Bendings of radio jets in BL Lacertae objects I: EVN and MERLIN observations

Several blazars, and BL Lac objects in particular, show a misalignment between the jet orientation on parsec and kiloparsec scales. Some authors (i.e. Conway & Murphy, 1993) have attempted to explain this behaviour invoking helical jets for misalignment angles around 90\degr, showing how in this case there are interesting implications for the understanding of the medium into which the jet is expanding. By comparing sensitive VLA observations (Cassaro et al., 1999) with images available in the literature for the BL Lac objects from the 1-Jy Sample (Stickel et al., 1991), it is clear that there is a wide range of misalignments between the initial jet direction and the kpc-scale jet, when detected. We have carried out VLBI observations of these BL Lac objects, in order to investigate the spatial evolution of the radio jets from few tens to hundreds of mas, and to search for helical jets in this class of sources. We present here the first dataset obtained from EVN+MERLIN observations at 5 GHz for seven objects. From these observations we never have a clear detection of helical jets, we only have a possible signature of their presence in 2 objects. In only one of the sources with a misalignment angle around 90\degr the presence of helical jets can be ruled out. This implies that it is not possible to invoke helical jets to explain the morphology of all the sources showing a misalignment of about 90\degr between the parsec and the kiloparsec scale jets.Comment: 12 pages, 9 figures, latex, accepted by Astronomy & Astrophysic

Extended radio emission in BL Lac objects - I: the images

We have observed 28 sources selected from the 1Jy sample of BL Lac objects (Stickel et al. 1991) with the Very Large Array (VLA) in A, B and D configurations at 1.36, 1.66 and 4.85 GHz, and/or with the Westerbork Synthesis Radio Telescope (WSRT) at 1.40 GHz. In this paper we present high sensitivity images at arcsecond resolution of the 18 objects showing extended structure in our images, and of another source from the FIRST (Faint Images of the Radio Sky at Twenty-cm) survey (Becker et al. 1995). In general our high sensitivity images reveal an amount of extended emission larger than previously reported. In some objects the luminosity of the extended structure is comparable with that of FR~II radio sources. A future paper will be devoted to the interpretation of these results.Comment: 12 pages, 35 figures, to appear on A&A Supp. Ser., postscript file with figures included available at http://www.ira.noto.cnr.it/staff/carlo/ds1030.ps.g

Comparison of Adaptive Control Architectures for Flutter Suppression

A study is conducted to derive and implement a state feedback model reference adaptive control (MRAC) solutions for a 2-D aeroelastic nonlinear system and in evaluating the robustness of different control strategies to damage leading to the deterioration of the structural stiffness characteristics. The standard MRAC, a modified MRAC and the adaptive controller are the three model reference adaptive control solutions analyzed. The standard direct MRAC solution serves as the threshold to assess whether or not the more complex algorithms are an effective improvement to it

Alteração da fertilidade do solo cultivado com cafeeiro conilon submetido a três níveis de fertilização com NPK.

Os solos do Estado de Rondônia, na extensão Noroeste do território brasileiro, apresentam grande variabilidade física e química. Na região norte do estado, onde se localiza o Munícipio de Porto Velho, os solos são, em sua maioria, ácidos, com porcentagem de saturação por alumínio acima de 50%, de baixa fertilidade química apresentando valores baixos para soma de bases, capacidade de troca de cátions e saturação por bases. O objetivo neste estudo foi avaliar as alterações na fertilidade do solo cultivado com cafeeiro ?Conilon? submetido à fertilização química com NPK. Os tratamentos estudados foram três níveis de fertilização com N, P e K (N1: 90-50-150; N2: 150-90-270 e N3: 210-130-390 kg ha-1) combinados com três camadas de avaliação 0-10; 10-20 e 20-40 cm de profundidade. O experimento foi conduzido em esquema de parcelas subdivididas 3x3 com três repetições no delineamento de blocos casualizados. Avaliou-se os atributos químicos do solo pH e os teores de P, K, Ca Mg, Al+H, Al, MO e V (%). Os atributos químicos dos solos não foram influenciados pelos três níveis de fertilizantes (NPK) empregados aos 14 meses após a implantação. Os atributos químicos do solo apresentaram condições mais favoráveis na camada superficial (0-10 e 10-20 cm), em relação à camada de 20-40 cm

Multi-scale modelling of an electrodialysis with bipolar membranes pilot plant and economic evaluation of its potential

Sodium hydroxide and hydrochloric acid are widely used chemicals in different industrial sectors. To minimize costs and risks associated with transportation, handling and storage, these hazardous chemicals can be produced in situ employing electrodialysis with bipolar membranes (EDBM). This work presents a multi-scale model capable of simulating large scale EDBM units with complex stack configuration (i.e., internal staging) that can be used to design and optimize the process. The model was validated in two different process configurations using experimental results obtained from an EDBM pilot plant. Discrepancies between model and experimental results in the range of 2–11 % were obtained. The validated model was used to conduct a techno-economic evaluation adopting the feed and bleed configuration. Results show that current efficiency increases as the current density rises. At 600 A m−2, values of current efficiency between 72 % and 96 % were found for sodium hydroxide concentration in the range of 0.5–1 mol L−1. The levelized cost of sodium hydroxide (LCoNaOH) was evaluated, in the same range of concentrations, demonstrating that values between 280 and 370 € ton−1 can be obtained, fixing the electricity prince (0.1 kWh kg−1) and the triplet specific cost (600 US$m−2). Moreover, assuming a reduced cost of electricity and triplet to 0.05 kWh kg−1 and 300 US$ m−2, respectively, an absolute minimum of 140 € ton−1 was found for the target 0.5 mol L−1. A double stage EDBM configuration was simulated to show the scale-up potentials of the multi-scale model. A reduction in the LcoNaOH of 10 % was obtained for a target concentration of 1 mol L−1. These results prove the attractiveness of the EDBM technology for producing in situ chemicals

Low Power Compact Radio Galaxies at High Angular Resolution

We present sub-arcsecond resolution multi-frequency (8 and 22 GHz) VLA images of five low power compact (LPC) radio sources, and phase referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA resolution we resolve the structure and identify component positions and flux densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum, compact cores (down to a few milliJansky) in four of the five sources. The absolute astrometry provided by the phase referencing allows us to identify the center of activity on the VLA images. Moreover, these data reveal rich structures, including two-sided jets and secondary components. On the basis of the arcsecond scale structures and of the nuclear properties, we rule out the presence of strong relativistic effects in our LPCs, which must be intrinsically small (deprojected linear sizes <~ 10 kpc). Fits of continuous injection models reveal break frequencies in the GHz domain, and ages in the range 10^5-10^7 yrs. In LPCs, the outermost edge may be advancing more slowly than in more powerful sources or could even be stationary; some LPCs might also have ceased their activity. In general, the properties of LPCs can be related to a number of reasons, including, but not limited to: youth, frustration, low kinematic power jets, and short-lived activity in the radio.Comment: 15 pages, 9 .eps figures, accepted by A&

Attenuated PGC-1 alpha Isoforms following Endurance Exercise with Blood Flow Restriction

Introduction: Exercise performed with blood flow restriction simultaneously enhances the acute responses to both myogenic and mitochondrial pathways with roles in training adaptation. We investigated isoform-specific gene expression of the peroxisome proliferator-activated receptor gamma (PPARG) coactivator 1 and selected target genes and proteins regulating skeletal muscle training adaptation. Methods: 9 healthy, untrained males participated in a randomized, counter-balanced, cross-over design in which each subject completed a bout of low-intensity endurance exercise performed with blood flow restriction (15 min cycling at 40% of VO2peak, BFR-EE), endurance exercise (30 min cycling at 70% of VO2peak, EE) or resistance exercise (4 x 10 repetitions of leg press at 70% of 1-repetition maximum, RE) separated by at least one week recovery. A single resting muscle biopsy (vastus lateralis) was obtained two weeks before the first exercise trial (rest) and 3 h after each boat. Results: Total PGC-1α mRNA abundance, along with all four isoforms, increased above rest with EE only (P<0.05) being higher than BFR-EE (P<0.05). PGC-1α1, 2 and 4 were higher after EE compared to RE (P<0.05). EE also increased VEGF, Hif-1α and MuRF-1 mRNA abundance above rest (P<0.05) while COXIV mRNA expression increased with EE compared to BFR-EE (P<0.05). Conclusion: The attenuated expression of all four PGC- 1α isoforms when endurance exercise is performed with blood flow restriction suggests this type of exercise provides an insufficient stimulus to activate the signaling pathways governing mitochondrial and angiogenesis responses observed with moderate- to high intensity endurance exercise