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Cheyenne kids under 14 are invited to enter a national photo contest. The competition was developed by landscape photographer Franklin B. Way to get kids out into nature and away from the TV this winter. Kids can enter at http://www.2ndNatureJustforKids.com. Call for entries for the 41st Annual Greeley National Art Exhibition is April 30 through May 8, 2004. Art will be juried by slides. All media may enter up to three entries for a non- refundable fee of $30. A cash prize of $1,000 will be awarded for best of show and cash and ribbons given for first, second and third place in various categroies. Slide deadline is Feb. 20, 2004. For a prospectus send an SASE to NGAE, P.O. Box 5332, Greeley, CO, 80634, or call 970-353-1051 or email dragonsc@ezlink.com.

On May 1, a new and romantic way to tour the former Soviet Union and Imperial Russia will be launched by Bolshoi Express (via Cox & Kings, Tel.: 1-800-999-1758). Among the cars on the train are six sleeping carriages, a cocktail car, three restaurant cars. A bathroom serves every two sleeping compartments. The train stops en route for sightseeing and cultural tours. The four different itineraries cost from $5,065 to $5,935 per person, including air fare round-trip from New York, meals, sightseeing and pre-train hotel nights in St. Petersburg or Moscow. Racing car enthusiasts can gear up for the huge, monthlong 500 Festival in Indianapolis in May. Car races (of course), the nation's second-largest parade and all kinds of events accelerate this gala (Tel.: 317-636-4456 or Indiana Tourism, Tel.: 1-800-933-3378). Did you know that the Snake River Stampede in Nampa, Idaho, is no small potato, but one of the country's top 25 rodeos? Now you do. And July 13-17, besides first-class rodeo events at the stampede (Tel.: 208-466-8497 or Idaho Tourism, Tel.: 1-800-635-7820), the nightly entertainment will feature Country and Western stars.

Specifically selected to leverage the unique ultraviolet capabilities of the Hubble Space Telescope, the Hubble Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) is a Director’s Discretionary program of approximately 1000 orbits—the largest ever executed—that produced a UV spectroscopic library of O and B stars in nearby low-metallicity galaxies and accreting low-mass stars in the Milky Way. Observations from ULLYSES combined with archival spectra uniformly sample the fundamental astrophysical parameter space for each mass regime, including spectral type, luminosity class, and metallicity for massive stars, and the mass, age, and disk accretion rate for low-mass stars. The ULLYSES spectral library of massive stars will be critical to characterize how massive stars evolve at different metallicities; to advance our understanding of the production of ionizing photons, and thus of galaxy evolution and the re-ionization of the Universe; and to provide the templates necessary for the synthesis of integrated stellar populations. The massive-star spectra are also transforming our understanding of the interstellar and circumgalactic media of low-metallicity galaxies. On the low-mass end, UV spectra of T Tauri stars contain a plethora of diagnostics of accretion, winds, and the warm disk surface. These diagnostics are crucial for evaluating disk evolution and provide important input to assess atmospheric escape of planets and to interpret powerful probes of disk chemistry, as observed with the Atacama Large Millimeter Array and the James Webb Space Telescope. In this paper, we motivate the design of the program, describe the observing strategy and target selection, and present initial results.

OB stars generally form in open clusters within the Milky Way’s thin disk, so when they are found at high Galactic latitudes, it is thought that they were ejected from their birth clusters during the past few tens of millions of years. Using Gaia Data Release 3 data, we traced the kinematic trajectories of 39 high-latitude B-type stars and 447 Galactic open clusters with high-quality astrometry to search for moments of past intersection. In cases where we found matching trajectories, we also considered the clusters’ Hertzsprung–Russell diagrams to confirm parent–orphan pairs have matching ages. Further analysis of the clusters’ core environments allowed us to determine a probable ejection mechanism. Through these paternity tests, we have identified possible origins for five of these orphaned B-type stars. Here we present the likely travel times, ejection velocities, and a discussion of the runaway mechanism for each case. We also identify one star whose trajectory did not bring it near the disk during the time period of our analysis, and we discuss its possible origins as well.

Chronic hepatitis B virus (HBV) infection remains a significant global health challenge. Accurate quantification of HBV relaxed circular DNA (rcDNA) is critical for monitoring viral replication and assessing disease progression. However, conventional isothermal amplification methods are often compromised by limited specificity. To address these limitations, we engineered a toehold-triggered switchable DNA three-way junction (3WJ) protective nanoprobe that synergizes RNase H-assisted target recycling amplification (RATRA) with toehold-mediated strand displacement (TMSD). Leveraging the programmability of DNA nanotechnology, we constructed a rigid 3WJ scaffold featuring a “protective” nanoscale cavity at the branching point. This architecture effectively sequesters the ribonucleotides via steric hindrance, preventing non-specific enzymatic cleavage in the absence of the target. Upon specific recognition of the HBV rcDNA gap region, the nanoprobe undergoes a precise conformational switch, initiating a cyclic cleavage and signaling cascade. Governed by a dual-verification mechanism, the assay demonstrates exceptional specificity, enabling the discrimination of single-base mutations. Under optimized conditions, the method achieved a limit of detection (LOD) of 87.28 fM with a broad linear dynamic range. Validation in clinical serum samples revealed strong concordance with gold-standard quantitative real-time PCR (qRT-PCR). Consequently, this work presents a robust, modular, and cost-effective platform for point-of-care viral diagnostics. Graphical Abstract A DNA three-way junction nanoprobe undergoes toehold-triggered structural switching that exposes a hidden RNA/DNA duplex for RNase H cleavage, enabling highly specific cyclic detection of HBV rcDNA

Hypervelocity stars (HVSs) are produced by the Hills mechanism when a stellar binary is disrupted by a supermassive black hole (SMBH). The HVS Survey detected 21 unbound B-type main-sequence stars in the Milky Way’s outer halo that are consistent with ejection via the Hills mechanism. We revisit the trajectories of these stars in light of proper motions from Gaia DR3 and modern constraints on the Milky Way–Large Magellanic Cloud (LMC) orbit. We find that half of the unbound HVSs discovered by the HVS Survey trace back not to the Galactic Center but to the LMC. Motivated by this finding, we construct a forward model for HVSs ejected from an SMBH in the LMC and observed through the selection function of the HVS Survey. The predicted spatial and kinematic distributions of the simulated HVSs are remarkably similar to the observed distributions. In particular, we reproduce the conspicuous angular clustering of HVSs around the constellation Leo. This clustering occurs because HVSs from the LMC are boosted by ∼300 km s−1 by the orbital motion of the LMC, and stars launched parallel to this motion are preferentially selected as HVS candidates. We find that the birth rate and clustering of LMC HVSs cannot be explained by supernova runaways or dynamical ejection scenarios not involving an SMBH. From the ejection velocities and relative number of Magellanic versus Galactic HVSs, we constrain the mass of the LMC SMBH to be 105.8−0.4+0.2M⊙ (≃6 × 105 M⊙).

We analyze 4859 O stars in the third phase of the Optical Gravitational Lensing Experiment photometric survey of the LMC, including 415 eclipsing binaries (EBs). After accounting for the geometrical probability of eclipses, the period distribution of O-type binaries across P = 2.5–200 days follows a power law flogP ∝ (logP)Π with Π = −0.34 ± 0.06, which is skewed toward shorter periods compared to Opik’s law (Π = 0). We divide our O stars into seven environments based on their clustering with B stars and other O stars. The EB fraction of O stars in young clusters is 10.2% ± 0.6%, which matches the 10.8% ± 2.1% for O stars in young Milky Way clusters. O stars in old clusters exhibit a lower EB fraction of 5.5% ± 0.9% due to the effects of binary evolution. O stars in young dense clusters, young sparse associations, and even low-mass clusters that formed in situ in the field have similar EB fractions. This uniformity suggests that the formation of close massive binaries depends on small-scale gas physics, e.g., fragmentation and migration within protostellar disks, whereas N-body interactions that scale with cluster density do not affect the close binary properties of massive stars that remain in clusters. Conversely, ejected O stars in the field exhibit a lower close binary fraction. The EB fractions of field walkaways (projected velocities vproj < 24.5 km s−1) and field runaways (vproj > 24.5 km s−1) are 7.3% ± 1.0% and 4.7% ± 1.0%, respectively. These values suggest that most field O stars were dynamically ejected via N-body interactions from their birth clusters, whereas field O stars that formed in situ or were kicked from supernova explosions in binaries contribute 17% and <28%, respectively, to the field population.

About 20% of all massive stars in the Milky Way have unusually high velocities, the origin of which has puzzled astronomers for half a century. We argue that these velocities originate from strong gravitational interactions between single stars and binaries in the centers of star clusters. The ejecting binary forms naturally during the collapse of a young (≤ 1 milion years old) star cluster. This model replicates the key characteristics of OB runaways in our galaxy, and it explains the presence of runaway stars of ≥ 100 solar masses (M ⊚ ) around young star clusters, such as R136 and Westerlund 2. The high proportion and the distributions in mass and velocity of runaways in the Milky Way are reproduced if the majority of massive stars are born in dense and relatively low-mass (5000 to 10,000 M ⊚ ) clusters.