Bacterial abundance, DOC concentrations, and bacterioplankton community structure (using PCR-based techniques) were measured in 5 seawater culture experiments conducted near the Bermuda Atlantic Time-series Study (BATS) site in the northwestern Sargasso Sea. Cultures were amended with inorganic and organic nutrients, alone or in combination, to test the existence of the 'malfunctioning microbial loop' during late spring and summer at BATS. Objectives of the study were to determine whether (1) alleviating grazing pressure and inorganic nutrient limitation stimulated DOC remineralization by bacterioplankton; (2) a combination of organic and inorganic nutrients affect bacterial production and utilization of seasonally accumulated DOC; and (3) shifts in bacterioplankton community structure are associated with nutrient amendment and DOC utilization. In unamended cultures natural assemblages of surface bacterioplankton did not utilize detectable amounts of naturally occurring 'semi-labile' DOC over time-scales of days to weeks. Neither bacterial production nor utilization of DOC was enhanced with the addition of inorganic N or P (alone or in combination). Labile DOC amendments stimulated bacterial production and DOC utilization, even in the absence of measurable inorganic nutrients, indicating that the bacterioplankton assemblage was initially energy limited, but did not stimulate utilization of seasonally accumulated DOC. The combination of inorganic N and P with labile DOC enhanced both bacterial production and utilization of 'semi-labile' DOC. Changes in bacterioplankton community rDNA gene profiles were minor in the control and inorganic treatments; however, utilization of 'semi-labile' DOC in the organic plus inorganic nutrient treatments coincided with significant changes in bacterioplankton community structure. These data suggest that bacterioplankton community structure, as well as nutrient regime, may be important factors governing the utilization of recalcitrant DOC substrates in the northwestern Sargasso Sea. KEY WORDS: Dissolved organic carbon · Nutrient limitation · 16S rRNA · BATSResale or republication not permitted without written consent of the publisher Aquat Microb Ecol 30: 19-36, 2002 Hodson 1977, Azam et al. 1983). Net DOC production within the euphotic zone has been documented for a variety of oceanic sites (Duursma 1963, Parsons et al. 1970, Eberlein et al. 1985, Copin-Montégut & Avril 1993, Carlson et al. 1994, Børsheim & Myklestad 1997, Hansell & Carlson, 1998b, Hansell & Carlson 2001. The subsequent vertical mixing of a portion of the accumulated DOC out of the surface waters can be a significant carbon export term in certain oceanic systems (Copin-Montégut & Avril 1993, Carlson et al. 1994, Hansell & Carlson 1998a, Hansell & Carlson 2001. However, for DOC to play a role in carbon export, the temporal scale of the DOC turnover has to be greater than the timescale of physical mixing processes (Thingstad 1993, Carlson et al. 1998, Hansell & Carlson 2002. Thus, factors that prevent ...

Diverse animals use Earth's magnetic field in orientation and navigation, but little is known about the molecular mechanisms that underlie magnetoreception. Recent studies have focused on two possibilities: (i) magnetite-based receptors; and (ii) biochemical reactions involving radical pairs. We used RNA sequencing to examine gene expression in the brain of rainbow trout () after exposure to a magnetic pulse known to disrupt magnetic orientation behaviour. We identified 181 differentially expressed genes, including increased expression of six copies of the gene, which encodes a subunit of the universal iron-binding and trafficking protein ferritin. Functions linked to the oxidative effects of free iron (e.g. oxidoreductase activity, transition metal ion binding, mitochondrial oxidative phosphorylation) were also affected. These results are consistent with the hypothesis that a magnetic pulse alters or damages magnetite-based receptors and/or other iron-containing structures, which are subsequently repaired or replaced through processes involving ferritin. Additionally, some genes that function in the development and repair of photoreceptive structures (e.g., ,, , and ) were also differentially expressed, raising the possibility that a magnetic pulse might affect structures and processes unrelated to magnetite-based magnetoreceptors.

No abstract

At IBM's 300 mm semiconductor plant in East Fishkill, New York, we developed and implemented the Enterprise Production Planning and Optimization System (EPOS), an advanced queueing network model for capacity planning. EPOS extends earlier queueing network models by adding the ability to model product-specific batch service and batch arrivals and multichamber process equipment, and by embedding a linear program for allocating lots to the right queues when route choices are present. EPOS addresses both short-term tactical capacity planning and long-term strategic capital investment planning. It has become an integral part of predicting factory bottlenecks, prioritizing continuous-improvement efforts, planning capital equipment investments, and managing factory lead times. EPOS results have guided IBM's efforts to improve factory performance and reduce tens of millions of dollars of expense.

No abstract