Extreme haze episodes repeatedly shrouded Beijing during the winter of 2012-2013, causing major environmental and health problems. To better understand these extreme events, we performed a ...model-assisted analysis of the hourly observation data of PM2.5 and its major chemical compositions. The synthetic analysis shows that (1) the severe winter haze was driven by stable synoptic meteorological conditions over northeastern China, and not by an abrupt increase in anthropogenic emissions. (2) Secondary species, including organics, sulfate, nitrate, and ammonium, were the major constituents of PM2.5 during this period. (3) Due to the dimming effect of high loading of aerosol particles, gaseous oxidant concentrations decreased significantly, suggesting a reduced production of secondary aerosols through gas-phase reactions. Surprisingly, the observational data reveals an enhanced production rate of secondary aerosols, suggesting an important contribution from other formation pathways, most likely heterogeneous reactions. These reactions appeared to be more efficient in producing secondary inorganics aerosols than organic aerosols resulting in a strongly elevated fraction of inorganics during heavily polluted periods. (4) Moreover, we found that high aerosol concentration was a regional phenomenon. The accumulation process of aerosol particles occurred successively from cities southeast of Beijing. The apparent sharp increase in PM2.5 concentration of up to several hundred mu g m-3 per hour recorded in Beijing represented rapid recovery from an interruption to the continuous pollution accumulation over the region, rather than purely local chemical production. This suggests that regional transport of pollutants played an important role during these severe pollution events.
•Pipeline steel corrosion is slight in abiotic soil.•Sulfate reducing bacteria (SRB) grow well in the soil.•SRB accelerates uniform corrosion of the steel and causes localized corrosion.•A high water ...content in the soil promote the SRB growth and steel corrosion.•The presence of CO2 in the soil favors the SRB growth and steel corrosion.
In this work, corrosion of an X52 pipeline steel was investigated in a field-collected soil containing sulfate-reducing bacteria (SRB) by weight-loss testing, bio-testing, electrochemical measurements and surface analysis techniques. The SRB can grow well in the soil and attach to the steel surface, leading to microbiologically influenced corrosion (MIC) of the steel. The SRB are able to accelerate corrosion of the steel remarkably. Compared to the corrosion rate of 0.0473mm/y in SRB-absent soil, the corrosion rate of the steel is up to 0.282mm/y when SRB are contained in the soil. An increase of the water content in the soil favors the growth of SRB, increasing the thickness of the biofilm formed on the steel surface and accelerating the steel MIC. At individual water contents, the presence of CO2 in the soil accelerates the steel MIC induced by SRB, which is associated with the increasing amount of SRB cells in CO2-containing soil. The SRB also result in localized corrosion of the steel. This is associated with the unique soil corrosion environment, where the sessile SRB cells and corrosion products do not move freely. The porous structure of the surface film contributes to the initiation of localized corrosion.
Susceptibility-weighted imaging (SWI) is a new neuroimaging technique, which uses tissue magnetic susceptibility differences to generate a unique contrast, different from that of spin density, T1, ...T2, and T2*. In this review (the first of 2 parts), we present the technical background for SWI. We discuss the concept of gradient-echo images and how we can measure local changes in susceptibility. Armed with this material, we introduce the steps required to transform the original magnitude and phase images into SWI data. The use of SWI filtered phase as a means to visualize and potentially quantify iron in the brain is presented. Advice for the correct interpretation of SWI data is discussed, and a set of recommended sequence parameters for different field strengths is given.
To evaluate the incidence of Acanthamoeba keratitis in the Netherlands between 2009 and 2015 and to analyse predicting factors for treatment outcome.
Patient characteristics, diagnostic methods, ...diagnostic delay, therapy prior to and after diagnosis, and visual outcome were obtained from medical files of all patients diagnosed with Acanthamoeba keratitis in the Netherlands between 2009 and 2015. A logistic regression analysis on treatment failure, defined as a best corrected visual acuity of less than 20/40 Snellen decimals (i.e. >0.3 logMAR or an approximate loss of three lines of visual acuity) and/or the need for keratoplasty, was performed to determine predicting factors.
Two hundred and twenty-four eyes of 224 patients were included. Ninety-five percent of the patients were contact lens wearers, of whom 74% wore soft contact lenses. The number of cases increased from 16 in 2009 to 49 in 2015. This resulted in an estimated incidence of 1 in 21,000 for soft contact lens wearers in 2015. Eighty-seven eyes (39%) met the criteria for treatment failure. In a multivariable regression analysis, higher age at presentation, a higher severity stage and corticosteroid use before diagnosis were positively correlated with treatment failure. Early referral to a cornea specialist was associated with better clinical outcomes.
Although Acanthamoeba keratitis is still a relatively uncommon disease, the incidence in soft contact lens wearers has increased to reach 1 in 21,000 in 2015. Treatment failure occurred in 39% of cases, with age, higher severity stage, corticosteroid use before diagnosis and indirect referral to a cornea specialist as important risks factors.
Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as ...photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5-15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes. The donor-acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.
The structure of metallic glasses (MGs) has been a long-standing mystery. On the one hand, MGs are amorphous materials with no long-range structural order; on the other hand, topological and chemical ...short-to-medium range order is expected to be pronounced in these alloys, due to their high atomic packing density and the varying chemical affinity between the constituent elements. The unique internal structure of MGs underlies their interesting properties, which render MGs potentially useful for various applications. While more and more glass-forming alloys have been developed in recent years, fundamental knowledge on the structural aspect of MGs remains seriously lacking. For example, how atoms pack on the short-to-medium range, how the structure differs in different MGs and changes with composition, temperature, and processing history, and more importantly, how the structure influences the properties of MGs, are still unresolved questions. In this paper, we review the tremendous efforts over the past 50years devoted to unraveling the atomic-level structure of MGs and the structural origin of their unique behaviors. Emphasis will be placed on the progress made in recent years, including advances in structural characterization and analysis of prototypical MGs, general structural models and fundamental principles, and the correlations of thermodynamic, kinetic, and mechanical properties with the MG structures. Some widely observed property-property correlations in MGs are also examined from the structural perspective. The insights summarized are shown to shed light on many intriguing behaviors of the MG-forming alloys and expected to impact the development of MGs. Outstanding questions in this important research area will also be outlined.
Summary
Background
Ustekinumab, an interleukin (IL)‐12 and IL‐23 blocker, has emerged as a new therapeutic option for patients with psoriasis. It is generally well tolerated but safety data on the ...use of ustekinumab in patients with viral hepatitis are limited.
Objective
To assess the safety profile of ustekinumab in the treatment of patients with psoriasis who have concomitant hepatitis B or hepatitis C.
Methods
This study included 18 patients with concurrent psoriasis and hepatitis B virus (HBV) infection (14 patients) or hepatitis C virus (HCV) infection (four patients) who were treated with at least two ustekinumab injections. Viral loads were measured at baseline and each time before the administration of ustekinumab. Relevant clinical data were recorded.
Results
Among 11 patients positive for hepatitis B surface antigen (HBsAg), two out of the seven (29%) patients who did not receive antiviral prophylaxis exhibited HBV reactivation during ustekinumab treatment. No viral reactivation was observed in the three occult HBV‐infected patients (HBsAg‐negative/hepatitis B core antibody‐positive patients). One patient with HCV, liver cirrhosis and treated hepatocellular carcinoma (HCC) experienced HCV reactivation and recurrent HCC during the ustekinumab treatment. No significant increase in aminotransferase levels was observed in any patient.
Conclusions
Antiviral prophylaxis appears to minimize the risk of viral reactivation in patients with concurrent psoriasis and HBV infection. Without effective anti‐viral prophylaxis, the risk/benefit of ustekinumab treatment should be carefully assessed in patients with psoriasis and HBV or HCV infection and/or HCC. Close monitoring for HBV and HCV viral load is recommended, particularly for patients with high‐risk factors. Serum aminotransferase determination may not be useful for early detection of viral reactivation.
What's already known about this topic?
Interleukin (IL)‐12 plays a central role in mounting an immune response directed towards the elimination of pathogens.
Ustekinumab, an IL‐12/23 blocker may theoretically carry the risk of hepatitis B (HBV) and hepatitis C virus (HCV) reactivation with its use.
What does this study add?
Ustekinumab appears to be well tolerated in patients with concurrent psoriasis and HBV infection under antiviral prophylaxis.
The risk of HCV reactivation during ustekinumab treatment does exist and appropriate vigilance should be exercised, especially in specific high‐risk patient groups.
Femtosecond laser pulses filamenting in various gases are shown to generate long- lived quasi-stationary cylindrical depressions or 'holes' in the gas density. For our experimental conditions, these ...holes range up to several hundred microns in diameter with gas density depressions up to ~20%. The holes decay by thermal diffusion on millisecond timescales. We show that high repetition rate filamentation and supercontinuum generation can be strongly affected by these holes, which should also affect all other experiments employing intense high repetition rate laser pulses interacting with gases.
In this work, corrosion of an X52 pipeline steel under soil layers with varied thicknesses soaked with a simulated soil solution was investigated in the absence and presence of sulfate-reducing ...bacteria (SRB) by weight-loss testing, bio-testing, electrochemical measurements and surface analysis techniques. Results demonstrate that, in anaerobic, sterile soil solutions, the presence of a soil layer on the steel surface accelerates the steel corrosion, with the corrosion rate increasing from 0.01 mm/y for uncovered steel to an average of 0.04 mm/y when the soil layer thickness exceeds 5 mm. The presence of SRB in the soil solution increases remarkably the corrosion of bare steel, with an average corrosion rate up to 0.68 mm/y. However, the presence of a layer of soil on the steel surface decreases the steel corrosion. As the soil layer thickness increases, the corrosion rate further decreases, along with the decreased counts of sessile SRB cells on the steel surface. This is attributed to the blocking effect of the soil layer on transport of SRB cells and nutrients towards the steel surface. A galvanic coupling effect exists between bare steel and the soil-covered steel, where SRB contribute to the galvanic corrosion effect. The galvanic current measured in the presence of SRB is considerably higher than that in the absence of SRB.
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