368 research outputs found
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 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 , we measure a three-body loss
coefficient 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
Exploring the Hydration Levels of Malosma laurina at Different Elevations on a Man-made Trail
The purpose of this study is to examine the water potential of Malosma laurina at different elevations of a man made trail in the chapparal of the Santa Monica Mountains. Chaparral in the Santa Monica Mountains have been depleted because of human involvement effecting the chaparral ecosystem. Fire breaks and man made trails are a few of the major causes of the rapidly changing ecosystem and continues to cause stress among the plants. We are testing the effect that man made trails have on the water potential of Malosma laurina. This was measured by taking samples of Malosma laurina at different altitudes of the trail. Collecting samples and measuring the water potentials of Malosma laurina at different regions led to conclusions about which Malosma laurina plants have the most, least water potential
eTextbook Exploration: Are Students Ready to Declare Their Independence From the Printed Text?
A team of faculty, library, IT, and bookstore staff collaborated on a longitudinal study to track how 50 students use e-textbooks and whether using them improves learning outcomes. The Fall 2010 pilot study, “Tracking Student Interest in e-Textbooks”, gathered both quantitative and qualitative data from students registered in online and physical sections of an upper level business course. Student participants accessed the e-textbook with their personal laptops, but several reported using a Kindle, iPad, and even an iPhone. Of particular interest to the researchers were the possible correlates of students’ successful use of the e-textbooks, e.g., their habits regarding the use of social network sites, electronic commerce, blogs, etc. Another purpose of the study was to discover the impact of assistive interventions offered students throughout the length of the study. These included: (1) e-textbook help sessions from both bookstore and IT staff; (2) e-textbook current event emails from a librarian with a reminder of help contacts, and (3) help consultations by phone, email, or in the Library. At the beginning and end of the study, participants completed pre- and post-surveys measuring their experience with and attitudes toward computers, the Internet, e-textbooks and print textbooks. Research findings indicate: (1) 65% of the students are willing to read another e-textbook and (2) cost savings is the most compelling reason to read the e-textbook. Students encountered technical difficulties (page/highlighting freezes, printing problems, and slow network) that were frustrating enough that 10% of the participants switched to print textbooks. Students acknowledge the need to focus when reading their e-textbook. Many students voiced a preference to read their next e-textbook on an e-reader because first, the reader was a physical object reminding the student to read and second, offered no distractions such as the ability to simultaneously access social networking sites. 10% of the students actively sought assistance and/or responded to email messages from the librarians. A review of recent literature indicates more needs to be learned about student digital reading comprehension, barriers to accepting e-textbooks, and the pedagogical implications for e-textbook use (as well as for online study). Bibliography available on request
- …