Large constellations of small satellites: A survey of near future challenges and missions

Constellations of satellites are being proposed in large numbers; most of them are expected to be in orbit within the next decade. They will provide communication to unserved and underserved communities, enable global monitoring of Earth and enhance space observation. Mostly enabled by technology miniaturization, satellite constellations require a coordinated effort to face the technological limits in spacecraft operations and space traffic. At the moment in fact, no cost-effective infrastructure is available to withstand coordinated flight of large fleets of satellites. In order for large constellations to be sustainable, there is the need to efficiently integrate and use them in the current space framework. This review paper provides an overview of the available experience in constellation operations and statistical trends about upcoming constellations at the moment of writing. It highlights also the tools most often proposed in the analyzed works to overcome constellation management issues, such as applications of machine learning/artificial intelligence and resource/infrastructure sharing. As such, it is intended to be a useful resource for both identifying emerging trends in satellite constellations, and enabling technologies still requiring substantial development efforts

Growth hormone plus resistance exercise attenuate structural changes in rat myotendinous junctions resulting from chronic unloading.

Myotendinous junctions (MTJs) are specialized sites on the muscle surface where forces generated by myofibrils are transmitted across the sarcolemma to the extracellular matrix. At the ultrastructural level, the interface between the sarcolemma and extracellular matrix is highly folded and interdigitated at these junctions. In this study, the effect of exercise and growth hormone (GH) treatments on the changes in MTJ structure that occur during muscle unloading, has been analyzed. Twenty hypophysectomized rats were assigned randomly to one of five groups: ambulatory control, hindlimb unloaded, hindlimb unloaded plus exercise (3 daily bouts of 10 climbs up a ladder with 50% body wt attached to the tail), hindlimb unloaded plus GH (2 daily injections of 1 mg/kg body wt, i.p.), and hindlimb unloaded plus exercise plus GH. MTJs of the plantaris muscle were analyzed by electron microscopy and the contact between muscle and tendon was evaluated using an IL/B ratio, where B is the base and IL is the interface length of MTJ's digit-like processes. After 10 days of unloading, the mean IL/B ratio was significantly lower in unloaded (3.92), unloaded plus exercise (4.18), and unloaded plus GH (5.25) groups than in the ambulatory control (6.39) group. On the opposite, the mean IL/B ratio in the group treated with both exercise and GH (7.3) was similar to control. These findings indicate that the interaction between exercise and GH treatments attenuates the changes in MTJ structure that result from chronic unloading and thus can be used as a countermeasure to these adaptations

Trade effects of geographical indication policy: The EU case

Using a new detailed dataset on country-product information on European Union (EU) Geographical Indications (GIs), we study the impact of this food quality policy on trade margins over the 1996–2014 period. We consider the effect of GIs on both intra- and extra-EU trade margins (extensive and intensive), as well as on export (and import) unit values. Our main results show that GIs affect trade flows differently depending on whether GIs are produced by the exporter or importer country. The presence of GIs in the exporter country systematically exerts a positive trade effect on both the extensive and intensive trade margin. When registered only in the importer country, GIs seem to act weakly as a trade-reducing measure, at least at the intensive trade margin. In addition, GIs positively affect export prices, consistent with the idea that GI products are perceived by consumers as higher quality goods. Importantly, extra-EU trade margins react similarly to those on intra-EU trade. These results have clear and interesting implications concerning the EU strategy of promoting the protection of GIs worldwide

Export behaviour of Italian food firms : Does product quality matter ?

Using firm-level data we investigate the export behaviour of Italian food firms, focusing on the link between total factor productivity (TFP), product quality, and export across heterogeneous destinations. We test the main predictions of an international trade model based on firm heterogeneity in product quality and non-homothetic preferences in consumption. In this setting, the firm\u2019s export intensity should be increasing in the per-capita income of foreign destinations, and the effect should be largely driven by firms\u2019 heterogeneity in product quality. Using different measures of revenue-TFP, and different proxies for product quality, we find strong support for the main model predictions. Moreover, consistent with the Alchian-Allen effect, we find a positive relationship between the quality of exported products and the distance of destination countries

Trade collapse, quality and food exports

This article revisits the so-called \u2018Collapse in Quality\u2019 hypothesis, according to which, during the 2008\u20132009 crisis, higher quality goods experienced a stronger export reduction compared to low-quality ones. Using disaggregated trade data from three European countries that traditionally export high-quality food products \u2013 France, Italy and Spain \u2013 we do not find any econometric evidence supporting this hypothesis. In contrast, we provide preliminary evidence for the concurrent hypothesis, namely that firms reduced their markup to preserve market shar

Do food standards affect the quality of EU imports?

This paper investigates the relationship between the diffusion of EU standards and product quality upgrading using highly disaggregated import data to the EU in the food industry. Results show that, on average, the diffusion of EU voluntary standards boosts the rate of quality upgrading. However, the results are heterogeneous when moving from primary to processed foods, and from ISO to non-ISO standard

Overestimating Self-Blame for Stressful Life Events and Adolescents’ Latent Trait Cortisol (LTC): The Moderating Role of Parental Warmth. Journal of Youth and Adolescence

Cognitive interpretations of stressful events impact their implications for physiological stress processes. However, whether such interpretations are related to trait cortisol—an indicator of individual differences in stress physiology—is unknown. In 112 early adolescent girls (M age = 12.39 years), this study examined the association between self-blame estimates for past year events and latent trait cortisol, and whether maternal warmth moderated effects. Overestimating self-blame (versus objective indices) for independent (uncontrollable) events was associated with lower latent trait cortisol, and maternal warmth moderated the effect of self-blame estimates on latent trait cortisol for each dependent (at least partially controllable) and interpersonal events. Implications for understanding the impact of cognitive and interpersonal factors on trait cortisol during early adolescence are discussed

Melatonin prevents chemical-induced Haemopoietic cell death

Melatonin (MEL), a methoxyindole synthesized by the pineal gland, is a powerful antioxidant in tissues as well as within cells, with a fundamental role in ameliorating homeostasis in a number of specific pathologies. It acts both as a direct radical scavenger and by stimulating production/activity of intracellular antioxidant enzymes. In this work, some chemical triggers, with different mechanisms of action, have been chosen to induce cell death in U937 hematopoietic cell line. Cells were pre-treated with 100 μM MEL and then exposed to hydrogen peroxide or staurosporine. Morphological analyses, TUNEL reaction and Orange/PI double staining have been used to recognize ultrastructural apoptotic patterns and to evaluate DNA behavior. Chemical damage and potential MEL anti-apoptotic effects were quantified by means of Tali® Image-Based Cytometer, able to monitor cell viability and apoptotic events. After trigger exposure, chromatin condensation, micronuclei formation and DNA fragmentation have been observed, all suggesting apoptotic cell death. These events underwent a statistically significant decrease in samples pre-treated with MEL. After caspase inhibition and subsequent assessment of cell viability, we demonstrated that apoptosis occurs, at least in part, through the mitochondrial pathway and that MEL interacts at this level to rescue U937 cells from death. © 2014 by the authors; licensee MDPI, Basel, Switzerland

Estimating the trade effects of the EU food quality policy

We investigate the relationship between international trade and product quality using the EU food policy on Geographical Indications (GIs). Building on the quality sorting model proposed by Crozet et al. (2012), we derive three predictions about the relationship between the EU quality policy and different trade margins (extensive and intensive) as well as firms export prices. To test these predictions, we create a new dataset that collects country information on GIs and bilateral trade flows during the period 1996-2014, at HS 6-digit level. We empirically test the theoretical model through Poisson Pseudo Maximum Likelihood (PPML) estimation procedure on panel data. The main results show that GIs affect trade but differently, depending on whether GIs are produced in the exporter or importer country. In particular, the presence of GIs in the exporter country seems to exert a pro-competitive effect, while when registered only in the importer country, GIs act as an anti-competitive measure