Multiparticle Bell's inequalities involving many measurement settings

We present a prescription for obtaining Bell's inequalities for N>2 observers involving more than two alternative measurement settings. We give examples of some families of such inequalities. The inequalities are violated by certain classes of states for which all standard Bell's inequalities with two measurement settings per observer are satisfied.Comment: 4 pages, RevTeX

Ultracold Akali Collisions

The nature of the interaction between ultracold atoms is sensitive to their internuclear separation distance r. When the collision partners are far apart, they are regarded as non-interacting and the state of the system is characterized by the internal degrees of the freedom of the individual atoms, namely their respective electronic and nuclear spins. However, as r begins to diminish, the atoms start to feel a weak attractive force represented by a sum of van der Waals terms with interaction energies on the order of 10−6 Hartree. This attractive force grows stronger as the particles continue to move towards each other, with associated interaction energies approaching ∼ 10−2 Hartree, until r reaches a point re, beyond which the atoms experience a strong repulsive force because the two cannot physically be on top of each other. Quantum defect theory (QDT) lends itself to calculations involving such systems because it exploits the natural separation of length and energy scales outlined above. In the simplest QDT approximation, two constants with respect to both field and energy, the singlet and triplet quantum defects, fully describe the short-range properties of the collision. These parameters are used to approximate the short-range reaction matrix Ksr with a frame transformation (FT) formula. In the long-range region, a collection of quantities that are smooth in energy and field characterize the physics. Moreover, at low collision energies, these long-range parameters behave as simple, analytic functions of energy to a good approximation. With the long-range parameters and Ksr in hand, the real properties of the atomic system, such as elastic cross sections, can be tabulated in a relatively few easy steps. We used this FT approximation to describe elastic s-wave collisions of 6Li, 7Li, 23Na, 39K and 87Rb atoms in which the particles enter and exit the lowest-lying interaction channel. For each, we calculated the elastic cross section as a function of magnetic field, finding that our FT method is able to reproduce the resonance features of a full coupled channels (FCC) calculation for systems where the hyperfine/Zeeman splitting of the collision channels is negligible in the area where the short- and long-range regions overlap

Homonuclear Ultracold Elastic \u3cem\u3es\u3c/em\u3e-wave Collisions of Alkali-Metal Atoms via Multichannel Quantum Defect Theory

Multichannel quantum-defect theory (MQDT) provides a powerful toolkit for describing and understanding collisions of cold alkali-metal atoms. Various MQDT approximations differ primarily in how they characterize the so-called short-ranged K matrix Ksr, which encapsulates the short-ranged physics into a handful of low-energy parameters that exhibit simple and smooth dependence on energy and field. Here, we compare three different methods for computing Ksr for homonuclear collisions of alkali-metal atoms, from lithium to cesium. The MQDT calculations are benchmarked against numerically converged coupled-channels calculations that use a log-derivative propagator out to the asymptotic region. We study how well these approximations reproduce positions of s-wave magnetic Feshbach resonances, comparing with experiment where possible, and identify the limitations of various approximations

The Effect of Individual Movements and Interventions on the Spread of Influenza in Long-Term Care Facilities

Background. Nosocomial influenza poses a serious risk among residents of long-term care facilities (LTCFs). Objective. We sought to evaluate the effect of resident and staff movements and contact patterns on the outcomes of various intervention strategies for influenza control in an LTCF. Methods. We collected contact frequency data in Canada's largest veterans' LTCF by enroling residents and staff into a study that tracked their movements through wireless tags and signal receivers. We analyzed and fitted the data to an agent-based simulation model of influenza infection, and performed Monte-Carlo simulations to evaluate the benefit of antiviral prophylaxis and patient isolation added to standard (baseline) infection control practice (i.e., vaccination of residents and staff, plus antiviral treatment of residents with symptomatic infection). Results. We calibrated the model to attack rates of 20%, 40%, and 60% for the baseline scenario. For data-driven movements, we found that the largest reduction in attack rates (12.5% to 27%; ANOVA P 0.2) among residents. In contrast, parameterizing the model with random movements yielded different results, suggesting that the highest benefit was achieved through patient isolation (69.6% to 79.6%; ANOVA P <0.001) while the additional benefit of prophylaxis was negligible in reducing the cumulative number of infections. Conclusions. Our study revealed a highly structured contact and movement patterns within the LTCF. Accounting for this structureinstead of assuming randomnessin decision analytic methods can result in substantially different predictions

High-resolution NMR studies of structure and dynamics of human ERp27 indicate extensive interdomain flexibility

ERp27 (endoplasmic reticulum protein 27.7 kDa) is a homologue of PDI (protein disulfide-isomerase) localized to the endoplasmic reticulum. ERp27 is predicted to consist of two thioredoxinfold domains homologous with the non-catalytic b and b domains of PDI. The structure in solution of the N-terminal blike domain of ERp27 was solved using high-resolution NMR data. The structure confirms that it has the thioredoxin fold and that ERp27 is a member of the PDI family. 15N-NMR relaxation data were obtained and ModelFree analysis highlighted limited exchange contributions and slow internal motions, and indicated that the domain has an average order parameter S 2 of 0.79. Comparison of the single-domain structure determined in the present study with the equivalent domain within fulllength ERp27, determined independently by X-ray diffraction, indicated very close agreement. The domain interface inferred from NMR data in solution was much more extensive than that observed in the X-ray structure, suggesting that the domains flex independently and that crystallization selects one specific interdomain orientation. This led us to apply a new rapid method to simulate the flexibility of the full-length protein, establishing that the domains show considerable freedom to flex (tilt and twist) about the interdomain linker, consistent with the NMR data