344 research outputs found
Uncertainty and the management of multi-state ecosystems : an apparently rational route to collapse
environmental policy;ecology;management;decision making
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
Movement ecology of a mobile predatory fish reveals limited habitat linkages within a temperate estuarine seascape
Large predatory fishes, capable of traveling great distances, can facilitate energy flow linkages among spatially separated habitat patches via extended foraging behaviors over expansive areas. Here, we tested this concept by tracking the movement of a large mobile estuarine fish, red drum (Sciaenops ocellatus). Specifically, we addressed the following two questions: (i) What are the spatial and temporal patterns of red drum movement (rates of dispersal) and activity space? (ii) Does red drum movement facilitate linkages among estuarine marsh complexes? Dispersal from the release location was greatest during the first 2 weeks at liberty before declining to less than 0.5 km·week–1 for the remainder of the study. Activity space initially increased rapidly before reaching an asymptote at 2.5 km2 2 weeks postrelease. Connectivity indices calculated among marsh complexes corroborated these observations, suggesting high residency and limited seascape-scale linkages via red drum movement behaviors. These data highlight potential within-estuary spatial structure for mobile fishes and could inform subsequent efforts to track energy flows in coastal food webs, predict the footprint of local habitat restoration benefits, and enhance the design of survey regimes to quantify overall population demography
Efficacy of Dupilumab in a Phase 2 Randomized Trial of Adults With Active Eosinophilic Esophagitis.
Eosinophilic esophagitis (EoE) is an allergen-mediated inflammatory disease with no approved treatment in the United States. Dupilumab, a VelocImmune-derived human monoclonal antibody against the interleukin (IL) 4 receptor, inhibits IL4 and IL13 signaling. Dupilumab is effective in the treatment of allergic, atopic, and type 2 diseases, so we assessed its efficacy and safety in patients with EoE.
We performed a phase 2 study of adults with active EoE (2 episodes of dysphagia/week with peak esophageal eosinophil density of 15 or more eosinophils per high-power field), from May 12, 2015, through November 9, 2016, at 14 sites. Participants were randomly assigned to groups that received weekly subcutaneous injections of dupilumab (300 mg, n = 23) or placebo (n = 24) for 12 weeks. The primary endpoint was change from baseline to week 10 in Straumann Dysphagia Instrument (SDI) patient-reported outcome (PRO) score. We also assessed histologic features of EoE (peak esophageal intraepithelial eosinophil count and EoE histologic scores), endoscopically visualized features (endoscopic reference score), esophageal distensibility, and safety.
The mean SDI PRO score was 6.4 when the study began. In the dupilumab group, SDI PRO scores were reduced by a mean value of 3.0 at week 10 compared with a mean reduction of 1.3 in the placebo group (P = .0304). At week 12, dupilumab reduced the peak esophageal intraepithelial eosinophil count by a mean 86.8 eosinophils per high-power field (reduction of 107.1%; P < .0001 vs placebo), the EoE-histologic scoring system (HSS) severity score by 68.3% (P < .0001 vs placebo), and the endoscopic reference score by 1.6 (P = .0006 vs placebo). Dupilumab increased esophageal distensibility by 18% vs placebo (P < .0001). Higher proportions of patients in the dupilumab group developed injection-site erythema (35% vs 8% in the placebo group) and nasopharyngitis (17% vs 4% in the placebo group).
In a phase 2 trial of patients with active EoE, dupilumab reduced dysphagia, histologic features of disease (including eosinophilic infiltration and a marker of type 2 inflammation), and abnormal endoscopic features compared with placebo. Dupilumab increased esophageal distensibility and was generally well tolerated. ClinicalTrials.gov, Number: NCT02379052
From thermal rectifiers to thermoelectric devices
We discuss thermal rectification and thermoelectric energy conversion from
the perspective of nonequilibrium statistical mechanics and dynamical systems
theory. After preliminary considerations on the dynamical foundations of the
phenomenological Fourier law in classical and quantum mechanics, we illustrate
ways to control the phononic heat flow and design thermal diodes. Finally, we
consider the coupled transport of heat and charge and discuss several general
mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture
Notes in Physics volume "Thermal transport in low dimensions: from
statistical physics to nanoscale heat transfer" (S. Lepri ed.
Amplifying actions for food system transformation: Insights from the Stockholm region
Food is essential to people and is one of the main ways in which people are connected to the world’s ecosystems. However, food systems often cause ecosystem degradation and produce ill-health, which has generated increasing calls to transform food systems to be more sustainable. The Swedish food system is currently undergoing substantial change. A varied set of local actors have created alternative sustainability initiatives that enact new ways of doing, thinking, and organizing. These actors can increase the transformative impact of their initiatives through multiple actions and a variety of amplification processes. We analyzed the actions adopted by 29 food initiatives active in the Stockholm region using information available online. We conducted 11 interviews to better understand the amplification processes of speeding up (i.e., accelerating impact), scaling up (i.e., influencing higher institutional levels), and scaling deep (i.e., changing values and mind-sets). Our results indicated that the initiatives mainly seek to stabilize and grow their impact while changing the awareness, values, and mind-sets of people concerning the food they consume (scaling deep). However, these approaches raise new questions about whether these actions subvert or reinforce current unsustainable and inequitable system dynamics. We suggest there are distinct steps that local and regional governments could take to support these local actors via collaborations with coordinated forms of initiatives, and fostering changes at the municipality level, but these steps require ongoing, adaptive approaches given the highly complex nature of transformative change and the risks of reinforcing current system dynamics
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Formation and Evolution of Supermassive Black Holes
The correlation between the mass of supermassive black holes in galaxy nuclei
and the mass of the galaxy spheroids or bulges (or more precisely their central
velocity dispersion), suggests a common formation scenario for galaxies and
their central black holes. The growth of bulges and black holes can commonly
proceed through external gas accretion or hierarchical mergers, and are both
related to starbursts. Internal dynamical processes control and regulate the
rate of mass accretion. Self-regulation and feedback are the key of the
correlation. It is possible that the growth of one component, either BH or
bulge, takes over, breaking the correlation, as in Narrow Line Seyfert 1
objects. The formation of supermassive black holes can begin early in the
universe, from the collapse of Population III, and then through gas accretion.
The active black holes can then play a significant role in the re-ionization of
the universe. The nuclear activity is now frequently invoked as a feedback to
star formation in galaxies, and even more spectacularly in cooling flows. The
growth of SMBH is certainly there self-regulated. SMBHs perturb their local
environment, and the mergers of binary SMBHs help to heat and destroy central
stellar cusps. The interpretation of the X-ray background yields important
constraints on the history of AGN activity and obscuration, and the census of
AGN at low and at high redshifts reveals the downsizing effect, already
observed for star formation. History appears quite different for bright QSO and
low-luminosity AGN: the first grow rapidly at high z, and their number density
decreases then sharply, while the density of low-luminosity objects peaks more
recently, and then decreases smoothly.Comment: 31 pages, 13 figures, review paper for Astrophysics Update
Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays
The lifetime and oscillation frequency of the B0 meson has been measured
using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP.
The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the
production flavour of the B0 mesons was determined using a combination of tags
from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d
= 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first
error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.
Observation of a Narrow Resonance of Mass 2.46 GeV/c^2 Decaying to D_s^*+ pi^0 and Confirmation of the D_sJ^* (2317) State
Using 13.5 inverse fb of e+e- annihilation data collected with the CLEO II
detector we have observed a narrow resonance in the Ds*+pi0 final state, with a
mass near 2.46 GeV. The search for such a state was motivated by the recent
discovery by the BaBar Collaboration of a narrow state at 2.32 GeV, the
DsJ*(2317)+ that decays to Ds+pi0. Reconstructing the Ds+pi0 and Ds*+pi0 final
states in CLEO data, we observe peaks in both of the corresponding
reconstructed mass difference distributions, dM(Dspi0)=M(Dspi0)-M(Ds) and
dM(Ds*pi0)=M(Ds*pi0)-M(Ds*), both of them at values near 350 MeV. We interpret
these peaks as signatures of two distinct states, the DsJ*(2317)+ plus a new
state, designated as the DsJ(2463)+. Because of the similar dM values, each of
these states represents a source of background for the other if photons are
lost, ignored or added. A quantitative accounting of these reflections confirms
that both states exist. We have measured the mean mass differences
= 350.0 +/- 1.2 [stat] +/- 1.0 [syst] MeV for the DsJ*(2317) state, and
= 351.2 +/- 1.7 [stat] +/- 1.0 [syst] MeV for the new DsJ(2463)+
state. We have also searched, but find no evidence, for decays of the two
states via the channels Ds*+gamma, Ds+gamma, and Ds+pi+pi-. The observations of
the two states at 2.32 and 2.46 GeV, in the Ds+pi0 and Ds*+pi0 decay channels
respectively, are consistent with their interpretations as (c anti-strange)
mesons with orbital angular momentum L=1, and spin-parities of 0+ and 1+.Comment: 16 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, version to be published in Physical
Review D; minor modifications and fixes to typographical errors, plus an
added section on production properties. The main results are unchanged; they
supersede those reported in hep-ex/030501
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