FTIR studies of polyimides. II. Factors affecting quantitative measurement

Measurement of imidization by IR spectroscopy has frequently been reported to give results that are either insensitive to changes in the latter part of the cure or in conflict with observations by other methods. However, an analysis of imide formation using the 1370 cm^?1 band (C? N stretch) in conjunction with the 1500 cm^?1 aromatic band as an internal standard appears capable of giving precise, internally consistent measurements for the most commonly used polyimide structures, for samples that are measured in transmission. Measurements of imide content in ultrathin films by grazing incidence reflection spectroscopy appear to be at least semiquantitative. © 1993 John Wiley & Sons, Inc.     

TRIGLYCERIDE–METHANOL MICROEMULSIONS

Even-numbered 1-alkanols from butanol to tetradecanol were evaluated for solubilizing and microemulsifying methanol in triolein and for their effectiveness on water tolerances of the hybrid fuels. Photon correlation spectroscopy determinations indicated molecular dispersions formed rather than nonaqueous microemulsions, but the addition of water to the solubilized systems did produce certain quarternary compositions that exhibited microemulsion properties. 1-Octanol imparted optimal, whereas 1-butanol and 1-tetradecanol imparted minimal, water tolerance for the hybrid fuels. Among four isomeric octanols studied, the 1- and 4-octanols were superior to the 2- and 3-octanols for water tolerance. This superiority is attributed to stronger hydrogen bonding and greater association in the 1-and 4-isomers compared to the 2- and 3-isomers.     

Hydrocarbon metal sulphide complexes : VI. A new type of rearrangement of a cyclopentadienylruthenium complex

The complexes C₅H₅Ru(CO)₂SR (R = C₆F₅ or CH₃) undergo photochemical conversion to binuclear and trinuclear derivatives which exhibit isomerism. A novel rearrangement has been detected for [C₅H₅Ru(CO)(SC₆F₅)]₂.     

Measurement of quantum weak values of photon polarization

We experimentally determine weak values for a single photon's polarization, obtained via a weak measurement that employs a two-photon entangling operation, and postselection. The weak values cannot be explained by a semiclassical wave theory, due to the two-photon entanglement. We observe the variation in the size of the weak value with measurement strength, obtaining an average measurement of the S1 Stokes parameter more than an order of magnitude outside of the operator's spectrum for the smallest measurement strengths.     

Measuring entangled qutrits and their use for quantum bit commitment

We produce and holographically measure entangled qudits encoded in transverse spatial modes of single photons. With the novel use of a quantum state tomography method that only requires two-state superpositions, we achieve the most complete characterization of entangled qutrits to date. Ideally, entangled qutrits provide better security than qubits in quantum bit commitment: we model the sensitivity of this to mixture and show experimentally and theoretically that qutrits with even a small amount of decoherence cannot offer increased security over qubits.     

Alkali-metal mediated zincation of N-heterocyclic substrates using the lithium zincate complex, (THF)Li(TMP)Zn(tBu)2 and applications in in situ cross coupling reactions

This study investigates the ability of the mixed-metal reagent [Li(TMP)Zn(tBu)₂] 1 to promote direct Zn-H exchange reactions (zincations) of a wide range of N-heterocyclic molecules. The generated metallated intermediates from these reactions are intercepted with I₂ and some of them are also employed as precursors in Pd-catalysed Negishi cross-coupling applications. A comparison with recent precedents in metallation chemistry reveals that for some of these heterocycles, 1 allows improved conversions, under milder conditions and in certain cases, even gives unique regioselectivities.     

Taking tomographic measurements for photonic qubits 88 ns before they are created

We experimentally demonstrate that tomographic measurements can be performed for states of qubits before they are prepared.A variant of the quantum teleportation protocol is used as a channel between two instants in time,allowing measurements for polarization states of photons to be implemented 88 ns before they are created.Measurement data taken at the early time and later unscrambled according to the results of the protocol's Bell measurements,produces density matrices with an average fidelity of 0.90±0.01 against the ideal states of photons created at the later time.Process tomography of the time reverse quantum channel finds an average process fidelity of 0.84±0.02.While our proof-of-principle implementation necessitates some post-selection,the general protocol is deterministic and requires no post-selection to sift desired states and reject a larger ensemble.     

New lithium-zincate approaches for the selective functionalisation of pyrazine: direct dideprotozincation vs. nucleophilic alkylation

Comparing the reactivity of the related lithium zincates [(THF)LiZn(TMP)(t)Bu(2)] (1) and [(PMDETA)LiZn(t)Bu(3)] (2) towards pyrazine discloses two new bimetallic approaches for the selective 2,5-dideprotonation and room temperature C-H alkylation of this sensitive heterocycle.     

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