Quantum dot capped magnetite nanorings as high performance nanoprobe for multiphoton fluorescence and magnetic resonance imaging

In the present study, quantum dot (QD) capped magnetite nanorings (NRs) with a high luminescence and magnetic vortex core have been successfully developed as a new class of magnetic-fluorescent nanoprobe. Through electrostatic interaction, cationic polyethylenimine (PEI) capped QD have been firmly graft into negatively charged magnetite NRs modified with citric acid on the surface. The obtained biocompatible multicolor QD capped magnetite NRs exhibit a much stronger magnetic resonance (MR) T2* effect where the r2* relaxivity and r2*/r1 ratio are 4 times and 110 times respectively larger than those of a commercial superparamagnetic iron oxide. The multiphoton fluorescence imaging and cell uptake of QD capped magnetite NRs are also demonstrated using MGH bladder cancer cells. In particular, these QD capped magnetite NRs can escape from endosomes and be released into the cytoplasm. The obtained results from these exploratory experiments suggest that the cell-penetrating QD capped magnetite NRs could be an excellent dual-modality nanoprobe for intracellular imaging and therapeutic applications. This work has shown great potential of the magnetic vortex core based multifunctional nanoparticle as a high performance nanoprobe for biomedical applications.     

Evaluation of heat capacity measurements by temperature-modulated differential scanning calorimetry

Temperature-modulated differential scanning calorimetry (TMDSC) is known to have the ability to measure heat capacity of materials more accurately than the conventional differential scanning calorimeter. However, the accuracy of the measured heat capacity displays significant dependence on various experimental parameters such as period of modulation (p), amplitude of modulation (a), geometry of sample (g), heating rate (r), etc. One of the key features of this system is the ability to measure heat capacity under quasi-isothermal conditions. In the present investigation, heat capacity of a well-established system namely sapphire and thoria was measured by TMDSC under dynamic mode and also under quasi-isothermal mode. The experimental parameters, mentioned above p, a, g, and r are varied to establish the conditions for measuring heat capacity accurately.     

Thermal expansion and heat capacity of dysprosium hafnate

Dysprosium hafnate is a candidate material for as control rods in nuclear reactor because dysprosium (Dy) and hafnium (Hf) have very high absorption cross-sections for neutrons. Dysprosium hafnate (Dy₂O₃·2HfO₂-fluorite phase solid solution) was prepared by solid-state as well as wet chemical routes. The fluorite phase of the compound was characterized by using X-ray diffraction (XRD). Thermal expansion characteristics were studied using high temperature X-ray diffraction (HTXRD) in the temperature range 298–1973 K. Heat capacity measurements of dysprosium hafnate were carried out using differential scanning calorimetry (DSC) in the temperature range 298–800 K. The room temperature lattice parameter and the coefficient of thermal expansion are 0.5194 nm and 7.69 × 10⁻⁶ K⁻¹, respectively. The heat capacity value at 298 K is 232 J mol⁻¹ K⁻¹.     

Electrochemistry of 4′-hydroxy and acetoxy flavones CV and NPP study

Electrochemical reduction behavior of 3-acetoxyflavone was compared with 3-hydroxyflavone on glassy carbon electrode with DMF and 60% DMF/Britton Robinson buffer at pH 3.8 & 10.1 using cyclic voltammetry (CV) and on dme using normal pulse polarography (NPP). Single irreversible reduction waves were observed due to the reduction of keto moiety. The effects of change in medium, pH and sweep rate were evaluated. The electrode process was found to be diffusion controlled and enhanced substituent effect was noticed due to extended conjugation. Kinetic parameters were calculated from CV & NPP measurements using R.S. Nicholson and I. Shain equation and Meites & Isreal equation, respectively. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Zero-Sum Differential Games Involving Hybrid Controls

We study a zero-sum differential game with hybrid controls in which both players are allowed to use continuous as well as discrete controls. Discrete controls act on the system at a given set interface. The state of the system is changed discontinuously when the trajectory hits predefined sets, an autonomous jump set A or a controlled jump set C, where one controller can choose to jump or not. At each jump, the trajectory can move to a different Euclidean space. One player uses all the three types of controls, namely, continuous controls, autonomous jumps, and controlled jumps; the other player uses continuous controls and autonomous jumps. We prove the continuity of the associated lower and upper value functions V⁻ and V⁺. Using the dynamic programming principle satisfied by V⁻ and V⁺, we derive lower and upper quasivariational inequalities satisfied in the viscosity sense. We characterize the lower and upper value functions as the unique viscosity solutions of the corresponding quasivariational inequalities. Lastly, we state an Isaacs like condition for the game to have a value This work was partially supported by Grants DRDO 508 and ISRO 050 to the Non-linear Studies Group, Indian Institute of Science. The first author is a University Grant Commission Research Fellow and the financial support is gratefully acknowledged. The authors thank Prof. M.K. Ghosh, Department of Mathematics, Indian Institute of Science, for introducing the problem and thank the referee for useful suggestions.     

Dynamical signatures of ‘phase transitions’: Chaos in finite clusters

Finite clusters of atoms or molecules, typically composed of about 50 particles (and often as few as 13 or even less) have proved to be useful prototypes of systems undergoing phase transitions. Analogues of the solid-liquid melting transition, surface melting, structural phase transitions and the glass transition have been observed in cluster systems. The methods of nonlinear dynamics can be applied to systems of this size, and these have helped elucidate the nature of the microscopic dynamics, which, as a function of internal energy (or ‘temperature’) can be in a solidlike, liquidlike, or even gaseous state. The Lyapunov exponents show a characteristic behaviour as a function of energy, and provide a reliable signature of the solid-liquid melting phase transition. The behaviour of such indices at other phase transitions has only partially been explored. These and related applications are reviewed in the present article.     

18‐Crown‐6 Catalyzed Microwave‐mediated Synthesis of Symmetric Bis‐Heterocyclic Compounds under Solvent‐free Condition

An efficient, solvent‐free and 18‐crown‐6 catalyzed method for the synthesis of N‐alkyl‐4‐(4‐(5‐(2‐(alkyl‐amino)thiazol‐4‐yl)pyridin‐3‐yl)phenyl)thiazol‐2‐amine, N‐alkyl‐4‐(5‐(2‐alkyamino)thiazol‐4‐yl)pyridine‐3‐yl)thiazol‐2‐amine, and 4,4′‐bis‐{2‐[amino]‐4‐thiazolyl}biphenyl bis‐heterocyclic derivatives via microwave accelerated cyclization is presented.     

Synthesis of dihydrochromeno[4,3-b]pyrrolo[3,2-f]quinolines via intramolecular aza Diels-Alder reaction

An efficient and convenient one-pot intramolecular aza Diels-Alder approach for the synthesis of dihydrochromeno[4,3-b]pyrrolo[3,2-f]quinolines has been reported. Particularly valuable features of this methodology include simple execution, inexpensive catalyst, and good product yields.     

Screening the optical properties of Ag-Au alloy gradients formed by bipolar electrodeposition using surface enhanced Raman spectroscopy

We report the synthesis of Ag-Au alloy gradients on stainless steel substrates using bipolar electrodeposition (BP-ED), a technique based on the existence of a potential gradient at the interface of a bipolar electrode (BPE) and an electrolytic solution. The interfacial potential gradient causes the rates of electrodeposition of Ag and Au to vary along the length of the BPE, leading to the electrodeposition of a chemical concentration gradient. The surface morphology of the electrodeposits was characterized using scanning electron microscopy (SEM), and their chemical composition was determined using energy dispersive X-ray spectroscopy (EDX). Self-assembled monolayers of a Raman-active probe molecule (benzene thiol) were allowed to form on the surface of the alloy gradients, and confocal Raman microscopy was employed to determine the alloy composition that resulted in the maximum surface enhanced Raman scattering (SERS) intensity. An alloy composition of ca. 70% Ag/30% Au was found to be optimum for SERS excited using 514.5 nm radiation, and it is explained on the basis of composition-dependent changes in the local surface plasmon resonance (LSPR) of the electrodeposited Ag-Au alloy.