Paul Jacobus Van Staden

Biomechanical comparison between pins and polymethylmethacrylate and the SOP locking plate system to stabilize canine lumbosacral fracture-luxation in flexion and extension

OBJECTIVE To determine the stability of a simulated complete L7-S1 fracture-luxation immobilized with SOP locking plate system, compared to pins and polymethylmethacrylate (PMMA). STUDY DESIGN In vitro biomechanical study. ANIMALS Cadaver specimens of 18 skeletally mature large-breed dogs. MATERIALS AND METHODS Specimens were randomly stabilized with one of the two fixation techniques. Lumbosacral spine specimens (L5-S3) were subjected to a bending moment applied to the caudal and cranial ends of the specimen. The biomechanical parameters (ie, range of motion [ROM], neutral zone [NZ], and elastic zone stiffness [EZS]) were compared between fixation techniques. RESULTS No difference was found between the means of the NZ in flexion (P = .3458), extension (P = .1255), and total value (P = .3458) of L7-S1 stabilized with the two fixation techniques. Mean ROM in flexion (P = .2386), extension (P = .1255), and mean of EZS in extension (P = .4094) did not differ between fixations. The only significant differences were in the means of total ROM and means of the EZS in flexion, with the means being smaller with SOP fixation. CONCLUSION The stability of the two fixation techniques in flexion and in extension was similar for the L7-S1 and adjacent L5-L6 junctions, while the mean of ROM of L6-L7 in flexion was smaller with SOP fixation. CLINICAL RELEVANCE Stability of the resulting construct should be considered when selecting an implant. Our results provide evidence that fixation via pin-PMMA or SOP provide similar stability for L7-S1 fracture-luxation. In this context, other factors become more important in selecting the fixation method.

Characteristics of matrix structures, and their effects on project success

This paper investigates the characteristics of matrix structures and their relationships with drivers of project success, such as communication, collaboration, and trust between project team members. Matrix characteristics that were expected to correlate positively with project success mostly did correlate with the success drivers. However, characteristics expected to impact negatively on project success did not show such significant correlations; some even correlated positively with success drivers. The success drivers investigated, in turn, correlated positively with perceived project success. A proposed model illustrates the effects of matrix characteristics on the drivers of success and their ultimate effect on project performance.

Exploring the impact of self-directed team learning in an air traffic control environment

Experienced military air traffic controllers (25 respondents, males = 15, females = 10, years of experience = less than one year = 5 respondents, more than one year but less than three years = 11 respondents and more than three years = 9 respondents) participated in this study to determine whether self-directed team learning exists within their air traffic control teams and to understand the impact of self-directed team learning on the air traffic control work environment. Data on self-directed team learning and learning approaches were collected using a Self-directed Team Learning Questionnaire (SDTLQ) and a Learning Approaches Questionnaire (LAQ). These data were analysed using an inductive reasoning mode for qualitative data analysis and quantitative data analysis followed a supporting deductive reasoning mode. Triangulation as a technique was used to determine whether multiple sources of data agreed and to obtain better, cross-checked insights (Burgess, 1985). Results revealed that these air traffic controllers and air traffic control teams investigated in the study do indeed function within self-directed working, training and learning environments. The quality of team performance was influenced by self-directed team learning initiatives. Furthermore, the quality of self-directed team learning relied upon the effectiveness of air traffic control team performances.

The use of cyproterone acetate in a forensic psychiatric cohort of male sex offenders and its associations with sexual activity and sexual functioning

Background Cyproterone acetate (CPA) is a steroidal anti-androgenic medication used in the field of psychiatry for the treatment of paraphilic disorders, hypersexuality, and inappropriate sexual behaviour which may be present in patients with disorders such as mild and major neurocognitive disorders. In the forensic psychiatric population, it is prescribed for these indications especially for patients with a history of committing a sexual offence or who are at moderate to high risk of recidivism. Objectives To investigate the use of CPA in a forensic psychiatric cohort of male sex offenders and its associations with sexual activity and sexual functioning. Methods Seventy-six forensic psychiatric patients from Weskoppies Hospital in Pretoria, South Africa, participated in the study which measured their sexual functioning. A specifically designed questionnaire was used to capture relevant background information. The use of CPA was studied. The Changes in Sexual Functioning Questionnaire, Male Clinical Version (CSFQ-M-C) was used to measure sexual functioning of participants. The CSFQ-M-C scores, and those of all its subscales, of participants on CPA were compared to those not on the drug. Relevant statistical analyses were performed. Results Thirteen out of the 76 participants were being treated with CPA (17.11%). In total, 53.85% of the participants on CPA and 65.08% not on CPA had scores indicating the presence of sexual dysfunction. The total CSFQ-M-C scores for participants on CPA (mean = 40.54; median = 42) were not statistically significantly lower than those not on the drug (mean = 41.22; median = 41). More notable is that the use of CPA in this population was associated with lower levels of desire, frequency of and pleasure from sexual activity. There was an association between having intellectual disability and being treated with CPA. Conclusion That all the participants were being treated with psychotropic medication could account for the high percentage of sexual dysfunction in any or all areas of sexual functioning and contribute to the small difference in CSFQ-M-C scores between the two groups. Only a tentative conclusion can be made that CPA may be more effective in decreasing levels of desire, frequency and pleasure related to sexual activity than other areas of sexual functioning. The indication for the use of CPA in this population should be assessed clinically according to patient circumstances and risk assessment.

Kurtosis of the logistic-exponential survival distribution

ABSTRACT In this article, the kurtosis of the logistic-exponential distribution is analyzed. All the moments of this survival distribution are finite, but do not possess closed-form expressions. The standardized fourth central moment, known as Pearson’s coefficient of kurtosis and often used to describe the kurtosis of a distribution, can thus also not be expressed in closed form for the logistic-exponential distribution. Alternative kurtosis measures are therefore considered, specifically quantile-based measures and the L-kurtosis ratio. It is shown that these kurtosis measures of the logistic-exponential distribution are invariant to the values of the distribution’s single shape parameter and hence skewness invariant.