Cycloaddition Reactions of the Metal Phosphorus Double Bonded Complexes CP(CO)2M=PR2 (M = MO,W; R = Alkyl,Aryl)

Abstract

The reaction of the metal phosphorus double bonded species Cp(CO)₂M=PR₂ (M = Mo, W; R = aryl, alkyl) (1)¹⁾ with diverse diazoalkanes, alkenes, alkines and dienes results in the facile formation of the [2+1]-, [2+2]1- and [2+4]-cycloaddition products 2a-c.     

Integrated chemical sensor array platform based on a light emitting diode, xerogel-derived sensor elements, and high-speed pin printing

We report a new, solid-state, integrated optical array sensor platform. By using pin printing technology in concert with sol-gel-processing methods, we form discrete xerogel-based microsensor elements that are on the order of 100 μm in diameter and 1 μm thick directly on the face of a light emitting diode (LED). The LED serves as the light source to excite chemically responsive luminophores sequestered within the doped xerogel microsensors and the analyte-dependent emission from within the doped xerogel is detected with a charge coupled device (CCD). We overcome the problem of background illumination from the LED reaching the CCD and the associated biasing that results by coating the LED first with a thin layer of blue paint. The thin paint layer serves as an optical filter, knocking out the LEDs red-edge spectral tail. The problem of the spatially-dependent fluence across the LED face is solved entirely by performing ratiometric measurements. We illustrate the performance of the new sensor scheme by forming an array of 100 discrete O₂-responsive sensing elements on the face of a single LED. The combination of pin printing with an integrated sensor and light source platform results in a rapid method of forming (∼1 s per sensor element) reusable sensor arrays. The entire sensor array can be calibrated using just one sensor element. Array-to-array reproducibly is <8%. Arrays can be formed using single or multiple pins with indistinguishable analytical performance.     

Measurements of the Decay KL-->e+ e- mu+ mu-

The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay K(L)-->e+ e- mu+ mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be [2.69+/-0.24(stat)+/-0.12(syst)]x10(-9), with a radiative cutoff of M(2)(ee mu mu)/M(2)(K)>0.95. The first measurement using this mode of the parameter alpha from the D'Ambrosio-Isidori-Portolès (DIP) model of the K(L)gamma*gamma* vertex yields a result of -1.59+/-0.37, consistent with values obtained from other decay modes. Because of the limited statistics, no sensitivity is found to the DIP parameter beta. We use this decay mode to set limits on CP and lepton violation.     

Relative substituent position on the strength of π-π stacking interactions

It was observed that the relative position of the arene substituents has a profound influence on the strength of π-π stacking in the 9-benzyl-substituted triptycene system. A new series of model compounds (3a-i) capable of revealing quantitatively π-π stacking interactions was studied. This series of compounds (3a-i) has an ortho-substituted methyl group in one of the two interacting arenes and the syn/anti ratios were determined and compared to a series previously studied compounds (4a-i) that have a para methyl group on the corresponding arene. A greater than 50% increase in the strength of π-π stacking interactions was observed with the methyl group in the ortho position comparing to that in the para position. No difference in π-π stacking interactions was observed when the other aromatic ring was a pentafluorobenzoate group.     

Implementing and Using Mathematics Standards in North Carolina

North Carolina has a history of supporting and using national standards in structuring the state-adopted mathematics curriculum framework. This focus is associated with increased achievement of North Carolina students. The connection of the 1989 revision of the framework to the 1989 National Council of Teachers of Mathematics standards seemed to increase acceptance of the framework by teachers, school boards, and the public; revisions since then have been explicitly responsive to evolving national standards. Plans for the next revision include attending to the Principles and Standards for School Mathematics. To inform leaders in North Carolina about the Principles and Standards, a symposium was held in September 2000. This symposium provided a model for making the Principles and Standards visible to different constituencies. It is also important to involve teacher education institutions in sharing the Principles and Standards with new teachers so that they enter teaching with a deep understanding of and appreciation for standards.     

Rotational isomerism in 3-chloro-1-propanol from the microwave spectrum

The rotational spectra of two conformations of 3-chloro-propanol were observed for the four possible $\text{Cl(35)}\text{Cl(37)}$ and $\text{H}\text{D}$ isotopic species. For both conformations the oxygen atom is gauche with respect to the C₂C₃ bond and the hydroxyl hydrogen is trans with respect to the C₂C₁ bond. In one conformation (T) the chlorine is trans with respect to C₁C₂ and it is gauche in the other form (G). The ground state of the G form is about 0.7 kcal/mole more stable than that of the T form. A discussion is given about the failure to observe the H bond species. The most likely reason is the too close approach of Cl and O in this hypothetical configuration. The quadrupole coupling constants were obtained for the G form. The rotational spectra of five excited states of the T form and of one excited state of the G species were measured. Partial r₀ and r_s structures are given.     

Effect of manifold design and firing order on the short term spectrum

Separation by homomorphic filtering of the engine speed dependent harmonics from the remaining components of a vehicle's acoustic emission involves selection of the optimum quefrency for the filter. This requires an understanding of the formation, on the short term log power spectrum, of harmonics of both the fundamental frequency from successive cylinder firings and also the frequency from firings of the same cylinder. It is shown that these harmonics depend on the combination of the design of the engine's exhaust manifold and on the cylinder firing order. Comparisons are made between the engine harmonics displayed from segments of time series containing different numbers of crankshaft rotations. Finally graphs are included where meaningful comparison can be made between homomorphed spectra of two different vehicles of the same type. As a result of this investigation an explanation is offered which resolves the problems encountered by workers analysing engine related harmonics.     

Thermodynamic binding parameters evaluated by using phase-resolved fluorescence spectrometry

Equilibrium binding constants as a function of temperature were determined for the binding of 4-amino-N-methylphthalimide (4-AMP) to β-cyclodextrin and to human and bovine serum albumins, and for 6-propionyl-2-(dimethylamino)naphthalene (PRODAN) to β-cyclodextrin, by using phase-resolved fluorimetry to eliminate errors from the significant fluorescence contribution from the free 4-AMP or PRODAN. Enthalpy and entropy values were also calculated from these experimental data.