Interference of coherent spin waves in micron-sized ferromagnetic waveguides

We present experimental observations of the interference of spin-wave modes propagating in opposite directions in micron-sized NiFe-waveguides. To monitor the local spin-wave intensity distribution and phase of the formed interference pattern, we use Brillouin light scattering microscopy. The two-dimensional spin-wave intensity map can be understood by considering the interference of several waveguide eigenmodes with different wavevectors quantized across the width of the stripe. The phase shows a transition from linear dependence on the space coordinate near the antennas characteristic for propagating waves to discrete values in the center region characteristic for standing waves

Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

The gravitational lensing effect provides various ways to study the mass environment of galaxies. We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006) and the Garching model by Guo et al. (2011). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster halos predicted by the models. Our study shows that galaxy-galaxy(-galaxy) lensing is a sensitive probe of galaxy evolution.Comment: 11 pages, 8 figures, accepted in A&

First year student expectations: Results from a university-wide student survey

Although much has been written on the first-year experience of students at higher education institutions, less attention has been directed to the expectations of students when they enter an institution for the first time. This paper provides additional insights into the expectations of students at an Australian university and highlights areas in which students’ expectations may not necessarily align with the realities of common university practices. By providing opportunities for students to articulate their expectations, staff are able to use the responses for a constructive dialogue and work towards a more positive alignment between perceived expectations and levels of student satisfaction with their experience.Geoffrey Crisp, Edward Palmer, Deborah Turnbull, Ted Nettelbeck, Lynn Ward, Amanda LeCouteur, Aspa Sarris, Peter Strelan, and Luke Schneide

Kinetic description of charmonium production in high-energy nuclear collisions

We study the evolution of charmonia as they collide with the constituents of the fireball produced in high-energy nucleus-nucleus collisions. The latter evolves in a manner controlled by the equation of state as given by lattice QCD, and is constructed in such a way that the observed hadronic spectra are correctly reproduced. A kinetic description of charmonium interactions with both quark-gluon and hadronic degrees of freedom allows to study in detail the evolution in different regimes, controlled by collision energy, kinematics and geometry. The data collected at the CERN-SPS accelerator are well described and new estimates for J/psi production at BNL-RHIC are presented.Comment: 19 pages, LaTeX, 13 .eps figure

Quasiparticle Description of Hot QCD at Finite Quark Chemical Potential

We study the extension of a phenomenologically successful quasiparticle model that describes lattice results of the equation of state of the deconfined phase of QCD for Tc <= T < 4 Tc, to finite quark chemical potential mu. The phase boundary line Tc(mu), the pressure difference (p(T,mu)-p(T,mu=0))/T^4 and the quark number density nq(T,mu)/T^3 are calculated and compared to recent lattice results. Good agreement is found up to quark chemical potentials of order mu = Tc.Comment: 12 pages, 7 figures; added reference

The Role of the Informal Sector in a Rurbanised Environment

Economic activities performed by rural populations linked to informal trading and markets have not received a broad attention in the literature. Thus, the question of the present investigation is the role of the informal sector in a rurbanised environment, and if there are differences in the waste management activities of the informal sector in cities and in an urbanised rural environment. To obtain information about the informal waste pickers in the rural areas, data were collected directly through a questionnaire from the following countries (sorting in alphabetic order): Austria, the Czech Republic, Germany, Jordan, Mexico, Nepal, South Africa and Vietnam. The methodology used for the data collection consisted of a background analysis (with a literature review), complemented with the collection of empirical evidence, field interviews and partially local field analysis. The informal collection of waste is a phenomenon that results in principle from social differences within society and the population. Therefore, it is not surprising that the perception of the activities of informal waste collectors in the scientific literature refers to developing and emerging countries, since social differences are more pronounced. These informal waste management systems in low- and middle-income countries exist usually in parallel with formal waste management systems, a fact that applies for urban as well as rural areas, and might be considered as a result of rurbanisation. The case studies show the development of the informal sector as an important part of the waste management activities, when a country evolves. With increasing economic development, the importance of the informal sector is shrinking step by step in relation with the improvement of the formal activities. Even this development goes faster in urban areas; the conclusion applies also to rural areas

The noise of cluster mass reconstructions from a source redshift distribution

The parameter-free reconstruction of the surface-mass density of clusters of galaxies is one of the principal applications of weak gravitational lensing. From the observable ellipticities of images of background galaxies, the tidal gravitational field (shear) of the mass distribution is estimated, and the corresponding surface mass density is constructed. The noise of the resulting mass map is investigated here, generalizing previous work which included mainly the noise due to the intrinsic galaxy ellipticities. Whereas this dominates the noise budget if the lens is very weak, other sources of noise become important, or even dominant, for the medium-strong lensing regime close to the center of clusters. In particular, shot noise due to a Poisson distribution of galaxy images, and increased shot noise owing to the correlation of galaxies in angular position and redshift, can yield significantly larger levels of noise than that from the intrinsic ellipticities only. We estimate the contributions from these various effects for two widely used smoothing operations, showing that one of them effectively removes the Poisson and the correlation noises related to angular positions of galaxies. Noise sources due to the spread in redshift of galaxies are still present in the optimized estimator and are shown to be relevant in many cases. We show how (even approximate) redshift information can be profitably used to reduce the noise in the mass map. The dependence of the various noise terms on the relevant parameters (lens redshift, strength, smoothing length, redshift distribution of background galaxies) are explicitly calculated and simple estimates are provided.Comment: 18 pages, A&A in pres

Dynamic Clustering in Object-Oriented Databases: An Advocacy for Simplicity

International audienceWe present in this paper three dynamic clustering techniques for Object-Oriented Databases (OODBs). The first two, Dynamic, Statistical & Tunable Clustering (DSTC) and StatClust, exploit both comprehensive usage statistics and the inter-object reference graph. They are quite elaborate. However, they are also complex to implement and induce a high overhead. The third clustering technique, called Detection & Reclustering of Objects (DRO), is based on the same principles, but is much simpler to implement. These three clustering algorithm have been implemented in the Texas persistent object store and compared in terms of clustering efficiency (i.e., overall performance increase) and overhead using the Object Clustering Benchmark (OCB). The results obtained showed that DRO induced a lighter overhead while still achieving better overall performance

Magnetotransport of SrIrO 3 -based heterostructures

Transition-metal oxide (TMO) based heterostructures provide fertile playground to explore or functionalize novel quantum materials. In this regard, the combination of 3d and 5d TMOs have gained special interest because of the simultaneous appearance of strong spin-orbit coupling and electron correlation at the interface of those heterostructures. Artificial breaking of the inversion symmetry in heterostructures may also result in a distinct interfacial Dzyaloshinskii- Moriya interaction (DMI) and the formation of non-collinear magnetic spin structures in case of magnetic TMOs. Among the 5d TMOs, SrIrO3 (SIO) has gained significant attention because of its large spin-orbit coupling and the semi-metallic ground state, which are highly susceptible to structural distortions. Here, we report on the preparation and the characterisation of structural, electronic and magnetic properties of epitaxial heterostructures consisting of the 5d TMO SIO and the 3d antiferromagnetic insulator LaFeO3

Photometric Redshifts with Surface Brightness Priors

We use galaxy surface brightness as prior information to improve photometric redshift (photo-z) estimation. We apply our template-based photo-z method to imaging data from the ground-based VVDS survey and the space-based GOODS field from HST, and use spectroscopic redshifts to test our photometric redshifts for different galaxy types and redshifts. We find that the surface brightness prior eliminates a large fraction of outliers by lifting the degeneracy between the Lyman and 4000 Angstrom breaks. Bias and scatter are improved by about a factor of 2 with the prior for both the ground and space data. Ongoing and planned surveys from the ground and space will benefit, provided that care is taken in measurements of galaxy sizes and in the application of the prior. We discuss the image quality and signal-to-noise requirements that enable the surface brightness prior to be successfully applied.Comment: 15 pages, 13 figures, matches published versio