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

Exploring Inter-Organizational Relationships Between Park and Recreation Agencies With Wounded Warrior Programs and Community Service Organizations

Public recreation departments are funded primarily by tax dollars and over the past thirty years the percentage of funding needed to operate quality recreation programs has steadily decreased and threatened the quantity and quality of programs offered. Presently, park and recreation agencies partner with community entities to offset funding reductions and to offer new and/or ancillary programs. Importantly, partnerships must provide mutual benefits to be successful and the antecedents and factors of inter-organizational relations (IOR) are important to discover. The purpose of this study was to determine factors that might predict IOR between park and recreation agencies with Wounded Warrior (WW) Programming, and community service organizations. IOR was measured as the ability and willingness to share manpower, resources, and funding among Park and Recreation Directors and CEO\u27s of community service organizations. Independent variables included military connectedness, patriotism, medical assistance available, community size, quality of life, knowledge of WW programming, shared philosophical orientations, cooperation barriers, and organizational goal congruence. Participants for the study included the CEO\u27s of nineteen community-based Wounded Warrior partnerships that completed a survey exploring IOR. The survey instrument was validated using Cronbach\u27s Alpha and validity was improved after administering a pilot test. The response rate included 250 surveys, or 22%. The data collected was analyzed using independent t-tests, bivariate correlations (Pearson r and Sig. 2-tailed) to determine whether to accept or reject study hypotheses. A Multiple Linear Regression (MLR) was performed to determine if any of the independent variables were predictors of IOR. Of the variables, MLR revealed that an organizations ability to provide resources for specific WW medical conditions (PTSD, severe burns, amputations, etc.) was significant at (p?.05). A Hierarchal Cluster Analysis (Ward\u27s Method) provided typological analysis that identified groups of partners with similar traits of IOR. Results of the study revealed that of the three measures of IOR, human resources were most likely to be shared in a WW partnership. Future studies should concentrate on establishing a framework for building partnerships between park and recreation departments and community service agencies. This study revealed five new measures of IOR which can be used to explore future IOR. The five new measures were named appropriately by the researcher as Sponsorship, Donation, and Cost Partners (SDCP), Recreational Facility and Equipment Partners (RFEP), Indoor Facilities Partners (IFP), Program Operation Partners (POP), and Specialized Assistance and Credentialed Partners (SACP)