Optimisation of a two-liquid component pre-filled acrylic bone cement system: a design of experiments approach to optimise cement final properties

The initial composition of acrylic bone cement along with the mixing and delivery technique used can influence its final properties and therefore its clinical success in vivo. The polymerisation of acrylic bone cement is complex with a number of processes happening simultaneously. Acrylic bone cement mixing and delivery systems have undergone several design changes in their advancement, although the cement constituents themselves have remained unchanged since they were first used. This study was conducted to determine the factors that had the greatest effect on the final properties of acrylic bone cement using a pre-filled bone cement mixing and delivery system. A design of experiments (DoE) approach was used to determine the impact of the factors associated with this mixing and delivery method on the final properties of the cement produced. The DoE illustrated that all factors present within this study had a significant impact on the final properties of the cement. An optimum cement composition was hypothesised and tested. This optimum recipe produced cement with final mechanical and thermal properties within the clinical guidelines and stated by ISO 5833 (International Standard Organisation (ISO), International standard 5833: implants for surgery—acrylic resin cements, 2002), however the low setting times observed would not be clinically viable and could result in complications during the surgical technique. As a result further development would be required to improve the setting time of the cement in order for it to be deemed suitable for use in total joint replacement surgery.     

Purification and kinetic properties of Mus booduga (Gray) hepatic arginase

Hepatic L-arginase from the Mus booduga (Gray) was purified and its kinetic characteristics were investigated. The enzyme was not adsorbed on DEAE-cellulose, but was retained on CM-cellulose column at pH 7.2. The Michaelis-Menten constant was 8.3 mM for L-arginine and was independent of pH in the range of 7.5-10.5. L-arginine concentrations as high as 0.4 M did not exert substrate inhibition in the pH range 7.4-10.0. Manganese was required at a concentration of 0.05 M for full activation of the enzyme. L-ornithine and L-lysine inhibited the enzyme competitively with inhibitory constants of 1.9 mM and 3.7 mM respectively. Several properties of the L-arginase from Mus booduga clearly identify it as an enzyme similar to ureotelic basic arginases from mammalian liver.     

Tackling COVID-19 Using Remdesivir and Favipiravir as Therapeutic Options

The human world is currently influenced largely by the outbreak of pandemic COVID-19. At this moment, most researchers focus on developing treatment strategies and measures to work against COVID-19. Treatment strategies specific for COVID-19 are lacking. This article provides an overview of the life cycle and routes of transmission of SARS-CoV-2. The therapeutic effects of two drugs [i. e., remdesivir (RDV) and favipiravir (FPV)] which can potentially tackle COVID-19 are discussed based on current published data. This review can serve as a reference for future studies.     

A study of electron paramagnetic resonance and optical absorption in calcium manganese phosphate glasses containing praseodymium

This paper reports on electron paramagnetic resonance (EPR) and optical absorption studies for Mn ions in praseodymium calcium manganese phosphate glasses. The EPR spectra exhibit three resonance signals at g2.0, g3.3 and g4.8. A six line hyperfine structure spectrum centered at g2.0 has been observed in the EPR spectra of all the glasses at lower concentration of Mn ions. The effects of the concentration of Mn ions and praseodymium oxide on resonance signals have been studied. The temperature dependence of EPR signals were also studied. The intensity of the resonance signals decreases with increase in temperature whereas the linewidths are found to be independent of temperature. As temperature is increased small fluctuations in hyperfine splitting are observed. From the optical absorption spectrum, the crystal field parameters and optical band gap energy were evaluated. The optical band gap energy is found to depend quite sensitively on added manganese content. The theoretical values of optical basicity were also evaluated.     

Influence of Plasma Electrolytic Oxidation on Corrosion Characteristics of Friction Stir Welded ZM21 Magnesium Alloy

Protection of Metals and Physical Chemistry of Surfaces - Magnesium alloys and their welds are prone to severe corrosion and require corrosion prevention treatment before being used for engineering...     

Enhanced electrical conductivity and structural,mechanical characterization of standalone poly(vinyl alcohol)-graphite nanoplatelets composite films

Polymer based nanocomposites are gaining attention in various fields of science and technology due to its tunable properties. In this work, we report for the first time, the preparation and study on electrical and mechanical properties of standalone poly(vinyl alcohol) (PVA) based graphite nanoplatelet (GnP) composite films using modified film casting technique. Our modified tape casting method can produce films with uniform thickness, and uniform dispersion of filler deprived of pinholes. This technique is scalable for the mass production of polymer composite films for device application. We have obtained a significant enhancement in the electrical conductivity of 9 orders of magnitude and a maximum value of 0.143 S/m using PVA–GnP composites. To the best of our knowledge, this increase is the highest among the reported values for PVA–GnP composite films. However, a reduction in crystallinity and tensile strength can be seen with the addition of GnP fillers. The maximum tensile strength obtained for PVA–GnP composite films was 15 MPa and is adequate for use in electronic applications and devices. The effect of filler addition in PVA is discussed in detail.     

Engaging zwitterions in carbon-carbon and carbon-nitrogen bond-forming reactions: A promising synthetic strategy

An Account of carbon-carbon and carbon-nitrogen bond-forming reactions mediated by zwitterions generated by the addition of organic nucleophiles to activated unsaturated systems highlighting their synthetic potential is presented.     

Incremental growth of short SWNT arrays by pulsed chemical vapor deposition

Very short arrays of continuous single-wall carbon nanotubes (SWNTs) are grown incrementally in steps as small as 25 nm using pulsed chemical vapor deposition (CVD). In-situ optical extinction measurements indicate that over 98% of the nanotubes reinitiate growth on successive gas pulses, and high-resolution transmission electron microscopy (HR-TEM) images show that the SWNTs do not exhibit segments, caps, or noticeable sidewall defects resulting from repeatedly stopping and restarting growth. Time-resolved laser reflectivity (3-ms temporal resolution) is used to record the nucleation and growth kinetics for each fast (0.2 s) gas pulse and to measure the height increase of the array in situ, providing a method to incrementally grow short nanotube arrays to precise heights. Derivatives of the optical reflectivity signal reveal distinct temporal signatures for both nucleation and growth kinetics, with their amplitude ratio on the first gas pulse serving as a good predictor for the evolution of the growth of the nanotube ensemble into a coordinated array. Incremental growth by pulsed CVD is interpreted in the context of autocatalytic kinetic models as a special processing window in which a sufficiently high flux of feedstock gas drives the nucleation and rapid growth phases of a catalyst nanoparticle ensemble to occur within the temporal period of the gas pulse, but without inducing growth termination.     

Optimal Short-term Reservoir Operation with Integrated Long-term Goals

A methodology to incorporate long-term goals within the short-term reservoir operation optimization model is proposed. Two conflicting objectives for the management of hydropower generation in two different power plants are incorporated. A chance-constrained optimization model is used to derive long-term (annual) operation strategies. With the time horizon of operation for the short-term optimization model kept equal to a single time-step of the long-term optimization model, the optimum end storages derived from the long-term model are incorporated as constraints (storage lower bounds) within the short-term model. The long-term benefits accrued from such an operation model are illustrated for a small reservoir, in South India. The solutions are compared with the historic operation. These are also compared with the solutions of a short-term optimal operation model ignoring long-term goals. The optimization model is solved using a multi-objective genetic algorithm.     

Thermodynamic characterization of poly (caprolactonediol) by inverse gas chromatography

Specific retention volumes, V _g ⁰, were determined for 21 solute probes on poly (caprolactonediol) (PCLD) in the temperature range 323.15–403.15 K by inverse gas chromatography. The retention diagrams drawn between ln V _g ⁰ versus 1/T are linear for all the solutes since PCLD with ten repeating units in its chain behaving like a non polymeric material under the conditions applied. The stationary phase with melting temperature ~321 K is in the liquid state in the GC column over the temperature range studied and hence found to be suitable to determine infinite dilution partial molar thermodynamic properties of mixing for solutes on PCLD. The V _g ⁰ values have been used to calculate weight fraction activity coefficients Ω^∞ and Flory–Huggins interaction parameters, χ ₁₂^∞. The average partial molar enthalpy of solution, [`(\Updelta H)]<sub>1</sub><sup>S</sup> , \overline{\Updelta H}_{1}^{S} , and partial molar enthalpy of mixing, [`(\Updelta H)]₁^￥ , \overline{\Updelta H}_{1}^{\infty } , are calculated using V _g ⁰ and Ω^∞ respectively. The average molar enthalpy of vaporization ΔH ₁ ^V for solutes have been calculated using [`(\Updelta H)]<sub>1</sub><sup>￥</sup> \overline{\Updelta H}_{1}^{\infty } and [`(\Updelta H)]₁^S \overline{\Updelta H}_{1}^{S} values and compared with the literature values at 363.15 K which is the average column temperature. The partial molar entropy of mixing, [`(\Updelta S)]<sub>1</sub><sup>￥</sup> \overline{\Updelta S}_{1}^{\infty } calculated at 363.15 K are in good correlation with the average [`(\Updelta H)]₁^￥ \overline{\Updelta H}_{1}^{\infty } values. The total solubility parameter due to Guillet and the Hansen solubility parameters (HSP) are calculated for PCLD using χ ₁₂^∞ values. In the present work the Hansen solubility parameters have been calculated using a new method following the Hansen theory and Huang method with less weight on polar and hydrogen bonding components. The errors in the solubility HSP are lower and the correlation coefficients are better in both the methods compared to unweighted three dimensional model.