bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reference‐free unwarping of EPI data using dynamic off‐resonance correction with multiecho acquisition (DOCMA)
Authors: Visser Eelke , Poser Benedikt A. , Barth Markus , Zwiers Marcel P. 
Published: January 2012

AbstractInhomogeneities of the main magnetic field cause geometric distortion in echo‐planar imaging, a method central to functional MRI. A number of correction methods have been proposed, most of which are based on the acquisition of a fieldmap providing the local offsets to the main magnetic field. Here, accelerated multiecho echo‐planar imaging is used, with echo times short enough to enable the construction of a fieldmap of comparable quality from the data themselves. This way, each volume in a time series can be unwarped using a fieldmap obtained from that volume, avoiding volume‐to‐volume field‐motion interactions that invalidate reference data in conventional approaches that use a single, static, fieldmap. The combination of accelerated acquisition with dynamic distortion correction yields volumes with very low distortion at repetition times similar to conventional echo‐planar imaging. The method is applied to data acquired at 3 and 7 T and is shown to effectively correct image geometry. Furthermore, it is shown that dynamic distortion correction yields better temporal signal stability than correction using a static fieldmap in the presence of subject motion. Magn Reson Med 2012. © 2011 Wiley Periodicals, Inc.
The effect of concomitant gradient fields on diffusion tensor imaging
Authors: Baron C. A. , Lebel R. M. , Wilman A. H. , Beaulieu C. 
Published: January 2012

AbstractConcomitant gradient fields are transverse magnetic field components that are necessarily present to satisfy Maxwell's equations when magnetic field gradients are utilized in magnetic resonance imaging. They can have deleterious effects that are more prominent at lower static fields and/or higher gradient strengths. In diffusion tensor imaging schemes that employ large gradients that are not symmetric about a refocusing radiofrequency pulse (unlike Stejskal–Tanner, which is symmetric), concomitant fields may cause phase accrual that could corrupt the diffusion measurement. Theory predicting the error from this dephasing is described and experimentally validated for both Reese twice‐refocused and split gradient single spin‐echo diffusion gradient schemes. Bias in apparent diffusion coefficient values was experimentally found to worsen with distance from isocenter and with increasing duration of gradient asymmetry in both a phantom and in the brain. The amount of error from concomitant gradient fields depends on many variables, including the diffusion gradient pattern, pulse sequence timing, maximum effective gradient amplitude, static magnetic field strength, voxel size, slice distance from isocenter, and partial Fourier fraction. A prospective correction scheme that can reduce concomitant gradient errors is proposed and verified for diffusion imaging. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Reducing the object orientation dependence of susceptibility effects in gradient echo MRI through quantitative susceptibility mapping
Authors: Li Jianqi , Chang Shixin , Liu Tian , Wang Qianfeng , Cui Deqi , Chen Xiaoyue , Jin Moonsoo , Wang Baocheng , Pei Mengchao , Wisnieff Cynthia , Spincemaille Pascal , Zhang Min , Wang Yi 
Published: January 2012

AbstractThis study demonstrates the dependence of non‐local susceptibility effects on object orientation in gradient echo MRI and the reduction of non‐local effects by deconvolution using quantitative susceptibility mapping. Imaging experiments were performed on a 3T MRI system using a spoiled 3D multi‐echo GRE sequence on phantoms of known susceptibilities, and on human brains of healthy subjects and patients with intracerebral hemorrhages. Magnetic field measurements were determined from multiple echo phase data. To determine the quantitative susceptibility mapping, these field measurements were deconvolved through a dipole inversion kernel under a constraint of consistency with the magnitude images. Phantom and human data demonstrated that the hypointense region in GRE magnitude image corresponding to a susceptibility source increased in volume with TE and varied with the source orientation. The induced magnetic field extended beyond the susceptibility source and varied with its orientation. In quantitative susceptibility mapping, these blooming artifacts, including their dependence on object orientation, were reduced, and the material susceptibilities were quantified. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
Myocardial T2 mapping with respiratory navigator and automatic nonrigid motion correction
Authors: Giri Shivraman , Shah Saurabh , Xue Hui , Chung Yiu‐Cho , Pennell Michael L. , Guehring Jens , Zuehlsdorff Sven , Raman Subha V. , Simonetti Orlando P. 
Published: January 2012

AbstractQuantitative T2 mapping was recently shown to be superior to T2‐weighted imaging in detecting T2 changes across myocardium. Pixel‐wise T2 mapping is sensitive to misregistration between the images used to generate the parameter map. In this study, utility of two motion‐compensation strategies—(i) navigator gating with prospective slice correction and (ii) nonrigid registration—was investigated for myocardial T2 mapping in short axis and horizontal long axis views. Navigator gating provides respiratory motion compensation, whereas registration corrects for residual cardiac and respiratory motion between images; thus, the two strategies provided complementary functions. When these were combined, respiratory‐motion‐induced T2 variability, as measured by both standard deviation and interquartile range, was comparable to that in breath‐hold T2 maps. In normal subjects, this combined motion‐compensation strategy increased the percentage of myocardium with T2 measured to be within normal range from 60.1% to 92.2% in short axis and 62.3% to 92.7% in horizontal long axis. The new motion‐compensated T2 mapping technique, which combines navigator gating, prospective slice correction, and nonrigid registration to provide through‐plane and in‐plane motion correction, enables a method for fully automatic and robust free‐breathing T2 mapping. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
Effects of school‐wide positive behavior support on teacher self‐efficacy
Authors: Kelm Joanna L. , McIntosh Kent 
Published: January 2012

AbstractThis study examined the relationships between implementation of a school‐wide approach to behavior, School‐wide Positive Behavior Support (SWPBS), and teacher self‐efficacy. Twenty‐two teachers from schools implementing SWPBS and 40 teachers from schools not implementing SWPBS completed a questionnaire measuring aspects of self‐efficacy. Differences in ratings of self‐efficacy were examined using multilevel modeling. Results showed that teachers at SWPBS schools reported significantly higher perceptions of teacher self‐efficacy when controlling for school‐level effects. Results are discussed in terms of implications for future research and practice. © 2011 Wiley Periodicals, Inc.
A meta‐analysis of school‐wide positive behavior support: An exploratory study using single‐case synthesis
Authors: Solomon Benjamin G. , Klein Suzanne A. , Hintze John M. , Cressey James M. , Peller Sarah L. 
Published: January 2012

AbstractPositive Behavior Support (PBS) for behavioral problems was included in the 1997 Individuals With Disabilities Education Act reauthorization, reflecting the increased implementation and strengthening empirical evidence for PBS in schools. Whereas PBS can be used reactively, its flexibility has led to a popular comprehensive school‐wide model used for prevention. School‐Wide Positive Behavioral Support (SWPBS) has been used across a variety of school environments and various demographics and has been evaluated using a variety of different outcome measures. The authors conducted a meta‐analysis of SWPBS research spanning 16 years and 20 articles. Specifically, single‐case studies were evaluated using a regression‐based procedure. Results show promising early trends in the data across dependent variables with a need for further research in specific areas. © 2011 Wiley Periodicals, Inc.
Anion effects on the phase transition ofN‐isopropylacrylamide hydrogels
Authors: Pastoor Kevin J. , Rice Charles V. 
Published: January 2012

AbstractNMR spectra were collected for poly(N‐isopropylacrylamide) (PNIPAAm) hydrogel using high‐resolution magic angle spinning (HRMAS) after gel pieces were hydrated in the presence of D2O, NaF, NaCl, and NaI aqueous solutions. Changes in the peak height intensity of the spectra provide quantitative insight into the phase transition process. The thermodynamic values of the phase transition were calculated using a van't Hoff analysis of the NMR data. Unlike the trend observed for decreases in the (LCST), changes in the enthalpy and entropy did not clearly display a linear dependence with respect to salt concentration. Rather, it was observed that increases in salt concentration did not affect the enthalpy and entropy to the extent as the initial change observed between no salt and 100 mM solutions. Finally, the effect of salts on the hysteresis of the rehydrating process was observed. Hysteresis occurs due to the need for hydrophobic interactions to break down before water is able to infiltrate the polymer matrix. NaF stabilizes hydrophobic interactions while NaI destabilize hydrophobic interactions, causing them to break down at higher temperatures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Effects of weather‐related episodic events in lakes: an analysis based on high‐frequency data
Authors: JENNINGS ELEANOR , JONES STUART , ARVOLA LAURI , STAEHR PETER A. , GAISER EVELYN , JONES IAN D. , WEATHERS KATHLEEN C. , WEYHENMEYER GESA A. , CHIU CHIH‐YU , DE EYTO ELVIRA 
Published: January 2012

Summary1. Weather‐related episodic events are typically unpredictable, and their duration is often short. Abiotic and biological responses are often missed in routine monitoring. These responses are, however, now of particular relevance given projected changes in extreme weather conditions.2. We present data from high‐frequency monitoring stations from lakes in Europe, North America and Asia that illustrate two classes of abiotic effects of weather events: (i) generally short‐lived effects of storms on lake thermal structure and (ii) the more prolonged effects of high rainfall events on dissolved organic matter levels and water clarity. We further relate these abiotic effects to changes in dissolved oxygen or in chlorophyll a levels.3. Three differing causes for weather‐related decreases in surface dissolved oxygen levels were observed: (i) entrainment of anoxic water from depth, (ii) reduction in primary productivity and (iii) increased mineralisation of organic carbon delivered from the catchment.4. The duration of in‐lake effects tended to be longer for events driven by weather conditions with a longer return period, that is, conditions that were relatively more severe and less frequent at a site. While the susceptibility of lakes to change was related in part to the severity of the meteorological drivers, the impacts also depended on site‐specific factors in some cases.5. The availability of high‐frequency data at these sites provided insight into the capacity of the lakes to absorb current and future pressures. Several of the changes we observed, including increases in carbon availability, decreases in photosynthetically active radiation and increased disturbance, have the capacity to shift lakes towards an increased degree of heterotrophy. The magnitude and direction of any such change will, however, also depend on the magnitude and direction of climate change for a given location and on lake and catchment characteristics.
Hydraulic conductivity traits predict growth rates and adult stature of 40 Asian tropical tree species better than wood density
Authors: Fan Ze‐Xin , Zhang Shi‐Bao , Hao Guang‐You , Ferry Slik J.W. , Cao Kun‐Fang 
Published: January 2012

Summary1. Stem xylem characteristics have a great impact on growth and adult stature of trees because of their role in mechanical support, long‐distance water transport and whole‐plant carbon allocation. Yet, despite the potential causal link between xylem traits and plant growth/adult stature, most studies have tried to link wood density, an indirect but easy to measure proxy for wood properties, to tree growth and size.2. To determine whether xylem traits outperform wood density as predictors of tree growth and stature, we evaluated the covariation among wood density, xylem anatomical traits, tree diameter growth rate and adult stature in 40 Asian tropical tree species through principal component analyses and through bivariate correlation, both across species and across phylogenetically independent contrasts.3. Vessel diameter exhibited a tight negative relationship with vessel frequency. Wood density showed a significant correlation with vessel diameter and density, but not with vessel fraction. Most correlations between functional traits indicate adaptive coordination, demonstrated by significant correlations between phylogenetically independent contrasts.4. Across species, diameter growth rate and adult stature were positively correlated with vessel lumen diameter and potential hydraulic conductivity, but not with wood density. Thus, our results suggest that xylem anatomical traits that are linked to hydraulic conductivity are better predictors of tree growth rate and adult stature than wood density.5. Synthesis. We found that xylem anatomical traits have a more significant influence on whole‐plant performance due to their direct association with stem hydraulic conductivity, whereas wood density is decoupled from hydraulic function due to complex variations in xylem components.
The Behavior Problems Inventory‐Short Form for individuals with intellectual disabilities: Part II: reliability and validity
Authors: Rojahn J. , Rowe E. W. , Sharber A. C. , Hastings R. , Matson J. L. , Didden R. , Kroes D. B. H. , Dumont E. L. M. 
Published: January 2012

AbstractBackground  The Behavior Problems Inventory‐01 (BPI‐01) is an informant‐based behaviour rating instrument for intellectual disabilities (ID) with 49 items and three sub‐scales: Self‐injurious Behavior, Stereotyped Behavior and Aggressive/Destructive Behavior. The Behavior Problems Inventory‐Short Form (BPI‐S) is a BPI‐01 spin‐off with 30 items.Methods  The psychometric properties of these two versions of the scale were computed using aggregated archival data from nine different sites in the USA, Wales, England, the Netherlands and Romania with a total of 1122 cases with a BPI‐01 total score >0.Results  The internal consistency of the BPI‐01 and the BPI‐S ranged from fair to excellent with the BPI‐01 showing slightly stronger reliability. Construct validity (confirmatory and discriminant) was computed by comparing BPI sub‐scale scores with the scores of four other behaviour rating scales (the Aberrant Behavior Checklist, the Diagnostic Assessment for the Severely Handicapped‐II, the Nisonger Child Behavior Rating Form and the Inventory for Client and Agency Planning). Strong evidence for confirmatory and discriminant validity was found for both the BPI‐01 and the BPI‐S. Confirmatory fit indices for the BPI and the BPI‐S were comparable and suggesting that the factor structures fit the data well.Conclusion  In summary, both BPI versions were found to be equally sound psychometrically and can be endorsed for future use. However, independent future studies are needed to replicate the psychometrics of the BPI‐S with new data.
Schizophrenia as variation in the sapiens‐specific epigenetic instruction to the embryo
Authors: Crow TJ 
Published: January 2012

Crow TJ. Schizophrenia as variation in the sapiens‐specific epigenetic instruction to the embryo.The psychoses (schizophrenia and bipolar disorder) occur in all populations with approximately uniform incidence and sex‐dependent age of onset. Core symptoms involve aspects of language; brain structural deviations are sex and hemisphere‐related. Genetic predisposition is unaccounted for by linkage or association. The hypothesis is proposed that the ‘missing heritability’ is epigenetic in form and generated in meiosis on a species‐specific XY chromosomal template. A duplication from Xq21.3 to Yp11.2 that occurred 6 million years ago is proposed as critical to hominin evolution. Within this block of homology the Protocadherin11XY gene pair is expressed as a cell surface adhesion factor in both X and Y forms; it has undergone a series of coding changes (16 in the Y sequence and 5 in the X including two to cysteines) in the hominin lineage. According to the hypothesis these sequence changes, together with one or more deletions and a paracentric inversion in the Y block, were successively selected; late events in this series established cerebral asymmetry (the ‘torque’) as the defining characteristic of the human brain. Built around this reference frame, an epigenetic message channels early development of the embryo in a sapiens‐specific format. Diversity in meiotic pairing is postulated as the basis for species‐specific deviations in development associated with psychosis.
Song Amplitude of Rival Males Modulates the Territorial Behaviour of Great Tits During the Fertile Period of Their Mates
Authors: Ritschard Mathias , van Oers Kees , Naguib Marc , Brumm Henrik 
Published: January 2012

AbstractBird song is a widely used model in the study of sexual selection. Variation in the expression of sexually selected traits is thought to reflect variation in male genetic and/or phenotypic quality. Vocal amplitude is a song parameter that has received little attention in the context of sexual selection, but there is some evidence that the intensity of bird song affects female preferences. Here, we tested whether the amplitude of broadcast song plays a role in male–male competition. We used song playback with varying song amplitude (within the natural amplitude range of the species) and a dummy bird taxidermy to simulate territorial intrusions in the great tit, Parus major, during the fertile period of the female and measured the response of the local male. The results show that playback amplitude significantly affected the subjects’ behaviour: after approaching to within 25 m around the loudspeaker, territorial males stayed longer within that perimeter after the playback of high‐amplitude songs compared with low‐amplitude songs. Our findings add to the small but growing body of evidence suggesting that vocal amplitude may be a sexually selected song trait.
Carbohydrate Dynamics in Leaves of Rapeseed (Brassica napus) Under Drought
Authors: Müller T. , Lentzsch P. , Müller M. E. H. 
Published: January 2012

AbstractUntil now, the carbohydrate dynamics in leaves of rapeseed under drought have largely been unknown. For this reason, a growth chamber study was conducted to examine whether the accumulation of carbohydrates under drought stress contributes to osmotic adjustment in leaf tissue. Plants of the cultivar Titan were subjected to temporary drought in the vegetative and reproductive stages. A third variant of long‐term drought covered the period from leaf development to flowering. The level of sucrose decreased under moderate water deficit, but accumulated under severe long‐term drought. Concentrations of glucose, fructose and trehalose were significantly enhanced and that of raffinose decreased in all the variants of drought. There was no evidence that any of the carbohydrates analysed in this study or the activities of soluble acid and cell wall invertases contributed to a drought‐induced accumulation of osmolytes. The results of this study indicate that osmotic adjustment in response to drought in leaves of the rapeseed cultivar Titan is only limited. It is virtually impossible that carbohydrates function as osmoprotectants in leaves of this cultivar, rising above that of the frequently detected accumulation of proline in rapeseed under water deficit.
Genetic influence on disease spread following arrival of infected carriers
Authors: Fellous Simon , Duncan Alison B. , Quillery Elsa , Vale Pedro F. , Kaltz Oliver 
Published: January 2012

Ecology Letters (2012)AbstractEpidemiology in host meta‐populations depends on parasite ability to disperse between, establish and persist in distinct sub‐populations of hosts. We studied the genetic factors determining the short‐term establishment, and long‐term maintenance, of pathogens introduced by infected hosts (i.e. carriers) into recipient populations. We used experimental populations of the freshwater ciliate Paramecium caudatum and its bacterial parasite Holospora undulata. Parasite short‐term spread (approximately one horizontal transmission cycle) was affected mainly by carrier genotype, and its interactions with parasite and recipient genotypes. By contrast, parasite longer term spread (2–3 horizontal transmission cycles) was mostly determined by parasite isolate. Importantly, measures of parasite short‐term success (reproductive number, R) were not good predictors for longer term prevalence, probably because of the specific interactions between host and parasite genotypes. Analogous to variation in vectorial capacity and super‐spreader occurrence, two crucial components of epidemiology, we show that carrier genotype can also affect disease spread within meta‐populations.
Dispersal‐mediated trophic interactions can generate apparent patterns of dispersal limitation in aquatic metacommunities
Authors: Verreydt Dino , De Meester Luc , Decaestecker Ellen , Villena María‐José , Van Der Gucht Katleen , Vannormelingen Pieter , Vyverman Wim , Declerck Steven A.J. 
Published: January 2012

Ecology Letters (2012)AbstractDispersal is a major organising force in metacommunities, which may facilitate compositional responses of local communities to environmental change and affect ecosystem function. Organism groups differ widely in their dispersal abilities and their communities are therefore expected to have different adaptive abilities. In mesocosms, we studied the simultaneous compositional response of three plankton communities (zoo‐, phyto‐ and bacterioplankton) to a primary productivity gradient and evaluated how this response was mediated by dispersal intensity. Dispersal enhanced responses in all three planktonic groups, which also affected ecosystem functioning. Yet, variation partitioning analyses indicated that responses in phytoplankton and bacterial communities were not only controlled by dispersal directly but also indirectly through complex trophic interactions. Our results indicate that metacommunity patterns emerging from dispersal can cascade through the food web and generate patterns of apparent dispersal limitation in organisms at other trophic levels.
The Impact of Labour Market Reforms and Economic Performance on the Matching of the Short‐term and the Long‐term Unemployed
Authors: Klinger Sabine , Rothe Thomas 
Published: January 2012

AbstractAs a reaction to high and persistent unemployment in Germany, the largest labour market reforms in post‐war history were implemented between 2003 and 2005. We analyse the impact of the reforms and its coincidence with an economic expansion on the efficiency of matching out of unemployment. Especially focussing on searcher heterogeneity, we estimate a system of stock‐flow matching functions for short‐term and long‐term unemployment (three‐stage least squares) on the basis of administrative data. In sum, the reforms increased matching efficiency for both groups, but the effect was larger for the long‐term unemployed. The interaction of reforms and economic expansion, however, was not influential.