Compact Modeling of Variability in Organic Thin-Film Transistors

En aquesta tesi doctoral, es van presentar una quantitat important d'investigacions sobre temes d’emmotllament de la variabilitat dels transistors de pel∙lícula prima (TFT, per les seves sigles en anglès) orgànics. Amb la finalitat de verificar‐los, es van fabricar i provar diversos substrats flexibles que contenien transistors de pel∙lícula prima orgànics i circuits basats en transistors de pel∙lícula prima, respectivament. Es va desenvolupar i es va verificar un model de variabilitat de corrent de drenatge basat en la càrrega física adequat per a transistors orgànics de pel∙lícula prima com a part central d’aquesta investigació. Posteriorment, es va presentar una alternativa eficient a la metodologia d'anàlisi estadística de Montecarlo que es pot fer servir per estudiar la variabilitat de circuits integrats. Es va provar el mètode proposat «Plantejament de la variabilitat basat en el soroll» (NOVA, per les seves sigles en anglès) en circuits basats en transistors de pel∙lícula prima orgànics i es va demostrar que és un mètode adequat per anàlisis de processament ràpid i desviacions de circuits estadístics. A continuació, es va implementar un model de soroll de freqüències baixes basat en la càrrega depenent del biaix semifísic per a transistors orgànics de pel∙lícula prima. El model que es proposa es basa en els efectes de la fluctuació de la mobilitat correlacionada amb la fluctuació del nombre de portadors de càrrega (ΔΝ) i els efectes de la fluctuació de la mobilitat (Hooge) (ΔΜ), i es pot aplicar a transistors de pel∙lícula prima fabricats a l'arquitectura de dispositius esglaonats invertits. A continuació, fent servir dades experimentals obtingudes fent servir miralls de corrent basats en transistors de pel∙lícula prima, es va analitzar la variabilitat de les característiques del circuit. Amb aquesta finalitat, es van fabricar i caracteritzar un gran nombre de miralls de corrent nominalment idèntics. Finalment, es va investigar el rendiment dels transistors de pel∙lícula prima orgànics quan són sotmesos a una flexió mecànica. El model compacte de corrent de drenatge que s’ha fet servir en aquest manuscrit pot captar aquest efecte ajustant el valor del paràmetre β exponencial de la llei de potència. En tots els casos, els resultats del model compacte que s’ha fet servir estan en concordança amb els resEsta tesis doctoral presenta una vasta y significativa investigación relacionada con temas que cubren aspectos de modelado de la variabilidad de TFT orgánicos. Por motivos de verificación, se fabricaron y probaron varios sustratos flexibles que contenían TFT orgánicos y circuitos basados en TFT, como corresponde. Como aspecto primordial de la investigación, se desarrolló y verificó un modelo de variabilidad de corriente de drenaje basado en carga física adecuado para transistores orgánicos de película fina. En consecuencia, se ha presentado una eficiente alternativa a la metodología del análisis estadístico Montecarlo que puede ser utilizada para el estudio de la variabilidad de circuitos integrados. El método propuesto, el "enfoque de variabilidad basado en el ruido" (NOVA), ha sido probado en circuitos basados en TFT orgánicos y ha demostrado ser adecuado para procesos rápidos y análisis estadísticos de desajustes de circuitos. A continuación, se implementó un modelo semifísico de ruido de baja frecuencia basado en la carga dependiente del sesgo para transistores orgánicos de película fina. El modelo propuesto se basa en los efectos de la fluctuación de la movilidad correlacionada con la fluctuación del número de portadores de carga (ΔΝ) y la fluctuación de la movilidad (Hooge) (ΔΜ), y puede aplicarse a TFT fabricados con arquitectura de dispositivo escalonado invertido. A continuación, a partir de los datos experimentales obtenidos de espejos de corriente basados en TFT, se analizó la variabilidad de las características del circuito. Para ello, se fabricaron y caracterizaron un gran número de espejos de corriente nominalmente idénticos. Finalmente, se investigó el rendimiento de los cambios de TFT orgánicos al ser sometidos a flexión mecánica. El modelo compacto de CC utilizado en el presente trabajo puede capturar este efecto ajustando el valor del parámetro β del exponente de la ley de potencia. En todos los casos, los resultados del modelo compacto aquí utilizado concuerdan con los resultados de la medición.In the current PhD thesis, a significant amount of research regarding topics that cover modeling aspects of variability of organic TFTs were presented. For verification reasons, seven flexible substrates containing organic TFTs and TFT-based circuits were fabricated and tested, accordingly. A physical charge-based drain-current variability model suitable for organic thin-film transistors was developed and verified, as the core of this research. Subsequently, an efficient alternative to the Monte Carlo statistical-analysis methodology that can be used for the variability study of integrated circuits has been presented. The proposed ''Noise-Based Variability Approach'' (NOVA) method has been tested on circuits based on organic TFTs and has been shown to be suitable for fast process and mismatch statistical circuit analyses. The principle advantage of NOVA over Monte Carlo is the significantly shorter processing time, which makes NOVA beneficial for circuit designers. Next, a semi-physical bias-dependent charge-based low-frequency noise model for organic thin-film transistors, a topic relevant to compact modeling of variability aspects, was implemented. The proposed model is based on charge carrier-number fluctuation-correlated mobility fluctuation (ΔΝ) and mobility-fluctuation (Hooge) (ΔΜ) effects, and it can be applied to TFTs fabricated in the inverted staggered device architecture. Using experimental data obtained from TFT-based current mirrors, the variability of the circuit characteristics were analyzed. For this purpose, a large number of nominally identical current mirrors were fabricated and characterized. Finally, the performance of organic TFTs changes when they are subjected to mechanical bending was investigated. The DC compact model utilized in the current manuscript is able to capture this effect by adjusting the value of the power-law exponent parameter β. In all cases, the results of the compact model utilized here are in good agreement with the measurement results

Detection of O-Linked-N-Acetylglucosamine Modification and Its Associated Enzymes in Human Degenerated Intervertebral Discs

Study DesignHuman herniated discs were obtained from discectomy specimens for the immunohistochemical detection of O-GlcNAc and O-GlcNAcase (OGA)/O-GlcNAc transferase (OGT).PurposeThis study aimed to quantify the extent of O-GlcNAcylation and its associated enzymes (OGT/OGA) in human degenerated intervertebral discs.Overview of LiteratureThe O-GlcNAcylation of nuclear, cytoplasmic, and mitochondrial proteins as well as the effects of such post-translational modifications are currently the focus of extensive research. O-GlcNAcylation is believed to contribute to the etiology of chronic illnesses by acting as a nutrient and stress sensor in the cellular environment. Mature intervertebral disc cells are chondrocyte-like cells, and O-GlcNAc has been shown to promote chondrocyte apoptosis in vitro. We believe that O-GlcNAcylation is a key regulator of disc degeneration.MethodsFifty-six specimens were fixed for 24 hours in a 10% solution of neutral-buffered formaldehyde, dehydrated, and embedded in paraffin. Tissue slices (4-µm-thick) were used for hematoxylin-eosin staining and immunohistochemistry.ResultsWe found that O-GlcNAcylation of cytoplasmic proteins was less than that of nuclear proteins in both single cells and cell clusters. Cytoplasmic O-GlcNAcylation occurs subsequent to nuclear O-GlcNAcylation and is directly proportional to disc degeneration. OGT and O-GlcNAc expression levels were identical in all specimens examined.ConclusionsO-GlcNAc and OGA/OGT expression is shown to correlate for the first time with intervertebral disc cell degeneration. Increasing disc degeneration is associated with increasing O-GlcNAcylation in both nuclear and cytoplasmic proteins in human disc cells

FOSS EKV2.6 Verilog-A Compact MOSFET Model

The EKV2.6 MOSFET compact model has had a considerable impact on the academic and industrial community of analog integrated circuit design, since its inception in 1996. The model is available as a free open-source software (FOSS) tool coded in Verilog-A. The present paper provides a short review of foundations of the model and shows its capabilities via characterization and modeling based on a test chip in 180 nm CMOS fabricated via Europractice

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Χαρακτηρισμός και μοντελοποίηση φαινομένων ακτινοβολίας και θορύβου χαμηλής συχνότητας σε συμβατική τεχνολογία CMOS

Μη διαθέσιμη περίληψηNot available summarizatio

Στατιστική μελέτη θορύβου χαμηλής συχνότητας σε Enclosed Gate MOSFETs

Μη διαθέσιμη περίληψηNot available summarizatio

Forward and Reverse Operation of Enclosed-Gate MOSFETs and Sensitivity to High Total Ionizing Dose

Frond-end electronics at the High Luminosity-Large Hadron Collider (HL-LHC) at CERN, will be exposed to ten-fold radiation doses. The use of enclosed gate (EG) MOSFETs of 65 nm Bulk CMOS process, is considered to be a viable solution in order to suppress performance degradation effects that occur after high TID exposure. The present paper presents a detailed analysis of the functionality of EG MOSFETs operating under high TID, taking into accountspecific layout characteristics