bluuebunny/crossref_metadata_2025_split huggingface dataset:
The transtheoretical model in the context of physical activity in a school‐based sample of German adolescents
Authors: Bucksch Jens , Finne Emily , Kolip Petra 
Published: November 2008

AbstractPhysical activity in adolescents is an important public health issue. Regular participation in physical activity is associated with various health benefits. However, problems with motivational adherence to physical activity have been documented. The transtheoretical model is a model of behaviour change. This model, which consists of stages of change, self‐efficacy, decisional balance, and processes of change, has not been extensively investigated in youth. In addition, the health‐enhancing physical activity concept has rarely been applied in this context.A cross‐sectional design was used. A random sample of seven junior high schools from Bremen (Germany) resulted in a sample of 588 adolescents (50.5% males, mean age=15.0 years, s=0.67). Respondents completed a self‐administered questionnaire assessing stages of change, self‐efficacy, decisional balance, and processes of change. Univariate analyses of variance were used to identify which constructs differed significantly across the stages of change. Discriminant analysis was used to determine which variables best discriminate the stages.Distribution of the sample across the stages was: precontemplation, n=175 (29.8%); contemplation, n=135 (22.0%); preparation, n=63 (10.7%); action, n=20 (3.4%); and maintenance, n=195 (33.2%). Significant effects of stages of change were found for self‐efficacy, pros, and seven of the ten processes of change. In general, scores of these constructs increased across the stages. Cons did not differ significantly across the stages.The results provide support for some of the assumptions of the transtheoretical model in a German sample of adolescents. Some of our findings raise questions about the usefulness of five discrete stages. From a public health viewpoint, tailored interventions based on motivational readiness to change would be fruitful, but further research is warranted.
An acute bout of high‐intensity intermittent swimming induces glycogen supercompensation in rat skeletal muscle
Authors: Sonou Tomohiro , Higuchi Mitsuru , Terada Shin 
Published: November 2008

AbstractHigh‐intensity intermittent exercise substantially increases muscle glucose transport, which is thought to be the rate‐limiting step for glycogen synthesis. In the present study, we compared muscle glycogen supercompensation after high‐intensity intermittent exercise with that observed after low‐intensity continuous exercise in rats. Four‐ to five‐week‐old male Sprague‐Dawley rats performed either low‐intensity swimming (240 min of swimming exercise with a weight equivalent to 1% of their body mass; LOW) or high‐intensity swimming (twenty 30‐s swimming bouts with 30 s rest between bouts with a weight equivalent to 16% of their body mass; HIGH) to deplete muscle glycogen. After the glycogen‐depleting exercise, rats were given a rodent chow diet plus 5% glucose solution for 6 h or 24 h. Immediately after the two types of exercise, glycogen concentration in rat epitrochlearis muscle was similarly depleted. After the 6‐h and 24‐h recovery periods, muscle glycogen concentrations in both the HIGH and LOW groups were restored well above the normally fed state. Furthermore, muscle glycogen accumulation in the HIGH group for the 6‐h and 24‐h recovery periods was not significantly different from that observed in the LOW group. The high‐intensity intermittent swimming exercise also induced muscle glycogen supercompensation in well‐trained rats that had performed 7 days of endurance swimming training (6 h per day). Our results indicate that high‐intensity intermittent exercise as well as low‐intensity continuous exercise could induce glycogen supercompensation in rat skeletal muscle.
Strength, power, and postural control in seniors: Considerations for functional adaptations and for fall prevention
Authors: Granacher Urs , Zahner Lukas , Gollhofer Albert 
Published: November 2008

AbstractThe ageing neuromuscular system is affected by structural and functional changes that lead to a general slowing down of neuromuscular performance and an increased risk of falling. As a consequence, the process of ageing results in a reduced ability to develop maximal and explosive force, as well as in deficits in static and dynamic postural control. A decrease in the number and size of type II fibres in particular accounts for the age‐related decline in muscle mass (sarcopaenia) and strength performance. Multiple denervation and re‐innervation processes of muscle fibres seem to be responsible for the reduced number of muscle fibres. Recently, it has been suggested that it is not the decline in motoneurons that accounts for the loss in number of muscle fibres but the disturbed potential of fibre regeneration and re‐innervation. Furthermore, an age‐related reduction in the number of satellite cells has also been associated with sarcopaenia. The ability to compensate for platform and gait perturbations deteriorates with ageing as reflected in longer onset latencies and inefficient postural responses. All sites within the somatosensory system are affected by ageing and therefore contribute to postural instability. However, morphological changes of muscle spindles appear primarily to be responsible for the impaired ability to compensate for balance threats in old age. Given these neuromuscular limitations in old age, it is important to apply adequate training interventions that delay or even reverse the onset of these constraints. Strength training has the potential to enhance maximal as well as explosive force production capacity. This is accomplished by neural factors, including an improved recruitment pattern, discharge rate, and synchronization of motor units. Furthermore, an increase in number of satellite cells most likely accounts for training‐induced muscle hypertrophy. Recent studies have investigated the impact of balance training in old age on the ability to develop maximal and explosive force. In addition, the effects of balance training on reflex activity during gait perturbations were also examined. Increases in maximal and explosive force production capacity and an improved ability to compensate for gait perturbations were observed. It is evident from the literature that researchers are increasingly studying the effects of more specifically designed training programmes on performance in populations of older adults. Thus, in the near future, strength training could be replaced by high‐velocity forms of power training and balance training by perturbation‐based training programmes. It is hypothesized that this new approach is more efficient in terms of fall prevention than the traditional approach.
An update on the big bang nucleosynthesis prediction for
7Li: the problem worsens
Authors: Cyburt Richard H , Fields Brian D , Olive Keith A 
Published: November 2008

The lithium problem arises from the significant discrepancy between the primordial
7Li
abundance as predicted by big bang nucleosynthesis (BBN) theory and the Wilkinson
Microwave Anisotropy Probe (WMAP) baryon density, and the pre-Galactic lithium
abundance inferred from observations of metal-poor (Population II) stars. This problem has
loomed for the past decade, with a persistent discrepancy of a factor of 2–3 in
7Li/H. Recent developments have sharpened all aspects of the Li problem. Namely: (1) BBN theory
predictions have sharpened due to new nuclear data; in particular, the uncertainty on the reaction rate
for3He(α,γ)7Be
has reduced to 7.4%, nearly a factor of 2 tighter than previous determinations.
(2) The WMAP five-year data set now yields a cosmic baryon density
with an uncertainty reduced to 2.7%. (3) Observations of metal-poor stars
have tested for systematic effects. With these, we now find that the
BBN+WMAP
predicts7Li/H = (5.24−0.67
+0.71) × 10−10. The central value represents an increase by 23%, most of which is due to the upward shift in the3He(α,γ)7Be
rate. More significant is the reduction in the7Li/H uncertainty by almost
a factor of 2, tracking
the reduction in the3He(α,γ)7Be
error bar. These changes exacerbate the Li problem; the discrepancy is now a factor 2.4 or
4.2σ (from globular
cluster stars) to 4.3 or 5.3σ
(from halo field stars). Possible resolutions to the lithium problem are briefly reviewed, and
key experimental and astronomical measurements highlighted.
Power enhancement via multivariate outlier testing with gene expression arrays
Authors: Asare Adam L. , Gao Zhong , Carey Vincent J. , Wang Richard , Seyfert-Margolis Vicki 
Published: November 2008

Abstract
Motivation: As the use of microarrays in human studies continues to increase, stringent quality assurance is necessary to ensure accurate experimental interpretation. We present a formal approach for microarray quality assessment that is based on dimension reduction of established measures of signal and noise components of expression followed by parametric multivariate outlier testing.
Results: We applied our approach to several data resources. First, as a negative control, we found that the Affymetrix and Illumina contributions to MAQC data were free from outliers at a nominal outlier flagging rate of α=0.01. Second, we created a tunable framework for artificially corrupting intensity data from the Affymetrix Latin Square spike-in experiment to allow investigation of sensitivity and specificity of quality assurance (QA) criteria. Third, we applied the procedure to 507 Affymetrix microarray GeneChips processed with RNA from human peripheral blood samples. We show that exclusion of arrays by this approach substantially increases inferential power, or the ability to detect differential expression, in large clinical studies.
Availability: http://bioconductor.org/packages/2.3/bioc/html/arrayMvout.html and http://bioconductor.org/packages/2.3/bioc/html/affyContam.html affyContam (credentials: readonly/readonly)
Contact: aasare@immunetolerance.org; stvjc@channing.harvard.edu
Training set expansion: an approach to improving the reconstruction of biological networks from limited and uneven reliable interactions
Authors: Yip Kevin Y. , Gerstein Mark 
Published: November 2008

Abstract
Motivation: An important problem in systems biology is reconstructing complete networks of interactions between biological objects by extrapolating from a few known interactions as examples. While there are many computational techniques proposed for this network reconstruction task, their accuracy is consistently limited by the small number of high-confidence examples, and the uneven distribution of these examples across the potential interaction space, with some objects having many known interactions and others few.
Results: To address this issue, we propose two computational methods based on the concept of training set expansion. They work particularly effectively in conjunction with kernel approaches, which are a popular class of approaches for fusing together many disparate types of features. Both our methods are based on semi-supervised learning and involve augmenting the limited number of gold-standard training instances with carefully chosen and highly confident auxiliary examples. The first method, prediction propagation, propagates highly confident predictions of one local model to another as the auxiliary examples, thus learning from information-rich regions of the training network to help predict the information-poor regions. The second method, kernel initialization, takes the most similar and most dissimilar objects of each object in a global kernel as the auxiliary examples. Using several sets of experimentally verified protein–protein interactions from yeast, we show that training set expansion gives a measurable performance gain over a number of representative, state-of-the-art network reconstruction methods, and it can correctly identify some interactions that are ranked low by other methods due to the lack of training examples of the involved proteins.
Contact: mark.gerstein@yale.edu
Availability: The datasets and additional materials can be found at http://networks.gersteinlab.org/tse.
SIRIUS: decomposing isotope patterns for metabolite identification
Authors: Böcker Sebastian , Letzel Matthias C. , Lipták Zsuzsanna , Pervukhin Anton 
Published: November 2008

Abstract
Motivation: High-resolution mass spectrometry (MS) is among the most widely used technologies in metabolomics. Metabolites participate in almost all cellular processes, but most metabolites still remain uncharacterized. Determination of the sum formula is a crucial step in the identification of an unknown metabolite, as it reduces its possible structures to a hopefully manageable set.
Results: We present a method for determining the sum formula of a metabolite solely from its mass and the natural distribution of its isotopes. Our input is a measured isotope pattern from a high resolution mass spectrometer, and we want to find those molecules that best match this pattern. Our method is computationally efficient, and results on experimental data are very promising: for orthogonal time-of-flight mass spectrometry, we correctly identify sum formulas for &gt;90% of the molecules, ranging in mass up to 1000 Da.
Availability: SIRIUS is available under the LGPL license at http://bio.informatik.uni-jena.de/sirius/
Contact: anton.pervukhin@minet.uni-jena.de
Supplementary information: Supplementary data are available at Bioinformatics online.
Effects of N : P loading ratios on phytoplankton community composition, primary production and N fixation in a eutrophic lake
Authors: VREDE TOBIAS , BALLANTYNE ASHLEY , MILLE‐LINDBLOM CECILIA , ALGESTEN GRETE , GUDASZ CRISTIAN , LINDAHL SANDRA , BRUNBERG ANNA KRISTINA 
Published: November 2008

Summary

1. The aim of this study was to assess the effects of different nitrogen (N) to phosphorus (P) loading ratios on phytoplankton community composition and primary production in a naturally eutrophic lake. Furthermore, the sources of N fuelling primary production were estimated using 15N stable isotope tracers.
2. A mesocosm experiment was performed with the same amount of P added to all mesocosms (similar to internal loading rates) but with a range of N additions (0–86 μm N), resulting in a gradient of N : P supply ratios.
3. Low N : P supply ratios resulted in a significant shift in the phytoplankton assemblage to a community dominated by N‐fixing cyanobacteria and a supply of atmospheric N2 estimated to be up to 60% of total supply.
4. The N : P loading ratio had no significant effect on primary production, total nitrogen (TN) concentration or particulate N concentration.
5. Our results imply that a reduced N : P ratio of the nutrient load does not necessarily result in a lower TN concentration and downstream N export due to compensation by N‐fixing cyanobacteria.
Sulphur stable isotopes can distinguish trophic dependence on sediments and plankton in boreal lakes
Authors: CROISETIÈRE LOUIS , HARE LANDIS , TESSIER ANDRÉ , CABANA GILBERT 
Published: November 2008

Summary1. Stable isotopes of carbon are useful for differentiating between freshwater food chains based on planktonic algae or benthic algae, but are reported to be of limited use for identifying food chains based on sedimentary detritus. Because data from marine systems suggest that stable isotopes of sulphur (δ34S values) have potential in this regard, we tested their utility in freshwater lakes.2. We found that sulphate in the water column of four boreal lakes was enriched in 34S compared to the sulphur in bulk sediments from these lakes. Furthermore, within a given lake, insects known to feed on sediment (directly or via predation) had δ34S values similar to those of sediment, whereas planktonic and benthic invertebrates known to feed on suspended particles had δ34S values similar to those of sulphate in the water column.3. Using the stable S isotope values of invertebrates that obtain their S from either the sediment or the water column as end members in a two‐source mixing model, we show that two fish species obtain their food from both planktonic and sedimentary sources. Furthermore, model results suggest that, as expected, the more benthic‐feeding fish species obtains more of its S from the sediment compartment than does the species that feeds in the water‐column.4. Our results suggest that measurements of stable sulphur isotopes provide a means of distinguishing between members of food chains that are based in the water column from those based on sedimentary detritus. As such, they would be a useful complement to stable C isotopes that are used to distinguish between food chains based on planktonic or benthic algae.
Twentieth century increase of Scots pine radial growth in NE Spain shows strong climate interactions
Authors: MARTÍNEZ‐VILALTA J. , LÓPEZ B. C. , ADELL N. , BADIELLA L. , NINYEROLA M. 
Published: November 2008

AbstractStem radial growth responds to environmental conditions, and has been widely used as a proxy to study long‐term patterns of tree growth and to assess the impact of environmental changes on growth patterns. In this study, we use a tree ring dataset from the Catalan Ecological and Forest Inventory to study the temporal variability of Scots pine (Pinus sylvestris L.) stem growth during the 20th century across a relatively large region (Catalonia, NE Spain) close to the southern limit of the distribution of the species. Basal area increment (BAI) was modelled as a function of tree size and environmental variables by means of mixed effects models. Our results showed an overall increase of 84% in Scots pine BAI during the 20th century, consistent with most previous studies for temperate forests. This trend was associated with increased atmospheric CO2 concentrations and, possibly, with a general increase in nutrient availability, and we interpreted it as a fertilization effect. Over the same time period, there was also a marked increase in temperature across the study region (0.19 °C per decade on average). This warming had a negative impact on radial growth, particularly at the drier sites, but its magnitude was not enough to counteract the fertilization effect. In fact, the substantial warming observed during the 20th century in the study area did not result in a clear pattern of increased summer drought stress because of the large variability in precipitation, which did not show any clear time trend. But the situation may change in the future if temperatures continue to rise and/or precipitation becomes scarcer. Such a change could potentially reverse the temporal trend in growth, particularly at the driest sites, and is suggested in our data by the relative constancy of radial growth after ca. 1975, coinciding with the warmer period. If this situation is representative of other relatively dry, temperate forests, the implications for the regional carbon balance would be substantial.
The age of the grasses and clusters of origins of C4 photosynthesis
Authors: VICENTINI ALBERTO , BARBER JANET C. , ALISCIONI SANDRA S. , GIUSSANI LILIANA M. , KELLOGG ELIZABETH A. 
Published: November 2008

AbstractAt high temperatures and relatively low CO2 concentrations, plants can most efficiently fix carbon to form carbohydrates through C4 photosynthesis rather than through the ancestral and more widespread C3 pathway. Because most C4 plants are grasses, studies of the origin of C4 are intimately tied to studies of the origin of the grasses. We present here a phylogeny of the grass family, based on nuclear and chloroplast genes, and calibrated with six fossils. We find that the earliest origins of C4 likely occurred about 32 million years ago (Ma) in the Oligocene, coinciding with a reduction in global CO2 levels. After the initial appearance of C4 species, photosynthetic pathway changed at least 15 more times; we estimate nine total origins of C4 from C3 ancestors, at least two changes of C4 subtype, and five reversals to C3. We find a cluster of C4 to C3 reversals in the Early Miocene correlating with a drop in global temperatures, and a subsequent cluster of C4 origins in the Mid‐Miocene, correlating with the rise in temperature at the Mid‐Miocene climatic optimum. In the process of dating the origins of C4, we were also able to provide estimated times for other major events in grass evolution. We find that the common ancestor of the grasses (the crown node) originated in the upper Cretaceous. The common ancestor of maize and rice lived at 52 ± 8 Ma.
Nutrient constraints to tropical agroecosystem productivity in long‐term degrading soils
Authors: NGOZE SOLOMON , RIHA SUSAN , LEHMANN JOHANNES , VERCHOT LOUIS , KINYANGI JAMES , MBUGUA DAVID , PELL ALICE 
Published: November 2008

AbstractSoil degradation is one of the most serious threats to sustainable crop production in many tropical agroecosystems where extensification rather than intensification of agriculture has occurred. In the highlands of western Kenya, we investigated soil nitrogen (N) and phosphorus (P) constraints to maize productivity across a cultivation chronosequence in which land‐use history ranged from recent conversion from primary forest to 100 years in continuous cropping. Nutrient treatments included a range of N and P fertilizer rates applied separately and in combination. Maize productivity without fertilizer was used as a proxy measure for indigenous soil fertility (ISF). Soil pools of mineral nitrogen, strongly bound P and plant‐available P decreased by 82%, 31% and 36%, and P adsorption capacity increased by 51% after 100 years of continuous cultivation. For the long rainy season (LR), grain yield without fertilizer declined rapidly as cultivation age increased from 0 to 25 years and then gradually declined to a yield of 1.6 Mg ha−1, which was maintained as time under cultivation increased from 60 to 100 years. LR grain yield in the old conversions was only 24% of the average young conversion grain yield (6.4 Mg ha−1). Application of either N or P alone significantly increased grain yield in both the LR and short rainy (SR) seasons, but only application of 120 kg N ha−1 on the old conversion increased yield by >1 Mg ha−1. In both SR and LR, there was a greater average yield increment response to N and P when applied together (ranging from 1 to 3.8 Mg ha−1 for the LR), with the greatest responses on the old conversions. The benefit–cost ratio (BCR) for applying 120 kg N ha−1 alone was <1 except on the old conversions, while BCRs were>1 for applying 25 kg P ha−1 alone at all levels of conversion for both seasons. Application of both N (120 kg N ha−1) and P (25 kg P ha−1) on the old conversions resulted in the greatest BCRs. This study clearly indicates that maize productivity responses to N and P fertilizer are significantly affected by the age of cultivation and its influence on ISF, but that loss of productivity can be restored rapidly when these limiting nutrients are applied. Management strategies should consider ISF and economic factors to determine optimal N and P input requirements for achieving and sustaining profitable crop production on degraded soils.