Search

Mucosal Associated Invariant T (MAIT) cells are an innate-like T cell type conserved in many mammals and especially abundant in humans. Their semi-invariant T cell receptor (TCR) recognises the MHC-like molecule MR1 presenting riboflavin intermediates associated with microbial metabolism. Full MAIT cell triggering requires co-stimulation via cytokines, and the cells can also be effectively triggered in a TCR-independent manner by cytokines (e.g. IL-12 and IL-18 in combination). Thus, triggering of MAIT cells is highly sensitive to local soluble mediators. Suppression of MAIT cell activation has not been well explored and could be very relevant to their roles in infection, inflammation, and cancer. Prostaglandins are major local mediators of these micro-environments which can have regulatory roles for T cells. Here, we explored whether prostaglandins suppressed MAIT cell activation in response to TCR-dependent and -independent signals. We found that PGE

Mucosal-associated invariant T cells or MAIT cells are an abundant cell type in humans and especially so in the liver. MAIT cells are a subset of T lymphocytes that sit at a bridge between innate and adaptive immunity, so-called innate-like or “unconventional” T cells. The specificity of their antigen receptor (T cell receptor or TCR) is for the conserved major histocompatibility complex (MHC)-related molecule MR1, which presents a modified bacterial metabolite from the vitamin B2 biosynthesis pathway – this allows them to respond in the presence of many bacteria or yeast. MAIT cells also possess an array of cytokine receptors, which allows triggering independently of the TCR. The combination of such signals drives their functionality – this means they can respond to a range of stimuli and likely play a role not only in infection or inflammation, but also under homeostatic conditions.In this review, we will look at the question of what MAIT cells are doing in the normal liver and how they behave in the setting of disease. These questions are of relevance because MAIT cells are such a distinctive cell type enriched in the liver under normal conditions, and their modulation could be of therapeutic benefit. The recent discovery that they appear to be involved in liver fibrosis is particularly of interest in this context.

In this work, performance of Double Gate Gaussian Doped Negative Capacitance Junctionless Transistor (DGGDNCJLT) has been studied for temperature range 200–500 K to explore the suitability of the d...

Background: Following a single dose of BNT162b2 mRNA vaccine, higher antibody titres are observed following prior SARS-CoV-2 infection than in infection-naive individuals, but T-cell responses are less well defined. Methods: We sampled healthcare workers (HCWs) enrolled in the UK PITCH study, before and after BNT162b2 mRNA vaccination. We measured spike-specific antibody, and quantified T-cell responses by IFNγ ELISpot assay and intracellular staining of peripheral blood mononuclear cells (PBMC), comparing SARS-CoV-2-naive individuals to those with prior infection. Findings: HCWs aged 22 to 71 years received one (n=216) or two (n=21) vaccine doses. After a single dose, the spike-specific T-cell response was six-fold higher in previously-infected vs. naive individuals (median 340 vs. 58 SFU/10 6 PBMC, p

In this paper, we study the impact of vertical Gaussian doping (GD) profile and ferroelectric (FE) negative capacitance phenomenon on the performance of nanoscale double-gate junctionless (JL) transistor. The device characteristics have been obtained by using the baseline approach of combining Landau–Khalatnikov equation with TCAD simulations. Doped HfO2 has been incorporated as FE gate insulator and parameters such as coercive field ( ${E}_{c}$ ) and remanent polarization ( ${P}_{r}$ ) have been optimized to achieve nonhysteretic voltage amplification along with substantial gain. The impact of GD profile in the channel and FE gate insulator is examined by studying device characteristics for a wide range of projected range ( ${R}_{p}$ ), straggle ( $\sigma$ ), and peak doping ( ${N}_{\mathbf {pk}}$ ) values for optimized ${E}_{c}$ and ${P}_{r}$ . It has been demonstrated that the proposed device exhibits reduced leakage current, increase in ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio by 4 orders, and approximately 2 times improvement in ${g}_{m}/{I}_{d}$ values compared to the conventional double-gate GD JL transistor. Furthermore, the proposed device exhibits reverse drain induced barrier lowering effect which leads to increase in barrier even in nanoscale regime.

In this work, the negative capacitance phenomenon exhibited by ferroelectric materials has been incorporated in Junctionless Cylindrical Surrounding Gate (JLCSG) transistor and an analytical model has been developed to study the electrical characteristics of the device by taking into account Landau Khalatnikov equation along with parabolic potential approximation. Using the derived model various electrical parameters such as potential, gain, drain current, gate capacitance etc have been obtained. Silicon doped hafnium oxide has been incorporated as the ferroelectric material and exhaustive study has been done to study the impact of interfacial layer and metal workfunction on device characteristics as these have significant impact on the performance of Junctionless devices. It has been demonstrated by analytical model and TCAD simulations that by incorporating ferroelectric layer and optimizing metal work function and interfacial layer thickness, the device performance of JLCSG can be substantially improved.

In this work, we present a study that explores the suitability of Double Gate Ferroelectric Junctionless Transistor (DGFJL) incorporating Si:HfO2 for high temperature applications. At present, very few studies are focussed on Si:HfO2 to investigate its integrability in the present CMOS design space. Therefore, in the present study, using analytical modeling and TCAD simulations, it is demonstrated that Si:HfO2 based DGFJL exhibits superior performance in terms of substantial gain, reduced leakage currents, improved current drivability and high Ion/Ioff ratio at elevated temperatures as compared to the DGJL counterpart. The study, thus, highlights the fact that DGFJL is a potential candidate for device applications at high temperatures.

In this work the performance of Junctionless Gaussian Doped Negative Capacitance Silicon-on-Insulator (JLGDNCSOI) transistor has been explored to examine the suitability of device for various analog and digital applications. The Negative Capacitance phenomenon of ferroelectric layer along with vertical Gaussian doped channel significantly enhances the performance of JL devices. To explore the electrical characteristics of JLGDNCSOI transistor TCAD models along with Landau-Khalatnikov equation which takes into account properties of Hafnium oxide based ferroelectric layer such as coercive field and remanent polarization have been used. It has been demonstrated that device exhibits substantially improved transfer characteristics, output characteristics, transconductance generation factor, output conductance and unity gain frequency.

Item description: Chapter 7 in book 'MAIT Cells' (2020), ed H Kaipe and I Magalhaes. Methods in Molecular Biology, volume 2098. Mucosal-associated invariant T (MAIT) cells are an abundant innate-like T cell subset in humans, enriched in mucosal tissues and the liver. MAIT cells express a semi-invariant T cell receptor (TCR) and recognize microbial-derived riboflavin metabolites presented on the MHC Class I-like molecule MR1. In addition to activation via the TCR, MAIT cells can also be activated in response to cytokines such as IL-12 and IL-18, in contrast to conventional T cells. Here we describe TCR-dependent and -independent methods for MAIT cell activation. The TCR-dependent approaches include stimulation with microbead- or plate-bound anti-CD3/anti-CD28 antibodies, and with 5-OP-RU or paraformaldehyde (PFA)-fixed E. coli in the presence of antigen-presenting cells (APCs). The latter method includes a combination of TCR- and cytokine-mediated stimulation. The TCR-independent methods include direct stimulation with the recombinant cytokines IL-12 and IL-18, and indirect stimulation with TLR-4/TLR-8 agonists or influenza A virus in the presence of APCs. Finally, we outline a protocol to analyze activated MAIT cells using flow cytometry.

Iron is critical for life but toxic in excess because of iron-catalysed formation of pro-oxidants that cause tissue damage in a range of disorders. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates cell-intrinsic protective antioxidant responses, while the peptide hormone hepcidin maintains systemic iron homoeostasis, but is pathophysiologically decreased in haemochromatosis and β-thalassaemia. Here, we show that Nrf2 is activated by iron-induced, mitochondria-derived pro-oxidants and drives bone morphogenetic protein 6 (Bmp6) expression in liver sinusoidal endothelial cells, which in turn increases hepcidin synthesis by neighbouring hepatocytes. In Nrf2 knockout mice, the Bmp6–hepcidin response to oral and parenteral iron is impaired, and iron accumulation and hepatic damage are increased. Pharmacological activation of Nrf2 stimulates the Bmp6–hepcidin axis, improving iron homoeostasis in haemochromatosis and counteracting the inhibition of Bmp6 by erythroferrone in β-thalassaemia. We propose that Nrf2 links cellular sensing of excess toxic iron to the control of systemic iron homoeostasis and antioxidant responses, and may be a therapeutic target for iron-associated disorders.

In this work we have proposed an analytical model for Double Gate Ferroelectric Junctionless Transistor (DGFJL), a novel device, which incorporates the advantages of both Junctionless (JL) transistor and Negative Capacitance phenomenon. A complete drain current model has been developed by using Landau-Khalatnikov equation and parabolic potential approximation to analyze device behavior in different operating regions. It has been demonstrated that DGFJL transistor acts as a step-up voltage transformer and exhibits subthreshold slope values less than 60 mV/dec. In order to assess the advantages offered by the proposed device, extensive comparative study has been done with equivalent Double Gate Junctionless Transistor (DGJL) transistor with gate insulator thickness same as ferroelectric gate stack thickness of DGFJL transistor. It is shown that incorporation of ferroelectric layer can overcome the variability issues observed in JL transistors. The device has been studied over a wide range of parameters and bias conditions to comprehensively investigate the device design guidelines to obtain a better insight into the application of DGFJL as a potential candidate for future technology nodes. The analytical results so derived from the model have been verified with simulated results obtained using ATLAS TCAD simulator and a good agreement has been found.

The present analysis is focused on studying the effect of ferroelectric (FE) insulator layer and non-uniform doping on the performance of short channel planar SOI Junctionless transistor. The channel is considered to be non-uniformly doped in vertical direction and hafnium oxide based ferroelectric material is considered in the gate stack. The device behavior has been studied by obtaining various device characteristics and the effect of FE insulator layer thickness along with doping profile parameters such as straggle and projected range has been explored. It has been observed that incorporation of non-uniform doping and ferroelectric layer significantly improves the performance of planar SOI Junctionless transistor.

Electrical characteristics of Double Gate Graded Channel Negative Capacitance Field Effect Transistor (DGGCNCFET) have been explored in this study to investigate the potential of DGGCNCFET for low voltage/power digital/analog applications. The device performance has been extensively studied by self-consistently solving Landau-Khalatnikov equation with TCAD models. Various metrics have been obtained for a wide range of ferroelectric layer thicknesses and drain bias voltages. It has been observed that DGGCNCFET exhibits substantial improvement for low voltage/power analog applications

This paper proposes a distributed Sliding Mode Controller (SMC) with network irregularities like time delay compensation for secondary voltage control of Microgrid. The distributed SMC is designed using the principle of multi-agent system and placed at each DGs of microgrid. The proposed DSM C controller is designed using the graph theory and so require the voltage information of neighbors DGs through communication network. However the neighbor voltage information might incur time delay in the communication network due to substantial distance between neighbors DGs and it may deteriorates the Microgrid performance. Pade Approximation technique is used to overcome the effect of communication network time delay. The efficacy of the proposed scheme is shown in simulation on a Microgrid test system.

In the present work, the impact of high-k spacers and Negative Capacitance (NC) has been examined on the performance of nanoscale Double Gate Junctionless Transistors by self consistently solving Landau Khalatnikov equation with TCAD simulations. Ferroelectric hafnium oxide is considered in gate stack with interfacial layer of silicon dioxide. The impact of different dielectric constants of spacer and different spacer lengths have been explored extensively on various electrical parameters. It has been demonstrated that high-k spacers significantly improve the gate controllability, thereby, further enhancing the negative capacitance (NC) effect of ferroelectric layer on device operation. The subthreshold swing values as low as 10mV/dec have been obtained along with substantial improvement in I on /I off ratio (about 3 orders), thereby, indicating suitability of the device for future ultra low power electronic applications.

In the present work, performance of short channel symmetric Double Gate Gaussian Doped Ferroelectric FET (DGGDFEFET) has been studied by using fully coupled TCAD simulations with Landau Khalatnikov equation. Ferroelectric layer of PVDF-TrFE (polyvinyledenedifluoride-trifluoroethylene) is considered as gate insulator with an intermediate layer of SiO 2 . The channel is non-uniformily doped in vertical direction and the analog and digital performance of DGGDFEFET has been investigated by obtaining transfer characteristics, subthreshold swing, transconductance ($g_{m}$), transconductance generation factor (TGF), output characteristics and output conductance ($g_{d}$). It has been demonstrated that due to negative capacitance and vertical non-uniform doping, DGGDFEFET shows superior analog and digital performance since it offers super steep transfer characteristics and substantially improved TGF and output characteristics.

In this work, the impact of negative capacitance effect and vertical Gaussian doping profile in the channel has been examined on short channel Double Gate FET by employing baseline approach. The electrical characteristics of Double Gate Gaussian Doped Negative Capacitance FET (DGGDNCFET) have been investigated considering ferroelectric layer of PVDF-TrFE (polyvinyledenedifluoride-trifluoroethylene) in the gate stack along with an interfacial layer of SiO 2 . A substantial improvement in performance of DGFET has been observed by incorporating negative capacitance effect and non-uniform doping profile in terms of surface potential, charge density, gate capacitance, drain current and subthreshold slope. Subthreshold slope values much lower than 60mV/dec have been observed at gate length = 20nm, which implies that the device is suitable for applications which require ultra low voltage/power.

In the present work, the impact of Negative Capacitance (NC) effect of ferroelectric materials has been studied on Elliptical Gate All Around Junctionless Transistors by incorporating these materials as gate insulator. Landau Devonshire theory and parabolic potential approximation has been used to develop an analytical model to obtain various electrical parameters like surface potential, gate capacitance, subthreshold slope etc. The effect of varying aspect ratio (AR) has been incorporated in the model by obtaining effective radius depending on lengths of major and minor axes. Using the developed model a comparative analysis has been done for devices with two different ferroelectric materials, PZT and SBT, to investigate the feasibility of these materials for integration into future CMOS technology. It has been observed that for different aspect ratios, the device exhibits gain > 1 which also leads to point subthreshold swing value as low as 9mV/dec for SBT and 11mV/dec for PZT for a small range of applied bias, thereby, signifying suitability of such devices for sub-60mV/dec, low power applications.

In this work, we have theoretically investigated the impact of temperature dependent Negative Capacitance (NC) effect on electrical characteristics of long channel Double Gate Ferroelectric Junctionless Transistor for temperature range 280 to 340K. We have considered metal-ferroelectric-semiconductor (MFS) structure and incorporated ferroelectric material Strontium Bismuth Tantalate (SBT) as gate insulator. The impact of temperature variation on electrical parameters such as surface potential, gain, gate capacitance, and mobile charge density has been studied. It has been observed that internal voltage amplification decreases with increase in temperature. Also, degradation of gain and gate capacitance is observed with gradual increase in temperature.

In this work high temperature performance of Elliptical Gate Ferroelectric Junctionless Transistor has been theoretically investigated and a temperature dependent analytical model has been developed to examine the effect of elliptical cross section along with negative capacitance (NC) phenomenon on junctionless devices. The electrical characteristics of Elliptical Gate Ferroelectric Junctionless Transistor have been studied for temperature range 300K to 360K and Strontium Bismuth Tantalate (SBT), a ferroelectric material has been considered as the gate insulator. The impact of temperature variation along with change in aspect ratio has been examined on various electrical parameters such as surface potential, gain, gate capacitance and subthreshold slope. It has been observed that voltage upconversion achieved due to NC phenomenon exhibited by ferroelectric material is less for device with aspect ratio 1, thereby, signifying its suitability for high temperature energy efficient applications.

We have developed a complete drain current model to study the impact of negative capacitance phenomenon exhibited by ferroelectric materials in Symmetric Double Gate Junctionless Transistor using Pao-Sah current formulation and Landau Devonshire theory. Strontium Bismuth Tantalate (SBT) is used as gate insulator and no interface layer is considered in the analysis i.e. metal-ferroelectric-semiconductor (MFS) structure has been studied. Using the analytical model the various parameters obtained are gain, gate capacitance, subthreshold swing, threshold voltage, mobile charge density and drain current. It has been observed that values of gain>1 and subthreshold swing

In this paper we have developed an analytical model for Double Gate Ferroelectric Junctionless (DGFJL) transistor using Landau's theory and parabolic potential approximation. We have obtained expressions for surface potential and electric field and have demonstrated negative capacitance effect provided by ferroelectric layer. The results also demonstrate the step-up conversion capability of this device, thereby signifying improved gate control and the suitability of this device for low voltage/low power switching applications.