Intersecting representation and communication infrastructures

We analyze the intersection of new forms of representation infrastructures in a particular dynamic mathematics software (SimCalc MathWorlds^®) with the affordances of available communication infrastructures (both hardware and software). We describe the fundamental design principles from a software and curriculum perspective of why these two infrastructures can be overlapped in educational environments for important and meaningful learning outcomes. The products of this intersection result in new modes of expression (in terms of gesture, deixis and informal/formal registers), classroom identity formation in mathematically-meaningful ways, and pedagogy in terms of activity structure and intentionality. We exemplify the results of such intersection on classroom learning, participation and motivation.     

Gold-catalyzed and N-iodosuccinimide-mediated cyclization of gamma-substituted allenamides

Chiral gamma-substituted allenamides have been shown to undergo efficient gold-catalyzed and N-iodosuccinimide-mediated cyclization to highly functionalized dihydrofurans. These reactions proceed rapidly and without loss of stereochemistry.     

Boron-mediated stereoselective syntheses of gamma,gamma-disubstituted allenamides

Propargylic boranes generated by lithiation of optically active N-propargyloxazolidinones undergo reaction with a range of aldehydes to produce gamma,gamma-disubstituted allenamides with good diastereoselectivity.     

Highly sensitive fluorescence probes for nitric oxide based on boron dipyrromethene chromophore-rational design of potentially useful bioimaging fluorescence probe

Boron dipyrromethene (BODIPY) is known to have a high quantum yield (phi) of fluorescence in aqueous solution but has not been utilized much for biological applications, compared to fluorescein. We developed 8-(3,4-diaminophenyl)-2,6-bis(2-carboxyethyl)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (DAMBO-P(H)), based on the BODIPY chromophore, as a highly sensitive fluorescence probe for nitric oxide (NO). DAMBO-P(H) had a low phi value of 0.002, whereas its triazole derivative (DAMBO-P(H)-T), the product of the reaction of DAMBO-P(H) with NO, fluoresced strongly (phi = 0.74). The change of the fluorescence intensity was found to be controlled by an intramolecular photoinduced electron transfer (PeT) mechanism. The strategy for development of DAMBO-P(H) was as follows: (1) in order to design a highly sensitive probe of NO, the reactivity of o-phenylenediamine derivatives as NO-reactive moieties was examined using 4,5-diaminofluorescein (DAF-2, a widely used NO fluorescence probe), (2) in order to avoid pH-dependency of the fluorescence intensity, the PeT process was controlled by modulating the spectroscopic and electrochemical properties of BODIPY chromophores according to the Rehm-Weller equation based on measurement of excitation energies of chromophores, ground-state reduction potentials of PeT acceptors (BODIPYs), and calculation of the HOMO energy level of the PeT donor (o-phenylenediamine moiety) at the B3LYP/6-31G level, (3) in order to avoid quenching of fluorescence by stacking of the probes and to obtain probes suitable for biological applications, hydrophilic functional groups were introduced. This strategy should be applicable for the rational design of other novel and potentially useful bioimaging fluorescence probes.     

N-functionalization of poly(ethylene glycol)-linked mono- and bis-dioxocyclams as potential ligands for Gd3+

A number of highly functionalized dioxocyclams with acetic acid side chains on the secondary amine sites and ethylene glycol side chains on 6 and 13-positions (12a, 12b) or a tetra(ethylene glycol) side chain linking the 6 and 13 positions (15) were synthesized and characterized, as was a bis-dioxocyclam bridged across the 6 and 13 positions by tetra(ethylene glycol) groups (16). These were screened for their ability to complex Gd3+. Only ligands 15 and 16, having tetra(ethylene glycol) groups, formed such complexes.     

Photolytic reaction of chromium and molybdenum carbene complexes with imines : Synthesis of cepham, oxapenam, and oxacepham derivatives

A variety of substituted β-lactams, including a cepham analog, were synthesized by the photochemical reaction of [(methoxy)(methyl)carbene]chromium complexes with substituted imines. Oxazines and oxazolines were inert towards chromium carbene complexes. Oxazines were converted to bicyclic β-lactams by the photolytic reaction of molybdenum carbene complexes. Oxazolines were considerably less reactive and produced only low yields of β-lactam product and an equivalent amount of the corresponding oxazinone, incorporating two (MeO)(Me)C(CO) groups.     

A novel, one-pot ring expansion of cyclobutanones. Syntheses of carbovir and aristeromycin

A novel, one-pot ring-expansion procedure was developed using Me3S(O)I, NaH, and Sc(OTf)3. The scope and limitations were briefly examined, and a tentative mechanism was proposed. Application of the methodology to known cyclobutanone 1 provided the corresponding cyclopentanone, which was successfully advanced to (+)-carbovir and (+)-aristeromycin.     

Electroweak phase transition in the minimal supersymmetric standard model: 4-dimensional lattice simulations

Lattice results show no standard model (SM) electroweak phase transition (EWPT) for Higgs masses approximately 72 GeV, which is below the present experimental limit. Perturbation theory and 3-dimensional simulations indicate an EWPT in the minimal supersymmetric SM (MSSM) that is strong enough for baryogenesis up to m(h) approximately 105 GeV. In this Letter we present the results of our large scale 4-dimensional MSSM EWPT simulations. We carried out infinite volume and continuum limits and found a transition whose strength agrees well with perturbation theory, allowing MSSM electroweak baryogenesis at least up to m(h) = 103+/-4 GeV. We determined the properties of the bubble wall.