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Prediction of Tensile Strength of 3D Printed Bronze PLA Part Using Response Surface Modelling

Palanisamy C, Nagarajan S

F1000Res, 2021;10:1030.
PMID: 35169462 DOI: 10.12688/f1000research.70641.1

Background - 3D printing is a dynamic process with many process parameters influencing the product, including the type of the material; it is often difficult to understand the combined influence of these parameters.  Purpose - The tensile strength of 3D printed parts is important for the functionality of components. The effects of process parameters on tensile strength must therefore be examined. The objective of this study is to develop a response surface model (RSM) to predict the final quality of a 3D printed bronze part from a different set of input parameters.  Methods - The tensile test specimen was built in a Makerbot 3D printer with bronze polylactic acid (PLA) material. The three controllable input parameters were; thickness of layers, number of shells, and infill density. The three levels of layer thickness were 0.1mm, 0.2mm and 0.3mm. The number of shells was 2, 3 and 4. The infill densities were 20%, 30% and 40%. A tensile experiment tested the strength of the specimens. RSM is a statistical approach for modelling and analyzing how different variables affect the response of interest, and for optimizing it.  Results - The result obtained shows that the specimen with a high layer thickness of 0.3mm and infill density of 40% is the best among all the other parameters. Finally, the regression equation produced was used for random values of layer thickness, the number of shells, and infill density, to see whether the values obtained from the tests fall into the range of experimental data.  Conclusion - Infill density and layer thickness are the two criteria that significantly influence the tensile property. The number of shells has the least influence on the tensile property. However, the best tensile strength is the part printed with higher infill density, a greater number of shells, and higher layer thickness.
Fulltext Factors influencing medical students' choice of future specialization in medical sciences: a cross-sectional questionnaire survey from medical schools in China, Malaysia and regions of South Asian Association for Regional Cooperation

Kumar A, Mitra K, Nagarajan S, Poudel B

N Am J Med Sci, 2014 Mar;6(3):119-25.
PMID: 24741550 DOI: 10.4103/1947-2714.128473

BACKGROUND: In future, increase in the number of healthcare professionals is dependent on the career interest among present undergraduate medical students. Based on their interest to pursue their specialty, the availability of medical doctors in each specialty could be done.
AIMS: This study was to find out future career interest and factors that influence undergraduate medical students to choose their future specialization.
MATERIALS AND METHODS: The study was carried out among first-year medical students from five countries. The students were asked to complete an 8-item questionnaire. Two thousand one hundred fifty three participants were enrolled in the study. Data were analyzed in Microsoft-Excel and Statistical Package for the Social Sciences.
RESULTS: Of the 2153 participants, only 1470 responded. Among the 1470 participants, 169 participants were excluded due to the ambiguity in responses, finally making it to 1301 participants. Among them, Anatomy (49.3%) followed by Biochemistry (26.7%) and Physiology (24%) were the most preferred subjects.
CONCLUSIONS: Anatomy was the most preferred basic science subject among the other subjects and the students were interested to pursuing surgery in future. Furthermore, the most preferred future specialties were surgery, internal medicine and pediatrics with gender variations; males preferring surgery and females in obstetrics and gynecology.
KEYWORDS: China; First year medical students; Malaysia; Medical Education; Post-Graduation; SAARC country
Fulltext Inhibition of Quorum Sensing and Biofilm Formation in Chromobacterium violaceum by Fruit Extracts of Passiflora edulis

Venkatramanan M, Sankar Ganesh P, Senthil R, Akshay J, Veera Ravi A, Langeswaran K, et al.

ACS Omega, 2020 Oct 13;5(40):25605-25616.
PMID: 33073086 DOI: 10.1021/acsomega.0c02483

Chromobacterium violaceum (C. violaceum) is a Gram-negative, rod-shaped facultatively anaerobic bacterium implicated with recalcitrant human infections. Here, we evaluated the anti-QS and antibiofilm activities of ethyl acetate extracts of Passiflora edulis (P. edulis) on the likely inactivation of acyl-homoserine lactone (AHL)-regulated molecules in C. violaceum both by in vitro and in silico analyses. Our investigations showed that the sub-MIC levels were 2, 1, and 0.5 mg/mL, and the concentrations showed a marked reduction in violacein pigment production by 75.8, 64.6, and 35.2%. AHL quantification showed 72.5, 52.2, and 35.9% inhibitions, inhibitions of EPS production (72.8, 36.5, and 25.9%), and reductions in biofilm formation (90.7, 69.4, and 51.8%) as compared to a control. Light microscopy and CLSM analysis revealed dramatic reduction in the treated biofilm group as compared to the control. GC-MS analysis showed 20 major peaks whose chemical structures were docked as the CviR ligand. The highest docking score was observed for hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester bonds in the active site of CviR with a binding energy of -8.825 kcal/mol. Together, we found that hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester remarkably interacted with CviR to inhibit the QS system. Hence, we concluded that hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester of P. edulis could likely be evaluated for treating C. violaceum infections.
Effect of blood pressure on the retinal vasculature in a multi-ethnic Asian population

Jeganathan VS, Sabanayagam C, Tai ES, Lee J, Sun C, Kawasaki R, et al.

Hypertens Res, 2009 Nov;32(11):975-82.
PMID: 19713968 DOI: 10.1038/hr.2009.130

Blood pressure has a significant effect on retinal arterioles. There are few data on whether this effect varies by race/ethnicity. We examined the relationship of blood pressure and retinal vascular caliber in a multi-ethnic Asian population. The study is population-based and cross sectional in design. A total of 3749 Chinese, Malay and Indian participants aged > or =24 years residing in Singapore were included in the study. Retinal vascular caliber was measured using a computer program from digital retinal photographs. The associations of retinal vascular caliber with blood pressure and hypertension in each racial/ethnic group were analyzed. The main outcome measures are retinal arteriolar caliber and venular caliber. The results show that retinal arterioles were narrower in persons with uncontrolled/untreated hypertension (140.0 microm) as compared with persons with controlled hypertension (142.1 microm, P=0.0001) and those with no hypertension (146.0 microm, P<0.0001). On controlling for age, gender, body mass index, lipids and smoking, each 10 mm Hg increase in mean arterial blood pressure was associated with a 3.1 microm decrease in arteriolar caliber (P<0.0001), with a similar magnitude seen in all three racial/ethnic groups: 3.1 microm in Chinese, 2.8 microm in Malays and 3.2 microm in Indians (P<0.0001 for all). Each 10 mm Hg increase in mean arterial blood pressure was associated with a 1.8 microm increase in venular caliber (P<0.0001); furthermore, the magnitude of this effect was similar across the three racial/ethnic groups. The effect of blood pressure on the retinal vasculature was similar across three major racial/ethnic groups in Asia.
Antioxidant, Diabetic and Inflammatory Activities of Alpinia calcarata Roscoe Extract

Devi NM, Nagarajan S, Singh CB, Khan MMA, Khan A, Khan N, et al.

Chem Biodivers, 2023 Sep 16.
PMID: 37715949 DOI: 10.1002/cbdv.202300970

BACKGROUND: Alpinia calcarata (AC) Roscoe of Zingiberaceae popularly known as lesser galangal has a widespread occurrence in China, India, Sri-Lanka, Bangladesh, Malaysia, Indonesia and Thailand. Essential oil (Eoil) was obtained from leaves/rhizomes of AC via hydro-distillation process.
METHODS: To identify chemical ingredients in oil from leaves/rhizomes of AC through GC/MS technique for volatile components and their anti-oxidant, inflammatory/diabetic activities.
RESULTS: The 38 and 65 components were found to make up 99.9 and 99.6 %, respectively in total of Eoil composition of AC leaves/rhizomes. Key chemical constituents were eucalyptol (28.7 % in leaves; 25.4 % in rhizomes), camphor (12.8 % in leaves; 4.2 % in rhizomes), and carotol (9.8 % in leaves; 5.6 % in rhizomes) found in oil of AC leaves/rhizomes. Colorimetric assay showed anti-oxidant activities in leaves and rhizomes are IC50 =71.01±0.71 μg/mL and IC50 =73.83±0.49 μg/mL, respectively in the Eoils. Eoils had high anti-oxidant capabilities in IC50 -values of AC-L-Eoil=43.09±0.82&AC-Rh-Eoil=68.11±0.87 in reducing power in μg/mL was found. Albumin test of rhizome oil had IC50 -values of 15.19±0.25 μg/mL. Concentrations range of 7.81 μg/mL and 250 μg/mL in the Eoils of AC leaves and rhizome, respectively by α-glucosidase inhibition assay.
CONCLUSION: Our findings demonstrated that leaf oil was slightly more promising results than rhizome oil of AC extract, which was ultimately showed medicinal potential of secondary metabolites with anti-oxidant, diabetic/inflammatory activities. Further, Eoils of AC have a wide range of pharmacological potential and promising anti-diabetic effects.
Fulltext JAK-STAT and G-protein-coupled receptor signaling pathways are frequently altered in epitheliotropic intestinal T-cell lymphoma

Nairismägi ML, Tan J, Lim JQ, Nagarajan S, Ng CC, Rajasegaran V, et al.

Leukemia, 2016 06;30(6):1311-9.
PMID: 26854024 DOI: 10.1038/leu.2016.13

Epitheliotropic intestinal T-cell lymphoma (EITL, also known as type II enteropathy-associated T-cell lymphoma) is an aggressive intestinal disease with poor prognosis and its molecular alterations have not been comprehensively characterized. We aimed to identify actionable easy-to-screen alterations that would allow better diagnostics and/or treatment of this deadly disease. By performing whole-exome sequencing of four EITL tumor-normal pairs, followed by amplicon deep sequencing of 42 tumor samples, frequent alterations of the JAK-STAT and G-protein-coupled receptor (GPCR) signaling pathways were discovered in a large portion of samples. Specifically, STAT5B was mutated in a remarkable 63% of cases, JAK3 in 35% and GNAI2 in 24%, with the majority occurring at known activating hotspots in key functional domains. Moreover, STAT5B locus carried copy-neutral loss of heterozygosity resulting in the duplication of the mutant copy, suggesting the importance of mutant STAT5B dosage for the development of EITL. Dysregulation of the JAK-STAT and GPCR pathways was also supported by gene expression profiling and further verified in patient tumor samples. In vitro overexpression of GNAI2 mutants led to the upregulation of pERK1/2, a member of MEK-ERK pathway. Notably, inhibitors of both JAK-STAT and MEK-ERK pathways effectively reduced viability of patient-derived primary EITL cells, indicating potential therapeutic strategies for this neoplasm with no effective treatment currently available.