Showing papers by "Russian Academy of Sciences published in 2004"

Theory of Cosmological Perturbations

Abstract: We present in a manifestly gauge-invariant form the theory of classical linear gravitational perturbations in part I, and a quantum theory of cosmological perturbations in part II. Part I includes applications to several important examples arising in cosmology: a univese dominated by hydrodynamical matter, a universe filled with scalar-field matter, and higher-derivative theories of gravity. The growth rates of perturbations are calculated analytically in most interesting cases. The analysis is applied to study the evolution of fluctuations in inflationary universe models. Part II includes a unified description of the quantum generation and evolution of inhomogeneities about a classial Friedmann background. The method is based on standard canonical quantization of the action for cosmological perturbations which has been reduced to an expression in terms of a single gauge-invariant variable. The spectrum of density perturbations originating in quantum fluctuations is calculated in universe with hydrodynamical matter, in inflationary universe models with scalar-field matter, and in higher-derivative theories of gravity. The gauge-invariant theory of classical and quantized cosmological perturbations developed in parts I and II is applied in part III to several interesting physical problems. It allows a simple derivation of the relation between temperature anistropes in the cosmic microwave background. radiation and the gauge-invariant potential for metric perturbations. The generation and evolution of gravitational waves is studied. As another example, a simple analysis of entropy perturbations and non-scale-invariant spectra in inflationary universe models is presented. The gauge-invariant theory of cosmological perturbations also allows a consistent and gauge-invariant definition of statistical fluctuations.

Strong coupling in a single quantum dot–semiconductor microcavity system

Abstract: Cavity quantum electrodynamics, a central research field in optics and solid-state physics, addresses properties of atom-like emitters in cavities and can be divided into a weak and a strong coupling regime. For weak coupling, the spontaneous emission can be enhanced or reduced compared with its vacuum level by tuning discrete cavity modes in and out of resonance with the emitter. However, the most striking change of emission properties occurs when the conditions for strong coupling are fulfilled. In this case there is a change from the usual irreversible spontaneous emission to a reversible exchange of energy between the emitter and the cavity mode. This coherent coupling may provide a basis for future applications in quantum information processing or schemes for coherent control. Until now, strong coupling of individual two-level systems has been observed only for atoms in large cavities. Here we report the observation of strong coupling of a single two-level solid-state system with a photon, as realized by a single quantum dot in a semiconductor microcavity. The strong coupling is manifest in photoluminescence data that display anti-crossings between the quantum dot exciton and cavity-mode dispersion relations, characterized by a vacuum Rabi splitting of about 140 microeV.

IAWA list of microscopic features for softwood identification

Abstract: Pieter Baas – Leiden, The Netherlands Nadezhda Blokhina – Vladivostok, Russia Tomoyuki Fujii – Ibaraki, Japan Peter Gasson – Kew, UK Dietger Grosser – Munich, Germany Immo Heinz – Munich, Germany Jugo Ilic – South Clayton, Australia Jiang Xiaomei – Beijing, China Regis Miller – Madison, WI, USA Lee Ann Newsom – University Park, PA, USA Shuichi Noshiro – Ibaraki, Japan Hans Georg Richter – Hamburg, Germany Mitsuo Suzuki – Sendai, Japan Teresa Terrazas – Montecillo, Mexico Elisabeth Wheeler – Raleigh, NC, USA Alex Wiedenhoeft – Madison, WI, USA

Superconductivity in diamond

Abstract: Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields1. With these physical properties, diamond is attractive for electronic applications2, particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond3; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2,500–2,800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature Tc ≈ 4 K; superconductivity survives in a magnetic field up to Hc2(0) ≥ 3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.

Direct Constraints on the Dark Matter Self-Interaction Cross Section from the Merging Galaxy Cluster 1E 0657–56

Abstract: We compare new maps of the hot gas, dark matter, and galaxies for 1E 0657-56, a cluster with a rare high-velocity merger occurring nearly in the plane of the sky. The X-ray observations reveal a bullet-like gas subcluster just exiting the collision site. A prominent bow shock gives an estimate of the subcluster velocity, 4500 km s-1, which lies mostly in the plane of the sky. The optical image shows that the gas lags behind the subcluster galaxies. The weak-lensing mass map reveals a dark matter clump lying ahead of the collisional gas bullet but coincident with the effectively collisionless galaxies. From these observations, one can directly estimate the cross section of the dark matter self-interaction. That the dark matter is not fluid-like is seen directly in the X-ray-lensing mass overlay; more quantitative limits can be derived from three simple independent arguments. The most sensitive constraint, ?/m < 1 cm2 g-1, comes from the consistency of the subcluster mass-to-light ratio with the main cluster (and universal) value, which rules out a significant mass loss due to dark matter particle collisions. This limit excludes most of the 0.5-5 cm2 g-1 interval proposed to explain the flat mass profiles in galaxies. Our result is only an order-of-magnitude estimate that involves a number of simplifying, but always conservative, assumptions; stronger constraints may be derived using hydrodynamic simulations of this cluster.

A Catalog of Neighboring Galaxies

Abstract: We present an all-sky catalog of 451 nearby galaxies, each having an individual distance estimate D 10 Mpc or a radial velocity VLG -17.0, which contribute about 4% to the local luminosity density, and roughly 10%–15% to the local H I mass density. The H I mass-to-luminosity and the H I mass-to-total (indicative) mass ratios increase systematically from giant galaxies toward dwarfs, reaching maximum values about 5 in solar units for the most tiny objects. For the Local Volume disklike galaxies, their H I masses and angular momentum follow Zasov's linear relation, expected for rotating gaseous disks being near the threshold of gravitational instability, favorable for active star formation. We found that the mean local luminosity density exceeds 1.7–2.0 times the global density, in spite of the presence of the Tully void and the absence of rich clusters in the Local Volume. The mean local H I density is 1.4 times its "global" value derived from the H I Parkes Sky Survey. However, the mean local baryon density Ωb(< 8 Mpc) = 2.3% consists of only a half of the global baryon density, Ωb = (4.7 ± 0.6)% (Spergel et al., published in 2003). The mean-square pairwise difference of radial velocities is about 100 km s-1 for spatial separations within 1 Mpc, increasing to ~300 km s-1 on a scale of ~3 Mpc. also We calculated the integral area of the sky occupied by the neighboring galaxies. Assuming the H I size of spiral and irregular galaxies to be 2.5 times their standard optical diameter and ignoring any evolution effect, we obtain the expected number of the line-of-sight intersections with the H I galaxy images to be dn/dz ~ 0.4, which does not contradict the observed number of absorptions in QSO spectra.

Making optimal use of empirical energy functions: Force-field parameterization in crystal space

Abstract: Today's energy functions are not able yet to distinguish reliably between correct and almost correct protein models. Improving these near-native models is currently a major bottle-neck in homology modeling or experimental structure determination at low resolution. Increasingly accurate energy functions are required to complete the "last mile of the protein folding problem," for example during a molecular dynamics simulation. We present a new approach to reach this goal. For 50 high resolution X-ray structures, the complete unit cell was reconstructed, including disordered water molecules, counter ions, and hydrogen atoms. Simulations were then run at the pH at which the crystal was solved, while force-field parameters were iteratively adjusted so that the damage done to the structures was minimal. Starting with initial parameters from the AMBER force field, the optimization procedure converged at a new force field called YAMBER (Yet Another Model Building and Energy Refinement force field), which is shown to do significantly less damage to X-ray structures, often move homology models in the right direction, and occasionally make them look like experimental structures. Application of YAMBER during the CASP5 structure prediction experiment yielded a model for target 176 that was ranked first among 150 submissions. Due to its compatibility with the well-established AMBER format, YAMBER can be used by almost any molecular dynamics program. The parameters are freely available from www.yasara.org/yamber.

Detection of Methane in the Atmosphere of Mars

Abstract: We report a detection of methane in the martian atmosphere by the Planetary Fourier Spectrometer onboard the Mars Express spacecraft. The global average methane mixing ratio is found to be 10 ± 5 parts per billion by volume (ppbv). However, the mixing ratio varies between 0 and 30 ppbv over the planet. The source of methane could be either biogenic or nonbiogenic, including past or present subsurface microorganisms, hydrothermal activity, or cometary impacts.

Rise and Fall of the Beringian Steppe Bison

Abstract: The widespread extinctions of large mammals at the end of the Pleistocene epoch have often been attributed to the depredations of humans; here we present genetic evidence that questions this assumption. We used ancient DNA and Bayesian techniques to reconstruct a detailed genetic history of bison throughout the late Pleistocene and Holocene epochs. Our analyses depict a large diverse population living throughout Beringia until around 37,000 years before the present, when the population's genetic diversity began to decline dramatically. The timing of this decline correlates with environmental changes associated with the onset of the last glacial cycle, whereas archaeological evidence does not support the presence of large populations of humans in Eastern Beringia until more than 15,000 years later.

Laser-induced ultrafast spin reorientation in the antiferromagnet TmFeO3.

Abstract: All magnetically ordered materials can be divided into two primary classes: ferromagnets and antiferromagnets. Since ancient times, ferromagnetic materials have found vast application areas, from the compass to computer storage and more recently to magnetic random access memory and spintronics. In contrast, antiferromagnetic (AFM) materials, though representing the overwhelming majority of magnetically ordered materials, for a long time were of academic interest only. The fundamental difference between the two types of magnetic materials manifests itself in their reaction to an external magnetic field-in an antiferromagnet, the exchange interaction leads to zero net magnetization. The related absence of a net angular momentum should result in orders of magnitude faster AFM spin dynamics. Here we show that, using a short laser pulse, the spins of the antiferromagnet TmFeO3 can indeed be manipulated on a timescale of a few picoseconds, in contrast to the hundreds of picoseconds in a ferromagnet. Because the ultrafast dynamics of spins in antiferromagnets is a key issue for exchange-biased devices, this finding can expand the now limited set of applications for AFM materials.

Strong spin-orbit splitting on bi surfaces.

Abstract: Using first-principles calculations and angle-resolved photoemission, we show that the spin-orbit interaction leads to a strong splitting of the surface-state bands on low-index surfaces of Bi. The dispersion of the states and the corresponding Fermi surfaces are profoundly modified in the whole surface Brillouin zone. We discuss the implications of these findings with respect to a proposed surface charge density wave on Bi(111) as well as to the surface screening, surface spin-density waves, electron (hole) dynamics in surface states, and to possible applications to the spintronics.

Poisson's ratio and the fragility of glass-forming liquids

Abstract: The nature of the transformation by which a supercooled liquid ‘freezes’ to a glass—the glass transition—is a central issue in condensed matter physics1,2,3 but also affects many other fields, including biology4. Substantial progress has been made in understanding this phenomenon over the past two decades, yet many key questions remain. In particular, the factors that control the temperature-dependent relaxation and viscous properties of the liquid phase as the glass transition is approached (that is, whether the glass-forming liquid is ‘fragile’ or ‘strong’5,6,7) remain unclear. Here we show that the fragility of a glass-forming liquid is intimately linked to a very basic property of the corresponding glass phase: the relative strength of shear and bulk moduli, or Poisson's ratio.

Large–scale geographical variation confirms that climate change causes birds to lay earlier

Abstract: Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long-term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement.

Modeling damage and deformation in impact simulations

Abstract: Numerical modeling is a powerful tool for investigating the formation of large impact craters but is one that must be validated with observational evidence. Quantitative analysis of damage and deformation in the target surrounding an impact event provides a promising means of validation for numerical models of terrestrial impact craters, particularly in cases where the final pristine crater morphology is ambiguous or unknown. In this paper, we discuss the aspects of the behavior of brittle materials important for the accurate simulation of damage and deformation surrounding an impact event and the care required to interpret the results. We demonstrate this with an example simulation of an impact into a terrestrial, granite target that produces a 10 km-diameter transient crater. The results of the simulation are shown in terms of damage (a scalar quantity that reflects the totality of fragmentation) and plastic strain, both total plastic strain (the accumulated amount of permanent shear deformation, regardless of the sense of shear) and net plastic strain (the amount of permanent shear deformation where the sense of shear is accounted for). Damage and plastic strain are both greatest close to the impact site and decline with radial distance. However, the reversal in flow patterns from the downward and outward excavation flow to the inward and upward collapse flow implies that net plastic strains may be significantly lower than total plastic strains. Plastic strain in brittle rocks is very heterogeneous; however, continuum modeling requires that the deformation of the target during an impact event be described in terms of an average strain that applies over a large volume of rock (large compared to the spacing between individual zones of sliding). This paper demonstrates that model predictions of smooth average strain are entirely consistent with an actual strain concentrated along very narrow zones. Furthermore, we suggest that model predictions of total accumulated strain should correlate with observable variations in bulk density and seismic velocity.

Black hole mass decreasing due to phantom energy accretion

Abstract: Solution for a stationary spherically symmetric accretion of the relativistic perfect fluid with an equation of state $p(\ensuremath{\rho})$ onto the Schwarzschild black hole is presented. This solution is a generalization of Michel solution and applicable to the problem of dark energy accretion. It is shown that accretion of phantom energy is accompanied by the gradual decrease of the black hole mass. Masses of all black holes tend to zero in the phantom energy Universe approaching the Big Rip.

Culture-Level Dimensions of Social Axioms and Their Correlates across 41 Cultures

Abstract: Leung and colleagues have revealed a five-dimensional structure of social axioms across individuals from five cultural groups. The present research was designed to reveal the culture level factor structure of social axioms and its correlates across 41 nations. An ecological factor analysis on the 60 items of the Social Axioms Survey extracted two factors: Dynamic Externality correlates with value measures tapping collectivism, hierarchy, and conservatism and with national indices indicative of lower social development. Societal Cynicism is less strongly and broadly correlated with previous values measures or other national indices and seems to define a novel cultural syndrome. Its national correlates suggest that it taps the cognitive component of a cultural constellation labeled maleficence, a cultural syndrome associated with a general mistrust of social systems and other people. Discussion focused on the meaning of these national level factors of beliefs and on their relationships with individual level factors of belief derived from the same data set.

Simple cDNA normalization using kamchatka crab duplex-specific nuclease

Abstract: We developed a novel simple cDNA normalization method [termed duplex-specific nuclease (DSN) normalization] that may be effectively used for samples enriched with full-length cDNA sequences. DSN normalization involves the denaturation-reassociation of cDNA, degradation of the double-stranded (ds) fraction formed by abundant transcripts and PCR amplification of the equalized single-stranded (ss) DNA fraction. The key element of this method is the degradation of the ds fraction formed during reassociation of cDNA using the kamchatka crab DSN, as described recently. This thermostable enzyme displays a strong preference for cleaving ds DNA and DNA in DNA-RNA hybrid duplexes compared with ss DNA and RNA, irrespective of sequence length. We developed normalization protocols for both first-strand cDNA [when poly(A)+ RNA is available] and amplified cDNA (when only total RNA can be obtained). Both protocols were evaluated in model experiments using human skeletal muscle cDNA. We also employed DSN normalization to normalize cDNA from nervous tissues of the marine mollusc Aplysia californica (a popular model organism in neuroscience) to illustrate further the efficiency of the normalization technique.

GFP-like Proteins as Ubiquitous Metazoan Superfamily: Evolution of Functional Features and Structural Complexity

Abstract: Homologs of the green fluorescent protein (GFP), including the recently described GFP-like domains of certain extracellular matrix proteins in Bilaterian organisms, are remarkably similar at the protein structure level, yet they often perform totally unrelated functions, thereby warranting recognition as a superfamily. Here we describe diverse GFP-like proteins from previously undersampled and completely new sources, including hydromedusae and planktonic Copepoda. In hydromedusae, yellow and nonfluorescent purple proteins were found in addition to greens. Notably, the new yellow protein seems to follow exactly the same structural solution to achieving the yellow color of fluorescence as YFP, an engineered yellow-emitting mutant variant of GFP. The addition of these new sequences made it possible to resolve deep-level phylogenetic relationships within the superfamily. Fluorescence (most likely green) must have already existed in the common ancestor of Cnidaria and Bilateria, and therefore GFP-like proteins may be responsible for fluorescence and/or coloration in virtually any animal. At least 15 color diversification events can be inferred following the maximum parsimony principle in Cnidaria. Origination of red fluorescence and nonfluorescent purple-blue colors on several independent occasions provides a remarkable example of convergent evolution of complex features at the molecular level.

Siberian Peatlands a Net Carbon Sink and Global Methane Source Since the Early Holocene

Abstract: Interpolar methane gradient (IPG) data from ice cores suggest the “switching on” of a major Northern Hemisphere methane source in the early Holocene. Extensive data from Russia9s West Siberian Lowland show (i) explosive, widespread peatland establishment between 11.5 and 9 thousand years ago, predating comparable development in North America and synchronous with increased atmospheric methane concentrations and IPGs, (ii) larger carbon stocks than previously thought (70.2 Petagrams, up to ∼26% of all terrestrial carbon accumulated since the Last Glacial Maximum), and (iii) little evidence for catastrophic oxidation, suggesting the region represents a long-term carbon dioxide sink and global methane source since the early Holocene.

Porous calcium carbonate microparticles as templates for encapsulation of bioactive compounds

Abstract: The paper describes the preparation and characterisation of porous calcium carbonate microparticles with an average size of 5 µm and their use for encapsulation of biomacromolecules. The average pore size of about 30–50 nm enables size selective and time-dependent permeation of different macromolecules. Layer-by-layer adsorption of polyelectrolytes into these particles followed by core dissolution leads to formation of interconnecting networks (matrix-like structure) made of polyelectrolyte complexes. The structure can be used for accumulation of bio-macromolecules, mainly proteins. Besides the inter-polyelectrolyte structure templated on porous CaCO3 microparticles the microgel particles (“ghost”) can also be made inside by complexing alginate and calcium. The adsorption of biomacromolecules inside the porous calcium carbonate particles is presumably regulated by electrostatic interactions on the microparticle surface within pores and protein–protein interactions. Protein adsorption into CaCO3 microparticle voids together with layer-by-layer assembly of biopolymers provide a way for fabrication of completely biocompatible microcapsules envisaging their use as biomaterials.

Origin, diffusion, and differentiation of Y-chromosome haplogroups E and J: inferences on the neolithization of Europe and later migratory events in the Mediterranean area.

Abstract: The phylogeography of Y-chromosome haplogroups E (Hg E) and J (Hg J) was investigated in >2,400 subjects from 29 populations, mainly from Europe and the Mediterranean area but also from Africa and Asia. The observed 501 Hg E and 445 Hg J samples were subtyped using 36 binary markers and eight microsatellite loci. Spatial patterns reveal that (1) the two sister clades, J-M267 and J-M172, are distributed differentially within the Near East, North Africa, and Europe; (2) J-M267 was spread by two temporally distinct migratory episodes, the most recent one probably associated with the diffusion of Arab people; (3) E-M81 is typical of Berbers, and its presence in Iberia and Sicily is due to recent gene flow from North Africa; (4) J-M172(xM12) distribution is consistent with a Levantine/Anatolian dispersal route to southeastern Europe and may reflect the spread of Anatolian farmers; and (5) E-M78 (for which microsatellite data suggest an eastern African origin) and, to a lesser extent, J-M12(M102) lineages would trace the subsequent diffusion of people from the southern Balkans to the west. A 7%–22% contribution of Y chromosomes from Greece to southern Italy was estimated by admixture analysis.

The effective mutation rate at Y chromosome short tandem repeats, with application to human population-divergence time.

Abstract: We estimate an effective mutation rate at an average Y chromosome short-tandem repeat locus as 6.9×10 −4 per 25 years, with a standard deviation across loci of 5.7×10 −4 , using data on microsatellite variation within Y chromosome haplogroups defined by unique-event polymorphisms in populations with documented short-term histories, as well as comparative data on worldwide populations at both the Y chromosome and various autosomal loci. This value is used to estimate the times of the African Bantu expansion, the divergence of Polynesian populations (the Maoris, Cook Islanders, and Samoans), and the origin of Gypsy populations from Bulgaria.

Magnetic-field-induced phase transition in BiFeO 3 observed by high-field electron spin resonance: Cycloidal to homogeneous spin order

Abstract: Bismuth ferrite is a magnetoelectric material, which simultaneously has polarization and spin orders. We have used electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic-field range of 0--25 T, in the frequency domain of 115--360 GHz, and at a temperature of 4.2 K. The data reveal significant changes in the ESR spectra with increasing field, which have been analyzed by taking into account the magnetic anisotropy of the crystal and a magnetoelectric Dzyaloshinsky-Moria-like interaction. The results demonstrate an induced phase transition from an incommensurately cycloidal modulated state to one with homogeneous spin order.

Line-by-line opacity stellar model atmospheres

Abstract: Modelling stellar atmospheres becomes increasingly demanding as more accurate observations draw a more complex picture of how real stars look like. What could be called a normal star becomes increasingly rare because of, e.g., significant deviations from the classical solar abundance pattern and clear evidence for stratification of elements in the atmospheres as well as surface inhomogeneities (spots) causing further severe deviations from "standard" atmospheres. We describe here a new code for calculating LTE plane-parallel stellar model atmospheres for early and intermediate type of stars which has been written in Compaq Fortran 95 and can be compiled for Windows and Linux/UNIX computer platforms. The code is based on modified  9 subroutines (Kurucz) and on spectrum synthesis codes written by V. Tsymbal with the main modifications of input physics concerning the block for opacity calculation. Each line contributing to opacity is taken into account for modelling the atmosphere, similar to synthetic spectrum calculations. This approach, which we call the line-by-line (LL) technique, avoids problems resulting from statistical methods (ODF, OS) and allows to calculate complex models with abundances which are not simply scaled from a standard pattern (usually the solar abundances) and which can be even depth dependent. Stratification is considered in this context as an empirical input parameter which has to be derived from observations. Due to the implemented numerical methods, mainly in the opacity calculation module, our code produces model atmospheres with modern PCs in a time comparable to that required by classical routines.

Phases of massive gravity

Abstract: We systematically study the most general Lorentz-violating graviton mass invariant under three-dimensional Eucledian group. We find that at general values of mass parameters the massive graviton has six propagating degrees of freedom, and some of them are ghosts or lead to rapid classical instabilities. However, there is a number of different regions in the mass parameter space where massive gravity is described by a consistent low-energy effective theory with cutoff ~ (mMPl)1/2. This theory is free of rapid instabilities and vDVZ discontinuity. Each of these regions is characterized by certain fine-tuning relations between mass parameters, generalizing the Fierz–Pauli condition. In some cases the required fine-tunings are consequences of the existence of the subgroups of the diffeomorphism group that are left unbroken by the graviton mass. We found two new cases, when the resulting theories have a property of UV insensitivity, i.e. remain well behaved after inclusion of arbitrary higher dimension operators without assuming any fine-tunings among the coefficients of these operators, besides those enforced by the symmetries. These theories can be thought of as generalizations of the ghost condensate model with a smaller residual symmetry group. We briefly discuss what kind of cosmology can one expect in massive gravity and argue that the allowed values of the graviton mass may be quite large, affecting growth of primordial perturbations, structure formation and, perhaps, enhancing the backreaction of inhomogeneities on the expansion rate of the Universe.

The molecular properties and applications of Anthozoa fluorescent proteins and chromoproteins.

Abstract: The green fluorescent protein (GFP) from the jellyfish Aequorea victoria and its fluorescent homologs from Anthozoa corals have become invaluable tools for in vivo imaging of cells and tissues. Despite spectral and chromophore diversity, about 100 cloned members of the GFP-like protein family possess common structural, biochemical and photophysical features. Anthozoa GFP-like proteins are available in colors and properties unlike those of A. victoria GFP variants and thus provide powerful new fluorophores for molecular labeling and intracellular detection. Although Anthozoa GFP-like proteins provide some advantages over GFP, they also have certain drawbacks, such as obligate oligomerization and slow or incomplete fluorescence maturation. In the past few years, effective approaches for eliminating some of these limitations have been described. In addition, several Anthozoa GFP-like proteins have been developed into novel imaging agents, such as monomeric red and dimeric far-red fluorescent proteins, fluorescent timers and photoconvertible fluorescent labels. Future studies on the structure of this diverse set of proteins will further enhance their use in animal tissues and as intracellular biosensors.