| 1. |
- Bergfur, Jenny, et al.
(författare)
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Effects of nutrient enrichment on C and N stable isotope ratios of invertebrates, fish and their food resources in boreal streams
- 2009
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 628, s. 67-79
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Tidskriftsartikel (refereegranskat)abstract
- Carbon and nitrogen stable isotopes are frequently used to study energy sources and food web structure in ecosystems, and more recently, to study the effects of anthropogenic stress on aquatic ecosystems. We investigated the effect of nutrient enrichment on d13C and d15N in fine (FPOM), coarse (CPOM) particulate organic matter, periphyton, invertebrates and fish in nine boreal streams in south-central Sweden. In addition, we analysed the diet of benthic consumers using stable isotope data. Increases in d15N of periphyton (R2 = 0.88), CPOM (0.78), invertebrates (0.92) and fish (0.89) were related to nutrient enrichment. In contrast, d13C signatures did not change along the nutrient gradient. Our results show that d15N has potential as a sensitive indicator of nutrient enrichment in boreal streams. Carbon and nitrogen isotopes failed to elucidate putative diets of selected aquatic consumers. Indeed, comparison of low- and high-impact sites showed that d13C of many consumers were found outside the ranges of basal resource d13C. Moreover, ranges of basal resource d13C and d15N overlapped at both low and high sites, making discrimination between the importance of allochthonous and autochthonous production difficult. Our findings show that a fractionation rate of 3.4% is not always be appropriate to assess trophic interactions, suggesting that more studies are needed on fractionation rates along gradients of impairment.
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| 2. |
- Bergstedt, Johan, et al.
(författare)
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In the eye of the beholder : bias and stochastic variation in cover estimates
- 2009
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Ingår i: PLANT ECOLOGY. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 204:2, s. 271-283
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Tidskriftsartikel (refereegranskat)abstract
- Cover estimates by eye is a prevailing method to assess abundance. We examined cover estimates with regard to bias and random variation. Ten observers working with a national forest vegetation survey estimated sixteen 100 m(2)-plots, placed in two different vegetation types. These had similar species composition but were clearly distinguishable in the field. In species-wise analyses, observer bias varied greatly, with Dicranum spp., Vaccinium vitis-idaea and Vaccinium myrtillus having the largest bias. Experience had a surprisingly small impact on variation. Power analysis revealed only small differences between observers in the ability to distinguish the two vegetation types, and little value in averaging the assessments from two, three or four observers. Cover estimates did better than presence/absence data in separating the two vegetation types and multivariate analyses were more powerful than univariate ones.
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| 3. |
- Bishop, Kevin, et al.
(författare)
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Nature as the "Natural" Goal for Water Management : A Conversation
- 2009
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Ingår i: Ambio. - : Springer Netherlands. - 0044-7447 .- 1654-7209. ; Volume 38:Issue 4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The goals for water-quality and ecosystem integrity are often defined relative to "natural" reference conditions in many water-management systems, including the European Union Water Framework Directive. This paper examines the difficulties created for water management by using "natural" as the goal. These difficulties are articulated from different perspectives in an informal (fictional) conversation that takes place after a workshop on reference conditions in water-resources management. The difficulties include defining the natural state and modeling how a system might be progressed toward the natural, as well as the feasibility and desirability of restoring a natural state. The paper also considers the appropriateness for developing countries to adopt the use of natural as the goal for water management. We conclude that failure to critically examine the complexities of having "natural" as the goal will compromise the ability to manage the issues that arise in real basins by not making the ambiguities associated with this "natural" goal explicit. This is unfortunate both for the western world that has embraced this model of "natural as the goal" and for the developing world in so far as they are encouraged to adopt this model.
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| 4. |
- Bolarin, A., et al.
(författare)
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Use of frozen-thawed semen aggravates the summer-autumn infertility of artificially inseminated weaned sows in the Mediterranean region
- 2009
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Ingår i: Journal of Animal Science. - : American Society of Animal Science. - 0021-8812 .- 1525-3163. ; 87:12, s. 3967-3975
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Tidskriftsartikel (refereegranskat)abstract
- Improvement of farrowing rate (FR) and litter size (LS) of sows that are AI with frozen-thawed (FT) semen can hardly be reached without identification of the factors behind the high variability seen among trials. Three experiments using weaned (4-d wean-to-estrus interval) multiparous (parity 2 to 7) sows were conducted to evaluate the effect of period of the year on FR and LS of FT-inseminated sows in southern Spain. Sows were grouped into 2 periods of the year: winter-spring (November to April; WS) and summer-autumn (May to October; SA). Ovarian status was monitored by transrectal ultrasonography to record how long before or after ovulation AI was performed (pre-, peri-, or postovulatory AI) and to determine the onset of estrus-to-ovulation interval (EOI). Inseminations were performed using deep intrauterine AI with 1.5 x 109 FT sperm per dose. The first experiment was designed to determine the influence of the period of the year on FR and LS of FT semen. Sows (116 in WS and 100 in SA) were AI at 33 and 39 h after the onset of estrus. The period of the year influenced the FR and LS (P less than 0.01). Farrowing rate and LS were least in SA (P less than 0.05). This pattern of annual variation was similar to that shown by sows on the same farm currently undergoing AI with liquid semen (cervical AI at 12 and 36 h after the onset of estrus with 3 x 109 sperm per dose). However, the FR reduction in SA respect to WS was more substantial in sows artificially inseminated with FT (77.6 vs. 50%, P less than 0.001) than those artificially inseminated with liquid semen (83.9 vs. 71.8%, P less than 0.05). More pre- and less periovulatory AI were performed in SA sows than in WS sows (P = 0.05). Experiment 2 was designed to evaluate whether the period of the year influenced EOI. Ovarian status was transrectal ultrasonography scanned every 6 h after the onset of estrus until the end of ovulation (WS: 30; SA: 31 sows). There were more sows with long EOI (greater than48 h) in SA than in WS (P = 0.05). Experiment 3 aimed to improve the reduced FR and LS recorded in SA sows when using FT semen (Exp. 1) by inducing ovulation with eCG + hCG. A single AI with FT semen was performed 5 h before the expected ovulation (55 sows). As a control, spontaneously ovulating sows (n = 53) were FT-inseminated as in Exp. 1. Hormonal induction of ovulation did not improve FR and LS (P greater than 0.05). In the Spanish Mediterranean area, a longer EOI during SA negatively influenced the FR and LS of weaned sows after AI. This effect was particularly evident when FT semen was used. These findings were not ameliorated by hormonal induction of ovulation.
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| 5. |
- Brandt, Y., et al.
(författare)
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Effects of continuous elevated cortisol concentrations during oestrus on concentrations and patterns of progesterone, oestradiol and LH in the sow
- 2009
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Ingår i: Animal Reproduction Science. - : Elsevier Masson. - 0378-4320 .- 1873-2232. ; 110:1-2, s. 172-185
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of continuous elevated cortisol concentrations during standing oestrus on time of ovulation and patterns Of progesterone. oestradiol and luteinising, hormone (LH) in sows. The elevation of cortisol concentrations was achieved through repeated intravenous injections of synthetic adrenocorticotropic hormone (ACTH) every 2 It for approximately 48 h, from the onset of the second standing oestrus alter weaning. Treatment was terminated when ovulation was detected (monitored by transrectal ultrasonography every 4h) or when (lie sow had received a maximum of 24 injections. The close of ACTH (2.5 mu g/kg) was chosen to mimic the cortisol concentrations seen during mixing of unfamiliar SOWS. The sows (n = 14) Were surgically fitted with jugular vein catheters and randomly divided into a control (C group) where only NaCl solution were injected) or an ACTH group. Blood samples were collected every 2 h. In parallel with the blood sampling, saliva samples for cortisol analyses were taken from eight sows before onset of treatment and from four of the sows during treatment. There was no difference in time from onset of standing, oestrus to ovulation between the two groups. The interval between the peaks of oestradiol and LH to ovulation was prolonged in the ACTH group compared to the C group (p less than 0.05). with a tendency towards all earlier decline of oestradiol in the ACTH group. Cortisol and progesterone Concentrations were significantly elevated during treatment in the ACTH group (p less than 0.001). with cortisol peak concentrations occurring between 40 and 80 min after each ACTH injection. Cortisol concentrations in saliva and Plasma were highly correlated (p less than 0.001). In conclusion, elevated cortisol concentrations from the onset of standing oestrus increase progesterone concentrations and prolong the interval between oestradiol and LH peaks to ovulation, the latter possible due to an early decline in oestradiol concentrations and a change of the LH peak outline. the effect these hormonal changes have on reproductive performance need to be further investigated. (C) 2008 Elsevier B.V. All rights reserved.
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| 6. |
- Brun, Anders, 1976-, et al.
(författare)
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Similar Tensor Arrays : A Framework for Storage of Tensor Array Data
- 2009. - 1
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Ingår i: Tensors in Image Processing and Computer Vision. - London : Springer. - 9781848822986 - 9781848822993 ; , s. 407-428
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Abstract This chapter describes a framework for storage of tensor array data, useful to describe regularly sampled tensor fields. The main component of the framework, called Similar Tensor Array Core (STAC), is the result of a collaboration between research groups within the SIMILAR network of excellence. It aims to capture the essence of regularly sampled tensor fields using a minimal set of attributes and can therefore be used as a “greatest common divisor” and interface between tensor array processing algorithms. This is potentially useful in applied fields like medical image analysis, in particular in Diffusion Tensor MRI, where misinterpretation of tensor array data is a common source of errors. By promoting a strictly geometric perspective on tensor arrays, with a close resemblance to the terminology used in differential geometry, (STAC) removes ambiguities and guides the user to define all necessary information. In contrast to existing tensor array file formats, it is minimalistic and based on an intrinsic and geometric interpretation of the array itself, without references to other coordinate systems.
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| 7. |
- Brun, Anders, 1976-, et al.
(författare)
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Tensor Glyph Warping : Visualizing Metric Tensor Fields using Riemannian Exponential Maps
- 2009. - XVII
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Ingår i: Visualization and Processing of Tensor Fields. - Berlin Heidelberg : Springer. - 9783540883777 - 9783540883784 ; , s. 139-160
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The Riemannian exponential map, and its inverse the Riemannian logarithm map, can be used to visualize metric tensor fields. In this chapter we first derive the well-known metric sphere glyph from the geodesic equation, where the tensor field to be visualized is regarded as the metric of a manifold. These glyphs capture the appearance of the tensors relative to the coordinate system of the human observer. We then introduce two new concepts for metric tensor field visualization: geodesic spheres and geodesically warped glyphs. These extensions make it possible not only to visualize tensor anisotropy, but also the curvature and change in tensor-shape in a local neighborhood. The framework is based on the exp p (v i ) and log p (q) maps, which can be computed by solving a second-order ordinary differential equation (ODE) or by manipulating the geodesic distance function. The latter can be found by solving the eikonal equation, a nonlinear partial differential equation (PDE), or it can be derived analytically for some manifolds. To avoid heavy calculations, we also include first- and second-order Taylor approximations to exp and log. In our experiments, these are shown to be sufficiently accurate to produce glyphs that visually characterize anisotropy, curvature, and shape-derivatives in sufficiently smooth tensor fields where most glyphs are relatively similar in size.
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| 8. |
- Buranaamnuay, K., et al.
(författare)
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Effects of Straw Volume and Equex-STM (R) on Boar Sperm Quality after Cryopreservation
- 2009
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Ingår i: Reproduction in domestic animals. - : Wiley-Blackwell. - 0936-6768 .- 1439-0531. ; 44:1, s. 69-73
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Tidskriftsartikel (refereegranskat)abstract
- The present experiments were designed to study the effect of adding the detergent Equex-STM (R) to freezing extender, and of straw volume (0.25 ml vs 0.5 ml), on boar sperm quality after cryopreservation. Three ejaculates from each of four purebred boars (three Landrace and one Yorkshire) were collected and frozen with a lactose-egg yolk extender containing glycerol with or without 1.5% Equex-STM (R). The extended semen was loaded into either 0.25- or 0.5-ml straws. The straws were placed in liquid nitrogen (LN2) vapour approximately 3 cm above the level of LN2 for 20 min and then were plunged into LN2. Thawing was achieved in warm water at 50 degrees C for 12 s and then was incubated in a 38 degrees C water-bath for 30 min before evaluating sperm quality. Results showed that the individual motility, viability and acrosomal normal apical ridge (NAR) were improved (p less than 0.001) when Equex-STM (R) was added to the freezing extender. There was no difference (p = 0.48) in sperm motility between 0.25- and 0.5-ml straws when Equex-STM (R) was added. The percentages of viable and of NAR sperm in 0.5-ml straws were higher than those in 0.25-ml straws (p = 0.02, p = 0.0003 respectively). The percentages of membrane intact sperm evaluated using the short hypo-osmotic swelling test were not affected by straw volume or the adding of Equex-STM (R) (p greater than 0.05). The results of these investigations suggested that Equex-STM (R) exerts a beneficial effect on the quality of cryopreserved boar semen and this cryopreservation protocol was favourable for a 0.5-ml straw.
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| 9. |
- Börjesson, Gunnar, et al.
(författare)
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A national landfill methane budget for Sweden based on field measurements, and an evaluation of IPCC models
- 2009
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Ingår i: Tellus, Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 1600-0889 .- 0280-6509. ; 61:2, s. 424-435
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Tidskriftsartikel (refereegranskat)abstract
- Seven Swedish landfills were investigated from 2001 to 2003. On each landfill, a measure of the total methane production was calculated from data on: (1) methane emissions (leakage); (2) methane oxidation and (3) from gas recovery. Methane emissions were determined via a tracer gas (N2O) release-based remote sensing method. N2O and CH4 were measured with an Fourier Transform infrared detector at a distance of more than 1 km downwind from the landfills. Methane oxidation in the landfill covers was measured with the stable carbon isotope method. The efficiency in gas recovery systems proved to be highly variable, but on an average, 51% of the produced landfill gas was captured. A first-order decay model, based on four fractions (waste from households and parks, sludges and industrial waste), showed that the use of a degradable organic carbon fraction (DOCf) value of 0.54, in accordance with the default value for DOCf of 0.50 in the latest IPCC model, gave an emission estimate similar to the official national reports.
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| 10. |
- Dahlgren, Lars Owe, et al.
(författare)
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Grading systems, features of assessment and students' approaches to learning
- 2009
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Ingår i: Teaching in Higher Education. - : Informa UK Limited. - 1356-2517 .- 1470-1294. ; 14:2, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- The Bologna process aims at harmonising the higher education systems in the Europe. One of the most important tools proposed for such a purpose is the European Credit Transfer System. A significant element of this system is a common seven-step grading scale. It has previously been shown that assessment characteristics impact on students' approaches to learning. Furthermore, there is also empirical evidence that judgement criteria have an effect on students' learning. The focus of this article is on the relationships between grading systems, assessment characteristics and students' learning. Empirical evidence from a Swedish survey study indicates that multi-step grading scales may have detrimental repercussions on the nature of the assessment tasks and thereby indirectly on the students' approaches to learning. We suggest that the effects of grading systems need to be considered in the current discussion in order to support quality in learning.
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