Key Experimental Parameters Research Articles

Extraction, purification, and biological activities of flavonoids from branches and leaves of Taxus cuspidata S. et Z.

The optimal operational and process parameters were determined for the enzymatic hydrolysis and ultrasound-assisted extraction (EHUE) method of flavonoids extracted from Taxus cuspidata branches and leaves (TCBL), and the biological activity of obtained flavonoids was evaluated. According to single factor and central composite design experiments, the optimum key experimental parameters for EHUE were that pectinase enzyme concentration was 0.10 mg·mL-1, enzymatic hydrolysis temperature was 48 °C, and enzymolysis time was 39 min. The yield of flavonoids from TCBL under the optimized conditions was 5.23% ± 0.18%. Four purified flavonoid compounds from TCBL extract were identified as 1) (E)-1-methoxy-2-O-(p-coumaroyl)-myo-inositol, 2) catechin, 3) epicatechin, and 4) quercetin-3-O-glucoside. Among the 4 compounds, compounds 2 and 3 showed higher antioxidant capacities, α-amylase, and α-glucosidase inhibitory activities. The statistical analysis showed that epicatechin and catechin were potent antioxidants and active agents for inhibiting type II diabetes. In addition, all 4 compounds exerted clear antitumor activity against MCF-7, Hela, and HepG2 cells. Especially, compound 4 had highest antitumor capacity against MCF-7 and Hela, while compound 1 was best at suppressing the proliferation of HepG2 cells.

Miniaturized solid-phase extraction using a mesoporous molecular sieve SBA-15 as sorbent for the determination of triterpenoid saponins from Pulsatilla chinensis by ultrahigh-performance liquid chromatography-charged aerosol detection

A simple, sensitive and efficient solid-phase extraction method, combined with ultrahigh-performance liquid chromatography-charged aerosol detection, was applied to the pre-concentration and determination of four triterpenoid saponins from Pulsatilla chinensis (P. chinensis) ultrasound extract samples. Mesoporous molecular sieve Santa Barbara Amorphous 15 (SBA-15) displayed higher selectivity compared to Mobil Composition of Matter 41 (MCM-41), NH2-SBA-15 and mesoporous carbon when it comes to being used in pretreatment methods. It was applied as an effective sorbent in the SPE for the enrichment of the target analytes. Additionally, several key experimental parameters including the kinds of sorbents, the amount of SBA-15, the elute pH and types of elution solvent were investigated in detail. Under the optimized conditions, the satisfactory linearity (r2 ≥ 0.9940) was acquired and the limits of detection reached 0.461−0.976 μg/mL for the target analytes. The recoveries ranged from 95.1%–103.2%. The experimental results showed that SBA-15 was a candidate material for the purification and concentration of target triterpenoid saponins from complex P. chinensis samples. The study provided theoretical support for the application of mesoporous materials in the field of drug separation and provided references for the extraction and determination of trace compounds in the complex systems of traditional Chinese medicine.

Zirconium(Ⅳ)-based metal-organic framework for determination of imidacloprid and thiamethoxam pesticides from fruits by UPLC-MS/MS

Zirconium(Ⅳ)-based metal-organic framework (MOF)-UiO-66-NH2 was fabricated to adsorb the imidacloprid and thiamethoxam in fruit samples before analysis using UPLC-MS/MS. The UiO-66-NH2 was confirmed by SEM, FTIR, and XRD. Key experimental parameters were investigated by response surface methodology (RSM). The desirability recovery of imidacloprid was 94.52% under optimum conditions (mount of adsorbent = 52.48 mg, volume of eluent = 5.18 mL, pH = 9, extraction time = 15 min). The desirability recovery of thiamethoxam was 93.57% under optimum conditions (mount of adsorbent = 50.58 mg, volume of eluent = 2.6 mL, pH = 5.65, extraction time = 11.94 min). Under the optimal conditions, the actual recovery of imidacloprid and thiamethoxam was 92.39% and 94.37%, respectively. Besides, the method was applied successfully to detect imidacloprid and thiamethoxam in different fruit samples. The results demonstrated that the UiO-66-NH2 is an excellent adsorbent for the extraction imidacloprid and thiamethoxam from fruit samples.

The initial inoculation ratio regulates bacterial coculture interactions and metabolic capacity

Coculture is an important model system in microbial ecology studies. As a key experimental parameter, the initial inoculation ratio has a crucial impact on the results of the coculture system. However, such an effect has never been investigated under multiple niche conditions. In this study, we established a simple coculture system with two model bacteria in various carbon sources and investigated the influence of initial inoculum ratios of 1:1000 to 1000:1 on community structure, function, and bacterial interaction. We found that the final ratio of the cocultures with different initial inoculum ratios differed in approximately five-sixths of the carbon sources, suggesting that the final ratio is highly dependent on the initial inoculum ratio, while the carbon source preferences of bacteria could not predict the final ratio of cocultures. Furthermore, we found that the initial ratio could regulate the metabolic capacity of the coculture, as only cocultures with initial ratios of 1:1 and 1000:1 gained high capacity on 14 specific carbon sources. The underlying reason may be that the pattern of species interaction is changed by the initial ratio. In conclusion, we showed that the initial ratio can induce emergent properties in coculture. These findings suggest that the initial ratio not only impacts the reproducibility of coculture experiments but also can influence our understanding of generic microbial ecology.

Impact of laser-induced breakdown spectroscopy implementation for the quantification of carbon content distribution in archaeological ferrous metals

The presence of carbon content is a key enabling factor in archaeological ferrous material studies because it can provide technological and temporal information on its fabrication. A strong relationship exists between the composition, the metallographic structure, and the mechanical properties of metals. Laser-induced breakdown spectroscopy (LIBS) is one of the techniques that can be used in situ to access the carbon content of samples.This paper presents a thorough investigation of the influence of key experimental parameters on the analytical implementation of LIBS, proposes a suitable protocol for carbon quantification, and discusses its limitations. We demonstrate that the global carbon concentration can be obtained with the help of a large laser spot, but this is not sufficient to separate all steel phases. To overcome this problem of spatial distribution and to achieve quantitative measurements, a smaller laser spot has been used and a specific analytical procedure has been developed. As a result, a smaller spot is needed for detecting the different steel phases and to show the metallographic structure. On a macro-scale, a preliminary sampling can be performed with a larger laser spot on the objects in situ in order to locate the high carbon content, such as cementite (Fe3C), for further analysis. On a micro-scale, the different phases of steel and their distribution in the object should be precisely and locally determined with a smaller laser spot, even on nonequilibrium structures. This opens up prospects for researchers to quantify the presence of different phases within the steel matrix and correlate such findings with the technological background behind steel making in historical times.

Thrust evaluation of compact ECR plasma source using 2-zone global model and plasma measurements

Plasma thrusters are required for deep space applications for reducing the fuel payload. This paper evaluates the capability of a compact ECR plasma source (CEPS) as a standalone plasma thruster in space. The unique magnetic field profile of CEPS’ ring magnets enables very efficient plasma production and electron heating within the CEPS plasma source section (ID ≈ 8.5 cm, length ≈ 11.6 cm) resulting in high plasma potentials. Experiments were undertaken with the CEPS attached coaxially to a larger expansion chamber (ID ≈ 48.2 cm, length ≈ 75 cm). Diagnostics included specially designed Langmuir probes (LP) and ion energy analyzers (IEA) that are capable of withstanding the harsh plasma conditions in front of and within the CEPS. LP measurements reveal high-density argon plasma (≈1012 cm−3), with high bulk electron temperatures (≈20 eV) and plasma potentials (≈100 V) at very modest microwave power (≈600 W) over a wide range of pressures (0.3–1 mTorr). An important observation is the fall of almost the full plasma potential inside the CEPS within a short distance close to its exit, giving rise to strong ambipolar electric fields suitable for accelerating ions. IEA measurements confirmed the presence of streaming ions with energies ≈87 eV at ≈2 cm in front of the CEPS. Estimates based on the IEA results yield thrust values ≈50 mN at ≈0.5 mTorr. A 2-zone, global model was developed to determine the steady state plasma parameters (including plasma flow velocity) in the geometry of the experimental system (without magnetic field). The model reproduced the key experimental plasma parameters and was extended to compute plasma thrust under actual space-like conditions. The computed thrust values for xenon are higher (≈80 mN) than that for argon (≈40–45 mN) at ≈600 W of microwave power.

All-inorganic dual-phase halide perovskite nanorings

In the present work, we report the growth of all-inorganic perovskite nanorings with dual compositional phases of CsPbBr3 and CsPb2Br5 via a facile hot injection process. The self-coiling of CsPbBr3-CsPb2Br5 nanorings is driven by the axial stress generated on the outside surface of the as-synthesized nanobelts, which results from the lattice mismatch during the transformation of CsPbBr3 to CsPb2Br5. The tailored growth of nanorings could be achieved by adjusting the key experimental parameters such as reaction temperature, reaction time and stirring speed during the cooling process. The photoluminescence intensity and quantum yield of nanorings are higher than those of CsPbBr3 nanobelts, accompanied by a narrower full width at half maximum (FWHM), suggesting their high potential for constructing self-assembled optoelectronic nanodevices.

(Invited) The Toolbox Concept for the Synthesis of Surfactant-Free Colloidal Nanoparticles as Electrocatalysts

The development of efficient electrocatalysts for fundamental research and research-and-development requires identifying, understanding and ultimately tuning key experimental parameters. This goal is achieved by performing systematic studies where only one of the multiple parameters influencing the catalytic properties is studied at a time, independently of the others. Even though a systematic investigation of catalyst properties can be tedious and time consuming, it provides deep and significant insights into catalyst design to improve catalytic activity, selectivity and/or stability. A toolbox concept developed along the years based on surfactant-free colloidal syntheses is here detailed. It is stressed how this toolbox approach leads to a better understanding of catalyst properties with the examples of platinum nanoparticles for the oxygen reduction reaction (ORR) and iridium nanoparticles for the oxygen evolution reaction (OER).

Experimental investigation on enhanced mechanical and damping performance of corrugated structure with metal rubber

Abstract A new type of sandwich construction with the metal rubber-filled corrugated hybrid core (MR-CHC) which was manufactured by filling the trapezoidal metal rubber materials into the interstices of corrugation, was proposed and it's structural characteristics were investigated via experimental method in present study. The quasi-static out-of-plane compressive experiments were carried out to study the stiffness and energy absorption ability of the sandwich construction. It is demonstrated that the compressive stiffness, the compressive strength and the energy absorption ability of MR-CHC composite structure are higher than those of empty corrugated core sandwich structure as well as single metal rubber material, and increase with the increasing relative density of metal rubber (MR). In addition, under the harmonic load, the hysteresis behavior of MR-CHC sandwich structure was investigated and found that the tangent modulus and loss factor of MR-CHC sandwich structure are significantly affected by the relative density of MR filler and the key experimental parameters including the amplitude, the pre-compression level and the excitation frequency. The loss factor of sandwich structures with MR-CHC ranges from 0.1 to 0.16, which is higher than that of single MR material and sandwiches with empty corrugated core. Furthermore, the effects of the relative density of MR filler and the experimental parameters on the tangent modulus and the loss factor of MR-CHC sandwich structure were discussed by associating the mechanical properties of sandwich construction with the contact states of the helix wires.

Compact magneto-optical trap with a quartz vacuum chamber for miniature gravimeters

The realization of a compact magneto-optical trap (MOT) with a quartz vacuum chamber via ultra-low power of a cooling laser is reported. The dependence of the properties of the MOT on key experimental parameters is investigated. The efficiency of capturing atoms of the novel MOT is compared with that of the metal vacuum chamber. The compact quartz vacuum chamber can achieve a maximum rubidium ( 87 R b ) atomic loading rate of about 8 × 10 9 / s with less than 60 mW of the total power of cooling lasers, while the metal chamber obtains the maximum atomic loading rate of about 3 × 10 9 / s with more than 240 mW of the total power of cooling lasers. The compact apparatus avoids undesired effects found in a metal chamber, such as high power consumption and the magnetic-field eddy current effect. This compact MOT is helpful in the design of miniature atomic gravimeters.

Plasma-catalytic degradation of ciprofloxacin in aqueous solution over different MnO2 nanocrystals in a dielectric barrier discharge system

The α-MnO2, β-MnO2 and γ-MnO2 samples were prepared by the hydrothermal method and were used for the degradation of ciprofloxacin (CIP) wastewater in a combined DBD-catalytic process. The physical and chemical properties of the samples were systematically studied by several analytical techniques including BET, XRD, SEM, HRTEM, XPS, and H2-TPR. The combination of DBD with α-MnO2 showed the highest CIP degradation efficiency, and the efficiency could reach 93.1% after 50 min, which was 10.8% and 18.1% higher, respectively, than those of β-MnO2 and γ-MnO2 catalysts in the plasma-catalytic system. According to the model of response surface methodology, the contribution of key experimental parameters on the CIP degradation decreased in the order: peak voltage > air flow rate > initial concentration > initial pH. The optimum operating parameters were peak voltage 17 kV, air flow rate 2.5 L min−1, an initial concentration 5 mg L−1 and an initial pH 6.9. The quenching experiments of active species showed that OH and O2− were critical to the CIP degradation. The generated O3 might be adsorbed by the α-MnO2 catalyst and resulted in more OH generation. The intermediate products of CIP degradation in DBD+α-MnO2 system were analyzed by LC-MS, and three possible degradation pathways were proposed. This research provides an insight into the use of the crystallographic structures in discharge plasma system for antibiotics in water.

PtNPs-GNPs-MWCNTs-β-CD nanocomposite modified glassy carbon electrode for sensitive electrochemical detection of folic acid.

A novel electrochemical sensor, platinum nanoparticles/graphene nanoplatelets/multi-walled carbon nanotubes/β-cyclodextrin composite (PtNPs-GNPs-MWCNTs-β-CD) modified carbon glass electrode (GCE), was fabricated and used for the sensitive detection of folic acid (FA). The PtNPs-GNPs-MWCNTs-β-CD nanocomposite was easily prepared with an ultrasound-assisted assembly method, and it was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of FA at PtNPs-GNPs-MWCNTs-β-CD/GCE was investigated in detail. Some key experimental parameters such as pH, amount of PtNPs-GNPs-MWCNTs-β-CD composite, and scan rate were optimized. A good linear relationship (R2 = 0.9942) between peak current of cyclic voltammetry (CV) and FA concentration in the range 0.02-0.50mmolL-1 was observed at PtNPs-GNPs-MWCNTs-β-CD/GCE. The detection limit was 0.48μmolL-1 (signal-to-noise ratio = 3). A recovery of 97.55-102.96% was obtained for the determination of FA in FA pills (containing 0.4mg FA per pill) at PtNPs-GNPs-MWCNTs-β-CD/GCE, indicating that the modified electrode possessed relatively high sensitivity and stability for the determination of FA in real samples.

Montmorillonite clay-modified disposable ink-jet-printed graphene electrode as a sensitive voltammetric sensor for the determination of cadmium(II) and lead(II)

This work describes a new sensitive sensor for the simultaneous electrochemical determination by square wave anodic stripping voltammetry of Cd2+ and Pb2+ ions in aqueous solution, based on a disposable ink-jet-printed graphene electrode (IPGE) modified by a thin film of montmorillonite (Mont) clay mineral. The clay was characterized by X-ray diffraction and scanning electron microscopy while the Mont–IPGE was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry before its exploitation for sensing studies. EIS results revealed a low electron transfer rate on Mont–IPGE during the electro-oxidation of [Fe(CN)6]3−. The stripping response on both Cd2+ and Pb2+ analytes was improved by the in situ co-deposition with bismuth, added to the electrolyte solution, on the clay substrate. The proposed electrode showed great stability and good reproducibility. The key experimental parameters governing the stripping analysis of Cd2+ and Pb2+ were optimized. A linear relationship between peak currents and concentrations of the analytes was obtained in the range from 0.01 to 0.21 µM, leading to detection limits of 0.42 nM for Cd2+and 1.14 nM for Pb2+ ions, respectively (S/N = 3). The sensitivities to Cd2+ and Pb2+ ions were 921.8 A cm−2 M−1 and 1960.8 A cm−2 M−1, respectively. The Mont–IPGE sensor was used for the quantification of lead and cadmium in a mineral water.

Nondestructive identification of gemstones by using a portable XRF–XRD system: an illuminating study for expanding its application in museums

Nine gemstone samples were analysed by using a portable X-ray fluorescence–X-ray diffraction (XRF–XRD) system without any destructive preparation processes. The samples were measured by groups based on the transparency and the complexity of molecular structure. The XRF and the XRD measurements for each sample were performed simultaneously. The key experimental parameters were optimized in order to obtain XRD patterns acceptable for phase identification in a limited time. The XRF spectrum of each sample was analysed first to acquire the elemental composition qualitatively, and the information was then applied to refining possible phases. The phase analysis process of each sample was described in detail and the most likely phases were determined. Normal XRD experiments were conducted in order to verify the results. Advantages, disadvantages and applicable range of the system were analysed. The results indicate that the portable XRF–XRD system can be applied to identifying particular gemstones effectively, while single-crystal gems may not be identified very well. Wider recognition and application of the portable XRF–XRD system in cultural heritage and gemological fields call for hardware development, software updating and more real application cases.

Optimization of in vitro trophoblast assay for real-time impedimetric sensing of trophoblast-erythrocyte interactions in Plasmodium falciparum malaria.

Sequestration of Plasmodium falciparum-infected erythrocytes (IEs) is responsible for the pathophysiology of placental malaria, leading to serious complications such as intrauterine growth restriction and low birth weight. However, it is an experimental challenge to study the biology of human placenta. Conventional cell culture-based in vitro placental models rely on immunostaining techniques and high-magnification microscopy is limited in providing real-time quantitative analysis. Impedimetric sensing in combination with cell culture may offer a useful tool. In this paper, we report that real-time label-free measurement of cellular electrical impedance using xCELLigence technology can be used to quantify the proliferation, syncytial fusion, and long-term response of BeWo cells to IEs cytoadhesion. Specifically, we optimized key experimental parameters of cell seeding density and concentration of forskolin, a compound used to promote cell syncitiation, based on electrical signals and immunostaining results. Prolonged time of infection with IEs that led to cell-cell junction vanishment in BeWo cells and release of inflammatory cytokines were monitored in real time by continuous change in electrical impedance. The results suggest that the impedimetric technique is sensitive and can offer new opportunities for the study of cellular responses of trophoblast cells to IEs. The developed system can provide potentially a high-throughput screening tool of anti-adhesion or anti-inflammatory drugs for placental malaria infections.

Experimental error assessment of laminar flame speed measurements for digital chemical kinetics databases

This paper focuses on the uncertainty sources in experimental techniques applied for laminar flame speed measurements. The work was motivated due to the necessity to develop flexible standard sets of the key experimental parameters and descriptors to be included in the machine-readable files of digitalized data repositories such as ReSpeTh, PriMe, CloudFlame, etc. Besides identifying and making the data findable through the associated parameterized descriptions, available information should be interoperable with numerical codes evaluating uncertainty of experimental data. These uncertainty boundaries are very important for interpreters of the data and for development of statistical methods applied for the kinetic model optimization. On this way, four most common used techniques – Heat Flux Method (HFM), Bunsen Flame Method (BFM), Spherical Flame Method (SFM) and Counter Flow Method (CFM) were analyzed. The possible sources of experimental uncertainties have been investigated using data published by different research groups. Respective principles and structures of the experimental uncertainty sources for each studied method have been described. The uncertainty sources, their parameters and descriptors have been classified and systematically summarized in a universal data set to be used in the XML files of digitalized data repositories.

Fluorescent nanoparticle-based Internet of things.

A prototypal molecular Internet of things (IoT) network is reported. Starting from the design of the communication architecture, we have theoretically simulated molecular messenger information exchange by means of fluid-based advection. The objective was to determine the key experimental parameters affecting information storage and transfer efficiency. The first working molecular-IoT prototype, based on a chemical communication network, was then developed. Its selectivity was ensured by employing as many different chemical messengers as networked devices; thus three different carbon nanoparticles, characterized by different fluorescence wavelengths, were employed to ensure an effective communication between three networked actuators.

Key factors influencing the low-field NMR characterisation of gas- and oil-bearing shales: a case study of the shales from the southern Sichuan Basin and Dongying sag, China

The response characteristics of transverse relaxation time (T2) of key experimental parameters [waiting time (TW), number of scans (NS) and echo number (NECH)], sample size and probe fluid, are analysed systematically based on NMR experiments of oil- and gas-bearing shales from the Shahejie Formation in Dongying sag and the Wufeng and Longmaxi Formations in the southern Sichuan Basin. The results indicate that: 1) the optimised NMR parameters for TW, NS and NECH are 1,500 ms, 64 and 6,000, respectively, which will ensure higher accuracy and signal-to-noise ratio (SNR); 2) the total signal amplitude of the T2 spectrum increases with decreasing grain size. The T2 spectra of shale which grain size bigger than 10 mesh can characterize the shale PSD; 3) water porosity clearly decreases with increasing brittle minerals but decreasing clay content than n-dodecane-saturated porosity, which indicates the hydration of clay and brittle minerals together controls the reconstruction of PSD. [Received: May 30, 2018; Accepted: October 24, 2018]

Establishment of patient derived xenograft model of high-grade mucinous carcinoma peritonei accompanied with signet ring cells and identification of biological characteristics

Objective: To establish the patient derived xenograft (PDX) model of pseudomyxoma peritonei (PMP), and identify the key characteristics of tumor biology of this model, in order to provide a reliable model for studying the pathological mechanisms and new therapeutic strategies of PMP. Methods: PMP tumor tissue was obtained from surgery and cut into pieces after washing. Then tumor pieces were implanted subcutaneously in BAL B/c-nu mice for 6 stable passages. In the 7th passage, tumor tissue was implanted orthotopically into abdomen. Subcutaneous tumor and orthotopic tumor were then homogenized to make tumor cell suspension, implanted into abdomen of 10 BAL B/c-nu mice through midline laparotomy, 100 μl for each. The key experimental parameters including body weight changes in the observation period, experimental peritoneal cancer index (ePCI) score at the autopsy, histopathological and immunohistochemical characteristics, and gene expression profiles by high-throughput whole-genome exon sequencing were detected and recorded. Results: The successful rate of established orthotopic PDX model of human PMP was 100% (10/10). The animals showed smooth body weight increases after tumor inoculation until day 27, then the body weight began to decrease steadily. Widespread tumor dissemination of PMP tumor through the whole abdomen was found by autopsy, including the diaphragm, liver, spleen, stomach, kidney, parietal peritoneum, bowel and mesenterium. Gelatinous ascites was also observed in abdominopelvic cavity. The ePCI score ranged from 5 to 9, with a 8 of median ePCI. Histopathological studies showed peritoneal mucinous carcinomatosis accompanied with signet ring cells (PMCA-S), obvious tumor cell atypia and parenchymal invasion.Immunohistochemistry showed the expressions of MUC1, MUC2, MUC5AC, CEA, CA199, CK20, CDX-2 and Ki-67 were positive, MUC6, CK7 and p53 were negative. Whole-exome sequencing identified that the most significant genetic alteration is the exon10 missense mutation c. 1621A>C of KIT gene, the mutation abundance was 89.7%. Conclusion: PDX model of PMCA-S is successfully established, which displays the characters of high-degree malignancy, high proliferation and strong aggressiveness.

Agreement between two large pan-cancer CRISPR-Cas9 gene dependency data sets

Genome-scale CRISPR-Cas9 viability screens performed in cancer cell lines provide a systematic approach to identify cancer dependencies and new therapeutic targets. As multiple large-scale screens become available, a formal assessment of the reproducibility of these experiments becomes necessary. We analyze data from recently published pan-cancer CRISPR-Cas9 screens performed at the Broad and Sanger Institutes. Despite significant differences in experimental protocols and reagents, we find that the screen results are highly concordant across multiple metrics with both common and specific dependencies jointly identified across the two studies. Furthermore, robust biomarkers of gene dependency found in one data set are recovered in the other. Through further analysis and replication experiments at each institute, we show that batch effects are driven principally by two key experimental parameters: the reagent library and the assay length. These results indicate that the Broad and Sanger CRISPR-Cas9 viability screens yield robust and reproducible findings.