Characterization of natural gas hydrates by nuclear magnetic resonance and dielectric relaxation

1977 ◽  
Vol 55 (20) ◽  
pp. 3641-3650 ◽  
Author(s):  
D. W. Davidson ◽  
S. K. Garg ◽  
S. R. Gough ◽  
R. E. Hawkins ◽  
J. A. Ripmeester
Keyword(s):  
Guest Molecule ◽  
Continuous Wave ◽  
Type I ◽  
Tetrahedral Symmetry ◽  
Guest Molecules ◽  
Line Shapes ◽  
Dielectric Absorption ◽  
Dielectric Data ◽  
First Time

Continuous-wave proton nmr spectra of the clathrate hydrates and/or deuteriohydrates of methane, ethane, propane, isobutane, and neopentane–D2S have been recorded down to 2 K. Between 50 and 200 K each H2O hydrate spectrum consists of a line 3 to 4 G wide from reorienting guest molecules and a broader band from rigid water molecules. Line shapes characteristic of non-rotating guests are obtained in D2O hydrates at low temperatures, except for methane which gives a narrow line to 2 K. Neopentane, shown for the first time to be capable of enclathration, exhibits a Resing effect and other features related to its tetrahedral symmetry. Low-temperature dielectric absorption from reorienting guest-molecule dipoles has been measured in H2S, propane, isobutane, and n-butane–H2S hydrates. For steric reasons n-butane is encaged as a gauche rather than the trans isomer. Average barriers to reorientation estimated from nmr and dielectric data are 1.2 kcal/mol for ethane in type I hydrate and 0.6, 1.2, 1.4, and 0.8 kcal/mol for propane, isobutane, n-butane, and neopentane in type II.

Dielectric and nuclear magnetic resonance characterization of unstable clathrate hydrates of acetaldehyde and propionaldehyde

1976 ◽  
Vol 54 (19) ◽  
pp. 3085-3088 ◽  
Author(s):  
D. W. Davidson ◽  
S. R. Gough ◽  
J. A. Ripmeester
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperatures ◽  
Proton Nmr ◽  
Clathrate Hydrates ◽  
Type Ii ◽  
Methyl Group ◽  
Line Shapes ◽  
Dielectric Absorption

Sub-MHz dielectric absorption at low temperatures is used to demonstrate the formation by acetaldehyde and propionaldehyde of unstable clathrate hydrates, probably of type II. This result is supported by the proton nmr line shapes of propionaldehyde enclathrated in D2O, which also show fast rotational tunnelling of the methyl group at 4 K.

scholarly journals Transport Characteristics of Fujifilm Ion-Exchange Membranes as Compared to Homogeneous Membranes АМХ and СМХ and to Heterogeneous Membranes MK-40 and MA-41

Membranes ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 84 ◽  
Author(s):  
Sarapulova ◽  
Shkorkina ◽  
Mareev ◽  
Pismenskaya ◽  
Kononenko ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Volume Fraction ◽  
Transport Numbers ◽  
Type I ◽  
Type Ii ◽  
Ion Exchange Membranes ◽  
Electrospinning Method ◽  
Microheterogeneous Model ◽  
First Time

Ion-exchange membranes (IEMs) find more and more applications; the success of an application depends on the properties of the membranes selected for its realization. For the first time, the results of a comprehensive characterization of the transport properties of IEMs from three manufactures (Astom, Japan; Shchekinoazot, Russia; and Fujifilm, The Netherlands) are reported. Our own and literature data are presented and analyzed using the microheterogeneous model. Homogeneous Neosepta AMX and CMX (Astom), heterogeneous MA-41 and MK-40 (Shchekinoazot), and AEM Type-I, AEM Type-II, AEM Type-X, as well as CEM Type-I, CEM Type-II, and CEM Type-X produced by the electrospinning method (Fujifim) were studied. The concentration dependencies of the conductivity, diffusion permeability, as well as the real and apparent ion transport numbers in these membranes were measured. The counterion transport number characterizing the membrane permselectivity increases in the following order: CEM Type-I MA-41 < AEM Type-I < MK-40<CMX CEM Type-II CEM Type-X AEM Type-II < AMX < AEM Type-X. It is shown that the properties of the AEM Type-I and CEM Type-I membranes are close to those of the heterogeneous MA-41 and MK-40 membranes, while the properties of Fujifilm Type-II and Type-X membranes are close to those of the homogeneous AMX and CMX membranes. This difference is related to the fact that the Type-I membranes have a relatively high parameter f2, the volume fraction of the electroneutral solution filling the intergel spaces. This high value is apparently due to the open-ended pores, formed by the reinforcing fabric filaments of the Type-I membranes, which protrude above the surface of these membranes.

scholarly journals A full characterization of the supermassive black hole in IRAS 09149–6206

2020 ◽  
Vol 499 (1) ◽  
pp. 1480-1498
Author(s):  
D J Walton ◽  
W N Alston ◽  
P Kosec ◽  
A C Fabian ◽  
L C Gallo ◽  
...  
Keyword(s):  
Black Hole ◽  
Broad Band ◽  
Seyfert Galaxy ◽  
Type I ◽  
Additional Absorption ◽  
X Ray ◽  
Full Characterization ◽  
Supermassive Black Hole ◽  
First Time

ABSTRACT We present new broad-band X-ray observations of the type-I Seyfert galaxy IRAS 09149–6206, taken in 2018 with XMM–Newton, NuSTAR, and Swift. The source is highly complex, showing a classic ‘warm’ X-ray absorber, additional absorption from highly ionized iron, strong relativistic reflection from the innermost accretion disc and further reprocessing by more distant material. By combining X-ray timing and spectroscopy, we have been able to fully characterize the supermassive black hole in this system, constraining both its mass and – for the first time – its spin. The mass is primarily determined by X-ray timing constraints on the break frequency seen in the power spectrum, and is found to be log [MBH/M⊙] = 8.0 ± 0.6 (1σ uncertainties). This is in good agreement with previous estimates based on the H α and H β line widths, and implies that IRAS 09149–6206 is radiating at close to (but still below) its Eddington luminosity. The spin is constrained via detailed modelling of the relativistic reflection, and is found to be $a^* = 0.94^{+0.02}_{-0.07}$ (90 per cent confidence), adding IRAS 09149–6206 to the growing list of radio-quiet active galactic nuclei (AGNs) that host rapidly rotating black holes. The outflow velocities of the various absorption components are all relatively modest (vout ≲ 0.03c), implying these are unlikely to drive significant galaxy-scale AGN feedback.

scholarly journals Adsorption and diffusion of H2 and CO on UiO-66: A Monte Carlo simulation study

2020 ◽  
Vol 11 (3) ◽  
pp. 217-222
Author(s):  
Negin Davoodian ◽  
Zahra Khoshbin
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Guest Molecule ◽  
Isosteric Heat ◽  
Simulation Method ◽  
Type I ◽  
Monte Carlo Simulation Study ◽  
Guest Molecules ◽  
Metal Organic ◽  
And Diffusion

Metal-organic frameworks (MOFs) are a new class of nanoporous materials that have attracted much attention for the adsorption of small molecules, due to the large size of the cavities. In this study, we investigate the adsorption and diffusion of hydrogen (H2) and carbon monoxide (CO) guest molecules to the UiO-66 framework, as one of the most widely used MOFs, by using Monte Carlo simulation method. The results prove that an increment in the temperature decreases the amount of the adsorbed H2 and CO on the UiO-66 framework. While an enhancement of the pressure increases the amount of the adsorbed H2 and CO on the UiO-66 framework. Besides, the adsorption of H2 and CO on UiO-66 is the type I isotherm. The calculated isosteric heat for CO/UiO-66 is slightly higher than that of H2/UiO-66. The means of square displacement (MSD) value is less for CO molecule; hence, the movement of the guest molecule within the host cavity slows down and the guest molecule travels a shorter distance over a period of time. The guest molecule with higher molecular mass possesses less mobility, and therefore, it will have less permeability.

IMMOBILIZATION AND CHARACTERIZATION OF AN ARTIFICIALLY ASSEMBLED TRI-STRAND β-SHEET STRUCTURE ON A RIGID Au(111) SURFACE

2006 ◽  
Vol 05 (06) ◽  
pp. 803-808
Author(s):  
WONBAE LEE ◽  
JUN CHUN ◽  
YOON KYUNG CHANG ◽  
YOUNG KWAN LIM ◽  
CHEON-GYU CHO ◽  
...  
Keyword(s):  
Guest Molecule ◽  
Rigid Surface ◽  
Guest Molecules ◽  
Binding Characteristics ◽  
Host Molecules ◽  
Nmr Study ◽  
Before And After ◽  
Β Sheet ◽  
Stm Images

We designed and synthesized diurea type host molecules for the recognition of the tri-peptide guest molecule through the artificial formation of three-strand β-sheet structures on a rigid surface. The immobilizations of those host molecules on Au (111) surface, and the insertion of the guest molecules into the corresponding sites of immobilized host molecules were successfully carried out. Their binding characteristics were monitored by analyzing STM images before and after the insertion of guest peptides, and the characterization of the insertion in bulk phase was accomplished by NMR study.

scholarly journals Niclosamide methanol solvate and niclosamide hydrate: structure, solvent inclusion mode and implications for properties

2014 ◽  
Vol 70 (8) ◽  
pp. 758-763 ◽  
Author(s):  
Bethany I. Harriss ◽  
Claire Wilson ◽  
Ivana Radosavljevic Evans
Keyword(s):  
Guest Molecule ◽  
Crystal Packing ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Consistent Picture ◽  
First Time ◽  
Facile Transformation

Structural studies have been carried out of two solid forms of niclosamide [5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide, NCL], a widely used anthelmintic drug, namely niclosamide methanol monosolvate, C13H8Cl2N2O4·CH3OH or NCL·MeOH, and niclosamide monohydrate, denoted HA. The structure of the methanol solvate obtained from single-crystal X-ray diffraction is reported for the first time, elucidating the key host–guest hydrogen-bonding interactions which lead to solvate formation. The essentially planar NCL host molecules interactviaπ-stacking and pack in a herringbone-type arrangement, giving rise to channels along the crystallographicaaxis in which the methanol guest molecules are located. The methanol and NCL molecules interactviashort O—H...O hydrogen bonds. Laboratory powder X-ray diffraction (PXRD) measurements reveal that the initially phase-pure NCL·MeOH solvate readily transforms into NCL monohydrate within hours under ambient conditions. PXRD further suggests that the NCL monohydrate, HA, is isostructural with the NCL·MeOH solvate. This is consistent with the facile transformation of the methanol solvate into the hydrate when stored in air. The crystal packing and the topology of guest-molecule inclusion are compared with those of other NCL solvates for which the crystal structures are known, giving a consistent picture which correlates well with known experimentally observed desolvation properties.

1,4-Dioxane Hydrate: Dielectric Absorption by a Nondipolar Enclathrated Molecule

1975 ◽  
Vol 53 (15) ◽  
pp. 2217-2222 ◽  
Author(s):  
S. R. Gough ◽  
J. A. Ripmeester ◽  
D. W. Davidson
Keyword(s):  
Continuous Wave ◽  
Effective Activation Energy ◽  
Water Molecules ◽  
Effective Activation ◽  
Large Structure ◽  
Total Dipole Moment ◽  
Guest Molecules ◽  
X Ray ◽  
Dielectric Absorption ◽  
Relaxation Studies

X-Ray, continuous-wave and pulsed n.m.r., and dielectric relaxation studies show the hydrate of 1,4-dioxane (D) to be a normal clathrate hydrate of von Stackelberg's structure II with composition D·∼17H2O. The reorientation rate of the relatively large D molecule is slower and the effective activation energy(l.6 kcal/mol) larger than for other guest molecules previously studied in hydrates of the same structure. Weak dielectric absorption associated with reorientation of nondipolar D molecules is attributed mainly to the induction of a total dipole moment of ∼0.2 D in the 28 water molecules of the large structure II cage by two equal and opposed dipoles in the chair form of D.

TBE in Sweden

2020 ◽  
Keyword(s):  
Genetic Characterization ◽  
Immunoglobulin M ◽  
Enzyme Linked Immunosorbent Assay ◽  
Second Phase ◽  
Serum Samples ◽  
Tick Borne Encephalitis ◽  
Specific Immunoglobulin ◽  
Tick Borne Encephalitis Virus ◽  
First Time

Tick-borne encephalitis virus (TBEV) was isolated for the first time in Sweden in 1958 (from ticks and from 1 tick-borne encephalitis [TBE] patient).1 In 2003, Haglund and colleagues reported the isolation and antigenic and genetic characterization of 14 TBEV strains from Swedish patients (samples collected 1991–1994).2 The first serum sample, from which TBEV was isolated, was obtained 2–10 days after onset of disease and found to be negative for anti-TBEV immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA), whereas TBEV-specific IgM (and TBEV-specific immunoglobulin G/cerebrospinal fluid [IgG/CSF] activity) was demonstrated in later serum samples taken during the second phase of the disease.

Incorporation of Multi Wall Carbon Nanotubes into Glass-Surfaces via Laser-Treatment

2003 ◽  
Vol 772 ◽  
Author(s):  
T. Seeger ◽  
G. de la Fuente ◽  
W.K. Maser ◽  
A.M. Benito ◽  
A. Righi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Continuous Wave ◽  
Silica Surface ◽  
Multi Wall Carbon Nanotubes ◽  
Composite Formation ◽  
Multi Walled Carbon Nanotubes ◽  
Glass Surfaces ◽  
Walled Carbon Nanotubes ◽  
First Time ◽  
Scanning Electron

AbstractCarbon nanotubes (CNT) are interesting candidates for the reinforcement in robust composites and for conducting fillers in polymers due to their fascinating electronic and mechanical properties. For the first time, we report the incorporation of multi walled carbon nanotubes (MWNTs) into silica-glass surfaces by means of partial surface-melting caused by a continuous wave Nd:YAG laser. MWNTs were detected being well incorporated in the silica-surface. The composites are characterized using scanning electron microscopy (SEM) and Raman-spectroscopy. A model for the composite-formation is proposed based on heatabsorption by MWNTs and a partial melting of the silica-surface.

Chemical Constituents and Antibacterial Activity of Cissus Aralioides.

2020 ◽  
Vol 17 ◽  
Author(s):  
Balogun Olaoye Solomon ◽  
Ajayi Olukayode Solomon ◽  
Owolabi Temitayo Abidemi ◽  
Oladimeji Abdulkarbir Oladele ◽  
Liu Zhiqiang
Keyword(s):  
Plant Extract ◽  
Chemical Constituents ◽  
Ethyl Acetate Fraction ◽  
Antibacterial Activities ◽  
Sub Saharan Africa ◽  
Chromatographic Purification ◽  
Whole Plant ◽  
Sub Saharan ◽  
First Time

: Cissus aralioides is a medicinal plant used in sub-Saharan Africa for treatment of infectious diseases; however the chemical constituents of the plant have not been investigated. Thus, in this study, attempt was made at identifying predominant phytochemical constituents of the plant through chromatographic purification and silylation of the plant extract, and subsequent characterization using spectroscopic and GC-MS techniques. The minimum inhibitory concentration (MICs) for the antibacterial activities of the plant extract, chromatographic fractions and isolated compounds were also examined. Chromatographic purification of the ethyl acetate fraction from the whole plant afforded three compounds: β-sitosterol (1), stigmasterol (2) and friedelin (3). The phytosterols (1 and 2) were obtained together as a mixture. The GC-MS analysis of silylated extract indicated alcohols, fatty acids and sugars as predominant classes, with composition of 24.62, 36.90 and 26.52% respectively. Results of MICs indicated that friedelin and other chromatographic fractions had values (0.0626-1.0 mg/mL) comparable with the standard antibiotics used. Characterization of natural products from C. aralioides is being reported for the first time in this study.

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