The past and future of global river ice.

More than one-third of Earth's landmass is drained by rivers that seasonally freeze over. Ice transforms the hydrologic1,2, ecologic3,4, climatic5 and socio-economic6-8 functions of river corridors. Although river ice extent has been shown to be declining in many regions of the world1, the seasonality, historical change and predicted future changes in river ice extent and duration have not yet been quantified globally. Previous studies of river ice, which suggested that declines in extent and duration could be attributed to warming temperatures9,10, were based on data from sparse locations. Furthermore, existing projections of future ice extent are based solely on the location of the 0-°C isotherm11. Here, using satellite observations, we show that the global extent of river ice is declining, and we project a mean decrease in seasonal ice duration of 6.10 ± 0.08 days per 1-°C increase in global mean surface air temperature. We tracked the extent of river ice using over 400,000 clear-sky Landsat images spanning 1984-2018 and observed a mean decline of 2.5 percentage points globally in the past three decades. To project future changes in river ice extent, we developed an observationally calibrated and validated model, based on temperature and season, which reduced the mean bias by 87 per cent compared with the 0-degree-Celsius isotherm approach. We applied this model to future climate projections for 2080-2100: compared with 2009-2029, the average river ice duration declines by 16.7 days under Representative Concentration Pathway (RCP) 8.5, whereas under RCP 4.5 it declines on average by 7.3 days. Our results show that, globally, river ice is measurably declining and will continue to decline linearly with projected increases in surface air temperature towards the end of this century.

Subducting carbon.

A hidden carbon cycle exists inside Earth. Every year, megatons of carbon disappear into subduction zones, affecting atmospheric carbon dioxide and oxygen over Earth's history. Here we discuss the processes that move carbon towards subduction zones and transform it into fluids, magmas, volcanic gases and diamonds. The carbon dioxide emitted from arc volcanoes is largely recycled from subducted microfossils, organic remains and carbonate precipitates. The type of carbon input and the efficiency with which carbon is remobilized in the subduction zone vary greatly around the globe, with every convergent margin providing a natural laboratory for tracing subducting carbon.

Kimberlites reveal 2.5-billion-year evolution of a deep, isolated mantle reservoir.

The widely accepted paradigm of Earth's geochemical evolution states that the successive extraction of melts from the mantle over the past 4.5 billion years formed the continental crust, and produced at least one complementary melt-depleted reservoir that is now recognized as the upper-mantle source of mid-ocean-ridge basalts1. However, geochemical modelling and the occurrence of high 3He/4He (that is, primordial) signatures in some volcanic rocks suggest that volumes of relatively undifferentiated mantle may reside in deeper, isolated regions2. Some basalts from large igneous provinces may provide temporally restricted glimpses of the most primitive parts of the mantle3,4, but key questions regarding the longevity of such sources on planetary timescales-and whether any survive today-remain unresolved. Kimberlites, small-volume volcanic rocks that are the source of most diamonds, offer rare insights into aspects of the composition of the Earth's deep mantle. The radiogenic isotope ratios of kimberlites of different ages enable us to map the evolution of this domain through time. Here we show that globally distributed kimberlites originate from a single homogeneous reservoir with an isotopic composition that is indicative of a uniform and pristine mantle source, which evolved in isolation over at least 2.5 billion years of Earth history-to our knowledge, the only such reservoir that has been identified to date. Around 200 million years ago, extensive volumes of the same source were perturbed, probably as a result of contamination by exogenic material. The distribution of affected kimberlites suggests that this event may be related to subduction along the margin of the Pangaea supercontinent. These results reveal a long-lived and globally extensive mantle reservoir that underwent subsequent disruption, possibly heralding a marked change to large-scale mantle-mixing regimes. These processes may explain why uncontaminated primordial mantle is so difficult to identify in recent mantle-derived melts.

Plate motion and a dipolar geomagnetic field at 3.25 Ga.

The paleomagnetic record is an archive of Earth's geophysical history, informing reconstructions of ancient plate motions and probing the core via the geodynamo. We report a robust 3.25-billion-year-old (Ga) paleomagnetic pole from the East Pilbara Craton, Western Australia. Together with previous results from the East Pilbara between 3.34 and 3.18 Ga, this pole enables the oldest reconstruction of time-resolved lithospheric motions, documenting 160 My of both latitudinal drift and rotation at rates of at least 0.55°/My. Motions of this style, rate, and duration are difficult to reconcile with true polar wander or stagnant-lid geodynamics, arguing strongly for mobile-lid geodynamics by 3.25 Ga. Additionally, this pole includes the oldest documented geomagnetic reversal, reflecting a stably dipolar, core-generated Archean dynamo.

Environmental and anthropogenic factors mediating the functional connectivity of the mesquite lizard along the eastern Trans-Mexican Volcanic Belt.

Functional connectivity, the extent to which a landscape facilitates or impedes the dispersal of individuals across the landscape, is a key factor for the survival of species. Anthropogenic activities, such as urbanization, agriculture and roads, negatively impact functional connectivity of most species, particularly low-vagility species like lizards. Here, we examine how a landscape modified by anthropogenic activities affects the functional connectivity, at both broad and fine scales, of a widely distributed generalist lizard Sceloporus grammicus in the eastern Trans-Mexican Volcanic Belt, Mexico. We estimated for the first time the species' genetic structure, gene flow and functional connectivity in agricultural and forest zones using genomic data, a comprehensive landscape characterization and novel methods including gravity models. Our results showed not only marked genetic differentiation across the study region but also that functional connectivity is maintained for tens of kilometres despite S. grammicus low vagility. Specifically, we found that substrate and air temperature facilitated connectivity over broad and fine scales, respectively, while agricultural cover, relative humidity and slope were important for connectivity and gene flow. Contrastingly, forest cover and roads favoured (broad-scale) and limited (fine-scale) connectivity, likely associated with movement facilitated by small forest patches and with thermoregulation. Altogether, these results support that S. grammicus alternates its thermoregulatory behaviour depending on the distance travelled and the habitat environmental conditions, and that it can disperse through relatively modified landscapes, mainly using agricultural zones. The information obtained is crucial to understanding the response of lizards to current anthropogenic pressures and their potential to adapt.

Influence of rock type and geophysical properties on radon flux density.

The most significant source of human exposure to ionizing radiation is the radioactive gas radon (basically 222Rn) and its daughter decay products, creating more than half of the effective dose from all natural sources. Radon enters buildings mainly from dense rocks, which are below building foundations at depths of 1 m and more. In this paper long-term measurements of radon flux density are analyzed, with radon exhalation from the surface of the most common rocks-loams, sandy loams, clays, clay shales, several types of sandy-gravel-pebble deposits, clay and rocky limestone. The influence of geophysical properties of rocks on radon flux density due to exhalation from surfaces of those rocks was studied. Based on the results obtained, a method of local assessment of the hazard from radon and its progeny in buildings is proposed, which is based on the geophysical properties of rocks below the foundations of those buildings.

Carbonate-hosted microbial communities are prolific and pervasive methane oxidizers at geologically diverse marine methane seep sites.

At marine methane seeps, vast quantities of methane move through the shallow subseafloor, where it is largely consumed by microbial communities. This process plays an important role in global methane dynamics, but we have yet to identify all of the methane sinks in the deep sea. Here, we conducted a continental-scale survey of seven geologically diverse seafloor seeps and found that carbonate rocks from all sites host methane-oxidizing microbial communities with substantial methanotrophic potential. In laboratory-based mesocosm incubations, chimney-like carbonates from the newly described Point Dume seep off the coast of Southern California exhibited the highest rates of anaerobic methane oxidation measured to date. After a thorough analysis of physicochemical, electrical, and biological factors, we attribute this substantial metabolic activity largely to higher cell density, mineral composition, kinetic parameters including an elevated Vmax, and the presence of specific microbial lineages. Our data also suggest that other features, such as electrical conductance, rock particle size, and microbial community alpha diversity, may influence a sample's methanotrophic potential, but these factors did not demonstrate clear patterns with respect to methane oxidation rates. Based on the apparent pervasiveness within seep carbonates of microbial communities capable of performing anaerobic oxidation of methane, as well as the frequent occurrence of carbonates at seeps, we suggest that rock-hosted methanotrophy may be an important contributor to marine methane consumption.

Lithogenic hydrogen supports microbial primary production in subglacial and proglacial environments.

Life in environments devoid of photosynthesis, such as on early Earth or in contemporary dark subsurface ecosystems, is supported by chemical energy. How, when, and where chemical nutrients released from the geosphere fuel chemosynthetic biospheres is fundamental to understanding the distribution and diversity of life, both today and in the geologic past. Hydrogen (H2) is a potent reductant that can be generated when water interacts with reactive components of mineral surfaces such as silicate radicals and ferrous iron. Such reactive mineral surfaces are continually generated by physical comminution of bedrock by glaciers. Here, we show that dissolved H2 concentrations in meltwaters from an iron and silicate mineral-rich basaltic glacial catchment were an order of magnitude higher than those from a carbonate-dominated catchment. Consistent with higher H2 abundance, sediment microbial communities from the basaltic catchment exhibited significantly shorter lag times and faster rates of net H2 oxidation and dark carbon dioxide (CO2) fixation than those from the carbonate catchment, indicating adaptation to use H2 as a reductant in basaltic catchments. An enrichment culture of basaltic sediments provided with H2, CO2, and ferric iron produced a chemolithoautotrophic population related to Rhodoferax ferrireducens with a metabolism previously thought to be restricted to (hyper)thermophiles and acidophiles. These findings point to the importance of physical and chemical weathering processes in generating nutrients that support chemosynthetic primary production. Furthermore, they show that differences in bedrock mineral composition can influence the supplies of nutrients like H2 and, in turn, the diversity, abundance, and activity of microbial inhabitants.

Geomorphic index-based landscape evolution study for the extraction and interpretation of knickpoint and channel steepness in the mandakini catchment, western himalaya.

Geomorphometric analysis using geomorphic indices is essential to comprehend the evolution of a river basin including denudation, surface runoff, subsurface infiltration, differential erosion, lithological variations, possible surface tilting, landslides, and the influence of geological formations and structure. Research in morphometric measurements continues to face many challenges and difficulties despite all the effort carried out. These include the inaccuracy of morphometric measurements and the time it takes to obtain the expected results in large basins. Under such condition, the purpose of the study is to conduct an analysis for the group of indices which includes SL index, transverse topographic symmetry factor, and hypsometry curve along with its integral value in the Mandakini Catchment. Examining the spatial distribution of knickzones has not been well documented, particularly in the Mandakini Catchment; hence, we further analyzed the spatial distribution of knickpoints, channel steepness index, and chi-index along with the longitudinal river profile. Through this analysis, we aim to determine how these indices collectively contribute to the comprehensive characterization of the landscape evolution within the study area and to find the landscape signatures of the uplift by comparing different river profiles. Various knickpoints were found mainly in the upper reaches at higher elevation, validated through aerial imagery and then through detailed field observation. During the field investigation, various geomorphic indicators such as fluvial terraces, entrenched river meandering, active landslides, extensive toe erosion, and waterfalls associated were observed. The study also found out that the places near the Kedarnath, Sonprayag, and Kalimath-Kotma, show high SL index and high steepness index that may correlate with the presence of active thrust and faults.

Calibrating the coevolution of Ediacaran life and environment.

The rise of animals occurred during an interval of Earth history that witnessed dynamic marine redox conditions, potentially rapid plate motions, and uniquely large perturbations to global biogeochemical cycles. The largest of these perturbations, the Shuram carbon isotope excursion, has been invoked as a driving mechanism for Ediacaran environmental change, possibly linked with evolutionary innovation or extinction. However, there are a number of controversies surrounding the Shuram, including its timing, duration, and role in the concomitant biological and biogeochemical upheavals. Here we present radioisotopic dates bracketing the Shuram on two separate paleocontinents; our results are consistent with a global and synchronous event between 574.0 ± 4.7 and 567.3 ± 3.0 Ma. These dates support the interpretation that the Shuram is a primary and synchronous event postdating the Gaskiers glaciation. In addition, our Re-Os ages suggest that the appearance of Ediacaran macrofossils in northwestern Canada is identical, within uncertainty, to similar macrofossils from the Conception Group of Newfoundland, highlighting the coeval appearance of macroscopic metazoans across two paleocontinents. Our temporal framework for the terminal Proterozoic is a critical step for testing hypotheses related to extreme carbon isotope excursions and their role in the evolution of complex life.

Linking health to geology-a new assessment and zoning model based on the frame of medical geology.

With the growing concerns about the Earth's environment and human health, there has been a surge in research focused on the intersection of health and geology. This study quantitatively assesses the relationship between human health and geological factors using a new framework. The framework considers four key geological environment indicators related to health: soil, water, geological landform, and atmosphere. Results indicate that the atmospheric and water resource indicators in the study area were generally favorable, while the scores of geological landforms varied based on topography. The study also found that the selenium content in the soil greatly exceeded the local background value. Our research underscores the importance of geological factors on human health, establishes a new health-geological assessment model, and provides a scientific foundation for local spatial planning, water resource development, and land resource management. However, due to varying geological conditions worldwide, the framework and indicators for health geology may need to be adjusted accordingly.

Influence assessment of urban expansion on groundwater level fluctuations in Gandhinagar, Gujarat, India.

Being the state capital of Gujarat, Gandhinagar is snowballing urban population, resulting in overexploitation of groundwater resources and consequent decline in local groundwater level. The key objective of the current research is to understand the impact of urban expansion on the groundwater level of Gandhinagar district for the last 3 decades. Long-term land use/land cover (LULC) alterations using Landsat images (1991-2021) reveal a 234% increase in overall built-up area and it is more prominent in western and southern parts than the eastern part of study area till 2021 due to urban sprawl of adjacent Ahmedabad City. Spatial distribution of groundwater levels exhibits the same pattern of groundwater level drop as that of the urban expansion and the drop of maximum depth of the groundwater level has also observed during study tenure. Rapid population growth indicates inevitable urban densification which may lead to increase in groundwater abstraction and consequent groundwater level depletion of Gandhinagar City in near future. The scenario may be worsened due to the reduction in groundwater recharge area owing to enhancement of impervious surfaces. A negative correlation is established between groundwater level and respective built-up areas from 1991 to 2011. After 2001, groundwater levels in some areas showed a rising trend and the number of those locations have increased from 2001 to 2021, indicating a sufficient supply of surface water, meeting the escalating water demand and subsequent reduction in groundwater abstraction. High fluoride content was found in many groundwater samples collected from Gandhinagar's shallow unconfined aquifer. In lieu of almost unperturbed natural groundwater recharge, built-up expansion, rising population, and over-exploitation result in groundwater level depletion in both shallow and deeper aquifers. To replenish the already depleted groundwater level and for sustainable water supply, an integration of rainwater-surface water-groundwater management plan and sustainable urban management plan is highly required. The future sustainable urban-groundwater management plan of Gandhinagar City must emphasized on the expansion of green and permeable spaces for groundwater recharge, mandatory rainwater harvesting system in every building possible, suitable area demarcation for artificial recharge, and identification of areas which are less prone to groundwater level depletion for city expansion. The outcomes of the present study will help the decision-makers to prepare inclusive and resilient urban management plan to accomplish the 6th and 11th Sustainable Development Goals of United Nations by 2030.

An integrated groundwater resource management approach for sustainable development in a tropical river basin, southern India.

Evaluation of aquifer potential is essential, as the potable water demand has increased globally over the last few decades. The present study delineated different zones of groundwater potential and groundwater quality of the Kallada River basin (KRB) in southern India, using geo-environmental and hydrogeochemical parameters, respectively. Geo-environmental variables considered include relative relief, land use/land cover, drainage density, slope angle, geomorphology, and geology, while hydrogeochemical parameters include pH, electrical conductivity (EC), Cl-, Fe3+, and Al3+ concentrations. Analytical hierarchy process (AHP) was used for categorizing groundwater potential and quality zones. Nearly 50% of KRB is categorized as very high and high groundwater potential zones, occupying the western and midland regions. The central and west-central parts of KRB are characterized by excellent groundwater quality zones, while the eastern and western parts are characterized by good and poor groundwater quality zones, respectively. By integrating the groundwater potential and groundwater quality, sustainable groundwater management is observed to be necessary at about 54% of the basin, where site-specific groundwater management structures such as percolation ponds, injection wells, and roof water harvesting have been proposed using a rule-based approach. This integrated groundwater potential-groundwater quality approach helps policymakers to implement the most suitable management strategies with maximum performance.

Late Quaternary climate change shapes island biodiversity.

Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration-extinction dynamics, or as geologically dynamic with biodiversity resulting from immigration-speciation-extinction dynamics influenced by changes in island characteristics over millions of years. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels and caused massive changes in island area, isolation and connectivity, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory. Consequences of these oscillations for present biodiversity remain unassessed. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics.

Numerical modeling as a tool for evaluating the renewability of geothermal resources: the case study of the Euganean Geothermal System (NE Italy).

Renewable natural resources are strategic for reducing greenhouse gas emissions and the human footprint. The renewability of these resources is a crucial aspect that should be evaluated in utilization of scenario planning. The renewability of geothermal resources is strictly related to the physical and geological processes that favor water circulation and heating. In the Veneto region (NE Italy), thermal waters of the Euganean Geothermal System are the most profitable regional geothermal resource, and its renewability assessment entails the evaluation of fluid and heat recharge, regional and local geological settings, and physical processes controlling system development. This renewability assessment is aimed at defining both the importance of such components and the resource amount that can be exploited without compromising its future preservation. In the second part of the twentieth century, the Euganean thermal resource was threatened by severe overexploitation that caused a sharp decrease in the potentiometric level of the thermal aquifers. Consequently, regulation for their exploitation is required. In this work, the renewability of the Euganean Geothermal System was assessed using the results from numerical simulations of fluid flow and heat transport. The simulations were based on a detailed hydrogeological reconstruction that reproduced major regional geological heterogeneities through a 3D unstructured mesh, while a heterogeneous permeability field was used to reproduce the local fracturing of the thermal aquifers. The model results highlight the role played by the resolved structural elements, in particular the subsurface high-angle faults of the exploitation field, and by the anomalous regional crustal heat flow affecting the central Veneto region.

Extra-genomic instructive influences in morphogenesis: A review of external signals that regulate growth and form.

Embryonic development and regeneration accomplish a remarkable feat: individual cells work together to create or repair complex anatomical structures. What is the source of the instructive signals that specify these invariant and robust organ-level outcomes? The most frequently studied source of morphogenetic control is the host genome and its transcriptional circuits. However, it is now apparent that significant information affecting patterning also arrives from outside of the body. Both biotic and physical factors, including temperature and various molecular signals emanating from pathogens, commensals, and conspecific organisms, affect developmental outcomes. Here, we review examples in which anatomical patterning decisions are strongly impacted by lateral signals that originate from outside of the zygotic genome. The endogenous pathways targeted by these influences often show transgenerational effects, enabling them to shape the evolution of anatomies even faster than traditional Baldwin-type assimilation. We also discuss recent advances in the biophysics of morphogenetic controls and speculate on additional sources of important patterning information which could be exploited to better understand the evolution of bodies and to design novel approaches for regenerative medicine.

Iron-Fueled Life in the Continental Subsurface: Deep Mine Microbial Observatory, South Dakota, USA.

Iron-bearing minerals are key components of the Earth's crust and potentially critical energy sources for subsurface microbial life. The Deep Mine Microbial Observatory (DeMMO) is situated in a range of iron-rich lithologies, and fracture fluids here reach concentrations as high as 8.84 mg/liter. Iron cycling is likely an important process, given the high concentrations of iron in fracture fluids and detection of putative iron-cycling taxa via marker gene surveys. However, a previous metagenomic survey detected no iron cycling potential at two DeMMO localities. Here, we revisited the potential for iron cycling at DeMMO using a new metagenomic data set including all DeMMO sites and FeGenie, a new annotation pipeline that is optimized for the detection of iron cycling genes. We annotated functional genes from whole metagenomic assemblies and metagenome-assembled genomes and characterized putative iron cycling pathways and taxa in the context of local geochemical conditions and available metabolic energy estimated from thermodynamic models. We reannotated previous metagenomic data, revealing iron cycling potential that was previously missed. Across both metagenomic data sets, we found that not only is there genetic potential for iron cycling at DeMMO, but also, iron is likely an important source of energy across the system. In response to the dramatic differences we observed between annotation approaches, we recommend the use of optimized pipelines where the detection of iron cycling genes is a major goal. IMPORTANCE We investigated iron cycling potential among microbial communities inhabiting iron-rich fracture fluids to a depth of 1.5 km in the continental crust. A previous study found no iron cycling potential in the communities despite the iron-rich nature of the system. A new tool for detecting iron cycling genes was recently published, which we used on a new data set. We combined this with a number of other approaches to get a holistic view of metabolic strategies across the communities, revealing iron cycling to be an important process here. In addition, we used the tool on the data from the previous study, revealing previously missed iron cycling potential. Iron is common in continental crust; thus, our findings are likely not unique to our study site. Our new view of important metabolic strategies underscores the importance of choosing optimized tools for detecting the potential for metabolisms like iron cycling that may otherwise be missed.

Pantheon habitat made from regolith, with a focusing solar reflector.

We describe a polar Moon base habitat using direct solar energy for construction, food production and atmospheric revitalization. With a growing area as large as 2000 m2, it could provide for 40 or more people. The habitat is built like the ancient Roman Pantheon, a stone structure with a top circular oculus, bringing in focused sunlight that is spread out to crops below. The conical, corbelled structure is built from cast regolith blocks, held in compression despite the large internal atmospheric pressure by a regolith overlayer 20-30 m thick. It is sealed on the inside against leaks with thin plastic. A solar mirror concentrator used initially to cast the building blocks is later used to illuminate the habitat through a small pressure window at the oculus. Three years of robotic preparation of the building blocks does not seem excessive for a habitat which can be expected to last for millennia, as has the Treasury of Atreus made by similar dry-stone construction. One goal of returning to the Moon is to demonstrate the practicality of long-term human habitation off the Earth. The off-axis, paraboloidal reflecting mirror is rotated about the vertical polar axis in order to direct horizontal sunlight downward to a focus. In this way, the heavy materials needed from Earth to build and power the habitat are largely limited to the solar concentrator and regolith moving and moulding equipment. By illuminating with a reflector rather than with electricity, the solar collection area is 20 times smaller than would be needed for PV cells. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades'.

Systemic lupus Erythematosus and geomagnetic disturbances: a time series analysis.

BACKGROUND: To examine the influence of solar cycle and geomagnetic effects on SLE disease activity. METHODS: The data used for the analysis consisted of 327 observations of 27-day Physician Global Assessment (PGA) averages from January 1996 to February 2020. The considered geomagnetic indices were the AP index (a daily average level for geomagnetic activity), sunspot number index R (measure of the area of solar surface covered by spots), the F10.7 index (measure of the noise level generated by the sun at a wavelength of 10.7 cm at the earth's orbit), the AU index (upper auroral electrojet index), and high energy (> 60 Mev) proton flux events. Geomagnetic data were obtained from the Goddard Space Flight Center Space Physics Data Facility. A time series decomposition of the PGA averages was performed as the first step. The linear relationships between the PGA and the geomagnetic indices were examined using parametric statistical methods such as Pearson correlation and linear regression, while the nonlinear relationships were examined using nonparametric statistical methods such as Spearman's rho and Kernel regression. RESULTS: After time series deconstruction of PGA averages, the seasonality explained a significant fraction of the variance of the time series (R2 = 38.7%) with one cycle completed every 16 years. The analysis of the short-term (27-day) relationships indicated that increases in geomagnetic activity Ap index (p < 0.1) and high energy proton fluxes (> 60 Mev) (p < 0.05) were associated with decreases in SLE disease activity, while increases in the sunspot number index R anticipated decreases in the SLE disease activity expressed as PGA (p < 0.05). The short-term correlations became statistically insignificant after adjusting for multiple comparisons using Bonferroni correction. The analysis of the long-term (297 day) relationships indicated stronger negative association between changes in the PGA and changes in the sunspot number index R (p < 0.01), AP index (p < 0.01), and the F10.7 index (p < 0.01). The long-term correlations remained statistically significant after adjusting for multiple comparisons using Bonferroni correction. CONCLUSION: The seasonality of the PGA averages (one cycle every 16 years) explains a significant fraction of the variance of the time series. Geomagnetic disturbances, including the level of geomagnetic activity, sunspot numbers, and high proton flux events may influence SLE disease activity. Studies of other geographic locales are needed to validate these findings.

Classification of airborne 3D point clouds regarding separation of vegetation in complex environments.

Classification of outdoor point clouds is an intensely studied topic, particularly with respect to the separation of vegetation from the terrain and manmade structures. In the presence of many overhanging and vertical structures, the (relative) height is no longer a reliable criterion for such a separation. An alternative would be to apply supervised classification; however, thousands of examples are typically required for appropriate training. In this paper, an unsupervised and rotation-invariant method is presented and evaluated for three datasets with very different characteristics. The method allows us to detect planar patches by filtering and clustering so-called superpoints, whereby the well-known but suitably modified random sampling and consensus (RANSAC) approach plays a key role for plane estimation in outlier-rich data. The performance of our method is compared to that produced by supervised classifiers common for remote sensing settings: random forest as learner and feature sets for point cloud processing, like covariance-based features or point descriptors. It is shown that for point clouds resulting from airborne laser scans, the detection accuracy of the proposed method is over 96% and, as such, higher than that of standard supervised classification approaches. Because of artifacts caused by interpolation during 3D stereo matching, the overall accuracy was lower for photogrammetric point clouds (74-77%). However, using additional salient features, such as the normalized green-red difference index, the results became more accurate and less dependent on the data source.