1,204 research outputs found
P04-37. Kinetic and thermodynamic factors determine HIV-1 neutralizing potency of MPER-specific antibodies
The Survival of Mafic Magmatic Enclaves and the Timing of Magma Recharge
Many intermediate to felsic intrusive and extrusive rocks contain mafic magmatic enclaves that are evidence for magma recharge and mixing. Whether enclaves represent records of prolonged mixing  or synâeruptive recharge depends on their preservation potential in their intermediate to felsic host magmas. We present a model for enclave consumption where an initial stage of diffusive equilibration loosens the crystal framework in the enclave followed by advective erosion and disaggregation of the loose crystal layer. Using experimental data to constrain the propagation rate of the loosening front leads to enclave âerosionâ rates of 10â5â10â8 cm/s for subvolcanic magma systems. These rates suggest that under some circumstances, enclave records are restricted to synâeruptive processes, while in most cases, enclave populations represent the recharge history over centuries to millennia. On these timescales, mafic magmatic enclaves may be unique recorders that can be compared to societal and written records of volcano activity.Plain Language SummaryTwo major questions in volcano research are how magma chambers are built through time and how they are disrupted to cause volcanic eruptions. One piece of evidence that chambers are assembled by episodic magma addition from below (called ârechargeâ) comes from mingled magmas, where mingling is expressed by the presence of two or more chemically distinct magmas. In particular, the more primitive magma in such mingled magmas is commonly present as discrete blobs, called mafic magmatic enclaves. These enclaves are often interpreted as evidence for rechargeâtriggered volcanic eruptions. However, they may also form during recharge episodes that are not associated with volcanic eruptions and instead only feed and sustain the magma chamber. Here, we develop a model that estimates how long mafic magmatic enclaves survive in a chemically distinct magma chamber to better understand how information drawn from enclaves informs the two major questions above. We find that under most common conditions, they survive for centuries to millennia. Therefore, the presence of enclaves is not explicitly evidence for a rechargeâtriggered eruption without studying them in greater detail. That detail can then potentially provide information regarding both the run up to eruption as well as magma assembly over centuries and millennia.Key PointsCommon survival times for mafic enclaves in felsic volcanic systems are centuries to millennia extending timescale records from mineralsMafic enclaves record only synâeruptive processes in hot magmatic systemsMafic enclaves in plutonic systems may represent recharge histories of 10,000â100,000 yearsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156204/3/grl60839-sup-0002-2020GL087274-ds01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156204/2/grl60868_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156204/1/grl60868.pd
Ground-State Properties of a Rotating Bose-Einstein Condensate with Attractive Interaction
The ground state of a rotating Bose-Einstein condensate with attractive
interaction in a quasi-one-dimensional torus is studied in terms of the ratio
of the mean-field interaction energy per particle to the
single-particle energy-level spacing. The plateaus of quantized circulation are
found to appear if and only if with the lengths of the plateaus
reduced due to hybridization of the condensate over different angular-momentum
states.Comment: 4 pages, 2 figures, Accepted for publication in Physical Reveiw
Letter
Serum microRNAs as non-invasive biomarkers for cancer
Human serum and other body fluids are rich resources for the identification of novel biomarkers, which can be measured in routine clinical diagnosis. microRNAs are small non-coding RNA molecules, which have an important function in regulating RNA stability and gene expression. The deregulation of microRNAs has been linked to cancer development and tumor progression. Recently, it has been reported that serum and other body fluids contain sufficiently stable microRNA signatures. Thus, the profiles of circulating microRNAs have been explored in a variety of studies aiming at the identification of novel non-invasive biomarkers
NGC 6738: not a real open cluster
A photometric, astrometric and spectroscopic investigation of the poorly
studied open cluster NGC 6738 has been performed in order to ascertain its real
nature. NGC 6738 is definitely not a physical stellar ensemble: photometry does
not show a defined mean sequence, proper motions and radial velocities are
randomly distributed, spectro-photometric parallaxes range between 10 and 1600
pc, and the apparent luminosity function is identical to that of the
surrounding field. NGC 6738 therefore appears to be an apparent concentration
of a few bright stars projected on patchy background absorption.Comment: A&A, in press (compared with first submission to astro-ph, now Table
2 and Figure 4 are replaced with corrected versions
Enhancement of the Deuteron-Fusion Reactions in Metals and its Experimental Implications
Recent measurements of the reaction d(d,p)t in metallic environments at very
low energies performed by different experimental groups point to an enhanced
electron screening effect. However, the resulting screening energies differ
strongly for divers host metals and different experiments. Here, we present new
experimental results and investigations of interfering processes in the
irradiated targets. These measurements inside metals set special challenges and
pitfalls which make them and the data analysis particularly error-prone. There
are multi-parameter collateral effects which are crucial for the correct
interpretation of the observed experimental yields. They mainly originate from
target surface contaminations due to residual gases in the vacuum as well as
from inhomogeneities and instabilities in the deuteron density distribution in
the targets. In order to address these problems an improved differential
analysis method beyond the standard procedures has been implemented. Profound
scrutiny of the other experiments demonstrates that the observed unusual
changes in the reaction yields are mainly due to deuteron density dynamics
simulating the alleged screening energy values. The experimental results are
compared with different theoretical models of the electron screening in metals.
The Debye-H\"{u}ckel model that has been previously proposed to explain the
influence of the electron screening on both nuclear reactions and radioactive
decays could be clearly excluded.Comment: 22 pages, 12 figures, REVTeX4, 2-column format. Submitted to Phys.
Rev. C; accepte
Performance of parallel-in-time integration for Rayleigh BĂ©nard convection
RayleighâBĂ©nard convection (RBC) is a fundamental problem of fluid dynamics, with many applications to geophysical, astrophysical, and industrial flows. Understanding RBC at parameter regimes of interest requires complex physical or numerical experiments. Numerical simulations require large amounts of computational resources; in order to more efficiently use the large numbers of processors now available in large high performance computing clusters, novel parallelisation strategies are required. To this end, we investigate the performance of the parallel-in-time algorithm Parareal when used in numerical simulations of RBC. We present the first parallel-in-time speedups for RBC simulations at finite Prandtl number. We also investigate the problem of convergence of Parareal with respect to statistical numerical quantities, such as the Nusselt number, and discuss the importance of reliable online stopping criteria in these cases
Instantons and radial excitations in attractive Bose-Einstein condensates
Imaginary- and real-time versions of an equation for the condensate density
are presented which describe dynamics and decay of any spherical Bose-Einstein
condensate (BEC) within the mean field appraoch. We obtain quantized energies
of collective finite amplitude radial oscillations and exact numerical
instanton solutions which describe quantum tunneling from both the metastable
and radially excited states of the BEC of 7Li atoms. The mass parameter for the
radial motion is found different from the gaussian value assumed hitherto, but
the effect of this difference on decay exponents is small. The collective
breathing states form slightly compressed harmonic spectrum, n=4 state lying
lower than the second Bogolyubov (small amplitude) mode. The decay of these
states, if excited, may simulate a shorter than true lifetime of the metastable
state. By scaling arguments, results extend to other attractive BEC-s.Comment: 6 pages, 3 figure
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