308 research outputs found
Non-magnetic Anomaly at 1K Arising in Ferromagnetic Ce2.15(Pd1-xAgx)1.95In0.9
Magnetic and thermal properties of Ferromagnetic (FM) Ce2.15(Pd1-xAgx)1.95In0.9 alloys were studied in order to determine the Quantum Critical Point (QCP) at TC \u2192 0. The in- crease of band electrons produced by Pd/Ag substitution depresses TC (x) from 4.1K down to TC (x = 0.5)=1.1K, with a QCP extrapolated to xQCP 65 0.5. Magnetic susceptibility from T > 30K indicates an effective moment slightly decreasing from \u3bceff =2.56\u3bcB to 2.4\u3bcB at x=0.5. These values and the paramagnetic temperature \u3b8P 48 -10K exclude significant Kondo screening effects. The TC (x) reduction is accompanied by a weakening of the FM magnetization and the emergence of a specific heat Cm(T) anomaly at T 17 48 1K, without signs of magnetism detected from AC-susceptibility. The magnetic entropy collected around 4K (i.e. the TC of the x = 0 sample) practically does not change with Ag concentration: Sm(4K) 48 0.8 Rln2, suggesting a progressive transfer of FM degrees of freedom to the non-magnetic (NM) compo- nent. No antecedent was found concerning any NM anomaly emerging from a FM system at such temperature. The origin of this anomaly is attributed to an entropy bottleneck originated in the nearly divergent power law dependence for T > T 17
Emerging frustration effects in ferromagnetic Ce_2[Pd_{1-x}Ag_x]_2In alloys
Magnetic and thermal properties of Ferromagnetic (FM)
Ce_{2.15}(Pd_{1-x}Ag_x)_{1.95}In_{0.9} alloys were studied in order to
determine the Quantum Critical Point (QCP) at T_C => 0. The increase of band
electrons produced by Pd/Ag substitution depresses T_C(x) from 4.1K down to
T_C(x=0.5)=1.1K, with a QCP extrapolated to x_{QCP}~ 0.6. Magnetic
susceptibility from T>30K indicates an effective moment slightly decreasing
from \mu_{eff}=2.56\mu_B to 2.4\mu_B at x=0.5. These values and the
paramagnetic temperature \theta_P~ -10K exclude significant Kondo screening
effects. The T_C(x) reduction is accompanied by a weakening of the FM
magnetization and the emergence of a specific heat C_m(T) anomaly at T*~ 1K,
without signs of magnetism detected from AC-susceptibility. The magnetic
entropy collected around 4K (i.e. the T_C of the x=0 sample) practically does
not change with Ag concentration: S_m(4K)~ 0.8 Rln2, suggesting a progressive
transfer of FM degrees of freedom to the non-magnetic (NM) component. No
antecedent was found concerning any NM anomaly emerging from a FM system at
such temperature. The origin of this anomaly is attributed to an 'entropy
bottleneck' originated in the nearly divergent power law dependence for T>T*.Comment: 5 pages, 4 figures, Int. Conf. ICM 201
CONTAINER LOCALISATION AND MASS ESTIMATION WITH AN RGB-D CAMERA
In the research area of human-robot interactions, the automatic estimation of the mass of a container manipulated by a person leveraging only visual information is a challenging task. The main challenges consist of occlusions, different filling materials and lighting conditions. The mass of an object constitutes key information for the robot to correctly regulate the force required to grasp the container. We propose a single RGB-D camera-based method to locate a manipulated container and estimate its empty mass i.e., independently of the presence of the content. The method first automatically selects a number of candidate containers based on the distance with the fixed frontal view, then averages the mass predictions of a lightweight model to provide the final estimation. Results on the CORSMAL Containers Manipulation dataset show that the proposed method estimates empty container mass obtaining a score of 71.08% under different lighting or filling conditions
Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter
The Thorium-229 isotope features a nuclear isomer state with an extremely low
energy. The currently most accepted energy value, 7.8 +- 0.5 eV, was obtained
from an indirect measurement using a NASA x-ray microcalorimeter with an
instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic
microcalorimeters with an energy resolution down to a few eV can be used to
measure the isomer energy. In particular, resolving the 29.18 keV doublet in
the \gamma-spectrum following the \alpha-decay of Uranium-233, corresponding to
the decay into the ground and isomer state, allows to measure the isomer
transition energy without additional theoretical input parameters, and increase
the energy accuracy. We study the possibility of resolving the 29.18 keV line
as a doublet and the dependence of the attainable precision of the energy
measurement on the signal and background count rates and the instrumental
resolution.Comment: 32 pages, 8 figures, eq. (3) correcte
THE EFFECT OF LEAF ORIENTATION TO SUNLIGHT ON STOMATAL PARAMETERS OF QUERCUS RUBRA AROUND THE BELGRADE LAKES, CENTRAL MAINE
ABSTRACT Stomatal frequencies of fossil-plant species are used to estimate past pCO 2 levels based on the physiological functions of living taxa. There is a demonstrable inverse relationship between increasing pCO 2 and stomatal frequency parameters, in which there is a decrease in both stomatal density (SD) and stomatal index (SI). Concentration of CO 2 is not the only factor known to affect SD and SI values, which are a product of leaf development and expansion, as studies have shown a positive correlation between SD and light intensity. The present study tests the hypothesis that SD and SI are not influenced by a leaf's physical orientation relative to the sun during the growing season. Sun leaves of northern red oak, Quercus rubra, were collected from trees around the margins of six lakes of the Belgrade Lakes Region, central Maine, United States, in 2007. Lakes in NE-SW, NW-SE, and E-W orientations allowed for sampling of trees exposed to varying light intensities throughout the growing-season day. The SD and SI of each tree were calculated, and statistical comparisons were made between populations exposed to predominant morning or afternoon light intensities for each lake and between populations on lakes of differing orientations. There is no statistically significant difference in either SD or SI between populations growing under different orientations to growing-season sunlight. These data indicate that exposure to various sunlight regimes on opposite sides of a lake does not play a role in the stomatal response as reflected in SD and SI of plants during a single growing season
Sidechain control of porosity closure in multiple peptide-based porous materials by cooperative folding
Porous materials find application in separation, storage and catalysis. We report a crystalline porous solid formed by coordination of metal centres with a glycylserine dipeptide. We prove experimentally that the structure evolves from a solvated porous into a non-porous state as result of ordered displacive and conformational changes of the peptide that suppress the void space in response to environmental pressure. This cooperative closure, which recalls the folding of proteins, retains order in three-dimensions and is driven by the hydroxyl groups acting as H-bond donors in the peptide sequence through the serine residue. This ordered closure is also displayed by multipeptide solid solutions in which the combination of different sequences of amino acids controls their guest response in a non-linear way. This functional control can be compared to the effect of single point mutations in proteins, where the exchange of single amino acids can radically alter structure and functio
HighSTEPS. A high strain temperature pèressure and speed apparatus to study earthquake mechanics
We present a state of-the-art biaxial apparatus able to study both earthquake rupture nucleation and propagation at conditions typical of the seismogenic crust. The HighSTEPS, High Strain TEmperature Pressure Speed, apparatus simulates fault deformation in a wide range of slip velocities, i.e., from 10-5m/s to 0.25 m/s. Within this velocity range, it is possible to study, the rate-and-state friction, the fault dynamic weakening, and healing under unique boundary conditions, i.e., normal stress up to 100 MPa, confining pressure up to 100 MPa, pore fluid pressure up to 100 MPa and temperature up to 120 °C. The apparatus consists of a hydraulic system integrated with four linear motors. The hydraulic system allows
for the application of normal stress, confining pressure and pore fluid pressure. The main peculiarity of this apparatus is the system of four linear motors that are mounted in series in order to apply shearing velocities up to 0.25 m/s, accelerations up to 10 m/s2 and shear stresses up to 200 MPa. Moreover, both experiments in sliding velocity control or shear stress control on the experimental faults are possible. Preliminary experiments on carbonate and silicate bearing rocks are coherent with the previous literature. The investigation of fault friction under a wide range of velocities, normal stresses, confining pressures and pore fluid pressures will provide insights into the mechanics of earthquakes and reduce the gap between
natural and laboratory observations
Controle biológico do ácaro rajado por ácaros predadores fitoseídeos (Acari: Tetranychidae, Phytoseiidae) em pepino.
Em janeiro de 1992 foi instalado no campo experimental do CNPDA, em Jaguariúna/SP, um experimento para testar a viabilidade técnica do controle biológico do ácaro rajado (Tetranychus urticae Koch) por ácaros predadores fitoseídeos. O delineamento experimental utilizado foi de blocos casualizados com 4 repetições e 5 tratamentos; T1= liberação de 10 ácaros rajados/planta + Malation (para eliminacao dos predadores nativos); T2= 10 ácaros rajados /planta; T3= 10 acaros rajados + 8 ácaros predadores Phytoseiulus macropilis (Banks)/planta; T4= 10 ácaros rajados + 8 ácaros predadores Amblyseius idaeus (Denmark & Muma)/planta; T5= Avermectina-testemunha sem liberação de ácaros. Esses tratamentos foram aplicados em 20 plantas tomadas ao acaso na área útil de cada parcela. Antes da liberação dos predadores não havia diferença significativa entre os tratamentos, exceto em relação a testemunha T5. Após a liberação dos predadores, destacou-se o tratamento T4 que apresentou o número de ácaros rajados significativamente menor em relação aos tratamentos T1, T2, T3. Assim, o predador A. idaeus foi capaz de controlar a população do ácaro rajado, mantendo-a em niveis inferiores em relação aos demais tratamentos (exceto T5). Esse predador esteve presente nas plantas de pepino desde a sua liberação ate o término do experimento. Já a população de P. macropilis extingui-se 10 dias após a liberação
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