Dissertations / Theses on the topic 'G switch'

The folding of DNA molecule into non-canonical secondary structures has been shown to be implicated in many important biological processes which regulate cell proliferation and proteins expression. In particular one of these peculiar secondary structures, called G-quadruplex (G4), has been shown to potentially impair cancer development. G4 occurs along DNA sequences rich of consecutive guanines which can fold through Hoostein pairs by forming stacked planes of guanines tetrads. This conformation prevalently forms along the termini of chromosomes (telomeres) but also along the promoter sites of several oncogenes directly involved in many cancers. The G4 formation leads to an hindrance on DNA molecule which hinder the telomere elongation and transcription process. The result is a switching off of these mechanisms which are directly involved in cancer progression. Several factors can influence the G4 equilibria for example, saline conditions, temperature, pH, the binding with specific proteins as well as the presence of dehydrating cosolutes. Additionally, the overall structural feature of the G4 is strictly dependent upon the DNA sequence. As a results, different G4 can be identified inside the cells. In this project, we focused on the conformational study of the promotorial regions of EGFR and BRAF oncogenes since, on these sites the existence of G4 putative forming regions was found. In particular, the sequences at positions -272, -37 of EGFR and -176 of BRAF from the transcription start site were analyzed. Indeed, no previous literature data were reported about the structural equilibria in solution of these sequences. We found that our tested sequences are actually able to fold into G4 by setting the most proper experimental conditions and also close to the intracellular physiological environment (KCl 150 mM, pH 7.5). However, oncogenes are double stranded sequences and the folding of the complementary cytosine rich strand into i-motif (iM) can be involved in the switching off of gene transcription. Although, so far, no physiological evidence has been observed for i-motif conformation, here, we aimed to investigate also the cytosine rich strand conformation, to assess if this folding in the case of our sequences is compatible with the physiological conditions and if it can synergically works with the G4 to destabilize the double strand. Our data showed that in physiological condition the preferential form is represented by the double strand . However, some selected ligands showed to shift the DNA B-form toward the non canonical conformation. Indeed, here we implemented our work with the screening of two libraries of compounds in order to find a selective and efficient binder. We carried on the binding study of anthraquinones and naphthalene diimides derivatives, known to have the chemical features of efficient G4 binders. These ligands were first tested on different G4 templates, known to be validated models for G4 binding study, and their efficiency on G4 has been compared with the double strand. The most G4 selective derivatives were than investigated towards our oncogenic G4s. Although more work is required to identify a lead compound, we were able to demonstrate how the use of asymmetrical substitution pattern on a aromatic core can implement the selectivity among different G4s. Finally, in order to map the occurrence of G4 conformation in vivo, we set up a novel technique which consists in an in vivo footprinting protocol. This work, performed at University of Mississippi, Oxford, MS (USA), under the supervision of Dr Tracy A. Brooks, should provide novel insight on the G4 formation in the cells according to their physiological and environmental conditions
Molti studi dimostrano che l’assunzione di strutture “non canoniche” da parte della molecola di DNA sia coinvolto in molti importanti processi biologici che regolano la proliferazione cellulare e l’espressione proteica. In particolare, è stata dimostrata l’implicazione di una di queste particolari strutture secondarie, chiamata G-quadruplex (G4), nel blocco della progressione del cancro. La struttura G4 è propria di sequenze di DNA ricche in guanine consecutive che assemblandosi tramite legami di Hoostein, formano piani di tetradi di guanine impilati tra loro. Questa particolare conformazione si forma prevalentemente lungo i tratti terminali dei cromosomi, i telomeri, ma anche lungo siti promotoriali di diversi oncogeni coinvolti in molti tipi di cancro. La formazione del G4 porta ad una sorta di ingombro sulla molecola di DNA che inibisce l’elongazione del telomero e i processi di trascrizione. Questo porta ad uno “spegnimento” di questi meccanismi che sono direttamente coinvolti nello sviluppo del cancro. Molti fattori possono influenzare gli equilibri delle conformazioni G4, per esempio, le condizioni saline, la temperatura, il pH, il legame con specifiche proteine, così come la presenza di cosoluti. Inoltre, la struttura globale del G4 é rigorosamente dipendente dalla sequenza oligonucleotidica. Pertanto, diverse strutture G4 possono essere identificate a livello cellulare. In questo progetto, è stato condotto uno studio conformazionale di regioni promotoriali degli oncogeni EGFR e BRAF, dal momento che, su questi oncogeni è stata riscontrata la presenza di regioni “G-rich” (ricche in guanine) potenzialmente in grado di assumere una struttura G4. In particolare, sono state analizzate le sequenze a partire dalle posizioni -272, -37 di EGFR e -176 di BRAF dal “transcription start site” (sito di inizio della trascrizione). Finora, non sono presenti dati in letteratura riguardanti la caratterizzazione strutturale di queste sequenze in soluzione. Con questo studio, è stata dimostrata la capacità delle suddette sequenze di assumere una conformazione G4 nelle idonee condizioni sperimentali e soprattutto in un ambiente che mimi quello fisiologico (150mM KCl e pH 7.5). Poiché gli oncogeni sono sequenze a doppio filamento, anche la conformazione i-motif assunta dal filamento complementare ricco in citosine (“C-rich”) può essere coinvolta nella regolazione del processo di trascrizione genica. Tuttavia, sinora non è stata riscontrata alcuna rilevanza fisiologica della conformazione i-motif. In questo lavoro, è stata caratterizzata anche la conformazione assunta dal filamento “C-rich”, in particolare se essa possa esistere in condizioni fisiologiche e se fosse in grado di destabilizzare la doppia elica insieme al G4. I dati ottenuti dimostrano che in condizioni fisiologiche la forma prevalente è il doppio filamento. Tuttavia, è stato dimostrato come alcuni ligandi siano in grado di spostare l’equilibrio del DNA dalla sua forma di doppia elica-B, verso le conformazioni non canoniche. È stato infatti condotto uno studio su due librerie di composti con lo scopo di evidenziare un composto selettivo ed efficace. Ci siamo focalizzati su derivati antrachinonici e di naftalendiimidi noti come efficaci ligandi per il G4. Questi composti sono stati prima testati su diversi templati G4, noti per essere dei modelli validati per lo studio di binding sul G4. Quindi la loro efficienza sul G4 è stata poi comparata a quella sul doppio filamento. I derivati più selettivi verso il G4 sono stati poi testati su G4 oncogenici. Sebbene una continuazione dello studio fosse necessaria per identificare un composto “lead”, con questo lavoro è stato dimostrato come l’uso di una sostituzione asimmetrica sull’anello aromatico possa implementare la selettività tra più G4. Infine, per identificare la formazione del G4 in vivo, è stata messa a punto una nuova tecnica che consiste in un protocollo di footprinting in vivo. Questo lavoro, svolto nell’Università del Mississippi, Oxford, MS (USA) sotto la supervisione della dr.ssa Tracy A. Brooks, dovrebbe fornire nuovi sviluppi per la formazione del G4 nelle cellule in accordo con le loro condizioni fisiologiche

MYC is overexpressed in many different cancer types and is an intensively studied oncogene because of its contributions to tumorigenesis. The regulation of MYC is complex, and the NHE III1 and FUSE elements rely upon noncanonical DNA structures and transcriptionally induced negative superhelicity. In the NHE III1 only the G-quadruplex has been extensively studied, whereas the role of the i-motif, formed on the opposite C-rich strand, is much less understood. We demonstrate here that the i-motif is formed within the 4CT element and is recognized by hnRNP K, which leads to a low level of transcription activation. For maximal hnRNP K transcription activation, two additional cytosine runs, located seven bases downstream of the i-motif-forming region, are also required. To access these additional runs of cytosine, increased negative superhelicity is necessary, which leads to a thermodynamically stable complex between hnRNP K and the unfolded i-motif. We also demonstrate mutual exclusivity between the MYC G-quadruplex and i-motif, providing a rationale for a molecular switch mechanism driven by SP1-induced negative superhelicity, where relative hnRNP K and nucleolin expression shifts the equilibrium to the on or off state.

Les applications microélectroniques telles que les communications sans fil ou les radars nécessitent des traitements d’information avec des débits ou des résolutions de plus en plus élevés. Cela implique de travailler à des fréquences millimétriques voir sub-millimétriques. Grâce aux progrès des technologies silicium, des circuits intégrés travaillant dans les gammes de fréquences millimétriques émergent mais souffrent d'un manque de solution de caractérisation complète. Par exemple, il n’existe à ce jour aucun analyseur vectoriel de réseaux commercial qui soit capable de mesurer les paramètres S dans la bande G (140-220 GHz) en 4 ports. La caractérisation classique des circuits millimétriques en n ports (avec n>2) consiste alors à utiliser un analyseur vectoriel de réseaux 2 ports et à adapter les autres ports non utilisés à 50Ω. Par permutation circulaire, on arrive ainsi à extraire la matrice S d’un dispositif à n ports (avec n>2). Ce protocole de mesure est très long et délicat à mettre en place car il nécessite d’une part un investissement en appareil de mesure très couteux aux fréquences millimétriques et d’autre part de mettre en œuvre des méthodes de calibrage et de de-embedding précises et dédiées.Le travail développé dans le cadre de cette thèse a visé à intégrer dans la puce, des systèmes de caractérisation petits signaux (paramètres S) au plus près du Dispositif Sous Test (DST). Le fait d’être au plus près du DST permet de réduire les pertes d’insertion, de réduire l’amplitude des vecteurs d’erreurs et donc les erreurs résiduelles après calibrage. Par ailleurs, il est possible de mieux contrôler la puissance du signal envoyé et de considérer des méthodes de calibrage utilisant des charges intégrées, ce qui permet de réduire le temps de traitement et le cout. La technologie utilisée est la technologie SiGe BiCMOS 55 nm développée par la société STMicroelectronics, technologie particulièrement adaptée aux circuits en bande millimétrique. La solution développée dans cette thèse consiste à connecter le wafer avec des pointes de mesure qui amènent un signal hyperfréquence balayant le spectre 35-55 GHz. Une fois dans la puce, ce signal hyperfréquence est quadruplé en fréquence et amplifié afin d’atteindre des niveaux de puissance suffisant (bon rapport Signal/bruit) dans la bande G aux bornes du DST. Les paramètres de réflexion (S11 et S22) sont ensuite extraits grâce à deux coupleurs très directifs, placés sur l’entrée et la sortie du DST respectivement. Les sorties du coupleur sont ensuite ramenées en basse fréquence (0.5GHz < IF < 2.4 GHz) par l’intermédiaire de mélangeurs de fréquence.L’approche choisie est argumentée en se basant sur une étude des systèmes de mesures existant présentée dans la première partie de ce manuscrit. Puis la conception et la caractérisation de chacun des blocs composant le système sont détaillées : le quadrupleur de fréquence en bande G (constitué d’un doubleur de fréquence en bande W cascadé avec un doubleur de fréquence en bande G), le transfert switch en bande G permettant de commuter entre l’entrée et la sortie du DST, le coupleur directif à ondes lentes, les mélangeurs permettant de ramener les mesures en basse fréquence, etc…. Une fois tous les différents blocs présentés, le manuscrit aborde les deux systèmes de mesure conçus. Un premier système un port a été développé pour valider cette approche. Le second système conçu permet de mesurer un DST à deux ports (HBT). Ce second système conserve l’architecture hétérodyne du premier, intégrant en plus un transfert switch en bande G qui dirige le signal incident vers l’un des deux ports du DST
Microelectronic applications such as wireless communications, radar or space detections require higher data rate resolutions, implying the use of millimeter wave and submillimeter frequencies. Thanks to the silicon technologies improvement, some microelectronic circuits are emerging working in the frequency range of 140-220 GHz (G-band) but they suffer from a lack of complete characterization tools involving costly investment. For example, there is currently no commercial vectorial network analyser (VNA) that can measure S parameters in the 4-ports G-band. The classical characterization of millimeter wave circuits in n ports (with n> 2) consists in using a vectorial analyzer of 2-ports networks and matching the other unused ports to 50Ω. By circular permutation, one thus manages to extract the S matrix from a device with n ports (with n> 2). This set up induces very long and difficult measurements and it requires on the one hand some very expensive measuring equipment at millimeter frequencies and on the other hand to implement accurate and dedicated calibration and de-embedding methods.Therefore, the work developed into this PhD study aimed to integrate in the die the measurement systems that would measure small signals "S-parameters" of the device under test (DUT). Being closer to the DST makes it possible to reduce the insertion losses, to reduce the amplitude of the error vectors and thus the residual errors after calibration. Moreover, it is possible to better control the power of the signal sent and to consider calibration methods using integrated loads, which reduces the time and cost processing. The technology used is the SiGe BiCMOS 55 nm technology developed by STMicroelectronics, a technology dedicated to RF and millimeter wave’s circuits.The system developed is a 1-port system. The solution developed consists on connecting the wafer with some probes and driving it with an external signal that spans the 35-55 GHz band. Once into the die, this signal is then quadrupled in frequency and amplified to reach good power level in G band at the DUT inputs. Some S-parameters (S11 and S22) are extracted from the DUT thanks to some very directive couplers designed respectively at the input and at the output of the DUT. The outputs of the couplers are then converted to low frequencies (IF =0.5-2.4 GHz) through passive frequency mixers.In a first part of the thesis manuscript, the way to work is argued, supported by a study of the state of the art concerning the measurement systems. Then, design and characterization of each blocks of the system are detailed: the frequency quadrupler in G band (composed of a W band frequency doubler, followed with a G band frequency doubler), the fully integrated transfer switch in G-band allowing driving the millimeter waves signal to the DUT input or to the DUT output, the directive couplers based on the slow wave lines, the frequency mixers used to bring back the results in base band frequency, etc… All the different blocks detailed, the measurement systems can be introduced. A first system, a one-port measurement system, has been designed as a proof of concept. Once the approach validated, a second system, two-ports measurement system, has been developed presenting an heterodyne architecture and a transfer switch in G band driving the input signal toward the DUT input or output

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As demandas por serviços de telecomunicações multimídia, garantia de QoS (Quality of Service) e mecanismos de gerenciamento e controle direcionam a evolução da rede de núcleo para adoção da tecnologia OTN (Optical Transport Network) como solução de rede de transporte. Para conduzir a evolução da tecnologia OTN a ITU-T (International Telecommunication Union Telecommunications Standardization Sector) estabelece uma série de recomendações, dentre elas, as específicas para o plano de gerenciamento de redes. Essas, por sua vez, apresentam deficiências no que se referem ao levantamento do inventário dos objetos gerenciados definidos pelas normas da ITU-T. A ITU-T define a representação dos elementos de rede em caráter funcional, mais especificamente como módulos de Funções Atômicas. Contudo, a falta de clareza na implementação das Funções Atômicas e a carência de integração com as representações físicas dos elementos de rede implica na omissão, por parte dos diversos fabricantes, da implementação dos mecanismos recomendados em norma. Esta dissertação tem como objetivo geral apresentar uma proposta de solução para o levantamento do inventário dos elementos de rede em redes OTN abrangendo de forma integrada as representações funcional e física do elemento de rede, além de possibilitar aos diversos fabricantes a aderência às normas da ITU-T bem como oferecer ao operador de rede a configuração dos componentes de uma forma mais intuitiva.

MYC is overexpressed in most types of tumors, but a means to selectively decrease its expression is yet to be found. Our recent findings on modulation of BCL2 gene expression through protein interactions with the BCL2 i-motif have provided a basis for further investigation of MYC gene control. It is proposed that the MYC i-motif could function by a similar molecular switch mechanism as in BCL2.Binding sites for heterogeneous nuclear ribonucleoprotein K (hnRNP K) within the MYC promoter also exist in the i-motif-forming sequence. Circular dichroism and bromine footprinting confirmed that this DNA sequence is able to form an i-motif, and systematic mutation of the cytosine residues in this sequence has revealed a 5:5:5 loop configuration. Indeed, all loops of the i-motif, when folded into a 5:5:5 loop configuration, contain the hnRNP K consensus sequence (CCCT). Previous studies show that hnRNP K binds to this i-motif-forming sequence, but it was assumed to be single-stranded. Binding studies revealed that hnRNP K has more binding affinity to its consensus sequence in the i-motif compared to a mutant sequence where the i-motif cannot form. Further investigation of the MYC promoter revealed an additional two runs of cytosine seven bases downstream of the MYC i-motif. Biophysical studies showed that the additional two runs were not involved in i-motif formation, however recent studies describe their importance for transcriptional activation. We found that hnRNP K preferred the longer 5CT sequence compared to the i-motif forming 4CT sequence when using a competitive binding assay. Utilizing luciferase reporters containing either the 4CT or 5CT sequence validated that hnRNP K required both the i-motif and 5th CT element for maximum transcriptional activation. Competition binding studies and bromine footprinting showed that hnRNP K bound to the downstream 5th CT element and the central and lateral loops of the i-motif.Additionally, we found that co-overexpression of Sp1 and hnRNP K induced a 10-fold increase in luciferase activity in the 5CT reporter only. We hypothesize that Sp1 continuously primes the promoter to initiate transcription inducing more negative superhelicity and increasing the melting of duplex DNA. This increased melting grants hnRNP K’s three KH domains access to the i-motif loops and the 5Th CT element. Confirmation by ChIP analysis validated that Sp1 overexpression causes an increase in hnRNP K occupancy at the MYC promoter. These findings provide new insight into the mechanisms of MYC transcriptional control by the i-motif and G-quadruplex.Recently, our group has demonstrated that two small molecules IMC-48 and IMC-76 can interact with the i-motif and can be an effective means to modulate BCL2 expression. Based on these results with the BCL2 i-motif, we employed a similar strategy and screened and identified small drug-like molecules that interact with MYC i-motif, using a FRET high-throughput assay. We then further validated that IMC-16 stabilizes the MYC i-motif through the interactions with the loops of the i-motif. No stabilization by IMC-16 treatment was observed with the MYC G-quadruplex and the BCL2 and PDGFRβi-motifs demonstrating selectivity for the MYC i-motif.Finally, we investigated the effects of IMC-16 on MYC expression in three lymphoma cell lines all expressing different levels of MYC. In the case of both Daudi and RAJI Burkitt’s lymphoma cell lines we demonstrated that selectively stabilizing the i-motif by IMC-16 could increase MYC expression. Furthermore, we demonstrated that the MYC G-quadruplex stabilizing compound GQC-05 and IMC-16, which stabilizes the MYC i-motif, have antagonistic effects on MYC expression, providing further evidence of a molecular switch mechanism in the NHEIII1. Directly targeting MYC expression through the i-motif offers advantages over targeting the G-quadruplex, because of the reduced stability and dynamic nature of the i-motif, additionally the i-motif is only found in DNA. The use of such i-motif interactive compounds is the first step into the development of new innovative approaches to treat cancers.

Tesis de licenciatura donde se concentra la información del trabajo de investigación realizado por el alumno
Las proteínas desempeñan diversas funciones biológicas dependiendo de su localización celular. Algunas proteínas utilizan la formación de enlaces disulfuro reversible como interruptor, regulando funciones biológicas como la activación y/o inhibición. Los enlaces disulfuro estabilizan la conformación de un péptido, sin embargo, la formación del enlace más común es la oxidación de dos moléculas de cisteína para llegar a la formación de cistina, resultando en un proceso redox. Los grupos tiol pueden ser sometidos a la trasferencia de uno o dos electrones para generar productos oxidados, ya que la reacción de Inter-conversión redox tiol-disulfuro se ve influenciada por el potencial redox, el estudio se verá enfocado al análisis estructural y descripción de los potenciales de reducción asociados a la formación del enlace.
Laboratorio Nacional de Cómputo de Alto Desempeño

Smart antenna technology in applications such as the next-G wireless communication networks may improve the quality of service (QoS). One category of smart antennas is the switched beam smart antenna (SBA). These antennas can be grouped into plug and play antennas and adaptive internal antennas. Four types of switched beam smart antennas were investigated including a six monopole array on circular ground plane with conducting sleeve, five monopoles on a circular ground plane without a conducting sleeve, a reconfigurable monopole on a cylindrical hollow ground structure, and a reconfigurable adaptive internal antenna. The first two antennas were constructed with a switched parasitic array of elements combined with an RF circuit with microcontroller. Two of the four antenna prototypes were capable for steering the beam pattern automatically based on signal strength (RSSI) or bit error rate (BER) scanning. The two remaining antennas were designed for electronic beamforming and electronic frequency tuning. Both numerical and empirical investigations were undertaken to measure performance and investigate manufacture difficulties. The numerical investigations were undertaken using both the method of moment (MoM)-NEC and the finite element method (FEM)-HFSS modeling. The fabrication and testing in an anechoic chamber were used to explore the actual performance of the designed antennas. The fabrication of the last two types of antennas was not implemented. Further work is required to find the optimal design for all antennas investigated. This study suggests significant promise for these antennas in wireless networks.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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碩士
國立臺灣大學
應用力學研究所
99
In this thesis, a centrifugal G-switch was designed and its performances were simulated by ANSYS/LS-DYNA. When a centrifugal G-switch subjected to a threshold centrifugal acceleration field, the switching mechanism inside the centrifugal G-switch will turn on and deliver signals to initiate the subsequent processes. A G-switch is a device as placed in a critical acceleration field, the accelerometer inside G-switch will turn on and delivers a output signal to trigger subsequent processes. As the G-switch receives an impulsive acceleration from environment, the proof mass experiences an inertial force which moves the contacts in touch to trigger a contact signal. The difference between a centrifugal G-switch and a general G-switch is that the centrifugal G-switch is designed for steady acceleration field. Therefore, the consideration of stability and safety is essential in the G-switch. Accordingly, the centrifugal G-switch designed in this thesis is composed of a latch mechanism and an accelerometer. Because the centrifugal acceleration is determined by the product of square of the angular speed and the distance between the mass centroid of the proofmass of the G-switch and rotation axis, we set the centrifugal G-switch will not turn on at 1,000 rpm and turn on at 2,000 rpm. With considerations of various geometry conditions, the proposed centrifugal G-switch can meet these two situations. Numerical simulations of the G-switch indicate that the designed G-switch can function properly under these two rotation situations. In addition to an axial acceleration impact of 1000G, all components of the centrifugal G-switch are in the elastic region of the silicon, based on which the G-switch will be fabricated.

碩士
國立臺灣大學
應用力學研究所
100
This thesis presents design and fabrication of a micro centrifugal G-switch by ANSYS/LS-DYNA and micro-electrical-mechanical system processing techniques. As the acceleration switch, also called the G-switch, subjected to sufficient levels of axial and centrifugal accelerations, the switch will turn from off to on, delivering signals to the connect circuits which can initiate subsequent processes. As the G-switch receives acceleration exceeding threshold from surroundings, the proof-mass in the G-switch experiences an inertial force which moves the contact components in touch to trigger output signals. To appropriately investigate the micro centrifugal G-switch, this thesis first designed suitable accelerators and latching mechanism, then simulated numerically the dynamic response of the G-switch subjected to applied impact conditions. As the projectile rotated with a centrifugal acceleration below 1,000 rpm, the installed G-switch was not turned on, staying in a safety mode. The device would be latched up as the spin rate above 2,000 rpm. An additionally axial acceleration impact of 1000G was also applied to the centrifugal G-switch to emulate the launching situation. Numerical results of dynamic response and stress distribution were revealed to evaluate the performances of accelerometers. A novel design of latching mechanism with releasing components was figured out. Based on the simulated numerical results, this thesis fabricated the micro centrifugal G-switch chips on a silicon-on-insulator (SOI) wafer via MEMS processing. Upon finishing the manufacturing processes, G-switch chips were tested by a centrifugal machine to investigate the performances of the fabricated devices. Test results show that the designed G-switch functioned properly as the acceleration reached the threshold, and all components of the G-switch were in the elastic region of the silicon without destruction. Heating the release mechanisms by applying 1 voltage DC source regulated with series resistors, this latched state was successfully discharged in a short time, fulfilling the purpose of reusing the G-switch.

碩士
國立臺灣大學
應用力學研究所
99
The facts of rapidly deepened applications and progressive techniques of micro-electro-mechanical systems (MEMS) attract many organizations and engineers devoting to the research of microsensors and microactuators, among which microaccelerometer and microgyroscopes are successive examples. An acceleration switch is a kind of accelerometers. As the applied acceleration beyond a threshold value, the switch will latch up and output a triggering signal. The acceleration switches made by MEMS techniques possess enormous commercial benefits due to its numerous advantages, such as low cost, miniature volume, high reliability, and reusability. It can also be widely applied in many industries such as airbags, crash recorders, and monitoring the cargos during shipping. This thesis designed and numerically simulated a high-G acceleration switch subjected in high-G impact environments. In this thesis, we aimed to design an acceleration switch which could resist impact with a threshold acceleration of 2000G. The mechanism of switching was designed by CAE software package, and the dynamic response was simulated using LS-DYNA. The goal was to examine whether the acceleration switch could function well to meet the impact specification of MIL-STD 883E. If there had any faults such as stress concentration or defects of structure, the design was changed immediately to reduce the research time and the cost before trial production or mass manufacture. The results of the simulation dictate that the proposed acceleration switch can function well with the acceleration threshold of 2000G, and the latch mechanism works successfully and stays in the latched position. Besides, the contact components keep in touch, and all the components work properly without any failures. Under the impact load of 1800G, the latch mechanism cannot be latched properly, and the contact component cannot be in contact. We conclude that the proposed acceleration switch can work when the applied acceleration is beyond the acceleration threshold.

碩士
國立臺灣大學
應用力學研究所
100
Nowadays the acceleration switch, a special type of accelerometer, has become one of peculiar sensing devices. As the acceleration reaches a threshold, the switch turns into locked state, and the contact components export a signal which can trigger the subsequent action. In recent years, rapid progressive technologies enable micro-nano electro-mechanical systems (MEMS) to develop more sophisticated functionality. Modern MEMS not only reduce the cost and scale, but also improve the reliability and the measuring range of accelerations. The products penetrate into many major businesses, such as home care systems, smart phones, amusement equipment, in addition to the traditional automotive industry, aerospace and defense industries. In this thesis, we aimed to design acceleration switches which are applicable to the impact of high-G environment. In order to reduce research cost and time, we utilized computer assisted design (CAD) software to create models, then imported to computer assisted engineering (CAE) software for dynamic simulation. From the analysis results, we validated that the G-switches can function well to fulfill the impact specifications of MIL-STD 883E conditions. As the accelerations reach their respective thresholds, the latch mechanism was successfully locked up, the contact elements delivered the touched signal, and materials of the switches did not damaged. Based on the simulation results, we employed MEMS processing technology to fabricate our designs of acceleration switches on SOI wafers. Upon cutting and simple packaging, the switches were examined on a centrifugal machine which was adjusted to specific acceleration levels. The tests proved that all acceleration switches were satisfactorily manufactured and functioned properly to meet the severe impact conditions. The latched mechanism could be quickly released by applying 1V DC power to the releasing device. This thermally releasing device allows the acceleration switch to reuse again.

Accelerometers are sensors that measure and record the acceleration of an object in motion. They typically contain spring and mass elements that are set into vibration upon any impressed acceleration. The characteristics of their continuous vibration are used to extract the acceleration information. MEMS g-switch accelerometers are a special class of such sensors that sense a threshold acceleration and act as a switch for some other action that must ensue only if the threshold acceleration is achieved. Such accelerometers are used for impact detection and very high-speed propulsion, e.g., rockets. There are two types of g-switches — Latch type and Non-latch type. Non-latch type accelerometers have a proof-mass suspended by springs (beams) and two stationary electrodes, on experiencing an acceleration, this proof-mass touches the two electrodes closing an external electrical circuit and allowing an electric current to flow through the circuit as long as there is contact. This current flow indicates that a particular level of acceleration is reached. Latch type accelerometers, on the other hand, have compliant electrodes that latch on to the proof-mass on experiencing the threshold acceleration, maintaining the switch in ON state permanently from the instant the threshold acceleration is reached. We have designed, developed and studied both types of g-switches in this work. Time of contact (in case of non-latch type switches), contact resistance, and response time are key parameters that affect the performance of these devices. Energy-based approach is used in the design of these switches with appropriate displacement and velocity constraints that enforce the threshold condition. Dynamic characterisation is done on the fabricated devices to extract their modal parameters. An impulse acceleration is generated by means of an impact using a drop test equipment and high-speed video imaging is used to extract the device response. The experimental response is compared with FEM simulation results. The high-speed video imaging is also used to study the dynamics of the contact at the micro-second time scale. Electrical switching experiments are done for varying magnitude of the shock profile to find the threshold g-level of the switches. For the latch type accelerometers, to reset the switch and make them reusable after latching, a Chevron beam (bent beam) type thermal actuator is designed to accomplish the unlatching. In case of large vertical off-set between the proof-mass and the electrode, a horizontally actuated bent beam mechanism is used to accomplish the unlatching. Thus the study undertaken reports a complete development of the target g-switches.

博士
中山醫學大學
生化暨生物科技研究所
96
Cardiac hypertrophy is an adaptive response of heart under varied stresses. When stress has been accumulated, the transition from physiological hypertrophy to pathological hypertrophy results in promotion of heart failure. Our previous studies demonstrated upregulations of insulin-like growth factor II (IGF-II) and mannose 6-phosphate/IGF-II receptor (IGF2R) dose-dependently correlating with the progression of heart disease following complete abdominal aorta ligation, may play a critical role in angiotensin II (ANGII)-induced cardiomyocyte apoptosis. However, the detailed mechanisms of IGF2R in the promotion of heart failure in response to IGF-II remain unclear. Additionally, how igf2r gene up-regulation in response to pathological stresses is also poorly understood. Therefore, in the study I, we found a significant association of IGF2R overexpression with myocardial infarction and myocardial scars. Results of specifically activating IGF2R signaling through either inhibition of the IGF1R activity by IGF1R siRNA and AG1024 or using Leu27IGF-II analog, a ligand interact only with the IGF2R, revealed that IGF2R activated by IGF-II binding acted like a G protein-coupled receptor to activate PKC-α/CaMKII and calcineurin by association with Gαq, leading to pathological hypertrophy and mitochondria-dependent cell apoptosis in cardiomyocytes. Furthermore, we also found that IGF2R signaling activation disrupted the balance of MMP-9/TIMP-2 expressions and increased plasminogen activator (PAs) expression, resulting in the development of myocardial remodeling. In study II, we found the histone acetylation, but not the DNA methylation, is required for the induction of igf2r gene by ANGII. Moreover, when responding to ANGII, HSF-1, identified as a suppressor of igf2r gene under normal condition, slipped out of the HSF-binding element within the IGF2R promoter that contributes up-regulation of igf2r gene expression. Taken together, our study provides new insight into the gene regulation of IGF2R and the role of the IGF2R in the pathogenesis of cardiac disease. Suppression of IGF2R gene expression and its signaling pathways may be a good strategy to prevent the progression of heart failure. We also discovered a novel gene of IGF2R isoform, 2R-α, which transcripts 4656 nucleic acid mRNA examined by using the rapid amplification of cDNA ends (RACE) PCR and northern blots. After compared with IGF2R mRNA sequences, regardless of the same sequences from IGF2R’s exon 10 to exon 35, the 2R-α gene sequence unexpectedly comprise a partial fragment of intron 9 (645~806 bp) of IGF2R in its 5’ region and a partial fragment of intron 35 (1~455 bp) in its 3’ region. In addition, we found a new TATA box exists in the 5’ upstream region of 2R-α gene and its coding region starts at the 14 bp of exon 10, then stops in the 48bp of intron 35 that may encode a 1358 amino acids protein predicted by Open Reading Frame Finder. Furthermore, creating the antibody that recognized the 15 amino acidic sequence in N terminal：AYDESEDDTSDTTPC of predicted 2R-α protein sequences to confirm the translation of gene transcript into the 2R-α protein. Further to identify the role and function of this novel 2R-α gene in the future may provide a new concept of IGFs in regulating cell physiology and heart function.

碩士
國立臺灣大學
電子工程學研究所
94
In this thesis, we present a new architecture of differential T/R switches for wireless local-area network (WLAN). If we use the balanced-type circuit, the number of the devices, such as a balun, can be reduced. The balanced circuit can also improve the poor ground and suppress the common-mode interference. In addiction, the proposed architecture consumes no DC power at the receiving mode, which is especially suitable for portable wireless applications. The LTCC (low temperature co-fired ceramic) is chosen for its low loss and multi-layer structure, which will give better insertion loss and give more freedom in balanced-type device design. The design procedure and measurement results of two differential switches operating at 2.4GHz and 5.2GHz are presented in this thesis.