Laccases are attractive biocatalysts for industry due to their broad substrate spectrum, the use of oxygen as final electron acceptor, and water as the sole byproduct. Increasing efforts have been ...devoted to the engineering of laccases to improve their properties. The droplet-based microfluidic screening (DMFS) technology can accelerate the screening procedure and probe the large sequence space. In this study, a DMFS system including a heating step and picoinjection was used to sort large laccase libraries, yielding 12 variants with enhanced thermotolerance. All the obtained amino acid substitutions are distributed on the surface of the laccase. Interestingly, recombination of three identified substitutions of Asp to Asn on the surface resulted in the best variant M20, exhibiting 24.0-fold higher remaining activity at 58.8 °C and 1.9–3.4-fold higher remaining activity after incubation in organic solvents solution (20% (v/v) methanol and ethanol) and ionic liquid solution (20% (v/v) 1-ethyl-3-methylimidazolium ethyl sulfate) for 12 h. Furthermore, molecular dynamic simulations revealed that the recombination of the three beneficial substitutions, Asp98Asn, Asp474Asn, and Asp340Asn on the surface introduced more hydrogen bonds compared to the wild type, which made M20 more thermostable. This study highlighted the importance of the DMFS system for an efficient identification of beneficial long-distance amino acid substitutions.
This paper introduces a novel multi‐variate volatility model that can accommodate appropriately defined network structures based on low‐frequency and high‐frequency data. The model offers substantial ...reductions in the number of unknown parameters and computational complexity. The model formulation, along with iterative multi‐step‐ahead forecasting and targeting parameterization are discussed. Quasi‐likelihood functions for parameter estimation are proposed and their asymptotic properties are established. A series of simulation studies are carried out to assess the performance of parameter estimation in finite samples. Furthermore, a real data analysis demonstrates that the proposed model outperforms the existing volatility models in prediction of future variances of daily return and realized measures.
The ensemble mean quantitative precipitation forecasts (QPFs) and probabilistic QPFs (PQPFs) from six operational global ensemble prediction systems (EPSs) in The Observing System Research and ...Predictability Experiment Interactive Grand Global Ensemble (TIGGE) data set are evaluated against the Tropical Rainfall Measuring Mission observations using a series of area‐weighted verification metrics during June to August 2008–2012 in the Northern Hemisphere (NH) midlatitude and tropics. Results indicate that generally the European Centre for Medium‐Range Weather Forecasts performs best while the Canadian Meteorological Centre (CMC) is relatively good for short‐range QPFs and PQPFs at light precipitation thresholds. The overall forecast skill is better in the NH midlatitude than in the NH tropics. QPFs and PQPFs from China Meteorological Administration (CMA) have very little discrimination ability of different observed rain events in the NH tropics. The day +1 QPFs from Japan Meteorological Agency have remarkably large moist biases in the NH tropics, which leads to the discontinuity of forecast performance with the lead times. Performance changes due to the major EPS upgrades during the five summers are also examined using the forecasts from CMA as the reference to eliminate the interannual variation. After the EPS upgrade, CMC improves the PQPF skill at light precipitation threshold while its excessively enlarged ensemble spread increases the overall QPF and PQPF errors.
Key Points
The model upgrade in EPS cannot always guarantee forecast skill improvements
The enlarged ensemble spread of CMC after the upgrade increases the QPF errors
The day +1 QPFs from JMA have unusually large moist biases in the NH tropics
Abstract
Short-range quantitative precipitation forecasts (QPFs) and probabilistic QPFs (PQPFs) are investigated for a time-lagged multimodel ensemble forecast system. One of the advantages of such ...an ensemble forecast system is its low-cost generation of ensemble members. In conjunction with a frequently cycling data assimilation system using a diabatic initialization such as the Local Analysis and Prediction System (LAPS), the time-lagged multimodel ensemble system offers a particularly appealing approach for QPF and PQPF applications. Using the NCEP stage IV precipitation analyses for verification, 6-h QPFs and PQPFs from this system are assessed during the period of March–May 2005 over the west-central United States. The ensemble system was initialized by hourly LAPS runs at a horizontal resolution of 12 km using two mesoscale models, including the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) and the Weather Research and Forecast (WRF) model with the Advanced Research WRF (ARW) dynamic core. The 6-h PQPFs from this system provide better performance than the NCEP operational North American Mesoscale (NAM) deterministic runs at 12-km resolution, even though individual members of the MM5 or WRF models perform comparatively worse than the NAM forecasts at higher thresholds and longer lead times. Recalibration was conducted to reduce the intensity errors in time-lagged members. In spite of large biases and spatial displacement errors in the MM5 and WRF forecasts, statistical verification of QPFs and PQPFs shows more skill at longer lead times by adding more members from earlier initialized forecast cycles. Combing the two models only reduced the forecast biases. The results suggest that further studies on time-lagged multimodel ensembles for operational forecasts are needed.
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•Understanding of adsorption sites plays an important role in improving the adsorption capacity of iodine.•The iodine uptake capacity is proportionate to hydroxyfunctional groups and ...graphitic nitrogen as adsorption sites.•Oxygen-doped carbon nanotubes act as potential carbon materials for adsorption of iodine.
The effective capture and storage of radioactive iodine is of great significance to the safe use of nuclear energy. In this study, nitrogen- and oxygen-doped carbon nanotubes acted as effective iodine capture agents in a low concentration of iodine solution of approximately 100 mg L−1. The iodine uptake capacity is proportionate to hydroxy-functional groups as oxygen species and graphitic nitrogen as nitrogen species, respectively, rather than defects and the specific surface area of carbon nanotubes. The essential adsorption activity of oxygen-doped carbon nanotubes is more than 2.5 times that of nitrogen-doped carbon nanotubes, indicating oxygen-doped carbon nanotubes as a potential carbon material in practical applications for the adsorption of iodine. Theoretical study further deepened the understanding of the iodine adsorption sites on carbon nanotubes. This work provided a new method for the design and synthesis of high-performance radioactive iodine solid adsorbents in the future.
Low-cost and high-efficient broadband near-infrared (NIR) phosphor converted light-emitting diodes (pc-LEDs) are desirable for the compact NIR spectrum system. In this work, a broadband NIR emission ...with a large full width at half maximum (FWHM) up to ∼160 nm is achieved in double perovskite NaLaMgWO6 phosphor via the non-equivalent substitution of Cr3+. The crystal structure analysis and first-principle calculation have revealed that Cr3+ prefers to substitute Mg2+. In order to keep charge balance, the random-distributed Na+ vacancies are formed. This behavior has constructed two different crystallographic sites for Cr3+ substitution and their effect on the NIR luminescence performances of NaLaMgWO6:Cr3+ is investigated in detail. Within the weak crystal field, the zero phonon line and broadband emissions ascribed to 4T2 → 4A2 transition are present simultaneously, which ensure the large FWHM acquired in NaLaMgWO6:Cr3+. The broadband NIR pc-LED prototype fabricated with the as-prepared phosphor and blue LED chip is achieved, which demonstrates that the NaLaMgWO6:Cr3+ is a new candidate for the broadband NIR phosphor applied in the miniaturized optical devices.
•A broadband NIR luminescence of Cr3+ doped NaLaMgWO6 were obtained at room temperature.•The luminescence behavior of NaLaMgWO6:Cr3+ related to non-equivalent substitution of Cr3+ has been discussed.•The prepared phosphor provides a new candidate in the broadband NIR pc-LEDs application.
•A NIR emission at 890 nm with 200 nm FWHM is realized in Ba2ScNbO6:Cr3+ phosphor.•The modulation of the host bandgap by turning composition enhances the NIR emission.•The structure-property ...relationship provides insights for new broadband NIR phosphors.
To fulfill the near-infrared (NIR) spectroscopy application in portable and appropriately sized equipment, it is necessary to develop novel NIR pc-LEDs that are fabricated from high-efficiency broadband NIR phosphors. Herein, a series of Cr3+ doped double perovskite type A2ScNbO6:Cr3+ (A = Ba, Sr) phosphors with an emission peaked around 890 nm and full width at half-maximum greater than 200 nm are developed. By replacing Ba with Sr in the host composition, the NIR emission intensity under near ultraviolet (NUV) excitation is significantly enhanced without narrowing the emission bandwidth. The underlying mechanism is investigated in detail by structural analysis, spectral analysis and density functional theory calculations, revealing a strong correlation with the introduction of Sr in terms of changes in the host bandgap and electron-phonon coupling effects. The compositional modulation strategy has unveiled the structure-property relationship in Cr3+ doped double perovskite, shedding new light on guiding the development of broadband NIR phosphors.
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Recently, the droplet microfluidic system attracts interests due to its high throughput and low cost to detect and screen. The picoliter micro-droplets from droplet microfluidics are uniform with ...respect to the size and shape, and could be used as monodispensed micro-reactors for encapsulation and detection of single cell or its metabolites. Therefore, it is indispensable to characterize micro-droplet and its application from droplet microfluidic system. We first constructed the custom-designed droplet microfluidic system for generating micro-droplets, and then used the micro-droplets to encapsulate important amino acids such as glutamic acid, phenylalanine, tryptophan or tyrosine to test the droplets' properties, including the stability, diffusivity and bio-compatibility for investigating its application for amino acid detection and sorting. The custom-designed droplet microfluidic system could generate the uniformed micro-droplets with a controllable size between 20 to 50 microm. The micro-droplets could be
A new volatility model: GQARCH‐ItÔ model Yuan, Huiling; Sun, Yulei; Xu, Lu ...
Journal of time series analysis,
20/May , Letnik:
43, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Volatility asymmetry is a hot topic in high‐frequency financial market. This article proposes a new econometric model, which could describe volatility asymmetry based on high‐frequency data and ...low‐frequency data. After providing the quasi‐maximum likelihood estimators for the parameters, we establish their asymptotic properties. We also conduct a series of simulation studies to check the finite sample performance and volatility forecasting performance of the proposed model and method. And a real data example is demonstrated that the new model has more substantial volatility prediction power than GARCH‐Itô model in the literature.
The evolutions of Mei-yu frontal storms during the Mei-yu season in 2018 were simulated in the Weather Research and Forecasting with Chemistry (WRF/Chem) model to investigate the effects of aerosols ...on the prediction of clouds and precipitation. Two groups of daily launched forecast experiments were conducted with a duration of 17 days, by turning the chemistry–aerosol module on (WRF/Chem) and off (WRF), and additional cloud droplet number concentration (Nd) experiments were perturbed in WRF. Comparison between the two groups of experiments suggested that activating the chemistry–aerosol module improved the forecast skill for precipitation exceeding 5 mm/h during the Mei-yu season, while had no positive forecast skill on precipitation exceeding 0.1 mm/h in terms of both traditional and neighborhood spatial verifications. In contrast to the uniform Nd distribution adopted in WRF, the inhomogeneous Nd distribution in WRF/Chem agreed better with in-situ aircraft observations collected during the field campaign. As Nd increases in WRF experiments, the warm clouds decreased and deep convective clouds significantly increased with more convective updraft mass flux and net heat budget. Scavenging in Mei-yu frontal storms generally reduced the median Nd in the WRF/Chem experiment. The fewer and larger cloud particles in WRF/Chem promoted the conversion of cloud to rain and the accretion of cloud by rain, thereby leading to invigoration of warm clouds and precipitation efficiency, which explains the improved forecast skill for precipitation exceeding 5 mm/h. Enhanced warm-rain processes caused fewer cloud particles for further ascent and ultimately resulted in suppression of deep convective clouds. The preliminary findings in this study highlights the potential significance of incorporating chemistry–aerosol schemes in the operational forecasting of Mei-yu rainfall.
•The inhomogeneous Nd distribution in WRF/Chem agreed better with in-situ aircraft observations.•WRF/Chem improved the forecast skill for precipitation exceeding 5 mm/h during the Mei-yu season.•Scavenging reduced the median Nd in WRF/Chem, leading to invigoration of warm clouds and precipitation efficiency.
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