Photoluminescence spectrum using DFT for double-walled carbon nanotubes with metallic constituents.

A theoretical study of the photoluminescence (PL) of double-walled carbon nanotubes (DWCNTs) using density functional theory (DFT) theory is reported in this work. The DWCNTs are of the armchair/armchair type and the structures studied have the arrangements (3,3)/(2,2), (8,8)/(4,4), (12,12)/(6,6), (16,16)/(8,8), (6,6)/(3,3), (10,10)/(5,5), (14,14)/(7,7), and (18,18)/(9,9). The PL spectra were obtained taking into account different DWCNT axial lengths ranging from 0.49 nm ≤ L ≤ 2.33 nm and their inner nanotube diameters in the range of 0.31 ≤ Dinn ≤ 1.22 nm; variations in their inter-wall separations were also considered, 0.18 ≤ Dinw ≤ 0.61 nm. Although the DWCNTs have metallic SWCNT constituents, such structures give rise to photoluminescence due mainly to both curvature effects and inter-wall interaction of the inner and outer nanotubes; these two factors modify significantly their electronic structure; besides, they also lead to these structures to exhibit the quenching effect. We realized calculations at a DFT level in which we used the generalized gradient approximation (GGA) to establish the molecular geometries and the fundamental state energies. To obtain the results of the PL spectra, the constituent SWCNTs were optimized in their ground state, with the hybrid function CAM-B3LYP, which is a mixed functional exchange and correlation, and the base set that was used is the 6-31G.

Carbofuran degraded by iron-doped anatase: Weakening the cholinesterase inhibitory activity in the photoproducts mixture.

Carbofuran is a toxic carbamate pesticide, and its use has increased in recent years. While marketing information indicates stability in different chemical media, carbofuran exhibits relative photolability. The aim of this research was to decompose carbofuran and to identify the photoproducts achieved when two different doped titania photocatalysts were employed under UV irradiation. The iron-doped TiO2 materials were obtained (a) via a hydrothermal method and (b) by an ultrasound-assisted sol-gel method. The precursors were TiOSO4⋅xH2O and Fe3(NO3)·9H2O. X-ray studies confirmed that the anatase phase of the iron-doped TiO2 resulted from the two preparation methods. The photocatalytic performance of the prepared materials was monitored by LC/ESI-QTOF-MS, enabling the identification of photoproducts: oxo-carbamates, hydroxylated benzofuranes, a carboxamide, and one amine. By using the iron-doped TiO2 materials, 2,2-dimethyl-2,3-dihydrobenzofuran-3,7-diol was the most abundant photoproduct, and N,2,2-trimethyl-2,3-dihydrobenzofuran-7-amine was the only compound that had not been previously reported in the photolysis and photocatalysis of carbofuran. The product 3-hydroxy carbofuran, a cholinesterase inhibitor, was quantified and was found to be transformed into compounds that lack this inhibitive property.

Premixed solutions of diamorphine in ropivacaine for epidural anaesthesia: a study on their long-term stability.

BACKGROUND: Local anaesthetics and opioid mixtures are commonly used to provide anaesthesia or analgesia during the perioperative period. In order to facilitate their preparation and storage it is necessary to establish the stability of such solutions. METHODS: In our study, diamorphine was added to ropivacaine 0.2% 200-ml polybags to give a concentration of 25 micro g ml(-1) and to ropivacaine 1% 50-ml syringes to give a concentration of 45 micro g ml(-1). The polybags and syringes were stored at 40 degrees C, 21 degrees C and 4 degrees C for up to 120 days. Samples were taken during this period for measurement of diamorphine and ropivacaine content and pH of the solutions. RESULTS: We found that the storage temperature and the initial concentration influenced the rate of degradation of diamorphine in both the polybags and the syringes. In the syringes, 10% degradation of diamorphine [T (0.9)] was: 6 days at 40 degrees C, 16 days at 21 degrees C and 30 days at 4 degrees C. In the polybags, diamorphine T (0.9) was 6 days at 40 degrees C, 28 days at 21 degrees C and 70 days at 4 degrees C. CONCLUSIONS: It is feasible to manufacture such solutions in pharmacy aseptic units and to store them for up to 1 month for routine use in epidural infusions.

Andrographis paniculata (Ness) induces relaxation of uterus by blocking voltage operated calcium channels and inhibits Ca(+2) influx.

The possible relaxation of uterine smooth muscle by Andrographis paniculata dried extract via a blockade of voltage operated calcium channels was investigated in rats. Uterine horns pretreated with oestradiol were incubated in Ca(+2) -free Jalon's solution and stimulated with KCl (20-60 mM) in order to produce depolarization of the membrane. The isometric contractile response to 1 mM or cumulative concentrations of CaCl2 were blockaded by 0.2, 0.4 and 0.8 mg/mL of A. paniculata. The maximum contractile response induced by acetylcholine was moderately antagonized by A. paniculata. The possible blockade of Ca(+2) entry by A. paniculata was evaluated with (45)Ca(+2) uptake in uterine rings incubated with free-Ca(+2)-Ringer's solution high in K+ (KCl 40 mM). The influx was completely blockaded with 0.4 mg/mL of A. paniculata. These results strongly suggest that A. paniculata blockades voltage operated calcium channels inhibiting the entry of Ca(+2) from the external medium.