Indirect Network Effects and Adoption Externalities

The conventional wisdom is that indirect network effects, unlike direct network effects, do not give rise to externalities. In this paper we show that under very general conditions, indirect network effects lead to adoption externalities. In particular we show that in markets where consumption benefits arise from hardware/software systems, adoption externalities will occur when there are (i) increasing returns to scale in the production of software, (ii) free-entry in software, and (iii) consumers have a preference for software variety. The private benefit of the marginal hardware purchaser is less than the social benefit since the marginal hardware purchaser does not internalize the welfare improving response of the software industry, particularly the increase in software variety, on inframarginal purchasers when the market for hardware expands.Network Externalities, Network Effects

Low-Mass X-ray Binaries and Globular Clusters in Early-Type Galaxies. I. Chandra Observations

We present a Chandra survey of LMXBs in 24 early-type galaxies. Correcting for detection incompleteness, the X-ray luminosity function (XLF) of each galaxy is consistent with a powerlaw with negative logarithmic differential slope, beta~2.0. However, beta strongly correlates with incompleteness, indicating the XLF flattens at low-Lx. The composite XLF is well-fitted by a powerlaw with a break at 2.21(+0.65,-0.56)E38 erg/s and beta=1.40(+0.10,-0.13) and 2.84(+0.39,-0.30) below and above it, respectively. The break is close to the Eddington limit for a 1.4Msun neutron-star, but the XLF shape rules out its representing the division between neutron-star and black-hole systems. Although the XLFs are similar, we find evidence of some variation between galaxies. The high-Lx XLF slope does not correlate with age, but may correlate with [alpha/Fe]. Considering only LMXBs with Lx>1E37 erg/s, matching the LMXBs with globular clusters (GCs) identified in HST observations of 19 of the galaxies, we find the probability a GC hosts an LMXB is proportional to LGC^alpha ZFe^gamma} where alpha=1.01+/-0.19 and gamma=0.33+/-0.11. Correcting for GC luminosity and colour effects, and detection incompleteness, we find no evidence that the fraction of LMXBs with Lx>1e37 erg/s in GCs (40%), or the fraction of GCs hosting LMXBs (~6.5%) varies between galaxies. The spatial distribution of LMXBs resembles that of GCs, and the specific frequency of LMXBs is proportional to the GC specific luminosity, consistent with the hypothesis that all LMXBs form in GCs. If the LMXB lifetime is tau and the duty cycle is Fd, our results imply ~1.5 (tau/1E8 yr)^-1 /Fd LMXBs are formed per Gyr per GC and we place an upper limit of 1 active LMXB in the field per 3.4E9Lsun of V-band luminosity.Comment: 24 pages, 17 figures and 6 tables. Accepted for publication in the Astrophysical Journal. Expanded discussion and various minor revisions to improve robustness of results. Conclusions unchange

Defending Australia: a history of Australia’s defence white papers

This paper provides a summary of each of Australia’s defence white papers issued between 1976 and 2013 and seeks to draw out common themes that emerge in some or all of them. Executive summary Australia published defence white papers in 1976, 1987, 1994, 2000, 2009 and 2013 and a new white paper is expected in 2015. A community consultation process was undertaken as part of the 2000 and 2009 defence white papers and a similar process is being carried out for the upcoming 2015 defence white paper. The need to defend Australia against a major aggressor remains the primary driver in Australian defence policy. Regional security and contributing to the global order have been secondary, but still important priorities in Australian defence planning. Each of the defence white papers has been created on the basis that Australia should be able to defend itself against a potential aggressor without outside assistance (the principle of self-reliance), while at the same time stressing the importance of the alliance with the United States. Threat perceptions have changed from the Cold War influences reflected in the 1976 and 1987 white papers to a contemporary focus on terrorism while also incorporating emerging threats such as cyber attacks and the rise of China. Defence white papers are not produced in a vacuum but are informed by key reviews of Australia’s strategic situation, industry policy and force posture. Defence policy is subject to the broader economic conditions of the time and the Department of Defence must contend with many other priorities for government funding. The financial plans set out in the various defence white papers are often ambitious and rarely brought to fruition. On the whole, capability choices have displayed continuity between the different white papers regardless of changes in government. This is understandable given the length of time required for major capital equipment acquisitions. Recent white papers have placed a greater emphasis on regional engagement. The contribution of the Australian Defence Force (ADF) to humanitarian assistance and disaster relief operations, as well as to border protection activities, has also been included in the most recent white papers

Mapping the YY1 and p65 binding sites on the transcription factor LSF

Late SV40 factor (LSF) is a CP2 family transcription factor involved in cell cycle regulation. In liver cancer, LSF is an oncogene, in part due to its role in upregulation of osteopontin leading to increase tumor size. As a result, LSF is a potential target for drug discovery. LSF binds the p65 subunit of the transcription factor NFkB and also the transcription factor ying yang 1 (YY1). In this thesis, I show that binding of both YY1 and p65 occurs at the ubiquitin-like domain of LSF in U2OS cell extracts. Interestingly, when phosphatase inhibitors are added during preparation of U2OS cell extracts, the binding of YY1 and p65 to LSF shifts from the ubiquitin-like domain of LSF to the DNA binding domain. The role of a yet unidentified docking protein may be responsible for this shift in binding. In an attempt to map the specific region of the LSF sequence that is involved in these interactions, I have developed a peptide identification assay which utilizes protease digestion, protein mediated peptide capture, and LC ESI-MS. Through the use of this assay, I'm confident that the sequence(s) involved in these LSF protein-protein interactions can be further defined

Optimisation of the Investigation of Antibody-Mediated Dysglycaemia

Two rare and severe disorders of insulin action, namely insulin autoimmune syndrome (IAS) and type B insulin resistance (TB-IR), are caused by pathogenic antibodies against insulin or the insulin receptor, respectively. These may arise in isolation or may complicate management of pre-existing diabetes mellitus, and milder forms of the conditions are often suspected in patients with insulin-treated diabetes and labile glycaemic control. Antibody depletion can effectively treat either condition in many cases. This research aimed to target major limitations of existing diagnostics, specifically, that anti-insulin antibody (IA) testing alone does not establish whether antibodies alter insulin action to a clinically-significant degree, and that no clinically-accredited diagnostic test for TB-IR currently exists. An initial collaborative study examined the ability of a panel of commercial insulin assays to quantify ten different insulin preparations. Significant variability in performance of assays against animal-derived and insulin analogues was seen, with certain insulin analogues not detected at all, with important implications for the use of insulin immunoassays in insulin-treated patients. A suite of techniques for investigation of the clinical significance of IAs were then developed and assessed. In a study of five widely-used insulin immunoassays, dilution of IAS plasma led to increased insulin recovery, and polyethylene glycol (PEG) precipitation of IAS plasma decreased insulin recovery in the majority of assays. Gel filtration chromatography (GFC) discriminated high molecular weight and monomeric insulin, while ex vivo addition of exogenous insulin to plasma increased sensitivity of insulin immunocomplex detection. An observational study was performed of 7 patients, all ultimately diagnosed with IAS. IAs were measured using radioligand-binding assay and enzyme-linked immunosorbent assay (ELISA). Method comparison showed results to differ in rank order and relative magnitude. For one patient whose screening IA result was not grossly elevated using either IA assay method, immunosubtraction studies were consistent with the presence of an IgA, a class of antibody under-/not detected in the IA assays studied. Competitive radioligand-binding studies demonstrated IAs to have a range of affinities. 4 patients treated with individualised regimens of immunosuppressive therapy varied in clinical response, and 3 were managed conservatively. Plasma insulin and C-peptide measurements made using mass spectrometry demonstrated under-estimation of insulin and over-estimation of C-peptide concentration using immunoassay in IAS. An observational laboratory and clinical study was also undertaken of 30 insulin-treated patients with diabetes and unexplained labile glycaemia. IA, and plasma insulin before and after PEG precipitation, were determined. Three groups were identified: the first were ‘negative’ for actionable IA; the second had demonstrable IAs of potential significance that warrant further study; and the third included 3 patients for whom immunomodulation therapy was indicated, with 1 other patient showing marked improvement of glycaemic control with close supervision and manipulation of insulin. Finally, anti-insulin receptor antibodies were detected using a newly developed ELISA utilising Chinese hamster ovary-expressed myc-tagged wild-type human insulin receptor. ‘Proof of principle’ was demonstrated for the new assay, with clear scope established for future diagnostic development. The ability to robustly prove, or conversely to rule out, the presence, of insulin–antibody complexes and/or anti-insulin receptor antibodies is invaluable in the investigation of patients with insulin resistance and/or unexplained labile glycaemia, and may decisively alter care pathways. Knowledge gained by this research has advanced understanding of the limitations of current laboratory diagnostics, and has thereby aided clinical-decision making for affected patients.PhD was funded by a Diabetes Research and Wellness Fellowship Sutherland–Earl Clinical Fellowship (RG68554). Funding was also received from the Medical Research Council (MRC_MC_UU_ 12012/5) and the United Kingdom National Institute for Health Research (NIHR) Cambridge Biomedical Research Centre

An empirical study of software design practices

Software engineers have developed a large body of software design theory and folklore, much of which was never validated. The results of an empirical study of software design practices in one specific environment are presented. The practices examined affect module size, module strength, data coupling, descendant span, unreferenced variables, and software reuse. Measures characteristic of these practices were extracted from 887 FORTRAN modules developed for five flight dynamics software projects monitored by the Software Engineering Laboratory (SEL). The relationship of these measures to cost and fault rate was analyzed using a contingency table procedure. The results show that some recommended design practices, despite their intuitive appeal, are ineffective in this environment, whereas others are very effective

Design, Operations, and Safety of High-Speed Approach Rural Roundabouts

High-speed approach rural roundabouts have been found to reduce overall crashes by 71% and injury crashes by 87% and have become an effective tool used by public agencies to improve safety and capacity at rural intersections. In this presentation we will discuss critical design features for effective implementation, including alignment on approach, deflection, splitter islands, lighting, signing, curbing, diameter, design vehicle, and landscaping. Before-and-after results involving safety, operations, and public acceptance will be highlighted at specific US roundabouts