1,235 research outputs found
Emergence of a measurement basis in atom-photon scattering
The process of quantum measurement has been a long standing source of debate.
A measurement is postulated to collapse a wavefunction onto one of the states
of a predetermined set - the measurement basis. This basis origin is not
specified within quantum mechanics. According to the theory of decohernce, a
measurement basis is singled out by the nature of coupling of a quantum system
to its environment. Here we show how a measurement basis emerges in the
evolution of the electronic spin of a single trapped atomic ion due to
spontaneous photon scattering. Using quantum process tomography we visualize
the projection of all spin directions, onto this basis, as a photon is
scattered. These basis spin states are found to be aligned with the scattered
photon propagation direction. In accordance with decohernce theory, they are
subjected to a minimal increase in entropy due to the photon scattering, while,
orthogonal states become fully mixed and their entropy is maximally increased.
Moreover, we show that detection of the scattered photon polarization measures
the spin state of the ion, in the emerging basis, with high fidelity. Lastly,
we show that while photon scattering entangles all superpositions of pointer
states with the scattered photon polarization, the measurement-basis states
themselves remain classically correlated with it. Our findings show that photon
scattering by atomic spin superpositions fulfils all the requirements from a
quantum measurement process
Comparison of the diagnostic yield and outcomes between standard 8 h capsule endoscopy and the new 12 h capsule endoscopy for investigating small bowel pathology
AIM: To evaluate the completion rate and diagnostic yield of the PillCam SB2-ex in comparison to the PillCam SB2. METHODS: Two hundred cases using the 8-h PillCam SB2 were retrospectively compared to 200 cases using the 12 h PillCam SB2-ex at a tertiary academic center. Endoscopically placed capsules were excluded from the study. Demographic information, indications for capsule endoscopy, capsule type, study length, completion of exam, clinically significant findings, timestamp of most distant finding, and significant findings beyond 8 h were recorded. RESULTS: The 8 and 12 h capsule groups were well matched respectively for both age (70.90 +/- 14.19 vs 71.93 +/- 13.80, P = 0.46) and gender (45.5% vs 48% male, P = 0.69). The most common indications for the procedure in both groups were anemia and obscure gastrointestinal bleeding. PillCam SB2-ex had a significantly higher completion rate than PillCam SB2 (88% vs 79.5%, P = 0.03). Overall, the diagnostic yield was greater for the 8 h capsule (48.5% for SB2 vs 35% for SB2-ex, P = 0.01). In 4/70 (5.7%) of abnormal SB2-ex exams the clinically significant finding was noted in the small bowel beyond the 8 h mark. CONCLUSION: In our study, we found the PillCam SB2-ex to have a significantly increased completion rate, though without any improvement in diagnostic yield compared to the PillCam SB2
Zero Field precession and hysteretic threshold currents in spin torque oscillators with tilted polarizer
Using non-linear system theory and numerical simulations we map out the
static and dynamic phase diagram in zero applied field of a spin torque
oscillator with a tilted polarizer (TP-STO).We find that for sufficiently large
currents, even very small tilt angles (beta>1 degree) will lead to steady free
layer precession in zero field. Within a rather large range of tilt angles, 1
degree< beta <19 degree, we find coexisting static states and hysteretic
switching between these using only current. In a more narrow window (1
degree<beta<5 degree) one of the static states turns into a limit cycle
(precession). The coexistence of static and dynamic states in zero magnetic
field is unique to the tilted polarizer and leads to large hysteresis in the
upper and lower threshold currents for TP-STO operation.Comment: 5 pages, 4 figure
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Measuring Red Blood Cell Velocity with a Keyhole Tracking Algorithm
A tracking algorithm is proposed to measure the velocity of red blood cells traveling through microvessels of tumors growing in skin flaps implanted on mice. The tracking is based on a keyhole model that describes the probable movement of a segmented cell between contiguous frames in a video sequence. When a history of movements exists, past, present and a predicted landing position define two regions of probability with a keyhole shape. This keyhole is used to de- termine if cells in contiguous frames should be linked to form tracks. Pre-processing segments cells from background and post-processing joins tracks and discards links that could have been formed due to noise or uncertainty. The algorithm pre- sents several advantages over traditional methods such as kymographs or particle image velocimetry: manual interven- tion is restricted to the thresholding, several vessels can be analyzed simultaneously, algorithm is robust to noise and a wealth of statistical measures can be obtained. Two tumors with different geometries were analyzed; average velocities were 211±136 [μm/s] (mean±std) with a range 15.9-797 [μm/s], and 89±62 [μm/s] with a range 5.5-300 [μm/s] respec- tively, which are consistent with previous results in the litera- ture
2-(4-Chlorophenyl)naphtho[1,8-de][1,3,2]diazaborinane
The title compound, C16H12BClN2, is one in a series of diazaborinanes, derived from 1,8-diaminonaphthalene, featuring substitution at the 1, 2 and 3 positions in the nitrogen-boron heterocycle. The structure deviates from planarity, the torsion angle subtended by the p-chlorophenyl ring relative to the nitrogen–boron heterocycle being −44-.3(3)°. The molecules form infinite chains with strong interactions between the vacant pz orbital of the B atom and the π-system of an adjacent molecule. The distance between the B atom and the 10-atom centroid of an adjacent naphthalene ring is 3.381 (4) Å. One N-H H atom is weakly hydrogen bonded to the Cl atom of an adjacent molecule. This combination of intermolecular interactions leads to the formation of an infinite two-dimensional network perpendicular to the c axis
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Microflow of fluorescently labelled red blood cells in tumours expressing single isoforms of VEGF and their response to VEGF-R tyrosine kinase inhibition
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.In this work we studied the functional differences between the microcirculation of murine tumours that only express single isoforms of vascular endothelial growth factor-A (VEGF), VEGF120 and VEGF188, and the effect of VEGF receptor tyrosine kinase (VEGF-R TK) inhibition on their functional response to the vascular disrupting agent, combretastatin A-4 phosphate (CA-4-P). We used measurement of fluorescentlylabelled
red blood cell (RBC) velocities in tumour microvessels to study this functional response. RBC velocity for control VEGF120-expressing tumours was over 50% slower than for control VEGF188-expressing tumours, which may be due to the immature and haemorrhagic vasculature of the VEGF120
tumour. After chronic treatment with a VEGF-R tyrosine kinase inhibitor, SU5416, RBC velocities in VEGF120 tumours were significantly increased compared to control VEGF120 tumours, and similar to velocities in both VEGF188 treatment groups. Control and SU5416 treated VEGF188 tumours were not
different from each other. Treatment of VEGF120 tumours with SU5416 reduced their vascular response to CA-4-P to a similar level to the VEGF188 tumours. Differential expression of VEGF isoforms not only affected vascular function in untreated tumours but also impacted on response to a vascular disrupting drug, CA-4-P, alone and in combination with an anti-angiogenic approach involving VEGF-R TK inhibition.
Analysis of RBC velocities is a useful tool in measuring functional responses to vascular targeted treatments.This study is funded by the Cancer Research UK
2-Phenylnaphtho[1,8-de][1,3,2]diazaborinane
The title compound, C16H13BN2, is one compound in a series of diazaborinanes featuring substitution at the 1, 2 and 3 positions in the nitrogen–boron heterocycle. The title compound is slightly distorted from planarity, with a dihedral angle of 9.0 (5)° between the mean planes of the naphthalene system and the benzene ring. The m-carbon atom of the benzene ring exhibits the greatest deviation of 0.164 (2) Å from the 19-atom mean plane defined by all non-H atoms. The two N—B—C—C torsion angles are 6.0 (3) and 5.6 (3)°. In the crystal, molecules are linked by π–π interactions into columns, with a distance of 3.92 (3) Å between the naphthalene ring centroids. Adjacent π-stacked columns, co-linear with the b-axis, are linked by C—H⋯π interactions
Quantum control of Sr in a miniature linear Paul trap
We report on the construction and characterization of an apparatus for
quantum information experiments using Sr ions. A miniature linear
radio-frequency (rf) Paul trap was designed and built. Trap frequencies above 1
MHz in all directions are obtained with 50 V on the trap end-caps and less than
1 W of rf power. We encode a quantum bit (qubit) in the two spin states of the
electronic ground-state of the ion. We constructed all the necessary
laser sources for laser cooling and full coherent manipulation of the ions'
external and internal states. Oscillating magnetic fields are used for coherent
spin rotations. High-fidelity readout as well as a coherence time of 2.5 ms are
demonstrated. Following resolved sideband cooling the average axial vibrational
quanta of a single trapped ion is and a heating rate of
ms is measured.Comment: 8 pages,9 figure
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