Use of tracers to characterize the effects of a CO2-saturated brine on the petrophysical properties of a low permeability carbonate caprock

To assess the long-term safety of a geological carbon dioxide storage site, the confining properties of the rocks sealing an underground reservoir (caprocks) and their evolution inthe presence of CO₂ must be characterized. The present study consists in the measurement of the transport parameters of dissolved CO₂ through low permeability carbonate-rich caprocks. The properties of interest are the effective permeability and the diffusion coefficients of carbon dioxide dissolution products in water. The impact of carbon dioxide has been evaluated when altering rock samples by diffusion of a CO₂-saturated brine under reservoir thermodynamic conditions, and by comparison of the pre- and post-alteration measured values. Permeability was measured by a gas-tracing method and, to study diffusion, radioactive isotopes of carbon (¹⁴C) and hydrogen (³H) were used. Despite a porosity increase observed for all the studied samples, the low values of transport parameters, measured initially, were also measured after alteration, showing a non-catastrophic alteration of the material.     

Flash sintering of cationic conductive ceramics: A way to build multilayer systems

Flash Sintering (FS), that allows densifying ceramics at low furnace temperature in a few seconds, requires a reversible electrochemical reaction to enable the current flow through the electrode / material interface. For Li⁺ pure ionic conductors such as Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), the best material to ensure this fast charge transfer reaction is a mixed Li⁺/e⁻ conductor, eg, LiCoO₂ (LCO). This paper demonstrates the feasibility of FS on LCO between two Pt electrodes and on multi-layers systems using LCO or LATP+LCO composite as electrodes. It is shown that a composite electrode both allows the flash event to occur and prevents the delamination possibly observed with pure LCO by lowering interfacial stresses.     

Reprogramming: Emerging Strategies to Rejuvenate Aging Cells and Tissues

Aging is associated with a progressive and functional decline of all tissues and a striking increase in many “age-related diseases”. Although aging has long been considered an inevitable process, strategies to delay and potentially even reverse the aging process have recently been developed. Here, we review emerging rejuvenation strategies that are based on reprogramming toward pluripotency. Some of these approaches may eventually lead to medical applications to improve healthspan and longevity.     

Is direct microwave heating well suited for sintering ceramics?

This paper presents a thorough analysis of direct microwave heating as a sintering process of ceramic materials. It questions why susceptor-assisted microwave heating is used in most experimental works, although direct microwave coupling is preferable for taking advantage of the possible beneficial effects of the microwave field on the sintering phenomena. This issue was investigated by conducting both experiments and numerical simulations. The experiments consisted of sintering alumina and yttria doped zirconia powder samples in a 2.45 GHz resonant cavity with automatic thermal monitoring, whereas the numerical simulations coupled electromagnetics, thermal transfer and sample deformation. Alumina and yttria doped zirconia are widely used materials and they exhibit different microwave field behaviours (transparent and absorbent, respectively), which are representative of most ceramic materials. The influence of the insulating material was discussed by considering different sintering cell designs. The very low coupling capacity of alumina made its direct heating very difficult. It was therefore necessary to apply a strong electric field to heat it. This situation promoted the absorption of microwave energy by other elements such as the insulating material, leading to heating instabilities and degradation of the insulation cell. In the case of zirconia, its coupling properties change abruptly with increasing temperature. It is poorly absorbent at low temperature, highly absorbent at intermediate temperature and it finally becomes reflective at the end of the sintering process. The consequences of this behaviour are (i) a very difficult control of direct heating (ii) a propensity to form damaging hot spots and (iii) the impossibility to reach high temperatures without forming plasma. Therefore, this experimental and numerical study showed that direct microwave heating is not suitable for conducting reliable and homogeneous sintering of classical ceramics. This explains why susceptor-assisted heating is most of time preferred.     

Tunable magnetocaloric effect in amorphous Gd-Fe-Co-Al-Si alloys

Journal of Materials Science - A magnetocaloric effect with wide tunability was observed in melt-spun amorphous Gd65Fe15-xCo5+xAl10Si5 (x?=?0, 5, 10) alloys of different Fe/Co ratios....     

Glutamate dehydrogenases in the oleaginous yeast Yarrowia lipolytica

Glutamate dehydrogenases (GDHs) are fundamental to cellular nitrogen and energy balance. Yet little is known about these enzymes in the oleaginous yeast Yarrowia lipolytica. The YALI0F17820g and YALI0E09603g genes, encoding potential GDH enzymes in this organism, were examined. Heterologous expression in gdh-null Saccharomyces cerevisiae and examination of Y. lipolytica strains carrying gene deletions demonstrate that YALI0F17820g (ylGDH1) encodes a NADP-dependent GDH whereas YALI0E09603g (ylGDH2) encodes a NAD-dependent GDH enzyme. The activity encoded by these two genes accounts for all measurable GDH activity in Y. lipolytica. Levels of the two enzyme activities are comparable during logarithmic growth on rich medium, but the NADP-ylGDH1p enzyme activity is most highly expressed in stationary and nitrogen starved cells by threefold to 12-fold. Replacement of ammonia with glutamate causes a decrease in NADP-ylGdh1p activity, whereas NAD-ylGdh2p activity is increased. When glutamate is both carbon and nitrogen sources, the activity of NAD-ylGDH2p becomes dominant up to 18-fold compared with that of NADP-ylGDH1p. Gene deletion followed by growth on different carbon and nitrogen sources shows that NADP-ylGdh1p is required for efficient nitrogen assimilation whereas NAD-ylGdh2p plays a role in nitrogen and carbon utilization from glutamate. Overexpression experiments demonstrate that ylGDH1 and ylGDH2 are not interchangeable. These studies provide a vital basis for future consideration of how these enzymes function to facilitate energy and nitrogen homeostasis in Y. lipolytica.     

Vitamin requirements and biosynthesis in Saccharomyces cerevisiae

Chemically defined media for yeast cultivation (CDMY) were developed to support fast growth, experimental reproducibility, and quantitative analysis of growth rates and biomass yields. In addition to mineral salts and a carbon substrate, popular CDMYs contain seven to nine B-group vitamins, which are either enzyme cofactors or precursors for their synthesis. Despite the widespread use of CDMY in fundamental and applied yeast research, the relation of their design and composition to the actual vitamin requirements of yeasts has not been subjected to critical review since their first development in the 1940s. Vitamins are formally defined as essential organic molecules that cannot be synthesized by an organism. In yeast physiology, use of the term “vitamin” is primarily based on essentiality for humans, but the genome of the Saccharomyces cerevisiae reference strain S288C harbours most of the structural genes required for synthesis of the vitamins included in popular CDMY. Here, we review the biochemistry and genetics of the biosynthesis of these compounds by S. cerevisiae and, based on a comparative genomics analysis, assess the diversity within the Saccharomyces genus with respect to vitamin prototrophy.     

Overexpression of diacylglycerol acetyltransferase from Euonymus europaeus in Yarrowia lipolytica leads to the production of single-cell oil enriched with 3-acetyl-1,2-diacylglycerols

The 3-acetyl-1,2-diacylglycerols (acTAGs) are the molecules that are structurally similar to triacylglycerols (TAGs). They are naturally produced by plants of the family Celastraceae and animals such as Cervus nippon and Eurosta solidaginis. The presence of acetate in the sn–3 position of the glycerol backbone confers advantages to these compounds, for example, lower viscosity and calorific value compared to classical TAGs. In this work, the gene EeDAcT, which encodes diacylglycerol acetyltransferase in a species of bush (Euonymus europaeus), was overexpressed in strains Po1d (capable of accumulating storage lipids) and JMY1877 (incapable of accumulating storage lipids) of Yarrowia lipolytica, to test the activity of the gene EeDAcT and the production of acTAGs in oleaginous and nonoleaginous genetic backgrounds. It was observed that both the strains containing the gene EeDAcT (YL33 and YL35 for Po1d and JMY1877 strains, respectively) produced acTAGs. The strain YL33 accumulated up to 20% intracellular lipids, 20% of which was acTAGs, and 40% was TAGs. On the other hand, the strain YL35, which showed interrupted TAGs accumulation, produced up to 10% acTAGs as the only storage lipid. Unfortunately, the quantity of acTAGs produced in YL35 was insignificant, as the overall lipid accumulated in the strain was not more than 4% of the biomass. The fatty acid profile of acTAGs produced by the YL33 strain was remarkably similar to TAGs, and both of these structures were rich in oleic (45%) and palmitic (25%) acids.