392 research outputs found
Dynamic Anchoring of PKA Is Essential during Oocyte Maturation
SummaryIn the final stages of ovarian follicular development, the mouse oocyte remains arrested in the first meiotic prophase, and cAMP-stimulated PKA plays an essential role in this arrest. After the LH surge, a decrease in cAMP and PKA activity in the oocyte initiates an irreversible maturation process that culminates in a second arrest at metaphase II prior to fertilization [1]. A-kinase anchoring proteins (AKAPs) mediate the intracellular localization of PKA and control the specificity and kinetics of substrate phosphorylation [2]. Several AKAPs have been identified in oocytes including one at 140 kDa [3, 4] that we now identify as a product of the Akap1 gene. We show that PKA interaction with AKAPs is essential for two sequential steps in the maturation process: the initial maintenance of meiotic arrest and the subsequent irreversible progression to the polar body extruded stage. A peptide inhibitor (HT31) that disrupts AKAP/PKA interactions stimulates oocyte maturation in the continued presence of high cAMP. However, during the early minutes of maturation, type II PKA moves from cytoplasmic sites to the mitochondria, where it associates with AKAP1, and this is shown to be essential for maturation to continue irreversibly
Magma production and growth of the lava dome of the Soufriere Hills Volcano, Montserrat, West Indies: November 1995 to November 1997
On whether azimuthal isotropy and alongshelf translational invariance are present in low-frequency acoustic propagation along the New Jersey shelfbreak
Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1762-1781, doi:10.1121/1.3672644.To understand the issues associated with the presence (or lack) of azimuthal isotropy and horizontal (along isobath) invariance of low-frequency (center frequencies of 600âHz and 900âHz) acoustic propagation in a shelfbreak environment, a series of experiments were conducted under the Autonomous Wide-Aperture Cluster for Surveillance component of the Shallow Water 2006 experiment. Transmission loss data reported here were from two mobile acoustic sources executing (nearly) circular tracks transmitting to sonobuoy receivers in the circle centers, and from one 12.5âkm alongshelf acoustic track. The circle radii were 7.5âkm. Data are from September 8, 2006. Details of the acoustic and environmental measurements are presented. Simple analytic and computer models are used to assess the variability expected due to the ocean and seabed conditions encountered. A comparison of model results and data is made, which shows preliminary consistency between the data and the models, but also points towards further work that should be undertaken specifically in enlarging the range and frequency parameter space, and in looking at integrated transmission loss.Office of Naval Research Code 32
Noneruptive Unrest at the Caldera of Alcedo Volcano (GalĂĄpagos Islands) Revealed by InSAR Data and Geodetic Modeling
Understanding volcanic unrest is crucial to forecasting eruptions. At active mafic calderas unrest culminates in eruption more frequently than at felsic calderas. However, the mafic caldera of Alcedo Volcano (Ecuador) has experienced repeated episodes of unrest without erupting, since at least 1992, when geodetic monitoring began. Here we investigate the unrest that occurred between 2007 and 2011 using interferometric synthetic aperture radar (InSAR) data and geodetic modeling. We observe an initial asymmetric uplift of the southern caldera floor (~30 cm of vertical motion) from 2007 to 2009, followed by subsidence of the uplifted area and contemporary uplift of the northwestern caldera rim between January and June 2010. Finally, from June 2010 through March 2011, caldera uplift resumed. The first uplift episode is best explained by inflation of a sill and the activation of an inner ring fault. Successive caldera subsidence and rim uplift are compatible with the withdrawal of magma from the previously inflated sill and its northwestern migration. The resumption of uplift is consistent with the repressurization of the sill. This evolution suggests episodic magma emplacement in a shallow reservoir beneath the caldera, with aborted lateral magma migration, probably due to the discontinuous supply from depth. This shortâterm deformation pattern matches well geological observations showing a longerâterm (hundreds of years at least) asymmetric uplift of the caldera floor, culminating in a weak resurgence of ~30 m. We propose that the monitored episodes of uplift represent shortâterm stages of the rarely observed incremental growth of a resurgent basaltic caldera
Long distance passive localization of vocalizing sei whales using an acoustic normal mode approach
Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1814-1825, doi:10.1121/1.3666015.During a 2âday period in mid-September 2006, more than 200, unconfirmed but identifiable, sei whale (Balaenoptera borealis) calls were collected as incidental data during a multidisciplinary oceanography and acoustics experiment on the shelf off New Jersey. Using a combined vertical and horizontal acoustic receiving array, sei whale movements were tracked over long distances (up to tens of kilometers) using a normal mode back propagation technique. This approach uses low-frequency, broadband passive sei whale call receptions from a single-station, two-dimensional hydrophone array to perform long distance localization and tracking by exploiting the dispersive nature of propagating normal modes in a shallow water environment. The back propagation approach is examined for accuracy and application to tracking the sei whale vocalizations identified in the vertical and horizontal array signals. This passive whale tracking, combined with the intensive oceanography measurements performed during the experiment, was also used to examine sei whale movements in relation to oceanographic features observed in this region.Office of Naval
Researc
Radioscience simulations in General Relativity and in alternative theories of gravity
In this communication, we focus on the possibility to test GR with
radioscience experiments. We present a new software that in a first step
simulates the Range/Doppler signals directly from the space time metric (thus
in GR and in alternative theories of gravity). In a second step, a
least-squares fit of the involved parameters is performed in GR. This software
allows one to get the order of magnitude and the signature of the modifications
induced by an alternative theory of gravity on radioscience signals. As
examples, we present some simulations for the Cassini mission in
Post-Einsteinian gravity and with the MOND External Field Effect.Comment: 4 pages; Proceedings of "Les Rencontres de Moriond 2011 - Gravitation
session
TOWARD IAVCEI GUIDELINES ON THE ROLES AND RESPONSIBILITIES OF SCIENTISTS INVOLVED IN VOLCANIC HAZARD EVALUATION, RISK MITIGATION AND CRISIS RESPONSE
The International Association for Volcanology and Chemistry
of the Earthâs Interior (IAVCEI), as the representative international
association of scientists working on volcanic hazard
evaluations and risk mitigation, promotes sustained open discussion
within the scientific community of many relevant issues,
including the following:
& how to best understand and forecast volcanic activity, the
associated hazards, and contribute to risk evaluations;
& the appropriate roles and responsibilities of scientists prior
to, during, and after crises;
& the nature of scientistsâ relationships with government authorities,
populations at risk, and the media;
& the manner and extent of involvement of scientists in processes
that eventually lead authorities to make decisions,
the extent of the liability or vulnerability of scientists to
the outcomes of these decisions, and the way that scientistsâ
input may be perceived and judged by others;
& the role of national and local culture and perception of risk
in both mitigation policy and communication of hazard
and risk;
& the effectiveness of descriptions of forecasted volcanic
phenomena and associated hazards, and of their related
uncertainties;
& how to best increase the awareness, preparedness and empowerment
of individuals, and society as a whole, in order
to reduce the impact of volcanic phenomena on society
In particular, IAVCEI, as a modern learned society wants to
offer through its media (e.g., its website, archives, documents,
recommendation notes) informative material, which can help
members and others to fulfill these roles and responsibilities.
In particular, scientists have a role in protecting populations
and societies from harm due to volcanic phenomena, within
the context of, and being cognizant of, diverse cultural needs
and settings.
Furthermore, IAVCEI wants to develop frameworks within
which relationships and communication with local communities,
media, and authorities can be fostered and improve
Significant internal waves and internal tides measured northeast of Taiwan
Author Posting. © The Author(s), 2013. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 71 (2013): 47-81, doi:10.1357/002224013807343416.Internal gravity waves in an area northeast of Taiwan are characterized using data from multiple sensor types. The data set includes intermittent information collected from a ship and short time series from moorings. Modeled nonlinear waves are fitted to observed nonlinear waves to provide self-consistent estimates of multiple wave parameters. A nonlinear internal wave of over 50 m amplitude, observed in deep water, is examined in detail. This wave was moving northward from the southern Okinawa Trough toward the continental shelf, and presumably formed from internal tides propagating northward from the Ilan Ridge area. A possible scenario for the formation of this wave from the internal tide is compared to related behavior south of Taiwan. On the outer continental shelf, a few large internal waves with maximum displacement greater than one-quarter of the water depth were measured with moorings. Sensors aboard ship and satellite recorded waves in this area traveling in many directions. Two possible causes (not mutually exclusive) for the multiple wave directions are scattering of nonlinear internal waves arriving from the south, and variable local generation of nonlinear gravity waves by the strong tidal and internal tidal currents. Internal tides on the shelf are relatively strong, among the strongest measured, having about 10 times greater kinetic energy density than numerous low-energy sites, which is consistent with the strong barotropic tides of the area. The ratio of diurnal baroclinic to barotropic kinetic energy found in this area is unusually high.Funding for the use of RV OR1 was provided by the National Science Council of
Taiwan. TFD was supported by the Office of Naval Research (ONR) Ocean Acoustics Program under
grants N00014-05-1-0482 and N00014-11-1-0194. AEN was supported under ONR grant N00014-
08-1-0763, and GG under ONR grant N00014-07-01-0482. HCG and MJC were supported by ONR
grants N00014-09-1-0392 and N00014-07-1-0650
Shallow Water â06 : a joint acoustic propagation/nonlinear internal wave physics experiment
Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 4 (2007): 156-167.Since the end of the Cold War,
the US Navy has had an increasing interest
in continental shelves and slopes as
operational areas. To work in such areas
requires a good understanding of ocean
acoustics, coastal physical oceanography,
and, in the modern era, autonomous
underwater vehicle (AUV) operations
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