2,925 research outputs found
Magnetic Properties of Pr0.7Ca0.3MnO3/SrRuO3 Superlattices
High-quality Pr0.7Ca0.3MnO3/SrRuO3 superlattices were fabricated by pulsed
laser deposition and were investigated by high-resolution transmission electron
microscopy and SQUID magnetometry. Superlattices with orthorhombic and
tetragonal SrRuO3 layers were investigated. The superlattices grew coherently;
in the growth direction Pr0.7Ca0.3MnO3 layers were terminated by MnO2- and
SrRuO3 layers by RuO2-planes. All superlattices showed antiferromagnetic
interlayer coupling in low magnetic fields. The coupling strength was
significantly higher for orthorhombic than for tetragonal symmetry of the
SrRuO3 layers. The strong interlayer exchange coupling in the superlattice with
orthorhombic SrRuO3 layers led to a magnetization reversal mechanism with a
partially inverted hysteresis loop.Comment: 12 pages, 4 figure
Scattering of non-uniform incident fields by long cylinders
Copyright University of BremenWe investigate experimentally far-field scattering from cylinders with illumination non-uniform along the axis of the cylinder. Scattered intensity as a function of angle in two orthogonal directions is examined. Variation along the scattering angle is found to be little affected by the illumination profile. However, variation in the transverse direction follows closely the Fourier transform of the illumination pattern and reproduces the angular distribution of the incident wave. These finding apply to circular as well as hexagonal cross-section cylinders
Avoiding unseen obstacles : Subcortical vision is not sufficient to maintain normal obstacle avoidance behaviour during reaching
Acknowledgement This work was funded by the RS MacDonald Charitable Trust (awarded to C. Hesse in June 2013). T. Schenk was supported by a grant from the German Research Council (DFG â SCHE 735/3-1). The authors would like to thank Dr Stefanie Biehl for her valuable advice on lesion localisation based on the CT and MRI scans of the patients. We would also like to thank all the patients for taking part in our experiments and for giving up so much of their free time.Peer reviewedPostprin
Conjugacy in Baumslag's group, generic case complexity, and division in power circuits
The conjugacy problem belongs to algorithmic group theory. It is the
following question: given two words x, y over generators of a fixed group G,
decide whether x and y are conjugated, i.e., whether there exists some z such
that zxz^{-1} = y in G. The conjugacy problem is more difficult than the word
problem, in general. We investigate the complexity of the conjugacy problem for
two prominent groups: the Baumslag-Solitar group BS(1,2) and the
Baumslag(-Gersten) group G(1,2). The conjugacy problem in BS(1,2) is
TC^0-complete. To the best of our knowledge BS(1,2) is the first natural
infinite non-commutative group where such a precise and low complexity is
shown. The Baumslag group G(1,2) is an HNN-extension of BS(1,2). We show that
the conjugacy problem is decidable (which has been known before); but our
results go far beyond decidability. In particular, we are able to show that
conjugacy in G(1,2) can be solved in polynomial time in a strongly generic
setting. This means that essentially for all inputs conjugacy in G(1,2) can be
decided efficiently. In contrast, we show that under a plausible assumption the
average case complexity of the same problem is non-elementary. Moreover, we
provide a lower bound for the conjugacy problem in G(1,2) by reducing the
division problem in power circuits to the conjugacy problem in G(1,2). The
complexity of the division problem in power circuits is an open and interesting
problem in integer arithmetic.Comment: Section 5 added: We show that an HNN extension G = < H, b | bab^-1 =
{\phi}(a), a \in A > has a non-amenable Schreier graph with respect to the
base group H if and only if A \neq H \neq
Computational Wind Engineering for Optimal Path Planning of Unmanned Aerial Vehicles
The current work represents an analysis of Computational Wind Engineering of a dense complex urban environment and translation of the results to optimizing the path planning for Unmanned Aerial Vehicles (UAV). Investigations into the behavior of the k-Δ and k-Ï SST turbulence models on sufficiently representative geometries were conducted. The steady-state simulations are done on the Architectural Institute of Japan (AIJ) Case B and Case F geometries. The steady-state data obtained will then need to be translated to transient data in order to better represent flow characteristics that an Unmanned Aerial Vehicles (UAV) will experience. The performance of the k-Ï SST is deemed better than that of the k-Δ model for path optimization
Parental loss of family members within two years of offspring birth predicts elevated absorption scores in college.
Liotti proposed that interactions during infancy with a parent suffering unresolved loss could lead to vulnerabilities to altered states of consciousness. Hesse and van IJzendoorn provided initial support for Liotti's hypothesis, finding elevated scores on Tellegen's Absorption Scale - a normative form of dissociation - for undergraduates reporting that their parents had experienced the loss of family members within two years of their birth. Here, we replicated the above findings in a large undergraduate sample (N = 927). Additionally, we investigated mother's and father's losses separately. Perinatal losses, including miscarriage, were also considered. Participants reporting that the mother or both parents had experienced loss within two years of their birth scored significantly higher on absorption than those reporting only perinatal, only father, or no losses. While not applicable to the assessment of individuals, the brief loss questionnaire utilized here could provide a useful addition to selected large-scale studies.This research was supported by a Medical Humanities New Investigator Award from the Wellcome Trust (Grant WT103343MA).This is the final version of the article. It first appeared from Taylor & Franics via http://dx.doi.org/10.1080/14616734.2016.118109
Orthorhombic to tetragonal transition of SrRuO3 layers in Pr0.7Ca0.3MnO3/SrRuO3 superlattices
High-quality Pr0.7Ca0.3MnO3/SrRuO3 superlattices with ultrathin layers were
fabricated by pulsed laser deposition on SrTiO3 substrates. The superlattices
were studied by atomically resolved scanning transmission electron microscopy,
high-resolution transmission electron microscopy, resistivity and
magnetoresistance measurements. The superlattices grew coherently without
growth defects. Viewed along the growth direction, SrRuO3 and Pr0.7Ca0.3MnO3
layers were terminated by RuO2 and MnO2, respectively, which imposes a unique
structure to their interfaces. Superlattices with a constant thickness of the
SrRuO3 layers, but varying thickness of the Pr0.7Ca0.3MnO3 layers showed a
change of crystalline symmetry of the SrRuO3 layers. At a low Pr0.7Ca0.3MnO3
layer thickness of 1.5 nm transmission electron microscopy proved the SrRuO3
layers to be orthorhombic, whereas these were non-orthorhombic for a
Pr0.7Ca0.3MnO3 layer thickness of 4.0 nm. Angular magnetoresistance
measurements showed orthorhombic (with small monoclinic distortion) symmetry in
the first case and tetragonal symmetry of the SrRuO3 layers in the second case.
Mechanisms driving this orthorhombic to tetragonal transition are briefly
discussed.Comment: 23 pages, 12 figure
A statement by Scientists for Future concerning the protests for more climate protection
In March 2019, German-speaking scientists and scholars calling themselves Scientists for Future, published a statement in support of the youth protesters in Germany, Austria, and Switzerland (Fridays for Future, Klimastreik/Climate Strike), verifying the scientific evidence that the youth protestors refer to. In this article, they provide the full text of the statement, including the list of supporting facts (in both English and German) as well as an analysis of the results and impacts of the statement. Furthermore, they reflect on the challenges for scientists and scholars who feel a dual responsibility: on the one hand, to remain independent and politically neutral, and, on the other hand, to inform and warn societies of the dangers that lie ahead
TYC 2675-663-1: A newly discovered W UMa system in an active state
The recently discovered eclipsing binary system TYC 2675-663-1 is a X-ray
source, and shows properties in the optical that are similar to the W UMa
systems, but are somewhat unusual compared to what is seen in other contact
binary systems. The goal of this work is to characterize its properties and
investigate its nature by means of detailed photometric and spectroscopic
observations. We have performed extensive V-band photometric measurements with
the INTEGRAL satellite along with ground-based multi-band photometric
observations, as well as high-resolution spectroscopic monitoring from which we
have measured the radial velocities of the components. These data have been
analysed to determine the stellar properties, including the absolute masses and
radii. Additional low-resolution spectroscopy was obtained to investigate
spectral features. From the measured eclipse timings we determine an orbital
period for the binary of P=0.4223576+-0.0000009 days. The light-curve and
spectroscopic analyses reveal the observations to be well represented by a
model of an overcontact system composed of main-sequence F5 and G7 stars
(temperature difference of nearly 1000 K), with the possible presence of a
third star. Low-resolution optical spectroscopy reveals a complex H alpha
emission, and other features that are not yet understood. The unusually large
mass ratio of q=0.81+-0.05 places it in the rare "H" (high mass ratio) subclass
of the W UMa systems, which are presumably on their way to coalescence.Comment: 12 pages in double column format. Accepted for publication in
Astronomy and Astrophysic
The young stellar population of NGC 4214 as observed with HST. II. Results
We present the results of a detailed UV-optical study of the nearby dwarf
starburst galaxy NGC 4214 using multifilter HST/WFPC2+STIS photometry. The
stellar extinction is found to be quite patchy, with some areas having values
of E(4405-5495)< 0.1 mag and others, associated with star forming regions, much
more heavily obscured, a result which is consistent with previous studies of
the nebular extinction. We determined the ratio of blue-to-red supergiants and
found it to be consistent with theoretical models for the metallicity of the
SMC. The stellar IMF of the field in the range 20-100 solar masses is found to
be steeper than Salpeter. A number of massive clusters and associations with
ages between a few and 200 million years are detected and their properties are
discussed.Comment: 49 pages, 12 figures, 6 table
- âŠ