bluuebunny/crossref_metadata_2025 huggingface dataset:
Estrogen receptor‐α and neural circuits to the spinal cord during pregnancy
Authors: Papka R.E. , Hafemeister J. , Puder B.A. , Usip S. , Storey‐Workley M.
Published: November 2002

Estrogen receptor immunoreactivity and mRNAs are present in spinal cord neurons in locations that are associated with sensory and autonomic innervation of female reproductive organs. The present study was undertaken to examine the expression of estrogen receptor‐α in the spinal cord during different stages of pregnancy and to determine whether estrogen receptor‐α‐expressing neurons are related to uterine afferent nerves bringing information to the spinal cord at parturition. Immunohistochemistry showed estrogen receptor‐α‐immunoreactive neurons in the dorsal one‐half of the spinal cord, i.e., dorsal horn, dorsal intermediate gray areas (dorsal commissural nucleus), and around the central canal and sacral parasympathetic autonomic nucleus of the lumbosacral spinal cord. Neurons in these areas corresponded topographically to the distribution of central processes of visceral primary afferent neurons (e.g., containing calcitonin gene‐related peptide and substance P) that innervate and activate second‐order spinal cord neurons (evidenced by their expression of Fos) at parturition. Western blots showed that estrogen receptor‐α increases in the spinal cord, with a peak at day 20 of gestation, followed by a slight decrease by 2 days postpartum. These studies show that estrogen receptor‐α is expressed by neurons in autonomic and sensory areas of the lumbosacral spinal cord that have connections with the female reproductive system and that the level of estrogen receptor‐α changes over the course of pregnancy, which may follow profiles of steroid hormones. Many of these neurons may be involved in processing information related to reproductive organ function, changes during pregnancy, and relays to other CNS centers. © 2002 Wiley‐Liss, Inc.
Chemokine regulation of macrophage recruitment into the olfactory epithelium following target ablation: Involvement of macrophage inflammatory protein‐1α and monocyte chemoattractant protein‐1
Authors: Getchell Thomas V. , Subhedar Nishikant K. , Shah Dharmen S. , Hackley Grant , Partin James V. , Sen Goutam , Getchell Marilyn L.
Published: November 2002

Target ablation by olfactory bulbectomy synchronizes the degenerative cell death of olfactory receptor neurons (ORNs), infiltration of macrophages, and proliferation of progenitor cells, leading to neurogenesis, ORN replacement, and regeneration of the sensory epithelium. Although macrophages participate in the degenerative and regenerative events, little is known of the molecular and cellular mechanisms associated with their recruitment during the earliest period following target ablation. Macrophage inflammatory protein‐1α (MIP‐1α) and monocyte chemoattractant protein‐1 (MCP‐1), which are members of the CC or β‐chemokine subfamily, are chemoattractants for monocytes/macrophages. Shortly after target ablation, the protein and mRNA levels for MIP‐1α and MCP‐1 were up‐regulated, showing peak expression levels from 16 hr to 3 days post‐OBX; this coincided with the pattern of infiltration of activated F4/80+ macrophages. The mRNAs for MIP‐1α and MCP‐1, as well as their cognate receptors CCR1 and CCR2, respectively, were localized in resident and infiltrating macrophages in numbers commensurate with those of F4/80‐immunopositive macrophages in adjacent tissue sections. The mRNA+ macrophages were localized within olfactory epithelial compartments that corresponded with their proposed functions associated with phagocytosis, proliferation, and infiltration. Our data support the hypothesis that MIP‐1α and MCP‐1 are chemoattractant chemokines associated with the recruitment of macrophages into the olfactory epithelium shortly after target ablation. © 2002 Wiley‐Liss, Inc.
Glial cell line‐derived neurotrophic factor released by synthetic guidance channels promotes facial nerve regeneration in the rat
Authors: Barras Florian M. , Pasche Philippe , Bouche Nicolas , Aebischer Patrick , Zurn Anne D.
Published: November 2002

Regeneration of the human facial nerve after lesion is often limited, leading to severe functional impairments, in particular when repair is delayed for several months, when cross‐facial nerve grafts have to be performed, or in elderly patients. To improve the outcome, the potential accelerating and maturating effects of the neurotrophic factors glial cell line‐derived neurotrophic factor (GDNF) and neurotrophin‐3 (NT‐3) on nerve regeneration were assessed using an axotomy model of the rat facial nerve. One‐centimeter‐long synthetic guidance channels releasing the neurotrophic factors over several weeks were used to bridge an 8 mm nerve gap, a distance that does not allow regeneration in the absence of growth factors. Nerve cables regenerated in the presence of GDNF showed a large number of myelinated axons 6 weeks after grafting (871 ± 373, n = 5), whereas only 106 ± 86 (n = 5) myelinated axons were counted in the presence of NT‐3. Retrograde labeling with fluorogold revealed 981 ± 450 (n = 5) and 53 ± 38 (n = 5) retrogradely labeled motoneurons in the facial nucleus in the presence of GDNF and NT‐3, respectively. No regenerated axons or retrogradely labeled cells were observed in the absence of growth factors (n = 6). These results demonstrate that GDNF, as previously described for the sciatic nerve, a mixed sensory and motor nerve, is also very efficient in promoting regeneration of the facial nerve, an essentially pure motor nerve. GDNF may therefore be useful in improving facial nerve regeneration in the clinic. © 2002 Wiley‐Liss, Inc.
Induction of radioprotective peroxiredoxin‐I by ionizing irradiation
Authors: Chen Wen‐Cheng , McBride William H. , Iwamoto Keisuke S. , Barber Chad L. , Wang Chun‐Chieh , Oh Young‐Taek , Liao Yu‐Pei , Hong Ji‐Hong , de Vellis Jean , Shau Hungyi
Published: November 2002

Results of this study indicate a radioprotective effect of peroxiredoxin‐I. Peroxiredoxin‐I is an antioxidant that scavenges hydroperoxides, whereas reactive oxygen species are the main mediators of ionizing radiation toxicity. We hypothesized that peroxiredoxin‐I might be induced by cellular exposure to radiation and act to protect them against its cytotoxic effects. Western blot and Northern blot analyses were used to assess peroxiredoxin‐I protein and mRNA expression. Rat C6 glioma cells were engineered to overexpress sense or antisense human peroxiredoxin‐I using retroviral vectors. Clonogenic cell survival was used to assess radiosensitivities of the engineered cells. Ionizing radiation induced peroxiredoxin‐I protein and mRNA expression in human HT29 colon cancer and rat C6 glioma cells in a dose‐ and time‐dependent manner over a 24 hr period. To determine the effect of peroxiredoxin‐I on radiation responses, C6 glioma cells were engineered to overexpress sense or antisense human peroxiredoxin‐I. In clonogenic assays, cells overexpressing peroxiredoxin‐I were more radioresistant. Cells transduced with antisense peroxiredoxin‐I were marginally more sensitive to radiation toxicity. Irradiation can induce peroxiredoxin‐I expression, and the increased peroxiredoxin‐I may protect cells from further radiation damage. These results suggest that protection by peroxiredoxin‐I may play an important role in the survival of glioma and colon cancer cells in patients undergoing radiation therapy. © 2002 Wiley‐Liss, Inc.
Alternative acetylcholinesterase molecular forms exhibit similar ability to induce neurite outgrowth
Authors: De Jaco A. , Augusti‐Tocco G. , Biagioni S.
Published: November 2002

Several groups have reported that acetylcholinesterase (AChE), through a mechanism not involving its catalytic activity, may have a role in fiber elongation. These observations were performed on experimental systems in which acetylcholine synthesis was active. Because neurite outgrowth can be modulated by neurotransmitters, we used the N18TG2 neuroblastoma line, which is defective for neurotransmitter production, to evaluate whether AChE may modulate neurite sprouting in nonenzymatic ways. To avoid the possibility that differences between transfected and mock‐transfected clones may be due to the selection procedure, N18TG2 cells were previously subcloned, and the FB5 subclone was used for transfections. We performed transfections of FB5 cells with three distinct constructs encoding for the glycosylphosphoinositol‐anchored AChE form, the tetrameric AChE form, and a soluble monomeric AChE form truncated in its C‐terminus. A morphometric analysis of retinoic acid‐differentiated clones was also undertaken. The results revealed that higher AChE expression following transfection brings about a greater ability of the clones to grow fibers with respect to nontransfected or mock‐transfected cells irrespective of the used construct. Having observed no differences between the morphology of the transfected clones, we tested the possibility that the culture substrate can affect the capability of the clones to extend fibers. Also in this case we revealed no differences between the clones cultured on uncoated or collagen‐pretreated dishes. These data indicate that alternative AChE molecular forms that differ in their C‐teminal region exhibit similar ability to induce fiber outgrowth and suggest that the protein region responsibile for this role is located in the invariant portion of the AChE molecule. © 2002 Wiley‐Liss, Inc.
New model of glutathione deficit during development: Effect on lipid peroxidation in the rat brain
Authors: Rougemont Michaël , Do Kim Quang , Castagné Vincent
Published: November 2002

Glutathione is a major regulator of the redox equilibrium, so its deficit weakens tissue resistance to oxidants. The nervous system is particularly susceptible to oxidative insults and is therefore very dependent on its glutathione content, especially during development, when brain metabolism and growth are maximal. In addition, various pathologies affecting the nervous system involve oxidative stress, possibly associated with a diminution of glutathione concentrations. To study the involvement of glutathione in brain redox homeostasis, we set up an experimental model of chronic glutathione deficit. Developing rats were treated daily with L‐buthionine‐(S,R)‐sulfoximine (BSO), an inhibitor of glutathione synthesis, and their brain levels of glutathione and lipid peroxidation products (TBARS) were measured. BSO induced a 40–50% glutathione deficit in the cortex, diencephalon, and pons/medulla. Despite the glutathione deficit induced by BSO, we did not observe any signs of oxidative stress. Because it is known that rats compensate for a glutathione deficit by enhancing their synthesis and tissue levels of ascorbic acid (AA), we performed the same experiment in osteogenic‐disorder Shionogi (ODS) rats, a mutant strain that cannot synthetize AA. Although BSO induced a glutathione deficit of comparable intensity in the two strains of rats, it elevated TBARS levels in the diencephalon and pons/medulla only in ODS and not in nonmutant rats. These results suggest that ODS rats, which closely mimic the human redox regulation, will allow study of the long‐term consequences of chronic glutathione deficit observed in various clinical situations. © 2002 Wiley‐Liss, Inc.
Transgenic zebrafish model of neurodegeneration
Authors: Tomasiewicz Henry G. , Flaherty Denise B. , Soria J.P. , Wood John G.
Published: November 2002

In Alzheimer's disease (AD), the microtubule‐associated protein, tau, is compromised in its normal association with microtubules and forms into paired helical filaments (PHF) that are the hallmark cytoskeletal pathology of the disease. Several posttranslational modifications of tau including phosphorylation have been implicated in AD pathogenesis. In addition, and importantly, mutations in the genes encoding human tau have recently been implicated in a variety of hereditary dementias, collectively termed frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP‐17). This has rekindled interest in the importance of tau in neurodegenerative diseases (cf. Vogel [1998] Science 280:1524–1525; Goedert et al. [1998] Neuron 21:955–958; D'Souza et al. [1999] PNAS 96:5598–5603). Despite significant progress in the field of tau biology and neurodegenerative diseases, several important issues remain unresolved. The early functional consequences of tau alterations in living neurons is incompletely understood, and it is not clear how tau in neurodegenerative diseases becomes redistributed from its normal concentration in neuronal axons to pathological inclusions in neuronal soma known as neurofibrillary tangles (NFT). One of the reasons for these gaps in knowledge is the relative paucity of model systems to study these processes. We have developed a transgenic model system to study the functional consequences and trafficking patterns in zebrafish neurons of human tau either mutated on sites associated with hereditary dementias or altered at select posttranslational modification sites. The overall guiding hypothesis is that the model allows dissection of a hierarchy of events relevant to potential mechanisms of neurodegenerative diseases related to critical early stages in development of disease. We showed that a FTDP‐17 mutant form of human tau expressed in zebrafish neurons produced a cytoskeletal disruption that closely resembled the NFT in human disease. This model system will prove useful in the study of other mutant taus in vertebrate neurons in vivo, and the approaches developed here will have broad usefulness in the study of functional consequences and potential genetic analyses of introducing into living vertebrate neurons other molecules involved in the pathogenesis of neurodegenerative diseases. © 2002 Wiley‐Liss, Inc.
Transcripts of damaged genes in the brain during cerebral oxidative stress
Authors: Liu Philip K. , Arora Tarun
Published: November 2002

Recent studies using ischemia/reperfusion models of brain injury suggest that there is a period of time during which the formation of oxidative DNA lesions (ODLs) exceeds removal. This interval is a window of opportunity in which to study the effect of gene damage on gene expression in the brain, because the presence of excessive ODLs mimics a deficiency in gene repair, which has been shown to be associated with neurological disorders. Evidence from studies using similar models indicates that expression of faulty transcripts from ODL‐infested genes and non‐sense mutation in repaired genes occur before the process of cell death. Preventing the formation of ODLs and enhancing ODL repair are shown to increase the expression of intact transcripts and attenuate cell death. Understanding this mechanism could lead to the development of therapeutic techniques (physiologic, pharmacological, and/or genomic) that can enhance recovery. © 2002 Wiley‐Liss, Inc.
Neuroectodermal and microglial differentiation of bone marrow cells in the mouse spinal cord and sensory ganglia
Authors: Corti S. , Locatelli F. , Donadoni C. , Strazzer S. , Salani S. , Del Bo R. , Caccialanza M. , Bresolin N. , Scarlato G. , Comi G.P.
Published: November 2002

There is now evidence that bone marrow (BM) can generate cells expressing neuronal antigens in adult mouse brain. In the present study, we examined the spinal cord and dorsal root ganglia (DRG) of adult mice 3 months after BM cell transplantation from transgenic donor mice expressing the enhanced green fluorescent protein (GFP). To determine whether GFP+ cells acquire neuroectodermal phenotypes, we tested, by immunocytochemistry followed by confocal analysis, the coexpression of the astrocytic marker glial fibrillary acidic protein (GFAP) and the neuronal markers NeuN, neurofilament (NF), and class III β‐tubulin (TuJ1). Rare GFP+ cells coexpressing TuJ1, NF, and NeuN were found both in spinal cord and in sensory ganglia. These cells have small dimensions and short cytoplasmic processes, probably reflecting an immature phenotype. Double GFP and GFAP positivity was found only in spinal cord. To determine whether cell fusion with endogenous cells occurred, we investigated the nuclear content of cells coexpressing GFP and neuronal or astrocytic markers, demonstrating that these cells have only one nucleus and a DNA ploidy that it is not different from that of surrounding neurons and astrocytes. Large numbers of GFP+ cells are also positively stained for F4/80, a microglial‐recognizing antibody, and present a characteristic microglial‐like morphology both in spinal cord and, with a higher frequency, in sensory ganglia. These data support a potential role for BM‐derived stem cells in spinal cord neuroneogenesis. They also confirm that the microglial compartment within the CNS and in DRG undergoes a relatively fast turnover, with the contribution of hematopoietic stem cells. Both these findings might prove useful for the development of treatments for spinal cord neurodegenerative and acquired disorders. © 2002 Wiley‐Liss, Inc.
A psychological contract perspective on organizational citizenship behavior
Authors: Coyle‐Shapiro Jacqueline A‐M.
Published: November 2002

This study examined the contribution of the psychological contract framework to understanding organizational citizenship behavior (OCB) using survey data gathered at three measurement points over a three‐year period from 480 public sector employees. Separating perceived contract breach into its two components (perceived employer obligations and inducements), the data suggest that perceived employer obligations explained unique variance in three dimensions of citizenship behavior (helping, advocacy and functional participation) beyond that accounted for by perceived employer inducements. Employees' acceptance of the norm of reciprocity moderated the relationship between employer inducements and the dimensions of advocacy and functional participation. Employees' trust in their employer moderated the relationship between perceived employer obligations and the dimensions of advocacy and functional participation. Contrary to the hypothesis, procedural or interactional justice did not moderate the relationship between employer inducements and OCB. The implications of the findings for psychological contract research are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
The impact of a large‐scale traumatic event on individual and organizational outcomes: exploring employee and company reactions to September 11, 2001
Authors: Byron Kristin , Peterson Suzanne
Published: November 2002

Much of the literature on stress and organizational outcomes has focused on organizational factors and has ignored extraorganizational stressors that lead to perceived stress. However, research in other fields and recent studies in management suggests that acute‐extraorganizational stressors, such as traumatic events, may have potentially negative and costly implications for organizations. This study tests a theoretical model of traumatic stress and considers the relationship between strain from an acute‐extraorganizational stressor, the terrorist attack on September 11, 2001, and absenteeism. Using a sample of 108 MBA and MPA students, this study suggests that strain caused by an acute‐extraorganizational stressor can have important consequences for organizations. Namely, employees who report more strain from a traumatic life event are more likely to be absent from work in the weeks following the event. Copyright © 2002 John Wiley & Sons, Ltd.
The Schrödinger equation and a multidimensional inverse scattering transform
Authors: Bernstein Swanhild
Published: November 2002

The Schrödinger equation is one of the most important equations in mathematics, physics and also engineering. We outline some connections between transformations of non‐linear equations, the Schrödinger equation and the inverse scattering transform. After some remarks on generalizations into higher dimensions we present a multidimensional ∂¯ method based on Clifford analysis. To explain the method we consider the formal solution of the inverse scattering problem for the n‐dimensional time‐dependent Schrödinger equations given by A.I. Nachman and M.J. Ablowitz. Copyright © 2002 John Wiley & Sons, Ltd.
Boundary value problems for Dirac operators and Maxwell's equations in non‐smooth domains
Authors: Mitrea Marius
Published: November 2002

We study the well‐posedness of the half‐Dirichlet and Poisson problems for Dirac operators in three‐dimensional Lipschitz domains, with a special emphasis on optimal Lebesgue and Sobolev‐Besov estimates. As an application, an elliptization procedure for the Maxwell system is devised. Copyright © 2002 John Wiley & Sons, Ltd.
An analogue of the Sommerfeld radiation condition for the Dirac operator
Authors: Kravchenko Vladislav V. , Castillo P. Raúl
Published: November 2002

A simple radiation condition at infinity for time‐harmonic massive Dirac spinors is proposed. This condition allows an analogue of the Cauchy integral formula in unbounded domains for null‐solutions of the Dirac equation to be proved. The result is obtained with the aid of methods of quaternionic analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Hermitian Clifford analysis and resolutions
Authors: Sabadini Irene , Sommen Frank
Published: November 2002

In this paper, we discuss the so‐called Witt basis in a Clifford algebra and we axiomatically define an algebra of abstract Hermitian vector variables similar to the ‘radial algebra’. In this setting, we introduce some linear partial differential operators and we study their resolutions. Copyright © 2002 John Wiley & Sons, Ltd.
Computational algebraic analysis methods in Clifford analysis
Authors: Sabadini Irene , Struppa Daniele C.
Published: November 2002

Recent advances in Computer Algebra have made it possible the study of algebraic analysis in an explicit and computational way. In this paper we show how these ideas have allowed the solution of a new class of problems in Clifford analysis and we describe the computational techniques that we have to develop to this purpose. Copyright © 2002 John Wiley & Sons, Ltd.
Weighted singular integral operators in Clifford analysis
Authors: Reyes Juan Bory , Abreu Blaya Ricardo
Published: November 2002

We consider the Cauchy‐type integral and singular integral operator having a weighted Cauchy kernel, both over a domain bounded by an n‐dimensional surface in ℝn+1, n⩾2. The aim of this paper is to study the behaviour of the weighted Cauchy singular integral operators near the integration boundary as well as to establish the basic relation among them. In certain sense, this approach has the advantage of being better related with boundary value problems than what is concerned in the setting of smooth surfaces. Copyright © 2002 John Wiley & Sons, Ltd.
Some properties of the Cauchy‐type integral for the time‐harmonic relativistic Dirac equation
Authors: Schneider Baruch , Shapiro Michael
Published: November 2002

In this paper we study an analogue of the Cauchy‐type integral for the theory of time‐harmonic solutions of the relativistic Dirac equation in case of a piece‐wise Liapunov surface of integration and we prove the Sokhotski–Plemelj theorem for it as well as the necessary and sufficient condition for the possibility to extend a given Hölder function from such a surface up to a solution of the relativistic Dirac equation in a domain. Formula for the square of the singular Cauchy‐type integral is given. The proofs of all these facts are based on intimate relations between time‐harmonic solutions of the relativistic Dirac equation and some versions of quaternionic analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Clifford analysis on projective hyperbolic space II
Authors: Sommen F. , Cerejeiras P. , Kähler U.
Published: November 2002

In this paper, we identify the hyperbolic unit ball with the manifold of rays within the future null cone. By means of theinduced Clifford algebra structure there we obtain the definition of Dirac operators on sections of homogeneous line bundles and a homogeneous version of the Borel–Pompeiu formula.

Finally, we introduce for this projective model of hyperbolic space a scale of the so‐called Qp‐spaces and study some of its basic properties. Copyright © 2002 John Wiley & Sons, Ltd.
Clifford–Bessel wavelets in Euclidean space
Authors: Brackx Fred F. , Sommen Frank C.
Published: November 2002

Specific wavelet functions, related to the Bessel functions, for the continuous wavelet transform in higher dimension, are constructed in the framework of Clifford analysis. Copyright © 2002 John Wiley & Sons, Ltd.
The spherical X‐ray transform
Authors: Cerejeiras P. , Schaeben H. , Sommen F.
Published: November 2002

The general objective of this communication is to present the basics of mathematical texture analysis as part of integral geometry involving spherical analogues of the X‐ray and Radon transform, and in particular to clarify its relationship with mathematical tomography. Copyright © 2002 John Wiley & Sons, Ltd.
Bergman kernels for rectangular domains and multiperiodic functions in Clifford analysis
Authors: Constales D. , S. Kraußhar R.
Published: November 2002

In this paper, we consider rectangular domains in real Euclidean spaces of dimension at least 2, where the sides can be finite, semi‐infinite, or fully infinite. The Bergman reproducing kernel for the space of monogenic and square integrable functions on such a domain is obtained in closed form as a finite sum of monogenic multiperiodic functions. The reproducing property leads to an estimate of the first derivative of the single‐periodic cotangent function in terms of the classical real‐valued Eisenstein series. Copyright © 2002 John Wiley Sons, Ltd.
Clifford analytic complete function systems for unbounded domains
Authors: Lakew Dejenie A. , Ryan John
Published: November 2002

The main theme of this paper is to construct Clifford analytic‐complete function systems in the generalized Bergman spaces: BpCln(Ω):=kerD(Ω)∩LpCln(Ω), and Bp,2Cln(Ω):=ker▵(Ω)∩LpCln(Ω). These systems are used to approximate null solutions of elliptic partial differential equations of the Dirac and Laplace operators over an unbounded domain Ω in ℝn. Copyright © 2002 John Wiley & Sons, Ltd.
Almansi‐type theorems in Clifford analysis
Authors: Malonek Helmuth R. , Ren Guangbin
Published: November 2002

In this paper, we consider functions defined in a star‐ike omain Ω⊂ℝn with values in the Clifford lgebra C𝓁0,n which are polymonogenic with respect to the (left) Dirac operator D=∑j=1n ej∂/∂xj, i.e. they belong to the kernel of Dk.

We prove that any polymonogenic function f has a ecomposition of the form

f=f1+xf2+···+xk−1fk
,
where x=x1e1+···+xnen and fj, j=1,…,k, are monogenic functions. This generalizes classical Almansi theorem for polyharmonic functions as well e Fischer decomposition of polynomials. Similar results tained for the powers of weighted Dirac operators of the form D̃=∣x∣−αxD, α∈ℝ\{0}. Copyright © John Wiley & Sons, Ltd.
On conjugate harmonic functions in Euclidean space
Authors: Brackx F. F. , Delanghe R. , Sommen F. C.
Published: November 2002

In this paper we consider the problem of constructing in domains Ωof ℝm+1 with a specific geometric property, a conjugate harmonic V to a given harmonic function U, as a direct generalization of the complex plane case. This construction is carried out in the framework of Clifford analysis which focusses on the so‐called monogenic functions, i.e. null solutions of the Dirac operator. An explicit formula of the associated monogenic function F=U+ē0 V in terms of a harmonic potential is constructed and the interconnection with the Stein–Weiss notion of conjugate harmonicity will be shown. Copyright © 2002 John Wiley & Sons, Ltd.
On finite difference potentials and their applications in a discrete function theory
Authors: Gürlebeck K. , Hommel A.
Published: November 2002

We present a potential theoretical method which is based on the approximation of the boundary value problem by a finite difference problem on a uniform lattice. At first the discrete fundamental solution of the Laplace equation is studied and the theory of difference potentials is described. In the second part we define a discrete Cauchy integral operator and a Teodorescu transform. In addition a Borel–Pompeiu formula can be formulated. Copyright © 2002 John Wiley & Sons, Ltd.
Reliability bounds for the NBUE distributions
Authors: Cheng Kan , Lam Yeh
Published: November 2002

In this paper, we study upper and lower bounds on the reliability in new better than used in expectation (NBUE) life distribution class with fixed first two moments. By a constructive proof, we determine the upper bounds on the reliability analytically in different regions and show that these bounds are sharp. For the lower bounds, similar results are obtained except in one region. For that region, a conjecture is given for further study. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 781–797, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10035
Minimizing weighted earliness and tardiness penalties in single‐machine scheduling with idle time permitted
Authors: Chen Jaw‐Yeh , Lin Sheng‐Fuu
Published: November 2002

In this paper, a single‐machine scheduling problem with weighted earliness and tardiness penalties is considered. Idle time between two adjacent jobs is permitted and due dates of jobs could be unequal. The dominance rules are utilized to develop a relationship matrix, which allows a branch‐and‐bound algorithm to eliminate a high percentage of infeasible solutions. After combining this matrix with a branching strategy, a procedure to solve the problem is proposed. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 760–780, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10039
Centralized inventory control in a two‐level distribution system with Poisson demand
Authors: Marklund Johan
Published: November 2002

This paper introduces a new replenishment policy for inventory control in a two‐level distribution system consisting of one central warehouse and an arbitrary number of nonidentical retailers. The new policy is designed to control the replenishment process at the central warehouse, using centralized information regarding the inventory positions and demand processes of all installations in the system. The retailers on the other hand are assumed to use continuous review (R, Q) policies. A technique for exact evaluation of the expected inventory holding and backorder costs for the system is presented. Numerical results indicate that there are cases when considerable savings can be made by using the new (α0, Q0) policy instead of a traditional echelon‐ or installation‐stock (R, Q) policy. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 798–822, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10040
A branch‐and‐price algorithm for a hierarchical crew scheduling problem
Authors: Faneyte Diego B.C. , Spieksma Frits C.R. , Woeginger Gerhard J.
Published: November 2002

We describe a real‐life problem arising at a crane rental company. This problem is a generalization of the basic crew scheduling problem given in Mingozzi et al. [18] and Beasley and Cao [6]. We formulate the problem as an integer programming problem and establish ties with the integer multicommodity flow problem and the hierarchical interval scheduling problem. After establishing the complexity of the problem we propose a branch‐and‐price algorithm to solve it. We test this algorithm on a limited number of real‐life instances. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 723–742, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10044
Suppression of enemy air defenses (SEAD) as an information duel
Authors: Barkdoll Timothy C. , Gaver Donald P. , Glazebrook Kevin D. , Jacobs Patricia A. , Posadas Sergio
Published: November 2002

Blue strike aircraft enter region ℛ to attack Red targets. In Case 1, Blue conducts (preplanned) SEAD to establish air superiority. In the (reactive) SEAD scenario, which is Case 2, such superiority is already in place, but is jeopardized by prohibitive interference from Red, which threatens Blue's ability to conduct missions. We utilize both deterministic and stochastic models to explore optimal tactics for Red in such engagements. Policies are developed which will guide both Red's determination of the modes of operation of his engagement radar, and his choice of Blue opponent to target next. An index in the form of a simple transaction kill ratio plays a major role throughout. Published 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 723–742, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10046
Stabilized finite element method for viscoplastic flow: formulation with state variable evolution
Authors: Maniatty Antoinette M. , Liu Yong
Published: November 2002

A stabilized, mixed finite element formulation for modelling viscoplastic flow, which can be used to model approximately steady‐state metal‐forming processes, is presented. The mixed formulation is expressed in terms of the velocity, pressure and state variable fields, where the state variable is used to describe the evolution of the material's resistance to plastic flow. The resulting system of equations has two sources of well‐known instabilities, one due to the incompressibility constraint and one due to the convection‐type state variable equation. Both of these instabilities are handled by adding mesh‐dependent stabilization terms, which are functions of the Euler–Lagrange equations, to the usual Galerkin method. Linearization of the weak form is derived to enable a Newton–Raphson implementation into an object‐oriented finite element framework. A progressive solution strategy is used for improving convergence for highly non‐linear material behaviour, typical for metals. Numerical experiments using the stabilization method with hierarchic shape functions for the velocity, pressure and state variable fields in viscoplastic flow and metal‐forming problems show that the stabilized finite element method is effective and efficient for non‐linear steady forming problems. Finally, the results are discussed and conclusions are inferred. Copyright © 2002 John Wiley & Sons, Ltd.
A fast boundary cloud method for exterior 2D electrostatic analysis
Authors: Shrivastava Vaishali , Aluru N. R.
Published: November 2002

An accelerated boundary cloud method (BCM) for boundary‐only analysis of exterior electrostatic problems is presented in this paper. The BCM uses scattered points instead of the classical boundary elements to discretize the surface of the conductors. The dense linear system of equations generated by the BCM are solved by a GMRES iterative solver combined with a singular value decomposition based rapid matrix–vector multiplication technique. The accelerated technique takes advantage of the fact that the integral equation kernel (2D Green's function in our case) is locally smooth and, therefore, can be dramatically compressed by using a singular value decomposition technique. The acceleration technique greatly speeds up the solution phase of the linear system by accelerating the computation of the dense matrix–vector product and reducing the storage required by the BCM. Copyright © 2002 John Wiley & Sons, Ltd.
Space‐time finite elements and an adaptive strategy for the coupled thermoelasticity problem
Authors: Larsson F. , Hansbo P. , Runesson K.
Published: November 2002

A space–time finite element method for the linear thermo‐elasticity problem is outlined. By establishing the appropriate dual problem in space–time, it is possible to establish an exact a posteriori error representation formula based on residuals and the dual solution. In particular, we focus on the error generation in time. An adaptive strategy in the time‐domain is proposed, and its performance is investigated with the aid of a numerical example in 2D. In particular, the excellent precision of the error estimate, in terms of the effectivity index being close to unity, is noted. Copyright © 2002 John Wiley & Sons, Ltd.
Blurred derivatives and meshless methods
Authors: Pardo Enrique
Published: November 2002

In this work we first introduce and describe the concept of blurred derivatives. It is shown how they can be used both to approximate differential equations and to re‐express them in alternative ways. In particular, formulations in terms of functional integrals can be obtained using blurred derivatives and extended to non‐linear problems. Blurred derivatives are shown to provide higher flexibility for selection of approximation functions than strong and weak formulations. Some computational implementations of one‐dimensional problems are discussed and the relationship between several well‐known numerical methods is analysed. Finally a meshless numerical scheme for the Poisson equation is described in detail. Its performance is compared with linear finite elements and generalized finite differences on unstructured meshes of points. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of rhizosphere 13C pulse signals in soil thin sections by laser ablation isotope ratio mass spectrometry
Authors: Bruneau Patricia M.C. , Ostle Nick , Davidson Donald A. , Grieve Ian C. , Fallick Anthony E.
Published: November 2002

In grassland ecosystems, soil animals act as key soil engineers and architects. The diversity of soil animals is also a regulator of ecosystem carbon flow. However, our understanding of the link between soil animals, carbon fluxes and soil physical organisation remains poor. An integrated approach based on soil micromorphology and laser ablation stable isotope ratio mass spectrometry (LA‐IRMS) was developed to provide spatially distributed data of pulse‐derived 13C tracer from roots in the soil environment. This paper describes the development and testing of a LA‐IRMS 13C/12C analytical method on soil thin sections as a means to determine the fate of root carbon derived from photosynthesis into soil. Results from this work demonstrated (1) that micro‐scale δ13C (‰) analysis could be made on targeted features located within a soil thin section and (2) that LA‐IRMS δ13C (‰) measurements made on samples obtained from 13CO2 pulse labelled plant‐soil blocks confirmed the presence of recent photosynthates in the rhizosphere (1 and 4 weeks post‐pulse). Copyright © 2002 John Wiley & Sons, Ltd.
Use of labelled nitrogen to measure gross and net rates of mineralization and microbial activity in permanent pastures following fertilizer applications at different time intervals
Authors: Hatch David J. , Sprosen Mike S. , Jarvis Steve C. , Ledgard Stewart F.
Published: November 2002

Measurements of some of the main internal N‐cycling processes in soil were obtained by labelling the inorganic N pool with the stable isotope of nitrogen (15N). The 15N mean pool dilution technique, combined with other field measurements, enabled gross and net N‐mineralization rates to be resolved in grassland soils, which had previously either received fertilizer N (F), or had remained unfertilized (U) for many years. The two soils were subdivided into plots that received N at different time intervals (over 3 weeks), prior to 15N measurements being made. By this novel approach, possible ‘priming’ effects over time were investigated to try to overcome some of the temporal problems of isotopic labelling of soil N (native plus fertilizer) and to identify possible changes in a range of primary N‐transformation processes. The results suggested that an overall stimulation of microbially mediated processes occurred with all N treatments, but there were inconsistencies associated with the release of N, both in the timing and the degree to which different processes responded to the application of fertilizer N. The rates of these processes were, however, within the range of previously reported data and the 15N measurements were not adversely affected by the differences in N pools created by the treatments. Thus, the mean pool dilution technique was shown to be applicable to agricultural soils, under conditions relevant to grass swards receiving fertilizer. For example, between the U and F treatments, the size of inorganic N pools increased by five‐fold and gross rates of mineralization reached 3.5 and 4.8 µg N g−1 (dry soil) d−1, respectively, but did not vary greatly with the timing of N applications. A correlation (r2 = 0.57) was found between soil respiration (which is relatively simple to measure) and net mineralization (which is more time consuming), suggesting that the former might be used as an indicator of the latter. Although this relationship was stronger in previously unfertilized soils, the similarities found with fertilized soils suggest that this approach could be used to obtain information of wider agronomic value and would, therefore, warrant further work under a range of soil conditions. Copyright © 2002 John Wiley & Sons, Ltd.
Development of a trace gas stable isotope capture system in a mobile laboratory for temporal and spatial sampling of field and laboratory experiments
Authors: McNamara Niall , Benham David , Sleep Darren , Grant Helen , Stott Andrew
Published: November 2002

We describe the development of a novel mobile field laboratory, purposely designed for the automated capture and subsequent stable isotopic analyses of multiple gas samples. The multiple capture system is integrated into a mobile laboratory that is fully capable of measuring the concentration of carbon dioxide, methane and nitrous oxide trace gases in a flow‐through system connected to a gas chromatograph fitted with both electron capture and flame ionisation detectors. The capture of gases is achieved by routing samples through a series of 135 mL gas flasks that are sealed by micro‐solenoid valves triggered by a timing system. Trace gas light stable isotope ratio mass spectrometry can then be carried out on gas samples collected by the system (NERC 15N Stable Isotope Facility). The excitingly unique potential of the system to the ecological research field is that it will allow the collection of cyclical data for three different trace gases both in real‐time and in situ. We present data arising from the validation of this mobile system as well as a preliminary experimental assessment of this technique. This technique was used to measure δ13C in CO2 and CH4 in soil gases released from waterlogged cores and δ13C‐CH4 values were significantly depleted in wet cores compared with dry ones (p < 0.001). Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of soil organic matter fractions from grassland and cultivated soils via C content and δ13C signature
Authors: Accoe Frederik , Boeckx Pascal , Van Cleemput Oswald , Hofman Georges , Hui Xu , Bin Huang , Guanxiong Chen
Published: November 2002

Variations in 13C natural abundance and distribution of total C among five size and density fractions of soil organic matter, water soluble organic C (WSOC) and microbial biomass C (MBC) were investigated in the upper layer (0–20 cm) of a continuous grassland soil (CG, C3 vegetation), a C3‐humus soil converted to continuous maize cultivation (CM, C4 vegetation) and a C3‐humus soil converted to a rotation of maize cultivation and grassland (R). The amounts of WSOC and MBC were both significantly larger in the CG than in the CM and the R. In the three soils, WSOC was depleted while MBC was enriched in 13C as compared with whole soil C. The relative contributions to the total C content of C stored in the macro‐organic matter and in the size fraction 50–150 µm decreased with decreasing total C contents in the order CG > R > CM, while the relative contribution of C associated with the clay‐ and silt‐sized fraction <50 µm increased. This reflects a greater stability and physical protection against microbial degradation associated with soil disruption (tillage) of the clay‐ and silt‐associated organic C, in relation to the organic C in larger size fractions. The size and density fractions from the CG soil showed significant differences in 13C enrichment, indicating different degrees of microbial degradation and stability of soil organic C associated with physically different soil organic matter (SOM) fractions. δ13C analysis of the size and density fractions from CM and R soils reflected a decreasing turnover rate of soil organic C with increasing density among the macro‐organic matter fractions and with decreasing particle size. Copyright © 2002 John Wiley & Sons, Ltd.
Invertebrate accessibility and vulnerability in the analysis of brown trout (Salmo trutta L.) summer habitat suitability
Authors: de Billy V. de Crespin , Dumont B. , Lagarrigue T. , Baran P. , Statzner B.
Published: November 2002

Water discharge regulation can affect food availability, accessibility and vulnerability and thus, the trophic habitat suitability for lotic salmonids. To analyse brown trout habitat suitability, we therefore combined the relative importance of the food availability (overall abundance of benthic and drifting invertebrates), with the potential food vulnerability (accessibility, conspicuousness and ease of handling), the latter depending on both physical habitat characteristics (flow patterns and structural complexity of habitat) and invertebrate traits (size and other biological traits). We considered the trophic patterns of trout at two spatial scales: the reach scale (unregulated reach versus regulated reach) and the macrohabitat scale (e.g. riffles and pools).

Discharge regulation reduced trout abundance, biomass, and temperature‐independent growth rates. In the regulated reach, trout had a lower total prey consumption, a higher consumption of terrestrial invertebrates and a higher diet diversity than in the unregulated reach, indicating that trout were food‐limited. However, the potential availability of food supplies per individual trout was similar for the two reaches. Thus, trout prey consumption in the regulated reach should have been predominantly affected by the decrease in both the availability of large invertebrates in the drift and their vulnerability in the total food supplies.

There were no macrohabitat‐specific differences in the total prey consumption and in the potential food availability within each reach. However, brown trout diets differed between the macrohabitats of each reach, in relation to differences in potential invertebrate vulnerability.

Therefore, the potential vulnerability of invertebrates to predation was more relevant in the ecological evaluation of salmonid habitat suitability than the total food availability. The analysis at the macrohabitat scale provided a better understanding of the switches in brown trout diet and enabled a finer and more realistic analysis of trout feeding patterns. Copyright © 2002 John Wiley & Sons, Ltd.
Controls on the size and occurrence of pools in coarse‐grained forest rivers
Authors: Buffington John M. , Lisle Thomas E. , Woodsmith Richard D. , Hilton Sue
Published: November 2002

Controls on pool formation are examined in gravel‐ and cobble‐bed rivers in forest mountain drainage basins of northern California, southern Oregon, and southeastern Alaska. We demonstrate that the majority of pools at our study sites are formed by flow obstructions and that pool geometry and frequency largely depend on obstruction characteristics (size, type, and frequency). However, the effectiveness of obstructions to induce scour also depends on channel characteristics, such as channel gradient, width:depth ratio, relative submergence (ratio of flow depth to grain size), and the calibre and rate of bed material supply. Moreover, different reach‐scale channel types impose different characteristic physical processes and boundary conditions that further control the occurrence of pools within a catchment. Our findings indicate that effective management of pools and associated aquatic habitat requires consideration of a variety of factors, each of which may be more or less important depending on channel type and location within a catchment. Consequently, strategies for managing pools that are based solely on single‐factor, regional target values (e.g. a certain number of wood pieces or pools per stream length) are likely to be ineffective because they do not account for the variety of local and catchment controls on pool scour and, therefore, may be of limited value for proactive management of complex ecosystems. Copyright © 2002 John Wiley & Sons, Ltd.