New method for calculating the windward area of irregular fragments.

Average windward area is an important index for calculating the trajectory, velocity attenuation and terminal effect of explosive fragments. In order to solve the problems that existing theoretical method cannot calculate windward area of irregular fragment and experiment method is not convenient for automatic calculation and has low accuracy, a Monte Carlo subdivision projection simulation algorithm is proposed. The average windward area of arbitrary shaped fragments can be obtained with coordinate translation, random rotation, plane projection, convex-hull triangulation, concave boundary searching and sorting with maximum edge length constraint, subdivision area calculation, and averaging by thousands of cycles. Results show that projection area obtained by the subdivision projection algorithm is basically the same as that obtained by software method of computer aided design. Moreover, the maximum calculation error of the algorithm is less than 7%, and its accuracy is much higher than that of the equivalent ellipsoid method. The average windward area calculated by the Monte Carlo subdivision projection simulation algorithm is consistent with theoretical formula for prefabricated fragments, and the error is less than 3%. The convergence and accuracy of the Monte Carlo subdivision projection algorithm are better than those of the icosahedral uniform orientation method.

The σ+π dual aromaticity of typical bi-tetrazole ring molecule TKX-50.

Two complexes of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) were employed to evaluate the aromaticity of their tetrazole rings via deep analysis such as the electronic structure, the ZZ component of the natural chemical shielding tensor (NICSZZ) and component orbitals, localized orbital locator purely contributed by σ-orbitals (LOL-σ) and localized orbital locator purely contributed by π-orbitals (LOL-π), the anisotropy of the induced current density (AICD) and the ZZ component of iso-chemical shielding surface (ICSSZZ) of these tetrazole rings thereof. The conclusion shows: that all tetrazole rings and bi-tetrazole rings in complexes have strong σ and a comparable strength π double aromaticity; all these magnetic shields almost symmetrically increase from the central axis to the tetrazole ring atoms; tetrazole rings in complex II show a little stronger dual aromaticity than that in complex I mainly due to the different orientation of the fragment 2 encompassing two hydroxylamine groups resulting in different effects on the contributions of σ orbitals and π orbitals to total aromaticity of tetrazole rings thereof; the difference in aromaticity is fundamentally caused by the atoms O with stronger electron-withdrawing than atom N in fragment 2 interact with bi-tetrazole ring through O in complex I but through N in complex II.

Theoretical study on intra-molecule interactions in TKX-50.

To fully and deeply understand the weak interactions in the gaseous structure of the TKX-50 molecule, two conformations I and II of the TKX-50 molecule confirmed in a crystal cell were optimized at the B3LYP/6-311g(d,p) level in the gas state, and the single point energy of the optimized structure was calculated at the M06-2X/ma-TZVPP level. Analyzing methods for weak interactions such as the interaction region indicator (IRI), topological basin analysis, and the extended transition state-natural orbitals for chemical valence (ETS-NOCV) theory with the help of Multiwfn code were employed to reveal the corresponding intramolecular weak interactions. The results showed that there were 5 kinds of intramolecular weak interaction in both conformations. They are two types of H bond, two types of intra-ring weak interaction, and one type of O-N bond within the molecular fragment containing the bis-tetrazole ring. The combined effect of all these weak interactions holds the bis-tetrazole ring of TKX-50 retaining an almost coplanar configuration. Meanwhile, the strength of these weak interactions is significantly different in conformation I and conformation II. The most obvious difference is that conformation II has a significant H transfer between intramolecular fragments due to the mirror rotation of almost 180° of cations (NH3OH)+ perpendicular to the N-O bond axis thereof as compared to the reference conformation I. This conformational difference not only makes the weak interaction between the two conformations very different but also forms a quasi-covalent bond in conformation II with much larger bonding energy than other H bonds, thus resulting in conformation II having lower electron energy and more stable geometry. In addition, the order of breaking various H bonds in the combustion decomposition process of TKX-50 is deduced by comparing various H bonds.

Self-cementation of gold tailings activated by nonthermal plasma irradiated calcium (hydro)oxide.

The alkalinity of CaO is commonly insufficient in alkali-activating raw soils or minerals for the formation of cementation or geopolymerization. In this study, nonthermal plasma (NTP) irradiation was employed to activate traditional CaO to enhance its efficacy in alkali activation and further intensify the self-cementation of gold tailings. The solidification/stabilization (S/S) of the gold tailings-based matrix activated by NTP-CaO was better than that of CaO. The NTP irradiation enhanced the surface hydroxyl groups and oxygen atoms, decreased the binding energy, formed nanoparticles, and significantly changed the morphologies of the calcium activator. The dosage of the NTP-irradiated CaO (NTP-CaO) directly affected the self-cemented solidification/stabilization of gold tailings. The Johnson-Mehl-Avrami-Kolmogorov model was appropriate for analysing the NTP-CaO-activated geopolymerization kinetics of gold tailings. Three-dimensional (3D) structural minerals covered with small pores were determined in the NTP-CaO-activated cemented samples. The employment of NTP-CaO facilitated the formation of aluminosilicate geopolymers during the self-cementation of gold tailings according to comprehensive characterization strategies. The study achieves the efficient self-remediation of gold tailings by activating calcium precursors, which further solves the contradiction between salinization and alkali activation in the field of noncalcined cementitious materials.

Nonthermal plasma-irradiated polyvalent ferromanganese binary hydro(oxide) for the removal of uranyl ions from wastewater.

Nonthermal plasma (NTP) irradiation was employed to adjust the morphological structures and valence distribution of ferromanganese (Fe-Mn)-based binary hydro (oxide) to enhance the heterogeneous adsorption of uranyl ions. The output voltage and the liquid-plate distance played a more vital role among the NTP factors in the irradiation system in influencing the polyvalent Fe-Mn binary hydro (oxide) (poly-Fe-Mn). The formation of plates, flakes, and nanoscale nodules was specifically observed, which caused more pores and fractures in the poly-Fe-Mn binary hydro (oxide). The poly-Fe-Mn performed explicitly better in the adsorption of uranium ions in comparison with the counterpart of the Fe-Mn, which was appropriately fitted by the pseudofirst-order kinetic and Elovich models. Maximum equilibrium adsorption capacities of 663.92 and 923.45 mg/g were obtained for the Fe-Mn and poly-Fe-Mn binary hydro (oxides) toward U ions in the orthogonal design, respectively. The maximum monolayer adsorption capacity achieved by the fitting of the Langmuir model was 1091.10 mg/g. Both physisorption and chemisorption contributed to the heterogeneous process of the poly-Fe-Mn toward uranium ions. The employment of NTP irradiation changed the monolayer adsorption of the traditional Fe-Mn materials and diversified the reaction mechanisms between the interface of the Fe-Mn materials and uranium ions. The elements, including O, N, and U exhibited higher compatibility and overlapped in the samples. The highly effective capture of uranium ions from the solution by the poly-Fe-Mn binary hydro (oxide) was mainly related to the chemical deposition of O and N radicals.

Effect of metal oxides on the light radiation intensity of Ba(NO3)2/Mg-containing pyrotechnic mixtures combustion.

Studying how to improve the performance of illuminating agents to meet the requirements of ammunition miniaturization of great importance. In this study, a simple method for increasing light radiation intensity through the adding of metal oxides was developed and tested. Results revealed that the metal oxides had a very strong effect on the light radiation intensity of the reaction system. Optical radiation intensity increased by 17.8%, - 5.4% and 25.9% after the addition 5% of MgO, Al2O3 and BaO to the Ba(NO3)2/Mg reaction system, respectively. This phenomenon may be related to the light radiation characteristics and reactivity of the metal oxide itself, as well as the temperature at which the added metal oxide can be excited to radiate light intensity.

Microwave irradiation coupled with zero-valent iron that enhances the composite geopolymerization of chromite ore processing residue and its mechanisms.

In this work, microwave (MW) irradiation was employed to enhance the zero-valent iron (ZVI)-dominated de-contamination of chromite ore processing residue (COPR). A coupling system and the traditional two-step procedure were both conducted to evaluate the effects of MW irradiation on the reduction and the incorporation of COPR into the composite materials-based geopolymers. The factors including the ratios of liquid to solid, the mass ratios of ZVI to COPR, and the acid dosage had some obvious influence on the reduction of COPR in the MW system. The compressive strengths of 31.54 and 41.56 MPa were determined from the two-step procedure and the coupling system at the COPR dosage of 10% (mass ratio), respectively. The employment of MW irradiation not only strengthened the formation of the geopolymer matrices but also improved the chemical stabilization of Cr species in the solidified blocks. The coupled process was more conducive to incorporating the treated COPR into the geopolymer-based crystalline microstructures compared with the subsequent usage of ZVI reduction and MW irradiation.

A green rust-coated expanded perlite particle electrode-based adsorption coupling with the three-dimensional electrokinetics that enhances hexavalent chromium removal.

A green rust-coated expanded perlite (GR-coated Exp-p) microelectrode was synthesized and incorporated into a column-mode three-dimensional electrokinetic (3D-EK) platform to effectively pursue a continuous Cr(VI) removal from the aqueous solution. Brucite-like layers of GR were decorated onto the Exp-p material. The molar ratio of Fe(II) to Fe(III) played a most vital role among the three synthesis factors in influencing the performance of the particle electrode. For the equilibrium adsorption experiments, the target maximum adsorption capacity of 122 mg/g was predicted by a target optimizer and desirability function at the conditions following the pH of 4.7, the initial concentration of 172.4 mg/L, the dosage of 0.28 g/L, and the temperature of 28.96 °C, respectively. SO42-, Cl-, and NO3- fiercely competed with Cr(VI) anions in the acidic conditions for the locally positive sites. A low concentration and a slow flow were favored in the column-mode 3D-EK platform. The pseudo-first-order and Langmuir models were suitable for describing the kinetics and isotherms of the adsorption process, respectively. Cr(VI) anions were electrostatically attracted to the silanol groups and GR surface of the adsorbent, subsequently reduced in both heterogeneity and homogeneity, and finally immobilized by coordinating with silanediol groups and silanetriol groups.

Hybrid CoO Nanowires Coated with Uniform Polypyrrole Nanolayers for High-Performance Energy Storage Devices.

Transition metal oxides with high theoretic capacities are promising materials as battery-type electrodes for hybrid supercapacitors, but their practical applications are limited by their poor electric conductivity and unsatisfied rate capability. In this work, a hybrid structure of CoO nanowires coated with conformal polypyrrole (Ppy) nanolayer is proposed, designed and fabricated on a flexible carbon substrate through a facile two-step method. In the first step, porous CoO nanowires are fabricated on flexible carbon substrate through a hydrothermal procedure combined with an annealing process. In the second step, a uniform nanolayer of Ppy is further coated on the surfaces of the CoO nanowires, resulting in a hybrid core-shell CoO@Ppy nanoarrays. The CoO@Ppy aligned on carbon support can be directly utilized as electrode material for hybrid supercapacitors. Since the conductive Ppy coating layer provides enhanced electric conductivity, the hybrid electrode demonstrates much higher capacity and superior rate capability than pure CoO nanowires. As a further demonstration, Ppy layer can also be realized on SnO2 nanowires. Such facile conductive-layer coating method can be also applied to other types of conducting polymers (as the shell) and metal oxide materials (as the core) for various energy-related applications.

Facile Activation of Commercial Carbon Felt as a Low-Cost Free-Standing Electrode for Flexible Supercapacitors.

High cost, low capacitance, and complicated synthesis process are still the key limitations for carbon-negative materials to meet their industrial production and application in high-energy-density asymmetric supercapacitors (ASCs). In this work, we demonstrate the facile preparation of ultrahigh-surface-area free-standing carbon material from low-cost industrial carbon felt (CF) and its application for flexible supercapacitor electrode with outstanding performance. Through a simple freeze-drying-assisted activation method, the as-prepared activated CF (ACF) was endowed with satisfactory flexibility, ultrahigh specific surface area of 2109 m2 g-1, good electric conductivity (311 S m-1), and excellent wettability to aqueous electrolyte. Owing to these merits, the ACF expressed an ultrahigh areal capacitance of 1441 mF cm-2, a high specific capacitance ( Cs) of 280 F g-1 based on the mass of the whole electrode, and an impressive cycling stability (87% retention after 5000 cycles). When applied as a flexible freestanding electrode for MnO2//ACF ASCs, the ACF-based device provided satisfactory areal energy densities of 0.283 and 0.104 mWh cm-2 in aqueous and quasi-solid electrolytes, respectively. The values outperform many previously reported carbon-based electrochemical devices. The low cost of raw material and the facile fabrication process, together with the high electrochemical performance, make our ACF electrode highly applicable for the mass production of flexible energy-storage devices.

Energy-Saving Synthesis of MOF-Derived Hierarchical and Hollow Co(VO3)2-Co(OH)2 Composite Leaf Arrays for Supercapacitor Electrode Materials.

A one-step and energy-saving method was proposed to synthesize hierarchical and hollow Co(VO3)2-Co(OH)2 composite leaf arrays on carbon cloth, which expressed high capacitance (522 mF cm-2 or 803 F g-1 at the current density of 0.5 mA cm-2), good rate capability (79.5% capacitance retention after a 30-fold increase of the current density) and excellent cycling stability (90% capacitance retention after 15 000 charge-discharge cycles) when tested as a supercapacitor electrode.

The regulatory effects of L. plantarum peptidoglycan microspheres on innate and humoral immunity in mouse.

OBJECTIVE: To study the effects of Lactobacillus Plantarum cell wall peptidoglycan (LPG) microspheres on mouse intestinal flora changes, peptidoglycan recognitions protein (PGRP) and cytokines expression levels. METHOD: Plate counting was used for enumeration of the intestinal flora. Real-time PCR was used for quantification PGRP in different tissues. Cytokines content were determined by ELISA kits. RESULT: The mouse administered orally with LPG microspheres showed significantly higher number of Lactobacillus and Bifidobacterium in caecum contents (p < 0.01). The amount of PGRP expression in different organs was highest in LPG microspheres-treated group. IL-4, 12, IFN-γ, TNF-α contents in serum from LPG microspheres-treated mouse were significantly higher than those in normal saline-treated group (p < 0.01). CONCLUSIONS: This study shows that the LPG microspheres can regulate intestinal flora imbalance and improve systemic immunity, improve both Th1 and Th2 immune response, which provide some basis for the use of LPG as potential adjuvants.

Voltammetric determination of tryptophan at a single-wall carbon nanotubes modified electrode.

A single-wall carbon nanotubes (SWNT)-film coated glassy carbon electrode (GCE) was described for the determination of tryptophan. In pH 2.5 Na2HPO4-citric acid buffer, tryptophan yields a well-defined and very sensitive oxidation peak at about 1.08 V at the SWNT-film coated GCE. The oxidation peak current increases greatly and the peak potential shifts toward more negative direction at the SWNT-modified GCE in contrast to that at the bare GCE. Under optimized conditions, the oxidation peak current is proportional to the concentration of tryptophan over the range from 4 x 10(-8) to 1 x 10(-5) mol/L. The detection limit is 1 x 10(-8) mol/L at 3 min of accumulation. Using the proposed method, tryptophan in the human's blood serum samples was determined.

Voltammetric determination of tinidazole using a glassy carbon electrode modified with single-wall carbon nanotubes.

An electrochemical method based on a single-wall carbon nanotubes (SWNTs) film-coated glassy carbon electrode (GCE) was described for the determination of tinidazole. In a 0.1 M Britton-Robinson buffer with a pH of 10.0, tinidazole yields a very sensitive and well-defined reduction peak at -0.78 V (vs. SCE) on a SWNTs-modified GCE. Compared with that on a bare GCE, the reduction peak of tinidazole increases significantly on the modified GCE. Thus, all of the experimental parameters were optimized and a sensitive voltammetric method is proposed for tinidazole determination. It is found that the reduction peak current is proportional to the concentration of tinidazole over the range from 5 x 10(-8) to 4 x 10(-5) M, and that the detection limit is 1 x 10(-8) M at 3 min open-circuit accumulation. This new analysis method was demonstrated with tinidazole drugs.

Simultaneous determination of 2-nitrophenol and 4-nitrophenol based on the multi-wall carbon nanotubes Nafion-modified electrode.

In this work, multi-wall carbon nanotubes (MWNT) were conveniently dispersed into Nafion-ethanol solution, and the MWNT-Nafion-modified glassy carbon electrode (GCE) was described for the simultaneous determination of 2-nitrophenol and 4-nitrophenol. At pH 4.0 phosphate buffer, the reduction peak currents of 2-nitrophenol (at -0.8 V) and 4-nitrophenol (at -1.0 V) increase significantly at the MWNT-Nafion-modified GCE, in comparison with that at the Nafion-modified GCE and the bare GCE. The experimental parameters, such as solution pH of phosphate buffer, accumulation potential and time, and the amounts of MWNT-Nafion onto the GCE surface, were optimized. The reduction peak currents are linear with the concentration of 2-nitrophenol from 5 x 10(-8) to 1 x 10(-5) mol L(-1) and with that of 4-nitrophenol from 1 x 10(-7) to 1 x 10(-5) mol L(-1). The detection limits after 3-min accumulation are 1 x 10(-8) mol L(-1) for 2-nitrophenol and for 4 x 10(-8) mol L(-1) for 4-nitrophenol. This modified electrode was applied to direct determination of 2-nitrophenol and 4-nitrophenol in lake water samples.

Anodic stripping voltammetric determination of mercury by use of a sodium montmorillonite-modified carbon-paste electrode.

A sodium montmorillonite (SWy-2)-modified carbon-paste electrode has been examined for determination of trace levels of mercury. Because of its strong cation-exchange and adsorptive characteristics, SWy-2 greatly improves the sensitivity of determination of Hg(2+). Hg(2+) is preconcentrated and reduced on the modified electrode surface at -0.40 V and then stripped from the electrode surface during the positive potential sweep. The conditions used for determination, e.g. supporting electrolyte, pH, amount of SWy-2, accumulation potential, and accumulation time, were optimized. The peak current was linearly dependent on the concentration of mercury from 1 x 10(-9) to 5 x 10(-7) mol L(-1). The detection limit (signal-to-noise ratio=3) was 1 x 10(-10) mol L(-1) after accumulation for 6 min. When the SWy-2-modified carbon-paste electrode was used to detect mercury in water samples the average recovery was 101.11%.