450 research outputs found
A Stronger Theorem Against Macro-realism
Macro-realism is the position that certain "macroscopic" observables must
always possess definite values: e.g. the table is in some definite position,
even if we don't know what that is precisely. The traditional understanding is
that by assuming macro-realism one can derive the Leggett-Garg inequalities,
which constrain the possible statistics from certain experiments. Since quantum
experiments can violate the Leggett-Garg inequalities, this is taken to rule
out the possibility of macro-realism in a quantum universe. However, recent
analyses have exposed loopholes in the Leggett-Garg argument, which allow many
types of macro-realism to be compatible with quantum theory and hence violation
of the Leggett-Garg inequalities. This paper takes a different approach to
ruling out macro-realism and the result is a no-go theorem for macro-realism in
quantum theory that is stronger than the Leggett-Garg argument. This approach
uses the framework of ontological models: an elegant way to reason about
foundational issues in quantum theory which has successfully produced many
other recent results, such as the PBR theorem.Comment: Accepted journal version. 10 + 7 pages, 1 figur
Numerical Modeling of Propellant Boiloff in Cryogenic Storage Tank
This Technical Memorandum (TM) describes the thermal modeling effort undertaken at Marshall Space Flight Center to support the Cryogenic Test Laboratory at Kennedy Space Center (KSC) for a study of insulation materials for cryogenic tanks in order to reduce propellant boiloff during long-term storage. The Generalized Fluid System Simulation program has been used to model boiloff in 1,000-L demonstration tanks built for testing the thermal performance of glass bubbles and perlite insulation. Numerical predictions of boiloff rate and ullage temperature have been compared with the measured data from the testing of demonstration tanks. A satisfactory comparison between measured and predicted data has been observed for both liquid nitrogen and hydrogen tests. Based on the experience gained with the modeling of the demonstration tanks, a numerical model of the liquid hydrogen storage tank at launch complex 39 at KSC was built. The predicted boiloff rate of hydrogen has been found to be in good agreement with observed field data. This TM describes three different models that have been developed during this period of study (March 2005 to June 2006), comparisons with test data, and results of parametric studies
Numerical Modeling of Propellant Boil-Off in a Cryogenic Storage Tank
A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaboration effort. The Generalized Fluid System Simulation Program, integrating flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC- 39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the sub-scale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicle
Use of XAS for the elucidation of metal structure and function: applications to nickel biochemistry, molecular toxicology, and carcinogenesis.
Nickel has been shown to be an essential trace element involved in the metabolism of several species of bacteria, archea, and plants. In these organisms, nickel is involved in enzymes that catalyze both non-redox (e.g., urease, glyoxalase I) and redox (e.g., hydrogenase, carbon monoxide dehydrogenase, superoxide dismutase) reactions, and proteins involved in the transport, storage, metallocenter assembly, and regulation of nickel concentration have evolved. Studies of structure/function relationships in nickel biochemistry reveal that cysteine ligands are used to stabilize the Ni(III/II) redox couple. Certain nickel compounds have also been shown to be potent human carcinogens. A likely target for carcinogenic nickel is nuclear histone proteins. Here we present X-ray absorption spectroscopic studies of a model Ni peptide designed to help characterize the structure of the nickel complexes formed with histones and place them in the context of nickel structure/function relationships, to gain insights into the molecular mechanism of nickel carcinogenesis
Opening up the Quantum Three-Box Problem with Undetectable Measurements
One of the most striking features of quantum mechanics is the profound effect
exerted by measurements alone. Sophisticated quantum control is now available
in several experimental systems, exposing discrepancies between quantum and
classical mechanics whenever measurement induces disturbance of the
interrogated system. In practice, such discrepancies may frequently be
explained as the back-action required by quantum mechanics adding quantum noise
to a classical signal. Here we implement the 'three-box' quantum game of
Aharonov and Vaidman in which quantum measurements add no detectable noise to a
classical signal, by utilising state-of-the-art control and measurement of the
nitrogen vacancy centre in diamond.
Quantum and classical mechanics then make contradictory predictions for the
same experimental procedure, however classical observers cannot invoke
measurement-induced disturbance to explain this discrepancy. We quantify the
residual disturbance of our measurements and obtain data that rule out any
classical model by > 7.8 standard deviations, allowing us for the first time to
exclude the property of macroscopic state-definiteness from our system. Our
experiment is then equivalent to a Kochen-Spekker test of quantum
non-contextuality that successfully addresses the measurement detectability
loophole
A note on the Landauer principle in quantum statistical mechanics
The Landauer principle asserts that the energy cost of erasure of one bit of
information by the action of a thermal reservoir in equilibrium at temperature
T is never less than . We discuss Landauer's principle for quantum
statistical models describing a finite level quantum system S coupled to an
infinitely extended thermal reservoir R. Using Araki's perturbation theory of
KMS states and the Avron-Elgart adiabatic theorem we prove, under a natural
ergodicity assumption on the joint system S+R, that Landauer's bound saturates
for adiabatically switched interactions. The recent work of Reeb and Wolf on
the subject is discussed and compared
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Energy and eventhood: the infrastructural set piece
‘Energy and Eventhood’ considers the relationship between infrastructure and the cinematic set piece. It proposes a working definition of the set piece as a distinctly (and perhaps excessively) effortful passage or sequence, and reflects on the tendency for narrative films to incorporate infrastructural sites and structures—such as bridges, dams and pipelines—into such set pieces. A number of writers on infrastructure, as both a cultural phenomenon and a representational object, have noted the aesthetic challenge of rendering it as visible and locatable; this article examines how that difficulty becomes manifest in the infrastructural set piece. It takes as its case studies Unstoppable (2010) and Night Moves (2013), two films noted for their distinctive rhythmic expressiveness, and each one deploying the convention of the set piece in ways which exemplify and reflect on the resistance of infrastructure to narrative containment
NUMERICAL MODELING OF PROPELLANT BOIL-OFF IN A CRYOGENIC STORAGE TANK
ABSTRACT A numerical model to predict boil-off of stored propellant in large spherical cryogenic tanks has been developed. Accurate prediction of tank boil-off rates for different thermal insulation systems was the goal of this collaborative effort. The Generalized Fluid System Simulation Program, which integrates flow analysis and conjugate heat transfer for solving complex fluid system problems, was used to create the model. Calculation of tank boil-off rate requires simultaneous simulation of heat transfer processes among liquid propellant, vapor ullage space, and tank structure. The reference tank for the boil-off model was the 850,000 gallon liquid hydrogen tank at Launch Complex 39B (LC-39B) at Kennedy Space Center, which is under study for future infrastructure improvements to support the Constellation program. The methodology employed in the numerical model was validated using a sub-scale model and tank. Experimental test data from a 1/15 th scale version of the LC-39B tank using both liquid hydrogen and liquid nitrogen were used to anchor the analytical predictions of the subscale model. Favorable correlations between sub-scale model and experimental test data have provided confidence in full-scale tank boil-off predictions. These methods are now being used in the preliminary design for other cases including future launch vehicles
Detectability, Invasiveness and the Quantum Three Box Paradox
Quantum pre- and post-selection (PPS) paradoxes occur when counterfactual
inferences are made about different measurements that might have been
performed, between two measurements that are actually performed. The 3 box
paradox is the paradigm example of such a paradox, where a ball is placed in
one of three boxes and it is inferred that it would have been found, with
certainty, both in box 1 and in box 2 had either box been opened on their own.
Precisely what is at stake in PPS paradoxes has been unclear, and classical
models have been suggested which are supposed to mimic the essential features
of the problem. We show that the essential difference between the classical and
quantum pre- and post-selection effects lies in the fact that for a quantum PPS
paradox to occur the intervening measurement, had it been performed, would need
to be invasive but non-detectable. This invasiveness is required even for null
result measurements. While some quasi-classical features (such as
non-contextuality and macrorealism) are compatible with PPS paradoxes, it seems
no fully classical model of the 3 box paradox is possible.Comment: 16 pages, no figure
Brief for Respondents, Grutter v. Bollinger, 539 US 306 (2003) (No. 02-241).
QUESTIONS PRESENTED
1. Whether this Court should reaffirm its decision in Regents of University of California v. Bakke, 438 U.S. 265 (1978) and hold that the educational benefits that flow from a diverse student body to an institution of higher education, its students, and the public it serves, are sufficiently compelling to permit the school to consider race and/or ethnicity as one of many factors in making admissions decisions through a properly devised admissions program.
2. Whether the Court of Appeals correctly held that the University of Michigan Law School\u27s admissions program is properly devised
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