1,623 research outputs found
The Doha Round’s Public Health Legacy: Strategies for the Production and Diffusion of Patented Medicines Under the Amended TRIPS Provisions
This entry into force of the World Trade Organization (WTO) TRIPS Agreement in 1995 transformed the international intellectual property system. The harmonization of basic intellectual property standards has operated to protect investment in innovation, limiting risks from unjustified \u27free riding.\u27 Yet these same harmonized IP standards sharply curtailed the traditional capacity of suppliers of public goods, such as health care and nutrition, to address the priority needs of less affluent members of society, particularly in (but not limited to) developing countries. In the Doha Declaration, the Waiver Decision of 30 August 2003 and the Article 31bis Protocol of Amendment, stakeholders concerned with re-opening policy space for the supply of newer pharmaceutical products pushed back against the restrictive elements of the TRIPS Agreement. Governments around the world are in the process of deciding whether to ratify and accept the Article 31bis Amendment. Based on their Study for the International Trade Committee of the European Parliament, the authors argue that acceptance of the Amendment will provide a \u27net benefit\u27 for countries seeking to improve access to medicines. At the insistence of WTO delegations acting on behalf of the originator pharmaceutical industry lobby, Article 31bis regrettably is saddled with unnecessary administrative hurdles. Nonetheless, through skillful lawyering, political determination and coordinated planning, the system can be made to work. Among other options, expeditious back-to-back compulsory licensing linked with pooled procurement strategies may effectively achieve economies of scale in production and distribution of medicines. The authors doubt that the international political environment would support renegotiation of an \u27improved\u27 solution. They express concern that failure to bring the Amendment into force will open the door to a campaign to undermine the Waiver Decision. Recent events in Brazil and Thailand illustrate both the opportunities and risks associated with implementing TRIPS exception mechanisms, and help to inform views on the negotiating environment. Specific proposals for regional cooperation in implementing the Amendment are laid out, and the authors emphasize the importance of pursuing concrete transfer of technology measures in support of developing country pharmaceutical manufacturing. Over-reliance on private market mechanisms for the supply of public health goods leaves the international community with an unresolved collective action problem on a large scale
Microscopic dynamics of supercooled liquids from first principles
Glasses are solid materials whose constituent atoms are arranged in a
disordered manner. The transition from a liquid to a glass remains one of the
most poorly understood phenomena in condensed matter physics, and still no
fully microscopic theory exists that can describe the dynamics of supercooled
liquids in a quantitative manner over all relevant time scales. Here we present
such a theoretical framework that yields near-quantitative accuracy for the
time-dependent correlation functions of a supercooled system over a broad
density range. Our approach requires only simple static structural information
as input and is based entirely based on first principles. Owing to this
first-principles nature, the framework offers a unique platform to study the
relation between structure and dynamics in glass-forming matter, and paves the
way towards a systematically correctable and ultimately fully quantitative
theory of microscopic glassy dynamics
Equilibrium ultrastable glasses produced by random pinning
Ultrastable glasses have risen to prominence due to their potentially useful
material properties and the tantalizing possibility of a general method of
preparation via vapor deposition. Despite the importance of this novel class of
amorphous materials, numerical studies have been scarce because achieving
ultrastability in atomistic simulations is an enormous challenge. Here we
bypass this difficulty and establish that randomly pinning the position of a
small fraction of particles inside an equilibrated supercooled liquid generates
ultrastable configurations at essentially no numerical cost, while avoiding
undesired structural changes due to the preparation protocol. Building on the
analogy with vapor-deposited ultrastable glasses, we study the melting kinetics
of these configurations following a sudden temperature jump into the liquid
phase. In homogeneous geometries, we find that enhanced kinetic stability is
accompanied by large scale dynamic heterogeneity, while a competition between
homogeneous and heterogeneous melting is observed when a liquid boundary
invades the glass at constant velocity. Our work demonstrates the feasibility
of large-scale, atomistically resolved, and experimentally relevant simulations
of the kinetics of ultrastable glasses.Comment: 9 pages, 5 figure
Relaxation Patterns in Supercooled Liquids from Generalized Mode-Coupling Theory
The mode-coupling theory of the glass transition treats the dynamics of
supercooled liquids in terms of two-point density correlation functions. Here
we consider a generalized, hierarchical formulation of schematic mode-coupling
equations in which the full basis of multipoint density correlations is taken
into account. By varying the parameters that control the effective
contributions of higher-order correlations, we show that infinite hierarchies
can give rise to both sharp and avoided glass transitions. Moreover, small
changes in the form of the coefficients result in different scaling behaviors
of the structural relaxation time, providing a means to tune the fragility in
glass-forming materials. This demonstrates that the infinite-order construct of
generalized mode-coupling theory constitutes a powerful and unifying framework
for kinetic theories of the glass transition
Theoretical investigation of electron-hole complexes in anisotropic two-dimensional materials
Trions and biexcitons in anisotropic two-dimensional materials are
investigated within an effective mass theory. Explicit results are obtained for
phosphorene and arsenene, materials that share features such as a direct
quasi-particle gap and anisotropic conduction and valence bands. Trions are
predicted to have remarkably high binding energies and an elongated
electron-hole structure with a preference for alignment along the armchair
direction, where the effective masses are lower. We find that biexciton binding
energies are also notably large, especially for monolayer phosphorene, where
they are found to be twice as large as those for typical monolayer transition
metal dichalcogenides.Comment: 3 figures, 5 pages + Supplementary Material, accepted for publication
in Phys. Rev.
Conductivity of disordered quantum lattice models at infinite temperature: Many-body localization
We reinvestigate the behavior of the conductivity of several disordered
quantum lattice models at infinite temperature using exact diagonalization.
Contrary to the conclusion drawn in a recent investigation of similar
quantities in identical systems, we find evidence of a localized regime for
strong random fields. We estimate the location of the critical field for the
many-body localization transition for the random-field XXZ spin chain, and
compare our findings with recent investigations in related systems.Comment: 5 pages, 4 figures. Accepted for publication in Phys. Rev.
Correlation of Local Order with Particle Mobility in Supercooled Liquids is Highly System Dependent
We investigate the connection between local structure and dynamical
heterogeneity in supercooled liquids. Through the study of four different
models we show that the correlation between a particle's mobility and the
degree of local order in nearby regions is highly system dependent. Our results
suggest that the correlation between local structure and dynamics is weak or
absent in systems that conform well to the mean-field picture of glassy
dynamics and strong in those that deviate from this paradigm. Finally, we
investigate the role of order-agnostic point-to-set correlations and reveal
that they provide similar information content to local structure measures, at
least in the system where local order is most pronounced.Comment: 6 pages, 3 figures and 6 page sup. with 5 figures and 1 tabl
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