2,561 research outputs found

    Probing the origin of UX Ori-type variability in the YSO binary CO Ori with VLTI/GRAVITY

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    The primary star in the young stellar object (YSO) binary CO Ori displays UX Ori-type variability: irregular, high amplitude optical and near-infrared photometric fluctuations where flux minima coincide with polarization maxima. This is attributed to changes in local opacity. In CO Ori A, these variations exhibit a 12.4 yr cycle. Here, we investigate the physical origin of the fluctuating opacity and its periodicity using interferometric observations of CO Ori obtained using VLTI/GRAVITY. Continuum K-band circum-primary and circum-secondary emission are marginally spatially resolved for the first time while Brγ\gamma emission is detected in the spectrum of the secondary. We estimate a spectral type range for CO Ori B of K2-K5 assuming visual extinction, AV=2A_{\rm{V}}=2 and a distance of 430 pc. From geometric modelling of the continuum visibilities, the circum-primary emission is consistent with a central point source plus a Gaussian component with a full-width-half-maximum of 2.31±\pm0.04 milliarcseconds (mas), inclined at 30.2±\pm2.2^{\circ} and with a major axis position angle of 40±\pm6^{\circ}. This inclination is lower than that reported for the discs of other UX Ori-type stars, providing a first indication that the UX Ori phenomena may arise through fluctuations in circumstellar material exterior to a disc, e.g. in a dusty outflow. An additional wide, symmetric Gaussian component is required to fit the visibilities of CO Ori B, signifying a contribution from scattered light. Finally, closure phases of CO Ori A were used to investigate whether the 12.4 yr periodicity is associated with an undetected third component, as has been previously suggested. We rule out any additional companions contributing more than 3.6% to the K-band flux within ~7.3-20 mas of CO Ori A.Comment: 7 pages, 4 figures, accepted for publication in MNRA

    Combined experimental and computational investigations of rhodium-catalysed C-H functionalisation of pyrazoles with alkenes

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    Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C(2)H(3)Y (Y=CO(2)Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF(3) (1 c)) using a [Rh(MeCN)(3)Cp*][PF(6)](2)/Cu(OAc)(2)⋅H(2)O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel Cu(I) dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results

    A Quantitative Comparison of Arm Activity between Women with Breast Cancer and Healthy

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    Purpose: Survivors of breast cancer (BC) on the non-dominant side have more persistent deficits than those with cancer on the dominant limb. What is not known is whether those with BC use their involved upper limbs more, less, or at the same level as women without BC. Accelerometer use offers a quantifiable method to measure activity levels of upper limbs. The purpose of this study was to quantify the activity levels of the non-dominant involved limb among survivors of BC and compare these values to their dominant limb, as well as the non-dominant limb of a control group. Methods: Participants (n = 30) were women with unilateral BC on the non-dominant limb, diagnosed between 6 and 24 months prior to data collection, and a matched healthy group of women as controls. Participants completed the following questionnaires: medical and demographics, Brief Fatigue Inventory, Brief Pain Inventory – Short form, Disabilities of the Arm, Shoulder and Hand (DASH), and Beck Depression Index. Participants wore an accelerometer on each wrist during waking hours for 7 days. Arm activity was measured using vector magnitude activity counts extracted from the accelerometers. Results: There were no significant differences in total vector magnitude activity counts between groups for either limb. Within group dominant to non-dominant comparison was significantly different (p ≤ 0.001). No significant difference in pain was present but significant differences for fatigue (p = 0.002), depression (p = 0.004), and DASH scores (p = 0.035) were present. Conclusions: Women with non-dominant BC use their involved limb similar to healthy controls but less than their dominant limb

    A Quantitative Comparison of Arm Activity between Survivors of Breast Cancer and Healthy Controls: Use of Accelerometry

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    Purpose Survivors of breast cancer (BC) on the non-dominant side have more persistent deficits than those with cancer on the dominant limb. What is not known is whether those with BC use their involved upper limbs more, less, or at the same level as women without BC. Accelerometer use offers a quantifiable method to measure activity levels of upper limbs. The purpose of this study was to quantify the activity levels of the non-dominant involved limb among survivors of BC and compare these values to their dominant limb, as well as the non-dominant limb of a control group. Methods Participants (n = 30) were women with unilateral BC on the non-dominant limb, diagnosed between 6 and 24 months prior to data collection, and a matched healthy group of women as controls. Participants completed the following questionnaires: medical and demographics, Brief Fatigue Inventory, Brief Pain Inventory – Short form, Disabilities of the Arm, Shoulder and Hand (DASH), and Beck Depression Index. Participants wore an accelerometer on each wrist during waking hours for 7 days. Arm activity was measured using vector magnitude activity counts extracted from the accelerometers. Results There were no significant differences in total vector magnitude activity counts between groups for either limb. Within group dominant to non-dominant comparison was significantly different (p ≤ 0.001). No significant difference in pain was present but significant differences for fatigue (p = 0.002), depression (p = 0.004), and DASH scores (p = 0.035) were present. Conclusions Women with non-dominant BC use their involved limb similar to healthy controls but less than their dominant limb

    ‘’It just happens’. Care home residents’ experiences and expectations of accessing GP care.

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    Background: Care homes provide personal care and support for older people who can no longer be supported in the community. As part of a larger study of integrated working between the NHS and care homes we asked older people how they accessed health care services. Our aim was to understand how older people resident in care homes access health services using the Andersen model of health care access. Methods: Case studies were conducted in six care homes with different socio-economic characteristics, size and ownership in three study sites. Residents in all care homes with capacity to participate were eligible for the study. Interviews explored how residents accessed NHS professionals. The Andersen model of health seeking behaviour was our analytic framework. Findings: Thirty-five participants were interviewed with an average of 4 different conditions. Expectations of their health and the effectiveness of services to mitigate their problems were low. Enabling factors were the use of intermediaries (usually staff, but also relatives) to seek access. Residents expected that care home staff would monitor changes in their health and seek appropriate help unprompted. Conclusions: Care home residents may normalise their health care needs and frame services as unable to remediate these which may combine to disincline older care home residents to seek care. Care access was enabled using intermediaries -either staff or relatives-and the expectation that staff would proactively seek care when they observed new/changed needs. Residents may over-estimate the health-related knowledge of care home staff and their ability to initiate referrals to NHS professionals.Peer reviewedFinal Accepted Versio

    Understanding electronic effects on carboxylate-assisted C-H activation at ruthenium:the importance of kinetic and thermodynamic control

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    Meta-and para-substituted 1-phenylpyrazoles (R-phpyz-H) react with [RuCl2(p-cymene)]2 in the presence of NaOAc to form cyclometallated complexes [M(R-phpyz)Cl(p-cymene)] (where R = NMe2, OMe, Me, H, F, CF3 and NO2). Experimental and DFT studies indicate that product formation can be reversible or irreversible depending on the substituents and the reaction conditions. Competition experiments show that the kinetic selectivity favours electron-donating substituents and correlate well with the Hammett parameter, giving a negative slope (ρ =-2.4) that is consistent with a cationic transition state. However, surprisingly, the thermodynamic selectivity is completely opposite, with substrates featuring electron-withdrawing groups being favoured. These trends are reproduced with DFT calculations that locate a rate-limiting transition state dominated by Ru-O bond dissociation and minimal C-H bond elongation. Detailed computational analysis of these transition states shows that C-H activation proceeds by an AMLA/CMD mechanism through a synergic combination of a C-H→Ru agostic interaction and C-H⋯O H-bonding. NBO calculations also highlight a syndetic bonding term, and the relative weights of these three components vary in a complementary fashion depending on the nature of the substituent. With meta-substituted ligands H/D exchange experiments signal kinetically accessible ortho-C-H activation when R = NMe2, OMe and Me. This is also modelled computationally and the calculations highlight the kinetic relevance of the HOAc/Cl exchange that occurs post C-H bond cleavage, in particular with the bulkier NMe2 and Me substituents. Our study highlights that the experimental substituent effects are dependent on the reaction conditions and so using such studies to assign the mechanism of C-H activation in either stoichiometric or catalytic reactions may be misleading.</p
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