219 research outputs found
Minimum Distance Estimation of Milky Way Model Parameters and Related Inference
We propose a method to estimate the location of the Sun in the disk of the
Milky Way using a method based on the Hellinger distance and construct
confidence sets on our estimate of the unknown location using a bootstrap based
method. Assuming the Galactic disk to be two-dimensional, the sought solar
location then reduces to the radial distance separating the Sun from the
Galactic center and the angular separation of the Galactic center to Sun line,
from a pre-fixed line on the disk. On astronomical scales, the unknown solar
location is equivalent to the location of us earthlings who observe the
velocities of a sample of stars in the neighborhood of the Sun. This unknown
location is estimated by undertaking pairwise comparisons of the estimated
density of the observed set of velocities of the sampled stars, with densities
estimated using synthetic stellar velocity data sets generated at chosen
locations in the Milky Way disk according to four base astrophysical models.
The "match" between the pair of estimated densities is parameterized by the
affinity measure based on the familiar Hellinger distance. We perform a novel
cross-validation procedure to establish a desirable "consistency" property of
the proposed method.Comment: 25 pages, 10 Figures. This version incorporates the suggestions made
by the referees. To appear in SIAM/ASA Journal on Uncertainty Quantificatio
Selective reduction of neurotransmitter release by cAMP-dependent pathways in mouse detrusor
Parasympathetic nerve-mediated contractions of detrusor smooth muscle are generated by ATP and acetylcholine (ACh) release from efferent nerve terminals. In humans, ACh is responsible for detrusor contractions in normal human bladders, whereas ATP has an additional role in overactive bladder pathologies. The ATP metabolite, adenosine, relaxes nerve-mediated contractions, with a potential action via presynaptic adenosine A1 receptor activation and subsequent suppression of neuronal ATP release. We investigated the effect of A1 receptor activation and downstream cAMP-dependent pathways on nerve-mediated ATP and ACh release, and detrusor contraction in mouse detrusor. Bladders from male C57BL/6 mice (12 wk) were used for in vitro experiments. Upon electrical field stimulation of intact preparations (detrusor and mucosal layers), ATP or ACh release was measured simultaneously with tension recordings. Activation of A1 receptors by adenosine or exogenous agonists reduced the lower frequency component of nerve-mediated contractions and neuronal ATP release. The A1 receptor antagonist abolished these effects. A1 receptor activation inhibits adenylyl cyclase (AC) activity and cAMP generation. The effect of A1 receptor activation was mimicked by a PKA antagonist but not by modulators of exchange proteins activated by cAMP, demonstrating that modulation of nerve-mediated ATP release is via PKA. Adenosine had no effect on ACh release or the higher frequency component of nerve-mediated contractions. Differential regulation of neurotransmitter release is possible at the detrusor nerve-muscle junction, as demonstrated by A1 receptor activation, and downstream inhibition of AC, cAMP generation, and PKA. The ability to specifically attenuate ATP release offers a potential to target purinergic motor pathways enhanced in overactive bladder pathologies
Stretch- and carbachol-induced ATP release from bladder wall preparations of young and aged mice
Aims
Bladder wall stretch increases tissue tension and releases adenosine 5'âtriphosphate (ATP) as part of a transduction process to sense bladder filling. Aging is associated with bladder fibrosis to produce a stiffer bladder wall: this may augment ATP release and contribute to ageâdependent urgency. Muscarinic agonists also release ATP and present a potential target for antimuscarinic agents, but its ageâdependency is unknown. This study aimed, in young and old mice, to: (a) quantify the relationship between bladder wall stiffness and stretchâdependent ATP release and; (b) characterize muscarinic agonistâdependent release.
Methods
ATP release from young (9â12 weeks) and aged (24 months) mouse bladder wall was measured in vitro, with a luciferinâluciferase assay, after stretch or carbachol exposure. Bladder wall stiffness, measured simultaneously during stretch, was compared to histological proportions of connective tissue and detrusor muscle.
Results
With young mice, stretchâactivated ATP release required an intact mucosa and was positively associated with wall stiffness. ATP release by carbachol was about fourâfold greater compared to stretch. With aged mice: ATP release varied a hundredâfold and no association with stiffness; carbachol release diminished; connective tissue and mucosa thickness increased.
Conclusions
With young mice, stretch, or muscarinic agonists potently induce bladder wall ATP release. Stretchâdependent release is proportional to bladder wall stiffness, independent of the extent of stretch. With aged mice dependence of stretchâactivated ATP release with stiffness was lost. The huge variability of release suggests that aged mice do not form a homogenous cohort and may underlie the heterogeneity in bladder filling sensations.</p
Quantum dot with spin-orbit interaction in noncommutative phase space and analog Landau levels
We have studied a quantum dot with Rashba spin orbit interaction on a plane
where the position and momentum coordinates are considered to be
noncommutative. The energy spectrum of the system is found to be equivalent to
that of a quantum dot with Rashba spin-orbit interaction in a magnetic field
under certain conditions.Comment: 12 page
Trigonocephaly pre- and post-operative evaluation by multidetector computed tomography
Trigonocephaly is the third most common single suture synostosis which is seen as bulging of the forehead due to early fusion of themetopic suture. It is linked with an increased level of neurodevelopmental delays. On imaging, multidetector computed tomographyshows anterior fontanelle ossification, hypoteliorism, narrowing of the anterior cranial fossa, and compensatory increase of themiddle cranial fossa with atrophic features of brain. Its reported incidence is 1 in 700-15,000 live births. Operative multipleosteotomies were done and imaged in follow-up
Multifractal scaling of electronic transmission resonances in perfect and imperfect Fibonacci -function potentials
We present here a detailed multifractal scaling study for the electronic
transmission resonances with the system size for an infinitely large one
dimensional perfect and imperfect quasiperiodic system represented by a
sequence of -function potentials. The electronic transmission
resonances in the energy minibands manifest more and more fragmented nature of
the transmittance with the change of system sizes. We claim that when a small
perturbation is randomly present at a few number of sites, the nature of
electronic states will change and this can be understood by studying the
electronic transmittance with the change of system size. We report the
different critical states manifested in the size variation of the transmittance
corresponding to the resonant energies for both perfect and imperfect cases
through multifractal scaling study for few of these resonances.Comment: 7 pages, (Hard copies of 5 figures available on request from
[email protected]
Large spontaneous exchange bias in a weak ferromagnet Pb6Ni9(TeO6)5
We report the magnetic and dielectric behavior of Pb6Ni9(TeO6)5, a new
compound comprising the honeycomb-like layers of S=1 spins, through detailed
structural, magnetic and dielectric investigation. An antiferromagnetic-type
transition at 25 K (TN) with weak-ferromagnetic behavior is revealed.
Interestingly, a large value of coercive field of 1.32 T at 2 K is observed.
The isothermal magnetization after zero-field-cooled condition, it exhibits the
presence of large spontaneous exchange bias (SEB) with a magnitude of 0.19 T at
2 K; which is rare in single bulk materials, especially without external
doping. The value of |HEB| further enhances to 0.24 T under 16 T field-cooled
condition, confirming the presence of large exchange bias in the material. In
addition, the dielectric constant shows an anomaly at the onset of TN,
indicating the presence of magnetodielectric coupling.Comment: 16 pages, 6 figures, 2 supplimentory figures, under revision of
Scientific Report
Characterisation of nerveâmediated ATP release from bladder detrusor muscle and its pathological implications
Background and Purpose.
To characterise the molecular mechanisms that determine variability of atropineâresistance of nerveâmediated contractions in human and guineaâpig detrusor smooth muscle
Experimental Approach.
Atropineâresistance of nerveâmediated contractions, and the role of P2X1 receptors, was measured in isolated preparations from guineaâpigs and also humans with or without overactive bladder syndrome, from which the mucosa was removed. Nerveâmediated ATP release was measured directly with amperometric ATPâsensitive electrodes. EctoâATPase activity of guineaâpig and human detrusor samples was measured in vitro by measuring the concentrationâdependent rate of ATP breakdown. The transcription of ectoâATPase subtypes in human samples was measured by qPCR.
Key Results
Atropine resistance was greatest in guineaâpig detrusor, absent in human tissue from normallyâfunctioning bladders and intermediate in human overactive bladder. Greater atropine resistance correlated with reduction of contractions by the ATPâdiphosphoâhydrolase apyrase, directly implicating ATP in their generation. EâNTPDaseâ1 was the most abundantly transcribed ectoâATPase of those tested and transcription was reduced in tissue from human overactive, compared to normal, bladders. EâNTPDaseâ1 enzymatic activity was inversely related to the magnitude of atropine resistance. Nerveâmediated ATP release was continually measured and varied with stimulation frequency over the range 1â16 Hz.
Conclusion and Implications
Atropineâresistance in nerveâmediated detrusor contractions is due to ATP release and its magnitude is inversely related to EâNTPDaseâ1 activity. ATP is released under different stimulation conditions compared to acetylcholine that implies different routes for their release</p
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