Cristallisation de couches GST amorphes dopées au N et riches en Ge déposées sur un modèle GST polycristallin

International audienceWe report on a detailed experimental study of the crystallization of amorphous N-doped Ge-rich GST layers (GGSTN) when in contact with a polycrystalline GST template. By combining in situ annealing in the TEM and ex situ chemical analysis, we show that, as observed in many materials, the layer in contact with the crystalline template crystallizes at a lower temperature than needed for bulk crystallization. At surprise, this characteristic is not due to the solid phase epitaxy of the GGSTN on the crystalline GST template but to a decrease of the Ge content in the GGSTN layer. Indeed, during annealing, Ge diffuses from the amorphous layer into the crystalline GST layer where it gets trapped and forms grains which grow, eventually leading to the formation of a pure crystalline Ge layer. As a result of this Ge depletion, the thermal budget necessary to drive the phase separation limiting the crystallization of the remaining GGSTN alloy is smaller.Nous rapportons une étude expérimentale détaillée de la cristallisation de couches GST amorphes dopées au N et riches en Ge (GGSTN) lorsqu'elles sont en contact avec un modèle GST polycristallin. En combinant le recuit in situ dans le TEM et l'analyse chimique ex situ, nous montrons que, comme observé dans de nombreux matériaux, la couche en contact avec le modèle cristallin cristallise à une température inférieure à celle nécessaire à la cristallisation globale. Étonnamment, cette caractéristique n'est pas due à l'épitaxie en phase solide du GGSTN sur la matrice cristalline GST mais à une diminution de la teneur en Ge dans la couche GGSTN. En effet, lors du recuit, le Ge diffuse de la couche amorphe vers la couche cristalline de GST où il est piégé et forme des grains qui se développent, conduisant finalement à la formation d'une couche de Ge cristalline pure. En raison de cet appauvrissement en Ge, le budget thermique nécessaire pour entraîner la séparation de phases limitant la cristallisation de l'alliage GGSTN restant est plus petit

An experimental study of Ge diffusion through Ge2Sb2Te5

International audienceGe thermal diffusion is not only the phenomenon limiting the decomposition and crystallization of Ge-rich GeSbTe alloys but is also responsible for some of the failures of the phase change memory devices using them. However, Ge diffusion in the canonical Ge2Sb2Te5 (GST-225) or in Ge-rich GeSbTe (GGST) alloys has been little studied experimentally. For these reasons, we have designed and set up a series of experiments aimed at highlighting and studying this diffusion within the solid phase, under technologically relevant conditions. For that, dedicated GST/Ge/GST structures have been grown at purpose, and the redistribution of Ge in GST-225 layers during isothermal and isochronal annealing has been studied using scanning and transmission electron microscopy based techniques. While Ge diffusion in amorphous GST-225 is negligible at low temperatures (i.e., below 140 °C), it is fast in crystalline GST-225 above 220 °C and proceeds via the grain boundaries. During such annealing, Ge diffusion is only limited by the emission of Ge atoms from the solid source and by the density of the grain boundaries providing diffusion paths to Ge through the polycrystalline layer, which tends to decrease as a function of the annealing time as the GST grains coalesce. These results show that diffusion phenomena can be activated at moderate temperatures in GST alloys and can change the chemical composition and morphology of Ge/GST composite materials. This supports the hypothesis that Ge diffusion may be responsible for the observed resistance drift and loss of integrity of the Phase Change Memories based on Ge-rich GeSbTe alloys in the SET state

Genetic evidence supporting a causal role of Janus kinase 2 in prostate cancer: a Mendelian randomization study

AbstractBackground Janus kinase-2 (JAK2) inhibitors are now being tried in basic research and clinical practice in prostate cancer (PCa). However, the causal relationship between JAK2 and PCa has not been uniformly described. Here, we examined the cause-effect relation between JAK2 and PCa.Methods Two-sample Mendelian randomization (MR) analysis of genetic variation data of JAK2, PCa from IEU OpenGWAS Project was performed by inverse variance weighted, MR-Egger, and weighted median. Cochran’s Q heterogeneity test and MR-Egger multiplicity analysis were performed to normalize the MR analysis results to reduce the effect of bias on the results.Results Five instrumental variables were identified for further MR analysis. Specifically, combining the inverse variance-weighted (OR: 1.0009, 95% CI: 1.0001–1.0015, p = 0.02) and weighted median (OR: 1.0009, 95% CI: 1.0000–1.0017, p = 0.03). Sensitivity analysis showed that there was no heterogeneity (p = 0.448) and horizontal multiplicity (p = 0.770) among the instrumental variables.Conclusions We found JAK2 was associated with the development of PCa and was a risk factor for PCa, which might be instructive for the use of JAK2 inhibitors in PCa patients

Construction and In Vitro Evaluation of a Tumor Acidic pH-Targeting Drug Delivery System Based on <i>Escherichia coli</i> Nissle 1917 Bacterial Ghosts

Synthetic nanocarriers are a promising therapeutic delivery strategy. However, these systems are often hampered by inherent disadvantages such as strong biotoxicity and poor biocompatibility. To overcome these issues, biological carriers with commonly used chemotherapy drugs have been developed. In this work, engineered bacterial ghosts (BGs) originated from probiotic Escherichia coli Nissle 1917 (EcN) were devised to specifically target acidic extracellular environments of tumor tissue. To improve the production efficiency and safety, a novel lysis protein E from phage α3 was applied to produce EcN BGs under high growth densities in high quality. In addition, the acidity-triggered rational membrane (ATRAM) peptides were displayed in EcN BGs to facilitate specific cancer cell internalization within the acidic tumor microenvironment before drug release. In conclusion, the engineered EcN BGs offer a promising means for bionic bacteria construction for hepatocellular carcinoma therapy

Agroecological Risk Assessment Based on Coupling of Water and Land Resources—A Case of Heihe River Basin

In the arid zone of northwest China, the Heihe River Basin (HRB), as a typical inland river basin, has a fragile regional ecological environment, obvious ecological degradation characteristics, and extremely serious problems in the utilization of agricultural land resources. Meanwhile, the shortage of water resources, the low reduction of land quality, and excessive agricultural activities have greatly increased the local water and land pressure. In this paper, firstly, using the Malmquist DEA model and coupling coordination degree model, the agroecological risk assessment system on account of the coupling of water and land resources (WLR) is constructed. Secondly, taking HRB from 1995 to 2020 as an example, we carry out spatial correlation analysis based on the degree of risk-correlated WLR. Thirdly, we analyze the evolution process and spatial correlation of ecological risk of agricultural WLR in the HRB at the county scale, then we conclude and put forward policy suggestions for improvement. The results show that: (1) On the whole, the average ecological risk of agricultural water resources in the HRB from 1995 to 2020 was 0.933, indicating that the risk was declining; the average ecological risk of agricultural land resources in the HRB from 1995 to 2020 was 0.938, indicating that the risk was declining also. (2) The degree of ecological risk coupling and coordination of agricultural soil and water resources upstream of the HRB is on the rise, while that in the middle and lower reaches is on the decline. (3) Through panel model analysis, the matching suitability of WLR drives agroecological risk. The correlation between them is positive. In conclusion, this method can effectively evaluate the agroecological risk of WLR and provide technical support for agricultural production and management in arid areas

Neighbor-Net of 21 Native American populations.

<p>The color of the squares indicates the geographic relationship of the populations (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044788#pone-0044788-g005" target="_blank">Figure 5</a> for more details).</p

Generative Design of Outdoor Green Spaces Based on Generative Adversarial Networks

Generative Adversarial Networks (GANs) possess a significant ability to generate novel images that adhere to specific guidelines across multiple domains. GAN-assisted generative design is a design method that can automatically generate design schemes without the constraints of human conditions. However, more research on complex objects with weak regularity, such as parks, is required. In this study, parks were selected as the research object, and we conducted our experiment as follows: (1) data preparation and collection; (2) pre-train the two neural network, then create the design layout generation system and the design plan generation system; (3) realize the data augmentation and enhanced hundred level dataset to thousand level dataset; (4) optimized training; (5) test the optimized training model. Experimental results show that (1) the machine learning model can acquire specific park layout patterns, quickly generate well-laid-out plan layout plans, and create innovative designs that differ from the human designer’s style within reasonable limits; (2) GAN-driven data augmentation methods can significantly improve the generative ability of algorithms, reduce generative pressure, and achieve better generative results; (3) pix2pix is prone to mode collapse, and CycleGAN has fixed rule errors in expressing certain design elements; and (4) GAN has the ability to mine design rules in the same way as humans

Moving from the two-population model to a four-population model.

<p>Moving from the two-population model to a four-population model.</p