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Biomedical subjects

C F Wong

Publications and source records attributed to C F Wong.

At least 19 recordsLinked to original sources
PubMed1997

Fast measurements of transmission of erythema effective irradiance through clothing fabrics.

For efficiently measuring ultraviolet transmission through clothing materials for a large number of samples, an automated measuring system with a broad-band method has been built and calibrated against a spectroradiometer based instrument. The apparatus can be used to test 60 samples in 25 min. A selection of clothing materials of known composition, weave, color and state have been tested, using the broad band method and the automated measuring system together with a solar ultraviolet simulator. Variations of about eleven times for different weave structure, about two times in the ultraviolet transmittance for different colors, and about 20 times for some stretched samples were observed. For wet conditions, an increment in ultraviolet transmittance for cotton and lycra materials and a decrement for polyester and polyester(65%)/cotton(35%) were also observed.

Clothing↗
PubMed1997

Predicting helical segments in proteins by a helix-coil transition theory with parameters derived from a structural database of proteins.

A novel helix-coil transition theory has been developed. This new theory contains more types of interactions than similar theories developed earlier. The parameters of the models were obtained from a database of 351 nonhomologous proteins. No manual adjustment of the parameters was performed. The interaction parameters obtained in this manner were found to be physically meaningful, consistent with current understanding of helix stabilizing/destabilizing interactions. Novel insights into helix stabilizing/destabilizing interactions have also emerged from this analysis. The theory developed here worked well in sorting out helical residues from amino acid sequences. If the theory was forced to make prediction on every residue of a given amino acid sequence, its performance was the best among ten other secondary structural prediction algorithms in distinguishing helical residues from nonhelical ones. The theory worked even better if one only required it to make prediction on residues that were "predictable" (identifiable by the theory); > 90% predictive reliability could be achieved. The helical residues or segments identified by the helix-coil transition theory can be used as secondary structural contraints to speed up the prediction of the three-dimensional structure of a protein by reducing the dimension of a computational protein folding problem. Possible further improvements of this helix-coil transition theory are also discussed.

Algorithms↗
PubMed1996

Determination of 1-benzo[b]thien-2-ylethanone and related impurities by high performance liquid chromatography.

1-Benzo[b]thien-2-ylethanone (2-acetylbenzothiophene, 2-ABT) and related impurities were determined using a reverse-phase high performance liquid chromatography system and UV detection at 254 nm. Separation was achieved isocratically on a 4.6 mm x 25 cm, 5 microns Zorbax Rx-C8 column using an eluent which is 0.2% perchloric acid/THF in a ratio of 60:40 (v/v). The chromatographic system resolved 2-ABT and known impurities in less than 45 min with near baseline resolution. Known impurities were quantitated versus 2-ABT with corrections made for differences in detector response at the specified wavelength. Linearity for 2-ABT was demonstrated with a correlation coefficient > 0.9999. Assay precision (RSD values) for impurities at 0.5% ranged from +/- 1.8% to +/- 14%, while precision (RSD values) for the 2-ABT determination ranged from +/- 0.81% to +/- 1.1%. A variety of different chromatographic columns and conditions are discussed for the application.

Chromatography, High Pressure Liquid↗
PubMed1996

Oral fluconazole in the treatment of pulmonary cryptococcosis in non-AIDS patients.

Four non-AIDS patients with pulmonary cryptococcus infection who could not tolerate amphotericin B treatment were given oral fluconazole at a dose of 600 mg once daily for 4-5 weeks followed by 400 mg once daily for 10-12 weeks resulting in cure. All patients did not have relapse of disease when followed-up for 8-24 months after cessation of treatment. The very good tolerance of oral fluconazole by these patients suggests that such effective monotherapy should be evaluated further in non-AIDS patients with pulmonary cryptococcosis.

Adult↗
PubMed1996

Low-dose methotrexate in the management of Chinese patients with steroid-dependent asthma.

Nine Chinese patients with severe asthma who were dependent on a systemic oral steroid for control were given oral methotrexate at a dose of 7.5 mg on alternate days for two weeks, followed by 15 mg once weekly. Only six patients were evaluable; they had received methotrexate for 6 to 24 months. All six patients could have reduction of daily oral prednisolone dosage by 5-15 mg (mean: 10.4 mg). Only four patients, however, had > or = 15% improvement of their best peak expiratory flow rates compared with baseline levels, though all six patients had symptomatic improvement. These beneficial effects were, however, transient and persisted only during methotrexate therapy. Four patients had liver enzyme changes and discontinuation of therapy was required in one patient. One patient also had infective spondylitis secondary to Salmonella bacteremia. Thus low-dose oral methotrexate may be useful in selected patients with severe steroid-dependent asthma with careful monitoring for response and drug toxicity.

Adult↗
PubMed1995

Parametric sensitivity analysis of avian pancreatic polypeptide (APP).

Computer simulations utilizing a classical force field have been widely used to study biomolecular properties. It is important to identify the key force field parameters or structural groups controlling the molecular properties. In the present paper the sensitivity analysis method is applied to study how various partial charges and solvation parameters affect the equilibrium structure and free energy of avian pancreatic polypeptide (APP). The general shape of APP is characterized by its three principal moments of inertia. A molecular dynamics simulation of APP was carried out with the OPLS/Amber force field and a continuum model of solvation energy. The analysis pinpoints the parameters which have the largest (or smallest) impact on the protein equilibrium structure (i.e., the moments of inertia) or free energy. A display of the protein with its atoms colored according to their sensitivities illustrates the patterns of the interactions responsible for the protein stability. The results suggest that the electrostatic interactions play a more dominant role in protein stability than the part of the solvation effect modeled by the atomic solvation parameters.

Animals↗
PubMed1995

UV-B radiometry and dosimetry for solar measurements.

Biologically effective irradiance or dose of solar UV radiation was determined using a spectroradiometer, two broadband radiometers and two types of passive UV-dosimeters. The absolute erythema irradiance and the actinic irradiance were calculated from the solar spectrum measured with the spectroradiometer. It was demonstrated that the erythema irradiance is proportional to the actinic irradiance of solar radiation. The erythema irradiance was also determined using the two broadband radiometers which utilize a filter transmitting erythema spectra. Personal UV-dosimeters such as polysulphone and CR-39 were used to determine the erythema dose for a selected period of time. These results were used to estimate the accuracy of the broadband radiometers and UV-dosimeters. It was found that the results obtained from the broadband radiometers deviate from the absolute erythema irradiance by less than 20% during clear days between the hours of 11:00 and 13:00 Eastern Standard Time (EST) in Australia. The assessment of the erythema dose using passive dosimeters such as polysulphone and CR-39 could introduce an error as high as 40% if the calibration was not performed before undertaking experimental measurements.

Dose-Response Relationship, Radiation↗
PubMed1995

Ciprofloxacin in the management of pulmonary tuberculosis in the face of hepatic dysfunction.

Twenty-five patients who had extensive pulmonary tuberculosis and hepatitis induced by antituberculosis drugs were treated with ciprofloxacin together with other relatively non-hepatotoxic drugs, either during the interim phase awaiting recovery of liver function in some, or as definitive therapy as required by the compromised hepatic status of others. Only 22 patients were assessable. All tolerated ciprofloxacin well during the phase of hepatic dysfunction. All patients improved with these ciprofloxacin-containing regimens, but the optimal dosage, specific efficacy and long-term safety of the drug in such cases require further evaluation.

Adult↗
PubMed1995

Ethambutol-induced pulmonary infiltrates with eosinophilia and skin involvement.

A 67 year old woman presented with miliary tuberculosis. She was treated with streptomycin, isoniazid, rifampicin, ethambutol and pyrazinamide. However, she developed rifampicin-induced thrombocytopenia after 6 weeks of treatment, and skin rash, blood eosinophilia and pulmonary infiltrates after 8 weeks of therapy. The latter was found to be ethambutol related. Additional evidence, including blood and sputum eosinophilia and the rapidity of its response to corticosteroid, suggested that the pulmonary infiltrates might also be eosinophilic in nature. To the best of our knowledge, this constitutes the first report of such adverse drug reaction, induced by ethambutol.

Aged↗
PubMed1994

Measuring and modeling vocal source-tract interaction.

The quality of synthetic speech is affected by two factors: intelligibility and naturalness. At present, synthesized speech may be highly intelligible, but often sounds unnatural. Speech intelligibility depends on the synthesizer's ability to reproduce the formants, the formant bandwidths, and formant transitions, whereas speech naturalness is thought to depend on the excitation waveform characteristics for voiced and unvoiced sounds. Voiced sounds may be generated by a quasiperiodic train of glottal pulses of specified shape exciting the vocal tract filter. It is generally assumed that the glottal source and the vocal tract filter are linearly separable and do not interact. However, this assumption is often not valid, since it has been observed that appreciable source-tract interaction can occur in natural speech. Previous experiments in speech synthesis have demonstrated that the naturalness of synthetic speech does improve when source-tract interaction is simulated in the synthesis process. The purpose of this paper is two-fold: 1) to present an algorithm for automatically measuring source-tract interaction for voiced speech, and 2) to present a simple speech production model that incorporates source-tract interaction into the glottal source model. This glottal source model controls: 1) the skewness of the glottal pulse, and 2) the amount of the first formant ripple superimposed on the glottal pulse. A major application of the results of this paper is the modeling of vocal disorders.

Algorithms↗
PubMed1994

Scattered ultraviolet radiation underneath a shade-cloth.

Ultraviolet (UV) radiometers and polysulphone film badges were used to study scattered UV radiation from sunlight underneath a shade-cloth of a size about 70 x 100 cm2. The transmittance of erythemal UV radiation through the shade-cloth was found to be 0.14 +/- 0.03. The results of the measurements were used to derive the shade ratio, defined as the ratio of the erythema UV irradiance or dose in the shadow to that outside the shadow. It was found that the shade ratio is not the same as the transmittance. Its value depends on the height and the orientation of the irradiated object. For a horizontal detector, the shade ratio decreases by more than 20% as the detector height increased from 0.37 m to 1.36 m. At a height of 1.36 m, the shade ratio decreased by about 100% as the horizontal meter was rotated to the vertical direction. The value of the shade-ratio (0.11) approached the value of the transmittance (0.14) as the height (1.53 m) of the horizontal meter approached the height of the shade-cloth (1.7 m). Polysulphone film badges were attached to 10 sites on 2 identical manikins. One manikin was exposed at the centre of the shadow underneath the shade-cloth and the other was exposed in open area for four orientations in both Durham and Brisbane. The experiments performed in Durham were under an overcast sky and those performed in Brisbane were under a clear sky. The results showed that the shade ratio varied from site to site. The mean ratios of the facial dose in the shadow to that outside the shadow were found to be 0.70 +/- 0.1 and 0.35 +/- 0.10 for Durham and Brisbane measurements respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Environmental Exposure↗
PubMed1993

Correlation of serum ofloxacin concentration and serum creatinine level in patients on prolonged therapy.

Serum ofloxacin concentrations were assessed by high performance liquid chromatography 4 h after drug administration in 86 patients with pulmonary tuberculosis. All patients had multidose, once-daily drug administration (200 mg to 800 mg p.o.) for at least 3 weeks prior to assessment. The serum creatinine levels were simultaneously assessed for these patients. A positive correlation was found between serum ofloxacin (Y) and serum creatinine x dose of ofloxacin administered/body surface area (X). The correlation can be represented mathematically by the equation: Y = 0.87X + 0.68 (r = 0.80, p < 0.001).

Adolescent↗