Showing papers by "National Cheng Kung University published in 1992"

Cognitive development of Yu-Cheng ("oil disease") children prenatally exposed to heat-degraded PCBs.

Abstract: Objective. —To compare the cognitive development in Taiwanese children who had been exposed prenatally to high levels of heat-degraded polychlorinated biphenyls (PCBs) with control children who were exposed to background levels. The disorder was called Yu-Cheng, "oil disease," in Taiwan. Design. —Matched-pair cohort study. Setting. —Communities in central Taiwan in which there had been a cooking-oil contamination and mass poisoning by heat-degraded PCBs in 1978 through 1979. Participants. —One hundred eighteen children born between June 1978 and March 1985 during or after their mothers' consumption of contaminated rice oil; 118 children matched for age, sex, neighborhood, maternal age, and parental education and occupational class; and 15 older siblings of exposed children, born before the poisoning. Main Outcome Measures. —Cognitive development measured from 1985 through 1990 using the Chinese versions of the Stanford-Binet test and the Wechsler Intelligence Scale for Children, Revised. Results. —The exposed children scored approximately 5 points lower on the Stanford-Binet test at the ages of 4 and 5 years and approximately 5 points lower on the Wechsler Intelligence Scale for Children, Revised, at the ages of 6 and 7 years. Children born up to 6 years after their mothers' exposure were as affected as children born within a year or two after exposure when examined at 6 and 7 years of age. Older siblings resembled the control children. Conclusion. —Children prenatally exposed to heat-degraded PCBs had poorer cognitive development than their matched controls. The effect persisted in the children up to the age of 7 years, and children born long after the exposure were still affected. ( JAMA . 1992;268:3213-3218)

Vibrio vulnificus Infection in Taiwan: Report of 28 Cases and Review of Clinical Manifestations and Treatment

Abstract: From May 1985 through July 1990, 28 episodes of Vibrio vulnificus infection in 27 patients were encountered in five major hospitals in Taiwan. The ages of patients ranged from 19 to 76 years; the ratio of male to female patients was 2:1. Eighteen episodes manifested as bacteremia and eight as wound infections alone. One patient each developed gastroenteritis and pneumonia after nearly drowning. Twenty-three patients exhibited skin manifestations. Twenty patients had underlying diseases. All patients were treated with antibiotics, and 14 also underwent some form of surgical treatment (incision and drainage, fasciotomy, debridement, or amputation). Thirteen of the 28 episodes were preceded by precipitating factors; most were due to ingestion of seafood or exposure of abraded skin to salt water. Ten of the 18 septicemic patients died--most within 48 hours of hospitalization. One patient without bacteremia who had a wound infection died. Results of in vitro susceptibility studies suggested that ampicillin or a third-generation cephalosporin would be effective. Susceptibility to aminoglycosides was observed for greater than 90% of isolates. We recommend combined therapy with a third-generation cephalosporin or ampicillin and an aminoglycoside along with appropriate surgical therapy for the treatment of V. vulnificus infection.

Detection of HCV RNA in saliva, urine, seminal fluid, and ascites

Abstract: Approximately half of the patients with type C hepatitis do not have a history of parenteral exposure. The route of nonparenteral infection remains unknown. To evaluate the possible role of body fluids, the existence of hepatitis C virus (HCV) RNA in saliva, urine, seminal fluid, and ascites was examined by "nested" polymerase chain reaction (PCR). Amplification of the HCV 5' noncoding sequences was carried out. The amplified product was confirmed by Southern blot hybridization and restriction endonuclease digestion. Among 34 patients with chronic liver disease who were positive for anti-HCV and serum HCV RNA, the prevalence of HCV RNA in body fluids was 100% (7/7) in ascites, 48% (15/31) in saliva, 24% (4/17) in seminal fluid, and 7% (2/29) in urine. The body fluids collected from 3 healthy subjects and 5 patients with chronic liver disease who were positive for anti-HCV but negative for serum HCV RNA were all negative for HCV RNA. Hence, the potential infectivity of body fluids in patients testing negative for serum HCV RNA can probably be discounted. Conversely, the presence of HCV RNA in saliva and seminal fluid of patients positive for serum HCV RNA suggests sexual and household contact as likely modes of nonparenteral transmission of type C hepatitis. Furthermore, the high prevalence of HCV RNA in ascites and saliva may have important implications in medical and dental practice.

A fuzzy linear programming approach to the reactive power/voltage control problem

Abstract: The integration of traditional and heuristic techniques is considered for the reactive power/voltage control program. The steady-state reactive power problem is addressed. Fuzzy sets are used to modify the linear programming (LP) approach to voltage control and to incorporate some heuristic concepts of the expert system approach. Multiple objectives and soft constraints are modeled using fuzzy sets. Piecewise linear convex membership functions for the fuzzy sets are defined. Under this definition, the fuzzy optimization problem is reformulated as a standard linear programming problem. The objective function represents the compromise among the original competing objectives and the soft constraints. In addition, discrete constraints are considered. Numerical examples demonstrate the approach. >

Mapping Slope Failure Potential Using Fuzzy Sets

Abstract: This paper documents a low-cost, qualitative evaluation scheme using a fuzzy set analysis for mapping slope failure potential (SFP). Four categories of factors affecting stability of natural slopes, i.e., geology, topography, meteorology, and environment, are considered. Each category involves two to five factors, and a total of 13 factors is used in the proposed evaluation scheme. A set of evaluation criteria was established for each adopted factor. In the proposed evaluation scheme, slope failure potential is assessed and recorded in linguistic terms based on the established criteria. The linguistic data or information obtained from the assessments is represented and processed using fuzzy sets. In this study, the analysis or computation involving fuzzy sets was performed using the Monte Carlo simulation technique. An SFP index to measure the slope failure potential is defined. Based on the computed SFP values for a large number of subareas or cells selected for an area studied, an SFP map can be developed. An example application is presented to demonstrate the method. The SFP map developed in the case study seems to be able to correctly predict the slope failure potential of the area studied.

A direct Newton-Raphson economic dispatch

Abstract: The authors present a method to solve the real-time economic dispatch problem using an alternative Jacobian matrix considering system constraints. The transmission loss is approximately expressed in terms of generating powers and the generalized generation shift distribution factor. Based on this expression, a set of simultaneous equations of the Jacobian matrix are formulated and solved by the Newton-Raphson method. The proposed method eliminates the penalty factor calculation and solves the economic dispatch directly. The method resulted in a very fast solution speed and maintained good accuracy in test examples. It is a good approach to solve the economic dispatch problem. >

Forcing level effects of internal acoustic excitation on the improvement of airfoil performance

Abstract: The effects of internal acoustic excitation on the leading-edge, separated boundary layers and the aerodynamic performance of NACA 633-018 cross section airfoil are examined as a function of forcing level and forcing frequency of the introduced acoustics. Tests are separately conducted in two suction, open-typed wind tunnels at the Reynolds number of 3.0 x 10 s for the measurements and 1.0 x 10 4 for the visualization. Results indicate that the flow separation is delayed at the angles of attack higher than the stalled angle of small level excitation with the forcing frequency fe near the shear layer instability frequency ft. As the forcing level is increased to some extent, the velocity fluctuations around the slot exit are demonstrated to be the primary governing parameter for modifying the separated boundary layers. Data also show that the effective forcing frequency (and the Strouhal number, 50 extends over wider range as compared to the lower level excitation. Meanwhile, the pressure distributions on the airfoil surface exhibit recovery behaviors with different forcing frequencies. The corresponding boundary layers are visualized to be reattached to the surface to form a recirculation region when the airfoil is around at the stalled angles.

Inhibition of platelet activation and endothelial cell injury by polyphenolic compounds isolated from Lonicera japonica Thunb

Abstract: Effects of the polyphenolic compounds isolated from Lonicera japonica Thunb on platelet aggregation, platelet thromboxane biosynthesis and hydrogen peroxide-induced endothelial cell injury were studied. With regard to the inhibitory effect on human platelet aggregation, methyl caffeate, 3,4-di-O-caffeoylquinic acid and methyl 3,4-di-O-caffeoylquinate had a strong effect. They significantly inhibited the second wave of platelet aggregation induced by ADP. Concerning thromboxane biosynthesis triggered by calcium ionophore A23187 in platelets, methyl caffeate and methyl 3,4-di-O-caffeoylquinate had the most potent inhibitory effect. Methyl 3,4-di-O-caffeoylquinate directly inhibited the conversion of arachidonic acid to thromboxane by platelet microsomes, while methyl caffeate did not have any significant effect on thromboxane biosynthesis in platelet microsomes. In the prevention of hydrogen peroxide-induced endothelial cell injury in culture, protocatechuic acid, methyl caffeate, methyl chlorogenic acid and luteolin were significantly effective. The inhibitory effect on platelet activation and the cytoprotective effect on hydrogen peroxide-induced cell injury may explain the possible role of polyphenolic compounds isolated from Lonicera japonica Thunb in maintaining vascular homeostasis.

Clinical implications of left atrial spontaneous echo contrast in nonrheumatic atrial fibrillation.

Abstract: The prevalence and clinical significance of left atrial (LA) spontaneous echo contrast were investigated in 103 consecutive patients with chronic nonrheumatic atrial fibrillation (AF) using transesophageal echocardiography. LA spontaneous echo contrast was visualized in 25 of 103 patients (24.3%). Age, sex, LA diameter, left ventricular diastolic and systolic dimensions, left ventricular ejection fraction, and the percentage of lone AF were not significantly different between patients with and without LA spontaneous echo contrast; however, those with LA spontaneous echo contrast were less likely to have moderate or severe mitral regurgitation. LA thrombi were observed in 7 patients (6.8%), and all 7 thrombi were found in the atria with spontaneous echo contrast. History of cerebral ischemia or peripheral embolism, or both, was significantly more frequent in patients with than without LA spontaneous echo contrast (84 vs 18%; p less than 0.001). The presence of LA spontaneous echo contrast was highly specific (94%) and predictive for thromboembolic events (positive and negative predictive values of 84 and 82%, respectively). Thus, transesophageal echo-detected LA spontaneous echo contrast is frequently found in patients with chronic nonrheumatic AF. This phenomenon may represent a precursor of thrombus formation, and its presence is associated with an increased thromboembolic risk.

Transient response of a peak voltage detector for sinusoidal signals

Abstract: A fast peak detector for constant frequency sinusoidal signals is proposed. This detector is based on the concept of the orthogonal function set. The theoretical response time of this detector is less than one-fourth of a cycle. When this detector is used, the transient response of the output voltage is different under different inception angles. The mathematical equations to describe transient phenomena are derived and simulated. Because its transient response performance is superior to the conventional sinusoidal amplitude detector used in an analog controller, it can improve the transient response performance of the controller. For practical applications, the effects of harmonics and frequency variation are also discussed, simulated, and tested. >

Immunomodulatory activity of various fractions derived from Physalis angulata L extract.

Abstract: The immunomodulatory effects of Physalis angulata L. extract fraction VII (PA-VII), PA-VII-A, PA-VII-B and PA-VII-C were investigated in this study. The results showed that PA-VII and PA-VII-C strongly enhanced blastogenesis response, PA-VII-B had moderate activity, and PA-VII-A exerted only slight effect on cell proliferation. A synergistic effect was observed when the suboptimal dosage of phytohemagglutinin (PHA) or lipopolysaccharide (LPS) was added to the culture. Furthermore, PA-VII and PA-VII-C possessed stimulatory activity on B cells and less effect on T cells. The antibody responses were also augmented by PA-VII, PA-VII-B and PA-VII-C, but not by PA-VII-A. The enhancement of antibody response could be observed both in BALB/c and C3H/HeJ mice.

Nonleptonic weak decays of charmed baryons.

Abstract: Two-body nonleptonic weak decays of charmed baryons are analyzed in the framework of the pole model, which is more general and pertinent than current algebra since its use is not restricted to the soft meson limit and to the pseudoscalar-meson final state. The $s$-wave amplitudes are dominated by the ${\mathrm{\textonehalf{}}}^{\ensuremath{-}}$ baryon resonances. Special attention is paid to the parity-violating ${\mathrm{\textonehalf{}}}^{\ensuremath{-}}$-${\mathrm{\textonehalf{}}}^{+}$ baryon matrix elements, which are evaluated using the MIT bag model. For definiteness, we compute the $\ensuremath{\alpha}$ asymmetry parameter and the branching ratios for the decay modes ${\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\rightarrow}p{\overline{K}}^{0}({\overline{K}}^{*0})$, $\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}({\ensuremath{\rho}}^{+})$, ${\ensuremath{\Sigma}}^{0}{\ensuremath{\pi}}^{+}({\ensuremath{\rho}}^{+})$, ${\ensuremath{\Sigma}}^{+}{\ensuremath{\pi}}^{0}({\ensuremath{\rho}}^{0}),p\ensuremath{\varphi}$, and find a good agreement with experiment. We conclude that (i) there is no color suppression in ${\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\rightarrow}p{\overline{K}}^{0}({\overline{K}}^{*0})$ and $p\ensuremath{\varphi}$, (ii) nonspectator contributions are in general smaller than the factorizable ones for the decay modes which receive contributions from the factorizable diagram, and (iii) the predicted branching ratios will be too small if the wave functions of the heavy-quark bag model are employed. A comparison of our work with current algebra and other theoretical calculations is made.

Aqueous dispersions of polyurethane anionomers: Effects of countercation

Abstract: The influence of counterions on the properties of aqueous dispersions of polyurethane (PU) anionomer have been investigated. The PU anionomers were prepared by polyaddition reaction of 4,4′-methylenebis(phenylisocyanate) with poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA), and 1,4-butanediol, followed by neutralization of pendant COOH groups by various bases. Stable dispersions are obtained for PU anionomers containing 0.8–1.1 wt % COOH groups (17.8–24.4 mmol/100 g polymer) that have been neutralized by ammonia, trimethylamine, triethylamine, LiOH, NaOH, and KOH, respectively. It is found that average particle size is determined mainly by the zeta potential of the dispersions. The number-average diameter of the dispersions containing metal cations (Li-, Na-, and K-0.9) is between 60–73 nm (zetal potential −65 to −70 mV), while that of the dispersions containing ammonium cations (AMM-, TMA-, and TEA-0.9) is between 104–251 nm (zeta potential −47 to −64 mV). The surface tension of the dispersions decreases with concentration rapidly and levels off at concentrations higher than 20 mmol/L. The decreased decomposition temperature of the PU anionomers, compared to unionized PUs, can be attributed to the disordering of hard domains after ionization or decomposition reaction catalyzed by alkali metal carboxylates. The thermal decomposition proceeds mainly via cyclic elimination.

The role of extracellular matrix in peripheral nerve regeneration: a wound chamber study.

Abstract: A wound chamber model was used for the study of the interaction between axon, Schwann cell and extracellular matrix during peripheral nerve regeneration. Impermeable silicone tubes, 8 mm long and 1.4 mm in internal diameter were sutured to transected rat sciatic nerve and the contents of the tubes were removed at intervals for chemical, histological, immunocytochemical and electron microscopic studies. There was an initial phase of fluid accumulation and the formation of a fibrin/fibronectin clot or cable which connected the cut ends of the nerve. The chamber fluid was shown to have a protein profile similar to that of rat serum. Schwann cells, endothelial cells and fibroblasts migrated first into the cable, apparently mediated by cell-fibrin interaction. Axons buried within the Schwann cell cytoplasm were led into the cable but an axon-fibrin interaction was not observed. After 1 week, the fibrin matrix underwent dissolution, with replacement by collagen. This marked the onset of myelination and the organization of nerve fibers into fascicles. The findings from the present study suggest that the interactions between axon and Schwann cell and between Schwann cell and a changing extracellular matrix are the essential driving force in nerve growth and differentiation during peripheral nerve regeneration.

Buckling and postbuckling of delaminated composite sandwich beams

Abstract: The paper presents elastic buckling and postbuckling analysis of an axially loaded plate with an across-the-width delamination symmetrically located at the interface of the upper face and core. Since the plate undergoes cylindrical bending deformations on the postbuckling states for the cases considered, only one-dimensional formulations are employed.

Pressure-Based Multigrid Algorithm for Flow at All Speeds

Abstract: A full multigrid/full approximation storage (FMG/FAS) method is developed along with a unified pressurebased algorithm to handle the complex fluid flow problems encompassing both compressible and incompressible regimes. Besides highlighting the key elements of the present algorithm on a curvilinear staggered grid system, several flow problems, ranging from incompressible to hypersonic speeds, are computed, in conjunction with an adaptive grid method, to demonstrate its computational capability. With wide variations in geometry, fluid physics, and grid distribution, speedup between the single- and multigrid procedures can be obtained. Because different pressure boundary conditions are needed for incompressible, subsonic, and supersonic inlet and outlet, the number of grid levels that can be effectively used by the present multigrid method appears flow dependent; the implications of this observation are discussed. I. Introduction U SE of pressure correction methods for solving incompressible viscous flow problems in Cartesian or cylindrical coordinates is well established, and a number of methods of this type such as SIMPLE,1'2 SIMPLER,2 and PISO3 have been developed. The basic similarity of these methods is that the momentum equations are first solved using a guessed pressure field, resulting in a tentative velocity field. An equation for the pressure corrections is obtained via manipulation of the momentum and continuity equations. This equation is solved to obtain the pressure corrections, and the velocities are then corrected to satisfy the continuity equation. The extension of the SIMPLE algorithm to a general nonorthogonal curvilinear coordinate system has been described in Refs. 4-6 and has been successfully applied to various problems as documented in Ref. 6. When solving a viscous flow problem using a pressure-based method, the computer time required to solve the pressure (correction) equation is often a sizable fraction of the total computational effort.7'8 Van Doormaal and Raithby7 report that this fraction can be as high as 80% of the total CPU time. This observation is also qualitatively confirmed in Ref. 8, which finds that, for high Reynolds number flows, the pressure-correction equation requires many more sweeps of a point-symmetric successive over-relaxation (point-SSOR) or line-SSOR method to converge than either the momentum equation or other scalar transport equations. This is because the pressure-correction equation, which has the form of an anisotropic elliptic equation, is diffusion dominated, whereas the other equations are convection dominated. It is well known that point- and line-iterative methods converge rather slowly on elliptic problems such as the Poisson equation, particularly as the number of mesh points becomes large. To expedite the convergence rates, the multigrid (MG) method9'10 has been found to be very useful for improving the performance of these single-grid (SG) solvers for elliptic equations.

Estimation of cutting temperature in high speed machining

Abstract: This paper presents a study of the inverse heat conduction problem for high speed machining. A finite element method with an inverse scheme and an experimental measurement using infrared (IR) pyrometer with fiber optic are applied to predict the tool-chip interface temperature and the total heat dissipating to both tungsten carbide and ceramic inserts. A one-dimensional ellipsoidal mapping model of the cutting temperature distribution is adopted here and the average transient cutting temperature is calculated by the inverse finite element method with measured surface temperatures adjacent to the tool edge. Also the analysis of the errors coming from the sensor location and mapping model is studied. The results show the estimated cutting temperature is well convergent and agrees to other previous investigations. It is found that the thermal conductivity of the tool material has significant effect on the heat dissipation but little effect on the tool-chip interface temperature in high speed machining.