Determination of optimal parameters of rhamnolipid biosurfactant production: An agent for emulsification of heavy crude oil

In oil and petroleum industries, emulsification process is important to transfer and upgrade heavy oil. Rhamnolipids are the essential molecules of biosurfactants that used for this goal and they are often produced from various types of Pseudomonas aeroginosa bacteria. In this research, rhamnolipid biosurfactant produced from Pseudomonas aeroginosa ATCC 9027. The goal of this study was to optimize the effective parameters in production of rhamnolipid in order to reach the minimum water droplet size using Taguchi method. The evaluated parameters include incubation temperature, RPM of incubation, C/N ratio and pH of aqueous phase. Response parameters were yield, cost and water droplet size in water in oil (w/o) microemulsion. The results illustrated that the temperature of incubation and pH of the aqueous phase were the most effective factors in the production of rhamnolipid. Optimum operation condition including yield, cost and water droplet size, were 5.2 ± 0.1 g/l, 2.4 ± 0.14 $/g and 70 ± 5%, respectively. Dynamic light scattering (DLS) analysis was used for determination of water droplet size. Also the emulsification index (E24) of (w/o) emulsion was 98% ± 4. The results of this study could reduce the cost of rhamnolipid production for the applications in oil industries.     

Carbon-Supported High-Entropy Oxide Nanoparticles as Stable Electrocatalysts for Oxygen Reduction Reactions

Nanoparticles supported on carbonaceous substrates are promising electrocatalysts. However, achieving good stability for the electrocatalysts during long-term operations while maintaining high activity remains a grand challenge. Herein, a highly stable and active electrocatalyst featuring high-entropy oxide (HEO) nanoparticles uniformly dispersed on commercial carbon black is reported, which is synthesized via rapid high-temperature heating (≈1 s, 1400 K). Notably, the HEO nanoparticles with a record-high entropy are composed of ten metal elements (i.e., Hf, Zr, La, V, Ce, Ti, Nd, Gd, Y, and Pd). The rapid high-temperature synthesis can tailor structural stability and avoid nanoparticle detachment or agglomeration. Meanwhile, the high-entropy design can enhance chemical stability to prevent elemental segregation. Using oxygen reduction reaction as a model, the 10-element HEO exhibits good activity and greatly enhances stability (i.e., 92% and 86% retention after 12 and 100 h, respectively) compared to the commercial Pd/C electrocatalyst (i.e., 76% retention after 12 h). This superior performance is attributed to the high-entropy compositional design and synthetic approach, which offers an entropy stabilization effect and strong interfacial bonding between the nanoparticles and carbon substrate. The approach promises a viable route toward synthesizing carbon-supported high-entropy electrocatalysts with good stability and high activity for various applications.     

Synthesis and in Vitro Evaluation of Novel 5-Nitroindole Derivatives as c-Myc G-Quadruplex Binders with Anticancer Activity

Lead-optimization strategies for compounds targeting c-Myc G-quadruplex (G4) DNA are being pursued to develop anticancer drugs. Here, we investigate the structure-activity- relationship (SAR) of a newly synthesized series of molecules based on the pyrrolidine-substituted 5-nitro indole scaffold to target G4 DNA. Our synthesized series allows modulation of flexible elements with a structurally preserved scaffold. Biological and biophysical analyses illustrate that substituted 5-nitroindole scaffolds bind to the c-Myc promoter G-quadruplex. These compounds downregulate c-Myc expression and induce cell-cycle arrest in the sub-G1/G1 phase in cancer cells. They further increase the concentration of intracellular reactive oxygen species. NMR spectra show that three of the newly synthesized compounds interact with the terminal G-quartets (5′- and 3′-ends) in a 2 : 1 stoichiometry.     

Effect of Foliar-Applied Silicon on Flower Yield and Essential Oil Composition of Damask Rose (Rosa damascena Miller) under Water Deficit Stress

Silicon - A field experiment was conducted to investigate the effect of silicon on the flower yield and essential oil composition of damask rose under water deficit stress. Silicon was applied as...     

Co/Zn-Grafted Mesoporous Silica Nanoparticles Catalyzed Cyclohexanimine Oxidation under UV Irradiation: High Performance Ozonation Process

Silicon - A new series of cobalt/zinc-grafted mesoporous silica nanoparticles (CZ-MSN) catalysts were synthesized and characterized using FTIR, SEM, TEM, XRD and nitrogen adsorption-desorption. The...     

β-Amyloid Targeting with Two-Dimensional Covalent Organic Frameworks: Multi-Scale In-Silico Dissection of Nano-Biointerface

Cytotoxic aggregation of misfolded β-amyloid (Aβ) proteins is the main culprit suspected to be behind the development of Alzheimer's disease (AD). In this study, Aβ interactions with the novel two-dimensional (2D) covalent organic frameworks (COFs) as therapeutic options for avoiding β-amyloid aggregation have been investigated. The results from multi-scale atomistic simulations suggest that amine-functionalized COFs with a large surface area (more than 1000 m²/gr) have the potential to prevent Aβ aggregation. Gibb's free energy analysis confirmed that COFs could prevent protofibril self-assembly in addition to inhibiting β-amyloid aggregation. Additionally, it was observed that the amine functional group and high contact area could improve the inhibitory effect of COFs on Aβ aggregation and enhance the diffusivity of COFs through the blood-brain barrier (BBB). In addition, microsecond coarse-grained (CG) simulations with three hundred amyloids reveal that the presence of COFs creates instability in the structure of amyloids and consequently prevents the fibrillation. These results suggest promising applications of engineered COFs in the treatment of AD and provide a new perspective on future experimental research.     

Artificial microcracking of granites subjected to salt crystallization aging test

Bulletin of Engineering Geology and the Environment - Salt crystallization-induced decay of Vardavard granodiorite and Shirkouh monzogranite, two Iranian building stones, were assessed with two...     

Incorporation of graphene oxide and calcium phosphate in the PCL/PHBV core-shell nanofibers as bone tissue scaffold

Bone tissue scaffolds should have both desired mechanical stability and cell activities including biocompatibility, cell differentiation, and maturation. Also, suitable mineralization is another key factor for these materials. Hence, in current work, in order to achieve a scaffold with desired mechanical and bioactivity properties, core-shell nanofibers based on the polycaprolactone and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with different concentration of graphene oxide (GO) (0.5, 1, and 1.5 wt%) and calcium phosphate (CP) (1 and 3 wt%) were prepared to utilize as bone scaffold. Microstructure of nanofibers observed by field emission scanning electron microscope (FE-SEM) and results exhibited that the most of nanofibers had 270–500 nm diameter. Attenuated total reflectance Fourier transform infrared spectroscopy and energy dispersive X-ray evaluations verified appearance of GO and CP into the electrospun scaffolds (ES). Transmission electron microscopy analysis endorsed core-shell structure of nanofibers. X-ray diffraction study moreover determination of semicrystalline structure, verified presence of GO and CaPO₄ into the nanofibers. Water contact angle demonstrates that, ES2 and ES3 situated in suitable domain of hydrophilicity. Tensile analysis determined that, ES2, ES3, and ES4 had the highest mechanical properties for use as bone scaffold. Cell viability assessment confirmed biocompatibility of scaffold during 7 days. Alkaline phosphatase and alizarin red staining exhibited maturating and differentiating of osteocytes after 21 days seeding on the scaffolds.     

Shed light on submerged DC arc discharge synthesis of low band gap gray Zn/ZnO nanoparticles: Formation and gradual oxidation mechanism

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical agent. Electric discharge current was set to 20, 50, 100 and 150?A during synthesis. Estimated values of plasma excitation energies were 2.41, 2.66, 2.86 and 3.04?eV and diameter size of nanoparticles were 63, 42, 37 and 29?nm for these applied currents respectively. Synthesized nanoparticles were dark gray as prepared and became more transparent gradually getting white color finally. XRD and UV–vis results revealed that the oxidation process was time dependent. The colloidal nanoparticles composed of two metal and metal-oxide phase and white crystalline ZnO was achieved after complete oxidation process. These results provided a flexible and versatile method to synthesize metal oxide nanoparticles with controlled composition.     

Hybrid material integration in silicon photonic integrated circuits

Hybrid integration ofⅢ-Ⅴand ferroelectric materials is being broadly adopted to enhance functionalities in silicon photonic integrated circuits(PICs).Bonding and transfer printing have been the popular approaches for integration of III–V gain media with silicon PICs.Similar approaches are also being considered for ferroelectrics to enable larger RF modulation bandwidths,higher linearity,lower optical loss integrated optical modulators on chip.In this paper,we review existing integration strategies ofⅢ-Ⅴmaterials and present a route towards hybrid integration of bothⅢ-Ⅴand ferroelectrics on the same chip.We show that adiabatic transformation of the optical mode between hybrid ferroelectric and silicon sections enables efficient transfer of optical modal energies for maximum overlap of the optical mode with the ferroelectric media,similar to approaches adopted to maximize optical overlap with the gain section,thereby reducing lasing thresholds for hybridⅢ-Ⅴintegration with silicon PICs.Preliminary designs are presented to enable a foundry compatible hybrid integration route of diverse functionalities on silicon PICs.