A validated high‐performance thin‐layer chromatography method for the identification and simultaneous quantification of six markers from Platanus orientalis and their cytotoxic profiles against skin cancer cell lines

Betulinic acid ( 1 ), betulinic acid‐3‐acetate ( 2 ), 3‐acetylbetulinaldehyde ( 3 ), oleanolic acid‐3‐acetate ( 4 ), 3‐β‐hydroxy‐28,19‐β‐olenolide ( 5 ), and β‐sitosterol ( 6 ) were isolated from Platanus orientalis and a high‐performance thin‐layer chromatography method was developed for their simultaneous quantification. The markers were first derivatized on the chromatogram with ceric ammonium sulfate and then high‐performance thin‐layer chromatography densitometry was carried out. Chromatographic separation of these markers was carried out on silica gel 60 plates using a ternary solvent system n‐hexane/toluene/acetone (6:3.5:1 v/v/v) as a mobile phase. For marker 1 , a deuterium (D₂) lamp and wavelength of 420 nm was used. A tungsten (W) lamp was used for markers 2 and 3 at 550 nm and for 4 – 6 at 500 nm. The method was validated for accuracy, precision, LOD, and LOQ. All calibration curves showed a good linear relationship (r > 0.9919). The precision evaluated by an intra‐ and interday study showed RSDs < 2.51% and accuracy validation recovery between 95.54 and 99.33% with RSDs < 1.55%. The successful application of the validated method showed 1 as the most abundant component (4.63%) and 5 (0.017%) the least. The markers displayed a significant cytotoxic effect against human keratinocyte, mouse melanoma, and human skin epithelial carcinoma cancer cells by using a 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay.     

Testing the tail index in autoregressive models

We propose a class of nonparametric tests on the Pareto tail index of the innovation distribution in the linear autoregressive model. The simulation study illustrates a good performance of the tests. Such tests have various applications in a study of flood flows, rainflow data, behavior of solids, atmospheric ozone layer and reliability analysis, in communication engineering, in stock markets and insurance. Research of J. Jurečková and J. Picek was partly supported by Czech Republic Grant 201/05/2340, by the Research Project LC06024 and by the NSF grant DMS 0071619. Research of H. L. Koul was partly supported by the NSF grants DMS 0071619 and 0704130.     

The electron spin resonance of polycarbonate track detectors

Polycarbonate films are widely used as solid state track detectors (SSTDs) of radiation, but as yet our knowledge of the microscopic nature of the latent track is limited. The processes of chemical etching and thermal annealing are not fully understood. The lack of stability of track parameters bears on the accuracy of the charge determination of energetic heavy nuclei.

We have applied the technique of electron spin resonance, (ESR) in order to seek a correlation between the density of tracks and the growth and decay of free radicals detected by ESR. Samples of polycarbonate were irradiated with thermal neutrons and then etched progressively with NaOH. The ESR signal increased initially and then became weaker as the bulk of the polycarbonate was removed. Other samples were annealed after partial etching. ESR monitoring of this annealing showed that free radicals were recombining, probably due to diffusion processes.     

On certain double integrals

We evaluate certain double integrals involving H-functions of two variables. These integrals are quite general and are capable of yielding a number of integrals as particular cases.     

Regression Quantiles and Related Processes Under Long Range Dependent Errors

This paper obtains asymptotic representations of the regression quantiles and the regression rank-scores processes in linear regression setting when the errors are a function of Gaussian random variables that ale stationary and long range dependent. These representations are then used to obtain the limiting behavior of L- and linear regression rank-scores statistics based on the above processes. The paper also obtains the asymptotic uniform linearity of the linear regression rank-scores processes and statistics based on residuals under the long range dependent setup. It thus generalizes some of the results of Jure ková [In Proceedings of the Meeting on Nonparametric Statistics and Related topics (A. K. Md. E. Saleh, Ed.) pp. 217-228. Elsevier, Amsterdam/New York] and Gutenbrunner and Jure ková [Ann. Statist. 20 305-329] for the case of independent errors to one of the highly useful dependent errors setup.     

Plectranthoic acid A & B, two new triterpenoids from Plectranthus rugosus

Two new triterpenoid acids, designated as plectranthoic acid A and plectranthoic acid B, have been isolated from P. rugosus and are characterised as (20-S)-3α-hydroxy-18α,19α-$\text{H}\text{-}$-urs-12-en-30β-oic acid and (14-S)-3α-hydroxy-18α, 19α $\text{H}\text{-}$-urs-12-en-27α-oic acid.     

Effect of alpha-tocopherol on pulmonary antioxidant defence system and lipid peroxidation in cigarette smoke inhaling mice

Background  

Free radicals generated in biological systems by cigarette smoke (CS) inhalation can cause oxidative stress in tissues, resulting in lipid peroxidation (LPO). In view of the antioxidant properties of α-tocopherol (AT), in the present study, effects of AT on antioxidant defence system and LPO were investigated in mice inhaling CS for different time intervals.     

On certain integral relations and their applications

The aim of this paper is to establish certain integral relations involving the H-function of two variables and employ these to evaluate certain double integrals involving the products of two H-function of two variables of generalised arguments. The results established in this paper are of a very general nature and are capable of yielding a number of results as particular cases.     

Applicability of OSL pre-dose phenomenon of quartz in the estimation of equivalent dose

The feasibility of utilizing the pre-dosed OSL signal in the estimation of the equivalent dose has been investigated. The results based on (i) the behavior of growth curve, (ii) dose recovery tests and (iii) non-bleachability of reservoir centres, R-centres, suggests that (i) the pre-dosed OSL does not seem to work satisfactorily in dose estimation unlike the pre-dosed 110 °C TL emission and (ii) it may not be applicable in case of bleached specimen.     

Synthesis and characterization of poly(N‐isopropylacrylamide) films by photopolymerization

A novel method used for the preparation of poly(N‐isopropylacrylamide) (PNIPAAm) films of varying crosslink density under homogeneous/heterogeneous conditions is described in this paper. Photopolymerization of the N‐isopropylacrylamide (NIPAAm) monomer in water (homogeneous at ～7°C and heterogeneous at ～40°C) or a mixture of water/ethanol (50:50, heterogeneous at ～7°C) was carried out using 1‐[4‐(2‐hydroxyethoxy)‐phenyl]‐2‐hydroxy‐2‐methyl‐1‐propane‐1‐one (hydrophilic) or 2‐hydroxy‐2‐methyl propiophenone (hydrophobic) photo‐initiator. In order to investigate the effect of temperature and crosslink density, polymerization was carried out at ～7°C [below lower critical soluble temperature (LCST)] and ～40°C (above LCST) using varying amounts of N,N′‐methylene bisacrylamide (BIS) ranging from 1–4 wt%. Degree of swelling (determined by optical microscopy), phase transition temperature [determined by differential scanning calorimetry (DSC)] as well as morphology (scanning electron microscopy) were found to be dependent on solvent system (homogeneous/heterogeneous), temperature of polymerization and crosslink density. Hydrogels prepared at ～7°C using hydrophobic photo‐initiator and water/ethanol (50:50) as solvent, showed much higher degree of swelling at all levels of crosslink density as compared to hydrogel prepared at ～7°C using hydrophilic photo‐initiator and water as solvent. Hydrogels were used for patterning which may find applications in microfluidic devices. Copyright © 2006 John Wiley & Sons, Ltd.