The gravitationally unstable gas disk of a starburst galaxy 12 billion years ago.

Galaxies in the early Universe that are bright at submillimetre wavelengths (submillimetre-bright galaxies) are forming stars at a rate roughly 1,000 times higher than the Milky Way. A large fraction of the new stars form in the central kiloparsec of the galaxy1-3, a region that is comparable in size to the massive, quiescent galaxies found at the peak of cosmic star-formation history4 and the cores of present-day giant elliptical galaxies. The physical and kinematic properties inside these compact starburst cores are poorly understood because probing them at relevant spatial scales requires extremely high angular resolution. Here we report observations with a linear resolution of 550 parsecs of gas and dust in an unlensed, submillimetre-bright galaxy at a redshift of z = 4.3, when the Universe was less than two billion years old. We resolve the spatial and kinematic structure of the molecular gas inside the heavily dust-obscured core and show that the underlying gas disk is clumpy and rotationally supported (that is, its rotation velocity is larger than the velocity dispersion). Our analysis of the molecular gas mass per unit area suggests that the starburst disk is gravitationally unstable, which implies that the self-gravity of the gas is stronger than the differential rotation of the disk and the internal pressure due to stellar-radiation feedback. As a result of the gravitational instability in the disk, the molecular gas would be consumed by star formation on a timescale of 100 million years, which is comparable to gas depletion times in merging starburst galaxies5.

Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago.

In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.

Decoding "drug imprints" at the millennium: a proposal to increase accuracy and reduce costs.

The State of Washington mandated the use of imprints on all prescription drugs in 1980 and for "OTC's" in 1991. The FDA implemented federal requirements in 1995. Unfortunately, the FDA permitted the continued use of symbols, logotypes, and trademarks as code components, limiting the use of automated recognition systems. Analyses of several week-long samples of phone inquiries documented imprinting calls, the staff's ability to respond with an identification, the information sources used, and apparent reasons for any failure. In the first week we received 666 decoding requests, which when projected for the year amounted to > 25,000 calls. A review of 1999 data exceeded that number. Staff was able to reach drug identification in 93.8% of inquiries. Uninterpretable symbols and absence of code listings contributed to the 36 failures. Projecting over the US suggested as many as 1.25 million calls costing poison centers $25 million/y. A touch-tone telephone or website response system could permit automated responses. Neither solution is feasible without the elimination of symbols or logotypes when using an exclusively alpha-numeric code.

A logic-based dynamical theory for a genesis of biological threshold.

To help the study of constructing a formal neuron by computer, we propose a logic-based dynamical theory for a genesis of the biological threshold which specific proteins, such as ion channel proteins, or their networks can produce. By viewing such a protein or a protein network as a computational machine, the statements concerning the states of reaction chains which eventually activate or inactivate the protein are treated. By introducing dynamical systems, associated with an inference process based on statements with continuous truth values, we investigated invariant characters of such dynamics and we obtained a sigmoidal function for an invariant distribution function of the truth values. The domain of solutions of the functional equations regarded as representing the self-description of proteins or protein networks as a machine indicates the emergence of a threshold, namely the realization of dyadic value, 0 or 1, based on the continuous truth values. The results obtained may highlight the mechanism of neuronal threshold in a framework which differs from population dynamics. The derived dynamical systems may also provide a simple model of 'demon' rectifying the thermal fluctuations to drive unidirectional movements.