An X-Ray Spectroscopic Study of the SMC X-1/Sk 160 System

We have investigated the composition and distribution of the wind of Sk 160, the supergiant companion of the X-ray star SMC X-1, by comparing an X-ray spectrum of the source, obtained with the ASCA observatory, during an eclipse with the computed spectra of reprocessed radiation from circumstellar matter with various density distributions. We show that the metal abundance in the wind of Sk 160 is no greater than a few tenths of solar, as has been determined for other objects in the Magellanic Clouds. We also show that the observed X-ray spectrum is not consistent with the density distributions of circumstellar matter of the spherically symmetric form derived for line-driven winds, nor with the density distribution derived from a hydrodynamic simulation of the X-ray perturbed and line-driven wind by Blondin & Woo (1995).Comment: 35 pages including 16 figures, uses AASTeX v5.0.2, accepted to Ap

Fuzzy Logic Controller Stability Analysis Using a Satisfiability Modulo Theories Approach

While many widely accepted methods and techniques exist for validation and verification of traditional controllers, at this time no solutions have been accepted for Fuzzy Logic Controllers (FLCs). Due to the highly nonlinear nature of such systems, and the fact that developing a valid FLC does not require a mathematical model of the system, it is quite difficult to use conventional techniques to prove controller stability. Since safety-critical systems must be tested and verified to work as expected for all possible circumstances, the fact that FLC controllers cannot be tested to achieve such requirements poses limitations on the applications for such technology. Therefore, alternative methods for verification and validation of FLCs needs to be explored. In this study, a novel approach using formal verification methods to ensure the stability of a FLC is proposed. Main research challenges include specification of requirements for a complex system, conversion of a traditional FLC to a piecewise polynomial representation, and using a formal verification tool in a nonlinear solution space. Using the proposed architecture, the Fuzzy Logic Controller was found to always generate negative feedback, but inconclusive for Lyapunov stability

Physiological Response to Feeding in Little Penguins

© 2006 by The University of Chicago.Specific dynamic action (SDA), the increase in metabolic rate above resting levels that accompanies the processes of digestion and assimilation of food, can form a substantial part of the daily energy budget of free-ranging animals. We measured heart rate (fH) and rate of oxygen consumption ( ) in 12 little penguins while they digested a meal of sardines in order to determine whether they show specific dynamic action. In contrast to some studies of other penguin species, little penguins showed a substantial SDA, the magnitude of which was proportional to the size of the meal. The energy utilized in SDA was equivalent to 13.4% of the available energy content of the fish. Furthermore, animals such as penguins that forage in a cold environment will probably expend further energy in heating their food to body temperature to facilitate efficient digestion. It is estimated that this additional energy expenditure was equivalent to 1.6%-2.3% of the available energy content of the fish, depending on the time of year and therefore the temperature of the water. Changes in fH during digestion were qualitatively similar to those in , implying that there were no substantial circulatory adjustments during digestion and that the relationship between fH and in penguins is unaffected by digestive state

Molecular and Morphological Analyses Confirm that All Loons (Aves: Gaviiformes) Form a Single Holobaramin

Loons or divers (Aves: Gaviiformes), a group of waterbirds found primarily in the Northern Hemisphere, are comprised of several extinct taxa as well as an extant family (Gaviidae) with one genus (Gavia) and five species. Recent phylogenetic studies suggest that the Sphenisciformes (penguins) and Procellariiformes (petrels, albatrosses, and shearwaters) form a sister group to the loons. Our previous research, based on hybridization, morphological, and vocalization data, found that all extant loons form a single holobaramin (i.e., created kind). This previous study, however, was inconclusive as to the membership of fossil taxa within the kind. The goal of the present study is to verify the baraminic status of the extant loons using new molecular baraminology techniques and to further evaluate extinct loon morphology to determine whether they also belong to the loon holobaramin. DNA sequences from four mitochondrial genes (CO1, CYTB, NADH1, and NADH2) were gathered, for all extant loons and several outgroups, from the BOLD and GenBank databases and aligned with ClustalW in MEGA. Corrected distance matrices were created with the TN93 + Gamma model and analyzed using hierarchical clustering, classic multidimensional scaling, and medoid partitioning in R software. A newly published dataset of skeletal characters, from extinct and extant loons as well as several outgroups, was also analyzed using statistical baraminology clustering methods (BARCLAY: DCA, MDS, PAM, FANNY). Extant loons consistently formed significant/separate clusters across all genes and molecular analyses, confirming they share significant continuity with one another and significant discontinuity from the outgroups. Morphological analyses demonstrated that all loons, extant and extinct, were positively associated/correlated with one another, sharing significant continuity, and negatively associated/correlated, displaying significant discontinuity, with several key avian outgroups. Based on considerable evidence of both continuity among loon species and discontinuity from other avian groups (including the supposed sister groups, Sphenisciformes and Procellariiformes), we conclude that all loons (Aves: Gaviiformes), both extant and extinct species, form a single holobaramin. These results are consistent with our previous research and Answers in Genesis’s brief analysis of loon hybridization for their Ark Encounter Project

Molecular and morphological analyses confirm that all loons (Aves: Gaviiformes) form a single holobaramin

Loons or divers (Aves: Gaviiformes), a group of waterbirds found primarily in the Northern Hemisphere, are comprised of several extinct taxa as well as an extant family (Gaviidae) with one genus (Gavia) and five species. Recent phylogenetic studies suggest that the Sphenisciformes (penguins) and Procellariiformes (petrels, albatrosses, and shearwaters) form a sister group to the loons. Our previous research, based on hybridization, morphological, and vocalization data, found that all extant loons form a single holobaramin (i.e., created kind). This previous study, however, was inconclusive as to the membership of fossil taxa within the kind. The goal of the present study is to verify the baraminic status of the extant loons using new molecular baraminology techniques and to further evaluate extinct loon morphology to determine whether they also belong to the loon holobaramin. DNA sequences from four mitochondrial genes (CO1, CYTB, NADH1, and NADH2) were gathered, for all extant loons and several outgroups, from the BOLD and GenBank databases and aligned with ClustalW in MEGA. Corrected distance matrices were created with the TN93 + Gamma model and analyzed using hierarchical clustering, classic multidimensional scaling, and medoid partitioning in R software. A newly published dataset of skeletal characters, from extinct and extant loons as well as several outgroups, was also analyzed using statistical baraminology clustering methods (BARCLAY: DCA, MDS, PAM, FANNY). Extant loons consistently formed significant/separate clusters across all genes and molecular analyses, confirming they share significant continuity with one another and significant discontinuity from the outgroups. Morphological analyses demonstrated that all loons, extant and extinct, were positively associated/correlated with one another, sharing significant continuity, and negatively associated/correlated, displaying significant discontinuity, with several key avian outgroups. Based on considerable evidence of both continuity among loon species and discontinuity from other avian groups (including the supposed sister groups, Sphenisciformes and Procellariiformes), we conclude that all loons (Aves: Gaviiformes), both extant and extinct species, form a single holobaramin. These results are consistent with our previous research and Answers in Genesis’s brief analysis of loon hybridization for their Ark Encounter Project

TFAP2C regulates transcription in human naive pluripotency by opening enhancers.

Naive and primed pluripotent human embryonic stem cells bear transcriptional similarity to pre- and post-implantation epiblast and thus constitute a developmental model for understanding the pluripotent stages in human embryo development. To identify new transcription factors that differentially regulate the unique pluripotent stages, we mapped open chromatin using ATAC-seq and found enrichment of the activator protein-2 (AP2) transcription factor binding motif at naive-specific open chromatin. We determined that the AP2 family member TFAP2C is upregulated during primed to naive reversion and becomes widespread at naive-specific enhancers. TFAP2C functions to maintain pluripotency and repress neuroectodermal differentiation during the transition from primed to naive by facilitating the opening of enhancers proximal to pluripotency factors. Additionally, we identify a previously undiscovered naive-specific POU5F1 (OCT4) enhancer enriched for TFAP2C binding. Taken together, TFAP2C establishes and maintains naive human pluripotency and regulates OCT4 expression by mechanisms that are distinct from mouse

Inventory of Ponds in the Brazos and Colorado River (Texas) Drainages, from NASA Color Infrared Photography.

15 p