Evidence of symmetry breaking in a Gd2 di-nuclear molecular polymer

A chiral 3D coordination compound, [Gd₂(L)₂(ox)₂(H₂O)₂], arranged around a dinuclear Gd unit has been characterized by X-ray photoemission and X-ray absorption measurements in the context of density functional theory studies. Core level photoemission of the Gd 5p multiplet splittings indicates that spin orbit coupling dominates over j-J coupling evident in the 5p core level spectra of Gd metal. Indications of spin-orbit coupling are consistent with the absence of inversion symmetry due to the ligand field. Density functional theory predicts antiferromagnet alignment of the Gd₂ dimers and a band gap of the compound consistent with optical absorption.

Molecular transistors as substitutes for quantum information applications

Applications of quantum information science (QIS) generally rely on the generation and manipulation of qubits. Still, there are ways to envision a device with a continuous readout, but without the entangled states. This concise perspective includes a discussion on an alternative to the qubit, namely the solid-state version of the Mach-Zehnder interferometer, in which the local moments and spin polarization replace light polarization. In this context, we provide some insights into the mathematics that dictates the fundamental working principles of quantum information processes that involve molecular systems with large magnetic anisotropy. Transistors based on such systems lead to the possibility of fabricating logic gates that do not require entangled states. Furthermore, some novel approaches, worthy of some consideration, exist to address the issues pertaining to the scalability of quantum devices, but face the challenge of finding the suitable materials for desired functionality that resemble what is sought from QIS devices.

Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H₂O)] with Ln = Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺ and Yb³⁺ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO₃)₃·xH₂O with the 1,3-bis(carboxymethyl)imidazolium [HL] ligand and oxalic acid (H₂ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb_{1- x} Eu _x (L)(ox)(H₂O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb³⁺ and Eu³⁺. The best sensitivities were obtained using the ratio between the emission intensities of Eu³⁺ (⁵D₀→⁷F₂ transition) and of the ligand as the thermometric parameter. [Tb_0.97Eu_0.03(L)(ox)(H₂O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%·K^-1 at 340 K.

Microwave-assisted functionalization of the Aurivillius phase Bi2SrTa2O9: diol grafting and amine insertion vs. alcohol grafting

The microwave-assisted functionalization of an Aurivillius phase is investigated towards various molecules – alcohols, diols and amino-alcohols – and the preferential reactivity of the various moieties is studied as a function of the reaction conditions.

Microwave-assisted functionalization of the layered Aurivillius phase Bi₂SrTa₂O₉ by alcohols is thoroughly investigated. The grafting of linear aliphatic and bulky alcohols is studied as a function of the starting material, underlining the importance of the prefunctionalization of the layered perovskite, for instance by butylamine. In addition, the functionalization by α,ω-alkanediols is explored. α,ω-alkanediols bearing long alkyl chains (n_C > 3) adopt an unprecedented pillaring arrangement, whereas 1,3-propanediol and ethyleneglycol adopt a bilayer arrangement, only one out of the two hydroxyl groups being coordinated. Finally, the reactivities of alcohols and amines towards insertion are compared: the preferential reactivity of the two functional groups appears to be strongly dependent of the reaction conditions, and especially of the water content. This study is further extended to the case of amino-alcohol insertion. In this case, the amine group is preferentially bound, but it is possible to control the grafting of the alcohol moiety, thus going from a bilayer arrangement to a pillaring one. This work is of particular importance to be able to functionalize easily and rapidly layered oxides with elaborated molecules, bearing several different potentially reactive groups.

Categorical Colormap Optimization with Visualization Case Studies

Mapping a set of categorical values to different colors is an elementary technique in data visualization. Users of visualization software routinely rely on the default colormaps provided by a system, or colormaps suggested by software such as ColorBrewer. In practice, users often have to select a set of colors in a semantically meaningful way (e.g., based on conventions, color metaphors, and logological associations), and consequently would like to ensure their perceptual differentiation is optimized. In this paper, we present an algorithmic approach for maximizing the perceptual distances among a set of given colors. We address two technical problems in optimization, i.e., (i) the phenomena of local maxima that halt the optimization too soon, and (ii) the arbitrary reassignment of colors that leads to the loss of the original semantic association. We paid particular attention to different types of constraints that users may wish to impose during the optimization process. To demonstrate the effectiveness of this work, we tested this technique in two case studies. To reach out to a wider range of users, we also developed a web application called Colourmap Hospital.

New metal phthalocyanines/metal simple hydroxide multilayers: experimental evidence of dipolar field-driven magnetic behavior

A series of new hybrid multilayers has been synthesized by insertion-grafting of transition metal (Cu(II), Co(II), Ni(II), and Zn(II)) tetrasulfonato phthalocyanines between layers of Cu(II) and Co(II) simple hydroxides. The structural and spectroscopic investigations confirm the formation of new layered hybrid materials in which the phthalocyanines act as pillars between the inorganic layers. The magnetic investigations show that all copper hydroxide-based compounds behave similarly, presenting an overall antiferromagnetic behavior with no ordering down to 1.8 K. On the contrary, the cobalt hydroxide-based compounds present a ferrimagnetic ordering around 6 K, regardless of the nature of the metal phthalocyanine between the inorganic layers. The latter observation points to strictly dipolar interactions between the inorganic layers. The amplitude of the dipolar field has been evaluated from X-band and Q-band EPR spectroscopy investigation (Bdipolar ≈ 30 mT).

Microwave-assisted post-synthesis modification of layered simple hydroxides

We show here that it is possible to post-functionalize metal simple hydroxide layers by performing in situ microwave-assisted reactions.

“Nanocasting”: Using SBA-15 Silicas as Hard Templates to Obtain Ultrasmall Monodispersed γ-Fe2O3 Nanoparticles

This work describes the use of mesoporous SBA-15 silicas as hard templates for the size-controlled synthesis of oxide nanoparticles, with the pores acting as nanoscale reactors. This fundamental work is mainly aimed at understanding unresolved issues concerning the occurrence and size dependence of phase transitions in oxide nanocrystals. Aqueous solutions of Fe(NO3)3*9H2O are deposited inside the pores of SBA-15 silicas with mesopore diameters of 4.3, 6.6, and 9.5 nm. By calcination, the nitrate salt transforms into FeOx oxides. The XRD peaks of nanocrystals are broad and overlapping, resulting in ambiguities attributed to a given allotropic variety of Fe2O3 (alpha, epsilon, or gamma) or Fe3O4. The association of XRD, SAED, and Raman information is necessary to solve these ambiguities. The metastable gamma-Fe2O3 variety is selectively formed at low Fe/Si atomic ratio (ca. 0.20) and when a low calcination temperature is used (773 or 873 K followed by quenching to room temperature once the targeted temperature is reached). The small size dispersion of the patterned nanoparticles, suggested on a local scale by TEM, is confirmed statistically by magnetic measurements. The nanoparticles have a superparamagnetic behavior around room temperature. Their magnetic moments (from 220 to 370 mB), their sizes (from 4.0 to 4.8 nm), and their blocking temperatures (from 36 to 58 K) increase with the silica template mesopore diameter. Their magnetic properties are compared to those of standard gamma-Fe2O3 nanoparticles of similar size, obtained by coprecipitation in water and stabilized by a citrate coating.

[New French recommendations for the prophylaxis of infectious endocarditis]

New French recommendations on infective endocarditis (IE) prevention were recently published and mark a turning point in the history of antibiotic prophylaxis. Endocarditis is an evolving disease, and its clinical and microbiological profile dramatically changes over time. The French surveys that were conducted in 1991 and 1999 showed variations in underlying heart disease with a decrease in native valvular disease and an increase of IE in patients without previously known heart disease. Moreover, the distribution of responsible microorganisms dramatically changed over time, with a marked decrease of oral streptococci. In addition, some dogmas are now challenged. First of all, the part of responsibility of dental procedures is debated, as dental bacteraemia possibly responsible of endocarditis are more likely due to daily manoeuvres such as tooth brushing or chewing gum than to occasional dental procedures. Moreover, as suggested by case-control studies, efficacy--or lack of efficacy--of antibiotic prophylaxis is far from being clinically proved. For all these reasons, the proportion of theoretically avoidable endocarditis seems very low, and the benefit of largely and systematically applied antibiotic prophylaxis may be discussed, not only in terms of financial cost but also in terms of microbiological threat of emergence of antibiotic resistant bacteria. So, the general idea of those new recommendations was to maintain the principle and the modalities of antibiotic prophylaxis, but to limit its indications to situations at high benefit to risk ratio, i.e. procedures at high risk in patients at high risk. Depending on the situation, antibiotic prophylaxis may be either recommended or become optional and decision-making factors are defined. Furthermore, the importance of general prophylaxis was emphasised, concerning more specifically oral and cutaneous hygiene, and patients and practitioners' education, such as, for example, recommendations on blood cultures to be performed before any antibiotic treatment in case on fever occurring in a patient at risk during the 3 months following a procedure at risk.

An ATP-based method for monitoring the microbiological drinking water quality in a distribution network

The titration of adenosine triphosphate (ATP) by bioluminescence permits rapid evaluation of the quantity of viable micro-organisms present in a water sample. During two sampling campaigns, Société Anonyme de Gestion des Eaux de Paris (SAGEP) tested a new extraction and titration system of bacterial ATP in the Paris drinking water distribution network. As far as the entire set of results of analyses of water in the network is concerned there is a linear relationship between log [ATP] and log(HPC-R2A/ml). Furthermore, as regards the drinking water originating from treatment of surface waters, some of the results obtained indicate a slight change as regards the Paris network in the microbiological quality. This is certainly linked to the distance travelled from the production location as well as to a reservoir effect observed on a site. Conversely, no change is apparent with regard to waters of underground origin. Lastly, despite changes in temperature and chlorine residual, no significant influence has been observed, essentially because of the very low density of culturable bacteria.

Retroviral display of functional binding domains fused to the amino terminus of influenza hemagglutinin

We have previously shown that retroviral vector particles derived from Moloney murine leukemia virus (Mo-MuLV) can efficiently incorporate influenza hemagglutinin (HA) glycoproteins from fowl plague virus (FPV), thus conferring a broad tropism to the vectors. To modify its host range, we have engineered the FPV HA to display four different polypeptides on its N terminus: the epidermal growth factor, an anti-human MHC class I molecules scFv (single-chain antibody), an anti-melanoma antigen scFv, and an IgG Fc-binding polypeptide. All recombinant HA glycoproteins were correctly expressed and processed, and efficiently incorporated into Mo-MuLV retroviral particles, indicating that amino-terminal insertion of large polypeptides did not alter the conformation of HA chimeras. Virions carrying the different chimeras bound specifically to cells expressing the targeted cell surface molecules of each ligand. In addition, all virion types were infectious but exhibited various degrees of specificity regarding the use of the targeted cell surface molecule versus the wild-type FPV HA receptor for cell entry and infection. For some ligands tested, infectivity was significantly increased on cells that express the targeted receptor, compared with cells that express only the wild-type HA receptor. Furthermore, some polypeptides could abolish infectivity via the wild-type FPV HA receptor. Our data therefore indicate that it is possible to engineer the HA envelope glycoprotein by fusing ligands to its amino-terminal end without affecting its fusion activity.