The convective-diffusive transport of sub-micron aerosols in an oscillatory laminar flow within a 2-D single bifurcation is studied, using order-of-magnitude analysis and numerical simulation using a commercial software (FEMLAB®). Based on the similarity between momentum and mass transfer equations, various transient mass transport regimes are classified and scaled according to Strouhal and beta numbers. Results show that the mass transfer rate is highest at the carinal ridge and there is a phase-shift in diffusive transport time if the beta number is greater than one. It is also shown that diffusive mass transfer becomes independent of the oscillating outer flow if the Strouhal number is greater than one. / Singapore-MIT Alliance (SMA)

The laws of classical mechanics show that mechanical properties are independent of sample sizes. However, based on extensive theoretical work and experimentation, it is believed that reducing the size of materials to the submicron scale can result in different mechanical properties than those found in bulk quantities. This size effect was explained by the strain gradient. Atomic simulations have shown that yield stress depends on size even in the absence of the strain gradient. All of the experiments done on material creep behaviour, reported in the literature, have been conducted in the presence of strain gradient. This thesis focuses on the fabrication methods of freestanding indium pillar samples created by two unique methods; focused ion beam (FIB) and the micro-fabrication approach. The low melting point indium metal limits the application of FIB to form the sub-micron pillars. As a result, two different micro-lithography techniques, ultra-violet radiation and electron-beam lithography, were developed to fabricate these nano-pillars. In order to monitor the creep mechanism, which was dominant in this testing, the samples were then divided into two groups: polycrystalline and single-crystal pillars, each in different sizes. These pillars will later be compressed by a nano-indenter using a flat punch. Compressive stress, strain, and stiffness of the pillars will be measured to verify if the indium mechanical behavior deviates from the bulk in the absence of strong strain gradient.

The laws of classical mechanics show that mechanical properties are independent of sample sizes. However, based on extensive theoretical work and experimentation, it is believed that reducing the size of materials to the submicron scale can result in different mechanical properties than those found in bulk quantities. This size effect was explained by the strain gradient. Atomic simulations have shown that yield stress depends on size even in the absence of the strain gradient. All of the experiments done on material creep behaviour, reported in the literature, have been conducted in the presence of strain gradient. This thesis focuses on the fabrication methods of freestanding indium pillar samples created by two unique methods; focused ion beam (FIB) and the micro-fabrication approach. The low melting point indium metal limits the application of FIB to form the sub-micron pillars. As a result, two different micro-lithography techniques, ultra-violet radiation and electron-beam lithography, were developed to fabricate these nano-pillars. In order to monitor the creep mechanism, which was dominant in this testing, the samples were then divided into two groups: polycrystalline and single-crystal pillars, each in different sizes. These pillars will later be compressed by a nano-indenter using a flat punch. Compressive stress, strain, and stiffness of the pillars will be measured to verify if the indium mechanical behavior deviates from the bulk in the absence of strong strain gradient.

The 2 micron plasmid of Saccharomyces cerevisiae resides in the nucleus as an extra-chromosomal element with a steady state copy number of 40-60 per cell. As a benign but selfish DNA element, the plasmid utilizes a self-encoded partitioning system and an amplification system to ensure its stable, high-copy propagation. The partitioning system consists of the plasmid encoded proteins, Rep1 and Rep2 and a cis-acting partitioning locus STB. The Rep proteins, together with several host factors, assembled at STB couple plasmid segregation to chromosome segregation. A plasmid lacking an active partitioning system is subject to a ‘diffusion barrier’, which causes it to be retained in the mother cell with a strong bias (mother bias). Currently available evidence favors the hitchhiking model for plasmid segregation, in which the tethering of plasmids to chromosome provides the basis for faithful plasmid partitioning. However, direct evidence to support this hypothesis has been difficult to obtain because of the small size of the budding yeast nucleus and the poor resolution of chromosomes in live cells or in chromosome spreads. In this study, we have attempted to verify the hitchhiking model using single copy derivatives of the 2 micron plasmid as reporters. We demonstrate, using two single copy reporters present in the same nucleus, that plasmid association with chromosome spreads is authentic, and is dependent on the partitioning system. By using a strategy that forces all chromosomes to stay in either the mother or the daughter compartment, we show that plasmid segregation can be uncoupled from nuclear envelope segregation. However, plasmid segregation cannot be uncoupled from chromosome segregation under this condition. This tight coupling between plasmid and chromosome segregation is consistent with the hitchhiking model for plasmid segregation. The plasmid partitioning complex is assembled de novo at STB during each cell cycle during the G1-S window. Plasmid replication or cell cycle cues that signal cellular DNA replication appear to trigger this assembly. Furthermore, there is an apparent temporal hierarchy in the association and dissociation of protein factors at STB. When DNA replication is delayed or blocked, the dissociation of factors from STB from the previous portioning cycle and the association of factors for the new partitioning cycle are delayed or blocked, respectively. The precise role of replication in plasmid segregation has not been elucidated. We have addressed this question by blocking either plasmid replication or all cellular DNA replication. We find that replication is not required for plasmid to overcome mother bias. However, replication is critical for the equal segregation of sister plasmid copies. These results provide a refinement of the hitchhiking model by suggesting that sister plasmids tether to sister chromatids in a replication-dependent manner and hitchhike on them during chromosome segregation. Finally, we have attempted to reconstitute the 2 micron plasmid partitioning system in mammalian cells with the goal of exploiting their larger nuclear size and the considerably higher chromosome resolution they provide. In experiments completed so far, we show that Rep2 expressed in COS7 cells localizes to chromosomes, and Rep1 does so in the presence of Rep2. Furthermore, they show co-localization on sister chromatids in a symmetric fashion, implying that plasmids associated with them are likely to follow suit. These observations suggest, by extrapolation, the Rep1-Rep2 assisted association of sister plasmids with sister chromatids in yeast as well, and are consistent with the refined hitchhiking model for plasmid segregation. / text

This master’s project report deals with the process development for patterning thesub-micron features using Deep-UV photolithography. Patterning of the sub-micronstructures in the resists UV26 and ZEP520A-7 has been demonstrated successfully. Using theKarl Süss-MJB4 DUV mask aligner, trenches of width down to 535 nm have been obtained.Good results have been obtained in these experiments considering the development time andthe exposure time, which are found to be shorter compared to previously published results.This provides a faster process and higher throughput. Experimental steps along with thefurther improvement areas are discussed.Equipment used include a Karl Süss-MJB4 DUV mask aligner, an optical microscope anda Scanning Electron Microscope (SEM).

A new data capturing technique for a potentially coupled bus of lines is proposed that always accommodates fast operation. The proposed method utilizes multiple reference voltages available within a line's receiving logic and the initial conditions of the involved wires in order to determine early and accurately the transmitted data in the current cycle. The presented data reading technique rarely requires repeater insertion and it can considerably accelerate signal propagation. The introduced logic at the receiver-end of a victim wire entails an affordable area overhead. Experimental results are given in the 65nm CMOS process for interconnects of various lengths. An architecture is proposed that allows for data reading with fault detection capability on lines which are likely to operate under a potentially wide range of capacitive coupling. In order to develop such a methodology, multiple reference or threshold voltages in the receiving logic of the lines are considered instead of typically one. The proposed technique utilizes the additional reference voltages to evaluate whether an intermittent fault has occurred during the capture of the transmitted data. Some combinational logic is introduced on the receiver side to accomplish this task. The mechanism is initially illustrated on a line with one adjacent aggressor. Subsequently, the case of a line with two adjacent aggressors is discussed and it is shown how to generalize the technique for wide buses. In this work the efficiency of the detection mechanism is evaluated for both single and multiple faulty occurrences. A novel circuit to treat crosstalk induced glitches on local interconnects is presented. Design irregularities and manufacturing defects on wires may result in spurious electrical events that impact the reliability of the interconnect infrastructure. The proposed methods act by dynamically adjusting the threshold voltage of the receiving gate on the victim line. The proposed technique can be used in combination with encoding algorithms on data buses. A comparative study in the 180nm CMOS process is presented that supports the applicability of the approach. Transient faults due to radiation have become increasingly observable in combinational logic. This is due to the weakening of inherent protective mechanisms that logic traditionally held against such flawed spurious events. Further boosting of such effects is increasingly probable due to the interaction of transients appearing at the inputs of logic gates. Such multiple instances of transients can arise either because of re-convergent circuit paths or because of significant reduction in the critical charge of modern technologies. The latter, in particular, makes more than one circuit nodes susceptible to the same high energy ions. A static transient propagation is employed to address possible transient interaction and to compute its worst-case effects in logic. The quantified effects of interest are the maximum duration and slope of the resulting hazards at the circuit outputs. A hardening methodology is also proposed to protect combinational logic from such events. For this purpose, filtering circuits are inserted in logic and several placement algorithms are developed and evaluated.

No description available.

Ce mémoire traite des systèmes intégrés sur puce (System-on-Chip) à faible consommation d'énergie tels que ceux qui seront utilisés dans les équipements portables de future génération (ordinateurs de poche (PDA), téléphones mobiles). S'agissant d'équipements alimentés par des batteries, la consommation énergétique est un problème critique. Ces plateformes contiendront probablement une douzaine de coeurs de processeur et une quantité importante de mémoire embarquée. Une architecture de communication optimisée sera donc nécessaire afin de les interconnecter de manière efficace. De nombreuses architectures de communication ont été proposées dans la littérature: bus partagés, bus pontés, bus segmentés et plus récemment, les réseaux intégrés (NoC). Toutefois, à l'exception des bus, la consommation d'énergie des réseaux d'interconnexion intégrés a été largement ignorée pendant longtemps. Ce n'est que très récemment que les premières études sont apparues dans ce domaine. Cette thèse présente: - Une analyse complète de l'espace de conception des architectures de communication intégrées. Sur base de cet espace de conception et d'un état de l'art détaillé, des techniques jusqu'alors inexplorées ont pu être identifiées et investiguées. - La conception d'environnements de simulation de bas et haut niveaux permettant de réaliser des comparaisons entre différentes architectures de communication en termes de consommation énergétique et de surface. - La conception et la validation d'une architecture de communication intégrée innovante basée sur le multiplexage spatial Ce dernier point a pour ambition de démontrer qu'un réseau basé sur le multiplexage spatial (SDM) constitue une alternative intéressante aux réseaux classiques principalement basés sur le multiplexage temporel dans le contexte très spécifique des architectures de communication intégrées. Nous démontrerons la validité de la solution proposée à l'aide de campagnes de simulation de haut niveau pour divers types de trafic ainsi que des simulations de plus bas niveau. L'étude concerne successivement la conception de routers SDM, des interfaces réseau et finalement d'un réseau complet. Les avantages et inconvénients d'une telle technique seront discutés en détails.

The 2 micron plasmid of the budding yeast Saccharomyces cerevisiae resides in the nucleus as an extra-chromosomal element with a steady state copy number around 40-60 per cell. As a benign but selfish DNA element, the plasmid utilizes a self-coded partitioning system and an amplification system to exhibit nearly chromosome-like stability in its host. Plasmid behavior under conditions that missegregate chromosomes suggest that the partitioning system couples plasmid segregation to chromosome segregation. However, the mechanism of this coupling has not been elucidated. A plausible model, consistent with current evidence, is the hitchhiking model, in which plasmid-chromosome tethering provides the basis for faithful plasmid partitioning. Testing this hypothesis unequivocally has been difficult, primarily because of the technical limitations posed by the small size of the budding yeast nucleus and poor resolution of chromosomes. As a result, cell biological assays based on fluorescence microscopy have had only modest success in addressing this problem. In the present study, I devised an experimental verification of the hitchhiking model using a single copy derivative of the 2 micron plasmid as a reporter. The rationale was to establish various conditions that force sister chromatids to co-segregate during mitosis in a bias-free manner or with a bias towards the daughter. The segregation patterns of plasmid sisters were followed under these conditions. The sum of the results from this analysis is accommodated by the hitchhiking model, with sister plasmids associating with sister chromatids in a one-to-one fashion. Episomes of mammalian viruses belonging to the gamma-herpes and papilloma families utilize a hitchhiking mechanism to persist in cells during the latent phase of their infection. Two of the viral partitioning systems have been reconstituted in S. cerevisiae. We wished to exploit these systems to characterize the efficiency of non-native chromosome tethering systems in promoting equal segregation of viral plasmids in S. cerevisiae. We find that the 2 micron plasmid partitioning system is considerably superior to the viral systems. This could be due to the higher efficiency of plasmid-chromosome association and/or due to the ability of plasmid sisters to tether to sister chromatids. / text

No description available.