Phosphate is commonly added to drinking water to inhibit lead release from lead service lines and lead-containing materials in premise plumbing. Phosphate addition promotes the formation of lead phosphate particles, and their aggregation behaviors may affect their transport in pipes. Here, lead phosphate formation and aggregation were studied under varied aqueous conditions typical of water supply systems. Under high aqueous PO4/Pb molar ratios (>1), phosphate adsorption made the particles more negatively charged. Therefore, enhanced stability of lead phosphate particles was observed, suggesting that although addition of excess phosphate can lower the dissolved lead concentrations in tap water, it may increase concentrations of particulate lead. Adsorption of divalent cations (Ca2+ and Mg2+) onto lead phosphate particles neutralized their negative surface charges and promoted their aggregation at pH 7, indicating that phosphate addition for lead immobilization may be more efficient in harder waters. The presence of natural organic matter (NOM, ≥ 0.05 mg C/L humic acid and ≥ 0.5 mg C/L fulvic acid) retarded particle aggregation at pH 7. Consequently, removal of organic carbon during water treatment to lower the formation of disinfection-byproducts (DBPs) may have the additional benefit of minimizing the mobility of lead-containing particles. This study provided insight into fundamental mechanisms controlling lead phosphate aggregation. Such understanding is helpful to understand the observed trends of total lead in water after phosphate addition in both field and pilot-scale lead pipe studies. Also, it can help optimize lead immobilization by better controlling the water chemistry during phosphate addition.
To evaluate pore structures of the Bakken Shale, which is one of the most important factors that affect petrophysical properties, high-pressure mercury intrusion was employed in this study. Pore structures such as pore-throat size, pore-throat ratio, and fractal attributes are investigated in this major shale play. Pore-throat size from 3.6 to 200 um is widely distributed in these shale samples. Accordingly, pore-throat size distributions demonstrate the multimodal behavior within the samples. The whole pore-throat network can be divided into four clusters: one set of large pores, two transitional/intermediate pore groups, and one set of smaller pores. The fractal analysis revealed that fractal dimensions decrease as the pore-throat size decreases. The multifractal analysis demonstrated that as the maturity of the shale samples increases, pore-throat size distributions would become more uniform and pore structures tend to become more homogeneous. The results are compared to our previous results obtained from nitrogen gas adsorption for further verifications of fractal behavior. Finally, although fractal analysis of mercury intrusion and nitrogen gas adsorption were comparable, the results of multifractal analysis from these two methods were not identical.
The natural draft dry cooling tower (NDDCT) has been increasingly used in power generation for its merits of excellent water-saving, high energy saving, simple maintenance and long life service. To study the performance of a newly installed 660 MW NDDCT under crosswind condition, a model with scale of 1:200 was built according to the scaling law of geometric similarity. The experiments were set up in self-similar region with high Reynolds to meet momentum similarity, while meeting the scaling law of Froude and Euler numbers. A first order law radiator resistance model is also proposed and verified by a systematic test. The exponent law profile of wind velocity above the ground was built and verified by experimental data. On the ground of a constant heating rate bases, the flow field inside the NDDCT and the ventilation rate were investigated at the crosswind range of 0–20 m/s.
Despite their crucial roles in health and climate concerns, the gas-particle partitioning of carbonyl compounds is poorly characterized in the ambient atmosphere. In this study, we investigate their partitioning by simultaneously measuring six carbonyl compounds (formaldehyde, acetaldehyde, acetone, propionaldehyde, glyoxal, and methylglyoxal) in gas and particle phase at an urban site in Beijing. The field-derived partitioning coefficients (Kpf) are in the range of 10−5−10−3 m3 µg−1, and corresponding effective Henry’s law coefficients (KHf) should be 107–109 M atm−1. The Pankow’s absorptive partitioning theory and the Henry’s law both significantly underestimate concentrations of particle-phase carbonyl compounds (105–106 times and >103 times, respectively). The observed “salting in” effects only partially explain the enhanced partitioning to particles, approximately one order of magnitude. The measured Kpf values are higher at low relative humidity and the overall effective vapor pressure of these carbonyl species are lower than their hydrates, indicating that carbonyl oligomers potentially formed in highly concentrated particle phase. The reaction kinetics of oligomer formation should be included if applying the Henry’s law to low-to-moderate RH and the high partitioning coefficients observed need further field and laboratory studies. These findings provide deeper insights into the formation of carbonyl secondary organic aerosols in the ambient atmosphere.
A gate-recessed normally OFF GaN metal-oxide-semiconductor high-electron-mobility transistor on silicon substrate has been fabricated using a self-terminated, plasma-free oxidation and wet etching process with pre-recess low-pressure chemical vapor deposition (LPCVD) Si3N4 passivation layer. The LPCVD Si3N4 serves the dual role of gate-recess mask and passivation layer. Unlike conventional oxidation etching process using Si3N4 as post gate-recess passivation, the gate channel region was prevented from additional plasma bombardment during the gate window re-opening. As a result, a high-effective channel mobility of 843 cm(2)/V . s, and low-channel resistance of 0.89 Omega . mm are achieved for a normally OFF channel with L-G = 1.5 mu m. For 3 mu m L-GD, the fabricated devices exhibit a threshold voltage (Vth) of 1.35 V, a maximum drain current of similar to 500 mA/mm, a high ON/OFF current ratio of similar to 1010, and 560-V OFF-state breakdown voltage together with a low-forward gate leakage current of similar to 10-7 mA/mm up to 10 V. A high Baliga's figure of merit of 1.26 GW/cm(2) is achieved in devices with 10-mu m gate-drain distance.
A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding 10 MeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30 fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic film stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons.
A scheme to radiate a highly collimated gamma-ray pulse is proposed through the interaction between an ultra-intense laser pulse and a narrow tube target. The gamma-ray pulse, with high conversion efficiency, can be generated as a result of electron acceleration in a longitudinal electric field. In a Particle-inCell simulation with a 10-PW laser, 18% of the laser energy is transferred into the forward gamma-ray in a divergence angle less than 3 degrees. It is also found that such a highly collimated gamma-ray pulse can be produced with a large range of tube diameters and laser intensities. This scheme could be realized in experiment with the coming 10-PW class lasers in the near future. Published by AIP Publishing.
C-reactive protein (CRP) is a sensitive biomarker of chronic low-grade inflammation and is associated with multiple complex diseases. The genetic determinants of chronic inflammation remain largely unknown, and the causal role of CRP in several clinical outcomes is debated. We performed two genome-wide association studies (GWASs), on HapMap and 1000 Genomes imputed data, of circulating amounts of CRP by using data from 88 studies comprising 204,402 European individuals. Additionally, we performed in silico functional analyses and Mendelian randomization analyses with several clinical outcomes. The GWAS meta-analyses of CRP revealed 58 distinct genetic loci (p < 5 x 10(-8)). After adjustment for body mass index in the regression analysis, the associations at all except three loci remained. The lead variants at the distinct loci explained up to 7.0% of the variance in circulating amounts of CRP. We identified 66 gene sets that were organized in two substantially correlated clusters, one mainly composed of immune pathways and the other characterized by metabolic pathways in the liver. Mendelian randomization analyses revealed a causal protective effect of CRP on schizophrenia and a risk-increasing effect on bipolar disorder. Our findings provide further insights into the biology of inflammation and could lead to interventions for treating inflammation and its clinical consequences.
Macronutrient intake, the proportion of calories consumed from carbohydrate, fat, and protein, is an important risk factor for metabolic diseases with significant familial aggregation. Previous studies have identified two genetic loci for macronutrient intake, but incomplete coverage of genetic variation and modest sample sizes have hindered the discovery of additional loci. Here, we expanded the genetic landscape of macronutrient intake, identifying 12 suggestively significant loci (P < 1 x 10(-6)) associated with intake of any macronutrient in 91,114 European ancestry participants. Four loci replicated and reached genome-wide significance in a combined meta-analysis including 123,659 European descent participants, unraveling two novel loci; a common variant in RARB locus for carbohydrate intake and a rare variant in DRAM1 locus for protein intake, and corroborating earlier FGF21 and FTO findings. In additional analysis of 144,770 participants from the UK Biobank, all identified associations from the two-stage analysis were confirmed except for DRAM1. Identified loci might have implications in brain and adipose tissue biology and have clinical impact in obesity-related phenotypes. Our findings provide new insight into biological functions related to macronutrient intake.