Fractional Retention Research Articles

Antimony(V) sorption and coprecipitation with ferrihydrite: An examination of retention mechanisms and the selectivity of commonly-applied extraction procedures

We investigated the mechanisms that control Sb(V) sorption and coprecipitation with ferrihydrite across a range of Sb(V) loadings, and examined the associated effects on Sb(V) extractability during the commonly-applied 1 M HCl extraction scheme and the BCR and Wenzel sequential extraction schemes. EXAFS spectroscopy reveals that Sb(V) sorption and coprecipitation mainly involved Sb(V) incorporation into the ferrihydrite structure via edge sharing and double-corner sharing between SbO6 and FeO6 octahedra. Large amounts of these linkages partially stabilized ferrihydrite against extraction with 1 M HCl. Negligible (< 0.5 %) ferrihydrite-bound Sb(V) was recovered in the “acid extractable” and “reducible” fractions of the BCR scheme, while 1–16 % was recovered in the “oxidizable” fraction. As such, the BCR scheme risks ferrihydrite-bound Sb(V) being misidentified as Sb residing mainly in “residual” phases. In contrast, in the Wenzel scheme, almost all sorbed- and coprecipitated-Sb(V) was recovered in the “amorphous hydrous oxide-bound” fraction, with only 0.6–3.3 % in the “specifically-bound” fraction (consistent with our finding of Sb(V) retention via incorporation into ferrihydrite, as opposed to adsorption by the ferrihydrite surface). Collectively, the results provide new insights into the retention mechanisms and extraction behaviour of ferrihydrite-bound Sb(V), enhancing our ability to assess Sb contamination in soils, sediments and geogenic wastes.

Bovine Serum Albumin Rejection by an Open Ultrafiltration Membrane: Characterization and Modeling.

The classic application of ultrafiltration (UF) is for the complete retention of proteins, and in that situation, the transport behavior is well established. More open membranes with fractional retention are used when separating different proteins. However, protein transport has not been well documented yet in the literature. The bovine serum albumin (∼69 kDa) observed rejection ranges from 0.65 to 1 using a 300 kDa molecular weight cut-off membrane at different pH, ionic strength, and pressure. We demonstrated that, especially with open UF, the transport of proteins through the membrane is dominated by advection, with insignificant diffusion effects (p value > 0.05). We showed that with open UF, retention is not only caused by size exclusion but also to a large extent by electrostatic interactions and oligomerization of the proteins. Mass transfer in the polarization layer was relatively independent of the pH and ionic strength. It was underestimated by common Sherwood relations due to a relatively large contribution of the reduction in the flow turbulence near the membrane by the removal of fluid through the membrane. We propose a model that allows relatively quick characterization of the rejection of proteins without prior knowledge of the pore sizes and charges based on just a limited set of experiments. Therefore, protein rejection with the open UF system can be targeted by tuning the processing conditions, which might be useful for designing protein fractionation processes.

Tillage and Cover Crop Systems Alter Soil Particle Size Distribution in Raised-Bed-and-Furrow Row-Crop Agroecosystems

Conservation alternatives that include no-tillage (NT) and cover crops (CCs) reduce soil erosion in row-crop agroecosystems. However, little information is available about how these alternatives affect soil textural properties responsible for soil fertility. This study evaluated the soil particle size distribution and volumetric water content after three years of consistent management in a raised bed system. There were four treatment systems in a dryland maize/soybean rotation on a silt loam soil (Oxyaquic Fraglossudalfs) that included: NT + CCs, conventional tillage (CT) + CCs, CT + winter weeds, and CT + bare soil in winter in northwest Mississippi. The NT + CC system retained 62% more coarse sand in the furrow than the other systems (2.1% compared to 1.3%; p = 0.02). Regardless of the location, the NT + CC system (2.5%) retained 39% more fine sand than the CT + CC system (1.8%; p = 0.01), suggesting that coarse and fine sands were being trapped in furrows combining NT + CC systems, minimizing their off-site transport. In furrows, CCs increased soil volumetric water content by 47% compared to other winter covers. In beds, NT + CCs increased bed water contents by 20% compared to CT + CCs (17.1 to 14.3%; p &lt; 0.01). Implementing conservation alternatives may promote the retention of sand fractions in silty loam soils that are important in supporting soil fertility and crop sustainability.

Mathematical solutions in internal dose assessment: A comparison of Python-based differential equation solvers in biokinetic modeling

In biokinetic modeling systems employed for radiation protection, biological retention and excretion have been modeled as a series of discretized compartments representing the organs and tissues of the human body. Fractional retention and excretion in these organ and tissue systems have been mathematically governed by a series of coupled first-order ordinary differential equations (ODEs). The coupled ODE systems comprising the biokinetic models are usually stiff due to the severe difference between rapid and slow transfers between compartments. In this study, the capabilities of solving a complex coupled system of ODEs for biokinetic modeling were evaluated by comparing different Python programming language solvers and solving methods with the motivation of establishing a framework that enables multi-level analysis. The stability of the solvers was analyzed to select the best performers for solving the biokinetic problems. A Python-based linear algebraic method was also explored to examine how the numerical methods deviated from an analytical or semi-analytical method. Results demonstrated that customized implicit methods resulted in an enhanced stable solution for the inhaled 60Co (Type M) and 131I (Type F) exposure scenarios for the inhalation pathway of the International Commission on Radiological Protection (ICRP) Publication 130 Human Respiratory Tract Model (HRTM). The customized implementation of the Python-based implicit solvers resulted in approximately consistent solutions with the Python-based matrix exponential method (expm). The differences generally observed between the implicit solvers and expm are attributable to numerical precision and the order of numerical approximation of the numerical solvers. This study provides the first analysis of a list of Python ODE solvers and methods by comparing their usage for solving biokinetic models using the ICRP Publication 130 HRTM and provides a framework for the selection of the most appropriate ODE solvers and methods in Python language to implement for modeling the distribution of internal radioactivity.

Influence of storage duration on retention of kernel tocopherols in vte4-based biofortified maize genotypes

The degradation of tocopherols during post-harvest storage poses a challenge to their efficacy in addressing vitamin E deficiency (VED), a problem faced by humans. Here, a diverse panel of vte4 gene-based inbreds along with their wild-type genotypes was analyzed to study genetic variation for retention of tocopherols during conventional storage (temperature: 25–30 °C and humidity: 42–82%) for six months. vte4-based inbreds possessed 2-fold higher tocopherol fractions over normal inbreds immediately after harvest [0 days after storage (DAS)]. High genetic variation for retention of tocopherol fractions viz. α-tocopherol (17.20–45.44%), γ-tocopherol (30.46–44.03%), and δ-tocopherol (20.51–33.87%) was observed after six months of storage (180 DAS) among vte4-based inbreds, whereas, normal inbreds possessed comparatively low genetic variation [α-tocopherol (8.54–12.29%), γ-tocopherol (23.74–27.48%) and δ-tocopherol (15.88–23.68%)]. A major fraction of α-tocopherol, and δ-tocopherol was lost during the last three months of storage (3rd month: 31.00% loss, 6th month: 75.22%), meanwhile, γ-tocopherol showed comparatively slower degradation (3rd month: 31.62% loss, 6th month: 65.56% loss). HKI323-PVE (45.44%), HKI1105-PVE (24.08%), HKI161-PVE (23.17%) and HKI1128-PVE (22.73%) were the promising maize inbreds with higher retention of α-tocopherol at 180 DAS. These potential inbreds can be effectively used as valuable genetic resources in the biofortification programme, and the contrasting genotypes distinctly differing for retention of tocopherols can be used to map the loci for higher retention of tocopherols.

A dynamic model to measure retention of solid and liquid digesta fractions in chickens fed diets with differing fibre sources.

Dietary fibres impact multiple digestive processes, and insights into the effects of various types of fibre on digesta retention time are required to optimise current feed formulation systems. Therefore, the objective of this study was to apply a dynamic modelling approach to generate estimates for the retention time of solid and liquid digesta in broilers fed different fibre sources. A maize-wheat-soybean meal control diet was compared against three diets in which wheat was partially substituted with oat hulls, rice husks, or sugar beet pulp (3% w/w). Non-starch polysaccharide (NSP) digestibility was evaluated in broilers between 23 and 25days of age (n=60 birds/treatment) using titanium dioxide (TiO2, 0.5g/kg) as a marker, after feeding the experimental diets for 21days. Digesta mean retention time (MRT) was measured in another 108 birds at 30days of age by the administration of an oral pulse dose of chromium sesquioxide (Cr2O3) as solid marker and Cobalt-EDTA as liquid marker, and subsequent measurement of marker recovery in compartments of the digestive tract (n=2 or 3 replicate birds/time point/treatment). Marker recovery models to estimate fractional passage rates for solid and liquid digesta in crop, gizzard, small intestine, and caeca compartments of the gastrointestinal tract were developed to predict MRT of solid and liquid digesta for each dietary treatment. The models were composed of a series of first-order differential equations, representing the variation of marker concentration in a compartment over time. Estimated MRT of solid and liquid digesta in the gizzard varied from 20min for oat hulls and 34min for rice husks diets to 14min for sugar beet pulp and 12min for control diets. In the caeca, liquid MRT was decreased compared to the control diet (989min) for the sugar beet pulp diet (516min), while it was increased for both the oat hulls and rice husks diets (≈1 500min). Overall, these estimates are greater than those previously reported, suggesting that liquid digesta retention in the caeca previously has been underestimated. Digestibility of total NSP was increased by dietary fibre inclusion, regardless of the fibre type, although degradation of constituent sugars of NSP varied among diets. In conclusion, the inclusion of fibre sources at a low level (3% w/w) in the diet of broiler modulated retention time mainly in the gizzard and caeca, and increased digestibility of NSP.

Quantification of Fat Graft Retention in the Translabyrinthine Approach Using Magnetic Resonance Imaging Volumetric Analysis.

To characterize the viability and volume of autologous free fat grafts over time, determine clinical/patient factors that may affect free fat graft survival and assess the clinical impact of free fat graft survival on patient outcomes in the translabyrinthine approach for lateral skull base tumor resection. Retrospective chart review. Tertiary neurotologic referral center. Forty-two adult patients who underwent translabyrinthine craniotomy for resection of a lateral skull base tumor with the mastoid defect filled by autologous abdominal fat graft and subsequently underwent more than one postoperative magnetic resonance imaging (MRI) scans of the brain. Mastoid obliteration with abdominal fat after craniotomy, postoperative MRI. Rate of fat graft volume loss, fraction retention of original fat graft volume, initial fat graft volume, time to steady-state fat graft retention, rate of postoperative cerebrospinal fluid (CSF) leak, and/or pseudomeningocele formation. Patients were followed postoperatively with MRI for a mean of 31.6 months with a mean of 3.2 postoperative MRIs per patient. Initial graft size was a mean of 18.7 cm3 with a steady-state fat graft retention of 35.5%. Steady-state graft retention (<5% loss per year) was achieved at a mean of 24.96 months postoperatively. No significant association was found in multivariate regression analysis of clinical factors impact on fat graft retention and CSF leak/pseudomeningocele formation. In the use of autologous abdominal free fat graft for filling mastoid defects after translabyrinthine craniotomy, there is a logarithmic decline in fat graft volume over time, reaching steady state in 2 years. Rates of CSF leak or pseudomeningocele formation were not significantly affected by initial volume of the fat graft, rate of fat graft resorption, nor the fraction of original fat graft volume at steady state. In addition, no analyzed clinical factors significantly influenced fat graft retention over time.

Coupling of iron and dissolved organic matter in lakes–selective retention of different size fractions

Increasing concentration of iron (Fe) is observed in many boreal lakes, such as for the present study in Oslo Østmark, SE-Norway (1983–2018). As Fe-regulating processes are complex and dynamic, the link between mobilizing and retention processes is still not well understood. A seasonal study (2017–2018) from two headwaters, with medium and high dissolved organic matter (DOM) concentrations, showed that the loading of Fe to the lakes was highly dependent on flow conditions. Significantly higher values of Fe were related to autumn and winter periods with high runoff of highly colored and aromatic DOM compared to a severe drought period with minimum Fe values in the lakes. Compared to DOM, a significantly larger part of Fe was in a colloidal form, and a size-selective process (dependent on flow and water retention time) seemed to preferentially settle Fe compared to DOM. In contrast to Fe, the variability in DOM concentrations was moderate through the whole year. However, there were significant changes in the spectroscopic properties of DOM, with decreased fluorescence intensity and increased spectral slope during the warm dry season, indicating increased importance of DOM turnover in the lake. As Fe was transported from the catchment during high flow condition, at the same time as the oxic form of sulfur (SO42−), there was no sign of retention of Fe as FeS. We conclude that the mobilization and retention of compounds that are mainly in a colloidal form, such as Fe, are especially vulnerable to changes in flow conditions, suggesting increased variation in Fe levels in a future climate with increased frequency of flooding and drought episodes.

Chemical Composition, but Not Specific Surface Area, Affects Calcium Retention of Nanostructured Calcium Compounds in Growing Rats

Background: Low dietary calcium intake and bioavailability may adversely affect bone health. Reducing the size of calcium compounds increases their specific surface area (SSA, expressed as m2/g) and may increase calcium dissolution and bioavailability.Objective: We investigated the influence of SSA and chemical composition on the bioavailability of calcium and compared in vitro calcium dissolution with in vivo absorption.Methods: Calcium dissolution was measured in 0.1 M phosphoric acid, whereas color and pH changes of foods were assessed as indicators for potential sensory performance. Calcium absorption, retention, and fractional retention were measured over a 5-d balance study in growing Sprague-Dawley male rats after 21 d of feeding. Femoral and vertebral bone mineral density (BMD) and extensive tissue histology were assessed at study end. The influence of SSA on calcium bioavailability was assessed by comparing the groups fed pure calcium carbonate (CaCO3) with increasing SSAs of 3, 36, and 64 m2/g (CaCO3_3, CaCO3_36 and CaCO3_64), whereas chemical composition was assessed by comparing the smallest CaCO3_64, a 50:50 wt:wt percent solution mixture of CaCO3 and hydroxyapatite_94, and pure hydroxyapatite_100.Results: In vivo, fractional calcium retention from hydroxyapatite_100 (mean ± SEM: 54.86% ± 0.95%/5 d) was significantly greater than from CaCO3_64 (49.66% ± 1.15%/5 d) (P = 0.044). Increasing SSA of the pure CaCO3 did not significantly improve calcium retention. Across all 5 groups, there were no significant differences in BMD or tissue calcification by histology. In vitro calcium dissolution did not correlate with SSA or calcium absorption. In selected food matrixes, hydroxyapatite_100 caused less color change and/or smaller pH increase than did the other calcium compounds.Conclusions: Our findings suggest that chemical composition rather than SSA is a predictor of nanostructured calcium bioavailability and that in vitro dissolution of nanostructured calcium does not predict in vivo absorption. Although its phosphorus content may limit use in some populations, nanostructured hydroxyapatite may be a promising calcium compound for food fortification.

Cyclic intercritical annealing to improve strength-ductility combinations in medium manganese steels

With the push for superior properties from third-generation advanced high-strength steels, particularly by the automotive industry, medium manganese steels have emerged as a viable candidate. Intercritical annealing of medium manganese steels promotes retention of large austenite fractions (>30%) at room temperature. While prior studies have established strong mechanical property dependence on the amount and mechanical stability of retained austenite, the effect of austenite distribution on mitigating local strain incompatibility has received less attention. The present study proposes a method to alter phase distribution: a novel cyclic intercritical annealing that promotes nucleation and efficient stabilization of retained austenite. Grain sizes were found to be comparable between isothermal- and cyclic-annealed samples, yet bulk neutron diffraction revealed greater austenite fractions in the latter, indicating more extensive austenite nucleation. Combining the cycle with an isothermal hold facilitated austenite growth and enrichment, improving work hardening while maintaining toughness relative to purely isothermal annealing.

Peculiarities of formation of water quality of surface sources of water supply as a factor of a choice of a method of water treatment

The current state and formation of water quality in reservoirs that serve as sources of drinking water supply were considered. It was revealed that phytoplankton becomes one of the main factors influencing the formation of water quality in reservoirs in the warm period from June to November, especially during the period of reservoirs “blooming”. Mostly these processes are triggered by the explosive development of blue-green algae (cyanobacteria). The factors accompanying this phenomenon are shown. The characteristic of the influence of global climate change and new composition of wastewater on water quality in surface water supply sources is given. If earlier the sewage contained significant volumes of heavy metals, oil products, phenols, etc., now they are observed to decrease at several times and vice versa - an increase in the volume of biogenic compounds, especially phosphates is observed. The emergence of phosphates is caused both by the ingress of phosphate fertilizers into water bodies, and by household reasons - the massive distribution of phosphate-based detergents and the inability of existing sewage treatment plants to efficiently process them. Screening monitoring of the Dnieper river basin showed extremely high levels of the predicted safe concentration of herbicides, insecticides, fungicides, as well as pharmaceutical substances such as carbomazepine, lopinavir, diclofenac, efavirenz, etc. in water.&#x0D; That is, among organic pollutants, the focus changes from classic petrochemical products to the products related to agricultural and pharmaceutical production, which, in certain concentrations, can stimulate the development of phytoplankton.&#x0D; The effective methods for treating surface water in modern conditions are as follows:&#x0D; - physical retention of coarse fractions of phytoplankton using new designs of water intake structures;&#x0D; - the use of new filter materials that effectively trap finely dispersed phytoplankton fractions at the main treatment facilities and are capable of regenerating the filter media;&#x0D; - the use of new oxidizing agents-disinfectants that do not form toxic organochlorine compounds, with preliminary extraction of phytoplankton masses;

The generalized inference on the ratio of mean differences for fraction retention noninferiority hypothesis.

The fraction retention non-inferiority hypothesis is often measured for the ratio of the effects of a new treatment to those of the control in medical research. However, the fraction retention non-inferiority test that the new treatment maintains the efficacy of control can be affected by the nuisance parameters. Herein, a heuristic procedure for testing the fraction retention non-inferiority hypothesis is proposed based on the generalized p-value (GPV) under normality assumption and heteroskedasticity. Through the simulation study, it is demonstrated that, the performance of the GPV-based method not only adequately controls the type I error rate at the nominal level but also is uniformly more powerful than the ratio test, Rothmann’s and Wang’s tests, the comparable extant methods. Finally, we illustrate the proposed method by employing a real example.

The influences of historic lake trophy and mixing regime changes on long-term phosphorus fraction retention in sediments of deep eutrophic lakes: a case study from Lake Burgäschi, Switzerland

Abstract. Hypolimnetic anoxia in eutrophic lakes can delay lake recovery to lower trophic states via the release of sediment phosphorus (P) to surface waters on short timescales in shallow lakes. However, the long-term effects of hypolimnetic redox conditions and trophic state on sedimentary P fraction retention in deep lakes are not clear yet. Hypolimnetic withdrawal of P-rich water is predicted to diminish sedimentary P and seasonal P recycling from the lake hypolimnion. Nevertheless, there is a lack of evidence from well-dated sediment cores, in particular from deep lakes, about the long-term impact of hypolimnetic withdrawal on sedimentary P retention. In this study, long-term sedimentary P fraction data since the early 1900s from Lake Burgäschi provide information on benthic P retention under the influence of increasing lake primary productivity (sedimentary green-pigment proxy), variable hypolimnion oxygenation regimes (Fe∕Mn ratio proxy), and hypolimnetic withdrawal since 1977. Results show that before hypolimnetic withdrawal (during the early 1900s to 1977), the redox-sensitive Fe∕Mn-P fraction comprised ∼50 % of total P (TP) in the sediment profile. Meanwhile, long-term retention of total P and labile P fractions in sediments was predominantly affected by past hypolimnetic redox conditions, and P retention increased in sedimentary Fe- and Mn-enriched layers when the sediment-overlaying water was seasonally oxic. However, from 1977 to 2017, due to eutrophication-induced persistent anoxic conditions in the hypolimnion and to hypolimnetic water withdrawal increasing the P export out of the lake, net burial rates of total and labile P fractions decreased considerably in surface sediments. By contrast, refractory Ca–P fraction retention was primarily related to lake primary production. Due to lake restoration since 1977, the Ca–P fraction became the primary P fraction in sediments (representing ∼39 % of total P), indicating a lower P bioavailability of surface sediments. Our study implies that in seasonally stratified eutrophic deep lakes (like Lake Burgäschi), hypolimnetic withdrawal can effectively reduce P retention in sediments and potential for sediment P release (internal P loads). However, after more than 40 years of hypolimnetic syphoning, the lake trophic state has not improved nor has lake productivity decreased. Furthermore, this restoration has not enhanced water column mixing and oxygenation in hypolimnetic waters. The findings of this study are relevant regarding the management of deep eutrophic lakes with mixing regimes typical for temperate zones.

Seasonal Variations in the Grain Size Distribution and Mineral Composition of Suspended Particulate Matter of the Northern Dvina River

The paper presents the first results of a study of seasonal variations in the grain size distribution and mineral compositions of suspended particulate matter (SPM) of the Northern Dvina River. The SPM samples were collected every month during 2016–2017 at the outlet of the Kuznetchiha arm to Dvina Bay of the White Sea. The grain size fractions were separated by Petelin’s water-mechanical method with retention of fractions for subsequent analyses using an electron microscope, energy-dispersion microanalyzer, and X-ray difractometer. The results demonstrated that the pelitic and subcolloidal fractions predominated in the grain size distribution of river SPM, with subordinate coarser fractions. Seasonal variations in the SPM concentration and the total amount of detrital and clay minerals are influenced by river water discharge and achieved a maximum in high water periods (spring flood and partly at the end of summer–autumn heavy rains). The subcolloidal fraction in the March sample stands out in the fine fraction distribution. Its share in this sample was the highest among these fractions throughout the year. The reason is probably related to the highest content of fine dispersed detrital minerals in the fraction. The question of why this is encountered only in March remains open.

Effects of filter structure, flow velocity, particle concentration and fouling on the retention efficiency of ultrafiltration for sub-20 nm gold nanoparticles

Ultrafiltration techniques with membranes of pore sizes under 100 nm have been widely applied in drinking water, wastewater, semiconductor and pharmaceutical process water treatments for nanoparticle (NP) and pathogen removal. The most direct way to evaluate the membrane performance is to experimentally obtain the size fractional retention efficiency. However, the real-life performance of the membrane in terms of fouling (or loading) characteristics and the effects of the concentration of challenging particles and rate of flux (or filtration velocities) on the filtration efficiency during fouling have not been well understood. In this study, systematic filtration experiments for filtration efficiency at clean and loaded conditions were conducted for three different 50 nm rated membrane filters, including PTFE (Polytetrafluoroethylene), PCTE (Polycarbonate Track-Etched) and MCE (Mixed Cellulose Ester) membranes, against 5, 10 and 20 nm Au NPs at different feed concentrations and fluxes. The results showed that the effects of feed concentration and flux are significant. This study provides important insights of retention mechanisms and efficiency for different ultrafiltration membrane structures at varied filtration velocities and fouling characteristics giving clear directions of future NP ultrafiltration research.

Cultivation, cultivar, and topdressing moisture effects on settling of topdressing sand

AbstractTwo desirable traits consistent in emerging creeping bentgrass (Agrostis stolonifera L.) cultivars are increased canopy density and fine leaf texture. Although the former is often associated with reduced incorporation of applied materials into the turf system, the effects of the latter have not yet been characterized. Some practitioners believe these boundaries can be overcome by topdressing with a dried sand, which they propose settles differently than conventional moist sand. In 2018, two topdressing studies were conducted to evaluate incorporation of moist and dried topdressing sands when applied to six creeping bentgrass cultivars of varying textures into vertically mowed and uncultivated systems. Cultivars were topdressed with dried sand or with moist sand and then incorporated with one of two brushing systems. Across trials, neither brush consistently outperformed the other. A larger proportion of applied topdressing sand was retained by the vertically mowed system and was unaffected by the moisture content of sand. Less sand was retained by uncultivated systems, and the distribution of both sands changed significantly. For moist sands, finer‐textured cultivars, in general, corresponded with greater removal of coarse fractions and a greater retention of fine fractions. Therefore, we provide supporting evidence that topdressing into vertically mowed systems, regardless of sand moisture content, results in enhanced sand incorporation. When topdressing uncultivated, fine‐textured bentgrass putting green systems, however, practitioners could benefit from topdressing with dried sands.

ISO 21083 – new international standard for determination of nanoparticles filtration efficienc

The new international standard ISO 21083 provides a method of testing filter media during the filtration of spherical shaped nanoparticles. The described procedure can be used to determine operating parameters of filtration materials of any classes. The filtration efficiency is determined on the basis of averaged results obtained for samples of the tested material in the initial state and after neutralization of the charge in the 2-propanol vapour. The standard does not introduce a division into filter classes, and in the final report of the tests, fractional particle retention efficiencies are given. This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

Membrane Characterisation for Fractionated Dextran Analysis in Sugar Industry

The separation characteristics of two polyethersulfone membranes (molecular weight cut-off (MWCO) specification of 4 kDa and 10 kDa) for the retention of different dextran fractions (T2000, T40, T10) from aqueous solutions were systematically investigated, aiming at implementing them as a preparatory step for dextran analysis in sugar industry practice. Ultrafiltration is used to cause differences in optical rotation due to mechanical separation of dextran from aqueous solutions. The membrane separation performance was evaluated using polarimetry and size exclusion chromatography. It was found that the presence of sucrose leads to dramatically improved separation efficiencies for both membrane settings. Specific cut-off values for the separation of dextran from aqueous sucrose solutions have been determined, 10 kDa and 50 kDa for the membranes with a MWCO specification of 4 kDa and 10 kDa, respectively. The data indicate that the basic membrane setting (MWCO of 4 kDa) enables the complete separation and therefore the analytical quantification of the whole molecular mass spectrum relevant for sugar industry. The combination of both membranes, furthermore, indicates that it is suited for the differentiation between a high and a low molecular mass dextran fraction. The application of this new approach for the determination of dextran with varying molecular masses at various contents in synthetic thin juices as well as in real sugar beet raw juices indicates promising prospects.

左室射血分数保留的心力衰竭的研究进展

左室射血分数保留的心力衰竭的研究进展

Differences in transport behavior of natural soil colloids of contrasting sizes from nanometer to micron and the environmental implications

Transport behaviors of nanoparticles (<100nm) and clay fractions (clay particles, <2μm; coarse clay particles, 1–2μm and fine clay particles, 0.1–1μm) extracted from two natural soils (Inceptisol from Jilin and Oxisol from Hainan, China) were investigated in saturated sand columns at 1–30mM NaCl and pH5–9. Increasing NaCl concentrations decreased the mobility, while increasing pH increased the mobility of soil particles of various sizes. At pH5 and 30mM NaCl, nanoparticles and clay fractions exhibited the different transport behaviors, and ripening was observed for Inceptisol nanoparticles while blocking for Oxisol nanoparticles in breakthrough curves (BTCs). The effluent mass recoveries (MRs) of nanoparticles were much more than that of clay particles for both two soils (>1.9-fold) at all tested conditions, except for Inceptisol at pH5 and 30mM NaCl (with comparable MR). According to Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations and particle-collector size ratios, both secondary energy minimum and physical straining led to the retention of clay fractions at pH5 and 30mM NaCl, whereas primary energy minimum and straining induced by simultaneous aggregation caused the retention of nanoparticles. The experimental attachment efficiency between soil particles of various sizes and sand collector for both two soils was in the order nanoparticles<fine clay particles<clay particles<coarse clay particles, indicating that soil nanoparticles had greater mobility than clay fractions. Consequently, nanoparticles are suggested to have greater risks to transport contaminants to surface and groundwater, once they are released from soils.