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1.  Thermally Driven Stability of Octadecylphosphonic Acid Thin Films Grown on SS316L 
Scanning  2010;32(5):304-311.
Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF and water flushes while untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a three hour period while the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface.
PMCID: PMC2962881  PMID: 20648546
Octadecylphosphonic acid; Stainless steel (SS316L); biomaterials; self-assembly; stability; contact angles; atomic force microscopy (AFM); IR spectroscopy
2.  Surface Characteristics and Bioactivity of a Novel Natural HA/Zircon Nanocomposite Coated on Dental Implants 
BioMed Research International  2014;2014:410627.
The surface characteristics of implant which influence the speed and strength of osseointegration include surface chemistry, crystal structure and crystallinity, roughness, strain hardening, and presence of impurities. The aim of this study was to evaluate the bioactivity and roughness of a novel natural hydroxyapatite/zircon (NHA/zircon) nanobiocomposite, coated on 316L stainless steel (SS) soaked in simulated body fluid (SBF). NHA/zircon nanobiocomposite was fabricated with 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% of zircon in NHA using ball mill for 20 minutes. The composite mixture was coated on 316L SS using plasma spray method. The results are estimated using the scanning electron microscopy (SEM) observation to evaluate surface morphology, X-ray diffraction (XRD) to analyze phase composition, and transmission electron microscopy (TEM) technique to evaluate the shape and size of prepared NHA. Surfaces roughness tester was performed to characterize the coated nanocomposite samples. The maximum average Ra (14.54 μm) was found in the NHA 10 wt.% of zircon coating. In addition, crystallinity (Xc) was measured by XRD data, which indicated the minimum value (Xc = 41.1%) for the sample containing 10 wt.% of zircon. Maximum bioactivity occurred in the sample containing 10 wt.% of zircon, which was due to two reasons: first, the maximum roughness and, second, the minimum crystallinity of nanobiocomposite coating.
PMCID: PMC4009196  PMID: 24822204
3.  Effect of Cell Moisture on the Thermal Inactivation Rate of Bacterial Spores 
Applied Microbiology  1968;16(8):1240-1244.
Thermal inactivation rates were determined for two strains of Bacillus subtilis var. niger spores after equilibration to various relative humidity (RH) levels. In these tests, small thin stainless-steel squares were each inoculated with a drop of spore suspension and equilibrated to 11, 33, or 85% RH. Following equilibration, the squares were placed on a hot plate preheated to 108, 125, 136, 164, or 192 C for various exposure times and then assayed for surviving organisms. The results revealed that spores of the A strain of B. subtilis were least resistant if preequilibrated to 11% RH and most resistant if preequilibrated to 85% RH. The same trend was obtained at all temperatures except 192 C, at which, no difference was noted, probably because the rapid kill time approaches the heat-up time of the stainless-steel square. The B strain of B. subtilis spores showed an opposite RH effect; that is, the cells preequilibrated to 11% RH were the most resistant. Because the two strains of spores were grown on different media, further studies were conducted at 136 C after subculturing the cells on different media. When the B strain was subcultured on the A strain medium, the pattern was reversed; the cells preequilibrated to low RH were then least resistant. Although it was not possible to reverse these cells to the original pattern by subculturing on the original B strain medium again, the pattern was altered to the point that there was no significant difference in heat resistance of these cells regardless of the preequilibration RH. The same result was obtained when the A strain was grown on the B strain medium; that is, the thermal resistance could not be reversed, but it was altered from the point where the low RH equilibrated cells were least resistant initially to the point where there was no significant difference in any of the cells regardless of what RH was used for preequilibration. The thermal resistance of spores seemed to be dependent on (i) the medium on which the spores are grown, (ii) the RH on which they are exposed before heating, and (iii) some genetic characteristic of the cell.
PMCID: PMC547626  PMID: 4970894
4.  Direct observation of Lomer-Cottrell Locks during strain hardening in nanocrystalline nickel by in situ TEM 
Scientific Reports  2013;3:1061.
Strain hardening capability is critical for metallic materials to achieve high ductility during plastic deformation. A majority of nanocrystalline metals, however, have inherently low work hardening capability with few exceptions. Interpretations on work hardening mechanisms in nanocrystalline metals are still controversial due to the lack of in situ experimental evidence. Here we report, by using an in situ transmission electron microscope nanoindentation tool, the direct observation of dynamic work hardening event in nanocrystalline nickel. During strain hardening stage, abundant Lomer-Cottrell (L-C) locks formed both within nanograins and against twin boundaries. Two major mechanisms were identified during interactions between L-C locks and twin boundaries. Quantitative nanoindentation experiments recorded show an increase of yield strength from 1.64 to 2.29 GPa during multiple loading-unloading cycles. This study provides both the evidence to explain the roots of work hardening at small length scales and the insight for future design of ductile nanocrystalline metals.
PMCID: PMC3544074  PMID: 23320142
5.  In Situ Measurement of the Junction Temperature of Light Emitting Diodes Using a Flexible Micro Temperature Sensor 
Sensors (Basel, Switzerland)  2009;9(7):5068-5075.
This investigation aimed to fabricate a flexible micro resistive temperature sensor to measure the junction temperature of a light emitting diode (LED). The junction temperature is typically measured using a thermal resistance measurement approach. This approach is limited in that no standard regulates the timing of data capture. This work presents a micro temperature sensor that can measure temperature stably and continuously, and has the advantages of being lightweight and able to monitor junction temperatures in real time. Micro-electro-mechanical-systems (MEMS) technologies are employed to minimize the size of a temperature sensor that is constructed on a stainless steel foil substrate (SS-304 with 30 μm thickness). A flexible micro resistive temperature sensor can be fixed between the LED chip and the frame. The junction temperature of the LED can be measured from the linear relationship between the temperature and the resistance. The sensitivity of the micro temperature sensor is 0.059 ± 0.004 Ω/°C. The temperature of the commercial CREE® EZ1000 chip is 119.97 °C when it is thermally stable, as measured using the micro temperature sensor; however, it was 126.9 °C, when measured by thermal resistance measurement. The micro temperature sensor can be used to replace thermal resistance measurement and performs reliably.
PMCID: PMC3274131  PMID: 22346688
LED; junction temperature; MEMS; flexible micro temperature sensor
6.  Viscoelastic properties of Staphylococcus aureus and Staphylococcus epidermidis mono‐microbial biofilms 
Microbial biotechnology  2009;2(6):634-641.
The viscoelastic properties of mono‐microbial biofilms produced by ocular and reference staphylococcal strains were investigated. The microorganisms were characterized for their haemolytic activity and agr typing and the biofilms, grown on stainless steel surface under static conditions, were analysed by Confocal Laser Scanning Microscopy. Static and dynamic rheometric tests were carried out to determine the steady‐flow viscosity and the elastic and viscous moduli. The analysed biofilms showed the typical time‐dependent behaviour of viscoelastic materials with considerable elasticity and mechanical stability except for Staphylococcus aureus ATCC 29213 biofilm which showed a very fragile structure. In particular, S. aureus 6ME biofilm was more compact than other staphylococcal biofilms studied with a yield stress ranging between 2 and 3 Pa. The data obtained in this work could represent a starting point for developing new therapeutic strategies against biofilm‐associated infections, such as improving the drug effect by associating an antimicrobial agent with a biofilm viscoelasticity modifier.
PMCID: PMC3815319  PMID: 21255298
7.  Fabrication of a Flexible Micro Temperature Sensor for Micro Reformer Applications 
Sensors (Basel, Switzerland)  2011;11(4):3706-3716.
Micro reformers still face obstacles in minimizing their size, decreasing the concentration of CO, conversion efficiency and the feasibility of integrated fabrication with fuel cells. By using a micro temperature sensor fabricated on a stainless steel-based micro reformer, this work attempts to measure the inner temperature and increase the conversion efficiency. Micro temperature sensors on a stainless steel substrate are fabricated using micro-electro-mechanical systems (MEMS) and then placed separately inside the micro reformer. Micro temperature sensors are characterized by their higher accuracy and sensitivity than those of a conventional thermocouple. To the best of our knowledge, micro temperature sensors have not been embedded before in micro reformers and commercial products, therefore, this work presents a novel approach to integrating micro temperature sensors in a stainless steel-based micro reformer in order to evaluate inner local temperature distributions and enhance reformer performance.
PMCID: PMC3231302  PMID: 22163817
MEMS; flexible micro temperature sensor; micro reformer
8.  Sensor Fabrication Method for in Situ Temperature and Humidity Monitoring of Light Emitting Diodes 
Sensors (Basel, Switzerland)  2010;10(4):3363-3372.
In this work micro temperature and humidity sensors are fabricated to measure the junction temperature and humidity of light emitting diodes (LED). The junction temperature is frequently measured using thermal resistance measurement technology. The weakness of this method is that the timing of data capture is not regulated by any standard. This investigation develops a device that can stably and continually measure temperature and humidity. The device is light-weight and can monitor junction temperature and humidity in real time. Using micro-electro-mechanical systems (MEMS), this study minimizes the size of the micro temperature and humidity sensors, which are constructed on a stainless steel foil substrate (40 μm-thick SS-304). The micro temperature and humidity sensors can be fixed between the LED chip and frame. The sensitivities of the micro temperature and humidity sensors are 0.06 ± 0.005 (Ω/°C) and 0.033 pF/%RH, respectively.
PMCID: PMC3274224  PMID: 22319303
LED; MEMS; flexible micro temperature; humidity sensors
9.  Assessment of hydrophobicity and roughness of stainless steel adhered by an isolate of Bacillus cereus from a dairy plant 
Brazilian Journal of Microbiology  2010;41(4):984-992.
The interaction between the surface of stainless steel and Bacillus cereus was studied in terms of the characteristics of interfacial interaction determined from the measurement of the contact angle of the surface of B. cereus and stainless steel in the presence or absence of B. cereus adherence. The microtopographies and the roughness of the surface of stainless steel and stainless steel adhered by B. cereus were evaluated with the help of atomic force microscopy and perfilometry. The strain of B. cereus studied was considered hydrophilic, whereas the stainless steel was considered hydrophobic. The adhesion was not thermodynamically favorable (ΔGadhesion > 0) between the stainless steel and the strain of B. cereus studied. Thus, the interaction between them was not favored by the thermodynamic aspect of adhesion. There was no difference (p > 0.05) in the roughness of the surfaces of stainless steel adhered by B. cereus when analyzed by atomic force microscope and perfilometry.
PMCID: PMC3769772  PMID: 24031578
hydrophobicity; roughness; Bacillus cereus; dairy plant; adhesion
10.  Shear Stress, Temperature, and Inoculation Concentration Influence the Adhesion of Water-Stressed Helicobacter pylori to Stainless Steel 304 and Polypropylene 
Although molecular techniques have identified Helicobacter pylori in drinking water-associated biofilms, there is a lack of studies reporting what factors affect the attachment of the bacterium to plumbing materials. Therefore, the adhesion of H. pylori suspended in distilled water to stainless steel 304 (SS304) coupons placed on tissue culture plates subjected to different environmental conditions was monitored. The extent of adhesion was evaluated for different water exposure times, using epifluorescence microscopy to count total cell numbers. High shear stresses—estimated through computational fluid dynamics—negatively influenced the adhesion of H. pylori to the substrata (P < 0.001), a result that was confirmed in similar experiments with polypropylene (P < 0.05). However, the temperature and inoculation concentration appeared to have no effect on adhesion (P > 0.05). After 2 hours, H. pylori cells appeared to be isolated on the surface of SS304 and were able to form small aggregates with longer exposure times. However, the formation of a three-dimensional structure was only very rarely observed. This study suggests that the detection of the pathogen in well water described by other authors can be related to the increased ability of H. pylori to integrate into biofilms under conditions of low shear stress. It will also allow a more rational selection of locations to perform molecular or plate culture analysis for the detection of H. pylori in drinking water-associated biofilms.
PMCID: PMC1449073  PMID: 16598000
11.  Perfluorocarbon thin films and polymer brushes on stainless steel 316L for control of interfacial properties 
Perfluorocarbon thin films and polymer brushes were formed on stainless steel 316L (SS316L) to control the surface properties of the metal oxide. Substrates modified with the films were characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), contact angle analysis, atomic force microscopy (AFM), and cyclic voltammetry (CV). Perfluorooctadecanoic acid (PFOA) was used to form thin films by self-assembly on the surface of SS316L. Polypentafluorostyrene (PFS) polymer brushes were formed by surface initiated polymerization using SAMs of 16-phosphonohexadecanoic acid (COOH-PA) as the base. PFOA and PFS were effective in significantly reducing the surface energy and thus the interfacial wetting properties of SS316L. The SS316L control exhibited a surface energy of 38 mN/m compared to PFOA and PFS modifications, which had surface energies of 22 and 24 mN/m, respectively. PFOA thin films were more effective in reducing the surface energy of the SS316L compared to PFS polymer brushes. This is attributed to the ordered PFOA film presenting aligned CF3 terminal groups. However, PFS polymer brushes were more effective in providing corrosion protection. These low energy surfaces could be used to provide a hydrophobic barrier that inhibits corrosion of the SS316L metal oxide surface.
PMCID: PMC3126892  PMID: 21631123
stainless steel 316L; fluorine; thin films; surface initiated polymerization; low surface energy
12.  The Effect of Temperature Gradients on Stress Development During Cryopreservation via Vitrification 
Cell preservation technology  2007;5(2):104-115.
This study addresses the problem of thermal stress development in bulky specimens during cryopreservation via vitrification (vitreous means glassy in Latin). While this study is a part of an ongoing effort to associate the developing mechanical stress with the relevant physical properties of the cryopreserved media and to its the thermal history, the current paper focuses exclusively on the role of temperature gradients. Temperature gradients arise due to the high cooling rates necessary to facilitate vitrification; the resulting non-uniform temperature distribution leads to differential thermal strain, possibly resulting in cracking. The cooling rate is assumed constant on the outer surface in this study, and the material properties are assumed constant. It is demonstrated that under these assumptions, mechanical stress develops only when the temperature distribution in the specimen approaches thermal equilibrium at a cryogenic storage temperature. It is shown that the maximum possible stresses for a given cooling rate can be computed with a simple thermo-elastic analysis; these stresses are associated with cooling to sufficiently low temperatures and are independent of the variation of viscosity with temperature. Analytic estimates for these stresses are obtained for several idealized shapes, while finite element analysis is used to determine stresses for geometries used in cryopreservation practice. Stresses that develop under a wider range of storage temperatures are also studied with finite element analysis, and the results are summarized with suitable normalizations. It is found that no stresses arise if cooling ceases above the set-temperature, which defines the transition from viscous-dominated to elastic-dominated behavior; the set-temperature is determined principally by the dependency of viscosity upon temperature. Strategies for rapidly reaching low temperatures and avoiding high stresses are inferred from the results.
PMCID: PMC2180391  PMID: 18185851
Vitrification; Solidification; Solid Mechanics; Thermal Stress; Set-Temperature
13.  Crack-Tip Strain Field Mapping and the Toughness of Metallic Glasses 
PLoS ONE  2013;8(12):e83289.
We have used high-energy x-ray scattering to map the strain fields around crack tips in fracture specimens of a bulk metallic glass under load at room temperature and below. From the measured strain fields we can calculate the components of the stress tensor as a function of position and determine the size and shape of the plastic process zone around the crack tip. Specimens tested at room temperature develop substantial plastic zones and achieve high stress intensities () prior to fracture. Specimens tested at cryogenic temperatures fail at reduced but still substantial stress intensities () and show only limited evidence of crack-tip plasticity. We propose that the difference in behavior is associated with changes in the flow stress and elastic constants, which influence the number density of shear bands in the plastic zone and thus the strain required to initiate fracture on an individual band. A secondary effect is a change in the triaxial state of stress around the crack tip due to the temperature dependence of Poisson's ratio. It is likely that this ability to map elastic strains on the microscale will be useful in other contexts, although interpreting shifts in the position of the scattering peaks in amorphous materials in terms of elastic strains must be done with caution.
PMCID: PMC3873938  PMID: 24386172
14.  Mechanical properties of hydroxyapatite single crystals from nanoindentation data 
In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals.
PMCID: PMC3123525  PMID: 21262492
15.  Study on cerium-doped nano-TiO2 coatings for corrosion protection of 316 L stainless steel 
Nanoscale Research Letters  2012;7(1):227.
Many methods have been reported on improving the photogenerated cathodic protection of nano-TiO2 coatings for metals. In this work, nano-TiO2 coatings doped with cerium nitrate have been developed by sol–gel method for corrosion protection of 316 L stainless steel. Surface morphology, structure, and properties of the prepared coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The corrosion protection performance of the prepared coatings was evaluated in 3 wt% NaCl solution by using electrochemical techniques in the presence and absence of simulated sunlight illumination. The results indicated that the 1.2% Ce-TiO2 coating with three layers exhibited an excellent photogenerated cathodic protection under illumination attributed to the higher separation efficiency of electron–hole pairs and higher photoelectric conversion efficiency. The results also showed that after doping with an appropriate concentration of cerium nitrate, the anti-corrosion performance of the TiO2 coating was improved even without irradiation due to the self-healing property of cerium ions.
PMCID: PMC3432000  PMID: 22515192
Nano-TiO2 coating; Cerium ion doping; Corrosion protection
16.  Strength, Hardening, and Failure Observed by In Situ TEM Tensile Testing** 
Advanced Engineering Materials  2012;14(11):960-967.
We present in situ transmission electron microscope tensile tests on focused ion beam fabricated single and multiple slip oriented Cu tensile samples with thicknesses in the range of 100–200 nm. Both crystal orientations fail by localized shear. While failure occurs after a few percent plastic strain and limited hardening in the single slip case, the multiple slip samples exhibit extended homogenous deformation and necking due to the activation of multiple dislocation sources in conjunction with significant hardening. The hardening behavior at 1% plastic strain is even more pronounced compared to compression samples of the same orientation due to the absence of sample taper and the interface to the compression platen. Moreover, we show for the first time that the strain rate sensitivity of such FIB prepared samples is an order of magnitude higher than that of bulk Cu.
PMCID: PMC3573867  PMID: 23447712
17.  Constitutive Law and Flow Mechanism in Diamond Deformation 
Scientific Reports  2012;2:876.
Constitutive laws and crystal plasticity in diamond deformation have been the subjects of substantial interest since synthetic diamond was made in 1950's. To date, however, little is known quantitatively regarding its brittle-ductile properties and yield strength at high temperatures. Here we report, for the first time, the strain-stress constitutive relations and experimental demonstration of deformation mechanisms under confined high pressure. The deformation at room temperature is essentially brittle, cataclastic, and mostly accommodated by fracturing on {111} plane with no plastic yielding at uniaxial strains up to 15%. At elevated temperatures of 1000°C and 1200°C diamond crystals exhibit significant ductile flow with corresponding yield strength of 7.9 and 6.3 GPa, indicating that diamond starts to weaken when temperature is over 1000°C. At high temperature the plastic deformation and ductile flow is meditated by the <110>{111} dislocation glide and a very active {111} micro-twinning.
PMCID: PMC3500768  PMID: 23166859
18.  Strain-specific functional and numerical responses are required to evaluate impacts on predator–prey dynamics 
The ISME Journal  2012;7(2):405-416.
We use strains recently collected from the field to establish cultures; then, through laboratory studies we investigate how among strain variation in protozoan ingestion and growth rates influences population dynamics and intraspecific competition. We focused on the impact of changing temperature because of its well-established effects on protozoan rates and its ecological relevance, from daily fluctuations to climate change. We show, first, that there is considerable inter-strain variability in thermal sensitivity of maximum growth rate, revealing distinct differences among multiple strains of our model species Oxyrrhis marina. We then intensively examined two representative strains that exhibit distinctly different thermal responses and parameterised the influence of temperature on their functional and numerical responses. Finally, we assessed how these responses alter predator–prey population dynamics. We do this first considering a standard approach, which assumes that functional and numerical responses are directly coupled, and then compare these results with a novel framework that incorporates both functional and numerical responses in a fully parameterised model. We conclude that: (i) including functional diversity of protozoa at the sub-species level will alter model predictions and (ii) including directly measured, independent functional and numerical responses in a model can provide a more realistic account of predator–prey dynamics.
PMCID: PMC3555124  PMID: 23151643
functional response; numerical response; model protozoa; Oxyrrhis marina; temperature
19.  Superior Tensile Ductility in Bulk Metallic Glass with Gradient Amorphous Structure 
Scientific Reports  2014;4:4757.
Over centuries, structural glasses have been deemed as a strong yet inherently ‘brittle’ material due to their lack of tensile ductility. However, here we report bulk metallic glasses exhibiting both a high strength of ~2 GPa and an unprecedented tensile elongation of 2–4% at room temperature. Our experiments have demonstrated that intense structural evolution can be triggered in theses glasses by the carefully controlled surface mechanical attrition treatment, leading to the formation of gradient amorphous microstructures across the sample thickness. As a result, the engineered amorphous microstructures effectively promote multiple shear banding while delay cavitation in the bulk metallic glass, thus resulting in superior tensile ductility. The outcome of our research uncovers an unusual work-hardening mechanism in monolithic bulk metallic glasses and demonstrates a promising yet low-cost strategy suitable for producing large-sized, ultra-strong and stretchable structural glasses.
PMCID: PMC3996486  PMID: 24755683
20.  Fiber optic micro sensor for the measurement of tendon forces 
A fiber optic sensor developed for the measurement of tendon forces was designed, numerically modeled, fabricated, and experimentally evaluated. The sensor incorporated fiber Bragg gratings and micro-fabricated stainless steel housings. A fiber Bragg grating is an optical device that is spectrally sensitive to axial strain. Stainless steel housings were designed to convert radial forces applied to the housing into axial forces that could be sensed by the fiber Bragg grating. The metal housings were fabricated by several methods including laser micromachining, swaging, and hydroforming. Designs are presented that allow for simultaneous temperature and force measurements as well as for simultaneous resolution of multi-axis forces.
The sensor was experimentally evaluated by hydrostatic loading and in vitro testing. A commercial hydraulic burst tester was used to provide uniform pressures on the sensor in order to establish the linearity, repeatability, and accuracy characteristics of the sensor. The in vitro experiments were performed in excised tendon and in a dynamic gait simulator to simulate biological conditions. In both experimental conditions, the sensor was found to be a sensitive and reliable method for acquiring minimally invasive measurements of soft tissue forces. Our results suggest that this sensor will prove useful in a variety of biomechanical measurements.
PMCID: PMC3494611  PMID: 23033868
Fiber Bragg grating sensor; Tendon forces
21.  In vitro study on the feasibility of magnetic stent hyperthermia for the treatment of cardiovascular restenosis 
Thermal treatment or hyperthermia has received considerable attention in recent years due to its high efficiency, safety and relatively few side-effects. In this study, we investigated whether it was possible to utilize targeted thermal or instent thermal treatments for the treatment of restenosis following percutaneous transluminal coronary angioplasty (PTCA) through magnetic stent hyperthermia (MSH). A 316L stainless steel stent and rabbit vascular smooth muscle cells (VSMCs) were used in the present study, in which the inductive heating characteristics of the stent under alternative magnetic field (AMF) exposure, as well as the effect of MSH on the proliferation, apoptosis, cell cycle and proliferating cell nuclear antigen (PCNA) expression of the rabbit VSMCs, were evaluated. The results demonstrated that 316L stainless steel coronary stents possess ideal inductive heating characteristics under 300 kHz AMF exposure. The heating properties were shown to be affected by the field intensity of the AMF, as well as the orientation the stent axis. MSH had a significant effect on the proliferation and apoptosis of VSMCs, and the effect was temperature-dependent. While a mild temperature of 43°C demonstrated negligible effects on the growth of VSMCs, MSH treatment above 47°C effectively inhibited the VSMC proliferation and induced apoptosis. Furthermore, a 47°C treatment exhibited a significant and long-term inhibitory effect on VSMC migration. The results strongly suggested that MSH may be potentially applied in the clinic as an alternative approach for the prevention and treatment of restenosis.
PMCID: PMC3786833  PMID: 24137187
magnetic stent hyperthermia; percutaneous transluminal coronary angioplasty; restenosis; vascular smooth muscle cells; alternative magnetic field
22.  Experimental Study of the Seismic Performance of L-Shaped Columns with 500 MPa Steel Bars 
The Scientific World Journal  2014;2014:105826.
Based on tests on six L-shaped RC columns with 500 MPa steel bars, the effect of axial compression ratios and stirrup spacing on failure mode, bearing capacity, displacement, and curvature ductility of the specimens is investigated. Test results show that specimens with lower axial load and large stirrup characteristic value (larger than about 0.35) are better at ductility and seismic performance, while specimens under high axial load or with a small stirrup characteristic value (less than about 0.35) are poorer at ductility; L-shaped columns with 500 MPa steel bars show better bearing capacity and ductility in comparison with specimens with HRB400 steel bars.
PMCID: PMC4055115  PMID: 24967420
23.  Application of an adsorptive-thermocatalytic process for BTX removal from polluted air flow 
Zero valent iron and copper oxide nanoparticles (30-60 nm) were coated on a bed of natural zeolite (Clinoptilolite) with 1-2 mm grains and arranged as a dual filter in a stainless steel cylindrical reactor (I.D 4.5 cm and L = 30 cm) to investigating the coated bed removal efficiency for BTX. The experiments were conducted in three steps. First, with an air flow of 1.5 L/min and temperature range of 38 (ambient temperature) to 600°C the BTX removal and mineralization was surveyed. Then, in an optimized temperature the effect of flow rate and pollution loading rate were surveyed on BTX removal.
The BTX removal at 300 and 400°C were respectively up to 87.47% and 94.03%. Also in these temperatures respectively 37.21% and 90.42% of BTX mineralization were achieved. In the retention times of 14.1 s and 7.05 s, respectively 96.18% and 78.42% of BTX was removed.
According to the results, this adsorptive-thermocatalytic process with using Clinoptilolite as an adsorbent bed and combined Fe0 and Cu2O nanoparticles as catalysts can be an efficient and competitive process in the condition of high flow rate and high pollution loading rate with an adequate process temperature of 350°C.
PMCID: PMC4053284  PMID: 24955244
Aromatic organics; Air pollution; Chemical process; Nanoparticles; Zeolite
24.  Validated stability indicating liquid chromatographic determination of ebastine in pharmaceuticals after pre column derivatization: Application to tablets and content uniformity testing 
An accurate, simple, sensitive and selective reversed phase liquid chromatographic method has been developed for the determination of ebastine in its pharmaceutical preparations. The proposed method depends on the complexation ability of the studied drug with Zn2+ ions. Reversed phase chromatography was conducted using an ODS C18 (150 × 4.6 mm id) stainless steel column at ambient temperature with UV-detection at 260 nm. A mobile phase containing 0.025%w/v Zn2+ in a mixture of (acetonitril/methanol; 1/4) and Britton Robinson buffer (65:35, v/v) adjusted to pH 4.2, has been used for the determination of ebastine at a flow rate of 1 ml/min. The calibration curve was rectilinear over the concentration range of 0.3 - 6.0 μg/ml with a detection limit (LOD) of 0.13 μg/ml, and quantification limit (LOQ) of 0.26 μg/ml. The proposed method was successfully applied for the analysis of ebastine in its dosage forms, the obtained results were favorably compared with those obtained by a comparison method. Furthermore, content uniformity testing of the studied pharmaceutical formulations was also conducted. The composition of the complex as well as its stability constant was also investigated. Moreover, the proposed method was found to be a stability indicating one and was utilized to investigate the kinetics of alkaline and ultraviolet induced degradation of the drug. The first-order rate constant and half life of the degradation products were calculated.
PMCID: PMC3113337  PMID: 21554731
25.  Evaluation of stresses developed in different bracket-cement-enamel systems using finite element analysis with in vitro bond strength tests 
Progress in Orthodontics  2014;15(1):33.
The purpose of this study was to determine the bond strength of different orthodontic bracket materials (ceramic, stainless steel, and titanium) as well as stresses developed in bracket-cement-enamel systems using finite element (FE) analysis.
One hundred and thirty-five extracted human caries-free upper central incisors were divided into three groups (n = 45/group) according to the type of orthodontic bracket materials (stainless steel, ceramic, and titanium). Each group was further subdivided into three subgroups (n = 15/group) according to the bond strength test loading mode (shear short side, shear long side, and tensile). After debonding, the fractured specimen was examined, and the adhesive remnant index (ARI) was determined. FE analysis models analyzed the stress distribution within the cement and enamel. Bond strengths were analyzed using ANOVA and Tukey's test, and the ARI scores were analyzed using chi-square (χ2) test.
Shear loading at the short side of the bracket resulted in the highest bond strength and lowest maximum principal stress both on cement and enamel compared with the other loading modes (P < 0.05). Ceramic brackets presented with higher bond strength and lower maximum principal stress than metallic brackets (P < 0.05). There was a significant difference for ARI scores between the type of brackets (χ2 = 64.852, P < 0.001).
The findings suggest that the manner of loading orthodontic brackets and the selection of orthodontic bracket materials affect the bond strength and stresses developed both on cement and enamel.
PMCID: PMC4047763  PMID: 24934213
Finite element analysis; Orthodontic brackets; Shear; Stresses; Tensile

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