Maximum or Minimum Differentiation? An Empirical Investigation into the Location of Firms

We empirically test some implications from location theory using the location of Los Angeles area gasoline stations in physical space and in the space of product attributes. We consider the effect of demand patterns, entry costs, and several proxies for competition -- the total number of stations, the proportion of independent stations, and the proportion of same-brand stations in a market -- on the tendency for a gasoline station to be physically located more or less closely to its competitors. Using an estimation procedure that controls for spatial correlation and controlling for market characteristics as well as non- spatial product attributes, we find that firms locate their stations in an attempt to spatially differentiate their product as general market competition increases. In other words, the incentive to differentiate in order to soften price competition dominates the incentive to cluster locations to attract consumers from rivals. We also find that spatial differentiation increases as stations become more differentiated in other station characteristics.product differentiation, spatial theory, location theory, retail gasoline

Fathering to meet the needs of children (2007)

"Information from Human Environmental Sciences Extension.""Human relations.""This publication was originally written by Denise E. Taylor and Janet A. Clark, Human Development and Family Studies Extension, University of Missouri-Columbia. Kim Leon, state specialist in Human Development and Family Studies, reviewed and revised this edition."New 4/00; Revised 4/07/Web

Investigating diet as the source of tetrodotoxin in Pleurobranchaea maculata

The origin of tetrodotoxin (TTX) is highly debated; researchers have postulated either an endogenous or exogenous source with the host accumulating TTX symbiotically or via food chain transmission. The aim of this study was to determine whether the grey side-gilled sea slug (Pleurobranchaea maculata) could obtain TTX from a dietary source, and to attempt to identify this source through environmental surveys. Eighteen non-toxic P. maculata were maintained in aquariums and twelve were fed a TTX-containing diet. Three P. maculata were harvested after 1 h, 24 h, 17 days and 39 days and TTX concentrations in their stomach, gonad, mantle and remaining tissue/fluids determined using liquid chromatography-mass spectrometry. Tetrodotoxin was detected in all organs/tissue after 1 h with an average uptake of 32%. This decreased throughout the experiment (21%, 15% and 9%, respectively). Benthic surveys at sites with dense populations of toxic P. maculata detected very low or no TTX in other organisms. This study demonstrates that P. maculata can accumulate TTX through their diet. However, based on the absence of an identifiable TTX source in the environment, in concert with the extremely high TTX concentrations and short life spans of P. maculata, it is unlikely to be the sole TTX source for this species

‘Why has my world become more confusing than it used to be?’ Professional doctoral students reflect on the development of their identity

This article reports on research into the experience of professional doctoral students and is written by the students themselves. We, the authors, are currently studying for the Doctorate in Education at the University of Manchester, UK. We place our work in the context of recent empirical research into the development of doctoral student identity, noting that these literatures are usually authored by programme directors and supervisors. Using a theoretical approach based on the work of Etienne Wenger, we examine how the aims and curriculum of our programme interplay with our professional learning. In interviews with our cohort of students, we explore the complexity and non-linearity of learning. We do not find a simple progression from practitioner to researcher; rather, we find a fluid and complex relationship between those two identities. We consider the extent to which Wenger’s modes of identification are a useful conceptual tool for understanding this interplay and for theorising about our findings. We conclude that there is further scope for the development of our theoretical framework by drawing on other scholarly work on identity development and reflexivit

Integrating children's perspectives in policy-making to combat poverty and social exclusion experienced by single-parent families: a transnational comparative approach

This is the final report of a research project that addressed social exclusion and poverty as it relates to single parent families and their children in particular. The rising numbers of single parent families and children throughout the EU and the increased likelihood that these families will live in poverty and experience many different forms of social exclusion in their daily lives brings in sharp focus the need to address the issue as an urgent one in our efforts to eradicate poverty and social exclusion. The focus on the children of single parent families seeks to rectify a long-standing problem in our knowledge and understanding of single parent families and the social problems they face, namely, the fact that little, if anything, is known about how these children experience and understand their lives as members of these families. The research set out to contribute to policy development and the transnational exchange of best practice by adding a much-neglected dimension on single parent families. The project used a cross-national comparative qualitative research design and methods (Mangen 1999) which involved all partners in the design of each research phase including the analysis; partners were England, Cyprus and Greece

Location-specific cutaneous electrical stimulation of the footsole modulates corticospinal excitability to the plantarflexors and dorsiflexors during standing

Non-noxious electrical stimulation to distinct locations of the foot sole evokes location-specific cutaneous reflex responses in lower limb muscles. These reflexes occur at latencies that may enable them to be mediated via a transcortical pathway. Corticospinal excitability to the plantarflexors and dorsiflexors was measured in 16 participants using motor evoked potentials (MEPs). Spinal excitability was measured in eight of the original participants using cervicomedullary motor evoked potentials (CMEPs). Measurements were collected with and without preceding cutaneous stimulus to either the heel (HEEL) or metatarsal (MET) locations of the foot sole, and evoked potentials were elicited to coincide with the arrival of the cutaneous volley at either the motor cortex or spinal cord. Plantarflexor MEPs and CMEPs were facilitated with cutaneous stimulation to the HEEL for MEPs (soleus p = 0.04, medial gastrocnemius (MG) p = 0.017) and CMEPs (soleus p = 0.047 and MG p = 0.015), but they were unchanged following MET stimulation for MEPs or CMEPs. Dorsiflexor MEPs were unchanged with cutaneous stimulation at either location, but dorsiflexor CMEPs increased with cutaneous stimulation (p = 0.05). In general, the increase in CMEP amplitudes was larger than the increase in MEP amplitudes, indicating that an increase in spinal excitability likely explains most of the increase in corticospinal excitability. The larger change observed in the CMEP also indicates that excitability from supraspinal sources likely decreased, which could be due to a net change in the excitability of intracortical circuits. This study provides evidence that cutaneous reflexes from foot sole skin are likely influenced by a transcortical pathway

Can mammogram readers swiftly and effectively learn to interpret first post-contrast acquisition subtracted (FAST) MRI, a type of abbreviated breast MRI? : a single centre data-interpretation study

To assess whether NHS breast screening programme (NHSBSP) mammogram readers could effectively interpret first post-contrast acquisition subtracted (FAST) MRI, for intended use in screening for breast cancer. Eight NHSBSP mammogram readers from a single centre (four who also read breast MRI (Group 1) and four who do not (Group 2)) were given structured FAST MRI reader training (median 4 h: 32 min). They then prospectively interpreted 125 FAST MRIs (250 breasts: 194 normal and 56 cancer) comprising a consecutive series of screening MRIs enriched with additional cancer cases from 2015, providing 2000 interpretations. Readers were blinded to other readers' opinions and to clinical information. Categorisation followed the NHSBSP MRI reporting categorisation, with categories 4 and 5 considered indicative of cancer. Diagnostic accuracy (reference standard: histology or 2 years' follow-up) and agreement between readers were determined. The accuracy achieved by Group 2 (847/1000 (85%; 95% confidence interval (CI) 82-87%)) was 5% less than that of Group 1 (898/1000 (90%; 95% CI 88-92)). Good inter-reader agreement was seen between both Group 1 readers (κ = 0.66; 95% CI 0.61-0.71) and Group 2 readers (κ = 0.63; 95% CI 0.58-0.68). The median time taken to interpret each FAST MRI was Group 1: 34 s (range 3-351) and Group 2: 77 s (range 11-321). Brief structured training enabled multiprofessional mammogram readers to achieve similar accuracy at FAST MRI interpretation to consultant radiologists experienced at breast MRI interpretation. FAST MRI could be feasible from a training-the-workforce perspective for screening within NHSBSP

Selective Theca Cell Dysfunction in Autoimmune Oophoritis Results in Multifollicular Development, Decreased Estradiol, and Elevated Inhibin B Levels

We describe the clinical course of three women with presumptive autoimmune oophoritis who developed multiple follicles but very low to undetectable estradiol levels. Multiple follicles developed spontaneously in all subjects and during pulsatile GnRH treatment for ovulation induction in subject 1. The development of multiple dominant follicles was accompanied by LH levels in the postmenopausal range and FSH levels at the upper limit for premenopausal women. Serum inhibin B levels were elevated appropriately in the setting of multifollicular development, but estradiol levels remained low. Measurement of estradiol precursors demonstrated androstenedione and estrone levels below the 95th percentile in normal women. Adrenal cortical antibodies, and antibodies to 21-hydroxylase and P450 side chain cleavage enzymes were identified in all subjects. All subjects met the criteria for premature ovarian failure during follow-up. Subject 1 later developed adrenal failure, whereas subject 3 had adrenal failure at the time of the study. These subjects elucidate the hormonal pattern in autoimmune oophoritis, before the full criteria for premature ovarian failure are met. The elevated inhibin A and B levels, which accompany the development of multiple small and dominant follicles in these women, suppress FSH relative to LH levels, virtually independent of estradiol. These data provide further evidence for an important role of inhibin B and inhibin A in the negative feedback control of FSH. In addition, the normal inhibin A and inhibin B production in the absence of estradiol precursors and estradiol provide insight into the selective dysfunction of the theca cells in autoimmune oophoritis

Tetrodotoxin Concentrations in Pleurobranchaea maculata: Temporal, Spatial and Individual Variability from New Zealand Populations

Tetrodotoxin (TTX) is a potent neurotoxin that has been identified in a range of phylogenetically unrelated marine and terrestrial organisms. Tetrodotoxin was recently detected in New Zealand in Pleurobranchaea maculata (the grey side-gilled sea slug). From June 2010 to June 2011 wild specimens were collected from 10 locations around New Zealand. At one site (Narrow Neck Beach, Auckland) up to 10 individuals were collected monthly for 6 months. Attempts were also made to rear P. maculata in captivity. Tetrodotoxin was detected in samples from eight of the ten sites. The highest average (368.7 mg kg−1) and maximum (1414.0 mg kg−1) concentrations were measured in samples from Illiomama Rock (Auckland). Of the toxic populations tested there was significant variability in TTX concentrations among individuals, with the highest difference (62 fold) measured at Illiomama Rock. Tetrodotoxin concentrations in samples from Narrow Neck Beach varied temporally, ranging from an average of 184 mg kg−1 in June 2010 to 17.5 mg kg−1 by December 2010. There was no correlation between TTX levels and mass. The highest levels correspond with the egg laying season (June–August) and this, in concert with the detection of high levels of TTX in eggs and early larval stages, suggests that TTX may have a defensive function in P. maculata. Only one larva was successfully reared to full maturation and no TTX was detected