Shock-Induced Damage and Dynamic Fracture in Cylindrical Bodies Submerged in Liquid.

Understanding the response of solid materials to shock loading is important for mitigating shock-induced damages and failures, as well as advancing the beneficial use of shock waves for material modifications. In this paper, we consider a representative brittle material, BegoStone, in the form of cylindrical bodies and submerged in water. We present a computational study on the causal relationship between the prescribed shock load and the resulting elastic waves and damage in the solid material. A recently developed three-dimensional computational framework, FIVER, is employed, which couples a finite volume compressible fluid solver with a finite element structural dynamics solver through the construction and solution of local, one-dimensional fluid-solid Riemann problems. The material damage and fracture are modeled and simulated using a continuum damage mechanics model and an element erosion method. The computational model is validated in the context of shock wave lithotripsy and the results are compared with experimental data. We first show that after calibrating the growth rate of microscopic damage and the threshold for macroscopic fracture, the computational framework is capable of capturing the location and shape of the shock-induced fracture observed in a laboratory experiment. Next, we introduce a new phenomenological model of shock waveform, and present a numerical parametric study on the effects of a single shock load, in which the shock waveform, magnitude, and the size of the target material are varied. In particular, we vary the waveform gradually from one that features non-monotonic decay with a tensile phase to one that exhibits monotonic decay without a tensile phase. The result suggests that when the length of the shock pulse is comparable to that of the target material, the former waveform may induce much more significant damage than the latter one, even if the two share the same magnitude, duration, and acoustic energy.

Parametric investigations on the saturation intensity of Coumarin 102 for stimulated emission depletion application.

Stimulated emission depletion (STED) microscopy performed using continuous-wave (CW) lasers has been investigated and developed by Willig et al. (Nature Methods, 2007, 4(11):915) for nearly a decade. Kuang et al. (Review of Scientific Instruments, 2010, 81:053709) developed the CW STED microscopy technique with 405 nm excitation and 532 nm depletion beams. In their research, Coumarin 102 dye was adopted and was found to be depletable. In this study, a parametric investigation of the depletion of Coumarin 102 dye is carried out experimentally. The influence of the excitation and depletion beam intensities and dye concentrations on the depletion efficiency are studied in detail. The results indicate the following: (1) The highest depletion occurs for the 100 µM Coumarin 102 solution, with a 1.4 µW excitation beam and a 115.3 mW depletion beam. (2) The minimum saturation intensity (Is) of STED, that is 13 MW cm-2 , is observed when the Coumarin 102 solution concentration is 10 µM. (3) Is values calculated directly from the depletion power derived with the cross-sectional area due to the full-width-at-half-maximum (FWHM) of the depletion beam show poor accuracy, where Is may be overestimated. Thus, a correction factor for the cross-sectional area is proposed. We also find that Is is not exactly constant for a fixed excitation beam power and dye concentration. This trend indicates that the conventional suppression function η(x)=e- ln (2)ISTED(x)/Is derived from picosecond STED may cause errors in evaluating the depletion process in CW STED microscopy.

Phase coarsening in multicomponent systems.

A theory for phase coarsening in multicomponent systems is developed in which both the multicomponent thermodynamic effect and kinetic effect from a nonzero volume fraction are considered. In contrast to previous theory, a diffusion screening zone for a coarsening particle due to nonzero volume fraction is introduced. The evolution equation for phase coarsening in multicomponent systems is derived in a rigorous way in the framework of the maximum rate of dissipation with the constraints of mass and energy conservation. Existing previous relations are recovered and generalized. Some findings such as the relationship between the maximum particle size and volume fraction and particle size distribution in multicomponent systems are discovered.

Continuous time random walk with generic waiting time and external force.

We derive an integrodifferential diffusion equation for decoupled continuous time random walk that is valid for a generic waiting time probability density function and external force. Using this equation we also study diffusion behaviors for a couple of specific waiting time probability density functions such as exponential, a combination of power law and generalized Mittag-Leffler function and a sum of exponentials under the influence of a harmonic trap. We show that first two waiting time probability density functions can reproduce the results of the ordinary and fractional diffusion equations for all the time regions from small to large times. But the third one shows a much more complicated pattern. Furthermore, from the integrodifferential diffusion equation we show that the second Einstein relation can hold for any waiting time probability density function.

Integrodifferential diffusion equation for continuous-time random walk.

In this paper, we present an integrodifferential diffusion equation for continuous-time random walk that is valid for a generic waiting time probability density function. Using this equation, we also study diffusion behaviors for a couple of specific waiting time probability density functions such as exponential and a combination of power law and generalized Mittag-Leffler function. We show that for the case of the exponential waiting time probability density function, a normal diffusion is generated and the probability density function is Gaussian distribution. In the case of the combination of a power law and generalized Mittag-Leffler waiting probability density function, we obtain the subdiffusive behavior for all the time regions from small to large times and probability density function is non-Gaussian distribution.

Anomalous diffusive behavior of a harmonic oscillator driven by a Mittag-Leffler noise.

The diffusive behavior of a harmonic oscillator driven by a Mittag-Leffler noise is studied. Using the Laplace analysis we derive exact expressions for the relaxation functions of the particle in terms of generalized Mittag-Leffler functions and its derivatives from a generalized Langevin equation. Our results show that the oscillator displays an anomalous diffusive behavior. In the strictly asymptotic limit, the dynamics of the harmonic oscillator corresponds to an oscillator driven by a noise with a pure power-law autocorrelation function. However, at short and intermediate times the dynamics has qualitative difference due to the presence of the characteristic time of the noise.

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.

Altered placental syncytin and its receptor ASCT2 expression in placental development and pre-eclampsia.

OBJECTIVE: To investigate the alterations of syncytin, a fusogenic membrane protein involved in syncytiotrophoblastic layer formation, and its receptor ASCT2 expression in placental development and pre-eclampsia. DESIGN: Analyses of syncytin and ASCT2 expression in placentas from different stages of pregnancy and women with pre-eclampsia and in cytotrophoblasts cultured in normoxic and hypoxic conditions. SETTING: Placental samples were collected from a tertiary medical centre. POPULATION: Sixteen women with pre-eclampsia and 58 pregnant women presented as pregnancy (5-19 weeks of gestation) for elective termination, preterm birth, or normal term delivery. METHODS: The quantitative real-time polymerase chain reaction was used to study the syncytin and ASCT2 expression during placental development in 35 placentas from women without pre-eclampsia (ranged from 5 to 40 weeks of gestation) and the alterations of pre-eclamptic placentas (n=16) compared with gestational-age-matched controls (n=16). Western blot analysis was performed to study the protein level of syncytin in pre-eclamptic placentas and gestational-age-matched controls. The hypoxic effect on trophoblastic syncytin and ASCT2 expression was further studied in cytotrophoblasts cultured in 2% oxygen (n= 7). MAIN OUTCOME MEASURES: Syncytin and ASCT2 messenger RNA (mRNA) in placental tissue and cytotrophoblasts. RESULTS: The level of syncytin mRNA expression increased significantly since the first trimester of pregnancy until 37 weeks of gestation, when the level of syncytin expression was reduced. The ASCT2 mRNA expression was decreased significantly since the second trimester and was relatively stable since then to 40 weeks of gestation. Furthermore, a significant reduction in syncytin mRNA expression was observed in pre-eclamptic placentas and cytotrophoblasts cultured in hypoxia, but not a reduction in ASCT2 mRNA expression. Correlatively, the protein level of syncytin was decreased in pre-eclamptic placentas. CONCLUSIONS: A reduced placental expression of syncytin but not ASCT2 may contribute to altered cytotrophoblastic cell fusion processes and disturbed placental function in pre-eclampsia. Correspondingly, hypoxia decreases syncytin but not ASCT2 gene expression in cultured cytotrophoblasts.

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.

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.

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.

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.

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.

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.

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.

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.

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.