•Windthrow was modelled for old growth boreal forests using a hybrid mechanistic wind risk model.•Model predictions was not statistically different from observations from experimental ...sites.•Windthrow levels in partial cuts ranged from 7 to 32% for expected peak winds.•Predictive wind duration was more important than wind speed for wind speeds over 20m/s.•The stage is set for inclusion of wind disturbance in ecosystem succession models.
Windthrow is a recurring disturbance process in regions that are influenced by maritime climates, including boreal forests. Within the circumboreal region, forest management approaches have been adapted to emulate natural disturbance in order to promote biodiversity and ecosystem resilience. Few studies have evaluated windthrow outcomes in natural or managed old-growth boreal mixed-species stands, and these studies are primarily empirical. The objective of this study was to adapt the hybrid empirical-mechanistic ForestGALES_BC model, to investigate windthrow dynamics in natural and managed boreal old-growth stands, under various wind regimes. ForestGALES_BC was updated by adding biomechanical data for balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.). The model has the ability to simulate damage propagation during wind events by recalculating wind loading on a subject tree after failure of upwind trees. The number of iterations of this recalculation provides insights into the potential for propagation during longer duration storms. A simulation space made up of 500, 20m×20m cells, was created using tree-lists from silviculture systems experiments in north eastern Quebec. The tree-lists for cells within the simulation space were edited to represent the plot conditions at the Quebec experimental sites, allowing simulation of a range of cell- (plot) and matrix-level (landscape) partial harvesting regimes. Above-canopy winds of various speeds were applied in order to test the initiation and propagation of damage within the simulated forest. Simulated outcomes were compared to observations of windthrow 6–7 years after partial harvesting at the field experimental site. Observed damage at the experimental site ranged from 1 to 40% of plot total basal area (mean=14%, se=1.96). For above-canopy wind speeds within the range expected for the experimental site, simulated windthrow levels in partial cuts ranged from 7 to 32% (mean=12%, se=1.94). When the combined effects of wind speed and number of iterations (∼event duration) were investigated, event duration was more important for wind speeds over 20m/s. By enabling simulation of outcomes at the tree, plot (cell) and stand (simulation space) levels, the model allows investigation of a wide range of harvesting strategies, and sets the stage for inclusion of wind disturbance in ecosystem succession models and other stand or landscape-level decision-support tools for forests in windy climates.
The Selecting Therapeutic Targets in Inflammatory Bowel Disease (STRIDE) program was initiated by the International Organization for the Study of Inflammatory Bowel Diseases (IOIBD). It examined ...potential treatment targets for inflammatory bowel disease (IBD) to be used for a "treat-to-target" clinical management strategy using an evidence-based expert consensus process.
A Steering Committee of 28 IBD specialists developed recommendations based on a systematic literature review and expert opinion. Consensus was gained if ≥75% of participants scored the recommendation as 7-10 on a 10-point rating scale (where 10=agree completely).
The group agreed upon 12 recommendations for ulcerative colitis (UC) and Crohn's disease (CD). The agreed target for UC was clinical/patient-reported outcome (PRO) remission (defined as resolution of rectal bleeding and diarrhea/altered bowel habit) and endoscopic remission (defined as a Mayo endoscopic subscore of 0-1). Histological remission was considered as an adjunctive goal. Clinical/PRO remission was also agreed upon as a target for CD and defined as resolution of abdominal pain and diarrhea/altered bowel habit; and endoscopic remission, defined as resolution of ulceration at ileocolonoscopy, or resolution of findings of inflammation on cross-sectional imaging in patients who cannot be adequately assessed with ileocolonoscopy. Biomarker remission (normal C-reactive protein (CRP) and calprotectin) was considered as an adjunctive target.
Evidence- and consensus-based recommendations for selecting the goals for treat-to-target strategies in patients with IBD are made available. Prospective studies are needed to determine how these targets will change disease course and patients' quality of life.
Background Clinicians who treat patients with Clostridium difficile–associated diarrhea (CDAD) in Quebec, Canada, have noted an apparent increase in the proportion of patients who experience relapse. ...Methods To determine whether there was an increase in the frequency of treatment failure and of recurrence of CDAD after treatment, we reviewed data on cases that had been diagnosed in a hospital in the province of Quebec during the period 1991–2004. The frequency of recurrences within 60 days after the initial diagnosis was measured using Kaplan-Meier analysis, and Cox regression was used for multivariate analysis. Results Among patients who had initially been treated with metronidazole, the proportion whose regimens were switched to vancomycin or for whom vancomycin was added because of a disappointing response did not vary between 1991 and 2002 (66 9.6% of 688 patients overall) but more than doubled in 2003–2004 (112 25.7% of 435; P<.001). Among 845 patients treated with metronidazole only, the 60-day probability of recurrence increased dramatically in 2003–2004 (47.2%), compared with 1991–2002 (20.8%; P<.001). During 1991–2002, the probabilities of recurrence were 20.0%, 13.8%, and 28.9% among individuals aged 0–17, 18–64, and ⩾65 years, respectively; during 2003–2004, the probabilities were 25.0%, 27.1%, and 58.4%, respectively. Conclusion In 2003–2004, there was an increase in the proportion of patients with CDAD believed, by their attending physicians, to have experienced metronidazole treatment failure, as well as an increase in the frequency of post–metronidazole therapy recurrences, especially among elderly persons.
Many biologists now recognize that environmental variance can exert important effects on patterns and processes in nature that are independent of average conditions. Jensen’s inequality is a ...mathematical proof that is seldom mentioned in the ecological literature but which provides a powerful tool for predicting some direct effects of environmental variance in biological systems. Qualitative predictions can be derived from the form of the relevant response functions (accelerating versus decelerating). Knowledge of the frequency distribution (especially the variance) of the driving variables allows quantitative estimates of the effects. Jensen’s inequality has relevance in every field of biology that includes nonlinear processes.
A new concept of hydrokinetic turbine using oscillating hydrofoils to extract energy from water currents (tidal or gravitational) is presented and tested in this investigation. This technology is ...particularly well suited for riverbeds and shallow waters near the coasts due to its rectangular extraction plane. Very encouraging hydrodynamic efficiencies are demonstrated in this study through field tests which showed good agreement with the theoretical predictions obtained in the design phase. Following detailed analysis based on CFD modeling, an experimental 2 kW prototype has been designed, built and tested. The turbine includes two rectangular oscillating hydrofoils of aspect ratio 7 in a tandem spatial configuration. The pitching motion of each hydrofoil is coupled to their cyclic heaving motion through four-link mechanisms which effectively yield a one-degree-of-freedom system driving a rotating shaft. The rotating shaft is connected to a speed-controlled electric generator which, in the present setup, is used to charge a battery bank. In order to facilitate testing at different water flow velocities, the turbine has been mounted on a custom-made pontoon boat and dragged on a lake. Very good flow conditions and repeatability have thus been obtained. Instantaneous extracted power was measured and cycle-averaged for several water flow velocities and hydrofoil oscillation frequencies. The heaving and pitching amplitudes of the hydrofoils were kept constant for all runs at values of 1 chord and 75° respectively. Results are demonstrated to be self-consistent and show optimal performances at a reduced frequency of about 0.11 at which condition the measured power extraction efficiency reaches 40% once the overall losses in the mechanical system are taken into account. The 40% hydrodynamic efficiency of this first prototype exceeds expectation and reaches levels comparable to the best performances achievable with modern rotor blades turbines. It thus demonstrates the promising potential of the oscillating hydrofoils technology to efficiently extract power from an incoming water flow.
We present first results on the cooling properties derived from Chandra X-ray observations of 83 high-redshift (0.3 < z < 1.2) massive galaxy clusters selected by their Sunyaev-Zel'dovich signature ...in the South Pole Telescope data. We measure each cluster's central cooling time, central entropy, and mass deposition rate, and compare these properties to those for local cluster samples. We find no significant evolution from z ~ 0 to z ~ 1 in the distribution of these properties, suggesting that cooling in cluster cores is stable over long periods of time. We also find that the average cool core entropy profile in the inner ~100 kpc has not changed dramatically since z ~ 1, implying that feedback must be providing nearly constant energy injection to maintain the observed "entropy floor" at ~10 keV cm super(2). While the cooling properties appear roughly constant over long periods of time, we observe strong evolution in the gas density profile, with the normalized central density (rhog, 0/rho sub(crit)) increasing by an order of magnitude from z ~ 1 to z ~ 0. When using metrics defined by the inner surface brightness profile of clusters, we find an apparent lack of classical, cuspy, cool-core clusters at z > 0.75, consistent with earlier reports for clusters at z > 0.5 using similar definitions. Our measurements indicate that cool cores have been steadily growing over the 8 Gyr spanned by our sample, consistent with a constant, ~150 M sub(middot in circle) yr super(-1) cooling flow that is unable to cool below entropies of 10 keV cm super(2) and, instead, accumulates in the cluster center. We estimate that cool cores began to assemble in these massive systems at z sub(cool) = 1.0 super(+1.0) sub(-0.2), which represents the first constraints on the onset of cooling in galaxy cluster cores. At high redshift (z > ~ 0.75), galaxy clusters may be classified as "cooling flows" (low central entropy, cooling time) but not "cool cores" (cuspy surface brightness profile), meaning that care must be taken when classifying these high-z systems. We investigate several potential biases that could conspire to mimic this cool core evolution and are unable to find a bias that has a similar redshift dependence and a substantial amplitude.
We present optical spectroscopy of galaxies in clusters detected through the Sunyaev-Zel'dovich (SZ) effect with the South Pole Telescope (SPT). We report our own measurements of 61 spectroscopic ...cluster redshifts, and 48 velocity dispersions each calculated with more than 15 member galaxies. This catalog also includes 19 dispersions of SPT-observed clusters previously reported in the literature. The majority of the clusters in this paper are SPT-discovered; of these, most have been previously reported in other SPT cluster catalogs, and five are reported here as SPT discoveries for the first time. By performing a resampling analysis of galaxy velocities, we find that unbiased velocity dispersions can be obtained from a relatively small number of member galaxies (lap30), but with increased systematic scatter. We use this analysis to determine statistical confidence intervals that include the effect of membership selection.We fit scaling relations between the observed cluster velocity dispersions and mass estimates from SZ and X-ray observables. In both cases, the results are consistent with the scaling relation between velocity dispersion and mass expected from dark-matter simulations. We measure a ~30% log-normal scatter in dispersion at fixed mass, and a ~10% offset in the normalization of the dispersion-mass relation when compared to the expectation from simulations, which is within the expected level of systematic uncertainty.
Wind causes significant damage to forests in central Québec, and with the current move to more refined silvicultural practices, concerns are increasing. This study investigates the mechanisms of ...windthrow resistance in stands dominated by balsam fir
(
Abies balsamea (L.) Mill.) with a minor component of white spruce
(
Picea glauca (Moench) Voss.), representing the dominant feature of a large section of the Eastern Canadian boreal forest. The aim was to compare the stability of trees of both species on mesic and rich mesic sites and then to compare the windthrow vulnerability of the entire stands on the same sites. Stability was measured by static tree-pulling tests. The resulting critical turning moments were calculated at the base of the stem and were related to a series of tree descriptors. Stem mass and tree mass were the variables showing the highest correlation coefficients. The effects of the site and the species on the critical turning moments were non-significant (
P
>
0.05). Influence diagnostics did not reveal the need for separating the stability of the pulled trees from their mode of failure. A similar analysis also showed that the amount of rot at the base of the stem did not affect significantly the vulnerability to windthrow in this study. Windthrow vulnerability was modelled using the methodology developed for the British
GALES model. By using the relationship between the drag of the air on a surface and its aerodynamic roughness, the wind speed over a forest canopy was transformed into a resulting turning moment at the base of the stem. Critical wind speeds at which trees would overturn or snap could then be inferred for typical balsam fir stands growing on two site indices corresponding to those where the tree-pulling study was conducted. The immediate effect of a thinning operation was simulated by reducing the number of stems in the stands. The critical wind speeds were invariably higher for stem breakage than for overturning. In the later case, they were close to 20
m
s
−1 on both sites before declining at senescence. A thinning treatment removing 30% of the basal area would reduce this speed by approximately 4
m
s
−1.
The South Pole Telescope (SPT) is currently surveying 2500 deg2 of the southern sky to detect massive galaxy clusters out to the epoch of their formation using the Sunyaev-Zel'dovich (SZ) effect. ...This paper presents a catalog of the 26 most significant SZ cluster detections in the full survey region. The catalog includes 14 clusters which have been previously identified and 12 that are new discoveries. These clusters were identified in fields observed to two differing noise depths: 1500 deg2 at the final SPT survey depth of 18 Delta *mK arcmin at 150 GHz and 1000 deg2 at a depth of 54 Delta *mK arcmin. Clusters were selected on the basis of their SZ signal-to-noise ratio (S/N) in SPT maps, a quantity which has been demonstrated to correlate tightly with cluster mass. The S/N thresholds were chosen to achieve a comparable mass selection across survey fields of both depths. Cluster redshifts were obtained with optical and infrared imaging and spectroscopy from a variety of ground- and space-based facilities. The redshifts range from 0.098 <= z <= 1.132 with a median of z med = 0.40. The measured SZ S/N and redshifts lead to unbiased mass estimates ranging from 9.8 X 1014 M h --1 70 <= M 200( Delta *rmean) <= 3.1 X 1015 M h --1 70. Based on the SZ mass estimates, we find that none of the clusters are individually in significant tension with the Delta *LCDM cosmological model. We also test for evidence of non-Gaussianity based on the cluster sample and find the data show no preference for non-Gaussian perturbations.
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