نتایج جستجو برای: nmr measurement
تعداد نتایج: 497834 فیلتر نتایج به سال:
Nuclear magnetic resonance (NMR) may be used for monitoring temperature changes within samples based on measurements of relaxation times, the diffusion coefficient of liquids, proton resonance frequency or phase shifts. Such methods may be extended to the explicit measurement of the thermal diffusivity of materials by NMR imaging. A method based on measuring nuclear spin phase shifts or changes...
Abstract Measurement of the liquid-solid mass transfer coefficient within a trickle bed (i.e. gas-liquid flow packed bed) porous silica pellets is achieved through use $${T}_{2}-{T}_{2}$$ T 2 - relaxation exchange nuclear magnetic...
BACKGROUND Gradient gel electrophoresis (GGE) and nuclear magnetic resonance (NMR) spectroscopy are both widely accepted methods for measuring LDL and HDL particle size. However, whether or not GGE- or NMR-measured LDL or HDL particle size predicts coronary heart disease (CHD) risk to a similar extent is currently unknown. METHODS We used GGE and NMR to measure LDL and HDL particle size in a ...
It is known that in the early stages of osteoarthritis (OA) the concentration of glycan proteins decreases in articular cartilage. This phenomenon is under active research to develop a means to characterise OA accurately in the early stages of the disease, when still reversible. However, no method of quantification has yet shown clear success in this area. In this paper we propose a novel appro...
We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesla and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely low ma...
Data sets that are acquired in many practical systems can be described as the output of a multidimensional linear separable-denominator system with Gaussian measurement noise. An important example is nuclear magnetic resonance (NMR) spectroscopy. In NMR spectroscopy, high-accuracy parameter estimation is of central importance. A classical result on the Cramér–Rao lower bound states that the inv...
Recently, some nondestructive methods for the assessment of albumen freshness were developed. Among others, visible near-infrared transmission spectroscopy and low-resolution proton nuclear magnetic resonance (LR (1)H NMR) measurements were proposed. This study was performed to evaluate the potential of the combined measurement of visible near-infrared transmission spectroscopy and LR (1)H NMR ...
From the ethyl acetate soluble fraction of twigs of Magnolia denudata (Magnoliaceae), seven new neolignan derivatives, 1-7, were isolated along with eighteen known lignan and neolignan derivatives, 8-25. The structures of the new neolignans were elucidated by means of spectral methods, especially by 1H-NMR and 13C-NMR spectra, and two dimensional NMR methods such as 1H-detected heteronuculear m...
Improvements in nuclear magnetic resonance (NMR) technology are generating an expanding variety of medical applications. In this investigation I have used high-field proton NMR to identify and quantity endogenous and ingested substances in human serum. After addition of a small amount of 2H2O and a reference compound to a 0.4-mL specimen, spectra were recorded for 3 min in Fourier-transform mod...
High-resolution NMR spectra under inhomogeneous fields via intermolecular double-quantum coherences.
High-resolution NMR spectroscopy is a powerful tool for analyzing molecular structures and compositions. Line-widths of conventional liquid NMR signals are directly proportional to the overall magnetic field inhomogeneity the sample experiences. In many circumstances, spatial and temporal homogeneity of the magnetic field is degraded. In this paper, a modified pulse sequence based on intermolec...
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