3,097 research outputs found
Extremal limits of the Cvetic-Youm black hole and nilpotent orbits of G2(2)
We study extremal cohomogeneity one five-dimensional asymptotically flat
black holes of minimal supergravity in terms of the geodesics generated by
nilpotent elements of the Lie algebra g2(2) on the coset manifold
G2(2)/SO(2,2). There are two branches of regular extremal black holes with
these properties: (i) the supersymmetric BMPV branch, and (ii) the
non-supersymmetric extremal branch. We show that both of these branches are
reproduced by nilpotent SO(2,2)-orbits. Furthermore, we show that the partial
ordering of nilpotent orbits of G2(2) is in one-to-one correspondence with the
phase diagram of these extremal black holes.Comment: 17 pages, 2 figures; v2 two minus sign typos in appendix A equation
(A.3) corrected, no other change
The Weak Coupling Spectrum around Isolated Vacua in N=4 Super Yang-Mills on T^3 with any Gauge Group
The moduli space of flat connections for maximally supersymmetric Yang-Mills
theories, in a space-time of the form T^3xR, contains isolated points,
corresponding to normalizable zero energy states, for certain simple gauge
groups G. We consider the low energy effective field theories in the weak
coupling limit supported on such isolated points and find that when quantized
they consist of an infinite set of harmonic oscillators whose angular
frequencies are completely determined by the Lie algebra of G. We then proceed
to find the isolated flat connections for all simple G and subsequently specify
the corresponding effective field theories.Comment: 32 pages, 11 figures, v4 Added chapter, Published versio
Implications of the band gap problem on oxidation and hydration in acceptor-doped barium zirconate
Charge carrier concentrations in acceptor-doped proton-conducting perovskites
are to a large extent determined by the hydration and oxidation of oxygen
vacancies, which introduce protons and holes, respectively. First-principles
modeling of these reactions involves calculation of formation energies of
charged defects, which requires an accurate description of the band gap and the
position of the band edges. Since density-functional theory (DFT) with local
and semi-local exchange-correlation functionals (LDA and GGA) systematically
fails to predict these quantities this can have serious implications on the
modeling of defect reactions. In this study we investigate how the description
of band gap and band edge positions affects the hydration and oxidation in
acceptor-doped BaZrO. First-principles calculations are performed in
combination with thermodynamic modeling in order to obtain equilibrium charge
carrier concentrations at different temperatures and partial pressures. Three
different methods have been considered: DFT with both semi-local (PBE) and
hybrid (PBE0) exchange-correlation functionals, and many-body perturbation
theory within the -approximation. All three methods yield similar
results for the hydration reaction, which are consistent with experimental
findings. For the oxidation reaction, on the other hand, there is a qualitative
difference. PBE predicts the reaction to be exothermic while the two others
predict an endothermic behavior. Results from thermodynamic modeling are
compared with available experimental data, such as enthalpies, concentrations
and conductivities, and only the results obtained with PBE0 and , with
an endothermic oxidation behavior, give a satisfactory agreement with
experiments.Comment: 15 pages, 12 figures + supplementary material (2 pages
Simple one pot preparation of chemical hydrogels from cellulose dissolved in cold LiOH/urea
In this work, non-derivatized cellulose pulp was dissolved in a cold alkali solution (LiOH/urea) and chemically cross-linked with methylenebisacrylamide (MBA) to form a robust hydrogel with superior water absorption properties. Different cellulose concentrations (i.e., 2, 3 and 4 wt%) and MBA/glucose molar ratios (i.e., 0.26, 0.53 and 1.05) were tested. The cellulose hydrogel cured at 60 °C for 30 min, with a MBA/glucose molar ratio of 1.05, exhibited the highest water swelling capacity absorbing ca. 220 g H2O/g dry hydrogel. Moreover, the data suggest that the cross-linking occurs via a basic Michael addition mechanism. This innovative procedure based on the direct dissolution of unmodified cellulose in LiOH/urea followed by MBA cross-linking provides a simple and fast approach to prepare chemically cross-linked non-derivatized high-molecular-weight cellulose hydrogels with superior water uptake capacity.Portuguese Foundation for Science and Technology, FCT, via the projects PTDC/AGR-TEC/4814/2014, PTDC/ASP-SIL/30619/2017 and UIDB/05183/2020, and the research grant IF/01005/2014.info:eu-repo/semantics/publishedVersio
Size and shape of oxygen vacancies and protons in acceptor-doped barium zirconate
The defect induced chemical expansion in acceptor-doped barium zirconate is
investigated using density-functional theory (DFT) calculations. The two defect
species involved in the hydration reaction, the +2 charged oxygen vacancy and
the proton interstitial forming a hydroxide ion, are considered both as free
defects and in association with the dopants Y, In, Sc and Ga. The defect
induced strain tensor lambda is introduced, which provides a natural
generalisation of the ordinary chemical expansion to three dimensions and to
anisotropic distortions. Both the addition of a vacancy and a proton cause
anisotropic distortions and a net contraction of the lattice, indicating that
both the vacancy and the hydroxide ion are smaller than the oxygen ion. The
contraction is considerably larger for the vacancy and the net effect in
hydration, when a vacancy is filled and two protons are added, is an expansion,
consistent with the experimental findings. The effect of the dopants on the
chemical expansion in hydration is found to be quite small, even if it is
assumed that both the vacancy and the proton are fully associated with a dopant
atom in the lattice
THE TERM OPEN SOURCE SOFTWARE RE-NEGOTIATED
Implementing Open Source Software (OSS) technology (tools and practices) entails potential for radical organisational transformation of software production. Not going there yet, this paper discusses the local re-negotiation of the term OSS itself in certain case companies. We claim that these processes (1. organisational change, and 2. renegotiation of the term OSS) are intertwined. Renegotiation of the term is needed in order to create an understanding of what it means to leverage OSS locally. Based on a systematic literature review, we investigate two cases to outline what kind of renegotiation of the term occurs when a company alters it\u27s software production. Initial findings indicate that future research on organizational OSS may benefit from a more critical review of the processes occurring under the term OSS
Vid livets slut har man bara en chans att göra rÀtt : Optimal palliativ vÄrd för personer med demenssjukdom
Syftet med det hÀr arbetet Àr att genom litteraturstudier beskriva en optimal palliativ vÄrd för personer med demenssjukdom. FrÄgestÀllningen Àr: Vad kÀnnetecknar en optimal palliativ vÄrd för personer med demenssjukdom?
Som teoretiska utgÄngspunkter fungerar Katharine Kolcabas teori om vÀlbefinnande samt Kerstin Segestens teori om trygghet. Arbetet Àr en systematisk litteraturstudie och som dataanalysmetod har kvalitativ innehÄllsanalys anvÀnts. Totalt 11 stycken vetenskapliga artiklar har analyserats.
I resultatet framkom att det Àr viktigt att det finns tillrÀckligt med resurser för att den palliativa vÄrden ska fungera smidigt. Det behöver ocksÄ finnas bra samarbete mellan olika instanser som ger service. Multiprofessionellt teamarbete kom ocksÄ fram som en viktig del och innebÀr att man som sjukskötare behöver stöd av experter och ledare. Det behöver ocksÄ finnas gott samarbete mellan de olika yrkesgrupperna som Àr inblandade i den palliativa vÄrden för personer med demenssjukdom.
Att vÄrdpersonalen Àr kompetent Àr betydelsefullt för att vÄrden ska fungera bra. OcksÄ en personcentrerad vÄrd Àr en viktig del av resultatet. Detta innebÀr att vÄrden Àr vÀlplanerad ocksÄ pÄ förhand, att bedömning och tillgodoseende av behov fungerar bra för patienter med demenssjukdom, att vÄrden sker pÄ ett empatiskt sÀtt samt att de nÀrstÄende fÄr det stöd de behöver.The purpose with this study is to describe the optimal palliative care for patients with dementia by conducting a literature study. The research question is: What characterizes optimal palliative care for patients with dementia?
The theoretical take-off points are the comfort theory by Katharine Kolcaba and the theory of safety by Kerstin Segesten. The study is a systematic literature study and data was analyzed with qualitative content analysis. 11 scientific articles were used in the analysis.
For the palliative care to function properly it is important that there is enough resources. Collaboration between services is also essential. Another important issue is multiprofessional teamwork between the different professions that give palliative care to patients with dementia.
Qualified staff is another crucial factor for making care work well. Person centered care is also an important part of the result, meaning that care must be well planned, also in advance. It also means that assessment of needs and adressing needs is done properly. Care must be given with compassion and the family members are to be offered the support they
need
Kaitsealuste pÀevaliblikate ökoloogia Eestis
VĂ€itekirja elektrooniline versioon ei sisalda publikatsioone.Paljude Euroopa pĂ€evaliblikaliblikaliikide seisund on halvenemas. Eduka looduskaitselise tegevuse jaoks on vaja mĂ”ista ohustatud liikide pĂ”hilisi ökoloogilisi nĂ”udmisi. Vastsena taimedel toituvatele putukatele on sobiva taimeliigi olemasolu mĂ”istagi peamine keskkonna sobivuse nĂ€itaja. Toidutaime olulisus siiski erineb monofaagsete (toituvad ĂŒhel taimeliigil), oligofaagsete (toituvad mĂ”nel suguluses oleval liigil) ja polĂŒfaagsete (toituvad mitmetel erinevatel taimeliikidel) putukate jaoks, samuti komplitseerib olukorda toidutaimekasutuse geograafiline varieerumine. SeetĂ”ttu on oluline teada, kas mĂ”nel ohustatud liblikaliigil on lokaalselt spetsiifilisemad taime-eelistused kui regioonis ĂŒldiselt.
Oma töös uurisin viie Euroopas ohustatuks peetava pĂ€evaliblikaliigi toidutaimekasutust Eestis kasutades erinevaid laborkatseid, vĂ€litöid ning levikuanalĂŒĂŒsi. Uuritavateks liikideks olid sÔÔrsilmik, vareskaera-aasasilmik, suur-kuldtiib, teelehe-mosaiikliblikas ja suur-mosaiikliblikas. Töö tulemused nĂ€itavad, et sÔÔrsilmik ja vareskaera-aasasilmik on polĂŒfaagsed, mistĂ”ttu ĂŒhegi konkreetse taimeliigi olemasolu ei mÀÀra elupaiga kvaliteeti ega limiteeri nende liikide levikut. Leidsime siiski, et vareskaera-aasasilmikul esineb mikroelupaigalisi eelistusi. Suur-kuldtiiva peamiseks toidutaimeks on tömbilehine oblikas, mis on kooskĂ”las liigi leviku analĂŒĂŒsi tulemusega. Nimelt eelistab liblikas kraavide ja inimasustusega alasid â need loovad usutavasti oblikale soodsaid kasvutingimusi. Teelehe-mosaiikliblikas nĂ€ib Eestis olevat monofaagne harilikul peetrilehel, mis on siiani jÀÀnud ainsaks tĂ”endatud selle liblika toidutaimeks. Suur-mosaiikliblika levik on seotud hariliku saarega â looduses on röövikuid leitud vaid sellelt taimeliigilt; liblikas on levinud vaid seal, kus toidutaim esineb.
Viie uuritud liblikaliigi ohustatuse hindamine ei olnud kĂŒll kĂ€esoleva töö otseseks eesmĂ€rgiks, kuid autorile teadaolevalt ei viita miski nende liikide populatsioonide kahanemisele Eestis. KĂ”ikide uuritud liblikaliikide olukord Eestis on hea, kuid teelehe- ja suur-mosaiikliblika jaoks vĂ”ib tulevik siiski olla ebakindlam. Seda just maakasutusmuutuste ning kiiresti leviva seenhaiguse tĂ”ttu, mis mĂ”jutavad nende liblikate peamisi toidutaimi, vastavalt peetrilehte ja saart. Kogutud informatsiooni on kindlasti vĂ”imalik kasutada nendes piirkondades, kus nimetatud viie liblikaliigi looduskaitseline seisund on halvem ning ka tĂ€helepanu vajavate kohalike populatsioonide kaitseks Eestis.Numerous European butterflies are declining. To develop successful conservation practices it is necessary to understand the basic ecological requirements of the endangered species. The presence of a suitable host species is the main criterion for herbivorous insects. The importance of the host plant is different for monophagous (feeding only on one host species), oligophagous (feeding on few related species) and polyphagous (feeding on wide range of host species) insects, as well as host plant use may vary geographically. Therefore, it is vital to know whether any endangered species has more specific food preferences locally than believed for the region as whole.
I explored the importance of host plant in Estonia for endangered buttefly species Lopinga achine, Coenonympha hero, Lycaena dispar, Euphydryas aurinia and E. maturna, using different laboratory experiments, field work and analyses of distribution. We found out that L. achine and C. hero are polyphagous, so the presence of a certain plant species does not determine the habitat quality or limit the distribution of these butterflies. Still, C. hero seems to have preferences at microhabitat level. Primary host plant for L. dispar in Estonia is the broad-leaved dock (Rumex obtusifolius), which is consistent with the results contry-wide distribution analyses: this butterfly species prefers areas with ditches and human settlemen, these factors likely creating favourable conditions for the host species. E. aurinia appears to be functionally monophagous on devil's-bit scabious (Succisa pratensis), which has remained the only confirmed host plant in the country. E. maturna is related to ash (Fraxinus excelsior): caterpillars have been found only on ash trees in the wild; the butterfly species is distributed only in the areas where the host species is present.
Assessment of the conservation status of the five butterfly species was not among the aims of the present study. However, there is no direct evidence of decline for any of these species in Estonia. The conservation status of all five butterfly species appears favourable. Although the the future of E. aurinia and E. maturna looks more uncertain due to changes in agriculture practice and a fungal disease which affect their main host plants. Local populations of these five butterfly species may still require attention. Also, the information gathered must be used in other regions where these species may be of higher conservation concern
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