Research and Development in Magnesium Alloys for Industrial and Biomedical Applications: A Review

Vaira Vignesh Ramalingam,Padmanaban Ramasamy,Mohan Das Kovukkal,Govindaraju Myilsamy 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.4

The work reviews the research and development status of magnesium alloy, with more attention to the methodologies andtechnologies adopted to improve the properties of AZ91 alloy. The drive force of utilizing magnesium alloys for automotiveand biomedical application is light weightiness and biocompatibility respectively. However, the softness and high activityof magnesium alloys result in high wear and high corrosion rate respectively. One of the essential factors influencing theproperties of magnesium alloy is its microstructure. Consequently, the grain size, morphology and distribution of phaseconstituents influence the properties of magnesium alloys. The modification of microstructure through processing route (hotworking and cold working), heat treatment, and alloying elements improves the mechanical, corrosion, biocompatible, andtribological properties of magnesium alloys. Besides microstructural modification processes, addition of reinforcements,and coatings improves the properties of magnesium alloys. This article emphasis on the recent research on the technologiesto improve the microstructure, hardness, tensile strength, ductility, yield strength, wear resistance, and corrosion resistanceof magnesium alloy AZ91. Moreover, this review addresses the key issues hindering the applications of magnesium alloysfor structural and biomedical applications.

Mitochondrial Akt Regulation of Hypoxic Tumor Reprogramming

Chae, Young Chan,Vaira, Valentina,Caino, M. Cecilia,Tang, Hsin-Yao,Seo, Jae Ho,Kossenkov, Andrew V.,Ottobrini, Luisa,Martelli, Cristina,Lucignani, Giovanni,Bertolini, Irene,Locatelli, Marco,Bryant, Ke Elsevier 2016 CANCER CELL Vol.30 No.2

<P><B>Summary</B></P> <P>Hypoxia is a universal driver of aggressive tumor behavior, but the underlying mechanisms are not completely understood. Using a phosphoproteomics screen, we now show that active Akt accumulates in the mitochondria during hypoxia and phosphorylates pyruvate dehydrogenase kinase 1 (PDK1) on Thr346 to inactivate the pyruvate dehydrogenase complex. In turn, this pathway switches tumor metabolism toward glycolysis, antagonizes apoptosis and autophagy, dampens oxidative stress, and maintains tumor cell proliferation in the face of severe hypoxia. Mitochondrial Akt-PDK1 signaling correlates with unfavorable prognostic markers and shorter survival in glioma patients and may provide an “actionable” therapeutic target in cancer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A pool of active Akt is recruited to tumor mitochondria during hypoxia </LI> <LI> Mitochondrial Akt phosphorylates PDK-1 in hypoxia on a T346 site </LI> <LI> Akt-PDK1 activation maintains tumor cell proliferation in hypoxia </LI> <LI> PDK1 phosphorylation by Akt is a negative prognostic factor in gliomas </LI> </UL> </P>

Metallurgical Characterization and Mechanical Properties of Solid–Liquid Compound Casting of Aluminum Alloy: Steel Bimetallic Materials

Pavan Kalyan Kota,Govindaraju Myilsamy,Vaira Vignesh Ramalingam 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.6

Integration of two metallurgically distinct materials (bimetallic) is an inevitable advancement in the automotive andmarine field. In this context, this study investigates the fabrication, characterization, and properties of solid–liquid compoundcast aluminum alloy AA5052 and ferrous alloy (mild steel and galvanized iron) based bimetallic materials. Microstructuralevolution, microhardness, and tensile strength of the developed bimetallic material are investigated. The results show thatthe formation of cracks at the interface in AA5052/Mild Steel caused the joint failure in the course of preliminary testing. InAA5052/Galvanized Iron, the growth of intermetallics at the oxide-free steel surface results in a shear strength of 19.9 MPa. XRD analysis attests to the presence of brittle intermetallics and Al bond at the interface of AA5052/Galvanized Iron bimetallicmaterial, which in turn confirms the development of a metallurgical.

Tribological behavior of friction stir process surface hybrid composite AA5083/MWCNT/Al2SiO5 using multi‑quadratic RBF algorithm

P. S. Samuel Ratna Kumar,R. Vaira Vignesh,P. M. Mashinini,S. Ramanathan 한국탄소학회 2023 Carbon Letters Vol.33 No.7

The present research focuses on the tribological behavior of the AA5083 alloy-based hybrid surface composite using aluminosilicate and multi-walled-carbon nanotube through friction stir processing for automotive applications. The friction stir processing parameters (tool rotation and traverse speed) are varied based on full factorial design to understand their influence on the tribological characteristics of the developed hybrid composite. The surface morphology and composition of the worn hybrid composite are examined using a field-emission scanning electron microscope and an energy-dispersive x-ray spectroscope. No synergistic interaction is observed between the wear rate and friction coefficient of the hybrid composite plate. Also, adhesive wear is the major wear mechanism in both base material and hybrid composite. The influence of friction stir process parameters on wear rate and the friction coefficient is analyzed using the hybrid polynomial and multi-quadratic radial basis function. The models are utilized to optimize the friction stir processing parameters for reducing the rate of wear and friction coefficient using multi-quadratic RBF algorithm optimization.

The coat protein of Alternanthera mosaic virus is the elicitor of a temperature-sensitive systemic necrosis in Nicotiana benthamiana, and interacts with a host boron transporter protein

Lim, H.S.,Nam, J.,Seo, E.Y.,Nam, M.,Vaira, A.M.,Bae, H.,Jang, C.Y.,Lee, C.H.,Kim, H.G.,Roh, M.,Hammond, J. Academic Press 2014 Virology Vol.452 No.-

Different isolates of Alternanthera mosaic virus (AltMV; Potexvirus), including four infectious clones derived from AltMV-SP, induce distinct systemic symptoms in Nicotiana benthamiana. Virus accumulation was enhanced at 15<SUP>o</SUP>C compared to 25<SUP>o</SUP>C; severe clone AltMV 3-7 induced systemic necrosis (SN) and plant death at 15<SUP>o</SUP>C. No interaction with potexvirus resistance gene Rx was detected, although SN was ablated by silencing of SGT1, as for other cases of potexvirus-induced necrosis. Substitution of AltMV 3-7 coat protein (CP<SUB>SP</SUB>) with that from AltMV-Po (CP<SUB>Po</SUB>) eliminated SN at 15<SUP>o</SUP>C, and ameliorated symptoms in Alternanthera dentata and soybean. Substitution of only two residues from CP<SUB>Po</SUB> [either MN(13,14)ID or LA(76,77)IS] efficiently ablated SN in N. benthamiana. CP<SUB>SP</SUB> but not CP<SUB>Po</SUB> interacted with Arabidopsis boron transporter protein AtBOR1 by yeast two-hybrid assay; N. benthamiana homolog NbBOR1 interacted more strongly with CP<SUB>SP</SUB> than CP<SUB>Po</SUB> in bimolecular fluorescence complementation, and may affect recognition of CP as an elicitor of SN.

Posterior Titanium Screw Fixation without Debridement of Infected Tissue for the Treatment of Thoracolumbar Spontaneous Pyogenic Spondylodiscitis

Mauro Dobran,Maurizio Iacoangeli,Davide Nasi,Niccolo Nocchi,Alessandro Di Rienzo,Lucia di Somma,Roberto Colasanti,Carmela Vaira,Roberta Benigni,Valentina Liverotti,Massimo Scerrati 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.3

Study Design: Retrospective study. Purpose: The aim of our study was to analyze the safety and effectiveness of posterior pedicle screw fixation for treatment of pyogenic spondylodiscitis (PSD) without formal debridement of the infected tissue. Overview of Literature: Posterior titanium screw fixation without formal debridement of the infected tissue and anterior column reconstruction for the treatment of PSD is still controversial. Methods: From March 2008 to June 2013, 18 patients with PSD underwent posterior titanium fixation with or without decompression, according to their neurological deficit. Postero-lateral fusion with allograft transplantation alone or bone graft with both the allogenic bone and the autologous bone was also performed. The outcome was assessed using the visual analogue scale (VAS) for pain and the Frankel grading system for neurological status. Normalization both of C-reactive protein (CRP) and erythrocyte sedimentation rate was adopted as criterion for discontinuation of antibiotic therapy and infection healing. Segmental instability and fusion were also analyzed. Results: At the mean follow-up time of 30.16 months (range, 24–53 months), resolution of spinal infection was achieved in all patients. The mean CRP before surgery was 14.32±7.9 mg/dL, and at the final follow-up, the mean CRP decreased to 0.5±0.33 mg/ dL (p <0.005). Follow-up computed tomography scan at 12 months after surgery revealed solid fusion in all patients. The VAS before surgery was 9.16±1.29 and at the final follow-up, it improved to 1.38±2.03, which was statistically significant (p <0.05). Eleven patients out of eighteen (61.11%) with initial neurological impairment had an average improvement of 1.27 grades at the final follow-up documented with the Frankel grading system. Conclusions: Posterior screw fixation with titanium instrumentation was safe and effective in terms of stability and restoration of neurological impairment. Fixation also rapidly reduced back pain.

Subcellular Localization of the Barley Stripe Mosaic Virus Triple Gene Block Proteins

Lim, Hyoun-Sub,Bragg, Jennifer N.,Ganesan, Uma,Ruzin, Steven,Schichnes, Denise,Lee, Mi Yeon,Vaira, Anna Maria,Ryu, Ki Hyun,Hammond, John,Jackson, Andrew O. American Society for Microbiology 2009 Journal of virology Vol.83 No.18

<B>ABSTRACT</B><P><I>Barley stripe mosaic virus</I> (BSMV) spreads from cell to cell through the coordinated actions of three triple gene block (TGB) proteins (TGB1, TGB2, and TGB3) arranged in overlapping open reading frames (ORFs). Our previous studies (D. M. Lawrence and A. O. Jackson, J. Virol. 75:8712-8723, 2001; D. M. Lawrence and A. O. Jackson, Mol. Plant Pathol. 2:65-75, 2001) have shown that each of these proteins is required for cell-to-cell movement in monocot and dicot hosts. We recently found (H.-S. Lim, J. N. Bragg, U. Ganesan, D. M. Lawrence, J. Yu, M. Isogai, J. Hammond, and A. O. Jackson, J. Virol. 82:4991-5006, 2008) that TGB1 engages in homologous interactions leading to the formation of a ribonucleoprotein complex containing viral genomic and messenger RNAs, and we have also demonstrated that TGB3 functions in heterologous interactions with TGB1 and TGB2. We have now used <I>Agrobacterium tumefaciens</I>-mediated protein expression in <I>Nicotiana benthamiana</I> leaf cells and site-specific mutagenesis to determine how TGB protein interactions influence their subcellular localization and virus spread. Confocal microscopy revealed that the TGB3 protein localizes at the cell wall (CW) in close association with plasmodesmata and that the deletion or mutagenesis of a single amino acid at the immediate C terminus can affect CW targeting. TGB3 also directed the localization of TGB2 from the endoplasmic reticulum to the CW, and this targeting was shown to be dependent on interactions between the TGB2 and TGB3 proteins. The optimal localization of the TGB1 protein at the CW also required TGB2 and TGB3 interactions, but in this context, site-specific TGB1 helicase motif mutants varied in their localization patterns. The results suggest that the ability of TGB1 to engage in homologous binding interactions is not essential for targeting to the CW. However, the relative expression levels of TGB2 and TGB3 influenced the cytosolic and CW distributions of TGB1 and TGB2. Moreover, in both cases, localization at the CW was optimal at the 10:1 TGB2-to-TGB3 ratios occurring in virus infections, and mutations reducing CW localization had corresponding effects on BSMV movement phenotypes. These data support a model whereby TGB protein interactions function in the subcellular targeting of movement protein complexes and the ability of BSMV to move from cell to cell.</P>

Extensive Drug Resistance Acquired During Treatment of Multidrug-Resistant Tuberculosis

Cegielski, J. Peter,Dalton, Tracy,Yagui, Martin,Wattanaamornkiet, Wanpen,Volchenkov, Grigory V.,Via, Laura E.,Van Der Walt, Martie,Tupasi, Thelma,Smith, Sarah E.,Odendaal, Ronel,Leimane, Vaira,Kvasnov Oxford University Press 2014 Clinical Infectious Diseases Vol.59 No.8

<P>Nearly 15% of multidrug-resistant (MDR) tuberculosis cases developed resistance to the fluoroquinolones, the second-line injectable drugs, or both during treatment for MDR tuberculosis. The rate of acquired resistance was significantly lower in programs that met specific performance criteria.</P><P><B><I>Background.</I></B> Increasing access to drugs for the treatment of multidrug-resistant (MDR) tuberculosis is crucial but could lead to increasing resistance to these same drugs. In 2000, the international Green Light Committee (GLC) initiative began to increase access while attempting to prevent acquired resistance.</P><P><B><I>Methods.</I></B> To assess the GLC's impact, we followed adults with pulmonary MDR tuberculosis from the start to the end of treatment with monthly sputum cultures, drug susceptibility testing, and genotyping. We compared the frequency and predictors of acquired resistance to second-line drugs (SLDs) in 9 countries that volunteered to participate, 5 countries that met GLC criteria, and 4 countries that did not apply to the GLC.</P><P><B><I>Results.</I></B> In total, 832 subjects were enrolled. Of those without baseline resistance to specific SLDs, 68 (8.9%) acquired extensively drug-resistant (XDR) tuberculosis, 79 (11.2%) acquired fluoroquinolone (FQ) resistance, and 56 (7.8%) acquired resistance to second-line injectable drugs (SLIs). The relative risk (95% confidence interval [CI]) of acquired resistance was lower at GLC-approved sites: 0.27 (.16–.47) for XDR tuberculosis, 0.28 (.17–.45) for FQ, and 0.15 (.06–.39) to 0.60 (.34–1.05) for 3 different SLIs. The risk increased as the number of potentially effective drugs decreased. Controlling for baseline drug resistance and differences between sites, the odds ratios (95% CIs) were 0.21 (.07–.62) for acquired XDR tuberculosis and 0.23 (.09–.59) for acquired FQ resistance.</P><P><B><I>Conclusions.</I></B> Treatment of MDR tuberculosis involves substantial risk of acquired resistance to SLDs, increasing as baseline drug resistance increases. The risk was significantly lower in programs documented by the GLC to meet specific standards.</P>