Master of Science

thesisTraumatic brain injury (TBI) is a leading cause of death and disability in children. One of the leading causes of severe TBI in infants is abusive head trauma (AHT). Shaken baby syndrome (SBS) is a subset of AHT in which brain injury is present without obvious signs of head impact, thus the head injury is thought to be caused by shaking. SBS is one of the most difficult forms of TBI to study as the injuries are complex and the histories surrounding the child's injuries are questionable, or unknown. In this thesis, we investigate potential mechanisms of brain and eye injury from AHT and SBS. In Chapter 2, we investigate the potential coupling effect of the physiological response to crying (i.e. increased intracranial pressure (ICP) and increased cerebral blood volume (CBV)) with repetitive head trauma. Increased ICP and CBV prior to and during head trauma did increase the amount of injury and there was some macroscopic findings unique to that group; however, levels of injury were not as severe as reported clinically in SBS. In Chapters 3 and 4, we investigated two potential mechanisms of retinal hemorrhage (RH), a common ocular injury reported in AHT. The first study investigated whether repetitive occlusion of the optic nerve (ON) could lead to RH. Occluding the ON for 1-10 minutes and then releasing resulted in large RH that spanned the posterior pole and periphery of the retina. Cyclic, repetitive occlusion of the ON, however, resulted in no hemorrhage. In the second study, rapid increases in intraocular pressure (IOP) were evaluated as a possible mechanism of RH from AHT. A device mechanically indented the eyes of 3-5-day-old piglets at different rates and depths to produce large changes in IOP. No hemorrhages were caused from the rapid changes in IOP, and it was concluded that rapid changes in IOP by itself does not cause RH. This work identified two mechanisms which can influence or cause injury from abuse, and another mechanism was shown to likely not be a factor in abuse

Low-Cost QCM Sensor System for Screening Semen Samples

Artificial insemination is a well-established part of modern agricultural practice. A viable semen sample is judged by the total number of spermatozoa (sperm) in the sample and the motility of the sperm. In this paper, we report the development of a reusable measurement cell and electronics for screening semen samples based on the Quartz Crystal Microbalance (QCM) and Universal Frequency to Digital Converter (UFDC-1) to produce a low-cost sensor system. After introducing the semen sample at one end of the measurement cell, sperm swim down a channel before causing a frequency change on the QCM. Data is presented that shows the different frequency changes using a commercial frequency counter caused by porcine semen samples, one two days old and one twenty one days old. Similar data is presented for a motile semen sample measurement using the low-cost UFDC-1

Low-Cost QCM Sensor System for Screening Semen Samples

Artificial insemination is a well-established part of modern agricultural practice. A viable semen sample is judged by the total number of spermatozoa (sperm) in the sample and the motility of the sperm. In this paper, we report the development of a reusable measurement cell and electronics for screening semen samples based on the Quartz Crystal Microbalance (QCM) and Universal Frequency to Digital Converter (UFDC-1) to produce a low-cost sensor system. After introducing the semen sample at one end of the measurement cell, sperm swim down a channel before causing a frequency change on the QCM. Data is presented that shows the different frequency changes using a commercial frequency counter caused by porcine semen samples, one two days old and one twenty one days old. Similar data is presented for a motile semen sample measurement using the low-cost UFDC-1

Identifying which septic patients have increased mortality risk using severity scores:a cohort study

Background: Early aggressive therapy can reduce the mortality associated with severe sepsis but this relies on prompt recognition, which is hindered by variation among published severity criteria. Our aim was to test the performance of different severity scores in predicting mortality among a cohort of hospital inpatients with sepsis. Methods: We anonymously linked routine outcome data to a cohort of prospectively identified adult hospital inpatients with sepsis, and used logistic regression to identify associations between mortality and demographic variables, clinical factors including blood culture results, and six sets of severity criteria. We calculated performance characteristics, including area under receiver operating characteristic curves (AUROC), of each set of severity criteria in predicting mortality. Results: Overall mortality was 19.4% (124/640) at 30 days after sepsis onset. In adjusted analysis, older age (odds ratio 5.79 (95% CI 2.87-11.70) for ≥80y versus <60y), having been admitted as an emergency (OR 3.91 (1.31-11.70) versus electively), and longer inpatient stay prior to sepsis onset (OR 2.90 (1.41-5.94) for >21d versus <4d), were associated with increased 30 day mortality. Being in a surgical or orthopaedic, versus medical, ward was associated with lower mortality (OR 0.47 (0.27-0.81) and 0.26 (0.11-0.63), respectively). Blood culture results (positive vs. negative) were not significantly association with mortality. All severity scores predicted mortality but performance varied. The CURB65 community-acquired pneumonia severity score had the best performance characteristics (sensitivity 81%, specificity 52%, positive predictive value 29%, negative predictive value 92%, for 30 day mortality), including having the largest AUROC curve (0.72, 95% CI 0.67-0.77). Conclusions: The CURB65 pneumonia severity score outperformed five other severity scores in predicting risk of death among a cohort of hospital inpatients with sepsis. The utility of the CURB65 score for risk-stratifying patients with sepsis in clinical practice will depend on replicating these findings in a validation cohort including patients with sepsis on admission to hospital

High-pressure X-ray diffraction studies of light lanthanides

The (trivalent) lanthanides exhibit a common sequence of phases upon the application of pressure: hcp → dhcp → fcc → “distorted-fcc”. The “distorted-fcc”’ phase (d-fcc), observed in the light lanthanides is known to be related by geometric distortions to the fcc unit cell, yet the d-fcc phase has been reported to comprise of one or two structures, with no prevailing consensus as to the solution(s). This thesis contains a detailed study of the d-fcc phase of the light lanthanides Pr and Nd. High-pressure angle-dispersive powder-diffraction techniques were employed to systematically study the phases adopted by Pr (up to 25GPa) and Nd (up to 44GPa). Particular attention was paid to solving the d-fcc of each of these elements, the structure of which is very unclear in published work. In Pr, the d-fcc between 7 and 20GPa is shown to comprise of two phases, the solutions of which are shown to be hR24 (R¯3m) and oC16 (Ibam) for the regions 7-14GPa and 14-20GPa, respectively. The pressure dependence of each of these structures over their stability range is presented. Revisions to previously-published volume vs. pressure data are made, with a different value for the volume collapse at the 4f electron delocalisation transition reported. Similarly, the d-fcc phase of Nd, stable over the pressure range 16-40GPa, is studied in detail. Nd differs from Pr by undergoing a further transition, to a hP3 (P63) structure, on pressurisation above 40GPa, before transforming to a α-Uranium phase. The distorted-fcc phase is shown, like that of Pr, to comprise of two phases, hR24 (R¯3m) and oC16 (Ibam) for the pressure regions 16-26GPa and 26-40GPa, respectively. Data on Nd are presented up to the maximum pressure achieved, 44GPa. Data from a preliminary study of La are also presented, along with a brief report on attempts to prepare a single crystal of Pr within a diamond anvil cell, by laser annealing of a powder of Pr

Time-course changes associated with PA Lumbar Mobilizations on Lumbar and Hamstring Range of Motion:A Randomized Controlled Crossover Trial

Objective: We aimed to compare the post-intervention time-course changes in active knee extension (AKE) and active lumbar flexion (ALF) range of motion in response to unilateral posterior–anterior (UPA) mobilizations of the lumbar spine (L4/5 zygapophyseal). Methods: Twenty-four asymptomatic participants (maleness: 0.58, age [mean ± standard deviation]: 32 ± 8 years, body mass index 25.9 ± 2.6 kg m2) were recruited to a fully controlled crossover trial. Following either the intervention (L4/5 zygapophyseal mobilizations) or control, participants immediately performed the AKE and ALF tests, which were also performed at baseline. Subsequent tests were made at intervals of 5, 10, 15, 20, 25, 30, 45 and 60 min. Results: After adjustment for baseline (mean AKE: 37.2° from full extension, mean ALF: 14.37 cm), sex and age, UPA lumbar mobilizations had a most likely moderate effect on AKE (9.8° closer to full extension; ±1.9) and a likely moderate effect on ALF (1.34 cm; ±90% confidence limits 0.43). The magnitude of the AKE effect became most likely small 20-min posttreatment (5.3; ±1.7) and possibly small/possibly trivial 60-min posttreatment (2.1; ±1.4). For ALF, the magnitude of the effect became most likely small 15-min posttreatment (0.76; ±0.25), possibly small/possibly trivial 25-min posttreatment (0.38; ±0.18) and likely trivial 60-min posttreatment (0.26; ±1.8). Discussion: UPA lumbar mobilizations increased lumbar Range of Motion and hamstring extensibility by a moderate magnitude, with the effect reducing after 10–20-min posttreatment. Clinicians should consider these time-course changes when applying UPA lumbar mobilizations