SPICE model for complementary resistive switching devices based on anti-serially connected quasi-static memdiodes

Acord transformatiu CRUE-CSICThis work was supported by the Spanish Ministry of Science, Innovation, and Universities through projects TEC2017-84321-C4-1-R and TEC2017-84321-C4-4-R.This paper reports the use of the Quasi-static Memdiode Model (QMM) for simulating Complementary Resistive Switching (CRS) devices. CRS arises from the anti-serial connection of two memristors and it is used for generating low and high-resistance regions in the I-V characteristic with the aim of mitigating the sneak-path conduction problem in crossbar arrays. Here, the use of the QMM for CRS in the form of a six terminal subcircuit is explored. While two terminals of the subcircuit correspond to the conventional input and output pins of the CRS structure, the rest provide information about the voltage at the central node, the low-voltage conductance of each device, and the low-voltage conductance of the whole structure. Special attention is paid to the simulation of the so-called table with legs hysteresis loop (resistance at fixed bias vs. write voltage), which is often invoked in connection with devices that exhibit switching activity at the two interfaces of a single dielectric layer. Because of the internal potential drop distribution, the switching process takes place alternately at one side of the structure or the other giving rise to a pseudo-CRS behavior. The flexibility of the proposed approach is demonstrated through a series of fitting exercises that involve experimental data reported in the literature. The model script for the SPICE simulator is also provided

Exploring Conductance Quantization Effects in Electroformed Filaments for Their Potential Application to a Resistance Standard

Altres ajuts: acords transformatius de la UABThe ballistic conduction through narrow constrictions connecting charge reservoirs exhibits conductance quantization effects. Since the quantum of conductance (Formula presented.) is only related to fundamental constants of nature, these effects might allow the implementation of a standard of resistance, fulfilling the requirements of the 2019 revised International System of Units. Moreover, this standard would be able to work at room temperature and without a magnetic field, thus allowing its on-chip implementation. In this work, the authors propose that breakdown filaments in thin oxide layers might be useful to this purpose. In particular, conductance quantization effects in nanolaminate AlO/HfO dielectrics are reported and the role of intrinsic values of conductance and extrinsic parasitic elements are analyzed. The fact that breakdown filaments are irreversible is an advantage due to their expected stability and to the lack of cycle-to-cycle variations (as compared to resistive switching devices). Although the reported sample-to-sample variations are still too large for a real application, there is room for improving the controlover breakdown filaments through material design and electroforming conditions. Provided that this control is achieved, an on-chip implementation of a resistance standard for the realization of self-calibrating electrical systems and equipment with zero-chain traceability would be possible

Modeling and simulation of successive breakdown events in thin gate dielectrics using standard reliability growth models

Altres ajuts: acords transformatius de la UABThe application of constant electrical stress to a metal-insulator-semiconductor (MOS) or metal-insulator-metal (MIM) structure can generate multiple breakdown events in the dielectric film. Very often, these events are detected as small jumps in the current-time characteristic of the device under test and can be treated from the stochastic viewpoint as a counting process. In this letter, a wide variety of standard reliability growth models for this process are assessed in order to determine which option provides the best simulation results compatible with the experimental observations. For the generation of the breakdown event arrivals, two alternative stochastic methods for the power-law Poisson process are investigated: first, the inversion algorithm for the cumulative distribution function and second, an on-the-fly method based on the so-called rejection algorithm. Though both methods are equivalent, the first one is more appropriate for data analysis using spreadsheet calculations while the second one is highly suitable for circuit simulation environments like LTSpice. The connection of the selected nonhomogeneous Poisson process with the Weibull model for dielectric breakdown is also discussed

Assessment of the variability of the I-V characteristic of HfO2-based resistive switching devices and its simulation using the quasi-static memdiode model

Altres ajuts: acords transformatius de la UABVariability of the conduction characteristics of filamentary-type resistive switching devices or resistive RAMs (RRAMs) is a hot research topic both in academia and industry because it is currently considered one of the major showstoppers for the successful development and application of this technology. In this work, we thoroughly investigate the statistics of the cycle-to-cycle (C2C) variability observed in the experimental current-voltage (I-V) curves of HfO-based memristive structures using the fitdistrplus package for the R language. This exploratory analysis allows us to identify which parametric probability distributions are the most suitable candidates for describing our data. This study involves graphical tools such as the density, skewness-kurtosis (S-K), and quantile-quantile (Q-Q) plots. The analysis is completed with the aid of goodness-of-fit statistics (Kolmogorov-Smirnov, Cramer-von Mises, Anderson-Darling) and criteria (Akaike's and Bayesian). The selected distributions are incorporated into the SPICE script of the quasi-static memdiode model for resistive switching devices and used for simulating uncorrelated C2C variability. Finally, a one-way sensitivity analysis is carried out in order to test the impact of the model parameters variation in the output characteristics of the device

Preocupações sobre a recorrência do câncer em mulheres mexicanas sobreviventes do câncer de mama. Propriedades psicométricas da escala CARS

Fear of recurrence is one of the main affectations of cancer survivors. In Latin-American exist a lack of evidence on the subject and of valid instruments to measure it. The objective of this study was to determine the psychometric properties of the Concerns About Recurrence Scale in Mexican breast cancer survivors. An instrumental study was carried out with 200 women breast cancer survivors with a mean age of 53 years old and a mean survival of 52.5 months. A confirmatory factor analysis of the original version of the scale identified four factors that explained 77 % of the variance and satisfactory goodness of fit indicators: CFI = .967, TLI = .957, SRMR = .035, RMSEA = .071 as well as high internal consistency α = .945. Significant associations were also identified between general fear subscale, anxiety subscale of the HADS and total HADS score (r = .638 and r = .607; p = .01). The CARS presented adequate validity, reliability and factorial structure. It is recommended for usage in clinical care and research with Mexican breast cancer survivors.El miedo a la recurrencia es una de las principales afectaciones de los supervivientes de cáncer. En América Latina existe una falta de evidencia en el tema y de instrumentos válidos para medirlo. El objetivo del presente estudio fue determinar las propiedades psicométricas de la Escala de Preocupaciones Acerca del Cáncer (CARS, por su sigla en inglés) en supervivientes de cáncer de mama mexicanas. Se llevó a cabo un estudio instrumental con 200 mujeres supervivientes de cáncer mamario con una edad promedio de 53 años y una sobrevida promedio de 52.5 meses. Un análisis factorial confirmatorio de la versión original del instrumento identificó cuatro factores que explicaron el 77 % de la varianza de la escala e indicadores de bondad de ajuste satisfactorios: CFI = .967, TLI = .957, SRMR = .035, RMSEA = .071, así como una elevada consistencia interna α = .945. Asimismo, se identificaron asociaciones significativas entre las subescalas de miedo general, ansiedad de la HADS y puntaje total de la HADS (r = .638 y r = .607; p = .01). La escala CARS presentó adecuada validez, confiabilidad y estructura factorial. Es recomendable su uso en escenarios clínicos y de investigación con supervivientes de cáncer de mama mexicanas.O medo da recorrência é uma das principais sequelas dos sobreviventes do câncer. Na América Latina há uma falta de evidências sobre o assunto e uma falta de instrumentos válidos para medi-lo. O objetivo do presente estudo foi determinar as propriedades psicométricas da Escala Preocupações sobre o Câncer (CARS) em sobreviventes do câncer de mama mexicanas. Foi realizado um estudo instrumental com 200 mulheres sobreviventes de câncer de mama com uma média de idade de 53 anos e uma sobrevivência média de 52,5 meses. Uma análise fatorial confirmatória da versão original do instrumento identificou quatro fatores que explicaram 77 % da variação da escala e indicadores satisfatórios de bondade de ajuste: CFI = 0,967, TLI = 0,957, SRMR = 0,035, RMSEA = 0,071, assim como alta consistência interna α = 0,945. Associações significativas também foram identificadas entre as subescalas de medo geral, ansiedade HADS e pontuação total HADS (r = 0,638 e r = 0,607; p = 0,01). A escala CARS mostrou adequada validade, confiabilidade e estrutura de fatores. É recomendado seu uso em ambientes clínicos e de pesquisa com sobreviventes do câncer de mama mexicanas

Concurrent chemo-radiotherapy following neoadjuvant chemotherapy in locally advanced breast cancer

<p>Abstract</p> <p>Background</p> <p>Despite broad advances in multimodal treatment of locally advanced breast cancer (LABC), 30 to 40% of patients develop loco-regional relapse. The aim of this study was to analyze in a retrospective manner the effectiveness of concurrent chemo-radiotherapy (CCRTh) after neoadjuvant chemotherapy (NCT) in patients with LABC.</p> <p>Methods</p> <p>One hundred twelve patients with LABC (stage IIB-IIIB) were treated with NCT (5-fluorouracil 500 mg/m², doxorubicin 50 mg/m², and cyclophosphamide 500 mg/m²(FAC), or doxorubicin 50 mg/m²and cyclophosphamide 500 mg/m²(AC) IV in four 21-day courses) followed by CCRTh (60 Gy breast irradiation and weekly mitomycin 5 mg/m², 5-fluorouracil 500 mg/m², and dexamethasone 16 mg, or cisplatin 30 mg/m², gemcitabine 100 mg/m²and dexamethasone 16 mg), and 6–8 weeks later, surgery and two additional courses of FAC, AC, or paclitaxel 90 mg/m²weekly for 12 weeks, and in case of estrogen-receptor positive patients, hormonal therapy.</p> <p>Results</p> <p>Stages IIB, IIIA and -B were 21.4, 42.9, and 35.7%, respectively. Pathological complete response (pCR) in the breast was 42% (95% CI, 33.2–50.5%) and, 29.5% (95% CI, 21.4–37.5%) if including both the breast and the axillary nodes. Multivariate analysis showed that the main determinant of pCR was negative estrogen-receptor status (HR = 3.8; 95% CI, 1.5–9; <it>p </it>= 0.016). The 5-year disease-free survival (DFS) was 76.9% (95% CI, 68.2–84.7%). No relationship between pCR and DFS was found. Multivariate analysis demonstrated that the main DFS determinant was clinical stage (IIB and IIIA <it>vs. </it>IIIB, HR = 3.1; 95% CI, 1.02–9.74; <it>p </it>= 0.04). Only one patient had local recurrence. Five-year overall survival was 84.2% (95% CI, 75–93.2%). The toxicity profile was acceptable.</p> <p>Conclusion</p> <p>This non-conventional multimodal treatment has good loco-regional control for LABC. Randomized clinical trials of preoperative CCRTh following chemotherapy, in patients with LABC are warranted.</p

The MAGIC survey in hormone receptor positive (HR+), HER2-negative (HER2−) breast cancer::When might multigene assays be of value?

A modest proportion of patients with early stage hormone receptor-positive (HR+), HER2-negative (HER2-) breast cancer benefit from adjuvant chemotherapy. Traditionally, treatment recommendations are based on clinical/pathologic criteria that are not predictive of chemotherapy benefit. Multigene assays provide prognostic and predictive information that can help to make more informed treatment decisions. The MAGIC survey evaluated international differences in treatment recommendations, how traditional parameters are used for making treatment choices, and for which patients treating physicians feel most uncertain about their decisions