Hydroxylammonium nitrate (HAN) is a promising green propellant because of its low toxicity, high volumetric specific impulse, and reduced development cost. Electrolytic decomposition of HAN is an efficient approach to prepare it for further ignition and combustion. This paper describes the investigation of a co-electrolysis effect on electrolytic decomposition of HAN-fuel mixtures using stainless steel-platinum (SS-Pt) electrodes. For the first time, different materials were utilized as electrodes to alter the cathodic reaction, which eliminated the inhibition effect and achieved a repeatable and consistent electrolytic decomposition of HAN solution. Urea and methanol were added as fuel components in the HAN-fuel mixtures. When the mass ratio of added urea ≥20%, the electrolytic decomposition of a HAN-urea ternary mixture achieved 67% increment in maximum gas temperature (Tgmax) and 185% increment in overall temperature increasing rate over the benchmark case of HAN solution. The co-electrolysis of urea released additional electrons into the mixtures and enhanced the overall electrolytic decomposition of HAN. In contrast, the addition of methanol did not improve the Tgmax but only increased the overall temperature increasing rate. This work has important implications in the development of an efficient and reliable electrolytic decomposition system of HAN and its mixtures for propulsion applications.
Corrosion is a natural deterioration process that destructs metal surface. Metal of highly
protected by passivation layer such as Stainless Steel 316L also undergoes pitting corrosion
when continuously exposed to aggressive environment. To overcome this phenomenon, application
of epoxy based coating with addition of zinc oxide- poly (3,4-ethylenedioxythiophene)
doped with poly (styrene sulphonate) hybrid nanocomposite additive was introduced as
paint/metal surface coating. The compatibility between these two materials as additive
was studied by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD),
Field Emission Scanning Electron Microscopy/Energy-Dispersive X-ray spectroscopy (FESEM/EDX)
and Transmission Electron Microscopy (TEM) analysis. The effect of nanocomposite
wt.% in epoxy based coating with immersion duration in real environment on corrosion
protection performance was analyzed through potentiodynamic polarization analysis. The
main finding showed that addition of hybrid nanocomposite had increased corrosion protection
yet enhanced corrosion process when excess additives was loaded into epoxy coating.
Addition of 2 wt.% ZnO-PEDOT:PSS was found significantly provided optimum corrosion
protection to stainless steel 316L as the corrosion rate for 0 day, 15 days and 30 days of
immersion duration is 0.0022 mm/yr, 0.0004 mm/yr and 0.0015 mm/yr; respectively.
Biodegradable stents are considered to be a recent innovation, and their feasibility and applicability have been proven in recent years. Research in this area has focused on materials development and biological studies, rather than on how to transform the developed biodegradable materials into the stent itself. Currently available stent technology, the laser cutting-based process, might be adapted to fabricate biodegradable stents. In this work, the fabrication, characterization and testing of biodegradable Fe-Mn stents are described. A standard process for fabricating and testing stainless steel 316L stents was referred to. The influence of process parameters on the physical, metallurgical and mechanical properties of the stents, and the quality of the produced stents, were investigated. It was found that some steps of the standard process such as laser cutting can be directly applied, but changes to parameters are needed for annealing, and alternatives are needed to replace electropolishing.
This study compared the surface roughness of selected tooth coloured restorative materials that were polished according to manufacturers’ instructions and Sof-Lex. It also assessed the surface roughness of polished materials after thermocycling.Filtek Z350XT, Beautifil-Bulk Restorative and Cention N, were used in this study. A stainless steel mould (10mm diameter x 2mm height) was used to fabricate 75 cylindrical specimens: 15 Filtek Z350XT (FZ), 30 Beautifil-Bulk Restorative (BB) and 30 Cention N (CN). All 15 FZ specimens were polished with Sof-Lex. Fifteen BB and CN specimens were polished according to manufacturers’ instructions. The remaining fifteen BB and CN specimens were polished using Sof-Lex. All the specimens were subjected to thermocycling (1000 cycles). Surface roughness was assessed quantitatively with profilometry after specimen preparation (Mylar stage), polishingand thermocycling. Data were analysed using SPSS version 25.0 at α=0.05. When polished according to manufacturers’ instructions, BB had the lowest mean surface roughness (Ra) values (0.13±0.01μm) followed sequentially by CN (0.14±0.03μm) and FZ (0.15±0.02μm). The differences were not statistically significant. When polished with Sof-Lex, BB exhibited the smoothest surface (0.116±0.03μm) followed sequentially by and FZ (0.150±0.02μm) and CN (0.157±0.02μm). Thermocycling caused an increase in the Ra. The differences were statistically significant. All materials tested had Ra values below the threshold value of 0.2 μm at Mylar stage and after polishing with their recommended polishing system and Sof-Lex. Thermocycling produced rougher surfaces that did not exceed the threshold Ra value. Polishability was material dependent.
This report aimed to describe an effective biomechanics to control the upper incisors inclination during the
correction of gummy smile with bimaxillary proclinations. A 14-year-old female presented with a Class II
division I incisor relationship complicated with bimaxillary proclination on a Class 2 skeletal base. The lips
were incompetent, showing 7 mm of upper incisors at rest and 5mm maxillary gingival display on smiling
with normal upper lip length. Treatment involved extraction of all first permanent premolars followed by
upper and lower fixed appliances. Intrusion of the upper incisors with controlled labial crown torque was
accomplished with mini-implant anchorage placed bilaterally on the infrazygomatic crests with the retraction
forces above the centre of resistance using 0.019x0.025-in stainless steel archwire in 0.022-in slot. The
0.019x0.025-in stainless steel archwire in 0.022-in slot provided the vertical play to favour lingual crown
tipping despite having forces above the centre of resistance for concurrent anterior segment intrusion.
Background: Majority of root canal treatment in Malaysia was provided by general dental practitioner. The purpose of this study was to evaluate the knowledge and practice (canal’s preparation, use of materials) by them. Methods: A questionnaire was structured and distributed to 120 registered general dental practitioners in selected areas in Perak, Johor and Klang Valley regarding the provision of root canal therapy in their practices. The questionnaires were hand delivered and collected after 1 to 2 weeks. Results: Reply rate was 95% (n=114). The result demonstrated that 62% respondents indicated that they performed the root canal therapy (RCT) themselves. Out of these only 26% included molars in the treatment. Three quarters of them (77%) used step-back technique and 54% used stainless steel instruments to prepare the canals. The majority of the respondents (69%) used calcium hydroxide as intracanal medicaments. Only 30% used rubber dam for isolation whereas the rest used cotton rolls. The numbers of routine radiographs taken were two for anterior teeth and three for molar. Half of the respondents indicated that they usually completed the RCT for the anterior tooth within two visits whereas three visits were needed for the molar tooth. The results were analyzed descriptively. Conclusions: This study indicates that most of the general dental practitioners’ do not comply with quality standards guidelines such as use of rubber dam as isolation. Cotton roll was the most popular isolation method. In spite of this, most of the respondents tend to update their knowledge and practices with current techniques and materials.
Immobilization of chlorhexidine (CHX) on stainless steel 316L (SS316L), assisted by a polydopamine film as an intermediate layer is projected as an approach in combating infection while aiding bone regeneration for coating development on orthopedic and dental implants. This study aimed to investigate the ability of CHX coating to promote apatite layer, osteoblast cells viability, adhesion, osteogenic differentiation and mineralization. Stainless steel 316L disks were pre-treated, grafted with a polydopamine film and immobilized with different concentrations of CHX (10-30mM). The apatite layer formation was determined through an in vitro simulated body fluid (SBF) test by ATR-FTIR and SEM-EDX analyses. The osteoblastic evaluations including cells viability, cells adhesion, osteogenic differentiation and mineralization were assessed with human fetal osteoblast cells through MTT assay, morphology evaluation under FESEM, ALP enzyme activity and Alizarin Red S assay. The apatite layer was successfully formed on the CHX coated disks, demonstrating potential excellent bioactivity property. The CHX coatings were biocompatible with the osteoblast cells at low CHX concentration (<20mM) with good adhesion on the metal surfaces. The increment of ALP activity and calcium deposition testified that the CHX coated disks able to support osteoblastic maturation and mineralization. These capabilities give a promising value to the CHX coating to be implied in bone regeneration area.
Total hip arthroplasty is a flourishing orthopedic surgery, generating billions of dollars of revenue. The cost associated with the fabrication of implants has been increasing year by year, and this phenomenon has burdened the patient with extra charges. Consequently, this study will focus on designing an accurate implant via implementing the reverse engineering of three-dimensional morphological study based on a particular population. By using finite element analysis, this study will assist to predict the outcome and could become a useful tool for preclinical testing of newly designed implants. A prototype is then fabricated using 316L stainless steel by applying investment casting techniques that reduce manufacturing cost without jeopardizing implant quality. The finite element analysis showed that the maximum von Mises stress was 66.88 MPa proximally with a safety factor of 2.39 against endosteal fracture, and micromotion was 4.73 μm, which promotes osseointegration. This method offers a fabrication process of cementless femoral stems with lower cost, subsequently helping patients, particularly those from nondeveloped countries.
The adhesion of colloidal probes of stainless steel, glass and cellulose to Pseudomonas fluorescens biofilms was examined using atomic force microscopy (AFM) to allow comparisons between surfaces to which biofilms might adhere.
Electrodeposition is commonly used to deposit ceramic or metal coating on metallic implants. Its utilization in depositing polymer microcapsule coating is currently being explored. However, there is no encapsulation of drug within polymer microcapsules that will enhance its chemical and biological properties. Therefore, in this study, ginseng which is known for its multiple therapeutic effects was encapsulated inside biodegradable poly(lactic-co-glycolic acid) (PLGA) microcapsules to be coated on pre-treated medical grade stainless steel 316L (SS316L) using an electrodeposition technique. Polyaniline (PANI) was incorporated within the microcapsules to drive the formation of microcapsule coating. The electrodeposition was performed at different current densities (1-3 mA) and different deposition times (20-60 s). The chemical composition, morphology and wettability of the microcapsule coatings were characterized through attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and contact angle analyses. The changes of electrolyte colors, before and after the electrodeposition were also observed. The addition of PANI has formed low wettability and uniform microcapsule coatings at 2 mA current density and 40 s deposition time. Reduction in the current density or deposition time caused less attachment of microcapsule coatings with high wettability records. While prolonging either one parameter has led to debris formation and melted microcapsules with non-uniform wettability measurements. The color of electrolytes was also changed from milky white to dark yellow when the current density and deposition time increased. The application of tolerable current density and deposition time is crucial to obtain a uniform microcapsule coating, projecting a controlled release of encapsulated drug.
The role of Escherichia coli H antigens in hydrophobicity and attachment to glass, Teflon and stainless steel (SS) surfaces was investigated through construction of fliC knockout mutants in E. coli O157:H7, O1:H7 and O157:H12. Loss of FliC(H12) in E. coli O157:H12 decreased attachment to glass, Teflon and stainless steel surfaces (p<0.05). Complementing E. coli O157:H12 ΔfliC(H12) with cloned wildtype (wt) fliC(H12) restored attachment to wt levels. The loss of FliCH7 in E. coli O157:H7 and O1:H7 did not always alter attachment (p>0.05), but complementation with cloned fliC(H12), as opposed to cloned fliCH7, significantly increased attachment for both strains compared with wt counterparts (p<0.05). Hydrophobicity determined using bacterial adherence to hydrocarbons and contact angle measurements differed with fliC expression but was not correlated to the attachment to materials included in this study. Purified FliC was used to functionalise silicone nitride atomic force microscopy probes, which were used to measure adhesion forces between FliC and substrates. Although no significant difference in adhesion force was observed between FliC(H12) and FliCH7 probes, differences in force curves suggest different mechanism of attachment for FliC(H12) compared with FliCH7. These results indicate that E. coli strains expressing flagellar H12 antigens have an increased ability to attach to certain abiotic surfaces compared with E. coli strains expressing H7 antigens.
Chlorhexidine (CHX) is known for its high antibacterial substantivity and is suitable for use to bio-inert medical devices due to its long-term antibacterial efficacy. However, CHX molecules require a crosslinking film to be stably immobilized on bio-inert metal surfaces. Therefore, polydopamine (PDA) was utilized in this study to immobilize CHX on the surface of 316L type stainless steel (SS316L). The SS316L disks were pre-treated, modified with PDA film and immobilized with different concentrations of CHX (10mM-50mM). The disks were then subjected to various surface characterization analyses (ATR-FTIR, XPS, ToF-SIMS, SEM and contact angle measurement) and tested for their cytocompatibility with human skin fibroblast (HSF) cells and antibacterial activity against Escherichia coli and Staphylococcus aureus. The results demonstrated the formation of a thin PDA film on the SS316L surface, which acted as a crosslinking medium between the metal and CHX. CHX was immobilized via a reduction process that covalently linked the CHX molecules with the functional group of PDA. The immobilization of CHX increased the hydrophobicity of the disk surfaces. Despite this property, a low concentration of CHX optimized the viability of HSF cells without disrupting the morphology of adherent cells. The immobilized disks also demonstrated high antibacterial efficacy against both bacteria, even at a low concentration of CHX. This study demonstrates a strong beneficial effect of the crosslinked PDA film in immobilizing CHX on bio-inert metal, and these materials are applicable in medical devices. Specifically, the coating will restrain bacterial proliferation without suffocating nearby tissues.
Objectives: To evaluate the effect of light-cure devices and curing times on the shear bond strength (SBS) of orthodontic brackets.
Material and Methods: 60-extracted human premolars were divided into 6-groups of 10-teeth each and bonded with stainless-steel brackets by using 3M Unitek Transbond XT composite. Specimens were cured with halogen, LED and plasma arc lights with two different times for each. The specimens were subjected to shear force till debond with a crosshead speed of 1mm/min and tested after 5min. The stress was calculated and data were subjected to statistical analysis.
Results: one-way ANOVA and Dunnett T3 post hoc comparison test were used. There were no significant differences between the 6 groups (p < 0.05).
Conclusions: all curing light methods with loading force after 5 min achieved SBS more than the normal range; therefore, arch wire can be inserted at the same visit using any of tested curing light device or curing time.
Heat exchanger performance degrades rapidly during operation due to formation of deposits on heat transfer surfaces which ultimately reduces service life of the equipment. Due to scaling, product deteriorates which causes lack of proper heating. Chemistry of milk scaling is qualitatively understood and the mathematical models for fouling at low temperatures have been produced but the behavior of systems at ultra high temperature processing has to be studied further to understand in depth. In diversified field, the effect of whey protein fouling along with pressure drop in heat exchangers were conducted by many researchers. Adding additives, treatment of heat exchanger surfaces and changing of heat exchanger configurations are notable areas of investigation in milk fouling. The present review highlighted information about previous work on fouling, influencing parameters of fouling and its mitigation approach and ends up with recommendations for retardation of milk fouling and necessary measures to perform the task.
Staphylococcus aureus and Salmonella Typhimurium have a propensity to develop biofilms on food contact surfaces, such as stainless-steel, that persist despite rigorous cleaning and sanitizing procedures. Since both bacterial species pose a significant public health risk within the food chain, improved anti-biofilm measures are needed. This study examined the potential of clays as antibacterial and anti-biofilm agents against these two pathogens on appropriate contact surfaces. Natural soil was processed to yield leachates and suspensions of both untreated and treated clays. Soil particle size, pH, cation-exchange capacity, and metal ions were characterized to assess their importance in bacterial killing. Initial antibacterial screening was performed on nine distinct types of natural Malaysian soil using a disk diffusion assay. Untreated leachate from Kuala Gula and Kuala Kangsar clays were found to inhibit S. aureus (7.75 ± 0.25 mm) and Salmonella Typhimurium (11.85 ± 1.63 mm), respectively. The treated Kuala Gula suspension (50.0 and 25.0 %) reduced S. aureus biofilms by 4.4 and 4.2 log at 24 and 6 h, respectively, while treated Kuala Kangsar suspension (12.5 %) by a 4.16 log reduction at 6 h. Although less effective, the treated Kuala Gula leachate (50.0 %) was effective in removing Salmonella Typhimurium biofilm with a decrease of >3 log in 24 h. In contrast to Kuala Kangsar clays, the treated Kuala Gula clays contained a much higher soluble metal content, especially Al (301.05 ± 0.45 ppm), Fe (691.83 ± 4.80 ppm) and Mg (88.44 ± 0.47 ppm). Elimination of S. aureus biofilms correlated with the presence of Fe, Cu, Pb, Ni, Mn and Zn irrespective of the pH of the leachate. Our findings demonstrate that a treated suspension is the most effective for eradication of S. aureus biofilms with a potential as a sanitizer-tolerant, natural antibacterial against biofilms for applications in the food industry.
Waterways are popular locations for the disposition of criminal evidence because the recovery of latent fingerprints from such evidence is difficult. Currently, small particle reagent is a method often used to visualize latent fingerprints containing carcinogenic and hazardous compounds. This study proposes an eco-friendly, safranin-tinted Candida rugosa lipase (triacylglycerol ester hydrolysis EC 3.1.1.3) with functionalized carbon nanotubes (CRL-MWCNTS/GA/SAF) as an alternative reagent to the small particle reagent. The CRL-MWCNTS/GA/SAF reagent was compared with the small particle reagent to visualize groomed, full fingerprints deposited on stainless steel knives which were immersed in a natural outdoor pond for 30 days. The quality of visualized fingerprints using the new reagent was similar (modified-Centre for Applied Science and Technology grade: 4; p > 0.05) to small particle reagent, even after 15 days of immersion. Despite the slight decrease in quality of visualized fingerprints using the CRL-MWCNTS/GA/SAF on the last three immersion periods, the fingerprints remained forensically identifiable (modified-Centre for Applied Science and Technology grade: 3). The possible chemical interactions that enabled successful visualization is also discussed. Thus, this novel reagent may provide a relatively greener alternative for the visualization of latent fingerprints on immersed non-porous objects.
Active ingredients of ginsenoside, Rg1 and Re, are able to inhibit the proliferation of vascular smooth muscle cells and promote the growth of vascular endothelial cells. These capabilities are of interest for developing a novel drug-eluting stent to potentially solve the current problem of late-stent thrombosis and poor endotheliazation. Therefore, this study was aimed to incorporate ginsenoside into degradable coating of poly(lactic-co-glycolic acid) (PLGA). Drug mixture composed of ginseng extract and 10% to 50% of PLGA (xPLGA/g) was coated on electropolished stainless steel 316L substrate by using a dip coating technique. The coating was characterized principally by using attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy and contact angle analysis, while the drug release profile of ginsenosides Rg1 and Re was determined by using mass spectrometry at a one month immersion period. Full and homogenous coating coverage with acceptable wettability was found on the 30PLGA/g specimen. All specimens underwent initial burst release dependent on their composition. The 30PLGA/g and 50PLGA/g specimens demonstrated a controlled drug release profile having a combination of diffusion- and swelling-controlled mechanisms of PLGA. The study suggests that the 30PLGA/g coated specimen expresses an optimum composition which is seen as practicable for developing a controlled release drug-eluting stent.
Adhesives serve many functions in daily life, starting from sticking envelopes to rejoining broken
materials. Adhesives are usually developed for a specific purpose and the performances can vary
according to their specific end-use. Most of the commercially available adhesives comprised nonrenewable or petroleum derived raw materials. Thus, in order to mitigate negative impact of using nonrenewable material as the raw material for adhesives, a new type of adhesive containing epoxidised
natural rubber (NR) latex is developed. Epoxidised NR latex adhesive was initially prepared and pigment
was subsequently added to produce desired colours of the adhesive. Hence, the newly developed adhesive
can serve as adhesive and also as paint for art. The adhesives were characterised and the results indicated
that they were free from heavy metal contents and volatile organic compounds (VOCs). The adhesives
exhibited comparable odour concentration to commercial synthetic-based adhesive. In terms of toxicity
level, the adhesive developed exhibited low acute oral toxicity. Peel adhesion test of A4 and drawing
papers on stainless steel and glass substrates, opacity and glossiness were also investigated in the present
study. This coloured adhesive is deemed to support the STEM (science, technology, engineering and
mathematics) learning by indirectly imparting polymer science and technology in art education and
further promotes creative learning among school children. The adhesive is also derived from renewable
material rendering it more environmentally friendly.
This study investigates metal removal rate (MRR) of the biomaterial by using discharge machine Neuar CNC A50 Electrical Discharge Machine Die Sinking (EDM DS). The purpose of this study is to compare machining curvature cup for material SKD 11 and stainless steel with shape curvature cup acetabular. The result showed that electrode wear is higher when high current is applied. For each applied current 0.5A and 3.0A could result electrode wear of 0.236 mm, 0.246 mm and 0.269 mm respectively. Mean time of complete discharged for each pit with 0.3mm depth with supply 0. 5A is 6.51 minutes; 1. 5A is 3.54 minutes and 3A is 1.52 minutes. The biggest mean parameter of the pit is 0.356 mm, with 3A of current is applied. From this study, it can be concluded that low current set may give lower electrode copper wear. The experiment will help a researcher to discharge biomaterial types of metal with small size of copper electrode use of EDM DS Neuar for discharge multi hole or micro pit.
One of the non-destructive methods used for the identification and verification of metals is by the energy-dispersive X-ray fluorescence (EDXRF) technique. EDXRF analysis provides several important advantages such as simultaneous determination of the elements present, enable to analyse a very wide concentration range, fast analysis with no tedious sample preparation. The paper shows how this technique is developed and applied in the identification and verification of different grades of stainless steels. Comparison of the results obtained from this analysis with certified reference standards show very small differences between them.