Synthesis of chromophores combining second harmonic generation and two photon induced fluorescence properties

The design of new chromophores presenting simultaneous SHG and TPEF properties is reported.     

Potent algicides based on the cyanobacterial alkaloid nostocarboline

[structure: see text] Nostocarboline and seven derivatives were prepared and displayed minimal inhibitory concentration (MIC) values >or=100 nM against the growth of Microcystis aeruginosa PCC 7806, Synechococcus PCC 6911, and Kirchneriella contorta SAG 11.81, probably via the inhibition of photosynthesis. The natural product hybrid nostocarboline/ciprofloxacin displayed additional antibacterial activity against several Gram-negative bacteria (MICs >or=0.7 microM). Nostocarboline can thus be considered a potent, selective, readily available, natural algicide.     

Structural effects on the ground and excited-state properties of photoswitchable hydrogen-bonding receptors

The ground- and excited-state properties of a series of photochromic barbiturate receptors (N,N'-bis{6-[omega-(anthracen-9-yloxy)alkanoylamino]pyridin-2-yl}-5-t-butyl-isophthalamide, Tn), in which anthracene chromophores are tethered via (CH2)n (n = 1, 3-6) polymethylene linkers to the H-bond receptor moiety, are described. In these systems, the thermally reversible [4pi + 4pi] photodimerization of the anthracenes yields macrocyclic receptors (TnC) that possess significantly reduced affinity toward barbital as compared to their acyclic counterparts. The length of the tether not only determines the overall binding ability of the cyclized receptor but also has a profound influence on the photochemical and photophysical properties of the anthracene chromophores. The reduced mobility experienced by the covalently bound anthracenes controls the reactivity of a fluorescent excimer that is proposed to be an intermediate in the photocyclization process.     

In solution sensitization of Er(III) luminescence by the 4-tetrathiafulvalene-2,6-pyridinedicarboxylic acid dimethyl antenna ligand

In the [Er(hfac)(3)(L)](2) complex (1) (L = 4-tetrathiafulvalene-2,6-pyridinecarboxylic acid dimethyl ester), the Er(III) ion is bonded to the tridentate coordination site. Electrochemical and photophysical measurements in solution reveal that the tetrathiafulvalene moiety is a versatile antenna for erbium luminescence sensitization at 6540 cm(-1) upon excitation in the low-energy charge transfer transition (donor to acceptor charge transfer) at 16600 cm(-1) assigned via time-dependent density functional theory calculations.     

Long-range effects on the capture and release of a chiral guest by a helical molecular capsule

Helically folded molecular capsules based on oligoamide sequences of aromatic amino acids which are capable of binding tartaric acid in organic solvents with high affinity and diastereoselectivity have been synthesized, and their structures and binding properties investigated by (1)H NMR, X-ray crystallography, circular dichroism, and molecular modeling. We found that elongating the helices at their extremities by adding monomers remote from the tartaric binding site results in a strong increase of the overall helix stability, but it does not influence the host-guest complex stability. The effect of this elongation on the binding and release rates of the guest molecules follows an unexpected non-monotonous trend. Three independent observations (direct monitoring of exchange over time, 2D-EXSY NMR, and molecular modeling) concur and show that guest exchange rates tend to first increase upon increasing helix length and then decrease when helix length is increased further. This investigation thus reveals the complex effects of adding monomers in a helically folded sequence on a binding event that occurs at a remote site and sheds light on possible binding and release mechanisms.     

Pressure–velocity coupling allowing acoustic calculation in low Mach number flow

Low Mach number flow computation in co-located grid arrangement requires pressure–velocity coupling in order to prevent the checkerboard phenomenon. Two broad categories of pressure–velocity coupling methods for unsteady flows can be distinguished based on the time-step dependency of the coupling coefficient in the definition of the transporting velocity on a face of a control volume. As an example of the time-step independent category, the AUSM⁺-up scheme is studied. As an example of the second category, Rhie–Chow momentum interpolation methods are studied. Within the momentum interpolation techniques, again two broad categories can be distinguished based on the time-step dependency of the coupling coefficient used for unsteady flow computations, but when a steady state is reached. Variants of Rhie–Chow interpolation methods in each subcategory are studied on critical test cases. The result of the study is that for a good representation of unsteady flows containing acoustic information, the pressure–velocity coupling coefficient must explicitly depend on the time-step, but that the transporting velocity must become independent of the time-step when a steady state is reached.     

Relating the CMSSM and SUGRA models with GUT-scale and super-GUT-scale supersymmetry breaking

While the constrained minimal supersymmetric standard model (CMSSM) with universal gaugino masses, m _1/2, scalar masses, m ₀, and A-terms, A ₀, defined at some high energy scale (usually taken to be the GUT scale) is motivated by general features of supergravity models, it does not carry all of the constraints imposed by minimal supergravity (mSUGRA). In particular, the CMSSM does not impose a relation between the trilinear and bilinear soft supersymmetry breaking terms, B ₀=A ₀?m ₀, nor does it impose the relation between the soft scalar masses and the gravitino mass, m ₀=m _3/2. As a consequence, tanβ is computed given values of the other CMSSM input parameters. By considering a Giudice–Masiero (GM) extension to mSUGRA, one can introduce new parameters to the Kähler potential which are associated with the Higgs sector and recover many of the standard CMSSM predictions. However, depending on the value of A ₀, one may have a gravitino or a neutralino dark matter candidate. We also consider the consequences of imposing the universality conditions above the GUT scale. This GM extension provides a natural UV completion for the CMSSM.     

Mueller matrix polarimetry for improved liver fibrosis diagnosis

An experimental Mueller matrix polarimeter is used to quantify human liver fibrosis by measuring retardance and depolarization of thin biopsies. The former parameter is sensitive to fibrillar collagen, the latter is specifically sensitive to fibrillar collagen around blood vessels, which is not significant for liver fibrosis diagnosis. By using depolarization like a filter, retardance distribution enables distinguishing between disease stages and limits the high degree of observer discrepancy.     

Variable temperature STM study of Co deposition on a dodecanethiol self assembled monolayer

The present scanning tunneling microscopy study reports on the growth processes of Co vapor-deposited on a dodecanethiol (DDT) self-assembled monolayer (SAM)/Au(111). We observe strongly modified surface and depth diffusions of Co adatoms depending on the growth temperature. Co deposited at 300 K shows an extremely incomplete regime of condensation on the organic layer. Besides, Co penetrates the DDT monolayer and resides at the DDT/Au(111) interface as 2D clusters. This phenomenon takes place through defects in the SAM which are transient channels. In contrast, Co deposited at 50 K shows a complete condensation and nucleates on defects of the SAM layer as 3D islands sitting most likely on top of the DDTs. These results are of interest in the growing field of organic spintronics where the quality of the organic/ferromagnetic interface is a key issue.     

Characterizations of Copulas Attaining the Bounds of Multivariate Kendall’s Tau

Kendall’s tau is one of the most popular measures of concordance, and even in the multivariate case exact upper and lower bounds of Kendall’s tau are known. The present paper provides characterizations of the copulas attaining the bounds of multivariate Kendall’s tau, mainly in terms of the copula measure, but also via Kendall’s distribution function and for shuffles of copulas.