Polymethyl methacrylate (PMMA) polymer is widely used in various fields today. In order to reveal the structural impact performance of PMMA materials in underwater engineering thoroughly, this paper ...firstly proposed a simplified plate model for a spherical shell hull under concentrative impact loading. Then, to simulate the hyper-elastic material properties of PMMA in the impact process, the Johnson–Cook constitutive model and damage failure model were adopted. And the least squares method was used to confirm accurately the J–C constitutive and damage failure model parameters of PMMA through material test data. Moreover, the dynamic process of the steel bullet impacting the PMMA plate structure was analyzed by the finite element software ABAQUS. The calculation results show that the numerical simulation results in this paper have a good convergence, and the residual velocities at different initial velocities and thicknesses of plates are in good agreement with the experimental test data. Therefore, the feasibility and accuracy of the impact analysis of PMMA structures based on J–C constitutive and damage failure models in this paper are verified accordingly. Finally, based on the presented finite element model, the structure response and the variation of residual velocity of the bullet with the PMMA plate thickness was analyzed in depth; that is, the results show that the residual velocity of the bullet has a certain linear relationship with the thickness, even in an underwater environment, and even in an underwater environment will increase both with a thicker structure or a higher pressure.
The IC50s of seven potent N,N′-arylurea compounds against juvenile and adult S. japonicum. Compounds 16 and 38 showed higher activities than the positive control MMV665852. Display omitted
Although ...the antischistosomal activities of N,N′-arylurea analogs were reported, systematic structure–activity relationships have not been conducted. In this Letter, we reported the design, synthesis and evaluation of 45 N,N′-arylurea analogs. Among these prepared compounds, 13 compounds were urea linker modified and 32 were N,N′-arylurea derivatives. The activity evaluation revealed 12 analogs exhibited IC50 values lower than 22.6μM, and 7 of them had IC50 less than 10μM against the juvenile Schistosoma japonicum in vitro. Their worm killing potency was even higher against adult worm. Unfortunately, low to moderate worm burden reduction of 0–33.4% was recorded after administration of a single oral dose of 200mg/kg or 400mg/kg to mice harboring S. japonicum.
For its high transparency, polymethyl methacrylate (PMMA) is widely applied as observation windows or detector protective covers of various aircraft and submersibles. Firstly, a modified viscoelastic ...Prony series model with three parameters has been derivated and applied into triaxial stress state. Based on stress relaxation test data of compression specimens made of PMMA, the relaxation parameters of the modified Prony series model are determined. Then, the PMMA specimens and conical viewports were simulated on software ABAQUS, coupled with presented improved stress relaxation model, and verified its accuracy in stress relaxation analysis. Moreover based on the finite element method (FEM) with improved stress relaxation model, the relaxation behavior of PMMA conical viewport with multiple parameters and structural optimization was accomplished accordingly, which shows that there is a good consistency between the numerical and experimental results. Finally, the presented numerical model had been applied into relaxation behavior analysis of conical viewport under high external pressure. Results indicates that, the structure of the conical viewport with a cone angle of 70° is more reasonable and optimized, and the stress relaxation level performance of viewport is better, which reveals that the thickness increasing, bigger than δ/Di = 1, will have a few response to its stress relaxation degree.
•A modified viscoelastic Prony series model with three parameters has been proposed and applied to solve triaxial stress, which validity and accuracy have been verified.•A numerical model with presented improved stress relaxation model has been provided and adopted to analyze the stress relaxation behavior of conical viewport, confirmed by the experimental results.•Based on the presented FEM, influent of multiple parameters to relaxation and structural performance of conical viewport has been studied and discussed accordingly.
Core ZHS-176 contains the paleoenvironmental records from the northern South China Sea （NSCS） since the Last Glacial Maximum （LGM）. A coupled approach based on clay mineral assemblages, planktonic ...foraminiferal oxygen and carbon isotopes, and calcium carbonate content is used to trace the sources of the fine-grained sediment and to investigate the paleoenviornmental evolution in this area. Clay mineral assemblages are dominated by illite （average about 39%） and chlorite （about 27%）, which comes mainly from Taiwan and the East China Sea. Kaolinite, which accounts for about 13%, comes mainly from the Zhujiang （Pearl） River, and Luzon Island is the main source for smectite （about 21%）. The planktonic foraminiferal oxygen isotopic oscillations during the last glacial period are coeval with climate variations recorded in the Greenland ice core and Western Pacific sediment. These variations include the LGM, Heinrich event 1, Bφlling-Allerφd （B/A）, and Younger Dryas. For the Holocene, three periods of strong precipitation （S1-S3） and three periods of weak precipitation （W1-W3） are identified. The oxygen isotopic record exhibits corre-lation with climate records from distant regions, including the high-latitude Northern Hemisphere, providing evidence for global tele-connection among regional climate. A brief, negative planktonic foraminiferal carbon isotopic excursion during B/A reflects increased methane released from marine gas hydrate due to the rapid warming of the water. By comparing calcium carbonate content curves of the core ZHS-176 with these of other five boreholes lying above the lysocline, a remarkable low calcium carbonate event is found during the early Holocene in NSCS.
High-resolution Chirp profiling and coring reveals an elongated （ca. 400 km） Holocene Zhujiang River （Pearl River）-derived mud area （maximum thickness 〉 20 m） extending from the Zhujiang River Delta, ...southwest-ward off the Guangdong coast, to the Leizhou Peninsula. Two depo-centers, one proximal and one distal, are identified. On the continental shelf off the west Guangdong Province, the mud is deposited in water depth shallower than 50 m; while to the southeast of the Zhujiang River Estuary, the mud area can extend to the -120 m isobath. A combined analysis with the stratigraphic sequences of other muddy deposits in the West-ern Pacific marginal seas （mainly Changjiang （Yangtze） and Huanghe （Yellow） Rivers derived） indicates that the initiation of the Zhujiang River muddy deposit can be further divided into two stages： Stage 1 is before the mid-Holocene sea-level highstand （ca. 7.0 cal. ka BP）, the proximal mud was mostly deposited after 9.0 cal. ka BP, when the sea-level rose slowly after the Meltwater Pulse -1C; Stage 2, after the mid-Holocene sea-level highstand, clinoform developed on the continental shelf off the west Guangdong Province, extending ca. 400 km from the Zhujiang River Estuary. The proximal clinoform thins offshore, from ca. 10 m thickness around 5-10 m water depth to less than 1-2 m around 20-30 m water depth. In addition, we also find a de-veloped distal clinoform in the east of the Leizhou Peninsula.
Sedimentary manganese (Mn) deposits in the southeastern Yangtze Platform of China have been newly discovered with considerable potential for resource exploration. Such deposits formed due to dynamic ...changes in the global environment, including the break-up of the supercontinent Rodinia, Snowball Earth glaciation, and the Neoproterozoic Oxygenation Event. The Mn-bearing sequences are hosted in the basal Datangpo Formation and are interbedded with black carbonaceous shale in a series of graben sub-basins in the Nanhua Rift Basin. We investigated the origin of these Mn deposits by analysing the major and trace elements, total organic carbon, and stable carbon and oxygen isotopes. Positive Eu anomalies were observed, indicating that the Mn was derived from a hydrothermal system. Redox-related elements, including Ce, Mo, U, V, S, and P, indicated that the depositional environment of the Mn layers was oxidative and that Mn
2+
was initially oxidized to Mn oxides. However, the host rock (i.e. black carbonaceous shale) was deposited under dysoxic - anoxic and even sulfidic water conditions. The alternating distribution of Mn ore and host rock suggested alternating redox conditions in the sub-basins. A negative correlation between the Mn content and δ
13
C
carb
values (−10‰-−7‰) and a deficiency of sulphide minerals indicate that the diagenetic degradation of organic matter (δ
13
C
org
from − 34‰ to − 31.9‰) took place through Mn oxide reduction rather than microbial sulphate reduction and can contribute to a considerable source of bicarbonates. The approximately homogeneous δ
13
C
carb
depletion and their apparent discrepancy with δ
13
C
org
indicate that the post-depositional genesis of the Mn carbonate ore occurred in a relatively open early diagenetic pore water system with a considerable contribution from seawater-derived carbon sources.
Two-dimensional materials (2DMs) are competitive candidates in replacing or supplementing conventional semiconductors owing to their atomically uniform thickness. However, current conventional ...micro/nanofabrication technologies realize hardly ultrashort channel and integration, especially for sub-10 nm. Meanwhile, experimental device performance associated with the scaling of dimension needs to be investigated, due to the short channel effects. Here, we show a novel and universal technological method to fabricate sub-10 nm gaps with sharp edges and steep sidewalls. The realization of sub-10 nm gaps derives from a corrosion crack along the cleavage plane of Bi2O3. By this method, ultrathin body field-effect transistors (FETs), consisting of 8.2 nm channel length, 6 nm high-k dielectric, and 0.7 nm monolayer MoS2, exhibit no obvious short channel effects. The corresponding current on/off ratio and subthreshold swing reaches to 106 and 140 mV/dec, respectively. Moreover, integrated circuits with sub-10 nm channel are capable of operating as digital inverters with high voltage gain. The results suggest our technological method can be used to fabricate the ultrashort channel nanopatterns, build the experimental groundwork for 2DMs FETs with sub-10 nm channel length and 2DMs integrated circuits, and offer new potential opportunities for large-scale device constructions and applications.
A new two-phase solution strategy has been developed for the synthesis of hybrid one-dimensional (1D) zinc oxide nanorod array@graphene (ZnO NA@graphene) nanostructures, in which ZnO NA@graphene were ...easily obtained at room temperature without using any catalysts, templates, or precursors. More importantly, an interesting formation mechanism of the 1D nanostructure in the benzene/water system and its distinctive morphology-controlling ability was discovered in this paper, respectively. Interestingly, the as-prepared ZnO nanorod@graphene composites exhibit exceedingly high activity and excellent selectivity in the photocatalytic reduction of CO2 to CH3OH (the maximum CH3OH yield is 375μmolgcat.−1 for 3.0h under UV light irradiation, which is 2.81 times as high as that on pure ZnO) as a result of the improved electron-hole pair separation rate on ZnO NA@graphene interface, as well as high light harvesting effects derived from the NA@graphene hierarchical structure.
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Magmatic sulfide formation and oxidative dissolution are effective in metal pre-enrichment and remobilization during magmatic processes, and are considered to be a prerequisite for the formation of ...magmatic–hydrothermal ore deposits in subduction zones. However, this sequential process and sulfide oxidation mechanism are poorly understood. In this study, we report fine-grained sulfides with variable degrees of oxidation distributed within mafic cumulates, brought into felsic magma as mafic magma intrusions in the southwestern Okinawa Trough. Thermodynamic modeling suggests that the oxygen fugacity (fO2) of primitive mafic magma is ∼FMQ + 2.5, reducing to ∼FMQ + 1 in evolved mafic magma and to ∼FMQ + 0.5 in felsic magma. This variation results from the continuous assimilation of reduced country rocks, as reflected by negative δ34SVCTD values (–0.62‰ ± 0.23‰) of magmatic sulfides and highly radiogenic Sr–Nd isotopic compositions of host dacite. Magmatic reduction and addition of crust-derived sulfur result in early formation of crystalline sulfides, dominantly pyrrhotite, enriched in Cu (0.93 ± 0.38 wt.%). A new injection of oxidized mafic magma triggers partial to complete oxidation of the earlier magmatic sulfides, ultimately transforming them into hematite–magnetite (HM) intergrowths. This means that sulfide oxidation is not directly associated with the mafic magma itself, but more likely with high-fO2 magmatic fluid exsolved from the primitive mafic magma. The oxidative dissolution process releases >90% of Cu from the primary sulfides, with this Cu preferentially moving into magmatic fluid. This indicates that metal remobilization and transfer is very efficient under HM buffer conditions, in which trisulfur S3− ions with high affinities for Au and Cu are probably the dominant sulfur species. We suggest that the periodic injection of oxidized mafic magma into continental crust containing reduced lithologies is essential for the sequential process of early sulfide formation and later oxidative dissolution in the Okinawa Trough and in other subduction zone settings with similar tectono-magmatic conditions. This process could be a precursor to the generation of metal-bearing magmatic fluid, contributing to mineralization in subduction zones.
