High-efficiency ozone generation via electrochemical oxidation of water using Ti anode coated with Ni–Sb–SnO<Subscript>2</Subscript>

Ozone (O₃) has been generated on Ni–Sb–SnO₂/Ti electrode as anode immersed in acidic media at 25 °C by electrochemical process. The anode was electrochemically characterized by cyclic voltammetry and morphologically characterized by scanning electron microscopy (SEM) and X-ray diffraction. The concentration of dissolved ozone was determined by a UV/Vis spectrophotometer. The type of electrode with different times coating on the titanium mesh and different acid type and various concentrations (C _acid) were used, and the stability of the electrode was investigated under the experimental conditions by SEM images. Results shows that higher efficiency (53.7%) for O₃ generation by electrochemical oxidation of water were obtained in HClO₄ (1 M) and an applied potential of 2.4 V vs. Ag/AgCl in 150 ml volume undivided electrochemical cell.     

Use of headspace solid-phase microextraction for the quantification of poly(3-hydroxybutyrate) in microbial cells

Biopolymers such as poly(hydroxyalkanoates) (PHAs) have received much attention due to their physico-chemical properties, biodegradability, and biocompatibility that make them good candidates for industrial and medical applications. Produced by some microorganisms PHAs accumulate within the cells of these organisms. The optimization of microbial processes to produce PHAs at a lower cost requires rapid and accurate techniques for quantification of the biopolymer in biomass. The present study describes a method based on solid-phase microextraction (SPME) coupled to gas chromatography (GC) for the determination of poly(3-hydroxybutyrate) (PHB) in Alcaligenes latus cells. First PHB was depolymerized by either methanolic or hydrolytic digestion into methyl 3-hydroxybutyrate (Me-3-HB) or crotonic acid (CA), respectively. The resulting analytes were then subjected to analysis by headspace SPME/GC with flame ionization detection (FID). The two depolymerization/SPME/GC-FID methods were optimized and applied to the analysis of PHB in bacterial biomass harvested from a fermentation process that uses A. latus. Results were compared with those obtained using GC-FID analysis of MeOH/CHCl(3) digested samples. Excellent agreement was found between the three methods but the two SPME-based methods were environmentally friendly and easier to perform.     

On the Synthesis of 3-Acetyl-1-aryl-1,4,5,6-tetrahydro-1 H-1,2,4-triazepin-7-ones by Reaction of Nitrilimines with 3-Aminopropanoic Acid

Nitrilimines were prepared from N-arylhydrazono chlorides and reacted with -alanine yielding the corresponding amidrazones, which were treated with 1,1-carbonyldiimidazole in THF affording the hitherto unknown 3-acetyl-1-aryl-1,4,5,6-tetrahydro-1,2,4-triazepin-7-ones.     

Miniaturization of GPS patch antennas based on novel dielectric ceramics Zn(1−x)MgxAl2O4 by sol–gel method

The need for miniaturization and weight reduction of GPS patch antennas has prompted the search for new microwave dielectric materials. In this study, a sol–gel method was used to prepare Zn_(1?x)Mg_xAl₂O₄ thin films and fabricate GPS patch antennas at a low annealing temperature (700 °C). X-ray diffraction (XRD) patterns, field emission scanning electron microscopy images, Fourier transform infrared spectra, and optical band gap analyses confirmed the nanostructure of (Mg/Zn)Al₂O₄. The XRD patterns displayed the characteristic peaks of (Mg/Zn)Al₂O₄ with a face-centered cubic structure. Mg addition decreased the crystallite size, surface morphology, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (? _r ). Based on the material investigated and microwave antenna theory, GPS patch antennas were fabricated using Zn_(1?x)Mg_xAl₂O₄ and then studied using a PNA series network analyzer. The fabricated patch antennas with different ? _r ceramics decreased in size from 12.5 to 10.8 cm². The patch antennas resonated at a frequency of 1.570 GHz and provided a return loss bandwidth between ?16.6 and ?20.0 dB; their bandwidth also improved from 90 to 255 MHz. The GPS patch antenna fabricated from Zn_0.70Mg_0.30Al₂O₄ showed an excellent combination of return loss (?20.0 dB), small size (10.8 cm²), and wide bandwidth (255 MHz). Therefore, addition of Mg improves antenna performance and decreases the dimensions of the device.     

Stability of Plasma Treated Non-vulcanized Polybutadiene Surfaces: Role of Plasma Parameters and Influence of Additives

Surface modification studies of non-vulcanized BR elastomers (butadiene rubber) by low-pressure air plasma treatment and the effect on ageing and adhesion performances are presented in this paper. In particular, the influence of discharge power and distance from the glow discharge, and impact of antioxidant molecules in the BR formulation were examined. To characterize the changes to the BR surface, XPS spectroscopy, contact angle measurements, AFM nanoindentation experiments and tack measurements were utilized. Oxidation and crosslinking were the main mechanisms observed on the polymer chains regardless of the plasma conditions used. Beyond a certain threshold of plasma energy (in our case, discharge power of ~60 W and exposure time of ~30 s), a steady state was reached irrespective of the distance from the glow discharge. The presence of antioxidant molecules considerably reduced crosslinking phenomena while maintaining oxidation processes on polymer chains and increasing the nitrogen content in the near surface region. The mechanisms responsible for these differences have been identified. Interestingly, the COOH/C=O ratio changed according to the balance between oxidation and crosslinking. The hydrophobic recovery rate was mainly driven by temperature-dependent dynamics and varied according to the degree of crosslinking in the surface region. It was found to be lower in air atmosphere in the presence of antioxidant molecules. Finally, the presence of antioxidant molecules in the BR formulation allowed the adhesion performances after plasma exposure to significantly increase.     

Grignard-Addition an Pyridin-N-oxid

Addition of phenyl-, alkyl-, alkenyl- and alkinyl-Grignard reagents to pyridine-N-oxide in THF leads to 5-substituted (2Z, 4E)-pentadien-aldoximes 6 having (E) (syn)-configuration of the C, N-double bond. The unsaturated oximes are shown to arise through an electrocyclic ring opening reaction from the primary Grignard adducts 5 . These can be trapped by protonation at low temperature.     

Anomalous scaling in surface roughness evaluation of electrodeposited nanocrystalline Pt thin films

Atomic force microscopy (AFM) is used to measure the surface roughness of crystalline Pt thin films as a function of film thickness and growth rate. Our films were electrodeposited on Au/Cr/glass substrates, under galvanostatic control (constant current density), from a single electrolyte containing Pt⁴⁺ ions. Crystalline structure of the films was confirmed by X-ray diffraction (XRD) technique. The effect of growth rate (deposition current density) and film thickness (deposition time) on the kinetic roughening of the films were studied using AFM and roughness calculation. The data is consistent with a rather complex behaviour known as “anomalous scaling” where both local and large scale roughnesses show power law dependence on the film thickness.     

Nondispersive wavelength-division sampling

We propose and demonstrate a new wavelength-division-sampling technique with high temporal resolution. A discrete-time true-time delay generates multiwavelength near-transform-limited pulses from a supercontinuum source. Pulses sample the analog signal in an electro-optic modulator and are subsequently demultiplexed in a wavelength-division-multiplexing filter. A 100-Gsample/s experimental demonstration of this concept is presented.     

Erratum

Peculiar transitions in the optical spectra of Mn atoms isolated in argon matrices confirm the existence of Mn₂ molecule. The temperature variation of the absorption and MCD intensity in the range 13-27 K demonstrate that the Mn₂ molecule is antiferromagnetic and allows a precise determination of its ground-state exchange energy: J = ?10.3 ± 0.6 cm^?1.     

Coupled-mode theory of the Raman effect in silicon-on-insulator waveguides

Coupled-mode theory is used to calculate Raman gain and spontaneous efficiency in silicon waveguides with cross-sectional areas ranging from 0.16 to 16 microm2. We find a monotonic increase in the Raman gain as the waveguide cross section decreases for the range of dimensions considered. It is also found that mode coupling between the Stokes modes is insignificant, and thus polarization multiplexing is possible. The results also demonstrate that for submicrometer waveguide dimensions the Einstein relation between spontaneous efficiency and stimulated gain no longer holds.