•A petrological classification is proposed adapting Earth classifications to Mars.•The classification involves the characterization of texture and chemistry.•The classification highlights the various ...categories of rocks analyzed by Curiosity.•Composition of in-place sedimentary rocks contrasts with that of igneous float rocks.
Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. To facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematic classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary rocks (e.g., potassic rocks) cannot be paired with any igneous rocks analyzed so far. In contrast, many float rocks, which cannot be classified from their poorly defined texture, plot on chemistry diagrams close to float rocks defined as igneous from their textures, potentially constraining their nature.
This study assessed the effectiveness of different concentrations of sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) (Vista Dental Products, Racine, WI), and BioPure MTAD (Dentsply ...Endodontics-Tulsa Dental, Tulsa, OK). Intracanal contents were collected from 10 patients diagnosed with chronic apical periodontitis. The samples were cultured on hemisections of root apices to generate a polymicrobial biofilm. Each biofilm was separately immersed in 6% NaOCl, 3% NaOCl, 1% NaOCl, 2% CHX, 1% NaOCl followed by BioPure MTAD, and sterile phosphate buffered solution (PBS). SEM analysis showed 6% NaOCl and 3% NaOCl were capable of disrupting and removing the biofilm; 1% NaOCl and 1% NaOCl followed by MTAD were capable of disrupting the biofilm, but not eliminating bacteria; 2% CHX was not capable of disrupting the biofilm. Viable bacteria could not be cultured from specimens exposed to 6% NaOCl, 2 % CHX, or 1% NaOCl followed by BioPure MTAD. These results indicate that 6% NaOCl was the only irrigant capable of both rendering bacteria nonviable and physically removing the biofilm.
A remote laser-induced breakdown spectrometer (LIBS) designed to simulate the ChemCam instrument on the Mars Science Laboratory Rover Curiosity was used to probe 100 geologic samples at a 9-m ...standoff distance. ChemCam consists of an integrated remote LIBS instrument that will probe samples up to 7m from the mast of the rover and a remote micro-imager (RMI) that will record context images. The elemental compositions of 100 igneous and highly-metamorphosed rocks are determined with LIBS using three variations of multivariate analysis, with a goal of improving the analytical accuracy. Two forms of partial least squares (PLS) regression are employed with finely-tuned parameters: PLS-1 regresses a single response variable (elemental concentration) against the observation variables (spectra, or intensity at each of 6144 spectrometer channels), while PLS-2 simultaneously regresses multiple response variables (concentrations of the ten major elements in rocks) against the observation predictor variables, taking advantage of natural correlations between elements. Those results are contrasted with those from the multivariate regression technique of the least absolute shrinkage and selection operator (lasso), which is a penalized shrunken regression method that selects the specific channels for each element that explain the most variance in the concentration of that element. To make this comparison, we use results of cross-validation and of held-out testing, and employ unscaled and uncentered spectral intensity data because all of the input variables are already in the same units. Results demonstrate that the lasso, PLS-1, and PLS-2 all yield comparable results in terms of accuracy for this dataset.
However, the interpretability of these methods differs greatly in terms of fundamental understanding of LIBS emissions. PLS techniques generate principal components, linear combinations of intensities at any number of spectrometer channels, which explain as much variance in the response variables as possible while avoiding multicollinearity between principal components. When the selected number of principal components is projected back into the original feature space of the spectra, 6144 correlation coefficients are generated, a small fraction of which are mathematically significant to the regression. In contrast, the lasso models require only a small number (<24) of non-zero correlation coefficients (β values) to determine the concentration of each of the ten major elements. Causality between the positively-correlated emission lines chosen by the lasso and the elemental concentration was examined. In general, the higher the lasso coefficient (β), the greater the likelihood that the selected line results from an emission of that element. Emission lines with negative β values should arise from elements that are anti-correlated with the element being predicted. For elements except Fe, Al, Ti, and P, the lasso-selected wavelength with the highest β value corresponds to the element being predicted, e.g. 559.8nm for neutral Ca. However, the specific lines chosen by the lasso with positive β values are not always those from the element being predicted. Other wavelengths and the elements that most strongly correlate with them to predict concentration are obviously related to known geochemical correlations or close overlap of emission lines, while others must result from matrix effects. Use of the lasso technique thus directly informs our understanding of the underlying physical processes that give rise to LIBS emissions by determining which lines can best represent concentration, and which lines from other elements are causing matrix effects.
► Compositions of 100 rocks are predicted from LIBS with PLS-1, PLS-2, and the lasso. ► All yield comparable results in terms of accuracy, but not interpretability. ► Lasso chooses channels from known atomic emissions.
The importance of founder events in promoting evolutionary changes on islands has been a subject of long-running controversy. Resolution of this debate has been hindered by a lack of empirical ...evidence from naturally founded island populations. Here we undertake a genetic analysis of a series of historically documented, natural colonization events by the silvereye species-complex (Zosterops lateralis), a group used to illustrate the process of island colonization in the original founder effect model. Our results indicate that single founder events do not affect levels of heterozygosity or allelic diversity, nor do they result in immediate genetic differentiation between populations. Instead, four to five successive founder events are required before indices of diversity and divergence approach that seen in evolutionarily old forms. A Bayesian analysis based on computer simulation allows inferences to be made on the number of effective founders and indicates that founder effects are weak because island populations are established from relatively large flocks. Indeed, statistical support for a founder event model was not significantly higher than for a gradual-drift model for all recently colonized islands. Taken together, these results suggest that single colonization events in this species complex are rarely accompanied by severe founder effects, and multiple founder events and/or long-term genetic drift have been of greater consequence for neutral genetic diversity.
Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical ...comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km−2, unfenced populations require budgets in excess of $2000 km−2 to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density‐independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20–40 years.
Laser-induced breakdown spectroscopy (LIBS) is demonstrated as a quantitative technique for geochemical analysis. This study demonstrates the applicability of LIBS to bulk elemental analysis of ...igneous rock powders. LIBS spectra of 100 igneous rocks with highly varying compositions were acquired at 9
m standoff distance under Mars atmospheric conditions. LIBS spectra were modeled using partial least squares regressions to predict major element compositions. A series of comparative tests determined the most effective methodologies for pre-processing of spectral and compositional data, and choice of calibration set. In the best cases, calculated 1−
σ errors are 1.6
wt.% SiO
2, 1.5
wt.% Al
2O
3, 0.4
wt.% TiO
2, 1.2
wt.% Fe
2O
3T, 1.6
wt.% MgO, 0.02
wt.% MnO, 1.1
wt.% CaO, 0.5
wt.% Na
2O, 0.2
wt.% P
2O
5, and 0.4
wt.% K
2O, with totals near 100%. The largest improvement came as a result of scaling the elemental distributions to equalize the ranges of variability. Optimal predictions for this data set were produced with calibration set compositions input as weight % oxides and not atomic fractions. Predictions were also improved when calibration sets represented the smallest range of compositional variability possible, and completely encompassed the compositional range encountered. Multiple calibration sets relevant to different rock types are preferred over a single all-encompassing calibration set. Baseline removal and transforming spectral data by their first derivative do not improve predictions and can even have negative effects. These results are directly applicable to spectra that will be acquired by the ChemCam experiment on Mars Science Laboratory, but also apply more broadly to terrestrial LIBS applications.
► LIBS analysis of geologic materials can provide quantitative geochemical information. ► PLS regressions yield predictions better than 1.5
wt.% oxide for major elements. ► Use of wt.% oxide is favored of atomic fractions. ► Weighting input compositions equally improves predictions. ► Carefully selected calibration sets improve predictions over random sets.
Laser‐induced breakdown spectroscopy (LIBS) is an active analytical technique that makes use of a laser pulse to analyze materials of interest at a distance by creating a plasma, which emits photons ...at characteristic emission line wavelengths. We validate the technique for planetary exploration under vacuum conditions. We review the capability and advantages of the LIBS technique for lunar regolith analysis at 1.5 m distance from a lunar rover, and we characterize its potential for the detection of resources for future exploration, such as the determination of regolith water content. The limits of detection determined for the major elements (typically <1 wt %) help to determine regolith parent material such as feldspathic highland rocks, rocks from the ancient magmatic high magnesian suite (Mg‐suite), Fe‐rich mare basalts or potassium, rare earth element, and phosphorus‐rich (KREEP‐rich) samples. Compositional parameters commonly used to classify lunar regoliths such as TiO2, Al2O3, and K2O abundances are readily determined by LIBS. Certain elements support regolith analysis: For example, Ba and Zr can be used to confirm KREEP‐like composition, while quantifying the Ni and Co content can be used to infer the amount of meteoritic material. Finally, it is shown that the ice content of lunar soil produces strong H emissions with the LIBS techniques at the 25 wt % H2O level, while measurements on altered basalts give a limit of detection of about 1 wt % for H2O content. This demonstrates that the 5.6 wt % water content detected by the recent LCROSS experiment should be easily detectable and quantifiable by LIBS analysis.
Key Points
Validation of LIBS technique for planetary exploration under vacuum conditions
LODs for major and minor elements are useful to determine lunar regolith sources
LIBS limit of detection for water content is about 1 wt %
Objective To describe the normative course of maternal sleep during the first 4 months postpartum. Study Design Sleep was objectively measured using continuous wrist actigraphy. This was a ...longitudinal, field-based assessment of nocturnal sleep during postpartum weeks 2 through 16. Fifty mothers participated during postpartum weeks 2 through 13; 24 participated during postpartum weeks 9 through 16. Results Maternal nocturnal sleep time was 7.2 (SD ± 0.95) hours and did not change significantly across postpartum weeks 2 through 16. Maternal sleep efficiency did improve across weeks 2 (79.7%; SD ± 5.5) through 16 (90.2%; SD ± 3.5) as a function of decreased sleep fragmentation across weeks 2 (21.7; SD ± 5.2) through 16 (12.8; SD ± 3.3). Conclusion Though postpartum mothers' total sleep time was higher than expected during the initial postpartum months, this sleep was highly fragmented (similar to fragmenting sleep disorders) and inefficient. This profile of disturbed sleep should be considered in intervention designs and family leave policies.
Variation in levels of multiple paternity (MP) among species, populations and individuals has important ecological and evolutionary ramifications including maintenance of genetic diversity and ...offspring fitness benefits. Within species, differences in breeding experience and body size may affect the levels of MP via mate choice preferences. The present study tested these ideas in an Australian loggerhead turtle (
Caretta caretta
) population at Mon Repos Beach (24°48°S, 152°27°E, Queensland) to determine if variation in MP was related female breeding history or body size, or influenced embryo and hatchling outcomes in clutches from 29 females and 552 hatchlings. MP was moderately high (65.5%), but experienced females did not have higher levels of MP than first-time breeders (neophytes), nor was female size related to the number of sires. Instead, more subtle patterns emerged: multiply sired clutches of experienced females were sired by more males than those of multiply sired neophyte clutches and primary fathers sired a greater proportion of offspring when mated to larger females. These findings are consistent with cross-seasonal sperm storage in experienced breeders contributing to a small proportion of paternity and size-dependent variation in polyandrous mating behaviour. MP did not influence offspring size, levels of within-clutch morphological variation or hatching success. However, the number of sires of a clutch was positively correlated with proportion of developed embryos, suggesting a fitness advantage of MP. From a population perspective, male-biased sex ratios likely contribute to the MP levels observed, and levels could decrease with projected feminisation of populations due to climate change.
Do birds show a different pattern of insular evolution from mammals? Mammals follow the 'island rule', with large-bodied species getting smaller on islands and small-bodied species getting bigger. By ...contrast, the traditional view on birds is that they follow no general island rule for body size, but that there is an insular trend for large bills. Insular shifts in feeding ecology are, therefore, widely assumed to be the primary cause of divergence in island birds. We use a comparative approach to test these ideas. Contrary to the traditional view, we find no evidence for increased bill size in insular populations. Instead, changes in both bill size and body size obey the 'island rule'. The differences between our results and the traditional view arise because previous analyses were based largely on passerines. We also investigate some ecological factors that are thought to influence island evolution. As predicted by the traditional view, shifts in bill size are associated with feeding ecology. By contrast, shifts in body size are associated with the potential for intraspecific competition and thermal ecology. All these results remain qualitatively unchanged when we use different methods to score the ecological factors and restrict our analyses to taxa showing pronounced morphological divergence. Because of strong covariation between ecological factors, however, we cannot estimate the relative importance of each ecological factor. Overall, our results show that the island rule is valid for both body size and bill length in birds and that, in addition to feeding ecology, insular shifts in the level of intraspecific competition and the abiotic environment also have a role.
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