272 research outputs found
Structural relationships of actin, myosin, and tropomyosin revealed by cryo-electron microscopy.
Refrustration and competing orders in the prototypical Dy2Ti2O7 spin ice material
Spin ices, frustrated magnetic materials analogous to common water ice, are
exemplars of high frustration in three dimensions. Recent experimental studies
of the low-temperature properties of the paradigmatic DyTiO spin
ice material, in particular whether the predicted transition to long-range
order occurs, raise questions as per the currently accepted microscopic model
of this system. In this work, we combine Monte Carlo simulations and mean-field
theory calculations to analyze data from magnetization, elastic neutron
scattering and specific heat measurements on DyTiO. We also
reconsider the possible importance of the nuclear specific heat, ,
in DyTiO. We find that is not entirely negligible
below a temperature K and must be taken into account in a
quantitative analysis of the calorimetric data of this compound below that
temperature. We find that small effective exchange interactions compete with
the magnetostatic dipolar interaction responsible for the main spin ice
phenomenology. This causes an unexpected "refrustration" of the long-range
order that would be expected from the incompletely self-screened dipolar
interaction and which positions the material at the boundary between two
competing classical long-range ordered ground states. This allows for the
manifestation of new physical low-temperature phenomena in DyTiO,
as exposed by recent specific heat measurements. We show that among the four
most likely causes for the observed upturn of the specific heat at low
temperature -- an exchange-induced transition to long-range order, quantum
non-Ising (transverse) terms in the effective spin Hamiltonian, the nuclear
hyperfine contribution and random disorder -- only the last appears to be
reasonably able to explain the calorimetric data.Comment: 24 pages, 18 figures. To appear in Physical Review
Homocysteine, grey matter and cognitive function in adults with cardiovascular disease
Background: Elevated total plasma homocysteine (tHcy) has been associated with cognitive impairment, vascular disease and brain atrophy. Methods: We investigated 150 volunteers to determine if the association between high tHcy and cerebral grey matter volume and cognitive function is independent of cardiovascular disease. Results: Participants with high tHcy (≥15 μmol/L) showed a widespread relative loss of grey matter compared with people with normal tHcy, although differences between the groups were minimal once the analyses were adjusted for age, gender, diabetes, hypertension, smoking and prevalent cardiovascular disease. Individuals with high tHcy had worse cognitive scores across a range of domains and less total grey matter volume, although these differences were not significant in the adjusted models. Conclusions: Our results suggest that the association between high tHcy and loss of cerebral grey matter volume and decline in cognitive function is largely explained by increasing age and cardiovascular diseases and indicate that the relationship is not causal
Excited electronic states of cyclohexene, 1,4‐cyclohexadiene, norbornene, and norbornadiene as studied by electron‐impact spectroscopy
One dimensional SU(3) bosons with function interaction
In this paper we solve one dimensional SU(3) bosons with repulsive
-function interaction by means of Bethe ansatz method. The features of
ground state and low-lying excited states are studied by both numerical and
analytic methods. We show that the ground state is a SU(3) color ferromagnetic
state. The configurations of quantum numbers for the ground state are given
explicitly. For finite system the spectra of low-lying excitations and the
dispersion relations of four possible elementary particles (holon, antiholon,
-coloron and -coloron) are obtained by solving Bethe-ansatz
equation numerically. The thermodynamic equilibrium of the system at finite
temperature is studied by using the strategy of thermodynamic Bethe ansatz, a
revised Gaudin-Takahashi equation which is useful for numerical method are
given . The thermodynamic quantities, such as specific heat, are obtain for
some special cases. We find that the magnetic property of the model in high
temperature regime is dominated by Curie's law: and the
system has Fermi-liquid like specific heat in the strong coupling limit at low
temperature.Comment: RevTex 28 pages, 10 figure
The PACE Study: A randomised clinical trial of cognitive activity (CA) for older adults with mild cognitive impairment (MCI)
<p>Abstract</p> <p>Background</p> <p>Research evidence from observational studies suggests that cognitive activity reduces the risk of cognitive impairment in later life as well as the rate of cognitive decline of people with dementia. The Promoting Healthy Ageing with Cognitive Exercise (PACE) study has been designed to determine whether a cognitive activity intervention decreases the rate of cognitive decline amongst older adults with mild cognitive impairment (MCI).</p> <p>Methods/Design</p> <p>The study will recruit 160 community-dwelling men and women aged 65 years of age or over with mild cognitive impairment (MCI). Participants will be randomly allocated to two treatment groups: non-specific education and cognitive activity. The intervention will consist of ten 90-minute sessions delivered twice per week over a period of five weeks. The primary outcome measure of the study is the change from baseline in the total score on the Cambridge Cognitive Score (CAMCOG). Secondary outcomes of interest include changes in memory, attention, executive functions, mood and quality of life. Primary endpoints will be collected 12, 52 and 104 weeks after the baseline assessment.</p> <p>Discussion</p> <p>The proposed project will produce the best available evidence on the merits of increased cognitive activity as a strategy to prevent cognitive decline among older adults with MCI. We anticipate that the results of this study will have implications for the development of evidence-based preventive strategies to reduce the rate of cognitive decline amongst older people at risk of dementia.</p> <p>Trial registration</p> <p>ACTRN12608000556347</p
Validity of a novel computerized cognitive battery for mild cognitive impairment
BACKGROUND: The NeuroTrax Mindstreams computerized cognitive assessment system was designed for widespread clinical and research use in detecting mild cognitive impairment (MCI). However, the capability of Mindstreams tests to discriminate elderly with MCI from those who are cognitively healthy has yet to be evaluated. Moreover, the comparability between these tests and traditional neuropsychological tests in detecting MCI has not been examined. METHODS: A 2-center study was designed to assess discriminant validity of tests in the Mindstreams Mild Impairment Battery. Participants were 30 individuals diagnosed with MCI, 29 with mild Alzheimer's disease (AD), and 39 healthy elderly. Testing was with the Mindstreams battery and traditional neuropsychological tests. Receiver operating characteristic (ROC) analysis was used to examine the ability of Mindstreams and traditional measures to discriminate those with MCI from cognitively healthy elderly. Between-group comparisons were made (Mann-Whitney U test) between MCI and healthy elderly and between MCI and mild AD groups. RESULTS: Mindstreams outcome parameters across multiple cognitive domains significantly discriminated among MCI and healthy elderly with considerable effect sizes (p < 0.05). Measures of memory, executive function, visual spatial skills, and verbal fluency discriminated best, and discriminability was at least comparable to that of traditional neuropsychological tests in these domains. CONCLUSIONS: Mindstreams tests are effective in detecting MCI, providing a comprehensive profile of cognitive function. Further, the enhanced precision and ease of use of these computerized tests make the NeuroTrax system a valuable clinical tool in the identification of elderly at high risk for dementia
Physical Frailty : ICFSR International Clinical Practice Guidelines for Identification and Management
Objective The task force of the International Conference of Frailty and Sarcopenia Research (ICFSR) developed these clinical practice guidelines to overview the current evidence-base and to provide recommendations for the identification and management of frailty in older adults. Methods These recommendations were formed using the GRADE approach, which ranked the strength and certainty (quality) of the supporting evidence behind each recommendation. Where the evidence-base was limited or of low quality, Consensus Based Recommendations (CBRs) were formulated. The recommendations focus on the clinical and practical aspects of care for older people with frailty, and promote person-centred care. Recommendations for Screening and Assessment The task force recommends that health practitioners case identify/screen all older adults for frailty using a validated instrument suitable for the specific setting or context (strong recommendation). Ideally, the screening instrument should exclude disability as part of the screening process. For individuals screened as positive for frailty, a more comprehensive clinical assessment should be performed to identify signs and underlying mechanisms of frailty (strong recommendation). Recommendations for Management A comprehensive care plan for frailty should address polypharmacy (whether rational or nonrational), the management of sarcopenia, the treatable causes of weight loss, and the causes of exhaustion (depression, anaemia, hypotension, hypothyroidism, and B12 deficiency) (strong recommendation). All persons with frailty should receive social support as needed to address unmet needs and encourage adherence to a comprehensive care plan (strong recommendation). First-line therapy for the management of frailty should include a multi-component physical activity programme with a resistance-based training component (strong recommendation). Protein/caloric supplementation is recommended when weight loss or undernutrition are present (conditional recommendation). No recommendation was given for systematic additional therapies such as cognitive therapy, problem-solving therapy, vitamin D supplementation, and hormone-based treatment. Pharmacological treatment as presently available is not recommended therapy for the treatment of frailty.Peer reviewe
A Multilevel Analysis of the Impact of Socio-Structural and Environmental Influences on Condom Use Among Female Sex Workers
This study uses multilevel analysis to examine individual, organizational and community levels of influence on condom use among female commercial sex workers (FSW) in the Philippines. A randomized controlled study involving 1,382 female commercial sex workers assigned to three intervention groups consisting of peer education, managerial training, combined peer and managerial intervention and a usual care control group was conducted. The results of the multilevel analysis show that FSWs who work in establishments with condom use rules tend to have a higher level of condom use (β = .70, P < 0.01). Among the different intervention groups, the combined peer and managerial intervention had the largest effect on condom use (β = 1.30, P < 0.01) compared with the usual care group. Using a three-level hierarchical model, we found that 62% of the variation lies within individuals, whereas 24% and 14% of the variation lies between establishments, and communities, respectively. Standard errors were underestimated when clustering of the FSWs in the different establishments and communities were not taken into consideration. The results demonstrate the importance of using multilevel analysis for community-based HIV/AIDS intervention programs to examine individual, establishment and community effects
Are MRI-defined fat infiltrations in the multifidus muscles associated with low back pain?
BACKGROUND: Because training of the lumbar muscles is a commonly recommended intervention in low back pain (LBP), it is important to clarify whether lumbar muscle atrophy is related to LBP. Fat infiltration seems to be a late stage of muscular degeneration, and can be measured in a non-invasive manner using magnetic resonance imaging. The purpose of this study was to investigate if fat infiltration in the lumbar multifidus muscles (LMM) is associated with LBP in adults and adolescents. METHODS: In total, 412 adults (40-year-olds) and 442 adolescents (13-year-olds) from the general Danish population participated in this cross-sectional cohort study. People with LBP were identified through questionnaires. Using MRI, fat infiltration of the LMM was visually graded as none, slight or severe. Odds ratios were calculated for both age groups, taking into account sex, body composition and leisure time physical activity for both groups, and physical workload (in adults only) or daily bicycling (in adolescents only). RESULTS: Fat infiltration was noted in 81% of the adults but only 14% of the adolescents. In the adults, severe fat infiltration was strongly associated with ever having had LBP (OR 9.2; 95% CI 2.0–43.2), and with having LBP in the past year (OR 4.1; 1.5–11.2), but there was no such association in adolescents. None of the investigated moderating factors had an obvious effect on the OR in the adults. CONCLUSION: Fat infiltration in the LMM is strongly associated with LBP in adults only. However, it will be necessary to quantify these measurements objectively and to investigate the direction of this link longitudinally in order to determine if the abnormal muscle is the cause of LBP or vice versa
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