Accretion Disc Evolution in Single and Binary T Tauri Stars

We present theoretical models for the evolution of T Tauri stars surrounded by circumstellar discs. The models include the effects of pre-main-sequence stellar and time dependent disc evolution, and incorporate the effects of stellar magnetic fields acting on the inner disc. For single stars, consistency with observations in Taurus-Auriga demands that disc dispersal occurs rapidly, on much less than the viscous timescale of the disc, at roughly the epoch when heating by stellar radiation first dominates over internal viscous dissipation. Applying the models to close binaries, we find that because the initial conditions for discs in binaries are uncertain, studies of extreme mass ratio systems are required to provide a stringent test of theoretical disc evolution models. We also note that no correlation of the infra-red colours of T Tauri stars with their rotation rate is observed, in apparent contradiction to the predictions of simple magnetospheric accretion models.Comment: 11 pages, MNRAS in pres

A Maitland–Japp inspired synthesis of dihydropyran-4-ones and their stereoselective conversion to functionalised tetrahydropyran-4-ones

The Maitland–Japp reaction has been extended to the synthesis of highly functionalised dihydropyran-4-ones. These dihydropyran-4-ones can in turn be converted stereoselectively into tetrahydropyran-4-ones with tertiary and quaternary stereocentres via the one-pot addition of hydride or carbon nucleophiles and trapping with carbon electrophiles. The utility of this method is demonstrated by providing access to the functionalised tetrahydropyran units present in a component of the Civet fragrance and the anticancer polyketide lasonolide A

Solid sample introduction in inductively coupled plasma emission spectrometry.

This Thesis describes the progress made in the area of solid sample introduction in Inductively Coupled Plasma Emission Spectrometry (ICP-ES). As an alternative to solution nebulisation two methods of introducing samples to the ICP are investigated. The first of these uses the direct insertion probe technique first described by Horlick and Salin (63). The assembly utilised an electrically operated graphite rod system. This could be used equally well with small volumes of solution sample (5ul) or small masses of solid sample (Ca.5mg). The variables of cup dimensions and material were investigated along with volume and masses of sample used. Results of calibration of both solution residues and solid samples are presented along with details of Limit of Detection and sample Relative Standard Deviation (RSD). The comparative data were found to be in good agreement and it was established that solutions derived calibration data could be used for the analysis of Ni-base samples. Other solid matrices, elemental and alloyed were investigated. These materials divided into two groups, (1) low volatility matrix, from which trace elements were released and only minimal emission from matrix elements was detected and there were no spectral interference effects, (2) volatile matrix in which the matrix vaporized in the same temperature range as the trace elements, giving rise to substantial matrix emission and spectral interferences. It was concluded that DI-ICP-ES is at its most useful when dealing with easily volatilized trace elements in a relatively involatile matrix. The second approach to sample introduction involved the use of an electrothermal vaporization cell. This provided precise control of temperature and offered considerably higher final temperatures than the direct insertion probe system. An Electrothermal Vaporization (ETV) device was designed and built in the laboratory and interfaced to the ICP such that vapour produced in the cell was carried into the plasma discharge by the 'injector' gas stream. ETV was used for liquid and solid samples and results for these samples are presented

Consumer representative experiences of partnership with health workers in Australia

We examine the experiences of Consumer Representatives participating in consumer engagement activities across a public health service in NSW, Australia. A team of Consumer Representatives and staff members use a participatory, constructivist paradigm and a hermeneutic phenomenological approach to analyse ten interviews with Consumer Representatives over three years 2017-2019, and three focus groups in 2020. We explore these experiences and identify the linked contextual factors from their points of view. Consumer Representatives were prepared to invest their time, but they needed respect. “Respect” from a consumer perspective was being meaningfully included, supported and heard, and activities needed to be purposeful and relevant. They operated in a complex environment of people and systems that were sometimes frustrating and hindered partnership. Nevertheless, they were optimistic their involvement made a difference although this may take time. Using hermeneutic phenomenology enabled the results to be seen clearly after a comprehensive and highly iterative process engaging with participants-as-researchers. The results challenge the usual default position of engaging consumers in committees and reveal other opportunities to focus on patient-centred care, as mandated by Australian National Standards for hospital accreditation. Respect is identified as a practice necessary to enhance engagement. Health organisations may improve consumer engagement outcomes as mandated for accreditation by being aware of the experiences of Consumer Representatives giving their time to partner with staff members and health systems. Staff may mitigate Consumer Representative negative experiences by being mindful of the complex people and system environment within health that can impede successful engagement. Experience Framework This article is associated with the Patient, Family & Community Engagement lens of The Beryl Institute Experience Framework (https://www.theberylinstitute.org/ExperienceFramework). Access other PXJ articles related to this lens. Access other resources related to this lens

Synthesis of 2,6-trans- and 3,3,6-Trisubstituted Tetrahydropyran-4-ones from Maitland-Japp Derived 2H-Dihydropyran-4-ones: A Total Synthesis of Diospongin B

6-Substituted-2H-dihydropyran-4-one products of the Maitland-Japp reaction have been converted into tetrahydropyrans containing uncommon substitution patterns. Treatment of 6-substituted-2H-dihydropyran-4-ones with carbon nucleophiles led to the formation of tetrahydropyran rings with the 2,6-trans-stereochemical arrangement. Reaction of the same 6-substituted-2H-dihydropyran-4-ones with l-Selectride led to the formation of 3,6-disubstituted tetrahydropyran rings, while trapping of the intermediate enolate with carbon electrophiles in turn led to the formation 3,3,6-trisubstituted tetrahydropyran rings. The relative stereochemical configuration of the new substituents was controlled by the stereoelectronic preference for pseudo-axial addition of the nucleophile and trapping of the enolate from the opposite face. Application of these methods led to a synthesis of the potent anti-osteoporotic diarylheptanoid natural product diospongin B

Gender and Entrepreneurship in the Renewable Energy Sector of Rwanda

Until recently, women have not been seen as having the potential for entrepreneurial success. Yet women’s engagement in the energy sector could substantially improve energy access for those most underserved. This article examines the role of women as energy entrepreneurs from the perspective of gender inequality within the energy industry. Data from Nuru Energy, a social business focused on providing solar lighting to the ultra‑poor, provide insights on how the inclusion of women sales agents can increase sales and how strategic modifications to the social business model can further support female-led businesses. Observational data from over 1,000 rural enterprises show that women, on average, sold significantly more units than men. Women operating in solo firms and leading groupbased teams consistently outsold men-led solo and group‑based enterprises. Findings further suggest that, when operating in groups, women tend to outperform men even more than when operating sole proprietorships

Picosecond time-resolved x-ray diffraction probe of coherent lattice dynamics (abstract) (invited)

The short pulses of hard x rays from synchrotron and laser based sources are sensitive probes of lattice dynamics on an ultrafast time scale. Using pump–probe time-resolved x-ray diffraction, we are able to follow the propagation of a picosecond coherent acoustic pulse in an ultrafast laser-strained single crystal. Comparison of the data with dynamical diffraction simulations allows for the quantitative determination of both the surface and bulk components of the associated strain. This technique is scalable to femtosecond and shorter time scales as x-ray pulses become shorter in duration, such as in fourth generation light sources. In addition, the diffraction of x rays off of coherent optical phonons may lead to the production of a femtosecond x-ray switch. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69893/2/RSINAK-73-3-1361-1.pd

Event Rates, Hospital Utilization, and Costs Associated with Major Complications of Diabetes: A Multicountry Comparative Analysis

Philip Clarke and colleagues examined patient-level data for over 11,000 participants with type 2 diabetes from 20 countries and find that major complications of diabetes significantly increased hospital use and costs across settings

The brown dwarf desert as a consequence of orbital migration

We show that the dearth of brown dwarfs in short-period orbits around Solar-mass stars - the brown dwarf desert - can be understood as a consequence of inward migration within an evolving protoplanetary disc. Brown dwarf secondaries forming at the same time as the primary star have masses which are comparable to the initial mass of the protoplanetary disc. Subsequent disc evolution leads to inward migration, and destruction of the brown dwarf, via merger with the star. This is in contrast with massive planets, which avoid this fate by forming at a later epoch when the disc is close to being dispersed. Within this model, a brown dwarf desert arises because the mass at the hydrogen burning limit is coincidentally comparable to the initial disc mass for a Solar mass star. Brown dwarfs should be found in close binaries around very low mass stars, around other brown dwarfs, and around Solar-type stars during the earliest phases of star formation.Comment: MNRAS (Letters), in pres