294 research outputs found
Alien invasions and livelihoods: Economic benefits of invasive Australian Red Claw crayfish in Jamaica
Invasive species have caused widespread economic and environmental disruption, which have been widely studied. However, their potential benefits have received much less attention. If invasive species contribute to livelihoods, their eradication may negatively impact wellbeing. Failing to value these benefits may lead to an undervaluation of invaded ecosystems. We assess the potential economic benefits of an invasive species within an artisanal fishery in Jamaica. We monitored catches over 259 fisherman-days, and conducted 45 semi-structured interviews, with 76 fishermen. We show that the invasive Australian Red Claw crayfish (Cherax quadricarinatus) is an important source of income for fishermen within the Black River Lower Morass of Jamaica and supplement incomes during periods when native shrimp (Macrobrachium spp.) catches decline. We also show that full-time fishermen and those who have no alternative occupations expend the greatest fishing effort. We use the intra-annual variation of fishermen's harvest effort between seasons (when catch per unit effort changes) as a proxy for dependence. Using this measure, we found that the least wealthy appear to be the most dependent on fishing, and consequently benefit the most from the invasive crayfish. Our results demonstrate the importance of considering the potential benefits of invasive species within integrated landscape management
Neutron density distributions from antiprotonic 208Pb and 209Bi atoms
The X-ray cascade from antiprotonic atoms was studied for 208Pb and 209Bi.
Widths and shifts of the levels due to the strong interaction were determined.
Using modern antiproton-nucleus optical potentials the neutron densities in the
nuclear periphery were deduced. Assuming two parameter Fermi distributions
(2pF) describing the proton and neutron densities the neutron rms radii were
deduced for both nuclei. The difference of neutron and proton rms radii /\r_np
equal to 0.16 +-(0.02)_{stat} +- (0.04)_{syst} fm for 208Pb and 0.14 +-
(0.04)_{stat} +- (0.04)_{syst} fm for 209Bi were determined and the assigned
systematic errors are discussed. The /\r_np values and the deduced shapes of
the neutron distributions are compared with mean field model calculations.Comment: 22 pages, 8 tables, 15 figure
Thermal excitation of heavy nuclei with 5-15 GeV/c antiproton, proton and pion beams
Excitation-energy distributions have been derived from measurements of
5.0-14.6 GeV/c antiproton, proton and pion reactions with Au target
nuclei, using the ISiS 4 detector array. The maximum probability for
producing high excitation-energy events is found for the antiproton beam
relative to other hadrons, He and beams from LEAR. For protons
and pions, the excitation-energy distributions are nearly independent of hadron
type and beam momentum above about 8 GeV/c. The excitation energy enhancement
for beams and the saturation effect are qualitatively consistent with
intranuclear cascade code predictions. For all systems studied, maximum cluster
sizes are observed for residues with E*/A 6 MeV.Comment: 14 pages including 5 figures and 1 table. Accepted in Physics Letter
B. also available at http://nuchem.iucf.indiana.edu
Personal traits predict conservationists’ optimism about outcomes for nature
In the face of unprecedented biodiversity loss, the belief that conservation goals can be met could play an important role in ensuring they are fulfilled. We asked conservationists how optimistic they felt about key biodiversity outcomes over the next 10 years; 2341 people familiar with conservation in 144 countries responded. Respondents expressed optimism that enabling conditions for conservation would improve but felt pressures would continue, and the state of biodiversity was unlikely to get better. Respondents with greater general optimism about life, at early-career stages, and working in practice and policy (compared to academia) reported higher conservation optimism. But most of our biodiversity and conservation status indicators were not associated with conservation optimism. Unbounded optimism without appropriate action would be misguided in the face of growing threats to biodiversity. However, supporting those struggling to see the light at the end of the tunnel could help sustain efforts to overcome these threats
Thermally-induced expansion in the 8 GeV/c + Au reaction
Fragment kinetic energy spectra for reactions induced by 8.0 GeV/c
beams incident on a Au target have been analyzed in
order to deduce the possible existence and influence of thermal expansion. The
average fragment kinetic energies are observed to increase systematically with
fragment charge but are nearly independent of excitation energy. Comparison of
the data with statistical multifragmentation models indicates the onset of
extra collective thermal expansion near an excitation energy of E*/A
5 MeV. However, this effect is weak relative to the radial
expansion observed in heavy-ion-induced reactions, consistent with the
interpretation that the latter expansion may be driven primarily by dynamical
effects such as compression/decompression.Comment: 12 pages including 4 postscript figure
The liquid to vapor phase transition in excited nuclei
For many years it has been speculated that excited nuclei would undergo a
liquid to vapor phase transition. For even longer, it has been known that
clusterization in a vapor carries direct information on the liquid- vapor
equilibrium according to Fisher's droplet model. Now the thermal component of
the 8 GeV/c pion + 197Au multifragmentation data of the ISiS Collaboration is
shown to follow the scaling predicted by Fisher's model, thus providing the
strongest evidence yet of the liquid to vapor phase transition.Comment: four pages, four figures, first two in color (corrected typo in Ref.
[26], corrected error in Fig. 4
Signals for a Transition from Surface to Bulk Emission in Thermal Multifragmentation
Excitation-energy-gated two-fragment correlation functions have been studied
between 2 to 9A MeV of excitation energy for equilibrium-like sources formed in
and p + Au reactions at beam momenta of 8,9.2 and 10.2 GeV/c.
Comparison of the data to an N-body Coulomb-trajectory code shows a decrease of
one order of magnitude in the fragment emission time in the excitation energy
interval 2-5A MeV, followed by a nearly constant breakup time at higher
excitation energy. The observed decrease in emission time is shown to be
strongly correlated with the increase of the fragment emission probability, and
the onset of thermally-induced radial expansion. This result is interpreted as
evidence consistent with a transition from surface-dominated to bulk emission
expected for spinodal decomposition.Comment: 11 pages including 3 postscript figures (1 color
Strong interaction and E2 effect in even- A antiprotonic Te atoms
The x-ray cascade from antiprotonic atoms was studied for Te-122, Te-124, Te-126, Te-128, and Te-130. Widths and shifts due to the strong interaction were deduced for several levels. The E2 nuclear resonance effect was observed in all investigated nuclei. In Te-130 the E2 resonance allowed to determine level widths and shifts of the LS-split deeply bound (n,l)=(6,5) state, otherwise unobservable. The measured level widths and shifts, corrected for the E2-resonance effect, were used to investigate the nucleon density in the nuclear periphery. The deduced neutron distributions are compared with results of the previously introduced radiochemical method and with Hartree-Fock-Bogoliubov model calculations
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