Numerical modelling of chemical effects of magma solidification problems in porous rocks

The solidification of intruded magma in porous rocks can result in the following two consequences: (1) the heat release due to the solidification of the interface between the rock and intruded magma and (2) the mass release of the volatile fluids in the region where the intruded magma is solidified into the rock. Traditionally, the intruded magma solidification problem is treated as a moving interface (i.e. the solidification interface between the rock and intruded magma) problem to consider these consequences in conventional numerical methods. This paper presents an alternative new approach to simulate thermal and chemical consequences/effects of magma intrusion in geological systems, which are composed of porous rocks. In the proposed new approach and algorithm, the original magma solidification problem with a moving boundary between the rock and intruded magma is transformed into a new problem without the moving boundary but with the proposed mass source and physically equivalent heat source. The major advantage in using the proposed equivalent algorithm is that a fixed mesh of finite elements with a variable integration time-step can be employed to simulate the consequences and effects of the intruded magma solidification using the conventional finite element method. The correctness and usefulness of the proposed equivalent algorithm have been demonstrated by a benchmark magma solidification problem. Copyright (c) 2005 John Wiley & Sons, Ltd.

Perioperative Temporary Occlusion of the Internal Iliac Arteries as Prophylaxis in Cesarean Section at Risk of Hemorrhage in Placenta Accreta

Purpose The purpose of this study was to describe the preliminary results of prophylactic temporary balloon occlusion of the internal iliac arteries for bleeding control in patients with placenta accreta during cesarean hysterectomy. Methods From May 2006 to March 2010, 21 patients diagnosed with placenta accreta using ultrasound and/or magnetic resonance imaging were submitted to prophylactic balloon occlusion before hysterectomy. Fluoroscopy, balloon occlusion time, surgical duration, intraoperative blood loss, transfusion volume, and procedure complications were analyzed. Results The mean age was 30.5 years with a mean of 3.6 previous gestations. Imaging studies revealed that all patients had placenta accreta and all were submitted to cesarean hysterectomy. One hysterectomy was due to previous diagnosis of fetal death and another due to cesarean with uterine curettage. Mean fluoroscopy time was 7.5 min, balloon occlusion time was 164 min, and surgery duration was 260 min. Estimated blood loss was 1,671.5 ml with mean reposition fluids of 3,538 ml of crystalloids, 309.5 ml of colloids, and 1.24 ml of packed red blood cells. Two patients were submitted to thromboembolectomy due to prolonged surgical time. There was no maternal or fetal mortality related to the procedure. Conclusions The results demonstrated that prophylactic balloon occlusion of internal iliac artery is a safe method and appears to reduce blood loss and transfusion requirements in patients diagnosed with placenta accreta who undergo cesarean hysterectomy. Antenatal imaging diagnosis of placenta accreta enables preoperative planning.

Numerical simulation of dendrite growth during solidification

A comprehensive probabilistic model for simulating dendrite morphology and investigating dendritic growth kinetics during solidification has been developed, based on a modified Cellular Automaton (mCA) for microscopic modeling of nucleation, growth of crystals and solute diffusion. The mCA model numerically calculated solute redistribution both in the solid and liquid phases, the curvature of dendrite tips and the growth anisotropy. This modeling takes account of thermal, curvature and solute diffusion effects. Therefore, it can simulate microstructure formation both on the scale of the dendrite tip length. This model was then applied for simulating dendritic solidification of an Al-7%Si alloy. Both directional and equiaxed dendritic growth has been performed to investigate the growth anisotropy and cooling rate on dendrite morphology. Furthermore, the competitive growth and selection of dendritic crystals have also investigated.

Intraosseous Anesthesia in Hemodynamic Studies in Children with Cardiopathy

Aliman AC, Piccioni MA, Piccioni JL, Oliva JL, Auler Junior JOC - Intraosseous Anesthesia in Hemodynamic Studies in Children with Cardiopathy. Background and objectives: Intraosseous (IO) access has been used with good results in emergency situations, when venous access is not available for fluids and drugs infusion. The objective of this study was to evaluate IO a useful technique for anesthesia and fluids infusion during hemodynamic studies and when peripheral intravascular access is unobtainable. The setting was an university hospital hemodynamics unit, and the subjects were twenty one infants with congenital heart disease enrolled for elective hemodynamic study diagnosis. Methods: This study compared the effectiveness of IO access in relation to IV access for infusion of anesthetics agents (ketamine, midazolann, and fentanyl) and fluids during hemodynamic studies. The anesthetic induction time, procedure duration, anesthesia recovery time, adequate hydration, and IV and IO puncture complications were compared between groups. Results: The puncture time was significantly smaller in IO group (3.6 min) that in IV group (9.6 min). The anesthetic onset time (56.3 second) for the IV group was faster than IO group (71.3 second). No significant difference between groups were found in relation to hydration (IV group, 315.5 mL vs IO group, 293.2 mL), and anesthesia recovery time (IO group, 65.2 min vs IV group, 55.0 min). The puncture site was reevaluated after 7 and 15 days without signs of infection or other complications. Conclusions: Results showed superiority for IO infusion when considering the puncture time of the procedure. Due to its easy manipulation and efficiency, hydration and anesthesia by IO access was satisfactory for hemodynamic studies without the necessity of other infusion access.

Standard Examination System for Laparoscopy in Penetrating Abdominal Trauma

Background: The high missed occult small bowel injuries (SBI) associated with laparoscopy in trauma (LIT) is a major reason why some surgeons still preclude LIT today. No standardized laparoscopic examination for evaluation of the peritoneal cavity is described for trauma. The objective of this article is to verify if a systematic standardized laparoscopic approach could correctly identify SBI in the peritoneal cavity for penetrating abdominal trauma (PAT). Methods: Victims with PAT were evaluated in a prospective, nonrandomized study. A total of 75 hemodynamically stable patients with suspected abdominal injuries were operated by LIT and converted to laparotomy if criteria were met: SBI and lesions to blind spot zones-retroperitoneal hematoma, injuries to segments VI or VII of the liver, or injuries to the posterior area of the spleen. Inclusion criteria were equivocal evidence of abdominal injuries or peritonea] penetration; systolic blood pressure >90 mm Hg and <3 L of IV fluids in the first hour of admission; Glasgow Coma Scale score >12; and age >12 years. Exclusion criteria were back injuries; pregnancy; previous laparotomy; and chronic cardiorespiratory disease. Results: Sixty patients were males and there were 38 stab wounds and 37 gunshot wounds. No SBI was missed, but a pancreatic lesion was undiagnosed due to a retroperitoneal hematoma. Twenty patients (26.6%) were converted. Unnecessary laparotomies were avoided in 73.33%. Therapeutic LIT was possible in 22.7%. Accuracy was 98.66% with 97.61% sensitivity and 100% specificity. Conclusions: Standard systematic laparoscopic exploration was 100% effective to detect SBI in the peritoneal cavity. Conversion from LIT to laparotomy should be done if injuries to blind spot zones are found which are poorly evaluated by LIT. Therapeutic LIT is feasible in PAT.

A controlled trial comparing the efficacy of rice-based and hypotonic glucose oral rehydration solutions in infants and young children with gastroenteritis

A prospective randomized trial was conducted to compare the efficacy of a rice-based oral rehydration solution (ORS) with glucose ORS in infants and children under 5 years of age with acute diarrhoea and mild to moderate dehydration (<10%). One hundred children presenting to a large metropolitan teaching hospital were eligible for entry to the study and were randomized to receive rice ORS or glucose ORS. Outcome measures were stool output (SO), duration of illness (DD) and recovery time to introduction of other fluids (RTF) and diet (RTD). Significant differences were found for all outcome measures in favour of the rice ORS group. Mean SO was lower (160 vs 213 mt; P<0.02), mean DD was reduced (17.3 vs 24.3 h; P = 0.03) and median RTF was decreased (12.7 vs 18.1 h; P< 0.001) in the rice ORS group compared with the glucose ORS group. The median rime to introduction of diet and mean length of hospital stay showed similar significant reductions. Our study has shown rice ORS to be an acceptable alternative to glucose ORS in young children and have shown that it is significantly more effective in reducing the course of diarrhoeal illness and the time taken to return to normal drinking and eating habits.

Numerical modelling of tide-induced beach water table fluctuations

Field studies have shown that the elevation of the beach groundwater table varies with the tide and such variations affect significantly beach erosion or accretion. In this paper, we present a BEM (Boundary Element Method) model for simulating the tidal fluctuation of the beach groundwater table. The model solves the two-dimensional flow equation subject to free and moving boundary conditions, including the seepage dynamics at the beach face. The simulated seepage faces were found to agree with the predictions of a simple model (Turner, 1993). The advantage of the present model is, however, that it can be used with little modification to simulate more complicated cases, e.g., surface recharge from rainfall and drainage in the aquifer may be included (the latter is related to beach dewatering technique). The model also simulated well the field data of Nielsen (1990). In particular, the model replicated three distinct features of local water table fluctuations: steep rising phase versus flat falling phase, amplitude attenuation and phase lagging.

Modeling the optical constants of solids using acceptance-probability-controlled simulated annealing with an adaptive move generation procedure

The acceptance-probability-controlled simulated annealing with an adaptive move generation procedure, an optimization technique derived from the simulated annealing algorithm, is presented. The adaptive move generation procedure was compared against the random move generation procedure on seven multiminima test functions, as well as on the synthetic data, resembling the optical constants of a metal. In all cases the algorithm proved to have faster convergence and superior escaping from local minima. This algorithm was then applied to fit the model dielectric function to data for platinum and aluminum.

Synchronization of mutually coupled chaotic systems

We report on the experimental observation of both basic frequency locking synchronization and chaos synchronization between two mutually coupled chaotic subsystems. We show that these two kinds of synchronization are two stages of interaction between coupled chaotic systems. in particular the chaos synchronization could be understood as a state of phase locking between coupled chaotic oscillations.

Self-organization with traveling waves: A case for a convective torus

A traveling wave of BaSO4 in the chlorite-thiourea reaction has shown concentric precipitation patterns upon being triggered by the autocatalyst HOCl. The precipitation patterns show circular rings of alternate null and full precipitation regions. This self-organization appears to be the result of the formation of a convective torus. The formation of the convective torus can be described as a Benard-Marangoni instability with lateral heating.

Characterization of the Biocompatible Magnetic Colloid on the Basis of Fe(3)O(4) Nanoparticles Coated with Dextran, Used as Contrast Agent in Magnetic Resonance Imaging

The magnetic resonance imaging contrast agent, the so-called Endorem (TM) colloidal suspension on the basis of superparamagnetic iron oxide nanoparticles (mean diameter of 5.5 nm) coated with dextran, were characterized on the basis of several measurement techniques to determine the parameters of their most important physical and chemical properties. It is assumed that each nanoparticle is consisted of Fe(3)O(4) monodomain and it was observed that its oxidation to gamma-Fe(2)O(3) occurs at 253.1 degrees C. The Mossbauer spectroscopy have shown a superparamagnetic behavior of the magnetic nanoparticles. The Magnetic Resonance results show an increase of the relaxation times T(1), T(2), and T(2)* with decreasing concentration of iron oxide nanoparticles. The relaxation effects of SPIONs contrast agents are influenced by their local concentration as well as the applied field strength and the environment in which these agents interact with surrounding protons. The proton relaxation rates presented a linear behavior with concentration. The measured values of thermooptic coefficient partial derivative n/partial derivative T, thermal conductivity K, optical birefringence Delta n(0), nonlinear refractive index n(2), nonlinear absorption beta` and third-order nonlinear susceptibility vertical bar chi((3))vertical bar are also reported.

Quantum chaos in the atomic gravitational cavity

We report quantum chaos phenomena in the atomic gravitational cavity. We consider the reflection of cold atoms from a temporally modulated evanescent wave. In the globally chaotic regime, for small modulation, the squared energy distribution as a function of time demonstrates dynamical localization. However, for larger modulation delocalization occurs.

Virtual plants - integrating architectural and physiological models

Recent advances in computer technology have made it possible to create virtual plants by simulating the details of structural development of individual plants. Software has been developed that processes plant models expressed in a special purpose mini-language based on the Lindenmayer system formalism. These models can be extended from their architectural basis to capture plant physiology by integrating them with crop models, which estimate biomass production as a consequence of environmental inputs. Through this process, virtual plants will gain the ability to react to broad environmental conditions, while crop models will gain a visualisation component. This integration requires the resolution of the fundamentally different time scales underlying the approaches. Architectural models are usually based on physiological time; each time step encompasses the same amount of development in the plant, without regard to the passage of real time. In contrast, physiological models are based in real time; the amount of development in a time step is dependent on environmental conditions during the period. This paper provides a background on the plant modelling language, then describes how widely-used concepts of thermal time can be implemented to resolve these time scale differences. The process is illustrated using a case study. (C) 1997 Elsevier Science Ltd.

Spatiotemporal solitons in multidimensional optical media with a quadratic nonlinearity

We consider solutions to the second-harmonic generation equations in two-and three-dimensional dispersive media in the form of solitons localized in space and time. As is known, collapse does not take place in these models, which is why the solitons may be stable. The general solution is obtained in an approximate analytical form by means of a variational approach, which also allows the stability of the solutions to be predicted. Then, we directly simulate the two-dimensional case, taking the initial configuration as suggested by the variational approximation. We thus demonstrate that spatiotemporal solitons indeed exist and are stable. Furthermore, they are not, in the general case, equivalent to the previously known cylindrical spatial solitons. Direct simulations generate solitons with some internal oscillations. However, these oscillations neither grow nor do they exhibit any significant radiative damping. Numerical solutions of the stationary version of the equations produce the same solitons in their unperturbed form, i.e., without internal oscillations. Strictly stable solitons exist only if the system has anomalous dispersion at both the fundamental harmonic and second harmonic (SH), including the case of zero dispersion at SH. Quasistationary solitons, decaying extremely slowly into radiation, are found in the presence of weak normal dispersion at the second-harmonic frequency.

Modeling of subcutaneous absorption kinetics of infusion solutions in the elderly using technetium

Absorption kinetics of solutes given with the subcutaneous administration of fluids is ill-defined. The gamma emitter, technitium pertechnetate, enabled estimates of absorption rate to be estimated independently using two approaches. In the first approach, the counts remaining at the site were estimated by imaging above the subcutaneous administration site, whereas in the second approach, the plasma technetium concentration-time profiles were monitored up to 8 hr after technetium administration. Boluses of technetium pertechnetate were given both intravenously and subcutaneously on separate occasions with a multiple dosing regimen using three doses on each occasion. The disposition of technetium after iv administration was best described by biexponential kinetics with a V-ss of 0.30 +/- 0.11 L/kg and a clearance of 30.0 +/- 13.1 ml/min. The subcutaneous absorption kinetics was best described as a single exponential process with a half-life of 18.16 +/- 3.97 min by image analysis and a half-life of 11.58 +/- 2.48 min using plasma technetium time data. The bioavailability of technetium by the subcutaneous route was estimated to be 0.96 +/- 0.12. The absorption half-life showed no consistent change with the duration of the subcutaneous infusion. The amount remaining at the absorption site with time was similar when analyzed using image analysis, and plasma concentrations assuming multiexponential disposition kinetics and a first-order absorption process. Profiles of fraction remaining at the absorption sire generated by deconvolution analysis, image analysis, and assumption of a constant first-order absorption process were similar. Slowing of absorption from the subcutaneous administration site is apparent after the last bolus dose in three of the subjects and can De associated with the stopping of the infusion. In a fourth subject, the retention of technetium at the subcutaneous site is more consistent with accumulation of technetium near the absorption site as a result of systemic recirculation.