The cardiovascular hemodynamic responses to various levels of orthostatic stress in children

The ability of the cardiovascular system to quickly and efficiently adapt to an orthostatic stress is vital for the human body to function on earth. The way in which the various aspects of the cardiovascular system work together to counteract an orthostatic stress has been previously quantified in the adult population. However, there are still many unknowns surrounding the topic of how the cardiovascular system functions to cope with this same stress in children. The purpose of this study was to describe the cardiovascular hemodynamic adaptations to various levels of orthostatic stress induced using a lower body negative pressure (LBNP) chamber in pre-pubertal boys. A secondary purpose was to determine indices of baroreceptor sensitivity (BRS) at both rest and during low levels of LBNP in this same pediatric sample. Finally, this study aimed to compare the relative responses to LBNP between the children and adults. To complete the study 20 healthy pre-pubertal boys and adult males (9.3 ± 1.1 and 23 ± 1.8 years of age respectively) were recruited and randomly exposed to three levels of LBNP (15, 20 and 25 mmHg). At rest and during the application of the LBNP heart rate (HR), manual and bcat-by-beat systolic (SBP), diastolic (DBP) and mean arterial blood pressure (MAP) were monitored continuously. Aortic diameter was measured at rest and peak aortic blood velocity (PV) was recorded continuously for at least I minute during each baseline and LBNP condition. From the raw data HR, stroke volume (SV), cardiac output (Q), total peripheral resistance (TPR), low frequency baroreceptor sensitivity (LF BRS), high frequency baroreceptor sensitivity (HF BRS) and LFIIIF ratio were calculated. At rest, llR wa'i higher and SBP, SV, Q and LF/HF ratio were lower in the children compared to the adult males (pgJ.05). In response to the increasing LEN!> IIR and TPR increased, and LF BRS. SV and Q decreased in the adult group (pSf).05). while the same levels of LBNP caused an increase in TPR and a decrease in SBP, SV and Q in the children (pSf).05). Although not significant, the LF/HF ratio in the adult group showed an increasing trend in response to increased negative pressure (p=O.088). As for resting BRS, there were no significant differences in LF or HF BRS between the children and the adults despite a tendency for both measures to be 18% lower in the children. Also the LF/HF ratio was almost significantly greater in the adults compared to the children (p=O.057). In addition, a comparison between the relative adult and child responses to LBNP yielded no significant group by level interactions. This result should be taken with caution though, as the low sample size and high measurement variability generated very low statistical power for this analysis. In conclusion, the results of this study suggest that the hemodynamic adaptations to an orthostatic stress were less pronounced in the prepubertal males, most likely due to an underdeveloped autonomic system. These results need to be strengthened by further research before any implications can be derived for health care purposes.

Polytypism and Silicon carbide : a solid state nuclear magnetic resonance study

A survey of predominantly industrial silicon carbide has been carried out using Magic Angle Spinning nuclear magnetic resonance (MAS nmr); a solid state technique. Three silicon carbide polytypes were studied; 3C, 6H, and 15R. The 13C and 29 Si MAS nmr spectra of the bulk SiC sample was identified on the basis of silicon (carbon) site type in the d iff ere n t pol Y t Y pes • Out to 5.00 A fro mac en t r a lsi 1 i con (0 r carbon) atom four types of sites were characterized using symmetry based calculations. This method of polytype analysis was also considered, in the prelminary stages, for applications with other polytypic material; CdBr 2 , CdI 2 , and PbI 2 " In an attempt to understand the minor components of silicon carbide, such as its surface, some samples were hydrofluoric acid washed and heated to extreme temperatures. Basically, an HF removable species which absorbs at -110 ppm (Si0 2 ) in the 29 Si MAS nmr spectrum is found in silicon carbide after heating. Other unidentified peaks observed at short recycle delays in some 29 Si MAS nmr spectra are considered to be impurities that may be within the lattice. These components comprise less than 5% of the observable silicon. A Tl study was carried out for 29 Si nuclei in a 3C ii polytype sample, using the Driven Equilibrium Single-Pulse Observation of T1 (DESPOT) technique. It appears as though there are a number of nuclei that have the same chemical shift but different T1 relaxation times. The T1 values range from 30 seconds to 11 minutes. Caution has to be kept when interpreting these results because this is the first time that DESPOT has been used for solid samples and it is not likely in full working order. MAS nmr indicates that the 13C and 29 Si ~sotropic chemical shifts of silicon carbide appear to have a reciprocal type of relationship_ Single crystal nmr analysis of a 6H sample is accordance with this finding when only the resultant isotropic shift is considered. However, single crystal nmr also shows that the actual response of the silicon and carbon nuclear environment to the applied magnetic field at various angles is not at all reciprocal. Such results show that much more single crystal nmr work is required to determine the actual behavior of the local magnetic environment of the SiC nuclei.

The Ontario Municipal Freedom of Information and Protection of Individual Privacy Act: an analysis of its application to school boards

In Canada freedom of information must be viewed in the context of governing -- how do you deal with an abundance of information while balancing a diversity of competing interests? How can you ensure people are informed enough to participate in crucial decision-making, yet willing enough to let some administrative matters be dealt with in camera without their involvement in every detail. In an age when taxpayers' coalition groups are on the rise, and the government is encouraging the establishment of Parent Council groups for schools, the issues and challenges presented by access to information and protection of privacy legislation are real ones. The province of Ontario's decision to extend freedom of information legislation to local governments does not ensure, or equate to, full public disclosure of all facts or necessarily guarantee complete public comprehension of an issue. The mere fact that local governments, like school boards, decide to collect, assemble or record some information and not to collect other information implies that a prior decision was made by "someone" on what was important to record or keep. That in itself means that not all the facts are going to be disclosed, regardless of the presence of legislation. The resulting lack of information can lead to public mistrust and lack of confidence in those who govern. This is completely contrary to the spirit of the legislation which was to provide interested members of the community with facts so that values like political accountability and trust could be ensured and meaningful criticism and input obtained on matters affecting the whole community. This thesis first reviews the historical reasons for adopting freedom of information legislation, reasons which are rooted in our parliamentary system of government. However, the same reasoning for enacting such legislation cannot be applied carte blanche to the municipal level of government in Ontario, or - ii - more specifially to the programs, policies or operations of a school board. The purpose of this thesis is to examine whether the Municipal Freedom of Information and Protection of Privacy Act, 1989 (MFIPPA) was a neccessary step to ensure greater openness from school boards. Based on a review of the Orders made by the Office of the Information and Privacy Commissioner/Ontario, it also assesses how successfully freedom of information legislation has been implemented at the municipal level of government. The Orders provide an opportunity to review what problems school boards have encountered, and what guidance the Commissioner has offered. Reference is made to a value framework as an administrative tool in critically analyzing the suitability of MFIPPA to school boards. The conclusion is drawn that MFIPPA appears to have inhibited rather than facilitated openness in local government. This may be attributed to several factors inclusive of the general uncertainty, confusion and discretion in interpreting various provisions and exemptions in the Act. Some of the uncertainty is due to the fact that an insufficient number of school board staff are familiar with the Act. The complexity of the Act and its legalistic procedures have over-formalized the processes of exchanging information. In addition there appears to be a concern among municipal officials that granting any access to information may be violating personal privacy rights of others. These concerns translate into indecision and extreme caution in responding to inquiries. The result is delay in responding to information requests and lack of uniformity in the responses given. However, the mandatory review of the legislation does afford an opportunity to address some of these problems and to make this complex Act more suitable for application to school boards. In order for the Act to function more efficiently and effectively legislative changes must be made to MFIPPA. It is important that the recommendations for improving the Act be adopted before the government extends this legislation to any other public entities.

A comparison of functional behaviour assessment rating scales in a sample of children and youth with autism spectrum disorders

This study sought to compare the results of the Motivation Assessment Scale (MAS; Durand & Crimmins, 1988), Questions About Behavior Function Scale (QABF; Matson & Vollmer, 1996) and Functional Analysis Screening Tool (FAST; Iwata & Deleon, 1996), when completed by parent informants in a sample of children and youth with autism spectrum disorders (ASD) who display challenging behaviour. Results indicated that there was low agreement between the functional hypotheses derived from each of three measures. In addition, correlations between functionally analogous scales were substantially lower than expected, while correlations between non-analogous subscales were stronger than anticipated. As indicated by this study, clinicians choosing to use FBA questionnaires to assess behavioural function, may not obtain accurate functional hypotheses, potentially resulting in ineffective intervention plans. The current study underscores the caution that must be taken when asking parents to complete these questionnaires to determine the function(s) of challenging behaviour for children/youth with ASD.

Forecasting the Yield Curve of Government Bonds: A Comparative Study

For the past 20 years, researchers have applied the Kalman filter to the modeling and forecasting the term structure of interest rates. Despite its impressive performance in in-sample fitting yield curves, little research has focused on the out-of-sample forecast of yield curves using the Kalman filter. The goal of this thesis is to develop a unified dynamic model based on Diebold and Li (2006) and Nelson and Siegel’s (1987) three-factor model, and estimate this dynamic model using the Kalman filter. We compare both in-sample and out-of-sample performance of our dynamic methods with various other models in the literature. We find that our dynamic model dominates existing models in medium- and long-horizon yield curve predictions. However, the dynamic model should be used with caution when forecasting short maturity yields