University of California, Santa Cruz

About: University of California, Santa Cruz is a education organization based out in Santa Cruz, California, United States. It is known for research contribution in the topics: Galaxy & Population. The organization has 15541 authors who have published 44120 publications receiving 2759983 citations. The organization is also known as: UCSC & UC, Santa Cruz.

Transient Water Vapor at Europa’s South Pole

Abstract: In November and December 2012 the Hubble Space Telescope (HST) imaged Europa’s ultraviolet emissions in the search for vapor plume activity. We report statistically significant coincident surpluses of hydrogen Lyman-α and oxygen OI130.4 nm emissions above the southern hemisphere in December 2012. These emissions are persistently found in the same area over ~7 hours, suggesting atmospheric inhomogeneity; they are consistent with two 200-km-high plumes of water vapor with line-of-sight column densities of about 1020 m−2. Nondetection in November and in previous HST images from 1999 suggests varying plume activity that might depend on changing surface stresses based on Europa’s orbital phases. The plume was present when Europa was near apocenter and not detected close to its pericenter, in agreement with tidal modeling predictions.

Individual variation in prey selection by sea otters: patterns, causes and implications

Abstract: Summary 1. Longitudinal records of prey selection by 10 adult female sea otters on the Monterey Peninsula, California, from 1983 to 1990 demonstrate extreme inter-individual variation in diet. Variation in prey availability cannot explain these differences as the data were obtained from a common spatial-temporal area. 2. Individual dietary patterns persisted throughout our study, thus indicating that they are life-long characteristics. 3. Individual dietary patterns in sea otters appear to be transmitted along matrilines, probably by way of learning during the period of mother‐young association. 4. Efficient utilization of different prey types probably requires radically different sensory/motor skills, each of which is difficult to acquire and all of which may exceed the learning and performance capacities of any single individual. This would explain the absence of generalists and inertia against switching, but not the existence of alternative specialists. 5. Such individual variation might arise in a constant environment from frequencydependent effects, whereby the relative benefit of a given prey specialization depends on the number of other individuals utilizing that prey. Additionally, many of the sea otter’s prey fluctuate substantially in abundance through time. This temporal variation, in conjunction with matrilineal transmission of foraging skills, may act to mediate the temporal dynamics of prey specializations. 6. Regardless of the exact cause, such extreme individual variation in diet has broad ramifications for population and community ecology. 7. The published literature indicates that similar patterns occur in many other species.

Changes in Soil Chemical Properties Resulting from Organic and Low-Input Farming Practices

Abstract: levels in the organic system indicate that animal manures did not increase salinity. Overall, our findings indicate that organic and lowSoil chemical properties during the transition from conventional input farming in the Sacramento Valley result in small but important to organic and low-input farming practices were studied over 8 yr in increases in soil organic C and larger pools of stored nutrients, which California’s Sacramento Valley to document changes in soil fertility are critical for long-term fertility maintenance. status and nutrient storage. Four farming systems differing in crop rotation and external inputs were established on land previously managed conventionally. Fertility in the organic system depended on animal manure applications and winter cover crops; the two conventional

The Rest-Frame Ultraviolet Luminosity Density of Star-forming Galaxies at Redshifts z > 3.5

Abstract: We have measured the rest-frame λ ~ 1500 A comoving specific luminosity density of star-forming galaxies at redshift 3.5 < z < 6.5 (Lyman break galaxies [LBGs]) selected from deep, multiband images taken with the Hubble Space Telescope and the Advanced Camera for Surveys, obtained as part of the Great Observatories Origins Deep Survey (GOODS). The samples cover ~0.09 deg2 and are also relatively deep, reaching between 0.2L and 0.5L, depending on the redshift, where L is the characteristic UV luminosity of LBGs at z ~ 3. The specific luminosity density appears to be nearly constant with redshift over the range 3 < z < 6, although the measure at z ~ 6 remains relatively uncertain, because it depends on the accurate estimate of the faint counts of the z ~ 6 sample. If LBGs are fair tracers of the cosmic star formation activity, our results suggest that at z ~ 6, namely, at less than ~7% of the current cosmic age, the universe was already producing stars as vigorously as it did near its maximum several gigayears later, at 1 z 3.

A computationally efficient superresolution image reconstruction algorithm

Abstract: Superresolution reconstruction produces a high-resolution image from a set of low-resolution images. Previous iterative methods for superresolution had not adequately addressed the computational and numerical issues for this ill-conditioned and typically underdetermined large scale problem. We propose efficient block circulant preconditioners for solving the Tikhonov-regularized superresolution problem by the conjugate gradient method. We also extend to underdetermined systems the derivation of the generalized cross-validation method for automatic calculation of regularization parameters. The effectiveness of our preconditioners and regularization techniques is demonstrated with superresolution results for a simulated sequence and a forward looking infrared (FLIR) camera image sequence.