23,885 research outputs found
Homogeneity and projective equivalence of differential equation fields
We propose definitions of homogeneity and projective equivalence for systems
of ordinary differential equations of order greater than two, which allow us to
generalize the concept of a spray (for systems of order two). We show that the
Euler-Lagrange fields of parametric Lagrangians of order greater than one which
are regular (in a natural sense that we define) form a projective equivalence
class of homogeneous systems. We show further that the geodesics, or base
integral curves, of projectively equivalent homogeneous differential equation
fields are the same apart from orientation-preserving reparametrization; that
is, homogeneous differential equation fields determine systems of paths
Application of Computational Chemical Shift Prediction Techniques to the Cereoanhydride Structure Problem-Carboxylate Complications.
Despite the vast array of techniques available to modern-day chemists, structural misassignments still occur. These misassignments are often only realized upon attempted synthesis, when the spectra of synthesized products do not match previously reported spectra. This was the case with marine natural product cereoanhydride. The originally proposed 7-membered ring anhydride (1) was shown to be incorrect, although a likely precursor to the correct structure (2) in both its laboratory synthesis and biosynthesis. Herein, in addition to showing how NMR computations could have been used to arrive at the correct structure, we show that the conversion of 1 to 2 is indeed energetically viable, and we highlight complications in predicting NMR chemical shifts for molecules with acidic protons
Measuring the Discrepancy Between Current and Ideal Spiritual and Religious Functioning in Problem Drinkers
The idea that spiritual and religious functioning (SRF) is associated with alcohol misuse is generally supported, but problems with typical research methods limit the utility of findings. Problems in SRF were conceptualized as discrepancies between current and ideal SRF. Two separate studies were conducted to develop and evaluate a scale to measure the subjective importance and adequacy of aspects of SRF that seem to be associated with alcohol problems. The 1st study suggested that a questionnaire developed to evaluate self-reported ratings of current and ideal SRF is both internally consistent and temporally stable. In the 2nd study, the questionnaire was administered to persons seeking treatment for alcohol problems and persons who indicated that they had never sought treatment for an alcohol problem. Results indicate that those with a drinking problem were more likely to report substantial discrepancies between current and ideal SRF, supporting the validity of the measure as an indicator of problems in SRF. The usefulness of this method for treatment and research is discussed
The average magnetic field draping and consistent plasma properties of the Venus magnetotail
A new technique has been developed to determine the average structure of the Venus magnetotail (in the range from −8 Rv to −12 Rv) from the Pioneer Venus magnetometer observations. The spacecraft position with respect to the cross-tail current sheet is determined from an observed relationship between the field-draping angle and the magnitude of the field referenced to its value in the nearby magnetosheath. This allows us statistically to remove the effects of tail flapping and variability of draping for the first time and thus to map the average field configuration in the Venus tail. From this average configuration we calculate the cross-tail current density distribution and J × B forces. Continuity of the tangential electric field is utilized to determine the average variations of the X-directed velocity which is shown to vary from −250 km/s at −8 Rv to −470 km/s at −12 Rv. From the calculated J × B forces, plasma velocity, and MHD momentum equation the approximate plasma acceleration, density, and temperature in the Venus tail are determined. The derived ion density is approximately ∼0.07 p+/cm³ (0.005 O+/cm³) in the lobes and ∼0.9 p+/cm³ (0.06 O+/cm³) in the current sheet, while the derived approximate average plasma temperature for the tail is ∼6×106 K for a hydrogen plasma or ∼9×107 K for an oxygen plasma
Insulation bonding test system
A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact
Learning To Be Affected: Social suffering and total pain at life’s borders.
The practice of Live Sociology in situations of pain and suffering is the author’s focus. An outline of the challenges of understanding pain is followed by a discussion of Bourdieu’s ‘social suffering’ (1999) and the palliative care philosophy of ‘total pain’. Using examples from qualitative research on disadvantaged dying migrants in the UK, attention is given to the methods that are improvised by dying people and care practitioners in attempts to bridge intersubjective divides, where the causes and routes of pain can be ontologically and temporally indeterminate and/or withdrawn. The paper contends that these latter phenomena are the incitement for the inventive bridging and performative work of care and Live Sociological methods, both of which are concerned with opposing suffering. Drawing from the ontology of total pain, I highlight the importance of (i) an engagement with a range of materials out of which attempts at intersubjective bridging can be produced, and which exceed the social, the material, and the temporally linear; and (ii) an empirical sensibility that is hospitable to the inaccessible and non-relational
Bayes-X: a Bayesian inference tool for the analysis of X-ray observations of galaxy clusters
We present the first public release of our Bayesian inference tool, Bayes-X,
for the analysis of X-ray observations of galaxy clusters. We illustrate the
use of Bayes-X by analysing a set of four simulated clusters at z=0.2-0.9 as
they would be observed by a Chandra-like X-ray observatory. In both the
simulations and the analysis pipeline we assume that the dark matter density
follows a spherically-symmetric Navarro, Frenk and White (NFW) profile and that
the gas pressure is described by a generalised NFW (GNFW) profile. We then
perform four sets of analyses. By numerically exploring the joint probability
distribution of the cluster parameters given simulated Chandra-like data, we
show that the model and analysis technique can robustly return the simulated
cluster input quantities, constrain the cluster physical parameters and reveal
the degeneracies among the model parameters and cluster physical parameters. We
then analyse Chandra data on the nearby cluster, A262, and derive the cluster
physical profiles. To illustrate the performance of the Bayesian model
selection, we also carried out analyses assuming an Einasto profile for the
matter density and calculated the Bayes factor. The results of the model
selection analyses for the simulated data favour the NFW model as expected.
However, we find that the Einasto profile is preferred in the analysis of A262.
The Bayes-X software, which is implemented in Fortran 90, is available at
http://www.mrao.cam.ac.uk/facilities/software/bayesx/.Comment: 22 pages, 11 figure
Homogeneous variational problems: a minicourse
A Finsler geometry may be understood as a homogeneous variational problem,
where the Finsler function is the Lagrangian. The extremals in Finsler geometry
are curves, but in more general variational problems we might consider extremal
submanifolds of dimension . In this minicourse we discuss these problems
from a geometric point of view.Comment: This paper is a written-up version of the major part of a minicourse
given at the sixth Bilateral Workshop on Differential Geometry and its
Applications, held in Ostrava in May 201
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