21 research outputs found
Computed Tomography–Based Quantitative Morphometry Reveals Distinct Airway Remodelling in COVID-19 versus Community-Acquired Pneumonia
Get PDFPurpose: To quantitatively characterize airway structural changes in COVID-19 and compare them to those observed in community-acquired pneumonia (CAP), using computed tomography (CT)-based Morphometry. The study aims to evaluate whether COVID-19 and CAP produce distinct patterns of airway remodelling across multiple geometric metrics. Materials and methods: High-resolution chest CT scans from 80 COVID-19 patients (stratified into low- and high-severity subgroups), 38 CAP patients, and 28 healthy controls were analysed. Airway parameters—hydraulic diameter (Dh (mm)), hydraulic ratio (Xh), airway circularity (Cr), and airway thickness (TA (mm))—were measured across the first 5–6 bronchial generations using 3D reconstruction and geodesic labelling. Statistical comparisons employed Kruskal–Wallis and regression analyses. Results: COVID-19 exhibited proximal airway enlargement but distal narrowing, contrasting with CAP’s uniform reduction in airway efficiency (p < 0.01). Xh gradients revealed compensatory adaptation in COVID-19’s major airways (steeper slope in severe cases, p = 0.013) but significant distal dysfunction (−12% Xh vs. CAP, p < 0.001). Circularity showed focal geometric distortion in COVID-19 versus CAP’s homogeneous expansion (p < 0.001). TA (mm) analysis identified diffuse thinning in COVID-19 (vs. CAP’s mild thickening, p = 0.189), with superimposed focal thromboinflammatory thickenings. Conclusions: COVID-19 and CAP induce fundamentally different patterns of airway remodelling. COVID-19 is associated with proximal airway dilation and disrupted distal tapering, whereas CAP results in uniform narrowing. These morphometric profiles may contribute to differences in airflow limitation and ventilation–perfusion mismatch, which could inform disease-specific monitoring, prognostication, and selection of therapeutic strategies. Future research should explore the relationship between these structural signatures and clinical outcomes, including recovery trajectory and long-term pulmonary function
Adapting authoritarianism: institutions and co-optation in Egypt and Syria
No full textThis PhD thesis compares Egypt and Syria’s authoritarian political systems. While the tendency in social science political research treats Egypt and Syria as similarly authoritarian, this research emphasizes differences between the two systems with special reference to institutions and co-optation. Rather than reducibly understanding Egypt and Syria as sharing similar histories, institutional arrangements, or ascribing to the oft-repeated convention that “Syria is Egypt but 10 years behind,” this thesis focuses on how events and individual histories shaped each states current institutional strengthens and weaknesses. Specifically, it explains the how varying institutional politicization or de-politicization affects each state’s capabilities for co-opting elite and non-elite individuals.
Beginning with a theoretical framework that considers the limited utility of democratization and transition theoretical approaches, the work underscores the persistence and durability of authoritarianism. Chapter two details the politicized institutional divergence between Egypt and Syria that began in the 1970s. Chapter three and four examines how institutional politicization or de-politicization affects elite and non-elite individual co-optation in Egypt and Syria. Chapter five discusses the study’s general conclusions and theoretical implications.
This thesis’s argument is that Egypt and Syria co-opt elites and non-elites differently because of the varying degrees of institutional politicization in each governance system. Rather than view one country as more politically developed than the other, this work argues that Syria’s political institutions are more politicized than their Egyptian counterparts. Syria’s political arena is, thus, described as politicized-patrimonialism. Syria’s politicized-patrimonial arena produces uneven co-optation of elites and non-elites as they are diffused through competing institutions. Conversely, the Egyptian political arena remains highly personalized as weak institutions and individuals are manipulated and molded according to the president’s ruling clique. This is referred to as personalized-patrimonialism. As a consequence, Egypt’s political establishment demonstrates more flexibility in ad hoc altering and adapting its arena depending on the emergence of crises.
This study’s theoretical implications suggest that, contrary to modernization and democratization theory’s adage that institutions lead to a political development, politicized institutions within a patrimonial order actually hinder regime adaptation because consensus is harder to achieve and maintain. It is within this context that Egypt’s de-politicized institutional framework advantages its top political elite. In this reading of Egyptian and Syrian politics, Egypt’s personalized political arena is more adaptable than Syria’s. These conclusions do not indicate that political reform is a process underway in either state
A Computational Framework to Optimize Piezoelectric Power Harvesting from a UAV Wing
Get PDFThis paper proposes a computational framework to optimize the ambient power harvesting from an unmanned air vehicle wing by means of piezoelectricity. First, the wing shape and material are selected based on specific design factors. The wing is then subjected to a vibrational analysis in order to predict the first torsional frequency required to calculate an optimum charging speed. The harvester module is then selected so that the vibration frequency of the charging speed fails within the resonance frequency of the harvester. A finite element modeling is conducted to predict the harvester output voltage during the chagrining speed. Finally, a power management circuit is designed to boost the harvester output voltage to 5V. The proposed framework was validated experimentally using the car-top rig method (error 2.18%). Twenty minutes of flight time were enough to recharge a 600mAh lithium-ion battery used to energize a 5V servomotor that controls the wing flap
The Concepts of Dār al-Islām and Dār al-Ḥarb and their Role in the Contemporary Global Ǧihād in the Understanding of Riḍwān al-Sayyid
No full textNowadays, terrorist attacks have become known worldwide and it appears that anybody anywhere can be a victim. This situation leads more than one to ask the question: ‘why do they hate us’? Based on this question, two more may be asked. Firstly, who are ‘they’? Secondly, who are ‘us’? In other words, what are the reasons that so angered ‘terrorists’ and what could be the objectives of this practice of terror? All these questions raised my desire to study the relation between the two concepts of the territory of Islam
(dar al islam) and the territory of war (dar al-harb) and their role in the contemporary global gihad according to the understanding of professor Ridwan al-Sayyid, to whom I will be referring as ‘my author’. In order to make a fair analysis of al-Sayyid’s reading of this worldwide situation, this study comprises three chapters.
In the first chapter, since my author is a Lebanese, I will be offering a historical review of Lebanon in order to situate the environment in which al-Sayyid was born and in which he is working. As we shall see, Lebanon’s history is marked by events similar to those of my topic of study. Those events to be studied appear on one hand as consequences and on the other hand as causes of the relation that exists between the two concepts and gihad.
The second chapter is my English translation of an Arabic text taken from one of my author’s books entitled: Siyasiyyat al-Islam al-mu‘asir: muraga‘at wa-mutaba‘at (‘The Politics of Contemporary Islam: Revisions and Follow Ups’) published in 1997. The translated text, which I will be referring to as ‘the text’, can be divided into two major parts. In the first part, the author shows how the definition of the two concepts engendered a discussion between three Sunni schools. Consequently, depending on how each school defined the two concepts, gihad and higra got connected or separated and were practiced or discouraged throughout the history of the spread of Islam, mainly in Islamic India, Algeria, Sudan and Libya during the European colonization. Consequently, at the level of territory, my author considers colonialism as one of the major causes of the disappearance of dar al-Islam in favour of the nation-state system of governance. However, at the conceptual level, the two concepts continued to exist even though undergoing significant changes in how they are interpreted and understood. In the second part of the text, my author shows that Muslims struggled in vain to find a substitute for dar al-Islam as a symbol of unity of the umma (Muslim community). Consequently, militant Muslims in modern time took up the task of bringing back dar al-Islam through violent acts that we call here ‘terrorism’.
In the third chapter I will argue that the causes and consequences of the relation between the two concepts and gihad constitute the origin and objectives of violent terrorism which, since it is being carried out worldwide, is termed as global gihad
CFD models of the bronchial airways with dynamic boundaries
No full textObtaining reliable CFD predictions of the bronchial flow that reflects the actual flow
within a living lung requires the development of a deforming airways model, and the
imposition of physiological subject-specific boundary conditions. This thesis addresses
these two issues by the development of dynamic CFD models of the bronchial airways
using a dynamic CT data set covering the breathing cycle of a laboratory animal. A
deformation algorithm is proposed that matches the CFD mesh of the subsequent
airway geometries generated from the dynamic CT data set. In addition, a novel
nonlinear dynamic airway model generated from a pair of CT images is introduced. The
proposed non-linear deforming model is capable of successfully capturing the non-linear
motion characteristics of the bronchial airways based on the clinical measurements of
the lung volume change. Furthermore, a technique to drive physiological subject specific
boundary conditions for the terminal surfaces of the CFD models of the
bronchial airways is introduced. The proposed technique depends on approximating the
lung volume associated to each terminal surface over several time points over the
breathing cycle based on the mechanical coupling between the bronchial airways and
the vascular tree. The computed dynamic subject-specific boundary conditions were
imposed on the terminal surfaces of the deforming airway model and the effect of wall
motion on the flow features during tidal breathing is investigated for the first time.
The outcome of this thesis is expected to improve the fidelity of the CFD predictions of
the bronchial flow compared to the actual flow within a living lung. In addition, the
availability of a new non-linear dynamic model of the bronchial airways that requires
one pair of CT images as input, which complies with the radiation dosage restrictions for
humans will facilitate the development of well-resolved CFD models of the human
bronchial airways
Non-uniform central airways ventilation model based on vascular segmentation
No full textImprovements in the understanding of the physiology of the central airways require an appropriate representation of the non-uniform ventilation at its terminal branches. This paper proposes a new technique for estimating the non-uniform ventilation at the terminal branches by modelling the volume change of their distal peripheral airways, based on vascular segmentation. The vascular tree is used for sectioning the dynamic CT-based 3D volume of the lung at 11 time points over the breathing cycle of a research animal. Based on the mechanical coupling between the vascular tree and the remaining lung tissues, the volume change of each individual lung segment over the breathing cycle was used to estimate the non-uniform ventilation of its associated terminal branch. The 3D lung sectioning technique was validated on an airway cast model of the same animal pruned to represent the truncated dynamic CT based airway geometry. The results showed that the 3D lung sectioning technique was able to estimate the volume of the missing peripheral airways within a tolerance of 2%. In addition, the time-varying non-uniform ventilation distribution predicted by the proposed sectioning technique was validated against CT measurements of lobar ventilation and showed good agreement. This significant modelling advance can be used to estimate subject-specific non-uniform boundary conditions to obtain subject- specific numerical models of the central airway flow. </p
Modelling the non-linear motion of the rat central airways
No full textAdvances in volumetric medical imaging techniques allowed the subject-specific modelling of the bronchial flow through the first few generations of the central airways using computational fluid dynamics (CFD). However, a reliable CFD prediction of the bronchial flow requires modelling of the inhomogeneous deformation of the central airways during breathing. This paper addresses this issue by introducing two models of the central airways motion. The first model utilises a node-to-node mapping between the discretised geometries of the central airways generated from a number of successive CT images acquired dynamically (without breath hold) over the breathing cycle of two Sprauge-Dawley rats. The second model uses a node-to-node mapping between only two discretised airway geometries generated from the CT images acquired at end-exhale and at end-inhale along with the ventilator measurement of the lung volume change. The advantage of this second model is that it uses just one pair of CT images, which more readily complies with the radiation dosage restrictions for humans. Three-dimensional computer aided design geometries of the central airways generated from the dynamic-CT images were used as benchmarks to validate the output from the two models at sampled time-points over the breathing cycle. The central airway geometries deformed by the first model showed good agreement to the benchmark geometries within a tolerance of 4%. The central airway geometry deformed by the second model better approximated the benchmark geometries than previous approaches that used a linear or harmonic motion model
Modelling the non-linear motion of the rat central airways
No full textAdvances in volumetric medical imaging techniques allowed the subject-specific modelling of the bronchial flow through the first few generations of the central airways using computational fluid dynamics (CFD). However, a reliable CFD prediction of the bronchial flow requires modelling of the inhomogeneous deformation of the central airways during breathing. This paper addresses this issue by introducing two models of the central airways motion. The first model utilises a node-to-node mapping between the discretised geometries of the central airways generated from a number of successive CT images acquired dynamically (without breath hold) over the breathing cycle of two Sprauge-Dawley rats. The second model uses a node-to-node mapping between only two discretised airway geometries generated from the CT images acquired at end-exhale and at end-inhale along with the ventilator measurement of the lung volume change. The advantage of this second model is that it uses just one pair of CT images, which more readily complies with the radiation dosage restrictions for humans. Three-dimensional computer aided design geometries of the central airways generated from the dynamic-CT images were used as benchmarks to validate the output from the two models at sampled time-points over the breathing cycle. The central airway geometries deformed by the first model showed good agreement to the benchmark geometries within a tolerance of 4%. The central airway geometry deformed by the second model better approximated the benchmark geometries than previous approaches that used a linear or harmonic motion model. </p
