University of California

About: University of California is a education organization based out in Oakland, California, United States. It is known for research contribution in the topics: Population & Layer (electronics). The organization has 55175 authors who have published 52933 publications receiving 1491169 citations. The organization is also known as: UC & University of California System.

Fungal Molecular Evolution: Gene Trees and Geologic Time

Abstract: Fungal phylogenetics has always been based on characters, but technological and intellectual advances are introducing new kinds of characters and new ways of thinking about them. First light microscopy, then electron microscopy, and now DNA sequencing successively upset previous views of fungal relationships. Phenetics, cladistics, and computerized data analysis and phylogenetic tree generation are now changing the intellectual rules for taxonomy and phylogenetics. The combination of new characters and new analytical tools have supported some taxonomic groups, established some new ones, and demolished a few old ones.

The role of predation in the decline and extirpation of woodland caribou

Abstract: To select appropriate recovery strategies for endangered populations, we must understand the dynamics of small populations and distinguish between the possible causes that drive such populations to low numbers. It has been suggested that the pattern of population decline may be inversely density-dependent with population growth rates decreasing as populations become very small; however, empirical evidence of such accelerated declines at low densities is rare. Here we analyzed the pattern of decline of a threatened population of woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada. Using information on the instantaneous rate of increase relative to caribou density in suitable winter foraging habitat, as well as on pregnancy rates and on causes and temporal distribution of mortalities from a sample of 349 radiocollared animals from 15 subpopulations, we tested 3 hypothesized causes of decline: (a) food regulation caused by loss of suitable winter foraging habitat, (b) predation-sensitive foraging caused by loss of suitable winter foraging habitat and (c) predation with caribou being secondary prey. Population sizes of caribou subpopulations ranged from 500 individuals. Our results showed that the rates of increase of these subpopulations varied from −0.1871 to 0.0496 with smaller subpopulations declining faster than larger subpopulations. Rates of increase were positively related to the density of caribou in suitable winter foraging habitat. Pregnancy rates averaged 92.4% ±2.24 and did not differ among subpopulations. In addition, we found predation to be the primary cause of mortality in 11 of 13 subpopulations with known causes of mortality and predation predominantly occurred during summer. These results are consistent with predictions that caribou subpopulations are declining as a consequence of increased predation. Recovery of these woodland caribou will thus require a multispecies perspective and an appreciation for the influence of inverse density dependence on population trajectories.

Laplacian Pyramid Reconstruction and Refinement for Semantic Segmentation

Abstract: CNN architectures have terrific recognition performance but rely on spatial pooling which makes it difficult to adapt them to tasks that require dense, pixel-accurate labeling. This paper makes two contributions: (1) We demonstrate that while the apparent spatial resolution of convolutional feature maps is low, the high-dimensional feature representation contains significant sub-pixel localization information. (2) We describe a multi-resolution reconstruction architecture based on a Laplacian pyramid that uses skip connections from higher resolution feature maps and multiplicative gating to successively refine segment boundaries reconstructed from lower-resolution maps. This approach yields state-of-the-art semantic segmentation results on the PASCAL VOC and Cityscapes segmentation benchmarks without resorting to more complex random-field inference or instance detection driven architectures.

The number field sieve

Abstract: The number field sieve is an algorithm to factor integers of the form re − s for small positive r and |s|. The algorithm depends on arithmetic in an algebraic number field. We describe the algorithm, discuss several aspects of its implementation, and present some of the factorizations obtained. A heuristic run time analysis indicates that the number field sieve is asymptotically substantially faster than any other known factoring method, for the integers that it applies to. The number field sieve can be modified to handle arbitrary integers. This variant is slower, but asymptotically it is still expected to beat all older factoring methods.

Bounded scheduling of process networks

Abstract: We present a scheduling policy for complete, bounded execution of Kahn process network programs. A program is a set of processes that communicate through a network of first-in first-out queues. In a complete execution, the program terminates if and only if all processes block attempting to consume data from empty communication channels. We are primarily interested in programs that operate on infinite streams of data and never terminate. In a bounded execution, the number of data elements buffered in each of the communication channels remains bounded. The Kahn process network model of computation is powerful enough that the questions of termination and bounded buffering are undecidable. No finite-time algorithm can decide these questions for all Kahn process network programs. Fortunately, because we are interested in programs that never terminate, our scheduler has infinite time and can guarantee that programs execute forever with bounded buffering whenever possible. Our scheduling policy has been implemented using Ptolemy, an object-oriented simulation and prototyping environment.