Carbon nanotubes as potential material for drug delivery—experiment and simulation

We discuss the factors influencing the properties of new drug delivery system, composed of carbon nanotubes and analgesic antipyretic drug—paracetamol. Basing on experimental data it is shown, that by a simple manipulation with the heating time at the stage of system preparation, one can easily change the rate of the drug delivery. Moreover, this rate can be changed in a very wide range. Finally, using Molecular Dynamics simulation we also discuss the orientation and properties of drug molecules at different stages of the hot melt deposition process.     

Intermolecular steric hindrance in 7-acylamino-[1H]-2-oxo-1,8-naphthyridines: NMR,ESI-MS,IR, and DFT calculation studies

Abstract  

Intermolecular interactions of 7-(RCONH)-[1H]-2-oxo-1,8-naphthyridines (R = Me, Et, i-Pr, t-Bu, 1-adamantyl (1-Ad), CF₃, and C₂F₅) containing ADAD quadruple hydrogen bonding motif were studied by liquid and solid state NMR, ESI-MS, IR, and DFT calculations. ¹H NMR was used to determine the dimerization constants of i-Pr and 1-Ad congeners in CDCl₃. ¹³C and ¹⁵N cross-polarization (CP) magic angle spinning (MAS) NMR data suggest that compounds possess similar solid state structures. Further, mass spectral data reveal that in gas phase both Me and 1-Ad derivatives form also multimers due to lack of competitive solvent interactions. The structures of the gas phase multimers depend on the size of the alkyl group. These results are in agreement with quantum chemical calculations. Geometry optimization and ¹H NMR spectra show that in dimers that carry bulky alkyl groups (t-Bu and 1-Ad) certain hydrogen bonds are weaker than in Me, Et, and i-Pr derivatives while strong electron acceptors, CF₃ and C₂F₅, deshields hydrogen bonded protons but creates significant electronic F/O repulsion yielding lowering of the energy of interaction. The influence of steric effect on dimerization of quadruply hydrogen bonded dimers was correlated with the Taft E _s values.     

A procedure for the determination of dichloromethane and tetrachloroethene in water using pervaporation and gas chromatography

In the present study, pervaporation was applied to the determination of tetrachloroethene (PCE) and dichloromethane (DCM) in liquid samples. PCE is the most commonly used solvent in drycleaning processes. PCE belongs to group 2A of carcinogens (probably carcinogenic to humans) according to the classification of the International Agency for Research on Cancer (IARC). DCM is also widely used as an industrial solvent for the purification and isolation of intermediates or products. DCM is classified as a “possible” human carcinogen by the IARC. The aim of this study was to evaluate a new procedure for the determination of DCM and PCE in liquid samples based on the pervaporative removal of DCM and PCE from liquid samples as an analyte isolation/enrichment technique, followed by a direct aqueous injection of the extracts onto the column of a gas chromatograph equipped with an electron capture detector (DAI-GC-ECD). The basic parameters of the new PV-DAI-GC-ECD procedure were evaluated.     

Filtered thermal contrast based technique for testing of material by infrared thermography

A new kind of thermal contrast, called “filtered contrast” is presented, which allows detecting and characterizing material defects using active thermography under some assumptions on physical and thermal parameters of materials. In opposition to known definitions of the thermal contrast, knowledge about defect-free area is not necessary and this contrast is less sensitive to nonuniformity of heat disposal to the material surface. The measurements were performed on an experimental setup equipped with a ThermaCAM PM 595 infrared camera and frame grabber. The step heating was chosen as heat excitation. The results demonstrate usefulness of the 1D model of heat transfer used for determination of depth of subsurface defects. The influence of the parameter of the smoothing filter, required for filtered contrast implementation, thermal parameters of the tested material and defect on expanded uncertainty of determination of defect depth is also presented. Due to significant complexity of the model of heat transfer, the conditions for the “law of propagation of uncertainty” were not fulfilled and a numerical method, i.e., Monte Carlo simulation is applied for the propagation of distributions.