5G隧道环境非平稳宽带双散射簇V2V信道建模

针对5G隧道V2V通信环境,提出了一种通用的3D非平稳宽带双散射簇信道模型。在该模型中,接收信号为视距(line-of-sight,LOS)传播的分量和通过双散射簇模型传播即非视距(non-line-of-sight,NLOS)传播的分量之和。为了研究散射簇的非平稳特性,引入生灭过程算法来模拟散射簇在阵列和时间轴上的出现和消失过程。通过推导空间互相关函数、时间空间自相关函数和多普勒功率谱密度等相关统计特性,研究了散射簇的非平稳特性对MIMO信道的影响。数值仿真结果与先验结果较匹配,表明该模型能够较好地描述实际5G隧道环境下的V2V通信。     

Pharmaceuticals Removal by Adsorption with Montmorillonite Nanoclay

The problem of purifying domestic and hospital wastewater from pharmaceutical compounds is becoming more and more urgent every year, because of the continuous accumulation of chemical pollutants in the environment and the limited availability of freshwater resources. Clay adsorbents have been repeatedly proposed as adsorbents for treatment purposes, but natural clays are hydrophilic and can be inefficient for catching hydrophobic pharmaceuticals. In this paper, a comparison of adsorption properties of pristine montmorillonite (MMT) and montmorillonite modified with stearyl trimethyl ammonium (hydrophobic MMT-STA) towards carbamazepine, ibuprofen, and paracetamol pharmaceuticals was performed. The efficiency of adsorption was investigated under varying solution pH, temperature, contact time, initial concentration of pharmaceuticals, and adsorbate/adsorbent mass ratio. MMT-STA was better than pristine MMT at removing all the pharmaceuticals studied. The adsorption capacity of hydrophobic montmorillonite to pharmaceuticals decreased in the following order: carbamazepine (97%) > ibuprofen (95%) > paracetamol (63–67%). Adsorption isotherms were best described by Freundlich model. Within the pharmaceutical concentration range of 10–50 µg/mL, the most optimal mass ratio of adsorbates to adsorbents was 1:300, pH 6, and a temperature of 25 °C. Thus, MMT-STA could be used as an efficient adsorbent for deconta×ating water of carbamazepine, ibuprofen, and paracetamol.     

Multivariate analysis of a biologically activated carbon (BAC) system and its efficiency for removing PAHs and aliphatic hydrocarbons from wastewater polluted with petroleum products

The efficiency of a biologically activated carbon system for treating wastewater polluted with petroleum products was examined and the effects of process parameters on its efficacy were evaluated. In each experiment 17 alkylated and 19 non-alkylated polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs, C₁₀–C₄₀) were extracted using semipermeable membrane devices from wastewater before and after treatment. The acquired data during experiments were analyzed using principal component analysis (PCA). The treatment system robustly removed dissolved PAHs across the studied ranges of the process parameters, providing overall removal efficiencies of 96.9–99.7% for the sum of 36 PAHs. However, the major contributor to their removal was sorption rather than biodegradation, and despite the general efficiency of the process there was up to a 9-fold range in the sums of quantified PAHs in the effluents between experiments. Combinations of long process contact time (24 h) with high temperature (24 °C) and moderate oxygen concentration (6–7 mg O₂ L⁻¹) resulted in good removal of bioavailable PAHs. The removal of TPHs was more dependent on biological activities during the wastewater treatment, and consequently more dependent on the process parameters. In addition, small but significant proportions of PAHs were volatilized and released during the wastewater treatment.     

Oil Production from De-shelled Aquilaria crassna Seeds Using Supercritical Carbon Dioxide Extraction

This study examined the use of supercritical carbon dioxide (SC-CO₂) in the extraction of triglycerides from de-shelled Aquilaria crassna seeds. A central composite response surface methodology was employed to evaluate the effects of pressure, temperature and solvent-to-solid ratio (SSR) on total yield (TY), concentration of triglycerides (C _TG) and recovery of triglycerides (R _TG). For this experimental design, pressures that ranged from 250 to 350 bar, temperatures that ranged from 313 to 333 K and SSR that ranged from 80 to 120 were investigated for the SC-CO₂ extractions of 15 g of powdered de-shelled A. crassna seeds at a CO₂ flow rate of 25 mL/min under the supercritical phase. The values of TY, C _TG and R _TG achieved were 36.89 %, 709.5 mg/g and 95.4 %, respectively, under the conditions of a pressure of 340 bar, a temperature of 333 K and an SSR of 115 obtained from the quadratic fitting models.     

Stereoselective block of hERG channel by bupivacaine scrutinized at molecular level

In the heart, the hERG voltage-gated potassium channel mediates the I(Kr) current, which is crucial for the duration of cardiac action potential. Undesired block of the channel may prolong the QT interval with increased risk of malignant ventricular arrhythmia called torsades de pointes. Although the molecular determinants of hERG block are intensively studied, stereoselectivity has been poorly investigated. Levo-(S)-bupivacaine was the first drug reported to have higher affinity for hERG than its enantiomer. This study aims at understanding the principles underlying the stereoselectivity of bupivacaine block with the help of molecular modeling. Putative binding modes of levo-(S)- and dextro-(R)-bupivacaine inside an open form model of hERG channel were predicted by docking simulations, allowing a clear depiction of ligand-protein interactions. Estimated binding energies for both enantiomers to wild-type channel are in line with previously published electrophysiology measurements. These results may be considered as a confirmation at the molecular level of bupivacaine stereoselective binding towards hERG. Moreover this information lays the foundations for a structural guideline to filter out potentially cardiotoxic drug candidates in silico.     

Electronic referencing techniques for quantitative NMR: pitfalls and how to avoid them using amplitude-corrected referencing through signal injection

NMR spectroscopy can be a superior analytical technique for quantification of compounds dissolved in solution. Traditionally a chemical reference standard of known concentration is added to the sample. The concentration of the solute can then be determined by comparing the signal integrals. However, it can be inconvenient or impossible to use internal references. Electronic referencing was developed to circumvent problems with internal standards and has been used successfully in well-controlled situations. However, it is not always possible or convenient to have samples where the dielectric sample properties do not change from one to the next. We propose a modification of the old electronic referencing technique that takes into account the electronic changes between dissimilar samples. We have called this new technique Amplitude-corrected Referencing Through Signal Injection or ARTSI.