Disk evaporation in a planetary nebula

We study the Galactic bulge planetary nebula M 2-29 (for which a 3-year eclipse event of the central star has been attributed to a dust disk) using HST imaging and VLT spectroscopy, both long-slit and integral field. The central cavity of M 2-29 is filled with a decreasing, slow wind. An inner high density core is detected, with radius less than 250 AU, interpreted as a rotating gas/dust disk with a bipolar disk wind. The evaporating disk is argued to be the source of the slow wind. The central star is a source of a very fast wind (1000 km/s). An outer, partial ring is seen in the equatorial plane, expanding at 12 km/s. The azimuthal asymmetry is attributed to mass-loss modulation by an eccentric binary. M 2-29 presents a crucial point in disk evolution, where ionization causes the gas to be lost, leaving a low-mass dust disk behind.Comment: 11 pages, accepted for publication in "Astronomy and Astrophysics

Construction Vibration Monitoring in the Charleston, South Carolina Area

Vibrations generated during construction often affect adjacent and surrounding buildings and disturb neighboring residents in tightly spaced urban environments. These vibrations can lead to structural damage, especially to older structures. In Charleston, South Carolina, construction vibrations are of special concern due to the tight spacing, age, construction, and historic significance of many of the city’s buildings. Of particular interest are the vibrations generated from pile driving activities. Due to the nature of the lower coastal plain soils in the Charleston, SC area, the majority of new commercial structures are being founded on driven pile foundations bearing within the underlying Cooper Marl Formation. This paper presents the development of vibration threshold levels for both historic and modern structures in Charleston, SC and the case histories of five construction projects in which the developed criteria was used. Vibration data, pre and post-construction surveys, and crack monitoring device data collected during these construction projects were then analyzed to evaluate the vibration criteria

Pile Driving Vibration Energy-Attenuation Relationships in the Charleston, South Carolina Area

Vibrations generated by driven pile installation often affect adjacent and surrounding buildings in tightly spaced urban environments. These vibrations can lead to complaints from neighboring residents and businesses and/or cause structural damage to adjacent structures, especially older and historic buildings. Pile driving vibrations are of particular interest in the Charleston, South Carolina area since the majority of new structures are founded on driven pile foundations bearing within the underlying Cooper Marl Formation. By knowing the vibration attenuation relationship of a project area (i.e. the decrease in vibration amplitude with distance), it is possible to develop pile installation plans that minimize discomfort to residents and the risk of damage to adjacent structures. In addition, knowledge of the vibration attenuation relationship for a site can assist in determining the limits for pre-condition surveys to document the existing conditions of adjacent structures prior to pile driving operations. This paper presents the case histories of vibrations monitored during seven driven pile and one vibratory pile construction projects in the Charleston, South Carolina area. The vibration data was then analyzed to evaluate the energy-attenuation relationships for the individual sites. Comparisons of these analyses were then made in an effort to determine typical energy-attenuation relationships for driven piles within the Charleston, SC area

Crosshole Sonic Logging Integrity Testing for the New Cooper River Bridge

A new cable-stayed bridge for US Highway 17 is currently under construction over the Cooper River between Mount Pleasant and Charleston, South Carolina. This new bridge will replace two existing structures, the Silas Pearlman and the Grace Memorial Bridges. When completed, the new bridge will have a 1,546 feet span over the Cooper River, making this bridge the longest cable-stayed span in North America. The foundations for this replacement bridge are drilled shafts embedded within the Cooper Marl formation, which underlies the near surface lower coastal plain soil deposits. Depending on the location within the bridge structure, the drilled shafts range from 1.07m (3.5ft) to 3.66m (12ft) in diameter with embedments of up to 56.4m (185ft) within the Cooper Marl. The deepest drilled shafts extend to depths of 71.3m (234ft) from mean sea level (MSL). A total of 410 drilled shafts will be used as the foundations for the new bridge. At of the time of submittal of this publication, a total of 384 of these drilled shafts were installed over a time period ranging fromMarch 2002 to September 2003. The design of the bridge left little redundancy in the drilled shaft foundations. Therefore, integrity testing of the drilled shafts, especially at critical areas such as the main bridge piers, was of major importance to verify that these foundations were capable of supporting the bridge superstructure. Crosshole Sonic Logging (CSL) was selected as the primary testing method to evaluate drilled shaft integrity. This paper presents the results of the drilled shaft CSL integrity testing and discusses the findings of the testing and lessons learned over the course of drilled shaft installation

The very fast evolution of Sakurai's object

V4334 Sgr (a.k.a. Sakurai's object) is the central star of an old planetary nebula that underwent a very late thermal pulse a few years before its discovery in 1996. We have been monitoring the evolution of the optical emission line spectrum since 2001. The goal is to improve the evolutionary models by constraining them with the temporal evolution of the central star temperature. In addition the high resolution spectral observations obtained by X-shooter and ALMA show the temporal evolution of the different morphological components.Comment: 2 pages, 2 figures to appear in the Proceedings of the IAU Symp. 323: "Planetary nebulae: Multi-wavelength probes of stellar and galactic evolution". Eds. X.-W. Liu, L. Stanghellini and A. Karaka

Complex effects of helper relatedness on female extrapair reproduction in a cooperative breeder

In cooperatively breeding species, the presence of male helpers in a group often reduces the breeding female’s fidelity to her social partner, possibly because there is more than one potential sire in the group. Using a long-term study of cooperatively breeding superb fairy-wrens (Malurus cyaneus) and records of paternity in 1936 broods, we show that the effect of helpers on rates of extrapair paternity varied according to the helpers’ relatedness to the breeding female. The presence of unrelated male helpers in a group increased average rates of extrapair paternity, from 57% for groups with no unrelated helpers, to 74% with one unrelated helper, to 86% with 2+ unrelated helpers. However, this increase was due in equal part to helpers within the group and males in other groups achieving increased paternity. In contrast, helpers who were sons of the breeding female did not gain paternity, nor did they affect the level of extra-group paternity (which occurred at rates of 60%, 58%, 61% in the presence of 0, 1, 2+ helper sons, respectively). There was no evidence of effects of helpers’ relatedness to the female on nest productivity or nestling performance. Because the presence of helpers per se did not elevate extrapair reproduction rates, our results undermine the “constrained female hypothesis” explanation for an increase in extrapair paternity with helper number in cooperative breeders. However, they indicate that dominant males are disadvantaged by breeding in “cooperative” groups. The reasons why the presence of unrelated helpers, but not of helper-sons, results in higher rates of extra-group reproduction are not clear.G.K.H. was supported by the U.K. Natural Environment Research Council (Grant NE/L002558/1) through the University of Edinburgh’s E3 Doctoral Training Partnership. The long-term research has been facilitated b

Steel Pipe Pile Design, Installation, and Dynamic Testing for a New Pier in Georgetown, SC

A new pier extension was constructed for the South Carolina State Ports Authority (SCSPA) at Pier 31C in Georgetown, South Carolina. This pier was founded on 28 steel open ended pipe (OEP) piles driven into the underlying limestone and silts of the Pee Dee Formation. To account for the expected high lateral loads the new pier may experience during ship impacts and movements, both vertical and batter piles were installed. To the authors’ knowledge, this is the first application of steel open ended pipe piles as a maritime foundation system in the Georgetown, South Carolina area. The soil stratigraphy at the site consisted of soft river deposits overlaying interbedded limestone and silt layers of the Pee Dee Formation. Significant pile penetration into the cohesive deposits of the Pee Dee Formation was necessary to generate the required tension pile capacity. The results of the geotechnical investigation suggested that the intermittent limestone layers would cause difficult driving conditions for pre-stressed concrete piles, which are traditionally used in the area. This paper provides an overview of the project, discusses the selection and design processes and installation of the steel OEP piles, and presents the results of the dynamic load testing program conducted to verify the pile design. In addition, measurements of time dependent pile capacity gain and pile plugging made during pile installation are also presented and discussed

Nucleotide Sequences within the U5 Region of the Viral RNA Genome Are the Major Determinants for an Human Immunodeficiency Virus Type 1 to Maintain a Primer Binding Site Complementary to tRNAHis

AbstractThe initiation of reverse transcription of the human immunodeficiency virus type 1 (HIV-1) genome requires cellular tRNALys,3as a primer and occurs at a site in the viral RNA genome, designated as the primer binding site (PBS), which is complementary to the 3′-terminal 18 nucleotides of tRNALys,3. We previously described an HIV-1 virus [designated as HXB2(His-AC)], which contained a sequence within the U5 region complementary to the anticodon region of tRNAHisin addition to a PBS complementary to the 3′-terminal 18 nucleotides of the tRNAHis. That virus maintained a PBS complementary to tRNAHisafter extendedin vitroculture (Wakefieldet al., J. Virol.70, 966–975, 1996). In the present study, we report that subcloning a 200-base-pair DNA fragment encompassing the U5 and PBS regions from an integrated provirus of HXB2(His-AC) back into the wild-type genome (pHXB2) resulted in an infectious virus, designated as HXB2(His-AC-gac), which again stably maintained a PBS complementary to tRNAHis. DNA sequence analysis of the 200-base-pair region revealed only three nucleotide changes from HXB2(His-AC): a T-to-G change at nucleotide 174, a G-to-A change at nucleotide 181, and a T-to-C change at nucleotide 200. The new mutant virus replicated in CD4+Sup T1 cells similarly to the wild-type virus. Comparison of the nucleotide sequence of nucleocapsid gene of the wild-type and HXB2 (His-AC-gac) virus revealed no differences. Although we found numerous mutations in the reverse transcriptase gene in proviral clones derived from HXB2 (His-AC-gac), no common mutations were found among the 13 clones examined. Comparison of the virion-associated tRNAs of HXB2(His-AC-gac) with those of the wild type revealed that both viruses incorporated a similar subset of cellular tRNAs, with tRNALys,3being the predominant tRNA found within virions. There was no selective enrichment for tRNAHiswithin virions of HXB2(His-AC-gac) virus which selectively use tRNAHisto initiate reverse transcription. The results of these studies suggest that the U5 and PBS regions in the viral RNA genome are important determinants for HXB2(His-AC) viruses in the selective use of tRNAHisto initiate reverse transcription

Relativistic Hamiltonians in many-body theories

We discuss the description of a many-body nuclear system using Hamiltonians that contain the nucleon relativistic kinetic energy and potentials with relativistic corrections. Through the Foldy-Wouthuysen transformation, the field theoretical problem of interacting nucleons and mesons is mapped to an equivalent one in terms of relativistic potentials, which are then expanded at some order in 1/m_N. The formalism is applied to the Hartree problem in nuclear matter, showing how the results of the relativistic mean field theory can be recovered over a wide range of densities.Comment: 14 pages, uses REVTeX and epsfig, 3 postscript figures; a postscript version of the paper is available by anonymous ftp at ftp://carmen.to.infn.it/pub/depace/papers/951