14 research outputs found
Many-Electron Systems with Constrained Current
A formulation for transport in an inhomogeneous, interacting electron gas is
described. Electronic current is induced by a constraint condition imposed as a
vector Lagrange multiplier. Constrained minimization of the total energy
functional on the manifold of an arbitrary constant current leads to a
many-electron Schroedinger equation with a complex, momentum-dependent
potential. Constant current Hartree-Fock and Kohn-Sham approximations are
formulated within the method and application to transport for quantum wires is
developed. No appeal is made to near equilibrium conditions or other
approximations allowing development of a general ab initio electronic transport
formulation
Conduction channels of superconducting quantum point contacts
Atomic quantum point contacts accommodate a small number of conduction
channels. Their number N and transmission coefficients {T_n} can be determined
by analyzing the subgap structure due to multiple Andreev reflections in the
current-voltage (IV) characteristics in the superconducting state. With the
help of mechanically controllable break-junctions we have produced Al contacts
consisting of a small number of atoms. In the smallest stable contacts, usually
three channels contribute to the transport. We show here that the channel
ensemble {T_n} of few atom contacts remains unchanged up to temperatures and
magnetic fields approaching the critical temperature and the critical field,
respectively, giving experimental evidence for the prediction that the
conduction channels are the same in the normal and in the superconducting
state.Comment: 8 pages, 5 .eps figures. To be published in Physica B 22
A Current Induced Transition in atomic-sized contacts of metallic Alloys
We have measured conductance histograms of atomic point contacts made from
the noble-transition metal alloys CuNi, AgPd, and AuPt for a concentration
ratio of 1:1. For all alloys these histograms at low bias voltage (below 300
mV) resemble those of the noble metals whereas at high bias (above 300 mV) they
resemble those of the transition metals. We interpret this effect as a change
in the composition of the point contact with bias voltage. We discuss possible
explanations in terms of electromigration and differential diffusion induced by
current heating.Comment: 5 pages, 6 figure
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe
Visual and proprioceptive information in goal directed movements: A system theoretical approach
Mechanical Maritime and Materials Engineerin