Elctron-impact studies of diazadiphosphetidines

Electron-impact studies of diazadiphosphetidines,[YF₂PNMe]₂(Y? F,Me, Ph, MeO,2,5-Me₂C₆H₃, and m-CF₃C₆H₄) are reported, the most abundant fragments corresponding to m/e [M/2–1]⁺, [M/2]⁺ and [M/2–1]⁺. It is concluded from metastable data that formation of the noval rearrangement ion, [M]⁺→[M/2+1]⁺is predominantly due to an electron-impact process. Variable temperature spectra of(F₃PNMe)2, (i.e. for Y=F), suggest that ions of m/e [M/2-1]⁺are formed, in part, by a thermal process. For the compound [(m-CF₃C₆H₄)F₂PNMe]₂ a well resolved negative ion spectrum has been obtained, with the molecular ion present in 100% abundance.     

Array-based capture, distribution, counting and multiplexed assaying of beads on a centrifugal microfluidic platform

We present a novel centrifugal microfluidic platform for the highly efficient manipulation and analysis of particles for applications in bead-based assays. The platform uses an array of geometrical V-cup barriers to trap particles using stopped-flow sedimentation under highly reproducible hydrodynamic conditions. The impact parameters governing the occupancy distribution and capture efficiency of the arrayed traps are investigated. The unique, nearly 100% capture efficiency paired with the capability to establish sharply peaked, single occupancy distributions enables a novel, digital readout mode for color-multiplexed, particle-based assays with low-complexity instrumentation. The presented technology marks an essential step towards a versatile platform for the integration of bead- and cell-based biological assays.     

Model basis states for photons and "empty waves"

From the perspective of physical realism (PR), a photon is a localized entity that carries energy and momentum, and which is surrounded by a wave packet (anempty wave) that is devoid of observable energy or momentum. In creating quantized PR basis states for a photon wave packet, three requirements must be met:(1) The basis states must each carry the frequency of the wave;(2) They must closely resemble the photon, so that e.g. they scatter in the same manner from an optical mirror;(3) They must have infinitesimal energy, linear momentum, and angular momentum. An essentially zero-energy "empty wave" quantum-a "zeron"-is defined which meets these requirements. It is created as an asymmetric single-particle (or single-antiparticle) excitation of the vacuum state, with the "particle" (or "antiparticle") and its associated "hole" (or "antihole") forming a rotational bound state. The photon is reproduced as a symmetric particle-antiparticle excitation of the vacuum state, with the "particle" and "antiparticle" also forming a rotational bound state. The relativistic transformation problem is discussed. A key point in this development is the deduction of the correct equation of motion for a "hole" state in an external electrostatic field.     

Studies in negative ion mass spectrometry: XIV—Electron attachment reactions of a series of η6-arenetricarbonylchromium(O) complexes

Electron attachment reactions of a series of (η⁶-arene)tricarbonylchromium(O) complexes have been examined in the gas phase. The electron capture process has been shown to be influenced by the structure of the η⁶-arene ligand and its substituents. Whereas (η⁶-benzene)- and (η⁶-mesitylene)tricarbonylchromium(O) undergo dissocative electron capture, or reductive decarbonylation, yielding [M? CO]^?˙ ions of highest abundance in their negative ion mass spectra, [η⁶-(2,2-dimethylindan-1,3-dione)]tricarbonylchromium(O) forms a molecular negative ion which undergoes sequential CO eliminations and finally a demetallation to give the arene radical ion. A localization of charge on the coordinated arene ligand is proposed for the formation of [M]^?˙ in this case. (η⁶-Methylbenzoate)tricarbonylchromium(O) also forms a molecular negative ion by secondary electron attachment which decomposes by simultaneous and consecutive eliminations of up to four CO molecules. The elucidation of a mechanism and sequence for these CO eliminations has been achieved by synthesizing and examining the negative ion mass spectrum of [η⁶-(C₆H₅·¹³CO₂Me)]Cr(CO)₃. The first CO loss in the principal fragmentation pathway occurs solely from the –Cr(CO)₃ group of [M]^?˙. The effect of para substituent groups on the stabilities of molecular negative ions and their fragmentations has been ascertained using a series of para-substituted (η⁶-methylbenzoate)tricarbonylchromium(O) compounds containing the groups NH₂, OH, OCH₃, CL and COOMe. The stabilities of the [M]^?˙ ions have been rationalized in terms of the Hammett and Taft parameters σ_P, σ_I, σ_R^P, σ_P^O and σ_R^O. The overall electronic substituent effect transmitted to the carbonyl groups of the –Cr(CO)₃ unit involves both resonance and inductive components. In this series of compounds the stability of [M]^?˙ decreases as the electron withdrawing capacities of the para substituents increase.