The gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable {delta} phase to the gallium-containing, monoclinic {alpha}{prime} phase near -100 C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment--wherein, following an anneal at 375 C, the sample is held at a sub-anneal temperature for a period of time--significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the {delta} {yields} {alpha}{prime} transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of {alpha}{prime} formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of …

Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

There are times when a laser beam needs to cross between tables or even go from one room to another. This presents an interesting traffic-flow and safety challenge to both the laser safety officer and laser user. Fortunately it is a challenge that has several solutions But the simplest solution may not be the best one. For example, the simplest way to get a beam from one optical table to another is just to put a sturdy tube around it. That's a permanent solution, and it completely contains the laser beam. While this is laser safe, there can be egress issues if it blocks a walkway. One comment this author often hears is, 'We can just duck under the tube.' The fire marshal, as well as the laser safety officer, might have issues with this. Especially in the case of a darkened lab, a blocked walkway can present a hazard of its own. One good solution is to transport the beam from Point A to Point B through a fiberoptic cable, when that is possible. One should easily be able to run the fiber up and over any walkway or down through a conduit on the floor. An important concern …

None

A pair of superconducting coupling magnets will be part of the Muon Ionization Cooling Experiment (MICE). They were designed and will be constructed by the Institute of Cryogenics and Superconductivity Technology, Harbin Institute of Technology, in collaboration with Lawrence Berkeley National Laboratory. The coupling magnet is to be cooled by using cryocoolers at 4.2K. In order to reduce the heat leak to the 4.2K cold mass from 300 K, a pair of current leads composed of conventional copper leads and high temperature superconductor (HTS) leads will be used to supply current to the magnet. This paper presents the optimization of the conventional conduction-cooled metal leads for the coupling magnet. Analyses on heat transfer down the leads using theoretical method and numerical simulation were carried out. The stray magnetic field around the HTS leads has been calculated and effects of the magnetic field on the performance of the HTS leads has also been analyzed.

Video images of laser beams imprinted with distinguishable features are used for alignment of 192 laser beams at the National Ignition Facility (NIF). Algorithms designed to determine the position of these beams enable the control system to perform the task of alignment. Centroiding is a common approach used for determining the position of beams. However, real world beam images suffer from intensity fluctuation or other distortions which make such an approach susceptible to higher position measurement variability. Matched filtering used for identifying the beam position results in greater stability of position measurement compared to that obtained using the centroiding technique. However, this gain is achieved at the expense of extra processing time required for each beam image. In this work we explore the possibility of using a field programmable logic array (FPGA) to speed up these computations. The results indicate a performance improvement of 20 using the FPGA relative to a 3 GHz Pentium 4 processor.

Polo-like kinase 1, PLK1, has important functions in maintaining genome stability and is involved in regulation of mitosis. PLK1 is up regulated in many invasive carcinomas. We asked whether it may also play a role in acquisition of invasiveness, a crucial step in transition to malignancy. In a model of metaplastic basal-like breast carcinoma progression, we found that PLK1 expression is necessary but not sufficient to induce invasiveness through laminin-rich extracellular matrix. PLK1 mediates invasion via Vimentin and {beta}1 integrin, both of which are necessary. We observed that PLK1 phosphorylates Vimentin on serine 82, which in turn regulates cell surface levels of {beta}1 integrin. We found PLK1 to be also highly expressed in pre-invasive in situ carcinomas of the breast. These results support a role for the involvement of PLK1 in the invasion process and point to this pathway as a potential therapeutic target for pre-invasive and invasive breast carcinoma treatment.

We demonstrate a preparative method which produces highly-monodisperse Pt-nanoparticles of tunable size without the external addition of seed particles. Hexachloroplatinic acid is dosed slowly to an ethylene glycol solution at 120 C and reduced in the presence of a stabilizing polymer poly-N-vinylpyrollidone (PVP). Slow addition of the Pt-salt first will first lead to the formation of nuclei (seeds) which then grow further to produce larger particles of any desired size between 3 and 8nm. The amount of added hexachloroplatinic acid precursor controls the size of the final nanoparticle product. TEM was used to determine size and morphology and to confirm the crystalline nature of the nanoparticles. Good reproducibility of the technique was demonstrated. Above 7nm, the particle shape and morphology changes suddenly indicating a change in the deposition selectivity of the Pt-precursor from (100) towards (111) crystal faces and breaking up of larger particles into smaller entities.

The cooling channel of the Muon Ionization Cooling Experiment (MICE) consists of eighteen superconducting solenoid coils, which are magnetically hooked together and contained in seven modules. The operations of a pair of MICE superconducting coupling magnets are affected directly by the other solenoid coils in the MICE channel. In order to meet the stringent requirement for the magnet center and axis azimuthal angle at 4.2 K, a self-centered tension-band cold mass support system with intermediate thermal interruption was applied for the MICE superconducting coupling magnet. The physical center of the magnet does not change as it is cooled down from 300 K to 4.2 K using this support system. This paper analyzed and calculated force loads on the coupling magnet under various operation modes of the MICE cooling channel. The performance parameters of a single-band cold mass support system were calculated also.

None

We report first light from a novel, new source of 10-ps 0.776-MeV gamma-ray pulses known as T-REX (Thomson-Radiated Extreme X-rays). The MeV-class radiation produced by TREX is unique in the world with respect to its brightness, spectral purity, tunability, pulse duration and laser-like beam character. With T-REX, one can use photons to efficiently probe and excite the isotope-dependent resonant structure of atomic nucleus. This ability will be enabling to an entirely new class of isotope-specific, high resolution imaging and detection capabilities.