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Hyperbranched poly(silyl ether)s are a new class of three-dimensional polymers with extremely branching structures. They possess intriguing physical and chemical properties, including intramolecular cavities, and an abundance of surface functional [...]

Quantum mechanical, or QM, calculations are described as ab initio methods for determining chemical properties of a system, divided into broadly two main approaches. Wavefunction, an approach that utilizes a [...]

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225-250°C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water-soluble crystallizable fraction and water-insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and 1H-NMR analysis. Glycolysis product was used for synthesis of PET-based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea-formaldehyde and melamine-formaldehyde resins for synthesis of epoxy ester-amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET-based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino-resin-modified epoxy ester resins that have improved physical and chemical surface coating properties., INTRODUCTION Polyethylene terephthalate) (PET) is a semicrystalline thermoplastic polyester produced by the reaction of terephthalic acid and ethylene glycol (EG) [1-3], There are two stages in PET synthesis. Bis (2-hydroxyethyl [...]

In this article, for the first time in the literature effects of phenylene diisocyanate (PDI)-based compatibilizer on the physical and chemical properties of citric acid (CA) modified thermoplastic starch (TPS)/poly(lactic acid) (PLA) blends were investigated with respect to PDI and CA content and blend composition. The blends were prepared by melt compounding in a laboratory micro-compounder. Fourier transformation infrared spectroscopy results showed that CA interacted with starch and PDI interacted by both starch and PLA through the hydroxyl groups. It was revealed from SEM micrographs that combinatorial usage of CA and PDI resulted in an improved, finer distribution of TPS in PLA matrix. This improvement affected the mechanical properties of blend, especially the toughness related properties such as impact strength and elongation at break. The thermal properties such as [T.sub.g] and [T.sub.m]., revealed from differential scanning calorimeter analysis were in line with the morphological structure of the blends by suggesting the compatibilization phenomena in the presence of PDI and CA together. Thermogravimetric analysis showed that compatibilization of two phases improved the thermal stability of the blends. As a general conclusion, the combinatorial usage of PDI and CA can be utilized to obtain tougher PLATT-PS blends-based materials to overcome the brittleness problem. POLYM. ENG. SCI., 53:2183-2193, 2013. [c] 2013 Society of Plastics Engineers, INTRODUCTION Awareness of the environmental problems caused by petroleum-based plastic materials over the last few decades has pushed the polymer researchers to produce eco-friendly plastics. The biodegradable polymers derived from [...]

Type IV secretion systems are secretion nanomachines spanning the two membranes of Gram-negative bacteria. Three proteins, Vir137, Vir139 and VirB10, assemble into a 1.05 megadalton (MDa) core spanning the inner and outer membranes. This core consists of 14 copies of each of the proteins and forms two layers, the I and O layers, inserting in the inner and outer membrane, respectively. Here we present the crystal structure of a ~0.6 MDa outer-membrane complex containing the entire O layer. This structure is the largest determined for an outer-membrane channel and is unprecedented in being composed of three proteins. Unexpectedly, this structure identifies VirB10 as the outer-membrane channel with a unique hydrophobic double-helical transmembrane region. This structure establishes VirB10 as the only known protein crossing both membranes of Gram-negative bacteria. Comparison of the cryo-electron microscopy (cryo-EM) and crystallographic structures points to conformational changes regulating channel opening and closing., Type IV secretion (T4S) systems are used by Gram-negative bacteria in a variety of processes, ranging from the delivery of virulence factors into eukaryotic cells to conjugative transfer of genetic [...]

Setting up Medical Clinics in Cambodia: A Model for Service Learning Abroad. Melissa K. Allen, University of Michigan--Flint, Department of Nursing; Bonnie M. Durbin, University of Michigan--Flint, Department; of Radiation [...]

Urea is highly concentrated in the mammalian kidney to produce the osmotic gradient necessary for water re-absorption. Free diffusion of urea across cell membranes is slow owing to its high polarity, and specialized urea transporters have evolved to achieve rapid and selective urea permeation. Here we present the 2.3 Å structure of a functional urea transporter from the bacterium Desulfovibrio vulgaris. The transporter is a homotrimer, and each subunit contains a continuous membrane-spanning pore formed by the two homologous halves of the protein. The pore contains a constricted selectivity filter that can accommodate several dehydrated urea molecules in single file. Backbone and side-chain oxygen atoms provide continuous coordination of urea as it progresses through the filter, and well-placed α-helix dipoles provide further compensation for dehydration energy. These results establish that the urea transporter operates by a channel-like mechanism and reveal the physical and chemical basis of urea selectivity., Urea is ubiquitous in nature. Bacteria take up urea and convert it to ammonia for use as a nitrogen source, and in certain enteric pathogens, a buffer for surviving the [...]

The thicknesses and Clapeyron slopes of mantle phase boundaries strongly influence the seismic detectability of the boundaries and convection in the mantle. The unusually large positive Clapeyron slope found for the boundary between perovskite (Pv) and post-perovskite (pPv) (1-3) (the 'pPv boundary') would destabilize high-temperature anomalies in the lowermost mantle (4), in disagreement with the seismic observations (5). Here we report the thickness of the pPv boundary in ([Mg.sub.0.91][Fe.sup.2+.sub.0.09])Si[O.sub.3] and ([Mg.sub.0.9][Fe.sup.3+.sub.0.1])([Al.sub.0.1][Si.sub.0.9])[O.sub.3] as determined in a laser-heated diamond-anvil cell under in situ high-pressure (up to 145 GPa), high-temperature (up to 3,000 K) conditions. The measured Clapeyron slope is consistent with the D' discontinuity (6). In both systems, however, the pPv boundary thickness increases to 400-600 ± 100 km, which is substantially greater than the thickness of the D' discontinuity (< 30 km) (7). Although the [Fe.sup.2+] buffering effect of ferropericlase (8-10) could decrease the pPv boundary thickness, the boundary may remain thick in a pyrolitic composition because of the effects of Al and the rapid temperature increase in the D' layer. The pPv boundary would be particularly thick in regions with an elevated Al content and/or a low Mg/Si ratio, reducing the effects of the large positive Clapeyron slope on the buoyancy of thermal anomalies and stabilizing compositional heterogeneities in the lowermost mantle. If the pPv transition is the source of the D' discontinuity, regions with sharp discontinuities may require distinct compositions, such as a higher Mg/Si ratio or a lower Al content., The lowest 200-400 km of the mantle (the D' layer) is known to have seismic properties distinct from those of the overlying mantle, including a laterally varying discontinuity at the [...]

Mistranslation arising from confusion of serine for alanine by alanyl-tRNA synthetases (AlaRSs) has profound functional consequences (1-3). Throughout evolution, two editing checkpoints prevent disease-causing mistranslation from confusing glycine or serine for alanine at the active site of AlaRS. In both bacteria and mice, Ser poses a bigger challenge than Gly (1,2). One checkpoint is the AlaRS editing centre, and the other is from widely distributed AlaXps--free-standing, genome-encoded editing proteins that clear Ser-[tRNA.sup.Ala]. The paradox of misincorporating both a smaller (glycine) and a larger (serine) amino acid suggests a deep conflict for nature-designed AlaRS. Here we show the chemical basis for this conflict. Nine crystal structures, together with kinetic and mutational analysis, provided snapshots of adenylate formation for each amino acid. An inherent dilemma is posed by constraints of a structural design that pins down the α-amino group of the bound amino acid by using an acidic residue. This design, dating back more than 3 billion years, creates a serendipitous interaction with the serine OH that is difficult to avoid. Apparently because no better architecture for the recognition of alanine could be found, the serine misactivation problem was solved through free-standing AlaXps, which appeared contemporaneously with early AlaRSs. The results reveal unconventional problems and solutions arising from the historical design of the protein synthesis machinery., The 20 aminoacyl-tRNA synthetases (AARSs; one for each amino acid) have a fundamental role in establishing faithful translation, through close control over the two-step aminoacylation reaction that establishes the genetic-code [...]

Abstract A sesquiterpenoid Bakkenolide (1), and two steroids, (3β, 22E)-Stigmasta-5, 22-diene-3-oI (Stigmasterol) (2) and stigmasterol 3β-glucoside (3), isolated from the Hertia cheirifolia (L.) chloroform extract, were evaluated respectively for their [...]

Abstract In this study, six major xanthones, isolated and identified from Halenia elliptica were investigated for their vasodilatory actions in isolated rat coronary artery. The xanthones, including l-hydroxy-2,3,5-trimethoxy-xanthone (HM-1), l-hydroxy-2,3,4,7-tetramethoxy-xanthone [...]

Abstract Vasorelaxant effects of essential oil of Alpinia zerumbet (EOAZ) and its main constituent, 1, 8-cineole (CIN) were studied. In rat isolated aorta preparations with intact endothelium, EOAZ (0.01-3000 (µg/ml) [...]

ABSTRACT Influenza epidemics cause numerous deaths and millions of hospitalizations each year. Because of the alarming emergence of resistance to anti-influenza drugs, there is a need to identify new naturally [...]

ABSTRACT Turmeric (the rhizomes of Curcuma longa L., Zingiberacease) is widely used as a dietary pigment and spice, and has been traditionally used for the treatment of inflammation, skin wounds [...]

ABSTRACT The present study was conducted to explore the anti-inflammatory activities of Pinus brutia bark extract and Pycnogenol® in a rat model of carrageenan-induced inflammation. Firstly, the compositions of both [...]

ABSTRACT Devil's Claw (Harpagophytum procumbens) a plant native to Southern Africa, has historically been used in traditional medicine to treat a wide range of diseases and currently is widely employed [...]

ABSTRACT The present study investigated whether the D-camphor-crataegus berry extract combination Korodin® elevates blood pressure and enhances cognitive performance in the elderly population. Eighty women aged between 50 and 8- [...]

ABSTRACT Antiangiogenic compounds are gaining more and more interest as a new approach in the prevention and treatment of cancer and inflammatory diseases. The objective of this study was the [...]

ABSTRACT Scoparone is known to have a wide range of pharmacological properties in vitro. However, the roles of scoparone in immediate-type allergic reactions have not yet been investigated. In this [...]

ABSTRACT This study investigates the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the ambient air of two municipal solid waste incinerators (MSWIs: GS and RW) and a coal-fired power [...]

ABSTRACT Temuco is one of the most highly wood-smoke-polluted cities in the world. Its population in 2004 was 340,000 inhabitants with 1587 annual deaths, of which 24% were due to [...]

ABSTRACT Concurrent 24-hr samples of particulate matter of median aerodynamic diameter less than 10 µm ([PM.sub.10]) were collected over a 10-day period in August 2000 at four sites along a [...]

ABSTRACT This paper presents the results of field emission measurements that have been carried out on the 4500-kW four-stroke main engine on-board a product tanker. Two fuel qualities--heavy fuel oil [...]

Abstract The leaves of Croton zehntnevi Pax et Hoffm (Euphorbiaceae) were subjected to hydrodistillation, and the essential ail extracted was examined with respect to antibacterial and antibiotic modifying activity by [...]

The discovery of ammonia oxidation by mesophilic and thermophilic Crenarchaeota and the widespread distribution of these organisms in marine and terrestrial environments indicated an important role for them in the global nitrogen cycle (1-7). However, very little is known about their physiology or their contribution to nitrification (8). Here we report oligotrophic ammonia oxidation kinetics and cellular characteristics of the mesophilic crenarchaeon 'Candidatus Nitrosopumilus maritimus' strain SCM1. Unlike characterized ammonia-oxidizing bacteria, SCM1 is adapted to life under extreme nutrient limitation, sustaining high specific oxidation rates at ammonium concentrations found in open oceans. Its half-saturation constant ([K.sub.m] = 133 nM total ammonium) and substrate threshold (≤ 10 nM) closely resemble kinetics of in situ nitrification in marine systems (9,10) and directly link ammonia-oxidizing Archaea to oligotrophic nitrification. The remarkably high specific affinity for reduced nitrogen (68,7001 per g cells per h) of SCM1 suggests that Nitrosopumilus-like ammonia-oxidizing Archaea could successfully compete with heterotrophic bacterio-plankton and phytoplankton. Together these findings support the hypothesis that nitrification is more prevalent in the marine nitrogen cycle than accounted for in current biogeochemical models (11)., Aerobic ammonia oxidation is the first, rate-limiting step of nitrification, a two-step process catalysed by ammonia-oxidizing and nitrite-oxidizing microorganisms. It is the only oxidative biological process linking reduced and oxidized [...]

Abstract We investigated the protective effects of magnolol, an active antioxidant and free radical scavenger extracted from Magnolia officinalis, in a hind limb ischemic-reperfusion animal model. Adult male Spraque-Dawley rats [...]

Abstract To control the quality of Rhizoma Coptidis, a method based on ultra performance liquid chromatography with photodiode array detector (UPLC-PAD) was developed for quantitative analysis of five active alkaloids [...]

Abstract Eugenia uniflora L. (Myrtaceae), known as Brazilian cherry tree, is a fruity tree spread all over Brazil used in popular medicine to treat inflammations, rheumatic pain and fever, as [...]

Cellulose nanoparticles obtained by acid hydrolysis of cellulose paper were used to reinforce polystyrene composite films. The nonionic surfactant sorbitan monostearate was utilized to improve the dispersion properties of the hydrophilic cellulose in hydrophobic matrix and to prevent the formation of aggregates. Turbidity tests were used to measure dispersion stability of the cellulose crystallites in the hydrophobic solvent used in the composite manufacture. A correlation was found between the dispersion stability in solvent and the formation of aggregates in the polymeric composites. Nanocomposite films were processed using a casting/evaporation technique. Thermal and mechanical properties of processed composites were studied by differential scanning calorimetry (DSC) and dynamical mechanical analyses (DMA), respectively. The results showed that the optimum addition of surfactant produced better dispersion of the cellulose particles in the polystyrene matrix and improved the mechanical properties of the resulting composite due to an enhanced compatibility. POLYM. ENG. SCI., 49:2054-2061, 2009. [C]2009 Society of Plastics Engineers, INTRODUCTION Cellulose-based microstructures offer unique opportunities due to their high stiffness/strength, hydrophilicity, biocompatibility, stereoregularity, biodegradability, chemical stability, and ability to form superstructures. Furthermore, the ease of surface chemical modification makes [...]

The foaming behavior of high-melt strength polypropylene (HMS-PP) and HMS-PP/Cloisite 20A nanocomposites (PPNC) was studied in a batch process. PPNCs with 2, 4, 8, and 10 wt% clay were prepared in a twin screw extruder. The morphology of the nanocomposites was studied using XRD and TEM. Subsequently, foaming experiments were conducted using supercritical [CO.sub.2] as the blowing agent in a batch process, and foams with cell sizes varying from the sub micrometer to the micro meter range were prepared. The effect of variation in saturation pressure and temperature, foaming temperature, foaming time, and quench temperature was determined experimentally. Dynamic rheological measurements were conducted to relate the influence of nanocomposites morphology with foam cell growth and nucleation. Extensional rheological measurements were also conducted to detect the presence of strain hardening effect at the foaming temperatures used in the experiment. It was found that the nucleation efficiency of clay reduces with increase in clay loading. Also, the optimum amount of filler for generation of fine celled foams was found to be around the percolation threshold of the polymer. The extended strain hardening effect shown by the polymer in presence of clay plays an important role in stabilizing foam cell sizes. POLYM. ENG. SCI., 49:2070-2084, 2009. [C]2009 Society of Plastics Engineers, INTRODUCTION Polymer foams have found application in multitude of industries over the years because of their improved properties such as light weight, high impact strength, and improved insulation properties. The [...]

This study presents a comprehensive parametric study on the effects of processing parameters on the poly(DL-lactide-co-glycolide) acid (PLGA) 85/15 scaffold's physical properties. Porous PLGA 85/15 scaffolds were prepared using a gas foaming/salt leaching technique. The processing parameters under examination for the gas foaming/salt leaching method included: gas saturation pressure (SP), gas saturation time, and NaCl/polymer mass ratio (NaCl/PMR). The physical properties considered in this study were the scaffold density, the scaffold porosity, and the average pore size of the scaffold. Young's moduli in compression, as well as the pore density (PD) inside the scaffold, were also studied. The results demonstrated optimum correlations of processing parameters are required to produce a scaffold with a high level of interconnectivity. In general, all scaffolds yielded by this experiment exhibited a porosity more than 90%, a relative density ranging from 0.0534 to 0.149 g/[cm.sup.3], a PD ranging from 1.51 x [10.sup.6] to 6.72 x [10.sup.6] pores/[cm.sup.3], and a compressive modulus ranging from 0.07 to 0.84 MPa. It was determined that the NaCl/PMR was the parameter that had the most significant effect on the physical properties of the scaffold. The average pore size was affected slightly by the SP only, and it was observed that the pore size was equivalent to the size of the NaCI particles used to make the scaffold. POLYM. ENG. SCI., 49:2062-2069, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION Recently, there has been an increased need for the design and the development of novel-engineered tissues because the demand for organ transplants far outpaces the supply (1-10). The fundamental [...]

Blends of polyamide-6 (PA6) or postindustry polyamide-6 (piPA6) and high-density polyethylene (HDPE) or recycled high-density polyethylene (rHDPE) were processed in single and twin-screw extruders. The use of rHDPE in the blends promotes a significant decrease of size domains and improvement in the mechanical properties. The thermal stability was also slightly improved compared with PA6 and HDPE blends. The Molau test exhibited a stable emulsion in formic acid, which can be attributed to the formation of an interfacial copolymer involving polar amino end groups of PA6 and the rHDPE, respectively. These results indicate that recycled polymers can be used in the production of polymer blends with improved properties. POLYM. ENG. SCI., 49:2005-2014, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION Compatibilization of immiscible binary blends during melting process has been extensively studied because it is an efficient way to produce polymeric materials with novel and targeted properties. Immiscible polymer [...]

Epoxy/graphite nanoplatelets (GNPs)/carbon black (CB) composites were prepared by liquid mixing method. The morphologies and microstructures of the composites were examined by scanning electron microscope and X-ray diffraction. The results indicated that CB can improve effectively the dispersion of GNPs and form excellent conductive network in the matrix. When the weight ratio of GNPs to CB was 9:1 (total filler content was 1 wt%), the conductivity of the composite was three orders of magnitude higher than that of composites with GNPs alone (1 wt%). The percolation threshold of [GNPs.sub.0.9][CB.sub.0.1]/epoxy resin composites was 0.5 wt. %, which was lower than that of composites with GNPs alone (1 wt%). The mechanism for the effect of CB on electrical property of GNPs/epoxy resin composites was also investigated. POLYM. ENG. SCI., 49:2041-2045, 2009. [C]2009 Society of Plastics Engineers, INTRODUCTION Conductive polymer composites are becoming increasingly useful because of their unique combination of metallic conductivity and polymer properties. These materials are used widely as microwave absorbing materials, electromagnetic shielding [...]

The purpose of this study is to determine under what conditions it is possible to use [CO.sub.2] to plasticize and, thereby, reduce the viscosity of an acrylonitrile (AN) copolymer in an extrusion process and render it melt processable. To assess whether it was possible to absorb adequate amounts of [CO.sub.2] in short residence times by injection into a single screw extruder, a slit-die rheometer was attached to the end of the extrusion system for the purpose of directly assessing the viscosity reduction. A chemorheological analysis was performed on 65 and 85% AN copolymers to establish the temperature at which the 85% material would be as stable as the melt-processable 65% material at its recommended extrusion temperature. This, coupled with studies correlating the degree of [T.sub.g] and viscosity reduction with the amount of absorbed [CO.sub.2], and comparison to previous data obtained in batch processes allowed one to predict conditions for melt extrusion of the 85% AN. Preliminary studies using a pressurized chamber attached to the exit of the die allowed one to assess the conditions under which suppression of foaming is possible. POLYM. ENG. SCI., 49:1990-2004, 2009. © 2009 Society of Plastics Engineers, INTRODUCTION Fibers based on acrylonitrile (AN) copolymers having AN content of 85 mol% or greater are typically spun via a solution spinning process to avoid the intramolecular cyclization and intermolecular [...]

Low-loss slab waveguides with air as overcladding based on a high glass transition temperature ([T.sub.g]) polycarbonate were fabricated through spin-coating. Optical absorption and thermo-optic coefficient were investigated by spectrum analysis and prism coupler, respectively. Prism-coupling and charge-coupled device (CCD) camera imaging method were exploited together to evaluate the overall propagation loss of slab waveguides. The measured results of prism coupler were 0.282 dB/cm at 1310 nm and 0.197 dB/cm at 632.8 nm, whereas 0.07 dB/cm at 632.8 nm using CCD camera imaging method. Based on the same material, straight ridge waveguides and multimode interference couplers were fabricated through photolithograph and reactive ion etching, revealing smooth sides and excellent definition. POLYM. ENG. SCI., 49:2015-2019, 2009. [C]2009 Society of Plastics Engineers, INTRODUCTION Polymer materials have great applications in the field of planar lightwave circuit in the past decade because of its merits of ease in fabrication and energy-saving property (e.g., large [...]

A process which comprised a tubular reactor (that can be packed with different internal structures) has been modeled and theoretically analyzed for conducting the hydrogenation of nitrile butadiene rubber (NBR). The dynamics of the tubular reactor and the intrinsic hydrogenation kinetics are coupled, and detailed numerical simulations are performed under isothermal and isobaric conditions. The proposed model thus obtained involves coupled, nonlinear, partial differential equations (distributed parameter system). The effect of different reactor design parameters such as Peclet number, carbon-carbon double bond loading, mass transfer to reaction resistance, and solubility of hydrogen with respect to hydrogenation of the NBR has been investigated numerically. The conversions predicted using the proposed model for tubular packed bed reactor are compared with those possible in conventional plug flow reactor and continuous stirred tank reactor models. The optimal parameters and operating conditions for efficient production of hydrogenated NBR are suggested. Finally, the validity of the proposed model is confirmed by comparing the predicted and the experimental degree of hydrogenation obtained in a tubular reactor packed with Intalox saddles. POLYM. ENG. SCI., 49:1979-1989, 2009. © 2009 Society of Plastics Engineers, INTRODUCTION Hydrogenated nitrile butadiene rubber (HNBR), which is known for its excellent elastomeric properties and mechanical retention properties after long time exposure to heat, oil, and air, is produced by [...]

To prepare the polystyrene (PS)-clay nanocomposites via an in situ emulsion polymerization, a clay predispersion method, i.e. dispersing the organic clay in the emulsifier solution by the assistance of ultrasonic, was proposed in this study. The conventional method, pre-dispersing the organic clay into the monomer, was also presented for the comparison. The morphology analysis based on the X-ray Deflection (XRD) and Transmission Electronic Microscopy (TEM) results suggested that the more uniform clay dispersion in the final nanocomposites could be achieved through the new method. The inorganic clay (Na-MMT) and two organic clays ([C.sub.18]-MMT and [VC.sub.18]-MMT) synthesized by exchanging inorganic cations with the trimethylocta-decyl ammonium chloride (OTAC) and the vinylbenzyl-dimethyloctadecyl ammoniun chloride (VOAC) were chosen to investigate the influence of the clay surface modification on the properties of nanocomposites. The Dynamic Mechanical Analysis (DMA) results showed the storage modulus G's of the nanocomposites had different enhancements over that of the pure PS, especially when the temperature approached the glass transition temperature ([T.sub.g]). The [T.sub.g]s of the nanocomposites, however, varied with the microstructure and the interactions between the polymer and the clay layers. The Na-MMT and [VC.sub.18]-MMT increased the [T.sub.g], while the [T.sub.g]s of [PS/[[C.sub.18]-MMT]] nanocomposites were slightly lower than that of the pure PS. POLYM. ENG. SCI., 49:1937-1944, 2009., INTRODUCTION Since the nylon 6-clay nanocomposite was synthesized by Toyota Central Research & Development Labs and exhibited a dramatically enhancement in modulus, strength and heat distort temperature, the polymer-clay nanocomposites [...]

Electrospinning is a complex process that requires numerous interacting physical instabilities. Assuming that a chosen polymer and solvent system can be spun, the chosen polymer exists in various states, which have variable crystallinities starting with the highest degree of crystallinity (when in bulk form) and ultimately being transformed into a non-woven mat. In an effort to better understand the effects that the electrospinning process has on the biopolymers chitin [practical grade (PG)] and chitosan [PG and medium molecular weight (MMW)], including post-production neutralization and cross-linking steps, field emission scanning electron microscopy (FESEM) and solubility studies were performed. An evaluation of diffraction peaks of the bulk, solution, and fibrous forms of chitin and chitosan were evaluated by X-ray diffraction (XRD) and determined that the formation of chitosan chains is influenced by the addition of solvent and cross-linking agent. This study is of importance since the crystallinity of chitin and chitosan directly relate to the ability of the biopolymers to chelate metals, and the chemical stability of non-woven mats aid in the creation of functional filtration membranes. POLYM. ENG. SCI., 49:1918-1928, 2009. © 2009 Society of Plastics Engineers, INTRODUCTION The electrospinning process fabricates non-woven fibrous mats, which have smaller fiber diameters and larger surface-to-volume ratios than mats produced by conventional methods of fiber production. The typical electrospinning apparatus [...]

To obtain polyethylene terephthalate (PET)/polypropyl-ene (PP) microfibrillar composite (MFC) with good mechanical properties, a high content of PET fibrils in the drawn strand (i.e. PET droplets in the extrudate) is preferred. However, a phase inversion (from PP matrix to PET matrix) takes place when the concentration of the PET reaches 40 wt% at the screw speed of 40 rpm (rounds per minute). This 'PP domains in PET matrix' phase structure is the undesired phase structure for preparing MFC. However, the desired phase structure of 'PET droplets in PP matrix' can be regained by adopting a low screw speed (20 rpm) during extrusion of the PET/PP (40/60); if a higher screw speed is adopted (80 rpm), then a suitable amount of PP grafted maleic anhydride (PP-g-MA) should be incorporated. The PET/PP blends which demonstrate the desired 'PET droplets in PP matrix' phase structure were stretched into strands, and PET/PP MFC was prepared. The MFC with high content of PET microfibrils as the reinforcement exhibits superior tensile properties than the neat PP. POLYM. ENG. SCI., 49:1929-1936, 2009. ©2009 Society of Plastics Engineers, INTRODUCTION It is well-known that melting-spinning or solid-state drawing of polymers produces high-modulus high-strength polymer fibers (1), (2) The superior properties of polymer fibers are attributed to the high molecular [...]

The peroxide-initiated cografting of maleic anhydride (MAn) and allylic coagents to polypropylene (PP) is described. Both triallyl trimesate (TAM) and triallyl phosphate (TAP) are shown to be compatible with MAn, as the presence of either coagent has no apparent effect on the yield or distribution of anhydride grafts within functionalized PP. Therefore, the influence of chain scission on the melt-state rheological properties of maleated PP can be mitigated using coagent-assisted crosslinking. The success of this cografting strategy for controlling melt viscosity is shown to depend on the extent that a bimodal, branched architecture can provide the rheological properties demanded by a given application. POLYM. ENG. SCI., 49:1945-1950, 2009., INTRODUCTION The peroxide-initiated addition of polyolefins to maleic anhydride (MAn) is used widely to prepare adhesives and blend compatibilization agents (1), (2). However, the scope of this process is somewhat [...]

The hot embossing process has so far been developed mainly for replication of surface structures on thermoplastic substrates. Because of the lack of a through-thickness action, fabrication of discrete microparts such as microgears is considered difficult. In this study, embossing molds having multiple microcavities were used in a through-thickness embossing process with a rubber-assisted ejection mechanism. Microparts made of HDPE and ABS with each part weighing approximately 1 and 1.4 mg, respectively, were produced. When in the mold, embossed microparts were intermittently connected to each other through thin residual films of a thickness approximately 20 µm. The residual films were detached from the microparts during a rubber-assisted ejection stage. Because no resin delivery paths, e.g., runners and gates, are needed for microcavities on the multicavity embossing mold, this micropart fabrication process could replace micro injection molding in many applications. POLYM. ENG. SCI., 49:1894-1901, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION The standard hot embossing process is designed for fabricating surface features on polymer substrates (1), (2), The substrate is relatively thick as compared with the feature size. During the [...]

Two types of random semicrystalline copolymers (ethylene-octene and ethylene-butene) were overmolded on a core polypropylene. Maximum solid-liquid interface temperature achieved for the overmolding injection process is used as the key parameter for adhesion control. The main bonding process is shown to be a Rouse-type fingering mechanism that develops in short time scales. Normalized peel tests were conducted on overmolded samples to measure the resulting polypropylene copolymers' bonding strength. All the ethylene random copolymers used for this study give good adhesion to polypropylene in overmolding processes, provided the right range of interface temperature is reached. Adhesion strength can be easily controlled for efficient debonding and recycling of used overmolded parts. POLYM. ENG. SCI., 49:1886-1893, 2009. [C] 2009 Society of Plastics Engineers, INTRODUCTION Sequential injection overmolding, also called two-stage sequential overmolding, is the process by which a rigid substrate is overmolded with a more flexible material. The final product is a single [...]

Novel phosphorus-containing binaphthyl epoxy DGEBN (diglycidyl ether of 2,2'-hydroxy-1, 1'-binaphthalene) with high thermal performance was obtained from the addition reaction of DGEBN and diethyl phosphite. The modified binaphthyl epoxy was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy. The dynamic mechanical property of the cured epoxy polymer was investigated by dynamic mechanical thermal analysis. The result revealed that the cured polymer with lower phosphorus content displayed higher value of the storage modulus when the networks reached rubbery state (above the glass transition temperature [T.sub.g]). The [T.sub.g]s decreased slightly with increasing phosphorous content. The thermal degradation was studied with thermogravimetric analysis and the evolved gas was analyzed using thermogravimetric analysis/Fourier transform infrared technique. The influence of phosphorus content and the chemical structure on the degradation behavior was discussed. The P-modified binaphthyl epoxy polymers exhibited higher thermal stability than the P-modified diglycidyl ether of bisphenol A polymer. Flammability measurements were performed by the examination of limited oxygen index and UL-94 test. Compared with unmodified DGEBN, P-containing epoxy polymers displayed higher limited oxygen index values and exhibited better flame retardance. POLYM. ENG. SCI., 49:1879-1885, 2009.[C] 2009 Society of Plastics Engineers, INTRODUCTION Epoxy polymers are widely used as encapsulating materials in the electronic industries and advanced composite matrices for structural laminates, because of their high tensile strength and modulus, good chemical [...]

This experiment performed was to determine the effect of the length of incubation time on the generation of benzene from ascorbic acid and potassium benzoate in Sierra Mist Free. The results would provide useful information on storage methods for soda which might allow people to reduce their benzene intake from soda, thus decreasing their carcinogen accumulation and possibly lowering their risk for developing associated cancers. A headspace gas chromatography and mass spectrometry method was used for the analysis of benzene. Quantitation was preformed using Agilent Enhanced Chem Station D.01.02. A calibration curve was generated by creating dilutions of benzene in deionized water. The range of detection was between 0.52 ng/mL and 20.0 ng/mL. Each sample of Sierra Mist Free was prepared for incubation by adding 10 mL of Sierra Mist Free to a headspace vial. There were 4 samples per group. Groups 1-8 were incubated at 50 °C for a certain amount of time over a 14 day period. Group 9 was the control group, incubated at room temperature. The data showed that no benzene was generated in any sample for any given period of incubation time at 50 °C or room temperature. The hypothesis, which stated that samples incubated at for a longer time at 50 °C would generate more benzene than samples incubated at 50 °C for a shorter period of time or at room temperature, was rejected, and the null hypothesis, which stated that incubation time would have no effect on the amount of benzene generated, was accepted., Introduction Anyone who indulges in Coke, Sprite, Mountain Dew, or other sodas generally recognizes the negative effects of drinking carbonated drinks: for example, the caffeine, the high sugar, the empty [...]

It has been thought that the lunar highland crust was formed by the crystallization and floatation of plagioclase from a global magma ocean (1,2), although the actual generation mechanisms are [...]

A long-sought goal in structural biology has been the imaging of membrane proteins in their membrane environments. This goal has been achieved with electron crystallography (1) in those special cases where a protein forms highly ordered arrays in lipid bilayers. It has also been achieved by NMR methods (1) in proteins up to 50 kilodaltons (kDa) in size, although milligram quantities of protein and isotopic labelling are required. For structural analysis of large soluble proteins in microgram quantities, an increasingly powerful method that does not require crystallization is single-particle reconstruction from electron microscopy of cryogenically cooled samples (electron cryomicroscopy (cryo-EM)) (2). Here we report the first single-particle cryo-EM study of a membrane protein, the human large-conductance calcium- and voltage-activated potassium channel (3) (BK), in a lipid environment. The new method is called random spherically constrained (RSC) single-particle reconstruction. BK channels, members of the six-transmembrane-segment (6TM) ion channel family, were reconstituted at low density into lipid vesicles (liposomes), and their function was verified by a potassium flux assay. Vesicles were also frozen in vitreous ice and imaged in an electron microscope. From images of 8,400 individual protein particles, a three-dimensional (3D) reconstruction of the BK channel and its membrane environment was obtained at a resolution of 1.7-2.0 run. Not requiring the formation of crystals, the RSC approach promises to be useful in the structural study of many other membrane proteins as well., The BK channel (3) has many physiological roles: it controls firing patterns in neurons, modulates the tone of blood vessels, and in some animals is an element of the electrical [...]

Zeolites--microporous crystalline aluminosilicates-are widely used in petrochemistry and fine-chemical synthesis (1-3) because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. But the very presence of the micropores, with aperture diameters below 1 run, often goes hand-in-hand with diffusion limitations (3-5) that adversely affect catalytic activity. The problem can be overcome by reducing the thickness of the zeolite crystals, which reduces diffusion path lengths and thus improves molecular diffusion°,. This has been realized by synthesizing zeolite nanocrystals (6), by exfoliating layered zeolites (7-9), and by introducing mesopores in the microporous material through templating strategies (10-17) or demetallation processes (18-22). But except for the exfoliation, none of these strategies has produced 'ultrathin' zeolites with thicknesses below 5 run. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously and thus yield MFI (ZSM-5, one of the most important catalysts in the petrochemical industry) zeolite nanosheets that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The large number of acid sites on the external surface of these zeolites renders them highly active for the catalytic conversion of large organic molecules, and the reduced crystal thickness facilitates diffusion and thereby dramatically suppresses catalyst deactivation through coke deposition during methanol-to-gasoline conversion. We expect that our synthesis approach could be applied to other zeolites to improve their performance in a range of important catalytic applications., In principle, zeolites will exhibit maximized molecular diffusion if the thickness of the crystal is reduced to the single unit cell dimension. Isolated zeolite unit cells (zero-dimensional crystal structure), nanowires [...]

Geochemical data (1-4) suggest that oxygenation of the Earth's atmosphere occurred in two broad steps. The first rise in atmospheric oxygen is thought to have occurred between ~2.45 and 2.2 [...]

Abstract Six phenolic compounds isolated from Curculigo orchioides, including 2,6-dimethoxy benzoic acid (1), curculigoside A (2), curculigoside B (3), curculigine A (4), curculigine D (5) and 3,3',5,5'-tetramethoxy-7,9';7',9-diepoxylignan-4,4'-di-O-β-D-glucopyranoside (6), together with [...]

Abstract Ononitol monohydrate, structurally similar to glycoside was isolated from Cassia tora L. leaves. Fifty Male rats were divided into five groups. Group I served as normal control. Group II, [...]