Probing the Structural and Electronic Properties of Dirhenium Halide Clusters: A Density Functional Theory Study.

Dirhenium halide dianions received considerable attention in past decades due to the unusual metal-metal quadruple bond. The systematic structural evolution of dirhenium halide clusters has not been sufficiently studied and hence is not well-understood. In this work, we report an in-depth investigation on the structures and electronic properties of doubly charged dirhenium halide clusters Re2X82- (X = F, Cl, Br, I). Our computational efforts rely on the well-tested unbiased CALYPSO (Crystal structure AnaLYsis by Particle Swarm Optimization) method combined with density functional theory calculations. We find that all ground-state Re2X82- clusters have cube-like structures of D4h symmetry with two Re atoms encapsulated in halogen framework. The reasonable agreement between the simulated and experimental photoelectron spectrum of the Re2Cl82- cluster supports strongly the reliability of our computational strategy. The chemical bonding analysis reveals that the δ bond is the pivotal factor for the ground-state Re2X82- (X = F, Cl, Br, I) clusters to maintain D4h symmetric cube-like structures, and the enhanced stability of Re2Cl82- is mainly attributed to the chemical bonding of 5d orbital of Re atoms and 3p orbital of Cl atoms.

Structural Stability and Evolution of Medium-Sized Tantalum-Doped Boron Clusters: A Half-Sandwich-Structured TaB12- Cluster.

Transition-metal (TM)-doped boron clusters have received considerable attention in recent years, in part, because of their remarkable size-dependent structural and electronic properties. However, the structures of medium-sized boron clusters doped with TM atoms are still not well-known because of the much increased complexity of the potential surface as well as the rapid increase in the number of low-energy isomers, which are the challenges in cluster structural searches. Here, by means of an unbiased structure search, we systematically investigated the structural evolution of medium-sized tantalum-doped boron clusters, TaBn0/- (n = 10-20). The results revealed that TaBn0/- (n = 10-15) clusters adopt half-sandwich molecular geometries, with the notable exception of TaB10-, while for n = 16-18 and 19-20, the lowest-energy clusters are characterized by drum-type geometries and tubular molecules with two B atoms on the top, respectively. Good agreement between the calculated and experimental photoelectron spectra strongly support the validity of our global minimum structures. Molecular orbital and adaptive natural density partitioning analyses indicate that the enhanced stability of half-sandwich TaB12- is due to the strong interaction of the Ta atom (5d orbitals) with surrounding B atoms (2p orbitals) and σ B-B bonds in the B12 moiety.

[Effects of different doses of dexmedetomidine combined with ropivacaine for brachial plexus nerve block in children undergoing polydactyly surgery].

OBJECTIVE: To observe the anesthetic effect and safety of different doses of dexmedetomidine combined with ropivacaine for brachial plexus nerve block in children undergoing polydactyly surgery. METHODS: Eighty children undergoing polydactyly surgery were randomized into 4 groups to receive brachial plexus nerve block with dexmedetomidine at 0.25, 0.50 or 0.75 µg/kg combined with 0.25% ropivacaine (0.20 mL/kg) (D1, D2, and D3 groups, respectively) or with 0.25% ropivacaine (0.20 mL/kg) only (control group). The onset time, duration of brachial plexus nerve block, awakening time, success rate, and incidence of complications were compared among the groups. Results In D2 and D3 groups, the onset time and awakening time were shorter and anesthesia lasted longer than those in the control group. The onset time and awakening time were shorter and anesthesia maintenance time was longer in D3 group than in D1 group. The success rates of brachial plexus nerve block were significantly higher in D1-3 groups than in the control group (P<0.05). Hematoma was found in one of the patients. In each of the 4 groups, laryngeal nerve block occurred in 1 child and respiratory depression in another; 2 or 3 patients had Horner syndrome, and 1 patient in D3 group experienced an episode of lowered heart beat to below 70 min-1. All the complications were managed properly and the patients all recovered uneventfully. CONCLUSION: Brachial plexus nerve block with 0.5 µg/kg dexmedetomidine combined with 0.25% ropivacaine (0.20 mL/kg) is safe for effective anesthesia in children undergoing surgery for polydactyly.

Evolution of the Structural and Electronic Properties of Medium-Sized Sodium Clusters: A Honeycomb-Like Na20 Cluster.

Sodium is one of the best examples of a free-electron-like metal and of a certain technological interest. However, an unambiguous determination of the structural evolution of sodium clusters is challenging. Here, we performed an unbiased structure search among neutral and anionic sodium clusters in the medium size range of 10-25 atoms, using the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method. Geometries are determined by CALYPSO structure searches, followed by reoptimization of a large number of candidate structures. For most cluster sizes the simulated photoelectron spectra of the lowest-energy structures are in excellent agreement with the experimental data, indicating that the current ground-state structures are the true minima. The equilibrium geometries show that, for both neutral and anionic species, the structural evolution from bilayer structures to layered outsides with interior atoms occurs at n = 16. A novel unprecedented honeycomb-like structure of Na20 cluster with C3 symmetry is uncovered, which is more stable than the prior suggested structure based on pentagonal structural motifs.

[Studies on the Analytical Potential Energies for Partial Electronic States of Li(2) with Variational Algebraic Energy Consistent Method].

The full vibrational spectra especially those high-lying vibrational energies in the dissociation region of four specific electronic states 1(3)Δ(g), 33Σ(+)(g), 1(3)Σ-(g) and b(3)Π(u) have been obtained by using the improved variational algebraic method (VAM). The analytical potential energy functions (APEFs) of these electronic states are also determined with corresponding adjustable parameter λ by using the variational algebraic energy consistent method (VAECM) based on the VAM vibrational spectra. The full vibrational energies, vibrational spectroscopic constants, force constants f(n), and expansion coefficients a(n) of the VAECM potential are also tabulated for each electronic state in this study. The results show that the VAECM analytical potentials are superior to some other widely used analytical ones, and do not have the unphysical tiny barriers existing in the precious AECM potentials.

[Comparison of double titanium plate and clavicular hook plate for the treatment of Neer II distal clavicular fracture].

OBJECTIVE: To compare clinical efficacy of double titanium plate and clavicular hook plate for the treatment of Neer II distal clavicular fracture. METHODS: From April 2013 to June 2015, 42 patients with Neer II distal clavicle fractures were non-randomly selected, including 25 males and 17 females. All patients were fresh closed fractures. Twenty patients were treated with double titanium plate with tight rope(group A), including 11 males and 9 females aged from 16 to 49 years old with an average age of(33.8±10.7) years;the time from injury to operation ranged from 2 to 5 days with an average of (3.5±1.8) days. Twenty-two patients were treated with clavicle hook plate(group B), including 14 males and 8 females aged from 27 to 53 years old with an average age of (37.7±9.9) years;the time from injury to operation ranged from 2 to 5 days with an average of (3.1±2.0) days. Operative time, blood loss, hospital stays and postoperative complications were observed and compared; fracture healing were compared among preoperative, postoperative at 1, 3 and 6 months; VAS and ASES scoring were used to evaluate shoulder function. RESULTS: All patients were followed up from 6 to 12 months with an average of 7.2 months. All incisions were healed at stage I. Blood loss in group A were less than that of group B(P<0.05); while there were no significant difference in hospital stays and operative time between two groups. No shoulder pain occurred in group A, 4 cases occurred shoulder pain in group B, and had significant difference. Fracture healing time ranged from 3 to 6 months with an average of 4.3 months. VAS score and ASES score in group A were higher than that of group B in pain, function and total score. CONCLUSIONS: Compared with clavicle hook plate, double titanium plate has advantages of shorter incision wound, less bleeding and simply operation, less complications, and could avoid pain for removing internal fixation. Over reduction of acromioclavicular joint during operation does not affect its superior curative effect. It is better choice for the treatment of Neer II distal clavicle fracture.

[Studies on the Q-branch spectral lines of high-lying rovibrational transitions of diatomic system].

An analytical formula was proposed recently to predict the accurate P-branch spectral lines of rovibrational transitions for diatomic systems by taking multiple spectral differences. A similar analytical expression was suggested here to predict the Q-branch spectral lines of rovibrational transitions. This formula was applied to study the high-lying Q-branch emission spectra of the (4,1) and (3,1) bands of the A 1Π - X1 Σ+ system of IrN molecule using fifteen known accurate experimental transition data. The results show that not only the known experimental transition lines were reproduced but also the correct values of the unknown spectral lines were predicted.

[Vibrational levels and dissociation energies of diatomic systems using algebraic method].

The fixed order in the algebraic method (AM) suggested by Sun et al. is changed to be a flexible one in the vibrational energy expansion because the order of diatomic potential energy expansion may not be a constant. The AM with a flexible order was used to tackle the possible "butterfly effect" that may be encountered in spectroscopic computations, and to study the full vibrational levels {E(v)} and the dissociation energies D(e) for N2 - a'(1) sigma(u)(-), Li2(+) - 2 2sigma(g)(+), 4HeD(+) - X 1sigma(-) and 39K 85Rb- (2) 3sigma(+) electronic systems. The results reproduced all known experimental vibrational energies, and predicted correct dissociation energies and all unknown high-lying levels that may not be given if one uses original AM. The calculations showed that the modified AM can be extended to study the full vibrational spectra for many more diatomic systems.

[Surface-enhanced raman spectra of thymine calculated by DFT and ab inition HF].

In the present paper, B3LYP (Becke's three-parameter hybrid method with the Lee, Yang, and Parr gradient corrected correlation functional) and HF (Hartree-Fock) methods at 6-31+G* * (C, H, N, O)/LANL2DZ(Ag) level were used to optimize molecular configurations of thymine. Base on the optimized structure, the normal Raman spectrum (NRS) of thymine and the surface-enhanced Raman spectrum (SERS) of thymine adsorbed on Ag and Ag2 were calculated, which were compared with the experimental values. The calculation results indicated that the result of the DFT for NRS was more approximate to the ever reported experimental date than those of HF results. A better conformity of SERS was found between the HF computed and the experimental results. At the end, detailed analysis of the Raman spectrum and more comprehensive assignments of the vibration mode for thymine were studied by the software of GaussView.

[Clinical study on treatment of chronic simple lichen by Qiangyue Cream].

OBJECTIVE: To explore the efficacy and safety of Qiangyue Cream (QYC) for treatment of chronic simple lichen (CSL). METHODS: A randomized, double-blinded, parallel controlled clinical trial was performed in 80 patients with CSL allocated in two groups, the 40 locally treated with QYC as the tested group, and the 40 treated with halometasone cream as the control group, with the treatment lasted for 2 successive weeks. RESULTS: A better effect in improving the scores of clinical symptoms, degree of itching and lichenoid change was shown in the tested group than that in the control group (P < 0.05), but insignificant difference was found between the two groups in the cure rate and the total effective rate. The occurrence of adverse reaction in both groups was in 1 case. CONCLUSION: QYC is a safe and effective external drug for CSL treatment, its efficacy might approach that of halometasone cream, with a better effect for relieving itching and milder adverse reactions.