Poly(pyridinium salt)s with organic counterions derived from an aromatic diamine containing tetraoxyethylene units exhibiting amphotropic liquid‐crystalline and photoluminescence properties

Several poly(pyridinium salt)s containing various organic counterions and tetraoxyethylene units in their backbones were synthesized by either ring‐transmutation polymerization reaction of 4,4'‐(1,4‐phenylene)bis(2,6‐diphenylpyrylium tosylate) with bis(2‐(2‐(4‐aminophenoxy)ethoxy)ethyl) ether on heating in dimethyl sulfoxide or metathesis reaction of the tosylate polymer with the corresponding lithium or sodium salts in acetonitrile. Their chemical structures were determined by ¹H‐NMR and ¹³C‐NMR spectroscopy, and elemental analyses. Their number‐average molecular weights and polydispersity indices were in the range of 34,000–52,000 and 1.14–1.38, respectively, as determined by gel permeation chromatography. They were characterized both for their thermotropic and lyotropic liquid‐crystalline properties by using differential scanning calorimetry and polarizing optical microscopy. As these polymers exhibited liquid‐crystalline phase both in the melt and in solutions, they are classified as an amphotropic class of ionic polymers. Their light‐emitting properties in a large number of organic solvents that ranged from nonpolar to polar solvents and in films cast from methanol and acetonitrile were also studied by using spectrofluorometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A dynamic spectrum management strategy based on cooperative bargaining framework

This work proposes a dynamic and fair spectrum management strategy to be adopted by a service provider (SP). Here, we consider a scenario where multiple access networks (ANs) of different (not necessarily competing) technologies are owned by a single SP. We envisage that an SP employs an entity, called local spectrum controller (LSC), which manages a common pool of spectrum and is responsible for distributing the spectrum to individual ANs in a fair manner. Since the available spectrum is inadequate to satisfy the aggregate demand from all ANs simultaneously, LSC has to employ a dynamic spectrum allocation strategy. We have modeled the problem as an n-player cooperative bargaining game and have solved the problem with the help of solution techniques namely, Nash bargaining solution (NBS), Kalai-Smorodinsky bargaining solution (KSBS) and modified Thomson bargaining solution (MTBS). We have presented two novel heuristics to compute KSBS and MTBS. Moreover, a suitable utility function for the AN with respect to its received spectrum have been presented. We have also identified possible objectives of LSC (i.e., SP), namely minimizing overall dissatisfaction (MOD) of heterogeneous network, maintaining equality of distribution (MED) and maximizing proportional fairness (MPF). Finally, we have compared performances of above solutions with max–min fairness solution and Shapley value solution with respect to the above objectives of LSC.     

Grinding-induced rapid,convenient and solvent free approach for the one pot synthesis of α-aminophosphonates using aluminium pillared interlayered clay catalyst

An easy to prepare aluminium pillared interlayered clay (PILC) has been developed as a stable, recyclable and heterogeneous catalyst to promote the one-pot three component synthesis of α-aminophosphonates under solvent-free conditions using grindstone chemistry. Utilization of mild reaction conditions, clean conversion and greater selectivity under grinding conditions along with effortless separation, and purification of reaction products make this process extra attractive.     

Ballistic Modification of Nitramine Propellants with Special Reference to NG‐PE‐PCP‐Based High Energy Propellants

The burning rate pressure relationship is one of the important criteria in the selection of the propellant for particular applications. The pressure exponent (η) plays a significant role in the internal ballistics of rocket motors. Nitramines are known to produce lower burning rates and higher pressure exponent (η) values. Studies on the burning rate and combustion behavior of advanced high‐energy NG/PE‐PCP/AP/Al‐ and NG/PE‐PCP/HMX/AP/Al‐based solid rocket propellants processed by a conventional slurry cast route were carried out. The objective of present study was to understand the effectiveness of various ballistic modifiers viz. iron oxide, copper chromite, lead/copper oxides, and lead salts in combination with carbon black as a catalyst on the burning rate and pressure exponent of these high‐energy propellants. A 7–9 % increase in the burning rates and almost no effect in pressure exponent values of propellant compositions without nitramine were observed. However, in case of nitramine‐based propellants as compared to propellant compositions without nitramines, slight increases of the burning rates were observed. By incorporation of ballistic modifiers, the pressure exponents can be lowered. The changes in the calorimetric values of the formulations by addition of the catalysts were also studied.     

Extracranial neuroblastomas and neurological complications

Between October 1989 and March 1997, 25 pediatric inpatients were treated for primary extracranial neuroblastoma (NB; n=20) or ganglioneuroblastoma (GNB; n=5) at the University of Istanbul, Institute of Pediatric Oncology, and these children were the subjects of this retrospective study. Seventeen (68%) of these patients experienced 19 neurological complications during the course of their disease. Fourteen had nervous system metastases or invasion. Nonmetastatic complications, including CNS infections (n=3) and new onset of seizures (n=2) secondary to metabolic encephalopathy were seen in 5 cases. By the time of the final analysis of the results, 8 of the 17 patients with neurological complications had died, 7 had either been lost to follow-up (n=4) or were in the terminal stage of their disease (n=3), and 2 were in remission. Both of the patients who were in remission had dumbbell neuroblastoma (DNB), and 1 of them, with congenital DNB, also had neurological sequelae, characterized by paraplegia and neurogenic bladder. Neurological complications occurred in 68% of NB and GNB cases. Metastatic complications were more common than nonmetastatic complications and had a poor prognosis. Neurological complications were the primary cause of mortality in this study, mortality being related to neurological complications in 63% of cases, and the final outcome was worse than expected. However, regardless of any differences in social, economic and geographic factors and different treatment protocols for NB in different pediatric oncology institutions, neurological complication rates in pediatric NB are similar in all.     

FEL oscillator performance optimization with astigmaticebeams

A model is presented for an FEL amplifier with an astigmatic electron beam propagating through a linearly polarized, linearly tapered wiggler. The model is used to examine FEL resonator performance as a function ofe-beam focusing in the wiggle plane perpendicular to the plane of polarization of the magnets.     

Ray trace evaluation of solar concentrators including limb darkening effects

The different correlations used to calculate intensity distribution over the sun's disc are compared. A new correlation is suggested which predicts the values to within ± 1.5 per cent of the experimental values. The distribution of local concentration ratio over a flat absorber placed in the focal plane of a cylindrical parabolic trough and that of a polygonal trough is determined using a ray-tracing technique.     

Estimation of hemispherical total emittance of tubular absorber from heat loss tests

The hemispherical total emittance of a selective coating on a tubular absorber is determined from the heat-loss factor obtained by an indoor test set-up. For this an analytical equation has been developed for the heat-loss factor of a tubular absorber with a concentric glass cover in the case of natural convection over the cover.