262 research outputs found
Can Deep Altruism Sustain Space Settlement?
Space settlement represents a long-term human effort that requires
unprecedented coordination across successive generations. In this chapter, I
develop a comparative hierarchy for the value of long-term projects based upon
their benefits to culture, their development of infrastructure, and their
contributions to lasting information. I next draw upon the concept of the time
capsule as an analogy, which enables a comparison of historical examples of
projects across generational, intergenerational, and deep time. The concept of
deep altruism can then be defined as the selfless pursuit of informational
value for the well-being of others in the distant future. The first steps
toward supporting an effort like space settlement through deep altruism would
establish governance and funding models that begin to support ambitions with
intergenerational succession.Comment: To be published in The Human Factor in a Mission to Mars: An
Interdisciplinary Approach, K. Szocik (Ed.), Springe
A comparison of RNA amplification techniques at sub-nanogram input concentration
<p>Abstract</p> <p>Background</p> <p>Gene expression profiling of small numbers of cells requires high-fidelity amplification of sub-nanogram amounts of RNA. Several methods for RNA amplification are available; however, there has been little consideration of the accuracy of these methods when working with very low-input quantities of RNA as is often required with rare clinical samples. Starting with 250 picograms-3.3 nanograms of total RNA, we compared two linear amplification methods 1) modified T7 and 2) Arcturus RiboAmp HS and a logarithmic amplification, 3) Balanced PCR. Microarray data from each amplification method were validated against quantitative real-time PCR (QPCR) for 37 genes.</p> <p>Results</p> <p>For high intensity spots, mean Pearson correlations were quite acceptable for both total RNA and low-input quantities amplified with each of the 3 methods. Microarray filtering and data processing has an important effect on the correlation coefficient results generated by each method. Arrays derived from total RNA had higher Pearson's correlations than did arrays derived from amplified RNA when considering the entire unprocessed dataset, however, when considering a gene set of high signal intensity, the amplified arrays had superior correlation coefficients than did the total RNA arrays.</p> <p>Conclusion</p> <p>Gene expression arrays can be obtained with sub-nanogram input of total RNA. High intensity spots showed better correlation on array-array analysis than did unfiltered data, however, QPCR validated the accuracy of gene expression array profiling from low-input quantities of RNA with all 3 amplification techniques. RNA amplification and expression analysis at the sub-nanogram input level is both feasible and accurate if data processing is used to focus attention to high intensity genes for microarrays or if QPCR is used as a gold standard for validation.</p
The association between insulin resistance and cytokines in adolescents: the role of weight status and exercise
Increased adiposity is associated with insulin resistance (IR) and an inflammatory response in adults. We tested the hypotheses that cytokines associated with adiposity are also correlated with IR in early adolescents and that these relationships are moderated by weight status, levels of vigorous physical activity (VPA), or maximal aerobic power (pVO2max). Body mass, stature, and a fasting blood sample were obtained from 120 mid-pubertal adolescents (60 girls & 60 boys). Habitual VPA was obtained by a survey. Predicted VO2max was determined using a cycle-ergometer test. Weight status was based on body mass index percentiles (normal weight = BMI 95th %tile). Glucose, insulin, adiponectin, resistin, tumor necrosis factor-α, and interleukin-6 were measured, and IR index was based on the Homeostatic Model Assessment (HOMA). Adiponectin, resistin and TNF-α were associated with IR in all adolescents (R2=0.329, p0.050). Exercise did not moderate the association between these cytokines and IR. However, higher levels of VPA and/or pVO2max were associated with higher adiponectin, lower resistin and lower TNF- α in at least one of the genders. Our results indicate that the pathophysiology of obesity is already established in early adolescents. Increased adiposity, resulting in reduced adiponectin and increased resistin and TNF-α may link these cytokines with insulin resistance in adolescents
Exoplanet Diversity in the Era of Space-based Direct Imaging Missions
This whitepaper discusses the diversity of exoplanets that could be detected
by future observations, so that comparative exoplanetology can be performed in
the upcoming era of large space-based flagship missions. The primary focus will
be on characterizing Earth-like worlds around Sun-like stars. However, we will
also be able to characterize companion planets in the system simultaneously.
This will not only provide a contextual picture with regards to our Solar
system, but also presents a unique opportunity to observe size dependent
planetary atmospheres at different orbital distances. We propose a preliminary
scheme based on chemical behavior of gases and condensates in a planet's
atmosphere that classifies them with respect to planetary radius and incident
stellar flux.Comment: A white paper submitted to the National Academy of Sciences Exoplanet
Science Strateg
Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs
Terrestrial planets in the habitable zones (HZs) of low-mass stars and cool
dwarfs have received significant scrutiny recently because their shorter
orbital periods increase their chances of detection and characterization
compared to planets around G-dwarfs. As these planets are likely tidal-locked,
improved 3D numerical simulations of such planetary atmospheres are needed to
guide target selection. Here we use a 3-D climate system model, updated with
new water-vapor absorption coefficients derived from the HITRAN 2012 database,
to study ocean covered planets at the inner edge of the HZ around late-M to
mid-K stars ( K <= Teff <= 4500K). Our results indicate that these
updated water-vapor coefficients result in significant warming compared to
previous studies, so the inner HZ around M-dwarfs is not as close as suggested
by earlier work. Assuming synchronously rotating planets with background 1 bar
N2 atmospheres, we find that planets at the inner HZ of stars with Teff > 3000K
undergo the classical "moist-greenhouse" (H2O mixing ratio > 10-3 in the
stratosphere) at significantly lower surface temperature (~ 280K) in our 3-D
model compared with 1-D climate models (~ 340K). This implies that some planets
around low mass stars can simultaneously undergo water-loss and remain
habitable. However, for star with Teff <= 3000K, planets at the inner HZ may
directly transition to a runaway state, while bypassing the moist greenhouse
water-loss entirely. We analyze transmission spectra of planets in a moist
green-house regime, and find that there are several prominent H2O features
within JWST instruments range. Thus, relying only upon standard Earth-analog
spectra with 24-hour rotation period around M-dwarfs for habitability studies
will miss the strong H2O features that one would expect to see on synchronously
rotating planets around M-dwarf stars, with JWST.Comment: Accepted to Astrophysical Journa
Relationships Between Circulating Metabolic Intermediates and Insulin Action in Overweight to Obese, Inactive Men and Women
Demarcating circulation regimes of synchronously rotating terrestrial planets within the habitable zone
We investigate the atmospheric dynamics of terrestrial planets in synchronous rotation within the habitable zone of low-mass stars using the Community Atmosphere Model (CAM). The surface temperature contrast between day and night hemispheres decreases with an increase in incident stellar flux, which is opposite the trend seen on gas giants. We define three dynamical regimes in terms of the equatorial Rossby deformation radius and the Rhines length. The slow rotation regime has a mean zonal circulation that spans from day to night side, with both the Rossby deformation radius and the Rhines length exceeding planetary radius, which occurs for planets around stars with effective temperatures of 3300 K to 4500 K (rotation period > 20 days). Rapid rotators have a mean zonal circulation that partially spans a hemisphere and with banded cloud formation beneath the substellar point, with the Rossby deformation radius is less than planetary radius, which occurs for planets orbiting stars with effective temperatures of less than 3000 K (rotation period < 5 days). In between is the Rhines rotation regime, which retains a thermally-direct circulation from day to night side but also features midlatitude turbulence-driven zonal jets. Rhines rotators occur for planets around stars in the range of 3000 K to 3300 K (rotation period ∼ 5 to 20 days), where the Rhines length is greater than planetary radius but the Rossby deformation radius is less than planetary radius. The dynamical state can be observationally inferred from comparing the morphology of the thermal emission phase curves of synchronously rotating planets
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