765 research outputs found
Comparison of gas-phase free-radical populations in tobacco smoke and model systems by HPLC.
We used an improved method for trapping carbon-centered radicals (.R) from the gas-phase to compare radical suites trapped from various tobacco smoke and model smoke systems. Using a nitroxide trap, 3-amino-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (3AP), on solid support, we trapped radicals directly from the gas phase, washed them off the support, and analyzed them with HPLC. Separation of the trapped radicals showed that each tobacco type produced a unique radical suite of 4-10 distinct peaks. Gas mixtures used to model tobacco smoke consisted of nitric oxide, air, isoprene, and methanol. The model systems produced radical suites of four major and several minor peaks, two of which matched peaks in tobacco smoke chromatograms. Quantities of radicals trapped from tobacco smoke were: 54 +/- 2 nmol .R per Marlboro cigarette, 66 +/- 9 nmol .R per Djarum clove cigarette, and 185 +/- 9 nmol .R per Swisher Sweet cigar. In these experiments oxygen competes with the nitroxide trap for gas-phase radicals. A kinetic analysis of the O2 competition shows that actual radical concentrations in the smoke were approximately 100-fold higher than measured
A microscopic Ginzburg--Landau theory and singlet ordering in SrRuO
The long-standing quest to determine the superconducting order of
SrRuO (SRO) has received renewed attention after recent nuclear
magnetic resonance (NMR) Knight shift experiments have cast doubt on the
possibility of spin-triplet pairing in the superconducting state. As a putative
solution, encompassing a body of experiments conducted over the years, a
-wave order parameter caused by an accidental near-degeneracy has been
suggested [S. A. Kivelson et al., npj Quantum Materials , 43 (2020)].
Here we develop a general Ginzburg--Landau theory for multiband
superconductors. We apply the theory to SRO and predict the relative size of
the order parameter components. The heat capacity jump expected at the onset of
the second order parameter component is found to be above the current threshold
deduced by the experimental absence of a second jump. Our results tightly
restrict theories of order, and other candidates caused by a
near-degeneracy, in SRO. We discuss possible solutions to the problem.Comment: 13 pages, 8 figure
Statistical mechanics of dimers on quasiperiodic tilings
We study classical dimers on two-dimensional quasiperiodic Ammann-Beenker
(AB) tilings. Despite the lack of periodicity we prove that each infinite
tiling admits 'perfect matchings' in which every vertex is touched by one
dimer. We introduce an auxiliary 'AB' tiling obtained from the AB tiling by
deleting all 8-fold coordinated vertices. The AB tiling is again
two-dimensional, infinite, and quasiperiodic. The AB tiling has a single
connected component, which admits perfect matchings. We find that in all
perfect matchings, dimers on the AB tiling lie along disjoint
one-dimensional loops and ladders, separated by 'membranes', sets of edges
where dimers are absent. As a result, the dimer partition function of the
AB tiling factorizes into the product of dimer partition functions along
these structures. We compute the partition function and free energy per edge on
the AB tiling using an analytic transfer matrix approach. Returning to the
AB tiling, we find that membranes in the AB tiling become
'pseudomembranes', sets of edges which collectively host at most one dimer.
This leads to a remarkable discrete scale-invariance in the matching problem.
The structure suggests that the AB tiling should exhibit highly inhomogenous
and slowly decaying connected dimer correlations. Using Monte Carlo
simulations, we find evidence supporting this supposition in the form of
connected dimer correlations consistent with power law behaviour. Within the
set of perfect matchings we find quasiperiodic analogues to the staggered and
columnar phases observed in periodic systems.Comment: 33 pages, 26 figure
Superconducting order of from a three-dimensional microscopic model
We compute and compare even- and odd-parity superconducting order parameters
of strontium ruthenate () in the limit of weak
interactions, resulting from a fully microscopic three-dimensional model
including spin-orbit coupling. We find that odd-parity helical and even-parity
-wave order are favored for smaller and larger values of the Hund's coupling
parameter , respectively. Both orders are found compatible with specific
heat data and the recently-reported nuclear magnetic resonance (NMR) Knight
shift drop [A. Pustogow et al. Nature 574, 72 (2019)]. The chiral -wave
order, numerically very competitive with helical order, sharply conflicts with
the NMR experiment.Comment: 11 pages, 8 figure
Exploring the phases of 3D artificial spin ice: From Coulomb phase to magnetic monopole crystal
Artificial spin-ices consist of lithographic arrays of single-domain magnetic
nanowires organised into frustrated lattices. These geometries are usually
two-dimensional, allowing a direct exploration of physics associated with
frustration, topology and emergence. Recently, three-dimensional geometries
have been realised, in which transport of emergent monopoles can be directly
visualised upon the surface. Here we carry out an exploration of the
three-dimensional artificial spin-ice phase diagram, whereby dipoles are placed
within a diamond-bond lattice geometry. We find a rich phase diagram,
consisting of a double-charged monopole crystal, a single-charged monopole
crystal and conventional spin-ice with pinch points associated with a Coulomb
phase. In our experimental demagnetised systems, broken symmetry forces
formation of ferromagnetic stripes upon the surface, a configuration that
forbids the formation of the lower energy double-charged monopole crystal.
Instead, we observe crystallites of single magnetic charge, superimposed upon
an ice background. The crystallites are found to form due to the intricate
distribution of magnetic charge around a three-dimensional nanostructured
vertex, which locally favours monopole formation. Our work suggests that
engineered surface energetics can be used to tune the ground state of
experimental three-dimensional ASI systems
Electronic spectroscopy of trans-azomethane by electron impact
The electron impact excitation of trans-azomethane (i.e., trans-dimethyl diazine CH3âNâNâCH3) has been studied by both trapped electron (TE) and differential electron scattering (DES) techniques. The nature of the excited state in each of several transitions has been identified by the energy and angular dependences of the excitation cross section. Two previously unreported singlet-->triplet transitions are observed with maxima at 2.75 and 4.84 eV. Theoretical calculations on the parent compound, trans-diimide (HâN=NâH), suggest that these are the Ď 1Ag-->1 3Bg (produced by excitation of an electron from an n + molecular orbital to a pi* molecular orbital) and the Ď 1Ag-->1 3Bu (pi-->pi*) transitions, respectively. The Ď 1Ag-->1 1Bg (n + -->pi*) transition is observed with a peak at 3.50 eV in the DES studies. A strong peak at 6.01 eV in the TE spectra appears as a weak shoulder in the DES studies and is interpreted as either a symmetry-forbidden or Rydberg-like singlet-->singlet transition. Allowed singlet-->singlet features overlap each other in the transition energy range from 6 to 10 eV. Peaks are seen in the DES spectra at 6.71, 7.8, and 9.5 eV and in the TE spectrum at 8.0 eV. Several significant differences between the TE and the DES spectra are analyzed on the basis of the different nature of the two experiments
Liesegang patterns: Effect of dissociation of the invading electrolyte
The effect of dissociation of the invading electrolyte on the formation of
Liesegang bands is investigated. We find, using organic compounds with known
dissociation constants, that the spacing coefficient, 1+p, that characterizes
the position of the n-th band as x_n ~ (1+p)^n, decreases with increasing
dissociation constant, K_d. Theoretical arguments are developed to explain
these experimental findings and to calculate explicitly the K_d dependence of
1+p.Comment: RevTex, 8 pages, 3 eps figure
\u27It promoted a positive culture around falls prevention\u27: staff response to a patient education programmeâa qualitative evaluation
Objectives: The purpose of this study was to understand how staff responded to individualized patient falls prevention education delivered as part of a cluster randomised trial, including how they perceived the education contributed to falls prevention on their wards.
Design: A qualitative explanatory study.
Methods: 5 focus groups were conducted at participatory hospital sites. The purposive sample of clinical staff (including nurses, physiotherapists and quality improvement staff ) worked on aged care rehabilitation wards when a cluster randomised trial evaluating a patient education programme was conducted. During the intervention period, an educator, who was a trained health professional and not a member of staff, provided individualised falls prevention education to patients with good levels of cognition (Mini-Mental State Examination \u3e23/30). Clinical staff were provided with training to support the programme and their feedback was sought after the trial concluded, to understand how they perceived the programme impacted on falls prevention. Data were thematically analysed using NVivo qualitative data analysis software.
Results: 5 focus groups were conducted at different hospitals (n=30 participants). Staff perceived that the education created a positive culture around falls prevention and further, facilitated teamwork, whereby patients and staff worked together to address falls prevention. The educator was perceived to be a valuable member of the team. Staff reported that they developed increased knowledge and awareness about creating a safe ward environment. Patients being proactive and empowered to engage in falls prevention strategies, such as ringing the bell for assistance, was viewed as supporting staff falls prevention efforts and motivating staff to change practice.
Conclusions: Staff responded positively to patient falls prevention education being delivered on their wards. Providing individualised patient education to older patients with good levels of cognition can empower staff and patients to work as a team to address falls prevention on hospital rehabilitation wards
Educatorsâ perspectives about how older hospital patients can engage in a falls prevention education programme: a qualitative process evaluation
Objectives - Falls are the most frequent adverse event reported in hospitals. Patient and staff education delivered by trained educators significantly reduced falls and injurious falls in an older rehabilitation population. The purpose of the study was to explore the educatorsâ perspectives of delivering the education and to conceptualise how the programme worked to prevent falls among older patients who received the education. Design - A qualitative exploratory study. Methods - Data were gathered from three sources: conducting a focus group and an interview (n=10 educators), written educator notes and reflective researcher field notes based on interactions with the educators during the primary study. The educators delivered the programme on eight rehabilitation wards for periods of between 10 and 40â
weeks. They provided older patients with individualised education to engage in falls prevention and provided staff with education to support patient actions. Data were thematically analysed and presented using a conceptual framework. Results - Falls prevention education led to mutual understanding between staff and patients which assisted patients to engage in falls prevention behaviours. Mutual understanding was derived from the following observations: the educators perceived that they could facilitate an effective three-way interaction between staff actions, patient actions and the ward environment which led to behaviour change on the wards. This included engaging with staff and patients, and assisting them to reconcile differing perspectives about falls prevention behaviours. Conclusions - Individualised falls prevention education effectively provides patients who receive it with the capability and motivation to develop and undertake behavioural strategies that reduce their falls, if supported by staff and the ward environment
- âŚ