Temporal variation in the genetic composition of an endangered marsupial reflects reintroduction history

The loss of genetic variation and genetic divergence from source populations are common problems for reintroductions that use captive animals or a small number of founders to establish a new population. This study evaluated the genetic changes occurring in a captive and a reintroduced population of the dibbler (Parantechinus apicalis) that were established from multiple source populations over a twelve-year period, using 21 microsatellite loci. While the levels of genetic variation within the captive and reintroduced populations were relatively stable, and did not differ significantly from the source populations, their effective population size reduced 10–16-fold over the duration of this study. Evidence of some loss of genetic variation in the reintroduced population coincided with genetic bottlenecks that occurred after the population had become established. Detectable changes in the genetic composition of both captive and reintroduced populations were associated with the origins of the individuals introduced to the population. We show that interbreeding between individuals from different source populations lowered the genetic relatedness among the offspring, but this was short-lived. Our study highlights the importance of sourcing founders from multiple locations in conservation breeding programs to avoid inbreeding and maximize allelic diversity. The manipulation of genetic composition in a captive or reintroduced population is possible with careful management of the origins and timings of founder releases

Adjustable Prone Trolley Design for People Suffering from Spinal Cords Injuries in Nepal

For people who suffer from spinal cord injuries in Nepal, rehabilitation and care are often difficult to receive, especially for those for whom fewer resources are available. Thankfully, International Nepal Fellowship (INF), a non-profit serving Nepal for nearly 70 years, aids patients with spinal cord injuries at Green Pastures Hospital and Rehabilitation Centre in Pokhara, Nepal. A crucial part of any rehabilitation is adequate exercise to improve circulation and prevent sores and muscular atrophy. Yet, due to the nature of the injury, using a traditional wheelchair is not an option to fulfill this need for those with spinal cord injuries. Therefore, Green Pastures uses prone trolleys so that these patients can exercise. A prone trolley is a horizontal cushioned board where the patient lies flat on their stomach and is able to move themselves using the wheels attached to the cushioned board. Despite the importance of the prone trolley, the trolleys at Green Pastures Hospital have a few critical issues. The major issue is that the prone trolleys are internationally imported, which not only means that delivery can take months, but also that the trolleys are also difficult to repair when damaged. Both these factors severely hamper Green Pastures Hospital’s ability to provide spinal cord injured patients with the care they need. The Nepal Prone Trolley team, a part of Messiah University Collaboratory, seeks to develop and design a fundamentally better prone trolley for INF. The goal of our project is to design a prone trolley that can be fabricated by the INF staff with locally sourced materials. The advantage of this new design is that it will be easier to obtain and can easily be repaired when needed. After creating a design that satisfies our goal and fulfills the criteria of a functional prone trolley as defined by INF, we were able to fabricate a prototype of the prone trolley using resources and techniques available in Pokhara. Moving forward, we will conduct testing and redesign the trolley so that our finalized prone trolley design will be able to transform how Green Pastures Hospital aids their spinal cord injury patients. Funding for this work provided by The Collaboratory for Strategic Partnerships and Applied Research.https://mosaic.messiah.edu/engr2022/1011/thumbnail.jp

Identification of a triplet pair intermediate in singlet exciton fission in solution.

Singlet exciton fission is the spin-conserving transformation of one spin-singlet exciton into two spin-triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction Shockley-Queisser limit. Most theoretical descriptions of singlet fission invoke an intermediate state of a pair of spin-triplet excitons coupled into an overall spin-singlet configuration, but such a state has never been optically observed. In solution, we show that the dynamics of fission are diffusion limited and enable the isolation of an intermediate species. In concentrated solutions of bis(triisopropylsilylethynyl)[TIPS]--tetracene we find rapid (<100 ps) formation of excimers and a slower (∼ 10 ns) break up of the excimer to two triplet exciton-bearing free molecules. These excimers are spectroscopically distinct from singlet and triplet excitons, yet possess both singlet and triplet characteristics, enabling identification as a triplet pair state. We find that this triplet pair state is significantly stabilized relative to free triplet excitons, and that it plays a critical role in the efficient endothermic singlet fission process.H.L.S was supported by the Winton Programme for the Physics of Sustainability and A.J.M received funding from the Engineering and Physical Sciences Research Council.This is the accepted manuscript. The final version is available at http://www.pnas.org/content/112/25/7656.abstract

Site-selective measurement of coupled spin pairs in an organic semiconductor.

From organic electronics to biological systems, understanding the role of intermolecular interactions between spin pairs is a key challenge. Here we show how such pairs can be selectively addressed with combined spin and optical sensitivity. We demonstrate this for bound pairs of spin-triplet excitations formed by singlet fission, with direct applicability across a wide range of synthetic and biological systems. We show that the site sensitivity of exchange coupling allows distinct triplet pairs to be resonantly addressed at different magnetic fields, tuning them between optically bright singlet ([Formula: see text]) and dark triplet quintet ([Formula: see text]) configurations: This induces narrow holes in a broad optical emission spectrum, uncovering exchange-specific luminescence. Using fields up to 60 T, we identify three distinct triplet-pair sites, with exchange couplings varying over an order of magnitude (0.3-5 meV), each with its own luminescence spectrum, coexisting in a single material. Our results reveal how site selectivity can be achieved for organic spin pairs in a broad range of systems.This work was supported by HFMLRU/ FOM and LNCMI-CNRS, members of the European Magnetic Field Laboratory (EMFL) and by EPSRC (UK) via its membership to the EMFL (grant no. EP/N01085X/1 and NS/A000060/1) and through grant no. EP/M005143/1. L.R.W. acknowledges support of the Gates-Cambridge and Winton Scholarships. We acknowledge support from Labex ANR-10-LABX-0039-PALM, ANR SPINEX, and DFG SPP-1601 (Bi-464/10-2)

Site-selective measurement of coupled spin pairs in an organic semiconductor

From organic electronics to biological systems, understanding the role of intermolecular interactions between spin pairs is a key challenge. Here we show how such pairs can be selectively addressed with combined spin and optical sensitivity. We demonstrate this for bound pairs of spin-triplet excitations formed by singlet fission, with direct applicability across a wide range of synthetic and biological systems. We show that the site-sensitivity of exchange coupling allows distinct triplet pairs to be resonantly addressed at different magnetic fields, tuning them between optically bright singlet (S=0) and dark triplet, quintet (S=1,2) configurations: this induces narrow holes in a broad optical emission spectrum, uncovering exchange-specific luminescence. Using fields up to 60 T, we identify three distinct triplet-pair sites, with exchange couplings varying over an order of magnitude (0.3-5 meV), each with its own luminescence spectrum, coexisting in a single material. Our results reveal how site-selectivity can be achieved for organic spin pairs in a broad range of systems.Comment: 8 pages, article, 7 pages, supporting informatio

Insights into the Structure and Self-Assembly of Organic-Semiconductor/Quantum-Dot Blends

Funder: Cambridge Commonwealth European and International TrustAbstract: Controlling the dispersibility of crystalline inorganic quantum dots (QD) within organic‐QD nanocomposite films is critical for a wide range of optoelectronic devices. A promising way to control nanoscale structure in these nanocomposites is via the use of appropriate organic ligands on the QD, which help to compatibilize them with the organic host, both electronically and structurally. Here, using combined small‐angle X‐ray and neutron scattering, the authors demonstrate and quantify the incorporation of such a compatibilizing, electronically active, organic semiconductor ligand species into the native oleic acid ligand envelope of lead sulphide, QDs, and how this ligand loading may be easily controlled. Further more, in situ grazing incidence wide/small angle X‐ray scattering demonstrate how QD ligand surface chemistry has a pronounced effect on the self‐assembly of the nanocomposite film in terms of both small‐molecule crystallization and QD dispersion versus ordering/aggregation. The approach demonstrated here shows the important role which the degree of incorporation of an active ligand, closely related in chemical structure to the host small‐molecule organic matrix, plays in both the self‐assembly of the QD and small‐molecule components and in determining the final optoelectronic properties of the system

Linking microscale morphologies to localised performance in singlet fission quantum dot photon multiplier thin films

Hybrid small-molecule/quantum dot films have the potential to reduce thermalization losses in single-junction photovoltaics as photon multiplication devices. Here grazing incidence X-ray scattering, optical microscopy and IR fluorescence microscopy (probing materials at two distinct wavelengths), provide new insight into highly complex morphologies across nm and μm lengthscales to provide direct links between morphologies and photon multiplication performance. Results show that within the small molecule crystallites three different QD morphologies may be identified; (i) large quantum dot aggregates at the crystallite nucleus, (ii) relatively well-dispersed quantum dots and (iii) as aggregated quantum dots “swept” from the growing crystallite and that regions containing aggregate quantum dot features lead to relatively poor photon multiplication performance. These results establish how combinations of scattering and microscopy may be employed to reveal new insights into the structure and function of small molecule:quantum dot blends

Search for astronomical neutrinos from blazar TXS 0506+056 in super-kamiokande

We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS 0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrinos from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from 1996 April to 2018 February we have searched for both a total excess above known backgrounds across the entire period as well as localized excesses on smaller timescales in that interval. No significant excess nor significant variation in the observed event rate are found in the blazar direction. Upper limits are placed on the electron- and muon-neutrino fluxes at the 90% confidence level as 6.0 × 10−7 and 4.5 × 10−7–9.3 × 10−10 [erg cm−2 s−1], respectively