943 research outputs found
States’ Rights and the Scope of the Treaty Power: Could the Patriot Act be Constitutional as a Treaty?
[Excerpt] “Consider the following hypothetical scenario: after an appeal by the American Civil Liberties Union, the Supreme Court determines that the Patriot Act is unconstitutional. This decision so infuriates President Bush that he seeks out the advice of his legal counsel in a frantic attempt to bypass the Court’s ruling. After some research, President Bush’s legal advisers give him two options: he can either attempt to pass an amendment to the constitution or, with the “advice and consent of the Senate,” he can sign the Patriot Act as a treaty with a foreign nation. Either of these measures will evade the severity of the Court’s decision. After some reflection, the President chooses the treaty method because the probability of ratification is greater.
This hypothetical is not merely the fruit of an imaginative mind. Rather, it is a reconstruction of an event that actually occurred, albeit in quite a different context.
Modeling Multicomponent Fuel Droplet Vaporization with Finite Liquid Diffusivity Using Coupled Algebraic-Dqmom with Delumping
Multicomponent fuel droplet vaporization models for use in combustion CFD codes often prioritize computational efficiency over model complexity. This leads to oversimplifying assumptions such as single component droplets or infinite liquid diffusivity. The previously developed Direct Quadrature Method of Moments (DQMoM) with delumping model demonstrated a computationally efficient and accurate approach to solve for every discrete species in a well-mixed vaporizing multicomponent droplet. To expand the method to less restrictive cases, a new solution technique is presented called the Coupled Algebraic-Direct Quadrature Method of Moments (CA-DQMoM). In contrast to previous moment methods for droplet vaporization, CA-DQMoM solves for the evolution of two liquid distributions by coupling a monovariate, homogeneous DQMoM approach with additional algebraic moment equations, allowing for a more complex droplet vaporization model with finite rates of liquid diffusion to be solved with computational efficiency. To further decrease computational expense, an approximation that employs the same nodes for both distributions can be used in certain cases. Finally, a delumping technique is adapted to the finite diffusivity model to reconstruct discrete species information at minimal computational cost. The model is proven to be accurate relative to a full discrete component model for both a kerosene droplet comprised of 36 species and a multicomponent droplet of 200 species while maintaining the computational efficiency of continuous thermodynamics models. The combined accuracy and computational efficiency demonstrated by the CA-DQMoM with delumping model for a multicomponent fuel droplet with finite liquid diffusivity makes it ideal for incorporation into CFD models for complex combustion process
QUANTUM SIMULATIONS OF THE ISING MODEL WITH TRAPPED IONS: DEVIL'S STAIRCASE AND ARBITRARY LATTICE PROPOSAL
A collection of trapped atomic ions represents one of the most attractive platforms for the quantum simulation of interacting spin networks and quantum magnetism. Spin-dependent optical dipole forces applied to an ion crystal create long-range eective spin-spin interactions and allow the simulation of spin Hamiltonians
that possess nontrivial phases and dynamics.
We trap linear chains of 171Yb+ ions in a Paul trap, and constrain the occupation of energy levels to the ground hyperne clock-states, creating a qubit or pseudo-spin 1/2 system. We proceed to implement spin-spin couplings between two ions using the far detuned Mlmer-Srenson scheme and perform adiabatic
quantum simulations of Ising Hamiltonians with long-range couplings. We then demonstrate our ability to control the sign and relative strength of the interaction between three ions. Using this control, we simulate a frustrated triangular lattice, and for the first time establish an experimental connection between frustration and
quantum entanglement. We then scale up our simulation to show phase transitions from paramagnetism to ferromagnetism for nine ions, and to anti-ferromagnetism for sixteen ions.
The experimental work culminates with our most complicated Hamiltonian - a long range anti-ferromagnetic Ising interaction between 10 ions with a biasing axial field.
Theoretical work presented in this thesis shows how the approach to quantum simulation utilized in this thesis can be further extended and improved. It is shown how appropriate design of laser elds can provide for arbitrary multidimensional spin-spin interaction graphs even for the case of a linear spatial array of ions.
This scheme uses currently existing trap technology and is scalable to levels where classical methods of simulation are intractable
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Constraining the Quenching Mechanisms in Galaxies
A number of theoretical mechanisms have been invoked to explain the transformation of star forming galaxies into quenched galaxies, such as the removal of gas by active galactic nuclei- (AGN) and star formation-driven galactic outflows, and the heating of the galaxy halo and subsequent halting of gas accretion caused by virial shocks and preventative AGN feedback. Nonetheless, we still lack a clear understanding of which mechanism is the most important for quenching galaxies. The goal of this thesis is to study galaxy quenching from an observational perspective and to address the following question: why do galaxies stop forming stars?
In the first part of this thesis I examine the relationship between molecular gas (observed with ALMA and NOEMA) and star formation on spatially resolved scales in seven green valley MaNGA galaxies. I find that both the star formation efficiency (SFE) and gas fraction of green valley galaxies is suppressed relative to typical star forming galaxies. These two effects are equally important for suppressing star formation in the outer disc, but it is not possible to rank their effect towards the strongly quenched galaxy centre, where SFE is only constrained to an upper limit. I also show that the significant reduction in gas fraction in the central regions is driven by an increase in stellar mass surface density rather than a decrease in molecular gas surface density, which disfavours quenching mechanisms that eject gas from galaxies.
In the second part of this thesis I develop a 2D inclined rotating disc model to estimate the kinematic properties of 1862 MaNGA galaxies, and I use a random forest analysis to explore the relationship between galaxy kinematics and quenching. I find that the average velocity dispersion is overwhelmingly the most important kinematic parameter for predicting galaxy quenching. Furthermore, a full and partial correlation analysis shows that many commonly discussed correlations between galaxy properties (such as stellar mass) and quenching are spurious, and indeed at fixed velocity dispersion these correlations are almost entirely removed. I interpret this finding in the context of the BH-σ relation and argue for a scenario in which quenching occurs due to preventative feedback from AGN.
In the third part of this thesis I attempt to directly probe preventative feedback from AGN by analysing a deep ALMA band 4 observation of HE0515-4414 to search for the Sunyaev-Zel'dovich (SZ) signal tracing the quasar's hot halo gas. I find marginal evidence (~3.3σ) of large scale (~300 kpc) heating in the visibility plane, as well as ~3.2σ evidence of localised heating to the south west of the central quasar in the image plane. Furthermore, I use SZ maps from the FABLE simulation to demonstrate that ALMA and the ACA are effective at detecting the SZ signal in band 3, and I discuss the optimal strategy for future observations.ERC Advanced Grant 695671 ”QUENCH
Οὐδε γέρων Ἀστραῖος ἀναίνετο: The Dancing God and the Mind of Zeus in Nonnos’ Dionysiaca
Nonnos’ Dionysiaca is designed as a revolutionary work in the epic genre, to evoke the eponymous god’s dancing energy. He has encoded a deep, pervasive structure in the poem that at once critiques the values implicit in Homeric epic and suggests that life is better lived in harmony with the rhythms of the apparently-chaotic forces in nature. Apparent chaos in Nonnos is bounded by patterns of anticipation, jarring macabre, and comically absurd resolution
Aggregated Cones in Pinus Halepensis
Aggregated female cones were found in 192 Pinus halepensis trees growing in 54 populations in Israel, in habitats of vastly differing ecological conditions. All of these trees also carried normal (1-5 in a whorl) female cones. The number of aggregates per tree varied from one to several dozen. Some of the trees formed aggregates every year, after the first year of aggregate formation, while others formed aggregates only once, or at long intervals. Not all cones in the aggregates reached maturity. The number of cones in an aggregate ranged from six to 62, and they were usually smaller than normal. Many of the trees with aggregates showed other abnormalities, e.g., individual female cone scales, proliferated dwarf shoots, three-needled dwarf shoots, shorter cone stalks, needles on cone stalks, larger terminal cones on the main axis in cones formed during the current year, proliferated female cones, and degradation of the main axis above the aggregate. The clusters probably result from replacement of dwarf shoots by ovulate cones
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