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.

Photosynthesis controls of rhizosphere respiration and organic matter decomposition

Abstract: The effects of shading wheat plants on rhizosphere respiration and rhizosphere priming of soil organic matter decomposition were investigated by using a natural abundance 13C tracer method and 14C pulse labeling simultaneously. Seven days with strongly reduced photosynthesis (12/60 h day/night period) resulted in only half of the total CO2 efflux from soil compared to the treatment with a 12/12 h day/night period. The CO2 efflux from unplanted soil amounted to only 12 and 20% of the total CO2 efflux from the soil with non-shaded and shaded plants, respectively. On average 75% of total CO2 efflux from the planted soil with prolonged night periods was root-derived. Rhizosphere respiration was tightly coupled with plant photosynthetic activity. Any factor affecting photosynthesis, or substrate supply to roots and rhizosphere microorganisms, is an important determinant of root-derived CO2 efflux, and thereby, total CO2 efflux from soils. Clear diurnal dynamics of the total CO2 efflux intensity indicate the existence of an endogenous control mechanism of rhizosphere respiration. The light-on events after prolonged dark periods lead to strong increases of root-derived and therefore of total CO2 efflux from soil. After 14C pulse labeling, two maxima of the root-derived 14CO2 efflux were measured (6 and 24 h). This result demonstrated the diurnal dynamics of the rhizosphere respiration of recently-assimilated C in both the normal light conditions and shaded plants as well. The total amount of root-derived C respired in the rhizosphere was 17.3 and 20.6% of the total assimilated C for non-shaded and shaded plants, respectively. Both methods used, 13C natural abundance and 14C pulse labeling, gave similar estimates of root-derived CO2 during the whole observation period: 1.80±0.27 and 1.67±0.37 mg C kg−1 h−1 (±SD), respectively. Both tracer methods show that the cultivation of wheat led to the increasing decomposition intensity of soil organic matter (priming effect). Additionally, 13C natural abundance allows tracing of the dynamics of the priming effect depending on the light-on events.

ENCODE data at the ENCODE portal

Abstract: The Encyclopedia of DNA Elements (ENCODE) Project is in its third phase of creating a comprehensive catalog of functional elements in the human genome. This phase of the project includes an expansion of assays that measure diverse RNA populations, identify proteins that interact with RNA and DNA, probe regions of DNA hypersensitivity, and measure levels of DNA methylation in a wide range of cell and tissue types to identify putative regulatory elements. To date, results for almost 5000 experiments have been released for use by the scientific community. These data are available for searching, visualization and download at the new ENCODE Portal (www.encodeproject.org). The revamped ENCODE Portal provides new ways to browse and search the ENCODE data based on the metadata that describe the assays as well as summaries of the assays that focus on data provenance. In addition, it is a flexible platform that allows integration of genomic data from multiple projects. The portal experience was designed to improve access to ENCODE data by relying on metadata that allow reusability and reproducibility of the experiments.

The alternating fixpoint of logic programs with negation

Abstract: We introduce and describe the alternating fixpoint of a logic program with negation. The underlying idea is to monotonically build up a set of negative conclusions until the least fixpoint is reached, using a transformation related to the one that defines stable models, developed by Gelfand and Lifschitz. From a fixed set of negative conclusions, we can derive the positive conclusions that follow (without deriving any further negative ones), by traditional Horn clause semantics. The union of positive and negative conclusions is called the alternating fixpoint partial model. The name “alternating” was chosen because the transformation runs in two passes; the first pass transforms an underestimate of the set of negative conclusions into an (intermediate) overestimate; the second pass transforms the overestimates into a new underestimate; the composition of the two passes is monotonic.Our main theorem is that the alternating fixpoint partial model is exactly the well-founded partial model.We also show that a system is fixpoint logic, which permits rule bodies to be first order formulas but requires inductive relations to be positive within them, can be transformed straightforwardly into a normal logic program whose alternating fixpoint partial model corresponds to the least fixpoint of the fixpoint logic system. Thus alternating fixpoint logic is at least as expressive as fixpoint logic. The converse is shown to hold for finite structures.

The big picture: masculinities in recent world history

Abstract: This chapter addresses the question of how we should study men in gender relations, and what view of modern world history an understanding of masculinity might give us. I start with the reasons why ‘masculinity’ has recently become a cultural and intellectual problem, and suggest a framework in which the intellectual work can be better done. The historicity of ‘masculinity’ is best shown by cross-cultural evidence on the differing gender practices of men in different social orders. The core of the chapter is a sketch of the historical evolution of the forms of masculinity now globally dominant. This shows their imbrication with the military, social, and economic history of North Atlantic capitalist states, and especially with imperialism. This history provides the necessary basis for an understanding of the major institutionalized forms of masculinity in contemporary ‘first world’ countries, and the struggles for hegemony among them. I conclude with a brief look at the dynamics of marginalized and subordinated masculinities.