A New Galactic 6cm Formaldehyde Maser

We report the detection of a new H2CO maser in the massive star forming region G23.71-0.20 (IRAS 18324-0820), i.e., the fifth region in the Galaxy where H2CO maser emission has been found. The new H2CO maser is located toward a compact HII region, and is coincident in velocity and position with 6.7 GHz methanol masers and with an IR source as revealed by Spitzer/IRAC GLIMPSE data. The coincidence with an IR source and 6.7 GHz methanol masers suggests that the maser is in close proximity to an embedded massive protostar. Thus, the detection of H2CO maser emission toward G23.71-0.20 supports the trend that H2CO 6cm masers trace molecular material very near young massive stellar objects.Comment: Accepted for publication in The Astrophysical Journal Letter

Methanol masers : Reliable tracers of the early stages of high-mass star formation

The GLIMPSE and MSX surveys have been used to examine the mid-infrared properties of a statistically complete sample of 6.7 GHz methanol masers. The GLIMPSE point sources associated with methanol masers are clearly distinguished from the majority, typically having extremely red mid-infrared colors, similar to those expected of low-mass class 0 young stellar objects. The intensity of the GLIMPSE sources associated with methanol masers is typically 4 magnitudes brighter at 8.0 micron than at 3.6 micron. Targeted searches towards GLIMPSE point sources with [3.6]-[4.5] > 1.3 and an 8.0 micron magnitude less than 10 will detect more than 80% of class II methanol masers. Many of the methanol masers are associated with sources within infrared dark clouds (IRDC) which are believed to mark regions where high-mass star formation is in its very early stages. The presence of class II methanol masers in a significant fraction of IRDC suggests that high-mass star formation is common in these regions. Different maser species are thought to trace different evolutionary phases of the high-mass star formation process. Comparison of the properties of the GLIMPSE sources associated with class II methanol masers and other maser species shows interesting trends, consistent with class I methanol masers tracing a generally earlier evolutionary phase and OH masers tracing a later evolutionary phase.Comment: 45 pages, 19 figures, accepted for publication in Ap

A performance measurement system for integrated production and maintenance planning

CITATION: Schreiber, M. et al. 2020. A performance measurement system for integrated production and maintenance planning. Procedia CIRP, 93:1037-1042. doi:10.1016/j.procir.2020.03.041The original publication is available at https://www.sciencedirect.com/journal/procedia-cirpThe increasing amount of production resources to be maintained and efficiency requirements are forcing manufacturing companies to improve production and maintenance effectiveness by a mutual consideration of both functions in an integrated planning process. However, less attention is paid to monitor the performance of manufacturing systems based on key performance indicators to identify the need for measures and adapting plans. Performance Measurement Systems (PMS) are applied to accomplish this task. Therefore, this paper presents an evaluation of existing PMS’s for production and maintenance planning. A new PMS that considers strategic and operational views is presented and validated by an industrial case study.https://www.sciencedirect.com/science/article/pii/S2212827120306375?via%3DihubPublishers versio

Blackbody-radiation-assisted molecular laser cooling

The translational motion of molecular ions can be effectively cooled sympathetically to temperatures below 100 mK in ion traps through Coulomb interactions with laser-cooled atomic ions. The distribution of internal rovibrational states, however, gets in thermal equilibrium with the typically much higher temperature of the environment within tens of seconds. We consider a concept for rotational cooling of such internally hot, but translationally cold heteronuclear diatomic molecular ions. The scheme relies on a combination of optical pumping from a few specific rotational levels into a ``dark state'' with redistribution of rotational populations mediated by blackbody radiation.Comment: 4 pages, 5 figure

Capacity self-assessment as a catalyst for improved municipal service delivery

CITATION: Van Baalen, S. M., Schutte, C. S. L. & Von Leipzig, K. 2015. Capacity self-assessment as a catalyst for improved municipal service delivery. Journal of the South African Institution of Civil Engineering, 57(1):2–15, doi:10.17159/2309-8775/2015/v57n1a1.The original publication is available at http://www.scielo.org.zaENGLISH ABSTRACT: This research paper illustrates that accurate and truthful capacity assessments are a fundamental phase of any capacity building process, and that capacity assessments play a fundamental role in reaching the necessary performance efficiency. Service delivery performance enhancements by municipalities are becoming increasingly necessary. At the same time, however, the majority of municipalities in South Africa find themselves under-capacitated. Some municipalities are aware of the lack of capacity within their organisation, but are unable to identify, define and quantify these shortcomings. Many other municipalities are not aware of their capacity shortfalls. In both cases, this is often caused by the lack of necessary systems and procedures to assess the different dimensions of organisational capacity. In this regard, this research paper introduces a proposed Subjective Municipal Capacity Self-Assessment Model (SMCSAM) as an alternative solution to the current practices of the Municipal Demarcation Board. It is intended that this model be used internally by municipalities to sustain internal capacity building and performance enhancement initiatives.AFRIKAANSE OPSOMMING: Geen opsomming beskikbaarhttp://www.scielo.org.za/scielo.php?script=sci_abstract&pid=S1021-20192015000100001&lng=en&nrm=iso&tlng=enPublisher's versio

Blockchain feasibility assessment: A quantitative approach

This article outlines the research and development of a blockchain assessment framework which enables the assessment of the technical suitability, high-level design, adoption approach, economic feasibility, and business value potential of a blockchain solution with a particular organization for a specific process. The framework is a comprehensive, high-level, and generic assessment approach that enables better decision-making regarding blockchain exploration. Blockchain is a novel technology with the potential to disrupt several industries through its possession of many desirable functional characteristics, including, but not limited to, immutability, transparency, decentralization, and secure. Cryptocurrencies and these desirable characteristics have created hype around blockchain, consequently leading to blockchain projects with minimal understanding of what the technology is capable of and beneficial for, resulting in excessively high failure rates. Attempts have been made by researchers to reduce these high failure rates by creating a better understanding of blockchain, as well as creating assessment approaches. However, these approaches tend to apply to specific narrow use cases, or the approach is not comprehensive and only considers one aspect of blockchain assessment. This emphasizes the need for a comprehensive and generic blockchain assessment approach to aid with better decision-making regarding blockchain within organizations. This article aims at addressing this need by creating a blockchain assessment framework to aids with deciding whether it is worthwhile investing more time, effort, and money into blockchain exploration. The context of the study is set in the introduction, this is then followed by a brief explanation of the blockchain technology. Thereafter, the blockchain assessment framework is presented, followed by a brief explanation of the demonstration and validation of the framework using a case study and expert analysis. The framework is most valuable during the initial stages of blockchain exploration and creates momentum for further blockchain exploration in an organization. The study concludes with the limitations and future research recommendations

Ices in the edge-on disk CRBR 2422.8-3423: Spitzer spectroscopy and Monte Carlo radiative transfer modeling

We present 5.2-37.2 micron spectroscopy of the edge-on circumstellar disk CRBR 2422.8-3423 obtained using the InfraRed Spectrograph (IRS) of the Spitzer Space Telescope. The IRS spectrum is combined with ground-based 3-5 micron spectroscopy to obtain a complete inventory of solid state material present along the line of sight toward the source. We model the object with a 2D axisymmetric (effectively 3D) Monte Carlo radiative transfer code. It is found that the model disk, assuming a standard flaring structure, is too warm to contain the very large observed column density of pure CO ice, but is possibly responsible for up to 50% of the water, CO2 and minor ice species. In particular the 6.85 micron band, tentatively due to NH4+, exhibits a prominent red wing, indicating a significant contribution from warm ice in the disk. It is argued that the pure CO ice is located in the dense core Oph-F in front of the source seen in the submillimeter imaging, with the CO gas in the core highly depleted. The model is used to predict which circumstances are most favourable for direct observations of ices in edge-on circumstellar disks. Ice bands will in general be deepest for inclinations similar to the disk opening angle, i.e. ~70 degrees. Due to the high optical depths of typical disk mid-planes, ice absorption bands will often probe warmer ice located in the upper layers of nearly edge-on disks. The ratios between different ice bands are found to vary by up to an order of magnitude depending on disk inclination due to radiative transfer effects caused by the 2D structure of the disk. Ratios between ice bands of the same species can therefore be used to constrain the location of the ices in a circumstellar disk. [Abstract abridged]Comment: 49 pages, accepted for publication in Ap

Methanol Masers as Tracers of Circumstellar Disks

We show that in many methanol maser sources the masers are located in lines, with a velocity gradient along them which suggests that the masers are situated in edge-on circumstellar, or protoplanetary, disks. We present VLBI observations of the methanol maser source G309.92+0.48, in the 12.2 GHz transition, which confirm previous observations that the masers in this source lie along a line. We show that such sources are not only linear in space but, in many cases, also have a linear velocity gradient. We then model these and other data in both the 6.7 GHz and the 12.2 GHz transition from a number of star formation regions, and show that the observed spatial and velocity distribution of methanol masers, and the derived Keplerian masses, are consistent with a circumstellar disk rotating around an OB star. We consider this and other hypotheses, and conclude that about half of these methanol masers are probably located in edge-on circumstellar disks around young stars. This is of particular significance for studies of circumstellar disks because of the detailed velocity information available from the masers.Comment: 38 pages, 13 figures accepted by Ap

On the Identification of High Mass Star Forming Regions using IRAS: Contamination by Low-Mass Protostars

We present the results of a survey of a small sample (14) of low-mass protostars (L_IR < 10^3 Lsun) for 6.7 GHz methanol maser emission performed using the ATNF Parkes radio telescope. No new masers were discovered. We find that the lower luminosity limit for maser emission is near 10^3 Lsun, by comparison of the sources in our sample with previously detected methanol maser sources. We examine the IRAS properties of our sample and compare them with sources previously observed for methanol maser emission, almost all of which satisfy the Wood & Churchwell criterion for selecting candidate UCHII regions. We find that about half of our sample satisfy this criterion, and in addition almost all of this subgroup have integrated fluxes between 25 and 60 microns that are similar to sources with detectable methanol maser emission. By identifying a number of low-mass protostars in this work and from the literature that satisfy the Wood & Churchwell criterion for candidate UCHII regions, we show conclusively for the first time that the fainter flux end of their sample is contaminated by lower-mass non-ionizing sources, confirming the suggestion by van der Walt and Ramesh & Sridharan.Comment: 8 pages with 2 figures. Accepted by Ap

Spatially Resolved Chemistry in Nearby Galaxies I. The Center of IC 342

We have imaged emission from the millimeter lines of eight molecules--C2H, C34S, N2H+, CH3OH, HNCO, HNC, HC3N, and SO--in the central half kpc of the nearby spiral galaxy IC 342. The 5" (~50 pc) resolution images were made with OVRO. Using these maps we obtain a picture of the chemistry within the nuclear region on the sizescales of individual GMCs. Bright emission is detected from all but SO. There are marked differences in morphology for the different molecules. A principal component analysis is performed to quantify similarities and differences among the images. This analysis reveals that while all molecules are to zeroth order correlated, that is, they are all found in dense molecular clouds, there are three distinct groups of molecules distinguished by the location of their emission within the nuclear region. N2H+, C18O, HNC and HCN are widespread and bright, good overall tracers of dense molecular gas. C2H and C34S, tracers of PDR chemistry, originate exclusively from the central 50-100 pc region, where radiation fields are high. The third group of molecules, CH3OH and HNCO, correlates well with the expected locations of bar-induced orbital shocks. The good correlation of HNCO with the established shock tracer molecule CH3OH is evidence that this molecule, whose chemistry has been uncertain, is indeed produced by processing of grains. HC3N is observed to correlate tightly with 3mm continuum emission, demonstrating that the young starbursts are the sites of the warmest and densest molecular gas. We compare our HNC images with the HCN images of Downes et al. (1992) to produce the first high resolution, extragalactic HCN/HNC map: the HNC/HCN ratio is near unity across the nucleus and the correlation of both of these gas tracers with the star formation is excellent. (Abridged).Comment: 54 pages including 10 figures and 8 tables. Accepted for publication in Ap