63 research outputs found
Correction: Corrigendum: Diabetes Onset at 31–45 Years of Age is Associated with an Increased Risk of Diabetic Retinopathy in Type 2 Diabetes
No full textScientific Reports 6: Article number: 38113; published online: 29 November 2016; updated: 26 May 2017 The original version of this Article incorrectly included Haibing Chen as a corresponding author. This error has now been corrected in the PDF and HTML versions of this Article.</jats:p
Acidic versus alkaline bacterial degradation of lignin through engineered strain E. coli BL21(Lacc): exploring the differences in chemical structure, morphology, and degradation products
No full textThere is increasing interest in research on lignin biodegradation compounds as potential building blocks in applications related to renewable products. More attention is necessary to evaluate the effects of the initial pH conditions during the bacterial degradation of lignin. In this study we performed experiments on lignin biodegradation under acidic and mild alkaline conditions. For acidic biodegradation, lignin was chemically pretreated with hydrogen peroxide. Alkaline biodegradation was achieved by developing the bacterial growth on Luria and Bertani medium with alkali lignin as the sole carbon source. The mutant strain Escherichia coli BL21(Lacc) was used to carry out lignin biodegradation over 10 days of incubation. Results demonstrated that under acidic conditions there was a predominance of aliphatic compounds of the C3–C4 type. Alkaline biodegradation was produced in the context of oxidative stress, with a greater abundance of aryl compounds. The final pH values of acidic and alkaline biodegradation of lignin were 2.53 and 7.90, respectively. The results of the gas chromatography mass spectrometry analysis detected compounds such as crotonic acid, lactic acid and 3-hydroxybutanoic acid for acidic conditions, with potential applications for adhesives and polymer precursors. Under alkaline conditions, detected compounds included 2-phenylethanol and dehydroabietic acid, with potential applications for perfumery and anti tumor/anti-inflammatory medications. Size-exclusion chromatography analysis showed that the weight-average molecular weight of the alkaline biodegraded lignin increased by 6.75-fold compared to the acidic method, resulting in a repolymerization of its molecular structure. Lignin repolymerization coincided with an increase in the relative abundance of dehydroabietic acid and isovanillyl alcohol, from 2.70 and 3.96% on day zero to 13.43 and 10.26% on 10th day. The results of the Fourier-transformed Infrared spectroscopy detected the presence of C = O bond and OH functional group associated with carboxylic acids in the acidic method. In the alkaline method there was a greater preponderance of signals related to skeletal aromatic structures, the amine functional group and the C – O – bond. Lignin biodegradation products from E. coli BL21(Lacc), under different initial pH conditions, demonstrated a promising potential to enlarge the spectrum of renewable products for biorefinery activities
BOOLEAN MATRIX DECOMPOSITION AND EXTENSION WITH APPLICATIONS
No full textBoolean matrix decomposition (BMD) refers to decomposing of an input Boolean matrix into a product of two Boolean matrices, where the first matrix represents a set of meaningful concepts, and the second describes how the observed data can be expressed as combinations of those concepts. As opposed to standard matrix factorization, BMD focuses on Boolean data and employs Boolean matrix prod-uct instead of standard matrix product. The key advantage of BMD is that BMD solutions provide much more interpretability, which enable BMD to have wide applications in multiple domains, including role mining, text mining, discrete pat-tern mining, and many others. There are three main challenges in the research of BMD. First, real applica-tions carry varying expectations and constraints on BMD solutions, which make the task of searching for a good BMD solution nontrivial. Second, BMD by itself has the issue of insufficiency in modeling some real data semantics, as only the set union operation is employed in combination. Third, BMD variants are generally i
High Efficiency Industrial p-type PERC and PERT Crystalline Silicon Solar Cells: Boron Junction Doping and Surface Passivation
No full textAs photovoltaic (PV) energy will gradually become one of the main renewable energy sources to replace conventional energy sources in the next decades, industry needs to pay attention to mass production of cost-efficient solar cells. At present, p-type crystalline silicon (c-Si) solar cell is the mainstream cell product in PV industry due to cost-efficiency. In p-type c-Si solar cells, industrial PERC (Passivated Emitter and Rear Cell) and PERT (Passivated Emitter and Rear Totally-diffused) cells are two potential candidates towards even higher cost-efficiency. To achive this, a systematic study is needed on both PERC and PERT cells from an industrial research perspective, which is the aim of this thesis.The first part of the thesis studies the industrial PERC cell. The key processes of Al2O3 passivation and screen-printing aluminium local back surface field, as well as integration of the entire PERC process are discussed, based on which a cost-efficient industrial PERC roadmap is presented. The loss mechanisms of cell efficiency and recombination are analyzed based on key characterizations combined with PC1D/PC2D simulations, and effective solutions are put forward to decrease these losses and thus to increase cell efficiency.
The second part of the thesis presents a study on boron implanted junction, junction passivation and metal/p+-Si ohmic contact, as well as their application into the industrial p-PERT cells. Firstly, the focus is placed on the impact of junction profile and surface passivation on boron emitter quality, which can be influenced by implantation and anneal parameters. High-quality boron emitters passivated with in-situ grown SiO2 are obtained. Secondly, a novel junction passivation scheme using SiO2/Al2O3/SiNx is presented, which demonstrates effective passivation on both p+ and n+ emitters due to an excellent chemical passivation combined with a weak field-effect passivation. Then, an industrial roadmap for p-PERT is presented, which is based on fully ion implanted (boron and phosphorus) technology and the presented two junction passivation schemes. The cell results indicate that p-PERT cell using this roadmap is promising candidate for the PV industry.
The final part of the thesis presents an outlook for a future roadmap extending the cell efficiency of industrial p-type c-Si solar cells towards and beyond 24%
Fault gouge graphitization as evidence of past seismic slip
No full textOne moderate- to large-magnitude earthquake (M > 6) nucleates in Earth's crust every three days n average, but the geological record of ancient fault slip at meters-per-second seismic velocities (as opposed to subseismic slow-slip creep) remains debated because of the lack of established fault-zone evidence of seismic slip. Here we show that the irreversible temperature-dependent transformation of carbonaceous material (CM, a constituent of many fault gouges) into graphite is a reliable tracer of seismic fault slip. We sheared CM-bearing fault rocks in the laboratory at just above subseismic and at seismic velocities under both water-rich and water-deficient conditions and modeled the temperature evolution with slip. By means of micro-Raman spectroscopy and focused-ion beam transmission electron microscopy, we detected graphite grains similar to those found in the principal slip zone of the A.D. 2008 Wenchuan (Mw 7.9) earthquake (southeast Tibet) only in experiments conducted at seismic velocities. The experimental evidence presented here suggests that high-temperature pulses associated with seismic slip induce graphitization of CM. Importantly, the occurrence of graphitized fault-zone CM may allow us to ascertain the seismogenic potential of faults in areas worldwide with incomplete historical earthquake catalogues.</p
Over-expression of the Arabidopsis proton-pyrophosphatase AVP1 enhances transplant survival, root mass, and fruit development under limiting phosphorus conditions
No full textabstract: Phosphorus (P), an element required for plant growth, fruit set, fruit development, and fruit ripening, can be deficient or unavailable in agricultural soils. Previously, it was shown that over-expression of a proton-pyrophosphatase gene AVP1/AVP1D (AVP1DOX) in Arabidopsis, rice, and tomato resulted in the enhancement of root branching and overall mass with the result of increased mineral P acquisition. However, although AVP1 over-expression also increased shoot biomass in Arabidopsis, this effect was not observed in tomato under phosphate-sufficient conditions. AVP1DOX tomato plants exhibited increased rootward auxin transport and root acidification compared with control plants. AVP1DOX tomato plants were analysed in detail under limiting P conditions in greenhouse and field trials. AVP1DOX plants produced 25% (P=0.001) more marketable ripened fruit per plant under P-deficient conditions compared with the controls. Further, under low phosphate conditions, AVP1DOX plants displayed increased phosphate transport from leaf (source) to fruit (sink) compared to controls. AVP1DOX plants also showed an 11% increase in transplant survival (P<0.01) in both greenhouse and field trials compared with the control plants. These results suggest that selection of tomato cultivars for increased proton pyrophosphatase gene expression could be useful when selecting for cultivars to be grown on marginal soils
Silicon Surface Passivation by Mixed Aluminum Precursors in Al2O3 Atomic Layer Deposition
No full textDimethylaluminum chloride (DMACl) is a cost-effective aluminium precursor alternative to conventional trimethylaluminium (TMA) for Atomic Layer Deposited (ALD) Al2O3. The DMACl water process shows better passivation after high temperature firing when compared with conventional TMA water process. However, after low-temperature post-anneal its passivation quality is slightly worse than with TMA. Here we show that a mixed use of TMA and DMACl precursors in the ALD process results in better surface passivation both after 400 °C post-anneal and after an 800 °C firing step. The high-quality passivation results from the low interface defect density and high negative charge at the surface. Specifically, we investigate the role of chlorine in the ALD Al2O3 passivation by varying the TMA and DMACl pulse proportions.Peer reviewe
Metal-Free Catalytic Preparation of Graphene Films on a Silicon Surface Using CO as a Carbon Source in Chemical Vapor Deposition
No full textThe metal-free synthesis of graphene films on Si substrates, the most common commercial semiconductors, is of paramount significance for graphene application on semiconductors and in the field of electronics. However, since current research mainly uses C-H gas as the carbon source in chemical vapor deposition (CVD), and Si does not have a catalytic effect on the decomposition and adsorption of C-H gas, it is challenging to prepare high-quality graphene on the Si surface directly. In this work, we report the growth of graphene directly on Si without metal catalysis by CVD using CO was selected as the carbon source. By controlling the growth temperature (1000–1150 °C), a process of 2–5 layers of graphene growth on silicon was developed. The electrical performance results showed that the graphene film had a sheet resistance of 79 Ω/sq, a resistivity of 7.06 × 10−7 Ω·m, and a carrier migration rate of up to 1473.1 cm2 V−1·S−1. This work would be a significant step toward the growth of graphene on silicon substrates with CO as the carbon source
Design of infrared signal processing system based on ZYNQ platform
No full text
A newly developed real-time infrared signal processing system based on the heterogeneous multi-processor system on chip (MPSoC) is proposed in this paper. The architecture, hardware configuration, image pre-processing algorithms used in the system and the experimental result are presented. Compared to the infrared signal processing system in being, Xilinx Zynq-7000 All Programmable SoC has been used in the proposed system which is more portable, integrated, and has excellent performance during its signal processing.</p
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