Crystallization kinetics of linear polyethylene: The maximum in crystal growth rate-temperature dependence

This rapid communication reports a summary of the key findings of crystallization kinetics studies of unfractionated high density (linear) polyethylene at extremely large supercoolings. We report, for the first time, the maximum in crystal growth rate-crystallization temperature data for linear polyethylene, which has been sought by many researchers since the 1950s. The maximum growth rate was found to occur in the range of 70-75 °C with two separate methods. The kinetics studies were performed using a newly developed quench-crystallization technique based on depolarized reflection light microscopy that is capable of achieving enormously higher quench rates than existing methods. Typical onset crystallization temperatures accessed with this technique range from 40 to 90 °C. Bulk growth rates of crystals were obtained as the reciprocal of crystallization half times measured from the change in the depolarized light intensity upon direct crystallization from the melt. Separately, radial growth rates of spherulites were measured over a wide range of supercoolings. Secondary nucleation analysis of the crystal growth rates resulted in single linear fits extending into deep regime III, suggesting no change in mechanism of formation of the crystals at the largest supercoolings. The deeply quenched films, crystallized at temperatures below the maximum, contain non-impinged spherulites, capable of further crystallization.     

Pressure sensitive paint demonstrates relationship between ejector wall pressure and aerodynamic performance

 This paper provides an example of the application of Pressure Sensitive Paint (PSP) to complex internal suspersonic flows and demonstrates the relationship between ejector wall pressure and aerodynamic performance. Details of such jet mixer-ejector nozzles are relevant to jet noise reduction programs. Several ejector configurations with straight, convergent, and divergent side walls were used in our experiments. The side-wall that was painted with PSP was also instrumented with an array of 156 pressure taps connected to Electronically Scanned Pressure (ESP) modules, enabling simultaneous measurement of “true” reference pressures. The PSP results agreed very well with the “true” reference pressures and also provided a detailed map of the complicated pressure patterns that could not be detected using the pressure taps. Finally, we also demonstrated the direct relationship between ejector side-wall pressure distribution and ejector performance characteristics such as exit mean flow uniformity, pumping, and thrust augmentation. Received: 16 December 1997/Accepted: 21 August 1998     

Metal‐based antitumor,cytotoxic and antimicrobial activity: pharmacological evaluation of Knoevenagel condensate β‐diketone Schiff base thiosemicarbazone Cu(II) and Zn(II) complexes

Knoevenagel condensate Schiff base ligands [L = 3‐cinnamalideneacetylacetone‐thiosemicarbazone (CAT)/3‐cinnama‐ lideneacetylacetoneethylthiosemicarbazone (CAET)/3‐cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)] and their copper/zinc complexes were synthesized. They were characterized by analytical and spectral techniques. From these data it was found that the ligands adopt square‐planar geometry on metalation with Cu²⁺ and Zn²⁺. To evaluate the antitumor and cytotoxic activity of the synthesized complexes in mice and human cancer cell lines, the antitumor activity of the complexes was evaluated against an Ehrlich ascites carcinoma (EAC) tumor model. The activity was assessed using survival time and short‐term in vitro cytotoxic activity. Oral administration of complexes (100 mg/kg) increased the survival time. The cytotoxic activity of complexes was evaluated using human breast cancer (MDA‐MB‐231), colon cancer (HCT‐116) and nonsmall lung cancer (NCI‐H‐23) cell lines. Both the complexes possessed significant antitumor and cytotoxic activity on EAC and human cancer cell lines. The in vitro antimicrobial screening effect of the investigated compounds was also tested against the various organisms by well diffusion method. Copyright © 2009 John Wiley & Sons, Ltd.     

Lower bounds for adaptive locally decodable codes

An error‐correcting code is said to be locally decodable if a randomized algorithm can recover any single bit of a message by reading only a small number of symbols of a possibly corrupted encoding of the message. Katz and Trevisan 12 showed that any such code C : {0, 1}ⁿ → Σ^m with a decoding algorithm that makes at most q probes must satisfy m = Ω((n/log |Σ|)^q/(q?1)). They assumed that the decoding algorithm is non‐adaptive, and left open the question of proving similar bounds for adaptive decoders. We show m = Ω((n/log |Σ|)^q/(q?1)) without assuming that the decoder is nonadaptive. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005     

Stability-Indicating HPTLC Method for Simultaneous Determination of Ezetimibe and Simvastatin

Simvastatin and ezetimibe are used to treat hyperlipidemia. A simple, selective and stability-indicating HPTLC method has been established for analysis of simvastatin and ezetimibe. The method has been validated so that both drugs can routinely be analyzed simultaneously. The method uses aluminum-backed silica gel 60F₂₅₄ TLC plates as stationary phase with n-hexane–acetone 6:4 (v/v) as mobile phase. Densitometric analysis of both drugs was carried out in absorbance mode at 234 nm. This system was found to give compact bands for simvastatin and ezetimibe (R _F 0.39 ± 0.05 and 0.50 ± 0.05, respectively). Linear relationships were obtained between response and amount of drug in the range 200–1,600 ng per band with high correlation coefficients (r ² = 0.9917 ± 0.0018 for simvastatin and r ² = 0.9927 ± 0.0021 for ezetimibe). The method was validated for precision, robustness, and recovery. The limits of detection and quantitation were 25 and 150 ng per band, respectively. Simvastatin and ezetimibe were subjected degradation by acid, pH 6.8 phosphate buffer, oxidation, dry heat, and wet heat. The degradation products were well resolved from the pure drug with significantly different R _F values. Because the method could effectively separate the drug from its degradation products, it can be used for stability-indicating analysis.     

On the existence of nested orthogonal arrays

A nested orthogonal array is an OA(N,k,s,g) which contains an OA(M,k,r,g) as a subarray. Here r<s and M<N. Necessary conditions for the existence of such arrays are obtained in the form of upper bounds on k, given N, M, s, r and g. Examples are given to show that these bounds are quite powerful in proving nonexistence. The link with incomplete orthogonal arrays is also indicated.