Complexation of metal ions with the novel azathia crown ethers carrying anthracene pendant in acetonitrile–dichloromethane

A series of crown ethers carrying an anthracene group with nitrogen–sulfur donor atom, which differ in having three, four and five sulfur atoms in the macrocycle was designed and synthesized by the reaction of the corresponding macrocyclic compound and 9-chloromethyl-anthracene. The influence of metal cations such as Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ on the spectroscopic properties of the ligands was investigated in acetonitrile–dichloromethane (1:1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Cu²⁺, Hg²⁺ and Pb²⁺ the results of which disclosed the complexation compositions and complex stability constants of the novel ligands with these cations. The monoazapentathia crown ether showed sensitivity for Al³⁺ with linear range and detection limit of 2.6 × 10⁻⁶ M–2.6 × 10⁻⁵ M and 8.1 × 10⁻⁷ M, respectively.     

Properties of small molecular drug loading and diffusion in a fluorinated PEG hydrogel studied by 1H molecular diffusion NMR and 19F spin diffusion NMR

R(f)-PEG (fluoroalkyl double-ended poly(ethylene glycol)) hydrogel is potentially useful as a drug delivery depot due to its advanced properties of sol-gel two-phase coexistence and low surface erosion. In this study, (1)H molecular diffusion nuclear magnetic resonance (NMR) and (19)F spin diffusion NMR were used to probe the drug loading and diffusion properties of the R(f)-PEG hydrogel for small anticancer drugs, 5-fluorouracil (FU) and its hydrophobic analog, 1,3-dimethyl-5-fluorouracil (DMFU). It was found that FU has a larger apparent diffusion coefficient than that of DMFU, and the diffusion of the latter was more hindered. The result of (19)F spin diffusion NMR for the corresponding freeze-dried samples indicates that a larger portion of DMFU resided in the R(f) core/IPDU intermediate-layer region (where IPDU refers to isophorone diurethane, as a linker to interconnect the R(f) group and the PEG chain) than that of FU while the opposite is true in the PEG-water phase. To understand the experimental data, a diffusion model was proposed to include: (1) hindered diffusion of the drug molecules in the R(f) core/IPDU-intermediate-layer region; (2) relatively free diffusion of the drug molecules in the PEG-water phase (or region); and (3) diffusive exchange of the probe molecules between the above two regions. This study also shows that molecular diffusion NMR combined with spin diffusion NMR is useful in studying the drug loading and diffusion properties in hydrogels for the purpose of drug delivery applications.     

Electrochemiluminescent aptamer biosensor for the determination of ochratoxin A at a gold-nanoparticles-modified gold electrode using N-(aminobutyl)-N-ethylisoluminol as a luminescent label

A highly selective electrochemiluminescent biosensor for the detection of target nephrotoxic toxin, ochratoxin A (OTA), was developed using a DNA aptamer as the recognition element and N-(4-aminobutyl)-N-ethylisoluminol (ABEI) as the signal-producing compound. The electrochemiluminescent aptamer biosensor was fabricated by immobilizing aptamer complementary DNA 1 sequence onto the surface of a gold-nanoparticle (AuNP)-modified gold electrode. ABEI-labeled aptamer DNA 2 sequence hybridized to DNA 1 and was utilized as an electrochemiluminescent probe. A decreased electrochemiluminescence (ECL) signal was generated upon aptamer recognition of the target OTA, which induced the dissociation of DNA 2 (ABEI-labeled aptamer electrochemiluminescent probe) from DNA 1 and moved it far away from the electrode surface. Under the optimal conditions, the decreased ECL intensity was proportional to an OTA concentration ranging from 0.02 to 3.0 ng mL^-1, with a detection limit of 0.007 ng mL^-1. The relative standard deviation was 3.8% at 0.2 ng mL^-1 (n = 7). The proposed method has been applied to measure OTA in naturally contaminated wheat samples and validated by an official method. This work demonstrates the combination of a highly binding aptamer with a highly sensitive ECL technique to design an electrochemiluminescent biosensor, which is a very promising approach for the determination of small-molecule toxins.     

Equivalent contributing depth investigated by a lateral wave with axial transmission in viscoelastic cortical bone

Cortical bone is a viscoelastic heterogeneous medium which may be assessed with axial transmission. This work aims at evaluating the average depth investigated by the lateral wave for radial variations of material properties in relatively thick cortical bone. The equivalent contributing depth (ECD) is derived from the finite element simulation results for spatial variations of a viscoelastic coefficient (η(11)) and of porosity. A value of ECD equal to around 1.6 mm is obtained for a spatial variation of η(11). The method fails to predict accurate values of the ECD for a spatial variation of porosity, because all parameters vary simultaneously.     

Strong and weak thermalization of infinite nonintegrable quantum systems

When a nonintegrable system evolves out of equilibrium for a long time, local observables are in general expected to attain stationary expectation values, independent of the details of the initial state. But the thermalization of a closed quantum system is not yet well understood. Here we show that it presents indeed a much richer phenomenology than its classical counterpart. Using a new numerical technique, we identify two distinct regimes, strong and weak, occurring for different initial states. Strong thermalization, intrinsically quantum, happens when instantaneous local expectation values converge to the thermal ones. Weak thermalization, well known in classical systems, shows convergence to thermal values only after time averaging. Remarkably, we find a third group of states showing no thermalization, neither strong nor weak, to the time scales one can reliably simulate.     

Teleportation of a general two-mode coherent-state superposition via attenuated quantum channels with ideal and/or threshold detectors

Three novel probabilistic yet conclusive schemes are proposed to teleport a general two-mode coherent-state superposition via attenuated quantum channels with ideal and/or threshold detectors. The calculated total success probability is highest (lowest) when only ideal (threshold) detectors are used.     

Bistable reflectivity in bulky semiconductors due to two photon-biexciton transitions

A new mechanism has been proposed for optical bistability in a bulk system of interacting photons and biexcitons. Bistable behaviour can occur for very low pumping intensities if the input light frequency is clearly less than the two-photon resonance of the biexciton.     

远红外激光等离子体散射系统的校准方法

本文依据多普勒效应,提出了利用转动细针对远红外激光的散射来模拟等离子体源对远红外激光的散射,从而对远红外激光等离子体散射系统进行校准,为完成等离子体散射实验作好准备。     

Application of stochastic analytic hierarchy process within a domestic appliance manufacturer

The stochastic analytic hierarchy process (SAHP) provides a mechanism for achieving more effective selection of alternatives in the form of considering multi and conflicting criteria using quantitative and qualitative information under uncertainty. In contrast to the traditional analytic hierarchy process, the SAHP uses probabilistic distributions to incorporate uncertainty that people have in converging their judgements of preferences into a Likert scale. The vector of priorities is calculated using Monte Carlo simulation, the final rankings are analysed for rank reversal using statistical analysis, and managerial aspects are introduced systematically. The present paper demonstrates an application of the SAHP in a world-class domestic appliance manufacturer. The case study was carried out by strictly following a disciplined and organized methodology for applying the SAHP developed by the authors. The results of this study were encouraging to key personnel within the company, establishing a greater opportunity to explore the applications of the SAHP in other core business processes.