19,004 research outputs found
Experimental validation of phase space conduits of transition between potential wells
A phase space boundary between transition and non-transition, similar to
those observed in chemical reaction dynamics, is shown experimentally in a
macroscopic system. We present a validation of the phase space flux across rank
one saddles connecting adjacent potential wells and confirm the underlying
phase space conduits that mediate the transition. Experimental regions of
transition are found to agree with the theory to within 1\%, suggesting the
robustness of phase space conduits of transition in a broad array of two or
more degree of freedom experimental systems, despite the presence of small
dissipation.Comment: 7 pages, 6 figure
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Documenting numerical experiments in support of the Coupled Model Intercomparison Project Phase 6 (CMIP6)
Numerical simulation, and in particular simulation of the earth system, relies on contributions from diverse communities, from those who develop models to those involved in devising, executing, and analysing numerical experiments. Often these people work in different institutions and may be working with significant separation in time (particularly analysts, who may be working on data produced years earlier), and they typically communicate via published information (whether journal papers, technical notes, or websites). The complexity of the models, experiments, and methodologies, along with the diversity (and sometimes inexact nature) of information sources, can easily lead to misinterpretation of what was actually intended or done. In this paper we introduce a taxonomy of terms for more clearly defining numerical experiments, put it in the context of previous work on experimental ontologies, and describe how we have used it to document the experiments of the sixth phase for the Coupled Model Intercomparison Project (CMIP6). We describe how, through iteration with a range of CMIP6 stakeholders, we rationalized multiple sources of information and improved the clarity of experimental definitions. We demonstrate how this process has added value to CMIP6 itself by (a) helping those devising experiments to be clear about their goals and their implementation, (b) making it easier for those executing experiments to know what is intended, (c) exposing interrelationships between experiments, and (d) making it clearer for third parties (data users) to understand the CMIP6 experiments. We conclude with some lessons learnt and how these may be applied to future CMIP phases as well as other modelling campaigns
Origin of the fast magnetization tunneling in the single-molecule magnet [Ni(hmp)(tBuEtOH)Cl]4
We present high-frequency angle-dependent EPR data for crystals of
[NixZn1-x(hmp)(t-BuEtOH)Cl]4 (x = 1 and 0.02). The x = 1 complex behaves as a
single-molecule magnet at low temperatures, displaying hysteresis and
exceptionally fast magnetization tunneling. We show that this behavior is
related to a 4th-order transverse crystal-field interaction, which produces a
significant tunnel-splitting (~10 MHz) of the ground state of this S = 4
system. The magnitude of the 4th-order anisotropy, and the dominant axial term
(D), can be related to the single-ion interactions (Di and Ei) at the
individual NiII sites, as determined for the x = 0.02 crystals.Comment: 11 pages including 2 figure
Physical aggression, compromised social support, and 10-year marital outcomes: Testing a relational spillover model
The purpose of the present study was to test a relational spillover model of physical aggression whereby physical aggression affects marital outcomes due to its effects on how spouses ask for and provide support to one another. Newlywed couples (n = 172) reported levels of physical aggression over the past year and engaged in interactions designed to elicit social support; marital adjustment, and stability were assessed periodically over the first 10 years of marriage. Multilevel modeling revealed that negative support behavior mediated the relationship between physical aggression and 10-year marital adjustment levels whereas positive support behavior mediated the relationship between physical aggression and divorce status. These findings emphasize the need to look beyond conflict when explaining how aggression affects relationships and when working with couples with a history of physical aggression who are seeking to improve their relationships
Direct observation of a hydrophobic bond in loop-closure of a capped (-OCH2CH2-)n oligomer in water
The small r variation of the probability density P(r) for end-to-end
separations of a -CH2CH3 capped (-OCH2CH2-)n oligomer in water is computed to
be closely similar to the CH4 ... CH4 potential of mean force under the same
circumstances. Since the aqueous solution CH4 ... CH4 potential of mean force
is the natural physical definition of a primitive hydrophobic bond, the present
result identifies an experimentally accessible circumstance for direct
observation of a hydrophobic bond which has not been observed previously
because of the low solubility of CH4 in water. The physical picture is that the
soluble chain molecule carries the capping groups into aqueous solution, and
permits them to find one another with reasonable frequency. Comparison with the
corresponding results without the solvent shows that hydration of the solute
oxygen atoms swells the chain molecule globule. This supports the view that the
chain molecule globule might have a secondary effect on the hydrophobic
interaction which is of first interest here. The volume of the chain molecule
globule is important for comparing the probabilities with and without solvent
because it characterizes the local concentration of capping groups. Study of
other capping groups to enable X-ray and neutron diffraction measurements of
P(r) is discussed.Comment: 4 pages, 3 figure
Reframing e-assessment: building professional nursing and academic attributes in a first year nursing course
This paper documents the relationships between pedagogy and e-assessment in two nursing courses offered at the University of Southern Queensland, Australia. The courses are designed to build the academic, numeracy and technological attributes student nurses need if they are to succeed at university and in the nursing profession. The paper first outlines the management systems supporting the two courses and how they intersect with the e-learning and e-assessment components of course design. These pedagogical choices are then reviewed. While there are lessons to be learnt and improvements to be made, preliminary results suggest students and staff are extremely supportive of the courses. The e-assessment is very positively received with students reporting increased confidence and competency in numeracy, as well as IT, academic, research and communication skills
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The Role of Perspective-Taking in Childrenâs Quantity Implicatures
Young children excel at pragmatic inferences known as ad hoc quantity implicatures: they can infer, for example, that a speaker who said âthe card with applesâ meant the card with nothing but apples. However, it is not known whether children take into account the speakerâs perspective in deriving such inferences, as adults are able to do, and as the received theories of pragmatics claim. In two experiments, we tested children (5-7 years, N = 33 and N = 25) and adults using a picture-matching director task, in which participants played a game giving cards to the speaker, with some cards being in common ground and some in privileged ground. We found that adults can both derive implicatures when all information is in common ground and not derive them when relevant information is in privileged ground. Children also derive ad hoc implicatures when relevant information is in common ground but, crucially, fail to not derive them when it is in privileged ground. Childrenâs difficulty to integrate perspective-taking with pragmatic inferencing challenges the received theories about the necessity of perspective-taking in pragmatics
Exploratory ASCA Observations of Broad Absorption Line Quasi-Stellar Objects
We present the analysis and interpretation of a sample of eight ASCA
observations of Broad Absorption Line Quasi-Stellar Objects (BALQSOs). This is
the first moderate-sized sample of sensitive BALQSO observations above 2 keV,
and the BALQSOs in our sample are among the optically brightest known
(B=14.5-18.5). Despite the ability of 2-10 keV X-rays to penetrate large column
densities, we find BALQSOs to be extremely weak sources above 2 keV, and we are
only able to add two new 2-10 keV detections (0226-104 and IRAS 07598+6508) to
those previously reported. By comparison with non-BALQSOs of similar optical
continuum magnitudes, we derive the column densities needed to suppress the
expected X-ray fluxes of our BALQSOs. In several cases we derive column
densities > 5x10^{23} cm^{-2} for a neutral absorber with solar abundances.
These are the largest X-ray column densities yet inferred for BALQSOs, and they
exceed ROSAT lower limits by about an order of magnitude. Optical brightness
does not appear to be a good predictor of 2-10 keV brightness for BALQSOs, but
our data do suggest that the BALQSOs with high optical continuum polarizations
may be the X-ray brighter members of the class. For example, the highly
polarized object PHL 5200 appears to be unusually X-ray bright for a BALQSO
given its optical magnitude. We discuss the implications of our results for
future observations with AXAF and XMM. If the objects in our sample are
representative of the BALQSO population, precision X-ray spectroscopy of most
BALQSOs will unfortunately prove difficult in the near future.Comment: 19 pages, ApJ in press, also available from
http://www.astro.psu.edu/users/niel/papers/papers.htm
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