Gemcitabine (dFdC), a modified deoxycytidine (dC) widely used in tumor treatment, is a prodrug that is phosphorylated to generate mono-, di-, and triphosphates. The triphosphate (dFdCTP) is ...incorporated into DNA to terminate DNA synthesis in cancer. Some incorporated dFdC nucleotides can be partially removed by the 3′–5′ exonuclease activity, namely its editing function, and the others escape the editing. However, whether there is an active mechanism for dFdC to escape the editing remains unclear. We have first discovered that unlike dFdC, its mono-, di-, and triphosphates can inhibit the 3′–5′ exonuclease of DNA polymerase I, suppress editing, and allow the active escaping mechanism, whereas its polymerase activity is not remarkably affected. As such, these phosphates can prevent the removal of the incorporated dFdC residue, thereby actively blocking DNA extension and synthesis. The inhibition efficiency of these phosphates follows the increased order of the mono-, di-, and triphosphates of gemcitabine (dFdC < dFdCMP < dFdCDP < dFdCTP). In addition, after the deletion of the 3′–5′ exonuclease of cellular DNA polymerase I, the Escherichia coli mutant is more sensitive to dFdCTP than is wild-type E. coli. Our new discovery of the ability of these dFdC phosphates to inhibit exonuclease activity suggests a novel anticancer mechanism of gemcitabine and its phosphate derivatives.
Efficient and durable thermal insulators combined with flame resistance are required for energy efficient buildings. Here, we fabricate poly(
p
-phenylene benzobisoxazole) (PBO) nanofiber aerogels ...(PBOAs) through a proton-consumption-induced gelation of PBO nanofiber sol and a controlled freeze-drying with a low cooling rate, followed by thermal cross-linking. Nanofibrous networks based on physical entanglement of nanofibers and chemical cross-linking at the junctions were obtained, leading to ultralow density (3.6–15.7 mg cm
−3
), high porosity (98.9–99.7%), high specific surface area (155.4 m
2
g
−1
), low thermal conductivity (26.2–37.7 mW m
−1
K
−1
) and superelasticity under an ultimate strain of 99%. More importantly, the aerogels achieve an excellent thermal stability, including a high decomposition temperature of 650 °C and a high long-term use temperature of 350 °C. Furthermore, the PBOAs are characterized by outstanding flame resistance, reach the nonflammable level in vertical burning tests (UL-94, V-0 class), and show a limiting oxygen index (LOI) as high as 52.8%. The aerogels cannot be ignited under simulated real-scale fire conditions, leaving suppressed smoke emission and reduced potential for flame spread and fire hazards. High thermal insulation and resistance to a 1000 °C flame has been achieved by compositing PBOAs with fumed silica. Thus, the PBOAs have promising applications in energy efficient areas, such as buildings, aerospace and many other fields, especially under harsh conditions.
An ultrasonically enhanced two-stage acid leaching process on extracting and recovering multiple heavy metals from actual electroplating sludge was studied in lab tests. It provided an effective ...technique for separation of valuable metals (Cu, Ni and Zn) from less valuable metals (Fe and Cr) in electroplating sludge. The efficiency of the process had been measured with the leaching efficiencies and recovery rates of the metals. Enhanced by ultrasonic power, the first-stage acid leaching demonstrated leaching rates of 96.72%, 97.77%, 98.00%, 53.03%, and 0.44% for Cu, Ni, Zn, Cr, and Fe respectively, effectively separated half of Cr and almost all of Fe from mixed metals. The subsequent second-stage leaching achieved leaching rates of 75.03%, 81.05%, 81.39%, 1.02%, and 0% for Cu, Ni, Zn, Cr, and Fe that further separated Cu, Ni, and Zn from mixed metals. With the stabilized two-stage ultrasonically enhanced leaching, the resulting over all recovery rates of Cu, Ni, Zn, Cr and Fe from electroplating sludge could be achieved at 97.42%, 98.46%, 98.63%, 98.32% and 100% respectively, with Cr and Fe in solids and the rest of the metals in an aqueous solution discharged from the leaching system. The process performance parameters studied were pH, ultrasonic power, and contact time. The results were also confirmed in an industrial pilot-scale test, and same high metal recoveries were performed.
Based on theoretical calculations, laboratory simulation research and industrial production data analysis combined with characterisations such as metallographic microscope, scanning electron ...microscope (SEM), transmission electron microscope (TEM) and microhardness testing, this study investigated the state of occurrence and the precipitation law of vanadium (V) in microalloyed steel to determine a reasonable production process for V microalloyed steel. The results showed that the V(C,N) precipitation phase was the main form of V in microalloyed steel that precipitated after the transformation of austenite to ferrite. The amount of V precipitation was positively correlated with the amount of V that was added. However, the precipitation temperature was not significantly correlated with the amount added. When the V content increased from 0.03% to 0.06%, the initial precipitation temperature only increased by 23 °C. The coiling temperature was identified as the core factor affecting the strength of V microalloyed steel. When the effects of precipitation strengthening and microstructure strengthening were considered, as the coiling temperature decreased, the strength first increased, then decreased and finally increased again. Under different processing conditions, the strengthening of vanadium in the material increased first and then decreased as the temperature decreased (700-200 °C). The corresponding temperatures for the best strengthening effect of aging treatment, industrial statistical data and simulating coiling were 550, 470 and 400 °C, respectively. The difference between laboratory research results and industrial production was found. When V precipitation strengthening was used to improve material properties, it was necessary to determine a reasonable quantity of V to add and the production process, according to different alloy systems, to make more effective use of V microalloyed resources.
The structural evolution of poly(butylene succinate) (PBS) during tensile deformation was investigated by in situ synchrotron X-ray scattering. Crystal transition during stretching was identified at ...30–90 °C. An increase of long period was observed during the α–β crystal transition, which was attributed to the increase of both amorphous layer thickness and crystalline layer thickness (lamellar thickness). The reversibility of crystal transition and correlation of lamellar thickening with crystal transition were confirmed by a “step-cycle” deformation measurement. The variation of the amorphous layer was partially recoverable, while the variation of lamellar thickness was nearly fully recoverable. The different repeating length in unit cell along the chain axis in different crystal forms resulted in the variation of the lamellar thickness. The different recoverability of structural parameters was interpreted by the different dynamics of the amorphous and crystalline phase.
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•The early Paleozoic gold mineralization exists in the Zhengguang Au deposit.•The mineralization has genetic relationship with the tonalite porphyry.•The ore-forming elements were ...derived from the mantle-sourced tonalite porphyry.•The deposit was formed in a porphyry-to-epithermal transition environment.
The Zhengguang gold deposit in the Duobaoshan ore field, hosted in volcanic rocks of the Middle Ordovician Duobaoshan Formation, is one of the largest gold deposits in the Northeastern Great Xing’an Range of the Central Asian Orogenic Belt (CAOB). The deposit comprises the No. I, II and III ore zones with a total resource exceeding 35tonnes of Au, 100,000tonnes of Zn and 100 tonnes of Ag. A genetic relationship between gold mineralization and concealed tonalite porphyry is inferred based on the characteristics of cryptoexplosive breccia and hydrothermal alteration indicative of porphyry-type and epithermal mineralization. Zircon LA-ICPMS U-Pb dating reveals that the tonalite porphyry was emplaced at 462.1±1.8Ma (Middle Ordovician). The δ34SV-CDT values of sulfide minerals range from −3.0‰ to −1.7‰ with an average of −2.33‰, indicating that sulfur was mainly derived from a magmatic source. The Pb isotopic compositions (206Pb/204Pb ranging from 17.572 to 17.629, 207Pb/204Pb from 15.424 to 15.486, and 208Pb/204Pb from 37.206 to 37.418) suggest a major mantle component for Pb and, by inference, for other ore metals. Therefore, we suggest that the ore-forming elements in the Zhengguang gold deposit may be related to the mantle-sourced tonalite porphyry. On the basis of the geological characteristics and geochemical signatures documented in this study, we conclude that the Zhengguang gold deposit was formed in a porphyry to epithermal transitional environment associated with the concealed tonalite porphyry, as part of the Duobaoshan porphyry-epithermal ore system that is related to the subduction of the Paleo-Asian Ocean during the Ordovician.
Multiblock copolymers consisting of crystalline poly(butylene succinate) and amorphous poly(1,2-propylene succinate) (PBS-co-PPS) are synthesized. The microstructure of the materials is investigated ...by the combination of thermal analysis and wide-angle/small-angle X-ray scattering (WAXS/SAXS). The noncrystalline PPS blocks are found to locate predominately in the amorphous phase between crystalline lamellae of PBS. By means of in situ WAXS coupled with optical-assisted strain measurement, the deformation process of PBS-co-PPS is studied. The stiffness and strength of PBS-co-PPS decrease with increasing PPS fraction, while the strain recovery behavior of PBS-co-PPS is similar to PBS homopolymer. Transition from α crystal to β crystal is observed for all the PBS-co-PPS samples. The critical stress for α–β transition of PBS-co-PPS is determined, which is found to be independent of PPS blocks. The universal critical stress for crystal transition is interpreted through a single-microfibril-stretching mechanism.
The decoction turns into a complex multiphase system following exposure to high temperature and a complex chemical environment. However, the differences in the concentration of key active ingredients ...in different phase states and the release of drugs in sedimentary phase have yet to be elucidated. A simple ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous quantitative determination of brucine, strychnine, liquiritin, isoliquiritin, isoliquiritigenin and glycyrrhizic acid concentrations and it was applied to compare the content of different phases and measure the release characteristics of the sedimentary phase in “Glycyrrhiza glabra-Nux vomica” decoction (NGD). The results show that the method’s selectivity, precision (intraday and interday ≤ 2%), matrix effect (101–108%), recovery and stability results were acceptable according to the guidelines. The method is sensitive and reliable. The content determination results show that the most toxic strychnine in the sedimentary phase accounted for 75.70% of the total components. The different components exhibited differential release in different media, and its components were released in the artificial intestinal fluid up to 81.02% in 12 h. Several components conformed to the primary kinetic model and the Ritger–Peppas model, and the most toxic compound exhibited slow release, thus conforming to the Ritger–Peppas model. This study provides a standard of reference for studies investigating reduction in toxicity of the combination of Glycyrrhiza glabra (Glycyrrhiza glabra L.) and Nux vomica (Strychnos nux-vomica L.).
