Dissolution Period Research Articles

1853-56 OSMANLI-RUS HARBİ’NDE DOĞU CEPHESİNDE BİR İNGİLİZ SUBAY: YARBAY WILLIAM FENWICK WILLIAMS'IN ASKERÎ RAPORLARI

Bu çalışma 19. yüzyılın ikinci yarısında modern savaşların başlangıcı sayılan Kırım Savaşı'nın doğu cephesine odaklanmaktadır. Bilindiği üzere Kırım Savaşı, Avrupalı büyük güçlerin ittifak hâlinde Slav yayılmacılığına karşı koyduğu ve modern teknolojilerin harp için kullanıldığı ilk savaş idi. Osmanlı Devleti hem ekonomik hem de harp becerisi açısından bu savaşı yürütecek yeterli donanıma sahip değildi. Ancak dönemi itibarıyla İngiltere ve Fransa gibi devletlerin deniz aşırı politikaları ve dış tehdit algıları, onları Osmanlı-Rus anlaşmazlığında Türklere ekonomik ve askerî destek vermeye mecbur kılmıştı. O nedenle Müttefikler, Osmanlı ordularının Ruslara karşı savaşma kabiliyetini artırmaya çalışırken diğer yandan da önemli subaylarını Türk ordusuna görevlendirmişlerdi. Müttefikler, Kırım'da yoğun çarpışmalar yaşadığından 1853-56 Osmanlı-Rus Harbi, tarihe daha çok Kırım Harbi olarak geçmiştir. Oysa aynı yıllarda Osmanlı orduları doğuda da Ruslara karşı ciddi mücadeleler yürütmüştür. Kırım'a nispeten coğrafyanın ve iklim koşullarının savaşın seyrine önemli etki ettiği Doğu cephesi bu bakımdan Kırım'ın popülaritesinin gölgesinde kalmıştır. Fakat savaş yıllarında aynı durum söz konusu olmadığı için Birleşik Krallık başarılı subaylarından William Fenwick Williams'ı Erzurum'da konuşlanan Anadolu ordularına müttefikler adına göndermiştir. Williams'ın bu doğrultuda İstanbul'daki İngiliz elçiliğine yazdığı raporlar, dağılma sürecindeki Osmanlı Devleti'nin ordusunu anlamamız açısından önemlidir. Çünkü Williams'ın aynı zamanda Osmanlı merkezine gönderdiği direktifler de Türk ordu yapısının değişmesinde etkili olabiliyordu. Dolayısıyla bu çalışma, 1853-56 Osmanlı-Rus Harbi esnasında Williams'ın gönderdiği askerî raporlara odaklanmakta, onların analizine çalışmaktadır.

Carbonation behavior of calcium silicate hydrate (C-S-H): Its potential for CO2 capture

Calcium silicate hydrate (C-S-H), as the main component of cementitious materials, is susceptible to carbonation presenting a potential to capture CO2. Although some researches paid attentions to the carbonation behaviors of C-S-H given the durability of concrete structure, the kinetics of C-S-H carbonation as well as changes of C-S-H itself under carbonation have not been fully addressed. In this study, the carbonation kinetics of C-S-H with various calcium to silica ratio (Ca/Si) were investigated and the evolution of carbonation products in terms of compositions and micro-mechanical properties was quantitatively characterized by quantitative X-ray diffraction (QXRD), energy dispersive spectroscopy (EDS), and nuclear magnetic resonance (NMR). Three distinct periods are found in the course of C-S-H carbonation, encompassing dissolution period, diffusion period and slowly ongoing reaction period. A progressive decrease in Ca/Si and pH is observed in dissolution period with the formation of calcium carbonate, the reaction rate of which is strongly dependent on the initial Ca/Si of C-S-H. In the diffusion period, a small proportion of crosslinking occurs in C-S-H structure before producing a large amount of calcium modified silica gel, during when the Ca/Si and pH remain unchanged due to the incongruent dissolution of C-S-H as revealed by thermodynamic modellings. In the slowly ongoing reaction period, C-S-H decomposed completely and the mixture of microcrystalline calcium carbonate and calcium modified silica gel becomes the final product. The micro-mechanical property of C-S-H was significantly weakened by the change of phase assemblage. Our findings do not only advance our understandings on the deterioration of cementitious material under carbonation but also provides new insights into the CO2 capture using C-S-H widely existing in cementitious materials.

Carbonation behaviors of calcium silicate hydrate (C-S-H): Effects of aluminum

The cement systems containing supplementary cementitious materials (SCMs) usually present lower resistance to carbonation compared with ordinary Portland cement (OPC) systems. However, the contribution of the main component in these systems, calcium aluminum silicate hydrate (C-A-S-H), to carbonation still remains unclear. In this study, the carbonation behaviors of C-S-H and C-A-S-H were compared by accelerated carbonation experiments. FTIR, XRD, TGA, NMR, and electron microscope were integrated to reveal the kinetics and thermodynamics of C-(A)-S-H carbonation. It is concluded that the carbonation of C-(A)-S-H experiences three periods including dissolution, diffusion, and stationary period, turning into calcium carbonate with different polymorphs, calcium and aluminum modified silica gel. In the end product of carbonation, aluminum modified silica gel is observed to have a similar Al/Si to the initial C-A-S-H. But such small incorporation of aluminum into C-S-H structure (maximum Al/Si ∼ 0.1) can hardly have a significant effect on its resistance to carbonation.

Phosphorus recovery from an igneous phosphate rock using organic acids and pyrolysis condensate

Directly applied igneous phosphate rocks (PR) are agronomically ineffective because they are intrinsically unreactive. The main process by which PRs are solubilised in soils by microorganisms and plants is through the exudation of low molecular weight organic acids, which have a short lifespan in soils, thereby limiting the period of PR dissolution and agronomic effectiveness. This study measured the amount of P recovered from Dorowa PR (DPR) by suspension in water and sequential leaching with citric, acetic, oxalic acids, and pyrolysis condensate at various pH values. Of the dilute acids tested, oxalic acid was more effective at solubilising P from the DPR, cumulatively liberating 46% of total P from the DPR after 3 extractions at pH 3. However, aqueous phase pyrolysis liquid from maize stover pyrolysis was less effective at recovering P, yielding less than 14% of the total P despite maintaining a pH range of 3 to 3.8 in leachates after sequential extractions. The poor solubilisation was due to the low concentrations of chelating and complexing acids in the pyrolysis liquid, with the dominant acid being acetic acid and the high Ca content. Further research on improving the dissolution potential of pyrolysis liquid by removing cations in the liquid before leaching and other alternative processes to produce complexing acids such as oxalic acid is recommended.

Facile one pot microbe-mediated in situ synthesis and antibacterial activity of reduced graphene oxide-silver nanocomposite

The present research deals with the development of a novel bioinspired in situ fabrication of reduced graphene oxide (rGO)-silver nanoparticle (AgNPs) nanocomposite (rGO@AgNCs) using microbes namely Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). The fabricated rGO@AgNCs were characterized using Ultraviolet-visible (UV–Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), particle size analysis, polydispersity index (PDI), zeta potential analysis, energy dispersive x-ray analysis (EDAX), Raman spectroscopy, powder x-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM) analysis, etc. Furthermore, the rGO@AgNCs-PA and rGO@AgNCs-SA interaction with serum protein, pH stability study, and in vitro dissolution of AgNPs were also performed. The research findings of the proposed study demonstrated the simultaneous reduction of graphene oxide (GO) and AgNPs and the formation of rGO@AgNCs in the presence of microbes. The in vitro dissolution studies of rGO@AgNCs composites showed better AgNPs dissolution with controlled release and offered remarkable matrix integrity throughout the dissolution period. The size and stability of rGO@AgNCs-PA and rGO@AgNCs-SA had no significant changes at physiological pH 7.4. A minimal decrease in the zeta potential of rGO@AgNCs was observed, which may be due to the weak interaction of nanocomposites and albumin. The antibacterial application of the synthesized nanocomposite was evaluated against a pathogenic mastitis-forming bacterium. The obtained results suggested an admirable antibacterial activity of synthesized nanocomposites against the tested microbes. This knowledge will assist the scientific fraternity in designing novel antibacterial agents with enhanced antibacterial activity against various veterinary pathogens in near future.

The revolution that ate its own children: The colourful revolution from consensus to discord

The main goal of this essay is to provide an in-depth analysis of the trajectory of the Colourful Revolution (CR) in North Macedonia as a social movement. From a more general perspective, the paper engages with the growing interest in the literature that explores the correlation between social movements and democratisation processes, especially in societies that fall into the category of hybrid regimes. The Colourful Revolution is a good example of a protest movement that has created effective regime change. It presented a complex social movement encompassing many fragmented social and political groups gathered around the idea of a common adversary. Additionally, the Colourful Revolution has one particularity: it is a social movement that has undergone a full developmental circle - formation through utilization of political opportunity frameworks, a period of activity and success and dissolution. Drawing on literature of the political process, opportunity frameworks and cycles of social movements, the paper argues that social movements such as the Colourful Revolution are not just temporary and unstable structures but are also highly dependent on the existence of a common target of the social activism in question. The removal from power of political actors that have been the reason for mobilisation of a complex and diverse network of social and political activism resulted in an absence of an adhesive factor holding together all the parts of this complex system. The absence initiated gradual discord and dissolution of different factions within the social movement (CR in this case) and reveals its true nature - temporary, ideologically diverse, conflictual, and even undemocratic in some respects.

Hydrochemical impact of a mantle plume recorded by petrology, geochemistry, and U[sbnd]Pb geochronology of a calcite vein within the Ottawa-Bonnechere graben, Ontario, Canada

Petrology, geochemistry, fluid inclusions and UPb dating of a wide (30 cm) calcite vein in Upper Ordovician (Sandbian) limestone characterize a hydrochemical microcosm of changing fluid sources and carbon pathways related to burial, then uplift during the Phanerozoic along the Ottawa-Bonnechere graben, central Canada. UPb dating of the host limestone produces an age younger than its chronostratigraphic age suggesting the impact of diagenesis, otherwise well-defined petographically. An interred calcite fragment dated as Cambrian may highlight a platform source in this part of the graben hitherto unrecognized stratigraphically. The vein was initiated with extension across a high-angle narrow (2 cm) fault gouge allowing incursion of hot (80–125 °C) basin-derived (Mg, Ca)-Cl2 brine recorded by a saddle dolomite–dedolomite–calcite succession, not isotopically datable. Microbial methanogenesis occurred in initial narrow structural recesses giving way to recycled sedimentary bicarbonate with fracture widening. The oldest datable vein calcite (122 ± 5 Ma) consists of microcrystalline geopetal cumulates of vadose meteoric origin demarcating renewed carbonate formation following a period of near-surface alteration, dissolution, and microfracturing of the prior vein calcite during uplift. Initial 207Pb/206Pb ratios are consistent with average crust (0.819 ± 0.003), and δ18O signatures identify a meteoric signature similar to the host rock. Subsequent interlayering of isopachous calcite and pyrite, with an age of 105 ± 3 Ma for the calcite, defines onset of a meteoric phreatic environment. The role of microbial sulphate reduction is characterized isotopically. Initial 207Pb/206Pb ratios scatter below the crustal average (0.84–0.76) that, along with a meteoric δ18O signature, suggest incursion of a new fluid reservoir. A subsequent Sr, Mn, Ba-bearing–magnesium calcite marks the beginning of sustained phreatic meteoric dilution for the remaining vein history. Stable (C, O) isotopes document varying temperature and bicarbonate mixtures of sedimentary and bacterial (sulphate reduction) origins associated with a meteoric fluid. This calcite has a mean age of 94 ± 2 Ma and displays the widest range of initial 207Pb/206Pb ratios, which scatter down to 0.65. Stable and radiogenic isotopic compositions suggest a meteoric setting largely influenced by a crustal fluid reservoir of long residence time and-or transport resulting in leaching of radiogenic minerals. The final vein calcite, also of meteoric origin, has an 87Sr/86Sr ratio similar to that of the initial basin brine, yet with 13C signatures that characterize a source of oxidized methane. UTh series analysis delimits an age older than 0.5 Ma. This stage of vein calcite likely arises through meteoric fracking of Ordovician source rocks during continued basin inversion. In summary, initial brine influx followed by a shallow-crustal meteoric realm document structurally focused fluid migration with and following early Mesozoic graben exhumation. The phreatic meteoric regime of Early Cretaceous age spans a ~ 20 Ma period coincident with transient magmatism arising from near passage of the Great Meteor Hotspot. Regional paleohydrology appears to have been influenced for ~10 Ma after plume passage.

3D printed multicompartmental capsules for a progressive drug release

The temporal delivery of chemical compounds to target organs and tissues is a key-topic for pharmacological and therapeutic applications. Dealing with ad hoc systems that can be properly designed to deliver drugs when are really needed is regarded as a valuable approach to improve the effectiveness of a clinical protocol. For this aim, 3D printing can be a suitable means to fabricate structured reservoirs to allow a prolonged release of the loaded pharmacological agent.This study reports the fabrication and characterization of multicompartmental capsules made of polyvinyl alcohol (PVA) processed by fused deposition modelling (FDM) to be considered for a time dependent release therapeutic approach. Thermal assessment of the printed devices was carried out to evaluate a possible influence of FDM high temperatures on the polymer, while dimensional consistency was evaluated through optical microscopy. Regarding the expected application, different designs were investigated in order to validate the proof-of-concept by in vitro assessing the release of curcumin, as a drug model. Three capsule models were tested, including single, double and triple reservoirs, which provided different dissolution periods, ranging from about 180 to 390 min.The collected results supported the potential to easily tailor 3D printed devices, specifically modified for drug delivery purposes.

Chemical Structural Effects of Amphipathic and Water-soluble Phospholipid Polymers on Formulation of Solid Dispersions.

For the polymeric carriers of solid dispersions, it is important that carriers themselves dissolve quickly and maintain the supersaturated state of amorphous drugs during their dissolution period to improve bioavailability. Amphipathic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers can be dissolved in water, owing to the extremely high hydrophilicity of the MPC units, and are used as an ideal feeder for drug molecules to form aggregates in aqueous conditions. We synthesized amphipathic MPC copolymers with different hydrophobic side chains and molar ratios of MPC units, and evaluated the effect of the polymers on dissolution rate and supersaturation maintenance of solid dispersions of indomethacin. In most of the water-soluble amphipathic MPC copolymers, "spring-parachute"-like dissolution behavior was observed, where the drug initially became supersaturated followed by slow precipitation. In particular, MPC copolymers with aromatic rings in their side chains or polymers with a high percentage of hydrophobic units remained in a supersaturated state for a longer period. In contrast, urethane groups, which form hydrogen bonds with drug molecules, could also interact with water and were not conducive to maintaining supersaturation. In addition, water solubility of the polymer is important for rapid dissolution.

Revising the History of Germanic Languages: The Concept of <i>Germance</i>

This paper puts forward a new division of the history of Germanic languages, taking into account the existence of three different historical periods (prehistoric, proto-historic, and literary) in the development from Common Germanic or Proto-Germanic to modern Germanic languages, analogously to the development of Romance or Romanic languages from Vulgar Latin (also called Proto-Romanic or Proto-Romance), in which three stages can be retraced: Vulgar Latin (prehistoric), Romance (proto-historic) and literary (historical). So far, only two stages have been considered in the linguistic history of Germanic languages, namely, the Common Germanic (not documented) and the literary Germanic languages (documented since the Middle Ages). Nevertheless, the history of both families of languages is similar in most aspects, so that the three aforementioned periods can be clearly recognized in both: a period of considerable linguistic unity, although poorly or not at all documented; a period of dissolution of this unity and fragmentation into several dialects not mutually intercomprehensible; and a period of full and intense literary production and official recognition of some of these dialects, now raised to the condition of culture languages. Due to this new historiographical division, the denomination Germance is proposed for the second of the three evolutionary stages of Germanic.

Microstructural Aspects of Corrosion

The effect of metal corrosion on the third-order microscopic properties, i.e., the root-mean-square deviation and internal residual stresses of the first-order, was studied. The corrosion process was studied on steel specimens under conditions of superheated steam (250°C) during 500 h. The X-ray diffraction method was taken as the basic research method. The process of corrosion failure was concluded to have two reproducible periods: the period of active metal dissolution and latent passivation period, followed by the corrosion initiation phase. The metal passivity occurs due to the compressive stresses.

An extended release ciprofloxacin/dexamethasone hydrogel for otitis media

ObjectiveOtitis media and associated otorrhea are frequent complications following tympanostomy tube insertion; the most common otologic procedure performed in children in the United States. Current treatments include the administration of antibiotic or antibiotic/anti-inflammatory combination drops to the affected ear. Several studies have demonstrated that using an antibiotic/anti-inflammatory combination product is more effective than the use of antibiotics alone. However, administration of any drops through the tympanostomy tube is very difficult in children, and patient compliance can be an issue. Our group has developed a novel combination drug/hydrogel formulation for the treatment of otitis media/otorrhea that releases both ciprofloxacin and dexamethasone over a 2–3 week period. This has the potential to offer significant advantages over current treatments in use in the clinic. MethodsThe release of drugs from the combination hydrogel was validated in vitro over the desired time frame and the activity of the released drugs was monitored via assays to confirm retention of full activity throughout the dissolution period. The safety of the ciprofloxacin/dexamethasone hydrogel and its inactive excipients was evaluated through in vivo otic toxicity studies in guinea pigs, including hearing tests, gross microscopy, and cytocochleogram analysis. ResultsExtended release of both drugs was demonstrated in vitro and antibiotic/anti-inflammatory activities were retained. The hydrogel components and its excipients did not cause adverse reactions in animals, demonstrating safety of the hydrogel combination in vivo. ConclusionThe studies presented lay the groundwork for extended release middle ear hydrogel formulations that are capable of safely releasing combinations of active pharmaceutical agents over a desired period of time. This would be more advantageous than therapeutics that are currently used in the clinic for the treatment of otitis media/otorrhea associated with tympanostomy tube insertion.

Digestion degree is a key factor to regulate the printability of pure tendon decellularized extracellular matrix bio-ink in extrusion-based 3D cell printing

Improving the printability of pure, decellularized extracellular matrix (dECM) bio-ink without altering its physiological components has been a challenge in three-dimensional (3D) cell printing. To improve the printability of the bio-ink, we first investigated the digestion process of the powdered dECM material obtained from porcine tendons. We manifested the digestion process of tendon derived dECM powders, which includes dissolution, gelatinization and solubilization. After a short dissolution period (around 10 min), we observed a ‘High viscosity slurry’ status (3 h) of the dECM precursors, i.e. the gelatinization process, followed by the solubilization processes, i.e. a ‘Medium viscosity slurry’ period (12 h) and a ‘Low viscosity slurry’ period (72 h). The ‘Medium viscosity slurry’ status of the dECM bio-ink was inhomogeneous and could not be extruded out from the barrel after the pH value was neutralized to 7.4. Although the ‘Low viscosity slurry’ status of the dECM bio-ink has been reported to be extrudable, it has poor printability. This study explores the printability of the ‘High viscosity slurry’ status of the dECM bio-ink, which has not been addressed thus far. The results demonstrate that this less digested status of the dECM bio-ink yields higher shape fidelity and stacking accuracy than the traditional over-digested status of the dECM bio-ink; this indicates better printability of this less digested dECM bio-ink. We compared the performance of the two bio-inks using cell viability tests for 3D cell printing. Bone marrow mesenchymal stem cells derived from rats was printed using the ‘High viscosity slurry’ status of the dECM bio-ink, yielding high cellular viability lasting for 7 d after printing. Thus, the ‘High viscosity slurry’ status of tendon dECM bio-ink can be utilized to fabricate complicated 3D organoid structures; it also shows promise for applications such as regenerative medicine and biomimetic tissue engineering.

1950 öncesi Sürrealizm ve Müzik İlişkisi: Anlaşmazlıklar ve Yakınlaşmalar

The Surrealist movement, which emerged as a revolutionary movement in poetry in 1924, quickly moved towards various other disciplines such as painting, sculpture, photography, architecture and cinema, but unlike Symbolism and Dada, the movement exhibits a conscious distance from music. However, this stance went through a change during the dissolution period of the movement in the late 1930s, and later in the exile years of artists such as Breton, Salvador Dali, Max Ernst, and André Masson in America. After 1950, the relationship between surrealism and music became more apparent. Developments in jazz music and post-modern practices have particularly been evaluated as the reflection of surrealist thought. The purpose of this study is to explore the relationship between music and surrealism by focusing on the pre-1950s period where this relation remains more unclear. The first part of the study discusses the reasons for the surrealist movement's negative attitude towards music, and furthermore gives examples from the composers who had felt close to surrealist thinking and whose music contains surrealist elements. In the final part of this study, we aim to examine the points where surrealist thinking meets with development of music on the path leading to serial and aleatoric music through the example of İlhan Usmanbaş's musical piece Three Painting from Dali (1952).

Gel Formation Induced Slow Dissolution of Amorphous Indomethacin.

Amorphous indomethacin (IMC) forms gel with a decreased dissolution behavior compared to crystalline IMC during dissolution. The current study aims to explore gelation mechanism and attempt to eliminate gelling effect by formulation development. Amorphous IMC was prepared by melt-quenching method. Dissolution tests of amorphous IMC were performed at various temperatures under sink condition. The formed gels were characterized by PLM, SEM, DSC and XRPD. Amorphous IMC exhibited an initial higher dissolution followed by a decreased dissolution lower than its crystalline counterpart at 32 and 37°C, and even a much lower dissolution during the whole dissolution period at 45°C. Meanwhile, a viscous soft mass ("gel") was observed to adhere upon the paddle or wall of the vessel. The formed gel could be characterized as a three-dimensional dense micro-fiber structure under SEM. The gel formation was proposed to be related to the decreased Tg of amorphous IMC when contacting aqueous medium, resulting in entering into supercooled liquid state with high viscosity. The addition of hydrophilic silica accelerated gel formation, while mixing with hydrophobic silica was able to weaken and even eliminate the gelation, and hence significantly enhancing dissolution. The present study recommends that gel formation should be included in the investigation of amorphous materials in order to find ways for resolving defects of amorphous materials while keeping their advantages in pharmaceutics.

InstaSpheres TA (Tartaric acid) as functional starter core for extended release formulations

The modulation of pH is used to develop products which have pH dependent solubility. The mechanism is still not clear on the extent and the duration of the pH-modifying effect. This requires that pH modifier should not leach out quickly from the dosage form instead it must be present in sufficient quantity until the complete drug release. The aim of the study is to demonstrate InstaSpheres TA (seal coated tartaric acid spheres) as pH modifier starter core for extended drug delivery of weakly basic drug and to confirm the effect of resultant acidic microenvironment on drug release at higher pH. We hypothesized that InstaSpheres TA can prevent direct contact between tartaric acid and the drug and control the release of tartaric acid to modulate the pH in the vicinity of the drug. We developed multilayered extended release (ER) pellets of dipyridamole using InstaSpheres TA as the starter core by fluid bed coating. The drug layered InstaSphere TA pellets were coated with protective coat followed by enteric coating to formulate stable ER dipyridamole pellets. The controlled release profile of dipyridamole and tartaric acid was observed as a result of low micro-environmental pH within the pellet throughout entire dissolution period. The formulation avoids direct contact of tartaric acid with drug, prevents premature release of dipyridamole and tartaric acid and increases drug release at higher pH. It shows similarity in dissolution with reference product and also stability over entire duration of accelerated stability studies. InstaSpheres TA is therefore a viable pH modifying functional starter core for weakly basic drugs.

Research on the effectiveness of polycarboxylate superplasticisers with different side-chain lengths

Polycarboxylate superplasticiser (PCSs) are commonly used and studies to enhance their compatibility with other concrete raw materials have been undertaken. However, the effect of the side-chain length (SCL) in PCSs on the properties of cement-based materials (CBMs) has not gained enough attention. To fill this research gap, five types of PCSs with different SCLs were synthesised through a redox initiator system. The workability, hydration behaviour, microstructure formation and cracking sensitivity of CBMs containing PCSs with different SCLs were thoroughly examined. The results showed that, with an increase in the SCL of the PCS, the initial fluidity of the cement paste increased first and then decreased but fluidity losses decreased gradually. Compared with PCSs with short side-chains, PCSs with long side-chains improved the hydration heat peak value and shortened the dissolution period, thus accelerating the hydration and microstructure formation of cement. The 28 d strength and anti-cracking behaviour of the CBMs increased first and then decreased with an increase in SCL. The results of this study suggest that there is an optimum SCL for PCSs that produces good workability and the lowest crack sensitivity in CBMs.

Effect of side-chain length in polycarboxylic superplasticizer on the early-age performance of cement-based materials

Abstract Varying the length of side-chain in Polycarboxylic superplasticizer (PCs) have been reported to greatly impact their molecular structure and their compatibility with other concrete raw materials. However, there is less study relating to the influence of side-chain length on early properties of cement-based materials. For this purpose, through a redox initiator system, five types of PCs with different side-chain lengths were synthesized by using 2-methyl allyl polyoxyethylene ether (HPEG) with different molecular weight and acrylic acid (AA) as monomers. The dispersing performance, hydration behavior, microstructure formation and cracking sensitivity in cement-based materials with these different types of PCs were thoroughly examined. The results showed that the initial fluidity of the cement paste increased first and then decreased but the fluidity losses decrease gradually with the increase of side-chain length in PCs. Compared to short side-chain PCs, the long ones can improve hydration heat peak value and shorten dissolution period, thus accelerating the hydration and microstructure formation of cement. The early-age strength increased, while 28-day strength and anti-cracking performance of cement-based materials increased first and then decreased with the increase of side-chain length in PCs. Such information also suggests that there exists a suitable side-chain length in PCs (53 PEO units) which makes cement-based materials have good dispersation, flow maintaining ability and the lowest crack sensitivity.

Sulfonation of graphene and its effects on tricalcium silicate hydration

Sulfonate graphene nanosheet (SGN), as a new chemical admixture obtained by sulfonation of graphene, has been used to investigate the effects on tricalcium silicate (C3S – Conventional cement chemistry notation is often used in this article to specify the composition of solid phase, whereby C = CaO, S = SiO2, F = Fe2O3 and H = H2O) hydration. Results show that SGN can prolong the dissolution period and induction period during C3S hydration owing to its adsorption behavior. In situ X-ray diffraction analysis demonstrated that the crystal growth on 001 planes of Calcium hydroxide (CH) will be enforced by addition of SGN, which is probably by the following steps: 1) Ca2+ released by C3S more likely diffused to the surface of SGN prior to nucleation of CH; 2) the nanosheets provide a template for aligned growth of the CH especially on the 001 planes. Meanwhile, scanning electron microscope photos directly show that the growth of CH is layer by layer on the 001 plane when SGN was added. Hopefully, the mechanism of C3S hydration cooperating with SGN proposed in this paper can make a guidance for the application of SGN in cement based materials.

Non-compendial vs compendial analytical tests - a powerful tool for predicting in vitro similarity of highly viscous oral suspension

In vitro dissolution profiles are increasingly used to evaluate drug release characteristics of pharmaceutical products. The dissolution methods is expected to be an appropriate tool for checking consistency of the pharmaceutical attributes by discriminating similarities and dissimilarities between different drug formulations. Expansion in development of novel “special” dosage forms, due to the manner in which these dosage forms release the active pharmaceutical ingredient, usually requires applying non-compendial dissolution strategy that differs from the traditional compendial recommendations. For demonstrating sameness in the dissolution profile, in vitro drug release comparison between test and reference product of highly viscous oral suspension by applying non-compendial peak vessel against conventional hemispheric vessel was demonstrated in this study. All reference batches exhibited high variability in dissolution data when using hemispheric vessel due to forming mound compact mass at the bottom of the vessel. Different strategies for samples manipulation, before and during dissolution period, were performed in order to eliminate additional variabilities. Modifications of conventional USP 2 apparatus such as using peak vessel provided with more reproducible and reliable result for distinguishing in vitro similarities between different formulations of oral suspensions. Misinterpretation of dissolution data can lead to negative impact on product development. Taking time to observe and evaluate what is happening to the product in the vessel during dissolution is of curtail consideration for proper selection of the dissolution strategy. Keywords: oral suspensions; in-vitro release; hydrodynamic variability; USP apparatus 2/ Paddle apparatus; peak vessel