869 research outputs found
Mechanism, reactivity, and selectivity of nickel-catalyzed [4 + 4 + 2] cycloadditions of dienes and alkynes.
Density functional theory (DFT) calculations with B3LYP and M06 functionals elucidated the reactivities of alkynes and Z/E selectivity of cyclodecatriene products in the Ni-catalyzed [4 + 4 + 2] cycloadditions of dienes and alkynes. The Ni-mediated oxidative cyclization of butadienes determines the Z/E selectivity. Only the oxidative cyclization of one s-cis to one s-trans butadiene is facile and exergonic, leading to the observed 1Z,4Z,8E-cyclodecatriene product. The same step with two s-cis or s-trans butadienes is either kinetically or thermodynamically unfavorable, and the 1Z,4E,8E- and 1Z,4Z,8Z-cyclodecatriene isomers are not observed in experiments. In addition, the competition between the desired cooligomerization and [2 + 2 + 2] cycloadditions of alkynes depends on the coordination of alkynes. With either electron-deficient alkynes or alkynes with free hydroxyl groups, the coordination of alkynes is stronger than that of dienes, and alkyne trimerization prevails. With alkyl-substituted alkynes, the generation of alkyne-coordinated nickel complex is much less favorable, and the [4 + 4 + 2] cycloaddition occurs
Infaunal and epifaunal secondary production in the Barents Sea, with focus on snow crab (Chionoecetes opilio) prey resources and consumption
Since the first observation of snow crab (Chionoecetes opilio) in the Barents Sea in 1996, the population has increased significantly, supporting a commercial fishery on the Norwegian shelf since 2012. To investigate whether the availability of benthic prey organisms may support a continued geographical snow crab expansion, benthic invertebrate production was studied across the central parts of the Barents Sea and around Svalbard, where snow crabs are currently absent or at low densities. Annual productivity (P/B ratio) from 66 stations collected by grab and beam trawl was estimated using a multiparameter artificial neural network model. Mean infaunal productivity and production were 0.43 yrâ1 and 38.4 g ww mâ2 yrâ1, respectively, while the epifaunal production was considerably lower with 2.5 g ww mâ2 yrâ1. The proportions of epi- and infaunal production suitable as prey for snow crab were 98 and 96%, respectively. Areas close to the Polar Front represent the most attractive snow crab foraging region, having the highest benthic secondary production, high estimated primary production, and bottom water temperatures within the snow crabâs preferences. At snow crab densities of 12800 ind. kmâ2, high enough to support commercial fishing, their mean consumption rate was estimated to be around 1.5 g ww mâ2 yrâ1, which amounts to 4% of mean infaunal prey production. Food availability is, therefore, not expected to be a hindrance to further population expansion of the snow crab in the Barents Sea.publishedVersio
Higher levels of bodily pain in people with long-term type 1 diabetes: associations with quality of life, depressive symptoms, fatigue and glycaemic control â the Dialong study
Aims
To compare reported level of bodily pain, overall and healthârelated quality of life (QoL), depression and fatigue in people with longâterm type 1 diabetes vs. a comparison group without diabetes. Further, to examine the associations of total bodily pain with QoL, depression, fatigue and glycaemic control in the diabetes group.
Methods
Crossâsectional study of 104 (76% of eligible) people with type 1 diabetes of â„ 45 yearsâ duration attending the Norwegian Diabetes Centre and 75 persons without diabetes who completed questionnaires measuring bodily pain (RANDâ36 bodily pain domain), shoulder pain (Shoulder Pain and Disability Index), hand pain (Australian/Canadian Osteoarthritis Hand Index), overall QoL (World Health Organization Quality of Life â BREF), healthârelated QoL (RANDâ36), diabetesâspecific QoL (Audit of DiabetesâDependent Quality of Life; only diabetes group), depression (Patient Health Questionnaire) and fatigue (Fatigue questionnaire). For people with type 1 diabetes, possible associations between the bodily pain domain (lower scores indicate higher levels of bodily pain) and other questionnaire scores, were measured with regression coefficients (B) per 10âunit increase in bodily pain score from linear regression.
Results
The diabetes group reported higher levels of bodily (P = 0.003), shoulder and hand pain (P < 0.001) than the comparison group. In the diabetes group, bodily pain was associated with lower overall and diabetesâspecific QoL [B (95% confidence intervals)]: 0.2 (0.1, 0.2) and 0.2 (0.1, 0.3); higher levels of depression â1.0 (â1.3, â0.7) and total fatigue â1.5 (â1.9, â1.2); and worse glycaemic control HbA1c (mmol/mol; %) â0.8 (â1.5, â0.1); â0.1 (â0.1, â0.01).
Conclusions
People with longâterm type 1 diabetes experience a high level of bodily pain compared with a comparison group. Total bodily pain was associated with worse QoL and glycaemic control.publishedVersio
Alternative splicing discriminates molecular subtypes and has prognostic impact in diffuse large B-cell lymphoma
Effect of alternative splicing (AS) on diffuse large B-cell lymphoma (DLBCL) pathogenesis and survival has not been systematically addressed. Here, we compared differentially expressed genes and exons in association with survival after chemoimmunotherapy, and between germinal center B-cell like (GCB) and activated B-cell like (ABC) DLBCLs. Genome-wide exon array-based screen was performed from samples of 38 clinically high-risk patients who were treated in a Nordic phase II study with dose-dense chemoimmunotherapy and central nervous system prophylaxis. The exon expression profile separated the patients according to molecular subgroups and survival better than the gene expression profile. Pathway analyses revealed enrichment of AS genes in inflammation and adhesion-related processes, and in signal transduction, such as phosphatidylinositol signaling system and adenosine triphosphate binding cassette transporters. Altogether, 49% of AS-related exons were protein coding, and domain prediction showed 28% of such exons to include a functional domain, such as transmembrane helix domain or phosphorylation sites. Validation in an independent cohort of 92 DLBCL samples subjected to RNA-sequencing confirmed differential exon usage of selected genes and association of AS with molecular subtypes and survival. The results indicate that AS events are able to discriminate GCB and ABC DLBCLs and have prognostic impact in DLBCL.Peer reviewe
Export of Ice Sheet Meltwater from Upernavik Fjord, West Greenland
Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(3), (2022): 363â382, https://doi.org/10.1175/jpo-d-21-0084.1.Meltwater from Greenland is an important freshwater source for the North Atlantic Ocean, released into the ocean at the head of fjords in the form of runoff, submarine melt, and icebergs. The meltwater release gives rise to complex in-fjord transformations that result in its dilution through mixing with other water masses. The transformed waters, which contain the meltwater, are exported from the fjords as a new water mass Glacially Modified Water (GMW). Here we use summer hydrographic data collected from 2013 to 2019 in Upernavik, a major glacial fjord in northwest Greenland, to describe the water masses that flow into the fjord from the shelf and the exported GMWs. Using an optimum multi-parameter technique across multiple years we then show that GMW is composed of 57.8% ± 8.1% Atlantic Water (AW), 41.0% ± 8.3% Polar Water (PW), 1.0% ± 0.1% subglacial discharge, and 0.2% ± 0.2% submarine meltwater. We show that the GMW fractional composition cannot be described by buoyant plume theory alone since it includes lateral mixing within the upper layers of the fjord not accounted for by buoyant plume dynamics. Consistent with its composition, we find that changes in GMW properties reflect changes in the AW and PW source waters. Using the obtained dilution ratios, this study suggests that the exchange across the fjord mouth during summer is on the order of 50 mSv (1 Sv ⥠106 m3 sâ1) (compared to a freshwater input of 0.5 mSv). This study provides a first-order parameterization for the exchange at the mouth of glacial fjords for large-scale ocean models.This work was partially supported by the Centre for Climate Dynamics (SKD) at the Bjerknes Centre for Climate Research. The authors thank NASA and the OMG consortium for making observational data freely available, and acknowledge M. Morlighem for good support in the early stages of this project. MM and LHS and would also like to thank Ă. Paasche, the ACER project, and the U.S. Norway Fulbright Foundation for the Norwegian Arctic Chair Grant 2019â20 that made the visit to Scripps Institution of Oceanography possible. FS acknowledges support from the DOE Office of Science Grant DE-SC0020073, Heising-Simons Foundation and from NSF and OCE-1756272. DAS acknowledges support from U.K. NERC Grants NE/P011365/1, NE/T011920/1, and NERC Independent Research Fellowship NE/T011920/1. MW was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, California Institute of Technology, administered by the Universities Space Research Association under contract with NASA. CSA would like to acknowledge Geocenter Denmark for support to the project âUpernavik Glacier.
Empirical Evaluation of the Difficulty of Finding a Good Value of k for the Nearest Neighbor
As an analysis of the classification accuracy bound for the Nearest Neighbor technique, in this work we have studied if it is possible to find a good value of the parmeter k for each example according to their attribute values. Or at least, if there is a pattern for the parameter k in the original search space. We have carried out different approaches based onthe Nearest Neighbor technique and calculated the prediction accuracy for a group of databases from the UCI repository. Based on the experimental results of our study, we can state that, in general, it is not possible to know a priori a specific value of k to correctly classify an unseen example
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