17,730 research outputs found
Scale invariant correlations and the distribution of prime numbers
Negative correlations in the distribution of prime numbers are found to
display a scale invariance. This occurs in conjunction with a nonstationary
behavior. We compare the prime number series to a type of fractional Brownian
motion which incorporates both the scale invariance and the nonstationary
behavior. Interesting discrepancies remain. The scale invariance also appears
to imply the Riemann hypothesis and we study the use of the former as a test of
the latter.Comment: 13 pages, 8 figures, version to appear in J. Phys.
The Impact of Differential Cost Sharing of Non-Steroidal Anti-Inflammatory Agents on the Use and Costs of Analgesic Drugs
OBJECTIVE: To estimate the effect of differential cost sharing (DCS) schemes for non-steroidal anti-inflammatory drugs (NSAIDs) on drug subsidy program and beneficiary expenditures. DATA SOURCES/STUDY SETTING: Monthly aggregate claims data from Pharmacare, the public drug subsidy program for seniors in British Columbia, Canada over the period 1989-11 to 2001-06. STUDY DESIGN: DCS limits insurance reimbursement of a group of therapeutically similar drugs to the cost of the lowest priced drugs, with beneficiaries responsible for costs above the reimbursement limit. Pharmacare introduced two different forms of DCS, generic substitution (GS) and reference pricing (RP), in April 1994 and November 1995, respectively, to the NSAIDs. Under GS, generic and brand versions of the same NSAID are considered interchangeable, whereas under RP different NSAIDs are. We extrapolated average reimbursement per day of NSAID therapy over the months before GS and RP to estimate what expenditures would have been without the policies. These counterfactual predictions were compared to actual values to estimate the impact of the policies; the estimated impacts on reimbursement rates were multiplied by the post-policy volume of NSAIDS dispensed, which appeared unaffected by the policies, to estimate expenditure changes. DATA COLLECTION: The cleaned NSAID claims data, obtained from Pharmacare’s databases, were aggregated by month and by their reimbursement status under the GS and RP policies. PRINCIPAL FINDINGS: After RP, program expenditures declined by 4 million annually, cutting expenditure by half. Most savings accrued from the substitution of low cost NSAIDs for more costly alternatives. About 20% of savings represented expenditures by seniors who elected to pay for partially-reimbursed drugs. GS produced one quarter the savings of RP. CONCLUSIONS: RP of NSAIDs achieved its goal of reducing drug expenditures and was more effective than GS. The effects of RP on patient health and associated health care costs remain to be investigated.Reference pricing; generic substitution; prescription drugs; drug cost containment; NSAIDs.
Path-integral calculation of the third virial coefficient of quantum gases at low temperatures
We derive path-integral expressions for the second and third virial
coefficients of monatomic quantum gases. Unlike previous work that considered
only Boltzmann statistics, we include exchange effects (Bose-Einstein or
Fermi-Dirac statistics). We use state-of-the-art pair and three-body potentials
to calculate the third virial coefficient of 3He and 4He in the temperature
range 2.6-24.5561 K. We obtain uncertainties smaller than those of the limited
experimental data. Inclusion of exchange effects is necessary to obtain
accurate results below about 7 K.Comment: The following article has been accepted by The Journal of Chemical
Physics. After it is published, it will be found at http://jcp.aip.org/
Version 2 includes the corrections detailed in the Erratu
Black hole lasers, a mode analysis
We show that the black hole laser effect discovered by Corley & Jacobson
should be described in terms of frequency eigenmodes that are spatially bound.
The spectrum contains a discrete and finite set of complex frequency modes
which appear in pairs and which encode the laser effect. In addition, it
contains real frequency modes that form a continuous set when space is
infinite, and which are only elastically scattered, i.e., not subject to any
Bogoliubov transformation. The quantization is straightforward, but the
calculation of the asymptotic fluxes is rather involved. When the number of
complex frequency modes is small, our expressions differ from those given
earlier. In particular, when the region between the horizons shrinks, there is
a minimal distance under which no complex frequency mode exists, and no
radiation is emitted. Finally, we relate this effect to other dynamical
instabilities found for rotating black holes and in electric fields, and we
give the conditions to get this type of instability.Comment: 19 pages, 3 figures, main changes: new figure and new Sec.6
`conditions for having a laser effect', final version accepted in PR
Ka-band (32-GHz) performance of 70-meter antennas in the Deep Space Network
Two models are provided of the Deep Space Network (DSN) 70 m antenna performance at Ka-band (32 GHz) and, for comparison purposes, one at X-band (8.4 GHz). The baseline 70 m model represents expected X-band and Ka-band performance at the end of the currently ongoing 64 m to 70 m mechanical upgrade. The improved 70 m model represents two sets of Ka-band performance estimates (the X-band performance will not change) based on two separately developed improvement schemes: the first scheme, a mechanical approach, reduces tolerances of the panels and their settings, the reflector structure and subreflector, and the pointing and tracking system. The second, an electronic/mechanical approach, uses an array feed scheme to compensate fo lack of antenna stiffness, and improves panel settings using microwave holographic measuring techniques. Results are preliminary, due to remaining technical and cost uncertainties. However, there do not appear to be any serious difficulties in upgrading the baseline DSN 70 m antenna network to operate efficiently in an improved configuration at 32 GHz (Ka-band). This upgrade can be achieved by a conventional mechanical upgrade or by a mechanical/electronic combination. An electronically compensated array feed system is technically feasible, although it needs to be modeled and demonstrated. Similarly, the mechanical upgrade requires the development and demonstration of panel actuators, sensors, and an optical surveying system
Preliminary results of the Mariner IV radio occultation measurements of the upper atmosphere of Mars
Mariner IV radio occultation measurements of Mars upper atmospher
Preliminary results of the Mariner IV OCCULATION measurement of the atmosphere of Mars
Mariner IV radio occultation measurement of Mars atmospher
Plastic flow of persistent currents in two dimensional strongly interacting systems
The local persistent current in two dimensional strongly interacting systems
is investigated. As the interaction strength is enhanced the current in the
sample undergoes a transition from diffusive to ordered flow. The strong
interacting flow has the characteristics of a plastic flow through dislocations
in the pinned charge density wave which develops in the system at low
densities.Comment: 12 pages, 4 figures, accepted for publication in Phys. Rev. B (RC
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