Quantum limits in interferometric measurements

Quantum noise limits the sensitivity of interferometric measurements. It is generally admitted that it leads to an ultimate sensitivity, the ``standard quantum limit''. Using a semi-classical analysis of quantum noise, we show that a judicious use of squeezed states allows one in principle to push the sensitivity beyond this limit. This general method could be applied to large scale interferometers designed for gravitational wave detection.Comment: 4 page

Modelling Transition And International Opening In Asia: The Case Of Vietnam With A Comparison With China And The "Asian Tigers"

This paper describes the multisectoral macroeconomic model of a small developing economy in transition, in order to highlight linkages between agriculture and the rest of the economy, and consequences of external opening up. Agriculture is a supply sector, sticky in the short range with market clearing by price adjustment. The non agricultural sector is demand-led, with imperfect competition (and hence sticky prices and indexed nominal wages). According to this dual theoretical pattern, labor market is segmented with an unlimited supply in the rural area. This part of labor force is employed in the agricultural sector and in the rural non agricultural one. Urban workers are employed in the non agricultural sector but may face unemployment. The wage gap between urban and ruralareas induces migration, according to a Harris Todaro mechanism. This framework is applied to the Vietnam case. A calibrated quantitative model performs a base line simulation from 1993 to 2010, following approximately the path designed by the Vietnamese government. Finally, this model is used to sketch various scenarios, among which traditional macroeconomic packages, structural reforms, and external shocks.Vietnam; multisectoral models; development; transition

About the Portability of the DIDASS-Package (an IBM Implementation)

The aim of this paper is to point out the portability of the program package for linear multiple criteria reference point optimization. This should be understood as a step to improve the user-oriented feature of software developed at IIASA and can be an example for further implementations of the software on other computer systems. The actual reason for transferring the DIDASS-package to INSEE is the need for solving problems of medium- and long-term planning for the national economy of France which can be described by dynamic multiple-criteria linear programming models. This paper is an initial note on implementation problems. As soon as there is substantive application in INSEE it will be reported. We first describe the implementation problems, then the solutions and an hypothetical example to demonstrate the workability of the software

Elimination of systematic errors in two-mode laser telemetry

4p.International audienceWe present a simple two-mode telemetry procedure which eliminates cyclic errors, to allow accurate absolute distance measurements. We show that phase drifts and cyclic errors are suppressed using a fast polarization switch that exchanges the roles of the reference and measurement paths. Preliminary measurements obtained using this novel design show a measurement stability better than 1 micron. Sources of residual noise and systematic errors are identified, and we expect that an improved but still simple version of the apparatus will allow accuracies in the nanometre range for absolute measurements of kilometre-scale distances

Enhanced spontaneous activity of the mu opioid receptor by cysteine mutations: characterization of a tool for inverse agonist screening.

BACKGROUND: The concept of spontaneous- or constitutive-activity has become widely accepted and verified for numerous G protein-coupled receptors and this ligand-independent activity is also acknowledged to play a role in some pathologies. Constitutive activity has been reported for the mu opioid receptor. In some cases the increase in receptor basal activity was induced by chronic morphine administration suggesting that constitutive activity may contribute to the development of drug tolerance and dependence. Constitutively active mutants represent excellent tools for gathering information about the mechanisms of receptor activation and the possible physiological relevance of spontaneous receptor activity. The high basal level of activity of these mutants also allows for easier identification of inverse agonists, defined as ligands able to suppress spontaneous receptor activity, and leads to a better comprehension of their modulatory effects as well as possible in vivo use. RESULTS: Cysteines 348 and 353 of the human mu opioid receptor (hMOR) were mutated into alanines and Ala(348,353 )hMOR was stably expressed in HEK 293 cells. [(35)S] GTPγS binding experiments revealed that Ala(348,353 )hMOR basal activity was significantly higher when compared to hMOR, suggesting that the mutant receptor is constitutively active. [(35)S] GTPγS binding was decreased by cyprodime or CTOP indicating that both ligands have inverse agonist properties. All tested agonists exhibited binding affinities higher for Ala(348,353 )hMOR than for hMOR, with the exception of endogenous opioid peptides. Antagonist affinity remained virtually unchanged except for CTOP and cyprodime that bound the double mutant with higher affinities. The agonists DAMGO and morphine showed enhanced potency for the Ala(348,353 )hMOR receptor in [(35)S] GTPγS experiments. Finally, pretreatment with the antagonists naloxone, cyprodime or CTOP significantly increased Ala(348,353 )hMOR expression. CONCLUSION: Taken together our data indicate that the double C348/353A mutation results in a constitutively active conformation of hMOR that is still activated by agonists. This is the first report of a stable CAM of hMOR with the potential to screen for inverse agonists

On the interpretation of Michelson-Morley experiments

Recent proposals for improved optical tests of Special Relativity have renewed interest in the interpretation of such tests. In this paper we discuss the interpretation of modern realizations of the Michelson-Morley experiment in the context of a new model of electrodynamics featuring a vector-valued photon mass. This model is gauge invariant, unlike massive-photon theories based on the Proca equation, and it predicts anisotropy of both the speed of light and the electric field of a point charge. The latter leads to an orientation dependence of the length of solid bodies which must be accounted for when interpreting the results of a Michelson-Morley experiment. Using a simple model of ionic solids we show that, in principle, the effect of orientation dependent length can conspire to cancel the effect of an anisotropic speed of light in a Michelson-Morley experiment, thus, complicating the interpretation of the results.Comment: To appear in Phys.Lett.

ABSOLUTE DISTANCE MEASUREMENTS USING TWO-MODE LASER TELEMETRY

A novel laser ranging method is described that uses a two-mode laser source, and detection of the phase of the return beam. The design eliminates the cyclic error usually associated with phase measurements and provides unambiguous, absolute distance determination. Measurements of an 8m path are obtained at a beat frequency of 13 GHz. We analyse the 1µm stability of the data obtained with this preliminary implementation, and expect that an improved version will allow accuracies well below 1 µm, for the kilometer-scale distances involved in satellite formation flight

IMPLEMENTATION OF TWO TELEMETER DESIGNS FOR HIGH ACCURACY LASER RANGING OF KILOMETER SCALE DISTANCES IN SPACE

We present two different laser ranging systems under development, both based on the use of a high frequency modulated beam. The first range meter makes no use of interferometry: only the phase of the return beam is detected, in a way that rejects cyclic errors due to optical and electronic crosstalk. An Allan deviation slightly better than 10nm has been obtained with this simple system. The other range meter should provide better resolution, at the expense of a somewhat more sophisticated procedure, as it involves both time-of-flight and interferometry measurements