315 research outputs found
Towards nonlinear quantum Fokker-Planck equations
It is demonstrated how the equilibrium semiclassical approach of Coffey et
al. can be improved to describe more correctly the evolution. As a result a new
semiclassical Klein-Kramers equation for the Wigner function is derived, which
remains quantum for a free quantum Brownian particle as well. It is transformed
to a semiclassical Smoluchowski equation, which leads to our semiclassical
generalization of the classical Einstein law of Brownian motion derived before.
A possibility is discussed how to extend these semiclassical equations to
nonlinear quantum Fokker-Planck equations based on the Fisher information
A Comparison of the Ovulation Method With the CUE Ovulation Predictor in Determining the Fertile Period
The purpose of this study was to compare the CUE Ovulation Predictor with the ovulation method in determining the fertile period. Eleven regularly ovulating women measured their salivary and vaginal electrical resistance (ER) with the CUE, observed their cervical-vaginal mucus, and measured their urine for a luteinizing hormone (LH) surge on a daily basis. Data from 21 menstrual cycles showed no statistical difference (T= 0.33, p= 0.63) between the CUE fertile period, which ranged from 5 to 10 days (mean = 6.7 days, SD = 1.6), and the fertile period of the ovulation method, which ranged from 4 to 9 days (mean = 6.5 days, SD = 2.0). The CUE has potential as an adjunctive device in the learning and use of natural family planning methods
Regularization of the Hamiltonian constraint and the closure of the constraint algebra
In the paper we discuss the process of regularization of the Hamiltonian
constraint in the Ashtekar approach to quantizing gravity. We show in detail
the calculation of the action of the regulated Hamiltonian constraint on Wilson
loops. An important issue considered in the paper is the closure of the
constraint algebra. The main result we obtain is that the Poisson bracket
between the regulated Hamiltonian constraint and the Diffeomorphism constraint
is equal to a sum of regulated Hamiltonian constraints with appropriately
redefined regulating functions.Comment: 23 pages, epsfig.st
Graphical Evolution of Spin Network States
The evolution of spin network states in loop quantum gravity can be described
by introducing a time variable, defined by the surfaces of constant value of an
auxiliary scalar field. We regulate the Hamiltonian, generating such an
evolution, and evaluate its action both on edges and on vertices of the spin
network states. The analytical computations are carried out completely to yield
a finite, diffeomorphism invariant result. We use techniques from the
recoupling theory of colored graphs with trivalent vertices to evaluate the
graphical part of the Hamiltonian action. We show that the action on edges is
equivalent to a diffeomorphism transformation, while the action on vertices
adds new edges and re-routes the loops through the vertices.Comment: 24 pages, 21 PostScript figures, uses epsfig.sty, Minor corrections
in the final formula in the main body of the paper and in the formula for the
Tetrahedral net in the Appendi
Brownian markets
Financial market dynamics is rigorously studied via the exact generalized
Langevin equation. Assuming market Brownian self-similarity, the market return
rate memory and autocorrelation functions are derived, which exhibit an
oscillatory-decaying behavior with a long-time tail, similar to empirical
observations. Individual stocks are also described via the generalized Langevin
equation. They are classified by their relation to the market memory as heavy,
neutral and light stocks, possessing different kinds of autocorrelation
functions
Quantum friction
The Brownian motion of a light quantum particle in a heavy classical gas is
theoretically described and a new expression for the friction coefficient is
obtained for arbitrary temperature. At zero temperature it equals to the de
Broglie momentum of the mean free path divided by the mean free path.
Alternatively, the corresponding mobility of the quantum particle in the
classical gas is equal to the square of the mean free path divided by the
Planck constant. The Brownian motion of a quantum particle in a quantum
environment is also discussed.Comment: The paper is dedicated to the 85th anniversary of N.N. Tyutyulko
Matrix Elements of Thiemann's Hamiltonian Constraint in Loop Quantum Gravity
We present an explicit computation of matrix elements of the hamiltonian
constraint operator in non-perturbative quantum gravity. In particular, we
consider the euclidean term of Thiemann's version of the constraint and compute
its action on trivalent states, for all its natural orderings. The calculation
is performed using graphical techniques from the recoupling theory of colored
knots and links. We exhibit the matrix elements of the hamiltonian constraint
operator in the spin network basis in compact algebraic form.Comment: 32 pages, 22 eps figures. LaTeX (Using epsfig.sty,ioplppt.sty and
bezier.sty). Submited to Classical and Quantum Gravit
Planned Cesarean or planned vaginal delivery for twins : secondary analysis of randomized controlled trial
ACKNOWLEDGMENTS We thank all the participants in the Twin Birth Study and the staff at the Centre for Mother, Infant, and Child Research for their hard work and dedication. The Twin Birth Study was supported by a grant (63164) from the Canadian Institute of Health Research. P.T. and M.H.Z. were supported by a grant from The Netherlands Organization for Scientific Research (NWO ‐ grant number 401.16.080). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
Structure-based exploration and pharmacological evaluation of N-substituted piperidin-4-yl-methanamine CXCR4 chemokine receptor antagonists
Using the available structural information of the chemokine receptor CXCR4, we present hit finding and hit exploration studies that make use of virtual fragment screening, design, synthesis and structure-activity relationship (SAR) studies. Fragment 2 was identified as virtual screening hit and used as a starting point for the exploration of 31 N-substituted piperidin-4-yl-methanamine derivatives to investigate and improve the interactions with the CXCR4 binding site. Additionally, subtle structural ligand changes lead to distinct interactions with CXCR4 resulting in a full to partial displacement of CXCL12 binding and competitive and/or non-competitive antagonism. Three-dimensional quantitative structure-activity relationship (3D-QSAR) and binding model studies were used to identify important hydrophobic interactions that determine binding affinity and indicate key ligand-receptor interactions
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Social sensemaking with AI: Designing an open-ended AI experience with a blind child
AI technologies are often used to aid people in performing discrete tasks with well-defned goals (e.g., recognising faces in images). Emerging technologies that provide continuous, real-time information enable more open-ended AI experiences. In partnership with a blind child, we explore the challenges and opportunities of designing human-AI interaction for a system intended to support social sensemaking. Adopting a research-through-design perspective, we refect upon working with the uncertain capabilities of AI systems in the design of this experience. We contribute: (i) a concrete example of an open-ended AI system that enabled a blind child to extend his own capabilities; (ii) an illustration of the delta between imagined and actual use, highlighting how capabilities derive from the human-AI interaction and not the AI system alone; and (iii) a discussion of design choices to craft an ongoing human-AI interaction that addresses the challenge of uncertain outputs of AI systems
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