Local turbulent energy dissipation rate in an agitated vessel: New approach to dimensionless definition

Using theory of turbulence, particularly using turbulence spectrum analysis, the relations ε^* = ε/(u ⁴/ν) = const., v_K/u = const. and Λ/η_K = const. were derived. Assuming that u ∝ (Nd) from this it follows that the widely used dimensionless local turbulent energy dissipation rate defined as ε/((N ³ d ²) is directly proportional to impeller Reynolds number, i.e. ε/((N ³ d ²) ∝ Re, and length scale ratio Λ/d is indirectly proportional to impeller Reynolds number, i.e. Λ/d ∝ Re^–1, in an agitated vessel at high Reynolds number. The relations obtained by turbulence spectrum analysis were used for estimation of local turbulent energy dissipation rates experimentally measured by Ståhl Wernersson and Trägårdh (1998, 1999) covering the range of Re = 87600–910200 and own experimental data covering the range of Re = 50000–189000. The experiments have been performed in tanks of 300 mm and 400 mm in the inner diameter for three different viscosities and for various impeller rotational speeds.     

Non-cytotoxic poly(amino acid) with excellent thermo-sensitivity from <Emphasis Type="Italic">L</Emphasis>-lysine and <Emphasis Type="Italic">L</Emphasis>-aspartic acid as a hydrophobic drug carrier

The thermo-sensitive poly(amino acid)s have aroused great concern due to their good biocompatibility, chirality and multi-functional groups. In this investigation, a group of poly(L-lysine ester -co- N-propionyl-L-aspartic acid)s (PLPA) with excellent thermo-sensitivity and non-cytotoxicity have been successfully synthesized by the polycondensation between α/ε-amino groups of L-lysine and α/γ-carboxyls from L-aspartic acid. The structure and properties of PLPA including monomers are characterized by FTIR, ¹H NMR, UV, DSC, GPC, SEM, Contact angle measurement, CCK-8 Cell Counting Kit assess and Confocal laser-scanning microscopy (CLSM). Among four designed PLPAs, only PLPAs possessing methyl/ethyl in the ester moiety show a reversible lower critical solution temperature (LCST) of 21.3–36.2 °C, very close to body temperature. The thermo-sensitivity of PLPAs is strongly affected by the polymer structure, its molecular weight and concentration. The contact angle measurement clearly reveals the effect of pendant groups and temperature on the hydrophlilicity/hydrophobicity of PLPAs. Furthermore, the viability of HeLa cells in 0.01–100 μg/mL PLPA solution is found to be in a range of 90–102% after 24, 48 and 72 h of incubation, indicating its no cytotoxicity. PLPA can facilely form a spherical nano-scale particle with core-shell structure via its thermo-sensitivity. CLSM observations manifest that the curcumin-loaded PLPA particles clearly internalize into the cellular inside. Overall, this noncytotoxic PLPA with excellent thermo-sensitivity is expected to be a promising material in the biomedical fields such as a hydrophobic drug carrier.     

Local Turbulent Energy Dissipation Rate in an Agitated Vessel: Experimental and Turbulence Scaling

The hydrodynamics and the flow field in an agitated vessel were measured using 2-D time resolved particle image velocimetry (2-D TR PIV). The experiments were carried out in fully baffled cylindrical flat bottom vessels 300 and 400 mm in inner diameter. The 300 mm inner diameter tank was agitated by a Rushton turbine 100 mm in diameter, and the 400 mm inner diameter tank was agitated by a Rushton turbine 133 mm in diameter. Three liquids of different viscosities were used as the agitated liquid: (i) distilled water (ν = 9.35 × 10^–7 m²/s), (ii) a 28 vol % aqueous solution of glycol (ν = 2 × 10^–6 m²/s), and (iii) a 43 vol % aqueous solution of glycol (ν = 3 × 10^–6 m²/s). The velocity fields were measured at an impeller rotation speed in the range from 300 to 850 rpm, which covers the Reynolds number range from 50000 to 189000. This means that fullydeveloped turbulent flow was reached. The experiments were performed to investigate the applicability of the following relations: ε* = ε/(u⁴/ν) = const, vK/u = const, Λ/ηK = const, τ_Λ/τ_K = const, ε* = ε/((Nd)4/ν) = const, Λ/d ∝ Re^–1, ηK/d ∝ Re^–1, vK/(Nd) = const, Nτ_Λ ∝ R^–1, Nτ_K ∝ Re^–1, and ε/(Nq) ∝ Re. These formulas were theoretically derived in our previous work, using turbulence theory, in particular, using turbulence spectrum analysis. The correctness of the proposed relations is investigated by statistical hypothesis testing.     

Influence of PLA stereocomplex crystals and thermal treatment temperature on the rheology and crystallization behavior of asymmetric poly(L-Lactide)/poly(D-lactide) blends

Asymmetric poly(L-lactide)/poly(D-Lactide) (PLLA/PDLA) blends were prepared by adding small amounts of PDLA into the PLLA matrix with the formation of stereocomplex crystallites (sc-crystallites). Rheological results indicated that the PLLA/PDLA melt at lower temperatures (<T_m,sc, the melting temperature of the formed stereocomplex crystallites) underwent the transition from liquid-like to solid-like viscoelastic behaviors with increasing of the PDLA concentration, which was related to the sc-crystallites reserved in the melt of asymmetric PLLA/PDLA blends. Dissolution experiment indicated the presence of sc-crystallites network structure in the PLLA/PDLA blends, and the size of the sc-crystallite junction particles network increased with increasing of the PDLA concentration. DSC and POM studies indicated that the PDLA concentration and the thermal treatment temperature had a significant influence on the PLLA crystallizability behavior. At low thermal treatment temperature (<T _m,sc ), reserved sc-crystallites showed an obvious promoting effect for PLLA crystallization. With increasing of the thermal treatment temperature, its promoting effect decreased due to melting of the sc-crystallites. This result suggests the sc-crystallites played two roles: nucleation sites and cross-linking points, and the two roles had a competitive relationship with change of the thermal treatment temperature and the PDLA concentration.     

Crystal structure and thermal expansion of ammonium pentaborate NH<Subscript>4</Subscript>B<Subscript>5</Subscript>O<Subscript>8</Subscript>

Anhydrous ammonium pentaborate NH₄B₅O₈ has been synthesized by thermal dehydration of larderellite NH₄[B₅O₇(OH)₂] · H₂O at a temperature of 290°C for 7 h. The crystal structure has been determined from the X-ray powder diffraction data: a = 7.58667(5) Å, b = 12.00354(8) Å, c = 14.71199(8) Å, R _p = 6.23, R _wp = 7.98, R _B = 12.7, R _F = 8.95, and β-KB₅O₈ structure type. The double interpenetrating framework is formed by pentaborate groups, each consisting of a boron-oxygen tetrahedron and four triangles, in which all oxygen atoms are bridging. The thermal behavior of the NH₄B₅O₈ compound has been investigated using thermal X-ray diffraction. As for other pentaborates of this type, the thermal expansion of the NH₄B₅O₈ compound is anisotropic and reaches a maximum along the a axis. The thermal expansion coefficients are as follows: α _a = 39 × 10^?6, α _b = 6 × 10^?6, α _c = 20 × 10^?6, and α _V = 65 × 10^?6 °C^?1.     

Suppression of β-crystal in iPP/PET Fiber Composites

The β-crystal formed in PP/PET fiber composites was investigated. The results indicate that PET fibers (PF) can preferably lead to α-crystal formation on their surface. Besides, α-crystals occur earlier than those in the bulk. The β-crystal, might be induced by temperature gradient, only formed away from the PF in composites with lower content of PF. The higher the content of PF is, more possible the PF network is constructed. The transcrystallinity induced by PF will rapidly occupy the region between the adjacent PFs. Consequently, owing to the spatial confinement, β-form is suppressed in the composites with higher content of PF.     

General trends in concentration and temperature behavior of equivalent conductance of <Emphasis Type="Italic">N,N</Emphasis>-diallylammonium polymers aqueous solutions: Effect of counterion nature and amine structure

The specific and equivalent conductivity of the diluted aqueous solutions of diallyammonium polyelectrolytes, initial monomers (N,N-diallylammonium trifluoroacetate, N,N-diallyl-N-methylammonium trifluoroacetate, N,N-diallyl-N,N-dimethylammonium chloride), and also potassium trifluoroacetate and trifluoroacetic acid solutions are studied. The limiting ionic mobility of diallylammonium cations and trifluoroacetate anion are found. The regularities of concentration changes in the equivalent conductance of polyelectolytes solutions are established. The degree of dissociation of diallyammonium polymers is shown to depend both on the counterion nature and on the amine structure.     

Oxidation of ash-free coal from sub-bituminous and bituminous coals in a direct carbon fuel cell

The present study proposes the production of ash-free coal (AFC) and its oxidation as a primary fuel in direct carbon fuel cells (DCFCs). The AFC was produced by the extraction of Arutmin sub-bituminous coal (AFC1) and Berau bituminous coal (AFC2) using polar solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). It was carried out at a temperature of around 202 °C under atmospheric conditions and using a microwave irradiation method. Using NMP as the solvent showed the highest extraction yield, and the values of 23.53% for Arutmin coal and 33.80% for Berau coal were obtained. When NMP was added to DMSO, DMA and DMF, the extraction yield in the solvents was greatly increased. The yield of AFC from a sub-bituminous coal was slightly lower than that from a bituminous coal. The AFC was evaluated in a coin-type DCFC with a mixture of AFC and carbonate electrolyte (3 g/3 g) at 850 °C. The AFC and gaseous H₂ fuels were compared using the electrochemical methods of steady-state polarisation and step chronopotentiometry. The DCFC ran successfully with the AFCs at 850 °C. The open-circuit voltages were about 1.35 V (AFC1) and 1.27 V (AFC2), and the voltages at 150 mA cm^?2 were 0.61 V (AFC1) and 0.74 V (AFC2).     

Mixed Stability and Antimicrobial Properties of Gluconamide-Type Cationic Surfactants

The stability of anionic-cationic surfactant solutions and the antimicrobial properties of novel N,N-dimethyl-N-[3-(gluconamide/lactobionamide)]propyl-N-alkylammonium bromides (CnDGPB and CnDLPB), N-methyl-N-hydroxyethyl group-N-[3-(gluconamide)-propyl]-N-alkylammonium bromide (CnMHGPB) and star-shaped gluconamide-type cationic surfactants N-dodecyl-N,N-bis[(3-d-gluconylamido)propyl]-N-alkylammonium bromide (CnDBGB) were investigated. Mixed stability in combination with sodium n-alkylbenzenesulfonate (LAS) was determined via transmittance; stability is achieved when percent transmittance was greater than 90 %. Transmittance results suggest that these cationic surfactants can form stable solutions with anionic surfactants over a broad concentration range. The inhibition activity of C _n DBGB is the best among the three kinds of glucocationic surfactants. Antimicrobial activity of C₁₂ surfactants was the best, C₁₄ was the second and C₁₀ was the worst. Moreover, antibacterial activity of glucose-based cationic surfactants was greater than lactose-based cationic surfactants.     

Bioengineering functional copolymers: synthesis and characterization of poly(<Emphasis Type="Italic">N</Emphasis>-isopropyl acrylamide-<Emphasis Type="Italic">co</Emphasis>-3,4-2H-dihydropyran)s

Novel bioengineering copolymers were synthesized by radical copolymerization of N-isopropylacrylamide (NIPA) and 3,4-2H-dihydropyran (DHP) with 2,2′-azobisisobutyronitrile as an initiator in acetone solution at 70 °C under nitrogen atmosphere. Structure, tacticity and compositons of the copolymers prepared in a wide range of monomer feed were confirmed by FTIR, ¹H{¹³C} NMR-DEPT and elemental analyses. The monomer reactivity ratios (r ₁ and r ₂) were detected using known two methods: r ₁ (NIPA)?=?1.25 and r ₂?=?0.035 (DHP), and r ₁ (NIPA) ?=?0.97 and r ₂?=?0.022 (DHP) by Kelen-Tüdös and Jaacks methods, respectively. It was demonstrated that the studied monomer pair has a tendency to form H-bonding beween amide/ether groups through ?NH...O< complexation which played an important role in the stereoselective chain growth, and significant decrease of allyl degradative chain transfer reactions. This phenomenon is also confirmed by the observed relatively high molecular weights of copolymers (M _v ). The synthesized water-soluble stimuli-responsive poly(NIPA-co-DHP)s exhibit thermal stability, higher glass-transition temperature, polyelectrolyte, pH- and temperature-sensitive behavior and can be attributed to the class of bioengineering functional copolymers useful for various bio- and gene-engineering, and drug delivery applications.     

Stability of polymer structures based on fullerene C<Subscript>60</Subscript> under their oxidation with oxygen

A comparative study of the oxidative destruction of the monomer face-centered cubic (FCC) lattice and various polymer [dimeric (D), orthorhombic (O), tetragonal (T), and rhombohedral (R)] phases of C₆₀ in an atmosphere of oxygen has been performed in the temperature range of 100–500°C with the use of a flow microunit connected to a gas chromatograph. From direct measurements of the content of CO₂ in the gaseous products of destruction, the temperature dependences of oxidation rates are measured for the materials under study. It has been established that, with respect to stability against oxidative destruction, different forms of C₆₀ may be arranged as follows: the monomer FCC phase of C₆₀ > D > O > T > R. The reasons behind this tendency are discussed.     

Dielectric Properties and Phase Transition in the PbSe + PbSeO<Subscript>3</Subscript> Composite Material

Electrochemical cells in the form of pressed pellets and polycrystalline films prepared from the PbSe + PbSeO₃ two-phase composite are investigated by impedance spectroscopy. The dispersion analysis of the frequencies of the real and imaginary parts of the complex impedance made it possible to reveal a unified equivalent electric circuit for these cells and to calculate its parameters. The optical (ε_hf) and static (ε_lf) permittivities of the PbSe and PbSeO₃ phases are determined. The permittivities ε_hf = 20–45 and ε_lf = 200–280 obtained for the PbSe phase are in reasonable agreement with the data available in the literature. The temperature dependences of the ac and dc resistances indicate that the PbSe + PbSeO₃ composite undergoes a phase transition at a temperature T _c ? 363 K.     

Influence of pH in the synthesis of ferric tannate pigment for application in antifouling coatings

Ferric tannate was synthesized at pH 4 and pH 7 (FT4 and FT7, respectively) as a new class of environmentally friendly antifouling pigments. The solubility of both pigments was evaluated by gravimetric tests, showing that FT4 is more soluble than FT7. A mixture of rosin/acrylic resin (9:1 w/w) was sufficient to form an antifouling coating due to improved matrix properties. Electrochemical impedance spectroscopy (EIS) measurements were used to determine the apparent water coefficient of diffusion (D) and coating behavior. The D in the coating formulated with FT4 exhibited better values than that obtained with FT7. EIS results showed that both coatings present Fickian behavior at the initial stages of immersion, while flat Nyquist plots revealed penetration of water in the films. The physicochemical characteristics of FT4 pigment were determined by thermogravimetry and Fourier transform infrared. Immersion tests in the Mediterranean Sea demonstrated the excellent efficacy of the FT4-containing coating against marine fouling after six months of immersion.     

Synthesis of MgAPO-31 nanocrystals via different heating methods and their catalytic performance in the hydroisomerization of <Emphasis Type="Italic">n</Emphasis>-decane

MgAPO-31 molecular sieves substituted by different magnesium contents were synthesized using microwave irradiation (MW) and conventional electrical heating method, respectively. The bifunctional catalysts Pd/MgAPO-31 were prepared by the incipient wetness impregnation technique. The structure and acidity of MgAPO-31 were characterized by XRD, SEM, N₂ physical adsorption, FT-IR, and Py-IR. The catalytic performance of Pd/MgAPO-31 were tested in the hydroisomerization of n-decane, which was used as the probe-reaction, and the effect of heating method on acidity of MgAPO-31 and the catalytic performance of Pd/MgAPO-31 were investigated. The results showed that all of the MgAPO-31 samples with ATO topology structure were pure phase and high crystalline materials. The Mg(II) heteroatoms were confirmed to isomorphously substitute for the framework atoms of AlPO₄-31 molecular sieve. These Pd/MgAPO-31catalysts showed good catalytic performance for the hydroisomerization in the temperature range of 330–370 °C. The activity of Pd/MgAPO-31 in the hydroisomerization of n-decane and the selectivity for i-decanes were considered to depend on the crystal size and acidity of MgAPO-31.The highest selectivity for i-decanes was obtained over the catalyst Pd/0.05MgA31-MW prepared using the MW method.     

Identification of the Unsaturated Heptadecyl Fatty Acids in the Seed Oils of <Emphasis Type="Italic">Thespesia populnea</Emphasis> and <Emphasis Type="Italic">Gossypium hirsutum</Emphasis>

The fatty acid composition of the seed oils of Thespesia populnea and cotton variety SG-747 (Gossypium hirsutum) were studied to identity their 17-carbon fatty acids. With a combination of chemical derivatization, gas chromatography, and mass spectrometry, 8-heptadecenoic acid, 9-heptadecenoic acid, and 8,11-heptadecadienoic acids were identified in both oils. Additionally, traces of 10-heptadecenoic acid were identified in the T. populnea oil. Although these odd-carbon number fatty acids are present in only minor amounts in cottonseed oil, they make up about ~2 % of the fatty acids in T. populnea seed oil. The identification of these acids indicates that fatty acid α-oxidation is not restricted to cyclopropene fatty acids in these plants, but also occurs with unsaturated fatty acids. Combined with malvalic acid (generally accepted as being formed by α-oxidation of sterculic acid), ~7 % of the fatty acids in T. populnea seed have under gone α-oxidization. The results should help clarify the composition of T. populnea seed oil, which has been reported inconsistently in the literature.     

Plant Volatiles Increase Sex Pheromone Attraction of <Emphasis Type="Italic">Holotrichia parallela</Emphasis> (Coleoptera: Scarabaeoidea)

Holotrichia parallela (Coleoptera: Scarabaeoidea) is a notorious pest of many crops. To improve the effectiveness of its female-produced sex pheromone (L-isoleucine methyl ester:(R)-(?)-linalool = 6:1), 14 plant volatiles, including dodecanoic acid, dodecanal, farnesol, α-farnesene, (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, (Z)-3-hexenyl acetate, (E)-2-hexenyl acetate, (R)-(+)-limonene, α-phellandrene, α-pinene, ocimene, methyl benzoate, and benzaldehyde, were individually evaluated using electroantennography and olfactometer assays. (E)-2-Hexenyl acetate and (Z)-3-hexenyl acetate were found to elicit the strongest responses in both males and females. Further testing of these two compounds in mixtures with the sex pheromone indicated that (E)-2-hexenyl acetate had a stronger synergistic effect than (Z)-3-hexenyl acetate. Field evaluations showed that mixtures of (E)-2-hexenyl acetate and the sex pheromone resulted in significantly higher catches than the sex pheromone alone. Using a 5:1 mixture of the sex pheromone and (E)-2-hexenyl acetate, the maximum number of females per trap per day was 14, showing a synergistic effect of a factor of four. For males, a 3:1 mixture of the sex pheromone and (E)-2-hexenyl acetate yielded a maximum number of 310 individuals per trap per day, equivalent to a synergistic effect of 175%. These results may provide the basis for the development of efficient pest management systems against H. parallela using plant volatiles and insect sex pheromones.     

Inhibition of Polyunsaturated Fatty Acids Synthesis Decreases Growth Rate and Membrane Fluidity of <Emphasis Type="Italic">Rhodosporidium kratochvilovae</Emphasis> at Low Temperature

The intention of this study was to investigate the role of polyunsaturated fatty acids (PUFA) in the cold adaptation of Rhodosporidium kratochvilovae YM25235 by knockout of the Δ¹²/Δ¹⁵-fatty acid desaturase gene (RKD12) to inactivate Δ¹²/Δ¹⁵-fatty acid desaturase. Polymerase chain reaction (PCR) amplification was used to detect the genomic structure of RKD12 gene in YM25235. The RKD12 gene was knocked out by DNA homologous recombination to inhibit the biosynthesis of PUFA. Then, the contents of linoleic acid (LNA) and α-linolenic acid (ALA) after gene knockout were investigated using a gas chromatography-mass spectrometer, followed by determination of the growth rate and membrane fluidity of YM25235 at low temperature. After PCR amplification, a 1611 bp genomic fragment was amplified from YM25235. When the RKD12 gene was knocked out, the contents of LNA and ALA in YM25235 significantly decreased. The growth rate and membrane fluidity of YM25235 decreased significantly at low temperature. Inhibition of PUFA biosynthesis by RKD12 gene knockout influenced cold adaptation of YM25235 by decreasing the PUFA content in cell membranes and reducing the growth rate and membrane fluidity of YM25235 at low temperature.     

Optimization of controlled ring-opening polymerization of <Emphasis Type="SmallCaps">l</Emphasis>-lactide to hydroxyl terminated polylactides using zinc acetate catalyst

Hydroxyl terminated polylactide polymers with number of average molecular weights (M _n ) varying from 1625 to 3459 g mol^?1 were synthesized by ring opening bulk polymerization of lactide in the presence of zinc acetate being a potent catalyst. The use of 1,4 butanediol (BDO) initiator leads to hydroxyl terminated polylactides, thus excellent precursors for shape-memory biodegradable polyurethanes. Different reaction conditions employed for the synthesis of hydroxyl terminated polylactide polymers via activated monomer mechanism may result in differences in M _n , percentage mass conversion and percentage degree of crystallinity (%χ _c ) of the product. Influence of process parameters, i.e. catalyst concentration, initiator concentration, reaction temperature and time on characteristics of hydroxyl terminated polylactides was studied. These polymers were characterized by Nuclear Magnetic Resonance (¹H-NMR) spectroscopy, Fourier transforms infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and X-ray diffraction (XRD) techniques. FTIR and ¹H-NMR confirmed the formation of hydroxyl terminated polylactides. M _n was determined by ¹H-NMR, GPC and end group analysis. %χ _c was calculated from XRD spectra. Maximum mass conversion, M _n and %χ _c were observed at 5 mol% SnOct₂ and 5 mol% BDO concentration. At optimum temperature of 145 °C, these characteristics improved linearly with polymerization time up to 6 h and declined thereafter.     

Density and microhardness of glasses in the SrO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

The density d at a temperature of 25°C is measured by the hydrostatic weighing method, the Vickers microhardness H _V is determined, and the fluctuation free volume fraction f _g is calculated for glasses in the SrO-B₂O₃-SiO₂ system with a constant strontium oxide content in the range from 35 to 45 mol %. It is demonstrated that the quantities H _V and f _g decrease and the density d increases with an increase in the SrO content.     

Biocatalytic production of extracellular exopolysaccharide dextran synthesized by cells of <Emphasis Type="Italic">Leuconostoc mesenteroides</Emphasis>

Results are presented from studies and a comparative analysis of the production of the commercially important product dextran from sucrose using fed-batch cultivated cells of the Leuconostoc mesenteroides subsp. dextranicum B-5481 bacterium either immobilized in a polyvinyl alcohol (PVA) cryogel or in the form of a suspension. It is shown that under identical process conditions, the concentration of dextran is 1.2 times higher when using immobilized cells instead of free cells. The high productivity of dextran formation (4.2 g/(L h)) under the conditions of fed-batch cultivation of the immobilized cells and the ability of these cells to function without losing their metabolic activity for at least five operating cycles are demonstrated. The productivity of the developed biocatalyst is 5 times higher than that of Weissella confusa cells immobilized in a calcium alginate gel and 34 times higher than that of Leuconostoc mesenteroides KIBGE HA1 cells immobilized in a polyacrylamide gel. The molecular weight of the dextran samples produced by the immobilized L. mesenteroides B-5481 cells is half that of the polymer produced by the free cells, expanding the range of possible applications of the polysaccharide with no additional hydrolysis.