3,391 research outputs found
Space charge enhanced plasma gradient effects on satellite electric field measurements
It has been recognized that plasma gradients can cause error in magnetospheric electric field measurements made by double probes. Space charge enhanced Plasma Gradient Induced Error (PGIE) is discussed in general terms, presenting the results of a laboratory experiment designed to demonstrate this error, and deriving a simple expression that quantifies this error. Experimental conditions were not identical to magnetospheric conditions, although efforts were made to insure the relevant physics applied to both cases. The experimental data demonstrate some of the possible errors in electric field measurements made by strongly emitting probes due to space charge effects in the presence of plasma gradients. Probe errors in space and laboratory conditions are discussed, as well as experimental error. In the final section, theoretical aspects are examined and an expression is derived for the maximum steady state space charge enhanced PGIE taken by two identical current biased probes
A New Test for Market Efficiency and Uncovered Interest Parity
We suggest a new single-equation test for Uncovered Interest Parity (UIP)
based on a dynamic regression approach. The method provides consistent and
asymptotically efficient parameter estimates, and is not dependent on
assumptions of strict exogeneity. This new approach is asymptotically more
efficient than the common approach of using OLS with HAC robust standard errors
in the static forward premium regression. The coefficient estimates when spot
return changes are regressed on the forward premium are all positive and
remarkably stable across currencies. These estimates are considerably larger
than those of previous studies, which frequently find negative coefficients.
The method also has the advantage of showing dynamic effects of risk premia, or
other events that may lead to rejection of UIP or the efficient markets
hypothesis
Adsorption configurations of Co-phthalocyanine on In2O3(111)
Indium oxide offers optical transparency paired with electric conductivity, a
combination required in many optoelectronic applications. The most-stable
In2O3(111) surface has a large unit cell (1.43 nm lattice constant). It
contains a mixture of both bulk-like and undercoordinated O and In atoms and
provides an ideal playground to explore the interaction of surfaces with
organic molecules of similar size as the unit cell. Non-contact atomic force
microscopy (nc-AFM), scanning tunneling microscopy (STM), and density
functional theory (DFT) were used to study the adsorption of Co-phthalocyanine
(CoPc) on In2O3(111). Isolated CoPc molecules adsorb at two adsorption sites in
a 7:3 ratio. The Co atom sits either on top of a surface oxygen ('F
configuration') or indium atom ('S configuration'). This subtle change in
adsorption site induces bending of the molecules, which is reflected in their
electronic structure. According to DFT the lowest unoccupied molecular orbital
of the undistorted gas-phase CoPc remains mostly unaffected in the F
configuration but is filled by one electron in S configuration. At coverages up
to one CoPc molecule per substrate unit cell, a mixture of domains with
molecules in F and S configuration are found. Molecules at F sites first
condense into a F-(2x2) structure and finally rearrange into a F-(1x1) symmetry
with partially overlapping molecules, while S-sited molecules only assume a
S-(1x1) superstructure
Application of carbon nanotubes in cancer vaccines: Achievements, challenges and chances
Tumour-specific, immuno-based therapeutic interventions can be considered as safe and effective approaches for cancer therapy. Exploitation of nano-vaccinology to intensify the cancer vaccine potency may overcome the need for administration of high vaccine doses or additional adjuvants and therefore could be a more efficient approach. Carbon nanotube (CNT) can be described as carbon sheet(s) rolled up into a cylinder that is nanometers wide and nanometers to micrometers long. Stemming from the observed capacities of CNTs to enter various types of cells via diversified mechanisms utilising energy-dependent and/or passive routes of cell uptake, the use of CNTs for the delivery of therapeutic agents has drawn increasing interests over the last decade. Here we review the previous studies that demonstrated the possible benefits of these cylindrical nano-vectors as cancer vaccine delivery systems as well as the obstacles their clinical application is facing
On a generalised model for time-dependent variance with long-term memory
The ARCH process (R. F. Engle, 1982) constitutes a paradigmatic generator of
stochastic time series with time-dependent variance like it appears on a wide
broad of systems besides economics in which ARCH was born. Although the ARCH
process captures the so-called "volatility clustering" and the asymptotic
power-law probability density distribution of the random variable, it is not
capable to reproduce further statistical properties of many of these time
series such as: the strong persistence of the instantaneous variance
characterised by large values of the Hurst exponent (H > 0.8), and asymptotic
power-law decay of the absolute values self-correlation function. By means of
considering an effective return obtained from a correlation of past returns
that has a q-exponential form we are able to fix the limitations of the
original model. Moreover, this improvement can be obtained through the correct
choice of a sole additional parameter, . The assessment of its validity
and usefulness is made by mimicking daily fluctuations of SP500 financial
index.Comment: 6 pages, 4 figure
Structure and apparent topography of TiO2 (110) surfaces
We present self-consistent ab-initio total-energy and electronic-structure
calculations on stoichiometric and non-stoichiometric TiO2 (110) surfaces.
Scanning tunneling microscopy (STM) topographs are simulated by calculating the
local electronic density of states over an energy window appropriate for the
experimental positive-bias conditions. We find that under these conditions the
STM tends to image the undercoordinated Ti atoms, in spite of the physical
protrusion of the O atoms, giving an apparent reversal of topographic contrast
on the stoichiometric 1x1 or missing-row 2x1 surface. We also show that both
the interpretation of STM images and the direct comparison of surface energies
favor an added-row structure over the missing-row structure for the
oxygen-deficient 2x1 surface.Comment: 6 pages, two-column style with 5 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#ng_tio
FlashCam: a fully-digital camera for the medium-sized telescopes of the Cherenkov Telescope Array
The FlashCam group is currently preparing photomultiplier-tube based cameras
proposed for the medium-sized telescopes (MST) of the Cherenkov Telescope Array
(CTA). The cameras are designed around the FlashCam readout concept which is
the first fully-digital readout system for Cherenkov cameras, based on
commercial FADCs and FPGAs as key components for the front-end electronics
modules and a high performance camera server as back-end. This contribution
describes the progress of the full-scale FlashCam camera prototype currently
under construction, as well as performance results also obtained with earlier
demonstrator setups. Plans towards the production and implementation of
FlashCams on site are also briefly presented.Comment: 8 pages, 6 figures. In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
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