Complementary electric-LC resonator antenna for WLAN applications

In this paper, a metamaterial antenna based on complementary electric-LC (CELC) resonator is proposed. The antenna consists of slot-loaded ELC on the ground plane as the main antennas radiating element and excited by a microstrip line. The CELC resonator is characterized by single-negative magnetic moment excited by coupling between the microstrip transmission line and slot-loaded CELC. The peak realized gain and efficiency of 2.63 dB and 86 % are obtained, respectively, at resonance frequency. Simulation and measurement results are presented to validate the design. The antenna is suitable for WLAN applications (2.39–2.48 GHz).     

Synthesis and mesophase characterization of liquid crystalline polyesters with bulky,rigid, lateral substituents

The synthesis and characterization of aromatic polyesters containing various symmetrically di-substituted hydroquinone monomers is described. The homopolyesters made from these monomers and terephthalic acid (TA) did not melt. Copolyesters of TA with mono- and di-substituted hydroquinone formed liquid crystalline melts. Optical microscopy showed schlieren, marbled, and droplet textures characteristic of the nematic phase. DSC experiments were also in accord with mesophase formation as multiple transitions characteristic of first-order phase changes were found. In general, the crystal-nematic transition was about 300°C, whereas the nematic-isotropic change was over 400°C. All the polyesters were prone to decomposition near or above the isotropization temperature. © 1994 John Wiley & Sons, Inc.     

Spectrophotometric determination of lodate,periodate, and persulfate in aqueous solution

Spectrophotometric methods for the trace determination of iodate, periodate, and persulfate have been worked out. They are based on the oxidation of ferrous ion, by the anions, in the presence of ferrocyanide to give an intense Prussian blue color. The methods do not resort to either solvent extraction or temperature control.     

p-Phenylenediamine as a chromogen for iodate and periodate in aqueous solution

Trace amounts of iodate and periodate in aqueous solution have been determined spectrophotometrically, based on the reaction of the ions with p-phenylenediamine, in acidic medium, to form pink-red-colored species with maximum absorption at 520 nm and adherence to Beer's law over wide concentration ranges of the ions. Further, the color reaction is fast and needs no extraction step.     

Photometric determination of nitrite

A sensitive colored reaction for nitrite determination is developed. It involves the reaction of the titled ion with p-aminobenzoic acid to form a diazonium ion, which is then coupled with α-naphthol in alkaline medium to form a pinkish red soluble azo dye absorbing maximum at 519 nm. The described method is capable of determining 0.1–1.3 ppm of nitrite with a relative standard deviation of 0.3–1.7% depending on the concentration level, molar absorptivity of 3.5 × 10⁴ liter mol⁻¹ cm⁻¹, and Sandell sensitivity index of 0.0013 μg cm⁻². Diazotization and coupling are very fast and control of temperature is unnecessary. Moreover, the colored azo dye is stable and its intensity is in direct proportion with nitrite concentration over a wide range.     

Spectrophotometric determination of trace amounts of acetylacetone in aqueous solutions

A sensitive spectrophotometric method for the determination of trace amounts of acetylacetone in aqueous solution is carried out. In the presence of bicarbonate solution, diazotized anthranilic acid reagent reacts rapidly with acetylacetone to form a yellow-colored compound with maximum absorption at 330 nm, which is water-soluble and reasonably stable. Adherence to Beer's law is observed in the range 20–200 μg of acetylacetone/25 ml, with a molar absorptivity of 19.5 × 10³ liters mol⁻¹ cm⁻¹, a sensitivity index of 0.0051 μg cm⁻², relative to + 0.3 to −0.9%, and a relative standard deviation of 0.5–1.4%, depending on the concentration level.     

An Update on COVID-19 Vaccine Induced Thrombotic Thrombocytopenia Syndrome and Some Management Recommendations

The thrombotic thrombocytopenia syndrome (TTS), a complication of COVID-19 vaccines, involves thrombosis (often cerebral venous sinus thrombosis) and thrombocytopenia with occasional pulmonary embolism and arterial ischemia. TTS appears to mostly affect females aged between 20 and 50 years old, with no predisposing risk factors conclusively identified so far. Cases are characterized by thrombocytopenia, higher levels of D-dimers than commonly observed in venous thromboembolic events, inexplicably low fibrinogen levels and worsening thrombosis. Hyper fibrinolysis associated with bleeding can also occur. Antibodies that bind platelet factor 4, similar to those associated with heparin-induced thrombocytopenia, have also been identified but in the absence of patient exposure to heparin treatment. A number of countries have now suspended the use of adenovirus-vectored vaccines for younger individuals. The prevailing opinion of most experts is that the risk of developing COVID-19 disease, including thrombosis, far exceeds the extremely low risk of TTS associated with highly efficacious vaccines. Mass vaccination should continue but with caution. Vaccines that are more likely to cause TTS (e.g., Vaxzevria manufactured by AstraZeneca) should be avoided in younger patients for whom an alternative vaccine is available.     

Thermodynamic Stability,Half-Metallic and Optical Properties of Sc2CoSi [001] Film:a DFT Study

The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the ?lms thermodynamic stability of the [001] direction in four cases including:Sc-Sc, Sc-Co, Sc-Si and Co-Si terminations are studied using the ?rst principles calculations(FPLAPW) within the framework of the density functional theory(DFT). The band structure calculations represent the ferromagnetic halfmetallic properties with 100% spin polarization and 0.54 e V indirect gap in spin down for Sc2 CoSi bulk with optimized lattice parameters of 6.25 A?. The total magnetic moment obtained for this compound is-1.0 μB, which is in accordance with Slater-Pauling rule. The half-metallic(HM) behavior by 100% spin polarization at Fermi level is occurred in the Sc-Si termination with a 0.32 eV gap in down spin. The optical responses have been calculated for the bulk and ScSi termination by a red shift in these parameters and the metallic treatments have been increased. According to the thermodynamic phase diagrams, it is shown the Sc-Si and Sc-Sc terminations are more stable than other terminations.