EhMAPK, the Mitogen-Activated Protein Kinase from Entamoeba histolytica Is Associated with Cell Survival

Mitogen Activated Protein Kinases (MAPKs) are a class of serine/threonine kinases that regulate a number of different cellular activities including cell proliferation, differentiation, survival and even death. The pathogen Entamoeba histolytica possess a single homologue of a typical MAPK gene (EhMAPK) whose identification was previously reported by us but its functional implications remained unexplored. EhMAPK, the only mitogen-activated protein kinase from the parasitic protist Entamoeba histolytica with Threonine-X-Tyrosine (TXY) phosphorylation motif was cloned, expressed in E. coli and functionally characterized under different stress conditions. The expression profile of EhMAPK at the protein and mRNA level remained similar among untreated, heat shocked and hydrogen peroxide-treated samples in all cases of dose and time. But a significant difference was obtained in the phosphorylation status of the protein in response to different stresses. Heat shock at 43°C or 0.5 mM H2O2 treatment enhanced the phosphorylation status of EhMAPK and augmented the kinase activity of the protein whereas 2.0 mM H2O2 treatment induced dephosphorylation of EhMAPK and loss of kinase activity. 2.0 mM H2O2 treatment reduced parasite viability significantly but heat shock and 0.5 mM H2O2 treatment failed to adversely affect E. histolytica viability. Therefore, a distinct possibility that activation of EhMAPK is associated with stress survival in E. histolytica is seen. Our study also gives a glimpse of the regulatory mechanism of the protein under in vivo conditions. Since the parasite genome lacks any typical homologue of mammalian MEK, the dual specificity kinases which are the upstream activators of MAPK, indications of the existence of some alternate regulatory mechanisms of the EhMAPK activity is perceived. These may include the autophosphorylation activity of the protein itself in combination with some upstream phosphatases which are not yet identified

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Steady-shear magnetorheological response of fluids containing solution-combustion-synthesized Ni-Zn ferrite powder

Magnetically soft nickel-zinc ferrite (Ni0.5Zn0.5Fe2O4) powder with high saturation magnetization was synthesized by solution combustion route using metal nitrates as precursors and glycine as fuel. The particles were found to have irregular morphology. Three different concentrations of magnetorheological fluids (MRFs) were prepared by dispersing 10, 20 and 40 wt% of these particles in thin silicone oil. The behaviours of the MRFs were studied under steady shear conditions at different applied magnetic field strengths (B). The yield strength (tau(Y)) and viscosity (eta) of all the MRFs were found to increase with B and particle fill fraction phi, while the response of the MRFs was strongly influenced by the morphology, microstructure and saturation magnetization of the particles. Owing to the low density of the particles, the observed off-state viscosity is high. However, the excellent thermo-oxidative and chemical stabilities of these magnetic oxide particles than metallic magnetic particles make these MRFs dependable for applications in harsh working environments. In addition, the low cost and feasibility of large scale preparation of these magnetic oxides make these MRFs further attractive for industrial applications. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

Magnetorheological fluids containing rod-shaped lithium-zinc ferrite particles: the steady-state shear response

We report the magnetic field and particle-concentration dependent steady-state shear-responses of rod shaped Li-Zn ferrite particle based magnetorheological fluids (MRFs). Rod-shaped soft ferrimagnetic Li-Zn ferrite (Li0.4Zn0.2Fe2.4O4) particles were synthesized using the combustion synthesis method. MRFs of three different particle-concentrations (phi = 0.1, 0.2 and 0.4, in weight fraction) were prepared using silicone oil. Their yield strength and dynamic viscosity were studied at different applied magnetic fields (B). With an increase in B and phi, the yield strength ((Y)) of the MRFs increases. This behaviour is assigned to the formation of stronger columnar structures of the magnetically interacting particles which resist the flow (shear) of the MRF. For the MRF with phi = 0.4 and B = 1.2 T, we observed a maximum (Y) value of approximate to 1.25 kPa. Furthermore, we observed that, based on the on-state to off-state viscosity ratio ((on)/(off)) at a particular operating B value, the optimum particle concentration required for energy- and cost-efficient operation of the MRFs can be chosen. The absence of a stabilizing-agent or de-agglomerating-coating, the low density, and the excellent oxidation- and corrosion-resistance of the soft ferrimagnetic rod-shaped Li-Zn ferrite particles make this MRF-system highly versatile and economical for many magneto-mechanical applications

Application of monodisperse Fe3O4 submicrospheres in magnetorheological fluids

Steady shear response of a magnetorheological fluid (MRF) system containing porous mono-disperse magnetite (Fe3O4) spheres synthesized by solvothermal method is demonstrated. In applied magnetic field the interaction between the spherical particles leads to form strong columnar structures enhancing the yield strength and viscosity of the MRFs. The yield strengths of the MRFs also scale up with the concentration of magnetic particles in the fluid. Considering magnetic dipolar interaction between the particles the magneto-mechanical response of the MRFs is explained. Unlike metallic iron particles, the low-density corrosion resistant soft-ferrimagnetic Fe3O4 spherical particles make our studied MRF system efficient and reliable for shock-mitigation/vibration-isolation applications. (C) 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved

Synthesis of highly magnetic Mn-Zn ferrite (Mn0.7Zn0.3Fe2O4) ceramic powder and its use in smart magnetorheological fluid

Manganese-zinc ferrite (Mn0.7Zn0.3Fe2O4) powder containing irregular-shaped particles with high saturation magnetization and high magnetic softness was synthesized via solution combustion method. By dispersing these magnetic ceramic particles in silicone oil, a magnetorheological fluid (MRF) was prepared and its magneto-mechanical property was studied. The yield strength ((Y)) exhibited by the MRF increases with increase in applied magnetic field, and a very high value of yield strength of similar to 10.5kPa (at B=1.2T) was observed. The viscosity () of the MRF also increases with B due to increased inter-particle magnetic interaction. The low density, low cost of the precursors and the industrial scalability of the Mn-Zn ferrite powder-production render these powders suitable for large-scale device applications. In addition, the thermal, oxidative and chemical stabilities of these ferrimagnetic oxide ceramics are advantageous for their application in corrosive and high temperature environments

Magnetic field dependent steady-state shear response of Fe3O4 micro-octahedron based magnetorheological fluids

We report the synthesis of single crystalline octahedron-shaped magnetite microcrystals, the preparation of magnetorheological fluids (MRFs) and their magnetorheological properties under steady-state shear conditions. The magnetite microcrystals were synthesized via the template-free hydrothermal route. MRFs with three different particle concentrations (10, 20 and 40 weight%) were prepared and were subjected to steady shear conditions at various externally applied magnetic fields of strength up to 1.2 T. The shear rates were chosen up to high enough values to observe the yield behaviour of the MRFs. The dynamic yield strengths of MRFs, estimated using the Bingham plastic model fit to the steady-state shear response curves, showed that they scale-up with the applied magnetic field strength and amount of magnetic particles in the fluid. The origin of the mechanical strength in the MRFs due to the inter-particle interaction is explained using a simple dipolar model. The observed high yield strengths of the MRFs were explained on the basis of the particle shape (octahedrons) and magnetic nature (saturation magnetization). By comparing the values of the yield strength with the on-state to off-state viscosity ratio for the MRFs (for each particle concentration), an optimum content of particles in the carrier fluid to obtain high efficiency is suggested. Because the particles are single crystalline, the off-state viscosity of the MRFs even at the highest studied (40 wt%) particle concentration was very low, which is ideal for their application as quickly responding MRFs

Composition dependent elastic and thermal properties of Li-Zn ferrites

We report the composition dependent elastic and thermal properties of LieZn ferrite (Li(0.5-x/2)ZnxFe(2.5-x/) O-2(4), x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) ceramics. The IR absorption frequencies (obtained from the Fourier transform infrared spectra), the lattice parameters and the mass-densities were used to evaluate the elastic and thermal parameters such as force constant, elastic moduli and Debye temperature of the studied LieZn ferrite samples as a function of Zn-content x. The observed force constants were low in value for the octahedral site complexes than that of the tetrahedral site complexes, but both the force constants were increasing with increasing Zn content. The longitudinal elastic wave velocities in the sample were higher than the transverse wave velocities. The elastic moduli such as Young's modulus (E), bulk modulus (B) and rigidity modulus (G) showed increasing trends with Zn concentration in the samples. The calculated Debye temperature (theta(D)) is near to the literature values obtained experimentally. Our results provide a better understanding of the variation of mechanical, elastic and thermal properties of LieZn ferrites. (C) 2017 Elsevier B.V. All rights reserved

Effect of annealing temperature on the structural and magnetic properties of Ba-Pb-hexaferrite powders synthesized by sol-gel auto-combustion method

The annealing temperature (T-a) dependent development in phase purity, morphology and magnetic properties of BaxPb1-xFe12O19 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) powders synthesized via sol-gel auto-combustion route were studied. The hexagonal phase of PbFe12O19 forms directly via solid-state-reaction between alpha-Fe2O3 and PbO during annealing of the combustion product at T-a similar to 900 degrees C, but the BaFe12O9 phase forms at T-a similar to 1200 degrees C through the formation of BaFe2O4 and alpha-Fe2O3 as intermediate-phases at low T-a. The BaxPb1-xFe12O19-phase purity of the samples depend on T-a. For T-a > 1000 degrees C, PbO evaporates from Pb-containing samples. With increasing T-a, growth of hexagonal-shaped sharp-edged particles was observed for Barium-rich samples, however, the sharp-edges dissolute for Lead-rich samples. High saturation magnetization was observed for Ba-rich samples annealed at 1100 degrees C. For all the studied samples, magnetic coercivity increases with x but decreases with T-a. The magnetic properties were correlated with the structure, microstructure and grain-size of the samples