Existence and uniqueness for Mean Field Games with state constraints

In this paper, we study deterministic mean field games for agents who operate in a bounded domain. In this case, the existence and uniqueness of Nash equilibria cannot be deduced as for unrestricted state space because, for a large set of initial conditions, the uniqueness of the solution to the associated minimization problem is no longer guaranteed. We attack the problem by interpreting equilibria as measures in a space of arcs. In such a relaxed environment the existence of solutions follows by set-valued fixed point arguments. Then, we give a uniqueness result for such equilibria under a classical monotonicity assumption

Improved charge-trapping properties of HfYON film for nonvolatile memory applications in comparison with HfON and Y 2O 3 films

The charge-trapping properties of HfYON film are investigated by using the Al/HfYON/SiO 2/Si structure. The physical features of this film were explored by transmission electron microscopy and x-ray photoelectron spectroscopy. The proposed device shows better charge-trapping characteristics than samples with HfON or Y 2O 3 as the charge-trapping layer due to its higher trapping efficiency, as confirmed by extracting their charge-trap centroid and charge-trap density. Moreover, the Al/Al 2O 3/HfYON/SiO 2/Si structure shows high program speed (4.5 V at 14 V, 1 ms), large memory window (6.0 V at 14 V, 1 s), and good retention property, further demonstrating that HfYON is a promising candidate as the charge-trapping layer for nonvolatile memory applications. © 2011 American Institute of Physics.published_or_final_versio

Nitrided SrTiO 3 as charge-trapping layer for nonvolatile memory applications

Charge-trapping characteristics of SrTiO 3 with and without nitrogen incorporation were investigated based on Al/ Al 2 O 3/SrTiO 3/SiO 2 /Si (MONOS) capacitors. A Ti-silicate interlayer at the SrTiO 3/SiO 2 interface was confirmed by x-ray photoelectron spectroscopy and transmission electron microscopy. Compared with the MONOS capacitor with SrTiO 3 as charge-trapping layer (CTL), the one with nitrided SrTiO 3 showed a larger memory window (8.4 V at ±10 V sweeping voltage), higher P/E speeds (1.8 V at 1 ms +8 V) and better retention properties (charge loss of 38% after 10 4s), due to the nitrided SrTiO 3 film exhibiting higher dielectric constant, higher deep-level traps induced by nitrogen incorporation, and suppressed formation of Ti silicate between the CTL and SiO 2 by nitrogen passivation. © 2011 American Institute of Physics.published_or_final_versio

Improved performance of yttrium-doped Al 2O 3 as inter-poly dielectric for flash-memory applications

Yttrium-doped Al 2O 3Y xAl yO) with different yttrium contents prepared by co-sputtering method is investigated as the inter-poly dielectric (IPD) for flash memory applications. A poor SiO 2-like interlayer formed at the IPD/Si interface is confirmed by X-ray photoelectron spectroscopy, and can be suppressed by Y doping through the transformation of silica into silicate. Compared with Al 2O 3 and Y 2O 3 films, the optimized Y xAl yO film shows lower interface-state density, lower bulk charge-trapping density, higher dielectric constant, and smaller gate leakage, due to the suppressed interlayer and good thermal property ascribed to appropriate Y and Al contents in the film. Therefore, the optimized Y xAl yO film is a promising candidate as the IPD for flash memory. © 2010 IEEE.published_or_final_versio

A novel MONOS memory with high-κ HfLaON as charge-storage layer

MIS capacitors with a high-κ HfLaON or HfLaO gate dielectric are fabricated by using a reactive sputtering method to investigate the applicability of the films as a novel charge-storage layer in a metaloxidenitrideoxidesilicon nonvolatile memory device. Experimental results indicate that the MIS capacitor with a HfLaON gate dielectric exhibits a large memory window, high program/erase speed, excellent endurance property, and reasonable retention. The involved mechanisms for these promising characteristics with HfLaON are thought to be in part from nitrogen incorporation leading to higher density of traps with deeper levels and, thus, higher trapping efficiency, stronger HfN and LaN bonds, and more stable atomic structure and HfLaONSiO 2 interface, as compared to the HfLaO dielectric. © 2011 IEEE.published_or_final_versio

Improved performance by using TaON/SiO2 as dual tunnel layer in Charge-Trapping nonvolatile memory

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Integrating knowledge tracing and item response theory: A tale of two frameworks

Traditionally, the assessment and learning science commu-nities rely on different paradigms to model student performance. The assessment community uses Item Response Theory which allows modeling different student abilities and problem difficulties, while the learning science community uses Knowledge Tracing, which captures skill acquisition. These two paradigms are complementary - IRT cannot be used to model student learning, while Knowledge Tracing assumes all students and problems are the same. Recently, two highly related models based on a principled synthesis of IRT and Knowledge Tracing were introduced. However, these two models were evaluated on different data sets, using different evaluation metrics and with different ways of splitting the data into training and testing sets. In this paper we reconcile the models' results by presenting a unified view of the two models, and by evaluating the models under a common evaluation metric. We find that both models are equivalent and only differ in their training procedure. Our results show that the combined IRT and Knowledge Tracing models offer the best of assessment and learning sciences - high prediction accuracy like the IRT model, and the ability to model student learning like Knowledge Tracing

Strain-dependent host transcriptional responses to toxoplasma infection are largely conserved in mammalian and avian hosts

Toxoplasma gondii has a remarkable ability to infect an enormous variety of mammalian and avian species. Given this, it is surprising that three strains (Types I/II/III) account for the majority of isolates from Europe/North America. The selective pressures that have driven the emergence of these particular strains, however, remain enigmatic. We hypothesized that strain selection might be partially driven by adaptation of strains for mammalian versus avian hosts. To test this, we examine in vitro, strain-dependent host responses in fibroblasts of a representative avian host, the chicken (Gallus gallus). Using gene expression profiling of infected chicken embryonic fibroblasts and pathway analysis to assess host response, we show here that chicken cells respond with distinct transcriptional profiles upon infection with Type II versus III strains that are reminiscent of profiles observed in mammalian cells. To identify the parasite drivers of these differences, chicken fibroblasts were infected with individual F1 progeny of a Type II x III cross and host gene expression was assessed for each by microarray. QTL mapping of transcriptional differences suggested, and deletion strains confirmed, that, as in mammalian cells, the polymorphic rhoptry kinase ROP16 is the major driver of strain-specific responses. We originally hypothesized that comparing avian versus mammalian host response might reveal an inversion in parasite strain-dependent phenotypes; specifically, for polymorphic effectors like ROP16, we hypothesized that the allele with most activity in mammalian cells might be less active in avian cells. Instead, we found that activity of ROP16 alleles appears to be conserved across host species; moreover, additional parasite loci that were previously mapped for strain-specific effects on mammalian response showed similar strain-specific effects in chicken cells. These results indicate that if different hosts select for different parasite genotypes, the selection operates downstream of the signaling occurring during the beginning of the host's immune response. © 2011 Ong et al

Sulfur isotopic signature of Earth established by planetesimal volatile evaporation

How and when Earth’s volatile content was established is controversial with several mechanisms postulated, including planetesimal evaporation, core formation and the late delivery of undifferentiated chondrite-like materials. The isotopes of volatile elements such as sulfur can be fractionated during planetary accretion and differentiation and thus are potential tracers of these processes. Using first-principles calculations, we examine sulfur isotope fractionation during core formation and planetesimal evaporation. We find no measurable sulfur isotope fractionation between silicate and metallic melts at core-forming conditions, indicating that the observed light sulfur isotope composition of the bulk silicate Earth relative to chondrites cannot be explained by metal–silicate fractionation. Our thermodynamic calculations show that sulfur evaporates mostly as H2S during planetesimal evaporation when nebular H2 is present. The observed bulk Earth sulfur isotope signature and abundance can be reproduced by evaporative loss of about 90% sulfur mainly as H2S from molten planetesimals before nebular H2 is dissipated. The heavy sulfur isotope composition of the Moon relative to the Earth is consistent with evaporative sulfur loss under 94–98% saturation condition during the Moon-forming giant impact. In summary, volatile evaporation from molten planetesimals before Earth’s formation probably played a key role in establishing Earth’s volatile element content