A Convenient Synthesis of Halogenated 2-Chloropyridines by Transformation of Halogenated 2-methoxypyridines Under Vilsmeier-Haack Conditions

Several halogenated 2-chloropyddines 2a-2h were conveniently synthesized by transformation of halogenated 2-methoxypyridines 1a-1h under Vilsmeier—Haack conditions in a yield of 50～71%.     

A comparative study of nozzle/diffuser micropumps with novel valves

This study conducts an experimental study concerning the improvement of nozzle/diffuser micropump design using some novel no-moving-part valves. A total of three micropumps, including two enhancement structures having two-fin or obstacle structure and one conventional micro nozzle/diffuser design, are made and tested in this study. It is found that dramatic increase of the pressure drops across the designed micro nozzles/diffusers are seen when the obstacle or fin structure is added. The resultant maximum flow rates are 47.07 mm3/s and 53.39 mm3/s, respectively, for the conventional micro nozzle/diffuser and the added two-fin structure in micro nozzle/diffuser operated at a frequency of 400 Hz. Yet the mass flow rate for two-fin design surpasses that of conventional one when the frequency is below 425 Hz but the trend is reversed with a further increase of frequency. This is because the maximum efficiency ratio improvement for added two-fin is appreciably higher than the other design at a lower operating frequency. In the meantime, despite the efficiency ratio of the obstacle structure also reveals a similar trend as that of two-fin design, its significant pressure drop (flow resistance) had offset its superiority at low operating frequency, thereby leading to a lesser flow rate throughout the test range.     

Modelling transportation and transformation of nitrogen compounds at different influent concentrations in sewer pipe

A mathematical model was established to describe the transportation and transformation of nitrogen compounds in the sewer pipe. In order to verify the consistency between the experimental data and model simulation data, four runs of experiments were carried out in a 21 m long, 0.15 m diameter model sewer. The results showed a good consistency between the experimental and simulation values (all correlation coefficients >0.81). According to the good consistency, it was proved that the attached heterotrophic biofilm on the sewer bottom played a dominant role on degradation of compounds in the system. Readily biodegradable substrate (S_S) decreased with the test time due to aerobic and anoxic growth of heterotrophs. Ammonia and ammonium nitrogen (S_NH) increased with the test time. But nitrate and nitrite nitrogen (S_NO) and soluble organic nitrogen (S_ND) decreased. Dissolved oxygen (S_O) declined due to the microbial consumption and subsequently increased due to reaeration, forming a sag curve. Furthermore, the transformation pathways of different compounds were identified in this study.     

Carbon dioxide-water phase equilibria results from the Wong-Sandler combining rules

A model based upon the Peng-Robinson equation of state with the Wong-Sandler mixture combining rule (W-S MCR) can correlate phase equilibria in CO₂ + H₂O. The W-S MCR requires two energy parameters for liquid behavior and one interaction parameter for gas behavior, k_ij. In this paper, we present expressions for the energy parameters which cover a wide temperature range, and we use a new procedure to obtain k_ij by relating it to experimental cross second virial coefficients, B_ij. The three-phase pressures calculated for this system using our proposed model agree with the experimental data within a fraction of 1 bar. The correlated phase behavior of CO₂ + H₂O appears to be accurate over the ranges 1 – 1000 bar and 298.15–623.15 K. The proposed model also confirms the advantage of using the W-S MCR for phase equilibrium calculations.     

Improved Theoretical Spectrum of Quasibound States and Resonances for H2(1∑g+)

The most recent ab initio potentials for H₂(¹∑g⁺), which include relativistic, adiabatic and radiative corrections, were used to calculate the spectrum of quasibound states. The levels, widths and tunneling permeability of resonant states were also studied by the quantum phase-shift method. A new set of relevant resonance states for the calculations of atomic recombination of hydrogen is indicated by the present work. In comparison with the previous studies, significant improvements have been found for the resonances.     

Thermokinetics evaluation and simulations for the polymerization of styrene in the presence of various inhibitor concentrations

Styrene is an important commodity chemical that is globally applied in various polymerization processes. The aim of this study was to obtain integrated thermokinetics and safety parameters for polymerization of styrene. We mainly used differential scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative methods to investigate thermal polymerization of styrene and styrene containing various levels of 4-tertiary-butylcatechol (TBC). The results obtained included the rate constant (k), reaction order (n), apparent activation energy (E _a), frequency factor (A), and so on, from various DSC curves and simulative methods. From DSC curves, the exothermic onset temperature (T ₀) was about 105 and 132°C for styrene and styrene containing 10 ppm TBC. On the other hand, the test results from TAM indicated that styrene polymerization displays an autocatalytic phenomenon from 50–85°C. By means of this study, the intrinsic safety of a system for styrene during transportation and storage could be established.     

Novel bone substitute composed of oligomeric proanthocyanidins-crosslinked gelatin and tricalcium phosphate

A biodegradable GTP composite composed of OPCs crosslinked gelatin with tricalcium phosphate was prepared as a novel bone substitute. The effects of the degree of crosslinking on the swelling ratio, in vitro degradation rate, and morphology of the GTP composite are discussed. Adding OPCs to GP and GTP composites markedly reduced the degradation rate, indicating that OPCs are good crosslinking reagents for gelatin. Cytotoxic tests demonstrated that OPCs, gelatin and tricalcium phosphate released from GTP composite promoted the proliferation of MG-63 cells. Results of this study suggest that the nontoxic GTP composite is suitable for use as a large defect bone substitute.     

Multiply Charged Anions,Maximum Charge Acceptance,and Higher Electron Affinities of Molecules,Superatoms,and ClustersSCI北大核心CSCD

The addition of electrons to form gas-phase multiply charged anions (MCAs) normally requires sophisticated experiments or calculations.In this work, the factors stabilizing the MCAs, the maximum electron uptake of gas-phase molecules, X, and the electronic stability of MCAs X^Q-, are discussed. The drawbacks encountered when applying computational and/or conceptual density functional theory (DFT) to MCAs are highlighted. We develop and test a different model based on the valence-state concept. As in DFT, the electronic energy, E(N, v_ex), is a continuous function of the average electron number, N, and the external potential, v_ex, of the nuclei. The valence-state-parabola is a second-order polynomial that allows extending E(N, v_ex) to dianions and higher MCAs. The model expresses the maximum electron acceptance, Q_max, and the higher electron affinities, A_Q, as simple functions of the first electron affinity, A₁, and the ionization energy, I, of the "ancestor" system. Thus, the maximum electron acceptance is Q_{max, calc} = 1 + 12A₁/7(I -A₁). The ground-state parabola model of the conceptual DFT yields approximately half of this value, and it is termed Q_{max, GS} = ${}^{1}\!\!\diagup\!\!{}_{2}\; $ + A₁/(I -A₁). A large variety of molecules are evaluated including fullerenes, metal clusters, super-pnictogens, super-halogens (OF₃), super-alkali species (OLi₃), and neutral or charged transition-metal complexes, AB_mL_n^0/+/-. The calculated second electron affinity A_{2, calc} = A₁-(7/12)(I -A₁) is linearly correlated to the literature references A_{2, lit} with a correlation coefficient R = 0.998. A₂ or A₃ values are predicted for further 24 species. The appearance sizes, n_ap^3-, of triply charged anionic clusters and fullerenes are calculated in agreement with the literature.     

Photoviscoelastic behavior of amorphous polymers during transition from the glassy to rubbery state

Tensile stress‐relaxation experiments with simultaneous measurements of Young's relaxation modulus, E, and the strain‐optical coefficient, C_?, were performed on two amorphous polymers—polystyrene (PS) and polycarbonate (PC)—over a wide range of temperatures and times. Master curves of these material functions were obtained via the time‐temperature superposition principle. The value of C_? of PS is positive in the glassy state at low temperature and time; then it relaxes and becomes negative and passes through a minimum in the transition zone from the glassy to rubbery state at an intermediate temperature and time and then monotonically increases with time, approaching zero at a large time. The stress‐optical coefficient of PS is calculated from the value of C_?. It is positive at low temperature and time, decreases, passes through zero, becomes negative with increasing temperature and time in the transition zone from the glassy to rubbery state, and finally reaches a constant large negative value in the rubbery state. In contrast, the value of C_? of PC is always positive being a constant in the glassy state and continuously relaxes to zero at high temperature and time. The value of C_σ of PC is also positive being a constant in the glassy state and increases to a constant value in the rubbery state. The obtained information on the photoelastic behavior of PS and PC is useful for calculating the residual birefringence and stresses in plastic products. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2252–2262, 2001     

Electronic specific heat of nanographite ribbons

The electronic specific heat of nanographite ribbons exhibits rich temperature dependence, mainly owing to the special band structures. The thermal property strongly depends on the geometric structures, the edge structure and the width. There is a simple relation between the ribbon width and the electronic specific heat for the metallic or semiconducting armchair ribbons. However, it is absent for the zigzag ribbons. The metallic armchair ribbons exhibit linear temperature dependence. The semiconducting armchair ribbons exhibit composite behavior of power and exponential functions. As for the zigzag ribbons, the temperature dependence of the specific heat is proportional to T^1−p. The value of p quickly increases from to 1 as the ribbon width gradually grows. The zigzag ribbons might be the first system which exhibits the novel temperature dependence. The nanographite ribbons differ from an infinite graphite sheet, which illustrates that the finite-size effects are significant.