Study on the Permeability Enhancement of Propped Fractures under the Action of a Coal Fine Plugging Removal Agent.

The retention of coal fines in propped fractures impedes the efficient flow of gas and water, leading to a substantial decrease in coal seam permeability and gas production efficiency. In this article, a coal fine plugging removal agent with good dispersion stability and powerful powder-carrying capacity was developed to study the coal fine plugging removal and permeability enhancement in the propped fracture. The results show that 0.8% SDS + 0.4% NaCl + 0.8% BS-12 was the most effective coal fine plugging removal agent compounding system. Increasing the injection rate of the plugging removal agent and performing recycles of intermittent unblocking when it was used as a plugging agent will effectively enhance the gas-liquid two-phase effective permeability of propped fractures and improve the release of retained coal fines. After three recycles of intermittent unblocking, the coal fine discharging rate can be increased to more than 90%, resulting in a 3.88 times increase of the gas-liquid two-phase permeability compared to that with the single unblocking cycle. This method has important practical significance and theoretical value for solving the problem of coal fine plugging in fractures and ensuring the stable and efficient discharge of coalbed gas-water-coal fines.

Oxidation behavior and atomic structural transition of size-selected coalescence-resistant tantalum nanoclusters.

Herein a series of size-selected TaN(N = 147, 309, 561, 923, 1415, 2057, 6525, 10 000, 20 000) clusters are generated using a gas-phase condensation cluster beam source equipped with a lateral time-of-flight mass-selector. Aberration-corrected scanning transmission electron microscopy (AC-STEM) imaging reveals good thermal stability of TaNclusters in this study. The oxidation-induced amorphization is observed from AC-STEM imaging and further demonstrated through x-ray photoelectron spectroscopy and energy-dispersive spectroscopy. The oxidized Ta predominantly exists in the +5 oxidation state and the maximum spontaneous oxidation depth of the Ta cluster is observed to be 5 nm under prolonged atmosphere exposure. Furthermore, the size-dependent sintering and crystallization processes of oxidized TaNclusters are observed with anin situheating technique, and eventually, ordered structures are restored. As the temperature reaches 1300 °C, a fraction of oxidized Ta309clusters exhibit decahedral and icosahedral structures. However, the five-fold symmetry structures are absent in larger clusters, instead, these clusters exhibit ordered structures resembling those of the crystalline Ta2O5films. Notably, the sintering and crystallization process occurs at temperatures significantly lower than the melting point of Ta and Ta2O5, and the ordered structures resulting from annealing remain well-preserved after six months of exposure to ambient conditions.

Influence of ligands on the optical properties of rod-shaped Au25 nanoclusters.

In this study, we successfully synthesized rod-shaped [Au25(PPh3)10(S-Adm)5Cl2]2+ nanoclusters using kinetic controls. The complete molecular structure was determined by single-crystal X-ray crystallography and electrospray ionization mass spectrometry. In comparison with the previously reported [Au25(PPh3)10(PET)5Cl2]2+ clusters, both nanoclusters have an icosahedral composition of Au13 linked by Au atoms that share a vertex, but [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters appear elongated due to the rigidity of adamantane. We conducted ultraviolet-visible spectrophotometry (UV-vis) measurements of [Au25(PPh3)10(PET)5Cl2]2+ and [Au25(PPh3)10(S-Adm)5Cl2]2+ in dichloromethane solvent to elucidate the modulation of the cluster properties of different ligands. The lowest energy absorption peak of [Au25(PPh3)10(S-Adm)5Cl2]2+ shifted to lower energies compared to the [Au25(PPh3)10(PET)5Cl2]2+ clusters in UV-vis measurements. Temperature-dependent absorption measurements revealed that [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters were less affected by temperature compared to [Au25(PPh3)10(PET)5Cl2]2+. This result is attributed to the exciton phonon coupling of [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters being weaker than [Au25(PPh3)10(PET)5Cl2]2+ clusters. Furthermore, the absorption spectra of [Au25(PPh3)10(PET)5Cl2]2+ and [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters were measured using different types of solutions, and it was found that the lowest energy absorption peaks of [Au25(PPh3)10(S-Adm)5Cl2]2+ were shifted and affected by the solution at room temperature, which suggested that the [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters with solution hydrogen bonds also interacted strongly at room temperature. Theoretical calculations show that changes in ligands affect the differences in the molecular orbitals and structures of the clusters, which cause changes in the optical properties.

Synergistic passivation and stepped-dimensional perovskite analogs enable high-efficiency near-infrared light-emitting diodes.

Formamidinium lead iodide (FAPbI3) perovskites are promising emitters for near-infrared light-emitting diodes. However, their performance is still limited by defect-assisted nonradiative recombination and band offset-induced carrier aggregation at the interface. Herein, we introduce a couple of cadmium salts with acetate or halide anion into the FAPbI3 perovskite precursors to synergistically passivate the material defects and optimize the device band structure. Particularly, the perovskite analogs, containing zero-dimensional formamidinium cadmium iodide, one-dimensional δ-FAPbI3, two-dimensional FA2FAn-1PbnI3n+1, and three-dimensional α-FAPbI3, can be obtained in one pot and play a pivotal and positive role in energy transfer in the formamidinium iodide-rich lead-based perovskite films. As a result, the near-infrared FAPbI3-based devices deliver a maximum external quantum efficiency of 24.1% together with substantially improved operational stability. Combining our findings on defect passivation and energy transfer, we also achieve near-infrared light communication with device twins of light emitting and unprecedented self-driven detection.

Study on temporal and spatial evolution law for dust pollution in double roadway ventilation system of short wall continuous mining face.

To explore the laws of variations in the evolution of dust pollution within a double tunnel ventilation system at a short wall continuous mining face, a numerical simulation of air flow movement was conducted in this study. Results showed that after the wind flowing in the supporting and heading tunnels reached the head, the wind sides returned at speeds of 6.5 and 10.3 m/s, respectively. Affected by the air volume and pressure differences between the two tunnels, part of the air flow entered the connecting tunnel at an average speed of 0.8 m/s and moved to the heading tunnel. Affected by the turbulence at the driving face, a high dust concentration zone with a maximum dust concentration of 1700 mg/m3 was formed in the tunnels at a distance of 15 m from the heading. Dust blocked by the shuttle car accumulated and settled near it and formed a dust zone with an approximate average concentration of 750 mg/m3 at a distance of 19-23 m from the heading. The dust produced by the bolt machine formed a dust mass with an average concentration of 900 mg/m3 at a distance of 0.5-4.5 m from the head. Quantitative analyses of the changes in dust concentration with time at the position of a driver of the continuous mining machine, shuttle car, and anchor bolt machine were conducted, and functional formulae for the quadratic distribution were obtained. Suggestions for dust control were then proposed.

Beam generation and structural optimization of size-selected Au923 clusters.

A size-selected beam of Au923±20 clusters is generated in a gas-phase condensation cluster source equipped with a lateral time-of-flight mass selector. The beam current reaches up to 9.13 nA for small clusters and 80 pA for Au923±20 clusters, which are then analyzed using a scanning transmission electron microscope. Four types of metastable structures are observed for the Au923±20 clusters, including ino-decahedron (Dh), cuboctahedron and icosahedron (Ih). The proportion of bulk-favorable cuboctahedron (i.e. face center cubic (Fcc)) structure takes up only 10-20%, while the penta-rotating symmetrical structures (Dh/Ih) are the dominant ones which take up over three quarters. Changing the beam condition may optimize the clusters from Dh-dominant to the Ih-dominant phase, which paves the way towards nanoparticle control beyond the diameters.

Numerical Simulation of Particulate Matter 2.5 Distribution in a Roadway.

Large amounts of dust particles pose serious hazards to the health and safety of China's coal miners during roadway blasting processes. It is known that among these dust particles, Particulate Matter 2.5 (PM2.5) does the greatest amount of harm. In order to study the distributions of the PM2.5 in roadway blasting processes, a mathematical model of the gas-solid two-phase flow was established in this study, which was based on a Direct Simulation Monte Carlo Method (DSMC). Then, a multiphase flow program was developed. This study's results indicated that following the blasting processes, fine dust particles gradually floated up and were suspended for long durations in the underground roadway space. The medium-sized dust particles slowly sink to the ground and were eventually expelled before settling to the floor of the roadway. The coarse particles were rapidly settled to the roadway floor. It was determined that the PM2.5 particles in the front end of the dust group could not be quickly diluted, and the concentrations were high until it is expelled from the roadway, whereas the PM2.5 dust particles in the back end of the underground roadway were found to be gradually diluted. Eventually, the PM2.5 concentrations exhibited an alternating thin to dense phase distribution. When compared with the Particulate Matter 5 (PM5), it was found that the PM2.5 was more difficult to discharge, and easily formed serious PM2.5 dust air pollution. This study's results were determined to be conductive to the future control of PM2.5 in the underground roadway blasting processes.

Gut Transit in Duchenne Muscular Dystrophy Is Not Impaired: A Study Utilizing Wireless Motility Capsules.

We examined gut transit in 7 young adults (18-24 years of age) with Duchenne muscular dystrophy using wireless motility capsules. Total and segmental gut transit times were normal in essentially all patients. Our study using a validated tool suggests normal transit constipation as the pathophysiologic basis for constipation in Duchenne muscular dystrophy.

MicroRNA and mRNA Expression Changes in Steroid Naïve and Steroid Treated DMD Patients.

BACKGROUND: Duchenne Muscular Dystrophy (DMD) is a recessive X-linked form of muscular dystrophy. Steroid therapy has clinical benefits for DMD patients, but the mechanism remains unclear. OBJECTIVE: This study was designed to identify mRNAs and microRNAs regulated in Duchenne Muscular Dystrophy patients prior to and after steroid therapy. METHODS: Genome wide transcriptome profiling of whole blood was performed to identify mRNAs and microRNAs regulated in DMD patients. RESULTS: The data show many regulated mRNAs and some microRNAs, including some muscle-specific microRNAs (e.g., miR-206), that were significantly altered in blood of young (age 3-10) DMD patients compared to young controls. A total of 95 microRNAs, but no mRNAs, were differentially expressed in older DMD patients compared to matched controls (age 11-20). Steroid treatment reversed expression patterns of several microRNAs (miR-206, miR-181a, miR-4538, miR-4539, miR-606, and miR-454) that were altered in the young DMD patients. As an example, the over-expression of miR-206 in young DMD patients is predicted to down-regulate a set of target genes (e.g., RHGAP31, KHSRP, CORO1B, PTBP1, C7orf58, DLG4, and KLF4) that would worsen motor function. Since steroids decreased miR-206 expression to control levels, this could provide one mechanism by which steroids improve motor function. CONCLUSIONS: These identified microRNA-mRNA alterations will help better understand the pathophysiology of DMD and the response to steroid treatment.

Comparison of the immunogenicity of intramuscular versus subcutaneous administration of trivalent inactivated influenza vaccine in individuals with neuromuscular diseases.

Individuals with neuromuscular disease show a wide spectrum of muscle pathology. To test the hypothesis that the immune response to trivalent inactivated influenza vaccine is potentially inadequate when given intramuscularly into a fibrosed muscle, this prospective randomized study compared the immunogenicity and safety of the standard intramuscular versus subcutaneous administration of the influenza vaccine in 22 nonambulatory subjects, of whom 10 have been on glucocorticoid therapy. Analysis of hemagglutination inhibition antibody titers showed high prevalence of seroprotection (prevaccination of 82% H1N1, 72% H3N2, 31% B; postvaccination of 100% H1N1, 77% H3N2, 59% B). Geometric mean titer ratios for each antigen showed no significant difference (P > .5) between intramuscular and subcutaneous routes. Seroprotection was not adversely affected by glucocorticoid therapy. Local tolerance was better with subcutaneous route. Larger studies are needed to confirm these preliminary results.

CRIM1 complexes with ß-catenin and cadherins, stabilizes cell-cell junctions and is critical for neural morphogenesis.

In multicellular organisms, morphogenesis is a highly coordinated process that requires dynamically regulated adhesion between cells. An excellent example of cellular morphogenesis is the formation of the neural tube from the flattened epithelium of the neural plate. Cysteine-rich motor neuron protein 1 (CRIM1) is a single-pass (type 1) transmembrane protein that is expressed in neural structures beginning at the neural plate stage. In the frog Xenopus laevis, loss of function studies using CRIM1 antisense morpholino oligonucleotides resulted in a failure of neural development. The CRIM1 knockdown phenotype was, in some cases, mild and resulted in perturbed neural fold morphogenesis. In severely affected embryos there was a dramatic failure of cell adhesion in the neural plate and complete absence of neural structures subsequently. Investigation of the mechanism of CRIM1 function revealed that it can form complexes with ß-catenin and cadherins, albeit indirectly, via the cytosolic domain. Consistent with this, CRIM1 knockdown resulted in diminished levels of cadherins and ß-catenin in junctional complexes in the neural plate. We conclude that CRIM1 is critical for cell-cell adhesion during neural development because it is required for the function of cadherin-dependent junctions.

DNA-binding and regulation mechanisms of the SIX family of retinal determination proteins.

The Six/sine oculis proteins are homeodomain transcription factors that are part of the Pax/Eya/Six/Dach retinal determination cascade involved in embryonic cell fate determination. There are six mammalian Six homologues, divided into three classes on the basis of sequence homology. In the present study we examined the DNA-binding specificity and mechanisms of Six2 and Six6 toward the Trex/MEF3 consensus sequence and the core tetranucleotide ATTA commonly recognized by homeodomain proteins. The results suggest that the Six homeodomain does not bind DNA owing to the absence of a key structural feature, the basic N-terminal arm, implicated in canonical homeodomain-DNA binding. Furthermore, the DNA-binding mechanisms and DNA sequence specificity differ among these Six proteins despite the complete conservation of predicted DNA-contacting residues in their homeodomains. Inclusion of 14 amino acid residues immediately C-terminal to the homeodomain of Six6 yields a protein construct able to bind both DNA sequences tested with nanomolar affinity. However, an analogous Six2 construct remains unable to bind DNA. Furthermore, we show that the DNA-binding affinity of Six2 is increased nearly 12-fold by complex formation with the Eyes Absent tyrosine phosphatase, while Six6-DNA binding is not similarly enhanced. This phenomenon could contribute to the synergy observed between Six2 and Eyes Absent in transcriptional activation and in eye development.

Evolution of the CYP2ABFGST gene cluster in rat, and a fine-scale comparison among rodent and primate species.

The evolution of gene families can be best understood by studying the modern organization and functions of family members, and by comparing parallel families in different species. In this study, the CYP2ABFGST gene cluster has been characterized in rat and compared to the syntenic clusters in mouse and human, providing an interesting example of gene family evolution. In the rat, 18 loci from six subfamilies have been identified by specifically amplifying and sequencing gene fragments from cloned DNA, and have been exactly placed on chromosome 1. The overall organization of the gene cluster in rat is relatively simple, with genes from each subfamily in tandem, and is more similar to the mouse than to the human cluster. We have reconstructed the probable structure of the CYP2ABFGST cluster in the common ancestor of primates and rodents, and inferred a model of the evolution of this gene cluster in the three species. Numerous nontandem and block duplications, inversions, and translocations have occurred entirely inside the cluster, indicating that pairing between duplicate genes is keeping the rearrangements within the cluster region. The initial tandem duplication of a CYP2 gene in an early mammalian ancestor has made this region particularly subject to such localized rearrangements. Even if duplicated genes do not have a large-scale effect on chromosomal rearrangements, on a local level clustered gene families may have contributed significantly to the genomic complexity of modern mammals.

Dynamic evolution of the CYP2ABFGST gene cluster in primates.

We have annotated and analyzed sequences from the CYP2ABFGST gene cluster for the chimpanzee and the Rhesus macaque, and compared them in detail to the complete map of the syntenic human cluster. While the macaque cluster has accumulated substantial differences in gene number and organization relative to the other two species, the chimpanzee cluster has remained surprisingly similar to the human cluster, given the evolutionary volatility of this gene family. The comparison will allow us to further refine our model of the evolution of this gene family in mammals.