VLBI Data Interchange Format (VDIF)

One important outcome of the 7th International e-VLBI Workshop in Shanghai in June 2008 was the creation of a task force to study and recommend a universal VLBI data format that is suitable for both on-the-wire e-VLBI data transfer, as well as direct disk storage. This task force, called the VLBI Data Interchange Format (VDIF) Task Force, is the first part of a two-part effort, the second of which will address standardization of e-VLBI data-transmission-protocols. The formation of the VDIF Task Force was prompted particularly by increased e-VLBI activity and the difficulties encountered when data arrive at a correlator in different formats from various instruments in various parts of the world. The task force created a streaming packetized data format that may be used for real-time and non-realtime e-VLBI, as well as direct disk storage. The data may contain multiple channels of time-sampled data with an arbitrary number of channels, arbitrary #bits/sample up to 32, and real or complex data; data rates in excess of 100 Gbps are supported. Each data packet is completely self-identifying via a short header, and data may be decoded without reference to any external information. The VDIF task force has completed its work, and the VDIF standard was ratified at the 2009 e-VLBI workshop in Madrid

Voice Onset Time as a Clinical Indicator of Hypofunctional Voice Disorders.

The purpose of this study was to measure and compare the voice onset times (VOTs) of healthy individuals using a normal and breathy voice in an effort to determine if VOT can be used as a noninvasive clinical indicator of laryngeal function. Recordings were made of 20 adults between the ages of 20-48 with normal laryngeal function, each using a normal (Group 1) and breathy voice (Group 2). The participants’ productions were designed and collected in such a manner to control for speaking rate, vowel context, pitch, and loudness; all of which have been shown to influence VOT. A mixed analyses of variance showed that hypofunctional productions demonstrated longer VOTs across all stop consonants when compared to normal productions. Within the stops, a significant difference between the voiced and voiceless stops was noted, although no gender differences were found. It was concluded that VOT can be used as an indirect clinical indicator of laryngeal function

Chemical and textural equilibration of garnet during amphibolite-facies metamorphism: The influence of coupled dissolution-reprecipitation

Metamorphic equilibration requires chemical communication between minerals and may be inhibited through sluggish volume diffusion and or slow rates of dissolution in a fluid phase. Relatively slow diffusion and the perceived robust nature of chemical growth zoning may preclude garnet porphyroblasts from readily participating in low temperature amphibolite-facies metamorphic reactions. Garnet is widely assumed to be a reactant in staurolite-isograd reactions, and the evidence for this has been assessed in the Late Proterozoic Dalradian pelitic schists of the Scottish Highlands. Three-D imaging of garnet porphyroblasts in staurolite-bearing schists reveal a good crystal shape and little evidence of marginal dissolution, however there is also lack of evidence for the involvement of either chlorite or chloritoid in the reaction. Staurolite forms directly adjacent to the garnet, and its nucleation is strongly associated with deformation of the muscovite-rich fabrics around the porphyroblasts. “Cloudy” fluid inclusion-rich garnet forms in both marginal and internal parts of the garnet porphyroblast and is linked both to the production of staurolite and to the introduction of abundant quartz inclusions within the garnet. Such cloudy garnet typically has a Mg-rich, Mn-poor composition and is interpreted to have formed during a coupled dissolution-reprecipitation process, triggered by a local influx of fluid. All garnet in the muscovite-bearing schists present in this area is potentially reactive, irrespective of the garnet composition, but very few of the schists contain staurolite. The staurolite-producing reaction appears to be substantially overstepped during the relatively high pressure Barrovian regional metamorphism reflecting the limited permeability of the schists in peak metamorphic conditions. Fluid influx and hence reaction progress appear to be strongly controlled by subtle differences in deformation history. The remaining garnet fails to achieve chemical equilibrium during the reaction creating distinctive patchy compositional zoning. Such zoning in metamorphic garnet created during coupled dissolution-reprecipitation reactions may be difficult to recognize in higher grade pelites due to subsequent diffusive re-equilibration. Fundamental assumptions about metamorphic processes are questioned by the lack of chemical equilibrium during this reaction and the restricted permeability of the regional metamorphic pelitic schists. In addition the partial loss of prograde chemical and textural information from the garnet porphyroblasts cautions against their routine use as a reliable monitor of metamorphic history. However the partial re-equilibration of the porphyroblasts during coupled dissolution-reprecipitation opens possibilities of mapping reaction progress in garnet as a means of assessing fluid access during peak metamorphic conditions

The use of the Long Baseline Array in Australia for precise geodesy and absolute astrometry

We report the results of a successful 12 hour 22 GHz VLBI experiment using a heterogeneous network that includes radio telescopes of the Long Baseline Array (LBA) in Australia and several VLBI stations that regularly observe in geodetic VLBI campaigns. We have determined positions of three VLBI stations, ATCA-104, CEDUNA and MOPRA, with an accuracy of 4-30mm using a novel technique of data analysis. These stations have never before participated in geodetic experiments. We observed 105 radio sources, and amongst them 5 objects which have not previously been observed with VLBI. We have determined positions of these new sources with the accuracy of 2-5 mas. We make conclusion that the LBA network is capable of conducting absolute astrometry VLBI surveys with accuracy better than 5 mas.Comment: Published in Publications of the Astronomical Society of Australia. 10 pages, 3 figures, 5 tables. Table 5 in a machine readable form is accessible in the source of this submissio

Using a College Curriculum to Integrate Informal Science Learning Opportunities for University and Middle School Students

We used community partnerships to develop an integrated science-learning program focused on two groups of learners – university and middle school (MS) students – to increase students’ interest and confidence in science as well as motivation to pursue science. Key program elements include a university course for undergraduate and graduate students, university student-led weekly afterschool clubs held at local middle schools (mostly Title I), and a capstone museum science festival led by university and MS students. Across nine course offerings, 78 university students conducted 25 clubs at seven middle schools and engaged at least 240 MS students. The capstone science festival engaged ~1,200 public participants across six events. We evaluated the program in two phases. Quantitative and qualitative assessments show that university students enjoyed the course and increased their ability to describe complex scientific phenomenon to youth. Middle school students reported significant increases in science interest, science understanding, and understanding scientists (1st evaluation phase); and increased interest in a career in science and in their perception of others seeing them as a scientist (2nd phase). Consistent with prior research, overall we found an increase in interest and understanding of science, science identity, and interest in future science careers for MS students

Embedded Stellar Populations towards Young Massive Star Formation Regions I. G305.2+0.2

We present deep, wide-field J, H and Ks images taken with IRIS2 on the Anglo Australian Telescope, towards the massive star formation region G305.2+0.2. Combined with 3.6, 4.5, 5.8 and 8.0 micron data from the GLIMPSE survey on the Spitzer Space Telescope, we investigate the properties of the embedded stellar populations. After removing contamination from foreground stars we separate the sources based on their IR colour. Strong extended emission in the GLIMPSE images hampers investigation of the most embedded sources towards the known sites of massive star formation. However, we find a sizeable population of IR excess sources in the surrounding region free from these completeness effects. Investigation reveals the recent star formation activity in the region is more widespread than previously known. Stellar density plots show the embedded cluster in the region, G305.24+0.204, is offset from the dust emission. We discuss the effect of this cluster on the surrounding area and argue it may have played a role in triggering sites of star formation within the region. Finally, we investigate the distribution of IR excess sources towards the cluster, in particular their apparent lack towards the centre compared with its immediate environs.Comment: 16 pages, 16 figures (significantly size reduced), 2 tables, accepted MNRA

Methionyl-tRNA synthetase synthetic and proofreading activities are determinants of antibiotic persistence

Bacterial antibiotic persistence is a phenomenon where bacteria are exposed to an antibiotic and the majority of the population dies while a small subset enters a low metabolic, persistent, state and are able to survive. Once the antibiotic is removed the persistent population can resuscitate and continue growing. Several different molecular mechanisms and pathways have been implicated in this phenomenon. A common mechanism that may underly bacterial antibiotic persistence is perturbations in protein synthesis. To investigate this mechanism, we characterized four distinct metG mutants for their ability to increase antibiotic persistence. Two metG mutants encode changes near the catalytic site of MetRS and the other two mutants changes near the anticodon binding domain. Mutations in metG are of particular interest because MetRS is responsible for aminoacylation both initiator tRNAMet and elongator tRNAMet indicating that these mutants could impact translation initiation and/or translation elongation. We observed that all the metG mutants increased the level of antibiotic persistence as did reduced transcription levels of wild type metG. Although, the MetRS variants did not have an impact on MetRS activity itself, they did reduce translation rates. It was also observed that the MetRS variants affected the proofreading mechanism for homocysteine and that these mutants’ growth is hypersensitive to homocysteine. Taken together with previous findings, our data indicate that both reductions in cellular Met-tRNAMet synthetic capacity and reduced proofreading of homocysteine by MetRS variants are positive determinants for bacterial antibiotic persistence