Astrometry with the Hubble Space Telescope: Trigonometric Parallaxes of Selected Hyads

We present absolute parallaxes and proper motions for seven members of the Hyades open cluster, pre-selected to lie in the core of the cluster. Our data come from archival astrometric data from FGS 3, and newer data for 3 Hyads from FGS 1R, both white-light interferometers on the Hubble Space Telescope (HST). We obtain member parallaxes from six individual Fine Guidance Sensor (FGS) fields and use the field containing van Altena 622 and van Altena 627 (= HIP 21138) as an example. Proper motions, spectral classifications and VJHK photometry of the stars comprising the astrometric refer- ence frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each Hyad. The parallax of vA 627 is significantly improved by including a perturbation orbit for this previously known spectroscopic binary, now an astrometric binary. Compared to our original (1997) determina- tions, a combination of new data, updated calibration, and improved analysis lowered the individual parallax errors by an average factor of 4.5. Comparing parallaxes of the four stars contained in the Hipparcos catalog, we obtain an average factor of 11 times improvement with the HST . With these new results, we also have better agreement with Hipparcos for the four stars in common. These new parallaxes provide an average distance for these seven members, = 47.5 pc, for the core a \pm 1 - {\sigma} dispersion depth of 3.6 pc, and a minimum depth from individual components of 16.0 \pm 0.9 pc. Absolute magnitudes for each member are compared to established main sequences, with excellent agreement. We obtain a weighted average distance modulus for the core of the Hyades of m-M=3.376 \pm 0.01, a value close to the previous Hipparcos values, m-M=3.33\pm 0.02.Comment: 21 pages, 7 figures, Astronomical Journal, accepted 2011-3-

Suggestion on the Incorporation of Cooperative Livestock Shipping Associations under the Laws of South Dakota

The cooperative shipping of livestock form South Dakota points has become so general that nearly every farm is familiar with the workings of the Cooperative Shipping Association. During the early stages of this movement; that is, up to the present time, these organizations have been for the most part loosely formed, unincorporated associations of producers with no very permanent existence. Where they were well managed, they have accomplished fairly well the principal purposes of a livestock shipping association; namely, the narrowing of the handling margin at the local points, better grading of the stock shipped, and the elimination of excessive duplication in the local handling agencies

“Tinder Will Know You Are A 6”: Users’ Perceptions of Algorithms on Tinder

Through in-depth interviews of 22 Tinder users, we explore how users interpret their algorithmically mediated experience on the platform. We find that users have various explanations of whether and how Tinder uses algorithms and that users have varying degrees of certainty about these explanations. In response, users report that they act in particular ways given their explanations and degree of certainty. We discuss how users, as part of their sensemaking practice around how algorithms work, engage in forms of improvisation. In addition, we argue that algorithm awareness leads to a more nuanced acknowledgement of inequality and power, including the power-laden roles of platforms themselves

The PL calibration for Milky Way Cepheids and its implications for the distance scale

The rationale behind recent calibrations of the Cepheid PL relation using the Wesenheit formulation is reviewed and reanalyzed, and it is shown that recent conclusions regarding a possible change in slope of the PL relation for short-period and long-period Cepheids are tied to a pathological distribution of HST calibrators within the instability strip. A recalibration of the period-luminosity relation is obtained using Galactic Cepheids in open clusters and groups, the resulting relationship, described by log L/L_sun = 2.415(+-0.035) + 1.148(+-0.044)log P, exhibiting only the moderate scatter expected from color spread within the instability strip. The relationship is confirmed by Cepheids with HST parallaxes, although without the need for Lutz-Kelker corrections, and in general by Cepheids with revised Hipparcos parallaxes, albeit with concerns about the cited precisions of the latter. A Wesenheit formulation of Wv = -2.259(+-0.083) - 4.185(+-0.103)log P for Galactic Cepheids is tested successfully using Cepheids in the inner regions of the galaxy NGC 4258, confirming the independent geometrical distance established for the galaxy from OH masers. Differences between the extinction properties of interstellar and extragalactic dust may yet play an important role in the further calibration of the Cepheid PL relation and its application to the extragalactic distance scale.Comment: Accepted for Publication (Astrophysics & Space Science

Discovery of the Host Cluster for the Fundamental Cepheid Calibrator Zeta Gem

New and existing CORAVEL, UBVJHKs, HST, HIP/Tycho, ARO, KPNO, and DAO observations imply that the fundamental Cepheid calibrator Zeta Gem is a cluster member. The following parameters were inferred for Zeta Gem from cluster membership and are tied to new spectral classifications (DAO) established for 26 nearby stars (e.g., HD53588/B7.5IV, HD54692/B9.5IV): E(B-V)=0.02+-0.02, log t=7.85+-0.15, and d=355+-15 pc. The mean distance to Zeta Gem from cluster membership and six recent estimates (e.g., IRSB) is d=363+-9(se)+-26(sd) pc. The results presented here support the color-excess and HST parallax derived for the Cepheid by Benedict et al. (2007). Forthcoming precise proper motions (DASCH) and Chandra/XMM-Newton observations of the broader field may be employed to identify cluster members, bolster the cluster's existence, and provide stronger constraints on the Cepheid's fundamental parameters.Comment: To appear in ApJ Letter

The Rise and Fall of Trust Based Intermediated Securites: An Economic Jurisprudential Approach to Trust Based Intermediated Securities

There has been a discussion for some years regarding the place of intermediated securities, how they should be legally underpinned and their technological basis. A particularly important source that formed a large portion of the inspiration of this thesis was Intermediated Securities: Legal Problems and Practical Issues edited by Louise Gullifer and Jennifer Payne at the University of Oxford.1 This key book provided a selection of papers outlining some theoretically and practically nuanced debates. While this book was exceptionally thought provoking, there was a particular issue that was apparent to the author. In short, this was a focus on the black letter law. There were questions that remained, particularly regarding why there was an insistence on utilising trust for underpinning intermediated securities in the UK when there has been significant strides in technology that could facilitate a more efficient mode of intermediation. This thesis therefore, seeks to answer this question. It hypothesises that, in combination with the recent advancements in technology, trust is an outmoded legal regime for intermediated securities. In particular, the thesis shows that technology has obfuscated the proprietary reasons underlying the use of trust, with investors able to hold full ownership of their shares and intermediaries acting as simple facilitators akin to agents. In order to highlight this change, the thesis undertakes an economic analysis of the law, especially using transaction cost analysis. Through this analysis, the efficiencies of the trust system vis-à-vis a new modality will be shown to be significantly diminished or eliminated. Therefore, this thesis presents a novel contribution to this field. Through undertaking an economic analysis of the current law and differing legal modalities, the thesis provides an innovative analysis and solution to the problems that permeate the intermediated securities system

New Evidence Supporting Cluster Membership for the Keystone Calibrator Delta Cephei

New and existing UBVJHKs, spectroscopic, NOMAD, HST, and revised HIP observations are employed to determine properties for delta Cep and its host star cluster. The multi-faceted approach ensured that uncertainties were mitigated (~2%). The following fundamental parameters were inferred for delta Cep: E(B-V)=0.073+-0.018, log(t)=7.9+-0.1, and d=272+-3(se)+-5(sd) pc. The cluster exhibits a turnoff near B6 (M*/Ms~5), and the brightest host cluster members are the supergiants zeta Cep (K1.5Ib) and delta Cep. To within the uncertainties, the two stars share common astrometric parameters (pi, mu_ra, mu_dec, RV\sim-17 km/s) and are tied to bluer members via the evolutionary track implied by the cluster's UBVJHKs color-color and color-magnitude diagrams. The cluster's existence is bolstered by the absence of an early-type sequence in color-magnitude diagrams for comparison fields. NOMAD data provided a means to identify potential cluster members (n~30) and double the existing sample. That number could increase with forthcoming precise proper motions (DASCH) for fainter main-sequence stars associated with classical Cepheids (e.g., delta Cep), which may invariably foster efforts to strengthen the Galactic Cepheid calibration and reduce uncertainties tied to H_0.Comment: Accepted for Publication (ApJ

Detectability of dissipative motion in quantum vacuum via superradiance

We propose an experiment for generating and detecting vacuum-induced dissipative motion. A high frequency mechanical resonator driven in resonance is expected to dissipate energy in quantum vacuum via photon emission. The photons are stored in a high quality electromagnetic cavity and detected through their interaction with ultracold alkali-metal atoms prepared in an inverted population of hyperfine states. Superradiant amplification of the generated photons results in a detectable radio-frequency signal temporally distinguishable from the expected background.Comment: 4 pages, 2 figure

Beyond Nanopore Sequencing in Space: Identifying the Unknown

Astronaut Kate Rubins sequenced DNA on the International Space Station (ISS) for the first time in August 2016 (Figure 1A). A 2D sequencing library containing an equal mixture of lambda bacteriophage, Escherichia coli, and Mus musculus was prepared on the ground with a SQK_MAP006 kit and sent to the ISS frozen and loaded into R7.3 flow cells. After a total of 9 on-orbit sequencing runs over 6 months, it was determined that there was no decrease in sequencing performance on-orbit compared to ground controls (1). A total of ~280,000 and ~130,000 reads generated on-orbit and on the ground, respectively, identified 90% of reads that were attributed to 30% lambda bacteriophage, 30% Escherichia coli, and 30% M. musculus (Figure 1B). Extensive bioinformatics analysis determined comparable 2D and 1D read accuracies between flight and ground runs (Figure 1C), and data collected from the ISS were able to construct directed assemblies of E.coli and lambda genomes at 100% and M. musculus mitochondrial genome at 96.7%. These findings validate sequencing as a viable option for potential on-orbit applications such as environmental microbial monitoring and disease diagnosis. Current microbial monitoring of the ISS applies culture-based techniques that provide colony forming unit (CFU) data for air, water, and surface samples. The identity of the cultured microorganisms in unknown until sample return and ground-based analysis, a process that can take up to 60 days. For sequencing to benefit ISS applications, spaceflight-compatible sample preparation techniques are required. Subsequent to the testing of the MinION on-orbit, a sample-to-sequence method was developed using miniPCR and basic pipetting, which was only recently proven to be effective in microgravity. The work presented here details the in- flight sample preparation process and the first application of DNA sequencing on the ISS to identify unknown ISS-derived microorganisms

Period-luminosity relations for Galactic Cepheid variables with independent distance measurements

In this paper, we derive the period-luminosity (PL) relation for Galactic Cepheids with recent independent distance measurements from open cluster, Barnes-Evans surface brightness, interferometry and HST astrometry techniques. Our PL relation confirms the results of Tammann et al. (2003), which showed that the Galactic Cepheids follow a different PL relation to their LMC counterparts. Our results also show that the slope of the Galactic PL relation is inconsistent with the LMC slope with more than 95% confidence level. We apply this Galactic PL relation to find the distance to NGC 4258. Our result of mu_o=29.49\pm0.06(random error)mag. agrees at the ~1.4sigma level with the geometrical distance of \mu_{geo}=29.28\pm0.15mag. from water maser measurements..Comment: 7 pages, 4 tables, 1 figure. MNRAS in-press, correct typesetting error in Table