198 research outputs found
Non-Newtonian effects in the peristaltic flow of a Maxwell fluid
We analyzed the effect of viscoelasticity on the dynamics of fluids in porous
media by studying the flow of a Maxwell fluid in a circular tube, in which the
flow is induced by a wave traveling on the tube wall. The present study
investigates novelties brought about into the classic peristaltic mechanism by
inclusion of non-Newtonian effects that are important, for example, for
hydrocarbons. This problem has numerous applications in various branches of
science, including stimulation of fluid flow in porous media under the effect
of elastic waves. We have found that in the extreme non-Newtonian regime there
is a possibility of a fluid flow in the direction {\it opposite} to the
propagation of the wave traveling on the tube wall.Comment: to Appear in Phys. Rev. E., 01 September 2001 issu
Search for the Rare Decay KL --> pi0 ee
The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay
KL--> pi0ee. This mode is expected to have a significant CP violating
component. The measurement of its branching ratio could support the Standard
Model or could indicate the existence of new physics. This letter reports new
results from the 1999-2000 data set. One event is observed with an expected
background at 0.99 +/- 0.35 events. We set a limit on the branching ratio of
3.5 x 10^(-10) at the 90% confidence level. Combining the results with the
dataset taken in 1997 yields the final KTeV result: BR(KL --> pi0 ee) < 2.8 x
10^(-10) at 90% CL.Comment: 4 pages, three figure
Relationship Between the Thermodynamic Parameters, Structure, and Anticorrosion Properties of Al-Zr-Ni-Fe-Y Alloys
The influence of the chemical composition on the crystallization process, amorphous phase
formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y alloys are presented. To reduce
the number of experiments, a thermodynamic approach was applied in which the entropy and
Gibbs free energy of representative alloys were optimized. The low glass-forming ability of
Al-Zr-Ni-Fe-Y alloy systems was related to the crystallization of the Al3Zr phase from the melt.
The structural analysis showed that phases containing Ni and Fe, such as Al19Ni5Y3, Al10Fe2Y,
and Al23Ni6Y4, played a key role in the formation of amorphous alloys. According to this, the
simultaneous addition of Ni/Fe and Y is important to prevent the crystallization of Al-based
alloys in the melt. The formation of an amorphous phase in Al80Zr5Ni5Fe5Y5 alloys and the
complete amorphization of Al85Ni5Fe5Y5 alloys were responsible for the high corrosion
resistance compared with fully crystalline alloys. Moreover, the addition of Y had a significant
impact on the anticorrosion properties. The XPS results showed that the alloys tended to form a
passive Al2O3 and Y2O3 layer on the surface
Measurements Of The Decay Kl → E+e-μ+μ-
Several 132 KL → e+e- μ+ μ- events were observed from the 1997 and 1999 runs of the KTeV experiments, with an estimated background of 0.8 events. In the first measurement of the parameter α using this decay mode, it was found that α=-1.59±0.37. No evidence was found for CP-violating contributions to the KLγ*γ* interaction.9014141801/1141801/5Wolfenstein, L., (1983) Phys. Rev. Lett., 51, p. 1945Belanger, G., Geng, C.Q., (1991) Phys. Rev. D, 43, p. 140Buras, A.J., Fleischer, R., (1998) Advanced Ser. Direct. High Energy Phys., 15, p. 65Uy, Z.E.S., (1991) Phys. Rev. D, 43, p. 802D'Ambrosio, G., Isidori, G., Portolès, J., (1998) Phys. Lett. B, 423, p. 385Alavi-Harati, A., (2001) Phys. Rev. Lett., 87, p. 71801. , KTeV CollaborationAlavi-Harati, A., (2001) Phys. Rev. Lett., 86, p. 5425. , KTeV CollaborationUy, Z.E.S., (2002) Eur. Phys. J. C, 23, p. 113Alavi-Harati, A., (2001) Phys. Rev. Lett., 87, p. 111802. , KTeV CollaborationHamm, J.C., (2002), Ph.D. thesis, The University of Arizona(Fermilab Report No. fERMILAB-THESIS-2002-09)Alavi-Harati, A., (1999) Phys. Rev. Lett., 83, p. 922. , KTeV CollaborationAlavi-Harati, A., (2000) Phys. Rev. D, 61, p. 072006. , KTeV CollaborationBrown, C., (1996) Nucl. Instrum. Methods Phys. Res., Sect. A, 369, p. 248Quinn, G.B., (2000), Ph.D. thesis, The University of ChicagoBarker, A.R., Huang, H., Toale, P.A., Engle, J., hep-ph/0210174Bergström, L., Massó, E., Singer, P., (1983) Phys. Lett., 131 B, p. 229Fanti, V., (1999) Phys. Lett. B, 458, p. 553. , NA48 Collaboratio
A search for the decay
We search for the rare flavor-changing neutral-current decay in a data sample of 82 fb collected with the {\sl BABAR}
detector at the PEP-II B-factory. Signal events are selected by examining the
properties of the system recoiling against either a reconstructed hadronic or
semileptonic charged-B decay. Using these two independent samples we obtain a
combined limit of
at the 90% confidence level. In addition, by selecting for pions rather than
kaons, we obtain a limit of using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let
High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe
We report on the realization of a high quality distributed Bragg reflector
with both high and low refractive index layers lattice matched to ZnTe. Our
structure is grown by molecular beam epitaxy and is based on binary compounds
only. The high refractive index layer is made of ZnTe, while the low index
material is made of a short period triple superlattice containing MgSe, MgTe,
and ZnTe. The high refractive index step of Delta_n=0.5 in the structure
results in a broad stopband and the reflectivity coefficient exceeding 99% for
only 15 Bragg pairs.Comment: 4 pages, 3 figure
EuFeAs under high pressure: an antiferromagnetic bulk superconductor
We report the ac magnetic susceptibility and resistivity
measurements of EuFeAs under high pressure . By observing nearly
100% superconducting shielding and zero resistivity at = 28 kbar, we
establish that -induced superconductivity occurs at ~30 K in
EuFeAs. shows an anomalous nearly linear temperature dependence
from room temperature down to at the same . indicates that
an antiferromagnetic order of Eu moments with ~20 K persists
in the superconducting phase. The temperature dependence of the upper critical
field is also determined.Comment: To appear in J. Phys. Soc. Jpn., Vol. 78 No.
Neuroimaging-based classification of PTSD using data-driven computational approaches: a multisite big data study from the ENIGMA-PGC PTSD consortium
Background: Recent advances in data-driven computational approaches have been helpful in devising tools to objectively diagnose psychiatric disorders. However, current machine learning studies limited to small homogeneous samples, different methodologies, and different imaging collection protocols, limit the ability to directly compare and generalize their results. Here we aimed to classify individuals with PTSD versus controls and assess the generalizability using a large heterogeneous brain datasets from the ENIGMA-PGC PTSD Working group. Methods: We analyzed brain MRI data from 3,477 structural-MRI; 2,495 resting state-fMRI; and 1,952 diffusion-MRI. First, we identified the brain features that best distinguish individuals with PTSD from controls using traditional machine learning methods. Second, we assessed the utility of the denoising variational autoencoder (DVAE) and evaluated its classification performance. Third, we assessed the generalizability and reproducibility of both models using leave-one-site-out cross-validation procedure for each modality. Results: We found lower performance in classifying PTSD vs. controls with data from over 20 sites (60 % test AUC for s-MRI, 59 % for rs-fMRI and 56 % for D-MRI), as compared to other studies run on single-site data. The performance increased when classifying PTSD from HC without trauma history in each modality (75 % AUC). The classification performance remained intact when applying the DVAE framework, which reduced the number of features. Finally, we found that the DVAE framework achieved better generalization to unseen datasets compared with the traditional machine learning frameworks, albeit performance was slightly above chance. Conclusion: These results have the potential to provide a baseline classification performance for PTSD when using large scale neuroimaging datasets. Our findings show that the control group used can heavily affect classification performance. The DVAE framework provided better generalizability for the multi-site data. This may be more significant in clinical practice since the neuroimaging-based diagnostic DVAE classification models are much less site-specific, rendering them more generalizable.Stress-related psychiatric disorders across the life spa
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