Minimax rates of convergence for nonparametric location-scale models

This paper studies minimax rates of convergence for nonparametric location-scale models, which include mean, quantile and expectile regression settings. Under Hellinger differentiability on the error distribution and other mild conditions, we show that the minimax rate of convergence for estimating the regression function under the squared $L_2$ loss is determined by the metric entropy of the nonparametric function class. Different error distributions, including asymmetric Laplace distribution, asymmetric connected double truncated gamma distribution, connected normal-Laplace distribution, Cauchy distribution and asymmetric normal distribution are studied as examples. Applications on low order interaction models and multiple index models are also given

Carbohydrate intake quality and gestational diabetes mellitus, and the modifying effect of air pollution

BackgroundNutritional management is the cornerstone of gestational diabetes mellitus (GDM) prevention. High quality instead of low quantity of carbohydrate intake has been paying attention in controlling glycemia. Air pollution exposure can be interacted with dietary sourced nutrients, which may modify the associations with GDM. This study aims to explore the associations between overall quality of carbohydrate intake and GDM as well as the modifying effect of prenatal air pollution exposure.MethodsCarbohydrate quality index (CQI) was calculated was calculated by summing scores of the four components; Land use regression prediction models were used to assess the air pollution exposure levels. GDM definition was based on 75 g glucose tolerance test results. Associations between pre-pregnancy CQI, pre-natal air pollution as well as the modifying effect on GDM were explored based on a birth cohort in China.ResultsA total of 3,183 participants were included, of which 784 (24.63%) were diagnosed with GDM. Higher pre-pregnancy CQI was associated with a lower incidence of GDM [odds ratio (OR) = 0.75, 95% confidence interval (CI): 0.56–0.99, Pfor trend = 0.04], especially for higher fasting blood glucose related GDM (OR = 0.66, 95% CI: 0.47, 0.91). Higher air pollution exposure before and during pregnancy was associated with a greater risk of GDM. Higher exposure to particulate matter with an aerodynamic diameter of < 2.5 μm (Pfor interaction < 0.01), particulate matter with an aerodynamic diameter of < 10 μm (Pfor interaction < 0.01), and sulfur dioxide (Pfor interaction = 0.02) during pregnancy decreased the beneficial effect of high pre-pregnancy CQI on GDM.ConclusionCQI related dietary interventions pre-pregnancy to prevent GDM incidence should be considered. Women who are planning to be pregnant should avoid high exposure to air pollution during pregnancy

Different Solvent Extracts from By-products of Corylus heterophylla Fisch. × Corylus avellana L.: Bioactivity Evaluation and Phenolic Composition Analysis by Ultra-high Performance Liquid Chromatography-Mass Spectrometry

Phenolics were extracted from the by-products (leaves, green leafy covers, shells, branches and seed coats) of the hybrid hazelnut Corylus heterophylla Fisch. × Corylus avellana L. using four different polar solvents (water, methanol, 80% ethanol and ethyl acetate) and their antioxidant, hypoglycemic and anti-inflammatory activities were evaluated in vitro. The phenolics were identified by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS). The leaf and branch extracts showed stronger antioxidant, hypoglycemic and anti-inflammatory activities in vitro than the extracts from green leafy covers, shells and seed coats. The biological activities were largely correlated with total phenols and proanthocyanidins in the by-products of hazelnut. The methanol extract of hazelnut branches had the highest content of total phenols (calculated as gallic acid equivalent per dry mass) and procyanidins (calculated as proanthocyanidin equivalent per dry mass), which were (37.13 ± 0.22) and (2.27 ± 0.04) mg/g, respectively. The content of total flavonoids (calculated as rutin equivalent per dry mass) in the 80% ethanol extract of hazelnut leaves was the highest, which was (18.21 ± 1.37) mg/g. For each plant part, the contents of total phenols, total flavonoids and proanthocyanidins in the ethyl acetate extract were lower than those in the other solvent extract, but the ethyl acetate extract inhibited the activities of α-amylase and lipoxygenase significantly (P < 0.05). The ethyl acetate extract of green leafy covers had the best inhibitory effect on α-amylase, while the ethyl acetate extract of leaves showed the strongest inhibitory activity on lipoxygenase. According to UPLC-MS analysis, the majority of phenolic compounds in hybrid hazelnut by-products were flavonoids along with many bioactive compounds such as terpenes, alkaloids, lignans and organic acids. Bioactive ingredients in hybrid hazelnut by-products have the potential to be used in functional foods or pharmaceuticals

The equilibria of Ta-W-Al-Si-O system at 1200 °C

Solid reactions among Ta-W-Al-Si oxides are discussed and the phase compatibilities of these oxides at 1200 °C have been investigated. The results showed that complex oxides of TaWO, TaWO, TaWO, AlWO and AlTaO could be formed by solid reactions. Liquid phase formed by AlO-WO in WO-SiO-AlO benefits the mullitization reaction, thus mullite can be formed at 1200 °C in ternary system. Solid solution with a formula of (1-x)TaO·xWO was formed, and up to 25.0% SiO and 6.0% AlO can be dissolved in the solid solution. Liquid phase first appeared in the TaO-WO-AlO ternary system at 1300 °C in the WO-rich corner. As the temperature increased, the liquidus area expanded towards the AlO- and the TaO-rich corners

Using noble gases to trace groundwater evolution and assess helium accumulation in Weihe Basin, central China

The severe shortage of helium resources is an impending global problem. However, the helium accumulation processes and conditions favorable for helium enrichment in reservoirs remain poorly understood, which makes helium exploration challenging. Noble gases are good tracers of subsurface fluids provenance, migration and storage, as well as indicators of the nature and quantity of associated phases. In this study the variation of major gases and noble gases data in Weihe Basin provide us with an excellent opportunity to understand the groundwater evolution and helium accumulation processes. Twelve gas samples collected from wellheads of geothermal wells can be classified into three groups, in which Group A has high concentrations of N2 (58.57% - 91.66%) and He (0.32% - 2.94%); Group B has high contents of CH4 (52.94% and 69.50%) and low concentrations of He (0.057% and 0.062%); Group C has a high content of CH4 (71.70%) and He (2.11%). Helium isotopic ratios are predominantly radiogenic in origin and therefore crustally derived. Measured elemental ratios of noble gases are compared with multiple fractionation models for Group A and B samples, implying that open system heavy oil-water fractionation with excess heavy noble gases has occurred in the basin with Voil/Vwater ratios of 0.06-0.18. The amount of helium in Group A and B samples requires the release of all 4He produced in the crust since 0.30Ma-1.98Ma into the groundwater. The Group C sample requires an additional He flux from adjacent granitic bodies. The accumulation of helium and hydrocarbon in the Weihe Basin can be explained by a 4-stage process. Accumulation of commercially viable helium requires high He flux from source rocks, the existence of a free gas phase of major gas components (CH4 in most cases, N2 or CO2) and minimal major gas addition after formation of the free gas phase