220 research outputs found
Applying machine learning to the problem of choosing a heuristic to select the variable ordering for cylindrical algebraic decomposition
Cylindrical algebraic decomposition(CAD) is a key tool in computational
algebraic geometry, particularly for quantifier elimination over real-closed
fields. When using CAD, there is often a choice for the ordering placed on the
variables. This can be important, with some problems infeasible with one
variable ordering but easy with another. Machine learning is the process of
fitting a computer model to a complex function based on properties learned from
measured data. In this paper we use machine learning (specifically a support
vector machine) to select between heuristics for choosing a variable ordering,
outperforming each of the separate heuristics.Comment: 16 page
Technological Devices in the Archives: A Policy Analysis
Doing research in the archive is the cornerstone of humanities scholarship.
Various archives institute policies regarding the use of technological
devices, such as mobile phones, laptops, and cameras in their reading rooms.
Such policies directly affect the scholars as the devices mediate the nature of
their interaction with the source materials in terms of capturing, organizing,
note taking, and record keeping for future use of found materials. In this paper,
we present our analysis of the policies of thirty archives regarding the use of
technology in their reading rooms. This policy analysis, along with data from
interviews of scholars and archivists, is intended to serve as a basis for developing
mobile applications for assisting scholars in their research activities. In this
paper we introduce an early prototype of such a mobile application—
AMTracker.Informatio
Anomalous behavior of spin wave resonances in Ga_{1-x}Mn_{x}As thin films
We report ferromagnetic and spin wave resonance absorption measurements on
high quality epitaxially grown Ga_{1-x}Mn_{x}As thin films. We find that these
films exhibit robust ferromagnetic long-range order, based on the fact that up
to seven resonances are detected at low temperatures, and the resonance
structure survives to temperatures close to the ferromagnetic transition. On
the other hand, we observe a spin wave dispersion which is linear in mode
number, in qualitative contrast with the quadratic dispersion expected for
homogeneous samples. We perform a detailed numerical analysis of the
experimental data and provide analytical calculations to demonstrate that such
a linear dispersion is incompatible with uniform magnetic parameters. Our
theoretical analysis of the ferromagnetic resonance data, combined with the
knowledge that strain-induced anisotropy is definitely present in these films,
suggests that a spatially dependent magnetic anisotropy is the most likely
reason behind the anomalous behavior observed.Comment: 9 pages, including 6 figure
The use of the antifungal agent miconazole as an inhibitor of Blastocystis hominis growth in Entamoeba histolytica/E. dispar cultures
Depression: An actionable outcome for those at clinical high-risk
Comorbid diagnoses are common in youth who are at clinical high-risk (CHR) for developing psychosis, with depression being the most common. The aim of this paper is to examine depression over two years in a large sample of CHR youth who do not make the transition to psychosis, considering both categorical and dimensional ratings of depression severity. The sample consisted of 267 CHR youth who were followed for two years. Based on DSM-IV diagnoses over this time period, 100 CHR individuals never received a diagnosis of depression, 64 individuals continuously met criteria for depression, 92 individuals received a diagnosis of depression at one or more timepoints, and 11 participants had a diagnosis of depression only at 24-months. These groupings were supported by six-monthly ratings on the Calgary Depression Scale. The majority of this sample experienced a major depressive episode on more than one occasion, suggesting that depression and depressive symptoms identify a domain of substantial unmet clinical need. Recommendations are that depression in CHR youth and young adults should be monitored more frequently and that there is a need for clinical trials to address depression systematically in this vulnerable population
Inclusive eta' Production from the Upsilon(1S)
Using the CLEO II detector at CESR, we measure the eta' - gluon - gluon
form-factor in Y(1S) decays. This form-factor especially at large eta' energies
may provide an explanation of the large rate for B -> Xs eta'. Our data do not
support a large anomalous coupling at higher q^2 and thus the large eta' rate
remains a mystery, possibly requiring a non-Standard Model explanation.Comment: 14 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
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