bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of chain architecture (branching) on the thermal and mechanical behavior of polystyrene thin films
Authors: Torres Jessica M. , Stafford Christopher M. , Uhrig David , Vogt Bryan D. 
Published: December 2011

AbstractThe modulus and glass transition temperature (Tg) of ultrathin films of polystyrene (PS) with different branching architectures are examined via surface wrinkling and the discontinuity in the thermal expansion as determined from spectroscopic ellipsometry, respectively. Branching of the PS is systematically varied using multifunctional monomers to create comb, centipede, and star architectures with similar molecular masses. The bulk‐like (thick film) Tg for these polymers is 103 ± 2 °C and independent of branching and all films thinner than 40 nm exhibit reductions in Tg. There are subtle differences between the architectures with reductions in Tg for linear (25 °C), centipede (40 °C), comb (9 °C), and 4 armed star (9 °C) PS for ≈ 5 nm films. Interestingly, the room temperature modulus of the thick films is dependent upon the chain architecture with the star and comb polymers being the most compliant (≈2 GPa) whereas the centipede PS is most rigid (≈4 GPa). The comb PS exhibits no thickness dependence in moduli, whereas all other PS architectures examined show a decrease in modulus as the film thickness is decreased below ∼40 nm. We hypothesize that the chain conformation leads to the apparent susceptibility of the polymer to reductions in moduli in thin films. These results provide insight into potential origins for thickness dependent properties of polymer thin films. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Study of the Effects of Aging under Humidity Control on the Thermal Decomposition of NC/NG/BTTN/RDX Propellants
Authors: McDonald Brian A. 
Published: December 2011

AbstractThe effects of aging under controlled humidity on the thermal decomposition of two nitrate ester/RDX propellants are examined. Propellant samples are artificially aged at 60 °C and 70 °C at various levels of relative humidity. Differential scanning calorimetry is used to study the post aged samples to determine the activation energy of the peak exotherm and peak temperature of these events. For each humidity level, differential scanning calorimetry is conducted on an aged and an unaged sample that is conditioned to the humidity of the environment to distinguish between aging effects and residual moisture effects. Nitrate ester stabilizer depletions rates are presented as a function of aging and humidity. The results of the study show that moisture level during aging irreversibly alters the activation energy of the primary heat release events and significantly influences the stabilizer depletion rates.
Physicomathematical Modeling of Explosive Dispersion of Liquid and Powders
Authors: Kudryashova Olga B. , Vorozhtsov Boris I. , Muravlev Eugene V. , Akhmadeev Igor R. , Pavlenko Anatoly A. , Titov Sergey S. 
Published: December 2011

AbstractStudies have been conducted with respect to the generation of fine‐disperse aerosols with the use of an explosive disperser model based on hydrodynamic shock tube. The physicomathematical model for the process of explosive dispersion with the aforesaid design is described [1]. The use of elements in the model design to produce cavitation bubbles under the action of shock wave and ensurance of slower outflow process of a water‐steam mixture makes it possible to obtain liquid disperse aerosols.The experimental results for aerosol disperse parameters and the processes of initiation and propagation of an aerosol cloud produced upon explosive dispersion of a variety of liquids and condensed powders are presented. Pressure values in the combustion chamber of the disperser, velocity of aerosol particles, and aerosol disperse parameters were obtained.The design of the explosive disperser with a nozzle, which provides favorable conditions for cavitation processes inside the dispersed liquid, is shown to allow the generation of a high dispersity aerosol (about 1–100 nm), which is essential for many practical problems. The function of distribution of such particles by size cannot be measured reliably and directly by methods available; however, indirect experiments (measurement of humidity when dispersing water) permit estimating the existence of particles in the aerosol with sizes below 1 μm in quantity of approx. 90 %.
Dependence of the Mechanical Sensitivity on the Fractal Characteristics of Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine Particles
Authors: Wang Yi , Song Xiaolan , Song Dan , Jiang Wei , Liu Hongying , Li Fengsheng 
Published: December 2011

AbstractThree fabrication methods were used to synthesize HMX powders with different particle sizes and microscopic morphologies. All as‐prepared samples were characterized by laser granularity measurements and scanning electron microscopy (SEM). The mechanical sensitivity and thermal stability of the different HMX powders were characterized using mechanical sensitivity tests and differential scanning calorimetry (DSC). Size distribution data and SEM images were used to find the size fractal dimension (D) and surface fractal dimension (Ds) of HMX samples, which were calculated by the least‐squares method and fractal image processing software (FIPS), respectively. The parameters D and Ds quantize two important properties of HMX particles, namely the complexity of the particle size distribution and the irregularity of the particle surface, which affect the thermal conductivity of the particle group if it is exposed to stimuli such as impact, friction or heating. The fractal dimensions reveal the dependence of the mechanical sensitivity of HMX on the powder size, size distribution and microscopic morphology. The results indicate that the proportion of fine particles in HMX powder increases as the D value increases, which causes decreased impact sensitivity. This occurs because hot spot formation leading to an explosion is more difficult because of the improved thermal conductivity of the particle group. Similarly, the surface roughness of HMX particles increases with an increase in Ds, causing an increase in friction sensitivity because of the excessive accumulation of frictional heat. In addition, thermal analysis results indicate that the maximum thermal decomposition rate of HMX decreases with increasing D and Ds.
Role of amino acid hydrophobicity, aromaticity, and molecular volume on IAPP(20–29) amyloid self‐assembly
Authors: Doran Todd M. , Kamens Alissa J. , Byrnes Nadia K. , Nilsson Bradley L. 
Published: December 2011

AbstractAromatic amino acids strongly promote cross‐β amyloid formation; whether the amyloidogenicity of aromatic residues is due to high hydrophobicity and β‐sheet propensity or formation of stabilizing π–π interactions has been debated. To clarify the role of aromatic residues on amyloid formation, the islet amyloid polypeptide 20–29 fragment [IAPP(20–29)], which contains a single aromatic residue (Phe 23), was adopted as a model. The side chain of residue 23 does not self‐associate in cross‐β fibrils of IAPP(20–29) (Nielsen et al., Angew Chem Int Ed 2009;48:2118–2121), allowing investigation of the amyloidogenicity of aromatic amino acids in a context where direct π–π interactions do not occur. We prepared variants of IAPP(20–29) in which Tyr, Leu, Phe, pentafluorophenylalanine (F5‐Phe), Trp, cyclohexylalanine (Cha), α‐naphthylalanine (1‐Nap), or β‐naphthylalanine (2‐Nap) (in order of increasing peptide hydrophobicity) were incorporated at position 23 (SNNXGAILSS‐NH2), and the kinetic and thermodynamic effects of these mutations on cross‐β self‐assembly were assessed. The Tyr, Leu, and Trp 23 variants failed to readily self‐assemble at concentrations up to 1.5 mM, while the Cha 23 mutant fibrillized with attenuated kinetics and similar thermodynamic stability relative to the wild‐type Phe 23 peptide. Conversely, the F5‐Phe, 1‐Nap, and 2‐Nap 23 variants self‐assembled at enhanced rates, forming fibrils with greater thermodynamic stability than the wild‐type peptide. These results indicate that the high amyloidogenicity of aromatic amino acids is a function of hydrophobicity, β‐sheet propensity, and planar geometry and not the ability to form stabilizing or directing π–π bonds. Proteins 2012;. © 2011 Wiley Periodicals, Inc.
Biological activity of the succinate dehydrogenase inhibitor fluopyram against Botrytis cinerea and fungal baseline sensitivity
Authors: Veloukas Thomas , Karaoglanidis George S 
Published: December 2011

AbstractBACKGROUND: Succinate dehydrogenase inhibitors (SDHIs) constitute a fungicide class with increasing relevance in crop protection. These fungicides could play a crucial role in successful management of grey mould disease. In the present study the effect of fluopyram, a novel SDHI fungicide, on several developmental stages of Botrytis cinerea was determined in vitro, and the protective and curative activity against the pathogen was determined on strawberry fruit. Furthermore, fungal baseline sensitivity was determined in a set of 192 pathogen isolates.RESULTS: Inhibition of germ tube elongation was found to be the most sensitive growth stage affected by fluopyram, while mycelial growth was found to be the least sensitive growth stage. Fluopyram provided excellent protective activity against B. cinerea when applied at 100 µg mL−1 96, 48 or 24 h before the artificial inoculation of the strawberry fruit. Similarly, fluopyram showed a high curative activity when it was applied at 100 µg mL−1 24 h post‐inoculation, but, when applications were conducted 48 or 96 h post‐inoculation, disease control efficacy was modest or low. The measurement of baseline sensitivity showed that it was unimodal in all the populations tested. The individual EC50 values for fluopyram ranged from 0.03 to 0.29 µg mL−1. In addition, no correlation was found between sensitivity to fluopyram and sensitivity to other fungicides, including cyprodinil, fenhexamid, fludioxonil, iprodione, boscalid and pyraclostrobin.CONCLUSIONS: The obtained biological activity, baseline sensitivity and cross‐resistance relationship data suggest that fluopyram could play a key role in grey mould management in the near future and encourage its introduction into spray programmes. Copyright © 2011 Society of Chemical Industry
Structure and electrical properties of (Bi0.5Na0.5)1–x–y–z(Bi0.5K0.5)xBay(Bi0.5Li0.5)zTiO3 lead‐free piezoelectric ceramics
Authors: Lin Dunmin , Zheng Qiaoji , Wu Xiaochun , Fan Ximing , Sun Hailing , Wu Lang , Xu Chenggang 
Published: December 2011

AbstractLead‐free (Bi0.5Na0.5)1–x–y–z(Bi0.5K0.5)xBay(Bi0.5Li0.5)zTiO3 piezoelectric ceramics have been prepared by a conventional ceramic technique and their structure and electrical properties have been studied. The results of XRD diffraction show that after the addition of K+, Ba2+, and Li+, a new Bi0.5Na0.5TiO3‐based solid solution with a pure perovskite structure is obtained and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases is formed at 0.10 < x < 0.20, 0.01 < y < 0.04, and z = 0.075. The partial substitutions of (Bi0.5K0.5)2+, Ba2+, and (Bi0.5Li0.5)2+ for the A‐site (Bi0.5Na0.5)2+ ions of Bi0.5Na0.5TiO3 decrease effectively the coercive field Ec and improve significantly the remanent polarization Pr. The piezoelectricity of the ceramics is greatly enhanced because of the MPB, lower Ec and higher Pr. The ceramic with x = 0.15, y = 0.02, and z = 0.075 situated at the MPB exhibits the optimum piezoelectric properties, giving d33 = 209 pC/N and kp = 30.5%. Two dielectric anomalies are observed, suggesting diffuse phase transition characteristics. The depolarization temperature Td reaches a minimum value near the MPB. The deformed P–E loop is observed near/above Td, indicating that the ceramics may contain both the polar and nonpolar regions.
Electronic structure and optical spectroscopy studies of HoNi5 and ErNi5 compounds doped with Cu
Authors: Knyazev Yu. V. , Lukoyanov A. V. , Kuz'min Yu. I. , Kuchin A. G. 
Published: December 2011

AbstractThe effect of Cu‐doping on the electronic structure and optical properties of intermetallic compounds (Ho,Er)Ni5−xCux (x = 0, 1, 2) has been studied. Band structure and interband optical conductivity were investigated theoretically using the LSDA + U method supplementing local spin density approximation with a correction for strong electron interaction on the 4f shell of rare earth element. Optical properties were studied by the ellipsometry method in the spectral range 0.22–15 µm. It was found that substitution of Cu for Ni atoms in these alloys leads to significant changes in the frequency dependence of the optical conductivity. Both the theoretical calculations and spectroscopic experiments revealed the appearance of a new absorption maximum near 4.5 eV formed by Cu 3d → Ni 3d interband transitions.
Critical scattering in the vicinity of the metal–insulator transition in Mn‐doped GaAs
Authors: Varpula A. , Novikov S. , Kuivalainen P. 
Published: December 2011

AbstractWe have developed an improved model for describing the electrical transport properties of diluted ferromagnetic semiconductors such as Mn‐doped GaAs. The model takes into account transport mechanisms in disordered semiconductors in the vicinity of the metal–insulator transition and the critical scattering due to the exchange interaction between the charge carrier spins and the localized magnetic moments. The model is based on Kubo–Greenwood formalism and the scaling theory of localization. The contribution from the critical scattering is calculated using the Green's function technique and the self‐consistent Born approximation. The model explains well the measured resistivity in Mn‐doped GaAs as a function of temperature, doping concentration, and magnetic field.
Application of emulsified zero‐valent iron: Four full‐scale remediation sites
Authors: Huff James E. 
Published: December 2011

AbstractEmulsified zero‐valent iron (EZVI) is a technology developed by the National Aeronautics and Space Administration (NASA) that is used to remediate soil and groundwater contaminated with chlorinated solvents. It consists of micro‐ and/or nano‐scale iron particles suspended in a water‐in‐vegetable oil emulsion. This allows EZVI to combine three remediation technologies: partitioning of the chlorinated volatile organic compounds (CVOCs) into vegetable oil, a chemical reaction between the CVOCs and elemental iron, and hydrogen production from the fermentation of the vegetable oil to promote biological degradation. A description of the chemistry and biology of this NASA technology is presented, followed by a description of four full‐scale case studies where EZVI has been applied, including post‐injection results extending over three years. At each of these sites, EZVI was determined to be the most cost‐effective remedy. The sustained treatment long after the injections resulted in contaminant reductions continuing for over three years and accelerated remediation times compared to traditional approaches, due to the combination of technologies. Furthermore, EZVI is consistent with US EPA's green remediation policy. © 2011 Wiley Periodicals, Inc.
Exosomes as Extrapulmonary Signaling Conveyors for Nanoparticle‐Induced Systemic Immune Activation
Authors: Zhu Motao , Li Yiye , Shi Jian , Feng Weiyue , Nie Guangjun , Zhao Yuliang 
Published: December 2011

AbstractEvaluation of systemic biosafety of nanomaterials urgently demands a comprehensive understanding of the mechanisms of the undesirable interference and systemic signaling that arises between man‐made nanomaterials and biological systems. It is shown that exosomes may act as signal conveyors for nanoparticle‐induced systemic immune responses. Exosomes are extracellularly secreted membrane vesicles which act as Trojan horses for the dissemination and intercellular communication of natural nanosized particles (like viruses). Upon exposure to magnetic iron oxide nanoparticles (MIONs), it is possible to dose‐dependently generate a significant number of exosomes in the alveolar region of BALB/c mice. These exosomes are quickly eliminated from alveoli into systemic circulation and largely transfer their signals to the immune system. Maturation of dendritic cells and activation of splenic T cells are significantly induced by these exosomes. Furthermore, exosome‐induced T‐cell activation is more efficient toward sensitized T cells and in ovalbumin (OVA)‐sensitized mice than in the unsensitized counterparts. Activation of systemic T cells reveals a T helper 1 polarization and aggravated inflammation, which poses potential hazards to the deterioration of allergic diseases in OVA‐sensitized mice. The studies suggest that exosomes may act as conveyors for extrapulmonary signal transduction in nanoparticle‐induced immune systemic responses, which are the key in vivo processes of manufactured nanoparticles executing either biomedical functions or toxic responses.
The merger of electrochemistry and molecular electronics
Authors: Mccreery Richard L. 
Published: December 2011

AbstractMolecular Electronics has the potential to greatly enhance existing silicon‐based microelectronics to realize new functions, higher device density, lower power consumption, and lower cost. Although the investigation of electron transport through single molecules and molecular monolayers in “molecular junctions” is a recent development, many of the relevant concepts and phenomena are derived from electrochemistry, as practiced for the past several decades. The past 10+ years have seen an explosion of research activity directed toward how the structure of molecules affects electron transport in molecular junctions, with the ultimate objective of “rational design” of molecular components with new electronic functions, such as chemical sensing, interactions with light, and low‐cost, low‐power consumer electronics. In order to achieve these scientifically and commercially important objectives, the factors controlling charge transport in molecules “connected” to conducting contacts must be understood, and methods for massively parallel manufacturing of molecular circuits must be developed. This Personal Account describes the development of reproducible and robust molecular electronic devices, starting with modified electrodes used in electrochemistry and progressing to manufacturable molecular junctions. Although the field faced some early difficulties in reliability and characterization, the pieces are now in place for rapid advances in understanding charge transport at the molecular level. Inherent in the field of Molecular Electronics are many electrochemical concepts, including tunneling, redox exchange, activated electron transfer, and electron coupling between molecules and conducting contacts. DOI 10.1002/tcr.201100006
Mass Transport to micro‐ and nanoelectrodes and their arrays: a review
Authors: Henstridge Martin C. , Compton Richard G. 
Published: December 2011

AbstractThe use of micro‐ and nanoelectrodes and their arrays has become commonplace in modern electrochemistry. Numerical simulation is often required for detailed analysis of voltammetric data and this relies upon an understanding of the prevailing mass transport operating under the experimental conditions. The theoretical basis of our understanding of mass transport, particularly diffusion and migration, has developed greatly in recent years. We review both theoretical and experimental studies which have probed the mass transport at micro‐ and nanoelectrodes and their arrays. DOI 10.1002/tcr.201100032
Hydrogels and microtechnologies for engineering the cellular microenvironment
Authors: Gauvin Robert , Parenteau‐Bareil Rémi , Dokmeci Mehmet R. , Merryman W. David , Khademhosseini Ali 
Published: December 2011

AbstractHydrogels represent a class of materials suitable for numerous biomedical applications such as tissue engineering and drug delivery. Hydrogels are by definition capable of absorbing large amount of fluid, making them adequate for cell seeding and encapsulation as well as for implantation because of their biocompatibility and excellent diffusion properties. They also possess other desirable properties for fundamental research as they have the ability to mimic the basic three‐dimensional (3D) biological, chemical, and mechanical properties of native tissues. Furthermore, their biological interactions with cells can be modified through the numerous side groups of the polymeric chains. Thus, the biological, chemical, and mechanical properties, as well as the degradation kinetics of hydrogels can be tailored depending on the application. In addition, their fabrication process can be combined with microtechnologies to enable precise control of cell‐scale features such as surface topography and the presence of adhesion motifs on the hydrogel material. This ability to control the microscale structure of hydrogels has been used to engineer tissue models and to study cell behavior mechanisms in vitro. New approaches such as bottom‐up and directed assembly of microscale hydrogels (microgels) are currently emerging as powerful methods to enable the fabrication of 3D constructs replicating the microenvironment found in vivo. WIREs Nanomed Nanobiotechnol 2012, 4:235–246. doi: 10.1002/wnan.171This article is categorized under:

Nanotechnology Approaches to Biology > Cells at the Nanoscale
Therapeutic Approaches and Drug Discovery > Emerging Technologies
Implantable Materials and Surgical Technologies > Nanomaterials and Implants
Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement
Two New Zinc(II) Coordination Polymers Based on 1, 6‐Bis(2‐methyl‐imidazole‐1‐yl)‐hexane Ligand: Synthesis, Structures, and Properties
Authors: Xu Li‐Li , Cheng Jian‐Guang , Yue Ke‐Fen , Liu Yong‐Liang , Wang Cheng‐Jun , Wang Yao‐Yu 
Published: December 2011

AbstractTwo coordination polymers based on 1, 6‐bis(2‐methyl‐imidazole‐1‐yl)‐hexane (bimh), namely {[Zn3(BTC)2(bimh)]·(bimh)}n (1) and {[Zn(IPA)(bimh)]·(CH3CH2OH)0.5}n (2) (H3BTC = trimesic acid, H2IPA = isophthalic acid), were synthesized through hydrothermal reactions. In compound 1, the zinc(II) ions are bridged by BTC3– ligands to form an undulating infinite two‐dimensional (2D) polymeric network. The 3D networks of 1 show a twofold interpenetrating net. In compound 2, zinc(II) ions are bridged by IPA2– ligands to form one‐dimensional (1D) helical structures. The 2D structures of 2 are further assembled into 3D networks through aromatic π–π stacking interactions. Both compounds exhibit strong photoluminescence at room temperature and may be good candidates for potential luminescence materials.