Wassily Leontief and Léon Walras: the Production as a Circular Flow

Leontief’s input-output models are usually viewed as simplified classical (neo-Ricardian) models. However, this interpretation hides two opposed views. On the one hand, the common interpretation, based on Koopmans and Samuelson’s works, considers the so-called “models of Leontief” as simplified Ricardian models, in the sense of Samuelson, which are shown to be special cases of general equilibrium theory. In their framework, general equilibrium theory might be interpreted as a generalized model of Leontief and, reversely, models of Leontief are simplified Walrasian general equilibrium models. According to this theoretical tradition, classical theory and Walrasian general equilibrium theory are intimately linked and Classical economics is an “archaic” general equilibrium theory. On the other hand, neo-Ricardians view models of Leontief as simplified classical models that are incompatible with Walras’ general equilibrium theory. Our paper examines in details the last argument: the incompatibility argument. Such a work will require to examine in details the definition of vague categories as "Walrasian", "Classical" and so forth. We show that incompatibility between models of Leontief and Walras’ general equilibrium theory is ultimately based on Sraffa’s worldview: “The connection of [my] work with the theories of the old classical economists has been alluded to in the preface... It is of course in Quesnay’s Tableau Economique that is found the original picture of the system of production and consumption as a circular process, and it stands in striking contrast to the view presented by modern theory of a one-way avenue that leads from ‘Factors of production’ to ‘Consumption goods’.” (Sraffa, 1960) Neo-Ricardian’s opposition between classical economics and Walrasian theory is based on the representation of production: classical economics refers to circular flow while Marginalist theory refers to a one-way avenue production process. As it makes a sharp distinction between the two theoretical traditions, we call this criterion "Sraffa’s Guillotine". Based on Leontief’s PhD dissertation (1928) and his early input-output model (1937), the main result of our inquiry is that this criterion is powerless to distinguish Leontief’s representation of production as a circular flow and Walras one. Indeed, while Leontief based his models on Marx’ reproduction scheme, his representation of production is the same than Walras’ complete one, in striking contrast with neo-Ricardian critical apparatus. Hence we argue in favor of a pluralist interpretation of the models of Leontief: both Classical and Walrasians.Walras, Sraffa, Leontief, input-output analysis, Marx, production, non substitution theorem, general equilibrium theory

On the Decades-Long Stability of the Interstellar Wind through the Solar System

We have revisited the series of observations recently used to infer a temporal variation of the interstellar helium flow over the last forty years. Concerning the recent IBEX-Lo direct detection of Helium neutrals, there are two types of precise and unambiguous measurements which do not rely on the exact response of the instrument: the count rate maxima as a function of the spin angle, which determines the ecliptic latitude of the flow, and the count rate maxima as a function of IBEX longitude, which determines a tight relationship between the ecliptic longitude of the flow and its velocity far from the Sun. These measurements provide parameters (and couples of parameters in the second case) remarkably similar to the canonical, old values. In contrast, the preferential choice of a lower velocity and higher longitude reported before from IBEX data is based only on the count rate variation (at each spin phase maximum) as a function of the satellite longitude, when drifting across the region of high fluxes. We have examined the consequences of dead time counting effects, and conclude that their inclusion at a realistic level is sufficient to reconcile the data with the old parameters, calling for further investigations. We discuss the analyses of the STEREO pickup ion (PUI) data and argue that the statistical method that has been preferred to infer the neutral flow longitude (instead of the more direct method based on the PUI maximum flux directions), is not appropriate. Moreover, transport effects may have been significant at the very weak solar activity level of 2007-2009, in which case the longitudes of the PUI maxima are only upper limits on the flow longitude. Finally, we found that the use of some flow longitude determinations based on UV glow data are not adequate. At variance with recent conclusions we find no evidence for a temporal variability of the interstellar helium flow.Comment: 8 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

Aditional Ultra-High-Resolution Observations of Ca+ Ions in the Local Insterstellar Medium

We present ultra-high-resolution (0.35 km s−1 FWHM) observations of the interstellar Ca K line towards seven nearby stars. The spectral resolution was sufficient to resolve the line profiles fully, thereby enabling us to detect hitherto unresolved velocity components, and to obtain accurate measurements of the velocity dispersions (b values). Absorption components with velocities similar to those expected for the Local Interstellar Cloud (LIC) and the closely associated ‘G cloud’ were identified towards six of the seven stars. However, in most cases the b values deduced for these components were significantly larger than the b ≈ 2.2 km s−1 (i.e. Tk ≈ 7000 K, vt ≈ 1 km s−1) expected for the LIC, and it is argued that this results from the presence of additional, spectrally unresolved, components having similar velocities and physical conditions. For two stars (δ Vel and α Pav) we detect interstellar components with much smaller b values (1.1 ± 0.3 and 0.8 ± 0.1 km s−1, respectively) than are expected for low-density clouds within the Local Bubble. In the case of the narrow α Pav component, we also find an anomalously large Na i/Ca ii column density ratio, which is indicative of a relatively high density. Thus it is possible that, in addition to LIC-type clouds, the local interstellar medium contains a population of previously undetected cooler and denser interstellar clouds

Microstructure of the Local Interstellar Cloud and the Identification of the Hyades Cloud

We analyze high-resolution UV spectra of the Mg II h and k lines for 18 members of the Hyades Cluster to study inhomogeneity along these proximate lines of sight. The observations were taken by the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope (HST). Three distinct velocity components are observed. All 18 lines of sight show absorption by the Local Interstellar Cloud (LIC), ten stars show absorption by an additional cloud, which we name the Hyades Cloud, and one star exhibits a third absorption component. The LIC absorption is observed at a lower radial velocity than predicted by the LIC velocity vector derived by Lallement & Bertin (1992) and Lallement et al. (1995), (v(predicted LIC) - v(observed LIC) = 2.9 +/- 0.7 km/s), which may indicate a compression or deceleration at the leading edge of the LIC. We propose an extention of the Hyades Cloud boundary based on previous HST observations of other stars in the general vicinity of the Hyades, as well as ground-based Ca II observations. We present our fits of the interstellar parameters for each absorption component. The availability of 18 similar lines of sight provides an excellent opportunity to study the inhomogeneity of the warm, partially ionized local interstellar medium (LISM). We find that these structures are roughly homogeneous. The measured Mg II column densities do not vary by more than a factor of 2 for angular separations of < 8 degrees, which at the outer edge of the LIC correspond to physical separations of < 0.6 pc.Comment: 35 pages, 11 figures, AASTEX v.5.0 plus EPSF extensions in mkfig.sty; accepted by Ap

Automated measurements of diffuse interstellar bands in early-type star spectra Correlations with the Color Excess

Stellar spectroscopic surveys may bring useful statistical information on the links between Diffuse Interstellar Bands (DIBs) and interstellar environment. DIB databases can also be used as a complementary tool for locating interstellar (IS) clouds. Our goal is to develop fully automated methods of DIB measurements to be applied to extensive data from stellar surveys. We present a method appropriate for early-type nearby stars, its application to high-resolution spectra of 130 targets recorded with ESO FEROS spectrograph, and comparisons with other determinations. Using a DIB average profile deduced from the most reddened stars, we performed an automated fitting of a combination of a smooth stellar continuum, the DIB profile, and, when necessary, a synthetic telluric transmission. Measurements are presented for 16 DIBs in the optical domain that could be extracted automatically: 4726.8, 4762.6, 4963.9, 5780.4, 5797.1, 5849.8, 6089.8, 6196.0, 6203.0-6204.5, 6269.8, 6283.8, 6379.3, 6445.3, 6613.6, 6660.7, and 6699.3 {\AA}.Comment: (A&A accepted

L’institution au prisme de la relation

La notion d’institution possède une longue et riche carrière en sciences sociales. Pour diverses raisons, elle a perdu du crédit en sociologie ces dernières années. En marchant sur les brisées d’Émile Durkheim, mais à l’écart néanmoins de toute tentation déterministe, cet article propose de réhabiliter l’institution en tant que processus multipolaire. Le programme relationnel s’avère à cette fin particulièrement heuristique. La décomposition de toute institution en quatre fonctions élémentaires, autonomes et donc potentiellement conflictuelles invite à repenser les faits sociaux les plus variés dans une perspective ouverte et dynamique. À ce titre, l’institution peut se définir comme un ensemble de relations de relations.The notion of institution has a long and rich history in social sciences. For many reasons, it has lost credibility in recent years. In keeping with Émile Durkheim’s work, while steering clear of determinism, this article proposes to rehabilitate the institution in terms of a multi-polar process. In this perspective, the relational program proves itself to be particularly revealing. The decomposition of all institutions into four basic functions which are autonomous and, therefore, potentially conflicting invites us to rethink how we see the varied social processes in an open and dynamic perspective. In this regard, the institution can be defined as a collection of relations of relations

Distance to the northern high-latitude HI shells

A detailed 3D distribution of interstellar matter in the solar neighborhood is increasingly necessary. As part of a 3D mapping program, we aim at assigning a precise distance to the high-latitude HI gas in particular the northern part (b \geq 55^{circ}) of the shell associated with the conspicuous radio continuum Loop I. This shell is thought to be the expanding boundary of an interstellar bubble inflated and recently reheated by the strong stellar winds of the nearby Scorpius-Centaurus OB. We recorded high-resolution spectra of 30 A-type target stars located at various distances in the direction of the northern part of Loop I. Interstellar NaI 5889-5895 and CaII K-H 3934-3968 {\AA} are modeled and compared with the HI emission spectra from the LAB Survey. About two-thirds of our stellar spectra possess narrow interstellar lines. Narrow lines are located at the velocity of the main, low-velocity Loop 1 HI shell ([-6,+1] km/s in the LSR). Using Hipparcos distances to the target stars, we show that the closest boundary of the b geq+70^{\circ} part of this low-velocity Loop I arch is located at of 98 \pm 6 pc. The corresponding interval for the lower-latitude part (55^{\circ} \leq b \leq 70^{\circ}) is 95-157 pc. However, since the two structures are apparently connected, the lower limit is more likely. At variance with this shell, the second HI structure, which is characterized by LSR Doppler velocities centered at -30 km/s, is NOT detected in any of the optical spectra. It is located beyond 200 parsecs or totally depleted in NaI and CaII. We discuss these results in the light of spherical expanding shells and show that they are difficult to reconcile with simple geometries and a nearby shell center close to the Plane. Instead, this high-latitude gas seems to extend the inclined local chimney wall to high distances from the Plane.Comment: Astronomy & Astrophysics (A&A in press

A catalog of 1.5273 micron diffuse interstellar bands based on APOGEE hot telluric calibrators

High resolution stellar spectroscopic surveys provide massive amounts of diffuse interstellar bands (DIBs) measurements. Data can be used to study the distribution of the DIB carriers and those environmental conditions that favor their formation. In parallel, recent studies have also proved that DIBs extracted from stellar spectra constitute new tools for building the 3D structure of the Galactic Interstellar Medium (ISM). The amount of details on the structure depends directly on the quantity of available lines of sight (LOS). Therefore there is a need to construct databases of high-quality DIB measurements as large as possible. We aim at providing the community with a catalog of high-quality measurements of the 1.5273 micron DIB towards a large fraction of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) hot stars observed to correct for the telluric absorption and not used for ISM studies so far. This catalog would complement the extensive database recently extracted from the APOGEE observations and used for 3D ISM mapping. We devised a method to fit the stellar continuum of the hot calibration stars and extracted the DIB from the normalized spectrum. Severe selection criteria based on the absorption characteristics are applied to the results. In particular limiting constraints on the DIB widths and Doppler shifts are deduced from the HI 21 cm measurements, following a new technique of decomposition of the emission spectra. From ~16 000 available hot telluric spectra we have extracted ~ 6700 DIB measurements and their associated uncertainties. The statistical properties of the extracted absorptions are examined and our selection criteria are shown to provide a robust dataset. The resulting catalog contains the DIB total equivalent widths, central wavelengths and widths. We briefly illustrate its potential use for the stellar and interstellar communities.Comment: The Astrophysical Journal Supplement, in press, 35 pages, 14 figure

An Experimental Investigation of Hot Machining with Induction to Improve Ti-5553 Machinability

The manufacturing of aeronautic parts with high mechanical properties requires the use of high performance materials. That’s why; new materials are used for landing gears such as the titanium alloy Ti-5553. The machining of this material leads to high cutting forces and temperatures, and poor machinability which requires the use of low cutting conditions. In order to increase the productivity rate, one solution could be to raise the workpiece initial temperature. Assisted hot machining consists in heating the workpiece material before the material removal takes place, in order to weaken the material mechanical properties, and thus reducing at least the cutting forces. First, a bibliography review has been done in order to determine all heating instruments used and the thermal alleviation that exists on conventional materials. An induction assisted hot machining was chosen and a system capable to maintain a constant temperature into the workpiece during machining (turning) was designed. Trails permit to identify the variation of cutting forces according to the initial temperature of the workpiece, with fixed cutting conditions according to the TMP (Tool-Material-Pair) methodology at ambient temperature. Tool life and deterioration mode are identified notably. The results analysis shows a low reduction of specific cutting forces for a temperature area compatible with industrial process. The reduction is more important at elevated temperature. However, it has consequences on quality of the workpiece surface and tool wear