1,010 research outputs found
A new model-discriminant training algorithm for hybrid NN-HMM systems
This paper describes a hybrid system for continuous speech recognition consisting of a neural network (NN) and a hidden Markov model (HMM). The system is based on a multilayer perceptron, which approximates the a-posteriori probability of a sequence of states, derived from semi-continuous hidden Markov models. The classification is based on a total score for each hybrid model, attained from a Viterbi search on the state probabilities. Due to the unintended discrimination between the states in each model, a new training algorithm for the hybrid neural networks is presented. The utilized error function approximates the misclassification rate of the hybrid system. The discriminance between the correct and the incorrect models is optimized during the training by the "Generalized Probabilistic Descent Algorithm\u27;, resulting in a minimum classification error. No explicit target values for the neural net output nodes are used, as in the usual backpropagation algorithm with a quadratic error function. In basic experiments up to 56% recognition rate were achieved on a vowel classification task and up to 69 % on a consonant cluster classification task
Biochemistry and functional aspects of human glandular kallikreins
Human urinary kallikrein was purified by gel filtration on Sephacryl S-200 and affinity chromatography on aprotinin-Sepharose, followed by ion exchange chromatography on DEAE-Sepharose. In dodecylsulfate gel electrophoresis two protein bands with molecular weights of 41,000 and 34,000 were separated. The amino acid composition and the carbohydrate content of the kallikrein preparation were determined; isoleucine was identified as the only aminoterminal amino acid. The bimolecular velocity constant for the inhibition by diisopropyl fluorophosphate was determined as 9±2 l molâ1 minâ1. The hydrolysis of a number of substrates was investigated and AcPheArgOEt was found to be the most sensitive substrate for human urinary kallikrein. Using this substrate an assay method for kallikrein in human urine was developed.
It was shown by radioimmunoassay that pig pancreatic kallikrein can be absorbed in the rat intestinal tract. Furthermore, in dogs the renal excretion of glandular kallikrein from blood was demonstrated by radioimmunological methods
The Nature of Heavy Quasiparticles in Magnetically Ordered Heavy Fermions
The optical conductivity of the heavy fermions UPd2Al3 and UPt3 has been
measured in the frequency range from 10 GHz to 1.2 THz (0.04 meV to 5 meV) at
temperatures 1 K < T < 300 K. In both compounds a well pronounced pseudogap of
less than a meV develops in the optical response at low temperatures; we relate
this to the antiferromagnetic ordering. From the energy dependence of the
effective electronic mass and scattering rate we derive the energies essential
for the heavy quasiparticle. We find that the enhancement of the mass mainly
occurs below the energy which is related to magnetic correlations between the
local magnetic moments and the itinerant electrons. This implies that the
magnetic order in these compounds is the pre-requisite to the formation of the
heavy quasiparticle and eventually of superconductivity.Comment: RevTeX, 4 pages, 3 figures, email:
[email protected]
Turbulence and jet-driven zonal flows: Secondary circulation in rotating fluids due to asymmetric forcing
We report on experiments and modeling on a rotating confined liquid that is forced by circumferential jets coaxial with the rotation axis, wherein system-scale secondary flows are observed to emerge. The jets are evenly divided in number between inlets and outlets and have zero net mass transport. For low forcing strengths the sign of this flow depends on the sign of a sloped end cap, which simulates a planetary ÎČ plane. For increased forcing strengths the secondary flow direction is insensitive to the slope sign, and instead appears to be dominated by an asymmetry in the forcing mechanism, namely, the difference in radial divergence between the inlet and outlet jet profiles. This asymmetry yields a net radial velocity that is affected by the Coriolis force, inducing secondary zonal flow
Local Moment Formation in the Periodic Anderson Model with Superconducting Correlations
We study local moment formation in the presence of superconducting
correlations among the f-electrons in the periodic Anderson model. Local
moments form if the Coulomb interaction U>U_cr. We find that U_cr is
considerably stronger in the presence of superconducting correlations than in
the non-superconducting system. Our study is done for various values of the
f-level energy and electronic density. The smallest critical U_cr values occur
for the case where the number of f- electrons per site is equal to one. In the
presence of d-wave superconducting correlations we find that local moment
formation presents a quantum phase transition as function of pressure. This
quantum phase transition separates a region where local moments and d-wave
superconductivity coexist from another region characterized by a
superconducting ground state with no local moments. We discuss the possible
relevance of these results to experimental studies of the competition between
magnetic order and superconductivity in CeCu_2Si_2.Comment: 4 pages. accepted for publication in Phys. Rev.
Coexistence of antiferromagnetism and superconductivity in heavy-fermions systems
We report the novel pressure(P)-temperature(T) phase diagrams of
antiferromagnetism (AF) and superconductivity (SC) in CeRhIn, CeIn and
CeCuSi revealed by the NQR measurement. In the itinerant helical magnet
CeRhIn, we found that the N\'eel temperature is reduced at
1.23 GPa with an emergent pseudogap behavior. The coexistence of AF and SC is
found in a narrow P range of 1.63 - 1.75 GPa, followed by the onset of SC with
line-node gap over a wide P window 2.1 - 5 GPa. In CeIn, the localized
magnetic character is robust against the application of pressure up to
1.9 GPa, beyond which the system evolves into an itinerant regime in which the
resistive superconducting phase emerges. We discuss the relationship between
the phase diagram and the magnetic fluctuations. In CeCuSi, the SC and
AF coexist on a microscopic level once its lattice parameter is expanded. We
remark that the underlying marginal antiferromagnetic state is due to
collective magnetic excitations in the superconducting state in CeCuSi.
An interplay between AF and SC is discussed on the SO(5) scenario that unifies
AF and SC. We suggest that the SC and AF in CeCuSi have a common
mechanism.Comment: 6 pages, 5 figures, proceeding of ISSP200
Coexistence of antiferromagnetism and superconductivity in the Anderson lattice
We study the interplay between antiferromagnetism and superconductivity in a
generalized infinite- Anderson lattice, where both superconductivity and
antiferromagnetic order are introduced phenomenologically in mean field theory.
In a certain regime, a quantum phase transition is found which is characterized
by an abrupt expulsion of magnetic order by d-wave superconductivity, as
externally applied pressure increases. This transition takes place when the
d-wave superconducting critical temperature, , intercepts the magnetic
critical temperature, , under increasing pressure. Calculations of the
quasiparticle bands and density of states in the ordered phases are presented.
We calculate the optical conductivity in the clean limit. It
is shown that when the temperature drops below a double peak structure
develops in .Comment: 18 pages, 13 figure
Self-Assembly of Atomically Thin Chiral Copper Heterostructures Templated by Black Phosphorus
The fabrication of 2D systems for electronic devices is not straightforward, with topâdown lowâyield methods often employed leading to irregular nanostructures and lower quality devices. Here, a simple and reproducible method to trigger selfâassembly of arrays of high aspectâratio chiral copper heterostructures templated by the structural anisotropy in black phosphorus (BP) nanosheets is presented. Using quantitative atomic resolution aberrationâcorrected scanning transmission electron microscopy imaging, in situ heating transmission electron microscopy and electron energyâloss spectroscopy arrays of heterostructures forming at speeds exceeding 100 nm sâ1 and displaying longârange order over micrometers are observed. The controlled instigation of the selfâassembly of the Cu heterostructures embedded in BP is achieved using conventional electron beam lithography combined with site specific placement of Cu nanoparticles. Density functional theory calculations are used to investigate the atomic structure and suggest a metallic nature of the Cu heterostructures grown in BP. The findings of this new hybrid material with unique dimensionality, chirality, and metallic nature and its triggered selfâassembly open new and exciting opportunities for next generation, selfâassembling devices
Correlation gap in the heavy-fermion antiferromagnet UPd_2Al_3
The optical properties of the heavy-fermion compound UPdAl have been
measured in the frequency range from 0.04 meV to 5 meV (0.3 to 40 cm) at
temperatures K. Below the coherence temperature K, the hybridization gap opens around 10 meV. As the temperature decreases
further ( K), a well pronounced pseudogap of approximately 0.2 meV
develops in the optical response; we relate this to the antiferromagnetic
ordering which occurs below K. The frequency dependent mass and
scattering rate give evidence that the enhancement of the effective mass mainly
occurs below the energy which is associated to the magnetic correlations
between the itinerant and localized 5f electrons. In addition to this
correlation gap, we observe a narrow zero-frequency conductivity peak which at
2 K is less than 0.1 meV wide, and which contains only a fraction of the
delocalized carriers. The analysis of the spectral weight infers a loss of
kinetic energy associated with the superconducting transition.Comment: RevTex, 15 pages, 7 figure
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