Fluorescence microscopy of single autofluorescent proteins for cellular biology

In this paper we review the applicability of autofluorescent proteins for single-molecule imaging in biology. The photophysical characteristics of several mutants of the Green Fluorescent Protein (GFP) and those of DsRed are compared and critically discussed for their use in cellular biology. The alternative use of two-photon excitation at the single-molecule level or Fluorescence Correlation Spectroscopy is envisaged for the study of individual autofluorescent proteins. Single-molecule experiments performed in live cells using eGFP and preferably eYFP fusion proteins are reviewed. Finally, the first use at the single-molecule level of citrine, a more photostable variant of the eYFP is reported when fused to a receptor for neurotransmitter in live cells. To cite this article: L. Cognet et al., C. R. Physique 3 (2002) 645–656.     

Single-molecule spectroscopy and microscopy

Advances in detector sensitivity and improvements in instrument design have recently provided scientists with tools to probe single molecules with light, and monitor their photophysical properties with exquisite sensitivity and spatial as well as temporal resolution. Spectroscopic and temporal information is used to explore molecular structure, conformational dynamics, local environment and intermolecular interactions of individual species. High-resolution single-molecule microscopy allows these methods to be used for in vitro or in vivo molecular colocalization with nanometer precision. The collected data have generated a wealth of new information in domains ranging from chemistry and biology to solid state physics. To cite this article: X. Michalet, S. Weiss, C. R. Physique 3 (2002) 619–644.     

Voltage addressable nanomemories in DNA?

Short single-stranded DNA (or RNA) molecules can be designed to have several long lived (> hours) secondary structures. In principle, such molecules could be used as nanomemories if they could be easily induced to switch between trapped states. We propose here that the necessary work required to drive the molecule into one particular trapped state can be provided by its own synthesis. Following this idea, we argue that a low voltage (<1 V) may induce a bistable DNA molecule to switch structure at will, by forcing it to thread through a nanopore and refold alternatively from either of its ends. To cite this article: H. Isambert, C. R. Physique 3 (2002) 391–396.     

Cross-correlated relaxation in NMR of macromolecules in the presence of fast and slow internal dynamics

In this paper we present an analysis of correlation and spectral density functions involved in autorelaxation and cross-correlated relaxation in the magnetic resonance of macromolecules. Internal dynamics of the macromolecule are described in terms of two distinct fluctuation processes with different, slow and fast, correlation times. The approach developed in this work takes into account the possible coupling between both fluctuating internal processes. To cite this article: L. Vugmeyster et al., C. R. Physique 5 (2004).     

The primordial sculpting of the Kuiper belt

Understanding how the Kuiper belt acquired its puzzling present orbital structure will provide insight into the formation of the outer planetary system and on its early evolution. We outline a scenario of primordial sculpting – issued from a combination of mechanisms proposed by various authors – that seems to explain most of the observed properties of the Kuiper belt. Several aspects are not yet totally clear, and some may not be totally correct. But, for the first time, we have a view – if not of the detailed sculpture – at least of its rough cast. To cite this article: A. Morbidelli, H.F. Levison, C. R. Physique 4 (2003).     

Dense flows of dry granular material

The behavior of dense assemblies of dry grains submitted to continuous shear deformation is still not well understood. Recently it has been the subject of several experiments and discrete particle simulations. For both confined and free surface geometries, we present the general features of such flows as well as grain-level information. We then describe the main rheological models and their predictions. To cite this article: O. Pouliquen, F. Chevoir, C. R. Physique 3 (2002) 163–175.     

Experimental evidence of magnetochiral interaction in Pasteur's tartrates

We have isolated the magnetochiral refraction in Pasteur's tartrates and deduced the associated magnetochiral absorption. The presence of a strong peak at 235 nm in the magnetochiral absorption spectrum of tartrates shows that Pasteur's first attempt to induce chirality with a magnetic field could perhaps have succeeded, provided that a UV source was simultaneously used. To cite this article: T. Ruchon et al., C. R. Physique 5 (2004).     

Organic thin film crystal growth for nonlinear optics: present methods and exploratory developments

We discuss different methods to grow organic single crystalline thin films from solution. Specifically, we address exploratory developments and apply them on the highly nonlinear material DAST (4′-dimethylamino-N-methyl-4-stilbazolium tosylate) in a DAST/methanol system. We describe the nucleation and growth thermodynamics in solution using a solubility diagram and its Ostwald–Meiers metastable region. The important experimental parameters for bidimensional growth are discussed and first promising results are presented. To cite this article: S. Manetta et al., C. R. Physique 3 (2002) 449–462.     

Strings on pp-waves and massive two-dimensional field theories

We find a general class of pp-wave solutions of type IIB string theory such that the light cone gauge worldsheet Lagrangian is that of an interacting massive field theory. When the light cone Lagrangian has (2,2) supersymmetry we can find backgrounds that lead to arbitrary superpotentials on the worldsheet. We consider situations with both flat and curved transverse spaces. We describe in some detail the background giving rise to the N=2 sine Gordon theory on the worldsheet. Massive mirror symmetry relates it to the deformed CP¹ model (or sausage model) which seems to elude a purely supergravity target space interpretation. To cite this article: J. Maldacena, L. Maoz, C. R. Physique 4 (2003).     

Unbinding of adhesive vesicles

We consider a vesicle, bound on one side to a pipette and sticking on the other side to a flat plate. When a pulling force f is applied to the pipette, the radius R_c of the contact patch decreases, and jumps to zero at a critical value of the force. We present here an extension of the Evans theory for these processes. Then we discuss the dynamics of separation for two distinct cases: (a) nonspecific adhesion; and (b) specific adhesion induced by mobile proteins. To cite this article: F. Brochard-Wyart, P.-G. de Gennes, C. R. Physique 4 (2003).     

Directional reconstruction and anisotropy studies

The incident directions of cosmic ray particles at the highest energies are readily measured by modern detectors. Provided that there are sufficient data, the interpretation of such directions should give strong information on the origin of cosmic rays. However, the choice of statistical methods used in such an analysis can be of paramount importance in the reliability of the interpretation. This article summarizes the conclusions which may be drawn from the present data, and proposes methods needed to interpret statistically the large quantities of data which will become available in the near future. To cite this article: R.W. Clay et al., C. R. Physique 5 (2004).     

Experimental results: an update

This article is a summary of experimental results from highest energy cosmic ray measurements, focusing on data and analyses that became available after 1999. To cite this article: R. Engel, H. Klages, C. R. Physique 5 (2004).     

Phase and spectral properties of optically injected semiconductor lasers

The main control parameters of a single mode semiconductor laser submitted to an injected external signal are the power and the frequency of the injected signal. Following their magnitude, many phenomena can be observed such as phase locking, frequency locking, frequency generation, push-pull effects, hysteresis phenomena and chaos,... We show here that the spectral signature of the slave laser enables a better understanding of the the nonlinear interaction between the two competing sources: the spontaneous emission and the external field for which spectra are equally amplified through the active medium. This amplification is then strongly dependent on their coherency. We describe the role of the injected laser as a filter and an amplifier. It follows that the laser can be used to process information in ways that are not yet completely exploited. To cite this article: S. Blin et al., C. R. Physique 4 (2003).     

Mechanical properties of carbon nanotubes: theoretical predictions and experimental measurements

Mechanical properties of carbon nanotubes are discussed based on recent advances in both modeling and experiment. To cite this article: R.S. Ruoff et al., C. R. Physique 4 (2003).     

Antisymmetrized Molecular Dynamics: a new insight into the structure of nuclei

The AMD theory for nuclear structure is explained by showing its actual applications. First the formulation of AMD including various refined versions is briefly presented and its characteristics are discussed, putting a stress on its nature as an ab initio theory. Then we demonstrate fruitful applications to various structure problems in stable nuclei, in order to explicitly verify the ab initio nature of AMD, especially the ability to describe both mean-field-type structure and cluster structure. Finally, we show the results of applications of AMD to unstable nuclei, from which we see that AMD is powerful in elucidating and understanding various types of nuclear structure of unstable nuclei. To cite this article: Y. Kanada-En'yo et al., C. R. Physique 4 (2003).     

Magnetic anisotropic interactions of nuclei in condensed matter

This article examines some problems dealing with the anisotropy of the internuclei magnetic interactions in condensed matter, namely the properties and the experimental measurement of the magnetic shielding tensor σ and of the indirect nuclear spin-spin coupling tensor J. The symmetry of the tensors is examined, with a special emphasis of the possible existence of antisymmetric components. Experiments which may allow to measure the antisymmetric components of σ and J are presented. The number of independent components of the tensors, and the number of signals which may be observed in a solid-state N.M.R. experiment are discussed according to the local symmetry of the nuclei. The calculation of the σ and J tensor components using a perturbation theory from a complete molecular Hamiltonian is presented. For the indirect spin-spin coupling tensor the calculation is performed using a relativistic treatment. Some experimental results are given on the determination of the individual components of the σ and J tensors. For the latter only a very few data have been obtained in condensed matter. The use of the σ tensor anisotropy for examining some problems of special interest such as the hydrogen bonding or the orientation of large molecules in biological membranes is presented.     

Scaling laws of turbulent dynamos

We consider magnetic fields generated by homogeneous isotropic and parity invariant turbulent flows. We show that simple scaling laws for the dynamo threshold, magnetic energy and Ohmic dissipation can be obtained depending on the value of the magnetic Prandtl number. To cite this article: S. Fauve, F. Pétrélis, C. R. Physique 8 (2007).     

Les matériaux magnétiques hyperfréquences à l'ère des métamatériaux

This article investigates the advances brought by metamaterials in order to obtain attractive magnetic microwave properties. Can magnetic metamaterials outperform conventional soft magnetic materials? In the case where permeability levels and bandwidth are the key figures of merit, it is acknowledged that copper-based metamaterials can exceed the performance of soft magnetic materials, but only at operating frequencies above 10 GHz. As for low frequency operation, magnetic metamaterials may also be preferred to conventional magnetic materials when requirements include excellent temperature stability or immunity to external magnetic fields. However, in many cases, metamaterials need to include certain conventional magnetic constituents in order to compete with conventional magnetic materials. Several types of metamaterials containing conventional magnetic inclusions and well suited for industrial production are presented. Last but not least, it is underlined that the investigations on metamaterials are beneficial to scientific exchanges between scientists from different areas. To cite this article: O. Acher, C. R. Physique 10 (2009).     

Archeops results

Archeops is a balloon-borne instrument, dedicated to measuring cosmic microwave background (CMB) temperature anisotropies at high angular resolution (∼12 arcmin.) over a large fraction (30%) of the sky in the (sub)millimetre domain (from 143 to 545 GHz). We describe the results obtained during the last flight: the Archeops estimate of the CMB angular power spectrum, linking for the first time Cobe scales and the first acoustic peak, consequences in terms of cosmological parameters favouring a flat-Λ Universe. We also present the first measurement of galactic dust polarization and accurate maps of the galactic plane diffuse (sub) millimetre emisson. To cite this article: J.-C. Hamilton et al., C. R. Physique 4 (2003).     

The τ lepton as a laboratory for quantum chromodynamics

Decays of the τ lepton provide a clean environment to study hadron dynamics in an energy regime dominated by resonances. Inclusive spectral functions are the basis for quantum chromodynamics (QCD) analyses, providing a most accurate determination of the strong coupling constant and quantitative information on nonperturbative contributions. The τ vector spectral function is used together with e⁺e⁻ data in order to compute vacuum polarization integrals arising in the calculations of the anomalous magnetic moment of the muon and the running of the electromagnetic coupling constant. To cite this article: M. Davier, A. Höcker, C. R. Physique 3 (2002) 1223–1233.