Crosstalk is defined as an unwanted coupling between the conductors. By this it is meant that signals from one of the signal conductors (a generator in this case) are coupled to another signal conductor (receptor), or conductors (receptors), depending on the number of conductors in the vicinity of the generator. Crosstalk in this way affects the signal level on the receptor and thereby affects the total system performance within the system. This can happen in several ways, one of which is through edge coupling. Edge coupling is a process where two signal conductors are placed beside each other in the same layer while the ground conductor could have been placed either under these conductors, in a separate layer like Mclin (Microstrip coupled lines) and Sclin (Coupled striplines), or beside the signal conductors as in Cpwcpl2 (Coplanar wave guide coupled lines). This then means that edge coupling occurs through the sides where the generator and the receptor are facing each other. Broadside coupling is another way, where it occurs when the signal conductors are broadside faced to each other in different layers with reference planes above and below these signal conductors. Coupling of the signals from the generator to the receptor can occur through capacitive coupling or inductive coupling. Capacitive coupling, also known as electrical coupling, occurs due to the difference in the characteristic impedance of the generator (usually 50 or 100 §Ù) and its heavy load (1 k§Ù or more) which results in high voltage difference between the generator and the reference conductor (ground). This leads to the creation of a charge across the generator and the receptor-facing sides and finally results in the electric field coupling between them. On the other hand, inductive coupling, also known as magnetic coupling, occurs when the load is less than the characteristic impedance of the generator, and this thereby results in a heavy current flow through the generator which in return results in a strong magnetic field around itself and so leads to magnetic coupling to the receptor. The aim in this thesis is to measure both the capacitive and inductive coupling load¡¯s impacts on both the edge coupling and the broadside coupling models through crosstalk on the receptor. This thesis starts with the background and corresponding theory and equations to the crosstalk coupling. Later on it tests both the edge- and broadside coupling models with different physical properties exploitation. Inductive and capacitive loads are used to measure the resulting crosstalk coupling. Particularly to see the effect of capacitive and inductive coupling in reality in multi layered PCB, a Sbclin (Broadside coupled striplines) model has been used with different angular placement of the generator. Finally mclin physical models are compared with the simulated models and corresponding differences are discussed. It can be concluded that crosstalk effect increases or decreases with physical properties exploitation. Crosstalk also increases with the wrong termination of the load.

The results obtained by this new method are shown to be able to account for most of the shortcomings of the earlier methods, in particular their failure satisfactorily to explain the quenching of luminescence in cis-polyacetylene and their poor predictions of the relative strengths of the two photoinduced absorption peaks in polythiophene. The ability of trans-polyacetylene (t-PA) to support a novel type of dynamic defect known as a breather is also verified. A quantitative estimate is made of the mobility of the fundamental defect in t-PA, known as a soliton, and this is in good agreement with experiment.

No description available.

No description available.

Various types of mammalian cells have an exceptional ability to adapt to externally applied mechanical stresses and strains. Because of this adaptation, cells can maintain their endogenous cytoskeletal stress at a preferred (homeostatic) state. This homeostasis of mechanical stress in cells, also known as tensional homeostasis, is essential for normal physiological functions of cells and tissues and provides protection against certain diseases. Recent experimental studies revealed a novel finding that isolated endothelial cells cannot maintain tensional homeostasis, whereas multicellular clusters can. Increasing size of the multicellular clusters played a critical role in attenuating temporal fluctuations of intracellular tension as it approached homeostasis. Here, we propose to interpret these experimental results with simple mathematical models and to gain insight into factors that contribute to homeostasis. The proposed models investigate solely on how mechanical interactions between cells influence tensional homeostasis and do not consider other physical and chemical factors such as biochemical signaling and substrate rigidity. Results of our model corroborated our earlier experimental findings that tensional homeostasis is multicellular phenomenon. We were able to identify two mechanisms that influence tensional homeostasis in confluent clusters, namely statistical averaging of stress fluctuations and stress buildup in the cluster that resulted from unbalanced portion of cell-substrate tractions at the cluster boundaries. To further investigate the role of cell-cell interactions in tensional homeostasis, we conducted traction measurements in thrombin-treated endothelial cells using micropatterned traction microscopy. Our expectation was that the presence of thrombin would stimulate cellular contractility to the point of severance of cell-cell adhesions. To our surprise, the cell-cell junctions remained intact. However, the measurements revealed a threshold in the cluster size after which attenuation in cellular tension rapidly progressed. The underlying mechanism that caused the presence of a threshold is still unknown. Current efforts of our research group are dedicated to reveal and understand those mechanisms.

First popularized in the 1970s, transition metal-catalyzed cross-couplings now constitute staple reactions for the formation of carbon-carbon and carbon-heteroatom bonds. Recent endeavours in the field have been invested towards expanding the range of compatible coupling partners, with the aim of accessing complex molecules from simple, widely available starting materials. Notably, esters represent an attractive class of alternative coupling partners compared to traditional aryl halides, due to their ubiquity and robustness. Moreover, different cleavage modes can be accessed with esters. Which bond cleavage occurs is highly dependent on which catalyst is used, providing an opportunity to quickly access diverse products from a common precursor. Chapter 1 of this thesis provides a literature overview of cross-couplings with carboxylic acid derivatives to contextualize our contributions described in Chapter 2 and 3. Chapter 2 describes the Pd-catalyzed cross-coupling of phenyl esters with alkyl boranes. Two reaction modes are enabled, namely C(acyl)–O bond activation with carbonyl-retention and C(acyl)–O bond activation with decarbonylation. As such, both alkyl ketones and alkylated arenes are accessed selectively by simple changes in the catalytic system. The disclosed reaction is applied to the diversification of bioactive molecules and discussed in light of recent mechanistic studies of related transformations. In Chapter 3, the first additive-free Ni-catalyzed amidation and transesterification of methyl esters are disclosed. In both transformations, a simple Ni catalyst enables widely available methyl or ethyl esters to be converted into value-added products, producing methanol as the only stoichiometric waste by-product. The Ni-catalyzed amidation protocol strongly contrasts wasteful yet common methods used to convert methyl esters into amides, involving wasteful hydrolysis and coupling with stoichiometric activating agents.

Les boucles fluides diphasiques à pompage thermo-capillaire (BFDPT) ont été identifiées comme des solutions de transport de chaleur alternatives dans le contexte des transports terrestres, afin de répondre au contrôle thermique de l’électronique de puissance. Le développement d’une architecture particulière de boucle, mettant à profit la gravité, a été mené afin d’adapter la capacité des BFDPT à ces nouvelles contraintes. Les investigations expérimentales et numériques ont permis de montrer le fort potentiel de ce nouveau système et amènent aujourd’hui à sa future utilisation industrielle.La conception d’une nouvelle boucle expérimentale avec trois évaporateurs, en parallèle, a pour objectif d’élargir son utilisation comme « bus thermique ». Le banc expérimental, finement instrumenté, a pour but d’approfondir les études antérieures et de caractériser les réponses de cette boucle à une application de puissance, en régime permanent et transitoire, avec un ou plusieurs évaporateurs. L’analyse des résultats obtenus met en évidence les nombreux couplages entre évaporateurs, réservoir et condenseur,notamment lors de phases transitoires sévères, et confirme la capacité du système à gérer le contrôle thermique de l’électronique quelles que soient les puissances appliquées sur les différents composants.Les résultats du travail de modélisation, basée sur la méthode nodale, s’avèrent prédire correctement le comportement thermohydraulique transitoire de la boucle, en fonctionnement nominal, en mode mono ou multi-évaporateurs. Malgré une représentation des évaporateurs et du réservoir encore simplifiée et tributaire de l’expérience, le modèle se révèle être un très bon outil de dimensionnement et d’analyse. / Two-phase fluid capillary pumped loop (TFCPL) have been identified as heat transfers alternative solutionsfor thermal control of power electronics, in the context of ground transportation. A special gravityloop has been improved to adapt TFCPL capacity to these new terrestrial constraints. Experimentaland numerical investigations have proved the great potential of this kind of system and lead today toits upcoming industrial use.The aim is now to employ this new system as « thermal busbar ». A new experimental loop withthree parallel evaporators was built to go further into the earlier studies. Thanks to many measurementinstruments, the goal is to define steady and transient thermohydraulic responses to a power solicitationwith a mono- or multi-evaporators loop. Results highlight many coupling between evaporators, reservoirand condenser, especially during strong transient phases. The thermal control of power electronics, withdifferent range of thermal dissipation on several separate areas, is furthermore demonstrated.The developed modeling is based on nodal method. Transient thermohydraulic behaviour of the gravityloop is very well predicted by numerical results during nominal operating, with one or more evaporators.Even if evaporators and reservoir models are still simplified and depend on empirical identifications, theglobal model of the loop proves to be a great design and analysis tool.

Abstract Nuclear magnetic resonance spectroscopic structure determination of proteins has been under rapid development during the last decade. The size limitation impeding structural studies of biological macromolecules in solution has increased from 10 kDa to 30 kDa thanks to exploitation of 15N/13C enrichment. Perdeuteration of non-exchangeable protons has pushed this limit even further, allowing backbone resonance assignment of 40 to 50 kDa proteins. Most recently, transverse relaxation optimized spectroscopy (TROSY) has been demonstrated to lengthen 15N and 1HN spin transverse relaxation times significantly, especially in large perdeuterated proteins, thus extending the size limit beyond 100 kDa systems. However, determination of structurally important nuclear Overhauser enhancements (NOE) suffers from perdeuteration, due to the lower density of proton spins available, eventually leading to imprecise protein structures. Very recently, residual dipolar couplings have been used to supplement NOE information, enabling accurate molecular structures to also be obtained with perdeuterated proteins. This thesis focuses on the measurement of the structurally important 3J-coupling between 1HN and 1Hα spins, and determination of residual dipolar couplings by utilizing the novel spin-state-selective subspectral editing together with the TROSY methodology. This approach allows precise measurement of a large number of dipolar couplings in larger protonated or perdeuterated proteins.

Thesis advisor: James P. Morken / The development of boron and palladium ligands for conjunctive cross-coupling provides access to new reactivity. Some of these advances are outlined in this dissertation. Chapter one describes an enantioselective and diastereoselective palladium catalyzed conjunctive cross-coupling of β-substituted alkenyl boron “ate” complexes to afford contiguous benzylic stereocenters. “Mac” diol was discovered as a useful boron ligand in conjunctive cross-coupling by reducing unwanted Suzuki-Miyaura cross-coupling. Chapter two describes the utilization of “mac” diol in the enantioselective conjunctive cross-coupling of α-substituted alkenyl boron “ate” complexes with carbamoyl chlorides. This transformation affords tertiary, β-boryl amides, which provide a complementary approach to Mannich, aldol, and conjugate borylation products. Water was an essential additive to enable high yield and high enantioselectivity, and its reaction role was investigated. The synthetic utility of this cross-coupling was demonstrated with the asymmetric synthesis of (+)-adalinine. Chapter three describes the thought process behind discovering a new palladium ligand for conjunctive cross-coupling. Phosphinooxazolines (PHOX) are useful and inexpensive ligands for enantioselective palladium-catalyzed conjunctive cross-coupling. A stereochemical model of this cross-coupling with this ligand was examined. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

In this work, we report the study of the catalytic activity of newly prepared coordination compounds of nickel(II) (complexes were prepared by prof. Kyritsis, University of Athens). The activities in model reactions of Kumada and Suzuki coupling and polymerization of 2,5- dibromo-3-hexylthiophene were tested. For Kumada coupling, the activity is comparable with known complex [Ni(dppp)Cl2]. On the other hand, selected complexes exhibit only limited activity for Suzuki coupling. GRIM polymerization of 2,5-dibromo-3-hexylthiophene was successful. Properties of prepared polymers are comparable with polymers prepared via known route with [Ni(dppp)Cl2].