bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization dependence of four‐wave mixing in dispersion‐shifted fibers and its application to nonlinear refractive index measurements using maximum mixing efficiency
Authors: Kawanami Kimiya , Ishizawa Yoji , Imai Masaaki , Kawabata Keisuke , Namihira Yoshinori
Published: February 2004

If the phase match condition is satisfied in a 1.55‐µm dispersion‐shifted fiber (DSF), four‐wave mixing (FWM) between the signals is generated at a lower optical power level than other nonlinear phenomena. In this paper, the polarization dependence of the FWM generating efficiency is discussed. From the maximum mixing efficiency, the nonlinear refractive index and the zero‐dispersion wavelength are simultaneously measured. Both DSFs of 20 and 4 km are used for studies of the polarization dependence of FWM light with respect to linear polarization from the wavelength variable DFB‐LD. For a 20‐km DSF, a nonlinear refractive index of n2 = 2.50 × 10−20 m2/W and a zero‐dispersion wavelength of λ0 = 1553.0 nm are obtained. For a 4‐km DSF, n2 = 2.42 × 10−20 m2/W and λ0 = 1557.9 nm. For the 4‐km DSF, it is confirmed by the CW‐SPM method that n2 = 2.40 × 10−20 m2/W. The measured results for the two methods are found to be in good agreement. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 45–54, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10146
Design of a continuous‐time Gm–C bandpass Delta‐Sigma modulator
Authors: Matsuura Koji , Waho Takao
Published: February 2004

A second‐order continuous‐time bandpass ΔΣ modulator using HEMTs (High‐Electron‐Mobility Transistors) is designed and its performance characteristics such as SNR (Signal‐to‐Noise Ratio) are evaluated by SPICE simulation. For high‐speed operation of the modulator, the bandpass ΔΣ scheme, which can reduce the quantization noise at high‐frequency regions, and the continuous‐time scheme using a continuous‐time filter as a loop filter are employed. First, the bandpass filter, quantizer, and D‐A converter are designed. Next, the modulator formed by combination of these is simulated. Excellent performance is obtained with an SNR = 44 dB (corresponding to a resolution of 7.0 bits) with a bandwidth of 32 MHz and with SNR = 52 dB (8.3 bits) at 8 MHz. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 39–44, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10168
Fingerprint sensor LSI
Authors: Machida Katsuyuki , Morimura Hiroki , Shigematsu Satoshi , Okazaki Yukio
Published: February 2004

Recently, verification systems using biometrics to prevent illegal use of information terminals have attracted attention. We looked at fingerprints as the biometric and developed a semiconductor capacitive fingerprint sensor LSI. In this paper, we describe the sensor structure of the capacitive fingerprint sensor LSI and the sensor process, and explain the reliability evaluation method concerning the electrostatic measures, the mechanical strength, and the long‐term reliability. We also describe the calibration function, a feature of this fingerprint sensor LSI. We implement calibration that adjusts the variable capacitance provided at each pixel to produce the same output signal at each pixel, is able to eliminate the effect of the sensor's surface state, and always obtains a clean image even when used for a long time. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 29–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10175
Test structure for precise measurement of MOSFET matching properties
Authors: Shimizu Yoshiyuki , Nakamura Mitsuo , Matsuoka Toshimasa , Taniguchi Kenji
Published: February 2004

We designed a new test structure for precise measurement of MOSFET matching properties. This structure consists of a MOSFET array including over 10,000 MOSFETs for measurement, and peripheral decoder circuits to choose an MOSFET in the array. The Kelvin technique was implemented in the structure to cancel parasitic resistances of metal wiring and transmission gates in such a way that any MOSFET in the array can be measured at a precise bias condition. Accurate electrical measurements using the structure make it possible to derive the statistical variations of the threshold voltage and transconductance of MOSFETs placed on a chip. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 21–28, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10178
Theoretical study on tunneling phenomena in asymmetrical rectangular double‐barrier structures with acceleration well
Authors: Hamaguchi Hiroki , Yamamoto Hiroaki , Yamada Norifumi
Published: February 2004

As a promising resonant tunneling structure for reduction of tunneling time, the “asymmetric rectangular double‐barrier structure with an acceleration well” is proposed. Analytical expressions are derived for the tunneling transmission coefficient of the electrons and for the resonant condition. Also, the condition for the shortest tunneling time is analytically studied by using the dwell time as the tunneling time. From the resonant condition, the width of each layer can be determined for a given resonant energy. The resultant dwell time is calculated and discussed in terms of both theoretical and numerical analysis. Although the model proposed in this research is an idealized one, the proposed structure and the obtained results are considered useful in the design of tunneling devices in the sense that the tunneling time can be controlled. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 1–11, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10197
DNase I behaves as a transcription factor which modulates Fas expression in human cells
Authors: Oliveri Mara , Daga Antonio , Lunardi Claudio , Navone Riccardo , Millo Romano , Puccetti Antonio
Published: February 2004

DNase I is the major nuclease present in biological fluids and is ubiquitously expressed in mammalian tissues. It is responsible for the removal of DNA from nuclear antigens, and consistently with this function, DNase I‐deficient mice show features of autoimmunity. The enzyme seems also to be involved in apoptosis (programmed cell death). We demonstrate that DNase I is internalized by human cells upon binding mannose 6‐phosphate receptor and gains access into the cells. Following internalization of the enzyme, the cells show an increased surface expression of Fas molecule, a key regulator of apoptosis. Here we show that DNase I up‐regulates fas transcription upon interaction with the fas gene promoter. Moreover, overexpression of the DNase I gene in human cells results in a similar modulation of the fas gene expression. Our data provide the first evidence that the endonuclease DNase I behaves as a transcription factor which selectively regulates cell surface Fas expression in human cells and point towards a fundamental role of DNase I in the regulation of the apoptotic machinery.
Complement C1q regulates LPS‐induced cytokine production in bone marrow‐derived dendritic cells
Authors: Yamada Masahide , Oritani Kenji , Kaisho Tsuneyasu , Ishikawa Jun , Yoshida Hitoshi , Takahashi Isao , Kawamoto Shinichirou , Ishida Naoko , Ujiie Hidetoshi , Masaie Hiroaki , Botto Marina , Tomiyama Yoshiaki , Matsuzawa Yuji
Published: February 2004

We show here that C1q suppresses IL‐12p40 production in LPS‐stimulated murine bone marrow‐derived dendritic cells (BMDC). Serum IL‐12p40 concentration of C1q‐deficient mice was higher than that of wild‐type mice after intraperitoneal LPS‐injection. Because neither globular head of C1q (gC1q) nor collagen‐like region of C1q (cC1q) failed to suppress LPS‐induced IL‐12p40 production, both gC1q and cC1q, and/or some specialized conformation of native C1q may be required for the inhibition. While C1q did not affect mRNA expression of Toll‐like receptor 4 (TLR4), MD‐2, and myeloid differentiation factor 88 (MyD88), BMDC treated with C1q showed the reduced activity of NF‐κB and the delayed phosphorylation of p38, c‐Jun N‐terminal kinase, and extracellular signal‐regulated kinase after LPS‐stimulation. CpG oligodeoxynucleotide‐induced IL‐12p40 and TNF‐α production, another MyD88‐dependent TLR‐mediated signal, was also suppressed by C1q treatment. Therefore, C1q is likely to suppress MyD88‐dependent pathway in TLR‐mediated signals. In contrast, C1q failed to suppress colony formation of B cells responding to LPS or LPS‐induced CD40 and CD86 expression on BMDC in MyD88‐deficient mice, indicating that inhibitory effects of C1q on MyD88‐independent pathways may be limited. Taken together, C1q may regulate innate and adaptive immune systems via modification of signalsmediated by interactions between invading pathogens and TLR.
Morphological changes during dendritic cell maturation correlate with cofilin activation and translocation to the cell membrane
Authors: Verdijk Pauline , van Veelen Peter A. , de Ru Arnoud H. , Hensbergen Paul J. , Mizuno Kensaku , Koerten Henk K. , Koning Frits , Tensen Cornelis P. , Mommaas A. Mieke
Published: February 2004

Upon activation, tissue residing immature dendritic cells (DC) start to migrate towards the draining lymph node and mature into efficient antigen‐presenting cells. During maturation DC loose their capacity to endocytose antigens, change their surface expression of adhesion molecules, chemokine receptors, and costimulatory molecules, and change morphology. We employed 2D‐PAGE and mass spectrometry to identify additional differentially expressed proteins in immature and mature DC. Human monocyte‐derived DC were matured with LPS and protein expression profiles were compared before andafter maturation. One of the proteins differentially expressed between immature and mature DC was identified as the actin‐binding protein cofilin. We show here that cofilin is dephosphorylated in response to several maturation stimuli (i.e. CD40 ligand, LPS or a combination of TNF‐α and prostaglandin E2). Moreover, dephosphorylated cofilin translocated towards the plasmamembrane during maturation. Importantly, this correlated with an increase in filamentous actin and the appearance of veils, suggesting a role for cofilin in cytoskeletal rearrangements during maturation.
An interaction between CD16 and CR3 enhances iC3b binding to CR3 but is lost during differentiation of monocytes into dendritic cells
Authors: Preynat‐Seauve Olivier , Villiers Christian L. , Jourdan Guillaume , Richard Marie‐Jeanne , Plumas Joël , Favier Alain , Marche Patrice N. , Favrot Marie‐Christine
Published: February 2004

The receptor for the iC3b fragment of complement, CR3, is involved in monocytes/macrophages and neutrophils phagocytosis. CR3 is known to interact with the low affinity receptor for Ig (CD16) and previous studies have suggested that this cooperation modulates CR3 functions. Herein we have studied the effect of CD16 on the ability of human monocytes CR3 to bind to iC3b. We show that iC3b binding to CR3 is inhibited by several reagents that are known to dissociate the CD16/CR3 complex. In addition, treatment of monocytes with soluble CD16 inhibited iC3b binding to CR3. Together, these data indicate that iC3b binding to monocyte CR3 is up‐regulated by an interaction between membrane CD16 and CR3. The implication of CD16 in CR3 binding to iC3b was also analyzed after monocyte differentiation into dendritic cells (DC). Differentiation of monocytes into DC abrogates the cooperation between CD16 and CR3, due to a loss of CD16/CR3 interaction. In accordance, this phenomenon is associated with a lack of iC3b binding to DC. As a consequence, deposition of iC3b on apoptotic cells does not modify their phagocytosis by DC. In conclusion, we demonstrate a cooperation between CD16 and CR3 that favors iC3b binding to CR3 but is lost on DC.
Intrahepatic B cell clonal expansions and extrahepatic manifestations of chronic HCV infection
Authors: Sansonno Domenico , Lauletta Gianfranco , De Re Valli , Tucci Felicia Anna , Gatti Pietro , Racanelli Vito , Boiocchi Mauro , Dammacco Franco
Published: February 2004

B cell repertoire in three biological compartments (liver, bone marrow and peripheral blood) of 30 unselected patients chronically infected with HCV has been characterized. Restriction of humoral immune response defined by enrichment of B cell clonal expansions occurred in the liver of 15 patients (50%), in the bone marrow and peripheral blood of 2 (6.7%) and 8 (26.7%) patients, respectively. An in situ hybridization technique was developed for the detection of dominant B cell clones in patients with monoclonal expansions. It was shown that morphologically distinct B cell expansion contributes to the formation of intraportal follicle‐like structures. Sequence analyses of CDRH3 gene segments revealed a wide range of variations. Clones derived from the same founder were demonstrated simultaneously in the three compartments explored. The occurrence of B cell clonal expansions profoundly influenced the clinical expression of HCV infection, since it was associated with extrahepatic manifestations. In sharp contrast, no extrahepatic signs or disease occurred in patients without evidence of intrahepatic B cell clonalities. These findings emphasize the profound B cell function derangement in at least half of HCV‐infected patients. Thus, the restriction of V gene usage has a direct impact on the clinical spectrum of HCV infection.
Knocking out IL‐6 by vaccination
Authors: Galle Pia , Hougs Lotte , Barington Torben , Svenson Morten , Svejgaard Arne , Thomsen Allan R. , Bendtzen Klaus , Hansen Morten B.
Published: February 2004

Inappropriate expression of IL‐6 plays a role in various inflammatory conditions, degenerative diseases, and cancers. Several model systems have been developed that can specifically block IL‐6‐receptor interactions. Here we present a simple and highly effective approach based on vaccination with a pool of specifically mutated IL‐6 analogues to induce a neutralizing IL‐6 antibody responsein mice. Judged by the ability of the analogues to bind to heterologous anti‐IL‐6 antibodies and cellular IL‐6 receptors the IL‐6 analogues seemed to have a three‐dimensional structure comparable to that of wild‐type IL‐6. Injection of them broke self‐tolerance and induced an immune response to IL‐6, presumably because of the amino acid differences between the analogues and wild‐type IL‐6. This resulted in a long‐lasting anti‐IL‐6 antibody‐mediated IL‐6 deficiency that blocked experimentally induced IL‐6‐mediated pathology.
The inhibitory NK cell receptor CD94/NKG2A and the activating receptor CD94/NKG2C bind the top of HLA‐E through mostly shared but partly distinct sets of HLA‐E residues
Authors: Wada Haruka , Matsumoto Naoki , Maenaka Katsumi , Suzuki Kazuhiro , Yamamoto Kazuo
Published: February 2004

The human non‐classical MHC class I molecule HLA‐E is a ligand for both an inhibitory NK cell receptor (CD94/NKG2A) and an activating receptor (CD94/NKG2C). To identify HLA‐E surface recognized by both receptors, especially to determine if both receptors recognize the same epitope, we made a series of individually Ala‐substituted HLA‐E proteins and analyzed their binding to CD94/NKG2A orCD94/NKG2C. Eight HLA‐E mutations that significantly impaired HLA‐E binding to CD94/NKG2A are all found in the top of α1/α2 domain of HLA‐E. These results suggest that CD94/NKG2A binds a HLA‐E surface equivalent to a NKG2D binding site on MICA. Of the eight mutations that impaired HLA‐E binding to CD94/NKG2A, six significantly impaired HLA‐E binding to CD94/NKG2C suggesting that CD94/NKG2C also binds a similar surface of HLA‐E. Unexpectedly, the two HLA‐E mutations (D69A and H155A) selectively abrogated HLA‐E binding to CD94/NKG2A, not largely affected CD94/NKG2C. These results indicate that a mostly shared, but partly distinct set of HLA‐E residues is discriminated by the two receptors.
Aggregation of MHC class I molecules on a CD8+ α β T cell clone specifically inhibits non‐antigen‐specific lysis of target cells
Authors: Caparrós Esther , de Heredia A. Beltrán , Carpio Emilio , Sancho David , Aguado Enrique , Aparicio Pedro
Published: February 2004

MHC class I molecules are target molecules recognized by TCR or NK receptors encoded in the NK gene cluster or leukocyte receptor cluster. We show that aggregation of MHC class I molecules by specific monoclonal antibodies on cytotoxic T cells, inhibits the anti‐CD94 redirected lysis of P815. This inhibition is not the consequence of apoptosis or anergy of the cytotoxic T lymphocytes. Incontrast, aggregation of MHC class I molecules does not inhibit either the anti‐CD3 redirected cytotoxicity or the CD94‐triggered up‐regulation of CD25 molecules of the same T cell clone. MHC classI ligand molecules expressed by antigen presenting cells and/or T lymphocytes could therefore be able to modulate nonspecific cytotoxicity upon interaction with MHC class I molecules expressed by effector cytotoxic T lymphocytes.
Characterization of MHC‐ and TCR‐binding residues of the myelin oligodendrocyte glycoprotein 38–51 peptide
Authors: Petersen Troels R. , Bettelli Estelle , Sidney John , Sette Alessandro , Kuchroo Vijay , Bäckström B. Thomas
Published: February 2004

Myelin oligodendrocyte glycoprotein (MOG) is a major experimental autoimmune encephalomyelitis (EAE) antigen in H‐2b mice and a potential autoantigen in multiple sclerosis. How well MOG peptides bind to MHC and how TCR recognize the peptide/MHC complex have important implications for thymic selection as well as T cell activation in the periphery. In this study, we have characterized amino acids in the MOG38–51 peptide important for peptide binding to I‐Ab, and for TCR recognition of the peptide/MHC complex. We found that the amino acids R41, F44, R46 and V47 constituted the major TCR contact residues, as alanine substitution at these positions abrogated T cell responses without decreasing their binding affinity to I‐Ab. In addition, G38 andW39 were found to be minor TCR contact residues. Finally, substituting tyrosine for alanine at position 40 decreased binding to I‐Ab by approximately 50% and prevented induction of T cell responses in C57BL/6J mice upon immunization. Thus, Y40 is the dominant MHC‐binding residue of the MOG38–51 peptide and most likely occupies the p1 pocket of I‐Ab. Our results could be useful to design peptides with altered agretopes and epitopes of the MOG38–51 peptide to study their therapeutic potential in the EAE model.
Non‐parametric–parametric model for random uncertainties in non‐linear structural dynamics: application to earthquake engineering
Authors: Desceliers Christophe , Soize Christian , Cambier Simon
Published: February 2004

This paper deals with the transient response of a non‐linear dynamical system with random uncertainties. The non‐parametric probabilistic model of random uncertainties recently published and extended to non‐linear dynamical system analysis is used in order to model random uncertainties related to the linear part of the finite element model. The non‐linearities are due to restoring forces whose parameters are uncertain and are modeled by the parametric approach. Jayne's maximum entropy principle with the constraints defined by the available information allows the probabilistic model of such random variables to be constructed. Therefore, a non‐parametric–parametric formulation is developed in order to model all the sources of uncertainties in such a non‐linear dynamical system. Finally, a numerical application for earthquake engineering analysis is proposed concerning a reactor cooling system under seismic loads. Copyright © 2003 John Wiley & Sons, Ltd.
Earthquake behavior of structures with copper energy dissipators
Authors: De la Llera Juan C. , Esguerra Carlos , Almazán José L.
Published: February 2004

The earthquake behavior of structures with supplemental copper dampers is evaluated in this study. The investigation is divided into two parts: (i) an experimental work with seven pairs of hourglass copper dampers of different aspect ratios and side profiles; and (ii) a parametric study of 6‐, 12‐, and 25‐story planar structures with elastic as well as inelastic behavior in the primary structure and copper dampers. The copper used in this study is electrolytic tough pitch (ETP) copper C11000; probably the most commonly used of all coppers; ductile, with a low‐yield, and highly resistant to corrosion. Experimental results demonstrate that all copper plates reached stable angular distortions of the order of γ=25%, which implies transverse distortions in the devices larger than 40mm. The behavior of the devices is highly dependent on the aspect ratio of the plate, h/t, and a recommendation is made to use plates in the range 11 h/t≤18. Plates beyond this range exhibit either large stress and strain concentrations in the neck of the device or a strong influence of axial deformations in their cyclic behavior. The inelastic earthquake response of structures with such devices shows that drift reduction factors of the order of 30 to 40% can be achieved with reasonably economic designs. It is also shown that the efficiency of these devices depends on the soil conditions and flexibility of the primary structure. Finally, it is concluded that supplemental copper dampers are a good alternative for drift reduction in a wide range of structural layouts, ranging from coupled shear‐wall systems to moment‐resisting frames, and for impulsive as well as non‐impulsive ground motions. Copyright © 2003 John Wiley & Sons, Ltd.
Estimating the seismic displacement of friction pendulum isolators based on non‐linear response history analysis
Authors: Ryan Keri L. , Chopra Anil K.
Published: February 2004

A procedure for developing equations that estimate the isolator displacement due to strong ground motion is applied to buildings isolated with the friction pendulum system. The resulting design equations, based on rigorous non‐linear analysis, offer an alternative to the iterative equivalent‐linear methods used by current U.S. building codes. The governing equations of the system are reduced to a form such that the median normalized displacement of the system due to an ensemble of ground motions is found to depend on only the isolation period—a function of the curvature of the isolator—and the friction force at incipient slip normalized by peak ground velocity. The normalization is effective in minimizing the dispersion of the normalized displacement for an ensemble of ground motions, implying that the median normalized displacement is a reliable estimate of response. The design equations reflect the significant (20 to 38%) increase in displacement when the excitation includes two lateral components of ground motion instead of just one component. Equivalent‐linear methods are shown to underestimate by up to 30% the exact median displacement determined by non‐linear response history analysis for one component of ground motion, and building codes include at most a 4.4% increase for a second component. Copyright © 2003 John Wiley & Sons, Ltd.
Seismic response of a cable‐stayed bridge deck under multi‐component non‐stationary random ground motion
Authors: Allam Said M. , Datta T. K.
Published: February 2004

A Markov method of analysis is presented for obtaining the seismic response of cable‐stayed bridges to non‐stationary random ground motion. A uniformly modulated non‐stationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s. ground acceleration. Both vertical and horizontal components of the motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of the earthquake, the spatial correlation of ground motion and the quasi‐static excitation. A cable‐stayed bridge is analysed under a set of parametric variations in order to study the non‐stationary response of the bridge. The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s. acceleration as input could provide more r.m.s. response than the peak r.m.s. response obtained by the non‐stationary analysis; (ii) the longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of the earthquake has considerable influence on the deck response. Copyright © 2003 John Wiley & Sons, Ltd.
Estimation of seismic demands on isolators in asymmetric buildings using non‐linear analysis
Authors: Ryan Keri L. , Chopra Anil K.
Published: February 2004

A procedure based on rigorous non‐linear analysis is presented that estimates the peak deformation among all isolators in an asymmetric building due to strong ground motion. The governing equations are reduced to a form such that the median normalized deformation due to an ensemble of ground motions with given corner period Td depends primarily on four global parameters of the isolation system: the isolation period Tb, the normalized strength η, the torsional‐to‐lateral frequency ratio Ωθ, and the normalized stiffness eccentricity eb/r. The median ratio of the deformations of the asymmetric and corresponding symmetric systems is shown to depend only weakly on Tb, η, and Ωθ, but increases with eb/r. The equation developed to estimate the largest ratio among all isolators depends only on the stiffness eccentricity and the distance from the center of mass to the outlying isolator. This equation, multiplied by an earlier equation for the deformation of the corresponding symmetric system, provides a design equation to estimate the deformations of asymmetric systems. This design equation conservatively estimates the peak deformation among all isolators, but is generally within 10% of the ‘exact’ value. Relative to the non‐linear procedure presented, the peak isolator deformation is shown to be significantly underestimated by the U.S. building code procedures. Copyright © 2003 John Wiley & Sons, Ltd.
Iterative solvers for quadratic discretizations of the generalized Stokes problem
Authors: Guénette R. , Fortin A. , Labbé J. , Marcotte J. P.
Published: February 2004

We present in this paper various iterative methods for the solution of large linear and non‐linear systems resulting from the discretization of the generalized Stokes problem. A second‐order (O(h2)) P2‐P1 mixed finite element is used for the approximation of the velocity and the pressure. Solution strategies based on conjugate gradient‐like methods, the Uzawa's and Arrow–Hurwicz's methods are presented. Schur complement methods are also explored in the context of a hierarchical decomposition of the velocity field. The ever present preconditioning problem is also addressed. The performance of these iterative methods will be discussed on complex flows of industrial interest. Copyright © 2004 John Wiley & Sons, Ltd.
Finite element solution of the Orr–Sommerfeld equation using high precision Hermite elements: plane Poiseuille flow
Authors: Mamou M. , Khalid M.
Published: February 2004

This paper presents a comprehensive review of the numerical techniques used during the past half century and their accuracy in hydrodynamic stability analysis of plane parallel flows. The paper also describes a finite element solution of the Orr–Sommerfeld equation using high precision Hermite elements. A stability analysis technique is performed by imposing an infinitesimal perturbation to the laminar base flow to determine the thresholds of neutral instabilities or the growth rate of the perturbation for any Reynolds and wave numbers. Validation of the present numerical technique is performed for plane Poiseuille flow. The numerical results, obtained with uniform and nonuniform meshes, show excellent agreement with the most accurate results available in the literature. Copyright © 2004 John Wiley & Sons, Ltd.
Verification and validation of impinging round jet simulations using an adaptive FEM
Authors: Pelletier Dominique , Turgeon Éric , Tremblay Dominique
Published: February 2004

This paper illustrates the use of an adaptive finite element method as a means of achieving verification of codes and simulations of impinging round jets, that is obtaining numerical predictions with controlled accuracy. Validation of these grid‐independent solution is then performed by comparing predictions to measurements. We adopt the standard and accepted definitions of verification and validation (Technical Report AIAA‐G‐077‐1998, American Institute of Aeronautics and Astronautics, 1998; Verification and Validation in Computational Science and Engineering. Hermosa Publishers: Albuquerque, NM, 1998). Mesh adaptation is used to perform the systematic and rigorous grid refinement studies required for both verification and validation in CFD. This ensures that discrepancies observed between predictions and measurements are due to deficiencies in the mathematical model of the flow. Issues in verification and validation are discussed. The paper presents an example of code verification by the method of manufactured solution. Examples of successful and unsuccessful validation for laminar and turbulent impinging jets show that agreement with experiments is achieved only with a good mathematical model of the flow physics combined with accurate numerical solution of the differential equations. The paper emphasizes good CFD practice to systematically achieve verification so that validation studies are always performed on solid grounds. Copyright © 2004 John Wiley & Sons, Ltd.
Operator‐splitting method for the analysis of cavitation in liquid‐lubricated herringbone grooved journal bearings
Authors: Jiankang Wu , Anfeng Li , Lee T. S. , Shu C. , Junmei Wan
Published: February 2004

This paper presents an operator‐splitting method (OSM) for the solution of the universal Reynolds equation. Jakobsson–Floberg–Olsson (JFO) pressure conditions are used to study cavitation in liquid‐lubricated journal bearings. The shear flow component of the oil film is first solved by a modified upwind finite difference method. The solution of the pressure gradient flow component is computed by the Galerkin finite element method. Present OSM solutions for slider bearings are in good agreement with available analytical and experimental results. OSM is then applied to herringbone grooved journal bearings. The film pressure, cavitation areas, load capacity and attitude angle are obtained with JFO pressure conditions. The calculated load capacities are in agreement with available experimental data. However, a detailed comparison of the present results with those predicted using Reynolds pressure conditions shows some differences. The numerical results showed that the load capacity and the critical mass of the journal (linear stability indicator) are higher and the attitude angle is lower than those predicted by Reynolds pressure conditions for cases of high eccentricities. Copyright © 2004 John Wiley & Sons, Ltd.
Reference values for drag and lift of a two‐dimensional time‐dependent flow around a cylinder
Authors: John Volker
Published: February 2004

This paper presents a numerical study of a two‐dimensional time‐dependent flow around a cylinder. Its main objective is to provide accurate reference values for the maximal drag and lift coefficient at the cylinder and for the pressure difference between the front and the back of the cylinder at the final time. In addition, the accuracy of these values obtained with different time stepping schemes and different finite element methods is studied. Copyright © 2004 John Wiley & Sons, Ltd.
Alluvial records of medieval and prehistoric tin mining on Dartmoor, southwest England
Authors: Thorndycraft Varyl R. , Pirrie Duncan , Brown Antony G.
Published: February 2004

The role of tin mining in the society of prehistoric Dartmoor and its impact on the local landscape have long been discussed despite equivocal evidence for prehistoric mine sites. A fluvial geomorphological approach, using floodplain stratigraphy, combined with sediment geochemistry and mineralogy, was employed to identify prehistoric tin mining at the catchment scale. Waste sediment, released during hydraulic mining of alluvial tin deposits, caused downstream floodplain aggradation of sands with a diagnostic signature of elevated Sn concentration within the silt fraction. At a palaeochannel site in the Erme Valley, sediment aggradation buried datable peat deposits. A period of aggradation postdating cal. A.D. 1288–1389 is consistent with the 13th century peak in tin production identified in the documentary record. An earlier phase of aggradation, however, occurred between the 4th and 7th centuries A.D., providing evidence of late Roman or early Post Roman tin mining activity on Dartmoor. © 2004 Wiley Periodicals, Inc.
Geochemical comparisons of silicified rhyolites from two prehistoric quarries and 11 prehistoric projectile points, Socorro County, New Mexico, U.S.A.
Authors: Dello‐Russo Robert D.
Published: February 2004

This paper documents the results of nondestructive X‐ray fluorescence (XRF) geochemical analyses and comparisons of silicified rhyolites from the Black Canyon and Sedillo Hill prehistoric quarries near Socorro, New Mexico, and subsequent comparisons of the quarry rhyolites with 11 temporally diagnostic projectile points. At the current level of analysis, findings indicate that (1) the two quarries are chemically distinct and (2) the lithic materials of two projectile points match the silicified rhyolite from the Black Canyon quarry, suggesting quarry use during the Early Archaic period (4800–3200 B.C.) and the Late Archaic period (1800–800 B.C.). A close match between the Black Canyon rhyolite and one other point provides tentative support for use of the quarry during the Clovis Paleoindian period (9500–9000 B.C.). Additional geochemical analyses of the two quarries and other regional sources should be undertaken to verify these results and further expand our understanding of prehistoric mobility in the Southwest. © 2004 Wiley Periodicals, Inc.
A comparison of techniques for hydrograph recession analysis
Authors: Sujono Joko , Shikasho Shiomi , Hiramatsu Kazuaki
Published: February 2004

A comparison between commonly used techniques for hydrograph recession analysis, namely the semi‐logarithmic plot of a single recession segment, the master recession and a relatively new approach based on wavelet transform was carried out. These methods were applied to a number of flood hydrograph events of two catchments in West Java, Indonesia. The results show that all the methods tested produce reasonable and comparable results. However, problems arise in the semi‐logarithmic plot and the master recession, i.e. determining the recession parameter K is not an easy task especially where the plotted data on a semi‐logarithmic plot is not a linear but a curved line. On a curved line, the end of direct flow or starting point of baseflow is not clear and it is quite difficult to identify. Hence, the best line as a basis for computing the recession parameter K becomes uncertain. The wavelet transform approach, however, produces promising results and minimizes a number of problems associated with hydrograph recession analysis. The end of direct flow and the location of the baseflow component are easily determined through the wavelet maps. Copyright © 2004 John Wiley & Sons, Ltd.
Hydrology and nitrogen balance of a seasonally inundated Danish floodplain wetland
Authors: Andersen Hans Estrup
Published: February 2004

This paper characterizes a seasonally inundated Danish floodplain wetland in a state close to naturalness and includes an analysis of the major controls on the wetland water and nitrogen balances.

The main inputs of water are precipitation and percolation during ponding and unsaturated conditions. Lateral saturated subsurface flow is low. The studied floodplain owes its wetland status to the hydraulic properties of its sediments: the low hydraulic conductivity of a silt–clay deposit on top of the floodplain maintains ponded water during winter, and parts of autumn and spring. A capillary fringe extends to the soil surface, and capillary rise from groundwater during summer maintains near‐saturated conditions in the root zone, and allows a permanently very high evapotranspiration rate. The average for the growing season of 1999 is 3·6 mm day−1 and peak rate is 5·6 mm day−1. In summer, the evapotranspiration is to a large degree supplied by subsurface storage in a confined peat layer underlying the silt–clay.

The floodplain sediments are in a very reduced state as indicated by low sulphate concentrations. All nitrate transported into the wetland is thus denitrified. However, owing to modest water exchange with surrounding groundwater and surface water, denitrification is low; 71 kg NO3–N ha−1 during the study period of 1999. Reduction of nitrate diffusing into the sediments during water ponding accounts for 75% of nitrate removal. Biomass production and nitrogen uptake in above‐ground vegetation is high—8·56 t dry matter ha−1 year−1 and 103 kg N ha−1 year−1. Subsurface ammonium concentrations are high, and convective upward transport into the root zone driven by evapotranspiration amounted to 12·8 kg N ha−1year−1. The floodplain wetland sediments have a high nitrogen content, and conditions are very favourable for mineralization. Mineralization thus constitutes 72% of above‐ground plant uptake.

The study demonstrates the necessity of identifying controlling factors, and to combine surface flow with vadose and groundwater flow processes in order to fully comprehend the flow and nitrogen dynamics of this type of wetland. Copyright © 2004 John Wiley & Sons, Ltd.
Evaluation of spatial variability in snow water equivalent for a high mountain catchment
Authors: Anderton S. P. , White S. M. , Alvera B.
Published: February 2004

Multivariate statistical analysis was used to explore relationships between catchment topography and spatial variability in snow accumulation and melt processes in a small headwater catchment in the Spanish Pyrenees. Manual surveys of snow depth and density provided information on the spatial distribution of snow water equivalent (SWE) and its depletion over the course of the 1997 and 1998 melt seasons. A number of indices expressing the topographic control on snow processes were extracted from a detailed digital elevation model of the catchment. Bivariate screening was used to assess the relative importance of these topographic indices in controlling snow accumulation at the start of the melt season, average melt rates and the timing of snow disappearance. This suggested that topographic controls on the redistribution of snow by wind are the most important influence on snow distribution at the start of the melt season. Furthermore, it appeared that spatial patterns of snow disappearance were largely determined by the distribution of snow water equivalent (SWE) at the start of the melt season, rather than by spatial variability in melt rates during the melt season. Binary regression tree models relating snow depth and disappearance date to terrain indices were then constructed. These explained 70–80% of the variance in the observed data. As well as providing insights into the influence of topography on snow processes, it is suggested that the techniques presented herein could be used in the parameterization of distributed snowmelt models, or in the design of efficient stratified snow surveys. Copyright © 2003 John Wiley & Sons, Ltd.
Contribution of storms to groundwater recharge in the semi‐arid region of Karnataka, India
Authors: Shivanna K. , Kulkarni U. P. , Joseph T. B. , Navada S. V.
Published: February 2004

This paper describes the application of environmental isotopes and injected tracer techniques in estimating the contribution of storms as well as annual precipitation to groundwater recharge and its circulation, in the semi‐arid region of Bagepalli, Kolar district, Karnataka. Environmental isotopes 2H, 18O and 3H were used to study the effect of storms on the hydrological system, and an isotope balance was used to compute the contribution of a storm component to the groundwater. Some of the groundwater samples collected during the post‐storm periods were highly depleted in stable isotope content with higher deuterium excess relative to groundwater from the pre‐storm periods. Significant variation in deuterium excess in groundwater from the same area, collected in two different periods, indicates the different origin of air masses. The estimated recharge component of a storm event of 600 mm to the groundwater was found to be in the range of 117–165 mm. There was no significant variation in environmental tritium content of post‐storm and pre‐storm groundwater, indicating the fast circulation of groundwater in the system. After completion of the environmental isotope work, an injected radiotracer 3H technique was applied to estimate the direct recharge of total precipitation to the groundwater. The estimated recharge to the groundwater is 33 mm of the 550 mm annual precipitation during 1992. Copyright © 2003 John Wiley & Sons, Ltd.
Flood hydrograph attenuation induced by a reservoir system: analysis with a distributed rainfall‐runoff model
Authors: Montaldo Nicola , Mancini Marco , Rosso Renzo
Published: February 2004

Spatially distributed hydrologic models can be effectively utilized for flood event simulation over basins where a complex system of reservoirs affecting the natural flow regime is present. Flood peak attenuation through mountain reservoirs can, in fact, mitigate the impact of major floods in flood‐prone areas of the lower river valley. Assessment of this effect for a complex reservoir system is performed with a spatially distributed hydrologic model where the surface runoff formation and the hydraulic routing through each reservoir and the river system are performed at a fine spatial and time resolution.

The Toce River basin is presented as a case study, because of the presence of 14 active hydroelectric dams that affect the natural flow regime. A recent extreme flood event is simulated using a multi‐realization kriging method for modelling the spatial distribution of rainfall. A sensitivity analysis of the key elements of the distributed hydrologic model is also performed. The flood hydrograph attenuation is assessed. Several possible reservoir storage conditions are used to characterize the initial condition of each reservoir. The results demonstrate how a distributed hydrologic model can contribute to defining strategies for reservoir management in flood mitigation. Copyright © 2004 John Wiley & Sons, Ltd.
Identification of physical processes inherent in artificial neural network rainfall runoff models
Authors: Jain Ashu , Sudheer K. P. , Srinivasulu Sanaga
Published: February 2004

The emergence of artificial neural network (ANN) technology has provided many promising results in the field of hydrology and water resources simulation. However, one of the major criticisms of ANN hydrologic models is that they do not consider/explain the underlying physical processes in a watershed, resulting in them being labelled as black‐box models. This paper discusses a research study conducted in order to examine whether or not the physical processes in a watershed are inherent in a trained ANN rainfall‐runoff model. The investigation is based on analysing definite statistical measures of strength of relationship between the disintegrated hidden neuron responses of an ANN model and its input variables, as well as various deterministic components of a conceptual rainfall‐runoff model. The approach is illustrated by presenting a case study for the Kentucky River watershed. The results suggest that the distributed structure of the ANN is able to capture certain physical behaviour of the rainfall‐runoff process. The results demonstrate that the hidden neurons in the ANN rainfall‐runoff model approximate various components of the hydrologic system, such as infiltration, base flow, and delayed and quick surface flow, etc., and represent the rising limb and different portions of the falling limb of a flow hydrograph. Copyright © 2004 John Wiley & Sons, Ltd.
Estimating the economic return to educational levels using data on twins
Authors: Isacsson Gunnar
Published: February 2004

This paper relaxes some restrictions of previous twin‐based estimates of the effects of education on earnings. First, it estimates the earnings premiums associated with different educational levels. Second, it estimates a piecewise linear relationship between the natural logarithm of annual earnings and years of schooling. Third, the measurement error corrections are based on a less restrictive, ‘non‐classical’, measurement error model. The estimation strategy implies that ability bias can be investigated separately in different parts of the educational distribution. The linear relationship between the logarithm of annual earnings and years of schooling is rejected. Furthermore, the results in the sample of identical (MZ) twins indicated both that the ability bias could be of different signs and of different magnitudes in different parts of the educational distribution. The twin‐based estimates in the sample of fraternal (DZ) twins did not display any marked differences as compared to the cross‐sectional estimates. Finally, the results indicated that the error‐corrected twin‐based estimates of the average return to years of schooling that rely on a classical measurement error model are upwards biased by approximately 30%. Copyright © 2004 John Wiley & Sons, Ltd.
Nonlinear effects of exchange rate volatility on the volume of bilateral exports
Authors: Baum Christopher F. , Caglayan Mustafa , Ozkan Neslihan
Published: February 2004

In this paper, we investigate empirically the impact of exchange rate volatility on real international trade flows utilizing a 13‐country data set of monthly bilateral real exports for 1980–1998. We compute one‐month‐ahead exchange rate volatility from the intra‐monthly variations in the exchange rate to better quantify this latent variable. We find that the effect of exchange rate volatility on trade flows is nonlinear, depending on its interaction with the importing country's volatility of economic activity, and that it varies considerably over the set of country pairs considered. Copyright © 2003 John Wiley & Sons, Ltd.
Can inflation data improve the real‐time reliability of output gap estimates?
Authors: Planas Christophe , Rossi Alessandro
Published: February 2004

Potential output plays a central role in monetary policy and short‐term macroeconomic policy making. Yet, characterizing the output gap involves a trend‐cycle decomposition, and unobserved component estimates are typically subject to a large uncertainty at the sample end. An important consequence is that output gap estimates can be quite inaccurate in real time, as recently highlighted by Orphanides and van Norden (2002), and this causes a serious problem for policy makers. For the cases of the US, EU‐11 and two EU countries, we evaluate the benefits of using inflation data for improving the accuracy of real‐time estimates. Copyright © 2004 John Wiley & Sons, Ltd.
On Markov error‐correction models, with an application to stock prices and dividends
Authors: Psaradakis Zacharias , Sola Martin , Spagnolo Fabio
Published: February 2004

This paper considers Markov error‐correction (MEC) models in which deviations from the long‐run equilibrium are characterized by different rates of adjustment. To motivate our analysis and illustrate the various issues involved, our discussion is structured around the analysis of the long‐run properties of US stock prices and dividends. It is shown that the MEC model is flexible enough to account for situations where deviations from the long‐run equilibrium are nonstationary in one of the states of nature and allows us to test for such a possibility. An empirical specification procedure to establish the existence of MEC adjustment in practice is also presented. This is based on a multi‐step test procedure that exploits the differences between the global and local characteristics of systems with MEC adjustment. Copyright © 2004 John Wiley & Sons, Ltd.