Ground-based Model Research Articles

Physical exercise restores adult neurogenesis deficits induced by simulated microgravity

Cognitive impairments have been reported in astronauts during spaceflights and documented in ground-based models of simulated microgravity (SMG) in animals. However, the neuronal causes of these behavioral effects remain largely unknown. We explored whether adult neurogenesis, known to be a crucial plasticity mechanism supporting memory processes, is altered by SMG. Adult male Long-Evans rats were submitted to the hindlimb unloading model of SMG. We studied the proliferation, survival and maturation of newborn cells in the following neurogenic niches: the subventricular zone (SVZ)/olfactory bulb (OB) and the dentate gyrus (DG) of the hippocampus, at different delays following various periods of SMG. SMG exposure for 7 days, but not shorter periods of 6 or 24 h, resulted in a decrease of newborn cell proliferation restricted to the DG. SMG also induced a decrease in short-term (7 days), but not long-term (21 days), survival of newborn cells in the SVZ/OB and DG. Physical exercise, used as a countermeasure, was able to reverse the decrease in newborn cell survival observed in the SVZ and DG. In addition, depending on the duration of SMG periods, transcriptomic analysis revealed modifications in gene expression involved in neurogenesis. These findings highlight the sensitivity of adult neurogenesis to gravitational environmental factors during a transient period, suggesting that there is a period of adaptation of physiological systems to this new environment.

Interpreting Geostationary Environment Monitoring Spectrometer (GEMS) geostationary satellite observations of the diurnal variation in nitrogen dioxide (NO2) over East Asia

Abstract. Nitrogen oxide radicals (NOx≡NO+NO2) emitted by fuel combustion are important precursors of ozone and particulate matter pollution, and NO2 itself is harmful to public health. The Geostationary Environment Monitoring Spectrometer (GEMS), launched in space in 2020, now provides hourly daytime observations of NO2 columns over East Asia. This diurnal variation offers unique information on the emission and chemistry of NOx, but it needs to be carefully interpreted. Here we investigate the drivers of the diurnal variation in NO2 observed by GEMS during winter and summer over Beijing and Seoul. We place the GEMS observations in the context of ground-based column observations (Pandora instruments) and GEOS-Chem chemical transport model simulations. We find good agreement between the diurnal variations in NO2 columns in GEMS, Pandora, and GEOS-Chem, and we use GEOS-Chem to interpret these variations. NOx emissions are 4 times higher in the daytime than at night, driving an accumulation of NO2 over the course of the day, offset by losses from chemistry and transport (horizontal flux divergence). For the urban core, where the Pandora instruments are located, we find that NO2 in winter increases throughout the day due to high daytime emissions and increasing NO2/NOx ratio from entrainment of ozone, partly balanced by loss from transport and with a negligible role of chemistry. In summer, by contrast, chemical loss combined with transport drives a minimum in the NO2 column at 13:00–14:00 local time (LT). Segregation of the GEMS data by wind speed further demonstrates the effect of transport, with NO2 in winter accumulating throughout the day at low winds but flat at high winds. The effect of transport can be minimized in summer by spatially averaging observations over the broader metropolitan scale, under which conditions the diurnal variation in NO2 reflects a dynamic balance between emission and chemical loss.

Spaceflight on the ISS changed the skeletal muscle proteome of two astronauts

Skeletal muscle undergoes atrophy and loss of force during long space missions, when astronauts are persistently exposed to altered gravity and increased ionizing radiation. We previously carried out mass spectrometry-based proteomics from skeletal muscle biopsies of two astronauts, taken before and after a mission on the International Space Station. The experiments were part of an effort to find similarities between spaceflight and bed rest, a ground-based model of unloading, focused on proteins located at the costameres. We here extend the data analysis of the astronaut dataset and show compartment-resolved changes in the mitochondrial proteome, remodeling of the extracellular matrix and of the antioxidant response. The astronauts differed in their level of onboard physical exercise, which correlated with their respective preservation of muscle mass and force at landing in previous analyses. We show that the mitochondrial proteome downregulation during spaceflight, particularly the inner membrane and matrix, was dramatic for both astronauts. The expression of autophagy regulators and reactive oxygen species scavengers, however, showed partially opposite expression trends in the two subjects, possibly correlating with their level of onboard exercise. As mitochondria are primarily affected in many different tissues during spaceflight, we hypothesize that reactive oxygen species (ROS) rather than mechanical unloading per se could be the primary cause of skeletal muscle mitochondrial damage in space. Onboard physical exercise might have a strong direct effect on the prevention of muscle atrophy through mechanotransduction and a subsidiary effect on mitochondrial quality control, possibly through upregulation of autophagy and anti-oxidant responses.

Nutritional Fuelling for Microgravity Environment of Space Missions

Abstract: Since the beginning of space missions, the food systems have undergone a sea change with prolonged manned missions and permanent space habitats. We have a better understanding of physiological changes which happen in humans in space and help in adaptation to the space environment. Yet, much remains underexplored and warrants further research. Space missions today involve a considerable number of individuals operating in a microgravity environment for both short and long periods. The provision of food for such missions and managing the physio-pathological changes that affect nutritional requirements continue to be challenging. Food systems (food and beverages) used during every program to date have been shelf‐stable and were composed primarily of rehydratable or thermostabilized food items. Such foods usually have a lower hedonic value than fresh or frozen foods. Consequently, a reliable food system must provide a wide range of palatable and attractive foods as well as the tools to prepare them (through rehydration, heating, and cooling) to enhance the taste sensation of the crew. Adequate nutrition with easily accessible food is essential to this effort. To deliver nutritional recommendations to crew members for long-duration space missions, it is important to understand how nutritional status and general physiology are linked and affected by microgravity exposure. In view of this, it has been pointed out that nutritional countermeasures could rectify the physiological and behavioural anomalies during microgravity exposure. In this comprehensive narrative review, we have provided an overview of a few recent advances such as silkworm protein, good mood-vegan diet, 3-D food printing, and space garden’s produce for onboard support to food systems. It has also been found that exercise could be an addition to nutritional interventions. Areas of space exploration that require more in-depth research using ground-based bed rest models, as well as inflight microgravity conditions, are highlighted.

Wind Profile Retrieval Based on LSTM Algorithm and Mobile Observation of Brightness Temperature over the Tibetan Plateau

Stationary or mobile microwave radiometers (MRs) can measure atmospheric temperature, relative humidity, and water vapor density profiles with high spatio-temporal resolution, but cannot obtain the vertical variations of wind field. Based on a dataset of brightness temperatures (TBs) measured with a mobile MR over the Three-River-Source Region of the Tibetan Plateau from 18 to 30 July 2021, we develop a direct retrieval method for the wind profile (WP) based on the Long Short-Term Memory (LSTM) network technique, and obtain the reliable dynamic variation characteristics of the WP in the region. Furthermore, the ground-based radiative transfer model for TOVS (RTTOV-gb) was employed to validate the reliability of the TB observation, and we analyzed the impact of weather conditions, altitude, observational mode, and TB diurnal variation on the accuracy of the TB measurement and the retrieval of the WP. Results show that the TB from the mobile observation (MOTB) on clear and cloudy days are close to those of the simulated TB with the RTTOV-gb model, while TB measurements on rainy days are far larger than the modeled TBs. When compared with radiosonde observations, the WPs retrieved with the LSTM algorithm are better than the ERA5 reanalysis data, especially below 350 hPa, where the root mean square errors for both wind speed and wind direction are smaller than those of ERA5. The major factors influencing WP retrieval include the weather conditions, altitude, observational mode, and TB diurnal variation. Under clear-sky and cloudy conditions, the LSTM retrieval method can reproduce the spatio-temporal evolution of wind field and vertical wind shear characteristics. The findings of this study help to improve our understanding of meso-scale atmospheric dynamic structures, characteristics of vertical wind shear, atmospheric boundary layer turbulence, and enhance the assessment and forecasting accuracy of wind energy resources.

Adaptation to full weight-bearing following disuse in rats: The impact of biological sex on musculoskeletal recovery.

With the technological advances made to expand space exploration, astronauts will spend extended amounts of time in space before returning to Earth. This situation of unloading and reloading influences human physiology, and readaptation to full weight-bearing may significantly impact astronauts' health. On Earth, similar situations can be observed in patients who are bedridden or suffer from sport-related injuries. However, our knowledge of male physiology far exceeds our knowledge of female's, which creates an important gap that needs to be addressed to understand the sex-based differences regarding musculoskeletal adaptation to unloading and reloading, necessary to preserve health of both sexes. Using a ground-based model of total unloading for 14 days and reloading at full weight-bearing for 7 days rats, we aimed to compare the musculoskeletal adaptations between males and females. Our results reveal the existence of significant differences. Indeed, males experienced bone loss both during the unloading and the reloading period while females did not. During simulated microgravity, males and females showed comparable muscle deconditioning with a significant decline in rear paw grip strength. However, after 7 days of recovery, muscle strength improved. Additionally, sex-based differences in myofiber size existing at baseline are significantly reduced or eliminated following unloading and recovery.

Surface flux equilibrium estimates of evaporative fraction and evapotranspiration at global scale: Accuracy evaluation and performance comparison

Accurate estimation of terrestrial evapotranspiration (ET) is crucial to understand the water cycle and partitioning of turbulent energy fluxes at the land surface. However, large-scale ET estimation is always difficult to achieve due to the complexity of controlling factors and the heterogeneity of landscapes. A recent model, referred to as the surface flux equilibrium (SFE) model, proposes that evaporative fraction (EF, the ratio of ET to available energy at the surface) can be estimated accurately from near-surface specific humidity and air temperature, which makes it applicable to common weather stations and climate reanalysis datasets. However, previous validation only focused on the evaluation of this model at site and basin scale for ET estimation, making the real performance of the SFE model for EF estimation heretofore unknown. There also exists a gap in the comparison between the SFE model and other existing products in the representation of global ET patterns and variation trend. Against this background, a comprehensive validation was performed in this study to evaluate the accuracy of the SFE model for both EF and ET estimation. The validation against 136 flux towers worldwide shows that the ground-based SFE model achieved EF estimation with a root-mean-square-error (RMSE) of 0.22 and 0.16 at daily and monthly scale, respectively. The corresponding RMSE of ET estimation was 0.94 mm/day and 16.37 mm/month. The application of the SFE model on a global scale was achieved by using two reanalysis products (ERA5-Land and GLDAS-CLSM) as inputs respectively. The results indicate that the SFE model did hold potential to reduce the RMSE of these two products for ET estimation, but the cost was the decrease in correlation coefficient (r). The comparison with five existing global ET products (BESS, GLEAM, AVHRR, MOD16, and SSEBop) shows that the SFE model performed on the basis of ERA5-Land product has achieved moderate accuracy among these products. Judged from r, mean absolute error, RMSE, and bias, its accuracy was ranked as fourth, fourth, second, and second, respectively. However, a further evaluation over different land cover types suggests that the ERA-based SFE model has significant superiority over cropland, relative superiority over forest and savannas, and significant inferiority over shrubland and grassland. This analysis is the first global validation of the SFE model for EF estimation as well as its comparison with existing global ET products. The validation analysis proves that this simple model has generally achieved comparable accuracy to existing complex models in the representation of global ET patterns and variation trend.

Grip Force Control in 21-Day Dry Immersion

During space flight, the changes in the functions of the upper limbs can affect the quality of operator activity. At the same time, there are very few data on this topic, because most of the research is focused on the structure and functions of the lower extremities. The aim was to study the characteristics of the grip force control during the decrease of the support and proprioceptive sensory signals in the conditions of the ground-based model of the effects of space flight – dry immersion (DI). The duration of DI exposure was 21 days. 10 male volunteers performed tests using a hand dynamometer for maximal voluntary contraction, the maintenance of the reference force, the reproduction of this force from memory, and the grip force gradation test. The subjects performed this series of tests before exposure to DI, then on days 1, 3, 5, 10, 15, and 20 of DI, and days 1 and 3 of the recovery period. The results show that DI exposure led to an increase in proprioceptive sensitivity in the tasks without visual feedback when with open eyes from day 5 of DI the subjects were more mistaken in the reproduction of the reference force using the dominant hand. The sensory processing/modulation disorder under DI factors may cause this phenomenon.

Surface Reflectance and Aerosol Retrieval from SPOT-VGT and PROBA-V in the Mission Exploitation Platform Environment

Observations acquired by the SPOT-VEGETATION and PROBA-V missions offer a unique opportunity to improve our understanding of the climate, providing global and continuous data over the land surface over 20 years. The possibility of generating a long-term climate data record from the entire archive, stored on the Mission Exploitation Platform (MEP), is here explored. For this purpose, in the framework of the ESA-funded SPAR@MEP project, the Combined Inversion of Surface and Aerosols (CISAR) algorithm has been applied to the SPOT-VGT and PROBA-V archive, following the harmonization of the observations according to the Fidelity and Uncertainty in Climate data records from Earth Observations (FIDUCEO) principles. CISAR has been applied to the full 20-year harmonized archive over key areas, as well as to one year of global acquisition from PROBA-V, processed at 5 km resolution, to derive aerosol single-scattering properties and surface reflectance. The retrieval is evaluated in terms of consistency among the three sensors and against reference datasets, including ground-based observations, models, and other sensor products. This activity has revealed the importance of characterizing the radiometric uncertainty for every processed pixel.

Spatial modeling of geotechnical soil parameters: Integrating ground-based data, RS technique, spatial statistics and GWR model

Ensuring the availability of a cost-effective method to predict soil behavior is imperative for newly developed construction sites. This research aims to create a model that can estimate the spatial distribution of soil properties and compaction characteristics using the Inverse Distance Weighting (IDW) and Geographic Weighted Regression (GWR) methods within the study area, specifically in Koya city, situated in Erbil, Iraq. To determine these soil parameters, 27 soil samples were collected from the fields based on stratified random sampling, and then tested and analyzed in the laboratory. The IDW spatial interpolation technique and GWR method were then used to create a spatial distribution map of soil properties and compaction characteristics. In the GWR model, the calculated soil properties and compaction characteristics served as the dependent variable, while the Modified Normalized Difference Water Index (MNDWI) derived from the Landsat8 satellite image was the independent variable. This process resulted in a spatial distribution map showing the soil properties and compaction characteristics. The results indicated a strong correlation between the MNDWI water indexes and various soil parameters, including water content, liquid limit, plastic limit, optimum moisture content, and maximum dry density, with respective coefficient of determination (R2) values of 0.91, 0.97, 0.98, 0.95, and 0.96. Additionally, the assessment of the precision in this correlation indicates that the results maintain a satisfactory level of accuracy, as demonstrated by the Root Mean Square Error (RMSE) values, which are 2.86 for water content, 5.4 for liquid limit, and 3.85 for plastic limit, 2.9 for optimum moisture, and 13.86 for maximum dry density. By integrating satellite-derived MNDWI water indexes with soil parameters, a fast, accurate, and cost-effective method for estimating soil parameters and modeling their spatial distribution in the study area can be developed. Additionally, the findings suggest that the IDW method, implemented using spatial analyst tools, performed exceptionally well for mapping the study area. In conclusion, the results of this research can be utilized by land use planners, municipalities, policymakers, and engineers to develop practical and effective plans.

Corticospinal excitability after 5-day Dry Immersion in women.

In light of the development of manned astronautics and the increasing participation of women in space flights, the question of female body adaptation to microgravity conditions becomes relevant. Currently, one of the important directions in this issue is to study the effects of support withdrawal as a factor of weightlessness on the human sensorimotor system. Dry Immersion is one of the well-known ground-based models, which adequately reproduces the main physiological effects of space flight. The aim of this study was to evaluate the changes in motor evoked potentials of the lower leg gravity-dependent muscles in women after a 5-day Dry Immersion. We analyzed evoked responses to transcranial and trans-spinal magnetic stimulation. In this method, areas of interest (the motor cortex and lumbosacral thickening of the spinal cord) are stimulated with an electromagnetic stimulus. The experiment was conducted with the participation of 16 healthy female volunteers with a natural menstrual cycle. The thresholds, amplitudes, and latencies of motor potentials evoked by magnetic stimulation were assessed. We showed that 5-day exposure to support withdrawal leads to a decrease in motor-evoked potential thresholds and central motor conduction time, although changes in motor response amplitudes were ambiguous. The data obtained correspond to the results of previous research on Dry Immersion effects on the sensorimotor system in men.

Enhancing microbial diversity as well as multi-organ health in hind-limb unloaded mice

During space travel, the gut microbiota is changed which can lead to health-related issues. Previously, we utilized the hind-limb unloaded (HU) mouse, which is an established ground-based in-vivo model of microgravity and observed altered gut microbiota. In this study, we evaluated the beneficial effects of novel bacterial conditioned media in HU mice to understand if they can offset the effects of unloading in the HU mouse model. We aimed to explore the influence of bacterial conditioned media on diversity and quantity of intestinal microbes in HU mice, and investigated the microarchitecture of mice retinas and kidneys to evaluate the potential systemic effects of bacterial conditioned media in HU mice. Four-month-old, male C57/Bl6 mice were separated into groups: including the ground-based control group, the HU group mice fed with vehicle as placebo (HU-placebo mice), and the HU group fed with bacterial conditioned media (HU-CP mice) and kept under controlled environmental conditions for three weeks. Next, mice were sacrificed; gut dissections were conducted, and metagenomic analysis of bacterial species was performed via DNA extraction and 16S rRNA analysis. The results revealed an HU-induced reduction in intestinal microbial diversity, and an increase in pathogenic bacteria dominated by Firmicutes (45%). In contrast, supplementation with bacterial conditioned media for three weeks led to a significant increase in gut microbial diversity with noticeable changes in the OTUs abundance in the HU mice. Additionally, HU-induced muscle weakness and structural abnormalities in the retina and kidney were partially prevented with bacterial conditioned media. Moreover, a greater diversity of several bacteria in the HU-CP was observed including, Bacteriodota, Firmicutes, Proteobacteria, Actionobacteriota, Verrucomicorbiota, Cyanobacteria, Gemmatimonadota, Acidobacteriota, Chloroflexi, Myxococcota, and others. Prospective research involving molecular mechanistic studies are needed to comprehend the systemic effects of bacterial metabolites conditioned media on experimental animal models under chronic stress.

Hemostasis System in Airline Passengers and Pilots

This review contains the results of the studies of the hemostasis system in airline passengers and crew members, as well as ground-based model experiments simulating the effect of specific flight factors. According to most researchers, flight factors shift the coagulation balance towards increasing the procoagulant potential. However, the occurrence of thrombotic conditions in passengers is associated with the individual presence of certain endogenous risk factors, such as age, constitution, the diseases of the cardiovascular system and hereditary pathology of the hemostasis system, some types of hormone therapy. Aircraft pilots whose flight time significantly exceeds that of passengers have described cases of thrombosis. No mention of cases of hemorrhagic conditions in civil aviation flight personnel has been found in the available literature.

Celebrity gossip headlines and reliability in a Common Ground-based framework

The paper is concerned with gossip communicated by headlines in a German celebrity magazine. It takes its starting point in a philosophical controversy on the question whether gossip is essentially epistemically (un-)reliable. As a theoretical framework, Farkas & Bruce's Common Ground-based Table model is adopted which distinguishes between different ways of introducing propositions into the Common Ground. Relating the model to the reliability status of propositions, it is argued that depending on the way in which a proposition is added to the Common Ground, it will be assigned varying epistemic status. Based on the quantitative and qualitative analysis of a corpus of 87 sentential gossip headlines from the German celebrity magazine BUNTE, it is shown that gossip is communicated both via assertion, presupposition, and conversational implicature, and that each of these ways of communication entails a different certainty status of the proposition added to the Common Ground. This means that gossip is neither essentially unreliable nor essentially reliable. Rather, the resulting ‘gossip Common Ground’ is best described as a set of epistemically heterogeneous propositions.

Aerosols heat up the Himalayan climate

The impact of aerosols, especially the absorbing aerosols, in the Himalayan region is important for climate. We closely examine ground-based high-quality observations of aerosol characteristics including radiative forcing from several locations in the Indo-Gangetic Plain (IGP), the Himalayan foothills and the Tibetan Plateau, relatively poorly studied regions with several sensitive ecosystems of global importance, as well as highly vulnerable large populations. This paper presents a state-of-the-art treatment of the warming that arises from these particles, using a combination of new measurements and modeling techniques. This is a first-time analysis of its kind, including ground-based observations, satellite data, and model simulations, which reveals that the aerosol radiative forcing efficiency (ARFE) in the atmosphere is clearly high over the IGP and the Himalayan foothills (80–135 Wm−2 per unit aerosol optical depth (AOD)), with values being greater at higher elevations. AOD is >0.30 and single scattering albedo (SSA) is ∼0.90 throughout the year over this region. The mean ARFE is 2–4 times higher here than over other polluted sites in South and East Asia, owing to higher AOD and aerosol absorption (i.e., lower SSA). Further, the observed annual mean aerosol-induced atmospheric heating rates (0.5–0.8 Kelvin/day), which are significantly higher than previously reported values for the region, imply that the aerosols alone could account for >50 % of the total warming (aerosols + greenhouse gases) of the lower atmosphere and surface over this region. We demonstrate that the current state-of-the-art models used in climate assessments significantly underestimate aerosol-induced heating, efficiency and warming over the Hindu Kush – Himalaya – Tibetan Plateau (HKHTP) region, indicating a need for a more realistic representation of aerosol properties, especially of black carbon and other aerosols. The significant, regionally coherent aerosol-induced warming that we observe in the high altitudes of the region, is a significant factor contributing to increasing air temperature, observed accelerated retreat of the glaciers, and changes in the hydrological cycle and precipitation patterns over this region. Thus, aerosols are heating up the Himalayan climate, and will remain a key factor driving climate change over the region.

Ground-based remote sensing provides alternative to satellites for monitoring cyanobacteria in small lakes

Cyanobacteria are the most prevalent bloom-forming harmful algae in freshwater systems around the world. Adequate sampling of affected systems is limited spatially, temporally, and fiscally. Remote sensing using space- or ground-based systems in large water bodies at spatial and temporal scales that are cost-prohibitive to standard water quality monitoring has proven to be useful in detecting and quantifying cyanobacterial harmful algal blooms. This study aimed to identify a regional ‘universal’ multispectral reflectance model that could be used for rapid, remote detection and quantification of cyanoHABs in small- to medium-sized productive reservoirs, such as those typical of Oklahoma, USA. We aimed to include these small waterbodies in our study as they are typically overlooked in larger, continental wide studies, yet are widely distributed and used for recreation and drinking water supply. We used Landsat satellite reflectance and in-situ pigment data spanning 16 years from 38 reservoirs in Oklahoma to construct empirical linear models for predicting concentrations of chlorophyll-a and phycocyanin, two key algal pigments commonly used for assessing total and cyanobacterial algal abundances, respectively. We also used ground-based hyperspectral reflectance and in-situ pigment data from seven reservoirs across five years in Oklahoma to build multispectral models predicting algal pigments from newly defined reflectance bands. Our Oklahoma-derived Landsat- and ground-based models outperformed established reflectance-pigment models on Oklahoma reservoirs. Importantly, our results demonstrate that ground-based multispectral models were far superior to Landsat-based models and the Cyanobacteria Index (CI) for detecting cyanoHABs in highly productive, small- to mid-sized reservoirs in Oklahoma, providing a valuable tool for water management and public health. While satellite-based remote sensing approaches have proven effective for relatively large systems, our novel results indicate that ground-based remote sensing may offer better cyanoHAB monitoring for small or highly dendritic turbid lakes, such as those throughout the southern Great Plains, and thus prove beneficial to efforts aimed at minimizing public health risks associated with cyanoHABs in supply and recreational waters.

Motion trajectory planning of a mobile robot flying in a fuzzy environment

Abstract.This study involved implementing a fuzzy controller approach to create a ground-based control model for an autonomous robot in a stable environment. In addition, a classical control method was developed and tested within the results. With the fuzzy controller approach, it was studied that the robot moves easily in the test environment and goes to desired targets. An autonomous mobile robot aims to minimize the energy consumption of the robot with a fuzzy controller algorithm. The energy consumption for processing time and data error between the coordinates where the robot should go and the coordinates it goes after the operations are completed are calculated separately. By utilizing a fuzzy controller algorithm, the mobile robot is capable of operating in a flexible manner. It was observed that the fuzzy approach performs 10 times faster and more accurately compared to the traditional method. In terms of being open to development and modular, the flying mobile robot fulfilled the functions envisaged in this work. In the future, the direction of a flying robot can be determined using a digital electronic compass to reach longer distances with external sensors.

Three-dimensional view of CO2 variability in the atmosphere over the Indian region

The study reports diurnal and seasonal variations of atmospheric CO2 across multiple locations in India using the dedicated ground-based observations, satellite observations and model simulations. Data from seven sites collected during different time periods are analysed to understand the role of biospheric, fossil fuel fluxes on diurnal and seasonal variations of atmospheric CO2. The study also examines the impact of land use/land cover on the variability of atmospheric CO2 concentration. Results show that CO2 mixing ratios are highest during night and lowest in the afternoon. Ponmudi station shows homogeneous daily CO2 mixing ratios because of an active ecosystem and free of boundary layer influence. A high altitude site Ooty exhibits higher diurnal and seasonal variations, possibly due to entrapped emissions from tourism and settlements, while Nagpur's (an urban site), CO2 mixing ratios remain moderate throughout the year due to active plantations. The observed CO2 is further compared with the simulations from atmospheric chemistry-transport model. The model is able to capture the observed seasonal cycle all over the study locations.

Exposure to multiple ion beams, broadly representative of galactic cosmic rays, causes perivascular cardiac fibrosis in mature male rats.

Long-duration space exploratory missions to the Earth's moon and the planet Mars are actively being planned. Such missions will require humans to live for prolonged periods beyond low earth orbit where astronauts will be continuously exposed to high energy galactic cosmic rays (GCRs). A major unknown is the potential impact of GCRs on the risks of developing degenerative cardiovascular disease, which is a concern to NASA. A ground-based rat model has been used to provide a detailed characterization of the risk of long-term cardiovascular disease from components of GCRs at radiation doses relevant to future human missions beyond low earth orbit. Six month old male WAG/RijCmcr rats were irradiated at a ground-based charged particle accelerator facility with high energy ion beams broadly representative of GCRs: protons, silicon and iron. Irradiation was given either as a single ion beam or as a combination of three ion beams. For the doses used, the single ion beam studies did not show any significant changes in the known cardiac risk factors and no evidence of cardiovascular disease could be demonstrated. In the three ion beam study, the total cholesterol levels in the circulation increased modestly over the 270 day follow up period, and inflammatory cytokines were also increased, transiently, 30 days after irradiation. Perivascular cardiac collagen content, systolic blood pressure and the number of macrophages found in the kidney and in the heart were each increased 270 days after irradiation with 1.5 Gy of the three ion beam grouping. These findings provide evidence for a cardiac vascular pathology and indicate a possible threshold dose for perivascular cardiac fibrosis and increased systemic systolic blood pressure for complex radiation fields during the 9 month follow up period. The development of perivascular cardiac fibrosis and increased systemic systolic blood pressure occurred at a physical dose of the three ion beam grouping (1.5 Gy) that was much lower than that required to show similar outcomes in earlier studies with the same rat strain exposed to photons. Further studies with longer follow up periods may help determine whether humans exposed to lower, mission-relevant doses of GCRs will develop radiation-induced heart disease.

Perception of length and orientation in dry immersion.

How does gravity (or lack thereof) affect sensory-motor processing? We analyze sensorimotor estimation dynamics for line segments with varying direction (orientation) in a 7-day dry immersion (DI), a ground-based model of gravitational unloading. The measurements were carried out before the start of the DI, on the first, third, fifth and seventh days of the DI, and after its completion. At the memorization stage, the volunteers led the leading hand along the visible segment on a touchscreen display, and at the reproduction stage they repeated this movement on an empty screen. A control group followed the same procedure without DI. Both in the DI and control groups, when memorizing, the overall error in estimating the lengths and directions of the segments was small and did not have pronounced dynamics; when reproducing, an oblique effect (higher variability of responses to oblique orientations compared to cardinal ones) was obtained. We then separated biases (systematic error) and uncertainty (random error) in subjects' responses. At the same time, two opposite trends were more pronounced in the DI group during the DI. On the one hand the cardinal bias (a repulsion of orientation estimates away from cardinal axes) and, to a small extent, the variability of direction estimates decreased. On the other hand, the overestimation bias in length estimates increased. Such error pattern strongly supports the hypotheses of the vector encoding, in which the direction and length of the planned movement are encoded independently of each other when the DI disrupts primarily the movement length encoding.