3,261 research outputs found
Modulation of calcium and potassium currents by lamotrigine
Actions of the new antiepileptic drug lamotrigine (LTG) were characterized using extracellular and whole cell patch clamp recordings from rat CAI and CA3 pyramidal cells in vitro. The results suggest that LTG, beside its previously described effect on the fast sodium inward current, also modulates - presumably voltage-gated - calcium currents and the transient potassium outward current ID. These may be effective mechanisms to inhibit pathological excitation in epilepsy and may be of potential benefit in treating: underlying cellular disturbances in bipolar disorder
Laser-induced fluorescence studies of HfF+ produced by autoionization
Autoionization of Rydberg states of HfF, prepared using the optical-optical
double resonance (OODR) technique, holds promise to create HfF+ in a particular
Zeeman level of a rovibronic state for an electron electric dipole moment
(eEDM) search. We characterize a vibronic band of Rydberg HfF at 54 cm-1 above
the lowest ionization threshold and directly probe the state of the ions formed
from this vibronic band by performing laser-induced fluorescence (LIF) on the
ions. The Rydberg HfF molecules show a propensity to decay into only a few ion
rotational states of a given parity and are found to preserve their orientation
qualitatively upon autoionization. We show empirically that we can create 30%
of the total ion yield in a particular |J+,M+> state and present a simplified
model describing autoionization from a given Rydberg state that assumes no
angular dynamics.Comment: 8 pages, 5 figure
Fundamental Neutron Physics at Spallation Sources
Low-energy neutrons have been a useful probe in fundamental physics studies for more than 70 years. With advances in accelerator technology, many new sources are spallation based. These new, high-flux facilities are becoming the sites for many next-generation fundamental neutron physics experiments. In this review, we present an overview of the sources and the current and upcoming fundamental neutron physics programs
Safety of Log Transportation After Regulation and Training in the State of Georgia, USA
Mechanical failure rates observed in highway accidents involving logging tractor-trailers have fallen significantly since Georgia subjected these vehicles to random roadside inspections. This improvement is attributed to both the regulation and the training efforts aimed at the log trucking community immediately before and after the implementation of the rules
Identification of the heart as the critical site of adenosine mediated embryo protection
<p>Abstract</p> <p>Background</p> <p>Our understanding of the mechanisms that protect the developing embryo from intrauterine stress is limited. Recently, adenosine has been demonstrated to play a critical role in protecting the embryo against hypoxia via adenosine A1 receptors (A1ARs), which are expressed in the heart, nervous system, and other sites during development. However, the sites of A1AR action that mediate embryo protection are not known. To determine if the heart is a key site of adenosine-mediated embryo protection, A1ARs were selectively deleted in the embryonic heart using a Cre-LoxP system in which the alpha-myosin heavy chain promoter drives Cre-recombinase expression and excision of the A1AR gene from cardiomyocytes.</p> <p>Results</p> <p>With increasing exposure of maternal hypoxia (10% O<sub>2</sub>) from 48-96 hours beginning at embryonic day (E) 8.5, embryo viability decreased in the cardiac-A1AR deleted embryos. 48 hours of hypoxia reduced embryonic viability by 49% in embryos exposed from E10.5-12.5 but no effect on viability was observed in younger embryos exposed to hypoxia from E8.5-10.5. After 72 hours of hypoxia, 57.8% of the cardiac-A1AR deleted embryos were either dead or re-absorbed compared to 13.7% of control littermates and after 96 hours 81.6% of cardiac-A1AR deleted embryos were dead or re-absorbed. After 72 hours of hypoxia, cardiac size was reduced significantly more in the cardiac-A1AR deleted hearts compared to controls. Gene expression analysis revealed clusters of genes that are regulated by both hypoxia and A1AR expression.</p> <p>Conclusions</p> <p>These data identify the embryonic heart as the critical site where adenosine acts to protect the embryo against hypoxia. As such these studies identify a previously unrecognized mechanism of embryo protection.</p
The Host Galaxy and Central Engine of the Dwarf AGN POX 52
We present new multi-wavelength observations of the dwarf Seyfert 1 galaxy
POX 52 in order to investigate the properties of the host galaxy and the active
nucleus, and to examine the mass of its black hole, previously estimated to be
~ 10^5 M_sun. Hubble Space Telescope ACS/HRC images show that the host galaxy
has a dwarf elliptical morphology (M_I = -18.4 mag, Sersic index n = 4.3) with
no detected disk component or spiral structure, confirming previous results
from ground-based imaging. X-ray observations from both Chandra and XMM show
strong (factor of 2) variability over timescales as short as 500 s, as well as
a dramatic decrease in the absorbing column density over a 9 month period. We
attribute this change to a partial covering absorber, with a 94% covering
fraction and N_H = 58^{+8.4}_{-9.2} * 10^21 cm^-2, that moved out of the line
of sight in between the XMM and Chandra observations. Combining these data with
observations from the VLA, Spitzer, and archival data from 2MASS and GALEX, we
examine the spectral energy distribution (SED) of the active nucleus. Its shape
is broadly similar to typical radio-quiet quasar SEDs, despite the very low
bolometric luminosity of L_bol = 1.3 * 10^43 ergs/s. Finally, we compare black
hole mass estimators including methods based on X-ray variability, and optical
scaling relations using the broad H-beta line width and AGN continuum
luminosity, finding a range of black hole mass from all methods to be M_bh =
(2.2-4.2) * 10^5 M_sun, with an Eddington ratio of L_bol/L_edd = 0.2-0.5.Comment: 19 pages, 16 figures, accepted for publication in Ap
The statistical mechanics of complex signaling networks : nerve growth factor signaling
It is becoming increasingly appreciated that the signal transduction systems
used by eukaryotic cells to achieve a variety of essential responses represent
highly complex networks rather than simple linear pathways. While significant
effort is being made to experimentally measure the rate constants for
individual steps in these signaling networks, many of the parameters required
to describe the behavior of these systems remain unknown, or at best,
estimates. With these goals and caveats in mind, we use methods of statistical
mechanics to extract useful predictions for complex cellular signaling
networks. To establish the usefulness of our approach, we have applied our
methods towards modeling the nerve growth factor (NGF)-induced differentiation
of neuronal cells. Using our approach, we are able to extract predictions that
are highly specific and accurate, thereby enabling us to predict the influence
of specific signaling modules in determining the integrated cellular response
to the two growth factors. We show that extracting biologically relevant
predictions from complex signaling models appears to be possible even in the
absence of measurements of all the individual rate constants. Our methods also
raise some interesting insights into the design and possible evolution of
cellular systems, highlighting an inherent property of these systems wherein
particular ''soft'' combinations of parameters can be varied over wide ranges
without impacting the final output and demonstrating that a few ''stiff''
parameter combinations center around the paramount regulatory steps of the
network. We refer to this property -- which is distinct from robustness -- as
''sloppiness.''Comment: 24 pages, 10 EPS figures, 1 GIF (makes 5 multi-panel figs + caption
for GIF), IOP style; supp. info/figs. included as brown_supp.pd
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