EYE-CLIMA: developing inverse modelling approaches for monitoring national GHG inventories

Emissions of greenhouse gases (GHG) reported by countries in their GHG inventories represent the central information used in international policies based on the Paris agreement and in the Global Stocktake process to help curb global GHG emissions. To maximize trust in these national emission inventories reported to the UNFCCC, procedures for quality control, quality assurance, and verification have been described in the IPCC 2006 national GHG inventory guidelines and extended further in its 2019 refinement. Quantifying emission fluxes via atmospheric measurements and inverse modelling provides an independent assessment of the inventories and can help determine the quality of national inventories and make improvements. While tested in scientific studies, routine applications of inverse modelling in national inventory reports are rare. As a new Horizon Europe project, EYE-CLIMA will perform inverse modelling of a range of important radiative forcers (methane, nitrous oxide, selected fluorinated gases, black carbon) as a monitoring tool on a national scale for selected European countries, together with national inventory agencies, to help develop complementary methods to ensure the robustness and lead to improvements in inventories. The presentation will lay out the overall project concept, including stakeholder involvement, and provide an overview on past experiences with inverse modelling approaches and strategies to implement them in a way useful for national inventory agencies

Decreased mitochondrial DNA content drives OXPHOS dysregulation in chromophobe renal cell carcinoma

Chromophobe renal cell carcinoma (chRCC) and renal oncocytoma (RO) are closely related, rare kidney tumors. Mutations in complex I (CI)-encoding genes play an important role in dysfunction of the oxidative phosphorylation (OXPHOS) system in RO but are less frequently observed in chRCC. As such, the relevance of OXPHOS status and role of CI mutations in chRCC remain unknown. To address this issue, we performed proteome and metabolome profiling as well as mitochondrial whole-exome sequencing to detect mitochondrial alterations in chRCC tissue specimens. Multi-omic analysis revealed downregulation of electron transport chain (ETC) components in chRCC that differed from the expression profile in RO. A decrease in mitochondrial (mt)DNA content, rather than CI mutations, was the main cause for reduced OXPHOS in chRCC. There was a negative correlation between protein and transcript levels of nuclear DNA- but not mtDNA-encoded ETC complex subunits in chRCC. In addition, the reactive oxygen species scavenger glutathione (GSH) was upregulated in chRCC due to decreased expression of proteins involved in GSH degradation. These results demonstrate that distinct mechanisms of OXPHOS exist in chRCC and RO and that expression levels of ETC complex subunits can serve as a diagnostic marker for this rare malignancy

RTN in GexSe1-x OTS Selector Devices

Random telegraph noise (RTN) signals in GexSe1-x ovonic threshold switching (OTS) selector have been analyzed in this work, both before and after the first-fire (FF) operation and at on- and off-states. It is observed that RTN appears after the FF, and its absolute amplitude at the off-state is small and negligible in comparison with the RTN signals in RRAM devices. At the on-state, large RTN signals are observed, which can either partially or fully block the conduction path, supporting that a conductive filament is formed or activated by FF and then modulated during switching. Statistical analysis reveals that the relative RTN amplitude at on-state in GexSe1-x OTS selector is smaller than or equivalent to those in RRAM devices

Stochastic computing based on volatile GeSe ovonic threshold switching selectors

Stochastic computing (SC) is a special type of digital compute strategy where values are represented by the probability of 1 and 0 in stochastic bit streams, which leads to superior hardware simplicity and error-tolerance. In this paper, we propose and demonstrate SC with GeSe based Ovonic Threshold Switching (OTS) selector devices by exploiting their probabilistic switching behavior. The stochastic bit streams generated by OTS are demonstrated with good computation accuracy in both multiplication operation and image processing circuit. Moreover, the bit distribution has been statistically studied and linked to the collective defect de/localization behavior in the chalcogenide material. Weibull distribution of the delay time supports the origin of such probabilistic switching, facilitates further optimization of the operation condition, and lays the foundation for device modelling and circuit design. Considering its other advantages such as simple structure, fast speed, and volatile nature, OTS is a promising material for implementing SC in a wide range of novel applications, such as image processors, neural networks, control systems and reliability analysis

GeSe-based Ovonic Threshold Switching Volatile True Random Number Generator

In this paper, we propose and demonstrate a novel technique for true random number generator (TRNG) application using GeSe-based Ovonic threshold switching (OTS) selector devices. The inherent variability in OTS threshold voltage results in a bimodal distribution of on/off states which can be easily converted into digital bits. The experimental evaluation shows that the proposed TRNG enables the generation of high-quality random bits that passed 12 tests in the National Institute of Standards and Technology statistical test suite without complex external circuits for post-processing. The randomness is further evidenced by the prediction rate of ∼50% using machine learning algorithm. Compared with the TRNGs based on non-volatile memories, the volatile nature of OTS avoids the reset operation, thus further simplifying the operation and improving the generation frequency

Papillary Renal Cell Carcinomas Rewire Glutathione Metabolism and Are Deficient in Both Anabolic Glucose Synthesis and Oxidative Phosphorylation

Papillary renal cell carcinoma (pRCC) is a malignant kidney cancer with a prevalence of 7–20% of all renal tumors. Proteome and metabolome profiles of 19 pRCC and patient-matched healthy kidney controls were used to elucidate the regulation of metabolic pathways and the underlying molecular mechanisms. Glutathione (GSH), a main reactive oxygen species (ROS) scavenger, was highly increased and can be regarded as a new hallmark in this malignancy. Isotope tracing of pRCC derived cell lines revealed an increased de novo synthesis rate of GSH, based on glutamine consumption. Furthermore, profound downregulation of gluconeogenesis and oxidative phosphorylation was observed at the protein level. In contrast, analysis of the The Cancer Genome Atlas (TCGA) papillary RCC cohort revealed no significant change in transcripts encoding oxidative phosphorylation compared to normal kidney tissue, highlighting the importance of proteomic profiling. The molecular characteristics of pRCC are increased GSH synthesis to cope with ROS stress, deficient anabolic glucose synthesis, and compromised oxidative phosphorylation, which could potentially be exploited in innovative anti-cancer strategies

Impact of relaxation on the performance of GeSe true random number generator based on Ovonic threshold switching

Volatile Ovonic threshold switching (OTS) are promising not only as the selector in crossbar resistive switching memory arrays, but also as true random number generators (TRNG) by utilizing its probabilistic switching characteristics. However, investigation on the reliability of OTS-based TRNG is still lacking, which hinders its practical application. Previously, we found that switching probability is dependent on the pulse amplitude and width. In this work, we report that relaxation which happens during the time interval between pulses can cause switching probability drift. Optimizing the bit-generation waveform and modulating the pulse conditions could provide a practical solution, in addition to the impact of external bias and temperature. This work provides useful guidance for the practical design and operation of OTS-based TRNGs

Dependence of switching probability on operation conditions in GexSe1-x ovonic threshold switching selectors

Ovonic threshold switching (OTS) selector is a promising candidate to suppress the sneak current paths in resistive switching memory (RRAM) arrays. Variations in the threshold voltage (Vth), and the hold voltage (Vhd) have been reported, but a quantitative analysis of the switching probability dependence on the OTS operation conditions is still missing. A novel characterization method is developed in this work, and the time-to-switch-on/off (ton/toff) at a constant VOTS is found following the Weibull distribution, based on which the dependence of switching probability on pulse bias and time can be extracted and extrapolated, and the switching probability can be ensured with appropriately chosen operation conditions. The difference between square and triangle switching pulses is also explained. This provides a practical guidance for predicting the switching probability under different operation conditions and for designing reliable one-selector-one-RRAM (1S1R) arrays

New Insights of the Switching Process in GeAsTe Ovonic Threshold Switching (OTS) Selectors

Experimental evidence and analysis in this work provide new insights into the fast switching process in GeAsTe ovonic threshold switching (OTS) selectors. For the first time, the full switching-OFF process, covering the defect cluster shrinking and rupture stages, can be measured and characterized. Two distinct switch-OFF mechanisms and their dependence on the total impedance of the selector and resistor (1S1Rs) circuit are identified. The impact of series resistance value on the switching process, the 1S1Rs operation, and the underlying mechanisms can be explained by the dynamic resistance of OTS that is induced by the transition of defect clusters. This research sheds new light on OTS switching mechanism and its impact on 1S1Rs operation

Cycling induced metastable degradation in GeSe Ovonic threshold switching selector

Ovonic threshold switching (OTS) selector is a promising candidate to suppress the sneak current paths in emerging memory arrays, but there is still a gap between its performance and the rigorous requirement from memory devices, especially its endurance improvement is hindered by insufficient understanding of the mechanism. In this work, cycling induced degradation of GeSe-based OTS selectors is studied with electrical characterization techniques. The existence of metastable state between the on- and off-state during cycling is observed and statistically analyzed alongside with the gradual off-state leakage current increase. Such metastable degradation may be attributed to the generation of unstable Ge-Ge bonds that might be induced by element segregation, which is also responsible for the higher off-state leakage current in GeSe selectors after large cycling or with higher Ge component. This work provides experimental guidance for optimizing OTS selectors