7,584 research outputs found
Real-time motion and magnetic field correction for GABA editing using EPI volumetric navigated MEGA-SPECIAL sequence: Reproducibility and Gender effects
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter and is of great interest to the magnetic resonance spectroscopy (MRS) community due to its role in several neurological diseases and disorders. Since GABA acquisition without macromolecule contamination requires long scan times and strongly depends on magnetic field (B0) stability, it is highly susceptible to motion and B0 inhomogeneity. In this work, a pair of three-dimensional (3D) echo planar imaging (EPI) volumetric navigators (vNav) with different echo times, were inserted in MEGA-SPECIAL to perform prospective correction for changes in the subject's head position and orientation, as well as changes in B0. The navigators do not increase acquisition time and have negligible effect on the GABA signal. The motion estimates are obtained by registering the first of the pairs of successive vNav volume images to the first volume image. The 3D field maps are calculated through complex division of the pair of vNav contrasts and are used for estimating zero- and first-order shim changes in the volume of interest (VOI). The efficacy of the vNav MEGA-SPECIAL sequence was demonstrated in-vitro and in vivo. Without motion and shim correction, spectral distortions and increases in spectral fitting error, linewidth and GABA concentration relative to creatine were observed in the presence of motion. The navigated sequence yielded high spectral quality despite significant subject motion. Using the volumetric navigated MEGA-SPECIAL sequence, the reproducibility of GABA measurements over a 40 minute period was investigated in two regions, the anterior cingulate (ACC) and medial parietal (PAR) cortices, and compared for different analysis packages, namely LCModel, jMRUI and GANNET. LCModel analysis yielded the most reproducible results, followed by jMRUI and GANNET. GABA levels in ACC were unchanged over time, while GABA levels in PAR were significantly lower for the second measurement. In ACC, GABA levels did not differ between males and females. In contrast, males had higher GABA levels in PAR. This gender difference was, however, only present in the first acquisition. Only in males did GABA levels in PAR decrease over time. These results demonstrate that gender differences are regional, and that GABA levels may fluctuate differently in different regions and sexes
Educational Department Website of Libyan Embassy in Malaysia
The educational departments of the Libyan embassy in Malaysia website plays major rule in different fields that explore and become important economic, commerce, military, health, education, diplomatic.
On the other hand many embassies in several countries are facing difficulties in accessing, organizing and collecting the data related to students specifically the registered students in education department of the Libyan embassy in Malaysia, So I studied design website the educational department Libyan embassy in Malaysia, and is interested in opening a file for the student follow-up to the most important news of the educational department, to insert some data, File Number, Student Name, Libyan Address, Phone Number, Support Direction, Current Institution, Scientific Grade, Major, Start Study, End Study, Malaysian Address and Mail's Student, also if there is any problem in the area of study a student can send a message to the educational
department website or the consulted educational department e-mail for the consideration and resolution as soon as possible
Moments of nonclassicality quasiprobabilities
A method is introduced for the verification of nonclassicality in terms of
moments of nonclassicality quasiprobability distributions. The latter are
easily obtained from experimental data and will be denoted as nonclassicality
moments. Their relation to normally-ordered moments is derived, which enables
us to verify nonclassicality by using well established criteria. Alternatively,
nonclassicality criteria are directly formulated in terms of nonclassicality
moments. The latter converge in proper limits to the usually used criteria, as
is illustrated for squeezing and sub-Poissonian photon statistics. Our theory
also yields expectation values of any observable in terms of nonclassicality
moments.Comment: 6 pages, 3 figure
Discriminating quantum-optical beam-splitter channels with number-diagonal signal states: Applications to quantum reading and target detection
We consider the problem of distinguishing, with minimum probability of error,
two optical beam-splitter channels with unequal complex-valued reflectivities
using general quantum probe states entangled over M signal and M' idler mode
pairs of which the signal modes are bounced off the beam splitter while the
idler modes are retained losslessly. We obtain a lower bound on the output
state fidelity valid for any pure input state. We define number-diagonal signal
(NDS) states to be input states whose density operator in the signal modes is
diagonal in the multimode number basis. For such input states, we derive series
formulas for the optimal error probability, the output state fidelity, and the
Chernoff-type upper bounds on the error probability. For the special cases of
quantum reading of a classical digital memory and target detection (for which
the reflectivities are real valued), we show that for a given input signal
photon probability distribution, the fidelity is minimized by the NDS states
with that distribution and that for a given average total signal energy N_s,
the fidelity is minimized by any multimode Fock state with N_s total signal
photons. For reading of an ideal memory, it is shown that Fock state inputs
minimize the Chernoff bound. For target detection under high-loss conditions, a
no-go result showing the lack of appreciable quantum advantage over coherent
state transmitters is derived. A comparison of the error probability
performance for quantum reading of number state and two-mode squeezed vacuum
state (or EPR state) transmitters relative to coherent state transmitters is
presented for various values of the reflectances. While the nonclassical states
in general perform better than the coherent state, the quantitative performance
gains differ depending on the values of the reflectances.Comment: 12 pages, 7 figures. This closely approximates the published version.
The major change from v2 is that Section IV has been re-organized, with a
no-go result for target detection under high loss conditions highlighted. The
last sentence of the abstract has been deleted to conform to the arXiv word
limit. Please see the PDF for the full abstrac
Adaptive Processing of Spatial-Keyword Data Over a Distributed Streaming Cluster
The widespread use of GPS-enabled smartphones along with the popularity of
micro-blogging and social networking applications, e.g., Twitter and Facebook,
has resulted in the generation of huge streams of geo-tagged textual data. Many
applications require real-time processing of these streams. For example,
location-based e-coupon and ad-targeting systems enable advertisers to register
millions of ads to millions of users. The number of users is typically very
high and they are continuously moving, and the ads change frequently as well.
Hence sending the right ad to the matching users is very challenging. Existing
streaming systems are either centralized or are not spatial-keyword aware, and
cannot efficiently support the processing of rapidly arriving spatial-keyword
data streams. This paper presents Tornado, a distributed spatial-keyword stream
processing system. Tornado features routing units to fairly distribute the
workload, and furthermore, co-locate the data objects and the corresponding
queries at the same processing units. The routing units use the Augmented-Grid,
a novel structure that is equipped with an efficient search algorithm for
distributing the data objects and queries. Tornado uses evaluators to process
the data objects against the queries. The routing units minimize the redundant
communication by not sending data updates for processing when these updates do
not match any query. By applying dynamically evaluated cost formulae that
continuously represent the processing overhead at each evaluator, Tornado is
adaptive to changes in the workload. Extensive experimental evaluation using
spatio-textual range queries over real Twitter data indicates that Tornado
outperforms the non-spatio-textually aware approaches by up to two orders of
magnitude in terms of the overall system throughput
Quantum entanglement distribution with 810 nm photons through telecom fibers
We demonstrate the distribution of polarization entangled photons of
wavelength 810 nm through standard telecom fibers. This technique allows
quantum communication protocols to be performed over established fiber
infrastructure, and makes use of the smaller and better performing setups
available around 800 nm, as compared to those which use telecom wavelengths
around 1550 nm. We examine the excitation and subsequent quenching of
higher-order spatial modes in telecom fibers up to 6 km in length, and perform
a distribution of high quality entanglement (visibility 95.6%). Finally, we
demonstrate quantum key distribution using entangled 810 nm photons over a 4.4
km long installed telecom fiber link.Comment: 5 pages, 5 figures, 1 tabl
Ionization-induced asymmetric self-phase modulation and universal modulational instability in gas-filled hollow-core photonic crystal fibers
We study theoretically the propagation of relatively long pulses with
ionizing intensities in a hollow-core photonic crystal fiber filled with a
Raman-inactive gas. Due to photoionization, previously unknown types of
asymmetric self-phase modulation and `universal' modulational instabilities
existing in both normal and anomalous dispersion regions appear. We also show
that it is possible to spontaneously generate a plasma-induced continuum of
blueshifting solitons, opening up new possibilities for pushing supercontinuum
generation towards shorter and shorter wavelengths.Comment: 5 pages, 4 figure
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