2,649 research outputs found
Droplet deformation by short laser-induced pressure pulses
When a free-falling liquid droplet is hit by a laser it experiences a strong
ablation driven pressure pulse. Here we study the resulting droplet deformation
in the regime where the ablation pressure duration is short, i.e. comparable to
the time scale on which pressure waves travel through the droplet. To this end
an acoustic analytic model for the pressure-, pressure impulse- and velocity
fields inside the droplet is developed in the limit of small density
fluctuations. This model is used to examine how the droplet deformation depends
on the pressure pulse duration while the total momentum to the droplet is kept
constant. Within the limits of this analytic model, we demonstrate that when
the total momentum transferred to the droplet is small the droplet
shape-evolution is indistinguishable from an incompressible droplet
deformation. However, when the momentum transfer is increased the droplet
response is strongly affected by the pulse duration. In this later regime,
compressed flow regimes alter the droplet shape evolution considerably.Comment: Submitted to JF
Recommended from our members
Chance-Constrained Efficiency Analysis
Data envelopment analysis (DEA) is extended to the case of stochastic inputs and outputs through the use of chance-constrained programming. The chance-constrained envelope envelops a given set of observations "most of the time." We show that the chance-constrained enveloping process leads to the definition of a conventional (certainty-equivalent) efficiency ratio (a ratio between weighted outputs and weighted inputs). Furthermore, extending the concept of Pareto and Koopmans efficiency to the case of chance-constrained dominance (to be defined), we establish the identity of the following two chance-constrained efficiency concepts: (i) the chance constrained DEA efficiency measure of a particular output-input point is unity, and all chance-constraints are binding; (ii) the point is efficient in the sense Pareto and Koopmans. Finally we discuss the implications of our approach for econometric frontier analysis.IC2 Institut
End of a Dark Age?
We argue that dark matter and dark energy phenomena associated with galactic
rotation curves, X-ray cluster mass profiles, and type Ia supernova data can be
accounted for via small corrections to idealized general relativistic spacetime
geometries due to disordered locality. Accordingly, we fit THINGS rotation
curve data rivaling modified Newtonian dynamics, ROSAT/ASCA X-ray cluster mass
profile data rivaling metric-skew-tensor gravity, and SCP Union2.1 SN Ia data
rivaling CDM without non-baryonic dark matter or a cosmological
constant. In the case of dark matter, we geometrically modify proper mass
interior to the Schwarzschild solution. In the case of dark energy, we modify
proper distance in Einstein-deSitter cosmology. Therefore, the phenomena of
dark matter and dark energy may be chimeras created by an errant belief that
spacetime is a differentiable manifold rather than a disordered graph.Comment: This version was accepted for publication in the International
Journal of Modern Physics D; revised version of an essay that won Honorable
Mention in the Gravity Research Foundation 2016 Awards for Essays on
Gravitation. 10 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1509.0928
The Missing Mass Problem as a Manifestation of GR Contextuality
In Newtonian gravity, mass is an intrinsic property of matter while in
general relativity (GR), mass is a contextual property of matter, i.e., matter
can simultaneously possess two different values of mass when it is responsible
for two different spatiotemporal geometries. Herein, we explore the possibility
that the astrophysical missing mass attributed to non-baryonic dark matter (DM)
actually obtains because we have been assuming the Newtonian view of mass
rather than the GR view. Since an exact GR solution for realistic astrophysical
situations is not feasible, we explore GR-motivated ansatzes relating proper
mass and dynamic mass for one and the same baryonic matter, as justified by GR
contextuality. We consider four GR alternatives and find that the GR ansatz
motivated by metric perturbation theory works well in fitting galactic rotation
curves (THINGS data), the mass profiles of X-ray clusters (ROSAT and ASCA data)
and the angular power spectrum of the cosmic microwave background (CMB, Planck
2015 data) without DM. We compare our galactic rotation curve fits to modified
Newtonian dynamics (MOND), Burkett halo DM and Navarro-Frenk-White (NFW) halo
DM. We compare our X-ray cluster mass profile fits to metric skew-tensor
gravity (MSTG) and core-modified NFW DM. We compare our CMB angular power
spectrum fit to scalar-tensor-vector gravity (STVG) and CDM. Overall,
we find our fits to be comparable to those of MOND, MSTG, STVG, CDM,
Burkett, and NFW. We present and discuss correlations and trends for the best
fit values of our fitting parameters. For the most part, the correlations are
consistent with well-established results at all scales, which is perhaps
surprising given the simple functional form of the GR ansatz.Comment: 18 pages text. Twice revised per referee/reviewer comments. Fit of
CMB angular power spectrum and dark matter halo fits adde
Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light
We present and experimentally validate a model describing the sensitivity of
the tilt angle, expansion and propulsion velocity of a tin micro-droplet
irradiated by a 1 {\mu}m Nd:YAG laser pulse to its relative alignment. This
sensitivity is particularly relevant in industrial plasma sources of extreme
ultraviolet light for nanolithographic applications. Our model has but a single
parameter: the dimensionless ratio of the laser spot size to the effective size
of the droplet, which is related to the position of the plasma critical density
surface. Our model enables the development of straightforward scaling arguments
in turn enabling precise control the alignment sensitivity.Comment: 7 pages, 5 figure
Microsatellite primers for red drum (Sciaenops ocellatus)
In this note, we document polymerase-chain-reaction (PCR) primer pairs for 101 nuclear-encoded microsatellites
designed and developed from a genomic library for red drum (Sciaenops ocellatus). Details of the genomic library construction, the sequencing of positive clones, primer design, and PCR protocols may be found in Karlsson et al. (2008). The 101 microsatellites (GENBA NK Accession Numbers
EU015882-EU015982) were amplified successfully and used to genotype 24 red drum obtained from Galveston Bay, Texas (Table 1). A total of 69 of the microsatellites had an uninterrupted (perfect) dinucleotide motif, and 30 had an imperfect dinucleotide motif; one microsatellite had an
imperfect tetranucleotide motif, and one had an imperfect and compound motif (Table 1 ). Sizes of the cloned alleles ranged from 84 to 252 base pairs. A ‘blast’ search of the GENBANK database indicated that all of the primers and the cloned alleles were unique (i.e., not duplicated)
- …