bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular model for solubility of gases in flexible polymers
Authors: Neergaard Jesper , Hassager Ole , Szabo Peter
Published: March 2003

We propose a model for a priori prediction of the solubility of gases in flexible polymers. The model is based on the concept of ideal solubility of gases in liquids. According to this concept, the mole fraction of gases in liquids is given by Raoult's law with the total pressure and the vapor pressure of the gas, where the latter may have to be extrapolated. However, instead of considering each polymer molecule as a rigid structure, we estimate the effective number of degrees of freedom from an equivalent freely jointed bead‐rod model for the flexible polymer. In this model, we associate the length of the rods with the molecular weight corresponding to a Kuhn step. The model provides a tool for crude estimation of the gas solubility on the basis of only the monomer unit of the polymer and properties of the gas. A comparison with the solubility data for several gases in poly(dimethylsiloxane) reveals agreement between the data and the model predictions within a factor of 7 and that better model results are achieved for temperatures below the critical temperature of the gas. The model predicts a decreasing solubility with increasing temperature (because of the increasing vapor pressure) and that smaller gas molecules exhibit a lower solubility than larger ones (e.g., CH4 has a smaller solubility than CO2), which agrees with the experimental data. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 701–706, 2003
Laryngotracheal involvement of relapsing polychondritis in a Korean girl
Authors: Kim Cheol‐Min , Kim Bong‐Seong , Cho Kyung‐Ja , Hong Soo‐Jong
Published: March 2003

We describe a young girl presenting with acute dyspnea because of laryngotracheal involvement of relapsing polychondritis (RP). RP, a multisystemic disorder of unknown etiology, is a very rare disease in children. It is characterized by inflammation and destruction of the cartilaginous structure of many organs, including the respiratory tract. Early respiratory tract involvement in younger patients is the greatest threat to life, and aggressive therapy, including tracheostomy and intravenous high‐dose steroids, is advocated. Pediatr Pulmonol. 2003; 35:314–317. © 2003 Wiley‐Liss, Inc.
Damage of a High‐Energy Solid Propellant and Its Deflagration‐to‐Detonation Transition
Authors: Zhang Taihua , Bai Yilong L. , Wang Shiying Y. , Liu Peide D.
Published: March 2003

In order to assess the safety of high‐energy solid propellants, the effects of damage on deflagration‐to‐detonation transition (DDT) in a nitrate ester plasticized polyether (NEPE) propellant, is investigated. A comparison of DDT in the original and impacted propellants was studied in steel tubes with synchronous optoelectronic triodes and strain gauges. The experimental results indicate that the microstructural damage in the propellant enhances its transition rate from deflagration to detonation and causes its increased sensitivity. It is suggested that the mechanical properties of the propellant should be improved to reduce its damage so that the probability of DDT might be reduced.
Application of the anharmonic coherent states to the vibronic interaction
Authors: Avram C.N. , Drăgănescu Gh.E.
Published: March 2003

We calculated the vibronic reduction factor (Ham factor) for the physical system (molecules, crystals) with octahedral symmetry. The vibrations of the nuclei of the systems are described by the anharmonic states of the Morse potential and also by the anharmonic coherent states of the same potential. The linear vibronic coupling of these vibration states with the electronic states of the system are considered.
Single qubit estimation from repeated unsharp measurements
Authors: Diósi L.
Published: March 2003

When estimating an unknown single pure qubit state, the optimum fidelity is 2/3. As it is well known, the value 2/3 can be achieved in one step, by a single ideal measurement of the polarization along a random direction. I analyze the opposite strategy which is the long sequence of unsharp polarization measurements. The evolution of the qubit under the influence of repeated measurements is quite complicated in the general case. Fortunately, in a certain limit of very unsharp measurements the qubit will obey simple stochastic evolution equations known for long under the name of time‐continuous measurement theory. I discuss how the outcomes of the very unsharp measurements will asymptotically contribute to our knowledge of the original qubit. It is reassuring that the fidelity will achieve the optimum 2/3 for long enough sequences of the unsharp measurements.
Wave packet motion and decoherence in an anharmonic potential
Authors: Földi P. , Benedict M.G. , Czirják A. , Molnár B.
Published: March 2003

The time evolution of wave packets in the Morse potential is investigated under the influence of the environment consisting of harmonic oscillators. We obtain a Markovian master equation that incorporates the fact that due to the nonequidistant spectrum, the relaxation rate of each energy eigenstate is different. The nonunitary time evolution is visualized by the aid of the Wigner function related to the reduced density operator of the Morse system. The time scale of decoherence is much shorter than that of dissipation, and gives rise to states which are mixtures of localized states along the phase space orbit of the corresponding classical particle. This behaviour is to a large extent independent of the coupling strength, the temperature of the environment and also of the initial state.
Test of the CPT symmetry using laser spectroscopy on antiprotonic atoms
Authors: Horváth D.
Published: March 2003

Antiprotons stopped in helium get trapped in long‐living orbits making possible to study their atomic transitions via laser spectroscopy. These measurements started at CERN, Geneva, 10 years ago at the Low Energy Antiproton Ring and now continue at CERN's Antiproton Decelerator. The main result of the ASACUSA experiment is an improvement in the measurement of the antiproton mass and charge, which tests the CPT invariance when compared with those of the proton.
Two‐mode Schrödinger cats, entanglement and teleportation
Authors: Janszky J. , Asbóth J. , Gábris A. , Vukics A. , Koniorczyk M. , Kobayashi T.
Published: March 2003

Two‐mode Schrödinger cats consisting of two and four coherent‐state terms are considered. It is shown that they are closely related to the quadrature entangled EPR pair. The properties of their wave functions are investigated from their aspects of entanglement. It is shown that at certain parameters the entangled properties of the two‐mode Schrödinger cats allow for good teleportation fidelity. A theoretical generalization to the teleportation of two qubits is also discussed.
A cavity with two‐level atoms and cellular automata simulations
Authors: Walczak M. , Leoński W.
Published: March 2003

We discuss here a system comprising a single cavity filled with a set of two‐level atoms. To study the dynamics of the system we propose to adapt the cellular automata method. We show that this approach could be a useful tool for investigation of systems containing a large number of atoms.
Dynamics of a single trapped ion in an optical underdamped cavity
Authors: Maniscalco S. , Messina A. , Di Fidio C. , Vogel W.
Published: March 2003

The dynamics of a single trapped ion placed inside a high Q optical cavity is studied in presence of cavity losses and far from the Lamb‐Dicke regime. In the underdamped cavity limit, analytical results for describing the dynamics of the system are derived making use of the secular approximation. Our method allows to obtain analytical expressions for the time evolution of the joint vibration‐photon number distribution and for the occupation probability of the upper electronic state of the ion.
Parametric down‐conversion experiments with stationary fields
Authors: Peřinová V. , Lukš A.
Published: March 2003

Returning from the Wigner to the Hilbert‐space formalism, we have augmented the detailed analysis of the four experiments by Casado et al. [Phys. Rev. A55, 3879 (1997)]. Starting from realistic, though arbitrary, parameters we have made numerical calculations of the visibility of fourth‐order interference. We have found that two of these experiments are rather proposals than reported ones and we have formulated an alternative to the description of one of them.
Spin triplet superconductivity in Sr2RuO4
Authors: Wysokiński Karol I. , Litak G. , Annett J. F. , Györffy B. L.
Published: March 2003

Sr2RuO4 is at present the best candidate for being a superconducting analogue of the triplet superfluidity in 3He. This material is a good (albeit correlated) Fermi liquid in the normal state and an exotic superconductor below Tc. The mechanism of superconductivity and symmetry of the order parameter are the main puzzling issues of on‐going research. Here we present the results of our search for a viable description of the superconducting state realised in this material. Our calculations are based on a three‐dimensional effective three‐band model with a realistic band structure. We have found a state with non‐zero order parameter on each of the three sheets of the Fermi surface. The corresponding gap in the quasi‐particle spectrum has line or point nodes on the α and β sheets and is complex with no nodes on the γ sheet. This state describes remarkably well a number of existing experiments including power low temperature dependence of the specific heat, penetration depth, thermal conductivity etc. The stability of the state with respect to disorder and different interaction parameters are also analyzed briefly.
A Monte Carlo study of the mixed phase region in the 3D Ashkin–Teller model
Authors: Musiał G.
Published: March 2003

Our MC method has been extended to check the type of ordering and to determine the character of phase transitions and the positions of the boundaries of the mixed phase region in the three‐dimensional Ashkin‐Teller spin‐lattice model. Some results for this model on a cubic lattice are presented, which confirm the existence of such a region and determine the positions of its boundaries as well as the character of phase transitions.
Computational modeling of complexes of penta‐ammine osmium (II) with aromatic ligands
Authors: Trindle Carl , Sacks Gavin , Harman W. Dean
Published: March 2003

Complexation of aromatic species with penta‐ammine osmlium (II)[Os]has remarkable effects on their structure and reactivity. The η2‐complexed dearomatized ligand can be encouraged to react in ways of great convenience in synthetic projects. We model the structure of complexes of [Os] with various descriptions of correlation and in various bases. The most satisfactory method for structures is a perturbation correlation corrected model (MP2) with a hybrid basis, 6‐31G* on all but osmium, and the LANL2DZ basis and associated pseudopotential for that heavy atom. A B3LYP/hybrid scheme seems to produce better estimates of binding and isomerization energies for a range of ligands, including hydrocarbons, heteroaromatics, and substituted benzenes. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Theoretical study of the reactions of the 1Σ+ ground state of MS+ (M = Sc, Y, and La) with oxygen‐transfer reagent MS+ + CO → ScO+ + CS in the gas phase
Authors: Xie Xiao‐Guang , Ye Song , Shi Nan‐Hua , Zhou Yong‐Ming , Cao Huai
Published: March 2003

The reaction mechanisms of the 1Σ+ ground state of MS+ (M = Sc, Y, and La) with oxygen‐transfer reagent MS+ + CO → MO+ + CS in the gas phase has been proposed and investigated by ab initio methods with the 6‐31G* basis set for nonmetal atoms and the effective core potentials of Lanl2dz for the metal atoms. A carbon migration from oxygen atom to sulfur atom via a four‐center transition state is involved on the reaction potential surface. The activation energies of the reactions are 34.0, 24.1, and 36.7 kcal/mol relative to their corresponding reactants and the reaction heats are 15.7, 18.6, and 18.0 kcal/mol (respectively, for M = Sc, Y, and La) at the MP4 (SDTQ)/6‐31G*//MP2/6‐31G* level plus zero‐point energy, which indicates that the cationic yttrium sulfide is more favorable for this type of reaction. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Dipole‐bound anions supported by charge–transfer interaction: Anionic states of HnF3−nN → BH3 and H3N → BHnF3−n (n = 0, 1, 2, 3)
Authors: Sawicka Agnieszka , Anusiewicz Iwona , Skurski Piotr , Simons Jack
Published: March 2003

The possibility of electron binding to five molecules (i.e., F3N → BH3, H2FN → BH3, HF2N → BH3, H3N → BH2F, H3N → BHF2) was studied at the coupled cluster level of theory with single, double, and noniterative triple excitations and compared to earlier results for H3N → BH3 and H3N → BF3. All these neutral complexes involve dative bonds that are responsible for significant polarization of these species that generates large dipole moments. As a consequence, all of the neutral systems studied, except F3N → BH3, support electronically stable dipole‐bound anionic states whose calculated vertical electron detachment energies are 648 cm−1 ([H2FN → BH3]−), 234 cm−1 ([HF2N → BH3]−), 1207 cm−1 ([H3N → BH2F]−), and 1484 cm−1 ([H3N → BHF2]−). In addition, we present numerical results for a model designed to mimic charge–transfer (CT) and show that the electron binding energy correlates with the magnitude of the charge flow in the CT complex. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Heterolytic activation of CH bond in methane with (HNCHCHNH)M(CH3) (M = Pd+, Pt+, Rh+, Ir+, Rh, Ir): Comparative density functional study of activation mechanisms
Authors: Heiberg Hanne , Gropen Odd , Swang Ole
Published: March 2003

Activation of methane by oxidative addition and σ‐bond metathesis has been investigated for (N‐N)M(CH3) (M = Pd+, Pt+, Rh+, Ir+, Rh, Ir; N‐N = (HNCHCHNH) using different density functional approaches. The pathway of oxidative addition is in general favored, the exceptions being Pd+ and Rh+. Oxidative addition is clearly more favorable for the third‐row metal complexes than those of the second row. The third‐row metal complexes also tend to have a lower activation barrier for σ‐bond metathesis than those of the second row. In each case, the oxidative addition is preceded by formation of a sigma complex. The bonding energies of these complexes are significantly stronger for the cationic systems. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
New Traversability Indices and Traversability Grid for Integrated Sensor/Map‐Based Navigation
Authors: Seraji Homayoun
Published: March 2003

This paper presents new measures of terrain traversability at short range and long range of a mobile robot; namely, local and global traversability indices. The sensor‐based local traversability index is related by a set of linguistic rules to large obstacles and surface softness within a short range of the robot measured by on‐board sensors. The map‐based global traversability index is obtained from the terrain topographic map, and is based on major surface features such as hills and lakes within a long range of the robot. These traversability indices complement the mid‐range sensor‐based regional traversability index introduced earlier. Each traversability index is represented by four fuzzy sets with the linguistic labels {POOR, LOW, MODERATE, HIGH}, corresponding to surfaces that are unsafe, moderately‐unsafe, moderately‐safe, and safe for traversal, respectively. The global terrain analysis also leads to the new concepts of traversability map and traversability grid for representation of terrain quality based on the global map information. The traversability indices are used in two sensor‐based traverse‐local and traverse‐regional behaviors and one map‐based traverse‐global behavior. These behaviors are integrated with a map‐based seek‐goal behavior to ensure that the mobile robot reaches its goal safely while avoiding both sensed and mapped terrain hazards. This provides a unified system in which the two independent sources of terrain quality information, i.e., prior maps and on‐board sensors, are integrated together for reactive robot navigation. The paper is concluded by a graphical simulation study. © 2003 Wiley Periodicals, Inc.
Automated Gripper Jaw Design and Grasp Planning for Sets of 3D Objects
Authors: Balan Lucian , Bone Gary M.
Published: March 2003

An algorithm for automatically generating a common jaw design and planning grasps for a given set of polyhedral objects is presented. The algorithm is suitable for a parallel‐jaw gripper equipped with three cylindrical fingers. The common jaw design eliminates the need for custom made grippers and tool changing. The proposed jaw configuration and planning approach reduces the search associated with locating the finger contacts from six degrees‐of‐freedom to one degree‐of‐freedom. Closed‐form algorithms for checking force closure and for predicting jamming are developed. Three quality metrics are introduced to improve the quality of the planned grasps. The first is a measure of the sensitivity of the grasp to errors between the actual and planned finger locations. The second is a measure of the efficiency of the grasp in terms of the contact forces. The third is a measure of the dependence of force closure on friction. These quality metrics are not restricted to cylindrical fingers and can be applied tonfinger grasps. Running on a standard PC, the algorithm generated a solution in less than five minutes for a set of five objects with a total of 456 triangular facets. © 2003 Wiley Periodicals, Inc.
Redundancy and the choice of hydrologic indices for characterizing streamflow regimes
Authors: Olden Julian D. , Poff N. L.
Published: March 2003

The utility of hydrologic indices for describing various aspects of streamflow regimes has resulted in their increased application in riverine research. Consequently, researchers are now confronted with the task of having to choose among a large number of competing hydrologic indices to reduce computational effort and variable redundancy prior to statistical analyses, while still adequately representing the major facets of the flow regime. The present study addresses this concern by providing a comprehensive review of 171 currently available hydrologic indices (including the commonly used Indicators of Hydrologic Alteration) using long‐term flow records from 420 sites from across the continental USA. We highlight patterns of redundancy among these hydrologic indices and provide a number of statistically and ecologically based recommendations for the selection of a reduced set of indices that can simultaneously (1) explain a dominant proportion of statistical variation in the complete set of hydrologic indices and (2) minimize multicollinearity while still adequately representing recognized, critical attributes of the flow regime. In addition, we examine the transferability of hydrologic indices across ‘stream types’ by identifying indices that consistently explain dominant patterns of variance across streams in varying climatic and geologic environments. Together, our results provide a framework from which researchers can identify hydrologic indices that adequately characterize flow regimes in a non‐redundant manner. In combination with ecological knowledge, this framework can guide researchers in the parsimonious selection of hydrologic indices for future hydroecological studies. Copyright © 2003 John Wiley & Sons, Ltd.
A comparison of methods for evaluating instream flow needs for recreation along rivers in southern Alberta, Canada
Authors: Rood Stewart B. , Tymensen Wilco , Middleton Ron
Published: March 2003

Four methods were compared for determining recreational instream flow needs (R‐IFN) for paddling canoes, kayaks and rafts on ten river reaches in the Oldman River Basin of southern Alberta. Two flow criteria were evaluated: ‘minimal flow’—the low flow that still provides a reasonable quality river trip; and ‘sufficient flow’—the lower end of the favoured flow range. A voluntary, mail‐in user survey from 1983 to 1997 produced 394 responses (4251 paddler days) relative to flow suitability. An expert judgment approach considered flow recommendations from three regional paddling guides that were considered comprehensive and credible. A flow comparison involved about 20 paddle trips per reach by the authors with differing groups, boats and flows. These subjective approaches produced quite consistent results (r2 = 0.63) and these were compared to results from an objective, hydraulic modelling method, the ‘depth, discharge method’ (DDM), that applied stage–discharge functions to determine flows that would satisfy depth criteria of 60 and 75 cm. The DDM minimal flows were closely correlated with the means of the subjective methods (r2 = 0.73). Thus, all four approaches produced generally consistent results, indicating that all methods were valid. Typical minimal and sufficient flows were about 15 and 30 m3 s−1, respectively, for the medium‐sized river reaches that had average annual discharges (mean Q) of about 20 m3 s−1. A close correlation (r2 = 0.90) between the minimal flow and mean Q suggests that mean Q can provide an initial estimate for R‐IFN for rivers of this type and size. We recommend that R‐IFN studies commence with the DDM since it is quick, inexpensive and objectively defensible. This would provide guidelines for subsequent subjective assessments that should involve more than one approach to increase the breadth of subjective consideration. Copyright © 2003 John Wiley & Sons, Ltd.
Microelectronic Bonding Processes Monitored by Integrated Sensors
Authors: Mayer M. , Schwizer J.
Published: March 2003

Real‐time monitoring methods are beneficial for the control, optimization, and failure analysis of microelectronic packaging processes. The focus of this chapter is on the real‐time monitoring of two widely used processes, soft solder die bonding and thermosonic ball bonding. The methods presented here use uniquely developed microsensors integrated on custom‐made test chips using commercial double‐metal CMOS processes.

For the soft solder die bonding process, nine aluminum‐based resistive temperature detectors were integrated on various locations on a test chip. The temperature was monitored during the placement of the test chip on the leadframe. The experimental results describe the wetting and spreading effects of the molten solder under the drip. Together with numerical results obtained with a transient thermal finite element model, the beginning of wetting can be quantified. For the soft solder PbSn10, wetting occurred around 30 ms after touch down. This method hence can be used to determine wetting times under different process conditions. The wetting time determines an upper limit of the through put of the process.

For the thermosonic ball bonding process, temperature and force sensors were integrated on test chips. The sensors are aluminum resistors and piezoresistivep+‐ andn+‐diffused resistors placed around bond pads. A bond quality parameter can be derived from the temperature signal variation during bonding. The piezoresistive sensors permit the measurement of forces in the x‐, y‐, and z‐directions simultaneously. The ultrasonic tangential force signal reached a typical value of 0.12 N on a 50μm diameter contact zone and revealed significant process characteristics. Four process phases are identified which are necessary for a successful ball bond formation. These phases are assigned to initial stiction, sliding, bond growth, and deformation effects.
XPS analysis of petroleum well tubing adherence
Authors: Cosultchi A. , Rossbach P. , Hernandez‐Calderon I.
Published: March 2003

Undesired material adhered to the internal surface of the tubing wall of some petroleum wells is critical for crude oil production. Field samples of steel with petroleum solid adherence were characterized by means of x‐ray photoelectron spectroscopy, x‐ray diffraction and atomic absorption spectroscopy. The deposit naturally adhered on the steel surface is structurally formed by a thin, black and hard corrosion product layer (inner layer) ∼15 µm thick under a thick, black and brittle organic deposit layer (outer layer) ∼0.01 m thick composed mainly of hydrocarbons. This outer layer contains small amounts of barium sulphate (BaSO4) co‐precipitated with organic compounds, which may contribute to the deposit's lack of cohesion. On the contrary, the inner layer of the deposit is firmly adhered to the steel substrate and contains clay minerals and iron compounds embedded in the hydrocarbon layer. Copyright © 2003 John Wiley & Sons, Ltd.
Transition models for change‐point estimation in logistic regression
Authors: Pastor‐Barriuso Roberto , Guallar Eliseo , Coresh Josef
Published: March 2003

Although a wide variety of change‐point models are available for continuous outcomes, few models are available for dichotomous outcomes. This paper introduces transition methods for logistic regression models in which the dose–response relationship follows two different straight lines, which may intersect or may present a jump at an unknown change‐point. In these models, the logit includes a differentiable transition function that provides parametric control of the sharpness of the transition at the change‐point, allowing for abrupt changes or more gradual transitions between the two different linear trends, as well as for estimation of the location of the change‐point. Linear‐linear logistic models are particular cases of the proposed transition models. We present a modified iteratively reweighted least squares algorithm to estimate model parameters, and we provide inference procedures including a test for the existence of the change‐point. These transition models are explored in a simulation study, and they are used to evaluate the existence of a change‐point in the association between plasma glucose after an oral glucose tolerance test and mortality using data from the Mortality Follow‐up of the Second National Health and Nutrition Examination Survey. Copyright 2002 John Wiley & Sons, Ltd.
The use of putative placebo in active control trials: two applications in a regulatory setting
Authors: Durrleman Sylvain , Chaikin Philip
Published: March 2003

For life‐threatening diseases, ethical considerations preclude the inclusion of an untreated control group in the investigation of a new therapeutic agent when a standard therapy exists. In these cases, active controlled studies are conducted, and may be planned to demonstrate either superiority or equivalence/non‐inferiority of the new drug over the standard therapy (active control). In the non‐inferiority study, an important aspect is the ability to detect an inferior drug (assay sensitivity). It has been suggested that assay sensitivity for a non‐inferiority study should be deduced from historical data, specifically placebo controlled studies with the standard therapy. The assessment of assay sensitivity may also be important in a superiority trial that fails to demonstrate a statistically significant difference between treatments, and the sponsor attempts to determine whether there is lack of inferiority as an alternative hypothesis for regulatory approval. This paper describes two methods of putative placebo analysis for assessing assay sensitivity in active controlled trials. One approach imputes a point estimate for the odds ratio (95 per cent confidence interval) for a new drug (T) compared to a placebo control (P). A Bayesian approach calculates the posterior probability that T is superior to P, or, that T is at least k per cent as good as the active control (A) and A is more effective than P. These methods are applied in two clinical/regulatory settings: a phase III trial comparing docetaxel (Taxotere) to doxorubicin in metastatic breast cancer patients, and a phase III programme with two trials comparing enoxaparin (Lovenox) plus aspirin to unfractionated heparin plus aspirin in patients with unstable angina or non‐Q‐wave myocardial infarction. The methodologies presented in this paper were used in securing regulatory approval for docetaxel in the treatment of locally advanced or metastatic breast cancer after failure of prior chemotherapy, and for enoxaparin in the treatment of acute coronary syndrome. Copyright © 2003 John Wiley & Sons, Ltd.
Mid‐course sample size modification in clinical trials based on the observed treatment effect
Authors: Jennison Christopher , Turnbull Bruce W.
Published: March 2003

It is not uncommon to set the sample size in a clinical trial to attain specified power at a value for the treatment effect deemed likely by the experimenters, even though a smaller treatment effect would still be clinically important. Recent papers have addressed the situation where such a study produces only weak evidence of a positive treatment effect at an interim stage and the organizers wish to modify the design in order to increase the power to detect a smaller treatment effect than originally expected. Raising the power at a small treatment effect usually leads to considerably higher power than was first specified at the original alternative. Several authors have proposed methods which are not based on sufficient statistics of the data after the adaptive redesign of the trial. We discuss these proposals and show in an example how the same objectives can be met while maintaining the sufficiency principle, as long as the eventuality that the treatment effect may be small is considered at the design stage. The group sequential designs we suggest are quite standard in many ways but unusual in that they place emphasis on reducing the expected sample size at a parameter value under which extremely high power is to be achieved. Comparisons of power and expected sample size show that our proposed methods can out‐perform L. Fisher's ‘variance spending’ procedure. Although the flexibility to redesign an experiment in mid‐course may be appealing, the cost in terms of the number of observations needed to correct an initial design may be substantial. Copyright © 2003 John Wiley & Sons, Ltd.
Non‐parametric estimators of a monotonic dose–response curve and bootstrap confidence intervals
Authors: Dilleen Maria , Heimann Günter , Hirsch Ian
Published: March 2003

In this paper we consider study designs which include a placebo and an active control group as well as several dose groups of a new drug. A monotonically increasing dose–response function is assumed, and the objective is to estimate a dose with equivalent response to the active control group, including a confidence interval for this dose. We present different non‐parametric methods to estimate the monotonic dose–response curve. These are derived from the isotonic regression estimator, a non‐negative least squares estimator, and a bias adjusted non‐negative least squares estimator using linear interpolation. The different confidence intervals are based upon an approach described by Korn, and upon two different bootstrap approaches. One of these bootstrap approaches is standard, and the second ensures that resampling is done from empiric distributions which comply with the order restrictions imposed. In our simulations we did not find any differences between the two bootstrap methods, and both clearly outperform Korn's confidence intervals. The non‐negative least squares estimator yields biased results for moderate sample sizes. The bias adjustment for this estimator works well, even for small and moderate sample sizes, and surprisingly outperforms the isotonic regression method in certain situations. Copyright © 2003 John Wiley & Sons, Ltd.
Resettable smart dampers for multi‐level seismic hazard mitigation of steel moment frames
Authors: Barroso Luciana R. , Chase J. Geoffrey , Hunt Stephen
Published: March 2003

A main goal of supplemental control devices is to manage the energy dissipation in the system. Resettable devices have emerged as a promising control device for application to civil structures as they are effective energy dissipators. This paper presents an investigation of the ability of semi‐active control methods utilizing resettable devices to mitigate structural response in the presence of hysteretic, geometric and yielding nonlinearities under various intensity level seismic hazard suites to define control efficacy and seismic hazard statistics. A major component of this research is to assess the effect of device placement on control benefit. Results show that resettable devices limited to realistic peak force/dissipation levels of ∼13% building weight are effective at limiting permanent deflections and indicate the importance of zero tracking for nonlinear systems. However, floor accelerations rise significantly as displacement is limited, and the performance improvement is not the same for all ground motions. Owing to predominantly first‐mode response of the case study structure, peak and permanent drifts saw larger reductions as more device authority was placed at the base of the structure, although the best overall results distributed device authority roughly proportional to the structural storey shears. Copyright © 2003 John Wiley & Sons, Ltd.
The cerebroplacental Doppler ratio revisited
Authors: Baschat A. A. , Gembruch U.
Published: March 2003

Objective

To evaluate the distribution of Doppler pulsatility index (PI) measurements of the umbilical and middle cerebral arteries in singleton fetuses of women with normal uterine artery blood flow and to construct reference ranges for the cerebroplacental PI Doppler ratio.

Methods

The PI was determined in the mid‐portion of the umbilical artery and the mid‐ or distal segment of the middle cerebral artery in 306 normal singleton fetuses. The cerebroplacental Doppler ratio (CPR) was determined from paired measurements. After determination of the best fit, reference ranges were constructed for each parameter against gestational age (GA).

Results

The PI for the umbilical artery had a linear relationship with GA (umbilical artery PI = − 0.0246 × GA + 1.7791, r2 = 0.4025, P < 0.001). The middle cerebral artery PI and the CPR both showed a quadratic relationship with GA (middle cerebral artery PI = − 0.0058 × GA2 + 0.3335 × GA − 2.7317, r2 = 0.2365, P < 0.01), (CPR = − 0.0059 × GA2 + 0.383 × GA − 4.0636, r2 = 0.2788, P < 0.001).

Conclusion

The CPR is not constant throughout gestation. Reference ranges constructed by a standardized Doppler technique may be of benefit in the monitoring of high‐risk pregnancies. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Does transvaginal sonographic measurement of cervical length before 14 weeks predict preterm delivery in high‐risk pregnancies?
Authors: Berghella V. , Talucci M. , Desai A.
Published: March 2003

Objective

To determine whether high‐risk patients manifest cervical length < 25 mm on transvaginal ultrasound before 14 weeks of gestation, and if this finding is predictive of preterm delivery.

Methods

Asymptomatic pregnancies at high risk for preterm birth were followed prospectively from 10 + 0 weeks to 13 + 6 weeks with transvaginal sonographic measurement of the cervix. A cervical length < 25 mm was considered a short cervix at this gestational age and at the follow‐up ultrasound examinations, performed between 14 and 24 weeks. The primary outcome was preterm birth at < 35 weeks of gestation.

Results

One hundred and eighty‐three pregnancies met the study criteria and were included in the analysis. Only 10 (5%) patients had a cervix < 25 mm before 14 weeks. The sensitivity, specificity and positive and negative predictive values of a short cervix were 14%, 97%, 50%, and 82%, respectively (relative risk, 2.8; 95% confidence interval, 1.4–5.6). The mean transvaginal sonographic cervical length before 14 weeks of gestation was 33.7 ± 6.9 mm in pregnancies which delivered preterm (n = 36), and 35.0 ± 6.8 mm in those delivering at term (n = 147) (P = 0.3). Follow‐up transvaginal ultrasound examination of the cervix to 24 weeks revealed that the average gestational age at which a short cervix was detected was 18.7 ± 2.9 weeks.

Conclusion

A cervical length < 25 mm on transvaginal sonographic assessment rarely occurs before 14 weeks even in high‐risk patients destined to deliver preterm; in these patients cervical changes predictive of preterm birth develop mostly after this gestational age. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Fetal nasal bone length: reference range and clinical application in ultrasound screening for trisomy 21
Authors: Bunduki V. , Ruano R. , Miguelez J. , Yoshizaki C. T. , Kahhale S. , Zugaib M.
Published: March 2003

Objectives

Fetuses with trisomy 21 typically present with subtle facial abnormalities, including a hypoplastic nasal bone. The aim of this study was to provide a reference range for the length of the fetal nasal bone and to test its value in second‐trimester ultrasound screening for trisomy 21.

Design

A reference range of fetal nasal bone length was established from cross‐sectional data on 1923 consecutive singleton pregnancies scanned at 16–24 weeks' gestation in women older than 35 years. Screening for trisomy 21 was prospectively studied using the measurement of fetal nasal bone lengths smaller than the 5th percentile as a cut‐off value.

Results

Follow‐up was possible in 1631 cases (84.8%). Trisomy 21 was found in 22 cases (1.35%). Nasal bone length measurement increased as a function of gestational age (P < 0.05) showing a linear relationship. Screening for trisomy 21 using the 5th percentile as a cut‐off value resulted in a sensitivity of 59.1% for a 5.1% false‐positive rate. The likelihood ratio was 11.6.

Conclusion

Screening for trisomy 21 using fetal nasal bone length measurements showed a sensitivity comparable to that of maternal biochemistry for a given false‐positive rate of 5%. Association of nasal bone lengths with other sonographic markers, taking into account the background risk for maternal and gestational age, may further improve sensitivity and reduce false positives, allowing avoidance of unnecessary invasive diagnostic procedures. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Invasive intrauterine treatment of pulmonary atresia/intact ventricular septum with heart failure
Authors: Arzt W. , Tulzer G. , Aigner M. , Mair R. , Hafner E.
Published: March 2003

The mortality and morbidity of children with pulmonary atresia/intact ventricular septum (PA/IVS) are linked to the degree of right ventricular (RV) hypoplasia. Opening up the pulmonary valve (PV) in fetal life could result in improved growth of the RV making it amenable to biventricular repair postnatally. Successful valvulotomy of the PV was performed in a fetus with heart failure at 28 weeks. Following the procedure there was significant growth of the tricuspid valve and RV. The neonate was delivered at 38 weeks with a RV suitable for biventricular repair. In utero pulmonary valvulotomy is feasible and may change the natural history of the condition in affected fetuses with PA/IVS. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Ba3P3I2 und Ba5P5I3: Stufenweise Oxidation von Bariumphosphid mit Iod
Authors: Nuss Jürgen , Jansen Martin
Published: March 2003

Durch Reaktion von Bariumphosphid mit Iod wurden die neuen Verbindungen Ba3P3I2 und Ba5P5I3 erhalten. Die luft‐ und hydrolyseempfindlichen Verbindungen kristallisieren jeweils in einem neuen Strukturtyp: Ba3P3I2 (oP32, Pnma, a = 1719.5(5) pm, b = 462.4(2) pm, c = 1427.2(4) pm, Z = 4, R(F)N′ = 0.067 (N′(hkl) = 2667); Ba5P5I3 (mC52, C2/m, a = 4266.4(13) pm, b = 456.3(2) pm, c = 943.1(3) pm, β = 92.20(3)°, Z = 4, R(F)N′ = 0.040 (N′(hkl) = 3909). Beide können als ein Doppelsalz zwischen einer hypothetischen Zintl‐Phase ('Ba2P3' bzw. 'Ba7P10') und einem Halogenid (BaI2) beschrieben werden. Charakteristische Strukturmerkmale sind gewinkelte P3‐ und P4‐Ketten gemäß Ba3[P3]I2 bzw. Ba10[P3]2[P4]I6. Die Bindungsverhältnisse werden auf der Basis der Strukturmerkmale und physikalischen Eigenschaften interpretiert.
Die Kristallstruktur von KPr3Te8
Authors: Stöwe Klaus
Published: March 2003

Von den Verbindungen der Zusammensetzung ALn3Q8 ( A = Na, K, Rb, Cs; Ln = Selten‐Erd‐Metall; Q = S, Se und Te) konnte die Struktur des Tellurids KPr3Te8 durch Einkristallstrukturanalyse gelöst und verfeinert werden. Kristalle der Verbindung konnten durch eine Synthese nach der Flux‐Technik mit K2Te3 als Flussmittel nach der Abtrennung des K2Te3‐Überschusses durch Extraktion mit absolutem Dimethylformamid (DMF) erhalten werden. Die Verbindung kristallisiert monoklin in der Raumgruppe P121/c1 mit den Gitterparametern a = 1390, 58(7) pm, b = 1291, 06(6) pm, c = 900, 18(5) pm und β = 99, 264(6)° isotyp zu KNd3Te8. Strukturmerkmale in der Kristallstruktur von KPr3Te8 sind gewinkelte Einheiten aus drei Telluratomen [Te3]2— sowie zick‐zack‐förmige unendliche Ketten aus Telluratomen [Te4]4—. Die kürzesten interatomaren Abstände in den Ketten alternieren mit 298 und 300 pm nur geringfügig und liegen im Bereich partieller Bindungen. Beide Strukturelemente sind in nahezu planaren Schichten angeordnet und untereinander durch ein System von sekundären Wechselwirkungen mit interatomaren Abständen im Bereich von 327 bis 349 pm verknüpft. Die Struktur von KPr3Te8 kann als Auffüllungs‐Defektvariante des binären NdTe3‐Typs verstanden werden. Dies wird anhand entsprechender Gruppe‐Untergruppe‐Beziehungen in Form eines Bärnighausen‐Stammbaums dargelegt.
Über Münzmetall‐Quecksilber‐Chalkogenidhalogenide. II Hydrothermalsynthese, Kristallstruktur und Phasenumwandlung von CuHgSCl und CuHgSBr
Authors: Beck Johannes , Rompel Matthias
Published: March 2003

CuHgSCl und CuHgSBr werden aus CuCl beziehungsweise CuBr und HgS in konzentrierter wässriger Halogenwasserstoffsäure HX (X = Cl, Br) durch hydrothermale Umsetzung bei 670 K in Form von gelb‐orangen Kristallen erhalten. Die Substanzen kristallisieren isotyp (orthorhombisch, Pbam, a = 984, 01(8), b = 1775, 1(2), c = 409, 59(3) pm für CuHgSCl und a = 1003, 7(4), b = 1833, 6(5), c = 412, 4(2) pm für CuHgSBr, Z = 8). Die Strukturen bestehen aus ebenen, gefalteten HgS‐Ketten, die durch verzerrte [CuS2X2/2]2‐Tetraederdoppel miteinander verknüpft werden. Die großen Schwingungsamplituden der Kupferatome sind auf thermisch angeregte Schwingungen zurückzuführen, was durch Strukturanalysen bei verschiedenen Temperaturen nachgewiesen wird. Die Einkristall‐Strukturbestimmung zeigt, dass das frühere, durch Pulverbeugung erhaltene Strukturmodell nicht korrekt ist. Die Kristallstrukturen von CuHgSCl und CuHgSBr weisen große Ähnlichkeiten zur Struktur der bereits bekannten Verbindungen CuHgSeBr, AgHgSBr und AgHgSI (MHgYX) auf. CuHgSBr geht bei 323 K in einem Phasenübergang 2. Ordnung in eine zu MHgYX isotype, höhersymmetrische Form (orthorhombisch, Pmam, a = 1009, 2(3), b = 918, 40(4), c = 413, 81(2) pm) mit halbierter b‐Achse über.
Beiträge zur Kristallchemie und zum thermischen Verhalten von wasserfreien Phosphaten. XXXIII [1] In2P2O7, ein Indium(I)‐diphosphato‐indat(III) und In4(P2O7)3 — Darstellung, Kristallisation und Kristallstrukturen
Authors: Thauern H. , Glaum Robert
Published: March 2003

Über Festkörperreaktionen unter Beteiligung der Gasphase wurde im System In/P/O das gemischtvalente Indium(I, III)‐diphosphat In2P2O7 erstmalig synthetisiert und mittels Einkristallstrukturanalyse charakterisiert. Farblose Kristalle von In2P2O7 für die Strukturverfeinerung entstanden beim isothermen Tempern (800 °C; 7d) mit Iod als Mineralisator aus InPO4 und InP. In In2P2O7 [P21/c, a = 7, 550(1) Å, b = 10, 412(1) Å, c = 8, 461(2) Å, b = 105, 82(1)°, 2813 unabhängige Reflexe, 101 Parameter, R1 = 0, 031, wR2 = 0, 078] werden erstmals isolierte In+‐Ionen in einer Umgebung von Sauerstoffionen beobachtet. Die Abstände d(InI‐O) sind ungewöhnlich lang (dmin(InI‐O) = 2, 82 Å) und sprechen für überwiegenden s‐Charakter des freien Elektronenpaares am In+‐Ion.

In4(P2O7)3 konnte mittels chemischer Transportexperimente im Temperaturgradienten (1000 → 900 °C, P/I‐Gemenge als Transportmittel) kristallisiert und phasenrein dargestellt werden. Im Unterschied zu Literaturangaben über die isostrukturellen Diphosphate M4(P2O7)3 (M = V, Cr, Fe) wurde für die Indiumverbindung monokline Symmetrie gefunden [P21/a, a = 13, 248(3) Å, b = 9, 758(1) Å, c = 13, 442(2) Å, b = 108, 94(1)°, 7221 unabhängige Reflexe, 281 Parameter, R1 = 0, 027, wR2 = 0, 067].
Synthese und Struktur der Komplexe [(Me2PhP)3Cl2Re≡N‐RuCl2(C6H6)] und [(Me2PhP)3Cl2Re≡N‐RhCl(COD)]
Authors: Schwarz Simon , Strähle Joachim
Published: March 2003

Der heteronukleare Zweikernkomplex [(Me2PhP)3Cl2Re≡N‐RuCl2(C6H6)] (1) entsteht bei der Reaktion von [ReNCl2(PMe2Ph)3] mit [RuCl2(C6H6)]2 in Benzonitril in Form roter, solvathaltiger Kristalle. Er kristallisiert als 1·C6H5CN in der monoklinen Raumgruppe P21/c mit a = 1149, 77(8); b = 3085, 9(3); c = 1172, 1(1) pm, β = 104, 766(9)° und Z = 4. Im Zweikernkomplex ist das Komplexfragment [RuCl2(C6H6)] über eine asymmetrische Nitridobrücke mit dem Nitridokomplex [ReNCl2(PMe2Ph)3] verknüpft. Die Nitridobrücke ist durch einen Bindungswinkel Re‐N‐Ru von 170, 6(3)° und Abstände Re‐N = 170, 2(5) pm und Ru‐N = 199, 0(5) pm charakterisiert.

Die Umsetzung von [ReNCl2(PMe2Ph)3] mit [RhCl(COD)]2 in Benzonitril ergibt orangerote, monokline Kristalle von [(Me2PhP)3Cl2Re≡N‐RhCl(COD)] (2) mit der Raumgruppe P21/c und a = 1522, 3(2); b = 1274, 85(4); c = 1921, 2(2) pm; β = 106, 759(7)° und Z = 4. Für das einwertige Rhodiumatom ergibt sich eine quadratisch‐planare Koordination, bei der die beiden π‐Bindungen des Cycloocta‐1, 5‐dienliganden in cis‐Position angeordnet sind. Die Abstände in der nahezu linearen Nitridobrücke (Re‐N‐Rh = 174, 8(4)°) betragen Re‐N = 172, 2(6) pm und Rh‐N = 195, 6(6) pm.
Fehlordnung bei Smectiten in Abhängigkeit vom Zwischenschichtkation
Authors: Breu Josef , Seidl Wolfgang , Stoll Alexander
Published: March 2003

Fluorosmectite, [M0.5]zwi[Mg2.5Li0.5]okt[Si4]tetO10F2 (M = Na, K, Rb, Cs), wurden über eine Schmelzsynthese in gasdicht verschweißten Mo‐Tiegeln dargestellt. Bei gleichbleibender, im Bereich der Smectite liegender, Schichtladung von x = 0.5 nimmt sowohl die Kristallitgröße als auch die Stapelordnung mit größer werdendem Zwischenschichtkation zu. Während beim mikrokristallinen Na‐Hectorit sowohl Rotations‐ (n120° und n60°) als auch Translationsfehlordnung (±0.145b) vorliegt, findet man für K‐Hectorit dagegen nur noch ±b/3 Translationsfehlordnung. Rb‐ und Cs‐Hectorit zeigen schließlich ein normales Bragg‐Beugungsmuster. Mit Cäsium als Zwischenschichtkation kann man vollkommen geordnete und sogar einkristalline Hectorite herstellen, die keinerlei diffuse Streuung mehr zeigen und eine Einkristallstrukturanalyse erlauben (monoklin, 1M—Polytyp, C2/m, a = 5.2401(10)Å, b = 9.0942(10) Å, c = 10.7971(10)Å, β = 99.21 (2)°, V = 507.90(12) Å3, Z = 2). Diese 3D geordneten Smectite besitzen immer noch eine ausreichende intrakristalline Reaktivität, die einen schnellen und vollständigen Austausch gegen Organokationen erlaubt.
Gangliosides are Transported from the Plasma Membrane to Intralysosomal Membranes as Revealed by Immuno-Electron Microscopy
Authors: Möbius W. , Herzog V. , Sandhoff K. , Schwarzmann G.
Published: March 2003

A biotin-labeled derivative of the ganglioside GM1 (biotin-GM1) was used to study its transport along the endocytic pathway of cultured fibroblasts by immuno-electron microscopy. Using electron dense endocytic tracers we could demonstrate that late endosomes and lysosomes of these cells are long living organelles with a high content of internal membranes. Our studies show that during endocytosis the biotin-GM1 was transported to these intraendosomal and intralysosomal membranes. These observations support the hypothesis that glycosphingolipids (GSL) are preferentially degraded in intralysosomal vesicles.