56,498 research outputs found
J. D. Denniston, Greek prose style, 1952
No full textFournier H. J. D. Denniston, Greek prose style, 1952. In: Revue des Études Anciennes. Tome 56, 1954, n°1-2. pp. 165-166
J. D. Denniston, Greek prose style, 1952
No full textFournier H. J. D. Denniston, Greek prose style, 1952. In: Revue des Études Anciennes. Tome 56, 1954, n°1-2. pp. 165-166
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Neural-network-based optimal attitude control using four impulsive thrusters
No full textThis paper tackles the problem of optimal attitude control using a minimal number of attitude thrusters. Three possible control solutions to this problem are presented: 1) a logic-based controller that is simple to implement, 2) a projective control that aims to optimally replicate an ideal continuous control as closely as possible, and 3) an optimal neural predictive control (NPC) that minimizes the total impulse during a maneuver. The NPC is based on a recurrent neural network using a nonlinear autoregressive exogenous configuration for state propagation in a finite-time horizon optimization. Typically, for continuous systems, a back-propagation algorithm for the receding horizon optimization is used, but this is not applicable to systems with discrete inputs. In this paper the NPC is adapted to boolean input systems by employing a robust genetic algorithm to undertake the receding horizon optimization. An automatic selection of the parameters of the cost function is proposed, which improves the performance of the NPC and reduces the tuning to only one parameter. In addition, a multilayer perceptron (MLP) is trained offline with the optimal control data obtained, thus replacing the CPU-intensive cost function with a significantly less computationally expensive metamodel. The NPC performance is compared with the proposed logic-based and projective control algorithms in simulation of a 12U CubeSat and is shown to be the most efficient in terms of total impulse requirement at equal settling time and the least sensitive to the choice of parameters. The MLP control drastically reduces the online computational cost with performance approaching those of the NPC
Study of B c + → J / ψ D s + and B c + → J / ψ D s ∗ + decays in pp collisions at s = 13 TeV with the ATLAS detector
No full textAbstract
A study of
B
c
+
→
J
/
ψ
D
s
+
and
B
c
+
→
J
/
ψ
D
s
∗
+
decays using 139 fb−1 of integrated luminosity collected with the ATLAS detector from
s
= 13 TeV pp collisions at the LHC is presented. The ratios of the branching fractions of the two decays to the branching fraction of the
B
c
+
→ J/ψπ+ decay are measured:
B
B
c
+
→
J
/
ψ
D
s
+
/
B
B
c
+
→
J
/
ψπ
+
= 2.76 ± 0.47 and
B
B
c
+
→
J
/
ψ
D
s
∗
+
/
B
B
c
+
→
J
/
ψπ
+
= 5.33 ± 0.96. The ratio of the branching fractions of the two decays is found to be
B
B
c
+
→
J
/
ψ
D
s
∗
+
/
B
B
c
+
→
J
/
ψ
D
s
∗
+
= 1.93 ± 0.26. For the
B
c
+
→
J
/
ψ
D
s
∗
+
decay, the transverse polarization fraction, Γ±±/Γ, is measured to be 0.70 ± 0.11. The reported uncertainties include both the statistical and systematic components added in quadrature. The precision of the measurements exceeds that in all previous studies of these decays. These results supersede those obtained in the earlier ATLAS study of the same decays with
s
= 7 and 8 TeV pp collision data. A comparison with available theoretical predictions for the measured quantities is presented
Force transmission in migrating cells
No full textDuring cell migration, forces generated by the actin cytoskeleton are transmitted through adhesion complexes to the substrate. To investigate the mechanism of force generation and transmission, we analyzed the relationship between actin network velocity and traction forces at the substrate in a model system of persistently migrating fish epidermal keratocytes. Front and lateral sides of the cell exhibited much stronger coupling between actin motion and traction forces than the trailing cell body. Further analysis of the traction - velocity relationship suggested that the force transmission mechanisms were different in different cell regions: at the front, traction was generated by a gripping of the actin network to the substrate, whereas at the sides and back, it was produced by the network's slipping over the substrate. Treatment with inhibitors of the actin - myosin system demonstrated that the cell body translocation could be powered by either of the two different processes, actomyosin contraction or actin assembly, with the former associated with significantly larger traction forces than the latter. © 2010 Fournier et al.LC
Measurement of the B0–B0 oscillation frequency Δmd with the decays B0→D−π+ and B0→ J/ψK∗0
No full textThe B
0
–B
0
oscillation frequency Δmd is measured by the LHCb experiment using a dataset corresponding
to an integrated luminosity of 1.0 fb−1
of proton–proton collisions at √
s = 7 TeV, and is found to be
Δmd
=0.5156±0.0051 (stat.)±0.0033 (syst.) ps−1
. The measurement is based on results from analyses
of the decays B
0
→ D
−π
+ (D
−
→ K
+π
−π
−) and B
0
→ J/ψK
∗0
(J/ψ →μ
+μ
−,K
∗0
→ K
+π
−) and
their charge conjugated modes
HIGHLY SENSITIVE PHOTOTHERMAL DEFLECTION SPECTROSCOPY AT SOLID-LIQUID INTERFACES
No full text A.C. Boccara, D, Fournier, and J. Badoz, Appl. Phys. Lett. 36 (2), 130,1980. D. Fournier, A.C. Boccara, and J. Badoz, Appl. Opt. 21 (1), 74, 1982.We have recently introduced a new photothermal technique based on the well-known . Used at a solid-liquid interface, this method was found to be two orders of magnitude more sensitive than conventional photoacoustic . The application of this method both to metal-electrolyte and semiconductor-electrolyte interfaces will be illustrated. By replacing the intensity modulation by a polarization modulation of the light, we have just improved the performance of our instrument significantly. For example, we have been able to work on electrochemical deposition corresponding to one tenth of a monolayer of Cu on an unprepared Pt electrode
Search for the rare decays J/y -> D-s(-) rho(+) and J/psi -> <(D)over bar(0)<(K)over bar*(0)
No full textA search for the rare decays of J/psi -> D-S(-) rho(+) + c.c. and J/psi -> D-S(-)rho(+) + c.c.) <1.3 x 10(-5) and beta(J/psi -
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
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