Particulate Organic Carbon Export Fluxes in The Canada Basin and Bering Sea as Derived from 234Th/238U Disequilibria

Seawater samples were collected in the water column of the Canada Basin and the Bering Sea from aboard the R/V Xue Long during August 1999. Activity concentrations of dissolved and particulate 234Th were measured using beta counting techniques to quantify the scavenging and residence time of 234Th and organic carbon export fluxes. Primary production (PP) and bacterial production were also determined in the study areas through in situ incubation experiments. Significant 234Th scavenging was observed in the upper 100 m of the water column in both study areas, with up to 40% of 234Th deficit found at Bering Sea stations and ~15% of 234Th deficit at the Canada Basin station. Measured PP decreased from ~12.5 µmol C/m³/h in surface water to near zero at ~100 m depth, with an integrated PP of 3.83 mmol C/m²/d in the Canada Basin. Bacterial production, on the other hand, was on the order of 2.0 mmol C/m²/d, which is up to 52% of the integrated PP. Particulate organic carbon (POC) export fluxes derived from 234Th/238U disequilibrium were ~1 mmol C/m²/d in the Canada Basin and ~10 mmol C/m²/d in the Bering Sea, with fluxes in the latter area being 5 to 10 times higher than those found in the Canada Basin. These export fluxes correspond to a ThE ratio (the ratio of 234Th-derived POC export to primary production) of 0.26 for the Canada Basin and 0.7 for the Bering Sea. The higher ThE ratios in the study areas suggest a decoupling of production and particulate export in the high-latitude ocean. Ratios of POC to particulate 234Th (µmol C/dpm) decreased consistently with increasing depth, suggesting that organic carbon is preferentially remineralized relative to 234Th. Interestingly, the profile of particulate 234Th in the Canada Basin showed a unique characteristic: particulate 234Th activities increased with increasing depth, suggesting a continuous scavenging of 234Th and a rapid settling rate of the particles.Au cours du mois d'août 1999, on a prélevé des échantillons d'eau de mer dans la colonne d'eau du bassin Canada et de la mer de Béring depuis le vaisseau RV Xue-Long. L'activité volumique du 234Th dissous et particulaire a été mesurée à l'aide de techniques de comptage au rayonnement bêta afin de quantifier le temps de balayage et le temps de séjour du 234Th et les flux d'exportation du carbone organique. On a aussi établi la production primaire (PP) et la production bactérienne dans les zones d'étude en réalisant des expériences d'incubation in situ. Dans les deux zones d'étude, on a observé un balayage marqué du 234Th dans les 100 m supérieurs de la colonne d'eau, avec jusqu'à 40 p. cent de déficit de 234Th aux postes de la mer de Béring et environ 15 p. cent au poste du bassin Canada. La PP mesurée baissait d'environ 12,5 µmol C/m³/h dans l'eau de surface à près de zéro à environ 100 m de profondeur, avec une PP intégrée de 3,83 mmol C/m²/j dans le bassin Canada. D'autre part, la production bactérienne était de l'ordre de 2,0 mmol C/m²/j, ce qui représente jusqu'à 52 p. cent de la PP intégrée. Les flux d'exportation du carbone organique particulaire (COP) calculés à partir du déséquilibre 234Th /238U étaient d'environ 1 mmol C/m²/j dans le bassin Canada et d'environ 10 mmol C/m²/j dans la mer de Béring, les flux dans cette région étant de 5 à 10 fois plus élevés que ceux trouvés dans le bassin Canada. Ces flux d'exportation correspondent à un rapport ThE (le rapport de l'exportation du COP dérivé du 234Th à la production primaire) de 0,26 pour le bassin Canada et de 0,7 pour la mer de Béring. Les rapports plus élevés de ThE dans les zones d'étude suggèrent un découplage de la production et de l'exportation de particules dans l'océan septentrional. Les rapports de COP au 234Th particulaire (µmol C/dpm) diminuaient de façon uniforme avec l'augmentation de la profondeur, ce qui suggère que le carbone organique est reminéralisé préférentiellement par rapport au 234Th. Il est à noter que le profil du 234Th particulaire dans le bassin Canada affichait une caractéristique unique: l'activité du 234Th particulaire augmentait avec la profondeur, ce qui suggère un balayage continu du 234Th et un taux rapide de sédimentation des particules

Zonal Patterns of Delta C-13, Delta N-15 and Po-210 In the Tropical and Subtropical North Pacific

Nitrogen fixation process may supply a significant fraction of bioavailable nitrogen to surface waters, increase the oceanic sequestration of atmospheric CO2, and alter the distribution of geochemical parameters. We report a zonal pattern of delta N-15 and delta C-13 in particulate organic matter (POM), and ratios of particulate Po-210 to dissolved Po-210 along a transect through the subtropical and tropical North Pacific. Both N-15 and Po-210 signals indicated an enhanced N-2 fixation in the northwestern subtropical North Pacific. The eastward decrease of N-2 fixation along this transect testified the role of aeolian Fe and P in controlling marine N-2 fixation. Associated with the zonal variations of N-15 and Po-210, the delta C-13 of suspended POM increased eastward, reflecting the decrease of anthropogenic CO2 concentration in surface seawater from west to east in the study area. Our results highlight the need to examine more closely the mechanisms of possible longitudinal variation in N-2 fixation in the ocean and the role of aeolian Fe and P in controlling marine N-2 fixation and anthropogenic CO2

The mean residence time of river water in the Canada Basin

Seawater was collected from the western Arctic Ocean for measurements of (18)O, (226)Ra and (228)Ra. The fractions of river runoff and sea ice melt-water in water samples were estimated by using delta (18)O-S-PO* tracer system. The mean residence time of river water in the Canada Basin was calculated based on the relationship between (228)Ra/(226)Ra)(A.R.) and the fractions of river runoff in the shelf and deep ocean. Our results showed that the river runoff fractions in the Canada Basin were significantly higher than those in the shelf regions, suggesting that the Canada Basin is a major storage region for Arctic river water. (228)Ra activity concentrations in the Chukchi shelf and the Beaufort shelf ranged from 0.16 to 1.22 Bq/m(3), lower than those reported for shelves in the low and middle latitudes, indicating the effect of sea ice melt-water. A good positive linear relationship was observed between (228)Ra/(226)Ra)(A.R.) and the fraction of river runoff for shelf waters, while the (228)Ra/(226)Ra)(A.R.) in the Canada Basin was located below this regressive line. The low (228)Ra/(226)Ra)(A.R.) in the Canada Basin was ascribed to (228)Ra decay during shelf waters transporting to the deep ocean. The residence time of 5.0-11.0 a was estimated for the river water in the Canada Basin, which determined the time response of surface freshening in the North Atlantic to the river runoff into the Arctic Ocean

The Relationship between a Competitive School Climate and School Bullying among Secondary Vocational School Students in China: A Moderated Mediation Model

School bullying is widespread in countries around the world and has a continuous negative impact on the physical and mental health of students. However, few studies have explored the influence mechanism of a competitive school climate on school bullying among Chinese secondary vocational school students. This study aims to explore the relationship between a competitive school climate and bullying in secondary vocational schools in the Chinese context, as well as the mediating role of school belonging and the moderating role of gender. Logit regression analysis and a moderated mediation model were used to analyze 1964 secondary vocational students from China based on PISA 2018 data from Beijing, Shanghai, Zhejiang, and Jiangsu, China. (1) The detection rate of school bullying in secondary vocational schools in China is 17.8%, lower than the world average. (2) A competitive school climate is significantly and positively correlated with secondary vocational school students’ exposure to school bullying. (3) A moderated mediation model suggests that school belonging is an important mechanism by which a competitive school climate influences the occurrence of school bullying, whereas gender moderates the direct effect of a competitive school climate and the indirect effect of school belonging, which mitigates the negative effects of a competitive school climate to some extent. The research results show that creating a healthy competitive climate in schools, cultivating students’ sense of belonging, and facing up to gender differences are helpful to prevent school bullying in secondary vocational schools

Let Artificial Intelligence Be Your Shelf Watchdog: The Impact of Intelligent Image Processing-Powered Shelf Monitoring on Product Sales

We collaborated with a leading fast-moving consumer goods (FMCG) manufacturer to investigate how intelligent image processing (IIP)-based shelf monitoring aids manufacturers’ shelf management by using data from a quasi-experiment and a field experiment. We discovered that such artificial intelligence (AI) assistance significantly and consistently improves product sales. Several underlying mechanisms were revealed by our quantitative and qualitative analysis. First, retailers are more likely to comply due to the greater monitoring effectiveness enabled by AI assistance. Second, the positive effect of IIP-based shelf monitoring partially persists after it is terminated, implying that human learning takes place. Third, the value of IIP-based shelf monitoring can be attributed to independent retailers rather than chain retailers. Since the degree of contract heterogeneity is the major difference between these retailers in terms of monitoring, this finding further suggests that AI is relatively more scalable when coping with more heterogeneous instances. Apart from these great benefits, we demonstrate the low marginal costs of implementing IIP-powered shelf monitoring, which indicates its long-term applicability and potential to generate incremental value. Our research contributes to several literature streams and provides managerial insights for practitioners who consider AI-assisted operational models

The Impact of AI-powered Shelf Monitoring on Product Sales

We collaborate with Danone to study how AI-based shelf monitoring helps with manufacturers\u27 shelf management efforts by using data from a field experiment. We find that AI-powered shelf monitoring significantly improves product sales. This effect is only partially persistent in that it diminishes after monitoring is terminated. We further reveal that the positive effect is attributed to independent retailers rather than chained retailers. Since the major difference in shelf monitoring between these two types of retailers is the degree of heterogeneity in shelf space rental contracts, this finding indicates that AI-powered monitoring is better than human monitoring when facing more heterogeneous shelf displays. The finding further suggests the better scalability of AI in coping with more heterogeneous objects. We also interview with the delegates and find a low marginal cost of adopting, which suggests a long-term applicability of AI-powered shelf monitoring to generate value for the manufacturer

Bacterial productivity in the Prydz Bay and its adjacent waters, Antarctic

Bacterial productivity was measured using (3)H-thymidine methods in the Prydz Bay and its adjacent waters in the Southern Ocean during the 16th National Antarctic Research Expedition of China (CHINARE). The results showed that bacterial productivity in our study areas ranged from 4.5 to 191 ngC * dm(-3) * h(-1), with an average of 50.4 ngC * dm(-3) * h(-1). These values were comparable to those reported for the Ross Sea. The mean ratio of bacterial productivity to primary productivity in our study areas was 41%. The general characteristics in the vertical profiles showed a sub-surface maximum at most of the stations, which was also consistent with those observed in the other sea areas in the Southern Ocean. The spatial distribution of bacterial productivity and dissolved organic carbon in the surface waters showed that their variations were inversely correlative. The relationship among bacterial productivity, primary productivity and dissolved organic carbon suggested that bacterial productivity in the Prydz Bay and its adjacent water was influenced mostly by phytoplankton activities and the hydrologic conditions

Measuring method for thermal conductivity of a pyrolysis layer

The thermo-physical parameters of the pyrolysis layer in charring material play a fundamental role in the design of the thermal protection system (TPS) in hypersonic vehicles, but there is still a lack of measuring methods for the pyrolysis layer including pyrolysis gases, carbon residue and resin. The measuring method for the thermal conductivity of the pyrolysis layer is presented by means of iteration inversion of temperature at measuring points, and experimental equipment is designed and manufactured. Furthermore, the thermal conductivity of the pyrolysis layer under different pressures is obtained by this method. The results reveal that its thermal conductivity is a nonlinear function of temperature; meanwhile, the pressure has a major effect on the thermal conductivity. This study can figure out the test problem of the thermal conductivity of the pyrolysis layer, which is helpful to the optimization of TPS

Determination of cosmogenic P-32 and P-33 in environmental samples

National Natural Science Foundation of China [41125020]; State Oceanic Administration [2010050012-3]Understanding phosphorus dynamics in marine environment is of great importance, and appropriate tracers for phosphorus cycling in oceans are invaluable. In this study, two methods were developed for extraction, purification, and determination of naturally occurring P-32 and P-33 in rainwater, marine plankton and sediments using both a low-level beta counter (LBC) and an ultra-low-level liquid scintillation spectrometer (LSS). Blanks, chemical yields and counting efficiencies were quantified for both methods. The chemical purification of P-32 and P-33 separated by both procedures was validated by their decay curves. The absorber thickness of aluminum for LBC was assessed as 39.2 mg/cm(2). P-32 and P-33 specific activities in some rain samples were determined by both methods and showed good consistent results. The advantage of the LSS over the LBC is apparent in its high counting efficiency and in determining samples with high concentration of stable phosphorus. However, when measuring environmental samples with low concentration of stable phosphorus, such as rainwater, both methods can be used and each has its distinct advantage

Unusually high (210)Po activities in the surface water of the Zhubi Coral Reef Lagoon in the South China Sea

National Science Foundation of China [41076043, 40806031]Recent researches revealed the exciting application of Po-210 in tracing carbon and nitrogen cycling in the coral reef system. In order to quantify the recycling of particulate organic nitrogen (PON), both Po-210 and Pb-210 were examined at both high and low tides in the Zhubi Coral Reef lagoon, the South China Sea. Unusually, much higher Po-210 activities and Po-210/Pb-210 ratios, in comparison with those found in the open seawater and the lagoon subsurface water, showed additional input of Po-210 besides production from in situ Pb-210 in the lagoon surface water. Statistical analysis identified that the reef flat seawater was the additional Po-210 source. Based on a mass balance model, the input rates of Po-210 varied from 0.04 Bq M-3 year(-1) to 8.41 Bq m(-3) year(-1). On average, the additional Po-210 contributed more than 60% of the total Po-210. The particulate Po-210 significantly correlated with the concentrations of PON, indicating that diffusion of Po-210 from sediment could be used to quantify the recycling of nitrogen. The average input rate of nitrogen was 16 mmol M-3 year(-1), which can support up to 11% of the primary production rate. These results suggested that the unusual behavior of Po-210 could provide new insight into the nitrogen recycling in the coral reef system. (C) 2011 Elsevier B.V. All rights reserved