Electronically conductive phospho-olivines as lithium storage electrodes

Lithium transition metal phosphates have become of great interest as storage cathodes for rechargeable lithium batteries because of their high energy density, low raw materials cost, environmental friendliness and safety. Their key limitation has been extremely low electronic conductivity, until now believed to be intrinsic to this family of compounds. Here we show that controlled cation non-stoichiometry combined with solid-solution doping by metals supervalent to Li+ increases the electronic conductivity of LiFePO4 by a factor of approximately 10(8). The resulting materials show near-theoretical energy density at low charge/discharge rates, and retain significant capacity with little polarization at rates as high as 6,000 mA x g(-1). In a conventional cell design, they may allow development of lithium batteries with the highest power density yet.

Physical and chemical properties of a new root-end filling material

This study determined the chemical composition, pH, and radiopacity of mineral trioxide aggregate (MTA), and also compared the setting time, compressive strength, and solubility of this material with those of amalgam, Super-EBA, and Intermediate Restorative Material (IRM). X-ray energy dispersive spectrometer in conjunction with the scanning electron microscope were used to determine the composition of MTA, and the pH value of MTA was assessed with a pH meter using a temperature-compensated electrode. The radiopacity of MTA was determined according to the method described by the International Organization for Standardization. The setting time and compressive strength of these materials were determined according to methods recommended by the British Standards Institution. The degree of solubility of the materials was assessed according to modified American Dental Association specifications. The results showed that the main molecules present in MTA are calcium and phosphorous ions. In addition, MTA has a pH of 10.2 initially, which rises to 12.5 three hours after mixing. MTA is more radiopaque than Super-EBA and IRM. Amalgam had the shortest setting time (4 min) and MTA the longest (2 h 45 min). At 24 h MTA had the lowest compressive strength (40 MPa) among the materials, but it increased after 21 days to 67 MPa. Finally, except for IRM, none of the materials tested showed any solubility under the conditions of this study.

Cooperative organization of inorganic-surfactant and biomimetic assemblies

A model that makes use of the cooperative organization of inorganic and organic molecular species into three dimensionally structured arrays is generalized for the synthesis of nanocomposite materials. In this model, the properties and structure of a system are determined by dynamic interplay among ion-pair inorganic and organic species, so that different phases can be readily obtained through small variations of controllable synthesis parameters, including mixture composition and temperature. Nucleation, growth, and phase transitions may be directed by the charge density, coordination, and steric requirements of the inorganic and organic species at the interface and not necessarily by a preformed structure. A specific example is presented in which organic molecules in the presence of multiply charged silicate oligomers self-assemble into silicatropic liquid crystals. The organization of these silicate-surfactant mesophases is investigated with and without interfacial silicate condensation to separate the effects of self-assembly from the kinetics of silicate polymerization.

45S5 Bioglass-derived glass-ceramic scaffolds for bone tissue engineering

Three-dimensional (3D), highly porous, mechanically competent, bioactive and biodegradable scaffolds have been fabricated for the first time by the replication technique using 45S5 Bioglass powder. Under an optimum sintering condition (1000 degrees C/1h), nearly full densification of the foam struts occurred and fine crystals of Na2Ca2Si3O9 formed, which conferred the scaffolds the highest possible compressive and flexural strength for this foam structure. Important findings are that the mechanically strong crystalline phase Na2Ca2Si3O9 can transform into an amorphous calcium phosphate phase after immersion in simulated body fluid for 28 days, and that the transformation kinetics can be tailored through controlling the crystallinity of the sintered 45S5 Bioglass. Therefore, the goal of an ideal scaffold that provides good mechanical support temporarily while maintaining bioactivity, and that can biodegrade at later stages at a tailorable rate is achievable with the developed Bioglass-based scaffolds.

Mineral trioxide aggregate: a comprehensive literature review--part II: leakage and biocompatibility investigations

INTRODUCTION

Mineral trioxide aggregate (MTA) was developed because existing materials did not have the ideal characteristics for orthograde or retrograde root-end fillings. MTA has been recommended primarily as a root-end filling material, but it has also been used in pulp capping, pulpotomy, apical barrier formation in teeth with open apexes, repair of root perforations, and root canal filling. Part I of this literature review presented a comprehensive list of articles regarding the chemical and physical properties as well as the antibacterial activity of MTA. The purpose of part II of this review is to present a comprehensive list of articles regarding the sealing ability and biocompatibility of this material.

METHODS

A review of the literature was performed by using electronic and hand-searching methods for the sealing ability and biocompatibility of MTA from November 1993-September 2009.

RESULTS

Numerous studies have investigated the sealing ability and biocompatibility of MTA.

CONCLUSIONS

On the basis of available evidence it appears that MTA seals well and is a biocompatible material.

Two-Dimensional Nanomaterials for Biomedical Applications: Emerging Trends and Future Prospects

Two-dimensional (2D) nanomaterials are ultrathin nanomaterials with a high degree of anisotropy and chemical functionality. Research on 2D nanomaterials is still in its infancy, with the majority of research focusing on elucidating unique material characteristics and few reports focusing on biomedical applications of 2D nanomaterials. Nevertheless, recent rapid advances in 2D nanomaterials have raised important and exciting questions about their interactions with biological moieties. 2D nanoparticles such as carbon-based 2D materials, silicate clays, transition metal dichalcogenides (TMDs), and transition metal oxides (TMOs) provide enhanced physical, chemical, and biological functionality owing to their uniform shapes, high surface-to-volume ratios, and surface charge. Here, we focus on state-of-the-art biomedical applications of 2D nanomaterials as well as recent developments that are shaping this emerging field. Specifically, we describe the unique characteristics that make 2D nanoparticles so valuable, as well as the biocompatibility framework that has been investigated so far. Finally, to both capture the growing trend of 2D nanomaterials for biomedical applications and to identify promising new research directions, we provide a critical evaluation of potential applications of recently developed 2D nanomaterials.

Physicochemical basis of the biologic properties of mineral trioxide aggregate

This study characterized the interactions of mineral trioxide aggregate with a synthetic tissue fluid composed of a neutral phosphate buffer saline solution and root canal dentin in extracted human teeth using inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. Mineral trioxide aggregate exposed to synthetic tissue fluid at 37 degrees C released its metallic constituents and produced precipitates with a composition and structure similar to that of hydroxyapatite [Ca10(PO4)6(OH)2-HA]. Endodontically prepared teeth filled with mineral trioxide aggregate and stored in synthetic tissue fluid at 37 degrees C for 2 months produced at the dentin wall an adherent interfacial layer that resembled hydroxyapatite in composition. The authors conclude that Ca, the dominant ion released from mineral trioxide aggregate, reacts with phosphates in synthetic tissue fluid, yielding hydroxyapatite. The dentin-mineral trioxide aggregate interfacial layer results from a similar reaction. The sealing ability, biocompatibility, and dentinogenic activity of mineral trioxide aggregate is attributed to these physicochemical reactions.

Age and timing of the Permian mass extinctions: U/Pb dating of closed-system zircons

The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. The U/Pb age of the main pulse of the extinction is 252.6 +/- 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty.

Bioactive nanoengineered hydrogels for bone tissue engineering: a growth-factor-free approach

Despite bone's impressive ability to heal after traumatic injuries and fractures, a significant need still exists for developing strategies to promote healing of nonunion defects. To address this issue, we developed collagen-based hydrogels containing two-dimensional nanosilicates. Nanosilicates are ultrathin nanomaterials with a high degree of anisotropy and functionality that results in enhanced surface interactions with biological entities compared to their respective three-dimensional counterparts. The addition of nanosilicates resulted in a 4-fold increase in compressive modulus along with an increase in pore size compared to collagen-based hydrogels. In vitro evaluation indicated that the nanocomposite hydrogels are capable of promoting osteogenesis in the absence of any osteoinductive factors. A 3-fold increase in alkaline phosphatase activity and a 4-fold increase in the formation of a mineralized matrix were observed with the addition of the nanosilicates to the collagen-based hydrogels. Overall, these results demonstrate the multiple functions of nanosilicates conducive to the regeneration of bone in nonunion defects, including increased network stiffness and porosity, injectability, and enhanced mineralized matrix formation in a growth-factor-free microenvironment.

Halloysite Clay Nanotubes for Loading and Sustained Release of Functional Compounds

Halloysite is an alumosilicate tubular clay with a diameter of 50 nm, an inner lumen of 15 nm and a length of 600-900 nm. It is a natural biocompatible nanomaterial available in thousands of tons at low price, which makes it a good candidate for nanoarchitectural composites. The inner lumen of halloysite may be adjusted by etching to 20-30% of the tube volume and loading with functional agents (antioxidants, anticorrosion agents, flame-retardant agents, drugs, or proteins) allowing for formulations with sustained release tuned by the tube end-stoppers for hours and days. Clogging the tube ends in polymeric composites allows further extension of the release time. Thus, antioxidant-loaded halloysite doped into rubber enhances anti-aging properties for at least 12 months. The addition of 3-5 wt% of halloysite increases the strength of polymeric materials, and the possibility of the tube's orientation promises a gradient of properties. Halloysite nanotubes are a promising mesoporous media for catalytic nanoparticles that may be seeded on the tube surface or synthesized exclusively in the lumens, providing enhanced catalytic properties, especially at high temperatures. In vitro and in vivo studies on biological cells and worms indicate the safety of halloysite, and tests for efficient adsorption of mycotoxins in animals' stomachs are also carried out.

Solid acids for green chemistry

Solid acids and especially those based on micelle-templated silicas and other mesoporous high surface area support materials are beginning to play a significant role in the greening of fine and specialty chemicals manufacturing processes. A wide range of important organic reactions can be efficiently catalyzed by these materials, which can be designed to provide different types of acidity as well as high degrees of reaction selectivity. The solid acids generally have high turnover numbers and can be easily separated from the organic components. The combination of this chemistry with innovative reaction engineering offers exciting opportunities for innovative green chemical manufacturing in the future.

Bioactive silicate nanoplatelets for osteogenic differentiation of human mesenchymal stem cells

Novel silicate nanoplatelets that induce osteogenic differentiation of human mesenchymal stem cells (hMSCs) in the absence of any osteoinductive factor are reported. The presence of the silicate triggers a set of events that follows the temporal pattern of osteogenic differentiation. These findings underscore the potential applications of these silicate nanoplatelets in designing bioactive scaffolds for musculoskeletal tissue engineering.

Nano-network electronic conduction in iron and nickel olivine phosphates

The provision of efficient electron and ion transport is a critical issue in an exciting new group of materials based on lithium metal phosphates that are important as cathodes for lithium-ion batteries. Much interest centres on olivine-type LiFePO(4), the most prominent member of this family. Whereas the one-dimensional lithium-ion mobility in this framework is high, the electronically insulating phosphate groups that benefit the voltage also isolate the redox centres within the lattice. The pristine compound is a very poor conductor (sigma approximately 10(-9) S cm(-1)), thus limiting its electrochemical response. One approach to overcome this is to include conductive phases, increasing its capacity to near-theoretical values. There have also been attempts to alter the inherent conductivity of the lattice by doping it with a supervalent ion. Compositions were reported to be black p-type semiconductors with conductivities of approximately 10(-2) S cm(-1) arising from minority Fe(3+) hole carriers. Our results for doped (and undoped) LiMPO(4) (M = Fe, Ni) show that a percolating nano-network of metal-rich phosphides are responsible for the enhanced conductivity. We believe our demonstration of non-carbonaceous-network grain-boundary conduction to be the first in these materials, and that it holds promise for other insulating phosphates.

Habitable zones around main sequence stars

A one-dimensional climate model is used to estimate the width of the habitable zone (HZ) around our Sun and around other main sequence stars. Our basic premise is that we are dealing with Earth-like planets with CO2/H2O/N2 atmospheres and that habitability requires the presence of liquid water on the planet's surface. The inner edge of the HZ is determined in our model by loss of water via photolysis and hydrogen escape. The outer edge of the HZ is determined by the formation of CO2 clouds, which cool a planet's surface by increasing its albedo and by lowering the convective lapse rate. Conservative estimates for these distances in our own Solar System are 0.95 and 1.37 AU, respectively; the actual width of the present HZ could be much greater. Between these two limits, climate stability is ensured by a feedback mechanism in which atmospheric CO2 concentrations vary inversely with planetary surface temperature. The width of the HZ is slightly greater for planets that are larger than Earth and for planets which have higher N2 partial pressures. The HZ evolves outward in time because the Sun increases in luminosity as it ages. A conservative estimate for the width of the 4.6-Gyr continuously habitable zone (CHZ) is 0.95 to 1.15 AU. Stars later than F0 have main sequence lifetimes exceeding 2 Gyr and, so, are also potential candidates for harboring habitable planets. The HZ around an F star is larger and occurs farther out than for our Sun; the HZ around K and M stars is smaller and occurs farther in. Nevertheless, the widths of all of these HZs are approximately the same if distance is expressed on a logarithmic scale. A log distance scale is probably the appropriate scale for this problem because the planets in our own Solar System are spaced logarithmically and because the distance at which another star would be expected to form planets should be related to the star's mass. The width of the CHZ around other stars depends on the time that a planet is required to remain habitable and on whether a planet that is initially frozen can be thawed by modest increases in stellar luminosity. For a specified period of habitability, CHZs around K and M stars are wider (in log distance) than for our Sun because these stars evolve more slowly. Planets orbiting late K stars and M stars may not be habitable, however, b ecause they can become trapped in synchronous rotation as a consequence of tidal damping. F stars have narrower (log distance) CHZ's than our Sun because they evolve more rapidly. Our results suggest that mid-to-early K stars should be considered along with G stars as optimal candidates in the search for extraterrestrial life.

An open source and reduce expenditure ROS generation strategy for chemodynamic/photodynamic synergistic therapy

The therapeutic effect of reactive oxygen species (ROS)-involved cancer therapies is significantly limited by shortage of oxy-substrates, such as hypoxia in photodynamic therapy (PDT) and insufficient hydrogen peroxide (H2O2) in chemodynamic therapy (CDT). Here, we report a H2O2/O2 self-supplying nanoagent, (MSNs@CaO2-ICG)@LA, which consists of manganese silicate (MSN)-supported calcium peroxide (CaO2) and indocyanine green (ICG) with further surface modification of phase-change material lauric acid (LA). Under laser irradiation, ICG simultaneously generates singlet oxygen and emits heat to melt the LA. The exposed CaO2 reacts with water to produce O2 and H2O2 for hypoxia-relieved ICG-mediated PDT and H2O2-supplying MSN-based CDT, acting as an open source strategy for ROS production. Additionally, the MSNs-induced glutathione depletion protects ROS from scavenging, termed reduce expenditure. This open source and reduce expenditure strategy is effective in inhibiting tumor growth both in vitro and in vivo, and significantly improves ROS generation efficiency from multi-level for ROS-involved cancer therapies.

Direct Demonstration of Enhanced Diffusion in Mesoporous ZSM-5 Zeolite Obtained via Controlled Desilication

A 2 orders of magnitude gas transport improvement in a medium pore ZSM-5 zeolite has been achieved upon introduction of intracrystalline mesoporosity in gradient-free crystals by desilication post-treatment in alkaline medium.

Spectroscopic Tags Using Dye-Embedded Nanoparticles and Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering is capable of providing rich vibrational information at the level of single molecules and single nanoparticles, but the practical applications of this enormous enhancement effect are still a challenge. Here we report a new class of dye-embedded core-shell nanoparticles that are highly efficient for surface Raman enhancement and could be used as spectroscopic tags for multiplexed detection and spectroscopy. The core-shell particles contain a metallic core for optical enhancement, a reporter molecule for spectroscopic signature, and an encapsulating silica shell for protection and conjugation. A surprising finding is that organic molecules with an isothiocyanate (-N=C=S) group or multiple sulfur atoms are compatible with silica encapsulation. In comparison with fluorescent dyes and quantum dots, enhanced Raman probes contain a built-in mechanism for signal amplification and provide rich spectroscopic information under ambient experimental conditions.

Atmospheric carbon dioxide concentrations before 2.2 billion years ago

The composition of the Earth's early atmosphere is a subject of continuing debate. In particular, it has been suggested that elevated concentrations of atmospheric carbon dioxide would have been necessary to maintain normal surface temperatures in the face of lower solar luminosity in early Earth history. Fossil weathering profiles, known as palaeosols, have provided semi-quantitative constraints on atmospheric oxygen partial pressure (pO2) before 2.2 Gyr ago. Here we use the same well studied palaeosols to constrain atmospheric pCO2 between 2.75 and 2.2 Gyr ago. The observation that iron lost from the tops of these profiles was reprecipitated lower down as iron silicate minerals, rather than as iron carbonate, indicates that atmospheric pCO2 must have been less than 10(-1.4) atm--about 100 times today's level of 360 p.p.m., and at least five times lower than that required in one-dimensional climate models to compensate for lower solar luminosity at 2.75 Gyr. Our results suggest that either the Earth's early climate was much more sensitive to increases in pCO2 than has been thought, or that one or more greenhouse gases other than CO2 contributed significantly to the atmosphere's radiative balance during the late Archaean and early Proterozoic eons.

Adhesion/cementation to zirconia and other non-silicate ceramics: where are we now?

Non-silicate ceramics, especially zirconia, have become a topic of great interest in the field of prosthetic and implant dentistry. A clinical problem with use of zirconia-based components is the difficulty in achieving suitable adhesion with intended synthetic substrates or natural tissues. Traditional adhesive techniques used with silica-based ceramics do not work effectively with zirconia. Currently, several technologies are being utilized clinically to address this problem, and other approaches are under investigation. Most focus on surface modification of the inert surfaces of high strength ceramics. The ability to chemically functionalize the surface of zirconia appears to be critical in achieving adhesive bonding. This review will focus on currently available approaches as well as new advanced technologies to address this problem.

Arginine-Rich Manganese Silicate Nanobubbles as a Ferroptosis-Inducing Agent for Tumor-Targeted Theranostics

Ferroptosis, an iron-based cell-death pathway, has recently attracted great attention owing to its effectiveness in killing cancer cells. Previous investigations focused on the development of iron-based nanomaterials to induce ferroptosis in cancer cells by the up-regulation of reactive oxygen species (ROS) generated by the well-known Fenton reaction. Herein, we report a ferroptosis-inducing agent based on arginine-rich manganese silicate nanobubbles (AMSNs) that possess highly efficient glutathione (GSH) depletion ability and thereby induce ferroptosis by the inactivation of glutathione-dependent peroxidases 4 (GPX4). The AMSNs were synthesized via a one-pot reaction with arginine (Arg) as the surface ligand for tumor homing. Subsequently, a significant tumor suppression effect can be achieved by GSH depletion-induced ferroptosis. Moreover, the degradation of AMSNs during the GSH depletion contributed to T₁-weighted magnetic resonance imaging (MRI) enhancement as well as on-demand chemotherapeutic drug release for synergistic cancer therapy. We anticipate that the GSH-depletion-induced ferroptosis strategy by using manganese-based nanomaterials would provide insights in designing nanomedicines for tumor-targeted theranostics.

The constitution of mineral trioxide aggregate

OBJECTIVES

The aim of this study was to determine the constitution of a commercially available root-end filling material, mineral trioxide aggregate, (MTA) (ProRoot MTA, Tulsa Dental, Tulsa, OK, USA). The surface morphology of the material with various treatment conditions was also evaluated.

METHODS

The constitution of two commercial versions of MTA was determined before and after mixing with water. The unset material was analysed using Energy Dispersive Analysis by X-ray (EDAX) in a scanning electron microscope (SEM) and X-ray diffraction (XRD). The first technique identified the constituent elements while XRD analysis identified the compounds or phases present. The set material was evaluated using EDAX. The surface morphology of the material stored under various conditions (100% humidity, immersion in water, or immersion in phosphate solution) was evaluated using SEM.

RESULTS

The EDAX showed the white MTA to be composed primarily of calcium, silicon, bismuth and oxygen, with the gray MTA also having small peaks for iron and aluminum. The XRD analysis showed gray MTA to be composed primarily of tricalcium silicate and dicalcium silicate. The surface morphology of the materials differed under the various conditions, particularly following immersion in phosphate solution with crystal formation.

SIGNIFICANCE

The commercial versions of MTA were shown to have broadly similar constitution to ordinary Portland cement except for the addition of bismuth compounds. The white MTA did not contain iron.

Hydration mechanisms of mineral trioxide aggregate

AIM

To report the hydration mechanism of white mineral trioxide aggregate (White MTA, Dentsply, Tulsa Dental Products, Tulsa, OK, USA).

METHODOLOGY

The chemical constitution of white MTA was studied by viewing the powder in polished sections under the scanning electron microscope (SEM). The hydration of both white MTA and white Portland cement (PC) was studied by characterizing cement hydrates viewed under the SEM, plotting atomic ratios, performing quantitative energy dispersive analyses with X-ray (EDAX) and by calculation of the amount of anhydrous clinker minerals using the Bogue calculation.

RESULTS

Un-hydrated MTA was composed of impure tri-calcium and di-calcium silicate and bismuth oxide. The aluminate phase was scarce. On hydration the white PC produced a dense structure made up of calcium silicate hydrate, calcium hydroxide, monosulphate and ettringite as the main hydration products. The un-reacted cement grain was coated with a layer of hydrated cement. In contrast MTA produced a porous structure on hydration. Levels of ettringite and monosulphate were low. Bismuth oxide was present as un-reacted powder but also incorporated with the calcium silicate hydrate.

CONCLUSIONS

White MTA was deficient in alumina suggesting that the material was not prepared in a rotary kiln. On hydration this affected the production of ettringite and monosulphate usually formed on hydration of PC. The bismuth affected the hydration mechanism of MTA; it formed part of the structure of C-S-H and also affected the precipitation of calcium hydroxide in the hydrated paste. The microstructure of hydrated MTA would likely be weaker when compared with that of PC.

Stimuli-Responsive Conductive Nanocomposite Hydrogels with High Stretchability, Self-Healing, Adhesiveness, and 3D Printability for Human Motion Sensing

Self-healing, adhesive conductive hydrogels are of great significance in wearable electronic devices, flexible printable electronics, and tissue engineering scaffolds. However, designing self-healing hydrogels with multifunctional properties such as high conductivity, excellent mechanical property, and high sensitivity remains a challenge. In this work, the conductive self-healing nanocomposite hydrogels based on nanoclay (laponite), multiwalled carbon nanotubes (CNTs), and N-isopropyl acrylamide are presented. The presented nanocomposite hydrogels displayed good electrical conductivity, rapid self-healing and adhesive properties, flexible and stretchable mechanical properties, and high sensitivity to near-infrared light and temperature. These excellent properties of the hydrogels are demonstrated by the three-dimensional (3D) bulky pressure-dependent device, human activity monitoring device, and 3D printed gridding scaffolds. Good cytocompatibility of the conductive hydrogels was also evaluated with L929 fibroblast cells. These nanocomposite hydrogels have great potential for applications in stimuli-responsive electrical devices, wearable electronics, and so on.

Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations

Arsenic removal by passive treatment, in which naturally present Fe(II) is oxidized by aeration and the forming iron(III) (hydr)oxides precipitate with adsorbed arsenic, is the simplest conceivable water treatment option. However, competing anions and low iron concentrations often require additional iron. Application of Fe(II) instead of the usually applied Fe(III) is shown to be advantageous, as oxidation of Fe(II) by dissolved oxygen causes partial oxidation of As(III) and iron(III) (hydr)oxides formed from Fe(II) have higher sorption capacities. In simulated groundwater (8.2 mM HCO3(-), 2.5 mM Ca2+, 1.6 mM Mg2+, 30 mg/L Si, 3 mg/L P, 500 ppb As(III), or As(V), pH 7.0 +/- 0.1), addition of Fe(II) clearly leads to better As removal than Fe(III). Multiple additions of Fe(II) further improved the removal of As(II). A competitive coprecipitation model that considers As(III) oxidation explains the observed results and allows the estimation of arsenic removal under different conditions. Lowering 500 microg/L As(III) to below 50 microg/L As(tot) in filtered water required > 80 mg/L Fe(III), 50-55 mg/L Fe(II) in one single addition, and 20-25 mg/L in multiple additions. With As(V), 10-12 mg/L Fe(II) and 15-18 mg/L Fe(III) was required. In the absence of Si and P, removal efficiencies for Fe(II) and Fe(III) were similar: 30-40 mg/L was required for As(II), and 2.0-2.5 mg/L was required for As(V). In a field study with 22 tubewells in Bangladesh, passive treatment efficiently removed phosphate, but iron contents were generally too low for efficient arsenic removal.

Mineral trioxide aggregate: a review of the constituents and biological properties of the material

This paper reviews the literature on the constituents and biocompatibility of mineral trioxide aggregate (MTA). A Medline search was conducted. The first publication on the material was in November 1993. The Medline search identified 206 papers published from November 1993 to August 2005. Specific searches on constituents and biocompatibility of mineral trioxide aggregate, however, yielded few publications. Initially all abstracts were read to identify which fitted one of the two categories required for this review, constituents or biocompatibility. Based on this assessment and a review of the papers, 13 were included in the constituent category and 53 in the biocompatibility category. Relatively few articles addressed the constituents of MTA, whilst cytological evaluation was the most widely used biocompatibility test.