Investigation of the spin structure of the nucleon at the COMPASS experiment

The spin structure of the nucleon is studied at the COMPASS experiment. Their subject is of special interest since the surprising findings of the European muon collaboration (EMC) that the contribution from the quark spins to the nucleon spin is rather small. This finding started the search for the various contributions to the nucleon spin. Their contributions are given by the spins of the quarks and gluons and their orbital angular momenta, where the contribution from the quark spins is about 30%. At the COMPASS experiment, a polarised muon beam is scattered off a polarised fixed target made out of either lithium deuteride or ammonia. In such reactions, the longitudinal double spin asymmetry and the spin-dependent structure function are measured. The longitudinal double spin asymmetry is obtained in two different kinematic regions. At low photon virtualities, Q^2 1 (GeV/c)^2, the results for the asymmetry obtained from the 2006 and 2011 data taking are presented. The results from the 2006 data taking improve the statistical precision of the spin-dependent structure function of the deuteron. For the 2011 data taking, the nominal beam momentum was increased from 160 GeV/c to 200 GeV/c. This extends the kinematic range towards lower Bjorken-x and higher photon virtualities. These results complete the previous results for the spin-dependent structure function of the proton using the data taken in 2007. The results on the spin-dependent structure function are used together with the world data on the spin-dependent structure function of the proton, deuteron and neutron measured in deep inelastic scattering in a QCD fit to obtain the parton helicity distributions. They can be interpreted similar as the parton distribution function, which describe the momentum fraction carried by quarks within a certain Bjorken-x range dx. The parton helicity distributions describe the contribution from the quark spins to the total nucleon spin within dx. From the QCD fit, the contribution from the quark spins to the total spin of the nucleon is obtained as well as the the contributions from the various quark flavours. The measured results on the spin-dependent structure functions are also used to evaluate their first moments, int_0^1 g_1(x,Q^2) dx. They are used to test QCD sum rules like the Bjorken and the Ellis-Jaffe sum rule. A violation of the Ellis-Jaffe sum rule is already known since the surprising results from EMC and was confirmed by various experiments. The Bjorken sum rule is of special interest since it connects the non-singlet structure function, g_1^NS = g_1^p - g_1^n, with the ratio g_A/g_V. Further on the evolution of the non-singlet structure function is independent of the poorly known gluon helicity distribution. Here, the Bjorken sum rule is confirmed at the level of 9%. The first moment of the spin-dependent structure function of the deuteron allows for the determination of the singlet axial charge a_0 = 0.32 +/- 0.02_{stat} +/- 0.04_{syst} pm 0.05_{evol}, which is identified with the contribution from the quark spins to the total nucleon spin in the MSbar scheme.Am COMPASS-Experiment wird die Spinstruktur des Nukleons untersucht. Diese ist von besonderen Interesse seit der überraschenden Entdeckung durch die europäische Myonkollaboration (EMC), dass nur ein kleiner Teil des Nukleonspins von den Spins der Quarks stammt. Mit dieser Entdeckung begann die Suche nach den verschiedenen Bestandteilen. Diese sind durch die Spins der Quarks und Gluonen sowie deren Bahndrehimpulsen gegeben, wobei der Beitrag der Quarks etwa 30% beträgt. Am COMPASS-Experiment wird für diese Untersuchung ein polarisierter Myonstrahl und ein polarisiertes Lithiumdeuterid- oder Ammoniaktarget genutzt. Aus diesen Messungen wurden die longitudinalen Doppelspinasymmetrien zusammen mit den spinabhängigen Strukturfunktionen bestimmt. Die longitudinale Doppelspinasymmetrie wurde in zwei verschiedenen kinematischen Bereichen gemessen. Bei niedrigen Photonvirtualitäten, Q^2 1 (GeV/c)^2, wurde die spinabhängige Strukturfunktion des Deuterons aus den Daten von 2006 bestimmt. Diese Ergebnisse verbessern die statistische Genauigkeit der bisherigen COMPASS Messung. Für die Messung in Jahr 2011 wurde die Strahlenergie von 160 GeV auf 200 GeV erhöht. Dadurch konnte die spinabhängige Strukturfunktion des Protons bei noch kleineren Bjorken-$x$ und größeren Photonvirtualitäten gemessen werden. Diese Messung vervollständigen die vorherige Messung bei 160 GeV. Die Ergebnisse der spinabhängigen Strukturfunktionen wurden zusammen mit den Weltdaten zur spinabhängigen Strukturfunktion des Proton, des Deuteron und des Neutron in einem QCD fit verwendet, um die Partonhelizitätsverteilungen zu bestimmen. Diese können ähnlich wie die Partonverteilungen interpretiert werden, die den Impulsbruchteil, der von Quarks innerhalb eines bestimmten Bjorken-x Bereichs dx getragen wird, angeben. Die Partonhelizitätsverteilungen hingegen geben den Beitrag zum Nukleonspin in so einem Intervall dx an. Zudem wurde der gesamte Beitrag der Quarkspins sowie der der einzelnen Quark-Flavour zum Nukleonspin aus diesem Fit bestimmt. Aus den Ergebnissen der spinabhängigen Strukturfunktionen wurden auch die ersten Momente, int_0^1 g_1(x,Q^2) dx, der Strukturfunktionen bestimmt. Diese wurden zum Prüfen von QCD Summenregeln, wie der Bjorken- oder Ellis-Jaffe-Summenregel, verwendet. Eine Verletzung der Ellis-Jaffe-Summenregel ist bereits seit Ergebnissen von EMC bekannt und wurde seitdem durch weitere Messungen bestätigt. Die Bjorken-Summenregel verbindet die non-singlet Strukturfunktion, g_1^NS = g_1^p - g_1^n, mit dem Verhältnis g_A/g_V. Zusätzlich ist die Abhängigkeit von der Photonvirtualität dieser Strukturfunktion von der wenig bekannten Gluonhelizitätsverteilung unabhängig. Die Bjorken-Summenregel wurde mit einem Fehler von 9% bestätigt. Das erste Moment der spinabhängigen Strukturfunktion des Deuterons wurde auch verwendet, um die axiale singlet Ladung a_0 = 0.32 +/- 0.02_{stat} +/- 0.04_{syst} pm 0.05_{evol} zu bestimmen. Diese gibt im MSbar Schema den Beitrag der Quarkspins zum Nukleonspin an.X, 227 Seite

Tin country

Tin Country, a novel in short stories, is a coming of age story that focuses on the turn of this century. The collection takes on the subject of girlhood, tracing childhood and adolescent experiences, relationships, and realizations that shape Ruth Wright\u27s, the narrator, struggle to reconcile the past and find self as she moves into womanhood. Tin Country is the narrative of one woman and her drive to live fully - to re-examine the important ties to other women who enable her to envision herself as a survivor, giving her strength to travel back and (re)envision her past. The stories in the first half of the collection place Ruth as a child. The stories look at the myths of girlhood, race and class issues, religion, and friendship. The second half of the collection addresses finding a sense of self, identifying the self as a survivor, accepting the past, and moving forward. The collection focuses on relationships between women, exploring the metaphorical divide between men and women in our society and examining how men, as a symbol of patriarchal culture, influence women. The stories look at the complicated effect that patriarchal society and organized religion have on women. Since women have limited access to public platforms even today, the women in Tin Country rely on myth and oral tradition because they do have access to that. The women use myth and fairytale as a means of protection and survival, borrowing myths from various cultures and creating their own myths. As Ruth journeys through her past, she realizes she is no longer a victim but a survivor. In rejecting traditional roles of women, Ruth rejects the patriarchal society that dominated her past and accepts the dark, realistic hope found within the natural world of her future. Water is an important theme in all of the stories. Water - sometimes overwhelming and suffocating and sometimes safe and mothering - works as a mirror, reflecting the self. The title of the collection comes from the fifth story. The title both represents the world within the story, Tin Country, and the place from which all the stories generate

Calculation and Comparison of Turbulence Attenuation by Different Methods

This paper is focused on the effect of turbulence in atmospheric transmission media. A short introduction of the origin of turbulent atmosphere is given. Two classical methods for the calculation of turbulence attenuation are mentioned and briefly described in the paper – the Rytov approximation and Andrews’s method, and a new technique designed by the authors of this paper – the method of available power – is presented in short as well. We have run simulations in Matlab to compare the results of turbulence attenuation given by the classical methods and by the new technique - the method of available power. These calculations were performed for communication wavelengths of 850 nm and 1550 nm. The distance between the optical transmitter and receiver of horizontal links was set to values ranging from 0 m to 2500 m. We have taken into account the homogenous turbulence with low (10^-16 m^-2/3), medium (10^-15 m^-2/3) and high (10^-14 m^-2/3) structure parameter of refractive index Cn2

An Introduction to Free-space Optical Communications

Over the last two decades free-space optical communication (FSO) has become more and more interesting as an adjunct or alternative to radio frequency communication. This article gives an overview of the challenges a system designer has to consider while implementing an FSO system. Typical gains and losses along the path from the transmitter through the medium to the receiver are introduced in this article. Detailed discussions of these topics can be found in this special issue of the Radioengineering Journal

Flies on the move: an inherited virus mirrors Drosophila melanogaster's elusive ecology and demography.

Journal ArticleResearch Support, Non-U.S. Gov'tCopyright © 2014 John Wiley & Sons LtdThis is the accepted version of the following article: Wilfert, L. and Jiggins, F. M. (2014), Flies on the move: an inherited virus mirrors Drosophila melanogaster's elusive ecology and demography. Molecular Ecology, 23: 2093–2104. doi: 10.1111/mec.12709, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/mec.12709/abstractVertically transmitted parasites rely on their host's reproduction for their transmission, leading to the evolutionary histories of both parties being intimately entwined. Parasites can thus serve as a population genetic magnifying glass for their host's demographic history. Here, we study the fruitfly Drosophila melanogaster's vertically transmitted sigma virus DMelSV. The virus has a high mutation rate and low effective population size, allowing us to reconstruct at a fine scale how the combined forces of the movement of flies and selection on the virus have shaped its migration patterns. We found that the virus is likely to have spread to Europe from Africa, mirroring the colonization route of Drosophila. The North American DMelSV population appears to be the result of a recent single immigration from Europe, invading together with its host in the late 19th century. Across Europe, DMelSV migration rates are low and populations are highly genetically structured, likely reflecting limited fly movement. Despite being intolerant of extreme cold, viral diversity suggests that fly populations can persist in harsh continental climates and that recolonization from the warmer south plays a minor role. In conclusion, studying DMelSV can provide insights into the poorly understood ecology of D. melanogaster, one of the best-studied organisms in biology.Leverhulme TrustRoyal Society University Research Fellowshi

Trypanosomatids are common and diverse parasites of Drosophila

SUMMARYDrosophila melanogasteris an important model system of immunity and parasite resistance, yet most studies use parasites that do not naturally infect this organism. We have studied trypanosomatids in natural populations to assess the prevalence and diversity of these gut parasites. We collected several species ofDrosophilafrom Europe and surveyed them for trypanosomatids using conserved primers for two genes. We have used the conserved GAPDH sequence to construct a phylogenetic tree and the highly variable spliced leader RNA to assay genetic diversity. All 5 of the species that we examined were infected, and the average prevalence ranged from 1 to 6%. There are several different groups of trypanosomatids, related to other monoxenous Trypanosomatidae. These may represent new trypanosomatid species and were found in different species of EuropeanDrosophilafrom different geographical locations. The detection of a little studied natural pathogen inD. melanogasterand related species provides new opportunities for research into both theDrosophilaimmune response and the evolution of hosts and parasites.</jats:p

The genetic architecture of susceptibility to parasites

<p>Abstract</p> <p>Background</p> <p>The antagonistic co-evolution of hosts and their parasites is considered to be a potential driving force in maintaining host genetic variation including sexual reproduction and recombination. The examination of this hypothesis calls for information about the genetic basis of host-parasite interactions – such as how many genes are involved, how big an effect these genes have and whether there is epistasis between loci. We here examine the genetic architecture of quantitative resistance in animal and plant hosts by concatenating published studies that have identified quantitative trait loci (QTL) for host resistance in animals and plants.</p> <p>Results</p> <p>Collectively, these studies show that host resistance is affected by few loci. We particularly show that additional epistatic interactions, especially between loci on different chromosomes, explain a majority of the effects. Furthermore, we find that when experiments are repeated using different host or parasite genotypes under otherwise identical conditions, the underlying genetic architecture of host resistance can vary dramatically – that is, involves different QTLs and epistatic interactions. QTLs and epistatic loci vary much less when host and parasite types remain the same but experiments are repeated in different environments.</p> <p>Conclusion</p> <p>This pattern of variability of the genetic architecture is predicted by strong interactions between genotypes and corroborates the prevalence of varying host-parasite combinations over varying environmental conditions. Moreover, epistasis is a major determinant of phenotypic variance for host resistance. Because epistasis seems to occur predominantly between, rather than within, chromosomes, segregation and chromosome number rather than recombination via cross-over should be the major elements affecting adaptive change in host resistance.</p

A genotypic trade-off between constitutive resistance to viral infection and host growth rate

This is the final version. Available on open access from Wiley via the DOI in this record.All data used in this study are made available in the supplementary informationGenotypic trade-offs are fundamental to the understanding of the evolution of life-history traits. In particular, the evolution of optimal host defence and the maintenance of variation in defence against infectious disease is thought to be underpinned by such evolutionary trade-offs. However, empirical demonstrations of these trade-offs that satisfy the strict assumptions made by theoretical models are rare. Additionally, none of these trade-offs have yet been shown to be robustly replicable using a variety of different experimental approaches to rule out confounding issues with particular experimental designs. Here, we use inbred isolines as a novel experimental approach to test whether a trade-off between viral resistance and growth rate in Plodia interpunctella, previously demonstrated by multiple selection experiments, is robust and meets the strict criteria required to underpin theoretical work in this field. Critically, we demonstrate that this trade-off is both genetic and constitutive. This finding helps support the large body of theory which relies on these assumptions, and makes this trade-off for resistance unique in being replicated through multiple experimental approaches and definitively shown to be genetic and constitutive

Fully Photonic Wireless Link for Transmission of Synchronization Signals

Rapid industrialization and increasing demand of business tools for high-speed communications supports the request for optical communications in free space. Copper cables and related technologies such as cable modems and Digital Subscriber Line (DSL) are common in existing networks, but do not meet the bandwidth requirement in the future, which opens the door to optical wireless communication technologies. Research in links for optical wireless communication (Infra Red Line of Sight, IR LOS) working in the atmosphere is due to the wide support of its development on the world market. Optical wireless communications research is currently focused on increasing the transmission quality of data links. A promising new trend in data connection through IR LOS includes the transfer of accurate time synchronization pulses (time transmission). The article presents problems of modeling and design of a transmitter and receiver with a fully photonic concept. The analysis of the power levels at the link and drawn a model for determining the connection losses at the receiver caused by optical coupling between a Schmidt-Cassegrain telescope and the receiving optical fiber is shown