| 1. |
- Hou, T. P., et al.
(författare)
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Magnetism and high magnetic-field-induced stability of alloy carbides in Fe-based materials
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the nature of the magnetic-field-induced precipitation behaviors represents a major step forward towards unravelling the real nature of interesting phenomena in Fe-based alloys and especially towards solving the key materials problem for the development of fusion energy. Experimental results indicate that the a pplied high magnetic field effectively promotes the precipitation of M 23 C 6 carbides. We build an integrated method, which breaks through the limitations of zero temperature and zero external field, to concentrate on the dependence of the stability induced by the magnetic effect, excluding the thermal effect. We investigate the intimate relationship between the external field and the origins of various magnetics structural characteristics, which are derived from the interactions among the various Wyckoff sites of iron atoms, antiparallel spin of chromium and Fe-C bond distances. The high-magnetic-field-induced exchange coupling increases with the strength of the external field, which then causes an increase in the parallel magnetic moment. The stability of the alloy carbide M 23 C 6 is more dependent on external field effects than thermal effects, whereas that of M 2 C, M 3 C and M 7 C 3 is mainly determined by thermal effects.
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| 2. |
- Yi, Peng, et al.
(författare)
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I-129 in the Baltic Proper and Bothnian Sea : application for estimation of water exchange and environmental impact
- 2013
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Ingår i: Journal of Environmental Radioactivity. - : Elsevier BV. - 0265-931X .- 1879-1700. ; 120, s. 64-72
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Tidskriftsartikel (refereegranskat)abstract
- We report here new data and a mass balance model for I-129 in the Baltic Proper and the Bothnian Sea covering the period from November-December 2009. The results showed that the general I-129 concentrations in the Bothnian Sea were two-four folds lower than in the Baltic Proper for both surface and deep water. Water exchange between the two basins based on the I-129 mass balance model suggests fluxes from the Baltic Proper to the Bothnian Sea and vice versa at 980 km(3)/y (600-1400 km(3)/y) and 1180 km(3)/y (780-1600 km(3)/y) respectively. Water retention time (residence time) in the Bothnian Sea was estimated at up to 4 years. Applying the I-129 exchange model, an estimate of total phosphorus and nitrogen inflow from the Baltic Proper to the Bothnian Sea indicates values of 20 +/- 7 x 10(3) tons/y and 300 +/- 50 x 10(3) tons/y respectively. The values for the outflow from the Bothnian Sea to the Baltic Proper hold 12 +/- 3 x 10(3) tons/y for total phosphorus and 283 +/- 55 x 10(3) tons/y for total nitrogen. These data and application of I-129 as a tracer of water masses provide information on small scale salinity changes which are vital for accurate understanding of the Baltic Sea ecosystems evolution through time.
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| 3. |
- Liu, Zihe, 1984, et al.
(författare)
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Improved Production of a Heterologous Amylase in Saccharomyces cerevisiae by Inverse Metabolic Engineering
- 2014
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 1098-5336 .- 0099-2240. ; 80:17, s. 5542-5550
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for industrial enzymes and biopharmaceutical proteins relies on robust production hosts with high protein yield and productivity. Being one of the best-studied model organisms and capable of performing posttranslational modifications, the yeast Saccharomyces cerevisiae is widely used as a cell factory for recombinant protein production. However, many recombinant proteins are produced at only 1% (or less) of the theoretical capacity due to the complexity of the secretory pathway, which has not been fully exploited. In this study, we applied the concept of inverse metabolic engineering to identify novel targets for improving protein secretion. Screening that combined UV-random mutagenesis and selection for growth on starch was performed to find mutant strains producing heterologous amylase 5-fold above the level produced by the reference strain. Genomic mutations that could be associated with higher amylase secretion were identified through whole-genome sequencing. Several single-point mutations, including an S196I point mutation in the VTA1 gene coding for a protein involved in vacuolar sorting, were evaluated by introducing these to the starting strain. By applying this modification alone, the amylase secretion could be improved by 35%. As a complement to the identification of genomic variants, transcriptome analysis was also performed in order to understand on a global level the transcriptional changes associated with the improved amylase production caused by UV mutagenesis.
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| 4. |
- Xia, Q. L., et al.
(författare)
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Infrared Laser Pulses Excite Action Potentials in Primary Cortex Neurons in Vitro∗
- 2019
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Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. ; , s. 5184-5187
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Konferensbidrag (refereegranskat)abstract
- Infrared neural modulation (INM) has been well studied in the peripheral nervous system (PNS) for potential clinical applications. However, limited research has been conducted on the central nervous systems (CNS). In this study, we aimed at investigating the feasibility of using pulsed infrared (IR) laser with a wavelength of 1940 nm to excite network activity of cultivated rat cortex neurons.We cultured rat cortex neurons, forming neural networks with spontaneous neural activity, on glass multi-electrode arrays (MEAs). Laser at a power of 600 mW and a pulse rate of 10 Hz were used to stimulate the neural networks using the optics of an inverted microscope. Pulse durations were varied from 200 μs to 1 ms. The spike rate was calculated to evaluate the change of the neural network activity during the IR stimuli and the corresponding frequency components of neural response were calculated to examine whether recorded spikes were evoked by the IR pulse or not. A temperature model was adapted from a previous study to estimate the temperature rise during laser pulsing.We observed that the IR irradiation with a pulse duration of 800 μs and 1 ms could excite neuronal action potentials. The temperature rose 18.5 and 23.9 °C, for pulse durations of 800 μs and 1 ms, respectively. Thus, in addition to previously shown inhibition of IR irradiation with a wavelength of 1550 nm, we demonstrate an optical method that can modulate neural network activity in vitro. The preliminary results from this paper also suggested that MEA recording technology coupled with a laser and microscope systems can be exploited as a new approach for future studies to understand mechanisms and characterize laser parameters of INM for CNS neurons.
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| 5. |
- Deng, B., et al.
(författare)
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Toughness Improvement in a Novel Martensitic Stainless Steel Achieved by Quenching–Tempering and Partitioning
- 2021
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Nature. - 1073-5623 .- 1543-1940. ; 52:11, s. 4852-4864
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, a novel medium carbon martensitic stainless steel (MCMSS) with an excellent combination of strength, ductility, and impact toughness was designed on the basis of quenching-tempering and partitioning (Q–T&P) technology. Q–T&P is an identical heat treatment with a standard quenching and tempering (Q–T) process but has the same role with quenching and partitioning (Q&P) on microstructure control, i.e., promoting carbon-rich retained austenite via inhibiting carbide precipitation. Results show that, without compromise on strength, the total elongation and room temperature impact toughness, i.e., 9.6 pct and 90 J cm−2, of the proposed alloy (23Cr13MnSi) increase by 14 and 110 pct, respectively, as compared to those of the commercial AISI 420. The significant improvement of ductility and impact toughness in the proposed alloy is mainly a result of the gradual transformation induced plasticity (TRIP) effects, which are caused by carbon-rich retained austenite with heterogeneous stability and carbide-free martensite formed in the Q–T&P process
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| 6. |
- Hou, R. -Q, et al.
(författare)
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Corrosion inhibition of pre-formed mussel adhesive protein (Mefp-1) film to magnesium alloy
- 2020
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Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 164
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Tidskriftsartikel (refereegranskat)abstract
- A range of ex situ and in situ analytical techniques were applied to gain insights into the formation and properties of the pre-formed Mefp-1 film on magnesium-1.0 wt.% calcium (Mg-1.0Ca) alloy. The results revealed that the Mefp-1 film pre-formed at pH 4.6 shows a net-like structure, whereas it is more packed at pH 8.5. in situ scanning micro-reference electrode technique results demonstrated the Mefp-1 films formed at both pH can effectively inhibit the localised corrosion of Mg-1.0Ca alloy. Moreover, the film pre-formed at pH 4.6 provides an increasing corrosion inhibition to Mg-1.0Ca alloy during 7 days of exposure.
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| 7. |
- Hou, R. -Q, et al.
(författare)
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Localized corrosion of binary Mg-Ca alloy in 0.9 wt% sodium chloride solution
- 2016
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Ingår i: Acta Metallurgica Sinica (English Letters). - : Chinese Society for Metals. - 1006-7191 .- 2194-1289. ; 29:1, s. 46-57
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Tidskriftsartikel (refereegranskat)abstract
- To further understand the localized corrosion of magnesium alloy, various in situ electrochemical techniques and ex situ electron microprobe analysis and SEM were used to monitor the corrosion process of Mg-1.0Ca alloy in 0.9 wt% sodium chloride solution. The results indicated that the localized corrosion was accompanied by the formation and thickening of a corrosion product film on the Mg-1.0Ca alloy. A localized corrosion of the alloy initiated selectively on the eutectic micro-constituent zones, then enhanced with the exposure, developed in depth with ring-shaped corrosion products accumulated around and finally formed a volcanic-like pitting. Based on the measurements, an electrochemical corrosion model was proposed accordingly to describe the formation mechanism of the volcanic-like pitting on the alloy in 0.9 wt% sodium chloride solution.
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| 8. |
- Hou, T. P., et al.
(författare)
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Magnetic-field-induced magnetism and thermal stability of carbides Fe6-xMoxC in molybdenum-containing steels
- 2016
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 102, s. 24-31
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid method combining first-principles calculations and Weiss molecular field theory with thermodynamic data has been implemented to explore the origin of magnetic-field-induced precipitation behaviors for alloy carbides. The paramagnetic Mo atom disturbed the order of magnetic moment and resulted in a decrease in the Curie temperature for alloy carbide Fe6-xMoxC. The temperature dependence of magnetic moment and saturation magnetization of Fe atoms at different Wyckoff positions, as well as the saturation or induced magnetization of Fe6-xMoxC, decreased with increasing temperature. The higher Fe content and external magnetic field greatly increased the magnetization of alloy carbides. Two kinds of stella quadrangula lattices were employed to account for the total magnetism which was derived from the contribution of different Wyckoff sites of Fe atoms and Fe-C distances. The calculated total free energy taking into account magnetic field, temperature and composition was sufficient to provide quantitative agreement with experiment. The investigation of the effects of external field on the carbide precipitation behaviors led to a better understanding of the magnetic-field-induced phase transformation mechanism in heat resistant steels.
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| 9. |
- Hou, T. P., et al.
(författare)
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The determining role of magnetic field in iron and alloy carbide precipitation behaviors under the external field
- 2016
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Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 120, s. 76-79
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Tidskriftsartikel (refereegranskat)abstract
- A combined approach to calculate the thermodynamic properties of iron and alloy carbides including the thermal and magnetic contribution is derived. Special emphasis is placed on the role of Fe and Mo to the Gibbs free energy. Lower Mo concentration in the carbides corresponds to a higher thermal Gibbs free energy change. The higher Fe content and external magnetic field greatly increase the induced magnetization, reducing the magnetic Gibbs free energy substantially and therefore increase the formation temperature. The stability of M 2 C and M 3 C are mainly determined by the thermal factors, whereas magnetic field has a predominant contribution for M 6 C.
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| 10. |
- Hou, Ziyong, 1986-, et al.
(författare)
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Importance of Microstructure on Precipitation in Tempering of Martensitic Steels
- 2022
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Ingår i: 42Nd Riso International Symposium On Materials Science. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- Precipitation hardening is one of most effective strengthening mechanisms in steels, and much research has been performed in the past. To evaluate the contribution of precipitates, the quantitative features of precipitates including mean size and particle size distribution etc., are vital and needed. However, the predictive modeling of precipitation is still a challenge so far, especially on a quantitative level. Thus, in the present work, precipitation of carbides after tempering of martensitic FeCr-C alloys, consisting of hierarchically arranged substructures within the prioraustenite grains, namely packets and blocks of individual laths, up to 1000h has been investigated. Experimental measurements using electron microscopy and modeling using a Langer-Schwartz theory with the Kampmann-Wagner -Numerical (KWN) method have been conducted. The importance of a proper definition of the initial microstructure for predictive modeling is discussed, in terms of the comparison of calculated and experimental results.
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