1,501 research outputs found
Observation of surface charge screening and Fermi level pinning on a synthetic, boron-doped diamond
Spectroscopic current-voltage (I-V) curves taken with a scanning tunneling microscope on a synthetic, boron-doped diamond single crystal indicate that the diamond, boiled in acid and baked to 500 °C in vacuum, does not exhibit ideal Schottky characteristics. These I-V curves taken in ultrahigh vacuum do not fit the traditional theory of thermionic emission; however, the deviation from ideal can be accounted for by charge screening at the diamond surface. At ambient pressure, the I-V curves have a sharp threshold voltage at 1.7 eV above the valence band edge indicating pinning of the Fermi energy. This measurement is in excellent agreement with the 1/3 band gap rule of Mead and Spitzer [Phys. Rev. 134, A713 (1964)]
An O(n^3)-Time Algorithm for Tree Edit Distance
The {\em edit distance} between two ordered trees with vertex labels is the
minimum cost of transforming one tree into the other by a sequence of
elementary operations consisting of deleting and relabeling existing nodes, as
well as inserting new nodes. In this paper, we present a worst-case
-time algorithm for this problem, improving the previous best
-time algorithm~\cite{Klein}. Our result requires a novel
adaptive strategy for deciding how a dynamic program divides into subproblems
(which is interesting in its own right), together with a deeper understanding
of the previous algorithms for the problem. We also prove the optimality of our
algorithm among the family of \emph{decomposition strategy} algorithms--which
also includes the previous fastest algorithms--by tightening the known lower
bound of ~\cite{Touzet} to , matching our
algorithm's running time. Furthermore, we obtain matching upper and lower
bounds of when the two trees have
different sizes and~, where .Comment: 10 pages, 5 figures, 5 .tex files where TED.tex is the main on
Morphological, Structural, and Spectral Characteristics of Amorphous Iron Sulfates
Current or past brine hydrologic activity on Mars may provide suitable conditions for the formation of amorphous ferric sulfates. Once formed, these phases would likely be stable under current Martian conditions, particularly at low- to mid-latitudes. Therefore, we consider amorphous iron sulfates (AIS) as possible components of Martian surface materials. Laboratory AIS were created through multiple synthesis routes and characterized with total X-ray scattering, thermogravimetric analysis, scanning electron microscopy, visible/near-infrared (VNIR), thermal infrared (TIR), and Mössbauer techniques. We synthesized amorphous ferric sulfates (Fe(III)2(SO4)3 · ~ 6–8H2O) from sulfate-saturated fluids via vacuum dehydration or exposure to low relative humidity
Theoretical Spectra and Atmospheres of Extrasolar Giant Planets
We present a comprehensive theory of the spectra and atmospheres of
irradiated extrasolar giant planets. We explore the dependences on stellar
type, orbital distance, cloud characteristics, planet mass, and surface
gravity. Phase-averaged spectra for specific known extrasolar giant planets
that span a wide range of the relevant parameters are calculated, plotted, and
discussed. The connection between atmospheric composition and emergent spectrum
is explored in detail. Furthermore, we calculate the effect of stellar
insolation on brown dwarfs. We review a variety of representative observational
techniques and programs for their potential for direct detection, in light of
our theoretical expectations, and we calculate planet-to-star flux ratios as a
function of wavelength. Our results suggest which spectral features are most
diagnostic of giant planet atmospheres and reveal the best bands in which to
image planets of whatever physical or orbital characteristics.Comment: 47 pages, plus 36 postscript figures; with minor revisions, accepted
to the Astrophysical Journal, May 10, 2003 issu
ZERO MEAN CURVATURE SURFACES IN LORENTZ-MINKOWSKI 3-SPACE WHICH CHANGE TYPE ACROSS A LIGHT-LIKE LINE
Rho GTPase Transcriptome Analysis Reveals Oncogenic Roles for Rho GTPase-Activating Proteins in Basal-like Breast Cancers
The basal-like breast cancer (BLBC) subtype accounts for a disproportionately high percentage of overall breast cancer mortality. The current therapeutic options for BLBC need improvement; hence, elucidating signaling pathways that drive BLBC growth may identify novel targets for the development of effective therapies. Rho GTPases have previously been implicated in promoting tumor cell proliferation and metastasis. These proteins are inactivated by Rho-selective GTPase-activating proteins (RhoGAPs), which have generally been presumed to act as tumor suppressors. Surprisingly, RNA-Seq analysis of the Rho GTPase signaling transcriptome revealed high expression of several RhoGAP genes in BLBC tumors, raising the possibility that these genes may be oncogenic. To evaluate this, we examined the roles of two of these RhoGAPs, ArhGAP11A (also known as MP-GAP) and RacGAP1 (also known as MgcRacGAP), in promoting BLBC. Both proteins were highly expressed in human BLBC cell lines, and knockdown of either gene resulted in significant defects in the proliferation of these cells. Knockdown of ArhGAP11A caused CDKN1B/p27-mediated arrest in the G1 phase of the cell cycle, whereas depletion of RacGAP1 inhibited growth through the combined effects of cytokinesis failure, CDKN1A/p21-mediated RB1 inhibition, and the onset of senescence. Random migration was suppressed or enhanced by the knockdown of ArhGAP11A or RacGAP1, respectively. Cell spreading and levels of GTP-bound RhoA were increased upon depletion of either GAP. We have established that, via the suppression of RhoA, ArhGAP11A and RacGAP1 are both critical drivers of BLBC growth, and propose that RhoGAPs can act as oncogenes in cancer
ERRATUM TO THE ARTICLE "ZERO MEAN CURVATURE SURFACES IN LORENTZ-MINKOWKI 3-SPACE WHICH CHANGE TYPE ACROSS A LIGHT-LIKE LINE" OSAKA J. MATH. 52 (2015), 285-297
Rendering an Account: An Open-State Archive in Postgraduate Supervision
The paper begins with a brief account of the transformation of research degree studies under the pressures of global capitalism and neo-liberal governmentality. A parallel transformation is occurring in the conduct of research through the use of information and communication technologies. Yet the potential of ICTs to shape practices of surveillance or to produce new student-supervisor relations and enhance the processes of developing the dissertation has received almost no critical attention. As doctoral supervisor and student, we then describe the features and uses of a web-based open state archive of the student's work-in-progress, developed by the student and accessible to his supervisor. Our intention was to encourage more open conversations between data and theorising, student and supervisor, and ultimately between the student and professional community. However, we recognise that relations of accountability, as these have developed within a contemporary "audit revolution" (Power, 1994, 1997) in universities, create particular "lines of visibility" (Munro, 1996). Thus while the open-state archive may help to redefine in less managerial terms notions of quality, transparency, flexibility and accountability, it might also make possible greater supervisory surveillance. How should we think about the panoptical potential of this archive? We argue that the diverse kinds of interactional patterns and pedagogical intervention it encourages help to create shifting subjectivities. Moreover, the archive itself is multiple, in bringing together an array of diverse materials that can be read in various ways, by following multiple paths. It therefore constitutes a collage, which we identify as a mode of cognition and of accounting distinct from but related to argument and narrative. As a more "open" text (Iser, 1978) it has an indeterminacy which may render it less open to abuse for the technologies of managerial accountability
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