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Haemosporidian parasites infecting birds show distinct heterogeneity in their distribution among host species. However, despite numerous studies on the prevalence and diversity of parasite communities across species, very little is known on patterns of differences between them. Such data is lacking because up to date the majority of studies explored the patterns of variation in infections in different years, different time of sampling within a year or a breeding cycle, different study sites or was based on a small sample size, all of which may affect the estimates of prevalence and parasite diversity. Here, the prevalence, richness and diversity of haemosporidian parasites from the genera Plasmodium and Haemoproteus were studied in two closely related non-migratory hole-nesting passerines: Great Tits and Blue Tits. Birds were sampled in sympatrically breeding populations during two seasons at the same stage of their breeding cycle – late nestling care. Great Tits were more prevalently infected with Plasmodium and Haemoproteus parasites (97·1 vs 71·2%), harboured a higher proportion of multiple infections (26·2 vs 3·2%) and had a more diverse parasite community (11 vs 5 parasite lineages) than Blue Tits. Observed differences between two host species are discussed with reference to their breeding densities and immunological and behavioural characteristics.
Δ9-Desaturase (stearoyl-CoA desaturase 1, SCD-1) regulates the desaturation of SFA, mainly stearic and palmitic, to MUFA. Δ6-Desaturase (D6D) and Δ5-desaturase (D5D) are involved in the metabolism of linoleic and α-linolenic acid to polyunsaturated metabolites. The objective of the present study was to study the effects of different types of dietary fat on indices of fatty acid desaturase (FADS) activity (evaluated as product:precursor ratios) in plasma and skeletal muscle in human subjects. A high SCD-1 index has been related to obesity and metabolic disorders, while the D5D index is associated with insulin sensitivity. Fatty acid composition of serum and skeletal muscle lipids was analysed by GLC during a randomised, controlled, 3-month dietary intervention in healthy subjects. A comparison of the effects of a diet containing butter fat (SFA, n 17) with a diet containing monounsaturated fat (MUFA, n 17), keeping all other dietary components constant, showed a reduced SCD-1 activity index by 20 % on the MUFA diet compared with the SFA diet assessed in serum cholesteryl esters. The D6D and D5D indices remained unaffected. Supplementation with long-chain n-3 fatty acids reduced the SCD-1 index by a similar magnitude while the D6D index decreased and the D5D index increased. It is concluded that changes in the type of fat in the diet affect the indices of FADS activity in serum and skeletal muscle in human subjects. The desaturase activity indices estimated from the serum lipid ester composition are significantly related to corresponding indices studied in skeletal muscle phospholipids.
A new approach has been taken for the fabrication of Quantum Dot materials to be used for physics as well as for opto-electronics applications. We used a generation technique of ultrafine aerosol Ag particles which are deposited onto the surface of GalnAs/InP quantum well structures grown by Metal Organic Vapor Phase Epitaxy (MOVPE). The particles, ranging in size between 30 and 40 nm, are subsequently used as an etching mask. The Ag aerosol produced by homogeneous nucleation and can have a mean diameter in the range 2 – 100 nm. After size-selection, monodisperse particles with a very narrow size distribution are deposited onto the semiconductor surface at a density of about 109 cm-2. Low energy CH4/H/Ar Electron Cyclotron Resonance (ECR) plasma etching results in the formation of free-standing InP columns 50 to 80 nm in diameter and 120 to 280 nm in height. Their size and stability were found to be dependent on the etching conditions and the diameter of the particles. Low-temperature cathodoluminescence (CL) was used to evaluate the quantum dot structures fabricated by this technique.
In the exploration of the nano-world of semiconductors there is a strong focus on low-dimensional structures and ultra-small devices. Two fundamental problems, which challenge progress in this field are: (i) large ensembles of nano-objects, like Quantum Dots (QDs), do not have identical geometrical shapes and electronic properties, and, (ii) the properties of a low-dimensional structure can be dominated by a few impurity atoms, whereas the properties of a macroscopic structure is determined by the quasi-continuous background of dopant impurities. To allow QDs and discrete impurities to be studied, novel experimental techniques are required. In this paper we describe how local luminescence has been excited from single QDs using electrons injected from a Scanning Electron Microscope (SEM), from the tip of a Scanning Tunneling Microscope (STM) or using highly focused photons for excitation. We present images of QDs as well as characteristic spectra of individual QDs. We finally show how the local character of the excitation enables us to excite and image individual impurities in low-dimensional structures, including the measurement of characteristic emission spectra from a single impurity atom in GaAs.
We investigate a concept of multivariate pricing, which includes claim history for more than one line of business and is a generalization of the Bühlmann-Straub model. The multivariate credibility model is extended to allow for the age of claims to influence the estimation of future claims. The model is applied to data from a portfolio of commercial lines of business.
This study compared the effects of high frequency oscillatory ventilation (HFOV) and intermittent mandatory ventilation (IMV) on the homeostasis of nitric oxide (NO) in the lower respiratory tract of healthy rabbits. The mechanisms underlying a putative stretch response of NO formation in the airways were further elucidated. Male New Zealand White rabbits were anaesthetized, tracheotomized and ventilated with IMV or HFOV in random order. Total NO excretion increased from 9σ6 ± 0σ8 nl min-1 (mean ± S.E.M.) during IMV to 22σ6 ± 2σ7 nl min-1 during HFOV (P < 0σ001). This increase was not explained by changes of functional residual capacity ([Delta]>FRC). A similar increase in NO excretion during HFOV was seen in isolated buffer-perfused lungs under constant circulatory conditions (P < 0σ05, n = 4). Intratracheal mean CO2 and NO concentrations, measured at 2σ5, 5, 7σ5 and 10 cm below tracheostomy, increased significantly with increasing distance into the lung during both IMV and HFOV (P < 0σ001 for each comparison). At every intratracheal location of the sampling catheter, particularly low in the airways, both CO2 and NO concentrations were significantly higher during HFOV than during IMV (P < 0σ01 for each comparison). We conclude that HFOV increases pulmonary NO production in healthy rabbits. Increased stretch activation of the respiratory system during HFOV is suggested as a possible underlying mechanism. The increase in mean airway NO concentrations may have biological effects in the respiratory tract. Whether it can account for some of the benefits of HFOV treatment needs to be considered.
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