7 resultados para Blue shift

em Brock University, Canada


Relevância:

60.00% 60.00%

Publicador:

Resumo:

(A) In recent years, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorophores have attracted considerable interest due to their unique photochemical properties. However detailed studies on the stability of BODIPY and analogues under acidic and basic conditions have been lacking. Thus the stability of a series of BODIPY analogues in acidic (di- and trichloroacetic acid) and basic (aqueous ammonium hydroxide) conditions was investigated using 11B NMR spectroscopy. Among the analogues tested, 4,4-diphenyl BODIPY was the most stable under the conditions used in the experiments. It was found that reaction of 4,4-dimethoxy BODIPY with dichloroacetic acid gave mixed anhydride 4,4-bis(dichloroacetoxy) BODIPY in good yields. Treatment of the latter mixed anhydride with alcohols such as methanol and ethanol in the presence of a base afforded corresponding borate esters, whereas treatment with 1,2-diols such as ethylene glycol and catechol in the presence of a base gave corresponding cyclic borate esters. Furthermore treatment of 4,4-difluoro-8-methyl-BODIPY with secondary amines in dihalomethane resulted in carbon–carbon bond formation at the meso-methyl position of BODIPY via Mannich-type reactions. The resulting modified BODIPY fluorophores possess high fluorescent quantum yields. Five BODIPY analogues bearing potential ion-binding moieties were synthesized via this Mannich-type reaction. Among these, the BODIPY bearing an aza-18-crown-5 tether was found to be selective towards copper (II) ion, resulting in a large blue shift in absorption and sharp fluorescent quenching, whereas aza-15-crown-4 analogue was selected towards fluoride ion, leading to effective florescent quenching and blue shift. (B) Peptide nucleic acids (PNA), as mimics of natural nucleic acids, have been widely applied in molecular biology and biotechnology. Currently, the preparation of PNA oligomers is commonly achieved by a coupling reaction between carboxyl and amino groups in the presence of an activator. In this thesis attempts were made towards the synthesis of PNA through the Staudinger ligation reactions between C-terminal diphenylphosphinomethanethiol thioesters and N-terminal α-azido PNA building blocks.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This study occurred in 2009 and questioned how Ontario secondary school principals perceived their role had changed, over a 7 year period, in response to the increased demands of data-driven school environments. Specifically, it sought to identify principals' perceptions on how high-stakes testing and data-driven environments had affected their role, tasks, and accountability responsibilities. This study contextualized the emergence of the Education Quality and Accountability Offices (EQAO) as a central influence in the creation of data-driven school environments, and conceptualized the role of the principal as using data to inform and persuade a shift in thinking about the use of data to improve instruction and student achievement. The findings of the study suggest that data-driven environments had helped principals reclaim their positional power as instructional leaders, using data as an avenue back into the classroom. The use of data shifted the responsibilities of the principal to persuade teachers to work collaboratively to improve classroom instruction in order to demonstrate accountability.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Inscribed on front paste-down: Rothschild division No.227; and in pencil: James Jackson; and on front free endpaper: Presented to James M Clark By Mrs Amanda Burns Robert at Stayner 25 Aug. 1878.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The Blue Badger was Brock University's first Campus Newsletter. It was designed to make faculty, officers, staff, and students aware of goings on around campus and events in the community. It was around from October 1964 to November 1965.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A place card with an illustration of a girl in a blue coat and bonnet.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A place card with an illustration of a girl in a blue dress and red flowers.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A place card with an illustration of a girl in a blue dress sitting on a yellow chest.