bluuebunny/crossref_metadata_2025 huggingface dataset:
The Ferroelectric Field Effect within an Integrated Core/Shell Nanowire
Authors: Nonnenmann Stephen S. , Islam Mohammad A. , Beatty Brian R. , Gallo Eric M. , McGuckin Terrence , Spanier Jonathan E.
Published: July 2012

The synthesis of cylindrical silicon‐core and ferroelectric oxide perovskite‐shell nanowires and their response characteristics as individual three‐terminal nanoscale electronic devices is reported. The co‐axial nanowire geometry facilitates large ferroelectric field‐effect modulation (>104) of nanowire conductivity following sequential application and removal of an applied dc field. Source‐drain current–voltage traces collected during sweeps of ferroelectric gate potential and switching of the component of shell outward and inward polarization provide direct evidence of ferroelectric coupling on nanowire channel conductance. Despite a very small (1:20) ferroelectric‐to‐semiconductor channel thickness ratio, an unexpectedly strong electrostatic coupling of ferroelectric polarization to channel conductance is observed because of the co‐axial gate geometry and curvature‐induced strain enhancement of ferroelectric polarization.
A Novel Solid Lipid Nanoparticle Formulation for Active Targeting to Tumor αvβ3 Integrin Receptors Reveals Cyclic RGD as A Double‐Edged Sword
Authors: Shuhendler Adam J. , Prasad Preethy , Leung Michael , Rauth Andrew M. , DaCosta Ralph S. , Wu Xiao Yu
Published: July 2012

The overexpression of αvβ3 integrin receptors on tumor cells and tumor vascular endothelium makes it a useful target for imaging, chemotherapy and anti‐angiogenic therapy. However integrin‐targeted delivery of therapeutics by nanoparticles have provided only marginal, if any, enhancement of therapeutic effect. This work was thus focused on the development of novel αvβ3‐targeted near infrared light‐emitting solid lipid nanoparticles (SLN) through conjugation to the αvβ3 integrin‐specific ligand cyclic Arg‐Gly‐Asp (cRGD), and the assessment of the effects of αvβ3 targeting on nanoparticle biodistribution. Since our previously developed non‐targeted “stealth” SLN showed little hepatic accumulation, unlike most reported liposomes and micelles, they served as a reference for quantifying the effects of cRGD‐conjugation on tumor uptake and whole animal biodistribution of SLN. Non‐targeted SLN, actively targeted (RGD‐SLN) and blocked RGD‐SLN were prepared to contain near infrared quantum dots for live animal imaging. They were injected intravenously to nude mice bearing xenograft orthotopic human breast tumors or dorsal window chamber breast tumors. Tumor micropharmacokinetics of various SLN formulations were determined using intravital microscopy, and whole animal biodistribution was followed over time by optical imaging. The active tumor targeting with cRGD was found to be a “double‐edged sword”: while the specificity of RGD‐SLN accumulation in tumor blood vessels and their tumor residence time increased, their distribution in the liver, spleen, and kidneys was significantly greater than the non‐targeted SLN, leaving a smaller amount of nanoparticles in the tumor tissue. Nevertheless the enhanced specificity and retention of RGD‐SLN in tumor neovasculature could make this novel formulation useful for tumor neovascular‐specific therapies and imaging applications.
Mussel‐Inspired Coating of Polydopamine Directs Endothelial and Smooth Muscle Cell Fate for Re‐endothelialization of Vascular Devices
Authors: Yang Zhilu , Tu Qiufen , Zhu Ying , Luo Rifang , Li Xin , Xie Yichu , Maitz Manfred F. , Wang Jin , Huang Nan
Published: July 2012

Polydopamine (PDAM), a mussel adhesive protein inspired coating that can be easily deposited onto a wide range of metallic, inorganic, and organic materials, gains interest also in the field of biomaterials. In this work, PDAM is applied as coating on 316L stainless steel (SS) stents and the response of cells of the blood vessel wall, human umbilical vein endothelial cell (HUVEC), and human umbilical artery smooth muscle cell (HUASMC) as predictors for re‐endothelialization is tested. It is found that the PDAM‐modified surface significantly enhances HUVEC adhesion, proliferation, and migration, release of nitric oxide (NO), and secretion of prostaglandin I2 (PGI2). Additionally, the PDAM‐modified surface shows a remarkable ability to decrease the adhesion and proliferation of HUASMCs. As a blood‐contacting material, the PDAM tends to improve the hemocompatibility compared with the substrate 316L SS. It is noteworthy that the PDAM coating shows good resistance to the deformation behavior of compression and expansion of a stent. These data suggest the potential of PDAM as a blood‐contacting material for the application in vascular stents or grafts.
Monomorphic Region of the Serotonin Transporter Promoter Gene in New World Monkeys
Authors: PASCALE ESTERINA , LUCARELLI MARCO , PASSARELLI FRANCESCA , BUTLER RICHARD H. , TAMELLINI ANDREA , ADDESSI ELSA , VISALBERGHI ELISABETTA , MANCIOCCO ARIANNA , VITALE AUGUSTO , LAVIOLA GIOVANNI
Published: July 2012

Genetic variation in the human serotonin system has long been studied because of its functional consequences and links to various neuropsychiatric and behavior‐related disorders. Among non‐human primates, the common marmosets (Callithrix jacchus) and tufted capuchins monkeys (Cebus apella) are becoming increasingly used as models to study the effects of genes, environments, and their interaction on physiology and complex behavior. In order to investigate the independent functions of and potential interactions between serotonin‐related genes, anxiety and neuropsychiatric disorders, we analyzed the presence and variability of the serotonin transporter gene‐linked polymorphic region (5‐HTTLPR) in marmoset and capuchin monkeys. By PCR and using heterologous primers from the human sequence, we amplified and then sequenced the corresponding 5‐HTT region in marmosets and capuchins. The resulting data revealed the presence of a tandem repeat sequence similar to that described in humans, but unlike humans and other Old World primates, no variable length alleles were detected in these New World monkeys, suggesting that if serotonin transporter is involved in modulating behavior in these animals it does so through different molecular mechanisms. Am. J. Primatol. 74:1028‐1034, 2012. © 2012 Wiley Periodicals, Inc.
Structure–activity relationship for dihydromyricetin as a new natural antioxidant in polymer
Authors: Xin Ming‐liang , Ma Yu‐jie , Xu Kai , Chen Ming‐cai
Published: July 2012

Dihydromyricetin (DMY), a natural product, was used as antioxidant in ethylene vinyl acetate copolymer (EVA) in our laboratory. Oxidation induction temperature (OIT) of EVA with the antioxidant of DMY and effect of pH on OIT was measured by means of differential scanning calorimeter (DSC). The mechanism on that antioxidation of DMY in EVA is produced on basis of determination of UV–Vis absorption, nuclear magnetic resonance (NMR) and the experiment of reacting the pyrogallic (PA) and DMY, respectively, with the DPPH. The result shows that the ortho‐trihydroxyl group (B ring) in DMY has mainly antioxidative activity and hydroxyl group of 7‐position (A ring) not only displayed reversibility to acidic or alkaline medium but also affected in some extent the antioxidative ability in EVA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Study on the preparation of Eu(Pht)3Phen/SBA‐15 hybrids and photoluminescence properties of silicone rubber composites with the hybrids
Authors: Xu Shengjie , Ren Wentan , Zhang Yong , Zhang Yinxi
Published: July 2012

In this work, Eu(Pht)3Phen/SBA‐15 hybrids were prepared by solution mixing and their morphologies and structures were characterized by X‐ray diffraction (XRD), scanning electronic microscopy (SEM), nitrogen adsorption–desorption and transmission electronic microscopy (TEM). The results showed that Eu(Pht)3Phen was successfully incorporated into the channels and assembled onto the surface of SBA‐15 and the long range ordered structure of SBA‐15 was preserved. The silicone rubber composites with Eu(Pht)3Phen/SBA‐15 hybrids were obtained by mechanical blending, and their morphologies and photoluminescence properties were studied. The results showed that the photoluminescence intensities of the composites with the hybrids increased as the content of the hybrids increased. The composite with the hybrids showed higher photoluminescence intensity and longer lifetime compared to the silicone rubber compounded with Eu(Pht)3Phen (Eu(Pht)3Phen/silicone rubber composite), Eu(Pht)3Phen and SBA‐15 ([Eu(Pht)3Phen+SBA‐15]/silicone rubber composite). Judd‐Ofelt theory was used to investigate the local environment of Eu3+ ions in the silicone rubber composites. The photoluminescence quantum efficiency of the silicone rubber composite with Eu(Pht)3Phen/SBA‐15 hybrids was calculated to be 31.0%, higher than that of Eu(Pht)3Phen/silicone rubber composite (26.4%) and [Eu(Pht)3Phen+SBA‐15]/silicone rubber composite (25.4%). The enhancement in photoluminescence intensity and increase in lifetime and photoluminescence quantum efficiency could be attributed to the rigid structure of SBA‐15 which reduced the nonradiative transition rate and the improvement of the dispersion of the hybrids in the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Sonochemical synthesis and characterization of amine‐modified graphene/conducting polymer nanocomposites
Authors: Sahoo Sumanta , Bhattacharya Pallab , Hatui Goutam , Ghosh Debasis , Das Chapal Kumar
Published: July 2012

The objective of this work is to modify graphene and study the effect of modification of graphene in thermal and electrical properties of graphene/polypyrrole and graphene/polyaniline nanocomposites. The amine functionalization of graphene was confirmed by Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The nanocomposites were prepared by insitu oxidative polymerization method using ammonium persulfate as oxidant. Field emission scanning electron microscopy and high‐resolution transmission electron microscopy were used to study the morphology of the nanocomposites which indicates toward the better dispersion of modified graphene within the polymer matrices as compared to unmodified composites. The modification of graphene played an important role in the noticeable improvements in electrical conductivity of the prepared composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Polypropylene/polyethylene blends as models for high‐impact propylene–ethylene copolymers, part 1: Interaction between rheology and morphology
Authors: Kock Cornelia , Gahleitner Markus , Schausberger Alois , Ingolic Elisabeth
Published: July 2012

In this work, composition effects on interfacial tension and morphology of binary polyolefin blends were studied using rheology and electron microscopy. The amount of dispersed phase (5–30 wt %) and its type [ethylene–octene copolymer, linear low‐density polyethylene (LLDPE), and high‐density polyethylene] was varied, and the influence of different matrix materials was also studied by using a polypropylene homopolymer and a ethylene–propylene (EP) random copolymer. The particle size distribution of the blends was determined using micrographs from transmission electron microscopy (TEM). A clear matrix effect on the flow behavior could be found from the viscosity curves of the blends. Analyzing the viscosity of the blends applying the logarithmic mixing rule indicated a partial miscibility of the EP random copolymer with low amounts of the LLDPE in the melt. Micrographs from TEM also showed a clear difference in morphology if the base polymer is changed, with PE lamellae growing out of the inclusions or being present directly embedded in the matrix. To verify these findings, the interfacial tension was determined. The applicability of Palierne's emulsion model was found to be limited for such complex systems, whereas Gramespacher–Meissner analysis led to interfacial tensions comparable with those already reported in the literature. The improved compatibility when changing the matrix polymer from the homopolymer to the random copolymer allows the development of multiphase materials with finer phase structure, which will also result in improved mechanical and optical performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Improving the oxygen barrier properties of polyethylene terephthalate by graphite nanoplatelets
Authors: Al‐Jabareen Ahmad , Al‐Bustami Hammam , Harel Hannah , Marom Gad
Published: July 2012

Enhancement of the oxygen gas barrier properties of polyethylene terephthalate (PET), used in the packaging industry, is the main objective here. For this purpose, nanocomposites of PET containing graphite nanoplatelets (GNPs) were prepared by melt compounding. The effects of the nanocomposites' structural morphology on oxygen gas permeability were analyzed using a range of thermal, microscopic, and mechanical characterization techniques. The investigated nanocomposite films exhibited GNP exfoliated morphology and good mixing with PET, as well as uniform dispersion within the polymer. All nanocomposite films were shown to possess superior oxygen barrier properties and improved thermal and dimensional stability compared with the plain PET films. In the best case, for 1.5 wt % GNP, the oxygen permeation was reduced by more than 99%. The improved barrier properties are attributed to the direct effect of the GNPs and to their induced increase of degree of crystallinity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Investigation of vegetable‐oil‐based coupling agents for kenaf‐fiber‐reinforced unsaturated polyester composites
Authors: Ren Xiaofeng , Li Kaichang
Published: July 2012

Kenaf fibers are modified with three novel coupling agents that consist of an isocyanate and acrylated epoxidized soybean oil. The untreated‐kenaf‐UPE (unsaturated polyester) composites and coupling‐agent‐treated‐kenaf‐UPE composites are obtained by a compression molding process. Modifications of kenaf fibers with coupling agents significantly increase mechanical properties, and enhance water resistance of the resulting kenaf‐UPE composites. Characterization of coupling‐agent‐treated‐fibers with Fourier transform infrared spectroscopy reveals that coupling agents are covalently bonded onto kenaf fibers. Improved interfacial adhesion between kenaf fibers and UPE resin is confirmed with scanning electron microscopy. The mechanisms on which the chemical treatments of kenaf fibers improve the mechanical properties and water resistance are discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Deformation and fracture behaviors of vinylester/fly ash composites
Authors: Stocchi A. , Rodríguez E. , Vázquez A. , Bernal C.
Published: July 2012

In this work, the deformation and fracture behaviors of a commercial vinylester resin reinforced with fly ash were investigated. Tensile, compressive, and fracture tests were performed on the matrix and the composites with different ash content. Most composites exhibited improved stiffness, tensile strength, and fracture properties in comparison to the vinylester matrix. From scanning electron microscopic analysis of fracture surfaces, the toughening mechanisms of crack pinning, crack deflection, particle debonding, and localized shear yielding were identified. In addition, the dependence of tensile and compressive modulus and fracture energy toward ash content was adequately fitted by simple models available in the literature. From the results of these models and energy‐dispersive X‐ray spectroscopy analysis, some interaction between vinylester and ash seemed to exist. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Preparation and utilization of microporous molecularly imprinted polymer for sustained release of tetracycline
Authors: Mirzaei Mohammad , Najafabadi Sayed Alireza Hassani , Abdouss Majid , Azodi‐Deilami Saman , Asadi Ebadullah , Hosseini Mohammad Reza Milani , Piramoon Majid
Published: July 2012

A polyacrylate tetracycline (TC) selective microporous molecularly imprinted polymer was prepared in three different porogenic solvents (chloroform, acetonitrile, and methanol) via precipitation polymerization, using methacrylic acid monomer, ethylene glycol dimethacrylate crosslinker, and TC as template. In all three solvents this method produced microporous particles in the scale range (200–400 nm), simply, quickly, cleanly, and in good yield. The effect of polarity of porogenic solvents on binding capacity was investigated. The imprinted polymer prepared in chloroform gave much higher binding capacity (KD = 198.6) for TC than the polymers prepared in acetonitrile (KD = 133.2) or methanol (KD = 104.7). The selectivity of imprinted polymers was evaluated by rebinding other structurally similar compounds. The results clearly indicated that the imprinted acrylate polymer exhibits an excellent selectivity toward TC, and has better ability to control the release of TC than the non‐imprinted polymer.© 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis and characterization of PLA nanocomposites containing nanosilica modified with different organosilanes I. Effect of the organosilanes on the properties of nanocomposites: Macromolecular, morphological, and rheologic characterization
Authors: Basilissi Luca , Silvestro Giuseppe Di , Farina Hermes , Ortenzi Marco Aldo
Published: July 2012

Polylactide nanocomposites containing different loadings of nanosilica were prepared by employing bulk ring opening polymerization from lactide. Nanosilica was used as such and after surface treatment with different amounts of two distinct silanes. The effects on the properties of the material were evaluated comparing the samples containing organosilane‐modified nanosilica with poly(lactic acid) (PLA) containing unmodified nanosilica. A standard linear PLA and an industrial “film grade” PLA (PLA Natureworks 4032D) were used as reference. Pure silica tends to decrease the molecular weight of the material, deactivating the catalytic system but when silanes are present on the surface, molecular weights are similar to the ones of standard and industrial PLA. Transmission electron microscopy analysis shows that silanes improve the dispersion of the mineral, while rheologic curves suggest that when silanes are present melt viscosity increases markedly at zero shear and decreases faster as the shear rate increases. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Leptin exacerbates collagen‐induced arthritis via enhancement of Th17 cell response
Authors: Deng Jun , Liu Yang , Yang Min , Wang Shengjun , Zhang Miaojia , Wang Xiaohui , Ko King‐Hung , Hua Zichun , Sun Lingyun , Cao Xuetao , Lu Liwei
Published: July 2012

Objective

To determine the role of leptin in modulating Th17 cell response and joint inflammation in mice with collagen‐induced arthritis (CIA).

Methods

Leptin receptor expression on T cells was examined by polymerase chain reaction (PCR) analysis, immunofluorescence microscopy, and flow cytometry. Effects of leptin on Th17 cell differentiation and proliferation were evaluated by quantitative PCR, carboxyfluorescein diacetate succinimidyl ester proliferation assay, and flow cytometry. Dynamic changes in leptin concentrations in the joint tissue and synovial fluid of mice with CIA were determined by immunohistochemistry analysis and enzyme‐linked immunosorbent assay (ELISA). Arthritis symptoms and joint pathology in mice with CIA were assessed after injection of leptin into the knee joint. Th1 and Th17 cell populations in the spleen, draining lymph nodes, and joint tissue were analyzed by flow cytometry and enzyme‐linked immunospot assay. Interleukin‐17 messenger RNA and protein levels in the joint tissue were measured by PCR analysis and ELISA.

Results

In culture, leptin treatment significantly increased Th17 cell generation from naive CD4+ T cells. During CIA development, markedly elevated levels of leptin were detected in the joint tissue and synovial fluid. Moreover, injection of leptin into the knee joint of collagen‐immunized mice resulted in an early onset of arthritis and substantially increased the severity of clinical symptoms, accompanied by more pronounced synovial hyperplasia and joint damage. Further examination by immunofluorescence microscopy confirmed the presence of significantly increased numbers of Th17 cells in the joint tissue and draining lymph nodes of leptin‐treated mice with CIA.

Conclusion

The results of this study identify a previously undescribed function of leptin in enhancing Th17 cell response and exacerbating joint inflammation in mice with CIA.
Genetic inhibition of fibroblast growth factor receptor 1 in knee cartilage attenuates the degeneration of articular cartilage in adult mice
Authors: Weng Tujun , Yi Lingxian , Huang Junlan , Luo Fengtao , Wen Xuan , Du Xiaolan , Chen Qian , Deng Chuxia , Chen Di , Chen Lin
Published: July 2012

Objective

Fibroblast growth factor (FGF) family members are involved in the regulation of articular cartilage homeostasis. The aim of this study was to investigate the function of FGF receptor 1 (FGFR‐1) in the development of osteoarthritis (OA) and its underlying mechanisms.

Methods

FGFR‐1 was deleted from the articular chondrocytes of adult mice in a cartilage‐specific and tamoxifen‐inducible manner. Two OA models (aging‐associated spontaneous OA, and destabilization‐induced OA), as well as an antigen‐induced arthritis (AIA) model, were established and tested in Fgfr1‐deficient and wild‐type (WT) mice. Alterations in cartilage structure and the loss of proteoglycan were assessed in the knee joints of mice of either genotype, using these 3 arthritis models. Primary chondrocytes were isolated and the expression of key regulatory molecules was assessed quantitatively. In addition, the effect of an FGFR‐1 inhibitor on human articular chondrocytes was examined.

Results

The gross morphologic features of Fgfr1‐deficient mice were comparable with those of WT mice at both the postnatal and adult stages. The articular cartilage of 12‐month‐old Fgfr1‐deficient mice displayed greater aggrecan staining compared to 12‐month‐old WT mice. Fgfr1 deficiency conferred resistance to the proteoglycan loss induced by AIA and attenuated the development of cartilage destruction after surgically induced destabilization of the knee joint. The chondroprotective effect of FGFR‐1 inhibition was largely associated with decreased expression of matrix metalloproteinase 13 (MMP‐13) and up‐regulation of FGFR‐3 in mouse and human articular chondrocytes.

Conclusion

Disruption of FGFR‐1 in adult mouse articular chondrocytes inhibits the progression of cartilage degeneration. Down‐regulation of MMP‐13 expression and up‐regulation of FGFR‐3 levels may contribute to the phenotypic changes observed in Fgfr1‐deficient mice.
Impact of digital archival collections on historical research
Authors: Sinn Donghee
Published: July 2012

A number of digital projects have been implemented for archival and special collections. The amount of funds and effort devoted to such projects is enormous, and now they are providing greater opportunities and convenience for researchers to view and make use of important, rare, and/or brittle historical materials. However, little attention has been paid in the information science field as to how much impact these projects to digitalize archival collections have had on actual historical research publications. Existing studies are largely devoted to system designs and the user/usability interface, as well as users' search behaviors. Little has been done to determine the direct relationship between digital resources and historical research. This study surveyed research articles in the field of history to observe how frequently and widely digital collections were used, what kinds of digital collections were used more extensively and for what purposes, and what the current status of digital archival collections among other resources is in historical research. Citations and figures in articles of the American Historical Review for the period 2001–2010 were analyzed with a specific focus on digital archives collection. The usage patterns by material types and formats of references and the impacts of digital archival collections among other sources are identified from two perspectives of impact: intensity and extensity. Observation of the direct relationships with digital collections and historical studies suggest some practical guidelines for future digital projects with concrete data.
PubMed searches by Dutch‐speaking nursing students: The impact of language and system experience
Authors: Vanopstal Klaar , Stichele Robert Vander , Laureys Godelieve , Buysschaert Joost
Published: July 2012

This study analyzes the search behavior of Dutch‐speaking nursing students with a nonnative knowledge of English who searched for information in MEDLINE/PubMed about a specific theme in nursing. We examine whether and to what extent their search efficiency is affected by their language skills. Our task‐oriented approach focuses on three stages of the information retrieval process: need articulation, query formulation, and relevance judgment. The test participants completed a pretest questionnaire, which gave us information about their overall experience with the search system and their self‐reported computer and language skills. The students were briefly introduced to the use of PubMed and MeSH (medical subject headings) before they conducted their keyword‐driven subject search. We assessed the search results in terms of recall and precision, and also analyzed the search process. After the search task, a satisfaction survey and a language test were completed. We conclude that language skills have an impact on the search results. We hypothesize that language support might improve the efficiency of searches conducted by Dutch‐speaking users of PubMed.
Extraction of Cupric Ions with Ionic Liquids Containing Polypyridine‐type Small Molecules or Peripherally Pyridine‐modified Dendrimers
Authors: Su Chung‐Jui , Tang Yi‐Hsuan , Yu Fu‐Lun , Wu Ru‐Rong , Hsu Sodio C. N. , Kao Chai‐Lin , Huang Hsin‐Yi , Chen Po‐Yu
Published: July 2012

The hydrophobic ionic liquid N‐butyl‐N‐methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (BMP‐TFSA IL), which contains a series of flexible ionophores of polypyridine‐type small molecules or two rigid ionophores of peripherally pyridine‐modified PAMAM dendrimers, was used to extract cupric ions from aqueous solutions. The polypyridine‐type ionophores show good selectivity toward cupric ions at pH 2. The selectivity is affected by the spacing between the two amino groups. However, the pyridine‐modified dendrimers showed poor selectivity, although their extraction efficiency still depended on the pH of the aqueous solution. The ionic liquids that contained small molecular ionophores and their dendrimer analogs were reused after acid washing or electrochemical reduction. During acid washing, the nitrogen atoms of the ionophores were protonated to release the cupric ions into the aqueous phase, and the copper atoms were deposited onto the electrode surface during the electrochemical reduction accompanied by the regeneration of the ionophores.
Excess molar enthalpies of nitrous oxide‐heptane in the liquid and supercritical regions
Authors: Pittau Barbara , Cabañas Albertina , Pando Concepción , Renuncio Juan A. R.
Published: July 2012

The excess molar enthalpies HEm of {xN2O+(1‐x)C7H16} were measured in the liquid and supercritical region covering the whole concentration range. Mixtures at 308.15 K and 7.64, 9.48 and 12.27 MPa show moderately endothermic and exothermic mixing in the heptane‐rich region and nitrous oxide‐rich region, respectively. The exothermic‐mixing region is confined to a smaller range of x as pressure increases and disappears completely at 308.15 K and 15.00 MPa. Mixtures at 318.15 K and 7.64 and 9.48 MPa show very exothermic mixing. Mixtures at 318.15 K and 12.27 and 15.00 MPa show moderately endothermic and exothermic mixing in the heptane‐rich region and nitrous oxide‐rich region, respectively. The changes observed in the excess enthalpy with temperature and pressure are discussed in terms of liquid‐vapor equilibrium and critical constants for nitrous oxide‐heptane. Excess enthalpies for nitrous oxide‐heptane mixtures are also calculated by means of the Peng‐Robinson equation of state and the resulting HEm values are compared with experiment.
Vapour pressures at several temperatures of binary mixtures of di‐n‐propylether+2‐methyl‐1‐propanol, +2‐butanol, or +2‐methyl‐2‐propanol, and excess functions, at T= 298.15 K. Thermodynamic description according to the ERAS‐model
Authors: Garriga R. , Sánchez F. , Fpérez P. , Gracia M.
Published: July 2012

Vapour pressures of di‐n‐propylether with 2‐methyl‐1‐propanol, 2‐butanol, and 2‐methyl‐2‐propanol were measured at several temperatures between 278.15 K and 323,15 K by a static method. Excess molar enthalpies and volumes for mixtures of di‐n‐propylether with 2‐methyl‐l‐propanol and 2‐butanol, were also measured at T=298.15 K. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs free energies was carried out by Barker's method. Mixtures containing 2‐butanol and 2‐methyl‐2‐propanol show azeotropy with a minimum boiling temperature. GE, HE, and VE, at 298.15 K, of these mixtures are compared with predictions of the ERAS‐model observing that the model reproduces acceptably the experimental behaviour.
Solid‐liquid equilibria in n‐alkanol+n‐alkane systems. Prediction by several group‐contribution theories
Authors: Hofman T. , Barbés B. , Casanova C.
Published: July 2012

Several, widely used, group contribution models have been used to predict solid‐liquid equilibria for n‐alcohol+n‐alkane binary mixtures. They are: modified UNIFAC [1], DISQUAC [2, 3], Nitta‐Chao [4] and the Hole Model (HM) [5]. Also a recently reported group contribution model (AssoDis) including association [6] has been taken into account. The results have been compared with experimental data.
Multinuclear high‐pressure NMR investigations of undercooled aqueous solutions of hydrophobic ions
Authors: Bradl S. , Schätz T. , Liegl B. , Lang E. W.
Published: July 2012

Multinuclear spin‐lattice relaxation rates, cross‐relaxation rates and self‐diffusion coefficient measurements are reported over wide ranges of temperature, pressure and concentration in undercooled aqueous solutions of tetraalkylammonium bromides. These dissolved organic cations with apolar surface groups provide model systems to investigate the effect of coulombic, hydrophobic and H‐bond interactions upon the solvent and solute dynamics within the random, transient H‐bond network of undercooled water.
A direct investigation of the reaction CH3+OH: Overall rate constant and CH2 formation at T=298 K
Authors: Deters R. , Otting M. , Gg. Wagner H. , Temps F. , László B. , Dóbé S. , Bérces T.
Published: July 2012

The rate constant and the product distribution of the reaction CH3+OH r̊ products (1) were studied at room temperature over a range of pressures (0.7 mbar ≤p≤467 mbar) with M=
He as inert bath gas. At pressures of 45 to 467 mbar, towards the high pressure range of the reaction, experimental determinations were performed using the laser flash photolysis technique with transient UV absorption spectrometry (LFP/TAS) for direct monitoring of the CH3 and OH radicals. In this range, the overall rate constant for the reaction was found to be practically independent of pressure at k1 (298 K)=(4.4±0.8)x1013 cm3 mol−1 s−1. At pressures of 0.7 mbar to 4.0 mbar, the reaction was studied using the discharge flow (DF) technique with laser magnetic resonance (LMR) for the direct detection of the reactants CH3 and OH and the reaction product CH2. The measured overall rate constants at the low pressures were found to increase slightly with increasing pressure and approach the value at “high” pressure from the LFP/TAS experiments. From simulations of the measured concentration‐versus‐time profiles of the CH3, OH, and CH2 radicals, the branching ratio for the reaction channel CH3+OHr̊ CH2+H2O (1.1) was determined at p=1.33 mbar, T=298 K to be k1.1lk1=(0.89±0.09). Implications of the results are discussed considering the fall‐off curve for the reaction, the reaction mechanism and the product distribution, and the available thermochemical data.
A high temperature study of the reaction SiH4+H ⇋ SiH3+H2
Authors: Kunz A. , Roth P.
Published: July 2012

The reaction of silane with H atoms

magnified image

was studied behind reflected shock waves at temperatures between 998 K and 1273 K and pressures around 1.5 bar. The thermal decomposition of a few ppm ethyl iodide (C2H5I) was used as a well known H‐atom source. The atomic resonance absorption spectroscopy (ARAS) was applied for time resolved and simultaneous measurements of H‐ and Si‐atom concentrations. The presence of an excess of SiH4 causes a fast consumption of H atoms according to reaction (R 5). The signals obtained were kinetically evaluated by computer simulations based on a simplified reaction mechanism. The rate coefficient for reaction (R 5) was found to be:
Formation kinetics and electrochemical behavior of an azobenzene self‐assembled monolayer on a gold electrode
Authors: Shao H. B. , Yu H. Z. , Cheng G. J. , Zhang H. L. , Liu Z. F.
Published: July 2012

The formation kinetics of the self‐assembled monolayer (SAM) of an azobenzenealkanethiol (HS‐CH2CH2NHC(O)‐ϕ‐N=N‐ϕ, denoted as AzoC2SH) on gold surface was studied using electrochemical techniques, while the variation of the voltammetric behavior of AzoC2SH monolayers prepared with different assembly time was investigated. A two‐step adsorption kinetics has been confirmed for the self‐assembly of AzoC2SH molecules on gold surface: the fast adsorption process and the following long‐term reorganization. The equilibrium constant (Keq) for the adsorption and the interaction factor between adsorbate‐adsorbate molecules (δ) were evaluated based on the Frumkin isotherm and determined to be (3.17±0.13)x106 M−1 and (‐0.34±0.04), respectively. We have also determined the adsorption rate constant (Kad) of (1.90±0.4)x103 M−1 s−1 on the basis of the Langmuir model. The value of kad is significantly larger than that of underivatized alkanethiols or ferrocenylalkanethiols, partially due to the strong attractive interaction between AzoC2SH molecules in the monolayer, which is evidenced by the negative interaction factor. Moreover, the electrochemical behavior shows a unique change when we prepare differently packed AzoC2SH monolayers by controlling the self‐assembling time. The apparent electron transfer rate constant (kapp) was found to show a remarkable decrease with the surface concentration of the adsorbate molecules in the monolayer increasing. Taking into account the molecular structural change associated with the reduction/oxidation of an azobenzene group, the decrease of kapp can be understood by considering that there is an increase of the structural inhibition effect when the packing density of the AzoC2SH monolayer on gold surface increases.
Physical characteristics of aluminium plating solutions containing quaternary aralkylammonium compounds
Authors: Simanavičius L. , Stakénas A. , Šarkis A.
Published: July 2012

Phase equilibria in ambient temperature molten salt systems prepared from aluminium bromide and dimethylethylphenylammonium bromide or trimethylphenylammonium iodide are described. The experimental densities of some solutions of the mentioned mixtures in aromatic hydrocarbon and the compositions of these layering solutions are given depending on temperature.
EXAFS investigation of mixed zirconium‐titanium alkoxides
Authors: Reinöhl U. , Ertel T. S. , Hörner W. , Weber A. , Bertagnolli H.
Published: July 2012

The structures of zirconium alkoxides Zr(OR)4, with R=n‐propoxide and n‐butoxide, and of the corresponding mixed zirconium‐titanium alkoxides, used as precursors in the sol‐gel process, were investigated by EXAFS spectroscopy at the Zr K‐edge in solution of their parent alcohols.

In all investigated systems the Zr‐atoms are surrounded by six O‐atoms. Additionally, a Zr‐Zr distance was found in the pure zirconium alkoxides, indicating the existence of dimers or oligomers. In the mixture of zirconium‐ and titanium alkoxides the hetero‐association is preferred, since a Zr‐Ti distance could be detected.
Dielectric study on ionic orientational disorder in the low‐temperature phases of ionic plastic crystal KNO2
Authors: Honda Hisashi , Onoda‐Yamamuro Noriko , Ishimaru Shin'Ichi , Ikeda Ryuichi , Yamamuro Osamu , Matsuo Takasuke
Published: July 2012

The complex dielectric permittivity of ionic plastic crystal KNO2 was measured in the frequency range 20‐106 Hz and the temperature range 22‐300 K. A small step‐like anomaly of the static dielectric permittivity appeared at the rhombohedral (phase II) to monoclinic (phase III) transition (Ttr2 = 264. 1 K). In phase III, the static dielectric permittivity decreased gradually on cooling over a wide temperature range 50‐264 K. These results indicate that the orientation of the NO−2 ion is still disordered at high temperatures in phase III and becomes ordered gradually with decreasing temperature. The dielectric dispersion associated with this motion occurred in the temperature range 70‐150 K. From these data and the previously reported 15N NMR data, we propose a model of the motion of NO2− in phase III in which the anion undergoes 180°‐flip motion about the axes perpendicular to the molecular C2 axis in an asymmetric double‐minimum potential.
A Raman spectroscopic study of hydration and water‐ligand replacement reaction in aqueous cadmium(II)‐sulfate solution: Inner‐sphere and outer‐sphere complexes
Authors: Rudolph Wolfram W.
Published: July 2012

Raman and infrared spectra of aqueous CdSO4 and (NH4)2SO4 solutions have been recorded over a broad concentration (0. 040 to 3. 51 mol/kg) and temperature range (‐10 to 109°C). Whereas the v1SO2‐4 band profile is symmetrical in (NH4)2SO4 solutions, in CdSO4 solutions a shoulder appears on the high frequency side at 989 cm−1, which increases in intensity with increasing concentration and temperature. The relative molar scattering coefficient of the v1SO42−v band is the same for all forms of sulfate in (NH4)2SO4 and CdSO4 solutions and is independent of temperature up to 109°C. The high frequency shoulder is attributed to the formation of a 1:1 inner‐sphere complex [Cd2+(OH2)5OSO32− The v3SO42− antisymmetric stretching mode, normally forbidden in the isotropic scattering, contains a contribution in concentrated CdSO4 solutions. The bending modes, v2SO42− and v4SO42−, also forbidden in the isotropic scattering, show contributions at 472 and 640 cm−1, well apart from the frequencies normally observed in the anisotropic spectrum in (NH4)2SO4 solution. A polarized band at 240 cm−1 has been assigned to the Cd2+‐OSO32− ligand vibration. Further spectroscopic evidence for contact ion pair formation at 25°C is provided by i.r. spectroscopy. Higher associates or anionic complexes are not required to interpret the spectroscopic data, but it has been established that at room temperature the favourable complex is an outer‐sphere complex whereas above 109°C the inner‐sphere complex is becoming the favourable one (inner‐sphere complex formation is entropically driven). The Raman spectroscopic results confirm the stepwise reaction mechanism of sulfato‐complex formation in aqueous CdSO4 solution.

The degree of association has been measured as a function of concentration and temperature. At concentrations above 1.0 mol · kg−1 the concentration quotient, QA equal to QU, has a relatively high and constant value of 0.14±0.02. The thermodynamic association constant, enthalpy and entropy for the outer‐sphere/inner‐sphere complex formation have been estimated to be: KII = 3.3±0.3, ΔH° =(6.2±0.2) kJ · mol−1 and ΔS° = (33±1)J · K−1 · mol−1.
Quantum cluster equilibrium theory of liquids part II: Temperature dependent chemical shifts, quadrupole coupling constants and vibrational frequencies in liquid ammonia
Authors: Ludwig R. , Weinhold F. , Farrar T. C.
Published: July 2012

Temperature dependent NMR chemical shifts for hydrogen and nitrogen, NMR quadrupole coupling constants for deuterium and nitrogen as well as all vibrational frequencies for liquid ammonia are calculated by the ab initio quantum cluster equilibrium (QCE) method and compared with experimental measurements. All properties were obtained from equilibrium populations of ammonia clusters calculated between the melting (196 K) and the boiling (239 K) point. The calculated vibrational frequencies and chemical shifts are in good agreement with experimental NMR and Raman measurements. The theoretical quadrupole coupling constants for liquid ammonia lie midway between the available experimental data for the solid and the gas phase.
A model of the electronic properties of activated carbon
Authors: Kastening Bertel
Published: July 2012

Activated carbon may be regarded as consisting of graphite nanocrystals forming the walls of the pores. These crystallites contain three graphene layers having sizes of 2‐4 nm perpendicular to the “c‐axis”. A model has been developed of the electronic properties of the material. The model is based on this nano‐structure and on experimental results concerning the variation of the conductivity, the thermoelectric power and the ESR signal of activated carbon, immersed in electrolyte solutions, on changing the electrode potential. According to the model, the graphene layers (“domains”) are charged with one, and preferentially two, electrons (or defect electrons) or uncharged, the π‐electron system being delocalized throughout a domain. The various types of domains are in thermodynamic equilibria with one another. Charge transport is regarded as transport of charged domains, resembling the “extra” conduction of protons in H‐bonding solvents like water, while uncharged domains (like neutral water clusters) do not contribute to the conductivity. Correspondence with electronic energy band models is obtained by constructing electronic levels from the energetic data. Close structural and mechanistic similarities to conducting polymers suggest the applicability of the model also to this material.
Radiative and nonradiative energy transfer between CO and pyrene involving higher excited states: A Spectroscopic Analysis
Authors: Gudipati Murthy S. , Kalb Martin
Published: July 2012

A detailed spectroscopic analysis of radiative and nonradiative electronic energy transfer (EET) between CO and pyrene involving the higher electronically excited states is presented. Spectroscopic investigations on CO and pyrene that are codeposited in Ar matrices reveal that when CO is excited between 160 and 120 nm, into the A1π(ν')← X1S̀+ (ν″ = 0) vibronic transitions, fluorescence of pyrene occurs in addition to the radiative transitions in CO itself. A part of the EET from CO to pyrene is due to the radiative EET, which is confirmed from the modulation of the Cameron emission bands of CO between 200 and 250 nm by the excitation spectrum of pyrene in the same wavelength region. An evidence for nonradiative EET of Förster‐type is also obtained by investigating sandwich matrices with layers of Ar containing only pyrene and pyrene as well as CO. Present results are in line with those observed between CO and anthracene [Chem. Phys. Lett. 268, 169 (1997)].
Computer modeling of formation of soot precursors in the oxidation of methane
Authors: Németh A. , Héberger K.
Published: July 2012

A previously developed method was extended for computer modeling of chemical processes involving large number of species. Improvements introduced for the combinatorial generation of stoichiometrically possible reaction steps include hierarchical structuring of the chemical system under study, replacing invariant atomic groups by symbols, as well as the combined application of two complexity constraints for the reduction of the set of reactions.

Modeling revealed that while in the oxidation of methane the formation of ethynyl benzene (phenylacetylene), 1‐naphtyl radical, diethynyl benzene and ethynyl naphtalene by acetylene addition to the precursor radicals can be accepted to proceed in a single elementary step, this is not valid for anthracyl radical. Formation of acenaphtylene, 12‐biphenyl radical, 3‐phenantryl radical, phenantrene, and pyrene needs further investigation in this respect. Furthermore, formation of benzene, phenyl, and biphenyl by recombination of propargyl or substituted propargyl radicals in a single elementary reaction was not supported by modeling. Results suggest the possibility of not yet identified intermediates participating in these processes.
The origin and nature of chemiluminescence in the dibenzoylperoxide‐dimethylaniline reaction
Authors: Vasvári Gábor , Hofmann Tibor
Published: July 2012

It has been established that the dibenzoylperoxide (POOP)+dimethylaniline (DMA) reaction is suitable to the slow production of free radicals at ambient temperature and in the absence of oxygen. The process is accompanied by a well measurable chemiluminescence (CL) without added sensitizer. The reaction carried out in acetonitrile is mainly ionic with the formation of radicals in between. We assume the existence of a 2:1 DMA/POOP complex as a possible source of radicals. The kinetics of CL is determined by the formation and decomposition rate of this complex. Calculated rate constant values: k(f) = 3 × 10−3 M−1 s−1 and k(d) = 1 × 10−3 s−1. Based on the spectrum of the CL light and taking into consideration the analytical results we assume that the energy of CL is delivered almost totally by the cage termination product (ΔH(r) =‐385 kJ/mol) formed in excited state and this energy is transferred to the triphenylmethane dye‐salt products (Malachite Green, Crystal Violet) which are the probable emitters of the CL light. Hydroperoxide is not formed in the reaction.
Hydrogen transfer: Experiment and theory
Authors: Limbach Hans‐Heinrich , Manz Jörn
Published: July 2012

This overview paper provides a short introduction into the topics discussed at the International Autumn Bunsen Discussion meeting 1997 on “Hydrogen Transfer Theory and Experiment” which took place in Berlin during 10–13 September 1997 under the auspices of the Deutsche Bunsengesellschaft für Physikalische Chemie and the Freie Universität Berlin.
Characterization of proton transfer in HO2−and HF2+: An atoms in molecules study
Authors: Hamilton L. P.
Published: July 2012

Proton transfer is examined in HO2−and HF2+. These species are isoelectronic and a direct comparison of their electron densities is possible. Electron densities are calculated at the QCISD/6‐311++G(2d,2p) level for the nonlinear equilibrium geometry and the C2vsaddle point and linear saddle point geometries. Bader's theory of atoms in molecules is applied to partition the electron density into its atomic components and atomic and molecular properties are calculated. These quantities are used to characterize the proton dynamics as being like internal rotation.