Gas phase polymerization of ethylene with a silica-supported metallocene catalyst: influence of temperature on deactivation

Ethylene was polymerized at 5 bar in a stirred powder bed reactor with silica supported rac-Me2Si[Ind]2ZrCl2/methylaluminoxane (MAO) at temperatures between 40°C and 80°C using NaCl as support bed and triethylaluminium (TEA) as a scavenger for impurities. For this fixed recipe and a given charge of catalyst. the average catalyst activity is reproducible within 10% for low temperatures. The polymerization rate and the rate of deactivation increase with increasing temperature. The deactivation could be modeled using a first order dependence with respect to the polymerization rate

Apprendere una lingua straniera: tempo e spazio nella cultura italiana

La conoscenza di almeno una lingua straniera è uno degli obiettivi principali dei programmi culturali e scientifici dell’Unione europea che, all’incirca dalla metà degli anni 80, la riconosce come uno strumento qualificante al fine di costruire un’identità comune tra i paesi europei

Canada's Strategy of Dispossession: Aboriginal Land and Rights Cessions in Comprehensive Land Claims

This paper offers a sociological interpretation of the Canadian Comprehensive Land Claims (CLC) process, arguing that CLC is a strategy used by the state to dispossess Aboriginal peoples. CLC does this through leveraging the cession of Aboriginal rights and the relinquishing of indigenous lands. Drawing upon the ongoing Innu Nation Tshash Petapen (?New Dawn?) agreement, I examine four related aspects of the process and the agreement which operate to dispossess the Innu: (1) the undemocratic social and political contexts in which agreement is elicited, (2) the depletion of Aboriginal rights of the indigenous party, (3) the depletion of indigenous lands, and (4) the creation of wealth and debt. Finally, I will interpret these processes as building on social changes inflicted on the Innu. These are characterized by imposed law and the state of exception

The quiescent progenitors of four Type II-P/L supernovae

We present Large Binocular Telescope difference imaging data for the final years of four Type II-P/L supernovae progenitors. For all four, we find no significant evidence for stochastic or steady variability in the U, B, V, or R-bands. Our limits constrain variability to no more than roughly 5-10% of the expected R-band luminosities of the progenitors. These limits are comparable to the observed variability of red supergiants in the Magellanic Clouds. Based on these four events, the probability of a Type II-P/L progenitor having an extended outburst after Oxygen ignition is <37% at 90% confidence. Our observations cannot exclude short outbursts in which the progenitor returns to within ~10% of its quiescent flux on the time scale of months with no dust formation.Comment: 9 pages, 8 figures, 1 table. Accepted to MNRA

Total photoionization cross sections of atomic oxygen from threshold to 44.3A

The relative cross section of atomic oxygen for the production of singly charged ions has been remeasured in more detail and extended to cover the wavelength range 44.3 to 910.5 A by the use of synchrotron radiation. In addition, the contribution of multiple ionization to the cross sections has been measured allowing total photoionization cross sections to be obtained below 250 A. The results have been made absolute by normalization to previously measured data. The use of synchrotron radiation has enabled measurements of the continuum cross section to be made between the numerous autoionizing resonances that occur near the ionization thresholds. This in turn has allowed a more critical comparison of the various theoretical estimates of the cross section to be made. The series of autoionizing resonances leading to the 4-P state of the oxygen ion have been observed for the first time in an ionization type experiment and their positions compared with both theory and previous photographic recordings

Doctor of Philosophy

dissertationHeparan sulfate proteoglycans (HSPGs) are biologically relevant molecules composed of core proteins and glycosaminoglycan (GAG) chains. The location of HSPGs, on the cell surface or in the extracellular matrix, and their structural heterogeneity place them at a unique advantage to influence signaling pathways and cellcell or cell-matrix interactions. Most of the genes that code for the core proteins and the enzymes that build and modify the GAG chains have been identified. One type of modification, 3-O-sulfation, is catalyzed by a family of 3-O-sulfotransferases (3-OSTs) in zebrafish. Gene expression studies suggest they could modulate different steps of zebrafish development, but the specific roles of each 3-OST have not been elucidated. My dissertation focused on the functions a particular 3-OST, 3-OST-7, perform in zebrafish heart development. To elucidate the functions of 3-OST-7 in zebrafish heart development, I knocked down 3-OST-7 using morpholinos and found that 3-OST-7 controls ventricular contraction. Analysis of the noncontracting ventricle phenotype in 3-OST-7 morphants demonstrated that tropomyosin4 is required to mediate 3-OST-7 regulation of ventricular contraction, placing 3-OST-7 upstream of a novel pathway that controls coordinated sarcomere assembly. Further analysis of the 3-OST-7 knockdown model illustrated that 3-OST-7 functions in two distinct pathways that regulate ventricular maturation. First, 3-OST-7 is necessary for transforming the isometric ventricular cardiomyocytes into their elongated form. Second, 3-OST-7 shares a feedback loop with bmp4 signaling to regulate contraction. These findings demonstrated the specificity of 3-OST-7 action towards influencing cardiac development. Moreover, these studies highlighted the strength of the 3-OST-7 knockdown model in teasing apart the relationship between structure and function. I anticipate that further investigation of this model could advance our understanding of the interrelationships between HSPGs and the signaling pathways that orchestrate cardiac formation