bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glyph and hyperstreamline representation of stress and strain tensors and material constitutive response
Authors: Hashash Youssef M. A. , Yao John I‐Chiang , Wotring Donald C. 
Published: May 2003

AbstractResults of numerical analyses of boundary value problems in geomechanics include output of three‐dimensional stress and strain states. Two‐dimensional plots of stress–stress or stress–strain quantities, often used to represent such output, do not fully communicate the evolution of stress and strain states. This paper describes the use of glyphs and hyperstreamlines for the visual representation of three dimensional stress and strain tensors in geomechanics applications. Glyphs can be used to represent principal stress states as well as normal stresses at a point. The application of these glyphs is extended in this paper to represent strain states. The paper introduces a new glyph, called HWY glyph for the representation of shear tensor components. A load step‐based hyperstreamline is developed to show the evolution of a stress or strain tensor under a general state of loading. The evolution of stress–strain states from simulated laboratory tests and a general boundary value problem of a deep braced excavation are represented using these advanced visual techniques. These visual representations facilitate the understanding of complex multidimensional stress–strain soil constitutive relationships. The visual objects introduced in this paper can be applied to stress and strain tensors from general boundary value problems. Copyright © 2003 John Wiley & Sons, Ltd.
A diffusible signal attracts olfactory sensory axons toward their target in the developing brain of the moth
Authors: Oland Lynne A. , Pott Wendy M. , Howard Charles T. , Inlow Mark , Buckingham Jocelyn 
Published: May 2003

AbstractThe signals that olfactory receptor axons use to navigate to their target in the CNS are still not well understood. In the moth Manduca sexta, the primary olfactory pathway develops postembryonically, and the receptor axons navigate from an experimentally accessible sensory epithelium to the brain along a pathway long enough for detailed study of regions in which axon behavior changes. The current experiments ask whether diffusible factors contribute to receptor axon guidance. Explants were made from the antennal receptor epithelium and co‐cultured in a collagen gel matrix with slices of various regions of the brain. Receptor axons were attracted toward the central regions of the brain, including the protocerebrum and antennal lobe. Receptor axons growing into a slice of the most proximal region of the antennal nerve, where axon sorting normally occurs, showed no directional preference. When the antennal lobe was included in the slice, the receptor axons entering the sorting region grew directly toward the antennal lobe. Taken together with the previous in vivo experiments, the current results suggest that an attractive diffusible factor can serve as one cue to direct misrouted olfactory receptor axons toward the medial regions of the brain, where local cues guide them to the antennal lobe. They also suggest that under normal circumstances, in which the receptor axons follow a pre‐existing pupal nerve to the antennal lobe, the diffusible factor emanating from the lobe acts in parallel and at short range to maintain the fidelity of the path into the antennal lobe. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 24–40, 2003
In vivo dynamics of CNS sensory arbor formation: A time‐lapse study in the embryonic leech
Authors: Baker Michael W. , Kauffman Brent , Macagno Eduardo R. , Zipser Birgit 
Published: May 2003

AbstractIn the embryo of the leech Hirudo medicinalis, afferent projections of peripheral sensory neurons travel along common nerve tracts to the CNS, where they defasciculate, branch, and arborize into separate, modality‐specific synaptic laminae. Previous studies have shown that this process requires, at least in part, the constitutive and then modality‐specific glycosylations of tractin, a leech L1 homologue. We report here on the dynamics of growth of these projections as obtained by examining the morphology of single growing dye‐filled sensory afferents as a function of time. Using 2‐photon laser‐scanning microscopy of the intact developing embryo, we obtained images of individual sensory projections at 3 to 30 min intervals, over several hours of growth, and at different stages of development. The time‐lapse series of images revealed a highly dynamic and maturation‐state‐dependent pattern of growth. Upon entering the CNS, the growth cone‐tipped primary axon sprouted numerous long filopodial processes, many of which appeared to undergo repeated cycles of extension and retraction. The growth cone was transformed into a sensory arbor through the formation of secondary branches that extended within the ganglionic neuropil along the anterior‐posterior axis of the CNS. Numerous tertiary and quaternary processes grew from these branches and also displayed cycles of extension and retraction. The motility of these higher‐order branches changed with age, with younger afferents displaying higher densities and greater motility than older, more mature sensory arbors. Finally, coincident with a reduction in higher order projections was the appearance of concavolar structures on the secondary processes. Rows of these indentations suggest the formation of presynaptic en‐passant specializations accompanying the developmental onset of synapse formation. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 41–53, 2003
Structural and functional changes in the olfactory pathway of adult Drosophila take place at a critical age
Authors: Devaud Jean‐Marc , Acebes Angel , Ramaswami Mani , Ferrús Alberto 
Published: May 2003

AbstractThe olfactory system of several holometabolous insect species undergoes anatomical changes after eclosion of the imago, following those occurring during metamorphosis. In parallel, odor experience and learning performance also evolve with age. Here, we analyze the case of adult Drosophila females. Synaptogenesis in the antennal lobe (AL) starts in late pupa and continues during the first days of adult life, at the same time as the behavioral response to odors matures. Individual olfactory glomeruli (DM6, DM2, and V) display specific growth patterns between days 1 and 12 of adult life. Experience can modify the olfactory pathway both structurally and functionally as shown by adaptation experiments. The modifications associated with this form of nonassociative learning seem to take place at a critical age. Exposure to benzaldehyde at days 2–5 of adult life, but not at 8–11, causes behavioral adaptation as well as structural changes in DM2 and V glomeruli. Altered levels in intracellular cAMP, caused by dunce and rutabaga mutants, do not affect the normal changes in glomerular size, at least at day 6 of development, but they prevent those elicited by experience, establishing a molecular difference between glomerular changes of intrinsic versus environmental origin. Taken together, these data demonstrate an imprinting‐like phenomenon in the olfactory pathway of young Drosophila adults, and illustrate its glomerulus‐specific dynamics. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 13–23, 2003
Blocking sensory inputs to identified antennal glomeruli selectively modifies odorant perception in Drosophila
Authors: Devaud Jean‐Marc , Keane John , Ferrús Alberto 
Published: May 2003

AbstractNeural coding of sensory input is a major unsolved issue in neuroscience. Current experimental methods rely on neural activity recording or visualization following sensory stimulation. Most of them, however, do not include behavioral correlates on the actual perception by the animal. We present a novel approach to address olfaction and coding in adult Drosophila. Sensory input was selectively blocked in two subsets of sensory neurons that project to different, albeit overlapping, groups of central targets, by means of tetanus toxin expressed under the control of the yeast transcription factor Gal4. Glomeruli DL1, DL2, VM1, and VM4 were tested following stimulation with benzaldehyde, ethyl acetate, propionic acid, butanol, or acetone at various concentrations. The behavioral response was found to be modified in an odorant‐specific and a concentration‐dependent manner. Sensory input to DL2 and, to a minor extent, VM1 and/or VM4, appear to be required for benzaldehyde perception, while acetone is processed through DL1. None of these glomeruli, however, seem necessary for butanol perception. In addition, sexual differences were observed for some stimuli. These results demonstrate the behavioral relevance of odor representation as maps of glomerular activity generated in the antennal lobes following specific sensory input. The strategy used here should be useful to characterize olfactory coding, as new and selective Gal4 lines become available. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 1–12, 2003
Endogenous neurotrophic factors enhance neurite growth by bag cell neurons of Aplysia
Authors: Vanmali Binaben H. , Romanova Elena V. , Messner Maria C. , Singh Mona , Maruniak Joel , Sweedler Jonathan , Kirk Mark D. 
Published: May 2003

AbstractMechanisms that regulate neurite outgrowth are phylogenetically conserved, including the signaling molecules involved. Here, we describe neurotrophic effects on isolated bag cell neurons (BCNs) of substrate‐bound growth factors endogenous to the sea slug Aplysia californica. Sheath cells dissociated from the pleural‐visceral connectives of the Aplysia CNS and arterial cells dissociated from the anterior aorta enhance neurite outgrowth when compared to controls, i.e., BCNs grown in defined medium alone. In addition, the substrate remaining after sheath cells or arterial cells are killed significantly enhances growth, relative to all other conditions tested. For instance, primary neurites are more numerous and greater in length for BCNs cultured on substrate produced by arterial cells. These results suggest that sheath and arterial cells produce growth‐promoting factors, some of which are found in the substrates produced by these cell types. Using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS), we found that Aplysia collagen‐like peptides are produced by dissociated arterial cells, and therefore likely contribute to the observed growth effects. Collagen‐like peptides and other factors produced by sheath and arterial cells likely influence neurite growth in the Aplysia CNS during development, learning and memory, and regeneration after injury. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 78–93, 2003
Estrogen alters excitability but not morphology of a sexually dimorphic neuromuscular system in adult rats
Authors: Fargo Keith N. , Foster Allison M. , Harty Mark W. , Sengelaub Dale R. 
Published: May 2003

AbstractIn rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) innervate the bulbocavernosus (BC) muscle, which surrounds the base of the penis. The SNB/BC is a sexually dimorphic, steroid‐sensitive neuromuscular system, which is critically important in male reproductive behavior. Androgens are necessary for the development, morphology, and function of the SNB/BC system. However, estradiol (E) is also necessary for the development of the SNB/BC system, and E is capable of maintaining BC EMG activity in adulthood. In this study, we used electrophysiological and anatomical methods to examine estrogenic effects on BC EMG activity. We used a modified H‐reflex testing method to investigate polysynaptic reflex characteristics in intact males, castrates, and castrates treated short term with estradiol benzoate (EB). Measures of EMG activity, response latency, and spike count were altered in castrates, but maintained in EB‐treated castrates to the levels of intact males. Furthermore, estrogenic effects were found in EMG activity that could be isolated to the periphery of the SNB/BC system. BC NMJ size and muscle fiber area have been demonstrated to be hormone sensitive, and we examined these for possible correlates of E's effects on BC EMG activity. BC muscles of intact males, castrates, and short‐term EB‐treated castrates were fixed and stained with zinc iodide and osmium tetroxide. NMJ size and muscle fiber area did not differ between groups. Together, these data suggest that E treatment results in changes in the neuromuscular periphery that maintain BC EMG activity, but this effect cannot be accounted for by changes in NMJ size or muscle fiber area. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 66–77, 2003
Sex differences and hormone influences on tyrosine hydroxylase immunoreactive cells in the leopard frog
Authors: Wilczynski Walter , Yang Eun‐Jin , Simmons Diana 
Published: May 2003

AbstractWe examined sex differences in tyrosine hydroxylase immunoreactive (TH‐ir) cell populations in the preoptic area (POA), suprachiasmatic nucleus (SCN), posterior tuberculum (TP), and caudal hypothalamus (Hy) in the leopard frog (Rana pipiens), in addition to the effects of natural variation in sex steroid hormones on these same populations in both sexes. All four of these populations have been shown to be dopaminergic. Gonadal sex, androgens, and estrogen all influenced TH‐ir cell numbers, but in a complicated pattern of interactions. After factoring out the effects of sex steroids by multiple regression, TH‐ir cell numbers in all four areas differed between the sexes, with males having a greater number of TH‐ir cells. The influence of androgens and estrogen differed by region and sex of the animals. Androgens were the main influence on TH‐ir cell numbers in the POA and SCN. Plasma androgen concentrations were positively correlated with TH‐ir cell numbers in both areas in males. In females, androgen concentration was negatively correlated with TH‐ir cell numbers in the POA; there was no significant relationship in the SCN in females. In the more caudal populations, estrogen (E2) levels were positively correlated with TH‐ir cell numbers in the TP of both males and females. In the caudal hypothalamus, E2 levels were positively correlated with TH‐ir cell numbers in females, but there was no significant correlation in males. The results indicate that gonadal sex imposes a baseline sex difference in the four TH‐ir (dopamine) populations, resulting in a higher number of such cells in males. Individual and sex‐linked differences in gonadal steroid hormones lead to variation around this baseline condition, with androgens having a greater influence on rostral populations and estrogen on caudal populations. Last, an individual's gonadal sex determines the effect that androgens and estrogen have on each population. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 54–65, 2003
Operator trigonometry of preconditioning, domain decomposition, sparse approximate inverses, successive overrelaxation, minimum residual schemes
Authors: Gustafson Karl 
Published: May 2003

AbstractThis paper extends the relationship between the author's operator trigonometry and convergence rates and other properties of important iterative methods. A new interesting trigonometric preconditioning lemma is given. The general relationship between domain decomposition methods and the operator trigonometry is established. A new basic conceptual link between sparse approximate inverse algorithms and the operator trigonometry is observed. A new underlying fundamental inherent trigonometry of the classical successive over‐relaxation scheme is exposed. Some improved trigonometric interpretations of minimum residual schemes are mentioned. Copyright © 2002 John Wiley & Sons, Ltd.
A note on bound for norms of Cauchy–Hankel matrices
Authors: Solak Süleyman , Bozkurt Durmuş 
Published: May 2003

AbstractWe determine bounds for the spectral and 𝓁p norm of Cauchy–Hankel matrices of the form Hn=[1/(g+h(i+j))]ni,j=1≡ ([1/(g+kh)]ni,j=1), k=0, 1,…, n –1, where k is defined by i+j=k (mod n). Copyright © 2002 John Wiley & Sons, Ltd.
An increasing‐angle property of the conjugate gradient method and the implementation of large‐scale minimization algorithms with line searches
Authors: Dai Yu‐Hong , Martínez José Mario , Yuan Jin‐Yun 
Published: May 2003

AbstractThe search direction in unconstrained minimization algorithms for large‐scale problems is usually computed as an iterate of the preconditioned) conjugate gradient method applied to the minimization of a local quadratic model. In line‐search procedures this direction is required to satisfy an angle condition that says that the angle between the negative gradient at the current point and the direction is bounded away from π/2. In this paper, it is shown that the angle between conjugate gradient iterates and the negative gradient strictly increases as far as the conjugate gradient algorithm proceeds. Therefore, the interruption of the conjugate gradient sub‐algorithm when the angle condition does not hold is theoretically justified. Copyright © 2002 John Wiley & Sons, Ltd.
Application of the Lanczos algorithm for solving the linear systems that occur in continuation problems
Authors: Chien C.‐S. , Chang S.‐L. 
Published: May 2003

AbstractWe study the Lanczos method for solving symmetric linear systems with multiple right‐hand sides. First, we propose a numerical method of implementing the Lanczos method, which can provide all approximations to the solution vectors of the remaining linear systems. We also seek possible application of this algorithm for solving the linear systems that occur in continuation problems. Sample numerical results are reported. Copyright © 2002 John Wiley & Sons, Ltd.
A nodal coupling of finite and boundary elements
Authors: Sayas Francisco‐Javier 
Published: May 2003

AbstractThis article presents and analyzes a simple method for the exterior Laplace equation through the coupling of finite and boundary element methods. The main novelty is the use of a smooth parametric artificial boundary where boundary elements fit without effort together with a straight approximate triangulation in the bounded area, with the coupling done only in nodes. A numerically integrated version of the algorithm is also analyzed. Finally, an isoparametric variant with higher order is proposed. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 555–570, 2003
Mass‐lumping or not mass‐lumping for eigenvalue problems
Authors: Armentano María G. , Durán Ricardo G. 
Published: May 2003

AbstractIn this article we analyze the effect of mass‐lumping in the linear triangular finite element approximation of second‐order elliptic eigenvalue problems. We prove that the eigenvalue obtained by using mass‐lumping is always below the one obtained with exact integration. For singular eigenfunctions, as those arising in non convex polygons, we prove that the eigenvalue obtained with mass‐lumping is above the exact eigenvalue when the mesh size is small enough. So, we conclude that the use of mass‐lumping is convenient in the singular case. When the eigenfunction is smooth several numerical experiments suggest that the eigenvalue computed with mass‐lumping is below the exact one if the mesh is not too coarse. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 653–664, 2003
A second‐order linearized difference scheme on nonuniform meshes for nonlinear parabolic systems with Dirichlet boundary value conditions
Authors: Zhang Ling‐Yun , Sun Zhi‐Zhong 
Published: May 2003

AbstractA linearized three‐level difference scheme on nonuniform meshes is derived by the method of the reduction of order for the Dirichlet boundary value problem of the nonlinear parabolic systems. It is proved that the difference scheme is uniquely solvable and second order convergent in L∞‐norm. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 638–652, 2003
Stimuli‐sensitive behaviour of novel betaine‐type polyampholytes
Authors: Didukh Alexander G , Koizhaiganova Raushan B , Khamitzhanova Gulzhan , Bimendina Larisa A , Kudaibergenov Sarkyt E 
Published: May 2003

AbstractNovel linear and crosslinked polyampholytes of betaine structure based on acrylic acid and ethyl 3‐aminocrotonate (ethyl ester of 3‐amino‐2‐butenoic acid) have been synthesized by Michael addition reaction followed by radical copolymerization. The mechanism of formation of monomer and polymer betaines is discussed. The linear polyampholyte has been characterized by potentiometric titration, IR, NMR and GPC. Crosslinked polymeric betaines were synthesized in the presence of N,N′‐methylenebisacrylamide. The stimuli‐sensitive properties of amphoteric gels have been studied as a function of pH, ionic strength, water–organic mixture composition, electric, and combined electric and magnetic fields. The isoelectric points of linear and crosslinked polymeric betaines correspond to pH 2.0–2.1. The effect of ionic strength on the solution and gel properties of polybetaine has been interpreted on the basis of destruction of inter‐chain, intra‐chain and intra‐group salt bonds. Water–acetone, water–ethanol or water–DMF mixtures cause the shrinking of amphoteric gel due to change of the dielectric constant of the medium and decrease of the osmotic pressure. Electrocollapse is observed under the action of DC electric field. Simultaneously cross action of electric and magnetic fields enhances the collapsing rate. Appearance of pH gradient within the volume of polyampholyte gel under the externally imposed DC electric field has been observed. Copyright © 2003 Society of Chemical Industry
Synthesis and properties of poly(methyl methacrylate)/montmorillonite (PMMA/MMT) nanocomposites
Authors: Li Yan , Zhao Bin , Xie Shaobo , Zhang Shimin 
Published: May 2003

AbstractPMMA/MMT nanocomposites were successfully synthesized via in situ intercalative polymerization, and characterized by means of wide‐angle X‐ray diffractometry, transmission electron microscopy, thermal gravimetric analysis, dynamic mechanical analysis and Fourier‐transform infrared analysis. The nanocomposites possess partially exfoliated and partially intercalated structure, in which the silicate layers are exfoliated into nanometre secondary particles with thickness of less than 20 nm and uniformly dispersed in the polymer matrix. In comparison with pure PMMA, the thermal stability, glass transition temperature, and mechanical properties of the polymer are notably improved by the presence of the nanometric silicate layers. It was found that part of the PMMA chains in the nanocomposites are well immobilized inside and/or onto the layered silicates and, therefore, the unique properties of the nanocomposites result from the strong interactions between the nanometric silicate layers and the polymer chains. Copyright © 2003 Society of Chemical Industry
Evaluation of bis(2‐pyridinal)ethylenediimine as ligand for atom transfer radical polymerization of methyl methacrylate: influence of polar solvents
Authors: Iovu Mihaela C , Maithufi Norah G , Mapolie Selwyn F 
Published: May 2003

AbstractBis(2‐pyridinal)ethylenediimine was used as a ligand for copper‐mediated atom transfer radical polymerization (ATRP) of methyl methacrylate. Reactions were performed at molar ratios of monomer:initiator:catalyst of 100:1:0.5 and catalyst:ligand ratios of 1:1 and 1:2. Polymerization reactions were performed in bulk as well as in the presence of polar solvents such as dimethylformamide and acetonitrile. Reactions carried out in bulk resulted in polymerizations with poor control due to the low solubility of the copper complex in the monomer. The control was however improved by carrying out the reactions in solution using either dimethylformamide or acetonitrile as solvent. Copyright © 2003 Society of Chemical Industry