Structure of Thermally Modified Wood Studied by Liquid State NMR Measurements

Holzforschung ◽  
2002 ◽  
Vol 56 (5) ◽  
pp. 522-528 ◽  
Author(s):  
S. Hietala ◽  
S. L. Maunu ◽  
F. Sundholm ◽  
S. Jämsä ◽  
P. Viitaniemi
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Spectroscopic Techniques ◽  
H Nmr ◽  
Yield Information ◽  
Cell Dimensions ◽  
Relaxation Measurements ◽  
Nmr Methods ◽  
Thermally Modified Wood ◽  
Pfg Nmr

Summary Thermal modification is a technique to produce wood with increased dimensional stability and lower equilibrium moisture content. 2H NMR relaxation measurements and pulsed field gradient (PFG-NMR) methods are non-invasive spectroscopic techniques that can be used to measure the response of liquid confined in porous materials and yield information on the size and distribution of the pores. These methods were used to study the structure and changes in structure of thermally modified Scots pine wood. The 2H longitudinal relaxation measurements of wood samples at different moisture contents showed different relaxation times and relaxation time distribution in the thermally treated samples. The effect of the thermal treatments on the cell size in wood samples was studied by PFG-NMR measurements with different dwell times. The PFG-NMR measurements showed no clear change in the cell dimensions of the thermally modified samples compared with control samples taken from the same log.

Surface Rotational Dynamics of Liquids Confined in Nanopores

1996 ◽  
Vol 464 ◽  
Author(s):  
J.-P. Korb ◽  
L. Malier ◽  
F. Cros ◽  
Shu Xu ◽  
J. Jonas
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Rotational Dynamics ◽  
Surface Relaxation ◽  
Nanoporous Silica ◽  
Silica Glasses ◽  
H Nmr ◽  
Fast Exchange ◽  
Nmr Relaxation Times ◽  
Different Time Scales

ABSTRACT2H NMR relaxation times of selectively deuterated polar molecules confined to a set of calibrated nanoporous silica glasses are reported. These experiments, combined with the consideration of different time scales in the theory of surface relaxation, show how confinement effects can provide detailed information on the rotational dynamics of temporarily adsorbed liquid layers in presence of biphasic fast exchange.

scholarly journals Developing NMR methods for macromolecular machines: Measurement of residual dipolar couplings to probe dynamic regions of the ribosome

2018 ◽  
Author(s):  
Xiaolin Wang ◽  
John P. Kirkpatrick ◽  
Hélène M. M. Launay ◽  
Alfonso de Simone ◽  
Daniel Häussinger ◽  
...  
Keyword(s):  
Residual Dipolar Couplings ◽  
3D Structure ◽  
Nmr Relaxation ◽  
Dipolar Couplings ◽  
Functional Regions ◽  
Chain Complexes ◽  
Relaxation Measurements ◽  
Nascent Chain ◽  
Dynamic Regions ◽  
Nmr Methods

ABSTRACTWe describe an NMR approach based on the measurement of residual dipolar couplings (RDCs) to probe the structural and motional properties of the dynamic regions of the ribosome. Alignment of intact 70S ribosomes in filamentous bacteriophage enabled measurement of RDCs in the stalk protein bL12, and this information was used to refine a 3D structure of its C-terminal domain (CTD). Orientational constraints on the CTD alignment arising from the semiflexible linker sequence were further probed by a paramagnetic alignment strategy, and provided direct experimental validation of a structural ensemble previously derived from SAXS and NMR relaxation measurements. Our results demonstrate the prospect of better characterising dynamical and functional regions of more challenging macromolecular machines and systems, for example ribosome–nascent chain complexes.

A study of aqueous sodium cholate by 2H nmr

1981 ◽  
Vol 59 (11) ◽  
pp. 1602-1606 ◽  
Author(s):  
William B. Smith ◽  
Gareth D. Barnard
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Sodium Cholate ◽  
2H Nmr ◽  
Hydrogen Bonding Interaction ◽  
Aqueous Sodium ◽  
H Nmr ◽  
Tetramer Formation ◽  
Bonding Interaction ◽  
Nmr Relaxation Times

Solutions of aqueous sodium 7-2H-cholate have been studied as a function of cholate concentration by 2H nmr. Relaxation times and solution viscosities have been used to show that cholate is monomeric in solution at 0.1 M. Increasing concentration leads to tetramer formation which is complete at 0.1 M. The tetramer solutions are stable up to 55 °C. Solutions of cholate in aqueous pyridine also form tetramers in the same fashion. Evidence was found, however, for a weak hydrogen bonding interaction between the two.

Molecular Motion in Solid Tetramethylammonium Tetrafluoroborate

1992 ◽  
Vol 47 (6) ◽  
pp. 721-727 ◽  
Author(s):  
S. Torre ◽  
P. Ferloni
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Quadrupole Coupling Constant ◽  
Thermomechanical Analysis ◽  
Scanning Calorimetry ◽  
Disorder Phase Transition ◽  
H Nmr ◽  
Quadrupole Coupling ◽  
Nmr Relaxation Times

AbstractMeasurements of 11B and 1H NMR relaxation times, differential scanning calorimetry and thermomechanical analysis, carried out on polycrystalline (CH3)4 NBF4 from room temperature to about 100 K, have permitted to discuss the crystal dynamics of this salt and to analyze the nature of the phase transition occurring at ≈ 150 K. Moreover, by means of an evaluation of the 11B quadrupole coupling constant, information about the position of the F atoms has been obtained. An explanation of the NMR data in terms of an order-disorder phase transition involving the F- ions is given.

Structural Phase Transition and Molecular Motion of p-Chlorobenzamide as Studied by the Temperature Variations of 35Cl NQR Frequencies, Chlorine Nuclear Quadrupolar Relaxation Times, and 1H Magnetic Dipolar Relaxation Times

1986 ◽  
Vol 41 (1-2) ◽  
pp. 270-274 ◽  
Author(s):  
Atsushi Kubo ◽  
Ryuichi Ikeda ◽  
Daiyu Nakamura
Keyword(s):  
High Temperature ◽  
Structural Phase ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Slow Motion ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Dipolar Relaxation ◽  
H Nmr ◽  
Quadrupolar Relaxation

The temperature dependences of 35Cl NQR frequencies, 35Cl (37Cl) nuclear quadrupolar relaxation times (T1ClQ), 1H NMR absorption, and of 1H NMR relaxation times were observed for p-chlorobenzamide, p-ClC6H4CONH2 and its N-deuterated analog. The existence of three 35Cl NQR lines already reported was confirmed for the known low temperature phase below 316 K. A single sharp 35Cl NQR line was detected in the high temperature phase up to 447 K just below the melting point 451 K. At lower temperatures, three different 35Cl T1ClQ values attributable to the fluctuation of the electric field gradient due to rotational oscillation were observed. With increasing temperature, these T1ClQ decreased rapidly and yielded almost the same value immediately below Ttr suggesting the onset of a slow motion. The 1H T1, of the high temperature phase gave a T1, minim um and could be explained through the 180° flip motion of the phenyl ring with an activation energy o f 44 kJ mol-1.

scholarly journals NMR Relaxation Measurements on Complex Samples Based on Real-Time Pure Shift Techniques

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 473
Author(s):  
Xiaoqing Lin ◽  
Haolin Zhan ◽  
Hong Li ◽  
Yuqing Huang ◽  
Zhong Chen
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Relaxation Method ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Transverse Spin ◽  
Complex Samples ◽  
Relaxation Measurements

Longitudinal spin-lattice relaxation (T1) and transverse spin-spin relaxation (T2) reveal valuable information for studying molecular dynamics in NMR applications. Accurate relaxation measurements from conventional 1D proton spectra are generally subject to challenges of spectral congestion caused by J coupling splittings and spectral line broadenings due to magnetic field inhomogeneity. Here, we present an NMR relaxation method based on real-time pure shift techniques to overcome these two challenges and achieve accurate measurements of T1 and T2 relaxation times from complex samples that contain crowded NMR resonances even under inhomogeneous magnetic fields. Both theoretical analyses and detailed experiments are performed to demonstrate the effectiveness and ability of the proposed method for accurate relaxation measurements on complex samples and its practicability to non-ideal magnetic field conditions.

Monitoring the degradation of a thermally aged EPDM terpolymer by 1 H NMR relaxation measurements of solvent swelled samples

Polymer ◽  
2002 ◽  
Vol 43 (4) ◽  
pp. 1349-1355 ◽  
Author(s):  
Roger A. Assink ◽  
Kenneth T. Gillen ◽  
Briana Sanderson
Keyword(s):  
Nmr Relaxation ◽  
H Nmr ◽  
Relaxation Measurements

scholarly journals Determination of Diethyl Phthalate and Polyhexamethylene Guanidine in Surrogate Alcohol from Russia

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Yulia B. Monakhova ◽  
Thomas Kuballa ◽  
Jenny Leitz ◽  
Dirk W. Lachenmeier
Keyword(s):  
Diethyl Phthalate ◽  
Rapid Screening ◽  
Multivariate Curve Resolution ◽  
Spectroscopic Techniques ◽  
Eosin Y ◽  
H Nmr ◽  
Polyhexamethylene Guanidine ◽  
Hawthorn Extract ◽  
Nmr Methods

Analytical methods based on spectroscopic techniques were developed and validated for the determination of diethyl phthalate (DEP) and polyhexamethylene guanidine (PHMG), which may occur in unrecorded alcohol. Analysis for PHMG was based on UV-VIS spectrophotometry after derivatization with Eosin Y and1H NMR spectroscopy of the DMSO extract. Analysis of DEP was performed with direct UV-VIS and1H NMR methods. Multivariate curve resolution and spectra computation methods were used to confirm the presence of PHMG and DEP in the investigated beverages. Of 22 analysed alcohol samples, two contained DEP or PHMG.1H NMR analysis also revealed the presence of signals of hawthorn extract in three medicinal alcohols used as surrogate alcohol. The simple and cheap UV-VIS methods can be used for rapid screening of surrogate alcohol samples for impurities, while1H NMR is recommended for specific confirmatory analysis if required.

The role of NMR in the study of partially ordered materials: Perspectives and challenges

2010 ◽  
Vol 83 (1) ◽  
pp. 67-94 ◽  
Author(s):  
Valentina Domenici
Keyword(s):  
Solid State ◽  
Liquid Crystalline ◽  
Pulse Sequences ◽  
Nmr Relaxation ◽  
Theoretical Models ◽  
Isotropic Phase ◽  
Partially Ordered ◽  
H Nmr ◽  
Fast Development ◽  
Nmr Methods

The development of NMR techniques applied in the last 10 years to partially oriented systems, and in particular to liquid crystals (LCs), is the object of this brief perspective. The evolution of NMR methods (i.e., new NMR pulse sequences) and the improvement of both theoretical models and mathematic tools for the analysis of NMR data (specifically, for partially ordered systems) allowed scientists to extend their research to increasingly complex materials, such as dendrimers, polymers, and membranes, and to investigate unique phenomena, such as field-induced alignment and confining effects. Furthermore, the fast development of nanoscience and biomedicine is offering a rich variety of new “physical chemical” problems related to partially ordered materials. Starting from a brief perspective of recent works on thermotropic and lyotropic LCs based on different NMR methods, new challenges in this field will be drawn. Moreover, recent selected research works will be discussed in detail with particular emphasis on: (i) the effect of high magnetic fields on the supramolecular structure of chiral liquid-crystalline phases, such as the SmC*, TGBA*, and “de Vries”-type SmA* phases, by means of solid-state 2H NMR; (ii) the slow dynamics in the isotropic phase of bent-core LCs (BLCs) and of liquid single-crystal elastomers evidenced by 2H NMR relaxation studies; and (iii) the influence of the LC environment on the conformational properties of rod-like mesogens studied by high-resolution solid-state 13C NMR methods. This work aims to offer an occasion of reflection on this field of physical chemistry with a glance at future trends and challenges in view of the celebration of the International Year of Chemistry, 2011.

Research of Calibration Curves NMR Relaxation Times of Nanoparticles Gadolinium Oxide

2014 ◽  
Vol 487 ◽  
pp. 94-97
Author(s):  
Chun Lin Yang ◽  
Mei Gui Ou ◽  
Jia Zeng ◽  
Xiu Qun Yang
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Gadolinium Oxide ◽  
Free Ions ◽  
Calibration Curves ◽  
Relaxation Measurements ◽  
Nmr Relaxation Times

In this paper, a method of assay based on NMR (Nuclear Magnetic Resonance) measurements was developed. A protocol for the dissolution of gadolinium oxide cores and calibration curves were established for Nanoparticles gadolinium oxide. After optimization this method was used for several applications such as checking the concentration in colloids after dialysis or controlling the concentration and the form (oxides or free ions) of lanthanides after in vivo injection. The Experiments showed the samples did not present any suspension or deposit after the dissolution treatment, The concentrations calculated from relaxation measurements are very close to the concentrations measured . According to measure relaxation times T1 and T2, we can approximately determinate the gadolinium concentration. .

Sign in / Sign up

Export Citation Format

Share Document