Resonant Elastic Soft X-Ray Scattering

Resonant (elastic) soft x-ray scattering (RSXS) offers a unique element, site, and valence specific probe to study spatial modulations of charge, spin, and orbital degrees of freedom in solids on the nanoscopic length scale. It cannot only be used to investigate single crystalline materials. This method also enables to examine electronic ordering phenomena in thin films and to zoom into electronic properties emerging at buried interfaces in artificial heterostructures. During the last 20 years, this technique, which combines x-ray scattering with x-ray absorption spectroscopy, has developed into a powerful probe to study electronic ordering phenomena in complex materials and furthermore delivers important information on the electronic structure of condensed matter. This review provides an introduction to the technique, covers the progress in experimental equipment, and gives a survey on recent RSXS studies of ordering in correlated electron systems and at interfaces

Ecological implications of motorboat noise on coral reef fish communities

Anthropogenic noise is recognised as a major pollutant of international concern. Motorised vessels are the dominant source of anthropogenic noise in the marine environment. Small motorboats are widespread among coastal regions, exposing shallow marine ecosystems to noise disturbance. Short-term exposure to motorboat noise can have a profound impact on fish physiology and behaviour. However, it remains unclear how such impacts translate to wild fish assemblages. No study has yet investigated the community-wide implications of motorboat noise. The aim of this thesis is to review the current understanding of motorboat noise on fish ecology; provide the first assessment of chronic motorboat noise on a wild fish community; and consider future directions in research, management and mitigation. Using existing spatial variation in motorboat traffic across coral reefs in French Polynesia we carried out visual census techniques to investigate the effect of chronic motorboat noise on a coral reef fish community. In addition, we conducted a month-long motorboat manipulation of a coral reef with minimal disturbance history to test whether community responses can be experimentally induced. There was no difference in the overall fish abundance, species richness and diversity on coral reefs exposed to chronic motorboat noise. Yet, 5 species had significantly lower abundances, whilst 8 species had significantly greater abundances on reef exposed to chronic motorboat noise, resulting in a significant difference in the overall community composition. In addition, the month-long motorboat manipulation replicated the same response in two species as the previous study; though this was not enough to significantly alter the community composition. This study demonstrates that fish species respond differently to chronic motorboat noise, and community implications are more complex than previously predicted. Future studies should consider the diversity of functional traits, noise tolerance and interspecific interactions when investigating the ecological implications of motorboat noise on fishes

Ferromagnetic InMnAs on InAs Prepared by Ion Implantation and Pulsed Laser Annealing

Ferromagnetic InMnAs has been prepared by Mn ion implantation and pulsed laser annealing. The InMnAs layer reveals a saturated magnetization of 2.6 mu_B/Mn at 5 K and a perpendicular magnetic anisotropy. The Curie temperature is determined to be 46 K, which is higher than those in previous reports with similar Mn concentrations. Ferromagnetism is further evidenced by the large magnetic circular dichroism.Comment: 9 pages, 3 figure

A Comparative Event-Related Potential Study

The phenomenon of social exclusion can be investigated by using a virtual ball-tossing game called Cyberball. In neuroimaging studies, structures have been identified which are activated during social exclusion. But to date the underlying mechanisms are not fully disclosed. In previous electrophysiological studies it was shown that the P3 complex is sensitive to exclusion manipulations in the Cyberball paradigm and that there is a correlation between P3 amplitude and self-reported social pain. Since this posterior event-related potential (ERP) was widely investigated using the oddball paradigm, we directly compared the ERP effects elicited by the target (Cyberball: “ball possession”) and non-target (Cyberball: “ball possession of a co-player) events in both paradigms. Analyses mainly focused on the effect of altered stimulus probabilities of the target and non-target events between two consecutive blocks of the tasks. In the first block, the probability of the target and non-target event was 33% (Cyberball: inclusion), in the second block target probability was reduced to 17%, and accordingly, non-target probability was increased to 66% (Cyberball: exclusion). Our results indicate that ERP amplitude differences between inclusion and exclusion are comparable to ERP amplitude effects in a visual oddball task. We therefore suggest that ERP effects–especially in the P3 range–in the Oddball and Cyberball paradigm rely on similar mechanisms, namely the probability of target and non-target events. Since the simulation of social exclusion (Cyberball) did not trigger a unique ERP response, the idea of an exclusion-specific neural alarm system is not supported. The limitations of an ERP-based approach will be discussed

The Faculty Evaluation Process: The First Step In Fostering Professional Development In An Online University

The presentation will trace the experiences of two program directors from Walden University and their examination of issues involved with faculty assessment.  Their experiences were used to create a simple but effective and workable model for faculty assessment and development.  Once a presentation of how data were obtained, and analyzed, to create an effective communication process, the specifics of how faculty members were engaged in the collegial methods to ensure a workable professional development process will be described.  The experiences of the directors in working with assessment will be utilized as they demonstrate how they regularly conduct an interactive evaluation process, involving the audience in using the model created at Walden in the Richard W. Riley College of Education and Leadership.  This model was developed using various metrics, such as student course evaluations, faculty self-assessments, checklists of activity, adherence to rubrics, etc.  The entire process begins with the premise that collegial interactions will provide the most sustainable changes.  The process concludes with the implementation of online professional development in response to the collected data

The UE46 PGM-1 beamline at BESSY II

The UE46 PGM-1 undulator beamline at the BESSY II storage ring provides soft x-rays of tunable polarization, linear and circular. With two permanent endstations, a versatile XUV diffractometer and a 7-Tesla High-Field diffractometer, the setup is dedicated to both, resonant spectroscopy and scattering/diffraction

Magnetic domain fluctuations in an antiferromagnetic film observed with coherent resonant soft x-ray scattering

We report the direct observation of slow fluctuations of helical antiferromagnetic domains in an ultra-thin holmium film using coherent resonant magnetic x-ray scattering. We observe a gradual increase of the fluctuations in the speckle pattern with increasing temperature, while at the same time a static contribution to the speckle pattern remains. This finding indicates that domain-wall fluctuations occur over a large range of time scales. We ascribe this non-ergodic behavior to the strong dependence of the fluctuation rate on the local thickness of the film.Comment: to appear in Phys. Rev. Let

Observation of Devil's Staircase in the Novel Spin Valve System SrCo6_6O11_{11}

Using resonant soft x-ray scattering as a function of both temperature and magnetic field, we reveal a large number of almost degenerate magnetic orders in SrCo6O11. The Ising-like spins in this frustrated material in fact exhibit a so-called magnetic devil's staircase. It is demonstrated how a magnetic field induces transitions between different microscopic spin configurations, which is responsible for the magnetoresistance of SrCo6O11. This material therefore constitutes a unique combination of a magnetic devil's staircase and spin valve effects, yielding a novel type of magnetoresistance system.Comment: 5 pages, 5 figure

Opening a nodal gap by fluctuating spin-density-wave in lightly doped La2−x_{2-x}Srx_xCuO4_4

We investigate whether the spin or charge degrees of freedom are responsible for the nodal gap in underdoped cuprates by performing inelastic neutron scattering and x-ray diffraction measurements on La$_{2-x}$Sr$_x$CuO$_4$, which is on the edge of the antiferromagnetic phase. We found that fluctuating incommensurate spin-density-wave (SDW) with a the bottom part of an hourglass dispersion exists even in this magnetic sample. The strongest component of these fluctuations diminishes at the same temperature where the nodal gap opens. X-ray scattering measurements on the same crystal show no signature of charge-density-wave (CDW). Therefore, we suggest that the nodal gap in the electronic band of this cuprate opens due to fluctuating SDW with no contribution from CDW