1,372 research outputs found
Large Deviations of the Smallest Eigenvalue of the Wishart-Laguerre Ensemble
We consider the large deviations of the smallest eigenvalue of the
Wishart-Laguerre Ensemble. Using the Coulomb gas picture we obtain rate
functions for the large fluctuations to the left and the right of the hard
edge. Our findings are compared with known exact results for finding
good agreement. We also consider the case of almost square matrices finding new
universal rate functions describing large fluctuations.Comment: 4 pages, 2 figure
Magnetic inflation and stellar mass. V. Intensification and saturation of M-dwarf absorption lines with Rossby number
In young Sun-like stars and field M-dwarf stars, chromospheric and coronal magnetic activity indicators such as Hα, X-ray, and radio emission are known to saturate with low Rossby number (Ro lesssim 0.1), defined as the ratio of rotation period to convective turnover time. The mechanism for the saturation is unclear. In this paper, we use photospheric Ti i and Ca i absorption lines in the Y band to investigate magnetic field strength in M dwarfs for Rossby numbers between 0.01 and 1.0. The equivalent widths of the lines are magnetically enhanced by photospheric spots, a global field, or a combination of the two. The equivalent widths behave qualitatively similar to the chromospheric and coronal indicators: we see increasing equivalent widths (increasing absorption) with decreasing Ro and saturation of the equivalent widths for Ro lesssim 0.1. The majority of M dwarfs in this study are fully convective. The results add to mounting evidence that the magnetic saturation mechanism occurs at or beneath the stellar photosphere.Published versio
Properties of nonaqueous electrolytes Sixth summary report, 20 Sep. 1967 - 19 Mar. 1968
Physical properties and structural studies on propylene carbonate, dimethyl formamide, and acetonitrile solvent electrolyte
Asphaltene detection using Surface Enhanced Raman Scattering (SERS)
Peer reviewedPostprin
Quantum Phase Transitions in Anti-ferromagnetic Planar Cubic Lattices
Motivated by its relation to an -hard problem, we analyze the
ground state properties of anti-ferromagnetic Ising-spin networks embedded on
planar cubic lattices, under the action of homogeneous transverse and
longitudinal magnetic fields. This model exhibits a quantum phase transition at
critical values of the magnetic field, which can be identified by the
entanglement behavior, as well as by a Majorization analysis. The scaling of
the entanglement in the critical region is in agreement with the area law,
indicating that even simple systems can support large amounts of quantum
correlations. We study the scaling behavior of low-lying energy gaps for a
restricted set of geometries, and find that even in this simplified case, it is
impossible to predict the asymptotic behavior, with the data allowing equally
good fits to exponential and power law decays. We can therefore, draw no
conclusion as to the algorithmic complexity of a quantum adiabatic ground-state
search for the system.Comment: 7 pages, 13 figures, final version (accepted for publication in PRA
A novel methodology for in vivo endoscopic phenotyping of colorectal cancer based on real-time analysis of the mucosal lipidome: a prospective observational study of the iKnife
Background: This pilot study assessed the diagnostic accuracy of rapid evaporative ionization mass spectrometry (REIMS) in colorectal cancer (CRC) and colonic adenomas. Methods: Patients undergoing elective surgical resection for CRC were recruited at St. Mary’s Hospital London and The Royal Marsden Hospital, UK. Ex vivo analysis was performed using a standard electrosurgery handpiece with aspiration of the electrosurgical aerosol to a Xevo G2-S iKnife QTof mass spectrometer (Waters Corporation). Histological examination was performed for validation purposes. Multivariate analysis was performed using principal component analysis and linear discriminant analysis in Matlab 2015a (Mathworks, Natick, MA). A modified REIMS endoscopic snare was developed (Medwork) and used prospectively in five patients to assess its feasibility during hot snare polypectomy. Results: Twenty-eight patients were recruited (12 males, median age 71, range 35–89). REIMS was able to reliably distinguish between cancer and normal adjacent mucosa (NAM) (AUC 0.96) and between NAM and adenoma (AUC 0.99). It had an overall accuracy of 94.4 % for the detection of cancer versus adenoma and an adenoma sensitivity of 78.6 % and specificity of 97.3 % (AUC 0.99) versus cancer. Long-chain phosphatidylserines (e.g., PS 22:0) and bacterial phosphatidylglycerols were over-expressed on cancer samples, while NAM was defined by raised plasmalogens and triacylglycerols expression and adenomas demonstrated an over-expression of ceramides. REIMS was able to classify samples according to tumor differentiation, tumor budding, lymphovascular invasion, extramural vascular invasion and lymph node micrometastases (AUC’s 0.88, 0.87, 0.83, 0.81 and 0.81, respectively). During endoscopic deployment, colonoscopic REIMS was able to detect target lipid species such as ceramides during hot snare polypectomy. Conclusion: REIMS demonstrates high diagnostic accuracy for tumor type and for established histological features of poor prognostic outcome in CRC based on a multivariate analysis of the mucosal lipidome. REIMS could augment endoscopic and imaging technologies for precision phenotyping of colorectal cancer
The Majorization Arrow in Quantum Algorithm Design
We apply majorization theory to study the quantum algorithms known so far and
find that there is a majorization principle underlying the way they operate.
Grover's algorithm is a neat instance of this principle where majorization
works step by step until the optimal target state is found. Extensions of this
situation are also found in algorithms based in quantum adiabatic evolution and
the family of quantum phase-estimation algorithms, including Shor's algorithm.
We state that in quantum algorithms the time arrow is a majorization arrow.Comment: REVTEX4.b4 file, 4 color figures (typos corrected.
Quantum Dynamics of a Bose Superfluid Vortex
We derive a fully quantum-mechanical equation of motion for a vortex in a
2-dimensional Bose superfluid, in the temperature regime where the normal fluid
density is small. The coupling between the vortex "zero mode" and
the quasiparticles has no term linear in the quasiparticle variables -- the
lowest-order coupling is quadratic. We find that as a function of the
dimensionless frequency , the standard
Hall-Vinen/Iordanskii equations are valid when (the
"classical regime"), but elsewhere, the equations of motion become highly
retarded, with significant experimental implications when .Comment: 12 pages (4 pages + supp info), 2 figures, accepted to PR
M-Dwarf Fast Rotators and the Detection of Relatively Young Multiple M-Star Systems
We have searched the Kepler light curves of ~3900 M-star targets for evidence
of periodicities that indicate, by means of the effects of starspots, rapid
stellar rotation. Several analysis techniques, including Fourier transforms,
inspection of folded light curves, 'sonograms', and phase tracking of
individual modulation cycles, were applied in order to distinguish the
periodicities due to rapid rotation from those due to stellar pulsations,
eclipsing binaries, or transiting planets. We find 178 Kepler M-star targets
with rotation periods, P_rot, of < 2 days, and 110 with P_rot < 1 day. Some 30
of the 178 systems exhibit two or more independent short periods within the
same Kepler photometric aperture, while several have three or more short
periods. Adaptive optics imaging and modeling of the Kepler pixel response
function for a subset of our sample support the conclusion that the targets
with multiple periods are highly likely to be relatively young physical binary,
triple, and even quadruple M star systems. We explore in detail the one object
with four incommensurate periods all less than 1.2 days, and show that two of
the periods arise from one of a close pair of stars, while the other two arise
from the second star, which itself is probably a visual binary. If most of
these M-star systems with multiple periods turn out to be bound M stars, this
could prove a valuable way of discovering young hierarchical M-star systems;
the same approach may also be applicable to G and K stars. The ~5% occurrence
rate of rapid rotation among the ~3900 M star targets is consistent with spin
evolution models that include an initial contraction phase followed by magnetic
braking, wherein a typical M star can spend several hundred Myr before spinning
down to periods longer than 2 days.Comment: 17 pages, 12 figures, 2 tables; accepted for publication in The
Astrophysical Journa
Quantum conductance problems and the Jacobi ensemble
In one dimensional transport problems the scattering matrix is decomposed
into a block structure corresponding to reflection and transmission matrices at
the two ends. For a random unitary matrix, the singular value probability
distribution function of these blocks is calculated. The same is done when
is constrained to be symmetric, or to be self dual quaternion real, or when
has real elements, or has real quaternion elements. Three methods are used:
metric forms; a variant of the Ingham-Seigel matrix integral; and a theorem
specifying the Jacobi random matrix ensemble in terms of Wishart distributed
matrices.Comment: 10 page
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