iDEA: Drexel E-repository and Archives

Sleep physiology and executive function during chronic partial sleep restriction

Title: Sleep physiology and executive function during chronic partial sleep restriction

Authors: Rider, Robert L.

Abstract: Introduction: The detrimental effects of sleep deprivation on waking performance are well documented, but questions remain regarding the relationship between sleep physiology and specific domains of cognitive function. Research suggests sleep may also play a role in waking executive functions. However, the existing studies investigating executive functioning have generally been carried out under conditions of total sleep deprivation and only in one instance was the specific relationship between physiological sleep stages and waking executive function investigated. Methods: In this study, N = 137 (22 – 45y, 77m, 60f) participants completed a chronic sleep restriction protocol of four hours time in bed for sleep for five consecutive nights. Following sleep restriction, the Hayling and Brixton tests of executive functioning (HBT) were administered. Sleep variables, recorded the night prior to test administration, were regressed on the HBT measures. In a secondary analysis, the performance of a small group of control participants was compared to the group of sleep restricted participants using t-tests. Results: The results supported our hypothesis that slow wave sleep would be the best predictor of subsequent performance on tests of executive function, though the amount of variability accounted for was less than 10%. Additionally, the performance of sleep restricted individuals was relatively worse than individuals obtaining normal sleep on certain measures of cognitive functioning, including attention and certain aspects of executive function. Discussion: These findings indicate that having more slow wave sleep during sleep restriction predicts fewer errors, shorter response latencies, and better overall performance on tests of executive function. Implications are discussed for clinical neuropsychological practice with respect to the potential impact of sleep loss on neuropsychological testing.

Chitosan thin films as metal ion sensors and structurally colored coatings

Title: Chitosan thin films as metal ion sensors and structurally colored coatings

Authors: McIlwee, Holly Alice

Abstract: The sensitive and selective detection of heavy metal ions is important in environmental and biomedical applications. A new system incorporating chitosan and optically interesting metallic nanoparticles has been used to create a cost-effective, selective metal ion sensing platform. The system utilizes surface plasmon resonance (SPR) and localized SPR spectroscopy (LSPR), which detect shifts in the oscillation frequency of gold films or nanoparticles induced by changes in the dielectric contrast of the surrounding matrix. High selectivity is achieved by introducing a known chelating polymer as the surrounding matrix. Chitosan is an attractive natural polymer for numerous reasons. It is a renewable resource and waste product of the seafood industry and it is in abundant supply. It is biocompatible, biodegradable, and it has been modified in previous studies to be selective for different metal ions. The dielectric contrast change in a gold nanoparticle containing chitosan thin film has been shown to be an effective sensor for Fe3+ and Cu2+. This system is of interest because of the possibility for sensitivity increase due to modification of the chitosan structure as well as nanoparticle size, shape, and configuration. In addition to being a known chelator, chitosan also exhibits structural color. The structural coloration of chitosan thin films have been studied previously, but new applications such as color tunable paints and cosmetics, as well as packaging and coatings call for structural color which is independent of a silicon substrate. Examples in nature are the intense coloration of butterflies, snakes, hummingbirds and peacocks whose color is created by the differences in the refractive index of stacked thin film layers comprised of alternating materials, such as chitin and air which have a high and low index of refraction respectively. Colored polymer thin films can undergo perceptible color shifts when geometric periodicity of the layers is varied. In our attempts to better understand these processes, stacking of structurally colored polymer thin films of varying index of refraction as well as altering geometries to achieve this effect were investigated herein.

Quantifying the effect of mutual coupling in ultra-wideband-multi-band multiple input multiple output systems

Title: Quantifying the effect of mutual coupling in ultra-wideband-multi-band multiple input multiple output systems

Authors: Dragone, Rocco Vincent Jr.

Abstract: The combination of ultra-wideband (UWB) spectrum with Multiple-Input Multiple-Output (MIMO) system techniques show great promise for developing very high bandwidth wireless personal area networks (WPANs). While these networks have been explored in theory, there is little literature regarding the practical limitations of this technology. Speci cally, the mutual coupling between the antennas in the system is usually ignored. This thesis quanti es the e ects of mutual coupling in MIMO UWB systems. A variety of antenna geometries and spacings were simulated. Several scenarios in a typical WPAN environment were simulated using electromagnetic ray tracing (ERT) techniques. These results were validated using network analyzer channel measurements. These results show mutual coupling has a signi cant impact on channel capacity. Furthermore, in most scenarios, mutual coupling can actually improve the channel capacity by decorrelating adjacent spatial channels. Knowledge of this potential bene t of mutual coupling in MIMO-UWB systems will allow future WPAN designers to develop systems using small, multi-antenna devices with very high capacities.

Electron beam induced current detection of sub-surface two-dimensional charge reservoir

Title: Electron beam induced current detection of sub-surface two-dimensional charge reservoir

Authors: Myers, Eric G.

Abstract: In conjunction with metal-semiconductor-metal heterostructure (HMSM) devices, the electron beam induced current (EBIC) detection method is ideal in two-dimensional sheet charge detection. Using a delta modulation-doped heterostructure, a scan-line plot comparison to its undoped structural equivalent exposes the electrical effects of the sheet charge existence. While electrically biasing both heterostructure types, each were placed in an SEM chamber and electrode-to-electrode scan-line plots were taken at different biasing levels. Based on experimental results, dark currents for the delta modulationdoped device are detrimental to its EBIC signal-to-noise ratio but its electron-hole pair collection rate is more effective in EBIC signaling than its undoped counterpart at higher biasing levels. Bypassing the charge transport limitation of a saturated group drift velocity in the active region, charge carriers are swept to the highly conductive twodimensional sheet charge in the doped structure resulting in higher EBIC signaling; the sheet charge shields the active region from the drift-current limitations by modifying the carrier transport path within the active region. Supported by experimental EBIC characterization data, biased delta modulation-doped HMSM device simulations predicted the presence of the two-dimensional sheet charge would effectively simulate smaller finger-gapped devices but without sacrificing its active region volume. Improvements in electron beam control, most notably beam depth within a sample, can aid in the development of a non-destructive EBIC method to determine sheet charge uniformity; an added feature to the established device failure and defect analysis EBIC techniques used today. Theoretical electrical dissimilarities with modulation-doped and undoped in-plane Schottky contact devices are discussed to support the EBIC method and its application; the advantages and/or disadvantages of using degenerate devices of this type in substitution of its undoped structural equivalent are demonstratd.

Scale-dependent/invariant local 3D geometric features and shape descriptors

Title: Scale-dependent/invariant local 3D geometric features and shape descriptors

Authors: Novatnack, John

Abstract: The quality and abundance of three-dimensional geometric data is rapidly increasing with the drastic improvement in the cost and effectiveness of 3D acquisition hardware. In fact, threedimensional geometric data already plays a central role in many computer vision and computer graphics applications such as autonomous vehicle navigation, 3D object recognition and the computerbased preservation of cultural artifacts. Despite the increasing relevance and importance of geometric data, current techniques of processing the data have neglected to explicitly model and exploit a significant source of information of the data - the scale variability of the local geometric structures. In this thesis we overcome the limitation of past techniques with a comprehensive framework of modeling the scale-variations in local geometric structures, effectively adding an additional dimension to geometric data. To accomplish this we derive the geometric scale-space, a representation of local geometric structures at various degrees of scale. This representation enables us to define scale-dependent geometric feature detectors, such as corners and edges, that determine not only the location of salient geometric features, but also their relative scales. The augmentation of a geometric feature with its intrinsic scale enables us to define scale-dependent/invariant local shape descriptors that together form both a hierarchical and scale-invariant representation of the local geometric structures of a 3D shape. We derive and present the theory of these methods and also demonstrate their effectiveness for the purposes of robust 3D feature detection and fully automatic range image registration.

Control design to reduce the effects of torsional resonance in coupled systems

Title: Control design to reduce the effects of torsional resonance in coupled systems

Authors: Lofaro, Daniel M.

Abstract: Connecting two rotary mechanical devices utilizes a flexible coupler to accommodate various shaft misalignments. These couplers, including belts and gear boxes, exhibit a spring constant and a viscous damping term. The spring constant causes the system to have a resonant frequency while the damping controls its amplitude. In the frequency domain this characteristic is called Torsional Resonance (TR).The TR frequencies can not be allowed into the pass band of closed loop servo because it will cause instability. Some conventional solutions to obtain stable operation include: reduction of the servo’s bandwidth below the TR frequencies; using stiffer, more expensive, components to increase the TR frequencies thus increasing the useable bandwidth; and using notch filters to reduce the resonant peak. The objective of this work is provide a control solution to allow systems using elastic parts, including loose belt drives and plastic gears, achieve sufficient bandwidth to obtain their desired performance. A model of a commercial application exhibiting the TR characteristic has been made using Matlab and Simulink. A test rig has been constructed with a brushless DC motor and a system able to control the location of the TR frequencies. This test rig is controlled by a hard real time target control system which accepts control through Matlab and Simulink.

Characterization of room-temperature ionic liquid solvent-based, free radical copolymerized network gels

Title: Characterization of room-temperature ionic liquid solvent-based, free radical copolymerized network gels

Authors: Stanzione, Joseph Francis III

Abstract: Cross-linked ionic liquid gels (ILG) were generated via a free radical copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N,N’methylenebis(acrylamide) (MBA) using 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO4] as a room temperature ionic liquid (RTIL) solvent medium. The AMPS and MBA solubility window in [EMIM][EtSO4] at 65°C was determined using a statistical design of experiments approach considering that potassium persulfate (PPS) was used as a fixed initiator concentration. In-situ attenuated total reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy showed complete conversion of carboncarbon double bonds in approximately 300 minutes, where an overall reaction rate constant of 0.069 min-1 was determined. Dynamic mechanical analysis and differential scanning calorimetry revealed that the glass transition temperature (Tg) of the resultant ILG could be varied from approximately -85 to -60°C. Additionally, quasi-static mechanical testing showed an elastic modulus in compression range of 10 to 11,400 kPa. The molecular weight between cross-links and the interaction parameter were found to have ranges of 5.0 x 102 to 4.0 x 105 and 0.54 to 1.40, respectively. Gravimetric analysis indicated that swelling of the ILG is dependent on the relative humidity of the atmosphere, but was found to be more environmentally stable than traditional collagen based gels. Furthermore, electrical conductivity analysis demonstrated a potential for the ILG as membranes in separations or as actuators.

Then and now: comparing juveniles’ comprehension of the Miranda Warning in the 1970s and today

Title: Then and now: comparing juveniles’ comprehension of the Miranda Warning in the 1970s and today

Authors: Riggs Romaine, Christina L.

Abstract: In addition to use in research, Grisso’s Instruments for Assessing Understanding and Appreciation of Miranda Rights (1998) have been used to help evaluate the validity of Miranda waivers in court proceedings and are commonly cited in testimony. Despite their extensive use, the admissibility of the instruments has been questioned in some cases because of the outdated vocabulary used and the assumption that Miranda comprehension has improved since the 1970s. To examine this assumption, the results of Grisso’s 1970s study were compared to data gathered from 183 21st century juvenile offenders. Twenty-first century youth were tested using the Miranda Rights Comprehension Instruments-II. Results indicated that scores on the two measures were comparable, and that juveniles today do not have better understanding of their rights than their counterparts in the 1970s. In fact, on some measures of understanding they showed significantly worse understanding. Verbal IQ continued to be the strongest predictor of Miranda rights comprehension in the 21st century. As in 1970s study, no relationship between Miranda comprehension and previous experience with the police was observed.

Chitosan and carboxymethyl chitosan as catalyst matrix materials

Title: Chitosan and carboxymethyl chitosan as catalyst matrix materials

Authors: Laudenslager, Michael John

Abstract: Chitosan, a polysaccharide derived from crab and shrimp shells, was investigated as a matrix material for catalytic platinum, gold, and silver nanoparticles. Not only is chitosan able to stabilize nanoparticles, it is able to reduce metal ions to a zero valent state while controlling nanoparticle growth. The size, morphology, and catalytic activity of nanoparticles produced were examined in chitosan, and carboxymethyl chitosan (CMC), a chemically modified form of chitosan. Carboxymethyl chitosan is reported to have a higher metal ion binding capacity, but has not been previously tested as a support material for catalytic nanoparticles. Nanoparticles were characterized through UV-vis absorbance and transmission electron microscopy. Platinum nanoparticles have a narrow size distribution with an average size of 3.5 nm while gold and silver have much broader size ranges with average particle sizes of 23 nm and 7 nm respectively. The size and morphology of the nanoparticles did not vary significantly between the two polymers for each type of catalyst. However, a higher aggregation rate was observed in CMC. Nanoparticles supported on chitosan flakes were shown to be active, reusable catalysts. The catalytic activity of chitosan supported nanoparticles was monitored through UV-vis absorbance of the reduction of 4-nitrophenol in the presence of sodium borohydride. The characteristic absorbance peak of 4-nitrophenol is directly proportional to its concentration. By using an excess of sodium borohydride, pseudo first order rate kinetics can be assumed. Rate constants show that all three types of nanoparticles are catalytically active with silver nanoparticles having the highest rate constant followed by platinum and gold. The three catalysts did not change in activity after several runs when supported in chitosan; however, carboxymethyl chitosan supported catalysts were not appreciably retained by the matrix material.

Blood model plasma separation in a microfabricated PDMS device exploiting capillary action driving forces

Title: Blood model plasma separation in a microfabricated PDMS device exploiting capillary action driving forces

Authors: Hinkle, Tyler Nathaniel

Abstract: The goal of this thesis was to successfully design and fabricate a point-of-care microfluidic device that effectively separates plasma from a blood model without external pumping or other applied driving forces. There is currently no commercially available or published microfluidic device that accomplishes blood plasma separation without pumping or externally applied driving forces. This pump-free device will decrease size and cost while increasing the number of possible applications. The final separated plasma could be further used for detection of biomarkers linked to specific diseases and conditions through tailored antibody based assays by future researchers. The separation device was fabricated using known lithography masking techniques to create a negative to be molded in PDMS using standardized molding fixtures to ensure device uniformity. Fluid flow through the device was promoted by using a plasma-free hydrophilic surface treatment greatly reducing the contact angle of PDMS from about 90 degrees to about 50 degrees. The effectiveness of this device was tested and validated using water emulsions of polystyrene beads adjusted to a viscosity equivalent to that of blood (4.0 +/- 0.5 cP) to represent a simple blood model. The final device is able to separate the model plasma cells (1-3um diameter) from the red (3-8um diameter) and white (8-12um diameter) blood cells with greater than 85% efficiency with a low filtration dead-volume of less than 10ul.