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Uranium extraction from seawater is regarded as the most promising strategy for solving the concerns regarding the increasing demands of the nuclear industry.

Vibrio collagenases of the M9A subfamily are closely related to Vibrio pathogenesis for their role in collagen degradation during host invasion. Although some Vibrio collagenases have been characterized, the collagen degradation mechanism of Vibrio collagenase is still largely unknown. Here, an M9A collagenase, VP397, from marine Vibrio pomeroyi strain 12613 was characterized, and its fragmentation pattern on insoluble type I collagen fibers was studied. VP397 is a typical Vibrio collagenase composed of a catalytic module featuring a peptidase M9N domain and a peptidase M9 domain and two accessory bacterial prepeptidase C-terminal domains (PPC domains). It can hydrolyze various collagenous substrates, including fish collagen, mammalian collagens of types I to V, triple-helical peptide [(POG)(10)](3), gelatin, and 4-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-o-Arg (Pz-peptide). Atomic force microscopy (AFM) observation and biochemical analyses revealed that VP397 first assaults the C-telopeptide region to dismantle the compact structure of collagen and dissociate tropocollagen fragments, which are further digested into peptides and amino acids by VP397 mainly at the Y-Gly bonds in the repeating Gly-X-Y triplets. In addition, domain deletion mutagenesis showed that the catalytic module of VP397 alone is capable of hydrolyzing type I collagen fibers and that its C-terminal PPC2 domain functions as a collagen-binding domain during collagenolysis. Based on our results, a model for the collagenolytic mechanism of VP397 is proposed. This study sheds light on the mechanism of collagen degradation by Vibrio collagenase, offering a better understanding of the pathogenesis of Vibrio and helping in developing the potential applications of Vibrio collagenase in industrial and medical areas. IMPORTANCE Many Vibrio species are pathogens and cause serious diseases in humans and aquatic animals. The collagenases produced by pathogenic Vibrio species have been regarded as important virulence factors, which occasionally exhibit direct pathogenicity to the infected host or facilitate other toxins’ diffusion through the digestion of host collagen. However, our knowledge concerning the collagen degradation mechanism of Vibrio collagenase is still limited. This study reveals the degradation strategy of Vibrio collagenase VP397 on type I collagen. VP397 binds on collagen fibrils via its C-terminal PPC2 domain, and its catalytic module first assaults the C-telopeptide region and then attacks the Y-Gly bonds in the dissociated tropocollagen fragments to release peptides and amino acids. This study offers new knowledge regarding the collagenolytic mechanism of Vibrio collagenase, which is helpful for better understanding the role of collagenase in Vibrio pathogenesis and for developing its industrial and medical applications.

Li Xiong,1,* Shi-Cheng Liu,2,* Si-Ying Huo,1 Lan-Qing Pu,1 Jun-Jie Li,1 Wen-Ya Bai,1 Yuan Yang,1 Jian-Lin Shao1 1Department of Anesthesiology, The First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, People’s Republic of China; 2Department of Oncology, The First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jian-Lin Shao, Department of Anesthesiology, The First Affiliated Hospital of Kunming Medical University, 295 Xichang Road, Kunming, Yunnan, 650032, People’s Republic of China, Email shaojl@ydyy.cnBackground: Ketamine is famous for its dissociative anesthetic properties. It is also analgesic, anti-inflammatory and anti-depressant, and even has a cerebral protective effect. We searched the evidence of the correlation between ketamine target and clinical efficacy and utilized network pharmacology to gather information about the multi-target mechanism of ketamine against cerebral ischemia (CI). We found that ketamine’s clinical significance may be more extensive than previously thought.Methods: The drug target of ketamine and CI-related genes were predicted by SwissTargetPrediction, DrugBank, PubChem, GeneCards and DisGeNET databases. The intersection of ketamine’s drug-targets and CI-related genes was analyzed by using GO and KEGG. We predicted the molecular docking between the potential target and ketamine.Results: The results indicated that the effect of ketamine on CI was primarily associated with the target of α-synuclein (SNCA), muscarinic acetylcholine receptor M1 (CHRM1) and nitric oxide synthase 1 (NOS1). It principally regulates the signal pathways of circadian transmission, calcium signaling pathway, dopaminergic synapse, cholinergic synapse and glutamatergic synapse. Molecular docking analysis exhibited that hydrogen bond and Pi-Pi interaction were the predominant modes of interaction.Conclusion: There are protein targets affected by ketamine in the treatment of CI. Three pivotal targets involving 298 proteins, SNCA, CHRM1 and NOS1, have emerged as multi-target mechanisms for ketamine in CI therapy. Similarly, this study also provides a new idea for introducing network pharmacology into the evaluation of multi-targeted drugs for CI and cerebral protection.Keywords: ketamine, cerebral ischemia, treatment target, network pharmacology

In this paper, a novel parabolic trough solar receiver-reactor (PTSRR) system of a locally-installed Kenics static mixer (KSM) is proposed for efficient solar thermal hydrogen production. A three-dimensional comprehensive model was established for PTSRRs of the methanol-steam reforming reaction (MSRR) for hydrogen production, by combining the Finite Volume Method and the Monte Carlo ray-tracing method with a MSRR comprehensive kinetic model. The validated model was preliminarily applied to study the effects and mechanisms of the concentrated solar flux nonuniformity and the locally-installed KSM on PTSRR photo-thermal-chemical comprehensive characteristics and performance, taking the methanol flow rate and the catalyst sintering temperature limitation into account. With a preliminary optimization on the concentrated solar flux nonuniformity, the optical efficiency and the solar flux nonuniformity are improved by 6.58% and 30.42% respectively. It is further revealed that these PTSRRs of better concentrated solar flux density nonuniformity also have better thermal-chemical comprehensive characteristics and performance. Novel PTSRRs of the locally-installed KSM have better comprehensive characteristics and performance than corresponding original PTSRRs or even optimized PTSRRs, with a maximum increase in the methanol conversion rate of 6.92%. It thus will operate more safely and more efficiently, by the cost of a little more pump power to overcome corresponding larger flow resistance caused by the locally-installed KSM. From the mechanism, this kind of novel PTSRR of a locally-installed KSM provides a useful option of high potential for improving uniformities of a series of key field variables in the whole photo-thermal-chemical conversion process, and thus improves the comprehensive characteristics and performance of PTSRRs.

Highly efficient extraction of uranium from seawater is regarded as an important guarantee for the promotion of nuclear electricity generation. Amidoxime based adsorbents are considered as the most promising materials for uranium recovery due to their high selectivity and binding capability to uranyl ions. Herein, natural celluloses with advantages of low cost, biodegradability, renewability were chosen as the raw materials. Moreover, amidoximated cellulose-based adsorbents are fabricated by two steps of homogeneous reactions including the Michael addition and amidoximation reaction. Compared with traditional surface grafting methods, both the grafting density of active adsorption sites and the utilization of raw materials could be greatly improved because of the lower steric hindrance as well as more exposed reactive sites during the homogeneous reactions. The adsorption capacity of our adsorbents can reach as high as 517.07 mg/g at pH = 7, one of the best cellulose-based adsorbents as far as we know. In addition, excellent hydrophilicity of the adsorbents, which is inherited from the natural cellulose, can endow them with enhanced mass transfer as well as resistance to marine pollutants. More importantly, the adsorption microspheres would be filled into filtration column for dynamic adsorption benefited from their aforementioned merits. The average adsorption capacity could maintain above 2.5 mg/g per day when the filtration column was exposed to simulated seawater for 24 days. All these characteristics make the amidoximated cellulose-based adsorbents potentially applicable to the uranium recovery from seawater.

For taking advantage of high speed machining(HSM) in complex curved surfaces as impeller, the virtual manufacturing technology is adopted before the real machining, which can eliminate tool collision interference phenomenon of the trial cutting, avoid complicated process of trial test , forecast machining results efficiently. The simulation tests were proceeded to the each impeller procedure NC program by using the VERICUT virtual manufacturing soft to modeling five-axis machine tool HSM600U, and the result compared with the real machining is identical with one other. So it is tested that applying this technology can forecast the machining process truly.

Fracture surface and crack propagation in low temperature brittle fracture (LTBF) of an 18Cr-18Mn-0.7N high nitrogen austenitic steel (HNAS) were examined by means of scanning electronic microscopy, and compared with behaviours of LTBF of low carbon steel. Similar to BCC low carbon steel, the HNAS experienced a typical ductile-to-brittle transition (DBT) with decreasing temperature, and the appearance of the fracture surface transited from fibrous to granular. Dual-surface observation revealed that there were three types of fracture modes in LTBF of the HNAS: annealing twin boundary fracture, intergranular fracture, and transgranular fracture. The annealing twin boundary fracture facets were parallel to {111} planes, and were fairly flat and smooth, with a pattern of three sets of parallel straight-lines intersecting at 60. There were also bent steps that originated and terminated at grain boundaries. The transgranular fracture facets were coarse and uneven, with uniformly distributed small pits and partially river pattern on them. The intergranular fracture facets were smoothly curved ones on which more than three sets of parallel deformation structure trace lines were observed. Careful observation on crack propagation demonstrated that during LTBF of the HNAS, microcracks formed firstly at grain boundary and annealing twin boundary, and then these microcracks came together and coalesced to induce crack propagation through grains, resulting in a fracture appearance with shiny facets distributing in dull facets.

The small punch (SP) tests were conducted at 77 K and 4 K using austenitic stainless steels JN 1, JJ 1 and JK 2, which have been recently developed for use as a cryogenic structural material. The tests were applied to the steels aged at 923-1073 K to investigate changes in their toughness at cryogenic temperature due to thermal aging. The area under the load-deflection curve up to the macro-crack initiation was defined as SP energy to evaluate the fracture toughness of the steels. The experimental results showed that the SP energy of JN 1 decreased monotonously with an increase in aging temperature. On the other hand, the SP energy of JK 2 showed no significant change even after the thermal aging at 923 K and 973 K and decreased after the thermal aging at 1023 K. Metallographic examination revealed that this difference in decrease of SP energy due to thermal aging was caused by the variation in amount and distribution of grain boundary M23C6 carbides. As a consequence, JN 1 was more susceptible to thermal aging embrittlement than the other steels, and high resistance of JK 2 to embrittlement was attributable to the depression of precipitation and coarsening of grain boundary precipitates.

Elastic-plastic fracture toughness tests were conducted at 77K and 4K to examine an influence of thermal aging on fracture properties of an austenitic stainless steel JN 1 at cryogenic temperature, which is a candidate material for superconducting magnet structures of fusion reactors. The tests were applied to solution-treated material and materials aged at 923-1073 K for 5 h. The experimental results showed that the fracture toughness JIC measured on the thermally aged materials were smaller than that on the solution-treated material and decreased with increasing aging temperature. This decrease in fracture toughness due to thermal aging was caused by precipitation and coarsening of grain boundary M23C6 carbides. Additionally, small punch (SP) tests were conducted at cryogenic temperatures to investigate the relationship between the obtained JIC and SP properties. It was found that the equivalent fracture strain eqf in SP specimens was linearly correlated with JIC irrespective of testing temperature. This correlation suggests that the SP testing technique provides a useful tool for evaluating JIC at cryogenic temperature.

Small-punch tests were conducted at 4, 77, and 293 K on three newly developed cryogenic austenitic stainless steels, JN1, JJ1, and JK2, which were solution treated, water-quenched, and then aged at 923, 973, 1023, and 1073 K for 5 h. Small-punch test energy was employed for the evaluation of the aging-induced embrittlement behavior in these materials. An SEM analysis of the fracture surface for the solution-treated steel specimens indicated a ductile fracture, having the highest SP test energy values. On the contrary, intergranular brittle fracture was observed in aged specimens. The small-punch test energy of materials decreased significantly as the aging process progressed. The highest and lowest decrease in small-punch test energy with aging temperature occurred in JN1 and JK2 steels, respectively. The decrease in small-punch test energy was shown to follow appropriately the aging-induced embrittlement in these materials. The difference in aging-induced embrittlement behavior for these steels was explained on the basis of the volume fraction of intergranular precipitates in aged samples.

Small-punch (SP) and fracture toughness tests were conducted at 4 and 77 K on newly developed cryogenic austenitic stainless steels after isothermal aging. Equivalent fracture strain eqf was determined by measuring the reduction in thickness of SP specimens. A linear dependence of JIC on eqf was found for these new materials. Regression analysis of experimental data produced the linear relation: J IC =1304.1e qf +8.09 ( kJ m −2 ) . An analysis of the correlation was pursued on the basis of material properties and evaluation method of JIC. The results showed that the slope value was influenced by the JIC evaluation method. This linear relation enables the prediction of JIC to be made from the equivalent fracture strain eqf by conducting small punch tests. Thus, it is expected that the SP testing method provides a useful basis for assessing the degradation of fracture toughness in small areas, such as heat-affected zones in welded components.

The fracture mode and crack propagation behavior of brittle fracture at 77 and 4 K in an 18Cr-18Mn-0.7N austenitic stainless steel were investigated using optical and scanning electron microscopy. The fracture path was examined by observing the side surface in a partially ruptured specimen. The relationship of the fracture facets to the microstructures was established by observing the fracture surface and the adjacent side surface simultaneously. Three kinds of fracture facets were identified at either temperature. The first is a smoothly curved intergranular fracture facet with characteristic parallel lines on it. The second is a fairly planar facet formed by parting along an annealing twin boundary, a real {111} plane. There are three sets of parallel lines on the facet and the lines in different sets intersect at 60 deg. The third is a lamellar transgranular fracture facet with sets of parallel steps on it. Fracture propagated by the formation of microcracks on a grain boundary, annealing twin boundary, and coalescence of these cracks. The observation suggests that the ease of crack initiation and propagation along the grain boundary and the annealing twin boundary may be the main reason for the low-temperature brittleness of this steel. A mechanism for grain boundary cracking, including annealing twin boundary parting, has been discussed based on the stress concentration induced by impinging planar deformation structures on the grain boundaries.

Fracture characteristics of a TIG welded joint and heat treated materials of JNI, which is an austenitic stainless steel recently developed for use as a cryogenic structural material, were evaluated by the small punch (SP) testing method using miniaturized specimens at 77K and 4K. The area under the load displacement curve up to the maximum load was defined as the SP energy to evaluate the fracture characteristics of the materials in SP tests. Fracture surfaces were also observed using a scanning clectron microscope. Solution-treated JN1 steel showed ductile fracture behavior with a high SP energy value even at 4K, and serrations were observed in the load displacement curve at 4K, In the weld metal and fusion line specimens of the TIG welded joint, serrations also occured at 4K, but the fusion line specimens showed lower SP energy values than weld metal and solutiontremed JN1 steel at 77K and 4K. In addition, the fusion line specimens showed pop in behavior at 4K, that is, cracks approximately 0.1-1mm long were induced by pop-in in the vicinity of the fusion line at the early stage of loading. JN1 materials heat treated under the conditions of 650°C 5h and 700°C In showed similar fracture characteristics to those of the fusion line specimens at 77 K and 4 K except for the cracks induced by pop-in. With increasing temperature and time of heat treatment, SP energy decreased significantly, and the fracture surface showed a transition from ductile dimple to brittle intergranular cracking. It is shown that the SP testing method is useful for evaluating the fracture behaviors of microscopic regions such as the fusion lines of welds at cryogenic temperatures.