Neural computations of threat in the aftermath of combat trauma

© 2019, The Author(s), under exclusive licence to Springer Nature America, Inc. By combining computational, morphological, and functional analyses, this study relates latent markers of associative threat learning to overt post-traumatic stress disorder (PTSD) symptoms in combat veterans. Using reversal learning, we found that symptomatic veterans showed greater physiological adjustment to cues that did not predict what they had expected, indicating greater sensitivity to prediction errors for negative outcomes. This exaggerated weighting of prediction errors shapes the dynamic learning rate (associability) and value of threat predictive cues. The degree to which the striatum tracked the associability partially mediated the positive correlation between prediction-error weights and PTSD symptoms, suggesting that both increased prediction-error weights and decreased striatal tracking of associability independently contribute to PTSD symptoms. Furthermore, decreased neural tracking of value in the amygdala, in addition to smaller amygdala volume, independently corresponded to higher PTSD symptom severity. These results provide evidence for distinct neurocomputational contributions to PTSD symptoms

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

Nanoparticles sintering technology for power electronics modules and beyond

IN advancing the ’More thanMoore’ paradigm, heterogeneous integration has emerged to facilitate the creation of highly efficient, compact, and multi-functional semiconductor systems. Addressing the challenges related to power efficiency, superior performance, and integration density, low-temperature nanoparticle sintering technology has become pivotal for integrating diverse materials and components in advanced semiconductor packaging. Traditional electronic packaging materials face limitations and process complexity, making low-temperature nanoparticle sintering an attractive option. With its benefits of low processing temperatures (< 0.4 Tm), exceptional electro-thermomechanical performance, and high process flexibility, this technology is gaining increasing attention, particularly in high-power electronics packaging applications. Over the past decade, silver (Ag) sintering technology has shown promise in the power electronics industry, serving as an effective solution for high-power die-attach. However, due to the high cost of materials, efforts have been directed towards pressure reduction and exploring alternative sinter materials to reduce overall process costs. In recent years, the concept of ’all copper (Cu) interconnect’ has transcended fromlow-power to high-power applications, with low-temperature Cu nanoparticle sintering showing substantial potential as a replacement for Ag in pressure-assisted sintering. Despite this promising avenue, the understanding of sintered Cu materials remains limited, primarily due to susceptibility to oxidation issues. Comprehensive studies comparing both sinter materials, extending beyond mere shear tests, are insufficient, leaving a significant gap in our understanding. Furthermore, methodologies for characterizing the sintered structure and providing detailed insights into its thermo-mechanical behavior are notably absent. In this dissertation, molecular dynamics (MD) simulation was employed at first to study the nanoparticles’ coalescence kinetics and mechanical and chemical performance of coalesced nanoparticles. A two-hemispherical nanoparticle model was built to simulate the impact of sintering temperature and pressure on low-temperature pressureassisted coalescence. The sintering dynamics and microstructure evolution were analyzed, including neck growth, shrinkage variation, grain boundary development, and dislocation activities. Furthermore, on the basics of pressure-assisted sintered nanoparticles, uniaxial tensile tests with a constant strain rate were employed to investigate its tensile performance. Subsequently, another mechanical nanoindentation simulation was implemented in a multi-nanoparticle sintered structure. The impact of indentation position and indenter size on the nanoindentation response was investigated. At the end of the first chapter, the chemical corrosion of sulphidation on multi-Ag nanoparticles’ sintered structure was simulated by the reactive-force-field (ReaxFF) MD method. The sulphidation on the dense Ag and porous sintered structures was compared and analyzed. Moreover, the sulphidation mechanism was revealed at an atomic level...Electronic Components, Technology and Material

Catalytic Oxidative Coupling of Methane: Heterogeneous or Homogeneous Reaction?

Direct valorization of methane via oxidative coupling of methane (OCM) is an encouraging alternative to conventional oil-based processes for the production of light hydrocarbons (ethane and ethylene). Abundant, inexpensive simple oxides such as MgO and La2O3 possess the ability to selectively activate methane. However, during OCM, the selective conversion to ethane and the following dehydrogenation to ethylene are threatened by the thermodynamically favored partial and total oxidation reactions to form CO and CO2, respectively. With the aid of spatially resolved operando analysis of temperature and gas concentration along the catalytic bed, we demonstrate the relevance of highly exothermic reaction paths developed in the gas phase, i.e., the homogeneous reaction, during OCM conditions at the front of the catalytic bed, largely determining the total C2 yield obtained on those systems. With the new insights provided by the analysis of temperature and concentration gradients along the bed, we redefine the positive effect of promoters (Li, Sr), which enhance the influence of catalyst surfaces. The effect of promoters is recognized in the suppression of the exothermic oxidation paths leading to undesired COx, thus limiting the formation of hotspots and driving the reaction toward the desired C2 products.ChemE/Catalysis Engineerin

Enabling complete conversion of CH₄ and CO₂ in dynamic coke-mediated dry reforming (DC-DRM) on Ni catalysts

Dynamic coke-mediated dry reforming of methane (DC-DRM) is an unsteady-state strategy to overcome the limitations of co-feed operation, including the fast deactivation of the catalysts and the loss of valuable H2 in the reverse water gas-shift reaction. This paper proves the feasibility of DC-DRM on Ni-based catalytic systems, identifying suitable metal oxides supports and evaluating the role of metallic promoters. A La-promoted Ni/ZrO2 catalyst exhibited excellent and stable catalytic performances at 800 °C approaching complete conversion of the CH4 and CO2 reactant pulses in the reaction loop, and separation of the H2 and CO product streams. Adding the redox functionality of reducible oxides (TiO2) in the catalyst support is demonstrated as a powerful tool to enable direct formation of syngas in the methane pulse with control on the H2/CO ratio.ChemE/Catalysis Engineerin

Effects of Defect and Temperature on the Mechanical Performance of WS₂: A Multiscale Analysis

This paper analyzes the mechanical properties of tungsten disulfide (WS2) by means of multiscale simulation, including density functional theory (DFT), molecular dynamic (MD) analysis, and finite element analysis (FEA). We first conducted MD analysis to calculate the mechanical properties (i.e., Young's modulus and critical stress) of WS2. The influence of different defect types (i.e., point defects and line defects) on the mechanical properties are discussed. The results reveal that WS2 has a high Young's modulus and high critical stress. Next, the effects of defect density and temperature on the mechanical properties of the material were analyzed. The results show that a lower defect density results in improved performance and a higher temperature results in better ductility, which indicate that WS2 can potentially be a strain sensor. Based on this result, FEA was employed to analyze the WS2 stress sensor and then fabricate and analyze the device for benchmarking. It is found that the FEA model proposed in this work can be used for further optimization of the device. According to the DFT results, a narrower band gap WS2 is found with the existence of defects and the applied strain. The proposed multiscale simulation method can effectively analyze the mechanical properties of WS2 and optimize the design. Moreover, this method can be extended to other 2D/nanomaterials, providing a reference for a rapid and effective systematic design from the nanoscale to macroscale. Electronic Components, Technology and Material

Copper Nanoparticle Sintering Enabled Hermetic Packaging With Fine Sealing Ring for MEMS Application

Driving by the increased demand for hermetic packaging in the more than Moore (MtM) roadmap, a Cu nanoparticle sintering-enabled hermetic sealing solution was developed with a small-size sealing ring. The developed technology simplifies microfabrication and requires less surface roughness using a sinterable Cu nanoparticle paste. A 50μm size Cu paste sealing ring was achieved using a lithography patterned photoresist as a stencil mask. A groove-structured chip was used to amplify localized stress. The Cu nanoparticle paste was fully sintered at 300 °C under pressure ranging from 10 to 40 MPa resulting in a robust bonding with a maximum shear strength of 280 MPa and implementing hermetic packaging. The deflection of the Si diaphragms estimated a vacuum level of 7 kPa. Vacuum sealing was maintained for over six months, and the lowest leak rate was calculated as 8.4× 10 -13Pa·m 3/s. The developed technology that comprises small-size patterning and pressure-assisted sintering offers the potential for a simple, cost-effective, but robust solution for hermetic packaging.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and MaterialsElectrical Engineering, Mathematics and Computer Scienc

Thermal kinetic and mechanical behaviors of pressure-assisted Cu nanoparticles sintering: A molecular dynamics study

A molecular dynamics (MD) simulation was performed on the coalescence kinetics and mechanical behavior of the pressure-assisted Cu nanoparticles (NPs) sintering at low temperature. To investigate the effects of sintering pressure and temperature on the coalescence of the nanoparticles, sintering simulations of two halve Cu NPs were conducted at the pressure of 0–300 MPa and the temperature of 300–500 K. A transition of the dominant coalescence kinetics from slight surface diffusion to intensive grain boundary diffusion and dislocation driven plastic flows were found when pressure was applied. Furthermore, atomic trajectories showed the effect of temperature on sintering was strongly dependent on the microstructures of Cu NPs. The atomic diffusion around defects can be significantly promoted by the elevated temperature. Additionally, based on the sintered structures, uniaxial tension simulation was implemented with a constant strain rate. Stress–strain curves and evolution of dislocation activities were derived. Improved mechanical behaviors, including larger elastic modulus and larger tensile strength, were obtained in the structure sintered under higher pressure and temperature. Among this study, sintering temperature and pressure consistently exhibited the same relative impact on affecting both coalescence and the mechanical properties of the sintered structure.Electronic Components, Technology and Material

Micro-cantilever Bending Test of Sintered Cu nanoparticles for Power Electronic Devices

The application of microporous sintered copper (Cu) as a bonding material to replace conventional die-attach materials in power electronic devices has attracted considerable interest. Many previous studies have focused on the effect of processing parameters (temperature, time, pressure) on the microstructure evolution of sintered Cu. However, there are only a few studies with regard to the mechanical properties of sintered Cu. As the die-attach layer undergoes thermal and mechanical stress during its application, it is essential to investigate the micro-scale mechanical properties of sintered Cu. Fracture toughness is a measure of the resistance of a material to crack propagation under predominantly linear-elastic conditions, which is an essential parameter for predicting fracture failure. As cracks and defects are difficult to avoid during fabrication and application processing for sintered Cu, which will definitely cause a significant effect on micromechanical properties. Thus, it is essential to reveal the effect of microstructure on fracture toughess of sintered Cu nanoparticles.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material

Study on Sintering Mechanism and Mechanical Properties of Nano-Cu based on Molecular Dynamics Simulation

Nano-metal materials sintering has received increasing attention in recent years for its promising performance in the wide bandgap semiconductor packaging. In this paper, molecular dynamics (MD) simulation method were applied to simulate the nano-Cu sintering mechanism and the subsequent mechanical behavior. Hybrid sintering, comprising nanosphere (NS) and nanoflake (NF), was carried out at temperatures ranging from 500K to 650K. Furthermore, shearing simulations were conducted with constant strain rates on the sintered structure at multiple temperatures, and subsequently correlated the extracted mechanical properties with the sintering behavior. The results indicated that the mechanical properties of nano-Cu sintered structure were improved by tuning material composition and increasing the sintering temperature. We established a relationship between the sintered microstructure and mechanical response, the shear modulus and shear strength of the sintered structure with NF particles increased to 41.2GPa and 3.51GPa respectively. It offers valuable insights into the preparation phase of nano Cu paste for sintering technology.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material