Wall Interface Research Articles

Successful Conservative Management of Placenta Previa Totalis and Extensive Percreta

The incidence of abnormal placentation, includingplacenta accreta, increta and percreta, ranges from 1in 540 to 1 in 93,000 deliveries [1]. Placenta percreta isdefined as the penetration of trophoblastic tissue intothe myometrium or serosa of the uterus. Severe hem-orrhage may occur with attempts to manually separatethe placenta from the uterus following delivery. The in-creased frequency of cesarean delivery over the past twodecades has resulted in a greater incidence of abnormalplacentation as more women enter into subsequent pre-gnancies with a history of operative deliveries [2]. Thetreatment of abnormal placentation has evolved withtime. We report a case of placenta previa totalis andextensive percreta that was successfully managed withpreservation of the uterus.A 32-year-old woman, gravida 2, para 1, was referredto our hospital at 7 weeks of gestation for evaluation ofan asymptomatic pregnancy within a cesarean scar, asdemonstrated by ultrasound. She had a history of ce-sarean section with an incision in the lower uterine seg-ment. Termination of the pregnancy was recommended.However, the patient decided to continue the pregnancybecause of religious beliefs. The antenatal examinationswere unremarkable with the exception of intermittentpainless vaginal spotting. An ultrasound examinationat 27 weeks of gestation showed the absence of a nor-mal subplacental sonolucent layer and deep invasionof the anterior lower uterine segment by the placenta.Magnetic resonance imaging (MRI) at 32 weeks of ges-tation demonstrated that the placenta occupied theentire lower uterine segment with some obliteration ofthe uteroplacental interface and small serosal interrup-tions of the left posterior wall of the bladder withoutmucosal invasion (Figure 1). The findings were consistentwith a diagnosis of placenta percreta.A classical cesarean section was performed at 34+weeks of gestation, after ultrasound examination indi-cated an adequate fetal body weight. Angioemboli-zation catheters were placed bilaterally through thefemoral arteries on the morning of surgery. At laparot-omy, the previous cesarean scar was nearly completelydehiscent and involved the lower one-third of theuterus. The placenta was visualized beneath a paper-thinmembrane-like peritoneum covering the area of dehis-cence, and engorged blood vessels crossing throughthe membrane were noted (Figure 2). The fetus wasdelivered via breech extraction, and had Apgar scoresof 5 and 9 at 1 and 5 minutes, respectively. The placentawas not removed and was left in place. Immediatelyafter the infant was delivered, bilateral transarterialembolization of the internal iliac arteries using Gelfoamwas performed by radiologists present in the deliveryroom. The embolization technique was done as previ-ously described [3]. The amount of intraoperative bloodloss was approximately 2,000mL. The postoperative

A case study on the behaviour of a deep excavation in sand

A complete case record of an excavation in sand is explored in this study. Numerical analyses were conducted to evaluate the influences of soil elasticity, creep and soil–wall interface. Back-analyses indicate small strain parameters should be used if an elastic–perfect plastic model is selected. In addition, excavation-induced seepage has only a limited effect on vertical displacements. Delayed installation of 3rd level struts and base slab construction caused significant time-dependent (creep) movements during the excavation. Back-analyses show that the dynamic viscosity ( D v) used in the visco-elastic model for creep simulation is in the range of 1.5 × 10 15–2.0 × 10 15 Pa, but there are still inconsistencies in movements both near to and far from the excavation. Interpreting from observation data, the creep rate of wall movement caused in the non-supported stage of the excavation varies between 0.14 and 0.38 mm/day. Finally, parametric studies of interface elements indicate that the most sensitive parameters are the normal ( K n) and shear stiffness ( K s) of the interface. Back-analyses using an elastic–perfect plastic model indicate that using 3 × 10 6 Pa for K n and K s produces more acceptable results.

Role of the polymeric hole injection layer on the efficiency and stability of organic light emitting diodes with small molecular emitters

In this paper, an improvement in the properties of the small molecular organic light emitting diode (OLED) upon application of a polymeric hole injection layer (HIL) was reported. The luminous efficiency, operating voltage and lifetime of devices with dye-doped small molecule emitters (fluorescent and phosphorescent) were found to be sensitive to the HIL/hole transport layer (HTL) combination used, where the improved injection and brightness was shown at the hole cascading structure and the longer lifetime behaviour was obtained at the hole-trapping structure. Use of a polymeric HIL significantly increased the luminous current efficiency and lifetime for both fluorescent blue and phosphorescent green/red light emitters. The polymeric HIL was effective in terms of the driving characteristics of phosphorescent OLED, since it provides higher brightness behaviour at lower current density. The apparent shade of the pixel image at light emission, which will probably induce degradation at the pixel wall interface, will be suppressed by the use of polymeric HIL. In spite of the ambiguity in the formation of such shaded pixels and their influence at the decay of OLED, intrinsic stability of polymeric HIL/anode would be advantageous for stable storage and operation of devices.

Evaluation of sonographic diagnostic criteria for placenta accreta

To compare the diagnostic value of reported sonographic criteria for placenta accreta and to develop a composite score system for antenatal evaluation. Sixty-six women at risk for placenta accreta were examined for 9 cases of placenta accreta that were confirmed at delivery. The performance of previously reported gray-scale and Doppler sonographic criteria for the diagnosis of placenta accreta was analyzed individually. A composite score system was developed by combining selected sensitive or specific sonographic criteria, and its performance was evaluated. The criteria of obliteration of retroplacental clear space, a myometrial thickness of <1 mm, presence of vessels bridging placenta and uterine margin, disruption of the placental-uterine wall interface, and vessels crossing the sites of interface disruption showed a statistically significant association with placenta accreta. The disruption of the placental-uterine wall interface and the presence of vessels crossing these sites were the only 2 individual criteria that could distinguish placenta accreta from non-accreta, which could also be achieved by our composite score system using a cutoff value of 40, with a sensitivity of 89% and specificity of 98%. The diagnostic performance of the sonographic diagnostic criteria used in the diagnosis of placenta accreta varies, and a composite score system improves the overall accuracy.

Antenatal topographical assessment of placenta accreta with ultrasound

The major risk of placenta accreta is severe haemorrhage when the placenta is separated at delivery. A case series of placenta accreta with antenatal sonographic topographical assessment of myometrial involvement is presented. The extent of myometrial involvement and the vascularity could be assessed by the observation of the extent of placental-uterine wall interface disruption and the vessels crossing the interface disruption sites. Such assessment results in strategic planning of management of the placenta at delivery with favourable pregnancy outcomes.

SU-GG-T-33: Accurate Localization of the Needle Position During the Real Time Seed Implant Procedure in OR

Purpose: Accurately localize the needle tip position to improve the dosimetry accuracy of real time prostate seed implant in the OR. Method and Materials: Variseed seed implant software version 7.2 was utilized to study the needle identification process. To accurately determine the needle position under the artifact reflection of ultrasoundimages in the real time planning mode is challenging. We have developed a simplified method to study the true location of the implemented needles during the real time based seed implant procedure. A zero mark pseudo contour was introduced to identify the needle end dwell position with the axial view of the prostate base. It was identified to correlate the true needle position before dropping the seeds. Bladder wall interface on the sagittal view also justified for the needle identification in finding actual seed location. Rotating the ultrasound probe along with the zero mark slice correlation helps to clarify the trajectory of the needles. Results: With the implant views needle correlation; we have performed the variation study from the optimized plan versus the plan after finishing the seeds dropping. Less than 1% variation of PTV coverage (criteria V100 > 90%, D90 < 115% prescription for prostate, V125 < 0 cc for both urethra and rectum) is achieved with great accuracy. Optimization criteria have not been disturbed by our method, and the post implant CTdosimetry shows great coverage for prostate day 1 and day 30 studies. Conclusion: Real time prostate implant procedure provides invaluable dosimetry benefit compared to the pre‐planned implant method. However, needle tip position correlation during the implant process presents challenging uncertainty for both pre‐plan and real time plan process. We developed a simple method to improve the confidence level of the real time implant dosimetry, with implant needle accurately projected during the seed loading process.

Investigation on highly ordered porous anodic alumina membranes formed by high electric field anodization

A simple and cost effective method for fabricating long-range ordered porous anodic alumina (PAA) membranes is presented, which explores a self-ordering regime with controllable interpore distances over a large scale (300–360 nm). The cohesive force at the hemi-spherical scallop/cell wall (HS/CW) interface is weaker than the other locations. When the PAA membranes were immersed in H 3PO 4 solution, regular cheese-like hexagonal patterns have been propagated at the cell boundaries. With increased etching time, numerous pores were observed at triple points where three cells met. The distinct fracture and etching behaviors in PAA can be ascribed to the intense ionic transport accompanied by the volume expansion in the barrier region under high electric field.

Placenta accreta in the first trimester of pregnancy: Sonographic findings

In a case of histologically confirmed placenta increta, decidual protrusion into the myometrium was observed sonographically at 6 weeks' gestation, corresponding to placental protrusion from a disrupted placental-uterine wall interface seen in the later part of the first and second trimester. It is hypothesized that the histologic finding of decidual scarcity in placenta accreta is not a cause but rather an end result of the recruitment of trophoblasts across the decidual-placental interface in a maternal attempt at healing and/or repair in the presence of uterine injury, disease, or malformation that accounts for the associated factors and course of the condition.

Thermal interactions in nanoscale fluid flow: molecular dynamics simulations with solid–liquid interfaces

Molecular dynamics (MD) simulations of nano-scale flows typically utilize fixed lattice crystal interactions between the fluid and stationary wall molecules. This approach cannot properly model interactions and thermal exchange at the wall–fluid interface. We present a new interactive thermal wall model that can properly simulate the flow and heat transfer in nano-scale channels. The new model utilizes fluid molecules freely interacting with the thermally oscillating wall molecules, which are connected to the lattice positions with “bonds”. Thermostats are applied separately to each layer of the walls to keep the wall temperature constant, while temperature of the fluid is sustained without the application of a thermostat. Two-dimensional MD simulation results for shear driven nano-channel flow shows parabolic temperature distribution within the domain, induced by viscous heating due to a constant shear rate. As a result of the Kapitza resistance, temperature profiles exhibit jumps at the fluid–wall interface. Time dependent simulation results for freezing of liquid argon in a nano-channel are also presented.

Polymer–mould interface heat transfer coefficient measurements for polymer processing

Reliable process and product design for plastics through simulation requires reliable heat transfer properties data. The thermal contact resistance of interfaces can have a significant influence in simulation predictions, in particular for micro-moulding, yet the availability of data is limited. Furthermore, the formation of air gaps at the polymer–wall interface due to shrinkage of the polymer on cooling are not adequately modelled in process simulations. To address these issues, an instrument has been developed for measuring the thermal contact resistance of interfaces relevant to polymer processing, in particular for injection moulding. It has been used to quantify the thermal resistance of the polymer–mould interface and also that of air gaps introduced between the mould surface and the polymer, thereby representing the interfaces occurring in injection moulding. Heat transfer coefficients (HTC) across a polymer–steel interface were measured to be of the order of 7000 W/(m 2 K). The thermal contact resistance of the polymer–air–steel interface were in reasonable agreement with predictions assuming heat transfer across an air gap based on thermal conduction through air.

Cosine law at the atomic scale: Toward realistic simulations of Knudsen diffusion

We propose to reconsider the diffusion of atoms in the Knudsen regime in terms of a complex dynamical reflection process. By means of molecular dynamics simulations, we emphasize the asymptotic nature of the cosine law of reflection at the atomic scale, and carefully analyze the resulting strong correlations in the reflection events. A dynamical interpretation of the accommodation coefficient associated with the slip at the wall interface is also proposed. Finally, we show that the first two moments of the stochastic process of reflection depend nonuniformly on the incident angle.

Hydronium and hydroxide at the interface between water and hydrophobic media

The behavior of hydronium and hydroxide ions at the water/alkane, water/vapor, and water/rigid wall interfaces was investigated by means of molecular dynamics simulations. All these interfaces exhibit a strong affinity for hydronium, which is in agreement with spectroscopic and low pH zeta-potential measurements. Except for the water/rigid wall interface, which strongly structures water and weakly attracts OH(-), none of the other investigated interfaces shows an appreciable accumulation of hydroxide. This computational result is at odds with the interpretation of higher pH zeta-potential and titration experiments, however, it is supported by surface selective spectroscopies of the surface of water and hydroxide solutions.

Ex vitro experimental study on concentration polarization of macromolecules (LDL) at an arterial stenosis

To verify the previous theoretical prediction that the disturbed flow distal to a stenosis enhances lipid accumulation at the blood/arterial wall interface, we designed a canine carotid arterial stenosis model and measured ex vitro the luminal surface concentration of bovine serum albumin (as a tracer macromolecule) by directly taking liquid samples from the luminal surface of the artery. The experimental results showed that due to the presence of a filtration flow, the luminal surface albumin concentration c(w) was higher than the bulk concentration c(0) as predicted by our theory. The measurement revealed that the luminal surface concentration of macromolecules was indeed enhanced significantly in regions of the disturbed flow. At Re = 50, the relative luminal surface concentration c(w)/c(0) was 1.66 +/- 0.10 in the vortex region, while the c(w)/c(0) was 1.37 +/- 0.06 in the laminar flow region. When Re increased to 100, the c(w)/c(0) in the vortex flow region and the laminar flow region reduced to 1.39 +/- 0.07 and 1.24 +/- 0.04, respectively. The effect of the filtration rate, v(w), on the luminal surface concentration of albumin was remarkably apparent. At Re = 50 and 100, when v(w) = 8.9 +/- 1.7 x 10(-6) cm/s, c(w) in the vortex region was 77% and 52% higher than c(0) respectively, meanwhile when v(w) = 4.8 +/- 0.6 x 10(-6) cm/s, c(w) in the vortex region was only 66% and 39% higher than c(0) respectively. In summary, the present study has provided further experimental evidence that concentration polarization can occur in the arterial system and fluid layer with highly concentrated lipids in the area of flow separation point may be responsible for the formation and development of atherosclerosis.

Mechanism of Crumb Toughening in Bread-like Products by Microwave Reheating

Comparing breads reheated in conventional and microwave ovens revealed that the latter considerably toughens the crumb texture when internal boiling is induced. Moisture loss in itself has a relatively minor toughening effect. The major changes, caused by boiling, occur only in systems with starch concentration in excess of a threshold level of about 37% (wet basis). Substantially greater amounts of amylose are leached out of the granules in the case of sustained boiling during microwave heating, as compared to conventional oven heating. The free amylose solution is being "pushed" by the generated steam pressure toward the air-cell wall interface. A rich amylose phase is accumulated at that interface and over the granules. Upon cooling, the amylose undergoes rapid phase changes; thus, toughening is apparent in a relatively short time after heating. Minimizing the textural deleterious effects in microwave reheating of bread-like products should entail (a) preventing or minimizing internal boiling, (b) diluting of the starch concentration below the threshold level, (c) interfering with the amylose phase change by using complex forming agents.

Comparison of Fast-Setting Calcium Phosphate Bone Cement and Fat Autograft in a Rabbit Model of Frontal Sinus Obliteration

Traditionally, chronic obstruction of the frontal recess is managed by frontal sinus obliteration (FSO). This often requires the harvest of abdominal fat as a filler with all of its associated morbidity. In this study, we investigate the efficacy of calcium phosphate bone cement (Craniofacial Repair System [CRS]) as a material for FSO. Eighteen New Zealand white rabbits were divided into three groups and carried out to two time periods. Six rabbits underwent FSO with fat autograft (control group) and 12 rabbits underwent FSO with CRS (study groups 1 and 2, respectively). At 52 weeks, six control and six study rabbits were killed. The remaining six rabbits were killed at 78 weeks. All specimens underwent radiological evaluation with spiral computed tomography (CT) followed by gross inspection. Histological evaluation was then performed to assess bony growth and to evaluate the interface of the sinus wall with the obliterative material. Sinuses obliterated with CRS showed complete obliteration radiographically. This was apparent at 52 weeks and remained static at 78 weeks. Histological analysis indicated persistent obliteration of the sinus cavity from 52 to 78 weeks and signs of osteoinduction. There were no complications observed as a result of the operative procedure or the materials used. CRS is an alternative to fat autograft for FSO in this noninfected animal model. Further studies are needed to evaluate its long-term efficacy as well as its behavior in chronically infected sinuses.

Entropic Wetting and the Free Isotropic−Nematic Interface of Hard Colloidal Platelets

We study bulk and interfacial properties of a model suspension of hard colloidal platelets with continuous orientations and vanishing thickness using both density functional theory, based on either a second virial approach or fundamental measure theory (FMT), and Monte Carlo (MC) simulations. We calculate the bulk equation of state, bulk isotropic-nematic (IN) coexistence, and properties of the (planar) free IN interface and of adsorption at a planar hard wall, where we find complete wetting of the nematic phase at the isotropic-wall interface upon approaching bulk IN coexistence. We investigate in detail the asymptotic decay of correlations at large distances. In all cases, the results from FMT and MC agree quantitatively. Our findings are of direct relevance to understanding interfacial properties of dispersions of colloidal platelets.

Input power flow in a submerged infinite cylindrical shell with doubly periodic supports

A submerged cylindrical shell reinforced by supports of rings and bulkheads is the primary structure of submarine, torpedo and all kinds of submerged aircrafts, so it is significant to study its characteristics of structure-borne sound. By means of periodic structure theory, the input power flow from a cosine harmonic line force into a submerged infinite cylindrical shell, reinforced by doubly periodic supports of rings and bulkheads, is studied analytically. The harmonic motion of the shell and the sound pressure field in the fluid are described by Flügge shell equations and Helmholtz equation, respectively. Since the fluid radical velocity and the shell radical velocity must be equal at the interface of the outer shell wall and the fluid, the motion equations of this coupled system are obtained. Both four kinds of forces (moments) between rings and shell and four kinds of forces (moments) between bulkheads and shell are considered. The solution is obtained in series form by expanding the system responses in terms of the space harmonics of the spacings of both stiffeners and bulkheads. The input vibrational power flow into the structure is obtained and the influences of different structural parameters on the results are analyzed. The analytic model is close to engineering practice, and it will give some guidelines for noise reduction of this kind of shell.

Modelization of flow electrification in a polymer melt

Flow electrification of polymer melts is an important side effect of polymer processing. The studies dealing with this phenomenon are few and most of the scientific work has been focused on flow electrification of aqueous and insulating Newtonian liquids. From these previous results it is well established that the flow electrification in Newtonian liquids is a consequence of the formation of an ionic double layer. Convection of this layer induces the electrification of the liquid at the outlet of the pipe. In these models, the key parameters governing the flow electrification are thus the intrinsic electrical properties of the polymer and the flow characteristics. In this work, we reconsider the assumptions made previously and we propose a new approach to modelize the flow electrification in the particular case of non-Newtonian polymer materials in laminar flow conditions. We establish that a key parameter for the electrification quantification in the polymer melt is the shape of the velocity profile. Additionally, in some cases, we show that a slip velocity at the polymer/die wall interface must be considered to accurately describe the electrification. As a consequence, we deduce that the slip velocity at the interface can be calculated by measuring the electrification: this work gives an alternative manner to measure the slip velocity during polymer flow.

Noninvasive Two-Dimensional Strain Imaging of Arteries: Validation in Phantoms and Preliminary Experience in Carotid Arteries In Vivo

Cardiac disease and stroke are the major causes of death in the Western World. Atherosclerosis of the carotid artery is the most important predictor of stroke. Elastography is a technique to assess the composition and vulnerability of an atherosclerotic plaque. Contrary to intravascular applications, the ultrasound beam and radial strain are not aligned in noninvasive acquisitions. In this study, 2D displacement and strain images were determined and used to calculate the radial and circumferential strain. Rf-data were acquired using a Philips SONOS 7500 live 3D ultrasound system, equipped with an 11_3L (3 to 11 MHz) linear array transducer and rf-interface. A homogeneous, hollow cylinder phantom [20% gelatin, 1% SiC scatterers (10 μm)] was measured in a water tank at different intraluminal pressures. In addition, measurements in patients (n = 12) were made to evaluate the in vivo applicability of the technique. Longitudinal and cross-sectional recordings were made, both in phantoms and patients. Strain along the ultrasound beam (axial strain) was determined using cross-correlation analysis for signal-windows from both the pre- and postcompression data. For lateral strain, new ultrasound lines were generated between the acquired lines using interpolation. A cross-correlation based search algorithm was applied to determine lateral displacement and strain. Longitudinal axial strain images in the phantom showed a decreasing strain from the lumen- vessel wall interface to the outer region that can be described by a 1 over r 2 relationship. The lateral strain image showed no strain in this direction indicating a plane strain situation. In the cross-sectional view, compression of the material in regions at 12 and 6 o’clock was observed, whereas expansion was observed in regions at 3 and 9 o’clock. This pattern is in accordance with theory, but can only be partly corrected for: in the transition regions, zero axial strain was measured. The lateral strain image showed a complementary pattern. In patients, low strain was observed in nonatherosclerotic artery walls. High and low strain regions were found in atherosclerotic plaques. High quality elastograms were generated both in longitudinal and cross-sectional views. In conclusion, 2D noninvasive elastography of atherosclerotic carotid plaques is feasible. Phantom studies revealed elastograms in accordance with theory. Additional in vivo validation is needed to assess the value of this technique for identifying plaque vulnerability and composition. (E-mail: c.dekorte@cukz.umcn.nl)

Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls

Magnetotransport measurements on small single crystals of Cr, the elemental antiferromagnet, reveal the hysteretic thermodynamics of the domain structure. The temperature dependence of the transport coefficients is directly correlated with the real-space evolution of the domain configuration as recorded by x-ray microprobe imaging, revealing the effect of antiferromagnetic domain walls on electron transport. A single antiferromagnetic domain wall interface resistance is deduced to be of order 5 x 10(-5) mu Omega cm(2) at a temperature of 100 K.