Dissolution Speed Research Articles

Water soluble polymer films for intravascular drug delivery of antithrombotic biomolecules

Over the past 10years, the number of percutaneous coronary intervention (PCI) procedures performed in the United States has increased by 33%; however, restenosis, which inhibits complete functional recovery of the vessel wall, remains a complication of this procedure. To traverse the complications associated with PCI, the investigation of therapeutic delivery has become an integral topic in modern research. One such therapeutic, a mimic of the proteoglycan decorin, termed DS-SILY, can mask exposed collagen and thereby effectively decrease platelet activation, has recently been developed by our lab. Drawing inspiration from coating technologies developed by the pharmaceutical industry, a fast-dissolving polymer film has been developed to deliver active therapeutic agents from a balloon catheter during PCI. This research investigates the release of DS-SILY from fast-dissolving polymer films composed of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG). Thin, uniform polymer films were produced via spin coating technique. The dissolution speed of the polymer films was found to be dependent on the concentration of polymer solution, where at least 65% of the films were shown to dissolve into nanometer sized polymer fragments within 2min. DS-SILY, up to 6.26μg/cm2, was loaded into the films and functional release of the mimic was demonstrated by its successful binding to collagen upon release. Furthermore, DS-SILY released from films resulted in increased platelet inhibition. These results indicate that use of fast-dissolving polymer films allow for the successful release of biomolecules and further investigation of their use for localized drug delivery during PCI procedures is warranted.

Study on Alkaline Mass Transfer Regularity with Dissolution in Porous Media

Inducting dissolution speed constant and multistage reaction series to the alkaline solution transmission equation, this article established the alkaline solution transmission equation with multistage reaction dynamics in the porous media of stratum mineral and calculated one-dimensional alkaline solution concentration distribution. Experimental results verified the correctness of transmission equation, moreover, it further analyzed the alkaline solution regularity in the porous media. The model will be used to predict alkali loss, optimize alkaline solution concentration and slug size, thereby alkaline waterflooding or combination drive can obtain better displacement characteristics and improve the oil recovery.

Solid dosage forms for active antiretroviral therapy (HAART): dissolution profile study of nevirapine by experimental factorial design

Nevirapine is the first antiretroviral member of non-nucleoside reverse transcriptase inhibitor used in active antiretroviral therapy (HAART). The aim of this work was the evaluation of the dissolution profile of nevirapine tablets by means of the Disk Intrinsic Dissolution Rate (DIDR) using a 23 factorial design. This study used a triplicate in central point and was based on three independent variables: the rotational speed of the apparatus, the compression force of nevirapine disk, and the distance of the tank dissolution. The dependent variable was set as intrinsic dissolution speed (IDS). IDS was strongly dependent on the rotational speed, compression force, and distance of the apparatus, analyzed by Student’s t test with 95% confidence, and confirmed by ANOVA. The rotational speed of nevirapine disks was the main factor contributing to the IDS, whereas the compression force and the distance of disks on the dissolution apparatus revealed no effects.

Preparation and Characterization of Honghua Powders by Ultrafine Pulverization

Honghua has been demonstrated useful for promoting blood circulation and stopping pain. The physicochemical characterization of Honghua powders was greatly influenced by ultrafine pulverization. To study the physicochemical characterization of Honghua, the raw plant material of Honghua was ground to powders by high speed centrifugal sheering (HSCS) pulverizer. The micron powders were characterized by laser scattering granulometric analyzer and scanning electron microscope (SEM). Hydroxysafflor yellow A is one of active ingredients of Honghua, and its dissolution speed was determined to evaluate the chemical characterization of Honghua powder. The results showed that after ultrafine pulverization, dissolution speed of hydroxysafflor yellow A was increased by 28.6% compared with the normal powders

Decomposition Mechanism and Decomposition Promoting Factors of Waste Hard Metal for Zinc Decomposition Process (ZDP)

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc steam pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 hrs at 650 °C, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of γ-β1 phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at 1000 °C. The small amount of zinc remaining in the tungsten carbide-cobalt powder which was completely decomposed was fully removed by using phosphate solution which had a slow cobalt dissolution speed.

Bovine pulp tissue dissolution ability of HealOzone®, Aquatine Alpha Electrolyte® and sodium hypochlorite

The aim of this study was to evaluate the bovine pulp tissue dissolution ability of HealOzone, Aquatine Alpha Electrolyte® and 0.5% sodium hypochlorite, used alone or in combination. Thirty bovine pulp fragments were weighed, divided into six groups and placed individually in Eppendorf tubes containing the tested solution until total dissolution occurred. The groups were: G1: saline (negative control), G2: Aquatine Alpha Electrolyte®, G3: 0.5% NaOCl (positive control), G4: Saline + HealOzone, G5: 0.5% NaOCl + HealOzone, G6: Aquatine Alpha Electrolyte® + HealOzone. HealOzone was activated for 2 min with a #6 cup covering the test tube opening on a fixed platform. Two blinded observers using 2× loupes magnification assessed the samples continuously for the first 2 h, and then every hour for the next 8 h. Dissolution speed was calculated by dividing pulp weight by dissolution time (mg min(-1) ). G3 (NaOCl) and G5 (NaOCl + HealOzone) dissolved the pulp tissue completely. The mean dissolution speed for G3 was 0.396 mg min(-1) (SD 0.032) and for G5 was 0.775 mg min(-1) (SD 0.2). Student's t-test showed that G5 dissolved bovine pulp tissue faster than G3 (P = 0.01). Only groups containing sodium hypochlorite dissolved pulp tissue, whilst HealOzone enhanced speed of dissolution.

Optimisation de la Synthèse des Apatites Phosphocalciques Vectrices D’antiseptiques Élaborées à Partir du Nitrate de Calcium et de L’Acide Phosphorique

Oxygenated phosphocalcic apatite is an apatite with an excellent biocompatibility, osteoconduction, and having antiseptic properties able to limit the proliferation of the micro-organisms in the site implementation, without using an antibiotic. However, the synthesis of this apatite encounters several difficulties. On one hand, it depends on many factors such as pH of the reaction, atomic ratio Ca/P of the reagents, temperature of the reaction (T), duration of reaction (D), and concentration in ions calcium ([Ca2+]). On the other hand, the product to be developed must have a chemical composition allowing it a dissolution speed in compliance with the bone neoformation and having antiseptic properties. Aiming to control the synthesis of these apatites and to limit the number of experiments necessary to this study, we applied the methodology of the experimental designs. The mathematical models elaborated in this study allowed us to forecast the optimum conditions of the oxygenated phosphocalcic apatite synthesis. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Food Science Education Publications and Websites

Bird The purpose of this column is to highlight innovative publications and websites in food science education. If you know of a website or a recent publication that you believe other readers would like to know about, please submit the full text of the article or the URL for the website and an annotation of not more than 125 words. We welcome your resources and comments on this column. Material should be submitted to: Jim Bird, Science & Engineering Center, Fogler Library, Univ. of Maine, Orono, ME 04469, or e-mail to Jim.Bird@umit.maine.edu. If e-mailing, please put “JFSE submission” in the subject line. College English (National Council of Teachers of English). 2008. Special topic: Food. 70(4):345–436. This issue of College English is devoted to food writing. Papers include: “Consuming prose: The delectable rhetoric of food writing”, “Food memoirs: What they are, why they are popular, and why they belong in the literature classroom”, and “Books that cook: Teaching food and food literature in the English classroom”. For a very brief description of each article in this special topic issue go to http://www.indiana.edu/~cedialog/?cat=10 Koch P, Barton AC, Contento I, and Crabtree M. 2008. Farm to table and beyond: Helping students make sense of the global food system. Sci Scope 31(9):36–9. The authors describe an activity, part of the Farm to Table & Beyond curriculum, where grade 5 to 6 students diagram the production and processing of food. This activity, utilizing observation and discussion, helps students put the food system into a biological and environmental context. Topics explored in the curriculum include food preservation, environmental effects of food systems, and transportation issues related to food. McDonald J. 2008. Enhancing food-safety education through shared teaching resources. J Vet Med Educ 35(2):207–11. The author describes an innovative project, Design to Dissemination (D2D), developed for veterinary teaching faculty to provide them with food safety resources. The information (called “learning objects”) is presented in various formats including text, animation, audio, powerpoint, and video. The project has three objectives (from p. 208–209): “To provide institutions, faculty, and students with high-quality, clinically relevant, interactive educational materials….; To provide easy access to the materials….; To help faculty use learning objects effectively to build or enhance a course.” A logon is required to fully utilize the site's capabilities but users can create an account. To view this ongoing project, go to the following website: Veterinary Food Safety Education Learning Object Repository http://webcls.utmb.edu/d2d Segner S and Scholthof K-BG. 2007. Environmental microbiology: Bacteria & fungi on the foods we eat. The Am Biol Teach 69(3):149–57. Utilizing fruits and vegetables, a laboratory exercise was developed for the undergraduate course “Pathogens, the Environment, and Society” at Texas A&M Univ. Students concentrated on the identity of cosmopolitan bacteria and fungi on both washed and unwashed fruits and vegetables. Detailed laboratory protocols are presented. The author presents a number of internet resources useful in lab and lecture preparation. Sorgo A, Hajdinjak Z, and Briski D. 2008. The journey of a sandwich: computer-based laboratory experiments about the human digestive system in high school biology teaching. Adv Physiol Educ 32(1):92–9. Based on results from a questionnaire, the authors found that high school students were most successful when hands-on, computer-based experiments were used to teach human digestion. Topics taught included jaw chewing force, dissolution speed, enzymatic breakdown of food, bacteriocidal activity of hydrochloric acid, and importance of the intestine lining's surface. These experiments will be upgraded in the future, based on student input. The authors plan to design experiments to teach other systems. Dairy Science and Food Technology http://www.dairyscience.info (accessed 11/17/2008) This website contains information on the industrial uses of lactic acid bacteria and their bacteriophages, antimicrobial systems in milk, and factors influencing the quality and yield of cheese. There are also sections on starter cultures, probiotics, modeling in food technology, and a summary of information on modified atmosphere packaging. The articles on general food technology include labeling, nutritional claims, wine making and thermal processing. There are calculators and models, such as one for predicting the grade value of Cheddar cheese, theoretical yield of cheese, and a calculator using linear programming for calculating ice cream mixes. The site is aimed at students and practitioners in dairy science and technology, and there are discussion area, extensive links, and literature citations. There are also significant sections aimed at helping students write papers and theses including a Harvard-style reference generator. (Contributed by Dr. Michael Mullan, Head of Higher Education Branch, Greenmount Campus, College of Agriculture, Food and Rural Enterprise, Antrim BT41 4PU, Northern Ireland. michael.mullan@dardni.gov.uk)

Commentary on Viewpoint “Heliox, nitrox, and trimix diving; hyperbaric oxygen treatment; and a flaw in Henry's law”

LETTERS TO THE EDITORCommentary on Viewpoint “Heliox, nitrox, and trimix diving; hyperbaric oxygen treatment; and a flaw in Henry's law”C. Balestra, and P. GermonpréC. Balestra, and P. GermonpréPublished Online:01 Apr 2007https://doi.org/10.1152/japplphysiol.00048.2007MoreSectionsPDF (28 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat to the editor: Although a nonlinear behavior on gas dissolution has been shown, both the nature of dissolved gases and the presence or not of bubbles (or micronuclei) have to be considered.A classical example has been shown with “hydreliox” (6), probably due in part to the polar nature of dissolved hydrogen in the final mix.Thus it seems probable that apart from the physical or electrolytic changes in solute behavior affecting the linearity of Henry's law, other mechanisms, such as gas-solute interfaces found in the presence of macroscopic bubbles or micronuclei or even the surface tension of such interfaces, play an important role (3).With helium, even local temperature gradients are likely to influence the driving forces of Henry's law.Recent experiments conducted in divers (2) show that changes in fluid compartments induce concomitant changes in surface tension of body fluids that will widely affect the radius of pre-existing or de novo gas (micro)bubbles (5) and thus the contact surface and finally dissolution speed of gases (4).In conclusion, it is undeniable that the simple linear concept of Henry's law is probably untrue, even in relatively “simple” circumstances and certainly in situations where “exotic gas” mixes are breathed. We cannot agree more with Arieli (1). We would like to stress, however, that, as the exact nature of these changes is extremely difficult to model, one has to consider that these changes can occur in both ways; therefore, the observation that nitrox dives seem to be safer than air dives is possibly also due to other factors, rather than this hypothesis alone.REFERENCES1 Arieli R. Heliox, nitrox, and trimix diving; hyperbaric oxygen treatment; and a flaw in Henry's law. J Appl Physiol. In press.Google Scholar2 Blatteau J, Boussuges A, Gempp E, Pontier JM, Castagna O, Galland FM, Robinet C, Bourdon L. Hemodynamic changes induced by sub-maximal exercise prior to a dive and its consequences on bubble formation. Br J Sports Med In press. [2006 Nov. 30. Epub ahead of print].Google Scholar3 Blatteau JE, Souraud JB, Gempp E, Boussuges A. Gas nuclei, their origin, and their role in bubble formation. Aviat Space Environ Med 77: 1068–1076, 2006.Google Scholar4 Boussuges A, Blanc F, Carturan D. Hemodynamic changes induced by recreational scuba diving. Chest 129: 1337–1343, 2006.Crossref | PubMed | ISI | Google Scholar5 Hjelde A, Koteng S, Eftendal O, Brubakk AO. Surface tension and bubble formation after decompression in the pig. Appl Cardiopulm Pathophys 1: 47–52, 2000.Google Scholar6 Sebert P, Barthelemy L, Caroff J, Cann-Moisan C. Effects of breathing an O2-H2 (20%–80%) mixture on the energy metabolism of the eel at 1 ATA. Aviat Space Environ Med 59: 754–757, 1988.Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: C. Balestra, 91, Ave. C. Schaller, Brussels, Belgium B-1160 (e-mail: [email protected]) Download PDF Previous Back to Top Next FiguresReferencesRelatedInformationCited ByEnvironmental Physiology and Diving Medicine2 February 2018 | Frontiers in Psychology, Vol. 9 More from this issue > Volume 102Issue 4April 2007Pages 1720-1720 Copyright & PermissionsCopyright © 2007 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00048.2007PubMed17409297History Published online 1 April 2007 Published in print 1 April 2007 Metrics

Nitric oxide delivery by ultrasonic cracking: Some limitations

Nitric oxide (NO) has been implicated in smooth muscle relaxation. Its use has been widespread in cardiology. Due to the effective scavenging of NO by hemoglobin, however, the drug has to be applied locally or in large quantities, to have the effect desired. We propose the use of encapsulated microbubbles that act as a vehicle to carry the gas to a region of interest. By applying a burst of high-amplitude ultrasound, the shell encapsulating the gas can be cracked. Consequently, the gas is released upon which its dissolution and diffusion begins. This process is generally referred to as (ultra)sonic cracking. To test if the quantities of released gas are high enough to allow for NO-delivery in small vessels (ø < 200 μm), we analyzed high-speed optical recordings of insonified stiff-shelled microbubbles. These microbubbles were subjected to ultrasonic cracking using 0.5 or 1.7 MHz ultrasound with mechanical index MI > 0.6. The mean quantity released from a single microbubble is 1.7 fmol. This is already more than the NO production of a 1 mm long vessel with a 50 μm diameter during 100 ms. However, we simulated that the dissolution time of typical released NO microbubbles is equal to the half-life time of NO in whole blood due to scavenging by hemoglobin (1.8 ms), but much smaller than the extravascular half-life time of NO (>90 ms). We conclude that ultrasonic cracking can only be a successful means for nitric oxide delivery, if the gas is released in or near the red blood cell-free plasma next to the endothelium. A complicating factor in the in vivo situation is the variation in blood pressure. Although our simulations and acoustic measurements demonstrate that the dissolution speed of free gas increases with the hydrostatic pressure, the in vitro acoustic amplitudes suggest that the number of released microbubbles decreases at higher hydrostatic pressures. This indicates that ultrasonic cracking mostly occurs during the expansion phase.

181 DIFFERENCES EXIST IN ZONA PELLUCIDA HARDNESS BETWEEN IN VIVO- AND IN VITRO-GENERATED BOVINE EMBRYOS

The zona pellucida (ZP) of mammalian ova plays an important role during maturation, fertilization, and early embryonic development. The hardness of ZP of mammalian ova has been mainly evaluated by a biochemical method, such as a difference in ova dissolution speed with an enzyme or an acid reagent treatment. However, the physical hardness of ZP in bovine embryos is largely unknown. Recently, we developed a system measuring the physical hardness of ZP of mammalian ova with a micro bio-sensor (MBS). The objective of this study was to examine the physical ZP hardness of in vivo- and in vitro-derived bovine embryos using an MBS. In the measurement system, the thin glass needle was connected at the tip of a piezo-electric ceramic tactile sensor, and the sample was pushed into a sensor at fixed speed under the computer-controlled micromanipulation system. The change in frequency at the time of displacement of the sample into the sensor was recorded using the computer program. Measurement of gelatin samples of known concentration (4 to 8%) was used to determine the basic characteristic of a sensor and to make a standard curve. In vivo-generated embryos were recovered from 6 superovulated Japanese Black cows with multiple injection of FSH. On Day 7 after insemination, morulae (M), early blastocysts (EB), and blastocysts (BL) were recovered by nonsurgical flushing of uterine horns. In vitro-generated embryos were produced as described earlier (Yoshida et al. 1998 J. Vet. Med. Sci. 60, 549–554). The M, EB, and BL at Days 5 to 7 of post-insemination in vitro were used for measurement of ZP hardness. When a sensor made contact with a harder gelatin sample, the change in frequency was large; the change in frequency has the characteristic of being small for a softer gelatin sample. By comparison with a standard curve, ZP hardness converted into gelatin concentration for each stage of bovine embryos generated in vivo was 3.95% (M: n = 9), 4.14% (EB: n = 32), and 3.92% (BL: n = 14), respectively. On the other hand, ZP hardness of bovine embryos generated in vitro was 3.42% (M: n = 56), 3.33% (EB: n = 36), and 3.25% (BL: n = 23), respectively. There was a significant difference (P &amp;lt; 0.01) in the hardness of ZP between in vivo- and in vitro-generated bovine embryos.

Dissolution of pulp tissue by aqueous solution of chlorhexidine digluconate and chlorhexidine digluconate gel.

To evaluate the activity of various root canal irrigants on bovine pulp tissue. The irrigants tested were: 0.5, 1.0 and 2.5% sodium hypochlorite; 2% aqueous solution of chlorhexidine digluconate; 2% chlorhexidine digluconate gel (Natrosol); and distilled water as control. Bovine pulp fragments were weighed and placed in contact with 20 mL of each tested substance in a centrifuge at 150 r.p.m. until total dissolution. Dissolution speed was calculated by dividing pulp weight by dissolution time. Statistical analysis was performed using the Kruskal-Wallis test. Distilled water and both solutions of chlorhexidine did not dissolve the pulp tissue within 6 h. Mean dissolution speeds for 0.5, 1.0 and 2.5% sodium hypochlorite solutions were 0.31, 0.43 and 0.55 mg min(-1), respectively. The solvent ability of chlorhexidine solutions was similar to that of distilled water. The results for sodium hypochlorite solutions, chlorhexidine solutions and distilled water were statistically different (P>0.01). Both chlorhexidine preparations and distilled water were not able to dissolve pulp tissue. All sodium hypochlorite solutions were efficient in dissolving pulp tissue; the dissolution speed varied with the concentration of the solution.

Electro-Oxidation of Molybdenum Concentrate Using Bipolar Cell, and Recovery of Rhenium.

With the purpose of extracting rhenium from molybdenum concentrate, electrolysis of slurry, prepared by mixing molybdenum sulfide concentrate and 10 mass% NaCl aqueous solution, was carried out at 1 A, 313 K. The slurry was continuously circulated into a vertical type 10 stack bipolar electrolytic cell consisted of carbon electrode disks, and the concentrate was dissolved by electrochemically generated oxidizers. The current efficiency for molybdenum dissolution was 73 % after 10 hours electrolysis, and the leach solution was found to contain 0.2 mol / l of molybdenum and 4×10-5 mol / l rhenium. This result shows the dissolution speed is more than 8 times faster than that obtained using a single cell at applied current of 1 A. Prior to rhenium separation from the leach solution, preliminary experiments for rhenium extraction by MEK (Methyl-ethyl-keton) were carried out using synthesized test solutions having similar composition. The behavior of molybdenum, rhenium, and sulfur was investigated for examining the extraction conditions and efficiency. The leach solution obtained by electro-oxidation was then subjected to a solvent extraction experiment, and rhenium present at several tens of mass ppm in the concentrate was enriched to more than 1,000 times, and recovered as sulfides. After rhenium separation, molybdenum was recovered by precipitation after changing pH of the solution.

Electrical conductivity measurement for quantitative evaluation of development speed of a photoresist

In a previous article, we reported on the possibility of predicting the development speed of a photoresist by measuring its electrical conductivity in an organic solvent [T. Takeda and M. Saka, J. Vac. Sci. Technol. B (submitted)]. The electrical conductivity of the organic solution of a photoresist base polymer at various frequencies was found to have a positive correlation with the dissolution speed of photoresist base polymers into an alkaline developer. In addition, the influence of the measurement temperature and the concentration of polymer solution on conductivity was investigated. Based on the collected data, this article derives the calibration equation, which was influenced neither by measurement temperature nor by the concentration of the solution.

Evaluation of development speed of a photoresist by means of electrical conductivity measurement

A method was examined for evaluating the electrical conductivity of a photoresist to predict its development speed. The conductivity of organic solutions of the photoresist base polymer at various frequencies was found to have a positive correlation with the dissolution speed of the photoresist base polymer into an alkaline developer. In addition, the influence of the measurement temperature and of the concentration of the polymer solution on the conductivity was investigated. It is shown that a prediction of development speed of a photoresist by measuring its conductivity is possible.

Theoretical model for early stages of porous silicon formationfrom n- and p-type silicon substrates

We present a stability analysis of the silicon-electrolyte interface for the etching of both n- and p-type silicon. The description is based on the model that we have developed in a preceding paper for n-type silicon. The model incorporates the transport phenomena of holes in the semiconductor and ions in the electrolyte, together with surface tension of silicon. Here, we have incorporated the kinetic effects of the electrochemical reaction in a coherent and transparent manner. We shall also consider the p-type silicon as well. Our numerical analysis shows that for n- and p-type silicon the electrolyte-silicon interface become linearly unstable below a critical dissolution speed (depending on the operating parameters), identified as the boundary between the regime of pore formation and electropolishing. Moreover, we extract scaling laws for the wavelength of the most dangerous interface fluctuations, which is expected to give a magnitude on the order of the interpore spacing. The results obtained for n-type silicon is consistent with available experimental data. We expect rather macropores. For p-type silicon, we find nanostructures for intermediate doping levels. We discuss the implication of our results together with theoretical suggestions for future work.

Compatibility of Ibuprofen and Ethenzamide

The compatibility of ibuprofen and various drugs was investigated by thermal analysis. The results showed a lower melting point with many drugs. The compound of ibuprofen and ethenzamide was selected for detailed compatibility investigation. First, a ratio composition of a eutectic of ibuprofen and ethenzamide was estimated. A ratio composition of a eutectic of ibuprofen and ethenzamide of weight ratio 3:2 was suggested, and its melting point was approximately 56°C. Further, we investigated crystallization by powder x-ray diffraction. The resulting powder x-ray diffraction pattern of the compound that was heat treated was almost the same as that of the physical mixture, indicating that the crystallinity of ibuprofen and ethenzamide were not affected by the heat treatment. Next, we investigated the chemical stability of ibuprofen, ethenzamide, and a small amount of various excipients in capsule form, stored under conditions of 65°, 50°, and 40°C. It was established that ibuprofen and ethenzamide are stable. However, it was found that there is a remarkable delay of dissolution speed under conditions above 50°C.

鉄と溶融アルミニウムの反応に及ぼす鉄の影響

Fe-Al alloy layers are formed on the surface of iron specimens, being simultaneously dissolved in liquid aluminum in the reaction between iron and liquid aluminum.Effects of the iron in liquid aluminum on the thickness of alloy layer have hardly been investigated in connection with the weight loss of iron specimen.In this study, behaviors of the iron in liquid aluminum were investigated by several methods. The following results were obtained.When an iron specimen is immersed in the upper portion of an aluminum bath, the iron content is uniform in the bath. In the case of immersing the iron specimen in the lower portion, however, the iron content is higher in the lower portion than in the upper portion of the bath.Thickness of the alloy layers rapidly increases above a certain value of the iron content in the bath. This critical value changes by the immersion time and compositions of the bath. On the other hand, the weight loss of the iron specimen decreases with increasing iron content.The reason why the alloy layers thicken with increasing iron content in liquid aluminum is that the iron content near the iron specimen in the bath with higher iron content increases faster than in the bath with lower iron content, and that the dissolution speed of the alloy layer into the bath, therefore, decreases remarkably.

Modelling of Exothermic Dissolution

A mathematical model which describes the exothermic dissolution of high melting point additions in liquid steel has been developed. The explicit finite difference method has been employed to solve the set of partial differential equations which describe the complex, heat transfer phenomena involved. The model predictions are supported with experimental results on dissolution of cylindrical specimens of zirconium, titanium and niobium in liquid steel. There is good agreement between experimental results and model predictions. The mathematical model has also been used to predict the dissolution of tantalum in liquid steel. The dissolution rate in liquid steel increases in the order Ta–Nb–Ti–Zr. For these elements, the heats of mixing with liquid iron as well as their melting points seem to be the most important factors affecting their dissolution speed.

The mechanism of the hydration in the system C 3S-pozzolana

A mixture of five kinds of Japanese pozzolanas and synthesized pure C 3S were hydrated. The hydration mechanism in the system C 3S-pozzolana was investigated. The hydration of C 3S was accelerated by the addition of pozzolanas. The reasons for the acceleration increase of the precipitation sites of hydrates and the increase of the dissolution speed of C 3S caused by the depression of Ca 2+ ionic concentration in the liquid phase was due to the addition of pozzolanas. The reaction between pozzolana and formed Ca(OH) 2 is pronounced after 1 to 3 days. Zonal hydrates existing between C 3S and pozzolana grains have Ca ionic concentration gradient from C 3S to pozzolana. It was often observed that in intact pozzolana grains which had no precipitated hydrates, there was clearance between pozzolanas and hydrates, and cast of trace. That tendency was pronounced in pozzolanas which had substantial alkalies. The mechanism of the hydration in the system C 3S-pozzolana was considered from those results.