Variable features in the Valles Marineris region of Mars

Transient phenomena on Mars have long been recognized in Mariner and Viking images as well as in decades of Earth based telescopic observations. These events are of interest because of the information they present on currently active meteorological and geological processes. Changes in surface albedo patterns and atmospheric conditions can also affect the analysis and interpretation of data based on spectral or morphological properties of geologic units on the surface. The mechanism responsible for albedo pattern change is currently under investigation. Generation and subsequent transportation and deposition of dark sands has been interpreted in the Valles. However, the removal of a bright dust layer is more consistent with the rapid time period of the change (about two months) and with preliminary multispectral mapping results which suggest that the dark streak south of Eos and Coprates Chasmata is spectrally distinguishable from the dark saltating materials found elsewhere in the canyon system. If a layer of bright dust was removed to affect the albedo change, questions concerning how such micron-sized particles are mobilized by the winds during a normally quiescent season (Southern Hemisphere Autumn) should be addressed

A Piece of Epic Action: The Trial of Aaron Burr

The trial of the former vice-president Aaron Burr for treason established such usable precedents, bringing to the fore the now-familiar issues of pre-trial publicity, leaks to the press, and executive privilege. The trial was, nonetheless, a piece of epic action, inspiring some of the most colorful courtroom histrionics ever seen in America. Masters of the rhetorical flourish, such as William Wirt and Luther Martin, played to packed houses throughout the six-month trial. Thanks to David Robertson, a Petersburg Virginia lawyer, who took down the entire proceeding in shorthand, a record of the trial was made available to the public. It amounted to over 1100 pages and constituted, according to its compiler, a valuable treatise on criminal law, and especially high treason. It is the only reliable account of the trial and while it does not conclusively demonstrate the innocence of Aaron Burr, it clearly points up the lack of evidence against him and the government\u27s zeal in prosecuting a charge of treason on the flimsiest grounds, suggesting that President Thomas Jefferson was, indeed, trying to commit judicial murder

Equilibrium free energies from fast-switching trajectories with large time steps

Jarzynski's identity for the free energy difference between two equilibrium states can be viewed as a special case of a more general procedure based on phase space mappings. Solving a system's equation of motion by approximate means generates a mapping that is perfectly valid for this purpose, regardless of how closely the solution mimics true time evolution. We exploit this fact, using crudely dynamical trajectories to compute free energy differences that are in principle exact. Numerical simulations show that Newton's equation can be discretized to low order over very large time steps (limited only by the computer's ability to represent resulting values of dynamical variables) without sacrificing thermodynamic accuracy. For computing the reversible work required to move a particle through a dense liquid, these calculations are more efficient than conventional fast switching simulations by more than an order of magnitude. We also explore consequences of the phase space mapping perspective for systems at equilibrium, deriving an exact expression for the statistics of energy fluctuations in simulated conservative systems

Elastic Forces Drive Nonequilibrium Pattern Formation in a Model of Nanocrystal Cation Exchange

Cation exchange is a useful tool for post-synthetic modification of nanocrystals, yet its mechanisms remain poorly understood. Here, we explore an idealized model for ion exchange in which a chemical potential drives compositional defects to accumulate at a crystal's surface. These impurities subsequently diffuse inward. We find that the nature of interactions between sites in a compositionally impure crystal strongly impacts exchange trajectories. In particular, elastic deformations which accompany lattice-mismatched species promote spatially modulated patterns in the composition. These same patterns can be produced at equilibrium in core/shell nanocrystals, whose structure mimics transient motifs observed in nonequilibrium trajectories. Moreover, the core of such nanocrystals undergoes a phase transition - from modulated to unstructured - as the thickness or stiffness of the shell is decreased. Our results help explain the varied patterns observed in heterostructured nanocrystals produced by cation exchange and suggest principles for the rational design of compositionally-patterned nanomaterials

Transitions in Health Insurance During the Perinatal Period Among Patients With Continuous Insurance Coverage

Importance Although health insurance continuity is important during the perinatal period to improve birth outcomes and reduce maternal morbidity and mortality, insurance disruptions are common. However, little is known about insurance transitions among insurance types for individuals who remained insured during the perinatal period. Objective To examine insurance transitions for birthing individuals with continuous insurance, including those with Medicaid and Medicaid managed care coverage, before, during, and after pregnancy. Design, Setting, and Participants This cohort study used January 1, 2014 to December 31, 2018 data from the Massachusetts All-Payer Claims Database. The sample included deliveries from January 1, 2015, to December 31, 2017, to birthing individuals aged 18 to 44 years old with continuous insurance for 12 months before and after delivery. Data were analyzed from November 9, 2021, to September 2, 2022. Exposure Insurance type at delivery. Main Outcomes and Measures The primary outcome was a binary indicator of any transition in insurance type from 12 months before and/or after delivery. The secondary outcomes were measures of any predelivery transition (12 months before delivery month) and any transition during the postpartum period (delivery month to 12 months post partum). Multivariate logit regression models were used to analyze the association of an insurance transition in the perinatal period with insurance type in the delivery month, controlling for age and socioeconomic status based on a 5-digit zip code. Results The analytic sample included 97 335 deliveries (mean [SD] maternal age at delivery, 30.4 [5.5] years). Of these deliveries, 23.4% (22 794) were insured by Medicaid and 28.1% (27 347) by Medicaid managed care in the delivery month. A total of 37.1% of the sample (36 127) had at least 1 insurance transition during the 12 months before and/or after delivery. In regression-adjusted analyses, those individuals covered by Medicaid and Medicaid managed care at delivery were 47.0 (95% CI, 46.3-47.7) percentage points and 50.1 (95% CI, 49.4-50.8) percentage points, respectively, more likely to have an insurance transition than those covered by private insurance. Those covered by Marketplace plans at delivery had a 33.1% (95% CI, 31.4%-34.8%) regression-adjusted predicted probability of having a postpartum insurance transition. Conclusions and Relevance Results of this study showed that insurance transitions during the perinatal period occurred for more than 1 in 3 birthing individuals with continuous insurance and were more common among those with Medicaid or Medicaid managed care at delivery. Further research is needed to examine the role of insurance transitions in health care use and outcomes during the perinatal period

Effective Invariant Theory of Permutation Groups using Representation Theory

Using the theory of representations of the symmetric group, we propose an algorithm to compute the invariant ring of a permutation group. Our approach have the goal to reduce the amount of linear algebra computations and exploit a thinner combinatorial description of the invariant ring.Comment: Draft version, the corrected full version is available at http://www.springer.com

A mineralized zone in Western Candor Chasma, Mars

Spectral evidence from Viking and Phobos orbiting spacecraft suggests the local development of crystalline ferric oxides in a small region within Mars' equatorial Valles Marineris canyon system. This is the same area noted for its anomalous coloration in Viking Orbiter image 583 A by McEwen. The unique hue of the region in Viking color data is due to a reduced green filter reflectance, relative to violet and red, in comparison to surrounding materials of similar albedo or average reflectance. For this reason, the region does not appear spectrally distinctive in later Survey Mission images which were acquired without the green filter. In high resolution, the spectral unit can be seen to correspond to two 20 km long depressions on the margins of Candor Mensa, a heavily eroded plateau-forming deposit on the canyon floor. Laminae are conspicuous in several places on the plateau, particularly where 15 to 20 cycles of alternating bright and dark laminae are exposed at approximately 200 meter vertical intervals. Laminae are also visible on the steep, vertically fluted cliffs to the south of this depression. Concentric laminae indicate a basis in the depression on the southeastern margin of Candor Mensa at the location of the less pronounced hue anomaly. A distinct lineation at the base of the scarp at the western end of the canyon transects mottled canyon floor deposits believed to be among the youngest in the Valles marineris. Water is implicated in the formation of the iron oxides, since the steep surfaces of layered sediments elsewhere on Candor Mensa show no evidence of unusual coloration despite the fact that these materials were deposited concurrently with the strata exposed in the depressions. This suggests that the mineralization is secondary in nature and developed locally in association with the depressions, which could have ponded surface runoff or groundwater seepage

Spectroscopic studies of fluorescent perylene dyes

The lowest electronic transition of the fluorescent perylene dye bis-(3,5-di-tertbutylphenyl)-perylene-3, 4:9,10-biscarboximide has been investigated