Initial Suspension Research Articles

A Study of Mn(II) Ion Capture by Mesoporous Silica

The removal of Mn(II) ions from water using mesoporous silica as the adsorbent material is discussed. The mesoporous silica was prepared in an economic manner through the use of sodium silicate as an inexpensive source of silica and decaoxyethylene cetyl ether [C-16(EO)(10)] as the template agent. The properties of the material were characterized and its adsorption capacity for Mn(II) ions from aqueous solution investigated by varying parameters such as the pH of the initial suspension, the contact time, the initial concentration of Mn(II) ions in the solution and the adsorbent dosage. With no subsequent modification, the prepared materials exhibited a high adsorption capability towards Mn(II) ions with q(e) = 44 mg/g. The adsorption isotherms could be described by both the Langmuir and Freundlich models, the former model providing a better representation of the adsorption process. Characterization using UV-vis spectroscopy, nitrogen sorption isotherms and thermogravimetric analysis after adsorption indicated that the Mn(II) ions were adsorbed onto the mesoporous silica surface. (Less)

A Mechanistic Study of the Selective Retention of SDS-Suspended Single-Wall Carbon Nanotubes on Agarose Gels

Elution chromatography through columns packed with agarose beads has been used to separate metallic from semiconducting single-wall carbon nanotubes (SWCNTs). Prior studies have attributed the separation to either selective adsorption or size-exclusion (due to selective aggregation) of semiconducting SWCNTs. Initial SWCNT suspensions with different aggregation states were prepared to test these compet- ing theories. Retention characteristics of the SWCNT suspen- sions were not affected by changes to aggregation state, except when the centrifugation time was short and aggregation ex- cessive. On the other hand, selective adsorption of nanotubes on the agarose matrix is confirmed by modifying the surfactant structure around the SWCNTs without changing the aggregation state of the suspension. In addition, salt-modifiers and solvent- modifiers allow systematic changes to the surfactant aggregation number, orientation, and sidewall coverage. The retention characteristics from these modified SWCNT suspensions suggest that surfactant orientation rather than the exposed regions on the surface of the nanotubes is the dominant factor in the adsorption process.

Turbidity and BOD removal of a paper recycling mill effluent by electro-coagulation technique

The purpose of this work was to provide an alternative to effluent treatment of an OCC paper recycling mill by electro-coagulation technique. The experiments carried out to find the optimum conditions for turbidity and biological oxygen demand (BOD) reduction of the effluent at four levels of electrolysis time (10, 20, 30 and 60 min), three initial suspension pH levels (3, 7.5 and 10), by two constant voltage of 9.0 and 12.0. The results indicated that electro-coagula tion is an effective technique for treatment of paper recycling mill effluent. At optimum conditions, more than 99.7% of turbidity and 96.1% of BOD were effectively removed.

STRUCTURAL OPTIMIZATION ALGORITHM FOR VEHICLE SUSPENSIONS

Stringent tolerances on mechanical components have created increasingly severe demands on the quality of new mechanical designs. The mathematical models used to analyze the various types of mechanical systems these days need to incorporate an optimization algorithm capable of minimizing the levels of vibrations coming from varied sources. The suggested method is based on the parallel combination of three methods; the Rayleigh-Ritz approach (to determine the first eigenfrequencies) which is incorporated into an efficient multicriterion optimization process based on the ESO (Evolutionary Structural Optimization) method and the finite element software ABAQUS. The analytical resolution and the numerical calculations of the mechanical component are, finally, validated by an experimental set-up which exploits a frequency analyser, acceleration sensors and an excitation hammer. The effectiveness of this approach is also demonstrated in the analysis of an upper car suspension arm. By gradually removing material from the initial car suspension design, the frequency of the component can be controlled in order to optimize the structural constraints.

The structure of the deposit produced by sedimentation of polydisperse suspensions

To interpret the deposits from particle-laden flows it is necessary to understand particle settling at their base. In this paper a quantitative model is developed that not only captures how particles settle out of suspension but also the composition of the final deposit in terms of its vertical distribution of grain sizes. The theoretical model is validated by comparison to published experimental data that has been used to interpret the field deposits of submarine sediment-laden flows (Amy et al., 2006). The model explains two intriguing features of the experimental deposits that are also observed in natural deposits. First, deposits commonly have an ungraded, or poorly normally graded, region overlain by a strongly normally graded region. Second, the normalized thickness of the ungraded region increases as the initial concentration of the suspension is increased. In the theoretical model, the poorly normally graded region results from a constant mass flux into the bed that persists until the largest grain size present within the flow has been completely deposited. The effect of increasing the concentration of the initial suspension is to increase the thickness of the poorly graded part of the deposit and to decrease its average grain size. This work suggests that deposits with relatively thick, poorly graded bases can form from relatively high-concentration polydisperse suspensions, when the initial volume fraction of sediment is greater than approximately 20% and indicates that it is important to include these hindered settling effects in models of depositing flows.

ChemInform Abstract: First Synthesis of 2‐Phosphonylated Quinoxaline 1,4‐Dioxides: An Extension to the Beirut Reaction.

AbstractGood yields are only obtained if the initial THF suspension is transformed to into a pasty film by slow evaporation of ca. 90& of the initial solvent volume.

Fungi, including Fusarium spp., on ears of conventionally and ecologically grown winter wheat

Ears of winter wheat cultivars (Bogatka and Legenda) grown under conventional and ecological (organic) farming systems, were sampled at different developmental stages and examined for their colonization by filamentous fungi, including Fusarium spp. Ears samples were shaken in sterile water containing 0.01% of Tween 80 and appropriate 10-fold dilutions of the initial suspension were inoculated onto agar medium containing antibiotics to inhibit bacterial contaminants. After 6-7 days of incubation at 28o C fungal colonies were counted and after further 4 days fragments of colonies were transferred onto other media for identification. On ears at flowering no Fusarium species were found in 2008 with dry and hot July, but in 2009 with more frequent rainfalls in July Fusarium poae, F. tricinctum and F. avenaceum were detected on winter wheat ears at the flowering stage. At the hard kernel stage the following species were isolated from winter wheat ears: F. poae and F. sporotrichioides in 2008 (17 and 18 isolates respectively) and F. avenacum, F. crookwellense, F. poae, F. sporotrichioides and F. tricinctum in 2009 (2, 18, 39, 2 and 17 isolates respectively, and 9 unidentified Fusarium). In 2008 more Fusarium spp. were found on winter wheat ears grown under the conventional system than under the ecological (organic) system. In the ecological system wheat stands are thinner but taller (due to the lack of any mineral fertilizers and plant growth regulators) and in consequence winter wheat ears in this system may keep moisture shorter than those in the conventional system. It seems that this difference may be the most important factor influencing colonization of winter wheat ears by Fusarium spp. and other fungi under the compared farming systems.

Selective redox degradation of chlorinated aliphatic compounds by Fenton reaction in pyrite suspension

Selective redox degradation of chlorinated aliphatics by Fenton reaction in pyrite suspension was investigated in a closed system. Carbon tetrachloride (CT) was used as a representative target of perchlorinated alkanes and trichloroethylene (TCE) was used as one of highly chlorinated alkenes. Degradation of CT in Fenton reaction was significantly enhanced by pyrite used as an iron source instead of soluble Fe. Pyrite Fenton showed 93% of CT removal in 140 min, while Fenton reaction with soluble Fe(II) showed 52% and that with Fe(III) 15%. Addition of 2-propanol to the pyrite Fenton system significantly inhibited degradation of TCE (99% to 44% of TCE removal), while degradation of CT was slightly improved by the 2-propanol addition (80–91% of CT removal). The result suggests that, unlike oxidative degradation of TCE by hydroxyl radical in pyrite Fenton system, an oxidation by the hydroxyl radical is not a main degradation mechanism for the degradation of CT in pyrite Fenton system but a reductive dechlorination by superoxide can rather be the one for the CT degradation. The degradation kinetics of CT in the pyrite Fenton system was decelerated (0.13–0.03 min −1), as initial suspension pH decreased from 3 to 2. The formation of superoxide during the CT degradation in the pyrite Fenton system was observed by electron spin resonance spectroscopy. The formation at initial pH 3 was greater than that at initial pH 2, which supported that superoxide was a main reductant for degradation of CT in the pyrite Fenton system.

Degradation of trichloroethylene by Fenton reaction in pyrite suspension

Degradation of trichloroethylene (TCE) by Fenton reaction in pyrite suspension was investigated in a closed batch system under various experimental conditions. TCE was oxidatively degraded by OH in the pyrite Fenton system and its degradation kinetics was significantly enhanced by the catalysis of pyrite to form OH by decomposing H 2O 2. In contrast to an ordinary classic Fenton reaction showing a second-order kinetics, the oxidative degradation of TCE by the pyrite Fenton reaction was properly fitted by a pseudo-first-order rate law. Degradation kinetics of TCE in the pyrite Fenton reaction was significantly influenced by concentrations of pyrite and H 2O 2 and initial suspension pH. Kinetic rate constant of TCE increased proportionally (0.0030 ± 0.0001–0.1910 ± 0.0078 min −1) as the pyrite concentration increased 0.21–12.82 g/L. TCE removal was more than 97%, once H 2O 2 addition exceeded 125 mM at initial pH 3. The kinetic rate constant also increased (0.0160 ± 0.005–0.0516 ± 0.0029 min −1) as H 2O 2 concentration increased 21–251 mM, however its increase showed a saturation pattern. The kinetic rate constant decreased (0.0516 ± 0.0029–0.0079 ± 0.0021 min −1) as initial suspension pH increased 3–11. We did not observe any significant effect of TCE concentration on the degradation kinetics of TCE in the pyrite Fenton reaction as TCE concentration increased.

Degradability of superparamagnetic nanoparticles in a model of intracellular environment:follow-up of magnetic, structural and chemical properties

The unique magnetic properties of iron oxide nanoparticles have paved the way for variousbiomedical applications, such as magnetic resonance cellular imaging or magneticallyinduced therapeutic hyperthermia. Living cells interact with nanoparticles by internalizingthem within intracellular acidic compartments. Although no acute toxicity of ironoxide nanoparticles has been reported up to now, the mechanisms of nanoparticledegradation by the cellular environment are still unknown. In the organism, thelong term integrity and physical state of iron-based nanoparticles are challengedby iron homeostasis. In this study, we monitored the degradation of 7 nm sizedmaghemite nanoparticles in a medium mimicking the intracellular environment.Magnetic nanoparticles with three distinct surface coatings, currently evaluated asMRI contrast agents, were shown to exhibit different kinetics of dissolution atan acidic pH in the presence of a citrate chelating agent. Our assessment of thephysical state of the nanoparticles during degradation revealed that the magneticproperties, size distribution and structure of the remaining nanocrystals were identicalto those of the initial suspension. This result suggests a model for nanoparticledegradation with rapidly dissolved nanocrystals and a reservoir of intact nanoparticles.

Photoluminescence of single‐wall carbon nanotube films

AbstractIn this work, we report the photoluminescence (PL) studies of the films produced by different methods from pristine single‐wall carbon nanotubes (SWNTs). The suspensions of CoMoCAT and HiPCO SWNTs were used to make two different types of films: the polymer films with embedded SWNTs and the SWNT films deposited onto quartz substrates through filtration. A density gradient ultracentrifugation (DGU) has been used for enrichment of the initial carbon nanotube suspensions with semiconducting SWNTs and extraction of various diameter nanotubes to reveal a role of the nanotube interaction in the films. Optical diagnostic techniques including Raman spectroscopy, UV–VIS–NIR absorption spectroscopy, and PL have been used for characterization and comparison of the initial suspensions and films formed from them. A PL mapping has revealed an arrangement of carbon nanotubes inside the films. A cross‐linkage between the individual SWNTs appeared to be higher inside the films deposited via filtration than in the polymer films with dispersed SWNTs. magnified image The images of objects under investigation (from left to right): a SWNT suspension after DGU; a film deposited onto quartz substrate and a polymer film with embedded SWNTs

First synthesis of 2-phosphonylated quinoxaline 1,4-dioxides: an extension to the Beirut reaction

An extension of the Beirut reaction for the preparation of the first members of the 2-phosphonylated quinoxaline 1,4-dioxide series is described. Contrary to their carboxylated equivalents, preparation of these new compounds could not be achieved under basic conditions but required the use of powdered molecular sieves. Good and reproducible yields were obtained only when the initial suspension in THF was transformed into a pasty film by slow evaporation of ca. 90% of the initial solvent volume.

Drying dissipative structures of colloidal crystals of silica spheres coated with polymer brushes of poly(carboxymethyl betaine)

Drying patterns of colloidal crystals of colloidal silica spheres coated with the brushes of zwitterionic poly(carboxymethyl betaine) (SiP-PCMB) and their parent silica spheres (SiP) were studied on a cover glass, a watch glass, and a Petri glass dish. Crystal structures kept the whole process of dryness of the suspensions of SiP-PCMB and SiP. Crystal structures of the dried films of SiP-PCMB were kept stable even when the initial suspensions contained 5 mM of sodium chloride, which is the important role of the excluded volume effects of the shells of the polymer brushes. On the other hand, crystal structures of SiP spheres in the dried films were much unstable and melted in the presence of 5 mM sodium chloride. In the suspension state, colloidal crystallization of SiP-PCMB took place stably by the contribution of the excluded volume effects besides the extended electrical double layers compared with that of SiP spheres, where only the double layer effect contributes to the crystallization. The fractal patterns of the complexation of SiP-PCMB or SiP spheres with sodium chloride were observed microscopically in the dried films. Several kinds of dissipative crystallization such as array and/or accumulation of the crystallites were observed, and the importance of the convectional and sedimentation processes during the course of dryness was demonstrated.

Mechanical properties of suspension plasma sprayed hydroxyapatite coatings submitted to simulated body fluid

Home synthesized (HA) powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto titanium substrate. The deposition process was optimized and the resulting coatings were soaked in simulated body fluid (SBF) for the periods of 3, 7, 14, 28, and 60 days at controlled temperature of 37 °C. The microstructural research enabled to find in the as-sprayed deposits two characteristic zones: (i) dense zone corresponding to the lamellas, observed usually in thermally sprayed coatings; (ii) sintered zone containing fine hydroxyapatite grains corresponding to the fine solids from initial suspension. The sintered zone disappears after soaking in SBF and the pores get filled by the reprecipitated calcium phosphates. The adhesion of the soaked coatings to the substrate was characterized by the critical load in the scratch test and was about 10 to 12 N. The Young modules of the coatings were determined with help of depth-sensing indentation test by the use of the technique developed by Oliver and Pharr. The modules were not depending on the time of soaking and their mean values were 15.6 and 28.4 GPa, depending on the coating operational parameters. The scratch test enables to determine the hardness of the coatings, which remained fairly constant during the time of soaking in the range of 3 to 5 GPa. This hardness was compared to that the Martens microhardness which doubled with time of soaking to reach up to 1 GPa.

Nano-Sized Ultrasound Contrast Agent: Salting-Out Method

Tumor imaging by ultrasound is greatly enhanced by the use of ultrasound contrast agents (UCAs), stabilized, gas-filled bodies. They are generally less than 7 microm to pass freely through the capillary bed. Development of a nano-sized agent would enable them to extravasate through the leaky pores of angiogenic vessels. We describe the development of an echogenic, nano-sized polylactic acid UCA by adaptation of a salting-out method. The viscosity of the initial colloidal suspension (concentration and molecular weight of protective colloid [polyvinyl alcohol (PVA)] and concentration of polymer) was key in determining particle size and polydispersity (increasing viscosity increased both). Addition of the porogens ammonium carbonate and camphor, required to produce hollow echogenic capsules, also increased the size (eg, 5 wt% PVA, mean solid nanocapsule size 386 +/- 25 nm, polydispersity index 0.367 +/- 0.14, and mean UCA size 640 +/- 18 nm, polydispersity index 0.308 +/- 0.027). Viscosity had the opposite effect on echogenicity of the resultant nano-UCA, which ranged from 21.69 +/- 0.78 dB for 2% PVA to 12.1 +/- 0.8 dB for 10% PVA. The UCA prepared with 10% PVA, however, had a longer half-life in the ultrasound beam (t(1/2) > 15 minutes vs t(1/2) < 10 minutes), suggesting a thicker shell. Optimization will require compromise among size, echogenicity, and stability.

The First-in-Human Study of the Hydrogen Sulfate (Hyd-Sulfate) Capsule of the MEK1/2 Inhibitor AZD6244 (ARRY-142886): A Phase I Open-Label Multicenter Trial in Patients with Advanced Cancer

In part A, the aim was to define the maximum tolerated dose (MTD) of the hydrogen sulfate (Hyd-Sulfate) oral capsule formulation of the mitogen-activated protein kinase kinase inhibitor AZD6244 (ARRY-142886). In part B, the aim was to compare the pharmacokinetic profile of the new Hyd-Sulfate capsule with the initial AZD6244 free-base suspension and further characterize the pharmacodynamic profile and efficacy of the new formulation. In part A, 30 patients received escalating doses of AZD6244 Hyd-Sulfate twice daily. In part B, 29 patients were randomized to a single dose of the Hyd-Sulfate capsule or free-base suspension, followed by a washout, then a single dose of the alternative formulation. Patients received the Hyd-Sulfate capsule twice daily at MTD of part A thereafter. The MTD of the Hyd-Sulfate capsule was 75 mg twice daily. Dose limiting toxicities were Common Terminology Criteria for Adverse Events grade 3 acneiform rash and pleural effusion. Fatigue (65.7%) and acneiform dermatitis (60.0%) were the most frequent adverse events at the MTD. Based on area under curve(0-24), exposure of the 75 mg Hyd-Sulfate capsule relative to the 100 mg free-base suspension was 197% (90% confidence interval, 161-242%). Pharmacodynamic analysis showed that inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced extracellular signal-regulated kinase phosphorylation in peripheral blood lymphocytes was related to plasma concentrations of AZD6244, with an estimated IC(50) of 352 ng/mL and maximum inhibition (E(max)) of approximately 91%, showing target inhibition. A patient with metastatic melanoma bearing a V600E BRAF mutation achieved a complete response persisting after 15 months of therapy. The AZD6244 Hyd-Sulfate capsule formulation has shown a favorable toxicity, pharmacokinetic, and pharmacodynamic profile, and is being taken forward in ongoing clinical trials.

Sedimentation of bidisperse suspensions

The average settling velocity of a suspension of identical particles through otherwise quiescent fluid is smaller than the settling velocity of a single particle in an unbounded fluid. When a suspension settles out to form a deposit, this hindered settling effect may lead to complicated sedimentation behaviour, even if the initial suspension is uniformly distributed. This study analyses the bulk sedimentation of bidisperse suspensions and calculates the evolution of the volume fraction of each species from an initially vertically uniform state through to the final steady state where both species have fully settled out of suspension and have formed a deposit. These calculations are analytical and employ the method of characteristics to reveal how both particle species evolve. The profiles often include ‘shocks’, across which discontinuous changes in volume fraction occur. Rarefaction fans may also be found across which the gradients of volume fraction are discontinuous. These new analytical solutions reveal the evolving composition of the suspension and the deposit and may be compared to experimental observations. They also provide test cases that can be used to verify recent numerical techniques for computing the bulk sedimentation behaviour of polydisperse suspensions.

High-amylose sodium carboxymethyl starch matrices for oral, sustained drug release: development of a spray-drying manufacturing process

Context: High-amylose sodium carboxymethyl starch (HASCA) was recently proposed as a material for oral, sustained drug-release tablets prepared by direct compression. It was produced on a pilot scale, but appeared to be unsuitable for tableting and sustained drug release. Pilot-scale dry powder HASCA was dispersed in hot water and then precipitated with ethanol to give a dry powder presenting the required properties, but very high volumes of ethanol were used to recover the product. Objective: A process was therefore designed to transform totally amorphous pregelatinized HASCA by spray-drying into a suitable sustained drug-release excipient for matrix tablets while decreasing ethanol quantities. Results and discussion: During the first manufacturing step, that is, heating of the initial hydro-alcoholic suspension, powder and water concentrations are key parameters for the acquisition of excellent binding properties. Hence, a variable ratio of amylose Vh, a crystalline polymorph of amylose, to the amorphous form, is observed depending on the key parameter values. As the most crystalline samples give the weakest tablets, binding properties do not appear to be linked to the presence of a Vh form of amylose. On the other hand, a high water concentration results in excessive tablet strength, that is, inverse conditions leading to the appearance of a Vh form of amylose. Finally, variations in hydro-alcoholic composition appear to affect only tableting properties and do not influence the drug-release rate. Conclusion: A process designed to transform totally amorphous pregelatinized HASCA by spray-drying is proposed for easier, economical industrial HASCA production.

Ability of sulfated glycoconjugates and disulfide-reductants to release bovine epididymal sperm bound to the oviductal epithelium in vitro

In Bos taurus, at ejaculation, epididymal sperm acquire a number of proteins secreted in the seminal plasma that increase their ability to interact with the female reproductive tract. Sperm-oviduct interaction comprises a transient sperm adhesion to the isthmus, the lower portion of the oviduct, followed by sperm release around ovulation. Oviductal fluid molecules, such as sulfated glycoconjugates and disulfide-reductants, are able to release bovine ejaculated sperm bound to the oviductal epithelium in vitro through the reduction of sperm surface protein disulfides to sulfhydryls. To understand whether the sperm molecules sensitive to releasing signals are already exposed on the surface of epididymal sperm, we studied the ability of cauda epididymal sperm to adhere to the oviductal epithelium and to be released by sulfated glycoconjugates and the disulfide-reductant penicillamine. Surface protein sulfhydryls in cauda epididymal sperm were analyzed in the initial suspension, in sperm bound to the in vitro–cultured oviductal epithelium, and in released sperm. Results showed that epididymal sperm are able to bind the oviductal epithelium in vitro, although at a lower extent than frozen-thawed ejaculated sperm; the interaction is mediated by oviductal cell microvilli that closely bind to the plasma membrane of the sperm head rostral region, as previously shown for ejaculated sperm. The sulfated glycoconjugates heparin, fucoidan, and dextran sulfate, as well as the disulfide-reductant penicillamine, are all powerful inducers of sperm release. The level of sulfhydryls in sperm surface proteins was (1) high in the initial sperm suspension; (2) low in bound sperm; (3) markedly increased in sperm released by heparin or by penicillamine. In conclusion, epididymal sperm are already able to bind the oviductal epithelium and to respond to the inducers of release through the reduction of sperm surface protein disulfides to sulfhydryls.

Degradation of trichloroethylene by Fe(II) chelated with cross-linked chitosan in a modified Fenton reaction

Degradation of trichloroethylene (TCE) by a modified Fenton reaction was investigated in aqueous solution. Fenton reaction can be significantly enhanced in the presence of Fe(II) chelated by cross-linked chitosan (CS) with glutaraldehyde (GLA) at neutral pH. A remarkable oxidative degradation of TCE (1.838 h(-1)) was observed in the modified Fenton system with Fe(II)-CS/GLA (10 mM and 2 g L(-1), respectively) and H(2)O(2) (318 mM), while no significant degradation (0.005 h(-1)) was observed in the classic Fenton reaction system with Fe(II) (10 mM) and H(2)O(2) (318 mM) at pH 7 in 5 h. The kinetic rate constants for the degradation of TCE in the modified Fenton system was dependent on the initial suspension pH, Fe(II) loading, CS/GLA dosage, and concentration of H(2)O(2). We observed the formation of surface Fe(II)-CS/GLA complex using microscopic analyses and identified Fe oxidation (Fe(II) to Fe(III)) coupled with H(2)O(2) reduction on the Fe(II)-CS/GLA surfaces during the modified Fenton reaction.