Mass Loss In M67 Giants: Evidence From Isochrone Fitting

We present a study of the stellar content of the open cluster M67. We have computed new evolutionary sequences of stellar models with solar abundance that cover all phases of evolution from the Zero-Age Main Sequence to the bright end of the Asymptotic Giant Branch (AGB). We examine the fit between the calculated and the observed red giant branch (RGB) in particular, and discuss factors that most influence its quality. The distinct color gap between the RGB and the clump giants is compared with the temperature gap between the He-burning tracks and the computed 5 Gyr isochrone. This purely differential approach strongly indicates that the clump giants have M \lta 0.70\msun\ , implying an amount of mass loss ($\approx 0.6$ \msun) well in excess of that found in globular cluster stars. Observational constraints on mass loss processes favor the interpretation that mass loss in cool low-mass giant stars increases with metallicity.Comment: 21pp., plain TeX astro-ph/yymmnn

An experimental test of all theories with predictive power beyond quantum theory

According to quantum theory, the outcomes of future measurements cannot (in general) be predicted with certainty. In some cases, even with a complete physical description of the system to be measured and the measurement apparatus, the outcomes of certain measurements are completely random. This raises the question, originating in the paper by Einstein, Podolsky and Rosen, of whether quantum mechanics is the optimal way to predict measurement outcomes. Established arguments and experimental tests exclude a few specific alternative models. Here, we provide a complete answer to the above question, refuting any alternative theory with significantly more predictive power than quantum theory. More precisely, we perform various measurements on distant entangled photons, and, under the assumption that these measurements are chosen freely, we give an upper bound on how well any alternative theory could predict their outcomes. In particular, in the case where quantum mechanics predicts two equally likely outcomes, our results are incompatible with any theory in which the probability of a prediction is increased by more than ~0.19. Hence, we can immediately refute any already considered or yet-to-be-proposed alternative model with more predictive power than this.Comment: 13 pages, 4 figure

Derived Parameters for NGC 6791 from High-Metallicity Isochrones

We have computed 8, 10, and 12 Gyr isochrones and physically consistent models of zero-age red horizontal branch stars for stellar masses between 0.55 and 1.3~\msun, all at [Fe/H] $=+0.15$. Comparison to the NGC 6791 BVI photometry of Ka{\l}u\.zny & Udalski (1992) and Montgomery, Janes & Phelps (1994) yields an age of $10.0\pm0.5$ Gyr at an apparent distance modulus 13.49 < \dmv < 13.70. The color offsets required to fit the isochrones, combined with the spectroscopic results of Friel & Janes, imply that the foreground reddening to NGC 6791 lies in the range 0.24 > \ebv >0.19 with $+0.27 <$ [Fe/H] $<+0.44$. The zero-age horizontal branch models suggest that the red horizontal branch stars of NGC 6791 have masses \lesssim 0.7\msun. The masses are similar to those found for M67 red clump stars by Tripicco, Dorman & Bell (1993) and for globular cluster red horizontal branch stars, despite higher and lower masses (respectively) in those cases. This suggests the presence of a mechanism that tends to reduce stellar envelopes on the zero-age horizontal branch {\it to} a given mass rather than {\it by} a given amount.Comment: 23 pages, postscript fil

Dietary Cholesterol Concentration and Duration Degrade Long-Term Memory of Classical Conditioning of the Rabbit's Nictitating Membrane Response

A rabbit model of Alzheimer's disease based on feeding a cholesterol diet for eight weeks shows sixteen hallmarks of the disease, including learning and memory changes. Although we have shown 2% cholesterol and copper in water can retard learning, other studies show feeding dietary cholesterol before learning can improve acquisition whereas feeding cholesterol after learning can degrade long-term memory. We explored this issue by manipulating cholesterol concentration and duration following classical trace conditioning of the rabbit's nictitating membrane response and assessed conditioned responding after eight weeks on cholesterol. First, rabbits given trace classical conditioning followed by 0.5%, 1%, or 2% cholesterol for eight weeks showed body weight and serum cholesterol levels that were a function of dietary cholesterol. Although all concentrations of cholesterol showed some sign of retarding long-term memory, the level of memory retardation was correlated with serum cholesterol levels. Second, rabbits given trace conditioning followed by different durations of a 2% cholesterol diet combined with different durations of a 0% control diet for 8 weeks showed duration and timing of a 2% cholesterol diet were important in affecting recall. The data support the idea that dietary cholesterol may retard long-term memory

Keyring models: an approach to steerability

If a measurement is made on one half of a bipartite system, then, conditioned on the outcome, the other half has a new reduced state. If these reduced states defy classical explanation -- that is, if shared randomness cannot produce these reduced states for all possible measurements -- the bipartite state is said to be steerable. Determining which states are steerable is a challenging problem even for low dimensions. In the case of two-qubit systems a criterion is known for T-states (that is, those with maximally mixed marginals) under projective measurements. In the current work we introduce the concept of keyring models -- a special class of local hidden state models. When the measurements made correspond to real projectors, these allow us to study steerability beyond T-states. Using keyring models, we completely solve the steering problem for real projective measurements when the state arises from mixing a pure two-qubit state with uniform noise. We also give a partial solution in the case when the uniform noise is replaced by independent depolarizing channels.Comment: 15(+4) pages, 5 figures. v2: references added, v3: minor change

Empirically Constrained Color-Temperature Relations. II. uvby

(Abriged) A new grid of theoretical color indices for the Stromgren uvby photometric system has been derived from MARCS model atmospheres and SSG synthetic spectra for cool dwarf and giant stars. At warmer temperatures this grid has been supplemented with the synthetic uvby colors from recent Kurucz atmospheric models without overshooting. Our transformations appear to reproduce the observed colors of extremely metal-poor turnoff and giant stars (i.e., [Fe/H]<-2). Due to a number of assumptions made in the synthetic color calculations, however, our color-temperature relations for cool stars fail to provide a suitable match to the uvby photometry of both cluster and field stars having [Fe/H]>-2. To overcome this problem, the theoretical indices at intermediate and high metallicities have been corrected using a set of color calibrations based on field stars having accurate IRFM temperature estimates and spectroscopic [Fe/H] values. Encouragingly, isochrones that employ the transformations derived in this study are able to reproduce the observed CMDs (involving u-v, v-b, and b-y colors) for a number of open and globular clusters (including M92, M67, the Hyades, and 47Tuc) rather well. Moreover, our interpretations of such data are very similar, if not identical, with those given by VandenBerg & Clem (2003, AJ, 126, 778) from a consideration of BV(RI)c observations for the same clusters. In the present investigation, we have also analyzed the observed Stromgren photometry for the classic Population II subdwarfs, compared our "final" (b-y)-Teff relationship with those derived empirically in a number of recent studies, and examined in some detail the dependence of the m1 index on [Fe/H].Comment: 70 pages, 26 figures. Accepted for publication in AJ (Feb 2004). Postscript version with high resolution figures and complete Table 3 available at http://astrowww.phys.uvic.ca/~jclem/uvb

The Production of Sodium and Aluminum in Globular Cluster Red Giant Stars

We study the production of Na and Al around the hydrogen shell of two red-giant sequences of different metallicity in order to explain the abundance variations seen in globular cluster stars in a mixing scenario. Using detailed stellar models together with an extensive nuclear reaction network, we have calculated the distribution of the various isotopic abundances around the hydrogen shell at numerous points along the red-giant branch. These calculations allow for the variation in both temperature and density in the shell region as well as the timescale of the nuclear processing, as governed by the outward movement of the hydrogen shell. The reaction network uses updated rates over those of Caughlin \& Fowler (1988). We find evidence for the production of Na and Al occurring in the NeNa and MgAl cycles. In particular, Na is significantly enhanced throughout the region above the hydrogen shell. The use of the newer reaction rates causes a substantial increase in the production of $^{27}$Al above the hydrogen shell through heavy leakage from the NeNa cycle and should have an important effect on the predicted surface abundances. We also find that the nuclear processing is considerably more extensive at lower metallicities.Comment: 4 pages with 4 EPS figures embedded, accepted by ApJL March 28, 199

Possible Applications of Surface Electromagnetic Waves to Measure Absorption Coefficients

We Show that Surface Electromagnetic Waves Can Probably Be Used to Measure the Absorption Coefficients of Materials overlaying Metals. the Proposed Experimental Method is Illustrated in the Infrared Frequency Range using Water, Teflon, and Polyethylene as Sample Materials