Evidence for a collective intelligence factor in the performance of human groups

Psychologists have repeatedly shown that a single statistical factor--often called "general intelligence"--emerges from the correlations among people's performance on a wide variety of cognitive tasks. But no one has systematically examined whether a similar kind of "collective intelligence" exists for groups of people. In two studies with 699 people, working in groups of two to five, we find converging evidence of a general collective intelligence factor that explains a group's performance on a wide variety of tasks. This "c factor" is not strongly correlated with the average or maximum individual intelligence of group members but is correlated with the average social sensitivity of group members, the equality in distribution of conversational turn-taking, and the proportion of females in the group.     

Diurnal and Seasonal Patterns in Ecosystem CO2 Fluxes and Their Controls in a Temperate Grassland

There is considerable interest in understanding processes of carbon dioxide (CO₂) uptake and release in grasslands and the factors that control them. Many studies have investigated how CO₂ fluxes vary over time (monthly, seasonally, annually). However, with the exception of net ecosystem CO₂ exchange (NEE) and ecosystem respiration (R_eco), little information is available on diurnal flux patterns, despite their importance in determining total ecosystem CO₂ gains and losses. To better understand these variations, we measured CO₂ fluxes (NEE, R_eco, soil respiration [R_soil], canopy respiration [R_canopy], plant assimilation [assimilation]) with a climate-controlled closed-chamber system over 24 h once a month from May to September during the 2005 growing season in a mesic grassland in Yellowstone National Park. We also assessed how environmental factors (photosynthetic active radiation [PAR], air temperature, soil temperature, soil moisture) were associated with these diurnal and seasonal flux patterns to identify the main drivers of the fluctuations in CO₂. Measurements were conducted simultaneously on two plots: one irrigated, the other unirrigated. Absolute values of all fluxes were greatest in midsummer (June–July), and lowest in spring and fall (May, September) at both plots. Variation in soil moisture as a result of irrigation did not lead to pronounced differences in seasonal CO₂ fluxes and did not influence the diurnal patterns of CO₂ uptake and release. Instead, the diurnal and seasonal variations of our ecosystem fluxes were related to PAR and temperature (air/soil) and soil moisture and temperature (air/soil), respectively, at both plots. Thus, continued anthropogenic increases in greenhouse gas emissions that are expected to change the intensity of radiation, temperature, and precipitation may strongly affect the diurnal and seasonal patterns in CO₂ uptake and release. Such chamber-based information combined with the measurement of environmental variables could be important for modeling CO₂ budgets when no continuous measurements are available or affordable.     

Micropropagation of Darjeeling orange (Citrus reticulata Blanco) by shoot-tip grafting

Summary

Micropropagation of Darjeeling orange (Darjeeling mandarin) was done by shoot-tip grafting on the local rootstocks rough lemon, sour orange and Rangpur lime. Seedlings of these plants were raised in MS medium in standard conditions of temperature, light duration and plant age. Microbuds (0.2 mm long), aseptically excised from the scion, were grafted onto the decapitated rootstock seedlings. The micrografts in culture medium were grown under standard lighting. Rootstock seedlings showed optimum growth at 25–30°C. Optimum growth of the micrografts resulted from treatment in complete darkness for 4 d after grafting followed by exposure to 750 W for 16 h d^?1 for 15 d and 1500–2000 W for 16 h d^?1 for 39 d. The success of micrografting depended on the age of the rootstock seedling which was 21 d, 14 d and 14 d for sour orange, rough lemon and Rangpur lime respectively. The micrografts were then double grafted to the two year old rootstocks seedlings of the respective species and the age of the micrografts for the successful double grafts was also standardized. The survival rate was high with 40 d, 45 d and 45 d micrografts on sour orange, rough lemon and Rangpur lime respectively. The double-grafts were then indexed for tristeza virus and greening disease after six months’ growth in an insect-proof screenhouse and found to be free from these graft transmissible diseases.     

N-acyl-homoserine lactones from Enterobacter sakazakii (Cronobacter spp.) and their degradation by Bacillus cereus enzymes

A chemical study of acyl-homoserine lactones (acyl-HSLs) produced by Enterobacter sakazakii resulted in the identification of three molecules: (S)-N-heptanoyl-HSL, (S)-N-dodecanoyl-HSL and (S)-N-tetradecanoyl-HSL. Mixed cultures of E. sakazakii and Bacillus cereus depleted E. sakazakii acyl-HSLs, suggesting acyl-HSL degradation by B. cereus hydrolases (hydrolysis of the lactone or amide moiety). The expression of B. cereus acyl-HSL lactonase and acyl-homoserine acylase was confirmed by monitoring the biotransformation of (S)-N-dodecanoyl-HSL into (S)-N-dodecanoyl-homoserine, dodecanoic acid and homoserine in the presence of B. cereus whole cells, using electrospray-mass spectrometry (ESI-MS).     

Quantification of seasonal sediment and phosphorus transport dynamics in an agricultural watershed using radiometric fingerprinting techniques

Purpose

Phosphorus (P) is a limiting nutrient for most US Midwestern aquatic systems and, therefore, increases of P, through point or non-point sources (NPS) of pollution such as agriculture, causes eutrophication. Identifying specific NPS contributions (e.g., upland vs. stream channels) for sediments and P is difficult due to the distributed nature of the pollution. Therefore, studies which link the spatial and temporal aspects of sediment and P transport in these systems can help better characterize the extent of NPS pollution.

Materials and methods

Our study used fingerprinting techniques to determine sources of sediments in an agricultural watershed (the North Fork of the Pheasant Branch watershed; 12.4 km² area) in Wisconsin, USA, during the spring, summer, and fall seasons of 2009. The primary sources considered were uplands (cultivated fields), stream bank, and streambed. The model used fallout radionuclides, ¹³⁷Cs, and ²¹⁰Pb_xs, along with total P to determine primary sediment sources. A shorter-lived fallout radioisotope, ⁷Be, was used to determine the sediment age and percent new sediments in streambed and suspended sediment samples (via the ⁷Be/²¹⁰Pb_xs ratio).

Results and discussion

Upland areas were the primary source of suspended sediments in the stream channels followed by stream banks. The sediment age and percent new sediment for the streambed and suspended sediments showed that the channel contained and transported newer (or more recently tagged with ⁷Be) sediments in the spring season (9–131 days sediment age), while relatively old sediments (165–318 days) were moving through the channel system during the fall season.

Conclusions

Upland areas are the major contributors to in-stream suspended sediments in this watershed. Sediment resuspension in stream channels could play an important role during the later part of the year. Best management practices should be targeted in the upland areas to reduce the export of sediments and sediment-bound P from agricultural watersheds.