1,358 research outputs found

    Development of selective, ultra-fast multiple co-sensitization to control dye loading in dye-sensitized solar cells

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    Enhancing the spectral response of dye-sensitized solar cells (DSC) is essential to increasing device efficiency and a key approach to achieve this is co-sensitization (i.e. the use of multiple dyes to absorb light from different parts of the solar spectrum). However, precise control of dye loading within DSC mesoporous metal oxide photo-anodes is non-trivial especially for very rapid processing (minutes). This is further complicated by dyes having very different partition (Kd) and molar extinction (ε) coefficients which strongly influence dye uptake and spectral response, respectively. Here, we present a highly versatile, ultra-fast (ca. 5 min) desorption and re-dyeing method for dye-sensitized solar cells which can be used to precisely control dye loading in photo-electrode films. This method has been successfully applied to re-dye, partially desorb and re-dye and selectively desorb and re-dye photo-electrodes using examples of a Ru-bipy dye (N719) and also organic dyes (SQ1 and D149) giving η up to 8.1% for a device containing the organic dye D149 and re-dyed with the Ru dye N719. The paper also illustrates how this method can be used to rapidly screen large numbers of dyes (and/or dye combinations) and also illustrates how it can also be used to selectively study dye loading

    The Effect of Time Variation in the Higgs Vacuum Expectation Value on the Cosmic Microwave Background

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    A time variation in the Higgs vacuum expectation value alters the electron mass and thereby changes the ionization history of the universe. This change produces a measurable imprint on the pattern of cosmic microwave background (CMB) fluctuations. The nuclear masses and nuclear binding energies, as well as the Fermi coupling constant, are also altered, with negligible impact on the CMB. We calculate the changes in the spectrum of the CMB fluctuations as a function of the change in the electron mass. We find that future CMB experiments could be sensitive to |\Delta m_e/m_e| \sim |\Delta G_F/G_F| \sim 10^{-2} - 10^{-3}. However, we also show that a change in the electron mass is nearly, but not exactly, degenerate with a change in the fine-structure constant. If both the electron mass and the fine-structure constant are time-varying, the corresponding CMB limits are much weaker, particularly for l < 1000.Comment: 6 pages, 3 figures, Fig. 3 modified, other minor correction

    Micron-sized atom traps made from magneto-optical thin films

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    We have produced magnetic patterns suitable for trapping and manipulating neutral atoms on a 1μ1 \mum length scale. The required patterns are made in Co/Pt thin films on a silicon substrate, using the heat from a focussed laser beam to induce controlled domain reversal. In this way we draw lines and "paint" shaped areas of reversed magnetization with sub-micron resolution. These structures produce magnetic microtraps above the surface that are suitable for holding rubidium atoms with trap frequencies as high as ~1 MHz.Comment: 6 pages, 7 figure

    Jet-ISM interactions near the microquasars GRS 1758-258 and 1E 1740.7-2942

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    We present Atacama Large Millimeter/Sub-millimeter Array observations of the candidate jet-ISM interaction zones near the black hole X-ray binaries GRS 1758-258 and 1E 1740.7-2942. Using these data, we map the molecular line emission in the regions, detecting emission from the HCN [J = 1-0], HCO+ [J = 1-0], SiO [J = 2-1], CS [J = 2-1], 13CO [J = 1-0], C18O [J = 1-0], HNCO [J = 40,4-30,3], HNCO [J = 50,5-40,4], and CH3OH [J = 21,1-11,0] molecular transitions. Through examining the morphological, spectral, and kinematic properties of this emission, we identify molecular structures that may trace jet-driven cavities in the gas surrounding these systems. Our results from the GRS 1758-258 region in particular, are consistent with recent work, which postulated the presence of a jet-blown cocoon structure in deep radio continuum maps of the region. Using these newly discovered molecular structures as calorimeters, we estimate the time averaged jet power from these systems, finding (1.1-5.7) × 1036 erg s-1 over 0.12-0.31 Myr for GRS 1758-258 and (0.7-3.5) × 1037 erg s-1 over 0.10-0.26 Myr for 1E 1740.7-2942. Additionally, the spectral line characteristics of the detected emission place these molecular structures in the central molecular zone of our Galaxy, thereby constraining the distances to the black hole X-ray binaries to be 8.0 ± 1.0 kpc. Overall, our analysis solidifies the diagnostic capacity of molecular lines, and highlights how astro-chemistry can both identify jet-ISM interaction zones and probe jet feedback from Galactic X-ray binaries

    Development of data representation standards by the human proteome organization proteomics standards initiative.

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    OBJECTIVE: To describe the goals of the Proteomics Standards Initiative (PSI) of the Human Proteome Organization, the methods that the PSI has employed to create data standards, the resulting output of the PSI, lessons learned from the PSI's evolution, and future directions and synergies for the group. MATERIALS AND METHODS: The PSI has 5 categories of deliverables that have guided the group. These are minimum information guidelines, data formats, controlled vocabularies, resources and software tools, and dissemination activities. These deliverables are produced via the leadership and working group organization of the initiative, driven by frequent workshops and ongoing communication within the working groups. Official standards are subjected to a rigorous document process that includes several levels of peer review prior to release. RESULTS: We have produced and published minimum information guidelines describing what information should be provided when making data public, either via public repositories or other means. The PSI has produced a series of standard formats covering mass spectrometer input, mass spectrometer output, results of informatics analysis (both qualitative and quantitative analyses), reports of molecular interaction data, and gel electrophoresis analyses. We have produced controlled vocabularies that ensure that concepts are uniformly annotated in the formats and engaged in extensive software development and dissemination efforts so that the standards can efficiently be used by the community.Conclusion In its first dozen years of operation, the PSI has produced many standards that have accelerated the field of proteomics by facilitating data exchange and deposition to data repositories. We look to the future to continue developing standards for new proteomics technologies and workflows and mechanisms for integration with other omics data types. Our products facilitate the translation of genomics and proteomics findings to clinical and biological phenotypes. The PSI website can be accessed at http://www.psidev.info

    Economic Fluctuations and Diffusion

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    Stock price changes occur through transactions, just as diffusion in physical systems occurs through molecular collisions. We systematically explore this analogy and quantify the relation between trading activity - measured by the number of transactions NΔtN_{\Delta t} - and the price change GΔtG_{\Delta t}, for a given stock, over a time interval [t,t+Δt][t, t+\Delta t]. To this end, we analyze a database documenting every transaction for 1000 US stocks over the two-year period 1994-1995. We find that price movements are equivalent to a complex variant of diffusion, where the diffusion coefficient fluctuates drastically in time. We relate the analog of the diffusion coefficient to two microscopic quantities: (i) the number of transactions NΔtN_{\Delta t} in Δt\Delta t, which is the analog of the number of collisions and (ii) the local variance wΔt2w^2_{\Delta t} of the price changes for all transactions in Δt\Delta t, which is the analog of the local mean square displacement between collisions. We study the distributions of both NΔtN_{\Delta t} and wΔtw_{\Delta t}, and find that they display power-law tails. Further, we find that NΔtN_{\Delta t} displays long-range power-law correlations in time, whereas wΔtw_{\Delta t} does not. Our results are consistent with the interpretation that the pronounced tails of the distribution of GΔtareduetoG_{\Delta t} are due to w_{\Delta t},andthatthelongrangecorrelationspreviouslyfoundfor, and that the long-range correlations previously found for | G_{\Delta t} |aredueto are due to N_{\Delta t}$.Comment: RevTex 2 column format. 6 pages, 36 references, 15 eps figure

    Brane Interaction as the Origin of Inflation

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    We reanalyze brane inflation with brane-brane interactions at an angle, which include the special case of brane-anti-brane interaction. If nature is described by a stringy realization of the brane world scenario today (with arbitrary compactification), and if some additional branes were present in the early universe, we find that an inflationary epoch is generically quite natural, ending with a big bang when the last branes collide. In an interesting brane inflationary scenario suggested by generic string model-building, we use the density perturbation observed in the cosmic microwave background and the coupling unification to find that the string scale is comparable to the GUT scale.Comment: 28 pages, 8 figures, 2 tables, JHEP forma

    On the derivative of the associated Legendre function of the first kind of integer order with respect to its degree

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    In our recent works [R. Szmytkowski, J. Phys. A 39 (2006) 15147; corrigendum: 40 (2007) 7819; addendum: 40 (2007) 14887], we have investigated the derivative of the Legendre function of the first kind, Pν(z)P_{\nu}(z), with respect to its degree ν\nu. In the present work, we extend these studies and construct several representations of the derivative of the associated Legendre function of the first kind, Pν±m(z)P_{\nu}^{\pm m}(z), with respect to the degree ν\nu, for mNm\in\mathbb{N}. At first, we establish several contour-integral representations of Pν±m(z)/ν\partial P_{\nu}^{\pm m}(z)/\partial\nu. They are then used to derive Rodrigues-type formulas for [Pν±m(z)/ν]ν=n[\partial P_{\nu}^{\pm m}(z)/\partial\nu]_{\nu=n} with nNn\in\mathbb{N}. Next, some closed-form expressions for [Pν±m(z)/ν]ν=n[\partial P_{\nu}^{\pm m}(z)/\partial\nu]_{\nu=n} are obtained. These results are applied to find several representations, both explicit and of the Rodrigues type, for the associated Legendre function of the second kind of integer degree and order, Qn±m(z)Q_{n}^{\pm m}(z); the explicit representations are suitable for use for numerical purposes in various regions of the complex zz-plane. Finally, the derivatives [2Pνm(z)/ν2]ν=n[\partial^{2}P_{\nu}^{m}(z)/\partial\nu^{2}]_{\nu=n}, [Qνm(z)/ν]ν=n[\partial Q_{\nu}^{m}(z)/\partial\nu]_{\nu=n} and [Qνm(z)/ν]ν=n1[\partial Q_{\nu}^{m}(z)/\partial\nu]_{\nu=-n-1}, all with m>nm>n, are evaluated in terms of [Pνm(±z)/ν]ν=n[\partial P_{\nu}^{-m}(\pm z)/\partial\nu]_{\nu=n}.Comment: LateX, 40 pages, 1 figure, extensive referencin
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