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.

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.

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.

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.

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.

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.

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.

Laparoscopic para-aortic lymph node sampling in the staging of invasive cervical carcinoma: including a comparative study of 21 laparotomy cases.

OBJECTIVES: To assess the efficacy and risks of laparoscopic para-aortic lymph node sampling compared with standard laparotomy in staging cervical carcinoma. METHODS: From August 1993 through July 1994, 38 patients with biopsy-proven invasive cervical carcinoma (24 early and 14 advanced invasive cancers) were entered into the study. This was a prospective study of laparoscopic para-aortic lymphadenectomy in invasive cervical carcinoma, with patients serving as their own controls. Video laparoscopic lymph node sampling was performed. In patients with early invasive cancer, the nodes were sent for frozen section and, if negative, laparotomy was performed to look for any residual nodes. Radical hysterectomy was performed immediately if residual nodes were negative. Patients with either nodal metastasis on frozen section or with advanced cancer underwent para-aortic lymphadenectomy only. The operative technique was also evaluated. RESULTS: Laparoscopy required an average of 77 min (S.D. 40), with an average blood loss of 116 ml (S.D. 321). The average number of nodes was 15 (S.D. 7). At subsequent laparotomy the average number of residual nodes found was 0.4 (S.D. 0.9) and none showed metastasis. One vena cava laceration and one ureteral injury required immediate repair, and two patients were too obese to undergo laparoscopy. CONCLUSIONS: Laparoscopic para-aortic lymph node sampling is a less invasive, reliable method for staging invasive cervical carcinoma and can substitute for traditional open procedures. The incidence of risks with this method appears to be low.

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.

Decreased amniotic fluid index in term pregnancy. Clinical significance.

In a study of 331 term pregnancies a four-quadrant technique was used to obtain amniotic fluid index measurements, and the results were compared with the current widely used single-pocket measurement. In contrast to the "2-cm rule," the amniotic fluid index measurements consistently demonstrated higher sensitivity in predicting poor fetal outcome with no decrease in specificity. It was noted that pregnancies with an index of < or = 8 cm showed higher incidences of meconium staining, cesarean delivery for fetal distress, abnormal fetal heart rate monitoring and Apgar scores of < or = 7 or less at one minute.

Amniotic fluid index measurement with the four-quadrant technique during pregnancy.

Eleven hundred thirty-four pregnant women with reliable dates underwent ultrasound evaluation for amniotic fluid index (AFI) measurement with the modified four-quadrant technique. We found that from 13 weeks' gestation the AFI rose progressively until 26 weeks. From then to 38 weeks the AFI measurements demonstrated little variation. After 38 weeks the AFI appeared to decline gradually. In the third trimester the mean AFI was 16.0 +/- 4.8 cm; 5% of cases had an AFI less than or equal to 8 cm, and 5% had an AFI greater than or equal to 24 cm. These results confirm the reproducibility of the semiquantitative technique and suggest that in estimating amniotic fluid volume, AFI measurement may be a more appropriate means than measurement of the single largest pocket or subjective assessment. Serial AFI measurement would be an effective way of assessing fetal status throughout pregnancy.

Effects of severe preeclampsia with different doppler velocimetries on extra- and intrauterine environments.

We evaluated the perinatal outcome of fetuses and maternal condition of 47 patients with severe preeclampsia. Antepartum fetal surveillance (within 2 days of delivery or fetal death) included the nonstress test, Doppler velocimetry of the umbilical and uterine arteries, amniotic fluid assessment, maternal blood chemistry and hemogram. Pregnancies with abnormal Doppler velocimetry in the umbilical and uterine arteries had poor perinatal outcomes as judged by the incidence of abnormal antepartum fetal surveillance, acute fetal distress mandating immediate delivery, small for gestational age infants, perinatal morbidity and mortality and prematurity. These fetuses were at a high risk of acute and chronic hypoxia. Maternal blood chemistries and hemograms revealed a high incidence of hepatocellular dysfunction, renal insufficiency, hemoconcentration and thrombocytopenia. In cases of severe preeclampsia, those with abnormal Doppler velocimetry of both umbilical and uterine arteries, had poor extra- and intrauterine environments. Therefore, aggressive rather than expectant management was more suitable. For those with normal umbilical artery resistance and either normal or abnormal uterine artery resistance, careful management with close monitoring of both maternal and fetal status was possible in patients who were far from term.

Implications of prolonged fetal heart rate deceleration during the second stage of labor.

In order to evaluate the neonatal outcomes of infants who had prolonged fetal heart rate (FHR) deceleration during the second stage of labor, the neonatal outcomes of 24 infants born after vaginal delivery at 37 to 42 weeks of gestation with prolonged FHR deceleration during the second stage of labor were compared with the outcomes of 28 infants of a similar gestational age who had normal FHR patterns. No differences in the Apgar scores, mean umbilical PaCO2, PaO2, HCO3- or base deficit values were observed between the two groups, but the mean pH values differed significantly. The occurrences of a 1-minute Apgar score < 7, umbilical arterial pH < 7.20, presence of meconium and admission to the neonatal intensive care unit were higher in the study group, but were not significantly different. None of the 24 infants with prolonged FHR deceleration experienced birth trauma, meconium aspiration, neonatal seizure or neonatal death, but three were found to have congenital heart disease. We conclude that prolonged FHR deceleration during the second stage of labor without FHR abnormalities during the first stage of labor is not always associated with an adverse neonatal outcome and does not mandate the need for surgical or immediate vaginal delivery. Their appearance on FHR tracings requires the implementation of additional methods to assess fetal well-being and also to diagnose fetal distress.

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.