NMR Spectroscopy Reveals the Presence and Association of Lipids and Keratin in Adhesive Gecko Setae

Lipid and protein aggregates are one of the fundamental materials of biological systems. Examples include cell membranes, insect cuticle, vertebrate epidermis, feathers, hair and adhesive structures known as ‘setae’ on gecko toes. Until recently gecko setae were assumed to be composed entirely of keratin, but analysis of footprints left behind by geckos walking on surfaces revealed that setae include various kinds of lipids. However, the arrangement and molecular-level behavior of lipids and keratin in the setae is still not known. In the present study we demonstrate, for the first time, the use of Nuclear Magnetic Resonance (NMR) spectroscopy techniques to confirm the presence of lipids and investigate their association with keratin in ‘pristine\u27 sheds, or natural molts of the adhesive toe pad and non-adhesive regions of the skin. Analysis was also carried on the sheds after they were ‘delipidized’ to remove surface lipids. Our results show a distribution of similar lipids in both the skin and toe shed but with different dynamics at a molecular level. The present study can help us understand the gecko system both biologically and for design of synthetic adhesives, but the findings may be relevant to the characteristics of lipid-protein interactions in other biological systems. http://dx.doi.org/10.1038/srep0959

Excavation of the first stars

The external pollution of the first stars in the Galaxy is investigated. The first stars were born in clouds composed of the pristine gas without heavy elements. These stars accreted gas polluted with heavy elements while they still remained in the cloud. As a result, it is found that they exhibit a distribution with respect to the surface metallicity. We have derived the actual form of this distribution function. This metallicity distribution function strongly suggests that the recently discovered most metal-deficient star HE0107-5240 with [Fe/H]=-5.3 was born as a metal-free star and accreted gas polluted with heavy elements. Thus the heavy elements such as Fe in HE0107-5240 must have been supplied from supernovae of later generations exploding inside the cloud in which the star had been formed. The elemental abundance pattern on the surface of stars suffering from such an external pollution should not be diverse but exhibit the average pattern of numerous supernovae. Future observations for a number of metal-deficient stars with [Fe/H]<-5 will be able to prove or disprove this external pollution scenario. Other possibilities to produce a star with this metallicity are also discussed.Comment: 4 pages, 5 figures, to appear in The Astrophysical Journal Letter

Algorithm for Linear Response Functions at Finite Temperatures: Application to ESR spectrum of s=1/2 Antiferromagnet Cu benzoate

We introduce an efficient and numerically stable method for calculating linear response functions $\chi(\vec{q},\omega)$ of quantum systems at finite temperatures. The method is a combination of numerical solution of the time-dependent Schroedinger equation, random vector representation of trace, and Chebyshev polynomial expansion of Boltzmann operator. This method should be very useful for a wide range of strongly correlated quantum systems at finite temperatures. We present an application to the ESR spectrum of s=1/2 antiferromagnet Cu benzoate.Comment: 4 pages, 4 figure

Reduction of thermal fluctuations in a cryogenic laser interferometric gravitational wave detector

The thermal fluctuation of mirror surfaces is the fundamental limitation for interferometric gravitational wave (GW) detectors. Here, we experimentally demonstrate for the first time a reduction in a mirror's thermal fluctuation in a GW detector with sapphire mirrors from the Cryogenic Laser Interferometer Observatory at 17\,K and 18\,K. The detector sensitivity, which was limited by the mirror's thermal fluctuation at room temperature, was improved in the frequency range of 90\,Hz to 240\,Hz by cooling the mirrors. The improved sensitivity reached a maximum of $2.2 \times 10^{-19}\,\textrm{m}/\sqrt{\textrm{Hz}}$ at 165\,Hz.Comment: Accepted for publication in Physical Review Letters, 5 pages, 2 figure

Accretion of dust grains as a possible origin of metal-poor stars with low alpha/Fe ratios

The origin of low alpha/Fe ratios in some metal-poor stars, so called low-alpha stars, is discussed. It is found that most of low-alpha stars in the Galaxy are on the main-sequence. This strongly suggests that these stars suffered from external pollution. It is also found that the abundance ratios Zn/Fe of low-alpha stars both in the Galaxy and in dwarf spheroidal galaxies are lower than the average value of Galactic halo stars whereas damped Ly alpha absorbers have higher ratios. This implies that some low-alpha stars accreted matter depleted from gas onto dust grains. To explain the features in these low-alpha stars, we have proposed that metal-poor stars harboring planetary systems are the origin of these low-alpha stars. Stars engulfing a small fraction of planetesimals enhance the surface content of Fe to exhibit low alpha/Fe ratios on their surfaces while they are on the main-sequence, because dwarfs have shallow surface convection zones where the engulfed matter is mixed. After the stars leave the main-sequence, the surface convection zones become deeper to reduce the enhancement of Fe. Eventually, when the stars ascend to the tip of the red giant branch, they engulf giant planets to become low-alpha stars again as observed in dwarf spheroidal galaxies. We predict that low-alpha stars with low Mn/Fe ratios harbor planetary systems.Comment: 6 pages, 4 figures, accepted for publication in The Astrophysical Journal Letters, references correcte

Sub-millimeter Observations of Giant Molecular Clouds in the Large Magellanic Cloud: Temperature and Density as Determined from J=3-2 and J=1-0 transitions of CO

We have carried out sub-mm 12CO(J=3-2) observations of 6 giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) with the ASTE 10m sub-mm telescope at a spatial resolution of 5 pc and very high sensitivity. We have identified 32 molecular clumps in the GMCs and revealed significant details of the warm and dense molecular gas with n(H2) $\sim$ 10$^{3-5}$ cm$^{-3}$ and Tkin $\sim$ 60 K. These data are combined with 12CO(J=1-0) and 13CO(J=1-0) results and compared with LVG calculations. We found that the ratio of 12CO(J=3-2) to 12CO(J=1-0) emission is sensitive to and is well correlated with the local Halpha flux. We interpret that differences of clump propeties represent an evolutionary sequence of GMCs in terms of density increase leading to star formation.Type I and II GMCs (starless GMCs and GMCs with HII regions only, respectively) are at the young phase of star formation where density does not yet become high enough to show active star formation and Type III GMCs (GMCs with HII regions and young star clusters) represents the later phase where the average density is increased and the GMCs are forming massive stars. The high kinetic temperature correlated with \Halpha flux suggests that FUV heating is dominant in the molecular gas of the LMC.Comment: 74 pages, including 41 figures, accepted for publication in ApJ

Evolution of Galactic Nuclei. I. orbital evolution of IMBH

Resent observations and theoretical interpretations suggest that IMBHs (intermediate-mass black hole) are formed in the centers of young and compact star clusters born close to the center of their parent galaxy. Such a star cluster would sink toward the center of the galaxy, and at the same time stars are stripped out of the cluster by the tidal field of the parent galaxy. We investigated the orbital evolution of the IMBH, after its parent cluster is completely disrupted by the tidal field of the parent galaxy, by means of large-scale N-body simulations. We constructed a model of the central region of our galaxy, with an SMBH (supermassive black hole) and Bahcall-Wolf stellar cusp, and placed an IMBH in a circular orbit of radius 0.086pc. The IMBH sinks toward the SMBH through dynamical friction, but dynamical friction becomes ineffective when the IMBH reached the radius inside which the initial stellar mass is comparable to the IMBH mass. This is because the IMBH kicks out the stars. This behavior is essentially the same as the loss-cone depletion observed in simulations of massive SMBH binaries. After the evolution through dynamical friction stalled, the eccentricity of the orbit of the IMBH goes up, resulting in the strong reduction in the merging timescale through gravitational wave radiation. Our result indicates that the IMBHs formed close to the galactic center can merge with the central SMBH in short time. The number of merging events detectable with DECIGO is estimated to be around 50 per year. Event rate for LISA would be similar or less, depending on the growth mode of IMBHs.Comment: 12 pages, 24 figures, submitted to Ap

Calculating response functions in time domain with non-orthonormal basis sets

We extend the recently proposed order-N algorithms (cond-mat/9703224) for calculating linear- and nonlinear-response functions in time domain to the systems described by nonorthonormal basis sets.Comment: 4 pages, no figure

Detecting ultra-high energy cosmic rays from space with unprecedented acceptance: objectives and design of the JEM-EUSO mission

The Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO) of the Interna- tional Space Station (ISS) is the first mission that will study from space Ultra High-Energy Cosmic Rays (UHECR). JEM-EUSO will observe Extensive Air Showers (EAS) pro- duced by UHECRs traversing the Earth's atmosphere from above. For each event, the detector will make accurate mea- surements of the energy, arrival direction and nature of the primary particle using a target volume far greater than what is achievable from ground. The corresponding increase in statistics will help to clarify the origin and sources of UHE- CRs as well as the environment traversed during production and propagation. Possibly this will bring new light onto par- ticle physics mechanisms operating at energies well beyond those achievable by man-made accelerators. The spectrum of scientific goals of the JEM-EUSO mission includes as ex- ploratory objectives the detection of high-energy gamma ray

Instabilities and Mixing in SN 1993J

Rayleigh-Taylor (R-T) instabilities in the explosion of SN 1993J are investigated by means of two-dimensional hydrodynamical simulations. It is found that the extent of mixing is sensitive to the progenitor's core mass and the envelope mass. Because the helium core mass (3 - 4 \ms) is smaller than that of SN 1987A, R-T instabilities at the He/C+O interfaces develop to induce a large scale mixing in the helium core, while the instability is relatively weak at the H/He interface due to the small envelope mass. The predicted abundance distribution, in particular the amount of the \ni~ mixing, is compared with those required in the theoretical light curves and the late time optical spectra. This enables us to specify the progenitor of SN 1993J in some detail.Comment: 20 pages, LaTeX (AASTeX), to appear in Ap