247 research outputs found
Plasmas and Controlled Nuclear Fusion
Contains reports on two research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070
Modeling Supply Networks and Business Cycles as Unstable Transport Phenomena
Physical concepts developed to describe instabilities in traffic flows can be
generalized in a way that allows one to understand the well-known instability
of supply chains (the so-called ``bullwhip effect''). That is, small variations
in the consumption rate can cause large variations in the production rate of
companies generating the requested product. Interestingly, the resulting
oscillations have characteristic frequencies which are considerably lower than
the variations in the consumption rate. This suggests that instabilities of
supply chains may be the reason for the existence of business cycles. At the
same time, we establish some link to queuing theory and between micro- and
macroeconomics.Comment: For related work see http://www.helbing.or
Effects of spoilage on nitrogen and carbon stable isotopes signatures of the clam Ruditapes decussatus
Fish and seafood products are highly susceptible to post-mortem
spoilage due to autolytic reactions at start, then microbiological activity and
eventually oxidative reactions. Chemical and microbiological parameters are
usually used to assess quality and make decisions for protecting public health,
but they lack precision in defining which spoilage pathway is occurring at each
moment. The objective of this work was to assess the effects of spoilage reactions
on nitrogen and carbon stable isotopes in the grooved carpet shell clam,
Ruditapes decussatus, and compare them to biochemical indicators of seafood
deterioration, in order to better understand the relations between the different
spoilage pathways during commercial storage conditions. Clams were kept in a
refrigerator at 5 ÂșC, to simulate normal commercial storage conditions, and
sampled in the beginning of the experiment, and after eight, ten and twelve
days. Moisture, condition index, percentage edibility, total volatile basic nitrogen
(TVB-N), pH, nitrogen and carbon percentages and stable isotopes were determined
for each sampling moment. Stable isotope analyses were performed
using a Costech Elemental Analyzer (ECS 4010) coupled to a ThermoFinnigan
Delta V Advantage. Stable isotopes analysis, especially for nitrogen, proved to
be a good tool for the study of clam deterioration. Nitrogen stable isotopes results
showed a relation with other spoilage indicators, such as pH and TVB-N,
and allowed identifying spoilage specific pathways, such as amino acids decarboxylation
and production of volatile nitrogen compounds.info:eu-repo/semantics/publishedVersio
Length of carotid stenosis predicts peri-procedural stroke or death and restenosis in patients randomized to endovascular treatment or endarterectomy.
BACKGROUND: The anatomy of carotid stenosis may influence the outcome of endovascular treatment or carotid endarterectomy. Whether anatomy favors one treatment over the other in terms of safety or efficacy has not been investigated in randomized trials.
METHODS: In 414 patients with mostly symptomatic carotid stenosis randomized to endovascular treatment (angioplasty or stenting; nâ=â213) or carotid endarterectomy (nâ=â211) in the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS), the degree and length of stenosis and plaque surface irregularity were assessed on baseline intraarterial angiography. Outcome measures were stroke or death occurring between randomization and 30 days after treatment, and ipsilateral stroke and restenosis â„50% during follow-up. RESULTS: Carotid stenosis longer than 0.65 times the common carotid artery diameter was associated with increased risk of peri-procedural stroke or death after both endovascular treatment [odds ratio 2.79 (1.17-6.65), Pâ=â0.02] and carotid endarterectomy [2.43 (1.03-5.73), Pâ=â0.04], and with increased long-term risk of restenosis in endovascular treatment [hazard ratio 1.68 (1.12-2.53), Pâ=â0.01]. The excess in restenosis after endovascular treatment compared with carotid endarterectomy was significantly greater in patients with long stenosis than with short stenosis at baseline (interaction Pâ=â0.003). Results remained significant after multivariate adjustment. No associations were found for degree of stenosis and plaque surface.
CONCLUSIONS: Increasing stenosis length is an independent risk factor for peri-procedural stroke or death in endovascular treatment and carotid endarterectomy, without favoring one treatment over the other. However, the excess restenosis rate after endovascular treatment compared with carotid endarterectomy increases with longer stenosis at baseline. Stenosis length merits further investigation in carotid revascularisation trials
Recommended from our members
The uronic acid content of coccolith-associated polysaccharides provides insight into coccolithogenesis and past climate
Unicellular phytoplanktonic algae (coccolithophores) are among the most prolific producers of calcium carbonate on the planet, with a production of âŒ1026 coccoliths per year. During their lith formation, coccolithophores mainly employ coccolith-associated polysaccharides (CAPs) for the regulation of crystal nucleation and growth. These macromolecules interact with the intracellular calcifying compartment (coccolith vesicle) through the charged carboxyl groups of their uronic acid residues. Here we report the isolation of CAPs from modern day coccolithophores and their prehistoric predecessors and we demonstrate that their uronic acid content (UAC) offers a species-specific signature. We also show that there is a correlation between the UAC of CAPs and the internal saturation state of the coccolith vesicle that, for most geologically abundant species, is inextricably linked to carbon availability. These findings suggest that the UAC of CAPs reports on the adaptation of coccolithogenesis to environmental changes and can be used for the estimation of past CO2 concentrations
Integrating isotopes and documentary evidence : dietary patterns in a late medieval and early modern mining community, Sweden
We would like to thank the Archaeological Research Laboratory, Stockholm University, Sweden and the Tandem Laboratory (Ă
ngström Laboratory), Uppsala University, Sweden, for undertaking the analyses of stable nitrogen and carbon isotopes in both human and animal collagen samples. Also, thanks to Elin Ahlin Sundman for providing the ÎŽ13C and ÎŽ15N values for animal references from VĂ€sterĂ„s. This research (BĂ€ckströmâs PhD employment at Lund University, Sweden) was supported by the Berit Wallenberg Foundation (BWS 2010.0176) and Jakob and Johan Söderbergâs foundation. The âSala projectâ (excavations and analyses) has been funded by Riksens Clenodium, Jernkontoret, Birgit and Gad Rausingâs Foundation, SAUâs Research Foundation, the Royal Physiographic Society of Lund, Berit Wallenbergs Foundation, Ă
ke Wibergs Foundation, Lars Hiertas Memory, Helge Ax:son Johnsonâs Foundation and The Royal Swedish Academy of Sciences.Peer reviewedPublisher PD
A role for diatom-like silicon transporters in calcifying coccolithophores
Biomineralization by marine phytoplankton, such as the silicifying diatoms and calcifying coccolithophores, plays an important role in carbon and nutrient cycling in the oceans. Silicification and calcification are distinct cellular processes with no known common mechanisms. It is thought that coccolithophores are able to outcompete diatoms in Si-depleted waters, which can contribute to the formation of coccolithophore blooms. Here we show that an expanded family of diatom-like silicon transporters (SITs) are present in both silicifying and calcifying haptophyte phytoplankton, including some globally important coccolithophores. Si is required for calcification in these coccolithophores, indicating that Si uptake contributes to the very different forms of biomineralization in diatoms and coccolithophores. Significantly, SITs and the requirement for Si are absent from highly abundant bloom-forming coccolithophores, such as Emiliania huxleyi. These very different requirements for Si in coccolithophores are likely to have major influence on their competitive interactions with diatoms and other siliceous phytoplankton
- âŠ