Manganese Complexes as Drying Catalysts for Alkyd Paints

Common alkyd paint will not have dried within two hours without drying catalysts. The drying catalyst (also called __drier__) that is generally used is based on the heavy metal cobalt. Since cobalt salts are suspected to be carcinogenic, it is of the utmost importance that alternative driers are found and that cobalt can be replaced as a drier in alkyd paint. In this thesis newly developed manganese compounds are presented which show a comparable or better drying activity than existing cobalt driers. These manganese driers are thus potential replacements for the toxic cobalt compounds. Results pertaining to the mechanism of action of the new manganese driers are also discussed. These results will make the future development of alkyd paint driers easier. Huis-tuin-en-keuken alkydverf is uit zichzelf niet binnen twee uur droog. Daarom worden drogingsversnellers (katalysatoren) aan de verf toegevoegd, om het drogingsproces te versnellen. De meest gebruikte drogingskatalysator (ook wel __droger__ genoemd) in alkydverf is gebaseerd op het zware metaal kobalt. Aangezien kobalt vermeend carcinogeen is, is het noodzaak om alternatieve drogers te vinden zodat kobalt vervangen kan worden. In dit proefschrift worden (nieuw ontwikkelde) mangaanverbindingen gepresenteerd die dezelfde of soms zelfs een betere drogingsactiviteit vertonen als de bestaande kobaltdroger en dus als mogelijke vervanger aangemerkt kunnen worden. Ook worden resultaten gepresenteerd mbt de precieze werking van de mangaandrogers, zodat het in de toekomst makkelijker zal zijn nieuwe drogers te ontwikkelen voor bijvoorbeeld een specifieke verfformulering.The work described in this thesis was financially supported by the Dutch Ministry of Economic Affairs, as part of the SENTER/Innovation Oriented Research Program on Heavy Metals (IOP) No. IZW99241c.UBL - phd migration 201

Effects of Vacancies near Substitutional Implants on Trapping and Desorption of Helium - A Simulation

Trapping of He by vacancies and drainage of He from substitutional implants (Ag and Kr in W) to nearby vacancies are investigated using static lattice calculations. The calculations indicate that drainage of He will occur to vacancies within a radius of 2.5 lattice units from the implant. Furthermore the trapping probability of substitutional and interstitial random walkers on a bcc lattice by substitutional traps or vacancies is calculated. When implantation-produced vacancies are present in the vicinity of the observed trap a shielding effect occurs. Trapping constants are calculated with two random walk models for both the unshielded and the shielded defect. For the latter several configurations were taken. The results show that shielding of a defect by one vacancy at a distance of three lattice units leads already to a reduction of He trapping by that defect of 30% to 40%.

Multidrug-resistant tuberculosis in prison inmates, Azerbaijan.

In a tuberculosis (TB) program in the Central Penitentiary Hospital of Azerbaijan, we analyzed 65 isolates of Mycobacterium tuberculosis by IS6110-based restriction fragment-length polymorphism (RFLP) and spoligotyping. From 11 clusters associated with 33 patients, 31 isolates had an IS6110-based banding pattern characteristic of the Beijing genotype of M. tuberculosis. In addition, 15 M. tuberculosis isolates with similar RFLP patterns constituted a single group by spoligotyping, matching the Beijing genotype. Multidrug resistance, always involving isoniazid and rifampin, was seen in 34 (52.3%) of 65 isolates, with 28 belonging to the Beijing genotype

Evaluation of a developed MRI-guided focused ultrasound system in 7 T small animal MRI and proof-of-concept in a prostate cancer xenograft model to improve radiation therapy

Focused ultrasound (FUS) can be used to physiologically change or destroy tissue in a non-invasive way. A few commercial systems have clinical approval for the thermal ablation of solid tumors for the treatment of neurological diseases and palliative pain management of bone metastases. However, the thermal effects of FUS are known to lead to various biological effects, such as inhibition of repair of DNA damage, reduction in tumor hypoxia, and induction of apoptosis. Here, we studied radiosensitization as a combination therapy of FUS and RT in a xenograft mouse model using newly developed MRI-compatible FUS equipment. Xenograft tumor-bearing mice were produced by subcutaneous injection of the human prostate cancer cell line PC-3. Animals were treated with FUS in 7 T MRI at 4.8 W/cm2 to reach ~45 °C and held for 30 min. The temperature was controlled via fiber optics and proton resonance frequency shift (PRF) MR thermometry in parallel. In the combination group, animals were treated with FUS followed by X-ray at a single dose of 10 Gy. The effects of FUS and RT were assessed via hematoxylin-eosin (H&E) staining. Tumor proliferation was detected by the immunohistochemistry of Ki67 and apoptosis was measured by a TUNEL assay. At 40 days follow-up, the impact of RT on cancer cells was significantly improved by FUS as demonstrated by a reduction in cell nucleoli from 189 to 237 compared to RT alone. Inhibition of tumor growth by 4.6 times was observed in vivo in the FUS + RT group (85.3%) in contrast to the tumor volume of 393% in the untreated control. Our results demonstrated the feasibility of combined MRI-guided FUS and RT for the treatment of prostate cancer in a xenograft mouse model and may provide a chance for less invasive cancer therapy through radiosensitization

p-type delta-doped layers in silicon: structural and electronic properties

We report on the properties of p-type delta-doped layers prepared in molecular beam epitaxy-Si by growth interruption and evaporation of elemental B. Secondary-ion mass spectrometry measurements at several primary ion energies have been used to show that the full width at half maximum is ~2 nm. Hall measurements confirm that the layers are completely activated at 300 K with a mobility of 30±5 cm2/V s for a carrier density of (9±2)×1012 cm−2. At temperatures below 70 K nonmetallic behavior is observed which we have attributed to conduction between impurity states. It is concluded that the critical acceptor separation for the Mott metal-insulator transition in this system is significantly less than the value found in uniformly doped Si:B