Hyperelastic characterization of the interlamellar domain and interphase layer in semicrystalline polyethylene

The interphase layer in semicrystalline polyethylene (PE) serves as the transition between the crystalline lamellae and the amorphous domains and is recognized as the third constituent of PE. When PE undergoes large deformations, this interphase layer together with the amorphous phase behaves hyperelastically. Because of the metastable nature and nanometric size of the interphase and its intimate mechanical coupling to the neighboring crystal and amorphous domains, detailed characterization of its hyperelastic properties have eluded detailed experimental evaluation. To extract these properties, a combined algorithm is proposed based on applying the constitutive relations of an isotropic, compressible, hyperelastic continuum to the molecular dynamics simulation results of a PE stack from Lee and Rutledge (Macromolecules 2011, 3096–3108). The simulation element is incrementally deformed to a large strain, during which the stress–strain information is recorded. Assuming a neo‐Hookean model, the tensorial constitutive equation is derived. The hyperelastic parameters for the central amorphous phase, the interphase layer, and the interlamellar domain are identified with the help of the optimization notion and a set of nonnegative objective functions. The identified hyperelastic parameters for the interlamellar domain are in good agreement with the ones estimated experimentally and frequently used in the literature for the noncrystalline phase. The specifically developed sensitivity analysis indicates that the shear modulus is identified with a higher degree of certainty, in contrast to the bulk modulus. It is also revealed that the presented continuum mechanics analysis is able to capture the melting/recrystallization and rotation of crystalline chains that take place during the deformation. The evolutions of the boundaries of the hyperelastic elements are also identified concurrently with the hyperelastic parameters as the by‐product of the presented methodology. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1692–1704     

Brain Iron Deficiency Changes the Stoichiometry of Adenosine Receptor Subtypes in Cortico-Striatal Terminals: Implications for Restless Legs Syndrome

Brain iron deficiency (BID) constitutes a primary pathophysiological mechanism in restless legs syndrome (RLS). BID in rodents has been widely used as an animal model of RLS, since it recapitulates key neurochemical changes reported in RLS patients and shows an RLS-like behavioral phenotype. Previous studies with the BID-rodent model of RLS demonstrated increased sensitivity of cortical pyramidal cells to release glutamate from their striatal nerve terminals driving striatal circuits, a correlative finding of the cortical motor hyperexcitability of RLS patients. It was also found that BID in rodents leads to changes in the adenosinergic system, a downregulation of the inhibitory adenosine A₁ receptors (A₁Rs) and upregulation of the excitatory adenosine A_2A receptors (A_2ARs). It was then hypothesized, but not proven, that the BID-induced increased sensitivity of cortico-striatal glutamatergic terminals could be induced by a change in A₁R/A_2AR stoichiometry in favor of A_2ARs. Here, we used a newly developed FACS-based synaptometric analysis to compare the relative abundance on A₁Rs and A_2ARs in cortico-striatal and thalamo-striatal glutamatergic terminals (labeled with vesicular glutamate transporters VGLUT1 and VGLUT2, respectively) of control and BID rats. It could be demonstrated that BID (determined by measuring transferrin receptor density in the brain) is associated with a selective decrease in the A₁R/A_2AR ratio in VGLUT1 positive-striatal terminals.     

Sorption of Hydrophobic Organic Compounds by Aqueous Latexes

Summary: Optical absorption measurements are used for the first time to investigate the uptake of pure organic solvents or solutions by latex particles. Sorption into glassy polymer particles is a two‐stage process with distinctly different characteristic times, which reflects that an initial softening of the outer particle layer facilitates further uptake. The sorption of solutions containing highly water‐insoluble compounds allows the preparation of composite nanoparticles, which are hardly accessible by other routes.

Photograph of the neat 100 nm latex (right) particles and the particles after dying by sorption with the hydrophobic pigment Sudan IV (left).     

Studies on pyrrolidinones. Preparation of 1,5,6‐10b‐tetrahydro‐2H‐pyrrolo[1,2‐c]quinazoline‐3‐ones from pyroglutamic acid

Tetrahydro‐2H‐pyrrolo[1,2‐c]quinazoline‐3‐ones are easily obtained from the Friedel‐Crafts cyclization of N‐arylaminomethyl pyroglutamic acids. This reaction occurrs via an acyliminium salt formed by decarboxylation of the acid function.     

Comparison Between the Induced Changes in the Intensities of Mid and Near Infrared Absorption Bands of Poly[Vinyl Alcohol] Due to Temperature and Solvents

The temperature induced changes in the intensities of the infrared absorption bands of PVA in both MID and NIR regions are presented. The absorption band at 1141cm^-1 is the only band among the bands in the mid region which is markedly affected by temperature. This band is taken as a measure of crystallinity of PVA. PVA shows two phase transitions at 80c⁰ and 120c⁰. The absorbances of the 1940nm in the near region is also temperature sensititve. The temperature dependence of the other bands in either mid or near regions is very weak. The effect of non polar and polar solvents such as n-hexane, carbon tetrachloride, toluene, chloroform, methanol and acetone is discussed. Comparison between the solvent induced changes in the intensities of the bands in mid and near regions is carried out. The data demonstrate that the bands in the near region ( overtone and combinations) are more sensitive to solvents than the bands in the mid regions. The combined effect of temperature and solvents on the intensities of absorption bands of PVA is also studied.     

Electrocatalytic Activity of Immobilized Co(II) on Porous Graphene Aerogels

The highly‐porous graphene aerogel (GA) with BET surface area of 810 m² g^?1 and three‐dimensional structure has been successfully fabricated using the hydrothermal technique. The modified glassy carbon electrode was then prepared by casting the graphene aerogel solution followed by immersing the GA/GCE in Co⁺² solution. The results showed that graphene aerogels improved the adsorption ability of the Co (II) ions. The electrocatalysis of oxygen evolution reaction (OER) at the Co‐GA modified glassy carbon elec‐ trode (Co‐GA/GCE) has been investigated using linear sweep voltammetry (LSV) in alkaline solution. The OER was noticeably enhanced at Co‐GA/GCE, representing a negative shift in the LSV curve at the Co‐GA/GCE compared to that obtained at the bare GCE. The high electrocatalytic activity, good reproducibility and low cost of proposed electrode provides desired characteristics of a potential candi‐ date in the industrial water electrolysis process.     

Nuclear Level Density with Non-zero Angular Momentum

The statistical properties of interacting fermions have been studied for various angular momentum with the inclusion of pairing interaction. The dependence of the critical temperature on angular momentum for several nuclei,have been studied. The yrast energy as a function of angular momentum for 28 Si and 24Mg nuclei have been calculated up to 60.0 MeV of excitation energy. The computed limiting angular momenta are compared with the experimental results for 26Al produced by 12C 14N reaction. The relevant nuclear level densities for non-zero angular momentum have been computed for 44Ti and l36Ba nuclei. The results are compared with their corresponding values obtained from the approximateformulas.     

Prediction of stable processes: Spectral and moving average representations

Summary For stable processes which are Fourier transforms of processes with independent increments, we obtain a Wold decomposition, we characterize their regularity and singularity, and, in the discrete-parameter case, we derive their linear predictors. In sharp contrast with the Gaussian case, regular stable processes which are Fourier transforms of processes with independent increments are not moving averages of stable motion.This research was supported by the Air Force Office of Scientific Research Grant No. F 49620 82C0009     

The base-free chemoselective ring opening of epoxides with carboxylic acids using [bmim]Br: a rapid entry into 1,2-diol mono-esters synthesis

A facile and highly convenient base-free protocol for the chemoselective preparation of 1,2-diol mono-esters is described. In this method, the regioselective ring opening of epoxides with carboxylic acids in the presence of [bmim]Br furnishes the corresponding 1,2-diol mono-esters in excellent yields. This method is efficient for various structurally diverse epoxides and carboxylic acids and it can be efficiently applied for the scale up synthesis of 1,2-diol mono-esters in reasonable to good yields. [bmim]Br remarkably influences the reaction progress and acts as both solvent and catalyst in this protocol.     

Synthesis,Characterization and Molecular Structure of a New Tetrameric Palladium(II) Complex Containing Schiff‐Bases Derived from AMTTO (AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one)

The reactions of AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) with 2‐hydroxybenzaldehyde (salicylaldehyde) and 4‐hydroxybenzaldehyde in methanol under reflux conditions led to the corresponding Schiff‐bases ( H₂L1 and H₂L2 ). The reaction of H₂L1 with palladium acetate in ethanol and additional recrystallization from toluene gave the tetrameric complex [Pd(L)]₄·2C₇H₈ ( 2 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for H₂L1 at ?80 °C: space group P2₁/c with a = 1285.4(1), b = 707.7(1), c = 1348.2(1) pm, β = 109.32(1)°, Z = 4, R₁ = 0.0328, H₂L2 at ?80 °C: space group P4₃2₁2 with a = 762.5(1), b = 762.5(1), c = 4038.9(2) pm, Z = 8, R₁ = 0.025 and for 2 at ?103 °C: space group C2/c with a = 2862.5(6), b = 2847.6(6), c = 1727.8(4) pm, β = 105.18(3)°, Z = 8, R₁ = 0.0704.