Effect of Stretching on Electrical Properties of Low Density Polyethylene/MgO Nanocomposites

Pulsed electroacoustic (PEA) method, dielectric analyzer, and high resistance meter were used to research the DC breakdown, space charge behavior, permittivity, loss tangent, and volume resistivity of neat low density polyethylene (LDPE) and LDPE/MgO nanocomposites with concentration of 1, 3, and 5 wt% with and without the elongation ratio of 1.1. Results indicate that the DC breakdown strengths of neat LDPE and nanocomposites decrease after stretching. The heterocharges near electrodes in neat LDPE change to homocharges after stretching and a large amount of positive and negative charges accumulated in samples with concentration of 3 and 5 wt%. Meanwhile, homocharges near cathode electrode in nanocomposite with concentration of 1 wt% decrease a little and a small amount of positive charges were observed in the samples after stretching. Furthermore, there are different increases in amplitudes of permittivity in all the samples after stretching, as well as the loss of tangents especially in the frequency domain from 10−1 to 102 Hz. The results of volume resistivity show that comparing with the nanocomposite with the concentration of 1 wt% whose volume resistivity decrease after stretching, larger volume resistivity is observed in neat LDPE and nanocomposites with the concentration of 3 and 5 wt%

Effects of Fasting on the Oral Microbiome

Humans are mostly made up of microbes. Multiple studies have estimated that bacterial cells outnumber human cells in the body, with our digestive systems harboring the highest concentrations of bacterial life. The oral microbiome is densely populated and of significant physiological importance. These microbial communities maintain tooth and gum health, aids in pre-digestion of foods, and even plays a defensive role — guarding their host from external threats that may lead to oral and systemic pathologies. Studies have shown that fasting can affect the gut microbiome, but there is currently insufficient research on how fasting intervals can affect the oral microbiome. This study will compare the oral microbiome of subjects with similar dietary and oral hygiene habits (n=3) before and after a 24-hour fasting period. If the abundance and diversity of bacteria in the subjects’ mouths change in a consistent and significant manner, then intermittent fasting could play a role in reshaping the oral microbiome and influence human wellbeing

Individual Parametric Insurance Product Design

This report presents a design of a parametric insurance product for individual consumers in two neighboring countries Ambernϊa and Palȍmϊnϊa. Unlike traditional insurance, this product issues a predetermined payout to a policyholder when a pre-agreed event has been triggered. By conducting analyses on given health data in the countries, we first projected individual losses and calculated premiums according to gender, age and risk factor information. Then we defined triggering events and modeled the payout scheme for our product. Comprehensive strategies are also provided for marketing and risk mitigation

Doxycycline Regulated Induction of AKT in Murine Prostate Drives Proliferation Independently of p27 Cyclin Dependent Kinase Inhibitor Downregulation

The PI3 kinase/AKT pathway has been shown to increase degradation of the p27 cyclin dependent kinase inhibitor through phosphorylation of consensus AKT sites on p27 and SKP2, and AKT driven proliferation may be checked by feedback mechanisms that increase p27 expression and induce senescence. However, these AKT sites are not conserved in mouse, and it has not been clear whether AKT negatively regulates murine p27. Transgenic mice with a probasin promoter controlled prostate specific reverse tetracycline transactivator (ARR2Pb-rtTA) were generated and used to achieve doxycycline inducible expression of a tetracycline operon regulated constitutively active myristoylated AKT1 transgene (tetO-myrAKT). Doxycycline induction of myrAKT occurred within 1 day and rapidly induced proliferation (within 4 days) and the development of prostatic intraepithelial neoplasia (PIN) lesions in ventral prostate, which did not progress to prostate cancer. Cells in these lesions expressed high levels of p27, had increased proliferation, and there was apoptosis of centrally located cells. Doxycycline withdrawal resulted in apoptosis of cells throughout the lesions and rapid clearing of hyperplastic glands, confirming in vivo the critical antiapoptotic functions of AKT. Significantly, analyses of prostates immediately after initiating doxycycline treatment further showed that p27 expression was rapidly increased, coincident with the induction of myrAKT and prior to the development of hyperplasia and PIN. These findings establish in vivo that murine p27 is not negatively regulated by AKT and indicate that proliferation in PI3 kinase/AKT pathway driven mouse models is mediated by p27 independent mechanisms that may be distinct from those in human. Further studies using prostate specific doxycycline regulated transgene expression may be useful to assess the acute effects of inducing additional transgenes in adult murine prostate epithelium, and to assess the requirements for continued transgene expression in transgene induced tumors

Effect of Nanoparticle Surface Modification and Filling Concentration on Space Charge Characteristics in TiO 2

This paper focuses on the space charge characteristics in TiO2/cross-linked polyethylene (XLPE) nanocomposites; the unmodified and modified by dimethyloctylsilane (MDOS) TiO2 nanoparticles were added to XLPE matrix with different mass concentrations (1 wt%, 3 wt%, and 5 wt%). The scanning electron microscope (SEM) showed that the MDOS coupling agent could improve the compatibility between TiO2 nanoparticles and XLPE matrix to some extent and reduce the agglomeration of TiO2 nanoparticles compared with unmodified TiO2 nanoparticles; the volume resistivity testing indicated that the volume resistivity of TiO2/XLPE nanocomposites was higher than Pure-XLPE and increased with the increase of filling concentrations. According to the pulsed electroacoustic (PEA) measurements, it was concluded that the space charge accumulation was suppressed by filling TiO2 nanoparticles and the distribution of electric field in samples was improved greatly. In addition, it was found that the injection of homocharge was more obvious in MDOS-TiO2/XLPE than that in UN-TiO2/XLPE and the homocharge injection decreased with the increase of filling concentration

Izdvajanje dihidromiricetina iz lišća biljke Ampelopsis grossedentata mikrovalnom i višefaznom protustrujnom ekstrakcijom

Microwave-assisted extraction (MAE) technique in combination with multi-stage countercurrent extraction (MCE), namely microwave multi-stage countercurrent extraction (MMCE), was evaluated for the extraction of dihydromyricetin (DMY) from Ampelopsis grossedentata. Ethanol, methanol and water were used as extract solvents in the MMCE method. Of the three solvents used, water was found to be the best in extracting DMY from Ampelopsis grossedentata because it had a good extraction yield and is inexpensive, non-toxic and environmentally friendly. The optimal conditions of MMCE for the extraction of DMY can be determined to be the ratio of the extraction solvent to plant material of 30:1, the extraction time of 5 min, the extraction temperature of 110 °C and the microwave power of 600 W. In addition, the extraction efficiency of the MMCE method was compared with that of the microwave static batch extraction (MSBE) under the optimum extraction conditions. It was found that the MMCE method offered higher extraction efficiency than the MSBE method. Thus, the study suggests that the MMCE method provides an alternative technique in terms of both cost and efficiency.Ekstrakcija dihidromiricetina iz lišća biljke Ampelopsis grossedentata pokusno je provedena metodom mikrovalne ekstrakcije u kombinaciji s višefaznom protustrujnom ekstrakcijom. Kao otapalo upotrijebljeni su etanol, metanol i voda. Voda je najbolja za ekstrakciju dihidromiricetina iz Ampelopsis grossedentata jer daje dobro iskorištenje, jeftina je, nije toksična i ekološki je prihvatljiva. Kao optimalni uvjeti ovako kombinirane metode za ekstrakciju dihidromiricetina određeni su: omjer otapala i biljnog materijala 30:1, vrijeme ekstrakcije od 5 min, temperatura od 110 °C i snaga mikrovalova od 600 W. Uspoređujući učinkovitost ove metode s metodom diskontinuirane mikrovalne ekstrakcije u optimalnim uvjetima, vidi se da se veća učinkovitost ekstrakcije postiže višefaznom nego diskontinuiranom mikrovalnom ekstrakcijom. Stoga se, s obzirom na troškove i njezinu učinkovitost, može preporučiti kao alternativna metoda

Effect of Doping Microcapsules on Typical Electrical Performances of Self-Healing Polyethylene Insulating Composite

Polyethylene cables, as important transmission equipment of modern power grid, would inevitably be slightly damaged, which seriously threatens the safety of the power supply. This paper has pioneered the preparation and typical performances of a self-healing polyethylene insulating composite. The self-healing performance to structural damage was verified by tests of electrical and mechanical damage. The effect mechanism of doping microcapsules on the electrical performance of polyethylene was emphatically analyzed. The results show that in appropriate conditions (such as 60 °C/30 min), the composite can not only repair the electrical tree and scratches, but also restore the insulation strength of damaged area. The effect of doping microcapsules on the electrical performances of polyethylene, such as breakdown strength, volumetric resistivity, dielectric properties, and space charge characteristics, are mainly related to impurity and the interface of microcapsule. Polarization and ionization of impurities can reduce the electrical performance of polyethylene. The interface not only improves the microstructure of polyethylene (such as how the heterogeneous nucleation effect increases the number of crystal regions, and the anchoring effect enhances the stability of amorphous regions), but also increases the charge traps. Moreover, the microstructure and charge trap can affect the characteristics of carrier transport, material polarization, and space charge accumulation, thus improving the electrical performance of polyethylene. In addition, the important electrical performance of the composite can meet the basic application requirements of polyethylene insulating material, which has good application prospects

Positive solutions of multi-point boundary value problems

This article concerns the boundary value problem consisting of the nonlinear differential equation $$u''+g(t)f(t,u(t))=0,\quad t\in(0, 1)$$ and the multi-point boundary conditions \displaylines{ u(0)=\alpha u'(0), \cr u(1)=\sum_{i=1}^m\beta_iu(\eta_i)+\sum_{i=1}^m\gamma_iu'(\eta_i), } where $0\leq \alpha \leq\infty$, $0<\eta_1<\eta_1<\eta_{2}<\dots<\eta_m<1$, $\beta_i>0$, $\gamma_i<0$ ($i=1,2,\dots, m$). By using the fixed point index theory, we establish the existences of at least one positive solution and at least two positive solutions

Reliability Evaluation Method for Oil–Paper Insulation in Power Transformers

The overall life of oil-immersed power transformers depends on the long-term life of the oil–paper insulation system throughout continuous operation. Studying the reliability assessment methods for oil–paper insulation can help determine the reliability level of power transformers accurately, and ensure their safe and stable operation. In the present paper, the life of oil–paper insulation is proven to obey the Weibull distribution under eight different temperatures set by the Weibull reliability probability paper; the failure mechanisms of the different temperatures are highly consistent. The Weibull distribution reliability curve cluster of oil–paper insulation is plotted under different temperatures by which an oil–paper insulation reliability assessment method is proposed. Lastly, the statistical validation experiment of the proposed method is conducted, which proves its theoretical validity. Thus, the present study puts forward a simple and effective method for the oil–paper insulation reliability assessment of power transformers under different temperatures at different life stages