Prospective randomized comparison of human oocyte cryopreservation with slow-rate freezing or vitrification

Objective: To compare cryopreservation of mature human oocytes with slow-rate freezing and vitrification and determine which is most efficient at establishing a pregnancy. Design: Prospective randomized. Setting: Academically affiliated, private fertility center. Patient(s): Consenting patients with concerns about embryo cryopreservation and more than nine mature oocytes at retrieval were randomized to slow-rate freezing or vitrification of supernumerary (more than nine) oocytes. Intervention(s): Oocytes were frozen or vitrified, and upon request oocytes were thawed or warmed, respectively. Main Outcome Measure(s): Oocyte survival, fertilization, embryo development, and clinical pregnancy. Result(s): Patient use has resulted in 30 thaws and 48 warmings. Women`s age at time of cryopreservation was similar. Oocyte survival was significantly higher following vitrification/warming (81%) compared with freezing/thawing (67%). Fertilization was more successful in oocytes vitrified/warmed compared with frozen/thawed. Fertilized oocytes from vitrification/warming had significantly better cleavage rates (84%) compared with freezing/thawing (71%) and resulted in embryos with significantly better morphology. Although similar numbers of embryos were transferred, embryos resulting from vitrified oocytes had significantly enhanced clinical (38%) pregnancy rates compared with embryos resulting from frozen oocyte (13%). Miscarriage and/or spontaneous abortion rates were similar. Conclusion(s): Our results suggest that vitrification/warming is currently the most efficient means of oocyte cryopreservation in relation to subsequent success in establishing pregnancy. (Fertil Steril (R) 2010; 94: 2088-95. (C) 2010 by American Society for Reproductive Medicine.)

Changes in slow and fast alpha bands in subjects submitted to different amounts of functional electrostimulation

Objective: To examine the changes in slow (8-10 Hz)and fast (10-12 Hz) alpha bands of EEG in three groups of subjects submitted to different amounts of functional electrostimulation (FES). Our hypothesis is that different amounts of electrostimulation may cause different patterns of activation in the sensorimotor cortex. In particular, we expect to see an increase in alpha power due to habituation effects. We examine the two bands comprised by alpha rhythm (i.e., slow and fast alpha), since these two sub-rhythms are related to distinct aspects: general energy demands and specific motor aspects, respectively. Methods: The sample was composed of 27 students, both sexes, aging between 25 and 40 years old. The subjects were randomly distributed in three groups: control (n = 9), G24 (n = 9) and G36 (n = 9). A FES equipment (Neuro Compact-2462) was used to stimulate the right index finger extension. Simultaneously, the electroencephalographic signal was acquired. We investigated the absolute power in slow and fast alpha bands in the sensorimotor cortex. Results: The G36 indicated a significant increasing in absolute power values in lower and higher alpha components, respectively, when compared with the control group. Particularly, in the following regions: pre-motor cortex and primary motor cortex. Discussion: FES seems to promote cortical adaptations that are similar to those observed when someone learns a procedural task. FES application in the G36 was more effective in promoting such neural changes. The lower and higher components of alpha rhythms behave differently in their topographical distribution during FES application. These results suggest a somatotopic organization in primary motor cortex which can be represented by the fast alpha component. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

A simple solution of the laminar dam break wave

The sudden release of a mass of fluid in a channel generates a highly unsteady flow motion, called dam break wave. While industrial fluids exhibit sometimes non-Newtonian behaviours, the viscous fluid flow assumption remains a useful approximation for simplified analyses. In this study, new solutions of laminar dam break wave are proposed for a semi-infinite reservoir based upon the method of characteristics. The solutions yield simple explicit expressions of the wave front location, wave front celerity and instantaneous free-surface profiles that compare favourably with experimental observations. Both horizontal and sloping channel configurations are treated. The simplicity of the equations may allow future extension to more complicated fluid flows.

Slow crack growth and reliability of dental ceramics

Objective. To determine the slow crack growth (SCG) and Weibull parameters of five dental ceramics: a vitreous porcelain (V), a leucite-based porcelain (D), a leucite-based glass-ceramic (E1), a lithium disilicate glass-ceramic (E2) and a glass-infiltrated alumina composite (IC). Methods. Eighty disks (empty set 12mm x 1.1mm thick) of each material were constructed according to manufacturers` recommendations and polished. The stress corrosion susceptibility coefficient (n) was obtained by dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates immersed in artificial saliva at 37 degrees C. Weibull parameters were calculated for the 30 specimens tested at 1MPa/s in artificial saliva at 37 degrees C. The 80 specimens were distributed as follows: 10 for each stress rate (10(-2), 10(-1), 10(1), 10(2) MPa/s), 10 for inert strength (10(2) MPa/s, silicon oil) and 30 for 10(0) MPa/s. Fractographic analysis was also performed to investigate the fracture origin. Results. E2 showed the lowest slow crack growth susceptibility coefficient (17.2), followed by D (20.4) and V (26.3). E1 and IC presented the highest n values (30.1 and 31.1, respectively). Porcelain V presented the lowest Weibull modulus (5.2). All other materials showed similar Weibull modulus values, ranging from 9.4 to 11.7. Fractographic analysis indicated that for porcelain D, glass-ceramics E1 and E2, and composite IC crack deflection was the main toughening mechanism. Significance. This study provides a detailed microstructural and slow crack growth characterization of widely used dental ceramics. This is important from a clinical standpoint to assist the clinician in choosing the best ceramic material for each situation as well as predicting its clinical longevity. It also can be helpful in developing new materials for dental prostheses. (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of ion exchange on strength and slow crack growth of a dental porcelain

Objectives. To determine the effect of ion exchange on slow crack growth (SCG) parameters (n, stress corrosion susceptibility coefficient, and sigma(f0), scaling parameter) and Weibull parameters (m, Weibull modulus, and sigma(0), characteristic strength) of a dental porcelain. Methods. 160 porcelain discs were fabricated according to manufacturer`s instructions, polished through 1 mu m and divided into two groups: GC (control) and GI (submitted to an ion exchange procedure using a KNO(3) paste at 470 degrees C for 15 min). SCG parameters were determined by biaxial flexural strength test in artificial saliva at 37 degrees C using five constant stress rates (n =10). 20 specimens of each group were tested at 1 MPa/s to determine Weibull parameters. The SPT diagram was constructed using the least-squares fit of the strength data versus probability of failure. Results. Mean values of m and sigma(0) (95% confidence interval), n and sigma(f0) (standard deviation) were, respectively: 13.8 (10.1-18.8) and 60.4 (58.5 - 62.2), 24.1 (2.5) and 58.1 (0.01) for GC and 7.4 (5.3 -10.0) and 136.8 (129.1-144.7), 36.7 (7.3) and 127.9 (0.01) for GI. Fracture stresses (MPa) calculated using the SPT diagram for lifetimes of 1 day, 1 year and 10 years (at a 5% failure probability) were, respectively, 31.8, 24.9 and 22.7 for GC and 71.2, 60.6 and 56.9 for GI. Significance. For the porcelain tested, the ion exchange process improved strength and resistance to SCG, however, the material`s reliability decreased. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was also higher for the ion treated group. (C) 009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of leucite content on slow crack growth of dental porcelains

Objectives. To determine the stress corrosion susceptibility coefficient, n, of seven dental porcelains (A: Ceramco I; B: Ceramco-II; C: Ceramco-III; D: d.Sign; E: Cerabien; F: Vitadur-Alpha; and G: Ultropaline) after aging in air or artificial saliva, and correlate results with leucite content (LC). Methods. Bars were fired according to manufacturers` instructions and polished before induction of cracks by a Vickers indenter (19.6 N, 20 s). Four specimens were stored in air/room temperature, and three in saliva/37 degrees C. Five indentations were made per specimen and crack lengths measured at the following times: similar to 0; 1; 3; 10; 30; 100; 300; 1000 and 3000 h. The stress corrosion coefficient n was calculated by linear regression analysis after plotting crack length as a function of time, considering that the slope of the curve was (2/(3n + 2)]. Microstructural analysis was performed to determine LC. Results. LC of the porcelains were 22% (A and B); 6% (C); 15% (D); 0% (E and F); and 13% (G). Except for porcelains A and D, all materials showed a decrease in their n values when stored in artificial saliva. However, the decrease was more pronounced for porcelains B, F, and G. Ranking of materials varied according to storage media (in air, porcelain G showed higher n compared to A, while in saliva both showed similar coefficients). No correlation was found between n values and LC in air or saliva. Significance. Storage media influenced the n value obtained for most of the materials. LC did not affect resistance to slow crack growth regardless of the test environment. (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of pH on slow crack growth of dental porcelains

Objectives. To evaluate the effect of pH of storage medium on slow crack growth (SCG) parameters of dental porcelains. Methods. Two porcelains were selected: with (UD) and without (VM7) leucite particles, in order to assess if the microstructure would affect the response of the material to the pH variation. Disc specimens were produced following manufacturers` instructions. Specimens were stored in artificial saliva in pHs 3.5, 7.0 or 10.0 for 10 days and after that the fatigue parameters (n: SCG susceptibility coefficient and sigma(0): scaling parameter) were obtained by the dynamic fatigue test using the same pH of storage. Microstructural analysis of the materials was also performed. Results. For VM7, the values of n obtained in the different pHs were similar and varied from 29.9 to 31.2. The sigma(0) value obtained in pH 7.0 for VM7 was higher than that obtained in the other pHs, which were similar. For porcelain UD, n values obtained in pHs 7.0 and 10.0 were similar (40.8 and 39.6, respectively), and higher than that obtained in pH 3.5 (26.5). With respect to sigma(0), the value obtained for porcelain UD in pH 10.0 was lower than those obtained in pHs 3.5 and 7.0, which were similar. Significance. The effect of pH on the stress corrosion susceptibility (n) depended on the porcelain studied. While the n value of VM7 was not affected by the pH, UD presented lower n value in acid pH. For both porcelains, storage in acid or basic pH resulted in strength degradation. (C) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Analytical solution and numerical model for the interface in a stratified long wave system

For a two layered long wave propagation, linearized governing equations, which were derived earlier from the Euler equations of mass and momentum assuming negligible friction and interfacial mixing are solved analytically using Fourier transform. For the solution, variations of upper layer water level is assumed to be sinosoidal having known amplitude and variations of interface level is solved. As the governing equations are too complex to solve it analytically, density of upper layer fluid is assumed as very close to the density of lower layer fluid to simplify the lower layer equation. A numerical model is developed using the staggered leap-forg scheme for computation of water level and discharge in one dimensional propagation having known amplitude for the variations of upper layer water level and interface level to be solved. For the numerical model, water levels (upper layer and interface) at both the boundaries are assumed to be known from analytical solution. Results of numerical model are verified by comparing with the analytical solutions for different time period. Good agreements between analytical solution and numerical model are found for the stated boundary condition. The reliability of the developed numerical model is discussed, using it for different a (ratio of density of fluid in the upper layer to that in the lower layer) and p (ratio of water depth in the lower layer to that in the upper layer) values. It is found that as ‘CX’ increases amplification of interface also increases for same upper layer amplitude. Again for a constant lower layer depth, as ‘p’ increases amplification of interface. also increases for same upper layer amplitude.

Life on the ocean wave: Testing some intergroup hypotheses in a naturalistic setting

A survey (N= 352) was conducted among British passengers of a cross-channel ferry. The survey aimed to test hypotheses drawn from Realistic Group Conflict, Social Identity and Contact theories using mainly a correlational design. However, an intervention by members of the outgroup (French fishermen blockading a port) also allowed a quasi-experimental test of the effects of a direct experience of intergroup conflict. Results supported the hypotheses since conflict and national identification were associated with more negative and with less positive attitudes toward the outgroup, while contact had the reverse effects. In addition, the salience of group membership in the contact relationship weakly moderated the effect of contact.

Predictions of quantum mechanics and stochastic electrodynamics in travelling wave second harmonic generation

We show that stochastic electrodynamics and quantum mechanics give quantitatively different predictions for the quantum nondemolition (QND) correlations in travelling wave second harmonic generation. Using phase space methods and stochastic integration, we calculate correlations in both the positive-P and truncated Wigner representations, the latter being equivalent to the semi-classical theory of stochastic electrodynamics. We show that the semiclassical results are different in the regions where the system performs best in relation to the QND criteria, and that they significantly overestimate the performance in these regions. (C) 2001 Published by Elsevier Science B.V.

Efficient time-independent wave packet scattering calculations within a Lanczos subspace: H+O-2 (J=0) state-to-state reaction probabilities

An efficient Lanczos subspace method has been devised for calculating state-to-state reaction probabilities. The method recasts the time-independent wave packet Lippmann-Schwinger equation [Kouri , Chem. Phys. Lett. 203, 166 (1993)] inside a tridiagonal (Lanczos) representation in which action of the causal Green's operator is affected easily with a QR algorithm. The method is designed to yield all state-to-state reaction probabilities from a given reactant-channel wave packet using a single Lanczos subspace; the spectral properties of the tridiagonal Hamiltonian allow calculations to be undertaken at arbitrary energies within the spectral range of the initial wave packet. The method is applied to a H+O-2 system (J=0), and the results indicate the approach is accurate and stable. (C) 2002 American Institute of Physics.

Lanczos subspace time-independent wave packet calculations of S(D-1)+H-2 reactive scattering

In this paper. we present the results of quantum dynamical simulations of the S (D-1) + H-2 insertion reaction on a newly developed potential energy surface (J. Chem. Phys. 2001, 114, 320). State-to-state reaction probabilities. product state distributions, and initial-state resolved cumulative reaction probabilities from a given incoming reactant channel are obtained from a time-independent wave packet analysis, performed within a single Lanczos subspace. Integral reaction cross sections are then estimated by J-shifting method and compared with the results from molecular beam experiment and QCT calculations.