Ethical Challenges of Preexposure Prophylaxis for HIV

On July 16, 2012, emtricitabine/tenofovir (Truvada) became the first drug approved by the US Food and Drug Administration for preexposure prophylaxis (PrEP) of human immunodeficiency virus (HIV) for adults at high risk. While PrEP appears highly effective with consistent adherence, effective implementation poses ethical challenges for the medical and public health community. For PrEP users, it is necessary to maintain adherence, safe sex practices, and routine HIV testing and medical monitoring, to maximize benefits and reduce risks. On a population level, comparative cost-effectiveness should guide priority-setting, while safety measures must address drug resistance concerns without burdening patients\u27 access. Equitable distribution will require addressing the needs of underserved populations, women (for whom efficacy data are mixed) and people living in developing countries with high HIV incidence; meanwhile, it is necessary to consider the fair use of drugs for treatment vs. prevention and the appropriate design of new HIV prevention studies

Mermin Inequalities for Perfect Correlations in Many-Qutrit Systems

The existence of Greenberger-Horne-Zeilinger (GHZ) contradictions in many-qutrit systems was a long-standing theoretical question until its (affirmative) resolution in 2013. To enable experimental tests, we derive Mermin inequalities from concurrent observable sets identified in those proofs. These employ a weighted sum of observables, called M, in which every term has the chosen GHZ state as an eigenstate with eigenvalue unity. The quantum prediction for M is then just the number of concurrent observables, and this grows asymptotically as 2N/3 as the number of qutrits N→∞. The maximum classical value falls short for every N≥3, so that the quantum to classical ratio (starting at 1.5 when N=3) diverges exponentially (∼1.064N) as N→∞, where the system is in a Schrödinger-cat-like superposition of three macroscopically distinct states

Entanglement Patterns in Mutually Unbiased Basis Sets

A few simply-stated rules govern the entanglement patterns that can occur in mutually unbiased basis sets (MUBs), and constrain the combinations of such patterns that can coexist (ie , the stoichiometry) in full complements of (pN + 1) MUBs. We consider Hilbert spaces of prime power dimension (as realized by systems of N prime-state particles, or qupits), where full complements are known to exist, and we assume only that MUBs are eigenbases of generalized Pauli operators, without using a particular construction. The general rules include the following: 1) In any MUB, a particular qupit appears either in a pure state, or totally entangled, and 2) in any full MUB complement, each qupit is pure in (p +1) bases (not necessarily the same ones), and totally entangled in the remaining (pN − p). It follows that the maximum number of product bases is p + 1, and when this number is realized, all remaining (p N − p) bases in the complement are characterized by the total entanglement of every qupit. This “standard distribution” is inescapable for two qupits (of any p), where only product and generalized Bell bases are admissible MUB types. This and the following results generalize previous results for qubits [13, 17] and qutrits [16], drawing particularly upon Ref. [17]. With three qupits there are three MUB types, and a number of combinations (p +2) are possible in full complements. With N = 4, there are 6 MUB types for p = 2, but new MUB types become possible with larger p, and these are essential to realizing full complements. With this example, we argue that new MUB types, showing new entanglement characteristics, should enter with every step in N , and when N is a prime plus 1, also at critical p values, p = N − 1. Such MUBs should play critical roles in filling complements

Rotational Covariance and Greenberger-Horne-Zeilinger Theorems for Three or More Particles of Any Dimension

Greenberger-Horne-Zeilinger (GHZ) states are characterized by their transformation properties under a continuous symmetry group, and N-body operators that transform covariantly exhibit a wealth of GHZ contradictions. We show that local or noncontextual hidden variables cannot duplicate the predicted measurement outcomes for covariant transformations, and we extract specific GHZ contradictions from discrete subgroups, with no restrictions on particle number N or dimension d except for the general requirement that N≥3 for GHZ states. However, the specific contradictions fall into three regimes distinguished by increasing demands on the number of measurement operators required for the proofs. The first regime consists of proofs found recently by Ryu et al. [Phys. Rev. A 88, 042101 (2013)], the first operator-based theorems for all odd dimensions d, covering many (but not all) particle numbers N for each d. We introduce alternative methods of proof that define second and third regimes and produce theorems that fill all remaining gaps down to N=3 for every d. The common origin of all such GHZ contradictions is that the GHZ states and measurement operators transform according to different representations of the symmetry group, which has an intuitive physical interpretation

THE HYDRODYNAMIC FLOW OF NEMATIC LIQUID CRYSTALS IN R\u3csup\u3e3\u3c/sup\u3e

This manuscript demonstrates the well-posedness (existence, uniqueness, and regularity of solutions) of the Cauchy problem for simplified equations of nematic liquid crystal hydrodynamic flow in three dimensions for initial data that is uniformly locally L3(R3) integrable (L3U(R3)). The equations examined are a simplified version of the equations derived by Ericksen and Leslie. Background on the continuum theory of nematic liquid crystals and their flow is provided as are explanations of the related mathematical literature for nematic liquid crystals and the Navier–Stokes equations