1,633 research outputs found

    Characterisation of porous solids using small-angle scattering and NMR cryoporometry

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    The characteristics of several porous systems have been studied by the use of small-angle neutron scattering [SANS] and nuclear magnetic resonance [NMR] techniques. The measurements reveal different characteristics for sol-gel silicas, activated carbons and ordered mesoporous silicas of the MCM and SBA type. Good agreement is obtained between gas adsorption measurements and the NMR and SANS results for pore sizes above 10 nm. Recent measurements of the water/ice phase transformation in SBA silicas by neutron diffraction are also presented and indicate a complex relationship that will require more detailed treatment in terms of the possible effects of microporosity in the silica substrate. The complementarity of the different methods is emphasised and there is brief discussion of issues related to possible future developments

    Resonance raman characterization of the forms of ground-state 8-substituted 7-hydroxyquinoline caged acetate compounds in aqueous solutions

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    Monday Poster Session: Resonance Raman in Biological and Chemical Systems (MP22) - Poster Number: 0978-substituted 7-hydroxyquinolines, like 8-chloro-7-hydroxyquinoline (CHQ) and 8-cyano-7-hydroxyquinoline (CyHQ), are able to be useful for 1PE and 2PE and their acetate acids CHQ−OAc and CyHQ−OAc were also able to undergo photolysis reactions in neutral aqueous buffer solutions. To examine the substituent effect on the relative populations of the forms of the ground state species of 8-substituted 7-hydroxyquinolines, ultraviolet absorption and resonance Raman spectroscopy experiments were done for CHQ–OAc and CyHQ–OAc in differnt solutions.postprintThe 22nd International Conference on Raman Spectroscopy (ICORS 2010), Boston, MA., 8-13 August 2010

    THE INFLUENCE OF BORON ON THE CHEMICAL COMPOSITION AND GROWTH OF THE TOMATO PLANT

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    Confinement effects on glass forming liquids probed by DMA

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    Many molecular glass forming liquids show a shift of the glass transition T-g to lower temperatures when the liquid is confined into mesoporous host matrices. Two contrary explanations for this effect are given in literature: First, confinement induced acceleration of the dynamics of the molecules leads to an effective downshift of T-g increasing with decreasing pore size. Second, due to thermal mismatch between the liquid and the surrounding host matrix, negative pressure develops inside the pores with decreasing temperature, which also shifts T-g to lower temperatures. Here we present dynamic mechanical analysis measurements of the glass forming liquid salol in Vycor and Gelsil with pore sizes of d=2.6, 5.0 and 7.5 nm. The dynamic complex elastic susceptibility data can be consistently described with the assumption of two relaxation processes inside the pores: A surface induced slowed down relaxation due to interaction with rough pore interfaces and a second relaxation within the core of the pores. This core relaxation time is reduced with decreasing pore size d, leading to a downshift of T-g proportional to 1/d in perfect agreement with recent differential scanning calorimetry (DSC) measurements. Thermal expansion measurements of empty and salol filled mesoporous samples revealed that the contribution of negative pressure to the downshift of T-g is small (<30%) and the main effect is due to the suppression of dynamically correlated regions of size xi when the pore size xi approaches

    Small and large polarons in nickelates, manganites, and cuprates

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    By comparing the optical conductivities of La_{1.67}Sr_{0.33}NiO_{4} (LSNO), Sr_{1.5}La_{0.5}MnO_4 (SLMO), Nd_2CuO_{4-y} (NCO), and Nd_{1.96}Ce_{0.04}CuO_{4} (NCCO), we have identified a peculiar behavior of polarons in this cuprate family. While in LSNO and SLMO small polarons localize into ordered structures below a transition temperature, in those cuprates the polarons appear to be large, and at low T their binding energy decreases. This reflects into an increase of the polaron radius, which may trigger coherent transport.Comment: File latex, 15 p. incl. 4 Figs. epsf, to appear on the Journal of Superconductivity - Proc. "Stripes 1996" - Roma Dec 199

    Multi-gap superconductivity in a BaFe1.84Co0.16As2 film from optical measurements at terahertz frequencies

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    We measured the THz reflectance properties of a high quality epitaxial thin film of the Fe-based superconductor BaFe1.84_{1.84}Co0.16_{0.16}As2_2 with Tc_c=22.5 K. The film was grown by pulsed laser deposition on a DyScO3_3 substrate with an epitaxial SrTiO3_3 intermediate layer. The measured RS/RNR_S/R_N spectrum, i.e. the reflectivity ratio between the superconducting and normal state reflectance, provides clear evidence of a superconducting gap ΔA\Delta_A close to 15 cm−1^{-1}. A detailed data analysis shows that a two-band, two-gap model is absolutely necessary to obtain a good description of the measured RS/RNR_S/R_N spectrum. The low-energy ΔA\Delta_A gap results to be well determined (ΔA\Delta_A=15.5±\pm0.5 cm−1^{-1}), while the value of the high-energy gap ΔB\Delta_B is more uncertain (ΔB\Delta_B=55±\pm7 cm−1^{-1}). Our results provide evidence of a nodeless isotropic double-gap scenario, with the presence of two optical gaps corresponding to 2Δ/kTc\Delta/kT_c values close to 2 and 7.Comment: Published Versio

    Factors associated with severity of hepatic fibrosis in people with chronic hepatitis C infection

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    The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.OBJECTIVE: To determine factors associated with hepatic fibrosis development in people with chronic hepatitis C virus (HCV) infection. METHODS: As a requirement for access to interferon therapy through the S100 scheme in Australia, individual pretreatment demographic and clinical information was collected on 2986 patients from 61 hospital-based liver clinics from 1 October 1994 through 31 December 1996. Patients with both a hepatic fibrosis score and an estimated duration of HCV infection (910) were divided into 540 with no or minimal hepatic fibrosis (stage 0–1) and 370 with moderate to severe hepatic fibrosis (stage 2–3). Seven factors were examined: age at HCV infection, sex, ethnicity, source of infection, duration of infection, alcohol intake, and mean ALT level. A further analysis was performed for all 1135 patients with a hepatic fibrosis score disregarding age at and duration of HCV infection. RESULTS: In multivariate analysis, four factors were significantly associated with moderate to severe hepatic fibrosis: age at infection (OR, 2.33 for age 31–40 years, 5.27 for age > 40 years, and 0.20 for age 30 years, compared with 3 times, compared with 1.5–2 times the upper limit of normal). In the analysis disregarding age at HCV infection and duration of HCV infection, older age was strongly associated with moderate to severe hepatic fibrosis (OR, 2.32 for age 36–40 years, 2.46 for age 41–50 years, 7.87 for age 51–60 years, and 7.15 for age > 60 years, compared with 16–30 years). There was no association in either analysis with sex or source of HCV infection. CONCLUSION: These factors may assist in targeting patients for both liver biopsy-based investigation and therapeutic intervention.Mark Danta, Gregory J Dore, Lisa Hennessy, Yueming Li, Chris R Vickers, Hugh Harley, Meng Ngu, William Reed, Paul V Desmond, William Sievert, Geoff C Farrell, John M Kaldor and Robert G Bate

    Infrared response of ordered polarons in layered perovskites

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    We report on the infrared absorption spectra of three oxides where charged superlattices have been recently observed in diffraction experiments. In La1.67_{1.67}Sr0.33_{0.33}NiO4_4, polaron localization is found to suppress the low-energy conductivity through the opening of a gap and to split the E2uE_{2u}-A2uA_{2u} vibrational manifold of the oxygen octahedra. Similar effects are detected in Sr1.5_{1.5}La0.5_{0.5}MnO4_4 and in La2_2NiO4+y_{4+y}, with peculiar differences related to the type of charge ordering.Comment: File latex, 11 p. + 3 Figures, to appear on Phys. Rev. B (Rapid Commun.), 1 Oct. 1996. The figures will be faxed upon request. E-mail:[email protected] Fax: +39-6-446315

    Dizajniranje i sinteza novih derivata tiofenkarbohidrazida, tienopirazola i tienopirimidina s antioksidativnim i antitumorskim djelovanjem

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    2-Amino-5-acetyl-4-methyl-thiophene-3-carboxylic acid ethyl ester (1) and 5-acetyl-2-amino-4-methylthiophene-3-carbohydrazide (2) were synthesized and used as starting materials for the synthesis of new series of 1-(5-amino-4-(3,5-dimethyl-1H-pyrazole-1-carbonyl)-3-methylthiophen-2-yl) ethanone (3a), 1-(5-amino-4-(4-chloro-3,5-dimethyl-1H-pyrazole-1-carbonyl)-3-methylthiophen-2-yl) ethanone (3b), 1-(4-methyl-2-amino-5-acetylthiophene-3-carbonyl) pyrazolidine-3,5-dione (4), (Z)-N\u27-(4-methyl-2-amino-5-acetylthiophene-3-carbonyl) formohydrazonic acid (5a), (Z)-ethyl-N\u27-(4-methyl-2-amino-5-acetylthiophene-3-carbonylformo hydrazonate (5b), 6-acetyl-3-amino-2,5-dimethylthieno2,3-dpyrimidin-4(3H)-one (8), 5-methyl-3-amino-2-mercapto-6-acetylthieno2,3-dpyrimidin-4(3H)-one (10) and 5-methyl-6-acetyl-2-thioxo-2,3-dihydrothieno2,3-dpyrimidin-4(1H)-one (12) as potential antioxidant and antitumor agents. Pharmacological results showed that compounds 6a, 6b, 8, 10 and 12 exhibited promising antitumor and antioxidant activity.Etilni ester 2-amino-5-acetil-4-metil-tiofen-3-karboksilne kiseline (1) i 5-acetil-2-amino-4-metiltiofen-3-karbohidrazid (2) sintetizirani su i upotrebljeni kao reaktanti u sintezi novih spojeva 1-(5-amino-4-(3,5-dimetil-1H-pirazol-1-karbonil)-3-metiltiofen-2-il) etanona (3a), 1-(5-amino-4-(4-klor-3,5-dimetil-1H-pirazol-1-karbonil)-3-metiltiofen-2-il) etanona (3b), 1-(4-metil-2-amino-5-acetiltiofen-3-karbonil) pirazolidin-3,5-diona (4), (Z)-N\u27-(4-metil-2-amino-5-acetiltiofen-3-karbonil) formohidrazonske kiseline (5a), (Z)-etil-N\u27-(4-metil-2-amino-5-acetiltiofen-3-karbonilformo hidrazonata (5b), 6-acetil-3-amino-2,5-dimetiltieno2,3-dpirimidin-4(3H)-one (8), 5-metil-3-amino-2-merkapto-6-acetiltieno2,3-dpirimidin-4(3H)-ona (10) i 5-metil-6-acetil-2-tiokso-2,3-dihidrotieno2,3-dpirimidin-4(1H)-ona (12) kao potencijalnih antioksidansa i citostatika. Farmakoloơka ispitivanja ukazuju na to da spojevi 6a, 6b, 8, 10 i 12 imaju značajno antitumorsko i antioksidativno djelovanje

    Supercooled confined water and the Mode Coupling crossover temperature

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    We present a Molecular Dynamics study of the single particle dynamics of supercooled water confined in a silica pore. Two dynamical regimes are found: close to the hydrophilic substrate molecules are below the Mode Coupling crossover temperature, TCT_C, already at ambient temperature. The water closer to the center of the pore (free water) approaches upon supercooling TCT_C as predicted by Mode Coupling Theories. For free water the crossover temperature and crossover exponent γ\gamma are extracted from power-law fits to both the diffusion coefficient and the relaxation time of the late α\alpha region.Comment: To be published, Phys. Rev. Lett., 4 pages, 3 figures, revTeX, minor changes in the figures, references added, changes in the tex
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