Thiazole orange (TO) as a light-switch probe: a combined quantum-mechanical and spectroscopic study

A Density Functional Theory (DFT) study of the absorbance and fluorescence emission characteristics of the cyanine thiazole orange (TO) in solution and when intercalated in DNA was carried out in combination with spectrophotometric and spectrofluorometric experiments under different conditions (temperature, concentration, solvent viscosity). T-jump relaxation kinetics of the TO monomer-dimer conversion enabled the thermodynamic parameters of this process to be evaluated. The overall data collected provided information on the features of the "light-switch" by the fluorescent TO and the comparison between experimental and calculated photo-physical properties allowed us to explain and rationalize both shifts and quenching/enhancing effects on fluorescence due to solvation, dimerisation and intercalation in the DNA.     

On-line laser heating setup for ED-XAS at ID24: preliminary optical design and test results

Double-sided laser heating (LH) combined with synchrotron X-ray radiation for in situ studies in the diamond anvil cell (DAC) has been the most productive and widely used high-temperature–high pressure technique in the past two decades. In the framework of the UPBL11 project (upgrade of ID24 beamline of European Synchrotron Radiation Facility), we developed a new on-line LH system for DACs. The preliminary optical scheme of the system is presented and discussed. Varying the settings, we are able to shape and to size the beam on the surface of the sample in the DAC. First pilot applications to the Fe case are shown.     

Enantioselective Alternating Olefin-Carbon Monoxide Copolymerization: A new concept for activity and stereoselectivity

Cationic Pd-complexes modified by dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine ( 1a ) give very active catalytic systems for the regioregular isotactic specific copolymerization of propene with CO. Other alk-1-enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as poly(4-alkyl-tetrahydrofuran-2,2,5,5-tetrayl-2-oxy-2-methylenes) B in the solid state and give the isomeric poly(2-alkyl-1-oxopropane-1,3-diyls) A by dissolution in (CF₃)₂CHOH. Solid polymer A (R = Et) is formed back at least partially when the dissolved material is reprecipitated from MeOH. The use of the related (ferrocenyl)diphosphine ligands 1b ? e and 2 as the catalyst modifier shows that the presence of both elements of chirality and of large substituents on the P-atoms of the ligand is necessary to achieve good stereocontrol, and that the large difference in basicity between the two P-atoms is probably the reason for the good catalytic activity.     

On topologically distinct solutions of the Dirichlet problem for Yang-Mills connections

We prove that for generic Dirichlet boundary data there exist infinitely many topologically distinct solutions to the Dirichlet problem for -Yang-Mills equations over . These are absolute Yang-Mills minimizers in topologically distinct connected components of the space of connections considered. There is a special case for which only finitely many topologically distinct solutions can be found by our method. This corresponds to the simultaneous existence of self dual and anti-self dual solutions, for the given boundary data. If the boundary data is non-flat there exists always more than one solution. This paper generalizes to Yang-Mills fields an important result by Brezis and Coron, who show existence of more than one minimizing harmonic map for non-constant Dirichlet data in two dimensions. Received February 1, 1996 / Accepted March 15, 1996     

Copolymerization of Ethene and Carbon Monoxide with (Diphosphine)nickel Catalysts

This work presents the results of the ethene–CO copolymerization with in situ generated catalysts based on atropisomeric 1,4‐diphosphines and nickel(II). The influence of the reaction conditions and the NMR characterization of the copolymers are described.     

A characterization of hyperelliptic Jacobians

In this paper we will prove a criterion for hyperelliptic Jacobians. LetD be a translation invariant vector field on an indecompssable principally polarized abelian variety (i.p.p.a.v.) (X, Θ), letDΘ be the divisor of the sectionDΘ∈H ⁰ (Θ,O(Θ)|Θ). We have that (X, Θ) is the Jacobian of an hyperelliptic curve iff (Theorem 1) all the component ofDΘ are non reduced and the singular locus of Θ has dimension less thang-2. We will prove our theorem by showing that under the above geometrical condition it is possible to construct a Kodomcev-Petviashvili (K.P.) equation which is satisfied by the theta function corresponding to the principal polarization onX.     

Study of the missing-mass spectra in the reactions π−d → K+ + MM and K−d → π+ + MM at 1.4 GeV/c to search for strange dibaryon states

The reactions π^?d → K⁺ + MM and K^?d → π⁺ + MM have been studied at 1.4 GeV/c to search for strange dibaryon states with quantum numbers Q = ?1, and S = ?1. No structures are found which could indicate the production of such states and upper limits for the cross sections are established.     

Reactivity of β-aluminas with water

The reactivity with air moisture of finely divided crystals of Na β and Li⁺-containing β-aluminas is analyzed with thermogravimetric and X-ray techniques. For Na β-alumina two distinct water intake processes are evident: 1) a fast one, controlled by the elastic interactions among water molecules near the crystal boundaries; 2) a slow one, driven by water diffusion away from the boundaries. For finely divided crystals of Li β-alumina the two processes cannot be distinguished but the slow one is observable in crystals of macroscopic dimensions. The water intake is generally accompanied by an expansion of the c-axis. However, the relationship between water content and c-parameter is highly non-linear and the c-axis length at room temperature depends upon the thermal history of the sample. Our results confirm previous reports suggesting that β-aluminas absorb about one water molecule per cation of the conducting plane.     

Estimates on path delocalization for copolymers at selective interfaces

Starting from the simple symmetric random walk {S_n}_n, we introduce a new process whose path measure is weighted by a factor exp with α,h≥0, {W_n}_n a typical realization of an IID process and N a positive integer. We are looking for results in the large N limit. This factor favors S_n>0 if W_n+h>0 and S_n<0 if W_n+h<0. The process can be interpreted as a model for a random heterogeneous polymer in the proximity of an interface separating two selective solvents. It has been shown [6] that this model undergoes a (de)localization transition: more precisely there exists a continuous increasing function λ↦h_c(λ) such that if h<h_c(λ) then the model is localized while it is delocalized if h≥h_c(λ). However, localization and delocalization were not given in terms of path properties, but in a free energy sense. Later on it has been shown that free energy localization does indeed correspond to a (strong) form of path localization [3]. On the other hand, only weak results on the delocalized regime have been known so far. We present a method, based on concentration bounds on suitably restricted partition functions, that yields much stronger results on the path behavior in the interior of the delocalized region, that is for h>h_c(λ). In particular we prove that, in a suitable sense, one cannot expect more than O( log N) visits of the walk to the lower half plane. The previously known bound was o(N). Stronger O(1)–type results are obtained deep inside the delocalized region. The same approach is also helpful for a different type of question: we prove in fact that the limit as α tends to zero of h_c(λ)/λ exists and it is independent of the law of ω₁, at least when the random variable ω₁ is bounded or it is Gaussian. This is achieved by interpolating between this class of variables and the particular case of ω₁ taking values ±1 with probability 1/2, treated in [6].     

Hydroformylation of 1, 1, 1-d3-2-butene. Isotope Effect on the Product Composition

In the hydroformylation of 1,1,1-trideuterio-2-butene with Rh₄ (CO)₁₂ the deuterated pentanals formed contain 75% of 5,5,5-trideuterio-pentanal, the rest being substantially 2,2-dideuterio-pentanal. On the contrary, using Co₂ (CO)₈ as the catalyst precursor, position 1 and 4 are formylated to the same extent.