Metacommunity stability and persistence for predation turnoff in selective patches

Predation as an important trophic interaction of ecological communities controls the large-scale patterns of species distribution, population abundance and community structure. Numerous studies address that predation can mediate diversity and regulate the ecological community and food web stability through changes in the behaviour, morphology, development, and abundance of prey. Since predation has large effects on persistence and diversity, the local loss or removal of predation in a community can trigger a cascade of extinctions. In ecological theory, the effect of predation removal has been well studied in foodwebs, but it remains unclear in the case of a spatially distributed community connected by dispersal. In this study, the interaction between local and spatial processes is taken into account, we present how a predation turnoff in selective patches affects the stability and persistence of a metacommunity. Using a simple predator-prey metacommunity with a diffusive dispersal, we show the impact of predation on synchronized, asynchronized and source-sink dynamics. Our results reveal that predation turnoff in very few patches alters a perfectly synchronized oscillatory state into multicluster states consisting of various patterns. In a source-sink behaviour, predation turnoff in a source patch reduces the number of sink patches and changes the clusters. In general, predation turnoff in a finite number of patches increases the number of clusters through asynchronized (inhomogeneous) states, whereas predation turnoff in a larger number of patches can lead to the complete extinction of predators. Typically, there exists a critical number of patches below which the predation turnoff results in asynchronized states and above that predation turnoff leads to a synchronized state in prey population with complete extinction of predators. Further, our results identify the network configurations that exhibit a unique number of clusters. Moreover, prey density from the patches where predation is absent goes to a saturating state near the carrying capacity. Thus, this study stresses that predation turnoff in selective patches acts as a stabilizing mechanism that can promote metacommunity persistence.

From Catastrophe to Recovery: Stories of Fishery Management Success

<i>Abstract</i>.—The Owens Pupfish <i>Cyprinodon radiosus</i> is a small fish (<6 cm [2.5 in]) in the killifish family once thought extinct but rediscovered in the early 1960s in Fish Slough in the Death Valley drainage area of eastern California, USA. At the time of discovery, the species was comprised of a single population of approximately 200 individuals. The species was listed as endangered on March 11, 1967 under the U.S. Endangered Species Preservation Act of 1966. During the summer of 1969, a spring that was feeding water to Fish Slough was discovered to have much reduced flow due to unusual precipitation patterns the previous 6 months and possibly water removals, and thus threatened complete extinction of the species. Quick actions by fish biologists prevented extinction by transporting the entire species in two buckets to nearby refuge waters similar to Fish Slough. The transplantation was successful, and six populations now exist 50 years later that each number from the hundreds to perhaps more than 10,000 fish. The species remains listed as endangered—but it did not go extinct!

CO2-Tea pulse clipping using pulsed high voltage preionization for high spatial resolution I.R. Lidar systems

An extra-cavity CO2-TEA laser pulse clipper for high spatial resolution atmospheric monitoring is presented. The clipper uses pulsed high voltageto facilitate the breakdown of the gas within the clipper cell. Complete extinction of the nitrogen tail, that degrades the range resolution of LIDARS, is obtained at pressures from 375 up to 1500 Torr for nitrogen and argon gases whereas an attenuation coefficient of almost 102 is achieved for helium. Excellent energy stability and pulse width repeatability were achieved using high voltage pre-ionized gas technique.

Multimodality Molecular Imaging-Guided Tumor Border Delineation and Photothermal Therapy Analysis Based on Graphene Oxide-Conjugated Gold Nanoparticles Chelated with Gd

Tumor cell complete extinction is a crucial measure to evaluate antitumor efficacy. The difficulties in defining tumor margins and finding satellite metastases are the reason for tumor recurrence. A synergistic method based on multimodality molecular imaging needs to be developed so as to achieve the complete extinction of the tumor cells. In this study, graphene oxide conjugated with gold nanostars and chelated with Gd through 1,4,7,10-tetraazacyclododecane-N,N′,N,N′-tetraacetic acid (DOTA) (GO-AuNS-DOTA-Gd) were prepared to target HCC-LM3-fLuc cells and used for therapy. For subcutaneous tumor, multimodality molecular imaging including photoacoustic imaging (PAI) and magnetic resonance imaging (MRI) and the related processing techniques were used to monitor the pharmacokinetics process of GO-AuNS-DOTA-Gd in order to determine the optimal time for treatment. For orthotopic tumor, MRI was used to delineate the tumor location and margin in vivo before treatment. Then handheld photoacoustic imaging system was used to determine the tumor location during the surgery and guided the photothermal therapy. The experiment result based on orthotopic tumor demonstrated that this synergistic method could effectively reduce tumor residual and satellite metastases by 85.71% compared with the routine photothermal method without handheld PAI guidance. These results indicate that this multimodality molecular imaging-guided photothermal therapy method is promising with a good prospect in clinical application.

DISTRIBUTION AND POPULATION GROWTH OF EURASIAN BEAVER (Castor fiber LINNAEUS, 1758) IN BOSNIA AND HERZEGOVINA 10 YEARS AFTER REINTRODUCTION

Beaver is a semiaquatic mammal which inhabits suitable watercourses and water surfaces coveredby rich vegetation of woody and herbaceous species. In the past, it inhabited large areas fromsouth to the north European mainland, but in the early XX century, there were only six isolatedautochthonous populations left. The reason that led to the complete extinction of Eurasian beaverin Bosnia and Herzegovina is the same as in Europe - excessive hunting.Thanks to the actions of the beaver reintroduction to former habitats across Europe at the beginningof the XXI century, the beaver is again spread over a wider area. In Bosnia and Herzegovinabeavers were reintroduced in 2005 and 2006, thus making it the 26th country that has helped toincrease the number of beavers. With the reintroduction of the beaver on the territory of Bosniaand Herzegovina, it became protected species.In the period from 2009 to 2016 a total of 964 records about the presence of beavers was collected.Currently on the territory of Bosnia and Herzegovina there are at least 43 registered families and eightindividuals (singles). Having in mind that on average three individuals per family were registered, thereal abundance of beaver in Bosnia and Herzegovina could be approximately 140 individuals.

Persistent vulnerability to relapse despite complete extinction of cocaine craving

ABSTRACTCraving often precedes relapse into cocaine addiction. This explains why considerable research effort is being expended to try to develop anti-craving strategies for relapse prevention. Recently, we discovered using the classic reinstatement model of cocaine craving that the reinstating or priming effect of cocaine can be extinguished with repeated priming in rats - a phenomenon dubbed extinction of cocaine priming. Here we sought to measure the potential beneficial effect of this novel extinction strategy on subsequent relapse (i.e., return to the pre-extinction pattern of cocaine self-administration once the drug is made again available after extinction). Overall and contrary to our initial hope, extensive and complete extinction of cocaine priming had no major impact on relapse. This lack of effect occurred despite evidence for post-extinction loss of neuronal responses to cocaine priming in brain regions critically involved in cocaine-induced reinstatement (i.e., the dorsomedial prefrontal cortex and the core of the nucleus accumbens). An effect of extinction of cocaine priming on relapse was only observed when cocaine was available for self-administration under more demanding conditions. However, this effect was modest and short-lived. Finally, we succeeded to trace the origin of our failure to prevent relapse to a persistent, extinction-resistant form of operant behavior that is not directly induced by cocaine. This extinction-resistant behavior is commonly reported, though generally ignored as causally irrelevant, in many other reinstatement studies. We propose that this behavior should become both a novel marker for long-term vulnerability to relapse and a novel target for preclinical development of potential relapse prevention interventions.

Research on Performance of H2Rich Blowout Limit in Bluff-Body Burner

In order to investigate H2rich blowout limit at different blockage ratios and flow velocities, a CFD software FLUENT was used to simulate H2burning flow field in bluff-body burner, and the software CHEMKIN was adopted to analyze the sensitivity of each elementary reaction. Composition Probability Density Function (C-PDF) model was adopted to simulate H2combustion field in turbulence flame. The numerical results show that reactions R2 and R9 possess the largest positive and negative temperature sensitivity. Temperature has a very important influence on these two reactions. When equivalence ratio is 1, the mixture is most ignitable, and the critical ignition temperature is 1550 K. There should be an optimal blockage ratio which can stabilize the flame best. When the blockage ratio remains unchanged, the relationship between H2RBL and flow velocity is a logarithmic function. When the flow velocity remains unchanged, the relationship between H2RBL and blockage ratio is a parabolic function. A complete extinction requires three phases: the temperature sudden decline in the main stream, the energy dissipation from the recirculation zone to the main stream, and the complete extinction of the flame.