30 research outputs found
Electron-impact spectroscopy of acetaldehyde
Acetaldehyde has been studied by the technique of lowâenergy variableâangle electron energyâloss spectroscopy. With this method the lowâlying spinâforbidden transitions have been located via the behavior of the relative differential cross sections, providing the first identification by this technique of such states in acetaldehyde. Highâlying states were also investigated and some assignments of dipole symmetryâforbidden/quadrupole symmetryâallowed excitations were made on the basis of characteristic angular behavior, evident for the asymmetric molecule acetaldehyde just as for the symmetric molecules formaldehyde and acetone. Through a comparison of the acetaldehyde results with those for formaldehyde and acetone the trends in the allowed and forbidden transition energies were examined as a function of methyl substitution and found to be relatively linear
The spectroscopy of the group VIb transition metal hexacarbonyls using the electron impact method
The electron energy-loss spectra of Cr(CO)6, Mo(CO)6, and W(CO)6 were measured at impact energies of 25, 50, and 100 eV and at scattering angles from 0° to 90°. The differential cross sections (DCS's) were obtained for several features in the 3â7 eV energy-loss region. The symmetry-forbidden nature of the 1A1g â 1A1g,2t2g(Ï) â 3t2g(Ï*) transition in these compounds was confirmed. Several low energy excitations were assigned to ligand field transitions on the basis of the energy and angular behavior of their associated DCS's. No transitions which could clearly be assigned to singlet â triplet excitations involving metal orbitals were located in these molecules. In addition, a number of states lying above the first ionization potential were observed for the first time. Several of these excitations seem to correspond quite well to some of the transitions observed in free CO
An electron-impact spectroscopy investigation of CH_3 and some of its pyrolytic precursors
The electronic spectrum of the methyl radical CH_3 was investigated by the technique of variableâangle electron energyâloss spectroscopy. By means of pyrolytic decomposition three possible sources of this radical were tried (tetramethyl tin, ethyl nitrite, and diâtâbutylâperoxide). The spectra of these precursors were obtained. Using diâtâbutylâperoxide, relative differential cross sections for the lowest allowed Aâł_2 3s Rydberg transition in CH_3 (5.73 eV) were determined at incident energies of 50 and 25 eV. The behavior of the differential cross section for this band is analogous to that of a spinâallowed transition in a closed shell system and, as expected, in the vicinity of this band no transition of a spinâforbidden nature is detected
Nonequilibrium transport through a spinful quantum dot with superconducting leads
We study the nonlinear cotunneling current through a spinful quantum dot
contacted by two superconducting leads. Applying a general nonequilibrium Green
function formalism to an effective Kondo model, we study the rich variation in
the IV-characteristics with varying asymmetry in the tunnel coupling to source
and drain electrodes. The current is found to be carried respectively by
multiple Andreev reflections in the symmetric limit, and by spin-induced
Yu-Shiba-Russinov bound states in the strongly asymmetric limit. The interplay
between these two mechanisms leads to qualitatively different
IV-characteristics in the cross-over regime of intermediate symmetry,
consistent with recent experimental observations of negative differential
conductance and re-positioned conductance peaks in sub-gap cotunneling
spectroscopy.Comment: 5 pages, 3 fig
Nonequilibrium transport via spin-induced sub-gap states in superconductor/quantum dot/normal metal cotunnel junctions
We study low-temperature transport through a Coulomb blockaded quantum dot
(QD) contacted by a normal (N), and a superconducting (S) electrode. Within an
effective cotunneling model the conduction electron self energy is calculated
to leading order in the cotunneling amplitudes and subsequently resummed to
obtain the nonequilibrium T-matrix, from which we obtain the nonlinear
cotunneling conductance. For even occupied dots the system can be conceived as
an effective S/N-cotunnel junction with subgap transport mediated by Andreev
reflections. The net spin of an odd occupied dot, however, leads to the
formation of sub-gap resonances inside the superconducting gap which gives rise
to a characteristic peak-dip structure in the differential conductance, as
observed in recent experiments.Comment: 13 pages, 13 figures (new version contains reformulations and
corrections of typos etc
Participant engagement with a UK community-based preschool childhood obesity prevention programme: : a focused ethnography study
Background
Childrenâs centres in the UK provide a setting for public health programmes; offering support to families living in the most disadvantaged areas where obesity prevalence is at its highest. Health, Exercise and Nutrition in the Really Young (HENRY) is an eight-week obesity prevention programme currently delivered in childrenâs centres across the UK. However, low participant engagement in some local authorities threatens its potential reach and impact. This study aimed to explore the factors influencing participant engagement with HENRY to describe where local intervention may support engagement efforts.
Method
A focused ethnography study was undertaken in five childrenâs centres delivering HENRY across the UK. One hundred and ninety hours of field observations, 22 interviews with staff (commissioners, HENRY co-ordinators, managers and facilitators) and six focus groups (36 parents), took place over five consecutive days in each centre. The Consolidated Framework for Implementation Research (CFIR) was used to guide the observations and analysis of the data.
Results
Three overarching themes described the factors influencing participant engagement with HENRY: local authority decision making around childrenâs centre programmes; childrenâs centre implementation of HENRY; and the participant experience of HENRY. The results indicate that factors influencing participant engagement with public health programmes begin at the commissioning body level, influencing childrenâs centre implementation and subsequently the experience of participants. Local authority funding priorities and constraints influence availability of places and who these places are offered to, with funding often targeted towards those deemed most at need. This was perceived to have a detrimental effect on participant experience of the programme.
Conclusion
In summary, participant engagement is affected by multiple factors, working at different levels of the childrenâs centre and local authority hierarchy, most of which are at play even before participants decide whether or not they choose to enrol and maintain attendance. For programmes to achieve their optimal reach and impact, factors at the commissioning and local implementation level need to be addressed prior to addressing participant facing issues
Preschool hyperactivity specifically elevates long-term mental health risks more strongly in males than females: a prospective longitudinal study through to young adulthood
Evidence of continuities between preschool hyperactivity and adult mental health problems highlight the potential value of targeting early identification and intervention strategies. However, specific risk factors are currently unclear. This large-scale prospective longitudinal study aimed to identify which hyperactive preschoolers are at greatest long-term risk of poor mental health. One hundred and seventy children (89 females) rated as hyperactive by their parents and 88 non-hyperactive controls (48 females) were identified from a community sample of 4,215 3 year-olds. Baseline data relating to behavioral/emotional problems and background characteristics were collected. Follow-up mental health and functional impairment outcomes were collected between 14 and 25 years of age. At age 3 years, males and females in the hyperactive group had similarly raised levels of hyperactivity and other behavior problems. In adolescence/young adulthood, these individuals showed elevated symptoms of ADHD, conduct disorder, mood disorder, anxiety and autism, as well as functional impairment. Preschool hyperactivity was strongly predictive of poor adolescent/adult outcomes for males across domains with effects being specifically driven by hyperactivity. For females, the effects of preschool hyperactivity were smaller and dropped to non-significant levels when other preschool problems were taken into account. Environmental risk factors also differed between the sexes, although these may also have been mediated by genetic risk. In conclusion, these results demonstrate marked sex differences in preschool predictors of later adolescent/adult mental health problems. Future research should include a measure of preschool inattention as well hyperactivity. The findings highlight the potential value of tailored approaches to early identification strategies
Changing Relationships through Interactions: Preliminary Accounts of Parent-Child Interactions after Undertaking Individual Parent Training
Purpose: Parent and child interaction training has been increasingly investigated over recent years. However, the mechanisms of change within individual training programmes are not well understood. To explore the factors that can facilitate or inhibit meaningful changes in interactions and ultimately relationships, the current study employed semi-structured interviews to obtain first person accounts from parents who had undertaken an individualised parent-training programme. Method: Three participants provided accounts of the training programme and their perceived impact upon interactions with their children were analysed using inductive thematic analysis. Results: The analysis resulted in three themes, which illustrate how participants adjusted their interactional style with their child to varying degrees through enhanced personal awareness, increased understanding of their childâs emotional and interactional needs, and accepting the reciprocity of interactional accountability. Discussion: Changes in interactional style enabled participants to alter their perceptions of their own behaviours, their childâs behaviours, and how they influenced one another through interactions. Recommendations for future research and therapeutic practice are discussed in the context of the findings and the existing evidence base
A comparison of the clinical effectiveness and cost of specialised individually-delivered parent training for preschool attention-deficit/hyperactivity disorder and a generic, group-based programme: a multi-centre, randomised controlled trial of the New Forest Parenting Programme versus Incredible Years
Objective: To compare the efficacy and cost of specialised individually-delivered parent training (PT) for preschool children with attention-deficit/ hyperactivity disorder (ADHD) against generic group-based PT and treatment as usual (TAU). Design: Multi-centre, three-arm parallel group randomised controlled trial. Research Setting: National Health Service Trusts. Participants: Preschool children (33-54 months) fulfilling ADHD research diagnostic criteria. Interventions: New Forest Parenting Programme (NFPP) â 12 week individual, home-delivered ADHD PT programme; Incredible Years (IY) â 12 week group-based, PT programme initially designed for children with behaviour problems. Main outcome measures: Primary outcome - Parent ratings of childâs ADHD symptoms (Swanson, Nolan & Pelham Questionnaire - SNAP-IV). Secondary outcomes - teacher ratings (SNAP-IV) and direct observations of ADHD symptoms and parent/teacher ratings of conduct problems. NFPP, IY and TAU outcomes were measured at baseline (T1) and post-treatment (T2). NFPP and IY outcomes only were measured 6 months post treatment (T3). Researchers, but not therapists or parents, were blind to treatment allocation. Analysis employed mixed effect regression models (multiple imputation). Intervention and other costs were estimated using standardized approaches. Results: NFPP and IY did not differ on parent-rated SNAP-IV, ADHD combined symptoms (mean difference -0.009 95%CI [-0.191, 0.173], p=0.921) or any other measure. Small, non-significant, benefits of NFPP over TAU were seen for parent-rated SNAP-IV, ADHD combined symptoms (-0.189 95%CI [-0.380, 0.003], p=0.053). NFPP significantly reduced parent-rated conduct-problems compared to TAU across scales (p-values.05). The cost per family of providing NFPP in the trial was significantly lower than IY (ÂŁ1,591 versus ÂŁ2,103).
Conclusions: Although, there were no differences between NFPP and IY with regards clinical effectiveness, individually-delivered NFPP cost less. However, this difference may be reduced when implemented in routine clinical practice. Clinical decisions should take into account parental preferences between delivery approaches.
Funding: National Institute of Health Research.
Trial Registration: Trial name: COPPI Trial; ISRCTN39288126