Mars exploration motivates the search for extraterrestrial life, the development of space technologies, and the design of human missions and habitations. Here, we seek new insights and pose unresolved questions relating to the natural history of Mars, habitability, robotic and human exploration, planetary protection, and the impacts on human society. Key observations and findings include:

1. – high escape rates of early Mars' atmosphere, including loss of water, impact present-day habitability;

2. – putative fossils on Mars will likely be ambiguous biomarkers for life;

3. – microbial contamination resulting from human habitation is unavoidable; and

4. – based on Mars' current planetary protection category, robotic payload(s) should characterize the local martian environment for any life-forms prior to human habitation.

Some of the outstanding questions are:

1. – which interpretation of the hemispheric dichotomy of the planet is correct;

2. – to what degree did deep-penetrating faults transport subsurface liquids to Mars' surface;

3. – in what abundance are carbonates formed by atmospheric processes;

4. – what properties of martian meteorites could be used to constrain their source locations;

5. – the origin(s) of organic macromolecules;

6. – was/is Mars inhabited;

7. – how can missions designed to uncover microbial activity in the subsurface eliminate potential false positives caused by microbial contaminants from Earth;

8. – how can we ensure that humans and microbes form a stable and benign biosphere; and

9. – should humans relate to putative extraterrestrial life from a biocentric viewpoint (preservation of all biology), or anthropocentric viewpoint of expanding habitation of space?

Studies of Mars' evolution can shed light on the habitability of extrasolar planets. In addition, Mars exploration can drive future policy developments and confirm (or put into question) the feasibility and/or extent of human habitability of space.

Establishing accurate population size estimates (PSE) is important for prioritising and planning provision of services. Multiple source capture−recapture sampling method increases PSE accuracy and reliability. In August 2018, the three-source capture−recapture (3S-CRC) method was employed with a stringent assumption of sample independence to estimate the number of female sex workers (FSW) in Rwanda. Using Rwanda 2017 FSW hotspots mapping data, street and venue-based FSW were sampled at the sector level of each province and tagged with two unique gifts. Each capture was completed within one week to minimise FSW migration between provinces and recall bias. The three captures had 1042, 1204 and 1488 FSW. There were 111 FSW recaptured between captures 1 and 2; 237 between captures 2 and 3; 203 between captures 1 and 3 and 46 captured in all three. The PSE for street and venue-based FSW in Rwanda lies within 95% credible set: 8328–22 806 with corresponding median of 13 716 FSW. The 3S-CRC technique was low-cost and relatively easy to use for PSE in hard-to-reach populations. This estimate provides the basis for determining the denominators to assess HIV programme performance towards FSW and epidemic control and warrants further PSE for home- and cyber-based FSW in Rwanda.

The control of bluff-body wakes for reduced drag and enhanced stability has traditionally relied on the so-called direct-wake control approach. By the use of actuators or passive devices, one can manipulate the aerodynamic loads that act on the rear of the model. An alternative approach for the manipulation of the flow is to move the position of the actuator upstream, hence interacting with an easier-to-manipulate boundary layer. The present paper comprises a bluff-body flow study via large-eddy simulations to investigate the effectiveness of an upstream actuator (positioned at the leading edge) with regard to the manipulation of the wake dynamics and its aerodynamic loads. A rectangular cylinder with rounded leading edges, equipped with actuators positioned at the front curvatures, is simulated at $Re=40\,000$. A genetic algorithm (GA) optimization is performed to find an effective actuation that minimizes drag. It is shown that the GA selects superharmonic frequencies of the natural vortex shedding. Hence, the induced disturbances, penetrating downstream in the wake, significantly reduce drag and lateral instability. A comparison with a side-recirculation-suppression approach is also presented, the latter case being worse in terms of reduced drag (only 8 % drag reduction achieved), despite the total suppression of the side recirculation bubble. In contrast, the GA optimized case contributes to a 20 % drag reduction with respect to the unactuated case. In addition, the large drag reduction is associated with a reduced shedding motion and an improved lateral stability.

The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.

Dietary supplementation with the organic chromium (Cr) has been shown to positively affect the immune function of poultry. However, to our knowledge, no experiment has been done to directly compare the impacts of Cr chloride and chromium picolinate (CrPic) on the immune responses of broilers vaccinated with Avian Influenza (AI) virus vaccine. Therefore, the present experiment was conducted to investigate the effects of supplemental Cr sources (Cr chloride and CrPic) and levels on the growth performance and immune responses of broilers vaccinated with AI virus vaccine so as to provide an effective nutritional strategy for improving immune function of broilers. A total of 432 1-day (d)-old male broiler chicks were used in a 1 plus 2×4 design. Chickens were given either a diet without Cr supplementation (control) or diets supplemented with 0.4, 0.8, 1.6, or 3.2 mg Cr/kg as either Cr chloride or CrPic for 42 d. Compared to the control, dietary Cr supplementation had no effect (P>0.05) on average daily gain, average daily feed intake and gain : feed of broilers during the starter and grower phases, but increased (P<0.05) the relative weights of bursa of fabricius on d 21 and thymus, spleen, or bursa of fabricius on d 42, serum antibody titers against AI virus on d 21, 28, 35 and 42, blood T-lymphocyte transformation rate on d 28 and 42, blood T-lymphocyte percentage on d 42, and serum interleukin-2 contents on d 28. Broilers fed the diets supplemented with the inorganic Cr chloride had higher (P<0.05) weights of thymus, spleen and bursa of fabricius than those fed the diets supplemented with the CrPic on d 42. In addition, broilers fed the diets supplemented with the CrPic had higher (P<0.05) antibody titers against AI virus than those fed the diets supplemented with the inorganic Cr chloride on d 21 and 35. These results indicate that dietary Cr supplementation improved immune responses of broilers vaccinated with AI virus, and the inorganic Cr chloride was more effective than the CrPic in increasing the relative weights of lymphoid organs, however, the CrPic was more effective than the inorganic Cr chloride in enhancing the serum antibody titer against AI virus.

The role of the protozoan parasite Toxoplasma gondii in the pathogenesis of liver disease has recently gained much interest. The aim of this study was to determine the prevalence and risk factors associated with T. gondii infection in patients with liver disease from three cities in Shandong and Henan provinces, China. A case–control study was conducted from December 2014 to November 2015 and included 1142 patients with liver disease and 1142 healthy controls. Serum samples were collected from all individuals and were examined with enzyme-linked immunosorbent assay for the presence of anti-T. gondii IgG and IgM antibodies. Information on the demographics, clinical, and lifestyle characteristics of the participants was collected from the medical records and by the use of a questionnaire. The prevalence of anti-T. gondii IgG was 19·7% in patients with liver disease compared with 12·17% in the controls. Only 13 patients had anti-T. gondii IgM antibodies compared with 12 control individuals (1·14% vs. 1·05%, respectively). The highest seroprevalence was detected in patients with liver cancer (22·13%), followed by hepatitis patients (20·86%), liver cirrhosis patients (20·42%), and steatosis patients (20%). Multivariate logistic regression analysis indicated that consumption of raw meat (odds ratio (OR) = 1·32; 95% confidence interval (CI) 1·01–1·71; P = 0·03) and source of drinking water from wells (OR = 1·56; 95% CI 1·08–2·27; P = 0·01) were independent risk factors for T. gondii infection in liver disease patients. These findings indicate that T. gondii infection is more likely to be present in patients with liver disease. Therefore, efforts should be directed toward health education of populations at high risk of T. gondii infection and measures should be taken to protect vulnerable patients with liver disease.

Introduction: Active substance use and unstable housing are both associated with increased emergency department (ED) utilization. This study examined ED health care costs among a cohort of substance using and/or homeless adults following an index ED visit, relative to a control ED population. Methods: Consecutive patients presenting to an inner-city ED between August 2010 and November 2011 who reported unstable housing and/or who had a chief presenting complaint related to acute or chronic substance use were evaluated. Controls were enrolled in a 1:4 ratio. Participants’ health care utilization was tracked via electronic medical record for six months after the index ED visit. Costing data across all EDs in the region was obtained from Alberta Health Services and calculated to include physician billing and the cost of an ED visit excluding investigations. The cost impact of ED utilization was estimated by multiplying the derived ED cost per visit by the median number of visits with interquartile ranges (IQR) for each group during follow up. Proportions were compared using non-parametric tests. Results: From 4679 patients screened, 209 patients were enrolled (41 controls, 46 substance using, 91 unstably housed, 31 both unstably housed and substance using (UHS)). Median costs (IQR) per group over the six-month period were $0 ($0-$345.42) for control, $345.42 ($0-$1139.89) for substance using, $345.42 ($0-$1381.68) for unstably housed and $1381.68 ($690.84-$4248.67) for unstably housed and substance using patients (p<0.05). Conclusion: The intensity of excess ED costs was greatest in patients who were both unstably housed and presenting with a chief complaint related to substance use. This group had a significantly larger impact on health care expenditure relative to ED users who were not unstably housed or who presented with a substance use related complaint. Further research into how care or connection to community resources in the ED can reduce these costs is warranted.

The allelochemicals 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA) in wheat are considered to have a role in plant defense against weeds. This study explored the effect of proximity to two weeds, wild oat and flixweed, on DIMBOA/MBOA production in wheat seedlings under hydroponic culture to identify whether the breeding of modern wheat varieties with higher concentrations of these compounds could ensure plant-mediated weed control. MBOA was detected and was noted to exert a significant response; its exudation by some wheat seedlings was significantly increased irrespective of whether the roots were in contact with or separate from those of the weeds. The weeds were a source of biotic stress to wheat when grown in proximity to it, and the stress resulted in production of higher levels of MBOA in wheat seedlings, although the concentration varied with the wheat cultivar. Therefore, the synthesis and exudation of DIMBOA/MBOA in wheat seedlings appears to be an active metabolic process influenced by the environment, particularly the presence of weeds.

Much can be learned from terrestrial planets that appear to have had the potential to be habitable, but failed to realize that potential. Mars shows evidence of a once hospitable surface environment. The reasons for its current state, and in particular its thin atmosphere and dry surface, are of great interest for what they can tell us about habitable zone planet outcomes. A main goal of the MAVEN mission is to observe Mars’ atmosphere responses to solar and space weather influences, and in particular atmosphere escape related to space weather ‘storms’ caused by interplanetary coronal mass ejections (ICMEs). Numerical experiments with a data-validated MHD model suggest how the effects of an observed moderately strong ICME compare to what happens during a more extreme event. The results suggest the kinds of solar and space weather conditions that can have evolutionary importance at a planet like Mars.

Introduction: Substance use and unstable housing are associated with heavy use of the Emergency Department (ED). This study examined the impact of substance use and unstable housing on the probability of future ED use. Methods: Case-control study of patients presenting to an urban ED. Patients were eligible if they were unstably housed for the past 30 days, and/or if their chief complaint was related to substance use. Following written informed consent, patients completed a baseline survey and health care use was tracked via electronic medical records for the next six months. Controls were enrolled in a 1:4 ratio. More than 2 ED visits during the follow-up was pre-specified as a measure of excess ED use. Descriptive analyses included proportions and medians with interquartile ranges (IQR). Binomial logistic regression models were used to estimate the impact of housing status, high-risk alcohol use (AUDIT) and drug use (DUDIT), and combinations of these factors on subsequent acute care system contacts (ED visits + admissions). We controlled for age, gender, comorbidities at baseline, and baseline presenting acuity. Results: 41 controls, 46 substance using, 91 unstably housed, and 31 both unstably housed and substance using patients were enrolled (n = 209). Median ED visits during follow up were 0 (IQR: 0-1.0) for controls, 1.0 (IQR: 0-3.3) for substance using, 1.0 (IQR: 0-4.0) for unstably housed and 4 (IQR: 2-12.3) for unstably housed and substance using patients. The median acute care system contacts over the same period was 1.0 (IQR 0-2.0) for controls, 1.0 (IQR: 0-4.0) for substance using, 1.0 (IQR: 0-5.0) for unstably housed and 4.5 (IQR: 2.8-14.3) for unstably housed and substance using patients. Being unstably housed was the factor most strongly associated with having > 2 ED visits (b=3.288, p<0.005) followed by high-risk alcohol and drug use (b=2.149, p<0.08); high risk alcohol use alone was not significantly associated with ED visits (b=1.939, p<0.1). The number of comorbidities present at baseline was a small but statistically significant additional risk factor (b=0.478, p<0.05). The model correctly predicted 70.1% of patients’ ED utilization status. Conclusion: Unstable housing is a substantial risk factor for ED use; high-risk alcohol and drug use, and comorbidities at baseline increased this risk. The intensity of excess ED use was greatest in patients who were unstably housed and substance using.

The magnetic reconnection (MR) configuration was constructed by using two approaching laser-produced plasma bubbles. The characteristics of the MR current sheet were investigated. The driving energy of the laser pulse affects the type of the current sheet. The experiments present “Y-type” and “X-type” current sheets for larger and smaller driving energy, respectively. The energetic electrons were found to be well-collimated. The formation and ejection of plasmoid from the “Y-type” current sheet was expected to enhance the number of accelerated electrons.

The characterization and properties of InN thin films grown on GaN templates by metalorganic chemical vapor deposition (MOCVD) at various growth temperatures were investigated. Their carrier concentrations ranged from 4.6 × 1018 to 4 × 1019 cm−3and mobility valued from 150 to 1300 cm2/V s. The variation of the growth temperature brought about different growth rates. It was also found that growth rate is increased with the increasing growth temperature and reached 470 nm/h for the InN epitaxial layer grown at 675 °C. The surface roughness of InN layers was obtained from AFM measurement. The structural quality of the InN layers was determined by TEM. The surface and cross-sectional morphologies of these films are evaluated by SEM. The layer crystalline quality was investigated by means of X-ray diffraction in the rocking curves. Photoluminescence measurements performed at 7 K and room temperature gave emission peaks at around 0.7 eV.

Grasslands are the most extensive terrestrial landscapes and ecosystems in China and face growing degradation. A policy to protect the grasslands established in 2001 (the Grassland Ban Policy [GBP]), involves four management practices including grazing bans, keeping grasslands fallow, grazing rotations and rearing livestock in sheds. A questionnaire was developed and used to establish attitudes towards and beliefs about the GBP in different sectors (farming households, local officials and extension workers), assess problems with GBP implementation and identify possible solutions. Acceptance of the GBP by farmers varied from 64% in the north to 95% in the north-west region. The responses of both local officials and extension workers indicated that GBP implementation was greater in the central region than in the north-west region. Most farmers changed their livestock production system from grazing to stall feeding after implementation of the GBP, while both farmers and extension workers reported that high input costs were the most serious problem in stall feeding. Incentives need to be provided for sustainable implementation of the GBP by different stakeholders. Improved collaboration among farmers, local officials and extension workers is needed for technology transfer and policy implementation. Furthermore, the role of non-governmental organizations needs to be strengthened in implementation of the GBP.