We introduce a novel soft antenna selection approach for multiple antenna systems through a joint design of both RF (radio frequency) and baseband signal processing. When only a limited number of ...frequency converters are available, conventional antenna selection schemes show severe performance degradation in most fading channels. To alleviate those degradations, we propose to adopt a transformation of the signals in the RF domain that requires only simple, variable phase shifters and combiners to reduce the number of RF chains. The constrained optimum design of these shifters, adapting to the channel state, is given in analytical form, which requires no search or iterations. The resulting system shows a significant performance advantage for both correlated and uncorrelated channels. The technique works for both transmitter and receiver design, which leads to the joint transceiver antenna selection. When only a single information stream is transmitted through the channel, the new design can achieve the same SNR gain as the full-complexity system while requiring, at most, two RF chains. With multiple information streams transmitted, it is demonstrated by computer experiments that the capacity performance is close to optimum.
Rhodium-catalyzed substrate-tunable oxidative annulation and spiroannulation reactions of 2-arylindoles with benzoquinone leading to 9H-dibenzoa,ccarbazol-3-ols and new spirocyclic products are ...reported. Intriguingly, with 2-aryl-substituted indoles, benzoquinone could act as a C2 synthon to afford dibenzoa,ccarbazoles. On the contrary, when 2-aryl-3-substituted indoles were used, benzoquinone switched to act as a C1 synthon to furnish spirocyclic compounds. In addition, further transformations of the obtained products demonstrate the synthetic utility of the present protocol.
Nanofiltration (NF) has attracted increasing interest for dye and NaCl fractionation in textile industry. However, it typically shows high rejections to divalent salts (i.e., Na2SO4), compromising to ...effectively purify dye from dye/Na2SO4 mixtures, which is crucial in digital ink-jet printing. This study used a tight ceramic ultrafiltration (UF) membrane (MWCO of 2410 Da) to desalinate diverse reactive dye species with molecular weights from 626.6 to 1205.4 Da. The UF membrane showed considerably high rejections to all the reactive dyes (> 98.12%) and nearly complete salt transmission (rejections < 0.1% and < 1.5% with 60 g L−1 NaCl and Na2SO4, respectively). Operational conditions, i.e., dye concentration, applied pressure and salt addition, have insignificant impacts on the dye rejection, due to dye aggregation. An integrated UF-diafiltration process, including pre-concentration, diafiltration and post-concentration, was designed to fractionate reactive dyes and Na2SO4. The model dye, reactive blue 19, can be concentrated to 142.60 g L−1 with a purity of 99.83% in the process, since low salt rejection and high dye retention of the membrane allows for 99.88% salt removal and 2.3% dye loss after ca. 9 diavolumes. These results indicate that tight ceramic UF membranes have high potential as a state-of-the-art technology in reactive dyes and Na2SO4 fractionation for digital ink-jet printing applications.
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•Tight UF membrane is used in efficient dye purification for digital printing.•Tight UF membrane has consistently high rejection (> 98.12%) for 7 reactive dyes.•Integrated UF-diafiltration process removes 99.88% of Na2SO4 with ~9 diavolumes.•Reactive blue 19 is concentrated to 142.60 g L−1 with 99.83% purity in diafiltration.•Complete flux recovery for UF membrane is obtained after NaOH/HCl cleaning.
Cd and Zn pollution was observed to often occur simultaneously in soils. However, previous studies focused on single heavy metal instead of Cd and Zn combined pollution. Castor (Ricinus communis) is ...considered to have great potential for contaminated soil remediation. The resistance of castor seedlings to heavy metals and the mechanism behind it remain unknown. In this study, the tolerance and accumulation ability of castor seedlings to Cd and Zn were investigated, and the accumulation mechanism involving the subcellular distribution in different tissues was further explored. The results on biomass and chlorophyll revealed that castor seedlings have good tolerance to the pollution with 0–5 mg/kg Cd and 380 mg/kg Zn, while not to the heavy pollution with 25 mg/kg Cd and 380 mg/kg Zn. The maximum accumulation concentrations of Cd and Zn, 175.3 mg Cd/kg and 386.8 mg/kg Zn, appeared in castor seedling root instead of stem and leaf, indicating that root played a significant part in accumulating Zn and Cd. The relative low dosage of Cd (0–5 mg/kg) promoted the accumulation of Zn in the subcellular component, while high dosage (25 mg/kg) inhibited the accumulation of Zn. In subcellular accumulation and distribution of castor seedlings, Cd (27.1%–69.4%) and Zn (39.6%–66.6%) in the cell wall was the highest. With the increase of Cd addition, the accumulation of Cd increased in cell wall while decreased in organelle and soluble fraction. Hydroxyl, amino, amides and carboxyl functional groups on cell wall might provided the main binding sites for Cd and Zn.
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•Tolerance of castor seedlings to Cd–Zn and their accumulation were studied for the first time.•Castor seedlings were deduced to have better tolerance to Cd and Zn than mature castors.•Cd and Zn mainly accumulated in root of castor seedlings.•Cd (51%–69%) and Zn (40%–62%) mainly accumulated in the cell wall of the root.•A synergistic and antagonistic accumulation effect existed in the co-presence of Cd and Zn.
Porphyrin (TMPyP) functionalized carbon quantum dots (CQDs-TMPyP), a novel and efficient carbon nanocomposite material, were developed as a novel luminescent material, which could be very useful for ...the sensitive detection of copper ions in the Cu2+ quenching luminescence of functionalized carbon quantum dots. Therefore, we constructed a sensitive “signal off” ECL biosensor for the detection of Cu2+. This sensor can sensitively respond to copper ions in the range of 10 nM to 10 μM, and the detection limit is 2.78 nM. At the same time, it has good selectivity and stability and a benign response in complex systems. With excellent properties, this proposed ECL biosensor provides an efficient and ultrasensitive method for Cu2+ detection.
Cadmium (Cd) due to its strong toxicity and high mobility, which poses a considerable threat to soil environment and human health, has aroused widespread concern. Biochar has been used for ...remediating Cd-contaminated soil recently, however this method has the risk of fixed-Cd re-release. Phytoremediation can make up for its shortcoming. In this study, a pot experiment was carried out, where Bidens pilosa L. (B.pilosa) was as the tested plant and biochars (maize straw biochar and wheat straw biochar with two particle sizes) were as amendments. The mechanism of how biochars promoted B.pilosa Cd accumulation in Cd-contaminated farmland soil was explored. Results showed that the application of 5% wheat straw fine biochar (WF), wheat straw coarse biochar (WC), maize straw fine biochar (MF) and maize straw coarse biochar (MC) increased the total Cd accumulation of B.pilosa to 251.57%, 217.41%, 321.64% and 349.66%, respectively. Biochars amendment significantly promoted B.pilosa growth and increased Cd accumulation by improving soil physical properties, nutrient levels (available nitrogen, available phosphorus (AP), available potassium (AK) and organic matter (OM)) and microbial activity, and changing the nutrients distribution in B.pilosa organs although tissues although DTPA-Cd reduced to some extent. The effect of MF on AP increase was better than MC, while the effect of WF on AK increase was better than WC. Fine-particle was superior to coarse-particle in increasing B.pilosa biomass of aboveground, OM and microbial activity in soil. The changes of N, P and K concentrations in B.pilsosa roots, stems and leaves were closely related to the changes of AN, AP and AK in soil after biochars application. The results indicated that the combination of straw biochars and hyperaccumulators had the synergistic effect. This study can provide data support and meaningful reference values for remediating actual Cd-contaminated soil.
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•Cd accumulation of B.pilosa were promoted remarkably after biochars amendment.•The highest Cd accumulation of B.pilosa was obtained after MC amendment.•Biochars amendment significantly increased B.pilosa biomass.•DTPA-Cd was decreased in all treatments of biochars amendment.•Biochars amendment increased soil nutrient levels and nutrients in B.pilosa.
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•A MOF-derived Ni/Co-NC cathode was first synthesized for CH4 production.•Enhanced CH4 production rate and CH4 yield were obtained with the Ni/Co-NC cathode.•The Ni/Co-NC cathode was ...beneficial for bioelectrocatalytic CO2 reduction to CH4.•Methanobacterium was the dominant methanogen in the Ni/Co-NC cathode biofilm.
Cathode materials play important roles in the optimization of methane upgrading in microbial electrolysis cell-coupled anaerobic digestion (MEC-AD) systems. In this study, metal organic framework (MOF)-derived carbon-based bimetallic hybrids (Ni/Co-NC) was synthesized as cathode material and its performances and microbial activities were evaluated in MEC-AD. A high methane production rate (0.57 m3 CH4/m3·d) and yield (0.34 m3 CH4/kgCOD) were achieved with a Ni/Co-NC cathode at a potential of 0.6 V. The methane content in the biogas was upgraded to ca. 90%. The enhanced methane production was likely related to the positive surface charge and the good conductive capacity and hydrogen evolution of the Ni/Co-NC cathode, as demonstrated by electrochemical assessment. Additionally, roughness and extensive surface areas provided additional room for cathodic biofilm adhesion via hydrogen bonding and electrostatic interactions. A significant enrichment of Methanobacterium (79.6%) in the MEC-AD-Ni/Co-NC system, especially in the biofilm of the cathode surface, indicated that the methane production pathway shifted from acetoclastic to hydrogenotrophic methanogenesis. Moreover, Methanosaeta harundinacea 6Ac species, which can directly accept electrons, were identified in the MEC-AD systems. These findings revealed that Ni/Co-NC cathode probably enhanced bioelectrochemical reduction of CO2 to CH4 by accelerating hydrogenotrophic methanogenesis and direct electron transfer.
Abstract
Non‐sidelooking airborne radar encounters significant non‐stationary and heterogeneous clutter environments, resulting in a severe shortage of samples. Sparse recovery‐based space‐time ...adaptive processing (SR‐STAP) methods can achieve good clutter suppression performance with limited samples. Nonetheless, grid‐based SR‐STAP algorithms encounter off‐grid effects in non‐sidelooking arrays, which can severely degrade the clutter suppression performance. In this study, the authors propose a novel gridless SR‐STAP method in the continuous spatial‐temporal domain to address the issue of off‐grid effects. Inspired by the fact that sparse Bayesian learning (SBL) framework implicitly performs a structured covariance matrix estimation, the authors reparameterise its cost function to directly estimate the block‐Toeplitz structured matrix from the measurements in a gridless manner. Since the proposed cost function is non‐convex, we utilise a majorisation‐minimisation‐based iterative procedure to estimate the clutter covariance matrix. Finally, using the standard concept of semidefinite programming, the authors derive a convex gridless implementation of the SBL cost function for uniformly sampled radar systems. Extensive simulation experiments demonstrate the exceptional clutter suppression and target detection performance of the proposed algorithm.
Recent studies indicate that both prefrontal and visual regions play critical roles in visual working memory (VWM), with prefrontal regions mainly associated with executive functions, and visual ...cortices linked to representations of memory contents. VWM involves the selective filtering of irrelevant information, yet the specific contributions of the prefrontal regions and visual cortex in this process remain unclear.
To understand the dynamic causal roles of prefrontal and visual regions in VWM.
The differentiation of VWM components was achieved using a computational model that incorporated a swap rate for non-target stimuli. Single-pulse magnetic transcranial stimulation (spTMS) was delivered to the early visual cortex (EVC) and the inferior frontal junction (IFJ) across different phases of an orientation recall task that with or without distractors.
Our results indicate that spTMS over the EVC and IFJ influences VWM particularly when distractors are present. VWM precision can be impacted by spTMS applied to either region during the early retention, while spTMS effect is especially prominent when EVC is stimulated during the late retention phase and when directed at the ipsilateral EVC. Conversely, the probability of accurately recalling the target exhibited comparable patterns when spTMS was administered to either the EVC or IFJ.
We highlight the “sensory recruitment” of VWM characterized by critical involvement of EVC particularly in the information-filtering process within VWM. The maintenance of memory content representations necessitates ongoing communication between the EVC and IFJ throughout the entirety of the VWM process in a dynamic pattern.
•This study explores EVC and IFJ's roles in Visual Working Memory, revealing their impacts on memory precision and quantity.•Using spTMS, resaerch pinpoints brain regions' causal influence on VWM, especially with endogenous distractors.•Findings highlight critical timing of the influences during various phases of VWM, offering new temporal modulation insights.
Space‐time adaptive processing (STAP) struggles to effectively suppress clutter in the heterogeneous clutter environment due to the lack of training samples. In order to enhance clutter suppression ...performance of STAP, a subspace‐weighted mixed‐norm minimisation approach is given. First, a roughly estimated clutter subspace is obtained using the subspace augment (SA) approach. The weight vector is then designed using the association between the dictionary matrix and the noise subspace, allowing the algorithm to penalise sparse coefficients democratically. Finally, in order to solve the subspace‐weighted mixed‐norm minimisation problem, we derive a fast algorithm based on the alternating direction multiplier method (ADMM) framework. The proposed algorithm does not require iteratively updating the weight vector in contrast to the iterative re‐weighted l1 ${l}_{1}$ (IRL1) algorithm. The simulation results demonstrate the effectiveness of the proposed algorithm in terms of computational efficiency and clutter suppression performance.
In the paper, a subspace‐weighted mixed‐norm minimisation approach is proposed, and the alternating direction multiplier method (ADMM) algorithm is utilised to solve the subspace‐weighted mixed‐norm minimisation problem.
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