San Francisco State University

About: San Francisco State University is a education organization based out in San Francisco, California, United States. It is known for research contribution in the topics: Population & Planet. The organization has 5669 authors who have published 11433 publications receiving 408075 citations. The organization is also known as: San Francisco State & San Francisco State Normal School.

Biomass and primary productivity of the cyanobacterium Trichodesmium spp. in the tropical N Atlantic ocean

Abstract: Primary production and standing crop, as chlorophyll- a (chl- a ), of Trichodesmium spp., and other phytoplankton as well as the abundance and depth distribution of Trichodesmium were measured on three cruises to the tropical North Atlantic Ocean. Trichodesmium abundance was greatest on a cruise in May–June 1994, with average surface densities of 2250 trichomes l −1 and depth integrated abundance of 91×10 6 trichomes m −2 . Average surface densities were 292 and 222 trichomes l −1 and depth integrated abundance 21 and 8.6×10 6 trichomes m −2 for the April 1996 and October 1996 cruises, respectively. Total (phytoplankton plus Trichodesmium ) chl- a standing crop and the percentage as Trichodesmium averaged 47 (62%), 22 (13%) and 30 (11%) mg chl- a m −2 for May–June 1994 and April and October 1996. On the May–June 1994 and April and October 1996 cruises 89%, 93% and 92% of the trichomes were in colonies, and the remainder occurred as free trichomes. Peak abundances of Trichodesmium were generally in the upper water column, with an average biomass maximum at 12 m on the May–June 94 and October 96 cruises and at 40 m during the April 96 cruise. The average C:N ratio (atomic) of Trichodesmium was 6.5. Mean rates of total primary production ( Trichodesmium and other phytoplankton together) for May–June 1994, and April and October 1996 were 1080, 932 and 804 mg C m −2 d −1 , and Trichodesmium accounted for an average of 47%, 7.9% and 11%, respectively, of the total primary production for each cruise. These primary production rates exceed those typically reported at oligotrophic open ocean sites. Trichodesmium C assimilation numbers (mg C fixed mg chl- a −1 h −1 ) were highest at the surface and were always lower than those of other phytoplankton. Average nitrogen demand, as calculated from the mean Trichodesmium C fixation from all three cruises, was about 40 mg N m −2 d −1 , about 10% of concurrently determined rates of N 2 fixation.

Device-Free Wireless Localization and Activity Recognition: A Deep Learning Approach

Abstract: Device-free wireless localization and activity recognition (DFLAR) is a new technique, which could estimate the location and activity of a target by analyzing its shadowing effect on surrounding wireless links. This technique neither requires the target to be equipped with any device nor involves privacy concerns, which makes it an attractive and promising technique for many emerging smart applications. The key question of DFLAR is how to characterize the influence of the target on wireless signals. Existing work generally utilizes statistical features extracted from wireless signals, such as mean and variance in the time domain and energy as well as entropy in the frequency domain, to characterize the influence of the target. However, a feature suitable for distinguishing some activities or gestures may perform poorly when it is used to recognize other activities or gestures. Therefore, one has to manually design handcraft features for a specific application. Inspired by its excellent performance in extracting universal and discriminative features, in this paper, we propose a deep learning approach for realizing DFLAR. Specifically, we design a sparse autoencoder network to automatically learn discriminative features from the wireless signals and merge the learned features into a softmax-regression-based machine learning framework to realize location, activity, and gesture recognition simultaneously. Extensive experiments performed in a clutter indoor laboratory and an apartment with eight wireless nodes demonstrate that the DFLAR system using the learned features could achieve 0.85 or higher accuracy, which is better than the systems utilizing traditional handcraft features.

Annual cycle and interannual variability of ecosystem metabolism in a temperate climate embayment

Abstract: We have studied the net and gross metabolism of Tomales Bay, a temperate climate estuary in northern California. Tomales Bay has proved to be heterotrophic, implying that the bay oxidizes a subsidy of organic carbon from outside the system, in excess of inorganic nutrients supplied to it from outside and in addition to material cycling within it. Net organic oxidation releases dissolved inorganic nutrients, and the system exports these dissolved inorganic products. Dissolved inorganic phosphorus is exported to the ocean via mixing and constitutes the most direct record of net ecosystem production (NEP). Excess dissolved inorganic nitrogen is lost to denitrification. Excess dissolved inorganic carbon largely results in alkalinity elevation and hydrographic export of alkalinity due to sulfate reduction. The negative NEP of this system results in little release of CO2 to the atmosphere, because of this alkalinity elevation. A major purpose of the study was to ascertain the relative importance of various sour...

Protein expression and genetic structure of the coral Porites lobata in an environmentally extreme Samoan back reef: does host genotype limit phenotypic plasticity?

Abstract: The degree to which coral reef ecosystems will be impacted by global climate change depends on regional and local differences in corals' susceptibility and resilience to environmental stressors. Here, we present data from a reciprocal transplant experiment using the common reef building coral Porites lobata between a highly fluctuating back reef environment that reaches stressful daily extremes, and a more stable, neighbouring forereef. Protein biomarker analyses assessing physiological contributions to stress resistance showed evidence for both fixed and environmental influence on biomarker response. Fixed influences were strongest for ubiquitin-conjugated proteins with consistently higher levels found in back reef source colonies both pre and post-transplant when compared with their forereef conspecifics. Additionally, genetic comparisons of back reef and forereef populations revealed significant population structure of both the nuclear ribosomal and mitochondrial genomes of the coral host (F(ST) = 0.146 P < 0.0001, F(ST) = 0.335 P < 0.0001 for rDNA and mtDNA, respectively), whereas algal endosymbiont populations were genetically indistinguishable between the two sites. We propose that the genotype of the coral host may drive limitations to the physiological responses of these corals when faced with new environmental conditions. This result is important in understanding genotypic and environmental interactions in the coral algal symbiosis and how corals may respond to future environmental changes.

Seasonally Hypersaline Estuaries in Mediterranean-climate Regions

Abstract: Data collected in three Californian estuaries indicate that hypersaline conditions exist during the dry summers typical of a Mediterranean climate. The generalised seasonal and longitudinal hydrographic structures are described and explained. It is argued that this seasonal hypersalinity is common and that it represents a major class of estuaries. The observed accumulation of salt indicates surprisingly long residence times in small basins which have free exchange with the ocean. This semi-isolation of the inner basin leads to a large build-up or severe depletion of nutrients, pollutants and plankton in these systems. Of concern are the trends to increase pollutant loading in the same systems that are experiencing an increase in residence times owing to freshwater extraction in the watershed.