Flexoelectric polarization in nematic liquid crystals measured by a field on-off pyroelectric technique

A novel technique based on the pyroelectric effect is developed for making direct measurements of the flexoelectric polarization P _f in hybrid aligned nematic cells. The pyroelectric response is measured first in the field-off regime and then with the bias field applied. The latter allows a direct comparison of P _f with the field-induced polarization over the whole range of the nematic phase of the standard compound 5CB. The sum of the flexoelectric coefficients (e ₁+e ₃) is shown to be negative, and its dependence on the nematic order parameter does not follow a simple law (linear or quadratic), as has been predicted theoretically. The dynamics of P _f is discussed in terms of the order parameter fluctuations. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 220–225 (10 February 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Studies on surface structures of poly(ethylene oxide)‐segmented nylon films

The surface structures of three kinds of poly(ethylene oxide)‐segmented nylon (PEO‐Ny) molten films were investigated using a scanning electron microscopy (SEM), an electron spectroscopy for a chemical analysis (ESCA), and a static secondary ion mass spectrometry (SSIMS). The PEO‐Ny's used were high semicrystalline PEO‐segmented poly(iminosebacoyliminohexamethylene) (PEO‐Ny610), low semicrystalline PEO‐segmented poly(iminosebacoylimino‐m‐xylene) (PEO‐NyM10), and amorphous PEO‐segmented poly(iminoisophthaloyliminomethylene‐1,3‐cyclohexylenemethylene) (PEO‐NyBI). SEM observations show that the surfaces of the PEO‐Ny610 and PEO‐NyM10 films are composed of spherulite, and that PEO‐NyBI film has a smooth surface. The results of ESCA and SSIMS exhibit the significant enrichments of PEO segment at the surfaces of all the films regardless of the crystallinity. The reason for the enrichment of PEO segment was discussed in terms of the surface tension of the corresponding homopolymers in the melting state. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1045–1056, 2000     

Excess Enthalpies of Binary Mixtures of Propanediamine+Propanediol at 298.15 K

The molar excess enthalpies of 1,2- and 1,3-propanediamine+1,2- and 1,3-propanediol have been determined at 298.15 K by using a twin-microcalorimeter which requires each component liquid 1 to 1.5 cm³ for a series of runs over the whole range of mole fraction. All excess enthalpies are exothermic and large. An equilibrium constant K₁ expressed in terms of mole fractions and standard enthalpy of formation of 1:1 complex have been evaluated by ideal mixtures of momomeric molecules and their associated complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of supramolecular boron complex with anthryl groups exhibiting specific optical response for chloride ion

Supramolecular boron complex having plural hydrogen bonding sites and anthracene moieties was synthesized and showed an excimer emission selectively accompanied with capture of chloride ions.     

Urinary metabolic profile of phenylketonuria in patients receiving total parenteral nutrition and medication

Nutrition and drugs are main environmental factors that affect metabolism. We performed metabolomics of urine from an 8‐year‐old patient (case 1) with epilepsy and an 11‐year‐old patient (case 2) with malignant lymphoma who was being treated with methotrexate. Both patients were receiving total parenteral nutrition (TPN). We used our diagnostic procedure consisting of urease pretreatment, partial adoption of stable isotope dilution, gas chromatography/mass spectrometry (GC/MS) measurement and target analysis for 200 analytes including organic acids and amino acids. Surprisingly, their metabolic profiles were identical to that of phenylketonuria. The neopterin level was markedly above normal in case 1, and both neopterin and biopterin were significantly above normal in case 2. Mutation analysis of genomic DNA from case 1 showed neither homozygosity nor heterozygosity for phenylalanine hydroxylase deficiency. The metabolic profiles of both cases were normal when they were not receiving TPN. TPN is presently prohibited for individuals who have inherited disorders that affect amino acid metabolism. Although the Phe content of the TPN was not the sole cause of the PKU profile, its effect, combined with other factors, e.g. specific medication or possibly underlying diseases, led to this metabolic abnormality. The present study suggests that GC/MS‐based metabolomics by target analysis could be important for assuring the safety of the treatments for patients receiving both TPN and methotrexate. Metabolomic profiling, both before and during TPN, is useful for determining the optimal nutritional formula not only for neonates, but also for young children who are known heterozygotes for metabolic disorders or whose status is unknown. Copyright © 2009 John Wiley & Sons, Ltd.     

Conversion of acoustic bending vibration frequency in a freely suspended ferroelectric liquid-crystal film

A nonlinear acoustic effect was observed experimentally in a freely suspended ferroelectric liquid-crystal film. The effect consisted of a change in the frequency of the film bending vibrations under the action of a varying electric field. The up-and down-conversion efficiencies were found to be 50 and 30%, respectively.     

A T-DNA insertion mutant of AtHMA1 gene encoding a Cu transporting ATPase in Arabidopsis thaliana has a defect in the water–water cycle of photosynthesis

The water–water cycle is the electron flow through scavenging enzymes for the reactive species of oxygen in chloroplasts, and is proposed to play a role in alternative electron sink in photosynthesis. Here we showed that the water–water cycle is impaired in the T-DNA insertion mutant of AtHMA1 gene encoding a Cu transporting ATPase in chloroplasts. Chlorophyll fluorescence under steady state was not affected in hma1, indicating that photosynthetic electron transport under normal condition was not impaired. Under electron acceptor limited conditions, however, hma1 showed distinguished phenotype in chlorophyll fluorescence characteristics. The most severe phenotype of hma1 could be observed in high (0.1%) CO₂ concentrations, indicating that hma1 has the defect other than photorespiration. The transient increase of chlorophyll fluorescence upon the cessation of the actinic light as well as the NPQ induction of chlorophyll fluorescence revealed that the two pathways of cyclic electron flow around PSI, NDH-pathway and FQR-pathway, are both intact in hma1. Based on the NPQ induction under 0% oxygen condition, we conclude that the water–water cycle is impaired in hma1, presumably due to the decreased level of Cu/Zn SOD in the mutant. Under high CO₂ condition, hma1 exhibited slightly higher NPQ induction than wild type plants, while this increase of NPQ in hma1 was suppressed when hma1 was crossed with crr2 having a defect in NDH-mediated PSI cyclic electron flow. We propose that the water–water cycle and NDH-mediated pathways might be regulated compensationally with each other especially when photorespiration is suppressed.     

Femtosecond-resolution measurement of soft-X-ray pulse duration using ultra-fast population increase of singly charged ions induced by optical-field ionization

We demonstrate sub-100-fs resolution of a cross-correlation method for measuring the duration of soft-X-ray pulses. The method uses the ultra-fast increase in a singly charged ion population induced by optical-field ionization as a soft-X-ray -absorption switch. We measured the pulse duration of the 51st harmonic of a Ti:sapphire laser pulse using Kr gas as a soft-X-ray absorption medium and found it to be 60 fs assuming that the harmonic envelope is equal to a squared secant hyperbolic. This confirmed that our method achieves a shorter temporal resolution than the 100-fs pulse duration of the ionizing laser pulse. The temporal resolution obtained in this way is expected to be from one-third to one-half the duration of the ionizing laser pulse, according to our calculation of the time-evolving population of the Kr⁺ ions. The experimental demonstration and calculation show that methods based on optical-field-induced ionization are promising for femtosecond temporal characterization of an ultra-short pulse in the soft-X-ray region. PACS 42.50.Hz; 42.65.Ky; 32.80.Rm; 06.60.Jn