17,912 research outputs found
3D model of amphioxus steroid receptor complexed with estradiol
The origins of signaling by vertebrate steroids are not fully understood. An important advance was the report that an estrogen-binding steroid receptor [SR] is present in amphioxus, a basal chordate with a similar body plan as vertebrates. To investigate the evolution of estrogen binding to steroid receptors, we constructed a 3D model of amphioxus SR complexed with estradiol. This 3D model indicates that although the SR is activated by estradiol, some interactions between estradiol and human ER[alpha] are not conserved in the SR, which can explain the low affinity of estradiol for the SR. These differences between the SR and ER[alpha] in the steroid-binding domain are sufficient to suggest that another steroid is the physiological regulator of the SR. The 3D model predicts that mutation of Glu-346 to Gln will increase the affinity of testosterone for amphioxus SR and elucidate the evolution of steroid binding to nuclear receptors
Off-resonance magnetisation transfer contrast (MTC) MRI using fast field-cycling (FFC)
Peer reviewedPostprin
Design and construction of an actively frequency-switchable RF coil for field-dependent Magnetisation Transfer Contrast MRI with fast field-cycling
Copyright Ā© 2010 Elsevier Inc. All rights reserved.Peer reviewedPostprin
Flavor SU(4) breaking between effective couplings
Using a framework in which all elements are constrained by Dyson-Schwinger
equation studies in QCD, and therefore incorporates a consistent, direct and
simultaneous description of light- and heavy-quarks and the states they
constitute, we analyze the accuracy of SU(4)-flavor symmetry relations between
{\pi}{\rho}{\pi}, K{\rho}K and D{\rho}D couplings. Such relations are widely
used in phenomenological analyses of the interactions between matter and
charmed mesons. We find that whilst SU(3)-flavor symmetry is accurate to 20%,
SU(4) relations underestimate the D{\rho}D coupling by a factor of five.Comment: 5 pages, two figure
High Performance, Continuously Tunable Microwave Filters using MEMS Devices with Very Large, Controlled, Out-of-Plane Actuation
Software defined radios (SDR) in the microwave X and K bands offer the
promise of low cost, programmable operation with real-time frequency agility.
However, the real world in which such radios operate requires them to be able
to detect nanowatt signals in the vicinity of 100 kW transmitters. This imposes
the need for selective RF filters on the front end of the receiver to block the
large, out of band RF signals so that the finite dynamic range of the SDR is
not overwhelmed and the desired nanowatt signals can be detected and digitally
processed. This is currently typically done with a number of narrow band
filters that are switched in and out under program control. What is needed is a
small, fast, wide tuning range, high Q, low loss filter that can continuously
tune over large regions of the microwave spectrum. In this paper we show how
extreme throw MEMS actuators can be used to build such filters operating up to
15 GHz and beyond. The key enabling attribute of our MEMS actuators is that
they have large, controllable, out-of-plane actuation ranges of a millimeter or
more. In a capacitance-post loaded cavity filter geometry, this gives
sufficient precisely controllable motion to produce widely tunable devices in
the 4-15 GHz regime.Comment: 12 pages 14 figures 2 table
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Nox2 redox signaling maintains essential cell populations in the brain.
Reactive oxygen species (ROS) are conventionally classified as toxic consequences of aerobic life, and the brain is particularly susceptible to ROS-induced oxidative stress and damage owing to its high energy and oxygen demands. NADPH oxidases (Nox) are a widespread source of brain ROS implicated in seizures, stroke and neurodegeneration. A physiological role for ROS generation in normal brain function has not been established, despite the fact that mice and humans lacking functional Nox proteins have cognitive deficits. Using molecular imaging with Peroxyfluor-6 (PF6), a new selective fluorescent indicator for hydrogen peroxide (H(2)O(2)), we show that adult hippocampal stem/progenitor cells (AHPs) generate H(2)O(2) through Nox2 to regulate intracellular growth signaling pathways, which in turn maintains their normal proliferation in vitro and in vivo. Our results challenge the traditional view that brain ROS are solely deleterious by demonstrating that controlled ROS chemistry is needed for maintaining specific cell populations
Features and flaws of a contact interaction treatment of the kaon
Elastic and semileptonic transition form factors for the kaon and pion are
calculated using the leading-order in a global-symmetry-preserving truncation
of the Dyson-Schwinger equations and a momentum-independent form for the
associated kernels in the gap and Bethe-Salpeter equations. The computed form
factors are compared both with those obtained using the same truncation but an
interaction that preserves the one-loop renormalisation-group behaviour of QCD
and with data. The comparisons show that: in connection with observables
revealed by probes with |Q^2|<~ M^2, where M~0.4GeV is an infrared value of the
dressed-quark mass, results obtained using a symmetry-preserving regularisation
of the contact-interaction are not realistically distinguishable from those
produced by more sophisticated kernels; and available data on kaon form factors
do not extend into the domain whereupon one could distinguish between the
interactions. The situation is different if one includes the domain Q^2>M^2.
Thereupon, a fully consistent treatment of the contact interaction produces
form factors that are typically harder than those obtained with QCD
renormalisation-group-improved kernels. Amongst other things also described are
a Ward identity for the inhomogeneous scalar vertex, similarity between the
charge distribution of a dressed-u-quark in the K^+ and that of the
dressed-u-quark in the pi^+, and reflections upon the point whereat one might
begin to see perturbative behaviour in the pion form factor. Interpolations of
the form factors are provided, which should assist in working to chart the
interaction between light-quarks by explicating the impact on hadron properties
of differing assumptions about the behaviour of the Bethe-Salpeter kernel.Comment: 17 pages, 9 figures, 4 table
Mems device with large out-of-plane actuation and low-resistance interconnect and methods of use
Source: United States Patent and Trademark Office, www.uspto.govāThe present application is directed to a MEMS device. The MEMS device includes a substrate having a first end and a second end extending along a longitudinal axis, the Substrate including an electrostatic actuator. The device also includes a movable plate having a first end and a second end. The device also includes a thermal actuator having a first end coupled to the first end of the substrate and a second end coupled to the first end of the plate. The actuator moves the plate in relation to the substrate. Further, the device includes a power source electrically coupled to the thermal actuator and the Substrate. The application is also directed to a method for operating a MEMS device
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