Transition of Molecule Orientation during Adsorption of Terephthalic Acid on Rutile TiO2(110)

Rahe P, Nimmrich M, Nefedov A, Naboka M, Wöll C, Kühnle A. Transition of Molecule Orientation during Adsorption of Terephthalic Acid on Rutile TiO2(110). Journal of Physical Chemistry C. 2009;113(40):17471-17478.The coverage-dependent mode of adsorption of terephthalic acid [C6H4(COOH)(2), TPA] on rutile TiO2(110) was investigated by means of noncontact atomic force microscopy (NC-AFM) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy under ultrahigh vacuum conditions at room temperature. Individual molecules are observed to adsorb in an disordered, flat-lying geometry at low coverages up to similar to 0.3 monolayer (ML). The molecules are immobile at room temperature. implying a diffusion barrier larger than 0.8 eV. This rather high value might be explained by anchoring to surface defect sites. A transition from flat-lying to upright-oriented molecules is revealed by NEXAFS when saturation coverage is achieved. High-resolution NC-AFM images reveal two different Structures at coverages between similar to 0.8 and 1 ML: (i) a well-ordered (2 x 1) structure and (ii) a structure of single and paired rows oriented along the [001] crystallographic direction. The latter structure might originate from a pairwise interaction of two neighboring molecules through the top carboxyl groups. Further increase in the exposure results in it saturation of the corresponding signal in the NEXAFS spectra, revealing that the growth of TPA oil TiO2(110) at room temperature is self-limiting

Effects of acute insulin deficiency on catecholamine and indoleamine content and catecholamine turnover in microdissected hypothalamic nuclei in streptozotocin-diabetic rats

The effects of streptozotocin-induced diabetes on catecholamine and indoleamine concentrations and catecholamine turnover rates in individual microdissected hypothalamic nuclei known, or believed, to be involved in the control of neuroendocrine function, were examined in control, insulin-treated diabetic and acutely insulin-withdrawn diabetic female rats. Streptozotocin-induced diabetes and acute insulin deficiency were demonstrated to result in increased concentrations of epinephrine in the suprachiasmatic nucleus, decreased turnover of epinephrine in the arcuate nucleus and decreased turnover of dopamine in the ventromedial nucleus was found to be increased in the insulin-treated diabetic animals. These data indicate that experimental diabetes and acute insulin deficiency result in the rapid onset of detectable alterations in epinephrine and dopamine activity in specific hypothalamic nuclei. These diabetes-induced changes may cause, or contribute to, the development of secondary neuroendocrine abnormalities known to occur in the diabetic condition