Tautomeric influence on the photoinduced birefringence of 4-substituted phthalimide 2-hydroxy Schiff bases in PMMA matrix.

The photoinduced birefringence of two 4-substituted phthalimide 2-hydroxy Schiff bases, containing salicylic (4) and 2-hydroxy-1-naphthyl (5) moieties has been investigated in PMMA matrix. Their optical behaviour as nanocomposite films was revealed by combined use of DFT quantum chemical calculations (in ground and excited state) and experimental optical spectroscopy (UV-Vis and fluorescence). The results have shown that solid-state reversible switching takes place by enol/keto tautomerization and Z/E isomerization. Birefringence study was performed in the PMMA nanocomposite films using pump lasers at λrec = 355 nm and λrec = 442 nm. Fast response time and high stability of anisotropy up to 58% for (4) and 95% for (5) after turning off the excitation laser, was observed, which makes these materials appropriate candidates for cutting-edge optical information technology materials. The possibility for multiple cycles of recording, reading and optical erasure of the photoinduced birefringence at λrec = 442 nm in 5 has been demonstrated. The obtained results have shown that the maximum value of the measured birefringence is close to the anisotropic characteristics of the most frequently used azo materials.

Synthesis and photochromic properties of some N-phthalimide azo-azomethine dyes. A DFT quantum mechanical calculations on imine-enamine tautomerism and trans-cis photoisomerization.

This paper presents synthesis, photophysical characterization and quantum mechanical calculations of some N-phthalimide azo-azomethine dyes. The dyes were synthesized via azo coupling reaction between 2,4-substituted aromatic anilines and salicylic aldehyde followed by condensation reactions between azo dyes and N-aminophtalimide. Quantum chemical calculations to optimise the molecular geometry and to determine the electron densities of the trans (E) imine ⇌ enamine and the cis (Z) imine ⇌ enamine isomers and their vibrational frequencies have been computed by using DFT at B3LYP/6-31 + G(d,p) level of theory in vacuo. The effect of the used DMF solvent on the molecular structure and bond energies has been determined by using the IEFPCM model. Thermodynamic parameters such as total electronic energy E(RB3LYP), enthalpy H298 (sum of electronic and thermal enthalpies), free Gibbs energy G298 (sum of electronic and thermal free Gibbs energies) and dipole moment µ were computed in order to estimate the ΔE, Δµ, ΔH, ΔG and ΔS values. The NBO analysis was performed in order to understand the intramolecular charge transfer and the energy of resonance stabilization. After molecular geometry optimization, the electronic spectra were obtained by TD-DFT calculations at the above mentioned basis set using the IEFPCM model of DMF as a solvent. The solvatochromic effect of the dyes in four solvents with different polarity has been studied by UV-VIS spectroscopy and compared with the theoretically predicted. The coincidence between measured and calculated spectra is satisfactory. The dynamic photoisomerization experiments were performed in DMF under irradiation with UV light at λ = 365 nm (mostly E → Z) and with VIS light at λ = 400-800 nm (mostly Z → E). The spectra were recorded in the spectral region from 300 to 800 nm at identical sample concentrations of the three dyes and illumination times in order to investigate the photodynamical E → Z → E conversion of the NN chromophore group of the dyes as well as the imine ⇌ enamine tautomerization.

ISO 9001 certification for hospitals in Bulgaria: does it help service?

The aim of our study is to review the published literature on establishment and implementation of ISO 9001 QMS in European hospitals, to study the availability of International Organization for Standardization (ISO) quality management systems (QMS) in Bulgarian hospitals and to outline the main advantages of ISO implementation in the hospitals in Bulgaria. The information on availability of ISO QMS in the hospitals in Bulgaria was gathered via Bulgarian certification register, the registries of various quality associations, websites of hospitals and certification companies presented in Bulgaria. A total number of 312 hospitals in Bulgaria were screened for the availability of QMS certified against the ISO 9001 requirements. The experience of European hospitals that implemented QMS is positive and the used approaches to improve the processes and the demonstrated effects from ISO implementation are analysed by the researchers. Unlike other European Union member states, the establishment of quality management systems in Bulgaria is not compulsory. However, our study revealed that 14.42% of the hospitals in Bulgaria have implemented and have certified quality systems against the requirements of ISO 9001. Our study confirmed that a quality management system using the ISO 9001 standard is useful for the hospitals as it can help to increase the operational efficiencies, to reduce errors, improve patient safety and produce a more preventive approach instead of a reactive environment.