Improved surface bioactivity of stainless steel substrates using osteocalcin mimetic peptide

Although stainless steel has a good biocompatibility for most clinical cases, the higher tissue response (bone bonding property) is required in orthopedic field. In this study, to improve bone-bonding ability of stainless steel substrates, a specific sequence of osteocalcin mimetic peptide is used as bioactive coating material to biochemically modify the surface of metallic samples. This sequence consists of thirteen amino acids present in the first helix of osteocalcin is synthesized in amidic form and physically adsorbed on the surface of 316LS (316 low carbon surgical grade) stainless steel substrates. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to characterize the surface of peptide coated and uncoated substrates. The bioactivity and bone bonding ability of coated and uncoated substrates are assessed by level of hydroxyapatite formation, using transmission electron microscopy (TEM), energy-dispersive x-ray (EDS), and scanning electron microscopy (SEM). The pre-osteoblast cell attachment and proliferation are also evaluated by MTT assay. The results show that the surface of coated sample is homogenously covered by the peptide and display a rougher surface relative to uncoated sample. TEM images reveal the formation of plate-like hydroxyapatite crystals in the presence of the peptide and an amorphous calcium phosphate phase without the peptide. Pre-osteoblast cells proliferation is significantly higher on the surface of peptide coated substrate, while cell attachment remains unaffected by the peptide coatings. Pre-osteoblast cells also demonstrate a higher degree of spreading on the surface of coated sample. It is believed that osteocalcin mimetic peptide improve surface bioactivity and promote hydroxyapatite crystal formation may lead to increased mineralization and bone formation on the surface of metallic biomedical devices.     

Mechanochemical synthesis and shock wave consolidation of TiN(Al) nanostructure solid solution

This paper aims to report the study of the synthesis of a titanium nitride nanostructure solid solution through the reduction of aluminum nitride with titanium based on the stoichiometric reaction of 2Ti + AlN by mechanical alloying (MA) process at a ball-to-powder weight ratio of 15:1. A nanostructure solid solution of in-situ titanium nitride was formed through exchange reaction between Ti and AlN at the initial time of MA. XRD, SEM, EPMA, TEM, and particle size analysis (PSA) were used to characterize the products. It was found that the amount of Al resulting from decomposition of aluminum nitride dissolved in the TiN lattice increased in accordance with milling time, leading to the formation of TiN(Al) solid solution and a reduction of the TiN lattice interplanar distance. The milled powder displayed equiaxed morphology and a narrow size distribution of about 1 μm at the end of the milling process. In-situ TiN(Al) crystallites were of an average size of 6 ± 2 nm. Subsequent to MA, an underwater shock compaction method was applied to the prolonged milled powders to obtain bulk sample. The effect of this shock compaction on the selected sample resulted in the preservation of its nanostructure characteristics with no additional phase transformation which are considered advantageous in the use of high dynamic compaction method for ceramic materials.     

Energy and exergy analysis of an indirect solar cabinet dryer based on mathematical modeling results

In the present study, using a previously developed dynamic mathematical model for performance analysis of an indirect cabinet solar dryer [1], a microscopic energy and exergy analysis for an indirect solar cabinet dryer is carried out. To this end, appropriate energy and exergy models are developed and using the predicted values for temperature and enthalpy of gas stream and the temperature, enthalpy and moisture content of the drying solid, the energy and exergy efficiencies are estimated. The validity of the model for predicting variations in gas and solid characteristics along the time and the length of the solar collector and/or dryer length was examined against some existing experimental data. The results show that in spite of high energy efficiency, the indirect solar cabinet dryer has relatively low exergy efficiency. Results show that the maximum exergy losses are in midday. Also the minimums of total exergy efficiency are 32.3% and 47.2% on the first and second days, respectively. Furthermore, the effect of some operating parameters, including length of the collector, its surface, and air flow rate was investigated on the exergy destruction and efficiency.     

Calculation of reactivity ratios of methacrylic acid-ethyl acrylate copolymer by on-line quantitative 1H NMR spectroscopy

The solution copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was studied by online proton nuclear magnetic resonance spectroscopy (¹H NMR) using 2,2′–azobisisobutyronitrile as an initiator in deuterated dimethyl sulfoxide at 60 °C. The chemical compositions of the copolymer and the comonomer concentrations were determined from the conversion of comonomers to copolymer by quantitative in situ NMR monitoring to estimate the reactivity ratios of the comonomers at low conversion. This is a new and easy methodology to analyze radical copolymerization. In this research, it is shown that monomer reactivity ratios can be calculated by data collected only from one initial comonomer mixture composition via online monitoring progress of the copolymerization reaction. The reactivity ratios of MAA and EA are equal to 2.360 and 0.414, respectively. This approach is used to compute the monomer reactivity ratios in a nonlinear integrated form of the copolymerization equation which is described by Mayo and Lewis terminal model. The fairly good agreement between the results and the literature data reported for the emulsion system represent the accuracy of the reactivity ratios calculated by this new approach. The calculated reactivity ratios for emulsion copolymerization are r _MAA = 2.040 and r _EA = 0.470, and the previous literature data are r _MAA = 2.580 and r _EA = 0.157.     

Application of Ozone Post-Harvest Treatment on Kabkab Date Fruits: Effect on Mortality Rate of Indian Meal Moth and Nutrition Components

Methyl bromide (MB) was used for years to treat infested stored date fruits; however, MB is due to be phased out by 2015. In this study ozone is used for disinfestations of Kabkab date against Indian meal moth in three life stage. They were exposed to four ozone concentrations (300 ± 10, 1050 ± 40, 2000 ± 40, and 4000 ± 50 ppm) during four periods (2, 4, 6, and 8 h). The findings show 2000 ppm of ozone concentration within 8 h resulted in complete mortality of larvae and adult insects and over 90% mortality of eggs. The proposed ozone treatment is a promising approach replacing application of MB for disinfestations of examined date fruits, as no remarkable changes were observed on pH of the date fruits and its chemical compositions (total phenolic content, anti-oxidant activity and free radicals).     

Effect of Ozone as a Disinfectant on Microbial Load and Chemical Quality of Raw Wheat Germ

ABSTRACT

While raw seed sprouts can threaten consumers’ health by foodborne pathogens, thermal or chemical disinfection of sprouts may cause some negative effects; instead, ozone can be a good alternative treatment. This study investigated the effect of nine ozone treatments (2000, 4000, and 6000 ppm within 1, 2, and 4 h) on wheat germ chemical compositions and microbial flora. The results indicated that ozonation with 2000 ppm during 4 h was the optimized treatment with the greatest effect on decreasing the microbial load while it had the minimum effect on antioxidant properties, lipid oxidation, and moisture content of raw wheat germ.     

A dual-mode tunable bandpass filter for GSM,UMTS, WiFi,and WiMAX standards applications

This paper presents a dual-mode tunable bandpass filter (BPF) for global system for mobile communication, universal mobile telecommunications system, wireless fidelity, and worldwide interoperability for microwave access standard applications. The proposed filter consists of a stepped-impedance resonator, single resonator, and coupled line, which are loaded with varactors. The center frequency and bandwidth of the proposed filter can be tuned with tuning varactors. Furthermore, the measurement results show that the BPF can be tuned over the frequency range of 1.8 to 2.5 GHz. Moreover, the bandwidth can be changed at each certain frequency. Furthermore, using PIN diodes, a bandstop filter is added to the tunable BPF to reduce the out-of-band frequencies around the desired frequencies. The values of LC equivalent circuits are calculated, and the results are compared with those obtained from the layout of the proposed structure. Finally, the measurement results justify the simulation results.     

Participatory Water-Food-Energy Nexus Approach for Evaluation and Design of Groundwater Governance

Water Resources Management - Improving the groundwater governance structure can help reduce groundwater decline and improve the state of an aquifer. This study develops an approach to modify...     

Ferrite‐based wideband circularly polarized microstrip antenna design

In this paper, a wideband, circularly polarized patch antenna is proposed that leverages the unidirectional resonant modes of a circular patch mounted on top of a grounded dielectric‐ferrite substrate. The proposed antenna is fed via the proximity coupling method and several parasitically coupled patches are placed on a dielectric superstrate to enhance the impedance bandwidth of the antenna. The resonant modes of the structure rotate only in the clockwise or counter clockwise directions. In the frequency range where the effective permeability of the ferrite layer is negative, the resonance frequencies of these modes differ significantly, which produces a large axial ratio (AR) bandwidth. For the proposed antenna, the numerical results show the 10 dB impedance bandwidth to be around 44% and the 3 dB axial ratio bandwidth to be higher than 64%.