bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stemflow estimation in a redwood forest using model‐based stratified random sampling
Authors: Lewis Jack 
Published: August 2003

AbstractModel‐based stratified sampling is illustrated by a case study of stemflow volume in a redwood forest. The approach is actually a model‐assisted sampling design in which auxiliary information (tree diameter) is utilized in the design of stratum boundaries to optimize the efficiency of a regression or ratio estimator. The auxiliary information is utilized in both the design and estimation phases. Stemflow and its variance were modelled as powers of diameter and a generalized non‐linear least squares model was used to estimate the exponents and to impute values for missing storm events prior to application of the ratio estimator. The advantage of the ratio estimator over standard stratified sampling formulas is greatest for species in which stemflow is strongly dependent on diameter. With measurements on 24 trees in a 1‐hectare stand, annual stemflow was estimated with coefficients of variation of 9 per cent and 10 per cent in 2 years of study. Striking stemflow differences were found between species. Copyright © 2003 John Wiley & Sons, Ltd.
On the distribution of wildfire sizes
Authors: Schoenberg Frederic Paik , Peng Roger , Woods James 
Published: August 2003

AbstractA variety of models for the wildfire size distribution are examined using data on Los Angeles County wildfires greater than 100 acres between 1950 and 2000. In addition to graphs and likelihood criteria, Kolmogorov–Smirnoff and Cramer–von Mises statistics are used to compare the models. The tapered Pareto distribution appears to fit the data quite well and offers some advantages over the untapered Pareto distribution, while alternatives including the lognormal, half‐normal, exponential and extremal distributions fit poorly. The size distribution appears to be quite stable over the examination period, though inspection of the transformed wildfire sizes for the tapered Pareto reveals some limited trend in the residuals, indicating a very slight gradual decrease in the average fire size in Los Angeles County over these 50 years. Copyright © 2003 John Wiley & Sons, Ltd.
Space–time modeling of vertical ozone profiles
Authors: Lee Jaeyong , Berger James O. 
Published: August 2003

AbstractOzonesondes collect data relevant to ozone level at various altitudes. Modeling these data involves a combination of spatial and temporal modeling. The spatial component can be conveniently modeled as a four component mixture of normal distributions. The (relatively few) parameters of this mixture can then be modeled in a time‐dependent fashion, via a dynamic linear model. Computations are carried out via Markov chain Monte Carlo methods. Copyright © 2003 John Wiley & Sons, Ltd.
A numerical model for the behaviour of masonry under elevated temperatures
Authors: Nadjai A. , O'Garra M. , A. Ali F. , Laverty D. 
Published: August 2003

AbstractA thermo‐structural finite element model for the behaviour of masonry panels exposed to fire conditions has been developed. The model has been specifically designed to simulate the behaviour of both loaded and unloaded brickwork panels in plane stress, which are subject to various types of temperature distribution associated with typical fire situations. The current model has been evaluated using experimental results from fire tests on half‐ and full‐scale masonry walls exposed to elevated temperature on one face. Analytical and experimental results for the fire tests were basically in good agreement, indicating that reliable results can be achieved provided that accurate material properties and test boundary conditions are known, and that reliable temperature distribution data through the thickness of the wall is available. Copyright © 2003 John Wiley & Sons, Ltd.
Locations of facilities with special programs for older substance abuse clients in the US
Authors: Schultz Susan K. , Arndt Stephan , Liesveld Jill 
Published: August 2003

AbstractBackgroundGiven the growth of our aging population, developing strategies for managing late‐life alcoholism is increasingly important.ObjectiveWe compared substance abuse treatment facilities with and without services designed for older adults and explored the location of these services relative to the regional distribution of older adults across the United States.MethodsA public use dataset from a national survey of facilities offering substance abuse treatment was used to address this issue. This survey included all identified substance abuse/dependence treatment facilities in the US and surveyed the facilities' treatment services, services for special groups, number of clients admitted, type of ownership (e.g. public, private for profit), and whether or not the facility was associated with a hospital, as well as questions about licensure and income sources.ResultsOf the 13 749 responding facilities, relatively few programs (17.7%) were specifically designed for older adults (i.e. over age 65). Facilities with such programs tended to be associated with hospitals, particularly those with a psychiatric inpatient service. Importantly, the number of facilities with special programs for older adults did not correlate with size of the older population in each state.ConclusionDespite an increasing need for older adult substance abuse services, there are relatively few programs available designed for this age group. The setting where patients with substance abuse are identified (e.g. in a hospital) may partially explain the pattern of locations of age‐specific programs. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of hippocampal cholinergic deafferentation on learning strategy selection in a visible platform version of the water maze
Authors: Bizon J.L. , Han J.‐S. , Hudon C. , Gallagher M. 
Published: August 2003

AbstractRecent evidence has suggested that the relative levels of acetylcholine (ACh) between brain structures may be an important factor in the choice of behavioral strategy in settings in which either hippocampal or dorsal striatal brain systems can be employed both effectively and independently (McIntyre and Gold. 1999. Soc Neurosci Abs 25:1388). The current investigation used the neurotoxin 192 IgG‐saporin to deplete the hippocampus of ACh selectively, while leaving ACh in other brain regions, including dorsal striatum, intact. Rats were then trained on a version of the Morris water maze, in which behavioral strategies attributed to the hippocampus and dorsal striatum are placed in direct competition. It was predicted that rats with hippocampal ACh depletion would display a cue bias. Contrary to this prediction, depleting hippocampal ACh did not bias against and, in fact, promoted use of a hippocampal place strategy in this task, as indicated by choice in competition tests and performance on hidden platform training trials. These data add to a growing literature demonstrating that the septohippocampal cholinergic system is not required for accurate spatial learning and suggest a complex role for basal forebrain projections in processing information about the spatial environment. © 2003 Wiley‐Liss, Inc.
Dorsal hippocampus and classical fear conditioning to tone and context in rats: Effects of local NMDA‐receptor blockade and stimulation
Authors: Bast Tobias , Zhang Wei‐Ning , Feldon Joram 
Published: August 2003

AbstractConsistent with the importance of the hippocampus in learning more complex stimulus relations, but not in simple associative learning, the dorsal hippocampus has commonly been implicated in classical fear conditioning to context, but not to discrete stimuli, such as a tone. In particular, a specific and central role in contextual fear conditioning has been attributed to mechanisms mediated by dorsal hippocampal N‐methyl‐D‐aspartate (NMDA)‐type glutamate receptors. The present study characterized the effects of blockade or tonic stimulation of dorsal hippocampal NMDA receptors by bilateral local infusion of the noncompetitive NMDA receptor antagonist MK‐801 (dizocilpine maleate; 6.25μg/side) or of NMDA (0.7μg/side), respectively, on classical fear conditioning to tone and context in Wistar rats. Freezing was used to measure conditioned fear. Regardless of whether conditioning was conducted with tone‐shock pairings or unsignaled footshocks (background or foreground contextual conditioning), both NMDA and MK‐801 infusion before conditioning resulted in reduced freezing during subsequent exposure to the conditioning context. Freezing during subsequent tone presentation in a new context, normally resulting from conditioning with tone‐shock pairings, was not impaired by MK‐801 but was strongly reduced by NMDA infusion before conditioning; this freezing was also reduced by NMDA infusion before tone presentation (in an experiment involving NMDA infusions before conditioning and subsequent tone presentation to assess the role of state‐dependent learning). It was assessed whether unspecific infusion effects (altered sensorimotor functions, state dependency) or infusion‐induced dorsal hippocampal damage contributed to the observed reductions in conditioned freezing. Our data suggest that formation of fear conditioning to context, but not tone, requires NMDA receptor‐mediated mechanisms in the dorsal hippocampus. As indicated by the effects of NMDA, some dorsal hippocampal processes may also contribute to fear conditioning to tone. The role of the dorsal hippocampus and local NMDA receptor‐mediated processes in fear conditioning to tone and context is discussed in comparison with ventral hippocampal processes. © 2003 Wiley‐Liss, Inc.
Dynamically detuned oscillations account for the coupled rate and temporal code of place cell firing
Authors: Lengyel Máté , Szatmáry Zoltán , Érdi Péter 
Published: August 2003

AbstractFiring of place cells in the exploring rat conveys doubly coded spatial information: both the rate of spikes and their timing relative to the phase of the ongoing field theta oscillation are correlated with the location of the animal. Specifically, the firing rate of a place cell waxes and wanes, while the timing of spikes precesses monotonically as the animal traverses the portion of the environment preferred by the cell. We propose a mechanism for the generation of this firing pattern that can be applied for place cells in all three hippocampal subfields and that encodes spatial information in the output of the cell without relying on topographical connections or topographical input. A single pyramidal cell was modeled so that the cell received rhythmic inhibition in phase with theta field potential oscillation on the soma and was excited on the dendrite with input depending on the speed of the rat. The dendrite sustained an intrinsic membrane potential oscillation, frequency modulated by its input. Firing probability of the cell was determined jointly by somatic and dendritic oscillations. Results were obtained on different levels of abstraction: a purely analytical derivation was arrived at, corroborated by numerical simulations of rate neurons, and an extension of these simulations to spiking neurons was also performed. Realistic patterns of rate and temporal coding emerged and were found to be inseparable. These results may have implications on the robustness of information coding in place cell firing and on the ways information is processed in structures downstream to the hippocampus. © 2003 Wiley‐Liss, Inc.
Comparison of commissural sprouting in the mouse and rat fascia dentata after entorhinal cortex lesion
Authors: Del Turco Domenico , Woods Alisa G. , Gebhardt Carl , Phinney Amie L. , Jucker Mathias , Frotscher Michael , Deller Thomas 
Published: August 2003

AbstractReactive axonal sprouting occurs in the fascia dentata after entorhinal cortex lesion. This sprouting process has been described extensively in the rat, and plasticity‐associated molecules have been identified that might be involved in its regulation. To demonstrate causal relationships between these candidate molecules and the axonal reorganization process, it is reasonable to analyze knockout and transgenic animals after entorhinal cortex lesion, and because gene knockouts are primarily generated in mice, it is necessary to characterize the sprouting response after entorhinal cortex lesion in this species. In the present study, Phaseolus vulgaris‐leucoagglutinin (PHAL) tracing was used to analyze the commissural projection to the inner molecular layer in mice with longstanding entorhinal lesions. Because the commissural projection to the fascia dentata is neurochemically heterogeneous, PHAL tracing was combined with immunocytochemistry for calretinin, a marker for commissural/associational mossy cell axons. Using both techniques singly as well as in combination (double‐immunofluorescence) at the light or electron microscopic level, it could be shown that in response to entorhinal lesion mossy cell axons leave the main commissural fiber plexus, invade the denervated middle molecular layer, and form asymmetric synapses within the denervated zone. Thus, the commissural sprouting response in mice has a considerable translaminar component. This is in contrast to the layer‐specific commissural sprouting observed in rats, in which the overwhelming majority of mossy cell axons remain within their home territory. These data demonstrate an important species difference in the commissural/associational sprouting response between rats and mice that needs to be taken into account in future studies. © 2003 Wiley‐Liss, Inc.
Changes in hippocampal histamine receptors across the hibernation cycle in ground squirrels
Authors: Sallmen Tina , Lozada Adrian F. , Anichtchik Oleg V. , Beckman Alexander L. , Leurs Rob , Panula Pertti 
Published: August 2003

AbstractHibernation is a physiological state characterized by a dramatic reduction in various functions, such as body temperature, heart rate, and metabolism. The hippocampus is thought to be important for regulation of the hibernation bout because it remains electrophysiologically active throughout this extremely depressed state. The question arises as to what neuronal influences act within the hippocampus during hibernation to sustain its activity. We hypothesized that histaminergic input might be an important contributor. Brain histamine is involved in functions relevant to hibernation, such as the regulation of diurnal rhythms, body temperature, and energy metabolism. Furthermore, we have previously shown that the histaminergic system appears to be activated during the hibernating state. In this study, we used receptor binding autoradiography, in situ hybridization, and GTP‐γ‐S binding autoradiography to study changes in histamine receptors across the hibernation bout. We were able to demonstrate an increase in histamine H1 and H2 receptors in the hippocampus during hibernation, whereas the mRNA expression and receptor density of the inhibitory H3 receptor decreased. Histamine H3 receptors were shown to exhibit both histamine‐activated and constitutive GTP‐γ‐S‐binding activity in the ground squirrel hippocampus, both of which decreased during hibernation, indicating a decrease in H3 receptor G‐protein activation. Taken together, our results indicate that histamine may be involved in maintaining hibernation by sustaining hippocampal activity, possibly through H1 and H2 receptor activity and decreased inhibition by H3 receptors. The involvement of brain histamine, which is generally thought of as an arousal molecule, in maintaining a depressed state of the brain suggests a more general role for the amine in controlling arousal state. © 2003 Wiley‐Liss, Inc.
Electrophysiological and morphological diversity of neurons from the rat subicular complex in vitro
Authors: Menendez de la Prida L. , Suarez F. , Pozo M.A. 
Published: August 2003

AbstractWe combined whole‐cell recordings with Neurobiotin labeling to examine the electrophysiological and morphological properties of neurons from the ventral subicular complex in vitro (including the subicular, presubicular, and parasubicular areas). No a priori morphological sampling criteria were used to select cells. Cells were classified as bursting (IB), regular‐spiking (RS), and fast‐spiking (FS) according to their firing patterns in response to depolarizing current pulses. A number of cells remained unclassified. We found 54% RS, 26% IB, 11% FS, and 9% unclassified cells out of a total of 131 neurons examined. We also found cells showing intrinsic membrane potential oscillations (MPO) (6%), which represented a subgroup of the unclassified cells. We analyzed several electrophysiological parameters and found that RS and IB cells can be subclassified into two separate subgroups. RS cells were subclassified as tonic and adapting, according to the degree of firing adaptation. Both responded with single spikes to orthodromic stimulation. IB cells were subclassified in two subgroups according to their capacity to fire more than one burst, and showed different responses to orthodromic stimulation. We observed that bursting in these two subgroups appeared to involve both Ca2+ and persistent Na+ components. Both IB and RS cells, as well as MPO neurons, were projecting cells. FS cells were morphologically identified as local circuit interneurons. We also analyzed the spatial distribution of these cell types from the vicinity of CA1 to the parasubicular areas. We conclude that, in contrast to the commonly accepted idea of the subicular complex as a bursting structure, there is a wide electrophysiological variability even within a given cellular group. © 2003 Wiley‐Liss, Inc.
Reelin‐expressing neurons in the postnatal and adult human hippocampal formation
Authors: Abraham Hajnalka , Meyer Gundela 
Published: August 2003

AbstractReelin plays a major role in the development of laminated brain structures. In the developing neocortex and hippocampus, Reelin is secreted by Cajal‐Retzius cells in the marginal zone. In the present report, we characterize Reelin‐immunoreactive neurons in the perinatal and adult human hippocampal formation. Two main populations of cells are described: Cajal‐Retzius cells and interneurons. Cajal‐Retzius cells are defined as neurons that coexpress Reelin and p73, a nuclear protein of the p53 family. Colocalization experiments of p73 with calcium‐binding proteins indicate that most Cajal‐Retzius cells express calretinin, but not calbindin. Cajal‐Retzius cell density decreases dramatically during the postnatal period, although a few Reelin/p73‐positive neurons are still found in the adult. At birth, Reelin‐positive, p73‐negative neurons are present in all layers of the hippocampal formation. Their morphology and localization indicate that they belong to a heterogeneous population of interneurons. They are numerous in the strata lacunosum‐moleculare and radiatum of CA1‐CA3, in the hilus, and in the molecular layer of the dentate gyrus, but less common in stratum oriens and alveus, and rare in the principal cell layers. Subpopulations of Reelin‐positive interneurons express calretinin or calbindin. The packing density of Reelin‐positive cells decreases postnatally, which may be related to the disappearance of Cajal‐Retzius cells and to the growth of the hippocampal formation. The presence of Reelin‐immunoreactive cells in the adult hippocampal formation indicates that Reelin is not restricted to development but that it may have additional functions in adult life. © 2003 Wiley‐Liss, Inc.
Entorhinal inputs to dentate gyrus are activated mainly by conditioned events with long time intervals
Authors: Talnov Arkadiy N. , Quiroga Rodrigo Quian , Meier Martin , Matsumoto Gen , Brankačk Jurij 
Published: August 2003

AbstractBrain mechanisms of mammalian learning and memory have long been associated with the hippocampus. Although the role of the hippocampus in spatial behavior is well established, there is no general consensus on the function of the hippocampus in nonspatial tasks. Task‐related changes in evoked potentials were first reported by Deadwyler and colleagues in the dentate gyrus, with a peak at 100 ms in rats trained in an auditory discrimination task (Deadwyler et al., Brain Res 161:211–225, 1979). Surprisingly, these results have not been confirmed by other investigators. In the present report, we set out to assess the task parameters that induce, modulate, and suppress this potential. Using multielectrode probes and current source density analysis, we monitored the entorhinal input to the dentate gyrus in behaving rats. Both differential and simple auditory conditioning led to the appearance of a large negative potential at 100 ms in the perforant path zone of the dentate gyrus. This negativity was found in averaged and in single‐trial, evoked potentials. Current source density analysis revealed sinks in the perforant path zone of the molecular layer of the dentate gyrus with corresponding sources in the hilus. Once trained for differential conditioning, decrements of target probability consistently increased the amplitude of this negativity. When using a single‐tone, stimulus‐response task, the negative potential occurred with long (70‐s), but not with short (10‐s) intertrial intervals. Appearance of the potential coincided with a switch in response strategy and disappeared under stereotypical behavior. These data are best explained under the assumption that long intertrial intervals lead to transitions in task‐related reference frames enabling a switch to more appropriate response strategies. Such transitions are not required during short interval stereotyped performance. © 2003 Wiley‐Liss, Inc.
Subsurface topography to enhance the prediction of the spatial distribution of soil wetness
Authors: Chaplot V. , Walter C. 
Published: August 2003

AbstractThe estimation of the spatial distribution of soil wetness within a catchment is one of the most important issues in hydrological and erosion modelling. So far, such models have been based on soil surface topographic information only. However, soil hydrology is also controlled by subsurface flow pathways that may not be explained only by surface terrain features. This study examined how the topography of the lower limit of the soil cover could improve quantitative modelling for the spatial prediction of soil wetness. The study was conducted in an agricultural catchment of the Armorican Massif (western France) characterized by impermeable granitic saprolites. Two digital elevation models (DEMs) with a 10‐m grid mesh and with a 0·3 m vertical resolution were generated from field investigations throughout the catchment. One DEM was a numerical representation of the soil surface and the other described the topography of the boundary between the soil cover and the underlying impermeable saprolite. Soil wetness (θ) was surveyed systematically from 1996 to 1997 along a hillslope. The sampling scheme consisted of 149 nodes of a 10‐m grid where θ at 0–10 cm was estimated using time‐domain reflectometry. The value of θ at depths of 20–30, 50–60 and 110–120 cm was estimated for a subset of 112 data points using a gravimetric method. For both surface and subsurface DEMs, soil wetness at all depths significantly correlated with the topographic attributes, namely the distance to the stream bank, the elevation above the stream bank (E), the downslope gradient, the revised compound topographic index (CTI), and the specific monodirectional and multidirectional catchment areas. The best correlations were observed between θ10 of winter 1996 and the physically based attributes E and CTI estimated by using the subsurface DEM (r = 0·83 and 0·86, respectively). Two multiple non‐linear regression models for θ10 spatial prediction were generated using non‐autocorrelated topographic attributes estimated from both surface and subsurface topography. Model validation using a new set of 41 data points showed root mean square errors (RMSE) lower than 10% of the θ10 range. The model based on subsurface topography decreased RMSE by 43%. Prediction errors were not spatially distributed. Finally, theses results are discussed in respect of processes involved in hillslope hydrology. Copyright © 2003 John Wiley & Sons, Ltd.