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Coupling of the spatial dynamic of picoplankton and nanoflagellate grazing pressure and carbon flow of the microbial food web in the subtropical pelagic continental shelf ecosystem
K.-P. Chiang,A.-Y. Tsai,P.-J. Tsai,G.-C. Gong
Biogeosciences Discussions , 2013, DOI: 10.5194/bgd-10-233-2013
Abstract: In order to investigate the mechanism of spatial dynamics of picoplankton community (bacteria and Synechococcus spp.) and estimate the carbon flux of the microbial food web in the oligotrophic Taiwan Warm Current Water of subtropical marine pelagic ecosystem, we conducted size-fractionation experiments in five cruises by the R/V Ocean Research II during the summers of 2010 and 2011 in the southern East China Sea. We carried out culture experiments using surface water which, according to a temperature-salinity (T-S) diagram, is characterized as oligotrophic Taiwan Current Warm Water. We found a negative correlation bettween bacteria growth rate and temperature, indicating that the active growth of heterotrophic bacteria might be induced by nutrients lifted from deep layer by cold upwelling water. This finding suggests that the area we studied was a bottom-up control pelagic ecosystem. We suggest that the microbial food web of an oligotrophic ecosystem may be changed from top-down control to resource supply (bottom-up control) when a physical force brings nutrient into the oligotrophic ecosystem. Upwelling brings nutrient-rich water to euphotic zone and promotes bacteria growth, increasing the picoplankton biomass which increased the consumption rate of nanoflagellate. The net growth rate (growth rate–grazing rate) becomes negative when the densities of bacteria and Synechococcus spp. are lower than the threshold values. The interaction between growth and grazing will limit the abundances of bacteria (105-106 cells mL-1 and Synechococcus spp. (104-105 cells mL-1) within a narrow range, forming a predator-prey eddy. Meanwhile, 62% of bacteria production and 55% of Synechococcus spp. production are transported to higher trophic level (nanoflagellate), though the cascade effect might cause an underestimation of both percentages of transported carbon. Based on the increasing number of sizes we found in the size-fractionation experiments, we estimated that the predation values were underestimated by 28.3% for bacteria and 34.6% for Synechococcus spp. Taking these corrections into consideration, we conclude that picoplankton production is balanced by nonoflagellate grazing and the diet of nanoflagellate is composed of 64% bacteria and 36% Synechococcus spp.
New particle growth and shrinkage observed in subtropical environments
L.-H. Young, S.-H. Lee, V. P. Kanawade, T.-C. Hsiao, Y. L. Lee, B.-F. Hwang, Y.-J. Liou, H.-T. Hsu,P.-J. Tsai
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2013,
Abstract: We present the first systematic analysis for new particle formation (NPF), growth and shrinkage of new particles at four different sites in subtropical central Taiwan. A total of 14 NPF events were identified from 137 days of ambient measurements during a cold and warm season. The measured formation rates of 10 nm particles (J10) and growth rates were in the range of 4.4–30 cm 3 s 1 and 7.4–24 nm h 1, respectively. The onset of NPF events coincided with decreases of condensation sink (CS) and increases of SO2 under enhanced atmospheric mixing and dilution. However, the lower or comparable SO2 on event days than on non-event days suggests that SO2 was not a limiting factor for NPF. On non-event days, the particle number concentrations were mostly driven by traffic emissions. We also observed shrinkage of new particles, the reversal of growth, during five out of the identified secondary formation. UFP particles events. In intense cases, the grown particles shrank back to the smallest measurable size of ~10 nm, thereby creating a unique "arch-like" shape in the size distribution contour plot. The particle shrinkage rates ranged from 5.1 to 7.6 nm h 1. The corresponding particle volume losses suggest that a notable fraction of the condensable species that contributed to growth was semi-volatile. The particle shrinkage was related to enhanced atmospheric dilution, high ambient temperature and low relative humidity, thus favoring the evaporation of semi-volatile species from the particulate phase to the gas phase. Our observations show that the new particle growth could be a reversible process, in which the evaporating semi-volatile species are important for the growth of new particles to sizes of environmental health concerns.
Density fractions versus size separates: does physical fractionation isolate functional soil compartments?
C. Moni,D. Derrien,P.-J. Hatton,B. Zeller
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-8405-2012
Abstract: Physical fractionation is a widely used methodology to study soil organic matter (SOM) dynamics, but concerns have been raised that the available fractionation methods do not well describe functional SOM pools. We also examine the question whether physical fractionation techniques isolate ecologically meaningful, functionally relevant soil compartments. In this study we explore whether the kind of information that aggregate density fractionation (ADF) and particle size-density fractionation (PSDF) yield on soil OM dynamics is method-specific, similar, or complimentary. We do so by following the incorporation of a 15N label into mineral soils of two European beech forests a decade after its application as 15N labelled litter. Both density and size-based fractionation methods suggested that OM became increasingly associated with the mineral phase as decomposition progressed, within aggregates and onto mineral surfaces. Our results suggest that physical fractionation methods do isolate ecologically relevant functional soil subunits. However, scientists investigating specific aspects of OM dynamics are pointed towards ADF when adsorption and aggregation processes are of interest, whereas PSDF is the superior tool to research the fate of particulate organic matter (POM). Some methodological caveats were observed mainly for the PSDF procedure, the most important one being that fine fractions isolated after sonication can not be linked to any defined decomposition pathway or stabilisation process. This also implies that historical assumptions about the "adsorbed" state of carbon associated with fine fractions need to be re-evaluated. Finally, this work demonstrates that establishing a comprehensive picture of whole soil OM dynamics requires a combination of both methodologies and we offer a suggestion for an efficient combination of the density and size-based approaches.
PIXE analysis of the obsidian support of two paintings from the Louvre by Murillo
T. Calligaro,P.-J. Chiappero,F. Gendron,E. Gonthier
Revista mexicana de física , 2007,
Abstract: Los inusuales soportes negros de dos pinturas representando Escenas de la Pasin del maestro espa nol Murillo (1617 1682), expuestas en el Museo del Louvre, han sido analizadas por PIXE en las instalaciones AGLAE del C2RMF. El soporte mostr ser obsidiana, un vidrio volc′anico ampliamente empleado para producir artefactos arqueolgicos, en particular en Sur y Mesoam′erica. Se han analizado cinco artefactos arqueolgicos originarios de Mexico, con forma similar a las pinturas llamados espejos de obsidiana y pertenecientes a la coleccin del Muse′e de l homme en Par′ s, se encontr′o que la composicin de cuatro de ellos es muy similar a las obsidianas de Murillo. La comparacin con los resultados obtenidos en muestras referencia de obsidianas de fuentes mexicanas y con datos de la literatura por activacin neutrnica instrumental (INAA) sugiere que la fuente de las obsidianas empleadas para la pintura es Ucareo/ Zinap′ecuaro, Michoacan, en Mexico. Por lo tanto, se organiz un viaje de estudios a ′esta ′area para colectar muestras cuya forma natural en bloque y composicin qu′ mica confirmaran la hiptesis de la procedencia de Ucareo. Los soportes rectangulares de las pinturas de Murillo son improbablemente artefactos arqueolgicos, son m′as bien objetos especialmente hechos por los artesanos mesoamericanos despu′es de la conquista espa nola, algunos de ellos fueron exportados a Europa, donde Murillo pas toda su vida. La observacin en las paredes de las iglesias y otros monumentos cristianos en Ucareo de incrustaciones de obsidiana, un material de importancia particular en la cultura prehisp′anica, subraya la compleja intrincaci′on de la cultura natal y las influencias europeas que tambi′en son llevadas por las pinturas de Murillo. Mientras tanto, en el Museo de las Bellas Artes de Houston, Texas, U.S.A. ha sido identificada una tercera pintura sobre obsidiana de Murillo. Este estudio tambi′en indica que incluso si el rango de elementos cuantificados por PIXE e INAA no se superpone completamente, las medidas obtenidas por ambas t′ecnicas pueden ser usadas eficientemente para determinar la procedencia de objetos de obsidiana.
Density fractions versus size separates: does physical fractionation isolate functional soil compartments?
C. Moni, D. Derrien, P.-J. Hatton, B. Zeller,M. Kleber
Biogeosciences (BG) & Discussions (BGD) , 2012,
Abstract: Physical fractionation is a widely used methodology to study soil organic matter (SOM) dynamics, but concerns have been raised that the available fractionation methods do not well describe functional SOM pools. In this study we explore whether physical fractionation techniques isolate soil compartments in a meaningful and functionally relevant way for the investigation of litter-derived nitrogen dynamics at the decadal timescale. We do so by performing aggregate density fractionation (ADF) and particle size-density fractionation (PSDF) on mineral soil samples from two European beech forests a decade after application of 15N labelled litter. Both density and size-based fractionation methods suggested that litter-derived nitrogen became increasingly associated with the mineral phase as decomposition progressed, within aggregates and onto mineral surfaces. However, scientists investigating specific aspects of litter-derived nitrogen dynamics are pointed towards ADF when adsorption and aggregation processes are of interest, whereas PSDF is the superior tool to research the fate of particulate organic matter (POM). Some methodological caveats were observed mainly for the PSDF procedure, the most important one being that fine fractions isolated after sonication can not be linked to any defined decomposition pathway or protective mechanism. This also implies that historical assumptions about the "adsorbed" state of carbon associated with fine fractions need to be re-evaluated. Finally, this work demonstrates that establishing a comprehensive picture of whole soil OM dynamics requires a combination of both methodologies and we offer a suggestion for an efficient combination of the density and size-based approaches.
Corrosion Mechanism of Cemented Soil in MgCl2 Solution
Bai, X.-H.,Han, P.-J.,Tong, T.,Zhang, W.-B.
- , 2014, DOI: 10.15255/KUI.2013.025
Abstract: Sa？etak Mechanical properties of the cemented soil will be reduced when cemented soils are applied in the MgCl2 corrosive environment to conduct seepage control in hydraulic engineering. The corrosive conditions will inevitably cause serious damage to the cement-soil composite, and further reduce stablity of the whole structure. Therefore, this cementation technique could be commonly used to stabilize infrastructures. More engineering practices regarding the reduction in mechanical properties of cemented soil in the MgCl2 environment are required. To simulate and study the corrosion process, a series of tests including photographing, unconfined compression tests, and measuring Mg2+ and Cl？ concentrations of solution were conducted on cured cemented soil blocks with different concentrations of MgCl2 solutions. Results show that the surface corrosion of the sample increases while the compression strength decreases with the increase in solution concentration given the same curing time of the concrete block. Chemical analysis of the corrosive environment indicates that the volumes of new products such as CaCl2 ？ 6 H2O and Mg2(OH)3Cl ？ 4 H2O amount to seven times that of Ca(OH)2 after reaction. The corrosion of cemented soil is a sort of crystallizing corrosion. The Mg(OH)2 takes chemical reactions with 3 CaO ？ 2 SiO2 ？ 3 H2O and forms new products such as MgO ？ SiO2 ？ H2O, which is a sort of dissolving corrosion. In addition, the authors analysed the relationships between the unconfined compressive strength of cemented soils cured for 28 days and the initial concentrations of Mg2+ and Cl？. Finally, the regression equations of the strength were established
Mehanizam korozije cementiranog tla u otopini MgCl2
Bai, X.-H.,Han, P.-J.,Tong, T.,Zhang, W.-B.
- , 2014, DOI: 10.15255/KUI.2013.025
Abstract: Sa？etak Mehani？ka svojstva cementiranog tla slabe kada je cementacija primjenjena u hidrotehnici za kontrolu propusnosti tla u korodiraju？em okru？enju s MgCl2. Korozija uzrokuje ozbiljnu ？tetu kompozitu tla i cementa te dodatno smanjuje stabilnost cijele strukture. Stoga je potrebno podrobnije istra？iti mehanizme kojima opadaju mehani？ka svojstva cementiranog tla pod utjecajem MgCl2. Kako bi se simulirali i prou？avali erozijski procesi, proveden je niz ispitivanja na blokovima cementiranog tla u otopinama MgCl2 razli？itih koncentracija, uklju？uju？i fotografiranje, ispitivanje neograni？ene tla？ne ？vrsto？e i mjerenja koncentracije Mg2+ i Cl？. S pove？anjem koncentracije raste stupanj korozije na povr？ini uzoraka dok se posmi？na ？vrsto？a smanjuje. Kemijska analiza korozijskog okoli？a pokazuje da novonastali spojevi kao ？to su CaCl2 ？ 6 H2O i Mg2(OH)3Cl ？ 4 H2O imaju sedam puta obujam ve？i od Ca(OH)2. Korozija cementiranog tla vrsta je kristalne korozije i Mg(OH)2 reagira s 3 CaO ？ 2 SiO2 ？ 3 H2O te nastaje MgO ？ SiO2 ？ H2O. Istodobno je analizirana veza izme？u po？etnih koncentracija iona Mg2+ i Cl？ i ？vrsto？e te na？ene regresijske funkcije ？vrsto？e
PIXE analysis of the obsidian support of two paintings from the Louvre by Murillo
Calligaro, T;Chiappero, P.-J;Gendrón, F;Gonthier, E;Meslay, O;Poupeau, G;Tenorio, D;
Revista mexicana de física , 2007,
Abstract: the very unusual black backings of two paintings by the spanish master murillo (1617-1682) representing passion scenes, on display at the louvre museum, have been analyzed by pixe with the aglae facility of the c2rmf. the support proved to be obsidian, a natural volcanic glass widely employed to produce archeological artefacts, in particular in south and meso-américa. five archeological artifacts with similar shape to the paintings called "obsidian mirrors", originating from méxico and belonging to the collections of the musée de l'homme in paris, have been analyzed and the composition of four of them showed to be very similar to murillo's obsidians. the comparison with the results obtained on reference obsidian samples from mexican sources and with data from the literature by instrumental neutron activation analysis (inaa) suggested that the ucareo/zinapécuaro, michoacán, méxico is the source of the obsidian employed for the paintings. a field trip to this area was therefore organized to collect samples whose natural slab shape and chemical composition confirmed the ucareo provenance hypothesis. the rectangular backing of murillo's paintings are unlikely archaeological artefacts but rather objects specially made after the spanish conquest by mesoamerican craftsmen, among which some were exported to europe where murillo spent all his life. the observation, in the walls of the church and other christian monuments in ucareo, of obsidian inlays, a material of particular significance in the pre-hispanic culture, underlines the complex intrication of native culture and european influences which are also carried by murillo's paintings. meanwhile, a third painting on obsidian by murillo as been identified in the museum of fine arts of houston, texas, u.s.a. this study also points out that even if the ranges of elements dosed by pixe and inaa do not fully overlap, the measurements obtained by both techniques can be efficiently used for provenancing obsidians objects.
Introduction to the Special Issue on Sensor Networks, Ubiquitous and Trustworthy Computing
Jeffrey J. P. Tsai
International Journal of Distributed Sensor Networks , 2007, DOI: 10.1080/15501320701252771
Abstract:
Magnetic field dependence of the penetration depth of d-wave superconductors with strong isolated impurities
Shan-Wen Tsai,P. J. Hirschfeld
Physics , 2003, DOI: 10.1016/j.physc.2004.03.178
Abstract: A d-wave superconductor with isolated strong non-magnetic impurities should exhibit an upturn in the penetration depth at low temperatures. Here we calculate how an external magnetic field supresses this effect.
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