Crown Ether-Modified Clays and their Polystyrene Nanocomposites

Crown ether-modified clays were obtained by the combination of sodium and potassium clays with crown ethers and cryptands. Polystyrene nanocomposites were prepared by bulk polymerization in the presence of these clays. The structures of nanocomposites were characterized by X-ray diffraction and transmission electron microscopy. Their thermal stability and flame retardancy were measured by thermogravimetric analysis and cone calorimetry, respectively. Nanocomposites can be formed only from the potassium clays; apparently the sodium clays are not sufficiently organophilic to enable nanocomposite formation. The onset temperature of the degradation is higher for the nanocomposites compared to virgin polystyrene, and the peak heat release rate is decreased by 25% to 30%

Rapid rotation of micron and submicron dielectric particles measured using optical tweezers

We demonstrate the use of a laser trap (‘optical tweezers’) and back-focal-plane position detector to measure rapid rotation in aqueous solution of single particles with sizes in the vicinity of 1 μm. Two types of rotation were measured: electrorotation of polystyrene microspheres and rotation of the flagellar motor of the bacterium Vibrio alginolyticus. In both cases, speeds in excess of 1000 Hz (rev s−1) were measured. Polystyrene beads of diameter about 1 μm labelled with smaller beads were held at the centre of a microelectrode array by the optical tweezers. Electrorotation of the labelled beads was induced by applying a rotating electric field to the solution using microelectrodes. Electrorotation spectra were obtained by varying the frequency of the applied field and analysed to obtain the surface conductance of the beads. Single cells of V. alginolyticus were trapped and rotation of the polar sodium-driven flagellar motor was measured. Cells rotated more rapidly in media containing higher concentrations of Na+, and photodamage caused by the trap was considerably less when the suspending medium did not contain oxygen. The technique allows single-speed measurements to be made in less than a second and separate particles can be measured at a rate of several per minute

Millimeter-Wave MMICs and Applications

As device technology improves, interest in the millimeter-wave band grows. Wireless communication systems migrate to higher frequencies, millimeter-wave radars and passive sensors find new solid-state implementations that promise improved performance, and entirely new applications in the millimeter-wave band become feasible. The circuit or system designer is faced with a new and unique set of challenges and constraints to deal with in order to use this portion of the spectrum successfully. In particular, the advantages of monolithic integration become increasingly important. This thesis presents many new developments in Monolithic Millimeter-Wave Integrated Circuits (MMICs), both the chips themselves and systems that use them. It begins with an overview of the various applications of millimeter waves, including a discussion of specific projects that the author is involved in and why many of them demand a MMIC implementation. In the subsequent chapters, new MMIC chips are described in detail, as is the role they play in real-world projects. Multi-chip modules are also presented with specific attention given to the practical details of MMIC packaging and multi-chip integration. The thesis concludes with a summary of the works presented thus far and their overall impact on the field of millimeter-wave engineering.</p

Use of Wearable Technology to Detect and Alter Subtle Gait Asymmetries Following Anterior Cruciate Ligament Reconstruction

Knee osteoarthritis is a significant problem post-anterior cruciate ligament (ACL) reconstruction. Knee osteoarthritis can develop due to subtle changes in knee mechanics that affect loading on knee joint cartilage. Gait deficits during the loading phase have been observed up to four years post-surgery. However, changes in peak shank angular velocity have not been established long-term post-surgery. Peak shank angular velocity could be increased via an inertial measurement unit (IMU) based-biofeedback protocol to ultimately improve knee mechanics. Therefore, the objective of this project was to understand gait characteristics one to four years post-ACL reconstruction and to examine the effect of an IMU-based biofeedback protocol. Twenty healthy participants and seven participants one to four years post-ACL reconstruction walked over-ground at 1.4 m/s while an IMU measured angular velocity of the shank and a three-dimensional motion capture system measured traditional gait kinematics and kinetics. Comparisons were made between groups and between limbs within the ACL-reconstructed group. Correlations were assessed between peak shank angular velocity traditionally measured kinematics and kinetics. Six participants in the ACL-reconstructed group then participated in a biofeedback session on a treadmill intended to increase peak shank angular velocity. Gait mechanics were assessed pre- and post-biofeedback for over-ground walking. Peak shank angular velocity was significantly decreased in both ACL-reconstructed limbs compared to the healthy group. Knee range of motion and peak internal knee extension moment, two primary risk factors for developing knee osteoarthritis in this population, did not differ from the healthy group. Hip and ankle kinematics and kinetics did differ between groups. Only knee flexion at initial contact was different between ACL-reconstructed limbs. Additionally, peak shank angular velocity was moderately correlated with knee and hip range of motion, and peak internal knee extension moment. Post-biofeedback, peak shank angular velocity increased in both limbs. Changes were primarily observed in hip mechanics and stance time, rather than at the knee. However, asymmetries were present post-biofeedback in peak shank angular velocity, knee flexion at initial contact, and peak knee flexion during the loading phase. This work demonstrates that an inexpensive and portable device can detect abnormal gait patterns long-term post-ACL reconstruction and has the potential to be used in a biofeedback protocol to alter gait parameters that may reduce the risk of knee osteoarthritis for individuals post-ACL reconstruction

Daubert and the Quest for Value-Free Scientific Knowledge in the Courtroom

In a world that grows more technologically complex every day and in which scientific research continually expands both our understanding of, and our questions about, the operation of the natural and man-made world, it is hardly surprising that science should show up with increasing frequency in our court-rooms. Science itself is sometimes at issue, for example, in proceedings on allegations of scientific misconduct or in disputes over the ownership or patentability of technologies. But more frequently, science enters in aid of resolving a case in which a complex question of causation is at issue. To establish or rebut causation, each side may seek to introduce evidence from expert witnesses. With crowded dockets, the simpler cases are more likely to settle, while more complex ones-especially class actions and mass tort suits-go to trial, which may explain why in some jurisdictions, experts take part in upwards of eighty percent of all trials