Adaptive Amphiphilic Dendrimer‐Based Nanoassemblies as Robust and Versatile siRNA Delivery Systems

siRNA delivery remains a major challenge in RNAi‐based therapy. Here, we report for the first time that an amphiphilic dendrimer is able to self‐assemble into adaptive supramolecular assemblies upon interaction with siRNA, and effectively delivers siRNAs to various cell lines, including human primary and stem cells, thereby outperforming the currently available nonviral vectors. In addition, this amphiphilic dendrimer is able to harness the advantageous features of both polymer and lipid vectors and hence promotes effective siRNA delivery. Our study demonstrates for the first time that dendrimer‐based adaptive supramolecular assemblies represent novel and versatile means for functional siRNA delivery, heralding a new age of dendrimer‐based self‐assembled drug delivery in biomedical applications.     

Redox Non‐Innocence of Coordinated 2‐(Arylazo) Pyridines in Iridium Complexes: Characterization of Redox Series and an Insight into Voltage‐Induced Current Characteristics

Two examples of a rare class of di‐radical azo‐anion complexes of 2‐(arylazo) pyridine with Ir^III carrier are introduced. Their electronic structures have been elucidated using a host of physical methods that include X‐ray crystallography, cyclic voltammetry, electron paramagnetic resonance spectroscopy, and density functional theory. Room temperature magnetic moments of these are consistent with two nearly non‐interacting azo‐anion radicals. These displayed rich electrochemical properties consisting of six numbers of reversible and successive one electron CV‐waves. Redox processes occur entirely at the coordinated ligands without affecting metal redox state. Apart from reporting their chemical characterization, I‐V characteristics of these complexes in film state are investigated using sandwich‐type devices comprising of a thin film of 100–125 nm thickness placed between two gold‐plated ITO electrodes. These showed memory switching properties covering a useful voltage range with a reasonable ON/OFF ratio and also are suitable for RAM/ROM applications. I‐V characteristics of two similar complexes of Rh and Cr with identical ligand environment and electronic structure are also referred for developing an insight into the memory switching ability of Ir‐ and Rh‐ complexes on the basis of comparative analysis of responses of the respective systems. In a nutshell, thorough analysis of voltage driven redox dynamics and corresponding solid and solution state current responses of all the systems are attempted and there from an unexplored class of switching devices are systematically introduced.     

Simultaneous recovery of plutonium and americium from assorted analytical waste solutions using extraction chromatography

A rapid extraction chromatography based methodology was developed for simultaneous recovery of plutonium and americium from various kinds of analytical waste obtained during chemical quality control of plutonium based nuclear materials using sulphonic acid based actinide? resin. Efforts were made to understand the effect of initial feed acidity, gamma radiation and the concentrations of Am³⁺ and Pu⁴⁺ on their k _d. values. Processing of assorted analytical waste solutions through this method revealed that more than 95 % of Am³⁺ and 90 % of Pu⁴⁺ were adsorbed on the resin while iso- propanol can be successfully employed for the quantitative recovery of both the actinides from the loaded resin phase.     

Studies on the radiolytic stability of newly developed solvent systems containing four calix-crown-6 ligands for radio-cesium recovery

Radiolytic stability of solvent systems containing four commercially available calix-crown-6 ligands termed as calix[4]arene-bis-crown-6 (CC), calix[4]arene-benzo-bis-crown-6 (CBC), calix[4]arene-naphtho-bis-crown-6 (CNC), and bis-(octyloxy)calix[4]arene-mono-crown-6 (CMC) dissolved in phenyl trifluoromethyl sulphone (PTMS) was studied which followed the order: CBC > CC > CNC ~ CMC. The radiolytic stability was evaluated by the absolute distribution ratio (D _Cs) vales at a given concentration of nitric acid as well as the nature of the extracted species. The radiolytic degradation products were identified by GC–MS analysis. The present study indicates that CBC in PTMS can be used as a solvent for radio-cesium recovery with good recycling possibilities.     

Device stability of inverted and conventional bulk heterojunction solar cells with MoO3 and ZnO nanoparticles as charge transport layers

The performance and stability of both inverted and conventional organic photovoltaic devices were examined with low temperature chemically synthesized ZnO nanoparticles as electron transporting layer and MoO₃ as hole transporting layer. The device efficiency and energy conversion efficiency in inverted devices were found to be 3.48% and 68%, respectively, whereas, in conventional devices these were 2.86% and 55%, respectively. This change of efficiency in inverted and conventional devices relates with the change of flatband voltage extracted from Mott-Schottky capacitance study. The inverted device shows excellent efficiency even after 250 h in unencapsulated condition. However, the conventional device efficiency degrades very quickly compared with the inverted one. Thus, the films deposition order plays a pivotal role for fabricating a stable and high performance organic photovoltaic device.     

Effects of Scattering on THz Spectra of Granular Solids

Experimental studies of granular solids have shown that significant scattering effects restrict the accurate determination of material absorption in the terahertz (THz) region. The present work investigates the grain size dependent scattering contribution on the extinction spectra of Ammonium Nitrate, flour and salt between 0.2 to 1.2 THz using THz time-domain spectroscopy. The scattering contribution can be estimated by applying Mie theory for spherical grains. The approach essentially separates the independent contributions of true absorption and scattering losses and thus determines the total extinction for different grain sizes of various materials. The separation of the intrinsic material absorption from scattering losses shows that the frequency dependence in weakly absorbing materials is predominantly particle size dependent. Consequently, that range of THz frequencies cannot be used to differentiate granular solids having no intrinsic absorption.     

Evidence for a nuclear phase transition in target nuclei after relativistic nuclear interactions

The degree of excitation of the emulsion target nuclei due to nuclear interactions of oxygen and sulfur projectiles at 200 GeV/nucleon incident energy has been investigated. Using the plausible assumption that the numberN _b of slow particles emitted from the struck target nucleus can be interpreted as a measure of the temperatureT of the residual nucleus, we have found that there exists a critical temperatureT _c of the excited target nucleus. For Ag and Br target nuclei this temperature corresponds to <N _b>≌12 and it is attained when the impact parameters are less than about 4 fm.     

Detection in incompletely characterized colored non-Gaussian noisevia parametric modeling

The problem of detecting a weak signal known except for amplitude in incompletely characterized colored non-Gaussian noise is addressed. The problem is formulated as a test of composite hypotheses, using parameteric models for the statistical behavior of the noise. A generalized likelihood ratio test (GLRT) is employed. It is shown that for a symmetric noise probability density function the detection performance is asymptotically equivalent to that obtained for a similar detector designed with a priori knowledge of the noise parameters. Non-Gaussian distributions are found to be more favorable for the purpose of detection than the Gaussian distribution. The computational burden of the GLRT may be partially reduced by employing a Rao efficient score test which shares all the nice asymptotic properties of the GLRT for small signal amplitudes. Computer simulations of the performance of the Rao detector support the theoretical results     

Capacity of Multivariate Channels with Multiplicative Noise: Random Matrix Techniques and Large-N Expansions (2)

We study memoryless, discrete time, matrix channels with additive white Gaussian noise and input power constraints of the form Y i = ∑ _j H _ij X _j + Z _i , where Y _i , X _j and Z _i are complex, i = 1… m, j = 1… n, and H is a complex m× n matrix with some degree of randomness in its entries. The additive Gaussian noise vector is assumed to have uncorrelated entries. Let H be a full matrix (non-sparse) with pairwise correlations between matrix entries of the form E[H ik H ^* jl] = 1/n C ij D kl, where C, D are positive definite Hermitian matrices. Simplicities arise in the limit of large matrix sizes (the so called large-n limit) which allow us to obtain several exact expressions relating to the channel capacity. We study the probability distribution of the quantity f(H) = log (1+PH ^† SH) . S is non-negative definite and hermitian, with TrS = n and P being the signal power per input channel. Note that the expectation E[f(H)], maximised over S, gives the capacity of the above channel with an input power constraint in the case H is known at the receiver but not at the transmitter. For arbitrary C, D exact expressions are obtained for the expectation and variance of f(H) in the large matrix size limit. For C = D = I, where I is the identity matrix, expressions are in addition obtained for the full moment generating function for arbitrary (finite) matrix size in the large signal to noise limit. Finally, we obtain the channel capacity where the channel matrix is partly known and partly unknown and of the form α; I+ β H, α,β being known constants and entries of H i.i.d. Gaussian with variance 1/n. Channels of the form described above are of interest for wireless transmission with multiple antennae and receivers.