A criterion for existence of right-induced model structures

Suppose that $F: \mathcal{N} \to \mathcal{M}$ is a functor whose target is a Quillen model category. We give a succinct sufficient condition for the existence of the right-induced model category structure on $\mathcal{N}$ in the case when $F$ admits both adjoints. We give several examples, including change-of-rings, operad-like structures, and anti-involutive structures on infinity categories. For the last of these, we explore anti-involutive structures for several different models of $(\infty, 1)$-categories, and show that known Quillen equivalences between base model categories lift to equivalences

Traganje za nedostajućim barionima snopom linearno polariziranog zračenja

The photoproduction of ω and ρ mesons from protons with a beam of linearlypolarized photons will be used to decouple baryon resonance production from texchange processes in the center-of-mass energy regime of 1.72 to 2.24 GeV at Hall B of Jefferson Lab. Both the ωN and ρN channels are expected to be a significant branch for baryon resonances. t-channel exchange contributions can only be disentangled by the use of a linearly-polarized photon beam. The measurement will employ a linearly-polarized beam of photons, produced by the approved Coherent Bremsstrahlung Facility, to measure the beam asymmetry as well as the spin density matrix elements of the decay spin-0 mesons of the parent vector meson. The spin density matrix elements and polarization asymmetry of the vector meson decay will be extracted as functions of the vector meson production angle θcm and the center-of-mass energy √ s in the center-of-mass frame. These measurements will expedite the search for baryon resonance contributions, and furthermore, will yield new physics information on diffractive, t- and u-channel processes. Our approved experiments will increase the world’s data set by three orders of magnitude.Fototvorba ω i ρ mezona na protonima snopom linearno polariziranih fotona će se rabiti za odvajanje rezonantne tvorbe bariona od procesa izmjena t kvarkova pri energijama 1,72 do 2,24 GeV u Hali B u Jeffersonovom laboratoriju. Očekuje se da su ωN i ρN kanali važne grane za barionske rezonancije. Doprinos izmjene t-kanalom može se razdvojiti samo upotrebom linearno polariziranih fotona. Mjerenja će se raditi linearno polariziranim snopom fotona proizvedenim odobrenim sustavom “Coherent Bremsstrahlung Facility”, a mjerit će se asimetrija kao i matrični elementi spinske gustoće u raspadu spin-0 mezona roditeljskog vektorskog mezona. Matrični elementi spinske gustoće i polarizacijska asimetrija u raspadu vektorskih mezona će se izvesti kao funkcije kuta tvorbe θcm i energije u centru-mase √ s u sustavu centra-mase. Ta će mjerenja ubrzati potragu za doprinosima barionskih rezonancija, te nadalje, dati fizičke podatke o difraktivnim procesima u t- i u-kanalnim procesima. Ova odobrena mjerenja povećat će skup svjetskih podataka za tri reda veličine

Synthesis and Characterisation of Water Soluble Polymer Drag Reducing Agents

Dilute solutions of high molecular weight (HMW) polymers can reduce friction experienced by a fluid in turbulent pipe flow, greatly decreasing energy required for transfer of the solution. These polymers are known as drag reducing agents (DRA). Polyacrylamide (PAM), synthesised using free-radical inverse-emulsion polymerisation, is most commonly used in commercial aqueous applications. Restrictions on the acrylamide monomer have recently been imposed due to its carcinogenicity, furthermore, the use of inverse-emulsions, containing oil and surfactant, has a negative impact on the environment. The susceptibility of HMW polymers to mechanical degradation in turbulent flow quickly decreases their drag reducing efficiency (DRE), a major problem for current systems. The aim of this project was to produce an effective water soluble polymer DRA with the following properties; 1) acrylamide free; 2) environmentally friendly; 3) oil/surfactant free; 4) mechanically stable; 5) economically viable. It was proposed that by the synthesis of HMW, acrylamide free, star polymers using Cu(0)-mediated polymerisation, effective water soluble drag reducing polymers with enhanced mechanical stability could be produced. An aqueous polymerisation method at ambient temperature would greatly reduce the environmental impact of the process. In Chapter 1, a general background of the drag reduction phenomenon, potential mechanisms of action and key properties for effective drag reducing polymers is given. This chapter also introduces branched polymers and controlled radical polymerisation methods; in particular, Cu(0)-mediated techniques. Chapter 2 focusses on the synthesis of water-soluble, poly(ethylene glycol) (PEG) containing macro-initiators (I4-S, I4-T and I2-S) for use in Cu(0)-mediated polymerisation reactions. By coupling a branching unit containing two potential initiation sites to each end of a PEG chain, multi-functional initiators for the synthesis of star polymers were produced and fully characterised using 1H and 13C NMR spectroscopy as well as MALDI-ToF mass spectrometry. In Chapter 3, the polymerisation of tert-butyl acrylate (tBA) is conducted in DMSO utilising a several initiators; 4,4’-oxybis(3,3-bis(2-bromopropionate)butane (4AE), I4-S, I4-T and I2-S, and a simple catalyst system (Cu(0)/TREN). The reactions proceeded as a self-generating bi-phasic system due to the insolubility of PtBA in the solvent. A model initiator, methyl 2-bromopropionate (MBP), was also used to investigate the polymerisation of tBA further by introducing several changes in reaction conditions. The initiators were used to prepare polymer samples for drag reduction testing. Chapter 4 describes the aqueous Cu(0)-mediated polymerisation of sodium acrylate (NaA) using the I4-S and I4-T macro-initiators. Kinetics study of the reaction using I4-T demonstrated the polymerisation proceeded via a free-radical mechanism. Although complete control over the reaction was not observed, a branched polymer was synthesised by the incorporation of the multi-functional macro-initiator in to the final product and HMW samples were generated for drag reduction testing. The drag reducing properties of the PtBA and PNaA samples are tested in Chapter 5 using a pipe flow test rig. The PtBA samples were first hydrolysed using trifluoroacetic acid (TFA) to provide water soluble poly(acrylic acid) (PAA). For comparison, several commercially available HMW PAM (Praestol, PAM-6M), poly(ethylene oxide) (PEO-8M) and PAA (PAA-1M) samples were also measured. The results demonstrated that the branched PAA/PNaA samples were effective as DRAs. Furthermore, by cycling the polymer solution through the test rig the mechanical stability of the polymer samples was investigated. An increased resistance to mechanical degradation was observed for the star polymers when compared to linear analogues. In Chapter 6 general conclusions and future perspectives for the work are discussed

Gluon Vortices and Induced Magnetic Field in Compact Stars

The natural candidates for the realization of color superconductivity are the extremely dense cores of compact stars, many of which have very large magnetic fields, especially the so-called magnetars. In this paper we discuss how a color superconducting core can serve to generate and enhance the stellar magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.Comment: To appear in the Proceedings of the VII Latin American Symposium on Nuclear Physics and Applications. Cusco (Peru) June 200

Measuring Neutrino Oscillations with Nuclear Reactors

Since the first direct observations of antineutrino events by Reines and Cowan in the 1950's [1], nuclear reactors have been an important tool in the study of neutrino properties. More recently, the study of neutrino oscillations has been a very active area of research. The pioneering observation of oscillations by the KamLAND experiment has provided crucial information on the neutrino mixing matrix. New experiments to study the remaining unknown mixing angle are currently under development. These recent studies and potential future developments will be discussed

The impact of sarcoptic mange Sarcoptes scabiei on the British fox Vulpes vulpes population

1. Disease epizootics can significantly influence host population dynamics and the structure and functioning of ecological communities. Sarcoptic mange Sarcoptes scabiei has dramatically reduced red fox populations Vulpes vulpes in several countries, including Britain, although impacts on demographic processes are poorly understood. We review the literature on the impact of mange on red fox populations, assess its current distribution in Britain through a questionnaire survey and present new data on resultant demographic changes in foxes in Bristol, UK. 2. A mange epizootic in Sweden spread across the entire country in < 10 years resulting in a decline in fox density of up to 95%; density remained lowered for 15–20 years. In Spain, mange has been enzootic for > 75 years and is widely distributed; mange presence was negatively correlated with habitat quality. 3. Localized outbreaks have occurred sporadically in Britain during the last 100 years. The most recent large-scale outbreak arose in the 1990s, although mange has been present in south London and surrounding environs since the 1940s. The questionnaire survey indicated that mange was broadly distributed across Britain, but areas of perceived high prevalence (> 50% affected) were mainly in central and southern England. Habitat type did not significantly affect the presence/absence of mange or perceived prevalence rates. Subjective assessments suggested that populations take 15–20 years to recover. 4. Mange appeared in Bristol’s foxes in 1994. During the epizootic phase (1994–95), mange spread through the city at a rate of 0.6–0.9 km/month, with a rise in infection in domestic dogs Canis familiaris c. 1–2 months later. Juvenile and adult fox mortality increased and the proportion of females that reproduced declined but litter size was unaffected. Population density declined by > 95%. 5. In the enzootic phase (1996–present), mange was the most significant mortality factor. Juvenile mortality was significantly higher than in the pre-mange period, and the number of juveniles classified as dispersers declined. Mange infection reduced the reproductive potential of males and females: females with advanced mange did not breed; severely infected males failed to undergo spermatogenesis. In 2004, Bristol fox population density was only 15% of that in 1994