Why has Russia failed to establish air superiority over Ukraine despite its superiority in personnel and resources within the air force compared to Ukraine? Previous research mentions the failed SEAD/DEAD operations as a contributing factor, yet these studies have focused on the strategic and operational levels. This study examines the factors contributing to the failed SEAD/DEAD operations at the tactical level. This is conducted through a qualitative text analysis using a theoretical framework derived from Warden and Pape, as well as a study by Bucki. The factors examined in the operations include; high-technology combat aircraft and missiles, the ability to conduct low-altitude flying, the position of airbases relative to the operational area, disabling sensors, intelligence, and electronic warfare capabilities. The results indicate that Russia did not achieve any of these factors except for positioning. However, this did not prove advantageous as the ability to conduct longer low-altitude flights was limited.

The research presented in this dissertation is on the development and application of advanced reduced rank adaptive signal processing techniques for high data rate wireless code division multiple access (CDMA) communications systems. This is an important area of research in the field of wireless communications. Current systems are moving towards the use of multiple simultaneous users in a given channel to increase system capacity as well as spatial and/or temporal diversity for improved performance in the presence of multipath and fading channels. Furthermore, to accommodate the demand for higher data rates, fast signal processing algorithms are required, which often translate into blind signal detection and estimation and the desire for optimal, low complexity detection techniques. The research presented here shows how minimum mean square error (MMSE) receivers implemented via the multistage Wiener filter (MWF) can be employed at the receiving end of a CDMA system to perform multiuser detection (MUD) or interference suppression (IS) with no loss in performance and significant signal subspace compression better than any previous reduced rank techniques have shown. This is important for optimizing performance because it implies a reduction in the number of required samples, so it lessens the requirement that the channel be stationary for a time duration long enough to obtain enough samples for an accurate MMSE estimate. The structure of these receivers is derived for synchronous and asynchronous systems for a multipath environment, and then it is shown that implementation of the receiver in a reduced rank subspace results in no loss in performance over full rank methods. It is also shown in some instances that reduced rank exceeds full rank performance. Multiuser detectors are also studied, and the optimal reduced rank detector is shown to be equivalent to a bank of parallel single user detectors performing interference suppression (IS). The performance as a function of rank for parallel and joint multiuser detectors are compared. The research is then extended to include joint space-code (i.e. a joint multiuser detector) and joint space-time processing algorithms which employ receiver diversity for low complexity diversity gain. Non-linear techniques, namely serial interference cancellation (SIC) and parallel interference cancellation (PIC), will also be studied. The conventional matched filter correlator will be replaced by the MWF, thereby incorporating IS at each stage of the interference canceller for improved performance. A closed form expression is derived for the probability of error, and performance gains are evaluated. It will be further shown how the receiver structure can be extended when space-time codes are employed at the transmitter for additional diversity gain with minimal impact on complexity. The MMSE solution is derived and implemented via the MWF with some examples. It is believed that these new techniques will have a significant impact on the design of fourth generation (4G) and beyond cellular CDMA systems. / Ph. D.

The optical power of satellites such as the Hubble telescope is directly related to the size of the primary mirror. However, due to the limited capacity of the shuttle bay, progress towards the development of more powerful satellites using traditional construction methods has come to a standstill. Therefore, to allow larger satellites to be launched into space significant interest has been shown in the development of ultra large inflatable structures that can be packaged inside the shuttle bay and then deployed once in space. To facilitate the packaging of the inflated device in its launch configuration, most structures utilize a thin film membrane as the optical or antenna surface. Once the inflated structure is deployed in space, it is subject to vibrations induced mechanically by guidance systems and space debris as well as thermally induced vibrations from variable amounts of direct sunlight. For the optimal performance of the satellite, it is crucial that the vibration of the membrane be quickly suppressed. However, due to the extremely flexible nature of the membrane structure, few actuation methods exist that avoid local deformation and surface aberrations. One potential method of applying damping to the membrane structure is to use magnetic damping. Magnetic dampers function through the eddy currents that are generated in a conductive material that experiences a time varying magnetic field. However, following the generation of these currents, the internal resistance of the conductor causes them to dissipate into heat. Because a portion of the moving conductor's kinetic energy is used to generate the eddy currents, which are then dissipated, a damping effect occurs. This damping force can be described as a viscous force due to the dependence on the velocity of the conductor. While eddy currents form an effective method of applying damping, they have normally been used for magnetic braking applications. Furthermore, the dampers that have been designed for vibration suppression have typically been ineffective at suppressing structural vibration, incompatible with practical systems, and cumbersome to the structure resulting in significant mass loading and changes to the dynamic response. To alleviate these issues, three previously unrealized damping mechanisms that function through eddy currents have been developed, modeled and tested. The dampers do not contact the structure, thus, allowing them to add damping to the system without inducing the mass loading and added stiffness that are typically common with other forms of damping. The first damping concept is completely passive and functions solely due to the conductor's motion in a static magnetic field. The second damping system is semi-active and improves the passive damper by allowing the magnet's position to be actively controlled, thus, maximizing the magnet's velocity relative to the beam and enhancing the damping force. The final system is completely active using an electromagnet, through which the current can be actively modified to induce a time changing magnetic flux on the structure and a damping effect. The three innovative damping mechanisms that have resulted from this research apply control forces to the structure without contacting it, which cannot be done by any other passive vibration control system. Furthermore, the non-contact nature of these dampers makes them compatible with the flexible membranes needed to advance the performance of optical satellites. / Ph. D.

Females continue to be underrepresented in leadership despite research demonstrating that leadership effectiveness does not vary by leader gender (Paustian-Underdahl et al., 2014). The current study examines the gender bias in leadership through the lens of leadership perceptions and evaluations; in particular, how perceivers' ratings of a leader would change as a function of the leader's gender. Leadership judgments are based on the leader prototype activated in the perceiver and how consistent/inconsistent the leader is perceived to be with the activated prototype (Lord et al., 2001). Due to the mismatch between the communal-oriented female gender stereotype and agentic-oriented expectations of a successful leader (Eagly and Karau, 2002), it was expected that the female leader would be rated more negatively than the male leader. Furthermore, the perceiver's gender and prior engagement in emotion suppression are investigated as two additional factors that could bias information processing when evaluating leaders. Male perceivers, who tend to hold a stronger masculine understanding of leadership (Koenig et al., 2011), were expected to evaluate the female leader more harshly than the male leader. Additionally, those depleted of their finite self-regulatory resources due to prior emotion suppression (i.e. being in a state of ego depletion; Baumeister et al., 1998) were predicted to rely more heavily on their stereotypes when making subsequent judgments; hence, ego-depleted individuals would demonstrate more bias in their ratings of the female leader relative to the male leader. In the current study, participants were randomly assigned to an emotion suppression or no suppression condition as they watched funny clips from the comedy series "The Office''. Then, they watched four business videos featuring a leader and three business managers. Participants were also randomly assigned to one of the two versions of the business videos portraying either a male or female leader. Leadership perception and leader effectiveness ratings were collected after each of the four business videos, and leader competence and leader warmth ratings were measured once after all four videos. Additionally, behavior recognition accuracy of agentic and communal leadership behaviors that were displayed in the four business videos was assessed. Contrary to expectations, the study findings demonstrate a dominant female leader effect; the female leader was evaluated more favorably than the male leader on all four leader judgments. This was observed both within the repeated measures and overall leadership ratings. An ego depletion effect was also observed; ego-depleted individuals showed lower accuracy in behavior recognition ratings and more leniency in leader warmth ratings. Furthermore, ego-depleted individuals showed less discernment by giving higher leader effectiveness ratings over time compared to non-ego-depleted individuals. Perceiver gender did not meaningfully affect leadership judgments. The unexpected pattern of bias in favor of the female leader instead of against her suggests that the nature of gender and leader stereotypes may be changing; the incongruence between the female stereotype and leader expectations may be decreasing, leading to more favorable evaluations of the female leader by both male and female perceivers. Moreover, the ability to provide fair and accurate judgments of leader effectiveness is reduced when depleted. Limitations and future research directions are discussed. / Doctor of Philosophy / The gender gap persists in leadership; although leader effectiveness has not been found to vary by the leader's gender, female leaders tend to be perceived and evaluated more negatively than male leaders. One reason for this is the mismatch between societal expectations for how women are ideally expected to behave and the expectations associated with a successful leader. In this study, gender bias in leader judgments and behavior recognition accuracy is examined by a leader's gender. Additionally, the perceiver's gender and prior engagement in emotion suppression are studied as two additional factors that can influence bias in leader ratings. Study findings demonstrate an unexpected but dominant female leader effect, where the female leader was perceived as more leader-like and rated more effective, more competent, and warmer than the male leader by both male and female perceivers. The amount of self-regulatory resources available also affected subsequent processing capabilities; those who suppressed their emotions and were depleted of their self-regulatory resources were less accurate in their behavior recognition ratings and were more lenient in their leader warmth ratings. Future research should explore if and how the nature of gender and leader stereotypes are changing, as evaluations of female leaders may not be as negatively-biased as it was previously.

There is an increasing demand for robotics in dangerous and extreme conditions to limit human exposure and risk. An area in which robots are being considered as a support tool is in firefighting operations to reduce the number of firefighter injuries and deaths. One such application is to increase firefighting performance through localized fire suppression. This research focused on developing an autonomous suppression system for use on a mobile robotic platform. This included a real-time close proximity fire suppression approach, appropriate feature selection and probabilistic classification of water leaks and sprays, real-time trajectory estimation, and a feedback controller for error correction in longer-range firefighting. The close proximity suppression algorithm uses IR fire detection IR stereo processing to localize a fire. Feedback of the fire size and fire target was used to manipulate the nozzle for effective placement of the suppressant onto the fire and experimentally validated with tests in high and low visibility environments. To improve performance of autonomous suppression and for inspection tasks, identification of water sprays and leaks is a critical component. Bayesian classification was used to identify the features associated with water leaks and sprays in thermal images. Appropriate first and second order features were selected by using a multi-objective genetic algorithm optimization. Four textural features were selected as a method of discriminating water sprays and leaks from other non-water, high motion objects. Water classification was implemented into a real-time suppression system as a method of determining the yaw and pitch angle of a water nozzle. Estimation of the angle orientation provided an error estimate between the current path and desired nozzle orientation. A proportional-integral (PI) controller was used to correct for forced errors in fire targeting and performance and response was shown through indoor and outdoor suppression tests with wood-crib fires. The autonomous suppression algorithm was demonstrated through fire testing to be at least three times faster compared with suppression by an operator using tele-operation. / Ph. D.

Polyimides epitomize one of the most versatile high-performance engineering polymers. Polyimides are inherently mechanically robust, chemically inert, and thermooxidatively stable to 400+ °C depending on their chemical structure, enabling their function in numerous aerospace, electronic, medical, and flame-retardant applications. Polyimides can be highly modular even within synthetic limitations, which promotes and sustains innovative research. One recent interest concerns the innovation of fire suppression foams. Aqueous film-forming foams (AFFFs) are regularly sought when engaging liquid fuel (gasoline, jet fuel) fires. AFFFs utilize perfluorinated compounds (PFCs) like perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), which exhibit toxicity, bioaccumulation, and persistence in the environment resulting in the presence of fluorosurfactant chemicals in environments either through direct or secondary exposure via chemical migration. Recently, the USEPA has even detected PFAS in drinking water at hundreds of military training facilities and civilian airports. While fluorinated compounds provide desirable thermooxidative stability and excellent fire retardancy, the environmental impact imposed by these chemicals strongly encourages research that targets the complete removal of PFCs in conventional formulations. This thesis focuses on the fundamental development of water-soluble sulfonated polyimide (sPI) and poly(amic acid) (sPAA) systems for next-generation polymer-based fire suppression foams. The use of sulfonated monomers and poly(amic acid) salt formation enables tunable structures and water solubilities. The polymers maintain competitive thermal stabilities to conventional polyimides and, when combined with readily available, non-toxic surfactants (SDS), produce stable foams. The MIL-F-24385F performance requirement evaluates foam quality/stability, drainage time, and burnback resistance to access viability and provides comparison to other systems; preliminary testing shows that sPI/sPAA formulations perform well. Solution rheology offers insights into fundamental scaling relationships of specific viscosity vs. concentration in both salt and salt-free solution that are important to future foam development. Additionally, the structural nature of the sPIs/ sPAAs allows for their modification with phosphonium moieties or siloxanes, which are slated to have positive effects on performance. Overall, these sPIs and sPAAs provide a promising platform for the future direction of fire suppression foams. / Master of Science / High-performance polymers are used in the most demanding of engineering applications. Polyimides represent one of the most versatile high-performance polymers. Polyimides are mechanically strong, chemically inert, and resistant to extreme temperatures depending on their chemical structure, allowing their use in numerous aerospace, electronic, medical, and flame-retardant applications. Polyimides are synthetically versatile, which enables the discovery of new uses after decades of research. One new targeted application is fire suppression foams. Aqueous film-forming foams (AFFFs) are the standard when battling liquid fuel (gasoline, jet fuel) fires. AFFFs contain perfluorinated compounds (PFCs), which are toxic and persist in the environment; they migrate easily to affect indirectly exposed ecosystems. Recently, the USEPA has even detected PFAS in drinking water at hundreds of military training facilities and civilian airports. While AFFFs with PFCs are highly effective, replacement materials are needed. This thesis focuses on the fundamental development of water-soluble sulfonated polyimide (sPI) and poly(amic acid) (sPAA) systems for fire suppression foams. The polymers remain thermally stable, and when combined with readily available surfactants (SDS), produce stable foams. Preliminary fire testing shows that sPI/sPAA formulations perform well against military specifications. Solution rheology (study of flow) explores the solution behavior of sPI, which offers insights into fundamental concentration-viscosity relationships that are important to future foam development. Additionally, the structural nature of the sPIs/ sPAAs allows for their modification with phosphonium groups or siloxanes, which changes their characteristics. Overall, these sPIs and sPAAs are initially promising for the future direction of fire suppression foams.

No / A series of analogues of cryptolepine (1) have been synthesized and evaluated for their in vitro antiplasmodial and cytotoxic properties. The IC50 values of several compounds (11a, 11k¿m, 11o, 13) against Plasmodium falciparum (strain K1) were <0.1 ¿M, 5¿10-fold lower than that of 1 but their cytotoxicities were only 2¿4 times greater than that of 1. Compounds with a halogen in the quinoline ring and a halogen or a nitro group in the indole ring have enhanced antiplasmodial activity. In mice infected with P. berghei, the 7-bromo-2-chloro (11k) and 2-bromo-7-nitro (13) derivatives of 1 suppressed parasitemia by >90% at doses of 25 mg kg-1 day-1 with no apparent toxicity to the mice. 2,7-Dibromocryptolepine (15) was evaluated at several dose levels, and a dose-dependent suppression of parasitemia was seen (ED90 = 21.6 mg kg-1 day-1). The antimalarial mode of action of 1 appears to be similar to that of chloroquine and involves the inhibition of hemozoin formation. A number of analogues were assessed for their effects on the inhibition of ß-hematin (hemozoin) formation, and the results were compared with their antiplasmodial activities having taken account of their predicted accumulation into the acidic parasite food vacuole. No correlation was seen (r2 = 0.0781) suggesting that the potent antimalarial activity of compounds such as 15 involves other mechanisms in addition to the inhibition of hemozoin formation.

Yes / Glycogen synthase kinase-3 (GSK3) is over-expressed and hyperactivated in non-small cell lung carcinoma (NSCLC) and plays a role in ensuring the correct alignment of chromosomes on the metaphase plate during mitosis through regulation of microtubule stability. This makes the enzyme an attractive target for cancer therapy. We examined the effects of a selective cell-permeant GSK3 inhibitor (CHIR99021), used alone or in combination with paclitaxel, using an in vitro cell growth assay, a quantitative chromosome alignment assay, and a tumor xenograft model. CHIR99021 inhibits the growth of human H1975 and H1299 NSCLC cell lines in a synergistic manner with paclitaxel. CHIR99021 and paclitaxel promoted a synergistic defect in chromosomal alignment when compared to each compound administered as monotherapy. Furthermore, we corroborated our in vitro findings in a mouse tumor xenograft model. Our results demonstrate that a GSK3 inhibitor and paclitaxel act synergistically to inhibit the growth of NSCLC cells in vitro and in vivo via a mechanism that may involve converging modes of action on microtubule spindle stability and thus chromosomal alignment during metaphase. Our findings provide novel support for the use of the GSK3 inhibitor, CHIR99021, alongside taxol-based chemotherapy in the treatment of human lung cancer. / Cancer Research UK Project Grant (C16929/A14402) and the Elizabeth Blackwell Institute, through its Wellcome Trust ISSF Award (105612/Z/14/Z). The Imperial NIHR/Biomedical Research Centre and the CR-UK/Dept of Health funded Imperial Experimental Cancer Medicine Centre.

Despite the American Academy of Pediatrics’ (2016) recommendation to limit screen exposure in the early years, toddlers’ screen use exceeds these guidelines (Rideout & Robb, 2020). Given the significant role of parental media use in children’s exposure to screens (Domoff et al., 2020; Lauricella et al., 2015), it is important to understand the factors that contribute to parental screen use. Digital technologies have been posited as tools for emotion regulation (Wadley et al., 2020), suggesting that parental emotion regulation may serve as a significant determinant of parental media use. Prior studies have shown the association between emotion regulation strategies and different types of screen use, including non-interactive and interactive media (Extremera et al., 2019; Rozgonjuk & Elhai, 2021). It has also been suggested that the role of emotion regulations strategies may differ by personality traits (Gross & John, 2003). However, limited research to date examined these associations with the focus on parents of toddlers. Therefore, the purpose of this study is to examine the association between parents’ emotion regulation strategies on their screen use and the moderating role of personality traits in this association. This study used secondary data collected from an online survey of 296 mothers of children between 18 to 36 months in the United States. Linear regression models were fitted to examine the association between emotion regulation strategies and parental screen use, with a focus on two specific regulation strategies and interactive and non-interactive screen use. They were founded that cognitive reappraisal was not related either non-interactive and interactive screen uses and that expressive suppression was only associated with non-interactive screen use. Cognitive reappraisal was related to agreeableness and expressive suppression was related to extraversion. No moderator roles of agreeableness on the association between cognitive reappraisal and both types of screen use and extraversion on the association between expressive suppression and both types of screen use were found. Future research is needed to test the possible biases resulting from the self-report technique, understand the causation between emotion regulation strategies and screen use, and include the context of screen media for deeper understanding. / Toddlers use screens, like smartphones and tablets, more than recommended by American Academy of Pediatrics (2016), and understanding why may help to support children’s healthy developmental outcomes. How much parents use screens is related to how much children use screens (Lauricella et al., 2015), making it valuable to examine parents' screen use. Screens may help individuals learn to control or regulate their emotions (Wadley et al., 2020), suggesting that parental emotion regulation may be one reason that parents use screens. Prior studies have shown that emotion regulation is related to different types of screen use, including non-interactive (e.g., video viewing) and interactive media (e.g., playing video games; Extremera et al., 2019; Rozgonjuk & Elhai, 2021). I examined two strategies of emotion regulation: cognitive reappraisal, which is reinterpreting the situation that cause emotions, and expressive suppression, which is hiding and inhibiting emotions. It has also been suggested that the role of emotion regulations strategies may differ by personality traits (Gross & John, 2003). However, limited research to date examined these associations with the focus on parents of toddlers. The current study examined how maternal cognitive reappraisal and expressive suppression related to both non-interactive and interactive screen use and moderating role of personality traits on these relations. Mothers of toddlers (N = 296; M_age = 31.8 years) completed surveys for this study. Findings showed that cognitive reappraisal was not related to either non-interactive or interactive screen use, although it was related to agreeableness and that expressive suppression was related to non-interactive screen use and extraversion. Associations between these two emotion regulation strategies and both types of screen use were not moderated by personality characteristics. Further explanation is needed to examine the context of screen media and the causal links between emotion regulation strategies and screen use.

Functional response is the framework thorough which we can quantify how predator hunting behaviors such as rate of successful attack and time spent handling prey interact with prey density to determine the rate at which prey are killed. Cheetahs are mesopredators and their behavior can be shaped by the need to avoid larger predators while hunting relatively large bodied and mobile prey. I used data from 34 years of observed cheetah hunts in Serengeti National Park in Tanzania to investigate how reproductive condition, prey density, seasonality, and the proximity of larger predators affect cheetah kill rates, probability of successful attack, and time spent handling prey. Mothers with cubs had an asymptotic Type II functional response where kill rate increased but eventually leveled-off at high prey densities, while cheetahs without cubs had a dome shaped Type IV functional response where kill rates actually declined at high prey density. Probability of successful attack on prey was higher for mothers with cubs, and increased slightly with prey density. Mothers with cubs had different prey handling behavior than other cheetahs. Cheetah mothers spend longer at kills then other cheetahs despite the risk that the carcass can attract lions and hyenas that could steal the carcass and potentially kill her cubs. Mothers must make sure their cubs have sufficient time at the carcass to eat their fill, thus they minimize risk from larger predators by being vigilant. In contrast, cheetahs without cubs are unconcerned with cub predation and can eat quickly to minimize the risk of kleptoparasitism. My results show how the pressures of cub rearing and coexisting with larger carnivores differentially shape the hunting behavior of cheetahs, and suggest that intensity of mesopredator suppression may depend on individual variability. This is the first time the functional response for a large mesopredator, has been quantified and the first time a dome shaped response has been recorded in a mammal. My work shows the value in accounting for individual variability in functional response and how linking of carnivore hunting behavior to multiple species interactions advances our understanding of how classical ecological theory applies to wild ecosystems. / Ph. D. / One of the most basic interactions between species is when one kills and eats another. Determining how many prey a predator kills is challenging, especially because it is difficult to observe hunting behavior in nature. To assess killing rates, we need information on prey density, the rate predators attack prey, and how long they spent killing and eating it. In smaller bodied predators (a.k.a. mesopredators), those behaviors are often influenced by the presence of larger, dangerous predators. I used 34 years of data on wild cheetahs in Serengeti National Park in Tanzania to examine whether their hunting behavior was influenced by having cubs, the proximity of lions and hyenas, and the season. I assessed how these factors affect the relationships between cheetah kill rates and gazelle density, the probability of a successful attack, and the time cheetahs spend handling their prey. I found that cheetah hunting behavior is largely shaped by whether or not they have cubs. Mothers’ kill rates are higher than cheetahs without cubs and stay high as gazelle densities increase. In contrast, the rate cheetahs without cubs kill declines at high gazelle density, the first time this relationship has been recorded in a wild mammal. Once prey are dead, mothers spend more time at the kill in order to ensure their cubs get enough time to eat. However, being at the kill is risky because lions and hyenas can arrive and kill her cubs. To minimize risks to cubs at the kill, mothers are more vigilant for predators than other cheetahs. Cheetahs without cubs spend less time at the kill, eating quickly without being vigilant. My results show how living in a landscape with multiple larger predators and mobile prey shapes the hunting behavior of all cheetahs, while providing detail on how having cubs can drive differences in those behaviors among individuals. The patterns of behavior seen in cheetahs may be indicative of how mesopredators alter hunting behavior to cope with pressures from larger predators. This is relevant as we craft conservation and management policies that take into account relationships among multiple carnivore species and their prey.