Fluorescence spectroscopy has been used to study the miscibility of methyl silsesquioxane (MSSQ)/poly(methyl methacrylate-co-dimethylaminoethyl methacrylate) [P(MMA-co-DMAEMA)] hybrid nanocomposites, which are useful in fabricating the next generation of spin-on, ultra-low dielectric constant materials in the microelectronic industries. In this work, we have attached the pyrene group into the PMMA side chains. MSSQ with different amount of initial -SiOH (silanol) endgroups are used to study the effect of endgroup functionality on the phase separation behavior of the hybrid nanocomposites. Pyrene excimer fluorescence results reveal that MSSQ is miscible with P(MMA-co-DMAEMA) only up to 6 wt% P(MMA-co-DMAEMA) loading level, thus establishing an upper limit on local miscibility with MSSQ. As the P(MMA-co-DMAEMA) loading level increases, the excimer to monomer ratios also increase, suggesting that the MSSQ/P(MMA-co-DMAEMA) hybrid nanocomposites move toward greater immiscibility. This ratio approaches that of the neat polymer for domain sizes > 5 nm (SAXS, SANS). The fluorescence results also show that, the lower the amount of initial silanol groups in MSSQ, the greater the immiscibility of the MSSQ and porogen, which ultimately translates into larger pores upon porogen burnout.

In the High Himalayan Crystalline Series of Northwest India, numerous peraluminous granites intruded the metasediments of the late Proterozoic to early late Cambrian Haimanta Group. Nd and Sr isotope systematics confirm that they were derived from heterogeneous crustal sources. New geochronological data from two plutons range in age from late Precambrian to early Ordovician: single zircon U–Pb dating yielded an age of 553 ± 2 (2σ) Ma for the Kaplas granite, whereas mineral Sm–Nd isotope systematics define a crystallization age of 496 ± 14 (2σ) Ma for the tholeiitic mafic rocks in the Mandi pluton, where evidence of magma mingling documents a close association between mafic and granitic melts. The end of this period of magmatic activity coincides with the depositional gap below the Ordovician transgression, caused by surface uplift and erosion, that is an important feature in the stratigraphy of the Northwest Himalaya. In Spiti, the transgression of the Ordovician basal conglomerates on a normal fault indicates pre-Ordovician extensional faulting. Therefore, the early Palaeozoic magmatic activities in the Northwest Himalaya could be correlated with a late extensional stage of the long-lasting Pan-African orogenic cycle which ended with the formation of the Gondwana supercontinent.

Las ruinas de Calakmul se encuentran en la cuenca del mismo nombre localizado dentro del 723,000 ha Reserva de la Biosfera Calakmul en el sureste del Estado de Campeche. Investigaciones del Centro de Investigaciones Históricas y Sociales de la Universidad Autónoma de Campeche han demostrado que Calakmul formaba una de las más grandes centros regionales en el área maya desde 600 a.C. hasta los fines del siglo IX dentro de su estado regional de 13,000 km2. Investigaciones de prospección remoto alrededor de Calakmul combinado con trabajos topográficos dentro de la ciudad misma han revelado 15 sac beob identificados por nosotros entre los tipos de vías terrestres descritos en los diccionarios de la idioma Maya formados durante el período colonial. Entre estos sac beob se encuentran tipos regionales, estatales y los sac beob registrados dentro de la ciudad de Calakmul. Aunque existe un traslapo entre varios tipos de sac beob, pensamos que excavaciones futuras van a ayudarnos a clasificar cada sac be en una forma más precisa.