Terms Of Mean Size Research Articles

Ammonium Glycyrrhizinate and Bergamot Essential Oil Co-Loaded Ultradeformable Nanocarriers: An Effective Natural Nanomedicine for In Vivo Anti-Inflammatory Topical Therapies.

Bergamot essential oil (BEO) and Ammonium glycyrrhizinate (AG), naturally derived compounds, have remarkable anti-inflammatory properties, thus making them suitable candidates for the treatment of skin disorders. Despite this, their inadequate physicochemical properties strongly compromise their topical application. Ultradeformable nanocarriers containing both BEO and AG were used to allow their passage through the skin, thus maximizing their therapeutic activity. Physicochemical characterization studies were performed using Zetasizer Nano ZS and Turbiscan Lab®. The dialysis method was used to investigate the release profile of the active compounds. In vivo studies were performed on human healthy volunteers through the X-Rite spectrophotometer. The nanosystems showed suitable features for topical cutaneous administration in terms of mean size, surface charge, size distribution, and long-term stability/storability. The co-delivery of BEO and AG in the deformable systems improved both the release profile kinetic of ammonium glycyrrhizinate and deformability properties of the resulting nanosystems. The topical cutaneous administration on human volunteers confirmed the efficacy of the nanosystems. In detail, BEO and AG-co-loaded ultradeformable vesicles showed a superior activity compared to that recorded from the ones containing AG as a single agent. These results are promising and strongly encourage a potential topical application of AG/BEO co-loaded nanocarriers for anti-inflammatory therapies.

Polyethylene Glycol-Stabilized Zein Nanoparticles Containing Gallic Acid

SUMMARYResearch backgroundGallic acid is a polyphenol with antioxidant and antitumor activities; however, its use as a nutraceutical or drug is hindered by its low bioavailability. Zein is a natural protein found in corn and has been applied as nanoparticle drug carrier. In this study, zein nanoparticles were obtained and stabilized with polyethylene glycol (PEG) as gallic acid carriers.Experimental approachNanoparticles were obtained by the liquid-liquid method and characterized in terms of mean size, polydispersity index, zeta potential, morphology, solid-state interactions and encapsulation efficiency/drug loading. The stability of nanoparticles was evaluated in simulated gastrointestinal fluids and food simulants, and the antioxidant activity was determined by the scavenging of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical.Results and conclusionsZein nanoparticles containing gallic acid were obtained and stabilized only in the presence of PEG. Under optimal conditions, nanoparticles with mean size <200 nm, low polydispersity index (<0.25) and negative zeta potential (−20 mV) were obtained. The gallic acid encapsulation efficiency was about 40%, loading about 5%, and it was encapsulated in an amorphous state. Fourier transform infrared spectroscopy (FTIR) did not identify chemical interactions after gallic acid nanoencapsulation. Zein nanoparticles were more prone to release the gallic acid in gastric than intestinal simulated medium; however, more than 50% of drug content was protected from premature release. In food simulants, the gallic acid release from nanoparticles was prolonged and sustained. Moreover, the nanoencapsulation did not reduce the antioxidant activity of gallic acid.Novelty and scientific contributionThe results show the importance of PEG in the formation and its effect on the properties of zein nanoparticles obtained by the liquid-liquid dispersion method. This study indicates that PEG-stabilized zein nanoparticles are potential carriers for oral intake of gallic acid, preserving its antioxidant properties and enabling its use in the pharmaceutical and food industries.

Optimization of dextran sulfate/poly-l-lysine based nanogels polyelectrolyte complex for intranasal ovalbumin delivery

The emerging trend in new vaccine development is to identify protective antigens and develop peptide-based vaccines able to offer a better immunogenicity/risk ratio. Nanogel (nGEL) can be designed to optimally present the delivered antigen to the immune system in controlled release formulations promoting their targeting to specific immune populations.Final properties of nGEL (size, surface charge) may be determining factors in designing the induced immune response. Taking into account these considerations, the aim of the study is the design of nGEL based on Dextran Sulfate (DS) and ϵ-Poly-lysine (εPL) of tunable size and surface charge by Response Surface Methodology (RSM) approach for nasal administration. nGEL systems were obtained by a mild and environmental-friendly physical cross-linking method. Based on the desirability function, the optimized formulation showed similar observed and predicted responses (errors <10%) in terms of mean size, polidispersity and surface charge. Stability studies were performed by Turbiscan® AGS technology on nGEL stored at 25 °C and 37 °C for 2 weeks and by dynamic light scattering on nGEL stored at 4 °C, 25 °C and 37 °C for 6 months. Citotoxicity evaluation was performed on HFF1, NCTC and Calu-3 cells after 24 h of treatment by MTT assay proving the safety of the optimized nGEL (≤0.117 mg/mL). The optimized formulation was successfully loaded with ovalbumin (OVA) as a model antigen and furtherly characterized for thermal behavior, encapsulation efficiency and in vitro release profile in phosphate buffer solution pH 5.8 to simulate the intranasal milieu. Loaded nGEL released nearly 43% of OVA within 72 h, assuring prolonged release to maximize exposure to the immune system.

Bioactivity and cytotoxicity of quercetin-loaded, lecithin-chitosan nanoparticles

Quercetin is a bioactive compound with potential application as an antioxidant in food matrices. However, the use of this flavonoid becomes a challenge due to its relative degree of hydrophobicity and low bioavailability. In order to improve its dispersibility in aqueous media, protection against degradation and the bioavailability of quercetin, this study aimed to develop quercetin-loaded, lecithin-chitosan nanoparticles (NPQ) and to characterize its physical, chemical and biological properties. The nanoparticles were characterized in terms of mean size, PDI, zeta potential, morphology, encapsulation efficiency, FT-IR, transmission electron microscopy (TEM) and thermal analysis (TGA and DSC). Stability over shelf life at 4 and 30 °C, antioxidant, antimicrobial and cytotoxicity activities were also determined. Quercetin was encapsulated in lecithin-chitosan nanoparticles (NP) with an efficiency of 98.31 ± 0.01%. NPQ presented a well-defined spherical morphology with a mean size of 240.81 ± 10.82 nm and a zeta potential of +38.9 ± 1.60 mV. Stability studies showed that NPQ are relatively stable over 28 days of storage at 4 °C and 30 °C. Regarding biological activities, NPQ were able to eliminate DPPH and ABTS radicals in the same way as free quercetin and showed antimicrobial activity, without presenting cytotoxicity against normal cells (L-929 and PBMC). These results suggest that quercetin-loaded, lecithin-chitosan nanoparticles have excellent potential for application in food matrices aiming at the development of new functional foods.

Zein-casein-lysine multicomposite nanoparticles are effective in modulate the intestinal permeability of ferulic acid

The objective of this study was to develop zein-casein-lysine nanoparticles to modulate the intestinal permeability of ferulic acid (FA), a bioactive compound with proven antioxidant properties. The nanoparticles were obtained by a liquid-liquid dispersion method and were characterized in terms of mean size, polydispersity index, zeta potential, association efficiency (AE), in vitro drug release, x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The in vitro intestinal permeability of nanoparticles was evaluated through Caco-2 and Caco-2/HT29-MTX monoculture and co-culture models, respectively. Nanoparticles presented a mean size of 199 nm and zeta potential of −26 mV. The AE of FA was 23% evaluated by high-performance liquid chromatography (HPLC). XRD showed amorphization of FA after association and FT-IR showed no changes in chemical structures of the compounds after nanoencapsulation. The cytotoxicity assays demonstrated that multicomposite nanoparticles presented a safe profile against Caco-2 and HT29-MTX cells. In the in vitro permeability assay, free FA exhibited higher permeability compared to FA-loaded nanoparticles, possibly due to prolonged FA release from nanoparticles. These new developed zein-casein-lysine nanoparticles may be used for FA sustained delivery by the oral route.

Optimal design for longitudinal studies to estimate pubertal height growth in individuals

Background: The SITAR model expresses individual pubertal height growth in terms of mean size, peak height velocity (PHV) and age at PHV.Aim: To use SITAR to identify the optimal time interval between measurements to summarise individual pubertal height growth.Subjects and methods: Heights in 3172 boys aged 9–19 years from Christ’s Hospital School measured on 128 679 occasions (a median of 42 heights per boy) were analysed using the SITAR (SuperImposition by Translation And Rotation) mixed effects growth curve model, which estimates a mean curve and three subject-specific random effects. Separate models were fitted to sub-sets of the data with measurement intervals of 2, 3, 4, 6, 12 and 24 months, and the different models were compared.Results: The models for intervals 2–12 months gave effectively identical results for the residual standard deviation (0.8 cm), mean spline curve (6 degrees of freedom) and random effects (correlations >0.9), showing there is no benefit in measuring height more often than annually. The model for 2-year intervals fitted slightly less well, but needed just four-to-five measurements per individual.Conclusions: Height during puberty needs to be measured only annually and, with slightly lower precision, just four biennial measurements can be sufficient.

Upper-Bound Efficiency of Spray Towers To Capture CO2 Using Polydispersed NH3 Droplets

Chemical absorption of CO2 with aqueous NH3 was numerically analyzed in an Eulerian manner for steady 1D spray towers in which gas velocity and liquid flow were uniform, and the results were formulated into a universal correlation. The capture efficiency η predicted by the proposed correlation is a sort of upper bound, and can be used as a base to evaluate the optimality of each design. Drop-size poly dispersity was considered; a spray of poly dispersed droplets was found to be equivalent in η to a spray of monodispersed droplets of an equivalent diameter, and a general formula for the equivalent size was attained in terms of mean size and geometric standard deviation. Total mass transfer coefficient was linearly proportional to the gas–liquid flow rate ratio, and the efficiency correlation agreed well with published results.

Nanoencapsulation strategies for the delivery of novel bifunctional antioxidant/σ1 selective ligands

Nowadays sigma-1 receptors are considered as new therapeutic objectives for central nervous system neurodegenerative diseases. Among different molecules, alpha lipoic acid has been identified as a natural potent antioxidant drug, whose therapeutic efficacy is limited by its many drawbacks, such as fast metabolism, poor bioavailability and high physico-chemical instability. Alfa-lipoic acid derivatives have been recently developed demonstrating their neuroprotective activity and effectiveness in different types of oxidative stress. In this work, two derivatives containing an amide or an ester functional group with different lipophilicity, were selected for their important affinity for sigma-1 receptors. Herein, in order to improve the in vitro stability and antioxidant effectiveness of alpha-lipoic acid derivatives, we focused our efforts in the nanoencapsulation strategies. Aqueous-core nanocapsules for the delivery of the hydrophilic compound and nanostructured lipid carrier for the lipophilic derivative, were properly designed and prepared using a direct or inverse eco-friendly organic solvent-free procedure. All nanosystems were characterized in terms of mean size, polydispersity, stability, morphology, encapsulation efficiency and in vitro release profiles. In order to evaluate the nanocarriers biocompatibility and antioxidant effectiveness, in vitro biological studies (cell viability, total antioxidant capacity and total oxidative status) were developed on primary human whole blood cell cultures, on both unloaded and derivatives-loaded nanodevices.

Study of two impinging flow microsystems arranged in series. Application to emulsified biofuel production

Development of alternative fuels and improvement of their combustion is a necessity in a general context of scarcity of fossil energy resources and of environmental pollution. In particular, the use of water dispersed in biofuels is known to improve combustion quality of diesel engine and to reduce pollution in gas emissions. This work aims at contributing in the development of a compact continuous emulsifier that could be used to feed energy systems. In order to fulfil requests such as convenient size of water droplets, absence of surfactant and needed flow rates of biofuel, the association of two micro-systems in series is investigated and compared to the use of a single one. The comparison of the emulsions obtained by the different systems is made in terms of mean size and size distribution of the water droplets in the dispersion, and process energy consumption. In the absence of surfactant, depending on applied flow-rates and water fraction, the use of two micro-systems in series allows to reduce the mean size of droplets by a factor 2 to about 3. Flow phenomena which lead to water phase fragmentation are described thanks to high-speed visualization of the flows in the micro-channels.

Entrapment of an EGFR inhibitor into nanostructured lipid carriers (NLC) improves its antitumor activity against human hepatocarcinoma cells.

BackgroundIn hepatocellular carcinoma (HCC), different signaling pathways are de-regulated, and among them, the expression of the epidermal growth factor receptor (EGFR). Tyrphostin AG-1478 is a lipophilic low molecular weight inhibitor of EGFR, preferentially acting on liver tumor cells. In order to overcome its poor drug solubility and thus improving its anticancer activity, it was entrapped into nanostructured lipid carriers (NLC) by using safe ingredients for parenteral delivery.ResultsNanostructured lipid carriers (NLC) carrying tyrphostin AG-1478 were prepared by using the nanoprecipitation method and different matrix compositions. The best system in terms of mean size, PDI, zeta potential, drug loading and release profile was chosen to evaluate the anti-proliferative effect of drug-loaded NLC versus free drug on human hepatocellular carcinoma HA22T/VGH cells.ConclusionsThanks to the entrapment into NLC systems, tyrphostin AG-1478 shows an enhanced in vitro anti-tumor activity compared to free drug. These finding raises hope of future drug delivery strategy of tyrphostin AG-1478 -loaded NLC targeted to the liver for the HCC treatment.

Transferrin-Conjugated SNALPs Encapsulating 2′-O-Methylated miR-34a for the Treatment of Multiple Myeloma

Stable nucleic acid lipid vesicles (SNALPs) encapsulating miR-34a to treat multiple myeloma (MM) were developed. Wild type or completely 2′-O-methylated (OMet) MiR-34a was used in this study. Moreover, SNALPs were conjugated with transferrin (Tf) in order to target MM cells overexpressing transferrin receptors (TfRs). The type of miR-34a chemical backbone did not significantly affect the characteristics of SNALPs in terms of mean size, polydispersity index, and zeta potential, while the encapsulation of an OMet miR-34a resulted in a significant increase of miRNA encapsulation into the SNALPs. On the other hand, the chemical conjugation of SNALPs with Tf resulted in a significant decrease of the zeta potential, while size characteristics and miR-34a encapsulation into SNALPs were not significantly affected. In an experimental model of MM, all the animals treated with SNALPs encapsulating miR-34a showed a significant inhibition of the tumor growth. However, the use of SNALPs conjugated with Tf and encapsulating OMet miR-34a resulted in the highest increase of mice survival. These results may represent the proof of concept for the use of SNALPs encapsulating miR-34a for the treatment of MM.

Use of β-galactosidase liposome model as a novel method to screen freeze-drying cryoprotectants

This study developed a novel method of screening cryoprotectants used to improve the survivability of lyophilized Lactobacillus helveticus. To develop a liposome encapsulated β-galactosidase (β-gal) as a cell membrane model, the β-gal liposome was characterized in terms of mean size, poly dispersity index, zeta potential, along with transmission electron microscopy. 800W of ultrasonic power and 10min of sonication time were the optimal experimental conditions to obtain the desirable β-gal liposome. Subsequently, different cryoprotectants were mixed with the β-gal liposome during freeze-drying. After freeze-drying, liposomes were hydrolized, and the protective effect of cryoprotectants was assessed as the release rate of encapsulated β-gal. The lowest release rate of β-gal was obtained using 10mg/100ml trehalose and 0.2mg/100ml hyaluronic acid.

Harmonisation of nanoparticle concentration measurements using GRIMM and TSI scanning mobility particle sizers

Regional studies focusing on the role of atmospheric nanoparticles in climate change have gained impetus in the last decade. Several multi- institutional studies involving measurement of nano- particles with several kinds of instruments are on the rise. It is important to harmonize these measurements as the instruments may work on different techniques or principles and are developed by different manufactur- ers. Scanning mobility particle sizers (SMPS) are often used to measure size distribution of nanoparti- cles in the airborne phase. Two such commercially available instruments namely, GRIMM and TSI- SMPS have been compared for ambient and laboratory generated conditions. A stand-alone condensation particle counter (CPC) of TSI make was used as a reference for particle concentration measurements. The consistency of the results in terms of mean size and geometric standard deviation was seen to be excellent for both the SMPSs, with GRIMM always showing slightly (approximately 10 %) lower mean size. The integrated number concentration from GRIMM-SMPS was seen to be closer to stand-alone reference CPC compared to TSI-SMPS, for an ambient overnight comparison. However, a concen- tration-dependent response, i.e. the variations between the two instruments increasing with the concentration, was observed and possible reasons for this have been suggested. A separate experiment was performed for studying the modifying effect of diffusion dryer and sheath air dryer on the measured aerosol size spectra. A significant hygroscopic growth was noted when diffusion dryer was attached to one of the SMPS. The introduction of sheath air dryer in GRIMM-SMPS produced a significant shift towards lower mean size. These results have been compared and discussed with the recent inter-comparison results to strengthen and harmonize the measurement protocols.

Development and Characterization of Niosomal Formulations of Doxorubicin Aimed at Brain Targeting

The aim of the present work was the development and characterization of a niosomal formulation functionalized with the glucose-derivative N-palmitoylglucosamine (NPG) to obtain a potential brain targeted delivery system for the anticancer agent doxorubicin. Five different methods have been examined for vesicle preparation. Light scattering and transmission electron microscopy were used for vesicle characterization, in terms of mean size, homogeneity and Zeta potential, and selection of the best composition and preparation conditions for developing NPG-functionalized niosomes. Drug entrapment efficiency was determined after separation of loaded from unloaded drug by size exclusion chromatography or dialysis. Preliminary in vivo studies were performed on rats, injected i.v. with 12 mg/kg of doxorubicin as commercial solution (Ebewe, 2 mg/mL) or NPG-niosomal formulation. Drug amounts in the blood and in the major organs of the animals, sacrificed 60 min post injection, were determined by HPLC. The selected formulation consisted in Span:cholesterol:Solulan:NPG (50:40:10:10 mol ratio) vesicles obtained by thin-layer evaporation, leading to homogeneous vesicles of less than 200 nm diameter. This formulation was used for preparation of NPG-niosomes loaded with doxorubicin (mean size 161±4 nm, encapsulation efficacy 57.8±1.8%). No significant changes (P>0.05) in vesicle dimensions, Zeta potential or entrapment efficiency were observed after six months storage at room temperature, indicative of good stability. I.v. administration to rats of the NPG-niosomal formulation allowed for reducing drug accumulation in the heart and keeping it longer in the blood circulation with respect to the commercial formulation. Moreover, a doxorubicin brain concentration of 2.9±0.4 μg/g was achieved after 60 min, while the commercial solution yielded undetectable drug brain concentrations (<0.1 μg/g). The developed NPG-niosomal formulation gave rise to stable, nano-sized vesicles, able to improve doxorubicin brain delivery. Positive results of preliminary in vivo studies require future pharmacokinetic studies to gain more insight into the mechanism of drug transport of functionalized niosomes.

Lipid nanoparticles as delivery vehicles for the Parietaria judaica major allergen Par j 2

Parietaria pollen is one of the major causes of allergic reaction in southern Europe, affecting about 30% of all allergic patients in this area. Specific immunotherapy is the only treatment able to modify the natural outcome of the disease by restoring a normal immunity against allergens. The preparation of allergen-solid lipid nanoparticles as delivery vehicles for therapeutic proteins, P. judaica major allergen Par j 2, was investigated. The Par j 2 allergen was expressed in a large amount in Escherichia coli and purified to homogeneity. Its immunological properties were studied by western blotting and enzyme-linked immunosorbent assay inhibition. Solid lipid nanoparticles were obtained by water-in-oil-in-water multiple emulsion method and characterized in terms of mean size and surface charge. These systems (approximately 250 nm diameter and negative surface charge) incorporated recombinant Par j 2 with 40% or greater efficiency. Moreover, the endotoxin level and anaphylactic activity of the empty solid lipid nanoparticles and recombinant Par j 2-loaded solid lipid nanoparticles were evaluated by looking at the overexpression of CD203c marker on human basophils. These results demonstrate that recombinant Par j 2-nanoparticles could be proposed as safe compositions for the development of new therapeutic dosage forms to cure allergic reactions.

In vitro anticancer activity of docetaxel-loaded micelles based on poly(ethylene oxide)-poly(epsilon-caprolactone) block copolymers: Do nanocarrier properties have a role?

In this paper we have investigated the behavior of core-shell poly(ethylene oxide)-poly(epsilon-caprolactone) (PEO-PCL) micelles derived from copolymers with linear triblock (TR) and 4-arm star-diblock (ST) architectures for the delivery of docetaxel (DTX). DTX was loaded inside micelles (DTX-TR m and DTX-ST m) with high efficiency and released slowly for more than two weeks. DTX-loaded micelles based on both copolymers had very similar properties in terms of mean size, zeta potential, loading ability and release rate in buffered saline. However, the stability of DTX-ST m was very poor in aqueous media with proteins resulting in a strong and progressive aggregation. We studied the effect of increasing concentrations of free DTX or DTX-loaded micelles on growth inhibition of human breast MCF-7 and MDA-MB468 and prostate PC3 and DU145 adenocarcinoma cell lines. DTX-loaded TR micelles induced cell growth inhibition similarly to free DTX whereas DTX-ST m showed lower cytotoxicity. On the other hand, by normalizing IC 50 values for the actual amount of DTX released from micelles in the medium, DTX-loaded ST micelles became more active than free DTX in all cell lines tested. Both free DTX and DTX-loaded TR micelles displayed a significantly lower cytotoxic activity in G 2/M phase synchronized cells, whereas cytotoxicity of DTX-loaded ST micelles did not change. Cytotoxicity was related to micelle stability, uptake and release rate in cell culture media. Our results suggest that for a correct interpretation of cytotoxicity of nanocarriers, the evaluation of their behavior in biologically relevant conditions is of utmost importance to select proper systems for further in vivo testing.

Biocompatible polymeric micelles with polysorbate 80 for use in brain targeting

In this paper, the synthesis and characterization of novel amphiphilic graft copolymers based on anα,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) backbone and D,L-polylactic acid (PLA)hydrophobic side chains are reported. These copolymers were obtained starting fromPHEA–ethylenediamine (PHEA–EDA), which was functionalized with polysorbate 80(PS80) and/or PLA in order toobtain the PHEA–EDA–PS80–PLA and PHEA–EDA–PLA samples, respectively. The degrees of derivatization,DDPS80 andDDPLA, ofPHEA–EDA–PS80–PLA,calculated by 1H-NMR,resulted in being 1.2 ± 0.03 mol% and 0.54 ± 0.05 mol%, respectively, while that of PHEA–EDA–PLA was found to be0.60 ± 0.05 mol%. Size exclusion chromatography (SEC) analysis confirmed theoccurrence of derivatization, the molecular weight values being close tothe theoretical ones. Polymeric micelles from PHEA–EDA–PLA andPHEA–EDA–PS80–PLA copolymers were obtained by using the dialysis method and were characterized in termsof mean size, zeta potential, critical aggregation concentration (CAC), and surface compositionby x-ray photoelectron spectroscopy (XPS) analysis, which demonstrated the presence ofPS80 onto thePHEA–EDA–PS80–PLA micelle surface. In vitro experiments demonstrated that these systems had no cytotoxiceffects on 16 HBE, Caco2, HuDe and K562 cell lines, and no haemolytic activity. Moreover, bothPHEA–EDA–PS80–PLA and PHEA–EDA–PLA micelles were able to penetrate into Neuro2a cells and, in the case ofPS80 decorated micelles, to escape from phagocytosis by the J774 A1 macrophages.

SOME PROBLEMS WITH ASSESSING COPE'S RULE

Cope's Rule states that the size of species tends to increase along an evolutionary lineage. A basic statistical framework is elucidated for testing Cope's Rule and some surprising complications are pointed out. If Cope's Rule is formulated in terms of mean size, then it is not invariant to the way in which size is measured. If Cope's Rule is formulated in terms of median size, then it is not invariant to the degree of separation between ancestral and descendant species. Some practical problems in assessing Cope's Rule are also described. These results have implications for the empirical assessment of Cope's Rule.

Effects of elevated CO2 on intra‐specific competition in Sinapis alba: an examination of the role of growth responses to red:far‐red ratio

Response of plants to elevated CO2 differs markedly between individually- and competitively-grown plants, both in terms of mean size and variation about the mean. Using Sinapis alba, we explored whether these contrasting effects are a consequence of the effect of competition on the red:far red (R:FR) light ratio. Plants were grown at both ambient and elevated (700 microl.l(-1)) CO2 in competitive stands, and as individuals at either a low (0.7) or high (1.25) R:FR ratio at a constant photosynthetic photon fluence rate. Elevated CO2 increased stand biomass by enhancing the growth of canopy dominants, but not the subordinates. As a consequence, elevated CO2 increased the coefficient of variation in size within the stands. Elevated CO2 did not enhance the growth of individually-grown plants at the low R:FR ratio, but did at the high R:FR ratio. Both the poor response of subordinate plants to elevated CO2 and the increased size inequalities of individuals within the stand can be explained in terms of the effect of the R:FR ratio on CO2 responsiveness. The effect of the R:FR ratio on CO2 response may be related to its effect on allocation patterns and nutrient uptake.

The role of SBR mixed liquor volume exchange ratio in aerobic granulation

Four sequencing batch reactors (SBR) were operated at different volume exchange ratios of 20–80%. Results showed that a rapid aerobic granulation could be achieved in SBR run at high volume exchange ratios, and the characteristics of mature aerobic granules in terms of mean size, SVI, granule fraction, EPS and calcium content were all closely related to the volume exchange ratio applied to SBR. To interpret the role of volume exchange ratio in aerobic granulation, a concept of minimum settling velocity of bioparticles was proposed, which is the function of both settling time and volume exchange ratio. It was further demonstrated that the effect of volume exchange ratio on aerobic granulation in SBR would be realized through selecting the minimum settling velocity of bioparticles. In fact, the minimum settling velocity would serve as a major selection pressure exerted on bioparticles. It appeared from this study that the production of EPS was stimulated significantly by high volume exchange ratio, which was associated with marketable accumulation of calcium ion in aerobic granulation. It is expected that this study may offer insights into the mechanism of aerobic granulation.