Numerical computations of rock dissolution and geomechanical effects for CO 2 geological storage

International audienceThe paper is motivated by the long term safety analysis of the CO 2 geological storage. We present a methodology for the assessment of the ge-omechanical impact of progressive rock dissolution. The method is based on the use of X-ray tomography and the numerical dissolution technique. The influence of evolution of the microstructure on the macroscopic properties of the rock is analysed by using periodic homogenization method. The numerical computations show progressive degradation of all components of the stiffness (orthotropic) tensor. Moreover, the evolution of associated mass transfer properties (as tortuosity and conductivity tensors), by using the periodic homogenization method, is also calculated. The correlation between the mechanical parameters and the transfer properties during the dissolution pro-cess is presented. The results show that the highest increase of the hydraulic conductivity (in direction Y) is not associated with the highest decrease of Young modulus in this direction. Moreover, the highest decrease of Young modulus (in the direction X) is not associated with percolation in this direction. Finally, an incremental law to calculate settlement, in case of a rock with evolving microstructure, is proposed. The solution of the macroscopic settlement problem under constant stress and drained conditions showed that the geomechanical effects of the rock dissolution are rather limited

Oral administration of Lactococcus lactis expressing synthetic genes of myelin antigens in decreasing experimental autoimmune encephalomyelitis in rats

ABSTRACT Background: Multiple sclerosis is a human autoimmunological disease that causes neurodegeneration. One of the potential ways to stop its development is induction of oral tolerance, whose effect lies in decreasing immune response to the fed antigen. It was shown on animal models that administration of specific epitopes of the three main myelin proteins, myelin oligodendrocyte glycoprotein (MOG), myelin basic protein (MBP) and proteolipid protein (PLP) results in induction of oral tolerance and suppression of disease symptoms. Application of bacterial cells to produce and deliver antigens to gut mucosa seems to be an attractive method for oral tolerance induction in treatment of diseases with autoimmune background. Material/Methods: Synthetic genes of MOG35-55, MBP85-97 and PLP139-151 myelin epitopes were generated and cloned in Lactococcus lactis under a CcpA-regulated promoter. The tolerogenic effect of bacterial preparations was tested on experimental autoimmune encephalomyelitis, the animal model of MS. EAE was induced in rats by intradermal injection of guinea pig homogenate into hind paws. Results: Rats were administered preparations containing whole-cell lysates of L. lactis producing myelin antigens using different feeding schemes. Our study demonstrates that 20-fold, but not 4-fold, intragastric administration of autoantigen-expressing L. lactis cells under specific conditions reduces the clinical symptoms of EAE in rats. Conclusions: The present study evaluates the use of myelin antigens produced in L. lactis in inhibiting the on-set of experimental autoimmune encephalomyelitis in rats. Obtained results indicate that application of such recombinant cells can be an attractive method of oral tolerance induction

Effect of recombinant Lactococcus lactis producing myelin peptides on neuroimmunological changes in rats with experimental allergic encephalomyelitis

Multiple sclerosis (MS) is a human autoimmune neurodegenerative disease with an unknown etiology. Despite various therapies, there is no effective cure for MS. Since the mechanism of the disease is based on autoreactive T-cell responses directed against myelin antigens, oral tolerance is a promising approach for the MS treatment. Here, the experiments were performed to assess the impact of oral administration of recombinant Lactococcus lactis producing encephalogenic fragments of three myelin proteins: myelin basic protein, proteolipid protein, and myelin oligodendrocyte glycoprotein, on neuroimmunological changes in rats with experimental allergic encephalomyelitis (EAE) – an animal model of MS. Lactococcus lactis whole-cell lysates were administered intragastrically at two doses (103 and 106 colony forming units) in a twenty-fold feeding regimen to Lewis rats with EAE. Spinal cord slices were subjected to histopathological analysis and morphometric evaluation, and serum levels of cytokines (IL-1b, IL-10, TNF-α and IFN-γ) were measured. Results showed that administration of the L. lactis preparations at the tested doses to rats with EAE, diminished the histopathological changes observed in EAE rats and reduced the levels of serum IL-1b, IL-10 and TNF-α, previously increased by evoking EAE. This suggests that oral delivery of L. lactis producing myelin peptide fragments could be an alternative strategy to induce oral tolerance for the treatment of MS

Tetra-n-propyl­ammonium chloride monohydrate

The crystal structure of the title salt hydrate, C12H28N+·Cl−·H2O, consists of non-inter­acting cations and anions. The water mol­ecule forms hydrogen bonds to two chloride ions, about a center of inversion, generating a planar eight-membered {⋯H—O—H⋯Cl}2 ring

Direction of the polymorphic form of entacapone using an electrochemical tuneable surface template

The ability to direct the surface crystallisation of different polymorphs of entacapone by tuning the electrochemical potential of Au(100) templates is demonstrated. Under quiescent conditions, without polarization (at open circuit potential), entacapone crystallises in its stable form A on the template surface and concomitantly in its metastable form D in the bulk solution. When Au(100) is negatively polarized (-150 mV), form D is still formed in the bulk solution but the metastable form α is found to crystallise at the edges of the template. Both crystals of form A and α were observed to grow epitaxially over the Au template surface. The electrochemical templating effect is consistent with the polarisation changing the structure of the initially adsorbed layers of supersaturated solution at the template surface which directs the nuclei formation and the subsequent crystal growth processes. This study demonstrates, for the first time, the direction of polymorphic form using a low field polarized nucleation template

REAL-TIME OBSERVATION OF CELLULOSE BIODEGRADATION BY ATOMIC FORCE MICROSCOPY

Cellulose, the major structural component of plant cell walls, is a homopolymer of β-1,4-linked glucose residues. As cellulose is the most abundant biopolymer on Earth comprising approx. 50% of the bioshpere, it has attracted renewed interest as a potential source of energy through its biodegradation and fermentation to biofuels. The biodegradation of cellulose involves the concerted action of three types of enzymes, cellulases (EC 3.2.1.4, endo-β-1,4-glucanases), cellobiohydrolases (EC 3.2.1.91; cellulose 1,4-β-cellobiosidase), and β-glucosidases (EC 3.2.1.21; β-d-glucoside glucohydrolase). The former two classes of enzymes function to hydrolyze insoluble cellulose into soluble oligosaccharides which then serve as substrates for β-glucosidases to release free glucose. In many cases, these enzymes are multi-modular, being comprised of distinct catalytic and carbohydrate-binding modules (CBMs). The CBMS appear to aid in both the adsorption of the enzymes to the insoluble cellulose substrate and the destabilization of the hydrogen-bonding network within the crystalline substrate. An understanding of this latter process is extremely important because it has been demonstrated that binding of the enzymes to the insoluble cellulose represents the rate-limiting step in its hydrolysis. To this end, we have developed a protocol for the direct and real-time observation of cellulose biodegradation by atomic force microscopy (AFM). Working electrodes for AFM experiments consisted of a 200 nm thick gold film vapor deposited onto a glass slide pre-treated with a deposition of a 2 nm thick layer of chromium. After annealing in a muffle furnace at 700°C for 60 s, the slides were treated with thioglucose to provide a highly-ordered monolayer of hydrophilic glucose for the stable adsorption of cellulose. Thin films of bacterial microcrystalline cellulose on these electrodes were prepared using the Langmuir-Blodgett technique. Optimized conditions were established to involve a dispersion of a 2 mg/ml suspension of cellulose in methanol/chloroform (1:5) on aqueous phosphate buffer using a compression of 5 mN/m. With this protocol, drying of the cellulose film thereby precluding any associated structural alterations. AFM images were captured using a Pico SPM Microscope with AFMS 182 scanner and Pico-scan 5.2 software system using silicon nitride tips which had a nominal spring constant of 0.06 N m-1 for contact mode, and magnetically coated silicon tips for MAC mode. Under these conditions, the diameters of the microfibrils in a 50 nm fiber were observed to be 3 - 4 nm, which is smaller than the 7.5 nm previously reported by others. Homogeneous samples of the cellulase CenA from the bacterium Cellulomonas fimi were introduced into the liquid cell through capillary ports for the in situ imaging of cellulose disruption and hydrolysis. This activity was monitored over the course of 19 hours and initial evidence of degradation of the fibers was observed within three minutes of enzyme addition. In addition, details of the process of fiber fraying could be readily discerned. Genetic engineering was used to provide a mutant form of CenA involving a replacement of its catalytic aspartate nucleophile with alanine. Studies with this catalytically inactive enzyme derivative permit the analysis of cellulose fibril destabilization prior to hydrolysis

Diaqua­bis­(seleno­cyanato-κN)bis­(pyrimidine-κN)manganese(II)

In the crystal structure of the title compound, [Mn(NCSe)2(C4H4N2)2(H2O)2], the manganese(II) cation is coordinated by two N-bonded pyrimidine ligands, two N-bonded seleno­cyanate anions and two O-bonded water mol­ecules in a distorted octa­hedral coordination mode. The asymmetric unit consists of one manganese(II) cation, located on a centre of inversion, as well as one seleno­cyanate anion, one water mol­ecule and one pyrimidine ligand in general positions. The crystal structure consists of discrete building blocks of composition [Mn(NCSe)2(pyrimidine)2(H2O)2], which are connected into layers parallel to (101) by strong water–pyrimidine O—H⋯N hydrogen bonds

Electric-Field-Driven Molecular Recognition Reactions of Guanine with 1,2-Dipalmitoyl- sn- glycero-3-cytidine Monolayers Deposited on Gold Electrodes

Monolayers of 1,2-dipalmitoyl-sn-glycero-3-cytidine were incubated with guanine in a 0.1 M NaF electrolyte at the surface of a Langmuir trough and transferred to gold (111) electrodes using the Langmuir–Schaefer technique. Chronocoulometry and photon polarization modulation infrared reflection absorption spectroscopy were employed to investigate the influence of the static electric field on the orientation and conformation of the cytidine nucleolipid molecules on the metal surface in the presence of guanine and to monitor the molecular recognition of guanine with the cytosine moiety. When the monolayer is exposed to guanine solutions, the cytosine moiety binds to the guanine residue in either a Watson–Crick complex at positively charged electrode surfaces or a noncomplexed state at negative surface charges. The positive electrostatic field causes the cytosine moiety and the cytosine–guanine complex to adopt a nearly parallel orientation with respect to the plane of the monolayer with a measured tilt angle of ∼10°. The parallel orientation is stabilized by the interactions between the permanent dipole of the cytosine moiety or the Watson–Crick complex and the static electric field. At negative charge densities, the tilt of the cytosine moiety increases by ∼15–20°, destabilizing the complex. Our results demonstrate that the static electric field has an influence on the molecular recognition reactions between nucleoside base pairs at the metal–solution interface and can be controlled by altering the surface charge at the metal