Structures and Electronic and Hydrogen Storage Properties of Magnesium Scandium Hydrides.

MgH2 is well known as a potential hydrogen storage material. However, its high thermodynamic stability, high dissociation temperature, slow absorption, and desorption kinetics severely limit its application. Aiming at these shortcomings, we try to improve the hydrogen storage property of MgH2 by doping with transition metal Sc atoms. The structures and electronic and hydrogen storage properties of Mg-Sc-H systems have been systematically studied by combining the crystal structure analysis by particle swarm optimization and density functional theory method. The results show that the structure of MgScH8 with the R3 space group is the most stable one, which is proved to be a wide-band gap (2.96 eV) semiconductor. The possible decomposition pathways, which are crucial for the applicability of R3-MgScH8 as a hydrogen storage material, are studied, and the pathway of MgScH8 → ScH6 + Mg + H2 is found to be the most favorable one under 107.8 GPa pressure, while above 107.8 GPa, MgScH8 → Mg + Sc + 4H2 becomes the most thermodynamically stable pathway and releases the maximum amount of hydrogen. Based on the root mean square deviation calculation, it is found that R3-MgScH8 begins to melt at 400 K. The result of ab initio molecular dynamics simulations shows that the hydrogen release capacity (4.04 wt %) can be easily achieved at 500 K, thus making MgScH8 a potential hydrogen storage material.

The efficacy and safety of neoadjuvant nimotuzumab for gastric cancer: A meta-analysis of randomized controlled studies.

INTRODUCTION: The efficacy of neoadjuvant nimotuzumab for gastric cancer remained controversial. We conducted a systematic review and meta-analysis to explore the efficacy of neoadjuvant nimotuzumab plus chemotherapy vs chemotherapy for gastric cancer. METHODS: We have searched PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through May 2019, and included randomized controlled trials assessing the efficacy of neoadjuvant nimotuzumab plus chemotherapy vs chemotherapy for gastric cancer. This meta-analysis was performed using the random-effect model. RESULTS: Four randomized controlled trials were included in the meta-analysis. There were 128 patients included in intervention group and 131 patients included in control group. Overall, compared with chemotherapy for gastric cancer, neoadjuvant nimotuzumab plus chemotherapy showed no substantial influence on response rate (risk ratio [RR] = 1.22; 95% CI = 0.78-1.89; P = .38), disease control rate (RR = 2.22; 95% confidence interval [CI] = 0.32-15.40; P = .42), rash (RR = 1.26; 95% CI = 0.96-1.66; P = .10), neutropenia (RR = 1.26; 95% CI = 0.96-1.66; P = .10), anemia (RR = 1.08; 95% CI = 0.62-1.89; P = .78), or nausea (RR = 1.19; 95% CI = 0.96-1.48; P = .12), but might improve the incidence of vomiting (RR = 1.60; 95% CI = 1.03-2.50; P = .04). CONCLUSIONS: Neoadjuvant nimotuzumab might provide no additional benefits to the treatment of gastric cancer.

Characteristics and kinetics of catalpol degradation and the effect of its degradation products on free radical scavenging.

BACKGROUND: The dried and steamed roots of Rehmannia glutinosa have different pharmacological functions and indications. Catalpol, the main active component of the dried root, was found to be entirely degraded together with amino acids and some oligosaccharides during preparation of the steamed root. Its degradation may contribute to the differences between dried and steamed roots. OBJECTIVE: To reveal the characteristics and kinetics of catalpol degradation, and evaluate its influence on the antioxidant properties of steamed Rehmannia roots. MATERIALS AND METHODS: Purified catalpol was heated under different pH and temperature values for different times, alone or with sugars or amino acids. Catalpol concentration was determined by high-performance liquid chromatography. Browning was expressed by the absorbance at 420 nm (A420), and antioxidation was displayed by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging ability (SADPPH). Activation energy was calculated using Arrhenius plotting. RESULTS: Catalpol was stable in neutral conditions and sensitive to acidic pH under high temperatures. Sugars had no influence on catalpol degradation; however, most amino acids, except for proline, could promote the degradation, and were associated with an increase in A420 and SADPPH values. These changes were proved to be mainly related with catalpol aglycone and were dependent on the presence of amino acids. Catalpol degradation was found to obey first-order kinetics. The activation energies were 81.7, 88.8 and 98.7 kJ/mol at pH 4.0, 5.0, and 6.0 respectively, and 70.7 kJ/mol at pH 4.0 value and in the presence of glycine. CONCLUSIONS: Catalpol degradation, especially, in the presence of amino acids can substantially boost antioxidant properties of the products; therefore, the traditional method for processing Rehmannia root seems rather apt.

[Discussion on the quality marker of rehmanniae radix praeparata in the Chinese Pharmacopoeia].

OBJECTIVE: In the Chinese Pharmacopoeia (2010 edition), the minimum limit of verbascoside (acteoside) in Rehmanniae Radix Praeparata (RRP) was set at 0.20%, the rationality of the standard was evaluated in this paper. METHODS: 10 samples of Rehmanniae Radix (RR) and RRP were collected or prepared. According to the traditional method, different samples of RRP were prepared from the same batch of RR, and the content of verbascoside was determined by HPLC. RESULTS: The average content of verbascoside in RR and RRP was 0.0226% and 0.0097%, respectively, and their difference was up to the level of P < 0.01. The content of verbascoside was found decreased with processing time increasing. Long-time storage also results in substantial loss of verbascoside. CONCLUSION: Processing results in verbascoside decreasing significantly. It is unreasonable that RR and RRP have the same standard in the content of verbascoside. It is suggested that the maximum limit of verboscoside should be set in the new version of Chinese pharmacopoeia.

Bis[2-(benzyl-idene-amino)-phen-yl] disulfide.

In the title mol-ecule, C(26)H(20)N(2)S(2), the two benzene rings connected by a disulfide chain form a dihedral angle of 84.9 (1)°, and the two benzene rings in the two benzyl-idene-amino-phenyl fragments form dihedral angles of 34.4 (1) and 32.8 (1)°. The crystal structure exhibits weak inter-molecular C-H⋯S hydrogen bonds, which link the mol-ecules into chains along [101].

Synthesis and upconversion luminescence of NaYF4:Yb3+,Tm3+/TiO2 nanocrystal colloidal solution.

NaYF4:Yb3+,Tm3+ upconversion nanocrystals were synthesized with oleic acid as a capping ligand. The as-prepared samples were redispersed in cyclohexane, forming transparent and stable solutions which perform bright blue upconversion. Inducing TiO2 as the outer layer of the fluoride cores, we investigated the effect of TiO2 on the upconversion process. The transmission electron microscopy (TEM) analysis indicated that titania successfully formed a coating layer on the surface of NaYF4:Yb3+, Tm3+ nanoparticles, and the average diameters of the NaYF4:Yb3+,Tm3+ nanocrystals and the NaYF4:Yb3+, Tm3+/TiO2 nanoparticles are about 14 and 40 nm, respectively. Under the excitation of a 980 nm laser, NaYF4:Yb3+, Tm3+ nanocrystals and TiO2-coated NaYF4:Yb3+, Tm3 core/shell structure sample exhibited distinct upconversion luminescent properties.

(E,E)-6,6'-Dimeth-oxy-2,2'-[o-phenyl-ene-bis(nitrilo-methyl-idyne)]diphenol.

In the title compound, C(22)H(20)N(2)O(4), the central benzene ring forms dihedral angles of 3.2 (2) and 61.1 (1)° with the two outer substituted benzene rings. Intra-molecular O-H⋯N hydrogen bonds are formed by both hydroxyl groups.

1,5-Bis(2-chloro-benzyl-idene)carbonohydrazide.

In the title mol-ecule, C(15)H(12)Cl(2)N(4)O, the two benzene rings are inclined at a dihedral angle of 14.5 (2)°. In the crystal, inter-molecular N-H⋯O hydrogen bonds link mol-ecules into chains propagated in [001].

1,5-Bis(4-bromo-phen-yl)-3-phenyl-pentane-1,5-dione.

The asymmetric unit of the title compound, C(23)H(18)Br(2)O(2), contains two independent mol-ecules with slightly different conformations. In the absence of classical inter-molecular inter-actions, the crystal packing is stabilized by van der Waals forces.

1,1'-[o-Phenyl-enebis(nitrilo-methyl-idyne)]di-2-naphthol ethanol hemisolvate.

The asymmetric unit of the title compound, C(28)H(20)N(2)O(2)·0.5C(2)H(5)OH, contains two independent mol-ecules of 1,1'-[o-phenyl-enebis(nitrilo-methyl-idyne)]di-2-naphthol, denoted A and B, and one ethanol solvent mol-ecule. The hydr-oxy groups are involved in intra-molecular O-H⋯N hydrogen bonds influencing the mol-ecular conformations, which are slightly different in mol-ecules A and B, where the two bicyclic systems form dihedral angles of 51.93 (9) and 58.52 (9)°, respectively. In the crystal structure, a number of short inter-molecular C⋯C contacts with distances of less than 3.5 Šsuggest the existence of π-π inter-actions, which contribute to the stability of the crystal packing.

1,5-Bis(4-chloro-phen-yl)-3-(2-thien-yl)pentane-1,5-dione.

In the title mol-ecule, C(21)H(16)Cl(2)O(2)S, the five-membered ring is rotationally disordered between two orientations in a 1:1 ratio. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules related by translation along the a axis into chains, which are further combined into layers parallel to the bc plane via C-H⋯π inter-actions. The crystal studied was a racemic twin with a 0.37 (19):0.63 (19) domain ratio.