Selective separation of aromatic hydrocarbons through supported liquid membranes based on ionic liquids

Ionic liquids are emerging as alternative solvents for volatile organic compounds traditionally used in liquid–liquid extraction and liquid membrane separation. In this paper, we examine whether room-temperature ionic liquids as a membrane solution can be utilized for hydrocarbon separation by using a supported liquid membrane. Aromatic hydrocarbons, benzene, toluene and p-xylene were successfully transported through the membrane based on the ionic liquids. Although the permeation rates through the membrane based on the ionic liquids were less than those of water, the selectivity of aromatic hydrocarbons was greatly improved. The maximum selectivity to heptane was obtained using benzene in the aromatic permeation and 1-n-butyl-3-methylimidazolium hexafluorophosphate in the liquid membrane phase.     

Search for new massive particles in cosmic rays

In this paper, some unusual cosmic ray events are reviewed. They are the Yunnan event recorded in 1972 using a cloud chamber at Yunnan Cosmic Ray Station (YCRS) near Kunming, the south-west of China; the six exotic events (Kolar events) collected during 1965 to 1975 in the Kolar Gold Mine Field (KGF) in south India; and a double-core event obtained also in KGF in 1979 at a depth different from that where the other six were obtained. In addition, some interesting phenomena were also noticed: the abnormal upward muon flux observed by the MINI collaboration, and several intriguing signals seen in the proton detector in KGF. A careful kinematics analysis has shown that all these exotic events are likely to be related to a kind of heavy and slow-moving (i.e. with a Lorentz factor γ ≈ 2–5) particles produced from cosmic ray interactions. Besides, the rough flux estimates in these experiments seem to indicate that the event rate does not depend on the depth. Thus a natural hypothesis is that there is a heavy and neutral component in the cosmic rays which might be related with the long-sought weakly interacting massive particle (WIMP) - one of the most promising candidates of the dark matter of our Universe. Moreover, from the tracks seen in these events, there is also a signal of the possible existence of a kind of heavy and charged particles with a relatively long lifetime (say, longer than 10⁻⁹s) which might be the interacting products of the unknown cosmic ray particles mentioned above. We then turn to the question of how to search for these exotic particles in cosmic rays, and propose to build a dedicated magnetic spectrometer for identifying them.     

Structure of nuclei far from stability

The structure of neutron-rich unstable nuclei is discussed by focusing on three different subjects; (i) a superdeformed halo nucleus ¹¹Be studied by a deformed Woods-Saxon potential, (ii) retarded β decay due to neutron halo in ¹¹Li, and (iii) giant neutron excitations in nuclei with neutron skin.     

A mesoscale study of thermal expansion behaviors of epoxy resin and carbon fiber/epoxy unidirectional composites based on periodic temperature and displacement boundary conditions

The thermal expansion behaviors of neat epoxy resin and carbon fiber/epoxy unidirectional (UD) composites were experimentally and numerically studied in this paper. The dynamic mechanical analysis (DMA), thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and thermal conductivity measurement were used to measure the thermo-mechanical properties of epoxy resin at different temperatures. The dilatometer was used to measure the thermal strains and linear CTEs of neat epoxy resin and UD composites. In addition, a mesoscale finite element model based on the periodic temperature and displacement boundary conditions was presented to analyze the thermal expansion behaviors of UD composites. The resin-voids representative volume element (RVE) was used to calculate the thermo-mechanical properties of several kinds of resin-voids mixed matrix. From the results it can be found that the glass transition temperature of epoxy resin, porosity and fiber orientation angle have significant effects on the thermal expansion behaviors of UD composites. The mesoscale finite element analyses (FEA) have obvious advantages than various existing analysis models by comparing their predictive results. The distributions of thermal displacement, thermal stress and thermal strain were extracted between the carbon fiber, resin-voids mixed matrix and their interface, and also between the front and back surfaces of the loading direction, to further investigate thermal expansion structure effects of UD composites. This paper revealed that the mesoscale FEA based on periodic temperature and displacement boundary conditions can be also used for thermal expansion researches of other complex structure composites.     

Preparation and reactions of tetrahedrane-type clusters containing a SCoFeM (M=Mo or W) core. The single crystal X-ray structure of the cluster (μ3-S)CoFeMo(CO)8[η5-C5H4C(O)CH2CH2CO2Me]

Treatment of the monoanions {M(CO)₃[η⁵-C₅H₄C(O)CH₂CH₂CO₂Me]}⁻ with FeCo₂(CO)₉(μ₃-S) in refluxing THF gave the novel cluster complexes (μ₃-S)CoFeM(CO)₈[η⁵-C₅H₄C(O)CH₂CH₂CO₂Me] (M=Mo, 1; M=W, 2). Reactions of the cluster (μ₃-S)CoFeMo(CO)₈[η⁵-C₅H₄C(O)Me] (3) with amine derivatives 2,4-dinitrophenylhydrazine, thiosemicarbazide, (−)-5-(α-phenyl)semioxamazide and l-(+)-menthydrazide respectively at room temperature yielded four new hydrazone cluster complexes (μ₃-S)CoFeMo(CO)₈[η⁵-C₅H₄C(NR)Me] [4–7, R=NHC₆H₃-2,4-(NO₂)₂, NHC(S)NH₂, NHC(O)C(O)NHCH(Me)(C₆H₅) and NHCO₂(menthyl)]. However, cluster 1 only reacted with 2,4-dinitrophenylhydrazine to give the cluster (μ₃-S)CoFeMo(CO)₈[η⁵-C₅H₄C(NR)Me] [8, R=NHC₆H₃-2,4-(NO₂)₂] under the same conditions. Although two kinds of optically active groups have been attached to the racemic cluster, the mixture of diastereoisomers produced cannot be separated chromatographically. The ¹³C NMR showed the presence of the diastereoisomers of clusters 5 and 6. Cluster 1 has been solved by single-crystal X-ray diffraction.     

Characteristics of molecular beam epitaxy-grown GaFeAs

Diluted magnetic semiconductors GaFeAs were grown by molecular beam epitaxy and characterized. Ga_1−xFe_xAs ternary alloys were obtained at the growth temperature T_s=200 °C ranging from x=0.005 to 0.03. The effects of thermal treatment on behaviors of defects, affecting to the magnetic properties of GaFeAs layer were particularly elucidated. As-grown samples were annealed at temperatures varying from 400 to 600 °C. From the measurement of double crystal X-ray diffraction, we observed Fe-related peak which shifted to a higher diffraction angle as the Fe content increased, indicating that the lattice constant decreases with increasing Fe content. In contrast, above the annealing temperature 500 °C, the lattice constant becomes smaller than that of GaAs. Using the deep level transient spectroscopy, various defects in GaFeAs layer were observed and identified in conjunction with magnetic properties.     

Microscopic multicluster description of the 7Li7Be, 8Li8B and 9Li9C mirror nuclei

The ⁹Li and ⁹C mirror systems are investigated in a microscopic α+³H+n+n and α+³He+p+p multicluster framework using the stochastic variational method. Possibility of existence of neutron (proton) halo structure is studied. The quadrupole moment of ⁹C is predicted to be −5.04 e fm².     

An experimental and modeling study of tetramethyl ethylene pyrolysis with polycyclic aromatic hydrocarbon formation

Iso-olefins, in the C₅–C₈ range can potentially be blended with renewable gasoline fuels to increase their research octane number (RON) and octane sensitivity (S). RON and S increase with the degree of branching in iso-olefins and this is a desirable fuel anti-knock quality in modern spark-ignited direct-injection engines. However, these iso-olefins tend to form larger concentrations of aromatic species leading to the formation of polycyclic aromatic hydrocarbons (PAHs). Thus, it is important to understand the pyrolysis chemistry of these iso-olefins. In this study, a new detailed chemical kinetic mechanism is developed to describe the pyrolysis of tetramethyl ethylene (TME), a symmetric iso-olefin. The mechanism, which includes the formation of PAHs, is validated against species versus temperature (700–1160 K) measurements in a jet-stirred reactor at atmospheric pressure and in a single-pulse shock tube at a pressure of 5 bar in the temperature range 1150–1600 K. Synchrotron vacuum ultraviolet photoionization mass spectrometer (SVUV-PIMS) and gas chromatography (GC) systems were used to quantify the species in the jet-stirred reactor and in the single-pulse shock tube, respectively. The mechanism derives its base and PAH chemistry from the LLNL PAH sub-mechanism. The predictions are accurate for most of the species measured in both facilities. However, there is scope for mechanism improvement by understanding the consumption pathways for some of the intermediate species such as isoprene. The formation of 1, 2, and 3-ring aromatic species such as benzene, toluene, naphthalene and phenanthrene measured experimentally is analyzed using the chemical kinetic mechanism. It is found that the PAH formation chemistry for TME under pyrolysis conditions is driven by both propargyl addition reactions and the HACA mechanism.     

Vesicles displaying aggregation-induced emission: Fabrication and applications

Vesicles displaying aggregation induced emission are very promising in fields related to biology. In this review, we summarized recent progresses in the creation of such vesicles and their applications. The following contents are included: 1) the general background of AIE vesicles; 2) creation of AIE vesicles with synthetic covalent compounds; 3) creation of AIE vesicles with supramolecular chemistry; 4) the application of AIE vesicles in real-time imaging, visualized drug delivery, cell communication and fission-fusion process, and light-harvesting. Finally, we envision AIE vesicles may have profound impact on medical science, biological science and material science.