Self-Retracting Motion of Graphite Microflakes

We report the observation of a novel phenomenon, the self-retracting motion of graphite, in which tiny flakes of graphite, after being displaced to various suspended positions from islands of highly orientated pyrolytic graphite, retract back onto the islands under no external influences. Our repeated probing and observing such flakes of various sizes indicate the existence of a critical size of flakes, approximately 35 micrometer, above which the self-retracting motion does not occur under the operation. This helps to explain the fact that the self-retracting motion of graphite has not been reported, because samples of natural graphite are typical larger than this critical size. In fact, reports of this phenomenon have not been found in the literature for single crystals of any kinds. A model that includes the static and dynamic shear strengths, the van der Waals interaction force, and the edge dangling bond interaction effect, was used to explain the observed phenomenon. These findings may conduce to create nano-electromechanical systems with a wide range of mechanical operating frequency from mega to giga hertzs

Licochalcone A Protects the Blood–Milk Barrier Integrity and Relieves the Inflammatory Response in LPS-Induced Mastitis

Background/Aims: Mastitis is an acute clinical inflammatory response. The occurrence and development of mastitis seriously disturb women's physical and mental health. Licochalcone A, a phenolic compound in Glycyrrhiza uralensis, has anti-inflammatory properties. Here, we examined the effect of licochalcone A on blood-milk barrier and inflammatory response in LPS-induced mice mastitis.Methods:In vivo, we firstly established mice models of mastitis by canal injection of LPS to mammary gland, and then detected the effect of licochalcone A on pathological indexes, inflammatory responses and blood-milk barrier in this model. In vivo, Mouse mammary epithelial cells (mMECs) were treated with licochalcone A prior to the incubation of LPS, and then the inflammatory responses, tight junction which is the basic structure of blood-milk barrier were analyzed. Last, we elucidated the anti-inflammatory mechanism by examining the activation of mitogen-activated protein kinase (MAPK) and AKT/NF-κB signaling pathways in vivo and in vitro.Result: The in vivo results showed that licochalcone A significantly decreased the histopathological impairment and the inflammatory responses, and improved integrity of blood-milk barrier. The in vitro results demonstrated that licochalcone A inhibited LPS-induced inflammatory responses and increase the protein levels of ZO-1, occludin, and claudin3 in mMECs. The in vivo and in vitro mechanistic study found that the anti-inflammatory effect of licochalcone A in LPS-induced mice mastitis was mediated by MAPK and AKT/NF-κB signaling pathways.Conclusions and Implications: Our experiments collectively indicate that licochalcone A protected against LPS-induced mice mastitis via improving the blood–milk barrier integrity and inhibits the inflammatory response by MAPK and AKT/NF-κB signaling pathways

Polydatin Prevents Lipopolysaccharide (LPS)-Induced Parkinson's Disease via Regulation of the AKT/GSK3β-Nrf2/NF-κB Signaling Axis

Parkinson's disease (PD) is a common neurodegenerative disease characterized by selective loss of dopaminergic neurons in the substantia nigra (SN). Neuroinflammation induced by over-activation of microglia leads to the death of dopaminergic neurons in the pathogenesis of PD. Therefore, downregulation of microglial activation may aid in the treatment of PD. Polydatin (PLD) has been reported to pass through the blood-brain barrier and protect against motor degeneration in the SN. However, the molecular mechanisms underlying the effects of PLD in the treatment of PD remain unclear. The present study aimed to determine whether PLD protects against dopaminergic neurodegeneration by inhibiting the activation of microglia in a rat model of lipopolysaccharide (LPS)-induced PD. Our findings indicated that PLD treatment protected dopaminergic neurons and ameliorated motor dysfunction by inhibiting microglial activation and the release of pro-inflammatory mediators. Furthermore, PLD treatment significantly increased levels of p-AKT, p-GSK-3βSer9, and Nrf2, and suppressed the activation of NF-κB in the SN of rats with LPS-induced PD. To further explore the neuroprotective mechanism of PLD, we investigated the effect of PLD on activated microglial BV-2 cells. Our findings indicated that PLD inhibited the production of pro-inflammatory mediators and the activation of NF-κB pathways in LPS-induced BV-2 cells. Moreover, our results indicated that PLD enhanced levels of p-AKT, p-GSK-3βSer9, and Nrf2 in BV-2 cells. After BV-2 cells were pretreated with MK2206 (an inhibitor of AKT), NP-12 (an inhibitor of GSK-3β), or Brusatol (BT; an inhibitor of Nrf2), treatment with PLD suppressed the activation of NF-κB signaling pathways and the release of pro-inflammatory mediators in activated BV-2 cells via activation of the AKT/GSK3β-Nrf2 signaling axis. Taken together, our results are the first to demonstrate that PLD prevents dopaminergic neurodegeneration due to microglial activation via regulation of the AKT/GSK3β-Nrf2/NF-κB signaling axis

Leitfähigkeit einzelner DNA-Moleküle gemessen mit regelbaren Bruchkontakten

In this thesis, we described our MCBJ setup which enable us to measure the conductivity of single (or a few) molecules at different conditions, ie. in solution, in ambient or in high vacuum. We characterized the performance of setup especially in buffer solution which is not established before. The setup also enables us to monitor the change of conductivity of studied molecules during its conformational change (stretched or relaxed). With the help of this special feature, we studied the conductance of DNA molecules in two different forms, double stranded DNA and G-quadruplex. Transport properties of DNA is important mainly because its potential usage in future nano-electronics. However at present it is limited by its poor measured conductivity. In order to enhance the conductance of the metal-DNA-metal systems, we used a novel protocol to bind the DNA molecules to the gold electrodes. The terminal thymine bases are modified with protected thiol- group at 5 position of the back instead of at backbone, which allow direct coupling between π system of DNA and electrodes. Strong bindings of the DNA to fresh gold surface are observed both with microscopy and during conductance measurement with MCBJ in solution. More important, we measured a higher conductance on the 21bp DNA duplex than results reported before, 0.16 ~ 0.2 mG0 for single DNA conductance in vacuum. Moreover, we studied the conductance of a G-quadruplex with MCBJ. The G-quadruplex has stacked planes made by four guanine bases and trapped ions in the center channel, so it is prospected to have better conductance. We observed a stable conductance plateau during opening and closing the MCBJ, which may corresponds to the unfolding/refolding process of the G-quadruplex. The non-linear I-V curves are qualitatively explained by an "off-resonance tunneling" model. Besides these improvements, the conductance of DNA is still below the requirement to use DNA directly as a conductive nanowire, and its transport mechanism is still not fully understood. Further studies should be done as following: 1. In order to fully understand the transport properties of both DNA duplex and G-quadruplex, detailed knowledge about their band structures are desired. Although our IV curves do show non-linear S-shapes or asymmetric, but quantitative estimate of band structure are impossible because of the thermal fluctuations. This can be realized by doing the measurement at low temperature. The challenge will be modification of our MCBJ setup to fit in the low temperature chamber. The whole setup may need to be redesigned. 2. During opening and closing of the MCBJ, the molecules in the junction, DNA duplex or G-quadruplex, are stretched and further denatured. However, the stretch processes of both molecules under external forces are not well known yet. There is no experimental report on the structure of these stretched molecules. Results from computer simulations are also limited and need to be verified. Moreover in our experiment, we do see some difference on the open-close curves measured in solution and in vacuum, i.e. the long stable plateau measured with dsDNA in solution vanished when measured in vacuum. This difference is attributed to the different stretch process of DNA in solution and in vacuum. So in order to understand the measurement results with MCBJ more quantitatively, we need more knowledge about the stretched structure of molecules (DNA duplex or G-quadruplex) both in solution and in vacuum. 3.In our G-quadruplex sample, the thiol functionality is attached on the terminal thymine bases, which is not part of quartet plane. So electrons from gold electrodes are not directly coupled to the π system of G-quadruplex. In future studies, it is desired to attach thiol functionality to the guanine bases. Only by this way, a good contact in the meaning of conductance measurement between G-quadruplex and gold electrodes can be established, so that we can probe the intrinsic transport properties of G-quadruplex without hindrance by the contact resistance. 4. In our experiments, the G-quadruplex sample has only 22 bases and contains three stacked quartet planes. It is needed to measure the dependence of conductance on the length of G-quadruplex, i.e. more quartet planes. More particular, we can measure the conductance of a G-wire, which is intermolecular G-quadruplex and can have length up to micrometers, by using micro-fabricated electrodes. If the conductance is good enough, it can be directly integrated into nanoelectronic circuit

Thiolated Nucleotides for Immobilisation of DNA Oligomers on Gold Surfaces

Thiols have a strong tendency to be chemisorbed to gold surfaces forming self-assembled monolayers. The feature of strong S-Au bond formation has been exploited in numerous applications including the immobilisation of DNA on gold surfaces for the generation of DNA microarrays or gold electrodes for measuring charge migration mediated by double stranded DNA. To be immobilised on gold, DNA has to be modified with thiol functionalities. Usually, for this purpose oligonucleotides are equipped with thioalkyl moieties at the 5 - or 3 -terminus. These modifications have been employed in studies dedicated to directly measure electrical transport through DNA molecules

Chemical Composition and Isotopic Characteristics of the Carbonate Cements in Sandstone Reservoir Layer of Dongying Sinking

AbstractThe chemical composition of the carbonate cements in reservoir sandstones was determined by the EPMA. The generation sequence is: calcite, dolomite, ferrous calcite, ankerite, and the latest are coarse-grained and fine-grained calcites which are veined. In the MnO-FeO-MgO triangular diagram, the samples fall clearly on the four areas. The carbon and oxygen isotope data on the carbonate cements show that δ13C are from −6.44 to +4.79, δ18O are from −4.25 to −15.21, focused on three areas in the map. The paleosalinity Z from 107 to 133 calculated by the carbon and oxygen isotope value reflects the characteristics that salinity changes are caused by fresh water filling lake water. The average temperature of calcite precipitation calculated by the oxygen isotope value is 650°C, while dolomite precipitation is 70.6°C. The precipitation temperature changes greatly and shows negative correlation with temperature and salinity, which reflects the characteristics of lake sediments

NPC Three-Level Inverter Open-Circuit Fault Diagnosis Based on Adaptive Electrical Period Partition and Random Forest

Fault detection can increase the reliability and efficiency of power electronic converters employed in power systems. Among the converters in the power system, a Neutral Point Clamped (NPC) three-level inverter is most commonly used to drive electric motors. In this paper, a new approach for open-circuit fault detection and location of the NPC three-level inverter for a shifting process using a constant voltage-to-frequency ratio is proposed. In order to diagnose open-circuit fault in as short a time as possible, an adaptive electrical period partition (AEPP) algorithm is proposed to pick single electrical periods from real-time three-phase current signals. The Maximal Overlap Discrete Wavelet Transformation (MODWT) and Park’s Vector Modulus (PVM) are used for feature analysis and normalization of electrical period signals. The statistical characteristics of the electrical period signals are extracted, and a random forest model is constructed to realize the state classification. Compared with the traditional fault diagnosis method, the proposed algorithm finds fault locations quickly and accurately. The effectiveness and accuracy of the proposed algorithm are verified by experiments