Tropospheric reactive odd nitrogen over the South Pacific in austral springtime

The distribution of reactive nitrogen species over the South Pacific during austral springtime appears to be dominated by biomass burning emissions and possibly lightning and stratospheric inputs. The absence of robust correlations of reactive nitrogen species with source-specific tracers (e.g., C2H2 [combustion], CH3Cl [biomass burning], C2Cl4 [industrial],210Pb [continental], and 7Be [stratospheric]) suggests significant aging and processing of the sampled air parcels due to losses by surface deposition, OH attack, and dilution processes. Classification of the air parcels based on CO enhancements indicates that the greatest influence was found in plumes at 3–8 km altitude in the distributions of HNO3 and peroxyacetyl nitrate (PAN). Here mixing ratios of these species reached 600 parts per trillion by volume (pptv), values surprisingly large for a location several thousand kilometers removed from the nearest continental areas. The mixing ratio of total reactive nitrogen (the NOy sum), operationally defined in this paper as measured (NO + HNO3 + PAN + CH3ONO2 + C2H5ONO2) + modeled (NO2), had a median value of 285 pptv within these plumes compared with 120 pptv in nonplume air parcels. Particle NO−3 was not included in this analysis of the NOy sum due to its 10- to 15-min sampling time resolution, but, in general, it was \u3c10% of the NOy sum. Comparison of the two air parcel classifications for NOy and alkyl nitrate distributions showed no perceivable plume influence, but recycling of reactive nitrogen may have masked this direct effect. In the marine boundary layer, the NOy sum averaged 50 pptv in both air parcel classifications, being somewhat isolated from the polluted conditions above it by the trade wind inversion. In this region, however, alkyl nitrates appear to have an important marine source where they comprise 20–80% of the NOy sum in equatorial and high-latitude regions over the South Pacific

Secret key exchange in ultra-long lasers by radio-frequency spectrum coding

We propose a new approach to the generation of an alphabet for secret key exchange relying on small variations in the cavity length of an ultra-long fiber laser. This new concept is supported by experimental results showing how the radio-frequency spectrum of the laser can be exploited as a carrier to exchange information. The test bench for our proof of principle is a 50 km-long fiber laser linking two users, Alice and Bob, where each user can randomly add an extra 1 km-long segment of fiber. The choice of laser length is driven by two independent random binary values, which makes such length become itself a random variable. The security of key exchange is ensured whenever the two independent random choices lead to the same laser length and, hence, to the same free spectral range

Binary and Millisecond Pulsars at the New Millennium

We review the properties and applications of binary and millisecond pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1300. There are now 56 binary and millisecond pulsars in the Galactic disk and a further 47 in globular clusters. This review is concerned primarily with the results and spin-offs from these surveys which are of particular interest to the relativity community.Comment: 59 pages, 26 figures, 5 tables. Accepted for publication in Living Reviews in Relativity (http://www.livingreviews.org

Sex-related variation in compact bone microstructure of the femoral diaphysis in juvenile rabbits

<p>Abstract</p> <p>Background</p> <p>While gross morphological changes in the skeleton between males and females are well know, differences between sexes in the histomorphology are less known. It is important to have knowledge on the bone structure of rabbits, as this is a widely used species in biomedical research. A study was performed to evaluate the association between sex and the compact bone morphology of the femoral diaphysis in juvenile rabbits.</p> <p>Methods</p> <p>Seventeen clinically healthy 2–3 month-old rabbits (9 females, 8 males) were included in the study. The rabbits were euthanized and the right femur was sampled for analysis. 70–80 microns thick bone sections of the femoral diaphysis were prepared using standard histological equipment. The qualitative histological characteristics were determined according to internationally accepted classification systems while the quantitative parameters were assessed using the software Scion Image. Areas, perimeters, minimum and maximum diameters of primary osteons' vascular canals, Haversian canals and secondary osteons were measured. Additionally, blood plasma concentrations of progesterone, corticosterone, IGF-I, testosterone and estradiol were analyzed.</p> <p>Results</p> <p>Qualitative histological characteristics were similar for both sexes. However, variations of certain quantitative histological characteristics were identified. Measured parameters of the primary osteons' vascular canals were higher in males than for females. On the other hand, females had significant higher values of secondary osteons parameters. Differences in Haversian canals parameters were only significant for minimum diameter.</p> <p>Conclusion</p> <p>The study demonstrated that quantitative histological characteristics of compact bone tissue of the femoral diaphysis in juvenile rabbits were sex dependent. The variations may be associated with different growth and modeling of the femur through influence by sex-specific steroids, mechanical loads, genetic factors and a multitude of other sources. The results can be applied in experimental studies focusing on comparison of the skeletal biology of the sexes.</p

Foundations of Black Hole Accretion Disk Theory

This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin) disks, slim disks, and advection-dominated accretion flows (ADAFs). After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of black hole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of black hole mass and spin, black hole vs. neutron star accretion disks, black hole accretion disk spectral states, and quasi-periodic oscillations (QPOs).Comment: 91 pages, 23 figures, final published version available at http://www.livingreviews.org/lrr-2013-

Exhaustive exercise training enhances aerobic capacity in American alligator (Alligator mississippiensis)

The oxygen transport system in mammals is extensively remodelled in response to repeated bouts of activity, but many reptiles appear to be ‘metabolically inflexible’ in response to exercise training. A recent report showed that estuarine crocodiles (Crocodylus porosus) increase their maximum metabolic rate in response to exhaustive treadmill training, and in the present study, we confirm this response in another crocodilian, American alligator (Alligator mississippiensis). We further specify the nature of the crocodilian training response by analysing effects of training on aerobic [citrate synthase (CS)] and anaerobic [lactate dehydrogenase (LDH)] enzyme activities in selected skeletal muscles, ventricular and skeletal muscle masses and haematocrit. Compared to sedentary control animals, alligators regularly trained for 15 months on a treadmill (run group) or in a flume (swim group) exhibited peak oxygen consumption rates higher by 27 and 16%, respectively. Run and swim exercise training significantly increased ventricular mass (~11%) and haematocrit (~11%), but not the mass of skeletal muscles. However, exercise training did not alter CS or LDH activities of skeletal muscles. Similar to mammals, alligators respond to exercise training by increasing convective oxygen transport mechanisms, specifically heart size (potentially greater stroke volume) and haematocrit (increased oxygen carrying-capacity of the blood). Unlike mammals, but similar to squamate reptiles, alligators do not also increase citrate synthase activity of the skeletal muscles in response to exercise