Multicomponent Matrix Research Articles

Multicomponent diffusion in gas mixtures

The known multicomponent diffusion calculation methods are compared. Main attention is focused on matrix methods of describing diffusion, which are well superior to analytical solutions from the standpoint of universality of description and ease of algorithmization of the computational procedure. Expedients used to calculate the elements of the multicomponent diffusion matrix have been analyzed, and an algorithm has been devised for calculating the dynamics of the formation of a concentration profile in a Stefan tube in the diffusion of a multicomponent mixture through an inert gas layer.

Development of new cement based matrices for safe disposal of hazardous metals: cadmium and caesium

The innovative multicomponent matrix for immobilising cadmium and caesium introduced in this paper consists of belite cement, gismondine type NaP zeolite and nanoadditions. With this innovative design, the solid blend was able to absorb a high proportion of simulated radioactive liquid waste. Matrix integrity and effect of the high waste/solid ratio were assessed by X-ray diffraction analysis, while BET-N2 surface area, pore size distribution and nanoporosity were determined with nitrogen adsorption isotherms. Matrices whose sole component was fly ash belite cement were used as a reference. This innovative material affords substantial social and environmental benefits, inasmuch as the cement used has a low CO2 content and low heat of hydration. Moreover, both the cement and the zeolite can be synthesised ecoefficiently from an industrial byproduct, thereby eliminating the need to stockpile waste while preserving natural resources and placing valorised byproducts on the market.

Separation possibilities of three-dimensional capillary electrophoresis

Separation possibilities of three-dimensional (3D) capillary electrophoresis (CE) were studied in this work. They were demonstrated using phthalic acid as a model analyte and human urine as a complex ionic model matrix. Complexity of the selected problem ordering from several facts, such as (i) analyte present on a trace concentration levels, (ii) analyte present in multicomponent matrix and (iii) analyte migrating in the region of electropherogram in which is naturally present the majority of ionizable organic compounds (i.e. potential interfering compounds). 3D tandem was created by (i) isotachophoresis (ITP) preseparation stage (first), (ii) ITP analytical stage (second), and (iii) capillary zone electrophoresis (CZE) analytical stage (third). Comparison of 2D and 3D CE employing two and three different CE stages, respectively, revealed considerably enhanced separation capability of the 3D CE system. Although no single ITP was sufficient for the effective sample pretreatment, the mutual combination of these two ITP steps do it. The proposed ITP tandem was based on the different migration pattern of two spacers–analyte–matrix constituents under different acid-base conditions (pH 3.1vs. pH 4.5 in ITP1 and ITP2, respectively), that can be, generally, very effective tool for acidic compounds present in multicomponent ionic matrices. Besides the enhanced separation selectivity/sample clean-up, the 3D CE method kept benefits of the hydrodynamically closed separation system with enhanced sample loadability, such as excellent (i) reproducibility of the measurements and (ii) concentration detection limits. Hence, this study clearly demonstrated great potentialities of 3D CE in the solving even the most advanced separation problems as can be found in bioanalytical field.

Pore Networks and Polymer Rearrangement on a Drug-Eluting Stent as Revealed by Correlated Confocal Raman and Atomic Force Microscopy

Drug release from and coating morphology on a CYPHER sirolimus-eluting coronary stent (SES) during in vitro elution were studied by correlated confocal Raman and atomic force microscopy (CRM and AFM, respectively). Chemical surface and subsurface maps of the SES were generated in the same region of interest by CRM and were correlated with surface topography measured by AFM at different elution times. For the first time, a direct correlation between drug-rich regions and the coating morphology was made on a drug-eluting medical device, linking drug release with pore formation, pore throats, and pore networks. Drug release was studied on a drug-eluting stent (DES) system with a multicomponent carrier matrix (poly(n-butyl methacrylate) [PBMA] and poly(ethylene-co-vinyl acetate) [PEVA]). The polymer was found to rearrange postelution because confluence of the carrier polymer matrix reconstituted the voids created by drug release.

Fabrication and characterization of a rapid prototyped tissue engineering scaffold with embedded multicomponent matrix for controlled drug release

Bone tissue engineering implants with sustained local drug delivery provide an opportunity for better postoperative care for bone tumor patients because these implants offer sustained drug release at the tumor site and reduce systemic side effects. A rapid prototyped macroporous polycaprolactone scaffold was embedded with a porous matrix composed of chitosan, nanoclay, and β-tricalcium phosphate by freeze-drying. This composite scaffold was evaluated on its ability to deliver an anthracycline antibiotic and to promote formation of mineralized matrix in vitro. Scanning electronic microscopy, confocal imaging, and DNA quantification confirmed that immortalized human bone marrow-derived mesenchymal stem cells (hMSC-TERT) cultured in the scaffold showed high cell viability and growth, and good cell infiltration to the pores of the scaffold. Alkaline phosphatase activity and osteocalcin staining showed that the scaffold was osteoinductive. The drug-release kinetics was investigated by loading doxorubicin into the scaffold. The scaffolds comprising nanoclay released up to 45% of the drug for up to 2 months, while the scaffold without nanoclay released 95% of the drug within 4 days. Therefore, this scaffold can fulfill the requirements for both bone tissue engineering and local sustained release of an anticancer drug in vitro. These results suggest that the scaffold can be used clinically in reconstructive surgery after bone tumor resection. Moreover, by changing the composition and amount of individual components, the scaffold can find application in other tissue engineering areas that need local sustained release of drug.

Srv Mediated Dispersal of Streptococcal Biofilms Through SpeB Is Observed in CovRS+ Strains

Group A Streptococcus (GAS) is a human specific pathogen capable of causing both mild infections and severe invasive disease. We and others have shown that GAS is able to form biofilms during infection. That is to say, they form a three-dimensional, surface attached structure consisting of bacteria and a multi-component extracellular matrix. The mechanisms involved in regulation and dispersal of these GAS structures are still unclear. Recently we have reported that in the absence of the transcriptional regulator Srv in the MGAS5005 background, the cysteine protease SpeB is constitutively produced, leading to increased tissue damage and decreased biofilm formation during a subcutaneous infection in a mouse model. This was interesting because MGAS5005 has a naturally occurring mutation that inactivates the sensor kinase domain of the two component regulatory system CovRS. Others have previously shown that strains lacking covS are associated with decreased SpeB production due to CovR repression of speB expression. Thus, our results suggest the inactivation of srv can bypass CovR repression and lead to constitutive SpeB production. We hypothesized that Srv control of SpeB production may be a mechanism to regulate biofilm dispersal and provide a mechanism by which mild infection can transition to severe disease through biofilm dispersal. The question remained however, is this mechanism conserved among GAS strains or restricted to the unique genetic makeup of MGAS5005. Here we show that Srv mediated control of SpeB and biofilm dispersal is conserved in the invasive clinical isolates RGAS053 (serotype M1) and MGAS315 (serotype M3), both of which have covS intact. This work provides additional evidence that Srv regulated control of SpeB may mediate biofilm formation and dispersal in diverse strain backgrounds.

Methods of detection and identification of manufactured nanoparticles

The actual methods of detection and identification of manufactured nanoparticles in both simple and complex multi-component matrix for assessing biological effects and safety of nanotechnology products have been reviewed. The detection of priority species of biologically active nanoparticles, which include fullerenes, single- and multi-walled carbon nanotubes, nanoparticles of silver, gold, titanium oxide, aluminum, cerium, zinc and silicon, has been given a special attention. The requirements for sample preparation have been discussed. The results of the successful application for the detection of manufactured nanoparticles in bioassays with methods of scanning and transmission electron microscopy, confocal laser scanning microscopy, atomic force microscopy, scanning tunneling microscopy, size exclusion chromatography, field-flow fractionation, electrophoretic, light scattering, spectrophotometry, fluorescent spectroscopy, X-ray and other spectrometry, mass spectrometry, "particle counters", immunochemistry have been reviewed. The possibilities and limitations of different techniques, and their complementarity have been analyzed.

Study of the critical points and the role of the pores and viscosity in carbamazepine hydrophilic matrix tablets

Percolation theory has been applied to estimate the Hypromellose (HPMC) percolation thresholds and the influence of the polymer viscosity and the initial porosity on these thresholds in carbamazepine multicomponent matrix formulations. Different batches containing two viscosity grades of HPMC as hydrophilic matrix forming polymer, MCC and lactose as fillers, and a lubricant mixture have been manufactured varying the compression pressure in order to obtain matrices with three levels of initial porosity. The results suggested the existence of an excipient percolation threshold between 13 and 15% v/v of HPMC for the different batches prepared. It has been found that the percolation threshold for this polymer is independent on the formulation factors studied in this paper: polymer viscosity and initial porosity of the matrices.

Unintended Water Mediated Cocrystal Formation in Carbamazepine and Aspirin Tablets

The water of crystallization released during dehydration of dibasic calcium phosphate dihydrate (DCPD) mediated the cocrystal formation between carbamazepine (CBZ) and nicotinamide (NMA) in intact tablets. The dehydration of DCPD, the disappearance of the reactants (CBZ and NMA) and the appearance of the product (CBZ-NMA cocrystal) were simultaneously monitored by quantitative powder X-ray diffractometry. In a second model system, the water of crystallization released by the dehydration of DCPD caused the chemical decomposition of aspirin. Salicylic acid, one of the decomposition products, reacted with CBZ to form CBZ-salicylic acid cocrystal in tablets. This is the first report of cocrystal formation in intact tablets, demonstrating water mediated noncovalent synthesis in a multicomponent matrix. While the potential implications of such transformations, on both the mechanical and biopharmaceutical properties, can be profound, their characterization, using conventional solution based analytical techniques, can be challenging.

Combination of chemical and electron-impact ionisation with GC×GC–qMS for characterization of fatty alcohol alkoxylate polymers in the low-molecular-weight range up to 700 Da

The class of fatty alcohol alkoxylates describes surfactants that are synthesised by reaction of fatty alcohols with alkoxides such as ethylene oxide or propylene oxide or a combination of both as copolymers. Such alkoxylates are used, for example, as nonionic surfactants in home and industrial cleaning and washing agents. Chemical characteristics of such alkoxylate copolymers, for example the degree of alkoxylation, the arrangement of building blocks (random or block polymerisation), the type of the starter, and endcapping, play an important role in application behaviour. The analysis of these characteristics is challenging because in many cases such copolymers have high polydispersity and a large number of constitutional isomers depending on the degree of alkoxylation. Furthermore, the alkoxylates often occur in a complex multicomponent matrix. Here we present a method for characterization of silylated fatty alcohol alkoxylates in the low-molecular-weight range by means of comprehensive two-dimensional gas chromatography-mass spectrometry with electron impact and chemical ionisation. This method also enables detailed analysis of the alkoxylates in a complex matrix such as modern detergents.

Diffusion Data in Silicate Melts

Atomic scale diffusion in silicate melts plays a critical role in a variety of magmatic processes, as long recognized by geologists (Bowen 1921). Geochemists have investigated diffusion in silicate melts (including stable liquids and supercooled liquids and glasses) using a variety of methods as micro-analytical tools becoming available (e.g., Medford 1973; Jambon and Carron 1976; Magaritz and Hofmann 1978a,b; Hofmann 1980; Shimizu and Kushiro 1984; Zhang et al. 1991a; Koepke and Behrens 2001; Saal et al. 2008). The investigations were aimed at understanding the mechanisms of diffusion, the effect of temperature, pressure, H2O content, f O2, and more generally melt composition on the diffusivities, and to measure the diffusivity values for geological applications. A large database is now available. This chapter reviews diffusion data relevant to magmatic systems. The large body of literature on diffusion in simple-system melts, of interests to glass and ceramic scientists, is not included in this review, nor are the calculated diffusivities from ab initio and molecular dynamics methods. This review covers literature diffusion data (except multicomponent diffusion matrix data, and those of H, C, O and noble gases) in multicomponent silicate melts (the term melts as used in this chapter also includes glasses), including melts with mineral compositions and including glasses. This chapter complements the other chapters on diffusion in silicate melts, which cover H, C and O diffusion (Zhang and Ni 2010, this volume), noble gas diffusion (Behrens 2010, this volume), theories and models of self and tracer diffusion (Lesher 2010, this volume), and multicomponent diffusion (Liang 2010, this volume). We have compiled experimental data on self, tracer and effective binary diffusion in Online Supplementary Table 1 (found at http://www.minsocam.org/MSA/RIM ), with about 3600 entries of individual diffusivity …

A model for the flow of gas mixtures in adsorption dominated dual-porosity reservoirs incorporating multi-component matrix diffusion—Part II numerical algorithm and application examples

In part one of this study a matrix-fracture transfer function was presented for multi-species gas migration in dual-porosity media. This second part presents the numerical implementation of this transfer function. Since the transfer function proposed in Part I is of an integral form with history-dependency and the resultant flow equations become a set of integro-(partial) differential equations, an algorithm is developed here for these equations. The algorithm is formulated using a step-by-step finite difference procedure combined with a fully implicit quadrature scheme. The quadrature scheme is based on the modified trapezoidal method and is designed for variable time-step size. The transfer function and the algorithm developed are incorporated into the commercial gas reservoir simulator SIMED II, and three examples are illustrated here. Example 1 demonstrates the performance and feasibility of the algorithm in applications, and Example 2 discusses the effect of higher order terms as well as its influence on flow profiles. The impact of mutual-diffusivity to flow profiles and well performance is illustrated in Example 3.

The multicomponent (2+1)-dimensional Glachette–Johnson (GJ) equation hierarchy and its super-integrable coupling system

This paper presents a set of multicomponent matrix Lie algebra, which is used to construct a new loop algebra ÃM. By using the Tu scheme, a Liouville integrable multicomponent equation hierarchy is generated, which possesses the Hamiltonian structure. As its reduction cases, the multicomponent (2+1)-dimensional Glachette–Johnson (GJ) hierarchy is given. Finally, the super-integrable coupling system of multicomponent (2+1)-dimensional GJ hierarchy is established through enlarging the spectral problem.

Three-Dimensional Wormhole and Ordered Mesostructures and Their Applicability as Optically Ion-Sensitive Probe Templates

Large-scale cubic Pm3n silica monoliths (HOM) were fabricated in wormhole and ordered mesostructures and in shape- and size-controlled cage pores by using a simple and fast strategy. The functional use of these 3D HOM monoliths as probe anchoring templates enabled the efficient designs of optical nanosensors. In this regard, the synthesized chromoionophore was physisorbed into the 3D HOM pore surface carriers without potential leaching. Results revealed that the structural features of the HOM monoliths such as ordered and worm-like cage pores substantially influenced the ion-sensing functionality in terms of their probe inclusion capacities, ion-transport diffusion, optical responsive profile, and visual color transition series during the detection of ultratraces of toxic Pb(II) ions. The nanosensors were selective in discriminating trace Pb(II) ions over multicomponent matrix species, with reliable and reproducible detection and quantification limits. A comparative study on the ion-sensing efficiency of ...

A new multi-component matrix loop algebra and a multi-component integrable couplings of the NLS-MKdV hierarchy and its Hamiltonian structure

A new multi-component matrix loop algebra is constructed, which is devoted to establishing an isospectral problem. By making use of Tu scheme, the multi-component integrable couplings of the NLS-MKdV hierarchy is obtained, then the bi-Hamiltonian structure of the above system is given.

Two types of multicomponent matrix loop algebras and its application

Two types of multicomponent matrix Lie algebras are constructed, which are devoted to obtain two types of new loop algebras ÃM−1. By making use of Tu scheme, integrable multicomponent Levi hierarchy and multicomponent Ablowitz-Kaup-Newell-Segur (AKNS) hierarchy are generated, which contain an arbitrary positive integer M. Furthermore, we expanded the multicomponent matrix loop algebra into a large one and work out integrable coupling of Levi hierarchy and AKNS hierarchy. This method proposed in this paper can be used generally.

Evaluation of a new peat-based sorbent for metals capture

A new peat-based sorbent was evaluated for the capture of heavy metals from waste streams. The media is a pelletted blend of organic humic material targeted for the capture of soluble metals from industrial waste streams and stormwater. The metals chosen for the media evaluation were Cd, Cu, Ni, and Zn due to their occurrence and abundance in waste streams and runoff. Sorption tests included an evaluation of the rate and extent of metals capture by the media, single versus multicomponent metals uptake, pH, anion influence, leaching effects and the effect of media moisture content on uptake rate and capacity. Isotherms of the sorption results showed that the presence of multiple metals increased the total sorption capacity of the media compared to the single component metal capacity; a result of site selectivity within the media. However the capacity for an individual metal in a multicomponent metal matrix was reduced compared to its single component capacity, due to competition for sites. Evidence of ion exchange behavior was observed but did not account for all metals capture. The media also provided a buffering action to counter the pH drop typically associated with metals capture.

Computer Simulation of the Precipitate Evolution during Industrial Heat Treatment of Complex Alloys

Precipitates are the key ingredient for the strength of heat treatable alloys. To optimize the mechanical properties of alloys it is important to know the response of precipitates to thermomechanical treatments. In the past, application of computer models to describe the evolution of precipitates in the course of these processes has proven difficult due to the complexity of the problem. In this work, a new model based on a mean-field representation of precipitates in a multicomponent matrix is applied to heat treatments of steels. Example simulations are presented for a 9- 12% Cr ferritic/martensitic heat resistant steel for power plant application and a complex tool steel with both carbides and intermetallic phases using the software MatCalc. The predictions of the model are verified on experimental results and the potential application to industrial heat treatment simulation is discussed.

Electrical properties of multicomponent CMM in correlation with their microstructure

In this work, electrical properties (resistance, resistance temperature coefficient, thermoelectric voltage, current–voltage curve) of multi-component ceramic matrix materials have been investigated. The influence of the structure of discrete particles on the microstructure and properties relations of CMM composites has been studied. Three groups of resistive materials were analyzed: (a) high resistance matrix and percolation clusters; (b) ionic or (c) covalent ceramic matrix and metal-like percolation clusters. The percolation threshold in composite materials is defined as the composition at which the conducting phase forms a continuous three-dimensional network through the material. However, in typical CMC we have observed a multi-threshold situation: at some content of conducting particles the first percolating clusters are formed; when the number of particles increases, clusters are destroyed to be created again at some higher content of conducting particles. These processes are strongly dependent on the starting materials properties, as well as on the thermal treatment of composites. Based on this approach a new product has been designed. Much attention was paid to the particulate structure and processing. A CMM with the resistance ratio R 800/ R 20 = 1.4 has been manufactured. Intensive resistance growth begins at 700 °C and the maximum is achieved at 1100 °C.

A model for the flow of gas mixtures in adsorption dominated dual porosity reservoirs incorporating multi-component matrix diffusion: Part I. Theoretical development

A matrix-fracture transfer function for multi-species gas flow with adsorption behavior is presented. This transfer function is developed from the extended Fick's law and therefore the coupling effect of mutual-diffusivity is included in the representation. The transfer function is formulated based on an exact formal solution of a set of linear partial differential equations for matrix blocks with regular geometry, and is expressed in the form of a series expansion with history-dependent integrals. This series, at first order, reduces to a simple algebraic expression that is of an equivalent computational efficiency in comparison with the extended Warren–Root model in which the mutual-diffusion effect is not present. The presented transfer function is compared with the Warren–Root relationship and it is shown that the Warren–Root model is a limiting case of the new model. It is also shown how the new model can be applied to reservoirs where gas is stored within the porosity rather than as an adsorbed phase.