ABSTRACT
We report a new graphene allotrope named HOT graphene containing carbon hexagons, octagons, and tetragons. A corresponding series of nanotubes are also constructed by rolling up the HOT graphene sheet. Ab initio calculations are performed on geometric and electronic structures of the HOT graphene and the HOT graphene nanotubes. Dirac cone and high Fermi velocity are achieved in a non-hexagonal structure of HOT graphene, implying that the honeycomb structure is not an indispensable condition for Dirac fermions to exist. HOT graphene nanotubes show distinctive electronic structures depending on their topology. The (0,1) n (n ≥ 3) HOT graphene nanotubes reveal the characteristics of semimetals, while the other set of nanotubes (1,0) n shows continuously adjustable band gaps (0~ 0.51 eV) with tube size. A competition between the curvature effect and the zone-folding approximation determines the band gaps of the (1,0) n nanotubes. Novel conversion between semimetallicity and semiconductivity arises in ultra-small tubes (radius < 4 Å, i.e., n < 3).
ABSTRACT
The electronic properties of vanadium atoms adsorbed on clean and graphene-covered Cu(111) surface have been systematically studied using ab initio theoretical method. Two coverages (1/9 ML and 1 ML) of vanadium adsorption are considered in this work. Our calculations indicate that V staying underneath the Cu surface is found to be the most stable adsorption site at the aforementioned two coverages for V/Cu(111). However, such adsorption may lead to undesired properties. Therefore, we introduce graphene as a buffer layer to effectively alleviate the direct interaction between V and Cu surface. The calculations show that electronic properties of the original graphene layer are significantly affected by the interactions of C atoms with the V adatoms; the Dirac point of graphene is "destroyed" as a consequence at both coverages. In the V/Gra/Cu(111) system, the interaction between graphene layer and the substrate Cu atoms remains weak as in the Gra/Cu(111) system. Moreover, a relatively low coverage of 1/9 ML gives rise to a spin-polarized system while a non-spin-polarized system is observed at the coverage of 1 ML. This finding offers a new way for the application of vanadium-based materials in reality.
ABSTRACT
Objective: To study the distribution of levofloxacin in the serum and ascites in patients with cirrhosis and to evaluate its efficacy in treatment of patients with spontaneous bacterial peritonitis(SBP). Methods:（1）Concentration of levofloxacin in the serum and ascites was detected with HPLC in 7 patients with cirrhosis at different time (in the serum: 0.5, 1, 1.5, 2 and 12 h;in the ascites:2, 4, 6 and 12 h). （2）The effects of levofloxacin were observed in treatment of 30 patients with SBP. Results:（1） Levofloxacin was determined in serum and ascites of patients with cirrhosis, whose concentration depended on the duration after oral administration. In serum: tmax was 1.5 h and cmax was (3.913±1.388) μg/ml. In ascites: tmax was 6.0 h and cmax was (2.520±1.213) μg/ml. The levels decreased gradually after reaching peak concentration, then stabilized from 12 h.（2）The symptoms and signs were significantly improved in patients with SBP treated with the levofloxacin. Conclusion: After the oral administration, levofloxacin can both distribute in serum and ascites, and it is efficient in the treatment of the patients with SBP.
ABSTRACT
Objective: To study the distribution of levofloxacin in the serum and ascites in patients with cirrhosis and to evaluate its efficacy in treatment of patients with spontaneous bacterial peritonitis(SBP). Methods:（1）Concentration of levofloxacin in the serum and ascites was detected with HPLC in 7 patients with cirrhosis at different time (in the serum: 0.5, 1, 1.5, 2 and 12 h;in the ascites:2, 4, 6 and 12 h). （2）The effects of levofloxacin were observed in treatment of 30 patients with SBP. Results:（1） Levofloxacin was determined in serum and ascites of patients with cirrhosis, whose concentration depended on the duration after oral administration. In serum: tmax was 1.5 h and cmax was (3.913±1.388) μg/ml. In ascites: tmax was 6.0 h and cmax was (2.520±1.213) μg/ml. The levels decreased gradually after reaching peak concentration, then stabilized from 12 h.（2）The symptoms and signs were significantly improved in patients with SBP treated with the levofloxacin. Conclusion: After the oral administration, levofloxacin can both distribute in serum and ascites, and it is efficient in the treatment of the patients with SBP.
