Magnetic field control of elastic scattering in a cold gas of fermionic lithium atoms

We study elastic collisions in an optically trapped spin mixture of fermionic lithium atoms in the presence of magnetic fields up to 1.5kG by measuring evaporative loss. Our experiments confirm the expected magnetic tunability of the scattering length by showing the main features of elastic scattering according to recent calculations. We measure the zero crossing of the scattering length that is associated with a predicted Feshbach resonance at 530(3)G. Beyond the resonance we observe the expected large cross section in the triplet scattering regime

Feshbach resonances in the 6Li-40K Fermi-Fermi mixture: Elastic versus inelastic interactions

We present a detailed theoretical and experimental study of Feshbach resonances in the 6Li-40K mixture. Particular attention is given to the inelastic scattering properties, which have not been considered before. As an important example, we thoroughly investigate both elastic and inelastic scattering properties of a resonance that occurs near 155 G. Our theoretical predictions based on a coupled channels calculation are found in excellent agreement with the experimental results. We also present theoretical results on the molecular state that underlies the 155G resonance, in particular concerning its lifetime against spontaneous dissociation. We then present a survey of resonances in the system, fully characterizing the corresponding elastic and inelastic scattering properties. This provides the essential information to identify optimum resonances for applications relying on interaction control in this Fermi-Fermi mixture.Comment: Submitted to EPJD, EuroQUAM special issues "Cold Quantum Matter - Achievements and Prospects", v2 with updated calibration of magnetic field (+4mG correction) and updated figures 4 and

Pure Gas of Optically Trapped Molecules Created from Fermionic Atoms

We report on the production of a pure sample of up to 3x10^5 optically trapped molecules from a Fermi gas of 6Li atoms. The dimers are formed by three-body recombination near a Feshbach resonance. For purification a Stern-Gerlach selection technique is used that efficiently removes all trapped atoms from the atom-molecule mixture. The behavior of the purified molecular sample shows a striking dependence on the applied magnetic field. For very weakly bound molecules near the Feshbach resonance, the gas exhibits a remarkable stability with respect to collisional decay.Comment: 4 pages, 5 figure

The Stem Cell “Sell”

In recent years, a growing number of clinics in Australia and overseas have begun to offer therapies that claim to restore health by using stem cells to replace or repair the patient's faulty or missing cells. For those who have been told that conventional medicine has nothing more to offer, a visit to a stem cell clinic may appear to be worth the time, effort and expense that this entails. What’s on Offer? Stem cell tourism is a phrase used to encompass travel – usually overseas – for a wide range of therapies involving stem cells. These therapies may involve the use of the patient’s own (autologous) stem cells from fat or their bone marrow, or donated stem cells from cord blood, embryos and foetal tissue. Therapy might be administered by having the patient inhale the cells, or by injecting the cells under the skin, into a vein or joint, directly into the fluid around the spinal cord or into the patient’s brain. Such therapies have been touted as effective treatments for many conditions and illnesses including arthritis, spinal cord injury, motor neurone disease, multiple sclerosis, cerebral palsy, neurodegenerative conditions and autism. Often the same treatment is offered for conditions with vastly different underlying pathology. Unlike other forms of medical tourism – such as travel for IVF, cosmetic surgery, joint replacement or dentistry, which are based on access to well-established conventional therapies that are available more quickly and at a more affordable price than in the patient’s home country – stem cell tourism provides patients with access to “treatments” that are yet to be proven. These treatments are not based upon rigorous scientific evidence, have not been clearly demonstrated to offer any benefit, and are not recognised or reimbursed by local health systems. The reality, sadly, is very different. Most people are unlikely to benefit, losing precious time, money, hope and trust in the course of pursuing this new form of medical tourism

Regulating the Stem Cell Industry: Needs and Responsibilities

Emerging biotechnologies pose public health challenges1 because of both the known and unforeseen risks they carry, the uncertain medical benefits they offer, the speed at which they have disseminated and their unproven mode of application.2 The development of therapies from advances in stem cell science reveals the need to pay critical attention to stem cell treatments. Stem cells have attracted scientific, clinical and public interest because they are self-renewing and have the capacity to develop into specific cell types, depending on the source of stem cells and their biological plasticity. The hope is that stem cells could be used either to replace damaged cells or to create an environment for cellular regeneration to treat several conditions, including osteoarthritis, diabetes, macular degeneration and Parkinson disease. Although promising in theory, so far very few stem cell therapies have proven to be safe and effective in clinical trials. Yet, despite the absence of evidence to support their use, there has been a global proliferation of clinics and associated businesses offering stem cell-based interventions to patients having serious medical conditions.3 These clinics operate mostly in the private health-care sector and typically market their interventions directly to patients over the Internet. The emergence of these clinics has not only created domestic markets in many highincome countries,3 but has also fomented stem cell tourism – the movement of people across international boundaries to access putative stem cell treatments. The global reach of this expanding industry exploits weaknesses and differences in national regulatory infrastructures4 and has revealed the need for an international approach to report and monitor the harms and benefits of these putative treatments

Ultra-cold Polarized Fermi Gases

Recent experiments with ultra-cold atoms have demonstrated the possibility of realizing experimentally fermionic superfluids with imbalanced spin populations. We discuss how these developments have shed a new light on a half- century old open problem in condensed matter physics, and raised new interrogations of their own.Comment: 27 pages; 8 figures; Published in Report in Rep. Prog. Phys. 73 112401 (2010

Exploring an ultracold Fermi-Fermi mixture: Interspecies Feshbach resonances and scattering properties of 6Li and 40K

We report on the observation of Feshbach resonances in an ultracold mixture of two fermionic species, 6Li and 40K. The experimental data are interpreted using a simple asymptotic bound state model and full coupled channels calculations. This unambiguously assigns the observed resonances in terms of various s- and p-wave molecular states and fully characterizes the ground-state scattering properties in any combination of spin states.Comment: 4 pages, 4 figures, 1 tabl