17 research outputs found
Failure Bounding And Sensitivity Analysis Applied To Monte Carlo Entry, Descent, And Landing Simulations
In the study of entry, descent, and landing, Monte Carlo sampling methods are often employed to study the uncertainty in the designed trajectory. The large number of uncertain inputs and outputs, coupled with complicated non-linear models, can make interpretation of the results difficult. Three methods that provide statistical insights are applied to an entry, descent, and landing simulation. The advantages and disadvantages of each method are discussed in terms of the insights gained versus the computational cost. The first method investigated was failure domain bounding which aims to reduce the computational cost of assessing the failure probability. Next a variance-based sensitivity analysis was studied for the ability to identify which input variable uncertainty has the greatest impact on the uncertainty of an output. Finally, probabilistic sensitivity analysis is used to calculate certain sensitivities at a reduced computational cost. These methods produce valuable information that identifies critical mission parameters and needs for new technology, but generally at a significant computational cost
Space-Based Sentinels for Measurement of Infrared Cooling in the Thermosphere for Space Weather Nowcasting
Infrared radiative cooling by nitric oxide (NO) and carbon dioxide (CO2) modulates the thermospheres density and thermal response to geomagnetic storms. Satellite tracking and collision avoidance planning require accurate density forecasts during these events. Over the past several years, failed density forecasts have been tied to the onset of rapid and significant cooling due to production of NO and its associated radiative cooling via emission of infrared radiation at 5.3 m. These results have been diagnosed, after the fact, through analyses of measurements of infrared cooling made by the Sounding of the Atmosphere using Broadband Emission Radiometry instrument now in orbit over 16 years on the National Aeronautics and Space Administration Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite. Radiative cooling rates for NO and CO2 have been further shown to be directly correlated with composition and exospheric temperature changes during geomagnetic storms. These results strongly suggest that a network of smallsats observing the infrared radiative cooling of the thermosphere could serve as space weather sentinels. These sentinels would observe and provide radiative cooling rate data in real time to generate nowcasts of density and aerodynamic drag on space vehicles. Currently, radiative cooling is not directly considered in operational space weather forecast models. In addition, recent research has shown that different geomagnetic storm types generate substantially different infrared radiative response, and hence, substantially different thermospheric density response. The ability to identify these storms, and to measure and predict the Earths response to them, should enable substantial improvement in thermospheric density forecasts
Measuring the Loschmidt amplitude for finite-energy properties of the Fermi-Hubbard model on an ion-trap quantum computer
Calculating the equilibrium properties of condensed matter systems is one of
the promising applications of near-term quantum computing. Recently, hybrid
quantum-classical time-series algorithms have been proposed to efficiently
extract these properties from a measurement of the Loschmidt amplitude from initial states and a
time evolution under the Hamiltonian up to short times . In this
work, we study the operation of this algorithm on a present-day quantum
computer. Specifically, we measure the Loschmidt amplitude for the
Fermi-Hubbard model on a -site ladder geometry (32 orbitals) on the
Quantinuum H2-1 trapped-ion device. We assess the effect of noise on the
Loschmidt amplitude and implement algorithm-specific error mitigation
techniques. By using a thus-motivated error model, we numerically analyze the
influence of noise on the full operation of the quantum-classical algorithm by
measuring expectation values of local observables at finite energies. Finally,
we estimate the resources needed for scaling up the algorithm.Comment: 18 pages, 12 figure
Vanadium Chloro-Substituted Schiff Base Catecholate Complexes are Reducible, Lipophilic, Water Stable, and Have Anticancer Activities
A hydrophobic Schiff base catecholate vanadium complex
was recently
discovered to have anticancer properties superior to cisplatin and
suited for intratumoral administration. This [VO(HSHED)(DTB)] complex,
where HSHED is N-(salicylideneaminato)-N′-(2-hydroxyethyl)-1,2-ethanediamine and the non-innocent
catecholato ligand is di-t-butylcatecholato (DTB),
has higher stability compared to simpler catecholato complexes. Three
new chloro-substituted Schiff base complexes of vanadium(V) with substituted
catecholates as co-ligands were synthesized for comparison with their
non-chlorinated Schiff base vanadium complexes, and their properties
were characterized. Up to four geometric isomers for each complex
were identified in organic solvents using 51V and 1H NMR spectroscopies. Spectroscopy was used to characterize
the structure of the major isomer in solution and to demonstrate that
the observed isomers are exchanged in solution. All three chloro-substituted
Schiff base vanadium(V) complexes with substituted catecholates were
also characterized by UV–vis spectroscopy, mass spectrometry,
and electrochemistry. Upon testing in human glioblastoma multiforme
(T98g) cells as an in vitro model of brain gliomas, the most sterically
hindered, hydrophobic, and stable compound [t1/2 (298 K) = 15 min in cell medium] was better than the two
other complexes (IC50 = 4.1 ± 0.5 μM DTB, 34
± 7 μM 3-MeCat, and 19 ± 2 μM Cat). Furthermore,
upon aging, the complexes formed less toxic decomposition products
(IC50 = 9 ± 1 μM DTB, 18 ± 3 μM 3-MeCat,
and 8.1 ± 0.6 μM Cat). The vanadium complexes with the
chloro-substituted Schiff base were more hydrophobic, more hydrolytically
stable, more easily reduced compared to their corresponding parent
counterparts, and the most sterically hindered complex of this series
is only the second non-innocent vanadium Schiff base complex with
a potent in vitro anticancer activity that is an order of magnitude
more potent than cisplatin under the same conditions