Predicting and verifying transition strengths from weakly bound molecules

We investigated transition strengths from ultracold weakly bound 41K87Rb molecules produced via the photoassociation of laser-cooled atoms. An accurate potential energy curve of the excited state (3)1Sigma+ was constructed by carrying out direct potential fit analysis of rotational spectra obtained via depletion spectroscopy. Vibrational energies and rotational constants extracted from the depletion spectra of v'=41-50 levels were combined with the results of the previous spectroscopic study, and they were used for modifying an ab initio potential. An accuracy of 0.14% in vibrational level spacing and 0.3% in rotational constants was sufficient to predict the large observed variation in transition strengths among the vibrational levels. Our results show that transition strengths from weakly bound molecules are a good measure of the accuracy of an excited state potential.Comment: 7 pages, 7 figure

Pattern Stability and Trijunction Motion in Eutectic Solidification

We demonstrate by both experiments and phase-field simulations that lamellar eutectic growth can be stable for a wide range of spacings below the point of minimum undercooling at low velocity, contrary to what is predicted by existing stability analyses. This overstabilization can be explained by relaxing Cahn's assumption that lamellae grow locally normal to the eutectic interface.Comment: 4 pages, 5 eps figure

Dynamics of a faceted nematic-smectic B front in thin-sample directional solidification

We present an experimental study of the directional-solidification patterns of a nematic - smectic B front. The chosen system is C_4H_9-(C_6H_{10})_2CN (in short, CCH4) in 12 \mu m-thick samples, and in the planar configuration (director parallel to the plane of the sample). The nematic - smectic B interface presents a facet in one direction -- the direction parallel to the smectic layers -- and is otherwise rough, and devoid of forbidden directions. We measure the Mullins-Sekerka instability threshold and establish the morphology diagram of the system as a function of the solidification rate V and the angle theta_{0} between the facet and the isotherms. We focus on the phenomena occurring immediately above the instability threshold when theta_{0} is neither very small nor close to 90^{o}. Under these conditions we observe drifting shallow cells and a new type of solitary wave, called "faceton", which consists essentially of an isolated macroscopic facet traveling laterally at such a velocity that its growth rate with respect to the liquid is small. Facetons may propagate either in a stationary, or an oscillatory way. The detailed study of their dynamics casts light on the microscopic growth mechanisms of the facets in this system.Comment: 12 pages, 19 figures, submitted to Phys. Rev.

Theory and Phenomenology of Heavy Flavor at RHIC

We review the problem of heavy-quark diffusion in the Quark-Gluon Plasma and its ramifications for heavy-quark spectra in heavy-ion collisions at RHIC. In particular, we attempt to reconcile underlying mechanisms of several seemingly different approaches that have been put forward to explain the large suppression and elliptic flow of non-photonic electron spectra. We also emphasize the importance of a quantitative description of the bulk medium evolution to extract reliable values for the heavy-quark diffusion coefficient.Comment: 8 pages latex, including 10 eps figures; plenary talk at SQM08, Beijing (China), Oct. 06-10, 200

Quasiperiodic Tip Splitting in Directional Solidification

We report experimental results on the tip splitting dynamics of seaweed growth in directional solidification of succinonitrile alloys with poly(ethylene oxide) or acetone as solutes. The seaweed or dense branching morphology was selected by solidifying grains which are oriented close to the {111} plane. Despite the random appearance of the growth, a quasiperiodic tip splitting morphology was observed in which the tip alternately splits to the left and to the right. The tip splitting frequency f was found to be related to the growth velocity V as a power law f V^{1.5}. This finding is consistent with the predictions of a tip splitting model that is also presented. Small anisotropies are shown to lead to different kinds of seaweed morphologies.Comment: 4 pages, 7 figures, submitted to Physical Review Letter

Reação de genótipos de soja diferenciadores à ferrugem da soja coletada no Brasil entre 2011 e 2014.

Asian soybean rust (ASR) is one of the important diseases which reduce soybean yield. Most economic control measure of the disease is the use of genetic resistance. To effectiveness of resistance genes to ASR, soybean reactions of differential genotypes were monitored during four cropping seasons from 2010/11 to 2013/14. Samples of leaflets infected with rust were collected from soybean fields in states of Rio Grande do Sul, Paraná, Mato Grosso do Sul, Mato Grosso, Goiás, Distrito Federal and Rondônia. Sixteen differential genotypes (18 in 2012/13 and 2013/14) for soybean rust, having resistance gene, Rpp1-Rpp6, Rpp2+Rpp4+Rpp5, and without resistance genes were inoculated with urediniospores collected from 19 samples. Soybean reaction was rated approximately 14 days after inoculation based on the number of uredinia per lesion and sporulation level. There was no clear evidence of geographical and temporal differentiation. Of the sixteen differentials used for all seasons, Shiranui (Rpp5), PI 587855 (Rpp1-b), PI 587880A (Rpp1-b), PI 587905 (Rpp1-b) and PI 594767A (Rpp1-b) showed a resistant reaction to half or more of samples throughout the period. No6-12 having Rpp2+Rpp4+Rpp5 was resistant to all the samples collected 2012/13 and 2013/14. There was a tendency that PI 459025 (Rpp4) increased the proportion of resistant reactions over the period

Coherent transfer of photoassociated molecules into the rovibrational ground state

We report on the direct conversion of laser-cooled 41K and 87Rb atoms into ultracold 41K87Rb molecules in the rovibrational ground state via photoassociation followed by stimulated Raman adiabatic passage. High-resolution spectroscopy based on the coherent transfer revealed the hyperfine structure of weakly bound molecules in an unexplored region. Our results show that a rovibrationally pure sample of ultracold ground-state molecules is achieved via the all-optical association of laser-cooled atoms, opening possibilities to coherently manipulate a wide variety of molecules.Comment: 4 pages, 4 figure

Optimising the multiplex factor of the frequency domain multiplexed readout of the TES-based microcalorimeter imaging array for the X-IFU instrument on the Athena Xray observatory

Athena is a space-based X-ray observatory intended for exploration of the hot and energetic universe. One of the science instruments on Athena will be the X-ray Integrated Field Unit (X-IFU), which is a cryogenic X-ray spectrometer, based on a large cryogenic imaging array of Transition Edge Sensors (TES) based microcalorimeters operating at a temperature of 100mK. The imaging array consists of 3800 pixels providing 2.5 eV spectral resolution, and covers a field of view with a diameter of of 5 arc minutes. Multiplexed readout of the cryogenic microcalorimeter array is essential to comply with the cooling power and complexity constraints on a space craft. Frequency domain multiplexing has been under development for the readout of TES-based detectors for this purpose, not only for the X-IFU detector arrays but also for TES-based bolometer arrays for the Safari instrument of the Japanese SPICA observatory. This paper discusses the design considerations which are applicable to optimise the multiplex factor within the boundary conditions as set by the space craft. More specifically, the interplay between the science requirements such as pixel dynamic range, pixel speed, and cross talk, and the space craft requirements such as the power dissipation budget, available bandwidth, and electromagnetic compatibility will be discussed