bluuebunny/crossref_metadata_2025 huggingface dataset:
New amphiphilic glycopolymers by click functionalization of random copolymers – application to the colloidal stabilisation of polymer nanoparticles and their interaction with concanavalin A lectin
Authors: Otman Otman , Boullanger Paul , Drockenmuller Eric , Hamaide Thierry
Published: June 2010

Glycopolymers with mannose units were readily prepared by click chemistry of an azido mannopyranoside derivative and a poly(propargyl acrylate-co-N-vinyl pyrrolidone). These glycopolymers were used as polymer surfactants, in order to obtain glycosylated polycaprolactone nanoparticles. Optimum stabilization for long time storage was achieved by using a mixture of glycopolymers and the non-ionic triblock copolymer Pluronic® F-68. The mannose moieties are accessible at the surface of nanoparticles and available for molecular recognition by concanavalin A lectin. Interaction of mannose units with the lectin were evaluated by measuring the changes in nanoparticles size by dynamic light scattering in dilute media.
Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP
Authors: Adekunle Olubummo , Tanner Susanne , Binder Wolfgang H
Published: June 2010

We report on the block copolymerization of two structurally different norbornene monomers (±)-endo,exo-bicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid dimethylester (7), and (±)-endo,exo-bicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid bis(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yl) ester (9) using ruthenium based Grubbs’ type initiators [(PCy3)2Cl2Ru(benzylidene)]G1(PCy3 = tricyclohexylphosphine), [(H2IMes)(PCy3)Cl2Ru(benzylidene)]G2(H2IMes = 1,3-bis(mesityl)-2-imidazolidinylidene), [(H2IMes)(py)2Cl2Ru(benzylidene)]G3(py = pyridine or 3-bromopyridine) and Umicore type initiators [(PCy3)2Cl2Ru(3-phenylinden-1-ylidene)]U1(PCy3 = tricyclohexylphosphine), [(H2IMes)(PCy3)Cl2Ru(3-phenylinden-1-ylidene)]U2(H2IMes = 1,3-bis(mesityl)-2-imidazolidinylidene), [(H2IMes)(py)Cl2Ru(3-phenylinden-1-ylidene)]U3(py = pyridine or 3-bromopyridine) via ring opening polymerization (ROMP). The crossover reaction and the polymerization kinetics were investigated using matrix assisted laser desorption ionization mass spectroscopy (MALDI-TOF) and nuclear magnetic resonance (NMR), respectively. MALDI showed that there was a complete crossover reaction after the addition of 25 equivalents of the second monomer. NMR investigation showed thatU3gave a faster rate of polymerization in comparison toU1. The synthesis of block copolymers with molecular weights up toMn= 31 000 g/mol with low polydispersities (Mw/Mn= 1.2) is reported.
Lipoprotein Subclasses Determined by Nuclear Magnetic Resonance Spectroscopy and Coronary Atherosclerosis in Patients with Rheumatoid Arthritis
Authors: CHUNG CECILIA P. , OESER ANNETTE , RAGGI PAOLO , SOKKA TUULIKKI , PINCUS THEODORE , SOLUS JOSEPH F. , LINTON MACRAE F. , FAZIO SERGIO , STEIN C. MICHAEL
Published: June 2010

Objective.

Patients with rheumatoid arthritis (RA) are at increased risk of atherosclerosis, but routine lipid measurements differ little from those of people without RA. We examined the hypothesis that lipid subclasses determined by nuclear magnetic resonance spectroscopy (NMR) differed in patients with RA compared to controls and are associated with disease activity and the presence of coronary-artery atherosclerosis.

Methods.

We measured lipoprotein subclasses by NMR in 139 patients with RA and 75 control subjects. Lipoproteins were classified as large low-density lipoprotein (LDL; diameter range 21.2–27.0 nm), small LDL (18.0–21.2 nm), large high-density lipoprotein (HDL; 8.2–13.0 nm), small HDL (7.3–8.2 nm), and total very low-density lipoprotein (VLDL; ≥ 27 nm). All subjects underwent an interview and examination; disease activity was quantified by the 28-joint Disease Activity Score (DAS28) and coronary artery calcification (CAC) was measured with electron-beam computed tomography.

Results.

Concentrations of small HDL particles were lower in patients with RA (18.2 ± 5.4 nmol/l) than controls (20.0 ± 4.4 nmol/l; p = 0.003). In patients with RA, small HDL concentrations were inversely associated with DAS28 (rho = −0.18, p = 0.04) and C-reactive protein (rho = −0.25, p = 0.004). Concentrations of small HDL were lower in patients with coronary calcification (17.4 ± 4.8 nmol/l) than in those without (19.0 ± 5.8 nmol/l; p = 0.03). This relationship remained significant after adjustment for the Framingham risk score and DAS28 (p = 0.025). Concentrations of small LDL particles were lower in patients with RA (1390 ± 722 nmol/l) than in controls (1518 ± 654 nmol/l; p = 0.05), but did not correlate with DAS28 or CAC.

Conclusion.

Low concentrations of small HDL particles may contribute to increased coronary atherosclerosis in patients with RA.
Canadian Recommendations for Use of Methotrexate in Patients with Rheumatoid Arthritis
Authors: KATCHAMART WANRUCHADA , BOURRÉ-TESSIER JOSIANE , DONKA TIMEA , DROUIN JULIE , ROHEKAR GINA , BYKERK VIVIAN P. , HARAOUI BOULOS , LECLERQ SHARON , MOSHER DIANNE P. , POPE JANET E. , SHOJANIA KAM , THOMSON JOHN , THORNE J. CARTER , BOMBARDIER CLAIRE
Published: June 2010

Objective.

To develop recommendations for the use of methotrexate (MTX) in patients with rheumatoid arthritis.

Methods.

Canadian rheumatologists who participated in the international 3e Initiative in Rheumatology (evidence, expertise, exchange) in 2007–2008 formulated 5 unique Canadian questions. A bibliographic team systematically reviewed the relevant literature on these 5 topics. An expert committee consisting of 26 rheumatologists from across Canada was convened, and a set of recommendations was proposed based on the results of systematic reviews combined with expert opinions using a nominal group consensus process.

Results.

The 5 questions addressed drug interactions, predictors of response, strategies to reduce non-serious side effects, variables to assess clinical response, and incorporating patient preference into decision-making. The systematic review retrieved 93 pertinent articles; this evidence was presented to the expert committee during the interactive workshop. After extensive discussion and voting, a total of 9 recommendations were formulated: 2 on drug interactions, 1 on predictors of response, 2 on strategies to reduce non-serious side effects, 3 on variables to assess clinical response, and 1 on incorporating patient preferences into decision-making. The level of evidence and the strength of recommendations are reported. Agreement among panelists ranged from 85% to 100%.

Conclusion.

Nine recommendations pertaining to the use of MTX in daily practice were developed using an evidence-based approach followed by expert/physician consensus with high level of agreement.
ADAMTS5 Is a Biomarker for Prediction of Response to Infliximab in Patients with Rheumatoid Arthritis
Authors: TSUZAKA KENSEI , ITAMI YUKA , TAKEUCHI TSUTOMU , SHINOZAKI NAOSHI , MORISHITA TETSUO
Published: June 2010

Objective.

To identify a biomarker for prediction of the response to infliximab (IFX) in patients with rheumatoid arthritis (RA), we focused on a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) that seems to play a key role in aggrecan degradation in cartilage.

Methods.

Seventy-three randomly selected patients with active RA were treated with IFX. Peripheral blood samples were collected at baseline and ADAMTS5 messenger RNA (mRNA) was quantified using real-time polymerase chain reaction.

Results.

Baseline ADAMTS5 mRNA levels in the good responder group were significantly lower (1.84 ± 1.56; p = 0.0408) than those in the moderate and nonresponder groups (2.54 ± 1.70) at 38 weeks of treatment with IFX. The 28-joint count Disease Activity Score (DAS28) at 38 weeks of treatment was significantly lower in the low ADAMTS5 group (2.30 ± 1.28; p = 0.0038) than in the high ADAMTS5 group (3.90 ± 1.61). The percentage reduction of the DAS28 was significantly higher in the low ADAMTS5 group (52.5% ± 28.8%; p = 0.0156) than in the high ADAMTS5 group (29.4% ± 27.2%). Further, the Δ Health Assessment Questionnaire (ΔHAQ) score, an estimate of the improvement in the HAQ score, at 38 weeks of treatment was significantly higher in the low ADAMTS5 group (1.18 ± 0.60; p = 0.0102) than in the high ADAMTS5 group (0.21 ± 0.78). The positive predictive value of a low baseline ADAMTS5 level for predicting good response and remission (DAS28 < 2.6 at 38 weeks) was 90.0% and 70.0%, respectively.

Conclusion.

The baseline ADAMTS5 mRNA level is a candidate biomarker for prediction of the response to IFX in patients with RA.
Clay raw materials from the Triassic Red Beds (Northern Jaen, Spain) for making ceramic construction materials
Authors: Vázquez M. , Jiménez-Millán J.
Published: June 2010

The suitability of Triassic Red Beds from northern Jaén in the production of structural clay products has been evaluated. These materials have high phyllosilicate contents (36-69%), although some samples are enriched in quartz (
Characterization and selection of mortars in the restoration of the Kings Portal (Benavente, Zamora)
Authors: De Luxan M. P. , Dorrego F.
Published: June 2010

In the selection of materials required by any work on Architectural Heritage, a series of special requirements must be borne in mind which are essential to guarantee the application of the repairs. In this work the guidelines and basic criteria for the selection of repair mortars that have led to the design of mortars to restore the Kings Portal of the church of San Juan del Mercado (Benavente, Zamora), carved in stone in the Romanesque style and later polychromed are shown. The study is based on the characteristics of the ancient historical mortars, the compatibility of the restoration mortars with the mortars already existing in the monument, and the application needs of the specific work. Finally, the characteristics and properties of the specific repair mortar chosen are shown
Constructive applications of composite gypsum reinforced with Typha Latifolia fibres
Authors: Garcia Santos A.
Published: June 2010

The present research analyses the possibility to reinforce gypsum using enea fibres (Typha Latifolia) creating a compound material in wich the fibres contribute to increase mechanical resistance, producing as well a reduction of the weight and a possible regulation of the set time.
Significance of steel electrical resistance method in the evaluation of reinforcement corrosion in cementitious systems
Authors: Krajci L. , Janotka I.
Published: June 2010

The suitable detection system of steel reinforcement corrosion in concrete structures contributes to the reduction of their maintenance costs. Method of steel electrical resistance represents non-destructive monitoring of steel in cementitious systems. Specially prepared and arranged test specimen of steel as a corrosion sensor is embedded in mortar specimen. Verification tests of this method based on chloride corrosion of steel in mortars as well as its visual inspection are introduced. Significance of steel electrical resistance method lies in the expression of steel corrosion by these quantitative parameters: reduction of cross-section of steel, thickness of corroded layer and loss of weight of steel material. This method is an integral method that allows the indirect determination of mentioned corrosion characteristics. The comparison of verified method with gravimetric evaluation of steel corrosion gives a good correspondence. Test results on mortars with calcium chloride dosages between 0.5% and 4.0% by weight of cement prove high sensitiveness and reliability of steel electrical resistance method.
Location of quarries of non traditional stony materials in the architecture of Madrid: the Crypt of the Cathedral of Santa María la Real de la Almudena
Authors: Gómez-Heras M. , Fort González R.
Published: June 2010

The combination between petrological data and historical documentation sources is necessary to establish an accurate methodology for the location of the original quarries of the stony materials used in a determinate historical building. The petrographical and petrophisical data correlation combined with a multivariate statistical analysis, by means of similarity indexes of both the materials in the building and the probable source geological formations, allows the location even when the documental sources would he incomplete or lost, or when the source areas would be modified. The works of location of original quarries used in architectural heritage are important since they allow improving the works of restoration on a building by means of the possibility of using identical materials for substitution or reintegration of decayed elements. The establishment of the original areas also offers the possibility of obtaining unaltered semipiés to evaluate the state and processes of decay of the building as well as to use this rough material to test the effectivity and durability of protective arid consolidant treatments in the building and monuments. The aim of this work has been to characterize and to locate the origin of the stony material in the stonework of the Crypt of the Cathedral of Santa María la Real de la Almudena (Madrid). These stone types came from quarries located in Viana de Jadraque (Guadalajara, Spain) and in the central area of Portugal. These materials do not correspond with the traditional ones used in the city of Madrid and its presence is due to the opening of new ways of transport in the second half of the 19"' centuiy.
Use of alternative fuels in cement manufacture. Effect on clinker and cement characteristics and properties
Authors: Puertas F. , Blanco-Varela M. T.
Published: June 2010

This paper compares industrial clinker and cement produced using conventional and alternative fuels (animal meal, tyres or a mixture of the two). The results show no relevant differences in terms of mineralogical composition between the clinker manufactured with alternative fuels and the product obtained using conventional fuel. Clinker produced with alternative fuels at any one factory have a very similar or even lower content in heavy metals than the product manufactured with conventional fuel in the same plant (with the sole exception of Zn when the alternative fuel used is shredded tyres). Mineralogical and morphological analyses reveal no significant differences between the two types of products that can be attributed to the type of fuel used in their manufacture. All six types of cement studied are compliant with the existing legislation as regards both physical and chemical properties. Cement compressive strength is found to be to legal standards regardless of the type of fuel used. Finally, the rheological properties of the cement paste are observed to be unaffected by the type of fuel.
Analysis of thermal process of pozzolan production
Authors: Mejía De Gutiérrez R. , Torres A. J. , Guerrero C. E.
Published: June 2010

The objective of this study was evaluated the effect of heat treatment parameters on the pozzolanic activity of natural kaolin clays. The experimental design included three factors: kaolin type, temperature and time. Five types of Colombian kaolin clays were thermally treated from 400 to 1000 °C by 1, 2, and 3 hours. The raw materials and the products obtained were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Differential Thermal / Thermo gravimetric Analysis (DTAJ TGA). The pozzolanic activity of thermally treated samples according to chemical and mechanical tests was investigated.
Carbonation kinetics in roman-like lime mortar
Authors: Sánchez-Moral S. , García-Guinea J. , Luque L. Luque , González-Martín R. , López-Arce P.
Published: June 2010

The kinetic parameterisation of lime mortar carbonation is a useful technique for understanding ancient building methods and the long-lived physical-chemical stability of roman monuments. Portlandite (Ca(OH)2) binders harden in the air on contact with atmospheric CO2, producing CaCO3. Water evaporation and the presence of silicate aggregates have a three-fold effect: prompting the development of a pore system that permits CO2, self-diffusion, reducing shrinkage and cracking during drying and (possibly) giving rise to subsequent pozzolanic reactions. The present survey involved air-hardening a series of roman-like lime mortars which differed in terms of: (i) type of aggregate, volcanic tephra and arkose; (ii) aggregate/binder ratio, 1:2 as used in the catacombs and 1:4 as found in standard roman construction and (iii) temperature, the 17 ºC prevailing in underground environments and the 30 ºC typical of warm Mediterranean areas. The analyses that provided the most useful information were performed in a classic X-ray diffractometer adapted to accommodate an author-designed chamber in which temperature control was achieved by an internal refrigerant and a PID-governed electrical heater Additional data were obtained with DTA and environmental scanning electron microscopy (ESEM). The tests conducted on the Roman-like lime mortars manufactured for the experiment showed that the hardening temperature is a critical factor in the initial phases of carbonation. Calcite precipitation rates and total mineral precipitation increased with temperature, but fell very quickly as calcite precipitated. In theoretical calculations assuming an open reactor with continuous CO2, input, total calcitisation time was found to be 156 m in. at 30 ºC and 175 min. at 17 ºC, whilst in the mortars actually hardened in the experimental part of the study, calcitisation gradually blocked the flow or CO2, gas into the system. Roman-like mortars air-hardened at 30 ºC displayed higher initial calcitisation rates, early system closure and low final carbonation levels. The calcitisation rates of mortars made with pozzolana aggregates were higher than the arkose mortar rates due to the higher intra-particle porosity (nearly 40%) of the volcanic rock fragments.
A comparative experimental study of steel fibre-additive reinforced concrete beams
Authors: Altun F. , Haktanir T.
Published: June 2010

Five different batches of class C20 concrete, containing Dramix-RC-80/60-BN steel fibers (SFs) as additives at doses of 0, 30, 40, 50 and 60 kg/m3, and six Ø 15x30 cm prisms were poured from each batch. Standard crushing tests were run on all the specimens and the respective load-displacement and stress-strain curves were plotted. Toughness, ultimate compressive strength and the modulus of elasticity were determined for all specimens. The compressive strength and modulus of elasticity declined in 30 kg/m3 steel-fiber-additive concrete (SFAC) by 9% and 7% compared to the reference C20 concrete without SFs, and the area under the load-deflection curve grew more than twofold. In concrete with a higher SF dosage, the differences in strength and elasticity were around I0% whilst toughness was about the same. Because toughness values were similar in 30, 40, 50 and 60 kg/m3 plain SF-additive concrete and the strength and modulus of elasticity were slightly better in the mixes with the smallest proportion of SF for reasons of economy, 30 kg/m3 was taken as the optimum dose of steel fiber to be added to the reinforced concrete used in a second phase of the study. Hence, of the six reinforced concrete (RC) beams made, all of equal size and with the same under-reinforced tensile reinforcement design, three were made with concrete containing the above-mentioned dose of SF. In addition to compressive strength, these beams were tested for flexural strength, which was found to be 18%) greater for the SFARC beams than the ordinary RC beams, and the upper arms of the load versus mid-span deflection curves prior to ultimate failure of the SFARC beams were considerably longer than the same arms on the curves for ordinary RC beams.
Intrinsic factors determining the physical behaviour and durability of the Miocene sandstones used to build the Zaghouan-Carthage aqueduct (Tunis)
Authors: Zoghlami K. , Gómez-Gras D. , De Luxán M. P.
Published: June 2010

The present paper addresses the relationship between the intrinsic factors, physical behaviour and durability of Miocene Age sandstone used to build Tunisian Heritage Monuments, and more specifically the Zaghouan-Carthage aqueduct. A petrography study (optical microscopy and mercury intrusion porosi metry) was conducted to characterize the porous system of the rock. Stone hydric behaviour was also determined by finding vacuum saturation, desorption, capillary and water vapor transmission. Finally, mechanical strength (compressive strength, abrasion resistance) and durability (via accelerated sodium sulfate crystallization ageing) were also found. The results obtained were indicative of good hydric performance due to the macroporous nature of the stone and the connectivity of its porous system. This rock was also found to have very low mechanical strength due to its scant lithification, making it particularly susceptible to salt weathering. It was also observed to be highly resistant to chemical alteration, given the absence of chemically unstable minerals in its composition. The durability of the material was consequently found to depend directly on the presence or absence of salts in the monument.
Performance of alkaline activated slag at high temperatures
Authors: Mejía de Gutiérrez R. , Maldonado J. , Gutiérrez C.
Published: June 2010

This paper presents an investigation into the performance of alkali-activated slag (AAS) mortar exposed to elevated temperatures. Sodium silicate, sodium hydroxide and a mix (waterglass) with a modulus (SiO2/Na20) of 1.5 were used as activators. The specimens were heated in an electric furnace up to 1000 ºC in steps of 200 ºC for a constant period of 2 hours. The weight loss, residual compressive strength, resistance to chloride ion penetration, porosity and capillary sorption were evaluated and the results were compared with those of ordinary and blended Portland cement mortar
Metakaolin sand – a promising addition for Portland cement
Authors: Janotka I. , Puertas F. , Palacios M. , Varga C. , Krajči L.
Published: June 2010

The kaolin sand resource at the Vyšný Petrovec quarry in Slovakia comes to a total of 20 megatonnes. The metakaolin material obtained by heating kaolin sand at 650 ºC contains from 31.5 to 40% (wt) metakaolinite, as well as illite, muscovite, quartz and feldspar. The aim of this study was to verify whether this calcined sand (MK1) is a pozzolanic material and characterize the cements and mortars prepared with it. The hydration reactions taking place in the blends were assessed with conduction calorimetry, X-ray diffraction (XRD) and differential thermal analysis-thermogravimetry (DTA-TG). Blend and mortar strength development and pore structure were also evaluated. The results obtained showed that this metakaolin sand (MK-1) is a pozzolanic material apt for use as a cement addition and for making mortars.
Environmental effects of urbanization – the role of urban designers
Authors: Emmanuel R
Published: May 2010

DOI: 10.4038/besl.v7i2.1940Built-Environment Sri Lanka Vol.7(2) 29-30
A Decision Support System for the Selection of Best Procurement System in Construction
Authors: Ratnasabapathy Shiyamini , Rameezdeen Raufdeen
Published: May 2010

The procurement system is a key means through which the client creates pre-conditions for successful achievement of project specific objectives. Wrong selection of procurement system generally leads to project failure and client dissatisfaction. Therefore, a systematic and realistic approach for the selection of the best procurement system is critical to the success of any project to achieve the clients' ultimate goals. As far as Sri Lankan construction industry is concerned, the practice of procurement selection is rather unstructured and ad hoc. Therefore, a realistic and consistent approach is essential to aid the clients in selecting the most appropriate procurement system. This paper presents a Decision Support System developed for the procurement selection based on Multi Attribute Utility Technique. Four rounds of Delphi surveys were carried out to investigate the most significant factors and their level of influence on various construction procurement systems. From the third and fourth round of Delphi, utility values for each factor against various procurement systems were derived. Based on decisive factors and the utility values derived form the survey, a multi-criteria model was developed. The special feature of the model is the inclusion of a set of exclusive selection criteria at macro level and wide range of various procurement options. The outcome of the model was evaluated for its applicability and efficiency with the use of multiple case studies and an expert opinion survey. Finally, the evaluated model was further enhanced to a Decision Support System. The model has the potential to assist the clients/their consultants and it seeks to overcome any inconsistency in the effective decision making process. DOI: 10.4038/besl.v7i2.1943 Built-Environment Sri Lanka Vol.7(2) 53-43
Biological production of methyl bromide by cultures of marine phytoplankton
Authors: Sœmundsdóttir Stefanía , Matrai Patricia A.
Published: May 2010

Methyl bromide production was followed in cultures of a selection of marine phytoplankton species throughout their growth cycle. The cultures were species common to coastal and(or) open ocean areas, as well as originating from various latitudinal bands. Methyl bromide was produced by 13 out of 19 species tested, with production rates ranging from 1.7 to 30.1 pg CH3Br µg−1 Chl a d−1. Species that are strictly coastal or more abundant in coastal areas appeared to be stronger producers of CH,Br than species that are more abundant in open ocean areas. The prymnesiophyte Phaeocystis sp., a bloom‐forming, ubiquitous species, showed the highest daily production rate normalized to Chl a of 30.1 pg CH3Br µg−1 Chl a d−1. The range of methyl bromide production by the phytoplankton cultures tested suggests that the input of methyl bromide by marine phytoplankton can be significant in coastal oceans.
Sources of inorganic carbon for marine microalgal photosynthesis: A reassessment of δ13C data from batch culture studies of Thalassiosira pseudonana and Emiliania huxleyi
Authors: A. Laws Edward , Thompson Peter A. , Popp Brian N. , Bidigure Robert R.
Published: May 2010

A reevaluation of previously published analyses of stable carbon isotope fractionation by batch cultures of Thalassiosira pseudonana and Emiliania huxleyi indicates that the Rayleigh distillation model was used to model δ13C uptake incorrectly. Correct use of the model shows that the relationship between the δ13C of the particulate organic carbon (δp) and the concentration of the dissolved inorganic carbon (DIC) at the time of harvest can be equally well described by a model assuming bicarbonate or CO2 uptake. The lack of a correlation between growth rate and δp in the T. pseudonana results suggests that growth rate and the intracellular CO2 concentration are directly proportional. Theoretical considerations indicate that the T. pseudonana cultures started at a pH of 9.2 would have become CO2 limited before harvest and that this species must have the ability to utilize bicarbonate when CO2 becomes limiting. The similarity of the T. pseudonana δp results from cultures started at pH 8.2 and 9.2 suggests that the form of DIC entering the cells was the same in both sets of experiments. The results are consistent with (1) uptake of bicarbonate or (2) uptake of CO2, with external carbonic anhydrasemediated conversion of bicarbonate to CO2 supplementing the uncatalyzed supply of CO2 when the latter becomes limiting. Analysis of the δ13C of both particulate organic carbon and coccolith carbon in the case of E. huxleyi suggests that the cells were taking up primarily bicarbonate at low growth rates, but that at high growth rates the DIC used for photosynthesis was derived almost entirely from uptake of CO2. The DIC utilized for coccolith formation seems to have been substantially diluted by isotopically light DIC derived from respiration at high growth rates.
Rapid potential rates of extracellular enzymatic hydrolysis in Arctic sediments
Authors: Arnosti C.
Published: May 2010

The extracellular enzymatic hydrolysis rates of three fluorescently‐labeled polysaccharides (pullulan, laminarin, and xylan) were measured in the upper ∼11 cm of sediment cores collected near Svalbard in the Arctic Ocean. The three polysaccharides differ in molecular weight (200,000, ∼6,000, and ∼8,000 Da for pullulan, laminarin, and xylan, respectively), as well as in monomer composition, linkage position, and anomeric configuration, and are most probably hydrolyzed by distinctly different enzymes. Potential hydrolysis rates of pullulan and laminarin were rapid throughout the sediment cores (average rates of 52 cuts per nmol glucose cm−3 hr−1 for pullulan, 38 cuts per nmol glucose cm−3 hr−1 for laminarin) and were comparable to rates measured in sediment cores from more temperate sites. Xylan potential hydrolysis rates were considerably slower at all Svalbard stations (average of 3 cuts per nmol xylose cm−3 hr−1). Rapid microbial remineralization of particulate organic carbon requires high levels of extracellular enzyme activity; the high potential hydrolysis rates of tluorescently‐labeled pullulan and laminarin in Svalbard sediments demonstrate that at least some types of extracellular enzymes can function rapidly in permanently cold environments.
Tagging crustacean larvae: Assimilation and retention of trace elements
Authors: Anastasia Jean R. , Morgan Steven G. , Fisher Nicholas S.
Published: May 2010

The uptake, assimilation, and retention of Se, Co, Ag, Ce, Eu, and Gd by crustacean larvae were measured to assess the suitability of these elements as tags for determining larval dispersal patterns and mortality rates. Gamma‐emitting radioisotopes were used to determine the uptake and retention of each element by larvae of three crabs, Dyspanopeus sayi, Uca pugnax, and Sesarma reticulatum, and one barnacle, Semibalanus bolunoides. Selenium was readily taken up by larvae from their food, was assimilated at efficiencies of 61–93%, was retained at concentrations detectable above background levels for weeks, and did not consistently affect larval survival or development in the laboratory. The other elements were not absorbed sufficiently from food or were not retained long enough to serve as appropriate tags for monitoring larval dispersal. Thus, only Se seemed to be transferred efficiently between trophic levels and is suitable as a larval tag.
Organic carbon partitioning during spring phytoplankton blooms in the Ross Sea polynya and the Sargasso Sea
Authors: Carlson Craig A. , Ducklow Hugh W. , Hansell Dennis A. , Smith Walker O.
Published: May 2010

In this study we evaluate the partitioning of organic carbon between the particulate and dissolved pools during spring phytoplankton blooms in the Ross Sea, Antarctica, and the Sargasso Sea. As part of a multidisciplinary project in the Ross Sea polynya we investigated the dynamics of the dissolved organic carbon (DOC) pool and the role it played in the carbon cycle during the 1994 spring phytoplankton bloom. Phytoplankton biomass during the bloom was dominated by an Antarctic Phaeocystis sp. We determined primary productivity (PP; via H14CO3, incubations), particulate organic carbon (POC), bacterial productivity (BP; via [3H]thymidine incorporation), and DOC during two occupations of 76°30′S from 175°W to 168°E. Results from this bloom are compared to blooms observed in the Sargasso Sea in the vicinity of the Bermuda Atlantic Time‐Series Study station (BATS). We present data that demonstrate clear differences in the production, biolability, and accumulation of DOC between the two ocean regions. Despite four‐ to fivefold greater PP in the Ross Sea, almost an order of magnitude less DOC (mmol m−2) accumulated during the Ross Sea bloom compared to the Sargasso Sea blooms. In the Ross Sea 89% (˜1 mol C m−2) of the total organic carbon (TOC) that accumulated during the bloom was partitioned as POC, with the remaining 11% (˜0.1 mol C m−2) partitioned as DOC. In contrast, a mean of 86% (0.7.5–1.0 mol m−2) of TOC accumulated as DOC during the 1992, 1993, and 1995 blooms in the Sargasso Sea, with as little as 14% (0.08–0.29 mol C m−2) accumulating as POC. Although a relatively small portion of the fixed carbon was produced as DOC in the Ross Sea, the bacterial carbon demand indicated that a qualitatively more labile carbon was produced in the Ross Sea compared to the Sargasso Sea. There are fundamental differences in organic carbon partitioning between the two systems that may be controlled by plankton community structure and food‐web dynamics.
Experimental study of microbial P limitation in the eastern Mediterranean
Authors: Zohary Tamar , Robarts Richard D.
Published: May 2010

In this study we experimentally tested the hypothesis that phosphorus was the primary nutrient limiting phytoplankton and bacterial growth in the eastern Mediterranean Sea, and examined the spatial variability in P limitation during winter. Complementary measurements were employed using water sampled during January 1995 from nine pelagic stations east of the Straits of Sicily. Ambient concentrations of inorganic P (Pi) in the upper 50 m of the water column in seven of the stations were 20–40 nM. The upper limit of bioavailable P ranged from 6 to 18 nM, suggesting severe P shortage. Orthophosphate turnover time ranged from 2 to 7 h in those Pi‐depleted waters. In nutrient‐enrichment bioassays using subsurface water from the Ionian and Levantine basins, P addition caused significant increases in bacterial activity, bacterial numbers, and chlorophyll a relative to unenriched controls. The addition of NH4+ + Fe + EDTA did not have these effects. In a similar bioassay using Cretan water, microbial growth was obtained even in the unemriched controls, suggesting that other factors (e.g. grazing, light) were influential. Higher ambient P, concentrations were encountered in the Cretan Sea (90 nM) and in the core of the Rhodes gyre (210 nM), where our sampling coincided with a convective mixing event. In those stations, P sufficiency was indicated. We concluded that in the pelagic waters of the eastern Mediterranean in winter, P was the primary limiting nutrient when other factors (such as light or grazing) did not control microbial biomass or activity. In ultra‐oligotrophic waters, a delicate and dynamic balance differentiates between times when the microbial populations are nutrient limited and times when growth becomes limited by other factors. We caution that the interpretation of data obtained using conventional methods that were developed and tested in more enriched systems may not be valid in ultra‐oligotrophic systems.
Photoinhibition and the availability of inorganic carbon restrict photosynthesis by surface blooms of cyanobacteria
Authors: Ibelings Bas W. , Maberly Stephen C.
Published: May 2010

When buoyant cyanobacteria form a surface bloom, they may obtain inorganic carbon from the water and the atmosphere. In this study, artificial blooms of cyanobacteria were exposed to different concentrations of CO2 in the atmosphere and HCO2-1, in the water. The conditions and photosynthetic activity within the bloom were measured with microelectrodes sensing O2, pH, and light. Net rates of photosynthesis increased with the concentration of CO2 in the atmosphere (air = 350 ppm). However, even under 3,500 ppm CO2 , reducing the concentration of inorganic carbon in the water reduced rates of photosynthesis. Thus, both air and water acted as sources of inorganic carbon. Bloom formation may give cyanobacteria an advantage in competition for light and inorganic carbon with other groups of phytoplankton; by placing a dense biomass close to the water surface they are able to intercept a large amount of the flux of light and inorganic carbon. The high surface pH produced in the bloom will promote influx of CO2 from the atmosphere by “chemical enhancement.” The obvious advantage of being close to the water surface may be offset by the risk of photoinhibition at high photon irradiance. The dense packing of colonies in the bloom furthermore caused a high local demand for inorganic carbon and consequently extreme carbon depletion. This combination of high photon irradiance and carbon limitation proved to be especially detrimental in blooms. When the availability of inorganic carbon was restricted, nonphotochemical quenching of fluorescence increased, showing some removal of excess excitation energy, but not to the extent that photodamage was prevented. Depending on the outcome of several interacting processes, surface bloom formation may be advantageous or deleterious for the cyanobacteria involved. This also depends on the environmental conditions to which cells were acclimated prior to bloom formation. Cyanobacteria have a better chance of withstanding the conditions in surface blooms if the cells were already acclimated to high average irradiance prior to floating to the surface.
Determining the contribution of pigments and the nonalgal fractions to total absorption: Toward an improved algorithm
Authors: Varela Ramiro A. , Figueras Francisco G. , Arbones Belén , Agustí Susana
Published: May 2010

Three methods that estimate the algal and nonalgal contributions to the total particulate matter light absorption were analyzed against the experimental Kishino method in a wide variety of environments. We found that one method gave better overall correlations and slopes closer to 1 than did the other methods, but the method overestimated the nonalgal fraction when the nonalgal absorption to total particulate matter absorption proportion in the sample was low. As a result, a correction is suggested and results are compared with those of the other methods, showing that the combined use of the original algorithm and the correction do configure a suitable basis for differentiating the algal and nonalgal fractions using as input only the total particulate light absorption data.
Oxidation of dissolved methane in a eutrophic, shallow lake: Lake Kasumigaura, Japan
Authors: Utsumi Motoo , Nojiri Yukihiro , Nakamura Takeshi , Takeshi Nozawa , Otsuki Akira , Seki Humitake
Published: May 2010

Long‐term seasonal variations in water‐column methane oxidation were studied in the eutrophic, shallow Lake Kasumigaura, Japan. The entire water column was oxic throughout the year. Measurements were taken monthly from July 1991 to March 1996. The oxidation rates were derived from time‐course dissolved methane concentration measurements during the bottle incubation at in situ temperature. The existence of methane oxidation activity in the oxic lake water was confirmed. Methane oxidation was distinctly seasonal, with low activity from January to April and high activity from August to November. Maximum methane oxidation was observed in late summer or early autumn, when the turnover time of dissolved methane was usually shorter than half a day. Methane oxidation activity does not depend on water temperature, dissolved methane concentration, dissolved oxygen, or dissolved inorganic nitrogen. The annual average methane consumption rate was 12.3 ± 15.5 mg CH4 m−2 d−1. Methane oxidation was the dominant methane sink. consuming an annual average of 74% of dissolved methane in the water column of Lake Kasumigaura.
Effects of desiccation/oxidation on the potential for bacterially mediated P release from sediments
Authors: Mitchell A. , Baldwin D. S.
Published: May 2010

The effect of desiccation/oxidation on the potential for phosphorus release from reservoir sediments under anoxic conditions was studied. When sediments were exposed to the air and subsequently dried, their ability to release P under anaerobic conditions was severely limited relative to sediments that were not exposed. Anaerobic P release in response to the addition of a toxicant (formaldehyde), bioavailable carbon sources (acetate or glucose), available sulfur (sulfate), and sulfide were used to infer possible causes for the decrease in anaerobic P release as a function of desiccation/oxidation. A substantial reduction in P release occurred in sediments that had not been exposed when formaldehyde was added. This suggests that anaerobic P release may be microbially driven. Addition of acetate and sulfate slightly enhanced P release from nondesiccated sediments, suggesting some C and(or) S limitation of the bacterial processes occurring in these sediments. Substantial P was released when sulfide was added to the nonexposed sediments, indicating that there is a significant amount of P associated with sulfide‐reducible minerals (e.g. iron oxyhydroxides). Sulfide addition to exposed sediments released only about one‐fourth of the P compared with nonexposed sediments. Furthermore, no additional P was released when sulfate was added to exposed sediments, but P was released in the presence of either glucose or acetate. Together these results indicate that the decrease in potential for P release from exposed sediments was caused by a shift in bacterial community structure (specifically the loss of viable sulfate‐reducing bacteria), carbon limitation as a result of drying, and aging of minerals with which P is associated.
The chemistry, fluxes, and sources of carbon dioxide in the estuarine waters of the Satilla and Altamaha Rivers, Georgia
Authors: Cai Wei‐Jun , Wang Yongchen
Published: May 2010

The pH, alkalinity (Alk), and dissolved inorganic carbon (DIC) in estuarine waters of several rivers of Georgia
in the southeastern United States are reported. Although they discharge into a narrow area in the South Atlantic
Bight, the rivers along the coast of Georgia differ significantly in their drainage area (Piedmont rivers vs. coastal
plain rivers), chemical composition (contents of carbonate and humics), and discharge rates. Large differences in
pH, DIC, and Alk between these rivers clearly reflect the differences of material inputs to the rivers. Dramatic pH
increases in the early stage of mixing (more obvious for the coastal plain rivers) reflect the low buffering capacity
of the river waters despite the high content of humic substances. Flux of riverine DIC to the South Atlantic Bight
is estimated to be 52.5 × l09 mol yr−1. We suggest that the presently available world total riverine DIC flux to the ocean could have much uncertainty if the small river fluxes are important. Calculated pC0, values from the pH and DIC measurements are extremely high in low‐salinity areas (1,000 to >6,000 patm at salinity < 10) as are the corresponding CO2 fluxes to the atmosphere (20 to >250 mol m−2 yr−1 at salinity <l0). Data presented suggest that the most likely causes that sustain the high pCO2 values and high water‐to‐air fluxes in the estuaries are CO2 inputs from organic carbon respiration in the tidally flooded salt marshes and groundwater.
Organic matter mineralization rates in sediments: A within‐ and among‐lake study
Authors: den Heyer Cornelia , Kalff Jacob
Published: May 2010

Organic matter mineralization rates were measured by the accumulation of DIC + CH4 in the water overlying intact cores taken from littoral and protimdal sediments of nine Quebec lakes. The variability in areal carbon mineralization is much greater within lakes than among lakes varying in trophic richness. Organic matter mineralization in littoral sediments is more variable and, on average, threefold higher than in the profundal sediments. Sixty percent of the variation in mean summer mineralization rates is explained by site depth, a surrogate variable that incorporates the effect of temperature and may also be reflecting substrate quality and(or) supply. The lakes‐pecific characteristics most strongly correlated to the residuals of the regression with depth are catchment area‐to‐lake area ratio (CA:LA) and water residence time. In lakes with a larger CA:LA and a shorter residence time, the amount and(or) the quality of organic matter settling to the sediments at a given depth may be reduced, resulting in the lower observed mineralization rates. Total mineralization in the sediments is, not surprisingly, greater in larger lakes but the rate per unit area is smaller, reflecting the decreased importance of the littoral zone. More than half (54–100%) of the DIC + CH4 produced in the sediments is from the littoral zone. Yet, because of the large biomass in epilinmetic waters, the littoral sediments account for <20% of the sum of metabolism in the epilimnetic water column and underlying sediments. The relative importance of the sediments in metabolism in lakes is a function of both the trophy and lake morphometry. In deep lakes a smaller proportion of total respiration occurs in the sediments than in shallow lakes, and in eutrophic lakes the sediments account for a smaller proportion of total respiration than in oligotrophic lakes.
The onset of meromixis during restoration of Mono Lake, California: Unintended consequences of reducing water diversions
Authors: Jellison Robert , Romero José , Melack John M.
Published: May 2010

Diversions of freshwater streams out of the Mono Lake basin since 1941 have led to a gradual decrease in size, an approximate doubling of lake‐water salinity, and associated environmental impacts. To restore Mono Lake, the state of California amended Los Angeles' water rights by restricting diversions until the surface elevation rises 6 m above its 1982 low stand. Given the reduced volume of the lake, the cessation of diversions and an above average snowmelt runoff in 1995 led to an abrupt l‐m rise in surface elevation and the onset of persistent chemical stratification (meromixis). Long‐term simulations using a one‐dimensional vertical mixing model modified for application to hypersaline Mono Lake predict the current episode of meromixis is likely to persist for several decades, given the management policy of the state. A similar episode of meromixis in the mid‐1980s following record snowmelt runoff in 1982–1983 and reduced diversions led to reductions in vertical mixing, recycling of nutrients, and primary productivity. That episode ended following an extended period of drought and the resumption of diversions. The ecological consequences of the predicted multidecade period of meromixis are largely unknown.
Effects of phosphorus‐deficient diets on the carbon and phosphorus balance of Daphnia magna
Authors: DeMott William R. , Gulati Ramesh D. , Siewertsen Klaas
Published: May 2010

We used laboratory growth and feeding experiments to study the balance of carbon (C) and phosphorus (P) in Daphnia magna. Daphnia were fed high‐concentration mixtures of P‐sufficient and P‐deficient green algae (Scenedesmus acutus; molar C:P 80 and 900, respectively) or mixtures of P‐deficient Scenedesmus and a P‐rich cyanobacterium (Synechococcus elongatus; C:P = 60). P‐deficient diets resulted in, rapid declines in the growth rates of Daphnia and unexpected declines in Daphnia's P‐to‐dry‐weight ratio. P‐deficient Scenedesmus and P‐rich Synechococcus supported poor growth as sole foods but improved growth in mixtures. A 2‐d experiment with a dietary C:P gradient from 120 to 900 revealed a linear relation between Daphnia's final P‐to‐dry‐weight ratio and its growth rate (r2 = 0.92). Growth in mass (mean ± SE) ranged from 0.54 ± 0.01 to 0.17 ± 0.02 d−1 whereas final specific P content ranged from 1.47 ± 0.01% to 1.08 ± 0.02%.

Supporting stoichiometric theory, experiments with dual‐labeled (14C/32P) Scenedesmus showed that C assimilation efficiency declines as the C:P ratio of the diet increases. Adding unlabeled P‐deficient algae reduced the C assimilation efficiency for labeled P‐sufficient algae, whereas adding unlabeled P‐rich algae improved the C assimilation efficiency for labeled P‐deficient algae. C gross growth efficiency (production/ingestion) steadily decreased with declining dietary P. In contrast, P gross growth efficiency exhibited a unimodal pattern with reduced values for both P‐rich and strongly P‐deficient resources. The unexpected decline with P‐deficient diets was apparently due to low but consistent P‐release rates by strongly P‐limited Daphnia. Mass‐balance calculations confirmed that Daphnia was a strong sink for P when resources exhibited intermediate levels of P deficiency. Our results support stoichiometric theory but show that P‐deficient diets lead to significant declines in Daphnia's P content.