7,437 research outputs found
Cryogenic propellant venting under low pressure conditions Final report
Wall temperatures and heat transfer coefficients for solid-vapor mixtures of para hydrogen and nitrogen venting under low pressur
A General Framework for Sound and Complete Floyd-Hoare Logics
This paper presents an abstraction of Hoare logic to traced symmetric
monoidal categories, a very general framework for the theory of systems. Our
abstraction is based on a traced monoidal functor from an arbitrary traced
monoidal category into the category of pre-orders and monotone relations. We
give several examples of how our theory generalises usual Hoare logics (partial
correctness of while programs, partial correctness of pointer programs), and
provide some case studies on how it can be used to develop new Hoare logics
(run-time analysis of while programs and stream circuits).Comment: 27 page
Excitation energy and deformation of the 1/2+[431] intruder band in
The already detailed study of nucleus was complemented by a search for microsecond isomers at very low energy. For this purpose, this neutron-rich nucleus was produced by thermal-neutron-induced fission of . We have found a new 30.1 keV microsecond isomeric state which deexcites to the ground state by a strongly-hindered E1 transition. This isomer was identified as the 3/2+ level of the 1/2+[431] intruder band in and is also the lowest-lying member of the band. The very low energy of the band head suggests a large quadrupole deformation. From a comparison with ,where more information is known about the intruder band, it is deduced that the 1/2+[431] band has a quadrupole deformation, 0.35 and a possible triaxial shape, 20°
Shocked Molecular Hydrogen in the 3C 326 Radio Galaxy System
The Spitzer spectrum of the giant FR II radio galaxy 3C 326 is dominated by
very strong molecular hydrogen emission lines on a faint IR continuum. The H2
emission originates in the northern component of a double-galaxy system
associated with 3C 326. The integrated luminosity in H2 pure-rotational lines
is 8.0E41 erg/s, which corresponds to 17% of the 8-70 micron luminosity of the
galaxy. A wide range of temperatures (125-1000 K) is measured from the H2 0-0
S(0)-S(7) transitions, leading to a warm H2 mass of 1.1E9 Msun. Low-excitation
ionic forbidden emission lines are consistent with an optical LINER
classification for the active nucleus, which is not luminous enough to power
the observed H2 emission. The H2 could be shock-heated by the radio jets, but
there is no direct indication of this. More likely, the H2 is shock-heated in a
tidal accretion flow induced by interaction with the southern companion galaxy.
The latter scenario is supported by an irregular morphology, tidal bridge, and
possible tidal tail imaged with IRAC at 3-9 micron. Unlike ULIRGs, which in
some cases exhibit H2 line luminosities of comparable strength, 3C 326 shows
little star-formation activity (~0.1 Msun/yr). This may represent an important
stage in galaxy evolution. Starburst activity and efficient accretion onto the
central supermassive black hole may be delayed until the shock-heated H2 can
kinematically settle and coolComment: 27 pages, 7 figures, accepted for publication in the Astrophysical
Journa
Effects of guanidine on synaptic transmission in the spinal cord of the frog
The effects of guanidine on motoneurons of the isolated frog spinal cord were studied by adding the drug to the solution bathing the cord during intracellular recording. Guanidine (5·10–4 M) did not alter the membrane potential of motoneurons.
The main effect was a marked increase of the amplitudes and frequencies of small spontaneously occurring inhibitory postsynaptic potentials. The hyperpolarizing component of postsynaptic potentials evoked by stimulation of dorsal roots was also enhanced by guanidine. Higher concentrations of guanidine (5·10–3 M) resulted in a very large and irreversible increase of the small spontaneously occurring inhibitory potentials, which now appeared in a regular, rhythmic pattern.
The effects of guanidine could easily be blocked by increasing the magnesium ions (15 mM) in the bath solution.
These results indicate that guanidine facilitates the release of an inhibitory transmitter in afferent terminals of the frog spinal cord either by a direct action on these terminals or indirectly by an action on nerve endings impinging on inhibitory interneurons
Cauchy horizon singularity without mass inflation
A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the
nature of the singularity along the Cauchy horizon of a charged spherically
symmetric black hole. For these solutions, conditions may prevail under which
the mass function is bounded and yet the curvature scalar
diverges.Comment: typeset in RevTex, 13 page
Recent measurements of the spherical and deformed isomers using the Lohengrin fission-fragment spectrometer
International audienc
Systematically Asymmetric Heliospheric Magnetic Field: Evidence for a Quadrupole Mode and Non-axisymmetry with Polarity Flip-flops
Recent studies of the heliospheric magnetic field (HMF) have detected
interesting, systematic hemispherical and longitudinal asymmetries which have a
profound significance for the understanding of solar magnetic fields. The in
situ HMF measurements since 1960s show that the heliospheric current sheet
(HCS) is systematically shifted (coned) southward during solar minimum times,
leading to the concept of a bashful ballerina. While temporary shifts can be
considerably larger, the average HCS shift (coning) angle is a few degrees,
less than the tilt of the solar rotation axis. Recent solar
observations during the last two solar cycles verify these results and show
that the magnetic areas in the northern solar hemisphere are larger and their
intensity weaker than in the south during long intervals in the late declining
to minimum phase. The multipole expansion reveals a strong quadrupole term
which is oppositely directed to the dipole term. These results imply that the
Sun has a symmetric quadrupole S0 dynamo mode that oscillates in phase with the
dominant dipole A0 mode. Moreover, the heliospheric magnetic field has a strong
tendency to produce solar tilts that are roughly opposite in longitudinal
phase. This implies is a systematic longitudinal asymmetry and leads to a
"flip-flop" type behaviour in the dominant HMF sector whose period is about 3.2
years. This agrees very well with the similar flip-flop period found recently
in sunspots, as well as with the observed ratio of three between the activity
cycle period and the flip-flop period of sun-like stars. Accordingly, these
results require that the solar dynamo includes three modes, A0, S0 and a
non-axisymmetric mode. Obviously, these results have a great impact on solar
modelling.Comment: 13 pages, 4 figures, Solar Physics, Topical Issue of Space Climate
Symposium, in pres
First-year sea-ice contact predicts bromine monoxide (BrO) levels better than potential frost flower contact
International audienceReactive halogens are responsible for boundary-layer ozone depletion and mercury deposition in Polar Regions during springtime. To investigate the source of reactive halogens in the air arriving at Barrow, Alaska, we measured BrO, a marker of reactive halogen chemistry, and correlated its abundance with airmass histories derived from meteorological back trajectories and remotely sensed sea ice properties. The BrO is found to be positively correlated to first-year sea-ice contact (R2=0.55), and weakly negatively correlated to potential frost flower (PFF) contact (R2=0.04). These data indicate that snow contaminated with sea salts on first-year sea ice is a more probable bromine source than are frost flowers. Recent climate-driven changes in Arctic sea ice are likely to alter frost flower and first year sea ice prevalence, suggesting a significant change in reactive halogen abundance, which will alter the chemistry of the overlying Arctic atmosphere
- …