Cytopathic effects of the cytomegalovirus-encoded apoptosis inhibitory protein vMIA

Replication of human cytomegalovirus (CMV) requires the expression of the viral mitochondria–localized inhibitor of apoptosis (vMIA). vMIA inhibits apoptosis by recruiting Bax to mitochondria, resulting in its neutralization. We show that vMIA decreases cell size, reduces actin polymerization, and induces cell rounding. As compared with vMIA-expressing CMV, vMIA-deficient CMV, which replicates in fibroblasts expressing the adenoviral apoptosis suppressor E1B19K, induces less cytopathic effects. These vMIA effects can be separated from its cell death–inhibitory function because vMIA modulates cellular morphology in Bax-deficient cells. Expression of vMIA coincided with a reduction in the cellular adenosine triphosphate (ATP) level. vMIA selectively inhibited one component of the ATP synthasome, namely, the mitochondrial phosphate carrier. Exposure of cells to inhibitors of oxidative phosphorylation produced similar effects, such as an ATP level reduced by 30%, smaller cell size, and deficient actin polymerization. Similarly, knockdown of the phosphate carrier reduced cell size. Our data suggest that the cytopathic effect of CMV can be explained by vMIA effects on mitochondrial bioenergetics

Sub-nT resolution of single layer sensor based on the AMR effect in La_2/_3Sr_1/_3MnO_3 Thin Films

Single-layer magnetoresistive sensors were designed in a Wheatstone bridge configuration using La_2/_3Sr_1/_3MnO_3 ferromagnetic oxide thin film. Uniaxial anisotropy was induced by performing epitaxial deposition of the films on top of vicinal SrTiO_3 substrate. X-ray scan confirms the high crystalline quality of the films and the magnetic anisotropy was checked by magneto-optical Kerr effect measurements. Thanks to the anisotropic magnetoresistive effect and the very low noise measured in the devices, sub-nT resolution was achieved above 100 Hz at 310 K

Interface engineering for vanadium dioxide (VO2) integration on silicon

International audienceNeuromorphic computing is being seen as a solution to address the memory bottleneck persistent with the present computing paradigm. To realize such an architecture, artificial synapses and neurons need to be built. One way to emulate a bio-synapse requires a material with an metal-insulator phase transition (MIT). VO2 undergoes a structural phase transformation (SPT) from monoclinic structure at room temperature to tetragonal at approximately 70°C. The SPT is accompanied by an IMT leading to a large variation in its electrical (about 4 orders of magnitude of its resistivity) and optical properties, in particular, in its complex refractive index in the mid-IR frequency range.To keep with the current trends of the microelectronic industry, it is imperative to integrate VO2 on silicon. However, the higher lattice mismatch and formation of oxides and silicates at the interface between VO2 and crystalline Si degrade the quality and functionality of VO2 film. Additionally, VO2(M1) is a challenging material to integrate into patterned heterostructures because it can exist not only as multiple polymorphs (A, B, M1) but the high-temperature depositions can lead to the formation of various oxidation states phases that are present in the V-O system (VnO2n-1, VnO2n+1). This work was conducted to study the growth of VO2 on silicon with oxide buffer layers using RF magnetron sputtering of a V2O5 ceramic target in argon atmosphere. We studied the structure-property relationships, specifically electrical and optical properties as a function of temperature across the Tc. Structural and compositional characterizations are carried out using x-ray diffraction, atomic force microscopy, and x-ray photoemission spectroscopy respectively, optical responses are studied under spectroscopic ellipsometry and electrical characterizations are performed using the four-point probe method. With the use of a very thin metal oxide buffer layer between the silicon substrate and VO2 film, we demonstrate a high resistivity ratio (of the order 3 between the two phases) and investigate the scope of improvement. The results show the influence of substrate temperature, VO2 grain size, and strain on it as well as the crystal structure of the buffer layer on the structural and physical properties of interfaces and film morphology which subsequently affect the electrical bistability of VO2. The preliminary findings mentioned here are being utilized to improve the electrical bistability, thus allowing us to improve the reproducibility in operational modes (switching, memory, logical operations, etc.) of neuromorphic devices

Thermal information processing using phase change materials

International audienceIndustrial waste heat in the EU is estimated about 300TWh/year. This freely available energy remains unharvested. With radiative thermal devices, it could in contrary power internet of things. Unlike its electronic counterparts, thermal information processing (thermotronics) via radiative heat flow and temperature control is a nascent technology. To achieve this goal, a thermal transistor has been proposed1. It consists of a membrane of a material undergoing a metal-insulator transition (MIT), e.g. VO2, which acts as the gate between two thermal reservoirs (source and drain), e.g. SiO2. VO2 undergoes a structural phase transformation (SPT) at approximately 70°C from insulating monoclinic structure at room temperature to metallic rutile. The two crystallographic structures have large variation in their complex refractive index in the mid-IR frequency range.To keep with the current trends of microelectronic industry, it is imperative to integrate VO2 on Si. However, the higher lattice mismatch and formation of oxides and silicates at the interface between VO2 and crystalline Si degrade the quality and functionality of VO2 film. Additionally, VO2(M1) is a challenging material to integrate into patterned heterostructures because it can exist not only as multiple polymorphs (A, B, M1) but the high temperature depositions can lead to formation of various oxidation states phases that are present in the V-O system (VnO2n-1, VnO2n+1).This work was conducted to study the growth of VO2 on silicon with oxide buffer layers using RF magnetron sputtering of a V2O5 ceramic target in argon atmosphere. We studied the structure-property relationships, specifically electrical and optical properties as a function of temperature across the Tc. Structural and compositional characterization are carried out using x-ray diffraction (XRD), atomic force microscopy (AFM), and x-ray photoemission spectroscopy (XPS) respectively; optical responses are studied using FTIR and electrical characterizations are performed using the four-point probe method.With the use of a very thin metal oxide buffer layer between silicon substrate and VO2 film, we demonstrate a high resistivity ratio (3 orders of magnitude between the two phases) and investigate the scope of improvement. The results show the influence of substrates temperature, VO2 grain size and strain on the amplitude of transition as well as the crystal structure of buffer layer on the structural and physical properties of interfaces and film morphology which subsequently affect the electrical bistability of VO2. The preliminary findings mentioned here are being utilized to improve the electrical bistability, thus allowing us to improve the reproducibility in operational modes of thermotronic devices

Interface engineering for vanadium dioxide (VO2) integration on silicon

International audienceNeuromorphic computing is being seen as a solution to address the memory bottleneck persistent with the present computing paradigm. To realize such an architecture, artificial synapses and neurons need to be built. One way to emulate a bio-synapse requires a material with an metal-insulator phase transition (MIT). VO2 undergoes a structural phase transformation (SPT) from monoclinic structure at room temperature to tetragonal at approximately 70°C. The SPT is accompanied by an IMT leading to a large variation in its electrical (about 4 orders of magnitude of its resistivity) and optical properties, in particular, in its complex refractive index in the mid-IR frequency range.To keep with the current trends of the microelectronic industry, it is imperative to integrate VO2 on silicon. However, the higher lattice mismatch and formation of oxides and silicates at the interface between VO2 and crystalline Si degrade the quality and functionality of VO2 film. Additionally, VO2(M1) is a challenging material to integrate into patterned heterostructures because it can exist not only as multiple polymorphs (A, B, M1) but the high-temperature depositions can lead to the formation of various oxidation states phases that are present in the V-O system (VnO2n-1, VnO2n+1). This work was conducted to study the growth of VO2 on silicon with oxide buffer layers using RF magnetron sputtering of a V2O5 ceramic target in argon atmosphere. We studied the structure-property relationships, specifically electrical and optical properties as a function of temperature across the Tc. Structural and compositional characterizations are carried out using x-ray diffraction, atomic force microscopy, and x-ray photoemission spectroscopy respectively, optical responses are studied under spectroscopic ellipsometry and electrical characterizations are performed using the four-point probe method. With the use of a very thin metal oxide buffer layer between the silicon substrate and VO2 film, we demonstrate a high resistivity ratio (of the order 3 between the two phases) and investigate the scope of improvement. The results show the influence of substrate temperature, VO2 grain size, and strain on it as well as the crystal structure of the buffer layer on the structural and physical properties of interfaces and film morphology which subsequently affect the electrical bistability of VO2. The preliminary findings mentioned here are being utilized to improve the electrical bistability, thus allowing us to improve the reproducibility in operational modes (switching, memory, logical operations, etc.) of neuromorphic devices

Integration of VO2 on Silicon for thermotronic applications

International audienc

Characterization of uncooled ultra low-NEP LSMO bolometers at 3.39 µm and in the MWIR and LWIR bands

International audienceLa0.7Sr0.3MnO3 (LSMO) uncooled suspended bolometers have been characterized at 3.39 μm (He-Ne laser) and with a blackbody source at different temperatures. These bolometers could achieve ultra low NEP values below 1 pW·Hz-1/2 with few microwatts power consumption at 300 K

Interface engineering for vanadium dioxide (VO2) integration on silicon

International audienceNeuromorphic computing is being seen as a solution to address the memory bottleneck persistent with the present computing paradigm. Artificial synapses and neurons need to be built to realize such an architecture. One way to emulate a bio-synapse requires a material with a metal-insulator phase transition (MIT). VO2 undergoes a structural phase transformation (SPT) from a monoclinic structure at room temperature to tetragonal at approximately 70°C. The SPT is accompanied by an MIT leading to a large variation in its electrical (about 4 orders of magnitude of its resistivity) and optical properties, in particular, in its complex refractive index in the mid-IR frequency range. To keep with the current trends of the microelectronic industry, it is imperative to integrate VO2 on silicon. However, the higher lattice mismatch and formation of oxides and silicates at the interface between VO2 and crystalline Si degrade the quality and functionality of VO2 film. Additionally, VO2(M1) is a challenging material to integrate into patterned heterostructures because it can exist not only as multiple polymorphs (A, B, M1) but the high-temperature depositions can lead to the formation of various oxidation states phases that are present in the V-O system (VnO2n-1, VnO2n 1). This work was conducted to study the growth of VO2 on silicon with oxide buffer layers using RF magnetron sputtering of a V2O5 ceramic target in an argon atmosphere. We studied the structure-property relationships, specifically electrical and optical properties as a function of temperature across the Tc. Structural and compositional characterization are carried out using x-ray diffraction, atomic force microscopy, and x-ray photoemission spectroscopy respectively, optical responses are studied under spectroscopic ellipsometry and electrical characterizations are performed using the four-point probe method. With the use of a very thin metal oxide buffer layer between the silicon substrate and VO2 film, we demonstrate a high resistivity ratio (of the order 3 between the two phases) and investigate the scope of improvement. The results show the influence of substrate temperature, VO2 grain size, and strain on it as well as the crystal structure of the buffer layer on the structural and physical properties of interfaces and film morphology which subsequently affect the electrical bistability of VO2. The preliminary findings mentioned here are being utilized to improve the electrical bistability, thus allowing us to improve the reproducibility in operational modes (switching, memory, logical operations, etc.) of neuromorphic devices