457 research outputs found
Parameter estimation of a bivariate diffusion process : the Heston model
No full textIncludes abstract.Includes bibliographical references (leaves 27-29).The main objective of the research is to estimate the parameters on the Heston (1993) model, which models the movement of asset prices assuming that the asset price volatility is stochastic. The paper concentrates on estimating these parameters by approximating the transitional probabilities of the diffusion process with a saddlepoint distribution. By solving a system of ordinary differential equations that are in terms of the system’s cumulants, and using these solutions to calculate the saddlepoint, the transitional probabilities of the diffusion process can be approximated
sj-docx-2-otj-10.1177_15394492231181104 – Supplemental material for Preferences for Participation Measurement Among Individuals Diagnosed With Cancer: A Qualitative Content Analysis
No full textSupplemental material, sj-docx-2-otj-10.1177_15394492231181104 for Preferences for Participation Measurement Among Individuals Diagnosed With Cancer: A Qualitative Content Analysis by Allison J. L’Hotta, Taniya E. Varughese, Kathleen D. Lyons, Audrey Trebelhorn, Annamayil Manohar and Allison A. King in OTJR: Occupational Therapy Journal of Research</p
sj-docx-1-otj-10.1177_15394492231181104 – Supplemental material for Preferences for Participation Measurement Among Individuals Diagnosed With Cancer: A Qualitative Content Analysis
No full textSupplemental material, sj-docx-1-otj-10.1177_15394492231181104 for Preferences for Participation Measurement Among Individuals Diagnosed With Cancer: A Qualitative Content Analysis by Allison J. L’Hotta, Taniya E. Varughese, Kathleen D. Lyons, Audrey Trebelhorn, Annamayil Manohar and Allison A. King in OTJR: Occupational Therapy Journal of Research</p
Effect sizes in ongoing randomized controlled critical care trials
No full textAbstract Background An important limitation of many critical care trial designs is that they hypothesize large, and potentially implausible, reductions in mortality. Interpretation of trial results could be improved by systematic assessment of the plausibility of trial hypotheses; however, such assessment has not been attempted in the field of critical care medicine. The purpose of this study was to determine clinicians’ views about prior probabilities and plausible effect sizes for ongoing critical care trials where the primary endpoint is landmark mortality. Methods We conducted a systematic review of clinical trial registries in September 2015 to identify ongoing critical care medicine trials where landmark mortality was the primary outcome, followed by a clinician survey to obtain opinions about ten large trials. Clinicians were asked to estimate the probability that each trial would demonstrate a mortality effect equal to or larger than that used in its sample size calculations. Results Estimates provided by individual clinicians varied from 0% to 100% for most trials, with a median estimate of 15% (IQR 10–20%). The median largest absolute mortality reduction considered plausible was 4.5% (IQR 3.5–5%), compared with a median absolute mortality reduction used in sample size calculations of 5% (IQR 3.6–10%) (P = 0.27). Conclusions For some of the largest ongoing critical care trials, many clinicians regard prior probabilities as low and consider that plausible effects on absolute mortality are less than 5%. Further work is needed to determine whether pooled estimates obtained by surveying clinicians are replicable and accurate or whether other methods of estimating prior probability are preferred
Positional Isomerism and Conformational Flexibility Directed Structural Variations in the Molecular Complexes of Dihydroxybenzoic Acids
No full textMutual disposition and conformational
preferences of functional
groups can induce variations in the nature and types of interactions
and hence the molecular arrangements in the rigid crystal environment.
We comprehensively analyzed this effect in a series of 13 (of which
9 are novel) (Khan et al. <i>Cryst. Growth Des.</i> <b>2009</b>, <i>9</i>, 2354–2362; Varughese et al. <i>Chem.Eur. J.</i> <b>2006</b>, <i>12</i>, 1597–1609) molecular complexes of positional isomers of
dihydroxybenzoic acid with <i>trans</i>-1,2-bis(4-pyridyl)ethene
and 1,2-bis(4-pyridyl)ethane. Seven of the complexes exist as salts,
with an observed carboxyl to pyridine heteroatom proton transfer,
which can be explained on the basis of Δp<i>K</i><sub>a</sub> analysis. In all the complexes, carboxyl/carboxylate functionalities
interact consistently with pyridine/pyridinium moieties. The −OH
groups, in contrast, are more versatile with the formation of diverse
interaction types: −OH···carboxyl (O–H···O),
−OH···carboxylate (O–H···O<sup>–</sup>), and −OH···pyridine (O–H···N)
hydrogen bonds. Hirshfeld surface analysis and computed interaction
energy values were utilized to determine the hierarchical ordering
of the interactions and further to highlight the significance of weak
interactions such as π···π and C–H···π
in structure stabilization. In ionic complexes, these secondary interactions
become more expressed, with an enhanced contribution from electrostatic
elements. The energetic bias toward the complex formation is evident
from the calculated cohesive energies of the complexes vis-à-vis
their parent components
Growth dynamics of the vestibular schwannoma
No full textIntroduction: Studies concerning vestibular schwannoma (VS) are inconsistent in reporting of tumor size and growth. This means that results found in one paper using one set of definitions cannot be compared directly with results found in another paper with another set of definitions. It is a challenge to make clinical decisions from studies with such disparate definitions, as it is difficult to know how reliable the individual findings are. This thesis thus aimed to empirically evaluate these different means of reporting tumor size and growth that can be found in the literature. In addition to this, we also present our own findings of the growth dynamics and predictors of untreated VS, as well as evaluating the treatment outcome and complication rates for tumors treated by gamma knife radiosurgery (GKRS). Methods: The management of VS patients is determined primarily based on the tumor size and observed tumor growth. The smallest tumors are conservatively treated by serial scans, and if growth is detected, they are offered active treatment by either microsurgery or GKRS. The papers in this thesis primarily focus on the conservatively treated cohort, and those among them that were later treated by GKRS. Tumor volumes were estimated by manual tracing on MRI. Mixed effects modeling was used to analyze relationships between observations. Results: The papers included in this thesis present a number of results. The first paper found several inherent flaws with the most commonly used measure, the maximum diameter. Empirical proportionality coefficients which were quite similar to theoretical values used in the literature were also found. The second paper showed that tumor growth was best described by volume doubling time (VDT) rather than in terms of mm/year. We found a VDT of 4.40 years among our cohort. We also discussed the use of a cutoff of 1 mm/year to distinguish between growing and non-growing tumors, and proposed a VDT cutoff of 5.22 years that could be used similarly. None of the baseline parameters investigated were predictive of tumor growth. The third paper described the risk of needing treatment with the wait-and-scan protocol to be 13.3% at two years, and 41.3% at five years. The study also found a decline of hearing function for conservatively managed patients. Neither tinnitus nor unsteadiness changed significantly from baseline, but there was a reduction in the number of patients reporting vertigo. Results also suggest that tumor growth may be associated with progression of tinnitus and imbalance problems. The fourth paper found a radiological tumor control rate of 71.1%. Higher age and larger tumor size were found to be positively associated with tumor control. Hearing was preserved in 79% of the patients who had serviceable hearing at the time of treatment. Permanent facial weakness as a result of GKRS treatment occurred in one patient. In terms of QoL, bodily pain and general health scores improved significantly after GKRS. Social function steadily declined throughout the follow-up period, which may be related to the increasing number of patients experiencing unilateral hearing loss. Conclusion: In the discussion of inconsistencies in reporting of tumor size and tumor growth, our studies propose that there exist both empirical and biological arguments for the use of volumes and VDT’s rather than diameters and linear growth rates. A VDT cutoff of 5.22 years can distinguish between clinically growing and non-growing tumors. Our findings support the continued use of a conservative approach among small, non-growing tumors. For medium-sized or growing tumors, we also suggest that GKRS is a preferable treatment to microsurgery, given the high tumor control rates and low rates of complication with GKRS. The tumor control can also be improved by taking into consideration the potential predictors found in our study when selecting patients for this treatment, namely the patient’s age and the tumor size (although from a radiobiological point of view, one would expect the opposite effect from these parameters). Several scales of QoL were also found to improve significantly after GKRS, thus supporting the practice of recommending this form of treatment to these tumors. The social function scale however got steadily worse from baseline
Positional Isomerism and Conformational Flexibility Directed Structural Variations in the Molecular Complexes of Dihydroxybenzoic Acids
No full textMutual disposition and conformational
preferences of functional
groups can induce variations in the nature and types of interactions
and hence the molecular arrangements in the rigid crystal environment.
We comprehensively analyzed this effect in a series of 13 (of which
9 are novel) (Khan et al. <i>Cryst. Growth Des.</i> <b>2009</b>, <i>9</i>, 2354–2362; Varughese et al. <i>Chem.Eur. J.</i> <b>2006</b>, <i>12</i>, 1597–1609) molecular complexes of positional isomers of
dihydroxybenzoic acid with <i>trans</i>-1,2-bis(4-pyridyl)ethene
and 1,2-bis(4-pyridyl)ethane. Seven of the complexes exist as salts,
with an observed carboxyl to pyridine heteroatom proton transfer,
which can be explained on the basis of Δp<i>K</i><sub>a</sub> analysis. In all the complexes, carboxyl/carboxylate functionalities
interact consistently with pyridine/pyridinium moieties. The −OH
groups, in contrast, are more versatile with the formation of diverse
interaction types: −OH···carboxyl (O–H···O),
−OH···carboxylate (O–H···O<sup>–</sup>), and −OH···pyridine (O–H···N)
hydrogen bonds. Hirshfeld surface analysis and computed interaction
energy values were utilized to determine the hierarchical ordering
of the interactions and further to highlight the significance of weak
interactions such as π···π and C–H···π
in structure stabilization. In ionic complexes, these secondary interactions
become more expressed, with an enhanced contribution from electrostatic
elements. The energetic bias toward the complex formation is evident
from the calculated cohesive energies of the complexes vis-à-vis
their parent components
Engaging learners as Homo ludens through a pedagogy of puppetry in learning about indigenous knowledge: affordances for self-directed learning
No full textMEd (Physical Science Education), North-West University, Potchefstroom CampusPuppetry, as example of a pedagogy of play (PoP), utilises storytelling, which has largely been
associated with indigenous knowledge systems (IKS) over millennia. It is believed that, by
infusing pedagogies such as puppetry, which foster indigenous knowledge (IK) in the South
African school curriculum, diverse learners would be better prepared for the 21st century, as it
might enhance self-directed learning (SDL). It has been argued that approaches such as
puppetry might aid embodied, situated and distributed cognition, which could result in more
engaged learning. However, studies show that teachers find it hard to infuse puppetry into their
teaching, especially in higher grades. Such assertions should be investigated. A one-day short learning programme (SLP) was therefore developed by North-West University
(NWU) for intermediate teachers who teach Natural Sciences and Technology (NSTECH). The
aim of the SLP was to investigate and enhance teachers’ pedagogical knowledge (PK) and also
to explore teachers’ lived experiences of engaging with puppetry as a pedagogy. The teachers
engaged in the SLP, where they collaborated with the research facilitators. The SLP was
designed using Warford’s ‘zone of proximal teacher development’ (ZPTD) (2011) according
to the teachers’ learning needs. Teachers engaged in various activities during the SLP, such as
cooperative learning and the writing of puppetry scripts, to assist them in using puppetry in the
classroom. Data were collected using qualitative methods. During the SLP, teachers had to complete the
pre- and post-intervention questionnaires. They also had to complete the multiple intelligence
(MI) questionnaire. Once the SLP was complete, the researcher studied the transfer that took
place by analysing teachers’ use of puppetry in their NSTECH classrooms. This was difficult,
due to Covid-19 restrictions, which prevented school visit. After teachers’ attempted puppetry
in their classrooms, the researcher collected data using post-intervention interviews, as well as
by studying artefacts, such as teachers’ lesson plans. Data collected was transcribed and
analysed using Saldaña’s (2015) code-to-theory model in order to evaluate the value of the SLP
in transforming teacher’s pedagogical knowledge. The study followed a constructivist approach, and the researcher used third-generation
Cultural-Historical-Activity Theory (CHAT) as a research lens. CHAT was used on a personal
plane, and assisted the researcher to gain a better understanding of the data. It also gave an
overview of the ‘tensions’ or ‘contradictions’ in the activity system, e.g., the factors that
negatively impacted on reformed teaching and learning. This assisted in distilling themes from
the data.Master
Positional Isomerism and Conformational Flexibility Directed Structural Variations in the Molecular Complexes of Dihydroxybenzoic Acids
No full textMutual disposition and conformational
preferences of functional
groups can induce variations in the nature and types of interactions
and hence the molecular arrangements in the rigid crystal environment.
We comprehensively analyzed this effect in a series of 13 (of which
9 are novel) (Khan et al. <i>Cryst. Growth Des.</i> <b>2009</b>, <i>9</i>, 2354–2362; Varughese et al. <i>Chem.Eur. J.</i> <b>2006</b>, <i>12</i>, 1597–1609) molecular complexes of positional isomers of
dihydroxybenzoic acid with <i>trans</i>-1,2-bis(4-pyridyl)ethene
and 1,2-bis(4-pyridyl)ethane. Seven of the complexes exist as salts,
with an observed carboxyl to pyridine heteroatom proton transfer,
which can be explained on the basis of Δp<i>K</i><sub>a</sub> analysis. In all the complexes, carboxyl/carboxylate functionalities
interact consistently with pyridine/pyridinium moieties. The −OH
groups, in contrast, are more versatile with the formation of diverse
interaction types: −OH···carboxyl (O–H···O),
−OH···carboxylate (O–H···O<sup>–</sup>), and −OH···pyridine (O–H···N)
hydrogen bonds. Hirshfeld surface analysis and computed interaction
energy values were utilized to determine the hierarchical ordering
of the interactions and further to highlight the significance of weak
interactions such as π···π and C–H···π
in structure stabilization. In ionic complexes, these secondary interactions
become more expressed, with an enhanced contribution from electrostatic
elements. The energetic bias toward the complex formation is evident
from the calculated cohesive energies of the complexes vis-à-vis
their parent components
Patients' Preferences for Cytoreductive Treatments in Newly Diagnosed Metastatic Prostate Cancer: The IP5-MATTER Study
No full textBACKGROUND AND OBJECTIVE: Cytoreductive treatments for patients diagnosed with de novo synchronous metastatic hormone-sensitive prostate cancer (mHSPC) confer incremental survival benefits over systemic therapy, but these may lead to added toxicity and morbidity. Our objective was to determine patients' preferences for, and trade-offs between, additional cytoreductive prostate and metastasis-directed interventions. METHODS: A prospective multicentre discrete choice experiment trial was conducted at 30 hospitals in the UK between December 3, 2020 and January 25, 2023 (NCT04590976). The individuals were eligible for inclusion if they were diagnosed with de novo synchronous mHSPC within 4 mo of commencing androgen deprivation therapy and had performance status 0-2. A discrete choice experiment instrument was developed to elicit patients' preferences for cytoreductive prostate radiotherapy, prostatectomy, prostate ablation, and stereotactic ablative body radiotherapy to metastasis. Patients chose their preferred treatment based on seven attributes. An error-component conditional logit model was used to estimate the preferences for and trade-offs between treatment attributes. KEY FINDINGS AND LIMITATIONS: A total of 352 patients were enrolled, of whom 303 completed the study. The median age was 70 yr (interquartile range [IQR] 64-76) and prostate-specific antigen was 94 ng/ml (IQR 28-370). Metastatic stages were M1a 10.9% (33/303), M1b 79.9% (242/303), and M1c 7.6% (23/303). Patients preferred treatments with longer survival and progression-free periods. Patients were less likely to favour cytoreductive prostatectomy with systemic therapy (Coef. -0.448; [95% confidence interval {CI} -0.60 to -0.29]; p < 0.001), unless combined with metastasis-directed therapy. Cytoreductive prostate radiotherapy or ablation with systemic therapy, number of hospital visits, use of a day-case" procedure, or addition of stereotactic ablative body radiotherapy did not impact treatment choice. Patients were willing to accept an additional cytoreductive treatment with 10 percentage point increases in the risk of urinary incontinence and fatigue to gain 3.4 mo (95% CI 2.8-4.3) and 2.7 mo (95% CI 2.3-3.1) of overall survival, respectively. CONCLUSIONS AND CLINICAL IMPLICATIONS: Patients are accepting of additional cytoreductive treatments for survival benefit in mHSPC, prioritising preservation of urinary function and avoidance of fatigue. PATIENT SUMMARY: We performed a large study to ascertain how patients diagnosed with advanced (metastatic) prostate cancer at their first diagnosis made decisions regarding additional available treatments for their prostate and cancer deposits (metastases). Treatments would not provide cure but may reduce cancer burden (cytoreduction), prolong life, and extend time without cancer progression. We reported that most patients were willing to accept additional treatments for survival benefits, in particular treatments that preserved urinary function and reduced fatigue."Published version, accepted version (12 month embargo)Journal content freely available via Open Access. Some content may be unavailable due to publisher embargo. Click on the 'Additional link' above to access the full-text
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