Gay men's estimates of the likelihood of HIV transmission in sexual behaviours

In 3 studies we recorded gay men's estimates of the likelihood that HIV would be transmitted in various sexual behaviours. In Study 1 (data collected 1993, n=92), the men were found to believe that transmissibility is very much greater than it actually is; that insertive unprotected anal intercourse (UAI) by an HIV-infected partner is made safer by withdrawal before ejaculation, and very much safer by withdrawal before either ejaculation or pre-ejaculation; that UAI is very much safer when an infected partner is receptive rather than insertive; that insertive oral sex by an infected partner is much less risky than even the safest variant of UAI; that HIV is less transmissible very early after infection than later on; and that risk accumulates over repeated acts of UAI less than it actually does. In Study 2 (data collected 1997/8, n=200), it was found that younger and older uninfected men generally gave similar estimates of transmissibility, but that infected men gave somewhat lower estimates than uninfected men; and that estimates were unaffected by asking the men to imagine that they themselves, rather than a hypothetical other gay man, were engaging in the behaviours. Comparison of the 1993 and 1997/8 results suggested that there had been some effect of an educational campaign warning of the dangers of withdrawal; however, there had been no effect either of a campaign warning of the dangers of receptive UAI by an infected partner, or of publicity given to the greater transmissibility of HIV shortly after infection. In Study 3 (data collected 1999, n=59), men induced into a positive mood were found to give lower estimates of transmissibility than either men induced into a neutral mood or men induced into a negative mood. It is argued that the results reveal the important contribution made to gay men's transmissibility estimates by cognitive strategies (such as the 'availability heuristic' and 'anchoring and adjustment') known to be general characteristics of human information-processing. Implications of the findings for AIDS education are discussed.

Generalized pseudo-likelihood estimates for markov random fields on lattice

In this paper we generalize Besag's pseudo-likelihood function for spatial statistical models on a region of a lattice. The correspondingly defined maximum generalized pseudo-likelihood estimates (MGPLEs) are natural extensions of Besag's maximum pseudo-likelihood estimate (MPLE). The MGPLEs connect the MPLE and the maximum likelihood estimate. We carry out experimental calculations of the MGPLEs for spatial processes on the lattice. These simulation results clearly show better performances of the MGPLEs than the MPLE, and the performances of differently defined MGPLEs are compared. These are also illustrated by the application to two real data sets.

Evolutionary structure learning algorithm for Bayesian network and penalized mutual information metric

This paper formulates the problem of learning Bayesian network structures from data as determining the structure that best approximates the probability distribution indicated by the data. A new metric, Penalized Mutual Information metric, is proposed, and a evolutionary algorithm is designed to search for the best structure among alternatives. The experimental results show that this approach is reliable and promising.

Predicting consumer innovative behavior using alternative theories and likelihood measures: a longitudinal study

This paper reports on a longitudinal study of consumers, where two dominant theories that purport to predict innovative behavior are applied and compared directly, using a methodology suggested as ideal by past researchers. Predictions made prior to launch were then evaluated against multiple measures of purchase likelihood, and against actual adoption behavior up to 12 months after launch. The results of this study suggest that perceptions of the innovations characteristics (PIC) predicted the selfreported likelihood of adoption better than the Domain Specific Innovativeness (DSI) scale, a personality-based measure. Prediction of actual adoption was largely inaccurate and both theories massively over predicted adoption levels, however the DSI scale was slightly more accurate. The conclusions here are that no one theory could make adequate predictions of behavior, that purchase likelihood measures are a poor substitute for measuring actual behavior but that purchase probability scales should be used more often in adoption research.

Physical activity and likelihood of depression in adults : a review

Objective : This review examines original research which has investigated associations between physical activity (PA) dose (i.e. frequency, intensity and duration) and domain and depression or symptoms of depression in adults.

Methods : A search of electronic databases and authors' own bibliographic libraries was performed between 2006 and 2007 for original research articles investigating associations between PA and depression in adults. A total of 27 observational and 40 intervention studies were included.

Results : Of the studies that focused on the association between duration of PA and likelihood of depression, all five observational studies, and five of the seven intervention studies found both shorter and longer durations of PA were associated with reduced likelihood of depression. Of the studies that focused on the association between intensity of PA and likelihood of depression, four of the six observational studies found that vigorous-intensity PA was more strongly associated with decreased likelihood of depression than lower intensities. Most intervention studies showed that both intensities were effective in reducing the likelihood of depression. Two observational studies found a stronger inverse relationship of leisure-time PA with depression than PA in other domains. There is insufficient evidence regarding the importance of the PA setting on depression.

Conclusion : Although the dose and domain of physical activity varied across studies reviewed, evidence suggests that even low doses of PA may be protective against depression. Further studies examining the optimal domain of PA for reducing the likelihood of depression are needed.

Predicting the likelihood of voiced complaints in the self-service technology context

There is considerable evidence to suggest that consumer dissatisfaction with self-service technologies is widespread. However, there has been little conceptual or empirical scrutiny of the likelihood that consumers will complain to an organization (likelihood of voice) in this context. This study contributes to the service domain by testing empirically a model of the antecedents of consumers' likelihood of voice in unsatisfactory encounters with self-service technologies. A model is tested that combines established antecedents of voice, such as likelihood of voice success, and those that have not yet been considered, including self-service technology powerlessness and need to vent. The results support the proposed model in general. Theoretical and managerial implications of the findings are discussed.

Maximum likelihood estimation for rician distributed data in analytical q-ball imaging

Analytical q-ball imaging is widely used for reconstruction of orientation distribution function (ODF) using diffusion weighted MRI data. Estimating the spherical harmonic coefficients is a critical step in this method. Least squares (LS) is widely used for this purpose assuming the noise to be additive Gaussian. However, Rician noise is considered as a more appropriate model to describe noise in MR signal. Therefore, the current estimation techniques are valid only for high SNRs with Gaussian distribution approximating the Rician distribution. The aim of this study is to present an estimation approach considering the actual distribution of the data to provide reliable results particularly for the case of low SNR values. Maximum likelihood (ML) is investigated as a more effective estimation method. However, no closed form estimator is presented as the estimator becomes nonlinear for the noise assumption of the Rician distribution. Consequently, the results of LS estimator is used as an initial guess and the more refined answer is achieved using iterative numerical methods. According to the results, the ODFs reconstructed from low SNR data are in close agreement with ODFs reconstructed from high SNRs when Rician distribution is considered. Also, the error between the estimated and actual fiber orientations was compared using ML and LS estimator. In low SNRs, ML estimator achieves less error compared to the LS estimator.

Maximum likelihood approach for tracking multiple mobile agents with a moving doppler radar system

Tracking mobile agents with a Doppler radar system mounted on a moving vehicle is considered in this paper. Dopplers modulated from mobile agents on the single frequency continuous wave signals are analyzed in order to estimate the positions and velocities of multiple mobile agents. The measurement noise is assumed to be Gaussian and the maximum likelihood estimation is utilized to enhance the localization accuracy.

Maximum-likelihood based estimation for Q-ball imaging using diffusion-weighted MRI data

Q-ball imaging has been presented to reconstruct diffusion orientation distribution function using diffusion weighted MRI. In this thesiis, we present a novel and robust approach to satisfy the smoothness constraint required in Q-ball imaging. Moreover, we developed an improved estimator based on the actual distribution of the MR data.

Is lower income associated with an increased likelihood of qualification for treatment for osteoporosis in Canadian women?

The authors examined whether low income was associated with an increased likelihood of treatment qualification for osteoporotic fracture probability determined by Canada FRAX in women aged ≥50 years. A significant negative linear association was observed between income and treatment qualification when FRAX included bone mineral density (BMD), which may have implications for clinical practice.

Human residential status and habitat quality affect the likelihood but not the success of lapwing breeding in an urban matrix

Wildlife living in the suburbs faces the challenge of dealing with human presence and yard management (including the occurrence of pets) which vary at the scale of the house block. This study examined the influence of ecological factors (e.g. extent of grass and food availability) and anthropogenic factors (e.g. human activity and garden usage) on breeding site choice and reproductive success of the ground-nesting masked lapwing Vanellus miles on Phillip Island, Australia. Lapwings nested less frequently in residential properties (high levels of human usage) compared with vacant blocks and holiday houses. They were also more likely to breed on properties with high food availability and larger areas of grass. None of these variables influenced clutch size or the probability of eggs hatching, although larger clutches and higher hatching rates tended to be associated with more food. This study shows that, for an urban exploiting species, habitat quality is not homogenous at the scale of the house block, and that human activity is avoided by a species generally considered highly tolerant of people.