We rely on a model with incomplete contracts and bargaining power to argue that trade credit (TC) can serve as a commitment device for making relationship-specific investments (RSIs). Unlike existing ...theories, we explain within a single theoretical framework why TC is affected by firms' bargaining power and by the specialized nature of transacted goods. Using a large panel of publicly listed firms and innovation-based proxies for RSI, we find strong support for the model's predictions: TC increases in upstream firm's RSI and downstream firm's market power. Endogeneity concerns are addressed by using the passage of innovation-increasing state laws to instrument for RSI and import penetration to instrument for bargaining power.
The β-Carboline FG-7142 is a partial inverse agonist at the benzodiazepine allosteric site on the GABA-A receptor that induces anxiogenic, proconvulsant, and appetite-reducing effects in many ...species, including humans. Seizure-kindling effects have been well studied, however anxiogenic properties are relatively unexplored. This study aimed to investigate concentration-dependent effects of FG-7142 on anxiety-like behaviour and fear responses in zebrafish (Danio rerio) using the open-field test (OF) and novel object approach test (NOA). A U-shaped distribution was found with maximal responses in increased immobility and reduced distance moved at 10 µM in the NOA but not the OF. Follow up experiments demonstrated a lack of effect in repeated OF testing and no changes in opercular movements. Furthermore, the effect of FG-7142 was reversed with ethanol treatment. These results suggest that FG-7142 elicits a 'freezing' response in zebrafish via the introduction of novelty, suggesting fear-induction. These findings indicate that FG-7142 may act as an agent to promote acute fear responses in zebrafish.
Abstract
We present radio and X-ray studies of A3444 and MS1455.0+2232, two galaxy clusters with radio minihalos in their cool cores. A3444 is imaged using the Giant Metrewave Radio Telescope (GMRT) ...at 333, 607, and 1300 MHz and the Very Large Array at 1435 MHz. Most of the minihalo is contained within
r
< 120 kpc, but a fainter extension, stretching out to 380 kpc southwest of the center, is detected at 607 MHz. Using Chandra, we detect four X-ray sloshing cold fronts: three in the cool core at
r
= 60, 120, and 230 kpc, and a fourth one at
r
= 400 kpc—in the region of the southwestern radio extension—suggesting that the intracluster medium (ICM) is sloshing on a cluster-wide scale. The radio emission is contained within the envelope defined by these fronts. We also analyzed archival 383 MHz GMRT and Chandra observations of MS 1455.0+2232, which exhibits a known minihalo with its bright part delineated by cold fronts inside the cool core, but with a faint extension beyond the core. Similarly to A3444, we find a cold front at
r
∼ 425 kpc, containing the radio emission. Thus the entire diffuse radio emission seen in these clusters appears to be related to large-scale sloshing of the ICM. The radio spectrum of the A3444 minihalo is a power law with a steep index
α
= 1.0 ± 0.1. The spectrum steepens with increasing distance from the center, as expected if the minihalo originates from reacceleration of relativistic particles by the sloshing-induced turbulence in the ICM.
Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. The X-ray luminosity and redshift-limited Extended GMRT Radio ...Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. Our bigger and more homogenous sample confirms that the X-ray luminous (L sub(500) > 5 x 10 super(44) erg s super(-1)) clusters branch into two populations-radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.
We investigate the link between a firm's leverage and the characteristics of its suppliers and customers. Specifically, we examine whether firms use decreased leverage as a commitment mechanism to ...induce suppliers/customers to undertake relationship-specific investments. We find that the firm's leverage is negatively related to the R&D intensities of its suppliers and customers. We also find lower debt levels for firms operating in industries in which strategic alliances and joint ventures with firms in supplier and customer industries are more prevalent. Consistent with a bargaining role for debt, we find a positive relation between firm debt level and the degree of concentration in supplier/customer industries.
During epithelial morphogenesis, cell contacts (junctions) are constantly remodeled by mechanical forces that work against adhesive forces. E-cadherin complexes play a pivotal role in this process by ...providing persistent cell adhesion and by transmitting mechanical tension. In this context, it is unclear how mechanical forces affect E-cadherin adhesion and junction dynamics. During Drosophila embryo axis elongation, Myosin-II activity in the apico-medial and junctional cortex generates mechanical forces to drive junction remodeling. Here we report that the ratio between Vinculin and E-cadherin intensities acts as a ratiometric readout for these mechanical forces (load) at E-cadherin complexes. Medial Myosin-II loads E-cadherin complexes on all junctions, exerts tensile forces, and increases levels of E-cadherin. Junctional Myosin-II, on the other hand, biases the distribution of load between junctions of the same cell, exerts shear forces, and decreases the levels of E-cadherin. This work suggests distinct effects of tensile versus shear stresses on E-cadherin adhesion.
Context. Giant radio halos (RH) are diffuse Mpc-scale synchrotron sources detected in some massive and merging galaxy clusters. An unbiased study of the statistical properties of RHs is crucial to ...constraining their origin and evolution. Aims. We investigate the occurrence of RHs and its dependence on the cluster mass in a Sunyaev-Zel'dovich (SZ)-selected sample of galaxy clusters, which is nearly a mass-selected sample. Moreover, we analyse the connection between RHs and merging clusters. Methods. We selected from the Planck SZ catalogue clusters with M > or = 6 x 10 super(14)Mmiddot in circle at z = 0.08-0.33 and we searched for the presence of RHs using the NVSS for z < 0.2 and the GMRT RH survey (GRHS) and its extension (EGRHS) for 0.2 < z < 0.33. We used archival Chandra X-ray data to derive information on the dynamical status of the clusters. Results. We confirm that RH clusters are merging systems while the majority of clusters without RH are relaxed, thus supporting the idea that mergers play a fundamental role in the generation of RHs. We find evidence for an increase in the fraction of clusters with RHs with the cluster mass and this is in line with expectations derived on the basis of the turbulence re-acceleration scenario. Finally, we discuss the effect of the incompleteness of our sample on this result.
The Extended GMRT Radio Halo Survey Kale, R; Venturi, T; Giacintucci, S ...
Astronomy and astrophysics (Berlin),
7/2015, Volume:
579
Journal Article
Peer reviewed
The intra-cluster medium contains cosmic rays and magnetic fields that are manifested through the large scale synchrotron sources, termed radio haloes, relics, and mini-haloes. The Extended Giant ...Metre-wave Radio Telescope (GMRT) Radio Halo Survey (EGRHS) is an extension of the GMRT Radio Halo Survey (GRHS) designed to search for radio haloes using GMRT 610/235 MHz observations. A new mini-halo in RX J2129.6+0005 and candidate diffuse sources in Z5247, A2552, and Z1953 have been discovered. A unique feature of this survey are the upper limits on the detections of 1 Mpc sized radio haloes; 4 new are presented here, making a total of 31 in the survey. Of the sample, 58 clusters with adequately sensitive radio information were used to obtain the most accurate occurrence fractions so far. The occurrence fractions of radio haloes, mini-haloes and relics in our sample are ~22%, ~16% and ~5%, respectively.
Context.
Radio relics are diffuse extended synchrotron sources that originate from shock fronts induced by galaxy cluster mergers. The particle acceleration mechanism at the shock fronts is still ...under debate. The galaxy cluster 1RXS J0603.3+4214 hosts one of the most intriguing examples of radio relics, known as the Toothbrush.
Aims.
In order to understand the mechanism(s) that accelerate(s) relativistic particles in the intracluster medium, we investigated the spectral properties of large-scale diffuse extended sources in the merging galaxy cluster 1RXS J0603.3+4214.
Methods.
We present new wideband radio continuum observations made with uGMRT and VLA. Our new observations, in combination with previously published data, allowed us to carry out a detailed high-spatial-resolution spectral and curvature analysis over a wide range of frequencies.
Results.
The integrated spectrum of the Toothbrush closely follows a power law over almost two orders of magnitude in frequency, with a spectral index of −1.16 ± 0.02. We do not find any evidence of spectral steepening below 8 GHz. The subregions of the Toothbrush also exhibit near-perfect power laws and identical spectral slopes, suggesting that the observed spectral index is rather set by the distribution of Mach numbers which may have a similar shape at different parts of the shock front. Indeed, numerical simulations show an intriguing similar spectral index, indicating that the radio spectrum is dominated by the average over the inhomogeneities within the shock, with most of the emission coming from the tail of the Mach number distribution. In contrast to the Toothbrush, the spectra of the fainter relics show a high-frequency steepening. Moreover, the integrated spectrum of the halo also follows a power law from 150 MHz to 3 GHz with a spectral index of −1.16 ± 0.04. We do not find any evidence for spectral curvature, not even in subareas of the halo. This suggest a homogeneous acceleration throughout the cluster volume. Between the “brush” region of the Toothbrush and the halo, the color-color analysis reveals emission that was consistent with an overlap between the two different spectral regions.
Conclusions.
None of the relic structures, that is, the Toothbrush as a whole or its subregions or the other two fainter relics, show spectral shapes consistent with a single injection of relativistic electrons, such as at a shock, followed by synchrotron aging in a relatively homogeneous environment. Inhomogeneities in some combination of Mach number, magnetic field strength, and projection effects dominate the observed spectral shapes.
Abstract
We present the first detailed analysis of the ultra-steep spectrum radio halo in the merging galaxy cluster A521, based on upgraded Giant Metrewave Radio telescope observations. The ...combination of radio observations (300–850 MHz) and archival X-ray data provides a new window into the complex physics occurring in this system. When compared to all previous analyses, our sensitive radio images detected the centrally located radio halo emission to a greater extent of ∼1.3 Mpc. A faint extension of the southeastern radio relic has been discovered. We detected another relic, recently discovered by MeerKAT, and coincident with a possible shock front in the X-rays, at the northwest position of the center. We find that the integrated spectrum of the radio halo is well-fitted with a spectral index of −1.86 ± 0.12. A spatially resolved spectral index map revealed the spectral index fluctuations, as well as an outward radial steepening of the average spectral index. The radio and X-ray surface brightness is well correlated for the entire and different subparts of the halo, with sublinear correlation slopes (0.50–0.65). We also found a mild anticorrelation between the spectral index and X-ray surface brightness. Newly detected extensions of the SE relic and the counter relic are consistent with the merger in the plane of the sky.
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