University of California, Davis

About: University of California, Davis is a education organization based out in Davis, California, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 78770 authors who have published 180033 publications receiving 8064158 citations. The organization is also known as: UC Davis & UCD.

Plant disease resistance genes encode members of an ancient and diverse protein family within the nucleotide‐binding superfamily

Abstract: The nucleotide binding site (NBS) is a characteristic domain of many plant resistance gene products. An increasing number of NBS-encoding sequences are being identified through gene cloning, PCR amplification with degenerate primers, and genome sequencing projects. The NBS domain was analyzed from 14 known plant resistance genes and more than 400 homologs, representing 26 genera of monocotyledonous, dicotyle-donous and one coniferous species. Two distinct groups of diverse sequences were identified, indicating divergence during evolution and an ancient origin for these sequences. One group was comprised of sequences encoding an N-terminal domain with Toll/Interleukin-1 receptor homology (TIR), including the known resistance genes, N, M, L6, RPP1 and RPP5. Surprisingly, this group was entirely absent from monocot species in searches of both random genomic sequences and large collections of ESTs. A second group contained monocot and dicot sequences, including the known resistance genes, RPS2, RPM1, I2, Mi, Dm3, Pi-B, Xa1, RPP8, RPS5 and Prf. Amino acid signatures in the conserved motifs comprising the NBS domain clearly distinguished these two groups. The Arabidopsis genome is estimated to contain approximately 200 genes that encode related NBS motifs; TIR sequences were more abundant and outnumber non-TIR sequences threefold. The Arabidopsis NBS sequences currently in the databases are located in approximately 21 genomic clusters and 14 isolated loci. NBS-encoding sequences may be more prevalent in rice. The wide distribution of these sequences in the plant kingdom and their prevalence in the Arabidopsis and rice genomes indicate that they are ancient, diverse and common in plants. Sequence inferences suggest that these genes encode a novel class of nucleotide-binding proteins.

Global threats from invasive alien species in the twenty-first century and national response capacities

Abstract: Invasive alien species (IAS) threaten human livelihoods and biodiversity globally. Increasing globalization facilitates IAS arrival, and environmental changes, including climate change, facilitate IAS establishment. Here we provide the first global, spatial analysis of the terrestrial threat from IAS in light of twenty-first century globalization and environmental change, and evaluate national capacities to prevent and manage species invasions. We find that one-sixth of the global land surface is highly vulnerable to invasion, including substantial areas in developing economies and biodiversity hotspots. The dominant invasion vectors differ between high-income countries (imports, particularly of plants and pets) and low-income countries (air travel). Uniting data on the causes of introduction and establishment can improve early-warning and eradication schemes. Most countries have limited capacity to act against invasions. In particular, we reveal a clear need for proactive invasion strategies in areas with high poverty levels, high biodiversity and low historical levels of invasion.

Mid-infrared selection of active galactic nuclei with the wide-field infrared survey explorer. i. characterizing wise-selected active galactic nuclei in cosmos

Abstract: The Wide-field Infrared Survey Explorer (WISE) is an extremely capable and efficient black hole finder. We present a simple mid-infrared color criterion, W1 – W2 ≥ 0.8 (i.e., [3.4]–[4.6] ≥0.8, Vega), which identifies 61.9 ± 5.4 active galactic nucleus (AGN) candidates per deg^2 to a depth of W2 ~ 15.0. This implies a much larger census of luminous AGNs than found by typical wide-area surveys, attributable to the fact that mid-infrared selection identifies both unobscured (type 1) and obscured (type 2) AGNs. Optical and soft X-ray surveys alone are highly biased toward only unobscured AGNs, while this simple WISE selection likely identifies even heavily obscured, Compton-thick AGNs. Using deep, public data in the COSMOS field, we explore the properties of WISE-selected AGN candidates. At the mid-infrared depth considered, 160 μJy at 4.6 μm, this simple criterion identifies 78% of Spitzer mid-infrared AGN candidates according to the criteria of Stern et al. and the reliability is 95%. We explore the demographics, multiwavelength properties and redshift distribution of WISE-selected AGN candidates in the COSMOS field.

Using the gravity equation to differentiate among alternative theories of trade

Abstract: The simple gravity equation explains a great deal about the data on bilateral trade flows and is consistent with several theoretical models of trade. We argue that alternative theories nev- ertheless predict subtle differences in key parameter values, depending on whether goods are homogeneous or differentiated and whether or not there are barriers to entry. Our empirical work for differentiated goods delivers results consistent with the theoretical predictions of the monopolistic-competition model, or a reciprocal-dumping model with free entry. Homo- geneous goods are described by a model with national (Armington) product differentiation or

Synchronous oscillations in neuronal systems: mechanisms and functions.

Abstract: How are the functions performed by one part of the nervous system integrated with those of another? This fundamental issue pervades virtually every aspect of brain function from sensory and cognitive processing to motor control. Yet from a physiological perspective we know very little about the neural mechanisms underlying the integration of distributed processes in the nervous system. Even the simplest of sensori-motor acts engages vast numbers of cells in many different parts of the brain. Such actions require coordination between a host of neural systems, each of which must carry out parallel computations involving large populations of interconnected neurons. It seems reasonable to assume that a mechanism or class of mechanisms has evolved to temporally coordinate the activity within and between subsystems of the central nervous system. For several reasons, neuronal rhythms have long been thought to play an important role in such coordination. Since the discovery of the Electroencephalogram (EEG) over 60 years ago it has been known that a number of structures in the mammalian brain engage in rhythmic activities. These patterned neuronal oscillations take many forms. They occur over a broad range of frequencies, and are present in a multitude of different systems in the b~ain, during a variety of different behavioral states. They are often the most salient aspect of observable electrical activity in the brain and typically encompass widespread regions of cerebral tissue. With the advent of new techniques of multielectrode recording and neural imaging, it is now within the realm of possibility 'to record from 100 single neurons simultaneously (Wilson and McNaughton, 1993), to optically measure the activity in a cortical area (Blasdel and Salama, 1986; T'so et al., 1990), or to noninvasively image the pattern of electric current flow in an alert human being performing a task (Pantev et al., 1991). These new techniques have revealed that spatially and temporally organized activity among distributed populations of cells often takes the form of synchronous rhythms. When combined with cellular neurophysiological and anatomical studies these findings provide new insights into the behavior and mechanisms controUing the coordination of activity in neuronal populations.