187 research outputs found
Available energy of the world ocean
The available energy of the ocean is the excess of the sum of the ocean\u27s internal and gravitational energies with respect to its equilibrium state, which is in thermodynamic equilibrium and has the same total entropy as the ocean. The equilibrium state for the world ocean is rigorously determined to be an isothermal ocean with a temperature of 3.66ËC and a horizontally uniform absolute salinity that increases monotonically from 27.30 g kgâ1 at the surface to 47.39 g kgâ1 at a depth of 5.5 km. This salinity profile is consistent with a uniform relative chemical potential of 47.44 J gâ1 salt. The ocean\u27s available energy is 220 Ă 1021 J or 630 MJ mâ2. Most (72%) of the available energy is due to the internal energy difference between the ocean and its equilibrium state; the remaining 28% is due to the gravitational energy difference. The ocean\u27s available energy is shown to be concentrated vertically in the upper half kilometer and geographically in the tropics and subtropics. This distribution is accurately represented by the temperature variance from the equilibrium temperature. The contributions of sea ice and variable sea surface height to the available energy are estimated to be small
Assessing phytoplankton nutritional status and potential impact of wet deposition in seasonally oligotrophic waters of the MidâAtlantic Bight
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 45 (2018): 3203-3211, doi:10.1002/2017GL075361.To assess phytoplankton nutritional status in seasonally oligotrophic waters of the southern MidâAtlantic Bight, and the potential for rain to stimulate primary production in this region during summer, shipboard bioassay experiments were performed using natural seawater and phytoplankton collected north and south of the Gulf Stream. Bioassay treatments comprised iron, nitrate, iron + nitrate, iron + nitrate + phosphate, and rainwater. Phytoplankton growth was inferred from changes in chlorophyll a, inorganic nitrogen, and carbonâ13 uptake, relative to unamended control treatments. Results indicated the greatest growth stimulation by iron + nitrate + phosphate, intermediate growth stimulation by rainwater, modest growth stimulation by nitrate and iron + nitrate, and no growth stimulation by iron. Based on these data and analysis of seawater and atmospheric samples, nitrogen was the proximate limiting nutrient, with a secondary limitation imposed by phosphorus. Our results imply that summer rain events increase new production in these waters by contributing nitrogen and phosphorus, with the availability of the latter setting the upper limit on rainâstimulated new production.US National Science Foundation Grant Numbers: OCEâ1260454, OCEâ1260454, OCEâ12605742018-09-1
Net community production in the North Atlantic Ocean derived from Volunteer Observing Ship data
The magnitude of marine plankton net community production (NCP) is indicative of both the biologically driven exchange of carbon dioxide between the atmosphere and the surface ocean and the export of organic carbon from the surface ocean to the ocean interior. In this study the seasonal variability in the NCP of five biogeochemical regions in the North Atlantic was determined from measurements of surface water dissolved oxygen and dissolved inorganic carbon (DIC) sampled from a Volunteer Observing Ship (VOS). The magnitude of NCP derived from dissolved oxygen measurements (NCPinline image) was consistent with previous geochemical estimates of NCP in the North Atlantic, with an average annual NCPinline image of 9.5 ± 6.5 mmol O2 mâ2 dâ1. Annual NCPinline image did not vary significantly over 35° of latitude and was not significantly different from NCP derived from DIC measurements (NCPDIC). The relatively simple method described here is applicable to any VOS route on which surface water dissolved oxygen concentrations can be accurately measured, thus providing estimates of NCP at higher spatial and temporal resolution than currently achieved
Reductive dimerization mechanisms of some streptocyanine dyes
Cyclic voltammetric studies of streptocyanine dyes were carried out on a glassy carbon electrode. For dye electroreduction, logarithmic analysis of the convoluted current indicates an EC2 mechanism with dimerization following electron transfer. Relevant kinetic and thermodynamic values are reported
Predicting Crop Yield With Machine Learning: An Extensive Analysis Of Input Modalities And Models On a Field and sub-field Level
We introduce a simple yet effective early fusion method for crop yield
prediction that handles multiple input modalities with different temporal and
spatial resolutions. We use high-resolution crop yield maps as ground truth
data to train crop and machine learning model agnostic methods at the sub-field
level. We use Sentinel-2 satellite imagery as the primary modality for input
data with other complementary modalities, including weather, soil, and DEM
data. The proposed method uses input modalities available with global coverage,
making the framework globally scalable. We explicitly highlight the importance
of input modalities for crop yield prediction and emphasize that the
best-performing combination of input modalities depends on region, crop, and
chosen model.Comment: 4 pages, 1 figure, 3 tables, IEEE IGARSS 202
Structure Guided Design of Potent and Selective Ponatinib-Based Hybrid Inhibitors for RIPK1
SummaryRIPK1 and RIPK3, two closely related RIPK family members, have emerged as important regulators of pathologic cell death and inflammation. In the current work, we report that the Bcr-Abl inhibitor and anti-leukemia agent ponatinib is also a first-in-class dual inhibitor of RIPK1 and RIPK3. Ponatinib potently inhibited multiple paradigms of RIPK1- and RIPK3-dependent cell death and inflammatory tumor necrosis factor alpha (TNF-α) gene transcription. We further describe design strategies that utilize the ponatinib scaffold to develop two classes of inhibitors (CS and PN series), each with greatly improved selectivity for RIPK1. In particular, we detail the development of PN10, a highly potent and selective âhybridâ RIPK1 inhibitor, capturing the best properties of two different allosteric RIPK1 inhibitors, ponatinib and necrostatin-1. Finally, we show that RIPK1 inhibitors from both classes are powerful blockers of TNF-induced injury in vivo. Altogether, these findings outline promising candidate molecules and design approaches for targeting RIPK1- and RIPK3-driven inflammatory pathologies
Anti-Insulin Receptor Autoantibodies Are Not Required for Type 2 Diabetes Pathogenesis in NZL/Lt Mice, a New Zealand Obese (NZO)-Derived Mouse Strain
The New Zealand obese (NZO) mouse strain shares with
the related New Zealand black (NZB) strain a number of
immunophenotypic traits. Among these is a high proportion
of B-1 B lymphocytes, a subset associated with autoantibody
production. Approximately 50% of NZO/HlLt
males develop a chronic insulin-resistant type 2 diabetes
syndrome associated with 2 unusual features: the presence
of B lymphocyteâenriched peri-insular infiltrates and
the development of anti-insulin receptor autoantibodies
(AIRAs). To establish the potential pathogenic contributions
ofBlymphocytes and AIRAs in this model, a disrupted immunoglobulin heavy chain gene (Igh-6) congenic on the
NZB/BlJ background was backcrossed 4 generations into
the NZO/HlLt background and was then intercrossed to
produce mice that initially segregated for wild-type versus
the mutant Igh-6 allele and thus permitted comparison
of syndrome development. A new flow cytometric assay
(AIRA binding to transfected Chinese hamster ovary
cells stably expressing mouse insulin receptor) showed IgM
and IgG subclass AIRAs in serum from Igh-6 intact males,
but not in Igh6null male serum. However, the absence of
B lymphocytes and antibodies distinguishing mutant from
wild-type males failed to significantly affect diabetes-free
survival. The Igh6nullmales gained weight less rapidly than
wild-type males, probably accounting for a retardation, but
not prevention, of hyperglycemia. Thus, AIRA and the Blymphocyte
component of the peri-insulitis in chronic diabetics
were not essential either to development of insulin
resistance or to eventual pancreatic beta cell failure and
loss. A new substrain, designated NZL, was generated by
inbreeding Igh-6 wild-type segregants. Currently at the F10
generation, NZL mice exhibit the same juvenile-onset obesity
as NZO/HlLt males, but develop type 2 diabetes at a
higher frequency (> 80%). Also, unlike NZO/HlLt mice that
are difficult to breed, the NZL/Lt strain breeds well and thus
offers clear advantages to obesity/diabetes researchers
Intracellular nitrate storage by diatoms can be an important nitrogen pool in freshwater and marine ecosystems
Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in aquatic ecosystems. The ubiquitous diatoms represent an overlooked nitrate pool as they can accumulate nitrate intracellularly and utilize it for nitrogen assimilation, dissipation of excess photosynthetic energy, and Dissimilatory Nitrate Reduction to Ammonium (DNRA). Here, we document the global co-occurrence of diatoms and intracellular nitrate in phototrophic microbial communities in freshwater (n = 69), coastal (n = 44), and open marine (n = 4) habitats. Diatom abundance and total intracellular nitrate contents in water columns, sediments, microbial mats, and epilithic biofilms were highly significantly correlated. In contrast, diatom community composition had only a marginal influence on total intracellular nitrate contents. Nitrate concentrations inside diatom cells exceeded ambient nitrate concentrations âŒ100â4000-fold. The collective intracellular nitrate pool of the diatom community accounted for <1% of total nitrate in pelagic habitats and 65â95% in benthic habitats. Accordingly, nitrate-storing diatoms are emerging as significant contributors to benthic nitrogen cycling, in particular through Dissimilatory Nitrate Reduction to Ammonium activity under anoxic conditions
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