299 research outputs found
Helping smallholder farmers mitigate climate change
Key messages
- Smallholder farmers can contribute significantly to climate change mitigation but will need incentives to adapt their practices. - Incentives from selling carbon credits are limited by low returns to farmers, high transaction costs, and the need for farmers to invest in mitigation activities long before they receive payments. - Improved food security, economic benefits and adaptation to climate change are more fundamental incentives that should accompany mitigation. - Designing agricultural investment and policy to provide up-front finance and longer term rewards for mitigation practices will help reach larger numbers of farmers than specialized mitigation interventions
Largeness and SQ-universality of cyclically presented groups
Largeness, SQ-universality, and the existence of free subgroups of rank 2 are measures of the complexity of a finitely presented group. We obtain conditions under which a cyclically presented group possesses one or more of these properties. We apply our results to a class of groups introduced by Prishchepov which contains, amongst others, the various generalizations of Fibonacci groups introduced by Campbell and Robertson
Abstract Learning Frameworks for Synthesis
We develop abstract learning frameworks (ALFs) for synthesis that embody the
principles of CEGIS (counter-example based inductive synthesis) strategies that
have become widely applicable in recent years. Our framework defines a general
abstract framework of iterative learning, based on a hypothesis space that
captures the synthesized objects, a sample space that forms the space on which
induction is performed, and a concept space that abstractly defines the
semantics of the learning process. We show that a variety of synthesis
algorithms in current literature can be embedded in this general framework.
While studying these embeddings, we also generalize some of the synthesis
problems these instances are of, resulting in new ways of looking at synthesis
problems using learning. We also investigate convergence issues for the general
framework, and exhibit three recipes for convergence in finite time. The first
two recipes generalize current techniques for convergence used by existing
synthesis engines. The third technique is a more involved technique of which we
know of no existing instantiation, and we instantiate it to concrete synthesis
problems
Integrating Comprehensive Geriatric Assessment for people with COPD and frailty starting pulmonary rehabilitation: the Breathe Plus feasibility trial protocol.
One in five people with COPD also lives with frailty. People living with both COPD and frailty are at increased risk of poorer health and outcomes, and face challenges to completing pulmonary rehabilitation. Integrated approaches that are adapted to the additional context of frailty are required. The aim of the present study is to determine the feasibility of conducting a randomised controlled trial of an integrated Comprehensive Geriatric Assessment for people with COPD and frailty starting pulmonary rehabilitation. This is a multicentre, mixed-methods, assessor-blinded, randomised, parallel group, controlled feasibility trial ("Breathe Plus"; ISRCTN13051922). We aim to recruit 60 people aged ≥50 with both COPD and frailty referred for pulmonary rehabilitation. Participants will be randomised 1:1 to receive usual pulmonary rehabilitation, or pulmonary rehabilitation with an additional Comprehensive Geriatric Assessment. Outcomes (physical, psycho-social and service use) will be measured at baseline, 90 days and 180 days. We will also collect service and trial process data, and conduct qualitative interviews with a sub-group of participants and staff. We will undertake descriptive analysis of quantitative feasibility outcomes (recruitment, retention, missing data, blinding, contamination, fidelity), and framework analysis of qualitative feasibility outcomes (intervention acceptability and theory, outcome acceptability). Recommendations on progression to a full trial will comprise integration of quantitative and qualitative data, with input from relevant stakeholders. This study has been approved by a UK Research Ethics Committee (ref.: 19/LO/1402). This protocol describes the first study testing the feasibility of integrating a Comprehensive Geriatric Assessment alongside pulmonary rehabilitation, and testing this intervention within a mixed-methods randomised controlled trial
Black Hole Entropy and Finite Geometry
It is shown that the symmetric entropy formula describing black
holes and black strings in D=5 is intimately tied to the geometry of the
generalized quadrangle GQ with automorphism group the Weyl group
. The 27 charges correspond to the points and the 45 terms in the
entropy formula to the lines of GQ. Different truncations with
and 9 charges are represented by three distinguished subconfigurations of
GQ, well-known to finite geometers; these are the "doily" (i. e.
GQ) with 15, the "perp-set" of a point with 11, and the "grid" (i. e.
GQ) with 9 points, respectively. In order to obtain the correct signs
for the terms in the entropy formula, we use a non- commutative labelling for
the points of GQ. For the 40 different possible truncations with 9
charges this labelling yields 120 Mermin squares -- objects well-known from
studies concerning Bell-Kochen-Specker-like theorems. These results are
connected to our previous ones obtained for the symmetric entropy
formula in D=4 by observing that the structure of GQ is linked to a
particular kind of geometric hyperplane of the split Cayley hexagon of order
two, featuring 27 points located on 9 pairwise disjoint lines (a
distance-3-spread). We conjecture that the different possibilities of
describing the D=5 entropy formula using Jordan algebras, qubits and/or qutrits
correspond to employing different coordinates for an underlying non-commutative
geometric structure based on GQ.Comment: 17 pages, 3 figures, v2 a new paragraph added, typos correcte
Initial results from the BIR National Linac Engineer Survey
Invited oral presentation at the 4th Annual BIR Radiotherapy and oncology Meeting, London 29 Feb – 1 Mar 202
A Counterexample Regarding Labelled Well-Quasi-Ordering
Korpelainen, Lozin, and Razgon conjectured that a hereditary property of graphs which is well-quasi-ordered by the induced subgraph order and defined by only finitely many minimal forbidden induced subgraphs is labelled well-quasi-ordered, a notion stronger than that of n-well-quasi-order introduced by Pouzet in the 1970s. We present a counterexample to this conjecture. In fact, we exhibit a hereditary property of graphs which is well-quasi-ordered by the induced subgraph order and defined by finitely many minimal forbidden induced subgraphs yet is not 2-well-quasi-ordered. This counterexample is based on the widdershins spiral, which has received some study in the area of permutation patterns
Isomorphisms of Brin-Higman-Thompson groups
Let be positive integers with . Let
denote the ring that is universal with an invertible matrix. Let
denote the ring of matrices over the tensor
product of copies of . In a natural way, is a
partially ordered ring with involution. Let denote the
group of positive unitary elements. We show that is
isomorphic to the Brin-Higman-Thompson group ; the case was
found by Pardo, that is, is isomorphic to the Higman-Thompson group
. We survey arguments of Abrams, \'Anh, Bleak, Brin, Higman, Lanoue,
Pardo, and Thompson that prove that if and only
if , and (if and only if
and are isomorphic as
partially ordered rings with involution).Comment: 24 page
The 28 November 2020 Landslide, Tsunami, and Outburst Flood – A Hazard Cascade Associated With Rapid Deglaciation at Elliot Creek, British Columbia, Canada
We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m3 of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km2 glacier lake and producing >100-m high run-up. Water overtopped the lake outlet and scoured a 10-km long channel before depositing debris on a 2-km2 fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real-time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose
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