bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the SN‐preconditioning method to the integral equations for a slot‐array antenna
Authors: Zhang Yu , Xie Yongjun , Liang Changhong
Published: April 2003

In this paper, a novel preconditioner scheme slot neighbour (SN) preconditioner is applied to dense matrix equations derived from integral equations for a slot‐array antenna in order to improve the convergence of iterative integral‐equation solvers, such as the conjugate‐gradient (CG) method. The preconditioner accounts for expansion‐function–testing‐function interactions in the vicinity of a given slot, requiring an order of Ns × Nb complexity for each Ns slot and each slot with Nb expansion unknowns. A typical slot‐array antenna is analyzed and good results demonstrate the validity of the proposed algorithms. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 302–305, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10901
Reduction of SAR in a human‐head model wrapped in clothing materials
Authors: Chen Hsing‐Yi , Shen Kun‐Yi
Published: April 2003

An analysis of clothing material for reducing RF energy absorption in a human‐head model has been studied using the finite‐difference time‐domain (FDTD) method. The local maximum specific absorption ratio (SAR) induced in the human head model is used for the evaluation of the clothing material's shielding effectiveness for EM exposure. It is found that clothing material with a dielectric constant close to that of human skin will induce higher RF energy absorption in the human‐head model. On the other hand, clothing material with a higher relative dielectric constant and permeability can greatly reduce RF energy absorption. If the clothing material is mixed with conducting materials or magnetic materials, a remarkable reduction of RF energy absorption in the human‐head model will be obtained. These preliminary results provide valuable knowledge to help in the manufacture of anti‐electromagnetic wave clothing. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 305–308, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10902
Cancellation of sub‐harmonic and second harmonic components to improve the linearity of a low‐power consumption LNA using SiGe HBT
Authors: Iturbide‐Sanchez Flavio , Jardon‐Aguilar Hildeberto , Tirado‐Mendez Jose Alfredo
Published: April 2003

Three simple methods to improve the third‐order intercept point (IP3) of a low‐noise amplifier (LNA) for personal communication systems (PCS) applications or CDMA cellular handsets are introduced. Both simulations and results from previous works in the literature are compared in order to demonstrate the effectiveness of these methods in improving the performance of the LNA in terms of linearity when low‐bias voltage is used. The LNA was designed to operate at 1.9 GHz, using a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) and 2.4 V bias voltage. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 308–311, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10903
A compact dual‐slot antenna for WLAN applications
Authors: Qing X. M. , Chia M. Y. W.
Published: April 2003

This paper proposes a novel compact dual‐slot antenna for 5‐GHz WLAN applications. The prototype comprises a rectangular slot, a H‐shaped slot, and an open‐circuited microstrip feed line. The simulation and experimental results indicate broad operating bandwidth from 4.9 GHz to 6.3 GHz at 10‐dB return loss and 3‐dBi gain. The proposed antenna is compact, easy to fabricate, and inexpensive, and it presents good broadband characteristics that cover all 5‐GHz WLAN bands. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 311–313, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10904
Direct assessment of structural resistance against pressurized fracture
Authors: Bolzon G. , Cocchetti G.
Published: April 2003

The determination of the load bearing capacity of hydraulic structures such as dams, reservoirs and retaining walls requires the consideration of mixed‐mode fracture, possibly driven by the fluid pressure, in correspondence to artificial and natural joints (or cracks, in the latter case). A friction‐cohesive softening interface model with coupled degradation of normal and tangential strength is introduced here to account for the essential features of the joint behaviour; its predictive capability is assessed through extensive calculations. Alternative numerical techniques resting on the discrete‐crack approach are considered, focusing on simplified approaches for the direct appraisal of the structural resistance. Comparison is made with the results of evolutionary analyses, based on a priori piecewise linearization of the interface model and on ‘exact integration’. Copyright © 2003 John Wiley & Sons, Ltd.
Inter‐relations between experimental and computational aspects of slope stability analysis
Authors: Baker R.
Published: April 2003

Most conventional slope stability calculations are based on the linear Mohr–Coulomb failure criterion. However, a substantial amount of experimental evidence suggests that failure criteria of many soils are not linear particularly in the range of small normal stresses. This departure from linearity is significant for slope stability calculations since for a wide range of practical stability problems, critical slip surfaces are shallow and normal stresses acting on such surfaces are small. There exists a technical difficulty in performing strength measurements in the range of small normal stresses relevant to such slope stability problems. As a result, in many practical situations strength measurements are performed at much larger normal stresses then those relevant for the stability problem under consideration. When this is the case, use of the Mohr–Coulomb criterion amounts to a linear extrapolation of experimental information (obtained at large normal stresses), into the range of small normal stresses, which is relevant to the problem. This extrapolation results with very significant overestimation of calculated safety factors in cases when there is large mismatch between experimental and relevant ranges of normal stresses. The present work delineates the extent of this problem and suggests a practical way to overcome it. Copyright © 2003 John Wiley & Sons, Ltd.
A micromechanical study of rolling and sliding contacts in assemblies of oval granules
Authors: Shodja Hossein M. , Nezami Erfan G.
Published: April 2003

The evolution of the microstructure of an assembly of cohesionless granular materials with associated pores, which carry the overall applied stresses through frictional contacts is a complex phenomenon. The macroscopic flow of such materials take place by the virtue of the relative rolling and sliding of the grains on the micro‐scale. A new discrete element method for biaxial compression simulations of random assemblies of oval particles with mixed sizes is introduced. During the course of deformation, the new positions of the grains are determined by employing the static equilibrium equations. A key aspect of the method is that, it is formulated for ellipse cross‐sectional particles, hence desirable inherent anisotropies are possible. A robust algorithm for the determination of the contact points between neighbouring grains is given. Employing the present methodology, many aspects of the behaviour of two‐dimensional assemblies of oval cross‐sectional rods have been successfully addressed. The effects of initial void ratio, interparticle friction angle, aspect ratio, and bedding angle on the rolling and sliding contacts are examined. The distribution of normals to the rolling and sliding contacts have different patterns and are concentrated along directions, which are approximately perpendicular to one another. On the other hand, the distribution of all contact normals (combined rolling and sliding) are close to that of rolling contacts, which confirm that rolling is the dominant mechanism. This phenomenon becomes more pronounced for higher intergranular friction angle. Characteristics of the rolling and sliding contacts are also discussed in the context of the force angle, which is the inclination of contact force with respect to the contact normal. Copyright © 2003 John Wiley & Sons, Ltd.
Capturing strain localization behind a geosynthetic‐reinforced soil wall
Authors: Lai Timothy Y. , Borja Ronaldo I. , Duvernay Blaise G. , Meehan Richard L.
Published: April 2003

This paper presents the results of finite element (FE) analyses of shear strain localization that occurred in cohesionless soils supported by a geosynthetic‐reinforced retaining wall. The innovative aspects of the analyses include capturing of the localized deformation and the accompanying collapse mechanism using a recently developed embedded strong discontinuity model. The case study analysed, reported in previous publications, consists of a 3.5‐m tall, full‐scale reinforced wall model deforming in plane strain and loaded by surcharge at the surface to failure. Results of the analysis suggest strain localization developing from the toe of the wall and propagating upward to the ground surface, forming a curved failure surface. This is in agreement with a well‐documented failure mechanism experienced by the physical wall model showing internal failure surfaces developing behind the wall as a result of the surface loading. Important features of the analyses include mesh sensitivity studies and a comparison of the localization properties predicted by different pre‐localization constitutive models, including a family of three‐invariant elastoplastic constitutive models appropriate for frictional/dilatant materials. Results of the analysis demonstrate the potential of the enhanced FE method for capturing a collapse mechanism characterized by the presence of a failure, or slip, surface through earthen materials. Copyright © 2003 John Wiley & Sons, Ltd.
A practical determination strategy of optimal threshold parameter for matrix compression in wavelet BEM
Authors: Koro Kazuhiro , Abe Kazuhisa
Published: April 2003

A practical strategy is developed to determine the optimal threshold parameter for wavelet‐based boundary element (BE) analysis. The optimal parameter is determined so that the amount of storage (and computational work) is minimized without reducing the accuracy of the BE solution. In the present study, the Beylkin‐type truncation scheme is used in the matrix assembly. To avoid unnecessary integration concerning the truncated entries of a coefficient matrix, a priori estimation of the matrix entries is introduced and thus the truncated entries are determined twice: before and after matrix assembly. The optimal threshold parameter is set based on the equilibrium of the truncation and discretization errors. These errors are estimated in the residual sense. For Laplace problems the discretization error is, in particular, indicated with the potential's contribution ∥c∥ to the residual norm ∥R∥ used in error estimation for mesh adaptation. Since the normalized residual norm ∥c∥/∥u∥ (u: the potential components of BE solution) cannot be computed without main BE analysis, the discretization error is estimated by the approximate expression constructed through subsidiary BE calculation with smaller degree of freedom (DOF). The matrix compression using the proposed optimal threshold parameter enables us to generate a sparse matrix with O(N1+γ) (0≤γ<1) non‐zero entries. Although the quasi‐optimal memory requirements and complexity are not attained, the compression rate of a few per cent can be achieved for N∼1000. Copyright © 2003 John Wiley & Sons, Ltd.
A two‐grid method for expanded mixed finite‐element solution of semilinear reaction–diffusion equations
Authors: Chen Yanping , Huang Yunqing , Yu Dehao
Published: April 2003

We present a scheme for solving two‐dimensional semilinear reaction–diffusion equations using an expanded mixed finite element method. To linearize the mixed‐method equations, we use a two‐grid algorithm based on the Newton iteration method. The solution of a non‐linear system on the fine space is reduced to the solution of two small (one linear and one non‐linear) systems on the coarse space and a linear system on the fine space. It is shown that the coarse grid can be much coarser than the fine grid and achieve asymptotically optimal approximation as long as the mesh sizes satisfy H=O(h1/3). As a result, solving such a large class of non‐linear equation will not be much more difficult than solving one single linearized equation. Copyright © 2003 John Wiley & Sons, Ltd.
Explicit calculation of smoothed sensitivity coefficients for linear problems
Authors: Białecki R. A. , Divo E. , Kassab A. J. , Ait Maalem Lahcen R.
Published: April 2003

A technique of explicit calculation of sensitivity coefficients based on the approximation of the retrieved function by a linear combination of trial functions of compact support is presented. The method is applicable to steady state and transient linear inverse problems where unknown distributions of boundary fluxes, temperatures, initial conditions or source terms are retrieved. The sensitivity coefficients are obtained by solving a sequence of boundary value problems with boundary conditions and source term being homogeneous except for one term. This inhomogeneous term is taken as subsequent trial functions. Depending on the type of the retrieved function, it may appear on boundary conditions (Dirichlet or Neumann), initial conditions or the source term. Commercial software and analytic techniques can be used to solve this sequence of boundary value problems producing the required sensitivity coefficients. The choice of the approximating functions guarantees a filtration of the high frequency errors. Several numerical examples are included where the sensitivity coefficients are used to retrieve the unknown values of boundary fluxes in transient state and volumetric sources. Analytic, boundary‐element and finite‐element techniques are employed in the study. Copyright © 2003 John Wiley & Sons, Ltd.
DSC solution for flow in a staggered double lid driven cavity
Authors: Zhou Y. C. , Patnaik B. S. V. , Wan D. C. , Wei G. W.
Published: April 2003

A benchmark quality solution is presented for flow in a staggered double lid driven cavity obtained by using the wavelet‐based discrete singular convolution (DSC). The proposed wavelet based algorithm combines local methods' flexibility and global methods' accuracy, and hence, is a promising approach for achieving the high accuracy solution of the Navier–Stokes equations. Block structured grids with pseudo‐overlapping subdomains are employed in the present simulation. A third order Runge–Kutta scheme is used for the temporal discretization. Quantitative results are presented, apart from the qualitative fluid flow patterns. The prevalence of rich features of flow morphology, such as two primary vortex patterns, merged single primary vortex patterns, and secondary eddies, makes this problem very attractive and interesting. The problem is quite challenging for the possible existence of numerically induced asymmetric flow patterns and elliptic instability. Important computational issues like consistence, convergence and reliability of the numerical scheme are examined. The DSC algorithm is tested on the single lid driven cavity flow and the Taylor problem with a closed form solution. The double lid driven cavity simulations are cross‐validated with the standard second order finite volume method. Copyright © 2003 John Wiley & Sons, Ltd.
Meshless local boundary integral equation method for 2D elastodynamic problems
Authors: Sladek J. , Sladek V. , Van Keer R.
Published: April 2003

A new meshless method for solving transient elastodynamic boundary value problems, based on the local boundary integral equation (LBIE) method and the moving least squares approximation (MLS), is proposed in this paper. The LBIE with the MLS is applied to both transient and steady‐state (Laplace transformed) elastodynamics. Applying the MLS approximation for spatially dependent terms in the first approach, the LBIEs are transformed into a system of ordinary differential equations for nodal unknowns. This system of ordinary differential equations is solved by the Houbolt finite difference scheme. In the second formulation, the time variable is eliminated by using the Laplace transformation. Unknown Laplace transforms of displacements and traction vectors are computed from the LBIEs with the MLS approximation. The time‐dependent values are obtained by the Durbin inversion technique. Copyright © 2003 John Wiley & Sons, Ltd.
A two‐dimensional BEM/FEM coupling applied to viscoelastic analysis of composite domains
Authors: Mesquita A. D. , Coda H. B.
Published: April 2003

A coupling between the boundary‐element and finite‐element methods is studied for the viscoelastic analysis of reinforced media. The viscous behaviour of the composed body is taken into account by an alternative BEM methodology developed for the Boltzmann model. This methodology is based on differential constitutive relations for viscoelasticity. The reinforcements are modelled by finite elements and are considered elastic. The coupling is based on the sub‐region technique due to its generality and easy implementation. The resulting time‐marching process is able to represent both the instantaneous and the time‐dependent behaviour of a body subjected to general boundary conditions. The method is validated by an experimental result and its accuracy tested by comparing numerical results with analytical solutions. The generality of the method is proved by an infinite domain application. Copyright © 2003 John Wiley & Sons, Ltd.
On the computation of design derivatives for Huber–Mises plasticity with non‐linear hardening
Authors: Wisniewski K. , Kowalczyk P. , Turska E.
Published: April 2003

This paper concerns design sensitivity analysis (DSA) for an elasto–plastic material, with material parameters depending on, or serving as, design variables. The considered constitutive model is Huber–Mises deviatoric plasticity with non‐linear isotropic/kinematic hardening, one which is applicable to metals.

The standard radial return algorithm for linear hardening is generalized to account for non‐linear hardening functions. Two generalizations are presented; in both the non‐linearity is treated iteratively, but the iteration loop contains either a scalar equation or a group of tensorial equations. It is proven that the second formulation, which is the one used in some parallel codes, can be equivalently brought to a scalar form, more suitable for design differentiation. The design derivatives of both the algorithms are given explicitly, enabling thus calculation of the ‘explicit’ design derivative of stresses entering the global sensitivity equation.

The paper addresses several issues related to the implementation and testing of the DSA module; among them the concept of verification tests, both outside and inside a FE code, as well as the data handling implied by the algorithm. The numerical tests, which are used for verification of the DSA module, are described. They shed light on (a) the accuracy of the design derivatives, by comparison with finite difference computations and (b) the effect of the finite element formulation on the design derivatives for an isochoric plastic flow. Copyright © 2003 John Wiley & Sons, Ltd.
Prenatal diagnosis of laryngeal atresia
Authors: Önderoǧlu L. , Saygan Karamürsel B. , Bulun A. , Kale G. , Tunçbilek E.
Published: April 2003

Prenatal diagnosis of congenital atresia of the larynx is difficult but is possible by the findings of increased lung echogenicity and size coexisting with fetal ascites in ultrasonography. Sonographic findings may not always be typical. We report on a case of congenital laryngeal atresia diagnosed prenatally by the findings of fetal hydrops and hyperechogenic lungs. Our case presented with oligohydramnios. We also review syndromes that demonstrate laryngeal anomalies. Copyright © 2003 John Wiley & Sons, Ltd.
Antenatal manifestation of congenital pancreatoblastoma in a fetus with Beckwith–Wiedemann syndrome
Authors: Pelizzo Gloria , Conoscenti Giancarlo , Kalache Karim D. , Vesce Francesco , Guerrini Paolo , Cavazzini Luigi
Published: April 2003

An Erratum has been published for this article in Prenatal Diagnosis 23(9) 2003, 771

Antenatal detection of an isolated abdominal cyst was found to be a pancreatoblastoma in a female fetus with Beckwith–Wiedemann syndrome. Prenatal and post‐natal features and management of this very rare tumour are discussed. Molecular investigation disclosed a mosaic paternal 11p15 uniparental disomy in the tumoral cells. The prognosis of a congenital pancreatoblastoma is good if complete surgical excision is achieved. However, the association with Beckwith–Wiedemann syndrome requires a prolonged follow‐up because of the increased risk of developing malignant tumours. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of the 100‐g oral glucose tolerance test on fetal acid–base balance
Authors: Weissman Amir , Lowenstein Lior , Drugan Arie , Zimmer Etan Z.
Published: April 2003

Objective

Previous studies have shown that maternal hyperglycemia may lead to fetal hypoxia and acidosis. The aim of the present study was to examine the impact of an oral 100‐g glucose tolerance test on the fetal acid–base balance at mid‐gestation.

Methods

The study was conducted in healthy women who were scheduled for termination of pregnancy. The study group (n = 18) received an oral solution containing 100‐g glucose and the control group (n = 18) received only water 1 h prior to termination of pregnancy. Termination of pregnancy was performed by fetal intracardiac injection of potassium chloride (KCl) and intraamniotic instillation of PGF2α. Acid–base variables were evaluated in the fetal blood and the amniotic fluid.

Results

The glucose levels differed significantly between the study group and the control group with regard to maternal blood (127 ± 28 versus 69 ± 11 mg/dL, p < 0.001), fetal blood (128 ± 24 versus 71 ± 17 mg/dL, p < 0.001) and amniotic fluid (39 ± 13 versus 28 ± 5 mg/dL, p < 0.006). A linear relationship was found between maternal, fetal and amniotic fluid levels of glucose after maternal glucose ingestion. No significant changes were observed in the acid–base balance variables (pH, base excess, bicarbonate, lactate) in the fetal blood and the amniotic fluid of the study and control groups.

Conclusion

The 100‐g oral glucose tolerance test has no adverse effect on the fetal acid–base balance when glucose levels reach a peak 1 h after the test in normal pregnancies. Copyright © 2003 John Wiley & Sons, Ltd.
The effect of image size on nuchal translucency measurement
Authors: Edwards Andrew , Mulvey Sheila , Wallace Euan M.
Published: April 2003

Objectives

To assess the effect of altering image size on the absolute nuchal translucency (NT) measurement.

Methods

NT was measured at three image magnifications (60%, 100% and 200%) in 120 singleton pregnancies.

Results

The mean ± SD NT measurements were 1.52 ± 0.57 mm, 1.35 ± 0.53 mm and 1.18 ± 0.48 mm at 60%, 100% and 200% magnification, respectively (p = 0.00001).

Conclusions

The measurement of NT decreases significantly with increasing image size. Optimisation of NT as a method of screening will require agreed standardisation of image magnification. Copyright © 2003 John Wiley & Sons, Ltd.
Feasibility, accuracy and safety of chorionic villus sampling: a report of 10 741 cases
Authors: Brun Jean‐Luc , Mangione Raphaelle , Gangbo Flore , Guyon Frederic , Taine Laurence , Roux Denis , Maugey‐Laulom Brigitte , Horovitz Jacques , Saura Robert
Published: April 2003

Objectives

To evaluate the feasibility, accuracy and safety of chorionic villus sampling (CVS).

Methods

Ten thousand seven hundred and forty one singleton pregnancies at risk of chromosome abnormalities (96.3%) and gene disorders (2.8%) were referred from 1990 to 1999 to the fetal medicine unit of a teaching hospital. CVS was performed transabdominally after 11 weeks, using a modified freehand ultrasonographically guided technique by 5 operators. Fetal karyotyping was obtained using a direct method before 1995 and was completed by cell culture after 1996. Failed results, feto‐placental discrepancy and fetal loss were assessed.

Results

Villi were sampled using extra‐amniotic puncture (89.4%) and one sampling‐device insertion (92.3%). The mean weight of the specimen was 15.2 ± 6.0 mg. All attempts at sampling were successful, except eight (0.07%). The number of failed results following direct preparation, cell culture and both methods was 20 (0.19%), 23 (0.21%) and 2 (0.02%), respectively. Light maternal cell contamination occurred in less than 1% of the samplings after microscopic selection of the villi, and never interfered with the assessment of karyotyping. All 3 false‐negative results (0.03%) were recorded after direct preparation and 2 were corrected by culture. The rate of chromosomal abnormalities confined to the placenta decreased from 1.08% before 1995 to 0.73% after 1996. True fetal mosaicisms were recorded in 7 cases (0.06%). The rate of fetal loss at <28 weeks was 1.64% in all pregnancies and 1.92% when CVS was performed before 13 weeks. Advanced maternal age was the single factor significantly associated with fetal loss.

Conclusions

CVS was feasible, accurate and safe in our institution, as a result of the increasing experience of the operators and the cytogeneticists. Copyright © 2003 John Wiley & Sons, Ltd.
Detection of trisomy 21 by quantitative fluorescent–polymerase chain reaction in uncultured amniocytes
Authors: Solassol Jérôme , Rahil Haíssam , Sapin Vincent , Lemery Didier , Dastugue Bernard , Boespflug‐Tanguy Odile , Creveaux Isabelle
Published: April 2003

Prenatal diagnosis of fetal trisomy 21 is usually performed by cytogenetic analysis. This requires lengthy laboratory procedures, high costs and is unsuitable for large‐scale screening of pregnant women. Today, trisomy 21 can be rapidly diagnosed within 24 h by molecular analysis of uncultured fetal cells using the semi‐quantification of fluorescent PCR products from short tandem repeat (STR) polymorphic markers. The aim of our study was to test a chromosome quantification method on the basis of the analysis of fluorescent PCR products derived from non‐polymorphic target genes. Co‐amplification of a portion of DSCR1 (Down syndrome Critical Region 1) and the reference gene, CFTR (cystic fibrosis transmembrane regulator) enabled molecular detection of trisomy 21. Our method was successfully tested on a total of 154 amniotic fluids in a blind prospective study. Calculation of the DSCR1/CFTR ratio allowed us to distinguish between 152 normal amniotic fluids (mean ratio 0.99) and 2 amniotic fluids presenting a trisomy 21 status (DSCR1/CFTR ratio of 1.53 and 1.61, respectively). The results obtained by conventional cytogenetic analysis and our quantitative PCR method were concordant in every case. Our gene‐based fluorescent PCR approach represents an alternative molecular method for rapid and reliable detection of trisomy 21, which can be helpful in the prenatal diagnosis of women at high risk of fetal trisomy 21. Copyright © 2003 John Wiley & Sons, Ltd.
Unusual case of a fetus with congenital cystic adenomatoid malformation of the lung associated with trisomy 13
Authors: Heling Kai‐Sven , Tennstedt Cornelia , Chaoui R.
Published: April 2003

Congenital cystic adenomatoid malformation of the lung can be detected with antenatal ultrasound as hyperechogenic areas in the fetal chest. Associated extrapulmonary malformations as well as chromosomal aberrations are described as very rare.

We present a case report of a fetus in the 23rd week of gestation who showed in the course of a routine ultrasound screening a large number of malformations: holoprosencephaly, arrhinencephaly, cleft palate, CCAM type III of the right inferior pulmonary lobe, ventricular septal defect and bilateral clubfeet. Chromosome analysis confirmed the suspicion of trisomy 13.

The present case shows how important it is—even with malformations that are rarely accompanied by associated anomalies and which have a very good prognosis—to carry out a directed diagnosis including a fetal karyotyping. Copyright © 2003 John Wiley & Sons, Ltd.
Association between prenatal sonographic findings and post‐natal outcomes in 30 cases of isolated spina bifida aperta
Authors: Peralta Cleisson Fábio A. , Bunduki Victor , Plese José Píndaro P. , Figueiredo Eberval Gadelha , Miguelez Javier , Zugaib Marcelo
Published: April 2003

This study presents 30 cases of fetal isolated spina bifida aperta (SBA) to identify prenatal ultrasound findings that could predict the prognosis. Comparisons between surviving patients who had normal (group 1) and abnormal (group 2) post‐natal neurological outcomes were made for three different prenatal signs, that is, site of vertebral lesion, presence and degree of ventriculomegaly and presence of talipes. The site of the lesion was the most significant outcome predictor, as high spinal dysraphisms were observed in 2 patients (2/7–28.6%) in group 1 and in 15 patients (15/19–79.0%) in group 2 (p = 0.03). The presence of fetal ventriculomegaly was associated with impaired post‐natal neurological development, as it occurred in 4 patients (4/7–57.1%) in group 1 and in 18 patients (18/19–94.7%) in group 2 (p = 0.04). The presence of talipes did not significantly differ between the two groups. Patients with abnormal intellectual outcome (8/26–30.8%) had significantly greater (p = 0.018) lateral ventricle/hemisphere ratios (mean = 0.74, standard deviation = 0.13) than those with normal intellectual development (mean = 0.54, standard deviation = 0.18). Mean post‐natal follow‐up was at 23 months (standard deviation = 15 months). Copyright © 2003 John Wiley & Sons, Ltd.
Correlation between biomagnetic and Doppler findings of umbilical artery in fetal growth restriction
Authors: Kotini A. , Avgidou K. , Koutlaki N. , Sigalas J. , Anninos P. , Anastasiadis P.
Published: April 2003

Objective

To assess the value of biomagnetic recordings of the umbilical artery over Doppler ultrasound screening in order to predict complications of impaired uteroplacental blood flow in fetuses with intrauterine growth restriction (IUGR).

Methods

Our study population included 11 IUGR preeclamptic (34–37‐weeks gestation; birth weight 1969 ± 129 g) and 19 normal pregnancies (34–37‐weeks gestation; birth weight 3195 ± 229 g). Umbilical artery Doppler ultrasound waveform measurements were expressed in terms of pulsatility index (PI). Biomagnetic signals (waveforms) recorded from the IUGR umbilical artery were expressed in terms of magnetic power spectral amplitudes.

Results

In all cases, the frequency band considered was 2 to 7 Hz. The spectral amplitudes were low (mean: 117±24 fT/√Hz) in most (90.9%) IUGR pregnancies and high (mean: 224±37 fT/√Hz) in most normal pregnancies (89.5%). There was a statistically significant difference between normal and IUGR pregnancies with respect to spectral amplitudes (p < 0.0001), Doppler PI (p < 0.0005), pH (p < 0.0005) and Apgar score (p < 0.0005). Multiple linear regression analysis revealed an influence of PI, pH and Apgar scores on the biomagnetic values (ANOVA: p < 0.0005).

Conclusion

Our data imply that biomagnetic values of the umbilical artery flow could prove to be a helpful method for the evaluation of fetal well being especially in pregnancies complicated with preeclampsia and growth restriction. Copyright © 2003 John Wiley & Sons, Ltd.
A new approach to antenatal screening for Fragile X syndrome
Authors: Wald N. J. , Morris J. K.
Published: April 2003

Objectives

To describe a new approach to antenatal screening for Fragile X syndrome and to evaluate its effectiveness.

Methods

We propose that Fragile X syndrome should be considered as a different disorder in males and in females. We also propose that only male Fragile X syndrome should be screened for, so the initial screening test would be the determination of fetal sex. This can now be performed from eight‐weeks gestation using a polymerase chain reaction (PCR) analysis on maternal serum. If this test reveals a male fetus, then the same blood sample can be used to determine the CGG repeat length in the DNA of the mother, again using the PCR technique and a Southern blot analysis where necessary. Mothers with positive results (>58 repeats) would be offered antenatal diagnosis (chorionic villus sampling or amniocentesis) to determine the CGG repeat length in cells from the fetus. The screening performance of this strategy was determined using the performance of the component tests.

Results

The proposed strategy for screening for male Fragile X syndrome would have a 99% detection rate and a 0.1% false‐positive rate.

Conclusion

After antenatal screening for Down syndrome, the proposed screening strategy would be the most effective method of preventing the birth of males with severe mental retardation. It would have a higher detection rate and a lower false‐positive rate than any other antenatal screening programme currently being undertaken, and there would be virtually no prenatal diagnosis of female Fragile X syndrome, which, because such a high proportion are phenotypically normal, has been a barrier to the introduction of screening. Copyright © 2003 John Wiley & Sons, Ltd.
False‐positive diagnosis of trisomy 21 using fluorescence in situ hybridisation (FISH) on uncultured amniotic fluid cells
Authors: George Alice M. , Oei Paul , Winship Ingrid
Published: April 2003

An amniocentesis was performed on a 22‐week pregnancy following the detection of foetal abnormalities on ultrasound. A rapid aneuploid screen using fluorescence in situ hybridisation on uncultured amniotic fluid cells revealed 3 signals for chromosome 21, consistent with trisomy 21. In situ metaphase cultures revealed a 46,XY normal male karyotype. These discordant results may be explained by a sub‐standard batch of the commercially available probe or alternatively, a very specific variation within the sample interacting with the probe. Alternative strategies are proposed in order to safeguard against inappropriate clinical action as a consequence of discordant results. Copyright © 2003 John Wiley & Sons, Ltd.
Integrated ultrasound and biochemical screening for trisomy 21 using fetal nuchal translucency, absent fetal nasal bone, free β‐hCG and PAPP‐A at 11 to 14 weeks
Authors: Cicero Simona , Bindra Renu , Rembouskos Georgios , Spencer Kevin , Nicolaides Kypros H.
Published: April 2003

Background

Screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free β‐hCG and pregnancy‐associated plasma protein‐A (PAPP‐A) at 11 to 14 weeks of gestation is associated with a detection rate of 90% for a false‐positive rate of 5%. Recent evidence suggests that in about 70% of fetuses with trisomy 21, the nasal bone is not visible at the 11th‐ to 14th‐week scan (Cicero et al., 2001). The aim of this study was to examine whether fetal NT thickness and the level of maternal serum biochemical markers is independent of the presence or absence of the nasal bone, and to estimate the performance of a screening test that integrates the two sonographic and the two biochemical markers.

Methods

This was a retrospective case‐control study comprising 100 trisomy 21 and 400 chromosomally normal singleton pregnancies at 11 to 14 weeks of gestation. Ultrasound examination was carried out for measurement of fetal NT and assessment of the presence or absence of the fetal nasal bone. Maternal serum free β‐hCG and PAPP‐A were measured using the Kryptor rapid random‐access immunoassay analyser (Brahms Diagnostica GmbH, Berlin). The distribution of fetal NT, maternal serum free β‐hCG and PAPP‐A in trisomy 21 fetuses with absent and present nasal bone was examined.

Results

The nasal bone was absent in 69 and present in 31 of the trisomy 21 fetuses. There were no significant differences in median maternal age, median gestational age, NT delta, free β‐hCG MoM and PAPP‐A MoM in trisomy 21 fetuses with and without a visible nasal bone. For a false‐positive rate of 5%, it was estimated that screening with the four markers in combination with maternal age would be associated with a detection rate of 97%. For a false‐positive rate of 0.5%, the detection rate was 90.5%.

Conclusions

An integrated sonographic and biochemical test at 11 to 14 weeks can potentially identify about 90% of trisomy 21 fetuses for a false‐positive rate of 0.5%. Copyright © 2003 John Wiley & Sons, Ltd.
Fetoplacental discrepancy involving structural abnormalities of chromosome 8 detected by prenatal diagnosis
Authors: Soler Anna , Sánchez Aurora , Carrió Ana , Badenas Cèlia , Milà Montserrat , Borrell Antoni
Published: April 2003

We describe the finding of three cell lines involving different structural abnormalities of chromosome 8 detected in a prenatal diagnosis. Chorionic villi sampling (CVS) was performed on a pregnant woman because of advanced maternal age. Semidirect cytogenetic analysis showed a mos46,XX,i(8q)/46,XX,del(8)(p11.2) karyotype, confirmed by fluorescence in situ hybridization (FISH). Amniocentesis was subsequently performed, and the karyotype obtained was 46,XX,dup(8)(p23p11.2). The pregnancy was terminated; pathologic findings included clubfeet, clenched left hand, subcutaneous edema and bilateral hydrocephalus. Molecular studies using chromosome 8 microsatellites performed on parents' blood and fetal tissues revealed a maternal meiotic origin of the inv dup(8p) with deletion of the distal p23 region and duplication of the remaining 8p. We propose a model to explain the cytogenetic findings, which includes a first maternal meiotic error giving rise to a large dicentric isochromosome 8 present in the ovum, a second error in one of the first zygote divisions with misdivision of the dicentric 8 giving rise to a cell line with del(8p) confined to the trophoblast and another cell line with inv dup(8p) confined to the fetal tissue and a third error in the trophoblast giving rise to a further cell line with isochromosome 8q. Copyright © 2003 John Wiley & Sons, Ltd.
A familial Xp+ chromosome detected during fetal karyotyping, which is associated with short stature in four generations of a Turkish family
Authors: Karaman B. , Wollnik B. , Ermiş H. , Yüksel‐Apak M. , Başaran S.
Published: April 2003

The short‐stature homeobox‐containing gene (SHOX) on chromosome Xp22.3 was recently identified as an important determinant of the stature phenotype. Deletions of the SHOX gene, some of them due to structural chromosome abnormalities, have been described in patients with idiopathic short stature and Leri‐Weill syndrome. Additionally, haploinsufficiency of SHOX is a main cause for short stature seen in patients with Turner syndrome.

Here we report an unusual X‐chromosome abnormality, which was detected during a fetal karyotyping performed because of a previous child with Down syndrome. GTG banding demonstrated an extra chromosome segment on the terminal part of the short arm of chromosome X in the index case (karyotype: 46,X,Xp+). The same chromosomal abnormality was found in the mother and the maternal grandmother. All carriers of this chromosomal abnormality presented with short stature but no other associated symptoms.

Whole chromosome painting of X revealed a homogeneous painting of the abnormal X chromosome indicating that no other chromosome was involved. Additional FISH studies with probe DXS1140 (Kallmann probe at Xp22.3), Quint‐Essential X‐Specific DNA (DMD probe at Xp21.2), XIST (at Xq13.2), and Tel Xq/Yq were performed, and no abnormality was observed in the intensities or the localizations of the probes signals. However, applying a specific SHOX gene probe (derived from cosmid LLNONO3M34F5) showed a loss of signal on the derivative X chromosome. Our results show that the Xp+ generation led to a deletion of the complete SHOX gene and caused short stature in the presented family. Copyright © 2003 John Wiley & Sons, Ltd.
Perinatal outcome in fetuses with megacystis in the first half of pregnancy
Authors: Jouannic Jean‐Marie , Hyett Jon A. , Pandya Pranav P. , Gulbis Béatrice , Rodeck Charles H. , Jauniaux Eric
Published: April 2003

Objective

To present the outcome of a consecutive series of 19 fetuses referred to our center for megacystis in the first half of the pregnancy.

Study Design

Retrospective analysis.

Methods

19 cases of early fetal megacystis were reviewed. Inclusion criteria were the visualization of an enlarged bladder with a maximum longitudinal diameter >10 mm and a gestational age of no more than 19 weeks.

Results

The median gestational age at diagnosis was 16 weeks (range 12–19 weeks). The median maximum longitudinal diameter of the fetal bladder at the time of diagnosis was 21 mm (range 11–35 mm). The fetal megacystis was associated with another extra renal anomaly in six cases (30%). There was no fetus with abnormal karyotype. Termination of pregnancy was performed in 11 cases because of the severity of the renal disease. One spontaneous intrauterine death occurred. A vesicoamniotic shunt was inserted in three cases, two of which died in utero. The surviving fetus that was shunted died in the neonatal period from acute renal failure. In the remaining four fetuses, resolution of the megacystis occurred spontaneously (n = 2) or following serial single‐needle aspiration (n = 2). One of these had renal insufficiency requiring kidney transplantation.

Conclusion

The outcome of fetuses with early obstructive uropathy is poor, with or without in utero therapy. Pathophysiology, clinical presentation and outcome of fetuses with early uropathy may differ from those previously described in the latter part of pregnancy. Copyright © 2003 John Wiley & Sons, Ltd.
Second‐trimester Down syndrome maternal serum screening in twin pregnancies: impact of chorionicity
Authors: Muller Françoise , Dreux Sophie , Dupoizat Henry , Uzan Serge , Dubin Marie‐Françoise , Oury Jean‐François , Dingeon Bernard , Dommergues Marc
Published: April 2003

Objective

To evaluate the diagnostic value of second‐trimester maternal serum screening for Down syndrome in twin pregnancies.

Method

On the basis of a prospective study of second‐trimester maternal serum screening, we studied the distribution of alpha‐fetoprotein (AFP) and free ß hCG in 3043 twin pregnancies with known outcome. There were 1561 dichorionic and 244 monochorionic pregnancies. The placental type was not available in 1238 cases. We compared 5 screening policies with the same risk, 1/250, cut‐off: maternal age, maternal age corrected for the risk of having at least one affected twin in dichorionic pregnancies, maternal serum marker screening using observed AFP and free ß‐hCG values divided by a factor of 2, by using the median values actually observed in the global twin population, or by the median values specific to mono‐ or dichorionic twins.

Results

When expressed in singleton‐derived MoMs, the median was 2.10 for AFP and 2.11 for free ß‐hCG. The median AFP did not differ between monochorionic and dichorionic pregnancies. The distribution of free ß‐hCG was significantly shifted towards greater values in monochorionic (2.16 MoM) compared to dichorionic (2.07) pregnancies (p < 0.0001). Screened‐positive and detection rates were, respectively, 6.6% and 27.3% using maternal age alone, 24.6% and 54.5% using maternal age corrected for the risk of having at least one affected twin in dichorionic pregnancies, 7.75% and 54.5% using observed AFP and free beta‐hCG values divided by a factor of 2, 8.05% and 54.5% using the median values actually observed in the global twin population, and 7.75% and 54.5% using the median values specific to mono‐ or dichorionic twins.

Conclusion

Trisomy 21 second‐trimester maternal serum screening is feasible in twins, and is better than a policy based on maternal age alone. Copyright © 2003 John Wiley & Sons, Ltd.
Transient pores in vesicles
Authors: Karatekin Erdem , Sandre Olivier , Brochard‐Wyart Françoise
Published: March 2003

We present our observations of transient pores in giant unilamellar vesicles, placed under tension, by optical illumination. When the membrane tension reached a certain level, transient pores appeared. Pore opening is driven by the membrane tension, σ, and its closure by the pore's line tension, 𝒯. By use of viscous mixtures of glycerol and water, we slowed down the leak out of the inner liquid in the presence of a pore. This allowed pores to reach large sizes (a few micrometres) and last at least a few seconds so that they could be visualized by fluorescence videomicroscopy. Line tension was inferred from the measurements of the closure velocity of the pores. By addition of cholesterol, which increased 𝒯 (reducing pore lifetimes), or of surfactants, which decreased 𝒯 (increasing pore lifetimes), we demonstrate how 𝒯, and consequently pore lifetimes, can be controlled over nearly two orders of magnitude. Addition of surfactants also has a dramatic effect on vesicle fusion. We discuss how our results can be extended to less viscous aqueous solutions which are more relevant for liposomal drug delivery formulations.

© 2003 Society of Chemical Industry
A thermophysical approach to the behaviour of gels and complex micellar solutions
Authors: Roux Alain H , Ballerat‐Busserolles Karine , Roux‐Desgranges Geneviève
Published: March 2003

DSC analysis, conductimetric and rheological techniques have been used to investigate the structural changes able to develop in the [water + hexadecyltrimethyl ammonium bromide (CTAB) + phenol] ternary micellar system. Specific, mainly electrostatic, interactions at the micellar interface between the surfactant polar head groups and phenol give rise to a swelling of aggregates into worm‐like micelles as evidenced by large changes of viscosity of the mixture in some phenol/CTAB ratio and temperature ranges. A thermophysical approach allowed us to determine the formation of a strong 1:1 complex between CTAB and phenol, as evidenced by either the viscoelastic properties of the solution or the formation of thermoreversible gels. At low temperature, a crystallized molecular surfactant complex is also observed. Its melting point differs from the Krafft temperature of CTAB.

© 2003 Society of Chemical Industry
HLD concept as a tool for the characterization of cosmetic hydrocarbon oils
Authors: Nardello Véronique , Chailloux Nelly , Poprawski Jérôme , Salager Jean‐Louis , Aubry Jean‐Marie
Published: March 2003

The HLD (hydrophilic lipophilic deviation) concept was applied to several water/i‐C13En/2‐propanol/hydrocarbon oil systems. For each oil, the optimum formulation, corresponding to HLD = 0, was determined by systematically changing the formulation as a monotonic variation of the surfactant ethylene oxide number (EON) scanned variable. The optimum value for EON (symbolized as EON*) was accurately pinpointed both by estimating the solubilization and by measuring the interfacial tension with a spinning‐drop tensiometer. This method allowed the classification of cosmetic hydrocarbon oils such as isohexadecane, paraffin oil, squalane, squalene and hydrogenated polydecenes in C30, C40, C40–C50, on an equivalent alkane carbon number (EACN) calibration scale based on five linear alkanes covering the liquid range (C5 to C16).

© 2003 Society of Chemical Industry