Enantiospecific Adsorption of (R)-3-Methylcyclohexanone on Naturally Chiral Surfaces Vicinal to Cu(110)

(R)-3-methylcyclohexanone (R-3MCHO) has been shown to adsorb enantiospecifically on naturally chiral Cu surfaces vicinal to the Cu(110) plane. Adsorption of R-3MCHO on seven Cu single crystal surfaces vicinal to (110) was studied using temperature programmed desorption. These surfaces include Cu(110), Cu(771), Cu(430), Cu(13,9,1) ^R&S and Cu(651) ^R&S . The Cu(13,9,1) ^R&S and Cu(651) ^R&S surfaces are naturally chiral surfaces with terrace-step-kink structures. Enantioselective adsorption of R-3MCHO takes place on the chiral kink sites of these surfaces. Three R-3MCHO desorption features were resolved in the TPD spectra on Cu(13,9,1) ^R&S and Cu(651) ^R&S surfaces. Based upon comparisons between these and other Cu single crystal surfaces, they were assigned to desorption of R-3MCHO from flat terrace, close-packed step and kink sites. The desorption of R-3MCHO from the row and trough structure of the Cu(110) surface resembled desorption from a step structure rather than from a flat Cu(111) terrace. R-3MCHO desorbs enantiospecifically from the Cu(13,9,1) ^R&S and Cu(651) ^R&S surfaces. The peaks associated with R-3MCHO desorbing from the R- and S-chiral kink sites on Cu(13,9,1) ^R&S differed in temperature by 2.4 ± 0.8 K. This corresponds to an enantiospecific difference in the desorption energies of 0.7 ± 0.2 kJ/mol, with a preference for R-3MCHO adsorption at the R-kinks. In contrast, R-3MCHO has a desorption energy from the S-kinks on the Cu(651) ^S surface that is 0.7 ± 0.2 kJ/mol higher than from the R-kinks on the Cu(651) ^R surface.     

Impact of Lipoprotein Lipase Gene Polymorphism,S447X,on Postprandial Triacylglycerol and Glucose Response to Sequential Meal Ingestion

Lipoprotein lipase (LPL) is a key rate-limiting enzyme for the hydrolysis of triacylglycerol (TAG) in chylomicrons and very low-density lipoprotein. Given that postprandial assessment of lipoprotein metabolism may provide a more physiological perspective of disturbances in lipoprotein homeostasis compared to assessment in the fasting state, we have investigated the influence of two commonly studied LPL polymorphisms (rs320, HindIII; rs328, S447X) on postprandial lipaemia, in 261 participants using a standard sequential meal challenge. S447 homozygotes had lower fasting HDL-C (p = 0.015) and a trend for higher fasting TAG (p = 0.057) concentrations relative to the 447X allele carriers. In the postprandial state, there was an association of the S447X polymorphism with postprandial TAG and glucose, where S447 homozygotes had 12% higher TAG area under the curve (AUC) (p = 0.037), 8.4% higher glucose-AUC (p = 0.006) and 22% higher glucose-incremental area under the curve (IAUC) (p = 0.042). A significant gene–gender interaction was observed for fasting TAG (p = 0.004), TAG-AUC (P_interaction = 0.004) and TAG-IAUC (P_interaction = 0.016), where associations were only evident in men. In conclusion, our study provides novel findings of an effect of LPL S447X polymorphism on the postprandial glucose and gender-specific impact of the polymorphism on fasting and postprandial TAG concentrations in response to sequential meal challenge in healthy participants.     

Potential control characteristics of short-chain thiols of thioctic acid and mercaptohexanol self-assembled on gold

In this article we systematically investigated self-assembly of short-chain thiols of thioctic acid (TA) and mercaptohexanol (MCH) on gold under potential control, E_dc (−0.4, +0.4 and +0.7 V) and compared the results obtained with open circuit potential (E_OCP). Effect of E_dc on thiol self-asembly was inspected based on the changes in electrochemical parameters including interfacial capacitance (C), phase angle (Φ_1Hz), current density difference (Δi), charge transfer resistance (R_ct) through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Experimental results showed that E_dc could not obtain stable short-chain self-assembled monolayers (SAMs) (TA and MCH) in a short time. Both TA and MCH had slow self-assembly dynamics and needed a long time (> 24 h) to achieve adsorption equilibrium. Furthermore, the negative potential E_dc (−0.4 V) did not facilitate the ordering of SAMs. The ordering of TA-SAMs was found to be the best when assembled under E_dc (+0.4 V), whereas that of MCH-SAMs was almost the same when assembled under either E_OCP or E_dc (+0.4, +0.7 V). We considered that permeation of ions and water molecules perhaps dominated the slow self-assembly dynamics of short-chain thiols (TA and MCH) under E_dc and mutual interaction between adjacent chains of thiols played an important role in the ordering of SAMs.     

Early-age hydration of fresh concrete monitored by non-contact electrical resistivity measurement

This paper reports the investigations on the early hydration process of fresh concrete using a non-contact electrical resistivity measurement. The bulk resistivity development (ρ(t)-t curves) and the pore solution resistivity development (ρ₀(t)-t curves) of fresh concrete, with and without fly ash replacement, were obtained for the period from casting to the age of 48 h. The porosity development (?(t)-t curves) was obtained from the ρ(t)-t and ρ₀(t)-t evolution curves with the calculated initial porosity and the measured porosity at 1 day by mercury intrusion porosimetry (MIP). The degree of hydration (α(t)-t) of the cement-based materials was then obtained based on the porosity change with time, which was caused by the increase of hydration products with a lower density as compared to that of the original cement in the hydration system. The comparison of the degree of hydration predicted from the porosities (?(t)-t) and obtained from the experimental measurement of non-evaporable water showed a good agreement of the two.The setting and hardening behavior of fresh concrete was characterized by the characteristic points on the ρ(t)-t and dρ(t)/dt-t curves. The retarded hydration caused by the fly ash incorporation could be identified by the characteristic points.     

Circular dichroism study of poly(l-tyrosine), poly(l-glutamic acid) and of random and sequential copolymers of l-glutamic acid and l-tyrosine in trimethylphosphate

Random and sequential copolypeptides containing l-glutamic acid and l-tyrosine, as well as poly(l-tyrosine) and poly(l-glutamic acid) were investigated by means of c.d. spectroscopy in trimethylphosphate as solvent. In random copolymers, variation of ellipticities at 202.5 and 230 nm versus tyrosyl content follows a smooth curve, without any sharp change. This led to the conclusion that poly(l-tyrosine) α-helix is right-handed. From c.d. studies on sequential copolymers we were able to recognize that the 230 nm contribution of tyrosyl side chains is closely related to the array in which tyrosyl residues are arranged in the chain. For instance, it was found that (n, n + 2) and (n, n + 3) pairings of tyrosyl side-chains in (Tyr-Glu)_n and (Glu-Tyr-Glu)_n respectively, were poorly effective, while the (n, n + 4) pairing in (Glu-Glu-Tyr-Glu)_n is more. However, the strongest contribution at 230 nm was observed on the alternating-páirs copolymer (Glu-Tyr-Tyr-Glu)_n. This result suggests a new conformational arrangement of tyrosyl side chains in sequential copolymers, as well as in poly(l-tyrosine) and other aromatic polypeptides, based on a regular pairing of the aromatic groups, arranged in two contiguous superhelices.     

Study of interfacial tension in poly(ethylene oxide)/polystyrene/diblock copolymer system by electric deformation method

We investigated the interfacial tension γ between poly(ethylene oxide) (PEO) and polystyrene (PS) focusing our attention on the dependence of γ on the molecular weight (M) of PEO and the surfactant effect of poly(ethylene oxide-b-styrene) diblock copolymer [P(EO-b-S)]. Measurements of γ were carried out by observing electric deformation of droplets of PEO suspended in bulk PS or in a concentrated solution of PS in dioctylphthalate (DOP). The results indicate that γ between PEO and PS is almost independent of M of PEO in the high molecular weight region, but exhibits a minimum around M = 500. Addition of 1 wt% of P(EO-b-S) to the PEO/PS system causes a decrease of γ due to the surfactant effect of the copolymer, but γ is almost independent of further addition of the copolymer. The decrement of the interfacial tension Δγ increases with increasing molecular weight of P(EO-b-S).     

Deposition of hydrogenated amorphous carbon films with enhanced sp3-C bonding on nanocrystalline palladium interlayer

The present study deals with the deposition of hydrogenated amorphous carbon (a-C:H) films on Si (100) substrates with and without an interlayer of nanocrystalline palladium (nc-Pd) on them, by high-voltage electro-dissociation of N,N-dimethyl formamide (DMF). Significant improvement in the sp³ carbon content has been observed for a-C:H films grown on nc-Pd interlayer as revealed by Fourier transformed infrared (FTIR), Raman, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopic techniques. It is inferred that H₂ activation on palladium sites leads to the stabilization of sp³-C bonding, thereby improving the quality of the deposits grown on them.     

The limiting diffusion current value on a macroscopically inhomogeneous electrode

The limiting diffusion current I_dN to an electrode in the form of system of alternating active and inactive sites has been calculated. It is shown that I_dN = I⁰_dπ(N,θ). Here I⁰_d is the limiting diffusion current to the same electrode with an all-active surface. The correction factor π(N,θ) depends on the degree of the surface activity θ and on the distribution of active sites N along the surface. The factor π(N,θ) does not depend on the intensity of stirring of electrolyte solution.     

Investigation of gas properties, design, and operational parameters on hydrodynamic characteristics, mass transfer, and biomass production from natural gas in an external airlift loop bioreactor

An external airlift loop bioreactor (EALB) was used for production of biomass from natural gas. The effect of riser to downcomer cross sectional area ratio (A_r/A_d), volume of gas-liquid separator, superficial gas velocity (U_sgr), and physical properties of gases and their mixtures [υ_g (μ/ρ) and D_g] were investigated on mixing time, gas hold-up, and volumetric gas liquid mass transfer coefficients (k_La). It was found that A_r/A_d has remarkable effects on gas hold-up and k_La due to its influence on mixing time. Kinematic viscosity (υ_g) showed its significant role on mixing time, gas hold-up and k_La when different gases used (mixing time changes directly whereas gas hold-up and k_La change indirectly). Moreover, it was found that diffusion coefficient of gas in water (D_g) has remarkable effect on k_La. The volumetric mass transfer coefficients for methane and its mixtures with oxygen (three different mixtures) were determined at different geometrical and operational factors. In average, the rate of oxygen utilization is approximately 1.8 times higher than that of methane. A gas mixture of 25 vol% methane and 75 vol% oxygen was the best gas mixture for biomass production in the EALB. The correlations developed for predicting the mixing time, gas hold-up, and k_La in terms of U_sgr, A_r/A_d, volume of gas-liquid separator, and gas phase properties have been found to be encouraging.     

Effects of ultrasound on the conformation and crystallization behavior of isotactic polypropylene and β-isotactic polypropylene

The effects of ultrasonic irradiation on conformation and crystalline structure of isotactic polypropylene (iPP) and β-isotactic polypropylene (β-iPP) were studied by means of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results demonstrate that ultrasonic irradiation decreases the helical conformation order and changes the crystalline structures: for iPP, T_m and T_onset decrease, T_m − T_onset becomes larger; for β-iPP, the β_c, (1 − λ)_β and k_β increase, the intensities of α(040) plane and α(130) plane in WAXD profiles decrease evidently. For both iPP and β-iPP, the crystallinity decreases, d-spacing increases, the crystallite size L decreases and ultrasound shows a selective effect on the growth of β-crystal. Furthermore, DSC and WAXD were employed to observe the effect of ultrasound on the “melting memory effect” of β-iPP. The results indicate that ultrasonic irradiation destructs the existing “locally ordered structure” in β-iPP melt, as a result greatly inhibits the βα-recrystallization of β-iPP samples during heating.     

Piezoelectric enhancements in K0.5Na0.5NbO3-based ceramics via structural evolutions

The current work aims to compare the effect of systematic A-site and B-site substitutions on the piezoelectricity of Ka_0.5Na_0.5NbO₃ (KNN)-based perovskite ceramics. The A-site elements was replaced by Li⁺ while Nb5⁺ was substituted by Sb⁵⁺ to form (K_0.4675Na_0.4675Li_0.065)NbO₃ (KNLN) and (K_0.4675Na_0.4675Li_0.065)(Nb_0.96Sb_0.04)O₃ (KNLNS) respectively. The ceramics were prepared using solid-state sintering method. The density of the ceramics steadily improved with the substitutions while the crystal structure evolved from monoclinic (in KNN) to the coexistence of monoclinic and tetragonal (in KNLN) and finally tetragonal in KNLNS. Distinct variations on size and morphology were recorded. Although density, crystal structure and morphology have minor effect on the E_c, they imposed considerable influences on P_r, d₃₃ and k_p. Despite relatively lower density, KNLN exhibited the highest P_r, d₃₃ and k_p at 9.80 μC/cm²,185 pC/N and 0.43 respectively signifying the positive enhancement brought by the co-existence of monoclinic and tetragonal crystal structures. More importantly, this work systematically proved that the co-existence of both structures signified the morphotropic phase boundary (MPB) composition as the primary factor for the enhancement of KNN piezoelectric properties.     

Use of HPLC in the identification of cis and trans-diaquabis(2,2′-bipyridine)ruthenium(II) complexes: crystal structure of cis-[Ru(H2O)2(bpy)2](PF6)2

[Ru(H₂O)₂(bpy)₂](PF₆)₂ complex was obtained by reacting HPF₆ in a [Ru(CO₃)(bpy)₂] aqueous solution. The complex can exist as cis and trans isomers and usually has been used in the preparation of several ruthenium–bipyridine species. Despite the possibility to have contamination of a specie in another, there is no analytical control involving the characterization of both complexes. Based on this we have proposed the use of high-performance liquid chromatography (HPLC) as an analytical technique to control the purity of cis and trans isomers. The separation was performed using a CLC-ODS column. The cis isomer eluted at 9.4 min while trans isomer eluted at 4.3 min. In aqueous solution the trans and cis isomer configurations were confirmed by NMR spectra (¹H). The attribution of cis isomer was also made based on the X-ray crystal structure (monoclinic, P2_1/c, a=12.320(2), b=13.852(2), c=34.220(3) Å, β=91.89(1)°, Z=8) which is reported. The six-coordinated ruthenium atom is chelated by two bipyridines and two molecules of H₂O.     

The effect of the electrode surface roughness at low level of coarseness on the polarization characteristics of electrochemical processes

In this study, it is considered: (a) the effect of the exchange current density to the limiting diffusion current density ratio (j₀/j_L) at low level of surface coarseness on the polarization characteristics of the electrochemical process, (b) the effect of the shape of surface protrusions on the electrode surface roughness, and (c) the effect of surface roughness on the j₀/j_L ratio. It was shown that the increase of the value of the j₀/j_L ratio produces a decrease of overpotential at fixed value of current density. At selected set of conditions, the j₀/j_L ratio can be increased by the increase of roughness of electrode surface by electrodeposition of disperse deposits at low level of coarseness. The increase of the value of the j₀/j_L ratio produces large saving of energy required for the evaluation of electrochemical reaction. The conditions in which the electrochemical process can become Ohmic controlled were also specified.     

Electrochemical impedance spectroscopy and cyclic voltammetry of ferrocene in acetonitrile/acetone system

The oxidation of ferrocene (FeCp₂) to ferrocenium cation (FeCp ₂ ⁺ ) (where Cp: cyclopentadienyl anion, C₅H₅ ^?) was investigated by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) on either platinum (Pt) or glassy carbon (G-C) electrodes in acetonitrile (ACN), acetone (ACE), and acetonitrile (ACN)/acetone (ACE) binary mixtures with n-tetrabutylammonium hexafluorophosphate (TBAPF₆) as background electrolyte at T = 294.15 K. The half-wave potentials (E _1/2), the diffusion coefficients (D), and the heterogeneous electron-transfer rate constants (k _s) were derived. The activation free energies for electron transfer (ΔG _exp ^≠ ) were experimentally determined and compared with the theoretical values (ΔG _cal ^≠ ). The electron-transfer process was reversible and diffusion-controlled in all investigated solvent mixtures. The changes on the metal–ligand bond lengths upon electron transfer were almost insignificant. The E _1/2 values were shifted to less positive potentials with the increase of the ACN content. The k _s values obtained on Pt electrode were slightly larger compared to k _s measured on G-C electrode, while in both cases the k _s values were diminished with the enrichment of the mixtures in ACN. The EIS spectra confirmed that the rate-determining step in the whole process is the diffusion of the FeCp₂ species and thus the process can be properly characterized as diffusion-controlled.     

Substituent-induced delocalization effects on hydrogen-bonding interaction in poly(N-phenyl methacrylamide) derivatives

Within small molecules, the hydrogen-bonding behaviors affected by delocalization have been studied thoroughly, but rare publication in macromolecules. Therefore, three poly(N-phenyl methacrylamide)s, poly(N-phenyl methacrylamide) (PNPAA), poly(N-4-methoxyphenyl methacrylamide) (PMPMA) and poly(N-4-bromophenyl methacrylamide) (PBPMA), with different inductive substitution at para position of benzene ring are prepared to investigate the substituent-induced delocalization effects on the hydrogen-bonding interaction behaviors. In this study, the variable-temperature FTIR spectrum is used as tool to study the self- and inter-association hydrogen-bonding interaction. FTIR analyses could provide evidences that there is relatively stronger inter-associative hydrogen bonding in poly(N-4-bromophenyl methacrylamide)/P4VP blends. High resolution ¹³C CP/MAS solid-state NMR analyses indicate that the spin-lattice relaxation time (T₁ρ^H) in all PBPMA blends are homogeneous on the scale at which spin-diffusion occurs within the time T₁ρ^H, also due to the enhancement by substituent inductive delocalization.     

Genome-Wide Identification and Expression Analysis of Udp-Glucuronosyltransferases in the Whitefly Bemisia Tabaci (Gennadius) (HemipterA: Aleyrodidae)

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is an important agricultural pest worldwide. Uridine diphosphate (UDP)-glucuronosyltransferases (UGTs) are one of the largest and most ubiquitous groups of proteins. Because of their role in detoxification, insect UGTs are attracting increasing attention. In this study, we identified and analyzed UGT genes in B. tabaci MEAM1 to investigate their potential roles in host adaptation and reproductive capacity. Based on phylogenetic and structural analyses, we identified 76 UGT genes in the B. tabaci MEAM1 genome. RNA-seq and real-time quantitative PCR (RT-qPCR) revealed differential expression patterns of these genes at different developmental stages and in association with four host plants (cabbage, cucumber, cotton and tomato). RNA interference results of selected UGTs showed that, when UGT352A1, UGT352B1, and UGT354A1 were respectively silenced by feeding on dsRNA, the fecundity of B. tabaci MEAM1 was reduced, suggesting that the expressions of these three UGT genes in this species may be associated with host-related fecundity. Together, our results provide detailed UGTs data in B. tabaci and help guide future studies on the mechanisms of host adaptation by B. tabaci.     

Study of geometry and operational conditions on mixing time, gas hold up, mass transfer, flow regime and biomass production from natural gas in a horizontal tubular loop bioreactor

A horizontal tubular loop bioreactor (HTLB) was used for production of biomass from natural gas. Hydrodynamic characterizations (mixing time and gas hold up) and mass transfer coefficients were considered in the HTLB (L=2.2 m, H=0.4 m and D=0.03 m) as functions of design parameters, i.e., horizontal length to diameter ratio (L/D) and volume of gas-liquid separator (S) as well as operational parameters, i.e., superficial gas and liquid velocities (U_sG, U_sL). In addition, flow regime in different gas and liquid flow rates was investigated. It was observed from experimental results that U_sL has remarkable effects on gas hold up and k_La due to its influence on mixing time. The volumetric mass transfer coefficients for oxygen (k_La_O2) and methane (k_La_CH4) were determined at different geometrical and operational factors. In average, the amount of oxygen consumption for metabolism is approximately 1.4 times higher than that of methane. In bubble flow regime, the HTLB was used for biomass production, too. A gas mixture of 50% methane and 50% oxygen (based on results of dry cell weight, optical density and doubling time) was the best gas mixture inlet for biomass production. The empirical correlations for mixing time, gas hold up and k_La in terms of U_sG, U_sL, L/D and volume of gas-liquid separator were obtained and expressed separately.     

Synthesis and characterization of graft copolymers with poly(epichlorohydrin-co-ethylene oxide) as backbone by combination of ring-opening polymerization with living anionic polymerization

Series of graft copolymers with [Poly(epichlorohydrin-co-ethylene oxide)] [Poly(ECH-co-EO)] as backbone and polystyrene (PS), poly(isoprene) (PI) or their block copolymers as side chains were successfully synthesized by combination of ring-opening polymerization (ROP) with living anionic polymerization. The Poly(ECH-co-EO) with high molecular weight (M_n = 3.3 × 10⁴ g/mol) and low polydispersity index (PDI = 1.34) was firstly synthesized by ring-ROP using ethylene glycol potassium as initiator and triisobutylaluminium (i-Bu₃Al) as activator. Subsequently, by “grafting onto” strategy, the graft copolymers Poly(ECH-co-EO)-g-PI, Poly(ECH-co-EO)-g-PS and Poly(ECH-co-EO)-g-(PI-b-PS) were obtained using the coupling reaction between living PI⁻Li⁺, PS⁻Li⁺ or PS-b-PI⁻Li⁺ species capped with or without 1,1-diphenylethylene (DPE) agent and chloromethyl groups on poly(ECH-co-EO). By model experiment, the addition of DPE agent was confirmed to have an important effect on the grafting efficiency at room temperature. Finally, the target graft copolymers and intermediates were characterized by SEC, ¹H NMR, MALLS and FTIR in detail, and thermal behaviours of the graft copolymers were also investigated by DSC measurement.     

Transition of the bounded polymer layer to a rigid amorphous phase: A computational and DSC study

The study focuses on the transition of the bounded to solid surfaces polymer layer to a rigid amorphous phase (RAP). Based on previous Monte Carlo (MC) simulation studies on bulk polyethylene (PE), we refine our numerical variable density Self Consistent Field (nSCF) method in order the calculated density in bulk to follow the predictions of the MC simulation. The proposed modification of the Sanchez–Lacombe equation of state allows us to examine thermodynamic aspects of the glass transition. By imposing a glass transition (T_g = 220 K) in the bulk we predict an earlier (during cooling), stronger transition of the bounded layer to a RAP, at ∼350 K. Also at short separation distances we record the appearance of undisturbed polymer bridges. Differential scanning calorimetry (DSC) experiments on polydimethylsiloxane (PDMS) and polyamide 6 (PA6) nanocomposites suggest that although the crystallization can be significantly suppressed by the addition of nanoparticles, the RAP layer may locally equilibrate, above T_g, for long experimental times with the melt phase. Our results support the idea that a significant free energy barrier of entropic origin appears due to the RAP formation, below the melting temperature (T_m) and above the T_g.     

Simulation of an extractive electrochemical reaction operated under limiting current conditions in a parallel-plate reactor

An extractive electrochemical reaction, which uses an extractive liquid (β) to separate the adherent product (S) on the electrode surface (e) in order to allow the continuation of the reaction (R) occurring electrochemically in a reacting phase (α), was investigated with the aim of studying the kinetics and reactor design. A kinetic model based on the competitive surface coverage (θ) by the reactant and the product, was developed to describe the performance in a parallel-plate reactor. The electrochemical reaction rate, defined asKmAX _α/e(1-θ)(C _R/α-C _R/e), is equal to the extraction rate, defined asKdAX _β/Seθ(C _S ^β/sat -C _S/β) under steady-state conditions whereX is the dispersion function andA is the specific surface area. Simulation under limiting current conditions reveals that this system is dependent on the volume ratio of the two liquids, the dispersion effect and the reactor geometry and diffusion coefficients. Three dimensionless parametersΦ _k(=K _m/K _d),Φ _x (=X _α/e/X _β/Se) andΦ _v ( =X _β/X _α) were used to describe this extractive electrochemical reaction.