3,236 research outputs found
Nighttime air quality under desert conditions
Nighttime concentrations of the gas phase nitrate radical (NO3) were successfully measured during a four week field campaign in an arid urban location, Reno Nevada, using long-path Differential Optical Absorbance Spectrometry (DOAS). While typical concentrations of NO3 ranged from 5 to 20ppt, elevated concentrations were observed during a wildfire event. Horizontal mixing in the free troposphere was considerable because the sampling site was above the stable nocturnal boundary layer every night and this justified a box modeling approach. Process analysis of box model simulations showed NO3 accounted for approximately half of the loss of internal olefins, 60% of the isoprene loss, and 85% of the Ξ±-pinene loss during the nighttime hours during a typical night of the field study. The NO3+aldehyde reactions were not as important as anticipated. On a polluted night impacted by wildfires upwind of the sampling location, NO3 reactions were more important. Model simulations overpredicted NO2 concentrations for both case studies and inorganic chemistry was the biggest influence on NO3 concentrations and on nitric acid formation. The overprediction may be due to additional NO2 loss processes that were not included in the box model, as deposition and N2O5 uptake had no significant effect on NO2 levels
Lambda-prophage induction modeled as a cooperative failure mode of lytic repression
We analyze a system-level model for lytic repression of lambda-phage in E.
coli using reliability theory, showing that the repressor circuit comprises 4
redundant components whose failure mode is prophage induction. Our model
reflects the specific biochemical mechanisms involved in regulation, including
long-range cooperative binding, and its detailed predictions for prophage
induction in E. coli under ultra-violet radiation are in good agreement with
experimental data.Comment: added referenc
Measurement-based modeling of bromine chemistry at the Dead Sea boundary layer ? Part 2: The influence of NO<sub>2</sub> on bromine chemistry at mid-latitude areas
International audienceUnderstanding the interaction between anthropogenic air pollution and Reactive Halogen Species (RHS) activity has had only limited support of direct field measurements, due to the fact that past field measurements of RHS have been mainly performed in Polar Regions. The present paper investigates the interaction between NO2 and Reactive Bromine Species (RBS) activity by model simulations based on extensive field measurements performed in the Dead Sea area, as described in a companion paper (Tas et al., 2006). The Dead Sea is an excellent natural laboratory for this investigation since elevated concentrations of BrO (up to more than 150 pptv) are frequently observed, while the average levels of NO2 are around several ppb. The results of the present study show that under the chemical mechanisms that occur at the Dead Sea, higher levels of NO2 lead to higher daily average concentrations of BrOX, as a result of an increase in the rate of the heterogeneous decomposition of BrONO2 that in turn causes an increase in the rate of the "Bromine Explosion" mechanism. The present study has shown that the influence of NO2 on BrOX production clearly reflects an enhancement of RBS activity caused by anthropogenic activity. However, above a certain threshold level of NO2 (daily average mixing ratios of 0.2 ppbv during RBS activity), the daily average concentrations of BrOX decrease for a further increase in the NO2 concentrations
Measurement-based modeling of bromine chemistry in the boundary layer: 1. Bromine chemistry at the Dead Sea
International audienceThe Dead Sea is an excellent natural laboratory for the investigation of Reactive Bromine Species (RBS) chemistry, due to the high RBS levels observed in this area, combined with anthropogenic air pollutants up to several ppb. The present study investigated the basic chemical mechanism of RBS at the Dead Sea using a numerical one-dimensional chemical model. Simulations were based on data obtained from comprehensive measurements performed at sites along the Dead Sea. The simulations showed that the high BrO levels measured frequently at the Dead Sea could only partially be attributed to the highly concentrated Br? present in the Dead Sea water. Furthermore, the RBS activity at the Dead Sea cannot solely be explained by a pure gas phase mechanism. This paper presents a chemical mechanism which can account for the observed chemical activity at the Dead Sea, with the addition of only two heterogeneous processes: the "Bromine Explosion" mechanism and the heterogeneous decomposition of BrONO2. Ozone frequently dropped below a threshold value of ~1 to 2 ppbv at the Dead Sea evaporation ponds, and in such cases, O3 became a limiting factor for the production of BrOx (BrO+Br). The entrainment of O3 fluxes into the evaporation ponds was found to be essential for the continuation of RBS activity, and to be the main reason for the jagged diurnal pattern of BrO observed in the Dead Sea area, and for the positive correlation observed between BrO and O3 at low O3 concentrations. The present study has shown that the heterogeneous decomposition of BrONO2 has a great potential to affect the RBS activity in areas influenced by anthropogenic emissions, mainly due to the positive correlation between the rate of this process and the levels of NO2. Further investigation of the influence of the decomposition of BrONO2 may be especially important in understanding the RBS activity at mid-latitudes
Assembly and use of new task rules in fronto-parietal cortex
Severe capacity limits, closely associated with fluid intelligence, arise in learning and use of new task rules. We used fMRI to investigate these limits in a series of multirule tasks involving different stimuli, rules, and response keys. Data were analyzed both during presentation of instructions and during later task execution. Between tasks, we manipulated the number of rules specified in task instructions, and within tasks, we manipulated the number of rules operative in each trial block. Replicating previous results, rule failures were strongly predicted by fluid intelligence and increased with the number of operative rules. In fMRI data, analyses of the instruction period showed that the bilateral inferior frontal sulcus, intraparietal sulcus, and presupplementary motor area were phasically active with presentation of each new rule. In a broader range of frontal and parietal regions, baseline activity gradually increased as successive rules were instructed. During task performance, we observed contrasting fronto-parietal patterns of sustained (block-related) and transient (trial-related) activity. Block, but not trial, activity showed effects of task complexity. We suggest that, as a new task is learned, a fronto-parietal representation of relevant rules and facts is assembled for future control of behavior. Capacity limits in learning and executing new rules, and their association with fluid intelligence, may be mediated by this load-sensitive fronto-parietal network
Evolutionary game theory in growing populations
Existing theoretical models of evolution focus on the relative fitness
advantages of different mutants in a population while the dynamic behavior of
the population size is mostly left unconsidered. We here present a generic
stochastic model which combines the growth dynamics of the population and its
internal evolution. Our model thereby accounts for the fact that both
evolutionary and growth dynamics are based on individual reproduction events
and hence are highly coupled and stochastic in nature. We exemplify our
approach by studying the dilemma of cooperation in growing populations and show
that genuinely stochastic events can ease the dilemma by leading to a transient
but robust increase in cooperationComment: 4 pages, 2 figures and 2 pages supplementary informatio
Combined antiproliferative activity of imatinib mesylate (STI-571) with radiation or cisplatin in vitro
Little is known about the interaction of novel anticancer drugs with other treatment modalities. The aim of this study was to examine the effect of combining imatinib mesylate (STI-571) with radiation or cisplatin on the survival of two human solid tumor cell lines β SKNMC cells derived from Ewing sarcoma and breast cancer MCF-7 cells. Methods: Cell proliferation was determined using the sulphorodamine B cytotoxicity assay. Cell cycle analysis was performed with flow cytometry. Apoptosis was determined using a commercial cell death ELISA plus kit. Phosphorylated AKT, which has been suggested to be involved in radiation resistance, was detected by Western blot analysis. Results: Exposure of SKNMC cells to STI-571 resulted in a dose-dependent antiproliferative effect and a decrease in phosphorylated AKT expression. There was no evidence of apoptosis. The combination of STI-571 with radiation or cisplatin had an additive antiproliferative effect in SKNMC cells (60% reduction in cell number). A similar effect was observed in human MCF-7 breast cancer cells. Conclusion: STI-571 improves the outcome of cisplatin or irradiation treatment in vitro. AKT pathway may play a role in the additive effect of STI-571 and irradiation.Π¦Π΅Π»Ρ: ΠΎΡΠ΅Π½ΠΈΡΡ Π°Π½ΡΠΈΠΏΡΠΎΠ»ΠΈΡΠ΅ΡΠ°ΡΠΈΠ²Π½ΡΠΉ ΡΡΡΠ΅ΠΊΡ ΠΈΠΌΠ°ΡΠΈΠ½ΠΈΠ±Π° (STI-571) Π² ΠΊΠΎΠΌΠ±ΠΈΠ½Π°ΡΠΈΠΈ Ρ ΠΎΠ±Π»ΡΡΠ΅Π½ΠΈΠ΅ΠΌ ΠΈΠ»ΠΈ ΡΠΈΡΠΏΠ»Π°ΡΠΈΠ½ΠΎΠΉ ΠΏΠΎ ΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΡ
ΠΊ Π΄Π²ΡΠΌ ΠΊΠ»Π΅ΡΠΎΡΠ½ΡΠΌ Π»ΠΈΠ½ΠΈΡΠΌ β ΠΊΠ»Π΅ΡΠΊΠ°ΠΌ Π»ΠΈΠ½ΠΈΠΈ SKNMC, ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΠΌ ΠΈΠ· ΡΠ°ΡΠΊΠΎΠΌΡ ΠΠ²ΠΈΠ½Π³Π°, ΠΈ ΠΊΠ»Π΅ΡΠΊΠ°ΠΌ ΡΠ°ΠΊΠ° ΠΌΠΎΠ»ΠΎΡΠ½ΠΎΠΉ ΠΆΠ΅Π»Π΅Π·Ρ
ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ° Π»ΠΈΠ½ΠΈΠΈ MCF-7. ΠΠ΅ΡΠΎΠ΄Ρ: Π΄Π»Ρ ΠΎΡΠ΅Π½ΠΊΠΈ ΠΏΡΠΎΠ»ΠΈΡΠ΅ΡΠ°ΡΠΈΠΈ ΠΊΠ»Π΅ΡΠΎΠΊ ΠΏΡΠΈΠΌΠ΅Π½ΡΠ»ΠΈ ΠΌΠ΅ΡΠΎΠ΄ Π°Π½Π°Π»ΠΈΠ·Π° ΡΠΈΡΠΎΡΠΎΠΊΡΠΈΡΠ½ΠΎΡΡΠΈ Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ
ΡΡΠ»ΡΡΠΎΡΠΎΠ΄Π°ΠΌΠΈΠ½Π° B. ΠΠ»Ρ Π°Π½Π°Π»ΠΈΠ·Π° ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΡ ΠΊΠ»Π΅ΡΠΎΠΊ ΠΏΠΎ ΡΠ°Π·Π°ΠΌ ΠΊΠ»Π΅ΡΠΎΡΠ½ΠΎΠ³ΠΎ ΡΠΈΠΊΠ»Π° ΠΏΡΠΈΠΌΠ΅Π½ΡΠ»ΠΈ ΠΌΠ΅ΡΠΎΠ΄ ΠΏΡΠΎΡΠΎΡΠ½ΠΎΠΉ ΡΠΈΡΠΎΠΌΠ΅ΡΡΠΈΠΈ,
Π°ΠΏΠΎΠΏΡΠΎΠ·Π° β Ρ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ΠΌ ΠΊΠΎΠΌΠΌΠ΅ΡΡΠ΅ΡΠΊΠΎΠ³ΠΎ Π½Π°Π±ΠΎΡΠ° Π΄Π»Ρ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ΠΈΡ ΠΠ€Π. Π£ΡΠΎΠ²Π΅Π½Ρ ΡΠΎΡΡΠΎΡΠΈΠ»ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΠΊΠΈΠ½Π°Π·Ρ ΠΠΠ’,
ΠΏΡΠ΅Π΄ΠΏΠΎΠ»ΠΎΠΆΠΈΡΠ΅Π»ΡΠ½ΠΎ ΡΠ²ΡΠ·Π°Π½Π½ΠΎΠΉ Ρ ΡΠ°Π΄ΠΈΠΎΡΠ΅Π·ΠΈΡΡΠ΅Π½ΡΠ½ΠΎΡΡΡΡ, ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΠ»ΠΈ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ ΠΠ΅ΡΡΠ΅ΡΠ½-Π±Π»ΠΎΡ Π°Π½Π°Π»ΠΈΠ·Π°. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ: ΠΈΠ½ΠΊΡΠ±Π°ΡΠΈΡ
ΠΊΠ»Π΅ΡΠΎΠΊ SKNMC STI-571 ΠΏΡΠΈΠ²ΠΎΠ΄ΠΈΠ»Π° ΠΊ Π΄ΠΎΠ·ΠΎΠ·Π°Π²ΠΈΡΠΈΠΌΠΎΠΌΡ Π°Π½ΡΠΈΠΏΡΠΎΠ»ΠΈΡΠ΅ΡΠ°ΡΠΈΠ²Π½ΠΎΠΌΡ ΡΡΡΠ΅ΠΊΡΡ ΠΈ ΡΠ½ΠΈΠΆΠ΅Π½ΠΈΡ ΡΠΎΡΡΠΎΡΠΈΠ»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ
AKT, Π½ΠΎ Π½Π΅ Π°ΠΏΠΎΠΏΡΠΎΠ·Ρ ΠΊΠ»Π΅ΡΠΎΠΊ. ΠΠΎΠΌΠ±ΠΈΠ½ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ΅ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ STI-571 ΠΈ ΠΎΠ±Π»Π΅Π½ΠΈΡ ΠΈΠ»ΠΈ ΡΠΈΡΠΏΠ»Π°ΡΠΈΠ½Ρ ΠΎΠΊΠ°Π·ΡΠ²Π°Π»ΠΎ Π΄ΠΎΠΏΠΎΠ»Π½ΠΈΡΠ΅Π»ΡΠ½ΠΎΠ΅
Π°Π½ΡΠΈΠΏΡΠΎΠ»ΠΈΡΠ΅ΡΠ°ΡΠΈΠ²Π½ΠΎΠ΅ Π²ΠΎΠ·Π΄Π΅ΠΉΡΡΠ²ΠΈΠ΅ Π½Π° ΠΊΠ»Π΅ΡΠΊΠΈ Π»ΠΈΠ½ΠΈΠΈ SKNMC (60% ΡΠΌΠ΅Π½ΡΡΠ΅Π½ΠΈΡ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²Π° ΠΊΠ»Π΅ΡΠΎΠΊ). ΠΠ½Π°Π»ΠΎΠ³ΠΈΡΠ½ΡΠ΅ ΡΡΡΠ΅ΠΊΡΡ
ΠΎΡΠΌΠ΅ΡΠ°Π»ΠΈ Π½Π° ΠΊΠ»Π΅ΡΠΊΠ°Ρ
Π»ΠΈΠ½ΠΈΠΈ MCF-7. ΠΡΠ²ΠΎΠ΄Ρ: ΠΎΠ±ΡΠ°Π±ΠΎΡΠΊΠ° ΠΎΠΏΡΡ
ΠΎΠ»Π΅Π²ΡΡ
ΠΊΠ»Π΅ΡΠΎΠΊ STI-571 ΡΡΠΈΠ»ΠΈΠ²Π°Π΅Ρ ΡΡΡΠ΅ΠΊΡ ΠΎΠ±Π»Π΅Π½ΠΈΡ ΠΈ ΡΠΈΡΠΏΠ»Π°ΡΠΈΠ½Ρ
in, ΠΏΡΠΈΡΠ΅ΠΌ ΡΠ°ΠΊΠΎΠ²ΠΎΠΉ ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΠΎΠΏΠΎΡΡΠ΅Π΄ΠΎΠ²Π°Π½ ΡΠΈΠ³Π½Π°Π»ΡΠ½ΡΠΌ ΠΊΠ°ΡΠΊΠ°Π΄ΠΎΠΌ AK
Seasonal shifts in bacterial community responses to phytoplankton-derived dissolved organic matter in the Western Antarctic Peninsula
Β© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 8 (2017): 2117, doi:10.3389/fmicb.2017.02117.Bacterial consumption of dissolved organic matter (DOM) drives much of the movement of carbon through the oceanic food web and the global carbon cycle. Understanding complex interactions between bacteria and marine DOM remains an important challenge. We tested the hypothesis that bacterial growth and community succession would respond differently to DOM additions due to seasonal changes in phytoplankton abundance in the environment. Four mesocosm experiments were conducted that spanned the spring transitional period (AugustβDecember 2013) in surface waters of the Western Antarctic Peninsula (WAP). Each mesocosm consisted of nearshore surface seawater (50 L) incubated in the laboratory for 10 days. The addition of DOM, in the form of cell-free exudates extracted from Thalassiosira weissflogii diatom cultures led to changes in bacterial abundance, production, and community composition. The timing of each mesocosm experiment (i.e., late winter vs. late spring) influenced the magnitude and direction of bacterial changes. For example, the same DOM treatment applied at different times during the season resulted in different levels of bacterial production and different bacterial community composition. There was a mid-season shift from Collwelliaceae to Polaribacter having the greatest relative abundance after incubation. This shift corresponded to a modest but significant increase in the initial relative abundance of Polaribacter in the nearshore seawater used to set up experiments. This finding supports a new hypothesis that starting community composition, through priority effects, influenced the trajectory of community succession in response to DOM addition. As strong inter-annual variability and long-term climate change may shift the timing of WAP phytoplankton blooms, and the corresponding production of DOM exudates, this study suggests a mechanism by which different seasonal successional patterns in bacterial communities could occur.CL was partially funded by the Graduate School and the
Department of Ecology and Evolutionary Biology at Brown
University and the Brown University-Marine Biological
Laboratory Joint Graduate Program. This material is based upon
work supported by the National Science Foundation under Grant
Nos. ANT-1142114 to LA-Z, OPP-0823101 and PLR-1440435
to HD, and ANT-1141993 to JR. The Gordon and Betty Moore
Foundation grant 1711 supported work by DR
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