•Novel pin fin-interconnected reentrant microchannels (PFIRM) were developed.•Operational characteristics of PFIRM in flow boiling were systematically explored using two coolants.•Effects of heat ...flux, mass flux, inlet subcooling and coolants on flow boiling performance of PFIRM were assessed.•PFIRM facilitated to provide ideal spaces for the bubble nucleation and movement and suppress bubble confinement effect.
Pin fin-interconnected reentrant microchannels (PFIRM) are proposed and developed for microchannel heat sinks cooling systems to combine both merits of reentrant cavities and micro pin fins in heat transfer enhancement. They feature two directions of reentrant microchannels with a intersection angle of 30° in the downside, and staggered arrays of micro diamond pin fins on the upper side. Micro-milling process is utilized to process the interconnected reentrant microchannels, which simultaneously induces the formation of micro diamond pin fins. Flow boiling experiments are conducted using two coolants (deionized water and ethanol) at inlet subcoolings of 40 °C and 10 °C, mass fluxes of 125–300 kg/(m2 s). Flow boiling heat transfer, pressure drop and two-phase flow instabilities of the PFIRM are systematically assessed. It is found that the PFIRM showed a 39–284% enhancement in two-phase heat transfer in water tests, and a 29–220% in ethanol tests compared to the parallel reentrant microchannels. Decrease of bubble confinement effect by the interconnected microchannels and ideal spaces for the bubble nucleation and movement supplied by the reentrant chambers contributed to the above boiling heat transfer enhancement of PFIRM. The PFIRM heat sink operated more efficiently using the coolant of water than ethanol.
Display omitted
•Dosing reducing agents resulted in enhanced pollutant degradation and expansion of pH range.•Dosing manner of RA was a key factor governing its roles in Fenton system.•Catalytic ...mechanisms of the three reducing agents in Fenton system were proposed.•Electrical energy per order was used to estimate the costs of three reducing agents.
Fenton reaction is widely used for hazardous pollutant degradation. Reducing agents (RAs) have been proven to be efficient in promoting the generation of HO• in Fenton reaction by accelerating the redox cycle of Fe3+/Fe2+. However, the roles of different RAs in Fenton reaction remain unrevealed. In this work, the catalytic activity of three RAs, i.e., hydroxylamine (NH2OH), ascorbic acid (AA) and cysteine (Cys), on the degradation of benzoic acid (BA) and the hydroxyl radical formation in the Fenton-RAs system were investigated. Results show the catalytic performance of RAs in BA degradation by Fenton reaction followed an order of NH2OH > AA > Cys. Compared with the conventional Fenton system, the effective pH range in the Fenton-NH2OH system extended from 3.0 to 5.0, while the optimal pH in the Fenton-AA and Fenton-Cys systems ranged from 3.0 to 4.0. The Fenton-AA system exhibited a two-stage reaction toward BA degradation, which was different from the Fenton-NH2OH and Fenton-Cys systems. Furthermore, the dosing manner of AA was found to be a key factor governing its role in the Fenton-AA system. This observation suggests the different mechanisms behind the enhancement of the three RAs in Fenton system. Different from NH2OH and Cys, AA would inhibit the generation of HO•, especially at the fast stage of degradation process, where Fe3+ has not accumulated yet. In addition, the economic analysis using the electrical energy per order indicates Fenton-NH2OH system was economically feasible with the lowest energy input, compared to Fenton-AA and Fenton-Cys systems. These results are useful to better understand the roles of RAs in Fenton system, and also provide guidance about the selection and dosing manner of suitable RAs in the advanced oxidation processes.
Abstract
An incremental analysis update (IAU) scheme is successfully implemented into a WRF/WRFDA-based hourly cycling data assimilation system with the goal to reduce the imbalance introduced by the ...high-frequency intermittent data assimilation, especially when radar data are included. With the application of IAU, the analysis increment is smoothly introduced into the model integration over a time window centered at the analysis time. As in digital filter initialization (DFI), the IAU scheme is able to limit large shocks in the early part of a model forecast. Compared to DFI, IAU does better in hydrometeor spinup and produces more continuous precipitation forecasts from cycle to cycle. The run with IAU is shown to improve the precipitation forecast skills (10+% for CSI scores) compared to the regular cycling forecasts without IAU. The data assimilation system with IAU is also able to accept more observations due to balanced first-guess fields. Comparable results are obtained in IAU tests when the time-varying weights are used versus constant weights. Because of its better property, the IAU with the time-varying weights is implemented in the operational system.
Long non-coding RNA (lncRNA) HOXD cluster antisense RNA 1 (HOXD-AS1) functions as a crucial regulator in the progression and development of tumors. The aim of this study is to unravel the underlying ...mechanisms of HOXD-AS1 on epithelial ovarian cancer (EOC).
43 paired EOC tissues and adjacent non-tumor tissues were collected postoperatively from patients. QRT-PCR was used to explore HOXD-AS1 expression in both EOC tissues and cell lines. Cell proliferation and invasion were monitored by MTT assay and transwell invasion assay.
In the current study, we found that the expression of HOXD-AS1 was upregulated in EOC tissues and cell lines. High HOXD-AS1 expression was correlated with advanced FIGO stage, lymph node metastasis, and poor overall survival in EOC patients. We also showed that HOXD-AS1 promoted cell proliferation, invasion, and epithelial-mesenchymal transition (EMT) via activating Wnt/β-catenin signaling in EOC cells. Furthermore, we found that miR-133a-3p was a direct downstream target of HOXD-AS1 in EOC. HOXD-AS1 promoted cell proliferation, invasion, and EMT process through sponging miR-133a-3p in EOC cells.
Our study indicated that lncRNA HOXD-AS1 promoted the proliferation, invasion, and EMT process of EOC cells via targeting miR-133a-3p and activating Wnt/β-catenin signaling pathway.
An indirect radar reflectivity assimilation scheme has been developed within the Weather Research and Forecasting model three-dimensional data assimilation system (WRF 3D-Var). This scheme, instead ...of assimilating radar reflectivity directly, assimilates retrieved rainwater and estimated in-cloud water vapor. An analysis is provided to show that the assimilation of the retrieved rainwater avoids the linearization error of theZ–qr
(reflectivity–rainwater) equation. A new observation operator is introduced to assimilate the estimated in-cloud water vapor. The performance of the scheme is demonstrated by assimilating reflectivity observations into the Rapid Update Cycle data assimilation and forecast system operating at Beijing Meteorology Bureau. Four heavy-rain-producing convective cases that occurred during summer 2009 in Beijing, China, are studied using the newly developed system. Results show that on average the assimilation of reflectivity significantly improves the short-term precipitation forecast skill up to 7 h. A diagnosis of the analysis fields of one case shows that the assimilation of reflectivity increases humidity, rainwater, and convective available potential energy in the convective region. As a result, the analysis successfully promotes the developments of the convective system and thus improves the subsequent prediction of the location and intensity of precipitation for this case.
Abstract
The diurnal cycle is the most prominent mode of rainfall variability in the tropics, governed mainly by the strong solar heating and land–sea interactions that trigger convection. Over the ...western Maritime Continent, complex orographic and coastal effects can also play an important role. Weather and climate models often struggle to represent these physical processes, resulting in substantial model biases in simulations over the region. For numerical weather prediction, these biases manifest themselves in the initial conditions, leading to phase and amplitude errors in the diurnal cycle of precipitation. Using a tropical convective-scale data assimilation system, we assimilate 3-hourly radiosonde data from the pilot field campaign of the Years of Maritime Continent, in addition to existing available observations, to diagnose the model biases and assess the relative impacts of the additional wind, temperature, and moisture information on the simulated diurnal cycle of precipitation over the western coast of Sumatra. We show how assimilating such high-frequency in situ observations can improve the simulated diurnal cycle, verified against satellite-derived precipitation, radar-derived precipitation, and rain gauge data. The improvements are due to a better representation of the sea breeze and increased available moisture in the lowest 4 km prior to peak convection. Assimilating wind information alone was sufficient to improve the simulations. We also highlight how during the assimilation, certain multivariate background error constraints and moisture addition in an ad hoc manner can negatively impact the simulations. Other approaches should be explored to better exploit information from such high-frequency observations over this region.
We present Mg and Fe isotopic data for whole rocks and separated minerals (olivine, clinopyroxene, orthopyroxene, garnet, and phlogopite) of garnet peridotites that equilibrated at depths of ...134–186km beneath the Kaapvaal and Siberian cratons. There is no clear difference in δ26Mg and δ56Fe of garnet peridotites from these two cratons. δ26Mg of whole rocks varies from −0.243‰ to −0.204‰ with an average of −0.225±0.037‰ (2σ, n=19), and δ56Fe from −0.038‰ to 0.060‰ with an average of −0.003±0.068‰ (2σ, n=19). Both values are indistinguishable from the fertile upper mantle, indicating that there is no significant Mg-Fe isotopic difference between the shallow and deep upper mantle. The garnet peridotites from ancient cratons show δ26Mg similar to komatiites and basalts, further suggesting that there is no obvious Mg isotopic fractionation during different degrees of partial melting of deep mantle peridotites and komatiite formation.
The precision of the Mg and Fe isotope data (⩽±0.05‰ for δ26Mg and δ56Fe, 2σ) allows us to distinguish inter-mineral isotopic fractionations. Olivines are in equilibrium with opx in terms of Mg and Fe isotopes. Garnets have the lowest δ26Mg and δ56Fe among the coexisting mantle minerals, suggesting the dominant control of crystal structure on the Mg-Fe isotopic compositions of garnets. Elemental compositions and mineralogy suggest that clinopyroxene and garnet were produced by later metasomatic processes as they are not in chemical equilibrium with olivine or orthopyroxene. This is consistent with the isotopic disequilibrium of Mg and Fe isotopes between orthopyroxene/olivine and garnet/clinopyroxene. Combined with one sample showing slightly heavy δ26Mg and much lighter δ56Fe, these disequilibrium features in the garnet peridotites reveal kinetic isotopic fractionation due to Fe-Mg inter-diffusion during reaction between peridotites and percolating melts in the Kaapvaal craton.
SINGV: A convective‐scale weather forecast model for Singapore Dipankar, Anurag; Webster, Stuart; Sun, Xiangming ...
Quarterly journal of the Royal Meteorological Society,
October 2020 Part B, 2020-10-00, 20201001, Letnik:
146, Številka:
733
Journal Article
Recenzirano
Odprti dostop
Numerical weather prediction (NWP) capabilities in the Maritime Continent are not as developed as in the midlatitudes. Countries in the region do not develop their own modelling systems; rather they ...adapt models primarily developed for the midlatitudes. Due to the complexity of processes involved in the region, this adaptation is non‐trivial. In this article the developments made by the Meteorological Service Singapore (MSS) and the United Kingdom Met Office (UKMO) to implement a convective‐scale NWP system for short‐range weather prediction for Singapore and the surrounding regions are presented. In particular, this article describes the changes to the initial model configuration, which was based on the UKMO's convective‐scale NWP system (the UKV), to produce operational forecasts over this region. Results presented here demonstrate the benefit of convection‐permitting simulations over convection parametrized simulations and show that the model performance is greatly affected by the choice of driving model, the cloud scheme, and the turbulence scheme.
Numerical weather prediction (NWP) over the Maritime Continent is challenging due to complex interaction of convection with the large‐scale circulations, which are strongly affected by the land–sea breeze circulations in the region. Convection‐permitting NWP model UKV from the UK Met Office has been proven to improve forecasts over the United Kingdom and other locations. In this article, we present details of the NWP model used by the Meteorological Service Singapore, SINGV, which is adapted and subsequently modified from UKV.
The observational association between gut microbiome and systemic lupus erythematosus (SLE) has been well documented. However, whether the association is causal remains unclear. The present study ...used publicly available genome-wide association study (GWAS) summary data to perform two-sample Mendelian randomization (MR), aiming to examine the causal links between gut microbiome and SLE. Two sets of MR analyses were conducted. A group of single nucleotide polymorphisms (SNPs) that less than the genome-wide statistical significance threshold (5 × 10
-8
) served as instrumental variables. To obtain a comprehensive conclusion, the other group where SNPs were smaller than the locus-wide significance level (1 × 10
-5
) were selected as instrumental variables. Based on the locus-wide significance level, the results indicated that there were causal effects of gut microbiome components on SLE risk. The inverse variance weighted (IVW) method suggested that
Bacilli
and
Lactobacillales
were positively correlated with the risk of SLE and
Bacillales
,
Coprobacter
and
Lachnospira
were negatively correlated with SLE risk. The results of weighted median method supported that
Bacilli
,
Lactobacillales
, and
Eggerthella
were risk factors for SLE and
Bacillales
and
Coprobacter
served as protective factors for SLE. The estimates of MR Egger suggested that genetically predicted
Ruminiclostridium6
was negatively associated with SLE. Based on the genome-wide statistical significance threshold, the results showed that
Actinobacteria
might reduce the SLE risk. However, Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) detected significant horizontal pleiotropy between the instrumental variables of
Ruminiclostridium6
and outcome. This study support that there are beneficial or detrimental causal effects of gut microbiome components on SLE risk.
The electrochemical oxygen reduction reaction in acidic media offers an attractive route for direct hydrogen peroxide (H2O2) generation and on-site applications. Unfortunately there is still a lack ...of cost-effective electrocatalysts with high catalytic performance. Here, we theoretically designed and experimentally demonstrated that a cobalt single-atom catalyst (Co SAC) anchored in nitrogen-doped graphene, with optimized adsorption energy of the *OOH intermediate, exhibited a high H2O2 production rate, which even slightly outperformed the state-of-the-art noble-metal-based electrocatalysts. The kinetic current of H2O2 production over Co SAC could reach 1 mA/cmdisk2 at 0.6 V versus reversible hydrogen electrode in 0.1 M HClO4 with H2O2 faraday efficiency > 90%, and these performance measures could be sustained for 10 h without decay. Further kinetic analysis and operando X-ray absorption study combined with density functional theory (DFT) calculation demonstrated that the nitrogen-coordinated single Co atom was the active site and the reaction was rate-limited by the first electron transfer step.
Display omitted
•Single-atom catalysts (SACs) for H2O2 production were theoretically designed•Cobalt SAC exhibited the highest activity and selectivity for H2O2 production•In situ XAS tracked the dynamic process of the CoN4 active sites•Kinetic analysis identified the rate-determining step of the reaction
Hydrogen peroxide is a valuable chemical with extensive applications, but the current industrial production method is energy-intensive and generates substantial waste. The electrochemical oxygen reduction reaction in acidic media offers an attractive route for direct hydrogen peroxide generation and on-site applications. Unfortunately, there is still a lack of cost-effective electrocatalysts with high catalytic performance. Here, by combining theoretical calculations and experimental methods, we demonstrate that an atomically dispersed cobalt anchored in nitrogen-doped carbon can function as a highly active and selective electrocatalyst for direct hydrogen peroxide synthesis. This cobalt single-atom catalyst combines the advantages of both homogeneous catalysts of cobalt macrocycles (well-defined active sites) and heterogeneous metal-nitrogen-carbon catalysts (high catalytic performance) together, showing promising application in electrosynthesis device.
By combining theoretical and experimental methods, Gao et al. systematically studied the relationship between the structure of transition metal (Mn, Fe, Co, Ni, and Cu) single-atom catalyst anchored in nitrogen-doped graphene and the catalytic performance of hydrogen peroxide (H2O2) synthesis via electrochemical two-electron oxygen reduction reaction (ORR) (2e− ORR). The thus designed Co single-atom catalyst can function as a highly active and selective catalyst for H2O2 synthesis and even slightly outperforms state-of-the-art noble-metal-based electrocatalysts in acidic media.
PDF
