Analysis of Indentation Loading of Cortical Bone Using Acoustic Emission Techniques

In this study, we recorded the number of Acoustic emission (AE) hits and related AE energy during indentation fracture of cortical bone using a PAC PCI-2 card and pico sensor. A threshold value of 43dB was used to filter premature trigger due to background noise. Registered AE hits had more than one count (threshold crossing). Amplifier gain was set at 40dB with a (0.1-1) MHz band pass filter. 8mm cubes of cortical bones were indented in the longitudinal direction at constant crosshead speed of 1 mm min-1 using a large 2D, 50˚ wedge indenter. We hypothesised that signals occurring as a result of microcracking would have low AE energy and occur prior to and during the period of maximum load whereas those associated with main crack propagation would have high AE energy and occur at fracture only

Indentation Fracture of Bovine Cortical Bone: Acoustic Emission Technique

Indentation cutting may result in microcracking and main crack growth which was previously reported. In this study, we recorded the AE signals produced by cracking processes during cutting on cortical bone, measuring the cutting force and correlating between load-displacement curves and AE activities

Detection of Microcracks During Bone Cutting Using Acoustic Emission Techniques

Surgeons may use a number of cutting instruments such as osteotomes and chisels to cut bone during operative procedures. The initial loading of cortical bone during the cutting process results in the formation of microcracks in the vicinity of the cutting zone with main crack propagation to failure occurring with continued loading; microcracking acts as a stimulus for main crack formation and has also been shown to occur during the propagation of the main crack. It has also been reported that Acoustic Emission (AE) is generated due to microcrack formation and crack growth, prior to, and during final fracture in tensile loading of bovine and human cortical bone. In this study, we recorded the number of AE hits and AE signal amplitudes during monotonic indentation cutting of cortical bone, to correlate between the intensity and duration of the signals and micro and macro crack formation and propagation

Analysis of Airport Performance using Surface Surveillance Data: A Case Study of BOS

Detailed surface surveillance datasets from sources such as the Airport Surface Detection Equipment, Model-X (ASDE-X) have the potential to be used for analysis of airport operations, in addition to their primary purpose of enhancing safety. In this paper, we describe how airport performance characteristics such as departure queue dynamics and throughput can be analyzed using surface surveillance data. We also propose and evaluate several metrics to measure the daily operational performance of an airport, and present them for the speci c case of Boston Logan International Airport

Cutting Rate Effect on Temperature During Cortical Bone Sawing

When bone is cut the occurrence of thermal damage to the bone is of major concern to the surgeon. If the temperature exceeds 44°C for longer than 1 min, bone repair is impaired (Eriksson et al, 1984) and necrosis may occur. Repeated use of cutting blades may reduce the cutting efficiency (Wevers et al, 1987; Toksvig-Larsen et al, 1992). Wevers et al also found that there is a greater force required to cut cortical bone using a blunt saw compared to new one

Tiki to Mickey: The Anglo - American Influence On New Zealand Commercial Music Radio 1931-2008

Emerging consensus tends to suggest there is overwhelming American dominance of New Zealand radio in music. This study sets out to investigate such claims by looking at music, and incorporating a study of technology, announcing and programming as well. There is evidence emerging that instead of overwhelming dominance, there is a mixture of American as well as British influence. Foreign influence in the radio scene has been apparent since the time it became a popular addition to the New Zealand household in the 1920’s. Over the following decades, the radio industry has turned to the dominant Anglo-American players for guidance and inspiration. Now with a maturing local industry that is becoming more confident in its own skin, this reliance on foreign industry is coming under question regarding its effect on indigenous culture. The cultural cringe is slowly disappearing, but what is replacing it has been the centre of cultural debate. Utilising methods of content analysis and interviews, we set out to question which theory best describes the new landscape that the radio industry finds itself in, and how this is affecting the production of content received by the listening public. Working within a framework of cultural imperialism and hybridity, the findings indicate a complex mixture of the local and the global that could not be explained by simplistic notions of hybridity

Deciphering Quaternary Geomagnetic, Glacial, and Depositional Histories Using Paleomagnetism in Tandem with Other Chronostratigraphic and Sedimentological Approaches

Stratigraphy and chronology are essential to sedimentological study of Earth system histories. And, stratigraphy and chronology are often challenging and interesting problems themselves. The Quaternary (2.588 Ma - present) experienced paleoenvironmental and paleo-geomagnetic variability well outside the range of the recent instrumental record, providing the opportunity to place recent observations in a more complete perspective. This dissertation presents three studies that combine paleomagnetism in concert with radiocarbon, stratigraphic correlation, and/or age-depth modeling to develop stratigraphy and assign chronology. This in turn, helps to better understand the evolution of these glacial, geomagnetic, and depositional systems. The first study investigates the glacial history of the Petermann Glacier, a major outlet glacier of the Greenland Ice Sheet, over the last ~7 ka. Petermann Glacier has been remarkably stable for as long as there have been historical observations apart from two anomalously large calving events of its floating ice tongue over the last decade. This is unique when compared with many other large marine terminating Greenland outlet glaciers. Yet, our geologic evidence clearly show the Petermann Ice Tongue was not present for much of the time recorded in the sediments of Petermann Fjord. While radiocarbon and paleomagnetic methods could not constrain the sediment’s chronology alone, due to large reservoir issues and uncertain regional paleomagnetic templates, using the two methods in tandem we determine the paleoenvironmental conditions that were required to maintain the stable ice tongue of the Late Holocene. Specifically, a stable ice tongue only formed around 2-2.5 ka after sea ice conditions intensified, limiting Ekman transport of warm modified Atlantic Waters into the fjord, and surface air temperatures were within ~2o C of preindustrial conditions, slowing the subglacial run-off driven circulation of the fjord. The second study investigates the geomagnetic history of Western North America from ~35-15 ka. While the Holocene has been the focus of most studies about past directional changes of the geomagnetic field, the Late Pleistocene spans a greater range of field intensity variations that have a largely unknown relationship with field morphology. Yet, late Pleistocene sediments that could be used to investigate these questions, particularly from terrestrial archives of Western North America, are notoriously difficult to date. This makes comparison of millennial scale directional variations, like other studies have done for the Holocene, difficult. Using new data from Fish Lake, Utah and existing data from Bessette Creek, British Columbia, and Bear Lake on the Utah and Idaho Border, we construct a composite stacked record to define these variations and we account for radiocarbon and magnetic uncertainties in the stack’s chronology. We demonstrate that this PSV template can provide new insight to longstanding chronostratigraphic debates, such as the implications of various proposed chronologies of the sediments in the Wilson Creek Formation at Mono Lake, California on the outcrop’s chronostratigraphy and radiometric age estimates. The third study investigates the depositional history of the Bengal Fan over the last ~1.25 Ma. Regionally extensive hemipelagic deposits with good reversal magnetostratigraphy offer constraints on the evolution of the fan’s channel levee system through climate and sea-level transitions of the Pleistocene. Yet, it has been challenging to assign ages to the turbiditic sediments of the fan due to the absence of reliable chronostratigraphic markers. To address this issue, we model sediment accumulation rates at seven drill sites, incorporating all available age control points and integrating seismic observations to establish the stratigraphic relationships of paleo-channel-levee systems. The model results are stacked to create a composite regional signal for the Lower Bengal Fan, which, in the additional context of other regional archives, suggests growth of the spatial extent of the Bengal Fan channel-levee system along with increases in glacial-interglacial sea level amplitude

CARING FOR PATIENTS WITH DIABETES IN SAFETY NET HOSPITALS AND HEALTH SYSTEMS

Safety net hospital systems provide health care to a high volume of underserved patients, including uninsured and low-income patients, racial/ethnic minorities, and those with chronic conditions. To assess the effects of programs designed to improve care for the undeserved, the National Public Health and Hospital Institute interviewed administrators about available programs and services and collected information on patient demographics, health care utilization, and clinical outcomes related to diabetes management. Services range from availability of special diabetes clinics to American Diabetes Association–certified classes. Compared with other health care providers, safety net hospital systems provide comparably high quality of care to patients with diabetes, despite serving higher volumes of underserved patients. However, even with programs and services designed to improve access to care for the underserved, disparities in quality of care and patient outcomes persist as a result of demographic risk factors, most notably, lack of insurance.https://www.commonwealthfund.org/Content/Publications/Fund-Reports/2005/Jun/Caring-for-Patients-with-Diabetes-in-Safety-Net-Hospitals-and-Health-Systems.asp

Does endurance fatigue increase the risk of injury when performing drop jumps?

Although from an athletic performance perspective it may be beneficial to undertake drop jump training when fatigued (principle of "specificity" of training), such endur-ance fatigue may expose the body to a greater risk of injury if it causes an increase in peak impact accelerations. This study aimed to determine if endurance fatigue resulted in an increase in tibial peak impact acceleration and an associated change in knee kinematics when completing plyometric drop jumps. Fifteen females performed drop jumps from 3 heights (15, 30, and 45 cm) when fatigued and nonfatigued. Treadmill running was used to induce endurance fatigue. The following variables were assessed: tibial peak impact acceleration, knee angle at initial ground contact, maximum angle of flexion, range of flexion, and peak knee angular velocity. Fatigue resulted in significantly greater (p < 0.05) tibial peak impact acceleration and knee flexion peak angular velocity in drop jumps from 15 and 30 cm, but not from 45 cm. Fatigue had no effect on any of the knee angles assessed. The neuromuscular system was affected negatively by endurance fatigue at 15 and 30 cm, indicating that coaches should be aware of a potential increased risk of injury in performing drop jumps when fatigued. Because from the greater drop height of 45 cm the neuromuscular system had a reduced capacity to attenuate the impact accelerations per se, whether nonfatigued or fatigued, this would suggest that this height may have been too great for the athletes examined

Arctic drainage of Laurentide Ice Sheet meltwater throughout the past 14,700 years

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sufke, F., Gutjahr, M., Keigwin, L. D., Reilly, B., Giosan, L., & Lippold, J. Arctic drainage of Laurentide Ice Sheet meltwater throughout the past 14,700 years. Communications Earth & Environment, 3(1), (2022): 98, https://doi.org/10.1038/s43247-022-00428-3.During the last deglaciation substantial volumes of meltwater from the decaying Laurentide Ice Sheet were supplied to the Arctic, Gulf of Mexico and North Atlantic along different drainage routes, sometimes as catastrophic flood events. These events are suggested to have impacted global climate, for example initiating the Younger Dryas cold period. Here we analyze the authigenic Pb isotopic composition of sediments in front of the Arctic Mackenzie Delta, a sensitive tracer for elevated freshwater runoff of the retreating Laurentide Ice Sheet. Our data reveal continuous meltwater supply to the Arctic along the Mackenzie River since the onset of the Bølling–Allerød. The strongest Lake Agassiz outflow event is observed at the end of the Bølling–Allerød close to the onset of the Younger Dryas. In context of deglacial North American runoff records from the southern and eastern outlets, our findings provide a detailed reconstruction of the deglacial drainage chronology of the disintegrating Laurentide Ice Sheet.Open Access funding enabled and organized by Projekt DEAL