Tunable narrow-band infrared emitters from hexagonal lattices

In this work, we present both the theoretical basis as well as supporting experimental measurements for development of a novel mid-infrared thermally stimulated narrow band emitter with a spectral bandwidth of less than 10%. To achieve this, we utilize a metallized-surface 2D photonic crystal of air voids in a silicon background with hexagonal structure symmetry. Our results are based on the generation of discrete surface plasmon (SP) modes in the thin metallized layer residing on the top surface. This yields a series of adequately spaced discrete peaks in the reflection spectrum, dominated by a single sharp feature corresponding to the lowest plasmon order, in an otherwise uniform highly reflective spectrum (>90%) over most of the IR spectrum. This, in turn, gives rise to a sharp absorption feature with a correspondingly narrow thermal emission peak in the emission spectrum. Transfer matrix calculations simulate well both the position and strengths of the absorption peaks. By altering the period of the surface photonic lattice, the SP peak and emissive band can be tuned to the desired wavelength. These devices promise a new class of tunable infrared emitters with high power in a narrow spectral bandwidth. Such narrow band sources are critical to achieving high efficiency gas sensors.     

Isothermal dimensional changes of some dental materials

The isothermal dimensional changes of four types of dental amalgams during the setting and for the next 24 hours after condensation have been studied by means of a Heraeus TA 500 thermal analysis system. The four types of dental amalgams were the lathe-cut conventional lowcopper amalgam (Amalcap), the spherical conventional low-copper amalgam (Spheralloy), the ternary unicomposition high-copper amalgam (Sybralloy) and the admixed high-copper (Dispersalloy) amalgam.The dimensional changes of the four types of amalgams are explained on the basis of their particle sizes and shapes and their constitutions.

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Zusammenfassung Mittels eines Heraeus TA 500 Thermoanalysensystemes wurden isotherme Größenveränderungen von Dentalamalgamen während des Setting und der 24 Stunden nach der Kondensation untersucht. Die Größenveränderungen der vier Amalgamgrundtypen (am Beispiel von Amalcap, Spheralloy, Sybralloy und Dispersalloy) wurden auf der Grundlage ihrer Teilchengröße und -form sowie auf der Grundlage ihrer Zusammensetzung erklärt.

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Synthesis and antimicrobial evaluation of novel 1,3-thiazoles and unsymmetrical azines

Research on Chemical Intermediates - 1,3-Thiazol derivatives have been synthesized via reaction of 1-(1-(5,6-dimethoxy-2-oxobenzo[d]thiazol-3(2H)-yl)propan-2-ylidene)-4-substituted...     

Three-dimensional nanofabrication with elastomeric phase masks

This Feature Article reviews recent work on an optical technique for fabricating, in a single exposure step, three-dimensional (3D) nanostructures with diverse structural layouts. The approach, which we refer to as proximity field nanopatterning, uses conformable, elastomeric phase masks to pattern thick layers of transparent, photosensitive materials in a conformal contact mode geometry. Aspects of the optics, the materials, and the physical chemistry associated with this method are outlined. A range of 3D structures illustrate its capabilities, and several application examples demonstrate possible areas of use in technologies ranging from microfluidics to photonic materials to density gradient structures for chemical release and high-energy density science.     

Poly(3-methylthiophene)/palladium sub-micro-modified sensor electrode. Part II: Voltammetric and EIS studies, and analysis of catecholamine neurotransmitters, ascorbic acid and acetaminophen

Promising voltammetric sensors based on the modification of Pt and poly(3-methylthiophene) (PMT) electrodes with Pd nanoparticles were achieved for the determination of catecholamine neurotransmitters, ascorbic acid and acetaminophen. Electrochemistry of the indicated compounds was studied at these electrodes and interesting electrocatalytic effects were found. Furthermore, simple, easily prepared one electrochemical step Pd-modified Pt electrode (Pt/Pd) is reported for the first time. Cyclic voltammetry (CV) and chronocoulometry (CC) were used for the determination of the apparent diffusion coefficients in different electrolytes at these electrodes and the values are in the range from 10⁻⁴ to 10⁻⁵ cm² s⁻¹. Furthermore, it was found that the method of polymer formation had a substantial effect on the synergism between the polymer film and the loaded metal particles towards the oxidation of dopamine (DA) in different supporting electrolytes. This was confirmed by the CV, CC and EIS (electrochemical impedance spectroscopy) as well as SEM (Scanning Electron Microscopy) results. Pt and PMT electrodes modified with Pd nanoparticles showed excellent results for the simultaneous determination of tertiary and quaternary mixtures of the studied compounds.     

Enhanced complete photonic band gap in the optimized planar diamond structure

The diamond photonic crystal with dielectric rods has been modified to enlarge the fundamental band gap. By planarizing the diamond structure and reducing the thickness of the hexagonal meshes, the band gap can be increased substantially. The band gap is 29% for a refractive index contrast of 3.6. The modified structure is amenable to fabrication at optical and infrared wavelengths using state-of-the-art silicon-processing methods. Transfer matrix calculations demonstrate a large attenuation within the band gap.     

Efficient reconstructed Legendre algorithm for solving linear-quadratic optimal control problems

In this paper, a new numerical approach via reconstructed Legendre orthogonal polynomials (LOPs) is presented to solve the linear quadratic optimal control problems (LQPs). By using the elegant operational properties of orthogonal polynomials, a computationally attractive algorithm is developed for calculating LQP. A numerical example illustrates the techniques and demonstrates the accuracy and efficiency of these controllers.     

Spinel structure of activated carbon supported MFe2O4 composites as an economic and efficient electrocatalyst for oxygen reduction reaction in neutral media

For more sustainability and marketing of microbial fuel cells (MFCs) in wastewater treatment, the sluggish kinetics of cathode oxygen reduction reaction (ORR) and platinum scarcity (with its high cost) should be swept away. So, this work aimed to synthesize metal ferrite (MFe₂O₄; M = Mn, Cu, and Ni) -based activated carbon composites as inexpensive ORR cathode catalysts. The composites were synthesized using a facile modified co-precipitation approach with low-thermal treatment and labeled as MnFe₂O₄/AC, CuFe₂O₄/AC, and NiFe₂O₄/AC. The as-synthesized catalysts are physicochemically characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared microscopy (FTIR), Barrett-Joyner-Halenda (BJH), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and electron spin resonance (ESR). The electrochemical catalytic performance toward ORR was studied in a phosphate buffer solution (PBS) at neutral media via cyclic voltammetry (CV) and linear sweep voltammetry (LSV). MnFe₂O₄/AC has the highest onset potential (E_onset) value of − 0.223 V compared to CuFe₂O₄/AC (− 0.280 V) and NiFe₂O₄/AC (− 0.270 V). MnFe₂O₄/AC also has the highest kinetic current density (j_K) and lowest Tafel slope (− 5 mA cm⁻² and − 330 mV dec⁻¹) compared to CuFe₂O₄/AC (− 3.05 mA cm⁻² and − 577 mV dec⁻¹) and NiFe₂O₄/AC (− 2.67 mA cm⁻² and − 414 mV dec⁻¹). The ORR catalyzed by MnFe₂O₄/AC at pH = 7 proceeds via a 4e⁻ -kinetic pathway. The ESR is in good agreement with the electrochemical analysis due to the highest ∆H_ppvalue for MnFe₂O₄/AC compared to CuFe₂O₄/AC and NiFe₂O₄/AC. Thus, MnFe₂O₄/AC is suggested as a promising alternative to Pt- electrocatalyst cathode for MFCs at neutral conditions.

Graphical Abstract

     

A novel integrated method realizing iteratively optimized modeling for proximity field patterning nanolithography

Processing methods used in photonics and nanotechnology have many limitations hindering the ability to realize devices and restricting the actual number of applications. An ideal processing method should require low-cost equipment, be able to produce very fine details, and be scalable to process large area specimens in an acceptable amount of time. Proximity field nanopatterning (PnP) is a lithography method possessing these features. By using interference patterns produced by a two-dimensional phase mask, the technique is able to generate a submicron detailed exposure on a millimeter-size slab of light sensitive photopolymer, which is then developed like a photographic plate to reveal three-dimensional interference patterns from the phase mask. While it is possible to use computer aided simulations to obtain the interference patterns produced by a mask with a certain pattern, the inverse problem of producing a mask for a desired interference pattern cannot be solved in the same way due to the intricacies of light interactions involved in producing the final interference pattern. An alternative method is to iteratively optimize the phase mask so that the interference patterns obtained converge to the desired pattern. The method is elaborated in this article.     

Certain Trace Metal Disorders in Urinary Bladder of Bilharzial Patients suffering Bladder Carcinoma

The objective of the present work is to investigate any possible role which could have been played by the long-term treatment with antimony as an antibilharzial drug, and the development of urinary bladder carcinoma in patients suffering bilharzial complications. The present work has been planned to investigate the concentration levels of copper, zinc and antimony in urinary bladder tissues sampled from normal, bilharzial and bladder cancer patients subjected to surgical intervention. Both atomic absorption spectrophotometry and neutron activation analysis have been utilized for elemental estimations. The data obtained showed significant increase in the concentration levels of the three investigated metals in bladder cancer tumours as compared with their control levels under either normal or cancer-free bilharzial complications. The results have been statistically evaluated and discussed in view of the relevant literature. It has been concluded that the contributing role of the antibilharzial antimonial treatment in development of urinary bladder cancer cases cannot be overlooked and awaits further investigation.