Modulation of cosmic-ray protons and helium nuclei near solar maximum

Balloon observations of proton and helium spectra in 1970, 1971 and 1972, reveal a factor of approximately 1.85 deviation from a single valued regression at low rigidities. This deviation decreases with increasing rigidity for both species. The period 1969-1970 is unique because time variations at low and high energies were anti-correlated. When satellite observations are used to extend the balloon observations to energies below 100 MeV/Nucleon, the proton spectrum showed a steeper slope in 1970 and 1972 than the characteristic J = AT spectrum observed during 1965-1969. The slope of the helium spectrum became continuously flatter during the same period (1970-1972). Computer generated spectra based on simple two parameter modulation models describe the basic features of the observations if one of the variable parameters is used to characterize the rigidity dependence of the diffusion coefficient. Models which do not allow such a variation are not consistent with the observations

An X-ray shadowgraph to locate transient high-energy celestial sources

A new technique has been developed to locate strong, transient X-ray sources such as the recently discovered gamma ray bursts. The instrument, termed a shadowgraph, locates sources by detecting the X-ray shadow cast by a large occulting mask pattern on an imaging detector. Angular resolutions of from 2 to 10 arc minutes are obtainable while essentially full sky coverage is maintained. The optimum energy range of operation is between 20 keV and 100 keV. The high efficiency X-ray imaging detectors, which make it possible to locate bursts with intensities down to approximately 10 photons/sq cm sec, are capable of detecting single 20 keV photons with a spatial resolution of approximately 0.2 mm. The detectors consist of an X-ray to optical conversion phosphor, a multistage image intensifier, and a CCD image readout

HLA-B27 predicts a more extended disease with increasing age at onset in boys with juvenile idiopathic arthritis

Poster presentatiopn at 15th Paediatric Rheumatology European Society (PreS) Congress London, UK. 14–17 September 200

Langtidsovervåking av miljøkvaliteten i kystområdene av Norge. Årsrapport 1996

Kystovervåkingsprogrammet skal gi en oversikt over miljøtilstanden m.h.t. næringssalter og effektene av disse på alge- og dyresamfunn fra svenskegrensen til Fedje. Utvikling over tid overvåkes innen fagdisiplinene hydrografi, hydrokjemi, planteplankton, bløtbunnsfauna og hardbunnsflora og -fauna. Året 1996 ble innledet med en kald vinter og vår. Vanntemperaturen i Skagerrak ned til ca. 25 m var i januar - februar kaldere enn gjennomsnittet for 1980-1990, mens samme periode i 1995 var uvanlig varm. Til forskjell fra 1995 var det ingen flom på kontinentet eller på Østlandet i 1996, og det resulterte i små tilførsler av næringssalter fra land. Sammenlignet med langtidsobservasjoner fra Arendalstasjonene (1980-90) var 1996 et år med lavere næringssaltkonsentrasjoner i de øvre vannmasser vinter og vår og for de løste næringssaltene også tildels sommeren og høsten. C/N-forholdet i stortare fra Sørlandskysten var meget høyt og kan indikere næringsbegrenset algevekst på Sørlandskysten sommeren 1996. Utbredelse og forekomst av fastsittende alger var generelt sett noe redusert i 1996 i forhold til 1995 og mer lik hva som ble funnet i 1993/94. Variasjonene kan sees i sammenheng med vinter/vår temperaturene. Fortsatt tilvekst av tareskog i Skagerrak gjør stasjonene mer homogene. Forekomst av organismer på bløt- og hardbunn viste en normal øst-vest gradient, med økende artsantall og diversitet mot vest. Bløtbunnsfaunaen viste ingen større endringer fra 1995 til 1996. For enkelte stasjoner ble det funnet en nedgang i individtall, mens det ble funnet en økning for andre stasjoner, uten at det er noen klar årsakssammenheng eller tendens i variasjonene

Ionization disequilibrium in K- and L-shell ions

Producción CientíficaTime-gated Sc K-shell and Ge L-shell spectra are presented from a range of characterized thermodynamic states spanning ion densities of 1e19-1e20cm-3 and plasma temperatures around 2000eV. For the higher densities studied and temperatures from 1000 to 3000 eV, the Sc and Ge x-ray emission spectra are consistent with steady-state calculations from the modern atomic kinetics model SCRAM. At the lower ion densities achieved through plasma expansion, however, the model calculations require a higher plasma temperature to reproduce the observed Ge spectrum. We attribute this to ionization disequilibrium of the Sc because the ionization time scales exceed the hydrodynamic timescale when the inferred temperatures diverge.This work has been supported by the Research Grant No. PID2019-108764RB-I00 from the Spanish Ministry of Science and Innovation

Multi-Messenger Measurements of the Static Structure of Shock-Compressed Liquid Silicon at 100 GPa

Ionic structure of high pressure, high temperature fluids is a challenging theoretical problem with applications to planetary interiors and fusion capsules. Here we report a multi-messenger platform using velocimetry and \textit{in situ} angularly and spectrally resolved X-ray scattering to measure the thermodynamic conditions and ion structure factor of materials at extreme pressures. We document the pressure, density, and temperature of shocked silicon near 100 GPa with uncertainties of 6%, 2%, and 20%, respectively. The measurements are sufficient to distinguish between and rule out some ion screening models.Comment: Main Paper: 5 pages, 4 figures. Supplementary Material: 9 pages, 8 figure

A computational study of the hydrodynamics in the nasal region of a hammerhead shark <em>(Sphyrna tudes)</em>:Implications for olfaction

The hammerhead shark possesses a unique head morphology that is thought to facilitate enhanced olfactory performance. The olfactory chambers, located at the distal ends of the cephalofoil, contain numerous lamellae that increase the surface area for olfaction. Functionally, for the shark to detect chemical stimuli, water-borne odors must reach the olfactory sensory epithelium that lines these lamellae. Thus, odorant transport from the aquatic environment to the sensory epithelium is the first critical step in olfaction. Here we investigate the hydrodynamics of olfaction in Sphyrna tudes based on an anatomically-accurate reconstruction of the head and olfactory chamber from high-resolution micro-CT and MRI scans of a cadaver specimen. Computational fluid dynamics simulations of water flow in the reconstructed model reveal the external and internal hydrodynamics of olfaction during swimming. Computed external flow patterns elucidate the occurrence of flow phenomena that result in high and low pressures at the incurrent and excurrent nostrils, respectively, which induces flow through the olfactory chamber. The major (prenarial) nasal groove along the cephalofoil is shown to facilitate sampling of a large spatial extent (i.e., an extended hydrodynamic "reach") by directing oncoming flow towards the incurrent nostril. Further, both the major and minor nasal grooves redirect some flow away from the incurrent nostril, thereby limiting the amount of fluid that enters the olfactory chamber. Internal hydrodynamic flow patterns are also revealed, where we show that flow rates within the sensory channels between olfactory lamellae are passively regulated by the apical gap, which functions as a partial bypass for flow in the olfactory chamber. Consequently, the hammerhead shark appears to utilize external (major and minor nasal grooves) and internal (apical gap) flow regulation mechanisms to limit water flow between the olfactory lamellae, thus protecting these delicate structures from otherwise high flow rates incurred by sampling a larger area