183 research outputs found
Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere
The dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy
A Bridge from Monty Hall to the Hot Hand: The Principle of Restricted Choice
We show how classic conditional probability puzzles, such as the Monty Hall problem, are intimately related to the recently discovered hot hand selection bias. We explain the connection by way of the principle of restricted choice, an intuitive inferential rule from the card game bridge, which we show is naturally quantified as the updating factor in the odds form of Bayes's rule. We illustrate how, just as the experimental subject fails to use available information to update correctly when choosing a door in the Monty Hall problem, researchers may neglect analogous information when designing experiments, analyzing data, and interpreting results.Financial support from Bocconi University, Bocconi Experimental Laboratory for the Social Sciences (BELSS), and the Spanish Ministry of Economics and Competitiveness (Project ECO2015-65820-P) is gratefully acknowledged. We also gratefully acknowledge Generalitat Valenciana (Research Projects Grupos 3/086 and PROMETEO/2013/037)
Surprised by the Hot Hand Fallacy? A Truth in the Law of Small Numbers
We prove that a subtle but substantial bias exists in a common measure of the conditional dependence of present outcomes on streaks of past outcomes in sequential data. The magnitude of this streak selection bias generally decreases as the sequence gets longer, but increases in streak length, and remains substantial for a range of sequence lengths often used in empirical work. We observe that the canonical study in the influential hot hand fallacy literature, along with replications, are vulnerable to the bias. Upon correcting for the bias, we find that the longstanding conclusions of the canonical study are reversed.Financial support from the Department of Decision Sciences at Bocconi University, and the Spanish Ministries of Education and Science and Economics and Competitiveness (ECO2015-65820-P) and Generalitat Valenciana (Research Projects Gruposo3/086 and PROMETEO/2013/037) is gratefully acknowledged
Screening of Bacterial Quorum Sensing Inhibitors in a Vibrio fischeri LuxR-Based Synthetic Fluorescent E. coli Biosensor
A library of 23 pure compounds of varying structural and chemical characteristics was screened for their quorum sensing (QS) inhibition activity using a synthetic fluorescent Escherichia coli biosensor that incorporates a modified version of lux regulon of Vibrio fischeri. Four such compounds exhibited QS inhibition activity without compromising bacterial growth, namely, phenazine carboxylic acid (PCA), 2-heptyl-3-hydroxy-4-quinolone (PQS), 1H-2-methyl-4-quinolone (MOQ) and genipin. When applied at 50 µM, these compounds reduced the QS response of the biosensor to 33.7% ± 2.6%, 43.1% ± 2.7%, 62.2% ± 6.3% and 43.3% ± 1.2%, respectively. A series of compounds only showed activity when tested at higher concentrations. This was the case of caffeine, which, when applied at 1 mM, reduced the QS to 47% ± 4.2%. In turn, capsaicin, caffeic acid phenethyl ester (CAPE), furanone and polygodial exhibited antibacterial activity when applied at 1mM, and reduced the bacterial growth by 12.8% ± 10.1%, 24.4% ± 7.0%, 91.4% ± 7.4% and 97.5% ± 3.8%, respectively. Similarly, we confirmed that trans-cinnamaldehyde and vanillin, when tested at 1 mM, reduced the QS response to 68.3% ± 4.9% and 27.1% ± 7.4%, respectively, though at the expense of concomitantly reducing cell growth by 18.6% ± 2.5% and 16% ± 2.2%, respectively. Two QS natural compounds of Pseudomonas aeruginosa, namely PQS and PCA, and the related, synthetic compounds MOQ, 1H-3-hydroxyl-4-quinolone (HOQ) and 1H-2-methyl-3-hydroxyl-4-quinolone (MHOQ) were used in molecular docking studies with the binding domain of the QS receptor TraR as a target. We offer here a general interpretation of structure-function relationships in this class of compounds that underpins their potential application as alternatives to antibiotics in controlling bacterial virulence
Magnetic properties of the frustrated AFM spinel ZnCr_2O_4 and the spin-glass Zn_{1-x}Cd_xCr_2O_4 (x=0.05,0.10)
The -dependence (2- 400 K) of the electron paramagnetic resonance (EPR),
magnetic susceptibility, , and specific heat, , of the
antiferromagnetic (AFM) spinel ZnCrO and the spin-glass
(SG) ZnCdCrO () is reported. These
systems behave as a strongly frustrated AFM and SG with K and -400 K K. At high-
the EPR intensity follows the and the -value is -independent.
The linewidth broadens as the temperature is lowered, suggesting the existence
of short range AFM correlations in the paramagnetic phase. For
ZnCrO the EPR intensity and decreases below 90 K and 50
K, respectively. These results are discussed in terms of nearest-neighbor
Cr (S %) spin-coupled pairs with an exchange coupling of 50 K. The appearance of small resonance modes for K,
the observation of a sharp drop in and a strong peak in
at K confirms, as previously reported, the existence of long range
AFM correlations in the low- phase. A comparison with recent neutron
diffraction experiments that found a near dispersionless excitation at 4.5 meV
for and a continuous gapless spectrum for ,
is also given.Comment: 17 pages, 8 figures, 1 Table. Submitted to Physical Review
Recommended from our members
Thermal and chemical degradation of inorganic membrane materials. Final report, August 1992--May 1995
SRI International conducted a theoretical and experimental program to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate the gaseous products of coal gasification. A variety of developmental efforts are underway, including a number of projects sponsored by the US Department of Energy (DOE), to improve the selectivity and permeability of porous inorganic membranes. DOE is also sponsoring efforts to extend the use of metallic membranes to new applications. Most developmental efforts have focused on hydrogen separation by inorganic membranes, which may be used to maximize hydrogen production from coal gas or to remove H{sub 2}S and NH{sub 3} contaminants via thermal or catalytic decomposition in integrated-gasification combined-cycle (IGCC) systems. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. Membrane materials that have been investigated include glass (silica), alumina, carbon, and metals (Pd and Pt). This report describes inorganic membrane materials, long term membrane exposure tests, membrane permeation tests, coal gasifier exposure tests, conclusions, and recommendations
4f-spin dynamics in La(2-x-y)Sr(x)Nd(y)CuO(4)
We have performed inelastic magnetic neutron scattering experiments on
La(2-x-y)Sr(x)Nd(y)CuO(4) in order to study the Nd 4f-spin dynamics at low
energies. In all samples we find at high temperatures a quasielastic line
(Lorentzian) with a line width which decreases on lowering the temperature. The
temperature dependence of the quasielastic line width Gamma/2(T) can be
explained with an Orbach-process, i.e. a relaxation via the coupling between
crystal field excitations and phonons. At low temperatures the Nd-4f magnetic
response S(Q,omega) correlates with the electronic properties of the
CuO(2)-layers. In the insulator La(2-y)Nd(y)CuO(4) the quasielastic line
vanishes below 80 K and an inelastic excitation occurs. This directly indicates
the splitting of the Nd3+ ground state Kramers doublet due to the static
antiferromagnetic order of the Cu moments. In La(1.7-x)Sr(x)Nd(0.3)CuO(4) with
x = 0.12, 0.15 and La(1.4-x)Sr(x)Nd(0.6)CuO(4) with x = 0.1, 0.12, 0.15, 0.18
superconductivity is strongly suppressed. In these compounds we observe a
temperature independent broad quasielastic line of Gaussian shape below T about
30 K. This suggests a distribution of various internal fields on different Nd
sites and is interpreted in the frame of the stripe model. In
La(1.8-y)Sr(0.2)Nd(y)CuO(4) (y = 0.3, 0.6) such a quasielastic broadening is
not observed even at lowest temperature.Comment: 8 pages, 10 figures included, to appear in Phys. Rev.
Theoretical Study on Superconductivity in Boron-Doped Diamond
We consider superconductivity in boron (B) doped diamond using a simplified
model for the valence band of diamond. We treat the effects of substitutional
disorder of B ions by the coherent potential approximation (CPA) and those of
the attractive force between holes by the ladder approximation under the
assumption of instantaneous interaction with the Debye cutoff. We thereby
calculate the quasiparticle life time, the evolution of the single-particle
spectra due to doping, and the effect of disorder on the superconducting
critical temperature . We in particular compare our results with those for
supercell calculations to see the role of disorder, which turns out to be of
crucial importance to .Comment: 9 pages, 13 figures, submitted to J. Phys. Soc. Jpn., Errors in
embedded eps figure files have been correcte
Ultrafast optical generation of coherent phonons in CdTe1-xSex quantum dots
We report on the impulsive generation of coherent optical phonons in
CdTe0.68Se0.32 nanocrystallites embedded in a glass matrix. Pump probe
experiments using femtosecond laser pulses were performed by tuning the laser
central energy to resonate with the absorption edge of the nanocrystals. We
identify two longitudinal optical phonons, one longitudinal acoustic phonon and
a fourth mode of a mixed longitudinal-transverse nature. The amplitude of the
optical phonons as a function of the laser central energy exhibits a resonance
that is well described by a model based on impulsive stimulated Raman
scattering. The phases of the coherent phonons reveal coupling between
different modes. At low power density excitations, the frequency of the optical
coherent phonons deviates from values obtained from spontaneous Raman
scattering. This behavior is ascribed to the presence of electronic impurity
states which modify the nanocrystal dielectric function and, thereby, the
frequency of the infrared-active phonons
- …