389 research outputs found
Integrating Black Bear Behavior, Spatial Ecology, and Population Dynamics in a Human-Dominated Landscape: Implications for Management
The New Jersey Division of Fish and Wildlife (NJDFW), in collaboration with Bear Trust International, presented us an opportunity to examine a long-term (33 years) American black bear (Ursus americanus) data set from northwestern New Jersey (NJ), USA. State agencies continue to grapple with uncertainty about the efficacy of socially divisive management actions such as recreational harvest and lethal control as tools to reduce escalating human-bear conflicts. We applied multistate capture-reencounter models to a large sample of black bear captures (\u3e5,000) and dead recoveries (\u3e1,300) between 1981 – 2014 to estimate cause-specific mortality and spatial dynamics between wildland and anthropogenic habitats. Additionally, we assessed temporal correlations between more than 26,500 reported human–black bear interactions and mortality rates. Adult females were twice as likely (0.163 ± 0.014) as males (0.087 ± 0.012) to be harvested, and cubs (0.444 ± 0.025) and yearlings (0.372 ± 0.022) had a high probability of dying, primarily from vehicle strikes. Nuisance behaviors reported declined with increasing harvest and lethal management (P = 0.028, R2 = 0.338). Adult bears previously designated as a nuisance and/or threat (hereafter, “problem”) were more likely to be harvested (0.176 ± 0.025) than those with no conflict history (0.109 ± 0.010).
Combined legal kills and vehicle strikes, the two greatest mortality causes for marked bears, occurred significantly less than expected per unit area in urban and agricultural areas, and more than expected in the wildland-urban interface and wildland habitats. Across all age-classes, problem bears were significantly more likely to transition to anthropogenic habitats, yet they died at lower rates than conspecifics with no history of conflict in wildlands. Cubs and yearlings died at significantly higher rates than adults in the risky interface habitat, corroborating independent estimates of their increased susceptibility to harvest and vehicle strikes. Ultimately, wildland habitats represented a population source (λ = 1.133) and anthropogenic habitats a sink (λ = 0.945). Harvest represents an important management tool to help meet population targets and decrease human-bear conflicts by disproportionately removing problem bears
Spectroscopy of Rydberg atoms in non-neutral cold plasmas
The electric field in mm-sized one-component non-neutral plasmas is measured using the Stark effect of Rydberg atoms embedded in them. The plasmas are clouds of cold Rb+Rb+-ions, which are produced by UV photoionization of laser-cooled Rb atoms in a magneto-optic trap. The dependence of the electric field on the number of ions and the Coulomb explosion of the ion clouds have been studied. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87634/2/89_1.pd
Wave Packet Echoes in the Motion of Trapped Atoms
We experimentally demonstrate and systematically study the stimulated revival
(echo) of motional wave packet oscillations. For this purpose, we prepare wave
packets in an optical lattice by non-adiabatically shifting the potential and
stimulate their reoccurence by a second shift after a variable time delay. This
technique, analogous to spin echoes, enables one even in the presence of strong
dephasing to determine the coherence time of the wave packets. We find that for
strongly bound atoms it is comparable to the cooling time and much longer than
the inverse of the photon scattering rate
The Hydrogen Atom in Combined Electric and Magnetic Fields with Arbitrary Mutual Orientations
For the hydrogen atom in combined magnetic and electric fields we investigate
the dependence of the quantum spectra, classical dynamics, and statistical
distributions of energy levels on the mutual orientation of the two external
fields. Resonance energies and oscillator strengths are obtained by exact
diagonalization of the Hamiltonian in a complete basis set, even far above the
ionization threshold. At high excitation energies around the Stark saddle point
the eigenenergies exhibit strong level repulsions when the angle between the
fields is varied. The large avoided crossings occur between states with the
same approximately conserved principal quantum number, n, and this
intramanifold mixing of states cannot be explained, not even qualitatively, by
conventional perturbation theory. However, it is well reproduced by an extended
perturbation theory which takes into account all couplings between the angular
momentum and Runge-Lenz vector. The large avoided crossings are interpreted as
a quantum manifestation of classical intramanifold chaos. This interpretation
is supported by both classical Poincar\'e surfaces of section, which reveal a
mixed regular-chaotic intramanifold dynamics, and the statistical analysis of
nearest-neighbor-spacingComment: two-column version, 10 pages, REVTeX, 10 figures, uuencoded,
submitted to Rhys. Rev.
Squeezing of Atoms in a Pulsed Optical Lattice
We study the process of squeezing of an ensemble of cold atoms in a pulsed
optical lattice. The problem is treated both classically and
quantum-mechanically under various thermal conditions. We show that a dramatic
compression of the atomic density near the minima of the optical potential can
be achieved with a proper pulsing of the lattice. Several strategies leading to
the enhanced atomic squeezing are suggested, compared and optimized.Comment: Latex, 9 pages, 10 figures, submitted to PR
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