Intraguild predation (IGP), i.e. feeding interaction between two consumers that share the same resource species, is commonly observed in natural food webs. IGP expands vertical niche space and slows down energy flows from lower to higher trophic levels, which potentially affects the diversity and dynamics of food webs. Here, we use food web models to investigate the effects of IGP on species diversity and ecosystem functioning. We first simulate a five‐species food web module with different strengths of IGP at the herbivore and/or carnivore level. Results show that as the strength of IGP within a trophic level increases, the biomass of its resource level increases because of predation release; this increased biomass in turn alters the energy fluxes and biomass of other trophic levels. These results are then extended by subsequent simulations of more diverse food webs. As the strength of IGP increases, simulated food webs maintain (1) higher species diversity at different trophic levels, (2) higher total biomasses at different trophic levels, and (3) larger energy fluxes across trophic levels. Our results challenge the intuitive hypothesis that food web structure should maximize the efficiency of energy transfer across trophic levels; instead, they suggest that the assembly of food webs should be governed by a balance between efficiency (of energy transfer) and persistence (i.e. the maintenance of species and biomasses). Our simulations also show that the relationship between biodiversity and ecosystem functioning (e.g. total biomass or primary production) is much stronger in the presence of IGP, reconciling the contrast from recent studies based on food‐chain and food‐web models. Our findings shed new light on the functional role of IGP and contribute to resolving the debate on structure, diversity and functioning in complex food webs. This article is protected by copyright. All rights reserved.
The North China Plain and the Yangtze River Delta are the two of the most heavily polluted regions in China. Observational studies revealed that 'explosive' PM2.5 mass concentration growths frequently occurred in the two regions. This study analyzed all the PM2.5 mass concentration growth processes from clean condition (i.e., <35 mu g m(-3)) to heavy pollution condition (i.e., >150 mu g m(-3)) in Beijing (BJ) and Shanghai (SH), two representative cities of the two regions, using hourly monitored PM2.5 concentrations during 2013-2016. 173 and 76 growth processes were identified in BJ and SH, respectively. PM2.5 rising rates (PMRR) and dynamic growth durations were calculated to illustrate the characteristics of the growth processes. Hourly particulate chemical composition data and meteorological data in BJ and SH were further analyzed. The 4-year averaged PMRR of PM2.5 total mass were similarly of 7.11 +/- 9.82 mu g m(-3) h(-1) in BJ and 6.71 +/- 6.89 mu g m(-3) h(-1) in SH. A decreasing trend was found for the PM2.5 growth processes in two cities from 2013 to 2016, reflecting the effectiveness of emission controls implemented in the past years. The contributions of particulate components to the PM2.5 total mass growth were different in BJ and SH. Average PMRR value of PM1 organic aerosols (OA), SO24-, NO3-, and NH4+ in BJ was 1.90, 0.95, 0.82, and 0.53 mu g m(-3) h(-1), respectively. Average PMRR of PM2.5 OA, SO42-, NO3-, and NH4+ in SH was 1.70, 1.18, 1.99 and 1.14 mu g m(-3) h(-1), respectively. Based on the contributions of different components, the PM2.5 mass concentration growth processes in BJ and SH were proposed to be classified into 'other components-dominant growth processes', 'all components-contributing growth processes', 'one or more explosive secondary components-dominant growth processes', and 'mixed-factor growth processes'. Potential source contribution function analysis and the meteorological condition analysis showed that source origins and prevailing wind for the two cities during different categories of growth processes had substantial difference. The important source areas included Hebei and Shandong for BJ, and Jiangsu and Anhui for SH. The dominant wind directions during growth processes were northeast, south and southwest in BJ, and were west to north in SH. The results suggested the contributing components, the prevailing wind conditions, and the formation processes were substantially different in the two cities, despite the similar PMRR of PM2.5 total mass during the growth processes between BJ and SH. Future research is needed to study the detailed formation mechanisms of the different PM2.5 mass concentration growth processes in the two cities. (C) 2019 Elsevier Ltd. All rights reserved.
As to gyrotron oscillators, operation at high harmonics is an effective solution to decrease the required magnetic field strengths and improve radiation frequencies towards the terahertz (THz) band. Unfortunately, significant challenges related to a harmonic gyrotron include weak interaction strengths and serious mode competition conditions. In this paper, we report on the excitation strategy and stable-state property of a THz second-harmonic (SH) gyro-BWO with the TE24,3 mode. Such an extremely high-order mode interaction system is inherently capable of providing high power capacity and advanced mode selectivity. A competition-free parameter space is created by increasing the Doppler sensitivity of one fundamental-harmonic (FH) competing mode at low magnetic fields and simultaneously suppressing the Q factor of another FH competing mode in the near-cutoff region at high magnetic fields. The SH quasi-whispering-gallery mode can be stimulated with a medium output power at around 0.5 THz during the FH mode switching process. This work contributes to further exploiting high frequency steps in the high-order multi-mode frequency-tuning gyro-BWO.
A novel gate and passivation dielectric stack consisting of a thin metal-organic chemical vapor deposition (MOCVD) grown in-situ Si3N4 (3 nm) and a thick low-pressure chemical vapor deposition (LPCVD) grown Si3N4 (30 nm) in AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) is proposed. The quality of the Si3N4/(Al) GaN interface and the effect on threshold voltage (V-TH) instability and dynamic R-ON in the MIS-HEMTs with/without the in-situ Si3N4 layer are investigated by high-frequency capacitance-voltage (HFCV), quasi-static (QS) C-V (QSCV), time-offly (TOF) stress/measure, and QS I-D-V-DS methods. It is founded that the in-situ Si3N4 interfacial layer is effective in improving the dielectric/III-N interface morphology. As a result, better V-TH stability and lower R-ON, D/R-ON,R-S ratio are observed in devices with the in-situ Si3N4 interfacial layer due to the reduced density of traps close to the dielectric/III-N interface. Time-dependent dielectric breakdown and Weibull performance further verified that the proposed bilayer gate dielectric stack is a promising structure for the high-reliability power transistors.
Seawater reverse osmosis (SWRO) is a commonly used desalination technique owing to its lesser environmental and economic impacts as compared to thermal desalination techniques. Antiscalants are used in SWRO to reduce membrane scaling caused by the supersaturation of salts present in feed water. However, to remain effective in reducing membrane scaling, antiscalants should be highly stable and resistant to biological degradation by seawater microorganisms. In this research, several bacteria from Qatar's seawater were isolated and screened for their ability to use antiscalants as a carbon and energy source. The biodiversity of antiscalant degrading seawater bacteria was demonstrated through combining the techniques of MALDI-TOF MS and principle component analysis. It was found that the bacteria isolated from Qatar's seawater such as H. aquamarina, H. elongata, P. fragi, P. stutzeri and others can degrade antiscalants and use them as a carbon and energy source. It was observed that the growth rates varied based on the type of antiscalant and the bacteria used. Among the tested strains, H. aquamarina, which is also known for its potential to cause biofouling, demonstrated the highest growth rates in antiscalants media. Thus, it was concluded that there is wide variety of bacteria in Qatar's seawater that can biodegrade the antiscalants; reducing their efficiency to combat membrane scaling. Since, these antiscalants will be used as a source of carbon and energy, microbial growth will increase resulting in enhanced membrane biofouling in SWRO.
Adsorption kinetics and conformational changes of a model protein, bovine serum albumin (BSA, 0.1, 0.5, or 1.0 g/L), on the surface of hematite (α-Fe2O3) particles in 39 ± 9, 68 ± 9, and 103 ± 8 nm, respectively, were measured using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. As the particle size increases, the amount of adsorbed BSA decreases, but the loss in the helical structure of adsorbed BSA increases due to the stronger interaction forces between adsorbed BSA and the larger particles. On 39 or 68 nm hematite particles, refolding of adsorbed BSA can be induced by protein–protein interactions, when the protein surface coverage exceeds certain critical values. Two-dimensional correlation spectroscopy (2D-COS) analysis of time-dependent ATR-FTIR spectra indicate that the increase in the amount of adsorbed BSA occurs prior to the loss in the BSA helical structure in the initial stage of adsorption processes, whereas an opposite sequence of the changes to BSA conformation and surface coverage is observed during the subsequent refolding processes. Desorption experiments show that replacing the protein solution with water can quench the refolding, but not the unfolding, of adsorbed BSA. A kinetic model was proposed to quantitatively describe the interplay of adsorption kinetics and conformational change, as well as the effects of particle size and initial protein concentration on the rate constants of elementary steps in protein adsorption onto a mineral surface.
Stretchable and movable 3D structure is a great choice for sensing stretching and bending. This paper reports a novel cross-shaped 3D buckling strain sensor based on polydimethylsiloxane (PDMS) substrate for detecting stretching and bending. Using pre-stretched PDMS, cross-shaped Polyimide (PI) film with conductive silver paint on its top surface as a 2D precursor can pop up as a dynamic 3D structure and possesses capacitive effect and triboelectric effect under different stretching and bending, which can detect stretching directions, strain value, bending axis direction and radius of curvature simultaneously, showing great potential in human and robot applications.
The oil sands industry in Alberta, Canada, represents a large anthropogenic source of secondary organic aerosol (SOA). Atmospheric emissions from oil sands operations are a complex mixture of gaseous and particulate pollutants. Their interaction can affect the formation and characteristics of SOA during plume dispersion, but their chemical evolution remains poorly understood. Oxidative processing of organic vapours in the presence of NOx can lead to particulate organo-nitrate (pON) formation, with important impacts on the SOA budgets, the nitrogen cycle and human health. We provide the first direct field evidence, from ground- and aircraft-based real-time aerosol mass spectrometry, that anthropogenic pON contributed up to half of SOA mass that was freshly produced within the emission plumes of oil sands facilities. Using a top-down emission-rate retrieval algorithm constrained by aircraft measurements, we estimate the production rate of pON in the oil sands region to be similar to 15.5 t d(-1). We demonstrate that pON formation occurs via photo-oxidation of intermediate-volatility organic compounds (IVOCs) in high-NOx environments, providing observational constraints to improve current SOA modelling frameworks. Our ambient observations are supported by laboratory photo-oxidation experiments of IVOCs from bitumen vapours under high-NOx conditions, which demonstrate that pON can account for 30 %-55 % of the observed SOA mass depending on the degree of photochemical ageing. The large contribution of pON to freshly formed anthropogenic SOA illustrates the central role of pON in SOA production from the oil and gas industry, with relevance for other urban and industrial regions with significant anthropogenic IVOC and NOx emissions.
Wearable sweat sensors have the potential to provide continuous measurements of useful biomarkers. However, current sensors cannot accurately detect low analyte concentrations, lack multimodal sensing or are difficult to fabricate at large scale. We report an entirely laser-engraved sensor for simultaneous sweat sampling, chemical sensing and vital-sign monitoring. We demonstrate continuous detection of temperature, respiration rate and low concentrations of uric acid and tyrosine, analytes associated with diseases such as gout and metabolic disorders. We test the performance of the device in both physically trained and untrained subjects under exercise and after a protein-rich diet. We also evaluate its utility for gout monitoring in patients and healthy controls through a purine-rich meal challenge. Levels of uric acid in sweat were higher in patients with gout than in healthy individuals, and a similar trend was observed in serum.
Concerns regarding microplastic contamination have spread from aquatic environments to terrestrial systems with a growing number of studies have been reported. Notwithstanding, the potential effects on soil ecosystems remain largely unexplored. In this study, the effects of polyethylene microplastics on soil enzymatic activities and the bacterial community were evaluated, and the microbiota colonizing on microplastics were also investigated. Microplastic amendment (2000 fragments per kg soil) significantly increased the urease and catalase activities in soil after 15 days, and no discernible alteration of invertase activities was detected. Results from high-throughput sequencing of 16S rRNA revealed that the alpha diversities (richness, evenness, and diversity) of the microbiota in soil were not obviously changed by the PE amendment, whereas the diversity indexes of microbiota on plastic fragments were significantly lower than those in the control and amended soils. Different taxonomic composition was observed in between the control and amended soils after 90 days of incubation. Bacterial assemblages with distinct community structure colonized the PE microplastics. Additionally, several taxa including plastic- degrading bacteria and pathogens were more abundant on microplastics. Simultaneously, the pre- dicted functional profiles showed that the pathways of amino acid metabolism and xenobiotics biodegradation and metabolism were higher on the microplastics. These results indicated that micro- plastics in soil, compared with those in aquatic environments, can also act as a distinct microbial habitat, potentially altering the ecological functions of soil ecosystems.&nbsp;
In low-pressure-turbines (LPT) around 60-70% of losses are generated away from end-walls, while the remaining 30-40% is controlled by the interaction of the blade profile with the endwall boundary layer. Experimental and numerical studies have shown how the strength and penetration of the secondary flow depends on the characteristics of the incoming end-wall boundary layer. This paper discusses the endwall flow characteristics of the T106 LPT profile at Re=120K and M=0.59 by benchmarking with experiments and investigating the impact of the incoming boundary layer state. The simulations are carried out with proven Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) solvers to determine if Reynolds Averaged models can capture the relevant flow details with enough accuracy to drive the design of this flow region. Part I of the paper focuses on the critical grid needs to ensure accurate LES, and on the analysis of the overall time averaged flow field and comparison between RANS, LES, and measurements when available. In particular, the growth of secondary flow features, the trace and strength of the secondary vortex system, its impact on the blade load variation along the span and end-wall flow visualizations are analyzed. The ability of LES and RANS to accurately predict the secondary flows is discussed together with the implications this has on design.
