Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment

A high resolution time-series analysis of stable carbon isotopic signatures in particulate organic carbon (δ<sup>13</sup>C<sub>POC</sub>) and associated biogeochemical parameters in sea ice and surface waters provides an insight into the factors affecting δ<sup>13</sup>C<sub>POC</sub> in the coastal western Antarctic Peninsula sea ice environment. The study covers two austral summer seasons in Ryder Bay, northern Marguerite Bay between 2004 and 2006. A shift in diatom species composition during the 2005/06 summer bloom to near-complete biomass dominance of <i>Proboscia inermis</i> is strongly correlated with a large ~10 ‰ negative isotopic shift in δ<sup>13</sup>C<sub>POC</sub> that cannot be explained by a concurrent change in concentration or isotopic signature of CO<sub>2</sub>. We hypothesise that the δ<sup>13</sup>C<sub>POC</sub> shift may be driven by the contrasting biochemical mechanisms and utilisation of carbon-concentrating mechanisms (CCMs) in different diatom species. Specifically, very low δ<sup>13</sup>C<sub>POC</sub> in <i>P. inermis</i> may be caused by the lack of a CCM, whilst some diatom species abundant at times of higher δ<sup>13</sup>C<sub>POC</sub> may employ CCMs. These short-lived yet pronounced negative δ<sup>13</sup>C<sub>POC</sub> excursions drive a 4 ‰ decrease in the seasonal average δ<sup>13</sup>C<sub>POC</sub> signal, which is transferred to sediment traps and core-top sediments and consequently has the potential for preservation in the sedimentary record. This 4 ‰ difference between seasons of contrasting sea ice conditions and upper water column stratification matches the full amplitude of glacial-interglacial Southern Ocean δ<sup>13</sup>C<sub>POC</sub> variability and, as such, we invoke phytoplankton species changes as a potentially important factor influencing sedimentary δ<sup>13</sup>C<sub>POC</sub>. We also find significantly higher δ<sup>13</sup>C<sub>POC</sub> in sea ice than surface waters, consistent with autotrophic carbon fixation in a semi-closed environment and possible contributions from post-production degradation, biological utilisation of HCO<sub>3</sub><sup>−</sup> and production of exopolymeric substances. This study demonstrates the importance of surface water diatom speciation effects and isotopically heavy sea ice-derived material for δ<sup>13</sup>C<sub>POC</sub> in Antarctic coastal environments and underlying sediments, with consequences for the utility of diatom-based δ<sup>13</sup>C<sub>POC</sub> in the sedimentary record

Proton strangeness form factors in (4,1) clustering configurations

We reexamine a recent result within a nonrelativistic constituent quark model (NRCQM) which maintains that the uuds\bar s component in the proton has its uuds subsystem in P state, with its \bar s in S state (configuration I). When the result are corrected, contrary to the previous result, we find that all the empirical signs of the form factors data can be described by the lowest-lying uuds\bar s configuration with \bar s in P state that has its uuds subsystem in $S$ state (configuration II). Further, it is also found that the removal of the center-of-mass (CM) motion of the clusters will enhance the contributions of the transition current considerably. We also show that a reasonable description of the existing form factors data can be obtained with a very small probability P_{s\bar s}=0.025% for the uuds\bar s component. We further see that the agreement of our prediction with the data for G_A^s at low-q^2 region can be markedly improved by a small admixture of configuration I. It is also found that by not removing CM motion, P_{s\bar s} would be overestimated by about a factor of four in the case when transition dominates over direct currents. Then, we also study the consequence of a recent estimate reached from analyzing the existing data on quark distributions that P_{s\bar s} lies between 2.4-2.9% which would lead to a large size for the five-quark (5q) system, as well as a small bump in both G^s_E+\eta G^s_M and G^s_E in the region of q^2 =< 0.1 GeV^2.Comment: Prepared for The Fifth Asia-Pacific Conference on Few-Body Problems in Physics 2011 in Seoul, South Korea, 22-26 August 201

Summary for Policymakers - Marine Ecosystem Assessment for the Southern Ocean

i. The Antarctic Treaty System (beginning in 1959 with the Antarctic Treaty) and its emphasis on conservation and protection, exemplified in the Convention on the Conservation of Antarctic Marine Living Resources (1980) and its Protocol on Environmental Protection to the Antarctic Treaty (1991), provide the most recent articulation of the global interest in Antarctica and the Southern Ocean and the need for their protection. ii. The Southern Ocean and its ecosystems play critical roles in the climate system. Ecosystem functions are at risk because of anthropogenic climate change. iii. Global policies and actions are urgently required to safeguard Southern Ocean ecosystems from the effects of climate change, ocean warming and acidification caused by greenhouse gas emissions. iv. Regional human pressures on Southern Ocean species and ecosystems have been dominated by fisheries, with human presence (science and tourism) and pollution having localised, but increasing, impacts. v. The Marine Ecosystem Assessment for the Southern Ocean (MEASO) has demonstrated the array of existing knowledge, data, tools and approaches available for informing decisions on conserving and sustaining the marine ecosystems in the region and the services they provide, and how implementation of those processes could be improved

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

An international circumpolar compilation of macronutrient concentrations in Antarctic land-fast sea ice: science highlights and open access data

info:eu-repo/semantics/nonPublishe

Nutrients in Antarctic land-fast sea ice and exchange with the surface ocean

info:eu-repo/semantics/nonPublishe