A calix[4]arene derivative-doped perchlorate-selective membrane electrodes with/without multi-walled carbon nanotubes

In this study, poly (vinyl chloride)(PVC) membrane electrodes with/without multi-walled carbon nanotubes (MWCNTs) based on a calix[4]arene derivative for perchlorate ion were described. The influence of membrane composition, pH, conditioning solution on the potentiometric response of the electrodes was investigated. Perchlorate-selective PVC membrane electrode exhibited a slope of 47.8 ± 0.6 mV/pClO₄ in the range of 1.0 × 10^?7–1.0 × 10^?1 mol L^?1at pH 4.0 while the coated Pt electrodes with MWCNT-OH, MWCNT-COOH and MWCNT displayed slopes of 46.1 ± 0.7 mV/pClO₄ (5.0 × 10^?6–1.0 × 10^?1 mol L^?1), 50.4 ± 1.9 mV/pClO₄ (1.0 × 10^?6–1.0 × 10^?1 mol L^?1) and 44.4 ± 0.3 mV/pClO₄ (1.0 × 10^?5–1.0 × 10^?1 mol L^?1), respectively. Other response characteristics of these electrodes such as response time, lifetime and detection limit were identified, and the selectivity coefficients towards various anions were calculated by separate solution method. Moreover, the perchlorate-selective electrodes described here were successfully used as an indicator electrode for the determination of perchlorate in real samples such as tap water, river water and human urine by direct calibration method.     

A New Piperidine Derivatized-Schiff Base Based “Turn-on” Cu<Superscript>2+</Superscript>Chemo-Sensor

In this study, we report the synthesis of new Schiff base E-1-(((1-benzylpiperidin-4-yl)imino)methyl)naphthalenee-2-ol (L) and evaluation of its fluorescence response toward Cu²⁺ ion. Preliminary, solvent effect, metal selectivity and metal ligand ratio were analyzed through UV-Visible study. Fluorescence response toward Cu²⁺ was carried to assess the fluorescent property of synthesized Schiff base. The probe exhibited a higher fluorescence enhancement in the presence of Cu²⁺ over other metal ions (Ni²⁺, Zn²⁺, Hg²⁺, Co²⁺, Cd²⁺, Al³⁺, Fe²⁺, and Pb²⁺). The binding stoichiometry between L and Cu²⁺ has been investigated using Job’s plot and Benesi-Hildebrand equation and it was found that ligand L can form 1:1 L-Cu²⁺ complex with binding constant (K _a) of 4?×?10⁴ LM^?1.     

Redox-Switchable New Phthalocyanines Containing Hydrazono-Thiazole-Carboxylate Fragments: Synthesis,Electrochemical, Spectroelectrochemical and Electrocolorimetric Investigation

New phthalonitrile compound with Schiff base, carbothioamide and thiazole moieties as substituents and its corresponding metal-free and metallophthalocyanines (Zn(II), Ni(II), Co(II), and Cu(II)) were synthesized and characterized for the first time. The solubilities of these novel phthalocyanines were high in organic solvents. The redox properties of the compounds have been researched by cyclic voltammetry, square wave voltammetry, controlled-potential coulometry and in situ spectroelectrochemistry in dimethylsulfoxide. The compounds displayed metal and/or phthalocyanine ring-based, generally reversible or quasi-reversible reduction and oxidation processes. The effect of aggregation on the redox behavior of these complexes was also discussed. In general, decreased intensity and broadening in the main Q absorption band and the appearance of a new blue-shifted band confirmed the presence of H-type aggregates in the solutions of the complexes 4, 6 and 8 in DMSO/TBAP. The color changes associated with the redox processes and electrogenerated anionic and cationic redox species were also recorded with in situ electrocolorimetric measurements. In situ UV–vis spectral and associated color changes monitored during the reduction processes of the complexes suggested their applicability in the fields of the electrochemical technologies.     

Microstructural and Radioluminescence Characteristics of Nd<Superscript>3+</Superscript> Doped Columbite-Type SrNb<Subscript>2</Subscript>O<Subscript>6</Subscript> Phosphor

Undoped and different concentration Nd³⁺ doped SrNb₂O₆ powders with columbite structure were synthesized by molten salt process using a mixture of strontium nitrate and niobium (V) oxide and NaCl-KCl salt mixture as a flux under relatively low calcining temperature. X-ray diffraction analysis results indicated that SrNb₂O₆ phases found to be orthorhombic columbite single phase for undoped, 0.5 and 3 mol% Nd³⁺ doping concentrations. Phase composition of the powders was examined by SEM-EDS analyses. Radioluminescence properties of Nd³⁺ doped samples from UV to near-IR spectral region were studied. The emissions increased with the doping concentration of up to 3 mol%, and then decreased due to concentration quenching effect. There is a sharp emission peak around 880 nm associated with ⁴F_5/2 → ⁴I_9/2 transition in the Nd³⁺ ion between 300 and 1100 nm. The broad emission band intensity was observed from 400 to 650 nm where the peak intensities increased by increasing Nd³⁺ doping concentration. All the measurements were taken under the room temperature.     

On the control of solutions of viscoelastic equations with boundary feedback

In this paper we consider a viscoelastic equation with a nonlinear feedback localized on a part of the boundary. For a wider class of relaxation functions and without imposing any restrictive growth assumption on the damping term, we establish an explicit and general decay rate result.     

The finite state projection algorithm for the solution of the chemical master equation

This article introduces the finite state projection (FSP) method for use in the stochastic analysis of chemically reacting systems. One can describe the chemical populations of such systems with probability density vectors that evolve according to a set of linear ordinary differential equations known as the chemical master equation (CME). Unlike Monte Carlo methods such as the stochastic simulation algorithm (SSA) or tau leaping, the FSP directly solves or approximates the solution of the CME. If the CME describes a system that has a finite number of distinct population vectors, the FSP method provides an exact analytical solution. When an infinite or extremely large number of population variations is possible, the state space can be truncated, and the FSP method provides a certificate of accuracy for how closely the truncated space approximation matches the true solution. The proposed FSP algorithm systematically increases the projection space in order to meet prespecified tolerance in the total probability density error. For any system in which a sufficiently accurate FSP exists, the FSP algorithm is shown to converge in a finite number of steps. The FSP is utilized to solve two examples taken from the field of systems biology, and comparisons are made between the FSP, the SSA, and tau leaping algorithms. In both examples, the FSP outperforms the SSA in terms of accuracy as well as computational efficiency. Furthermore, due to very small molecular counts in these particular examples, the FSP also performs far more effectively than tau leaping methods.     

Electron microscopy of bulk metallic glass machining chips

Machined Zr_52.5Ti₅Cu_17.9Ni_14.6Al₁₀ bulk metallic glass (BMG) chips were characterized using high resolution electron microscopy. Compared to conventional processing techniques, machining produces very high heating/cooling, and deformation rates. It is therefore of interest to compare structural changes in machining chips with those produced by conventional processing. Large (～1 μm) crystalline grain, residual amorphous region, and phase separation in the amorphous–crystalline transition region were detected in bright field TEM images. Three equilibrium phases, Zr₂Cu, ZrAl₂, and Zr₂Ni, which have been identified in samples undergoing conventional annealing, were revealed from selected area electron diffraction patterns of the chips. High magnification TEM micrographs showed nanocrystallites, about 10 nm in size, in the amorphous–crystalline transition region.     

Impedance‐based viscoelastic flow cytometry

Elastic nature of the viscoelastic fluids induces lateral migration of particles into a single streamline and can be used by microfluidic based flow cytometry devices. In this study, we investigated focusing efficiency of polyethylene oxide based viscoelastic solutions at varying ionic concentration to demonstrate their use in impedimetric particle characterization systems. Rheological properties of the viscoelastic fluid and particle focusing performance are not affected by ionic concentration. We investigated the viscoelastic focusing dynamics using polystyrene (PS) beads and human red blood cells (RBCs) suspended in the viscoelastic fluid. Elasto‐inertial focusing of PS beads was achieved with the combination of inertial and viscoelastic effects. RBCs were aligned along the channel centerline in parachute shape which yielded consistent impedimetric signals. We compared our impedance‐based microfluidic flow cytometry results for RBCs and PS beads by analyzing particle transit time and peak amplitude at varying viscoelastic focusing conditions obtained at different flow rates. We showed that single orientation, single train focusing of nonspherical RBCs can be achieved with polyethylene oxide based viscoelastic solution that has been shown to be a good candidate as a carrier fluid for impedance cytometry.     

Chemical Epigenetics: The Impact of Chemical and Chemical Biology Techniques on Bromodomain Target Validation

Epigenetics is currently the focus of intense research interest across a broad range of disciplines due to its importance in a multitude of biological processes and disease states. Epigenetic functions result partly from modification of the nucleobases in DNA and RNA, and/or post‐translational modifications of histone proteins. These modifications are dynamic, with cellular machinery identified to modulate and interpret the marks. Our focus is on bromodomains, which bind to acetylated lysine residues. Progress in the study of bromodomains, and the development of bromodomain ligands, has been rapid. These advances have been underpinned by many disciplines, but chemistry and chemical biology have undoubtedly played a significant role. Herein, we review the key chemistry and chemical biology approaches that have furthered our study of bromodomains, enabled the development of bromodomain ligands, and played a critical role in the validation of bromodomains as therapeutic targets.     

Piperidinium Hydrogen Sulfate (PHS) as an Efficient Ionic Liquid Catalyst for the Synthesis of Imidazole Derivative under Solvent‐Free Condition

Piperidinium hydrogen sulfate is used as a very important new catalyst for the synthesis of the biologically active compounds from a series of multi‐substituted imidazole components by the simple reaction of benzyl with different aromatic aldehydes, ammonium acetate, and phenethylamine or butylamine as amine derivatives. The key merits of this method are very shorter reaction times, excellent yield, and ease of stabilization. Furthermore, the produced products can be purified by a non‐chromatographic technique, and the catalyst is reusable. All of these new synthesized components have been characterized and checked from spectral data: IR, ¹H‐NMR, and ¹³C‐NMR spectra and elemental analyses.