Novel miniaturized folded UWB microstrip antenna‐based metamaterial for RF energy harvesting

This paper presents a design of an ultra‐wideband (UWB) cylindrical metamaterial (MTM) antenna for radio frequency (RF) energy harvesting to suit the fields of Internet of Things (IoT) applications. The patch circuitry is based on 3×5 Hilbert‐shaped MTM unit cells array to enhance the antenna bandwidth. While, the antenna ground plane is defected with an electromagnetic band gap structure to enhance the gain. The antenna is mounted on a polytetrafluoroethylene cylindrical substrate of an outer diameter of 15 mm and length of 32 mm with 1 mm in thickness. The substrate relative permittivity is 2.04, and the loss tangent is 0.0002. The antenna patch and the ground plane structures are printed with silver nanoparticles ink using a ^2.5D CNC plotter machine. The fabricated prototype provides an UWB over the frequency range from 3.77 up to 13.89 GHz with a first separate resonant mode at 3 GHz. The antenna performance is tested numerically using two different software packages of CST MWS and HFSS. Then, an experimental validation is conducted to realize the performance of the proposed antenna in harvesting the RF energy. Excellent conversion efficiency, about 90%, is achieved at 5.8 GHz. Finally, the antenna radiation patterns and S₁₁ spectrum are measured and compared against their simulated results to achieve good agreements.     

Multifunctional covalent and ionic coupling agents of maleic anhydride modified polyethylene

Amine and alcohol functional dendritic polymers were used as covalent coupling agents for maleic anhydride grafted polyethylene and their efficiency compared with metallic salt and zinc acetate, acting as an ionic coupling agent. The crosslinking reactions in the molten state were carried out at 150°C in an internal mixer and the resulting modified polyethylenes were characterized by dynamic mechanical analysis and Small angle X‐ray Scattering. These agents led to efficient coupling and crosslinking. The covalent coupling reactions were conducted in a heterogeneous multiphase system: The kinetics of crosslinking depends on the nature of the coupling agent: at 150°C, the reactions were completed within 5 min. with the amine hyperbranched polymer and 20 min. with the alcohol functionalized dendritic polymer. The zinc acetate forms ionic interactions with the grafted polyethylene in less than 1 min. Ionic interactions are thermo mechanically reversible; they correspond to electronic density fluctuations evidenced by SAXS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Combatting Ambiguity Attacks via Selective Detection of Embedded Watermarks

This paper focuses on a problem that is common to most watermarking-based ownership dispute resolutions and ownership assertion systems. Such systems are vulnerable to a simple but effective class of attacks that exploit the high false-positive rate of the watermarking techniques to cast doubt on the reliability of a resulting decision. To mitigate this vulnerability, we propose embedding multiple watermarks, as opposed to embedding a single watermark, and detecting a randomly selected subset of them while constraining the embedding distortion. The crux of the scheme lies in both watermark generation, which deploys a family of one-way functions and selective detection, which injects uncertainty into the detection process. The potential of this approach in reducing the false-positive probability is analyzed under various operating conditions and compared to single watermark embedding. The multiple watermark embedding and selective detection technique is incorporated analytically into the additive watermarking technique and results obtained through numerical solutions are presented to illustrate its effectiveness.     

Neutrophils, Helicobacter pylori, and nonsteroidal anti-inflammatory drug ulcers

BACKGROUND & AIMS: Gastric injury by nonsteroidal anti-inflammatory drugs (NSAIDs) is minimal in neutropenic animals. This study examined peptic ulcer development in the presence or absence of gastric neutrophils in patients requiring long-term use of NSAIDs. METHODS: Gastric histology, neutrophils, and Helicobacter pylori were assessed in 120 patients randomized to receive placebo or 20 or 40 mg famotidine twice daily as prophylaxis against NSAID-related ulcers and who underwent endoscopy at 0, 4, 12, and 24 weeks. RESULTS: In 43 patients without gastric neutrophils, ulcers developed in 1 of 14 (7.7%) taking placebo, 2 of 16 (12.5%) taking 20 mg famotidine, and none of 13 taking 40 mg famotidine. However, in 77 patients with neutrophils, ulcers developed in 13 of 28 (47. 4%) taking placebo (P < 0.001), 3 of 26 (12.6%) taking 20 mg famotidine, and 3 of 23 (13%) taking 40 mg famotidine. Eight of 46 patients (17%) without H. pylori had neutrophils compared with 69 of 74 (93%) with both H. pylori and neutrophils (P < 0.001). CONCLUSIONS: Gastric neutrophils increase the incidence of ulceration in long-term NSAID users. Because neutrophils exist with H. pylori, eradicating this infection might prevent NSAID-related peptic ulcers.     

Phase transfer methodology for the synthesis of substituted stilbenes under Knoevenagel condensation condition

This work describes the use of phase transfer catalyst (PTC) for the Knoevenagel condensation in the synthesis of several substituted stilbenes derived from weak acidic substrates such as p-nitro toluene (pK_a = 20.4) and phenylacetonitrile (pK_a = 21.9) with benzaldehyde using TBAB (tetrabutylammonium bromide) or 18-crown-6 as PTCs, respectively. Reaction of p-nitro toluene with benzaldehyde suffered from the competitive Cannizzaro reaction along with Knoevenagel condensation. Nevertheless, the problem has been solved and the novel procedure yielded >90% of isolated p-nitro stilbene. Utilizing a solid potassium carbonate as base and crown-ether as PTC proved to be the best reaction conditions for phenylacetonitrile and benzaldehyde, which showed 100% conversion of phenylacetonitrile to the corresponding stilbene (1,2-diphenyl-1′-nitrile ethene). To explore the role of PTC, we carried out a thorough kinetic investigation of these reactions. This includes modifying the catalyst nature and structure, the stirring rate, temperature effect and varying the concentration of the reactants and catalysts. Here, we prove for the first time that the PTC extraction mechanism taking place in a solid–liquid system for the carbonate anion. We conclude that it behaves as a typical second order reaction.     

Photochemical “Self-healing” pyrrole based treatment of CdS/CdTe photovoltaics

An improved post-deposition treatment for CdS/CdTe photovoltaic devices has been developed. Aqueous solutions containing pyrrole and sodium chloride provide a treatment of the CdTe surface when the device is illuminated with visible light. Evaporating gold metal on the CdTe surface completes the device structure. Comparison of the JV characteristics of the device treated with illumination to those not illuminated reveals a significant enhancement in device output. While most of the electronic properties (J_sc, FF, R_s and R_sh) are very similar the V_oc for the treated sample is higher (circa 0.79 V versus 0.71 V) leading to a higher efficiency of 12.3% for the treated cell versus 11.0% for the untreated cell. The performance of this treatment is very much the same as that observed when the photochemically induced treatment employs aniline, the benefit of the herein described method is the decreased level of toxicity associated with pyrrole relative to that of aniline. Characterization of the CdTe surface with SEM does not reveal any noticeable features and could be interpreted as indicating that treatment leads to a very thin coating of material. The GIXRD data reveal the presence of elemental tellurium on the surface of the CdTe.     

Optical Fibers by Reactive Extrusion of Butyl Methacrylate

Summary: A process for the production of poly(butyl methacrylate) optical fibers by reactive extrusion is developed. The reactive system is adapted to the reduced reaction time in the extruder combining concepts based on the free volume theory and a kinetic model for the mass polymerization of butyl methacrylate. A kinetic model is proposed and the reaction evolution is simulated at different temperatures and initiator concentrations. This allows the choice of reaction conditions adequate for reactive extrusion technical limitations. Reactive extrusion experiments are carried out in a twin‐screw extruder and the effect of the different kinetic and process conditions on the reaction are analyzed in relation to the residence time distribution measured by an UV fluorescence method. Some optical properties of poly(butyl methacrylate) fibers are reported.

Conversion versus the position along the screw length.     

Volumetric measurement of human calf muscle from magnetic resonance imaging

Muscle mass is a determining factor in skeletal muscle function and is affected by inactivity, immobilization, disease, and aging. The aim of this study was to develop an objective and timeefficient method to quantify the volume and cross-sectional area of human calf muscles using three-dimensional magnetic resonance images. We have estimated the errors incurred in muscle volume measurements arising from artifacts known to occur in magnetic resonance imaging (MRI). The largest source of error was due to partial volume effects, which resulted in overestimation of phantom volumes ranging from 145 to 900 cc by 6% to 13%. The magnitude of this effect has been shown to increase with decreasing object size and decreasing spatial resolution. We have presented a straightforward correction for this effect, which has reduced the volume measurement error to less than 4% for all cases. Through the use of computer simulations, the correction algorithm has been shown to be independent of object shape and orientation. To reduce user subjectivity, a semiautomated computer program has been developed to segment MRI data for particular muscle groups. Images from seven human subjects were analyzed by the program, yielding muscle volumes of 154.2±23.2, 281.2±35.8, and 432.2±83.7 for the lateral gastrocnemius, medial gastrocnemius, and soleus, respectively.