Detecting 6 MV X-rays using an organic photovoltaic device

An organic photovoltaic (OPV) device has been used in conjunction with a flexible inorganic phosphor to produce a radiation tolerant, efficient and linear detector for 6 MV Xrays. The OPVs were based on a blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). We show that the devices have a sensitivity an order of magnitude higher than a commercial silicon detector used as a reference. Exposure to 360 Grays of radiation resulted in a small (2%) degradation in performance demonstrating that these detectors have the potential to be used as flexible, real-time, in vivo dosimeters for oncology treatments. (C) 2009 Elsevier B.V. All rights reserved

Linearizability with Ownership Transfer

Linearizability is a commonly accepted notion of correctness for libraries of concurrent algorithms. Unfortunately, it assumes a complete isolation between a library and its client, with interactions limited to passing values of a given data type. This is inappropriate for common programming languages, where libraries and their clients can communicate via the heap, transferring the ownership of data structures, and can even run in a shared address space without any memory protection. In this paper, we present the first definition of linearizability that lifts this limitation and establish an Abstraction Theorem: while proving a property of a client of a concurrent library, we can soundly replace the library by its abstract implementation related to the original one by our generalisation of linearizability. This allows abstracting from the details of the library implementation while reasoning about the client. We also prove that linearizability with ownership transfer can be derived from the classical one if the library does not access some of data structures transferred to it by the client

The transition zone as a host for recycled volatiles: Evidence from nitrogen and carbon isotopes in ultra-deep diamonds from Monastery and Jagersfontein (South Africa)

Sublithospheric (ultra-deep) diamonds provide a unique window into the deepest parts of Earth's mantle, which otherwise remain inaccessible. Here, we report the first combined C- and N-isotopic data for diamonds from the Monastery and Jagersfontein kimberlites that sample the deep asthenosphere and transition zone beneath the Kaapvaal Craton, in the mid Cretaceous, to investigate the nature of mantle fluids at these depths and the constraints they provide on the deep volatile cycle. Both diamond suites exhibit very light δ13C values (down to − 26‰) and heavy δ15N (up to + 10.3‰), with nitrogen abundances generally below 70 at. ppm but varying up to very high concentrations (2520 at. ppm) in rare cases. Combined, these signatures are consistent with derivation from subducted crustal materials. Both suites exhibit variable nitrogen aggregation states from 25 to 100% B defects. Internal growth structures, revealed in cathodoluminescence (CL) images, vary from faintly layered, through distinct cores to concentric growth patterns with intermittent evidence for dissolution and regular octahedral growth layers in places. Modelling the internal co-variations in δ13C-δ15N-N revealed that diamonds grew from diverse C-H-O-N fluids involving both oxidised and reduced carbon species. The diversity of the modelled diamond-forming fluids highlights the complexity of the volatile sources and the likely heterogeneity of the deep asthenosphere and transition zone. We propose that the Monastery and Jagersfontein diamonds form in subducted slabs, where carbon is converted into either oxidised or reduced species during fluid-aided dissolution of subducted carbon before being re-precipitated as diamond. The common occurrence of recycled C and N isotopic signatures in super-deep diamonds world-wide indicates that a significant amount of carbon and nitrogen is recycled back to the deep asthenosphere and transition zone via subducting slabs, and that the transition zone may be dominated by recycled C and N

Minimally invasive surgery to the aortic arch – endovascular repair combined with debranching: 4 case reports

Traditional repair of aortic arch aneurysms requires cardiopulmonary bypass and a period of profound hypothermia and circulatory arrest - allowing detachment of the head vessels off the aneurysm, and their anastomosis onto the graft. The procedure is safe and reproducible, however morbidity is significant and includes air embolism, stroke, excessive bleeding and acidosis. In addition the procedures are time-consuming, and cardioplegic arrest is also necessary, resulting in the potential for low cardiac output. Aortic arch aneurysms are not typically suitable for endovascular intervention. With improving techniques of descending aortic repair with stent grafts, hybrid techniques, which involve aortic arch debranching - thereby creating a proximal landing zone of adequate length, followed by stenting over the aortic arch are becoming popular. Methods: Four cases are presented. The technique involves initial sternotomy or upper sternal split, detachment of the innominate and left common carotid arteries, and their reattachment to the ascending aorta by separate grafts (debranching procedure). During this time a side clamp is placed on the ascending aorta. The left subclavian is usually left intact for technical reasons, unless there is a dominant left vertebral artery. This is safe as the shoulder has adequate collateral circulation, and stenting over this vessel is therefore well tolerated. The aortic arch is then completely covered with a stent graft which is inserted via the femoral artery. Arteriography was performed at the end of the procedure to confirm stent graft position and exclusion of the lesion. Results: All surgical transpositions were successful, and the patients recovered without neurologic, bleeding or cardiac complications. Surgical conversion for aortic graft was never required. There were no endoleaks. Mean duration of follow up was 53.5 months (range 21-77). Conclusions: Endovascular repair of the descending thoracic aorta, initially reserved for inoperable patients, is now becoming the accepted initial management. With improved technology and endografts it is now the safest option, especially for traumatic dissection. These techniques have now extended to the aortic arch. Debranching of the aortic arch enables endovascular grafting in this area, thereby avoiding cardiopulmonary bypass and circulatory arrest. Good pre-operative planning is necessary to make the procedure feasible

Adaptation and development pathways for different types of farmers

One of the greatest challenges humanity faces is feeding the world's human population in a sustainable, nutritious, equitable and ethical way under a changing climate. Urgent transformations are needed that allow farmers to adapt and develop while also being climate resilient and contributing minimal emissions. This paper identifies several illustrative adaptation and development pathways, recognising the variety of starting points of different types of farmers and the ways their activities intersect with global trends, such as population growth, climate change, rapid urbanisation dietary changes, competing land uses and the emergence of new technologies. The feasibility of some pathways depends on factors such as farm size and land consolidation. For other pathways, particular infrastructure, technology, access to credit and market access or collective action are required. The most viable pathway for some farmers may be to exit agriculture altogether, which itself requires careful management and planning. While technology offers hope and opportunity, as a disruptor, it also risks maladaptations and can create tradeoffs and exacerbate inequalities, especially in the context of an uncertain future. For both the Sustainable Development Goals and the 2015 Paris Agreement to be achieved, a mix of levers that combine policy, technology, education and awareness-raising, dietary shifts and financial/economic mechanisms is required, attending to multiple time dimensions, to assist farmers along different pathways. Vulnerable groups such as women and the youth must not be left behind. Overall, strong good governance is needed at multiple levels, combining top-down and bottom-up processes

Polarized neutron scattering studies of the kagome lattice antiferromagnet KFe3(OH)6(SO4)2

We report polarized neutron scattering studies of spin-wave excitations and spin fluctuations in the S=5/2 kagome lattice antiferromagnet KFe3(OH)6(SO4)2 (jarosite). Inelastic polarized neutron scattering measurements at 10 K on a single crystal sample reveal two spin gaps, associated with in-plane and out-of-plane excitations. The polarization analysis of quasi-elastic scattering at 67 K shows in-plane spin fluctuations with XY symmetry, consistent with the disappearance of the in-plane gap above the Neel temperature T_N = 65 K. Our results suggest that jarosite is a promising candidate for studying the 2D XY universality class in magnetic systems.Comment: 3 pages, 3 figures, Proceeding to the 7th International Workshop on Polarized Neutrons for Condensed Matter Investigations and 2nd International Symposium of Quantum Beam Science Directorat

Distributed Symmetry Breaking in Hypergraphs

Fundamental local symmetry breaking problems such as Maximal Independent Set (MIS) and coloring have been recognized as important by the community, and studied extensively in (standard) graphs. In particular, fast (i.e., logarithmic run time) randomized algorithms are well-established for MIS and $\Delta +1$-coloring in both the LOCAL and CONGEST distributed computing models. On the other hand, comparatively much less is known on the complexity of distributed symmetry breaking in {\em hypergraphs}. In particular, a key question is whether a fast (randomized) algorithm for MIS exists for hypergraphs. In this paper, we study the distributed complexity of symmetry breaking in hypergraphs by presenting distributed randomized algorithms for a variety of fundamental problems under a natural distributed computing model for hypergraphs. We first show that MIS in hypergraphs (of arbitrary dimension) can be solved in $O(\log^2 n)$ rounds ($n$ is the number of nodes of the hypergraph) in the LOCAL model. We then present a key result of this paper --- an $O(\Delta^{\epsilon}\text{polylog}(n))$-round hypergraph MIS algorithm in the CONGEST model where $\Delta$ is the maximum node degree of the hypergraph and $\epsilon > 0$ is any arbitrarily small constant. To demonstrate the usefulness of hypergraph MIS, we present applications of our hypergraph algorithm to solving problems in (standard) graphs. In particular, the hypergraph MIS yields fast distributed algorithms for the {\em balanced minimal dominating set} problem (left open in Harris et al. [ICALP 2013]) and the {\em minimal connected dominating set problem}. We also present distributed algorithms for coloring, maximal matching, and maximal clique in hypergraphs.Comment: Changes from the previous version: More references adde

Continent stabilisation by lateral accretion of subduction zone-processed depleted mantle residues; insights from Zealandia

To examine how the mantle lithosphere stabilises continents, we present a synthesis of the mantle beneath Zealandia in the SW Pacific Ocean. Zealandia, Earth's “8th continent”, occurs over 4.9 M km2 and comprises a fore-arc, arc and back-arc fragment rifted from the Australia–Antarctica Gondwana margin 85 Myr ago. The oldest extant crust is ∼500 Ma and the majority is Permian–Jurassic. Peridotitic rocks from most known locations reveal the underpinning mantle to comprise regional domains varying from refractory (Al2O3 < 1 wt%, olivine Mg# > 92, spinel Cr# up to 80, Pt/Ir < 1) to moderately depleted (Al2O3 = 2–4 wt%, olivine Mg# ∼90.5, spinel Cr# < ∼60). There is no systematic distribution of these domains relative to the former arc configuration and some refractory domains underlie crust that is largely devoid of magmatic rocks. Re-depletion Os model ages have no correlation with depletion indices but do have a distribution that is very similar to global convecting mantle. Whole rock, mineral and isotopic data are interpreted to show that the Zealandia mantle lithosphere was constructed from isotopically heterogeneous convecting mantle fragments swept into the sub-arc environment, amalgamated, and variably re-melted under low-P hydrous conditions. The paucity of mafic melt volumes in most of the overlying crust that could relate to the depleted domains requires melting to have been followed by lateral accretion either during subduction or slab rollback. Recent Australia–Pacific convergence has thickened portions of the Zealandia mantle to >160 km. Zealandia shows that the generation of refractory and/or thick continental lithosphere is not restricted to the Archean. Since Archean cratons also commonly display crust–mantle age decoupling, contain spinel peridotites with extreme Cr# numbers that require low-P hydrous melting, and often have a paucity of mafic melts relative to the extreme depletion indicated by their peridotitic roots, they too may – in part – be compilations of peridotite shallowly melted and then laterally accreted at subduction margins

Water intake, faecal output and intestinal motility in horses moved from pasture to a stabled management regime with controlled exercise

Reasons for performing study: A change in management from pasture to stabling is a risk factor for equine colic. Objectives: To investigate the effect of a management change from pasture with no controlled exercise to stabling with light exercise on aspects of gastrointestinal function related to large colon impaction. The hypothesis was that drinking water intake, faecal output, faecal water content and large intestinal motility would be altered by a transition from a pastured to a stabled regime. Study design: Within-subject management intervention trial involving changes in feeding and exercise using noninvasive techniques. Methods: Seven normal horses were evaluated in a within-subjects study design. Horses were monitored while at pasture 24 h/day, and for 14 days following a transition to a stabling regime with light controlled exercise. Drinking water intake, faecal output and faecal dry matter were measured. Motility of the caecum, sternal flexure and left colon (contractions/min) were measured twice daily by transcutaneous ultrasound. Mean values were pooled for the pastured regime and used as a reference for comparison with stabled data (Days 1–14 post stabling) for multilevel statistical analysis. Results: Drinking water intake was significantly increased (mean ± s.d. pasture 2.4 ± 1.8 vs. stabled 6.4 ± 0.6 l/100 kg bwt/day), total faecal output was significantly decreased (pasture 4.62 ± 1.69 vs. stabled 1.81 ± 0.5 kg/100 kg bwt/day) and faecal dry matter content was significantly increased (pasture 18.7 ± 2.28 vs. stabled 27.2 ± 1.93% DM/day) on all days post stabling compared with measurements taken at pasture (P<0.05). Motility was significantly decreased in all regions of the large colon collectively on Day 2 post stabling (-0.76 contractions/min), and in the left colon only on Day 4 (-0.62 contractions/min; P<0.05). Conclusions: There were significant changes in large intestinal motility patterns and parameters relating to gastrointestinal water balance during a transition from pasture to stabled management, particularly during the first 5 days

Hole Dispersions for Antiferromagnetic Spin-1/2 Two-Leg Ladders by Self-Similar Continuous Unitary Transformations

The hole-doped antiferromagnetic spin-1/2 two-leg ladder is an important model system for the high-$T_c$ superconductors based on cuprates. Using the technique of self-similar continuous unitary transformations we derive effective Hamiltonians for the charge motion in these ladders. The key advantage of this technique is that it provides effective models explicitly in the thermodynamic limit. A real space restriction of the generator of the transformation allows us to explore the experimentally relevant parameter space. From the effective Hamiltonians we calculate the dispersions for single holes. Further calculations will enable the calculation of the interaction of two holes so that a handle of Cooper pair formation is within reach.Comment: 16 pages, 26 figure