scholarly journals Molecular Dynamics Investigation of Graphene Nanoplate Diffusion Behavior in Poly-α-Olefin Lubricating Oil

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 361 ◽  
Author(s):  
Lupeng Wu ◽  
Baoyu Song ◽  
Leon Keer ◽  
Le Gu
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Functional Groups ◽  
Lubricating Oil ◽  
Diffusion Behavior ◽  
Long Term Stability ◽  
Temperature And Pressure ◽  
First Time ◽  
Graphene Nanoplates

Graphene as a type of novel additive significantly enhanced the tribological performance of blended lubricating oil. However, the dispersibility of graphene with long-term stability in lubricating oil is still a challenge. Chemical modification for graphene, rather than using surfactants, provided a better method to improve the dispersibility of graphene in lubricants. In this study, the equilibrium molecular dynamics (EMD) simulations were carried out to investigate the diffusion behavior of graphene nanoplates in poly-α-olefin (PAO) lubricating oil. The effects of graphene-size, edge-functionalization, temperature, and pressure on the diffusion coefficient were studied. In order to understand the influence of edge-functionalization, three different functional groups were grafted to the edge of graphene nanoplates: COOH, COON(CH3)2, CONH(CH2)8CH3 (termed GO, MG, and AG, respectively). The EMD simulations results demonstrated that the relationships between diffusion coefficient and graphene-size and number of functional groups were linear while the temperature and pressure had a nonlinear influence on the diffusion coefficient. It was found that the larger dimension and more functional groups provided the lower diffusion coefficient. AG with eight CONH(CH2)8CH3 groups exhibited the lowest diffusion coefficient. Furthermore, the experimental results and radial distribution function for graphene-PAO illustrated that the diffusion coefficient reflected the dispersibility of nanoparticles in nanofluids to some degree. To our best knowledge, this study is the first time the diffusion behavior of graphene in PAO lubricating oil was investigated using EMD simulations.

scholarly journals Structure-Properties Correlation of Cross-Linked Penicillin G Acylase Crystals

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 451
Author(s):  
Marta Kubiak ◽  
Janine Mayer ◽  
Ingo Kampen ◽  
Carsten Schilde ◽  
Rebekka Biedendieck
Keyword(s):  
Mechanical Stability ◽  
Structural Characteristics ◽  
Penicillin G ◽  
Bacillus Species ◽  
Diffusion Limitations ◽  
Small Water ◽  
Long Term Stability ◽  
Atomic Force ◽  
First Time

In biocatalytic processes, the use of free enzymes is often limited due to the lack of long-term stability and reusability. To counteract this, enzymes can be crystallized and then immobilized, generating cross-linked enzyme crystals (CLECs). As mechanical stability and activity of CLECs are crucial, different penicillin G acylases (PGAs) from Gram-positive organisms have proven to be promising candidates for industrial production of new semisynthetic antibiotics, which can be crystallized and cross-linked to characterize the resulting CLECs regarding their mechanical and catalytic properties. The greatest hardness and Young’s modulus determined by indentation with an atomic force microscope were observed for CLECs of Bacillus species FJAT-PGA CLECs (26 MPa/1450 MPa), followed by BmPGA (Priestia megaterium PGA, 23 MPa/1170 MPa) and BtPGA CLECs (Bacillus thermotolerans PGA, 11 MPa/614 MPa). In addition, FJAT- and BtPGA CLECs showed up to 20-fold higher volumetric activities compared to BmPGA CLECs. Correlation to structural characteristics indicated that a high solvent content and low number of cross-linking residues might lead to reduced stability. Furthermore, activity seems to be restricted by small water channels due to severe diffusion limitations. To the best of our knowledge, we show for the first time in this study that the entire process chain for the characterization of diverse industrially relevant enzymes can be performed at the microliter scale to discover the most important relationships and limitations.

scholarly journals Scribing Method for Carbon Perovskite Solar Modules

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1589 ◽  
Author(s):  
Simone M. P. Meroni ◽  
Katherine E. A. Hooper ◽  
Tom Dunlop ◽  
Jenny A. Baker ◽  
David Worsley ◽  
...  
Keyword(s):  
Screen Printing ◽  
Fill Factor ◽  
Transparent Electrode ◽  
Perovskite Solar Cell ◽  
Metal Contacts ◽  
Good Efficiency ◽  
Long Term Stability ◽  
First Time

The fully printable carbon triple-mesoscopic perovskite solar cell (C-PSC) has already demonstrated good efficiency and long-term stability, opening the possibility of lab-to-fab transition. Modules based on C-PSC architecture have been reported and, at present, are achieved through the accurate registration of each of the patterned layers using screen-printing. Modules based on this approach were reported with geometric fill factor (g-FF) as high as 70%. Another approach to create the interconnects, the so-called scribing method, was reported to achieve more than 90% g-FF for architectures based on evaporated metal contacts, i.e., without a carbon counter electrode. Here, for the first time, we adopt the scribing method to selectively remove materials within a C-PSC. This approach allowed a deep and selective scribe to open an aperture from the transparent electrode through all the layers, including the blocking layer, enabling a direct contact between the electrodes in the interconnects. In this work, a systematic study of the interconnection area between cells is discussed, showing the key role of the FTO/carbon contact. Furthermore, a module on 10 × 10 cm2 substrate with the optimised design showing efficiency over 10% is also demonstrated.

scholarly journals Targeted Release of Probiotics from Enteric Microparticulated Formulations

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1668 ◽  
Author(s):  
Cristina Yus ◽  
Ruben Gracia ◽  
Ane Larrea ◽  
Vanesa Andreu ◽  
Silvia Irusta ◽  
...  
Keyword(s):  
Targeted Delivery ◽  
Target Tissue ◽  
Release Formulation ◽  
Long Term Stability ◽  
Pharmaceutical Ingredients ◽  
Efficient Delivery ◽  
Synthesized Materials ◽  
First Time ◽  
Targeted Release

The development of advanced probiotic delivery systems, which preserve bacteria from degradation of the gastrointestinal tract and achieve a targeted release mediated by pH-independent swelling, is of great interest to improve the efficient delivery of probiotic bacteria to the target tissue. Gram-positive and Gram-negative bacteria models (Lactobacillus acidophilus (Moro) Hansen and Mocquot (ATCC® 4356™) and Escherichia coli S17, respectively) have been successfully encapsulated for the first time in pH-independent microparticulate polymethacrylates (i.e., Eudraguard biotic) used for the targeted delivery of nutraceuticals to the colon. These bacteria have also been encapsulated within the mucoadhesive polymethacrylate Eudragit RS 100 widely used as targeted release formulation for active pharmaceutical ingredients. The enteric microparticles remained unaltered under simulated gastric conditions and released the contained viable microbial cargo under simulated intestinal conditions. Buoyancies of 90.2% and 57.3% for Eudragit and Eudraguard microparticles, respectively, and long-term stability (5 months) for the encapsulated microorganisms were found. Cytotoxicity of the microparticles formulated with both polymers was evaluated (0.5–20 mg/mL) on Caco-2 cells, showing high cytocompatibility. These results underline the suitability of the synthesized materials for the successful delivery of probiotic formulations to the target organ, highlighting for the first time the potential use of Eudraguard biotic as an effective enteric coating for the targeted delivery of probiotics.

Enhancement of efficiency and long-term stability in graphene/Si-quantum-dot heterojunction photodetectors by employing bis(trifluoromethanesulfonyl)-amide as a dopant for graphene

2017 ◽  
Vol 5 (48) ◽  
pp. 12737-12743 ◽  
Author(s):  
Dong Hee Shin ◽  
Chan Wook Jang ◽  
Ju Hwan Kim ◽  
Jong Min Kim ◽  
Ha Seung Lee ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Term Stability ◽  
Long Term Stability ◽  
Si Quantum Dot ◽  
First Time ◽  
Si Quantum Dots

Bis(trifluoromethanesulfonyl)-amide (TFSA) is for the first time employed as a dopant for graphene for graphene/Si-quantum-dots-based photodetectors.

scholarly journals Optical Axis Perturbation Analysis for the Unit-Magnification Multipass System

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Yin Guo ◽  
Liqun Sun ◽  
Zheng Yang
Keyword(s):  
Optical Axis ◽  
Optical Element ◽  
Transfer Model ◽  
Tolerance Range ◽  
Long Term Stability ◽  
Generalized Sensitivity ◽  
Sensitivity Factors ◽  
Element Transfer ◽  
First Time

The optical axis sensitivity for the unit-magnification multipass system (UMS) is presented by using a general misaligned optical element transfer model. The generalized sensitivity factors SD1, SD2, ST1, and ST2 influenced by both the axial and angular misalignments of the objective mirrors in a UMS have been calculated for the first time. The Bernstein-Herzberg White Cells are used as an example, and their alignment tolerance and stability properties are found when their configurations change. The analysis in this paper is helpful for the design of other kinds of multipass gas cells (MGC) with high robustness and avoiding the violent vibration of the optical axis when the misalignment of each mirror is controlled within the tolerance range. Among the five possible perturbations sources, the misaligned factors δix,δiy,θix have more effects on the output beam’s position and the perturbed sources from δix,θix and δiy,θiy have more impacts on the output beam’s slope referred to as x-axis and y-axis, respectively. Higher reflection times mean smaller tolerance range. The results benefit the multipass cell design and the precise alignment of the mirrors within the cell with the purpose of long-term stability in measurements.

scholarly journals Diffusion of Water and Diatomic Oxygen in Poly(3-hexylthiophene) Melt: A Molecular Dynamics Simulation Study

2012 ◽  
Vol 11 (1 and 2) ◽  
Author(s):  
Julia Deitz ◽  
Yeneneh Yimer ◽  
Mesfin Tsige
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Molecular Dynamics Simulation ◽  
Simulation Study ◽  
Dynamics Simulation ◽  
Fick’S Law ◽  
Fick's Law ◽  
Diffusion Behavior

Diffusion behavior of water, diatomic oxygen, and a mixture of both into a poly(3-hexylthiophene)[P3HT] melt were investigated using Molecular Dynamics Simulation. Once simulations were complete, the data was analyzed to determine the diffusion coefficient of those molecules in P3HT using Fick’s law. The diffusion coefficient values were then plotted as a function of concentration and temperature to determine if trends existed. For both water and oxygen, no dependence was observed of the diffusion coefficient on concentration and temperature for the ranges studied. However, a variation in the diffusion coefficient on concentration was observed due to the expected inhomogeneity of the P3HT melt. In the presence of O2, the diffusion of H2O decreased significantly by a factor between four and five, while in the presence of H2O, the diffusion of O2 slightly decreased.

A Discussion on the measurement and interpretation of changes of strain in the Earth - Strain measurement in Australia with particular reference to the Cooney Observatory

1973 ◽  
Vol 274 (1239) ◽  
pp. 323-330 ◽  
Keyword(s):  
New England ◽  
Research Programme ◽  
Instrument Error ◽  
Crustal Movements ◽  
Long Term Stability ◽  
The Earth ◽  
Temperature And Pressure ◽  
Strain Determination ◽  
The University

A number of groups in Australia are concerned with Earth crustal movement measurement and interpretation. A brief description is given of their activities. Monitoring crustal movements requires methods of strain determination which have the best attainable precision and long-term stability. Paramount to improvement of the established techniques is need for a facility where the various methods can be compared in a reliable manner. The remainder of the paper describes the research programme of the Cooney Observatory (operated by the University of New England) which has a dominant theme of instrument development and verification. Rod, wire and laser strain-meters and the necessary peripheral equipment are described. Of interest is the continuing improvement of stable intermediate-length measuring bases in which a controlled temperature and pressure environment is created to eliminate the main systematic sources of instrument error during testing and calibration.

scholarly journals Extinction-resistant attention to long-term conditioned threat is indexed by selective visuocortical alpha suppression in humans

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Christian Panitz ◽  
Andreas Keil ◽  
Erik M. Mueller
Keyword(s):  
Visual Attention ◽  
Time Windows ◽  
Alpha Power ◽  
Physiological Measures ◽  
Time Frequency ◽  
Long Term Stability ◽  
Electrophysiological Studies ◽  
First Time

Abstract Previous electrophysiological studies in humans have shown rapid modulations of visual attention after conditioned threat vs. safety cues (<500 ms post-stimulus), but it is unknown whether this attentional prioritization is sustained throughout later time windows and whether it is robust to extinction. To investigate sustained visual attention, we assessed visuocortical alpha suppression in response to conditioned and extinguished threat. We reanalysed data from N = 87 male participants that had shown successful long-term threat conditioning and extinction in self reports and physiological measures in a two-day conditioning paradigm. The current EEG time-frequency analyses on recall test data on Day 2 revealed that previously threat-conditioned vs. safety cues evoked stronger occipital alpha power suppression from 600 to 1200 ms. Notably, this suppression was resistant to previous extinction. The present study showed for the first time that threat conditioning enhances sustained modulation of visuocortical attention to threat in the long term. Long-term stability and extinction resistance of alpha suppression suggest a crucial role of visuocortical attention mechanisms in the maintenance of learned fears.

Nanostructured SnS-N-doped graphene as an advanced electrocatalyst for the hydrogen evolution reaction

2015 ◽  
Vol 51 (86) ◽  
pp. 15716-15719 ◽  
Author(s):  
S. S. Shinde ◽  
Abdul Sami ◽  
Dong-Hyung Kim ◽  
Jung-Ho Lee
Keyword(s):  
Hydrothermal Synthesis ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Term Stability ◽  
Long Term Stability ◽  
Highly Active ◽  
Doped Graphene ◽  
First Time

The scalable hydrothermal synthesis of the SnS/N-rGr hybrid is presented for the first time, which is used as a highly-active electrocatalyst with long-term stability in different media.

scholarly journals Experimental Determination of CO2 Diffusion Coefficient in a Brine-Saturated Core Simulating Reservoir Condition

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 540
Author(s):  
Zerong Li ◽  
Lei Yuan ◽  
Guodong Sun ◽  
Junchen Lv ◽  
Yi Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Co2 Storage ◽  
Co2 Diffusion ◽  
Nacl Concentration ◽  
Reservoir Conditions ◽  
Temperature And Pressure ◽  
The Relationship ◽  
Crucial Part

CO2 diffusion coefficient plays a crucial part in saline aquifers for the CO2 storage and the safety of long-term sequestration. Therefore, it is particularly important to measure the diffusion coefficient accurately. As far as we know, there are currently no CO2 brine diffusion data in real cores under reservoir temperature and pressure conditions. In this paper, a study on the CO2 diffusion coefficient diffused in a brine-saturated Berea core along the radial direction was conducted at temperatures of 313.15 K to 373.15 K and pressures of 8 MPa to 30 MPa. On account of the experimental results, the effect of permeability, NaCl concentration, temperature and pressure on the CO2 diffusivity is analyzed. The results in this study indicate that the diffusion coefficient increases with increasing permeability, pressure and temperature and decreases with increasing NaCl concentration. However, the relationship between pressure and the diffusion coefficient is not linear. As the pressure gradually increases, the effect of pressure will become weak. In addition, an empirical correlation of the relationship between temperature–pressure and the CO2 diffusion coefficient could be obtained based on the experimental data. The data in this paper fill the blank on the study of the CO2 diffusivity in brine under reservoir conditions, which has positive significance for the study of supercritical CO2 diffusion in a brine-saturated core.

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