imaging can be used as an alternate imaging modality to monitor and to evaluate ablative therapies for liver tumors. This paper describes a biomechanical model used to study RF electrode deformation-based strain imaging, in conjunction with a simulated medical ultrasound linear array transducer. The computer simulations reported here are important steps toward understanding this biomechanical system in vivo, thus providing a basis for improving system design, including the motion tracking algorithm and image guidance for performing RF electrode displacement-strain imaging in vivo.     

Doped Ca(Ca1/4A2/4Ti1/4)O3 (A=Nb, Ta) Dielectrics for Microwave Telecommunication Applications

Ca(Ca_1/4A_2/4Ti_1/4)O₃ (A=Nb, Ta) dielectric resonator materials have been prepared by the solid-state ceramic route. The effects of various amounts of di-, tri-, tetra-, penta-, and hexavalent impurities on the structure, microstructure, density, and microwave dielectric properties of the complex perovskites have been investigated. The structure of the parent materials remained unchanged while slight increase in density was observed with a small amount of certain dopants. An improvement in dielectric constant, quality factor, and temperature coefficient of resonant frequency was observed with the doping of small amounts of MgO, ZnO, NiO, CuO, Co₃O₄, Cr₂O₃, SnO₂, and Sb₂O₅. A correlation between the microwave dielectric properties of Ca(Ca_1/4A_2/4Ti_1/4)O₃ (A=Nb, Ta) ceramics and ionic radius of the dopant has been observed. The reported ceramics are potential candidates for dielectric resonator applications in wireless communication devices operating in the S and C bands.     

Vertically oriented Ti-Fe-O nanotube array films: toward a useful material architecture for solar spectrum water photoelectrolysis

In an effort to obtain a material architecture suitable for high-efficiency visible spectrum water photoelectrolysis, herein we report on the fabrication and visible spectrum (380-650 nm) photoelectrochemical properties of self-aligned, vertically oriented Ti-Fe-O nanotube array films. Ti-Fe metal films of variable composition, iron content ranging from 69% to 3.5%, co-sputtered onto FTO-coated glass are anodized in an ethylene glycol + NH4F electrolyte. The resulting amorphous samples are annealed in oxygen at 500 degrees C, resulting in nanotubes composed of a mixed Ti-Fe-O oxide. Some of the iron goes into the titanium lattice substituting titanium ions, and the rest either forms alpha-Fe2O3 crystallites or remains in the amorphous state. Depending upon the Fe content, the band gap of the resulting films ranges from about 380 to 570 nm. The Ti-Fe oxide nanotube array films are utilized in solar spectrum water photoelectrolysis, demonstrating 2 mA/cm2 under AM 1.5 illumination with a sustained, time-energy normalized hydrogen evolution rate by water splitting of 7.1 mL/W.hr in a 1 M KOH solution with a platinum counter electrode under an applied bias of 0.7 V. The surface morphology, structure, elemental analysis, optical, and photoelectrochemical properties of the Ti-Fe oxide nanotube array films are considered.