22,646 research outputs found
New Wrinkles on an Old Model: Correlation Between Liquid Drop Parameters and Curvature Term
The relationship between the volume and surface energy coefficients in the
liquid drop A^{-1/3} expansion of nuclear masses is discussed. The volume and
surface coefficients in the liquid drop expansion share the same physical
origin and their physical connection is used to extend the expansion with a
curvature term. A possible generalization of the Wigner term is also suggested.
This connection between coefficients is used to fit the experimental nuclear
masses. The excellent fit obtained with a smaller number of parameters
validates the assumed physical connection.Comment: 6 pages, 2 figure
An inter-university consortium on multi-party conflict, interim funding
Issued as Proposal and Progress repor
Deterministic amplification of Schroedinger cat states in circuit quantum electrodynamics
We propose a dynamical scheme for deterministically amplifying photonic
Schroedinger cat states based on a set of optimal state-transfers. The scheme
can be implemented in strongly coupled qubit-cavity systems and is well suited
to the capabilities of state of the art superconducting circuits. The ideal
analytical scheme is compared with a full simulation of the open
Jaynes-Cummings model with realistic device parameters. This amplification tool
can be utilized for practical quantum information processing in non-classical
continuous-variable states.Comment: A revised manuscript has 6 figure
The long gamma-ray burst rate and the correlation with host galaxy properties
To answer questions on the start and duration of the epoch of reionisation,
periods of galaxy mergers and properties of other cosmological encounters, the
cosmic star formation history (CSFH), is of fundamental importance. Using the
association of long gamma-ray bursts (LGRBs) with the death of massive stars
and their ultra-luminous nature, the CSFH can be probed to higher redshifts
than current conventional methods. Unfortunately, no consensus has been reached
on the manner in which the LGRB rate (LGRBR) traces the CSFH, leaving many of
the questions mentioned mostly unexplored by this method. Observations by the
GRB NIR detector (GROND) over the past 4 years have, for the first time,
acquired highly complete LGRB samples. Driven by these completeness levels and
new evidence of LGRBs also occurring in more massive and metal rich galaxies
than previously thought, the possible biases of the LGRBR-CSFH connection are
investigated over a large range of galaxy properties. The CSFH is modelled
using empirical fits to the galaxy mass function and galaxy star formation
rates. Biasing the CSFH by metallicity cuts, mass range boundaries, and other
unknown redshift dependencies, a LGRBR is generated and compared to the highly
complete GROND sample. It is found that there is no strong preference for a
metallicity cut or fixed galaxy mass boundaries and that there are no unknown
redshift effects, in contrast to previous work which suggest values of
Z/Z_sun~0.1-0.3. From the best-fit models, we predict that ~1.2% of the LGRB
burst sample exists above z=6. The linear relationship between the LGRBR and
the CSFH suggested by our results implies that redshift biases present in
previous LGRB samples significantly affect the inferred dependencies of LGRBs
on their host galaxy properties. Such biases can lead to, e.g., an
interpretation of metallicity limitations and evolving LGRB luminosity
functions.Comment: 15 pages, 14 figures, 7 tables, accepted for publication in Astronomy
& Astrophysic
The Interference Term between the Spin and Orbital Contributions to M1 Transitions
We study the cross-correlation between the spin and orbital parts of magnetic
dipole transitions M1 in both isoscalar and isovector channels. In particular,
we closely examine certain cases where is very close to , implying a cancellation of the summed
interference terms. We gain some insight into this problem by considering
special cases approaching the SU(3) limit, and by examining the behaviour of
single-particle transitions at the beginning and towards the end of the s-d
shell.Comment: 9 pages of latex file and no figure
Direct Use of Low Enthalpy Deep Geothermal Resources in the East African Rift Valley
Geothermal energy is already harnessed across East Africa to provide hundreds of megawatts of electricity, with significant plans for future expansion towards generation at the gigawatt scale. This power generation utilizes the high steam temperatures (typically more than 200 °C) that are available in several locations in Kenya, Ethiopia and elsewhere. The presence of these high enthalpy resources has deflected attention from the often attractive low and medium enthalpy resources present across a more extensive portion of the region. Geothermally heated water at cooler temperatures (less than 90 °C) could be widely produced by drilling shallower and cheaper boreholes than those required for power production. This low enthalpy resource could be widely exploitable throughout the Rift Valley, offering a low carbon, sustainable, reliable and commercially competitive source of heating, drying and cooling (via absorption chillers) to local farmers and growers, and for low temperature commercial and industrial uses. Applications of this type would displace expensive fossil fuels, reducing costs and carbon emissions as well as improving the region’s energy and food security. The power input for pump systems can be accommodated by relatively small generators, so direct heat projects could be beneficial to consumers in areas with no grid access
The effect of reflux in the continuous separation of hydrocarbon mixtures by rectification
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1924.Includes bibliographical references.by L. P. Elliott and Emil H. M. Lehnhardt.M.S
The structural effects of mutations can aid in differential phenotype prediction of beta-myosin heavy chain (Myosin-7) missense variants
MOTIVATION: High-throughput sequencing platforms are increasingly used to screen patients with genetic disease for pathogenic mutations, but prediction of the effects of mutations remains challenging. Previously we developed SAAPdap (Single Amino Acid Polymorphism Data Analysis Pipeline) and SAAPpred (Single Amino Acid Polymorphism Predictor) that use a combination of rule-based structural measures to predict whether a missense genetic variant is pathogenic. Here we investigate whether the same methodology can be used to develop a differential phenotype predictor, which, once a mutation has been predicted as pathogenic, is able to distinguish between phenotypes-in this case the two major clinical phenotypes (hypertrophic cardiomyopathy, HCM, and dilated cardiomyopathy, DCM) associated with mutations in the beta-myosin heavy chain (MYH7) gene product (Myosin-7). RESULTS: A random forest predictor trained on rule-based structural analyses together with structural clustering data gave a Matthews' correlation coefficient (MCC) of 0.53 (accuracy, 75%). A post hoc removal of machine learning models that performed particularly badly, increased the performance (MCC = 0.61, Acc = 79%). This proof of concept suggests that methods used for pathogenicity prediction can be extended for use in differential phenotype prediction
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