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A large number of experiments show that PtCu catalyst has a good catalytic effect on methanol decomposition. Therefore, density functional theory (DFT) was used to further study the dehydrogenation of methanol catalyzed by PtnCum (n = 1–3, m = 0–2). The energy diagrams of O-adsorption path and H-adsorption path were drawn. By calculation, the Pt is the active site of the whole reaction process, and the barrier energy of the rate-determining step is 11.09 kcal mol−1 by Pt2Cu, which is lower than that of Pt3 and PtCu2. However, the complete dehydrogenation product of methanol, CO, is easier to dissociate from PtCu2 clusters than from Pt3 and Pt2Cu clusters. Therefore, Cu doping can improve the catalytic activity and anti-CO toxicity of Pt to a certain extent.

We have comparatively investigated the adsorption behaviors of Sc atom on the external and internal surfaces of the pristine, Stone-Wales (SW), and single-vacancy (SV) defect nanotubes based on the density functional theory. Our results reveal that the stability of Sc atom onto the external and internal surfaces of the carbon nanotubes is in following orders by defect: SV>SW1>SW2>pristine (external surfaces), SV>SW2>SW1>pristine (internal surfaces). To explore the reactivity of Sc@CNT/SW/SV complexes which can serve as a gas sensor or a catalyst in direct methanol fuel cell (DMFC), the interaction between a CO molecule and Sc@CNT/SW/SV is also examined. The SV defect in carbon nanotubes can make the confined Sc atom with good CO adsorption property, while the confined Sc in the SW defect carbon nanotube has good anti-CO poisoning. By our studies, it plays an important guidance role in improving the activity of metal catalyst and the sensitivity and stability of metal particles to functional molecules, and provides the theoretical basis for designing new carbon nanotube-based metal catalyst.

The targeting protein for Xenopus kinesin-like protein 2 (TPX2) has been demonstrated to be associated with the tumourigenesis of many cancers. In the present study, we investigated the role and preliminary mechanism of TPX2 in the resistance of lung squamous carcinoma to radiation therapy. The results showed that SK-MES-1R and NCI-H226R cells were more resistant to X-ray irradiation than the parental cells (SK-MES-1 and NCI-H226). Moreover, TPX2 was upregulated in the radioresistant cells compared with the parental cells. TPX2 knockdown significantly decreased TPX2 expression in SK-MES-1 cells, while TPX2 overexpression increased TPX2 expression in NCI-H226 cells compared with the corresponding control cells. TPX2 knockdown enhanced the radiosensitivity of SK-MES-1 and promoted cell apoptosis following exposure to irradiation, whereas TPX2 overexpression decreased the radiosensitivity of NCI-H226 and inhibited cell apoptosis. In in vivo studies, the combination of TPX2 knockdown and irradiation significantly inhibited tumour growth, decreased tumour weight, downregulated TPX2 expression in tumour tissue and induced cell apoptosis in nude mice, while TPX2 overexpression exerted an opposite effect. Our results indicated that TPX2 was correlated with cell radioresistance and it might be served as a therapeutic target to enhance cell radiosensitivity in the radiation therapy of lung squamous carcinoma.

The mechanism of the cyclic reaction N2O(X1Σ+) + CO(1Σ+) → N2(X1Σg+) + CO2(1Σg+) catalysed by Y+ ions has been investigated on both singlet and triplet potential energy surfaces. The reactions were investigated by means of the relativistic effective core potential together with the Stuttgart basis sets on Y and the UB3LYP/6-311G** level of theory on non-metal atoms. The crossings involved between the singlet and triplet energy surfaces have been investigated by means of the intrinsic reaction coordinate approach used by Yoshizawa et al. Furthermore, both steps of the reaction are exothermic and the overall reaction is exothermic by 361.12 kJ mol−1.

Based on the DFT, the adsorption and dehydrogenation reactions of methanol over PtCo@SV have been extensively investigated. When PtCo binary metal is adsorbed on the defect of single vacancy graphene (SV) by Co atom, its stability is obviously stronger than that of pure platinum on defect of SV. Both the H-adsorption and O-adsorption on Pt and Co sites are considered as initial reaction steps. Compared with Cu site, methanol is more likely to dehydrogenate at Pt site. Although the H-adsorption on the Pt site is weaker than the O-adsorption, the dehydrogenation by the H-adsorption path has much lower energy barrier than that by the O-adsorption path. Generally, for the H-adsorption path, the adsorption is rate determining step because of the rather low dehydrogenation barrier for the H-adsorption complex (thermodynamic control), whereas the O-adsorption path is determined by its dehydrogenation step (kinetic control). Among all the PtCo@SV investigated, PtCo-2 and PtCo-3 are found to enhance the activity of catalytic dehydrogenation by the H-adsorption path on the Pt site as compared with that on Pt2@SV, which explains why PtCo catalyst has become the focus of fuel cell research in recent years.

The reaction mechanism of the gas-phase PtCH2 + with H2S has been systematically investigated on the doublet and quartet potential energy surfaces at BPW91/6-311++G(2d, p)∪ SDD level. The Pt in PtCH2 + prefers to attack S–H bond in H2S. For PtCH2 + + H2S reaction, the potential energy surfaces (PESs), including three reaction pathways of hydrogen (including one and two hydrogen elimination) and methane elimination, have been explored and characterized. By contrast with hydrogen elimination, methane elimination reaction channel is energetically favorable, which is in good agreement with the experimental observation. The optimal S–H bond activation is the first step, followed by cleavage of Pt–C and Pt–S bond. About the path a and b, the lowering of activation barrier is mainly caused by the more stabilizing transition state interaction $$\varDelta E_{\text{int}}^{ \ne }$$ , which is the actual interaction energy between the deformed reactants in the transition state.

The gas-phase reaction of C–H bond activation in ethane by CrO 2 + has been investigated using density functional theory (DFT) at the UB3LYP/6-311G(2d,p) level. Our results reveal that the activation process is actually a spin-forbidden reaction. The involved crossing point between the doublet and quartet potential energy surfaces (PES) has been discussed by two well-known methods, i.e., intrinsic reaction coordinate (IRC) approach for crossing point (CP) and Harvey’s algorithm for minimum energy crossing point (MECP). The obtained single ( P 1 ISC = 2.48 × 10 −3 ) and double ( P 1 ISC = 4.95 × 10 −3 ) passes estimated at MECP show that the intersystem crossing (ISC) occurs with a little probability. The C–H bond activation processes should proceed to be endothermic by 73.16 kJ/mol on the doublet surface without any spin change.

Platinum nanoparticles on phosphorus-doped carbon materials exhibit high electrocatalytic activity and long-time stability as shown in recent experimental studies. In the present work, we use density functional theory calculations to study the adsorption nature of atomic platinum on phosphorus-doped carbon nanotube. Our calculation results demonstrate enhancement of the binding energy of Pt on P-doped CNT compared to pristine and nitrogen-doped CNTs. This increase in binding energy primarily results from the significant orbital hybridization between Pt sd hybridized orbital and P sp hybridized orbital.

To evaluate therapeutic outcomes of intraluminal brachytherapy (ILBT) for malignant obstructive jaundice (MOJ) against stent alone. The PubMed, EMBASE, Cochrane Library, CNKI, Wan Fang, VIP and ClinicalTrials.gov databases were searched for all relevant comparative studies from the earliest available date up to 1 May 2017. Subgroup analyses were performed according to the type of study design and type of stent. Twelve studies that compared ILBT versus stent alone were eligible. A total of 641 participants with MOJ were included in our meta-analysis. A total of 340 participants were treated with intraluminal brachytherapy (ILBT); the other 301 participants were treated with biliary stent alone (stent group). ILBT was associated with lower risk of stent occlusion (OR 0.19; 95% CI 0.13–0.28; P

In the present work, density functional theory (DFT) is used to investigate the binding mechanism of atomic platinum on several heteroatom (Be, B, N, and O) doped (6, 6) single-walled carbon nanotubes. The binding abilities in ascending order by dopants are found to be pristine, nitrogen, boron, beryllium, and oxygen. The adsorption mechanisms of Pt on these nanotubes have been discussed based on the adsorption geometries, frontier orbitals, and projected density of states. Due to the unused binding site of the carbon atom created by O-doping, the O-doped CNT presents the strongest binding for atomic Pt. It is found that the degree of s-orbital of the carbon atom involved in the C–Pt bond could reflect the binding strength of Pt on these doped CNT supports.

Gas-phase CS2 activation by M+ (M = Ta, W, Re) was studied by the B3LYP density functional method.The geometries for reactants, transition states, and products were completely optimized. CS2 activation mediated by M+ (M = Ta, W, Re) were found to be a spin-forbidden process as a result of the crossing among the multistate energetic profiles. On the basis of the Hammond postulate, this was a typical two-state reactivity reaction. Among the different potential energy surfaces, the crossing points had been explored. The spin–orbit coupling (SOC) was also calculated between the electronic states of different multiplicities at the crossing point to estimate the intersystem crossing probability. For CP1, CP2, and CP4, the computed SOC constants were 80.28, 128.65, and 526.77 cm−1, which obtained by using one-electron spin–orbit Hamiltonian in Gaussian 09.

The mechanism of the cyclic reaction N2O(1∑) + CO(1∑+) → N2(1∑ g + ) + CO2(1∑ g + ) catalyzed by Re+ has been investigated on quintet and septet potential energy surfaces (PES). The reactions were studied by the B3LYP density functional method and the CCSD(T) theory. The calculated results of different PES show that the reaction proceeds in a two-step manner and spin crossing between different PES occurs. The involving crossing points (CPs) between the quintet and septet PES have been discussed by means of the intrinsic reaction coordinate approach. And the O-atom affinities testified that Re+ can capture O from N2O and transfer O atom to CO in the two spin state, which are thermodynamically allowed. Furthermore, the spin–orbit coupling (SOC) is calculated between electronic states of different multiplicities at the CPs. For CP1 and CP2, the computed SOC constants are 8.34 and 10.09 cm−1, respectively, obtained by using one-electron spin–orbit Hamiltonian in GAMESS. Therefore, the intersystem crossing at CP1 and CP2 occurs with a little probability because of the small SOC involved.

The mechanism of the cyclic reaction N 2 O ( 1 Σ ) + CO ( 1 Σ + ) → N 2 ( 1 Σ g + ) + CO 2 ( 1 Σ g + ) catalyzed by Co+ has been investigated on both triplet and quintet potential energy surfaces (PESs). The reactions were studied by the UB3LYP density functional method and the CCSD(T) theory. The calculated results of different spin PES show that the reaction proceeds in a two-step manner and spin crossing between different PES occurs. The involved crossing between the PES has been discussed by means of the intrinsic reaction coordinate approach used by Yoshizawa et al., and the crossing points were located. Furthermore, the spin–orbit coupling (SOC) is calculated between electronic states of different multiplicities at the crossing points to estimate the intersystem crossing probabilities.

In this work, the enzymatic degradation of poly(butylene succinate- co -butylene terephthalate) (PBST) copolyesters was studied using the lipase from Pseudomonas (Lipase PS ® ). The biodegradation behavior was found to strongly depend on the overall impacts of several important factors as the BT comonomer structure and molar content, thermal characteristics, morphology, the enzyme-substrate, and so forth. Further, the biodegraded residual film samples were allowed to be analyzed by means of gel permeation chromatography (GPC), proton nuclear magnetic resonance ( 1 H NMR), differential scanning calorimeter (DSC), small angle X-ray scattering (SAXS), and scanning electron microscope (SEM). On the experimental evidences, an exo-type mechanism of enzymatic chain hydrolysis preferentially occurring in the amorphous region was suggested for the PBST film samples.

In this study, thermal degradation and their related kinetics have been investigated mainly by means of thermal gravimetrical analyzer (TGA) under the dynamic nitrogen and air atmospheres for the chemically prepared biodegradable aliphatic–aromatic copolyesters of poly(butylene succinate-co-butylene terephthalate) (PBST). To further shed new lights on the comonomer molar composition and experimental condition dependences of thermal degradation kinetics, the as-known Friedman model was at first applied to quantitatively evaluate the kinetic parameters in terms of activation energy (E), degradation reaction order (n) and the frequency factor (Z). The results clearly demonstrated that thermal stabilities of these PBST copolyesters were substantially enhanced with the incorporation of more rigid butylene terephthalate comonomer, and tended to be much better in nitrogen than in air. Furthermore, the Friedman, Freeman–Carroll and Chang models were concurrently employed to quantitatively evaluate the thermal degradation kinetic parameters of the PBST copolyesters in nitrogen at different heating rates of 1, 2 and 5 K/min. It was found that the thermal degradation kinetic parameters for the PBST copolyesters were strongly dependent on the heating rate and calculating models. In addition, life-time parameters of the biodegradable PBST copolyesters were first calculated to predict the maximum usable temperatures, and this would be useful for practical application of these new bio-based green plastics.

In this work, new investigations on the effect of comonomer sequential structure on the thermal and crystallization behaviors and biodegradability have been implemented for the biodegradable poly(butylene succinate-co-butylene terephthalate) (PBST) as well as aliphatic poly(butylene succinate) (PBS). At first, these copolyesters were efficiently synthesized from dimethyl succinate and/or dimethyl terephthalate and 1,4-butanediol via condensation polymerization in bulk. Subsequently, their molecular weights and macromolecular chain structures were analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. By means of differential scanning calorimeter (DSC) and wide-angle X-ray diffractometer (WAXD), thermal and crystallization behaviors of these synthesized aromatic-aliphatic copolyesters were further explored. It was demonstrated that the synthesized copolyesters were revealed to have random comonomer sequential structures with thermal and crystallization properties strongly depending on their comonomer molar compositions, and that crystal lattice structures of the new crystallizable copolyesters shifted from the monoclinic crystal of semicrystalline PBS to triclinic lattice of the poly(butylene terephthalate) (PBT) with increasing the terephthalate comonomer composition, and the minor comonomer components were suggested to be trapped in the crystallizable component domains as defects. In addition, the enzymatic degradability was also characterized for the copolyesters film samples. (c) 2006 Wiley Periodicals, Inc.

Containerized Chinese fir (Cunninghamia lanceolata (Lamb) Hook) were reared from seed at four fertilizer levels (0, 15, 45, 75 mg N seedling-1 season-1) and two topdressing schedules (conventional or exponential) for a 22-week greenhouse rotation to assess growth, nutrition and nutrient loading capacity of seedlings. Extra P supplemented high fertilization (or nutrient loading) treatments to test for induced deficiency of this element. The schedule and rate of fertilization significantly affected growth and nutrient dynamics of the seedlings. Steady-state nutrition and superior growth performance were achieved by seedlings fertilized exponentially at the operational dose (15 mg N), yielding 23, 72 and 52% more in respective biomass, N uptake and P uptake than seedlings fertilized conventionally at the equivalent dose. The improved growth and fertilizer efficiency were attributed to close synchronization of exponential nutrient supply with exponential growth and nutrient demand of plants. High dose exponential fertilization (45 and 75 mg N) induced steady state-nutrition late in the season, increasing seedling N and P uptake by 72–83% and 50–96% compared to low dose exponential fertilization, demonstrating effective nutrient loading of plants without changing biomass. The extra P stimulated P uptake without altering growth or N uptake, thus P was probably not limiting during the greenhouse culture despite high N additions.