ESFK 20-100 watt S-band amplifier Quarterly report

Electrostatically focused klystron tube modification

ESFK 20-100 watt S-band amplifier

Electrostatically focused klystron development for use in interplanetary spaceborne communication system

A search for interstellar molecules in the spectra of highly reddened stars

A total of ten stars were observed with cameras of the International Ultraviolet Explorer (IUE) in both high and low dispersion. One star, X Persei (HD 24534, 6.0 BE), was analyzed in detail. Ultraviolet observations of the column densities of CO match those derived from the radio to within a factor of 4, with the difference probably due to the larger beam size of the radio measurement and the assumption of a thermal population in the rotational levels of CO. Upper limits are given to the log column densities for OH, HCl, and CH2 of 14.0, 12.3 and 12.8. The carbon abundance was found to be about solar with a possible depletion of about a factor of 2. With precautions concerning both noise and correct background, the IUE can be used for studies of interstellar molecules

Chemistry of lakes in the Nordic region - Denmark, Finland with Åland, Iceland, Norway with Svalbard and Bear Island, and Sweden

This report presents the first common evaluation of water chemistry in the Nordic countries (except for the Faroe Islands and Greenland): Denmark, Finland including Åland, Iceland, Norway including Svalbard and Bear Island, and Sweden. The Nordic countries exhibit large gradients in many chemical constituents in lake water, from Iceland in the west, Svalbard and Bear Island in the north via Denmark to Sweden, Finland and Norway, due to large differences in geology, hydrology, vegetation and air pollution. The data are interpreted relative to these factors

Platelet-Derived Growth Factor Receptor β Is Critical for Zebrafish Intersegmental Vessel Formation

Background: Platelet-derived growth factor receptor β (PDGFRβ) is a tyrosine kinase receptor known to affect vascular development. The zebrafish is an excellent model to study specific regulators of vascular development, yet the role of PDGF signaling has not been determined in early zebrafish embryos. Furthermore, vascular mural cells, in which PDGFRβ functions cell autonomously in other systems, have not been identified in zebrafish embryos younger than 72 hours post fertilization. Methodology/Principal Findings: In order to investigate the role of PDGFRβ in zebrafish vascular development, we cloned the highly conserved zebrafish homolog of PDGFRβ. We found that pdgfrβ is expressed in the hypochord, a developmental structure that is immediately dorsal to the dorsal aorta and potentially regulates blood vessel development in the zebrafish. Using a PDGFR tyrosine kinase inhibitor, a morpholino oligonucleotide specific to PDGFRβ, and a dominant negative PDGFRβ transgenic line, we found that PDGFRβ is necessary for angiogenesis of the intersegmental vessels. Significance/Conclusion: Our data provide the first evidence that PDGFRβ signaling is required for zebrafish angiogenesis. We propose a novel mechanism for zebrafish PDGFRβ signaling that regulates vascular angiogenesis in the absence of mural cells

The reliability of the general functioning scale in Norwegian 13–15-year-old adolescents and association with family dinner frequency

Background Family environment is crucial to the development of health behaviors into adolescence and adulthood. The aims of this study were (1) to explore the reliability of the General Functioning Scale (GFS) among Norwegian 13-15-year-olds, and (2) to assess whether family functioning reported by adolescents was associated with family dinner frequency. Methods In total 440 secondary-school students were invited to participate in this cross-sectional web-based questionnaire survey, with 54 participating in the test-retest study. Test-retest and internal consistency were assessed for the 12-item GFS-scale. Associations between family functioning and family dinner frequency were tested using multiple logistic regression. Results The GFS had high internal consistency (corrected item-total correlations ranging from 0.40 to 0.65, Cronbach’s α = 0.85), and excellent test–retest reliability (intra-class correlation coefficient = 0.83). In the logistic regression model, a higher score on GFS (poorer family functioning) was associated with a reduced likelihood of having dinner together on a daily basis (i.e., 6–7 times per week, OR = 0.36, CI = 0.20–0-64) after adjusting for age, gender, ethnicity, living situation and parental education level. Conclusions The GFS had high reliability. As poorer family functioning was associated with less frequent family dinners, the family environment may be an important (contextual) target to influence adolescent health behaviors. It would be of interest to further explore the role of family functioning in relation to adolescents’ dietary habits, besides shared family meals, and to reveal the mechanisms underlying such relationships.publishedVersio

Penetration of hot electrons through a cold disordered wire

We study a penetration of an electron with high energy E<<T through strongly disordered wire of length L<<a (a being the localization length). Such an electron can loose, but not gain the energy, when hopping from one localized state to another. We have found a distribution function for the transmission coefficient t. The typical t remains exponentially small in L/a, but with the decrement, reduced compared to the case of direct elastic tunnelling. The distribution function has a relatively strong tail in the domain of anomalously high t; the average ~(a/L)^2 is controlled by rare configurations of disorder, corresponding to this tail.Comment: 4 pages, 5 figure

Evidence of extended emission in GRB 181123B and other high-redshift short GRBs

We study the high-energy properties of GRB 181123B, a short gamma-ray burst (sGRB) at redshift z$\approx$1.75. We show that, despite its nominal short duration with T90 < 2 s, this burst display evidence of a temporally extended emission (EE) at high energies and that the same trend is observed in the majority of sGRBs at z > 1. We discuss the impact of instrumental selection effects on the GRB classification, stressing that the measured T90 is not an unambiguous indicator of the burst physical origin. By examining their environment (e.g. stellar mass, star formation, offset distribution), we find that these high-z sGRBs share many properties of long GRBs at a similar distance and are consistent with a short-lived progenitor system. If produced by compact binary mergers, these sGRBs with EE may herald a larger population of sGRBs in the early universe.Comment: 10 pages, 6 figures, 2 tables. Submitted to ApJ

Ecosystem effects of thermal manipulation of a whole lake, Lake Breisjøen, southern Norway (THERMOS project)

International audienceWe conducted a 3-year artificial deepening of the thermocline in the dimictic Lake Breisjøen, southern Norway, by means of a large submerged propeller. An adjacent lake served as untreated reference. The manipulation increased thermocline depth from 6 to 20 m, caused a significant increase in the heat content, and delayed ice-on by about 20 days. There were only minor changes in water chemistry. Concentrations of sulphate declined, perhaps due to greater reduction of sulphate at the sediment-water interface. Concentrations of particulate carbon and nitrogen decreased, perhaps due to increased sedimentation velocity. Water transparency increased. There was no significant change in concentration of phosphorus, the growth-limiting nutrient. There were few significant changes in principal biological components. Phytoplankton biomass and productivity did not change, although the chlorophyll-a concentration showed a small decrease. Phytoplankton species richness increased, and the species composition shifted. Growth of periphyton increased. There was no change in the macrophyte community. The manipulation did not affect the zooplankton biodiversity, but caused a significant shift in the relative abundance (measured as biomass) in the two major copepod species. The manipulation did not affect the individual density, but appeared to have changed the vertical distribution of zoobenthos. Fish populations were not affected. The lake is oligotrophic and clearwater and the manipulation did not change the supply of phosphorus, and thus there were only minor changes in lake chemistry and biology. Effects might be larger in eutrophic and dystrophic lakes in which internal processes are stronger