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Biomedical subjects

K G Wang

Publications and source records attributed to K G Wang.

At least 19 recordsLinked to original sources
PubMed2006

Correlations and fluctuations in phase coarsening.

Three-dimensional phase coarsening at various volume fractions is simulated by employing multiparticle diffusion methods. The dynamic process of phase coarsening is visualized through a three-dimensional movie. The present study also characterizes interparticle spacings in polydispersed particle systems and clarifies the controversial mathematical expressions for interparticle spacings used in the literature for 30 years. Consequently, this study reveals spatial, temporal, and nearest-neighbor correlations in polydispersed particle systems. A new three-dimensional movie of a Voronoi network demonstrating these correlations is provided. Our simulation and experiments show that growth rates of individual particles deviate from those of the mean-field theory, which is caused by their differing local environments. Multiplicative noise provides a good basis to describe the stochastic nature of fluctuations during phase coarsening.

Journal Article↗
PubMed2004

Modeling and simulation for phase coarsening: a comparison with experiment.

The phase coarsening of precipitates is modeled in the framework of Debye-Hückel theory. The interactions observed among a population of precipitates dispersed throughout a matrix can be described by diffusion screening. The relationship between the maximum particle radius and the volume fraction of the phases is established, and the rate of coarsening is related to the volume fraction and the self-similar particle size distribution. We simulated the dynamics of late-stage phase separation using multiparticle diffusion methods. Experimental measurements on the rates of coarsening of delta(') ( Al3 Li) precipitates in binary Al-Li alloys are compared with our results using modeling and simulation. The theoretically predicted particle size distributions and the maximum radius expected for particles in the microstructure agree well with recent experimental results.

Journal Article↗
PubMed2003

Noise of microstructural environments in late-stage phase coarsening.

Multiparticle diffusion equations were modeled to simulate the dynamics of late-stage phase coarsening in the region of lower volume fractions. Local environmental information and particle interactions within each coarsening "locale" are included in our simulations. These studies reveal that locale fluctuations occur in the growth rates of particles due to their differing environments. Multiplicative noise provides a sound basis to describe locale fluctuation in late-stage coarsening. A Fokker-Planck equation for the particle size distribution and its asymptotic solution are obtained.

Journal Article↗
PubMed1999

Stroke complicating pregnancy and the puerperium.

BACKGROUND: The role of nonobstetric factors, such as stroke, in maternal mortality has become of increasing importance because maternal deaths resulting directly from obstetric causes are decreasing. Strokes contribute to high mortality and morbidity, and are severe complications during pregnancy and puerperium. The objective of this study was to investigate the maternal outcome of patients with complications of stroke during pregnancy and puerperium. The causes, incidence and essential management of stroke are also reviewed. METHODS: During the 10-year period from January, 1986, to January, 1996, women who suffered from stroke during pregnancy, or up to six weeks postpartum, and were discharged from our hospital were identified. Stroke was defined as the abrupt onset of a focal neurologic syndrome that consisted of hemorrhagic and ischemic central nervous system events. All were assessed using computerized tomography or magnetic resonance imaging. Neurologists reviewed each case from the medical records. RESULTS: Thirteen women who had had a stroke during pregnancy or puerperium were identified. Nine of these women had intracerebral hemorrhage and four had ischemic strokes. During this 10-year period, approximately 85,321 women gave birth at the Mackay Memorial Hospital, and the incidence of stroke was approximately 1 in 6,500 pregnancies. Among the nine cases of hemorrhagic strokes, three women had preeclampsia and one had gestational diabetes mellitus. Mortality from strokes was 38%, and 63% of survivors had residual neurologic deficits; 46% of the strokes occurred during the puerperium. CONCLUSIONS: Stroke during pregnancy and puerperium causes high mortality and morbidity. Early diagnosis and adequate treatment cannot be overemphasized, as prompt and proper management is beneficial for outcome. The same meticulous care provided during the antepartum and intrapartum periods should be continued into the puerperium.

Adult↗
PubMed1998

Accuracy of frozen section diagnosis in gynecology.

OBJECTIVE: A retrospective study was undertaken to evaluate the accuracy of frozen section diagnosis in gynecological surgery. METHODS: We compared the results of 792 consecutive gynecological frozen section diagnoses with their final diagnoses from January 1991 to June 1996. Slides for which the frozen section diagnosis was uncertain or incompatible with the final diagnosis were reviewed by an attending pathologist to determine the possible causes. RESULTS: A total of 299 ovarian, 390 lymph node, 56 uterine lesions, and 77 other tissue samples were obtained. The frozen section diagnosis was compatible with the final diagnosis in 97.5% of cases. The sensitivity for nonbenign lesions was 90.9%, and the specificity was 99.5%. There were no false positives or overestimated cases; 1.3% of cases were falsely negative, 0.4% underestimated the degree of malignancy, and 0.9% were uncertain. Possible causes for incompatible or uncertain frozen section diagnoses were analyzed. The accuracy of frozen section diagnoses for ovarian, lymph node, uterine, and other tissues was also evaluated. Frozen section was found to identify correctly 13 of 17 ovarian malignancies metastaic from other organs, 14 of 15 germ cell malignancies, and 3 of 4 dysgerminomas. The low sensitivity in ovarian borderline malignancy was due to the even lower sensitivity in its mucinous subgroup. The relationship between section numbers and accuracy of frozen section diagnosis in mucinous ovarian tumors was assessed. CONCLUSIONS: Frozen section diagnosis in gynecology is sufficiently accurate for clinical use, with a low false negative rate and an even lower false positive rate. Most incompatible frozen section diagnoses occurred in ovarian lesions, especially in mucinous ovarian tumors. Performing multiple sections (at least one section for every 10 cm in diameter) is recommended in the frozen section diagnosis of mucinous ovarian tumors.

Female↗
PubMed1998

Periurethral fat injection in the treatment of recurrent genuine stress incontinence.

PURPOSE: We evaluated the efficacy, safety and mechanism of periurethral fat injection in the treatment of recurrent genuine stress incontinence. MATERIALS AND METHODS: Periurethral fat injections were performed in 26 patients for the treatment of recurrent genuine stress incontinence. A complete urogynecological study, including a 1-hour pad test, urodynamic studies and chain urethrocystography were done in each case and were repeated at least 3 months after operation. Each patient was followed for at least 12 months. RESULTS: Of 26 patients 13 (50%) were dry after operation and 4 (15.4%) showed improvement and were satisfied with the results of the operation, giving a total success rate of 65.4%. There were 6 cases of immediate postoperative minor complications (23%). Average volume of injected fat was 14.8 +/- 4.8 cc, which did not affect the success rate. Preoperative and postoperative chain urethrocystographic values for bladder neck descent in reference to the pubosacral tip line showed no statistical difference between successfully and unsuccessfully treated groups. Urodynamic studies in all cases showed no differences relating to operation. However, minimal urethral resistance increased from 0.122 +/- 0.061 to 0.205 +/- 0.134 (p = 0.023) in the treatment success group. This change was not demonstrated in the treatment failure group. CONCLUSIONS: Periurethral fat injection for the treatment of recurrent genuine stress incontinence is a simple technique that works by the increment of urethral resistance. It has an acceptable success rate without financial outlay for the injected material.

Adipose Tissue↗
PubMed1998

Primary retroperitoneal liposarcoma mimicking ovarian cancer: a case report.

Primary retroperitoneal liposarcoma is a rare malignancy comprising about only 0.1% of all cancers. It produces nonspecific symptoms and is often extensive when diagnosed. In this report, we present a case of a 68-year-old female patient who had a 29-kg retroperitoneal liposarcoma. Her early symptoms--including vague digestive disturbances, increasing abdominal girth and an abdominal mass, and clinical examinations such as sonography and computed tomography scan led to a preoperative diagnosis of ovarian cancer, until surgical and pathologic confirmation. Gross, radical resection of the tumor was successfully performed, and provided the most effective primary therapeutic approach. Histopathology revealed a mixed-type liposarcoma, with metastasis to the appendix. A poor prognosis was expected. Postoperative periodic follow-up was started to monitor for early detection of recurrence.

Aged↗
PubMed1998

Impact of reverse end-diastolic flow velocity in umbilical artery on pregnancy outcome after the 28th gestational week.

BACKGROUND: The aim of this study was to discuss pregnancy outcome in chromosomally and structurally normal fetuses having reverse end-diastolic flow velocity (REDFV) on Doppler umbilical artery velocimetry (DUAV) in the third trimester. METHODS: DUAV was performed in the high risk pregnancy antepartum fetal surveillance. We excluded gestational age less than 28 weeks, multiple pregnancies, and chromosomal or congenital anomalies. Thirty cases were categorized as having REDFV The pregnancy outcome was investigated in these cases. RESULTS: There were three stillbirths and 12 neonatal deaths, resulting in a perinatal mortality rate of 50%. Twenty-eight patients (93.3%) had complications with preeclampsia (20 of severe degree and eight moderate). Cesarean section was performed on 24 patients (80%) due to acute fetal distress. The mean gestational age at delivery was 31.8+/-3.2 weeks. The mean diagnosis-to-delivery interval was 10+/-8.2 hours. The average birth weight was 970+/-270 gm, 28 (93.3%) were found to be below the 10th percentile of ideal birth weight. An umbilical artery pH less than 7.2 at delivery was found in 12 of 18 examined cases (66.7%). Twelve out of 15 placentae (80%) showed significant infarcts on pathological examination. All newborns (100%) needed admission to the neonatal intensive care unit. CONCLUSIONS: REDFV on DUAV represents an ominous and severe fetal condition with an adverse pregnancy outcome, especially in conditions associated with preeclampsia and/or intrauterine growth retardation. Intensive and frequent surveillance and aggressive management at the appropriate time would improve perinatal outcome.

Adult↗
PubMed1997

Cervical cancer in young women in Taiwan: prognosis is independent of papillomavirus or tumor cell type.

The objective of this study was to address the hypotheses that younger patients with cervical cancer have a uniquely worse clinical outcome and/or are more likely to have adverse tumor cell types or specific human papillomaviruses (HPV). Cases of stage Ib-IIa cervical cancer among women 35 years of age or younger (82) and over 35 (54) were analyzed and compared with respect to the following: (1) histologic type (squamous vs nonsquamous), (2) human papillomavirus (HPV) type via polymerase chain reaction, and (3) clinical parameters, including tumor size, nodal metastases, and recurrence/persistence. Patients 35 years of age or younger had a survival similar (71.2% vs 72.4%) to that of older women from the same institution. In the younger group, outcome was not correlated with the presence or absence of HPV or HPV type. Nonsquamous carcinomas, including adenocarcinoma and small cell carcinoma, were strongly associated with HPV18, were more prevalent in the younger group, and had a slightly higher risk of recurrence/persistence; however, these differences were not significant and 71% of the recurrences were squamous cell carcinomas. Thus, in young Taiwanese women with stage Ib-IIa cervical cancer, the majority of deaths cannot be attributed to a specific HPV type or unique tumor morphology.

Adult↗
PubMed1997

First report of distal obstructive uropathy and prune-belly syndrome in an infant with amniotic band syndrome.

We describe the first report of distal obstructive uropathy and prune-belly syndrome in an infant with amniotic band syndrome. Prenatal ultrasonographic examination in the third trimester revealed intermittent oligohydramnios, bilateral hydronephrosis, and megacystis. Postnatally, the infant was found to have a scalp defect, a skin pedicle, pseudosyndactyly and constriction rings on the hands, marked distention of the abdomen, a fibrous band attached to the proximal urethra causing urethral stricture, a swollen penile shaft, bilateral talipes equinovarus, and syndactyly of the feet. Multiple fibrous amniotic bands could be identified in the placenta. Our case shows that fetal distal obstructive uropathy can be associated with the congenital constriction band syndrome.

Adult↗
PubMed1997

Prospective comparison of laparoscopic and traditional colposuspensions in the treatment of genuine stress incontinence.

OBJECTIVE: To compare prospectively the results of laparoscopic and traditional colposuspensions in the treatment of genuine stress incontinence and to evaluate the efficacy, technique, and functional and anatomical changes after these two procedures. MATERIALS AND METHODS: Ninety-two patients with urodynamically proven genuine stress incontinence participated in this study, with 46 patients randomly allocated to laparoscopic colposuspension, and the other 46 patients to the traditional procedures. All patients had repeat studies at least 3 months after operation. RESULTS: The bladder neck position was significantly elevated after operation either at rest or during straining in both groups (all p < 0.001), but it was higher in the traditional group than the laparoscopy group during straining (p < 0.05). Comparison of urodynamics before and after operation in both groups showed significantly increased minimal urethral resistance and improved pressure transmission ratios at the proximal urethra (Q2). The blood loss was less in the laparoscopy group. The duration of bladder drainage after laparoscopic colposuspension was shorter, and was not affected by subsequent laparotomy. The operative time was almost the same. The success rate of the laparoscopy group was lower than that of the traditional group (80.4% vs. 95.6%, p = 0.044). The complication rates were 10.8% and 17.4% respectively. CONCLUSION: Laparoscopic colposuspension is an effective method for the treatment of GSI, as documented by anatomical and functional assessments. However, the success rate is still lower than for the traditional procedure.

Adult↗
PubMed1996

Prenatal diagnosis of partial monosomy 13q associated with occipital encephalocoele in a fetus.

The pre- and postnatal findings of a fetus with a de novo del(13)(pter-->q21:) and an occipital encephalocoele are described. Maternal serum alpha-fetoprotein (AFP) screening at 19 weeks' gestation demonstrated a high level of 2.5 multiples of the median (MOM) and ultrasonography at 27 weeks' gestation showed severe intrauterine growth retardation, cardiomegaly, an occipital encephalocoele, and a calvarial defect. Genetic amniocentesis revealed a karyotype of 46,XX,del(13)(pter-->q21:). The proband postnatally displayed additional abnormalities such as microphthalmia, hypertelorism, large low-set ears, and micrognathia. We discuss the association of central nervous system (CNS) malformations with 13q deletions and emphasize that pregnancies with neural tube defects warrant cytogenetic analysis, especially when additional fetal abnormalities and neonatal dysmorphism are observed.

Adult↗
PubMed1996

Treatment of cervical pregnancy with methotrexate.

OBJECTIVES: To review our experience with early ultrasonographic diagnosis and fertility-preserving complete medical treatment of cervical pregnancy. METHODS: From January 1989 to December 1994, 11 cases of cervical pregnancy diagnosed by ultrasonography and treated with methotrexate were evaluated. Patients were treated as follows: systemic administration of methotrexate with leucovorin rescue, a single dose of 50 mg of methotrexate intramuscular injection, or transvaginal ultrasonographically-guided intra-amniotic instillation of 50 mg of methotrexate. RESULTS: The mean age of these patients was 33.3 +/- 6.2 years and gestational age at diagnosis ranged from 32 to 73 days. The maximal serum beta-hCG measured was 135,000 mIU/ml, and the time required for return to normal levels ranged from 20 to 157 days. The ectopic gestation was successfully ablated in all cases, and none required hysterectomy. CONCLUSION: If a cervical pregnancy is present and diagnosed early, methotrexate treatment, administered either systemically or locally, is effective as the definitive therapy.

Adult↗
PubMed1996

Risk factors for preterm birth in an upper middle class Chinese population.

OBJECTIVE: To examine the risk factors associated with preterm birth in an upper middle class Chinese population. STUDY DESIGN: From March 1994 to February 1995, a total of 301 cases (gestational age between 20 and 37 weeks) and 656 controls (gestational age at or greater than 37 weeks) were recruited at Mackay Memorial Hospital, Taipei, Taiwan. Using a case-control study design, logistic regression was used to examine the relative significance of various risk factors associated with preterm birth. RESULTS: Age and educational level were identified as significant risk factors for preterm birth. Multiple pregnancies, fetal congenital anomalies, placenta previa or abruptio placentae, and preeclampsia were found to be strongly associated with preterm birth (crude odds ratios between 6.37 and 25.89); vaginal bleeding during or after the first trimester, prior history of preterm delivery, and two or more previous first trimester abortions were associated with preterm birth to a lesser extent (crude odds ratios between 1.67 and 2.9). The magnitude of the increased risk associated with these variables in preterm birth did not show change to any great extent after age and educational level were adjusted for. Further stratification of these cases into groups with and without premature rupture of the membranes (PROM), showed that a multiple pregnancy was still the leading risk factor of preterm birth in both groups. Carrying an abnormal fetus was the next important risk factor for preterm birth in cases with PROM, but was less important in the group without PROM. However, placenta previa or abruptio placentae and preeclampsia were the next most important factors in the group without PROM. CONCLUSIONS: Unfavorable current obstetric conditions and a history of more than two prior abortions and preterm delivery were positively associated with preterm birth.

Abruptio Placentae↗
PubMed1996

Cryptococcal meningitis in pregnancy.

The case of an 18-year-old pregnant woman with cryptococcal meningitis treated with amphotericin B and flucytosine since the third trimester of pregnancy is reported. She delivered a normal baby. The maternal outcome was favorable. There is no evidence of congenital infection in the newborn.

Adolescent↗
PubMed1996

Prenatal detection of the separation of the great toe, toe syndactyly, and large bilateral choroid plexus cysts in a fetus with trisomy 18.

Prenatal sonographic presentation of toe deformities is associated with fetal aneuploidies. This report presents a second-trimester fetus with large bilateral choroid plexus cysts, clenched hands, separation of the great toe, toe syndactyly, abnormal double maternal serum biochemical screening results, and trisomy 18. We suggest a careful ultrasound screening of the fetal limbs and other organs once a choroid plexus cyst has been identified. If abnormal sonographic findings are present, or if the results of the maternal serum biochemical screening are abnormal, karyotyping should be recommended.

Abnormalities, Multiple↗
PubMed1996

Factors influencing the prolonged second stage and the effects on perinatal and maternal outcomes.

OBJECTIVE: To examine the factors influencing the prolonged second stage and the maternal-perinatal outcomes after a prolonged second stage of labor. METHODS: Between January 1993 and June 1993, 165 women who delivered with a prolonged second stage of labor were enrolled in this study. The control group was 1750 term pregnancies that delivered under 2 hours in the second stage. Maternal and neonatal outcomes included one and 5 minute Apgar scores, umbilical blood gas determination, thick meconium stain, fetal trauma, and length of hospital stay. RESULTS: Factors such as nulliparity (p < 0.005), maternal weight gained during pregnancy (p < 0.01), active phase length (p < 0.05), persistent occiput posterior position (p < 0.05), station at complete cervical dilation (p < 0.05) and a need of instrumental vaginal delivery (p < 0.05) were significantly associated with a prolonged second stage of labor. Maternal and neonatal outcomes were not different significantly between the study and control group. CONCLUSION: The maternal and perinatal well-beings from the normal second stage group did not appear to be more favorable than the prolonged second stage. Under monitored condition, if the fetal heart rate is considered normal, then the natural labor course could be continued.

Adult↗