bluuebunny/crossref_metadata_2025 huggingface dataset:
Resolution of the flow in clarifiers by using a stabilized finite element method
Authors: Vellando P. , Puertas J. , Colominas I.
Published: December 2003

The description of the flow that takes place in clarifiers and other wastewater treatment basins may be a powerful tool to attain an optimum design of these structures, in order to make the most of the wastewater treatment plant resources. Some authors have attempted so by making use of the potential flow or the Stokes equations. When these simplifications are used, an approximation of the flow for slow creeping conditions is obtained, but only the resolution of the all‐term‐including Navier–Stokes equations will allow us to detect the real streamlines and the vortices that show up for even very slow water flows. The use of the Navier–Stokes formulae as the governing equations involves the appearance of complex stability problems that do not show up for the previously mentioned simplifications. In the present work a stable finite element method for the resolution of the Navier–Stokes equations is presented, verified, and used in the resolution of some wastewater treatment flow problems with very interesting results. Copyright © 2004 John Wiley & Sons, Ltd.
Indirect boundary element method for unsteady linearized flow over prolate and oblate spheroids and hemispheroidal protuberances
Authors: Shatz Lisa F.
Published: December 2003

The indirect boundary element method was used to study the hydrodynamics of oscillatory viscous flow over prolate and oblate spheroids, and over hemispheroidal bodies hinged to a plate. Analytic techniques, such as spheroidal coordinates, method of images, and series representations, were used to make the numerical methods more efficient. A novel method for computing the hydrodynamic torque was used, since for oscillatory flow the torque cannot be computed directly from the weightings. Instead, a Green's function for torque was derived to compute the torque indirectly from the weightings. For full spheroids, the method was checked by comparing the results to exact solutions at low and high frequencies, and to results computed using the singularity method. For hemispheroids hinged to a plate, the method for low frequencies was checked by comparing the results to previous results, and to exact solutions at high frequencies. Copyright © 2004 John Wiley & Sons, Ltd.
Implementation and validation of a slender vortex filament code: Its application to the study of a four‐vortex wake model
Authors: Margerit D. , Brancher P. , Giovannini A.
Published: December 2003

A computational code EZ‐vortex is developed for the motion of slender vortex filaments of closed or open shape. The integro‐differential equations governing the motion of the vortex centre lines are either the Callegari and Ting equations, which are the leading order solution of a matched asymptotic analysis, or equivalent forms of these equations. They include large axial velocity and nonsimilar profiles in the vortical cores. The fluid may be viscous or inviscid. This code is validated both against known solutions of these equations and results from linear stability analyses. The linear and non‐linear stages of a perturbed two‐vortex wake and of a four‐vortex wake model are then computed. Copyright © 2004 John Wiley & Sons, Ltd.
Euler solutions for aerodynamic inverse shape design
Authors: de Bortoli A. L. , de Quadros R.
Published: December 2003

Contributions to the aerodynamics development have to be involved to achieve an increase in quality, reducing time and computer costs. Therefore, this work develops an optimization method based on the finite volume explicit Runge–Kutta multi‐stage scheme with central spatial discretization in combination with multigrid and preconditioning. The multigrid approach includes local time‐stepping and residual smoothing. Such a method allows getting the goal of compressible and almost incompressible solution of fluid flows, having a rate of convergence almost independent from the Mach number. Numerical tests are carried out for the NACA 0012 and 0009 airfoils and three‐dimensional wings based on NACA profiles for Mach‐numbers ranging from 0.8 to 0.002 using the Euler equations. These calculations are found to compare favorably with experimental and numerical data available in the literature. Besides, it is worth pointing out that these results build on earlier ones when finding appropriate new three‐dimensional aerodynamical geometries. Copyright © 2004 John Wiley & Sons, Ltd.
Finite element analysis of filling stage in die‐casting process using marker surface method and adaptive grid refinement technique
Authors: Jeong J. H. , Yang D. Y.
Published: December 2003

The marker surface method and the adaptive grid refinement technique have been applied to the three‐dimensional (3‐D) finite element analysis of the filling stage in the die‐casting process. Especially, the marker surface plugging technique and the marker surface regeneration technique incorporated in the marker surface method have been proposed for the efficient analysis of 3‐D practical problems. Through the marker surface plugging technique, new parts of marker surface are effective lycreated in order to eliminate the gaps between the parts of marker surface or between the edge of marker surface and cavity wall. By using the marker surface regeneration technique, the marker surface including a great number of marker elements is recreated on the basis of its original shape in order to decrease the number of marker elements and computational time. A3‐D example used as the benchmark test and a typical industrial problem of the die‐casting process have been analysed. The numerical results have been in good agreement with the experimental results and the efficiency of the adaptive grid refinement technique has been verified. It has been shown that the proposed techniques incorporated in the marker surface method and the adaptive grid refinement technique can be effectively applied to general industrial problems. Copyright © 2004 John Wiley & Sons, Ltd.
Krylov subspace accelerated inexact Newton method for linear and nonlinear equations
Authors: Harrison Robert J.
Published: December 2003

A Krylov subspace accelerated inexact Newton (KAIN) method for solving linear and nonlinear equations is described, and its relationship to the popular direct inversion in the iterative subspace method [DIIS; Pulay, P., Chem Phys Lett 1980, 393, 73] is analyzed. The two methods are compared with application to simple test equations and the location of the minimum energy crossing point of potential energy surfaces. KAIN is no more complicated to implement than DIIS, but can accommodate a wider variety of preconditioning and performs substantially better with poor preconditioning. With perfect preconditioning, KAIN is shown to be very similar to DIIS. For these reasons, KAIN is recommended as a replacement for DIIS. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 328–334, 2004
A simple computational scheme for obtaining localized bonding schemes and their weights from a CASSCF wave function
Authors: Bachler Vinzenz
Published: December 2003

We devise and apply a simple computational scheme for obtaining localized bonding schemes and their weights from a CASSCF wave function. These bonding schemes are close to resonance structures drawn by chemists. Firstly, a CASSCF wave function is computed. Secondly, the CASSCF computation is repeated but now the delocalized complete active space MOs are substituted by Weinhold's localized natural atomic orbitals. In this way the original CASSCF wave function is represented by a sequence of Slater determinants composed of localized natural atomic orbitals. Thus, a standard CASSCF wave function can be reinterpreted in terms of a local picture. To test the method we obtain localized bonding schemes and their weights for the ground and the π–π* excited state of ethylene. Moreover, bonding schemes and their weights are derived for the ground, the 11Bu, and the 21Ag π–π* excited states oftrans‐butadiene. The large weight bonding schemes are shown to be a qualitative indicator for the known photochemistry of butadiene. The remarkable stability of the Arduengo carbene is discussed by obtaining bonding schemes that indicate a stabilizing delocalization of the π electrons. We illustrate that the large weight bonding schemes are in line with the observed reactivity of the Arduengo carbene. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 343–367, 2004
New developments in the symmetry‐adapted algorithm of the Polarizable Continuum Model
Authors: Frediani Luca , Cammi Roberto , Pomelli Christian S. , Tomasi Jacopo , Ruud Kenneth
Published: December 2003

We present recent developments in the symmetry implementation of the Polarizable Continuum Model (PCM). The structure of the matrix, which defines the PCM solvent response, is examined, and we demonstrate how this matrix can be transformed to a block diagonal form where each block belongs to different irreducible representations of the molecular point group. This development is especially important at the Multi‐configurational Self‐Consistent Field (MCSCF) level where symmetry is needed to avoid problems with symmetry breaking in the wave function and facilitate the optimization of electronic excited states. Moreover, although only the totally symmetric part of the solvent interaction is needed for energy calculations, in response or perturbation theory calculations of molecular properties, other irreps play an important role and the classification of solvent interaction terms by irrep is, therefore, desirable. In addition, the use of symmetry reduces the computational cost. The implementation presented here is illustrated with a series of calculations of absorption and emission processes in solution on the diazines pyrazine, pyrimidine, and pyridazine. These calculations allow us to illustrate both formal aspects of the implementation such as the choice of active spaces based on orbital symmetry as well as practical aspects such as the speed‐up of the calculation. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 375–385, 2004
QM/MM study of aqueous solvation of the uranyl fluoride [UO2F] complex
Authors: Infante Ivan , Visscher Lucas
Published: December 2003

The aqueous solvation of the uranylfluoride complex [UO2F] was studied using full quantum mechanical (QM) and hybrid QM/molecular mechanics (MM) methods. Inclusion of a complete first solvation shell was found necessary to reproduce the experimentally observed heptacoordination of uranium. An efficient and accurate computational model is proposed that consists of structure optimization of the coordinated uranium complex as QM region, followed by single‐point full QM calculations to compute relative energies. This method is proven feasible for studies of large solvated actinide complexes. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 386–392, 2004
Automated docking of highly flexible ligands by genetic algorithms: A critical assessment
Authors: Cecchini Marco , Kolb Peter , Majeux Nicolas , Caflisch Amedeo
Published: December 2003

An improved version of the fragment‐based flexible ligand docking approach SEED–FFLD is tested on inhibitors of human immunodeficiency virus type 1 protease, human α‐thrombin and the estrogen receptor β. The docking results indicate that it is possible to correctly reproduce the binding mode of inhibitors with more than ten rotatable bonds if the strain in their covalent geometry upon binding is not large. A high degree of convergence towards a unique binding mode in multiple runs of the genetic algorithm is proposed as a necessary condition for successful docking. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 412–422, 2004
Time‐reversible always stable predictor–corrector method for molecular dynamics of polarizable molecules
Authors: Kolafa Jiří
Published: December 2003

An improved method for classic molecular dynamics of polarizable molecules is proposed. The method uses a predictor, one evaluation of the electrostatic field per integration step, and relaxation (damping). The self‐consistent solution is approximated with error of the second order (with respect to the timestep). The time reversibility (long‐time energy conservation) error is of the (2n − 1)th order, where n is the predictor length. The method is easy to implement, efficient, accurate, and suitable for any model of polarizability. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 335–342, 2004
Calculation of affinities of peptides for proteins
Authors: Donnini Serena , Juffer André H.
Published: December 2003

Several methodologies were employed to calculate the Gibbs standard free energy of binding for a collection of protein–ligand complexes, where the ligand is a peptide and the protein is representative for various protein families. Almost 40 protein–ligand complexes were employed for a continuum approach, which considers the protein and the peptide at the atomic level, but includes solvent as a polarizable continuum. Five protein–ligand complexes were employed for an all‐atom approach that relies on a combination of the double decoupling method with thermodynamic integration and molecular dynamics. These affinities were also computed by means of the linear interaction energy method. Although it generally proved rather difficult to predict the absolute free energies correctly, for some protein families the experimental ranking order was correctly reproduced by the continuum and all‐atom approach. Considerable attention has also been given to correctly analyze the affinities of charged peptides, where it is required to judge the effect of one or more ions that are being decoupled in an all‐atom approach to preserve electroneutrality. The various methods are further judged upon their merits. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 393–411, 2004
Class I ribonucleotide reductase revisited: The effect of removing a proton on Glu441
Authors: Pelmenschikov Vladimir , Cho Kyung‐Bin , Siegbahn Per E. M.
Published: December 2003

The substrate mechanism of class I ribonucleotide reductase has been revisited using the hybrid density functional B3LYP method. The molecular model used is based on the X‐ray structure and includes all the residues of the R1 subunit commonly considered in the RNR substrate conversion scheme: Cys439 initiating the reaction as a thiyl radical, the redox‐active cysteines Cys225 and Cys462, and the catalytically important Glu441 and Asn437. In contrast to previous theoretical studies of the overall mechanism, Glu441 is added as an anion. All relevant transition states have been optimized, including one where an electron is transferred 8 Å from the disulfide to the substrate simultaneously with a proton transfer from Glu441. The calculated barrier for this step is 19.1 kcal/mol, which can be compared to the rate‐limiting barrier indicated by experiments of about 17 kcal/mol. Even though the calculated barrier is somewhat higher than the experimental limit, the discrepancy is within the normal error bounds of B3LYP. The suggestion from the present modeling study is thus that a protonated Glu441 does not need to be present at the active site from the beginning of the catalytic cycle. However, the previously suggested mechanism with an initial protonation of Glu441 cannot be ruled out, because even with the cost added for protonation of Glu441 with a typical pKa of 4, the barrier for that mechanism is lower than the one obtained for the present mechanism. The results are compared to experimental results and suggestions. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 311–321, 2004
A finite B‐spline basis set for accurate diatomic molecule calculations
Authors: Artemyev A. N. , Ludeña E. V. , Karasiev V. V. , Hernández A. J.
Published: December 2003

A finite basis set particularly adapted for solving the Hartree–Fock equation for diatomic molecules in prolate spheroidal coordinates has been constructed. These basis functions have been devised as products of B‐splines times associated Legendre polynomials. Due to the large number of B‐splines, the resulting set of eigenfunctions is amply distributed over excited states. This gives the possibility of using these basis sets to calculate sums over excited states, appearing in various orders of perturbation theory. As an illustration, the second‐order corrections to the ground‐state energy of some atoms and diatomic molecules with closed electron shells have been calculated. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 368–374, 2004
Isomers of C20: An energy profile III
Authors: Chavez Jennifer I. , Carrillo Maira M. , Beran Kyle A.
Published: December 2003

Semiempirical calculations, at the PM3 level provided within the Winmopac v2.0 software package, are used to geometrically optimize and determine the absolute energies (heats of formation) of a variety of C20 isomers that are predicted to exist in and around the ring and cage isomers. Using the optimized Cartesian coordinates for the ring and the cage isomers, a saddle‐point calculation was performed. The resulting energy profile, consisting of a series of peaks and valleys, is used as a starting point for the identification and location of fifteen additional isomers of C20 that are predicted to be energetically stable, both via geometry optimizations and force constant analysis. These additional isomers were subsequently determined to lie adjacent to one another on the potential surface and establish a step‐wise transformation between the ring and the cage. Transition‐state optimization of the Cartesian coordinates at the saddle point between adjacent isomers was performed to quantify the energy of the transition state. The step‐wise process from one isomer to another, which extends out over the three‐dimensional surface, is predicted to require ∼15% less energy than that of the direct, two‐dimensional transformation predicted in the bowl‐cage profile. However, the net atomic rearrangement for the step‐wise process is about four times greater than that of the direct process. Although less in energy, the amount of atomic rearrangement in the step‐wise process would make the occurrence of such a route prohibitive. Utilizing the direct distance separating the three primary isomers (ring, bowl, cage), the method of triangulation is performed to quantitatively position other C20 structures on the potential surface, relative to the ring, bowl, and cage isomers. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 322–327, 2004
Second‐order atomic Fukui indices from the electron‐pair density in the framework of the atoms in molecules theory
Authors: Fradera Xavier , Solà Miquel
Published: December 2003

Atomic Fukui indices, which are obtained from the electron density, have been previously shown to be useful in predicting which atoms in a molecule are most likely to suffer nucleophilic, electrophilic, or radicalary attacks. Here, we present a second‐order generalization of these indices based on the electron pair density. We show how second‐order atomic Fukui indices can be used to analyze the effects of electron loss or gain in several molecules from an electron pair point of view. Further, these indices also highlight which atoms or pairs of atoms are more likely to suffer nucleophilic, electrophilic, or radical attacks. In conclusion, second‐order indices can complement first‐order ones by affording relevant information on molecular reactivity from an electron pair perspective. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 439–446, 2004
Biosorption of palladium and platinum by sulfate‐reducing bacteria
Authors: de Vargas Inmaculada , Macaskie Lynne E , Guibal Eric
Published: December 2003

The biosorption capacities of palladium and platinum were studied in three different species of Desulfovibrio: Desulfovibrio desulfuricans, Desulfovibrio fructosivorans and Desulfovibrio vulgaris. The influence of several parameters such as pH, acidic background and competitor anions on biosorption equilibria and biosorption kinetics were evaluated. Differences were observed between the three strains of Desulfovibrio with respect to the optimum biosorption parameters of both metals, suggesting differences in the metal speciation–dependent sorption mechanisms involved. The most promising Pd and Pt biosorption results were obtained using D desulfuricans with rapid achievement of equilibrium (90% of total sorption was achieved in 5–15 min) and a maximum value of 190 mg g−1 dry biomass and 90 mg g−1 dry biomass for Pd and Pt accumulation respectively, at pH 3. Copyright © 2003 Society of Chemical Industry
Potassium hexacyanocobalt ferrate and ammonium molybdophosphate sorption bags for the removal of 137Cs from aqueous solutions and a simulated waste
Authors: Raouf MW Abdel
Published: December 2003

In the present study, the removal and immobilization of 137Cs from aqueous waste solutions and a simulated waste was investigated. Two inorganic ion‐exchange complexes: di‐potassium hexacyanocobalt(II)‐ferrate(II), K2CoFe(CN)6·xH2O (KCFC), and ammonium‐12‐molybdophosphate [(NH4)3PMo12O40·aq] (AMP), were charged separately into porous nylon bags (sorption bags) of 5 µm pore diameter. The first complex (KCFC) was prepared in our laboratory. The second (AMP) was used for comparison. Easy handling and increased potential for reuse characterize the sorption bag technique. The KCFC complex was investigated by thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), porosity, infra‐red (IR) and X‐ray powder diffraction (XRD). The chemical and structural investigations revealed that the KCFC complex has adequate ion‐exchange capacity and high affinity for 137Cs. The sorption bag technique showed promising results for the removal of 137Cs from aqueous waste solutions. The KCFC bags showed the highest 137Cs removal (∼0.91 g g−1), at pH 8.5; AMP bags gave the highest 137Cs removal (∼0.97 g g−1) in 0.1 N HNO3 and 1.5 N HNO3, both with a waste: sorbent ratio of 80 cm3 g−1. Sorption data for both KCFC and AMP revealed a good fit to the Freundlich sorption isotherm. To assess the potential of sorption bags, the used bags were regenerated in different leachants and reused in further sorption investigations. 137Cs recovery from the used sorbents was ∼0.46 g g−1 using 6 N HCl as leachant for AMP, compared with ∼0.253 g g−1 for KCFC using 6 N NaCl. These results indicated stronger cesium immobilization in the KCFC complex. Copyright © 2003 Society of Chemical Industry
Effect of ammonium chloride on plasmid DNA production in high cell density batch culture for biopharmaceutical use
Authors: Voss Carsten , Schmidt Torsten , Schleef Martin , Friehs Karl , Flaschel Erwin
Published: December 2003

In this paper the influence of ammonium salt concentration on the production of pharmaceutical grade plasmid DNA from unfed high cell density batch culture on synthetic glycerol media is presented. Ammonium chloride in different concentrations (0 mmol dm−3, 18.7 mmol dm−3, 37 mmol dm−3 and 74 mmol dm−3 supplemented) was used beside sodium glutamate as nitrogen source. Plasmid DNA concentrations of more than 50 mg dm−3 were obtained with 37 mmol dm−3 ammonium. The homogeneity of the DNA produced was confirmed by agarose and capillary gel electrophoresis and found to fulfil the quality requirements set for biopharmaceutical plasmid DNA with more than 90% in the supercoiled form. Copyright © 2003 Society of Chemical Industry
Preparation and characterization of acrylic acid‐treated bacterial cellulose cation‐exchange membrane
Authors: Choi Yong‐Jin , Ahn Yeonghee , Kang Moon‐Sung , Jun Hong‐Ki , Kim In Soo , Moon Seung‐Hyeon
Published: December 2003

The feasibility of using bacterial cellulose as a source for environmentally compatible ion‐exchange membranes (IEM) was studied. Bacterial cellulose was modified with cation‐exchangeable acrylic acid (AAc) by UV‐graft polymerization to prepare membranes having ion‐exchange capacity (IEC) and greater structural density. Fourier transform infrared (FTIR) spectra showed that acrylic acids were successfully bound to bacterial cellulose. Morphological changes of acrylic acid‐treated bacterial cellulose were examined through scanning electron microscopy. A dense structure of the membrane increased with increasing UV‐irradiation time. Acrylic‐modified bacterial cellulose membrane showed reasonable mechanical properties, such as tensile strength of 12 MPa and elongation of 6.0%. Also the prepared membranes were comparable to the commercial membrane CMX in terms of the electrochemical properties, ie IEC of 2.5 meq g−1‐dry mem, membrane electric resistance of 3 ohm cm2, and transport number of 0.89. Copyright © 2003 Society of Chemical Industry
Kinetic behaviour and stability of glucose oxidase entrapped in liposomes
Authors: Rodriguez‐Nogales José Manuel
Published: December 2003

Glucose oxidase (EC 1.1.3.4) was encapsulated in liposomes (prepared from phosphatidyl choline and cholesterol) by the dehydration–rehydration method. The enzymatic activities of native and liposomal glucose oxidase were followed by the amount of H2O2 obtained in the enzymatic β‐D‐glucose oxidation. Some characteristics of the liposomal and free glucose oxidase were compared. The enzyme encapsulated in liposomes showed an apparent inhibition by glucose at concentrations higher than 0.28 mol dm−3 with a substrate inhibition constant of 0.95 ± 0.12 mol dm−3. The enzyme entrapped showed an apparent Km value higher than that of the free enzyme. The apparent Vmax of liposomal enzyme decreased by a factor of 0.35 with respect of that of the native enzyme. The optimum temperature of the free and entrapped enzymes remained similar but the liposomal enzyme showed maximal activity at a more acid pH (5.2). The thermal and proteolytic stabilities were enhanced by encapsulation in liposomes. The stabilization factors (relationship between half‐lives of entrapped form and free enzyme) at 45, 50 and 55 °C for liposomal glucose oxidase were 2.6, 1.6 and 1.6, respectively. Copyright © 2003 Society of Chemical Industry
In vitro investigation of detectability of colorectal lymph nodes and diagnosis of lymph node metastasis in colorectal cancer using B‐mode sonography
Authors: Tateishi Tsutomu , Machi Junji , Feleppa Ernest J. , Oishi Andrew J. , Furumoto Nancy L. , Oishi Robert H. , McCarthy Laurence J. , Yanagihara Eugene , Shirouzu Kazuo
Published: December 2003

Purpose

The aim of this in vitro study was to assess the feasibility of using high‐frequency sonography to identify colorectal lymph nodes and to diagnose colorectal lymph node metastasis.

Methods

In part 1 of this study, resected colorectal tissues from 13 patients with colorectal cancer were scanned in a water bath using B‐mode sonography performed at high frequency (10 MHz) to identify lymph nodes. The colorectal tissues were then carefully dissected to remove all lymph nodes. Detectability was calculated as the ratio of the number of sonographically detected nodes to the total number of histopathologically confirmed nodes. Student's t test was performed to compare sizes between these groups; a p value of less than 0.05 was considered significant. In part 2, 4 features of lymph nodes identified on B‐mode sonography—size, shape, border, and echogenicity—and their combinations were evaluated for their ability to diagnose lymph node metastasis. Discriminant and receiver operating characteristic curve analyses were performed.

Results

In part 1, B‐mode sonography performed in vitro detected 79 (48%) of the 165 histopathologically identified lymph nodes and 34 (87%) of the 39 histopathologically identified metastatic nodes. The mean size, or mean longest axis (± standard deviation), of the sonographically detected nodes (6.4 ± 2.9 mm) was significantly larger than that of undetected nodes (3.6 ± 1.7 mm; p < 0.01). In part 2, the most effective feature distinguishing metastatic from nonmetastatic lymph nodes was echogenicity, followed by size, shape, and border. However, a combination of at least 2 features (eg, echogenicity and size) provided better distinction of nodes than did any 1 feature. In the receiver operating characteristic curve of the 4‐feature combination, an increase in sensitivity is accompanied by a decrease in specificity: at a sensitivity of 100%, specificities decreased to 60% or less. However, even with the optimal combination of features, the sensitivity and specificity did not both reach 85% at any operating point.

Conclusions

The results of this node‐by‐node in vitro study show the current limitations and potential of sonography for assessing colorectal lymph nodes. High‐frequency sonography may be insufficient for identifying lymph node metastasis in colorectal cancer. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 32:1–7, 2004
Timing of early amniocentesis as a function of membrane fusion
Authors: Pinette Michael G. , Wax Joseph , Blackstone Jacquelyn , Cartin Angelina , McCrann Donald
Published: December 2003

Purpose

The purpose of this prospective study was to evaluate sonographically the timing of membrane fusion and to determine its possible effect on the timing of amniocentesis.

Methods

Between May 18, 1998, and January 31, 2002, the status of amnion fusion in pregnant patients at 9–15 weeks' menstrual age was identified in women who were to undergo obstetric sonography. Amniocentesis was performed if even a small area of fused membranes that could be traversed was identified; if the membranes were completely unfused, amniocentesis was delayed. The effect of membrane fusion in terms of the need to reschedule amniocentesis was evaluated.

Results

We examined a total of 594 patients. Membrane fusion occurred progressively with increasing menstrual age. One hundred six early amniocenteses were scheduled, and 70 were performed; the others were delayed because the membranes were unfused. Our requirement that an area of membrane fusion be found before we would perform amniocentesis resulted in rescheduling the procedure 24–38% of the time.

Conclusions

Membrane fusion, as seen sonographically, is a function of menstrual age. Even by 15 weeks, a portion of the amnion may be unfused with the chorion. Amniocenteses scheduled for early in the pregnancy may need to be delayed until later, when the membranes are at least partially fused, allowing safe passage of a needle. Delaying the procedure may incur higher expense but may be important in terms of lessening the risk involved. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 32:8–11, 2004
Popliteal artery pseudoaneurysm: A rare complication of brucellosis
Authors: Harman Mustafa , Irmak Hasan , Arslan Halil , Arslan Ünal , Kayan Mustafa
Published: December 2003

Brucellosis is still a public health problem, particularly in developing countries. After the primary infection subsides, a chronic stage characterized by nonspecific manifestations can develop, during which it may not be possible to isolate Brucella organisms and agglutination test titers may or may not be high. We present the case of a 49‐year‐old man who had only nonspecific symptoms and a 2‐month history of a pulsatile painful swelling in his right popliteal region. He had no history of trauma or surgery in that region, but he did ingest unpasteurized milk products. The patient's agglutination test titers were high, and Brucella melitensis was isolated from a bone marrow culture. Color Doppler sonography, T2‐weighted MRI, and digital subtraction angiography were performed. Treatment with ultrasound‐guided compression of the pseudoaneurysm failed because of high blood flow in its neck. Aneurysmectomy was undertaken, and the excised material was consistent with that from a mycotic pseudoaneurysm. Although both MRI and angiography provided useful information, the color Doppler sonography findings were characteristic of a pseudoaneurysm in the popliteal artery, and only that modality could detect the flow dynamics within the pseudoaneurysm. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 32:33–36, 2004
Sonographic findings in a patient with cystic hypersecretory duct carcinoma of the breast
Authors: Park Changsook , Jung Jung Im , Lee Ah‐Won , Cheon Hae Myung , Hahn Seong Tai , Lee Jae Mun
Published: December 2003

In this report, we describe a case of a rare form of intraductal carcinoma of the breast known as cystic hypersecretory duct carcinoma in a 49‐year‐old woman with a palpable mass and no history of breast disease. Mammography showed heterogeneous dense breast tissue with no definite abnormally increased density or microcalcifications. Gray‐scale sonography detected multiple small aggregated, anechoic cysts with good through‐transmission in the upper outer quadrant of the left breast, corresponding to the location of the palpable mass. The patient underwent an excision biopsy, and histopathologic examination of the surgical specimen revealed multiple cysts of different size containing an eosinophilic material resembling thyroid colloid. The locations of the cysts corresponded to those of the anechoic cysts detected on sonography. The epithelium lining the cysts showed micropapillary growth consistent with a diagnosis of cystic hypersecretory duct carcinoma. The mammographic and sonographic findings in this case differed somewhat from those reported previously for this rare form of breast carcinoma. Because the imaging findings and low‐power microscopic appearance of the mass in our patient's case closely resembled those of some benign breast lesions, we recommend careful differentiation of this type of lesion using high‐power microscopy during histopathologic evaluation. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 32:29–32, 2004
Clinical applications of diffusion tensor imaging
Authors: Dong Qian , Welsh Robert C. , Chenevert Thomas L. , Carlos Ruth C. , Maly‐Sundgren Pia , Gomez‐Hassan Diana M. , Mukherji Suresh K.
Published: December 2003

Directionally‐ordered cellular structures that impede water motion, such as cell membranes and myelin, result in water mobility that is also directionally‐dependent. Diffusion tensor imaging characterizes this directional nature of water motion and thereby provides structural information that cannot be obtained by standard anatomic imaging. Quantitative apparent diffusion coefficients and fractional anisotropy have emerged from being primarily research tools to methods enabling valuable clinical applications. This review describes the clinical utility of diffusion tensor imaging, including the basic principles of the technique, acquisition, data analysis, and the major clinical applications. J. Magn. Reson. Imaging 2004;19:6–18. © 2003 Wiley‐Liss, Inc.
Proton magnetic resonance spectroscopic imaging of human breast cancer: A preliminary study
Authors: Jacobs Michael A. , Barker Peter B. , Bottomley Paul A. , Bhujwalla Zaver , Bluemke David A.
Published: December 2003

Purpose

To investigate the diagnostic value of proton magnetic resonance spectroscopic imaging (MRSI) in patients with breast lesions.

Materials and Methods

Eighteen patients underwent breast MRSI and MRI at 1.5 T. Contrast‐enhanced MR was used to identify the lesion, after which single‐slice MRSI (TR/TE = 2000/272 msec, 10‐mm slice thickness) was performed. Water, lipid, and choline (Cho) images were reconstructed from MRSI data. The area of the Cho was measured in the lesion and expressed relative to the background noise level (signal‐to‐noise ratio (SNR)), measured between 7.0 and 9.0 ppm. Cho SNRs were compared between benign and malignant lesions as determined by histopathology.

Results

Three cases were considered technical failures on MRSI. Of the remaining 15 cases, on histopathology, eight were classified as malignant carcinoma and seven were benign. The Cho SNR from malignant tissue was significantly elevated compared to benign tissue (6.2 ± 2.1 vs. 2.4 ± 0.7, P < 0.0008).

Conclusions

MRSI measurements of Cho are feasible in the human breast, and the SNR for Cho was significantly different between benign and malignant lesions. The potential advantages of MRSI over SV spectroscopy include the ability to assess multiple lesions as well as tissue with normal MRI appearance, as well as to perhaps gauge lesion borders and infiltration into surrounding tissue. J. Magn. Reson. Imaging 2004;19:68–75. © 2003 Wiley‐Liss, Inc.
Cine MR imaging of heart valve dysfunction with segmented true fast imaging with steady state free precession
Authors: Krombach Gabriele A. , Kühl Harald , Bücker Arno , Mahnken Andreas H. , Spüntrup Elmar , Lipke Claudia , Schröder Jörg , Günther Rolf W.
Published: December 2003

Purpose

To evaluate the value of cine true fast imaging with steady‐state free precession (SSFP) for semiquantitative assessment of valvular dysfunction in the heart and to compare the results to that obtained with a standard breath‐hold segmented gradient‐recalled echo‐planar imaging sequence (GE‐EPI).

Materials and Methods

Twenty‐three patients with known valvular dysfunction (main component: 16 with aortic valve stenosis, nine with aortic valve insufficiency, three with mitral stenosis, two with mitral regurgitation, two with tricuspidal regurgitation, and one with pulmonary stenosis) and 23 control subjects with normal valvular function underwent MR imaging on a 1.5‐T system (ACS‐NT, Philips, Best, The Netherlands). Cine SSFP and GE‐EPI images were acquired in identical long‐axis views. Images were evaluated for the presence and extent of the signal void arising from the valves and for image quality consensus by two experienced radiologists. Results were compared to those obtained by cardiac catheterization (in 16 patients) or color Doppler (in the remaining seven patients).

Results

On SSPF images, the complex flow pattern in valvular regurgitant or stenotic lesions caused signal void within the bright blood pool of the atria or ventricles, similar to GE‐EPI, in all patients. Valvular dysfunction was delineated using SSFP with the same high sensitivity (100%) as using the GE‐EPI sequence. Results correlated to those obtained by cardiac catheterization or color Doppler ultrasonography (P < 0.001, r = 0.97). However, the jet phenomenon was slightly more pronounced in five patients on GE‐EPI. There was no significant signal void in the 23 control subjects with both sequences. In all 46 subjects, the image quality of SSFP images was rated higher (P < 0.05; 2.6 ± 0.1; using a scale ranging from 0–3) compared to GE‐EPI (1.7 ± 0.1).

Conclusion

The results of this study suggest that valvular dysfunction can be semiquantitatively assessed using SSFP cine MR imaging. J. Magn. Reson. Imaging 2004;19:59–67. © 2003 Wiley‐Liss, Inc.
Asymmetry and gender effect in functionally lateralized cortical regions: A proton MRS imaging study
Authors: Nagae‐Poetscher Lidia M. , Bonekamp David , Barker Peter B. , Brant Larry J. , Kaufmann Walter E. , Horská Alena
Published: December 2003

Purpose

to compare metabolite concentrations and ratios in gray matter regions known for their anatomical/functional asymmetry and evaluate gender effect.

Materials and Methods

Proton MRS imaging was performed at 1.5 T with TR/TE 2300/280 msec in 20 healthy right‐handed subjects (mean age 29.6 ± 5.3 years, 10 men). Concentrations of N‐acetyl aspartate (NAA), choline (Cho), and creatine (Cr), and the peak area ratios NAA/Cho, NAA/Cr, and Cho/Cr were evaluated in hippocampal and parahippocampal gyri, thalamus, insula, Broca's and Wernicke's areas (and corresponding contralateral areas), primary and secondary visual areas, temporal, inferior parietal, cingulate, supplemental motor, dorsolateral prefrontal, and sensorimotor areas. Linear mixed‐effects regression models were used for statistical analyses.

Results

NAA concentration and NAA/Cho were higher in the left thalamus by 21.9% and 20%, respectively (both P < 0.001). NAA concentration was 13% higher in the region contralateral to Wernicke's area (P < 0.02). No gender differences were found.

Conclusion

Metabolite concentrations and ratios were symmetric and gender independent in most brain regions, however small hemispheric side differences in the thalamus and in Wernicke's area were found. J. Magn. Reson. Imaging 2004;19:27–33. © 2003 Wiley‐Liss, Inc.
Echo planar MR imaging of the liver: Comparison of images with and without motion probing gradients
Authors: Moteki Takao , Sekine Tomoyuki
Published: December 2003

Purpose

To determine whether MR images with motion‐probing gradients (MPGs) usefully improve lesion detection in comparison with MR images without MPGs.

Materials and Methods

Echo planar (EP) images without MPGs and with small and intermediate MPGs (gradient factor b = 2, 18, and 188 second/mm2, respectively) were acquired for 61 hepatic lesions (21 hepatocellular carcinomas (HCCs), 19 metastases, eight hemangiomas, and 13 cysts). The lesion‐to‐liver signal intensity ratios (SIRs) of these lesions were calculated using EP images with and without MPGs. Qualitative analysis for detection of HCCs and metastases were also performed between the images without MPGs and with small MPGs.

Results

The SIRs of HCCs and metastases for the images with small MPGs were significantly higher than the values for the images without MPGs (P < 0.05), although no significant differences were found in the case of hemangiomas and cysts. In comparison to images without MPGs, images with small MPGs improved lesion detection of three metastases and six HCCs, and worsened lesion detection of two HCCs.

Conclusion

Images with small MPGs may improve HCC and metastasis detection over images without MPGs. J. Magn. Reson. Imaging 2004;19:82–90. © 2003 Wiley‐Liss, Inc.
Size “H” oxygen cylinder: Accidental MR projectile at 1.5 Tesla
Authors: Colletti Patrick M.
Published: December 2003

The risks of ferromagnetic compressed gas cylinders becoming projectiles in an MR environment are well known (1, 2). The recent death of a child from such an incident reinforces the potential for disaster (3). J. Magn. Reson. Imaging 2004;19:141–143. © 2003 Wiley‐Liss, Inc.
Magnetic resonance imaging of periosteum with ultrashort TE pulse sequences
Authors: Reichert Ines L.H. , Benjamin Michael , Gatehouse Peter D. , Chappell Karyn E. , Holmes Joanne , He Taigang , Bydder Graeme M.
Published: December 2003

Purpose

To assess the values of pulse sequences with ultrashort echo times (0.08 msec) for detecting and characterizing periosteum.

Materials and Methods

Two normal volunteers aged 33 and 58 years and 12 patients aged seven to 55 years were studied. A total of 10 of the patients had contrast enhancement with intravenous Gadodiamide. Two ovine tibias were examined before and after the periosteum was stripped from the bone.

Results

High signal regions were observed adjacent to cortical bone in all parts of the skeleton imaged. They were generally more conspicuous after fat suppression and contrast administration. In the ovine tibia there was a reduction in the high signal normally seen at the surface of the bone after periosteal stripping. The detached periosteum produced a high signal. Mean T2* values for adult human periosteum ranged from 5.3 to 11.4 msec. After enhancement the signal intensity increased. In two patients with tibial fractures, increased periosteal signal was seen and this showed marked enhancement. Signals from periosteum could be simulated by fat, contrast‐enhanced blood and artifacts.

Conclusion

The periosteum can be visualized with ultrashort echo time pulse sequences in health and disease. J. Magn. Reson. Imaging 2004;19:99–107. © 2003 Wiley‐Liss, Inc.
Diffusion tensor imaging in the diagnosis of primary lateral sclerosis
Authors: Uluğ Aziz M. , Grünewald Thomas , Lin Michael T. , Kamal Ayeesha K. , Filippi Christopher G. , Zimmerman Robert D. , Beal M. Flint
Published: December 2003

Purpose

To evaluate the utility of MR diffusion tensor imaging in diagnosing primary lateral sclerosis (PLS).

Materials and Methods

Five patients who met clinical criteria for a diagnosis of PLS, and two patients with possible PLS of less than three years duration and eight normal volunteers were studied using MR diffusion tensor imaging.

Results

All seven patients showed decreased diffusion anisotropy and increased diffusion constant in the PLIC, with complete separation from a normal control group, including patients early in the course of the illness.

Conclusion

Quantitative diffusion tensor imaging appears to be a useful test to detect upper motor neuron damage and hence to help to establish the diagnosis of PLS. J. Magn. Reson. Imaging 2004;19:34–39. © 2003 Wiley‐Liss, Inc.
Improved spectral selectivity and reduced susceptibility in SSFP using a near zero TE undersampled three‐dimensional PR sequence
Authors: Lu Aiming , Barger Andrew V. , Grist Thomas M. , Block Walter F.
Published: December 2003

Purpose

To improve the performance of fat/water separation and reduce the sensitivity to susceptibility variation in balanced SSFP sequences.

Materials and Methods

Decreasing the repetition time (TR) reduces susceptibility artifacts in SSFP imaging. A shorter TR may also improve the spectral selectivity obtained when linearly combining data acquired using different radiofrequency phase cycling schedules. The desired short TR is achieved by using an angularly undersampled three‐dimensional radial acquisition sequence that achieves a near zero echo time (TE) and also a short TR.

Results

Images from human volunteers demonstrate broad coverage of the cervical spine and knee with isotropic resolution. Excellent fat/water separation is achieved in these studies.

Conclusion

The short TR capability of the proposed sequence greatly improves the fat suppression in SSFP imaging. High‐resolution volumetric T2‐like contrast imaged with reduced susceptibility artifacts can be obtained from a single acquisition using this technique. J. Magn. Reson. Imaging 2004;19:117–123. © 2003 Wiley‐Liss, Inc.
Assessment of anal fistulas with high‐resolution subtraction MR‐fistulography: Comparison with surgical findings
Authors: Schaefer Oliver , Lohrmann Christian , Langer Mathias
Published: December 2003

Purpose

To investigate a new MR‐imaging protocol defined as subtraction MR‐fistulography for the detection of fistula‐in‐ano.

Materials and Methods

A total of 36 patients (18 men, 18 women) with the clinical diagnosis of anal fistula or abscess who were scheduled for surgical exploration were preoperatively imaged at 1.5 T in the supine position; coronal STIR sequences and axial T1‐weighted three‐dimensional FLASH sequences before and after intravenous injection of gadobenate dimeglumine (Gd‐BOPTA) were obtained. Image subtraction was routinely used. The image findings were compared with the findings at surgical exploration according to a uniform classification system.

Results

A total of 46 fistulas were seen on subtraction MR‐fistulography, whereas surgery described 41 fistulas. MRI and surgery concordantly depicted a total number of 40 fistulas, six fistulas were only described by MRI, and one fistula was only seen during surgery. A total of 27 abscesses were detected with MRI, compared to 22 during surgery. A total of 22 abscesses were concordantly diagnosed. Complete agreement between subtraction MR‐fistulography and surgery occurred in 32 (89%) of the 36 patients. The four patients in whom both procedures disagreed had complex anal sepsis with multiple fistulas and/or abscesses due to Crohn disease.

Conclusion

High‐resolution subtraction MR‐fistulography is an important complement to surgical exploration and especially suitable for investigating complex anal sepsis. J. Magn. Reson. Imaging 2004;19:91–98. © 2003 Wiley‐Liss, Inc.