1,067 research outputs found
Desirable qualities of REDD plus projects not considered in decisions of project locations
Reducing emissions from deforestation and forest degradation (REDD+) has become a major conservation and development concept for international climate change mitigation over the past years with hundreds of so-called âdemonstrationâ or âpilotâ projects being planned and implemented across the Global South. Since the broad aim of such projects is to demonstrate climate benefits from reduced deforestation, as well as social co-benefits in receiving countries, the decision on REDD+ locations should ideally center on specific geographical and socioeconomic characteristics, such as high deforestation threat, low opportunity costs, large forest area size, and high local willingness to engage. Based on recent literature supplemented with opinions and perspectives from REDD+ specialists, we compare these desirable qualities for REDD+ locations with actual location of REDD+ projects. We illustrate how locating REDD+ projects is often in the hands of external organizations and tightly connected to their previous engagements in the location. We also show how specific characteristics of these externally driven REDD+ project locations vary according to the sub-objectives of the individual projects and do not always correspond with the overall goal of REDD+. These pre-conditioned decisions and diverging objectives at the meso-level may further complicate global REDD+ agreements
Quantum key distribution with finite resources: Taking advantage of quantum noise
We compare the effect of different noise scenarios on the achievable rate of
an epsilon-secure key for the BB84 and the six-state protocol. We study the
situation where quantum noise is added deliberately, and investigate the
remarkable benefit for the finite key rate. We compare our results to the known
case of added classical noise and the asymptotic key rate, i.e. in the limit of
infinitely many signals. As a complementary interpretation we show that under
the realistic assumption that the noise which is unavoidably introduced by a
real channel is not fully dedicated to the eavesdropper, the secret key rate
increases significantly.Comment: 14 pages, 8 figure
Active wetting of epithelial tissues
Development, regeneration and cancer involve drastic transitions in tissue
morphology. In analogy with the behavior of inert fluids, some of these
transitions have been interpreted as wetting transitions. The validity and
scope of this analogy are unclear, however, because the active cellular forces
that drive tissue wetting have been neither measured nor theoretically
accounted for. Here we show that the transition between 2D epithelial
monolayers and 3D spheroidal aggregates can be understood as an active wetting
transition whose physics differs fundamentally from that of passive wetting
phenomena. By combining an active polar fluid model with measurements of
physical forces as a function of tissue size, contractility, cell-cell and
cell-substrate adhesion, and substrate stiffness, we show that the wetting
transition results from the competition between traction forces and contractile
intercellular stresses. This competition defines a new intrinsic lengthscale
that gives rise to a critical size for the wetting transition in tissues, a
striking feature that has no counterpart in classical wetting. Finally, we show
that active shape fluctuations are dynamically amplified during tissue
dewetting. Overall, we conclude that tissue spreading constitutes a prominent
example of active wetting --- a novel physical scenario that may explain
morphological transitions during tissue morphogenesis and tumor progression
Observation of Spontaneous Brillouin Cooling
While radiation-pressure cooling is well known, the Brillouin scattering of
light from sound is considered an acousto-optical amplification-only process.
It was suggested that cooling could be possible in multi-resonance Brillouin
systems when phonons experience lower damping than light. However, this regime
was not accessible in traditional Brillouin systems since backscattering
enforces high acoustical frequencies associated with high mechanical damping.
Recently, forward Brillouin scattering in microcavities has allowed access to
low-frequency acoustical modes where mechanical dissipation is lower than
optical dissipation, in accordance with the requirements for cooling. Here we
experimentally demonstrate cooling via such a forward Brillouin process in a
microresonator. We show two regimes of operation for the Brillouin process:
acoustical amplification as is traditional, but also for the first time, a
Brillouin cooling regime. Cooling is mediated by an optical pump, and scattered
light, that beat and electrostrictively attenuate the Brownian motion of the
mechanical mode.Comment: Supplementary material include
Participatory analysis for adaptation to climate change in Mediterranean agricultural systems: possible choices in process design (versĂŁo Pre Print)
There is an increasing call for local measures to adapt to climate change, based on foresight analyses in collaboration with actors. However, such analyses involve many challenges, particularly because the actors concerned may not consider climate change to be an urgent concern. This paper examines the methodological choices made by three research teams in the design and implementation of participatory foresight analyses to explore agricultural and water management options for adaptation to climate change. Case studies were conducted in coastal areas of France, Morocco, and Portugal where the groundwater is intensively used for irrigation, the aquifers are at risk or are currently overexploited, and a serious agricultural crisis is underway. When designing the participatory processes, the researchers had to address four main issues: whether to avoid or prepare dialogue between actors whose relations may be limited or tense; how to select participants and get them involved; how to facilitate discussion of issues that the actors may not initially consider to be of great concern; and finally, how to design and use scenarios. In each case, most of the invited actors responded and met to discuss and evaluate a series of scenarios. Strategies were discussed at different levels, from farming practices to aquifer management. It was shown that such participatory analyses can be implemented in situations which may initially appear to be unfavourable. This was made possible by the flexibility in the methodological choices, in particular the possibility of framing the climate change issue in a broader agenda for discussion with the actors
Lowest Q^2 Measurement of the gamma*p -> Delta Reaction: Probing the Pionic Contribution
To determine nonspherical angular momentum amplitudes in hadrons at long
ranges (low Q^2), data were taken for the p(\vec{e},e'p)\pi^0 reaction in the
Delta region at Q^2=0.060 (GeV/c)^2 utilizing the magnetic spectrometers of the
A1 Collaboration at MAMI. The results for the dominant transition magnetic
dipole amplitude and the quadrupole to dipole ratios at W=1232 MeV are:
M_{1+}^{3/2} = (40.33 +/- 0.63_{stat+syst} +/- 0.61_{model})
(10^{-3}/m_{\pi^+}),Re(E_{1+}^{3/2}/M_{1+}^{3/2}) = (-2.28 +/- 0.29_{stat+syst}
+/- 0.20_{model})%, and Re(S_{1+}^{3/2}/M_{1+}^{3/2}) = (-4.81 +/-
0.27_{stat+syst} +/- 0.26_{model})%. These disagree with predictions of
constituent quark models but are in reasonable agreement with lattice
calculations with non-linear (chiral) pion mass extrapolations, with chiral
effective field theory, and with dynamical models with pion cloud effects.
These results confirm the dominance, and general Q^2 variation, of the pionic
contribution at large distances.Comment: 6 pages, 3 figures, 1 tabl
Phase-Locked Spatial Domains and Bloch Domain Walls in Type-II Optical Parametric Oscillators
We study the role of transverse spatial degrees of freedom in the dynamics of
signal-idler phase locked states in type-II Optical Parametric Oscillators.
Phase locking stems from signal-idler polarization coupling which arises if the
cavity birefringence and/or dichroism is not matched to the nonlinear crystal
birefringence. Spontaneous Bloch domain wall formation is theoretically
predicted and numerically studied. Bloch walls connect, by means of a
polarization transformation, homogeneous regions of self-phase locked
solutions. The parameter range for their existence is analytically found. The
polarization properties and the dynamics of walls in one- and two transverse
spatial dimensions is explained. Transition from Bloch to Ising walls is
characterized, the control parameter being the linear coupling strength. Wall
dynamics governs spatiotemporal dynamical states of the system, which include
transient curvature driven domain growth, persistent dynamics dominated by
spiraling defects for Bloch walls, and labyrinthine pattern formation for Ising
walls.Comment: 27 pages, 16 figure
Deconfinement of Mott Localized Electrons into Topological and Spin-Orbit Coupled Dirac Fermions
The interplay of electronic correlations, spin-orbit coupling and topology
holds promise for the realization of exotic states of quantum matter. Models of
strongly interacting electrons on honeycomb lattices have revealed rich phase
diagrams featuring unconventional quantum states including chiral
superconductivity and correlated quantum spin Hall insulators intertwining with
complex magnetic order. Material realizations of these electronic states are
however scarce or inexistent. In this work, we propose and show that stacking
1T-TaSe into bilayers can deconfine electrons from a deep Mott insulating
state in the monolayer to a system of correlated Dirac fermions subject to
sizable spin-orbit coupling in the bilayer. 1T-TaSe develops a
Star-of-David (SoD) charge density wave pattern in each layer. When the SoD
centers belonging to two adyacent layers are stacked in a honeycomb pattern,
the system realizes a generalized Kane-Mele-Hubbard model in a regime where
Dirac semimetallic states are subject to significant Mott-Hubbard interactions
and spin-orbit coupling. At charge neutrality, the system is close to a quantum
phase transition between a quantum spin Hall and an antiferromagnetic
insulator. We identify a perpendicular electric field and the twisting angle as
two knobs to control topology and spin-orbit coupling in the system. Their
combination can drive it across hitherto unexplored grounds of correlated
electron physics including a quantum tricritical point and an exotic
first-order topological phase transition.Comment: 8 pages, 3 figures, Supplemental Material with 6 pages and 4 figures,
hopping data files include
The impact of swidden decline on livelihoods and ecosystem services in Southeast Asia: a review of the evidence from 1990 to 2015
Global economic change and policy interventions are driving transitions from long-fallow swidden (LFS) systems to alternative land uses in Southeast Asiaâs uplands. This study presents a systematic review of how these transitions impact upon livelihoods and ecosystem services in the region. Over 17 000 studies published between 1950 and 2015 were narrowed, based on relevance and quality, to 93 studies for further analysis. Our analysis of land-use transitions from swidden to intensified cropping systems showed several outcomes: more households had increased overall income, but these benefits came at significant cost such as reductions of customary practice, socio-economic wellbeing, livelihood options, and staple yields. Examining the effects of transitions on soil properties revealed negative impacts on soil organic carbon, cation-exchange capacity, and aboveground carbon. Taken together, the proximate and underlying drivers of the transitions from LFS to alternative land uses, especially intensified perennial and annual cash cropping, led to significant declines in pre-existing livelihood security and the ecosystem services supporting this security. Our results suggest that policies imposing land-use transitions on upland farmers so as to improve livelihoods and environments have been misguided; in the context of varied land uses, swidden agriculture can support livelihoods and ecosystem services that will help buffer the impacts of climate change in Southeast AsiaThe authors wish to acknowledge the support of
the Centre for International Forestry Research (CIFOR) via the award
of an Evidence-Based Forestry grant administered on behalf of the
UK Governmentâs Department for International Development (DfID)
under the KNOW-FOR programme
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