Microstructure Analysis of Hydroxyapatite Coating on Stainless Steel 316L Using Investment Casting Technique for Implant Application

Osteoporosis and traffic accident are major factor that causes bone fracture in Indonesia. One of solution for the bones fracture treatment is by using fixation implant that has similar characteristics with the human bones. Stainless Steel (SS) 316L is one of biomaterial that has been used as an implant material due to its corrosion resistance, good biocompatibility, and excellent mechanical properties. However, the bioactivity properties of the material is needed to improve by coating it with hydroxyapatite (HA). In this research, HA was coated to the surface of 316L SS by using investment casting technique. A slurry of HA was poured into casting cavity surface prior to metal casting process, and then followed by sintering at temperatures of 850oC, 900oC, and 950oC. Characterization of HA coating layer on specimen surface was conducted by Optical Microscope, Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX). Hardness of  the samples was measured by Vickers Hardness Tester. Result of the experiment shows that the invvestment casting is successfully to coat the HA on the SS 316L surface. Pouring method produces HA layer with thickness (spongy and porous surface) in the range of 60 µm – 110 µm. The increasing of sintering temperature increases the hardness number of the surfaces, and affect the purity of HA, but it is not related to coating thickness. Optimum sintering temperature is obtained at 900oC which produces the best calcium and phosphate ratio. The investment casting method is found as a simple and non-expensive technique that can be used to coat HA powder to SS 316L that produces good properties and optimum crystallinity of HA that suitable for orthopedic implant application

Microstructure analysis of hydroxyapatite coating on stainless steel 316L using investment casting technique for implant application

Osteoporosis and traffic accidents are a significant factor that causes a bone fracture in Indonesia. One solution for the bones fracture treatment is by using fixation implant that has similar characteristics with the human bones. Stainless Steel (SS) 316L is one of biomaterial that has been used as an implant material due to its corrosion resistance, excellent biocompatibility, and excellent mechanical properties. However, the bioactivity properties of the material are needed to improve by coating it with hydroxyapatite (HA). In this research, HA was coated to the surface of 316L SS by using investment casting technique. A slurry of HA was poured into the casting cavity surface prior to the metal casting process and then followed by sintering at temperatures of 850°C, 900°C, and 950°C. Characterization of HA coating layer on specimen surface was conducted by Optical Microscope, Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX). The hardness of the samples was measured by Vickers Hardness Tester. The result of the experiment shows that the investment casting is successfully to coat the HA on the SS 316L surface. Pouring method produces HA layer with thickness (spongy and porous surface) in the range of 60 μm - 110 μm. The increasing of sintering temperature increases the hardness number of the surfaces, and affect the purity of HA, but it is not related to coating thickness. The optimum sintering temperature is obtained at 900°C which produces the best calcium and phosphate ratio. The investment casting method is found as a simple and non-expensive technique that can be used to coat HA powder to SS 316L that produces good properties and optimum crystallinity of HA that suitable for orthopaedic implant application

Delineating the distinct role of AKT in mediating cell survival and proliferation induced by CD154 and IL-4/IL-21 in chronic lymphocytic leukemia

The functional significance of AKT in chronic lymphocytic leukemia (CLL) remains unclear. Given the importance of non-malignant T cells in regulating clonal expansion in CLL, we investigated the role of AKT in T cell-mediated cytoprotection and proliferation using an established co-culture system in which primary CLL cells were incubated on a monolayer of transfected mouse fibroblasts expressing human CD40L (CD154). Stimulation of CLL cells via CD40 induced activation of AKT, which was closely associated with downregulation of its negative regulator PTEN, and protected CLL cells from killing by bendamustine. This cytoprotective effect of CD40 stimulation was prevented by a selective inhibitor of AKT. Stimulation of CLL cells with CD154 + IL-4 or IL-21 induced proliferation detected as reduced fluorescence of cells pre-stained with CFSE. AKT inhibition produced a significant, consistent reduction in proliferation induced by CD154 + IL-4 and a reduction in proliferation induced by CD154 + IL-21 in most but not all cases. In contrast, AKT inhibition had no effect on the proliferation of normal B cells induced by CD154 + IL-4 or IL-21. These findings indicate that AKT contributes in a significant way to T-cell mediated survival and proliferation signalling in CLL and support the clinical evaluation of AKT inhibitors in this disease

On RR couplings on D-branes at order O(α′2)O(\alpha'^2)

Recently, it has been found that there are couplings of the RR field strength $F^{(p)}$ and the B-field strength $H$ on the world volume of D$_p$-branes at order ${\cal O}(\alpha'^2)$. These couplings which have both world-volume and transverse indices, are invariant under the linear T-duality transformations. Consistency with the nonlinear T-duality indicates that the RR field strength $F^{(p)}$ in these couplings should be replaced by ${\cal F}^{(p)}=d{\cal C}^{(p-1)}$ where ${\cal C}=e^{B}C$. This replacement, however, reproduces some non-gauge invariant terms. On the other hand, the nonlinear terms are invariant under the linear T-duality transformations at the level of two B-fields. This allows one to remove some of the nonlinear terms in ${\cal F}^{(p)}$. We fix this by comparing the nonlinear couplings with the S-matrix element of one RR and two NSNS vertex operators. Our results indicate that in the expansion of ${\cal F}^{(p)}$ one should keep only the B-field gauge invariant terms, e.g. $B\wedge dC^{(p-3)}$ where both indices of B-field lie along the brane. Moreover, in this case one should replace $B$ with $B+2\pi\alpha'f$ to have the $B$-field gauge invariance.Comment: 23 pages, Latex file, 1 figure; v2:typos corrected, to appear in JHE

Unemployment and retirement and ill-health: a cross-sectional analysis across European countries

Objective To determine the associations between different measures of health and labor market position across ten European countries. Methods We studied 11,462 participants of the Survey on Health and Ageing in Europe (SHARE) who were 50–64 years old. Logistic regression was used to calculate the associations between health and other determinants and being retired, unemployed, or a homemaker. Results A large variation across European countries was observed for the proportion of persons 50–65 years with paid employment, varying among men from 42% in Austria to 75% in Sweden and among women from 22% in Italy to 69% in Sweden. Among employed workers 18% reported a poor health, whereas this proportion was 37% in retirees, 39% in unemployed persons, and 35% in homemakers. A perceived poor health was strongly associated with non-participating in labor force in most European countries. A lower education, being single, physical inactivity and a high body mass index were associated with withdrawal from the labor force. Long-term illnesses such as depression, stroke, diabetes, chronic lung disease, and musculoskeletal disease were significantly more common among those persons not having paid employment. Conclusion In many European countries a poor health, chronic diseases, and lifestyle factors were associated with being out of the labor market. The results of this study suggest that in social policies to encourage employment among older persons the role of ill-health and its influencing factors needs to be incorporated

Enhanced gas sensing and photocatalytic activity of reduced graphene oxide loaded TiO2 nanoparticles

In the present study, we have evaluated the gas sensing and photocatalytic activity of reduced graphene oxide (rGO) conjugated titanium dioxide (TiO2) nanoparticles (NPs) formed by the hydrothermal method. The as-synthesized rGO-TiO2 nanocomposite were characterized for the physicochemical properties such as the nature of crystallinity, functionalization, and morphology by making use of the powder X-ray diffraction, Fourier transform-infrared spectroscopy, and scanning electron microscopy, respectively. On testing the gas sensing properties, we found that the rGO-TiO2 nanocomposite can serve as the chemoresistive-type sensor because of its sensitivity and selectivity towards different concentrations of hydrogen and oxygen at room temperature conditions. However, the rGO-TiO2 sensor’s response and recovery speed towards hydrogen and oxygen needs further optimization. Test of photocatalytic activity of TiO2-rGO catalyst for the removal of two model contaminant dyes, RhB and MB showed effective removal, with respective degradation percentages of about 80 and 90% within the first 50 min of irradiation under visible light irradiation. Besides, MB was more effectively degraded using TiO2-rGO than pure TiO2 during the first 30 min of irradiation and this enhanced activity can be attributed to the increased capacity of light absorption, the efficiency of charge carriers separation, and the specific surface area maintained by the rGO-TiO2 nanocomposite to effectively utilize the photo-generated holes (h+) and superoxide radicals (O2−radical dot), responsible for the degradation of the dye. Based on the overall analysis, the formation of rGO-TiO2 nanocomposite can significantly improve the gas sensing and photocatalytic properties of TiO2 NPs and thus can be potential for practical applications in future nanotechnology

Antimicrobial Resistance, Virulence Factors and Genetic Diversity of Escherichia coli Isolates from Household Water Supply in Dhaka, Bangladesh

Background: Unsafe water supplies continue to raise public health concerns, especially in urban areas in low resource countries. To understand the extent of public health risk attributed to supply water in Dhaka city, Bangladesh, Escherichia coli isolated from tap water samples collected from different locations of the city were characterized for their antibiotic resistance, pathogenic properties and genetic diversity. Methodology/Principal Findings: A total of 233 E. coli isolates obtained from 175 tap water samples were analysed for susceptibility to 16 different antibiotics and for the presence of genes associated with virulence and antibiotic resistance. Nearly 36% (n = 84) of the isolates were multi-drug(≥3 classes of antibiotics) resistant (MDR) and 26% (n = 22) of these were positive for extended spectrum β-lactamase (ESBL). Of the 22 ESBL-producers, 20 were positive for blaCTX-M-15, 7 for blaOXA-1-group(all had blaOXA-47) and 2 for blaCMY-2. Quinolone resistance genes, qnrS and qnrB were detected in 6 and 2 isolates, respectively. Around 7% (n = 16) of the isolates carried virulence gene(s) characteristic of pathogenic E. coli; 11 of these contained lt and/or st and thus belonged to enterotoxigenic E. coli and 5 contained bfp and eae and thus belonged to enteropathogenic E. coli. All MDR isolates carried multiple plasmids (2 to 8) of varying sizes ranging from 1.2 to >120 MDa. Ampicillin and ceftriaxone resistance were co-transferred in conjugative plasmids of 70 to 100 MDa in size, while ampicillin, trimethoprim-sulfamethoxazole and tetracycline resistance were co-transferred in conjugative plasmids of 50 to 90 MDa. Pulsed-field gel electrophoresis analysis revealed diverse genetic fingerprints of pathogenic isolates. Significance: Multi-drug resistant E. coli are wide spread in public water supply in Dhaka city, Bangladesh. Transmission of resistant bacteria and plasmids through supply water pose serious threats to public health in urban areas

Ethnic differences in body fat distribution among Asian pre-pubertal children: A cross-sectional multicenter study

Background Ethnic differences in body fat distribution contribute to ethnic differences in cardiovascular morbidities and diabetes. However few data are available on differences in fat distribution in Asian children from various backgrounds. Therefore, the current study aimed to explore ethnic differences in body fat distribution among Asian children from four countries. Methods A total of 758 children aged 8-10 y from China, Lebanon, Malaysia and Thailand were recruited using a non-random purposive sampling approach to enrol children encompassing a wide BMI range. Height, weight, waist circumference (WC), fat mass (FM, derived from total body water [TBW] estimation using the deuterium dilution technique) and skinfold thickness (SFT) at biceps, triceps, subscapular, supraspinale and medial calf were collected. Results After controlling for height and weight, Chinese and Thai children had a significantly higher WC than their Lebanese and Malay counterparts. Chinese and Thais tended to have higher trunk fat deposits than Lebanese and Malays reflected in trunk SFT, trunk/upper extremity ratio or supraspinale/upper extremity ratio after adjustment for age and total body fat. The subscapular/supraspinale skinfold ratio was lower in Chinese and Thais compared with Lebanese and Malays after correcting for trunk SFT. Conclusions Asian pre-pubertal children from different origins vary in body fat distribution. These results indicate the importance of population-specific WC cut-off points or other fat distribution indices to identify the population at risk of obesity-related health problems