Realization of a Resonant Fermi Gas with a Large Effective Range

We have measured the interaction energy and three-body recombination rate for a two-component Fermi gas near a narrow Feshbach resonance and found both to be strongly energy dependent. Even for deBroglie wavelengths greatly exceeding the van der Waals length scale, the behavior of the interaction energy as a function of temperature cannot be described by atoms interacting via a contact potential. Rather, energy-dependent corrections beyond the scattering length approximation are required, indicating a resonance with an anomalously large effective range. For fields where the molecular state is above threshold, the rate of three-body recombination is enhanced by a sharp, two-body resonance arising from the closed-channel molecular state which can be magnetically tuned through the continuum. This narrow resonance can be used to study strongly correlated Fermi gases that simultaneously have a sizeable effective range and a large scattering length.Comment: to appear in Phys. Rev. Let

Three-body recombination in a three-state Fermi gas with widely tunable interactions

We investigate the stability of a three spin state mixture of ultracold fermionic $^6$Li atoms over a range of magnetic fields encompassing three Feshbach resonances. For most field values, we attribute decay of the atomic population to three-body processes involving one atom from each spin state and find that the three-body loss coefficient varies by over four orders of magnitude. We observe high stability when at least two of the three scattering lengths are small, rapid loss near the Feshbach resonances, and two unexpected resonant loss features. At our highest fields, where all pairwise scattering lengths are approaching $a_t = -2140 a_0$, we measure a three-body loss coefficient $L_3 \simeq 5\times 10^{-22} \mathrm{cm}^6/\mathrm{s}$ and a trend toward lower decay rates for higher fields indicating that future studies of color superfluidity and trion formation in a SU(3) symmetric Fermi gas may be feasible

A Global Semi-Analytic Model of the First Stars and Galaxies Including Dark Matter Halo Merger Histories

We present a new self-consistent semi-analytic model of the first stars and galaxies to explore the high-redshift ($z{>}15$) Population III (PopIII) and metal-enriched star formation histories. Our model includes the detailed merger history of dark matter halos generated with Monte Carlo merger trees. We calibrate the minimum halo mass for PopIII star formation from recent hydrodynamical cosmological simulations that simultaneously include the baryon-dark matter streaming velocity, Lyman-Werner (LW) feedback, and molecular hydrogen self-shielding. We find that the resulting star formation rate density (SFRD) is dramatically increased compared to calibrations based on previous simulations (e.g., the PopIII SFRD is over two orders of magnitude higher at $z{\gtrsim}22.5$). We evaluate the effect of the halo-to-halo scatter in this critical mass and find that it increases the PopIII stellar mass density by a factor of ${\sim}1.5$ at $z{>}15$. Additionally, we assess the impact of various semi-analytic/analytic prescriptions for halo assembly and star formation previously adopted in the literature. For example, we find that models assuming smooth halo growth computed via abundance matching predict SFRDs similar to the merger tree model for our fiducial model parameters, but that they may underestimate the PopIII SFRD in cases of strong LW feedback. Finally, we simulate sub-volumes of the Universe with our model both to quantify the reduction in total star formation in numerical simulations due to a lack of density fluctuations on spatial scales larger than the simulation box, and to determine spatial fluctuations in SFRD due to the diversity in halo abundances and merger histories.Comment: Submitted to ApJ -- 21 Pages, 9 Figure

Students’ Experience of Family Counseling Role-Play with Developmental Considerations

A need exists to explore student experiences with pedagogical approaches, particularly those commonly used in counselor education such as role-play. Nine counselors-in-training (CITs) who participated in a semester-long family counseling role-play shared their experiences with the pedagogical approach. Through semi-structured interview protocol, we explored CITs’ lived experience and meaning-making with the learning strategy. Existing literature denotes that cognitive complexity influences how CITs make sense of their experiences. As such, cognitive complexity scores, rooted in Perry’s intellectual development model, are provided for each participant. Data were analyzed using transcendental phenomenology, which resulted in three superordinate themes: impact of class structure, increased confidence, and gained meta-awareness. Findings suggest the value of role-play as a pedagogical strategy for counselors-in-training of various cognitive developmental levels

MULTISCALE MATRIX-FRACTURE TRANSFER FUNCTIONS FOR NATURALLY FRACTURED RESERVOIRS USING AN ANALYTICAL, INFINITE CONDUCTIVITY, DISCRETE FRACTURE MODEL

Fracture matrix transfer functions have long been recognized as tools in modelling naturally fractured reservoirs. If a significant degree of fracturing is present, models involving single matrix blocks and matrix block distributions become relevant. However, this captures only the largest fracture sets and treats the matrix blocks as homogeneous, though possibly anisotropic. Herein, we produce the steady and transient baseline solutions for depletion for such models. Multiscale models pass below grid scale information to the larger scale system with some numerical cost. Instead, for below block scale information, we take the analytic solution to the Diffusivity Equation for transient inflow performance of wells of arbitrary trajectory, originally developed for Neumann boundary conditions, and recast it for Dirichlet boundaries with possible internal fractures of variable density, length, and orientation. As such, it represents the analytical solution for a heterogeneous matrix block surrounded by a constant pressure sink, we take to be the primary fracture system. Instead of using a constant rate internal boundary condition on a fracture surrounded by matrix, we segment the fracture and, through imposed material balance, force the internal complex fracture feature to be a constant pressure element with net zero flux. In doing so, we create a representative matrix block with infinite conductivity subscale fractures that impact the overall drainage into the surrounding fracture system. We vary the internal fracture structure and delineate sensitivity to fracture spacing and extent of fracturing. We generate the complete transient solution, enabling new well test interpretation for such systems in characterization of block size distributions or extent of below block-scale fracturing. The initial model for fully-penetrating fractures can be extended to 3D, generalized floating fractures of arbitrary inclination, and internal complex fracture networks

Epistemic Schmagency?

Constructivist approaches in epistemology and ethics offer a promising account of normativity. But constructivism faces a powerful Schmagency Objection, raised by David Enoch. While Enoch’s objection has been widely discussed in the context of practical norms, no one has yet explored how the Schmagency Objection might undermine epistemic constructivism. In this paper, I rectify that gap. First, I develop the objection against a prominent form of epistemic constructivism, Belief Constitutivism. Belief Constitutivism is susceptible to a Schmagency Objection, I argue, because it locates the source of normativity in the belief rather than the agent. In the final section, I propose a version of epistemic constructivism that locates epistemic normativity as constitutive of agency. I argue that this version has the resources to respond to the Schmagency Objection

A Test of Temporal Variation in Risk and Food Stimuli on Behavioral Tradeoffs in the Rusty Crayfish, Orconectes rusticus : Risk Allocation and Stimulus Degradation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72936/1/j.1439-0310.2006.01156.x.pd