Red-green color vision in three catarrhine primates

The evolution of the red-green visual subsystem in trichromatic primates has been linked to foraging advantages, specifically the detection of either ripe fruits or young leaves amid mature foliage, and to the intraspecific socio-sexual communication, namely the signal of the male rank, the mate choice and the reproductive strategies in females. New data should be added to the debate regarding the evolution of trichromatic color vision. Three catarrhine primates were observed to achieve this goal. The research was performed on captive groups of vervet monkeys (Chlorocebus aethiops), pig-tailed macaques (Macaca nemestrina) and chimpanzees (Pan troglodytes) housed at Parco Natura Viva - Garda Zoological Park (Italy). Using pairs of red-green bags containing the same hidden reward in comparable outdoor enclosures, we recorded the choices by observed individuals (n = 25) to investigate the role of color cues in choosing an object. The results indicate that chimpanzees used red color as cue to choose an object that contains food by showing a preference toward red objects; in contrast, vervet monkeys and pig-tailed macaques do not demonstrate a clear choice based on the color of the object. Our findings highlight the importance of the foraging hypothesis but not rule out the potential role of the intraspecific socio-sexual communication and may serve to add useful information to the debate regarding the adaptive value of the evolution of color vision in order to fill a phylogenetic gap from Old World monkeys to humans. Future studies should address the role of socio-sexual communication, such as the selection of the reproductive partner of both high genetic quality and with compatible genes, to determine how this influenced the evolution of color vision in non-human primates

Jensen-Shannon divergence as a measure of distinguishability between mixed quantum states

We discuss an alternative to relative entropy as a measure of distance between mixed quantum states. The proposed quantity is an extension to the realm of quantum theory of the Jensen-Shannon divergence (JSD) between probability distributions. The JSD has several interesting properties. It arises in information theory and, unlike the Kullback-Leibler divergence, it is symmetric, always well defined and bounded. We show that the quantum JSD (QJSD) shares with the relative entropy most of the physically relevant properties, in particular those required for a "good" quantum distinguishability measure. We relate it to other known quantum distances and we suggest possible applications in the field of the quantum information theory.Comment: 14 pages, corrected equation 1

EARLIER INTERVENTION IN TYPE 2 DIABETES

In type 2 diabetes, the onset and progression of complications is significantly delayed by improving glycaemic control. However, the proportion of patients reaching and sustaining guideline recommendations for glycaemic targets remains unacceptably low. Recent clinical trials and predictive physiologically based mathematical simulations (Archimedes model) indicate that benefits can be enhanced with earlier intervention and timely achievement of glycaemic targets. This article reviews the evidence for early intervention, showing that intensive approaches, including earlier introduction of combination therapy, allow more patients to achieve glycaemic targets and hence reduce complications and delay disease progression

Identifying Young Brown Dwarfs Using Gravity-Sensitive Spectral Features

We report the initial results of the Brown Dwarf Spectroscopic Survey Gravity Project, to study gravity sensitive features as indicators of youth in brown dwarfs. Low-resolution (R~2000) J-band and optical (R~1000) observations using NIRSPEC and LRIS at the W.M. Keck Observatory reveal transitions of TiO, VO, K I, Na I, Cs I, Rb I, CaH, and FeH. By comparing these features in late-type giants and in old field dwarfs we show that they are sensitive to the gravity (g = GM/R^2) of the object. Using low-gravity spectral signatures as age indicators, we observed and analyzed J-band and optical spectra of two young brown dwarfs, G 196-3B (20-300 Myr) and KPNO Tau-4 (1-2 Myr), and two possible low mass brown dwarfs in the sigma Orionis cluster (3-7 Myr). We report the identification of the phi bands of TiO near 1.24 microns and the A-X band of VO near 1.18 microns together with extremely weak J-band lines of K I in KPNO-Tau4. This is the first detection of TiO and VO in the J-band in a sub-stellar mass object. The optical spectrum of KPNO-Tau4 exhibits weak K I and Na I lines, weak absorption by CaH, and strong VO bands, also signatures of a lower gravity atmosphere. G 196-3B shows absorption features in both wavelength regions like those of KPNO-Tau4 suggesting that its age and mass are at the lower end of published estimates. Whereas sigma Ori 51 appears to be consistent with a young sub-stellar object, sigma Ori 47 shows signatures of high gravity most closely resembling an old L1.5/L0, and can not be a member of the sigma Orionis cluster.Comment: 14 pages, 4 figures. To appear in the January 10, 2004 issue of the Astrophysical Journa

Smooth stable and unstable manifolds for stochastic partial differential equations

Invariant manifolds are fundamental tools for describing and understanding nonlinear dynamics. In this paper, we present a theory of stable and unstable manifolds for infinite dimensional random dynamical systems generated by a class of stochastic partial differential equations. We first show the existence of Lipschitz continuous stable and unstable manifolds by the Lyapunov-Perron's method. Then, we prove the smoothness of these invariant manifolds

Investigating disk evolution: A high spatial resolution mid-infrared survey of T Tauri stars

We present a high spatial resolution, 10-20 micron survey of 65 T Tauri binary stars in Taurus, Ophiuchus, and Corona Australis using the Keck 10 m telescopes. Designed to probe the inner ~1 AU region of the circumstellar disks around the individual stellar components in these binary systems, this study increases the number of binaries with spatially resolved measurements at 10 micron by a factor of ~5. Combined with resolved near-infrared photometry and spectroscopic accretion diagnostics, we find that ~10% of stars with a mid-infrared excess do not appear to be accreting. In contrast to an actively accreting disk system, these passive disks have significantly lower near-infrared colors that are, in most cases, consistent with photospheric emission, suggesting the presence of an inner disk hole. In addition, there appears to be a spectral type/mass dependence associated with the presence of a passive disk, with all passive disks occurring around M type stars. The possibility that the passive disks are caused by the presence of an as yet undetected companion at a small separation (0.3-3 AU) is possible for any individual system, however, it cannot account for the spectral type dependence of the passive disk sample as a whole. We propose that these passive disks represent a subset of T Tauri stars that are undergoing significant disk evolution. The fraction of observed passive disks and the observed spectral type dependence can both be explained by models of disk evolution that include disk photoevaporation from the central star. (abridged).Comment: 51 pages, 3 figures, to be published in ApJ, January 200

Breakdown rates and macroinvertebrate colonisation of alder (Alnus glutinosa) leaves in an acid lake (Lake Orta, N Italy), before, during and after a liming intervention

To test the effectiveness of the liming intervention on Lake Orta, the speed of leaves decay and of colonisation processes by macrobenthonic fauna were studied on alder leaves (Alnus glutinosa) placed on the bottom of the lake and recovered after appropriate time intervals. Experiments were performed at two sites (North and South) and two depths (-3 and –18 m), during three successive winters: 1988-1989 (pre-liming), 1989-1990 (liming), 1990-1991 (post-liming). Two main results emerged: 1) alder leaves, which are known to have a medium to high decaying speed in a number of aquatic environments, behave in Lake Orta as a low speed species. Decaying processes in the three years are significantly different only in station N3, where the mean breakdown rate in 1988- 1989 is more than twice that measured in the two subsequent winters. 2) The species richness of colonising benthic fauna is low: the community is made up almost exclusively of Chironomidae, which form 70 to 100% of the whole population; among them, the genus Phenopsectra is always present, while Tanytarsus was collected only during the first year and in the less deep sampling sites. The mean population abundances were higher before liming

Carbon based substrates for interfacing neurons: Comparing pristine with functionalized carbon nanotubes effects on cultured neuronal networks

Pristine (as prepared) carbon nanotube (CNT) based substrates have been widely used to grow and interface neurons in culture. Nerve cells normally differentiate on CNTs and the synaptic networks, newly formed at the interface with this material, usually show an improved robustness in signal transfer. However manipulation of pristine CNTs is often prevented by their low dispersibility and tendency to aggregate in most solvents. This issue can be at least partially solved by adding solubilizing groups to the surface of CNT, which also helps improving their biocompatibility. It becomes therefore of crucial importance to determine whether chemically manipulated CNTs may maintain their performance in improving nerve signaling. Here we study and compare the impact in vitro on neuronal signaling of two classes of chemically modified multiwalled CNTs in reference to pristine CNTs, which are known to be a substrate able to boost neuronal growth and communication. We found that the extent of functionalization and the nature of the functional groups on MWNT sidewalls affect the conductivity and the biological effects of the final derivatives. This information is important for the future design of biointegrated devices

Follow-Up Observations of PTFO 8-8695: A 3 MYr Old T-Tauri Star Hosting a Jupiter-mass Planetary Candidate

We present Spitzer 4.5\micron\ light curve observations, Keck NIRSPEC radial velocity observations, and LCOGT optical light curve observations of PTFO~8-8695, which may host a Jupiter-sized planet in a very short orbital period (0.45 days). Previous work by \citet{vaneyken12} and \citet{barnes13} predicts that the stellar rotation axis and the planetary orbital plane should precess with a period of $300 - 600$ days. As a consequence, the observed transits should change shape and depth, disappear, and reappear with the precession. Our observations indicate the long-term presence of the transit events ($>3$ years), and that the transits indeed do change depth, disappear and reappear. The Spitzer observations and the NIRSPEC radial velocity observations (with contemporaneous LCOGT optical light curve data) are consistent with the predicted transit times and depths for the $M_\star = 0.34\ M_\odot$ precession model and demonstrate the disappearance of the transits. An LCOGT optical light curve shows that the transits do reappear approximately 1 year later. The observed transits occur at the times predicted by a straight-forward propagation of the transit ephemeris. The precession model correctly predicts the depth and time of the Spitzer transit and the lack of a transit at the time of the NIRSPEC radial velocity observations. However, the precession model predicts the return of the transits approximately 1 month later than observed by LCOGT. Overall, the data are suggestive that the planetary interpretation of the observed transit events may indeed be correct, but the precession model and data are currently insufficient to confirm firmly the planetary status of PTFO~8-8695b.Comment: Accepted for publication in The Astrophysical Journa

Surface Gravities for 228 M, L, and T Dwarfs in the NIRSPEC Brown Dwarf Spectroscopic Survey

We combine 131 new medium-resolution (R~2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass stars and brown dwarfs spanning spectral types M5-T9. Specifically, we use an established set of spectral indices to determine surface gravity classifications for all M6-L7 objects in our sample by measuring equivalent widths (EW) of the K I lines at 1.1692, 1.1778, 1.2529 um, and the 1.2 um FeHJ absorption index. Our results are consistent with previous surface gravity measurements, showing a distinct double peak - at ~L5 and T5 - in K I EW as a function of spectral type. We analyze K I EWs of 73 objects of known ages and find a linear trend between log(Age) and EW. From this relationship, we assign age ranges to the very low gravity, intermediate gravity, and field gravity designations for spectral types M6-L0. Interestingly, the ages probed by these designations remain broad, change with spectral type, and depend on the gravity sensitive index used. Gravity designations are useful indicators of the possibility of youth, but current datasets cannot be used to provide a precise age estimate.Comment: 33 pages, 13 figures, ApJ in pres