566 research outputs found
Percolation with long-range correlated disorder
Long-range power-law correlated percolation is investigated using Monte Carlo
simulations. We obtain several static and dynamic critical exponents as
function of the Hurst exponent which characterizes the degree of spatial
correlation among the occupation of sites. In particular, we study the fractal
dimension of the largest cluster and the scaling behavior of the second moment
of the cluster size distribution, as well as the complete and accessible
perimeters of the largest cluster. Concerning the inner structure and transport
properties of the largest cluster, we analyze its shortest path, backbone, red
sites, and conductivity. Finally, bridge site growth is also considered. We
propose expressions for the functional dependence of the critical exponents on
Characterization of PARIS LaBr(Ce)-NaI(Tl) phoswich detectors upto 22 MeV
In order to understand the performance of the PARIS (Photon Array for the
studies with Radioactive Ion and Stable beams) detector, detailed
characterization of two individual phoswich (LaBr(Ce)-NaI(Tl)) elements has
been carried out. The detector response is investigated over a wide range of
= 0.6 to 22.6 MeV using radioactive sources and employing
reaction at = 163 keV and = 7.2 MeV. The
linearity of energy response of the LaBr(Ce) detector is tested upto 22.6
MeV using three different voltage dividers. The data acquisition system using
CAEN digitizers is set up and optimized to get the best energy and time
resolution. The energy resolution of 2.1% at = 22.6~MeV is
measured for the configuration giving best linearity upto high energy. Time
resolution of the phoswich detector is measured with a Co source after
implementing CFD algorithm for the digitized pulses and is found to be
excellent (FWHM 315~ps). In order to study the effect of count rate on
detectors, the centroid position and width of the = 835~keV peak
were measured upto 220 kHz count rate. The measured efficiency data with
radioactive sources are in good agreement with GEANT4 based simulations. The
total energy spectrum after the add-back of energy signals in phoswich
components is also presented.Comment: Accepted in JINS
Building consensus: shifting strategies in the territorial targeting of Turkey's public transport investment
© 2019, © 2019 Regional Studies Association. A growing amount of research explores how the allocation of regional development monies follows electoral reasons. Yet, the existing literature on distributive politics provides different and contrasting expectations on which geographical areas will be targeted. The paper focuses on proportional representation (PR) systems. While in such settings governments have incentives to target core districts and punish foes, it is suggested that when incumbents attempt to build a state–party image they may broaden the territorial allocation of benefits and even target opposition out-groups. The paper exploits data on Turkey's public transport investment for the period 2003–14 and in-depth interviews to provide results in support of the hypothesis.Harvard Emirates Leadership Initiative Fellowshi
Fluorescent detection of hydrogen sulfide (H2S) through the formation of pyrene excimers enhances H2S quantification in biochemical systems
Hydrogen sulfide (H2S) is produced endogenously by several enzymatic pathways and modulates physiological functions in mammals. Quantification of H2S in biochemical systems remains challenging because of the presence of interferents with similar reactivity, particularly thiols. Herein, we present a new quantification method based on the formation of pyrene excimers in solution. We synthesized the probe 2-(maleimido)ethyl 4-pyrenylbutanoate (MEPB) and determined that MEPB reacted with H2S in a two-step reaction to yield the thioether-linked dimer (MEPB)2S, which formed excimers upon excitation, with a broad peak of fluorescence emission centered at 480 nm. In contrast, we found that the products formed with thiols showed peaks at 378 and 398 nm. The difference in emission between the products prevented the interference. Furthermore, we showed that the excimer fluorescence signal yielded a linear response to H2S, with a limit of detection of 54 nM in a fluorometer. Our quantification method with MEPB was successfully applied to follow the reaction of H2S with glutathione disulfide and to quantify the production of H2S from cysteine by Escherichia coli. In conclusion, this method represents an addition to the toolkit of biochemists to quantify H2S specifically and sensitively in biochemical systems.MEC: I/FVF2017/069ANII: FCE_1_2017_1_136043CSIC: I+D 2017; I+D 202
Aging Studies for the Large Honeycomb Drift Tube System of the Outer Tracker of HERA-B
The HERA-B Outer Tracker consists of drift tubes folded from polycarbonate
foil and is operated with Ar/CF4/CO2 as drift gas. The detector has to stand
radiation levels which are similar to LHC conditions. The first prototypes
exposed to radiation in HERA-B suffered severe radiation damage due to the
development of self-sustaining currents (Malter effect). In a subsequent
extended R&D program major changes to the original concept for the drift tubes
(surface conductivity, drift gas, production materials) have been developed and
validated for use in harsh radiation environments. In the test program various
aging effects (like Malter currents, gain loss due to anode aging and etching
of the anode gold surface) have been observed and cures by tuning of operation
parameters have been developed.Comment: 14 pages, 6 figures, to be published in the Proceedings of the
International Workshop On Aging Phenomena In Gaseous Detectors, 2-5 Oct 2001,
Hamburg, German
The Outer Tracker Detector of the HERA-B Experiment Part I: Detector
The HERA-B Outer Tracker is a large system of planar drift chambers with
about 113000 read-out channels. Its inner part has been designed to be exposed
to a particle flux of up to 2.10^5 cm^-2 s^-1, thus coping with conditions
similar to those expected for future hadron collider experiments. 13
superlayers, each consisting of two individual chambers, have been assembled
and installed in the experiment. The stereo layers inside each chamber are
composed of honeycomb drift tube modules with 5 and 10 mm diameter cells.
Chamber aging is prevented by coating the cathode foils with thin layers of
copper and gold, together with a proper drift gas choice. Longitudinal wire
segmentation is used to limit the occupancy in the most irradiated detector
regions to about 20 %. The production of 978 modules was distributed among six
different laboratories and took 15 months. For all materials in the fiducial
region of the detector good compromises of stability versus thickness were
found. A closed-loop gas system supplies the Ar/CF4/CO2 gas mixture to all
chambers. The successful operation of the HERA-B Outer Tracker shows that a
large tracker can be efficiently built and safely operated under huge radiation
load at a hadron collider.Comment: 28 pages, 14 figure
Advanced Technologies for Oral Controlled Release: Cyclodextrins for oral controlled release
Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g. as osmotic pumps) and/ or hydrophobic CDs. New controlled delivery systems based on nanotechonology carriers (nanoparticles and conjugates) have also been reviewed
The Outer Tracker Detector of the HERA-B Experiment. Part II: Front-End Electronics
The HERA-B Outer Tracker is a large detector with 112674 drift chamber
channels. It is exposed to a particle flux of up to 2x10^5/cm^2/s thus coping
with conditions similar to those expected for the LHC experiments. The
front-end readout system, based on the ASD-8 chip and a customized TDC chip, is
designed to fulfil the requirements on low noise, high sensitivity, rate
tolerance, and high integration density. The TDC system is based on an ASIC
which digitizes the time in bins of about 0.5 ns within a total of 256 bins.
The chip also comprises a pipeline to store data from 128 events which is
required for a deadtime-free trigger and data acquisition system. We report on
the development, installation, and commissioning of the front-end electronics,
including the grounding and noise suppression schemes, and discuss its
performance in the HERA-B experiment
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