| 1. |
- Galan, C., et al.
(författare)
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International observational campaigns of the last two eclipses in EE Cephei : 2003 and 2008/9
- 2012
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 544, s. A53-
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Tidskriftsartikel (refereegranskat)abstract
- Context. EECep is an unusual long-period (5.6 yr) eclipsing binary discovered during the mid-twentieth century. It undergoes almost-grey eclipses that vary in terms of both depth and duration at different epochs. The system consists of a Be type star and a dark dusty disk around an invisible companion. EECep together with the widely studied epsilon Aur are the only two known cases of long-period eclipsing binaries with a dark, dusty disk component responsible for periodic obscurations.Aims. Two observational campaigns were carried out during the eclipses of EECep in 2003 and 2008/9 to verify whether the eclipsing body in the system is indeed a dark disk and to understand the observed changes in the depths and durations of the eclipses.Methods. Multicolour photometric data and spectroscopic observations performed at both low and high resolutions were collected with several dozen instruments located in Europe and North America. We numerically modelled the variations in brightness and colour during the eclipses. We tested models with different disk structure, taking into consideration the inhomogeneous surface brightness of the Be star. We considered the possibility of disk precession.Results. The complete set of observational data collected during the last three eclipses are made available to the astronomical community. The 2003 and 2008/9 eclipses of EECep were very shallow. The latter is the shallowest among all observed. The very high quality photometric data illustrate in detail the colour evolution during the eclipses for the first time. Two blue maxima in the colour indices were detected during these two eclipses, one before and one after the photometric minimum. The first (stronger) blue maximum is simultaneous with a "bump" that is very clear in all the UBV(RI)(C) light curves. A temporary increase in the I-band brightness at the orbital phase similar to 0.2 was observed after each of the last three eclipses. Variations in the spectral line profiles seem to be recurrent during each cycle. The Na I lines always show at least three absorption components during the eclipse minimum and strong absorption is superimposed on the H alpha emission.Conclusions. These observations confirm that the eclipsing object in EECep system is indeed a dark, dusty disk around a low luminosity object. The primary appears to be a rapidly rotating Be star that is strongly darkened at the equator and brightened at the poles. Some of the conclusions of this work require verification in future studies: (i) a complex, possibly multi-ring structure of the disk in EECep; (ii) our explanation of the "bump" observed during the last two eclipses in terms of the different times of obscuration of the hot polar regions of the Be star by the disk; and (iii) our suggested period of the disk precession (similar to 11-12 P-orb) and predicted depth of about 2(m) for the forthcoming eclipse in 2014.
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| 2. |
- Foster, R. A., et al.
(författare)
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Structural elucidation of the O-antigen of the Shigella flexneri provisionalserotype 88-893 : structural and serological similarities with S. flexneri provisional serotype Y394 (1c)
- 2011
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 346:6, s. 872-876
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the repeating unit of the O-antigen polysaccharide from Shigella flexneri provisional serotype 88-893 has been determined. 1H and 13C NMR spectroscopy as well as 2D NMR experiments were employed to elucidate the structure. The carbohydrate part of the hexasaccharide repeating unit is identical to the previously elucidated structure of the O-polysaccharide from S. flexneri prov. serotype Y394. The O-antigen of S. flexneri prov. serotype 88-893 carries 0.7 mol O-acetyl group per repeating unit located at O-2 of the 3-substituted rhamnosyl residue, as identified by H2BC and BS-CT-HMBC NMR experiments. The O-antigen polysaccharide is composed of hexasaccharide repeating units with the following structure: →2)-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-l-Rhap2Ac-(1→3)[α-d-Glcp-(1→2)-α-d-Glcp-(1→4)]-β-d-GlcpNAc-(1→. Serological studies showed that type antigens for the two provisional serotypes are identical; in addition 88-893 expresses S. flexneri group factor 6 antigen. We propose that provisional serotypes Y394 and 88-893 be designated as two new serotypes 7a and 7b, respectively, in the S. flexneri typing scheme.
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| 3. |
- Sliwa, E, et al.
(författare)
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Influence of dexamethasone and alpha-ketoglutarate on growth and development of the skeletal system of pigs
- 2005
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Ingår i: Medycyna Weterynaryjna. - 0025-8628. ; 61:5, s. 526-531
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to establish the influence of dexamethasone and/or alpha-ketoglutarate (AKG) on the growth, mineralization, geometric and mechanical properties of ribs as a methodological model. The experiment was conducted during the final 24 days of prenatal life and first 14 days of neonatal life. The volumetric bone density of the trabecular and cortical bone was determined separately using the quantitative computed tomography (QCT) method and Somatom AR. T - Siemens apparatus. The mechanical properties were determined using the three-point bending test according to the method by Ferretti et al. The obtained results indicate that maternal administration of dexamethasone increased volumetric mineral density, although the mechanical parameters had lower values. Prenatal administration of AKG decreased all the geometric and mechanical parameters of the investigated ribs. The results obtained during the administration of the compound in neonatal life were the opposite of the prenatal results. Dexamethasone and AKG given together had the same influence on mineralization and other properties AND increasing their values during prenatal and neonatal life. This model of administrating dexamethasone and AKG maternally during prenatal life with the intention of provoking structural growth of the skeleton may be useful in further elucidating some biological and pharmacological factors on bone formation in prenatal life.
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| 4. |
- Tatara, MR, et al.
(författare)
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Effect of alpha-ketoglutarate (AKG) on mineralisation, morphology and mechanical endurance of femur and tibia in turkey
- 2004
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Ingår i: Bulletin of the Veterinary Institute in Puławy. - 0042-4870. ; 48:3, s. 305-309
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the influence of alpha-ketoglutarate (AKG) on volumetric bone density, geometrical and mechanical properties of femur and tibia in farm turkeys. All animals were kept under standard rearing conditions with constant access to water and appropriate feed, supplied in accordance with the stage of production cycle. Bone samples were collected 14 weeks after beginning of the experiment. To the first group belonged control turkeys. The second group of animals consisted of turkeys that were administered AKG from the 22(nd) to 110(th) d of life. Using Quantitative Computed Tomography (QCT) method, volumetric bone density of femur and tibia were estimated for trabecular and cortical bone. Both the mechanical and geometrical properties of femur and tibia were assessed according to Ferretti's method. The obtained results indicate positive influence of enteral AKG administration on skeletal system quality in turkeys.
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| 5. |
- Tatara, MR, et al.
(författare)
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Effects of alpha-ketoglutarate on bone homeostasis and plasma amino acids in turkeys
- 2005
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Ingår i: Poultry Science. - 1525-3171. ; 84:10, s. 1604-1609
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the study was to evaluate the effect of denervation and alpha-ketoglutarate (AKG) administration on the development of osteopenia in the turkey radius. At 22 d of age, all turkeys were subjected to neurectomy of the right radius. Control turkeys were given a saline solution into the crop each day for 97 d. Experimental turkeys were given 0.4 g of AKG/kg of BW into the crop each day. After 98 d, BW was not affected by the AKG treatment. Volumetric bone mineral density of the radius was measured by quantitative computed tomography. Mechanical properties were tested using a 3-point bending test. Cross-sectional area, second moment of inertia, and mean relative wall thickness were measured as well. An-Lino acid concentrations were assessed with the use of ion-exchange chromatography. Denervation had a negative effect on all bone characteristics that were measured except bone length. The AKG had a positive effect on all bone characteristics except bone length. Plasma concentrations of proline and leucine were increased by AKG, whereas concentrations of taurine and glutamine were decreased. The turkey radius appears to be a good model for studying osteopenia because its development can be affected by treatments such as denervation and AKG administration.
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