bluuebunny/crossref_metadata_2025_split huggingface dataset:
Firing with Multiple‐Spike Discharges in the Slowly Adapting Stretch Receptor Neuron of the Lobster
Authors: Gramp Wolfgang 
Published: November 2009

AbstractThe phenomenon of firing with multiple‐spike discharges in the slowly adapting nerve cell of the isolated abdominal stretch receptor organ of the lobster (Homarus gammarus) was studied. All cells investigated fired with single action potentials at temperatures below, but with multiple‐spike discharges at temperatures above a critical value which being different for different cells usually occurred above 20d̀ C. In all cells the number of the impulses making up the multiple‐spike discharges increased with rising, and decreased with falling temperature. In most cases at any constant temperature the spike number of the discharges could be increased by relaxing, and decreased by stretching the receptor muscle; in a few cells the contrary was the case. The initiation of the extra spikes took place during the course of three different types of after‐depolarizations which succeeded the first and, sometimes, a number of the subsequent impulses of the multiple‐spike discharges. From its reproducibility and reversibility it is concluded that the phenomenon of firing with multiple‐spike discharges reflects a (reversible) modification of the cell's excitatory state due to changes of the conditions of the external milieu.
Geochemistry of K‐feldspar and Muscovite in Rare‐element Pegmatites and Granites from the Totoral Pegmatite Field, San Luis, Argentina
Authors: Oyarzábal Julio , Galliski Miguel Ángel , Perino Ernesto 
Published: November 2009

AbstractThe geochemistry of K‐feldspar for K, P, Sr, Ba, Rb, Cs, Ga, and of muscovite for the same elements plus Nb and Ta, was used for proving the parental relationships of S‐type granites and LCT (Li, Cs, Ta) rare‐element pegmatites in the southernmost pegmatitic field of the Pampean pegmatite province in Argentina. The variation of K/Rb‐Cs, K/Cs‐Rb, K/Rb‐Rb/Sr, K/Rb‐Ba in K‐feldspar from the granites and pegmatites show that they form an association with the evolutional sequence: granites → barren‐ to transitional pegmatites → beryl type, beryl‐columbite‐phosphate pegmatites → complex type of spodumene subtype pegmatites → albite‐spodumene type → albite type pegmatites. This sequence reflects the regional distribution of the different magmatic units. The Ta‐Cs diagram for muscovite reveals that none of the studied pegmatites exceed the threshold established in previous studies for being considered with important tantalum oxide mineralization. The granites and pegmatites constitute a rare‐element pegmatitic field in which different magmatic units form a continuous fractionation trend, extended from the less evolved granitic facies to the most geochemically specialized pegmatites
Samarium–Neodymium and Rubidium–Strontium Isotopic Dating of Veined REE Mineralization for the Bayan Obo REE‐Nb‐Fe Deposit, Northern China
Authors: Hu Fang‐Fang , Fan Hong‐Rui , Liu Shuang , Yang Kui‐Feng , Chen Fukun 
Published: November 2009

AbstractThe Bayan Obo REE‐Nb‐Fe deposit in Inner Mongolia, China, consists of later REE‐mineralizing fluorocarbonate veins cutting the earlier banded and massive ores in the deposit. Samarium–neodymium dating using the minerals including huanghoite and rubidium–strontium dating using single‐grain biotites both from the later veins show concordant isochrons corresponding to 442 ± 42 Ma (2σ uncertainty) and 459 ± 41 Ma, respectively. The isochron ages suggest that the later REE vein mineralization took place during the middle Paleozoic at Bayan Obo, consistent with geological observations and age data previously reported.
Environmental factors associated with reproductive barrier breakdown in sympatric trout populations on Vancouver Island
Authors: Heath Daniel , Bettles Cory M. , Roff Derek 
Published: November 2009

AbstractThe incidence of hybridization between coastal cutthroat (Oncorhynchus clarki clarki) and rainbow trout (Oncorhynchus mykiss) varies widely among populations. The breakdown of reproductive isolation is of concern to managers, and raises the question: how have the two species retained their genetic and morphological divergence? Using a combination of mitochondrial DNA and nuclear DNA markers coupled with watershed attribute and disturbance data, we determined the distribution and frequency of trout hybridization on Vancouver Island, BC and the environmental factors associated with the hybridization. We found 284 hybrids (among 1004 fish) in 29 of 36 sampled populations. High variation in levels of hybridization was observed among populations, and no single environmental factor was found to dominate in determining hybridization levels. However, logging activity, urban infrastructure development, and stocking of hatchery rainbow trout played significant roles in determining hybridization levels, and populations in small watersheds are more at risk of reproductive barrier breakdown. This study illustrates that cutthroat–rainbow trout reproductive barrier breakdown is widespread on Vancouver Island and that anthropogenic disturbance plays a role in the process. As similar environmental disturbance is common in much of coastal trout habitat, large‐scale hybridization may be occurring elsewhere and thus may represent a critical management issue for Pacific trout species.
‘Lord God! Jesus! What a House!’: Describing and Visiting Strawberry Hill
Authors: CLARKE STEPHEN 
Published: November 2009

AbstractThis paper analyses the transmission of the text of Horace Walpole's Description of Strawberry Hill from the printing of its first component in 1760 to its last appendix in 1791 and beyond. It uses Walpole's copious manuscript amendments in a number of copies to consider the purpose of the book in the context both of the steady stream of visitors to Walpole's collection at Strawberry Hill and of Walpole's passionate engagement in recording that ever‐expanding collection. It also discusses a number of unrecorded examples of printing from Walpole's Strawberry Hill Press, which the research for the paper has revealed.
Overexpression of Alpha2A-Adrenergic Receptors Contributes to Type 2 Diabetes
Authors: Rosengren Anders H. , Jokubka Ramunas , Tojjar Damon , Granhall Charlotte , Hansson Ola , Li Dai-Qing , Nagaraj Vini , Reinbothe Thomas M. , Tuncel Jonatan , Eliasson Lena , Groop Leif , Rorsman Patrik , Salehi Albert , Lyssenko Valeriya , Luthman Holger , Renström Erik 
Published: November 2009

Ratting Out a Diabetes GeneInbred animals with inherited susceptibility to disease can be especially informative regarding pathogenetic mechanisms because they carry naturally occurring genetic variants of the same type that cause disease in humans. This principle is illustrated byRosengrenet al.(p.217; published online 19 November), whose analysis of an inbred strain of rats prone to develop type 2 diabetes led to the discovery of a gene whose aberrant overexpression suppresses pancreatic insulin secretion in both rats and humans. The culprit gene, ADRA2A, encodes the alpha2A adrenergic receptor and is potentially a valuable lead for diabetes therapy because it can be targeted pharmacologically.
Arrestin Orchestrates Crosstalk Between G Protein-Coupled Receptors to Modulate the Spatiotemporal Activation of ERK MAPK
Authors: Cervantes David , Crosby Catherine , Xiang Yang 
Published: November 2009

Rationale:G protein-coupled receptors (GPCRs) respond to diversified extracellular stimuli to modulate cellular function. Despite extensive studies investigating the regulation of single GPCR signaling cascades, the effects of concomitant GPCR activation on downstream signaling and cellular function remain unclear.Objective:We aimed to characterize the cellular mechanism by which GPCR crosstalk regulates mitogen-activated protein kinase (MAPK) activation.Methods and Results:Adrenergic receptors on cardiac fibroblasts were manipulated to examine the role of arrestin in the spatiotemporal regulation of extracellular signal-regulated kinase (ERK)1/2 MAPK signaling. We show a general mechanism in which arrestin activation by one GPCR is capable of regulating signaling originating from another GPCR. Activation of Gq coupled-receptor signaling leads to prolonged ERK1/2 MAPK phosphorylation, nuclear accumulation, and cellular proliferation. Interestingly, coactivation of these receptors with the β-adrenergic receptors induced transient ERK signaling localized within the cytosol, which attenuated cell proliferation. Further studies revealed that recruitment of arrestin3 to the β2-adrenergic receptor orchestrates the sequestration of Gq-coupled receptor-induced ERK to the cytosol through direct binding of ERK to arrestin.Conclusions:This is the first evidence showing that arrestin3 acts as a coordinator to integrate signals from multiple GPCRs. Our studies not only provide a novel mechanism explaining the integration of mitogenic signaling elicited by different GPCRs, but also underscore the critical role of signaling crosstalk among GPCRs in vivo.
Ebbinghaus Revisited: Influences of the BDNF Val66Met Polymorphism on Backward Serial Recall Are Modulated by Human Aging
Authors: Li Shu-Chen , Chicherio Christian , Nyberg Lars , von Oertzen Timo , Nagel Irene E. , Papenberg Goran , Sander Thomas , Heekeren Hauke R. , Lindenberger Ulman , Bäckman Lars 
Published: November 2009

Abstract
The brain-derived neurotrophic factor (BDNF) plays an important role in activity-dependent synaptic plasticity, which underlies learning and memory. In a sample of 948 younger and older adults, we investigated whether a common Val66Met missense polymorphism (rs6265) in the BDNF gene affects the serial position curve—a fundamental phenomenon of associative memory identified by Hermann Ebbinghaus more than a century ago. We found a BDNF polymorphism effect for backward recall in older adults only, with Met-allele carriers (i.e., individuals with reduced BDNF signaling) recalling fewer items than Val homozygotes. This effect was specific to the primacy and middle portions of the serial position curve, where intralist interference and associative demands are especially high. The poorer performance of older Met-allele carriers reflected transposition errors, whereas no genetic effect was found for omissions. These findings indicate that effects of the BDNF polymorphism on episodic memory are most likely to be observed when the associative and executive demands are high. Furthermore, the findings are in line with the hypothesis that the magnitude of genetic effects on cognition is greater when brain resources are reduced, as is the case in old age.
Neural Mechanisms of Context Effects on Face Recognition: Automatic Binding and Context Shift Decrements
Authors: Hayes Scott M. , Baena Elsa , Truong Trong-Kha , Cabeza Roberto 
Published: November 2009

Abstract
Although people do not normally try to remember associations between faces and physical contexts, these associations are established automatically, as indicated by the difficulty of recognizing familiar faces in different contexts (“butcher-on-the-bus” phenomenon). The present fMRI study investigated the automatic binding of faces and scenes. In the face–face (F–F) condition, faces were presented alone during both encoding and retrieval, whereas in the face/scene–face (FS–F) condition, they were presented overlaid on scenes during encoding but alone during retrieval (context change). Although participants were instructed to focus only on the faces during both encoding and retrieval, recognition performance was worse in the FS–F than in the F–F condition (“context shift decrement” [CSD]), confirming automatic face–scene binding during encoding. This binding was mediated by the hippocampus as indicated by greater subsequent memory effects (remembered &gt; forgotten) in this region for the FS–F than the F–F condition. Scene memory was mediated by right parahippocampal cortex, which was reactivated during successful retrieval when the faces were associated with a scene during encoding (FS–F condition). Analyses using the CSD as a regressor yielded a clear hemispheric asymmetry in medial temporal lobe activity during encoding: Left hippocampal and parahippocampal activity was associated with a smaller CSD, indicating more flexible memory representations immune to context changes, whereas right hippocampal/rhinal activity was associated with a larger CSD, indicating less flexible representations sensitive to context change. Taken together, the results clarify the neural mechanisms of context effects on face recognition.
Memory Capacities for Synaptic and Structural Plasticity
Authors: Knoblauch Andreas , Palm Günther , Sommer Friedrich T. 
Published: November 2009

Neural associative networks with plastic synapses have been proposed as computational models of brain functions and also for applications such as pattern recognition and information retrieval. To guide biological models and optimize technical applications, several definitions of memory capacity have been used to measure the efficiency of associative memory. Here we explain why the currently used performance measures bias the comparison between models and cannot serve as a theoretical benchmark. We introduce fair measures for information-theoretic capacity in associative memory that also provide a theoretical benchmark. In neural networks, two types of manipulating synapses can be discerned: synaptic plasticity, the change in strength of existing synapses, and structural plasticity, the creation and pruning of synapses. One of the new types of memory capacity we introduce permits quantifying how structural plasticity can increase the network efficiency by compressing the network structure, for example, by pruning unused synapses. Specifically, we analyze operating regimes in the Willshaw model in which structural plasticity can compress the network structure and push performance to the theoretical benchmark. The amount C of information stored in each synapse can scale with the logarithm of the network size rather than being constant, as in classical Willshaw and Hopfield nets (⩽ ln 2 ≈ 0.7). Further, the review contains novel technical material: a capacity analysis of the Willshaw model that rigorously controls for the level of retrieval quality, an analysis for memories with a nonconstant number of active units (where C ⩽ 1/eln 2 ≈ 0.53), and the analysis of the computational complexity of associative memories with and without network compression.
Development and validation of prognostic models designed to predict wheelchair skills at discharge from spinal cord injury rehabilitation
Authors: de Groot S. , Bevers GE , Dallmeijer AJ , Post MWM , van Kuppevelt HJM , van der Woude LHV 
Published: November 2009

Objective: To develop and validate a statistical model to predict wheelchair skills at discharge (t 2) from personal and lesion characteristics and wheelchair skills at the start of spinal cord injury inpatient rehabilitation (t1). Design: Prospective cohort study Setting: Eight Dutch rehabilitation centres. Subjects: One hundred and forty-two patients with a spinal cord injury. Main measures: Models were developed with the performance time and ability score at t2 as dependent variables and t1 scores of performance time and ability score, age, gender, body mass index, level and completeness of the lesion as independent variables. The statistical models were evaluated by comparing individual estimated scores with actual measured scores. Results: The main independent variables to predict wheelchair skills at discharge were the t1 performance time and ability score, age, gender and lesion level. The intraclass correlation coefficient between the estimated and actual ability score was 0.79 and for the performance time 0.86. However, the 95% limits of agreement and their confidence intervals were relatively wide for both ability score (—2.3 to 3.4, range 0—8) and performance time (—12.5 to 8.2, range 11—40 seconds). Conclusion: The prognostic models developed in this study to predict future wheelchair skills might help planning the course of rehabilitation. The models should be used with caution in daily clinical practice, but may add useful information to clinical expertise and knowledge of the individual patient.
Engineering characteristics of sand-clay mixtures used for clay cores of earth-fill dams
Authors: Gökalp Z. 
Published: November 2009

AbstractClay is the main construction material for clay cores of earth-fill dams. Clay minerals swell when they become wet and shrink when they dry out; cracks develop as they lose moisture. If precautions are not taken to prevent seepage through these cracks, dam failures may result. In this study, sand was added to montmorillonite-dominant clay soils to investigate the effect of sand-inclusion rates on the engineering characteristics of clay soils used in the construction of clay cores of earth-fill dams. Changes in the consistency limits, compaction characteristics, permeability, stress-strain relationships and swelling characteristics with increasing sand inclusion rates were evaluated. Based on the results from experimental trials, a 30% sand inclusion rate appears to be the optimum proportion; most of the swelling occurred in the voids of grains and led to permeability levels below the allowable limits for earth-fill dams.
Impacts of clay mineralogy and physiographic units on the distribution of potassium forms in calcareous soils in Iran
Authors: Rezapour S. , Jafarzadeh A. A. , Samadi A. , Oustan S. 
Published: November 2009

AbstractThe potassium pools of five major physiographic units of the Urmia region situated in western Azerbaijan province, north-west Iran, were studied to determine the distribution of K forms as functions of clay mineralogy and physiographic units. Soil samples from horizons of ten pedons were selected and analysed for physiochemical properties, clay mineralogy and forms of K. X-ray diffraction patterns revealed that the soils were similar in clay-mineral compositions, consisting of illite, smectite, chlorite, and kaolinite, for the different physiographic units, but vary in the relative amounts of these minerals. The illite content was highest in piedmont plain (P.P) followed by plateau (Pl), river alluvial plain (R.A.P), colluvial alluvial plain (C.A.R) and lowland (L.L) units. Smectite content was highest in Pl followed by P.P, L.L, R.A.P and C.A.P units. Several processes, such as the diversity of weathering rate, biocyclying processes of K accumulation, geomorphologic conditions and soil formation processes, caused significant differences in most K forms in the soils. A wide variation in total K (HF-extractable K) (0.54–1.1%), non-exchangeable K (280–450 mg kg–1) and exchangeable K (217–330 mg kg–1) occurred among the physiographic units, corresponding to variations in their mineralogical compositions, mainly the abundance of illite. Significant differences (P⩽ 0.05) were found for K, HNO3-extractable K and non-exchangeable K between the soils with large illite contents (30–50%) and with small illite contents (10–30%). A significant positive relationship existed between mineral K and illite content (r2= 0.85,P⩽ 0.001) and non-exchangeable K and illite content (r2= 0.84,P⩽ 0.001). The results indicated that these pools of K are mainly released from the frayed edges and wedge zones of illite.
Theoretical calculations of [AlO4/M+]0
defects in quartz and crystal-chemical controls on the uptake of Al
Authors: Botis S. M. , Pan Yuanming 
Published: November 2009

Abstract
The
[AlO4/M+]0
(where M = H, Li, Na and K) defects in α-quartz have
been investigated by ab initio calculations at the
density functional theory (DFT) level, using the
CRYSTAL06 code, 72-atom supercells, and all-electron
basis sets. Our DFT calculations yielded substantially improved results than
previous cluster calculations with minimal basis sets. For example, the
[AlO4/M+(a<)]0
defects with M = H, Li and Na have been shown to be
more stable than their
[AlO4/M+(a>)]0
structural analogues (where a> and a< denote the location of the
charge-compensating ion on the long-bond and short-bond side respectively),
correctly predicting the common occurrence of paramagnetic
[AlO4/M+(a>)]+
centres. In addition, the [AlO4/K+]0
defects have been investigated for the first time and are shown to be stable in
quartz. Moreover, our calculations confirm previous
suggestions that incorporation of the
[AlO4/M+]0
defects results in significant structural relaxations that extend at least to the
nearest Si atoms and give Li—O and Na—O bond distances in better agreement with
the experimentally obtained values. The present theoretical results on the
[AlO4/M+]0
defects provide a more complete picture for the coupled
Al3+—M+
substitutions and hence new insights into crystal-chemical controls on the uptake
of Al in quartz.
Oxygen isotope sector zoning in natural hydrothermal quartz
Authors: Jourdan A.-L. , Vennemann T. W. , Mullis J. , Ramseyer K. 
Published: November 2009

Abstract
Oxygen isotope measurements using SIMS and laser-fluorination methods confirm
the presence of concentric and sector zoning in low-temperature (200°C to
<400°C) hydrothermal quartz from Alpine veins. While concentric zoning is most
readily explained by changes in the chemical composition of the fluid or
temperature of crystallization, the reasons for sector zoning are more difficult
to explain. Relative enrichment in 18O for
crystallographically different sectors of quartz corresponds to
m >r
>z. Sector zoning is, however, largely limited to
the exterior zones of crystals and/or to crystals with large Al (>1000 ppm) and
trace element contents, probably formed at temperatures <250°C. Differences in
δ18O between the prismatic (m)
relative to the rhombohedral (r and z) growth sectors of up to 2% can be explained
by a combination of a face-related crystallographic and/or a growth rate control.
In contrast, isotopic sector zoning of up to about 1.5% amongst the different
rhombohedral faces increases in parallel with the trace element content and is
likely to represent disequilibrium growth. This is indicated by non-systematic, up
to 2%, differences within single growth zones and the irregular, larger or
smaller, δ18O values (of several permil) of the exterior
compared to the inner zones of the same crystals. Disequilibrium growth may be
related to the large trace element content incorporated into the growing quartz at
lower temperatures (<250°C) and/or be related to fluid-vapour separation,
allowing crystal growth from both a vapour as well as a liquid phase.