Product-state distribution after isotopic substitution in ultracold atom-molecule collisions

We show that products of the isotopic substitution reactions in experimentally accessible molecules such as NaK, RbCs, and SrF are cold according to their translational energy below hundreds of mK. For these chemical reactions, molecular products may occupy only the lowest rotational states. We also discuss the possibility of controlling the chemical reactions by the electric field in ultracold mixtures of molecules and atoms with low kinetic energy release, where one of the constituent atoms of colliding molecule is replaced by its isotope. This letter opens new avenues in investigating the branching ratios of chemical reactions in ultracold conditions

Dilute Gd hydroxycarbonate particles for localized spin qubit integration

Molecular spins are considered as the quantum hardware to build hybrid quantum processors in which coupling to superconducting devices would provide the means to implement the necessary coherent manipulations. As an alternative to large magnetically-dilute crystals or concentrated nano-scale deposits of paramagnetic molecules that have been studied so far, the use of pre-formed sub-micronic spherical particles of a doped Gd@Y hydroxycarbonate is evaluated here. Particles with an adjustable number of spin carriers are prepared through the control of both particle size and doping. Bulk magnetic properties and continuous wave and time-domain-EPR spectroscopy show that the Gd spins in these particles are potential qubits with robust quantum coherence. Monolayers of densely-packed particles are then formed interfacially and transferred successfully to the surface of Nb superconducting resonators. Alternatively, these particles are disposed at controlled localizations as isolated groups of a few particles through Dip-Pen Nanolithography using colloidal organic dispersions as ink. Altogether, this study offers new material and methodologies relevant to the development of viable hybrid quantum processors

Dissecting the function of Atg1 complex in Dictyostelium autophagy reveals a connection with the pentose phosphate pathway enzyme transketolase

The network of protein–protein interactions of the Dictyostelium discoideum autophagy pathway was investigated by yeast two-hybrid screening of the conserved autophagic proteins Atg1 and Atg8. These analyses confirmed expected interactions described in other organisms and also identified novel interactors that highlight the complexity of autophagy regulation. The Atg1 kinase complex, an essential regulator of autophagy, was investigated in detail here. The composition of the Atg1 complex in D. discoideum is more similar to mammalian cells than to Saccharomyces cerevisiae as, besides Atg13, it contains Atg101, a protein not conserved in this yeast. We found that Atg101 interacts with Atg13 and genetic disruption of these proteins in Dictyostelium leads to an early block in autophagy, although the severity of the developmental phenotype and the degree of autophagic block is higher in Atg13-deficient cells. We have also identified a protein containing zinc-finger B-box and FNIP motifs that interacts with Atg101. Disruption of this protein increases autophagic flux, suggesting that it functions as a negative regulator of Atg101.We also describe the interaction of Atg1 kinase with the pentose phosphate pathway enzyme transketolase (TKT). We found changes in the activity of endogenous TKT activity in strains lacking or overexpressing Atg1, suggesting the presence of an unsuspected regulatory pathway between autophagy and the pentose phosphate pathway in Dictyostelium that seems to be conserved in mammalian cellsThis work was supported by grant nos. BFU2009-09050 and BFU2012-32536 from the Spanish Ministerio de Economía y competitividad. The cost of this publication has been paid in part by FEDER funds. A.M. was recipient of a predoctoral fellowship (FPI associated to the grant no. BFU2012-32536). L.C.T. is recipient of a FPU fellowship from Ministerio de Educación, cultura y deport

An interferometric study of the Fomalhaut inner debris disk. I. Near-infrared detection of hot dust with VLTI/VINCI

The innermost parts of dusty debris disks around main sequence stars are currently poorly known due to the high contrast and small angular separation with their parent stars. Using near-infrared interferometry, we aim to detect the signature of hot dust around the nearby A4 V star Fomalhaut, which has already been suggested to harbor a warm dust population in addition to a cold dust ring located at about 140 AU. Archival data obtained with the VINCI instrument at the VLTI are used to study the fringe visibility of the Fomalhaut system at projected baseline lengths ranging from 4 m to 140 m in the K band. A significant visibility deficit is observed at short baselines with respect to the expected visibility of the sole stellar photosphere. This is interpreted as the signature of resolved circumstellar emission, producing a relative flux of 0.88% +/- 0.12% with respect to the stellar photosphere. While our interferometric data cannot directly constrain the morphology of the excess emission source, complementary data from the literature allow us to discard an off-axis point-like object as the source of circumstellar emission. We argue that the thermal emission from hot dusty grains located within 6 AU from Fomalhaut is the most plausible explanation for the detected excess. Our study also provides a revised limb-darkened diameter for Fomalhaut (2.223 +/- 0.022 mas), taking into account the effect of the resolved circumstellar emission.Comment: 13 pages, accepted for publication in Ap

Tagging, encoding, and jones optimality

A partial evaluator is said to be Jones-optimal if the result of specializing a self-interpreter with respect to a source program is textually identical to the source program, modulo renaming. Jones optimality has already been obtained if the self-interpreter is untyped. If the selfinterpreter is typed, however, residual programs are cluttered with type tags. To obtain the original source program, these tags must be removed.; ; A number of sophisticated solutions have already been proposed. We observe, however, that with a simple representation shift, ordinary partial evaluation is already Jones-optimal, modulo an encoding. The representation shift amounts to reading the type tags as constructors for higherorder abstract syntax. We substantiate our observation by considering a typed self-interpreter whose input syntax is higher-order. Specializing this interpreter with respect to a source program yields a residual program that is textually identical to the source program, modulo renaming.Publicado en Basic Research in Computer Science, April, 2003.Laboratorio de Investigación y Formación en Informática Avanzad

Diastereomerically Pure Heterodi- and Heterotetrametallic (Pd and Pt) Compounds: A Study of the Effect Induced by the Binding Mode of a Ferrocene-Containing Ligand on Their Electrochemical Properties.

The reaction of (1S,2R)-[(η5-C5H5)Fe{(η5-C5H4)-CH=NCH(Me)-CH(OH)(C6H5)}] (1) with Na2[PdCl4] in the presence of Na(OAc)·3H2O produced three diastereomerically pure tetrametallic cyclopalladated complexes (6bI-6bIII). In two of them (6bI and 6bII), the imine 1 adopts the [C(sp2,ferrocene), N]- mode of binding, but they differ in the planar chirality of the 1,2-ferrocenyl unit (Sp in 6bI and Rp in 6bII), whereas ligand 1 in 6bIII acts as a [C(sp2,phenyl),N]- group. Treatment of 6bI-6bIII with PPh3 gave [Pd{κ2-C,N{(η5-C5H3)-CH=N-CH(Me)-CH(OH)(C6H5)}Fe(η5-C5H5)}Cl(PPh3)] (7bI,7bII) and [Pd{κ2-C,N{(C6H4)-CH(OH)-CH(Me)-N=CH-(η5-C5H4)}Fe(η5-C5H5)}Cl(PPh3)] (7bIII). The PtII compounds [Pt{κ2-C,N{(η5-C5H3)-CH=NCH(Me)CH(OH)(C6H5)}Fe(η5-C5H5)}Cl(PPh3)] [(Sp,1S,2R) and (Rp,1S,2R) diastereomers, 7aII and 7aII, respectively)] have also been prepared. The results of electrochemical studies of 6bI-6bIII, 7bI-7bIII, 7aI, 7aII and related PtII complexes with 1 acting as an (N) or (N,O)- ligand are also reported. Comparison of the results provides conclusive evidence for the relative influence of the mode of binding of the ligand, the nature of the MII atom, the type of metallated atom C(sp2,phenyl or ferrocenyl), the ancillary ligands and their relative disposition on the electrochemical properties of this type of compound

A ferric guest inside a spin crossover ferrous helicate

A designed dimetallic Fe(II) helicate made with biphenylenebridged bispyrazolylpyridine ligands and exhibiting a process of spin crossover at temperatures above ambient is shown to encapsulate an S = 5/2 tris-oxalato Fe(III) ion. The spin relaxation dynamics of this guest are strongly reduced upon encapsulatio