Plasma-activated direct bonding of diamond-on-insulator wafers to thermal oxide grown silicon wafers

Diamond-on-insulator (DOI) wafers featuring ultrananocrystalline diamond are studied via atomic force microscopy, profilometer and wafer bow measurements. Plasma-activated direct bonding of DOI wafers to thermal oxide grown silicon wafers is investigated under vacuum. DOI wafer with chemical mechanical polishing (CMP) on the diamond surface makes a poor bonding to silicon wafers with thermal oxide. Our results show that plasma enhanced chemical vapor deposition of silicon dioxide on top of the DOI wafer, CMP of the oxide layer and annealing are essential to achieve very high quality direct bonding to thermal oxide grown on silicon wafers. Plasma activation results in the formation of high quality bonds without exceeding 550 °C in the direct wafer bonding process.     

An efficient,heterogeneous, reusable atom transfer radical polymerization catalyst

Melamine based porous polymer (MPP) was prepared as a template solid to incorporate Cu(I) cations into the framework through chelating with nitrogen groups of the melamine. The copper integrated porous material (Cu(I)@MPP) was used as a heterogeneous catalyst and displayed high activity in copper catalyzed atom transfer radical polymerization of methyl methacrylate. The characterization of the Cu(I)@MPP was performed using nitrogen adsorption experiments and wide‐angle X‐ray and Fourier transform infrared spectroscopies. The atomic absorption spectroscopy measurements confirmed that the catalyst is practically non‐leaching and Cu(I) was found to be below 20 ppb after each atom transfer radical polymerization. Moreover, the catalyst showed reusability without any significant change in its activity. © 2017 Society of Chemical Industry     

纤维增强复合材料提高圆形桥柱延展性的修复设计

建筑物中柱和桥墩的修复设计要求对结构变形能力进行精确预测。本文提出分析模型近似计算经纤维增强聚合物修复的钢筋混凝土柱的潜在塑性关键区的延展性。提出能够代表纤维增强聚合物混凝土响应的双线性应力一应变模型，该模型在低压下混凝土响应降低，在高压下混凝土响应增强。对于承受轴力和弯矩的圆柱，模型采用近似形式的组合分析，根据无量纲柱参数和纤维增强聚合物提供的约束压力来计算经纤维增强聚合物修复的截面延展性。通过比较组合分析的模型估计结果和试验结果，验证纤维增强聚合物修复柱延展性模型的精确性。随后，建立了循环桥柱纤维增强聚合物简单非重复抗震修复设计程序。最后，对不同轴向荷载、含筋率、纤维增强聚合物数量进行典型桥柱参数研究，计算结果以无量纲形式给出，有助于工程师采用纤维增强聚合物进行提高柱延展性的抗震修复设计。     

Coronary artery bypass grafting versus percutaneous coronary intervention in end-stage kidney disease: A systematic review and meta-analysis of clinical studies

The most significant complication of end-stage kidney disease (ESKD) is cardiovascular disease, mainly coronary artery disease (CAD). Although the effective treatment of CAD is an important prognostic factor, whether percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) is better for treating CAD in this group of patients is still controversial. We searched Pubmed/Medline, Web of Science, Embase, the Cochrane Central Register of Controlled Trials articles that compared the outcomes of CABG versus PCI in patients with ESKD requiring dialysis. A total of 10 observational studies with 39,666 patients were included. Our analysis showed that when compared to PCI, CABG had lower risk of need for repeat revascularization (relative risk [RR] = 2.25, 95% confidence interval [CI] 2.1–2.42, p < 0.00001) and cardiovascular death (RR = 1.19, 95% CI 1.14–1.23, p < 0.00001) and higher risk for short-term mortality (RR = 0.43, 95% CI 0.38–0.48, p < 0.00001). There was no statistically significant difference between the PCI and CABG groups in the risk for late mortality (RR = 1.05, 95% CI 0.97–1.14, p = 0.25), myocardial infarction (RR = 1.05, 95% CI 0.46–2.36, p = 0.91) or stroke (RR = 1.02, 95% CI 0.64–1.61, p = 0.95). This meta-analysis showed that in ESKD patients requiring dialysis, CABG was superior to PCI in regard to cardiovascular death and need for repeat revascularization and inferior to PCI in regard to short term mortality. However, this meta-analysis has limitations and needs confirmation with large randomized controlled trials.     

Nanoscale communication with molecular arrays in nanonetworks

Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 μs and 2 nm, respectively.     

Er-Doped Y2O3 Nanoparticles: A Comparison of Different Synthesis Methods

Nanoparticles of erbium-doped yttria (Er:Y₂O₃) are important precursors to transparent ceramics for high-power solid-state lasers systems. As structure influences properties and, subsequently, performance the purpose of this work is to compare the morphological and chemical nature of the nanoparticles synthesized using two common methods: solution precipitation and combustion synthesis. A thorough characterization of as-prepared and calcined powders was performed using Fourier transform infrared spectroscopy, X-ray diffraction, conventional and high-resolution transmission electron microscopy, and Brunauer–Emmet–Teller methods. Solution precipitation was found to lead to two different precursor compositions (yttrium carbonate or yttrium hydroxide) depending on the precipitating reagent whereas combustion synthesis yielded only phase-pure, cubic Er:Y₂O₃. The hydroxide precipitation and combustion synthesis methods exhibited agglomerated particles with low surface area after calcining the precursors at 900°C. The addition of a small amount of ammonium sulfate during combustion synthesis was found to reduce the level of agglomeration, resultant particle size, and degree of crystallinity of the calcined Er:Y₂O₃ nanoparticles. The amount of carbon dioxide (CO₂) and water (H₂O) on the surface of the Er:Y₂O₃ powders is dependent on the powder surface area, however, increasing levels of gas absorption on the particle surfaces do not have a detrimental effect on the sinterability. The sintered density increases with increasing surface area and decreasing agglomeration.     

盐胁迫环境下腐植酸类物质对小麦生长及矿物营养吸收的影响

对在不同浓度的盐胁迫条件下,叶面喷施液态腐植酸和土壤施用腐植酸类物质对小麦作物生长和矿物营养吸收的影响进行了研究。通过添加不同量的NaCl得到不同的盐浓度环境。腐植酸类物质在作物种植前一个月施用,液态腐植酸在种苗发芽后20d和35d喷施于小麦叶面。腐植酸类物质的施用量为0、1g/kg、2g/kg,液态腐植酸的浓度为0、0.1%、0.2%。盐度对小麦生长具有负面影响,它会降低小麦对除Na、Mn以外的矿物营养的吸收,影响小麦干重。通过在土壤施用腐植酸类物质可以增加小麦对N的吸收,叶面施用腐植酸可增加其对P、K、Mg、Na、Cu和Zn的吸收。研究结果显示：在土壤中施用腐植酸类物质,不同盐浓度与施用量之间存在较好的相关性,但叶面喷施时盐度和喷施量之间相关性并不明显。在盐胁迫环境的影响下,叶面喷施腐植酸的初始浓度和土壤中施用的腐植酸类物质的初施量都增加了作物对营养元素的吸收。     

Modeling the probability of arsenic in groundwater in New England as a tool for exposure assessment

We developed a process-based model to predict the probability of arsenic exceeding 5 microg/L in drinking water wells in New England bedrock aquifers. The model is being used for exposure assessment in an epidemiologic study of bladder cancer. One important study hypothesis that may explain increased bladder cancer risk is elevated concentrations of inorganic arsenic in drinking water. In eastern New England, 20-30% of private wells exceed the arsenic drinking water standard of 10 micrograms per liter. Our predictive model significantly improves the understanding of factors associated with arsenic contamination in New England. Specific rock types, high arsenic concentrations in stream sediments, geochemical factors related to areas of Pleistocene marine inundation and proximity to intrusive granitic plutons, and hydrologic and landscape variables relating to groundwater residence time increase the probability of arsenic occurrence in groundwater. Previous studies suggest that arsenic in bedrock groundwater may be partly from past arsenical pesticide use. Variables representing historic agricultural inputs do not improve the model, indicating that this source does not significantly contribute to current arsenic concentrations. Due to the complexity of the fractured bedrock aquifers in the region, well depth and related variables also are not significant predictors.