Analysis of Resolution and Noise Properties of Nonquadratically Regularized Image Reconstruction Methods for PET

We present accurate and efficient methods for estimating the spatial resolution and noise properties of nonquadratically regularized image reconstruction for positron emission tomography (PET). It is well known that quadratic regularization tends to over-smooth sharp edges. Many types of edge-preserving nonquadratic penalties have been proposed to overcome this problem. However, there has been little research on the quantitative analysis of nonquadratic regularization due to its nonlinearity. In contrast, quadratically regularized estimators are approximately linear and are well understood in terms of resolution and variance properties. We derive new approximate expressions for the linearized local perturbation response (LLPR) and variance using the Taylor expansion with the remainder term. Although the expressions are implicit, we can use them to accurately predict resolution and variance for nonquadratic regularization where the conventional expressions based on the first-order Taylor truncation fail. They also motivate us to extend the use of a certainty-based modified penalty to nonquadratic regularization cases in order to achieve spatially uniform perturbation responses, analogous to uniform spatial resolution in quadratic regularization. Finally, we develop computationally efficient methods for predicting resolution and variance of nonquadratically regularized reconstruction and present simulations that illustrate the validity of these methods.     

Performance of Hybrid Laser Diodes Consisting of Silicon Slab and InP/InGaAsP Deep‐Ridge Waveguides

The fundamental transverse mode lasing of a hybrid laser diode is a prerequisite for efficient coupling to a single‐mode silicon waveguide, which is necessary for a wavelength‐division multiplexing silicon interconnection. We investigate the lasing mode profile for a hybrid laser diode consisting of silicon slab and InP/InGaAsP deep ridge waveguides. When the thickness of the top silicon is 220 nm, the fundamental transverse mode is lasing in spite of the wide waveguide width of 3.7µm. The threshold current is 40 mA, and the maximum output power is 5 mW under CW current operation. In the case of a thick top silicon layer (1 µm), the higher modes are lasing. There is no significant difference in the thermal resistance of the two devices.     

Gas Pickering Emulsion Templated Hollow Carbon for High Rate Performance Lithium Sulfur Batteries

A CO₂ in water nanoparticle stabilized Pickering emulsion is used to template micrometer sized hollow porous nitrogen doped carbon particles for high rate performance lithium sulfur battery. For the first time, nanoparticles serve the dual role of an emulsion stabilizer and a pore template for the shell, directly utilizing in situ generated CO₂ bubbles as template for the core. The minimalistic nature of this method does not require expensive surfactants or additional core templates. Upon polymerization of melamine formaldehyde onto CO₂, a robust polymer/silica composite shell is formed and transformed into a porous shell upon washing. The micrometer‐sized hollow morphology in combination with its nitrogen rich porous shell demonstrates impressive rate capabilities of 670 and 500 mAh g^?1 even at a high rate of 7C and 9C, respectively. This material also possesses excellent cycle durability, exhibiting a low capacity decay of 0.088%/cycle over 300 cycles. Measurement of the shuttle current and impedance provides interesting insight into the polysulfide mass transfer mechanism of hollow structured sulfur hosts.     

Development of Dual‐Pore Coexisting Branched Silica Nanoparticles for Efficient Gene–Chemo Cancer Therapy

Various strategies for combination therapy to overcome current limitations in cancer therapy have been actively investigated. Among them, simultaneous delivery of multiple drugs is a subject of high interest due to anticipated synergistic effect, but there have been difficulties in designing and developing effective nanomaterials for this purpose. In this work, dual‐pore coexisting hybrid porous silica nanoparticles are developed through Volmer–Weber growth pathway for efficient co‐delivery of gene and anticancer drug. Based on the different pore sizes (2–3 and 40–45 nm) and surface modifications of the core and branch domains, loading and controlled release of gene and drug are achieved by appropriate strategies for each environment. With excellent loading capacity and low cytotoxicity of the present platform, the combinational cancer therapy is successfully demonstrated against human cervical cancer cell line. Through a series of quantitative analyses, the excellent gene–chemo combinational therapeutic efficiency is successfully demonstrated. It is expected that the present nanoparticle will be applicable to various biomedical fields that require co‐delivery of small molecule and nucleic acid.     

A flexible and highly sensitive strain-gauge sensor using reversible interlocking of nanofibres

Flexible skin-attachable strain-gauge sensors are an essential component in the development of artificial systems that can mimic the complex characteristics of the human skin. In general, such sensors contain a number of circuits or complex layered matrix arrays. Here, we present a simple architecture for a flexible and highly sensitive strain sensor that enables the detection of pressure, shear and torsion. The device is based on two interlocked arrays of high-aspect-ratio Pt-coated polymeric nanofibres that are supported on thin polydimethylsiloxane layers. When different sensing stimuli are applied, the degree of interconnection and the electrical resistance of the sensor changes in a reversible, directional manner with specific, discernible strain-gauge factors. The sensor response is highly repeatable and reproducible up to 10,000 cycles with excellent on/off switching behaviour. We show that the sensor can be used to monitor signals ranging from human heartbeats to the impact of a bouncing water droplet on a superhydrophobic surface.     

Synthesis and electrochemical properties of polyaniline nanofibers by interfacial polymerization

Polyaniline nanofibers were prepared by interfacial polymerization with different organic solvents such as chloroform and carbon tetrachloride. Field emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties of polyaniline nanofibers. Chemical characterization was carried out using Fourier transform infrared spectroscopy, UV-Vis spectroscopy, and X-ray diffraction spectroscopy and surface area was measured using BET isotherm. Polyaniline nanofibers doped with lithium hexafluorophosphate were prepared and their electrochemical properties were evaluated.     

Influence of dietary vitamin E on behavior of Listeria monocytogenes and color stability in ground turkey meat following electron beam irradiation

There is growing concern that the free radical scavenging effect of antioxidants added to meats might reduce the antimicrobial effectiveness of ionizing radiation. A study was conducted to determine the effect of vitamin E on the behavior (growth) of Listeria monocytogenes and color stability in turkey meat following electron beam irradiation. Raw ground turkey breast meat from birds fed diets containing 0 (control), 50, 100, and 200 IU/kg of vitamin E was inoculated with a five-strain mixture of L. monocytogenes to give approximately 10(7) CFU/g. Inoculated samples were irradiated at 0, 0.5, 1, and 2 kGy and stored aerobically (12 days) or under vacuum (42 days) at 4 degrees C. L. monocytogenes survivors were determined by plating samples on modified Oxford medium and counting colonies on modified Oxford medium plates after 48 h at 35 degrees C. Meat color was measured using a colorimeter. Irradiation at 2.0 kGy resulted in an approximately 3.5-log reduction of initial numbers of L. monocytogenes. There were no significant differences in D-values (decimal reduction times) for L. monocytogenes in meat irrespective of vitamin E treatment (P > 0.05). Also, vitamin E treatments did not affect growth of the pathogen in aerobic or vacuum-packaged samples following irradiation (P > 0.05). Compared with controls, irradiated meat from birds fed 100 or 200 IU/kg of vitamin E demonstrated significant improvement in color stability (lightness and redness values) during aerobic storage (P < 0.05). Dietary vitamin E (100 to 200 IU/kg) has good potential for improving the color stability of turkey meat without compromising the microbial safety of the irradiated product.     

Analysis of kimchi microflora using denaturing gradient gel electrophoresis

A polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique was used to determine the microfloral composition during the fermentation of kimchi, a traditional Korean fermented vegetable food. The kimchi was fermented at 10 degrees C or 20 degrees C for 30 or 20 days, respectively. DGGE of the partially amplified 16S rDNA was performed and the most intense bands sequenced. The application of this culture-independent molecular technique determined that the lactic acid bacteria Weissella confusa, Leuconostoc citreum, Lactobacillus sakei, and Lactobacillus curvatus were the main microorganisms responsible for kimchi fermentation.     

Phage-borne peptidomimetics accelerate the development of polyclonal antibody-based heterologous immunoassays for the detection of pesticide metabolites

Competitive immunoassays for the detection of small analytes, such as pesticides and their metabolites, use haptens that compete with the target compounds for binding to the antibody. This competing hapten can be either the same as the immunizing hapten (homologous assay) or structurally modified mimics of the immunizing hapten (heterologous assay). Polyclonal antibody-based heterologous immunoassays have shown superior sensitivities to homologous ones, butthe synthesis of heterologous haptens may be time-consuming, requiring expertise in synthetic chemistry. In this work we demonstrate that phage display peptide libraries can be used as a source of phage-borne peptidomimetics to facilitate the development of sensitive heterologous assays. Different strategies for the isolation of these peptides were explored using two metabolites of pyrethroid insecticides. The sensitivities of the best competitive phage heterologous enzyme-linked immunosorbent assays were 13 fold and 100 fold better than the homologous assay, for the glycine conjugate of trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid and 3-phenoxybenzoic acid, respectively. The phage particles were highly versatile as tracer reagents, allowing the use of enzymatic, chemiluminescent, or immuno-polymerase chain reaction detection. The data presented here shows a new systematic procedure that enables the fast generation of several competing haptens for the rapid development of sensitive heterologous immunoassays.