ALBERT

Description: The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed an occultation of the Sun by the water vapor plume at the south polar region of Saturn's moon Enceladus. The Extreme Ultraviolet (EUV) spectrum is dominated by the spectral signature of H2O gas, with a nominal line-of-sight column density of 0.90 ± 0.23 × 1016 cm−2 (upper limit of 1.0 × 1016 cm−2). The upper limit for N2 is 5 × 1013 cm−2, or

Description: We present a programmable droplet-based microfluidic device that combines the reconfigurable flow-routing capabilities of integrated microvalve technology with the sample compartmentalization and dispersion-free transport that is inherent to droplets. The device allows for the execution of user-defined multistep reaction protocols in 95 individually addressable nanoliter-volume storage chambers by consecutively merging programmable sequences of picoliter-volume droplets containing reagents or cells. This functionality is enabled by “flow-controlled wetting,” a droplet docking and merging mechanism that exploits the physics of droplet flow through a channel to control the precise location of droplet wetting. The device also allows for automated cross-contamination-free recovery of reaction products from individual chambers into standard microfuge tubes for downstream analysis. The combined features of programmability, addressability, and selective recovery provide a general hardware platform that can be reprogrammed for multiple applications. We demonstrate this versatility by implementing multiple single-cell experiment types with this device: bacterial cell sorting and cultivation, taxonomic gene identification, and high-throughput single-cell whole genome amplification and sequencing using common laboratory strains. Finally, we apply the device to genome analysis of single cells and microbial consortia from diverse environmental samples including a marine enrichment culture, deep-sea sediments, and the human oral cavity. The resulting datasets capture genotypic properties of individual cells and illuminate known and potentially unique partnerships between microbial community members.

Description: Sublimation at the ice-substrate interface with pressure build-up is an accepted mechanism for the production of fan deposits on the southern polar CO2 ice cap on Mars. Fluid dynamics modeling has been used to investigate gas outflow through vents in a CO2 slab ice. Small (5–25 m in length) fan deposits seen on the annual southern CO2 ice cap can be produced by a steady-state in which open vents continuously outgas in response to sub-surface sublimation generated by diurnal energy input through translucent impermeable (to gas) ice slabs. This would produce diurnally-controlled deposits which would change orientation with time in response to winds thereby explaining observations made by HiRISE on MRO. Gas flow below the ice can reach up to 25 m/s close to the vent. Dust flow in the sub-ice cavity has also been computed but velocities are much lower with the main acceleration occurring

Description: The mechanisms underlying the acquisition of speech-production ability in human infancy are not well understood. We tracked 4–12-mo-old English-learning infants’ and adults’ eye gaze while they watched and listened to a female reciting a monologue either in their native (English) or nonnative (Spanish) language. We found that infants shifted their attention from the eyes to the mouth between 4 and 8 mo of age regardless of language and then began a shift back to the eyes at 12 mo in response to native but not nonnative speech. We posit that the first shift enables infants to gain access to redundant audiovisual speech cues that enable them to learn their native speech forms and that the second shift reflects growing native-language expertise that frees them to shift attention to the eyes to gain access to social cues. On this account, 12-mo-old infants do not shift attention to the eyes when exposed to nonnative speech because increasing native-language expertise and perceptual narrowing make it more difficult to process nonnative speech and require them to continue to access redundant audiovisual cues. Overall, the current findings demonstrate that the development of speech production capacity relies on changes in selective audiovisual attention and that this depends critically on early experience.

Description: In this paper, we use morphological and numerical methods to test the hypothesis that seasonally formed fracture patterns in the Martian polar regions result from the brittle failure of seasonal CO2 slab ice. The observations by the High Resolution Imaging Science Experiment (HiRISE) of polar regions of Mars show very narrow dark elongated linear patterns that are observed during some periods of time in spring, disappear in summer and re-appear again in the following spring. They are repeatedly formed in the same areas but they do not repeat the exact pattern from year to year. This leads to the conclusion that they are cracks formed in the seasonal ice layer. Some of models of seasonal surface processes rely on the existence of a transparent form of CO2 ice, so-called slab ice. For the creation of the observed cracks the ice is required to be a continuous media, not an agglomeration of relatively separate particles like a firn. The best explanation for our observations is a slab ice with relatively high transparency in the visible wavelength range. This transparency allows a solid state green-house effect to act underneath the ice sheet raising the pressure by sublimation from below. The trapped gas creates overpressure and the ice sheet breaks at some point creating the observed cracks. We show that the times when the cracks appear are in agreement with the model calculation, providing one more piece of evidence that CO2 slab ice covers polar areas in spring.

Description: We use data from the High Resolution Imaging Science Experiment (HiRISE) camera and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) imaging spectrometer onboard the Mars Reconnaissance Orbiter to follow the evolution of the appearance and composition of 12 regions of the south polar layered deposits from spring to summer time. We distinguish three steps in the evolution of the volatile layer: a decrease of both CO2 band strength and albedo until Ls = 190°–210°, a significant increase in both until Ls = 240°–260° and finally a rapid decrease until the complete defrosting of the ground. In contrast, the water ice band displays a more monotonic decrease. Analysis of HiRISE color images acquired simultaneously with CRISM data allows a plausible interpretation of this evolution. In early springtime (Ls 〈 200°), intense jet activity results in deposition of fans of large mineral grains and a wide spatial distribution of fine grains. The small-scale topography controls the presence and location of the jets by allowing more solar energy to be collected on slopes. Grains from the dust fans warm and sink through the CO2 layer, resulting in a bluish color at the locations of the fans around Ls = 190°–210°. As the atmosphere warms up, the surface of the ice layer sublimes and releases dust and water, resulting in its brightening. The last phase of the process consists in a progressive defrosting resulting in a patchwork of frozen and unfrozen areas.

Description: Ecological Applications, Volume 24, Issue 3, Page 484-502, April 2014. Many protected areas may not be adequately safeguarding biodiversity from human activities on surrounding lands and global change. The magnitude of such change agents and the sensitivity of ecosystems to these agents vary among protected areas. Thus, there is a need to assess vulnerability across networks of protected areas to determine those most at risk and to lay the basis for developing effective adaptation strategies. We conducted an assessment of exposure of U.S. National Parks to climate and land use change and consequences for vegetation communities. We first defined park protected-area centered ecosystems (PACEs) based on ecological principles. We then drew on existing land use, invasive species, climate, and biome data sets and models to quantify exposure of PACEs from 1900 through 2100. Most PACEs experienced substantial change over the 20th century (〉740% average increase in housing density since 1940, 13% of vascular plants are presently nonnative, temperature increase of 1°C/100 yr since 1895 in 80% of PACEs), and projections suggest that many of these trends will continue at similar or increasingly greater rates (255% increase in housing density by 2100, temperature increase of 2.5°–4.5°C/100 yr, 30% of PACE areas may lose their current biomes by 2030). In the coming century, housing densities are projected to increase in PACEs at about 82% of the rate of since 1940. The rate of climate warming in the coming century is projected to be 2.5–5.8 times higher than that measured in the past century. Underlying these averages, exposure of individual park PACEs to change agents differ in important ways. For example, parks such as Great Smoky Mountains exhibit high land use and low climate exposure, others such as Great Sand Dunes exhibit low land use and high climate exposure, and a few such as Point Reyes exhibit high exposure on both axes. The cumulative and synergistic effects of such changes in land use, invasives, and climate are expected to dramatically impact ecosystem function and biodiversity in national parks. These results are foundational to developing effective adaptation strategies and suggest policies to better safeguard parks under broad-scale environmental change.

Description: New Zealand’s geographic isolation, lack of native terrestrial mammals, and Gondwanan origins make it an ideal location to study evolutionary processes. However, since the archipelago was first settled by humans 750 y ago, its unique biodiversity has been under pressure, and today an estimated 49% of the terrestrial avifauna is...

Description: Human parvovirus B19 (B19V) is a ubiquitous human pathogen associated with a number of conditions, such as fifth disease in children and arthritis and arthralgias in adults. B19V is thought to evolve exceptionally rapidly among DNA viruses, with substitution rates previously estimated to be closer to those typical of RNA...

Description: Ecological Applications, Volume 0, Issue 0, Ahead of Print. Many protected areas may not be adequately safeguarding biodiversity from human activities on surrounding lands and global change. The magnitude of such change agents and the sensitivity of ecosystems to these agents vary among protected areas. Thus, there is a need to assess vulnerability across networks of protected areas to determine those most at risk and to lay the basis for developing effective adaptation strategies. We conducted an assessment of exposure of U.S. National Parks to climate and land use change and consequences for vegetation communities. We first defined park protected-area centered ecosystems (PACEs) based on ecological principles. We then drew on existing land use, invasive species, climate, and biome data sets and models to quantify exposure of PACEs from 1900 through 2100. Most PACEs experienced substantial change over the 20th century (〉740% average increase in housing density since 1940, 13% of vascular plants are presently non-native, +1 0C / 100 years since 1895 in 80% of PACEs), and projections suggest that many of these trends will continue at similar or increasingly greater rates (255% increase in housing density by 2100, +2.5-4.5 0C/ 100 years, 30% of PACE areas may lose their current biomes by 2030). In the coming century, housing densities are projected to increase in PACEs at about 82% of the rate of since 1940. The rate of climate warming in the coming century is projected to be 2.5 - 5.8 times higher than that measured in the past century. Underlying these averages, exposure of individual-park PACEs to change agents differ in important ways. For example, parks such as Great Smoky Mountains exhibit high land use and low climate exposure, others such as Great Sand Dunes exhibit low land use and high climate exposure, and a few such as Point Reyes exhibit high exposure on both axes. The cumulative and synergistic effects of such changes in land use, invasives, and climate are expected to dramatically impact ecosystem function and biodiversity in national parks. These results are foundational to developing effective adaptation strategies and suggest policies to better safeguard parks under broad-scale environmental change.