The Pt‐Organometallic Version of Perigraniline: Going Blue

Four conjugated push–pull organometallic polymers ( [Pt]‐AQ )_n ( [Pt] = trans‐bis(phenylacetylene)bis(tributylphosphine)platinum(II); AQ = 2‐bromo‐, 2,6‐dibromo‐, 2,6‐diamino‐, and unsubstituted anthraquinone diimine) were prepared and characterized by UV–vis spectroscopy and electrochemistry. A low‐energy charge transfer, CT, band ( [Pt] *→ AQ ; confirmed by density functional theory calculations), was found in the 445–500 nm window rather than the expected red‐shifted range above 630 nm. X‐ray structures of four model compounds reveal that steric hindrance induces large dihedral angles between the C₆H₄ and NCC₂ planes, rendering π‐orbital overlap difficult between the [Pt] and AQ units. The position of the CT band is mainly driven the reduction potential of the anthraquinone diimine unit.     

Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope

We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting Earth's shadow, which is offset in opposite directions for opposite charges due to Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 and 200?GeV. We confirm that the fraction rises with energy in the 20-100?GeV range. The three new spectral points between 100 and 200?GeV are consistent with a fraction that is continuing to rise with energy.     

Efficient and Rapid Synthesis of Radioactive Gold Nanoparticles by Dielectric Barrier Discharge

A compact bench‐top system based on a dielectric barrier plasma discharge (DBD), enables the rapid, automatable, and continuous‐flow synthesis of gold nanoparticles (AuNPs) and radioactive gold nanoparticles (¹⁹⁸AuNPs). AuNPs are used as radiosensitizers in oncology, and ¹⁹⁸AuNPs (half‐life: 2.7 d) have been suggested as potential cancer brachytherapy sources. Plasma applied at the surface of a liquid containing gold ions (AuCl₄^?) and dextran induces the production of AuNPs directly in water. This synthesis is monitored in real time by UV–visible spectrometry: the change of absorbance of the solution provides new insights on the growth dynamics of AuNPs by plasma synthesis. By balancing gold ions and surfactant molecules, particles with a diameter lying in the optimal range for radiosensitizing applications (28 ± 9 nm) are produced. The method yields a reduction of more than 99% of the gold ions within only 30 min of plasma treatment. A postsynthesis ripening of the AuNPs is revealed, monitored by UV–visible spectrometry, and quantified within the first few hours following plasma treatment. Radioactive ¹⁹⁸AuNPs are also produced by DBD synthesis and characterized by electron microscopy and single‐photon emission computed tomography imaging. The results confirm the efficiency of DBD reactors for AuNPs synthesis in oncology applications.     

Interpretations of Quantum Theory in the Light of Modern Cosmology

The difficult issues related to the interpretation of quantum mechanics and, in particular, the “measurement problem” are revisited using as motivation the process of generation of structure from quantum fluctuations in inflationary cosmology. The unessential mathematical complexity of the particular problem is bypassed, facilitating the discussion of the conceptual issues, by considering, within the paradigm set up by the cosmological problem, another problem where symmetry serves as a focal point: a simplified version of Mott’s problem.     

Q-subdifferential and Q-conjugate for global optimality

Normal cone and subdifferential have been generalized through various continuous functions; in this article, we focus on a non separable Q-subdifferential version. Necessary and sufficient optimality conditions for unconstrained nonconvex problems are revisited accordingly. For inequality constrained problems, Q-subdifferential and the lagrangian multipliers, enhanced as continuous functions instead of scalars, allow us to derive new necessary and sufficient optimality conditions. In the same way, the Legendre-Fenchel conjugate is generalized into Q-conjugate and global optimality conditions are derived by Q-conjugate as well, leading to a tighter inequality.     

Study of the band edge in CdIn2S4 by photovoltaic effect

Photovoltaic spectra were measured at 300 and 100 K on AuCdIn₂S₄ Schottky barriers in the spectral range near the band edge of the compound. Analysis of the spectra gives the values of the direct and indirect gaps at both temperatures together with the associated phonon energies. The results are compared with the predictions of the most recent band calculations on CdIn₂S₄.     

Are fem solutions of incompressible flows really incompressible? (or how simple flows can cause headaches!)

It is generally accepted that mixed and penalty finite element methods can routinely solve the incompressible Navier–Stokes equations. This paper shows by means of simple examples that problems can arise even for the simpler Stokes equations. The causes of the problem fall in either of two categories: round-off and ill conditioning, or a poor choice of pressure discretization. Nonsensical solutions can be obtained. Computation of the discrete divergence of the flow field is a simple and powerful tool to diagnose such conditions. In the first part of the paper several simple techniques for minimizing the effect of round-off are reviewed. In the second part it is shown that, for coupled flow problems, care must be exercised in the choice of the pressure approximation. A unified treatment of various observations by different workers is presented. This should prove useful for general users of the finite element method.     

Experiments with several elements for viscous incompressible flows

We present a numerical procedure to eliminate internal nodes from elements designed to approximate incompressible flow problems. We compare six elements in academic and industrial like flow problem and we discuss their relative qualities. A surprising conclusion is that richer elements may behave less well than simple ones if a good enforcement of incompressibility is not maintained.     

tert-Butylmethoxyphenylsilyl ether - a new selective,stable alcohol protecting group with remarkable lability to fluoride.

$\text{tert}$-Butylmethoxyphenylsilyl ethers, which can be formed from primary, secondary or tertiary alcohols and $\text{tert}$-butylmethoxyphenylsilyl bromide, are selectively cleaved by fluoride in the presence of other silyl ethers.