Syntheses and optical properties of <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-cyano-poly(<Emphasis Type="Italic">p</Emphasis>-phenylene vinylene) derivatives

Two light emitting molecules with the cyano group at different positions on the vinylene i.e., 2,5-bis(2-thienyl-1-cyanovinyl)-1-(2_-ethylhexyloxy)-4-methoxybenzene (-TPT) and 2,5-bis(2-thienyl-2-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene (-TPT), and corresponding polymers, i.e., poly[2,5-bis(2-thienyl-1-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene] (denoted as P1) and poly[2,5-bis(2-ethienyl-2-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene] (denoted as P2) were synthesized. -TPT and -TPT, respectively, were blended into two host polymers, poly(methyl methacrylate (PMMA) and poly(9-vinylcarbazole) (PVK), to study the optical properties of the dopants in different host polymer matrices. Although -TPT and -TPT have the same backbone structure, their optical properties are much different. The PL emission maximum ( _max) of -TPT was found blue-shifted, compared with that of -TPT, while the PL intensity of -TPT was stronger than that of -TPT. Concentration effect in the optical properties was found, 1 wt% of -TPT in PVK had the maximum fluorescent emission.The PL maximum peak wavelengths for polymer films (P1 and P2) were found red-shifted; while their PL intensities were weaker when compared with those of blends.     

Dynamic-mechanical behavior of polyethylenes and ethene/<Emphasis Type="Italic">α</Emphasis>-olefin-copolymers: Part II. <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-relaxation

Several ethylene homopolymers and ethene/ α-olefin-copolymers with crystallinities ranging between 85 and 12% were characterized by dynamic-mechanical measurements. The occurring relaxations were correlated to the crystallinity of the polymeric materials and to morphology. The α-relaxation, being attributed to interlamellar shear, was found to be around 60 °C with activation energies of about 120 kJ/mol in samples with more than 42% crystallinity. The β-transition shows a much greater variety among the different samples characterized. Its relaxation temperatures vary between −40 and 10 °C with activation energies between 200 and 400 kJ/mol. The α- and β-relaxation of several quenched samples with crystallinities between 63 and 42% were found to overlap, thus producing bimodal maxima and different activation energies from the Arrhenius plots. A separation of these overlapping relaxations was only possible by measuring the relaxations over a frequency range of more than three orders of magnitude.     

Dynamic-mechanical behavior of polyethylenes and ethene-/<Emphasis Type="Italic">α</Emphasis>-olefin-copolymers: Part III. <Emphasis Type="Italic">γ</Emphasis>-relaxation

The temperature- and frequency-dependent dynamic-mechanical properties in the temperature regime of the γ-transition were determined for a number of polyethylenes and ethylene/α-olefin-copolymers differing in their crystallinity and crystal morphology. The temperature dependence of the γ-transition was found to obey the Arrhenius law for thermally activated processes. The γ-transition temperature determined at a frequency of 1 Hz and the corresponding activation energy were analyzed as a function of the crystallinity. As an overall trend, both quantities are found to decrease with decreasing crystallinity, which is explained by the increase in free volume due to the incorporation of short-chain branches or the thermal pretreatment (e.g., quenching). Taking into account that the crystal morphology of polyethylenes can be classified into four different groups, a more detailed picture appears. Within one type of morphology both quantities, namely the transition temperature and the activation energy, increase with decreasing crystallinity independent of the α-olefin used as the comonomer. These findings can be explained by partial orientations of the molecule segments in the interlamellar amorphous space in the case of HDPE or by the increased steric hindrance of the crankshaft motion by the short-chain branches. From the findings of this series of studies, it was concluded that the glass transition in polyethylene and polyethylene/α-olefin-copolymers is the β- and not the γ-transition.     

Cellulose–<Emphasis Type="Italic">co</Emphasis>-polyacrylonitrile blends: Properties of combined solutions in <Emphasis Type="Italic">N</Emphasis>-metylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide and the formation and thermolysis of composite fibers

Combined solutions of cellulose and an acrylonitrile-based copolymer in N-methylmorpholine-N-oxide have been prepared for the first time, new composite fibers have been formed, and the properties of the solutions and fibers under standard conditions and during thermal treatment have been studied. On the basis of studying the phase state and morphological peculiarities of combined cellulose solutions with polyacrylonitrile additives, it has been shown that the completed solutions make emulsions in the entire range of investigated concentrations. The rheological behavior of combined solutions changes with temperature. With the use of IR spectroscopy methods, it has been found that the addition of polyacrylonitrile to cellulose results in the association of nitrile groups with hydroxyl groups of cellulose, which favors the cyclization of CN groups during heating and the appearance of polyconjugated bonds in polyacrylonitrile chains. Thermal transformations of cellulose and polyacrylonitrile in the course of mixed-fiber carbonization have been studied via DSC and TGA. It has been shown that polyacrylonitrile inhibits the dehydration processes in cellulose and reduces the intensity of the peak due to the first stage of the structural rearrangement, i.e., acts as a “catalyst” of pyrolysis.     

Enhanced <Emphasis Type="Italic">β</Emphasis>-carotene production by <Emphasis Type="Italic">Rhodotorula glutinis</Emphasis> using high hydrostatic pressure

High hydrostatic pressure (HHP) technology was used for improving the ability of β-carotene biosynthesis of Rhodotorula glutinis R68. After the treatments of five repeated cycles at 300 MPa for 15 min, the barotolerant mutant PR68 was obtained. After 72 h of culture, the biomass of mutant PR68 was 21.6 g/L, decreased by 8.5% compared to the parent strain R68, but its β-carotene production reached 19.4 mg/L, increased by 52.8% compared to the parent strain R68. The result of restriction fragment length polymorphism analysis suggested that mutant strain PR68 was likely to change in nucleic acid level, and thus enhanced β-carotene production in this strain was a result of gene mutation induced by HHP treatment. HHP technology seems a promising approach for improving industrial microbes.     

Stereoselective Chemical Defense in the <Emphasis Type="Italic">Drosophila</Emphasis> Parasitoid <Emphasis Type="Italic">Leptopilina heterotoma</Emphasis> is Mediated by (−)-Iridomyrmecin and (+)-Isoiridomyrmecin

Chemical defense mechanisms are widespread among insects but have rarely been demonstrated in parasitoid wasps. Here, we show that the Drosophila parasitoid Leptopilina heterotoma (Hymenoptera, Figitidae) produces (−)-iridomyrmecin and (+)-isoiridomyrmecin in a cephalic gland, and that these chemicals have a highly repellent effect on ants. Stereoselective synthesis of 4 stereoisomers of iridomyrmecin allowed us to demonstrate that the repellent effect of iridomyrmecins depends on the stereochemistry. Potential food items impregnated with natural doses of (−)-iridomyrmecin were avoided by ants much longer than those impregnated with (+)-iridomyrmecin, (+)-isoiridomyrmecin, or (−)-isoiridomyrmecin, respectively. Quantitative headspace analyses revealed furthermore that females and males of L. heterotoma released iridomyrmecins in higher amounts when confronted with ants. This is the first time, that (−)-iridomyrmecin and (+)-isoiridomyrmecin are reported as natural products. Females synthesize more iridomyrmecins than males, and the most active (−)-iridomyrmecin is produced by females only. We, therefore, hypothesize that this defense mechanism is used mainly by female wasps when foraging for Drosophila larvae on rotten fruits, but also may protect male wasps during dispersal.     

Distribution of nonequilibrium carriers in the region of a <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> junction under various photogeneration conditions

A model is described, which makes it possible to calculate the distribution of nonequilibrium carriers and an electric field near the p–n junction, which arose as a result of the internal photoeffect. Using laser illumination, the possibilities to control the properties of nanolayered structures sensitive to the concentration of free carriers are analyzed. The mutual location of the region of the intense absorption of radiation and the p–n junction itself is varied and the linear and square mechanisms of carrier recombination are analyzed.     

Crystallization and melting of <Emphasis Type="Italic">α</Emphasis> and <Emphasis Type="Italic">β</Emphasis> phases in bulk syndiotactic polystyrene as monitored in situ via high-temperature wide-angle X-ray diffraction

Direct and non-intrusive observations of crystallization and melting behavior of and polymorphs in bulk syndiotactic polystyrene were made by means of temperature-programmed x-ray diffraction. Results indicated that the highest sustainable temperature identifiable via wide-angle x-ray diffraction using stepwise annealing at increasingly higher temperatures (T _a) for the perfected (with the initial crystallization temperature T _c = 245 °C, followed by annealing at stepwise increased T _a above 250 °C) phase may be at least 286 °C. In a similar manner, the highest sustainable temperature of the perfected (with T _c = 265 °C, followed by annealing at stepwise increased T _a above 275 °C) phase may be at least 280 °C. These observations suggest complete melting should occur only above the respective sustainable temperatures. It thus follows that equilibrium melting of the and the phases should occur at temperatures higher than 286 and 280 °C, respectively. Perfection of the less ordered form into the better ordered form within the family is observed to occur in the vicinity of 270 °C; no evidence of transformation between and phases is identified.     

Cadmium acetate as a ring opening polymerization catalyst for the polymerization of <Emphasis Type="Italic">rac</Emphasis>-lactide, <Emphasis Type="Italic">ε</Emphasis>-caprolactone and as a precatalyst for the polymerization of ethylene

In the present study, we have discussed the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA) and ε-caprolactone (ε-CL) using Cd(OAc)₂. Cd(OAc)₂ appeared to be a good catalyst for the polymerization of rac-LA and ε-CL yielding high molecular weight (M _n) polymers with narrow molecular weight distributions (MWDs). The catalytic activity of the system can be increased markedly upon using catalytic amount of BnOH as external alcoholic initiator. There is a first order dependence of the rate constant with respect to monomer concentrations as understood from the kinetic studies. The rate was found to be faster in the presence of BnOH. The polymerization process was controlled. The polymerization proceeded via the coordination-insertion mechanism without BnOH as well as activated monomer mechanism in the presence of BnOH. In the absence of BnOH, the acetyl group initiated the polymerization as understood from the ¹H NMR and MALDI-TOF analysis. The benzyloxy group initiated the polymerization in the presence of BnOH. Moderate activity towards the polymerization of ethylene was observed using MAO as alkyl aluminum activator. The polymerization parameters towards the polymerization of ethylene were widely investigated.

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Graphical abstract The catalytic activity of Cd(OAc)₂ towards the ROP of rac-LA and ε-CL and precatalyst for the polymerization of ethylene were investigated.

     

Synthesis and Properties of Alkyl <Emphasis Type="Italic">β</Emphasis>-<Emphasis Type="SmallCaps">d</Emphasis>-Galactopyranoside

A series of alkyl β-d-galactopyranosides were prepared by the trichloroacetimidate method with d-galactose and alcohols with different chain lengths as raw materials. Their solubility, surface tension, emulsification, foaming, wettability, thermotropic liquid crystalline properties, and thermal stability were investigated. Alkyl β-d-galactopyranosides are soluble in water and ethanol, and the solubility decreases with increasing alkyl chain length. Decyl β-d-galactopyranoside was insoluble in water, but soluble in ethanol. Dissolution of alkyl β-d-galactopyranoside in water is an endothermic process with dissolution enthalpies greater than zero. Nonyl β-d-galactopyranoside had an excellent emulsifying property, better foaming ability and the best foam stability. The CMC values of alkyl β-d-galactopyranosides decrease with increasing of alkyl chain length. Alkyl β-d-galactopyranosides are thermally stable up to 270 °C. Alkyl β-d-galactopyranosides show the distinctive optical texture of a thermotropic liquid crystal smectic A type phase. Decyl β-d-galactopyranoside showed the strongest wettability.     

Identification and Functional Expression of a Δ9-Fatty Acid Desaturase from <Emphasis Type="Italic">Psychrobacter urativorans</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis>

The Δ9-fatty acid desaturase is a key enzyme in the synthesis of unsaturated fatty acids. The fatty acid composition of membrane phospholipids in Psychrobacter urativorans is characterized by a high degree of desaturation at Δ9 position. Based on CODEHOP-mediated PCR strategy, a novel gene designated as PuFAD9, putatively encoding a Δ9-fatty acid desaturase (PuFAD9), was isolated from P. urativorans. The gene consists of 1,455 bp and codes for 484 amino acids. Analysis of the amino acid sequence reveals three histidine clusters and a hydropathy profile, typical for membrane-bound desaturases. Activity of the PuFAD9 protein, recombinantly expressed in Escherichia coli was confirmed by GC-MS analysis of the cellular fatty acid composition. It was found that the ratio between palmitoleic and palmitic acid in E. coli cells heterologously expressing the PuFAD9 gene was significantly affected by IPTG induction and the growth temperature.     

A novel ∈-lysine acylase from <Emphasis Type="Italic">Streptomyces mobaraensis</Emphasis> for synthesis of <Emphasis Type="Italic">N∈</Emphasis>-acyl-<Emphasis Type="SmallCaps">l</Emphasis>-lysines

A novel ∈-lysine acylase (N ₆-acyl-l-lysine amidohydrolase; EC 3.5.1.17) was isolated from Streptomyces mobaraensis and purified to homogeneity by SDS-PAGE from the culture broth. The purified enzyme was monomeric, with a molecular mass of approximately 60 kDa. The enzyme was inactivated by the presence of 1,10-phenanthroline and activated in the presence of Co²⁺ and Zn²⁺. The enzyme showed a pH optimum of 8.0 and was stable at temperatures of up to 50°C for 1 h at pH 8.0. The enzyme specifically catalyzed the hydrolysis of the amide bond of various N∈-acyl-l-lysines. Furthermore, the enzyme efficiently catalyzed the synthesis of N∈-acyl-l-lysines with fatty and aromatic acyl groups in an aqueous buffer. In the syntheses of N∈-decanoyl-l-lysine, N∈-lauroyl-l-lysine, and N∈-myristoyl-l-lysine, the product precipitated and the yield was 90% or higher using 10 mM FA and 0.5 M l-lysine as the substrate.     

Probing the Structural,Electronic, and Magnetic Properties of Ag<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>V (<Emphasis Type="Italic">n</Emphasis> = 1–12) Clusters

The structural, electronic, and magnetic properties of Ag _n V (n?=?1–12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy Ag_nV clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag _n?+?1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag _n V (n?=?1–12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag₂ excepted. The most possible dissociation channels are Ag _n V?=?Ag?+?Ag _n???1V for n?=?1 and 4–12 and Ag _n V?=?Ag₂?+?Ag _n???2V for n?=?2 and 3. The energy gap of Ag _n V cluster with odd n is much smaller than that of Ag _n?+?1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag _n V cluster mostly comes from V atom and varies from 1 to 5 μ _B. The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.     

Thermogravimetric characteristics of <Emphasis Type="Italic">α</Emphasis>-cellulose and decomposition kinetics in a micro-tubing reactor

The pyrolysis characteristics and kinetics of α-cellulose were investigated using thermogravimetric analyzer (TGA) and micro tubing reactor, respectively. Most of the α-cellulose decomposed between 250 and 400 °C at heating rate of 5–20 °C/min. The apparent activation energy was observed in the range of 263.02 kJ mol^?1 to 306.21 kJ mol^?1 at the conversion of 10-80%. The kinetic parameters were determined by nonlinear least-squares regression of the experimental data, assuming first-order kinetics. It was found from the kinetic rate constants that the predominant reaction pathway was A(α-cellulose) to B(bio-oil) rather than A(α-cellulose) to C(gas; C₁-C₄) and/or to B(bio-oil) to C(gas; C₁-C₄) at temperatures of 340-360 °C.     

Variation of Insect Attracting Odor in Endophytic <Emphasis Type="Italic">Epichloë</Emphasis> Fungi: Phylogenetic Constrains <Emphasis Type="Italic">Versus</Emphasis> Host Influence

Odor is a key trait for pollinator attraction in flowering plants, and many studies have investigated odor evolution in the light of pollinator selection by emphasizing the importance of the plant phylogenetic history. By contrast, little is known on the evolution of odors in fungus–insect interactions. In this study, profiles of three volatile compounds that are emitted by grass-inhabiting Epichloë fungi (Clavicipitaceae, Ascomycota) and that have a confirmed or likely role in the attraction of gamete-transferring Botanophila flies were investigated. We collected headspace samples from stromata of six European Epichloë species (including various host races) that originated from different locations in Switzerland, France, Poland, and UK for conducting gas chromatography analyses. Odor profiles exhibited considerable variation, but profiles of most species overlapped and did not discriminate at the species level. The exception was Epichloë festucae, which had a profile dominated by methyl (Z)-3-methyldodec-2-enoate. Based on an Epichloë phylogeny, there was some hierarchical structuring regarding levels of chokol K, another confirmed Botanophila attractant. However, patterns of odor profiles appeared to be largely dependant on particular Epichloë–host associations. The observed variation may be the result of complex selective pressures imposed by Botanophila gametic vectors, local environment, and mycoparasites.     

Study on 2-thiophenecarbonyl chloride-quenched olefin polymerization with <Emphasis Type="Italic">α</Emphasis>-diimine nickel catalysts

The number of active centers in α-diimine nickel-catalyzed olefin homogeneous polymerization system is rarely studied before. A systemic study on quenching method with 2-thiophenecarbonyl chloride (TPCC) in homogeneous catalytic system is presented. Ethylene and propylene polymerizations catalyzed with homogeneous α-diimine nickel catalysts (ArN=C(An)–C(An)=NAr)NiBr₂ (cat.1, Ar=2,6-C₆H₃(i-Pr)₂) and (ArN=C(C₁₂H₈)C=NAr)NiBr₂ (cat.2, Ar=2,6-C₆H₃(i-Pr)₂, C₁₂H₈=acenaphthene-1,8-diyl) were quenched by TPCC. The potential side reaction between TPCC and alkyl aluminum-terminated polymer chain caused by chain transfer to cocatalyst under different quenching conditions was investigated. Samples were obtained with different TPCC/Al_MAO molar ratios and had similar sulfur contents; a confirmation that the excess TPCC in the system did not cause obvious side reactions which could lead to place more thiophene groups to the polymer chains. Moreover, when the quenching time was in the range of 3–20 min, the sulfur contents remained stable and the value of N_pol (number of moles of polymer chains) was not obviously changed, supporting that sufficient quenching reaction had already accomplished within the first 3 min. We claimed that the side reaction could be ignored under controllable conditions. TPCC was confirmed to be an effective quenching agent in homogeneous catalytic system. The quenching method with TPCC was also established.     

Hepatic Lipase Gene −514<Emphasis Type="Italic">C</Emphasis>/<Emphasis Type="Italic">T</Emphasis> Polymorphism in the Guangxi Hei Yi Zhuang and Han Populations

Hei Yi Zhuang is an isolated subgroup of the Zhuang minority in China. This study was designed to compare the difference in the hepatic lipase gene (LIPC) -514C/T polymorphism and its association with lipid profiles between the Guangxi Hei Yi Zhuang and Han populations. Genotyping of the LIPC -514C/T was performed in 873 subjects of Hei Yi Zhuang and 867 participants of Han Chinese. The frequency of -514T allele was 43.47% in Hei Yi Zhuang, and 36.10% in Han (P < 0.001). The frequencies of CC, CT and TT genotypes were 30.01, 53.04 and 16.95% in Hei Yi Zhuang, and 40.95, 45.91 and 13.14% in Han (P < 0.001); respectively. Serum high-density lipoprotein cholesterol (HDL-C) and apolipoprotein B levels in both ethnic groups were higher in LIPC -514T carriers than in C carriers. In addition, serum triglyceride levels in Han were higher in TT genotype individuals than in CC genotype subjects (P < 0.05). Serum HDL-C levels were positively correlated with age, alcohol consumption and LIPC -514C/T genotypes, and negatively associated with hypertension and cigarette smoking in Hei Yi Zhuang (P < 0.05-0.01), whereas HDL-C levels were positively correlated with age, alcohol consumption and LIPC -514C/T genotypes, and negatively associated with body mass index and cigarette smoking in Han (P < 0.05-0.001). The differences in serum HDL-C levels between the two ethnic groups might partially attribute to the differences in the LIPC -514C/T polymorphism.     

Regiospecific Analyses of Triacylglycerols of Hoki (<Emphasis Type="Italic">Macruronus novaezelandiae</Emphasis>) and Greenshell™ Mussel (<Emphasis Type="Italic">Perna canaliculus</Emphasis>)

The lipid profiles of the two most important New Zealand marine oil sources were investigated, with particular attention to the regioisomeric compositions of triacylglycerides (TAG), using ¹³C-nuclear magnetic resonance analysis. Oils from hoki (Macruronus novaezelandiae) and Greenshell™ mussel (Perna canaliculus) (GSM) were analyzed for their lipid content, lipid class and fatty acid profile. The regiospecific distribution of long chain (C ≥ 20) polyunsaturated fatty acids (LC-PUFA) between the sn-1,3 and sn-2 glycerol positions was calculated from ¹³C responses in the carbonyl region in the triacylglycerol fraction. Rendered hoki oil (RHO) produced from the viscera and filleting discards, had a similar lipid profile to that of hoki liver oil (HLO) confirming that the liver is the major source of oil in RHO. The regioisomeric distribution of fatty acids showed differences between the two oil sources. Docosahexaenoic acid (DHA) had a regioisomeric distributional preference to the sn-2 position in TAG from all the oils (59.2% HLO, 54.3% RHO and 63.4% GSM). Eicosapentaenoic acid (EPA) had a more even distribution along the triacylglycerol backbone in hoki TAG (29.1% HLO, 33.6% RHO) while there was a slight sn-2 positional preference in the GSM TAG (37.6%). This regioisomeric information is vital to distinguish LC-PUFA-rich marine oils from other marine sources for authentication purposes.     

Effects of various factors on capacitive properties of VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O powders in aqueous electrolyte

In this work, effects of drying temperature, pH of aqueous electrolyte and current density on capacitive performance of VO _x ·nH₂O material were firstly investigated. VO _x ·nH₂O powders were prepared by a melt quenching method. The samples were characterized by X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR). The capacitive properties of VO _x ·nH₂O samples were examined by cyclic voltammetry and galvanostatic charge/discharge test. VO _x ·nH₂O sample which was obtained at the drying temperature of 80 °C, delivers a maximum specific capacitance of 227.3 F g⁻¹ and exhibits excellent capacity retention in the potential range of −0.3 to 0.7 V at a current density of 200 mA g⁻¹ in NaNO₃ solution with pH 2.