Hysteresis in memristors produces conduction inductance and conduction capacitance effects.

Memristors are devices in which the conductance state can be alternately switched between a high and a low value by means of a voltage scan. In general, systems involving a chemical inductor mechanism as solar cells, asymmetric nanopores in electrochemical cells, transistors, and solid state memristive devices, exhibit a current increase and decrease over time that generates hysteresis. By performing small signal ac impedance spectroscopy, we show that memristors, or any other system with hysteresis relying on the conductance modulation effect, display intrinsic dynamic inductor-like and capacitance-like behaviours in specific input voltage ranges. Both the conduction inductance and the conduction capacitance originate in the same delayed conduction process linked to the memristor dynamics and not in electromagnetic or polarization effects. A simple memristor model reproduces the main features of the transition from capacitive to inductive impedance spectroscopy spectra, which causes a nonzero crossing of current-voltage curves.

Linker histone H1 regulates homeostasis of heterochromatin-associated cRNAs.

Chromatin-associated RNAs (cRNAs) are a poorly characterized fraction of cellular RNAs that co-purify with chromatin. Their full complexity and the mechanisms regulating their packaging and chromatin association remain poorly understood. Here, we address these questions in Drosophila. We find that cRNAs constitute a heterogeneous group of RNA species that is abundant in heterochromatic transcripts. We show that heterochromatic cRNAs interact with the heterogeneous nuclear ribonucleoproteins (hnRNP) hrp36/hrp48 and that depletion of linker histone dH1 impairs this interaction. dH1 depletion induces the accumulation of RNA::DNA hybrids (R-loops) in heterochromatin and, as a consequence, increases retention of heterochromatic cRNAs. These effects correlate with increased RNA polymerase II (RNAPII) occupancy at heterochromatin. Notably, impairing cRNA assembly by depletion of hrp36/hrp48 mimics heterochromatic R-loop accumulation induced by dH1 depletion. We also show that dH1 depletion alters nucleosome organization, increasing accessibility of heterochromatin. Altogether, these perturbations facilitate annealing of cRNAs to the DNA template, enhancing R-loop formation and cRNA retention at heterochromatin.

The zinc-finger protein Z4 cooperates with condensin II to regulate somatic chromosome pairing and 3D chromatin organization.

Chromosome pairing constitutes an important level of genome organization, yet the mechanisms that regulate pairing in somatic cells and the impact on 3D chromatin organization are still poorly understood. Here, we address these questions in Drosophila, an organism with robust somatic pairing. In Drosophila, pairing preferentially occurs at loci consisting of numerous architectural protein binding sites (APBSs), suggesting a role of architectural proteins (APs) in pairing regulation. Amongst these, the anti-pairing function of the condensin II subunit CAP-H2 is well established. However, the factors that regulate CAP-H2 localization and action at APBSs remain largely unknown. Here, we identify two factors that control CAP-H2 occupancy at APBSs and, therefore, regulate pairing. We show that Z4, interacts with CAP-H2 and is required for its localization at APBSs. We also show that hyperosmotic cellular stress induces fast and reversible unpairing in a Z4/CAP-H2 dependent manner. Moreover, by combining the opposite effects of Z4 depletion and osmostress, we show that pairing correlates with the strength of intrachromosomal 3D interactions, such as active (A) compartment interactions, intragenic gene-loops, and polycomb (Pc)-mediated chromatin loops. Altogether, our results reveal new players in CAP-H2-mediated pairing regulation and the intimate interplay between inter-chromosomal and intra-chromosomal 3D interactions.

Hardware implementation of memristor-based artificial neural networks.

Artificial Intelligence (AI) is currently experiencing a bloom driven by deep learning (DL) techniques, which rely on networks of connected simple computing units operating in parallel. The low communication bandwidth between memory and processing units in conventional von Neumann machines does not support the requirements of emerging applications that rely extensively on large sets of data. More recent computing paradigms, such as high parallelization and near-memory computing, help alleviate the data communication bottleneck to some extent, but paradigm- shifting concepts are required. Memristors, a novel beyond-complementary metal-oxide-semiconductor (CMOS) technology, are a promising choice for memory devices due to their unique intrinsic device-level properties, enabling both storing and computing with a small, massively-parallel footprint at low power. Theoretically, this directly translates to a major boost in energy efficiency and computational throughput, but various practical challenges remain. In this work we review the latest efforts for achieving hardware-based memristive artificial neural networks (ANNs), describing with detail the working principia of each block and the different design alternatives with their own advantages and disadvantages, as well as the tools required for accurate estimation of performance metrics. Ultimately, we aim to provide a comprehensive protocol of the materials and methods involved in memristive neural networks to those aiming to start working in this field and the experts looking for a holistic approach.

Thermal Compact Modeling and Resistive Switching Analysis in Titanium Oxide-Based Memristors.

Resistive switching devices based on the Au/Ti/TiO2/Au stack were developed. In addition to standard electrical characterization by means of I-V curves, scanning thermal microscopy was employed to localize the hot spots on the top device surface (linked to conductive nanofilaments, CNFs) and perform in-operando tracking of temperature in such spots. In this way, electrical and thermal responses can be simultaneously recorded and related to each other. In a complementary way, a model for device simulation (based on COMSOL Multiphysics) was implemented in order to link the measured temperature to simulated device temperature maps. The data obtained were employed to calculate the thermal resistance to be used in compact models, such as the Stanford model, for circuit simulation. The thermal resistance extraction technique presented in this work is based on electrical and thermal measurements instead of being indirectly supported by a single fitting of the electrical response (using just I-V curves), as usual. Besides, the set and reset voltages were calculated from the complete I-V curve resistive switching series through different automatic numerical methods to assess the device variability. The series resistance was also obtained from experimental measurements, whose value is also incorporated into a compact model enhanced version.

TiN/Ti/HfO2/TiN memristive devices for neuromorphic computing: from synaptic plasticity to stochastic resonance.

We characterize TiN/Ti/HfO2/TiN memristive devices for neuromorphic computing. We analyze different features that allow the devices to mimic biological synapses and present the models to reproduce analytically some of the data measured. In particular, we have measured the spike timing dependent plasticity behavior in our devices and later on we have modeled it. The spike timing dependent plasticity model was implemented as the learning rule of a spiking neural network that was trained to recognize the MNIST dataset. Variability is implemented and its influence on the network recognition accuracy is considered accounting for the number of neurons in the network and the number of training epochs. Finally, stochastic resonance is studied as another synaptic feature. It is shown that this effect is important and greatly depends on the noise statistical characteristics.

A new species of Caecilia Linnaeus, 1758 (Amphibia: Gymnophiona: Caeciliidae) from the Pacific lowlands of Colombia, with comments on the status of C. tenuissima Taylor, 1973.

We here describe a new species of the genus Caecilia from the Pacific lowlands of Colombia that was mistaken in previous literature as C. tenuissima, but which has more primary and secondary grooves than that species (among other differences). The description of Caecilia wilkinsoni sp. nov. restricts the known distribution of C. tenuissima to Guayaquil, Ecuador, re-establishing its status as an endemic species. We comment on the type locality of C. tenuissima, the current condition of its holotype, and on the distributions of the Caecilia that inhabit the Pacific region of Colombia.

A new Bolitoglossa (Amphibia, Caudata, Plethodontidae) from the Cordillera Oriental of Colombia.

A new salamander species of the genus Bolitoglossa is here described from the cloud forests of the western slopes of the Cordillera Oriental of Colombia, in the Cundinamarca department. The most salient characters of this new species are its numerous maxillary and vomerine teeth, its moderate webbing on hands and feet, its short and robust tail, and its chromatic variation. Based on molecular analyses this new species is assigned to the adspersa species group and its status established as the sister species of B.adspersa, with which it was previously confused. Lastly, the distribution, natural history, and conservation status of the new species are discussed.

ResumenDescribimos una nueva especie de salamandra del género Bolitoglossa proveniente de los bosques nublados de la vertiente occidental de la Cordillera Oriental de Colombia, en el departamento de Cundinamarca. Los caracteres más sobresalientes de esta nueva especie son sus numerosos dientes maxilares y vomerinos, su palmeadura moderada en pies y manos, su cola corta pero robusta, y su variación cromática. Basados en análisis moleculares asignamos esta nueva especie al grupo de especies adspersa y establecemos su estatus como especie hermana de B.adspersa, con la cual era previamente confundida. Finalmente, discutimos algunos aspectos de su distribución, historia natural y su estado de conservación.

Somatic chromosome pairing has a determinant impact on 3D chromatin organization.

In the nucleus, chromatin is intricately structured into multiple layers of 3D organization important for genome activity. How distinct layers influence each other is not well understood. In particular, the contribution of chromosome pairing to 3D chromatin organization has been largely neglected. Here, we address this question in Drosophila, an organism that shows robust chromosome pairing in interphasic somatic cells. The extent of chromosome pairing depends on the balance between pairing and anti-pairing factors, with the anti-pairing activity of the CAP-H2 condensin II subunit being the best documented. Here, we identify the zinc-finger protein Z4 as a strong anti-pairer that interacts with and mediates the chromatin binding of CAP-H2. We also report that hyperosmotic cellular stress induces fast and reversible chromosome unpairing that depends on Z4/CAP-H2. And, most important, by combining Z4 depletion and osmostress, we show that chromosome pairing reinforces intrachromosomal 3D interactions. On the one hand, pairing facilitates RNAPII occupancy that correlates with enhanced intragenic gene-loop interactions. In addition, acting at a distance, pairing reinforces chromatin-loop interactions mediated by Polycomb (Pc). In contrast, chromosome pairing does not affect which genomic intervals segregate to active (A) and inactive (B) compartments, with only minimal effects on the strength of A-A compartmental interactions. Altogether, our results unveil the intimate interplay between inter-chromosomal and intra-chromosomal 3D interactions, unraveling the interwoven relationship between different layers of chromatin organization and the essential contribution of chromosome pairing.

On the identities of Caecilia degenerata Dunn, 1942 and of C. corpulenta Taylor, 1968 (Amphibia: Gymnophiona: Caeciliidae) with descriptions of three new species of Caecilia Linnaeus, 1758 from the Cordillera Oriental of Colombia.

The Central portion of the Cordillera Oriental of Colombia is currently reported to harbor two species of Caecilia distributed at comparable elevations on opposite versants of these Mountains. These are C. corpulenta, known from Virolín, Santander, at 1700-2000 m on the western slopes of the Cordillera Oriental and C. degenerata, known from Garagoa, Boyacá, and Choachí and Fomequé, Cundinamarca, at 1800-2100 m on the eastern slopes of the Cordillera Oriental. Both species have dermal scales and lack secondary grooves, and have been subjected to misidentifications by herpetologists studying the Gymnophiona of the Eastern Andes of Colombia. Our results indicate that only the latter species is found in Colombia and the former is restricted to Peru, leaving those populations previously referred to C. corpulenta and those distinct from C. degenerata pending names. We here present an account for C. degenerata based on material from Choachí and Fómeque, Cundinamarca, as well as descriptions of three new species from the Cordillera Oriental and adjacent Venezuela: C. atelolepis sp. nov., C. epicrionopsoides sp. nov., and C. macrodonta sp. nov. We also provide additional morphological information for the recently described C. pulchraserrana.

Holistic Variability Analysis in Resistive Switching Memories Using a Two-Dimensional Variability Coefficient.

We present a new methodology to quantify the variability of resistive switching memories. Instead of statistically analyzing few data points extracted from current versus voltage (I-V) plots, such as switching voltages or state resistances, we take into account the whole I-V curve measured in each RS cycle. This means going from a one-dimensional data set to a two-dimensional data set, in which every point of each I-V curve measured is included in the variability calculation. We introduce a new coefficient (named two-dimensional variability coefficient, 2DVC) that reveals additional variability information to which traditional one-dimensional analytical methods (such as the coefficient of variation) are blind. This novel approach provides a holistic variability metric for a better understanding of the functioning of resistive switching memories.

Thermal Characterization of Conductive Filaments in Unipolar Resistive Memories.

A methodology to estimate the device temperature in resistive random access memories (RRAMs) is presented. Unipolar devices, which are known to be highly influenced by thermal effects in their resistive switching operation, are employed to develop the technique. A 3D RRAM simulator is used to fit experimental data and obtain the maximum and average temperatures of the conductive filaments (CFs) that are responsible for the switching behavior. It is found that the experimental CFs temperature corresponds to the maximum simulated temperatures obtained at the narrowest sections of the CFs. These temperature values can be used to improve compact models for circuit simulation purposes.

Hybrid 2D-CMOS microchips for memristive applications.

Exploiting the excellent electronic properties of two-dimensional (2D) materials to fabricate advanced electronic circuits is a major goal for the semiconductor industry1,2. However, most studies in this field have been limited to the fabrication and characterization of isolated large (more than 1 µm2) devices on unfunctional SiO2-Si substrates. Some studies have integrated monolayer graphene on silicon microchips as a large-area (more than 500 µm2) interconnection3 and as a channel of large transistors (roughly 16.5 µm2) (refs. 4,5), but in all cases the integration density was low, no computation was demonstrated and manipulating monolayer 2D materials was challenging because native pinholes and cracks during transfer increase variability and reduce yield. Here, we present the fabrication of high-integration-density 2D-CMOS hybrid microchips for memristive applications-CMOS stands for complementary metal-oxide-semiconductor. We transfer a sheet of multilayer hexagonal boron nitride onto the back-end-of-line interconnections of silicon microchips containing CMOS transistors of the 180 nm node, and finalize the circuits by patterning the top electrodes and interconnections. The CMOS transistors provide outstanding control over the currents across the hexagonal boron nitride memristors, which allows us to achieve endurances of roughly 5 million cycles in memristors as small as 0.053 µm2. We demonstrate in-memory computation by constructing logic gates, and measure spike-timing dependent plasticity signals that are suitable for the implementation of spiking neural networks. The high performance and the relatively-high technology readiness level achieved represent a notable advance towards the integration of 2D materials in microelectronic products and memristive applications.

Hardware implementation of a true random number generator integrating a hexagonal boron nitride memristor with a commercial microcontroller.

The development of the internet-of-things requires cheap, light, small and reliable true random number generator (TRNG) circuits to encrypt the data-generated by objects or humans-before transmitting them. However, all current solutions consume too much power and require a relatively large battery, hindering the integration of TRNG circuits on most objects. Here we fabricated a TRNG circuit by exploiting stable random telegraph noise (RTN) current signals produced by memristors made of two-dimensional (2D) multi-layered hexagonal boron nitride (h-BN) grown by chemical vapor deposition and coupled with inkjet-printed Ag electrodes. When biased at small constant voltages (≤70 mV), the Ag/h-BN/Ag memristors exhibit RTN signals with very low power consumption (∼5.25 nW) and a relatively high current on/off ratio (∼2) for long periods (>1 hour). We constructed TRNG circuits connecting an h-BN memristor to a small, light and cheap commercial microcontroller, producing a highly-stochastic, high-throughput signal (up to 7.8 Mbit s-1) even if the RTN at the input gets interrupted for long times up to 20 s, and if the stochasticity of the RTN signal is reduced. Our study presents the first full hardware implementation of 2D-material-based TRNGs, enabled by the unique stability and figures of merit of the RTN signals in h-BN based memristors.

Restauraciones indirectas para el manejo de la Hipomineralización de Molares e Incisivos: un abordaje conservador / Restaurações indiretas para o tratamento da hipomineralização de molares e incisivos: uma abordagem conservadora / Indirect restorations for the management of hypomineralization of molars and incisors: a conservative approach

Introducción: Técnicas adhesivas contemporáneas permiten la rehabilitación conservadora y estética de dientes afectados por caries dental, trauma dentoalveolar y defectos del desarrollo del esmalte. Para el tratamiento restaurador de la hipomineralización de molares e incisivos (HMI) se ha recomendado el uso de restauraciones indirectas. Reporte de caso: Paciente sintomático de sexo femenino, 8 años, portadora de HMI severa y comportamiento levemente negativo. Los dientes 16, 36 y 46 presentaban opacidades demarcadas asociadas a dolor provocado. El tratamiento se enfocó en educar a la familia con respecto a la HMI, orientar el comportamiento, controlar la sintomatología y restaurar la función y estética de los dientes afectados por la HMI. Debido a la extensión, severidad y localización de los defectos en los dientes 16, 36 y 46, se optó por realizar restauraciones indirectas con resina compuesta. Luego de 12 meses la paciente presentaba comportamiento definitivamente positivo, no relataba sintomatología dolorosa, las restauraciones estaban sin cambio de color, bien adaptadas, con buena salud gingival y con adecuada anatomía oclusal, lisas y sin signos de lesiones de caries dental. Conclusión: En este caso de HMI severa, la restauración con resina indirecta fue una estrategia estética, conservadora, viable y efectiva durante un periodo de seguimiento de 12 meses.

Introdução: As técnicas adesivas atuais permitem a reabilitação conservadora e estética de dentes acometidos por cáries, traumas dentoalveolares e defeitos de desenvolvimento do esmalte. Para o tratamento restaurador da hipomineralização de molares e incisivos (HMI), o uso de restaurações indiretas tem sido recomendado. Relato de caso: Paciente do sexo feminino, sintomática, 8 anos, com HMI severa e comportamento levemente negativo. Os dentes 16, 36 e 46 apresentaram opacidades acentuadas associadas à dor provocada. O tratamento teve como foco a educação da família sobre a HMI, orientando o comportamento, controlando os sintomas e restaurando a função e a estética dos dentes afetados pela HMI. Devido à extensão, severidade e localização dos defeitos nos dentes 16, 36 e 46, optou-se pela realização de restaurações indiretas com resina composta. Após 12 meses, a paciente apresentou um comportamento definitivamente positivo, não relatou sintomatologia dolorosa, as restaurações estavam sem alteração de cor, bem adaptadas, com boa saúde gengival e anatomia oclusal adequada, lisas e sem sinais de lesões de cárie. Conclusão: Neste caso de MHI severa, a restauração indireta em resina foi uma estratégia estética, conservadora, viável e eficaz com um período de acompanhamento de 12 meses.

Introduction: Contemporary adhesive techniques allow the conservative and aesthetic rehabilitation of teeth affected by dental caries, dentoalveolar trauma, and enamel development defects. For the restorative treatment of hypomineralization of molars and incisors (HMI), indirect restorations have been recommended. Case report: Symptomatic female patient, 8 years old, with severe HMI and slightly negative behavior. Teeth 16, 36, and 46 presented marked opacities associated with provoked pain. The treatment focused on educating the family regarding the HMI, guiding behavior, controlling the symptoms, and restoring the function and aesthetics of the teeth affected by the HMI. Due to the extension, severity, and location of the defects in teeth 16, 36, and 46, it was decided to perform indirect restorations with composite resin. After 12 months, the patient presented definitively positive behavior, and did not report painful symptoms, the restorations were without color change, well adapted, with good gingival health and adequate occlusal anatomy, smooth and without signs of dental caries lesions. Conclusion: In this case of severe MHI, indirect resin restoration was an esthetic, conservative, viable, and effective strategy during a 12-month follow-up period

Memristive technologies for data storage, computation, encryption, and radio-frequency communication.

Memristive devices, which combine a resistor with memory functions such that voltage pulses can change their resistance (and hence their memory state) in a nonvolatile manner, are beginning to be implemented in integrated circuits for memory applications. However, memristive devices could have applications in many other technologies, such as non-von Neumann in-memory computing in crossbar arrays, random number generation for data security, and radio-frequency switches for mobile communications. Progress toward the integration of memristive devices in commercial solid-state electronic circuits and other potential applications will depend on performance and reliability challenges that still need to be addressed, as described here.

Hybridization fuelled diversification in Spialia butterflies.

The importance of hybridization and introgression is well documented in the evolution of plants but, in insects, their role is not fully understood. Given the fact that insects are the most diverse group of organisms, assessing the impact of reticulation events on their evolution may be key to comprehend the emergence of such remarkable diversity. Here, we used an insect model, the Spialia butterflies, to gather genomic evidence of hybridization as a promoter of novel diversity. By using double-digest RADseq (ddRADseq), we explored the phylogenetic relationships between Spialia orbifer, S. rosae and S. sertorius, and documented two independent events of interspecific gene flow. Our data support that the Iberian endemism S. rosae probably received genetic material from S. orbifer in both mitochondrial and nuclear DNA, which could have contributed to a shift in the ecological preferences of S. rosae. We also show that admixture between S. sertorius and S. orbifer probably occurred in Italy. As a result, the admixed Sicilian populations of S. orbifer are differentiated from the rest of populations both genetically and morphologically, and display signatures of reproductive character displacement in the male genitalia. Additionally, our analyses indicated that genetic material from S. orbifer is present in S. sertorius along the Italian Peninsula. Our findings add to the view that hybridization is a pervasive phenomenon in nature and in butterflies in particular, with important consequences for evolution due to the emergence of novel phenotypes.

Microabrasión e infiltración como alternativa de tratamiento para Fluorosis Dental severa: reporte de caso / Microabrasão e infiltração como tratamento alternativo para Fluorose Dentária severa: relato de caso / Microabrasion and resin infiltration for treatment of severe Dental Fluorosis: a case report

Resumen La Fluorosis Dental (FD) es un defecto del desarrollo del esmalte tipo hipomineralización atribuido a la exposición crónica y excesiva de fluoruro durante el período de amelogénesis. Clínicamente, en los casos más leves se pueden observar finas líneas blancas y opacas, mientras que en casos moderados y severos las líneas se pueden fundir y formar bandas más gruesas comprometiendo toda la superficie del diente pudiendo estar asociadas con pérdidas de estructura y cambios de color. El tratamiento de la FD puede incluir desde microabrasión, infiltración, aclaramiento y restauraciones con resina compuesta hasta carillas y coronas. El objetivo de este caso clínico fue asociar la técnica de microabrasión e infiltración como alterantiva de tratamiento estético para el manejo de la FD. Paciente de sexo femenino y 9 años que presentaba opacidades blancas en forma de bandas gruesas y pérdidas de estructura dental en los incisivos superiores permanentes (FD severa). Para el tratamiento se optó por realizar microabrasión con ácido clorhídrico, seguido de infiltración con resina de baja viscosidad, logrando un resultado estético favorable y estable a tres meses. Se concluye que la combinación de estas dos técnicas micro-invasivas es una estrategia viable y efectiva para enmascarar efectivamente opacidades producidas por la FD.

Resumo A Fluorose Dentária (FD) é um defeito de desenvolvimento do esmalte do tipo hipomineralização atribuído à exposição crônica e excessiva de fluoreto durante a amelogênese. Clinicamente, os casos leves apresentam finas linhas brancas que acompanham a formação dentária, enquanto casos moderados ou severos apresentam faixas brancas mais amplas acometendo toda a superfície e podem estar associados à perdas estruturais e pigmentações. O tratamento da FD inclui desde microabrasão, infiltração e aclaramento até restaurações com resina composta, facetas e coroas. O objetivo deste caso clínico foi associar as técnicas de microabrasão e infiltração como alternativa de tratamento estético para a abordagem da FD. Paciente do sexo feminino de 9 anos que apresentava nos incisivos superiores permanentes áreas brancas opacas e perda de estrutura (FD severa). Para o tratamento, optou-se por realizar microabrasão com ácido clorídrico, seguido de infiltração com uma resina de baixa viscosidade, atingindo um resultado estético e favorável. Conclui-se que a combinação da microabrasão e da infiltração é uma estratégia viável e efetiva para mascar efetivamente opacidades produzidas pela FD.

Abstract Dental Fluorosis (DF) is a developmental defect of the enamel type hypomineralization attributed to chronic and excessive fluoride exposure during the period of amelogenesis. Clinically, in the mildest cases fine white and opaque lines can be observed, while in moderate and severe cases the lines can melt and form thicker bands, compromising the entire tooth surface, which may be associated with loss of structure and color changes. Treatment of DF can range from microabrasion, infiltration, dental whitening, and composite resin restorations to veneers and crowns. The objective of this clinical case was to associate the microabrasion and infiltration technique as an alternative to aesthetic treatment for the management of dental fluorosis. A 9-year-old female patient presented white opacities in the form of thick bands and loss of tooth structure in the permanent upper incisors (severe dental fluorosis). For the treatment, it was decided to perform microabrasion with hydrochloric acid, followed by infiltration with low viscosity resin, achieving a favorable and stable aesthetic result after three months. It is concluded that the combination of these two micro-invasive techniques is a viable and effective strategy to effectively mask opacities produced by DF.

Consideraciones diagnósticas para la exodoncia de primeros molares permanentes severamente afectados por la Hipomineralización de Molares e Incisivos / Considerações diagnósticas para a exodontia de primeiros molares permanentes severamente afetados pela Hipomineralização de Molares e Incisivos / Diagnostic considerations for extraction of first permanent molars severely affected by Molar-Incisor Hypomineralization

Resumen La Hipomineralización de Molares e Incisivos (HMI) es un defecto de desarrollo del esmalte de origen multifactorial que afecta de uno a cuatro primeros molares permanentes y frecuentemente está asociada con incisivos permanentes. Clínicamente se caracteriza por presentar opacidades demarcadas de color blanco-crema y/o amarillo-café. En casos severos puede haber dolor, fracturas posteruptivas, lesiones de caries dental y/o restauraciones atípicas. Entre las opciones de tratamiento se encuentran restauraciones temporales con cemento de ionómero de vidrio, restauraciones en resina compuesta, coronas, restauraciones indirectas y exodoncia. El objetivo de este caso es analizar las consideraciones diagnósticas de la exodoncia de primeros molares permanentes severamente afectados por la HMI. Paciente de sexo femenino, 9 años de edad, patrón esquelético Clase I, maloclusión Clase I bilateral e HMI severa. Para el tratamiento se optó por realizar la exodoncia de los cuatro primeros molares permanentes bajo anestesia general. Luego de 10 meses, se observa que los segundos molares permanentes están clínicamente sanos y presentan inclinaciones y posiciones favorables para el cierre espontáneo del espacio. Se concluye que la exodoncia de primeros molares permanentes severamente afectados por la HMI es una estrategia que mejora el pronóstico del paciente y para realizarla, se requiere trabajar en conjunto con el ortodoncista para diagnosticar y planear individualmente cada caso.

Resumo A Hipomineralização de Molares e Incisivos (HMI) é um defeito de desenvolvimento do esmalte, de origem multifatorial que afecta de um a quatro primeiros molares permanentes e frequentemente está associada aos incisivos permanentes. Clinicamente se caracteriza como opacidades demarcadas de coloração branco-creme e/ou amarelo-café. Em casos severos pode haver dor, fraturas pós-irruptivas, lesões de cárie dentária e restaurações atípicas. Dentre as opções de tratamento estão as restaurações temporárias com cimento de ionômero de vidro, restaurações em resina composta, coroas, restaurações indiretas e a exodontia. Esta última opção permite que o segundo molar permanente se reposicione espontaneamente desde que realizada a tempo, portanto, é considerada uma alternativa viável e custo-efetiva. O objetivo deste caso foi analisar as considerações diagnósticas de exodontia de primeiros molares permanentes severamente afetados pela HMI. Paciente do sexo feminino, 9 anos de idade, padrão esquelético Classe I, maloclusão Classe I bilateral e HMI severa. Para o tratamento, optou-se por realizar a exodontia dos quatro primeiros molares permanentes sob anestesia geral. Após 10 meses, se observa que os segundos molares permanentes estão clinicamente saudáveis e apresentam inclinações e posicionamentos favoráveis para o fechamento espontâneo do espaço. Conclui-se que a exodontia de primeiros molares permanentes melhora o prognóstico do paciente e para realizá-la requer um trabalho em conjunto com o ortodontista para diagnosticas e planejar individualmente cada caso.

Abstract Molar and Incisor Hypomineralization (MIH) is an enamel development defect of multifactorial origin that affects one-to-four permanent first molars and is frequently associated with permanent incisors. Clinically it is characterized by demarcated white-cream and/ or yellow-brown opacities. In severe cases, there may be tooth pain, posteruptive fractures, dental caries lesions, and/ or atypical restorations. Treatment options include temporary restorations with glass ionomer cement, restorations with composite resin, crowns, indirect restorations, and tooth extraction. When extractions are performed at the right time, it allows the spontaneous replacement of the second permanent molar, therefore, it is considered a viable and cost/effective treatment. The objective of this case report is to analyze the diagnostic considerations for the extraction of first permanent molars severely affected by MIH. Female patient, 9 years old, Class I skeletal pattern, Class I malocclusion, and severe MIH. For the treatment, it was decided to perform the extraction of the first four permanent molars under general anesthesia. After 10 months, it is observed that the second permanent molars are clinically healthy and have favorable inclinations and positions for spontaneous closure of the space. It is concluded that the extraction of first permanent molars severely affected by MIH is a strategy that improves the patient's prognosis and to carry out, it is necessary to work together with the orthodontist to diagnose and plan each case individually.

Standards for the Characterization of Endurance in Resistive Switching Devices.

Resistive switching (RS) devices are emerging electronic components that could have applications in multiple types of integrated circuits, including electronic memories, true random number generators, radiofrequency switches, neuromorphic vision sensors, and artificial neural networks. The main factor hindering the massive employment of RS devices in commercial circuits is related to variability and reliability issues, which are usually evaluated through switching endurance tests. However, we note that most studies that claimed high endurances >106 cycles were based on resistance versus cycle plots that contain very few data points (in many cases even <20), and which are collected in only one device. We recommend not to use such a characterization method because it is highly inaccurate and unreliable (i.e., it cannot reliably demonstrate that the device effectively switches in every cycle and it ignores cycle-to-cycle and device-to-device variability). This has created a blurry vision of the real performance of RS devices and in many cases has exaggerated their potential. This article proposes and describes a method for the correct characterization of switching endurance in RS devices; this method aims to construct endurance plots showing one data point per cycle and resistive state and combine data from multiple devices. Adopting this recommended method should result in more reliable literature in the field of RS technologies, which should accelerate their integration in commercial products.