Definition Of Habit Research Articles

Thermodynamic modeling of calcium or magnesium chloride, chlorate, and perchlorate ternary mixtures deliquescence at Mars-relevant temperatures

The definition of habitability on Mars is intimately linked to the stability of liquid water on the surface or near sub-surface. Brines provide the best pathway to stabilize liquid water, and form through deliquescence where a solid salt crystal transitions into an aqueous solution when exposed to a humid atmosphere. In a typical brine controlled by temperature and water relative humidity, ternary mixtures represent the best potential liquid brines. Here we modeled the deliquescence relative humidity (DRH) and the eutonic relative humidity (RH) of ternary salt mixtures. Chloride, chlorate, and perchlorate were modeled with either calcium or magnesium as the cation at temperatures ranging from 223 to 273 K. For the calcium ternary mixtures, the main salt composition precipitating at the DRH was dominated by calcium chloride, and by magnesium perchlorate in the magnesium ternary system. The hydration state of the precipitating salts systematically increased as temperature decreased. The eutonic RH for the calcium mixtures ranged from 14.24% at 273 K and increased to 43.54% by the coldest temperature of 223 K. The eutonic RH for the magnesium mixtures was significantly higher than the calcium counterpart, at 49.76% at 273 K and increased to 53.09% by 223 K. Calcium perchlorate was the predominate eutonic precipitate for the calcium mixtures, and magnesium chlorate for the magnesium mixtures., This study shows that ternary mixtures bring a slight improvement to the stability of brines on Mars compared to single salts or binary mixtures.

The habitability conditions of possible Mars landing sites for life exploration

A major focus of Mars exploration is the search for life. Since the Viking landers in the 1970's, no mission has searched for evidence of modern life. Future landed missions with this objective will require a landing site that optimizes the potential for current or geologically-recent habitable conditions. While the definition of habitability is broad, we concentrate on two conditions for habitability of temperature and water activity. In addition, we consider the access to subsurface ice (e.g., via a lander drill) as a major requirement. To examine potential landing sites, we utilize a standard model of temperature and ground-ice stability to explore a range of latitudes for the past 2.5 Myrs of orbitally induced climate change. We find that in the current epoch, habitable conditions do not occur within the ice-rich permafrost, where stable ice is limited to poleward of ∼47°N. Habitable conditions defined as favorable to metabolic activity in Earth-like potential Mars organisms did occur seasonally during periods of high obliquity >33°, when ground ice would have been more ubiquitous. The most recent occurrence was about 510 kyrs ago when temperatures and water activities seasonally exceeded the threshold for metabolic activity of −40 °C and 0.6, respectively. Periods such as these last 10s of kyrs at each occurrence. At no time or location do habitability conditions favor propagation (cell replication above −18 °C) in Earth-like Mars organisms. We present a model of subsurface stratigraphy based on the occurrence of ground ice, the age of the ice, and history of habitable conditions. From this stratigraphy we find that all latitudes offer some potential for life exploration. However, middle-latitude sites (47°N to 61°N) offer access to 100-kyr-old ice that experienced past habitable conditions, while high-latitudes sites (>61°N) offer this plus access to “ancient ice” > > 1 Myrs old. Access to, and comparison between, multiple stratigraphic layers with differing ages and histories will maximize the science results of a life exploration mission. These latitude limits may vary slightly with surface conditions of slope and soil properties.

A target list for searching for habitable exomoons

ABSTRACT We investigate the habitability of hypothetical moons orbiting known exoplanets. This study focuses on big, rocky exomoons that are capable of maintaining a significant atmosphere. To determine their habitability, we calculate the incident stellar radiation and the tidal heating flux arising in the moons as the two main contributors to the energy budget. We use the runaway greenhouse and the maximum greenhouse flux limits as a definition of habitability. For each exoplanet, we run our calculations for plausible ranges of physical and orbital parameters for the moons and the planet using a Monte Carlo approach. We calculate the moon habitability probability for each planet, which is the fraction of the investigated cases that lead to habitable conditions. Based on our results, we provide a target list for observations of known exoplanets of which the top 10 planets have more than 50 per cent chance for hosting habitable moons on stable orbits. Two especially promising candidates are Kepler-62 f and Kepler-16 b, both of them with known masses and radii. Our target list can help to detect the first habitable exomoon.

Striatal ensembles continuously represent animals kinematics and limb movement dynamics during execution of a locomotor habit

The sensorimotor striatum contributes to the normal execution of motor habits but the mechanisms underlying this function are largely unknown[1]. Motor habits are stereotyped sequences of movements learned through a long trial-and-error process, automatically triggered by a set of sensory cues and that tend to persist despite outcome degradation (e.g. reward omission). We found that rats running on a treadmill become proficient in a fixed time interval estimation task by developing a highly stereotyped locomotor routine. Consistently with the definition of habits, the routine was acquired slowly (at least 2 months of daily practice), and once learned, it persisted for several sessions when the rewarding outcome was omitted. We took advantage of this unexpected behavior and used tetrode arrays to record the spiking activity of dorsolateral striatal ensembles while rats perform the locomotor habit. We report sequential activations of striatal neurons during the entire execution of the task. Importantly, we found that the firing rate of a large fraction of neurons was either locked to the locomotor limb movements or correlated with the kinematics of the habit (running speed, acceleration, position and time). These results contrast with the long-standing view that striatum is mainly concerned with action selection[2]. Rather movements and task kinematics encoding suggest that the striatum continuously control the execution of habitual action. Additional experiments are currently being performed to further investigate this hypothesis.

Measurement of exercise habits and prediction of leisure-time activity in established exercise

Habit formation may be important to maintaining repetitive healthy behaviors like exercise. Existing habit questionnaires only measure part of the definition of habit (automaticity; frequency). A novel habit questionnaire was evaluated that measured contextual cueing. We designed a two-stage observational cohort study of regular exercisers. For stage 1, we conducted an in-person interview on a university campus. For stage 2, we conducted an internet-based survey. Participants were 156 adults exercising at least once per week. A novel measure, The Exercise Habit Survey (EHS) assessed contextual cueing through 13 questions on constancy of place, time, people, and exercise behaviors. A subset of the Self-Report Habit Index (SRHI), measuring automaticity, was also collected along with measures of intention and self-efficacy, and the International Physical Activity Questionnaire (IPAQ), leisure-time section. The EHS was evaluated using factor analysis and test–retest reliability. Its correlation to other exercise predictors and exercise behavior was evaluated using Pearson’s r and hierarchical regression. Results suggested that the EHS comprised four subscales (People, Place, Time, Exercise Constancy). Only Exercise Constancy correlated significantly with SRHI. Only the People subscale predicted IPAQ exercise metabolic equivalents. The SRHI was a strong predictor. Contextual cueing is an important aspect of habit but measurement methodologies warrant refinement and comparison by different methods.

Limits of photosynthesis in extrasolar planetary systems for earth-like planets.

We present a general modeling scheme for investigating the possibility of photosynthesis-based life on extrasolar planets. The scheme focuses on the identification of the habitable zone in main-sequence-star planetary systems with planets of Earth mass and size. Our definition of habitability is based on the long-term possibility of photosynthetic biomass production as a function of mean planetary surface temperature and atmospheric CO2-content. All the astrophysical, climatological, biogeochemical, and geodynamic key processes involved in the generation of photosynthesis-driven life conditions are taken into account. Implicitly, a co-genetic origin of the central star and the orbiting planet is assumed. The numerical solution of an advanced geodynamic model yields realistic look-up diagrams for determining the limits of photosynthesis in extrasolar planetary systems, assuming minimum CO2 levels set by the demand of C4 photosynthesis.

Determination of habitable zones in extrasolar planetary systems: Where are Gaia's sisters?

A general modeling scheme for assessing the suitability for life of extrasolar planets is presented. The scheme focuses on the identification of the “habitable zone” in main sequence star planetary systems accommodating Earth‐like components. Our definition of habitability is based on the long‐term possibility of photosynthetic biomass production under geodynamic conditions. Therefore all the pertinent astrophysical, climatological, biogeochemical, and geodynamic processes involved in the generation of photosynthesis‐driven life conditions are taken into account. Implicitly, a cogenetic origin of the central star and the orbiting planet is assumed. A geostatic model version is developed and investigated in parallel for demonstration purposes. The numerical solution of the advanced geodynamic model yields realistic lookup diagrams for convenient habitability determination. As an illustration, the MACHO‐98‐BLG‐35 event is scrutinized. It is shown that this event is definitely not tantamount to the discovery of one of Gaia's sisters.

Correction to “Initial results from radio occultation measurements with Mars Global Surveyor” by D. P. Hinson et al.

A general modeling scheme for assessing the suitability for life of extrasolar planets is presented. The scheme focuses on the identification of the “habitable zone” in main sequence star planetary systems accommodating Earth‐like components. Our definition of habitability is based on the long‐term possibility of photosynthetic biomass production under geodynamic conditions. Therefore all the pertinent astrophysical, climatological, biogeochemical, and geodynamic processes involved in the generation of photosynthesis‐driven life conditions are taken into account. Implicitly, a cogenetic origin of the central star and the orbiting planet is assumed. A geostatic model version is developed and investigated in parallel for demonstration purposes. The numerical solution of the advanced geodynamic model yields realistic lookup diagrams for convenient habitability determination. As an illustration, the MACHO‐98‐BLG‐35 event is scrutinized. It is shown that this event is definitely not tantamount to the discovery of one of Gaia's sisters.

Habit, Health, and Happiness

The notion of habit figures prominently in theories of health-related behavior and in efforts to encourage people to develop consistency and regularity in the healthful behavior of daily life. The consensus definition of habit as automatic and mindless behavior, however, presents three logical and philosophical problems. First, this definition of habit is at odds with the way most of our theories of health behavior try to employ the notion. Second, the behaviors of concern to most health, exercise, and sport psychologists are not the kinds of behaviors to which this definition of habit applies easily, if at all. Third, the kind of mindless behavior suggested by this definition may be conducive to enhancing physical health and athletic performance, but it may be inconsistent with the essential elements of happiness or subjective well-being according to Eastern philosophies such as Taoism and Buddhism, and according to the growing research on the psychology of happiness.