9,815 research outputs found
Whipping Instabilities in Electrified Liquid Jets
A liquid jet may develop different types of instabilities, like the so-called
Rayleigh-Plateau instability, which breaks the jet into droplets. However,
another type of instabilities may appear when we electrify a liquid jet and
induce some charge at his surface. Among them, the most common is the so-called
Whipping Instability, which is characterized by violent and fast lashes of the
jet. In the submitted fluid dynamic video(see
http://hdl.handle.net/1813/11422), we will show an unstable charged glycerine
jet in a dielectric liquid bath, which permits an enhanced visualization of the
instability. For this reason, it is probably the first time that these
phenomena are visualized with enough clarity to analyze features as the effect
of the feeding liquid flow rate through the jet or as the surprising
spontaneous stabilization at some critical distance to the ground electrode.Comment: 3 pages, no figures, links to videos, Submission to the 26th Gallery
of Fluid Motion (2009
Vacuum stability of the effective Higgs potential in the Minimal Supersymmetric Standard Model
The parameters of the Higgs potential of the Minimal Supersymmetric Standard
Model (MSSM) receive large radiative corrections which lift the mass of the
lightest Higgs boson to the measured value of 126 GeV. Depending on the MSSM
parameters, these radiative corrections may also lead to the situation that the
local minimum corresponding to the electroweak vacuum state is not the global
minimum of the Higgs potential. We analyze the stability of the vacuum for the
case of heavy squark masses as favored by current LHC data. To this end we
first consider an effective Lagrangian obtained by integrating out the heavy
squarks and then study the MSSM one-loop effective potential V_eff, which
comprises all higher-dimensional Higgs couplings of the effective Lagrangian.
We find that only the second method gives correct results and argue that the
criterion of vacuum stability should be included in phenomenological analyses
of the allowed MSSM parameter space. Discussing the cases of squark masses of 1
and 2 TeV we show that the criterion of vacuum stability excludes a portion of
the MSSM parameter space in which (mu tanbeta) and A_t are large.Comment: minor changes in text and list of references, figures in eps format,
matches published version; Erratum added and sent to PR
Ready-to-use post-Newtonian gravitational waveforms for binary black holes with non-precessing spins: An update
For black-hole binaries whose spins are (anti-) aligned with respect to the
orbital angular momentum of the binary, we compute the frequency domain phasing
coefficients including the quadratic-in-spin terms up to the third
post-Newtonian (3PN) order, the cubic-in-spin terms at the leading order,
3.5PN, and the spin-orbit effects up to the 4PN order. In addition, we obtain
the 2PN spin contributions to the amplitude of the frequency-domain
gravitational waveforms for non-precessing binaries, using recently derived
expressions for the time-domain polarization amplitudes of binaries with
generic spins, complete at that accuracy level. These two results are updates
to Arun et al. (2009) [1] for amplitude and Wade et al. (2013) [2] for phasing.
They should be useful to construct banks of templates that model accurately
non-precessing inspiraling binaries, for parameter estimation studies, and or
constructing analytical template families that accounts for the
inspiral-merger-ringdown phases of the binary.Comment: 8 pages, an additional file (readable in MATHEMATICA) containing all
the key results included in the sourc
Optical Probe of Quantum Shot Noise Reduction at a Single-Atom Contact
Visible and infra-red light emitted at a Ag-Ag(111) junction has been
investigated from tunneling to single atom contact conditions with a scanning
tunneling microscope. The light intensity varies in a highly nonlinear fashion
with the conductance of the junction and exhibits a minimum at conductances
close to the conductance quantum. The data are interpreted in terms of current
noise at optical frequencies, which is characteristic of partially open
transport channels
The Devil is in the Shadow Do institutions affect income and productivity or only official income and official productivity
This paper assesses the relationship between institutions, output, and productivity, when official output is corrected for the size of the shadow economy. Our results confirm the usual positive impact of institutional quality on official output and total factor productivity, and its negative impact on the size of the underground economy. However, once output is corrected for the shadow economy, the relationship between institutions and output becomes weaker. The impact of institutions on total (corrected) factor productivity even becomes insignificant. Differences in corrected output must then be attributed to differences in factor endowments. These results survive several tests for robustness. --shadow economy,income,aggregate productivity,development accounting
On tidal capture of primordial black holes by neutron stars
The fraction of primordial black holes (PBHs) of masses g
in the total amount of dark matter may be constrained by considering their
capture by neutron stars (NSs), which leads to the rapid destruction of the
latter. The constraints depend crucially on the capture rate which, in turn, is
determined by the energy loss by a PBH passing through a NS. Two alternative
approaches to estimate the energy loss have been used in the literature: the
one based on the dynamical friction mechanism, and another on tidal
deformations of the NS by the PBH. The second mechanism was claimed to be more
efficient by several orders of magnitude due to the excitation of particular
oscillation modes reminiscent of the surface waves. We address this
disagreement by considering a simple analytically solvable model that consists
of a flat incompressible fluid in an external gravitational field. In this
model, we calculate the energy loss by a PBH traversing the fluid surface. We
find that the excitation of modes with the propagation velocity smaller than
that of PBH is suppressed, which implies that in a realistic situation of a
supersonic PBH the large contributions from the surface waves are absent and
the above two approaches lead to consistent expressions for the energy loss.Comment: 7 page
Courbes d'excitation des réactions 18O(p,p1γ) 18O* et 18O(p,α1,2,3γ)15N* de 3,2 à 5,4 MeV
Les courbes d'excitation des réactions 18O(p, p1) 18O* et 18O(p, α1,2,3)15N* ont été mesurées pour les énergies incidentes de 3,2 à 5,4 MeV. Les courbes montrent, pour certaines énergies, des anticorrélations entre les voies de sortie proton et alpha. Si cet effet peut être attribué à la conservation du spin isobarique dans les réactions, il détermine le spin isobarique de quelques états excités du noyau composé 19F
La liturgia del trabajo. «Levantado de la tierra, atraeré a todos hacia mí» (Jn 12, 32) en la experiencia de San Josemaría Escrivá de Balaguer.
Con la exaltación de la
Cruz, las palabras de Jn 12, 32 profetizan
el abajamiento y la glorificación
de Cristo, cuyo amor así manifestado
atrae a todos los hombres. San Josemaría
recibe el texto joánico de manera
original: es el trabajo del hombre lo
que eleva la cruz en el mundo y lleva a
la humanidad entera hacia ella. Jn 12,
32 se interpreta también como anuncio
del culto cristiano, y particularmente
de la Eucaristía. Así, culto y
trabajo se encuentran: son obra de Dios, oración, sacrificio y apostolado.
En torno a la ofrenda de la vida se perfila
una verdadera liturgia del trabajo
Influence of shear stress applied during flow stoppage and rest period on the mechanical properties of thixotropic suspensions
We study the solid mechanical properties of several thixotropic suspensions
as a function of the shear stress history applied during their flow stoppage
and their aging in their solid state. We show that their elastic modulus and
yield stress depend strongly on the shear stress applied during their
solid-liquid transition (i.e., during flow stoppage) while applying the same
stress only before or only after this transition may induce only second-order
effects: there is negligible dependence of the mechanical properties on the
preshear history and on the shear stress applied at rest. We also found that
the suspensions age with a structuration rate that hardly depends on the stress
history. We propose a physical sketch based on the freezing of a microstructure
whose anisotropy depends on the stress applied during the liquid-solid
transition to explain why the mechanical properties depend strongly on this
stress. This sketch points out the role of the internal forces in the colloidal
suspensions' behavior. We finally discuss briefly the macroscopic consequences
of this phenomenon and show the importance of using a controlled-stress
rheometer
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