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121 results on '"Chang, D.-S."'

9. Cutaneous microvascular flow in the foot during simulated variable gravities

Author

Chang, D. S, Breit, G. A, Styf, J. R, and Hargens, A. R

Subjects
Life Sciences (General)
Abstract

Our objective was to understand how weight bearing with varying gravitational fields affects blood perfusion in the sole of the foot. Human subjects underwent whole body tilting at four angles: upright [1 gravitational vector from head to foot (Gz)], 22 degrees (0.38 Gz), 10 degrees (0.17 Gz), and supine (0 Gz), simulating the gravitational fields of Earth, Mars, Moon, and microgravity, respectively. Cutaneous capillary blood flow was monitored on the plantar surface of the heel by laser Doppler flowmetry while weight-bearing load was measured. At each tilt angle, subjects increased weight bearing on one foot in graded load increments of 1 kg beginning with zero. The weight bearing at which null flow first occurred was determined as the closing load. Subsequently, the weight bearing was reduced in reverse steps until blood flow returned (opening load). Mean closing loads for simulated Earth gravity, Mars gravity, Moon gravity, and microgravity were 9.1, 4.6, 4.4, and 3.6 kg, respectively. Mean opening loads were 7.9, 4.1, 3.5, and 3.1 kg, respectively. Mean arterial pressures in the foot (MAP(foot)) calculated for each simulated gravitational field were 192, 127, 106, and 87 mmHg, respectively. Closing load and opening load were significantly correlated with MAP(foot) (r =0.70, 0.72, respectively) and were significantly different (P < 0.001) from each other. The data suggest that decreased local arterial pressure in the foot lowers tolerance to external compression. Consequently, the human foot sole may be more prone to cutaneous ischemia during load bearing in microgravity than on Earth.

Published
1996

10. Ultrasound measurement of transcranial distance during head-down tilt

Author

Torikoshi, S, Wilson, M. H, Ballard, R. E, Watenpaugh, D. E, Murthy, G, Yost, W. T, Cantrell, J. H, Chang, D. S, and Hargens, A. R

Subjects
Aerospace Medicine
Abstract

Exposure to microgravity elevates blood pressure and flow in the head, which may increase intracranial volume (ICV) and intracranial pressure (ICP). Rhesus monkeys exposed to simulated microgravity in the form of 6 degree head-down tilt (HDT) experience elevated ICP. With humans, twenty-four hours of 6 degree HDT bed rest increases cerebral blood flow velocity relative to pre-HDT upright posture. Humans exposed to acute 6 degree HDT experiments increased ICP, measured with the tympanic membrane displacement (TMD) technique. Other studies suggest that increased ICP in humans and cats causes measurable cranial bone movement across the sagittal suture. Due to the slightly compliant nature of the cranium, elevation of the ICP will increase ICV and transcranial distance. Currently, several non-invasive approaches to monitor ICP are being investigated. Such techniques include TMD and modal analysis of the skull. TMD may not be reliable over a large range of ICP and neither method is capable of measuring the small changes in pressure. Ultrasound, however, may reliably measure small distance changes that accompany ICP fluctuations. The purpose of our study was to develop and evaluate an ultrasound technique to measure transcranial distance changes during HDT.

Published
1995

19. First neutral beam injection experiments on KSTAR tokamak

Author

Jeong, S. H., primary, Chang, D. H., additional, Kim, T. S., additional, In, S. R., additional, Lee, K. W., additional, Jin, J. T., additional, Chang, D. S., additional, Oh, B. H., additional, Bae, Y. S., additional, Kim, J. S., additional, Park, H. T., additional, Watanabe, K., additional, Inoue, T., additional, Kashiwagi, M., additional, Dairaku, M., additional, Tobari, H., additional, and Hanada, M., additional

Published
2012
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28. An ion optics study for KSTAR neutral beam injector development

Author

Kim, Jinchoon, primary, Chang, D. H., additional, Chang, D. S., additional, In, S. R., additional, Jeong, S. H., additional, Jin, J. T., additional, Jung, K. S., additional, Kim, B. Y., additional, Kim, T. S., additional, Lee, K. W., additional, Oh, B. H., additional, Seo, C. S., additional, Seo, M. S., additional, Song, W. S., additional, and Yoon, B. J., additional

Published
2008
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29. Embracing the High SMAS for Facial Rejuvenation.

Author

Eisenmann-Klein, Marita, Neuhann-Lorenz, Constance, Toth, B. A., and Chang, D. S.

Abstract

Operations centered on the superficial musculo-aponeurotic system (SMAS) have been the mainstay of facial rejuvenation procedures for nearly three decades. Since its initial description by Mitz and Peyronie in 1976 [6], the SMAS has been successfully used by plastic surgeons as the foundation for different face-lift techniques. Whether a SMAS lift or plication is performed, the basic principle of utilizing the SMAS to restore facial youth has withstood the test of time and has become a reliable technique to achieve facial rejuvenation. Despite the successful use of the SMAS, most plastic surgeons limit their dissection of the SMAS inferior to the zygomatic arch. These operations have not traditionally addressed the changes associated with mid-facial aging. The changes associated with mid-facial aging include: deepening of the nasolabial fold, descent of the malar fat pad with loss of malar prominence, descent of the lower eyelid skin below the orbital rim and deepening of the tear trough. These changes cannot be adequately addressed with an infra-zygomatic operation. [ABSTRACT FROM AUTHOR]

Published
2008
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33. Comparing approaches to screening for angle closure in older Chinese adults.

Author

Andrews, J, Chang, D S, Jiang, Y, He, M, Foster, P J, Munoz, B, Kashiwagi, K, and Friedman, D S

Subjects
*ANGLE-closure glaucoma, *CHINESE people, *OLDER people, *BLINDNESS, *GONIOSCOPY, *OPHTHALMOLOGY, ANTERIOR chamber of the eye surgery
Abstract

AimsPrimary angle-closure glaucoma is expected to account for nearly 50% of bilateral glaucoma blindness by 2020. This study was conducted to assess the performance of the scanning peripheral anterior chamber depth analyzer (SPAC) and limbal anterior chamber depth (LACD) as screening methods for angle closure.MethodsThis study assessed two clinical populations to compare SPAC, LACD, and gonioscopy: the Zhongshan Angle-closure Prevention Trial, from which 370 patients were eligible as closed-angle participants and the Liwan Eye Study, from which 72 patients were selected as open-angle controls. Eligible participants were assessed by SPAC, LACD, and gonioscopy.ResultsAngle status was defined by gonioscopy. Area under the receiver operating characteristic curve (AUROC) for SPAC was 0.92 (0.89-0.95) whereas AUROC for LACD was 0.94 (0.92-0.97). Using conventional cutoff points, sensitivity/specificity was 93.0%/70.8% for SPAC and 94.1%/87.5% for LACD. Sequential testing using both SPAC and LACD increased the specificity to 94.4% and decreased the sensitivity to 87.0%.ConclusionSPAC has significantly lower specificity than LACD measurement using conventional cutoffs but interpretation of the findings can be performed by modestly trained personnel. [ABSTRACT FROM AUTHOR]

Published
2012
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36. Influence of sodium perchlorate on thiourylene antithyroid drug accumulation in mice

Author

Connell, J. M. C., Ferguson, M. M., Chang, D. S. C., and Alexander, W. D.

Abstract

Radiolabelled [35S]propylthiouracil and [35S]methimazole were shown to accumulate in mouse thyroid gland in vivo, with maximal tissue/plasma ratios and maximal intrathyroidal levels of 35S-labelled drug being seen at the lowest dose of drug studied (0·1 μg/animal). Pretreatment with sodium perchlorate (10 mg) abolished iodide trapping by the thyroid and caused a fall in accumulation of both [35S]methimazole and [35S]propylthiouracil, although this effect was not seen at higher doses of drug, when tissue/plasma ratios approached unity. These data suggest that thiourylene antithyroid drug accumulation by the thyroid gland does not depend directly on the anion trap, and it is suggested that this accumulation might depend on subsequent intrathyroidal drug metabolism.

Published
1983
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37. Mice with genetic gamma-glutamyl transpeptidase deficiency exhibit glutathionuria, severe growth failure, reduced life spans, and infertility.

Author

Harding, C O, Williams, P, Wagner, E, Chang, D S, Wild, K, Colwell, R E, and Wolff, J A

Abstract

A mouse mutant with glutathionuria was discovered by screening for amino acidurias in the progeny of ethylnitrosourea-mutagenized mice. Total glutathione concentration was increased in both blood and urine but decreased in liver homogenates from affected mice. Glutathionuric mice exhibited lethargy, severe growth failure, shortened life spans and infertility. gamma-Glutamyl transpeptidase activity was deficient in kidney homogenates of glutathionuric mice. The glutathionuric phenotype in these mice is inherited as an autosomal recessive trait. This mouse mutant will be a useful animal model for the study of gamma-glutamyl transpeptidase physiology and glutathione metabolism.

Published
1997

39. Reliability of in vitro susceptibility tests for detecting coagulase-negative staphylococcal resistance to penicillinase-resistant semisynthetic penicillins

Author

Lowy, F D, Chang, D S, Aning, V, Williams, S, and Szilagyi, G

Abstract

The reliabilities of five in vitro susceptibility tests (agar dilution, broth microdilution, automated MS-2, Kirby-Bauer disk diffusion, and ability to grow on methicillin-containing agar) to predict the susceptibility of 204 coagulase-negative staphylococcal isolates to penicillinase-resistant semisynthetic penicillins were compared. There was wide variation in susceptibility, with results ranging from 86.3% susceptible by MS-2 to 38.2% by growth on methicillin-containing agar. The results of the broth dilution techniques, including the MS-2, were significantly different (P less than 0.02) from the remaining tests. Nafcillin disks were less effective (P less than 0.02) than oxacillin disks in predicting resistance. Kirby-Bauer oxacillin disks and the ability to grow on methicillin-containing agar were the most reliable predictors of resistance. The MS-2 did not reliably predict resistance.

Published
1983
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40. Cassegrain Reflector Sidelobe Reduction Study

Author

AEROSPACE CORP EL SEGUNDO CA ELECTRONICS RESEARCH LAB, King, H. E., Lazar, S., Berry, G. G., Dyson, H. B., Wales, W. S., Wysock, W. C., Chang, D. S., AEROSPACE CORP EL SEGUNDO CA ELECTRONICS RESEARCH LAB, King, H. E., Lazar, S., Berry, G. G., Dyson, H. B., Wales, W. S., Wysock, W. C., and Chang, D. S.

Abstract

This report presents the results of a 4-month study to reduce the sidelobe levels of a 38 GHz, 2 ft diameter Cassegrain reflector. Both partial and full circumferential shrouds were added to the main reflector. Various shielding techniques to reduce the horn and subreflector radiation characteristics were evaluated. Measured primary patterns for the various horn-subreflector combinations were used to compute the secondary reflector patterns to evaluate the sidelobe improvement. The computed patterns were compared with measured results. Keywords include: Cassegrain reflectors, Space frame radome, Horn-subreflector feed patterns, and Tunnel reflector antennas.

Published
1985

41. EHF Attenuation Derived from Emission Temperatures in Light Rain.

Author

AEROSPACE CORP EL SEGUNDO CA ELECTRONICS RESEARCH LAB, Shimabukuro,F I, Tavis,M T, Chang,D S, AEROSPACE CORP EL SEGUNDO CA ELECTRONICS RESEARCH LAB, Shimabukuro,F I, Tavis,M T, and Chang,D S

Abstract

Atmospheric emission measurements have routinely been used to determine the total attenuation on an earth-space path at the centimeter and millimeter wavelengths. In the presence of rain, scattering effects have to be taken into account at frequencies 20 GHz when one interprets emission data to derive the total attenuation. If one uses the radiometric relation to derive the attenuation, assuming an absorptive medium, one finds that the predicted attenuation underestimates the true attenuation. The reason for this the rain scatters more emission energy out of the direct ray path than into it. Calculations of the atmospheric emission temperature and attenuation in light-to-moderate rain at different frequencies and rain rates are performed, taking into account molecular absorption, and varying cloud cover and ground temperature. The results show that for typically encountered meteorological conditions, the radiometric formula can be used to derive the total attenuation ( 10 dB) from emission measurements with accuracies of the order less than 1 dB, provided that the empirical constant in the radiometric formula, dependent on the ambient temperature, is a function of frequency and ground temperature.

Published
1984

42. The Asymptotic Distribution of the Product Estimator.

Author

WISCONSIN UNIV-MADISON MATHEMATICS RESEARCH CENTER, Wu,C -F, Chang,D -S, WISCONSIN UNIV-MADISON MATHEMATICS RESEARCH CENTER, Wu,C -F, and Chang,D -S

Abstract

The exact formulas for the bias and variance of the product estimator under simple random sampling are given. Its asymptotic normality is rigorously established under weak and interpretable regularity conditions on the finite populations. No superpopulation model is assumed. Hajek's projection method is the key tool in our proofs. (Author)

Published
1981

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