Engineering phase change materials (PCM) to realize superior data storage devices requires a detailed understanding of crystallization kinetics and its temperature dependence. The temperature ...dependence of crystallization differs distinctly between crystallizing from the glassy phase and the undercooled liquid (UCL). Hence, knowing the phase from which crystallization occurs is necessary for predicting the switching ability. Here, we measure the glassy dynamics and crystallization kinetics using calorimetry for heating rates spanning over six orders of magnitude. Our results show that the prominent PCM (Ag,In)-doped Sb2Te (AIST) exhibits a change from crystallizing from the glassy phase to crystallizing from the UCL at a critical heating rate of 5000 K/s. Above the glass transition, the activation energy of crystallization changes drastically enabling rapid crystallization at elevated temperatures.
Calorimetric data on the excess heat capacity Cpexc and the crystallization peak temperature Tp is combined to identify the amorphous state the phase change material AIST crystallizes from, i.e. the glassy phase or the undercooled liquid. When glass transition and crystallization interfere, the Kissinger activation energy Ek drops by more than threefold, enabling rapid crystallization. The glass transition temperature Tg is estimated to be about 182.5 °C. Hence, at conventional heating rates, AIST unconventionally crystallizes ~ 27.5 °C below the actual glass transition. Display omitted
Engineering phase change materials (PCM) to realize superior data storage devices requires a detailed understanding of crystallization kinetics and its temperature dependence. The temperature ...dependence of crystallization differs distinctly between crystallizing from the glassy phase and the undercooled liquid (UCL). Hence, knowing the phase from which crystallization occurs is necessary for predicting the switching ability. Here, we measure the glassy dynamics and crystallization kinetics using calorimetry for heating rates spanning over six orders of magnitude. Our results show that the prominent PCM (Ag,In)-doped Sb2Te (AIST) exhibits a change from crystallizing from the glassy phase to crystallizing from the UCL at a critical heating rate of 5,000 K/s. Above the glass transition, the activation energy of crystallization changes drastically enabling rapid crystallization at elevated temperatures.
Nitric oxide (NO) is considered to be involved in the modulation of uterine contractility. In the present pilot study, the direct detection of intracellular NO in pregnant human myometrial tissues ...has been investigated by using the fluorescent indicator 4,5-diaminofluorescein-2 diacetate (DAF-2DA). Pregnant myometrial tissue samples were obtained during Cesarean sections between week 34 and 40 of gestation before the onset of labor. Living explants were loaded with 10 μM DAF-2DA, stimulated with 1 mM arginine, subsequently fixed with glutaraldehyde and examined by fluorescence microscopy. The presence of NO synthases (NOS) was studied by immunohistochemistry. After application of DAF-2DA, DAF fluorescence was located primarily in blood vessels and to a minor extent in myometrial cells. By immunohistochemistry, strong endothelial NOS (eNOS) staining was found in vessel walls. In myometrial cells weak staining of eNOS and inducible NOS was observed. We conclude that the direct NO detection by DAF-2DA provides a new and independent method to identify sites of NO production in myometrium and other heterogeneous tissues.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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