EVALUASI EKONOMI PRODUKSI La2NiO4 DENGAN BAHAN BAKAR BERBEDA METODE SOL-GEL COMBUSTION

Lanthanum nickelate (La2NiO4) is a precursor for producing lanthanum pentanickel (LaNi5) alloys for nickel–metal hydride battery (NiMH; a type of rechargeable battery), which has been developed quite rapidly for many applications, such as hybrid electric vehicles. The purpose of this study is to analyze feasibility of the lanthanum nickelate (La2NiO4) project. This study compared two fuels, glycine (F-G) and citric acid (F-CA) using the sol-gel combustion method. Technical analysis was carried out by changing the lab scale into an industrial scale and was made the process design. Several economic evaluation parameters were analyzed to inform the potential of La2NiO4 production, such as gross profit margin (GPM), internal rate of return (IRR), payback period (PBP), cumulative net present value (CNPV), and so on. Analysis of economic evaluation parameters is calculated under ideal conditions and in some cases. These cases are internal conditions (changes in raw materials, sales, utilities, labor, variable costs) external conditions (tax) as well as changes in production capacity. The results were showed that La2NiO4 production is prospective from the engineering and economic. However, production of La2NiO4 with F-CA were better than F-G. This is base on the quantity and quality produced by La2NiO4. Projects with F-CA produce more La2NiO4 than projects with F-G, 1154 kg with F-CA and 773 kg with F-G. From the economy, Economic analysis of GPM, PBP, BEP, CNPV and PI were positive while IRR and ROI were negative. This project is feasiblility to run. However, the Project will only benefit in certain economic conditions. Thus, since this material is very important to reduce dependence on imports, additional further technology for improving process and support from Corporate Social Responsibility (CSR) and government are important for maintaining this project

A study of public parking facilities at HUSM Kubang Kerian

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Resin-modified glass ionomer containing calcium glycerophosphate: physico-mechanical properties and enamel demineralization

Sources of calcium and phosphate have been added to dental restorative materials to improve their anticaries effect. Objective: This study evaluated the effect of adding calcium glycerophosphate (CaGP) to resin-modified glass ionomer cement (RMGIC) on the physico-mechanical properties, ion release, and enamel demineralization. Material and Methods: Specimens were fabricated for each experimental group: RMGIC without CaGP (Control), RMGIC with 1, 3 and 9% CaGP. To determine the release of fluoride (F), calcium (Ca) and phosphorus (P), six specimens were immersed in demineralization and remineralization solutions for 15 days. In another experimental trial, the following physico-mechanical properties were evaluated at time intervals of 1 and 7 days after fabrication: compressive strength (n=12), diametral tensile strength (n=12), surface hardness of material (n=6) and the degree of conversion of monomers (n=8). To study enamel demineralization, specimens (n=12) were attached to enamel blocks and submitted to pH-cycling. Subsequently, surface and cross-sectional hardness and the concentration of F, Ca and P in enamel were determined. Results: The addition of CaGP to RMGIC led to higher mean release of F, Ca and P when compared with control (p<0.001). Mechanical properties were within the range of those of the ionomer cements after addition of 1% and 3% CaGP. The degree of conversion did not differ between groups at the 1st and the 7th day (p>0.439). The addition of 3% and 9% CaGP reduced mineral loss and increased F, Ca and P in the enamel when compared with control (p<0.05). Conclusion: The addition of 3% CaGP in RMGIC increased the release of F, P and Ca, reduced enamel demineralization, and maintained the physico-mechanical properties within the parameters for this material

The Influence of Strontium Substitution in Fluorapatite Glasses and Glass-Ceramics

Strontium is often substituted for calcium in order to confer radio-opacity in glasses used for dental cements, Biocomposites and bio glass-ceramics. The present paper investigates the influence of substituting strontium for calcium in a glass of the following composition: 4.5SiO23Al2O 31.5P2O53CaO2CaF2, having a Ca:P ratio of 1.67 corresponding to calcium fluorapatite (Ca5(PO 4)3F). The glasses were characterized by magic angle spinning nuclear magnetic resonance (MAS-NMR), by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). The 29Si, 27Al and 31P NMR spectra for the glasses with different strontium contents were identical. The 19F spectra indicated the presence of F-Ca(n) and Al-F-Ca(n) species in the calcium glasses and in the strontium glasses F-Sr(n) and Al-F-Sr(n). It can be concluded that strontium substitutes for calcium with little change in the glass structure as a result of their similar charge to size ratio. The low strontium glasses bulk nucleated to a calcium apatite phase. Intermediate strontium content glasses surface nucleated to a mixed calcium-strontium apatite and the fully strontium substituted glass to strontium fluorapatite. © 2004 Elsevier B.V. All rights reserved

Chemical bond and electronic states in the CaF2-Si(111) and Ca-Si(111) interfaces

The first stage of formation of the CaF2-Si(111) and Ca-Si(111) interfaces is studied through the employment of the surface linear-muffin-tin-orbital approach in the atomic-sphere approximation. The interfaces are simulated by monolayers of F-Ca and Ca on Si(111), respectively. Both valence- and core-electron states have been calculated: their analysis gives important information about the nature of the Ca-Si and Ca-F bonds. These results are successfully compared with the available experimental data. The importance of considering the Madelung contribution in the interpretation of surface-core-level shifts is pointed out

The Influence of Fluorine, Chlorine and Water on the Rheology and Structure of Na2O-CaO-Al2O3-SiO2 Melts

In dieser Studie wurde der alleinige und gemeinsame Einfluss von 1.6 bis 14.5 mol% Wasser, 1.1 bis 18.3 mol% Fluor (F) und 0.5 bis 1.4 mol% Chlor (Cl) auf die Struktur und Viskosität von peralkalinen und peraluminösen Na2O CaO Al2O3 SiO2 Gläsern und Schmelzen mit ~ 66 mol% SiO2 (auf volatilfreier Basis) untersucht. Die Zusammensetzung der peralkalinen Proben entspricht einem Modellsystem für Phonolithschmelzen. Die wasserfreien Proben wurden in 1 atm Öfen aus Oxid und Karbonatverbindungen sowie Halogeniden hergestellt. Die wasserhaltigen peralkalinen Proben wurden in einer innenbeheizten Gasdruckanlage und die wasserhaltigen peraluminösen Proben in einer Stempelzylinderpresse hergestellt. Die Viskosität der Proben wurde mit der Mikropenetrationstechnik (108.5 1013 Pa s) und der „parallel plate“ Methode (105.5 Pa s 109 Pa s) gemessen. Die Struktur der Gläser wurde mittels „magic angle spinning“ (MAS) Kernspinresonanzspektroskopie (NMR) anhand der Nuklide 19F, 23Na, 27Al, 29Si and 35Cl analysiert. Fluor und Wasser allein oder in Kombination verringern die Viskosität der Schmelzen, wobei der Effekt von Wasser stärker ist als der von F. Beide Volatile verringern die Viskosität von peraluminösen Schmelzen stärker als in den peralkalinen Schmelzen. Für die peralkalinen Schmelzen wurde eine Verringerung der Viskosität durch F bis zu einer Konzentration von 1.9 mol% F festgestellt, jedoch für eine Konzentration von 6.2 mol% F wurde keine weitere Verringerung der Viskosität festgestellt. In den peraluminösen Schmelzen hingegen wurde bis zu einer Konzentration von 18.3 mol% F ein stetiger Abfall der Viskosität mit zunehmendem Fluorgehalt beobachtet. Der gemeinsame Einfluss von F und Wasser ist auf Grund ihrer jeweiligen Einzeleffekte geringer als angenommen, was zeigt, dass die Effekte von F und Wasser auf die Viskosität nicht unabhängig voneinander sind. Der zusammensetzungs und konzentrationsabhängige Effekt von F auf die Viskosität der Schmelzen stimmt mit Unterschieden im Einbaumechanismus von F überein. 19F MAS NMR Spektren zeigen, dass in den peralkalinen Gläsern F sowohl in „salzartigen“ F Ca(n) und F Na(n) als auch in nicht brückenbildenden Si F Na(n), Al F Ca(n), Al F Na(n) und brückenbildenden Al F Al Umgebungen vorkommt („n“ bedeutet, dass die Anzahl der Atome unklar oder variabel ist). F Ca(n) ist die am häufigsten vorkommende Umgebung, obwohl Ca das am wenigsten häufige Kation in den Proben ist. In den peraluminösen Gläsern existiert F nur in Si F und Al F Umgebungen, wobei Al F Na(n) die am häufigsten vorkommende Umgebung ist. Die Bildung von salzartigen F Ca(n) und F Na(n) Umgebungen sollte zu einem Anstieg der Viskosität durch eine Verringerung der netzwerkmodifizierenden Kationen führen. Die Bildung von Si F und Al F Umgebungen sollte die Viskosität entweder auf Grund einer Reduzierung von brückenbildenden Sauerstoffen durch nicht brückenbildende F oder durch einen Austausch von brückenbildenden Sauerstoffen durch brückenbildende F, welche eine niedrigere Bindungsstärke haben, verringern. Daraus lässt sich schließen, dass F die Viskosität in peralkalinen Schmelzen weniger stark verringert als in peraluminösen Schmelzen, weil F in den peralkalinen Schmelzen in Umgebungen existiert, welche die Viskosität erhöhen oder erniedrigen können, während F in den peraluminösen Schmelzen nur in Umgebungen existiert, welche die Viskosität verringern. Der konzentrationsabhängige Einfluss von F auf die Viskosität in den peralkalinen Schmelzen scheint in Zusammenhang mit einer Änderung in der Fluorspeziation zu stehen: Der relative Anteil von F Ca(n) Umgebungen, von denen anzunehmen ist, dass sie die Viskosität erhöhen, steigt von 42 auf 53% bei einem Anstieg im F Gehalt von 1.2 auf 6.2 mol% F. Veränderungen in der Fluorspeziation scheinen ebenfalls verantwortlich dafür zu sein, dass der Effekt von F und Wasser in Kombination geringer ist als erwartet. 19F MAS NMR Spektren von fluor und wasserhaltigen Proben zeigen, dass der relative Anteil von Al F Umgebungen, von denen anzunehmen ist, dass sie die Viskosität verringern, mit zunehmendem Wassergehalt abnimmt und dass im Gegenzug der relative Anteil von F Ca(n) Umgebungen zunimmt. Mit IR Spektroskopie wurde in den peralkalinen Proben kein Unterschied im OH/H2O Verhältnis bei gleichem Gesamtwassergehalt durch die Präsenz von F beobachtet. Im Gegensatz dazu gibt es starke Hinweise darauf, dass F in den peraluminösen Proben das OH/H2O Verhältnis bei gleichem Gesamtwassergehalt verringert, was erklären würde, weshalb F und Wasser in Kombination die Viskosität weniger verringern als von ihren Einzeleffekten zu erwarten wäre. Der Einfluss von Cl auf die Viskosität und Struktur der Schmelzen und Gläser ist sehr unterschiedlich verglichen mit F. Cl erhöht die Viskosität in den peralkalinen Schmelzen und verringert die Viskosität in den peraluminösen Schmelzen. Viskositätsmessungen von wasserhaltigen, chlorfreien und chlorhaltigen peralkalinen Schmelzen zeigen, dass der Effekt von Cl auf die Viskosität nicht durch die Präsenz von Wasser beeinflusst wird. Das beobachtete 35Cl NMR Signal zeigt, dass sowohl in den peralkalinen als auch in den peraluminösen Gläsern Cl in Na Ca Cl Umgebungen mit einem hohen Na Anteil existiert, was auf Grund des Ca/Na Verhältnisses von 1/5 zu erwarten war. Die Cl Umgebung in den peralkalinen und peraluminösen Gläsern ist ähnlich, jedoch beinhaltet die Cl Umgebung in den peraluminösen Gläsern mehr Ca. In den 35Cl MAS NMR Spektren wurde im Vergleich zu einem Natriumsilikatglas nur ein Teil des 35Cl NMR Signals der peralkalinen und der peraluminösen Proben beobachtet. Das fehlende Signal deutet darauf hin, dass ein Teil der Cl Atome in verzerrten oder ungeordneten Umgebungen existiert, welche eine Signalbreite haben, die zu groß ist, um mit den verwendeten NMR Spektroskopie Methoden gemessen werden zu können. Der Anstieg der Viskosität durch Cl in den peralkalinen Schmelzen kann dadurch erklärt werden, dass Cl die Anzahl der netzwerkmodifizierenden Kationen reduziert, während mehrere Möglichkeiten zur Diskussion stehen, weshalb Cl die Viskosität in peraluminösen Schmelzen verringert. Die Effekte von F und Cl auf die Viskosität sind unabhängig voneinander und summieren sich auf. Es wurde mit NMR Spektroskopie kein Hinweis dafür gefunden, dass F einen Einfluss auf den Einbaumechanismus von Cl hat

Letter from John Muir to [John] Swett, [ca. 1876].

1419 Taylor St, S. F. [ca.1876] Tuesday noon –Dear bro S[illegible]tt. I was delighted to learn through Mr Sonimlaw Parkhurst that a position on this board of normal school trustees had been offered you. Dont I pray you for a moment hesitate to accept. It is of all things the best for you of anything in Heavens gift. The medicine for your sore & sudden lonely heart sickness. You must accept. Anyhow dont refuse until I see you Of course you are much better – but not yet to be trusted in such matters Ill probably be home Saturday or Sunday though home here Ever your friend truly John Muir

Calcium and fluorine signals in HS-LEIS for CaF2(111) and powder-Quantification of atomic surface concentrations using LiF(001), Ca, and Cu references

The powder of CaF2 has been proposed as a practical reference for the quantitation of Ca and F in low energy ion scattering (LEIS) analysis. It is chemically inert, easy to clean, and inexpensive. LEIS is extremely surface sensitive. Thus, in contrast to surface analytic techniques such as x-ray photoelectron spectroscopy and secondary ion mass spectroscopy, the surface termination of a sample is clearly reflected in the LEIS results. It is, thus, unlikely that in LEIS, the F/Ca ratio for CaF2 is 2.0. This paper supports the reliability of the CaF2 powder reference by evaluating the calcium and fluorine atomic surface concentrations, roughness factor and shows that the surface termination of the powder is the same as that of CaF2(111). The CaF2 samples are treated by annealing at 725 K and measured at 625 K. The presented spectra are practically free of contamination. Ion scattering by LiF (001), an evaporated Ca layer, and a Cu foil are used as basic references for Ca and F. The atomic sensitivity factors and the relative sensitivity factors have been determined for F, Ca, and Cu (3 keV He+, 145 degrees). The F/Ca atomic ratio is found to be the same (2.3 +/- 0.1) for CaF2(111) and its powder. For the powder, the Ca and F signals are reduced by a factor of 0.77 +/- 0.03 in comparison with those for the single crystal

Structural and Setting reaction studies of Glass Polyalkenoate Cements by MAS- NMR Spectrocopy

Glass polyalkenoate cements (GPCs) are produced from a reaction between fluoroaluminosilicate glass powder with poly(acrylic acid) (PAA). These cements are widely used in dentistry as adhesive and tooth restorative materials. During the setting reaction, the Al(IV) changes its coordination number to Al(VI) and crosslink to PAA chains. In the present work, the structure of the glass and the setting reaction of GPCs were studied by 29Si, 31P, 19F and 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The influences of alumina content as well as mixed cation such as Ca/Na and Ca/Sr on the glass structure were studied. The Q structure of the glass changed with the alumina content as the number of neighbouring Al in SiO4 network decreased. The decrease in alumina content also resulted in more disrupted glasses and a higher tendency to undergo amorphous separation and crystallization because there are more Ca cation available to form NBO and F-Ca(n). Furthermore, the influence of substituting sodium for calcium was investigated. The Q structure of the glass was not affected with the addition of Na. It was found that Na penetrates the phosphorus and fluorine environments and forms Na/Ca pyrophosphate and F-Ca(2)/Na(1) and Al-F-Na(n) species. The effect of Sr substituting for Ca was also studied. It was suggested that Sr may have a little influence on the glass structure due to their similarity in charge to size ratio. The Sr may slightly affect the phosphorus environment due to the difference in field strength of Ca and Sr. In this study, the setting reaction of GPCs was followed by 29Si, 31P, 19F and 27Al MAS-NMR spectroscopy. All GPCs continue to have a pyrophosphate environment of Q1 Al-O-PO3 3- regardless of the original glass composition. This suggests that the Al(IV) from the Al-O-P bonds are not released from the glass network, thus are not available to crosslink to PAA chains. Therefore, the phosphate content is important for controlling the working and the setting time of GPCs. The conversion of Al(IV) to Al(VI) was determined from the 27Al MAS-NMR data and the Al(VI):Al(IV) + Al(V) ratio was calculated in order to follow the setting reaction of the GPCs. The addition of fluorine in the GPCs was found to enhance the acid attack during the setting reaction. In contrast, it was suggested that Na delays the setting reaction by forming Na polysalts and hence, disrupting the crosslinking of Al3+ to PAA. Although the presence of Sr has little influence on the structure of the glass, the conversion of Al(IV) to Al(VI) is lower for Sr and mixed Ca/Sr cements than Ca cement. The difference is not yet fully understood, but it is suggested that it may be due to the larger size of Sr ions. A commercial GPC, Carbomer® containing fluoroapatite (FAP) designed to remineralise in the mouth was also studied. This study showed the involvement of the FAP component in the setting reaction and hence, the amount of FAP available for promoting the remineralisation process decreases. The Al(V) is present in all GPCs regardless of the setting time. In addition, the participation of Al(VI) from the glass in the setting reaction is not clear because both Al(VI) in the glass and in the cement matrix have very similar chemical shift. The present work suggests that there are two sites of Al(IV) after the setting reaction, which are attributed to the Al(IV) in the original glass and in the degraded layer of the glass. The reduction of Al-F-Na(n) and Al-F-Ca(n) species after the setting reaction and the unavailability of Al-O-P bonds for acid attack suggest that ion exchange between cations (Na and Sr) with protons from PAA may take place during the setting reaction. All GPCs show similar fluorine environments after setting. It was suggested that fluorine maybe bonded to Al in higher coordination states than four. Finally, there is a reconstruction of the silicate network during the setting reaction, as a result of the release of Al3+ and other ions from the glass network. It is assumed that the reconstruction of the silicate network depends on the release rate of the Al(IV). It is hoped that the improved structural understanding of the glass and the setting reaction of the GPCs obtained during this study will lead to the design of new GPCs for specific applications

Communication apprehension and exercise adherence: An exploratory study

This thesis explored whether adhering to an exercise program could significantly predict an individual’s level of communication apprehension (CA). The project expands the study o f CA by analyzing a potentially new treatment option for alleviating this fear of communication. Specifically, it asked if an individual’s level o f exercise adherence (EA) - as measured by the four components of intensity, frequency, duration, and longevity - could significantly predict an individual’s level CA in each o f the four contexts - interpersonal conversations, group discussion, meetings and public speaking - and overall. Five research questions were posited (one for each context and trait) and tested utilizing the Personal Report o f Communication Apprehension instrument (McCroskey, 1982) and an EA measure. Due to the study’s exploratory nature demographics such as age and gender were also examined in supplemental analyses. Results using SPSS-X stepwise multiple regression, Pearson r correlations and Deviations of Linearity indicated partial support that a significant linear relationship exists between three o f the EA components and four o f the five CA scores, and a significant deviation from linearity relationship exists between one demographic variable and three of the five CA scores. Discussion and interpretation of results as well as recommendations for future research are given