Threshold Voltage Instability and Relaxation in Hydrogenated Amorphous Silicon Thin Film Transistors

This thesis presents a study of the bias-induced threshold voltage metastability phenomenon of the hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs). An application of gate bias stress shifts the threshold voltage of a TFT. After the bias stress is removed, the threshold voltage eventually returns to its original value. The underlying physical mechanisms for the shift in threshold voltage during the application of the bias and after the removal of the bias stress are investigated. The creation of extra defect states in the band gap of a-Si:H close to the gate dielectric interface, and the charge trapping in the silicon nitride (SiN) gate dielectric are the most commonly considered instability mechanisms of threshold voltage. In the first part of this work, the defect state creation mechanism is reviewed and the kinetics of the charge trapping in the SiN is modelled assuming a simplified mono-energetic and a more realistic Gaussian distribution of the SiN traps. The charge trapping in the mono-energetic SiN traps was approximated by a logarithmic function of time. However, the charge trapping with a Gaussian distribution of SiN traps results in a more complex behavior. The change in the threshold voltage of a TFT after the gate bias has been removed is referred to threshold voltage relaxation, and it is investigated in the second part of this work. A study of the threshold voltage relaxation sheds more light on the metastability mechanisms of a-Si:H TFTs. Possible mechanisms considered for the relaxation of threshold voltage are the annealing of the extra defect states and the charge de-trapping from the SiN gate dielectric. The kinetics of the charge de-trapping from a mono-energetic and a Gaussian distribution of the SiN traps are analytically modelled. It is shown that the defect state annealing mechanisms cannot explain the observed threshold voltage relaxation, but a study of the kinetics of charge de-trapping helps to bring about a very good agreement with the experimentally obtained results. Using the experimentally measured threshold voltage relaxation results, a Gaussian distribution of gap states is extracted for the SiN. This explains the threshold voltage relaxation of TFT after the bias stress with voltages as high as 50V is removed. Finally, the results obtained from the threshold voltage relaxation make it possible to calculate the total charge trapped in the SiN and to quantitatively distinguish between the charge trapping mechanism and the defect state creation mechanisms. In conclusion, for the TFTs used in this thesis, the charge trapping in the SiN gate dielectric is shown to be the dominant threshold voltage metastability mechanism caused in short bias stress times

Advanced MEMS Microprobes for Neural Stimulation and Recording

The in-vivo observation of the neural activities generated by a large number of closely located neurons is believed to be crucial for understanding the nervous system. Moreover, the functional electrical stimulation of the central nervous system is an effective method to restore physiological functions such as limb control, sound sensation, and light perception. The Deep Brain Stimulation (DBS) is being successfully used in the treatment of tremor and rigidity associated with advanced Parkinson's disease. Cochlear implants have also been employed as an effective treatment for sensorineural deafness by means of delivering the electrical stimulation directly to the auditory nerve. The most significant contribution of this PhD study is the development of next-generation microprobes for the simultaneous stimulation and recording of the cortex and deep brain structures. For intracortical applications, millimetre length multisite microprobes that are rigid enough to penetrate into the cortex while integrated with flexible interconnection cables are demanded. In chronic applications, the flexibility of the cable minimizes the tissue damage caused by the relative micro-motion between the brain and the microprobe. Although hybrid approaches have been reported to construct such neural microprobes, these devices are brittle and may impose severe complications if they break inside the tissue. In this project, MEMS fabrication processes were employed to produce non-breakable intracortical microprobes with an improved structural design. These 32 channel devices are integrated with flexible interconnection cables and provide enough mechanical strength for penetration into the tissue. Polyimide-based flexible implants were successfully fabricated and locally reinforced at the tip with embedded 15 µm-thick gold micro-needles. In DBS applications, centimetre long microprobes capable of stimulating and recording the neural activity are required. The currently available DBS probes, manufactured by Medtronic, provide only four cylindrical shaped electrode sites, each 1.5 mm in height and 1.27 mm in diameter. Although suitable for the stimulation of a large brain volume, to measure the activity of a single neuron but to avoid measuring the average response of adjacent cells, recording sites with dimensions in the range of 10 - 20 µm are required. In this work, novel Three Dimensional (3D) multi channel microprobes were fabricated offering 32 independent stimulation and recording electrodes around the shaft of the implant. These microprobes can control the spatial distribution of the charge injected into the tissue to enhance the efficacy and minimize the adverse effects of the DBS treatment. Furthermore, the device volume has been reduced to one third the volume of a conventional Medtronic DBS lead to significantly decrease the tissue damage induced by implantation of the microprobe. For both DBS and intracortical microprobes, the impedance characteristics of the electrodes were studied in acidic and saline solutions. To reduce the channel impedance and enhance the signal to noise ratio, iridium (Ir) was electroplated on gold electrode sites. Stable electrical characteristics were demonstrated for the Ir and gold electrodes over the course of a prolonged pulse stress test for 100 million cycles. The functionality and application potential of the fabricated microprobes were confirmed by the in-vitro measurements of the neural activity in the mouse hippocampus. In order to reduce the number of channels and simplify the signal processing circuitry, multiport electrostatic-actuated switch matrices were successfully developed, fabricated, and characterized for possible integration with neural microprobes to construct a site selection matrix. Magnetic-actuated switches have been also investigated to improve the operation reliability of the MEMS switching devices

The Sensitivity and Specificity of Potassium Hydroxide Smear and Fungal Culture Relative to Clinical Assessment in the Evaluation of Tinea Pedis: A Pooled Analysis

Background. There are relatively few studies published examining the sensitivity and specificity of potassium hydroxide (KOH) smear and fungal culture examination of tinea pedis. Objective. To evaluate the sensitivity and specificity of KOH smear and fungal culture for diagnosing tinea pedis. Methods. A pooled analysis of data from five similarly conducted bioequivalence trials for antifungal drugs was performed. Data from 460 patients enrolled in the vehicle arms of these studies with clinical diagnosis of tinea pedis supported by positive fungal culture were analyzed 6 weeks after initiation of the study to determine the sensitivity and specificity of KOH smear and fungal culture. Results. Using clinical assessment as the gold standard, the sensitivities for KOH smear and culture were 73.3% (95% CI: 66.3 to 79.5%) and 41.7% (34.6 to 49.1%), respectively. The respective specificities for culture and KOH smear were 77.7% (72.2 to 82.5%) and 42.5% (36.6 to 48.6%). Conclusion. KOH smear and fungal culture are complementary diagnostic tests for tinea pedis, with the former being the more sensitive test of the two, and the latter being more specific

In silico characterization of competing endogenous RNA network in glioblastoma multiforme with a systems biology approach

Glioblastoma multiforme (GBM) is the most frequent malignant type of primary brain cancers and is a malignancy with poor prognosis. Thus, it is necessary to find novel therapeutic modalities based on molecular events occur at different stages of tumor progression. We used expression profiles of GBM tissues that contained long non-coding RNA (lncRNA), microRNA (miRNA) and mRNA signatures to make putative ceRNA networks. Our strategy led to identification of 1080 DEmRNAs, including 777 downregulated DEmRNAs (such as GJB6 and SLC12A5) and 303 upregulated DEmRNAs (such as TOP2A and RRM2), 19 DElncRNAs, including 16 downregulated DElncRNAs (such as MIR7-3HG and MIR124-2HG) and 3 upregulated DElncRNAs (such as CRNDE and XIST) and 49 DEmiRNAs, including 10 downregulated DEmiRNAs (such as hsa-miR-10b-5p and hsa-miR-1290) and 39 upregulated DEmiRNAs (such as hsa-miR-219a-2-3p and hsa-miR-338-5p). We also identified DGCR5, MIAT, hsa-miR-129-5p, XIST, hsa-miR-128-3p, PART1, hsa-miR-10b-5p, LY86-AS1, CRNDE, and DLX6-AS1 as 10 hub genes in the ceRNA network. The current study provides novel insight into molecular events during GBM pathogenesis. The identified molecules can be used as therapeutic targets for GBM

Thermal Scanning of Dental Pulp Chamber by Thermocouple System and Infrared Camera during Photo Curing of Resin Composites

Introduction: Due to thermal hazard in composite restorations, this study was designed to scan the pulp temperature by thermocouple and infrared camera during photo polymerizing different composites. Methods and Materials: A mesio-occlso-distal (MOD) cavity was prepared in an extracted tooth and the K-type thermocouple was fixed in its pulp chamber. Subsequently, 1 mm increment of each composites were inserted (four composite types were incorporated) and photo polymerized employing either LED or QTH systems for 60 sec while the temperature was recorded with 10 sec intervals. Ultimately, the same tooth was hemisected bucco-lingually and the amalgam was removed. The same composite curing procedure was repeated while the thermogram was recorded using an infrared camera. Thereafter, the data was analyzed by repeated measured ANOVA followed by Tukey’s HSD Post Hoc test for multiple comparisons (α=0.05). Results: The pulp temperature was significantly increased (repeated measures) during photo polymerization (P=0.000) while there was no significant difference among the results recorded by thermocouple comparing to infrared camera (P>0.05). Moreover, different composite materials and LCUs lead to similar outcomes (P>0.05). Conclusion: Although various composites have significant different chemical compositions, they lead to similar pulp thermal changes. Moreover, both the infrared camera and the thermocouple would record parallel results of dental pulp temperature.Keywords:Exothermic Reaction; Infrared Camera; Light Curing Unit; Pulp Temperature; Resin Composite; Thermocouple

Expression pattern of non-coding RNAs in non-functioning pituitary adenoma

Non-functioning pituitary adenoma (NFPA) is a benign tumor arising from the adenohypophyseal cells. They can be associated with symptoms arising from mass effect. Although these tumors are regarded to be benign tumors, they are associated with increased comorbidity and mortality. Several studies have indicated abnormal expression of genes in these tumors. In the current study, we have used existing methods to identify differentially expressed genes (DEGs) including DE long non-coding RNAs (DElncRNAs) and DE microRNAs (DEmiRNAs) in NFPAs compared with normal samples. Then, we have assessed the relation between these genes and important signaling pathways. Our analyses led to identification of 3131 DEGs, including 189 downregulated DEGs (such as RPS4Y1 and DDX3Y) and 2898 upregulated DEGs (such as ASB3 and DRD4), and 44 DElncRNAs, including 8 downregulated DElncRNAs (such as NUTM2B-AS1 and MALAT1) and 36 upregulated DElncRNAs (such as BCAR4 and SRD5A3-AS1). GnRH signaling pathway, Tight junction, Gap junction, Melanogenesis, DNA replication, Nucleotide excision repair, Mismatch repair and N-Glycan biosynthesis have been among dysregulated pathways in NFPAs. Taken together, our study has revealed differential expression of several genes and signaling pathways in this type of tumors

Threshold Voltage Instability and Relaxation in Hydrogenated Amorphous Silicon Thin Film Transistors

I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii This thesis presents a study of the bias-induced threshold voltage metastability phenomenon of the hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs). An application of gate bias stress shifts the threshold voltage of a TFT. After the bias stress is removed, the threshold voltage eventually returns to its original value. The underlying physical mechanisms for the shift in threshold voltage during the application of the bias and after the removal of the bias stress are investigated. The creation of extra defect states in the band gap of a-Si:H close to the gate dielectric interface, and the charge trapping in the silicon nitride (SiN) gate dielectric are the most commonly considered instability mechanisms of threshold voltage. In the first part of this work, the defect state creation mechanism is reviewed and the kinetics of the charge trappin

Central Catheter Infection in Patients on Acute and Chronic Hemodialysis: A Cross Sectional Study

Background and Aim: The most common complication of central venous catheter (CVC) in hemodialysis (HD) is infection. Identifying CVC- related infection (CVC-RI) risk factors and causative micro - organisms is essential for setting prevention policies. This study aims to determine the prevalence of CVCRIs and identify any associated risk factors among these patients. Methods: We conducted a cross-sectional study from 2017 to 2018 to determine the prevalence of central catheter - related infections among all adult patients on both acute and chronic hemodialysis who had central catheters in place at a tertiary care hospital in Qazvin City. Data on demographics, comorbidities, dialysis duration, catheter - related complications, catheter removal, dialysis details (frequency, duration), catheter insertion site, and any history of central catheter - related infections were collected from medical records. A central catheter - related infection is defined as a positive blood culture obtained from a central venous catheter tip or any other related site (e.g., tunnel, exit site) with clinical signs of infection such as fever, chills, or localized pain and tenderness. Micro - organisms isolated from cultures of CVC, catheter tips, and blood cultures were identified. Chi-square and t-test were performed to compare demographic and clinical variables.              P < 0.05 was considered statistically significant. Results: 171 patients (214 hospital admissions) enrolled in the study. Of these hospital admissions, 91 (42.5%) had              CVC-RI. There was no significant relationship between CVC-RI and age, gender, body mass index (BMI), marital status, education, residency, comorbidities, addiction, and etiology of kidney failure. Variables such as smoking (p = 0.012), catheter type (p = 0.031), CVC location (p = 0.026), emergency catheter placement (p = 0.005), previous catheter history          (p = 0.004), and number of previous catheter (p = 0.006), previous catheter infection history (p = 0.002), and antibiotic use in the recent month (p = 0.001) were associated with an increased CVC-RI. Of the positive blood cultures, the majority were gram - positive bacteria. Conclusion: CVC-RI in HD is high and smoking, CVC location, number of previous catheters and their infection history, and antibiotic use in the recent month are risk factors related to CVC-RI. Education on proper hygiene for the prevention of CVC-RI is essential for patients that had no previous intravascular line. Staphylococcus aureus must be taken into account for empirical therapy.   *Corresponding Author: Abbas Allami; Email: [email protected] Please cite this article as: Akhavan L, Najjari H, Bijani B, Kordi A, Allami A. Central Catheter Infection in Patients on Acute and Chronic Hemodialysis: A Cross Sectional Study. Arch Med Lab Sci. 2023;9:1-11 (e5). https://doi.org/10.22037/amls.v9.3920

Investigating the relationship between sexual intimacy, emotion regulation and attachment styles

Background and objective: Marriage is an intimate relationship with authority and is undergoing transformation, therefore intimacy in marriage is different from the type of relationship experienced between mother and child. The purpose of this research is to investigate the relationship between sexual intimacy, emotion regulation and attachment dimensions in married people. Methods: The research method is cross-sectional correlation. The statistical population of the current study includes all married men and women living in Tehran province, which was selected using available sampling method. The data were obtained using the close relationship experience questionnaire (Brennen, Clark and Shaver, 1998), the cognitive regulation of emotion questionnaire (Garnefsky, Kraij and Spinhaven, 2002) and Bagaroosi's intimacy needs questionnaire (2001). The data were analyzed by mean, standard deviation, correlation coefficient and multivariate regression and SPSS 21 and AMOS statistical software. Results: The results showed that there is a significant relationship between the dimensions of anxious attachment and intensity of sexual need (r=0.167, P<0.01) and sexual participation (r=0.157, P<0.01) in married people. There is. The relationship between the dimensions of avoidant attachment and sexual intimacy in the sexual need satisfaction component was significant (p<0.01, r=0.155). The correlation between anxiety style and negative emotional regulation strategies was significant (r=0.132). But there was a significant correlation between the dimension of avoidant attachment and positive emotional regulation (r=0.237). Sexual intimacy and positive emotional regulation were also related (r=0.174). Conclusion: It can be concluded that both dimensions of attachment are correlated with sexual intimacy, but there is no significant correlation between emotional regulation and attachment styles

A Holistic Study on the Effect of Annealing Temperature and Time on CH3NH3PbI3-Based Perovskite Solar Cell Characteristics

International audienceThe time and annealing temperature for the film crystallization in perovskite solar cells (PSCs) is critical and is at the stake of device optimization. It governs the crystallization process, the film’s morphorlogy and texture and the level of non-radiative defects, which in whole control the power conversion efficiency (PCE). However, deciphering each of these parameters in the device cell characteristics remains not totally clear. In this work, we led a holistic study considering temperature and time for the MAPbI 3 crystallization as a free parameter to study how the latter is impacting on the film’s characteristics and how the device figure of merit is affected. The results suggest that the crystallinity level of the grains plays an important role in the photo-current value whereas the morphology and PbI 2 impurities resulting from the onset of thermal decomposition of MAPbI 3 penalizes the cell photovoltage and the fill factor values. Based on this study, it is highlighted that flash high temperature annealing is beneficial to limit out-of-plane substrate grain boundaries, resulting in a device exhibiting 18.8% power conversion efficiency compared to 18.0% when more standard post-annealing procedure is employed