The CAMELS data set:Catchment attributes and meteorology for large-sample studies

We present a new data set of attributes for 671 catchments in the contiguous United States (CONUS) minimally impacted by human activities. This complements the daily time series of meteorological forcing and streamflow provided by Newman et al. (2015b). To produce this extension, we synthesized diverse and complementary data sets to describe six main classes of attributes at the catchment scale: Topography, climate, streamflow, land cover, soil, and geology. The spatial variations among basins over the CONUS are discussed and compared using a series of maps. The large number of catchments, combined with the diversity of the attributes we extracted, makes this new data set well suited for large-sample studies and comparative hydrology. In comparison to the similar Model Parameter Estimation Experiment (MOPEX) data set, this data set relies on more recent data, it covers a wider range of attributes, and its catchments are more evenly distributed across the CONUS. This study also involves assessments of the limitations of the source data sets used to compute catchment attributes, as well as detailed descriptions of how the attributes were computed. The hydrometeorological time series provided by Newman et al

A comparative study of computational solutions to flow over a backward-facing step

A comparative study was conducted for computational fluid dynamic solutions to flow over a backward-facing step. This flow is a benchmark problem, with a simple geometry, but involves complicated flow physics such as free shear layers, reattaching flow, recirculation, and high turbulence intensities. Three Reynolds-averaged Navier-Stokes flow solvers with k-epsilon turbulence models were used, each using a different solution algorithm: finite difference, finite element, and hybrid finite element - finite difference. Comparisons were made with existing experimental data. Results showed that velocity profiles and reattachment lengths were predicted reasonably well by all three methods, while the skin friction coefficients were more difficult to predict accurately. It was noted that, in general, selecting an appropriate solver for each problem to be considered is important

Os casos de ensino na formação-investigação de professores dos anos iniciais

Este estudo se insere nos processos de formação que investigou as possibilidades dos casos de ensino serem propulsores de processos reflexivos sobre os conhecimentos da docência. Os casos de ensino são narrativas de episódios extraídos geralmente de dados reais do cotidiano escolar e que dão visibilidade às vivências dos professores, os quais, ao analisá–los ou construí-los, articulam e revivem experiências, estabelecendo processos reflexivos e relações entre a teoria e a prática. Para a realização da pesquisa, de abordagem qualitativa, objetivou-se investigar e avaliar as potencialidades dos casos de ensino, enquanto narrativa de episódios escolares, quando utilizados com professores alfabetizadores, ao lidarem com o ensino e a aprendizagem da leitura e da escrita dos alunos, auxiliando-os a reconstruir suas bases de conhecimento para o ensino. Para tanto foram trabalhados casos que retratavam eventos relacionados ao cotidiano das alfabetizadoras que atuam no anos iniciais da educação básica. O processo de formação-investigação foi realizado num ambiente virtual de aprendizagem, na perspetiva de formação continuada de docentes dos anos iniciais. As respostas dos professores participantes apontaram que a adoção de casos de ensino no desenvolvimento profissional dos professores possibilitou que as reflexões se fizessem muito presentes, posto que, ao analisarem as narrativas dos conhecimentos profissionais de colegas e seus, refletiam suas concepções, num movimento reflexivo possibilitador de aprendizagens na/da docência.This study falls in the field of the processes of formation that researched the possibilities of teaching cases being propellers of reflexive processes on knowledge in teaching. Teaching cases are narratives of episodes usually drawn from real daily school life, that bring to light teachers' experiences, establishing reflexive processes and relations between theory and practice. In order to realize this research, with a qualitative approach, it was established the objective of investigating and evaluating the potentiality of the teaching cases as narratives of school episodes, when used with primary school teachers, dealing with the teaching and learning of their students' reading and writing, helping them the re-construe their knowledge foundations in their teaching role. To attain this goal, some cases that pictured events related to the daily work of the primary teachers who play their educational role in the beginning years of basic education. The process of training-research was realized in a virtual learning environment, with a view to an ongoing training of the teachers of the first basic education years. The answers provided by the teachers who participated in the research suggest that the adoption of teaching cases in the professional development of teachers made it possible for the reflexions to become very actual, since, while analysing their colleagues' and their own narratives of professional knowledge, they were reflecting their own ideals, in a reflexive moment that fostered learning in/of teaching.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT

Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2

Since the 1985 discovery of the phase transition at $T_{\rm HO}=17.5$ K in the heavy-fermion metal URu$_2$Si$_2$, neither symmetry change in the crystal structure nor magnetic ordering have been observed, which makes this "hidden order" enigmatic. Some high-field experiments have suggested electronic nematicity which breaks fourfold rotational symmetry, but direct evidence has been lacking for its ground state at zero magnetic field. Here we report on the observation of lattice symmetry breaking from the fourfold tetragonal to twofold orthorhombic structure by high-resolution synchrotron X-ray diffraction measurements at zero field, which pins down the space symmetry of the order. Small orthorhombic symmetry-breaking distortion sets in at $T_{\rm HO}$ with a jump, uncovering the weakly first-order nature of the hidden-order transition. This distortion is observed only in ultrapure sample, implying a highly unusual coupling nature between the electronic nematicity and underlying lattice.Comment: 17 pages, 3 figures. Submitted version. Revisions have been made through the review process. See the published version in Nature Communication

Bribeproof mechanisms for two-values domains

Schummer (Journal of Economic Theory 2000) introduced the concept of bribeproof mechanism which, in a context where monetary transfer between agents is possible, requires that manipulations through bribes are ruled out. Unfortunately, in many domains, the only bribeproof mechanisms are the trivial ones which return a fixed outcome. This work presents one of the few constructions of non-trivial bribeproof mechanisms for these quasi-linear environments. Though the suggested construction applies to rather restricted domains, the results obtained are tight: For several natural problems, the method yields the only possible bribeproof mechanism and no such mechanism is possible on more general domains.Comment: Extended abstract accepted to SAGT 2016. This ArXiv version corrects typos in the proofs of Theorem 7 and Claims 28-29 of prior ArXiv versio

A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)2

In a superconductor, the ratio of the carrier density, $n$, to their effective mass, $m^*$, is a fundamental property directly reflecting the length scale of the superfluid flow, the London penetration depth, $\lambda_L$. In two dimensional systems, this ratio $n/m^*$ ($\sim 1/\lambda_L^2$) determines the effective Fermi temperature, $T_F$. We report a sharp peak in the $x$-dependence of $\lambda_L$ at zero temperature in clean samples of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ at the optimum composition $x = 0.30$, where the superconducting transition temperature $T_c$ reaches a maximum of 30\,K. This structure may arise from quantum fluctuations associated with a quantum critical point (QCP). The ratio of $T_c/T_F$ at $x = 0.30$ is enhanced, implying a possible crossover towards the Bose-Einstein condensate limit driven by quantum criticality.Comment: Main text (5 pages, 4 figures) + Supplementary Materials (5 pages, 5 figures). Published on June 22, 201

Mapping (dis)agreement in hydrologic projections

Hydrologic projections are of vital socio-economic importance. However, they are also prone to uncertainty. In order to establish a meaningful range of storylines to support water managers in decision making, we need to reveal the relevant sources of uncertainty. Here, we systematically and extensively investigate uncertainty in hydrologic projections for 605 basins throughout the contiguous US. We show that in the majority of the basins, the sign of change in average annual runoff and discharge timing for the period 2070–2100 compared to 1985–2008 differs among combinations of climate models, hydrologic models, and parameters. Mapping the results revealed that different sources of uncertainty dominate in different regions. Hydrologic model induced uncertainty in the sign of change in mean runoff was related to snow processes and aridity, whereas uncertainty in both mean runoff and discharge timing induced by the climate models was related to disagreement among the models regarding the change in precipitation. Overall, disagreement on the sign of change was more widespread for the mean runoff than for the discharge timing. The results demonstrate the need to define a wide range of quantitative hydrologic storylines, including parameter, hydrologic model, and climate model forcing uncertainty, to support water resource planning

Particle-generated turbulence in homogeneous dilute dispersed flows

Homogeneous turbulence generated by uniform fluxes of round glass beads (0.5, 1.0 and 2.0 mm dia) falling through stagnant (in the mean) air was studied for particle Reynolds numbers in the range 100-800 and particle volume fractions <0.0004%. Moments, probability density functions, spatial correlations and temporal spectra of air velocity fluctuations were measured using two-point phase-discriminating laser velocimetry. Predictions based on a simplified stochastic analysis, involving linear superposition of randomly-arriving particle velocity fields, were used to help interpret the measurements. Guided by the theory, correlations of turbulence properties were achieved for both the present particle/air and earlier particle/water measurements. Turbulence intensities (referenced to mean particle relative velocities) and integral scales are functions of the rate of dissipation of particle mechanical energy and particle drag properties; however, normalized probability density functions, spatial correlations and temporal spectra are largely independent of particle properties.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30083/1/0000454.pd

mTORC2 signaling drives the development and progression of pancreatic cancer

mTOR signaling controls several critical cellular functions and is deregulated in many cancers, including pancreatic cancer. To date, most efforts have focused on inhibiting the mTORC1 complex. However, clinical trials of mTORC1 inhibitors in pancreatic cancer have failed, raising questions about this therapeutic approach. We employed a genetic approach to delete the obligate mTORC2 subunit Rictor and identified the critical times during which tumorigenesis requires mTORC2 signaling. Rictor deletion resulted in profoundly delayed tumorigenesis. Whereas previous studies showed most pancreatic tumors were insensitive to rapamycin, treatment with a dual mTORC1/2 inhibitor strongly suppressed tumorigenesis. In late-stage tumor-bearing mice, combined mTORC1/2 and PI3K inhibition significantly increased survival. Thus, targeting mTOR may be a potential therapeutic strategy in pancreatic cancer

Thermodynamic evidence for field-angle dependent Majorana gap in a Kitaev spin liquid

The exactly-solvable Kitaev model of two-dimensional honeycome magnet leads to a quantum spin liquid (QSL) characterized by Majorana fermions, relevant for fault-tolerant topological quantum computations.In the high-field paramagnetic state of $\alpha$-RuCl$_3$, half-integer quantization of thermal Hall conductivity has been reported as a signature of Majorana fermions, but the bulk nature of this state remains elusive.Here, from high-resolution heat capacity measurements under in-plane field rotation, we find strongly angle-dependent low-energy excitations in the bulk of $\alpha$-RuCl$_3$. The excitation gap has a sextuple node structure, and the gap amplitude increases with field, exactly as expected for itinerant Majorana fermions in the Kitaev model.Our thermodynamic results are fully linked with the transport quantization properties, providing the first demonstration of the bulk-edge correspondence in a Kitaev QSL.Comment: 8 pages, 7 figure