Properties Of Long Chains Research Articles

Calculation of the Differential Breit–Rosenthal Effect in the 6s6p 3P1,2 States of Hg

Studies of the hyperfine anomaly has found a renewed interest with the recent development of techniques to study the properties of long chains of unstable nuclei. By using the hyperfine structure for determining the nuclear magnetic dipole moments, the hyperfine anomaly puts a limit to the accuracy. In this paper, the differential Breit–Rosenthal effect is calculated for the 6s6p3P1,2 states in 199Hg as a function of the change in nuclear radii, using the MCDHF code, GRASP2018. The differential Breit–Rosenthal effect was found to be of the order of 0.1%fm−2, in most cases much less than the Bohr-Weisskopf effect. The results also indicate that large calculations might not be necessary, with the present accuracy of the experimental values for the hyperfine anomaly.

High performance branched poly(lactide) induced by reactive extrusion with low-content cyclic organic peroxide and multifunctional acrylate coagents

In this work, acrylates with various functionalities are employed as the branching coagent for improving the properties of long chain branched polylactide (LCB-PLA) induced by reactive extrusion with low content of cyclic organic peroxide (COP). It is discovered that the heat resistance and foaming performance of COP-initiated LCB-PLA are remarkably improved by the coagent. Specifically, the Vicat softening temperature and expansion ratio of 0.3 wt% COP-initiated LCB-PLA with 0.3 wt% coagent are sharply increased to above 150 °C and 27.0-fold, respectively (60 °C and 9.8-fold for 0.3 wt% COP modified PLA). This is due to the simultaneously enhanced melt strength and crystallization properties of LCB-PLA induced by the obviously enhanced branching degree by the coagent. Moreover, the branch-promotion efficiency of various coagents is found to be independent of the functionality due to the steric hindrance. The possible mechanisms on the formation of topological structures of COP modified PLA with coagents are proposed.

Preparation and properties of long chain based polyacrylate latex

The long carbon chain monomer modified polyacrylate latex was successfully prepared by semi-continuous seeded emulsion polymerization. In this work, methyl methacrylate and butyl acrylate were used as main monomers; stearyl acrylate was used as functional monomer, which were emulsified with the novel mixed surfactants of disodium laureth sulfosuccinate (AEMES) and alkylphenol ethoxylates (OP-10) and initiated with 2,2′-azobis (2-methyl propion- amidine) dihydrochloride initiator. The structure of the resultant latex was characterized by Fourier transform infrared spectroscopy. The differential scanning calorimetry, thermogravimetric analysis and contact angle were used to test the properties of the latex film. The particle size of the latex was measured by the Zetatrac dynamic light scattering detector. Factors, which have an influence on the properties of the latex and its film, have been investigated in detail. Results show that the optimal condition of synthesizing the latex is as follows: the amount of emulsifiers is 4%; the mass ratio of AEMES to OP-10 is 3:1; the amount of initiator is 0.7%; the content of SA is 6%.

A polymer model of bacterial supercoiled DNA including structural transitions of the double helix

DNA supercoiling, the under or overwinding of DNA, is a key physical mechanism both participating to compaction of bacterial genomes and making genomic sequences adopt various structural forms. DNA supercoiling may lead to the formation of braided superstructures (plectonemes), or it may locally destabilize canonical B-DNA to generate denaturation bubbles, left-handed Z-DNA and other functional alternative forms. Prediction of the relative fraction of these structures has been limited because of a lack of predictive polymer models that can capture the multiscale properties of long DNA molecules. In this work, we address this issue by extending the self-avoiding rod-like chain model of DNA so that every site of the chain is allocated with an additional structural degree of freedom reflecting variations of DNA forms. Efficient simulations of the model reveal its relevancy to capture multiscale properties of long chains (here up to 21 kb) as reported in magnetic tweezers experiments. Well-controlled approximations further lead to accurate analytical estimations of thermodynamic properties in the high force regime, providing, in combination with experiments, a simple, yet powerful framework to infer physical parameters describing alternative forms. In this regard, using simulated data, we find that extension curves at forces above 2 pN may lead, alone, to erroneous parameter estimations as a consequence of an underdetermination problem. We thus revisit published data in light of these findings and discuss the relevancy of previously proposed sets of parameters for both denatured and left-handed DNA forms. Altogether, our work paves the way for a scalable quantitative model of bacterial DNA.

Preparation and properties of long chain branched high-density polyethylene based on nano-SiO2 grafted glycidyl methacrylate

A compounded nanoparticle with multiple double bonds (C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C) was prepared by grafting glycidyl methacrylate (GMA) onto the surface of nano-SiO2. Then gel-free long chain branched polyethylene (LCBPE) was prepared by melt branching reaction in a Haake torque rheometer in the presence of initiator peroxide and GMA grafted nano-SiO2 (SiO2-g-GMA). The sampling time corresponded to the summit of the reaction peak in the torque curve. Fourier transform infrared results indicated that SiO2-g-GMA had been grafted onto the HDPE backbone via radical reaction. The reaction mechanism and the topological structure of the PE products are also discussed. Rheological results showed that the relaxation time and molecular weight distribution of modified PE were increased owing to the introduction of LCB structure, and the more SiO2-g-GMA was added, the more apparent variation could be observed. Compared with linear HDPE, both the melt strength and mechanical properties of LCBPE were improved obviously. From the differential scanning calorimetry and polarized optical microscopy results, smaller crystal size and lower growth rate were observed compared with linear HDPE, which are ascribed to the nucleation and restriction of long branching chains in the system. Well distributed nano-SiO2 without any agglomeration in the PE matrix was observed in the scanning electron microscope images when the SiO2-g-GMA content was less than 3 phr.

Blood pressure-lowering effects of long chain n-3 fatty acids from meals enriched with liquid fish oil and from microencapsulated powder

Background: Diet plays an important role in the etiology of hypertension. Blood pressure (BP)-lowering properties of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) are promising. The aim was to investigate whether different formulations of fish oil differently affect blood pressure in community-dwelling adults. The hypothesis was that fish oil formulations would improve BP in comparison with a placebo.Methods: In this 4-week randomized, placebo-controlled, doubly-blinded dietary intervention study, participants (N = 99, >50 years) from the capital area of Iceland were randomized into three groups. Group 1 (n = 38) received 6 meals/week fortified with a liquid fish oil and placebo powder. Group 2 (n = 30) received conventional (unfortified) meals and microencapsulated powder. Group 3 (n = 31) was the control group which received conventional meals and placebo powder. Calculated on a weekly basis, the amount of EPA + DHA provided was 1.5 g/d. Systolic (SBP) and diastolic BP (DBP) were measured before and after the intervention period.Results: Seventy-seven subjects finished the study (77.8%). Drop-out rates were not different between groups. According to multivariate statistics, endpoint SBP was lower in Group 1 (−7.0 mmHg, p = 0.037) and in Group 2 (−7.2 mmHg, p = 0.037) as compared with Group 3. There was no significant difference in DBP between the groups.Conclusion: Our study shows that LC n-3 PUFA from microencapsulated powder are equally effective to meaningfully reduce SBP as LC n-3 PUFA from meals enriched with liquid fish oil in comparison with a control group.

Effect of Conformational Symmetry upon the Formation of Cysteine Clusters on the Au(110)-(1 × 1) Surface: A First-Principles Study

The physical properties of cysteine clusters formed on the Au(110)-(1 × 1) surface are investigated by means of density-functional theory. We take into account the clusters formed from three types of rotational conformers of cysteine; for each structure we investigate the protonated and unprotonated forms. Our investigations are based on three different geometrical models for the surface–adsorbate system, allowing us to describe the formation of new nucleation centers on the surface as well as the properties of long chains of cysteine molecules adsorbed on the Au(110)-(1 × 1) surface. We point out significant differences between the relaxed structures formed by each conformer as well as the specific physicochemical properties leading to formation of new nucleation centers compared with those of already formed large cysteine structures. In particular, we emphasize the role of the NH2 group of cysteine in these processes, by correlating our data with its relative position with respect to the gold surface.

Development of Arginine Based Monopeptides as Cationic Surfactants from Pure Amino Acid

A mino acid-based surfactants constitute a class of cationic surfactants with excellent surface p roperties, wide biological activ ity, low potential to xicity. Essential structural factors for their antimicrobial activity include both the length of the fatty residue and the presence of the protonated guanidine function. These features and the use of natural raw materials such as Arginine and fatty acids for their synthesis, make them interesting candidates as preservatives and antiseptics in pharmaceutical, food and cosmetic fo rmulat ions. The present work describes the synthesis (at lab scale), the physicochemical properties of long chain N α -acyl arginine ethyl esters with a chain of 8 and 9 carbon atoms. These compounds have been prepared by condensation of L-arg inine ethyl ester dihydrochloride with corresponding acyl chlorides in the presence of base. The basic charastristic properties such as physical appearance, structural identificat ion by IR/ H 1 NMR, water solubility at different pH and surface tension studies of the synthesized co mpounds are discussed. The Antimicrobial properties of the co mpounds of invention are studied by determin ing their M inimu m inhibitory concentration for different microorganisms.

Electron correlation effects on the electric properties of fluorinated polyacetylene

Using the Hartree-Fock (HF) and second-order Mo̸ller-Plesset perturbation theory (MP2) methods with the 6-31G(d) basis set, we have investigated the chain length dependence of the longitudinal dipole moment and longitudinal components of the static linear polarizability, first and second hyperpolarizabilities of fluorinated polyacetylene chains. It is found that geometry changes caused by the electron correlation (EC) effects imply in marked increases of the electric properties but to obtain a reliable description it is necessary to properly account for both geometric and electronic changes. Based on the fast convergence pattern presented by the MP2∕HF ratios and from the converged HF oligomeric results, we have estimated the MP2 electric properties of long chains. The asymptotic value for the MP2 second hyperpolarizability per unit cell is estimated in 1.9 × 10(8) a.u. This result is one order of magnitude larger than the corresponding result reported for the unsubstituted polyacetylene chains.

Synthesis, characterization and surface properties of long chain β-hydroxy-γ-alkyloxy- N-methylimidazolium surfactants

A series of long chain water soluble cationics have been synthesized by reacting β-hydroxy-γ-alkyloxy bromo or chloro ethers with N-methylimidazole. The surface activity of the molecules has been determined by measurement of their conductance and surface tension in aqueous solution. The dynamics of surface activity of these surfactants have also been investigated in the presence of sodium halides, NaCl and NaBr by surface tension measurement. A series of useful parameters like critical micelle concentration (cmc), surface tension at the cmc ( γ cmc), adsorption efficiency (p C 20), effectiveness of surface tension reduction ( Π cmc), Gibbs free energy of the micellization (Δ G 0 mic) and Gibbs free energy of adsorption (Δ G 0 ads) have been determined from the measurements obtained by surface tension and conductivity method. Further with the application of the Gibbs adsorption isotherm, maximum surface excess concentration ( τ max) and minimum surface area/molecule ( A min) at the air–water interface were also estimated. Thermal stability of these long chain cationics has been measured by thermal gravimetric analysis under nitrogen atmosphere. Analysis of thermal stability measurement indicated that the thermal stability of these long chain imidazoliniums increase with an increase in chain length.

Rheological properties of long chain branched polyethylene melts at high shear rate

Capillary extrusion experiments involving a number of polyethylenes with emphasis on assessing the effect of long chain branching (LCB) are performed. None of the metallocene catalyzed linear low density polyethylenes (mLLDPE) produced by Dow Chemicals, which are believed to have some level of LCB, show temperature dependence on the viscosity at the gross melt fracture regime. Furthermore, these materials do not show spurt or stick-slip flow, in contrast with most linear polyethylenes. LDPE and blends of LDPE with LLDPE having LCB also show the absence of stick-slip flow, but show temperature dependence on the viscosity. From these observations, we conclude that the stick-slip flow is very sensitive to the existence of LCB.

Non-equilibrium all-atom molecular dynamics simulations of free and tethered DNAmolecules in nanochannel shear flows

In order to gain insight into the mechanical and dynamical behaviour of free and tetheredshort chains of ss/ds DNA molecules in flow, and in parallel to investigate the properties oflong chain molecules in flow fields, we have developed a series of quantum andmolecular methods to extend the well developed equilibrium software CHARMM tohandle non-equilibrium dynamics. These methods have been applied to casesof DNA molecules in shear flows in nanochannels. Biomolecules, both free andwall-tethered, have been simulated in the all-atom style in solvent-filled nanochannels.The new methods were demonstrated by carrying out NEMD simulations of freesingle-stranded DNA (ssDNA) molecules of 21 bases as well as double-strandedDNA (dsDNA) molecules of 21 base pairs tethered on gold surfaces in an ionicwater shear flow. The tethering of the linker molecule (6-mercapto-1-hexanol) toperfect Au(111) surfaces was parametrized based on density functional theory(DFT) calculations. Force field parameters were incorporated into the CHARMMdatabase. Gold surfaces are simulated in a Lennard-Jones style model that wasfitted to the Morse potential model of bulk gold. The bonding force of attachmentof the DNA molecules to the gold substrate linker molecule was computed tobe up to a few nN when the DNA molecules are fully stretched at high shearrates. For the first time, we calculated the relaxation time of DNA molecules inpicoseconds (ps) and the hydrodynamic force up to a few nanoNewtons (nN)per base pair in a nanochannel flow. The velocity profiles in the solvent due tothe presence of the tethered DNA molecules were found to be nonlinear only athigh shear flow rates. Free ssDNA molecules in a shear flow were observed tobehave differently from each other depending upon their initial orientation inthe flow field. Both free and tethered DNA molecules are clearly observed to bestretching, rotating and relaxing. Methods developed in this initial work can beincorporated into multiscale simulations including quantum mechanical, molecular andthe microfluidic continuum regimes. The results may also be useful in extendingexisting macroscopic empirical models of DNA response dynamics in shear flows.

Synthesis and Properties of Long Chains of sp‐Hybridized Carbon Atoms: Polyynes

Polyynes, a class of molecules described by the general formula H‐(C≡C)mH (where m is an integer) can be synthesized using an electric arc between graphite electrodes submerged in an organic solvent such as methanol, n‐hexane, n‐dodecane, decalin, or acetonitrile. The longest polyyne chain has been obtained when the electric arc is struck in acetonitrile at −40°C; polyyne chains up to 18 carbon atoms (m=9) have been produced together with monocyanopolyyne series as by‐products. When the arc between graphite electrodes is struck in liquid nitrogen, a mixture of dicyanopolyynes are obtained. The most recent development results on the rationalization of the mechanism of formation of polyynes from the submerged arc with new and noteworthy results are reviewed. The chemistry and the photochemistry of the polyynes solution are discussed including the reduction of polyynes to ene‐ynes. The application of polyynes range from astrochemistry to biochemistry. For instance cyanopolyynes are present in circumstellar media; polyynes are involved as intermediates in the formation of fullerenes, PAHs (polycyclic aromatic hydrocarbons), and soot. Polyynes are also biologically active molecules having antibiotic and antitumoral properties.

Molecular structure characterization of linear and branched polystyrene blends by size exclusion chromatography coupled with viscometry

Owing to their low polydispersity and their well controlled molecular architecture, 3-arms stars polystyrenes made by anionic synthesis are suitable models to study the solution properties of long chain branched polymers. A fine characterization of such polymers by size exclusion chromatography–viscometry has shown that they often contain unwanted linear chains, leading to chromatograms presenting overlapping peaks. A mathematical procedure has been developed in order to deconvolute these chromatograms and has been validated, thanks to blends of polystyrene standards. It allows one to calculate the purity of the sample as well as the intrinsic viscosity and molar mass distribution of each component. For stars with three arms of the same length, branching parameters have also been calculated and a viscosity law has been established.

Finite-bandwidth effects in one-dimensional Wigner lattices

The Feynman path-integral formalism is used to calculate the thermodynamic properties of a one-dimensional (1D) spinless fermion model with nearest- and next-nearest-neighbor interaction. The mapping of this 1D quantum model on a two-dimensional classical model allows the use of a Monte Carlo method to calculate the properties of long chains. We present results for typical values of the interaction parameters, density, and temperature. We find that a finite bandwidth smears out the details of the classical ground-state configurations discussed by Hubbard. If the density $\ensuremath{\rho}\ensuremath{\ne}\frac{1}{2}$, we find that the static structure factor and the static susceptibility display a maximum at $2{k}_{F}$ only when the next-nearest-neighbor interaction is nonzero.

Surface active N‐acylglutamate: II. Physicochemical properties of long chain N‐acylglutamic acids and their sodium salts

AbstractThe physicochemical properties of long chain N‐acylglutamic acids (AGA) and their sodium salts (AGSn) are described. The solubility, Krafft point, pH value, critical micelle concentration, surface tension and foaming power were measured. The properties of the optically active AGA or AGSn differed from those of the corresponding racemates, especially in solubility. The monosodium salts generally had high Krafft points, but monosodium N‐oleoylglutamate had a low Krafft point. The monosodium salts hydrolyzed in the diluted aqueous solution to liberate the AGA. The aqueous solutions of the monosodium salts had low surface tensions and good foaming properties. The disodium salts were highly soluble in water, while surface tensions and foaming properties were inferior to those of the corresponding monosodium salts.

Dielectric properties of long chains with one short dipole

We study theoretically dielectric relaxation of macromolecules with one single electric dipole in the center of the chain.