As climate change exacerbates heat stress during the summer season, it becomes increasingly critical to develop effective strategies to safeguard the productivity of tomato plants (Solanum Lycopersicon L.). This research delves into the tools and techniques aimed at enhancing the cultivation of summer tomatoes in the coastal region of Virginia. The study explores the optimization of transplant dates, the implementation of reflective mulches, and the application of kaolin clay particle films. Field trials spanning two seasons were carried out, comparing different planting dates in May, June, and July, as well as the use of reflective, black, and white plastic mulches, both with and without foliar kaolin sprays. The findings of this study underscore the impact of transplanting tomatoes in May, demonstrating a substantial increase in yields when compared to transplanting in June and July. Reflective mulches enhanced plant height and fruit production relative to the conventional black plastic mulch. The combination of kaolin clay sprays with standard black mulch, resulting in yield increases of over 35%, rivaling the outcomes achieved with reflective and white mulch treatments. The application of kaolin did not significantly affect leaf-level physiological processes. These results highlight the significant potential of strategic early planting and the adoption of emerging heat mitigation technologies, such as kaolin clay films, in sustaining and enhancing the productivity of summer tomatoes. This becomes particularly relevant as growing conditions continue to evolve due to rising temperatures and the increasing extremity of weather events resulting from climate change. / Master of Science in Life Sciences / With the challenge of hotter summers due to climate change, finding effective ways to grow tomatoes is more crucial than ever. In our two-season study in Virginia's coastal region, we experimented with various methods to improve tomato growth in these warmer conditions. What we discovered was quite promising. Planting tomatoes in early May resulted in significantly better yields than later planting times. Using reflective mulch was beneficial too; it helped the plants grow taller and produce more fruit compared to traditional black mulch. However, the most impressive result came from combining kaolin clay spray with black mulch. This approach led to a matching of the performance of black plastic plus the combination of kaolin clay against reflective and white mulches. It's interesting to note that the kaolin spray didn't alter the basic functioning of the plants at the leaf level. These findings are encouraging. They suggest that early planting and innovative approaches like kaolin clay sprays can effectively boost tomato production, even as we contend with rising temperatures and evolving climate patterns. Embracing these strategies could be key to successful tomato farming in an era of climate change

<p dir="ltr">Following the development of laser technology in the 1960s, radiation pressure was soon employed to manipulate particles by Arthur Ashkin in the 1970s. Since then, levitated optomechanics has been widely studied across physics, engineering, chemistry, and biology. In this dissertation, we first experimentally demonstrate GHz rotation and sensing with an optically levitated nanodumbbell near a surface. Then, we propose achieving optical refrigeration below liquid nitrogen temperature using near-field Purcell enhancement.</p><p dir="ltr">The first part of this dissertation focuses on fast rotation and sensing with a non-spherical silica nanoparticle levitated near a surface. Specifically, we optically levitate a nanodumbbell at 430 nm away from a surface in high vacuum and drive it to rotate at 1.6 GHz. This corresponds to a relative linear velocity of 1.4 km/s between the tip of the nanodumbbell and the surface at sub-micrometer separation. The near-surface rotating nanodumbbell demonstrates a superior torque sensitivity of (5.0 +/- 1.1 ) x 10^-26 Nm at room temperature. Our numerical simulation shows that such an ultra-sensitive nanodumbbell levitated near nanostructures can be used to detect fundamental physics, such as Casimir torque and non-Newtonian gravity. </p><p dir="ltr">In the latter part of this dissertation, we propose that optical refrigeration of solid with anti-Stokes fluorescence can be enhanced by Purcell effect. The spontaneous emission rate of high-energy photons is Purcell enhanced by coupling with a near-field cavity. The enhanced emission shifts the mean emission wavelength and enables optical refrigeration with high-absorption cooling laser. We estimate a minimum achievable temperature of 38 K with a Yb³⁺:YLiF₄ nanocrystal near a cavity using our proposed Purcell enhanced optical refrigeration method. This method can be applied to other rare-earth ion doped materials and enable applications that require solid-state cooling below liquid nitrogen temperature.</p>

Experimental investigations were conducted with and without the presence of the surface-mounted obstacle to quantify its effects on the far wake. The obstacle chosen for this study was a 3:2 elliptical nose NACA 0020 tail wing-body (Rood body), approximately of height equal to the boundary layer thickness at one of the measurement locations of the flow. The experiments were performed by varying the Reynolds number of the flow and manipulating the pressure gradient distributions using a NACA 0012 airfoil placed within the wind tunnel test section. The measurements were acquired utilizing a spanwise traversing boundary layer rake and a point pressure sensing microphone array. The findings reveal that the presence of the obstacle introduces disruptions in the flow, such as vortex and jet regions in the wake. However, the overall flow behavior remains consistent with that of an undisturbed turbulent boundary layer, for varying Reynolds numbers and pressure gradients. Notably, an adverse pressure gradient and lower Reynolds number both accentuate the prominence of the jet and vortex region within the wake, with the trend reversing towards the other end of the spectrum. This behavior is akin to the larger turbulent boundary layer under adverse pressure gradients and lower Reynolds numbers. Furthermore, the presence of obstacles induces an increase in the overall level of the wall pressure spectrum by approximately 2 dB, regardless of the flow condition. Additionally, it leads to a deviation in the slope of the mid-frequency range of the autospectra compared to the smooth wall case. Specifically, the mid-slope frequency of an undisturbed turbulent boundary layer is steeper than that observed in the disturbed wake flow caused by the obstacle. / Master of Science / The interaction between turbulence and aerodynamic surfaces gives rise to wall-pressure fluctuations, which in turn induce structural vibrations and acoustic noise. On surfaces turbulent flows meet, antennae, flaps, and other frequently mounted measuring devices. The flow in their wake is impacted by the coherence of a turbulent boundary layer being disrupted by these impediments mounted on aerodynamic surfaces. They also alter the nature of the pressure fluctuations that are generated on the surface of interest. The far wake of a Rood Body obstacle was studied using a point pressure sensing microphone array and a spanwise traversing boundary layer rake. Experimental measurements were taken for a range of Reynolds numbers and pressure gradient environments at the Virginia Tech Stability Wind Tunnel. Results show that the boundary layer rake measurements resolve the presence of the obstacle wake successfully, by characterizing the wake structures and confirming the presence of jet and vortex regions in the wake of the obstacle. Surface pressure measurements reveal that the presence of the obstacle causes the low-frequency content of the wall pressure to be less dominant than the no obstacle case, while the high-frequency content becomes more dominant in the presence of the obstacle. The presence of obstacles also increases the overall levels of the wall pressure spectrum by approximately 2 dB.

Thesis advisor: Pablo Guerron-Quintana / This thesis consists of two self-contained essays on topics in applied macroeconomics. In the first chapter, I study how heterogeneous sensitivities to weather fluctuations and interregional production networks impact the measurement of weather shocks’ impact on economic activity in the United States. I start the analysis by building a general equilibrium model where the impact of weather fluctuations on productivity is state-sector dependent, and networks expose sectors to weather shocks from other regions through the use of intermediate inputs. Then, I quantify the relevance of these mechanisms, combining the model’s predictions with annual data on sectoral GDP and average temperatures by state from 1970 to 2019. My estimates show that models that do not consider these characteristics underestimate the aggregateimpact of weather fluctuations by at least a factor of 3. In particular, when the whole economy faces an unexpected increase in temperature of 1 Celsius degree, the contraction in economic activity increases from -0.13 to -0.37 percent once heterogeneity is considered and -1.14 percent when networks are included. In the second chapter, I propose a new methodology to disentangle between terms of trade movements caused by global shocks and those resulting from country-specific terms-of-trade fluctuations. This methodology extends the so-called maximum-share approach in two ways. Firstly, a global shock is identified as the shock with the highest explanatory power on the forecast error variance of a set of exogenous variables. This is in contrast to the typical approach of using only one variable as a source of information to identify a shock. Secondly, country-specific terms-of-trade shocks are identified as shocks that satisfy two conditions: (i) maximum explanation power on terms-of-trade variability and (ii) orthogonality to global shocks, allowing me to isolate the main drivers of terms of trade that are not related to global fluctuations. I apply this methodology to data on ten small open economies(SOEs) and show that global shocks contribute - on average- to 33 percent of their business cycle fluctuations. The contribution of global shocks to terms-of-trade variability is close to 20 percent, meaning that around 80 percent of terms-of-trade movements have country-specific origins. Interestingly, on average, country-specific terms-of-trade shocks are responsible for less than 10 percent of SOE business cycle variability. These results help to reconcile current estimates on the importance of terms of trade and suggest an intensive evaluation of the origins of terms-of-trade movements by policymakers before any intervention. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Surface flow noise results from fluid-surface interactions, manifesting as surface vibrations or far-field noise. Decomposing the surface pressure field reveals distinct components, with the sub-convective component being particularly critical due to its coupling with structural modes, inducing vibrations. This component, characterized by wavenumbers lower than convective wavenumbers, is significantly weaker than its convective counterpart, making it difficult to measure and model accurately. Existing studies rely on limited measurements, constrained by instrumentation and facility capabilities, leading to empirical wall pressure models with restricted accuracy and applicability. This study presents the first high-resolution measurements of sub-convective pressure fluctuations, enabling validation of wall pressure spectrum models. A novel measurement approach inspired by acoustic metamaterials was developed, employing sub-resonant cavity sensors that integrate seamlessly into existing geometries. These sensors, leveraging off-the-shelf pressure transducers, operate effectively in grazing flow environments without disturbing the flow. Their dynamic response, determined by geometry, can be optimized for specific flow conditions, offering versatility across applications. To minimize aliasing effects at low wavenumbers, an optimized sensor array with spanwise-elongated geometries was deployed linearly along the flow direction. Wind tunnel experiments across varying Reynolds numbers and pressure gradients provided crucial insights. Long statistical averages ($mathcal{O}(10^6delta/U_e)$) revealed the statistical characteristics of large-scale turbulent motions. Results showed an asymmetric convective ridge about the convective line, a sharp transition into the sub-convective domain, and sub-convective levels 30–35 dB below convective levels. Comparisons with existing models revealed discrepancies, with all models overpredicting measured levels. While the Chase model aligned over certain ranges, deviations highlight the need for improved wall pressure models. This study lays the groundwork for enhanced vibroacoustic analysis and model refinement through innovative measurement techniques. Overall, these measurements provide a refined insight into the nature of sub-convective pressure fluctuations and will aid in the development of more accurate wall pressure models, crucial for fluid-structure interaction analysis. / Doctor of Philosophy / Imagine traveling in a car or flying in a plane, tuning out conversations or music to focus on the background noise. What you'd mostly hear is a whooshing sound, a symphony of the vehicle's HVAC system, engines, and other mechanical components. But there's another significant, often overlooked, contributor to this noise: the fluid flowing around the vehicle. This phenomenon is not limited to cars and planes—it's also true for underwater vehicles. As air or water flows around a vehicle, it interacts with its surface through a thin layer called the boundary layer, whether it's the fuselage of an aircraft or the body of a car. This interaction generates fluctuating pressure forces on the surface, causing the structure to vibrate and produce noise. Unlike sticking your head out of a moving vehicle, which creates its own kind of noise, this source involves a complex interplay between the fluid flow and the structural dynamics of the vehicle. The vibrations generated from this interaction manifest as structural waves that travel much faster than the fluid itself. These waves, characterized by large spatial scales or low wavenumbers, depend on specific pressure fluctuations in the boundary layer to excite them. These particular fluctuations, called sub-convective or low-wavenumber pressure fluctuations, are much weaker—about 10,000 times less intense—than the turbulence carried by the flow. However, their overlap with the structural wave's characteristics allows for coupling, making them a crucial but elusive noise source. Measuring these weak fluctuations is incredibly challenging. Classical techniques often struggle because stronger noises, such as flow self-noise or external disturbances, can easily overwhelm the data. While some progress has been made using spatial filtering methods, these approaches often lack resolution and provide inconsistent results across studies, signaling the need for better techniques. This study introduces an innovative method inspired by acoustic metamaterials to measure these elusive pressure fluctuations with greater precision and reliability. By designing custom sensors based on multi-neck Helmholtz resonators, capable of filtering out unwanted noise, this approach offers a breakthrough in the field. The sensor design, working principle, and testing process under various flow conditions are detailed, providing insights into how flow speed impacts the fluctuations. Comparisons with existing models and measurements validate the findings, and updates to current models are proposed, paving the way for more accurate noise prediction and mitigation strategies in vehicles of all kinds.

The results reported in this thesis contribute to the understanding of disordered systems, to mesoscopic physics on the one hand, and to the physics of spin glasses on the other hand. The first part of this thesis studies numerically coherent electronic transport in a non magnetic metal accurately doped with frozen magnetic impurities (a low temperature spin glass). Thanks to a recursive code that calculates the two terminal conductance of the system, we study in detail the metallic regime of conduction (large conductance) as well as the insulating regime (small conductance). In both regimes, we highlight a universal behavior of the system. Moreover, a study of correlations between the conductance of different spin configurations of impurities allows us to link these correlations with correlations between spin configurations. This study opens the route for the first experimental determination of the overlap via transport measurements. A second part of this thesis deals with the study of the mean field Sherrington-Kirkpatrick model, which describes the low temperature phase of an Ising spin glass. We are interested here in the generalization of this model to quantum spins (i.e including the possibility to flip by quantum tunneling) of this classical model that was well studied during the past thirty years. We deduce analytically motion equations at the semi-classical level, for which the influence of quantum tunneling is weak, and we compare them with the classical case. We finally solve numerically these equations using a pseudo-spectral method.

Les mollusques sont des indicateurs de perturbations anthropiques et environnementales. Ce groupe de macroinvertébrés représente en outre une source importante de nourriture pour les poissons et les oiseaux aquatiques du littoral. Les hypothèses de cette étude sont que la communauté de mollusques est influencée indirectement par les tributaires agricoles et/ou par des variables environnementales (comme la dessiccation et l'exposition aux vagues) puisque ces perturbations sont susceptibles de modifier leurs sources alimentaires et leur habitat. Les indicateurs de la réponse des mollusques aux agents perturbateurs sont la composition, la diversité, la densité, ainsi que la biomasse des espèces. En septembre 2013, des mesures de paramètres physico-chimiques de l'eau ont été réalisées, et des échantillons de mollusques et de végétation aquatique ont été prélevés à 14 sites le long des rives du lac Saint-Pierre (Fleuve Saint-Laurent, Québec, Canada). Le long de la rive nord, les sites fortement exposés à l'action du vent, situés à de plus grandes élévations, affichaient une plus faible densité, biomasse et richesse spécifique de mollusques que les sites de la rive sud, en milieu plus abrité et profond. Les sites physiquement perturbés étaient caractérisés par de faibles biomasses en macrophytes submergés. Les sphaeriidae apparaissent comme des exceptions à ces patrons, montrant une abondance plus élevée aux sites presque dépourvus de macrophytes. Bien que les variables physiques et l'habitat exercent une influence déterminante sur les communautés de mollusques, les gastéropodes et les moules unionidés étaient également affectés par la dégradation de la qualité de l'eau dans le panache des tributaires agricoles. La richesse, la densité et la biomasse des gastéropodes étaient négativement influencées par des teneurs élevées de matières en suspension et de fer dissous. Les résultats de notre étude montrent que la communauté de mollusques du lac Saint-Pierre est directement affectée par l'émersion périodique, l'exposition au vent, et indirectement par l'effet de ces variables physiques sur les macrophytes qui constituent leur habitat. / Molluscs are indicators of anthropogenic and environmental disturbances and constitute an important food source for littoral fish and aquatic birds. The main hypotheses put forward for our study are that the mollusc community is impacted by the agricultural tributaries and/or by physical variables (desiccation, exposure to waves) through changes in food and habitat. The indicators used were mollusc species composition, diversity, density, and biomass. Over the course of two weeks in September 2013, we sampled physical/chemical water variables, collected aquatic vegetation and molluscs at 14 sites on both shores of Lake Saint-Pierre (St. Lawrence River, Quebec, Canada). Sites located at higher elevations, subjected to recent water level fluctuations, and exposed to wind fetch along the north shore, had lower gastropod and unionid mussel richness, density, and biomass than less-exposed sites located at lower elevations along the south shore. These physically disturbed sites were characterized by low biomasses of submerged macrophytes. Sphaerid clams appeared to be notable exceptions to these patterns, showing their highest abundances at sites almost devoid of macrophytes. In spite of the fact that physical and habitat variables exerted a strong effect on mollusc communities, gastropod and unionid mussels were additionally affected by degraded water quality originating from agricultural tributaries. Gastropod richness, density, and biomass were negatively influenced by high levels of total suspended matter and dissolved iron. Our results show that the mollusc community in Lake Saint-Pierre was primarily affected by the direct influence of periodic emersion, wind exposure, and indirectly through the effect of these physical variables on macrophyte habitat.

Exploiter des effets dépendants du temps pour induire et contrôler des courants à travers des conducteurs mésoscopiques et nanoscopiques est un enjeu majeur dans le domaine du transport quantique. Dans cette thèse, nous considérons deux systèmes de taille nanométrique pour lesquels un courant est induit grâce au couplage entre champs extérieurs dépendants du temps et le transport d'électrons. Nous étudions d'abord un problème de pompage quantique au sein d'un système à trois sites en configuration d'anneau, en considérant la possibilité d'induire un courant continu par modulation temporelle des paramètres de contrôle. Nous nous intéressons en particulier à la transition entre régime adiabatique et antiadiabatique en présence d'un mécanisme de dissipation modélisé par un couplage entre le système et un bain extérieur.Nous montrons que le modèle dissipatif admet une solution analytique complète valable pour la composante DC du courant à fréquence arbitraire. Ceci nous permet de bien comprendre comment le courant induit dépend de la fréquence de pompage. Nous nous concentrons ensuite sur un autre système de contrôle du courant exploitant le phénomène des oscillations tunnel à un électron (SETOs). Contrairement au cas précédent, ici la circulation d'un courant continu à travers un circuit comportant une jonction tunnel produit, pour le régime approprié, un courant quasi-périodique d'électrons. On étudie le spectre de bruit à température nulle d'une jonction tunnel dans différents environnements résistifs dans le but de déterminer les limites du régime des SETOs et de quantifier leur degré de périodicité. Nous généralisons par la suite les résultats à température finie et discutons des effets des fluctuations quantiques. / Exploiting time-dependent effects to induce and control currents through mesoscopic and nano\-scopic conductors is a major challenge in the field of quantum transport. In this dissertation we consider two nanoscale systems in which a current can be induced through intriguing mechanisms of coupling between excitations by external fields and electron transport.We first study a quantum pumping problem, analyzing the possibility to induce a DC response to an AC parametric driving through a three-site system in a ring configuration. We are interested in particular in the crossover between adiabatic and antiadiabatic driving regimes and in the presence of dissipation, which is accounted for by coupling with an external bath. We show that for a clever choice of this coupling the dissipative model admits a full analytical solution for the steady state current valid at arbitrary frequency, which allows us to fully understand the pumping-frequency dependence of the induced current. We then focus on a different current-controlling scheme exploiting the phenomenon of single-electron tunneling oscillations (SETOs). In this case, opposite to what happens for pumping, an AC effect, an almost periodic current of single electrons, arises through a tunnel junction circuit as a consequence of a DC bias. We study the zero-temperature noise spectrum of a tunnel junction in different resistive environments with the aim to determine the boundaries of the SETOs regime and quantify their quality in terms of periodicity. We then discuss the finite-temperature generalization and the possibility to account for the effects of quantum fluctuations.

Les fluctuations électriques des composants sont une limitation à la miniaturisation des circuits. Malgré des procédés de fabrications en continuelle évolution, les variations des caractéristiques électriques dues au désappariement entre deux dispositifs limitent les performances des circuits. Concernant les applications à faible consommation, ces fluctuations locales peuvent devenir très critiques. Dans le contexte du développement d’une technologie CMOS 90nm avec mémoire Flash embarquée pour des applications basse consommation, l’appariement de transistors MOS est étudié. Une analyse de l’impact du dopage de grille des transistors NMOS est menée. L’étude se focalise sur l’appariement en tension des paires différentielles polarisées dans la zone de fonctionnement sous le seuil. Il est démontré que cet appariement peut être dégradé à cause de l’effet « hump », c'est-à-dire la présence de transistors parasites en bord d’active. Un macro-modèle permettant aux concepteurs de modéliser cet effet est présenté. Il est étudié au niveau composant, au niveau circuit et en température. Enfin, une étude de la dégradation de l’appariement des transistors MOS sous stress porteurs chauds est réalisée, validant un modèle de dégradation. Des transistors octogonaux sont proposés pour supprimer l’effet « hump » et donnent d’excellents résultats en termes d’appariement ainsi qu’en fiabilité. / Electrical fluctuations of devices limit chip miniaturization. Despite manufacturing processes in continuous evolution, circuit performances are limited by electrical characteristics variations due to mismatch between two devices. Concerning low power applications, local fluctuations can become very critical. In the context of development of a 90nm CMOS technology with Embedded Flash memory for low power applications, MOS transistors matching is studied. A study of NMOS transistors gate doping impact is conducted. Study focuses on voltage matching of differential pairs biased under threshold. It is demonstrated that this matching can be degraded due to « hump » effect, meaning presence of parasitic devices on active edge. A macro-model allowing designers to model this effect is presented. It is studied at device level, circuit level and for different temperatures. Finally, a degradation study of MOS transistors mismatch under Hot Carriers Injection stress is performed, validating a degradation model. Octagonal devices are proposed to suppress « hump » effect and give good results in terms of matching as well as reliability.

L’objectif de la thèse est d’étudier les cycles économiques en Tunisie en se centrant principalement sur les questions suivantes : quel est leur degré de synchronisation avec les fluctuations économiques des pays développés et quels sont les mécanismes de transmission de ces fluctuations sur l’économie tunisienne ? Pour répondre à cette problématique, le travail est divisé en trois chapitres. Le premier chapitre cherche à retracer les cycles économiques tunisien comparés aux cycles économiques mondiaux, représentés par quatre pays développés (PDE) : la France, l'Italie, l'Allemagne (qui sont les principaux partenaires commerciaux de la Tunisie) et les Etats-Unis (du fait de leur poids dans l'économie mondiale). Dans le deuxième chapitre, le travail introduit l’extraction des composantes cycliques d’autres variables macro-économiques internes (globales et sectorielles) et externes à l’économie tunisienne, afin d’identifier les sources des chocs et les canaux à travers ces chocs sont transmis. Le dernier chapitre a pour objet une validation économétrique des résultats descriptifs des faits stylisés données au premier et au deuxième chapitre, et de savoir à quel degré la nouvelle synthèse néoclassique peut être appliquée à l'économie tunisienne. Les résultats des faits stylisés montrent que le cycle économique tunisien est sensible aux trois catégories de variables étudiées, réelles, monétaires et financières, confirmant ainsi la théorie de la nouvelle synthèse néoclassique. L'application des modèles, VAR structurel et modèle dynamique à composante inobservable, valide les résultats des faits stylisés. En effet, les estimations du modèle VAR structurel montrent que les trois chocs qui contribuent le plus à la variance du PIB tunisien sont les chocs d'offre, les chocs monétaires et les chocs extérieurs. Concernant l'évaluation de la synchronisation du cycle tunisien avec ceux des PDE à partir du modèle à facteur inobservable de Stock et Watson, les résultats montrent un rôle significatif du facteur commun sur le cycle tunisien. Pour les déterminants de la synchronisation du cycle tunisien avec ceux des PDE, la transmission des fluctuations des pays partenaires commerciaux paraît se faire à travers les demandes intérieures, l'indice des prix des matières premières et le taux du marché monétaire en zone euro. Les exportations et les importations tunisiennes n'ont montré un rôle significatif qu'avec le premier partenaire commercial, la France. Pour les Etats-Unis, les fluctuations sont transmises à travers deux variables "européennes", le taux du marché monétaire en zone euro et les envois de fonds des immigrés, suggérant le rôle intermédiaire des pays partenaires commerciaux européens dans la transmission des fluctuations américaines et internationales à l'économie tunisienne. / The aim of the thesis is to study the Tunisian business cycles. We focus mainly on the following questions: To what extent do they synchronize with the economic fluctuations of the developed countries and what are transmission mechanisms of such fluctuations on the Tunisian business cycles? To tackle this problem, the work is organized into three chapters. The first chapter seeks to compare the Tunisian business cycles to international business cycles, represented by four developed countries: France, Italy, Germany (which are the main trade partners of Tunisia) and the United States (due to their importance in the world economy). In the second chapter, the work introduces the extraction of cyclical components of domestic and external macroeconomic variables (global and sector levels) in order to identify the sources of shocks and channels through which these shocks are transmitted. The last chapter deals with an econometric validation of the stylized facts presented in the first and second chapter and seeks to find out the degree to which the new neoclassical synthesis can be applied to the Tunisian business cycles. The stylized facts show that the Tunisian business cycle is sensitive to three categories of variables, (real, monetary and financial variables), this result confirms the theory of the New Neoclassical Synthesis. The structural VAR model and the dynamic latent factor model validate the stylized facts. Indeed, the estimation of the structural VAR model shows that the three shocks that contribute the most to the variance of the Tunisian GDP are supply shocks, monetary shocks and external shocks. Concerning the synchronization of the Tunisian business cycle with those of developed countries according to unobservable factor model of Stock and Watson, the results show a significant role of the common factor on the Tunisian business cycle. For the determinants of synchronization of the Tunisian business cycle with those of developed countries, the transmission of fluctuations in trading partner countries seems to be carried out through domestic demand, the international price index of raw materials and the money market rates in the Euro zone. Tunisian exports and imports showed a significant role with the first trading partner, France. For the United States, the fluctuations are transmitted through two "European" variables, the money market rates in the euro zone and remittances of immigrants, suggesting the intermediary role of European trade partners in the transmission of American and international fluctuations to the Tunisian economy.