Small Aggregate Fractions Research Articles

Optimizing granular anammox retention via hydrocycloning during two-stage deammonification of high-solid sludge anaerobic digester supernatant

High-solid sludge anaerobic digestion leads to increased organic matters in digester supernatant, which promotes heterotrophic competition and reduces anaerobic ammonium oxidation (anammox) retention. This research demonstrated effective anammox retention by hydrocycloning during a two-stage deammonification. Anammox retention was evaluated by dividing large (>0.425 mm), medium (0.25 to 0.425 mm), and small (<0.25 mm) aggregate fractions via a sieve, whereby Candidatus Kuenenia abundance in each size aggregate was measured to be 16.8%, 5.0%, and 0.9% respectively. After hydrocyclone separation, large particles took up only 1.7% to 2.7% in the overflow discharge (upper discharge from the reactor), whereas its initial proportion was 19.4%, indicating limited anammox loss. The volume ratio change of large particles to total aggregates was defined for particle breakdown evaluation. Breakdown (23% to 32% large particles) occurred mainly during pumping (influenced by pump frequency and type), while little happened in the hydrocyclone. This research provided methods to use a sieve to evaluate anammox retention by hydrocyclone during high-solid sludge anaerobic digester supernatant deammonification, and information for reducing particle breakdown, pumping selection, and separation optimization.

The response of soil multi-functionality to agricultural management practices can be predicted by key soil abiotic and biotic properties

Soil organisms play an essential role in ecosystem functioning, including nutrient cycling and climate regulation. Most of soil functions have a microbial origin and recent findings suggest that various microbial community attributes (e.g. diversity, composition, abundance) are linked to the rate of soil functions in natural ecosystems. However, no such evidence is available from the agronomically managed systems. The types of agronomic practice and mechanisms (biotic vs. abiotic) that could impact microbial regulation of soil functions remain poorly understood. We collected soil samples from three long-term field trials across three geographically distinct regions with multiple management treatments (e.g. tillage, stubble management and fertiliser application) and measured the response of a number soil abiotic (e.g. soil aggregate stability, pH, nutrient status) and biotic (e.g. bacterial and fungal community structure, abundance of various microbial taxa) variables, and soil functions linked to nutrient cycling and nutrient availability. We used information theory and multi-model inference to identify key biotic and abiotic predictors of soil functions, and to model their response to land management through a multi-functionality index. Results indicated that no-till treatment generally impacted microbial community (42% decrease in the average gene copy number of all microbes compared to other management practices) and promoted soil structure (27% increase in the small aggregate fraction) but reduced some process rates, while stubble retention increased nutrient availability in the presence of fertilisation (59% on average). But these responses were site specific. The multi-functionality index associated with nutrient cycling declined under no-till system (47% on average) but increased when no-till was combined with stubble retention (49% on average) and fertiliser application (44%). Our modelling suggested that the best models that explained most of the variation in MF always included both abiotic and biotic variables. Amongst the latter, fungal community structure and beta(β)-Proteobacteria abundance were of importance as the model’s R² dropped by 12% when biotic attributes were removed providing evidence that the link between microbial community and soil functions was maintained in agricultural soils. This study provides support for the inclusion of microbial data in decision support systems for sustainable farming practices.

Synthesis of Gold Nanoparticles in Cyclodextrin-Tetrachloroaurate System

Tetrachloroaurate reduction with α-, β-, and γ-cyclodextrin at pH 10.56 was studied in this study by dual-angle dynamic light scattering and spectrophotometry. The nanoparticles were also characterized by scanning electron microscopy. In contrast with our previous study, the nanoparticles were purified by centrifugation prior to characterization. The reaction is considered to be a promising one-step method for preparation of gold nanoparticles with immobilized cyclodextrins without the need for seeding. Unlike in our previous study, the reaction mixture was boiled under reflux conditions instead of an open vial. This change sped up the reaction, and extensive aggregation was avoided. For the first time, this study demonstrated that all three cyclodextrins were able to reduce tetrachloroaurate at room temperature as well, but long incubation periods were necessary. This is the first publication discussing the mechanism of tetrachloroaurate reduction by cyclodextrins. The first stage of the reaction involved tetrachloroaurate hydrolysis despite presence of hydrochloric acid in the commercial preparation of tetrachloroauric acid (HAuCl4). Tetrachloroaurate was therefore the precursor but not the actual oxidant. The previous hypothesis on autocatalytic decarboxylation of cyclodextrins was therefore proven wrong. Particle growth was accompanied by nucleation, leading to coexistence of nanoparticles and nanoclusters. The resulting nanoparticles contained a small fraction of aggregates, probably because of sodium chloride generated from hydrochloric acid. However, besides playing this detrimental role, chloride ions facilitated nucleation by stabilizing gold intermediates. The nanoparticles solutions could be stored at least for three months, which contrasted with our previous work, where the nanoparticles were stable for only three days. For the first time, freeze-drying and reconstitution of the resulting nanoparticles were investigated, and they were shown to be free from aggregation. The synthesized gold nanoparticles are recommended for use as drug carriers.

Nitrogen addition promotes the transformation of heavy metal speciation from bioavailable to organic bound by increasing the turnover time of organic matter: An analysis on soil aggregate level

Nitrogen (N) addition can change physicochemical properties and biogeochemical processes in soil, but whether or not these changes further affect the transport and transformation of heavy metal speciation is unknown. Here, a long-term (2004–2016) field experiment was conducted to assess the responses of different heavy metal speciation in three soil aggregate fractions to N additions in a temperate agroecosystem of North China. The organic matter turnover time was quantified based on changes in δ13C following the conversion from C3 (wheat) to C4 crop (corn). Averagely, N addition decreases and increases the heavy metal contents in bioavailable and organic bound fractions by 27.5% and 16.6%, respectively, suggesting N addition promotes the transformation of heavy metal speciation from bioavailable to organic bound, and such a promotion in a small aggregate fraction is more remarkable than that in a large aggregate fraction. The transformations of heavy metal speciation from bioavailable to organic bound in all soil aggregate fractions are largely dependent on the increments in the turnover time of organic matter. The increase in organic matter turnover time induced by N addition may inhibit the desorption of heavy metals from organic matter by prolonging the interaction time between heavy metals and organic matter and enhance the capacity of organic matter to adsorb heavy metals by increasing the humification degree and functional group. Our work can provide insights into the accumulation, migration, and transformation of heavy metals in soils in the context of increasing global soil N input from a microenvironmental perspective.

Thermosensitive star-shaped poly-2-ethyl-2-oxazine. Synthesis, structure characterization, conformation, and self-organization in aqueous solutions

Star-shaped four-arm poly-2-ethyl-2-oxazine with calix[4]arene core was synthesized. Molar masses of the polymer star and its arms were 7100 and 1300 g·mol−1, respectively. The self-organization of molecules in aqueous solutions was investigated using light scattering and turbidity within a wide concentration interval. At room temperature, in solutions of synthesized polymer, in addition to macromolecules, a small fraction of aggregates is observed, which result from the interactions of hydrophobic branching centers. Phase separation temperatures decrease with increase in concentration. Low critical solution temperature for the investigated star-shaped poly-2-ethyl-2-oxazine is lower than LCST for aqueous solutions of linear and star-shaped poly-2-ethyl-oxazoline and higher than that for star-shaped poly-2-isopropyl-2-oxazine with calix[4]arene core and similar molar mass.

Improving soil aggregation, aggregate‐associated C and N, and enzyme activities by green manure crops in the Loess Plateau of China

AbstractGreen manure and fertilization practices have substantial impacts on soil chemical and biological properties over time. A field experiment was conducted on Cumulic Haplustoll to investigate the effects of leguminous green manure (LGM) crops and nitrogen (N) fertilizer on dry‐stable soil aggregate distributions and stability, the concentrations of organic carbon (OC) and N in the bulk soil and separated aggregate fractions, and soil enzyme activities in dry croplands on the Loess Plateau of China. Species tested as LGM crops were Huai bean (Glycine ussuriensis Regel et Maack.), soybean (G. max (L.) Merr.) and mung bean (Phaseolus radiatus L.). Two rates of N fertilizer (0 and 162 kg N ha−1) applied to winter wheat sown after LGM was incorporated into surface soil. Results showed that the inclusion of LGM crops for 6 years significantly increased the total nitrogen (TN), soil organic carbon (SOC), aggregate‐associated N and OC concentrations, enhanced the values of aggregate content with &gt;0.25 mm size (R0.25) and mean weight diameter (MWD), and boosted soil enzyme (invertase, urease, dehydrogenase and aryl‐sulfatase) activities at the 0–20‐cm depth compared to the bare fallow system under dryland conditions. The long‐term application of N fertilizer substantially increased the proportion of macroaggregates (&gt;5.0 mm), MWD and N contents in the 0.25–5‐mm size aggregates, and promoted the relative activities of invertase, alkaline phosphatase, dehydrogenase and aryl‐sulphatase, but decreased the urease activity. The correlations among macroaggregate fractions and soil chemical properties, aggregate stability and enzyme activities were significant and positive; however, the correlations between small aggregate fractions (&lt;2 mm) and corresponding parameters were negative, or there were no correlations. Overall, combining green manuring practices with suitable N fertilizer application should be recommended to improve the soil quality in dryland regions similar to the Loess Plateau of China.Highlights Green manure crops significantly increased soil enzyme activities, SOC and total N contents. Green manure crops increased macroaggregate (&gt;5 mm) formation and stability. Application of N fertilizer significantly increased the proportions and stability of macroaggregates. Green manure crops along with N fertilizer helped to build better soil quality in a dry loess cropland.

Low-amplitude dynamic tests of fine gravel in a resonant column

Construction of industrial and civil buildings, taking into account the dynamic effects on the foundations, requires special experiments on the mechanical properties of soils. This article presents the results of studying the dynamic properties of coarse gravelly soils using the resonant column method. These studies are relevant, since the determination of the dynamic properties of coarse-grained soils under laboratory conditions is associated with a restriction on the size of the fractions in the sample volume. This circumstance leads to the fact that at the moment most of the laboratory tests of the dynamic properties of coarse-grained soils are performed on smaller aggregate fractions, which, in general, significantly reduces the resulting mechanical properties of soils. It does not reflect the real operation of the foundation of buildings during dynamic effects. This paper presents a description of the available laboratory equipment, the sequence of preparation of samples of coarse grained crushed stone soil and sample assembly in the working chamber of the installation. The article contains the main graphs characterizing the change in shear modulus and damping coefficient depending on shear deformations. It is noted that the results obtained are particularly relevant for modeling the dynamic effects of natural and man-made character on the foundations of industrial and civil buildings, the bases of which are composed of coarse-grained soils. Dynamic parameters considered in this paper, can and must be used in numerical calculations by finite element method with the use of modern groundwater models in geotechnical software systems.

Distribution and availability of copper in aggregate size fractions of some calcareous soils

The difference in copper (Cu) availability between soils can be a result of different distribution of Cu forms in various size fractions of aggregates. This study aimed to determine different Cu forms in bulk soils and aggregate size fractions of some heavy metal-contaminated soils from Isfahan Province, Iran and to examine the relationship between Cu forms associated with different soil aggregates and plant indices. Bulk soil of five contaminated soils was partitioned into four aggregate size fractions (2.0 to 4.0 mm (large macro-aggregates), 0.25 to 2.0 mm (small macro-aggregates), 0.05 to 0.25 mm (micro-aggregates), and < 0.05 mm (mineral fraction)) by dry sieving. Copper was fractionated into soluble and exchangeable (F1), carbonate-bound (F2), Fe-Mn oxide-bound (F3), and organic-bound (F4) by Tessier’s method. Copper concentration and dry weight of shoots and roots of corn (corn indices) were determined in a pot experiment to assay the Cu availability in the five studied soils. Relationship between the Cu bound to different chemical fractions in different size aggregates and corn indices was assessed using cluster analysis. The results showed that the 0.25–2.0-mm fraction, with the highest mass percentage in the soils, had higher contribution to the total content of Cu in the bulk soils. Copper was mainly associated with the organic-bound and residual fractions in the bulk soils and aggregates. Principal component analysis (PCA) represented that the distribution patterns of Cu chemical fractions in different aggregates were strongly related to the soil type. The study of relationship between Cu fractions and the corn indices demonstrated that the organic-bound fraction of Cu in 2.0–4.0 mm aggregates was remarkably correlated with the Cu concentration in corn root and suggested that the organic-bound fraction of Cu in larger aggregates constitutes the chief plant-available Cu pool in the soils. Soil type and aggregate size distribution were important factors controlling availability and distribution patterns of Cu fractions in studied soils. The organic-bound fraction of Cu in the larger aggregate fractions appeared to be more readily available for plant than in the smaller aggregate fractions. Therefore, soil aggregate size fractionation can be used to assess the distribution, bioavailability, and environmental hazard of Cu in soils.

Altered Lipid Composition of Surfactant and Lung Tissue in Murine Experimental Malaria-Associated Acute Respiratory Distress Syndrome.

Malaria-associated acute lung injury (MA-ALI) and its more severe form malaria-associated acute respiratory distress syndrome (MA-ARDS) are common, often fatal complications of severe malaria infections. However, little is known about their pathogenesis. In this study, biochemical alterations of the lipid composition of the lungs were investigated as possible contributing factors to the severity of murine MA-ALI/ARDS. C57BL/6J mice were infected with Plasmodium berghei NK65 to induce lethal MA-ARDS, or with Plasmodium chabaudi AS, a parasite strain that does not induce lung pathology. The lipid profile of the lung tissue from mice infected with Plasmodium berghei NK65 developing MA-ALI/ARDS, but not that from mice without lung pathology or controls, was characterized by high levels of phospholipids -mainly phosphatidylcholine- and esterified cholesterol. The high levels of polyunsaturated fatty acids and the linoleic/oleic fatty acid ratio of the latter reflect the fatty acid composition of plasma cholesterol esters. In spite of the increased total polyunsaturated fatty acid pool, which augments the relative oxidability of the lung membranes, and the presence of hemozoin, a known pro-oxidant, no excess oxidative stress was detected in the lungs of Plasmodium berghei NK65 infected mice. The bronchoalveolar lavage (BAL) fluid of Plasmodium berghei NK65 infected mice was characterized by high levels of plasma proteins. The phospholipid profile of BAL large and small aggregate fractions was also different from uninfected controls, with a significant increase in the amounts of sphingomyelin and lysophosphatidylcholine and the decrease in phosphatidylglycerol. Both the increase of proteins and lysophosphatidylcholine are known to decrease the intrinsic surface activity of surfactant. Together, these data indicate that an altered lipid composition of lung tissue and BAL fluid, partially ascribed to oedema and lipoprotein infiltration, is a characteristic feature of murine MA-ALI/ARDS and possibly contribute to lung dysfunction.

Effect of breakdown and dispersion of soil aggregates by erosion on soil CO2 emission

Soil erosion is a serious problem around the world, in addition to soil loss, erosion is also considered to have a significant impact on SOC dynamics and CO2 release to the atmosphere. There is disagreement on the overall effect of soil erosion on CO2 emission at the landscape level. We measured the proportion of various aggregate size fractions at different slope positions which were affected by erosion. The cumulative CO2 emitted from bulk soil samples and different aggregate sizes fractions from five slope positions in a landscape was examined in a 128-d incubation study to estimate how the breakdown and dispersion of soil aggregates by erosion affect C loss to the atmosphere via CO2 emission. The proportion of coarse size aggregate fractions (>0.25mm) at eroded slope positions was greater than that at depositional positions. Bulk soil samples at the summit emitted the greatest cumulative CO2-C (0.49±0.04gCkg−1soil) among all the slope positions. During the initial 22days of incubation, the CO2 emission rate from coarse size aggregate fractions (0.024±0.009gCkg−1soild−1) was six times higher than that from small size aggregate fractions (0.0038±0.0011gCkg−1soild−1) at the depositional toe-slope position. The CO2 emission rate from coarse size aggregate fractions at depositional slope positions (toe-slope and foot-slope) was significantly greater than that at eroded slope positions (summit, shoulder-slope and back-slope). We concluded that the breakdown and dispersion of aggregates by erosion impacts both aggregate size distribution and CO2 emission from the aggregates at different slope positions, thus, affects the C loss to the atmosphere.

Utilization of Reclaimed Asphalt Pavements in Indian Low-Volume Roads

Utilization of reclaimed asphalt pavement (RAP) in the construction industry is gaining an advantage over conventional materials in terms of sustainable credits. However, the amount of production of RAP and its utilization has no comparison. The general practice is to replace a small fraction of virgin aggregates with RAP, usually restricted to a maximum of 30%, in base layers to promote RAP usage in the pavement industry. The present study focuses on the utilization of a high proportion of RAP (>50%>50%) substitution in virgin aggregates (VA) as a base material in low volume roads (LVR). Mixes containing 100∶0100∶0, 80∶2080∶20, and 60∶4060∶40 proportions of RAP∶VARAP∶VA stabilized with different dosages of fly ash were evaluated for maximum dry density (MDD), optimum moisture content (OMC), unconfined compressive strength (UCS), resilient modulus (MrMr) and California bearing ratio (CBR). It was observed that the 80∶2080∶20 RAP∶VARAP∶VA design mix with 40% fly ash meets the design requirements (UCS>1.7 MPaUCS>1.7 MPa and CBR>80%CBR>80%) specified by the Ministry of Rural Development (MoRD), Government of India, and was considered to be an optimum mix. An example is discussed to design an LVR with an optimum mix according to the Indian Roads Congress (IRC) and AASHTO methods. The results revealed that the fatigue and rutting strains are well within the permissible limits for the new mix. The new mix design proved economical, as there was a 50% reduction in base layer thickness compared with the conventional design mix. Read More: http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29MT.1943-5533.0001374

Influence of aggregate type and size on properties of pervious concrete

This study investigates the influence of aggregate type and size on the properties of pervious concrete. Five different concrete mixtures were prepared, including a standard dense concrete mixture and four pervious concrete mixtures with varied aggregate types (dolomite or steel slag) and differing proportions of 4–8mm to 8–16mm aggregate fractions (30:60 or 60:30). The results suggest that a higher amount of small aggregate fractions (4–8mm) yielded higher density concrete mixtures and greater flexural strength. However, connected porosity as a main parameter for estimating pervious concrete efficiency was surprisingly influenced more by the aggregate type than the size.

Effect of hydrostatic pressure treatment on the structure–foaming relationships of β-lactoglobulin

The effect of hydrostatic pressure treatment (150 and 250 MPa) on the structure and foaming characteristics of dimeric β-lactoglobulin (β-LG) at pH 7.0 is investigated. Angle- and concentration-dependent dynamic light scattering is used to probe pressure-induced changes in size under ambient conditions. The cumulant method is used to analyze correlation functions of the dynamic light scattering experiments and to estimate hydrodynamic radii and the width of their distribution. Instead of a decrease, hydrodynamic radii slightly increase after pressure treatment and depend on protein concentration. Both native and pressurized samples are almost free of aggregates as indicated by a small polydispersity index, PDI < 0.25. A small fraction of larger aggregates in the native sample is not affected by the pressure treatment and only bias the scattering signal at low scattering angles. Circular dichroism measurements indicate transformation of the secondary structure into a random coil for the pressurized samples. Only slightly unfolded β-LG stabilizes foam best because the largest effect is observed for samples treated with 150 MPa. Pressure-modified β-LG could have the potential to be used as a stabilizer in the food industry because of the low pressure needed during processing.

Soil aggregate isolation method affects measures of intra-aggregate extracellular enzyme activity

Within soil aggregates, binding of organic matter is known to occlude it from microbial attack. Within aggregate fractions of different sizes, microbial communities and activities have also been shown to differ. As a result the soil physical structure, organic inputs and microbial activity together impact the rate at which organic matter is decomposed and stored within soil. However, methods developed for isolating soil aggregates may affect subsequent biological assays. In this study, we sought to understand how enzyme activity within soil aggregates is influenced by aggregate isolation methodology, including wet, dry, and ‘optimal moisture’ sieving procedures within two contrasting ecosystems (a corn agroecosystem and a 2-yr old, diverse planted tallgrass prairie). Mass distribution of aggregates from wet-sieving was skewed toward small macroaggregates (250–1000 μm) and microaggregates (<250 μm), but the distribution of dry and optimal moisture aggregates was highly skewed toward large macroaggregates (>2000 μm). Wet-sieved macroaggregates (>1000 μm) had greater aggregate potential enzyme activity (nmol substrate h−1 g−1 dry aggregate) than smaller aggregate fractions and whole soil, particularly for C-cycling enzymes cellobiohydrolase and β-glucosidase. Also, wet-sieved aggregates from corn systems had higher potential cellobiohydrolase and β-glucosidase activity than aggregates isolated from prairie. Neither of these relationships was observed in dry and optimal moisture aggregates, suggesting that elevated activities are characteristic of water-stable aggregates and possibly stimulated by soil rewetting. The proportional contribution to total enzyme activity observed in water-stable microaggregates accounted for 46–62% of whole soil activity; although water-stable large macroaggregates (>2000 μm) had greater aggregate enzyme activity, they contributed a minority of overall soil activity. In contrast, the proportional contribution of large macroaggregates comprised 70–78% of whole soil activity when dry sieved and 38–66% under optimal moisture sieving. Wet-sieving soil aggregates is most useful to examine long-term changes in soil organic matter and microbial activity between soil types. Optimal moisture and dry sieved aggregates may be useful alternatives to more closely capture short-term in situ measures of seasonal and intra-annual soil microbial activity.

Using an organically-modified montmorillonite to compatibilize a biodegradable blend

Glycerol-plasticized cornstarch and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blends were prepared by melt-extrusion at a constant 70:30 (mass/mass) ratio in the presence of a commercial organoclay. The effect of increasing the organoclay content on the morphology and physical properties of the blends was investigated soon after processing and after aging for 12months. After processing, the materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). The results indicated that increasing clay mineral contents promoted significant improvements in the compatibility between the components. After aging, the samples were characterized by SEM, XRD and small-angle X-ray scattering (SAXS). Unexpectedly, the reduced size of the PHBV dispersed phase and the decreased crystallinity of both phases in the hybrids were maintained. XRD and SAXS results unambiguously proved the presence of both exfoliated layers and a small volume fraction of organoclay aggregates in the aged clay polymer nanocomposites.

Aggregate dynamics and associated soil organic matter contents as influenced by prolonged arable cropping in the South African Highveld

Converting grassland soils to cropland changes the turnover of aggregates and their protective effects on soil organic matter (SOM). Our aim was to elucidate how rapid soil aggregation and associated SOM contents change with increased duration of long-term cropping. The study was conducted in the South African Highveld in three agro-ecosystems with different cropping durations (0–98 years) after conversion of the native grassland. Soil samples (0–20 cm; Plinthustalfs) were analyzed for aggregate size distribution (six water-stable aggregate fractions) and the C and N contents in each single fraction. Additionally, sieved and ground bulk soil was oxidized with 0.33 M KMnO 4. With an increase of cultivation time the aggregate size distribution changed remarkably: the large macroaggregates (2000–2800 μm) and peds (> 2800 μm) broke down into finer size classes (exponential rate constant k = 0.20 year −1), accompanied especially by an increase of the contents of small macroaggregates (250–2000 μm) and not of the microaggregates as previously reported for other soil types. The C and N concentrations decreased in all aggregates ( k = 0.05 to 0.52 year −1) and the rate of decline was fastest in the peds. Most C was lost from the 250–2000 μm and 53–250 μm sized fractions (about 60%). At the primary grassland, the peds (> 2800 μm) stored 47% of total C, but less than 10% after 90 years of cropping. Parts of this C were recovered in smaller aggregate fractions. Especially the C stored in the small macroaggregates (250–2000 μm) increased from 27 ± 1% to 61 ± 1% of total C. The total loss of SOM and large aggregates went along with an accelerated loss of its C resistant to oxidation. While 40% of soil C was not oxidizable with KMnO 4 from the grassland soil, the contents of this C resistant to chemical oxidation were reduced by up to 50% as cultivation proceeded. Grinding the soil hardly changed this amount. We conclude that the loss of soil structure made also resistant SOM available for decay, which might then be difficult to replace when a restoration of the sites is anticipated.

Impact of antibody aggregation on a flowthrough anion‐exchange membrane process

The impact of typical anion-exchange flowthrough conditions on the IgG mass loading of an anion-exchange membrane scale-down unit (Mustang Q coin) was investigated. High performance size-exclusion chromatography and multiangle laser light scattering results suggested the presence of a small fraction of IgG aggregates with average radius >100 nm under anion-exchange flowthrough conditions. The small filtration area presented by the 0.35 mL membrane volume Mustang Q coin limited the membrane throughput due to fouling from the aggregates at higher antibody loading. Data in this report indicated that a 0.2 μm hybrid polyethersulfone and polyvinylidene fluoride membrane in-line prefilter with a minimum filtration area of 20 sq cm alleviated the Mustang Q coin fouling. The combined cake filtration and intermediate blocking model was proposed as the most likely membrane pore blocking mechanism. Increasing the filtration area in the in-line prefilter resulted in higher IgG mass throughput. Thus, using an appropriately sized in-line prefilter could provide more robust antibody throughput performance on scale-down membrane anion-exchange units.

Earthworm impacts on soil organic matter and fertilizer dynamics in tropical hillside agroecosystems of Honduras

Abstract Earthworms are important processors of soil organic matter (SOM) and nutrient turnover in terrestrial ecosystems. In agroecosystems, they are often seen as beneficial organisms to crop growth and are actively promoted by farmers and extension agents, yet their contribution to agroecosystem services is uncertain and depends largely on management. The Quesungual slash-and-mulch agroforestry system (QSMAS) of western Honduras has been proposed as a viable alternative to traditional slash-and-burn (SB) practices and has been shown to increase earthworm populations, yet the effect of earthworms on soil fertility and SOM in QSMAS is poorly understood. This study examined the role of Pontoscolex corethrurus in QSMAS by comparing their influence on aggregate-associated SOM and fertilizer dynamics with their effects under SB and secondary forest in a replicated field trial. Both the fertilized QSMAS and SB treatments had plots receiving additions of inorganic 15N and P, as well as plots with no inorganic N additions. Earthworm populations were manipulated in field microcosms at the beginning of the rainy season within each management treatment via additions of P. corethrurus or complete removal of existing earthworm populations. Microcosms were destructively sampled at harvest of Zea mays and soils were wet-sieved (using 53, 250 and 2000 μm mesh sizes) to isolate different aggregate size fractions, which were analyzed for total C, N and 15N. The effects of management system were smaller than expected, likely due to disturbance associated with the microcosm installation. Contrary to our hypothesis that earthworms would stabilize organic matter in soil aggregates, P. corethrurus decreased total soil C by 3% in the surface layer (0–15 cm), predominantly through a decrease in the C concentration of macroaggregates (>250 μm) and a corresponding depletion of C in coarse particulate organic matter occluded within macroaggregates. Earthworms also decreased bulk density by over 4%, but had no effect on aggregate size distribution. Within the two fertilized treatments, the QSMAS appeared to retain slightly more fertilizer derived N in smaller aggregate fractions (

Molecular characterisation of soybean polysaccharides: an approach by size exclusion chromatography, dynamic and static light scattering methods

Water soluble polysaccharides from soybean (SSPS) have a pectin-like structure and are used as stabilisers in acidified beverages. Physicochemical properties such as structure, molecular weight and shape or conformation are primary factors controlling their functional properties. Two soybean polysaccharides, a native SSPS and a modified SSPS treated with β-(1→4)- d-galactosidase (GPase/SSPS) were studied by dynamic and static light scattering (DLS, SLS) and size exclusion chromatography (SEC). Consecutive filtrations using a range of membrane pore size removed a small fraction of macromolecular aggregates from dilute polysaccharide solutions with relatively little effect on the major component molecules as monitored by DLS and SEC measurements. Access to aggregate-free dilute solutions of SSPS and GPase/SSPS allowed the direct measurement of molecular characteristics. SLS results showed that SSPS had a weight average molecular weight of (645 ± 11) × 10 3 g/mol and a radius of gyration, R g, of (23.5 ± 2.8) nm. By comparing R g with the hydrodynamic radius, R h (21.1 ± 0.5 nm) obtained from DLS, the structural parameter ρ ( R g/ R h) was found to be 1.1, suggesting that SSPS has an overall globular shape due to a highly branched structure. The modified SSPS had a significantly lower molecular weight (287 ± 18) × 10 3 g/mol but a similar radius of gyration (23.2 ± 1.7 nm). The structure parameter ρ of GPase/SSPS was higher ( ρ = 1.3) because of a smaller hydrodynamic radius (17.7 ± 1.8 nm). This suggests that GPase/SSPS has a much less branched structure yet still differs significantly from a linear random coil conformation ( ρ = 1.7–2.0). The results derived from SLS and DLS are in agreement with the conclusions obtained from a chemical analysis where the reduction of molecular weight of GPase/SSPS was caused by the cleavage of galactan side chains.

Laser light scattering and isothermal titration calorimetric studies of poly(ethylene oxide) aqueous solution in presence of sodium dodecyl sulfate

The aqueous solution of poly(ethylene oxide) (PEO) in the presence of different concentrations of sodium dodecyl sulfate (SDS) was examined by laser light scattering and isothermal titration calorimetric techniques. A small fraction of PEO aggregates were found to coexist with unimeric PEO chains in dilute solution. The presence of monovalent salt does not alter the hydrodynamic properties of PEO in aqueous solution. Addition of a monovalent anionic surfactant, such as SDS, induces cooperative binding of surfactant monomers to PEO backbones at SDS concentrations ranging from 4.0 mM (critical aggregation concentration) to 16.5 mM (saturation concentration). The hydrodynamic radius of PEO unimers decreases initially and then increases with SDS concentration, resulting from the structural reorganization of the PEO/SDS complex. Beyond the saturation concentration, the hydrodynamic radii of PEO/SDS complex are independent of SDS concentration.