Mercury assisted fluorescent supramolecular assembly of hexaphenylbenzene derivative for femtogram detection of picric acid

Aggregates of hexaphenylbenzene derivatives 3, having pyrene groups form network of fluorescent nanofibres in presence of mercury ions. Further, fluorescent nanofibres of 3-Hg²⁺ supramolecular ensemble exhibit sensitive and pronounced response towards the picric acid. In addition, the solution coated paper strips of 3-Hg²⁺ supramolecular ensemble can detect picric acid in the range of 2.29 fg/cm², thus, providing a simple, portable and low cost method for detection of picric acid in solution and in contact mode.     

Atomistic molecular dynamics simulations on the interaction of TEMPO-oxidized cellulose nanofibrils in water

Atomistic molecular dynamics simulations were carried out to obtain information on the rheological, aggregation and disintegration properties of carboxylated (TEMPO-oxidized) cellulose nanofibrils with different functionalization levels. The magnitude of the inter-fibril interaction was quantified for parallel nanofibrils using the umbrella sampling method. The obtained potential of mean force was found highly sensitive to the charge configuration for intermediate functionalization levels. This feature was further studied with an electrostatic model for similar charge configurations and system periodicity as in the case of the molecular dynamics simulations. The electrostatic contribution of the charged surfaces varied from repulsive to attractive depending on the distribution of the carboxylate groups and nearby counter-ions, as well as the distance between the fibrils. The simulated deviations from average behavior for single fibrils in both models suggest heterogeneity in their aggregation and disintegration behavior. This was seen in disintegration experiments, where the differences in disintegration energy and in the structural variation qualitatively agreed with the model predictions. As to aggregation behavior, the studied case with parallel fibrils reflects the upper boundary of the repulsive interaction.     

Facile synthesis of hollow urchin-like Nb2O5 nanostructures and their performance in dye-sensitized solar cells

Journal of Solid State Electrochemistry - In present study, hollow urchin-like nanostructures of Nb2O5 with elongated nanofilaments as photoanode material for dye-sensitized solar cells (DSSCs) are...     

Design and Applications of Small Molecular Probes for Calcium Detection

The physiological significance of calcium ions such as the role in cellular signalling, cell growth, etc. have driven the development of methods to detect and monitor the level of Ca²⁺ ions, both in vivo and in vitro. Although various approaches for the detection of calcium ions have been reported, methods based on small molecular fluorescent probes have unique advantages including small probe size, easy monitoring of detection processes and applicability in biological systems. In this review article, we will discuss the progress in the development of Ca²⁺‐binding fluorescent probes by taking into account the types of chelating groups that have been employed for Ca²⁺ binding.     

Comparison of various dispersion compensation techniques at high bit rates using CSRZ format

In this paper, the dispersion compensation techniques are compared on the basis of eye opening, eye closure, bit error rate and Q-factor. These techniques are applied to CSRZ system, which operates at bit rates of 2.5, 5, 10, 15 and 20 Gbps bit rates. The technique using fiber Bragg grating (FBG) for dispersion compensation is the best technique as this technique gives larger values of eye opening at 10 and 20 Gbps bit rate, smaller values of eye closure at 10 and 20 Gbps, minimum value of BER at 15 Gbps and maximum value of Q-factor at 15 Gbps when compared with other techniques. The RDF technique is the next best technique since this technique gives maximum value of eye opening when other techniques give almost similar values of eye opening at 15 Gbps, minimum value of eye closure at 15 Gbps, minimum value of BER at 15 Gbps and maximum value of Q-factor at 15 Gbps when compared with other techniques. The DCF is the next best technique as this technique gives maximum and minimum values of eye opening and eye closure at 20 Gbps (next best to FBG at 20 Gbps).     

A variable-wavelength-based approach of phase retrieval for contrast transfer function based methods

X-ray phase-contrast imaging has emerged as an important method for improving contrast and sensitivity in the field of X-ray imaging. This increase in the sensitivity is attributed to the fact that, in the hard X-ray regime, the phase shift is more prominent as compared with the attenuation for materials having a low X-ray absorption coefficient. Among all the methods using the X-ray phase-contrast technique, in-line phase-contrast imaging scores over the other methods in terms of ease of implementation and efficient use of available X-ray flux. In order to retrieve the projected phase map of the object from the recorded intensity pattern, a large number of algorithms have been proposed. These algorithms generally use either the transport of intensity or contrast transfer function based approach for phase retrieval. In this paper it is proposed to use multiple wavelengths for phase retrieval using the contrast transfer function based formalism.     

驱动模式对具有库源平衡的黏性流体中空间反射时间反演联合对称性的影响

满足空间反射时间反演parity and time-reversal(PT)联合对称性的库源平衡宏观开放系统近几年成为一个研究热点.本文将PT对称性引入到动力学系统,用格子玻尔兹曼方法求解Navier-Stokes方程,发现在二维黏性流体中,如果进口和出口的条件完全等同,在低雷诺数流动中,流场的PT对称函数(ρ)随雷诺数(Re)的增高以ρn～Ren指数增长.用三种不同的速度剖面来驱动流体,计算流场达到稳定状态时的PT对称性.结果发现,进出口平衡的黏性管流中,ρn～Ren的规律在三种驱动模式中出现,表明流场的PT对称性是由流体本身决定的,与驱动模式没有关系,从此论证所得到的指数率的谱适性.     

A study of angular correlations of projectile and target fragments in 1.4 A GeV Kr+Ag(Br) collisions

A sample of high multiplicity quasi-central Kr⁸⁴+Ag(Br) interactions has been'analysed in terms of angular correlations between projectile and target fragments. The azimuthal correlation of PFs and TFs suggests the presence of a weak collective (bounce-off) effect. Other observations like, target recoil velocity,F/B ratio of TFs with respect to direction of their source etc. are interpreted in terms of a simple two body quasi-elastic scattering and a modified Maxwell-Boltzmann distribution.     

Theoretical lifetimes,transition energies,fluorescence yields,and nonradiative branching ratios for highly excited states of lithium-like argon

We have calculated theoretical transition rates and transition energies for the states of the excited electron configurations, 1s 2s nl and 1s 2p nl, of lithium-like argon. The values of n considered range from n=2 to n=4 with all allowed values of l included, l=0 to l=n-1. We present numerical results for the theoretical lifetimes, transition energies, fluorescence yields, and nonradiative branching ratios. These quantities are related to the dielectronic recombination rates and cross sections of helium-like argon.     

Band gap variation in laser irradiated polytypic crystals of cadmium iodide

Highly purified single crystals of cadmium iodide obtained through repeated zone refining have been subjected to laser beam exposure (Argon ion laser), both for various time durations and to various beam intensities, and then subjected to band gap determination by UV spectroscopy. The band gap has been found to decrease gradually with increase in the laser beam intensity, whereas its variation with increase in time of exposure shows an unusual behaviour such that it initially falls sharply followed by a gradual rise back to its original value. The results have been analysed and interpreted in terms of indirect band gap character of the material and an unusual variation in phonon frequency. The interpretation is well supported by X-ray diffraction and scanning electron microscopy (SEM) studies. Received: 26 May 1997 / Revised: 6 August 1997 / Accepted: 15 September 1997