Do product market regulations in upstream sectors curb productivity growth? Panel data evidence for OECD countries

The paper focuses on the influence of upstream competition for productivity outcomes in downstream sectors. This relation is illustrated with a neo-Schumpeterian theoretical model of innovation (Aghion et al., 1997) with market imperfections in the production of intermediate goods. In this context, upstream market imperfections create barriers to competition in downstream markets and upstream producers use their market power to share innovation rents sought by downstream firms. Thus, lack of competition in upstream markets curbs incentives to improve productivity downstream, negatively affecting productivity outcomes. We test this prediction by estimating an error correction model that differentiates the potential downstream effects of lack of upstream competition in situations close and far from the global technological frontier. We measure competition upstream with regulatory burden indicators derived from OECD data on sectoral product market regulation and the industry-level efficiency improvement and the distance to frontier variables by means of a multifactor productivity (MFP) index. Panel regressions are run for 15 OECD countries and 20 sectors over the 1985-2007 period with country, sector and year fixed effects. We find clear evidence that anticompetitive regulations in upstream sectors have curbed MFP growth downstream over the past 15 years. These effects tend to be strongest for observations (i.e. country/sector/period triads) that are close to the global technological frontier. Our results suggest that, measured at the average distance to frontier and average level of anticompetitive regulations, the marginal effect of increasing competition by easing such regulations is to increase MFP growth by between 1 and 1.5 per cent per year in the OECD countries covered by our sample. Our results are robust to changes in the way MFP and the regulatory burden indicators are constructed, as well as to variations in the sample of countries and/or sectors.Productivity, Growth, Regulations, Competition, Catch-up.

Optical Transmittance of a Rice Leaf via Ray Tracing

Optical reflectance from a plant leaf increases in response to stress and disease. Previous studies at the University of Arkansas at Little Rock found that, while the reflectance from a rice leaf increased with increased salinity, reflectance changes could not be used to differentiate one stress or disease from another. The objective of this study is to characterize the angular distribution of optical transmittance for a healthy rice leaf using a ray tracing technique and assuming a three-media optical model. The ultimate goal is to relate this distribution to specific plant pathologies. Three rays are traced through the cross section of a healthy rice leaf by applying laws of geometric optics and considering air, cell wall, and chloroplast as media. The angular distribution of transmittance is calculated for each ray trace. Lei is defined as the length of irradiated upper epidermal surface leading to a continuous transmittance Tbi(0) at the bottom surface. The total transmittance is defined as the sum over i of Tbi(theta). Delta thetai is defined as the angle over which Tbi(theta) extends and (thetaj - thetai) is defined as the angular difference between the bisector of Delta thetai and the bisector of Delta thetaj. The probability density functions pdf(Delta theta) and pdf(thetaj -thetai) are defined and shown to have diagnostic potential

Pump frequency resonances for light-induced incipient superconductivity in YBa2_2Cu3_3O6.5_{6.5}

Optical excitation in the cuprates has been shown to induce transient superconducting correlations above the thermodynamic transition temperature, $T_C$, as evidenced by the terahertz frequency optical properties in the non-equilibrium state. In YBa$_2$Cu$_3$O$_{6+x}$ this phenomenon has so far been associated with the nonlinear excitation of certain lattice modes and the creation of new crystal structures. In other compounds, like La$_{2-x}$Ba$_x$CuO$_4$, similar effects were reported also for excitation at near infrared frequencies, and were interpreted as a signature of the melting of competing orders. However, to date it has not been possible to systematically tune the pump frequency widely in any one compound, to comprehensively compare the frequency dependent photo-susceptibility for this phenomenon. Here, we make use of a newly developed optical parametric amplifier, which generates widely tunable high intensity femtosecond pulses, to excite YBa$_2$Cu$_3$O$_{6.5}$ throughout the entire optical spectrum (3 - 750 THz). In the far-infrared region (3 - 25 THz), signatures of non-equilibrium superconductivity are induced only for excitation of the 16.4 THz and 19.2 THz vibrational modes that drive $c$-axis apical oxygen atomic positions. For higher driving frequencies (25 - 750 THz), a second resonance is observed around the charge transfer band edge at ~350 THz. These observations highlight the importance of coupling to the electronic structure of the CuO$_2$ planes, either mediated by a phonon or by charge transfer.Comment: 47 pages, 21 figures, 2 table

Dynamical decoherence of the light induced interlayer coupling in YBa2_{2}Cu3_{3}O6+δ_{6+\delta}

Optical excitation of apical oxygen vibrations in YBa$_{2}$Cu$_{3}$O$_{6+\delta}$ has been shown to enhance its c-axis superconducting-phase rigidity, as evidenced by a transient blue shift of the equilibrium inter-bilayer Josephson plasma resonance. Surprisingly, a transient c-axis plasma mode could also be induced above T$_{c}$ by the same apical oxygen excitation, suggesting light activated superfluid tunneling throughout the pseudogap phase of YBa$_{2}$Cu$_{3}$O$_{6+\delta}$. However, despite the similarities between the above T$_{c}$ transient plasma mode and the equilibrium Josephson plasmon, alternative explanations involving high mobility quasiparticle transport should be considered. Here, we report an extensive study of the relaxation of the light-induced plasmon into the equilibrium incoherent phase. These new experiments allow for a critical assessment of the nature of this mode. We determine that the transient plasma relaxes through a collapse of its coherence length rather than its carrier (or superfluid) density. These observations are not easily reconciled with quasiparticle interlayer transport, and rather support transient superfluid tunneling as the origin of the light-induced interlayer coupling in YBa$_{2}$Cu$_{3}$O$_{6+\delta}$.Comment: 27 pages (17 pages main text, 10 pages supplementary), 5 figures (main text

The Stat3-Fam3a axis promotes muscle stem cell myogenic lineage progression by inducing mitochondrial respiration.

Metabolic reprogramming is an active regulator of stem cell fate choices, and successful stem cell differentiation in different compartments requires the induction of oxidative phosphorylation. However, the mechanisms that promote mitochondrial respiration during stem cell differentiation are poorly understood. Here we demonstrate that Stat3 promotes muscle stem cell myogenic lineage progression by stimulating mitochondrial respiration in mice. We identify Fam3a, a cytokine-like protein, as a major Stat3 downstream effector in muscle stem cells. We demonstrate that Fam3a is required for muscle stem cell commitment and skeletal muscle development. We show that myogenic cells secrete Fam3a, and exposure of Stat3-ablated muscle stem cells to recombinant Fam3a in vitro and in vivo rescues their defects in mitochondrial respiration and myogenic commitment. Together, these findings indicate that Fam3a is a Stat3-regulated secreted factor that promotes muscle stem cell oxidative metabolism and differentiation, and suggests that Fam3a is a potential tool to modulate cell fate choices

Infrared study of the charge-ordered multiferroic LuFe(2)O(4)

The reflectivity of a large LuFe(2)O(4) single crystal has been measured with the radiation field either perpendicular or parallel to the c axis of its rhombohedral structure, from 10 to 500K, and from 7 to 16000 cm-1. The transition between the two-dimensional and the three-dimensional charge order at T_(CO) = 320 K is found to change dramatically the phonon spectrum in both polarizations. The number of the observed modes above and below T_(CO), according to a factor-group analysis, is in good agreement with a transition from the rhombohedral space group R{bar 3}m to the monoclinic C2/m. In the sub-THz region a peak becomes evident at low temperature, whose origin is discussed in relation with previous experiments.Comment: Physical Review B in pres

The ATLAS discovery potential for MSSM neutral Higgs bosons decaying to a mu+mu- pair in the mass range up to 130 GeV

Results are presented on the discovery potential for MSSM neutral Higgs bosons in the Mh-{max}scenario. The region of large tan beta, between 15 and 50, and mass between ~ 95 and 130 GeV is considered in the framework of the ATLAS experiment at the Large Hadron Collider (LHC), for a centre-of-mass energy = 14 TeV. This parameter region is not fully covered by the present data either from LEP or from Tevatron. The h/A bosons, supposed to be very close in mass in that region, are studied in the channel h/A -> mu+mu- accompanied by two b-jets. The study includes a method to control the most copious background, Zo -> mu+mu- accompanied by two b-jets. A possible contribution of the H boson to the signal is also considered

Theory for Anomalous Terahertz Emission in Striped Cuprate Superconductors

Recent experiments in the doped cuprates La2−xBaxCuO4 have revealed the emission of anomalous terahertz radiation after impulsive optical excitation. The spectrum of this emission is sharply peaked in frequency at the Josephson plasma resonance. Notably, a prerequisite to this effect is that both superconducting and charge orders are present simultaneously. Here, we theoretically investigate the nonlinear electrodynamics of such striped superconductors and explore the origin of the observed radiation. We argue that photoexcitation is converted into a shift current by a second-order optical nonlinearity, which is activated by the breaking of inversion symmetry in certain stripe configurations. While such a low-frequency current impulsively drives both bulk and surface collective modes, we demonstrate that the observed emission is dominated by oscillations of the surface Josephson plasmon. Typically, surface excitations lie outside the light cone and are therefore silent; however, they can become bright due to the Bragg scattering off the charge order. We point out the importance of including Umklapp shift currents modulated at the stripe periodicity itself, which impulsively drive surface Josephson plasmons and lead to a resonant structure of outgoing radiation, consistent with the experiments