Theoretical spin-wave dispersions in the antiferromagnetic phase AF1 of MnWO4_4 based on the polar atomistic model in P2

The spin wave dispersions of the low temperature antiferromagnetic phase (AF1) MnWO$_4$ have been numerically calculated based on the recently reported non-collinear spin configuration with two different canting angles. A Heisenberg model with competing magnetic exchange couplings and single-ion anisotropy terms could properly describe the spin wave excitations, including the newly observed low-lying energy excitation mode $\omega_2$=0.45 meV appearing at the magnetic zone centre. The spin wave dispersion and intensities are highly sensitive to two differently aligned spin-canting sublattices in the AF1 model. Thus this study reinsures the otherwise hardly provable hidden polar character in MnWO$_4$.Comment: 7 pages, 5 figure

Turbulent flow over a wavy boundary

CER71-72PSB-JEC44.Includes bibliographical references (pages 53-57).May 1972.An experimental study was made of turbulent flow over a wavy surface. Sinusoidal waves of three sizes were used to explore the variations of flow with wave size. Measurements of mean and turbulent velocities were taken with a two-wire method. Local heat transfer rates and pressures on the wavy surface were also measured. An equilibrium turbulent boundary layer, which conforms to Rotta's and Clauser's self-preservation requirements, develops in the region far downstream from the first wave. In the lower portion of this layer, the mean velocity is represented by the logarithmic velocity profile when the form-drag measurements of skin friction are used to determine the shift-in-origin. The roughness function is related to the wave height since the wavy surface is shown to be a "k" type surface. The velocity defect profile in the logarithmic form extends to higher values of yu*/ϐ*U∞ than those for smooth wall flows. Eddy viscosity results support the assumed logarithmic velocity variation in the lower part of the boundary layer. Measurements of shear stress by either the two-wire or the heated-film method disagree with the form drag measurements of skin friction. The wavy surface is an extended surface windbreak since it reduces the overall wind speed above the surface and creates vortices between the waves. However, surface shear stresses are increased, and the erosion rate of field waves is a function of wave height.U.S. Department of Interior, Office of Water Resources Research, Contract No. 14-01-0001, U.S. Department of Defense, Office of Naval Research, Contract No. N00014-68-A-0493-0001

Magnetic excitations of the charge stripe electrons below half doping in La2−xSrxNiO4 (x = 0.45, 0.4)

The low energy magnetic excitation spectrum of charge stripe ordered La2−xSrxNiO4, x = 0.4 and x = 0.45 were studied by neutron scattering. Two excitation modes are observed in both materials, one from the ordered magnetic moments, and a second mode consistent with pseudo-onedimensional antiferromagnetic excitations of the charge stripe electrons (q-1D). The dispersion of the q-1D excitation follows the same relation as in x = 1/3 composition, with even spectral weight in the two counter-propagating branches of the x = 0.4, however in the x = 0.45 only one dispersion branch has any measurable spectral weight. The evolution of the q-1D excitations on doping to the checkerboard charge ordered phase is discussed

The METCRAX II Field Experiment: A Study of Downslope Windstorm-Type Flows in Arizona\u2019s Meteor Crater

The second Meteor Crater Experiment (METCRAX II) was conducted in October 2013 at Arizona\u2019s Meteor Crater. The experiment was designed to investigate nighttime downslope windstorm 12type flows that form regularly above the inner southwest sidewall of the 1.2-km diameter crater as a southwesterly mesoscale katabatic flow cascades over the crater rim. The objective of METCRAX II is to determine the causes of these strong, intermittent, and turbulent inflows that bring warm-air intrusions into the southwest part of the crater. This article provides an overview of the scientific goals of the experiment; summarizes the measurements, the crater topography, and the synoptic meteorology of the study period; and presents initial analysis results

From the zero-field metal-insulator transition in two dimensions to the quantum Hall transition: a percolation-effective-medium theory

Effective-medium theory is applied to the percolation description of the metal-insulator transition in two dimensions with emphasis on the continuous connection between the zero-magnetic-field transition and the quantum Hall transition. In this model the system consists of puddles connected via saddle points, and there is loss of quantum coherence inside the puddles. The effective conductance of the network is calculated using appropriate integration over the distribution of conductances, leading to a determination of the magnetic field dependence of the critical density. Excellent quantitative agreement is obtained with the experimental data, which allows an estimate of the puddle physical parameters

The German Young Geoscientists Group – promoting exchange and information among the next generation of geoscientists

The group „Young geoscientists” of the Senate Commission for Joint Geoscientific Research (Geokommisson, www.geokommission.de) of the German Research Foundation (DFG), is dedicated towards the development of the working environment, workforce and scientific outcome of the next generation of geoscientists in Germany.Geoscientific research – basic as, well as applied – provides crucial contributions for mastering the economic, environmental and societal challenges of the near and medium-term future. Politics and society call for immediate answers, while geoscientific phenomena are complex and act on a large range of temporal and spatial scales.These demands, together with increases mobility requirements, lead to increasing pressure especially on young geoscientists. In this situation the main goals of the group “Young geoscientists” are:Promotion of networking among young geoscientistsInformation about science policy developments, funding opportunities and other relevant mattersRepresenting the interests of young scientists towards (science)-policy makersThe dynamic development of geoscientific research, particularly collaborations across traditional disciplines, as well as in increasing demands from public and policy, calls for a continuous integration of young scientists. We promote this process by organizing round-table discussions, e.g. on “Guaranteeing good scientific praxis” or on “Hot topics and research funding”, by communicating information via the internet and by identifying structural deficiencies that might hinder the advancement of the geosciences and reporting them to decision makers. In this context, we are looking for:European or international collaboratorsYoung geoscientists wishing to participate in / contribute to our activitiesSuggestions on how to improve working conditions of the young and advancing geoscientists</ul

Magnetic ordering in non-centrosymmetric CePdAl3_{3} and CePtAl3_{3}

Owing to the hybridization of cerium's localised 4$f$ electron and conduction band composed of $d$-electrons, cerium based intermetallics exhibit various kinds of magnetic interactions. In crystals, these can result in exotic types of magnetic ordering. In this study, we report a detailed single-crystal neutron diffraction study on CePdAl$_3$ and CePtAl$_3$. We have synthesized a large crystal of CePdAl$_3$, which crystallizes in a non-centrosymmetric, orthorhombic structure with space group $Cmc2_1$, a new, distorted variant of the tetragonal BaNiSn$_3$ structure observed in other Ce$T$Al$_3$ compounds, such as CePtAl$_3$. Low-temperature diffraction measurements showed that CePdAl$_3$ orders in a collinear antiferromagnetic structure below T$_N$=5.3 (1) K, with magnetic moments pointing along the $a$-axis direction and an ordered magnetic moment $\mu$=1.64(3) $\mu_B$/Ce$^{3+}$. Tetragonal CePtAl$_3$ shows a modulated, cycloidal type of ordering with $\vec{k}=(\frac{2}{3}\,0\,0)$, and a transition temperature T$_N$=3.2 K. Symmetry analysis allows two types of ordering, which show modulation of both amplitude and direction of magnetic moments. These results allow to conclude that in Ce$T$Al$_3$ system the orthorhombic distortion ($T$=Pd, Ag) releases some underlying magnetic frustration that results in modulated types of magnetic ordering in tetragonal compounds ($T$=Cu,Au,Pt)

What determines auditory similarity? The effect of stimulus group and methodology.

Two experiments on the internal representation of auditory stimuli compared the pairwise and grouping methodologies as means of deriving similarity judgements. A total of 45 undergraduate students participated in each experiment, judging the similarity of short auditory stimuli, using one of the methodologies. The experiments support and extend Bonebright's (1996) findings, using a further 60 stimuli. Results from both methodologies highlight the importance of category information and acoustic features, such as root mean square (RMS) power and pitch, in similarity judgements. Results showed that the grouping task is a viable alternative to the pairwise task with N > 20 sounds whilst highlighting subtle differences, such as cluster tightness, between the different task results. The grouping task is more likely to yield category information as underlying similarity judgements

TALEN-mediated editing of the mouse Y chromosome

The functional study of Y chromosome genes has been hindered by a lack of mouse models with specific Y chromosome mutations. We used transcription activator-like effector nuclease (TALEN)-mediated gene editing in mouse embryonic stem cells (mESCs) to produce mice with targeted gene disruptions and insertions in two Y-linked genes—Sry and Uty. TALEN-mediated gene editing is a useful tool for dissecting the biology of the Y chromosome.National Institutes of Health (U.S.) (US NIH grant R01-HG000257)National Institutes of Health (U.S.) (US NIH grant R01-CA084198)National Institutes of Health (U.S.) (US NIH grant R37-HD045022)Croucher Foundation (Scholarship)Howard Hughes Medical Institute (Investigator