bluuebunny/crossref_metadata_2025 huggingface dataset:
Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly C13-labeled systems
Authors: Chan Jerry C. C. , Tycko Robert
Published: April 2003

We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole–dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole–dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed C13 MAS NMR experiments on uniformly C13-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the C13 CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the β-amyloid peptide associated with Alzheimer’s disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids.
Accurate ab initio study of the energetics of phosphorus nitride: Heat of formation, ionization potential, and electron affinity
Authors: Kemeny Andre E. , Francisco Joseph S. , Dixon David A. , Feller David
Published: April 2003

High level ab initio electronic structure calculations at the coupled cluster CCSD(T) level with augmented correlation-consistent basis sets extrapolated to the complete basis set limit have been performed on PN, PN+, and PN−. The geometries were optimized up through the aug-cc-pV5Z level and vibrational frequencies were calculated with the aug-cc-pVQZ basis set. The heat of formation of PN at 0 K is predicted to be 43.7±0.9 kcal/mol and is within the error limits of the revised experimental value at 41.2±3.6 kcal/mol. The calculated adiabatic ionization potential is 11.90±0.05 eV as compared to the experimental value of 11.88±0.01 eV and the calculated adiabatic electron affinity is 0.126±0.01 eV as compared to the experimental value of 0.32±0.20 eV.
Weighted-density-functional approach to the structure of nonuniform fluids
Authors: Patra Chandra N. , Ghosh Swapan K.
Published: April 2003

The structure of simple nonuniform fluids is studied using a new weighted-density-functional approach based on the concept of universality of the free energy density functional and an assumption of a local dependence of its functional derivative on the weighted density. The theory uses as input the second-order direct correlation function and the radial distribution function of the corresponding uniform fluid which are obtained here from the integral equation theory with an accurate closure relation. The calculated numerical results on the density profiles of several confined inhomogeneous fluids are shown to compare quite well with the available simulation data.
Density functional approach on wetting behavior of binary associating mixtures
Authors: Yeh Ming-Chih , Chen Li-Jen
Published: April 2003

A density functional theory is applied to study wetting behaviors of binary associating mixtures, which are described by the statistical associating fluid theory of Wertheim. When the associating interaction is strong, the phase behavior of the binary associating mixture falls into the type-VI mixtures of the classification scheme of van Konynenburg and Scott. There are two types of closed-loop phase behaviors for the type-VI mixture. That is, a closed-loop phase diagram for vapor–liquid–liquid coexistence (along its triple line) at low pressures and the other one for liquid–liquid coexistence at a relatively high pressure. In this study, the wetting behavior of the lower liquid phase at the surface of the upper liquid phase is carefully examined for both vapor–liquid–liquid coexistence and liquid–liquid coexistence regimes. In the latter regime, a third inert air phase is introduced since wetting behavior always involves three phases. For both regimes the binary associating mixture exhibits a sequence of wetting transitions, complete wetting→partial wetting→complete wetting, along with increasing temperature. The order of wetting transitions is carefully examined. It is found that the order of wetting transitions is the consequence of the competition between the attractive interaction range and the associating strength of unlike pair molecules. The most intriguing behavior is that it is possible to observe the sequence of wetting transitions along with increasing temperature at two different orders for air–liquid–liquid coexistence at a high pressure. That is, the upper wetting transition is first order and the lower wetting transition is second order. The pressure effect on the order of wetting transitions for liquid–liquid coexistence is also discussed.
High-pressure photochemistry of furane crystal
Authors: Santoro Mario , Ceppatelli Matteo , Bini Roberto , Schettino Vincenzo
Published: April 2003

The role of light absorption in triggering the high-pressure reaction of solid furane is investigated. When the sample is irradiated with the 458.0-nm line of an Ar+ ion laser the reaction is found to occur just above 3 GPa, well below the pressure value (10 GPa) where it takes place without irradiation. The pressure threshold of the transformation increases as the excitation line is shifted to the red. The analysis of the pressure evolution of the UV-VIS absorption spectrum allows us to identify the injection mechanism as a two-photon absorption process to the lowest excited states of furane. The aromatic ring opening shows, in this case, additional reaction paths with respect to the purely pressure induced reaction, as attested by the presence of CO2 and by the larger amount of carbonyl groups found in the recovered product. These results suggest the ring opening mechanism to be mainly controlled by the relative molecular orientation both in the disordered phase IV and in the ordered phase III.
An optical trap for relativistic plasma
Authors: Zhang Ping , Saleh Ned , Chen Shouyuan , Sheng Zhengming , Umstadter Donald
Published: April 2003

The first optical trap capable of confining relativistic electrons, with kinetic energy ⩽350 keV was created by the interference of spatially and temporally overlapping terawatt power, 400 fs duration laser pulses (⩽2.4×1018 W/cm2) in plasma. Analysis and computer simulation predicted that the plasma density was greatly modulated, reaching a peak density up to 10 times the background density (ne/n0∼10) at the interference minima. Associated with this charge displacement, a direct-current electrostatic field of strength of ∼2×1011 eV/m was excited. These predictions were confirmed experimentally by Thomson and Raman scattering diagnostics. Also confirmed were predictions that the electron density grating acted as a multi-layer mirror to transfer energy between the crossed laser beams, resulting in the power of the weaker laser beam being nearly 50% increased. Furthermore, it was predicted that the optical trap acted to heat electrons, increasing their temperature by two orders of magnitude. The experimental results showed that the number of high energy electrons accelerated along the direction of one of the laser beams was enhanced by a factor of 3 and electron temperature was increased ∼100 keV as compared with single-beam illumination.
H-mode threshold and dynamics in the National Spherical Torus Experiment
Authors: Bush C. E. , Bell M. G. , Bell R. E. , Boedo J. , Fredrickson E. D. , Kaye S. M. , Kubota S. , LeBlanc B. P. , Maingi R. , Maqueda R. J. , Sabbagh S. A. , Soukhanovskii V. A. , Stutman D. , Swain D. W. , Wilgen J. B. , Zweben S. J. , Davis W. M. , Gates D. A. , Johnson D. W. , Kaita R. , Kugel H. W. , Lee K. C. , Mastrovito D. , Medley S. , Menard J. E. , Mueller D. , Ono M. , Paoletti F. , Park H. , Paul S. J. , Peng Y-K. M. , Raman R. , Roney P. G. , Roquemore A. L. , Skinner C. H. , Synakowski E. J. , Taylor G. ,   NSTX Team
Published: April 2003

Edge parameters play a critical role in high confinement mode (H-mode) access, which is a key component of discharge optimization in present day toroidal confinement experiments and the design of next generation devices. Because the edge magnetic topology of a spherical torus (ST) differs from a conventional aspect ratio tokamak, H-modes in STs exhibit important differences compared with tokamaks. The dependence of the National Spherical Torus Experiment (NSTX) [C. Neumeyer et al., Fusion Eng. Des. 54, 275 (2001)] edge plasma on heating power, including the low confinement mode (L-mode) to H-mode (L-H) transition requirements and the occurrence of edge-localized modes (ELMs), and on divertor configuration is quantified. Comparisons between good L-modes and H-modes show greater differences in the ion channel than the electron channel. The threshold power for the H-mode transition in NSTX is generally above the predictions of a recent International Tokamak Experimental Reactor (ITER) [ITER Physics Basis Editors, Nucl. Fusion 39, 2175 (1999)] scaling. Correlations of transition and ELM phenomena with turbulent fluctuations revealed by gas puff imaging and reflectometry are observed. In both single-null and double-null divertor discharges, the density peaks off-axis, sometimes developing prominent “ears” which can be sustained for many energy confinement times, τE, in the absence of ELMs. A wide variety of ELM behavior is observed, and ELM characteristics depend on configuration and fueling.
Measurement of the ion drag force on falling dust particles and its relation to the void formation in complex (dusty) plasmas
Authors: Zafiu C. , Melzer A. , Piel A.
Published: April 2003

Experiments on the quantitative determination of the weaker forces (ion drag, thermophoresis, and electric field force) on free-falling dust particles in a rf discharge tube are presented. The strongest force, gravity, is balanced by gas friction and the weaker forces are investigated in the radial (horizontal) plane. Under most discharge conditions, the particles are found to be expelled from the central plasma region. A transition to a situation where the falling particles are focused into the plasma center is observed at low gas pressures using small particles. These investigations allow a quantitative understanding of the mechanism of unwanted dust-free areas (so-called voids) in dusty plasmas under microgravity. Good quantitative agreement with standard models of the ion drag is found.
Sharp ferromagnet/semiconductor interfaces by electrodeposition of Ni thin films onto n-GaAs(001) substrates
Authors: Scheck C. , Evans P. , Zangari G. , Schad R.
Published: April 2003

We report on the chemical, electrical, and magnetic properties of Ni/GaAs(001) interfaces prepared using electrodeposition. Electrodeposition is an equilibrium process which thus releases much less energy per absorbed atom than other deposition techniques. This allows preparation of chemically sharp interfaces which otherwise show a high degree of reactivity and interdiffusion. This is demonstrated by the example of Ni grown on GaAs(001). Photoelectron spectroscopy shows the absence of surface segregation of substrate material or diffusion into the Ni layer. This is confirmed by the electrical and magnetic properties of the films.
Shifting students’ to experts’ complex systems knowledge
Authors: Hansmann Ralf , Mieg Harald A. , Crott Helmut W. , Scholz Roland W.
Published: April 2003

This paper includes three analyses concerning: expert support in the selection of impact variables for scientific models relevant to environmental planning, the quality of students’ individual estimates of corresponding impacts before and after a group discussion, and the accuracy of artificially‐aggregated judgments of independent groups. Participants were students of environmental sciences at ETH Zurich. The first analysis revealed that during participation in an environmental case study, students’ individual estimates of impacts of variables which have been suggested by experts increased, as compared to the estimates of impacts of additional variables, which have been selected by the students. The remaining analyses consider group discussions on the strength of particular environmental impacts. The quality of the estimates was analyzed referring to expert estimates of the impacts.
Ligand‐induced changes in dynamics in the RT loop of the C‐terminal SH3 domain of Sem‐5 indicate cooperative conformational coupling
Authors: Ferreon Josephine C. , Hilser Vincent J.
Published: April 2003

We report the effects of peptide binding on the15N relaxation rates and chemical shifts of the C‐SH3 of Sem‐5.15N spin‐lattice relaxation time (T1), spin‐spin relaxation time (T2), and {1H}‐15N NOE were obtained from heteronuclear 2D NMR experiments. These parameters were then analyzed using the Lipari‐Szabo model free formalism to obtain parameters that describe the internal motions of the protein. High‐order parameters (S2> 0.8) are found in elements of regular secondary structure, whereas some residues in the loop regions show relatively low‐order parameters, notably the RT loop. Peptide binding is characterized by a significant decrease in the15N relaxation in the RT loop. Concomitant with the change in dynamics is a cooperative change in chemical shifts. The agreement between the binding constants calculated from chemical shift differences and that obtained from ITC indicates that the binding of Sem‐5 C‐SH3 to its putative peptide ligand is coupled to a cooperative conformational change in which a portion of the binding site undergoes a significant reduction in conformational heterogeneity.
Stator-Rotor Interactions in a Transonic Compressor— Part 1: Effect of Blade-Row Spacing on Performance
Authors: Gorrell Steven E. , Okiishi Theodore H. , Copenhaver William W.
Published: April 2003

Usually less axial spacing between the blade rows of an axial flow compressor is associated with improved efficiency. However, mass flow rate, pressure ratio, and efficiency all decreased as the axial spacing between the stator and rotor was reduced in a transonic compressor rig. Reductions as great as 3.3% in pressure ratio, and 1.3 points of efficiency were observed as axial spacing between the blade rows was decreased from far apart to close together. The number of blades in the stator blade-row also affected stage performance. Higher stator blade-row solidity led to larger changes in pressure ratio efficiency, and mass flow rate with axial spacing variation. Analysis of the experimental data suggests that the drop in performance is a result of increased loss production due to blade-row interactions. Losses in addition to mixing loss are present when the blade-rows are spaced closer together. The extra losses are associated with the upstream stator wakes and are most significant in the midspan region of the flow.
Unsteady and Calming Effects Investigation on a Very High-Lift LP Turbine Blade—Part I: Experimental Analysis
Authors: Coton Thomas , Arts Tony , Lefebvre Michae¨l , Liamis Nicolas
Published: April 2003

An experimental and numerical study was performed about the influence of incoming wakes and the calming effect on a very high-lift low-pressure turbine rotor blade. The first part of the paper describes the experimental determination of the pressure loss coefficient and the heat transfer around the blade mounted in a high-speed linear cascade. The cascade is exposed to incoming wakes generated by high-speed rotating bars. Their aim is to act upon the transition/separation phenomena. The measurements were conducted at a constant exit Mach number equal to 0.8 and at three Reynolds number values; namely, 190,000, 350,000, and 650,000. The inlet turbulence level was fixed at 0.8%. An additional feature of this work is to identify the boundary layer status through heat transfer measurements. Compared to the traditionally used hot films, thin film heat flux gages provide fully quantitative data required for code validation. Numerical computations are presented in the second part of the paper.
Combustor Turbine Interface Studies—Part 2: Flow and Thermal Field Measurements
Authors: Colban W. F. , Lethander A. T. , Thole K. A. , Zess G.
Published: April 2003

Most turbine inlet flows resulting from the combustor exit are nonuniform in the near-platform region as a result of cooling methods used for the combustor liner. These cooling methods include injection through film-cooling holes and injection through a slot that connects the combustor and turbine. This paper presents thermal and flow field measurements in the turbine vane passage for a combustor exit flow representative of what occurs in a gas turbine engine. The experiments were performed in a large-scale wind tunnel facility that incorporates combustor and turbine vane models. The measured results for the thermal and flow fields indicate a secondary flow pattern in the vane passage that can be explained by the total pressure profile exiting the combustor. This secondary flow field is quite different than that presented for past studies with an approaching flat plate turbulent boundary layer along the upstream platform. A counter-rotating vortex that is positioned above the passage vortex was identified from the measurements. Highly turbulent and highly unsteady flow velocities occur at flow impingement locations along the stagnation line.
Lower Pliocene Hominid Remains from Sterkfontein
Authors: Partridge T. C. , Granger D. E. , Caffee M. W. , Clarke R. J.
Published: April 2003

Cosmogenic aluminum-26 and beryllium-10 burial dates of low-lying fossiliferous breccia in the caves at Sterkfontein, South Africa, show that associated hominid fossils accumulated in the Lower Pliocene. These dates indicate that the skeleton StW 573 and newly discovered specimens from Jacovec Cavern have much the same age: approximately 4 million years. These specimens are thus of an age similar to
Australopithecus anamensis
from East Africa.
1,3-Dipolar Cycloadditions of D-Erythrose- and D-Threose-Derived Alkenes with Nitrones
Authors: Blanáriková-Hlobilová Iva , Fišera Lubor , Prónayová Naďa , Koman Marian
Published: April 2003

The new chiral terminal alkenes derived from cyclic acetals of D-erythrose 1-3 and D-threose 5, 6 were prepared. The alkenes 1, 2 and 5 react with chiral nitrones to afford the corresponding diastereomeric isoxazolidines 19-21. The stereoselectivity was dependent on the steric hindrance of the nitrone. In all cases the cycloadditions are endo-selective. The major products were found to have the C-3/C-4 erythro- and C-3/C-3a cis-configuration. Its formation can be rationalized by a less hindered endo-attack of the (Z)-nitrone in an antiperiplanar manner with respect to the largest group of the cyclic acetal.
RECENT ADVANCES AND FUTURE TRENDS IN MODERN ELECTRONICS
Authors: PARK YOON-SOO
Published: April 2003

We discuss recent advances in various fields of modern electronic and optoelectronic devices. The major trends in electronics point to the nanoscale, to giga to terahertz operation, and to very low power consumption. These trends will require the development of advanced physics concepts and new device processing and characterization techniques. Various novel material systems will be researched. These approaches will greatly improve the performance of the electronic devices, and novel devices will further improve the level of human life as they have done before.
SYNCHRONIZING CHAOS BY IMPULSIVE FEEDBACK METHOD
Authors: ZHANG Y. , DU G. H. , JIANG J. J.
Published: April 2003

In this letter, the impulsive feedback synchronization method is suggested. Synchronization condition is given by investigating the mechanism of the impulsive feedback synchronization. Furthermore, we consider the influences of noise and parameter mismatch since they inevitably exist in the practical experiment. Finally, a visual circuit implementation of impulsive feedback synchronization is performed. The research demonstrates that impulsive operator can spread frequency spectrum of chaotic solution. Impulsive feedback can synchronize chaotic systems and has the robustness to noise and parameter mismatch. It shows the potential application in chaotic communication.
ON A CENTRAL LIMIT THEOREM FOR MONOTONE NOISE
Authors: LIEBSCHER VOLKMAR
Published: April 2003

We study a special central limit theorem for monotone noise. If we represent all operators on suitable symmetric Fock spaces we obtain a statement of strong convergence.
WAVELET DE-NOISING OF OPTICAL TERAHERTZ PULSE IMAGING DATA
Authors: FERGUSON BRADLEY , ABBOTT DEREK
Published: April 2003

Terahertz pulse imaging (TPI) systems are used to obtain sub-millimeter spectroscopic measurements for a wide range of applications. This letter highlights the use of wavelet de-noising to markedly improve the SNR of the obtained data, increasing the SNR by up to 10 dB. A comparison of different wavelet families and properties is presented and the results demonstrated on THz image data of an oak leaf and an Australian $100 note.
HIGH SIGNAL-TO-NOISE RATIO GAIN BY STOCHASTIC RESONANCE IN A DOUBLE WELL
Authors: GINGL ZOLTAN , MAKRA PETER , VAJTAI ROBERT
Published: April 2003

We demonstrate that signal-to-noise ratio (SNR) can be significantly improved by stochastic resonance in a double well potential. The overdamped dynamical system was studied using mixed signal simulation techniques. The system was driven by wideband Gaussian white noise and a periodic pulse train with variable amplitude and duty cycle. Operating the system in the non-linear response range, we obtained SNR gains much greater than unity. In addition to the classical SNR definition, the ratio of the total power of the signal to the power of the noise part was also measured and it showed better signal improvement.
LOW-FREQUENCY NOISE IN AlGaN/GaN HETEROSTRUCTURE FIELD EFFECT TRANSISTORS AND METAL OXIDE SEMICONDUCTOR HETEROSTRUCTURE FIELD EFFECT TRANSISTORS
Authors: RUMYANTSEV S. L. , PALA N. , SHUR M. S. , LEVINSHTEIN M. E. , IVANOV P. A. , KHAN M. ASIF , SIMIN G. , YANG J. , HU X. , TARAKJI A. , GASKA R.
Published: April 2003

The dependence of the 1/f noise on 2D electron concentration in the channel n Ch of AlGaN/GaN Heterostructure Field Effect Transistors and Metal Oxide Semiconductor Heterostructure Field Effect Transistors has been studied and compared. The dependencies of Hooge parameter αCh for the noise sources located in the channel of the transistors on sheet electron concentration are found identical for both types of devices. The increase of the Hooge parameter αCh with the decrease of the channel concentration observed in both types of devices confirms that the noise sources are located in the region under the gate in the AlGaN/GaN heterostructure and that electron tunneling from the 2D electron gas into the traps in GaN or AlGaN layers is a probable noise mechanism.
Utility of a Prognostic Scoring System for Allogeneic Stem Cell Transplantation in Patients with Chronic Myeloid Leukemia
Authors: Qazilbash Muzaffar H. , Devetten Marcel P. , Abraham Jame , Lynch Joseph P. , Beall Charles L. , Weisenborn Robin , Bunner Pam , Ericson Solveig G.
Published: April 2003

Allogeneic stem cell transplantation (SCT) is the treatment of choice for selected patients with chronic myeloid leukemia (CML). However, it is associated with a high risk of treatment-related mortality (TRM) and morbidity. To assist in decision making about transplantation, a simple scoring system to assess the risk is needed. We analyzed the utility of a scoring system, first reported by the European Group for Blood and Marrow Transplantation (EBMT). We analyzed the data from 31 patients who underwent allogeneic transplantation at our institution, using the EBMT scoring system. It was based on five pretransplant risk factors: donor type, stage of disease at time of transplantation, age of recipient, sex of donor and recipient, and interval between diagnosis and transplant. Seventeen patients had a risk score of 0–2, and 14 patients had a score of 3–7. Using Kaplan-Meier analysis, the estimated 4-year leukemia-free (LFS) and overall survival (OS) for patients with a score of 0–2 were 47 and 53%, respectively. In contrast, the estimated 4-year LFS and OS for patients with a score of 3–7 were 10.5 and 10.5%, respectively. Four-year TRM was 47% for the low-risk group (0–2), and 85% for the high-risk group (3– 7). This simple scoring system may play an important role in predicting the outcome of allogeneic SCT, and in choosing the appropriate therapy for patients with CML.
Prevalence of Hemochromatosis Gene (HFE) Mutations in Greece
Authors: Papazoglou Dimitrios , Exiara Triada , Speletas Matthaios , Panagopoulos Ioannis , Maltezos Efstratios
Published: April 2003

The frequencies of the hereditary hemochromatosis gene (HFE) mutations C282Y and H63D vary between different populations. There are a limited number of reports regarding the frequency of these mutations in populations of southeastern Europe. Two hundred and sixty-four adult individuals of Greek origin were examined for the C282Y and H63D mutations to determine the allele and genotype frequencies. The HFE gene region of DNA samples extracted from peripheral leukocytes was amplified by the polymerase chain reaction. Restriction enzyme analysis was performed using RsaI for C282Y and MboI for H63D. None of the 264 individuals carried the mutation C282Y. Forty-three individuals (16.2%) were heterozygous carriers of the H63D allele and 2 were homozygous for this mutation (0.75%). The overall H63D allele prevalence is thus estimated at 8.9%. HFE mutation frequencies were low in the population studied and this may explain, in part, the relative rarity of clinical cases of hereditary hemochromatosis in Greece.
Mixed Myelodysplastic Syndrome and Myeloproliferative Disorder with Bone Marrow and Pulmonary Fibrosis: The Role of Megakaryocytes
Authors: Rosenstingl Sophie , Brouland Jean-Philippe , Zini Jean-Marc , Tobelem Gérard , Dupuy Evelyne
Published: April 2003

The case of an 80-year-old woman displaying myelodysplastic syndrome evolving into a myeloproliferative disorder with myelofibrosis and pulmonary fibrosis, is reported. This case is characterized by an initial presentation of a myelodysplastic syndrome with normal karyotype and moderate fibrosis, its evolution towards a myeloproliferative disorder with myelofibrosis and the worsening of pulmonary fibrosis in parallel to the acceleration of the myeloproliferative disorder and myelofibrosis. These features and the high concentration of plasma platelet factor-4 suggest a role of megakaryocyte/platelet degranulation in the development of fibrosis.
Demographic Factors for Utilization of Invasive Genetic Testing after Multifetal Pregnancy Reduction
Authors: Baker Carol L. , Feldman Baruch , Shalhoub Alex G. , Ayoub Melissa A. , Krivchenia Eric L. , Yaron Yuval , Evans Mark I.
Published: April 2003

Objective: Pregnant infertility patients are commonly old enough to be offered prenatal diagnosis. However, they may be reluctant to undergo an additional invasive procedure. We, therefore, sought to determine what demographic factors, including race and ethnic group, influenced patients’ decisions to undergo genetic testing in addition to multifetal pregnancy reduction (MFPR). Methods: We retrospectively reviewed MFPR patients from July 1997 to June 1999 at our institution. Invasive genetic testing was routinely discussed. Maternal age, race, ethnicity, religion, egg source for in vitro fertilization (IVF) patients, and the remaining fetuses following MFPR were analyzed for invasive genetic testing determinants and were compared to our experiences with genetic referents to us for singleton pregnancies. 132 consecutive patients, of whom 49 were ≧35 years, including 15 having IVF with donor eggs, were included. Results: Maternal age was the single most significant determinant of testing. In donor egg cases, donor age was significant. Ethnic background, previous children, and the remaining number of fetuses after MFPR were also significant determinants. Conclusion: MFPR patients share similar demographics to the advanced maternal age population. Despite the very stressful situations, our data suggest that maternal age, and therefore genetic risk, is the most important determinant of choosing whether or not to have testing. However, patients’ decisions are, to varying degrees, modified by religious and ethnic considerations.
Prenatal Diagnosis of the Hemodynamics of Fetal Renal Disease by Color Doppler Ultrasound
Authors: Iura T. , Makinoda S. , Miyazaki S. , Fujita S. , Inoue H. , Hirosaki N. , Imafuku N.
Published: April 2003

Objective: Hemodynamic analysis of the fetal renal artery elucidated the function of the renal glomerulus and renal tubule in normal growth fetus and was weighed against fetal renal disease. Design: The subjects were fetuses from pregnant women who gave informed consent. There were 6 cases of polycystic kidney, 4 cases of hydronephrosis and 33 cases of fetuses presenting with normal growth. A longitudinal study was performed for normal growth fetuses. Using maximum systolic velocity (Vmax), pulsatility index (PI) and resistance index (RI), the blood flow was measured initially at 20–24 weeks of pregnancy and every 4 weeks thereafter. The measurement was performed 5 times in total. Also, for fetal renal disease, the measurement was performed using the same indexes. Results: In 2 cases of polycystic kidney, which led to death due to postpartum afunctional kidney, Vmax indicated the lower level of less than mean –1.5 SD. In 1 case of single hydronephrosis, the single afunctional kidney was observed postpartum due to blood flow disruption. In 7 cases of normal renal function after birth, it indicated the lower level in some gestational ages but was generally in the normal range. Conclusions: Using indexes to evaluate the glomerulus and renal tubule of fetal renal disease, mean –1.5 SD of Vmax can be considered to be the lower limit in the normal range and expected to be an important factor for the final outcome.
Only Two-Phase Models, Computed Independently for Males and Females, Are Appropriate to Describe Fetal Head Growth
Authors: Pineau Jean-Claude , Guihard-Costa Anne-Marie , Droullé Pierre
Published: April 2003

Objective: To establish an accurate mathematical model describing fetal head growth, taking into account gender differences and changes in growth rate during gestation. Methods: Ultrasound measurements of head circumference and biparietal diameter were made on 1,336 normal fetuses (684 males and 652 females) in the Maternité Régionale de Nancy (France). A new two-phase model, taking into account an alteration in growth kinetics at 30 gestational weeks, was computed independently for male and female data. The accuracy of this model was tested and compared with three current mathematical models: a linear-quadratic, a linear-cubic, and the Rossavik and Deter (1984) models. Results: In all models, including ours, the coefficients of determination (R2) were high (≧0.999), so long as male and female data were computed separately. However, the standard error estimates (SEE) of our two-phase model were much lower (0.13 ≤ SEE ≤ 0.57) than the SEE of the three other models when computed over the whole gestational period (0.49 ≤ SEE ≤ 2.69); nevertheless, when these three other models were computed for these two successive periods, their SEE decreased, and data fitting was improved. Conclusion: Only two-phase mathematical models, computed independently for male and female data, accurately describe the kinetics of fetal head growth. They should be used to calculate growth standards and to perform an exact diagnosis of impaired growth.
Availability of Percutaneous Closure for an Adult Population with Interatrial Shunts
Authors: Johansson Magnus , Söderberg Björn , Eriksson Peter
Published: April 2003

Objectives: To report the availability of percutaneous closure for an adult population with interatrial septal defects. Methods: Observational study with 66 consecutive patients referred to a tertiary center for evaluation of the possibility of percutaneous closure. The patients were selected initially after review of transesophageal echocardiography (TEE) and finally after heart catheterization. Results: Out of 66 patients, 50 were selected after the review of TEE and 38 of them were selected after catheterization; all of the 38 were effectively closed. Conclusion: Percutaneous closure is possible and can be carried out safely in a majority of the adult population with interatrial shunts.
An in vitro Study on the Active Conversion of Flucytosine to Fluorouracil by Microorganisms in the Human Intestinal Microflora
Authors: Vermes András , Kuijper Ed J. , Guchelaar Henk-Jan , Dankert Jacob
Published: April 2003

Background: Investigation of the rate of active conversion of flucytosine to fluorouracil by microorganisms in the intestinal microflora. Methods: Active conversion of flucytosine was investigated using viable and nonviable Escherichia coli at different flucytosine concentrations. Additionally, flucytosine conversion was studied in fecal specimens from 3 neutropenic patients at the start of the antimicrobial/antifungal prophylaxis (C/A regimen) and 1 week later. Results: Flucytosine levels decreased by an average of 72, 71 and 72% flucytosine after incubation for 48 h of 1010 viable E. coli/ml suspension in broth containing 13, 130 and 1,300 mg/l flucytosine, respectively. The decreasing flucytosine levels corresponded approximately to an identical increase in fluorouracil levels. Also, a 44% decrease of flucytosine levels occurred when nonviable E. coli were used, indicating that bacterial viability is not necessary for this conversion. When fecal specimens of 2 patients were investigated prior to the C/A regimen, significant flucytosine conversion occurred, whereas this conversion was not observed in the corresponding fecal specimens after 1 week of C/A regimen. Conclusion: These in vitro experiments showed that extensive flucytosine conversion can occur in the human intestinal microflora by E. coli. Consequently, fluorouracil exposure and fluorouracil-related toxicity may occur in the flucytosine-treated patient.
Stroke and Ischemic Heart Disease Mortality Trends in Brazil from 1979 to 1996
Authors: de Padua Mansur Antonio , de Fátima Marinho do Souza Maria , Favarato Desidério , Avakian Solange Desirée , Machado César Luiz Antonio , Mendes Aldrigui José , Franchini Ramires José Antonio
Published: April 2003

Stroke and ischemic heart disease (IHD) mortality rates were analyzed in Brazilian subjects older than 30 years of age from 1979 to 1996. Population estimates were based on census surveys. Mortality data were obtained from the Ministry of Health. For stroke, the age-adjusted death rate (ADR) dropped from 200 to 164 and from 168 to 130 deaths/100,000 population in men and women, respectively (p < 0.001), in the interval study. For IHD, the ADR dropped from 194 to 164 and from 119 to 105 deaths/100,000 population in men and women, respectively (p < 0.001), in the same time period. Mortality from stroke and IHD combined was greater in men for all age groups (p < 0.001). Stroke was the most frequent cause of death in both women and men except for men aged between 40 and 69 years, in whom IHD was more common. Stroke and IHD were the main causes of death in the Brazilian population.
In vivo Dopamine Pre-Synaptic Receptors and Antioxidant Activities in Patients with Alzheimer’s Disease, Dementia with Lewy Bodies and in Controls
Authors: Tabet Naji , Walker Zuzana , Mantle David , Costa Durval , Orrell Martin
Published: April 2003

The degeneration of dopaminergic cells in dementia with Lewy bodies (DLB) may provide an important source of additional free radical generation. As a result, the oxidative stress status in DLB could be significantly enhanced. Subsequently, the levels of endogenous antioxidants, which are an indirect measure of free radical activities, may be different in DLB patients when compared with Alzheimer’s disease (AD) patients and controls. In this preliminary study, we measured the activities of superoxide dismutase (SOD), catalase (CAT), glutathione (GLU) and total antioxidant capacity in the blood of DLB, AD and control subjects. The state of nigrostriatal dopaminergic system was also assessed in vivo by using a radioactive ligand with an affinity for the dopamine pre-synaptic receptors and by imaging with single-photon emission tomography. Data obtained showed a decrease in dopamine pre-synaptic receptors in all the brain regions of DLB patients. The levels of SOD did not differ significantly between DLB, AD and control subjects. However, GLU levels were significantly higher in the DLB patients when compared with AD patients (p < 0.05) and controls (p < 0.01). CAT blood levels were also higher in DLB when compared with AD, but this did not reach statistical significance. The results suggest that a different oxidative stress state may exist in DLB. This may occur due to increased free radical production from the degeneration of dopaminergic cells and auto-oxidation of dopamine, the availability of which may be maintained in early-stage DLB disease as a result of the compensatory increase in its turnover from the remaining dopaminergic cells.
Inhibition of Experimental Choroidal Neovascularization by Irsogladine, an Anti-Gastric Ulcer Agent
Authors: Kuroki Akiko Mera , Kitaoka Takashi , Matsuo Yoko , Amemiya Tsugio
Published: April 2003

Purpose: To determine whether irsogladine inhibits experimental choroidal neovascularization (CNV) induced by laser photocoagulation in pigmented rats. Methods: Focal laser photocoagulation (argon green 50 mW, 0.04 s, 200 µm) was applied to the retinochoroid of normal Brown Norway rats. Oral administration of irsogladine (5 mg/kg/day or 50 mg/kg/day) was started 1 week before and continued for 2 weeks after laser photocoagulation. Choroidal vascular casts were made 2 weeks after laser photocoagulation and were examined with a scanning electron microscope (SEM). CNV formation was classified according to three grades and evaluated. Results: Laser-induced CNV formation was significantly reduced in rats given 5 mg/kg/day (p < 0.01) or 50 mg/kg/day of irsogladine (p < 0.001). Administration of 50 mg/kg/day of irsogladine was more effective in preventing CNV formation than 5 mg/kg/day (p < 0.001). The development of the vascular bud was especially inhibited by 50 mg/kg/day of irsogladine (p < 0.001). CNVs in rats treated with 50 mg/kg/day of irsogladine looked less well developed than those in controls. There was no significant side effect of irsogladine. Conclusions: Irsogladine inhibits the development of experimental CNV induced by photocoagulation in pigmented rats.
Signal Transducer and Activator of Transcription 5 Activation Is Sufficient to Drive Transcriptional Induction of Cyclin D2 Gene and Proliferation of Rat Pancreatic β-Cells
Authors: Friedrichsen Birgitte N. , Richter Henrijette E. , Hansen Johnny A. , Rhodes Christopher J. , Nielsen Jens H. , Billestrup Nils , Møldrup Annette
Published: April 2003

Signal transducer and activator of transcription 5 (STAT5) activation plays a central role in GH- and prolactin-mediated signal transduction in the pancreatic β-cells. In previous experiments we demonstrated that STAT5 activation is necessary for human (h)GH-stimulated proliferation of INS-1 cells and hGH-induced increase of mRNA-levels of the cell cycle regulator cyclin D2. In this study we have further characterized the role of STAT5 in the regulation of cyclin D expression and β-cell proliferation by hGH. Cyclin D2 mRNA and protein levels (but not cyclin D1 and D3) were induced in a time-dependent manner by hGH in INS-1 cells. Inhibition of protein synthesis by coincubation with cycloheximide did not affect the hGH-induced increase of cyclin D2 mRNA levels at 4 h. Expression of a dominant negative STAT5 mutant, STAT5aΔ749, partially inhibited cyclin D2 protein levels. INS-1 cells transiently transfected with a cyclin D2 promoter-reporter construct revealed a 3- to 5-fold increase of transcriptional activity in response to hGH stimulation. Furthermore, coexpression of a constitutive active STAT5 mutant (either CA-STAT5a or CA-STAT5b) was sufficient to drive transactivation of the promoter. CA-STAT5b was stably expressed in INS-1 cells under the control of a doxycycline-inducible promoter. Gel retardation experiments using a probe representing a putative STAT5 binding site in the cyclin D2 promoter revealed binding of the doxycycline-induced CA-STAT5b. Furthermore, induction of CA-STAT5b stimulated transcriptional activation of the cyclin D2 promoter and induced hGH-independent proliferation in these cells. In primary β-cells, adenovirus-mediated expression of CA-STAT5b profoundly stimulated DNA-synthesis (5.3-fold over control) in the absence of hGH. Our studies indicate that STAT5 activation is sufficient to drive proliferation of the β-cells and that cyclin D2 may be a critical target gene for STAT5 in this process.
Temporal growth and vertical propagation of perturbations in the winter atmosphere
Authors: Christiansen Bo
Published: April 2003

We present a general‐circulation model study of the temporal growth and vertical propagation of perturbations following transient, vertically confined forcings. Five ensembles of perturbation experiments are performed, each with eight different initial conditions and with the perturbations enforced at ten different vertical levels from the lower troposphere to the upper stratosphere. The motivation for the study is the recent recognition of downward propagation of anomalies from the stratosphere to the troposphere and its implications both for medium‐range forecasts and for a possible physical mechanism for stratospheric impacts on weather and climate.

The perturbations grow in an initial period after which they saturate to a level comparable to the natural variability. In the initial period the growth of the perturbations is quadratic in time. This power‐law growth suggests a predictability time which converges towards a finite value in the limit of small perturbations. In the troposphere the predictability time, defined as when perturbations reach a size of 50% of the natural variability, is 20–30 days. In the stratosphere the response is delayed and a predictability time of 30–40 days is observed.

In the initial period of growth, the vertical spread of perturbations seems decoupled from the background vacillations in the sense that no vertical propagation of perturbations with the time‐scale of the vacillations is observed. Forcings confined to the stratosphere result instantaneously in perturbations of the troposphere and vice versa. Thus, stratospheric vacillations seem to have no active role in the propagation of perturbations from the stratosphere to the troposphere: stratospheric vacillations are not a vehicle for transient perturbations in the stratosphere to be transported to the troposphere. The disconnected nature of the stratospheric vacillations and the growth of perturbations is further substantiated in experiments with a time‐independent troposphere. In these experiments the periodic stratospheric vacillations are shown not to support the growth of perturbations. Copyright © 2003 Royal Meteorological Society
Regional climate‐model predictions of extreme rainfall for a changing climate
Authors: Huntingford C. , Jones R.G. , Prudhomme C. , Lamb R. , Gash J. H. C. , Jones D. A.
Published: April 2003

Major floods occurred in the United Kingdom during autumn 2000. These were caused by a rapid sequence of heavy rainfall events that occurred over a period of many weeks leading to record‐breaking monthly‐to‐seasonal rainfall totals. The question was raised as to whether such rainfall events may be related to human‐induced climate change.

Climate‐model predictions of future changes in mean precipitation behaviour are well established. However, to understand flooding requires an examination of predictions of extreme rainfall behaviour at a relatively small spatial scale. For three areas within the United Kingdom, output from a Hadley Centre regional climate model, ‘nested’ within one of its general‐circulation models, is compared with raingauge data averaged over these areas for the period 1961–1990. This shows that the modelling system is good at predicting the statistical likelihood of extreme rainfall events seen in historical data. This result holds for extreme rainfall totals over daily to monthly timescales.

When the modelling system is used to predict changes in these extreme events resulting from atmospheric CO2 concentrations that may be representative of the period 2080–2100, significant reductions in the return periods of such events are seen. For example, 30‐day rainfall totals, which happened in the recent past on average once in 20 years, are predicted to happen once in 3–5 years. An interpolation method based upon climate‐model output and incorporating raingauge data is used to estimate how rainfall extremes may have changed between the middle of the 19th century, and for a period centred on the year 2000. This also predicts that increased greenhouse gases have led to reduced return periods of extreme rainfall events for three sites of interest, though in this case the changes are not statistically significant. © Royal Meteorological Society, 2003. R. G. Jones's contribution is Crown copyright
Geographical and organisational variation in the structure of primary care services: implications for study design
Authors: Adams Geoffrey , Gulliford Martin , Ukoumunne Obioha , Chinn Susan , Campbell Michael
Published: April 2003

Aims: To evaluate the extent to which structural variation between English general practices is accounted for at higher organisational levels in the National Health Service (NHS).

Methods: We analysed data for 11 structural characteristics of all general practices in England. These included characteristics of general practitioners (GPs), the practice list and the services provided by practices. A four-level random effects model was used for analysis and components of variance were estimated at the levels of practice, primary care group (PCG), health authority and region.

Results: The proportion of single-handed practices ranged from 0% to 74% at PCG level and from 14% to 43% in different regions. The proportion of practices providing diabetes services ranged from 0% to 100% at PCG level and from 71% to 96% in different regions. The list size per GP ranged from 1314 to 2704 patients per GP at PCG level and from 1721 to 2225 at regional level. Across the 11 variables analysed, components of variance at general practice level accounted for between 43% and 95% of the total variance. The PCG level accounted for between 1% and 29%, the health authority level for between 2% and 15% and the regional level for between 0% and 13% of the total variance. Adjusting for an index of deprivation and the supply of GPs gave a median 8% decrease in the sum of variance components.

Conclusion: Geographical and organisational variation in the structure of primary care services should be considered in designing studies in health systems such as the English NHS. Stratified designs may be used to increase study efficiency, but variation between areas may sometimes compromise generalisability.
Effect of Molecular Orientation of Epitaxially Grown Platinum(II) Octaethyl Porphyrin Films on the Performance of Field‐Effect Transistors
Authors: Noh Y.‐Y. , Kim J.‐J. , Yoshida Y. , Yase K.
Published: April 2003

The molecular alignment of platinum(II) octaethyl porphyrin (PtOEP) crystals evaporated on KBr (see atomic force microscopy image, Figure) can be readily changed from perpendicular to parallel by changing the substrate temperature. The field‐effect mobility of transisitors prepared using epitaxially grown PtOEP films aligned perpendicularly to a substrate is 100 times higher than that of those of parallel alignment.