The Gay-Berne mesogen: a paradigm shift?

A Commentary on the paper “Computer simulation studies of anisotropic systems XIX. Mesophases formed by the Gay-Berne model mesogen„, by G.R. Luckhurst, R.A. Stephens and R.W. Phippen. First published in Liquid Crystals, 8, 451-464 (1990).     

Switching the dipole moment for 5CB on and off

A Commentary on the paper “A molecular dynamics study of the nematic phase of 4-n-pentyl-4'-cyanobiphenyl„, by S. J. Picken, W. F. van Gunsteren, P. Th. van Duijnen and W. H. de Jeu. First published in Liquid Crystals, 6, 357-371 (1989).     

Nutritional Profiling and Antioxidant Property of Three Wild Edible Mushrooms from North East India

The mushroom is an important food for the rural tribal populations in Manipur, because of its high nutritional contents. In this study, we report on the nutritional profile of three wild edible mushrooms consumed by the tribal populations of Manipur viz.: Macrocybe gigantea J124; Lactifluus leptomerus J201 and Ramaria thindii J470. The studied mushrooms possess a high protein content of 37.6%, 20.8% and 16.4%, respectively. They have a high vitamin C content with low vitamin B1, B2 and folic acid. Among the three mushrooms, M. gigantea J124 possesses the highest mineral content, followed by R. thindii J470 and L. leptomerus J201. The total phenolic content of L. leptomerus J201, M. gigantea J124 and R. thindii J470 were 26.206, 29.23 and 30.99 mg GAE/g, with flavonoid content of 6.646, 6.854 and 9.187 mg quercetin/g, respectively. R. thindii J470 has the highest TPC and TFC content, which correlates with its DPPH radical scavenging activity. The IC50 values for R. thindii J470, M. gigantea J124 and L. leptomerus J201 are 242.0 µg/mL, 550.4 µg/mL and 689.0 µg/mL, respectively, which suggest that the higher content of phenolic compounds in R. thindii J470 contributes to its radical scavenging properties.     

Holographic storage via the liquid crystal state: a success story

A Commentary on the paper “Molecular addressing? Studies on light-induced reorientation in liquid crystalline side chain polymers”, by K. Anderle, R. Birenheide, M. J. A. Werner and J.H. Wendorff. First published in Liquid Crystals, 9, 691-699 (1991).     

Letter to the editor: Electronic data formats for open storage of published chemical kinetic data

In support of the Editor's goal of providing open storage of chemical kinetic data published in the International Journal of Chemical Kinetics, we propose the adoption of XML formats from PrIMe ( www.primekinetics.org ) for species identification and thermochemical data, and of Chemical Markup Language (CML) for three‐dimensional molecular geometries. Examples are provided in the online supplemental material of an article in this issue (Snitsiriwat, S.; Asatryan, R.; Bozzelli, J. W. Int J Chem Kinet 2010, 42, 181–199). We invite the input and assistance of the international chemical kinetics community in developing and refining these standards. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 200–201, 2010     

Release of electrolytes from W/O/W double emulsions stabilized by a soluble complex of modified pectin and whey protein isolate

W/O/W double emulsions (DEs) stabilized by charged soluble complexes of whey protein isolate (WPI) and modified pectins were investigated in relation to their stability and the release of two types of electrolytes, NaCl and sodium ascorbate.WPI alone cannot properly stabilize the DEs. The droplet size is relatively large (100 μm) and increases with time. However, addition of modified pectin to form a soluble complex with WPI significantly improved the stability.DEs prepared with two types of oils (medium chain triglycerides (MCT) and R(+)-limonene) were studied by measuring droplet size, creaming, viscosity, and electrolyte release. Irrespective of their very different oil phase nature, both emulsions were stable against coalescence, but R(+)-limonene formed smaller droplets (25 μm) than MCT (35 μm). The electrolyte release rate was significantly higher from the R(+)-limonene that formed DEs with much lower viscosity. R(+)-limonene-DE released 75% of the NaCl after 28 days, while MCT-DE released only 50%. NaCl was released more slowly than sodium ascorbate.Apparently, the release mechanism from R(+)-limonene-DE was found to be “thinning the outer interface and release of the entire inner droplets” while it seems that the release from MCT-DE was slower and “diffusion controlled”.DEs stabilized by WPI/C63 released 12% of the sodium ascorbate after 1 day in milk and remained stable for at least 8 days. However, DEs stabilized with only WPI released about 50% of the sodium ascorbate after 1 day, and phase separated after 8 days.     

Liquid-crystalline phthalocyanines revisited

A Commentary on the paper ”Homologous series of liquid‐crystalline metal free and copper octa‐n‐alkoxyphthalocyanines?, by J. F. van der Pol, E. Neeleman, J. W. Zwikker, R. J. M. Nolte, W. Drenth, J. Aerts, R. Visser and S. J. Picken. First published in Liquid Crystals, 6, 577‐592 (1989).     

BOOK REVIEW

Structure and Bonding , Volume 41, Edited by J. D. D unitz , J. B. G oodenough , P. H emmerich , J. A. I bers , C. K. J ørgensen , J. B. N eilands , D. R einen and R. J. P. W illiams .     

Drainage and critical thickness of foam films from aqueous solutions of mixed nonionic surfactants

The thinning and the critical thickness (of rupture or “black spots” formation) of foam films from aqueous solutions of mixed nonionic surfactants are studied under varied experimental conditions, as a function of film radius (0.05–0.15 mm), surfactant concentration (0.01–1.0 CMC) and ionic strength (0.001–0.1 M NaCl). The experimental values of the drainage coefficient (), determined from the film thickness versus time dependences, were used to calculate the theoretical values of the film critical thickness.

The real velocity of film thinning is a major factor in the process of reaching the state of kinetic instability when approaching the critical thickness (Scheludko's criterion). The classical equation used to describe the film thinning rate, proposed and named by Scheludko (1955) “Reynolds Law”, is applicable for small film radii (r < 0.05 mm). At larger radii the velocity of thinning follows the equation of Manev et al. [E.D. Manev, R. Tsekov, B. Radoev, J. Colloid Interf. Sci. 18 (1997) 769], which takes into account the effect of the film thickness local non-homogeneity.

The studied stabilizing surfactants include n-dodecyl-β-d-maltoside (β-C12G2) and hexaethyleneglycol monododecyl ether (C12E6). Along with confirming the dependences following from the theories of the critical thickness [B. Radoev, A. Scheludko, E.D. Manev, J. Colloid Interf. Sci. 95 (1983) 254] and film thinning [E.D. Manev, R. Tsekov, B. Radoev, J. Colloid Interf. Sci. 18 (1997) 769], the results of the present investigation established also certain deviations for films stabilized with mixed surfactants (β-C12G2 + C12E6). The effectiveness of the empirical equation, employing the drainage coefficient () to describe the film thinning, is emphatically proven here.     

Computer simulation study of metastable ice VII and amorphous phases obtained by its melting

Molecular dynamics simulations of metastable ice VII and cubic ice Ic are carried out in order to examine (1) the ability of commonly used water interaction potentials to reproduce the properties of ices, and (2) the possibility of generating low-density amorphous (LDA) structures by heating ice VII, which is known to transform to LDA at approximately 135 K at normal pressure [S. Klotz, J. M. Besson, G. Hamel, R. J. Nelmes, J. S. Loveday, and W. G. Marshall, Nature (London) 398, 681 (1999)]. We test four simple empirical interaction potentials of water: TIP4P [W. L. Jorgensen, J. Chandrasekhar, J. D. Madura, R. W. Impey, and M. L. Klein, J. Chem. Phys. 79, 926 (1983)], SPC/E [H. J. C. Berendsen, J. R. Grigera, and T. P. Straatsma, J. Phys. Chem. B 91, 6269 (1987)], TIP5P [M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys. 112, 8910 (2000)], and ST2 [F. H. Stillinger and A. Rahman, J. Chem. Phys. 60, 1545 (1974)]. We have found that TIP5P ice VII melts at 210 K, TIP4P at 90 K, and SPC/E at 70 K. Only TIP5P water after transition has a structure similar to that of LDA. TIP4P and SPC/E have almost identical structures, dissimilar to any known water or amorphous phases, but upon heating both slowly evolve towards LDA-like structure. ST2 ice VII is remarkably stable up to 430 K. TIP4P and SPC/E predict correctly the cubic ice collapse into a high-density amorphous ice (HDA) at approximately 1 GPa whereas TIP5P remains stable up to approximately 5 GPa. The densities of the simulated ice phases differ significantly, depending on the potential used, and are generally higher than experimental values. The importance of proper treatment of long-range electrostatic interactions is also discussed.     

The behavior of single-molecule junctions predicted by atomistic simulations

Molecular dynamic simulations in combination with energy minimizations are used in order to understand the basis of the novel experiments reported recently by Haiss et al. (W. Haiss, C. Wang, I. Grace, A.S. Batsanov, D.J. Schiffrin, S.J. Higgins, M.R. Bryce, C.J. Lambert, R.J. Nichols, Nature Mater. 5 (2006) 995). Our model suggests that single-molecule junctions produced by the trapping method can be reached when the STM tip – substrate surface separation is smaller than 8 Å. Additionally, our model predicts that the effect of the electric field on the attachment/detachment process can be neglected.     

Tungsten monocarbide, WC: pure rotational spectrum and 13C hyperfine interaction

The J = 1→2 pure rotational transitions in the X(3)Δ(1)(ν = 0) state of (186)W(12)C and (184)W(12)C were recorded using a pump/probe microwave optical double resonance (PPMODR) technique and analyzed to give fine structure parameters. The field-free [17.6]2←X(3)Δ(1) (1, 0) bands of the W(13)C isotopologues were recorded using laser induced fluorescence and analyzed to produce the (13)C(I = 1/2) magnetic hyperfine parameter. Bonding in the [17.6]2(ν = 1) and X(3)Δ(1)(ν = 0) states is discussed and a comparison of the experimentally determined properties of the X(3)Δ(1)(ν = 0) state with those predicted as a prelude to the electron electric dipole moment (eEDM) measurements [J. Lee, E. R. Meyer, R. Paudel, J. L. Bohn, and A. E. Leanhardt, J. Mod. Opt. 56, 2005 (2009)] is given.     

BOOK REVIEWS

Book reviewed in this article:
Primitive Sensory and Communication Systems. Edited by M. J. C arlile ,
Chemical Kinetics, Edited by D. R. Herschbach.
An Introduction to Radiation Chemistry (2nd Edition). J. W. T. Spinks and R. J. Woods     

Dimethylacetylene: the theory required to analyse the infrared and Raman perpendicular bands

In this paper we give a detailed account of the theory required to simulate and analyse the infrared and Raman perpendicular fundamental bands of the dimethylacetylene molecule at high resolution. A summary of this theory has appeared in a previous paper (P.R. Bunker, J.W.C. Johns, A.R.W. McKellar and C. di Lauro, J. Mol. Spectry. 162 (1993) 142) in which an analysis of the infrared methyl rocking fundamental band was given. As well as detailing the effect of various terms in the Hamiltonian we also discuss the Raman selection rules and show that the analysis of the ΔK = 2 component of the perpendicular fundamental bands will lead to a determination of the sign of the torsional barrier. The sign of the barrier (i.e. whether the minimum energy conformation is staggered or eclipsed) cannot be determined from the analysis of the infrared perpendicular bands.     

Flow-injection determination of phenylephrine hydrochloride in pharmaceutical dosage forms with on-line solid-phase extraction and spectrophotometric detection

A flow injection method is proposed for the determination of phenylephrine hydrochloride in pharmaceutical dosage forms. The method involves the use of on-line solid-phase extraction by means of a microcolumn containing Dowex 50W X8 ion-exchange resin for the separation of the analyte prior to colour development and spectrophotometric detection in the visible region.

The influence of preconcentration flow, preconcentration pH and elution volume was studied.

The method exhibits appropriate linearity (r² = 0.9999) which was proved statistically by means of the “F”-test. When applied to commercial samples containing several active ingredients and excipients, a significant reduction of interferences was found. Accuracy, evaluated by means of the spike recovery method was in the range 99.7–100.8%, with precision (R.S.D., %) better than 1%.

In order to achieve the automation the system was controlled from a notebook computer by means of a program written in QuickBASIC language. Under these conditions, a sampling frequency of 40 samples per hour could be attained.     

IR,Multinuclear-NMR,and Structural Studies on [WH(CO)2(NO)(PR3)2]: cis-Influence of Phosphorus Ligands on Hydride Character

A thorough IR and ¹H-, ¹³C-, ³¹P-, ¹⁸³W-NMR spectroscopic, and X-ray structural study was carried out on complexes of the type trans, trans-[WH(CO)₂(NO)(PR₃)₂], (R = Et, Me, Ph, i-PrO, MeO, and PhO). Linear correlations could be found between Tolman's parameter X and v(CO), v(WH), v(NO), δ(¹³C) (CO), as well as 1n(k), k being the H/D exchange rate constant for the hydride in CD₃OD. The ¹J(¹⁸³W,³¹P), ²J(³¹P,¹H), and ²J(³¹P,¹³C) as well as the ¹J(¹⁸³W,¹H) values are related to the electronegativity of the R groups on the phosphorus ligands. This is also indicated by EHT calculations of s-orbital populations of appropiate W model complexes. The X-ray structures of [WH(CO)₂(NO)(PR₃)₂] (R = Me, Ph, and MeO) were determined. Minor differences were observed in the W? P bond lenghts and in the P? W? P and C? W? C angles. No obvious relationship between X-ray data and spectroscopic parameters could be found. All three structures reveal a bending of both the CO and PR₃ ligands towards the hydride atom. The total octahedral distortion is remarkably constant (25.6, 29.4, and 27.0° tilt, respectively), although the ligands individually are very different. This is attributed to redistribution of π-electron density between CO and PR₃ groups toward the central W-atom in the three complexes.     

The writhing on the wall: first tentative steps toward a comprehensive theory of liquid crystal surfaces

A Commentary on the paper “Theory of the nematic-isotropic transition in a restricted geometry„, by A. Poniewierski and T.J. Sluckin. First published in Liquid Crystals, 2, 281-311 (1987).     

PDLC shutters: where has this technology gone?

A Commentary on the paper “Response times and voltages for PDLC shutters„, by Bao-Gang Wu, John H. Erdman and J. William Doane. First published in Liquid Crystals, 5, 1453-1465 (1989).