bluuebunny/crossref_metadata_2025 huggingface dataset:
COARSE-GRAINING INVARIANT PATTERNS OF ONE-DIMENSIONAL TWO-STATE LINEAR CELLULAR AUTOMATA
Authors: BARBÉ A. , HAESELER F. V. , PEITGEN H.-O. , SKORDEV G.
Published: November 2004

We consider one-dimensional two state cellular automata and their orbital patterns. We are particulary interested in initial states and their orbital pattern which are invariant under a certain coarse-graining operation. We show that invariant initial states are automatic. Moreover, we numerically study the complex nature of the initial states and their invariant orbits.
BIFURCATION AND PREDICTABILITY ANALYSIS OF A LOW-ORDER ATMOSPHERIC CIRCULATION MODEL
Authors: SHIL'NIKOV A. , NICOLIS G. , NICOLIS C.
Published: November 2004

A comprehensive bifurcation analysis of a low-order atmospheric circulation model is carried out. It is shown that the model admits a codimension-2 saddle-node-Hopf bifurcation. The principal mechanisms leading to the appearance of complex dynamics around this bifurcation are described and various routes to chaotic behavior are identified, such as the transition through the period doubling cascade, the breakdown of an invariant torus and homoclinic bifurcations of a saddle-focus. Non-trivial limit sets in the form of a chaotic attractor or a chaotic repeller are found in some parameter ranges. Their presence implies an enhanced unpredictability of the system for parameter values corresponding to the winter season.
AUTOMATIC MAPS ON A SEMIRING WITH DIGITS
Authors: ALLOUCHE J.-P. , CATELAND E. , PEITGEN H.-O. , SKORDEV G. , SHALLIT J.
Published: November 2004

A general framework for substitutions and automaticity of maps from a ring (or even from a semiring) with radix representation to a finite set is given. Our definition contains the classical notion of automaticity as well as the case of multidimensional automatic sequences and the case of sequences indexed by rational integers, by Gaussian integers or by quadratic irrationals.
FRACTALS AND SECONDARY MIGRATION
Authors: MEAKIN PAUL , WAGNER GERI , FRETTE VIDAR , FEDER JENS , JØSSANG TORSTEIN
Published: November 2004

The process of secondary migration, in which oil and gas are transported from the source rocks, through water saturated sedimentary carrier rocks, to a trap or reservoir can be described in terms of the gravity driven penetration of a low-density non-wetting fluid through a porous medium saturated with a wetting fluid. This process has been modeled in the laboratory and by computer simulations using homogeneous porous media. Under these conditions, the pattern formed by the migrating fluid can be described in terms of a string of fractal blobs. The low density internal structure of the fractal blobs and the concentration of the transport process onto the self-affine strings of blobs (migration channels) both contribute to the small effective hydrocarbon saturation in the carrier rocks. This allows the hydrocarbon fluids to penetrate the enormous volume of carrier rock without all of the hydrocarbon being trapped in immobile isolated bubbles. In practice, heterogeneities in the carrier rocks play an important role. In some cases, these heterogeneities can be represented by fractal models and these fractal heterogeneity models provide a basis for more realistic simulations of secondary migration. Fractures may play a particularly important role and migration along open fractures was simulated using a self-affine fractal model for the fluctuating fracture aperture.
LONG RANGE CORRELATION PROPERTIES OF AFTERSHOCK RELAXATION SIGNALS
Authors: VESPIGNANI A. , PETRI A. , ALIPPI A. , PAPARO G. , COSTANTINI M.
Published: November 2004

Relaxation processes taking place after microfracturing of laboratory samples give rise to ultrasonic acoustic emission signals. Statistical analysis of the resulting time series has revealed many features which are characteristic of critical phenomena. In particular, the autocorrelation functions obey a power-law behavior, implying a power spectrum of the kind 1/f. Also the amplitude distribution N(V) of such signals follows a power law, and the obtained exponents are consistent with those found in other experiments: N(V) dV≃V–γ dV, with γ=1.7±0.2. We also analyzed the distribution N(τ) of the delay time τ between two consecutive acoustic emission events. We found that a N(τ) distribution rather close to a power law constitutes a common feature of all the recorded signals. These experimental results can be considered as a striking evidence for a critical dynamics underlying the microfracturing processes.
DISPERSIVE FRACTAL CHARACTERIZATION OF KIDNEY ARTERIES BY THREE-DIMENSIONAL MASS-RADIUS-ANALYSIS
Authors: SERNETZ M. , JUSTEN M. , JESTCZEMSKI F.
Published: November 2004

Three-dimensional data sets of kidney arterial vessels were obtained from resin casts by serial sectioning and by micro-NMR-tomography, and were analyzed by the mass-radius-relation both for global and local scaling properties. We present for the first time the spatial resolution of local scaling and thus the dispersion of the fractal dimension within the organs. The arterial system is characterized as a non-homogeneous fractal. We discuss and relate the fractal structure to the scaling and allometry of metabolic rates in living organisms.
COMPLEX BIOLOGICAL GROWTH: NEURONAL MORPHOGENESIS
Authors: HENTSCHEL H.G.E. , FINE ALAN
Published: November 2004

It has been observed that neurons and certain other cell types have dendritic arbors which appear to be self-similar. This biological pattern formation is consistent with the concept that shape is controlled by the local submembrane concentration of a morphogen believed to be the calcium ion. Such diffusion-controlled growth of the cellular cytoskeleton has recently been shown to lead to dendritic instabilities. Linear stability analysis suggests that dendritic arboring will be greatly enhanced in the presence of excitable membranes provided the cell is large enough. Computer simulations of this class of models have established many similarities to the growth and form of real neurons including a dendritic morphology reminicent of neuronal arbors and the existence of growth cones observed during real neuronal development; bioelectrical activity; effects of changes in membrane conductivity on morphology; galvanotropism; and chemotropism.
SOUND PULSE SIMULATION IN DEEP OCEAN
Authors: ALENITSYN A. G. , BULDYREV V. S. , GRIKUROV V. E. , FEDOTOV A. A.
Published: November 2004

In this paper, the computer sound pulse simulation in deep stratified ocean is embodied. The restrictions on sound speed profiles are minimal. Pulse spectra are assumed to be wide band. Reasonable combination of numerical and asymptotic techniques is applied to construct an effective algorithm. The principle points of discussion here are the normal mode method for low frequencies, the numerical asymptotic approach to calculate the eigenvalues and eigenfunctions, the ray method for high frequencies, and the numerical results.
LATTICE GAS WAVE PROPAGATION MODELS INCLUDING DISSIPATION
Authors: SUDO YASUSHI , SPARROW VICTOR W.
Published: November 2004

New lattice gas models for one-dimensional (1D) and two-dimensional (2D) sound propagation have been recently proposed by the authors. These models were dissipationless and deterministic. In this paper, it will be shown how dissipation effects can be included into these lattice gas wave models. To simulate these dissipation effects, the lattice gas particles are assumed to take a random walk. The resulting models combine the authors' lattice gas wave models with published lattice gas models for the diffusion equation. The formulations are stable and consistent.
A FRAMEWORK FOR EVALUATING BOUNDARY CONDITIONS
Authors: HARIHARAN S. I. , JOHNSON DAVID K.
Published: November 2004

This paper explores solutions to the spherically symmetric Euler equations. Motivated by the work of Hagstrom and Hariharan7 and Geer and Pope,5 we model the effect of a pulsating sphere in a compressible medium. The literature available on this suggests that an accurate numerical solution requires artificial boundary conditions which simulate the propagation of nonlinear waves in open domains. Until recently, the boundary conditions available are in general linear, and based on non-reflection. Exceptions to this are the nonlinear nonreflective conditions of Thompson,11 and the nonlinear reflective condition of Ref. 7. The former is based on the rate of change of the incoming characteristics, while the latter relies on asymptotic analysis and the method of characteristics and accounts for the coupling of incoming and outgoing characteristics. Furthermore in Ref. 7 it was shown in a test situation in which the flow would reach a steady state over a long time, the method proposed in Ref. 11 could lead to an incorrect steady state. The current study considers periodic flows. Moreover, various other types and techniques of boundary conditions are included in this study. The technique recommended by Ref. 7 proved superior to all others considered, and matched the results of asymptotic methods which are valid for low subsonic Mach numbers.
EVALUATION OF TWO EFFICIENT TARGET TRACKING ALGORITHMS FOR MATCHED-FIELD PROCESSING WITH HORIZONTAL ARRAYS
Authors: WILMUT MICHAEL J. , OZARD JOHN M. , BROUWER PETER
Published: November 2004

A tracking algorithm may be used to reduce the ambiguity of the positions of a moving underwater acoustic source. The objective of this paper is to evaluate two efficient target tracking algorithms suitable for use with Matched-Field Processing (MFP). The detection after tracking algorithms described here are applicable to targets moving linearly at constant speed and depth that produce low Signal-to-Noise Ratio (SNR) signals at the receivers. The input to the tracker consists of the positions of the largest Bartlett statistics or peaks on the MFP ambiguity surfaces. Even at very low SNRs, these largest peaks usually include the match at or near the source position sufficiently often that the detection performance of our efficient tracker rivals that of an exhaustive tracker. In this paper efficient algorithms are developed and evaluated based on examining either the sum of the uniformly weighted Bartlett array outputs or the sum of the Bartlett array outputs weighted by predicted received signal strength. This sum is evaluated along a set of linear tracks that connect the largest peaks. Detection performance is shown to be better for the signal-strength weighted tracker. The performance difference is largest for tracks along a constant bearing from the array.
EVALUATION OF SEVERAL NONREFLECTING COMPUTATIONAL BOUNDARY CONDITIONS FOR DUCT ACOUSTICS
Authors: WATSON WILLIE R. , ZORUMSKI WILLIAM E. , HODGE STEVE L.
Published: November 2004

Several nonreflecting computational boundary conditions that meet certain criteria and have potential applications to duct acoustics are evaluated for their effectiveness. The same interior solution scheme, grid, and order of approximation are used to evaluate each condition. Sparse matrix solution techniques are applied to solve the matrix equation resulting from the discretization. Modal series solutions for the sound attenuation in an infinite duct are used to evaluate the accuracy of each nonreflecting boundary condition. The evaluations are performed for sound propagation in a softwall duct, for several sources, sound frequencies, and duct lengths. It is shown that a recently developed nonlocal boundary condition leads to sound attenuation predictions considerably more accurate than the local ones considered. Results also show that this condition is more accurate for short ducts. This leads to a substantial reduction in the number of grid points when compared to other nonreflecting conditions.
MULTIPLE-SCATTERING APPROACH TO SURFACE EXAFS: THEORY VERSUS EXPERIMENT
Authors: REHR J.J.
Published: November 2004

Recent advances in polarized, high-order multiple-scattering calculations of extended X-ray absorption find structure (EXAFS) in surface systems are reviewed. Our method is based on curved-wave multiple-scattering (MS) theory and a scattering matrix formalism, which provides an efficient, unified treatment of XAFS, encompassing both EXAFS and X-ray absorption near-edge structure (XANES). Combined with multipath fits in r-space, such calculations have the potential to extend the capability of surface EXAFS experiments, going well beyond the first near-neighbor. The theory is illustrated with theoretical simulations. Our approach also gives a MS interpretation of continuum σ* shape-resonances.
LOCAL DENSITY CALCULATIONS FOR LARGE SYSTEMS USING MULTIPLE SCATTERING THEORY
Authors: NICHOLSON D.M.C. , STOCKS G.M. , WANG Y. , SHELTON W.A. , SZOTEK Z. , TEMMERMAN W.M.
Published: November 2004

The accuracy of energy differences calculated from first principles within the local density approximation (LDA) has been demonstrated for a large number of systems. Armed with these energy differences researchers are addressing questions of phase stability and structural relaxation. However, these techniques are very computationally intensive and are therefore not being used for the simulation of large complex systems. Many of the methods for solving the Kohn-Sham equations of the LDA rely on basis set methods for solution of the Schrodinger equation. An alternative approach is multiple scattering theory (MST). We feel that the locally exact solutions of the Schrodinger equation which are at the heart of the multiple scattering method give the method an efficiency which cannot be ignored in the search for methods with which to attack large systems. Furthermore, the analytic properties of the Green function which is determined directly in MST result in computational shortcuts.
IN SITU STUDIES WITH LOW-ENERGY ELECTRON MICROSCOPY
Authors: TROMP RUUD M.
Published: November 2004

This paper gives a brief review of low-energy electron microscopy (LEEM) as used for in situ studies of surface dynamical processes. The capabilities of LEEM are illustrated with two examples. One is a kinetic instability observed during growth of the first layer of CaF 2 on Si (111). The second concerns the nucleation of misfit dislocations during the growth of thicker, epitaxial CaF 2 films on Si (111), as the critical thickness is exceeded. Both examples highlight the importance of real time, in situ observations of surface dynamical processes.
AP-FIM INVESTIGATION OF THE INITIAL STAGE OF OXIDATION ON THE SURFACE OF ALLOYS
Authors: REN D.G.
Published: November 2004

This paper reports a study of the initial stage of oxidation on the surface of alloys by field-ion microscopy and atom probe (AP-FIM). The samples used in this investigation contained Ni, Ni-Cr, Ni-Al, Ti-Al , and Pt-Rh metals and alloys. A clean-tip surface, after atom-probe analysis, was exposed in the atmosphere of residual oxygen (vacuum 10−4 torr) for a few hours. AP analysis found that a small quantity of oxygen was adsorbed on the surface of the alloys. The clusters of a combination of a metal atom with an oxygen, i.e., PtO +2, NiO +2, and TiO +2 were determined by AP. The experiment found that the binding energy between metal atom on the surface of alloys was reduced when oxygen was adsorbed on the surface. The binding energy of surface atoms was determined according to the field strength of the tip surface. The reduction of the binding energy was about 0.5–2.0 eV, which changed following the exposure period in the atmosphere and depending on the kind of alloys used. The difference in field-ion image due to adsorption of oxygen was observed as compared to without the oxygen. The results of the experiment show that oxygen was absorbed on the “clean surface” of alloys. First the oxygen molecule was dissociated to oxygen atoms by the reaction with metal atoms and then formed the metal-oxygen bonding (M+O→MO) . This is an initial stage of oxidation on the surface of alloys. The clusters of combining oxygen did not dissociate during the field-evaporation process with 4.5 V/Å field strength.
INTERFACIAL REACTION AND SURFACE STRUCTURES OF THE Pb/Si(113) SYSTEM
Authors: ZHAO R.G. , HU CHUAN , YANG W.S.
Published: November 2004

In the present work the Pb/Si (113) system has been studied with LEED, AES, EELS, and QKLEED calculations. The interface is very reactive rather than abrupt as previously concluded. As a result, a specific intermixed phase, which is very similar to that in the Pb/Si and Pb/Ge systems studied earlier, forms at the interface even at room temperature. The atomic structure of the 1×1 Pb surface of the intermixed phase has been determined with QKLEED and there is one ordered Pb atom in each unit cell. Primary results indicate that Pb atoms are likely to randomly occupy the interstitial sites in the intermixed phase.
STRUCTURAL PROPERTIES OF ALKALI-METAL ATOMS ADSORBED ON Ru(0001)
Authors: OVER H. , BLUDAU H. , GIERER M. , ERTL G.
Published: November 2004

The structural properties of the ordered overlayers of Li, Na, K, Rb , and Cs on Ru (0001) are summarized. The major result is that the adsorption site depends on the coverage while the hard-sphere radii of the alkali-metal atoms do not change (if corrected for different numbers of coordination). This comparison also emphasizes the singular behavior of Cs for which adsorption takes place over single Ru atoms at a Cs coverage of 0.25. While on other close-packed substrate surfaces potassium and rubidium occupy ontop positions at low temperatures, this has not been found with Ru (0001). This finding points towards the important role of the substrate. For the ontop adsorption to be favored, an inward displacement of the substrate atoms directly underneath the alkali-metal atoms by a substantial amount is necessary which results in the formation of a quasisevenfold-coordinated bond geometry in connection with a reduction of the dipole-dipole repulsion. The stiffness of the substrate determines the energy cost for this local reconstruction, and consequently ontop adsorption on the hard Ru (0001) substrate has only been observed for the biggest alkali metal Cs where the energy difference between various adsorption sites [on the unrelaxed Ru (0001) surface] is assumed to be small. In order to force potassium to reside in the ontop position, the Ru (0001) surface has to be “softened” which task was accomplished by adding CO molecules to the K-(2×2) overlayer.
FREE-ELECTRON LASER SPECTROSCOPY OF SURFACES AND INTERFACES
Authors: TOLK N.H. , MCKINLEY J.T. , MARGARITONDO G.
Published: November 2004

Synchrotron-radiation sources have become, since the late 1960’s, one of the fundamental experimental tools for surface and interface research. Only recently, however, a related type of photon sources - the free-electron lasers (FELs) — has begun to make important contributions to this field. For example, FELs have been used to reach unprecedented levels of accuracy and reliability in measuring semiconductor interface energy barriers. We review some of the present and proposed experiments that are made possible by the unmatched brightness and broad tunability of infrared FELs. Practical examples discussed in the review are supplied by our own programs at the Vanderbilt Free-Electron Laser. We also briefly analyze the possible future development of FELs and of their applications to surface and interface research, in particular, the possibility of x-ray FELs.
MODIFIED VAN DER WAALS MODEL FOR SURFACE-MELTING DISCUSSION
Authors: WOJTCZAK L. , RUTKOWSKI J.H.
Published: November 2004

The thermodynamic potential governing the surface-melting, considered in terms of the crystallinity and its profile is related to the Gibbs free-energy functional, leads to van der Waals equation of state. The presented construction allows us to determine the mean-field coefficients by their reference to material constants. The model is applied to the surface-melting discussion within the Landau-type mean-field theory of phase-transitions. In particular, the surface-melting temperature is estimated and temperature dependence of the surface liquid-like layer thickness profile is obtained.
CALABI QUASIMORPHISMS FOR THE SYMPLECTIC BALL
Authors: BIRAN PAUL , ENTOV MICHAEL , POLTEROVICH LEONID
Published: November 2004

We prove that the group of compactly supported symplectomorphisms of the standard symplectic ball admits a continuum of linearly independent real-valued homogeneous quasimorphisms. In addition these quasimorphisms are Lipschitz in the Hofer metric and have the following property: the value of each such quasimorphism on any symplectomorphism supported in any "sufficiently small" open subset of the ball equals the Calabi invariant of the symplectomorphism. By a "sufficiently small" open subset we mean that it can be displaced from itself by a symplectomorphism of the ball. As a byproduct we show that the (Lagrangian) Clifford torus in the complex projective space cannot be displaced from itself by a Hamiltonian isotopy.
Human platelets contain forms of factor V in disulfide-linkage with multimerin
Authors: Fuller Nola , Zheng Shilun , Adam Frédéric , Jeimy Samira , Horsewood Ian , Quinn-Allen Mary , Kane William , Hayward Catherine
Published: November 2004

Factor V is an essential cofactor for blood coagulation that circulates in platelets and plasma. Unlike plasma factor V, platelet factorV is stored complexed with the polymeric α-granule protein multimerin. In analyses of human platelet factor V on nonreduced denaturing multimer gels, we identified that approximately 25% was variable in size and migrated larger than single chain factor V, the largest form in plasma. Upon reduction, the unusually large, variably-sized forms of platelet factor V liberated components that comigrated with other forms of platelet factor V, indicating that they contained factor V in interchain disulfide-linkages. With thrombin cleavage, factor Va heavy and light chain domains, but not B-domains, were liberated from the components linked by interchain disulfide bonds, indicating that the single cysteine in the B-domain at position 1085 was the site of disulfide linkage. Since unusually large factor V had a variable size and included forms larger than factor V dimers, the data suggested disulfide-linkage with another platelet protein, possibly multimerin. Immunoprecipitation experiments confirmed that unusually large factor V was associated with multimerin and it remained associated in 0.5 M salt. Moreover, platelets contained a subpopulation of multimerin polymers that resisted dissociation from factor V by denaturing detergent and comigrated with unusually large platelet factor V, before and after thrombin cleavage.The disulfide-linked complexes of multimerin and factor V in platelets, which are cleaved by thrombin to liberate factor Va, could be important for modulating the function of platelet factor V and its delivery onto activated platelets. Factor Va generation and function from unusually large platelet factor V is only speculative at this time.
Treatment of venous thromboembolism with vitamin K antagonists: patients’ health state valuations and treatment preferences
Authors: Bossuyt Patrick , Stalmeier Peep , Sprangers Mirjam , van Dongen Carlo , Middeldorp Saskia , Bank Ivan , van der Meer Jan , Hamulyák Karly , Prins Martin , Locadia Mirjam
Published: November 2004

Determining the optimal duration of vitamin K antagonist (VKA) therapy for patients with venous thromboembolism (VTE) requires a weighting of the benefits and risks of treatment. The objectives of our study were to investigate patient variability in health state valuations associated with VKA therapy and treatment preferences, and to investigate the extent to which valuations and treatment preferences are associated with prior experience with these health states and other patient characteristics. Valuations of outcomes after VTE scaled from 0 (tantamount to death) to 1 (tantamount to perfect health) were elicited from 53 patients who had experienced VTE, 23 patients who had experienced major bleeding during treatment, and 48 patients with the post-thrombotic syndrome. In addition, patients’ treatment preferences were evaluated using treatment trade-off questions. Median health state valuations ranged from 0.33 for ‘non-fatal haemorrhagic stroke’ to 0.96 for ‘no VKA treatment’. Variability between patients was substantial. Patients’ treatment preferences also varied: 25% of patients chose cessation of treatment, regardless of the probability of recurrent VTE presented, whereas 23% of patients were never willing to choose cessation of treatment. Differences in valuations and treatment preferences were not associated with type of event experienced. Due to the substantial and unpredictable variability in valuations and treatment preferences, recommendations regarding treatment duration should be tailored to patients’ specific values and concerns.
Genetic variation in Fcγ receptor IIa protects against advanced peripheral atherosclerosis
Authors: van der Meer Irene , Hofman Albert , Kluft Cornelis , de Maat Moniek , Witteman Jacqueline
Published: November 2004

Immune processes play a substantial role in atherosclerotic disease. The role in atherosclerosis of Fcγ receptor IIa (FcγRIIa), a receptor for immunoglobulin G and for the inflammatory mediator C-reactive protein, is not yet clear. Since the R/H131 polymorphism in the FcγRIIa gene strongly influences binding to FcγRIIa, we investigated the association of the R/H131 polymorphism with advanced peripheral atherosclerosis. Within the Rotterdam Study, a population-based cohort study, we determined FcγRIIa genotype in 430 subjects with advanced peripheral atherosclerosis as indicated by the ankle-arm index, and 411 controls. Heterozygous and homozygous carriers of the H131 allele were protected against advanced peripheral atherosclerosis (age- and gender-adjusted odds ratio (OR) 0.77 (0.54–1.12) and 0.65 (0.44–0.98), respectively, P trend=0.04). This effect was most pronounced in subjects with modestly elevated levels of inflammation as indicated by the leukocyte count (OR 0.52 (0.29–0.93) and 0.45 (0.23–0.86), for heterozygotes and H131 homozygotes, respectively; P trend=0.02). This is the first study showing that the H131 allele of FcγRIIa protects against advanced peripheral atherosclerosis.
Proinflammatory properties of murine aortic endothelial cells exclusively expressing a non cleavable form of TNFα
Authors: Canault Matthias , Peiretti Franck , Mueller Christoph , Deprez Paule , Bonardo Bernadette , Bernot Denis , Juhan-Vague Irène , Nalbone Gilles
Published: November 2004

Soluble (sTNF) and transmembrane (tmTNF) forms of TNFα (TNF) have distinct proinflammatory effects. We investigated whether tmTNF altered the synthesis of some proinflammatory proteins involved in atherothrombosis, in murine aortas and aortic endothelial cells (MAEC). Samples were obtained from wild-type (WT) mice and TNF-deficient mice that express a mutated non cleavable tmTNF transgene (tmTNFnc).The levels of secreted MCP-1, RANTES, IL-6, PAI-1, soluble ICAM-1, and soluble TNF receptor type 1 (TNFR1; CD120a) antigens, MMP-9 activity and of cell surface ICAM-1 were not significantly different between the two types of MAEC.The magnitude of endotoxin-stimulated production of RANTES, MCP-1 and IL-6 was similar in the two types of cells. Of note, the amount of synthesized TNF receptor type 2 (TNFR2; CD120b), measured by its secreted (in aorta and MAEC), intracellular and mRNA levels (in MAEC), was significantly 4-fold lower in tmTNFnc than in WT mice, both in basal and endotoxin-stimulated conditions. A neutralizing anti-TNF antibody or the recombinant murine TNF did not modify the magnitude of the difference in TNFR2 production between the two types of cells, suggesting a preponderant role of tmTNF in the down-regulation of TNFR2 synthesis. Macrophages of tmTNFnc mice also produced less TNFR2 than WT macrophages (−30%). Plasmas of tmTNFnc mice contained significantly less sTNFR2 than WT mice (−75%). In conclusion, an increase in tmTNF levels, rather than the lack of sTNF, significantly down-modulated TNFR2 synthesis in aortic endothelial cells, but had no major influence on the synthesis of some major pro-inflammatory and pro-atherothrombotic proteins.
Platelet morphology, soluble P selectin and platelet P-selectin in acute ischaemic stroke
Authors: Nadar Sunil , Blann Andrew , Lip Gregory
Published: November 2004

The pathophysiology of ischaemic stroke involves the platelet. In this study, we hypothesised that abnormalities in platelet morphology, as well as soluble (sPsel) and total platelet P-selectin (pPsel) levels would be present in patients presenting with an acute ischaemic stroke, and that these changes would improve at ≥ 3 months’ follow-up. We studied 59 hypertensive patients (34 male; mean age 68± 12 years) who presented with an acute ischaemic stroke (ictus< 24 hours), and compared them with 2 groups: (i) age-, sex-and ethnic-origin matched normotensive healthy controls; and (ii) uncomplicated ‘ high risk’ hypertensive patients as ‘ risk factor control’ subjects. Platelet morphology (volume and mass) was quantified, and sPsel (plasma marker of platelet activation) was measured (ELISA) in citrated plasma. The mass of P-selectin in each platelet (pPsel) was determined by lysing a fixed number of platelets and then determining the levels of P-selectin in the lysate. Results show that patients who presented with a stroke had significantly higher levels of sPsel and pPsel (both p< 0.001), compared to the normal controls and the hypertensive patients. Patients with an acute stroke had lower mean platelet mass (MPM) and mean platelet volume (MPV) as compared to the uncomplicated hypertensive patients, who had significantly higher mean MPM and MPV values, as compared to normal controls. On follow-up, the levels of both sPsel (p = 0.011), pPsel (< 0.001) and MPV (p = 0.03) were significantly lower. Mean MPM levels remained unchanged. We conclude that patients presenting with an acute ischaemic stroke have activated platelets, as evident by the increased levels of soluble and platelet P-selectin. Further study of platelet activation and the role of P-selectin is warranted.
Conformational Asn187Asp/Lys antithrombin variants and thrombosis
Authors: Bauters Anne , Khairy Mahnouch , Ochat Nadège , Jude Brigitte , Aiach Martine , Alhenc-Gelas Martine , Picard Véronique
Published: November 2004

Antithrombin Rouen VI (N187D) is a rare conformational thermolabile variant.The unique symptomatic carrier reported in the literature developed 3 thrombotic events during pregnancy, in each case in a context of pyrexial infection. In fresh plasma, antithrombin activity and antigen level were normal but in vitro experiments demonstrated the presence of a thermolabile variant, suggesting that fever could be a trigger for thrombosis in N187D carriers.The RouenVI variant was further found in two asymptomatic brothers. In these subjects, it was associated with normal antigen level but reduced activity. In order to better delineate the functional and clinical consequences of the N187 variants,we have studied a series of seven subjects from two distinct families heterozygous for the Rouen VI mutation. Antithrombin levels were normal or borderline in these patients. Thermostability of plasma antithrombin was normal. We have also studied six subjects heterozygous for a new mutation, 6462C>G,which results in an asparagine to lysine substitution at residue 187. In these patients, the N187K mutation is associated with a clear type II deficiency and decreased thermostability of the plasma protein has been demonstrated. That the N187D mutation has milder consequences on plasma antithrombin activity than the N187K mutation is in agreement with structural predictions. About 50% of the N187 carriers studied have suffered venous thrombotic events, strongly suggesting that both mutations are risk factors for thrombosis, but none occurred during pyrexial infections.
Long-Term Healthcare and Cost Outcomes of Disease Management in a Large, Randomized, Community-Based Population With Heart Failure
Authors: Galbreath Autumn Dawn , Krasuski Richard A. , Smith Brad , Stajduhar Karl C. , Kwan Michael D. , Ellis Robert , Freeman Gregory L.
Published: November 2004

Background—

Because of the prevalence and expense of congestive heart failure (CHF), significant efforts have been made to develop disease management (DM) programs that will improve clinical and financial outcomes. The effectiveness of such programs in a large, heterogeneous population of CHF patients remains unknown.

Methods and Results—

We randomized 1069 patients (aged 70.9±10.3 years) with systolic (ejection fraction 35±9%) or echocardiographically confirmed diastolic heart failure (HF) to assess telephonic DM over an 18-month period. Data were collected at baseline and at 6-month intervals. Survival analysis was performed by Kaplan-Meier and Cox regression methods. Healthcare utilization was defined after extensive record review, with an attempt to account for all inpatient and outpatient visits, medications, and diagnostic tests. We obtained data on 92% of the patients, from nearly 53 000 health-related encounters. Total cost per patient was defined by adding estimated costs for the observed encounters, excluding the cost of the DM. Kaplan-Meier analysis showed that DM patients had a reduced mortality rate (
P
=0.037), with DM patients surviving an average of 76 days longer than controls. Subgroup analysis showed that DM had beneficial outcomes in patients with systolic HF (hazard ratio 0.62;
P
=0.040), which was more pronounced in NYHA classes III and IV. Although improvements in NYHA class were more likely with DM (
P
<0.001), 6-minute walk data from 217 patients in whom data were available at each visit showed no significant benefit from DM (
P
=0.08). Total and CHF-related healthcare utilization, including medications, office or emergency department visits, procedures, or hospitalizations, was not decreased by DM. Repeated-measures ANOVA for cost by group showed no significant differences, even in the higher NYHA class groups.

Conclusions—

Participation in DM resulted in a significant survival benefit, most notably in symptomatic systolic HF patients. Although DM was associated with improved NYHA class, 6-minute walk test results did not improve. Healthcare utilization was not reduced by DM, and it conferred no cost savings. DM in HF results in improved life expectancy but does not improve objective measures of functional capacity and does not reduce cost.
Technical Assistance Programs and the Diffusion of Environmental Technologies in the Printing Industry: The Case of SMEs
Authors: Rothenberg Sandra , Becker Monica
Published: November 2004

The goal of this article is to better understand the diffusion of environmentally preferable manufacturing technology (as distinct from pollution control technology) in small-and medium-sized firms (SMEs) and the influence of technical assistance programs on the diffusion of these technologies. The authors draw their insights from the printing industry, a sector where small firms predominate. They find that smaller firms lag slightly in the adoption of environmental technologies. With regard to technical assistance, they find that printers identify suppliers and other industry sources as more useful than government in providing information that leads to active exploration of new environmental technologies. In addition, in comparison to larger firms, smaller firms reported to be less familiar with government-sponsored programs and perceived some of the programs to be less useful. They point to several ways in which regulatory agencies are experimenting to make government sponsored programs more effective.
Querying Keywords
Authors: Baker Paul
Published: November 2004

The corpus analysis program WordSmith Tools allows two corpora to be compared against each other in order to acquire a list of keywords: words that appear statistically more often in one text than the other. This article examines some potential problems of analyzing keywords and ways to overcome them. A keywords analysis may force the researcher to overplay differences rather than similarities, and it focuses on difference at the lexical rather than the semantic, grammatical, or pragmatic levels. An examination of dispersion patterns, concordances, and key clusters are useful supplementary forms of analysis. The use of annotated data to derive key categories or grouping like words into similar groups is also helpful.
A Cost-Utility Analysis of Neonatal Circumcision
Authors: Van Howe Robert S.
Published: November 2004

A cost-utility analysis, based on published data from multiple observational studies, comparing boys circumcised at birth and those not circumcised was undertaken using the Quality of Well-being Scale, a Markov analysis, the standard reference case, and a societal perspective. Neonatal circumcision increased incremental costs by $828.42 per patient and resulted in an incremental 15.30 well-years lost per 1000 males. If neonatal circumcision was cost-free, pain-free, and had no immediate complications, it was still more costly than not circumcising. Using sensitivity analysis, it was impossible to arrange a scenario that made neonatal circumcision cost-effective. Neonatal circumcision is not good health policy, and support for it as a medical procedure cannot be justified financially or medically.
A Comparison of 3 Valuation Methods for Temporary Health States in Patients Treated with Oral Anticoagulants
Authors: Locadia Mirjam , Stalmeier Peep F. M. , Oort Frans J. , Prins Martin H. , Sprangers Mirjam A. G. , Bossuyt Patrick M. M.
Published: November 2004

Background. The application of the time tradeoff (TTO) method in temporary health states may lead to less valid results because an unrealistic scenario is presented to patients. The chained TTO has been proposed to solve this problem. Objectives. To compare a chained TTO method with a conventional TTO method in the valuation of temporary health states, in terms of consistency and reliability. To compare both TTO methods with direct rating. Patients and Methods. Eighty-four patients treated with oral anticoagulants were interviewed twice. During the 1st interview, values for 5 temporary health states were obtained with a rank ordering procedure, direct rating, and the chained TTO method. During the 2nd interview, either the 1st interview was repeated (n = 30) or health state values were obtained with the conventional TTO method (n = 54). Consistency was assessed by comparing the 3 valuation methods with the rank ordering procedure. Generalizability theory was used to assess reliability. Results. The 3 methods produced significantly different valuations of health states. Chained TTO values were higher than values obtained with direct rating and the conventional TTO. Consistency and reliability did not differ across the 3 methods. Conclusion. The authors found no evidence for a difference in consistency and reliability between the chained TTO method and the conventional TTO method in the valuation of temporary health states. As direct rating is simpler to administer than both TTO methods, one could consider using direct ratings for the valuation of temporary health states. Biases associated with the conventional and the chained TTO method are discussed.
Reader Variability in Mammography and Its Implications for Expected Utility over the Population of Readers and Cases
Authors: Wagner Robert F. , Beam Craig A. , Beiden Sergey V.
Published: November 2004

The multiple-reader, multiple-case (MRMC) approach to receiver operating characteristic (ROC) analysis is becoming the dominant assessment paradigm in medical imaging. Its most common version involves having many readers read every patient case in the study, a critical feature since differences among competing imaging modalities are often dominated by differences in reader performance. The present authors have carried out MRMC ROC analysis on a uniquely large data set for mammography. The analysis quantifies the great range of observed reader skill in that data set. It also demonstrates that the sample sizes are sufficiently large that the conclusions generalize to the populations sampled here with little uncertainty from the finite sample size. A schematic approach to bracketing the utility matrix is then used to study trends in the resulting expected utility functions that correspond to the range of observed ROC curves. This is done for both the screening and the diagnostic context. The results raise 2 hypotheses for further investigation. First, it is possible that the present ambiguity surrounding the effectiveness of mammography is due in part to the observed range of reader skills and corresponding expected utility functions. Second, it is possible that computer-assisted modalities for mammography may lead to improvements in the expected utility function not only for screening but also in the diagnostic context, especially for the lower performing readers.
The Application of the Heuristic-Systematic Processing Model to Treatment Decision Making about Prostate Cancer
Authors: Steginga Suzanne K. , Occhipinti Stefano
Published: November 2004

The study investigated the utility of the Heuristic-Systematic Processing Model as a framework for the investigation of patient decision making. A total of 111 men recently diagnosed with localized prostate cancer were assessed using Verbal Protocol Analysis and self-report measures. Study variables included men’s use of nonsystematic and systematic information processing, desire for involvement in decision making, and the individual differences of health locus of control, tolerance of ambiguity, and decision-related uncertainty. Most men (68%) preferred that decision making be shared equally between them and their doctor. Men’s use of the expert opinion heuristic was related to men’s verbal reports of decisional uncertainty and having a positive orientation to their doctor and medical care; a desire for greater involvement in decision making was predicted by a high internal locus of health control. Trends were observed for systematic information processing to increase when the heuristic strategy used was negatively affect laden and when men were uncertain about the probabilities for cure and side effects. There was a trend for decreased systematic processing when the expert opinion heuristic was used. Findings were consistent with the Heuristic-Systematic Processing Model and suggest that this model has utility for future research in applied decision making about health.
On Uncertainty in Medical Testing
Authors: Winkler Robert L. , Smith James E.
Published: November 2004

There is confusion in the medical decision-making literature about how to handle uncertainty in medical tests. In this article, the authors consider the situation in which there is uncertainty about the pretest probability of a disease in a patient as well as uncertainty about the sensitivity and specificity of a diagnostic test for that disease. They discuss how to calculate posttest probabilities of a disease under such uncertainty and how to calculate a distribution for a posttest probability. They show that given certain independence assumptions, uncertainty about these parameters need not complicate the calculation of patient positive predictive values: One can simply use the expected values of the parameters in the standard Bayesian formula for posttest probabilities. The discussion on how to calculate distributions for positive predictive values corrects a common and potentially important error.
Combining Correlated Diagnostic Tests: Application to Neuropathologic Diagnosis of Alzheimer’s Disease
Authors: Xiong Chengjie , McKeel Daniel W. , Miller J. Philip , Morris John C.
Published: November 2004

This article studies the problem of combining correlated diagnostic tests to maximize the discriminating power between the diseased population and the healthy population. The authors consider all possible linear combinations of multiple diagnostic tests and search for the one that achieves the largest area under the receiver operating characteristic (ROC) curve. They discuss the statistical estimation of the optimum linear combination test and the associated maximum area under the ROC curve. Their approach is based on the assumption of multivariate normal distribution of the multiple diagnostic tests. They also present the application of the proposed techniques to the neuropathologic diagnosis of Alzheimer’s disease based on brain lesions from 5 different brain locations using a data set from the Washington University Alzheimer’s Disease Research Center.
Decision Making in a Multidisciplinary Cancer Team: Does Team Discussion Result in Better Quality Decisions?
Authors: Kee Frank , Owen Tracy , Leathem Ruth
Published: November 2004

To establish whether treatment recommendations made by clinicians concur with the best outcomes predicted from their prognostic estimates and whether team discussion improves the quality or outcome of their decision making, the authors studied real-time decision making by a lung cancer team. Clinicians completed pre- and postdiscussion questionnaires for 50 newly diagnosed patients. For each patient/doctor pairing, a decision model determined the expected patient outcomes from the clinician’s prognostic estimates. The difference between the expected utility of the recommended treatment and the maximum utility derived from the clinician’s predictions of the outcomes (the net utility loss) following all potential treatment modalities was calculated as an indicator of quality of the decision. The proportion of treatment decisions changed by the multidisciplinary team discussion was also calculated. Insofar as the change in net utility loss brought about by multidisciplinary team discussion was not significantly different from zero, team discussion did not improve the quality of decision making overall. However, given the modest power of the study, these findings must be interpreted with caution. In only 23 of 87 instances (26%) in which an individual specialist’s initial treatment preference differed from the final group judgment did the specialist finally concur with the group treatment choice after discussion. This study does not support the theory that team discussion improves decision making by closing a knowledge gap.
Alternative Tree-Structured Survival Analysis Based on Variance of Survival Time
Authors: Jin Hua , Lu Ying , Stone Kaite , Black Dennis M.
Published: November 2004

Tree-structured survival analysis (TSSA) is a popular alternative to the Cox proportional hazards regression in medical research of survival data. Several methods for constructing a tree of different survival profiles have been developed, including TSSA based on log-rank statistics, martingale residuals, Lp Wasserstein metrics between Kaplan-Meier survival curves, and a method based on a weighted average of the within-node impurity of the death indicator and the within-node loss function of follow-up times. Lu and others used variance of restricted mean lifetimes as an index of degree of separation (DOS) to measure the efficiency in separations of survival profiles by a classification method. Like tree-based regression analysis that uses variance as a criterion for node partition and pruning, the variance of restricted mean lifetimes between different groups can be an alternative index to log-rank test statistics in construction of survival trees. In this article, the authors explore the use of DOS in TSSA. They propose an algorithm similar to the least square regression tree for survival analysis based on the variance of the restricted mean lifetimes. They apply the proposed method to prospective cohort data from the Study of Osteoporotic Fracture that motivated the research and then compare their classification rule to those rules based on the conventional TSSA mentioned above. A limited simulation study suggests that the proposed algorithm is a competitive alternative to the log-rank or martingale residual-based TSSA approaches.