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Biomedical subjects

F Deng

Publications and source records attributed to F Deng.

44 records · Page 3Linked to original sources
PubMed1995

Off-resonance effects on 2D NMR nutation spectra of I = 3/2 quadrupolar nuclei in static samples.

The off-resonance effects on 2D NMR nutation of I = 3/2 quadrupolar nuclei are demonstrated with perturbation theory and numerical calculation in static samples. The off-resonant (delta omega) rf field (omega 1) enlarges a nutation frequency and consequently increases the measurement range of nuclear quadrupolar interaction parameters. When omega e > omega Qmax, and arctg(omega 1/delta omega) = +/- 54.7 degrees (magic angle), the satellite lines (produced by coherence transfers) in a nutation spectrum are superimposed with the line of central transition, and hence the nutation spectrum is simplified and its sensitivity is enhanced. The nuclear quadrupolar interaction parameters of 23Na nuclei in Na omega molecular sieve are obtained using 2D NMR nutation.

Magnetic Resonance Spectroscopy↗
PubMed1995

[Transscleral suture fixation of posterior chamber intraocular lenses].

PURPOSE: To determine the effects of posterior chamber intraocular lens implantation in patients with ruptured capsules of after intracapsules cataract extraction. METHODS: Using transscleral suture fixation, posterior chamber intraocular lenses were implanted in 23 eyes (23 cases), including 13 eyes after intracapsular cataract extraction and 10 eyes with ruptured capsules due to complicated extracapsular cataract extraction or traumatic cataract. RESULTS: All the patients obtained satisfactory visual acuities of 20/40 or better. Few complications were observed in the follow-up period of 3 to 16 months. CONCLUSIONS: This technique makes it possible for almost all eyes after cataract extraction to be implanted posterior chamber intraocular lens.

Adult↗
PubMed1994

[Bacteriological detection of anterior chamber aspirate after extracapsular cataract extraction with intraocular lens implantation].

We cultured the anterior chamber aspirates of 83 patients with extracapsular cataract extraction and IOL implantation. Of the 83 cases, 5 (6.1%) had positive aspirates including 3 cases of staphylococcus epidermidis and 2 cases of staphylococcus aureus. No eye in our study developed bacterial endophthalmitis. Our study suggests that the anterior chamber of human eyes is capable of clearing a low inoculum of bacteria after cataract surgery without the development of bacterial endophthalmitis.

Aged↗
PubMed1993

Adsorption of Na+ onto gamma-alumina studied by solid-state 23Na and 27Al nuclear magnetic resonance spectroscopy.

The adsorption of Na+ on gamma-alumina surfaces at four coverages of Na2CO3[5, 10, 15 and 20% w/w)] was characterized by solid-state 23Na and 27Al nuclear magnetic resonance (NMR) spectroscopy. The experimental results suggest that two distinct adsorbed species are present on the alumina surface: surface species and surface salts. At the lower coverages of Na2CO3 (5 and 10%), the surface species is predominant, in which the Na+ cations are associated with the oxygen atoms of gamma-alumina. Increasing the loading level to 15% results in the appearance of a second adsorbed species that is attributed to the surface salt, Na2CO3, deposited on the solid surface. Further adsorption of Na2CO3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. 1H-27Al Cross-polarization magic angle spinning (CP-MAS) experiments give the evidence that some Na+ cations in the form of surface species are coordinated with the Brönsted acid sites of gamma-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of an Na2CO3-Al2O3 catalyst.

Adsorption↗
PubMed1993

Solid-state NMR studies of 1H spin diffusion in adsorbed organic molecules.

1H spin diffusion times of toluene (MB) and tetrahydrofuran (THF) adsorbed on a series of porous solids (charcoal, SiO2 and Al2O3) were measured by a selective inversion technique. The experimental results show that they cover a wide range (from less than one millisecond to several hundreds of milliseconds). For all samples, a tri-exponential behavior was observed in the magnetization recovery processes of the negative peaks. This is attributed to the existence of the two different kinds of spin diffusion processes in addition to the T1 relaxation. One is assigned to the intermolecular spin diffusion between the surface acidic protons of the adsorbent and the organic molecules adsorbed on the solid surface, the other to the intramolecular spin diffusion of adsorbed molecules. Due to hydrogen bonding between the surface hydroxyl groups and the adsorbate, the intermolecular spin diffusion of THF adsorbed on various solids is more effective compared to that of adsorbed MB. In addition, the intermolecular 1H spin diffusion between charcoal and adsorbed THF molecules was confirmed by indirect measurement suggested by Tekely et al.

Charcoal↗
PubMedDate not supplied

Ring-opening bulk polymerization of epsilon-caprolactone and trimethylene carbonate catalyzed by lipase Novozym 435.

The affects of lipase concentration on ring-opening bulk polymerizations of epsilon-caprolactone and trimethylene carbonate were studied by using Novozym 435 (immobilized form of lipase B from Candida antarctica) as biocatalyst. The polymerization of epsilon-caprolactone was carried out in bulk at 70 degrees C. Three lipase concentrations of 9.77, 1.80 and 0.50 mg/mmol epsilon-CL were used in the experiment. The results showed that increasing the lipase concentration used in the polymerization system resulted in an increased rate of monomer consumption. For an enzyme concentration of 9.8 mg lipase per mmol monomer, an 80% monomer conversion was achieved in a 4-h time period, while for the lower enzyme concentration of 1.8 mg lipase per mmol monomer, 48 h were needed to reach monomer conversion. Linear relationships between Mn and monomer conversions were observed in all three enzyme concentrations, suggesting that the product molecular weight may be controlled by the stoichiometry of the reactants for these systems. At the same monomer conversion level, however, Mn decreased with increasing enzyme concentration. After correcting for the amount of monomer consumed in initiation, the plot of ln[([M]o - [M]i)/([Mt] - [M]i)] versus reaction time was found to be linear, suggesting that the monomer consumption followed a first-order rate law and no chain termination occurred. For the TMC systems, the polymerization was carried out in bulk at 55 degrees C. Similar to the epsilon-CL systems, increasing the Novozym 435 concentration from 8.3 to 23.6 mg/mmol TMC increased the rate of monomer conversion. Unlike the epsilon-CL systems, however, nonlinear relationships were obtained between Mn and monomer conversion, indicating that possible chain transfer and/or slow initiation had taken place in these systems. Consistent with the above result, nonlinear behavior was observed for the plot of ln[[M]o/[M]t] versus reaction time.

Candida↗