Theoretical prediction of new noble-gas molecules FNgBNR (Ng = Ar, Kr, and Xe; R = H, CH3, CCH, CHCH2, F, and OH).

We have computationally predicted a new class of stable noble-gas molecules FNgBNR (Ng = Ar, Kr, Xe; R = H, CH3, CCH, CHCH2, F, and OH). The FNgBNR were found to have compact structures with F-Ng bond lengths of 1.9-2.2 Å and Ng-B bond lengths of ~1.8 Å. The endoergic three-body dissociation energies of FNgBNH to F + Ng + BNH were calculated to be 12.8, 31.7, and 63.9 kcal mol(-1), for Ng = Ar, Kr, and Xe, respectively at the CCSD(T)/CBS level. The energy barriers of the exoergic two-body dissociation to Ng + FBNH were calculated to be 16.1, 24.0, and 33.2 kcal mol(-1) for Ng = Ar, Kr, and Xe, respectively. Our results showed that the dissociation energetics is relatively insensitive to the identities of the terminal R groups. The current study suggested that a wide variety of noble-gas containing molecules with different types of R groups can be thermally stable at low temperature, and the number of potentially stable noble-gas containing molecules would thus increase very significantly. It is expected some of the FNgBNR molecules could be identified in future experiments under cryogenic conditions in noble-gas matrices or in the gas phase.

Theoretical prediction on the structures and stability of the noble-gas containing anions FNgCC- (Ng=He, Ar, Kr, and Xe).

We have made high-level theoretical study on a new type of noble-gas (Ng) containing anions FNgCC(-). The calculated short Ng-CC bond lengths of 1.13, 1.77, 1.89, and 2.04 Šfor Ng=He, Ar, Kr, and Xe, respectively, and the electron density distributions indicated strong covalent interactions between the Ng and CC induced by the polarizing fluoride ion. Except for FHeCC(-), the structures of all other FNgCC(-) were predicted to be linear. The intrinsic stability of the FNgCC(-) was studied by calculating the energies of the three-body dissociation reaction: FNgCC(-) → F(-) + Ng + CC and by calculating the energy barriers of the two-body dissociation reaction: FNgCC(-) → Ng + FCC(-). The results showed that FNgCC(-) (Ng=Ar, Kr, Xe) could be kinetically stable in the gas phase with the three-body dissociation energies of 17, 37, and 64 kcal/mol and two body-dissociation barriers of 22, 31, and 42 kcal/mol, respectively, at the coupled-cluster single double (triple)/aug-cc-pVQZ level of theory. The structures and the stability were also confirmed using the multi-reference CASPT2 calculation. Future experimental identification of the FNgCC(-) anions is expected under cryogenic conditions.

Benchmark of density functional theory methods on the prediction of bond energies and bond distances of noble-gas containing molecules.

We have tested three pure density functional theory (DFT) functionals, BLYP, MPWPW91, MPWB95, and ten hybrid DFT functionals, B3LYP, B3P86, B98, MPW1B95, MPW1PW91, BMK, M05-2X, M06-2X, B2GP-PLYP, and DSD-BLYP with a series of commonly used basis sets on the performance of predicting the bond energies and bond distances of 31 small neutral noble-gas containing molecules. The reference structures were obtained using the CCSD(T)∕aug-cc-pVTZ theory and the reference energies were based on the calculation at the CCSD(T)∕CBS level. While in general the hybrid functionals performed significantly better than the pure functionals, our tests showed a range of performance by these hybrid functionals. For the bond energies, the MPW1B95∕6-311+G(2df,2pd), BMK∕aug-cc-pVTZ, B2GP-PLYP∕aug-cc-pVTZ, and DSD-BLYP∕aug-cc-pVTZ methods stood out with mean unsigned errors of 2.0-2.3 kcal∕mol per molecule. For the bond distances, the MPW1B95∕6-311+G(2df,2pd), MPW1PW91∕6-311+G(2df,2pd), and B3P86∕6-311+G(2df,2pd), DSD-BLYP∕6-311+G(2df,2pd), and DSD-BLYP∕aug-cc-pVTZ methods stood out with mean unsigned errors of 0.008-0.013 Å per bond. The current study showed that a careful selection of DFT functionals is very important in the study of noble-gas chemistry, and the most recommended methods are MPW1B95∕6-311+G(2df,2pd) and DSD-BLYP∕aug-cc-pVTZ.

[Spectrum characteristics of habitat quality changes in Gansu Province, China]. / 甘肃省生境质量变化的图谱特征.

Habitat quality is an important factor affecting regional ecosystem service value and protecting the biodiversity of the earth. Gansu Province is located in the intersection of the three nature areas in China. On the basis of quantitative estimation of the regional habitat quality in Gansu during 2000 to 2018, based on the spectrum change analysis theory and InVEST model, we explored the spatio-temporal differentiation pattern of the regional habitat quality status and its spectrum transformation and change intensity. The results showed that the habitat quality of Gansu Province generally maintained a middle level and improved slightly, showing a step-by-step change from the north to south in the spatial distribution, with the coexistence of both high and low habitat quality. The structure of habitat quality in Gansu Province was stable based on the view of the spectrum transformation, and the spectrum units which did not appear state transition were dominant in quantity. The transition of each other of those spectrum units which had occurred transition of the habitat quality, such as higher  lower, higher  high, higher  low was most obvious, with the spatial distribution in aggregation. The change intensity of habitat quality in Gansu Province presented a general tendency with active in the north and moderate in the south, presenting as active intensity area, complex intensity area, moderate intensity area, and slight intensity area from the north to south.

Volatile organic profiles and photochemical potentials from motorcycle engine exhaust.

This study surveyed emissions from 2- and 4-stroke new and in-use motorcycles. Emission tests were carried out on a dynamometer following the designated test procedure of the Economic Commission for Europe (ECE). Samples were derived during various driving stages, which included idle, acceleration, 30 km/hr cruise, 50 km/hr cruise, and deceleration. All test motorcycles (10 new and 15 in-use) complied with Taiwan Environmental Protection Administration's Phase III Motorcycle Emission Standards. The dominant volatile organic carbon (VOC) species were isopentane (53 and 295 mg/km, 2- and 4-stroke, respectively), 2-methylpentane (75 and 83 mg/km), 3-methylpentane (34 and 66 mg/km), and toluene (30 and 100 mg/km). The VOC emission factors for the 2-/4-stroke motorcycles were 311/344 (new) and 1479/433 (in-use) mg/km, respectively. In addition, the dominant carbonyl species for the new and in-use motorcycles were formaldehyde (0.4 and 0.7 mg/km, respectively), acetaldehyde (0.6 and 1.2 mg/km), and acetone (0.5 and 0.7 mg/km). The carbonyl compound emission factors for the 2- and 4-stroke motorcycles were 3.2/3.1 (new) and 5.3/4.6 (in-use) mg/km, respectively. The ozone formation potentials, based on an ECE test cycle, show that the values from the in-use motorcycles were higher than those from the new motorcycles. The dominant VOC species for the ozone formation potential were propylene (65 and 502 mg-O3/km, respectively), isopentane (98 and 501 mg-O3/km), 2-methylpentane (152 and 167 mg-O3/ km), 3-methylpentane (79 and 253 mg-O3/km), and toluene (127 and 398 mg-O3/km). Further, the dominant carbonyl species were formaldehyde (4.1 and 6.2 mg-O3/ km, new and in-use, respectively) and acetaldehyde (4.8 and 9 mg-O3/km).

Analysis of olfactory ensheathing glia transplantation-induced repair of spinal cord injury by electrophysiological, behavioral, and histochemical methods in rats.

This study examined the efficacy of transplanting olfactory ensheathing glia (OEG) in repairing spinal cord injury (SCI) using behavioral tests, retrograde labeling, as well as somatosensory and motor evoked potentials in rats. One week after surgery, motor function in OEG-treated rats was significantly superior to untreated controls (P < 0.05). Also, we found that up to 8 weeks following surgery to induce SCI, somatosensory and motor evoked potentials were found in the OEG-treated groups, but not in the transplantation and damage control groups. Retrograde labeling from the area distal to the SCI produced a higher number of labeled neurons in the ventrolateral division of red nucleus and motor cortex of OEG-treated rats compared to controls, which showed no retrograde labeling (P < 0.05). We believe that this study has important implications for characterizing the mechanisms of OEG transplantation as a treatment for SCI.