3,753 research outputs found
An Administrative Meter Maid: Using Inter Partes Review and Post-Grant Review to Curb Exclusivity Parking via the Failure to Market Provision of the Hatch-Waxman Act
Congress created the unique Hatch-Waxman framework in 1984 to increase the availability of low-cost generic drugs while preserving patent incentives for new drug development. The Hatch-Waxman Act rewards generic drug companies that successfully challenge a pharmaceutical patent: 180 days of market exclusivity before any other generic firm can enter the market. When a generic firm obtains this reward, sometimes drug developers agree to pay generic firms to delay entering the market. These pay-for-delay agreements give rise to exclusivity parking and run counter to congressional intent by delaying full generic drug competition. The Medicare Prescription Drug, Improvement, and Modernization Act created several statutory forfeiture provisions that proved only marginally effective at curbing the practice of exclusivity parking. More recently, Congress created new quasi-judicial administrative proceedings that effectively replace certain kinds of district court patent litigation. This Note describes the complex statutory scheme that gave rise to exclusivity parking, explains why previous and current attempts to curtail exclusivity parking were and remain ineffective, and suggests amending the âfailure to marketâ provision to include these new administrative proceedings as a way to help curb exclusivity parking
Heisenberg antiferromagnet with anisotropic exchange on the Kagome lattice: Description of the magnetic properties of volborthite
We study the properties of the Heisenberg antiferromagnet with spatially
anisotropic nearest-neighbour exchange couplings on the kagome net, i.e. with
coupling J in one lattice direction and couplings J' along the other two
directions. For J/J' > 1, this model is believed to describe the magnetic
properties of the mineral volborthite. In the classical limit, it exhibits two
kinds of ground states: a ferrimagnetic state for J/J' < 1/2 and a large
manifold of canted spin states for J/J' > 1/2. To include quantum effects
self-consistently, we investigate the Sp(N) symmetric generalisation of the
original SU(2) symmetric model in the large-N limit. In addition to the
dependence on the anisotropy, the Sp(N) symmetric model depends on a parameter
kappa that measures the importance of quantum effects. Our numerical
calculations reveal that in the kappa-J/J' plane, the system shows a rich phase
diagram containing a ferrimagnetic phase, an incommensurate phase, and a
decoupled chain phase, the latter two with short- and long-range order. We
corroborate these results by showing that the boundaries between the various
phases and several other features of the Sp(N) phase diagram can be determined
by analytical calculations. Finally, the application of a block-spin
perturbation expansion to the trimerised version of the original spin-1/2 model
leads us to suggest that in the limit of strong anisotropy, J/J' >> 1, the
ground state of the original model is a collinearly ordered antiferromagnet,
which is separated from the incommensurate state by a quantum phase transition.Comment: 21 pages, 22 figures. Final version, PRB in pres
Spatially anisotropic Heisenberg Kagome antiferromagnet
In the search for spin-1/2 kagome antiferromagnets, the mineral volborthite
has recently been the subject of experimental studies [Hiroi et al.,2001]. It
has been suggested that the magnetic properties of this material are described
by a spin-1/2 Heisenberg model on the kagome lattice with spatially anisotropic
exchange couplings. We report on investigations of the Sp(N) symmetric
generalisation of this model in the large N limit. We obtain a detailed
description of the dependence of possible ground states on the anisotropy and
on the spin length S. A fairly rich phase diagram with a ferrimagnetic phase,
incommensurate phases with and without long range order and a decoupled chain
phase emerges.Comment: 6 pages, 6 figures, proceedings of the HFM2006 conference, to appear
in a special issue of J. Phys.: Condens. Matte
Renormalization-group analysis of the one-dimensional extended Hubbard model with a single impurity
We analyze the one-dimensional extended Hubbard model with a single static
impurity by using a computational technique based on the functional
renormalization group. This extends previous work for spinless fermions to
spin-1/2 fermions. The underlying approximations are devised for weak
interactions and arbitrary impurity strengths, and have been checked by
comparing with density-matrix renormalization-group data. We present results
for the density of states, the density profile and the linear conductance.
Two-particle backscattering leads to striking effects, which are not captured
if the bulk system is approximated by its low-energy fixed point, the Luttinger
model. In particular, the expected decrease of spectral weight near the
impurity and of the conductance at low energy scales is often preceded by a
pronounced increase, and the asymptotic power laws are modified by logarithmic
corrections.Comment: 36 pages, 13 figures, revised version as publishe
Disorder Effects in Fluctuating One-Dimensional Interacting Systems
The zero temperature localization of interacting electrons coupled to a
two-dimensional quenched random potential, and constrained to move on a
fluctuating one-dimensional string embedded in the disordered plane, is studied
using a perturbative renormalization group approach. In the reference frame of
the electrons the impurities are dynamical and their localizing effect is
expected to decrease. We consider several models for the string dynamics and
find that while the extent of the delocalized regime indeed grows with the
degree of string fluctuations, the critical interaction strength, which
determines the localization-delocalization transition for infinitesimal
disorder,does not change unless the fluctuations are softer than those of a
simple elastic string.Comment: 15 page
Heat conduction and Wiedemann-Franz Law in disordered Luttinger Liquids
We consider heat transport in a Luttinger liquid (LL) with weak disorder and
study the Lorenz number for this system. We start at a high- regime, and
calculate both the electrical and thermal conductivities using a memory
function approach. The resulting Lorenz number is independent of but
depends explicitly on the LL exponents. Lowering , however, allows for a
renormalization of the LL exponents from their bare values by disorder, causing
a violation of the Wiedemann-Franz law. Finally, we extend the discussion to
quantum wire systems and study the wire size dependence of the Lorenz number.Comment: 4 pages, 1 eps figure; Changes made to address Referees' comment
Emissions of Volatile Organic Compounds Inferred From Airborne Flux Measurements over a Megacity
Toluene and benzene are used for assessing the ability to measure disjunct eddy covariance (DEC) fluxes of Volatile Organic Compounds (VOC) using Proton Transfer Reaction Mass Spectrometry (PTR-MS) on aircraft. Statistically significant correlation between vertical wind speed and mixing ratios suggests that airborne VOC eddy covariance (EC) flux measurements using PTR-MS are feasible. City-median midday toluene and benzene fluxes are calculated to be on the order of 14.1&plusmn;4.0 mg/m<sup>2</sup>/h and 4.7&plusmn;2.3 mg/m<sup>2</sup>/h, respectively. For comparison the adjusted CAM2004 emission inventory estimates toluene fluxes of 10 mg/m<sup>2</sup>/h along the footprint of the flight-track. Wavelet analysis of instantaneous toluene and benzene measurements during city overpasses is tested as a tool to assess surface emission heterogeneity. High toluene to benzene flux ratios above an industrial district (e.g. 10â15 g/g) including the International airport (e.g. 3â5 g/g) and a mean flux (concentration) ratio of 3.2&plusmn;0.5 g/g (3.9&plusmn;0.3 g/g) across Mexico City indicate that evaporative fuel and industrial emissions play an important role for the prevalence of aromatic compounds. Based on a tracer model, which was constrained by BTEX (BTEXâ Benzene/Toluene/Ethylbenzene/m, p, o-Xylenes) compound concentration ratios, the fuel marker methyl-tertiary-butyl-ether (MTBE) and the biomass burning marker acetonitrile (CH<sub>3</sub>CN), we show that a combination of industrial, evaporative fuel, and exhaust emissions account for >87% of all BTEX sources. Our observations suggest that biomass burning emissions play a minor role for the abundance of BTEX compounds in the MCMA (2â13%)
Delocalization in Coupled Luttinger Liquids with Impurities
We study effects of quenched disorder on coupled two-dimensional arrays of
Luttinger liquids (LL) as a model for stripes in high-T_c compounds. In the
framework of a renormalization-group analysis, we find that weak inter-LL
charge-density-wave couplings are always irrelevant as opposed to the pure
system. By varying either disorder strength, intra- or inter-LL interactions,
the system can undergo a delocalization transition between an insulator and a
novel strongly anisotropic metallic state with LL-like transport. This state is
characterized by short-ranged charge-density-wave order, the superconducting
order is quasi long-ranged along the stripes and short-ranged in the
transversal direction.Comment: 6 pages, 5 figures, substantially extended and revised versio
Dynamics of a large spin with weak dissipation
We investigate the generalization of the spin-boson model to arbitrary spin
size. The Born-Markov approximation is employed to derive a master equation in
the regime of small coupling strengths to the environment. For spin one half,
the master equation transforms into a set of Bloch equations, the solution of
which is in good agreement with results of the spin-boson model for weak ohmic
dissipation. For larger spins, we find a superradiance-like behavior known from
the Dicke model. The influence of the nonresonant bosons of the dissipative
environment can lead to the formation of a beat pattern in the dynamics of the
-component of the spin. The beat frequency is approximately proportional to
the cutoff of the spectral function.Comment: 11 pages, 3 figures, to appear in Chemical Physics Special Issue on
the Spin-Boson Problem, ed. by H. Grabert and A. Nitza
Monte Carlo Simulation of the Heisenberg Antiferromagnet on a Triangular Lattice: Topological Excitations
We have simulated the classical Heisenberg antiferromagnet on a triangular
lattice using a local Monte Carlo algorithm. The behavior of the correlation
length , the susceptibility at the ordering wavevector , and
the spin stiffness clearly reflects the existence of two temperature
regimes -- a high temperature regime , in which the disordering
effect of vortices is dominant, and a low temperature regime ,
where correlations are controlled by small amplitude spin fluctuations. As has
previously been shown, in the last regime, the behavior of the above quantities
agrees well with the predictions of a renormalization group treatment of the
appropriate nonlinear sigma model. For , a satisfactory fit of the
data is achieved, if the temperature dependence of and is
assumed to be of the form predicted by the Kosterlitz--Thouless theory.
Surprisingly, the crossover between the two regimes appears to happen in a very
narrow temperature interval around .Comment: 13 pages, 8 Postscript figure
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