Abstract
We report both experimentally and numerically that an acoustic suppressed topological refraction is realized by two kagome-lattice valley sonic crystals (VSCs). By simply rotating triangle ...rods in the VSCs, acoustic valley Hall phase transitions can be obtained. In a designed topological waveguide composed of two VSCs with distinct valley topological phases, two types of valley edge states can be observed in the domain wall. Furthermore, the topological waveguide can support a suppressed topological refraction of sound, which arises from the excitation of an acoustic dipole mode at the exit of the domain wall. Such a phenomenon is experimentally demonstrated by scanning topological refractions of the edge states from a zigzag termination, in which the theoretical prediction of a negative refraction almost overlaps with the perpendicular bisector of the dipole mode, and thus it is suppressed totally. Finally, the robustness of the suppressed topological refraction is demonstrated experimentally. Our work can find potential applications in designing the devices of robust directional sound transports and communications.
Most photoredox catalysts in current use are precious metal complexes or synthetically elaborate organic dyes, the cost of which can impede their application for large-scale industrial processes. We ...found that a combination of triphenylphosphine and sodium iodide under 456-nanometer irradiation by blue light-emitting diodes can catalyze the alkylation of silyl enol ethers by decarboxylative coupling with redox-active esters in the absence of transition metals. Deaminative alkylation using Katritzky's N-alkylpyridinium salts and trifluoromethylation using Togni's reagent are also demonstrated. Moreover, the phosphine/iodide-based photoredox system catalyzes Minisci-type alkylation of N-heterocycles and can operate in tandem with chiral phosphoric acids to achieve high enantioselectivity in this reaction.
This study aimed to analyze the association between Attention Deficit/Hyperactivity Disorder (ADHD) and Internet addiction (IA).
A systematic literature search was performed in four online databases ...in total including CENTRAL, EMBASE, PubMed and PsychINFO. Observational studies (case-control, cross-sectional and cohort studies) measuring the correlation between IA and ADHD were screened for eligibility. Two independent reviewers screened each article according to the predetermined inclusion criteria. A total of 15 studies (2 cohort studies and 13 cross-sectional studies) met our inclusion criteria and were included in the quantitative synthesis. Meta-analysis was conducted using RevMan 5.3 software.
A moderate association between IA and ADHD was found. Individuals with IA were associated with more severe symptoms of ADHD, including the combined total symptom score, inattention score and hyperactivity/impulsivity score. Males were associated with IA, whereas there was no significant correlation between age and IA.
IA was positively associated with ADHD among adolescents and young adults. Clinicians and parents should pay more attention to the symptoms of ADHD in individuals with IA, and the monitoring of Internet use of patients suffering from ADHD is also necessary. Longitudinal studies controlling for baseline mental health are needed.
Excessive use of agro-chemicals （such as mineral fertilizers） poses potential risks to soil quality. Application of organic amendments and reduction of inorganic fertilizer are economically feasible ...and environmentally sound approaches to de- velop sustainable agriculture. This study investigated and evaluated the effects of mineral fertilizer reduction and partial substitution of organic amendment on soil fertility and heavy metal content in a 10-season continually planted vegetable field during 2009-2012. The experiment included four treatments： 100% chemical fertilizer （CF100）, 80% chemical fertilizer （CF80）, 60% chemical fertilizer and 20% organic fertilizer （CF60＋OM20）, and 40% chemical fertilizer and 40% organic fertilizer （CF40＋OM40）. Soil nutrients, enzyme activity and heavy metal content were determined. The results showed that single chemical fertilizer reduction （CF80） had no significant effect on soil organic matter content, soil catalase activity and soil heavy metal content, but slightly reduced soil available N, P, K, and soil urease activity, and significantly reduced soil acid phosphatase activity. Compared with CF100, 40 or 60% reduction of chemical fertilizer supplemented with organic fertilizer （CF60＋OM20, CF40＋OM40） significantly increased soil organic matter, soil catalase activity and urease activity especially in last several seasons, but reduced soil available P, K, and soil acid phosphatase activity. In addition, continu- ous application of organic fertilizer resulted in higher accumulation of Zn, Cd, and Cr in soil in the late stage of experiment, which may induce adverse effects on soil health and food safety.
•Oxidizing biochars at their lowered pH did not increase ammonium adsorption.•Adsorption was not fully reversible in aqueous solution.•Extraction with KCl extracts nearly all adsorbed ...ammonium.•Unrecovered ammonium was negligible at high oxidation, but increased at high pH.•Unrecovered ammonium has likely been volatilized as ammonia.
The objective of this work was to investigate the retention mechanisms of ammonium in aqueous solution by using progressively oxidized maple wood biochar at different pH values. Hydrogen peroxide was used to oxidize the biochar to pH values ranging from 8.1 to 3.7, with one set being adjusted to a pH of 7 afterwards. Oxidizing the biochars at their lowered pH did not increase their ability to adsorb ammonium. However, neutralizing the oxygen-containing surface functional groups on oxidized biochar to pH 7 increased ammonia adsorption two to three-fold for biochars originally at pH 3.7–6, but did not change adsorption of biochars oxidized to pH 7 and above. The adsorption characteristics of ammonium are well described by the Freundlich equation. Adsorption was not fully reversible in water, and less than 27% ammonium was desorbed in water in two consecutive steps than previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 2M KCl increased from 34% to 99% of ammonium undesorbed by both preceding water extractions with increasing oxidation, largely irrespective of pH adjustment. Unrecovered ammonium in all extractions and residual biochar was negligible at high oxidation, but increased to 39% of initially adsorbed amounts at high pH, likely due to low amounts adsorbed and possible ammonia volatilization losses.
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•A simple hydrothermal method facilitates one-step synthesis of high-performance amorphous ZnO/crystalline Sn3O4.•The sequential-crystallization-based adsorption inducted design ...promotes the interfacial coupling of amorphous ZnO and Sn3O4.•The hierarchical pore structure of heterojunction increases the oxygen vacancy concentration and provides more transport channels.•Removal efficiency of 0.2 g/L Cr(VI) in 100 min was as high as 59 %.
This paper is devoted to the construction of amorphous/crystalline heterojunction by a simple one-step hydrothermal method to realize the effective photocatalytic reduction of high concentration chromium. Taking amorphous ZnO/crystalline Sn3O4 (Z/S) as an example, the precursor of Sn(II) preferentially formed crystalline Sn3O4 based on the difference of complex constant (1010.8vs 104.4). The precursor of Zn(II) is then hydrolyzed and bonded to the surface of Sn3O4 by sn-O-Zn. The capping effect produced by citric acid selective adsorption on crystal surface significantly improves the proportion and stability of amorphous ZnO (aZnO). Interestingly, the introduction of aZnO transformed the surface structure of the Sn3O4 from micropore to hierarchical pore structure, which accelerated the adsorption of pollutants. The typical catalytic and characterization result illustrated that rich interfacial chemical bonds, abundant of oxygen vacancies and high interfacial potential energy difference collectively expedite the photoreduction of Cr(VI) on Z/S heterojunction. Up to 95.6 % (60 min for 0.1 g/L) and 59.1 % (100 min for 0.2 g/L) removal efficiency, importantly, proved that sequential-crystallization-based adsorption inducted design has advantages in the simple construction of high-quality amorphous heterostructures.
Abstract
The rotations of the polarization angle (PA) with time (energy) can lead to the depolarization of the time-integrated (energy-integrated) polarization. However, we do not know how and when ...it will rotate. Here, we consider a magnetic reconnection model to investigate the polarizations, especially the PA rotations of gamma-ray burst (GRB) prompt emission. For a large-scale ordered aligned magnetic field configuration, we find that within
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PAs will rotate with time (energy) for slight off-axis observations. Our studies show that the rotations of the PAs are due to changes in the observed image of the emitting region before being averaged over the equal arrival time surface for the unresolved sources. We apply our model to the single-pulse bursts of GRB 170101A and GRB 170114A with time-resolved PA observations. We find it can interpret the violent PA variation of GRB 170101A, while the model could not predict the two 90° PA changes in GRB 170114A. A more detailed model should be considered.
A meta‐analysis was performed to assess and compare the accuracies of magnetic resonance elastography (MRE) and diffusion‐weighted imaging (DWI) for the staging of hepatic fibrosis. Online journal ...databases and a manual search from January 2000 to May 2011 were used. We identified 41 studies, but only 14 met the criteria to perform a meta‐analysis assessing MRE (five trials) or DWI (10 trials). Fibrosis was categorized by redistribution into five stages according to histopathological description. A bivariate binomial model was used to combine the sensitivity and specificity and their 95% confidence intervals (CIs), from which diagnostic odds ratio (DOR), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and summary receiver operating characteristic (sROC) were derived to indicate the diagnostic accuracy of imaging modalities. With MRE, the sensitivity, specificity, DOR, PLR, NLR, and area under sROC curve (with 95% CIs) for staging F0 ∼ F1 versus F2 ∼ F4 and F0 ∼ F2 versus F3 ∼ F4 were 0.94 (0.81‐0.98), 0.95 (0.87‐0.98), 20 (7‐57), 0.06 (0.02‐0.22), 317 (55‐1,796), 0.98 (0.97‐0.99) and 0.92 (0.85‐0.96), 0.96 (0.91‐0.98), 21 (10‐45), 0.08 (0.04‐0.16), 251 (103‐609), and 0.98 (0.96‐0.99), respectively; and with DWI, these values were 0.77 (0.71‐0.82), 0.78 (0.69‐0.85), 3 (2‐5), 0.30 (0.22‐0.40), 12 (6‐21), 0.83 (0.79‐0.86) and 0.72 (0.60‐0.81), 0.84 (0.77‐0.89), 5 (3‐7), 0.34 (0.23‐0.50), 13 (6‐29), and 0.86 (0.83‐0.89), respectively. A z test demonstrated that MRE had a significantly higher accuracy than DWI in those indicators (P < 0.05). Conclusion: MRE is more reliable for staging hepatic fibrosis, compared with DWI, with a high combination of sensitivity, specificity, likelihood ratios, DOR, and area under sROC curve. (HEPATOLOGY 2012;56:239–247)
Before researchers apply nanomaterials (NMs) in biomedicine, they need to understand the blood circulation and clearance profile of these materials in vivo. These qualities determine the balance ...between nanomaterial-induced activity and unwanted toxicity. NMs have heterogeneous characteristics: they combine the bulk properties of solids with the mobility of molecules, and their highly active contact interfaces exhibit diverse functionalities. Any new and unexpected circulation features and clearance patterns are of great concern in toxicological studies and pharmaceutical screens. A number of studies have reported that NMs can enter the bloodstream directly during their application or indirectly via inhalation, ingestion, and dermal exposure. Due to the small size of NMs, the blood can then transport them throughout the circulation and to many organs where they can be stored. In this Account, we discuss the blood circulation and organ clearance patterns of NMs in the lung, liver, and kidney. The circulation of NMs in bloodstream is critical for delivery of inhalable NMs to extrapulmonary organs, the delivery of injectable NMs, the dynamics of tissue redistribution, and the overall targeting of drug carriers to specific cells and organs. The lung, liver, and kidney are the major distribution sites and target organs for NMs exposure, and the clearance patterns of NMs in these organs are critical for understanding the in vivo fate of NMs. Current studies suggest that multiple factors control the circulation and organ clearance of NMs. The size, shape, surface charge, surface functional groups, and aspect ratio of NMs as well as tissue microstructures strongly influence the circulation of NMs in bloodstream, their site-specific extravasation, and their clearance profiles within organs. Therefore structure design and surface modification can improve biocompatibility, regulate the in vivo metabolism, and reduce the toxicity of NMs. The biophysicochemical interactions occurring between NMs and between NMs and the biological milieu after the introduction of NMs into living systems may further influence the blood circulation and clearance profiles of NMs. These interactions can alter properties such as agglomeration, phase transformations, dissolution, degradation, protein adsorption, and surface reactivity. The physicochemical properties of NMs change dynamically in vivo thereby making the metabolism of NMs complex and difficult to predict. The development of in situ, real-time, and quantitative techniques, in vitro assays, and the adaptation of physiologically-based pharmacokinetic (PBPK) and quantitative structure–activity relationship (QNSAR) modeling for NMs will streamline future in vivo studies.
When planning for the evacuation guidance, how to efficiently set the trained evacuation leaders is an important problem which has great impact on the evacuation process. This paper investigates the ...effect of the number and positions of evacuation leaders on the evacuation dynamics in rooms with limited visibility range. In the improved social force model, only the trained leaders exactly know the exit positions, and the others could only follow the guidance according to the positions and directions of evacuation leaders. According to the simulation results, only one or two leaders could get remarkable effect for a single-exit configuration. But for configurations with multi-exits, evacuation leaders would make the dynamic slower unless the guidance sufficiently utilizes every exit. The results indicate that, we should set as many leaders as the number of exits in the center of the multi-exits regular squared room, and when emergencies occur, each leader heads to a different exit. Moreover, if we do like this, the evacuation would be even faster than that with 20 random-position-leaders. This work may shed some light on the drawing up of emergency scheme for large public-gathering places like stadiums and shopping malls.
•The effect of the number and positions of evacuation leaders on the evacuation dynamics with limited visibility range is investigated.•Only one or two leaders could get remarkable effect for a single-exit configuration.•For configurations with multi-exits, evacuation leaders would make the dynamic slower unless the guidance sufficiently utilizes every exit.
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