Smoothing and mean-covariance estimation of functional data with a Bayesian hierarchical model

Functional data, with basic observational units being functions (e.g., curves, surfaces) varying over a continuum, are frequently encountered in various applications. While many statistical tools have been developed for functional data analysis, the issue of smoothing all functional observations simultaneously is less studied. Existing methods often focus on smoothing each individual function separately, at the risk of removing important systematic patterns common across functions. We propose a nonparametric Bayesian approach to smooth all functional observations simultaneously and nonparametrically. In the proposed approach, we assume that the functional observations are independent Gaussian processes subject to a common level of measurement errors, enabling the borrowing of strength across all observations. Unlike most Gaussian process regression models that rely on pre-specified structures for the covariance kernel, we adopt a hierarchical framework by assuming a Gaussian process prior for the mean function and an Inverse-Wishart process prior for the covariance function. These prior assumptions induce an automatic mean-covariance estimation in the posterior inference in addition to the simultaneous smoothing of all observations. Such a hierarchical framework is flexible enough to incorporate functional data with different characteristics, including data measured on either common or uncommon grids, and data with either stationary or nonstationary covariance structures. Simulations and real data analysis demonstrate that, in comparison with alternative methods, the proposed Bayesian approach achieves better smoothing accuracy and comparable mean-covariance estimation results. Furthermore, it can successfully retain the systematic patterns in the functional observations that are usually neglected by the existing functional data analyses based on individual-curve smoothing.Comment: Submitted to Bayesian Analysi

Vaginal Microbicide Preferences Among Midwestern Urban Adolescent Women

Purpose The purpose of this study was to assess adolescent women's preferences for specific microbicide characteristics including pregnancy prevention, timing of application, potential for side effects, and whether it targeted human immunodeficiency virus (HIV) or other sexually transmitted infections (STI). Potential differences in microbicide preferences by adolescent age group and behavioral patterns including engaging in sexual intercourse and use of hormonal contraception were examined, as it was hypothesized that as adolescents progress into adulthood and gain sexual experience their preferences in microbicide characteristics may shift. Method Adolescent and young women (N = 405, 56.0% African American; 24.0% Euro-American) between the ages of 14 and 20 (mean = 17.0, SD = 1.8) were recruited from urban community-based clinics. Video-Audio Computer-Assisted Self-Interviews were conducted with the young women, during which they were asked about their preferences regarding the characteristics of hypothetical vaginal microbicides. Conjoint analysis was utilized to determine adolescent women's relative preferences for each microbicide characteristic and intent-to-purchase microbicides based upon a combination of the selected properties. Results Overall, the results suggest adolescent and young women had an ordered preference for a microbicide with (1) no side effects, (2) pregnancy prevention, (3) postcoital application, and (4) protection against HIV. Age and behavioral group conjoint analyses resulted in the same pattern of preferences as those reported for the entire group. However, women having sex and not using hormonal contraception had a stronger preference for postcoital application. Conclusion The findings suggest that young women's ratings of microbicides were sensitive to characteristics such as side effects, pregnancy prevention, and timing of application and should be considered in microbicide development. The conjoint analysis approach is useful in understanding microbicide preferences, and should be utilized with other populations to assess preferences for specific microbicide characteristics

Standard methods for Apis mellifera anatomy and dissection

An understanding of the anatomy and functions of internal and external structures is fundamental to many studies on the honey bee Apis mellifera. Similarly, proficiency in dissection techniques is vital for many more complex procedures. In this paper, which is a prelude to the other papers of the COLOSS BEEBOOK, we outline basic honey bee anatomy and basic dissection techniques

Is group cognitive behaviour therapy for postnatal depression evidence-based practice? A systematic review

Background: There is evidence that psychological therapies including cognitive behaviour therapy (CBT) may be effective in reducing postnatal depression (PND) when offered to individuals. In clinical practice, this is also implemented in a group therapy format, which, although not recommended in guidelines, is seen as a cost-effective alternative. To consider the extent to which group methods can be seen as evidence-based, we systematically review and synthesise the evidence for the efficacy of group CBT compared to currently used packages of care for women with PND, and we discuss further factors which may contribute to clinician confidence in implementing an intervention. Methods: Seventeen electronic databases were searched. All full papers were read by two reviewers and a third reviewer was consulted in the event of a disagreement on inclusion. Selected studies were quality assessed, using the Cochrane Risk of Bias Tool, were data extracted by two reviewers using a standardised data extraction form and statistically synthesised where appropriate using the fixed-effect inverse-variance method. Results: Seven studies met the inclusion criteria. Meta-analyses showed group CBT to be effective in reducing depression compared to routine primary care, usual care or waiting list groups. A pooled effect size of d = 0.57 (95% CI 0.34 to 0.80, p < 0.001) was observed at 10–13 weeks post-randomisation, reducing to d = 0.28 (95% CI 0.03 to 0.53, p = 0.025) at 6 months. The non-randomised comparisons against waiting list controls at 10–13 weeks was associated with a larger effect size of d = 0.94 (95% CI 0.42 to 1.47, p < 0.001). However due to the limitations of the available data, such as ill-specified definitions of the CBT component of the group programmes, these results should be interpreted with caution. Conclusions: Although the evidence available is limited, group CBT was shown to be effective. We argue, therefore, that there is sufficient evidence to implement group CBT, conditional upon routinely collected outcomes being benchmarked against those obtained in trials of individual CBT, and with other important factors such as patient preference, clinical experience, and information from the local context taken into account when making the treatment decision

Vaginal microbicide preferences among midwestern urban adolescent women

Abstract: Purpose The purpose of this study was to assess adolescent women&apos;s preferences for specific microbicide characteristics including pregnancy prevention, timing of application, potential for side effects, and whether it targeted human immunodeficiency virus (HIV) or other sexually transmitted infections (STI). Potential differences in microbicide preferences by adolescent age group and behavioral patterns including engaging in sexual intercourse and use of hormonal contraception were examined, as it was hypothesized that as adolescents progress into adulthood and gain sexual experience their preferences in microbicide characteristics may shift. Method Adolescent and young women (N = 405, 56.0% African American; 24.0% Euro-American) between the ages of 14 and 20 (mean = 17.0, SD = 1.8) were recruited from urban communitybased clinics. Video-Audio Computer-Assisted Self-Interviews were conducted with the young women, during which they were asked about their preferences regarding the characteristics of hypothetical vaginal microbicides. Conjoint analysis was utilized to determine adolescent women&apos;s relative preferences for each microbicide characteristic and intent-to-purchase microbicides based upon a combination of the selected properties. Results Overall, the results suggest adolescent and young women had an ordered preference for a microbicide with (1) no side effects, (2) pregnancy prevention, (3) postcoital application, and (4) protection against HIV. Age and behavioral group conjoint analyses resulted in the same pattern of preferences as those reported for the entire group. However, women having sex and not using hormonal contraception had a stronger preference for postcoital application. Conclusion The findings suggest that young women&apos;s ratings of microbicides were sensitive to characteristics such as side effects, pregnancy prevention, and timing of application and should be considered in microbicide development. The conjoint analysis approach is useful in understanding microbicide preferences, and should be utilized with other populations to assess preferences for specific microbicide characteristics. microbicides | adolescent women | sexuality | conjoint analysis | adolescent health | Keywords: sexual health Article: The search for a woman-initiated prevention method has led to focus on topical microbicides for sexually transmitted infection (STI)/ human immunodeficiency virus (HIV) prevention. Microbicides are substances that may substantially reduce transmission of STI when applied in the vagina or rectum [1]. Some microbicides may also prevent pregnancy, although not all microbicides will be contraceptive [2]. Microbicides are not currently commercially available; products are in various phases of clinical trials [1]. Most microbicides under development are coitus dependent, requiring women to recognize and prepare for sexual situations and be willing to use a product that requires some comfort with touching their genitals [3]. The process of inserting a microbicide into the vagina may be challenging, as the dialogue around young women&apos;s sexuality and their bodies is often lacking [4]. Acceptability research, therefore, remains crucial to anticipate and prospectively address the kinds of obstacles previously associated with other female-initiated products, such as the female condom [5] and [6]. For instance, although women enjoyed having more control in using the female condom, they often did not like the size and discomfort associated with use or the inability to use it covertly [6]. Extant microbicide acceptability research with young women has suggested that contraceptive and disease prevention properties, timing of use, and associated side effects are important characteristics [7]. The findings suggest that young women generally prefer both pregnancy and disease prevention in a single product and insertion with an applicator up to 8 hours in advance [8]. In addition, there is a preference for lubricating products [9] and [10] with low amounts of messiness [9] and leakage [8]. Previous research also indicated that relevant potential side effects may impact microbicide use, including yeast infections, vaginal itching, and allergic reactions [7] and [11]. Furthermore, access was an important gauge of acceptability in a group of adolescent women. Women indicated that microbicides should be promoted through &quot;adolescentspecific and girl-specific venues,&quot; including women&apos;s magazines [7]. There was also a reported desire for microbicides that would be small enough to carry in their pocket, bra, or within cell phone or palm pilot cases, and should be distributed through schools and sexuality education classes [7]. Most young women preferred over-the-counter availability of microbicides, yet stated they would be embarrassed if purchasing the product in the presence of others [7] and [8]. Thus far, microbicide acceptability research with adolescents has been conducted primarily with older adolescents, using individual interview and focus group methodologies [7] [16]. These qualitative methodologies allow for an in-depth assessment of individual as well as relational and age-related issues that may influence microbicide use [13] and [17]. However, social desirability is often a concern when studying stigmatized or socially sensitive issues associated with sexuality [18] and [19]. Past research has shown that using a video-audio computer-assisted self-interview (VACASI) format (participants privately responding to questions on a computer) for presenting survey questions alleviates the tendency for individuals to present themselves positively and answer questions in a socially desirable fashion [20]. In addition, women and adolescents report sensitive behaviors more frequently when questions are asked using computer interviewing techniques than when participating in a face-to-face interview [20], [21] and [22]. Existing microbicide acceptability research with adolescents also often lacks detailed attention to the multiple dimensions that must be considered simultaneously in a decision to try a product such as a microbicide. The addition of quantitative biopsychosocial studies addressing these issues thus complements the existing qualitative microbicide acceptability research [8], [23] and [24]. The purpose of this study was to quantitatively assess, using full-profile ratings based conjoint analysis, preferences for specific microbicide characteristics among a young, urban population of women. Building on the existing literature we chose to assess young women&apos;s preferences for pregnancy and STI (including HIV) prevention as well as timing of application and side effect potential. It was hypothesized that as women progress through the adolescent years, their relative preferences for specific microbicide characteristics may change as a function of their age and sexual experience. Methods Study participants Participants were 405 adolescent and young women between the ages of 14 and 20 (mean = 17, SD = 1.8) recruited from community-based urban health clinics in the Midwestern United States in an area with relatively low rates of HIV [25]. See Study procedure After informed consent was received, the young women were given a computer and headphones in a private exam room to begin the questionnaire. The VACASI began with participants being asked to choose one of four possible &quot;guides&quot; whose face and voice were used throughout the VACASI. Guides were young women (approximately 18-20 years old) who were professional actors of varied ethnic appearance and voice. The guides were used to increase young women&apos;s level of comfort with the interview [27]. Following the choice of a guide, more information was given about the microbicide and a product sample was shown. The participant was then asked multiple demographic and sexual behaviors questions and presented with microbicide vignettes that asked her to rate the likelihood of buying each microbicide. The self-interviews were completed in English and lasted 25-45 minutes. Participants received $20 compensation for the time and effort involved in completing the questionnaire. The protocols for the entire project were approved by the University&apos;s institutional review board

Delays in Leniency Application: Is There Really a Race to the Enforcer's Door?

This paper studies cartels’ strategic behavior in delaying leniency applications, a take-up decision that has been ignored in the previous literature. Using European Commission decisions issued over a 16-year span, we show, contrary to common beliefs and the existing literature, that conspirators often apply for leniency long after a cartel collapses. We estimate hazard and probit models to study the determinants of leniency-application delays. Statistical tests find that delays are symmetrically affected by antitrust policies and macroeconomic fluctuations. Our results shed light on the design of enforcement programs against cartels and other forms of conspiracy

Parker/buoyancy instabilities with anisotropic thermal conduction, cosmic rays, and arbitrary magnetic field strength

We report the results of a local stability analysis for a magnetized, gravitationally stratified plasma containing cosmic rays. We account for cosmic-ray diffusion and thermal conduction parallel to the magnetic field and allow beta to take any value, where p is the plasma pressure and B is the magnetic field strength. We take the gravitational acceleration to be in the -z-direction and the equilibrium magnetic field to be in the y-direction, and we derive the dispersion relation for small-amplitude instabilities and waves in the large-|k_x| limit. We use the Routh-Hurwitz criterion to show analytically that the necessary and sufficient criterion for stability in this limit is n k_B dT/dz + dp_cr/dz + (1/8pi)dB^2/dz > 0, where T is the temperature, n is the number density of thermal particles, and p_cr is the cosmic-ray pressure. We present approximate analytical solutions for the normal modes in the low- and high-diffusivity limits, show that they are consistent with the derived stability criterion, and compare them to numerical results obtained from the full, unapproximated, dispersion relation. Our results extend earlier analyses of buoyancy instabilities in galaxy-cluster plasmas to the beta <= 1 regime. Our results also extend earlier analyses of the Parker instability to account for anisotropic thermal conduction, and show that the interstellar medium is more unstable to the Parker instability than was predicted by previous studies in which the thermal plasma was treated as adiabatic.Comment: 36 pages, 2 figures, Accepted for publication in Ap

Replication for Web Hosting Systems

Replication is a well-known technique to improve the accessibility of Web sites. It generally offers reduced client latencies and increases a site’s availability. However, applying replication techniques is not trivial, and various Content Delivery Networks (CDNs) have been created to facilitate replication for digital content providers. Th