Wide-band electrical and electromechanical properties of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) piezoelectric films using electro-acoustic reflectometry.

Thin piezoelectric polymer films are used in increasingly more high frequency applications. However, they are not well characterized up to the gigahertz range. In this paper, polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) films are mechanically and electrically characterized using the electro-acoustic reflectometry (EAR) method from 20 MHz to 2 GHz. In addition to mechanical and electrical properties, nonuniform poling is detected in the tested PVDF-TrFE samples showing a larger piezoelectric constant in the middle of the film and thus generating even and odd resonance modes.

Collective Spin Modes of a Trapped Quantum Ferrofluid.

We report on the observation of a collective spin mode in a spinor Bose-Einstein condensate. Initially, all spins point perpendicular to the external magnetic field. The lowest energy mode consists of a sinusoidal oscillation of the local spin around its original axis, with an oscillation amplitude that linearly depends on the spatial coordinates. The frequency of the oscillation is set by the zero-point kinetic energy of the BEC. The observations are in excellent agreement with hydrodynamic equations. The observed spin mode has a universal character, independent of the atomic spin and spin-dependent contact interactions.

Competition between Bose-Einstein Condensation and Spin Dynamics.

We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.

Cooling of a Bose-Einstein Condensate by Spin Distillation.

We propose and experimentally demonstrate a new cooling mechanism leading to purification of a Bose-Einstein condensate (BEC). Our scheme starts with a BEC polarized in the lowest energy spin state. Spin excited states are thermally populated by lowering the single particle energy gap set by the magnetic field. Then, these spin-excited thermal components are filtered out, which leads to an increase of the BEC fraction. We experimentally demonstrate such cooling for a spin 3 ^{52}Cr dipolar BEC. Our scheme should be applicable to Na or Rb, with the perspective to reach temperatures below 1 nK.

Nonequilibrium quantum magnetism in a dipolar lattice gas.

We report on the realization of quantum magnetism using a degenerate dipolar gas in an optical lattice. Our system implements a lattice model resembling the celebrated t-J model. It is characterized by a nonequilibrium spinor dynamics resulting from intersite Heisenberg-like spin-spin interactions provided by nonlocal dipole-dipole interactions. Moreover, due to its large spin, our chromium lattice gases constitute an excellent environment for the study of quantum magnetism of high-spin systems, as illustrated by the complex spin dynamics observed for doubly occupied sites.

Truncating mutations in CCM1, encoding KRIT1, cause hereditary cavernous angiomas.

Cavernous angiomas are vascular malformations mostly located in the central nervous system and characterized by enlarged capillary cavities without intervening brain parenchyma. Clinical symptoms include seizures, haemorrhage and focal neurological deficits. Cavernous angiomas prevalence is close to 0.5% in the general population. They may be inherited as an autosomal dominant condition in as much as 50% of cases. Cerebral cavernous malformations (CCM) loci were previously identified on 7q, 7p and 3q (refs 4,5). A strong founder effect was observed in the Hispano-American population, all families being linked to CCM1 on 7q (refs 4,7). CCM1 locus assignment was refined to a 4-cM interval bracketed by D7S2410 and D7S689 (ref. 8). Here we report a physical and transcriptional map of this interval and that CCM1, a gene whose protein product, KRIT1, interacts with RAP1A (also known as KREV1; ref. 9), a member of the RAS family of GTPases, is mutated in CCM1 families. Our data suggest the involvement of the RAP1A signal transduction pathway in vasculogenesis or angiogenesis.

Hybrid quantum systems with high-T[Formula: see text] superconducting resonators.

Superconducting microwave resonators are crucial elements of microwave circuits, offering a wide range of potential applications in modern science and technology. While conventional low-T[Formula: see text] superconductors are mainly employed, high-T[Formula: see text] cuprates could offer enhanced temperature and magnetic field operating ranges. Here, we report the realization of [Formula: see text] superconducting coplanar waveguide resonators, and demonstrate a continuous evolution from a lossy undercoupled regime, to a lossless overcoupled regime by adjusting the device geometry, in good agreement with circuit model theory. A high-quality factor resonator was then used to perform electron spin resonance measurements on a molecular spin ensemble across a temperature range spanning two decades. We observe spin-cavity hybridization indicating coherent coupling between the microwave field and the spins in a highly cooperative regime. The temperature dependence of the Rabi splitting and the spin relaxation time point toward an antiferromagnetic coupling of the spins below 2 K. Our findings indicate that high-Tc superconducting resonators hold great promise for the development of functional circuits. Additionally, they suggest novel approaches for achieving hybrid quantum systems based on high-T[Formula: see text] superconductors and for conducting electron spin resonance measurements over a wide range of magnetic fields and temperatures.

Thermodynamics of a Bose-Einstein condensate with free magnetization.

We study thermodynamic properties of a gas of spin 3(52)Cr atoms across Bose-Einstein condensation. Magnetization is free, due to dipole-dipole interactions. We show that the critical temperature for condensation is lowered at extremely low magnetic fields, when the spin degree of freedom is thermally activated. The depolarized gas condenses in only one spin component, unless the magnetic field is set below a critical value, below which a nonferromagnetic phase is favored. Finally, we present a spin thermometry efficient even below the degeneracy temperature.

Anisotropic excitation spectrum of a dipolar quantum Bose gas.

We measure the excitation spectrum of a dipolar chromium Bose-Einstein condensate with Raman-Bragg spectroscopy. The energy spectrum depends on the orientation of the dipoles with respect to the excitation momentum, demonstrating an anisotropy that originates from the dipole-dipole interactions between the atoms. We compare our results with the Bogoliubov theory based on the local density approximation and, at large excitation wavelengths, with the numerical simulations of the time-dependent Gross-Pitaevskii equation. Our results show an anisotropy of the speed of sound.

Spontaneous demagnetization of a dipolar spinor Bose gas in an ultralow magnetic field.

We study the spinor properties of S = 3 (52)Cr condensates, in which dipole-dipole interactions allow changes in magnetization. We observe a demagnetization of the Bose-Einstein condensate (BEC) when the magnetic field is quenched below a critical value corresponding to a phase transition between a ferromagnetic and a nonpolarized ground state, which occurs when spin-dependent contact interactions overwhelm the linear Zeeman effect. The critical field is increased when the density is raised by loading the BEC in a deep 2D optical lattice. The magnetization dynamics is set by dipole-dipole interactions.

Spin relaxation and band excitation of a dipolar Bose-Einstein condensate in 2D optical lattices.

We observe interband transitions mediated by dipole-dipole interactions for an array of 1D quantum gases of chromium atoms, trapped in a 2D optical lattice. Interband transitions occur when dipolar relaxation releases an energy larger than the lattice band gap. For symmetric lattice sites, and a magnetic field parallel to the lattice axis, we compare the measured dipolar relaxation rate with a Fermi golden rule calculation. Below a magnetic field threshold, we obtain an almost complete suppression of dipolar relaxation, leading to metastable 1D gases in the highest Zeeman state.

Collective excitations of a dipolar Bose-Einstein condensate.

We have measured the effect of dipole-dipole interactions on the frequency of a collective mode of a Bose-Einstein condensate. At relatively large numbers of atoms, the experimental measurements are in good agreement with zero temperature theoretical predictions based on the Thomas-Fermi approach. Experimental results obtained for the dipolar shift of a collective mode show a larger dependency to both the trap geometry and the atom number than the ones obtained when measuring the modification of the condensate aspect ratio due to dipolar forces. These findings are in good agreement with simulations based on a Gaussian ansatz.

Bioinformatic strategies to provide functional clues to the unknown genes in Plasmodium falciparum genome.

The fight against Plasmodium falciparum, the species responsible for 90% of the lethal forms of human malaria, took a new direction with the publication of its genome in 2002. However, the hopes that the genome should help bringing to the foreground the expected new "vaccines candidates" or "targets of new medicines" were disappointed by the low number of genes that could be functionally annotated--less than 40% upon the genome publication, just over 50% eight years later. This 10% gain of knowledge was made possible by the efforts of the entire scientific community in many directions which include: the production of transcriptomic and proteomic profiles at various stages of the parasite development and in response to drug or stress treatments; the proteomic study of subcellular compartments; the sequencing of numerous Plasmodium related species (allowing whole genome comparisons) and the sequencing of numerous P. falciparum strains (allowing investigations of gene polymorphism). In parallel with this production of experimental biological data, the development of original mining tools adapted to the P falciparum specificities quickly appeared as a priority, as the performances of "classical" bioinformatic tools, used successfully for other genomes, had limited efficacy. This was the aim of the PlasmoExplore project launched in 2007. This brief review does not cover all efforts made by the international community to decipher the P falciparum genome but focuses on improvements and novel mining methods investigated by the PlasmoExplore consortium, and some of the lessons we could learn from these efforts.

Abscisic acid signaling through cyclic ADP-ribose in plants.

Abscisic acid (ABA) is the primary hormone that mediates plant responses to stresses such as cold, drought, and salinity. Single-cell microinjection experiments in tomato were used to identify possible intermediates involved in ABA signal transduction. Cyclic ADP-ribose (cADPR) was identified as a signaling molecule in the ABA response and was shown to exert its effects by way of calcium. Bioassay experiments showed that the amounts of cADPR in Arabidopsis thaliana plants increased in response to ABA treatment and before ABA-induced gene expression.

Out-of-equilibrium quantum magnetism and thermalization in a spin-3 many-body dipolar lattice system.

Understanding quantum thermalization through entanglement build up in isolated quantum systems addresses fundamental questions on how unitary dynamics connects to statistical physics. Spin systems made of long-range interacting atoms offer an ideal experimental platform to investigate this question. Here, we study the spin dynamics and approach towards local thermal equilibrium of a macroscopic ensemble of S = 3 chromium atoms pinned in a three dimensional optical lattice and prepared in a pure coherent spin state, under the effect of magnetic dipole-dipole interactions. Our isolated system thermalizes under its own dynamics, reaching a steady state consistent with a thermal ensemble with a temperature dictated from the system's energy. The build up of quantum correlations during the dynamics is supported by comparison with an improved numerical quantum phase-space method. Our observations are consistent with a scenario of quantum thermalization linked to the growth of entanglement entropy.

Exploring functional genomics for drug target and therapeutics discovery in Plasmodia.

Functional genomics approaches are indispensable tools in the drug discovery arena and have recently attained increased attention in antibacterial drug discovery research. However, the application of functional genomics to post-genomics research of Plasmodia is still in comparatively early stages. Nonetheless, with this genus having the most species sequenced of any eukaryotic organism so far, the Plasmodia could provide unique opportunities for the study of intracellular eukaryotic pathogens. This review presents the status quo of functional genomics of the malaria parasite including descriptions of the transcriptome, proteome and interactome. We provide examples for the in silico mining of the X-ome data sets and illustrate how X-omic data from drug challenged parasites might be used in elucidating amongst others, the mode-of-action of inhibitory compounds, validate potential targets and discover novel targets/therapeutics.

The apicoplast: a new member of the plastid family.

Protozoan parasites of the phylum Apicomplexa include pathogens such as Plasmodium, Toxoplasma and Cryptosporidium. They have been shown to contain a vestigial nonphotosynthetic plastid, the apicoplast, which might have arisen by secondary endosymbiosis. Little is known about the function of the apicoplast but the parasites exhibit delayed cell death when their apicoplast is impaired. The discovery of the apicoplast opens an unexpected opportunity to link current fundamental research on plant and algal plastids to the physiology of apicomplexans. For example, the apicoplast might provide new targets for innovative drugs that act as herbicides and do not affect the mammalian host.

Genetic heterogeneity and absence of founder effect in a series of 36 French cerebral cavernous angiomas families.

Cerebral cavernous angiomas malformations (CCM) can be inherited as an autosomal dominant condition. CCM1, a yet unidentified gene mapping on 7q21-q22, was shown to be involved in all CCM Hispano-American families, with a strong founder effect. Genetic heterogeneity in non Hispano-American families was established in two families. We conducted a genetic linkage analysis on 36 French CCM families using eight microsatellite markers mapping within the CCM1 interval. Admixture analysis showed that 65% of these families were linked to the CCM1 locus. Haplotypes analysis of CCM1-linked families did not show any evidence for a strong founder effect.

Comparison of the kinetic properties of MGDG synthase in mixed micelles and in envelope membranes from spinach chloroplast.

We have applied the 'membrane partition' kinetic modelling approach proposed by Heirwegh et al. [(1988) Biochem. J. 254, 101-108] to MGDG synthase in isolated envelope vesicles. Comparison of the kinetic parameters obtained for MGDG synthase assayed in purified envelope membranes and in mixed-micelles demonstrates that the latter are relevant to the situation in envelope membranes and that MGDG synthase has a very high affinity for dilinoleoylglycerol. Our results provide additional evidence for the hypothesis that the high affinity of the envelope MGDG synthase for dilinoleoylglycerol could be responsible for the presence of C18 fatty acids at both the sn-1 and sn-2 position of the glycerol backbone in MGDG.