Approximate twistors and positive mass

In this paper the problem of comparing initial data to a reference solution for the vacuum Einstein field equations is considered. This is not done in a coordinate sense, but through quantification of the deviation from a specific symmetry. In a recent paper [T. B\"ackdahl, J.A. Valiente Kroon, Phys. Rev. Lett. 104, 231102 (2010)] this problem was studied with the Kerr solution as a reference solution. This analysis was based on valence 2 Killing spinors. In order to better understand this construction, in the present article we analyse the analogous construction for valence 1 spinors solving the twistor equation. This yields an invariant that measures how much the initial data deviates from Minkowski data. Furthermore, we prove that this invariant vanishes if and only of the mass vanishes. Hence, we get a proof of the positivity of mass.Comment: 18 pages, corrected typos, updated reference

Superselection Sectors in Asymptotic Quantization of Gravity

Using the continuity of the scalar $\Psi_2$ (the mass aspect) at null infinity through $i_o$ we show that the space of radiative solutions of general relativity can be thought of a fibered space where the value of $\Psi_2$ at $i_o$ plays the role of the base space. We also show that the restriction of the available symplectic form to each ``fiber'' is degenerate. By finding the orbit manifold of this degenerate direction we obtain the reduced phase space for the radiation data. This reduced phase space posses a global structure, i.e., it does not distinguishes between future or past null infinity. Thus, it can be used as the space of quantum gravitons. Moreover, a Hilbert space can be constructed on each ``fiber'' if an appropriate definition of scalar product is provided. Since there is no natural correspondence between the Hilbert spaces of different foliations they define superselection sectors on the space of asymptotic quantum states.Comment: 22 pages, revtex fil

Energy Measurements of Speech Sounds

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The effect of ACTH on parturition as defence mechanism stimulator in sows

International audienc

Influence from dialectal background on the score in hearing tests employing speech stimuli

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Influence of microphone position in the recording of speech signals

Sound pressure levels of various speech sounds are measured simultaneously at different distances from the mouth. The observed values for low vowels and [s] differ especially close to the mouth from those predicted from the distance law for sound radiation. The variation of sound pressure with distance seems to depend on the speech sound in question. Some consequences hereof are pointed out. The results are compared with calculated values of the sound pressure from a sound source on a rigid sphere. Some of the observed deviations from the distance law seem attributable to the different frequency composition of the speech sounds. However, some of the observations (e.g. the difference between the variation of low and high vowels at positions close to the mouth) cannot be accounted for by the model

’Til Death Do Us Part? What Every Legal Practitioner Should Know About Premarital Agreements: A Law Student’s Perspective

It is rare that a couple will enter into a marriage expecting to divorce each other. It may be the romance or the excitement of the impending nuptials, but couples do not include an expiration date on their marriage certificate. However, not all marriages last until “death do us part.” The United States Census Bureau conducted its first survey into marriages, divorces, and widowhood in America in 2009, finding that 9.2 of every 1,000 men and 9.7 of every 1,000 women over the age of fifteen reported being divorced. Despite these rates, research suggests that only one-fourth of Americans believe that premarital agreements (also known as prenuptial agreements or a “prenup”) are financially smart for those contemplating marriage. As a legal practitioner, it is imperative to be able to draft a valid, all-encompassing premarital agreement while navigating state law and the ethical considerations involved in the process. This guide will provide you with the necessary resources to draft a solid, comprehensive premarital agreement for your love-struck clients

Spredning og persistens av antibiotika resistens gener i tarmfloraen hos honningbier

Bacteria residing in the gut – the gut microbiota (GM) – are important for host health. Several parallels between the human and honeybee GM exist: i) the GM is host specific (core microbiota), ii) age dependent development of the GM microbiota, iii) the GM composition is gut part dependent, and iv) the GMs ability to provide the host with additional dietary benefits. Due to their simple GM composition, honeybees have emerged as a model to understand host-bacteria interactions. In addition, the honeybee GM has been used to study its associations with perturbations like antibiotic exposure. Although short-term perturbations by antibiotic treatment have been extensively studied, we have limited knowledge about the long-term effects. The human and animal GM is a reservoir for different antibiotic resistant genes (ARGs) that can transfer to pathogenic bacteria, a scenario that is already a global and serious threat to human infection management. In this thesis, we addressed several intriguing questions regarding this scenario: e.g. in what way do long-term antibiotic treatment affect the GM composition, how do ARG spread to and within the GM, and how are they persistent within the GM? We used honeybees from different antibiotic treatment regimes as a model to address if antibiotic exposure will select for antibiotic resistant bacterial strains and/or if ARGs will transfer horizontally within the core microbiota. We used an experimental set up of two honeybee populations: one from Arizona, USA and one from Ås, Norway. In the USA, tetracycline is widely used in agriculture as well as to treat honeybee infections, while in Norway it is not. This set up in combination with the use of a low complex model system, allowed us to identify spread of ARG within the GM population at the bacterial strain level, and associate it with antibiotic exposure. We used a combination of techniques to investigate the honeybee GM composition and the prevalence of ARG: e.g. Bacteria culturing, quantitative PCR, Illumina whole genome shotgun sequencing, phenotypical testing and microscopy. We focused on two bacteria important for honeybee health: Gilliamella apicola and Snodgrassella alvi. To investigate the phylogeny composition in our dataset, we compared genes found in all bacteria (of the same species) and found that strains of G. apicola separated into three subgroups found in bees from both Norway and Arizona. This showed that strain diversity is maintained despite long-term antibiotic exposure to the Arizonan bee population. We also found that antibiotic exposure has an effect on the horizontal spread of transposon associated ARG within the Arizonan honeybee GM, wherein these ARGs were detected in all subgroups of G. apicola as well as its transfer to S. alvi. Moreover, our results showed that unique tetracycline resistance genes associated differently with unique bacterial subgroups. One subgroup differed substantially both phenotypically and genotypically from the type strain of G. apicola and therefore it was characterized, described and proposed as a new species: G. apis sp. nov. Overall, these findings show that ARG are prevalent in the core microbiota of honeybees and that long-term antibiotic exposure influences the spread of ARG within the honeybee core microbiota population rather than selecting for a few antibiotic resistant strains. This suggests that persistence of ARGs in the GM is sustained by host selection of core bacteria harboring ARGs, and that antibiotic exposure maintains the GM as a potent reservoir for ARGs. These results highlight the need to reduce unnecessary antibiotic usage to prevent spread of ARGs and demonstrate the suitability of honeybees as a model for investigating ARGs spread in bacterial populations.Bakteriene som lever i tarmen – tarmfloraen – er viktig for vertens helse. Det kan dras mange paralleller mellom tarmfloraen til mennesker og honningbier: i) tarmfloraen er verts spesifikk (kjerneflora), ii) begge utvikles med alder, iii) sammensetningen av tarmfloraen er avhengig hvor i tarmen det er, og iv) tarmfloraen kan tilføre verten energi ved nedbryting av næringsstoffer. På grunn av at honningbier har en enkelt sammensatt tarmflora, har de begynt å bli brukt som modell i studier om bakterie-vert interaksjoner. I tillegg har honningbier blitt brukt i studier hvor det er sett på hvordan tarmfloraen er assosiert med ytre påvirkninger. Selv om forandringer som skyldes kortvarige antibiotika behandlinger har blitt grundig studert, har vi heller liten kunnskap om langtids effekter. Tarmfloraen i mennesker og dyr er et reservoar for antibiotika resistens gener (ARG) som kan overføres til patogene bakterier, et senario som allerede er en global og alvorlig trussel for behandling av infeksjonssykdommer. I dette doktorgradsarbeidet, adresserte vi flere spennende spørsmål relatert til dette senarioet, som f.eks.: på hvilken måte påvirker lang-tids eksponering med antibiotika tarmfloraen sammensetning, hvordan spes ARG til og i tarmfloraen, og på hvilken måte kan ARG persistere i tarmfloraen? Vi brukte honningbier fra områder med ulik bruk av antibiotika som en modell for å adressere om antibiotika eksponering vil kunne selektere for antibiotika resistente bakterier og/ eller om ARG vil kunne overføres mellom bakteriemedlemmene i kjernefloraen. Vi brukte et eksperimentelt oppsett med to honningbie populasjoner: en fra Arizona, USA og en fra Ås, Norge. I USA blir tetrasyklin bruk i landbruksindustrien og likeså som til behandling av infiserte bikuber, mens i Norge blir tetrasyklin ikke brukt slik. Dette oppsettet i kombinasjon med en modell som har en enkel tarmflorasammensetning, gjorde slik at vi kunne identifisere spredning av ARG innad in tarmfloraen på bakteriestamme nivå, og assosiere dette med antibiotika eksponering. Vi brukte flere ulike metoder for å undersøke honningbienes tarmflora sammensetning og prevalens av ARG der i: dyrkning av bakterier, kvantitativ PCR, Illumina hel-genom sekvensering, phenotypiske tester og mikroskopering. Vi fokuserte på to bakterier som er viktige for honningbie helse: Gilliamella apicola og Snodgrassella alvi. For å kunne undersøke den fylogenetiske sammensetningen i vårt datasett, så sammenlignet vi genene som finnes i alle bakteriene (innenfor en bakterie spesies), og fant at ulike stammer av G. apicola grupperte seg i tre sub-grupper, og disse var tilstede i bier både fra Norge og Arizona. Dette viste at mangfoldet av stammer beholdes selv under langvarig antibiotika eksponering. Vi fant også at antibiotika eksponering har en effekt på overføring av transposon-assosierte ARG i tarmfloraen hos honningbier fra Arizona, hvor i disse ARG kunne detekteres i alle sub-grupper av G. apicola og også i S. alvi. I tillegg viser våre resultater at ulike tetrasyklinresistens gener assosierer seg ulike med ulike bakterie sub-grupper. En av disse sub-gruppene var så ulik både phenotypisk og genotypisk type-stammen G. apicola, at den derfor ble karakterisert, beskrevet og foreslått til å være en ny spesies: G. apis sp. nov. Sett i sammenheng så viser disse funnene at ARG er prevalente i kjernefloraen hos honningbier og at langtids eksponering med antibiotika påvirker i større grad spredningen av ARG i tarmfloraen enn at den selekterer for noe få antibiotika resistente stammer. Fra dette kan det tenkes at persistens av ARG i tarmfloraen opprettholdes på grunn av verts seleksjon av kjerne floraen, og at antibiotika eksponering understøtter at tarmfloraen forblir et reservoar for ARG. Disse resultatene påpeker at det er viktig å redusere unødvendig bruk av antibiotika for å forebygge spredning av ARG og de demonstrerer at honningbier er nyttige som modell til å undersøke hvordan ARG sprer seg i bakteriepopulasjoner