Electronic controller for reciprocating rotary crystallizer

An electronic controller for a reciprocating rotary crystallizer is described. The heart of this system is the electronic timer circuit. A schematic along with a detailed description of its operation is given

Chandra Confirmation of a Pulsar Wind Nebula in DA 495

As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nonthermal nebula 40'' in diameter exhibiting a power-law spectrum with photon index Gamma = 1.6+/-0.3, typical of a pulsar wind nebula. The implied spin-down luminosity of the neutron star, assuming a conversion efficiency to nebular flux appropriate to Vela-like pulsars, is ~10^{35} ergs/s, again typical of objects a few tens of kyr old. Morphologically, the nebular flux is slightly enhanced along a direction, in projection on the sky, independently demonstrated to be of significance in radio polarization observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5'' from the point source, a distance consistent with the sizes of resolved wind termination shocks around many Vela-like pulsars. Finally, we argue based on synchrotron lifetimes in the estimated nebular magnetic field that DA 495 represents a rare pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind, and that this high magnetization factor may account for the nebula's low luminosity.Comment: 26 pages, 5 figures, AASTeX preprint style. Accepted for publication in The Astrophysical Journa

1,1′-diacetyl-2,2′-biimidazole

A crystallographic twofold rotation axis passes through the C-C bond joining the imidazole rings of the title compound, C10H10N4O2. the molecule crystallizes in a cis disposition. the planar acetyl group is twisted by 5.0 (3)° with respect to the imidazole ring and the two imidazole rings are tilted by 60.53 (5)° in relation to one another

A VLA Search for Water Masers in Six HII Regions: Tracers of Triggered Low-Mass Star Formation

We present a search for water maser emission at 22 GHz associated with young low-mass protostars in six HII regions -- M16, M20, NGC 2264, NGC 6357, S125, and S140. The survey was conducted with the NRAO Very Large Array from 2000 to 2002. For several of these HII regions, ours are the first high-resolution observations of water masers. We detected 16 water masers: eight in M16, four in M20, three in S140, and one in NGC 2264. All but one of these were previously undetected. No maser emission was detected from NGC 6357 or S125. There are two principle results to our study. (1) The distribution of water masers in M16 and M20 does not appear to be random but instead is concentrated in a layer of compressed gas within a few tenths of a parsec of the ionization front. (2) Significantly fewer masers are seen in the observed fields than expected based on other indications of ongoing star formation, indicating that the maser-exciting lifetime of protostars is much shorter in HII regions than in regions of isolated star formation. Both of these results confirm predictions of a scenario in which star formation is first triggered by shocks driven in advance of ionization fronts, and then truncated approximately 10^5 years later when the region is overrun by the ionization front.Comment: 30 pages, 20 figures, 3 tables. Accepted for publication by ApJ. Full resolution figures and PS and PDF versions with full-res figures available at http://eagle.la.asu.edu/healy/preprints/hhc0

Student Nurses Participate in Public Health Research and Practice Through a School-Based Screening Program

Obesity has reached epidemic proportions among children in minority populations, placing them at risk for diabetes and hypertension. The importance of educating a generation of nurses who have the knowledge, skills, and passion to address this public health need is crucial to the profession and to America\u27s health. This article describes the use of a Community Partnership Model to frame baccalaureate nursing students\u27 (B.S.N.) service learning within the context of a research study to screen middle- and high-school students for health risks. The missions of education, research, and practice are linked together in the model by three processes: evidence-based practice, service learning, and scholarly teaching. The aim of the project was early identification of obesity, hypertension, and type 2 diabetes and their predictors in a high-risk student population, between 12 and 19 years of age. Early evidence indicates that the model is feasible and effective for directing student learning and addressing public health problems in the community

Note and Comment

The Effect of the Carmack Amendment to the Hepburn Act Upon Limitation by Common Carrier of the Amount of their Liability - Two cases, decided by the Supreme Court of the United States on March 10, 1913, may be considered together. They are developments of the cases reviewed in II MICH. L. Rev. 460. Plaintiff shipped two boxes and a barrel of \u27household goods under an agreement that the goods, in case of loss, should be valued at $5 per hundred-weight. One box, weighing not over 200 pounds and actually worth$75, was lost. The Supreme Court of Arkansas affirmed a judgment against the carrier for the full value. On error the Supreme Court of the United States reversed and remanded the case for further proceedings. In the other oase the plaintiff shipped four bulls and thirteen cows, show cattle, worth $10,640. The finding of the Texas Court of Civil Appeals, was reversed on the ground that the recovery should have been limited to$30 for each bull and $20 for each cow

Particle-in-cell simulations of shock-driven reconnection in relativistic striped winds

By means of two- and three-dimensional particle-in-cell simulations, we investigate the process of driven magnetic reconnection at the termination shock of relativistic striped flows. In pulsar winds and in magnetar-powered relativistic jets, the flow consists of stripes of alternating magnetic field polarity, separated by current sheets of hot plasma. At the wind termination shock, the flow compresses and the alternating fields annihilate by driven magnetic reconnection. Irrespective of the stripe wavelength "lambda" or the wind magnetization "sigma" (in the regime sigma>>1 of magnetically-dominated flows), shock-driven reconnection transfers all the magnetic energy of alternating fields to the particles, whose average Lorentz factor increases by a factor of sigma with respect to the pre-shock value. In the limit lambda/(r_L*sigma)>>1, where r_L is the relativistic Larmor radius in the wind, the post-shock particle spectrum approaches a flat power-law tail with slope around -1.5, populated by particles accelerated by the reconnection electric field. The presence of a current-aligned "guide" magnetic field suppresses the acceleration of particles only when the guide field is stronger than the alternating component. Our findings place important constraints on the models of non-thermal radiation from Pulsar Wind Nebulae and relativistic jets.Comment: 25 pages, 14 figures, movies available at https://www.cfa.harvard.edu/~lsironi/sironi_movies.tar ; in press, special issue of Computational Science and Discovery on selected research from the 22nd International Conference on Numerical Simulation of Plasma

Modes of Multiple Star Formation

This paper argues that star forming environments should be classified into finer divisions than the traditional isolated and clustered modes. Using the observed set of galactic open clusters and theoretical considerations regarding cluster formation, we estimate the fraction of star formation that takes place within clusters. We find that less than 10% of the stellar population originates from star forming regions destined to become open clusters, confirming earlier estimates. The smallest clusters included in the observational surveys (having at least N=100 members) roughly coincide with the smallest stellar systems that are expected to evolve as clusters in a dynamical sense. We show that stellar systems with too few members N < N_\star have dynamical relaxation times that are shorter than their formation times (1-2 Myr), where the critical number of stars N_\star \approx 100. Our results suggest that star formation can be characterized by (at least) three principal modes: I. isolated singles and binaries, II. groups (N<N_\star), and III. clusters (N>N_\star). Many -- if not most -- stars form through the intermediate mode in stellar groups with 10<N<100. Such groups evolve and disperse much more rapidly than open clusters; groups also have a low probability of containing massive stars and are unaffected by supernovae and intense ultraviolet radiation fields. Because of their short lifetimes and small stellar membership, groups have relatively little effect on the star formation process (on average) compared to larger open clusters.Comment: accepted to The Astrophysical Journa

PSR B1951+32: A Bow Shock-Confined X-ray Nebula, a Synchrotron Knot and an Optical Counterpart Candidate

The radio pulsar B1951+32 and the supernova remnant CTB 80 provide a rich laboratory for the study of neutron stars and supernova remnants. Here, we present ground-based optical and near-infrared observations of them, along with X-ray observations with Chandra and a re-analysis of archival data obtained with the Hubble Space Telescope. The X-ray observations reveal a cometary pulsar wind nebula which appears to be confined by a bow shock produced by high-velocity motion of the pulsar, making PSR B1951+32 a rare pulsar exhibiting both an H alpha bow shock and a shocked X-ray pulsar wind nebula. The distribution of H alpha and radio continuum emission is indicative of a contact discontinuity of the shocked pulsar winds and shocked ambient medium at \~0.05 pc. On the other hand, the optical synchrotron knot of PSR B1951+32 likely has a flat spectrum in the optical and near-infrared wavebands, and our astrometry is consistent with only one of the two reported optical counterpart candidates for the pulsar.Comment: To appear in ApJ Letter