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1.
J Environ Manage ; 346: 118932, 2023 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-37703612

RESUMO

Soil disturbances that accompany energy development can damage local habitats. Prior to oil and gas extraction, it is commonly recommended that topsoil stockpiles be created to aid future restoration. Our study area, a retired fracking pond in the western Rio Grande Plains, Texas, was restored in 2017 with stockpiled topsoil that was collected in 2013. We segregated the existing stockpile into three layers that were ∼1.5 m in thickness and distributed these layers, along with a non-amended control surface (consisting of former subsoil that made up the perimeter of the fracking pond), in strips over the restoration area. Each of the four surfaces was seeded with a mixture of (1) 13 native grasses, (2) 13 native grasses plus an annual warm-season grass cover crop, or (3) non-seeded. We monitored plant density and species composition two through five years post-restoration. The non-amended control surface had higher seeded grass density during the final 2 sampling periods; stockpiled surfaces seldom differed from each other. Previous year's competing plant density had little effect on restoration success. Providing supplemental seed initially increased seeded plant density but benefits diminished over time; adding a cover crop was not advantageous. Changes in community composition over time were similar on stockpile surfaces but more variable than observed on the control surface. Results suggest that stockpiling topsoil may not be necessary, but that supplemental seeding was beneficial, to restoration success.

2.
Irrig Sci ; 40(4-5): 515-530, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36172251

RESUMO

Characterization of model errors is important when applying satellite-driven evapotranspiration (ET) models to water resource management problems. This study examines how uncertainty in meteorological forcing data and land surface modeling propagate through to errors in final ET data calculated using the Satellite Irrigation Management Support (SIMS) model, a computationally efficient ET model driven with satellite surface reflectance values. The model is applied to three instrumented winegrape vineyards over the 2017-2020 time period and the spatial and temporal variation in errors are analyzed. We illustrate how meteorological data inputs can introduce biases that vary in space and at seasonal timescales, but that can persist from year to year. We also observe that errors in SIMS estimates of land surface conductance can have a particularly strong dependence on time of year. Overall, meteorological inputs introduced RMSE of 0.33-0.65 mm/day (7-27%) across sites, while SIMS introduced RMSE of 0.55-0.83 mm/day (19-24%). The relative error contribution from meteorological inputs versus SIMS varied across sites; errors from SIMS were larger at one site, errors from meteorological inputs were larger at a second site, and the error contributions were of equal magnitude at the third site. The similar magnitude of error contributions is significant given that many satellite-driven ET models differ in their approaches to estimating land surface conductance, but often rely on similar or identical meteorological forcing data. The finding is particularly notable given that SIMS makes assumptions about the land surface (no soil evaporation or plant water stress) that do not always hold in practice. The results of this study show that improving SIMS by eliminating these assumptions would result in meteorological inputs dominating the error budget of the model on the whole. This finding underscores the need for further work on characterizing spatial uncertainty in the meteorological forcing of ET. Supplementary Information: The online version contains supplementary material available at 10.1007/s00271-022-00808-9.

3.
J Med Internet Res ; 23(4): e23948, 2021 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-33714935

RESUMO

BACKGROUND: Effectively and efficiently diagnosing patients who have COVID-19 with the accurate clinical type of the disease is essential to achieve optimal outcomes for the patients as well as to reduce the risk of overloading the health care system. Currently, severe and nonsevere COVID-19 types are differentiated by only a few features, which do not comprehensively characterize the complicated pathological, physiological, and immunological responses to SARS-CoV-2 infection in the different disease types. In addition, these type-defining features may not be readily testable at the time of diagnosis. OBJECTIVE: In this study, we aimed to use a machine learning approach to understand COVID-19 more comprehensively, accurately differentiate severe and nonsevere COVID-19 clinical types based on multiple medical features, and provide reliable predictions of the clinical type of the disease. METHODS: For this study, we recruited 214 confirmed patients with nonsevere COVID-19 and 148 patients with severe COVID-19. The clinical characteristics (26 features) and laboratory test results (26 features) upon admission were acquired as two input modalities. Exploratory analyses demonstrated that these features differed substantially between two clinical types. Machine learning random forest models based on all the features in each modality as well as on the top 5 features in each modality combined were developed and validated to differentiate COVID-19 clinical types. RESULTS: Using clinical and laboratory results independently as input, the random forest models achieved >90% and >95% predictive accuracy, respectively. The importance scores of the input features were further evaluated, and the top 5 features from each modality were identified (age, hypertension, cardiovascular disease, gender, and diabetes for the clinical features modality, and dimerized plasmin fragment D, high sensitivity troponin I, absolute neutrophil count, interleukin 6, and lactate dehydrogenase for the laboratory testing modality, in descending order). Using these top 10 multimodal features as the only input instead of all 52 features combined, the random forest model was able to achieve 97% predictive accuracy. CONCLUSIONS: Our findings shed light on how the human body reacts to SARS-CoV-2 infection as a unit and provide insights on effectively evaluating the disease severity of patients with COVID-19 based on more common medical features when gold standard features are not available. We suggest that clinical information can be used as an initial screening tool for self-evaluation and triage, while laboratory test results should be applied when accuracy is the priority.


Assuntos
COVID-19 , Aprendizado de Máquina , SARS-CoV-2 , Índice de Gravidade de Doença , Triagem , China , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Teóricos , Reprodutibilidade dos Testes
4.
Phys Chem Chem Phys ; 21(31): 17176-17189, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31342979

RESUMO

Ionic liquids are a unique class of materials with several potential applications in electrochemical energy storage. When used in electrolytes, these highly coordinating solvents can influence device performance through their high viscosities and strong solvation behaviors. In this work, we explore the effects of pyrrolidinium cation structure and Li+ concentration on transport processes in ionic liquid electrolytes. We present correlated experimental measurements and molecular simulations of Li+ mobility and O2 diffusivity, and connect these results to dynamic molecular structural information and device performance. In the context of Li-O2/Li-air battery chemistries, we find that Li+ mobility is largely influenced by Li+-anion coordination, but that both Li+ and O2 diffusion may be affected by variations of the pyrrolidinium cation and Li+ concentration.

5.
PLoS Comput Biol ; 13(2): e1005350, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28231282

RESUMO

Mindboggle (http://mindboggle.info) is an open source brain morphometry platform that takes in preprocessed T1-weighted MRI data and outputs volume, surface, and tabular data containing label, feature, and shape information for further analysis. In this article, we document the software and demonstrate its use in studies of shape variation in healthy and diseased humans. The number of different shape measures and the size of the populations make this the largest and most detailed shape analysis of human brains ever conducted. Brain image morphometry shows great potential for providing much-needed biological markers for diagnosing, tracking, and predicting progression of mental health disorders. Very few software algorithms provide more than measures of volume and cortical thickness, while more subtle shape measures may provide more sensitive and specific biomarkers. Mindboggle computes a variety of (primarily surface-based) shapes: area, volume, thickness, curvature, depth, Laplace-Beltrami spectra, Zernike moments, etc. We evaluate Mindboggle's algorithms using the largest set of manually labeled, publicly available brain images in the world and compare them against state-of-the-art algorithms where they exist. All data, code, and results of these evaluations are publicly available.


Assuntos
Algoritmos , Pontos de Referência Anatômicos/diagnóstico por imagem , Encefalopatias/diagnóstico por imagem , Encefalopatias/patologia , Encéfalo/patologia , Imagem de Difusão por Ressonância Magnética , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Imageamento Tridimensional , Masculino , Tamanho do Órgão , Reconhecimento Automatizado de Padrão , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Software , Técnica de Subtração
6.
Nano Lett ; 17(11): 6974-6982, 2017 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-29058442

RESUMO

Efficient and reversible charge transfer is essential to realizing high-performance solid-state batteries. Efforts to enhance charge transfer at critical electrode-electrolyte interfaces have proven successful, yet interfacial chemistry and its impact on cell function remains poorly understood. Using X-ray photoelectron spectroscopy combined with electrochemical techniques, we elucidate chemical coordination near the LiCoO2-LIPON interface, providing experimental validation of space-charge separation. Space-charge layers, defined by local enrichment and depletion of charges, have previously been theorized and modeled, but the unique chemistry of solid-state battery interfaces is now revealed. Here we highlight the non-Faradaic migration of Li+ ions from the electrode to the electrolyte, which reduces reversible cathodic capacity by ∼15%. Inserting a thin, ion-conducting LiNbO3 interlayer between the electrode and electrolyte, however, can reduce space-charge separation, mitigate the loss of Li+ from LiCoO2, and return cathodic capacity to its theoretical value. This work illustrates the importance of interfacial chemistry in understanding and improving solid-state batteries.

7.
Nano Lett ; 16(8): 4799-806, 2016 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-27326464

RESUMO

Understanding the catalyzed formation and evolution of lithium-oxide products in Li-O2 batteries is central to the development of next-generation energy storage technology. Catalytic sites, while effective in lowering reaction barriers, often become deactivated when placed on the surface of an oxygen electrode due to passivation by solid products. Here we investigate a mechanism for alleviating catalyst deactivation by dispersing Pd catalytic sites away from the oxygen electrode surface in a well-structured anodic aluminum oxide (AAO) porous membrane interlayer. We observe the cross-sectional product growth and evolution in Li-O2 cells by characterizing products that grow from the electrode surface. Morphological and structural details of the products in both catalyzed and uncatalyzed cells are investigated independently from the influence of the oxygen electrode. We find that the geometric decoration of catalysts far from the conductive electrode surface significantly improves the reaction reversibility by chemically facilitating the oxidation reaction through local coordination with PdO surfaces. The influence of the catalyst position on product composition is further verified by ex situ X-ray photoelectron spectroscopy and Raman spectroscopy in addition to morphological studies.

8.
Nano Lett ; 15(1): 434-41, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25546408

RESUMO

Controlling the mesoscale geometric configuration of catalysts on the oxygen electrode is an effective strategy to achieve high reversibility and efficiency in Li-O2 batteries. Here we introduce a new Li-O2 cell architecture that employs a catalytic polymer-based membrane between the oxygen electrode and the separator. The catalytic membrane was prepared by immobilization of Pd nanoparticles on a polyacrylonitrile (PAN) nanofiber membrane and is adjacent to a carbon nanotube electrode loaded with Ru nanoparticles. During oxide product formation, the insulating PAN polymer scaffold restricts direct electron transfer to the Pd catalyst particles and prevents the direct blockage of Pd catalytic sites. The modified Li-O2 battery with a catalytic membrane showed a stable cyclability for 60 cycles with a capacity of 1000 mAh/g and a reduced degree of polarization (∼ 0.3 V) compared to cells without a catalytic membrane. We demonstrate the effects of a catalytic membrane on the reaction characteristics associated with morphological and structural features of the discharge products via detailed ex situ characterization.

9.
Beilstein J Org Chem ; 12: 1925-1938, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27829899

RESUMO

Homoleptic zinc(II) complexes of di(phenylacetylene)azadipyrromethene (e.g., Zn(WS3)2) are potential non-fullerene electron acceptors for organic photovoltaics. To tune their properties, fluorination of Zn(WS3)2 at various positions was investigated. Three fluorinated azadipyrromethene-based ligands were synthesized with fluorine at the para-position of the proximal and distal phenyl groups, and at the pyrrolic phenylacetylene moieties. Additionally, a CF3 moiety was added to the pyrrolic phenyl positions to study the effects of a stronger electron withdrawing unit at that position. The four ligands were chelated with zinc(II) and BF2+ and the optical and electrochemical properties were studied. Fluorination had little effect on the optical properties of both the zinc(II) and BF2+ complexes, with λmax in solution around 755 nm and 785 nm, and high molar absorptivities of 100 × 103 M-1cm-1 and 50 × 103 M-1cm-1, respectively. Fluorination of Zn(WS3)2 raised the oxidation potentials by 0.04 V to 0.10 V, and the reduction potentials by 0.01 V to 0.10 V, depending on the position and type of substitution. The largest change was observed for fluorine substitution at the proximal phenyl groups and CF3 substitution at the pyrrolic phenylacetylene moieties. The later complexes are expected to be stronger electron acceptors than Zn(WS3)2, and may enable charge transfer from other conjugated polymer donors that have lower energy levels than poly(3-hexylthiophene) (P3HT).

11.
Phys Chem Chem Phys ; 16(7): 3230-7, 2014 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-24406938

RESUMO

Understanding the interactions between catalyst and electrolyte in Li-O2 systems is crucial to improving capacities, efficiencies, and cycle life. In this study, supported noble metal catalysts Pt/C, Pd/C, and Au/C were paired with popular Li-O2 electrolyte solvents dimethoxyethane (DME), tetraglyme (TEGDME), and dimethyl sulfoxide (DMSO). The effects of these combinations on stability, kinetics, and activity were assessed. We show evidence of a synergistic effect between Pt and Pd catalysts and a DMSO-based electrolyte which enhances the kinetics of oxygen reduction and evolution reactions. DME and TEGDME are more prone to decomposition and less kinetically favorable for oxygen reduction and evolution than DMSO. While the order of oxygen reduction onset potentials with each catalyst was found to be consistent across electrolyte (Pd > Pt > Au), larger overpotentials with DME and TEGDME, and negative shifts in onset after only five cycles favor the stability of a DMSO electrolyte. Full cell cycling experiments confirm that catalyst-DMSO combinations produce up to 9 times higher discharge capacities than the same with TEGDME after 20 cycles (∼707.4 vs. 78.8 mA h g(-1) with Pd/C). Ex situ EDS and in situ EIS analyses of resistive species in the cathode suggest that improvements in capacity with DMSO are due to a combination of greater electrolyte conductivity and catalyst synergies. Our findings demonstrate that co-selection of catalyst and electrolyte is necessary to exploit chemical synergies and improve the performance of Li-O2 cells.

12.
Nat Ecol Evol ; 8(2): 229-238, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38168941

RESUMO

A steady rise in fires in the Western United States, coincident with intensifying droughts, imparts substantial modifications to the underlying vegetation, hydrology and overall ecosystem. Drought can compound the ecosystem disturbance caused by fire, although how these compound effects on hydrologic and ecosystem recovery vary among ecosystems is poorly understood. Here we use remote sensing-derived high-resolution evapotranspiration (ET) estimates from before and after 1,514 fires to show that ecoregions dominated by grasslands and shrublands are more susceptible to drought, which amplifies fire-induced ET decline and, subsequently, shifts water flux partitioning. In contrast, severely burned forests recover from fire slowly or incompletely, but are less sensitive to dry extremes. We conclude that moisture limitation caused by droughts influences the dynamics of water balance recovery in post-fire years. This finding explains why moderate to extreme droughts aggravate impacts on the water balance in non-forested vegetation, while moisture accessed by deeper roots in forests helps meet evaporative demands unless severe burns disrupt internal tree structure and deplete fuel load availability. Our results highlight the dominant control of drought on altering the resilience of vegetation to fires, with critical implications for terrestrial ecosystem stability in the face of anthropogenic climate change in the West.


Assuntos
Ecossistema , Incêndios , Estados Unidos , Secas , Florestas , Água
13.
Aesthetic Plast Surg ; 36(3): 638-48, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22083413

RESUMO

BACKGROUND: Little is written in the plastic surgery literature about thyroid-associated ophthalmopathy (TAO), a condition that is separate from Graves-Basedow disease and may not be accompanied by hyperthyroidism. Many patients with this disease frequently seek periocular aesthetic reconstruction prior to medical workup. METHODS: This study presents a comprehensive review of the literature surrounding TAO in order to better understand the prevalence, diagnosis, pathophysiology, and appropriate management of TAO. RESULTS: TAO is frequently under- or misdiagnosed by health-care providers. Patients seeking blepharoplasty or other oculoplastic procedures may have underlying TAO, and the prevalence of TAO in patients who have had a blepharoplasty is approximately 3%. This condition occurs five times more often in women than in men. As a product of the relatively high prevalence of this disease and its underdiagnosis, TAO patients may experience perioperative and late complications due to surgery. CONCLUSION: Blepharoplasties performed on TAO patients must be undertaken with care and insight to avoid cosmetic and functional complications.


Assuntos
Oftalmopatia de Graves/diagnóstico , Oftalmopatia de Graves/terapia , Algoritmos , Oftalmopatia de Graves/etiologia , Humanos
14.
BJS Open ; 5(2)2021 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-33688942

RESUMO

BACKGROUND: Surgical incidents can have significant effects on both patients and health professionals, including emotional distress and depression. The aim of this study was to explore the personal and professional impacts of surgical incidents on operating theatre staff. METHODS: Face-to-face semistructured interviews were conducted with a range of different healthcare professionals working in operating theatres, including surgeons and anaesthetists, operating department practitioners, and theatre nurses, and across different surgical specialties at five different hospitals. All interviews were audio recorded, transcribed verbatim, and analysed using an inductive thematic approach, which involved reading and re-reading the transcripts, assigning preliminary codes, and searching for patterns and themes within the codes, with the aid of NVivo 12 software. These emerging themes were discussed with the wider research team to gain their input. RESULTS: Some 45 interviews were conducted, generally lasting between 30 and 75 min. Three overarching themes emerged: personal and professional impact; impact of the investigation process; and positive consequences or impact. Participants recalled experiencing negative emotions following surgical incidents that depended on the severity of the incident, patient outcomes, and the support that staff received. A culture of blame, inadequate support, and lack of a clear and transparent investigative process appeared to worsen impact. CONCLUSION: The study indicated that more support is needed for operating theatre staff involved in surgical incidents. Greater transparency and better information during the investigation of such incidents for staff are still needed.


Assuntos
Erros Médicos/psicologia , Corpo Clínico Hospitalar/psicologia , Salas Cirúrgicas , Atitude do Pessoal de Saúde , Depressão/etiologia , Humanos , Entrevistas como Assunto , Angústia Psicológica , Sistemas de Apoio Psicossocial , Pesquisa Qualitativa , Autoimagem
15.
J Geophys Res Space Phys ; 126(9): e2021JA029208, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35865829

RESUMO

The properties of cold, dense, low energy ( < 150 eV) ions within Earth's magnetosphere between 6 and 14 R E distance are examined using data sampled by Time History of Events and Macroscale Interactions during Substorms spacecraft during a new low-energy plasma mode that operated from June 2016 to July 2017. These ions are a persistent feature of the magnetosphere during enhanced solar wind dynamic pressure and/or magnetospheric activity. These ions have densities ranging from 0.5 to tens of c m - 3 , with a mean of ∼ 1 c m - 3 and temperatures of a few to tens of eV, with a mean of ∼ 13 eV. These yield cold to hot ion density and temperature ratios that are 4.4 and 4 × 1 0 - 3 , respectively. Comparisons reveal that the cold ion densities are positively correlated with solar wind dynamic pressure. These ions are organizable, according to their pitch-angle distribution, as being transverse/convection dominated (interpreted as plume plasma) or magnetic field-aligned (FAL) (uni- or bi-directional characteristic of ion outflow or cloak plasma). Transverse ions preferentially occur in the prenoon to dusk sectors during sustained active magnetospheric conditions driven by enhanced solar wind dynamic pressure under southward B z and westward B y IMF orientations. Transverse ion velocities (reaching several tens of km/s) have a westward directed tendency with a slight radially outward preference. In contrast FAL ions preferentially occur from morning to noon during northward IMF orientations, enhanced solar wind dynamic pressure, and quiet magnetospheric conditions within several hours after moderate to strong activity. The FAL ions also have bulk velocities ≲ 30 km/s, with an eastward and radially outward tendency.

16.
Chem Commun (Camb) ; 56(93): 14665-14668, 2020 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-33156306

RESUMO

Non-destructive Li nuclear reaction analysis techniques were used to profile the Li distribution at the surface of graphitic Li-ion battery anodes. These techniques show that Li concentrations are elevated within 300 nm of the anode surface, even in fully delithiated states. The surface region, which includes the solid electrolyte interphase, contains at least 60% of the total Li irreversibly lost during formation and cycling.

17.
ACS Appl Mater Interfaces ; 12(50): 55865-55875, 2020 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-33283495

RESUMO

Layered lithium nickel, manganese, and cobalt oxides (NMC) are among the most promising commercial positive electrodes in the past decades. Understanding the detailed surface and bulk redox processes of Ni-rich NMC can provide useful insights into material design options to boost reversible capacity and cycle life. Both hard X-ray absorption (XAS) of metal K-edges and soft XAS of metal L-edges collected from charged LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) showed that the charge capacity up to removing ∼0.7 Li/f.u. was accompanied with Ni oxidation in bulk and near the surface (up to 100 nm). Of significance to note is that nickel oxidation is primarily responsible for the charge capacity of NMC622 and 811 up to similar lithium removal (∼0.7 Li/f.u.) albeit charged to different potentials, beyond which was followed by Ni reduction near the surface (up to 100 nm) due to oxygen release and electrolyte parasitic reactions. This observation points toward several new strategies to enhance reversible redox capacities of Ni-rich and/or Co-free electrodes for high-energy Li-ion batteries.

18.
Mol Hum Reprod ; 15(3): 195-204, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19126782

RESUMO

Pre-eclampsia is a common serious disorder of human pregnancy, which is associated with significant maternal and perinatal morbidity and mortality. The suspected aetiology of pre-eclampsia is complex, with susceptibility being attributable to multiple environmental factors and a large genetic component. Recently, we reported significant linkage to chromosome 2q22 in 34 Australian/New Zealand (Aust/NZ) pre-eclampsia/eclampsia families, and activin A receptor type IIA (ACVR2A) was identified as a strong positional candidate gene at this locus. In an attempt to identify the putative risk variants, we have now comprehensively re-sequenced the entire coding region of the ACVR2A gene and the conserved non-coding sequences in a subset of 16 individuals from these families. We identified 45 single nucleotide polymorphisms (SNPs), with 9 being novel. These SNPs were genotyped in our total family sample of 480 individuals from 74 Aust/NZ pre-eclampsia families (including the original 34 genome-scanned families). Our best associations between ACVR2A polymorphisms and pre-eclampsia were for rs10497025 (P = 0.025), rs13430086 (P = 0.010) and three novel SNPs: LF004, LF013 and LF020 (all with P = 0.018). After correction for multiple hypothesis testing, none of these associations reached significance (P > 0.05). Based on these data, it remains unclear what role, if any, ACVR2A polymorphisms play in pre-eclampsia risk, at least in these Australian families. However, it would be premature to rule out this gene as significant associations between ACVR2A SNPs and pre-eclampsia have recently been reported in a large Norwegian (HUNT) population sample.


Assuntos
Receptores de Activinas Tipo II/genética , Predisposição Genética para Doença/genética , Pré-Eclâmpsia/genética , Estudos de Coortes , Feminino , Genótipo , Humanos , Polimorfismo de Nucleotídeo Único/genética , Gravidez
19.
Science ; 261(5123): 872-8, 1993 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-8346439

RESUMO

A genetic algorithm is a form of evolution that occurs on a computer. Genetic algorithms are a search method that can be used for both solving problems and modeling evolutionary systems. With various mapping techniques and an appropriate measure of fitness, a genetic algorithm can be tailored to evolve a solution for many types of problems, including optimization of a function of determination of the proper order of a sequence. Mathematical analysis has begun to explain how genetic algorithms work and how best to use them. Recently, genetic algorithms have been used to model several natural evolutionary systems, including immune systems.


Assuntos
Algoritmos , Simulação por Computador , Software , Formação de Anticorpos , Evolução Biológica , Ecologia , Genes de Imunoglobulinas , Região Variável de Imunoglobulina/genética
20.
Science ; 255(5049): 1240-3, 1992 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-17816833

RESUMO

Stratigraphic patterns preserved under translating surface undulations or ripples in a depositional eolian environment are computed on a grain by grain basis using physically based cellular automata models. The spontaneous appearance, growth, and motion of the simulated ripples correspond in many respects to the behavior of natural ripples. The simulations show that climbing strata can be produced by impact alone; direct action of fluid shear is unnecessary. The model provides a means for evaluating the connection between mechanical processes occurring in the paleoenvironment during deposition and the resulting stratigraphy preserved in the geologic column: vertical compression of small laminae above a planar surface indicates nascent ripple growth; supercritical laminae are associated with unusually intense deposition episodes; and a plane erosion surface separating sets of well-developed laminae is consistent with continued migration of mature ripples during a hiatus in deposition.

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