Air services on thin routes: Regional versus low-cost airlines

An examination of the impact in the US and EU markets of two major innovations in the provision of air services on thin routes - regional jet technology and the low-cost business model - reveals significant differences. In the US, regional airlines monopolize a high proportion of thin routes, whereas low-cost carriers are dominant on these routes in Europe. Our results have different implications for business and leisure travelers, given that regional services provide a higher frequency of flights (at the expense of higher fares), while low-cost services offer lower fares (at the expense of lower flight frequencies). Keywords: air transportation; regional jet technology; low-cost business model; thin markets. JEL Classification Numbers: L13; L2; L93.

Nature et historicité : essai sur la philosophie de Herbert Marcuse

Résumé de Thèse Proche de Horkheimer, d'Adorno ou encore de Benjamin, ce philosophe issu de l'École de Francfort ne manque pas moins d'attirer la curiosité. On a tôt fait de classer Herbert Marcuse (1898-1979) aux oubliettes alors que sa pensée était peu connue, nonobstant une médiatisation très importante qui a dépassé le cadre classique des universités. Ce philosophe allemand atypique dont le nom surgit notamment suite à la publication de L'Homme unidimensionnel fut abondamment lu mais peu systématisé. Repris à tort et à travers, instrumentalisé aux temps des révoltes étudiantes des années 60, il ne lègue pas moins une pensée qui doit apparaître sous une forme nouvelle et prospective. Cette recherche vise prioritairement à l'extraire de ce brouhaha qui l'enveloppa et menaça de le faire disparaître. Cet essai insiste sur un retour à l'exigence scientifique via l'exhumation des textes méconnus du grand public et une insertion indispensable dans l'histoire des penseurs philosophiques. Accéder à la connaissance de ce philosophe passe par un certain nombre de clefs parmi lesquelles le concept de nature. Pour y arriver, cependant, la quête des fondements d'une philosophie dont les sources sont plurielles et inconciliables s'impose comme étape primordiale et pleine de promesses. A la vérité, le peu de systématisation de la pensée marcusienne est en grande partie liée à cette « prolifération » de références auxquelles s'est adonné Marcuse, laissant une mince passerelle susceptible de dégager une architecture globale et cohérente de sa pensée. Certes, la présentation de Marcuse est restée jusque-là prisonnière de l'influence de Hegel, Marx et Freud. L'auteur de cette thèse tente de démontrer que la pensée marcusienne s'oriente à partir de Kant. Attaché à la tradition philosophique germanique de l'Aufklärung, l'oeuvre du philosophe francfortois combat toutes sortes d'irrationalités qui obstruent la voie menant vers un humanisme réel. La nature reste un concept polémique parce qu'il ne saurait se résumer à l'étant. Ni la nature intérieure, ni la nature extérieure ne se limitent à cet horizon dépourvu de subjectivité. Disciple de Heidegger, Marcuse définit la nature à partir du Dasein, un être-là qui est jeté dans l'histoire et qui porte en lui la qualité de l'historicité. Contre la société dite unidimensionnelle postindustrielle qui annonce l'acmé du capitalisme triomphant, les travaux de Marcuse visent un retour à la nature autant qu'ils font de celle-ci un futur. La nature n'est pas seulement ce qu'elle a été, elle est aussi ce qui est à être. En invalidant le consumérisme ambiant, il décrit la publicité marchande comme un acte de négation des vraies valeurs humaines. Ni la superfluité secrétée par le marché, ni les systèmes communiste (le marxisme soviétique et ses sbires) et capitaliste ne sont capables de provoquer l'idéal de l'humain. Le discours marcusien fécondé par la « Théorie Critique » invente le concept de « Grand Refus » adossé à la dialectique hégélienne, obligeant la conscience à veiller sur le réel pour le conduire vers l'émancipation plutôt que vers un « chemin qui ne mène nulle part ». Attachée à la concrétude et la transformation historique héritée de Marx, il réoriente le Dasein heideggérien en lui donnant plus de chair. Nature et historicité, cette réalité duelle se complique parce qu'elle incarne une difficile révolution qui nécessitera davantage d'imagination. Le « Grand Refus » aura besoin d'un allié plus subtile : l'esthétique qui laisse apparaître la Troisième critique kantienne. Au-delà de ce refuge dans l'art, on aura toujours besoin de Marcuse pour mieux comprendre nos sociétés en pleine mutation et pour habiter en conséquence notre monde perfectible.

Physicochemical aspects and efficiency of albuterol nebulization: comparison of three aerosol types in an in vitro pediatric model.

BACKGROUND: Advances in nebulizer design have produced both ultrasonic nebulizers and devices based on a vibrating mesh (vibrating mesh nebulizers), which are expected to enhance the efficiency of aerosol drug therapy. The aim of this study was to compare 4 different nebulizers, of 3 different types, in an in vitro model using albuterol delivery and physical characteristics as benchmarks. METHODS: The following nebulizers were tested: Sidestream Disposable jet nebulizer, Multisonic Infra Control ultrasonic nebulizer, and the Aerogen Pro and Aerogen Solo vibrating mesh nebulizers. Aerosol duration, temperature, and drug solution osmolality were measured during nebulization. Albuterol delivery was measured by a high-performance liquid chromatography system with fluorometric detection. The droplet size distribution was analyzed with a laser granulometer. RESULTS: The ultrasonic nebulizer was the fastest device based on the duration of nebulization; the jet nebulizer was the slowest. Solution temperature decreased during nebulization when the jet nebulizer and vibrating mesh nebulizers were used, but it increased with the ultrasonic nebulizer. Osmolality was stable during nebulization with the vibrating mesh nebulizers, but increased with the jet nebulizer and ultrasonic nebulizer, indicating solvent evaporation. Albuterol delivery was 1.6 and 2.3 times higher with the ultrasonic nebulizer and vibrating mesh nebulizers devices, respectively, than with the jet nebulizer. Particle size was significantly higher with the ultrasonic nebulizer. CONCLUSIONS: The in vitro model was effective for comparing nebulizer types, demonstrating important differences between nebulizer types. The new devices, both the ultrasonic nebulizers and vibrating mesh nebulizers, delivered more aerosolized drug than traditional jet nebulizers.

Occupational choice and development

The rise in world trade since 1970 has been accompanied by a rise in the geographic span of control of management and, hence, also a rise in the e ective international mobility of labor services. We study the e ect of such a globalization of the world's labor markets. The world's welfare gains depend positively on the skill-heterogeneity of the world's labor force. We nd that when peoplecan choose between wage work and managerial work, the worldwide labor market raises output by more in the rich and the poor countries, and by less in the middle-income countries. This is because the middle-income countries experience the smallest change in the factor-price ratio, and where the option to choose between wage work and managerial work has the least value in the integratedeconomy. Our theory also establishes that after economic integration, the high skill countries see a disproportionate increase in managerial occupations. Using aggregate data on GDP, openness and occupations from 115 countries, we find evidence for these patterns of occupational choice.

On forward induction and evolutionary and strategic stability

We analyze which normal form solution concepts capture the notion offorward induction, as defined by van Damme (JET, 1989) in the classof generic two player normal form games preceded by an outsideoption. We find that none of the known strategic stability concepts(including Mertens stable sets and hyperstable sets) captures this form of forward induction. On the other hand, we show that the evolutionary concept of EES set (Swinkels, JET, 1992) is always consistent with forward induction.

Neurologie et voyages

Le mal de voyage, l'insomnie, les troubles du sommeil, la fatigue, le jet-lag et des troubles sensitifs transitoires sont des symptômes très fréquents lors des voyages et pour la plupart banals. Les maladies neurologiques déclenchées ou causées par le voyage sont rares et incluent des accidents vasculaires cérébraux (AVC) liés aux emboles paradoxaux après un voyage prolongé en avion, des crises d'épilepsie ou des troubles du sommeil déclenchés par le décalage horaire, des symptômes de décompression lors de la plongée ou montée en altitude. Dans cet article sont aussi discutées les maladies liées à la haute altitude(céphalée de haute altitude, mal aigu des montagnes), des troubles neurologiques liés à la déshydratation et à la chaleur ainsi que les infections acquises lors de voyages.

Electromagnetic radiation initiated by hadronic jets from microquasars in the ISM

Microquasars are potential candidates to produce a non-negligible fraction of the observed galactic cosmic rays. The protons accelerated at the jet termination shock interact with the interstellar medium and may produce detectable fluxes of extended emission at different energy bands: high-energy and very high-energy gamma-rays produced by neutral pion-decay, synchrotron and bremsstrahlung emission in a wide energy range generated by the secondary electrons produced by charged pion-decay. We discuss the association between this scenario and some of the unidentified EGRET sources in the galactic plane.

A numerical model for the gamma-ray emission of the microquasar LS 5039

The possible association between the microquasar LS 5039 and the EGRET source 3EG J1824-1514 suggests that microquasars could also be sources of high energy gamma-rays. In this paper, we explore, with a detailed numerical model, if this system can produce the emission detected by EGRET (>100 MeV) through inverse Compton (IC) scattering. Our numerical approach considers a population of relativistic electrons entrained in a cylindrical inhomogeneous jet, interacting with both the radiation and the magnetic fields, taking into account the Thomson and Klein-Nishina regimes of interaction. The computed spectrum reproduces the observed spectral characteristics at very high energy.

A search for microquasar candidates at low galactic latitudes

Recent studies of relativistic jet sources in the Galaxy, also known as microquasars, have been very useful in trying to understand the accretion/ejection processes that take place near compact objects. However, the number of sources involved in such studies is still small. In an attempt to increase the number of known microquasars we have carried out a search for new Radio Emitting X-ray Binaries (REXBs). These sources are the ones to be observed later with VLBI techniques to unveil their possible microquasar nature. To this end, we have performed a cross-identification between the X-ray ROSAT all sky survey Bright Source Catalog (RBSC) and the radio NRAO VLA Sky Survey (NVSS) catalogs under very restrictive selection criteria for sources with |b|<5 degrees. We have also conducted a deep observational radio and optical study for six of the selected candidates. At the end of this process two of the candidates appear to be promising, and deserve additional observations aimed to confirm their proposed microquasar nature.

The extraordinarily bright optical afterglow of GRB 991208 and its host galaxy

Observations of the extraordinarily bright optical afterglow (OA) of GRB 991208 started 2.1 d after the event. The flux decay constant of the OA in the R-band is -2.30 +/- 0.07 up to 5 d, which is very likely due to the jet effect, and after that it is followed by a much steeper decay with constant -3.2 +/- 0.2, the fastest one ever seen in a GRB OA. A negative detection in several all-sky films taken simultaneously to the event implies either a previous additional break prior to 2 d after the occurrence of the GRB (as expected from the jet effect). The existence of a second break might indicate a steepening in the electron spectrum or the superposition of two events. Once the afterglow emission vanished, contribution of a bright underlying SN is found, but the light curve is not sufficiently well sampled to rule out a dust echo explanation. Our determination of z = 0.706 indicates that GRB 991208 is at 3.7 Gpc, implying an isotropic energy release of 1.15 x 10E53 erg which may be relaxed by beaming by a factor > 100. Precise astrometry indicates that the GRB coincides within 0.2' with the host galaxy, thus given support to a massive star origin. The absolute magnitude is M_B = -18.2, well below the knee of the galaxy luminosity function and we derive a star-forming rate of 11.5 +/- 7.1 Mo/yr. The quasi-simultaneous broad-band photometric spectral energy distribution of the afterglow is determined 3.5 day after the burst (Dec 12.0) implying a cooling frequency below the optical band, i.e. supporting a jet model with p = -2.30 as the index of the power-law electron distribution.

High-energy gamma-ray emission from microquasars: LS 5039 and LS I+61303

The possible associations between the microquasars LS 5039 and LS I +61 303 and the EGRET sources 3EG J1824-1514 and 3EG J0241+6103 suggest that microquasars could also be sources of high-energy gamma-rays. In this work, we present a detailed numerical inverse Compton (IC) model, based on a microquasar scenario, that reproduces the high-energy gamma-ray spectra and variability observed by EGRET for the mentioned sources. Our model considers a population of relativistic electrons entrained in a cylindrical inhomogeneous jet that interact through IC scattering with both the radiation and the magnetic fields.

Leptonic secondary emission in a hadronic microquasar model

Context.It has been proposed that the origin of the very high-energy photons emitted from high-mass X-ray binaries with jet-like features, so-called microquasars (MQs), is related to hadronic interactions between relativistic protons in the jet and cold protons of the stellar wind. Leptonic secondary emission should be calculated in a complete hadronic model that includes the effects of pairs from charged pion decays inside the jets and the emission from pairs generated by gamma-ray absorption in the photosphere of the system. Aims.We aim at predicting the broadband spectrum from a general hadronic microquasar model, taking into account the emission from secondaries created by charged pion decay inside the jet. Methods.The particle energy distribution for secondary leptons injected along the jets is consistently derived taking the energy losses into account. The spectral energy distribution resulting from these leptons is calculated after assuming different values of the magnetic field inside the jets. We also compute the spectrum of the gamma-rays produced by neutral pion-decay and processed by electromagnetic cascades under the stellar photon field. Results.We show that the secondary emission can dominate the spectral energy distribution at low energies (~1 MeV). At high energies, the production spectrum can be significantly distorted by the effect of electromagnetic cascades. These effects are phase-dependent, and some variability modulated by the orbital period is predicted.

INTEGRAL and XMM-Newton observations towards the unidentified MeV source GRO J1411-64.

The COMPTEL unidentified source GRO J1411-64 was observed by INTEGRAL, and its central part, also by XMM-Newton. The data analysis shows no hint for new detections at hard X-rays. The upper limits in flux herein presented constrain the energy spectrum of whatever was producing GRO J1411-64, imposing, in the framework of earlier COMPTEL observations, the existence of a peak in power output located somewhere between 300-700 keV for the so-called low state. The Circinus Galaxy is the only source detected within the 4$\sigma$ location error of GRO J1411-64, but can be safely excluded as the possible counterpart: the extrapolation of the energy spectrum is well below the one for GRO J1411-64 at MeV energies. 22 significant sources (likelihood $> 10$) were extracted and analyzed from XMM-Newton data. Only one of these sources, XMMU J141255.6-635932, is spectrally compatible with GRO J1411-64 although the fact the soft X-ray observations do not cover the full extent of the COMPTEL source position uncertainty make an association hard to quantify and thus risky. The unique peak of the power output at high energies (hard X-rays and gamma-rays) resembles that found in the SED seen in blazars or microquasars. However, an analysis using a microquasar model consisting on a magnetized conical jet filled with relativistic electrons which radiate through synchrotron and inverse Compton scattering with star, disk, corona and synchrotron photons shows that it is hard to comply with all observational constrains. This and the non-detection at hard X-rays introduce an a-posteriori question mark upon the physical reality of this source, which is discussed in some detail.