Metal-organic chemical vapor deposition of 2D van der Waals materials-The challenges and the extensive future opportunities

The last decade has witnessed significant progress in two-dimensional van der Waals (2D vdW) materials research; however, a number of challenges remain for their practical applications. The most significant challenge for 2D vdW materials is the control of the early stages of nucleation and growth of the material on preferred surfaces to eventually create large grains with digital thickness controllability, which will enable their incorporation into high-performance electronic and optoelectronic devices. This Perspective discusses the technical challenges to be overcome in the metal-organic chemical vapor deposition (MOCVD) growth of 2D group 6 transition metal dichalcogenide (TMD) atomic crystals and their heterostructures, as well as future research aspects in vdW epitaxy for 2D TMDs via MOCVD. In addition, we encourage the traditional MOCVD community to apply their expertise in the field of "2D vdW materials," which will continue to grow at an exponential rate

Taurine reduces ER stress in C. elegans

<p>Abstract</p> <p>Background</p> <p>ER stress is a strong indicator of whether or not a cell is undergoing physiological stress. C. elegans is a practical system of characterizing the effect of ER stress at the <it>in vivo</it> or organismal level.</p> <p>Methods</p> <p>This study characterized taurine’s anti-ER stress potential employing western blotting on ER stress markers and assays of motility, lifespan comparison, and fecundity measurement.</p> <p>Results</p> <p>When treated with tunicamycin, C. elegans showed the typical ER stress symptoms. It showed a higher expression of hsp-70 and skn-1 than the non-treated control. Survivorship significantly decreased under tunicamycin treatment, and the offspring number also decreased. During the synchronized culture under ER stress conditions, the C. elegans showed early signs of aging especially between L3 and L4 within their life span, along with lowered motility. The worms, however, showed a positive response to the taurine treatment under ER stress conditions.</p> <p>Conclusions</p> <p>When C. elegans were treated with taurine before or after the tunicamycin treatment, they showed a less severe level of ER stress, including an enhanced survivorship, increased motility, and augmented fecundity. Taken together, these results strongly indicate that taurine works positively to cope with ER stress from the organismal perspective.</p

A Personalized Recommender System Based on Explanation Facilities Using Collaborative Filtering

Collaborative filtering (CF) is the most successful recommendation method, but its widespread use has exposed some limitations, such as sparsity, scalability, and black box. Many researchers have focused on sparsity and scalability problem but a little has tried to solve the black box problem. Most CF recommender systems are black boxes, providing no transparency into the working of the recommendation. This research suggests an improved CF recommender system with explanation facilities to overcome the black box problem. Explanation facilities make it possible to expose the reasoning and data behind a recommendation. Therefore, explanations provide us with a mechanism for handling errors that come with a recommendation. Furthermore, it is proposed to use web usage mining and product taxonomy to enhance the recommendation quality for e-commerce environment. For such purposes, it is developed a recommender system named WebCF-Exp, Web usage mining driven Collaborative Filtering with Explanation facilities. To test the performance of WebCF-Exp, EBIB research internet shopping mall and explanation interfaces are developed. Experiments are conducted with the data provided by EBIB Research Internet shopping mall

Synthesis and fabrication of graphene-based organic transparent electrodes for flexible optoelectronic devices

Department of Materials Science and EngineeringWith the advance of electronic devices, the continued down-scaling of electronic devices has aroused the thirst for transparent electrodes (TEs) with not only excellent optoelectrical performance but also great mechanical and environmental stabilities. There are various candidates for flexible applications, such as two-dimensional (2D) materials, e.g., graphene (Gr) and transition metal dichalcogenides (TMDs) and one-dimensional (1D) materials, e.g., metal nanowire and carbon nanotube and conducting polymer. However, each candidate material has drawbacks for the use in practical applications. A carbon-based 2D hexagonal structure, graphene has attracted lots of attention, owing to outstanding properties such as, excellent electrical and thermal conductivities, high optical transparency, gas impermeable property and great mechanical properties. However, the graphene films grown by chemical vapor deposition (CVD) are polycrystalline and synthesized on catalytic metal surfaces, leading to deterioration in its unique properties and demands for additional transfer process. As an alternative TE, there is conducting polymer. Among the conducting polymers, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has attracted lots of attentions in organic optoelectronic devices, such as organic light-emitting diodes (OLEDs) and thin film solar cells, due to its solution processability, facile functionalization, flexibility and transparency. The organic materials, however, is vulnerable to oxygen and moisture and its acidic characteristics can damage adjacent metal layers, resulting in a degradation of the device performance. Each representative TE material has huge drawback for the use in optoelectronics. Therefore, it is necessary to design optimal TE structures and establish proper fabrication processes for the use in next-optoelectronic applications. In this thesis, we evaluate that the potential of graphene/PEDOT:PSS organic TE composite for flexible optoelectronic devices. At first, we check the possibility for excellent optoelectrical properties, which is comparable to ITO, and compatibility of graphene/PEDOT:PSS structures via facile functionalization processes. In addition to the property of each materials, clean interfaces is very important for formation of hybrid TE composites and conventional graphene wet transfer process should be revised because the processes hugely affect the surface quality of as-grown graphene. Based on the previous study, we devised two kinds of direct transfer strategies for the fabrication of high-quality and large-area graphene-based composite: (1) Lamination process and (2) transparent and colorless polyimide(TCPI) solution process. The direct fabrication processes without unnecessary organic layer provided excellent optoelectrical properties and better interface conditions between two heterolayers, demonstrating the relevance between optoelectrical properties and interface conditions of the TE composites. Moreover, using hall measurement and Physical Property Measurement System (PPMS), the role of graphene in graphene/functionalized PEDOT:PSS heterostructure was demonstrated in terms of electrical properties. Furthermore, we evaluate the environmental stability of graphene-based organic TE structure under various unfavorable situations, including mechanical stress (e.g., bending and stretching) and exposure to high temperature, humidity, ultraviolet light and so on. Finally, we applied the graphene-based TE to anode for flexible polymer light-emitting diodes (PLEDs). From the harmony of each component in the TE structure, the corresponding PLEDs showed excellent performance with improved current and power efficiencies and mechanical flexibility, exceeding those of indium-tin-oxide anode-based PLEDs. These results suggest that it is important to select and design proper materials and fabrication process for hybrid transparent conducting films in practical optoelectronics.clos

The Proctolin Gene and Biological Effects of Proctolin in the Blood-Feeding Bug, Rhodnius prolixus

We have reinvestigated the possible presence or absence of the pentapeptide proctolin in Rhodnius prolixus and report here the cloning of the proctolin cDNA. The transcript is expressed in the central nervous system (CNS) and some peripheral tissues. The proctolin prepropeptide encodes a single copy of proctolin along with a possible proctolin-precursor-associated peptide. We have biochemically identified proctolin in CNS extracts and shown its distribution using proctolin-like immunoreactivity. Immunostained processes are found on the salivary glands, female and male reproductive tissues, and heart and associated alary muscles. Proctolin-like immunoreactive bipolar neurons are found on the lateral margins of the common oviduct and bursa. Proctolin is biologically active on R. prolixus tissues, stimulating increases in contraction of anterior midgut and hindgut muscles, and increasing heartbeat frequency. Contrary to the previous suggestion that proctolin is absent from R. prolixus, proctolin is indeed present and biologically active in this medically important bug

A Synergistic Anti-Diabetic Effect by Ginsenosides Rb1 and Rg3 through Adipogenic and Insulin Signaling Pathways in 3T3-L1 Cells

Although ginsenosides Rb1 and Rg3 have been identified as the significant ginsenosides found in red ginseng that confer anti-diabetic actions, it is unclear whether insulin-sensitizing effects are mediated by the individual compounds or by their combination. To determine the effect of ginsenosides Rb1 and Rg3 on adipocyte differentiation, 3T3-L1 preadipocytes were induced to differentiate the standard hormonal inducers in the absence or presence of ginsenosides Rb1 or Rg3. Additionally, we determined the effects of Rb1, Rg3, or their combination on the expression of genes related to adipocyte differentiation, adipogenic transcription factors, and the insulin signaling pathway in 3T3-L1 cells using semi-quantitative RT-PCR. Rb1 significantly increased the expression of CEBP alpha, PPAR gamma, and aP2 mRNAs. However, Rg3 exerted its maximal stimulatory effect on these genes at 1 mu M concentration, while a high concentration (50 mu M) showed inhibitory effects. Similarly, treatment with Rb1 and Rg3 (1 mu M) increased the expression of IRS-1, Akt, PI3K, GLUT4, and adiponectin. Importantly, co-treatment of Rb1 and Rg3 (9:1) induced the maximal expression levels of these mRNAs. Our data indicate that the anti-diabetic activity of red ginseng is, in part, mediated by synergistic actions of Rb1 and Rg3, further supporting the significance of minor Rg3

Environmental tobacco smoke and children's health

Passive exposure to tobacco smoke significantly contributes to morbidity and mortality in children. Children, in particular, seem to be the most susceptible population to the harmful effects of environmental tobacco smoke (ETS). Paternal smoking inside the home leads to significant maternal and fetal exposure to ETS and may subsequently affect fetal health. ETS has been associated with adverse effects on pediatric health, including preterm birth, intrauterine growth retardation, perinatal mortality, respiratory illness, neurobehavioral problems, and decreased performance in school. A valid estimation of the risks associated with tobacco exposure depends on accurate measurement. Nicotine and its major metabolite, cotinine, are commonly used as smoking biomarkers, and their levels can be determined in various biological specimens such as blood, saliva, and urine. Recently, hair analysis was found to be a convenient, noninvasive technique for detecting the presence of nicotine exposure. Because nicotine/cotinine accumulates in hair during hair growth, it is a unique measure of long-term, cumulative exposure to tobacco smoke. Although smoking ban policies result in considerable reductions in ETS exposure, children are still exposed significantly to tobacco smoke not only in their homes but also in schools, restaurants, child-care settings, cars, buses, and other public places. Therefore, more effective strategies and public policies to protect preschool children from ETS should be consolidated