Cloaking a receiving antenna or a sensor with plasmonic metamaterials

In this contribution, we discuss the possibility of applying the scattering-cancellation-based plasmonic cloaking technique to reduce the scattering from a sensing device, lowering its disturbance on sensing without affecting its ability to measure and “sense” the external world. The plasmonic cloak, while allowing the external fields to penetrate into the cover, may be able to suppress the scattering without necessarily shielding its interiors from the impinging light, which may be of great use if we wish to “sense” the external world, or receive an external signal, from inside the cloak. Our results may provide a unique sensing system that may receive and transmit signals, while its presence may not be perceived by the surrounding. This may be of great importance in a wide range of biological, optical, physical and engineering applications.     

Thermal inactivation of Campylobacter jejuni in broth

New Zealand has a high rate of reported campylobacteriosis compared with other developed countries. One possible reason is that local strains have greater heat tolerance and thus are better able to survive undercooking; this hypothesis is supported by the remarkably high D-values reported for Campylobacter jejuni in The Netherlands. The objective of this study was to investigate the thermal inactivation of isolates from New Zealand in broth, using strains that are commonly found in human cases and food samples in New Zealand. Typed Campylobacter strains were heated to a predetermined temperature using a submerged-coil heating apparatus. The first-order kinetic model has been used extensively in the calculation of the thermal inactivation parameters, D and z; however, nonlinear survival curves have been reported, and a number of models have been proposed to describe the patterns observed. Therefore, this study compared the conventional first-order model with eight nonlinear models for survival curves. Kinetic parameters were estimated using both one- and two-step regression techniques. In general, nonlinear models fit the individual inactivation data sets better than the log-linear model. However, the log-linear and the (nonlinear) Weibull models were the only models that could be successfully fitted to all data sets. For seven relevant New Zealand C. jejuni strains, at temperatures from 51.5 to 60°C, D- and z-values were obtained, ranging from 1.5 to 228 s and 4 to 5.2°C, respectively. These values are in broad agreement with published international data and do not indicate that the studied New Zealand C. jejuni strains are more heat resistant than other strains, in contrast with some reports from The Netherlands.     

A low‐power,area‐efficient multichannel receiver for micro MRI

A new integrated, low‐noise, low‐power, and area‐efficient multichannel receiver for magnetic resonance imaging (MRI) is described. The proposed receiver presents an alternative technique to overcome the use of multiple receiver front‐ends in parallel MRI. The receiver consists of three main stages: low‐noise pre‐amplifier, quadrature down‐converter, and a band pass filter (BPF). These components are used to receive the nuclear magnetic resonance signals from a 3 × 3 array of micro coils. These signals are combined using frequency domain multiplexing (FDM) method in the pre‐amplifier and BPF stages, then amplified and filtered to remove any out‐of‐band noise before providing it to an analog‐to‐digital converter at the low intermediate frequency stage. The receiver is designed using a 90 nm CMOS technology to operate at the main B₀ magnetic field of 9.4 T, which corresponds to 400 MHz. The receiver has an input referred noise voltage of 1.1 nV/√Hz, a total voltage gain of 87 dB, a power consumption of 69 mA from a 1 V supply voltage, and an area of 305 µm × 530 µm including the reference current and bias voltage circuits. Copyright © 2013 John Wiley & Sons, Ltd.     

Electrochemical Synthesis of Ammonium Persulfate (NH4)2S2O8 Using Oxygen-Depolarized Porous Silver Cathodes Produced by Powder Metallurgy Methods

Powder Metallurgy and Metal Ceramics - The stage-by-stage mechanism of the reduction process proceeding in an acidic environment in the cathodic depolarization of ammonium sulfate (NH4)2SO4...     

Analysis of a Passive Power Converter as a Nonlinear Feedback System

An orthogonal-flux passive power converter operating under conditions of sinusoidal excitation is analyzed, using a non-linear feedback approach based on the principle of harmonic balance. The stability of possible states of oscillation is discussed via a frequency domain approach. Analytical bounds on system parameters and an expression for the secondary flux oscillation amplitude are derived.     

Detection of algal blooms over optically complex waters of the Arabian Gulf and Sea of Oman using MODIS fluorescence data

The Arabian Gulf and the Sea of Oman are two of the most complex and turbid ecosystems in the world where algal blooms frequently occur. The conventional blue/green band ratio shows low performance to detect these algal batches in this region due to the effect of the non-algal parameters, shallow water depth, and atmospheric aerosols. Thus, an attempt to use MODIS (Moderate Resolution Imaging Spectroradiometer) fluorescence for the detection of algal blooms in this region have been undertaken using in situ measurements (Chlorophyll a: Chl-a, coloured dissolved organic matters: CDOM, Secchi disk depth: SDD, and radiometric) collected in 2006, 2013, and 2014, and MODIS satellite images. MODIS fluorescence line height (FLH in W m^?2 µm^?1 sr^?1) data showed low correlation (coefficient of determination: R² ~0.46) with near-concurrent in situ Chl-a (mg m^?3). This disparity is caused by the effect of the suspended sediments (SDD), CDOM (<2 mg m^?3 or >2 mg m^?3), and bottom reflectance (water depth: WD) parameters, where an increase of 1% in their magnitudes can cause a respective change of 13.4%, ?0.8% or 6%, and 1.4% in the FLH. In this work, the positions of the FLH bands have been relocated to include 645 nm to reduce the effect of these parameters on Chl-a, which has improved the performance to R² of 0.76. This modified FLH (MFLH) model was found to perform well in the Arabian Gulf where the estimated bias, root-mean-square error (RMSE), and coefficient of determination are, respectively, 0.03, 1.06, and 0.76. High values of MFLH are indicating the areas of the algal blooms, while no overestimation was observed in the mixed pixel coastal areas. This result is explained by less sensitivity of this model to the non-algal particles, shallow water, and aerosols.     

Correlation of In Vivo and In Vitro Assay Results for Assessment of Free Radical Scavenging Activity of Green Tea Nutraceuticals

Green tea (GT)‐derived catechins; epigallocatechin gallate (EGCG) in particular are commonly used nutraceuticals for their free‐radical scavenging activity (FRSA). The influence of photodegradation on the protective power of GT nutracenticals against oxidative stress was thoroughly explored. Photodegradation of GT extracts was carried out and monitored using orthogonal stability‐indicating testing protocol; in vitro and in vivo assays. Total polyphenol content (TPC) and FRSA were determined spectrophotometrically while EGCG was selectively monitored using SPE‐HPLC. In vivo assessment of photodegraded samples was investigated via measuring a number of biomarkers for hepatic oxidative stress and apoptosis (caspase‐3, inducible nitric oxide synthase, nitric oxide, mitogen‐activated protein kinase, glutathione, thiobarbituric acid reactive substances, nuclear factor kappa beta, and nuclear factor erythroid 2‐related factor) as well as liver damage (alanine transaminase and aspartate transaminase) in serum of rats previously subjected to oxidative stress. Results showed complete degradation of EGCG in photodegraded green tea samples with no correlation with either TPC or FRSA. On the other hand, in vivo assay results revealed not only loss of activity but formation of harmful pro‐oxidants. Photostability was found crucial for the protective effect of GT extract against lead acetate insult. Results confirmed that careful design of quality control protocols requires correlation of chemical assays to bioassays to verify efficacy, stability, and most importantly safety of nutraceuticals.