Soaking Experiments Research Articles

Application of digital rock technology for formation damage evaluation in tight sandstone reservoir

Formation damage is a common phenomenon and is impaired to the reservoir by reducing the productivity. Formation damage is usually caused by solids plugging, clay swelling, saturation changes, etc., and fracturing fluids with a series of chemical additives are pumped into the well for production enhancement. It is difficult to optimize the fracture fluids and well shut-in time due to lack of fundamental understandings. Currently, little research has been done to investigate the mechanisms of formation damage at the pore scale. In this study, a combination of digital rock technology and core sample laboratory soaking experiments is used to evaluate the formation damages for different fracture fluids in tight sandstone reservoir. Three core samples from a full-diameter core are soaked in three different fracture fluids (surfactant, polymer, and gel) for eight different durations (from 2 h to 15d) to simulate well shut-in process. The samples in various soak times are scanned by X-ray micro-computer tomography (Micro-CT) to obtain the 3D images of the true geometry. The images are then compared to optimize the fracture fluids and quantify the damage degree after various well shut-in times. Then, displacement processes are simulated using lattice Boltzmann method (LBM) to evaluate the residual oil saturations and optimize the well shut-in time. The study suggests that the well shut-in process can cause irreversible damage to tight sandstone reservoir even for optimized fracture fluid. In the initial shut-in stages, clays swelling dominates pore structure alteration and reduces the porosity. Calcite will dissolute after which lead to slight porosity increase. In the flowback process after well shut-in, the simulated residual oil saturation will decrease initially and then increase after, which is complied with the porosity variation. The digital rock technology combined with the soaking experiments will provide alternative method for the evaluation of formation damage and the optimization of well shut-in time in tight sandstone reservoir, which can guide the selection of the fracture fluids and onsite fracturing operation.

Intelligent reversible electrochromic flexible electronic fabric based on electronic ink microcapsules

In the last several decades, electronic ink (e-ink) microcapsules have been extensively employed in display screens owing to their high reflectivity and contrast under visible light irradiation, as well as their flexibility, low cost, and low power consumption. Herein, a simple coating technique serves to combine e-ink microcapsules containing multiple color particles with fabrics to design an intelligent reversible electrochromic flexible electronic fabric. E-ink microcapsules, transparent Ag nanowires (T-AgNWs), and single-walled carbon nanotubes (SWCNT) are sequentially and uniformly coated on the surface of the double-layer conductive strip structure composed of conductive fabric and insulating fabric. The electrophoretic discoloration of the e-ink microcapsules can be achieved by applying voltages of a certain magnitude between the bottom conductive fabric strip layer and the T-AgNWs/SWCNT composite conductive layer. Large-area flexible electrochromic fabrics can be formed by weaving strips coated with e-ink microcapsules materials based on the results of the continuous bending and soaking experiments, which has great application potential in the research of adaptive camouflage smart fabrics in the visible light field.

Crystal Structure of the Human Copper Chaperone ATOX1 Bound to Zinc Ion.

The bioavailability of copper (Cu) in human cells may depend on a complex interplay with zinc (Zn) ions. We investigated the ability of the Zn ion to target the human Cu-chaperone Atox1, a small cytosolic protein capable of anchoring Cu(I), by a conserved surface-exposed Cys-X-X-Cys (CXXC) motif, and deliver it to Cu-transporting ATPases in the trans-Golgi network. The crystal structure of Atox1 loaded with Zn displays the metal ion bridging the CXXC motifs of two Atox1 molecules in a homodimer. The identity and location of the Zn ion were confirmed through the anomalous scattering of the metal by collecting X-ray diffraction data near the Zn K-edge. Furthermore, soaking experiments of the Zn-loaded Atox1 crystals with a strong chelating agent, such as EDTA, caused only limited removal of the metal ion from the tetrahedral coordination cage, suggesting a potential role of Atox1 in Zn metabolism and, more generally, that Cu and Zn transport mechanisms could be interlocked in human cells.

Bioactive glass-collagen/poly (glycolic acid) scaffold nanoparticles exhibit improved biological properties and enhance osteogenic lineage differentiation of mesenchymal stem cells.

Today’s using tissue engineering and suitable scaffolds have got attention to increase healing of non-union bone fractures. In this study, we aimed to prepare and characterize scaffolds with functional and mechanical properties suitable for bone regeneration. Porous scaffolds containing collagen-poly glycolic acid (PGA) blends and various quantities of bioactive glass (BG) 45S5 were fabricated. Scaffolds with different compositions (BG/collagen-PGA ratios (w/w): 0/100; 40/60; 70/30) were characterized for their morphological properties, bioactivity, and mechanical behavior. Then, biocompatibility and osteogenic differentiation potential of the scaffolds were analyzed by seeding mesenchymal stem cells (MSCs). Scaffolds made with collagen-PGA combined with the BG (45S5) were found to have interconnected pores (average pore diameter size 75–115 µm) depending on the percentage of the BG added. Simulated body fluid (SBF) soaking experiments indicated the stability of scaffolds in SBF regardless of their compositions, while the scaffolds retained their highly interconnected structure. The elastic moduli, cell viability, osteogenic differentiation of the BG/collagen-PGA 40/60 and 70/30 scaffolds were superior to the original BG/collagen-PGA (0/100). These results suggest that BG incorporation enhanced the physical stability of our collagen-PGA scaffold previously reported. This new scaffold composition provides a promising platform to be used as a non-toxic scaffold for bone regeneration and tissue engineering.

Cryo-EM structures of wild-type and E138K/M184I mutant HIV-1 RT/DNA complexed with inhibitors doravirine and rilpivirine

Structures trapping a variety of functional and conformational states of HIV-1 reverse transcriptase (RT) have been determined by X-ray crystallography. These structures have played important roles in explaining the mechanisms of catalysis, inhibition, and drug resistance and in driving drug design. However, structures of several desired complexes of RT could not be obtained even after many crystallization or crystal soaking experiments. The ternary complexes of doravirine and rilpivirine with RT/DNA are such examples. Structural study of HIV-1 RT by single-particle cryo-electron microscopy (cryo-EM) has been challenging due to the enzyme's relatively smaller size and higher flexibility. We optimized a protocol for rapid structure determination of RT complexes by cryo-EM and determined six structures of wild-type and E138K/M184I mutant RT/DNA in complexes with the nonnucleoside inhibitors rilpivirine, doravirine, and nevirapine. RT/DNA/rilpivirine and RT/DNA/doravirine complexes have structural differences between them and differ from the typical conformation of nonnucleoside RT inhibitor (NNRTI)-bound RT/double-stranded DNA (dsDNA), RT/RNA-DNA, and RT/dsRNA complexes; the primer grip in RT/DNA/doravirine and the YMDD motif in RT/DNA/rilpivirine have large shifts. The DNA primer 3'-end in the doravirine-bound structure is positioned at the active site, but the complex is in a nonproductive state. In the mutant RT/DNA/rilpivirine structure, I184 is stacked with the DNA such that their relative positioning can influence rilpivirine in the pocket. Simultaneously, E138K mutation opens the NNRTI-binding pocket entrance, potentially contributing to a faster rate of rilpivirine dissociation by E138K/M184I mutant RT, as reported by an earlier kinetic study. These structural differences have implications for understanding molecular mechanisms of drug resistance and for drug design.

Effect of supercritical CO2 on limestone's pore structure based on NMR and SEM

Supercritical CO2 (SC-CO2), as a new type of energizing fluid, has been widely applied in fracturing and acidizing treatment on tight sandstone, shale and carbonate formation. However, the effect of SC-CO2 on limestone's pore structure is unclear. To explore the effect, SC-CO2 reactor featuring high-temperature and high-pressure was used to carry out soaking experiments of SC-CO2-brine-limestone and SC-CO2-limestone respectively. With the help of NMR and SEM, this paper studies the effect of SC-CO2 on limestone's pore structure when the soaking time is different. It is found that in the experiment of SC-CO2-brine-limestone, SC-CO2 will react with brine to produce carbonic acid, which would react with calcite to augment limestone's porosity and permeability. Yet at the same time, Ca2+ and Mg2+ in the brine deposit continuously, which would lessen limestone's porosity and permeability. Besides, it is the generation of large pores that leads to augmentation of porosity, and more large pores are produced as time increases. While in the experiment of SC-CO2-limestone, volume expansion caused by transforming SC-CO2 into gaseous CO2 also augments limestone's porosity, and the augmentation is due to small pores. However, the increase of porosity in experiments without brine is much lower than that with brine.

Asymmetric Proton Transfer Catalysis by Stereocomplementary Old Yellow Enzymes for C═C Bond Isomerization Reaction

Native and promiscuous catalytic activities of flavin-dependent Old Yellow Enzymes (OYEs) reported to date are initiated by the reduced flavin upon electron transfer. As a rare exception, the isomerization of a nonactivated C═C bond was shown to be hydride-independent with two nonstereoselective yeast OYEs. Here, we report the asymmetric isomerization of a prochiral model substrate, γ-methyl β,γ-butenolide, to the corresponding (R)- and (S)-enantiomers of the γ-methyl α,β-butenolide in up to >99% ee by two stereocomplementary OYEs of algal and fungal origin, respectively, which operate by asymmetric proton transfer. Mechanistic studies based on two newly solved crystal structures, along with soaking experiments and site-directed mutagenesis, support the crucial role of partially nonconserved tyrosine residues for the activity and stereoselectivity of both (R)- and (S)-isomerases. This study offers a unique view on the potential of flavoproteins in nonredox catalysis and provides hints for scouting olefin isomerases in likely stereodivergent classes of OYEs.

Structural Dynamics of a Common Mutagenic Oxidative DNA Lesion in Duplex DNA and during DNA Replication.

N6-(2-Deoxy-α,β-d-erythro-pentofuranosyl)-2,6-diamino-4-hydroxy-5-formamido pyrimidine (Fapy•dG) is a prevalent form of genomic DNA damage. Fapy•dG is formed in greater amounts under anoxic conditions than the well-studied, chemically related 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodGuo). Fapy•dG is more mutagenic in mammalian cells than 8-oxodGuo. A distinctive property of Fapy•dG is facile epimerization, but prior works with Fapy•dG analogues have precluded determining its effect on chemistry. We present crystallographic characterization of natural Fapy•dG in duplex DNA and as the template base for DNA polymerase β (Pol β). Fapy•dG adopts the β-anomer when base paired with cytosine but exists as a mixture of α- and β-anomers when promutagenically base paired with adenine. Rotation about the bond between the glycosidic nitrogen atom and the pyrimidine ring is also affected by the opposing nucleotide. Sodium cyanoborohydride soaking experiments trap the ring-opened Fapy•dG, demonstrating that ring opening and epimerization occur in the crystalline state. Ring opening and epimerization are facilitated by propitious water molecules that are observed in the structures. Determination of Fapy•dG mutagenicity in wild type and Pol β knockdown HEK 293T cells indicates that Pol β contributes to G → T transversions but also suppresses G → A transitions. Complementary kinetic studies have determined that Fapy•dG promotes mutagenesis by decreasing the catalytic efficiency of dCMP insertion opposite Fapy•dG, thus reducing polymerase fidelity. Kinetic studies have determined that dCMP incorporation opposite the β-anomer is ∼90 times faster than the α-anomer. This research identifies the importance of anomer dynamics, a feature unique to formamidopyrimidines, when considering the incorporation of nucleotides opposite Fapy•dG and potentially the repair of this structurally unusual lesion.

Experimental Study on the Interaction Between CO2 and Rock During CO2 Pre-pad Energized Fracturing Operation in Thin Interbedded Shale

To investigate the impact of CO2 on rocks during the whole period of CO2 pre-pad energized fracturing operation for thin interbedded shale reservoir, including fracturing and well shut-in, a series of laboratory triaxial fracturing experiments and CO2 soaking experiments were conducted on thin interbedded shale (from Jimsar formations). In these experiments, combined with computed tomography (CT), the effect of fracturing fluid, horizontal principal stress difference, vertical principal stress, and natural fractures on fracture morphology were studied respectively. And based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) experiments, the dissolution of minerals and the changes of pore structure before and after CO2 soaking were analyzed. The results of the fracturing experiment show that the bedding planes are easy to be opened by low viscosity of CO2 and the longitudinal fractures intersect with bedding planes to build a complex fracture network. During CO2 fracturing of thin interbedded shale, the horizontal principal stress difference is no longer a crucial factor to form a complex fracture network, but the vertical stress and natural fractures play important roles. And the soaking experiments indicate that the main dissolved mineral is carbonate whose dissolution ratio can reach 45.2% after soaking for 5 days, leading to the expansion of original pores or the exposure of new pores.

Soaking and hydrous pyrolysis of Indian oil shale: Identification of produced hydrocarbons and moieties

In the present study, soaking and hydrous pyrolysis experiments were performed on Indian oil shale in the presence of de-ionized (DI) water and brine solution under isothermal conditions of 300, 350, and 400 °C, and residence time of 72 h to simulate the effect of underground aquifers on the expulsion and composition of hydrocarbons from source rocks. During soaking pyrolysis, the oil yield increased minutely with the increase in soaking time from 1 to 4 weeks but was not influenced by the presence of brine solution (8.82 wt/wt%) or DI water (8.46 wt/wt%). A similar trend in the generation of oil yield was observed during hydrous pyrolysis in both DI water and brine solution. GC analysis of the gas samples showed methane (CH4) as the prominent gas produced during soaking and hydrous pyrolysis. During soaking pyrolysis, the concentration of C2 to C5 gases decreased with increased pyrolysis temperature. However, during hydrous pyrolysis, the concentration of C4 and C5 gases increased with an increase in pyrolysis temperature. GC-SimDist analysis of the oil samples obtained from soaking pyrolysis at 400 °C showed the compounds ranged from C8 to C38 in brine solution and from C6 to C34 in DI water. Nevertheless, during hydrous pyrolysis in both DI water and brine solution, the carbon number distribution of the oil samples was observed to be in the range of C8 to C38. GC–MS analysis of the oil samples obtained from the soaking and hydrous pyrolysis experiments showed that the molecular weight of the identified compounds ranged from 86 to 380 g/mol. GC–MS, ATR, and 1H NMR analyses showed that the oil samples obtained from soaking and hydrous pyrolysis experiments were rich in aliphatic compounds. The organic acids content appeared to be higher in the presence of DI water as compared to the brine solution.

Improving Fracture Complexity and Conductivity in Shale Formation with Calcite-Filled Natural Fractures by a Novel CO2-Assisted Fracturing: An Experimental Study

Summary Given the advantages of using CO2 as a fracturing fluid to enhance unconventional oil/gas production and urge of carbon neutrality, CO2-assisted fracturing draws increasing attention in China recently. However, several critical issues related to this fracturing technology, such as the mechanism of hydraulic fracture (HF) growth, still need to be clarified. A novel CO2-assisted fracturing design, which can increase the HF complexity and conductivity, as well as improve the porosity/permeability of surrounding rock matrix, bedding planes (BPs), and natural fractures (NFs), was proposed. In the design, the carbonated water, formed by dissolving surpercritical CO2 in the slickwater, is used as the slug fluid to soften the calcite-sealed NFs that intersect with the precreated HFs. Subsequently, the slickwater is injected as the carrying fluid to dilate the NFs. To verify this design, a series of true triaxial fracturing simulations and static soaking experiments were conducted on the Longmaxi shale in Sichuan basin, China. Scanning electron microscopy results show that carbonated water, a weakly acidic fluid, can react vigorously with the carbonate-rich shale with time going on, thereby resulting in numerous dissolved pores with the diameter of dozens of microns. Eventually, the reaction between rock and carbonated water increases porosity/permeability and reduces mechanical strength. Notable dissolution of calcite, which could soften the calcite-sealed NFs, can occur in a short time (0.5 hours). Pretreating the specimen with carbonated water can lower the breakdown pressure of the rock by 2.7 MPa for half an hour and 11.7 MPa for 2 hours and promote HFs to propagate along the BPs and NFs in the shear-dominant mode. The shear dislocation and uneven erosion of fracture surface are of great significance in improving the permeability or conductivity of HFs. Notably, well shut-in for an optimized period may allow the sufficient interaction between carbonated water and shale, thereby improving the effectiveness of composite fracturing. This innovative design, which takes advantage of the special physical-chemical properties of supercritcal CO2, is feasible and conducive to enhancing production from unconventional reservoirs.

Improved sintering performance of β-SiAlON-Si3N4 and its osteogenic differentiation ability by adding β-SiAlON.

To improve the sintering performance of silicon nitride bioceramics, we explored the effect of β-SiAlON's Z-value on the physical, chemical, and biological properties of β-SiAlON-Si3N4 composites. Results showed that the phase product was β-Si3N4. As the Z-value increased, the X-ray diffraction peaks gradually shifted to a smaller angle, the material grains were more tightly packed, and the bulk density and compressive strength increased, reaching the highest values (2.71g/cm3 and 1157MPa, respectively) at Z = 4. Soaking and ion-release experiments show that in an aqueous environment, a small amount of Al and Si ions were released, and no obvious decomposition occurred on the surface of the material. The biological performance showed that the growth of cultured cells in each group was in good condition, there was no obvious difference in morphology and adhesion, and the materials had good biological performance. An increase in the Z-value promotes the formation of mineralized nodules and osteogenic differentiation of MC3T3-E1 cells, which may be because the release of Si can promote osteogenic differentiation. Therefore, the addition of β-SiAlON could improve the sintering performance of β-Si3N4 without degrading its biological properties. The prepared β-SiAlON-Si3N4 composite ceramic is a latent bioceramic material.

3D-Printing-Assisted Extraluminal Anti-Reflux Diodes for Preventing Vesicoureteral Reflux through Double-J Stents.

This paper presents novel umbrella-shaped flexible devices to prevent vesicoureteral reflux along double-J stents, which is a backward flow of urine from the bladder to the kidney and is a critical issue in patients with urinary stones. The anti-reflux devices were designed to mechanically attach to the stent and were manufactured using three-dimensional (3D) printing and polymer casting methods. Based on the umbrella shapes, four different devices were manufactured, and the anti-reflux efficiency was demonstrated through in vitro experiments using a urination model. Consequently, penta-shaped devices exhibited the best anti-reflux performance (44% decrease in reflux compared to the stent without the device), and maximum efficiency occurred when the device was attached near the bladder-ureter junction. In addition, a disadvantage of 3D printing (i.e., unwanted rough surface) helped the device strongly adhere to the surface of the stent during the insertion operation. Finally, long-term soaking experiments revealed that the fabricated devices were mechanically robust and chemically stable (safe) even being soaked in urine for 4 weeks. The findings of this study support the use of additive manufacturing to make various flexible and biocompatible urological devices to mitigate critical issues in patients with urinary stones.

Supercritical CO2-Shale interaction induced natural fracture closure: Implications for scCO2 hydraulic fracturing in shales

Multi-stage hydraulic fracturing has been identified as a must to develop shale gas reservoirs by increasing the stimulated reservoir volume (SRV). Supercritical CO2 (scCO2) has been studied as an alternating fracturing fluid due to its tendency to solve numerous problems associated with conventional aqueous based hydraulic fracturing such as formation damage, clay swelling, water scarcity and ground water contamination. However, its consequences to the host rock are not well understood. It has been recognized that scCO2-shale interaction alters the petrophysical properties during the long-term exposure of shale into scCO2, far little attention has been paid to understand the impact of this process for the short term. Thus, laboratory fracturing experiments using scCO2 on cubic shale samples (50 × 50 × 50 mm) in true triaxial stress cell (TTSC) were conducted. X-ray computed tomography (CT) imaging and low-pressure N2 adsorption were also performed to gain a deeper understanding of the fluid-rock interactions on the studied shales at a short-time process. Post-fracturing x-ray CT scans revealed a significant reduction, in the range of 14% to 46%, in the aperture of the natural fractures, indicating towards a possible scCO2 induced swelling. Mechanical compression test on the sample results in around 12% reduction in the fracture aperture, ruling out the possibility of confining stress being the key factor behind the fracture closure observed during fracturing. scCO2 soaking and N2 adsorption experiments showed the narrowing down of the macropores after scCO2 treatment implying the adsorption swelling as one of the controlling factors for the reduction of fracture aperture. Taken together, our results suggest that scCO2-shale interactions during the short term process of hydraulic fracturing can contribute to decreasing the conductivity of pathways between matrix and hydraulic fractures and hence adversely affecting the post-fracturing productivity of the rock.

Experimental Evaluation on the Conductivity of Branch Fracture with Low Sand Laying Concentration and Its Influencing Factors in Shale Oil Reservoirs

Abstract The productivity of shale oil reservoirs is mainly determined by the hydraulic fractured reservoir volume. The branch fractures with low sand laying concentration are the main channels connecting the shale matrix and the main fractures. Maintaining the branch fracture conductivity is significant to the production of shale oil. In this study, a series of shale branch fracture conductivity and soaking experiments were conducted using a core flooding device and a small reactor, and the influences of different factors on the fracture conductivity were evaluated. The results show that when the sand laying concentration in fractures is less than 3 kg/m2, the branch fractures present a significant stress sensitivity. Particularly when the sand laying concentration is less than 1 kg/m2, and the closure pressure is greater than 15 MPa, there will be a risk of proppant embedded and fracture closed. The antiswelling agent has an inhibitory effect on the shale swelling. When the concentration of the antiswelling agent in the gel-breaking fluid is 2%, the swelling factor of shale powder is only 1.84%. Comparatively, the 0.5% of the antiswelling agent has a poor effect which can cause the shale rock to crack when the effective stress decreases. It can cause the fracture conductivity to decline by 70-90% when the gel-breaking fluid flows back associated with the shale oil. The probability of core breaking and proppant embedding will increase. The frequent shut-in and rapid open-flow for production can accelerate the damage of fracture conductivity. It is necessary to optimize the fracturing fluid and the open flow scheme to prevent the rapid decline of production in shale oil reservoirs.

Environmental Safety Analysis of Red Mud-Based Cemented Backfill on Groundwater.

As one of the main industrial solid wastes, there are a large number of free alkaloids, chemically bound alkaloids, fluoride, and heavy metal ions in Bayer process red mud (BRM), which are difficult to remove and easily pollute groundwater as a result of open storage. In order to realize the large-scale industrial application of BRM as a backfilling aggregate for underground mining and simultaneously avoid polluting groundwater, the material characteristics of BRM were analyzed through physical, mechanical, and chemical composition tests. The optimum cement–sand ratio and solid mass concentration of the backfilling were obtained based on several mixture proportion tests. According to the results of bleeding, soaking, and toxic leaching experiments, the fuzzy comprehensive evaluation method was used to evaluate the environmental impact of BRM on groundwater. The results show that chemically bound alkaloids that remained in BRM reacted with Ca2+ in PO 42.5 cement, slowed down the solidification speed, and reduced the early strength of red mud-based cemented backfill (RMCB). The hydration products in RMCB, such as AFT and C-S-H gel, had significant encapsulation, solidification, and precipitation inhibition effects on contaminants, which could reduce the contents of inorganic contaminants in soaking water by 26.8% to 93.8% and the leaching of toxic heavy metal ions by 57.1% to 73.3%. As shown by the results of the fuzzy comprehensive evaluation, the degree of pollution of the RMCB in bleeding water belonged to a medium grade Ⅲ, while that in the soaking water belonged to a low grade II. The bleeding water was diluted by 50–100 times to reach grade I after flowing into the water sump and could be totally recycled for drilling and backfilling, thus causing negligible effects on the groundwater environment.

Bark Effects on Stemflow Chemistry in a Japanese Temperate Forest II. The Role of Bark Anatomical Features

A fraction of rainfall drains to the soil surface down tree stems (as “stemflow”), and the resulting stemflow waters can be highly enriched with dissolved nutrients due to prolonged bark contact. To date, stemflow chemistry has been examined mostly in regards to the external morphology of the bark, while its relationship with bark anatomy has received little attention. Arguably, this represents a major knowledge gap, because bark anatomical traits are linked to the storage and transport of soluble (and insoluble) organic materials, and control the proximity of these materials to passing stemflow waters. To initiate this line of investigation, here, we examine bark-water leaching rates for common leachable macronutrient ions (Mg2+, Ca2+, and K+) across six different tree species with varying bark anatomical traits (four deciduous broadleaved and two evergreen coniferous species). These different bark types were subjected to laboratory experiments, including observations of bark anatomy and soaking experiments. Laboratory-derived estimates of leaching rates for Mg2+, Ca2+, and K+ were then analyzed alongside bark anatomical traits. Leaching rates of Mg2+ and Ca2+ appear to be controlled by the thickness of the rhytidome and periderm; while K+ leaching rates appeared to be driven by the presence of cellular structures associated with resource storage (parenchyma) and transfer (sieve cells). Other species-specific results are also identified and discussed. These results suggest that the anatomical features of bark and the concentration of leachable macronutrient ions in stemflow are related, and that these relationships may be important to understand nutrient cycle through the bark. We also conclude that future work on the mechanisms underlying stemflow solute enrichment should consider bark anatomy.

Remarkable and Unexpected Mechanism for (S)-3-Amino-4-(difluoromethylenyl)cyclohex-1-ene-1-carboxylic Acid as a Selective Inactivator of Human Ornithine Aminotransferase.

Human ornithine aminotransferase (hOAT) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that was recently found to play an important role in the metabolic reprogramming of hepatocellular carcinoma (HCC) via the proline and glutamine metabolic pathways. The selective inhibition of hOAT by compound 10 exhibited potent in vivo antitumor activity. Inspired by the discovery of the aminotransferase inactivator (1S,3S)-3-amino-4-(difluoromethylene)cyclopentane-1-carboxylic acid (5), we rationally designed, synthesized, and evaluated a series of six-membered-ring analogs. Among them, 14 was identified as a new selective hOAT inactivator, which demonstrated a potency 22× greater than that of 10. Three different types of protein mass spectrometry approaches and two crystallographic approaches were employed to identify the structure of hOAT-14 and the formation of a remarkable final adduct (32') in the active site. These spectral studies reveal an enzyme complex heretofore not observed in a PLP-dependent enzyme, which has covalent bonds to two nearby residues. Crystal soaking experiments and molecular dynamics simulations were carried out to identify the structure of the active-site intermediate 27' and elucidate the order of the two covalent bonds that formed, leading to 32'. The initial covalent reaction of the activated warhead occurs with *Thr322 from the second subunit, followed by a subsequent nucleophilic attack by the catalytic residue Lys292. The turnover mechanism of 14 by hOAT was supported by a mass spectrometric analysis of metabolites and fluoride ion release experiments. This novel mechanism for hOAT with 14 will contribute to the further rational design of selective inactivators and an understanding of potential inactivation mechanisms by aminotransferases.

Osmo-solar drying of bottle gourd (Legeneria Siceraria)

The bottle gourd is a common vegetable in India subcontinental. Osmotic dehydration increases the storage ability of fruits and vegetables making them available throughout the year. Dehydrated products also play a great role in processed foods of all kinds and the way to achieve high quality dehydrated products are desired. The combination of osmosis with solar drying has been put forward, mainly for tropical fruit. A 24-hour cycle has been suggested combining osmodehydration, performed during the night, solar drying during the day. The well washed bottle gourd fruits were then peeled off with help of stainless-steel hand peeler. Pieces of bottle gourd cubes (1cmx1cmx1cm) were then cut out using a ruler and knife. The salt solution with 5, 10, 15, 20, and 25% (w/w) concentration were prepared. Bottle gourd cubes were immersed in the osmotic reagents with a fruit to osmotic solution mass ratio of 10:1, 20:1 and 30:1 soaking experiments were conducted at 400C, 500C and 600C in a 500 mi capacity water bath. The osmotic dehydration was done for a period of 1, 3, 5, 7 and 9 h and replicated thrice. The dependent variable studied was moisture content after dehydration. Moisture content of sample was determined by standard air oven method (Ranganna, 1995). The minimum moisture content was 46.9% (wb) for samples osmotically dehydrated at 600C for 9 h at 30:1 fruit to osmotic solution at 25% concentration. The moisture content of bottle gourd cubes observed decreases with higher concentration, temperature and mass ratio. Solar drying characteristics of 9 h bottle gourd cubes at 600C are determined by solar tray dryer. During the process of solar drying of 9 h bottle gourds cubes, the air temperature inside the cabinet varies 44 to 810C. and relative humidity inside the chamber was measures 34 to 58 percent. The minimum value of final moisture content of osmo-solar dried bottle gourd cubes was 8.3% at 600C for sample of 10:1 mass ratio and maximum value of final moisture content was 24.4% of at 600C for 30:1 sample.

The Influence of Injected Fluids on Microscopic Pore Structures in the Intersalt Dolomitic Shale Oil Reservoirs

Given their low porosity and permeability, intersalt dolomitic shale oil reservoirs need to be developed via large-scale hydraulic fracturing to achieve economic effects. However, various lithologies and salt materials make these reservoirs vulnerable to salt mineral dissolution and recrystallization and salt plugging during development. This study investigated the variation rules of pore structures, porosity, and permeability of intersalt dolomitic shale oil reservoirs under the influence of hydraulic fracturing fluid. Correspondingly, a series of experiments (i.e., high-temperature and high-pressure soaking experiments, focused ion beam scanning helium ion microscope analyses, and porosity and pulse permeability tests) is performed on the Qian 34-10 rhythmic intersalt dolomitic shales. Results show that distilled water dissolves the salt crystals inside the matrix pores to improve the reservoir permeability. However, the distilled water-rock interaction will cause the massive migration of salt minerals. By contrast, the supercritical CO2 can disperse salt particles, dredge the channels, and enlarge pores by expansion, but it has an overall weak capability of changing the pore structure and matrix permeability. To simulate the supercritical CO2 composite fracturing, the mixed solution of supercritical CO2 and distilled water favors the salt dissolution effect in the water-based fracturing fluid and recovery enhancement by CO2. This solution can remarkably improve the reservoir porosity and permeability and avoid massive salt mineral migration and salt crystallization damage. This study is theoretically and practically important to the effective and enhanced development of intersalt dolomitic shale oil reservoirs.