4,005 research outputs found
Sofic-Dyck shifts
We define the class of sofic-Dyck shifts which extends the class of
Markov-Dyck shifts introduced by Inoue, Krieger and Matsumoto. Sofic-Dyck
shifts are shifts of sequences whose finite factors form unambiguous
context-free languages. We show that they correspond exactly to the class of
shifts of sequences whose sets of factors are visibly pushdown languages. We
give an expression of the zeta function of a sofic-Dyck shift
Magnetic and electronic structures of superconducting RuSrGdCuO
The coexistence of ferromagnetism and superconductivity in
RuSrGdCuO was reported both from experiments (by Tallon et. al.)
and first-principles calculations (by Pickett et. al.). Here we report that our
first-principles full-potential linearized augmented plane wave (FLAPW)
calculations, employing the precise crystal structure with structural
distortions (i.e., RuO rotations) determined by neutron diffraction,
demonstrate that antiferromagnetic ordering of the Ru moments is energetically
favored over the previously proposed ferromagnetic ordering. Our results are
consistent with recently performed magnetic neutron diffraction experiments
(Lynn et. al). Ru states, which are responsible for the magnetism,
have only a very small interaction with Cu states, which results in a
small exchange splitting of these states. The Fermi surface, characterized by
strongly hybridized orbitals, has nesting features similar to those
in the two-dimensional high cuprate superconductors.Comment: 6 pages,6 figures, accepted for publication in Phys. Rev.
The Equivalence Problem for Deterministic MSO Tree Transducers is Decidable
It is decidable for deterministic MSO definable graph-to-string or
graph-to-tree transducers whether they are equivalent on a context-free set of
graphs
The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star Forming Clumps
We sort molecular clouds between from the
Bolocam Galactic Plane Survey based on observational diagnostics of star
formation activity: compact sources, mid-IR color-selected
YSOs, and masers, and UCHII regions. We also
present a combined -derived gas kinetic temperature and maser catalog for clumps from our own GBT 100m observations and
from the literature. We identify a subsample of () starless
clump candidates, the largest and most robust sample identified from a blind
survey to date. Distributions of flux density, flux concentration, solid angle,
kinetic temperature, column density, radius, and mass show strong ( dex)
progressions when sorted by star formation indicator. The median starless clump
candidate is marginally sub-virial () with of clumps
with known distance being gravitationally bound (). These samples
show a statistically significant increase in the median clump mass of M from the starless candidates to clumps associated with
protostars. This trend could be due to (i) mass growth of the clumps at
Msun Myr for an average free-fall Myr
time-scale, (ii) a systematic factor of two increase in dust opacity from
starless to protostellar phases, (iii) and/or a variation in the ratio of
starless to protostellar clump lifetime that scales as . By
comparing to the observed number of maser containing clumps we
estimate the phase-lifetime of massive ( M) starless clumps to
be ; the majority
( M) have phase-lifetimes longer than their average free-fall
time.Comment: Accepted for publication in ApJ; 33 pages; 22 figures; 7 table
Genetically Encoded Biosensors Reveal PKA Hyperphosphorylation on the Myofilaments in Rabbit Heart Failure
RATIONALE:
In heart failure, myofilament proteins display abnormal phosphorylation, which contributes to contractile dysfunction. The mechanisms underlying the dysregulation of protein phosphorylation on myofilaments is not clear.
OBJECTIVE:
This study aims to understand the mechanisms underlying altered phosphorylation of myofilament proteins in heart failure.
METHODS AND RESULTS:
We generate a novel genetically encoded protein kinase A (PKA) biosensor anchored onto the myofilaments in rabbit cardiac myocytes to examine PKA activity at the myofilaments in responses to adrenergic stimulation. We show that PKA activity is shifted from the sarcolemma to the myofilaments in hypertrophic failing rabbit myocytes. In particular, the increased PKA activity on the myofilaments is because of an enhanced ÎČ2 adrenergic receptor signal selectively directed to the myofilaments together with a reduced phosphodiesterase activity associated with the myofibrils. Mechanistically, the enhanced PKA activity on the myofilaments is associated with downregulation of caveolin-3 in the hypertrophic failing rabbit myocytes. Reintroduction of caveolin-3 in the failing myocytes is able to normalize the distribution of ÎČ2 adrenergic receptor signal by preventing PKA signal access to the myofilaments and to restore contractile response to adrenergic stimulation.
CONCLUSIONS:
In hypertrophic rabbit myocytes, selectively enhanced ÎČ2 adrenergic receptor signaling toward the myofilaments contributes to elevated PKA activity and PKA phosphorylation of myofilament proteins. Reintroduction of caveolin-3 is able to confine ÎČ2 adrenergic receptor signaling and restore myocyte contractility in response to ÎČ adrenergic stimulation
The Green Bank Ammonia Survey: Unveiling the Dynamics of the Barnard 59 star-forming Clump
Understanding the early stages of star formation is a research field of
ongoing development, both theoretically and observationally. In this context,
molecular data have been continuously providing observational constraints on
the gas dynamics at different excitation conditions and depths in the sources.
We have investigated the Barnard 59 core, the only active site of star
formation in the Pipe Nebula, to achieve a comprehensive view of the kinematic
properties of the source. These information were derived by simultaneously
fitting ammonia inversion transition lines (1,1) and (2,2). Our analysis
unveils the imprint of protostellar feedback, such as increasing line widths,
temperature and turbulent motions in our molecular data. Combined with
complementary observations of dust thermal emission, we estimate that the core
is gravitationally bound following a virial analysis. If the core is not
contracting, another source of internal pressure, most likely the magnetic
field, is supporting it against gravitational collapse and limits its star
formation efficiency.Comment: 18 pages, 18 figure
Disruption of a Proto-Planetary Disk by the Black Hole at the Milky Way Centre
Recently, an ionized cloud of gas was discovered plunging toward the
supermassive black hole, SgrA*, at the centre of the Milky Way. The cloud is
being tidally disrupted along its path to closest approach at ~3100
Schwarzschild radii from the black hole. Here, we show that the observed
properties of this cloud of gas can naturally be produced by a proto-planetary
disk surrounding a low-mass star, which was scattered from the observed ring of
young stars orbiting SgrA*. As the young star approaches the black hole, its
disk experiences both photo-evaporation and tidal disruption, producing a
cloud. Our model implies that planets form in the Galactic centre, and that
tidal debris from proto-planetary disks can flag low mass stars which are
otherwise too faint to be detected.Comment: Accepted to Nature Communications; new Figure 4b provides predicted
Br-gamma emission as a function of tim
Chemiluminescence in activated human neutrophils
Human neutrophils (PMNs) suspended in Hanks' balanced salt solution (HBSS), which are stimulated either by polycation-opsonized streptococci or by phorbol myristate acetate (PMA), generate nonamplified (CL), luminol-dependent (LDCL), and lucigenin-dependent chemiluminescence (LUCDCL). Treatment of activated PMNs with azide yielded a very intense CL response, but only a small LDCL or LUCDCL responses, when horse radish peroxidase (HRP) was added. Both CL and LDCL depend on the generation of Superoxide and on myeloperoxidase (MPO). Treatment of PMNs with azide followed either by dimethylthiourea (DMTU), deferoxamine, EDTA, or detapac generated very little CL upon addition of HRP, suggesting that CL is the: result of the interaction among H 2 O 2 , a peroxidase, and trace metals. In a cell-free system practically no CL was generated when H 2 O 2 was mixed with HRP in distilled water (DW). On the other hand significant CL was generated when either HBSS or RPMI media was employed. In both cases CL was markedly depressed either by deferoxamine or by EDTA, suggesting that these media might be contaminated by trace metals, which catalyzed a Fenton-driven reaction. Both HEPES and Tris buffers, when added to DW, failed to support significant HRP-induced CL. Nitrilotriacetate (NTA) chelates of Mn 2+ , Fe 2+ , Cu 2+ , and Co 2+ very markedly enhanced CL induced by mixtures of H 2 O 2 and HRP when distilled water was the supporting medium. Both HEPES and Tris buffer when added to DW strongly quenced NTA-metal-catalyzed CL. None of the NTA-metal chelates could boost CL generation by activated PMNs, because the salts in HBSS and RPMI interfered with the activity of the added metals. CL and LDCL of activated PMNs was enhanced by aminotriazole, but strongly inhibited by diphenylene iodonium (an inhibitor of NADPH oxidase) by azide, sodium cyanide (CN), cimetidine, histidine, benzoate, DMTU and moderately by Superoxide dismutase (SOD) and by deferoxamine. LUCDCL was markedly inhibited only by SOD but was boosted by CN. Taken together, it is suggested that CL generated by stimulated PMNs might be the result of the interactions among, NADPH oxidase, (inhibitable by diphenylene iodonium), MPO (inhibitable by sodium azide), H 2 O 2 probably of intracellular origin (inhibitable by DMTU but not by catalase), and trace metals that contaminate salt solutions. The nature of the salt solutions employed to measure CL in activated PMNs is critical.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44510/1/10753_2004_Article_BF00918987.pd
Representing addition and subtraction : learning the formal conventions
The study was designed to test the effects of a structured intervention in teaching children to represent addition and subtraction. In a post-test only control group design, 90 five-year-olds experienced the intervention entitled Bi-directional Translation whilst 90 control subjects experienced typical teaching. Post-intervention testing showed some significant differences between the two groups both in terms of being able to effect the addition and subtraction operations and in being able to determine which operation was appropriate. The results suggest that, contrary to historical practices, children's exploration of real world situations should precede practice in arithmetical symbol manipulation
Basal Ganglia Involvement in the Playfulness of Juvenile Rats
Play is an important part of normal childhood development and can be readily studied in the laboratory rat in the form of roughâandâtumble play. Given the robust nature of roughâandâtumble play, it has often been assumed that the basal ganglia would have a prominent role in modulating this behavior. Recent work using câfos expression as a metabolic marker for neural activity combined with temporary inactivation of relevant corticostriatal regions and pharmacological manipulations of opioid, cannabinoid, and dopamine systems has led to a better understanding of how basal ganglia circuitry may be involved in modulating social play in the juvenile rat. Studies using selective play deprivation have also provided insight into the consequences of playful experiences on basal ganglia function. Data reviewed in this paper support a role for the basal ganglia in social play and also suggest that corticostriatal functioning also benefits from playful activities
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