Reply to the comment by G. Barbero and N. V. Madhusudana ‘On a theoretical analysis on the influence of non-uniformity of the order parameter on the surface energy in nematics’ (1990, Liquid Crystals, 7, 299)

Abstract

In their comment to our recent paper [I] Barbero and Madhusudana argue that the mathematical problem is ill-posed and thus the consideration should be revised. The objection is based on the ideas published in a set of papers [2–4], where it has been shown that if the K₁₃term is used in the usual nematic free energy density, the function n(z) may be discontinuous at the surface and in this case we have to include second order elasticity ～(V ²n)² into our consideration. In principal, we agree with this objection, although it is very difficult to estimate whether the corresponding contribu-tion to n(z) is essential, because no real problem with second order elasticity has been solved up to now. At the same time it is obvious that if we do not take the K_l3 term into account, the solution of the minimizing problem with the traditional nematic free energy remains correct and does not contradict experimental observations.     

Response on “Regulations in the field of residue and doping analysis should ensure a well-defined risk of a false positive declaration” by N. M. Faber

Dr. Faber provided support for a valuable methodology for the comparison of mass spectra. However, since many other factors are involved in the evaluation process before declaring a sample “positive”, i.e. reporting an adverse analytical finding, his conclusions on this subject are incorrect. In this paper a number of arguments are listed showing that Dr. Faber did not take all factors under consideration when making his claims. These factors involve parameters directly related to mass spectrometric criteria, but also to other equally important factors including sample preparation specificity, retention time (since in doping control mass spectrometry is used as part of a hyphenated technique), etc. These arguments clearly illustrate that the risks for a false positive declaration can not be calculated according to Dr. Faber’s proposed methodology. Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.     

Comment on "Autoionization at the surface of neat water: is the top layer pH neutral, basic, or acidic?" by R. Vácha, V. Buch, A. Milet, J. P. Devlin and P. Jungwirth, Phys. Chem. Chem. Phys., 2007, 9, 4736

The surface of near-neutral water is basic due to the adsorption of hydroxide ions, not acidic as has been recently claimed.     

Studies on the biosynthesis of arteannuin——Ⅳ.The biosynthesis of arteanniuin and arteannuin B by the leaf homogenate of Artemisia annua L.

Arteannuic acid and(-)11R,13-d ydroarteannuic acid are the key intermediates in thebiosynthesis of arteannuin by the leaf homogenate of Artemisia annua L.,and arteannuic acid andepoxyarteannuic acid are the intermediates of arteannuin B.and epoxyarteannuic acid can not betransformed into arteannuin by the homogenate.     

Label-free and sensitive impedimetric nanosensor for the detection of cocaine based on a supramolecular complexation with β-cyclodextrin,immobilized on a nanostructured polymer film

Cocaine, a powerful addictive stimulant drug, has a variety of adverse effects on the body, thus its sensitive detection is very important. Here, we report on a simple, label-free, and sensitive impedimetric sensor for determination of cocaine based on its affinity to form an inclusion complex with β-cyclodextrin (β-CD). First, we prepared nanostructured poly N-acetylaniline film via electropolymerization of its monomer on a glassy carbon electrode (PNAANI/GC), subsequently overoxidized it, and conjugated β-CD to the polymer backbone. The designed and synthesized nanostructured PNAANI film serves a dual function in the sensor: on one hand, it maintains a high effective surface area on a geometrically small electrode that significantly enhances the number of β-CD molecules immobilized on the electrode; on the other hand, it provides an upright-oriented β-CD conjugation to the polymer backbone, thus all the β-CD receptors are actively involved in responding to the target. Sensitivity of the sensor was further enhanced by preconcentration of cocaine on the modified electrode surface. We attributed the changes in the interfacial charge transfer resistance (R _ct) of the electrode to cocaine concentration. Under optimized condition (pH 7.4, 5-min accumulation at an open circuit voltage), the sensor responded to cocaine concentration in the range of 100 nM–1.0 mM with a detection limit of 50 nM. Selectivity of the sensor for cocaine relative to some potential inferring compounds was also investigated, and the results were promising. The proposed approach exhibited an extended dynamic range, low detection limit, good sensitivity, and a desirable selectivity, which provides an efficient application prospect for on-field cocaine sensing.     

Correct derivation of a combined version of the Jouyban–Acree and van’t Hoff model and some comments on ‘Determination and correlation of the solubility of myricetin in ethanol and water mixtures from 288.15 to 323.15 K’

The experimental data reported in the paper by Cai and co-workers [DOI: 10.1080/00319104.2016.1163560] pertaining to the solubility of myricetin dissolved in binary aqueous–ethanol solvent mixtures has been reanalysed. A correct mathematical derivation is provided for the correlation expression from a combination of the van’t Hoff and Jouyban–Acree models. Cai et al. who used the expression in their study, however, erroneously implied that the expression resulted from a simple transformation of the Jouyban–Acree model. No mention was made that one needed to assume a van’t Hoff-type mathematical representation for how the solute solubility varied with temperature in the two mixture co-solvents.     

Study of the Effects of N Fertilization and Plant Density on the Essential Oil Composition and Yield of Cuminum cyminum L. Seeds by HS–SME

Headspace-solvent microextraction (HS–SME) with sample ultrasound irradiation was successfully used for the study of the influence of nitrogen fertilization and plant density on the essential oil yield and composition of cumin (Cuminum cyminum L.) seeds. The components were collected into a single microdrop of n-heptadecane and directly injected into a GC–MS injection port for analysis. A simplex method was used for fast optimization of the extraction parameters. The experiments were executed as split-plot based on randomized complete block design. Nitrogen fertilization as the main factor (in four levels) and plant density as subsidiary factor (in three levels) were applied. It was shown that the total GC peak areas of the HS–SME extract, is proportional to the essential oil yield of the cumin seeds obtained by a hydrodistillation method. Furthermore, similar trends in the concentrations of cuminaldehyde and most other volatile components were obtained by the two methods.     

Understanding the extraction mechanism,radiolytic stability and stripping behavior of thorium by ionic liquid based solvent systems: evidence of ‘ion-exchange’ and ‘solvation’ mechanism

The extraction efficiency for thorium followed the trend: Cyanex-923 > Cyanex-272 > DHOA > TBP. In case of TBP and DHOA the extraction proceeded via ‘solvation mechanism’ through Th(NO₃)₄·2L, while for Cyanex-923 and Cyanex-272 it proceeded via ‘ion exchange’ mechanism through (Th(NO₃)₂·2L)²⁺. The extraction process followed slower kinetics while change in Gibb’s energy revealed the spontaneity of the process. These ionic liquid based systems were found to be radiolytically stable, highly efficient and selective for Th. Oxalic acid was found to be suitable for almost quantitative stripping of Th from extracted ionic liquid phase.     

Study on the fluorescence depolarization of a chromophore attached to polymer chain end. Aggregation behaviours of poly(γ-benzyl l-glutamate) in semi-concentrated solution up to liquid crystal region

The emission anisotropics of PBLG-RhB [rhodamine B chemically bound to the terminal amino group of poly(γ-benzyl l-glutamate)] have been measured in a semi-concentrated solution of PBLG. The results show that the extent of the aggregation behaviour of PBLG gradually increases with increasing concentration of PBLG in chloroform and N,N-dimethylformamide.