3,432 research outputs found

    UML Deficiencies from the perspective of Automatic Performance Model Generation

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    A discussion surrounding the use of UML for distributed system design

    The sea – or mariners’s astrolabe

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    Effect of genotype on duodenal expression of nutrient transporter genes in dairy cows

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    peer-reviewedBackground Studies have shown clear differences between dairy breeds in their feed intake and production efficiencies. The duodenum is critical in the coordination of digestion and absorption of nutrients. This study examined gene transcript abundance of important classes of nutrient transporters in the duodenum of non lactating dairy cows of different feed efficiency potential, namely Holstein-Friesian (HF), Jersey (JE) and their F1 hybrid. Duodenal epithelial tissue was collected at slaughter and stored at -80°C. Total RNA was extracted from tissue and reverse transcribed to generate cDNA. Gene expression of the following transporters, namely nucleoside; amino acid; sugar; mineral; and lipid transporters was measured using quantitative real-time RT-PCR. Data were statistically analysed using mixed models ANOVA in SAS. Orthogonal contrasts were used to test for potential heterotic effects and spearman correlation coefficients calculated to determine potential associations amongst gene expression values and production efficiency variables. Results While there were no direct effects of genotype on expression values for any of the genes examined, there was evidence for a heterotic effect (P < 0.05) on ABCG8, in the form of increased expression in the F1 genotype compared to either of the two parent breeds. Additionally, a tendency for increased expression of the amino acid transporters, SLC3A1 (P = 0.072), SLC3A2 (P = 0.081) and SLC6A14 (P = 0.072) was also evident in the F1 genotype. A negative (P < 0.05) association was identified between the expression of the glucose transporter gene SLC5A1 and total lactational milk solids yield, corrected for body weight. Positive correlations (P < 0.05) were also observed between the expression values of genes involved in common transporter roles. Conclusion This study suggests that differences in the expression of sterol and amino acid transporters in the duodenum could contribute towards the documented differences in feed efficiency between HF, JE and their F1 hybrid. Furthermore, positive associations between the expression of genes involved in common transporter roles suggest that these may be co-regulated. The study identifies potential candidates for investigation of genetic variants regulating nutrient transport and absorption in the duodenum in dairy cows, which may be incorporated into future breeding programmes

    Exercise testing after myocardial infarction: A perspective

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    Notes From Cardiology Clinic: When Our Responsibilities Extend Beyond the Patient.

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    A new form of endemic peripheral neuritis

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    Currents mediated by non-NMDA glutamate receptors in rat magnocellular basal forebrain neurones in primary culture

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    Patch-clamp techniques were used to record glutamate receptor-mediated responses from magnocellular rat basal forebrain neurones maintained in dissociated culture. Both NMDA and non-NMDA receptor-mediated responses were observed and could be distinguished pharmacologically. AMPA and kainate elicited inward currents. Responses to AMPA but not to kainate showed rapid desensitization. EC50S for steady-state responses to AMPA and kainate were 2.7 and 138µM respectively. Responses were potentiated by cyclothiazide but not by Concanavalin A and were inhibited by GYKI 53655. These data indicate that non-NMDA receptor-mediated responses result predominantly from activation of an AMPA receptor. In the presence of GYKI 53655 small inward currents were observed upon kainate application. Responses decreased in amplitude during prolonged application, were insensitive to cyclothiazide and potentiated by Concanavalin A. These responses probably reflect kainate receptor activation. Steady-state current-voltage relationships were examined in nucleated patches. With 30µM spermine in the pipette mildly outwardly rectifying through linear to strongly doubly-rectifying relationships were observed, suggesting a range of calcium permeabilities. AMPA receptor calcium permeabilities were quantitated using constant field theory to interpret the effects of solution exchanges on reversal potentials in acutely dissociated neurones. Relative calcium:sodium permeability ranged from 0.26 to 3.6, median 1.27. Extracellular calcium ions also reduced current amplitude, an effect mimicked by cadmium and by cobalt ions. The effect of cadmium was dose-dependent (EC50 44µM) and voltage-sensitive. Kainate application to acutely dissociated neurones resulted in calcium current inhibition. GYKI 53655 sensitivity indicated that the probable mechanism is calcium-dependent inactivation of calcium channels following calcium influx through AMPA receptors. These data may explain the sensitivity of magnocellular cholinergic basal forebrain neurones to non-NMDA receptor agonists in vivo and are consistent with the suggestion that glutamate-induced calcium influx may contribute to selective loss of cholinergic neurones in dementia

    Doctor of Philosophy

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    dissertationThis work focuses on the study of low-magnetic field (<10mT) magnetoresistance effects of organic polymer diodes based on the n-conjugated polymer MEH-PPV in presence of oscillating magnetic fields in the radio frequency range. In these conditions, the combination of static and ac fields can magnetic resonantly influence the electronspin degree of freedom of localized charge-carrier states. As long as bipolar injection conditions influence the net current of the polymer diode, magnetic-resonance changes of the charge carrier spin state can affect spin-dependent charge carrier recombination rates and therefore the material's conductivity. Since the observed spin-dependent recombination currents are governed by the charge carrier pair's spin-permutation symmetry, magnetoresistance measurements under ac drive allow for the electrical detection of magnetic resonance under very low magnetic field conditions where inductive magnetic resonance detection schemes fail due to a lack of spin polarization. In this thesis, this effect was utilized for two effects. Firstly, for the exploration of a magnetic resonance regime where the driving field B 1 approaches the same magnitude as the static magnetic field B0. When Bi approaches B0, a regime where magnetic resonance effects become nonlinear emerges and interesting collective spin-phenomena occur. This includes spin-cooperativity, where the resonantlydriven spin ensemble assumes a macroscopically collective state. Experiments are presented that tested and confirmed previous theoretical predictions. When B}~B0, the emerging spin-cooperativity of recombining polaron pairs in organic semiconductors can be observed through magnetoresistance measurements. The experiments confirmed the theory in all aspects and demonstrated the emergence of the spin-Dicke effect. Secondly, for the exploration of whether magnetic resonantly-controlled spindependent currents can be used for magnetometry of inhomogeneous magnetic fields. This work is a continuation of the previously introduced idea to utilize spin-dependent charge carrier recombination in organic semiconductors for an absolute low-magnetic field magnetometry that is robust against fluctuating environmental conditions. The work focuses on the measurement of magnetic field distributions in gradient magnetic fields. It is shown that organic semiconductor-based magnetic resonance magnetometers can reveal magnetic field distributions. However, this measurement approach can be compromised by inductive resonance artifacts introduced by the large-bandwidth RF stripline resonators needed to operate the magnetometer

    Notes From Cardiology Clinic: The Patients We Dislike.

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    Communications software performance prediction

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    Software development can be costly and it is important that confidence in a software system be established as early as possible in the design process. Where the software supports communication services, it is essential that the resultant system will operate within certain performance constraints (e.g. response time). This paper gives an overview of work in progress on a collaborative project sponsored by BT which aims to offer performance predictions at an early stage in the software design process. The Permabase architecture enables object-oriented software designs to be combined with descriptions of the network configuration and workload as a basis for the input to a simulation model which can predict aspects of the performance of the system. The prototype implementation of the architecture uses a combination of linked design and simulation tools
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