531 research outputs found
Influence of Laser-mode Statistics On Noise In Nonlinear-optical Processes - Application To Single-shot Broad-band Coherent Anti-stokes Raman-scattering Thermometry
Simulation and analysis of pulse shapes from highly segmented HPGe detectors for the Îł-ray tracking array MARS
A flexible program to calculate the pulse shapes from highly segmented HPGe detectors of various geometrical shapes has been developed. Signals originating from single points of interaction in both the quasi-true-coaxial and the closed-end part of the detector are discussed. In order to present the main features of these signals, we have introduced simplified characteristic curves. These curves are analysed with regard to the application of pulse shape analysis for three-dimensional position determination in detectors for a g-ray tracking array. # 2001 Elsevier Science B.V. All rights reserved
High fidelity readout scheme for rare-earth solid state quantum computing
We propose and analyze a high fidelity readout scheme for a single instance
approach to quantum computing in rare-earth-ion-doped crystals. The scheme is
based on using different species of qubit and readout ions, and it is shown
that by allowing the closest qubit ion to act as a readout buffer, the readout
error can be reduced by more than an order of magnitude. The scheme is shown to
be robust against certain experimental variations, such as varying detection
efficiencies, and we use the scheme to predict the expected quantum fidelity of
a CNOT gate in these solid state systems. In addition, we discuss the potential
scalability of the protocol to larger qubit systems. The results are based on
parameters which we believed are experimentally feasible with current
technology, and which can be simultaneously realized.Comment: 7 pages, 5 figure
Complexity Bounds for Relational Algebra over Document Spanners
We investigate the complexity of evaluating queries in Relational Algebra
(RA) over the relations extracted by regex formulas (i.e., regular expressions
with capture variables) over text documents. Such queries, also known as the
regular document spanners, were shown to have an evaluation with polynomial
delay for every positive RA expression (i.e., consisting of only natural joins,
projections and unions); here, the RA expression is fixed and the input
consists of both the regex formulas and the document. In this work, we explore
the implication of two fundamental generalizations. The first is adopting the
"schemaless" semantics for spanners, as proposed and studied by Maturana et al.
The second is going beyond the positive RA to allowing the difference operator.
We show that each of the two generalizations introduces computational hardness:
it is intractable to compute the natural join of two regex formulas under the
schemaless semantics, and the difference between two regex formulas under both
the ordinary and schemaless semantics. Nevertheless, we propose and analyze
syntactic constraints, on the RA expression and the regex formulas at hand,
such that the expressive power is fully preserved and, yet, evaluation can be
done with polynomial delay. Unlike the previous work on RA over regex formulas,
our technique is not (and provably cannot be) based on the static compilation
of regex formulas, but rather on an ad-hoc compilation into an automaton that
incorporates both the query and the document. This approach also allows us to
include black-box extractors in the RA expression
Nanosecond image processing using stimulated photon echoes
Processing of two-dimensional images on a nanosecond time scale is demonstrated using the stimulated photon echoes in a rare-earth-doped crystal (0.1 at. \% Pr3:LaF3). Two spatially encoded laser pulses (pictures) resonant with the 3P0-3H4 transition of Pr3 were stored by focusing the image pulses sequentially into the Pr3:LaF3 crystal. The stored information is retrieved and processed by a third read pulse, generating the echo that is the spatial convolution or correlation of the input images. Application of this scheme to high-speed pattern recognition is discussed
Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage
Coherent control of collective spontaneous emission in an extended atomic
ensemble resonantly interacting with single-photon wave packets is analyzed. A
scheme for coherent manipulation of collective atomic states is developed such
that superradiant states of the atomic system can be converted into subradiant
ones and vice versa. Possible applications of such a scheme for optical quantum
state storage and single-photon wave packet shaping are discussed. It is shown
that also in the absence of inhomogeneous broadening of the resonant line,
single-photon wave packets with arbitrary pulse shape may be recorded as a
subradiant state and reconstructed even although the duration of the wave
packets is larger than the superradiant life-time. Specifically the
applicability for storing time-bin qubits, which are used in quantum
cryptography is analyzed.Comment: 11 pages, 4 figures, submitted to PR
Pulse shape analysis in segmented detectors as a technique for background reduction in Ge double-beta decay experiments
The need to understand and reject backgrounds in Ge-diode detector
double-beta decay experiments has given rise to the development of pulse shape
analysis in such detectors to discern single-site energy deposits from
multiple-site deposits. Here, we extend this analysis to segmented Ge detectors
to study the effectiveness of combining segmentation with pulse shape analysis
to identify the multiplicity of the energy deposits.Comment: 12 pages, 13 figures, will be submitted to NI
Does Greater Low Frequency EEG Activity in Normal Immaturity and in Children with Epilepsy Arise in the Same Neuronal Network?
Greater low frequency power (<8Hz) in the electroencephalogram (EEG) at rest is normal in the immature developing brain of children when compared to adults. Children with epilepsy also have greater low frequency interictal resting EEG activity. Whether these power elevations reflect brain immaturity due to a developmental lag or the underlying epileptic pathophysiology is unclear. The present study addresses this question by analyzing spectral EEG topographies and sources for normally developing children and children with epilepsy. We first compared the resting EEG of healthy children to that of healthy adults to isolate effects related to normal brain immaturity. Next, we compared the EEG from 10 children with generalized cryptogenic epilepsy to the EEG of 24 healthy children to isolate effects related to epilepsy. Spectral analysis revealed that global low (delta: 1-3Hz, theta: 4-7Hz), medium (alpha: 8-12Hz) and high (beta: 13-25Hz) frequency EEG activity was greater in children without epilepsy compared to adults, and even further elevated for children with epilepsy. Topographical and tomographic EEG analyses showed that normal immaturity corresponded to greater delta and theta activity at fronto-central scalp and brain regions, respectively. In contrast, the epilepsy-related activity elevations were predominantly in the alpha band at parieto-occipital electrodes and brain regions, respectively. We conclude that lower frequency activity can be a sign of normal brain immaturity or brain pathology depending on the specific topography and frequency of the oscillating neuronal networ
Time- and temperature-dependent postmortem concentration changes of the (synthetic) cannabinoids JWH-210, RCS-4, as well as â9-tetrahydrocannabinol following pulmonary administration to pigs
In forensic toxicology, interpretation of postmortem (PM) drug concentrations might be complicated due to the lack of data concerning drug stability or PM redistribution (PMR). Regarding synthetic cannabinoids (SC), only sparse data are available, which derived from single case reports without any knowledge of dose and time of consumption. Thus, a controlled pig toxicokinetic study allowing for examination of PMR of SC was performed. Twelve pigs received a pulmonary dose of 200 ”g/kg BW each of 4-ethylnaphthalene-1-yl-(1-pentylindole-3-yl)methanone (JWH-210), 2-(4-methoxyphenyl)-1-(1-pentyl-indole-3-yl)methanone (RCS-4), and Î9-tetrahydrocannabinol via an ultrasonic nebulizer. Eight hours after, the pigs were put to death with T61 and specimens of relevant tissues and body fluids were collected. Subsequently, the animals were stored at room temperature (nâ=â6) or 4 °C (nâ=â6) and further samples were collected after 24, 48, and 72 h each. Concentrations were determined following enzymatic cleavage and solid-phase extraction by liquid-chromatography tandem mass spectrometry applying the standard addition approach. High concentrations of the parent compounds were observed in lung, liver, kidney and bile fluid/duodenum content as well as brain. HO-RCS-4 was the most prevalent metabolite detected in PM specimens. In general, changes of PM concentrations were found in every tissue and body fluid depending on the PM interval as well as storage temperature
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