Transport and Retention of High Concentrated Nano-Fe/Cu Particles Through Highly Flow-Rated Packed Sand Column

The design of an efficient field-scale remediation based on the use of nanoscale zero valent iron (NZVI) requires an accurate assessment of the mobility of such particles in saturated porous media, both during injection in the subsurface (short-term mobility) and later (long-term mobility). In this study, the mobility of highly concentrated dispersions of bimetallic Fe/Cu nanoparticles (d50= 70±5 nm) in sand-packed columns (0.5 m length and 0.025 m inner diameter) was studied. In particular, the influence of flow rate (V = 5×10-4, 1×10-3, 2×10-3 m/s) and injected particle concentrations (2, 5, 8, 12 g/l) was addressed. Breakthrough curves and water pressure drop along the column, averaged effective porosity and final distribution of retained particles along the column were measured. Experimental results evidenced a good mobility of the Fe/Cu particles, with significant breakthrough in all explored experimental conditions of flow rate and C0, without requiring the addition of any stabilizing agent. Clogging phenomenon of the column and also the pore pressure variation during injection period are strongly affected by injected concentration. Clogging due to deposition of particles following a ripening dynamics was observed in particular for C0= 8 and 12 g/l. The experimental data were 23 modeled using the E-MNM1D software. The study has implications for field injection of bimetallic nanoparticles, suggesting that particular care is to be devoted when selecting injection concentration, to avoid porous medium clogging and control the radius of influenc

Differential modulation of Bax/Bcl-2 ratio and onset of caspase-3/7 activation induced by derivatives of Justicidin B in human melanoma cells A375.

Diphyllin and its derivatives are well known cytotoxic natural products structurally related to the anti-cancer drug podophyllotoxin. We here study their structure-activity relationship upon human melanoma cells for first time. To this end, human melanoma A375 cells were incubated with Justicidin B and its 4-methoxylated or 4-glycosylated derivatives to evaluate their selective cytotoxicity and study their effects on cell cycle distribution, caspase activation, apoptosis induction using Annexin V-FITC/PI staining, cell morphology and western blot analysis. Diphyllin methyl ether (GI50 = 3.66 μM) and Justicidin B (GI50 = 1.70 μM) caused an elevation of both early and late apoptosis populations whereas Diphyllin apioside (GI50 = 0.84 μM) and its acetate (GI50= 0.39 μM) enhanced late apoptosis population only (Annexin V-positive/PI-positive). All induced cell cycle arrest at S phase and classic morphological indicators of apoptosis (blebbing, apoptotic bodies, and nuclear fragmentation) accompanied with an elevation of cells with low DNA content (sub-G1). All compounds increased the Bax/Bcl-2 ratio by enhancing Bax expression which evidences the involvement of the mitochondria (intrinsic pathway) in the apoptotic process. These caspase-3/7 results evidence that 4-methoxylation or 4-O-glycosylation of Justicidin B -a caspase independent mitochondrial apoptosis-inducer- triggers caspase-3/7 activation at different times (24h vs. 48h, respectively). Interestingly, the methoxylation causes attenuation of Bcl-2 protein expression contrarily to Diphyllin methyl ether or the O-glycosylated derivatives. Finally, the compounds exhibited significantly less toxicity when tested in adult human dermal fibroblasts and their GI50 in melanoma Sk-Mel-5 cells was not influenced by MDR1/Pgp inhibitors. This study may inform the synthesis of future Diphyllin derivatives with different apoptosis mechanism of action towards human melanoma cells

Designing chitosan-tripolyphosphate microparticles with desired size for specific pharmaceutical or forensic applications

Chitosan (CS) is a natural cationic polymer obtained by the partial N-deacetylation of chitin. Chitosan microparticles can be prepared by cross-linking with tripolyphosphate (TPP) via the ionic interaction between positively charged amino groups (CS) and negatively charged counter ions (TPP). This can be controlled by the charge density of CS and TPP, which depend on the pH and ionic strength of the solution. The purpose of this study is to investigate the combined effects of three independent variables (pH, ionic strength and CS: TPP ratio) on three important physico-chemical properties (viscosity, zeta potential and particle size) during the preparation of microparticles. CS: TPP microparticles were prepared using experimental design and equations were generated and used to predict relative viscosity, zeta potential and particle size under different conditions. This gives us the ability to design tuneable CS-TPP microparticles with desired size for specific pharmaceutical or forensic applications e.g. latent fingerprint visualisation

Green stabilization of microscale iron particles using guar gum: bulk rheology, sedimentation rate and enzymatic degradation

Guar gum can be used to effectively improve stability and mobility of microscale zerovalent iron particles (MZVI) used in groundwater remediation. Guar gum is a food-grade, environment friendly natural polysaccharide, which is often used as thickening agent in a broad range of food, pharmaceutical and industrial applications. Guar gum solutions are non-Newtonian, shear thinning fluids, characterized by high viscosity in static conditions and low viscosity in dynamic conditions. In particular, the high zero shear viscosity guarantees the MZVI dispersion stability, reducing the sedimentation rate of the particles thus enabling its storage and field operations. In this work, a comprehensive rheological characterization of guar gum-based slurries of MZVI particles is provided. First, we derived a model to link the bulk shear viscosity to the concentration of guar gum and then we applied it for the derivation of a modified Stokes law for the prediction of the sedimentation rate of the iron particles. The influence of the preparation procedure (cold or hot dissolution and high shear processing) on the viscosity and on the stability of the suspensions was then assessed. Finally, the dosage and concentration of enzymes - an environment friendly breaker - were studied for enhancing and controlling the degradation kinetics of the suspensions. The derived empirical relationships can be used for the implementation of an iron slurry flow and transport model and for the design of full scale injection intervention

First-principles study of the incorporation and diffusion of helium in cubic zirconia

The incorporation and diffusion of helium (He) with and without intrinsic vacancy defects in cubic ZrO$_{2}$ are investigated through first-principles total-energy calculations, in which the projector-augmented-wave (PAW) method with the generalized gradient approximation (GGA) is used. The calculated formation energies of intrinsic point defects indicate that cubic ZrO$_{2}$ has a tolerant resistance to radiation damage. The incorporation energy of He impurity shows that it is preferable to occupy the Zr vacancy at first, whereas the solution energy suggests that He would be accommodated in the interstitial site at thermodynamic equilibrium concentration. By calculating the He migration energies corresponding to both interstitial and vacancy assisted mechanisms, we suggest that it is most likely for He to diffuse by hopping through a single vacancy. Remarkably, our calculated vacancy-assisted diffusion energy of He is consistent well with the experimental measurement.Comment: 8 pages, 8 figure

Understanding the mechanisms of cooperative physico-chemical treatment and mechanical disintegration of biomass as a route for enhancing enzyme saccharification

A novel chemico-kinetic disintegration model has been applied to study the cooperative relationship between physico-chemical treatment and supplementary wet-state milling of biomass, as an efficient process route to achieve high enzyme accessibility. Wheat straw, Miscanthus and short-rotation willow were studied as three contrasting biomass species, which were subjected to controlled hydrothermal pretreatment using a microwave reactor, followed by controlled wet-state ball-milling. Comparative particle disintegration behaviour and related enzyme digestibilities have been interpreted on the basis of model parameters and with evaluation of textural and chemical differences in tissue structures, aided by the application of specific material characterisation techniques. Supplementary milling led to a 1.3×, 1.6× and 3× enhancement in glucose saccharification yield after 24 h for straw, Miscanthus and willow, respectively, following a standardised 10-min hydrothermal treatment, with corresponding milling energy savings of 98, 97 and 91% predicted from the model, compared to the unmilled case. The results confirm the viability of pretreatment combined with supplementary wet-milling as an efficient process route. The results will be valuable in understanding the key parameters for process design and optimisation and also the key phenotypical parameters for feedstock breeding and selection for highest saccharification yield

Simulation of char-pellet combustion and sodium release inside porous char using lattice Boltzmann method

Char-pellet combustion is studied with the lattice Boltzmann method (LBM) including sodium release and the ash inhibition effect on oxygen diffusion in the porous char. The sodium release and the shrinking of the char pellet are simulated by accounting for the reactions occurring both in the solid and gas phases. The combustion of a single char pellet is considered first, and the results are compared against measurements. The simulation of the pellet mass, pellet temperature and sodium release agreed well with in-house optical measurements. The validated lattice Boltzmann approach is then extended to investigate the combustion of porous char and sodium release inside the porous medium. The pore-structure evolution and the flow path variation are simulated as combustion proceeds. The simulations reproduce the expected different behaviors between the combustion products (CO and CO2) and the released volatile, here the sodium vapor. The combustion products are mostly generated at the flame front and then transported by the flow and molecular diffusion inside the complex porous char structure. However, the volatile sodium vapor forms in the entire porous char and tends to accumulate in regions where the flow motion stays weak, as in internal flow microchannels, or blocked, as in closed pores. These results confirm the potential of the LBM formalism to tackle char-pellet combustion accounting for the topology of the porous medium.National Natural Science Foundation of China; China Postdoctoral Science Foundation; Royal Society and the Engineering and Physical Sciences Research Council (EPSRC) (UK

Repeated PTZ Treatment at 25-Day Intervals Leads to a Highly Efficient Accumulation of Doublecortin in the Dorsal Hippocampus of Rats

BACKGROUND: Neurogenesis persists throughout life in the adult mammalian brain. Because neurogenesis can only be assessed in postmortem tissue, its functional significance remains undetermined, and identifying an in vivo correlate of neurogenesis has become an important goal. By studying pentylenetetrazole-induced brain stimulation in a rat model of kindling we accidentally discovered that 25±1 days periodic stimulation of Sprague-Dawley rats led to a highly efficient increase in seizure susceptibility. METHODOLOGY/PRINCIPAL FINDINGS: By EEG, RT-PCR, western blotting and immunohistochemistry, we show that repeated convulsive seizures with a periodicity of 25±1 days led to an enrichment of newly generated neurons, that were BrdU-positive in the dentate gyrus at day 25±1 post-seizure. At the same time, there was a massive increase in the number of neurons expressing the migratory marker, doublecortin, at the boundary between the granule cell layer and the polymorphic layer in the dorsal hippocampus. Some of these migrating neurons were also positive for NeuN, a marker for adult neurons. CONCLUSION/SIGNIFICANCE: Our results suggest that the increased susceptibility to seizure at day 25±1 post-treatment is coincident with a critical time required for newborn neurons to differentiate and integrate into the existing hippocampal network, and outlines the importance of the dorsal hippocampus for seizure-related neurogenesis. This model can be used as an in vivo correlate of neurogenesis to study basic questions related to neurogenesis and to the neurogenic mechanisms that contribute to the development of epilepsy