The mitotic chromosomes of a macropod hybrid

In a yard at Hermitage Research Station, Warwick, a male agile wallaby (Wallabia agilis (Gould)) was observed mating with two female red kangaroos (Megaleia rufa (Desmarest)) and by late 1970 these females were carrying furred pouch young of phenotypic appearance intermediate between the species. A mitotic chromosome count of 2n = 18 was obtained for both progeny, male and female, of Wallabia agilis (Gould), (2n = 16) x Megaleia rufa (Desmarest), (2n = 20)

Isometric exercise-induced hemodynamic load strongly predicts left ventricular mass in hypertension

C

Keck Imaging of Binary L Dwarfs

We present Keck near-infrared imaging of three binary L dwarf systems, all of which are likely to be sub-stellar. Two are lithium dwarfs, and a third exhibits an L7 spectral type, making it the coolest binary known to date. All have component flux ratios near 1 and projected physical separations between 5 and 10 AU, assuming distances of 18 to 26 pc from recent measurements of trigonometric parallax. These surprisingly similar binaries represent the sole detections of companions in ten L dwarf systems which were analyzed in the preliminary phase of a much larger dual-epoch imaging survey. The detection rate prompts us to speculate that binary companions to L dwarfs are common, that similar-mass systems predominate, and that their distribution peaks at radial distances in accord both with M dwarf binaries and with the radial location of Jovian planets in our own solar system. To fully establish these conjectures against doubts raised by biases inherent in this small preliminary survey, however, will require quantitative analysis of a larger volume-limited sample which has been observed with high resolution and dynamic range.Comment: LaTex manuscript in 13 pages, 3 postscript figures, Accepted for publication in the Letters of the Astrophysical Journal; Postscript pre-print version available at: http://www.hep.upenn.edu/PORG/papers/koerner99a.p

Reproductive Consequences of Population Divergence through Sexual Conflict

AbstractSexual-selection research increasingly focuses on reproductive conflicts between the sexes [1–4]. Sexual conflict, divergent evolutionary interests of males and females [5], can cause rapid antagonistic coevolution of reproductive traits [6] and is a potentially powerful speciation engine [7–11]. This idea has theoretical and comparative support [10–12] but remains controversial [13–14]. Recent experimental evidence from Sepsis cynipsea indicates that populations with greater sexual conflict diverged more quickly; females were less likely to mate with males from other populations when flies had evolved under high levels of sexual conflict [15]. The consequences of this divergence have not been addressed, so here we assess two female fitness surrogates after 44 generations of evolving (and diverging) under three different levels of sexual conflict. Longevity after copulation was negatively associated with the degree of sexual conflict under which flies evolved, and housing females with males also reduced female longevity. Female lifetime reproductive success (LRS) also tended to decrease with increasing conflict. However, there was evidence of either sexual-selection fitness benefits at intermediate levels of sexual selection and conflict or inbreeding depression in the smallest populations (those with the lowest levels of conflict). Nevertheless, the results indicate that there can be a fitness load associated with sexual selection [2] and support claims that sexual conflict can lead to reproductive isolation [7–11, 15]

Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Luminous Infrared Galaxy Candidates

We present Spitzer 3.6 and 4.5 $\mu$m photometry and positions for a sample of 1510 brown dwarf candidates identified by the WISE all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12); Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify 7 fainter (4.5 $\mu$m $\sim$ 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy (HyLIRG) candidates. For this control sample we find another 6 brown dwarf candidates, suggesting that the 7 companion candidates are not physically associated. In fact, only one of these 7 Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this there is no evidence for any widely separated ($>$ 20 AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of $\sim$ 7.33 $\times 10^5$ objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5 $\mu$m photometry, along with positionally matched $B$ and $R$ photometry from USNO-B; $J$, $H$, and $K_s$ photometry from 2MASS; and $W1$, $W2$, $W3$, and $W4$ photometry from the WISE all-sky catalog

Den norske boikotten av OL i Moskva i 1980: Boikott-vedtaket med hovedfokus på de norske idrettsutøverne

Denne oppgaven er en analyse av de norske idrettsutøverne sin deltagelse i debatten rundt boikotten av OL i Moskva i 1980. Etter Sovjetunionens invasjonen av Afghanistan i 1979 ble forskjellige sanksjoner ovenfor landet foreslått, og boikotten av olympiaden var en av de. Norsk idrett hadde siden andre verdenskrig vært preget av autonomi, noe som gjorde at idretten selv som skulle ta beslutningen om deltagelse eller ikke. Etter diskusjoner i både Norges idrettsforbund og Norges olympiske komite ble beslutningen tatt på Idrettstinget der idretts-Norge stemte for boikott. Tre ulike standpunkter vil bli brukt til å analysere synspunktene til idrettslederne og idrettsutøverne i denne oppgaven. Standpunktene er det idrettslige, moralske og realistiske. Hovedfokuset vil ligge på de aktive utøverne og deres argumenter og plass i debatten som utspilte seg det første halvåret av 1980, der avismaterialet fra perioden vil bli brukt hyppig

Optimized annealing of traveling salesman problem from the nth-nearest-neighbor distribution

We report a new statistical general property in traveling salesman problem, that the $n$th-nearest-neighbor distribution of optimal tours verifies with very high accuracy an exponential decay as a function of the order of neighbor $n$. With defining the energy function as the deviation $\lambda$ from this exponential decay, which is different to the tour length $d$ in normal annealing processes, we propose a distinct highly optimized annealing scheme which is performed in $\lambda$-space and $d$-space by turns. The simulation results of some standard traveling salesman problems in TSPLIB95 are presented. It is shown that our annealing recipe is superior to the canonical simulated annealing.Comment: 11 pages, 3 figures, preprin

Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. IV. Discovery of an M9 + L6 BInary Separated by Over 100 AU

We report the discovery of a faint L6 \pm 1 companion to the previously known M9 dwarf, 2MASS J01303563-4445411, based on our near-infrared imaging and spectroscopic observations with the 3m Infrared Telescope Facility SpeX imager/spectrometer. The visual binary is separated by 3. 28 \pm 0. 05 on the sky at a spectrophotometric distance of 40 \pm 14 pc. The projected physical separation is 130 \pm 50 AU, making it one of the widest VLM field multiples containing a brown dwarf companion. 2MASS J0130-4445 is only one of ten wide VLM pairs and only one of six in the field. The secondary is considerably fainter ({\Delta}K ~ 2.35 mag) and redder ({\Delta} (J - Ks) ~ 0.81 dex), consistent with component near-infrared types of M9.0 \pm 0.5 and L6 \pm 1 based on our resolved spectroscopy. The component types suggest a secondary mass well within the hydrogen-burning limit and an age-dependent mass ratio of 0.6-0.9. The system's space motion and spectroscopic indicators suggest an age of 2-4 Gyr while the model-dependent masses and binding energies suggest that this system is unlikely to have formed via dynamical ejection. The age, composition, and separation of the 2MASS J01303563-4445411 system make it useful for tests of VLM formation theories and of condensate cloud formation in L dwarfs.Comment: Accepted by the AJ (8 pages, emulateapj format

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

Simplest random K-satisfiability problem

We study a simple and exactly solvable model for the generation of random satisfiability problems. These consist of $\gamma N$ random boolean constraints which are to be satisfied simultaneously by $N$ logical variables. In statistical-mechanics language, the considered model can be seen as a diluted p-spin model at zero temperature. While such problems become extraordinarily hard to solve by local search methods in a large region of the parameter space, still at least one solution may be superimposed by construction. The statistical properties of the model can be studied exactly by the replica method and each single instance can be analyzed in polynomial time by a simple global solution method. The geometrical/topological structures responsible for dynamic and static phase transitions as well as for the onset of computational complexity in local search method are thoroughly analyzed. Numerical analysis on very large samples allows for a precise characterization of the critical scaling behaviour.Comment: 14 pages, 5 figures, to appear in Phys. Rev. E (Feb 2001). v2: minor errors and references correcte