A comparison of two-stage segmentation methods for choice-based conjoint data: a simulation study.

Due to the increasing interest in market segmentation in modern marketing research, several methods for dealing with consumer heterogeneity and for revealing market segments have been described in the literature. In this study, the authors compare eight two-stage segmentation methods that aim to uncover consumer segments by classifying subject-specific indicator values. Four different indicators are used as a segmentation basis. The forces, which are subject-aggregated gradient values of the likelihood function, and the dfbetas, an outlier detection measure, are two indicators that express a subject’s effect on the estimation of the aggregate partworths in the conditional logit model. Although the conditional logit model is generally estimated at the aggregate level, this research obtains individual-level partworth estimates for segmentation purposes. The respondents’ raw choices are the final indicator values. The authors classify the indicators by means of cluster analysis and latent class models. The goal of the study is to compare the segmentation performance of the methods with respect to their success rate, membership recovery and segment mean parameter recovery. With regard to the individual-level estimates, the authors obtain poor segmentation results both with cluster and latent class analysis. The cluster methods based on the forces, the dfbetas and the choices yield good and similar results. Classification of the forces and the dfbetas deteriorates with the use of latent class analysis, whereas latent class modeling of the choices outperforms its cluster counterpart.Two-stage segmentation methods; Choice-based conjoint analysis; Conditional logit model; Market segmentation; Latent class analysis;

On "Sexual contacts and epidemic thresholds," models and inference for Sexual partnership distributions

Recent work has focused attention on statistical inference for the population distribution of the number of sexual partners based on survey data. The characteristics of these distributions are of interest as components of mathematical models for the transmission dynamics of sexually-transmitted diseases (STDs). Such information can be used both to calibrate theoretical models, to make predictions for real populations, and as a tool for guiding public health policy. Our previous work on this subject has developed likelihood-based statistical methods for inference that allow for low-dimensional, semi-parametric models. Inference has been based on several proposed stochastic process models for the formation of sexual partnership networks. We have also developed model selection criteria to choose between competing models, and assessed the fit of different models to three populations: Uganda, Sweden, and the USA. Throughout this work, we have emphasized the correct assessment of the uncertainty of the estimates based on the data analyzed. We have also widened the question of interest to the limitations of inferences from such data, and the utility of degree-based epidemiological models more generally. In this paper we address further statistical issues that are important in this area, and a number of confusions that have arisen in interpreting our work. In particular, we consider the use of cumulative lifetime partner distributions, heaping and other issues raised by Liljeros et al. in a recent working paper.Comment: 22 pages, 5 figures in linked working pape

An efficient algorithm for constructing Bayesian optimal choice designs.

Recently, Kessels et al. (2006) developed a way to produce Bayesian G- and V-optimal designs for the multinomial logitmodel. These designs allow for precise response predictions which is the goal of conjoint choice experiments. The authors showed that the G- and V- optimality criteria outperform the D- and A-optimality criteria for prediction. However, their G- and V-optimal design algorithm is computationally intensive, which is a barrier to its use in practice. In this paper, we present an efficient algorithm for calculating Bayesian optimal designs by means of the different criteria. Particularly, the speed of computation for the V-optimality criterion has improved dramatically.The new algorithm makes it possible to use Bayesian D-, A-, G- and V-optimal designs that are tailored to individual respondents in computerized conjoint choice studies.Adaptive algorithm; Bayesian D-,A-,G- and V-optimality; Cholesky decomposition; Conjoint choice design; Coordinate-exchange; Conjoint choice experiments;

Reactive nitrogen restructures and weakens microbial controls of soil N2O emissions

Long-term, replicated fertilization field trials show that increased potential N2O production is associated with specific phylogenetic shifts in communities of frequently occurring soil microbes. This sheds light on the link between legacy effects of reactive nitrogen on microbial communities and altered regulation of N2O emissions.The global surplus of reactive nitrogen (N-r) in agricultural soils is accelerating nitrous oxide (N2O) emission rates, and may also strongly influence the microbial controls of this greenhouse gas resulting in positive feedbacks that further exacerbate N2O emissions. Yet, the link between legacy effects of N-r on microbial communities and altered regulation of N2O emissions is unclear. By examining soils with legacies of N-r-addition from 14 field experiments with different edaphic backgrounds, we show that increased potential N2O production is associated with specific phylogenetic shifts in communities of frequently occurring soil microbes. Inputs of N-r increased the complexity of microbial co-association networks, and altered the relative importance of biotic and abiotic predictors of potential N2O emissions. Our results provide a link between the microbial legacy of N-r addition and increased N2O emissions by demonstrating that biological controls of N2O emissions were more important in unfertilized soils and that these controls are weakened by increasing resource levels in soil

An exploration of reception class teachers’ experiences of supporting children with Autism Spectrum Disorder in the first year of mainstream school.

Increasing numbers of children with Autism Spectrum Disorder (ASD) are being educated in mainstream schools and literature reflects a need to address how best to support this process. Previous studies exploring perceptions of mainstream education for children with ASD have highlighted the importance of the teacher’s role. This research recognises the importance of the Early Years and addresses a lack of research around supporting children with ASD in the first year of school. Interviews were conducted with six reception class teachers with the aim of gathering an in-depth picture of their perspectives around including children with ASD in a mainstream class. The purpose of this was to gain an understanding of their experiences which can be used to guide future thinking around support for teachers in this position. Interpretative Phenomenological Analysis (IPA) was used to shape an exploration of the teachers’ accounts resulting in the identification of key themes across the group. Two overarching themes derived from the analysis: ‘The psychological and emotional process of striving to meet the needs of the child as part of the class’ and ‘Being a part of the system of support’. The associated themes are discussed wit h reference to the developing research base around supporting children with ASD in mainstream schools. Opportunities to support reception class teachers and the associated implications for EPs are presented

Timing Is Everything: International Variations in Historical Sexual Partnership Concurrency and HIV Prevalence

Higher prevalence of concurrent partnerships is one hypothesis for the severity of the HIV epidemic in the countries of Southern Africa. But measures of the prevalence of concurrency alone do not adequately capture the impact concurrency will have on transmission dynamics. The importance of overlap duration and coital exposure are examined here.We conducted a comparison of data from three studies of sexual behavior carried out in the early 1990s in Uganda, Thailand and the US. Using cumulative concurrency measures, the three countries appeared somewhat similar. Over 50% of both Thai and Ugandan men reported a concurrency within the last three partnerships and over 20% reported a concurrency in the last year, the corresponding rates among US men were nearly 20% for Blacks and Hispanics, and about 10% for other racial/ethnic groups. Concurrency measures that were more sensitive to overlap duration, however, showed large differences. The point prevalence of concurrency on the day of interview was over 10% among Ugandan men compared to 1% for Thai men. Ugandan concurrencies were much longer duration – a median of about two years – than either the Thai (1 day) or US concurrencies (4–9 months across all groups), and involved 5–10 times more coital risk exposure with the less frequent partner. In the US, Blacks and Hispanics reported higher prevalence, longer duration and greater coital exposure than Whites, but were lower than Ugandans on nearly every measure. Together, the differences in the prevalence, duration and coital exposure of concurrent partnerships observed align with the HIV prevalence differentials seen in these populations at the time the data were collected.There were substantial variations in the patterns of concurrent partnerships within and between populations. More long-term overlapping partnerships, with regular coital exposure, were found in populations with greater HIV epidemic severity

Production and characterization of specific monoclonal antibodies binding the Plasmodium falciparum diagnostic biomarker, histidine-rich protein 2

BACKGROUND: Early and accurate diagnosis of Plasmodium falciparum infection is important for providing appropriate treatment to patients with malaria. However, technical limitations of currently available diagnostic tests limit their use in control programs. One possible explanation for the vulnerability of current antibodies used in RDTs is their propensity to degrade at high ambient temperatures. Isolation of new antibodies with better thermal stability represents an appealing approach to improve the performance of RDTs. METHODS: In this study, phage display technology was deployed to isolate novel binders by screening a human naïve scFv antibody library against recombinant Plasmodium falciparum histidine rich protein 2 (rPfHRP2). The isolated scFv clones were reformatted to whole IgG and the recombinant mAbs were produced in a mammalian CHO cell expression system. To verify the biological activity of these purified recombinant mAbs, range of functional assays were characterized. RESULTS: Two unique clones (D2 and F9) were isolated after five rounds of biopanning. The reformatted and expressed antibodies demonstrated high binding specificity to malaria recombinant PfHRP2 and native proteins. When 5 μg/mL of mAbs applied, mAb C1-13 had the highest sensitivity, with an OD value of 1, the detection achieved 5 ng/mL of rPfHRP2, followed by mAbs D2 and F9 at 10 ng/mL and 100 ng/mL of rPfHRP2, respectively. Although the sensitivity of mAbs D2 and F9 was lower than the control, these recombinant human mAbs have shown better stability compared to mouse mAb C1-13 at various temperatures in DSC and blot assays. In view of epitope mapping, the predominant motif of rPfHRP2 recognized by mAb D2 was AHHAADAHHA, whereas mAb F9 was one amino acid shorter, resulting in AHHAADAHH. mAb F9 had the strongest binding affinity to rPfHRP2 protein, with a K(D) value of 4.27 × 10(−11) M, followed by control mAb C1-13 at 1.03 × 10(−10) M and mAb D2 at 3.05 × 10(−10) M. CONCLUSIONS: Overall, the performance of these mAbs showed comparability to currently available PfHRP2-specific mouse mAb C1-13. The stability of these novel binders indicate that they merit further work to evaluate their utility in the development of new generation point of care diagnosis of malaria

Exploring the phenomenon of intrusive mental imagery after suicide bereavement: A qualitative interview study in a British sample

INTRODUCTION: Each year an estimated 48 million people are bereaved by suicide internationally. Following traumatic events, experiencing intrusive mental imagery relating to the trauma is not uncommon. This phenomenological study aimed to explore the nature, experience and impact of intrusive mental imagery after suicide bereavement. METHODS: Semi-structured interview transcripts with 18 adults bereaved by the suicide of a close contact were analysed using thematic analysis to explore patterns and themes within the data, with particular consideration of the content of images, how people experience and relate to the imagery, and the impact that the imagery has on the bereaved. RESULTS: Thematic analysis identified common characteristics in the experience of intrusive mental imagery following suicide loss, summarised under two main themes capturing: 1) the descriptive characteristics and 2) the emotional experience of intrusive mental imagery following suicide loss. The majority of participants found the experience of intrusive imagery distressing, but most also described positive aspects, including help in making sense of the death and retaining memories of the deceased. CONCLUSION: Findings inform our understanding of the distressing experience of intrusive imagery after suicide loss, also revealing perceived value in processing the death

Educating for Indigenous health equity: An international consensus statement

The determinants of health inequities between Indigenous and non-Indigenous populations include factors amenable to medical education’s influence, for example, the competence of the medical workforce to provide effective and equitable care to Indigenous populations. Medical education institutions have an important role to play in eliminating these inequities. However, there is evidence that medical education is not adequately fulfilling this role, and in fact may be complicit in perpetuating inequities. This article seeks to examine the factors underpinning medical education’s role in Indigenous health inequity, in order to inform interventions to address these factors. The authors developed a consensus statement that synthesizes evidence from research, evaluation, and the collective experience of an international research collaboration including experts in Indigenous medical education. The statement describes foundational processes that limit Indigenous health development in medical education and articulates key principles that can be applied at multiple levels to advance Indigenous health equity. The authors recognize colonization, racism, and privilege as fundamental determinants of Indigenous health that are also deeply embedded in Western medical education. In order to contribute effectively to Indigenous health development, medical education institutions must engage in decolonization processes and address racism and privilege at curricular and institutional levels. Indigenous health curricula must be formalized and comprehensive, and must be consistently reinforced in all educational environments. Institutions’ responsibilities extend to advocacy for health system and broader societal reform to reduce and eliminate health inequities. These activities must be adequately resourced and underpinned by investment in infrastructure and Indigenous leadership