title: Melatonin and sleep responses following exercise in elite female athletes

authors: O'Donnell, Shannon Lea

subjects: Actigraphy

abstract: Objective: To determine the melatonin concentrations and subsequent sleep indices of elite netball athletes following a training day when compared to a control day. Methods: Ten elite female netball athletes (mean ± SD; age = 23 ± 6 yrs) provided saliva samples PRE (17:15h) and POST (22:00h) a training session, and a day with no training (CONTROL). Sleep monitoring was performed using wrist actigraphy to assess total time in bed (TTB), total sleep time (TST), sleep efficiency (SE) and sleep latency (SL). Results: Melatonin levels were significantly lower (p < 0.05), both PRE and POST the training condition (6.2 and 17.6 pg/mL, respectively) when compared to the CONTROL (14.8 and 24.3 pg/mL, respectively). There were no significant differences observed between conditions for any of the sleep variables. However, a small reduction in TST could be observed following the training session condition compared to the CONTROL condition. Conclusion: The scheduling of netball training in the evening is shown to suppress salivary melatonin levels. This may have an influence on subsequent sleep following night-time exercise.

text: Melatonin and sleep responses following exercise in elite female athletes Objective: To determine the melatonin concentrations and subsequent sleep indices of elite netball athletes following a training day when compared to a control day. Methods: Ten elite female netball athletes (mean ± SD; age = 23 ± 6 yrs) provided saliva samples PRE (17:15h) and POST (22:00h) a training session, and a day with no training (CONTROL). Sleep monitoring was performed using wrist actigraphy to assess total time in bed (TTB), total sleep time (TST), sleep efficiency (SE) and sleep latency (SL). Results: Melatonin levels were significantly lower (p < 0.05), both PRE and POST the training condition (6.2 and 17.6 pg/mL, respectively) when compared to the CONTROL (14.8 and 24.3 pg/mL, respectively). There were no significant differences observed between conditions for any of the sleep variables. However, a small reduction in TST could be observed following the training session condition compared to the CONTROL condition. Conclusion: The scheduling of netball training in the evening is shown to suppress salivary melatonin levels. This may have an influence on subsequent sleep following night-time exercise.

year: 2019

title: Novel polymeric microcapsules for targeted drug delivery

authors: Lin, Yuewen

subjects: polymer

abstract: Microencapsulation is a technology in which small particles or droplets are entrapped by a coating to give the particles with many useful properties. Microcapsules have been used to protect the encapsulated material from the environmental conditions or to release the active agent in a sustained and controlled manner into the surrounding medium. This thesis investigated how to develop a post-ruminal delivery system based on polymeric microencapsulation. A major criterion was to develop microcapsules with reversible switching in response to changes of pH in the in vivo environment so contents could be released. The microcapsules must have a thin shell strong enough to withstand harsh physical conditions and a large hollow centre, which will maximise drug-carrying capacity. Two processes were developed to manufacture pH-responsive microcapsules - conventional interfacial polymerisation with plasma-induced grafting and a novel phase-inversion technique with chemical grafting. This research demonstrated that microcapsules with a porous shell could be manufactured by interfacial polymerisation. Carboxyl groups introduced onto the pores in the microcapsule by plasma-induced graft polymerisation of acrylic acid allowed pore openings to be controlled by the pH change of the environment. Polyamide microcapsules made by interfacial polymerisation had a hollow core and a porous shell with smooth external and rough internal surfaces. Their average diameter of 28 µm decreased with increased stirring rate during polymerisation. Shell porosity could be changed by adjusting the ratio of amine monomers used to form the microcapsule shell. An argon plasma treatment was developed to graft acrylic acid onto the microcapsule surface. Plasma treatment with 90 seconds produced 0.56 mmol/g of grafting extent. The effect of pH on releasing contents from poly(acrylic acid)-grafted microcapsules was investigated using two different sized molecules (vitamin B12 and cytochrome c) to simulate model drugs. Release rate was not significantly affected by molecular size; contents were retained when pH was between 7 and 5.5 and released when pH was between 5 and 3.5. Full release occurred at pH below 3. Further studies showed that micron-sized microcapsules with a hollow core and a thick matrix wall could be made from polycaprolactone, polysulfone and polystyrene. A modified solvent evaporation process reduced shell thickness but the microcapsules still had a non-porous skin. Process parameters such as polymer concentration, temperature, surfactant, solvent composition, stirring speed, processing pressure, and co-polymer additives influenced structure and internal morphology of the microcapsules. Morphological characteristics of the microcapsules strongly depended on the way the coating polymer is precipitated, particularly the non solvent–polymer–solvent interactions. Chemical grafting was not successful for grafting acrylic acid onto the polycaprolactone and polysulfone microcapsules. Polystyrene microcapsules with a hollow core and porous micro-channel shell structure were successfully produced using a novel formulation in a phase-inversion process. The outer skin could be removed by re-dissolving the formed microcapsules in a suitable solvent. Open pores with inter-connected micro-channels on the microcapsule surface can be produced by carefully controlling the time the microcapsules are in the solvent. The microcapsule was functionalised using free radical polymerisation to graft acrylic acid onto its surface. However, these microcapsules did not completely retain their contents at pH 7 and had a slow release profile when pH was decreased. Recommendations are given on how to improve and optimise the process. Polystyrene microcapsules made with a simple and inexpensive phase-inversion technique have potential as a targeted drug delivery system. They could be re-usable, compared to most other systems that degrade or disintegrate, and may have other applications as a carrier to immobilise desired molecules onto the microcapsules. Further investigations to optimise manufacturing polystyrene microcapsules should include: larger scale trials; further investigations, using orthogonal tests with multi-variation analysis to optimise factors affection microcapsule porosity and extent of grafting; identifying an alternative, faster way to analyse pore size; and developing a mathematical model for the release rate.

text: Novel polymeric microcapsules for targeted drug delivery Microencapsulation is a technology in which small particles or droplets are entrapped by a coating to give the particles with many useful properties. Microcapsules have been used to protect the encapsulated material from the environmental conditions or to release the active agent in a sustained and controlled manner into the surrounding medium. This thesis investigated how to develop a post-ruminal delivery system based on polymeric microencapsulation. A major criterion was to develop microcapsules with reversible switching in response to changes of pH in the in vivo environment so contents could be released. The microcapsules must have a thin shell strong enough to withstand harsh physical conditions and a large hollow centre, which will maximise drug-carrying capacity. Two processes were developed to manufacture pH-responsive microcapsules - conventional interfacial polymerisation with plasma-induced grafting and a novel phase-inversion technique with chemical grafting. This research demonstrated that microcapsules with a porous shell could be manufactured by interfacial polymerisation. Carboxyl groups introduced onto the pores in the microcapsule by plasma-induced graft polymerisation of acrylic acid allowed pore openings to be controlled by the pH change of the environment. Polyamide microcapsules made by interfacial polymerisation had a hollow core and a porous shell with smooth external and rough internal surfaces. Their average diameter of 28 µm decreased with increased stirring rate during polymerisation. Shell porosity could be changed by adjusting the ratio of amine monomers used to form the microcapsule shell. An argon plasma treatment was developed to graft acrylic acid onto the microcapsule surface. Plasma treatment with 90 seconds produced 0.56 mmol/g of grafting extent. The effect of pH on releasing contents from poly(acrylic acid)-grafted microcapsules was investigated using two different sized molecules (vitamin B12 and cytochrome c) to simulate model drugs. Release rate was not significantly affected by molecular size; contents were retained when pH was between 7 and 5.5 and released when pH was between 5 and 3.5. Full release occurred at pH below 3. Further studies showed that micron-sized microcapsules with a hollow core and a thick matrix wall could be made from polycaprolactone, polysulfone and polystyrene. A modified solvent evaporation process reduced shell thickness but the microcapsules still had a non-porous skin. Process parameters such as polymer concentration, temperature, surfactant, solvent composition, stirring speed, processing pressure, and co-polymer additives influenced structure and internal morphology of the microcapsules. Morphological characteristics of the microcapsules strongly depended on the way the coating polymer is precipitated, particularly the non solvent–polymer–solvent interactions. Chemical grafting was not successful for grafting acrylic acid onto the polycaprolactone and polysulfone microcapsules. Polystyrene microcapsules with a hollow core and porous micro-channel shell structure were successfully produced using a novel formulation in a phase-inversion process. The outer skin could be removed by re-dissolving the formed microcapsules in a suitable solvent. Open pores with inter-connected micro-channels on the microcapsule surface can be produced by carefully controlling the time the microcapsules are in the solvent. The microcapsule was functionalised using free radical polymerisation to graft acrylic acid onto its surface. However, these microcapsules did not completely retain their contents at pH 7 and had a slow release profile when pH was decreased. Recommendations are given on how to improve and optimise the process. Polystyrene microcapsules made with a simple and inexpensive phase-inversion technique have potential as a targeted drug delivery system. They could be re-usable, compared to most other systems that degrade or disintegrate, and may have other applications as a carrier to immobilise desired molecules onto the microcapsules. Further investigations to optimise manufacturing polystyrene microcapsules should include: larger scale trials; further investigations, using orthogonal tests with multi-variation analysis to optimise factors affection microcapsule porosity and extent of grafting; identifying an alternative, faster way to analyse pore size; and developing a mathematical model for the release rate.

year: 2009

title: Do two rights fix a wrong? A study of employee and organizational responses to abusive supervision in New Zealand

authors: de Fluiter, Alida Jane

subjects: Abusive supervision

abstract: Organizational justice theories suggest that employees who are abused by their supervisor are likely to respond with lower job and personal outcomes. However, an under-explored area has been the influence of support perceptions. The present study suggests that perceived supervisor support (PSS) and perceived organizational support (POS) may moderate the influence of abusive supervision, and this was tested with three-way interactions. Data was collected from two samples: (1) 100 blue-collar workers in construction and (2) 218 random Maori employees from a variety of industries and professions. Structural equation modeling confirmed the unique constructs of the study measures towards abusive supervision and PSS and POS. Direct effects showed abusive supervision was significant and negative in both samples towards life satisfaction, job satisfaction, and organizational-based self-esteem (OBSE), and significant and positive in both samples towards turnover intentions, anxiety, depression, and insomnia. The results indicated that abusive supervision accounted for large amounts of variance towards all outcomes, with the exception of life satisfaction in study two (7%), and insomnia (8% in study one, and 4% in study two), ranging from 13%-32% variance. Significant three-way interactions were found for all outcomes except turnover intentions and insomnia. The three-way interaction towards life satisfaction in study one indicated that under abusive supervision, respondents with high PSS and high POS experienced the greatest levels of life satisfaction. Similar relationships were found toward depression (study one and two) and anxiety (study one), showing that respondents who experienced high abusive supervision, high PSS, and high POS had the lowest levels of negative mental health outcomes amongst all abused respondents. This suggested a potentially cumulative effect of multiple sources of support. Furthermore, towards job satisfaction in study two, findings show respondents with high abusive supervision and high POS reported the highest job satisfaction, irrespective of levels of PSS. A similar relationship was found toward OBSE in study two, suggesting that of the support variables examined, POS may have greater effect on outcomes, thereby supporting research of Dawley, Andrews and Bucklew (2008) who found POS to be the best predictor of organizational outcomes. Overall, this paper supports the notion that perceptions of support may moderate the influence of abusive supervision perceptions on employee’s work and personal outcomes. The findings show that while abusive supervision can play a dominant role on outcomes, this can be somewhat nullified by greater support from the organization. This has strong implications for firms dealing with problem supervisors, signaling the importance of establishing POS, and emphasizing that creating a supportive organization may be the first step to enabling employees to develop positive work and individual outcomes.

text: Do two rights fix a wrong? A study of employee and organizational responses to abusive supervision in New Zealand Organizational justice theories suggest that employees who are abused by their supervisor are likely to respond with lower job and personal outcomes. However, an under-explored area has been the influence of support perceptions. The present study suggests that perceived supervisor support (PSS) and perceived organizational support (POS) may moderate the influence of abusive supervision, and this was tested with three-way interactions. Data was collected from two samples: (1) 100 blue-collar workers in construction and (2) 218 random Maori employees from a variety of industries and professions. Structural equation modeling confirmed the unique constructs of the study measures towards abusive supervision and PSS and POS. Direct effects showed abusive supervision was significant and negative in both samples towards life satisfaction, job satisfaction, and organizational-based self-esteem (OBSE), and significant and positive in both samples towards turnover intentions, anxiety, depression, and insomnia. The results indicated that abusive supervision accounted for large amounts of variance towards all outcomes, with the exception of life satisfaction in study two (7%), and insomnia (8% in study one, and 4% in study two), ranging from 13%-32% variance. Significant three-way interactions were found for all outcomes except turnover intentions and insomnia. The three-way interaction towards life satisfaction in study one indicated that under abusive supervision, respondents with high PSS and high POS experienced the greatest levels of life satisfaction. Similar relationships were found toward depression (study one and two) and anxiety (study one), showing that respondents who experienced high abusive supervision, high PSS, and high POS had the lowest levels of negative mental health outcomes amongst all abused respondents. This suggested a potentially cumulative effect of multiple sources of support. Furthermore, towards job satisfaction in study two, findings show respondents with high abusive supervision and high POS reported the highest job satisfaction, irrespective of levels of PSS. A similar relationship was found toward OBSE in study two, suggesting that of the support variables examined, POS may have greater effect on outcomes, thereby supporting research of Dawley, Andrews and Bucklew (2008) who found POS to be the best predictor of organizational outcomes. Overall, this paper supports the notion that perceptions of support may moderate the influence of abusive supervision perceptions on employee’s work and personal outcomes. The findings show that while abusive supervision can play a dominant role on outcomes, this can be somewhat nullified by greater support from the organization. This has strong implications for firms dealing with problem supervisors, signaling the importance of establishing POS, and emphasizing that creating a supportive organization may be the first step to enabling employees to develop positive work and individual outcomes.

year: 2011