Semiempirical Modeling of Reset Transitions in Unipolar Resistive-Switching based Memristors

We have measured the transition process from the high to low resistivity states, i.e., the reset process of resistive switching based memristors based on Ni/HfO2/Si-n+ structures, and have also developed an analytical model for their electrical characteristics. When the characteristic curves are plotted in the current-voltage (I-V) domain a high variability is observed. In spite of that, when the same curves are plotted in the charge-flux domain (Q-phi), they can be described by a simple model containing only three parameters: the charge (Qrst) and the flux (rst) at the reset point, and an exponent, n, relating the charge and the flux before the reset transition. The three parameters can be easily extracted from the Q-phi plots. There is a strong correlation between these three parameters, the origin of which is still under study

Ocean currents modify the coupling between climate change and biogeographical shifts

Biogeographical shifts are a ubiquitous global response to climate change. However, observed shifts across taxa and geographical locations are highly variable and only partially attributable to climatic conditions. Such variable outcomes result from the interaction between local climatic changes and other abiotic and biotic factors operating across species ranges. Among them, external directional forces such as ocean and air currents influence the dispersal of nearly all marine and many terrestrial organisms. Here, using a global meta-dataset of observed range shifts of marine species, we show that incorporating directional agreement between flow and climate significantly increases the proportion of explained variance. We propose a simple metric that measures the degrees of directional agreement of ocean (or air) currents with thermal gradients and considers the effects of directional forces in predictions of climate-driven range shifts. Ocean flows are found to both facilitate and hinder shifts depending on their directional agreement with spatial gradients of temperature. Further, effects are shaped by the locations of shifts in the range (trailing, leading or centroid) and taxonomic identity of species. These results support the global effects of climatic changes on distribution shifts and stress the importance of framing climate expectations in reference to other non-climatic interacting factors

Variability and power enhancement of current controlled resistive switching devices

characterized using both current and voltage sweeps, with the device resistance and its cycle-to-cycle variability being analysed in each case. Experimental measurements indicate a clear improvement on resistance states stability when using current sweeps to induce both set and reset processes. Moreover, it has been found that using current to induce these transitions is more efficient than using voltage sweeps, as seen when analysing the device power consumption. The same results are obtained for devices with a Ni top electrode and a bilayer or pentalayer of HfO2/Al2O3 as dielectric. Finally, kinetic Monte Carlo and compact modelling simulation studies are performed to shed light on the experimental resultsConsejería de Conocimiento, Investigaci´on y Universidad, Junta de Andalucía (Spain)FEDER program for the project B-TIC-624-UGR20Spanish Consejo Superior de Investigaciones Científicas (CSIC) for the intramural project 20225AT012Ramón y Cajal grant No. RYC2020-030150-I

Phase-type distributions for studying variability in resistive memories

A new statistical approach has been developed to analyze Resistive Random Access Memory (RRAM) variability. The stochastic nature of the physical processes behind the operation of resistive memories makes variability one of the key issues to solve from the industrial viewpoint of these new devices. The statistical features of variability have been usually studied making use of Weibull distribution. However, this probability distribution does not work correctly for some resistive memories, in particular for those based on the Ni/HfO2/Si structure that has been employed in this work. A completely new approach based on phase-type modeling is proposed in this paper to characterize the randomness of resistive memories operation. An in-depth comparison with experimental results shows that the fitted phase-type distribution works better than the Weibull distribution and also helps to understand the physics of the resistive memories

Specific gene correction of the AGXT gene and direct cell reprogramming for the treatment of Primary Hyperoxaluria Type 1

P428 Primary Hyperoxaluria Type 1 (PH1) is an inherited rare metabolic liver disease caused by the deficiency in the alanine: glyoxylate aminotransferase enzyme (AGXT), involved in the glyoxylate metabolism. The only potentially curative treatment is organ transplantation. Thus, the development of new therapeutic approaches for the treatment of these patients appears as a priority.We propose the combination of site-specific gene correction and direct cell reprogramming for the generation of autologous phenotypically healthy induced hepatocytes (iHeps) from skin-derived fibroblast of PH1 patients. For the correction of AGXT mutations, we have designed specific gene editing tools to address gene correction by two different strategies, assisted by CRISPR/Cas9 system. Accurate specific point mutation correction (c.853T-C) has been achieved by homologydirected repair (HDR) with ssODN harbouring wild-type sequence. In the second strategy, an enhanced version ofAGXTcDNAhas been inserted near the transcription start codon of the endogenous gene, constituting an almost universal correction strategy for PH1 mutations. Direct reprogramming of fibroblasts has been conducted by overexpression of hepatic transcription factors and in vitro culture in defined media. In vitro characterization of healthy induced hepatocytes (iHeps) has demonstrated hepatic function of the reprogrammed cells. PH1 patient fibroblasts and , ,

Disrupted in schizophrenia 1 (DISC1) L100P mutants have impaired activity-dependent plasticity in vivo and in vitro

Major neuropsychiatric disorders are genetically complex but share overlapping etiology. Mice mutant for rare, highly penetrant risk variants can be useful in dissecting the molecular mechanisms involved. The gene disrupted in schizophrenia 1 (DISC1) has been associated with increased risk for neuropsychiatric conditions. Mice mutant for Disc1 display morphological, functional and behavioral deficits that are consistent with impairments observed across these disorders. Here we report that Disc1 L100P mutants are less able to reorganize cortical circuitry in response to stimulation in vivo. Molecular analysis reveals that the mutants have a reduced expression of PSD95 and pCREB in visual cortex and fail to adjust expression of such markers in response to altered stimulation. In vitro analysis shows that mutants have impaired functional reorganization of cortical neurons in response to selected forms of neuronal stimulation, but there is no altered basal expression of synaptic markers. These findings suggest that DISC1 has a critical role in the reorganization of cortical plasticity and that this phenotype becomes evident only under challenge, even at early postnatal stages. This result may represent an important etiological mechanism in the emergence of neuropsychiatric disorders

Variability approaching the thermal limits can drive diatom community dynamics

Organismal distributions are largely mediated by temperature, suggesting thermal trait variability plays a key role in defining species\u27 niches. We employed a trait‐based approach to better understand how inter‐ and intraspecific thermal trait variability could explain diatom community dynamics using 24 strains from 5 species in the diatom genusSkeletonema, isolated from Narragansett Bay (NBay), where this genus can comprise up to 99% of the microplankton. Strain‐specific thermal reaction norms were generated using growth rates obtained at temperatures ranging from −2°C to 36°C. Comparison of thermal reaction norms revealed inter‐ and intraspecific similarities in the thermal optima, but significant differences approaching the thermal limits. Cellular elemental composition was determined for two thermally differentiated species and again, the most variation occurred approaching the thermal limits. To determine the potential impact of interspecific variability on community composition, a species succession model was formulated utilizing each species\u27 empirically determined thermal reaction norm and historical temperature data from NBay. Seasonal succession in the modeled community resembled the timing of species occurrence in the field, but not species\u27 relative abundance. The model correctly predicted the timing of the dominant winter–spring species, Skeletonema marinoi, within 0–14 d of its observed peak occurrence in the field. Interspecific variability approaching the thermal limits provides an alternative mechanism for temporal diatom succession, leads to altered cellular elemental composition, and thus has the potential to influence carbon flux and nutrient cycling, suggesting that growth approaching the thermal limits be incorporated into both empirical and modeling efforts in the future

Multivariate analysis and extraction of parameters in resistive RAMs using the Quantum Point Contact model

A multivariate analysis of the parameters that characterize the reset process in RRAMs has been performed. The different correlations obtained can help to shed light on the current components that contribute in the Low Resistance State (LRS) of the technology considered. In addition, a screening method for the Quantum Point Contact (QPC) current component is presented. For this purpose the second derivative of the current has been obtained using a novel numerical method which allows determining the QPC model parameters. Once the procedure is completed, a whole RS series of thousands of curves is studied by means of a genetic algorithm. The extracted QPC parameter distributions are characterized in depth to get information about the filamentary pathways associated with LRS in the low voltage conduction regime.Spanish Ministry of Economy and Competitiveness TEC2014-52152-C3-2-R , MTM2013-47929-P (also supported by the FEDER program)IMB-CNM Spanish Ministry of Economy and Competitiveness TEC2014-52152-C3-1-R and TEC2014-54906-JIN (supported by the FEDER program)ENIAC Joint Undertaking-PANACHE project.Spanish ICTS Network MICRONANOFAB

A thorough investigation of the switching dynamics of TiN/Ti/10 nm-HfO2/W resistive memories

Producción CientíficaThe switching dynamics of TiN/Ti/HfO2/W-based resistive memories is investigated. The analysis consisted in the systematic application of voltage sweeps with different ramp rates and temperatures. The obtained results give clear insight into the role played by transient and thermal effects on the device operation. Both kinetic Monte Carlo simulations and a compact modeling approach based on the Dynamic Memdiode Model are considered in this work with the aim of assessing, in terms of their respective scopes, the nature of the physical processes that characterize the formation and rupture of the filamentary conducting channel spanning the oxide film. As a result of this study, a better understanding of the different facets of the resistive switching dynamics is achieved. It is shown that the temperature and, mainly, the applied electric field, control the switching mechanism of our devices. The Dynamic Memdiode Model, being a behavioral analytic approach, is shown to be particularly suitable for reproducing the conduction characteristics of our devices using a single set of parameters for the different operation regimes.Ministerio de Ciencia e Innovación de España - FEDER [PID2022-139586NB-C41, PID2022-139586NB-C42, PID2022-139586NB-C43, PID2022-139586NB-C44]Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía [B-TIC-624-UGR20]Consejo Superior de Investigaciones Científicas (CSIC)- FEDER [20225AT012]Ramón y Cajal grant number RYC2020-030150-IEuropean project MEMQuD (code 20FUN06) which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme

Electronic neutron personal dosemeters: their performance in mixed radiation fields in nuclear power plants

This work describes spectral distributions of neutrons obtained as function of energy and direction at four workplace fields at the Krümmel reactor in Germany. Values of personal dose equivalent Hp(10) and effective dose E are determined for different directions of a person's orientation in these fields and readings of personal neutron dosemeters—especially electronic dosemeters—are discussed with respect to Hp(10) and