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The formation of gullies on Mars today
A decade of high-resolution monitoring has revealed extensive activity in fresh Martian gullies. Flows within the gullies are diverse: they can be relatively light, neutral or dark, colourful or bland, and range from superficial deposits to 10 m-scale topographic changes. We observed erosion and transport of material within gullies, new terraces, freshly eroded channel segments, migrating sinuous curves, channel abandonment, and lobate deposits. We also observed early stages of gully initiation, demonstrating that these processes are not merely modifying pre-existing land-forms. The timing of activity closely correlates with the presence of seasonal CO2 frost, so the current changes must be part of ongoing gully formation that is driven largely by its presence. We suggest that the cumulative effect of many flows erodes alcoves and channels, and builds lobate aprons, with no involvement of liquid water. Instead, flows may be fluidized by sublimation of entrained CO2 ice or other mechanisms. The frequent activity is likely to have erased any features dating from high-obliquity periods, so fresh gully geomorphology at middle and high latitudes is not evidence for past liquid water. CO2 ice-driven processes may have been important throughout Martian geological history and their deposits could exist in the rock record, perhaps resembling debris-flow sediments.Mars Data Analysis Program [NNH13AV85I]; Mars Reconnaissance Orbiter HiRISE project12 month embargo; published 27 November 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird
This is the final version of the article. Available from the publisher via the DOI in this record.In many animals, processes occurring in one season carry over to influence reproductive success and survival in future seasons. The strength of such carry-over effects is unlikely to be uniform across years, yet our understanding of the processes that are capable of modifying their strength remains limited. Here we show that female light-bellied Brent geese with higher body mass prior to spring migration successfully reared more offspring during breeding, but only in years where environmental conditions during breeding were favourable. In years of bad weather during breeding, all birds suffered reduced reproductive output irrespective of pre-migration mass. Our results suggest that the magnitude of reproductive benefits gained by maximising body stores to fuel breeding fluctuates markedly among years in concert with conditions during the breeding season, as does the degree to which carry-over effects are capable of driving variance in reproductive success among individuals. Therefore while carry-over effects have considerable power to drive fitness asymmetries among individuals, our ability to interpret these effects in terms of their implications for population dynamics is dependent on knowledge of fitness determinants occurring in subsequent seasons. XAH was funded by NERC grant (NE⁄F008058⁄1) with a Wildfowl & Wetlands Trust CASE partnership and RI by NERC grant (NE⁄F021690⁄1),
both awarded to SB. SB is funded by an ERC Consolidator's Grant: STATEMIG 310820. The funders had no role in study design, data collection and
analysis, decision to publish, or preparation of the manuscript
Approximate Decoherence of Histories and 't Hooft's Deterministic Quantum Theory
This paper explores the possibility that an exactly decoherent set of
histories may be constructed from an approximately decoherent set by small
distortions of the operators characterizing the histories. In particular, for
the case of histories of positions and momenta, this is achieved by doubling
the set of operators and then finding, amongst this enlarged set, new position
and momentum operators which commute, so decohere exactly, and which are
``close'' to the original operators. The enlarged, exactly decoherent, theory
has the same classical dynamics as the original one, and coincides with the
so-called deterministic quantum theories of the type recently studied by 't
Hooft. These results suggest that the comparison of standard and deterministic
quantum theories may provide an alternative method of characterizing emergent
classicality. A side-product is the surprising result that histories of momenta
in the quantum Brownian motion model (for the free particle in the
high-temperature limit) are exactly decoherent.Comment: 41 pages, plain Te
Somewhere in the Universe: Where is the Information Stored When Histories Decohere?
We investigate the idea that decoherence is connected with the storage of
information about the decohering system somewhere in the universe. The known
connection between decoherence of histories and the existence of records is
extended from the case of pure initial states to mixed states. Records may
still exist but are necessarily imperfect. We formulate an
information-theoretic conjecture about decoherence due to an environment: the
number of bits required to describe a set of decoherent histories is
approximately equal to the number of bits of information thrown away to the
environment in the coarse-graining process. This idea is verified in a simple
model consisting of a particle coupled to an environment that can store only
one bit of information. We explore the decoherence and information storage in
the quantum Brownian motion model. It is shown that the variables that the
environment naturally measures and stores information about are the Fourier
components of the function (describing the particle trajectory). The
records storing the information about the Fourier modes are the positions and
momenta of the environmental oscillators at the final time. Decoherence is
possible even if there is only one oscillator in the environment. The
information count of the histories and records in the environment add up
according to our conjecture. These results give quantitative content to the
idea that decoherence is related to ``information lost''.Comment: 48 pages, plain Tex. Second revisio
Evaluation of the function and quality of life of patients submitted to girdlestone's resection arthroplasty
OBJECTIVES: To evaluate function and quality of life of patients submitted to Girdlestone's arthroplasty, and to compare outcomes between unilateral Girdlestone's group with the group with contralateral total hip prosthesis. METHODS: Cross-sectional study where 9 patients were evaluated with unilateral Girdlestone's and 3 with Girdlestone's in one hip and contralateral total hip prosthesis. The evaluation consisted in filling in a generic questionnaire on quality of life SF-36 and a specific questionnaire for hip function Harris Hip Score (HHS). The comparison between groups was made by using the Student's t-test and the Fisher's test. RESULTS: The patients of the unilateral Girdlestone's group presented a higher number of SF-36 domains classified as high, although 77.8% of these showed poor results on the HHS. All patients had a leg-length discrepancy and positive Trendelenburg's test, which led to limping gait in 11 of 12 patients evaluated. Of these, only 6 underwent physiotherapy after surgery. CONCLUSION: Girdlestone's postoperative quality of life and function in a Brazilian population still requires further studies, because these outcomes are indicative of study variables' behavior and cannot be regarded as definite.OBJETIVOS: Avaliar a função e a qualidade de vida dos pacientes pós-artroplastia de Girdlestone e comparar os resultados entre os grupos Girdlestone unilateral e o grupo com prótese total de quadril contralateral. MÉTODOS: estudo transversal no qual foram avaliados 9 pacientes com Girdlestone unilateral e 3 com Girdlestone em um quadril e prótese total no quadril contralateral. A avaliação constitui-se em aplicar o questionário genérico de qualidade de vida SF-36 e um questionário funcional específico para o quadril, Harris Hip Score (HHS). A comparação dos grupos foi realizada usando-se o teste t- Student e o teste de Fisher. RESULTADOS: Os pacientes do grupo Girdlestone unilateral apresentaram maior quantidade de domínios do SF-36 classificados como elevados, embora 77,8% destes tenham obtido resultados ruins no HHS. Todos os pacientes apresentaram o teste de Trendelenburg positivo e discrepância de membros, o que levou à marcha claudicante em 11 dos 12 pacientes avaliados. Destes, apenas 6 submeteram-se a fisioterapia pós-operatória. CONCLUSÃO: A qualidade de vida e a função pós-operatória de Girdlestone, na população brasileira, ainda necessita ser mais pesquisada, pois estes resultados são indicações do comportamento das variáveis de estudo e não podem ser consideradas encerradas.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Departamento de Ortopedia e TraumatologiaUNIFESP-EPM DOTUNIFESP, EPM, Depto. de Ortopedia e TraumatologiaUNIFESP, EPM DOTSciEL
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