8,121 research outputs found
Observations of Galactic Gamma-Ray Sources with H.E.S.S
H.E.S.S. results from the first three years of nominal operation are
presented. Among the many exciting measurements that have been made, most
gamma-ray sources are of Galactic origin. I will concentrate here on an
overview of Galactic observations and summarise and discuss observations of
selected objects of the different source types.Comment: 13 pages, 10 figures, based on a talk presented at the workshop
'Energy Budget in the High Energy Universe', Kashiwa, Japan 22 - 24 February
200
Impact of Geomagnetically Induced Currents on Power Transformers
This thesis deals with the impact of Geomagnetically Induced Current (GIC) on power transformers in electrical power systems. A simulator to calculate the flows of GIC in an electrical power network, based on an assumed or measured induced geoelectric potential is proposed. This simulator includes all needed mapping techniques to handle a system that cover a large geographical area.
A correlation between GIC and the reactive power absorbed in the core of the saturated transformer is proposed. That correlation is used to estimate GIC in a transformer utilizing existing reactive power measuring infrastructure within the electrical grid without the need for dedicated measurement equipment. This technique is validated by simulations with electromagnetic transients software, laboratory work and through data recorded during a GIC event on the Hydro One network. The slope correlating reactive power absorption to GIC from an electromagnetic transient model of the transformer may be used to predict GIC levels in the actual transformers.
The application of the technique correlating GIC with reactive power absorption is examined on a segment of a real 500 kV power transmission system. This technique allows GIC to be taken into account during load flow studies. Additionally, some benefits of increased visibility of GIC in the system are shown. A method to determine the frequency and magnitude of the harmonic currents generated by a saturated transformer is also proposed. It is expected that studies conducted in this thesis will be of value to utilities like Hydro One in planning mitigation measures against GICs
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Ethnically Biased? Experimental Evidence from Kenya
Ethnicity has been shown to shape political, social, and economic behavior in Africa, but the underlying mechanisms remain contested. We utilize lab experiments to isolate one mechanism - an individual's bias in favor of coethnics and against non-coethnics - that has been central in both theory and in the conventional wisdom about the impact of ethnicity. We employ an unusually rich research design involving a large sample of 1300 participants from Nairobi, Kenya; the collection of multiple rounds of experimental data with varying proximity to national elections; within-lab priming conditions; both standard and novel experimental measures of coethnic bias; and an implicit association test (IAT). We find very little evidence of an ethnic bias in the behavioral games, which runs against the common presumption of extensive coethnic bias among ordinary Africans and suggests that mechanisms other than a coethnic bias in preferences must account for the associations we see in the region between ethnicity and political, social, and economic outcomes
Neutrino-Nucleus Cross Section Measurements using Stopped Pions and Low Energy Beta Beams
Two new facilities have recently been proposed to measure low energy
neutrino-nucleus cross sections, the nu-SNS (Spallation Neutron Source) and low
energy beta beams. The former produces neutrinos by pion decay at rest, while
the latter produces neutrinos from the beta decays of accelerated ions. One of
the uses of neutrino-nucleus cross section measurements is for supernova
studies, where typical neutrino energies are 10s of MeV. In this energy range
there are many different components to the nuclear response and this makes the
theoretical interpretation of the results of such an experiment complex.
Although even one measurement on a heavy nucleus such as lead is much
anticipated, more than one data set would be still better. We suggest that this
can be done by breaking the electron spectrum down into the parts produced in
coincidence with one or two neutrons, running a beta beam at more than one
energy, comparing the spectra produced with pions and a beta beam or any
combination of these.Comment: 6 pages, 6 figure
Krill oil attenuates left ventricular dilatation after myocardial infarction in rats
Background: In the western world, heart failure (HF) is one of the most important causes of cardiovascular mortality. Supplement with n-3 polyunsaturated fatty acids (PUFA) has been shown to improve cardiac function in HF and to decrease mortality after myocardial infarction (MI). The molecular structure and composition of n-3 PUFA varies between different marine sources and this may be of importance for their biological effects. Krill oil, unlike fish oil supplements, contains the major part of the n-3 PUFA in the form of phospholipids. This study investigated effects of krill oil on cardiac remodeling after experimental MI. Rats were randomised to pre-treatment with krill oil or control feed 14 days before induction of MI. Seven days post-MI, the rats were examined with echocardiography and rats in the control group were further randomised to continued control feed or krill oil feed for 7 weeks before re-examination with echocardiography and euthanization. Results: The echocardiographic evaluation showed significant attenuation of LV dilatation in the group pretreated with krill oil compared to controls. Attenuated heart weight, lung weight, and levels of mRNA encoding classical markers of LV stress, matrix remodeling and inflammation reflected these findings. The total composition of fatty acids were examined in the left ventricular (LV) tissue and all rats treated with krill oil showed a significantly higher proportion of n-3 PUFA in the LV tissue, although no difference was seen between the two krill oil groups. Conclusions: Supplement with krill oil leads to a proportional increase of n-3 PUFA in myocardial tissue and supplement given before induction of MI attenuates LV remodeling
Resipientundersøkelse av Begna, Storelva og Nordfjorden i 1997 ved Norske Skogindustrier ASA - Follum
Rapporten dokumenterer effektene av at det biologiske renseanlegget for fjerning av løst organisk stoff ble satt i drift i juni 1995. Det er ogsü gjort sammenligninger med forholdene før og etter installeringen av kjemisk fellingsanlegg sommeren 1991. Etter installeringen av det biologiske renseanlegget, er TOC redusert fra ca 5000 tonn til ca 2000 tonn karbon pr. ür. Tilførslene av fosfor er imidlertid økt fra ca 3 tonn til ca 8 tonn fordi fosfor mü tilsettes til det biologiske anlegget. Follums egne og mer nøyaktige utslippsmülinger avviker noe fra elvemülingene, men trendene er de samme, klar reduksjon av organisk stoff og like klar økning av fosfor. Undersøkelse av bunndyr og begroing viser at Begna fortsatt er püvirket av utslipp av organisk stoff nedstrøms Follum. Det er en klar bedring i miljøkvalitet etter samløp med Randselva, men Storelva für igjen en redusert vannkvalitet ved Busund (nedstrøms Monserud). Forholdene i Begna (nedstrøms Monserud). Forholdene i Begna (nedstrøms Follum) er i 1997 merkbart bedre enn i 1993. Dette gir seg utslag i bedret biologisk mangfold, dvs. flere dyre- og plantegrupper (arter). Elvebunnen er ogsü mindre dekket av bakterier og sopp, som vanligvis indikerer overbelastning av organisk stoff, noe som hovedsakelig skyldes tilførsler fra tidligere ür. Hovedvannmassene i Tyrifjorden er imidlertid fortsatt i bedring, og algeinnholdet er nü pü et nivü som tilsvarer miljømület satt opp av Vannbruksplanutvalget
Tenecteplase for the treatment of acute ischemic stroke: a review of completed and ongoing randomized controlled trials
Alteplase has been the mainstay of thrombolytic treatment since the National Institutes of Neurological Disorders and
Stroke trial was published in 1995. Over recent years, several trials have investigated alternative thrombolytic agents.
Tenecteplase, a genetically engineered mutant tissue plasminogen activator, has a longer half-life, allowing single intravenous
bolus administration without infusion, is more fibrin specific, produces less systemic depletion of circulating
fibrinogen, and is more resistant to plasminogen activator inhibitor compared to alteplase. Tenecteplase is established as
the first-line intravenous thrombolytic drug for myocardial infarction, where it has been shown to achieve comparable
reperfusion with reduced risk of systemic bleeding in comparison to alteplase. We review the literature on tenecteplase
for the treatment of acute ischemic stroke, with a focus on the major completed and ongoing trials. Overall, tenecteplase
shows promise for treatment of acute ischemic stroke, both in populations currently eligible for alteplase and also in
groups not currently treated with thrombolysis
Enumeration of maps with self avoiding loops and the O(n) model on random lattices of all topologies
We compute the generating functions of a O(n) model (loop gas model) on a
random lattice of any topology. On the disc and the cylinder, they were already
known, and here we compute all the other topologies. We find that the
generating functions (and the correlation functions of the lattice) obey the
topological recursion, as usual in matrix models, i.e they are given by the
symplectic invariants of their spectral curve.Comment: pdflatex, 89 pages, 12 labelled figures (15 figures at all), minor
correction
Quark cluster signatures in deuteron electromagnetic interactions
A suggestion is made for distinguishing 2N and 6q short range correlations
within the deuteron. The suggestion depends upon observing high momentum
backward nucleons emerging from inelastic electromagnetic scattering from a
deuteron target. A simple model is worked out to see the size of effects that
may be expected.Comment: 18 pages (3 figures available as hard copy), WM-94-10
On-Off Intermittency in Time Series of Spontaneous Paroxysmal Activity in Rats with Genetic Absence Epilepsy
Dynamic behavior of complex neuronal ensembles is a topic comprising a
streamline of current researches worldwide. In this article we study the
behavior manifested by epileptic brain, in the case of spontaneous
non-convulsive paroxysmal activity. For this purpose we analyzed archived
long-term recording of paroxysmal activity in animals genetically susceptible
to absence epilepsy, namely WAG/Rij rats. We first report that the brain
activity alternated between normal states and epilepsy paroxysms is the on-off
intermittency phenomenon which has been observed and studied earlier in the
different nonlinear systems.Comment: 11 pages, 6 figure
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