Environmental and Occupational Health Sciences Institute
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Comprehensive evaluation of emigration regimes: the case of Jordan, Tunisia, Lebanon and Morocco
No full textThis dissertation examines underexplored aspects of emigration regimes and policies enacted by sending countries, focusing specifically on Jordan, Tunisia, Lebanon, and Morocco. While existing literature predominantly addresses immigration policies of receiving nations, this study shifts the spotlight to the active role and strategic motivations behind sending states' emigration policies. Through a qualitative analysis involving official documents, migration flow data, and semi-structured interviews with 12 experts, this research delineates the evolution, mechanisms, and actors influencing emigration regimes within these Arab states. The investigation is structured around three main objectives: to trace the development of emigration policies over time; to analyze the interplay between these policies and the immigration frameworks of key receiving countries (France, Italy, Spain, Saudi Arabia, the United Arab Emirates, and the United States); and to identify the primary motivations, components, and stakeholders of emigration regimes. The findings reveal the necessity of understanding the socio-economic, cultural, historical and geopolitical factors driving the development of emigration policies. It demonstrates that a comprehensive grasp of these factors is essential for understanding the complexities of migration governance. By examining the effectiveness of these policies, the study identifies best practices and areas for improvement. Finally, it offers a methodological framework for future research, particularly in replicating this study in different contexts.Ph.D.Includes bibliographical reference
Synthesis, properties and applications of functionalized porphyrins and carboranes compounds
No full textIn the first part of the thesis, we described the design, synthesis, and characterization of five fluorinated zinc tetraphenyl porphyrins (FnZnTPPs). The compounds were fluorinated either on all ortho positions of the meso phenyl rings or in β-positions with two, four, six or eight fluorine groups. The FnZnTPPs were employed to investigate the effect of fluorine in on-surface synthesis approaches. Additionally, derivatives with bulkier substituents were synthesized and studied for a direct comparison with the corresponding fluorinated compounds. The structures and properties of the compounds were characterized by X-ray crystallography, UV-vis absorption, and fluorescence spectroscopies as well as electronic structure calculations of the ground state molecular properties. Steric and electronic effects of fluorination were also explored. Moreover, we investigated their application towards C−C bond formation on the surfaces of single metal crystals such as Cu(100), Ag(100), and Au(111) by dehydrofluorination. In the second part of the thesis, we reported two ortho-carborane triads, DMA-oCB-PhEPy and p-BrPh-oCB-PhEPy, where DMA is p-N,N-Dimethylaniline, PhEPy is 1-(p-phenylethynyl)pyrene and p-BrPh is p-Bromobenzene were studied in solution, as crystals and in the solid state. Both compounds exhibited aggregation-induced emission. The crystal structures of both triads exhibit novel non-covalent interactions between pyrene units and the carborane cages resulting in intermolecular charge transfer between the pyrene units and o-carborane moiety. Remarkably, these molecules display multiple emissive species, positioning them as potential candidates for single molecule white-light emission and thermally activated delayed fluorescence (TADF). Moreover, we also explored about how to modulate the efficiency of electron transfer in donor–bridge–acceptor (DBA) system by mid-infrared excitation. We employed carboranes (C2B10H12) as IR-sensitive bridge which connects the donor (D) and an acceptor (A) in DBA assemblies. Initially, we select a meta-carborane as the bridge(B), pyrene with a phenylethynyl unit (A) and N,N-dimethylaniline (D). The ortho-(1,2) carborane triad (DMA-oC-Preppy), meta-(1,7) carborane triad (DMA-much-PhEPy) and meta-(1,7) carborane triad (DMO-TPA-CB-ph-C2-NAP) are studied, as each will differ in D-A distance and electronic properties.Ph.D.Includes bibliographical reference
Maintaining healthy gestational weight via pregnancy tracking app: OVIA
No full textPurpose of the Project: The aim of this quality improvement project was to help expecting mothers to maintain a healthy gestational weight within the recommended guidelines provided by the Institute of Medicine (IOM) with early prenatal nutritional counseling and by using the mobile application, Ovia.Methodology: For this DNP project, 13 participants were enrolled to assess the significance of nutrition in pregnancy. All participants received a nutrition knowledge questionnaire, followed by counseling and the incorporation of the Ovia mobile application to monitor their individual progress.
Results: Women in their initial pregnancies exhibited a lower level of awareness regarding nutritional requirements during pregnancy. Greater utilization of the mobile application correlated with participants achieving weight gain on the lower end of the recommended range. Spearman Correlation test was conducted for the relationship between scores and number of pregnancy, resulting with a coefficient of 0.23 indicating that there is a weak positive relationship; meaning that those who are multiparous have more knowledge about nutritional needs in pregnancy. Pearson correlation test was conducted for the relationship between Ovia usage and weight gain, resulting with a coefficient of -0.29 meaning that there is negative weak relationship; meaning the more frequently an individual uses Ovia, the lesser the weight gain.
Implications for Practice: Incorporating mobile applications such as Ovia into clinical practice, which offers evidence-based information and a platform for women to monitor their progress, is a strategy to enhance self-efficacy and deliver a cost-effective primary preventive measure.
Keywords: Nutrition in pregnancy, excessive gestational weight gain, mobile applicationD.N.P.Includes bibliographical reference
Under pressure: the diversity and physiology of the hydrothermal vent microbiome
No full textHydrothermal vents form where warm, buoyant magma upwells from deep within the Earth and interacts across or through the crust with cold sea water. These phenomena occur globally, in all ocean basins, and in both shallow and deep water. Depending on the chemical composition of the magma or the rocks across which it interacts, there are several different vent chemistries that can ensue, but basalt hosted mafic vents are the most common. The derivative fluids form a unique chemical milieu enriched in reduced species of geological origin, while mixing with sea water sufficiently to present oxidants of sufficient strength to facilitate a habitat ~99% supported by autochthonous chemosynthesis, as opposed to the photosynthesis which facilitates the rest of the world’s trophic network. Simultaneously, as the majority of known hydrothermal vents occur in deep water, hydrostatic pressure imposes a unique set of opportunities and challenges biology must respond to in order to successfully colonize and persist within the habitat, yet hydrostatic pressure is the physical barrier condition least understood by biologists. Organisms can have one of three relationships to hydrostatic pressure; piezosensitivity, where growth is inhibited by hydrostatic pressure, piezotolerance, where growth is neither particularly supported or inhibited by hydrostatic pressure, or piezophily, where growth is stimulated by high pressure. As the cellular membranes are thought to be the parts of the cell most responsive to hydrostatic pressure, the so called ‘homeoviscous response’ or adaptations made by the cell to keep their membranes a liquid crystal are used to classify the organismal response to elevated hydrostatic pressure.
The objectives of this dissertation are to ascertain the community structure and metabolism of chemosynthetic biofilms from a deep sea hydrothermal vent, how those properties change over time and across a redox gradient, interrogate the metabolism of a novel isolate from a deep sea hydrothermal vent under in situ and experimental conditions, and to investigate the relationship to elevated hydrostatic pressure in closely related organisms from hydrothermal vents to find markers for piezophily as opposed to piezotolerance. To do so, biofilms were collected from established natural substrates (basalt, animal exteriors) as well as pioneer populations from artificial colonizers across a redox gradient at a basalt hosted deep sea hydrothermal vent, and analyzed at the metagenomics and metaproteomic levels. Pioneer populations were overwhelmingly dominated by the family Campylobacterales within the Campylobacterota (aka Epsilonproteobacteria). Over time, the population diversified at both the taxonomic and physiological levels, both within the Epsilonproteobacteria and by the recruitment of additional populations, and there appears to be niche zonation across the geochemical gradient. The most important metabolic processes were carbon fixation via the reductive TCA cycle, sulfur/sulfide oxidation, and nitrate/nitrite reduction, though numerous other processes were expressed at the proteomic level at the time of sampling including (micro)aerobic respiration, hydrogen oxidation, and heavy metal detoxification.
Subsequently, an isolate from one such biofilm was physiologically and genetically characterized and compared to the other members of the second family within the Epsilonprotoebacteria, the Nautiliales. Said isolate, Nautilia sp. strain PV-1, was found to be an obligate hydrogen oxidizing, carbon fixing, and nitrate and/or sulfur reducing thermophile, in broad concurrence with its close relatives. An integrated prophage was discovered, and efforts were made to induce it. However, this strain’s growth was also found to be highly stimulated by in situ pressures via growth in a high pressure chemostat, while not being dependent on elevated pressure for growth. As the only known piezophile among the Epsilonproteobacteria to date, and the second known facultative thermopiezophile, its closest relative at the 16S rRNA gene level, Nautilia abyssi strain PH1209T was also physiologically and genetically characterized, either to identify another piezophilic Epsilonproteobacterium, or to query the adaptations that define an organism as piezophilic or piezotolerant. While both organisms were found to be different strains of the same species, and largely exhibit corresponding metabolic and genomic similarity, strain PH1209T was found to be piezotolerant, rather than piezophilic, and to lack the integrated phage. The membrane lipid profiles of both organisms were investigated under a variety of growth conditions, and it was determined that strain PV-1 has a (thus far) unique homeoviscous response that contains some elements of the traditional ‘psychropiezophile’ response at the membrane level, and some elements of the canonical obligate thermopiezophile homeoviscous response. Thus, a tentative lipidomic definition of a facultative thermopiezophile can be put forth.Ph.D.Includes bibliographical reference
Architecture and design considerations for next-generation mobile networks with integrated edge computing
No full textThe 5G and beyond network aims to deliver higher bandwidth, lower latency and support high device density for ensuring efficient performance of next-generation services. Meeting these demands requires significant performance improvements in mobile/wireless network efficiency, performance, and functionality. In this thesis, we propose and validate networkarchitectures to overcome the limitations of the standards based network. Integrating mobile edge cloud platforms with the network supports time-critical applications such as augmented reality and autonomous vehicles by localizing compute, storage, and networking resources, thereby reducing propagation delay.
The first part of the thesis presents rearchitecting the mobile core network making it flat and distributed, without the use of vendor-specific gateways. The distributed flat core network design uses the concept of identifiers to achieve optimal routing without data packets traveling through tunnels and gateways, enabling seamless mobility and scalability. Next, a popular 5G mobile core technology, the cloud-native architecture, is analyzed to meet the diverse service requirements. The cloud-native core presents a microservice architecture for network function virtualization. It is assisted by a logically centralized orchestrator hosted in the mobile edge cloud (MEC) that proactively manages and orchestrates resources for removing control and data plane bottlenecks. The MEC orchestrator enables maximizing resource utilization and consequently helps to achieve diverse quality-of-service (QoS) requirements of NextG services.
Chapter 3 addresses technical limitations associated with the dynamic mobility of end users. Clusters of users hosting their respective services in mobile edge cloud (MEC) platforms may migrate from one access network to another. MEC faces resource assignment and load balancing challenges to support user mobility because the edge cloud is intrinsically local with limited compute capability. Therefore, a compute and network-aware lightweight resource-sharing framework with dynamic container migration, ShareOn, is proposed. The migration framework is validated using mobility data trace of San Fransisco city. The end-to-end system is implemented using a container hypervisor called LXD (Linux Container Hypervisor), executing a real-time application for detecting license plates in automobiles. A thorough migration cost analysis improves the system response time by 22% even when the edge cloud nodes are 3.5x loaded.
Chapter 4 explores the implications of using latency-sensitive applications from remote sites, as investigated through international experiments on the COSMIC platform. It was observed when applications are remotely accessed over a high-bandwidth-delay product (BDP) link, TCP over wide-area links can result in performance bottleneck, making it more difficult to meet service requirements. The service migration approach to a local edge cloud platform, closer to the target user, enhances the responsiveness of the application by 70%.
In the concluding part of the thesis, we investigate network latency in edge-based remote rendering over mobile networks and identify the bottleneck limiting the performance of latency-sensitive applications such as virtual reality (VR) gaming. We describe a proof-of-concept prototype framework developed to support and facilitate experimentation to study the components of network latency and identify the network parameters degrading VR application performance. Additionally, we enhance the quality-of-experience (QoE) for VR applications by prioritizing a traffic sub-flow; this is achieved by ensuring reliable delivery of VR tracking messages over a low-latency slice using TCP in the uplink, whileaudio and video frames are streamed over UDP in the downlink.Ph.D.Includes bibliographical reference
Electronic Raman scattering in bismuth based metals with helical spin texture
No full textThe subject of this dissertation is the investigation of the collective modes and electronic excitations in the three-dimensional Rashba metal BiTeI and the three-dimensional topological insulators BiTeSe by using polarization resolved Raman spectroscopy. In particular, I have focused on probing the collective modes and chiral electronic continua in BiTeI in the 1-1000,meV energy range and the surface phonons and surface electronic continuum in BiTeSe () . In both classes of materials, strong spin-orbit interaction results in a helical spin-texture of the electronic states, leading to several novel phenomena.
In BiTeI, the degeneracy of the bulk bands are spin-split by the Rashba interaction into two sub-bands of opposite spin-helicity, where the spin and momentum of the states are intrinsically connected. By studying the low temperature secondary emission spectra at large Raman shifts, we detected the continua of excitations between sub-bands of opposite helicity. We also observed a strong in-gap collective mode in the with A symmetry (C) at a higher energy than the lattice collective modes. The resonance and symmetry properties of this mode indicate that it is a pure plasmon mode, despite the previous understanding that naked plasmons are undetectable using Raman.
In BiTeSe, the degeneracy of the electronic bands is similarly lifted, but results in a Dirac-like band structure instead of a Rashba-like one. The Dirac-cone exists within the bulk band gap, leading to gapless metallic surface states. The broken inversion symmetry at the surface allowed both Raman and IR active modes to be detected simultaneously by the Raman probe. We used the surface phonons to probe the properties of the continuum of excitations between the spin-split bands at the surface.Ph.D.Includes bibliographical reference
Experimental study of the characteristics of a hydrogen flame from a small leak
No full textWith a rising interest in hydrogen-fueled aircraft comes many design and safety concerns. There are many problems to be solved and safety standards and precautions established if aircrafts are going to be equipped with hydrogen. To that end, the objective of this project is to understand the fundamental characteristics of hydrogen flames. More specifically, small hydrogen flames resulting from leaks in diameter of less than 2mm will be studied and their flame characteristics recorded. To simulate leak conditions, a small-scale, horizontal custom hydrogen burner was made with five interchangeable nozzles, each representing a different leak. The nozzles varied in shape between circular and slot orifices, varied in size under 2mm, and the standard leakage flow rate varied was between 1SLPM (Standard Liters Per Minute) and 5SLPM. Nozzle exit-sensor spacing was an additional parameter which was varied between 1in (25mm), 2in (50mm), and 4in (100mm). A water-cooled gardon gauge was utilized to record impinging flame heat flux and K-type thermocouples were used to record cross-sectional flame temperature. Additionally, a flame tracking software was used to estimate the horizontal flame length from the nozzle exit up to the furthest horizontal reach of the flame. Results show that the most influential parameters for leakage flames are the leak size and the flow rate of hydrogen, while the leak shape (whether a crack or a pore) has little influence on the flame characteristics. Generally, increasing standard flow rate (SFR) of hydrogen while keeping leak size constant resulted in an increase in flame heat flux and flame temperature, while increasing the leak size for a given flow resulted in a decrease in flame heat flux and flame temperature. Additionally, reducing the nozzle exit-sensor spacing generally resulted in an increase in flame heat flux while a decrease in flame temperature.M.S.Includes bibliographical reference
Dual-function radar-communication system: when the radar also communicates
No full textDual-function radar-communication (DFRC) systems use the same hardware platform and the same waveform to achieve sensing and communication simultaneously. Due to their high spectral, hardware and power efficiency, DFRC systems are prime candidates for 6G wireless systems. The contribution of this dissertation is three-fold. First, we propose a novel DFRC system design, which, unlike existing methods that are communication- or sensing-centric can flexibly trade off communication rate for improved sensing performance. Second, we study a secure DFRC system for protecting communication information against unknown eavesdroppers. Third, we propose ways to improve the performance of DFRC systems via antenna selection and the use of double-phase shifters (DPS).
The proposed DFRC system is a monostatic multiple-input multiple-output (MIMO) radar and transmits orthogonal frequency division multiplexing (OFDM) waveforms from its antennas. The system subcarriers are divided into two groups, i.e., shared and private. On a shared subcarrier, all antennas can transmit simultaneously thus efficiently exploiting the available bandwidth, while on a private one only one antenna can transmit at a time. The private subcarriers enable the construction of a virtual array with larger aperture than the physical receive array. The use of private subcarriers trades off communication rate for sensing performance. By controlling the number of private subcarriers, a flexible trade-off between communication and sensing is achieved.
As DFRC systems use the same waveform for sensing and communication, the communication information is exposed to potential eavesdroppers. To mitigate this problem, we propose to leverage directional modulation (DM) enabled by a time-modulated array (TMA) that transmits OFDM waveforms. DM can scramble the signal in all directions except the directions of the legitimate users. However, the signal reflected by the targets is also scrambled, thus complicating the extraction of target parameters. We propose a novel method to estimate target parameters from the scrambled returns. The proposed DFRC system can securely communicate with users while having high-precision sensing functionality.
A hybrid MIMO DFRC structure has fewer RF chains than antennas and can be designed to approximate the performance of a full MIMO structure at reduced hardware cost.However, such a structure may have a rank-deficient beamforming matrix, resulting in degraded sensing performance. We propose antenna selection as means to ensure a full-rank beamforming matrix, and also select the communication channels so that a high communication rate can be achieved.
Phased array is the most widely used radar and has been employed in DFRC systems due to its low cost and simple structure. In a phased array, all the antenna elements are connected to a single radio-frequency (RF) chain through phase shifters. However, the phase shifters change only the phase of the signal coming from the RF chain, which results in limited beamforming capability. To tackle this issue, we propose to feed each antenna the output of two phase shifters. This enables the control of the signal magnitude as well as the phase, introducing more degrees of freedom in beampattern design. The advantages of the DPS-phase array are demonstrated via simulations and also via experiments with a self-fabricated prototype. The performance of the DPS-phase array in multi-target remote vital sign monitoring is demonstrated.Ph.D.Includes bibliographical reference
Explainable AI for human and science
No full textArtificial Intelligence (AI) goes beyond merely making predictions. Its explainability is crucial not only for enhancing user satisfaction but also for facilitating more effective decision-making. Given the remarkable advancements in AI models and their critical roles in both human-centered applications and scientific research in recent years, the demand for explainable AI has never been greater.
Among all available methods for achieving explainable AI, this dissertation focuses on the specialized domain of counterfactual explanations. Counterfactual explanations offer a unique interpretation of systems by providing "what-if" scenarios that illuminate how a given outcome could differ if the system input were altered. The model-agnostic nature of counterfactual explanations makes them exceptionally well-suited for elucidating the intrinsic mechanisms of advanced AI systems. This is particularly critical in an era where such systems, especially those employing deep neural networks, are becoming increasingly opaque and complex.
An in-depth investigation is conducted into the applicability of counterfactual explainable AI across both human-centered and science-oriented AI models. Within the context of human-centered AI systems, such as recommender systems, the incorporation of counterfactual explanations can enhance user trust and satisfaction. This is achieved by explaining not only why the system recommends some items, but also what the users can do to change the recommendation results.This approach further enhances user engagement with the system and fosters a more interactive and controllable paradigm for human users.
In the scientific field, counterfactual explainable AI offers a valuable contribution. It helps researchers identify key factors behind model predictions in a straightforward manner and promotes trust and credibility in AI-generated outcomes, thereby accelerating both the human comprehension of natural phenomena and the pace of scientific innovation.
This dissertation offers a thorough and methodical exploration of counterfactual explainable AI, encompassing its underlying philosophy, stated objectives, methodological framework, practical applications, and evaluation metrics. First, Chapter 1 and Chapter 2 introduce the core objectives of counterfactual explanations and the attributes that define a high-quality counterfactual explanation. The theoretical foundation is largely based on the Occam's Razor principle. Then, Chapter 3 and Chapter 4 outline the methodology for generating counterfactual explanations and explore their usage in human-centered applications such as recommender systems. At last, Chapter 5 and Chapter 6 discuss their use in scientific applications such as molecule property prediction and protein structure prediction, respectively.Ph.D.Includes bibliographical reference
Towards trustworthy recommender systems
No full textRecommender systems (RS), serving at the forefront of Human-centered AI, are widely deployed in almost every corner of the web and facilitate the human decision-making process. However, despite their enormous capabilities and potential, RS may also lead to undesired effects on users, items, producers, platforms, or even the society at large, such as compromised user trust due to non-transparency, unfair treatment of different consumers, or producers, privacy concerns due to extensive use of user’s private data for personalization, just to name a few. All of these underscore a pressing need for the development of Trustworthy Recommender Systems (TRS) to alleviate or circumvent such detrimental impacts and risks.
In this thesis, we study three core dimensions of trustworthiness in RS, namely, fairness, robustness and explainability. It is important to note that these are not the only perspectives of a trustworthy recommender system. However, they are several widely discussed topics in the literature that are deeply connected with trustworthiness of an intelligent system such as recommender system. Moreover, unlike many existing works in TRS, which only consider one perspective, we mainly concentrate on studying the interplay between them. To this end, we aim to address this multi-faceted problem from three distinct angles, which are shown as follows,
• The trade-off between fairness and recommendation performance.
• The robustness of fairness under the dynamic nature of RS.
• The transparency and explainability of model fairness.
For the first angle, we seek to identify the Pareto efficient/optimal solutions to guarantee optimal compromises between utility and fairness, where a Pareto efficient/optimal solution means no single objective can be further improved without hurting the others. In addressing the second angle, we delve into the concept of “Robustness of Fairness”, which explores the capability of RS to sustain fairness in the face of various uncertainties, disturbances, and changes encountered throughout the recommendation processes. Lastly, for the third perspective, we explore the idea of “Explainable Fairness”, intending to furnish coherent explanations that can aid users, system architects, or policymakers in comprehending the reasons behind the perceived fairness or unfairness of the recommender system. Our proposed methods in this thesis have outperformed several state-of-the-art methods on numerous real-world datasets. The experimental results demonstrate the effectiveness of the proposed methods in achieving satisfying recommendation accuracy and recommendation fairness.Ph.D.Includes bibliographical reference