WorldWideScience

Sample records for hyicus exfoliative toxin

  1. Production of exfoliative toxin by isolates of Staphylococcus hyicus from different countries

    DEFF Research Database (Denmark)

    Andresen, Lars Ole

    2005-01-01

    A total of 218 isolates of Staphylococcus hyicus from pigs in eight countries (Belgium, Croatia, Germany, Japan, Korea, Slovenia, the UK and the USA) and 44 isolates from other animals in Belgium, India, Japan and the USA were examined for the genes encoding the exfoliative toxins ExhA, ExhB, Exhc...

  2. Staphylococcus hyicus exfoliative toxins selectively digest porcine desmoglein 1

    DEFF Research Database (Denmark)

    Fudaba, Y.; Nishifuji, K.; Andresen, Lars Ole

    2005-01-01

    . Recently, genes for ExhA, ExhB, ExhC and ExhD were cloned. Exfoliative toxins produced by S. aureus have been shown to selectively cleave human or mouse desmoglein 1, a desmosomal adhesion molecule, that when inactivated results in blisters. In this study, we attempted to identify the molecular target...... that Exh selectively degrade porcine desmoglein 1. In vitro incubation of the recombinant extracellular domains of desmoglein I and desmoglein 3 of human, mouse or canine origin demonstrated that only mouse desmogleins 1 alpha and 1 beta were cleaved by ExhA and ExhC at high concentration. Furthermore...

  3. Differentiation and distribution of three types of exfoliative toxin produced by Staphylococcus hyicus from pigs with exudative epidermitis

    DEFF Research Database (Denmark)

    Andresen, Lars Ole

    1998-01-01

    were antigenically distinct. The three toxins were designated ExhA, ExhB and ExhC. From 60 diseased pigs, each representing an outbreak of exudative epidermitis, a total of 584 isolates of S. hl icus were phage typed and tested for production of exfoliative toxin. ExhA-, ExhB- and ExhC-producing S....... hyicus isolates were found in 12 (20%), 20 (33%) and 11 (18%); respectively, of the 60 pig herds investigated. Production of the different types of exfoliative toxin was predominantly associated with certain phage groups. However. toxin production was found in all of the six phage groups defined...

  4. Development and evaluation of an indirect ELISA for detection of exfoliative toxin ExhA, ExhB or ExhC produced by Staphylococcus hyicus

    DEFF Research Database (Denmark)

    Andresen, Lars Ole

    1999-01-01

    Immunoblot analysis and enzyme-linked immunosorbent assay (ELISA) confirmed previous reports that the Staphylococcus hyicus exfoliative toxins ExhA and ExhB are metalloproteins, and further indicated that ExhC is also a metalloprotein. An indirect ELISA. was developed for the detection of toxigenic...... strains as an alternative method to the use of phage typing for selection of S. hyicus isolates to be used in autogenous vaccine against exudative epidermitis in pigs. The indirect ELISA was evaluated by investigating the presence of toxin among a total of 655 S. hyicus isolates from 69 pig skin samples......, one from each of the 69 pig herds with outbreak of exudative epidermitis. Toxigenic S. hyicus were detected in 74% of the cases by ELISA. From each of the five cases, in which initially no toxigenic S. hyicus were found, a further 40 S. hyicus-like colonies were tested in ELISA. Testing of this number...

  5. Studies on the effect of divalent metal ions on exfoliative toxins from Staphylococcus hyicus: indications of ExhA and ExhB being metalloproteins.

    Science.gov (United States)

    Andresen, L O

    1999-04-01

    The exfoliative toxins ExhA and ExhB produced by Staphylococcus hyicus strains NCTC10350 and 1289D-88, respectively, were investigated with regard to the effect of divalent metal ions on toxin production as measured in indirect enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies. Data were obtained as endpoint titer values and used as semiquantitative measures for the amount of exfoliative toxin detected in culture supernatants. It was shown that the endpoint titers of ExhA in supernatants from cultures of strain NCTC10350 grown in the presence of 0.5 mM CaCl2, Cu(NO3)2 or ZnSO4 were higher compared to titers obtained by growth in medium supplemented with a number of other divalent metal salts. The titer of ExhB as determined in the indirect ELISA was increased by addition of 0.5 mM CoCl2, Cu(NO3)2 or CuSO4 to the growth medium. When ExhA or ExhB, prepared without addition of metal salt to the liquid growth medium, was subsequently incubated with 25 mM of Co2+, Cu2+ or Zn2+, the endpoint titers of the toxins were increased. Dialysis of ExhA and ExhB prepared with Zn2+ and Co2+, respectively, against certain metal chelators, resulted in a reduction of the titer determined in ELISA. Other metal chelators had varied effect in the detection of the toxins in ELISA. It was, however, not possible to restore the recognition of toxins by the monoclonal antibodies by incubation of EDDHA-dialyzed toxin preparations with Co2+, Cu2+ or Zn2+. The results of this study suggest that ExhA and ExhB are metalloproteins.

  6. Studies on the effect of divalent metal ions on exfoliative toxins from Staphylococcus hyicus: indications of ExhA and ExhB being metalloproteins

    DEFF Research Database (Denmark)

    Andresen, Lars Ole

    1999-01-01

    determined in ELISA. Other metal chelators had varied effect in the detection of the toxins in ELISA. It was, however, not possible to restore the recognition of toxins by the monoclonal antibodies by incubation of EDDHA-dialyzed toxin preparations with Co2+, Cu2+ or Zn2+. The results of this study suggest...

  7. Comparative genomics of toxigenic and non-toxigenic Staphylococcus hyicus

    DEFF Research Database (Denmark)

    Leekitcharoenphon, Pimlapas; Pamp, Sünje Johanna; Andresen, Lars Ole

    2016-01-01

    The most common causative agent of exudative epidermitis (EE) in pigs is Staphylococcus hyicus. S. hyicus can be grouped into toxigenic and non-toxigenic strains based on their ability to cause EE in pigs and specific virulence genes have been identified. A genome wide comparison between non......-toxigenic and toxigenic strains has never been performed. In this study, we sequenced eleven toxigenic and six non-toxigenic S. hyicus strains and performed comparative genomic and phylogenetic analysis. Our analyses revealed two genomic regions encoding genes that were predominantly found in toxigenic strains...... (polymorphic toxin) and was associated with the gene encoding ExhA. A clear differentiation between toxigenic and non-toxigenic strains based on genomic and phylogenetic analyses was not apparent. The results of this study support the observation that exfoliative toxins of S. hyicus and S. aureus are located...

  8. Superficial Dsg2 Expression Limits Epidermal Blister Formation Mediated by Pemphigus Foliaceus Antibodies and Exfoliative Toxins

    Directory of Open Access Journals (Sweden)

    Donna Brennan

    2010-01-01

    Full Text Available Cell-cell adhesion mediated by desmosomes is crucial for maintaining proper epidermal structure and function, as evidenced by several severe and potentially fatal skin disorders involving impairment of desmosomal proteins. Pemphigus foliaceus (PF and staphylococcal scalded skin syndrome (SSSS are subcorneal blistering diseases resulting from loss of function of the desmosomal cadherin, desmoglein 1 (Dsg1. To further study the pathomechanism of these diseases and to assess the adhesive properties of Dsg2, we employed a recently established transgenic (Tg mouse model expressing Dsg2 in the superficial epidermis. Neonatal Tg and wild type (WT mice were injected with purified ETA or PF Ig. We showed that ectopic expression of Dsg2 reduced the extent of blister formation in response to both ETA and PF Ig. In response to PF Ig, we observed either a dramatic loss or a reorganization of Dsg1-α, Dsg1-β, and, to a lesser extent, Dsg1-γ, in WT mice. The Inv-Dsg2 Tg mice showed enhanced retention of Dsg1 at the cell-cell border. Collectively, our data support the role for Dsg2 in cell adhesion and suggest that ectopic superficial expression of Dsg2 can increase membrane preservation of Dsg1 and limit epidermal blister formation mediated by PF antibodies and exfoliative toxins.

  9. Characteristic bacteriolytic activities of Staphylococcus hyicus.

    OpenAIRE

    Lämmler, C

    1989-01-01

    Staphylococcus hyicus demonstrated characteristic bacteriolytic activities towards a Micrococcus luteus reference strain. This lytic activity was demonstrated on medium containing M. luteus cells as large zones of transparency around the culture streak. Smaller zones of transparency were observed with Staphylococcus intermedius, Staphylococcus chromogenes, and some strains of Staphylococcus aureus but not with other coagulase-negative staphylococcal species. The distribution and extent of the...

  10. Two highly divergent lineages of exfoliative toxin B-encoding plasmids revealed in impetigo strains of Staphylococcus aureus.

    Science.gov (United States)

    Botka, Tibor; Růžičková, Vladislava; Svobodová, Karla; Pantůček, Roman; Petráš, Petr; Čejková, Darina; Doškař, Jiří

    2017-09-01

    Exfoliative toxin B (ETB) encoded by some large plasmids plays a crucial role in epidermolytic diseases caused by Staphylococcus aureus. We have found as yet unknown types of etb gene-positive plasmids isolated from a set of impetigo strains implicated in outbreaks of pemphigus neonatorum in Czech maternity hospitals. Plasmids from the strains of clonal complex CC121 were related to archetypal plasmid pETB TY4 . Sharing a 33-kb core sequence including virulence genes for ETB, EDIN C, and lantibiotics, they were assigned to a stand-alone lineage, named pETB TY4 -based plasmids. Differing from each other in the content of variable DNA regions, they formed four sequence types. In addition to them, a novel unique plasmid pETB608 isolated from a strain of ST130 was described. Carrying conjugative cluster genes, as well as new variants of etb and edinA genes, pETB608 could be regarded as a source of a new lineage of ETB plasmids. We have designed a helpful detection assay, which facilitates the precise identification of the all described types of ETB plasmids. Copyright © 2017 Elsevier GmbH. All rights reserved.

  11. Severity of nonbullous Staphylococcus aureus impetigo in children is associated with strains harboring genetic markers for exfoliative toxin B, Panton-Valentine leukocidin, and the multidrug resistance plasmid pSK41

    NARCIS (Netherlands)

    S. Koning (Sander); A.F. van Belkum (Alex); S.V. Snijders (Susan); J.L. Nouwen (Jan); M. op 't Veld; J.C. van der Wouden (Hans); C.M. Verduin (Cees); H.A. Verbrugh (Henri); W.B. van Leeuwen (Willem); L.W.A. van Suijlekom-Smit (Lisette)

    2003-01-01

    textabstractNonbullous impetigo is a common skin infection in children and is frequently caused by Staphylococcus aureus. Staphylococcal toxins and especially exfoliative toxin A are known mediators of bullous impetigo in children. It is not known whether this is also true for

  12. Development of a phage typing system for Staphylococcus hyicus

    DEFF Research Database (Denmark)

    Wegener, Henrik Caspar

    1993-01-01

    Bacteriophages were released by 98% of 100 Staphylococcus hyicus strains studied after treatment with mitomycin C. Twenty-three phages with different lytic spectra were included in a phage typing system and used f or typing S. hyicus. On a test-set of 100 epidemiologically unrelated S. hyicus...... strains isolated from Danish pig herds, the phages were able to type 92% of the strains, producing 16 different phage types. Reproducibility of the phage typing system after subculture of the strains and using fresh phage stock was 96%. Typability ranged from 52 to 80% when typing porcine strains...... originating from other countries. Although phages were isolated from porcine skin strains exclusively, the system produced phage types in S. hyicus strains of bovine origin. Ten strains of S. aureus and S. chromogenes were not typable by these phages. Strains belonging to one phage type (A/B/C/W) were...

  13. Purification and substrate specificity of Staphylococcus hyicus lipase.

    Science.gov (United States)

    van Oort, M G; Deveer, A M; Dijkman, R; Tjeenk, M L; Verheij, H M; de Haas, G H; Wenzig, E; Götz, F

    1989-11-28

    The Staphylococcus hyicus lipase gene has been cloned and expressed in Staphylococcus carnosus. From the latter organism the enzyme was secreted into the medium as a protein with an apparent molecular mass of 86 kDa. This protein was purified, and the amino-terminal sequence showed that the primary gene product was indeed cleaved at the proposed signal peptide cleavage site. The protein was purified from large-scale preparations after tryptic digestion. This limited proteolysis reduced the molecular mass to 46 kDa and increased the specific activity about 3-fold. Although the enzyme had a low specific activity in the absence of divalent cations, the activity increased about 40-fold in the presence of Sr2+ or Ca2+ ions. The purified lipase has a broad substrate specificity. The acyl chains were removed from the primary and secondary positions of natural neutral glycerides and from a variety of synthetic glyceride analogues. Thus triglycerides were fully hydrolyzed to free fatty acid and glycerol. The enzyme hydrolyzed naturally occurring phosphatidylcholines, their synthetic short-chain analogues, and lysophospholipids to free fatty acids and water-soluble products. The enzyme had a 2-fold higher activity on micelles of short-chain D-lecithins than on micelles composed of the L-isomers. Thus the enzyme from S. hyicus has lipase activity and also high phospholipase A and lysophospholipase activity.

  14. A longitudinal study of Staphylococcus hyicus colonization of vagina of gilts and transmission to piglets

    DEFF Research Database (Denmark)

    Wegener, Henrik Caspar; Skov Jensen, E.W.

    1992-01-01

    High Staphylococcus hyicus colonization rates were found in vaginal samples of healthy breeding sows and in skin samples of their offspring. Twenty-two different phage types were identified among the 720 isolates of S. hyicus examined. Two to 13 different phage types were isolated per herd. Phage...... 24 h after birth were identical to strains isolated 3 weeks after birth from the same litter, indicating that the vaginal strains became part of a stable skin flora....

  15. Antimicrobial susceptibility of Staphylococcus hyicus Isolated from exudative epidermitis in pigs

    DEFF Research Database (Denmark)

    Wegener, Henrik Caspar; Watts, J.L.; Salmon, S.A.

    1994-01-01

    for their activities against 100 S. hyicus strains isolated from pigs with exudative epidermitis. Novobiocin was the most active compound tested, with an MIC for 90% of the strains tested (MIC(90)) of less than or equal to 0.06 mu g/ml. Enrofloxacin, ampicillin, and ceftiofur were the next most active compounds...

  16. Pulsed-field gel electrophoresis of Staphylococcus hyicus and Staphylococcus chromogenes genomic DNA and its taxonomic, epidemiologic and ecologic applications in veterinary medicine.

    Science.gov (United States)

    Shimizu, A; Kloos, W E; Berkhoff, H A; George, C G; Ballard, D N

    1997-06-01

    One hundred and thirty-eight strains of Staphylococcus hyicus and 21 strains of S. chromogenes isolated from animals were analyzed by pulsed-field gel electrophoresis (PFGE) after restriction endonuclease Smal digestion of chromosomal DNA. Eighty-eight strains of S. hyicus from pigs with or without exudative epidermitis (EE) generated 16 to 26 fragments in the size range of chromogenes from pigs and cows generated 17 to 24 fragments ranging from chromogenes strains were more highly conserved than those of S. hyicus. S. chromogenes strains could be distinguished from S. hyicus strains by fragments within the range of 305 to 545 kb. The results indicate that PFGE analysis could be used to distinguish between S. hyicus and S. chromogenes. We conclude that PFGE analysis is a useful tool not only for species or strain identification but also for epidemiologic or ecologic studies of S. hyicus and S. chromogenes.

  17. Thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  18. Exudative epidermitis in pigs caused by toxigenic Staphylococcus chromogenes

    DEFF Research Database (Denmark)

    Andresen, Lars Ole; Ahrens, Peter; Daugaard, Lise

    2005-01-01

    Staphylococcus chromogenes is closely related to Staphylococcus hyicus, which is recognised as the causative agent of exudative epidermitis (EE) in pigs. S. chromogenes is part of the normal skin flora of pigs, cattle and poultry and has so far been considered non-pathogenic to pigs. A strain of S....... chromogenes producing exfoliative toxin type B, ExhB, was identified by the use of a multiplex PCR specific for the exfoliative toxins from S. hyicus. The exfoliative toxin from S. chromogenes reacted in immunoblot analysis with polyclonal and monoclonal antibodies specific to ExhB from S. hyicus and had...... an apparent molecular weight of 30 kDa. Sequencing the gene encoding the exfoliative toxin from S. chromogenes revealed that the molecular weight of the toxin with the signal peptide and the mature toxin was 30,553 and 26,694 Da, respectively. Comparison of the exhB genes from S. chromogenes strain VA654...

  19. Formation of Exfoliation Joints

    Science.gov (United States)

    Martel, S. J.

    2004-12-01

    The Earth's internal stresses interact with the topographic surface to affect many phenomena. Exfoliation joints, or sheeting joints, are widespread manifestations of this interaction. These opening-mode fractures form subparallel to the Earth's surface, bounding roughly concentric slabs of rock that resemble the layers of an onion. They occur worldwide in all major bedrock types, attain in-plane dimensions of hundreds of meters, exert a strong influence on groundwater flow, and help produce spectacular scenery, as in Yosemite National Park. The mechanism that causes them has been enigmatic. They are widely regarded as forming in response to "removal of overburden", but large fractures do not open in rocks merely by relieving a compressive stress. High fluid pressures, thermal effects, rock heterogeneity, and weathering also are rejected as primary causes of these fractures. Tensile stresses normal to the surface are required for large exfoliation fractures to open. Intriguingly, high surface-parallel compressive stresses are widely documented where exfoliation joints occur. Both numerical and analytical solutions for two-dimensional elastic bodies show that localized tensile stresses perpendicular to the ground surface must develop beneath certain topographies subject to strong compressive stresses parallel to the surface. This highly non-intuitive effect reflects the profound influence that topography can have on stresses near the surface of the Earth, and it can explain how exfoliation joints open. The theoretical results also indicate that exfoliation joint distributions could be used to infer the horizontal stresses near the Earth's surface.

  20. DIFFERENTIATION BETWEEN Staphylococcus aureus, S. intermedius AND S. hyicus USING PHENOTYPICAL TESTS AND PCR

    Directory of Open Access Journals (Sweden)

    E. A. GANDRA

    2009-01-01

    Full Text Available

    The aim of this work was to compare the use of two phenotypical tests (beta-galactosidase and acriflavine sensitivity and PCR for the coa and nuc gene sequences, for the identification of three species of coagulase positive staphylococcus (CPS: S. aureus, S. intermedius and S. hyicus. Sixty five staphylococcus isolates, previously characterized as CPS through the coagulase, thermonuclease and catalase production tests and Gram staining, were identified at species level using the beta-galactosidase production tests and sensitivity to acriflavine (7 g.mL-1. At the same time, the DNA of these isolates was extracted and amplified by PCR, using primers for the coa gene, specific for S. aureus, and for the nuc gene, specific for S. intermedius and for S. hyicus. It was possible to differentiate the three species of Staphylococcus through phenotypical tests as well as through the molecular technique. There was no difference in discriminatory power between the two techniques used, but the reproducibility and reliability of the technique based on PCR make this technique more precise.

  1. A model for blister exfoliation

    International Nuclear Information System (INIS)

    Deb, S.K.; Sood, D.K.

    1983-01-01

    We describe a mechanism for exfoliation of blisters by taking into account the temperature rise of the blister cover due to the incident beam heating. The rise in temperature is calculated by solving the time dependent heat conduction equation. The exfoliation is initiated either by a local melting or by the reduction of material strength due to the temperature rise leading to rupture of the blister skin by the pressure of the gas in the blister cavity. We propose two types of exfoliation: peripheral and non-peripheral, depending on the blister size. This model agrees well with the various experimental results reported on blister exfoliation. It is argued that this thermally assisted exfoliation of blisters may render the first wall erosion by high energy helium flux more serious than considered hitherto, in an actual fusion reactor system. (author)

  2. Recompressed exfoliated graphite articles

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  3. Stool C difficile toxin

    Science.gov (United States)

    ... toxin; Colitis - toxin; Pseudomembranous - toxin; Necrotizing colitis - toxin; C difficile - toxin ... be analyzed. There are several ways to detect C difficile toxin in the stool sample. Enzyme immunoassay ( ...

  4. Thermal influences on spontaneous rock dome exfoliation

    Science.gov (United States)

    Collins, Brian D.; Stock, Greg M.; Eppes, Martha C.; Lewis, Scott W.; Corbett, Skye C.; Smith, Joel B.

    2018-01-01

    Rock domes, with their onion-skin layers of exfoliation sheets, are among the most captivating landforms on Earth. Long recognized as integral in shaping domes, the exact mechanism(s) by which exfoliation occurs remains enigmatic, mainly due to the lack of direct observations of natural events. In August 2014, during the hottest days of summer, a granitic dome in California, USA, spontaneously exfoliated; witnesses observed extensive cracking, including a ~8000 kg sheet popping into the air. Subsequent exfoliation episodes during the following two summers were recorded by instrumentation that captured—for the first time—exfoliation deformation and stress conditions. Here we show that thermal cycling and cumulative dome surface heating can induce subcritical cracking that culminates in seemingly spontaneous exfoliation. Our results indicate that thermal stresses—largely discounted in dome formation literature—can play a key role in triggering exfoliation and therefore may be an important control for shaping domes worldwide.

  5. Granite Exfoliation, Cosumnes River Watershed, Somerset, California

    Science.gov (United States)

    Crockett, I. Q.; Neiss-Cortez, M.

    2015-12-01

    In the Sierra Nevada foothills of California there are many exposed granite plutons within the greater Sierra Nevada batholith. As with most exposed parts of the batholith, these granite slabs exfoliate. It is important to understand exfoliation for issues of public safety as it can cause rock slides near homes, roads, and recreation areas. Through observation, measuring, and mapping we characterize exfoliation in our Cosumnes River watershed community.

  6. Exfoliation syndrome in Northern Nigeria

    Directory of Open Access Journals (Sweden)

    Idakwo U

    2018-01-01

    Full Text Available Ugbede Idakwo,1 Olusola Olawoye,2 Benedictus GK Ajayi,1 Robert Ritch3 1Eleta Eye Institute, Ibadan, Nigeria; 2Department of Ophthalmology, College of Medicine, University of Ibadan, Ibadan, Nigeria; 3Einhorn Clinical Research Center, Department of Ophthalmology, New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA Purpose: To estimate the frequency of exfoliation syndrome (XFS and its association with ocular diseases in Northern Nigeria.Materials and methods: Consecutive patients who presented to the outpatient department of ECWA Eye Hospital Kano from February 2015 to May 2015 were included in the study. Each patient had a complete ophthalmic examination. The anterior segment examination included tonometry, gonioscopy, and detailed slit-lamp examination to assess for the presence or absence of exfoliation material, inflammatory cells, and other abnormal findings. Patients with exfoliation material on the anterior lens surface and/or pupillary margin in either or both eyes were considered to have XFS. Statistical analysis was performed using the Statistical Package for the Social Sciences version 16.0.Results: A total of 620 patients living in Northern Nigeria from the 6 geopolitical zones were examined. The majority of them (34.5% were indigenous Hausas. There was a male preponderance of 56.6%, while the mean age at presentation for examination in all age groups was 55.7±13.7 years. There were 9 patients with XFS; the frequency was 1.5%, with most of the patients being 70–80 years old. In patients who were ≥50 years, the frequency was 2.5%. Patients with XFS had a higher mean age of 68±4.9 years. The frequency of XFS among glaucoma patients was 4.4%, while among cataract patients it was 3.7%. No other associated ocular disease was found in the patients with XFS.Conclusion: This study shows that XFS does exist in Northern Nigeria, as was found in the South. The prevalence of XFS was, however, not reported in the Nigerian

  7. Separation medium containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

    2012-01-01

    A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

  8. Exudative epidermitis in pigs caused by toxigenic Staphylococcus chromogenes.

    Science.gov (United States)

    Andresen, Lars Ole; Ahrens, Peter; Daugaard, Lise; Bille-Hansen, Vivi

    2005-02-25

    Staphylococcus chromogenes is closely related to Staphylococcus hyicus, which is recognised as the causative agent of exudative epidermitis (EE) in pigs. S. chromogenes is part of the normal skin flora of pigs, cattle and poultry and has so far been considered non-pathogenic to pigs. A strain of S. chromogenes producing exfoliative toxin type B, ExhB, was identified by the use of a multiplex PCR specific for the exfoliative toxins from S. hyicus. The exfoliative toxin from S. chromogenes reacted in immunoblot analysis with polyclonal and monoclonal antibodies specific to ExhB from S. hyicus and had an apparent molecular weight of 30 kDa. Sequencing the gene encoding the exfoliative toxin from S. chromogenes revealed that the molecular weight of the toxin with the signal peptide and the mature toxin was 30,553 and 26,694 Da, respectively. Comparison of the exhB genes from S. chromogenes strain VA654 and S. hyicus strain 1289D-88 showed differences in seven base pairs of the DNA sequences and in two amino acid residues in the deduced amino acid sequences. Pigs were experimentally inoculated with S. chromogenes strain VA654. By clinical observations and histopathological evaluation of the skin alterations, all pigs revealed development of generalized exudative epidermitis. No toxin producing S. hyicus was isolated from the pigs and all ExhB-positive bacterial isolates were identified as S. chromogenes. This confirmed that the disease-causing agent was the inoculated S. chromogenes strain VA654. The results of this study show that S. chromogenes may cause exudative epidermitis in pigs.

  9. Polyamine toxins

    DEFF Research Database (Denmark)

    Strømgaard, Kristian; Jensen, Lars S; Vogensen, Stine B

    2005-01-01

    Polyamine toxins, isolated from spiders and wasps, have been used as pharmacological tools for the study of ionotropic receptors, but their use have so far been hampered by their lack of selectivity. In this mini-review, we describe how careful synthetic modification of native polyamine toxins ha...

  10. Characterization of recombinant fusion constructs of human b1,4-galactosyltransferase 1 and the lipase pre-propeptide from Staphylococcus hyicus

    Czech Academy of Sciences Publication Activity Database

    Sauerzapfe, B.; Namdjou, D-J.; Schumacher, T.; Linden, N.; Křenek, Karel; Křen, Vladimír; Elling, L.

    2008-01-01

    Roč. 50, 2-4 (2008), s. 128-140 ISSN 1381-1177 R&D Projects: GA AV ČR IAA400200503; GA MŠk(CZ) LC06010; GA MŠk OC D25.001 Grant - others:AV ČR(CZ) Bilateral DAAD-AVCR project PPP-D7-CZ 26/04–05D/03/44448 Institutional research plan: CEZ:AV0Z50200510 Keywords : fusion protein * lipase propeptide * staphylococcus hyicus Subject RIV: CC - Organic Chemistry Impact factor: 2.015, year: 2008

  11. Ultrasound exfoliation of inorganic analogues of graphene.

    Science.gov (United States)

    Stengl, Václav; Henych, Jiří; Slušná, Michaela; Ecorchard, Petra

    2014-04-05

    High-intensity ultrasound exfoliation of a bulk-layered material is an attractive route for large-scale preparation of monolayers. The monolayer slices could potentially be prepared with a high yield (up to 100%) in a few minutes. Exfoliation of natural minerals (such as tungstenite and molybdenite) or bulk synthetic materials (including hexagonal boron nitride (h-BN), hexagonal boron carbon nitride (h-BCN), and graphitic carbon nitride (g-C3N4)) in liquids leads to the breakdown of the 3D graphitic structure into a 2D structure; the efficiency of this process is highly dependent upon the physical effects of the ultrasound. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were employed to verify the quality of the exfoliation. Herein, this new method of exfoliation with ultrasound assistance for application to mono- and bilayered materials in hydrophobic and hydrophilic environments is presented.

  12. Botulinum toxin

    Directory of Open Access Journals (Sweden)

    Nigam P

    2010-01-01

    Full Text Available Botulinum toxin, one of the most poisonous biological substances known, is a neurotoxin produced by the bacterium Clostridium botulinum. C. botulinum elaborates eight antigenically distinguishable exotoxins (A, B, C 1 , C 2 , D, E, F and G. All serotypes interfere with neural transmission by blocking the release of acetylcholine, the principal neurotransmitter at the neuromuscular junction, causing muscle paralysis. The weakness induced by injection with botulinum toxin A usually lasts about three months. Botulinum toxins now play a very significant role in the management of a wide variety of medical conditions, especially strabismus and focal dystonias, hemifacial spasm, and various spastic movement disorders, headaches, hypersalivation, hyperhidrosis, and some chronic conditions that respond only partially to medical treatment. The list of possible new indications is rapidly expanding. The cosmetological applications include correction of lines, creases and wrinkling all over the face, chin, neck, and chest to dermatological applications such as hyperhidrosis. Injections with botulinum toxin are generally well tolerated and side effects are few. A precise knowledge and understanding of the functional anatomy of the mimetic muscles is absolutely necessary to correctly use botulinum toxins in clinical practice.

  13. Exfoliation of two-dimensional zeolites in liquid polybutadienes

    KAUST Repository

    Sabnis, Sanket; Tanna, Vijesh A.; Li, Chao; Zhu, Jiaxin; Vattipalli, Vivek; Nonnenmann, Stephen S.; Sheng, Guan; Lai, Zhiping; Winter, H. Henning; Fan, Wei

    2017-01-01

    Layered zeolite precursors were successfully exfoliated by brief shearing or sonication with the assistance of commercially available telechelic liquid polybutadienes at room temperature. The exfoliated zeolite nanosheets can form a stable

  14. Management of exfoliative glaucoma: challenges and solutions.

    Science.gov (United States)

    Holló, Gábor; Katsanos, Andreas; Konstas, Anastasios Gp

    2015-01-01

    Exfoliative glaucoma is the most common type of secondary open-angle glaucoma worldwide. It is characterized by high intraocular pressure (IOP) and worse 24-hour IOP characteristics. In order to minimize progression, treatment of exfoliative glaucoma has to provide a low long-term mean IOP and good 24-hour IOP control. To achieve these goals, fixed-dose combination eye drops, argon and selective laser trabeculoplasty, and various forms of surgery (trabeculectomy, deep sclerectomy, viscocanalostomy, ab interno trabeculotomy, trabecular aspiration, and cataract surgery) all need to be considered during the long-term management of the disease. Since exfoliative glaucoma is a disease of the elderly, and is frequently associated with systemic vascular disease, interdisciplinary consultations are of great clinical importance. These management aspects and the current medical, laser, and surgical results are covered in this review, with a special focus on the needs of the general ophthalmologist.

  15. Liquid phase exfoliated graphene for electronic applications

    Science.gov (United States)

    Sukumaran, Sheena S.; Jinesh, K. B.; Gopchandran, K. G.

    2017-09-01

    Graphene dispersions were prepared using the liquid phase exfoliation method with three different surfactants. One surfactant was used from each of the surfactant types, anionic, cationic, and non-ionic; those used, were sodium dodecylbenzene sulfonate (SDBS), cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP), respectively. Raman spectroscopy was used to investigate the number of layers and the nature of any defects present in the exfoliated graphene. The yield of graphene was found to be less with the non-ionic surfactant, PVP. The deconvolution of 2D peaks at ~2700 cm-1 indicated that graphene prepared using these surfactants resulted in sheets consisting of few-layer graphene. The ratio of intensity of the D and G bands in the Raman spectra showed that edge defect density is high for samples prepared with SDBS compared to the other two, and is attributed to the smaller size of the graphene sheets, as shown in the electron micrographs. In the case of the dispersion in PVP, it is found that the sizes of the graphene sheets are highly sensitive to the concentration of the surfactant used. Here, we have made an attempt to investigate the local density of states in the graphene sheets by measuring the tunnelling current-voltage characteristics. Graphene layers have shown consistent p-type behaviour when exfoliated with SDBS and n-type behaviour when exfoliated with CTAB, with a larger band gap for graphene exfoliated using CTAB. Hence, in addition to the known advantages of liquid phase exfoliation, we found that by selecting suitable surfactants, to a certain extent it is possible to tune the band gap and determine the type of majority carriers.

  16. The porcine skin associated T-cell homing chemokine CCL27: molecular cloning and mRNA expression in piglets infected experimentally with Staphylococcus hyicus

    DEFF Research Database (Denmark)

    Johnsen, C. K.; Jensen, Annette Nygaard; Ahrens, P.

    2003-01-01

    CCL27 (also named CTACK, ALP, ILC and ESkine) is a CC chemokine primarily expressed by keratinocytes of the skin. The cognate receptor of CCL27 named CCR10 (GPR-2), is also expressed in skin-derived cells, and in addition by a subset of peripheral blood T-cells and in a variety of other tissues....... In this paper, we report the cloning of porcine CCL27 cDNA and investigation of CCL27 mRNA expression in Staphylococcus hyicus infected piglets. At the protein level, 77 and 74% homology was found to human and mouse CCL27 sequences, respectively. The results of the expression analyses show that CCL27 m...

  17. Tire containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

  18. Ultrasound exfoliation of inorganic analogues of graphene

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Henych, Jiří; Slušná, Michaela; Ecorchard, Petra

    2014-01-01

    Roč. 9, APR (2014), s. 1-14 ISSN 1556-276X R&D Projects: GA ČR(CZ) GA14-05146S Institutional support: RVO:61388980 Keywords : Ultrasound * Exfoliation * Graphene inorganic analogues Subject RIV: CA - Inorganic Chemistry Impact factor: 2.779, year: 2014

  19. Chronic lymphocytic leukaemia manifestating as exfoliative dermatitis

    Directory of Open Access Journals (Sweden)

    Dhir R

    1995-01-01

    Full Text Available A 60-year-old patient reported with a history of redness and peeling of the skin, and sensations of chills and tightness of the skin of three months duration. Clinical examination revealed exfoliative dermatitis, generalised lymphadenopathy and hepatosplenomegely. A peripheral smear showed features of chronic lymphocytic leukaemia.

  20. Hydrogen Selective Exfoliated Zeolite Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Tsapatsis, Michael [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Daoutidis, Prodromos [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Elyassi, Bahman [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Lima, Fernando [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Iyer, Aparna [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Agrawal, Kumar [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Sabnis, Sanket [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science

    2015-04-06

    The objective of this project was to develop and evaluate an innovative membrane technology at process conditions that would be representative of Integrated Gasification Combined Cycle (IGCC) advanced power generation with pre-combustion capture of carbon dioxide (CO2). This research focused on hydrogen (H2)-selective zeolite membranes that could be utilized to separate conditioned syngas into H2-rich and CO2-rich components. Both experiments and process design and optimization calculations were performed to evaluate the concept of ultra-thin membranes made from zeolites nanosheets. In this work, efforts in the laboratory were made to tackle two fundamental challenges in application of zeolite membranes in harsh industrial environments, namely, membrane thickness and membrane stability. Conventional zeolite membranes have thicknesses in the micron range, limiting their performance. In this research, we developed a method for fabrication of ultimately thin zeolite membranes based on zeolite nanosheets. A range of layered zeolites (MWW, RWR, NSI structure types) suitable for hydrogen separation was successfully exfoliated to their constituent nanosheets. Further, membranes were made from one of these zeolites, MWW, to demonstrate the potential of this group of materials. Moreover, long-term steam stability of these zeolites (up to 6 months) was investigated in high concentrations of steam (35 mol% and 95 mole%), high pressure (10 barg), and high temperatures (350 °C and 600 °C) relevant to conditions of water-gas-shift and steam methane reforming reactions. It was found that certain nanosheets are stable, and that stability depends on the concentration of structural defects. Additionally, models that represent a water-gas-shift (WGS) membrane reactor equipped with the zeolite membrane were developed for systems studies. These studies had the aim of analyzing the effect of the membrane reactor integration into IGCC plants

  1. Characterization of exfoliated/delamination kaolinite

    International Nuclear Information System (INIS)

    Sun, Dewen; Li, Bin; Li, Yanfeng; Yu, Cui; Zhang, Bo; Fei, Huafeng

    2011-01-01

    A novel and facile approach for the preparation of exfoliated/delamination kaolinite was reported in this study. Kaolinite was mechanochemically activated by grinding with dimethylsulfoxide in a globe mill for different periods of time, and then the activated samples were treated for several hours at 120 o C to obtain the precursors of kaolinite. The resulting materials were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The experimental data indicated that the clay layers were well exfoliated/delamination under mechanochemical effect in a significantly short intercalation time. The expansion of the basal spacing (d 001 ) of raw kaolinite by 0.40 nm pointed out that the hydrogen bonds between adjacent kaolinite layers were partially broken as a result of the intercalation with dimethylsulfoxide.

  2. Raman spectroscopy and oral exfoliative cytology

    Science.gov (United States)

    Sahu, Aditi; Shah, Nupur; Mahimkar, Manoj; Garud, Mandavi; Pagare, Sandeep; Nair, Sudhir; Krishna, C. Murali

    2014-03-01

    Early detection of oral cancers can substantially improve disease-free survival rates. Ex vivo and in vivo Raman spectroscopic (RS) studies on oral cancer have demonstrated the applicability of RS in identifying not only malignant and premalignant conditions but also cancer-field-effects: the earliest events in oral carcinogenesis. RS has also been explored for cervical exfoliated cells analysis. Exfoliated cells are associated with several advantages like non-invasive sampling, higher patient compliance, transportation and analysis at a central facility: obviating need for on-site instrumentation. Thus, oral exfoliative cytology coupled with RS may serve as a useful adjunct for oral cancer screening. In this study, exfoliated cells from healthy controls with and without tobacco habits, premalignant lesions (leukoplakia and tobacco-pouch-keratosis) and their contralateral mucosa were collected using a Cytobrush. Cells were harvested by vortexing and centrifugation at 6000 rpm. The cellular yield was ascertained using Neubauer's chamber. Cell pellets were placed on a CaF2 window and Raman spectra were acquired using a Raman microprobe (40X objective) coupled HE-785 Raman spectrometer. Approximately 7 spectra were recorded from each pellet, following which pellet was smeared onto a glass slide, fixed in 95% ethanol and subjected to Pap staining for cytological diagnosis (gold standard). Preliminary PC-LDA followed by leave-one-out cross validation indicate delineation of cells from healthy and all pathological conditions. A tendency of classification was also seen between cells from contralateral, healthy tobacco and site of premalignant lesions. These results will be validated by cytological findings, which will serve as the basis for building standard models of each condition.

  3. Raman exfoliative cytology for oral precancer diagnosis

    Science.gov (United States)

    Sahu, Aditi; Gera, Poonam; Pai, Venkatesh; Dubey, Abhishek; Tyagi, Gunjan; Waghmare, Mandavi; Pagare, Sandeep; Mahimkar, Manoj; Murali Krishna, C.

    2017-11-01

    Oral premalignant lesions (OPLs) such as leukoplakia, erythroplakia, and oral submucous fibrosis, often precede oral cancer. Screening and management of these premalignant conditions can improve prognosis. Raman spectroscopy has previously demonstrated potential in the diagnosis of oral premalignant conditions (in vivo), detected viral infection, and identified cancer in both oral and cervical exfoliated cells (ex vivo). The potential of Raman exfoliative cytology (REC) in identifying premalignant conditions was investigated. Oral exfoliated samples were collected from healthy volunteers (n=20), healthy volunteers with tobacco habits (n=20), and oral premalignant conditions (n=27, OPL) using Cytobrush. Spectra were acquired using Raman microprobe. Spectral acquisition parameters were: λex: 785 nm, laser power: 40 mW, acquisition time: 15 s, and average: 3. Postspectral acquisition, cell pellet was subjected to Pap staining. Multivariate analysis was carried out using principal component analysis and principal component-linear discriminant analysis using both spectra- and patient-wise approaches in three- and two-group models. OPLs could be identified with ˜77% (spectra-wise) and ˜70% (patient-wise) sensitivity in the three-group model while with 86% (spectra-wise) and 83% (patient-wise) in the two-group model. Use of histopathologically confirmed premalignant cases and better sampling devices may help in development of improved standard models and also enhance the sensitivity of the method. Future longitudinal studies can help validate potential of REC in screening and monitoring high-risk populations and prognosis prediction of premalignant lesions.

  4. Mechanical exfoliation of two-dimensional materials

    Science.gov (United States)

    Gao, Enlai; Lin, Shao-Zhen; Qin, Zhao; Buehler, Markus J.; Feng, Xi-Qiao; Xu, Zhiping

    2018-06-01

    Two-dimensional materials such as graphene and transition metal dichalcogenides have been identified and drawn much attention over the last few years for their unique structural and electronic properties. However, their rise begins only after these materials are successfully isolated from their layered assemblies or adhesive substrates into individual monolayers. Mechanical exfoliation and transfer are the most successful techniques to obtain high-quality single- or few-layer nanocrystals from their native multi-layer structures or their substrate for growth, which involves interfacial peeling and intralayer tearing processes that are controlled by material properties, geometry and the kinetics of exfoliation. This procedure is rationalized in this work through theoretical analysis and atomistic simulations. We propose a criterion to assess the feasibility for the exfoliation of two-dimensional sheets from an adhesive substrate without fracturing itself, and explore the effects of material and interface properties, as well as the geometrical, kinetic factors on the peeling behaviors and the torn morphology. This multi-scale approach elucidates the microscopic mechanism of the mechanical processes, offering predictive models and tools for the design of experimental procedures to obtain single- or few-layer two-dimensional materials and structures.

  5. Edge orientations of mechanically exfoliated anisotropic two-dimensional materials

    Science.gov (United States)

    Yang, Juntan; Wang, Yi; Li, Yinfeng; Gao, Huajian; Chai, Yang; Yao, Haimin

    2018-03-01

    Mechanical exfoliation is an approach widely applied to prepare high-quality two-dimensional (2D) materials for investigating their intrinsic physical properties. During mechanical exfoliation, in-plane cleavage results in new edges whose orientations play an important role in determining the properties of the as-exfoliated 2D materials especially those with high anisotropy. Here, we systematically investigate the factors affecting the edge orientation of 2D materials obtained by mechanical exfoliation. Our theoretical study manifests that the fractured direction during mechanical exfoliation is determined synergistically by the tearing direction and material anisotropy of fracture energy. For a specific 2D material, our theory enables us to predict the possible edge orientations of the exfoliated flakes as well as their occurring probabilities. The theoretical prediction is experimentally verified by examining the inter-edge angles of the exfoliated flakes of four typical 2D materials including graphene, MoS2, PtS2, and black phosphorus. This work not only sheds light on the mechanics of exfoliation of the 2D materials but also provides a new approach to deriving information of edge orientations of mechanically exfoliated 2D materials by data mining of their macroscopic geometric features.

  6. Exfoliation syndrome: assembling the puzzle pieces.

    Science.gov (United States)

    Pasquale, Louis R; Borrás, Terete; Fingert, John H; Wiggs, Janey L; Ritch, Robert

    2016-09-01

    To summarize various topics and the cutting edge approaches to refine XFS pathogenesis that were discussed at the 21st annual Glaucoma Foundation Think Tank meeting in New York City, Sept. 19-20, 2014. The highlights of three categories of talks on cutting edge research in the field were summarized. Exfoliation syndrome (XFS) is a systemic disorder with a substantial ocular burden, including high rates of cataract, cataract surgery complications, glaucoma and retinal vein occlusion. New information about XFS is akin to puzzle pieces that do not quite join together to reveal a clear picture regarding how exfoliation material (XFM) forms. Meeting participants concluded that it is unclear how the mild homocysteinemia seen in XFS might contribute to the disarrayed extracellular aggregates characteristic of this syndrome. Lysyl oxidase-like 1 (LOXL1) variants are unequivocally genetic risk factors for XFS but exactly how these variants contribute to the assembly of exfoliation material (XFM) remains unclear. Variants in a new genomic region, CACNA1A associated with XFS, may alter calcium concentrations at the cell surface and facilitate XFM formation but much more work is needed before we can place this new finding in proper context. It is hoped that various animal model and ex vivo systems will emerge that will allow for proper assembly of the puzzle pieces into a coherent picture of XFS pathogenesis. A clear understanding of XFS pathogenesis may lead to 'upstream solutions' to reduce the ocular morbidity produced by XFS. © 2015 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  7. Exfoliation of two-dimensional zeolites in liquid polybutadienes

    KAUST Repository

    Sabnis, Sanket

    2017-06-16

    Layered zeolite precursors were successfully exfoliated by brief shearing or sonication with the assistance of commercially available telechelic liquid polybutadienes at room temperature. The exfoliated zeolite nanosheets can form a stable suspension in an organic solvent, providing exciting potential for the fabrication of zeolite membranes, composite materials and hierarchical zeolites.

  8. Botulinum toxin injection - larynx

    Science.gov (United States)

    Injection laryngoplasty; Botox - larynx: spasmodic dysphonia-BTX; Essential voice tremor (EVT)-btx; Glottic insufficiency; Percutaneous electromyography - guided botulinum toxin treatment; Percutaneous indirect laryngoscopy - guided botulinum toxin treatment; ...

  9. Defense against Toxin Weapons

    National Research Council Canada - National Science Library

    Franz, David

    1998-01-01

    .... We typically fear what we do not understand. Although un- derstanding toxin poisoning is less useful in a toxin attack than knowledge of cold injury on an Arctic battlefield, information on any threat reduces its potential to harm...

  10. Surfactant mediated liquid phase exfoliation of graphene

    Science.gov (United States)

    Narayan, Rekha; Kim, Sang Ouk

    2015-10-01

    Commercialization of graphene based applications inevitably requires cost effective mass production. From the early days of research on graphene, direct liquid phase exfoliation (LPE) of graphite has been considered as the most promising strategy to produce high-quality mono or few-layer graphene sheets in solvent dispersion forms. Substantial success has been achieved thus far in the LPE of graphene employing numerous solvent systems and suitable surfactants. This invited review article principally showcase the recent research progress as well as shortcomings of surfactant assisted LPE of graphene. In particular, a comprehensive assessment of the quality and yield of the graphene sheets produced by different categories of the surfactants are summarized. Future direction of LPE methods is also proposed for the eventual success of commercial applications.

  11. Preparation and characterization of exfoliated polyaniline/montmorillonite nanocomposites

    International Nuclear Information System (INIS)

    Narayanan, Binitha N.; Koodathil, Ranjana; Gangadharan, Tripti; Yaakob, Zahira; Saidu, Femina K.; Chandralayam, Soumini

    2010-01-01

    Transition metal ions were exchanged with the interlamellar cations of montmorillonite clays and polymerization of aniline was done within the layers. The delaminated clay layers upon ion exchange resulted in exfoliated polyaniline/clay nanocomposite formation which has profound effects on polymer structure, properties and electrical conduction mechanisms. Here we offer polyaniline (PANI)/montmorillonite exfoliated nanocomposite synthesized through a simple, cheap route which need not require complicated and less economical organophilic modification. The prepared composites were characterized using XRD, FTIR, and TG/DTA to prove exfoliation.

  12. Preparation and characterization of exfoliated polyaniline/montmorillonite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Narayanan, Binitha N., E-mail: binithann@yahoo.co.i [Department of Chemistry, Sree Neelakanta Government Sanskrit College, Pattambi, Palakkad 679306, Kerala (India); Department of Chemical and Process Engineering, Faculty of Engineering, National University of Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Koodathil, Ranjana; Gangadharan, Tripti [Department of Chemistry, Sree Neelakanta Government Sanskrit College, Pattambi, Palakkad 679306, Kerala (India); Yaakob, Zahira [Department of Chemical and Process Engineering, Faculty of Engineering, National University of Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Saidu, Femina K.; Chandralayam, Soumini [Department of Chemistry, Sree Neelakanta Government Sanskrit College, Pattambi, Palakkad 679306, Kerala (India)

    2010-04-15

    Transition metal ions were exchanged with the interlamellar cations of montmorillonite clays and polymerization of aniline was done within the layers. The delaminated clay layers upon ion exchange resulted in exfoliated polyaniline/clay nanocomposite formation which has profound effects on polymer structure, properties and electrical conduction mechanisms. Here we offer polyaniline (PANI)/montmorillonite exfoliated nanocomposite synthesized through a simple, cheap route which need not require complicated and less economical organophilic modification. The prepared composites were characterized using XRD, FTIR, and TG/DTA to prove exfoliation.

  13. Genotoxic and histopathological biomarkers for assessing the effects of magnetic exfoliated vermiculite and exfoliated vermiculite in Danio rerio

    International Nuclear Information System (INIS)

    Cáceres-Vélez, Paolin Rocio; Fascineli, Maria Luiza; Koppe Grisolia, Cesar; Oliveira Lima, Emília Celma de; Sousa, Marcelo Henrique; Morais, Paulo César de; Bentes de Azevedo, Ricardo

    2016-01-01

    Magnetic exfoliated vermiculite is a synthetic nanocomposite that quickly and efficiently absorbs organic compounds such as oil from water bodies. It was developed primarily to mitigate pollution, but the possible adverse impacts of its application have not yet been evaluated. In this context, the acute toxicity of magnetic exfoliated vermiculite and exfoliated vermiculite was herein assessed by genotoxic and histopathological biomarkers in zebrafish (Danio rerio). DNA fragmentation was statistically significant for all groups exposed to the magnetic exfoliated vermiculite and for fish exposed to the highest concentration (200 mg/L) of exfoliated vermiculite, whereas the micronucleus frequency, nuclear abnormalities and histopathological alterations were not statistically significant for the fish exposed to these materials. In the intestinal lumen, epithelial cells and goblet cells, we found the presence of magnetic exfoliated vermiculite and exfoliated vermiculite, but no alterations or presence of the materials-test in the gills or liver were observed. Our findings suggest that the use of magnetic exfoliated vermiculite and exfoliated vermiculite during standard ecotoxicological assays caused DNA damage in D. rerio, whose alterations may be likely to be repaired, indicating that the magnetic nanoparticles have the ability to promote genotoxic damage, such as DNA fragmentation, but not mutagenic effects. - Highlights: • MEV is a synthetic nanocomposite that quickly and efficiently absorbs organic compounds such as oil from water bodies. • The use of MEV and EV during standard ecotoxicological assays caused DNA fragmentation in zebrafish. • The magnetic nanoparticles showed ability to promote genotoxic damage, but did not induce micronucleus in peripheral erythrocytes at 96 h of exposure. • The tested concentrations of MEV and EV do not cause significant histopathological alterations in the gills, liver and intestine of zebrafish.

  14. Genotoxic and histopathological biomarkers for assessing the effects of magnetic exfoliated vermiculite and exfoliated vermiculite in Danio rerio

    Energy Technology Data Exchange (ETDEWEB)

    Cáceres-Vélez, Paolin Rocio; Fascineli, Maria Luiza; Koppe Grisolia, Cesar [Department of Genetics and Morphology, Institute of Biological Sciences, Brasília University, Brasília (Brazil); Oliveira Lima, Emília Celma de [Chemistry Institute, Federal University of Goiás, Goiânia (Brazil); Sousa, Marcelo Henrique [Green Nanotechnology Group, Faculty of Ceilândia, Brasília University, Brasília (Brazil); Morais, Paulo César de [Physics Institute, Brasília University, Brasília (Brazil); Huazhong University of Science and Technology, School of Automation, Wuhan 430074 (China); Bentes de Azevedo, Ricardo, E-mail: razevedo@unb.br [Department of Genetics and Morphology, Institute of Biological Sciences, Brasília University, Brasília (Brazil)

    2016-05-01

    Magnetic exfoliated vermiculite is a synthetic nanocomposite that quickly and efficiently absorbs organic compounds such as oil from water bodies. It was developed primarily to mitigate pollution, but the possible adverse impacts of its application have not yet been evaluated. In this context, the acute toxicity of magnetic exfoliated vermiculite and exfoliated vermiculite was herein assessed by genotoxic and histopathological biomarkers in zebrafish (Danio rerio). DNA fragmentation was statistically significant for all groups exposed to the magnetic exfoliated vermiculite and for fish exposed to the highest concentration (200 mg/L) of exfoliated vermiculite, whereas the micronucleus frequency, nuclear abnormalities and histopathological alterations were not statistically significant for the fish exposed to these materials. In the intestinal lumen, epithelial cells and goblet cells, we found the presence of magnetic exfoliated vermiculite and exfoliated vermiculite, but no alterations or presence of the materials-test in the gills or liver were observed. Our findings suggest that the use of magnetic exfoliated vermiculite and exfoliated vermiculite during standard ecotoxicological assays caused DNA damage in D. rerio, whose alterations may be likely to be repaired, indicating that the magnetic nanoparticles have the ability to promote genotoxic damage, such as DNA fragmentation, but not mutagenic effects. - Highlights: • MEV is a synthetic nanocomposite that quickly and efficiently absorbs organic compounds such as oil from water bodies. • The use of MEV and EV during standard ecotoxicological assays caused DNA fragmentation in zebrafish. • The magnetic nanoparticles showed ability to promote genotoxic damage, but did not induce micronucleus in peripheral erythrocytes at 96 h of exposure. • The tested concentrations of MEV and EV do not cause significant histopathological alterations in the gills, liver and intestine of zebrafish.

  15. Surface Modification of Exfoliated Graphite Nano-Reinforcements, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Phase I results showed that two surface treatments, oxidative plasma and reactive finishes, are effective means of modifying the surface chemistry of exfoliated...

  16. Expansion and exfoliation of graphite to form graphene

    KAUST Repository

    Patole, Shashikan P.; Da Costa, Pedro M. F. J.

    2017-01-01

    Graphene production methods are described based on subjecting non- covalent graphite intercalated compounds, such as graphite bisulfate, to expansion conditions such as shocks of heat and/or microwaves followed by turbulence-assisted exfoliation

  17. Adhesive tape exfoliation: Why it works for graphene

    Science.gov (United States)

    Bohr, Jakob

    2015-03-01

    Single-crystal graphite can be cleaved by the use of an adhesive tape. This was also the initial route for obtaining graphene, a one-layer thick graphite slab. In this letter a few simple and fun considerations are presented in an attempt to shed some light on why this procedure is successful. In particular on the nature of the surprisingly small number of repetitive steps that are needed in order to obtain a single-layer slab. Two frameworks for exfoliation are investigated: parallel exfoliation involving repetitive simultaneous cleaving, the other, serial exfoliation, which involves the repetitive cleaving of a single chunk of graphite. For both cases, parallel and serial exfoliation, it is investigated how many generations of cleavages are needed. An approximate model with the probability distribution expressed as a simple closed form is presented and compared with the simulations.

  18. Bioterrorism: toxins as weapons.

    Science.gov (United States)

    Anderson, Peter D

    2012-04-01

    The potential for biological weapons to be used in terrorism is a real possibility. Biological weapons include infectious agents and toxins. Toxins are poisons produced by living organisms. Toxins relevant to bioterrorism include ricin, botulinum, Clostridium perfrigens epsilson toxin, conotoxins, shigatoxins, saxitoxins, tetrodotoxins, mycotoxins, and nicotine. Toxins have properties of biological and chemical weapons. Unlike pathogens, toxins do not produce an infection. Ricin causes multiorgan toxicity by blocking protein synthesis. Botulinum blocks acetylcholine in the peripheral nervous system leading to muscle paralysis. Epsilon toxin damages cell membranes. Conotoxins block potassium and sodium channels in neurons. Shigatoxins inhibit protein synthesis and induce apoptosis. Saxitoxin and tetrodotoxin inhibit sodium channels in neurons. Mycotoxins include aflatoxins and trichothecenes. Aflatoxins are carcinogens. Trichothecenes inhibit protein and nucleic acid synthesis. Nicotine produces numerous nicotinic effects in the nervous system.

  19. Group B streptococcus exploits vaginal epithelial exfoliation for ascending infection.

    Science.gov (United States)

    Vornhagen, Jay; Armistead, Blair; Santana-Ufret, Verónica; Gendrin, Claire; Merillat, Sean; Coleman, Michelle; Quach, Phoenicia; Boldenow, Erica; Alishetti, Varchita; Leonhard-Melief, Christina; Ngo, Lisa Y; Whidbey, Christopher; Doran, Kelly S; Curtis, Chad; Waldorf, Kristina M Adams; Nance, Elizabeth; Rajagopal, Lakshmi

    2018-04-09

    Thirteen percent of pregnancies result in preterm birth or stillbirth, accounting for fifteen million preterm births and three and a half million deaths annually. A significant cause of these adverse pregnancy outcomes is in utero infection by vaginal microorganisms. To establish an in utero infection, vaginal microbes enter the uterus by ascending infection; however, the mechanisms by which this occurs are unknown. Using both in vitro and murine models of vaginal colonization and ascending infection, we demonstrate how a vaginal microbe, group B streptococcus (GBS), which is frequently associated with adverse pregnancy outcomes, uses vaginal exfoliation for ascending infection. GBS induces vaginal epithelial exfoliation by activation of integrin and β-catenin signaling. However, exfoliation did not diminish GBS vaginal colonization as reported for other vaginal microbes. Rather, vaginal exfoliation increased bacterial dissemination and ascending GBS infection, and abrogation of exfoliation reduced ascending infection and improved pregnancy outcomes. Thus, for some vaginal bacteria, exfoliation promotes ascending infection rather than preventing colonization. Our study provides insight into mechanisms of ascending infection by vaginal microbes.

  20. Radiolabelling of cholera toxin

    Energy Technology Data Exchange (ETDEWEB)

    Santos, R.G.; Neves, Nicoli M.J. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil); Abdalla, L.F.; Brandao, R.L.; Etchehebehere, L. [Ouro Preto Univ., MG (Brazil). Escola de Farmacia. Lab. de Fisiologia e Bioquimica de Microorganismos; Lima, M.E. de [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Inst. de Ciencias Biologicas. Dept. de Bioquimica e Imunologia; Nicoli, J.R. [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Inst. de Ciencias Biologicas. Dept. de Microbiologia

    1999-11-01

    Binding of cholera toxin to ganglioside receptors of enterocyte microvilli catalyzes the activation of adenylate cyclase causing a rise in cAMP which final result is a copious diarrhea. Saccharomyces boulardii, a nonpathogenic yeast has been used to prevent diarrhea. Although the antidiarrheic properties of S. boulardii are widely recognized, this yeast has been used on empirical basis, and the mechanism of this protective effect is unknown. The addition of cholera toxin to S. boulardii induces the raising of cAMP that triggers the activation of neutral trehalase. This suggests that toxin specifically binding to cells, is internalized and active the protein phosphorylation cascade. Our objective is labeling the cholera toxin to verify the presence of binding sites on yeast cell surfaces for the cholera toxin. Cholera toxin was radiolabelled with Na {sup 125} I by a chloramine-T method modified from Cuatrecasas and Griffiths et alii. The {sup 125} I-Cholera toxin showed a specific radioactivity at about 1000 cpm/fmol toxin. Biological activity of labeled cholera toxin measured by trehalase activation was similar to the native toxin. (author) 5 refs., 3 figs.; e-mail: nevesmj at urano.cdtn.br

  1. Radiolabelling of cholera toxin

    International Nuclear Information System (INIS)

    Santos, R.G.; Neves, Nicoli M.J.; Abdalla, L.F.; Brandao, R.L.; Etchehebehere, L.; Lima, M.E. de; Nicoli, J.R.

    1999-01-01

    Binding of cholera toxin to ganglioside receptors of enterocyte microvilli catalyzes the activation of adenylate cyclase causing a rise in cAMP which final result is a copious diarrhea. Saccharomyces boulardii, a nonpathogenic yeast has been used to prevent diarrhea. Although the antidiarrheic properties of S. boulardii are widely recognized, this yeast has been used on empirical basis, and the mechanism of this protective effect is unknown. The addition of cholera toxin to S. boulardii induces the raising of cAMP that triggers the activation of neutral trehalase. This suggests that toxin specifically binding to cells, is internalized and active the protein phosphorylation cascade. Our objective is labeling the cholera toxin to verify the presence of binding sites on yeast cell surfaces for the cholera toxin. Cholera toxin was radiolabelled with Na 125 I by a chloramine-T method modified from Cuatrecasas and Griffiths et alii. The 125 I-Cholera toxin showed a specific radioactivity at about 1000 cpm/fmol toxin. Biological activity of labeled cholera toxin measured by trehalase activation was similar to the native toxin. (author)

  2. [Intoxication of botulinum toxin].

    Science.gov (United States)

    Chudzicka, Aleksandra

    2015-09-01

    Botulinum toxin is an egzotoxin produced by Gram positive bacteria Clostridium botulinum. It is among the most potent toxins known. The 3 main clinical presentations of botulism are as follows: foodborne botulism, infant botulism and wound botulism. The main symptom of intoxication is flat muscles paralysis. The treatment is supportive care and administration of antitoxin. In prevention the correct preparing of canned food is most important. Botulinum toxin is accepted as a biological weapon. © 2015 MEDPRESS.

  3. Controlling the properties of graphene produced by electrochemical exfoliation

    International Nuclear Information System (INIS)

    Hofmann, Mario; D Nguyễn, Tuân; Chiang, Wan-Yu; Hsieh, Ya-Ping

    2015-01-01

    The synthesis of graphene with controllable electronic and mechanical characteristics is of significant importance for its application in various fields ranging from drug delivery to energy storage. Electrochemical exfoliation of graphite has yielded graphene with widely varying behavior and could be a suitable approach. Currently, however the limited understanding of the exfoliation process obstructs targeted modification of graphene properties. We here investigate the process of electrochemical exfoliation and the impact of its parameters on the produced graphene. Using in situ optical and electrical measurements we determine that solvent intercalation is the required first step and the degree of intercalation controls the thickness of the exfoliated graphene. Electrochemical decomposition of water into gas bubbles causes the expansion of graphite and controls the functionalization and lateral size of the exfoliated graphene. Both process steps proceed at different time scales and can be individually addressed through application of pulsed voltages. The potential of the presented approach was demonstrated by improving the performance of graphene-based transparent conductors by 30times. (paper)

  4. Standard guide for conducting exfoliation corrosion tests in aluminum alloys

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1992-01-01

    1.1 This guide differs from the usual ASTM standard in that it does not address a specific test. Rather, it is an introductory guide for new users of other standard exfoliation test methods, (see Terminology G 15 for definition of exfoliation). 1.2 This guide covers aspects of specimen preparation, exposure, inspection, and evaluation for conducting exfoliation tests on aluminum alloys in both laboratory accelerated environments and in natural, outdoor atmospheres. The intent is to clarify any gaps in existent test methods. 1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  5. The mechanisms of surface exfoliation in H and He implanted Si crystals

    International Nuclear Information System (INIS)

    Reboh, S.; Mattos, A.A.D. de; Schaurich, F.; Fichtner, P.F.P.; Beaufort, M.F.; Barbot, J.F.

    2011-01-01

    We report on the exfoliation mechanisms in light gas implanted Si. Microstructure characterization, extensive statistical analysis and solid mechanics theory show that exfoliation is caused by microcracks growing close to equilibrium pressure for high fluences. For lower fluences, cracks evolve at under-equilibrium pressure and exfoliation relies on a coalescence mechanism assisted by cleavage. This provides long-range, collective and efficient stress relief for clusters of cracks, causing enhancement of the exfoliation. The physical processes are independent of the irradiation energy.

  6. Expansion and exfoliation of graphite to form graphene

    KAUST Repository

    Patole, Shashikan P.

    2017-07-27

    Graphene production methods are described based on subjecting non- covalent graphite intercalated compounds, such as graphite bisulfate, to expansion conditions such as shocks of heat and/or microwaves followed by turbulence-assisted exfoliation to produce few-layer, high quality graphene flakes. Depending on the approach selected for the exfoliation step, free-flowing graphene powder, graphene slurry, or an aqueous graphene mixture can be obtained. Surfactants can aid in dispersion, and graphene inks can be formed. The parameters of the process are simple, efficient and low-cost enabling therefore the scale- up of production. Applications include electrodes and energy storage devices.

  7. Exfoliation and thermal transformations of Nb-substituted layered titanates

    DEFF Research Database (Denmark)

    Song, H.; Sjåstad, Anja O.; Fjellvåg, Helmer

    2011-01-01

    Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating...... factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates...

  8. Friction anisotropy-driven domain imaging on exfoliated monolayer graphene.

    Science.gov (United States)

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Lee, Mi Jung; Park, Bae Ho; Lee, Changgu; Yoon, Duhee; Cheong, Hyeonsik; Lee, Ki Ho; Son, Young-Woo; Park, Jeong Young; Salmeron, Miquel

    2011-07-29

    Graphene produced by exfoliation has not been able to provide an ideal graphene with performance comparable to that predicted by theory, and structural and/or electronic defects have been proposed as one cause of reduced performance. We report the observation of domains on exfoliated monolayer graphene that differ by their friction characteristics, as measured by friction force microscopy. Angle-dependent scanning revealed friction anisotropy with a periodicity of 180° on each friction domain. The friction anisotropy decreased as the applied load increased. We propose that the domains arise from ripple distortions that give rise to anisotropic friction in each domain as a result of the anisotropic puckering of the graphene.

  9. Microalgal toxin(s): characteristics and importance

    African Journals Online (AJOL)

    Prokaryotic and eukaryotic microalgae produce a wide array of compounds with biological activities. These include antibiotics, algicides, toxins, pharmaceutically active compounds and plant growth regulators. Toxic microalgae, in this sense, are common only among the cyanobacteria and dinoflagellates. The microalgal ...

  10. Automotive body panel containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Adamson, Douglas (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    An automotive body panel containing a polymer composite formed of at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g.

  11. Exfoliative Dermatitis Due To Carbamazepine In An Epileptic Patient

    Directory of Open Access Journals (Sweden)

    Ghosh Sadhan Kr

    1995-01-01

    Full Text Available A young epileptic girl of 17 years who was being treated with carbamazepine suddenly developed exanthematous skin eruption all over the body resulting in exfoliative dermatitis within 2 days of onset. The drug was withdrawn and the patient responded well with symptomatic treatment.

  12. Exfoliative liver cytology in Oreochromis mossambicus as a bio ...

    African Journals Online (AJOL)

    The use of exfoliative cytology as a bio-assessment tool was evaluated to (1) identify and describe different cell types of normal liver cytology of Oreochromis mossambicus, (2) identify and describe changes in the cell types after exposure to cadmium and zinc, and (3) determine if non-imaging-guided fine-needle aspiration ...

  13. Evaluation of Efficacy and Toxicity of Exfoliated Silicate Nanoclays as a Feed Additive for Fumonisin Detoxification.

    Science.gov (United States)

    Yuan, Chiao-Wei; Huang, Jie-Ting; Chen, Ching-Chin; Tang, Pin-Chi; Huang, Jenn-Wen; Lin, Jiang-Jen; Huang, San-Yuan; Chen, Shuen-Ei

    2017-08-09

    The efficacy of nanosilicate clay platelets (NSCP), exfoliated silicates from natural montmorillonites, as a feed additive for ameliorating fumonisin B1 (FB1) toxicosis was evaluated. Toxicological mechanisms by NSCP were examined through proteomic and biochemical analyses. Dietary supplementation with NSCP at a low level of 40 mg/kg of feed improved growth performances in chickens with respect to FB1 toxicosis. Other issues of ameliorated symptoms including serum and/or hepatic aspartate aminotransferase activity, oxidative stress indicators, and sphinganine/sphingosine ratio, a hallmark of FB1 toxicosis, were considered. Chickens with NSCP inclusion alone at 1000 mg/kg of feed exhibited no changes in hepatic histology, oxidative status, and serum parameters and even had a higher feed intake. Proteomic analysis with liver tissues identified 45 distinct proteins differentially affected by FB1 and/or NSCP, in which proteins involved in thiol metabolism and redox regulation, glycolysis, carcinogenesis, and detoxification by glutathione S-transferase were promoted by FB1, whereas NSCP caused differential changes of protein abundances related to methionine/cysteine and choline/glycine interconversion for glutathione synthesis, redox regulation by peroxiredoxin, toxin/metabolite delivery by albumin, glycolysis, tricarboxylic acid cycle, adenosine triphosphate (ATP) synthesis, and chaperon escort for endoplasmic reticulum stress relief. Functional analyses confirmed the enhancement of hepatic metabolic processes for ATP and NAD(P)H production to meet the need for detoxification, antioxidative defense, and toxin/metabolite clearance by FB1 or NSCP ingestion. On the basis of the amelioration of FB1 toxicosis, global profile of hepatic protein expressions, and validated toxicological mechanisms, NSCP were concluded as a safe and effective agent for FB1 detoxification.

  14. Topical botulinum toxin.

    Science.gov (United States)

    Collins, Ashley; Nasir, Adnan

    2010-03-01

    Nanotechnology is a rapidly growing discipline that capitalizes on the unique properties of matter engineered on the nanoscale. Vehicles incorporating nanotechnology have led to great strides in drug delivery, allowing for increased active ingredient stability, bioavailability, and site-specific targeting. Botulinum toxin has historically been used for the correction of neurological and neuromuscular disorders, such as torticollis, blepharospasm, and strabismus. Recent dermatological indications have been for the management of axillary hyperhydrosis and facial rhytides. Traditional methods of botulinum toxin delivery have been needle-based. These have been associated with increased pain and cost. Newer methods of botulinum toxin formulation have yielded topical preparations that are bioactive in small pilot clinical studies. While there are some risks associated with topical delivery, the refinement and standardization of delivery systems and techniques for the topical administration of botulinum toxin using nanotechnology is anticipated in the near future.

  15. Role of imprint/exfoliative cytology in ulcerated skin neoplasms.

    Science.gov (United States)

    Ramakrishnaiah, Vishnu Prasad Nelamangala; Babu, Ravindra; Pai, Dinker; Verma, Surendra Kumar

    2013-12-01

    Imprint cytology is a method of studying cells by taking an imprint from the cut surface of a wedge biopsy specimen or from the resected margins of a surgical specimen. It is rapid, simple and fairly accurate. Exfoliative cytology is an offshoot from the imprint cytology where in cells obtained from the surface of ulcers, either by scrape or brush, are analyzed for the presence of malignant cells. We undertook this study to see the role of imprint/exfoliative cytology in the diagnosis of ulcerated skin neoplasm and to check the adequacy of resected margins intra-operatively. This was a prospective investigative study conducted from September 2003 to July 2005. All patients presenting to surgical clinic with ulcerated skin and soft tissue tumours were included in the study. A wedge biopsy obtained from the ulcer and imprint smears were taken from the cut surface. Exfoliative cytology was analyzed from the surface smears. Wedge biopsy specimen was sent for histopathological (HPE) examination. The cytology and HPE were analyzed by a separate pathologist. Imprint cytology was also used to check the adequacy of resected margins in case of wide excision. This was compared with final HPE. Total of 107 patients was included in the present study and 474 imprint smears were done, with an average of 4.43 slides per lesion. Out of 59 wide excision samples, 132 imprint smears were prepared for assessing resected margins accounting for an average of 2.24 slides per each excised lesion. On combining imprint cytology with exfoliative cytology the overall sensitivity, specificity and positive predictive value were 90.38 %, 100 % and 90.38 % respectively. Only one out of 59 cases had a positive resected margin which was not picked by imprint cytology. Imprint cytology can be used for rapid and accurate diagnosis of various skin malignancies. It can also be used to check the adequacy of the resected margin intraoperatively.

  16. Raman spectroscopic studies on exfoliated cells of oral and cervix

    Science.gov (United States)

    Hole, Arti; Sahu, Aditi; Shaikh, Rubina; Tyagi, Gunjan; Murali Krishna, C.

    2018-01-01

    Visual inspection followed by biopsy is the standard procedure for cancer diagnosis. Due to invasive nature of the current diagnostic methods, patients are often non-compliant. Hence, it is necessary to explore less invasive and rapid methods for early detection. Exfoliative cytology is a simple, rapid, and less invasive technique. It is thus well accepted by patients and is suitable for routine applications in population screening programs. Raman spectroscopy (RS) has been increasingly explored for disease diagnosis in the recent past. In vivo RS has previously shown promise in management of both oral and cervix cancers. In vivo applications require on-site instrumentation and stringent experimental conditions. Hence, RS of less invasive samples like exfoliated cells has been explored, as this facilitates collection at multiple screening centers followed by analysis at a centralized facility. In the present study, efficacy of Raman spectroscopy in classification of 15 normal and 29 abnormal oral exfoliated cells specimens and 28 normal and 38 abnormal cervix specimens were explored. Spectra were acquired by Raman microprobe (HE 785, Horiba-Jobin-Yvon, France) from several areas to span the pellet. Spectral acquisition parameters were: microscopic objective: 40X, power: 40 mW, acquisition time: 15 s and average: 3. PCA and PC-LDA of pre-processed spectra was carried out on a 4-model system of normal and tumor of both cervix and oral specimens. Leave-one-out-cross-validation findings indicate 73 % correct classification. Findings suggest RS of exfoliated cells may serve as a patient-friendly, non-invasive, rapid and objective method for management of cervix and oral cancers.

  17. Marine and freshwater toxins.

    Science.gov (United States)

    Hungerford, James M

    2006-01-01

    In a very busy and exciting year, 2005 included First Action approval of a much needed official method for paralytic shellfish toxins and multiple international toxin symposia highlighted by groundbreaking research. These are the first-year milestones and activities of the Marine and Freshwater Toxins Task Force and Analytical Community. Inaugurated in 2004 and described in detail in last year's General Referee Report (1) this international toxins group has grown to 150 members from many regions and countries. Perhaps most important they are now making important and global contributions to food safety and to providing alternatives to animal-based assays. Official Method 2005.06 was first approved in late 2004 by the Task Force and subsequently Official First Action in 2005 (2) by the Methods Committee on Natural Toxins and Food Allergens and the Official Methods Board. This nonproprietary method (3) is a precolumn oxidation, liquid chromatographic method that makes good use of fluorescence detection to provide high sensitivity detection of the saxitoxins. It has also proven to be rugged enough for regulatory use and the highest level of validation. As pointed out in the report of method principle investigator and Study Director James Lawrence, approval of 2005.06 now provides the first official alternative to the mouse bioassay after many decades of shellfish monitoring. This past year in April 2005 the group also held their first international conference, "Marine and Freshwater Toxins Analysis: Ist Joint Symposium and AOAC Task Force Meeting," in Baiona, Spain. The 4-day conference consisted of research and stakeholder presentations and symposium-integrated subgroup sessions on ciguatoxins, saxitoxin assays and liquid chromatography (LC) methods for saxitoxins and domoic acids, okadaiates and azaspiracids, and yessotoxins. Many of these subgroups were recently formed in 2005 and are working towards their goals of producing officially validated analytical methods

  18. Orofacial pain and headaches associated with exfoliation glaucoma.

    Science.gov (United States)

    Noma, Noboru; Iwasa, Mayumi; Young, Andrew; Ikeda, Mariko; Hsu, Yung-Chu; Yamamoto, Maasa; Inoue, Kenji; Imamura, Yoshiki

    2017-12-01

    Exfoliation syndrome is the most common identifiable cause of open-angle glaucoma. The authors report a case of exfoliation glaucoma in a patient who had orofacial pain. A 77-year-old woman was treated at the orofacial pain clinic for left-sided facial pain and headaches of 7 months' duration. Her cataracts and open-angle glaucoma had been diagnosed approximately 3 years earlier. Her main symptoms were orofacial pain, eye redness, inflammation of the eyelids, and eyelid edema. Magnetic resonance imaging showed no evidence of intracranial or extracranial pathology. Hemicrania continua was considered as a possible diagnosis. Indomethacin was prescribed but did not affect her headaches. She then went to an ophthalmologist to rule out secondary headaches. Intraocular pressure was 13 millimeters of mercury in the right eye and 67 mm Hg in the left eye. The ophthalmologist made a diagnosis of exfoliation glaucoma, and the patient underwent surgical treatment for the glaucoma and cataracts. After surgery, she was free of symptoms, and intraocular pressure was 15 mm Hg in the left eye. During differential diagnosis, dentists need to consider intraoral and systemic conditions that can mimic odontogenic or orofacial pain disorders in the patient's medical history and that have a higher incidence associated with the patient's age. Copyright © 2017 American Dental Association. Published by Elsevier Inc. All rights reserved.

  19. Intercalation and Exfoliation of Kaolinite with Sodium Dodecyl Sulfate

    Directory of Open Access Journals (Sweden)

    Xiaochao Zuo

    2018-03-01

    Full Text Available Kaolinite (Kaol was intercalated with dimethyl sulfoxide (DMSO and subsequently methanol (MeOH to prepare intercalation compounds Kaol-DMSO and Kaol-MeOH. Kaol-MeOH was used as an intermediate to synthesize Kaol-sodium dodecyl sulfate (SDS intercalation compound (Kaol-SDS via displacement reaction. The ultrasonic exfoliation of Kaol-SDS produced a resultant Kaol-SDS-U. The samples were characterized by X-ray diffraction (XRD, Fourier transformation infrared spectroscopy (FTIR, thermal analysis, scanning electronic microscopy (SEM, transmission electron microscopy (TEM and particle size analysis. The results revealed that the intercalation of sodium dodecyl sulfate into kaolinite layers caused an obvious increase of the basal spacing from 0.72–4.21 nm. The dehydroxylation temperature of Kaol-SDS was obviously lower than that of original kaolinite. During the intercalation process of sodium dodecyl sulfate, a few kaolinite layers were exfoliated and curled up from the edges of the kaolinite sheets. After sonication treatment, the kaolinite layers were further transformed into nanoscrolls, and the exfoliated resultant Kaol-SDS-U possessed a smaller particle size close to nanoscale.

  20. Toxins of filamentous fungi.

    Science.gov (United States)

    Bhatnagar, Deepak; Yu, Jiujiang; Ehrlich, Kenneth C

    2002-01-01

    Mycotoxins are low-molecular-weight secondary metabolites of fungi. The most significant mycotoxins are contaminants of agricultural commodities, foods and feeds. Fungi that produce these toxins do so both prior to harvest and during storage. Although contamination of commodities by toxigenic fungi occurs frequently in areas with a hot and humid climate (i.e. conditions favorable for fungal growth), they can also be found in temperate conditions. Production of mycotoxins is dependent upon the type of producing fungus and environmental conditions such as the substrate, water activity (moisture and relative humidity), duration of exposure to stress conditions and microbial, insect or other animal interactions. Although outbreaks of mycotoxicoses in humans have been documented, several of these have not been well characterized, neither has a direct correlation between the mycotoxin and resulting toxic effect been well established in vivo. Even though the specific modes of action of most of the toxins are not well established, acute and chronic effects in prokaryotic and eukaryotic systems, including humans have been reported. The toxicity of the mycotoxins varies considerably with the toxin, the animal species exposed to it, and the extent of exposure, age and nutritional status. Most of the toxic effects of mycotoxins are limited to specific organs, but several mycotoxins affect many organs. Induction of cancer by some mycotoxins is a major concern as a chronic effect of these toxins. It is nearly impossible to eliminate mycotoxins from the foods and feed in spite of the regulatory efforts at the national and international levels to remove the contaminated commodities. This is because mycotoxins are highly stable compounds, the producing fungi are ubiquitous, and food contamination can occur both before and after harvest. Nevertheless, good farm management practices and adequate storage facilities minimize the toxin contamination problems. Current research is

  1. Headache and botulinum toxin

    OpenAIRE

    Porta, M.; Camerlingo, M.

    2005-01-01

    The authors discuss clinical and international experience about botulinum toxins (BTX types A and B) in headache treatment. Data from literature suggest good results for the treatment of tensiontype headache, migraine and chronic tension–type headache. In the present paper mechanisms of action and injection sites will also be discussed.

  2. Botulinum Toxin for Rhinitis.

    Science.gov (United States)

    Ozcan, Cengiz; Ismi, Onur

    2016-08-01

    Rhinitis is a common clinical entity. Besides nasal obstruction, itching, and sneezing, one of the most important symptoms of rhinitis is nasal hypersecretion produced by nasal glands and exudate from the nasal vascular bed. Allergic rhinitis is an IgE-mediated inflammatory reaction of nasal mucosa after exposure to environmental allergens. Idiopathic rhinitis describes rhinitis symptoms that occur after non-allergic, noninfectious irritants. Specific allergen avoidance, topical nasal decongestants, nasal corticosteroids, immunotherapy, and sinonasal surgery are the main treatment options. Because the current treatment modalities are not enough for reducing rhinorrhea in some patients, novel treatment options are required to solve this problem. Botulinum toxin is an exotoxin generated by Clostridium botulinum. It disturbs the signal transmission at the neuromuscular and neuroglandular junction by inhibiting the acetylcholine release from the presynaptic nerve terminal. It has been widely used in neuromuscular, hypersecretory, and autonomic nerve system disorders. There have been a lot of published articles concerning the effect of this toxin on rhinitis symptoms. Based on the results of these reports, intranasal botulinum toxin A administration appears to be a safe and effective treatment method for decreasing rhinitis symptoms in rhinitis patients with a long-lasting effect. Botulinum toxin type A will be a good treatment option for the chronic rhinitis patients who are resistant to other treatment methods.

  3. Diffusion of Botulinum Toxins

    Directory of Open Access Journals (Sweden)

    Matthew A. Brodsky

    2012-08-01

    Full Text Available Background: It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion.Methods: This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method. It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB.Results: Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others.Discussion: Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected.

  4. Topical Botulinum Toxin

    OpenAIRE

    Collins, Ashley; Nasir, Adnan

    2010-01-01

    Nanotechnology is a rapidly growing discipline that capitalizes on the unique properties of matter engineered on the nanoscale. Vehicles incorporating nanotechnology have led to great strides in drug delivery, allowing for increased active ingredient stability, bioavailability, and site-specific targeting. Botulinum toxin has historically been used for the correction of neurological and neuromuscular disorders, such as torticollis, blepharospasm, and strabismus. Recent dermatological indicati...

  5. Autoproteolytic Activation of Bacterial Toxins

    Directory of Open Access Journals (Sweden)

    Aimee Shen

    2010-05-01

    Full Text Available Protease domains within toxins typically act as the primary effector domain within target cells. By contrast, the primary function of the cysteine protease domain (CPD in Multifunctional Autoprocessing RTX-like (MARTX and Clostridium sp. glucosylating toxin families is to proteolytically cleave the toxin and release its cognate effector domains. The CPD becomes activated upon binding to the eukaryotic-specific small molecule, inositol hexakisphosphate (InsP6, which is found abundantly in the eukaryotic cytosol. This property allows the CPD to spatially and temporally regulate toxin activation, making it a prime candidate for developing anti-toxin therapeutics. In this review, we summarize recent findings related to defining the regulation of toxin function by the CPD and the development of inhibitors to prevent CPD-mediated activation of bacterial toxins.

  6. Toxins and drug discovery.

    Science.gov (United States)

    Harvey, Alan L

    2014-12-15

    Components from venoms have stimulated many drug discovery projects, with some notable successes. These are briefly reviewed, from captopril to ziconotide. However, there have been many more disappointments on the road from toxin discovery to approval of a new medicine. Drug discovery and development is an inherently risky business, and the main causes of failure during development programmes are outlined in order to highlight steps that might be taken to increase the chances of success with toxin-based drug discovery. These include having a clear focus on unmet therapeutic needs, concentrating on targets that are well-validated in terms of their relevance to the disease in question, making use of phenotypic screening rather than molecular-based assays, and working with development partners with the resources required for the long and expensive development process. Copyright © 2014 The Author. Published by Elsevier Ltd.. All rights reserved.

  7. Percolation scaling in composites of exfoliated MoS2 filled with nanotubes and graphene

    NARCIS (Netherlands)

    Cunningham, G.; Lotya, M.; McEvoy, N.; Duesberg, G.S.; Schoot, van der P.P.A.M.; Coleman, J.N.

    2012-01-01

    Applications of films of exfoliated layered compounds in many areas will be limited by their relatively low electrical conductivity. To address this, we have prepared and characterised composites of a nano-conductor (nanotubes or graphene) embedded in a matrix of exfoliated MoS2 nanosheets. Solvent

  8. Scanning laser polarimetry in eyes with exfoliation syndrome.

    Science.gov (United States)

    Dimopoulos, Antonios T; Katsanos, Andreas; Mikropoulos, Dimitrios G; Giannopoulos, Theodoros; Empeslidis, Theodoros; Teus, Miguel A; Holló, Gábor; Konstas, Anastasios G P

    2013-01-01

    To compare retinal nerve fiber layer thickness (RNFLT) of normotensive eyes with exfoliation syndrome (XFS) and healthy eyes.
 Sixty-four consecutive individuals with XFS and normal office-time intraocular pressure (IOP) and 72 consecutive healthy controls were prospectively enrolled for a cross-sectional analysis in this hospital-based observational study. The GDx-VCC parameters (temporal-superior-nasal-inferior-temporal [TSNIT] average, superior average, inferior average, TSNIT standard deviation (SD), and nerve fiber indicator [NFI]) were compared between groups. Correlation between various clinical parameters and RNFLT parameters was investigated with Spearman coefficient. 
 The NFI, although within normal limits for both groups, was significantly greater in the XFS group compared to controls: the respective median and interquartile range (IQR) values were 25.1 (22.0-29.0) vs 15.0 (12.0-20.0), ppolarimetry-determined RNFLT was lower in XFS eyes with normal IOP. Therefore, close monitoring of RNFLT may facilitate early identification of those XFS eyes that convert to exfoliative glaucoma.

  9. Soluble, Exfoliated Two-Dimensional Nanosheets as Excellent Aqueous Lubricants.

    Science.gov (United States)

    Zhang, Wenling; Cao, Yanlin; Tian, Pengyi; Guo, Fei; Tian, Yu; Zheng, Wen; Ji, Xuqiang; Liu, Jingquan

    2016-11-30

    Dispersion in water of two-dimensional (2D) nanosheets is conducive to their practical applications in fundamental science communities due to their abundance, low cost, and ecofriendliness. However, it is difficult to achieve stable aqueous 2D material suspensions because of the intrinsic hydrophobic properties of the layered materials. Here, we report an effective and economic way of producing various 2D nanosheets (h-BN, MoS 2 , MoSe 2 , WS 2 , and graphene) as aqueous dispersions using carbon quantum dots (CQDs) as exfoliation agents and stabilizers. The dispersion was prepared through a liquid phase exfoliation. The as-synthesized stable 2D nanosheets based dispersions were characterized by UV-vis, HRTEM, AFM, Raman, XPS, and XRD. The solutions based on CQD decorated 2D nanosheets were utilized as aqueous lubricants, which realized a friction coefficient as low as 0.02 and even achieved a superlubricity under certain working conditions. The excellent lubricating properties were attributed to the synergetic effects of the 2D nanosheets and CQDs, such as good dispersion stability and easy-sliding interlayer structure. This work thus proposes a novel strategy for the design and preparation of high-performance water based green lubricants.

  10. A Nanoporous Carbon/Exfoliated Graphite Composite For Supercapacitor Electrodes

    Science.gov (United States)

    Rosi, Memoria; Ekaputra, Muhamad P.; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal

    2010-12-01

    Nanoporous carbon was prepared from coconut shells using a simple heating method. The nanoporous carbon is subjected to different treatments: without activation, activation with polyethylene glycol (PEG), and activation with sodium hydroxide (NaOH)-PEG. The exfoliated graphite was synthesized from graphite powder oxidized with zinc acetate (ZnAc) and intercalated with polyvinyl alcohol (PVA) and NaOH. A composite was made by mixing the nanoporous carbon with NaOH-PEG activation, the exfoliated graphite and a binder of PVA solution, grinding the mixture, and annealing it using ultrasonic bath for 1 hour. All of as-synthesized materials were characterized by employing a scanning electron microscope (SEM), a MATLAB's image processing toolbox, and an x-ray diffractometer (XRD). It was confirmed that the composite is crystalline with (002) and (004) orientations. In addition, it was also found that the composite has a high surface area, a high distribution of pore sizes less than 40 nm, and a high porosity (67%). Noting that the pore sizes less than 20 nm are significant for ionic species storage and those in the range of 20 to 40 nm are very accessible for ionic clusters mobility across the pores, the composite is a promising material for the application as supercapacitor electrodes.

  11. Rockfall triggering by cyclic thermal stressing of exfoliation fractures

    Science.gov (United States)

    Collins, Brian D.; Stock, Greg M.

    2016-01-01

    Exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cliff in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the efficacy of other, more typical rockfall triggers.

  12. Detection of Genes for Superantigen Toxins in Methicillin-Resistant Staphylococcus aureus Clinical Isolates in Karachi

    International Nuclear Information System (INIS)

    Taj, Y.; Fatima, I.; Ali, S. W.; Kazmi, S. U.

    2014-01-01

    Objective: To detect genes for enterotoxins, exfoliative and toxic shock syndrome toxins in Staphylococcus aureus (S. aureus) strains isolated from clinical specimens. Study Design: Cross-sectional observational study. Place and Duration of Study: Department of Molecular Genetics, Dr. Ziauddin Hospital, Karachi, from January to December 2010. Methodology: Two hundred and ninety eight S. aureus clinical isolates were obtained from various clinical samples received at Dr. Ziauddin Hospital, Karachi. Out of these, 115 were detected as methicillin resistant (MRSA) by cefoxitin disk diffusion test showing a prevalence rate of 38.6%. Detection of individual toxin genes was performed by Polymerase Chain Reaction (PCR) by using only one primer pair for each tube. Uniplex primers were preferred as multiplex primers are longer in base pairs and have the potential for cross reaction due to non-specific binding and increase in optimization time. Results: The possession of a single gene or more than a single gene in MRSA isolates was found in 61.73% of clinical samples; the highest number was found in pus swab, followed by sputum, blood, urethral swab, and urine. The prevalence of toxin genes was higher in MRSA as compared to methicillin sensitive (MSSA) isolates (19.12%). Conclusion: PCR detects strains possessing toxin genes independent of their expression. The possession of genes for super-antigens seems to be a frequent and habitual trait of S. aureus more so in MRSA. (author)

  13. The toxins of Cyanobacteria.

    Science.gov (United States)

    Patocka, J

    2001-01-01

    Cyanobacteria, formerly called "blue-green algae", are simple, primitive photosynthetic microorganism wide occurrence in fresh, brackish and salt waters. Forty different genera of Cyanobacteria are known and many of them are producers of potent toxins responsible for a wide array of human illnesses, aquatic mammal and bird morbidity and mortality, and extensive fish kills. These cyanotoxins act as neurotoxins or hepatotoxins and are structurally and functionally diverse, and many are derived from unique biosynthetic pathways. All known cyanotoxins and their chemical and toxicological characteristics are presented in this article.

  14. One-step exfoliation and surface modification of lamellar hydroxyapatite by intercalation of glucosamine

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Honglin [Research Institute for Biomaterials and Transportation, East China Jiaotong University, Nanchang, 330013 (China); School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Li, Wei; Ji, Dehui [Research Institute for Biomaterials and Transportation, East China Jiaotong University, Nanchang, 330013 (China); Zuo, Guifu [Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials, College of Materials Science and Engineering, Hebei United University, Tangshan, 063009 (China); Xiong, Guangyao, E-mail: xiongguangyao@163.com [Research Institute for Biomaterials and Transportation, East China Jiaotong University, Nanchang, 330013 (China); Zhu, Yong [School of Chemical Engineering, Tianjin University, Tianjin, 300072 (China); Li, Lili; Han, Ming [Research Institute for Biomaterials and Transportation, East China Jiaotong University, Nanchang, 330013 (China); Wu, Caoqun [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Wan, Yizao, E-mail: yzwantju@126.com [Research Institute for Biomaterials and Transportation, East China Jiaotong University, Nanchang, 330013 (China); School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China)

    2016-04-15

    Effective exfoliation is crucial to the application of layered materials in many fields. Herein, we report a novel effective, scalable, and ecofriendly method for the exfoliation of lamellar HAp by glucosamine intercalation such that individual HAp nanoplates can be obtained. The as-exfoliated HAp nanoplates were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric (TG) analysis. It is found that the glucosamine intercalation not only results in complete exfoliation of lamellar HAp but also introduces the glucosamine molecules onto the surface of individual HAp nanoplates, thus obtaining separated glucosamine-grafted HAp nanoplates (Glu-HAps). Results from MTT assay demonstrate that glucosamine grafting on HAp nanoplates greatly improves the cell growth and proliferation as compared to nongrafted HAp counterparts. - Highlights: • Glucosamine was used as intercalation agent to exfoliate lamellar hydroxyapatite. • Glucosamine was grafted onto the as-exfoliated nanoplate-like hydroxyapatite. • Exfoliation and surface grafting were accomplished in one step. • Glucosamine-grafted HAp showed improved biocompatibility over nongrafted one.

  15. Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide

    Directory of Open Access Journals (Sweden)

    Simona eLongo

    2013-11-01

    Full Text Available Supercritical carbon dioxide (scCO2 treatments of a montmorillonite (MMT intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline δ form of syndiotactic polystyrene (s-PS, have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersion of the clay layers, higher elastic modulus and larger surface area than aerogels with the intercalated OMMT. Extremely light materials with relevant transport properties could be prepared. Moreover, s-PS-based aerogels with exfoliated OMMT could be helpful for the handling of exfoliated clay minerals.

  16. Acetone improves the topographical homogeneity of liquid phase exfoliated few-layer black phosphorus flakes.

    Science.gov (United States)

    Gomez Perez, Juan; Konya, Zoltan; Kukovecz, Akos

    2018-06-12

    Liquid phase exfoliation of 2D materials has issues related to the sorption of the solvent, the oxidation of the sample during storage, and the topographical inhomogeneity of the exfoliated material. N-methyl-2-pyrrolidone (NMP), a common solvent for black phosphorus (BP) exfoliation, has additional drawbacks like the formation of by-products during sonication and poor solvent volatility. Here we demonstrate an improvement in the topographical homogeneity (i.e. thickness and lateral dimensions) of NMP-exfoliated BP flakes after resuspension in acetone. The typical size of monolayers and bilayers stabilised in acetone was 99.8±27.4 nm and 159.1±57 nm, respectively. These standard deviations represent a threefold improvement over those of the NMP-exfoliated originals. Phosphorene can also be exfoliated directly in acetone by very long ultrasonication. The product suspension enjoys the same dimensional homogeneity benefits, which confirms that this effect is an intrinsic property of the acetone-BP system. The quality and stability of the exfoliated flakes was checked by XRD, TEM, electron diffraction and Raman spectroscopy. Thermal expansion coefficients of the A1g, B2g and A2g Raman modes were calculated for drop-casted samples as -0.01828 cm-1/K, -0.03056 cm-1/K and -0.03219 cm-1/K, respectively. The flakes withstand 20 minutes in O2 flow at 373 K without lattice distortion. . © 2018 IOP Publishing Ltd.

  17. Lymphocyte receptors for pertussis toxin

    Energy Technology Data Exchange (ETDEWEB)

    Clark, C.G.; Armstrong, G.D. (Univ. of Alberta, Edmonton (Canada))

    1990-12-01

    We have investigated human T-lymphocyte receptors for pertussis toxin by affinity isolation and photoaffinity labeling procedures. T lymphocytes were obtained from peripheral human blood, surface iodinated, and solubilized in Triton X-100. The iodinated mixture was then passed through pertussis toxin-agarose, and the fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography of the fixed, dried gels revealed several bands in the pertussis toxin-bound fraction that were not observed in fractions obtained from histone or fetuin-agarose. Further investigations employed a photoaffinity labeling reagent, sulfosuccinimidyl 2-(p-azido-salicylamido)-1,3'-dithiopropionate, to identify pertussis toxin receptors in freshly isolated peripheral blood monocytic cells, T lymphocytes, and Jurkat cells. In all three cell systems, the pertussis toxin affinity probe specifically labeled a single protein species with an apparent molecular weight of 70,000 that was not observed when the procedure was performed in the presence of excess unmodified pertussis toxin. A protein comparable in molecular weight to the one detected by the photoaffinity labeling technique was also observed among the species that bound to pertussis toxin-agarose. The results suggest that pertussis toxin may bind to a 70,000-Da receptor in human T lymphocytes.

  18. Botulinum toxin: bioweapon & magic drug.

    Science.gov (United States)

    Dhaked, Ram Kumar; Singh, Manglesh Kumar; Singh, Padma; Gupta, Pallavi

    2010-11-01

    Botulinum neurotoxins, causative agents of botulism in humans, are produced by Clostridium botulinum, an anaerobic spore-former Gram positive bacillus. Botulinum neurotoxin poses a major bioweapon threat because of its extreme potency and lethality; its ease of production, transport, and misuse; and the need for prolonged intensive care among affected persons. A single gram of crystalline toxin, evenly dispersed and inhaled, can kill more than one million people. The basis of the phenomenal potency of botulinum toxin is enzymatic; the toxin is a zinc proteinase that cleaves neuronal vesicle associated proteins responsible for acetylcholine release into the neuromuscular junction. As a military or terrorist weapon, botulinum toxin could be disseminated via aerosol or by contamination of water or food supplies, causing widespread casualties. A fascinating aspect of botulinum toxin research in recent years has been development of the most potent toxin into a molecule of significant therapeutic utility . It is the first biological toxin which is licensed for treatment of human diseases. In the late 1980s, Canada approved use of the toxin to treat strabismus, in 2001 in the removal of facial wrinkles and in 2002, the FDA in the United States followed suit. The present review focuses on both warfare potential and medical uses of botulinum neurotoxin.

  19. Toxin-Based Therapeutic Approaches

    Directory of Open Access Journals (Sweden)

    Itai Benhar

    2010-10-01

    Full Text Available Protein toxins confer a defense against predation/grazing or a superior pathogenic competence upon the producing organism. Such toxins have been perfected through evolution in poisonous animals/plants and pathogenic bacteria. Over the past five decades, a lot of effort has been invested in studying their mechanism of action, the way they contribute to pathogenicity and in the development of antidotes that neutralize their action. In parallel, many research groups turned to explore the pharmaceutical potential of such toxins when they are used to efficiently impair essential cellular processes and/or damage the integrity of their target cells. The following review summarizes major advances in the field of toxin based therapeutics and offers a comprehensive description of the mode of action of each applied toxin.

  20. Toxin-Based Therapeutic Approaches

    Science.gov (United States)

    Shapira, Assaf; Benhar, Itai

    2010-01-01

    Protein toxins confer a defense against predation/grazing or a superior pathogenic competence upon the producing organism. Such toxins have been perfected through evolution in poisonous animals/plants and pathogenic bacteria. Over the past five decades, a lot of effort has been invested in studying their mechanism of action, the way they contribute to pathogenicity and in the development of antidotes that neutralize their action. In parallel, many research groups turned to explore the pharmaceutical potential of such toxins when they are used to efficiently impair essential cellular processes and/or damage the integrity of their target cells. The following review summarizes major advances in the field of toxin based therapeutics and offers a comprehensive description of the mode of action of each applied toxin. PMID:22069564

  1. Engineering monolayer poration for rapid exfoliation of microbial membranes.

    Science.gov (United States)

    Pyne, Alice; Pfeil, Marc-Philipp; Bennett, Isabel; Ravi, Jascindra; Iavicoli, Patrizia; Lamarre, Baptiste; Roethke, Anita; Ray, Santanu; Jiang, Haibo; Bella, Angelo; Reisinger, Bernd; Yin, Daniel; Little, Benjamin; Muñoz-García, Juan C; Cerasoli, Eleonora; Judge, Peter J; Faruqui, Nilofar; Calzolai, Luigi; Henrion, Andre; Martyna, Glenn J; Grovenor, Chris R M; Crain, Jason; Hoogenboom, Bart W; Watts, Anthony; Ryadnov, Maxim G

    2017-02-01

    The spread of bacterial resistance to traditional antibiotics continues to stimulate the search for alternative antimicrobial strategies. All forms of life, from bacteria to humans, are postulated to rely on a fundamental host defense mechanism, which exploits the formation of open pores in microbial phospholipid bilayers. Here we predict that transmembrane poration is not necessary for antimicrobial activity and reveal a distinct poration mechanism that targets the outer leaflet of phospholipid bilayers. Using a combination of molecular-scale and real-time imaging, spectroscopy and spectrometry approaches, we introduce a structural motif with a universal insertion mode in reconstituted membranes and live bacteria. We demonstrate that this motif rapidly assembles into monolayer pits that coalesce during progressive membrane exfoliation, leading to bacterial cell death within minutes. The findings offer a new physical basis for designing effective antibiotics.

  2. Covalent modification and exfoliation of graphene oxide using ferrocene

    Science.gov (United States)

    Avinash, M. B.; Subrahmanyam, K. S.; Sundarayya, Y.; Govindaraju, T.

    2010-09-01

    Large scale preparation of single-layer graphene and graphene oxide is of great importance due to their potential applications. We report a simple room temperature method for the exfoliation of graphene oxide using covalent modification of graphene oxide with ferrocene to obtain single-layer graphene oxide sheets. The samples were characterized by FESEM, HRTEM, AFM, EDAX, FT-IR, Raman and Mössbauer spectroscopic studies. HRTEM micrograph of the covalently modified graphene oxide showed increased interlayer spacing of ~2.4 nm due to ferrocene intercalation. The presence of single-layer graphene oxide sheets were confirmed by AFM studies. The covalently modified ferrocene-graphene oxide composite showed interesting magnetic behavior.Large scale preparation of single-layer graphene and graphene oxide is of great importance due to their potential applications. We report a simple room temperature method for the exfoliation of graphene oxide using covalent modification of graphene oxide with ferrocene to obtain single-layer graphene oxide sheets. The samples were characterized by FESEM, HRTEM, AFM, EDAX, FT-IR, Raman and Mössbauer spectroscopic studies. HRTEM micrograph of the covalently modified graphene oxide showed increased interlayer spacing of ~2.4 nm due to ferrocene intercalation. The presence of single-layer graphene oxide sheets were confirmed by AFM studies. The covalently modified ferrocene-graphene oxide composite showed interesting magnetic behavior. Electronic supplementary information (ESI) available: Magnetic data; AFM images; TEM micrographs; and Mössbauer spectroscopic data. See DOI: 10.1039/c0nr00024h

  3. Binding of ATP by pertussis toxin and isolated toxin subunits

    International Nuclear Information System (INIS)

    Hausman, S.Z.; Manclark, C.R.; Burns, D.L.

    1990-01-01

    The binding of ATP to pertussis toxin and its components, the A subunit and B oligomer, was investigated. Whereas, radiolabeled ATP bound to the B oligomer and pertussis toxin, no binding to the A subunit was observed. The binding of [ 3 H]ATP to pertussis toxin and the B oligomer was inhibited by nucleotides. The relative effectiveness of the nucleotides was shown to be ATP > GTP > CTP > TTP for pertussis toxin and ATP > GTP > TTP > CTP for the B oligomer. Phosphate ions inhibited the binding of [ 3 H]ATP to pertussis toxin in a competitive manner; however, the presence of phosphate ions was essential for binding of ATP to the B oligomer. The toxin substrate, NAD, did not affect the binding of [ 3 H]ATP to pertussis toxin, although the glycoprotein fetuin significantly decreased binding. These results suggest that the binding site for ATP is located on the B oligomer and is distinct from the enzymatically active site but may be located near the eukaryotic receptor binding site

  4. Binding of ATP by pertussis toxin and isolated toxin subunits

    Energy Technology Data Exchange (ETDEWEB)

    Hausman, S.Z.; Manclark, C.R.; Burns, D.L. (Center for Biologics Evaluation and Research, Bethesda, MD (USA))

    1990-07-03

    The binding of ATP to pertussis toxin and its components, the A subunit and B oligomer, was investigated. Whereas, radiolabeled ATP bound to the B oligomer and pertussis toxin, no binding to the A subunit was observed. The binding of ({sup 3}H)ATP to pertussis toxin and the B oligomer was inhibited by nucleotides. The relative effectiveness of the nucleotides was shown to be ATP > GTP > CTP > TTP for pertussis toxin and ATP > GTP > TTP > CTP for the B oligomer. Phosphate ions inhibited the binding of ({sup 3}H)ATP to pertussis toxin in a competitive manner; however, the presence of phosphate ions was essential for binding of ATP to the B oligomer. The toxin substrate, NAD, did not affect the binding of ({sup 3}H)ATP to pertussis toxin, although the glycoprotein fetuin significantly decreased binding. These results suggest that the binding site for ATP is located on the B oligomer and is distinct from the enzymatically active site but may be located near the eukaryotic receptor binding site.

  5. Food toxin detection with atomic force microscope

    Science.gov (United States)

    Externally introduced toxins or internal spoilage correlated pathogens and their metabolites are all potential sources of food toxins. To prevent and protect unsafe food, many food toxin detection techniques have been developed to detect various toxins for quality control. Although several routine m...

  6. Botulinum Toxin (Botox) for Facial Wrinkles

    Science.gov (United States)

    ... Stories Español Eye Health / Eye Health A-Z Botulinum Toxin (Botox) for Facial Wrinkles Sections Botulinum Toxin (Botox) ... Facial Wrinkles How Does Botulinum Toxin (Botox) Work? Botulinum Toxin (Botox) for Facial Wrinkles Leer en Español: La ...

  7. Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry

    Science.gov (United States)

    Ryder, Christopher R.; Wood, Joshua D.; Wells, Spencer A.; Yang, Yang; Jariwala, Deep; Marks, Tobin J.; Schatz, George C.; Hersam, Mark C.

    2016-06-01

    Functionalization of atomically thin nanomaterials enables the tailoring of their chemical, optical and electronic properties. Exfoliated black phosphorus (BP)—a layered two-dimensional semiconductor—exhibits favourable charge-carrier mobility, tunable bandgap and highly anisotropic properties, but it is chemically reactive and degrades rapidly in ambient conditions. Here we show that covalent aryl diazonium functionalization suppresses the chemical degradation of exfoliated BP even after three weeks of ambient exposure. This chemical modification scheme spontaneously forms phosphorus-carbon bonds, has a reaction rate sensitive to the aryl diazonium substituent and alters the electronic properties of exfoliated BP, ultimately yielding a strong, tunable p-type doping that simultaneously improves the field-effect transistor mobility and on/off current ratio. This chemical functionalization pathway controllably modifies the properties of exfoliated BP, and thus improves its prospects for nanoelectronic applications.

  8. Packaging material and flexible medical tubing containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A packaging material or flexible medical tubing containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g.

  9. Exfoliated polypyrrole-organically modified montmorillonite clay nanocomposite as a potential adsorbent for Cr (VI) removal

    CSIR Research Space (South Africa)

    Setshedi, KZ

    2013-01-01

    Full Text Available Exfoliated polypyrrole-organically modified montmorillonite clay nanocomposite (PPy OMMT NC), was prepared as a potential adsorbent, via in situ polymerization of pyrrole monomer for adsorption of toxic Cr(VI) from aqueous solution. The WAXD...

  10. Production of High-quality Few-layer Graphene Flakes by Intercalation and Exfoliation

    KAUST Repository

    Alzahrani, Areej A.

    2017-01-01

    , the source material was a commercially available graphiteintercalated compound, also known as expandable graphite. Several exfoliation-inducing tools were investigated including the use of blenders, homogenizers, and ultrasonic processors. To aid

  11. Photoluminescence of MoS2 Prepared by Effective Grinding-Assisted Sonication Exfoliation

    Directory of Open Access Journals (Sweden)

    Jing-Yuan Wu

    2014-01-01

    Full Text Available Exfoliation of bulk molybdenum disulfide (MoS2 using sonication in appropriate solvent is a promising route to large-scale preparation of few-layered or monolayered crystals. Grinding-assisted sonication exfoliation was used for preparing monolayered MoS2 nanosheets from natural mineral molybdenite. By controlling the sonication time, larger crystallites could be further exfoliated to smaller as well as thinner nanosheets without damaging their structures. The concentration of 1.6 mg mL−1 of final solution could be achieved. Several microscopic techniques like scanning electron microscopy, transmission electron microscopy, and atomic force microscopy were employed to evaluate the exfoliation results. Strong photoluminescence with the peak centered at 440 nm was also observed in the resulting dispersion which included several small lateral-sized (~3 nm nanostructures.

  12. Self-Assembled BN and BCN Quantum Dots Obtained from High Intensity Ultrasound Exfoliated Nanosheets

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Henych, Jiří; Kormunda, M.

    2014-01-01

    Roč. 6, č. 6 (2014), s. 1106-1116 ISSN 1947-2935 Institutional support: RVO:61388980 Keywords : Ultrasound * Exfoliation * BN * BCN * Quantum Dots Subject RIV: CA - Inorganic Chemistry Impact factor: 2.598, year: 2014

  13. Micromechanical exfoliation of two-dimensional materials by a polymeric stamp

    International Nuclear Information System (INIS)

    Costa, M C Ferraz da; Ribeiro, H B; Kessler, F; Souza, E A T de; Fechine, G J M

    2016-01-01

    In this work, an alternative technique to the traditional micromechanical exfoliation of two-dimensional materials is proposed, consisting of isolated flakes of graphite and molybdenum disulphide onto polymeric surfaces films. The set made up of polymer and flakes is fabricated by using a hot-press machine called polymeric stamp. The polymeric stamp was used to allocate flakes and also to allow the exfoliation process to take place just in one face of isolated flake. Optical microscopy, Raman spectroscopy and photoluminescence spectroscopy results showed that multilayers, bilayers and single layers of graphene and MoS 2 were obtained by using a polymeric stamp as tool for micromechanical exfoliation. These crystals were more easily found because the exfoliation process concentrates them in well-defined locations. The results prove the effectiveness of the method by embedding two-dimensional materials into polymers to fabricate fewer layers crystals in a fast, economic and clean way. (paper)

  14. Micromechanical exfoliation of two-dimensional materials by a polymeric stamp

    Science.gov (United States)

    Ferraz da Costa, M. C.; Ribeiro, H. B.; Kessler, F.; de Souza, E. A. T.; Fechine, G. J. M.

    2016-02-01

    In this work, an alternative technique to the traditional micromechanical exfoliation of two-dimensional materials is proposed, consisting of isolated flakes of graphite and molybdenum disulphide onto polymeric surfaces films. The set made up of polymer and flakes is fabricated by using a hot-press machine called polymeric stamp. The polymeric stamp was used to allocate flakes and also to allow the exfoliation process to take place just in one face of isolated flake. Optical microscopy, Raman spectroscopy and photoluminescence spectroscopy results showed that multilayers, bilayers and single layers of graphene and MoS2 were obtained by using a polymeric stamp as tool for micromechanical exfoliation. These crystals were more easily found because the exfoliation process concentrates them in well-defined locations. The results prove the effectiveness of the method by embedding two-dimensional materials into polymers to fabricate fewer layers crystals in a fast, economic and clean way.

  15. Electromagnetic properties and performance of exfoliated graphite (EG) - thermoplastic polyurethane (TPU) nanocomposites at microwaves

    Czech Academy of Sciences Publication Activity Database

    Valentini, M.; Piana, Francesco; Pionteck, J.; Lamastra, F. R.; Nanni, F.

    2015-01-01

    Roč. 114, 19 June (2015), s. 26-33 ISSN 0266-3538 Institutional support: RVO:61389013 Keywords : exfoliated graphite * functional composites * nano composites Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.897, year: 2015

  16. Genotoxicity assessment data for exfoliated buccal cells exposed to mobile phone radiation

    Directory of Open Access Journals (Sweden)

    F.M. de Oliveira

    2017-12-01

    Full Text Available Healthy mobile phone users aged 18–30 y.o. provided exfoliated buccal cells samples from the right and left inner cheeks. A total of 2000 cells per subject were screened for the presence of micronuclei as a sign of genotoxic damage, according to the mobile phone use profile of each user. Keywords: Electromagnetic fields, Mobile phones, Genotoxicity, Micronuclei, Exfoliated buccal cells, Feulgen stain

  17. Bio Warfare and Terrorism: Toxins and Other Mid-Spectrum Agents

    National Research Council Canada - National Science Library

    Madsen, James M

    2005-01-01

    ... counterparts are still by definition toxins. Related terms include phycotoxins (toxins from algae), mycotoxins (fungal toxins), phytotoxins (plant toxins), and venoms (toxins from animals, especially vertebrates...

  18. WS{sub 2} nanosheets based on liquid exfoliation as effective electrocatalysts for hydrogen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Han, Guan-Qun [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580 (China); College of Science, China University of Petroleum (East China), Qingdao 266580 (China); Liu, Yan-Ru; Hu, Wen-Hui [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580 (China); Dong, Bin, E-mail: dongbin@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580 (China); College of Science, China University of Petroleum (East China), Qingdao 266580 (China); Li, Xiao; Chai, Yong-Ming; Liu, Yun-Qi [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580 (China); Liu, Chen-Guang, E-mail: cgliu@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580 (China)

    2015-11-01

    WS{sub 2} nanosheets (WS{sub 2} NSs) as electrocatalysts for hydrogen evolution reaction (HER) have been prepared based on liquid exfoliation in dimethyl-formamide (DMF) via a direct dispersion and ultrasonication method. X-ray diffraction (XRD) shows the decreasing crystalline of the exfoliated WS{sub 2} (E-WS{sub 2}). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the as prepared E-WS{sub 2} consists of a few two-dimensional nanosheets, with large wrinkles on the surface. Electrochemical measurements show an excellent activity and stability of the E-WS{sub 2}, with a low overpotential of 80 mV and high current density (10 mA cm{sup −2}, at η = 205 mV), which indicates that through the process of exfoliation in DMF, both the dispersion and the amount of active sites have been improved greatly. Therefore, DMF is a promising alternative for exfoliating two-dimensional nanomaterials for highly efficient HER electrocatalysts. - Highlights: • A facile exfoliation process in DMF has been used to prepare E-WS{sub 2} for HER. • E-WS{sub 2} shows the better electrocatalytic activity than bulk WS{sub 2}. • DMF provides a promising alternative for enhancing exfoliation of 2D materials.

  19. WS_2 nanosheets based on liquid exfoliation as effective electrocatalysts for hydrogen evolution reaction

    International Nuclear Information System (INIS)

    Han, Guan-Qun; Liu, Yan-Ru; Hu, Wen-Hui; Dong, Bin; Li, Xiao; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2015-01-01

    WS_2 nanosheets (WS_2 NSs) as electrocatalysts for hydrogen evolution reaction (HER) have been prepared based on liquid exfoliation in dimethyl-formamide (DMF) via a direct dispersion and ultrasonication method. X-ray diffraction (XRD) shows the decreasing crystalline of the exfoliated WS_2 (E-WS_2). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the as prepared E-WS_2 consists of a few two-dimensional nanosheets, with large wrinkles on the surface. Electrochemical measurements show an excellent activity and stability of the E-WS_2, with a low overpotential of 80 mV and high current density (10 mA cm"−"2, at η = 205 mV), which indicates that through the process of exfoliation in DMF, both the dispersion and the amount of active sites have been improved greatly. Therefore, DMF is a promising alternative for exfoliating two-dimensional nanomaterials for highly efficient HER electrocatalysts. - Highlights: • A facile exfoliation process in DMF has been used to prepare E-WS_2 for HER. • E-WS_2 shows the better electrocatalytic activity than bulk WS_2. • DMF provides a promising alternative for enhancing exfoliation of 2D materials.

  20. Controlling the number of graphene sheets exfoliated from graphite by designed normal loading and frictional motion

    International Nuclear Information System (INIS)

    Lee, Seungjun; Lu, Wei

    2014-01-01

    We use molecular dynamics to study the exfoliation of patterned nanometer-sized graphite under various normal loading conditions for friction-induced exfoliation. Using highly ordered pyrolytic graphite (HOPG) as well as both amorphous and crystalline SiO 2 substrate as example systems, we show that the exfoliation process is attributed to the corrugation of the HOPG surface and the atomistic roughness of the substrate when they contact under normal loading. The critical normal strain, at which the exfoliation occurs, is higher on a crystalline substrate than on an amorphous substrate. This effect is related to the atomistic flatness and stiffness of the crystalline surface. We observe that an increase of the van der Waals interaction between the graphite and the substrate results in a decrease of the critical normal strain for exfoliation. We find that the magnitude of the normal strain can effectively control the number of exfoliated graphene layers. This mechanism suggests a promising approach of applying designed normal loading while sliding to pattern controlled number of graphene layers or other two-dimensional materials on a substrate surface.

  1. Botulinum toxin in trigeminal neuralgia.

    Science.gov (United States)

    Castillo-Álvarez, Federico; Hernando de la Bárcena, Ignacio; Marzo-Sola, María Eugenia

    2017-01-06

    Trigeminal neuralgia is one of the most disabling facial pain syndromes, with a significant impact on patients' quality of life. Pharmacotherapy is the first choice for treatment but cases of drug resistance often require new strategies, among which various interventional treatments have been used. In recent years a new therapeutic strategy consisting of botulinum toxin has emerged, with promising results. We reviewed clinical cases and case series, open-label studies and randomized clinical trials examining the use of botulinum toxin for drug-refractory trigeminal neuralgia published in the literature. The administration of botulinum toxin has proven to be a safe and effective therapeutic strategy in patients with drug-refractory idiopathic trigeminal neuralgia, but many questions remain unanswered as to the precise role of botulinum toxin in the treatment of this disease. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

  2. Toxin-Based Therapeutic Approaches

    OpenAIRE

    Itai Benhar; Assaf Shapira

    2010-01-01

    Protein toxins confer a defense against predation/grazing or a superior pathogenic competence upon the producing organism. Such toxins have been perfected through evolution in poisonous animals/plants and pathogenic bacteria. Over the past five decades, a lot of effort has been invested in studying their mechanism of action, the way they contribute to pathogenicity and in the development of antidotes that neutralize their action. In parallel, many research groups turned to explore the pharmac...

  3. Age estimation using exfoliative cytology and radiovisiography: A comparative study.

    Science.gov (United States)

    Nallamala, Shilpa; Guttikonda, Venkateswara Rao; Manchikatla, Praveen Kumar; Taneeru, Sravya

    2017-01-01

    Age estimation is one of the essential factors in establishing the identity of an individual. Among various methods, exfoliative cytology (EC) is a unique, noninvasive technique, involving simple, and pain-free collection of intact cells from the oral cavity for microscopic examination. The study was undertaken with an aim to estimate the age of an individual from the average cell size of their buccal smears calculated using image analysis morphometric software and the pulp-tooth area ratio in mandibular canine of the same individual using radiovisiography (RVG). Buccal smears were collected from 100 apparently healthy individuals. After fixation in 95% alcohol, the smears were stained using Papanicolaou stain. The average cell size was measured using image analysis software (Image-Pro Insight 8.0). The RVG images of mandibular canines were obtained, pulp and tooth areas were traced using AutoCAD 2010 software, and area ratio was calculated. The estimated age was then calculated using regression analysis. The paired t -test between chronological age and estimated age by cell size and pulp-tooth area ratio was statistically nonsignificant ( P > 0.05). In the present study, age estimated by pulp-tooth area ratio and EC yielded good results.

  4. Study of novel carbon fiber composite used exfoliated carbon fibers

    Energy Technology Data Exchange (ETDEWEB)

    Toyoda, Masahiro [Oita Univ., 700 Dannoharu, Oita 870-1192 (Japan)], E-mail: toyoda22@cc.oita-u.ac.jp; Kohara, Ryotaro; Tsumura, Tomoki [Oita Univ., 700 Dannoharu, Oita 870-1192 (Japan); Mutoh, Hiroyuki; Sakai, Mototsugu [Toyohashi Univ. of Tech., Toyohashi 441-8580 (Japan)

    2009-04-15

    One of the applications for carbon nanotubes (CNTs), CNT composite has been studied to reinforce of polymer. However, CNTs have not shown enough reinforced effect, because of poor dispersibility of itself and low purification. These characteristics are connected with the lowering mechanical strength in CNT's reinforced polymer composite. On the other hand, exfoliated carbon fibers (ExCFs) prepared through electrochemical processing were found to have unique morphology such as nanometer or sub-micrometer sized fibrils and well dispersibility. Fabrication of composite using its ExCFs was investigated. ExCFs changed in nanometer-sized fibrils by using ultrasonication and CNTs dispersed by using ultrasonication were compounded with polymethyl methacrylate (PMMA) in situ process through polymerization, and then their mechanical properties were examined. Flexural strength and elasticity of PMMA composite reinforced by ExCFs increased 166 and 171% respectively at addition of only 2.0 wt.% comparison with bulk PMMA. There was no significant aggregation in fracture surface, and homogeneous dispersion of ExCFs throughout the PMMA matrix was recognized. It was better than that of PMMA composite reinforced by CNTs. Homogeneous dispersion might be strongly related to mechanical properties. ExCFs might be expected to be applied to nano-composite instead of CNTs.

  5. Phonon shift in chemically exfoliated WS2 nanosheet

    Science.gov (United States)

    Sarkar, Abdus Salam; Pal, Suman Kalyan

    2018-04-01

    We have synthesized few layer WS2 nanosheets in a low boiling point solvent. Few layer of WS2 sheets are characterized by various techniques such as UV-visible and Raman spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). UV-Vis absorption spectra confirm the well dispersed in isopropyl alcohol. SEM and TEM images indicate the sheet like morphology of WS2. Atomic force microscopy image and room temperature Raman spectroscopy confirm the exfoliation of few layer (4-5 layer) of WS2. Further, Raman spectroscopy was used as a meteorology tool to determine the temperature co-efficient. We have systematically investigated the temperature dependent Raman spectroscopic behavior of few layer WS2. Our results depict the softening of the Raman modes E12g in plane vibration and A1g out of plane vibration with increasing the temperature from 77 K to 300 K. Softening of the Raman modes could be explained in terms of the double resonance which is active in the layered materials. The observed temperature coefficients for two Raman peaks E12g and A1g, are - 0.022 cm-1 and -0.009 cm-1, respectively.

  6. Exfoliation syndrome and exfoliation glaucoma-associated LOXL1 variations are not involved in pigment dispersion syndrome and pigmentary glaucoma.

    Science.gov (United States)

    Rao, Kollu Nageswara; Ritch, Robert; Dorairaj, Syril K; Kaur, Inderjeet; Liebmann, Jeffrey M; Thomas, Ravi; Chakrabarti, Subhabrata

    2008-07-09

    Single nucleotide polymorphisms (SNPs) in the LOXL1 gene have been implicated in exfoliation syndrome (XFS) and exfoliation glaucoma (XFG). We have shown that these SNPs are not associated with the primary glaucomas such as primary open-angle (POAG) glaucoma and primary angle-closure glaucoma (PACG). To further establish the specificity of LOXL1 SNPs for XFS and XFG, we determined whether these SNPs were involved in pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG). Three SNPs of LOXL1 (rs1048661, rs3825942, and rs2165241) were screened in a cohort of 78 unrelated and clinically well characterized glaucoma cases comprising of PG (n=44) and PDS (n=34) patients as well as 108 ethnically matched normal controls of Caucasian origin. The criteria for diagnosis of PDS/PG were Krukenberg spindle, hyperpigmentation of the trabecular meshwork, and wide open angle. Transillumination defects were detected by infrared pupillography, and the presence of a Zentmayer ring was considered as a confirmatory sign. All three SNPs were genotyped in cases and controls by resequencing the genomic region of LOXL1 harboring these variants and were further confirmed by polymerase chain reaction (PCR)-based restriction digestions. Haplotypes were generated from the genotype data, and the linkage disequilibrium (LD) and haplotype analysis were done with Haploview software that uses the expectation maximization (EM) algorithm. The LOXL1 SNPs showed no significant association with PDS or PG. There was no significant difference in the frequencies of the risk alleles of rs1048661 ('G' allele; p=0.309), rs3825942 ('G' allele' p=0.461), and rs2165241 ('T' allele; p=0.432) between PG/PDS cases and controls. Similarly, there was no involvement of the XFS/XFG-associated haplotypes, 'G-G' (p=0.643; [OR=1.08, 95%CI, 0.59-1.97]) and 'T-G' (p=0.266; [OR=1.35, 95%CI, 0.70-2.60]), with the PDS/PG phenotypes. The risk haplotype 'G-G' was observed in ~55% of the normal controls. There was no

  7. Exfoliated MoS2 nanosheets as efficient catalysts for electrochemical hydrogen evolution

    International Nuclear Information System (INIS)

    Ji, Shanshan; Yang, Zhe; Zhang, Chao; Liu, Zhenyan; Tjiu, Weng Weei; Phang, In Yee; Zhang, Zheng; Pan, Jisheng; Liu, Tianxi

    2013-01-01

    Graphical abstract: An efficient electrocatalyst for hydrogen evolution has been developed based on exfoliation of bulk MoS 2 crystals via a direct dispersion and ultrasonication method. Drop-casting method is used to fabricate the exfoliated MoS 2 nanosheets modified glass carbon electrode (E-MoS 2 /GCE) with various loadings. The E-MoS 2 /GCE with electrode loading of 48 μg cm −1 exhibits high catalytic activity for hydrogen evolution with a low overpotential (−0.12 V) and a high current density (1.26 mA cm −2 , at η = 150 mV). -- Highlights: • Two-dimensional MoS 2 nanosheets have been obtained by exfoliation of bulk MoS 2 crystals. • Exfoliated MoS 2 nanosheets show high electrocatalytic activity for H 2 production. • This study provides a new approach for renewable and economic H 2 production. -- Abstract: An efficient electrocatalyst for hydrogen evolution has been developed based on liquid exfoliation of bulk MoS 2 via a direct dispersion and ultrasonication method. Transmission electron microscopy and atomic force microscopy measurements show that the exfoliated MoS 2 consists of two-dimensional nanosheets. The exfoliated MoS 2 nanosheets modified glass carbon electrode (E-MoS 2 /GCE) with various loadings is fabricated via a drop-casting method. The electrocatalytic activity of E-MoS 2 /GCE toward hydrogen evolution reaction is examined using linear sweep voltammetry. It is shown that the E-MoS 2 /GCE with an electrode loading of 48 μg cm −2 exhibits a high catalytic activity for hydrogen evolution with a low overpotential (−0.12 V) and a high current density (1.26 mA cm −2 , at η = 150 mV)

  8. Botulinum toxin in pain treatment.

    Science.gov (United States)

    Colhado, Orlando Carlos Gomes; Boeing, Marcelo; Ortega, Luciano Bornia

    2009-01-01

    Botulinum toxin (BTX) is one of the most potent bacterial toxins known and its effectiveness in the treatment of some pain syndromes is well known. However, the efficacy of some of its indications is still in the process of being confirmed. The objective of this study was to review the history, pharmacological properties, and clinical applications of BTX in the treatment of pain of different origins. Botulinum toxin is produced by fermentation of Clostridium botulinum, a Gram-positive, anaerobic bacterium. Commercially, BTX comes in two presentations, types A and B. Botulinum toxin, a neurotoxin with high affinity for cholinergic synapses, blocks the release of acetylcholine by nerve endings without interfering with neuronal conduction of electrical signals or synthesis and storage of acetylcholine. It has been proven that BTX can selectively weaken painful muscles, interrupting the spasm-pain cycle. Several studies have demonstrated the efficacy and safety of BTX-A in the treatment of tension headaches, migraines, chronic lumbar pain, and myofascial pain. Botulinum toxin type A is well tolerated in the treatment of chronic pain disorders in which pharmacotherapy regimens can cause side effects. The reduction in the consumption of analgesics and length of action of 3 to 4 months per dose represent other advantages of its use. However, further studies are necessary to establish the efficacy of BTX-A in chronic pain disorders and its exact mechanism of action, as well as its potential in multifactorial treatments.

  9. Structure, temperature and frequency dependent electrical conductivity of oxidized and reduced electrochemically exfoliated graphite

    Science.gov (United States)

    Radoń, Adrian; Włodarczyk, Patryk; Łukowiec, Dariusz

    2018-05-01

    The article presents the influence of reduction by hydrogen in statu nascendi and modification by hydrogen peroxide on the structure and electrical conductivity of electrochemically exfoliated graphite. It was confirmed that the electrochemical exfoliation can be used to produce oxidized nanographite with an average number of 25 graphene layers. The modified electrochemical exfoliated graphite and reduced electrochemical exfoliated graphite were characterized by high thermal stability, what was associated with removing of labile oxygen-containing groups. The presence of oxygen-containing groups was confirmed using Fourier-transform infrared spectroscopy. Influence of chemical modification by hydrogen and hydrogen peroxide on the electrical conductivity was determined in wide frequency (0.1 Hz-10 kHz) and temperature range (-50 °C-100 °C). Material modified by hydrogen peroxide (0.29 mS/cm at 0 °C) had the lowest electrical conductivity. This can be associated with oxidation of unstable functional groups and was also confirmed by analysis of Raman spectra. The removal of oxygen-containing functional groups by hydrogen in statu nascendi resulted in a 1000-fold increase in the electrical conductivity compared to the electrochemical exfoliated graphite.

  10. Graphene prepared by one-pot solvent exfoliation as a highly sensitive platform for electrochemical sensing

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Can; Cheng, Qin [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wu, Kangbing, E-mail: kbwu@hust.edu.cn [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wu, Gang [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Qing, E-mail: qing_li_2@brown.edu [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2014-05-01

    Highlights: • Graphene was prepared by one-step solvent exfoliation as superior electrode material. • Compared with RGO, prepared graphene exhibited stronger signal enhancement. • A widespread and highly-sensitive electrochemical sensing platform was constructed. - Abstract: Graphene was easily obtained via one-step ultrasonic exfoliation of graphite powder in N-methyl-2-pyrrolidone. Scanning electron microscopy, transmission electron microscopy, Raman and particle size measurements indicated that the exfoliation efficiency and the amount of produced graphene increased with ultrasonic time. The electrochemical properties and analytical applications of the resulting graphene were systematically studied. Compared with the predominantly-used reduced graphene oxides, the obtained graphene by one-step solvent exfoliation greatly enhanced the oxidation signals of various analytes, such as ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XA), hypoxanthine (HXA), bisphenol A (BPA), ponceau 4R, and sunset yellow. The detection limits of AA, DA, UA, XA, HXA, BPA, ponceau 4R, and sunset yellow were evaluated to be 0.8 μM, 7.5 nM, 2.5 nM, 4 nM, 10 nM, 20 nM, 2 nM, and 1 nM, which are much lower than the reported values. Thus, the prepared graphene via solvent exfoliation strategy displays strong signal amplification ability and holds great promise in constructing a universal and sensitive electrochemical sensing platform.

  11. New insight of high temperature oxidation on self-exfoliation capability of graphene oxide

    Science.gov (United States)

    Liu, Yuhang; Zeng, Jie; Han, Di; Wu, Kai; Yu, Bowen; Chai, Songgang; Chen, Feng; Fu, Qiang

    2018-05-01

    The preparation of graphene oxide (GO) via Hummers method is usually divided into two steps: low temperature oxidation at 35 °C (step I oxidation) and high temperature oxidation at 98 °C (step II oxidation). However, the effects of these two steps on the exfoliation capability and chemical structure of graphite oxide remain unclear. In this study, both the functional group content of graphite oxide and the entire evolution of interlayer spacing were investigated during the two steps. Step I oxidation is a slowly inhomogeneous oxidation step to remove unoxidized graphite flakes. The prepared graphite oxide can be easily self-exfoliated but contains a lot of organic sulfur. During the first 20 min of step II oxidation, the majority of organic sulfur can be efficiently removed and graphite oxide still remains a good exfoliation capability due to sharp increasing of carboxyl groups. However, with a longer oxidation time at step II oxidation, the decrease of organic sulfur content is slowed down apparently but without any carboxyl groups forming, then graphite oxide finally loses self-exfoliation capability. It is concluded that a short time of step II oxidation can produce purer and ultralarge GO sheets via self-exfoliation. The pure GO is possessed with better thermal stability and liquid crystal behavior. Besides, reduced GO films prepared from step II oxidation show better mechanical and electric properties after reducing compared with that obtained only via step I oxidation.

  12. Mechanisms of nanoclay-enhanced plastic foaming processes: effects of nanoclay intercalation and exfoliation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Anson; Wijnands, Stephan F. L.; Kuboki, Takashi; Park, Chul B., E-mail: park@mie.utoronto.ca [University of Toronto, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering (Canada)

    2013-08-15

    The foaming behaviors of high-density polypropylene-nanoclay composites with intercalated and exfoliated nanoclay particles blown with carbon dioxide were examined via in situ observation of the foaming processes in a high-temperature/high-pressure view-cell. The intercalated nanoclay particles were 300-600 nm in length and 50-200 nm in thickness, while the exfoliated nanoclay particles were 100-200 nm in length and 1 nm in thickness. Contrary to common belief, it was discovered that intercalated nanoclay yielded higher cell density than exfoliated nanoclay despite its lower particle density. This was attributed to the higher tensile stresses generated around the larger and stiffer intercalated nanoclay particles, which led to increase in supersaturation level for cell nucleation. Also, the coupling agent used to exfoliate nanoclay would increase the affinity between polymer and surface of nanoclay particles. Consequently, the critical work needed for cell nucleation would be increased; pre-existing microvoids, which could act as seeds for cell nucleation, were also less likely to exist. Meanwhile, exfoliated nanoclay had better cell stabilization ability to prevent cell coalescence and cell coarsening. This investigation clarifies the roles of nanoclay in plastic foaming processes and provides guidance for the advancement of polymer nanocomposite foaming technology.

  13. Entry of Shiga toxin into cells

    DEFF Research Database (Denmark)

    Sandvig, Kirsten; van Deurs, Bo

    1994-01-01

    Cellebiologi, Shiga toxin, receptors, glycolipids, endocytosis, trans-Golgi network, endoplasmic reticulum, retrograde transport......Cellebiologi, Shiga toxin, receptors, glycolipids, endocytosis, trans-Golgi network, endoplasmic reticulum, retrograde transport...

  14. Inhibition of cholera toxin and other AB toxins by polyphenolic compounds

    Science.gov (United States)

    All AB-type protein toxins have intracellular targets despite an initial extracellular location. These toxins use different methods to reach the cytosol and have different effects on the target cell. Broad-spectrum inhibitors against AB toxins are therefore hard to develop because the toxins use dif...

  15. Toxin synergism in snake venoms

    DEFF Research Database (Denmark)

    Laustsen, Andreas Hougaard

    2016-01-01

    Synergism between venom toxins exists for a range of snake species. Synergism can be derived from both intermolecular interactions and supramolecular interactions between venom components, and can be the result of toxins targeting the same protein, biochemical pathway or physiological process. Few...... simple systematic tools and methods for determining the presence of synergism exist, but include co-administration of venom components and assessment of Accumulated Toxicity Scores. A better understanding of how to investigate synergism in snake venoms may help unravel strategies for developing novel...

  16. Ex situ integration of iron oxide nanoparticles onto the exfoliated expanded graphite flakes in water suspension

    Directory of Open Access Journals (Sweden)

    Jović Nataša

    2014-01-01

    Full Text Available Hybrid structures composed of exfoliated expanded graphite (EG and iron oxide nanocrystals have been produced by an ex situ process. The iron oxide nanoparticles coated with meso-2,3-dimercaptosuccinic acid (DMSA, or poly(acrylic acid (PAA were integrated onto the exfoliated EG flakes by mixing their aqueous suspensions at room temperature under support of 1-ethyl-3-(3-dimethylaminopropylcarbodiimide (EDC and N-hydroxysuccin-nimide (NHS. EG flakes have been used both, naked and functionalized with branched polyethylenimine (PEI. Complete integration of two constituents has been achieved and mainteined stable for more than 12 months. No preferential spatial distribution of anchoring sites for attachement of iron oxide nanoparticles has been observed, regardless EG flakes have been used naked or functionalized with PEI molecules. The structural and physico-chemical characteristics of the exfoliated expanded graphite and its hybrids nanostructures has been investigated by SEM, TEM, FTIR and Raman techniques. [Projekat Ministarstva nauke Republike Srbije, br. 45015

  17. Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite

    Science.gov (United States)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Lizcano, Maricela; Kelly, Marisabel

    2017-01-01

    Exfoliated hexagonal boron nitride (hBN)/alumina composite can be fabricated by following the process of (1) heating a mixture of hBN, AlCl3, and NaF in nitrogen for intercalation; (2) heating the intercalated product in air for exfoliation and at the same time converting the intercalate (AlCl3) into Al2O3, (3) rinsing the oxidized product, (4) coating individual exfoliated hBN platelets that contain Al2O3 with new layers of aluminum oxide, and finally, (5) hot pressing the product into the composite. The composite thus obtained has a composition of approximately 60 percent by weight hBN and 40 percent by weight alumina. Its in-plane and through-plane thermal conductivity were measured to be 86 and 18 watts per meter Kelvin, respectively, at room temperature.

  18. Epoxy based nanocomposites with fully exfoliated unmodified clay: mechanical and thermal properties.

    Science.gov (United States)

    Li, Binghai; Zhang, Xiaohong; Gao, Jianming; Song, Zhihai; Qi, Guicun; Liu, Yiqun; Qiao, Jinliang

    2010-09-01

    The unmodified clay has been fully exfoliated in epoxy resin with the aid of a novel ultrafine full-vulcanized powdered rubber. Epoxy/rubber/clay nanocomposites with exfoliated morphology have been successfully prepared. The microstructures of the nanocomposites were characterized by means of X-ray diffraction and transmission electron microscopy. It was found that the unmodified clay was fully exfoliated and uniformly dispersed in the resulting nanocomposite. Characterizations of mechanical properties revealed that the impact strength of this special epoxy/rubber/clay nanocomposite increased up 107% over the neat epoxy resin. Thermal analyses showed that thermal stability of the nanocomposite was much better than that of epoxy nanocomposite based on organically modified clay.

  19. Time-dependent study of the exfoliation process of carbon nanotubes in aqueous dispersions by using UV-visible spectroscopy

    NARCIS (Netherlands)

    Grossiord, N.; Regev, O.; Loos, J.; Meuldijk, J.; Koning, C.E.

    2005-01-01

    In this paper we demonstrate that the sonication-driven exfoliation of aggregates and bundles of single-wall carbon nanotubes (SWNTs) in an aqueous surfactant solution can be easily monitored by UV-vis spectroscopy. The different stages of the exfoliation process were directly visualized by

  20. Liquid-Phase Exfoliation of Phosphorene: Design Rules from Molecular Dynamics Simulations.

    Science.gov (United States)

    Sresht, Vishnu; Pádua, Agílio A H; Blankschtein, Daniel

    2015-08-25

    The liquid-phase exfoliation of phosphorene, the two-dimensional derivative of black phosphorus, in the solvents dimethyl sulfoxide (DMSO), dimethylformamide (DMF), isopropyl alcohol, N-methyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone is investigated using three molecular-scale "computer experiments". We modeled solvent-phosphorene interactions using an atomistic force field, based on ab initio calculations and lattice dynamics, that accurately reproduces experimental mechanical properties. We probed solvent molecule ordering at phosphorene/solvent interfaces and discovered that planar molecules such as N-methyl-2-pyrrolidone preferentially orient parallel to the interface. We subsequently measured the energy required to peel a single phosphorene monolayer from a stack of black phosphorus and analyzed the role of "wedges" of solvent molecules intercalating between phosphorene sheets in initiating exfoliation. The exfoliation efficacy of a solvent is enhanced when either molecular planarity "sharpens" this molecular wedge or strong phosphorene-solvent adhesion stabilizes the newly exposed phosphorene surfaces. Finally, we examined the colloidal stability of exfoliated flakes by simulating their aggregation and showed that dispersion is favored when the cohesive energy between the molecules in the solvent monolayer confined between the phosphorene sheets is high (as with DMSO) and is hindered when the adhesion between these molecules and phosphorene is strong; the molecular planarity in solvents like DMF enhances the cohesive energy. Our results are consistent with, and provide a molecular context for, experimental exfoliation studies of phosphorene and other layered solids, and our molecular insights into the significant role of solvent molecular geometry and ordering should complement prevalent solubility-parameter-based approaches in establishing design rules for effective nanomaterial exfoliation media.

  1. Large-scale exfoliation of inorganic layered compounds in aqueous surfactant solutions

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Ronan J.; King, Paul J.; Lotya, Mustafa; Wirtz, Christian; Khan, Umar; De, Sukanta; O' Neill, Arlene; Coleman, Jonathan N. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); CRANN, Trinity College Dublin, Dublin 2 (Ireland); Duesberg, Georg S. [CRANN, Trinity College Dublin, Dublin 2 (Ireland); School of Chemistry, Trinity College Dublin, Dublin 2 (Ireland); Grunlan, Jaime C.; Moriarty, Gregory [Department of Mechanical Engineering, Texas A and M University, College Station, Texas 77843 (United States); Chen, Jun [Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, AIIM Facility, University of Wollongong, NSW 2522 (Australia); Wang, Jiazhao [Institute for Superconducting and Electronic Materials, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, NSW 2522 (Australia); Minett, Andrew I. [Laboratory for Sustainable Technology, School of Chemical and Biomolecular Engineering, University of Sydney, Sydney, NSW 2006 (Australia); Nicolosi, Valeria [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2011-09-08

    A method to exfoliate MoS{sub 2} in large quantities in surfactant-water solutions is described. The layered material tends to be exfoliated as dispersions of thin, relatively defect-free flakes with lateral sizes of hundreds of nanometers. This method can be extended to a range of other layered compounds. The dispersed flakes can be mixed with nanotubes or graphene to greate functional hybrid materials. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Urea-assisted liquid-phase exfoliation of natural graphite into few-layer graphene

    Science.gov (United States)

    Hou, Dandan; Liu, Qinfu; Wang, Xianshuai; Qiao, Zhichuan; Wu, Yingke; Xu, Bohui; Ding, Shuli

    2018-05-01

    The mass production of graphene with high quality is desirable for its wide applications. Here, we demonstrated a facile method to exfoliate natural graphite into graphene in organic solvent by assisting of urea. The exfoliation of graphite may originate from the "molecular wedge" effect of urea, which can intercalate into the edge of natural graphite, thus facilitating the production of graphene dispersion with a high concentration up to 1.2 mg/mL. The obtained graphene is non-oxidized with negligible defects. Therefore, this approach has great promise in bulk production of graphene with superior quality for a variety of applications.

  3. One-Pot Exfoliation of Graphite and Synthesis of Nanographene/Dimesitylporphyrin Hybrids

    Science.gov (United States)

    Bernal, M. Mar; Pérez, Emilio M.

    2015-01-01

    A simple one-pot process to exfoliate graphite and synthesize nanographene-dimesitylporphyrin hybrids has been developed. Despite the bulky mesityl groups, which are expected to hinder the efficient π–π stacking between the porphyrin core and graphene, the liquid-phase exfoliation of graphite is significantly favored by the presence of the porphyrins. Metallation of the porphyrin further enhances this effect. The resulting graphene/porphyrin hybrids were characterized by spectroscopy (UV-visible, fluorescence, and Raman) and microscopy (STEM, scanning transmission electron microscopy). PMID:25984598

  4. Influence of Retrogression and Re-aging on the Exfoliation Corrosion Behavior of AA 7085 Sheets

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Ajay; Raja, V. S. [Indian Institute of Technology Bombay, Mumbai (India); Mukhopadhyay, A. K. [Defence Metallurgical Research Laboratory, Hyderabad (India)

    2016-08-15

    An attempt has been made to understand the influence of retrogression and re-aging (RRA) on the exfoliation corrosion behaviour of AA 7085 alloy in comparison with the peak aged condition (PA). Immersion tests using ASTM G34 and studies involving electrochemical impedance spectroscopy showed that the RRA treated alloy provided higher resistance to exfoliation corrosion than the PA treated alloy. The improved resistance was attributed to the enhanced Cu content and the discontinuous nature of the grain boundary precipitate, which was revealed through transmission electron microscopy.

  5. Applications of the oral scraped (exfoliative) cytology in oral cancer and precancer.

    Science.gov (United States)

    Acha, Amelia; Ruesga, María T; Rodríguez, María J; Martínez de Pancorbo, María A; Aguirre, José M

    2005-01-01

    Scraped (exfoliative) cytology is a simple and harmless procedure, which has been a controversial technique according to its real validity in oral pathology. Lately it has re-emerged due to its application in oral precancer and cancer as a diagnostic and predictive method as well as for monitoring patients. New diagnostic techniques have been developed, such as "brush biopsy" and multiple molecular studies using the cells collected. In this review we are going to analyse the more novel aspects related with the applications of the scraped or exfoliative cytology in oral precancerous and cancerous pathology, specially focusing on molecular studies and their diagnostic and prognostic implications.

  6. Exfoliation Propensity of Oxide Scale in Heat Exchangers Used for Supercritical CO2 Power Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Sabau, Adrian S [ORNL; Shingledecker, John P. [Electric Power Research Institute (EPRI); Kung, Steve [Electric Power Research Institute (EPRI); Wright, Ian G. [WrightHT, Inc.; Nash, Jim [Brayton Energy, LLC, Hampton, NH

    2016-01-01

    Supercritical CO2 (sCO2) Brayton cycle systems offer the possibility of improved efficiency in future fossil energy power generation plants operating at temperatures of 650 C and above. As there are few data on the oxidation/corrosion behavior of structural alloys in sCO2 at these temperatures, modeling to predict the propensity for oxide exfoliation is not well developed, thus hindering materials selection for these novel cycles. The ultimate goal of this effort is to provide needed data on scale exfoliation behavior in sCO2 for confident alloy selection. To date, a model developed by ORNL and EPRI for the exfoliation of oxide scales formed on boiler tubes in high-temperature, high-pressure steam has proven useful for managing exfoliation in conventional steam plants. A major input provided by the model is the ability to predict the likelihood of scale failure and loss based on understanding of the evolution of the oxide morphologies and the conditions that result in susceptibility to exfoliation. This paper describes initial steps taken to extend the existing model for exfoliation of steam-side oxide scales to sCO2 conditions. The main differences between high-temperature, high-pressure steam and sCO2 that impact the model involve (i) significant geometrical differences in the heat exchangers, ranging from standard pressurized tubes seen typically in steam-producing boilers to designs for sCO2 that employ variously-curved thin walls to create shaped flow paths for extended heat transfer area and small channel cross-sections to promote thermal convection and support pressure loads; (ii) changed operating characteristics with sCO2 due to the differences in physical and thermal properties compared to steam; and (iii) possible modification of the scale morphologies, hence properties that influence exfoliation behavior, due to reaction with carbon species from sCO2. The numerical simulations conducted were based on an assumed sCO2 operating schedule and several

  7. Mechanistic examination of pre-exfoliating confinement of surface-active polystyrene nanobeads within pristine clay.

    Science.gov (United States)

    Khvan, Svetlana; Kim, Junkyung; Lee, Sang-Soo

    2007-02-01

    Hydrophobic polymer (PS) nanoparticles preformed through an emulsifier-free emulsion polymerization method were successfully incorporated into a gallery of pristine sodium montmorillonite via interfacial cation exchange. The polymer beads confined between clay nanosheets were capable of (1) preventing the silicate layers from restacking and (2) maintaining the exfoliated state of clay. The increase in the abundance of surface groups promoted adsorption of the nanobeads onto the silicate surface and eventually led to the establishment of strong polymer-clay interactions. These findings suggest that, on the basis of the obtained pre-exfoliated clay masterbatch, the presence of strong polymer-clay interactions could improve the mechanical performance of nanocomposites.

  8. Optimization of the size and yield of graphene oxide sheets in the exfoliation step

    OpenAIRE

    Botas, Cristina; Pérez, A.M. (Ana); Álvarez, Patricia; Santamaría, Ricardo; Granda, Marcos; Blanco, Clara; Menéndez, Rosa

    2017-01-01

    In this paper we demonstrate that the yield and size of the graphene oxide sheets (GO) obtained by sonication of graphite oxide (GrO) can be optimized not only by selecting the appropriate exfoliation conditions but also as a function of the crystalline structure of the parent graphite. A larger crystal size in the parent graphite favors GrO exfoliation and yields larger sheets in shorter sonication times, independently of the oxygen content of the GrO. A maximum yield of GO is obtained in al...

  9. Preparation and Characterization of EG-Chitosan Nanocomposites via Direct Exfoliation: A Green Methodology

    Directory of Open Access Journals (Sweden)

    Christian Demitri

    2015-12-01

    Full Text Available In this study, free-standing expanded graphite chitosan (EG-chitosan nanocomposite films have been prepared using a novel green and simple preparation method, starting from a commercial expandable graphite (GIC. The in situ exfoliation of GIC by a solvent-free sonication method was monitored as a function of the process parameters using X-ray diffraction (XRD, transmission electron microscopy (TEM, dynamic light scattering (DLS and UV-visible transmittance (UV-VIS analyses. The optimal process parameters were selected in order to obtain an efficient dispersion of EG in chitosan solutions. The effective EG amount after the in situ exfoliation was also determined by thermogravimetric analyses.

  10. [Environmental toxins in breast milk].

    Science.gov (United States)

    Bratlid, Dag

    2009-12-17

    Breast milk is very important to ensure infants a well-composed and safe diet during the first year of life. However, the quality of breast milk seems to be affected by an increasing amount of environmental toxins (particularly so-called Persistent, Bioaccumulative Toxins [PBTs]). Many concerns have been raised about the negative effects this may have on infant health. The article is a review of literature (mainly review articles) identified through a non-systematic search in PubMed. The concentration of PBTs in breast milk is mainly caused by man's position as the terminal link in the nutritional chain. Many breast-fed infants have a daily intake of such toxins that exceed limits defined for the population in general. Animal studies demonstrate effects on endocrine function and neurotoxicity in the offspring, and a number of human studies seem to point in the same direction. However the "original" optimal composition of breast milk still seems to protect against long-term effects of such toxicity. There is international consensus about the need to monitor breast milk for the presence of PBTs. Such surveillance will be a good indicator of the population's general exposure to these toxins and may also contribute to identifying groups as risk who should not breast-feed their children for a long time.

  11. Risk Assessment of Shellfish Toxins

    Directory of Open Access Journals (Sweden)

    Rex Munday

    2013-11-01

    Full Text Available Complex secondary metabolites, some of which are highly toxic to mammals, are produced by many marine organisms. Some of these organisms are important food sources for marine animals and, when ingested, the toxins that they produce may be absorbed and stored in the tissues of the predators, which then become toxic to animals higher up the food chain. This is a particular problem with shellfish, and many cases of poisoning are reported in shellfish consumers each year. At present, there is no practicable means of preventing uptake of the toxins by shellfish or of removing them after harvesting. Assessment of the risk posed by such toxins is therefore required in order to determine levels that are unlikely to cause adverse effects in humans and to permit the establishment of regulatory limits in shellfish for human consumption. In the present review, the basic principles of risk assessment are described, and the progress made toward robust risk assessment of seafood toxins is discussed. While good progress has been made, it is clear that further toxicological studies are required before this goal is fully achieved.

  12. Food irradiation and bacterial toxins

    International Nuclear Information System (INIS)

    Tranter, H.S.; Modi, N.K.; Hambleton, P.; Melling, J.; Rose, S.; Stringer, M.F.

    1987-01-01

    The authors' findings indicate that irradiation confers no advantage over heat processing in respect of bacterial toxins (clostridium botulinum, neurotoxin A and staphylococcal enterotoxin A). It follows that irradiation at doses less than the ACINF recommended upper limit of 10 kGy could not be used to improve the ambient temperature shelf life on non-acid foods. (author)

  13. Botulinum toxin for vaginismus treatment.

    Science.gov (United States)

    Ferreira, Juliana Rocha; Souza, Renan Pedra

    2012-01-01

    Vaginismus is characterized by recurrent or persistent involuntary contraction of the perineal muscles surrounding the outer third of the vagina when penile, finger, tampon, or speculum penetration is attempted. Recent results have suggested the use of botulinum toxin for the treatment of vaginismus. Here, we assessed previously published data to evaluate the therapeutic effectiveness of botulinum toxin for vaginismus. We have carried out a systematic review followed by a meta-analysis. Our results indicate that botulinum toxin is an effective therapeutic option for patients with vaginismus (pooled odds ratio of 8.723 with 95% confidence interval limits of 1.942 and 39.162, p = 0.005). This may hold particularly true in treatment-refractory patients because most of the studies included in this meta-analysis have enrolled these subjects in their primary analysis. Botulinum toxin appears to bea reasonable intervention for vaginismus. However, this conclusion should be read carefully because of the deficiency of placebo-controlled randomized clinical trials and the quality issues presented in the existing ones.

  14. Shigella Sonnei and Shiga Toxin

    Centers for Disease Control (CDC) Podcasts

    2016-07-28

    Katherine Lamba, an infectious disease epidemiologist with the California Department of Public Health, discusses Shiga Toxin producing Shigella sonnei.  Created: 7/28/2016 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 7/28/2016.

  15. Exfoliation of Threading Dislocation-Free, Single-Crystalline, Ultrathin Gallium Nitride Nanomembranes

    KAUST Repository

    Elafandy, Rami T.; Cha, Dong Kyu; Majid, Mohammed Abdul; Ng, Tien Khee; Ooi, Boon S.; Zhao, Lan

    2014-01-01

    -efficiency, low-cost, GaN-based heterostructure devices. For the first time, the chemical exfoliation of completely TD-free, single-crystalline, ultrathin (tens of nanometers) GaN nanomembranes is demonstrated using UV-assisted electroless chemical etching

  16. Ultrathin Topological Insulator Bi 2 Se 3 Nanoribbons Exfoliated by Atomic Force Microscopy

    KAUST Repository

    Hong, Seung Sae; Kundhikanjana, Worasom; Cha, Judy J.; Lai, Keji; Kong, Desheng; Meister, Stefan; Kelly, Michael A.; Shen, Zhi-Xun; Cui, Yi

    2010-01-01

    Ultrathin topological insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi2Se 3), a single Dirac-cone topological insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi2Se3 nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1-2 QLs and 4-5 QLs. Transport measurement carried out on an exfoliated (>5 QLs) Bi2Se3 device shows nonmetallic temperature dependence of resistance, in sharp contrast to the metallic behavior seen in thick (>50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for studying the transition from quantum spin Hall surface to edge states. © 2010 American Chemical Society.

  17. Gas storage cylinder formed from a composition containing thermally exfoliated graphite

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2012-01-01

    A gas storage cylinder or gas storage cylinder liner, formed from a polymer composite, containing at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m(exp 2)/g to 2600 m(exp 2)2/g.

  18. Heterocyclic aramid nanoparticle-assisted graphene exfoliation for fabrication of pristine graphene-based composite paper

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Yao; Liu, Qi; Fan, Jinchen, E-mail: Jinchen.fan@shiep.edu.cn; Shi, Penghui; Min, Yulin, E-mail: ahaqmylin@126.com; Xu, Qunjie [Shanghai University of Electric Power, Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, College of Environmental and Chemical Engineering (China)

    2015-07-15

    Mechanically strong, electrically conductive, and flexible pristine graphene-based composite paper was prepared based on heterocyclic aramid nanoparticle-assisted liquid-phase exfoliation of graphite. The macroscopic heterocyclic aramid yarns were split and assembled into heterocyclic aramid nanoparticles with the size of ∼30 nm by deprotonation in dimethylsulfoxide in the presence of potassium hydroxide. The obtained heterocyclic aramid nanoparticles dimethylsulfoxide dispersion was used as good medium solvent for highly efficiency liquid-phase exfoliation of graphite. The results demonstrated that the concentration of exfoliated graphene can facile reaches ∼2.72 mg/mL after direct sonication of 7 h with assist of heterocyclic aramid nanoparticles. After exfoliation, the self-assembled pristine graphene-based composite paper was fabricated by vacuum-assisted filtration. Due to the introduction of heterocyclic aramid nanoparticles, the self-assembled pristine graphene/heterocyclic aramid nanoparticles composite paper exhibited good mechanical property with tensile strength of ∼129.7 MPa, meantime, has a high electrical conductivity of ∼1.42 × 10{sup 4} S/m.

  19. High-yield exfoliation of graphene using ternary-solvent strategy for detecting volatile organic compounds

    Science.gov (United States)

    Zhang, Shao-Lin; Zhang, Zhijun; Yang, Woo-Chul

    2016-01-01

    Despite the great progress in the theory and experimental verification we made in past decade, the practical application of graphene is still hindered by the lack of efficient, economical, scalable, ease-processing exfoliation method. Herein, we propose a facile, low-cost, and efficient liquid-phase exfoliation process using low boiling-temperature solvent mixture to fabricate few-layer graphene in large scale. The Hansen solubility parameter theory was applied to help optimize the composition of solvent mixture. Aqueous-based ternary-solvent mixture, for the first time, was adapted to exfoliate graphene. We demonstrate that the exfoliation efficiency using ternary-solvent mixture surpasses that from binary-solvent approach. The final product concentration after optimization was over 260 μg/ml. The concentrated graphene dispersion was used to fabricate gas sensor for detecting volatile organic gases. Taking advantage of large surface area, large number of adsorption sites, and well-preserved basal plane, the mass-produced graphene nanosheets exhibited promising sensing potential toward ethanol and methanol vapors.

  20. Micronucleus Assay in Exfoliated Buccal Epithelial Cells Using Liquid Based Cytology Preparations in Building Construction Workers.

    Science.gov (United States)

    Arul, P; Smitha, Shetty; Masilamani, Suresh; Akshatha, C

    2018-01-01

    Cytogenetic damage in exfoliated buccal epithelial cells due to environmental and occupational exposure is often monitored by micronucleus (MN) assay using liquid based cytology (LBC) preparations. This study was performed to evaluate MN in exfoliated buccal epithelial cells of building construction workers using LBC preparations. LBC preparations of exfoliated buccal epithelial cells from 100 subjects [50 building construction workers (cases) and 50 administrative staffs (controls)] was evaluated by May-Grunwald Giemsa, Hematoxylin and Eosin and Papanicolaou stains. Student's t test was used for statistical analysis and a P value of 5 years) and smokers and non-smokers of cases (P=0.001). However, there were meaningful differences regarding mean frequencies of MN between smokers, non-smokers, those with alcohol consumption or not in cases and controls using various stains (P=0.001). There was an increased risk of cytogenetic damage in building construction workers. However, evaluation of MN of exfoliated buccal epithelial cells in building construction workers serve as a minimally invasive biomarker for cytogenetic damage. LBC preparations can be applied for MN assay as it improves the quality of smears and cell morphology, decreases the confounding factors and reduces false positive results.

  1. Synthesis of SnSe nanosheets by hydrothermal intercalation and exfoliation route and their photoresponse properties

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Xiaohui; Qi, Xiang, E-mail: xqi@xtu.edu.cn; Shen, Yongzhen; Xu, Guanghua; Li, Jun; Li, Zhenqing; Huang, Zongyu; Zhong, Jianxin

    2016-12-15

    Two dimensional Tin Selenide (SnSe) nanosheets (NSs) have been prepared via a facile hydrothermal intercalation and exfoliation route. Morphological test verifies high yield of SnSe NSs with good quality. Additional X-ray diffraction pattern and Raman spectra are carried out and confirm the exfoliated SnSe nanosheet is pure and well crystalized. AFM measurement, along with the SEM images and Raman shifts, reveals few-layers SnSe nanosheet has been successfully obtained after hydrothermal intercalation and exfoliation route. Photoelectrochemical tests also demonstrate the photocurrent density of SnSe NSs is greatly improved compare to that of bulk SnSe. Photocurrent density of exfoliated SnSe NSs can achieve 16 μA/cm{sup 2} when the applied potential is 0.8 V, which is nearly four times higher than that of bulk SnSe. This work demonstrates that the two-dimensional SnSe NSs may have a great potential application in photovoltaic devices.

  2. Synthesis of SnSe nanosheets by hydrothermal intercalation and exfoliation route and their photoresponse properties

    International Nuclear Information System (INIS)

    Ren, Xiaohui; Qi, Xiang; Shen, Yongzhen; Xu, Guanghua; Li, Jun; Li, Zhenqing; Huang, Zongyu; Zhong, Jianxin

    2016-01-01

    Two dimensional Tin Selenide (SnSe) nanosheets (NSs) have been prepared via a facile hydrothermal intercalation and exfoliation route. Morphological test verifies high yield of SnSe NSs with good quality. Additional X-ray diffraction pattern and Raman spectra are carried out and confirm the exfoliated SnSe nanosheet is pure and well crystalized. AFM measurement, along with the SEM images and Raman shifts, reveals few-layers SnSe nanosheet has been successfully obtained after hydrothermal intercalation and exfoliation route. Photoelectrochemical tests also demonstrate the photocurrent density of SnSe NSs is greatly improved compare to that of bulk SnSe. Photocurrent density of exfoliated SnSe NSs can achieve 16 μA/cm"2 when the applied potential is 0.8 V, which is nearly four times higher than that of bulk SnSe. This work demonstrates that the two-dimensional SnSe NSs may have a great potential application in photovoltaic devices.

  3. Mobilization of dust and exfoliation of erosion product films in tokamaks

    International Nuclear Information System (INIS)

    Martynenko, Yu. V.; Nagel, M. Yu.

    2012-01-01

    The mobilization of dust (i.e., detachment and removal of dust grains from a substrate) and the exfoliation of a film of erosion products in tokamaks have been studied theoretically. The following mechanisms of dust mobilization have been taken into account: (i) sharp heating (thermal shock) as a result of, e.g., plasma disruption and edge instabilities; (ii) substrate vibrations; and (iii) gas and plasma flow (wind) action. The most effective mobilization takes place under the action of sharp heating. Power fluxes that are characteristic of edge instabilities can mobilize dust grains with dimensions within or even greater than 0.1–1 μm. The velocities of detached grains reach ν ∼ 100 m/s for heavy grains and up to ν ∼ 300 m/s for the light ones. Conditions favoring the exfoliation of a film of erosion products are determined. It is shown that exfoliation under the action of edge instabilities can take place at a film thickness of h > 1 μm. Under the action of thermal-shock-induced stresses, the exfoliated film flakes with a size ranging from fractions of a millimeter to several centimeters break into pieces.

  4. Mobilization of dust and exfoliation of erosion product films in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Martynenko, Yu. V.; Nagel, M. Yu. [National Research Centre Kurchatov Institute (Russian Federation)

    2012-04-15

    The mobilization of dust (i.e., detachment and removal of dust grains from a substrate) and the exfoliation of a film of erosion products in tokamaks have been studied theoretically. The following mechanisms of dust mobilization have been taken into account: (i) sharp heating (thermal shock) as a result of, e.g., plasma disruption and edge instabilities; (ii) substrate vibrations; and (iii) gas and plasma flow (wind) action. The most effective mobilization takes place under the action of sharp heating. Power fluxes that are characteristic of edge instabilities can mobilize dust grains with dimensions within or even greater than 0.1-1 {mu}m. The velocities of detached grains reach {nu} {approx} 100 m/s for heavy grains and up to {nu} {approx} 300 m/s for the light ones. Conditions favoring the exfoliation of a film of erosion products are determined. It is shown that exfoliation under the action of edge instabilities can take place at a film thickness of h > 1 {mu}m. Under the action of thermal-shock-induced stresses, the exfoliated film flakes with a size ranging from fractions of a millimeter to several centimeters break into pieces.

  5. Heterocyclic aramid nanoparticle-assisted graphene exfoliation for fabrication of pristine graphene-based composite paper

    International Nuclear Information System (INIS)

    Mo, Yao; Liu, Qi; Fan, Jinchen; Shi, Penghui; Min, Yulin; Xu, Qunjie

    2015-01-01

    Mechanically strong, electrically conductive, and flexible pristine graphene-based composite paper was prepared based on heterocyclic aramid nanoparticle-assisted liquid-phase exfoliation of graphite. The macroscopic heterocyclic aramid yarns were split and assembled into heterocyclic aramid nanoparticles with the size of ∼30 nm by deprotonation in dimethylsulfoxide in the presence of potassium hydroxide. The obtained heterocyclic aramid nanoparticles dimethylsulfoxide dispersion was used as good medium solvent for highly efficiency liquid-phase exfoliation of graphite. The results demonstrated that the concentration of exfoliated graphene can facile reaches ∼2.72 mg/mL after direct sonication of 7 h with assist of heterocyclic aramid nanoparticles. After exfoliation, the self-assembled pristine graphene-based composite paper was fabricated by vacuum-assisted filtration. Due to the introduction of heterocyclic aramid nanoparticles, the self-assembled pristine graphene/heterocyclic aramid nanoparticles composite paper exhibited good mechanical property with tensile strength of ∼129.7 MPa, meantime, has a high electrical conductivity of ∼1.42 × 10 4  S/m.

  6. Exfoliation of the tungsten fibreform nanostructure by unipolar arcing in the LHD divertor plasma

    Science.gov (United States)

    Tokitani, M.; Kajita, S.; Masuzaki, S.; Hirahata, Y.; Ohno, N.; Tanabe, T.; LHD Experiment Group

    2011-10-01

    The tungsten nanostructure (W-fuzz) created in the linear divertor simulator (NAGDIS) was exposed to the Large Helical Device (LHD) divertor plasma for only 2 s (1 shot) to study exfoliation/erosion and microscopic modifications due to the high heat/particle loading under high magnetic field conditions. Very fine and randomly moved unipolar arc trails were clearly observed on about half of the W-fuzz area (6 × 10 mm2). The fuzzy surface was exfoliated by continuously moving arc spots even for the very short exposure time. This is the first observation of unipolar arcing and exfoliation of some areas of the W-fuzz structure itself in a large plasma confinement device with a high magnetic field. The typical width and depth of each arc trail were about 8 µm and 1 µm, respectively, and the arc spots moved randomly on the micrometre scale. The fractality of the arc trails was analysed using a box-counting method, and the fractal dimension (D) of the arc trails was estimated to be D ≈ 1.922. This value indicated that the arc spots moved in Brownian motion, and were scarcely influenced by the magnetic field. One should note that such a large scale exfoliation due to unipolar arcing may enhance the surface erosion of the tungsten armour and act as a serious impurity source for fusion plasmas.

  7. Hole-doping of mechanically exfoliated graphene by confined hydration layers

    NARCIS (Netherlands)

    Bollmann, Tjeerd Rogier Johannes; Antipina, L.Y.; Temmen, M.; Reichling, M.; Sorokin, P.B.

    2015-01-01

    By the use of non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM), we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CaF2(111). Hydration layers confined between the graphene and the

  8. Exfoliation of the tungsten fibreform nanostructure by unipolar arcing in the LHD divertor plasma

    International Nuclear Information System (INIS)

    Tokitani, M.; Masuzaki, S.; Kajita, S.; Hirahata, Y.; Ohno, N.; Tanabe, T.

    2011-01-01

    The tungsten nanostructure (W-fuzz) created in the linear divertor simulator (NAGDIS) was exposed to the Large Helical Device (LHD) divertor plasma for only 2 s (1 shot) to study exfoliation/erosion and microscopic modifications due to the high heat/particle loading under high magnetic field conditions. Very fine and randomly moved unipolar arc trails were clearly observed on about half of the W-fuzz area (6 x 10 mm 2 ). The fuzzy surface was exfoliated by continuously moving arc spots even for the very short exposure time. This is the first observation of unipolar arcing and exfoliation of some areas of the W-fuzz structure itself in a large plasma confinement device with a high magnetic field. The typical width and depth of each arc trail were about 8 μm and 1 μm, respectively, and the arc spots moved randomly on the micrometre scale. The fractality of the arc trails was analysed using a box-counting method, and the fractal dimension (D) of the arc trails was estimated to be D ∼ 1.922. This value indicated that the arc spots moved in Brownian motion, and were scarcely influenced by the magnetic field. One should note that such a large scale exfoliation due to unipolar arcing may enhance the surface erosion of the tungsten armour and act as a serious impurity source for fusion plasmas. (letter)

  9. Electrospray painted article containing thermally exfoliated graphite oxide and method for their manufacture

    Science.gov (United States)

    Korkut, Sibel (Inventor); Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A painted polymer part containing a conductive polymer composition containing at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the painted polymer part has been electrospray painted.

  10. Imidazolium Ionic Liquid Mediates Black Phosphorus Exfoliation while Preventing Phosphorene Decomposition.

    Science.gov (United States)

    Chaban, Vitaly V; Fileti, Eudes Eterno; Prezhdo, Oleg V

    2017-06-27

    Forthcoming applications in electronics and optoelectronics make phosphorene a subject of vigorous research efforts. Solvent-assisted exfoliation of phosphorene promises affordable delivery in industrial quantities for future applications. We demonstrate, using equilibrium, steered and umbrella sampling molecular dynamics, that the 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF 4 ] ionic liquid is an excellent solvent for phosphorene exfoliation. The presence of both hydrophobic and hydrophilic moieties, as well as substantial shear viscosity, allows [EMIM][BF 4 ] simultaneously to facilitate separation of phosphorene sheets and to protect them from getting in direct contact with moisture and oxygen. The exfoliation thermodynamics is moderately unfavorable, which indicates that an external stimulus is necessary. Unexpectedly, [EMIM][BF 4 ] does not coordinates phosphorene by π-electron stacking with the imidazole ring. Instead, the solvation proceeds via hydrophobic side chains, while polar imidazole rings form an electrostatically stabilized protective layer. The simulations suggest that further efforts in solvent engineering for phosphorene exfoliation should concentrate on use of weakly coordinating ions and grafting groups that promote stronger dispersion interactions and on elongation of nonpolar chains.

  11. Sequential structural and optical evolution of MoS2 by chemical synthesis and exfoliation

    Science.gov (United States)

    Kim, Ju Hwan; Kim, Jungkil; Oh, Si Duck; Kim, Sung; Choi, Suk-Ho

    2015-06-01

    Various types of MoS2 structures are successfully obtained by using economical and facile sequential synthesis and exfoliation methods. Spherically-shaped lumps of multilayer (ML) MoS2 are prepared by using a conventional hydrothermal method and were subsequently 1st-exfoliated in hydrazine while being kept in autoclave to be unrolled and separated into five-to-six-layer MoS2 pieces of several-hundred nm in size. The MoS2 MLs are 2nd-exfoliated in sodium naphthalenide under an Ar ambient to finally produce bilayer MoS2 crystals of ~100 nm. The sequential exfoliation processes downsize MoS2 laterally and reduce its number of layers. The three types of MoS2 allotropes exhibit particular optical properties corresponding to their structural differences. These results suggest that two-dimensional MoS2 crystals can be prepared by employing only chemical techniques without starting from high-pressure-synthesized bulk MoS2 crystals.

  12. Two-dimensional materials from high-throughput computational exfoliation of experimentally known compounds

    Science.gov (United States)

    Mounet, Nicolas; Gibertini, Marco; Schwaller, Philippe; Campi, Davide; Merkys, Andrius; Marrazzo, Antimo; Sohier, Thibault; Castelli, Ivano Eligio; Cepellotti, Andrea; Pizzi, Giovanni; Marzari, Nicola

    2018-02-01

    Two-dimensional (2D) materials have emerged as promising candidates for next-generation electronic and optoelectronic applications. Yet, only a few dozen 2D materials have been successfully synthesized or exfoliated. Here, we search for 2D materials that can be easily exfoliated from their parent compounds. Starting from 108,423 unique, experimentally known 3D compounds, we identify a subset of 5,619 compounds that appear layered according to robust geometric and bonding criteria. High-throughput calculations using van der Waals density functional theory, validated against experimental structural data and calculated random phase approximation binding energies, further allowed the identification of 1,825 compounds that are either easily or potentially exfoliable. In particular, the subset of 1,036 easily exfoliable cases provides novel structural prototypes and simple ternary compounds as well as a large portfolio of materials to search from for optimal properties. For a subset of 258 compounds, we explore vibrational, electronic, magnetic and topological properties, identifying 56 ferromagnetic and antiferromagnetic systems, including half-metals and half-semiconductors.

  13. Preparation and characterization of self-assembly hydrogels with exfoliated montmorillonite nanosheets and chitosan

    Science.gov (United States)

    Wang, Wei; Zhao, Yunliang; Yi, Hao; Chen, Tianxing; Kang, Shichang; Li, Hongqiang; Song, Shaoxian

    2018-01-01

    Novel montmorillonite-nanosheet/chitosan (MMTNS/CS) hydrogels fabricated via the self-assembly of exfoliated MMTNS and CS chains were investigated. The exfoliation of MMTNS, self-assembly mechanism and structure of MMTNS/CS hydrogels were characterized by an atomic force microscope, scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscope, energy-dispersive x-ray spectroscope and Brunauer-Emmett-Teller analyzer, respectively. The results indicated that MMT could be easily exfoliated to nanosheets with a thickness of 1 ˜ 5 nm in aqueous solution by an ultrasonic base upon interlayer hydration. The formation mechanism of the self-assembly hydrogels was due to the hydrogen bond (-OH ··· +NH3-) and electrostatic interaction between the MMTNS and CS. The MMTNSs were connected consecutively by CS in-plane to form a huge slice. The porous structure of the hydrogels was controllable by adjusting the MMTNS/CS mass ratio. The hydrogels could be used as adsorbents for sewage treatments, carriers for drugs, microorganisms and catalyzers due to their controllable porous structure and tremendous specific surface area which were derived from the completely exfoliated MMTNS.

  14. Fabrication of two-dimensional nanosheets via water freezing expansion exfoliation

    International Nuclear Information System (INIS)

    Li, Chen; Wang, Tailin; Wu, Yongzhong; Ma, Fukun; Zhao, Gang; Hao, Xiaopeng

    2014-01-01

    Layered materials, if exfoliated effectively, will exhibit several unique properties, offering great potential for diverse applications. To this end, in this study, we develop a novel, universal, and environmentally friendly method named as ‘water freezing expansion exfoliation’ for producing two-dimensional nanosheets. This method exploits the expansion in the volume of water upon freezing. When the water freezing expansion condition is reproduced in layered materials, the layers exfoliate to overcome the van der Waals force between them. The expansion process is performed by repeated cycling between 4 °C and −20 °C to effectively exfoliate layered materials of graphite, hexagonal boron nitride (h-BN), MoS 2 and WS 2 . Systematic characterization of the samples thus obtained using electron microscopy and optical studies substantiate the formation of thin flakes (graphene, h-BN, MoS 2 , and WS 2 nanosheets). The method demonstrated in this study is cost-effective and does not demand sophisticated equipment and stringent high temperature conditions. Given this general applicability, this method holds great promise for exfoliating layered materials that are sensitive to elevated temperature. (paper)

  15. Isocyanate toughening of pCBT/organoclay nanocomposites with exfoliated structure and enhanced mechanical properties

    Directory of Open Access Journals (Sweden)

    T. Abt

    2014-12-01

    Full Text Available Cyclic butylene terephthalate (CBT® is an interesting matrix material for the preparation of nanocomposites due to its very low, water-like melt viscosity which favours clay exfoliation. Nevertheless, polymerized CBT (pCBT is inherently brittle. This paper reports the preparation of isocyanate-toughened nanocomposites made from CBT and organo-modified montmorillonite. The role of the organoclay as reinforcement and the polymeric isocyanate (PMDI as toughening agent on the properties of pCBT was studied. The organoclay increased the stiffness and strength by up to 20% whereas the PMDI improved the deformation behaviour. However, the PMDI did not affect the degree of clay dispersion or exfoliation and flocculated-intercalated structures were observed. The compatibility between the pCBT matrix and clay was further increased by preparing PMDI-tethered intercalated organoclay. The modified organoclay then exfoliated during ring-opening polymerization and yielded true pCBT/clay nanocomposites. This work demonstrates that reactive chain extension of CBT with a polyfunctional isocyanate is an effective method to obtain toughened pCBT nanocomposites. Moreover, isocyanates can enhance the compatibility between pCBT and nanofiller as well as the degree of exfoliation.

  16. Ultrathin Topological Insulator Bi 2 Se 3 Nanoribbons Exfoliated by Atomic Force Microscopy

    KAUST Repository

    Hong, Seung Sae

    2010-08-11

    Ultrathin topological insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi2Se 3), a single Dirac-cone topological insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi2Se3 nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1-2 QLs and 4-5 QLs. Transport measurement carried out on an exfoliated (>5 QLs) Bi2Se3 device shows nonmetallic temperature dependence of resistance, in sharp contrast to the metallic behavior seen in thick (>50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for studying the transition from quantum spin Hall surface to edge states. © 2010 American Chemical Society.

  17. High-quality graphene flakes exfoliated on a flat hydrophobic polymer

    DEFF Research Database (Denmark)

    Pedrinazzi, Paolo; Caridad, José M.; Mackenzie, David M. A.

    2018-01-01

    the environment of the graphene flake is completely changed, by encapsulating preselected flakes between hexagonal boron nitride layers. The exfoliation of clean, pristine graphene layers directly on flat polymer substrates enables high performance, supported, and non-encapsulated graphene devices for flexible...

  18. Decolorizing of azo dye Reactive red 24 aqueous solution using exfoliated graphite and H2O2 under ultrasound irradiation.

    Science.gov (United States)

    Li, Mei; Li, Ji-Tai; Sun, Han-Wen

    2008-07-01

    At its natural pH (6.95), the decolorization of Reactive red 24 in ultrasound, ultrasound/H2O2, exfoliated graphite, ultrasound/exfoliated graphite, exfoliated graphite/H2O2 and ultrasound/exfoliated graphite/H2O2 systems were compared. An enhancement was observed for the decolorization in ultrasound/exfoliated graphite/H2O2 system. The effect of solution pH, H2O2 and exfoliated graphite dosages, and temperature on the decolorization of Reactive red 24 was investigated. The sonochemical treatment in combination with exfoliated graphite/H2O2 showed a synergistic effect for the decolorization of Reactive red 24. The results indicated that under proper conditions, there was a possibility to remove Reactive red 24 very efficient from aqueous solution. The decolorization of other azo dyes (Reactive red 2, Methyl orange, Acid red 1, Acid red 73, Acid red 249, Acid orange 7, Acid blue 113, Acid brown 75, Acid green 20, Acid yellow 42, Acid mordant brown 33, Acid mordant yellow 10 and Direct green 1) was also investigated, at their natural pH.

  19. Why do we study animal toxins?

    Science.gov (United States)

    ZHANG, Yun

    2015-01-01

    Venom (toxins) is an important trait evolved along the evolutionary tree of animals. Our knowledges on venoms, such as their origins and loss, the biological relevance and the coevolutionary patterns with other organisms are greatly helpful in understanding many fundamental biological questions, i.e., the environmental adaptation and survival competition, the evolution shaped development and balance of venoms, and the sophisticated correlations among venom, immunity, body power, intelligence, their genetic basis, inherent association, as well as the cost-benefit and trade-offs of biological economy. Lethal animal envenomation can be found worldwide. However, from foe to friend, toxin studies have led lots of important discoveries and exciting avenues in deciphering and fighting human diseases, including the works awarded the Nobel Prize and lots of key clinic therapeutics. According to our survey, so far, only less than 0.1% of the toxins of the venomous animals in China have been explored. We emphasize on the similarities shared by venom and immune systems, as well as the studies of toxin knowledge-based physiological toxin-like proteins/peptides (TLPs). We propose the natural pairing hypothesis. Evolution links toxins with humans. Our mission is to find out the right natural pairings and interactions of our body elements with toxins, and with endogenous toxin-like molecules. Although, in nature, toxins may endanger human lives, but from a philosophical point of view, knowing them well is an effective way to better understand ourselves. So, this is why we study toxins. PMID:26228472

  20. Superhydrophilic graphite surfaces and water-dispersible graphite colloids by electrochemical exfoliation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli, 320 Taiwan (China); Chen, Shih-Ming; Lai, Wei-Hao [Materials and Chemical Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu, 31040 Taiwan (China); Sheng, Yu-Jane [Department of Chemical Engineering, National Taiwan University, Taipei, 106 Taiwan (China); Tsao, Heng-Kwong [Department of Chemical and Materials Engineering, Department of Physics, National Central University, Jhongli, 320 Taiwan (China)

    2013-08-14

    Superhydrophilic graphite surfaces and water-dispersible graphite colloids are obtained by electrochemical exfoliation with hydrophobic graphite electrodes. Such counterintuitive characteristics are caused by partial oxidation and investigated by examining both graphite electrodes and exfoliated particles after electrolysis. The extent of surface oxidation can be explored through contact angle measurement, scanning electron microscope, electrical sheet resistance, x-ray photoelectron spectroscopy, zeta-potential analyzer, thermogravimetric analysis, UV-visible, and Raman spectroscopy. The degree of wettability of the graphite anode can be altered by the electrolytic current and time. The water contact angle declines generally with increasing the electrolytic current or time. After a sufficient time, the graphite anode becomes superhydrophilic and its hydrophobicity can be recovered by peeling with adhesive tape. This consequence reveals that the anodic graphite is oxidized by oxygen bubbles but the oxidation just occurs at the outer layers of the graphite sheet. Moreover, the characteristics of oxidation revealed by UV peak shift, peak ratio between D and G bands, and negative zeta-potential indicate the presence of graphite oxide on the outer shell of the exfoliated colloids. However, thermogravimetric analysis for the extent of decomposition of oxygen functional groups verifies that the amount of oxygen groups is significantly less than that of graphite oxide prepared via Hummer method. The structure of this partially oxidized graphite may consist of a graphite core covered with an oxidized shell. The properties of the exfoliated colloids are also influenced by pH of the electrolytic solution. As pH is increased, the extent of oxidation descends and the thickness of oxidized shell decreases. Those results reveal that the degree of oxidation of exfoliated nanoparticles can be manipulated simply by controlling pH.

  1. On the exfoliating polymeric cellular dosage forms for immediate drug release.

    Science.gov (United States)

    Blaesi, Aron H; Saka, Nannaji

    2016-06-01

    The most prevalent pharmaceutical dosage forms at present-the oral immediate-release tablets and capsules-are granular solids. Though effective in releasing drug rapidly, development and manufacture of such dosage forms are fraught with difficulties inherent to particulate processing. Predictable dosage form manufacture could be achieved by liquid-based processing, but cast solid dosage forms are not suitable for immediate drug release due to their resistance to fluid percolation. To overcome this limitation, we have recently introduced cellular dosage forms that can be readily prepared from polymeric melts. It has been shown that open-cell structures comprising polyethylene glycol 8000 (PEG 8k) excipient and a drug exfoliate upon immersion in a dissolution medium. The drug is then released rapidly due to the large specific surface area of the exfoliations. In this work, we vary the molecular weight of the PEG excipient and investigate its effect on the drug release kinetics of structures with predominantly open-cell topology. We demonstrate that the exfoliation rate decreases substantially if the excipient molecular weight is increased from 12 to 100kg/mol, which causes the drug dissolution time to increase by more than a factor of ten. A model is then developed to elucidate the exfoliation behavior of cellular structures. Diverse transport processes are considered: percolation due to capillarity, diffusion of dissolution medium through the cell walls, and viscous flow of the saturated excipient. It is found that the lower exfoliation rate and the longer dissolution time of the dosage forms with higher excipient molecular weight are primarily due to the greater viscosity of the cell walls after fluid penetration. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Computational Studies of Snake Venom Toxins

    OpenAIRE

    Paola G. Ojeda; David Ramírez; Jans Alzate-Morales; Julio Caballero; Quentin Kaas; Wendy González

    2017-01-01

    Most snake venom toxins are proteins, and participate to envenomation through a diverse array of bioactivities, such as bleeding, inflammation, and pain, cytotoxic, cardiotoxic or neurotoxic effects. The venom of a single snake species contains hundreds of toxins, and the venoms of the 725 species of venomous snakes represent a large pool of potentially bioactive proteins. Despite considerable discovery efforts, most of the snake venom toxins are still uncharacterized. Modern bioinformatics t...

  3. Collaborative Research Program on Seafood Toxins

    Science.gov (United States)

    1988-08-14

    Crystallographic Structures of Saxitoxins Cl and C2 Appendix C: Collaborative Research Program an Seafcod Toxins Progress Report on Ciguatera and Related...radioimmunoassay for PSP were also evalumted. The Hokama stick test for ciguatera toxin was also evaluated. 4. initiate Studies on the Accumulation...tco•d which caie a form of b-mnn poisoning referred to as ciguatera . The respcnsible toxins originate from ll1ular rine algae of the division

  4. Failure of botulinum toxin injection for neurogenic detrusor overactivity: Switch of toxin versus second injection of the same toxin.

    Science.gov (United States)

    Peyronnet, Benoit; Castel-Lacanal, Evelyne; Manunta, Andréa; Roumiguié, Mathieu; Marque, Philippe; Rischmann, Pascal; Gamé, Xavier

    2015-12-01

    To evaluate the efficacy of a second injection of the same toxin versus switching to a different botulinum toxin A after failure of a first detrusor injection in patients with neurogenic detrusor overactivity. The charts of all patients who underwent detrusor injections of botulinum toxin A (either abobotulinumtoxinA or onabotulinumtoxinA) for the management of neurogenic detrusor overactivity at a single institution were retrospectively reviewed. Patients in whom a first detrusor injection had failed were included in the present study. They were managed by a second injection of the same toxin at the same dosage or by a new detrusor injection using a different botulinum toxin A. Success was defined as a resolution of urgency, urinary incontinence and detrusor overactivity in a patient self-catheterizing seven times or less per 24 h. A total of 58 patients were included for analysis. A toxin switch was carried out in 29 patients, whereas the other 29 patients received a reinjection of the same toxin at the same dose. The success rate was higher in patients who received a toxin switch (51.7% vs. 24.1%, P = 0.03). Patients treated with a switch from abobotulinumtoxinA to onabotulinumtoxinA and those treated with a switch from onabotulinumtoxinA to abobotulinumtoxinA had similar success rates (52.9% vs. 50%, P = 0.88). After failure of a first detrusor injection of botulinum toxin for neurogenic detrusor overactivity, a switch to a different toxin seems to be more effective than a second injection of the same toxin. The replacement of onabotulinumtoxin by abobotulinumtoxin or the reverse provides similar results. © 2015 The Japanese Urological Association.

  5. Thermal monitoring of a granitic exfoliation sheet and cliff in Yosemite Valley, California (USA)

    Science.gov (United States)

    Guerin, Antoine; Matasci, Battista; Collins, Brian D.; Stock, Greg M.; Derron, Marc-Henri; Jaboyedoff, Michel

    2015-04-01

    In recent years, new remote sensing techniques such as Terrestrial Laser Scanner (TLS) and Infrared Thermography (IRT) have been used in parallel for rock weathering and weakness detection in slope stability analysis. Nevertheless, the effects of thermal stresses on rock face deformation are still poorly quantified, especially for steep and inaccessible cliffs. To better understand how daily temperature fluctuations influence the behavior of exfoliation joints (i.e., fractures separating exfoliation sheets), we monitored a granitic exfoliation sheet in detail using TLS and IRT over a several day period and also compiled a single TLS-IRT thermal panorama of a larger nearby granitic cliff composed of hundreds to thousands of similar exfoliation sheets. The exfoliation sheet had been previously instrumented for 3.5 years beginning in May 2010 using crackmeters and temperature sensors (Collins and Stock, 2010 and 2012), thereby providing an important baseline to compare our IRT measurements. For several consecutive days, a series of infrared thermal images (collected every 20 min.) of the exfoliation flake (19 m by 4 m by 0.1 m) was taken with a long range IRISYS IRI 4040 thermal imager, as well as several ground-based LiDAR scans, collected at 4 mm point spacing. These pictures were draped on the TLS triangular meshes to quantify the lateral propagation of temperature during the warming and cooling periods. The evolution of vertical and horizontal temperature profiles was also investigated. Results show that the sheet edge undergoes the most significant temperature changes and that warming takes place from the inside part to the border of the flake; conversely cooling takes place from the outside-inwards. Furthermore, the comparison of point clouds indicates a maximum crack aperture of over 1 cm occurring in the afternoon (12:00 to 15:00), when temperatures are at their maximum. The thermal panoramic image of the cliff (600 m wide by 300 m tall) was created using over

  6. Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakes.

    Science.gov (United States)

    Lin, Liangxu; Zhang, Shaowei

    2012-10-21

    We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.

  7. High-yield exfoliation of tungsten disulphide nanosheets by rational mixing of low-boiling-point solvents

    Science.gov (United States)

    Sajedi-Moghaddam, Ali; Saievar-Iranizad, Esmaiel

    2018-01-01

    Developing high-throughput, reliable, and facile approaches for producing atomically thin sheets of transition metal dichalcogenides is of great importance to pave the way for their use in real applications. Here, we report a highly promising route for exfoliating two-dimensional tungsten disulphide sheets by using binary combination of low-boiling-point solvents. Experimental results show significant dependence of exfoliation yield on the type of solvents as well as relative volume fraction of each solvent. The highest yield was found for appropriate combination of isopropanol/water (20 vol% isopropanol and 80 vol% water) which is approximately 7 times higher than that in pure isopropanol and 4 times higher than that in pure water. The dramatic increase in exfoliation yield can be attributed to perfect match between the surface tension of tungsten disulphide and binary solvent system. Furthermore, solvent molecular size also has a profound impact on the exfoliation efficiency, due to the steric repulsion.

  8. Botulinum toxin in bruxism treatment

    Directory of Open Access Journals (Sweden)

    Piotr Piech

    2017-07-01

    Full Text Available Introduction: Bruxism is defined as abnormal, fixed, unconscious chewing organ function, deviating qualitatively and quantitatively from normal function. Another definition speaks of motor dysfunction in the mouth, characterized by grinding and clenching of the teeth, occurring during sleep. The etiology of this disorder has not been explained until now, but it is believed to be related to localized, mental, nervous and neurotransmitter disorders. Purpose: The aim of the study is to review literature and knowledge about the use of botulinum toxin in the treatment of bruxism. Methods of treatment: The patient reports to the physician usually after a distressing, difficult to locate pain. The basis for proper treatment is to detect parafunctions and to make the patient aware of their existence. Diagnostic symptoms include dentinal lesions, recesses, enamel cracks and abfractive cavities, as well as changes in the mucosal area of the cheeks. Treatment begins with the use of an occlusive therapy to relax muscles, reduce parafunction and relieve pain. In the form of severe pain, NSAIDs are introduced and, if necessary, anxiolytics, sedatives and antidepressants. In the absence of response to the treatment used, botulinum toxin type A injections are used. The dose of the agent depends on the initial muscle tone and the effect of decrease in its activity is maintained for 4 to 6 months. Conclusions: The use of botulinum toxin makes it possible to selectively exclude overactive muscles, which is a great advantage over other techniques. An additional benefit of this therapy is achieved good cosmetic effect, reversible effect and minimal amount of side effects.

  9. Reliable Exfoliation of Large-Area High-Quality Flakes of Graphene and Other Two-Dimensional Materials.

    Science.gov (United States)

    Huang, Yuan; Sutter, Eli; Shi, Norman N; Zheng, Jiabao; Yang, Tianzhong; Englund, Dirk; Gao, Hong-Jun; Sutter, Peter

    2015-11-24

    Mechanical exfoliation has been a key enabler of the exploration of the properties of two-dimensional materials, such as graphene, by providing routine access to high-quality material. The original exfoliation method, which remained largely unchanged during the past decade, provides relatively small flakes with moderate yield. Here, we report a modified approach for exfoliating thin monolayer and few-layer flakes from layered crystals. Our method introduces two process steps that enhance and homogenize the adhesion force between the outermost sheet in contact with a substrate: Prior to exfoliation, ambient adsorbates are effectively removed from the substrate by oxygen plasma cleaning, and an additional heat treatment maximizes the uniform contact area at the interface between the source crystal and the substrate. For graphene exfoliation, these simple process steps increased the yield and the area of the transferred flakes by more than 50 times compared to the established exfoliation methods. Raman and AFM characterization shows that the graphene flakes are of similar high quality as those obtained in previous reports. Graphene field-effect devices were fabricated and measured with back-gating and solution top-gating, yielding mobilities of ∼4000 and 12,000 cm(2)/(V s), respectively, and thus demonstrating excellent electrical properties. Experiments with other layered crystals, e.g., a bismuth strontium calcium copper oxide (BSCCO) superconductor, show enhancements in exfoliation yield and flake area similar to those for graphene, suggesting that our modified exfoliation method provides an effective way for producing large area, high-quality flakes of a wide range of 2D materials.

  10. Botulinum toxin: The Midas touch.

    Science.gov (United States)

    Shilpa, P S; Kaul, Rachna; Sultana, Nishat; Bhat, Suraksha

    2014-01-01

    Botulinum Toxin (BT) is a natural molecule produced during growth and autolysis of bacterium called Clostridium botulinum. Use of BT for cosmetic purposes has gained popularity over past two decades, and recently, other therapeutic uses of BT has been extensively studied. BT is considered as a minimally invasive agent that can be used in the treatment of various orofacial disorders and improving the quality of life in such patients. The objective of this article is to review the nature, mechanism of action of BT, and its application in various head and neck diseases.

  11. Synthesis and biology of cyclic imine toxins, an emerging class of potent, globally distributed marine toxins.

    Science.gov (United States)

    Stivala, Craig E; Benoit, Evelyne; Aráoz, Rómulo; Servent, Denis; Novikov, Alexei; Molgó, Jordi; Zakarian, Armen

    2015-03-01

    From a small group of exotic compounds isolated only two decades ago, Cyclic Imine (CI) toxins have become a major class of marine toxins with global distribution. Their distinct chemical structure, biological mechanism of action, and intricate chemistry ensures that CI toxins will continue to be the subject of fascinating fundamental studies in the broad fields of chemistry, chemical biology, and toxicology. The worldwide occurrence of potent CI toxins in marine environments, their accumulation in shellfish, and chemical stability are important considerations in assessing risk factors for human health. This review article aims to provide an account of chemistry, biology, and toxicology of CI toxins from their discovery to the present day.

  12. Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

    Science.gov (United States)

    Yu, Yi-Hsien; Wang, Xuezhen; Shinde, Abhijeet; Cheng, Zhengdong

    2016-01-01

    Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2·H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior. PMID:27284765

  13. Studies on incorporation of exfoliated bentonitic clays in polyurethane foams for increasing flame retardancy

    International Nuclear Information System (INIS)

    Quagliano, J; García, Irma Gavilán

    2012-01-01

    In this contribution we report the results of studying the incorporation of exfoliated bentonitic clays into polyurethane foams. A suspension in water of a sodium bentonite from Argentine Patagonia was interchanged with cetyl trimethyl ammonium bromide (CTAB) for 4 h at 80°C, rendering an exfoliated clay, which is nanometric in only one dimension. This nanoclay, when dispersed in the polyurethane, resulted in the same fire retardancy rating (UL-94) than when polyurethane was treated with a commercial nanoclay. Scanning electron microscopy (SEM) at low augmentations of polyurethane samples treated with the synthethized nanoclay (2,5% w/w) showed no differences respect to untreated polyurethane, except for the irregularity of void edges.

  14. Morphological, viscoelastic and mechanical characterization of polypropylene/exfoliated graphite nanocomposites

    Directory of Open Access Journals (Sweden)

    Creusa Iara Ferreira

    2013-01-01

    Full Text Available The viscoelastic, mechanical and morphological properties of polypropylene/exfoliated graphite nanocomposites with different contents of nanofiller were investigated. According to transmission electron microscopy results, the nanofiller particles were homogeneously dispersed in the matrix. The rheological properties indicated that incorporation of graphite improved the matrix stiffness and had a reinforcing effect. Exfoliated graphite had a weak interaction with the polypropylene. The behavior of the nanocomposites was similar to that of polypropylene in terms of the interfacial detachment inferred from the transmission electron microscopy images and of their G' (storage and G'' (loss moduli, and viscosity. The mechanical properties of the nanocomposites compared to the matrix improved significantly for the flexural and storage moduli with little loss of impact strength.

  15. Glycerin Borax Treatment of Exfoliative Cheilitis Induced by Sodium Lauryl Sulfate: a Case Report.

    Science.gov (United States)

    Thongprasom, Kobkan

    2016-06-01

    This paper reports on the results of a case study of a 19-year-old female who presented to the Oral Medicine clinic with a chief complaint of scaly and peeling lips. The lesions had persisted on her lips for more than 7 years and were refractory to previous treatment. Her physician's diagnosis was contact dermatitis. We diagnosed this patient as having exfoliative cheilitis (EC). A patch test using the toothpaste containing sodium lauryl sulfate (SLS) was positive and the patient discontinued using it. Instead, she started using a toothpaste not containing SLS. One year after treating her lesions with hydrogen peroxide mouthwash 1% and glycerin borax, a gradual improvement was observed until returning to normal. Glycerin borax was safe, low cost and simple to use in treatment of refractory exfoliative cheilitis. SLS may have been a precipitating factor in EC in this case.

  16. Glycerin Borax Treatment of Exfoliative Cheilitis Induced by Sodium Lauryl Sulfate: a Case Report

    Directory of Open Access Journals (Sweden)

    Kobkan Thongprasom

    2016-01-01

    Full Text Available This paper reports on the results of a case study of a 19-year-old female who presented to the Oral Medicine clinic with a chief complaint of scaly and peeling lips. The lesions had persisted on her lips for more than 7 years and were refractory to previous treatment. Her physician’s diagnosis was contact dermatitis. We diagnosed this patient as having exfoliative cheilitis (EC. A patch test using the toothpaste containing sodium lauryl sulfate (SLS was positive and the patient discontinued using it. Instead, she started using a toothpaste not containing SLS. One year after treating her lesions with hydrogen peroxide mouthwash 1% and glycerin borax, a gradual improvement was observed until returning to normal. Glycerin borax was safe, low cost and simple to use in treatment of refractory exfoliative cheilitis. SLS may have been a precipitating factor in EC in this case.

  17. Performance of Liquid Phase Exfoliated Graphene As Electrochemical Double Layer Capacitors Electrodes

    Science.gov (United States)

    Huffstutler, Jacob; Wasala, Milinda; Richie, Julianna; Winchester, Andrew; Ghosh, Sujoy; Kar, Swastik; Talapatra, Saikat

    2014-03-01

    We will present the results of our investigations of electrochemical double layer capacitors (EDLCs) or supercapacitors (SC) fabricated using liquid-phase exfoliated graphene. Several electrolytes, such as aqueous potassium hydroxide KOH (6M), ionic 1-Butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and ionic 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate[BMP][FAP] were used. These EDLC's show good performance compared to other carbon nanomaterials based EDLC's devices. We found that the liquid phase exfoliated graphene based devices possess specific capacitance values as high as 262 F/g, when used with ionic liquid electrolyte[BMP][FAP], with power densities (~ 454 W/kg) and energy densities (~ 0.38Wh/kg). Further, these devices indicated rapid charge transfer response even without the use of any binders or specially prepared current collectors. A detailed electrochemical impedance spectroscopy analysis in order to understand the phenomenon of charge storage in these materials will be presented.

  18. Morphological, viscoelastic and mechanical characterization of polypropylene/exfoliated graphite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Creusa Iara; Oliveira, Ricardo Vinicius Bof de; Mauler, Raquel Santos, E-mail: raquel.mauler@ufrgs.br [Universidade Federal do Rio Grande do Sul (PGCIMAT/IQ/UFRGS), Porto Alegre, RS (Brazil); Bianchi, Otavio [Universidade de Caxias do Sul (PGMAT/CCET/UCS), RS (Brazil); Oviedo, Mauro Alfredo Soto [Braskem S/A, Rio de Janeiro, RJ (Brazil)

    2013-07-01

    The viscoelastic, mechanical and morphological properties of polypropylene/exfoliated graphite nanocomposites with different contents of nanofiller were investigated. According to transmission electron microscopy results, the nanofiller particles were homogeneously dispersed in the matrix. The rheological properties indicated that incorporation of graphite improved the matrix stiffness and had a reinforcing effect. Exfoliated graphite had a weak interaction with the polypropylene. The behavior of the nanocomposites was similar to that of polypropylene in terms of the interfacial detachment inferred from the transmission electron microscopy images and of their G' (storage) and G' (loss) moduli, and viscosity. The mechanical properties of the nanocomposites compared to the matrix improved significantly for the flexural and storage moduli with little loss of impact strength. (author)

  19. Anion-exchange membranes derived from quaternized polysulfone and exfoliated layered double hydroxide for fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wan; Liang, Na; Peng, Pai; Qu, Rong; Chen, Dongzhi; Zhang, Hongwei, E-mail: hanqiujiang@163.com

    2017-02-15

    Layered double hydroxides (LDH) are prepared by controlling urea assisted homogeneous precipitation conditions. Morphology and crystallinity of LDHs are confirmed by X-ray diffraction and scanning electron microscope. After LDHs are incorporated into quaternized polysulfone membranes, transmission electron microscope is used to observe the exfoliated morphology of LDH sheets in the membranes. The properties of the nanocomposite membranes, including water uptake, swelling ratio, mechanical property and ionic conductivity are investigated. The nanocomposite membrane containing 5% LDH sheets shows more balanced performances, exhibiting an ionic conductivity of 2.36×10{sup −2} S cm{sup −1} at 60 °C. - Graphical abstract: Anion-exchange membrane based on quaternized polysulfone and exfoliated layered double hydroxide is optically transparent and has good ionic properties.

  20. Exfoliative cytology of oral epithelial cells from patients with type 2 diabetes: cytomorphometric analysis.

    Science.gov (United States)

    Rivera, César; Núñez-de-Mendoza, Camila

    2013-01-01

    This research objective is to identify cytomorphometrical changes using exfoliative cytology (EC) and later Papanicolaou (Pap) staining, for oral epithelial cells of patients with type 2 diabetes (DM2) (n = 30), while being compared to patients without the disease (n = 30). Additionally, we investigated an association between cellular changes and salivary flow levels; relationship that until now has not been reported. Results show that the cell diameter and the nuclear-cytoplasmic ratio was significantly higher compared to those patients without the disease (p ≤ 0.001 Student and Welch test). Decreased salivary flow was significantly associated with increased cell diameter and nuclear-cytoplasmic ratio (p ≤ 0.001 ANOVA with Tukey test). Evidence and clinical observations show that DM2 and decreased salivary flow are related to detectable cytomorphometrical changes in exfoliated cells, which may extend the horizon of this cytological technique.

  1. Mechanical behaviour of cyclic olefin copolymer/exfoliated graphite nanoplatelets nanocomposites foamed through supercritical carbon dioxide

    Directory of Open Access Journals (Sweden)

    A. Biani

    2016-12-01

    Full Text Available A cycloolefin copolymer matrix was melt mixed with exfoliated graphite nanoplatelets (xGnP and the resulting nanocomposites were foamed by supercritical carbon dioxide. The density of the obtained foams decreased with the foaming pressure. Moreover, xGnP limited the cell growth during the expansion process thus reducing the cell diameter (from 1.08 to 0.22 mm with an XGnP amount of 10 wt% at 150 bar and increasing the cell density (from 12 to 45 cells/mm2 with a nanofiller content of 10 wt% at 150 bar. Electron microscopy observations of foams evidenced exfoliation and orientation of the nanoplatelets along the cell walls. Quasi-static compressive tests and tensile creep tests on foams clearly indicated that xGnP improved the modulus (up to a factor of 10 for a xGnP content of 10 wt% and the creep stability.

  2. Evaluation of the capacity of heavy metal adsorption in exfoliated vermiculite

    International Nuclear Information System (INIS)

    Lima, J.F.; Silva, P.S.; Hanken, R.B.L.; Raposo, C.M.O.

    2009-01-01

    Many groups from modern society have seen with attention the issues of pollutants, generally present in nature, those same that have caused irreversible damages to the environment. The Vermiculite, a phyllosilicate, with t-o-t structure, have high interlamelar charge, has been studied as cationic exchanger, whose application when exfoliated, are increased. This work has the objective of evaluate the absorption capacity of chromium (III), in different concentrations, in high, slim and medium concentrations of exfoliated vermiculites. The results obtained from the characterization by spectroscopy in infrared and by diffraction of x-ray from prepared solids showed important variations in the quantity of adsorbed metal in order the size of the concentrated particles. (author)

  3. Orientation and the extent of exfoliation of clay on scratch damage in polyamide 6 nanocomposites

    International Nuclear Information System (INIS)

    Dasari, Aravind; Yu Zhongzhen; Mai Yiuwing; Kim, Jang-Kyo

    2008-01-01

    The major objectives of this work are to understand the effects of organoclay, its extent of exfoliation and orientation, and indenter geometry on the scratch characteristics of polyamide 6/organoclay nanocomposites. Two different organically treated clays are used for this purpose and their structural parameters in a polyamide 6 matrix quantified. It is shown that, while the material properties are important for scratching resistance, they are not the only determinants of the scratch performance of materials. Further, despite proving beneficial to scratch resistance, in terms of residual depth, the presence (and exfoliation) of organoclay promotes the formation of brittle cracks during scratching. But with no organoclay layers, plastic flow controls the scratch damage in neat polyamide 6 with large residual depths. Factors such as orientation of clay layers and variations of indenter tip geometry also exert dominant effects on scratch penetration resistance and damage. Additionally, significant plastic flow and rotation of organoclay layers from the original configuration are observed underneath the sliding indenter

  4. Morphological, viscoelastic and mechanical characterization of polypropylene/exfoliated graphite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Creusa Iara; Oliveira, Ricardo Vinicius Bof de; Mauler, Raquel Santos, E-mail: raquel.mauler@ufrgs.br [Universidade Federal do Rio Grande do Sul (PGCIMAT/IQ/UFRGS), Porto Alegre, RS (Brazil); Bianchi, Otavio [Universidade de Caxias do Sul (PGMAT/CCET/UCS), RS (Brazil); Oviedo, Mauro Alfredo Soto [Braskem S/A, Rio de Janeiro, RJ (Brazil)

    2013-07-01

    The viscoelastic, mechanical and morphological properties of polypropylene/exfoliated graphite nanocomposites with different contents of nanofiller were investigated. According to transmission electron microscopy results, the nanofiller particles were homogeneously dispersed in the matrix. The rheological properties indicated that incorporation of graphite improved the matrix stiffness and had a reinforcing effect. Exfoliated graphite had a weak interaction with the polypropylene. The behavior of the nanocomposites was similar to that of polypropylene in terms of the interfacial detachment inferred from the transmission electron microscopy images and of their G' (storage) and G' (loss) moduli, and viscosity. The mechanical properties of the nanocomposites compared to the matrix improved significantly for the flexural and storage moduli with little loss of impact strength. (author)

  5. Large-strain Soft Sensors Using Elastomers Blended with Exfoliated/Fragmented Graphite Particles

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sungmin; Nam, Gyungmok; Kim, Jonghun; Yoon, Sang-Hee [Inha Univ., Incheon (Korea, Republic of)

    2016-09-15

    An elastic polymer (e.g., PDMS) blended with EFG particles is a promising conductive composite for fabricating soft sensors that can detect an object's deformation up to or more than 50 %. Here, we develop large-strain, sprayable soft sensors using a mixture of PDMS and EFG particles, which are used as a host elastomer and electrically conductive particles, respectively. A solution for a conductive composite mixture is prepared by the microwave-assisted graphite exfoliation, followed by ultrasonication-induced fragmentation of the exfoliated graphite and ultrasonic blending of PDMS and EFG. Using the prepared solutions for composite and pure PDMS, 1-, 2-, and 3-axis soft sensors are fabricated by airbrush stencil technique where composite mixture and pure PDMS are materials for sensing and insulating layers, respectively. We characterize the soft strain sensors after investigating the effect of PDMS/EFG wt % on mechanical compliance and electrical conductance of the conductive composite.

  6. Strongly luminescent monolayered MoS2 prepared by effective ultrasound exfoliation.

    Science.gov (United States)

    Štengl, Václav; Henych, Jiří

    2013-04-21

    Intense ultrasound in a pressurized batch reactor was used for preparation of monolayered MoS2 nanosheets from natural mineral molybdenite. Exfoliation of bulk MoS2 using ultrasound is an attractive route to large-scale preparation of monolayered crystals. To evaluate the quality of delamination, methods like X-ray diffraction, Raman spectroscopy and microscopic techniques (TEM and AFM) were employed. From single- or few-layered products obtained from intense sonication, MoS2 quantum dots (MoSQDs) were prepared by a one-pot reaction by refluxing exfoliated nanosheets of MoS2 in ethylene glycol under atmospheric pressure. The synthesised MoSQDs were characterised by photoluminescence spectroscopy and laser-scattering particle size analysis. Our easy preparation leads to very strongly green luminescing quantum dots.

  7. Studies of physicochemical properties of graphite oxide and thermally exfoliated/reduced graphene oxide

    Directory of Open Access Journals (Sweden)

    Drewniak Sabina Elżbieta

    2015-12-01

    Full Text Available The aim of the experimental research studies was to determine some electrical properties of graphite oxide and thermally exfoliated/reduced graphene oxide. The authors tried to interpret the obtained physicochemical results. For that purpose, both resistance measurements and investigation studies were carried out in order to characterize the samples. The resistance was measured at various temperatures in the course of composition changes of gas atmospheres (which surround the samples. The studies were also supported by such methods as: scanning electron microscopy (SEM, Raman spectroscopy (RS, atomic force microscopy (AFM and thermogravimetry (TG. Moreover, during the experiments also the elemental analyses (EA of the tested samples (graphite oxide and thermally exfoliated/reduced graphene oxide were performed.

  8. An ultrahigh pressure homogenization technique for easily exfoliating few-layer phosphorene from bulk black phosphorus

    Science.gov (United States)

    Guan, Qing-Qing; Zhou, Hua-Jing; Ning, Ping; Lian, Pei-Chao; Wang, Bo; He, Liang; Chai, Xin-Sheng

    2018-05-01

    We have developed an easy and efficient method for exfoliating few-layer sheets of black phosphorus (BP) in N-methyl-2-pyrrolidone, using ultra-high pressure homogenization (UPH). The BP was first exfoliated into sheets that were a few atomic layers thick, using a homogenizer for only 30 min. Next, a double centrifugation procedure was used to separate the material into few-layer nanosheets that were examined by X-ray diffraction, atomic force microscopy (AFM), transmission electron microscopy (TEM), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), and energy-dispersive X-ray (EDX) spectroscopy. The results show that the products are specimens of phosphorene that are only a few-layer thick.

  9. Sulfuric acid intercalated-mechanical exfoliation of reduced graphene oxide from old coconut shell

    Science.gov (United States)

    Islamiyah, Wildatun; Nashirudin, Luthfi; Baqiya, Malik A.; Cahyono, Yoyok; Darminto

    2018-04-01

    We report a fecile preparation of reduced grapheme oxide (rGO) from an old coconut shell by rapid reduction of heating at 400°C, chemical exfoliation using H2SO4 and HCl intercalating and mechanical exfoliation using ultrasonication. The produced samples consist of random stacks of nanometer-sized sheets. The dispersions prepared from H2SO4 had broader size distributions and larger particle sizes than the that from HCl. An average size of rGO in H2SO4 and HCl is respectively 23.62 nm and 570.4 nm. Furthermore, sample prepared in H2SO4 exhibited a high electronical conductivity of 1.1 × 10-3 S/m with a low energy gap of 0.11 eV.

  10. Properties of spray-deposited liquid-phase exfoliated graphene films

    Science.gov (United States)

    Sales, Maria Gabriela C.; Dela Vega, Ma. Shanlene D. C.; Vasquez, Magdaleno R., Jr.

    2018-01-01

    In this study, we demonstrate the feasibility of spray-depositing exfoliated graphene on flexible polyimide (PI) and rigid (soda lime glass) substrates for optoelectronic applications. The water contact angles of the substrates increased by 13% (for PI) and 49% (for glass) when the surfaces are pretreated with hexamethyldisiloxane, which significantly improved the adhesion of the films. Raman spectral analyses confirmed a minimum of 15 and a maximum of 23 layers of exfoliated graphene deposited on the substrates. After deposition, the films were exposed to 13.56 MHz radio-frequency plasma containing an admixture of argon and nitrogen gases. Plasma treatment modified the electrical properties with a response analogous to that of a rectifier. A 39% increase in transmittance in the visible region was also observed especially for glass substrates after plasma treatment without a significant change in film electrical conductivity.

  11. Synthesis, characterization and photocatalytic performance of chemically exfoliated MoS2

    Science.gov (United States)

    Prabhakar Vattikuti, S. V.; Shim, Jaesool

    2018-03-01

    Two-dimensional (2D) layered structure transition metal dichalcogenides (TMDs) has gained huge attention and importance for photocatalytic energy conversion because of their unique properties. Molybdenum disulfide (MoS2) nanosheets were synthesized via one-pot method and exfoliated in (dimethylformamide) DMF solution. Subsequent exfoliated MoS2 nanosheets (e-MoS2) were used as photocatalysts for degradation of Rhodamine B (RhB) pollutant under solar light irradiation. The e-MoS2 nanosheets exhibited excellent photocatalytic activity than that of pristine MoS2, owing to high specific surface area with enormous active sites and light absorption capacity. In addition, e-MoS2 demonstrated remarkable photocatalytic stability.

  12. Study of surface exfoliation on 6H-SiC induced by H{sub 2}{sup +} implantation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, L. [Department of Physics, School of Science, Lanzhou University of Technology, Lanzhou 730050 (China); Li, B.S., E-mail: b.s.li@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2017-03-01

    The effect of lattice damage generated by the H{sub 2}{sup +}-implantation on exfoliation efficiency in 6H-SiC wafers is investigated. <0001> 6H-SiC wafers were implanted with 134 keV H{sub 2}{sup +} ions to ion fluences from 1.5×10{sup 16} to 5×10{sup 16} H{sub 2}{sup +} cm{sup −2} and subsequently annealed at temperatures from 973 K to 1373 K. The samples were studied by a combination of optical microscopy and transmission electron microscopy. Only after 1373 K annealing for 15 min, blisters and exfoliation occur on the H{sub 2}{sup +}-implanted sample surface. With increasing the implantation fluences from 1.5×10{sup 16} to 3.75×10{sup 16} H{sub 2}{sup +} cm{sup −2}, the exfoliation mean size decreases, while the exfoliation density increases. For the highest fluence of 5×10{sup 16} H{sub 2}{sup +} cm{sup −2}, seldom exfoliations occur on the sample surface. Microstructure analysis shows that exfoliation efficiency is largely controlled by the H{sub 2}{sup +}-implantation-induced lattice damage. The depth of the microcrack is related to the implantation fluence. The effect of implantation fluence on dislocation loops, platelet nucleation and growth is investigated.

  13. Laminated exfoliated graphite composite-metal compositions for fuel cell flow field plate or bipolar plate applications

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2014-05-20

    An electrically conductive laminate composition for fuel cell flow field plate or bipolar plate applications. The laminate composition comprises at least a thin metal sheet having two opposed exterior surfaces and a first exfoliated graphite composite sheet bonded to the first of the two exterior surfaces of the metal sheet wherein the exfoliated graphite composite sheet comprises: (a) expanded or exfoliated graphite and (b) a binder or matrix material to bond the expanded graphite for forming a cohered sheet, wherein the binder or matrix material is between 3% and 60% by weight based on the total weight of the first exfoliated graphite composite sheet. Preferably, the first exfoliated graphite composite sheet further comprises particles of non-expandable graphite or carbon in the amount of between 3% and 60% by weight based on the total weight of the non-expandable particles and the expanded graphite. Further preferably, the laminate comprises a second exfoliated graphite composite sheet bonded to the second surface of the metal sheet to form a three-layer laminate. Surface flow channels and other desired geometric features can be built onto the exterior surfaces of the laminate to form a flow field plate or bipolar plate. The resulting laminate has an exceptionally high thickness-direction conductivity and excellent resistance to gas permeation.

  14. A Quantitative Electrochemiluminescence Assay for Clostridium perfringens alpha toxin

    National Research Council Canada - National Science Library

    Merrill, Gerald A; Rivera, Victor R; Neal, Dwayne D; Young, Charles; Poli, Mark A

    2006-01-01

    .... Biotinylated antibodies to C. perfringens alpha toxin bound to streptavidin paramagnetic beads specifically immunoadsorbed soluble sample alpha toxin which subsequently selectively immunoadsorbed ruthenium (Ru...

  15. Elastomeric Nanocomposite Based on Exfoliated Graphene Oxide and Its Characteristics without Vulcanization

    OpenAIRE

    Nasser Abdullah Habib; Buong Woei Chieng; Norkhairunnisa Mazlan; Umer Rashid; Robiah Yunus; Suraya Abdul Rashid

    2017-01-01

    Rubber nanocomposites have emerged as one of the advanced materials in recent years. The aim of this work was to homogeneously disperse graphene oxide (GO) sheets into Nitrile Butadiene Rubber (NBR) and investigate the characteristics of GO/NBR nanocomposite without vulcanization. A suitable solvent was found to dissolve dry NBR while GO was exfoliated completely in an aqueous base solution using sonication. GO was dispersed into NBR at different loadings by solution mixing to produce unvulca...

  16. Gastric washing by distilled water can reduce free gastric cancer cells exfoliated into the stomach lumen.

    Science.gov (United States)

    Ohki, Atsuko; Abe, Nobutsugu; Yoshimoto, Eri; Hashimoto, Yoshikazu; Takeuchi, Hirohisa; Nagao, Gen; Masaki, Tadahiko; Mori, Toshiyuki; Ohkura, Yasuo; Sugiyama, Masanori

    2018-04-25

    Intragastric free cancer cells in patients with gastric cancer have rarely been studied. The purpose of this study was to investigate the detection rate of intragastric free cancer cells in gastric washes using two types of solutions during endoscopic examination. We further clarified risk factors affecting the presence of exfoliated free cancer cells. A total of 175 patients with gastric cancer were enrolled. Lactated Ringer's solution (N = 89) or distilled water (DW; N = 86) via endoscopic working channel was sprayed onto the tumor surface, and the resultant fluid was collected for cytological examination. We compared the cancer-cell positivity rate between the two (Ringer and DW) groups. We also tested the correlation between cancer-cell positivity and clinicopathological factors in the Ringer group to identify risk factors for the presence of exfoliated cancer cells. The cancer-cell positivity rate was significantly higher in the Ringer group than that in the DW group (58 vs 6%). Cytomorphology in the Ringer group was well maintained, but not in the DW group. The larger tumor size (≥ 20 mm) and positive lymphatic involvement were significant risk factors of exfoliated free cancer cells. Cancer cells can be highly exfoliated from the tumor surface into the gastric lumen by endoscopic irrigation in large gastric cancer with lymphatic involvement. Gastric washing by DW can lead to cytoclasis of free cancer cells; therefore, it may minimize the possibility of cancer-cell seeding in procedures carrying potential risks of tumor-cell seeding upon transluminal communication, such as endoscopic full-thickness resection and laparoscopy-endoscopy cooperative surgery.

  17. Toxin-Antitoxin Battle in Bacteria

    DEFF Research Database (Denmark)

    Cataudella, Ilaria

    This PhD thesis consists of three research projects revolving around the common thread of investigation of the properties and biological functions of Toxin-Antitoxin loci. Toxin-Antitoxin (TA) loci are transcriptionally regulated via an auto-inhibition mechanism called conditional cooperativity, ...

  18. Plant insecticidal toxins in ecological networks.

    Science.gov (United States)

    Ibanez, Sébastien; Gallet, Christiane; Després, Laurence

    2012-04-01

    Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects' vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology.

  19. Plant Insecticidal Toxins in Ecological Networks

    Directory of Open Access Journals (Sweden)

    Sébastien Ibanez

    2012-04-01

    Full Text Available Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects’ vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology.

  20. Stealth and mimicry by deadly bacterial toxins

    DEFF Research Database (Denmark)

    Yates, S.P.; Jørgensen, Rene; Andersen, Gregers Rom

    2006-01-01

    Diphtheria toxin and exotoxin A are well-characterized members of the ADP-ribosyltransferase toxin family that serve as virulence factors in the pathogenic bacteria, Corynebacterium diphtheriae and Pseudomonas aeruginosa.  New high-resolution structural data of the Michaelis complex...

  1. Supercritical fluid extraction of bi & multi-layer graphene sheets from graphite by using exfoliation technique

    Science.gov (United States)

    Xavier, Gauravi; Dave, Bhoomi; Khanna, Sakshum

    2018-05-01

    In recent times, researchers have turned to explore the possibility of using Supercritical Fluid (SCFs) system to penetrate into the inert-gaping of graphite and exfoliate it into a number of layer graphene sheets. The supercritical fluid holds excellent wetting surfaces with low interfacial tension and high diffusion coefficients. Although SCFs exfoliation approach looks promising to developed large scale & low-cost graphene sheet but has not received much attention. To arouse interest and reflection on this approach, this review is organized to summarize the recent progress in graphene production by SCF technology. Here we present the simplest route to obtained layers of graphene sheets by intercalating and exfoliating graphite using supercritical CO2 processing. The layers graphene nano-sheets were collected in dichloromethane (DCM) solution which prevents the restocking of sheets. The obtained graphene sheets show the desired characteristics and thus can be used in physical, chemical and biological sciences. Thus this method provides an effortless and eco-friendly approach for the synthesis of layers of graphene sheets.

  2. Environmental Synthesis of Few Layers Graphene Sheets Using Ultrasonic Exfoliation with Enhanced Electrical and Thermal Properties.

    Directory of Open Access Journals (Sweden)

    Monir Noroozi

    Full Text Available In this paper, we report how few layers graphene that can be produced in large quantity with low defect ratio from exfoliation of graphite by using a high intensity probe sonication in water containing liquid hand soap and PVP. It was founded that the graphene powder obtained by this simple exfoliation method after the heat treatment had an excellent exfoliation into a single or layered graphene sheets. The UV-visible spectroscopy, FESEM, TEM, X-ray powder diffraction and Raman spectroscopy was used to analyse the graphene product. The thermal diffusivity of the samples was analysed using a highly accurate thermal-wave cavity photothermal technique. The data obtained showed excellent enhancement in the thermal diffusivity of the graphene dispersion. This well-dispersed graphene was then used to fabricate an electrically conductive polymer-graphene film composite. The results demonstrated that this low cost and environmental friendly technique allowed to the production of high quality layered graphene sheets, improved the thermal and electrical properties. This may find use in the wide range of applications based on graphene.

  3. Paper Electrodes Coated with Partially-Exfoliated Graphite and Polypyrrole for High-Performance Flexible Supercapacitors

    Directory of Open Access Journals (Sweden)

    Leping Huang

    2018-01-01

    Full Text Available Flexible paper electrodes for supercapacitors were prepared with partially-exfoliated graphite and polypyrrole as the active materials. Graphite was coated on paper with pencil drawing and then electrochemically exfoliated using the cyclic voltammetry (CV technique to obtain the exfoliated graphite (EG-coated paper (EG-paper. Polypyrrole (PPy doped with β-naphthalene sulfonate anions was deposited on EG-paper through in-situ polymerization, leading to the formation of PPy-EG-paper. The as-prepared PPy-EG-paper showed a high electrical conductivity of 10.0 S·cm−1 and could be directly used as supercapacitor electrodes. The PPy-EG-paper electrodes gave a remarkably larger specific capacitance of 2148 F∙g−1 at a current density of 0.8 mA∙cm−2, compared to PPy-graphite-paper (848 F∙g−1. The capacitance value of PPy-EG-paper could be preserved by 80.4% after 1000 charge/discharge cycles. In addition, the PPy-EG-paper electrodes demonstrated a good rate capability and a high energy density of 110.3 Wh∙kg−1 at a power density of 121.9 W∙kg−1. This work will pave the way for the discovery of efficient paper-based electrode materials.

  4. Exfoliated graphite/titanium dioxide nanocomposites for photodegradation of eosin yellow

    Energy Technology Data Exchange (ETDEWEB)

    Ndlovu, Thabile, E-mail: atkuvarega@gmail.com [University of Swaziland, Department of Chemistry, Private Bag 4, Kwaluseni (Swaziland); Kuvarega, Alex T.; Arotiba, Omotayo A. [University of Johannesburg, Department of Applied Chemistry, P.O. Box 17011, Doornfontein 2028, Johannesburg (South Africa); Sampath, Srinivasan [Indian Institute of Science, Department of Inorganic and Physical Chemistry, Bangalore 560012 (India); Krause, Rui W. [Rhodes University, Department of Chemistry, P.O. Box 94, Grahamstown 6140 South Africa (South Africa); Mamba, Bhekie B., E-mail: bmamba@uj.ac.za [University of Johannesburg, Department of Applied Chemistry, P.O. Box 17011, Doornfontein 2028, Johannesburg (South Africa)

    2014-05-01

    Graphical abstract: - Highlights: • Preparation of exfoliated graphite (EG) from natural graphite. • Sol–gel anchoring of TiO{sub 2} on exfoliated graphite. • High adsorption and photoactivity was observed for the EG-TiO{sub 2} nanocomposite. • Mechanism of enhancement was proposed. - Abstract: An improved photocatalyst consisting of a nanocomposite of exfoliated graphite and titanium dioxide (EG-TiO{sub 2}) was prepared. SEM and TEM micrographs showed that the spherical TiO{sub 2} nanoparticles were evenly distributed on the surface of the EG sheets. A four times photocatalytic enhancement was observed for this floating nanocomposite compared to TiO{sub 2} and EG alone for the degradation of eosin yellow. For all the materials, the reactions followed first order kinetics where for EG-TiO{sub 2}, the rate constant was much higher than for EG and TiO{sub 2} under visible light irradiation. The enhanced photocatalytic activity of EG-TiO{sub 2} was ascribed to the capability of graphitic layers to accept and transport electrons from the excited TiO{sub 2}, promoting charge separation. This indicates that carbon, a cheap and abundant material, can be a good candidate as an electron attracting reservoir for photocatalytic organic pollutant degradation.

  5. Swelling, intercalation, and exfoliation behavior of layered ruthenate derived from layered potassium ruthenate

    International Nuclear Information System (INIS)

    Fukuda, Katsutoshi; Kato, Hisato; Sato, Jun; Sugimoto, Wataru; Takasu, Yoshio

    2009-01-01

    The intercalation chemistry of a layered protonic ruthenate, H 0.2 RuO 2.1 .nH 2 O, derived from a layered potassium ruthenate was studied in detail. Three phases with different hydration states were isolated, H 0.2 RuO 2.1 .nH 2 O (n=∼0, 0.5, 0.9), and its reactivity with tetrabutylammonium ions (TBA + ) was considered. The layered protonic ruthenate mono-hydrate readily reacted with TBA + , affording direct intercalation of bulky tetrabutylammonium ions into the interlayer gallery. Fine-tuning the reaction conditions allowed exfoliation of the layered ruthenate into elementary nanosheets and thereby a simplified one-step exfoliation was achieved. Microscopic observation by atomic force microscopy and transmission electron microscopy clearly showed the formation of unilamellar sheets with very high two-dimensional anisotropy, a thickness of only 1.3±0.1 nm. The nanosheets were characterized by two-dimensional crystallites with the oblique cell of a=0.5610(8) nm, b=0.5121(6) nm and γ=109.4(2) o on the basis of in-plane diffraction analysis. - Graphical abstract: Layered protonic ruthenate derived from a potassium form was directly reacted with bulky tetrabutylammonium ions to trigger exfoliation into nanosheets as long as it is highly hydrated.

  6. Chemical exfoliation and optical characterization of threading-dislocation-free gallium-nitride ultrathin nanomembranes

    KAUST Repository

    Elafandy, Rami T.

    2014-11-13

    Semiconductor nanostructures have generated tremendous scientific interests as well as practical applications stemming from the engineering of low dimensional physics phenomena. Unlike 0D and 1D nanostructures, such as quantum dots and nanowires, respectively, 2D structures, such as nanomembranes, are unrivalled in their scalability for high yield manufacture and are less challenging in handling with the current transfer techniques. Furthermore, due to their planar geometry, nanomembranes are compatible with the current complementary metal oxide semiconductor (CMOS) technology. Due to these superior characteristics, there are currently different techniques in exfoliating nanomembranes with different crystallinities, thicknesses and compositions. In this work we demonstrate a new facile technique of exfoliating gallium nitride (GaN) nanomembranes with novel features, namely with the non-radiative cores of their threading-dislocations (TDs) being etched away. The exfoliation process is based on engineering the gallium vacancy (VGa) density during the GaN epitaxial growth with subsequent preferential etching. Based on scanning and transmission electron microscopies, as well as micro-photoluminescence measurements, a model is proposed to uncover the physical processes underlying the formation of the nanomembranes. Raman measurements are also performed to reveal the internal strain within the nanomembranes. After transferring these freely suspended 25 nm thin GaN nanomembranes to other substrates, we demonstrate the temperature dependence of their bandgap by photoluminescence technique, in order to shed light on the internal carrier dynamics. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  7. Black tea assisted exfoliation using a kitchen mixer allowing one-step production of graphene

    Science.gov (United States)

    Ismail, Zulhelmi; Farhana Abu Kassim, Nurul; Hannifa Abdullah, Abu; Sakinah Zainal Abidin, Anis; Sameha Ismail, Fadwa; Yusoh, Kamal

    2017-07-01

    A kitchen mixer is one of the possible tools for the exfoliation of graphene. While organic solvents such as NMP or DMF are suitable for the exfoliation of graphite, the majority are toxic and dangerously harmful when exposed to humans and the environment. Therefore, an alternative solvent must be proposed for green and sustainable production of graphene. In this initial work, we have developed a new synthesis method for graphene through the direct exfoliation of graphite in commercial black tea. We found that our maximum yield concentration of graphene is Y  =  0.032 mg ml-l after 15 min of mixing. From the data of Raman, the level of defects in our produced graphene is suggested as being very minor (I D/I G  =  0.17), despite possible graphene functionalization by oxygen groups in tea. Incorporation of our graphene into PMMA results in shifting the onset temperature from 300 °C to 326 °C, which impressively validates the potential of the produced graphene as a thermal reinforcement material for polymer composites.

  8. Exfoliation of graphene with an industrial dye: teaching an old dog new tricks

    Science.gov (United States)

    Schlierf, Andrea; Cha, Kitty; Schwab, Matthias Georg; Samorı, Paolo; Palermo, Vincenzo

    2014-12-01

    We describe the exfoliation, processing and inclusion in polymer composites of few-layers graphene nanoplatelets (GNPs) by using the molecule indanthrone blue sulphonic acid sodium salt (IBS), a very common industrial dyestuff and intermediate for liquid crystal preparation. We show how IBS can be used to successfully exfoliate graphite into few-layers graphene yielding highly stable dispersions in water. To demonstrate that the method is suitable for applications in composites, these graphene-organic hybrids are processed into a commercial commodity polymer (polyvinyl alcohol, PVA), enhancing its electrical bulk conductivity by ten orders of magnitude by adding as few as 3% of GNP. We attribute the good performance of IBS in dispersing GNPs in water to its amphiphilic nature and the tendency to self-assemble through π-π interaction of its large aromatic core with the graphene surface. The molecule studied here, unlike many specialty organic surfactants or solvents commonly known to exfoliate graphene, is already used as a blue pigment dispersant additive in the industrial production of polymers and thus does not need to be removed from the final product.

  9. Exfoliation of graphite into graphene in aqueous solutions of inorganic salts.

    Science.gov (United States)

    Parvez, Khaled; Wu, Zhong-Shuai; Li, Rongjin; Liu, Xianjie; Graf, Robert; Feng, Xinliang; Müllen, Klaus

    2014-04-23

    Mass production of high-quality graphene sheets is essential for their practical application in electronics, optoelectronics, composite materials, and energy-storage devices. Here we report a prompt electrochemical exfoliation of graphene sheets into aqueous solutions of different inorganic salts ((NH4)2SO4, Na2SO4, K2SO4, etc.). Exfoliation in these electrolytes leads to graphene with a high yield (>85%, ≤3 layers), large lateral size (up to 44 μm), low oxidation degree (a C/O ratio of 17.2), and a remarkable hole mobility of 310 cm(2) V(-1) s(-1). Further, highly conductive graphene films (11 Ω sq(-1)) are readily fabricated on an A4-size paper by applying brush painting of a concentrated graphene ink (10 mg mL(-1), in N,N'-dimethylformamide). All-solid-state flexible supercapacitors manufactured on the basis of such graphene films deliver a high area capacitance of 11.3 mF cm(-2) and an excellent rate capability of 5000 mV s(-1). The described electrochemical exfoliation shows great promise for the industrial-scale synthesis of high-quality graphene for numerous advanced applications.

  10. Exfoliated graphite/titanium dioxide nanocomposites for photodegradation of eosin yellow

    International Nuclear Information System (INIS)

    Ndlovu, Thabile; Kuvarega, Alex T.; Arotiba, Omotayo A.; Sampath, Srinivasan; Krause, Rui W.; Mamba, Bhekie B.

    2014-01-01

    Graphical abstract: - Highlights: • Preparation of exfoliated graphite (EG) from natural graphite. • Sol–gel anchoring of TiO 2 on exfoliated graphite. • High adsorption and photoactivity was observed for the EG-TiO 2 nanocomposite. • Mechanism of enhancement was proposed. - Abstract: An improved photocatalyst consisting of a nanocomposite of exfoliated graphite and titanium dioxide (EG-TiO 2 ) was prepared. SEM and TEM micrographs showed that the spherical TiO 2 nanoparticles were evenly distributed on the surface of the EG sheets. A four times photocatalytic enhancement was observed for this floating nanocomposite compared to TiO 2 and EG alone for the degradation of eosin yellow. For all the materials, the reactions followed first order kinetics where for EG-TiO 2 , the rate constant was much higher than for EG and TiO 2 under visible light irradiation. The enhanced photocatalytic activity of EG-TiO 2 was ascribed to the capability of graphitic layers to accept and transport electrons from the excited TiO 2 , promoting charge separation. This indicates that carbon, a cheap and abundant material, can be a good candidate as an electron attracting reservoir for photocatalytic organic pollutant degradation

  11. Exfoliation of graphene with an industrial dye: teaching an old dog new tricks

    International Nuclear Information System (INIS)

    Schlierf, Andrea; Palermo, Vincenzo; Cha, Kitty; Georg Schwab, Matthias; Samorı, Paolo

    2014-01-01

    We describe the exfoliation, processing and inclusion in polymer composites of few-layers graphene nanoplatelets (GNPs) by using the molecule indanthrone blue sulphonic acid sodium salt (IBS), a very common industrial dyestuff and intermediate for liquid crystal preparation. We show how IBS can be used to successfully exfoliate graphite into few-layers graphene yielding highly stable dispersions in water. To demonstrate that the method is suitable for applications in composites, these graphene-organic hybrids are processed into a commercial commodity polymer (polyvinyl alcohol, PVA), enhancing its electrical bulk conductivity by ten orders of magnitude by adding as few as 3% of GNP. We attribute the good performance of IBS in dispersing GNPs in water to its amphiphilic nature and the tendency to self-assemble through π–π interaction of its large aromatic core with the graphene surface. The molecule studied here, unlike many specialty organic surfactants or solvents commonly known to exfoliate graphene, is already used as a blue pigment dispersant additive in the industrial production of polymers and thus does not need to be removed from the final product. (paper)

  12. Brown spider dermonecrotic toxin directly induces nephrotoxicity

    International Nuclear Information System (INIS)

    Chaim, Olga Meiri; Sade, Youssef Bacila; Bertoni da Silveira, Rafael; Toma, Leny; Kalapothakis, Evanguedes; Chavez-Olortegui, Carlos; Mangili, Oldemir Carlos; Gremski, Waldemiro; Dietrich, Carl Peter von; Nader, Helena B.; Sanches Veiga, Silvio

    2006-01-01

    Brown spider (Loxosceles genus) venom can induce dermonecrotic lesions at the bite site and systemic manifestations including fever, vomiting, convulsions, disseminated intravascular coagulation, hemolytic anemia and acute renal failure. The venom is composed of a mixture of proteins with several molecules biochemically and biologically well characterized. The mechanism by which the venom induces renal damage is unknown. By using mice exposed to Loxosceles intermedia recombinant dermonecrotic toxin (LiRecDT), we showed direct induction of renal injuries. Microscopic analysis of renal biopsies from dermonecrotic toxin-treated mice showed histological alterations including glomerular edema and tubular necrosis. Hyalinization of tubules with deposition of proteinaceous material in the tubule lumen, tubule epithelial cell vacuoles, tubular edema and epithelial cell lysis was also observed. Leukocytic infiltration was neither observed in the glomerulus nor the tubules. Renal vessels showed no sign of inflammatory response. Additionally, biochemical analyses showed such toxin-induced changes in renal function as urine alkalinization, hematuria and azotemia with elevation of blood urea nitrogen levels. Immunofluorescence with dermonecrotic toxin antibodies and confocal microscopy analysis showed deposition and direct binding of this toxin to renal intrinsic structures. By immunoblotting with a hyperimmune dermonecrotic toxin antiserum on renal lysates from toxin-treated mice, we detected a positive signal at the region of 33-35 kDa, which strengthens the idea that renal failure is directly induced by dermonecrotic toxin. Immunofluorescence reaction with dermonecrotic toxin antibodies revealed deposition and binding of this toxin directly in MDCK epithelial cells in culture. Similarly, dermonecrotic toxin treatment caused morphological alterations of MDCK cells including cytoplasmic vacuoles, blebs, evoked impaired spreading and detached cells from each other and from

  13. Interplay between toxin transport and flotillin localization

    DEFF Research Database (Denmark)

    Pust, Sascha; Dyve, Anne Berit; Torgersen, Maria L

    2010-01-01

    The flotillin proteins are localized in lipid domains at the plasma membrane as well as in intracellular compartments. In the present study, we examined the importance of flotillin-1 and flotillin-2 for the uptake and transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin and we...... for flotillin-1 or -2. However, the Golgi-dependent sulfation of both toxins was significantly reduced in flotillin knockdown cells. Interestingly, when the transport of ricin to the ER was investigated, we obtained an increased mannosylation of ricin in flotillin-1 and flotillin-2 knockdown cells. The toxicity...... of both toxins was twofold increased in flotillin-depleted cells. Since BFA (Brefeldin A) inhibits the toxicity even in flotillin knockdown cells, the retrograde toxin transport is apparently still Golgi-dependent. Thus, flotillin proteins regulate and facilitate the retrograde transport of Stx and ricin....

  14. Crystallization of isoelectrically homogeneous cholera toxin

    International Nuclear Information System (INIS)

    Spangler, B.D.; Westbrook, E.M.

    1989-01-01

    Past difficulty in growing good crystals of cholera toxin has prevented the study of the crystal structure of this important protein. The authors have determined that failure of cholera toxin to crystallize well has been due to its heterogeneity. They have now succeeded in overcoming the problem by isolating a single isoelectric variant of this oligomeric protein (one A subunit and five B subunits). Cholera toxin purified by their procedure readily forms large single crystals. The crystal form has been described previously. They have recorded data from native crystals of cholera toxin to 3.0-angstrom resolution with our electronic area detectors. With these data, they have found the orientation of a 5-fold symmetry axis within these crystals, perpendicular to the screw dyad of the crystal. They are now determining the crystal structure of cholera toxin by a combination of multiple heavy-atom isomorphous replacement and density modification techniques, making use of rotational 5-fold averaging of the B subunits

  15. Immunotoxins: The Role of the Toxin

    Directory of Open Access Journals (Sweden)

    David FitzGerald

    2013-08-01

    Full Text Available Immunotoxins are antibody-toxin bifunctional molecules that rely on intracellular toxin action to kill target cells. Target specificity is determined via the binding attributes of the chosen antibody. Mostly, but not exclusively, immunotoxins are purpose-built to kill cancer cells as part of novel treatment approaches. Other applications for immunotoxins include immune regulation and the treatment of viral or parasitic diseases. Here we discuss the utility of protein toxins, of both bacterial and plant origin, joined to antibodies for targeting cancer cells. Finally, while clinical goals are focused on the development of novel cancer treatments, much has been learned about toxin action and intracellular pathways. Thus toxins are considered both medicines for treating human disease and probes of cellular function.

  16. Ionic Liquid-Modified Thermosets and Their Nanocomposites: Dispersion, Exfoliation, Degradation, and Cure

    Science.gov (United States)

    Throckmorton, James A.

    This dissertation explores the application of a room temperature ionic liquid (RTIL) to problems in the chemistry, processing, and modification of thermosetting polymers. In particular, the solution properties and reaction chemistry of 1-ethyl-3-methyl imidazolium dicyanamide (EMIM-DCN) are applied to problems of nanoparticle dispersion and processing, graphite exfoliation, cyanate ester (CE) cure, and the environmental degradation of CEs. Nanoparticle Dispersion: Nanocomposite processing can be simplified by using the same compound as both a nanoparticle solvent and an initiator for polymerization. This dual-function molecule can be designed both for solvent potential and reaction chemistry. EMIM-DCN, previously shown by our lab to act as an epoxy initiator, is used in the synthesis of silica and acid expanded graphite composites. These composites are then characterized for particle dispersion and physical properties. Individual particle dispersion of silica nanocomposites is shown, and silica nanocomposites at low loading show individual particle dispersion and improved modulus and fracture toughness. GNP nanocomposites show a 70% increase in modulus along with a 10-order of magnitude increase in electrical conductivity at 6.5 vol%, and an electrical percolation threshold of 1.7 vol%. Direct Graphite Exfoliation By Laminar Shear: This work presents a laminar-shear alternative to chemical processing and chaotic flow-fields for the direct exfoliation of graphite and the single-pot preparation of nanocomposites. Additionally, we develop the theory of laminar flow through a 3-roll mill, and apply that theory to the latest developments in the theory of graphite interlayer shear. The resulting nanocomposite shows low electrical percolation (0.5 vol%) and low thickness (1-3 layer) graphite/graphene flakes. Additionally, the effect of processing conditions by rheometry and comparison with solvent-free conditions reveal the interactions between processing and matrix

  17. Cyanobacterial toxins: risk management for health protection

    International Nuclear Information System (INIS)

    Codd, Geoffrey A.; Morrison, Louise F.; Metcalf, James S.

    2005-01-01

    This paper reviews the occurrence and properties of cyanobacterial toxins, with reference to the recognition and management of the human health risks which they may present. Mass populations of toxin-producing cyanobacteria in natural and controlled waterbodies include blooms and scums of planktonic species, and mats and biofilms of benthic species. Toxic cyanobacterial populations have been reported in freshwaters in over 45 countries, and in numerous brackish, coastal, and marine environments. The principal toxigenic genera are listed. Known sources of the families of cyanobacterial toxins (hepato-, neuro-, and cytotoxins, irritants, and gastrointestinal toxins) are briefly discussed. Key procedures in the risk management of cyanobacterial toxins and cells are reviewed, including derivations (where sufficient data are available) of tolerable daily intakes (TDIs) and guideline values (GVs) with reference to the toxins in drinking water, and guideline levels for toxigenic cyanobacteria in bathing waters. Uncertainties and some gaps in knowledge are also discussed, including the importance of exposure media (animal and plant foods), in addition to potable and recreational waters. Finally, we present an outline of steps to develop and implement risk management strategies for cyanobacterial cells and toxins in waterbodies, with recent applications and the integration of Hazard Assessment Critical Control Point (HACCP) principles

  18. Computational Studies of Snake Venom Toxins.

    Science.gov (United States)

    Ojeda, Paola G; Ramírez, David; Alzate-Morales, Jans; Caballero, Julio; Kaas, Quentin; González, Wendy

    2017-12-22

    Most snake venom toxins are proteins, and participate to envenomation through a diverse array of bioactivities, such as bleeding, inflammation, and pain, cytotoxic, cardiotoxic or neurotoxic effects. The venom of a single snake species contains hundreds of toxins, and the venoms of the 725 species of venomous snakes represent a large pool of potentially bioactive proteins. Despite considerable discovery efforts, most of the snake venom toxins are still uncharacterized. Modern bioinformatics tools have been recently developed to mine snake venoms, helping focus experimental research on the most potentially interesting toxins. Some computational techniques predict toxin molecular targets, and the binding mode to these targets. This review gives an overview of current knowledge on the ~2200 sequences, and more than 400 three-dimensional structures of snake toxins deposited in public repositories, as well as of molecular modeling studies of the interaction between these toxins and their molecular targets. We also describe how modern bioinformatics have been used to study the snake venom protein phospholipase A2, the small basic myotoxin Crotamine, and the three-finger peptide Mambalgin.

  19. Computational Studies of Snake Venom Toxins

    Directory of Open Access Journals (Sweden)

    Paola G. Ojeda

    2017-12-01

    Full Text Available Most snake venom toxins are proteins, and participate to envenomation through a diverse array of bioactivities, such as bleeding, inflammation, and pain, cytotoxic, cardiotoxic or neurotoxic effects. The venom of a single snake species contains hundreds of toxins, and the venoms of the 725 species of venomous snakes represent a large pool of potentially bioactive proteins. Despite considerable discovery efforts, most of the snake venom toxins are still uncharacterized. Modern bioinformatics tools have been recently developed to mine snake venoms, helping focus experimental research on the most potentially interesting toxins. Some computational techniques predict toxin molecular targets, and the binding mode to these targets. This review gives an overview of current knowledge on the ~2200 sequences, and more than 400 three-dimensional structures of snake toxins deposited in public repositories, as well as of molecular modeling studies of the interaction between these toxins and their molecular targets. We also describe how modern bioinformatics have been used to study the snake venom protein phospholipase A2, the small basic myotoxin Crotamine, and the three-finger peptide Mambalgin.

  20. Botulinum toxin for the treatment of bruxism.

    Science.gov (United States)

    Tinastepe, Neslihan; Küçük, Burcu Bal; Oral, Koray

    2015-10-01

    Botulinum toxin, the most potent biological toxin, has been shown to be effective for a variety of disorders in several medical conditions, when used both therapeutically and cosmetically. In recent years, there has been a rising trend in the use of this pharmacological agent to control bruxing activity, despite its reported adverse effects. The aim of this review was to provide a brief overview to clarify the underlying essential ideas for the use of botulinum toxin in bruxism based on available scientific papers. An electronic literature search was performed to identify publications related to botulinum toxin and its use for bruxism in PubMed. Hand searching of relevant articles was also made to identify additional studies. Of the eleven identified studies, only two were randomized controlled trials, compared with the effectiveness of botulinum toxins on the reduction in the frequency of bruxism events and myofascial pain after injection. The authors of these studies concluded that botulinum toxin could be used as an effective treatment for reducing nocturnal bruxism and myofascial pain in patients with bruxism. Evidence-based research was limited on this topic. More randomized controlled studies are needed to confirm that botulinum toxin is safe and reliable for routine clinical use in bruxism.

  1. Engineering toxins for 21st century therapies.

    Science.gov (United States)

    Chaddock, John A; Acharya, K Ravi

    2011-04-01

    'Engineering Toxins for 21st Century Therapies' (9-10 September 2010) was part of the Royal Society International Seminar series held at the Kavli International Centre, UK. Participants were assembled from a range of disciplines (academic, industry, regulatory, public health) to discuss the future potential of toxin-based therapies. The meeting explored how the current structural and mechanistic knowledge of toxins could be used to engineer future toxin-based therapies. To date, significant progress has been made in the design of novel recombinant biologics based on domains of natural toxins, engineered to exhibit advantageous properties. The meeting concluded, firstly that future product development vitally required the appropriate combination of creativity and innovation that can come from the academic, biotechnology and pharma sectors. Second, that continued investigation into understanding the basic science of the toxins and their targets was essential in order to develop new opportunities for the existing products and to create new products with enhanced properties. Finally, it was concluded that the clinical potential for development of novel biologics based on toxin domains was evident. © 2011 The Authors Journal compilation © 2011 FEBS.

  2. Role of Botulinum Toxin in Depression.

    Science.gov (United States)

    Parsaik, Ajay K; Mascarenhas, Sonia S; Hashmi, Aqeel; Prokop, Larry J; John, Vineeth; Okusaga, Olaoluwa; Singh, Balwinder

    2016-03-01

    The goal of this review was to consolidate the evidence concerning the efficacy of botulinum toxin type A (onabotulinumtoxinA) in depression. We searched MEDLINE, EMBASE, Cochrane, and Scopus through May 5, 2014, for studies evaluating the efficacy of botulinum toxin A in depression. Only randomized controlled trials were included in the meta-analysis. A pooled mean difference in primary depression score, and pooled odds ratio for response and remission rate with 95% confidence interval (CI) were estimated using the random-effects model. Heterogeneity was assessed using Cochran Q test and χ statistic. Of the 639 articles that were initially retrieved, 5 studies enrolling 194 subjects (age 49±9.6 y) were included in the systematic review, and 3 randomized controlled trials enrolling 134 subjects were included in the meta-analysis. The meta-analysis showed a significant decrease in mean primary depression scores among patients who received botulinum toxin A compared with placebo (-9.80; 95% CI, -12.90 to -6.69) with modest heterogeneity between the studies (Cochran Q test, χ=70). Response and remission rates were 8.3 and 4.6 times higher, respectively, among patients receiving botulinum toxin A compared with placebo, with no heterogeneity between the studies. The 2 studies excluded from the meta-analysis also found a significant decrease in primary depression scores in patients after receiving botulinum toxin A. A few subjects had minor side effects, which were similar between the groups receiving botulinum toxin and those receiving placebo. This study suggests that botulinum toxin A can produce significant improvement in depressive symptoms and is a safe adjunctive treatment for patients receiving pharmacotherapy for depression. Future trials are needed to evaluate the antidepressant effect per se of botulinum toxin A and to further elucidate the underlying antidepressant mechanism of botulinum toxin A.

  3. Botulinum toxin: yesterday, today, tomorrow

    Directory of Open Access Journals (Sweden)

    A. R. Artemenko

    2013-01-01

    Full Text Available Botulinum toxin (BoNT is a bacterial neurotoxin presented with seven serotypes that inhibit neurotransmitter release from nerve endings. The serotypes of BoNT are antigenically dissimilar, act via different, but interconnected mechanisms, and are not interchangeable. The activity of BoNT is associated with impaired neuroexocytosis occurring in several steps: from the binding of BoNT to its specific receptor on the axon terminal membrane to the proteolytic enzymatic cleavage of SNARE substrate. The effect of BoNT is considered to be restricted to the peripheral nervous system, but when given in particularly high doses, it has been recently shown to affect individual brain structures. In addition, by modulating peripheral afferentation, BoNT may influence the excitability of central neuronal structures at both spinal and cortical levels. Only BoNT serotypes A and B are used in clinical practice and aesthetic medicine. The type A has gained the widest acceptance as a therapeutic agent for more than 100 abnormalities manifesting themselves as muscular hyperactivity, hyperfunction of endocrine gland, and chronic pain. The effect of BoNT preparations shows itself 2-5 days after injection, lasts 3 months or more, and gradually decreases with as a result of pharmacokinetic and intracellular reparative processes. Biotechnology advances and potentialities allow purposefully modification of the protein molecular structure of BoNT, which expands the use and efficiency of performed therapy with neurotoxins. Recombinant technologies provide a combination of major therapeutic properties of each used BoNT serotype and expand indications for recombinant chimeric toxins.

  4. Toxin production in Dinophysis and the fate of these toxins in marine mussels

    DEFF Research Database (Denmark)

    Nielsen, Lasse Tor

    Diarrhetic shellfish poisoning (DSP) poses a considerable threat to food safety and to the economy of shellfish fishers and farmers in many parts of the world. Thousands of DSP intoxications have been reported, and bivalve harvesting can sometimes be closed down several months in a row. The toxins....... acuta. I grew the two species in laboratory cultures at different irradiances (7-130 μmol photons m-2 s-1) and with different food availability. The results showed that irradiance had no effects on toxin profiles, and only limited effects of the cellular toxin contents. Rather, toxin production rates...... are primarily produced by the marine mixotrophic dinoflagellates Dinophysis spp., known to occur in most parts of the world. Dinophysis can, along with other planktonic organisms, be consumed by filter-feeding bivalves, and thus the toxins can accumulate. Dinophysis can produce the three toxin groups, okadaic...

  5. Conditional Toxin Splicing Using a Split Intein System.

    Science.gov (United States)

    Alford, Spencer C; O'Sullivan, Connor; Howard, Perry L

    2017-01-01

    Protein toxin splicing mediated by split inteins can be used as a strategy for conditional cell ablation. The approach requires artificial fragmentation of a potent protein toxin and tethering each toxin fragment to a split intein fragment. The toxin-intein fragments are, in turn, fused to dimerization domains, such that addition of a dimerizing agent reconstitutes the split intein. These chimeric toxin-intein fusions remain nontoxic until the dimerizer is added, resulting in activation of intein splicing and ligation of toxin fragments to form an active toxin. Considerations for the engineering and implementation of conditional toxin splicing (CTS) systems include: choice of toxin split site, split site (extein) chemistry, and temperature sensitivity. The following method outlines design criteria and implementation notes for CTS using a previously engineered system for splicing a toxin called sarcin, as well as for developing alternative CTS systems.

  6. Preparation of Graphene Sheets by Electrochemical Exfoliation of Graphite in Confined Space and Their Application in Transparent Conductive Films.

    Science.gov (United States)

    Wang, Hui; Wei, Can; Zhu, Kaiyi; Zhang, Yu; Gong, Chunhong; Guo, Jianhui; Zhang, Jiwei; Yu, Laigui; Zhang, Jingwei

    2017-10-04

    A novel electrochemical exfoliation mode was established to prepare graphene sheets efficiently with potential applications in transparent conductive films. The graphite electrode was coated with paraffin to keep the electrochemical exfoliation in confined space in the presence of concentrated sodium hydroxide as the electrolyte, yielding ∼100% low-defect (the D band to G band intensity ratio, I D /I G = 0.26) graphene sheets. Furthermore, ozone was first detected with ozone test strips, and the effect of ozone on the exfoliation of graphite foil and the microstructure of the as-prepared graphene sheets was investigated. Findings indicate that upon applying a low voltage (3 V) on the graphite foil partially coated with paraffin wax that the coating can prevent the insufficiently intercalated graphite sheets from prematurely peeling off from the graphite electrode thereby affording few-layer (graphene sheets in a yield of as much as 60%. Besides, the ozone generated during the electrochemical exfoliation process plays a crucial role in the exfoliation of graphite, and the amount of defect in the as-prepared graphene sheets is dependent on electrolytic potential and electrode distance. Moreover, the graphene-based transparent conductive films prepared by simple modified vacuum filtration exhibit an excellent transparency and a low sheet resistance after being treated with NH 4 NO 3 and annealing (∼1.21 kΩ/□ at ∼72.4% transmittance).

  7. Design of amine modified polymer dispersants for liquid-phase exfoliation of transition metal dichalcogenide nanosheets and their photodetective nanocomposites

    Science.gov (United States)

    Lee, Jinseong; Hahnkee Kim, Richard; Yu, Seunggun; Babu Velusamy, Dhinesh; Lee, Hyeokjung; Park, Chanho; Cho, Suk Man; Jeong, Beomjin; Sol Kang, Han; Park, Cheolmin

    2017-12-01

    Liquid-phase exfoliation (LPE) of transition metal dichalcogenide (TMD) nanosheets is a facile, cost-effective approach to large-area photoelectric devices including photodetectors and non-volatile memories. Non-destructive exfoliation of nanosheets using macromolecular dispersing agents is beneficial in rendering the TMD nanocomposite films suitable for mechanically flexible devices. Here, an efficient LPE of molybdenum disulfide (MoS2) with an amine modified poly(styrene-co-maleic anhydride) co-polymer (AM-PSMA) is demonstrated, wherein the maleic anhydrides were converted into maleic imides with primary amines using N-Boc-(CH2) n -NH2. The exfoliation of nanosheets was facilitated through Lewis acid-base interaction between the primary amine and transition metal. The results demonstrate that the exfoliation depends upon both the fraction of primary amines in the polymer chain and their distance from the polymer backbone. Under optimized conditions of primary amine content and its distance from the backbone, AM-PSMA gave rise to a highly concentrated MoS2 nanosheet suspension that was stable for over 10 d. Exfoliation of several other TMDs was also achieved using the optimized AM-PSMA, indicating the scope of AM-PSMA applications. Furthermore, a flexible composite film of AM-PSMA and MoS2 nanosheets fabricated by vacuum-assisted filtration showed excellent photoconductive performances including a high I on/I off ratio of 102 and a fast photocurrent switching of 300 ms.

  8. NNDSS - Table II. Shiga toxin to Shigellosis

    Data.gov (United States)

    U.S. Department of Health & Human Services — NNDSS - Table II. Shiga toxin to Shigellosis - 2015. In this Table, provisional cases of selected notifiable diseases (≥1,000 cases reported during the preceding...

  9. Toxins and antimicrobial peptides: interactions with membranes

    Science.gov (United States)

    Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

    2009-08-01

    The innate immunity to pathogenic invasion of organisms in the plant and animal kingdoms relies upon cationic antimicrobial peptides (AMPs) as the first line of defense. In addition to these natural peptide antibiotics, similar cationic peptides, such as the bee venom toxin melittin, act as nonspecific toxins. Molecular details of AMP and peptide toxin action are not known, but the universal function of these peptides to disrupt cell membranes of pathogenic bacteria (AMPs) or a diverse set of eukaryotes and prokaryotes (melittin) is widely accepted. Here, we have utilized spectroscopic techniques to elucidate peptide-membrane interactions of alpha-helical human and mouse AMPs of the cathelicidin family as well as the peptide toxin melittin. The activity of these natural peptides and their engineered analogs was studied on eukaryotic and prokaryotic membrane mimics consisting of resistant pathogens.

  10. Bacterial toxins as pathogen weapons against phagocytes

    Directory of Open Access Journals (Sweden)

    Ana edo Vale

    2016-02-01

    Full Text Available Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favour microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signalling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.

  11. How Parkinsonian Toxins Dysregulate the Autophagy Machinery

    Directory of Open Access Journals (Sweden)

    Ruben K. Dagda

    2013-11-01

    Full Text Available Since their discovery, Parkinsonian toxins (6-hydroxydopamine, MPP+, paraquat, and rotenone have been widely employed as in vivo and in vitro chemical models of Parkinson’s disease (PD. Alterations in mitochondrial homeostasis, protein quality control pathways, and more recently, autophagy/mitophagy have been implicated in neurotoxin models of PD. Here, we highlight the molecular mechanisms by which different PD toxins dysregulate autophagy/mitophagy and how alterations of these pathways play beneficial or detrimental roles in dopamine neurons. The convergent and divergent effects of PD toxins on mitochondrial function and autophagy/mitophagy are also discussed in this review. Furthermore, we propose new diagnostic tools and discuss how pharmacological modulators of autophagy/mitophagy can be developed as disease-modifying treatments for PD. Finally, we discuss the critical need to identify endogenous and synthetic forms of PD toxins and develop efficient health preventive programs to mitigate the risk of developing PD.

  12. Botulinum toxin type a for chronic migraine.

    Science.gov (United States)

    Ashkenazi, Avi

    2010-03-01

    Chronic migraine (CM) is the leading cause of chronic daily headache, a common and debilitating headache syndrome. The management of CM patients is challenging, with only limited benefit from available oral preventive medications. Botulinum neurotoxin (BoNT) has been used extensively to treat disorders associated with increased muscle tone. More recent scientific data support an analgesic effect of the toxin. The pharmacokinetic and pharmacodynamic profiles of BoNT make it an appealing candidate for migraine prevention. Results from older clinical trials on the efficacy of the toxin in CM were inconclusive. However, recent trials using more stringent inclusion criteria have shown positive results, supporting the use of the toxin in some patients with this disorder. This review summarizes the scientific data on the analgesic properties of BoNT, as well as the clinical data on the efficacy of the toxin in treating CM.

  13. NNDSS - Table II. Shiga toxin to Shigellosis

    Data.gov (United States)

    U.S. Department of Health & Human Services — NNDSS - Table II. Shiga toxin to Shigellosis - 2016. In this Table, provisional* cases of selected† notifiable diseases (≥1,000 cases reported during the preceding...

  14. Updates on tetanus toxin: a fundamental approach

    Directory of Open Access Journals (Sweden)

    Md. Ahaduzzaman

    2015-03-01

    Full Text Available Clostridium tetani is an anaerobic bacterium that produces second most poisonous protein toxins than any other bacteria. Tetanus in animals is sporadic in nature but difficult to combat even by using antibiotics and antiserum. It is crucial to understand the fundamental mechanisms and signals that control toxin production for advance research and medicinal uses. This review was intended for better understanding the basic patho-physiology of tetanus and neurotoxins (TeNT among the audience of related field.

  15. Exfoliative Cytology in the Oral Mucosa of Patients with Fanconi Anaemia: A Morphometric Approach

    Directory of Open Access Journals (Sweden)

    Maria Angela Naval Machado

    2017-04-01

    Full Text Available Patients with Fanconi anaemia (FA are prone to develop squamous cell carcinomas at an early age. Exfoliative cytology can be used to detect changes to the health of the oral mucosa. Objective: The aim of this study was to evaluate morphometrical and morphological changes using exfoliative cytology and to analyse and quantify the proliferative activity using silver nucleolar organiser regions (AgNOR in epithelial cells of the tongue in FA patients,after haematopoietic stem cell transplantation (HSCT. Methods: Oral smears were collected from the tongues of 20 FA children and adolescents after haematopoietic stem cell transplantation (FA and 20 healthy children (C using exfoliative cytology. The smears were stained using the Papanicolaou technique and silver impregnation. The cells were morphologically analysed and the nuclear area (NA, the cytoplasmic area (CA, and the nucleusto-cytoplasm area ratio (NA/CA were calculated. Results: Mean values for the FA and C groups were: NA (71.85 and 55.21μm.; p< 0.01; CA (2127.48 and 1441.61μm.; p< 0.01; NA/CA (0.03 and 0.04; p< 0.01, respectively. A significant increase in the NA and CA for the FA group (p< 0.01 was seen, and an alteration in the NA/CA ratio. No morphological differences were found between the groups. Class I smears were predominant in both groups. No differences were found between the groups for the mean values of AgNORs per nucleus. Conclusion: This study suggests that morphological changes occurred in the oral epithelium cells of children and adolescents with Fanconi anaemia when subjected to HSCT.

  16. Prevalence of micronuclei in exfoliated uterine cervical cells from patients with risk factors for cervical cancer.

    Science.gov (United States)

    Reis Campos, Lízia Maria Franco dos; Luz Dias, Francisca da; Antunes, Lusânia Maria Greggi; Murta, Eddie Fernando Candido

    2008-11-01

    Pap smears are the most common and inexpensive screening method for cervical cancer. We analyzed micronucleus prevalence in exfoliated cervical mucosa cells, to investigate associations between increased numbers of micronuclei and risk factors for cervical cancer. Analytical cross-sectional study, at Instituto de Pesquisa em Oncologia (IPON). Exfoliated cervical cells were obtained from 101 patients between September 2004 and November 2005. Patients' ages, habits (passive or active smoking, alcoholism and numbers of sexual partners), age at first sexual intercourse, contraceptive methods used, histories of sexually transmitted diseases, use of hormone replacement therapy, numbers of pregnancies and abortions, inflammatory cytology and cervical intraepithelial neoplasia (CIN) were obtained. Cells were collected using Ayre spatulas, transferred to vials containing 0.9% saline solution for micronucleus tests and analyzed at 1000x magnification. The number of micronuclei in 1,000 epithelial cells per patient sample was counted. Comparisons between groups with active (7.9 +/- 7.8) and passive (7.2 +/- 10.6) smoking versus no smoking (3.7 +/- 5.1); with/without alcoholism (7.8 +/- 1.4 and 6.9 +/- 10.1); with/without inflammatory cytology (10.7 +/- 10.5 and 1.3 +/- 1.7); and with CIN I, II and III and no CIN (respectively 4.3 +/- 4.3, 10.6 +/- 5.3, 22.7 +/- 11.9 and 1.3 +/- 1.4) found elevated micronucleus prevalence (P < 0.05). We concluded that the prevalence of micronuclei in exfoliated uterine cervical cells was greater in patients with one or more risk factors for uterine cervical cancer than in patients without risk factors.

  17. Increased frequency of micronucleated exfoliated cells among humans exposed in vivo to mobile telephone radiations

    International Nuclear Information System (INIS)

    Manoj Kumar Sharma; Abhay Singh Yadav

    2007-01-01

    Complete text of publication follows. The health concerns have been raised following the enormous increase in the use of wireless mobile telephones through out the world. This investigation had been taken, with the motive to find out whether mobile phone radiations cause any in vivo effects on the frequency of micronucleated exfoliated cells in the exposed subjects. A total of 109 subjects including 85 regular mobile phone users (exposed) and 24 non-users (controls) had participated in this study. Exfoliated cells were obtained by swabbing the buccal-mucosa from exposed as well as sex-age-matched controls. One thousand exfoliated cells were screened from each individual for nuclear anomalies including micronuclei (MN), karyolysis (KL), karyorrhexis (KH), broken egg (BE) and bi-nucleated (BN) cells. The average daily duration of exposure to mobile phone radiations is 61.26 minutes with an overall average duration of exposure in term of years is 2.35 years in exposed subjects along with the 9.84±0.745 MNC (micronucleated cells) and 10.72±0.889 TMN (total micronuclei) as compared to zero duration of exposure along with average 3.75±0.774 MNC and 4.00±0.808 TMN in controls. The means are significantly different in case MNC and TMN at 0.01% level of significance. For all other nuclear anomalies (KL, KH, BE and BN cells) the means are found statistically nonsignificant. A positive correlation was found in the frequency of MNC and TMN with respect to duration of exposure time.

  18. Prevalence of micronuclei in exfoliated uterine cervical cells from patients with risk factors for cervical cancer

    Directory of Open Access Journals (Sweden)

    Lízia Maria Franco dos Reis Campos

    Full Text Available CONTEXT AND OBJECTIVE: Pap smears are the most common and inexpensive screening method for cervical cancer. We analyzed micronucleus prevalence in exfoliated cervical mucosa cells, to investigate associations between increased numbers of micronuclei and risk factors for cervical cancer. DESIGN AND SETTING: Analytical cross-sectional study, at Instituto de Pesquisa em Oncologia (IPON. METHODS: Exfoliated cervical cells were obtained from 101 patients between September 2004 and November 2005. Patients' ages, habits (passive or active smoking, alcoholism and numbers of sexual partners, age at first sexual intercourse, contraceptive methods used, histories of sexually transmitted diseases, use of hormone replacement therapy, numbers of pregnancies and abortions, inflammatory cytology and cervical intraepithelial neoplasia (CIN were obtained. Cells were collected using Ayre spatulas, transferred to vials containing 0.9% saline solution for micronucleus tests and analyzed at 1000x magnification. The number of micronuclei in 1,000 epithelial cells per patient sample was counted. RESULTS: Comparisons between groups with active (7.9 ± 7.8 and passive (7.2 ± 10.6 smoking versus no smoking (3.7 ± 5.1; with/without alcoholism (7.8 ± 1.4 and 6.9 ± 10.1; with/without inflammatory cytology (10.7 ± 10.5 and 1.3 ± 1.7; and with CIN I, II and III and no CIN (respectively 4.3 ± 4.3, 10.6 ± 5.3, 22.7 ± 11.9 and 1.3 ± 1.4 found elevated micronucleus prevalence (P < 0.05. CONCLUSIONS: We concluded that the prevalence of micronuclei in exfoliated uterine cervical cells was greater in patients with one or more risk factors for uterine cervical cancer than in patients without risk factors.

  19. Fabrication of single phase 2D homologous perovskite microplates by mechanical exfoliation

    Science.gov (United States)

    Li, Junze; Wang, Jun; Zhang, Yingjun; Wang, Haizhen; Lin, Gaoming; Xiong, Xuan; Zhou, Weihang; Luo, Hongmei; Li, Dehui

    2018-04-01

    The two-dimensional (2D) Ruddlesden-Popper type perovskites have attracted intensive interest for their great environmental stability and various potential optoelectronic applications. Fundamental understanding of the photophysical and electronic properties of the 2D perovskites with pure single phase is essential for improving the performance of the optoelectronic devices and designing devices with new architectures. Investigating the optical and electronic properties of these materials with pure single phase is required to obtain pure single phase 2D perovskites. Here, we report on an alternative approach to fabricate (C4H9NH3)2(CH3NH3) n-1Pb n I3n+1 microplates with pure single n-number perovskite phase for n  >  2 by mechanical exfoliation. Micro-photoluminescence and absorption spectroscopy studies reveal that the as-synthesized 2D perovskite plates for n  >  2 are comprised by dominant n-number phase and small inclusions of hybrid perovskite phases with different n values, which is supported by excitation power dependent photoluminescence. By mechanical exfoliation method, 2D perovskite microplates with the thickness of around 20 nm are obtained, which surprisingly have single n-number perovskite phase for n  =  2-5. In addition, we have demonstrated that the exfoliated 2D perovskite microplates can be integrated with other 2D layered materials such as boron nitride, and are able to be transferred to prefabricated electrodes for photodetections. Our studies not only provide a strategy to prepare 2D perovskites with a single n-number perovskite phase allowing us to extract the basic optical and electronic parameters of pure phase perovskites, but also demonstrate the possibility to integrate the 2D perovskites with other 2D layered materials to extend the device’s functionalities.

  20. Mechanical exfoliation of epitaxial graphene on Ir(111) enabled by Br2 intercalation.

    Science.gov (United States)

    Herbig, Charlotte; Kaiser, Markus; Bendiab, Nedjma; Schumacher, Stefan; Förster, Daniel F; Coraux, Johann; Meerholz, Klaus; Michely, Thomas; Busse, Carsten

    2012-08-08

    We show here that Br(2) intercalation is an efficient method to enable exfoliation of epitaxial graphene on metals by adhesive tape. We exemplify this method for high-quality graphene of macroscopic extension on Ir(111). The sample quality and the transfer process are monitored using low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), scanning electron microscopy (SEM) and Raman spectroscopy. The developed process provides an opportunity for preparing graphene of strictly monatomic thickness and well-defined orientation including the transfer to poly(ethylene terephthalate) (PET) foil.

  1. Production of graphene by exfoliation of graphite in a volatile organic solvent

    International Nuclear Information System (INIS)

    Choi, Eun-Young; Choi, Won San; Lee, Young Boo; Noh, Yong-Young

    2011-01-01

    The production of unfunctionalized and nonoxidized graphene by exfoliation of graphite in a volatile solvent, 1-propanol, is reported. A stable homogeneous dispersion of graphene was obtained by mild sonication of graphite powder and subsequent centrifugation. The presence of a graphene monolayer was observed by atomic force microscopy and transmission electron microscopy. The solvent, 1-propanol, from the deposited dispersion was simply and quickly removed by air drying at room temperature, without the help of high temperature annealing or vacuum drying, which shortens production time and does not leave any residue of the solvent in the graphene sheets.

  2. Hydrazine-Assisted Liquid Exfoliation of MoS2 for Catalytic Hydrodeoxygenation of 4-Methylphenol.

    Science.gov (United States)

    Liu, Guoliang; Ma, Hualong; Teixeira, Ivo; Sun, Zhenyu; Xia, Qineng; Hong, Xinlin; Tsang, Shik Chi Edman

    2016-02-24

    A simple but effective method to exfoliate bulk MoS2 in a range of solvents is presented for the preparation of colloid flakes consisted of one to a few molecular layers by application of ultrasonic treatment in N2 H4 . Their high yield in solution and exposure of more active surface sites allows the synthesis of corresponding solid catalysts with remarkably high activity in hydrodeoxygenation of 4-methylphenol and this method can also be applied to other two dimensional materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Liftoff process for exfoliation of thin film photovoltaic devices and back contact formation

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Richard A.; Hannon, James B.; Oida, Satoshi

    2018-04-03

    A method for forming a back contact on an absorber layer in a photovoltaic device includes forming a two dimensional material on a first substrate. An absorber layer including Cu--Zn--Sn--S(Se) (CZTSSe) is grown over the first substrate on the two dimensional material. A buffer layer is grown on the absorber layer on a side opposite the two dimensional material. The absorber layer is exfoliated from the two dimensional material to remove the first substrate from a backside of the absorber layer opposite the buffer layer. A back contact is deposited on the absorber layer.

  4. Interlayer catalytic exfoliation realizing scalable production of large-size pristine few-layer graphene

    OpenAIRE

    Geng, Xiumei; Guo, Yufen; Li, Dongfang; Li, Weiwei; Zhu, Chao; Wei, Xiangfei; Chen, Mingliang; Gao, Song; Qiu, Shengqiang; Gong, Youpin; Wu, Liqiong; Long, Mingsheng; Sun, Mengtao; Pan, Gebo; Liu, Liwei

    2013-01-01

    Mass production of reduced graphene oxide and graphene nanoplatelets has recently been achieved. However, a great challenge still remains in realizing large-quantity and high-quality production of large-size thin few-layer graphene (FLG). Here, we create a novel route to solve the issue by employing one-time-only interlayer catalytic exfoliation (ICE) of salt-intercalated graphite. The typical FLG with a large lateral size of tens of microns and a thickness less than 2?nm have been obtained b...

  5. Turbulence-assisted shear exfoliation of graphene using household detergent and a kitchen blender

    Science.gov (United States)

    Varrla, Eswaraiah; Paton, Keith R.; Backes, Claudia; Harvey, Andrew; Smith, Ronan J.; McCauley, Joe; Coleman, Jonathan N.

    2014-09-01

    To facilitate progression from the lab to commercial applications, it will be necessary to develop simple, scalable methods to produce high quality graphene. Here we demonstrate the production of large quantities of defect-free graphene using a kitchen blender and household detergent. We have characterised the scaling of both graphene concentration and production rate with the mixing parameters: mixing time, initial graphite concentration, rotor speed and liquid volume. We find the production rate to be invariant with mixing time and to increase strongly with mixing volume, results which are important for scale-up. Even in this simple system, concentrations of up to 1 mg ml-1 and graphene masses of >500 mg can be achieved after a few hours mixing. The maximum production rate was ~0.15 g h-1, much higher than for standard sonication-based exfoliation methods. We demonstrate that graphene production occurs because the mean turbulent shear rate in the blender exceeds the critical shear rate for exfoliation.To facilitate progression from the lab to commercial applications, it will be necessary to develop simple, scalable methods to produce high quality graphene. Here we demonstrate the production of large quantities of defect-free graphene using a kitchen blender and household detergent. We have characterised the scaling of both graphene concentration and production rate with the mixing parameters: mixing time, initial graphite concentration, rotor speed and liquid volume. We find the production rate to be invariant with mixing time and to increase strongly with mixing volume, results which are important for scale-up. Even in this simple system, concentrations of up to 1 mg ml-1 and graphene masses of >500 mg can be achieved after a few hours mixing. The maximum production rate was ~0.15 g h-1, much higher than for standard sonication-based exfoliation methods. We demonstrate that graphene production occurs because the mean turbulent shear rate in the blender exceeds

  6. Botulinum toxin therapy for limb dystonias.

    Science.gov (United States)

    Yoshimura, D M; Aminoff, M J; Olney, R K

    1992-03-01

    We investigated the effectiveness of botulinum toxin in 17 patients with limb dystonias (10 with occupational cramps, three with idiopathic dystonia unrelated to activity, and two each with post-stroke and parkinsonian dystonia) in a placebo-controlled, blinded study. We identified affected muscles clinically and by recording the EMG from implanted wire electrodes at rest and during performance of tasks that precipitated abnormal postures. There were three injections given with graded doses of toxin (average doses, 5 to 10, 10 to 20, and 20 to 40 units per muscle) and one with placebo, in random order. Subjective improvement occurred after 53% of injections of botulinum toxin, and this was substantial in 24%. Only one patient (7%) improved after placebo injection. Subjective improvement occurred in 82% of patients with at least one dose of toxin, lasting for 1 to 4 months. Response rates were similar between clinical groups. Objective evaluation failed to demonstrate significant improvement following treatment with toxin compared with placebo. The major side effect was transient focal weakness after 53% of injections of toxin.

  7. Botulinum toxin for the treatment of strabismus.

    Science.gov (United States)

    Rowe, Fiona J; Noonan, Carmel P

    2017-03-02

    The use of botulinum toxin as an investigative and treatment modality for strabismus is well reported in the medical literature. However, it is unclear how effective it is in comparison to other treatment options for strabismus. The primary objective was to examine the efficacy of botulinum toxin therapy in the treatment of strabismus compared with alternative conservative or surgical treatment options. This review sought to ascertain those types of strabismus that particularly benefit from the use of botulinum toxin as a treatment option (such as small angle strabismus or strabismus with binocular potential, i.e. the potential to use both eyes together as a pair). The secondary objectives were to investigate the dose effect and complication rates associated with botulinum toxin. We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 6), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2016), Embase (January 1980 to July 2016), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to July 2016), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 11 July 2016. We handsearched the British and Irish Orthoptic Journal, Australian Orthoptic Journal, proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and International Orthoptic Association (IOA) (www.liv.ac.uk/orthoptics/research/search.htm) and American Academy of Paediatric Ophthalmology and Strabismus meetings (AAPOS). We contacted researchers who are active in this field for information about further

  8. Application of liquid-based cytology preparation in micronucleus assay of exfoliated buccal epithelial cells in road construction workers.

    Science.gov (United States)

    Arul, P

    2017-01-01

    Asphalts are bitumens that consist of complex of hydrocarbon mixtures and it is used mainly in road construction and maintenance. This study was undertaken to evaluate the micronucleus (MN) assay of exfoliated buccal epithelial cells in road construction workers using liquid-based cytology (LBC) preparation. Three different stains (May-Grunwald Giemsa, hematoxylin and eosin, and Papanicolaou) were used to evaluate the frequency of MN in exfoliated buccal epithelial of 100 participants (fifty road construction workers and fifty administrative staff) using LBC preparation. Statistical analysis was performed with Student's t-test, and Proad construction exhibit a higher frequency of MN in exfoliated buccal epithelial cells and they are under the significant risk of cytogenetic damage. LBC preparation has potential application for the evaluation of frequency of MN. This technique may be advocated in those who are occupationally exposed to potentially carcinogenic agents in view of improvement in the smear quality and visualization of cell morphology.

  9. Ultrahigh-throughput exfoliation of graphite into pristine ‘single-layer’ graphene using microwaves and molecularly engineered ionic liquids

    Science.gov (United States)

    Matsumoto, Michio; Saito, Yusuke; Park, Chiyoung; Fukushima, Takanori; Aida, Takuzo

    2015-09-01

    Graphene has shown much promise as an organic electronic material but, despite recent achievements in the production of few-layer graphene, the quantitative exfoliation of graphite into pristine single-layer graphene has remained one of the main challenges in developing practical devices. Recently, reduced graphene oxide has been recognized as a non-feasible alternative to graphene owing to variable defect types and levels, and attention is turning towards reliable methods for the high-throughput exfoliation of graphite. Here we report that microwave irradiation of graphite suspended in molecularly engineered oligomeric ionic liquids allows for ultrahigh-efficiency exfoliation (93% yield) with a high selectivity (95%) towards ‘single-layer’ graphene (that is, with thicknesses oligomeric ionic liquids up to ~100 mg ml-1, and form physical gels in which an anisotropic orientation of graphene sheets, once induced by a magnetic field, is maintained.

  10. Affinity chromatography of tetanus toxin, tetanus toxoid, and botulinum A toxin on synaptosomes, and differentiation of their acceptors

    Energy Technology Data Exchange (ETDEWEB)

    Habermann, E [Giessen Univ. (Germany, F.R.). Pharmakologisches Inst.

    1976-01-01

    /sup 125/I-labelled tetanus toxin and /sup 125/I-labelled botulinum A neurotoxin are known to be specifically bound to brain synaptosomes. In order to discriminate between active toxin and inactive admixtures present in the starting material or arising during iodination, synaptosome columns were prepared using bromacetylcellulose and/or kieselgur (Celite) as carriers. Both types of columns adsorb the toxins from low ionic strength medium and release them if the pH and ionic strength are raised. Botulinum toxin was eluted with lower ionic strength than tetanus toxin, and could be freed from nontoxic admixtures. Analysis by affinity chromatography disclosed partially toxoided tetanus toxin in both labelled and unlabelled toxin samples. High concentrations of formaldehyde (0.5%) destroyed both toxicity and affinity to the synaptosomes of tetanus toxin. Low concentrations of formaldehyde (0.05%) yielded a derivative of low toxicity which was still, however less firmly, bound to synaptosomes. Tetanus and botulinum toxin differ by their acceptors. Whereas unlabelled botulinum toxin is unable to compete with labelled tetanus toxin, unlabelled tetanus toxin slightly competes with botulinum toxin. Both labelled toxins display anomalous binding behaviour in that they cannot be displaced completely even with a large excess of unlabelled toxin.

  11. Affinity chromatography of tetanus toxin, tetanus toxoid, and botulinum A toxin on synaptosomes, and differentiation of their acceptors

    International Nuclear Information System (INIS)

    Habermann, E.

    1976-01-01

    125 I-labelled tetanus toxin and 125 I-labelled botulinum A neurotoxin are known to be specifically bound to brain synaptosomes. In order to discriminate between active toxin and inactive admixtures present in the starting material or arising during iodination, synaptosome columns were prepared using bromacetylcellulose and/or kieselgur (Celite) as carriers. Both types of columns adsorb the toxins from low ionic strength medium and release them if the pH and ionic strength are raised. Botulinum toxin was eluted with lower ionic strength than tetanus toxin, and could be freed from nontoxic admixtures. Analysis by affinity chromatography disclosed partially toxoided tetanus toxin in both labelled and unlabelled toxin samples. High concentrations of formaldehyde (0.5%) destroyed both toxicity and affinity to the synaptosomes of tetanus toxin. Low concentrations of formaldehyde (0.05%) yielded a derivative of low toxicity which was still, however less firmly, bound to synaptosomes. Tetanus and botulinum toxin differ by their acceptors. Whereas unlabelled botulinum toxin is unable to compete with labelled tetanus toxin, unlabelled tetanus toxin slightly competes with botulinum toxin. Both labelled toxins display anomalous binding behaviour in that they cannot be displaced completely even with a large excess of unlabelled toxin. (orig.) [de

  12. Electrochemical Exfoliation of Graphite in Aqueous Sodium Halide Electrolytes toward Low Oxygen Content Graphene for Energy and Environmental Applications.

    Science.gov (United States)

    Munuera, J M; Paredes, J I; Enterría, M; Pagán, A; Villar-Rodil, S; Pereira, M F R; Martins, J I; Figueiredo, J L; Cenis, J L; Martínez-Alonso, A; Tascón, J M D

    2017-07-19

    Graphene and graphene-based materials have shown great promise in many technological applications, but their large-scale production and processing by simple and cost-effective means still constitute significant issues in the path of their widespread implementation. Here, we investigate a straightforward method for the preparation of a ready-to-use and low oxygen content graphene material that is based on electrochemical (anodic) delamination of graphite in aqueous medium with sodium halides as the electrolyte. Contrary to previous conflicting reports on the ability of halide anions to act as efficient exfoliating electrolytes in electrochemical graphene exfoliation, we show that proper choice of both graphite electrode (e.g., graphite foil) and sodium halide concentration readily leads to the generation of large quantities of single-/few-layer graphene nanosheets possessing a degree of oxidation (O/C ratio down to ∼0.06) lower than that typical of anodically exfoliated graphenes obtained with commonly used electrolytes. The halide anions are thought to play a role in mitigating the oxidation of the graphene lattice during exfoliation, which is also discussed and rationalized. The as-exfoliated graphene materials exhibited a three-dimensional morphology that was suitable for their practical use without the need to resort to any kind of postproduction processing. When tested as dye adsorbents, they outperformed many previously reported graphene-based materials (e.g., they adsorbed ∼920 mg g -1 for methyl orange) and were useful sorbents for oils and nonpolar organic solvents. Supercapacitor cells assembled directly from the as-exfoliated products delivered energy and power density values (up to 15.3 Wh kg -1 and 3220 W kg -1 , respectively) competitive with those of many other graphene-based devices but with the additional advantage of extreme simplicity of preparation.

  13. Electrolytic exfoliation of graphite in water with multifunctional electrolytes: en route towards high quality, oxide-free graphene flakes.

    Science.gov (United States)

    Munuera, J M; Paredes, J I; Villar-Rodil, S; Ayán-Varela, M; Martínez-Alonso, A; Tascón, J M D

    2016-02-07

    Electrolytic--usually referred to as electrochemical--exfoliation of graphite in water under anodic potential holds enormous promise as a simple, green and high-yield method for the mass production of graphene, but currently suffers from several drawbacks that hinder its widespread adoption, one of the most critical being the oxidation and subsequent structural degradation of the carbon lattice that is usually associated with such a production process. To overcome this and other limitations, we introduce and implement the concept of multifunctional electrolytes. The latter are amphiphilic anions (mostly polyaromatic hydrocarbons appended with sulfonate groups) that play different relevant roles as (1) an intercalating electrolyte to trigger exfoliation of graphite into graphene flakes, (2) a dispersant to afford stable aqueous colloidal suspensions of the flakes suitable for further use, (3) a sacrificial agent to prevent graphene oxidation during exfoliation and (4) a linker to promote nanoparticle anchoring on the graphene flakes, yielding functional hybrids. The implementation of this strategy with some selected amphiphiles even furnishes anodically exfoliated graphenes of a quality similar to that of flakes produced by direct, ultrasound- or shear-induced exfoliation of graphite in the liquid phase (i.e., almost oxide- and defect-free). These high quality materials were used for the preparation of catalytically efficient graphene-Pt nanoparticle hybrids, as demonstrated by model reactions (reduction of nitroarenes). The multifunctional performance of these electrolytes is also discussed and rationalized, and a mechanistic picture of their oxidation-preventing ability is proposed. Overall, the present results open the prospect of anodic exfoliation as a competitive method for the production of very high quality graphene flakes.

  14. Exfoliation on stainless steel and inconel produced by 0.8-4 MeV helium ion bombardment

    International Nuclear Information System (INIS)

    Paszti, F.; Mezey, G.; Pogany, L.; Fried, M.; Manuaba, A.; Kotai, E.; Lohner, T.; Pocs, L.

    1982-11-01

    Trying to outline the energy dependence of surface deformations such as exfoliation and flaking on candidate CTR first-wall materials, stainless steel and two types of inconels were bombarded by 0.8, 1 and 4 MeV helium ions. All the bombarded spots could be characterized by by large exfoliations covering almost the total implanted area. No spontaneous rupture was observed except on one type of inconel where flaking took place right after reaching the critical dose. After mechanical opening of the formations, similar inner morphology was found as in our previous studies on gold. (author)

  15. Environmentally benign graphite intercalation compound composition for exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Jang, Bor Z.

    2014-06-17

    A carboxylic-intercalated graphite compound composition for the production of exfoliated graphite, flexible graphite, or nano-scaled graphene platelets. The composition comprises a layered graphite with interlayer spaces or interstices and a carboxylic acid residing in at least one of the interstices, wherein the composition is prepared by a chemical oxidation reaction which uses a combination of a carboxylic acid and hydrogen peroxide as an intercalate source. Alternatively, the composition may be prepared by an electrochemical reaction, which uses a carboxylic acid as both an electrolyte and an intercalate source. Exfoliation of the invented composition does not release undesirable chemical contaminants into air or drainage.

  16. Botulinum toxin in parkinsonism: The when, how, and which for botulinum toxin injections.

    Science.gov (United States)

    Cardoso, Francisco

    2018-06-01

    The aim of this article is to provide a review of the use of injections of botulinum toxin in the management of selected symptoms and signs of Parkinson's disease and other forms of parkinsonism. Sialorrhea is defined as inability to control oral secretions, resulting in excessive saliva in the oropharynx. There is a high level of evidence for the treatment of sialorrhea in parkinsonism with injections of different forms of botulinum toxin type A as well as botulinum toxin type B. Tremor can be improved by the use of botulinum toxin injections but improved tremor control often leads to concomitant motor weakness, limiting its use. Levodopa induced dyskinesias are difficult to treat with botulinum toxin injections because of their variable frequency and direction. Apraxia of eyelid opening, a sign more commonly seen in progressive supranuclear palsy and other tauopathies, often improves after botulinum toxin injections. Recent data suggest that regardless of the underlying mechanism, pain in parkinsonism can be alleviated by botulinum toxin injections. Finally, freezing of gait, camptocormia and Pisa syndrome in parkinsonism almost invariably fail to respond to botulinum toxin injections. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Recurrent aphthous stomatitis (RAS and exfoliative cheilitis in elderly psoriasis sufferer

    Directory of Open Access Journals (Sweden)

    Siti Hardiyanti Nurhasanah

    2016-04-01

    Full Text Available Recurrent Aphthous Stomatitis (RAS is a disorder in the oral cavity, with a characterized symptom as ulceration, recurrent and very painfull. The etiology is idiopathic, with multifactorial predisposition. Exfoliative cheilitis is a persistent lesion on the lip, with a characterized cracking and desquamative, with crustae and inflammation. An elderly male (72 yrs suffered with ulcer on his oral cavity, cracking lips and pain on both of his cheeks, skin, since 5 years ago. The pain is recurrent. On the clinical examination, there were some desquamation, both on the skin and vermilion border, whether on the inner lips (labial fold mucosa, there were ulcers with diameter about 1 cm. The laboratory test was within normal limits, except the LED was 40 mm/hour (n:<15. The diagnosis was Recurrent Aphthous Stomatitis (RAS for the ulcer and Exfoliative cheilitis for the cracking lips. The treatment he received was a gargle liquid, topical corticosteroid and supplement. The skin’s disorder was revered to the skin and genital disease department, for further management. As a dental general practioner, had to be very careful and familiar for every changes that may be occur both in the outer or inner oral cavity. Other disorder that need refferal, had to be done with team work, to the colleague from the right connection.

  18. Synchronous exfoliation and assembly of graphene on 3D Ni(OH)2 for supercapacitors.

    Science.gov (United States)

    Ma, Liguo; Zheng, Maojun; Liu, Shaohua; Li, Qiang; You, Yuxiu; Wang, Faze; Ma, Li; Shen, Wenzhong

    2016-11-08

    Nowadays, new approaches to fabricate high-performance electrode materials are of vital importance in the renewable energy field. Here, we present a facile synthesis procedure of 3D Ni(OH) 2 /graphene hybrids for supercapacitors via synchronous electrochemical-assisted exfoliation and assembly of graphene on 3D Ni(OH) 2 networks. With the assistance of an electric field, the electrochemically exfoliated high-quality graphene can be readily, uniformly assembled on the surfaces of 3D Ni(OH) 2 . When serving as electrode materials for supercapacitors, the resulting 3D Ni(OH) 2 /graphene composites exhibited excellent specific capacitance (263 mF cm -2 at 2 mA cm -2 ), remarkable rate capability and super-long cycle life (retention of 94.1% even after 10 000 continuous charge-discharge cycles), which may be attributed to their highly porous, stable 3D architecture as well as uniform, firm anchoring of ultrathin graphene on their surfaces. Therefore, our approach provides a facile strategy for the large-scale synthesis of high-quality graphene based composites towards various applications.

  19. Exfoliated graphite with graphene flakes as potential candidates for TL dosimeters at high gamma doses.

    Science.gov (United States)

    Ortiz-Morales, A; López-González, E; Rueda-Morales, G; Ortega-Cervantez, G; Ortiz-Lopez, J

    2018-06-06

    Graphite powder (GP) subjected to microwave radiation (MWG) results in exfoliation of graphite particles into few-layered graphene flakes (GF) intermixed with partially exfoliated graphite particles (PEG). Characterization of MWG by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Raman spectroscopy reveal few-layer GF with sizes ranging from 0.2 to 5 µm. Raman D, G, and 2D (G') bands characteristic of graphitic structures include evidence of the presence of bilayered graphene. The thermoluminescent (TL) dosimetric properties of MWG are evaluated and can be characterized as a gamma-ray sensitive and dose-resistant material with kinetic parameters (activation energy for the main peak located at 400 and 408 K is 0.69 and 0.72 eV) and threshold dose (~1 kGy and 5 kGy respectively). MWG is a low-Z material (Z eff = 6) with a wide linear range of TL dose-response (0.170-2.5 kGy) tested at doses in the 1-20 kGy range with promising results for applications in gamma-ray dosimetry. Results obtained in gamma irradiated MWG are compared with those obtained in graphite powder samples (GP) without microwave treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  20. Exfoliation and reassembly of cobalt oxide nanosheets into a reversible lithium-ion battery cathode.

    Science.gov (United States)

    Compton, Owen C; Abouimrane, Ali; An, Zhi; Palmeri, Marc J; Brinson, L Catherine; Amine, Khalil; Nguyen, SonBinh T

    2012-04-10

    An exfoliation-reassembly-activation (ERA) approach to lithium-ion battery cathode fabrication is introduced, demonstrating that inactive HCoO(2) powder can be converted into a reversible Li(1-x) H(x) CoO(2) thin-film cathode. This strategy circumvents the inherent difficulties often associated with the powder processing of the layered solids typically employed as cathode materials. The delamination of HCoO(2) via a combination of chemical and mechanical exfoliation generates a highly processable aqueous dispersion of [CoO(2) ](-) nanosheets that is critical to the ERA approach. Following vacuum-assisted self-assembly to yield a thin-film cathode and ion exchange to activate this material, the generated cathodes exhibit excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO(2) (~83 mAh g(-1) ), with this good electrochemical performance attributable to the high degree of order in the reassembled cathode. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Characterizing edge and stacking structures of exfoliated graphene by photoelectron diffraction

    International Nuclear Information System (INIS)

    Matsui, Fumihiko; Ishii, Ryo; Matsuda, Hiroyuki; Morita, Makoto; Kitagawa, Satoshi; Koh, Shinji; Daimon, Hiroshi; Matsushita, Tomohiro

    2013-01-01

    The two-dimensional C 1s photoelectron intensity angular distributions (PIADs) and spectra of exfoliated graphene flakes and crystalline graphite were measured using a focused soft X-ray beam. Suitable graphene samples were selected by thickness characterization using Raman spectromicroscopy after transferring mechanically exfoliated graphene flakes onto a 90-nm-thick SiO 2 film. In every PIAD, a Kagomé interference pattern was observed, particularly clearly in the monolayer graphene PIAD. Its origin is the overlap of the diffraction rings formed by an in-plane C-C bond honeycomb lattice. Thus, the crystal orientation of each sample can be determined. In the case of bilayer graphene, PIAD was threefold-symmetric, while those of monolayer graphene and crystalline graphite were sixfold-symmetric. This is due to the stacking structure of bilayer graphene. From comparisons with the multiple scattering PIAD simulation results, the way of layer stacking as well as the termination types in the edge regions of bilayer graphene flakes were determined. Furthermore, two different C 1s core levels corresponding to the top and bottom layers of bilayer graphene were identified. A chemical shift to a higher binding energy by 0.25 eV for the bottom layer was attributed to interfacial interactions. (author)

  2. CVD growth of graphene under exfoliated hexagonal boron nitride for vertical hybrid structures

    International Nuclear Information System (INIS)

    Wang, Min; Jang, Sung Kyu; Song, Young Jae; Lee, Sungjoo

    2015-01-01

    Graphical abstract: We have demonstrated a novel yet simple method for fabricating graphene-based vertical hybrid structures by performing the CVD growth of graphene at an h-BN/Cu interface. Our systematic Raman measurements combined with plasma etching process indicate that a graphene film is grown under exfoliated h-BN rather than on its top surface, and that an h-BN/graphene vertical hybrid structure has been fabricated. Electrical transport measurements of this h-BN/graphene, transferred on SiO2, show the carrier mobility up to approximately 2250 cm 2 V −1 s −1 . The developed method would enable the exploration of the possibility of novel hybrid structure integration with two-dimensional material systems. - Abstract: We have demonstrated a novel yet simple method for fabricating graphene-based vertical hybrid structures by performing the CVD growth of graphene at an h-BN/Cu interface. Our systematic Raman measurements combined with plasma etching process indicate that a graphene film is grown under exfoliated h-BN rather than on its top surface, and that an h-BN/graphene vertical hybrid structure has been fabricated. Electrical transport measurements of this h-BN/graphene, transferred on SiO 2 , show the carrier mobility up to approximately 2250 cm 2 V −1 s −1 . The developed method would enable the exploration of the possibility of novel hybrid structure integration with two-dimensional material systems

  3. Homogeneously dispersed CeO2 nanoparticles on exfoliated hexaniobate nanosheets

    Science.gov (United States)

    Marques, Thalles M. F.; Strayer, Megan E.; Ghosh, Anupama; Silva, Alexandre; Ferreira, Odair P.; Fujisawa, Kazunori; Alves da Cunha, Jose R.; Abreu, Guilherme J. P.; Terrones, Mauricio; Mallouk, Thomas E.; Viana, Bartolomeu C.

    2017-12-01

    Hexaniobate nanosheets derived from the parent compound K4Nb6O17 have been decorated with CeO2 nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO2 nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO2 nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO2 nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO2 nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA+ and K+ by Ce4+. Cerium ion exchange on the acid exchanged parent compound, H2.9K1.1Nb6O17, revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce4+/Ce3+ is around 4.4, in agreement with the formation of fluorite structure (CeO2). Thus, these CeO2 nanoparticle/nanosheet composites may be useful for catalytic processes.

  4. Non-isothermal cure and exfoliation of tri-functional epoxy-clay nanocomposites

    Directory of Open Access Journals (Sweden)

    F. Shiravand

    2015-08-01

    Full Text Available The non-isothermal cure kinetics of polymer silicate layered nanocomposites based on a tri-functional epoxy resin has been investigated by differential scanning calorimetry. From an analysis of the kinetics as a function of the clay content, it can be concluded that the non-isothermal cure reaction can be considered to consist of four different processes: the reaction of epoxy groups with the diamine curing agent; an intra-gallery homopolymerisation reaction which occurs concurrently with the epoxy-amine reaction; and two extra-gallery homopolymerisation reactions, catalysed by the onium ion of the organically modified clay and by the tertiary amines resulting from the epoxy-amine reaction. The final nanostructure displays a similar quality of exfoliation as that observed for the isothermal cure of the same nanocomposite system. This implies that the intra-gallery reaction, which is responsible for the exfoliation, is not significantly inhibited by the extra-gallery epoxy-amine cross-linking reaction.

  5. Raman spectral signatures of cervical exfoliated cells from liquid-based cytology samples

    Science.gov (United States)

    Kearney, Padraig; Traynor, Damien; Bonnier, Franck; Lyng, Fiona M.; O'Leary, John J.; Martin, Cara M.

    2017-10-01

    It is widely accepted that cervical screening has significantly reduced the incidence of cervical cancer worldwide. The primary screening test for cervical cancer is the Papanicolaou (Pap) test, which has extremely variable specificity and sensitivity. There is an unmet clinical need for methods to aid clinicians in the early detection of cervical precancer. Raman spectroscopy is a label-free objective method that can provide a biochemical fingerprint of a given sample. Compared with studies on infrared spectroscopy, relatively few Raman spectroscopy studies have been carried out to date on cervical cytology. The aim of this study was to define the Raman spectral signatures of cervical exfoliated cells present in liquid-based cytology Pap test specimens and to compare the signature of high-grade dysplastic cells to each of the normal cell types. Raman spectra were recorded from single exfoliated cells and subjected to multivariate statistical analysis. The study demonstrated that Raman spectroscopy can identify biochemical signatures associated with the most common cell types seen in liquid-based cytology samples; superficial, intermediate, and parabasal cells. In addition, biochemical changes associated with high-grade dysplasia could be identified suggesting that Raman spectroscopy could be used to aid current cervical screening tests.

  6. Pioneers of exfoliative cytology in the 19th century: the predecessors of George Papanicolaou.

    Science.gov (United States)

    Diamantis, A; Magiorkinis, E

    2014-08-01

    The purpose of our study was to summarize the knowledge on exfoliative cytology during the 19th century and to track down Papanicolaou's predecessors. A thorough study of texts, medical books and reports, together with a review of the available literature in PubMed, was undertaken. The study of cytological preparations as a diagnostic procedure can be traced back to the work of the famous French microscopist Alfred François Donné. However, the systematic study and the criteria for the diagnosis of malignant cells should be attributed to Johannes Müller. The increasing interest in the cytological examination of various fluids of the human body can be confirmed by a plethora of studies published during this period. By the end of the 19th century, the invention of new techniques in pathology, such as the introduction of cell block techniques, tissue sections and new staining methods which provided the opportunity to study surgical specimens in three dimensions, led to a decrease in the interest in exfoliative cytology, which was re-discovered by George Papanicolaou almost three decades later. © 2013 John Wiley & Sons Ltd.

  7. In vivo exfoliating efficacy of biodegradable beads and the correlation with user's satisfaction.

    Science.gov (United States)

    Kitsongsermthon, J; Kreepoke, J; Duangweang, K; Tansirikongkol, A

    2018-02-01

    By the end of 2017, non-biodegradable microbeads will be prohibited in USA, UK and Europe, due to their environmental issue. There are biodegradable beads available, but their effect on skin desquamation has not been evaluated yet. This study aimed to understand the skin renewal time, moisturizing effect and user's satisfaction of gel scrubs containing different exfoliating beads. Gel scrubs, containing polyethylene, mannan or wax beads, were used in this study. The stratum corneum turnover time (SCTT) and skin hydration were evaluated by dansyl chloride staining technique and Corneometer ® , respectively. The self-assessment was also performed after a 3-week home use trial. The SCTTs of three different gel scrubs were not significantly different. A numerical increase in the skin hydration level was found in all groups. Satisfaction scores for the appearance and usability attributes were similar, but scores for improvement in the skin hydration and skin smoothness were higher in the gel scrubs with mannan or wax beads. All three gel scrubs provided a similar effect on the SCTT and skin hydration, but gel scrubs with mannan or wax beads were more favorable. Thus, these two biodegradable exfoliating beads may be good substitutes in scrubbing products. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Blistering and exfoliation of 304 stainless steel studied by SEM and RBS

    International Nuclear Information System (INIS)

    Braun, M.; Emmoth, B.; Whitton, J.L.

    1981-01-01

    Blistering and exfoliation induced by helium irradiation have been studied in polycrystalline stainless steel with the aim of measuring flake or blister skin thicknesses for different implantation energies in the keV region. The authors present measurements of skin thicknesses determined both by direct SEM observations and RBS techniques. The results of the RBS studies show for all implantation energies used that the thickness measured in target atoms/unit area of a flake equals the calculated implantation range with an accuracy of about 10%. Conversely, the SEM measurements show that swelling gives rise to a geometrical skin thickness much greater than the corresponding implantation range. Thus from the SEM and RBS data swelling as a function of the implantation energy is obtained and the linear relative swelling is shown to be strongly dependent on the energy. In addition a comparison between the skin thickness of blisters and flakes has been made for the same material. Blisters were observed at low implantation temperatures and room temperature while exfoliation occurs at elevated temperatures. The result of this comparison is that within the experimental accuracy the flake and blister thicknesses are the same. (Auth.)

  9. Phonon and thermal properties of exfoliated TaSe{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Z.; Jiang, C.; Renteria, J. [Nano-Device Laboratory, Department of Electrical Engineering, Bourns College of Engineering, University of California–Riverside, Riverside, California 92521 (United States); Pope, T. R.; Tsang, C. F.; Stickney, J. L.; Salguero, T. T., E-mail: salguero@uga.edu, E-mail: balandin@ee.ucr.edu [Department of Chemistry, University of Georgia, Athens, Georgia 30602 (United States); Goli, P. [Materials Science and Engineering Program, Bourns College of Engineering, University of California–Riverside, Riverside, California 92521 (United States); Balandin, A. A., E-mail: salguero@uga.edu, E-mail: balandin@ee.ucr.edu [Nano-Device Laboratory, Department of Electrical Engineering, Bourns College of Engineering, University of California–Riverside, Riverside, California 92521 (United States); Materials Science and Engineering Program, Bourns College of Engineering, University of California–Riverside, Riverside, California 92521 (United States)

    2013-11-28

    We report on the phonon and thermal properties of thin films of tantalum diselenide (2H-TaSe{sub 2}) obtained via the “graphene-like” mechanical exfoliation of crystals grown by chemical vapor transport. The ratio of the intensities of the Raman peak from the Si substrate and the E{sub 2g} peak of TaSe{sub 2} presents a convenient metric for quantifying film thickness. The temperature coefficients for two main Raman peaks, A{sub 1g} and E{sub 2g}, are −0.013 and −0.0097 cm{sup −1}/{sup o}C, respectively. The Raman optothermal measurements indicate that the room temperature thermal conductivity in these films decreases from its bulk value of ∼16 W/mK to ∼9 W/mK in 45-nm thick films. The measurement of electrical resistivity of the field-effect devices with TaSe{sub 2} channels shows that heat conduction is dominated by acoustic phonons in these van der Waals films. The scaling of thermal conductivity with the film thickness suggests that the phonon scattering from the film boundaries is substantial despite the sharp interfaces of the mechanically cleaved samples. These results are important for understanding the thermal properties of thin films exfoliated from TaSe{sub 2} and other metal dichalcogenides, as well as for evaluating self-heating effects in devices made from such materials.

  10. Phonon and thermal properties of exfoliated TaSe2 thin films

    International Nuclear Information System (INIS)

    Yan, Z.; Jiang, C.; Renteria, J.; Pope, T. R.; Tsang, C. F.; Stickney, J. L.; Salguero, T. T.; Goli, P.; Balandin, A. A.

    2013-01-01

    We report on the phonon and thermal properties of thin films of tantalum diselenide (2H-TaSe 2 ) obtained via the “graphene-like” mechanical exfoliation of crystals grown by chemical vapor transport. The ratio of the intensities of the Raman peak from the Si substrate and the E 2g peak of TaSe 2 presents a convenient metric for quantifying film thickness. The temperature coefficients for two main Raman peaks, A 1g and E 2g , are −0.013 and −0.0097 cm −1 / o C, respectively. The Raman optothermal measurements indicate that the room temperature thermal conductivity in these films decreases from its bulk value of ∼16 W/mK to ∼9 W/mK in 45-nm thick films. The measurement of electrical resistivity of the field-effect devices with TaSe 2 channels shows that heat conduction is dominated by acoustic phonons in these van der Waals films. The scaling of thermal conductivity with the film thickness suggests that the phonon scattering from the film boundaries is substantial despite the sharp interfaces of the mechanically cleaved samples. These results are important for understanding the thermal properties of thin films exfoliated from TaSe 2 and other metal dichalcogenides, as well as for evaluating self-heating effects in devices made from such materials

  11. Phonon and thermal properties of exfoliated TaSe2 thin films

    Science.gov (United States)

    Yan, Z.; Jiang, C.; Pope, T. R.; Tsang, C. F.; Stickney, J. L.; Goli, P.; Renteria, J.; Salguero, T. T.; Balandin, A. A.

    2013-11-01

    We report on the phonon and thermal properties of thin films of tantalum diselenide (2H-TaSe2) obtained via the "graphene-like" mechanical exfoliation of crystals grown by chemical vapor transport. The ratio of the intensities of the Raman peak from the Si substrate and the E2g peak of TaSe2 presents a convenient metric for quantifying film thickness. The temperature coefficients for two main Raman peaks, A1g and E2g, are -0.013 and -0.0097 cm-1/oC, respectively. The Raman optothermal measurements indicate that the room temperature thermal conductivity in these films decreases from its bulk value of ˜16 W/mK to ˜9 W/mK in 45-nm thick films. The measurement of electrical resistivity of the field-effect devices with TaSe2 channels shows that heat conduction is dominated by acoustic phonons in these van der Waals films. The scaling of thermal conductivity with the film thickness suggests that the phonon scattering from the film boundaries is substantial despite the sharp interfaces of the mechanically cleaved samples. These results are important for understanding the thermal properties of thin films exfoliated from TaSe2 and other metal dichalcogenides, as well as for evaluating self-heating effects in devices made from such materials.

  12. Exfoliation approach for preparing high conductive reduced graphite oxide and its application in natural rubber composites

    Energy Technology Data Exchange (ETDEWEB)

    Wipatkrut, Pattharaporn [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Poompradub, Sirilux, E-mail: sirilux.p@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemical and Advanced Material, Chulalongkorn University, Bangkok 10330 (Thailand)

    2017-04-15

    Highlights: • Graphite waste was exfoliated by oxidation and chemical and thermal reduction. • The obtained graphene-T was a single layer sheet with a high electrical conductivity. • Graphene-T incorporation at 5 phr improved the electrical conductivity of NR. • Graphene-T incorporation at 5–25 phr improved the mechanical properties of NR. - Abstract: High conductivity reduced graphite oxide (RGO) was prepared by exfoliation of graphite waste from the metal smelting industry. To improve the surface properties of the RGO, the graphite oxide obtained based on Hummers’ method was reduced by L-ascorbic acid to give RGOV, which was then subjected to thermal reduction to obtain RGOT. The residual oxygen-containing groups in RGOV were almost completely removed by the thermal reduction and the conjugated graphene networks were restored in RGOT. The effect of the RGOT content in natural rubber (NR) on the cure, electrical and mechanical properties of the NR-RGOT (NG) composites was evaluated. The electrical conductivity of NR was increased by the inclusion of RGOT at a percolation threshold of 5 phr, with an electrical conductivity of 8.71 × 10{sup −6} S/m. The mechanical properties, i.e., the modulus, tensile strength and hardness, of NG were comparable with those of conductive carbon black filled NR ones.

  13. Assessing the polycyclic aromatic hydrocarbon anisotropic potential with application to the exfoliation energy of graphite.

    Science.gov (United States)

    Totton, Tim S; Misquitta, Alston J; Kraft, Markus

    2011-11-24

    In this work we assess a recently published anisotropic potential for polycyclic aromatic hydrocarbon (PAH) molecules (J. Chem. Theory Comput. 2010, 6, 683-695). Comparison to recent high-level symmetry-adapted perturbation theory based on density functional theory (SAPT(DFT)) results for coronene (C(24)H(12)) demonstrate the transferability of the potential while highlighting some limitations with simple point charge descriptions of the electrostatic interaction. The potential is also shown to reproduce second virial coefficients of benzene (C(6)H(6)) with high accuracy, and this is enhanced by using a distributed multipole model for the electrostatic interaction. The graphene dimer interaction energy and the exfoliation energy of graphite have been estimated by extrapolation of PAH interaction energies. The contribution of nonlocal fluctuations in the π electron density in graphite have also been estimated which increases the exfoliation energy by 3.0 meV atom(-1) to 47.6 meV atom(-1), which compares well to recent theoretical and experimental results.

  14. Controllable Edge Oxidation and Bubbling Exfoliation Enable the Fabrication of High Quality Water Dispersible Graphene.

    Science.gov (United States)

    Tian, Suyun; Sun, Jing; Yang, Siwei; He, Peng; Wang, Gang; Di, Zengfeng; Ding, Guqiao; Xie, Xiaoming; Jiang, Mianheng

    2016-09-26

    Despite significant progresses made on mass production of chemically exfoliated graphene, the quality, cost and environmental friendliness remain major challenges for its market penetration. Here, we present a fast and green exfoliation strategy for large scale production of high quality water dispersible few layer graphene through a controllable edge oxidation and localized gas bubbling process. Mild edge oxidation guarantees that the pristine sp 2 lattice is largely intact and the edges are functionalized with hydrophilic groups, giving rise to high conductivity and good water dispersibility at the same time. The aqueous concentration can be as high as 5.0 mg mL -1 , which is an order of magnitude higher than previously reports. The water soluble graphene can be directly spray-coated on various substrates, and the back-gated field effect transistor give hole and electron mobility of ~496 and ~676 cm 2 V -1 s -1 , respectively. These results achieved are expected to expedite various applications of graphene.

  15. Morphological and electrical properties of epoxy-based composites reinforced with exfoliated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Lamberti, Patrizia; Spinelli, Giovanni, E-mail: gspinelli@unisa.it; Tucci, Vincenzo [Department of Information and Electrical Engineering and Applied Mathematics University of Salerno, Via Giovanni Paolo II, Fisciano (Italy); Guadagno, Liberata; Raimondo, Marialuigia; Vertuccio, Luigi [Department of Industrial Engineering University of Salerno, Via Giovanni Paolo II, Fisciano (Italy)

    2016-05-18

    An experimental study has been carried out to prepare and characterize epoxy/amine-based composites filled with different percentages of partially exfoliated graphite (i.e. pEG) particles having an exfoliation degree of 56% in order to analyze the effect of the filler amounts on the electrical properties of the resulting nanocomposites. Moreover, in order to fully investigate the direct relationship between the physical properties of the employed filler and the results of the electrical characterization, a structural and morphological characterization of the pEG samples is carried out by means of various type of analysis such as X-ray diffraction patterns, micro-Raman and Scanning Electron Microscopy (SEM) images. The DC electrical characterization reveals a percolation thresholds (EPT) that falls in the range [2–3] wt% and an electrical conductivity of about 0.66 S/m at the highest filler loading (6.5 wt%). From the analysis of the percolative curve it is possible to derive the percolation law parameters and in particular the critical exponent t, whose value (i.e. 1.2) reflects an effective 2D organization of the percolating structure consistent with the type of filler used (2-dimensional). Finally, an extensive analysis concerning the electrical properties in the frequency domain has been carried out in order to evaluate the effectiveness of pEG-loaded composites in terms of electromagnetic interference compatibility (EMC) and their applicability as radar absorbers materials (RAMs).

  16. Controllable Edge Oxidation and Bubbling Exfoliation Enable the Fabrication of High Quality Water Dispersible Graphene

    Science.gov (United States)

    Tian, Suyun; Sun, Jing; Yang, Siwei; He, Peng; Wang, Gang; di, Zengfeng; Ding, Guqiao; Xie, Xiaoming; Jiang, Mianheng

    2016-09-01

    Despite significant progresses made on mass production of chemically exfoliated graphene, the quality, cost and environmental friendliness remain major challenges for its market penetration. Here, we present a fast and green exfoliation strategy for large scale production of high quality water dispersible few layer graphene through a controllable edge oxidation and localized gas bubbling process. Mild edge oxidation guarantees that the pristine sp2 lattice is largely intact and the edges are functionalized with hydrophilic groups, giving rise to high conductivity and good water dispersibility at the same time. The aqueous concentration can be as high as 5.0 mg mL-1, which is an order of magnitude higher than previously reports. The water soluble graphene can be directly spray-coated on various substrates, and the back-gated field effect transistor give hole and electron mobility of ~496 and ~676 cm2 V-1 s-1, respectively. These results achieved are expected to expedite various applications of graphene.

  17. Direct synthesis of hydrophobic graphene-based nanosheets via chemical modification of exfoliated graphene oxide.

    Science.gov (United States)

    Wang, Jigang; Wang, Yongsheng; He, Dawei; Liu, Zhiyong; Wu, Hongpeng; Wang, Haiteng; Zhao, Yu; Zhang, Hui; Yang, Bingyang; Xu, Haiteng; Fu, Ming

    2012-08-01

    Hydrophobic graphene-based material at the nanoscale was prepared by treatment of exfoliated graphene oxide with organic isocyanates. The lipophilic modified graphene oxide (LMGO) can then be exfoliated into the functionalized graphene nanoplatelets that can form a stable dispersion in polar aprotic solvents. AFM image shows the thickness of LMGO is approximately 1 nm. Characterization of LMGO by elemental analysis suggested that the chemical treatment results in the functionalization of the carboxyl and hydroxyl groups in GO via formation of amides and carbamate esters, respectively. The degree of GO functionalization can be controlled via either the reactivity of the isocyanate or the reaction time. Then we investigated the thermal properties of the SPFGraphene by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the TGA curve shows a greater weight loss of approximately 20% occurred indicating removal of functional groups from the LMGO sheets and an obvious exothermic peak at 176 degrees can be observed from 150 to 250 degrees. We also compared the structure of graphene oxide with the structure of chemical treated graphene oxide by FT-IR spectroscopy. The morphology and microstructure of the LMGO nanosheets were also characterized by SEM and XRD. Graphene can be used to fabricate a wide range of simple electronic devices such as field-effect transistors, resonators, quantum dots and some other extensive industrial manufacture such as super capacitor, li ion battery, solar cells and even transparent electrodes in device applications.

  18. Single-layered graphene oxide nanosheet/polyaniline hybrids fabricated through direct molecular exfoliation.

    Science.gov (United States)

    Chen, Guan-Liang; Shau, Shi-Min; Juang, Tzong-Yuan; Lee, Rong-Ho; Chen, Chih-Ping; Suen, Shing-Yi; Jeng, Ru-Jong

    2011-12-06

    In this study, we used direct molecular exfoliation for the rapid, facile, large-scale fabrication of single-layered graphene oxide nanosheets (GOSs). Using macromolecular polyaniline (PANI) as a layered space enlarger, we readily and rapidly synthesized individual GOSs at room temperature through the in situ polymerization of aniline on the 2D GOS platform. The chemically modified GOS platelets formed unique 2D-layered GOS/PANI hybrids, with the PANI nanorods embedded between the GO interlayers and extended over the GO surface. X-ray diffraction revealed that intergallery expansion occurred in the GO basal spacing after the PANI nanorods had anchored and grown onto the surface of the GO layer. Transparent folding GOSs were, therefore, observed in transmission electron microscopy images. GOS/PANI nanohybrids possessing high conductivities and large work functions have the potential for application as electrode materials in optoelectronic devices. Our dispersion/exfoliation methodology is a facile means of preparing individual GOS platelets with high throughput, potentially expanding the applicability of nanographene oxide materials. © 2011 American Chemical Society

  19. Abnormal Multiple Charge Memory States in Exfoliated Few-Layer WSe2 Transistors.

    Science.gov (United States)

    Chen, Mikai; Wang, Yifan; Shepherd, Nathan; Huard, Chad; Zhou, Jiantao; Guo, L J; Lu, Wei; Liang, Xiaogan

    2017-01-24

    To construct reliable nanoelectronic devices based on emerging 2D layered semiconductors, we need to understand the charge-trapping processes in such devices. Additionally, the identified charge-trapping schemes in such layered materials could be further exploited to make multibit (or highly desirable analog-tunable) memory devices. Here, we present a study on the abnormal charge-trapping or memory characteristics of few-layer WSe 2 transistors. This work shows that multiple charge-trapping states with large extrema spacing, long retention time, and analog tunability can be excited in the transistors made from mechanically exfoliated few-layer WSe 2 flakes, whereas they cannot be generated in widely studied few-layer MoS 2 transistors. Such charge-trapping characteristics of WSe 2 transistors are attributed to the exfoliation-induced interlayer deformation on the cleaved surfaces of few-layer WSe 2 flakes, which can spontaneously form ambipolar charge-trapping sites. Our additional results from surface characterization, charge-retention characterization at different temperatures, and density functional theory computation strongly support this explanation. Furthermore, our research also demonstrates that the charge-trapping states excited in multiple transistors can be calibrated into consistent multibit data storage levels. This work advances the understanding of the charge memory mechanisms in layered semiconductors, and the observed charge-trapping states could be further studied for enabling ultralow-cost multibit analog memory devices.

  20. An investigation into graphene exfoliation and potential graphene application in MEMS devices

    Science.gov (United States)

    Fercana, George; Kletetschka, Gunther; Mikula, Vilem; Li, Mary

    2011-02-01

    The design of microelectromecanical systems (MEMS) and micro-opto-electromechanical systems (MOEMS) are often materials-limited with respect to the efficiency and capability of the material. Graphene, a one atom thick honeycomb lattice of carbon, is a highly desired material for MEMS applications. Relevant properties of graphene include the material's optical transparency, mechanical strength, energy efficiency, and electrical and thermal conductivity due to its electron mobility. Aforementioned properties make graphene a strong candidate to supplant existing transparent electrode technology and replace the conventionally used material, indium-tin oxide. In this paper we present preliminary results on work toward integration of graphene with MEMS structures. We are studying mechanical exfoliation of highly ordered pyrolytic graphite (HOPG) crystals by repeatedly applying and separating adhesive materials from the HOPG surface. The resulting graphene sheets are then transferred to silicon oxide substrate using the previously applied adhesive material. We explored different adhesive options, particularly the use of Kapton tape, to improve the yield of graphene isolation along with chemical cross-linking agents which operate on a mechanism of photoinsertion of disassociated nitrene groups. These perfluorophenyl nitrenes participate in C=C addition reactions with graphene monolayers creating a covalent binding between the substrate and graphene. We are focusing on maximizing the size of isolated graphene sheets and comparing to conventional exfoliation. Preliminary results allow isolation of few layer graphene (FLG) sheets (ntechnology to be used in future deep space telescopes.

  1. Congenital adrenal hyperplasia: a case report with premature teeth exfoliation and bone resorption.

    Science.gov (United States)

    Angelopoulou, Matina V; Kontogiorgos, Elias; Emmanouil, Dimitris

    2015-06-01

    Congenital adrenal hyperplasia (CAH) is an inherited autosomal recessive disorder characterized by insufficient production of cortisol. The aim of this case report was to present a child with CAH, premature exfoliation of primary teeth and accelerated eruption of his permanent teeth related to bone resorption. A 4.5-year-old Caucasian boy with CAH and long-term administration of glucocorticoids was referred for dental restoration. Clinical examination revealed primary molars with worn stainless steel crowns, severe attrition of the upper canines, and absence of the upper incisors. Before the completion of treatment, abnormal mobility of the first upper primary molars and the lower incisors was detected, and a few days later the teeth exfoliated prematurely. Histologic examination revealed normal tooth structure. Alkaline phosphatase and blood cells values were normal. Eruption of the permanent dentition was also accelerated. Tooth mobility was noticed in the permanent teeth as soon as they erupted, along with bone destruction. Examination revealed an elevated level of receptor activator of nuclear factor-κB ligand and lower-than-normal osteoprotegerin and vitamin D levels. The patient was treated with vitamin D supplements, and his teeth have been stable ever since. CAH is a serious chronic disorder appearing in children with accelerated dental development and possibly premature loss of primary teeth. Copyright © 2015 by the American Academy of Pediatrics.

  2. Single toxin dose-response models revisited

    Energy Technology Data Exchange (ETDEWEB)

    Demidenko, Eugene, E-mail: eugened@dartmouth.edu [Department of Biomedical Data Science, Geisel School of Medicine at Dartmouth, Hanover, NH03756 (United States); Glaholt, SP, E-mail: sglaholt@indiana.edu [Indiana University, School of Public & Environmental Affairs, Bloomington, IN47405 (United States); Department of Biological Sciences, Dartmouth College, Hanover, NH03755 (United States); Kyker-Snowman, E, E-mail: ek2002@wildcats.unh.edu [Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH03824 (United States); Shaw, JR, E-mail: joeshaw@indiana.edu [Indiana University, School of Public & Environmental Affairs, Bloomington, IN47405 (United States); Chen, CY, E-mail: Celia.Y.Chen@dartmouth.edu [Department of Biological Sciences, Dartmouth College, Hanover, NH03755 (United States)

    2017-01-01

    The goal of this paper is to offer a rigorous analysis of the sigmoid shape single toxin dose-response relationship. The toxin efficacy function is introduced and four special points, including maximum toxin efficacy and inflection points, on the dose-response curve are defined. The special points define three phases of the toxin effect on mortality: (1) toxin concentrations smaller than the first inflection point or (2) larger then the second inflection point imply low mortality rate, and (3) concentrations between the first and the second inflection points imply high mortality rate. Probabilistic interpretation and mathematical analysis for each of the four models, Hill, logit, probit, and Weibull is provided. Two general model extensions are introduced: (1) the multi-target hit model that accounts for the existence of several vital receptors affected by the toxin, and (2) model with a nonzero mortality at zero concentration to account for natural mortality. Special attention is given to statistical estimation in the framework of the generalized linear model with the binomial dependent variable as the mortality count in each experiment, contrary to the widespread nonlinear regression treating the mortality rate as continuous variable. The models are illustrated using standard EPA Daphnia acute (48 h) toxicity tests with mortality as a function of NiCl or CuSO{sub 4} toxin. - Highlights: • The paper offers a rigorous study of a sigmoid dose-response relationship. • The concentration with highest mortality rate is rigorously defined. • A table with four special points for five morality curves is presented. • Two new sigmoid dose-response models have been introduced. • The generalized linear model is advocated for estimation of sigmoid dose-response relationship.

  3. Contagem de Staphylococcus sp. e detecção de enterotoxinas estafilocócicas e toxina da síndrome do choque tóxico em amostras de leite cru refrigerado Staphylococcus sp. counting and detection of staphylococcal enterotoxins and toxic shock toxin syndrome from cooled raw milk

    Directory of Open Access Journals (Sweden)

    H.C. Lamaita

    2005-10-01

    Full Text Available Analisaram-se 80 amostras de leite cru refrigerado a 4°C e estocado por 48 horas em tanques refrigeradores de propriedades rurais do estado de Minas Gerais quanto à contagem e identificação de Staphylococcus sp. e detecção de enterotoxinas estafilocócicas (SE e da toxina da síndrome do choque tóxico (TSST-1. Staphylococcus sp. foi detectado em 100% das amostras de leite de tanque refrigerador em contagens que variaram de 1,0 × 10(5 a 2,5 × 10(7 UFC/ml (média = 5,60 log UFC/ml; s = 0,53 e CV = 9,5%. Isolaram-se e identificaram-se 436 estirpes como: S. aureus, S hyicus, S. epidermidis, S. intermedius, S. cohnii, S. sciuri, S. schleirferi e S. delphini. As estirpes de mesmo perfil bioquímico, oriundas da mesma amostra, foram agrupadas (pools e induzidas a produzir SE e TSST-1. A detecção dessas enterotoxinas foi feita pelo método optimum sensitivity plate, usando-se técnica de celofane sobre ágar. Identificou-se a produção de SEA, SEB, SEC, SED e de TSST-1 em percentuais variados. Dos 138 pools preparados, 91 produziram, pelo menos, uma toxina isoladamente ou em associação a outras toxinas. Dos pools enterotoxigênicos, 24,6% eram coagulase positiva e 41,3%, coagulase negativa. A confirmação de estirpes enterotoxigênicas de Staphylococcus coagulase negativa isoladas de amostras de leite é importante em relação à saúde pública.In order to count and identify Staphylococcus sp., the detection of the Staphylococcal enterotoxins (SE and toxic shock toxin syndrome (TSST-1, 80 raw milk samples cooled at 4°C and stored in bulk tanks for 48 hours in different farms from Minas Gerais State were analyzed. Staphylococcus sp. was observed in all samples and the counts varied from 1.0 × 10(5 to 2.5 × 10(7 CFU/ml (mean = 5.60 log CFU/ml; sd = 0.53 and CV = 9.46 %. A total of 436 strains of Staphylococcus were isolated and identified as S. aureus, S hyicus, S. epidermidis, S. intermedius, S. cohnii, S. sciuri, S. schleirferi and S

  4. Botulinum Toxin in Management of Limb Tremor

    Directory of Open Access Journals (Sweden)

    Elina Zakin

    2017-11-01

    Full Text Available Essential tremor is characterized by persistent, usually bilateral and symmetric, postural or kinetic activation of agonist and antagonist muscles involving either the distal or proximal upper extremity. Quality of life is often affected and one’s ability to perform daily tasks becomes impaired. Oral therapies, including propranolol and primidone, can be effective in the management of essential tremor, although adverse effects can limit their use and about 50% of individuals lack response to oral pharmacotherapy. Locally administered botulinum toxin injection has become increasingly useful in the management of essential tremor. Targeting of select muscles with botulinum toxin is an area of active research, and muscle selection has important implications for toxin dosing and functional outcomes. The use of anatomical landmarks with palpation, EMG guidance, electrical stimulation, and ultrasound has been studied as a technique for muscle localization in toxin injection. Earlier studies implemented a standard protocol for the injection of (predominantly wrist flexors and extensors using palpation and EMG guidance. Targeting of muscles by selection of specific activators of tremor (tailored to each patient using kinematic analysis might allow for improvement in efficacy, including functional outcomes. It is this individualized muscle selection and toxin dosing (requiring injection within various sites of a single muscle that has allowed for success in the management of tremors.

  5. Crystal structure of Clostridium difficile toxin A

    Energy Technology Data Exchange (ETDEWEB)

    Chumbler, Nicole M.; Rutherford, Stacey A.; Zhang, Zhifen; Farrow, Melissa A.; Lisher, John P.; Farquhar, Erik; Giedroc, David P.; Spiller, Benjamin W.; Melnyk, Roman A.; Lacy, D. Borden

    2016-01-11

    Clostridium difficile infection is the leading cause of hospital-acquired diarrhoea and pseudomembranous colitis. Disease is mediated by the actions of two toxins, TcdA and TcdB, which cause the diarrhoea, as well as inflammation and necrosis within the colon. The toxins are large (308 and 270 kDa, respectively), homologous (47% amino acid identity) glucosyltransferases that target small GTPases within the host. The multidomain toxins enter cells by receptor-mediated endocytosis and, upon exposure to the low pH of the endosome, insert into and deliver two enzymatic domains across the membrane. Eukaryotic inositol-hexakisphosphate (InsP6) binds an autoprocessing domain to activate a proteolysis event that releases the N-terminal glucosyltransferase domain into the cytosol. Here, we report the crystal structure of a 1,832-amino-acid fragment of TcdA (TcdA1832), which reveals a requirement for zinc in the mechanism of toxin autoprocessing and an extended delivery domain that serves as a scaffold for the hydrophobic α-helices involved in pH-dependent pore formation. A surface loop of the delivery domain whose sequence is strictly conserved among all large clostridial toxins is shown to be functionally important, and is highlighted for future efforts in the development of vaccines and novel therapeutics.

  6. Array biosensor for detection of toxins

    Science.gov (United States)

    Ligler, Frances S.; Taitt, Chris Rowe; Shriver-Lake, Lisa C.; Sapsford, Kim E.; Shubin, Yura; Golden, Joel P.

    2003-01-01

    The array biosensor is capable of detecting multiple targets rapidly and simultaneously on the surface of a single waveguide. Sandwich and competitive fluoroimmunoassays have been developed to detect high and low molecular weight toxins, respectively, in complex samples. Recognition molecules (usually antibodies) were first immobilized in specific locations on the waveguide and the resultant patterned array was used to interrogate up to 12 different samples for the presence of multiple different analytes. Upon binding of a fluorescent analyte or fluorescent immunocomplex, the pattern of fluorescent spots was detected using a CCD camera. Automated image analysis was used to determine a mean fluorescence value for each assay spot and to subtract the local background signal. The location of the spot and its mean fluorescence value were used to determine the toxin identity and concentration. Toxins were measured in clinical fluids, environmental samples and foods, with minimal sample preparation. Results are shown for rapid analyses of staphylococcal enterotoxin B, ricin, cholera toxin, botulinum toxoids, trinitrotoluene, and the mycotoxin fumonisin. Toxins were detected at levels as low as 0.5 ng mL(-1).

  7. Behaviour of the surface hydroxide groups of exfoliated kaolinite in the gas phase and during water adsorption.

    Science.gov (United States)

    Táborosi, Attila; Szilágyi, Róbert K

    2016-02-14

    The chemical and physical properties, and thus the reactivity of phylloaluminosilicates can be tailored by intercalation, delamination, and exfoliation processes. In going from the periodic crystalline to the molecular exfoliated phase, surface defects and modifications gain importance as each face of the phylloaluminosilicate comes in direct contact with the external chemical environment. In this work, we extend our earlier studies on the molecular cluster modelling of exfoliated kaolinite sheets by evaluating the positions and orientations of surface hydroxide groups and bridging oxide anions, as the sites of reactivity. The previous focus on the inner chemical environment of a single kaolinite layer is shifted to the surface exposed octahedral aluminium-hydroxide and tetrahedral silicon-oxide sheets. The combination of semi-empirical, ab initio wave function, and density functional calculations unanimously support the amphoteric nature of the surface hydroxide groups with respect to H-bonding donor/acceptor capabilities. To a lesser extent, we observe the same for the bridging oxide anions. This is in contrast to the crystalline phase, which manifests only donor orientation for maintaining an inter-layer H-bond network. These results suggest that both electrophilic and nucleophilic characteristics of the octahedral and tetrahedral sheets need to be considered during intercalation and concomitant exfoliation of the kaolinite sheets.

  8. Speciation of arsenic in exfoliated urinary bladder epithelial cells from individuals exposed to arsenic in drinking water

    Czech Academy of Sciences Publication Activity Database

    Hernández-Zavala, A.; Valenzuela, O.L.; Matoušek, Tomáš; Drobná, Z.; Dědina, Jiří; Garcia-Vargas, G.G.; Thomas, D. J.; Del Razo, L.M.; Stýblo, M.

    2008-01-01

    Roč. 116, č. 12 (2008), s. 1656-1660 ISSN 0091-6765 R&D Projects: GA AV ČR IAA400310507 Institutional research plan: CEZ:AV0Z40310501 Keywords : arsenic species * drinking water * exfoliated human urinary bladder epithelial cells Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 6.123, year: 2008

  9. Interfacial-Bonding-Regulated CO Oxidation over Pt Atoms Immobilized on Gas-Exfoliated Hexagonal Boron Nitride

    KAUST Repository

    Liu, Xin; Zhu, Hongdan; Linguerri, Roberto; Han, Yu; Chambaud, Gilberte; Meng, Changgong

    2017-01-01

    We compared the electronic structure and CO oxidation mechanisms over Pt atoms immobilized by both B-vacancies and N-vacancies on gas-exfoliated hexagonal boron nitride. We showed that chemical bonds are formed between the B atoms associated

  10. Genetic association study of exfoliation syndrome identifies a protective rare variant at LOXL1 and five new susceptibility loci

    DEFF Research Database (Denmark)

    Aung, Tin; Ozaki, Mineo; Lee, Mei Chin

    2017-01-01

    Exfoliation syndrome (XFS) is the most common known risk factor for secondary glaucoma and a major cause of blindness worldwide. Variants in two genes, LOXL1 and CACNA1A, have previously been associated with XFS. To further elucidate the genetic basis of XFS, we collected a global sample of XFS c...

  11. Facile and Green Production of Impurity-Free Aqueous Solutions of WS2 Nanosheets by Direct Exfoliation in Water.

    Science.gov (United States)

    Pan, Long; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying

    2016-12-01

    To obtain 2D materials with large quantity, low cost, and little pollution, liquid-phase exfoliation of their bulk form in water is a particularly fascinating concept. However, the current strategies for water-borne exfoliation exclusively employ stabilizers, such as surfactants, polymers, or inorganic salts, to minimize the extremely high surface energy of these nanosheets and stabilize them by steric repulsion. It is worth noting, however, that the remaining impurities inevitably bring about adverse effects to the ultimate performances of 2D materials. Here, a facile and green route to large-scale production of impurity-free aqueous solutions of WS 2 nanosheets is reported by direct exfoliation in water. Crucial parameters such as initial concentration, sonication time, centrifugation speed, and centrifugation time are systematically evaluated to screen out an optimized condition for scaling up. Statistics based on morphological characterization prove that substantial fraction (66%) of the obtained WS 2 nanosheets are one to five layers. X-ray diffraction and Raman characterizations reveal a high quality with few, if any, structural distortions. The water-borne exfoliation route opens up new opportunities for easy, clean processing of WS 2 -based film devices that may shine in the fields of, e.g., energy storage and functional nanocomposites owing to their excellent electrochemical, mechanical, and thermal properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. In situ growth of capping-free magnetic iron oxide nanoparticles on liquid-phase exfoliated graphene

    NARCIS (Netherlands)

    Tsoufis, T.; Syrgiannis, Z.; Akhtar, N.; Prato, M.; Katsaros, F.; Sideratou, Z.; Kouloumpis, A.; Gournis, D.; Rudolf, P.

    2015-01-01

    We report a facile approach for the in situ synthesis of very small iron oxide nanoparticles on the surface of high-quality graphene sheets. Our synthetic strategy involved the direct, liquid-phase exfoliation of highly crystalline graphite (avoiding any oxidation treatment) and the subsequent

  13. Mechanism of Shiga Toxin Clustering on Membranes

    DEFF Research Database (Denmark)

    Pezeshkian, Weria; Gao, Haifei; Arumugam, Senthil

    2017-01-01

    between them. The precise mechanism by which this clustering occurs remains poorly defined. Here, we used vesicle and cell systems and computer simulations to show that line tension due to curvature, height, or compositional mismatch, and lipid or solvent depletion cannot drive the clustering of Shiga...... toxin molecules. By contrast, in coarse-grained computer simulations, a correlation was found between clustering and toxin nanoparticle-driven suppression of membrane fluctuations, and experimentally we observed that clustering required the toxin molecules to be tightly bound to the membrane surface...... molecules (several nanometers), and persist even beyond. This force is predicted to operate between manufactured nanoparticles providing they are sufficiently rigid and tightly bound to the plasma membrane, thereby suggesting a route for the targeting of nanoparticles to cells for biomedical applications....

  14. Update on botulinum toxin and dermal fillers.

    Science.gov (United States)

    Berbos, Zachary J; Lipham, William J

    2010-09-01

    The art and science of facial rejuvenation is an ever-evolving field of medicine, as evidenced by the continual development of new surgical and nonsurgical treatment modalities. Over the past 10 years, the use of botulinum toxin and dermal fillers for aesthetic purposes has risen sharply. Herein, we discuss properties of several commonly used injectable products and provide basic instruction for their use toward the goal of achieving facial rejuvenation. The demand for nonsurgical injection-based facial rejuvenation products has risen enormously in recent years. Used independently or concurrently, botulinum toxin and dermal filler agents offer an affordable, minimally invasive approach to facial rejuvenation. Botulinum toxin and dermal fillers can be used to diminish facial rhytides, restore facial volume, and sculpt facial contours, thereby achieving an aesthetically pleasing, youthful facial appearance.

  15. Marine toxins and their toxicological significance: An overview

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.

    , Hemolysins-1 and hemolysin-2, saxitoxin, neosaxitoxin, gonyautoxin, tetrodotoxin, ptychodiscus brevis toxin and theonellamide F. According to their mode of action, these toxins are classified into different categories such as cytotoxin, enterotoxin...

  16. Vth Pan American Symposium on Animal, Plant and Microbial Toxins

    National Research Council Canada - National Science Library

    Ownby, Charlotte

    1996-01-01

    .... Presentations on arthropod toxins included work on scorpion neurotoxins, K+ channel-blocking peptides, lice and wasp proteins, stinging insect venom allergens and Australian funnel-web spider toxins...

  17. Stabilization of antioxidant gallate in layered double hydroxide by exfoliation and reassembling reaction

    Science.gov (United States)

    Ansy, Kanakappan Mickel; Lee, Ji-Hee; Piao, Huiyan; Choi, Goeun; Choy, Jin-Ho

    2018-06-01

    As for the stabilization of chemically sensitive bioactive molecule in this study, gallic acid (GA) with antioxidant property was intercalated into interlayer space of layered double hydroxide (LDH), which was realized by exfoliation and reassembling reaction. At first, the pristine nitrate-type Zn2Al-LDH in solid state was synthesized via co-precipitation followed by the hydrothermal treatment at 80 °C for 6 h, and then exfoliated in formamide to form a colloidal solution of exfoliated LDH nanosheets, and finally reassembled in the presence of GA to prepare GA intercalated LDH (GA-LDH) desired, where the pH was adjusted to 8.0 in order to deprotonate GA to form gallate anion. According to the XRD analysis, GA-LDH showed well-developed (00l) diffraction peaks with a basal spacing of 1.15 nm, which was estimated to be larger than that of the pristine LDH (0.88 nm), indicating that gallate molecules were incorporated into LDH layers with perpendicular orientation. From the FT-IR spectra it was found that gallic acid was completely deprotonated into gallate, and stabilized in between LDH lattices via electrostatic interaction. The content of GA in GA-LDH was determined to be around 23 wt% by UV-vis spectroscopic study, which was also confirmed by HPLC analysis. According to the in-vitro release of GA out of GA-LDH in PBS solution (pH 7.4) at 4 °C, GA was sustainably released from GA-LDH nanohybrid up to 86% within 72 h. The antioxidant property of GA-LDH was almost the same with that of intact GA which was examined by DPPH. The photostability of GA-LDH under UV light irradiation was immensely enhanced compared to intact GA. It is, therefore, concluded that the present GA-LDH nanohybrid can be considered as an excellent antioxidant material with high chemical- and photo-stabilities, and controlled release property.

  18. Cellular Entry of Clostridium perfringens Iota-Toxin and Clostridium botulinum C2 Toxin

    Directory of Open Access Journals (Sweden)

    Masaya Takehara

    2017-08-01

    Full Text Available Clostridium perfringens iota-toxin and Clostridium botulinum C2 toxin are composed of two non-linked proteins, one being the enzymatic component and the other being the binding/translocation component. These latter components recognize specific receptors and oligomerize in plasma membrane lipid-rafts, mediating the uptake of the enzymatic component into the cytosol. Enzymatic components induce actin cytoskeleton disorganization through the ADP-ribosylation of actin and are responsible for cell rounding and death. This review focuses upon the recent advances in cellular internalization of clostridial binary toxins.

  19. Cellular Entry of Clostridium perfringens Iota-Toxin and Clostridium botulinum C2 Toxin.

    Science.gov (United States)

    Takehara, Masaya; Takagishi, Teruhisa; Seike, Soshi; Oda, Masataka; Sakaguchi, Yoshihiko; Hisatsune, Junzo; Ochi, Sadayuki; Kobayashi, Keiko; Nagahama, Masahiro

    2017-08-11

    Clostridium perfringens iota-toxin and Clostridium botulinum C2 toxin are composed of two non-linked proteins, one being the enzymatic component and the other being the binding/translocation component. These latter components recognize specific receptors and oligomerize in plasma membrane lipid-rafts, mediating the uptake of the enzymatic component into the cytosol. Enzymatic components induce actin cytoskeleton disorganization through the ADP-ribosylation of actin and are responsible for cell rounding and death. This review focuses upon the recent advances in cellular internalization of clostridial binary toxins.

  20. Therapeutic Approaches of Botulinum Toxin in Gynecology

    OpenAIRE

    Marius Alexandru Moga; Oana Gabriela Dimienescu; Andreea Bălan; Ioan Scârneciu; Barna Barabaș; Liana Pleș

    2018-01-01

    Botulinum toxins (BoNTs) are produced by several anaerobic species of the genus Clostridium and, although they were originally considered lethal toxins, today they find their usefulness in the treatment of a wide range of pathologies in various medical specialties. Botulinum neurotoxin has been identified in seven different isoforms (BoNT-A, BoNT-B, BoNT-C, BoNT-D, BoNT-E, BoNT-F, and BoNT-G). Neurotoxigenic Clostridia can produce more than 40 different BoNT subtypes and, recently, a new BoNT...

  1. Oleic acid-assisted exfoliated few layer graphene films as counter electrode in dye-sensitized solar cell

    International Nuclear Information System (INIS)

    Liu, Jincheng; Wang, Yinjie; Sun, Darren Delai

    2012-01-01

    Highlights: ► Few layer graphene was obtained by liquid exfoliation in oleic acid (OLA). ► The concentration of exfoliated few layer graphene is as high as 1.3 mg/mL. ► OLA-assisted graphite (OLA-G) film has high catalytic activity. ► A power conversion efficiency of 3.56% can be gained by DSSCs with the counter electrode of OLA-G film. - Abstract: We have demonstrated a facile sonication method to exfoliate graphite into few layer graphene with a high concentration of 1.3 mg/mL in oleic acid (OLA). The exfoliations of natural graphite in oleylamine (OA) and trioctylphosphine (TOP) are investigated as a comparison. The few layer graphene dispersion in OLA and the graphite nanoparticles in OA are confirmed by transmission electron microscopy (TEM) observation. The exfoliated graphene dispersion in OLA (OLA-G) and graphite dispersion in OA (OA-G) are fabricated into a film on the FTO substrate by the doctor-blading method. The morphology and catalytic activity in the redox couple regeneration of all the graphite films are examined by field emission scanning electron microscopy and cyclic voltammograms. The OLA-G films on FTO glass with few layer graphene flakes shows better catalytic activity than the OA-G films. The energy conversion efficiency of the cell with the OLA-G film as counter electrode reached 3.56%, which is 70% of dye-sensitized solar cell (DSSC) with the sputtering-Pt counter electrode under the same experimental condition.

  2. 77 FR 9888 - Shiga Toxin-Producing Escherichia coli

    Science.gov (United States)

    2012-02-21

    ... Toxin-Producing Escherichia coli in Certain Raw Beef Products AGENCY: Food Safety and Inspection Service... toxin-producing Escherichia coli (STEC) serogroups (O26, O45, O103, O111, O121, and O145). This new date..., that are contaminated with Shiga toxin-producing Escherichia coli (STEC) O26, O45, O103, O111, O121...

  3. Military Importance of Natural Toxins and Their Analogs.

    Science.gov (United States)

    Pitschmann, Vladimír; Hon, Zdeněk

    2016-04-28

    Toxin weapon research, development, production and the ban on its uses is an integral part of international law, with particular attention paid to the protection against these weapons. In spite of this, hazards associated with toxins cannot be completely excluded. Some of these hazards are also pointed out in the present review. The article deals with the characteristics and properties of natural toxins and synthetic analogs potentially constituting the basis of toxin weapons. It briefly describes the history of military research and the use of toxins from distant history up to the present age. With respect to effective disarmament conventions, it mentions certain contemporary concepts of possible toxin applications for military purposes and the protection of public order (suppression of riots); it also briefly refers to the question of terrorism. In addition, it deals with certain traditional as well as modern technologies of the research, synthesis, and use of toxins, which can affect the continuing development of toxin weapons. These are, for example, cases of new toxins from natural sources, their chemical synthesis, production of synthetic analogs, the possibility of using methods of genetic engineering and modern biotechnologies or the possible applications of nanotechnology and certain pharmaceutical methods for the effective transfer of toxins into the organism. The authors evaluate the military importance of toxins based on their comparison with traditional chemical warfare agents. They appeal to the ethics of the scientific work as a principal condition for the prevention of toxin abuse in wars, military conflicts, as well as in non-military attacks.

  4. Charge transfer in carbon composites based on fullerenes and exfoliated graphite

    Science.gov (United States)

    Berezkin, V. I.

    2017-07-01

    Kinetic processes have been studied in composites based on fullerenes and exfoliated graphite at the initial proportions of components from 1: 16 to 16: 1 in mass. The samples are produced by heat treatment of initial dispersed mixtures in vacuum in the diffusion-adsorption process, their further cold pressing, and annealing. It is shown that the annealing almost does not influence the conduction mechanisms and only induces additional structural defects acting as electron traps. As a whole, the results obtained at the noted proportions of components make it possible to consider the material as a compensated metallic system with a structural disorder in which the charge transfer at temperatures from 4.2 K to room temperature is controlled by quantum interference phenomena. At low temperatures, the effect of a weak localization is observed, and the electron-electron interactions take place at medium and high temperatures.

  5. Exfoliated graphite/titanium dioxide nanocomposites for photodegradation of eosin yellow

    Science.gov (United States)

    Ndlovu, Thabile; Kuvarega, Alex T.; Arotiba, Omotayo A.; Sampath, Srinivasan; Krause, Rui W.; Mamba, Bhekie B.

    2014-05-01

    An improved photocatalyst consisting of a nanocomposite of exfoliated graphite and titanium dioxide (EG-TiO2) was prepared. SEM and TEM micrographs showed that the spherical TiO2 nanoparticles were evenly distributed on the surface of the EG sheets. A four times photocatalytic enhancement was observed for this floating nanocomposite compared to TiO2 and EG alone for the degradation of eosin yellow. For all the materials, the reactions followed first order kinetics where for EG-TiO2, the rate constant was much higher than for EG and TiO2 under visible light irradiation. The enhanced photocatalytic activity of EG-TiO2 was ascribed to the capability of graphitic layers to accept and transport electrons from the excited TiO2, promoting charge separation. This indicates that carbon, a cheap and abundant material, can be a good candidate as an electron attracting reservoir for photocatalytic organic pollutant degradation.

  6. Ferroelectric field-effect transistors based on solution-processed electrochemically exfoliated graphene

    Science.gov (United States)

    Heidler, Jonas; Yang, Sheng; Feng, Xinliang; Müllen, Klaus; Asadi, Kamal

    2018-06-01

    Memories based on graphene that could be mass produced using low-cost methods have not yet received much attention. Here we demonstrate graphene ferroelectric (dual-gate) field effect transistors. The graphene has been obtained using electrochemical exfoliation of graphite. Field-effect transistors are realized using a monolayer of graphene flakes deposited by the Langmuir-Blodgett protocol. Ferroelectric field effect transistor memories are realized using a random ferroelectric copolymer poly(vinylidenefluoride-co-trifluoroethylene) in a top gated geometry. The memory transistors reveal ambipolar behaviour with both electron and hole accumulation channels. We show that the non-ferroelectric bottom gate can be advantageously used to tune the on/off ratio.

  7. Aqueous Exfoliation of Graphite into Graphene Assisted by Sulfonyl Graphene Quantum Dots for Photonic Crystal Applications.

    Science.gov (United States)

    Zeng, Minxiang; Shah, Smit A; Huang, Dali; Parviz, Dorsa; Yu, Yi-Hsien; Wang, Xuezhen; Green, Micah J; Cheng, Zhengdong

    2017-09-13

    We investigate the π-π stacking of polyaromatic hydrocarbons (PAHs) with graphene surfaces, showing that such interactions are general across a wide range of PAH sizes and species, including graphene quantum dots. We synthesized a series of graphene quantum dots with sulfonyl, amino, and carboxylic functional groups and employed them to exfoliate and disperse pristine graphene in water. We observed that sulfonyl-functionalized graphene quantum dots were able to stabilize the highest concentration of graphene in comparison to other functional groups; this is consistent with prior findings by pyrene. The graphene nanosheets prepared showed excellent colloidal stability, indicating great potential for applications in electronics, solar cells, and photonic displays which was demonstrated in this work.

  8. Weak antilocalization effect in exfoliated black phosphorus revealed by temperature- and angle-dependent magnetoconductivity

    KAUST Repository

    Hou, Zhipeng

    2018-01-10

    Recently, there have been increasingly debates on whether there exists a surface resonance state (SRS) in black phosphorus (BP), as suggested by recent angle-resolved photoemission spectroscopy (ARPES) results. To resolve this issue, we have performed temperature- and angle-dependent magnetoconductivity measurements on exfoliated, high-quality BP single crystals. A pronounced weak-antilocalization (WAL) effect was observed within a narrow temperature range of 8 - 16 K, with the electrical current flowing parallel to the cleaved ac-plane (along the a- or c-axis) and the magnetic field along the b-axis. The angle-dependent magnetoconductivity and the Hikami-Larkin-Nagaoka (HLN) model-fitted results have revealed that the observed WAL effect shows surface-bulk coherent features, which supports the existence of SRS in black phosphorus.

  9. Method of producing exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z.

    2010-11-02

    The present invention provides a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm. The method comprises (a) dispersing particles of graphite, graphite oxide, or a non-graphite laminar compound in a liquid medium containing therein a surfactant or dispersing agent to obtain a stable suspension or slurry; and (b) exposing the suspension or slurry to ultrasonic waves at an energy level for a sufficient length of time to produce separated nano-scaled platelets. The nano-scaled platelets are candidate reinforcement fillers for polymer nanocomposites. Nano-scaled graphene platelets are much lower-cost alternatives to carbon nano-tubes or carbon nano-fibers.

  10. Weak antilocalization effect in exfoliated black phosphorus revealed by temperature- and angle-dependent magnetoconductivity

    KAUST Repository

    Hou, Zhipeng; Gong, Chen; Wang, Yue; Zhang, Qiang; Yang, Bingchao; Zhang, Hongwei; Liu, Enke; Liu, Zhongyuan; Zeng, Zhongming; Wu, Guangheng; Wang, Wenhong; Zhang, Xixiang

    2018-01-01

    Recently, there have been increasingly debates on whether there exists a surface resonance state (SRS) in black phosphorus (BP), as suggested by recent angle-resolved photoemission spectroscopy (ARPES) results. To resolve this issue, we have performed temperature- and angle-dependent magnetoconductivity measurements on exfoliated, high-quality BP single crystals. A pronounced weak-antilocalization (WAL) effect was observed within a narrow temperature range of 8 - 16 K, with the electrical current flowing parallel to the cleaved ac-plane (along the a- or c-axis) and the magnetic field along the b-axis. The angle-dependent magnetoconductivity and the Hikami-Larkin-Nagaoka (HLN) model-fitted results have revealed that the observed WAL effect shows surface-bulk coherent features, which supports the existence of SRS in black phosphorus.

  11. Ambipolar thermoelectric power of chemically-exfoliated RuO2 nanosheets

    Science.gov (United States)

    Kim, Jeongmin; Yoo, Somi; Moon, Hongjae; Kim, Se Yun; Ko, Dong-Su; Roh, Jong Wook; Lee, Wooyoung

    2018-01-01

    The electrical conductivity and Seebeck coefficient of RuO2 nanosheets are enhanced by metal nanoparticle doping using Ag-acetate solutions. In this study, RuO2 monolayer and bilayer nanosheets exfoliated from layered alkali metal ruthenates are transferred to Si substrates for device fabrication, and the temperature dependence of their conductivity and Seebeck coefficients is investigated. For pristine RuO2 nanosheets, the sign of the Seebeck coefficient changes with temperature from 350-450 K. This indicates that the dominant type of charge carrier is dependent on the temperature, and the RuO2 nanosheets show ambipolar carrier transport behavior. By contrast, the sign of the Seebeck coefficient for Ag nanoparticle-doped RuO2 nanosheets does not change with temperature, indicating that the extra charge carriers from metal nanoparticles promote n-type semiconductor behavior.

  12. Facile method for liquid-exfoliated graphene size prediction by UV-visible spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Zulhelmi, E-mail: helmie83@hotmail.com [Faculty of Manufacturing Engineering, Universiti Malaysia Pahang, 26600 Pekan, Pahang (Malaysia); Yusoh, Kamal, E-mail: kamal@ump.edu.my [Faculty of Chemical Engineering and Natural Resources, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Kuantan, Pahang (Malaysia)

    2016-07-19

    In this work, an application of UV spectroscopy for facile prediction of liquid –exfoliated graphene size is discussed. Dynamic light scattering method was used to estimate the graphene flake size ( whilst UV spectroscopy measurement was carried out for extinction coefficient value (ε) determination. It was found that the value of (ε) decreased gradually as the graphene size was further reduced after intense sonication time (7h). This observation showed the influence of sonication time on electronic structure of graphene. A mathematical equation was derived from log-log graph for correlation between () and (ε) value. Both values can be expressed in a single equation as ( = (3.4 × 10{sup −2}) ε{sup 1.2}).

  13. Gas-exfoliated porous monolayer boron nitride for enhanced aerobic oxidative desulfurization performance

    Science.gov (United States)

    Wu, Yingcheng; Wu, Peiwen; Chao, Yanhong; He, Jing; Li, Hongping; Lu, Linjie; Jiang, Wei; Zhang, Beibei; Li, Huaming; Zhu, Wenshuai

    2018-01-01

    Hexagonal boron nitride has been regarded to be an efficient catalyst in aerobic oxidation fields, but limited by the less-exposed active sites. In this contribution, we proposed a simple green liquid nitrogen gas exfoliation strategy for preparation of porous monolayer nanosheets (BN-1). Owing to the reduced layer numbers, decreased lateral sizes and artificially-constructed pores, increased exposure of active sites was expected, further contributed to an enhanced aerobic oxidative desulfurization (ODS) performance up to ˜98% of sulfur removal, achieving ultra-deep desulfurization. This work not only introduced an excellent catalyst for aerobic ODS, but also provided a strategy for construction of some other highly-efficient monolayer two-dimensional materials for enhanced catalytic performance.

  14. Exfoliation of graphite into graphene in polar solvents mediated by amphiphilic hexa-peri-hexabenzocoronene.

    Science.gov (United States)

    Kabe, Ryota; Feng, Xinliang; Adachi, Chihaya; Müllen, Klaus

    2014-11-01

    A water-soluble surfactant consisting of hexa-peri-hexabenzocoronene (HBC) as hydrophobic aromatic core and hydrophilic carboxy substituents was synthesized. It exhibited a self-assembled nanofiber structure in the solid state. Profiting from the π interactions between the large aromatic core of HBC and graphene, the surfactant mediated the exfoliation of graphite into graphene in polar solvents, which was further stabilized by the bulky hydrophilic carboxylic groups. A graphene dispersion with a concentration as high as 1.1 mg L(-1) containing 2-6 multilayer nanosheets was obtained. The lateral size of the graphene sheets was in the range of 100-500 nm based on atomic force microscope (AFM) and transmission electron microscope (TEM) measurements. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu

    International Nuclear Information System (INIS)

    Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Whang, Dongmok; Joo, Won-Jae; Hwang, SungWoo

    2015-01-01

    Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer graphene showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps. (paper)

  16. Hole-doping of mechanically exfoliated graphene by confined hydration layers

    Institute of Scientific and Technical Information of China (English)

    Tjeerd R. J. Bollmann[1,2; Liubov Yu. Antipina[3,4; Matthias Temmen[2; Michael Reichling[2; Pavel B. Sorokin[5

    2015-01-01

    By the use of non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM), we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CAF2(111). Hydration layers confined between the graphene and the CaF2 substrate, resulting from the graphene's preparation under ambient conditions on the hydrophilic substrate surface, are found to electronically modify the graphene as the material's electron density transfers from graphene to the hydration layer. Density functional theory (DFT) calculations predict that the first 2 to 3 water layers adjacent to the graphene hole-dope the graphene by several percent of a unit charge per unit cell.

  17. Percolation transition in carbon composite on the basis of fullerenes and exfoliated graphite

    Science.gov (United States)

    Berezkin, V. I.; Popov, V. V.

    2018-01-01

    The electrical conductivity of a carbon composite on the basis of C60 fullerenes and exfoliated graphite is investigated in the range of relative contents of components from 0 to 100%. The samples are obtained by the thermal treatment of the initial dispersed mixtures in vacuum in the diffusion-adsorption process and their further cold pressing. The resistivity of the samples gradually increases with an increase in the fraction of fullerenes, and a sharp transition from the conductive state to the dielectric one is observed after achieving certain concentrations of C60. The interpretation of the results within the percolation theory makes it possible to evaluate the percolation threshold (expressed as a relative content of graphite) as equal to 4.45 wt % and the critical conductivity index as equal to 1.85 (which is typical for three-dimensional twocomponent disordered media including those having pores).

  18. The period between exfoliation of primary teeth and the emergence of permanent successors.

    Science.gov (United States)

    Nyström, M; Peck, L

    1989-02-01

    The dates of natural exfoliation of primary teeth and of clinical eruption of their successors were recorded in 141 children, a total of 660 teeth. The aim of this investigation was to study the length of the period between these two developmental events. In the mandible, the mean length of the toothless period for the central incisor was 2 weeks and that for the lateral incisors and canines 6 weeks. In the maxilla, the corresponding period was 6 weeks for the central incisor and over 4 months for the lateral incisor and the canine. The mean length of the toothless period was shortest, 0-6 days, between the primary molars and the succeeding premolars. Individual variation was great. No difference was detected between the sexes. In some cases the length of the toothless period for the maxillary lateral incisors and for the canines in both jaws exceeded one year. This was associated with crowding, which caused the premature loss of primary teeth.

  19. CVD growth of graphene under exfoliated hexagonal boron nitride for vertical hybrid structures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Min [SKKU Advanced Institute of Nanotechnology (SAINT) (Korea, Republic of); Center for Human Interface Nanotechnology (HINT) (Korea, Republic of); Jang, Sung Kyu [SKKU Advanced Institute of Nanotechnology (SAINT) (Korea, Republic of); Song, Young Jae [SKKU Advanced Institute of Nanotechnology (SAINT) (Korea, Republic of); Department of Physics, Sungkyunkwan University (SKKU), Suwon 440-746 (Korea, Republic of); Lee, Sungjoo, E-mail: leesj@skku.edu [SKKU Advanced Institute of Nanotechnology (SAINT) (Korea, Republic of); Center for Human Interface Nanotechnology (HINT) (Korea, Republic of); College of Information and Communication Engineering, Sungkyunkwan University (SKKU), Suwon 440-746 (Korea, Republic of)

    2015-01-15

    Graphical abstract: We have demonstrated a novel yet simple method for fabricating graphene-based vertical hybrid structures by performing the CVD growth of graphene at an h-BN/Cu interface. Our systematic Raman measurements combined with plasma etching process indicate that a graphene film is grown under exfoliated h-BN rather than on its top surface, and that an h-BN/graphene vertical hybrid structure has been fabricated. Electrical transport measurements of this h-BN/graphene, transferred on SiO2, show the carrier mobility up to approximately 2250 cm{sup 2} V{sup −1} s{sup −1}. The developed method would enable the exploration of the possibility of novel hybrid structure integration with two-dimensional material systems. - Abstract: We have demonstrated a novel yet simple method for fabricating graphene-based vertical hybrid structures by performing the CVD growth of graphene at an h-BN/Cu interface. Our systematic Raman measurements combined with plasma etching process indicate that a graphene film is grown under exfoliated h-BN rather than on its top surface, and that an h-BN/graphene vertical hybrid structure has been fabricated. Electrical transport measurements of this h-BN/graphene, transferred on SiO{sub 2}, show the carrier mobility up to approximately 2250 cm{sup 2} V{sup −1} s{sup −1}. The developed method would enable the exploration of the possibility of novel hybrid structure integration with two-dimensional material systems.

  20. Production of High-quality Few-layer Graphene Flakes by Intercalation and Exfoliation

    KAUST Repository

    Alzahrani, Areej A.

    2017-11-30

    Graphene, a two-dimensional nanomaterial, has been given much attention since it was first isolated in 2004. Driving this intensive research effort are the unique properties of this one atom thick sheet of carbon, in particular its electrical, thermal and mechanical properties. While the technological applications proposed for graphene abound, its low-cost production in large scales is still a matter of interrogation. Simple methods to obtain few-layered graphene flakes of high structural quality are being investigated with the exfoliation of graphite taking a prominent place in this arena. From the many suggested approaches, the most promising involve the use of liquid media assisted by intercalants and shear forces acting on the basal layers of graphite. In this thesis, it is discussed how a novel method was developed to produce flakes with consistent lateral dimensions that are also few-layered and retain the expected structural and chemical characteristics of graphene. Here, the source material was a commercially available graphiteintercalated compound, also known as expandable graphite. Several exfoliation-inducing tools were investigated including the use of blenders, homogenizers, and ultrasonic processors. To aid in this process, various solvents and intercalants were explored under different reactive conditions. The more efficient approach in yielding defect-free thin flakes was the use of thermally expanded graphite in boiling dimethylformamide followed by ultrasonic processing and centrifugation. In parallel, a method to fraction the flakes as a function of their lateral size was developed. Ultimately, it was possible to obtain samples of graphene flakes with a lateral dimension of a few micrometers (<5 μm) and thickness of 1-3 nm (i.e. <10 layers).

  1. Fate of Fusarium Toxins during Brewing.

    Science.gov (United States)

    Habler, Katharina; Geissinger, Cajetan; Hofer, Katharina; Schüler, Jan; Moghari, Sarah; Hess, Michael; Gastl, Martina; Rychlik, Michael

    2017-01-11

    Some information is available about the fate of Fusarium toxins during the brewing process, but only little is known about the single processing steps in detail. In our study we produced beer from two different barley cultivars inoculated with three different Fusarium species, namely, Fusarium culmorum, Fusarium sporotrichioides, and Fusarium avenaceum, producing a wide range of mycotoxins such as type B trichothecenes, type A trichothecenes, and enniatins. By the use of multi-mycotoxin LC-MS/MS stable isotope dilution methods we were able to follow the fate of Fusarium toxins during the entire brewing process. In particular, the type B trichothecenes deoxynivalenol, 3-acetyldeoxynivalenol, and 15-acetyldeoxynivalenol showed similar behaviors. Between 35 and 52% of those toxins remained in the beer after filtration. The contents of the potentially hazardous deoxynivalenol-3-glucoside and the type A trichothecenes increased during mashing, but a rapid decrease of deoxynivalenol-3-glucoside content was found during the following steps of lautering and wort boiling. The concentration of enniatins greatly decreased with the discarding of spent grains or finally with the hot break. The results of our study show the retention of diverse Fusarium toxins during the brewing process and allow for assessing the food safety of beer regarding the monitored Fusarium mycotoxins.

  2. Botulinum Toxin in Neurogenic Detrusor Overactivity

    Directory of Open Access Journals (Sweden)

    Carlos Arturo Levi D'Ancona

    2012-09-01

    Full Text Available Purpose To evaluate the effects of botulinum toxin on urodynamic parameters and quality of life in patients with neurogenic detrusor overactivity. Methods Thirty four adult patients with spinal cord injury and detrusor overactivity were selected. The patients received 300 units of botulinum toxin type A. The endpoints evaluated with the episodes of urinary incontinence and measured the maximum cystometric capacity, maximum amplitude of detrusor pressure and bladder compliance at the beginning and end of the study (24 weeks and evaluated the quality of life by applying the Qualiveen questionnaire. Results A significant decrease in the episodes of urinary incontinence was observed. All urodynamic parameters presented a significant improvement. The same was observed in the quality of life index and the specific impact of urinary problems scores from the Qualiveen questionnaire. Six patients did not complete the study, two due to incomplete follow-up, and four violated protocol and were excluded from the analyses. No systemic adverse events of botulinum toxin type A were reported. Conclusions A botulinum toxin type A showed a significantly improved response in urodynamics parameters and specific and general quality of life.

  3. Bioengineered kidney tubules efficiently excrete uremic toxins

    NARCIS (Netherlands)

    Jansen, Jitske; Fedecostante, M.; Wilmer, M.; Peters, J.G.; Kreuser, U.M.; Broek, P.H.; Mensink, R.A.; Boltje, T.J.; Stamatialis, Dimitrios; Wetzels, J.F.; van der Heuvel, L.P.; Hoenderop, J.G.; Masereeuw, R.

    2016-01-01

    The development of a biotechnological platform for the removal of waste products (e.g. uremic toxins), often bound to proteins in plasma, is a prerequisite to improve current treatment modalities for patients suffering from end stage renal disease (ESRD). Here, we present a newly designed

  4. Treatment diary for botulinum toxin spasticity treatment

    DEFF Research Database (Denmark)

    Biering-Sørensen, Bo; Iversen, Helle K; Frederiksen, Inge M S

    2017-01-01

    The aim of this study is to develop a treatment diary for patients receiving spasticity treatment including botulinum toxin injection and physiotherapy and/or occupational therapy. The diary focuses on problems triggered by skeletal muscle overactivity; agreed goals for treatment and the patient...

  5. Diffusion, spread, and migration of botulinum toxin.

    Science.gov (United States)

    Ramirez-Castaneda, Juan; Jankovic, Joseph; Comella, Cynthia; Dashtipour, Khashayar; Fernandez, Hubert H; Mari, Zoltan

    2013-11-01

    Botulinum toxin (BoNT) is an acetylcholine release inhibitor and a neuromuscular blocking agent used for the treatment of a variety of neurologic and medical conditions. The efficacy and safety of BoNT depends on accurate selection and identification of intended targets but also may be determined by other factors, including physical spread of the molecule from the injection site, passive diffusion, and migration to distal sites via axonal or hematogenous transport. The passive kinetic dispersion of the toxin away from the injection site in a gradient-dependent manner may also play a role in toxin spread. In addition to unique properties of the various BoNT products, volume and dilution may also influence local and systemic distribution of BoNT. Most of the local and remote complications of BoNT injections are thought to be due to unwanted spread or diffusion of the toxin's biologic activity into adjacent and distal muscles. Despite widespread therapeutic and cosmetic use of BoNT over more than three decades, there is a remarkable paucity of published data on the mechanisms of distribution and its effects on clinical outcomes. The primary aim of this article is to critically review the available experimental and clinical literature and place it in the practical context. © 2013 International Parkinson and Movement Disorder Society.

  6. Mutant with diphtheria toxin receptor and acidification function but defective in entry of toxin

    International Nuclear Information System (INIS)

    Kohno, Kenji; Hayes, H.; Mekada, Eisuke; Uchida, Tsuyoshi

    1987-01-01

    A mutant of Chinese hamster ovary cells, GE1, that is highly resistant to diphtheria toxin was isolated. The mutant contains 50% ADP-ribosylatable elongation factor 2, but its protein synthesis was not inhibited by the toxin even at concentrations above 100 μg/ml. 125 I-labeled diphtheria toxin was associated with GE1 cells as well as with the parent cells but did not block protein synthesis of GE1 cells even when the cells were exposed to low pH in the presence or absence of NH 4 Cl. The infections of GE1 cells and the parent cells by vesicular stomatitis virus were similar. GE1 cells were cross-resistant to Pseudomonas aeruginosa exotoxin A and so were about 1,000 times more resistant to this toxin than the parent cells. Hybrids of GE1 cells and the parent cells or mutant cells lacking a functional receptor were more sensitive to diphtheria toxin than GE1 cells. These results suggest that entry of diphtheria toxin into cells requires a cellular factor(s) in addition to those involved in receptor function and acidification of endosomes and that GE1 cells do not express this cellular factor. This character is recessive in GE1 cells

  7. Higher cytotoxicity of divalent antibody-toxins than monovalent antibody-toxins

    International Nuclear Information System (INIS)

    Won, JaeSeon; Nam, PilWon; Lee, YongChan; Choe, MuHyeon

    2009-01-01

    Recombinant antibody-toxins are constructed via the fusion of a 'carcinoma-specific' antibody fragment to a toxin. Due to the high affinity and high selectivity of the antibody fragments, antibody-toxins can bind to surface antigens on cancer cells and kill them without harming normal cells [L.H. Pai, J.K. Batra, D.J. FitzGerald, M.C. Willingham, I. Pastan, Anti-tumor activities of immunotoxins made of monoclonal antibody B3 and various forms of Pseudomonas exotoxin, Proc. Natl. Acad. Sci. USA 88 (1991) 3358-3362]. In this study, we constructed the antibody-toxin, Fab-SWn-PE38, with SWn (n = 3, 6, 9) sequences containing n-time repeated (G 4 S) between the Fab fragment and PE38 (38 kDa truncated form of Pseudomonas exotoxin A). The SWn sequence also harbored one cysteine residue that could form a disulfide bridge between two Fab-SWn-PE38 monomers. We assessed the cytotoxicity of the monovalent (Fab-SWn-PE38), and divalent ([Fab-SWn-PE38] 2 ) antibody-toxins. The cytotoxicity of the dimer against the CRL1739 cell line was approximately 18.8-fold higher than that of the monomer on the ng/ml scale, which was approximately 37.6-fold higher on the pM scale. These results strongly indicate that divalency provides higher cytotoxicity for an antibody-toxin.

  8. Characterization of Hemagglutinin Negative Botulinum Progenitor Toxins

    Directory of Open Access Journals (Sweden)

    Suzanne R. Kalb

    2017-06-01

    Full Text Available Botulism is a disease involving intoxication with botulinum neurotoxins (BoNTs, toxic proteins produced by Clostridium botulinum and other clostridia. The 150 kDa neurotoxin is produced in conjunction with other proteins to form the botulinum progenitor toxin complex (PTC, alternating in size from 300 kDa to 500 kDa. These progenitor complexes can be classified into hemagglutinin positive or hemagglutinin negative, depending on the ability of some of the neurotoxin-associated proteins (NAPs to cause hemagglutination. The hemagglutinin positive progenitor toxin complex consists of BoNT, nontoxic non-hemagglutinin (NTNH, and three hemagglutinin proteins; HA-70, HA-33, and HA-17. Hemagglutinin negative progenitor toxin complexes contain BoNT and NTNH as the minimally functional PTC (M-PTC, but not the three hemagglutinin proteins. Interestingly, the genome of hemagglutinin negative progenitor toxin complexes comprises open reading frames (orfs which encode for three proteins, but the existence of these proteins has not yet been extensively demonstrated. In this work, we demonstrate that these three proteins exist and form part of the PTC for hemagglutinin negative complexes. Several hemagglutinin negative strains producing BoNT/A, /E, and /F were found to contain the three open reading frame proteins. Additionally, several BoNT/A-containing bivalent strains were examined, and NAPs from both genes, including the open reading frame proteins, were associated with BoNT/A. The open reading frame encoded proteins are more easily removed from the botulinum complex than the hemagglutinin proteins, but are present in several BoNT/A and /F toxin preparations. These are not easily removed from the BoNT/E complex, however, and are present even in commercially-available purified BoNT/E complex.

  9. Discovery of novel bacterial toxins by genomics and computational biology.

    Science.gov (United States)

    Doxey, Andrew C; Mansfield, Michael J; Montecucco, Cesare

    2018-06-01

    Hundreds and hundreds of bacterial protein toxins are presently known. Traditionally, toxin identification begins with pathological studies of bacterial infectious disease. Following identification and cultivation of a bacterial pathogen, the protein toxin is purified from the culture medium and its pathogenic activity is studied using the methods of biochemistry and structural biology, cell biology, tissue and organ biology, and appropriate animal models, supplemented by bioimaging techniques. The ongoing and explosive development of high-throughput DNA sequencing and bioinformatic approaches have set in motion a revolution in many fields of biology, including microbiology. One consequence is that genes encoding novel bacterial toxins can be identified by bioinformatic and computational methods based on previous knowledge accumulated from studies of the biology and pathology of thousands of known bacterial protein toxins. Starting from the paradigmatic cases of diphtheria toxin, tetanus and botulinum neurotoxins, this review discusses traditional experimental approaches as well as bioinformatics and genomics-driven approaches that facilitate the discovery of novel bacterial toxins. We discuss recent work on the identification of novel botulinum-like toxins from genera such as Weissella, Chryseobacterium, and Enteroccocus, and the implications of these computationally identified toxins in the field. Finally, we discuss the promise of metagenomics in the discovery of novel toxins and their ecological niches, and present data suggesting the existence of uncharacterized, botulinum-like toxin genes in insect gut metagenomes. Copyright © 2018. Published by Elsevier Ltd.

  10. Radioimmunoassay for yeast killer toxin from Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Siddiqui, F.A.; Bussey, H.

    1981-01-01

    A radioimmunoassay was developed for the K1 killer toxin from strain T158C/S14a of Saccharomyces cerevisiae. Iodine 125-labelled toxin was made to a specific activity of 100 μCi/mg of protein. Antibody to purified toxin was prepared in rabbits using toxin cross-linked to itself. These antibodies, partially purified by 50 percent ammonium sulfate precipitation and Sepharose CL-6B column chromatography, produced one precipitation band with killer toxin and bound 125 I-labelled toxin in a radioimmunoassay. The antibody preparation also bound with the toxins from another K1 killer, A364A, and three chromosomal superkiller mutants derived from it. (auth)

  11. A flexible and transparent graphene/ZnO nanorod hybrid structure fabricated by exfoliating a graphite substrate

    Science.gov (United States)

    Nam, Gwang-Hee; Baek, Seong-Ho; Cho, Chang-Hee; Park, Il-Kyu

    2014-09-01

    We demonstrate the fabrication of a graphene/ZnO nanorod (NR) hybrid structure by mechanical exfoliation of ZnO NRs grown on a graphite substrate. We confirmed the existence of graphene sheets on the hybrid structure by analyzing the Raman spectra and current-voltage (I-V) characteristics. The Raman spectra of the exfoliated graphene/ZnO NR hybrid structure show G and 2D band peaks that are shifted to lower wavenumbers, indicating that the exfoliated graphene layer exists under a significant amount of strain. The I-V characteristics of the graphene/ZnO NR hybrid structure show current flow through the graphene layer, while no current flow is observed on the ZnO NR/polydimethylsiloxane (PDMS) composite without graphene, thereby indicating that the few-layer graphene was successfully transferred onto the hybrid structure. A piezoelectric nanogenerator is demonstrated by using the fabricated graphene/ZnO NR hybrid structure. The nanogenerator exhibits stable output voltage up to 3.04 V with alternating current output characteristics.We demonstrate the fabrication of a graphene/ZnO nanorod (NR) hybrid structure by mechanical exfoliation of ZnO NRs grown on a graphite substrate. We confirmed the existence of graphene sheets on the hybrid structure by analyzing the Raman spectra and current-voltage (I-V) characteristics. The Raman spectra of the exfoliated graphene/ZnO NR hybrid structure show G and 2D band peaks that are shifted to lower wavenumbers, indicating that the exfoliated graphene layer exists under a significant amount of strain. The I-V characteristics of the graphene/ZnO NR hybrid structure show current flow through the graphene layer, while no current flow is observed on the ZnO NR/polydimethylsiloxane (PDMS) composite without graphene, thereby indicating that the few-layer graphene was successfully transferred onto the hybrid structure. A piezoelectric nanogenerator is demonstrated by using the fabricated graphene/ZnO NR hybrid structure. The nanogenerator

  12. General synthesis of β-alanine-containing spider polyamine toxins and discovery of nephila polyamine toxins 1 and 8 as highly potent inhibitors of ionotropic glutamate receptors

    DEFF Research Database (Denmark)

    Lucas, Simon; Poulsen, Mette H; Nørager, Niels G

    2012-01-01

    Certain spiders contain large pools of polyamine toxins, which are putative pharmacological tools awaiting further discovery. Here we present a general synthesis strategy for this class of toxins and prepare five structurally varied polyamine toxins. Electrophysiological testing at three ionotrop...

  13. Botulinum Toxin: Pharmacology and Therapeutic Roles in Pain States.

    Science.gov (United States)

    Patil, Shilpadevi; Willett, Olga; Thompkins, Terin; Hermann, Robert; Ramanathan, Sathish; Cornett, Elyse M; Fox, Charles J; Kaye, Alan David

    2016-03-01

    Botulinum toxin, also known as Botox, is produced by Clostridium botulinum, a gram-positive anaerobic bacterium, and botulinum toxin injections are among the most commonly practiced cosmetic procedures in the USA. Although botulinum toxin is typically associated with cosmetic procedures, it can be used to treat a variety of other conditions, including pain. Botulinum toxin blocks the release of acetylcholine from nerve endings to paralyze muscles and to decrease the pain response. Botulinum toxin has a long duration of action, lasting up to 5 months after initial treatment which makes it an excellent treatment for chronic pain patients. This manuscript will outline in detail why botulinum toxin is used as a successful treatment for pain in multiple conditions as well as outline the risks associated with using botulinum toxin in certain individuals. As of today, the only FDA-approved chronic condition that botulinum toxin can be used to treat is migraines and this is related to its ability to decrease muscle tension and increase muscle relaxation. Contraindications to botulinum toxin treatments are limited to a hypersensitivity to the toxin or an infection at the site of injection, and there are no known drug interactions with botulinum toxin. Botulinum toxin is an advantageous and effective alternative pain treatment and a therapy to consider for those that do not respond to opioid treatment. In summary, botulinum toxin is a relatively safe and effective treatment for individuals with certain pain conditions, including migraines. More research is warranted to elucidate chronic and long-term implications of botulinum toxin treatment as well as effects in pregnant, elderly, and adolescent patients.

  14. High-efficiency exfoliation of layered materials into 2D nanosheets in switchable CO2/Surfactant/H2O system

    Science.gov (United States)

    Wang, Nan; Xu, Qun; Xu, Shanshan; Qi, Yuhang; Chen, Meng; Li, Hongxiang; Han, Buxing

    2015-11-01

    Layered materials present attractive and important properties due to their two-dimensional (2D) structure, allowing potential applications including electronics, optoelectronics, and catalysis. However, fully exploiting the outstanding properties will require a method for their efficient exfoliation. Here we present that a series of layered materials can be successfully exfoliated into single- and few-layer nanosheets using the driving forces coming from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). The effect of variable experimental parameters including CO2 pressure, ethanol/water ratio, and initial concentration of bulk materials on the exfoliation yield have been investigated. Moreover, we demonstrate that the exfoliated 2D nanosheets have their worthwhile applications, for example, graphene can be used to prepare conductive paper, MoS2 can be used as fluorescent label to perform cellular labelling, and BN can effectively reinforce polymers leading to the promising mechanical properties.

  15. Sulfur-doped graphene via thermal exfoliation of graphite oxide in H2S, SO2, or CS2 gas.

    Science.gov (United States)

    Poh, Hwee Ling; Šimek, Petr; Sofer, Zdeněk; Pumera, Martin

    2013-06-25

    Doping of graphene with heteroatoms is an effective way to tailor its properties. Here we describe a simple and scalable method of doping graphene lattice with sulfur atoms during the thermal exfoliation process of graphite oxides. The graphite oxides were first prepared by Staudenmaier, Hofmann, and Hummers methods followed by treatments in hydrogen sulfide, sulfur dioxide, or carbon disulfide. The doped materials were characterized by scanning electron microscopy, high-resolution X-ray photoelectron spectroscopy, combustible elemental analysis, and Raman spectroscopy. The ζ-potential and conductivity of sulfur-doped graphenes were also investigated in this paper. It was found that the level of doping is more dramatically influenced by the type of graphite oxide used rather than the type of sulfur-containing gas used during exfoliation. Resulting sulfur-doped graphenes act as metal-free electrocatalysts for an oxygen reduction reaction.

  16. Powder, paper and foam of few-layer graphene prepared in high yield by electrochemical intercalation exfoliation of expanded graphite.

    Science.gov (United States)

    Wu, Liqiong; Li, Weiwei; Li, Peng; Liao, Shutian; Qiu, Shengqiang; Chen, Mingliang; Guo, Yufen; Li, Qi; Zhu, Chao; Liu, Liwei

    2014-04-09

    A facile and high-yield approach to the preparation of few-layer graphene (FLG) by electrochemical intercalation exfoliation (EIE) of expanded graphite in sulfuric acid electrolyte is reported. Stage-1 H2SO4-graphite intercalation compound is used as a key intermediate in EIE to realize the efficient exfoliation. The yield of the FLG sheets (papers made of the FLG flakes retain excellent conductivity (≈24,500 S m(-1)). Three-dimensional (3D) graphene foams with light weight are fabricated from the FLG flakes by the use of Ni foams as self-sacrifice templates. Furthermore, 3D graphene/Ni foams without any binders, which are used as supercapacitor electrodes in aqueous electrolyte, provide the specific capacitance of 113.2 F g(-1) at a current density of 0.5 A g(-1), retaining 90% capacitance after 1000 cycles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. A "Tandem" Strategy to Fabricate Flexible Graphene/Polypyrrole Nanofiber Film Using the Surfactant-Exfoliated Graphene for Supercapacitors.

    Science.gov (United States)

    Shu, Kewei; Chao, Yunfeng; Chou, Shulei; Wang, Caiyun; Zheng, Tian; Gambhir, Sanjeev; Wallace, Gordon G

    2018-06-19

    The surfactant-assisted liquid-phase exfoliation of expanded graphite can produce graphene sheets in large quantities with minimal defects. However, it is difficult to completely remove the surfactant from the final product, thus affecting the electrochemical properties of the produced graphene. In this article, a novel approach to fabricate flexible graphene/polypyrrole film was developed: using surfactant cetyltrimethylammonium bromide as a template for growth of polypyrrole nanofibers (PPyNFs) instead of removal after the exfoliation process; followed by a simple filtration method. The introduction of PPyNF not only increases the electrochemical performance, but also ensures flexibility. This composite film electrode offers a capacitance up to 161 F g -1 along with a capacitance retention rate of over 80% after 5000 cycles.

  18. Salt-assisted direct exfoliation of graphite into high-quality, large-size, few-layer graphene sheets.

    Science.gov (United States)

    Niu, Liyong; Li, Mingjian; Tao, Xiaoming; Xie, Zhuang; Zhou, Xuechang; Raju, Arun P A; Young, Robert J; Zheng, Zijian

    2013-08-21

    We report a facile and low-cost method to directly exfoliate graphite powders into large-size, high-quality, and solution-dispersible few-layer graphene sheets. In this method, aqueous mixtures of graphite and inorganic salts such as NaCl and CuCl2 are stirred, and subsequently dried by evaporation. Finally, the mixture powders are dispersed into an orthogonal organic solvent solution of the salt by low-power and short-time ultrasonication, which exfoliates graphite into few-layer graphene sheets. We find that the as-made graphene sheets contain little oxygen, and 86% of them are 1-5 layers with lateral sizes as large as 210 μm(2). Importantly, the as-made graphene can be readily dispersed into aqueous solution in the presence of surfactant and thus is compatible with various solution-processing techniques towards graphene-based thin film devices.

  19. Investigation of exfoliation joints in Navajo sandstone at the Zion National Park and in granite at the Yosemite National Park by tectonofractographic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bahat, D.; Grossenbacher, K.; Karasaki, K.

    1995-04-01

    Tectonofractographic techniques have been applied to the study of joint exfoliation in the Navajo sandstone at Zion National Park and in the granite at Yosemite National Park. New types of fracture surface morphologies have been observed which enabled the discerning of incipient joints and consequent fracture growth in these rocks. Incipient jointing in the sandstone is mostly manifested by elliptical and circular fractures (meters to tens meters across) initiating from independent origins. They interfere with each other and grow to larger circular fractures producing exfoliation surfaces up to hundreds of meters across. Less frequently, series of large concentric undulations demonstrate the propagation of a large fracture front producing exfoliation from an individual origin. One such fracture front reveals refraction of undulations at a layer boundary. Certain en echelon fringes surround the joint mirror plane with well defined rims of en echelons and hackles which enable the determination of the tensile fracture stress, {sigma}f. Arches in Zion National Park are ubiquitous in shape and size, revealing stages in their evolution by a mechanical process, which was associated with exfoliation, but independent of local faulting. Exfoliation and arching mostly occurred on vertical surfaces of N-NNW and NE sets of prominent joints, but there are also deviations from this general trend. In Yosemite National Park large exfoliations (hundreds of meters in size) developed on the El Capitan cliff by the interaction and merging of many previous smaller incipient joints that vary in size from meters to tens of meter.

  20. A common variant mapping to CACNA1A is associated with susceptibility to exfoliation syndrome

    DEFF Research Database (Denmark)

    Aung, Tin; Ozaki, Mineo; Mizoguchi, Takanori

    2015-01-01

    Exfoliation syndrome (XFS) is the most common recognizable cause of open-angle glaucoma worldwide. To better understand the etiology of XFS, we conducted a genome-wide association study (GWAS) of 1,484 cases and 1,188 controls from Japan and followed up the most significant findings in a further ......-wide significance for XFS and provide insight into the biology and pathogenesis of the disease....

  1. Poly(meth)acrylate nanocomposite membranes containing in situ exfoliated graphene platelets: synthesis, characterization and gas barrier properties

    Czech Academy of Sciences Publication Activity Database

    Poláková, Lenka; Sedláková, Zdeňka; Ecorchard, Petra; Pavlova, Ewa; Peter, Jakub; Paruzel, Bartosz; Beneš, Hynek

    2017-01-01

    Roč. 94, September (2017), s. 431-445 ISSN 0014-3057 R&D Projects: GA ČR(CZ) GA17-08273S; GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 ; RVO:61388980 Keywords : graphite intercalation compounds * quaternary ammonium salt * exfoliation Subject RIV: CD - Macromolecular Chemistry ; CA - Inorganic Chemistry (UACH-T) OBOR OECD: Polymer science; Inorganic and nuclear chemistry (UACH-T) Impact factor: 3.531, year: 2016

  2. Uniaxial Drawing of Graphene-PVA Nanocomposites: Improvement in Mechanical Characteristics via Strain-Induced Exfoliation of Graphene

    OpenAIRE

    Jan, Rahim; Habib, Amir; Akram, Muhammad Aftab; Zia, Tanveer-ul-Haq; Khan, Ahmad Nawaz

    2016-01-01

    Polyvinyl alcohol (PVA)-stabilized graphene nanosheets (GNS) of lateral dimension (L) ~1??m are obtained via liquid phase exfoliation technique to prepare its composites in the PVA matrix. These composites show low levels of reinforcements due to poor alignment of GNS within the matrix as predicted by the modified Halpin-Tsai model. Drawing these composites up to 200?% strain, a significant improvement in mechanical properties is observed. Maximum values for Young?s modulus and strength are ~...

  3. Effective Chemical Route to 2D Nanostructured Silicon Electrode Material: Phase Transition from Exfoliated Clay Nanosheet to Porous Si Nanoplate

    International Nuclear Information System (INIS)

    Adpakpang, Kanyaporn; Patil, Sharad B.; Oh, Seung Mi; Kang, Joo-Hee; Lacroix, Marc; Hwang, Seong-Ju

    2016-01-01

    Graphical abstract: Effective morphological control of porous silicon 2D nanoplate can be achieved by the magnesiothermically-induced phase transition of exfoliated silicate clay nanosheets. The promising lithium storage performance of the obtained silicon materials with huge capacity and excellent rate characteristics underscores the prime importance of porously 2D nanostructured morphology of silicon. - Highlights: • 2D nanostructured silicon electrode materials are successfully synthesized via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. • High discharge capacity and rate capability are achieved from the 2D nanoplates of silicon. • Silicon 2D nanoplates can enhance both Li"+ diffusion and charge-transfer kinetics. • 2D nanostructured silicon is beneficial for the cycling stability by minimizing the volume change during lithiation-delithiation. - Abstract: An efficient and economical route for the synthesis of porous two-dimensional (2D) nanoplates of silicon is developed via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. The magnesiothermic reaction of precursor clay nanosheets prepared by the exfoliation and restacking with Mg"2"+ cations yields porous 2D nanoplates of elemental silicon. The variation in the Mg:SiO_2 ratio has a significant effect on the porosity and connectivity of silicon nanoplates. The porous silicon nanoplates show a high discharge capacity of 2000 mAh g"−"1 after 50 cycles. Of prime importance is that this electrode material still retains a large discharge capacity at higher C-rates, which is unusual for the elemental silicon electrode. This is mainly attributed to the improved diffusion of lithium ions, charge-transfer kinetics, and the preservation of the electrical connection of the porous 2D plate-shaped morphology. This study highlights the usefulness of clay mineral as an economical and scalable precursor of high-performance silicon electrodes with

  4. Luminescent monolayer MoS{sub 2} quantum dots produced by multi-exfoliation based on lithium intercalation

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Wen [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Yan, Shiming [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); College of Science, Henan University of Technology, Zhengzhou 450001 (China); Song, Xueyin; Zhang, Xing; He, Xueming [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Zhong, Wei, E-mail: wzhong@nju.edu.cn [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Du, Youwei [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China)

    2015-12-30

    Graphical abstract: - Highlights: • A new preparation, multi-exfoliation method based on lithium (Li) intercalation, has been demonstrated for preparing monolayer molybdenum disulfide (MoS{sub 2}) quantum dots (QDs). • The advantage of this approach is that it is capable of producing monolayer MoS{sub 2} QDs in a large number, regardless of whether the raw material is bulk or nanoparticles. • The PL intensity excited at 300 nm can be enhanced by five times after ultrasonicated heating treatment. - Abstract: An effective multi-exfoliation method based on lithium (Li) intercalation has been demonstrated for preparing monolayer molybdenum disulfide (MoS{sub 2}) quantum dots (QDs). The cutting mechanism of MoS{sub 2} QDs may involve the complete breakup around the defects and edges during the reaction of Li{sub x}MoS{sub 2} with water and its following ultrasonication process. The multiply exfoliation make the MoS{sub 2} fragile and easier to break up. After the third exfoliation, a large number of monolayer MoS{sub 2} QDs is formed. The as-prepared MoS{sub 2} QDs show photoluminescence (PL) inactive due to the existence of 1T phase. After heating treatment, the PL intensity excited at 300 nm is enhanced by five times. The MoS{sub 2} QDs solution has an excitation-dependent luminescence emission which shifts to longer wavelengths when the excitation wavelength changes from 280 nm to 370 nm. The optical properties are explored based on the quantum confinement and edge effect.

  5. Diphtheria toxin translocation across cellular membranes is regulated by sphingolipids

    International Nuclear Information System (INIS)

    Spilsberg, Bjorn; Hanada, Kentaro; Sandvig, Kirsten

    2005-01-01

    Diphtheria toxin is translocated across cellular membranes when receptor-bound toxin is exposed to low pH. To study the role of sphingolipids for toxin translocation, both a mutant cell line lacking the first enzyme in de novo sphingolipid synthesis, serine palmitoyltransferase, and a specific inhibitor of the same enzyme, myriocin, were used. The serine palmitoyltransferase-deficient cell line (LY-B) was found to be 10-15 times more sensitive to diphtheria toxin than the genetically complemented cell line (LY-B/cLCB1) and the wild-type cell line (CHO-K1), both when toxin translocation directly across the plasma membrane was induced by exposing cells with surface-bound toxin to low pH, and when the toxin followed its normal route via acidified endosomes into the cytosol. Toxin binding was similar in these three cell lines. Furthermore, inhibition of serine palmitoyltransferase activity by addition of myriocin sensitized the two control cell lines (LY-B/cLCB1 and CHO-K1) to diphtheria toxin, whereas, as expected, no effect was observed in cells lacking serine palmitoyltransferase (LY-B). In conclusion, diphtheria toxin translocation is facilitated by depletion of membrane sphingolipids

  6. Toxins for Transgenic Resistance to Hemipteran Pests

    Science.gov (United States)

    Chougule, Nanasaheb P.; Bonning, Bryony C.

    2012-01-01

    The sap sucking insects (Hemiptera), which include aphids, whiteflies, plant bugs and stink bugs, have emerged as major agricultural pests. The Hemiptera cause direct damage by feeding on crops, and in some cases indirect damage by transmission of plant viruses. Current management relies almost exclusively on application of classical chemical insecticides. While the development of transgenic crops expressing toxins derived from the bacterium Bacillus thuringiensis (Bt) has provided effective plant protection against some insect pests, Bt toxins exhibit little toxicity against sap sucking insects. Indeed, the pest status of some Hemiptera on Bt-transgenic plants has increased in the absence of pesticide application. The increased pest status of numerous hemipteran species, combined with increased prevalence of resistance to chemical insecticides, provides impetus for the development of biologically based, alternative management strategies. Here, we provide an overview of approaches toward transgenic resistance to hemipteran pests. PMID:22822455

  7. Electrochemically exfoliated graphene anodes with enhanced biocurrent production in single-chamber air-breathing microbial fuel cells.

    Science.gov (United States)

    Najafabadi, Amin Taheri; Ng, Norvin; Gyenge, Előd

    2016-07-15

    Microbial fuel cells (MFCs) present promising options for environmentally sustainable power generation especially in conjunction with waste water treatment. However, major challenges remain including low power density, difficult scale-up, and durability of the cell components. This study reports enhanced biocurrent production in a membrane-free MFC, using graphene microsheets (GNs) as anode and MnOx catalyzed air cathode. The GNs are produced by ionic liquid assisted simultaneous anodic and cathodic electrochemical exfoliation of iso-molded graphite electrodes. The GNs produced by anodic exfoliation increase the MFC peak power density by over 300% compared to plain carbon cloth (i.e., 2.85Wm(-2) vs 0.66Wm(-2), respectively), and by 90% compared to conventional carbon black (i.e., Vulcan XC-72) anode. These results exceed previously reported power densities for graphene-containing MFC anodes. The fuel cell polarization results are corroborated by electrochemical impedance spectroscopy indicating three times lower charge transfer resistance for the GN anode. Material characterizations suggest that the best performing GN samples were of relatively smaller size (~500nm), with higher levels of ionic liquid induced surface functionalization during the electrochemical exfoliation process. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Exfoliation and van der Waals heterostructure assembly of intercalated ferromagnet Cr1/3TaS2

    Science.gov (United States)

    Yamasaki, Yuji; Moriya, Rai; Arai, Miho; Masubuchi, Satoru; Pyon, Sunseng; Tamegai, Tsuyoshi; Ueno, Keiji; Machida, Tomoki

    2017-12-01

    Ferromagnetic van der Waals (vdW) materials are in demand for spintronic devices with all-two-dimensional-materials heterostructures. Here, we demonstrate mechanical exfoliation of magnetic-atom-intercalated transition metal dichalcogenide Cr1/3TaS2 from its bulk crystal; previously such intercalated materials were thought difficult to exfoliate. Magnetotransport in exfoliated tens-of-nanometres-thick flakes revealed ferromagnetic ordering below its Curie temperature T C ~ 110 K as well as strong in-plane magnetic anisotropy; these are identical to its bulk properties. Further, van der Waals heterostructure assembly of Cr1/3TaS2 with another intercalated ferromagnet Fe1/4TaS2 is demonstrated using a dry-transfer method. The fabricated heterojunction composed of Cr1/3TaS2 and Fe1/4TaS2 with a native Ta2O5 oxide tunnel barrier in between exhibits tunnel magnetoresistance (TMR), revealing possible spin injection and detection with these exfoliatable ferromagnetic materials through the vdW junction.

  9. Tunable UV-visible absorption of SnS2 layered quantum dots produced by liquid phase exfoliation.

    Science.gov (United States)

    Fu, Xiao; Ilanchezhiyan, P; Mohan Kumar, G; Cho, Hak Dong; Zhang, Lei; Chan, A Sattar; Lee, Dong J; Panin, Gennady N; Kang, Tae Won

    2017-02-02

    4H-SnS 2 layered crystals synthesized by a hydrothermal method were used to obtain via liquid phase exfoliation quantum dots (QDs), consisting of a single layer (SLQDs) or multiple layers (MLQDs). Systematic downshift of the peaks in the Raman spectra of crystals with a decrease in size was observed. The bandgap of layered QDs, estimated by UV-visible absorption spectroscopy and the tunneling current measurements using graphene probes, increases from 2.25 eV to 3.50 eV with decreasing size. 2-4 nm SLQDs, which are transparent in the visible region, show selective absorption and photosensitivity at wavelengths in the ultraviolet region of the spectrum while larger MLQDs (5-90 nm) exhibit a broad band absorption in the visible spectral region and the photoresponse under white light. The results show that the layered quantum dots obtained by liquid phase exfoliation exhibit well-controlled and regulated bandgap absorption in a wide tunable wavelength range. These novel layered quantum dots prepared using an inexpensive method of exfoliation and deposition from solution onto various substrates at room temperature can be used to create highly efficient visible-blind ultraviolet photodetectors and multiple bandgap solar cells.

  10. Chemically exfoliated Mo S2 layers: Spectroscopic evidence for the semiconducting nature of the dominant trigonal metastable phase

    Science.gov (United States)

    Pal, Banabir; Singh, Anjali; Sharada, G.; Mahale, Pratibha; Kumar, Abhinav; Thirupathaiah, S.; Sezen, H.; Amati, M.; Gregoratti, Luca; Waghmare, Umesh V.; Sarma, D. D.

    2017-11-01

    A metastable trigonal phase, existing only as small patches on a chemically exfoliated few-layered, thermodynamically stable 1 H phase of Mo S2 , is believed to critically influence the properties of Mo S2 -based devices. The electronic structure of this metastable phase is little understood in the absence of a direct experimental investigation of its electronic properties, complicated further by conflicting claims from theoretical investigations. We address this issue by investigating the electronic structure of this minority phase in chemically exfoliated Mo S2 few-layered systems by enhancing its contributions with the use of highly spatially resolved (≤120 nm resolution) photoemission spectroscopy and Raman spectroscopy in conjunction with state-of-the-art electronic structure calculations. Based on these results, we establish that the ground state of this phase, arrived at by the chemical exfoliation of Mo S2 using the usual Li intercalation technique, is a small gap (˜90 ±40 meV ) semiconductor in contrast to most claims in the literature; we also identify the specific trigonal structure it has among many suggested ones.

  11. Fabrication of fluorographene nanosheets with high yield and good quality based on supercritical fluid-phase exfoliation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qi; Ji, Yan; Zhang, Danying; Shi, Jia [Nanjing University of Science and Technology, Key Laboratory of Soft Chemistry and Functional Materials, College of Chemical Engineering (China); Xiao, Yinghong, E-mail: yhxiao@njnu.edu.cn [Nanjing Normal University, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, College of Chemistry and Materials Science (China); Che, Jianfei, E-mail: xiaoche@mail.njust.edu.cn [Nanjing University of Science and Technology, Key Laboratory of Soft Chemistry and Functional Materials, College of Chemical Engineering (China)

    2016-07-15

    This article presents a novel and simple method of supercritical fluid-phase exfoliation to fabricate fluorographene (FG) nanosheets with high yield and good quality. After soaking with supercritical CO{sub 2} and glycol at 10 MPa and 50 °C for 24 h, fluoride graphite powder was exfoliated by the intercalated CO{sub 2} and glycol molecules during an abrupt depressurization step. Here, supercritical CO{sub 2} acted as a penetrant and glycol acted as a “molecular wedge” to exfoliate fluoride graphite very well. The properties of FG nanosheets were detected by TEM, AFM, UV spectra, FTIR, XPS, Raman spectra, and XRD, which show the possibility of producing thickness-controlled FG nanosheets by varying numbers of supercritical CO{sub 2} process and the high yield of pure FG nanosheets of 32 wt%, four times higher than that of the sample treated only by the traditional method of sonication. Its simplicity, high productivity, low cost, and short processing time make this technique suitable for large-scale manufacturing of FG nanosheets.

  12. Exfoliation rate of mammary epithelial cells in milk on bovine mastitis caused by Staphylococcus aureus is associated with bacterial load.

    Science.gov (United States)

    Nagasawa, Yuya; Kiku, Yoshio; Sugawara, Kazue; Tanabe, Fuyuko; Hayashi, Tomohito

    2018-01-01

    The exfoliation rate of mammary epithelial cells (MECs) in milk is affected by physiological, breeding and environmental factors. Little is known about the relationship between the MEC exfoliation into milk and mammary-infected Staphylococcus aureus (S. aureus) load on bovine mastitis caused by S. aureus. The aim of this study was to investigate the relationship between S. aureus load and the proportion of MEC exfoliation in milk using five substantial bovine mastitis models. In 64 randomly extracted milk samples from udders at 3-21 days after S. aureus infusion, there were various samples with different numbers of S. aureus counts and somatic cell counts. No significant correlations were found between the S. aureus counts and somatic cell count (r = 0.338). In contrast, a significant correlation was noted between S. aureus counts and the proportion of cytokeratin-positive cells in the milk from the infused udders (r = 0.734, P mastitis udders caused by S. aureus may contribute to reduced milk yield. © 2017 Japanese Society of Animal Science.

  13. In Situ Exfoliation of Graphene in Epoxy Resins: A Facile Strategy to Efficient and Large Scale Graphene Nanocomposites.

    Science.gov (United States)

    Li, Yan; Zhang, Han; Crespo, Maria; Porwal, Harshit; Picot, Olivier; Santagiuliana, Giovanni; Huang, Zhaohui; Barbieri, Ettore; Pugno, Nicola M; Peijs, Ton; Bilotti, Emiliano

    2016-09-14

    Any industrial application aiming at exploiting the exceptional properties of graphene in composites or coatings is currently limited by finding viable production methods for large volumes of good quality and high aspect ratio graphene, few layer graphene (FLG) or graphite nanoplatelets (GNP). Final properties of the resulting composites are inherently related to those of the initial graphitic nanoparticles, which typically depend on time-consuming, resource-demanding and/or low yield liquid exfoliation processes. In addition, efficient dispersion of these nanofillers in polymer matrices, and their interaction, is of paramount importance. Here we show that it is possible to produce graphene/epoxy nanocomposites in situ and with high conversion of graphite to FLG/GNP through the process of three-roll milling (TRM), without the need of any additives, solvents, compatibilisers or chemical treatments. This readily scalable production method allows for more than 5 wt % of natural graphite (NG) to be directly exfoliated into FLG/GNP and dispersed in an epoxy resin. The in situ exfoliated graphitic nanoplatelets, with average aspect ratios of 300-1000 and thicknesses of 5-17 nm, were demonstrated to conferee exceptional enhancements in mechanical and electrical properties to the epoxy resin. The above conclusions are discussed and interpreted in terms of simple analytical models.

  14. Liquid-phase exfoliated graphene self-assembled films: Low-frequency noise and thermal-electric characterization

    International Nuclear Information System (INIS)

    Tubon Usca, G.; Hernandez-Ambato, J.; Pace, C.; Caputi, L.S.; Tavolaro, A.

    2016-01-01

    Highlights: • Graphene was exfoliated in liquid phase also in the presence of zeolite 4A. • Films were obtained by drop-casting. • SEM, Raman, low-frequency noise and thermal electric measurements show that the presence of zeolite improves the quality of the FLG films. - Abstract: In few years, graphene has become a revolutionary material, leading not only to applications in various fields such as electronics, medicine and environment, but also to the production of new types of 2D materials. In this work, Liquid Phase Exfoliation (LPE) was applied to natural graphite by brief sonication or mixer treatment in suitable solvents, in order to produce Few Layers Graphene (FLG) suspensions. Additionally, zeolite 4A (Z4A) was added during the production of FLG flakes-based inks, with the aim of aiding the exfoliation process. Conductive films were obtained by drop casting three types of suspensions over Al 2 O 3 substrates with interdigitated electrodes, with total channel surface of 1.39 mm 2 . The morphology characterization resulted in the verification of the presence of thin self-assembled flakes. Raman studies gave evidence of 4 to 10 layers graphene flakes. Electrical measurements were performed to state the Low-Frequency Noise and Thermal-Electric characteristics of the samples. We observe interesting relations between sample preparation procedures and electrical properties.

  15. Exfoliation of graphene flake from SiC substrate using hydrogen injection; a first-principle study

    Science.gov (United States)

    Lee, Bora; Han, Seungwu; Kim, Yong-Sung

    2009-03-01

    Recently there is an immense interest in studying graphene for investigating its unique electronic properties as well as practical applications to nanoscale devices. Up to now there are two methods to obtain graphene layers. The first one is a mechanical method in which the single graphene sheet is split off the bulk graphite crystals using adhesives. The other method is graphitization of SiC surfaces by annealing at elevated temperatures. Even though the latter approach can provide a graphene layer in a more controlled way, the exfoliation of the graphene layer still poses a big challenge. In this presentation, based on the first-principles results, we propose a novel exfoliation method using hydrogen. As a model system, the 6H-SiC(0001) 4x4 cell is used, which corresponds to the 3x3 graphene cell. We calculate the binding energy of single hydrogen atom in various places; above and below graphene surface and inside the first SiC layer. The binding energies of hydrogen are calculated for different coverages. It is found that at high coverages, the hydrogen atoms prefer to bind below the graphene surface, cutting the graphene-SiC bonds. This means that the graphene can be exfoliated in the hydrogen-rich environment. The detailed analysis including the electronic structures will be presented.

  16. Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe2 Films

    Energy Technology Data Exchange (ETDEWEB)

    Link, Elisa M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nanayakkara, Sanjini U [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Todt, Michael A. [Colorado State University; Isenberg, Allan E. [Colorado State University; Sambur, Justin B. [Colorado State University

    2018-03-06

    Semiconducting transition-metal dichalcogenide (TMD) nanoflake thin films are promising large-area electrodes for photo-electrochemical solar energy conversion applications. However, their energy conversion efficiencies are typically much lower than those of bulk electrodes. It is unclear to what extent this efficiency gap stems from differences among nanoflakes (e.g., area, thickness, and surface structural features). It is also unclear whether individual exfoliated nanoflakes can achieve energy conversion efficiencies similar to those of bulk crystals. Here, we use a single-nanoflake photo-electrochemical approach to show that there are both highly active and completely inactive nanoflakes within a film. For the exfoliated MoSe2 samples studied herein, 7% of nanoflakes are highly active champions, whose photocurrent efficiency exceeds that of the bulk crystal. However, 66% of nanoflakes are inactive spectators, which are mostly responsible for the overall lower photocurrent efficiency compared to the bulk crystal. The photocurrent collection efficiency increases with nanoflake area and decreases more at perimeter edges than at interior step edges. These observations, which are hidden in ensemble-level measurements, reveal the underlying performance issues of exfoliated TMD electrodes for photo-electrochemical energy conversion applications.

  17. Therapeutic Approaches of Botulinum Toxin in Gynecology.

    Science.gov (United States)

    Moga, Marius Alexandru; Dimienescu, Oana Gabriela; Bălan, Andreea; Scârneciu, Ioan; Barabaș, Barna; Pleș, Liana

    2018-04-21

    Botulinum toxins (BoNTs) are produced by several anaerobic species of the genus Clostridium and, although they were originally considered lethal toxins, today they find their usefulness in the treatment of a wide range of pathologies in various medical specialties. Botulinum neurotoxin has been identified in seven different isoforms (BoNT-A, BoNT-B, BoNT-C, BoNT-D, BoNT-E, BoNT-F, and BoNT-G). Neurotoxigenic Clostridia can produce more than 40 different BoNT subtypes and, recently, a new BoNT serotype (BoNT-X) has been reported in some studies. BoNT-X has not been shown to actually be an active neurotoxin despite its catalytically active LC, so it should be described as a putative eighth serotype. The mechanism of action of the serotypes is similar: they inhibit the release of acetylcholine from the nerve endings but their therapeutically potency varies. Botulinum toxin type A (BoNT-A) is the most studied serotype for therapeutic purposes. Regarding the gynecological pathology, a series of studies based on the efficiency of its use in the treatment of refractory myofascial pelvic pain, vaginism, dyspareunia, vulvodynia and overactive bladder or urinary incontinence have been reported. The current study is a review of the literature regarding the efficiency of BoNT-A in the gynecological pathology and on the long and short-term effects of its administration.

  18. Therapeutic Approaches of Botulinum Toxin in Gynecology

    Directory of Open Access Journals (Sweden)

    Marius Alexandru Moga

    2018-04-01

    Full Text Available Botulinum toxins (BoNTs are produced by several anaerobic species of the genus Clostridium and, although they were originally considered lethal toxins, today they find their usefulness in the treatment of a wide range of pathologies in various medical specialties. Botulinum neurotoxin has been identified in seven different isoforms (BoNT-A, BoNT-B, BoNT-C, BoNT-D, BoNT-E, BoNT-F, and BoNT-G. Neurotoxigenic Clostridia can produce more than 40 different BoNT subtypes and, recently, a new BoNT serotype (BoNT-X has been reported in some studies. BoNT-X has not been shown to actually be an active neurotoxin despite its catalytically active LC, so it should be described as a putative eighth serotype. The mechanism of action of the serotypes is similar: they inhibit the release of acetylcholine from the nerve endings but their therapeutically potency varies. Botulinum toxin type A (BoNT-A is the most studied serotype for therapeutic purposes. Regarding the gynecological pathology, a series of studies based on the efficiency of its use in the treatment of refractory myofascial pelvic pain, vaginism, dyspareunia, vulvodynia and overactive bladder or urinary incontinence have been reported. The current study is a review of the literature regarding the efficiency of BoNT-A in the gynecological pathology and on the long and short-term effects of its administration.

  19. The Biology of the Cytolethal Distending Toxins

    Directory of Open Access Journals (Sweden)

    Teresa Frisan

    2011-03-01

    Full Text Available The cytolethal distending toxins (CDTs, produced by a variety of Gram-negative pathogenic bacteria, are the first bacterial genotoxins described, since they cause DNA damage in the target cells. CDT is an A-B2 toxin, where the CdtA and CdtC subunits are required to mediate the binding on the surface of the target cells, allowing internalization of the active CdtB subunit, which is functionally homologous to the mammalian deoxyribonuclease I. The nature of the surface receptor is still poorly characterized, however binding of CDT requires intact lipid rafts, and its internalization occurs via dynamin-dependent endocytosis. The toxin is retrograde transported through the Golgi complex and the endoplasmic reticulum, and subsequently translocated into the nuclear compartment, where it exerts the toxic activity. Cellular intoxication induces DNA damage and activation of the DNA damage responses, which results in arrest of the target cells in the G1 and/or G2 phases of the cell cycle and activation of DNA repair mechanisms. Cells that fail to repair the damage will senesce or undergo apoptosis. This review will focus on the well-characterized aspects of the CDT biology and discuss the questions that still remain unanswered.

  20. Perfringolysin O: The Underrated Clostridium perfringens Toxin?

    Science.gov (United States)

    Verherstraeten, Stefanie; Goossens, Evy; Valgaeren, Bonnie; Pardon, Bart; Timbermont, Leen; Haesebrouck, Freddy; Ducatelle, Richard; Deprez, Piet; Wade, Kristin R; Tweten, Rodney; Van Immerseel, Filip

    2015-05-14

    The anaerobic bacterium Clostridium perfringens expresses multiple toxins that promote disease development in both humans and animals. One such toxin is perfringolysin O (PFO, classically referred to as θ toxin), a pore-forming cholesterol-dependent cytolysin (CDC). PFO is secreted as a water-soluble monomer that recognizes and binds membranes via cholesterol. Membrane-bound monomers undergo structural changes that culminate in the formation of an oligomerized prepore complex on the membrane surface. The prepore then undergoes conversion into the bilayer-spanning pore measuring approximately 250-300 Å in diameter. PFO is expressed in nearly all identified C. perfringens strains and harbors interesting traits that suggest a potential undefined role for PFO in disease development. Research has demonstrated a role for PFO in gas gangrene progression and bovine necrohemorrhagic enteritis, but there is limited data available to determine if PFO also functions in additional disease presentations caused by C. perfringens. This review summarizes the known structural and functional characteristics of PFO, while highlighting recent insights into the potential contributions of PFO to disease pathogenesis.

  1. Perfringolysin O: The Underrated Clostridium perfringens Toxin?

    Directory of Open Access Journals (Sweden)

    Stefanie Verherstraeten

    2015-05-01

    Full Text Available The anaerobic bacterium Clostridium perfringens expresses multiple toxins that promote disease development in both humans and animals. One such toxin is perfringolysin O (PFO, classically referred to as θ toxin, a pore-forming cholesterol-dependent cytolysin (CDC. PFO is secreted as a water-soluble monomer that recognizes and binds membranes via cholesterol. Membrane-bound monomers undergo structural changes that culminate in the formation of an oligomerized prepore complex on the membrane surface. The prepore then undergoes conversion into the bilayer-spanning pore measuring approximately 250–300 Å in diameter. PFO is expressed in nearly all identified C. perfringens strains and harbors interesting traits that suggest a potential undefined role for PFO in disease development. Research has demonstrated a role for PFO in gas gangrene progression and bovine necrohemorrhagic enteritis, but there is limited data available to determine if PFO also functions in additional disease presentations caused by C. perfringens. This review summarizes the known structural and functional characteristics of PFO, while highlighting recent insights into the potential contributions of PFO to disease pathogenesis.

  2. EGA Protects Mammalian Cells from Clostridium difficile CDT, Clostridium perfringens Iota Toxin and Clostridium botulinum C2 Toxin.

    Science.gov (United States)

    Schnell, Leonie; Mittler, Ann-Katrin; Sadi, Mirko; Popoff, Michel R; Schwan, Carsten; Aktories, Klaus; Mattarei, Andrea; Azarnia Tehran, Domenico; Montecucco, Cesare; Barth, Holger

    2016-04-01

    The pathogenic bacteria Clostridium difficile, Clostridium perfringens and Clostridium botulinum produce the binary actin ADP-ribosylating toxins CDT, iota and C2, respectively. These toxins are composed of a transport component (B) and a separate enzyme component (A). When both components assemble on the surface of mammalian target cells, the B components mediate the entry of the A components via endosomes into the cytosol. Here, the A components ADP-ribosylate G-actin, resulting in depolymerization of F-actin, cell-rounding and eventually death. In the present study, we demonstrate that 4-bromobenzaldehyde N-(2,6-dimethylphenyl)semicarbazone (EGA), a compound that protects cells from multiple toxins and viruses, also protects different mammalian epithelial cells from all three binary actin ADP-ribosylating toxins. In contrast, EGA did not inhibit the intoxication of cells with Clostridium difficile toxins A and B, indicating a possible different entry route for this toxin. EGA does not affect either the binding of the C2 toxin to the cells surface or the enzyme activity of the A components of CDT, iota and C2, suggesting that this compound interferes with cellular uptake of the toxins. Moreover, for C2 toxin, we demonstrated that EGA inhibits the pH-dependent transport of the A component across cell membranes. EGA is not cytotoxic, and therefore, we propose it as a lead compound for the development of novel pharmacological inhibitors against clostridial binary actin ADP-ribosylating toxins.

  3. EGA Protects Mammalian Cells from Clostridium difficile CDT, Clostridium perfringens Iota Toxin and Clostridium botulinum C2 Toxin

    Science.gov (United States)

    Schnell, Leonie; Mittler, Ann-Katrin; Sadi, Mirko; Popoff, Michel R.; Schwan, Carsten; Aktories, Klaus; Mattarei, Andrea; Tehran, Domenico Azarnia; Montecucco, Cesare; Barth, Holger

    2016-01-01

    The pathogenic bacteria Clostridium difficile, Clostridium perfringens and Clostridium botulinum produce the binary actin ADP-ribosylating toxins CDT, iota and C2, respectively. These toxins are composed of a transport component (B) and a separate enzyme component (A). When both components assemble on the surface of mammalian target cells, the B components mediate the entry of the A components via endosomes into the cytosol. Here, the A components ADP-ribosylate G-actin, resulting in depolymerization of F-actin, cell-rounding and eventually death. In the present study, we demonstrate that 4-bromobenzaldehyde N-(2,6-dimethylphenyl)semicarbazone (EGA), a compound that protects cells from multiple toxins and viruses, also protects different mammalian epithelial cells from all three binary actin ADP-ribosylating toxins. In contrast, EGA did not inhibit the intoxication of cells with Clostridium difficile toxins A and B, indicating a possible different entry route for this toxin. EGA does not affect either the binding of the C2 toxin to the cells surface or the enzyme activity of the A components of CDT, iota and C2, suggesting that this compound interferes with cellular uptake of the toxins. Moreover, for C2 toxin, we demonstrated that EGA inhibits the pH-dependent transport of the A component across cell membranes. EGA is not cytotoxic, and therefore, we propose it as a lead compound for the development of novel pharmacological inhibitors against clostridial binary actin ADP-ribosylating toxins. PMID:27043629

  4. Electron-beam nanosculpting and materials analysis of exfoliated bismuth selenide

    Science.gov (United States)

    Friedensen, Sarah; Parkin, William; Mlack, Jerome; Drndic, Marija

    We report on nanosculpting Bi2Se3 with a highly-focused electron beam in a scanning transmission electron microscope (STEM). Exfoliated Bi2Se3 flakes were transferred onto silicon nitride TEM windows and structures at least 100 nm by 100 nm in size were selected for shaping. Focused ion beam (FIB) cutting was used to carve larger features into the structures and provide preliminary thinning if desired. Then, a STEM probe was used to sculpt more delicate features, including nanowires of approximately 20 nm in width, point contacts, and T-shaped junctions. During STEM cutting, the structures were monitored using energy dispersive X-ray spectroscopy (EDS) mapping, electron diffraction, and high-resolution imaging, and it was found that the crystal structure remains largely intact. This process opens the way for in-situ determination of the effects of size and structure on electrical and thermal properties of Bi2Se3 and fabrication of nanodevices with more elaborate geometries than can be achieved with growth methods alone.

  5. Assessment of nuclear abnormalities in exfoliated cells from the oral epithelium of mobile phone users.

    Science.gov (United States)

    Souza, Leonardo da Cunha Menezes; Cerqueira, Eneida de Moraes Marcílio; Meireles, José Roberto Cardoso

    2014-06-01

    Transmission and reception of mobile telephony signals take place through electromagnetic wave radiation, or electromagnetic radiofrequency fields, between the mobile terminal and the radio base station. Based on reports in the literature on adverse effects from exposure to this type of radiation, the objective of this study was to evaluate the genotoxic and cytotoxic potential of such exposure, by means of the micronucleus test on exfoliated cells from the oral epithelium. The sample included 45 individuals distributed in 3 groups according to the amount of time in hours per week (t) spent using mobile phones: group I, t > 5 h; group II, t > 1 h and ≤ 5 h; and group III, t ≤ 1 h. Cells from the oral mucosa were analyzed to assess the numbers of micronuclei, broken egg structures and degenerative nuclear abnormalities indicative of apoptosis (condensed chromatin, karyorrhexis and pyknosis) or necrosis (karyolysis in addition to these changes). The occurrences of micronuclei and degenerative nuclear abnormalities did not differ between the groups, but the number of broken egg (structures that may be associated with gene amplification) was significantly greater in the individuals in group I (p < 0.05).

  6. Raman Spectroscopy Study of Annealing-Induced Effects on Graphene Prepared by Micromechanical Exfoliation

    International Nuclear Information System (INIS)

    Song, Ji Eun; Ko, Taeg Yeoung; Ryu, Sun Min

    2010-01-01

    Raman spectroscopy was combined with AFM to investigate the effects of thermal annealing on the graphene samples prepared by the widely used micromechanical exfoliation method. Following annealing cycles, adhesive residues were shown to contaminate graphene sheets with thin molecular layers in their close vicinity causing several new intense Raman bands. Detailed investigation shows that the Raman scattering is very strong and may be enhanced by the interaction with graphene. Although the current study does not pinpoint detailed origins for the new Raman bands, the presented results stress that graphene prepared by the above method may require extra cautions when treated with heat or possibly solvents. Since its isolation from graphite, graphene has drawn a lot of experimental and theoretical research. These efforts have been mostly in pursuit of various applications such as electronics, sensors, stretchable transparent electrodes, and various composite materials. To accomplish such graphene-based applications, understanding chemical interactions of this new material with environments during various processing treatments will become more important. Since thermal annealing is widely used in various research of graphene for varying purposes such as cleaning, nanostructuring, reactions, etc., understanding annealing-induced effects is prerequisite to many fundamental studies of graphene. In this regard, it is to be noted that there has been a controversy on the cause of the annealing-induced hole doping in graphene

  7. Is mobile phone radiation genotoxic? An analysis of micronucleus frequency in exfoliated buccal cells.

    Science.gov (United States)

    de Oliveira, F M; Carmona, A M; Ladeira, C

    2017-10-01

    Electromagnetic fields (EMF) are classified as "possibly carcinogenic" by the International Agency for Research on Cancer (IARC). Some publications have reported associations between EMF exposure and DNA damage, but many other studies contradict such findings. Cytomorphological changes, such as micronuclei (MN), indicative of genomic damage, are biomarkers of genotoxicity. To test whether mobile phone-associated EMF exposure affects the MN frequency in exfoliated buccal cells, we obtained cells smears from the left and right inner cheeks of healthy mobile phone users, aged 18-30 (n=86), who also completed a characterization survey. MN frequencies were tested for potential confounding factors and for duration of phone use and preferential side of mobile phone use. No relationship was observed between MN frequency and duration of mobile phone use in daily calls. Cells ipsilateral to mobile phone use did not present a statistically significantly higher MN frequency, compared to cells contralateral to exposure. A highly statistically significant (pphone-associated EMF do not to induce MN formation in buccal cells at the observed exposure levels. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. The application of exfoliated graphite electrode in the electrochemical degradation of p-nitrophenol in water.

    Science.gov (United States)

    Ntsendwana, Bulelwa; Peleyeju, Moses G; Arotiba, Omotayo A

    2016-01-01

    We report the application of exfoliated graphite (EG) as an electrode material in the electrochemical degradation of p-nitrophenol in water. Bulk electrolysis (degradation) of p-nitrophenol was carried out at a potential of 2.0 V (vs. Ag/AgCl) in the presence of 0.1 M Na2SO4 supporting electrolyte, while UV-Vis spectrophotometry was used to monitor the degradation efficiency. An initial p-nitrophenol load concentration of 0.2 mM for 3 h electrolysis time was studied under the optimized conditions of pH 7, and 10 mAcm(-2) current density. The electro-degradation reaction displayed a pseudo-first-order kinetic behavior with a rate constant (k(r)) of 11×10(-3) min(-1). The removal efficiency was found to be 91.5%. Chromatography coupled with time of flight mass spectrometry revealed p-benzoquinone as a major intermediate product. These results demonstrate the potential and viability of electrochemical technology as an alternative approach to water treatment using a low cost graphite electrode.

  9. Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water.

    Directory of Open Access Journals (Sweden)

    Nicklas Blomquist

    Full Text Available The number of applications based on graphene, few-layer graphene, and nanographite is rapidly increasing. A large-scale process for production of these materials is critically needed to achieve cost-effective commercial products. Here, we present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. This process, based on hydrodynamic tube shearing, produced nanometer-thick and micrometer-wide flakes of nanographite with a production rate exceeding 500 gh-1 with an energy consumption about 10 Whg-1. In addition, to facilitate large-area coating, we show that the nanographite can be mixed with nanofibrillated cellulose in the process to form highly conductive, robust and environmentally friendly composites. This composite has a sheet resistance below 1.75 Ω/sq and an electrical resistivity of 1.39×10-4 Ωm and may find use in several applications, from supercapacitors and batteries to printed electronics and solar cells. A batch of 100 liter was processed in less than 4 hours. The design of the process allow scaling to even larger volumes and the low energy consumption indicates a low-cost process.

  10. Liquid-Phase Co-Exfoliated Graphene/MoS2 Nanocomposite for Methanol Gas Sensing.

    Science.gov (United States)

    Zhang, Shao-Lin; Yue, Hongyan; Liang, Xishuang; Yang, Woo-Chul

    2015-10-01

    We developed an efficient method to co-exfoliate graphite and MoS2 to fabricate graphene/MoS2 nanocomposite. The size, morphology, and crystal structure of the graphene/MoS2 nanocomposite were carefully examined. The as-prepared graphene/MoS2 nanocomposite was fabricated into thin film sensor by a facile drop casting method and tested with methanol gas in various concentrations. The sensitivity, response time, and repeatability of the graphene/MoS2 nanocomposite sensor towards methanol gas were systematically investigated. A pure MoS2 based thin film sensor was also prepared and compared with the nanocomposite sensor to better understand the synergetic effect in the sensing performance. Our research demonstrated that compositing MoS2 with graphene could overcome the shortcoming of MoS2 as a sensor material and bring in a promising gas-sensing performance with a quicker response/recovery time and an enhanced sensitivity. Moreover, this composited material with a distinct structure and an excellent electronic property is expected to have potential application in various fields, such as optoelectronic.

  11. Nanostructured MnO2/exfoliated graphite composite electrode as supercapacitors

    International Nuclear Information System (INIS)

    Yang Yanjing; Liu Enhui; Li Limin; Huang Zhengzheng; Shen Haijie; Xiang Xiaoxia

    2009-01-01

    Nanostructured manganese oxides/exfoliated graphite composite (MnO 2 /EG) were synthesized via a new sol-gel route. Scanning electron microscope (SEM) was employed for surface morphology and X-ray diffraction (XRD) was used for structure characterization. Cyclic voltammetry (CV), galvanostatic charge/discharge, and the electrochemical impedance measurements were applied to investigate the electrochemical performance of the MnO 2 /EG composite electrodes. When used for electrodes of supercapacitors, the as-prepared MnO 2 /EG and the pure MnO 2 exhibited excellent capacitance characteristics in 6 mol L -1 KOH electrolyte and showed high specific capacitance values of 398 F g -1 and 326 F g -1 ,respectively, at a scan rate of 10 mV s -1 . The galvanostatic charge-discharge measurements showed approximately 0.5% loss of capacitance after 500 cycles, and charge-discharge efficiency above 99%. In addition, the synthesized nanomaterial showed a good reversibility and cycling stability.

  12. Physico-Chemical Properties of Personal Care Products Containing Guava Scrub Granules as Exfoliating Agent

    International Nuclear Information System (INIS)

    Zahariah Ismail; Mohd Fadlly Jumadi; Nurdiyana Mohamed Johari

    2015-01-01

    Treated guava scrub granules (GSG) as an exfoliating agent were obtained from the decanter waste at Sime Darby Food and Beverages, Sungai Wangi, Perak (SDFB). The treated GSG and tocotrienol were the main active ingredients incorporated in a basic formulation containing 87 % palm-based derivatives. Guava body scrub (GBS) and guava facial scrub (GFS) lotions were developed at skin pH 5.5 and pH 5.6 respectively. Both products were found to be stable for three years due to the liquid crystalline structure in the emulsion system , having small particle size (490 nm and 880 nm) and high zeta potential values (-54 mv and -39 mv). The rheological properties showed that the GBS lotion had a viscosity at 900 Pas and a yield value at 98 Pa, whereas the GFS lotion 60 Pas and 6 Pa viscosity and yield values respectively. The formulations were designed to be soft and flowable, with the firmness force indicated at 111 g and 66 g for GBS lotion and GFS lotion respectively. Efficacy testing on 20 healthy subjects showed a significant decrease of 21 % and 22 % in skin sebum removal for GBS lotion and GFS lotion respectively. (author)

  13. Elastomeric Nanocomposite Based on Exfoliated Graphene Oxide and Its Characteristics without Vulcanization

    Directory of Open Access Journals (Sweden)

    Nasser Abdullah Habib

    2017-01-01

    Full Text Available Rubber nanocomposites have emerged as one of the advanced materials in recent years. The aim of this work was to homogeneously disperse graphene oxide (GO sheets into Nitrile Butadiene Rubber (NBR and investigate the characteristics of GO/NBR nanocomposite without vulcanization. A suitable solvent was found to dissolve dry NBR while GO was exfoliated completely in an aqueous base solution using sonication. GO was dispersed into NBR at different loadings by solution mixing to produce unvulcanized GO/NBR nanocomposites. Scanning Electron Microscopy (SEM, Fourier-Transform Infrared Spectroscopy (FTIR, and X-Ray Diffraction (XRD were used to characterize the samples. Furthermore, mechanical and electrical properties of unvulcanized GO/NBR nanocomposites were carried out to determine the influence of GO on the NBR properties. The results showed that the modulus of GO/NBR nanocomposite at 1 wt% of GO was enhanced by about 238% compared with unfilled NBR. These results provide insight into the properties of unvulcanized GO/NBR nanocomposite for application as coatings or adhesives.

  14. Application of graphene from exfoliation in kitchen mixer allows mechanical reinforcement of PVA/graphene film

    Science.gov (United States)

    Ismail, Zulhelmi; Abdullah, Abu Hannifa; Zainal Abidin, Anis Sakinah; Yusoh, Kamal

    2017-08-01

    Mechanical properties of polyvinyl alcohol (PVA) can be reinforced from the addition of graphene into its matrix. However, pristine graphene lacks solubility in water and thus makes dispersion a challenging task. Notably, functionalisation of graphene is required to accommodate graphene presence in the water. In this work, we have used a kitchen mixer to produce gum Arabic-graphene (GGA) for the first time as filler for mechanical reinforcement of PVA. For the characterisation of exfoliated graphene, mean lateral size of GGA was measured from the imaging by transmission electron microscopy while the mean thickness of graphene was predicted from the obtained spectra by Raman spectroscopy. During the preparation of PVA/graphene film by solution casting, GGA was varied between 0, 0.05, 0.075, 0.10 and 0.15 wt% in concentration. We found that the presence of GGA in PVA improves the tensile stress and elastic modulus about 72-200 and 19-187% from the original values. The data from Halpin-Tsai meanwhile suggested that the mechanical reinforcement of PVA/graphene film is due to the random distribution network of GGA in PVA.

  15. Liquid-Phase Exfoliation into Monolayered BiOBr Nanosheets for Photocatalytic Oxidation and Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hongjian [Beijing; Huang, Hongwei [Beijing; Xu, Kang [Center; Hao, Weichang [Center; Guo, Yuxi [Beijing; Wang, Shuobo [Beijing; Shen, Xiulin [Beijing; Pan, Shaofeng [Beijing; Zhang, Yihe [Beijing

    2017-09-26

    Monolayered photocatalytic materials have attracted huge research interests in terms of their large specific surface area and ample active sites. Sillén-structured layered BiOX (X = Cl, Br, I) casts great prospects owing to their strong photo-oxidation ability and high stability. Fabrication of monolayered BiOX by a facile, low-cost, and scalable approach is highly challenging and anticipated. Herein, we describe the large-scale preparation of monolayered BiOBr nanosheets with a thickness of ~0.85 nm via a readily achievable liquid-phase exfoliation strategy with assistance of formamide at ambient conditions. The as-obtained monolayered BiOBr nanosheets are allowed diverse superiorities, such as enhanced specific surface area, promoted band structure, and strengthened charge separation. Profiting from these benefits, the advanced BiOBr monolayers not only show excellent adsorption and photodegradation performance for treating contaminants, but also demonstrate a greatly promoted photocatalytic activity for CO2 reduction into CO and CH4. Additionally, monolayered BiOI nanosheets have also been obtained by the same synthetic approach. Our work offers a mild and general approach for preparation of monolayered BiOX, and may have huge potential to be extended to the synthesis of other single-layer two-dimensional materials.

  16. In vivo cleansing efficacy of biodegradable exfoliating beads assessed by skin bioengineering techniques.

    Science.gov (United States)

    Kitsongsermthon, J; Duangweang, K; Kreepoke, J; Tansirikongkol, A

    2017-11-01

    The plastic microbeads, used in many cleansers, will be banned in cosmetic and personal care products within 2017 since they are non-degradable and can disturb the living organisms in water reservoirs. Various choices of biodegradable beads are commercially available, but their efficacy has not been proven yet. This study aimed to compare the cleansing efficacy in dirt and sebum removal aspects of three types of exfoliating beads. The gel scrubs with polyethylene (PE) beads, mannan beads or wax beads, were formulated and evaluated for their stability. The in vivo evaluation was done in 38 healthy volunteers and the skin irritation, efficacy for dirt and sebum removal were measured by Mexameter ® , Colorimeter ® , and Sebumeter ® , respectively. The selected gel scrubs did not cause an irritation in any volunteers. The differences in dirt residues between before and after scrubbing were not statistically significant among three gel scrubs and the similar result was also reported in the sebum removal study. All gel scrubs demonstrated the comparable cleansing efficacy in term of dirt and sebum removal. Thus, mannan beads and wax beads may be replaced non-biodegradable PE beads to achieve the similar cleansing effect. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. A Plasma Metabolomic Signature of the Exfoliation Syndrome Involves Amino Acids, Acylcarnitines, and Polyamines.

    Science.gov (United States)

    Leruez, Stéphanie; Bresson, Thomas; Chao de la Barca, Juan M; Marill, Alexandre; de Saint Martin, Grégoire; Buisset, Adrien; Muller, Jeanne; Tessier, Lydie; Gadras, Cédric; Verny, Christophe; Amati-Bonneau, Patrizia; Lenaers, Guy; Gohier, Philippe; Bonneau, Dominique; Simard, Gilles; Milea, Dan; Procaccio, Vincent; Reynier, Pascal

    2018-02-01

    To determine the plasma metabolomic signature of the exfoliative syndrome (XFS), the most common cause worldwide of secondary open-angle glaucoma. We performed a targeted metabolomic study, using the standardized p180 Biocrates Absolute IDQ p180 kit with a QTRAP 5500 mass spectrometer, to compare the metabolomic profiles of plasma from individuals with XFS (n = 16), and an age- and sex-matched control group with cataract (n = 18). A total of 151 metabolites were detected correctly, 16 of which allowed for construction of an OPLS-DA model with a good predictive capability (Q2cum = 0.51) associated with a low risk of over-fitting (permQ2 = -0.48, CV-ANOVA P-value <0.001). The metabolites contributing the most to the signature were octanoyl-carnitine (C8) and decanoyl-carnitine (C10), the branched-chain amino acids (i.e., isoleucine, leucine, and valine), and tyrosine, all of which were at higher concentrations in the XFS group, whereas spermine and spermidine, together with their precursor acetyl-ornithine, were at lower concentrations than in the control group. We identified a significant metabolomic signature in the plasma of individuals with XFS. Paradoxically, this signature, characterized by lower concentrations of the neuroprotective spermine and spermidine polyamines than in controls, partially overlaps the plasma metabolomic profile associated with insulin resistance, despite the absence of evidence of insulin resistance in XFS.

  18. Nuclear anomalies in exfoliated buccal epithelial cells of petrol station attendants in Udaipur, Rajasthan

    Directory of Open Access Journals (Sweden)

    Rashmi Metgud

    2015-01-01

    Full Text Available Aim: The petroleum derivatives consist of a complex mixture of chemical compounds one among which is benzene. Petrol station workers who pump fuel to vehicles absorb the products of fuel fumes and the products of combustion. Materials and Methods: To study the occupational exposure to petroleum derivatives such as benzene, exfoliated buccal cells from 40 petrol station attendants and 40 age-matched control subjects were examined for micronuclei, binucleation, karyorrhexis and karyolysis frequency by using feulgen and Giemsa stains. Statistical evaluation was performed with ANOVA test. Results: In the present study, inter-comparison of mean values for micronuclei, binucleation, karyorrhexis and karyolysis using Fuelgen stain between smokers of study and control group, as well as between smokers and non-smokers of study and control group revealed statistically highly significant results with P value 0.00002 and 0.0001 respectively. Whereas inter comparison between non-smokers of study and control group using Feulgen stain and inter comparison between smokers of study and control group, using Giemsa stain revealed statistically significant results with P value 0.0034 and 0.0004, respectively. Conclusion: This study revealed that the studied individuals belong to a risk group and should periodically undergo biological monitoring and proper care.

  19. The effect of stem cell from human exfoliated deciduous teeth on T lymphocyte proliferation.

    Science.gov (United States)

    Alipour, Razieh; Adib, Minoo; Hashemi-Beni, Batool; Sadeghi, Farzaneh

    2014-01-01

    Mesenchymal stem cells (MSC), a specific type of adult tissue stem cell; have the immunosuppressive effects that make them valuable targets for regenerative medicine and treatment of many human illnesses. Hence, MSC have been the subject of numerous studies. The classical source of MSC is adult bone marrow (BM). Due to many shortcomings of harvesting MSC from BM, finding the alternative sources for MSC is an urgent. Stem cells from human exfoliated deciduous teeth (SHED) are relative new MSC populations that fulfill these criteria but their potential immunosuppressive effect has not been studied enough yet. Thus, in this work the effect of SHED on the proliferation of in vitro activated T lymphocytes were explored. In this study, both mitogen and alloantigen activated T cells were cultured in the presence of different numbers of SHED. In some co-cultures, activated T cells were in direct contact to MSCs and in other co-cultures; they were separated from SHED by a permeable membrane. In all co-cultures, the proliferation of T cells was measured by ELISA Bromodeoxyuridine proliferation assay. In general, our results showed that SHED significantly suppress the proliferation of activated T cells in a dose-dependent manner. Moreover, the suppression was slightly stronger when MSCs were in physical contact to activated T cells. This study showed that SHED likewise other MSC populations can suppress the activation of T lymphocytes, which can be used instead of BM derived MSCs in many investigational and clinical applications.

  20. Polyaniline/partially exfoliated multi-walled carbon nanotubes based nanocomposites for supercapacitors

    International Nuclear Information System (INIS)

    Potphode, Darshna D.; Sivaraman, P.; Mishra, Sarada P.; Patri, Manoranjan

    2015-01-01

    In the present study, polyaniline (PANI)/partially exfoliated multi-walled carbon nanotubes (Px-MWCNT) nanocomposites were investigated for supercapacitor application. Nanocomposites with varying weight/weight ratio of PANI and Px-MWCNT were prepared by in-situ polymerization of aniline over Px-MWCNT. Transmission and scanning electron microscopic analysis showed that the MWCNT was partial unzipped along the length of tubes. The morphology of PANI/Px-MWCNT nanocomposites exhibited wrapping of PANI over Px-MWCNT. Symmetric supercapacitors containing PANI/Px-MWCNT nanocomposites as the electrode material were fabricated. The electrochemical characterization of the nanocomposites was carried by two electrode method (unit cell configuration). Cyclic voltammetric analysis showed a synergistic increase in specific capacitance of the nanocomposites. Charge-discharge cycle study indicated that nanocomposites have greater charge-discharge rate capability than pure PANI. The observed result is attributed to the shorter diffusion length of ions in the nanocomposites as compared to that of pure PANI. The electrochemical impedance spectra of supercapacitors were resolved into real and losscapacitances. The loss capacitance indicated that the time constant of the nanocomposites decreases with increase in the Px-MWCNT content. The supercapacitors showed enhanced stability during continuous charge-discharge cycling as the PX-MWCNT content in the nanocomposites increased. PANI-50 and PANI-25 nanocomposites based supercapacitors exhibited 91% and 93% capacitive retention after 2000 charge-discharge cycle while pure PANI showed only 67% capacitance retention for the same number of cycles

  1. Exfoliation of non-oxidized graphene flakes for scalable conductive film.

    Science.gov (United States)

    Park, Kwang Hyun; Kim, Bo Hyun; Song, Sung Ho; Kwon, Jiyoung; Kong, Byung Seon; Kang, Kisuk; Jeon, Seokwoo

    2012-06-13

    The increasing demand for graphene has required a new route for its mass production without causing extreme damages. Here we demonstrate a simple and cost-effective intercalation based exfoliation method for preparing high quality graphene flakes, which form a stable dispersion in organic solvents without any functionalization and surfactant. Successful intercalation of alkali metal between graphite interlayers through liquid-state diffusion from ternary KCl-NaCl-ZnCl(2) eutectic system is confirmed by X-ray diffraction and X-ray photoelectric spectroscopy. Chemical composition and morphology analyses prove that the graphene flakes preserve their intrinsic properties without any degradation. The graphene flakes remain dispersed in a mixture of pyridine and salts for more than 6 months. We apply these results to produce transparent conducting (∼930 Ω/□ at ∼75% transmission) graphene films using the modified Langmuir-Blodgett method. The overall results suggest that our method can be a scalable (>1 g/batch) and economical route for the synthesis of nonoxidized graphene flakes.

  2. Efficient electrocatalytic performance of thermally exfoliated reduced graphene oxide-Pt hybrid

    Energy Technology Data Exchange (ETDEWEB)

    Antony, Rajini P., E-mail: raji.anna@gmail.com; Preethi, L.K.; Gupta, Bhavana; Mathews, Tom, E-mail: tom@igcar.gov.in; Dash, S.; Tyagi, A.K.

    2015-10-15

    Highlights: • Synthesis of Pt–RGO nanohybrids of very high electrochemically active surface area. • Electrocatalytic activity-cum-stability: ∼10 times that of commercial Pt-C catalyst. • TEM confirms narrow size distribution and excellent dispersion of Pt nanoparticles. • SAED and XRD indicate (1 1 1) orientation of Pt nanoparticles. • Methanol oxidation EIS reveal decrease in charge transfer resistance with potential - Abstract: High quality thermally exfoliated reduced graphene oxide (RGO) nanosheets decorated with platinum nanocrystals have been synthesized using a simple environmentally benign process. The electrocatalytic behaviour of the Pt–RGO nanohybrid for methanol oxidation was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. High resolution transmission electron microscopy shows uniform dispersion of Pt nanoparticles of ∼2–4 nm size. X-ray diffraction and selected area diffraction studies reveal (1 1 1) orientation of the platinum nanoparticles. The cyclic voltammetry and chronoamperometry results indicate higher catalytic activity and stability for Pt–RGO compared to commercial Pt-C. The electrochemical active surface area of Pt–RGO (52.16 m{sup 2}/g) is found to be 1.5 times that of commercial Pt-C. Impedance spectroscopy shows different impedance behaviour at different potential regions, indicating change in methanol oxidation reaction mechanism with potential. The reversal of impedance pattern to the second quadrant, at potentials higher than ∼0.40 V, indicates change in the rate determining reaction.

  3. Efficacy of oral exfoliative cytology in diabetes mellitus patients: a light microscopic and confocal microscopic study.

    Science.gov (United States)

    Gopal, Deepika; Malathi, N; Reddy, B Thirupathi

    2015-03-01

    Diabetes mellitus (DM) has become a global problem. By monitoring the health status of these individuals, diabetic complications can be prevented. We aimed to analyze alterations in the morphology and cytomorphometry of buccal epithelial cells of type 2 DM patients using oral exfoliative cytology technique and determine its importance in public health screening, diagnosis and monitoring of diabetes mellitus. The study was carried out in 100 type 2 DM patients and 30 healthy individuals. Smears were taken from the right buccal mucosa and stained by the Papanicolaou technique. Staining with Acridine orange was carried out to view qualitative changes with confocal laser scanning microscope (LSM-510 Meta). The cytomorphometry was evaluated using IMAGE PRO PLUS 5.5 software with Evolution LC camera. All findings were statistically analyzed. The results showed that with increase in fasting plasma glucose levels, there is significant increase in nuclear area, decrease in cytoplasmic area, and increase in nuclear cytoplasmic ratio (p inclusion, candida and keratinization. In the present study, we found significant alterations in the cytomorphometry and cytomorphology of buccal epithelial cells of type 2 DM patients. This study supports and extends the view that these cellular changes can alert the clinician to the possibility of diabetes and aid in monitoring of diabetes throughout the lifetime of the patient.

  4. Exfoliation of Threading Dislocation-Free, Single-Crystalline, Ultrathin Gallium Nitride Nanomembranes

    KAUST Repository

    Elafandy, Rami T.

    2014-04-01

    Despite the recent progress in gallium nitride (GaN) growth technology, the excessively high threading dislocation (TD) density within the GaN crystal, caused by the reliance on heterogeneous substrates, impedes the development of high-efficiency, low-cost, GaN-based heterostructure devices. For the first time, the chemical exfoliation of completely TD-free, single-crystalline, ultrathin (tens of nanometers) GaN nanomembranes is demonstrated using UV-assisted electroless chemical etching. These nanomembranes can act as seeding layers for subsequent overgrowth of high-quality GaN. A model is proposed, based on scanning and transmission electron microscopy as well as optical measurements to explain the physical processes behind the formation of the GaN nanomembranes. These novel nanomembranes, once transferred to other substrates, present a unique and technologically attractive path towards integrating high-efficiency GaN optical components along with silicon electronics. Interestingly, due to their nanoscale thickness and macroscopic sizes, these nanomembranes may enable the production of flexible GaN-based optoelectronics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Exfoliative cytology of oral mucosa among smokers, opium addicts and non-smokers: a cytomorphometric study.

    Science.gov (United States)

    Hashemipour, Maryam Alsadat; Aghababaie, Mahbobeh; Mirshekari, Toraj Reza; Asadi-Shekaari, Majid; Tahmasbi-Arashlow, Mehrnaz; Tahmasbi-Arashlow, Farzad; Gandjalikhan Nassab, Sayed Amir Hossein

    2013-12-01

    The present study was conducted to evaluate keratinization as well as nuclear and cytoplasmic changes of oral epithelial cells among smokers, opium addicts and non-smokers through exfoliative cytology technique. Smears of buccal mucosa and mouth floor were collected from 300 males (100 smokers, 100 opium addicts and 100 non-smokers). The nucleus and cytoplasm sizes were determined using image analysis software. Data was analyzed with Mann-Whitney test and Student's t-test on SPSS version 13 statistical software. Statistical significance was defined as P opium addicts and non-smokers in different age groups. The mean size of the nucleus compared to that of cytoplasm was significantly higher in smokers and opium addicts compared to non-smokers after correction for age. The results of this study indicate different rates of epithelial cell keratinization in oral cavity among smokers, opium addicts and non-smokers. Also, our results suggest a possible relationship between the number of cigarettes per day, daily opium consumption and an increase in the rate of cellular proliferation of oral mucosal cells. The present study indicated a decrease in cellular diameter as well as an increase in nuclear diameter and nuclear/cytoplasmic ratio in smears taken from both smokers and opium addicts compared to non-smokers.

  6. Understanding the Growth Mechanism of GaN Epitaxial Layers on Mechanically Exfoliated Graphite.

    Science.gov (United States)

    Li, Tianbao; Liu, Chenyang; Zhang, Zhe; Yu, Bin; Dong, Hailiang; Jia, Wei; Jia, Zhigang; Yu, Chunyan; Gan, Lin; Xu, Bingshe; Jiang, Haiwei

    2018-04-27

    The growth mechanism of GaN epitaxial layers on mechanically exfoliated graphite is explained in detail based on classic nucleation theory. The number of defects on the graphite surface can be increased via O-plasma treatment, leading to increased nucleation density on the graphite surface. The addition of elemental Al can effectively improve the nucleation rate, which can promote the formation of dense nucleation layers and the lateral growth of GaN epitaxial layers. The surface morphologies of the nucleation layers, annealed layers and epitaxial layers were characterized by field-emission scanning electron microscopy, where the evolution of the surface morphology coincided with a 3D-to-2D growth mechanism. High-resolution transmission electron microscopy was used to characterize the microstructure of GaN. Fast Fourier transform diffraction patterns showed that cubic phase (zinc-blend structure) GaN grains were obtained using conventional GaN nucleation layers, while the hexagonal phase (wurtzite structure) GaN films were formed using AlGaN nucleation layers. Our work opens new avenues for using highly oriented pyrolytic graphite as a substrate to fabricate transferable optoelectronic devices.

  7. In situ TEM visualization of superior nanomechanical flexibility of shear-exfoliated phosphorene.

    Science.gov (United States)

    Xu, Feng; Ma, Hongyu; Lei, Shuangying; Sun, Jun; Chen, Jing; Ge, Binghui; Zhu, Yimei; Sun, Litao

    2016-07-14

    Recently discovered atomically thin black phosphorus (called phosphorene) holds great promise for applications in flexible nanoelectronic devices. Experimentally identifying and characterizing nanomechanical properties of phosphorene are challenging, but also potentially rewarding. This work combines for the first time in situ transmission electron microscopy (TEM) imaging and an in situ micro-manipulation system to directly visualize the nanomechanical behaviour of individual phosphorene nanoflakes. We demonstrate that the phosphorene nanoflakes can be easily bent, scrolled, and stretched, showing remarkable mechanical flexibility rather than fracturing. An out-of-plane plate-like bending mechanism and in-plane tensile strain of up to 34% were observed. Moreover, a facile liquid-phase shear exfoliation route has been developed to produce such mono-layer and few-layer phosphorene nanoflakes in organic solvents using only a household kitchen blender. The effects of surface tensions of the applied solvents on the ratio of average length and thickness (L/T) of the nanoflakes were studied systematically. The results reported here will pave the way for potential industrial-scale applications of flexible phosphorene nanoelectronic devices.

  8. Method of producing exfoliated graphite composite compositions for fuel cell flow field plates

    Energy Technology Data Exchange (ETDEWEB)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2014-04-08

    A method of producing an electrically conductive composite composition, which is particularly useful for fuel cell bipolar plate applications. The method comprises: (a) providing a supply of expandable graphite powder; (b) providing a supply of a non-expandable powder component comprising a binder or matrix material; (c) blending the expandable graphite with the non-expandable powder component to form a powder mixture wherein the non-expandable powder component is in the amount of between 3% and 60% by weight based on the total weight of the powder mixture; (d) exposing the powder mixture to a temperature sufficient for exfoliating the expandable graphite to obtain a compressible mixture comprising expanded graphite worms and the non-expandable component; (e) compressing the compressible mixture at a pressure within the range of from about 5 psi to about 50,000 psi in predetermined directions into predetermined forms of cohered graphite composite compact; and (f) treating the so-formed cohered graphite composite to activate the binder or matrix material thereby promoting adhesion within the compact to produce the desired composite composition. Preferably, the non-expandable powder component further comprises an isotropy-promoting agent such as non-expandable graphite particles. Further preferably, step (e) comprises compressing the mixture in at least two directions. The method leads to composite plates with exceptionally high thickness-direction electrical conductivity.

  9. Functionalization of liquid-exfoliated two-dimensional 2H-MoS2.

    Science.gov (United States)

    Backes, Claudia; Berner, Nina C; Chen, Xin; Lafargue, Paul; LaPlace, Pierre; Freeley, Mark; Duesberg, Georg S; Coleman, Jonathan N; McDonald, Aidan R

    2015-02-23

    Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2 . We found that the reaction of liquid-exfoliated 2D MoS2 , with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2 -M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT-IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Chromosomal damage and apoptosis analysis in exfoliated oral epithelial cells from mouthwash and alcohol users

    Science.gov (United States)

    Rocha, Rodrigo dos Santos; Meireles, José Roberto Cardoso; de Moraes Marcílio Cerqueira, Eneida

    2014-01-01

    Chromosomal damage and apoptosis were analyzed in users of mouthwash and/or alcoholic beverages, using the micronucleus test on exfoliated oral mucosa cells. Samples from four groups of 20 individuals each were analyzed: three exposed groups (EG1, EG2 and EG3) and a control group (CG). EG1 comprised mouthwash users; EG2 comprised drinkers, and EG3 users of both mouthwashes and alcoholic beverages. Cell material was collected by gently scraping the insides of the cheeks. Then the cells were fixed in a methanol/acetic acid (3:1) solution and stained and counterstained, respectively, with Schiff reactive and fast green. Endpoints were computed on 2,000 cells in a blind test. Statistical analysis showed that chromosomal damage and apoptosis were significantly higher in individuals of groups EG1 and EG3 than in controls (p < 0.005 and p < 0.001, respectively). No significant difference in chromosomal damage and apoptosis was observed between the exposed groups. In EG2, only the occurrence of apoptosis was significantly higher than in the controls. These results suggest that mouthwashes alone or in association with alcoholic drinks induce genotoxic effects, manifested as chromosomal damage and apoptosis. They also suggest that alcoholic drinks are effective for stimulating the process of apoptosis. However, these data need to be confirmed in larger samples. PMID:25505845

  11. Interlayer catalytic exfoliation realizing scalable production of large-size pristine few-layer graphene

    Science.gov (United States)

    Geng, Xiumei; Guo, Yufen; Li, Dongfang; Li, Weiwei; Zhu, Chao; Wei, Xiangfei; Chen, Mingliang; Gao, Song; Qiu, Shengqiang; Gong, Youpin; Wu, Liqiong; Long, Mingsheng; Sun, Mengtao; Pan, Gebo; Liu, Liwei

    2013-01-01

    Mass production of reduced graphene oxide and graphene nanoplatelets has recently been achieved. However, a great challenge still remains in realizing large-quantity and high-quality production of large-size thin few-layer graphene (FLG). Here, we create a novel route to solve the issue by employing one-time-only interlayer catalytic exfoliation (ICE) of salt-intercalated graphite. The typical FLG with a large lateral size of tens of microns and a thickness less than 2 nm have been obtained by a mild and durative ICE. The high-quality graphene layers preserve intact basal crystal planes owing to avoidance of the degradation reaction during both intercalation and ICE. Furthermore, we reveal that the high-quality FLG ensures a remarkable lithium-storage stability (>1,000 cycles) and a large reversible specific capacity (>600 mAh g-1). This simple and scalable technique acquiring high-quality FLG offers considerable potential for future realistic applications.

  12. Photoinduced charge separation in a colloidal system of exfoliated layered semiconductor controlled by coexisting aluminosilicate clay.

    Science.gov (United States)

    Nakato, Teruyuki; Yamada, Yoshimi; Miyamoto, Nobuyoshi

    2009-02-05

    We investigated photoinduced charge separation occurring in a multicomponent colloidal system composed of oxide nanosheets of photocatalytically active niobate and photochemically inert clay and electron accepting methylviologen dications (MV2+). The inorganic nanosheets were obtained by exfoliation of layered hexaniobate and hectorite clay. The niobate and clay nanosheets were spatially separated in the colloidally dispersed state, and the MV2+ molecules were selectively adsorbed on the clay platelets. UV irradiation of the colloids led to electron transfer from the niobate nanosheets to the MV2+ molecules adsorbed on clay. The photoinduced electron transfer produced methylviologen radical cations (MV*+), which was characterized by high yield and long lifetime. The yield and stability of the MV*+ species were found to depend strongly on the clay content of the colloid: from a few mol % to approximately 70 mol % of the yield and several tens of minutes to more than 40 h of the lifetime. The contents of the niobate nanosheets and MV2+ molecules and the aging of the colloid also affected the photoinduced charge separation. In the absence of MV2+ molecules in the colloid, UV irradiation induced electron accumulation in the niobate nanosheets. The stability of the electron-accumulated state also depended on the clay content. The variation in the photochemical behavior is discussed in relation to the viscosity of the colloid.

  13. Chromosomal Damage and Apoptosis in Exfoliated Buccal Cells from Individuals with Oral Cancer

    Science.gov (United States)

    Dórea, Lavínia Tércia Magalhães; Meireles, José Roberto Cardoso; Lessa, Júlia Paula Ramos; Oliveira, Márcio Campos; de Bragança Pereira, Carlos Alberto; Polpo de Campos, Adriano; Cerqueira, Eneida de Moraes Macílio

    2012-01-01

    This study aimed to investigate cytological abnormalities indicative of chromosome damage (micronuclei) and apoptosis (karyorrhexis, pyknosis, and condensed chromatin) in exfoliated cells from the buccal mucosa of patients with oral cancer and control subjects. The sample included twenty individuals with oral cancer and forty individuals with normal buccal mucosa. Material was collected from the cheek epithelium in areas with lesions and areas without abnormalities. A minimum of one thousand cells was analyzed. Micronuclei were found significantly more frequently in cells collected from lesions than in cells from normal areas, independent of the presence/absence of cancer (P < 0.0001). They were also significantly more frequent in smokers and in mouthwash users (P < 0.0001). Apoptosis occurred significantly less frequently in individuals with oral cancer (P < 0.0001). These results show that oral cancer is associated with higher frequency of chromosomal damage and suggest that apoptosis is compromised in the buccal cells of individuals with this kind of neoplasia. PMID:22315605

  14. Osteogenic differentiation and mineralization of human exfoliated deciduous teeth stem cells on modified chitosan scaffold

    Energy Technology Data Exchange (ETDEWEB)

    Su, Wen-Ta, E-mail: f10549@ntut.edu.tw [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei, Taiwan (China); Wu, Pai-Shuen [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei, Taiwan (China); Ko, Chih-Sheng [PhytoHealth Corporation, Maywufa Biopharma Group, Taipei, Taiwan (China); Huang, Te-Yang [Mackay Memorial Hospital, Taipei, Taiwan (China)

    2014-08-01

    Stem cells from human exfoliated deciduous teeth (SHEDs) have been considered as alternative sources of adult stem cells in tissue engineering because of their potential to differentiate into multiple cell lineages. Strontium has an important function in bone remodeling because it can simulate bone formation and decrease bone resorption. In this study, the effects of strontium phosphate on the osteogenic differentiation of SHEDs were investigated. Strontium phosphate was found to enhance the osteogenic differentiation of SHEDs with up-regulated osteoblast-related gene expression. The proliferation of SHEDs was slightly inhibited by chitosan scaffolds; however, type-I collagen expression, alkaline phosphatase activity, and calcium deposition on chitosan scaffolds containing strontium were significantly enhanced. Furthermore, cells seeded in a 3D scaffold under dynamic culture at an optimal fluid rate might enhance cellular differentiation than static culture in osteoblastic gene expression. This experiment might provide a useful cell resource and dynamic 3D culture for tissue engineering and bone repair. - Highlights: • SHEDs have been considered as alternative sources of adult stem cells in tissue engineering • Strontium phosphate can enhance the osteogenic differentiation of SHEDs • 3D scaffold under dynamic culture with optimal fluid rate enhance cellular differentiation.

  15. Osteogenic differentiation and mineralization of human exfoliated deciduous teeth stem cells on modified chitosan scaffold

    International Nuclear Information System (INIS)

    Su, Wen-Ta; Wu, Pai-Shuen; Ko, Chih-Sheng; Huang, Te-Yang

    2014-01-01

    Stem cells from human exfoliated deciduous teeth (SHEDs) have been considered as alternative sources of adult stem cells in tissue engineering because of their potential to differentiate into multiple cell lineages. Strontium has an important function in bone remodeling because it can simulate bone formation and decrease bone resorption. In this study, the effects of strontium phosphate on the osteogenic differentiation of SHEDs were investigated. Strontium phosphate was found to enhance the osteogenic differentiation of SHEDs with up-regulated osteoblast-related gene expression. The proliferation of SHEDs was slightly inhibited by chitosan scaffolds; however, type-I collagen expression, alkaline phosphatase activity, and calcium deposition on chitosan scaffolds containing strontium were significantly enhanced. Furthermore, cells seeded in a 3D scaffold under dynamic culture at an optimal fluid rate might enhance cellular differentiation than static culture in osteoblastic gene expression. This experiment might provide a useful cell resource and dynamic 3D culture for tissue engineering and bone repair. - Highlights: • SHEDs have been considered as alternative sources of adult stem cells in tissue engineering • Strontium phosphate can enhance the osteogenic differentiation of SHEDs • 3D scaffold under dynamic culture with optimal fluid rate enhance cellular differentiation

  16. Screening of Oral Potentially Malignant Disorders Using Exfoliative Cytology: A Diagnostic Modality

    International Nuclear Information System (INIS)

    Kabiraj, A.

    2016-01-01

    Oral exfoliative cytology (OEC) has been implemented in the diagnosis of pathologic lesions for ages. The present study was undertaken to evaluate the cytomorphological features of some of the commonest potentially malignant disorders (leukoplakia, lichen planus, and oral sub mucous fibrosis) through a simple procedure and illustrate its importance in mass screening. Materials and Method. A total of 160 subjects with 25-50 years of age were included in the study. Among them, 40 were clinically diagnosed with oral leukoplakia, 40 were diagnosed with oral lichen planus, 40 were diagnosed with oral sub mucous fibrosis, and 40 were in the control group. The prepared smears were subjected to Papanicolaou stain and analyzed microscopically for the evaluation of the cytomorphological features. Results and Discussion. When analyzed microscopically, 36 (90%) out of the 40 oral leukoplakic lesions showed Class II cytological features whereas 4 (10%) revealed Class I features. Among 40 patients with oral lichen planus, 26 (65%) showed Class II features while the remaining 14 (35%) revealed Class I features. In 40 subjects with oral sub mucous fibrosis, 32 (80%) showed Class II features while the other 8 (20%) showed Class I features. All the 40 control subjects showed Class I features. Thus, OEC can be widely advocated as an addition to clinical conclusion and an adjunct to biopsy.

  17. Oxide growth and exfoliation of materials in steam tubing. Lesson 9

    Energy Technology Data Exchange (ETDEWEB)

    Dooley, R. Barry; Bursik, Albert

    2011-04-15

    University 101 courses are typically designed to help incoming first-year undergraduate students to adjust to the university, develop a better understanding of the college environment, and acquire essential academic success skills. Why are we offering a special Boiler and HRSG Tube Failures PPChem 101? The answer is simple, yet very conclusive: - There is a lack of knowledge on the identification of tube failure mechanisms and for the implementation of adequate counteractions in many power plants, particularly at industrial power and steam generators. - There is a lack of knowledge to prevent repeat tube failures. The vast majority of BTF/HTF have been, and continue to be, repeat failures. It is hoped that the information about the failure mechanisms of BTF supplied in this course will help to put plant engineers and chemists on the right track. The major goal of this course is the avoidance of repeat BTF. This ninth lesson is focused on Oxide Growth and Exfoliation of Materials in Steam Tubing. (orig.)

  18. [Botulinum toxin: An important complement for facial rejuvenation surgery].

    Science.gov (United States)

    Le Louarn, C

    2017-10-01

    The improved understanding of the functional anatomy of the face and of the action of the botulinum toxin A leads us to determine a new injection procedure which consequently decreases the risk of eyebrow and eyelid ptosis and increases the toxin's injection possibilities and efficiencies. With less units of toxin, the technique herein described proposes to be more efficient on more muscles: variable toxin injections concentration adapted to each injected muscle are used. Thanks to a new procedure in the upper face, toxin A injection can be quite close to an endoscopic surgical action. In addition, interesting results are achievable to rejuvenate the lateral canthus with injection on the upper lateral tarsus, to rejuvenate the nose with injection at the alar base, the jawline and the neck region. Lastly, a smoothing effect on the skin (meso botox) is obtained by the anticholinergic action of the toxin A on the dermal receptors. Copyright © 2017. Published by Elsevier Masson SAS.

  19. AB toxins: a paradigm switch from deadly to desirable.

    Science.gov (United States)

    Odumosu, Oludare; Nicholas, Dequina; Yano, Hiroshi; Langridge, William

    2010-07-01

    To ensure their survival, a number of bacterial and plant species have evolved a common strategy to capture energy from other biological systems. Being imperfect pathogens, organisms synthesizing multi-subunit AB toxins are responsible for the mortality of millions of people and animals annually. Vaccination against these organisms and their toxins has proved rather ineffective in providing long-term protection from disease. In response to the debilitating effects of AB toxins on epithelial cells of the digestive mucosa, mechanisms underlying toxin immunomodulation of immune responses have become the focus of increasing experimentation. The results of these studies reveal that AB toxins may have a beneficial application as adjuvants for the enhancement of immune protection against infection and autoimmunity. Here, we examine similarities and differences in the structure and function of bacterial and plant AB toxins that underlie their toxicity and their exceptional properties as immunomodulators for stimulating immune responses against infectious disease and for immune suppression of organ-specific autoimmunity.

  20. Recent Insights into Clostridium perfringens Beta-Toxin

    Directory of Open Access Journals (Sweden)

    Masahiro Nagahama

    2015-02-01

    Full Text Available Clostridium perfringens beta-toxin is a key mediator of necrotizing enterocolitis and enterotoxemia. It is a pore-forming toxin (PFT that exerts cytotoxic effect. Experimental investigation using piglet and rabbit intestinal loop models and a mouse infection model apparently showed that beta-toxin is the important pathogenic factor of the organisms. The toxin caused the swelling and disruption of HL-60 cells and formed a functional pore in the lipid raft microdomains of sensitive cells. These findings represent significant progress in the characterization of the toxin with knowledge on its biological features, mechanism of action and structure-function having been accumulated. Our aims here are to review the current progresses in our comprehension of the virulence of C. perfringens type C and the character, biological feature and structure-function of beta-toxin.

  1. Electrochemical performance of 3D porous Ni-Co oxide with electrochemically exfoliated graphene for asymmetric supercapacitor applications

    International Nuclear Information System (INIS)

    Kim, Dae Kyom; Hwang, Minsik; Ko, Dongjin; Kang, Jeongmin; Seong, Kwang-dong; Piao, Yuanzhe

    2017-01-01

    Graphical abstract: The paper reported the Ni-Co oxide/electrochemically exfoliated graphene nanocomposites with 3D porous nano-architectures (NC-EEG) using a simple low temperature solution method combined with a thermal annealing treatment. 3D porous architectures provide large surface areas and shorten electron diffusion pathways for high performance asymmetric supercapacitors. Display Omitted -- Highlights: •A simple low temperature solution method was used for preparing NC-EEG. •Graphene sheets were obtained by electrochemically exfoliation process. •A high capacity of NC-EEG in a three-electrode system, as high as 649 C g −1 , was recorded. •Asymmetric supercapacitor based on NC-EEG exhibited excellent energy density and power density. -- Abstract: Ni-Co oxide, one of the binary metal oxides, has many advantages for use in high-performance supercapacitor electrode materials due to its relatively high electronic conductivity and improved electrochemical performance. In this work, Ni-Co oxide/electrochemically exfoliated graphene nanocomposites (NC-EEG) are successfully synthesized using a simple low temperature solution method combined with a thermal annealing treatment. Graphene sheets are directly obtained by an electrochemical exfoliation process with graphite foil, which is very simple, environmentally friendly, and has a relatively short reaction time. This electrochemically exfoliated graphene (EEG) can improve the electrical conductivity of the Ni-Co oxide nanostructures. The as-prepared NC-EEG nanocomposites have 3D porous architectures that can provide large surface areas and shorten electron diffusion pathways. Electrochemical properties were performed by cyclic voltammetry and galvanostatic charge/discharge in a 6 M KOH electrolyte. The NC-EEG nanocomposites exhibited a high capacity value of 649 C g −1 at a current density of 1.0 A g −1 . The asymmetric supercapacitors, manufactured on the basis of NC-EEG nanocomposites as a positive

  2. Cnidarian Toxins Acting on Voltage-Gated Ion Channels

    Directory of Open Access Journals (Sweden)

    Robert M. Greenberg

    2006-04-01

    Full Text Available Abstract: Voltage-gated ion channels generate electrical activity in excitable cells. As such, they are essential components of neuromuscular and neuronal systems, and are targeted by toxins from a wide variety of phyla, including the cnidarians. Here, we review cnidarian toxins known to target voltage-gated ion channels, the specific channel types targeted, and, where known, the sites of action of cnidarian toxins on different channels.

  3. Bacterial toxin-antitoxin systems: more than selfish entities?

    OpenAIRE

    Laurence Van Melderen; Manuel Saavedra De Bast

    2009-01-01

    Bacterial toxin?antitoxin (TA) systems are diverse and widespread in the prokaryotic kingdom. They are composed of closely linked genes encoding a stable toxin that can harm the host cell and its cognate labile antitoxin, which protects the host from the toxin's deleterious effect. TA systems are thought to invade bacterial genomes through horizontal gene transfer. Some TA systems might behave as selfish elements and favour their own maintenance at the expense of their host. As a consequence,...

  4. Military Importance of Natural Toxins and Their Analogs

    Directory of Open Access Journals (Sweden)

    Vladimír Pitschmann

    2016-04-01

    Full Text Available Toxin weapon research, development, production and the ban on its uses is an integral part of international law, with particular attention paid to the protection against these weapons. In spite of this, hazards associated with toxins cannot be completely excluded. Some of these hazards are also pointed out in the present review. The article deals with the characteristics and properties of natural toxins and synthetic analogs potentially constituting the basis of toxin weapons. It briefly describes the history of military research and the use of toxins from distant history up to the present age. With respect to effective disarmament conventions, it mentions certain contemporary concepts of possible toxin applications for military purposes and the protection of public order (suppression of riots; it also briefly refers to the question of terrorism. In addition, it deals with certain traditional as well as modern technologies of the research, synthesis, and use of toxins, which can affect the continuing development of toxin weapons. These are, for example, cases of new toxins from natural sources, their chemical synthesis, production of synthetic analogs, the possibility of using methods of genetic engineering and modern biotechnologies or the possible applications of nanotechnology and certain pharmaceutical methods for the effective transfer of toxins into the organism. The authors evaluate the military importance of toxins based on their comparison with traditional chemical warfare agents. They appeal to the ethics of the scientific work as a principal condition for the prevention of toxin abuse in wars, military conflicts, as well as in non-military attacks.

  5. Staphylococcus aureus α-Toxin: Nearly a Century of Intrigue

    Directory of Open Access Journals (Sweden)

    Bryan J. Berube

    2013-06-01

    Full Text Available Staphylococcus aureus secretes a number of host-injurious toxins, among the most prominent of which is the small β-barrel pore-forming toxin α-hemolysin. Initially named based on its properties as a red blood cell lytic toxin, early studies suggested a far greater complexity of α-hemolysin action as nucleated cells also exhibited distinct responses to intoxication. The hemolysin, most aptly referred to as α-toxin based on its broad range of cellular specificity, has long been recognized as an important cause of injury in the context of both skin necrosis and lethal infection. The recent identification of ADAM10 as a cellular receptor for α-toxin has provided keen insight on the biology of toxin action during disease pathogenesis, demonstrating the molecular mechanisms by which the toxin causes tissue barrier disruption at host interfaces lined by epithelial or endothelial cells. This review highlights both the historical studies that laid the groundwork for nearly a century of research on α-toxin and key findings on the structural and functional biology of the toxin, in addition to discussing emerging observations that have significantly expanded our understanding of this toxin in S. aureus disease. The identification of ADAM10 as a proteinaceous receptor for the toxin not only provides a greater appreciation of truths uncovered by many historic studies, but now affords the opportunity to more extensively probe and understand the role of α-toxin in modulation of the complex interaction of S. aureus with its human host.

  6. Intraday monitoring of granitic exfoliation sheets with LiDAR and thermal imaging (Yosemite Valley, California, USA)

    Science.gov (United States)

    Guerin, Antoine; Derron, Marc-Henri; Jaboyedoff, Michel; Abellán, Antonio; Dubas, Olivier; Collins, Brian D.; Stock, Greg M.

    2016-04-01

    Rockfall activity in Yosemite Valley is often linked to the presence of exfoliation sheets associated with other structures such as faults, joints or geological contacts. Daily and seasonal temperature variations or freeze-thaw cycles may strongly promote crack propagation along discontinuities, ultimately leading to rockfalls (Stock et al., 2013). However, little is known concerning the impact of thermal variations on rock face deformation, despite its occurrence at all times of year. To understand the influence of daily temperature fluctuations on the behavior of exfoliation joints (i.e., fractures separating exfoliation sheets), we carried out two different experiments in October 2015: (a) We first monitored a sub-vertical granodiorite flake (19 m by 4 m by 0.1 m ; Collins and Stock, 2014) for 24 consecutive hours using LiDAR and infrared thermal sensors; (b) We monitored a rock cliff (60 m by 45 m) composed of tens of exfoliation sheets located on the southeast face of El Capitan (an ~1000-m-tall cliff located in western Yosemite Valley) for several hours (from 05:30 pm to 01:30 am) to investigate the diurnal cooling effect on rocks of different lithologies. To calibrate the raw apparent temperature measured by the thermal imager (FLIR T660 infrared camera), we fixed pieces of reflective paper (aluminum foil) and black duct tape on both monitored cliffs to measure the reflected temperature and the emissivity of the different rocks. In addition, ambient temperature and relative humidity readings were performed for each acquisition. We then compared the calibrated temperatures to the values registered by resistance temperature detectors (Pt100 sensors), also attached to the rock. Finally, we compared the millimeter scale deformations observed with LiDAR to the values measured by manual crackmeters (standard analog comparators with springs) installed beforehand in the fractures. For the first experiment (24-hour monitoring), a series of measurements were carried

  7. Toxins That Affect Voltage-Gated Sodium Channels.

    Science.gov (United States)

    Ji, Yonghua

    2017-10-26

    Voltage-gated sodium channels (VGSCs) are critical in generation and conduction of electrical signals in multiple excitable tissues. Natural toxins, produced by animal, plant, and microorganisms, target VGSCs through diverse strategies developed over millions of years of evolutions. Studying of the diverse interaction between VGSC and VGSC-targeting toxins has been contributing to the increasing understanding of molecular structure and function, pharmacology, and drug development potential of VGSCs. This chapter aims to summarize some of the current views on the VGSC-toxin interaction based on the established receptor sites of VGSC for natural toxins.

  8. Tumor Targeting and Drug Delivery by Anthrax Toxin

    Directory of Open Access Journals (Sweden)

    Christopher Bachran

    2016-07-01

    Full Text Available Anthrax toxin is a potent tripartite protein toxin from Bacillus anthracis. It is one of the two virulence factors and causes the disease anthrax. The receptor-binding component of the toxin, protective antigen, needs to be cleaved by furin-like proteases to be activated and to deliver the enzymatic moieties lethal factor and edema factor to the cytosol of cells. Alteration of the protease cleavage site allows the activation of the toxin selectively in response to the presence of tumor-associated proteases. This initial idea of re-targeting anthrax toxin to tumor cells was further elaborated in recent years and resulted in the design of many modifications of anthrax toxin, which resulted in successful tumor therapy in animal models. These modifications include the combination of different toxin variants that require activation by two different tumor-associated proteases for increased specificity of toxin activation. The anthrax toxin system has proved to be a versatile system for drug delivery of several enzymatic moieties into cells. This highly efficient delivery system has recently been further modified by introducing ubiquitin as a cytosolic cleavage site into lethal factor fusion proteins. This review article describes the latest developments in this field of tumor targeting and drug delivery.

  9. Tumor Targeting and Drug Delivery by Anthrax Toxin.

    Science.gov (United States)

    Bachran, Christopher; Leppla, Stephen H

    2016-07-01

    Anthrax toxin is a potent tripartite protein toxin from Bacillus anthracis. It is one of the two virulence factors and causes the disease anthrax. The receptor-binding component of the toxin, protective antigen, needs to be cleaved by furin-like proteases to be activated and to deliver the enzymatic moieties lethal factor and edema factor to the cytosol of cells. Alteration of the protease cleavage site allows the activation of the toxin selectively in response to the presence of tumor-associated proteases. This initial idea of re-targeting anthrax toxin to tumor cells was further elaborated in recent years and resulted in the design of many modifications of anthrax toxin, which resulted in successful tumor therapy in animal models. These modifications include the combination of different toxin variants that require activation by two different tumor-associated proteases for increased specificity of toxin activation. The anthrax toxin system has proved to be a versatile system for drug delivery of several enzymatic moieties into cells. This highly efficient delivery system has recently been further modified by introducing ubiquitin as a cytosolic cleavage site into lethal factor fusion proteins. This review article describes the latest developments in this field of tumor targeting and drug delivery.

  10. Tumor Targeting and Drug Delivery by Anthrax Toxin

    OpenAIRE

    Bachran, Christopher; Leppla, Stephen H.

    2016-01-01

    Anthrax toxin is a potent tripartite protein toxin from Bacillus anthracis. It is one of the two virulence factors and causes the disease anthrax. The receptor-binding component of the toxin, protective antigen, needs to be cleaved by furin-like proteases to be activated and to deliver the enzymatic moieties lethal factor and edema factor to the cytosol of cells. Alteration of the protease cleavage site allows the activation of the toxin selectively in response to the presence of tumor-associ...

  11. Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins.

    Science.gov (United States)

    Mantzouki, Evanthia; Lürling, Miquel; Fastner, Jutta; de Senerpont Domis, Lisette; Wilk-Woźniak, Elżbieta; Koreivienė, Judita; Seelen, Laura; Teurlincx, Sven; Verstijnen, Yvon; Krztoń, Wojciech; Walusiak, Edward; Karosienė, Jūratė; Kasperovičienė, Jūratė; Savadova, Ksenija; Vitonytė, Irma; Cillero-Castro, Carmen; Budzyńska, Agnieszka; Goldyn, Ryszard; Kozak, Anna; Rosińska, Joanna; Szeląg-Wasielewska, Elżbieta; Domek, Piotr; Jakubowska-Krepska, Natalia; Kwasizur, Kinga; Messyasz, Beata; Pełechaty, Aleksandra; Pełechaty, Mariusz; Kokocinski, Mikolaj; García-Murcia, Ana; Real, Monserrat; Romans, Elvira; Noguero-Ribes, Jordi; Duque, David Parreño; Fernández-Morán, Elísabeth; Karakaya, Nusret; Häggqvist, Kerstin; Demir, Nilsun; Beklioğlu, Meryem; Filiz, Nur; Levi, Eti E.; Iskin, Uğur; Bezirci, Gizem; Tavşanoğlu, Ülkü Nihan; Özhan, Koray; Gkelis, Spyros; Panou, Manthos; Fakioglu, Özden; Avagianos, Christos; Kaloudis, Triantafyllos; Çelik, Kemal; Yilmaz, Mete; Marcé, Rafael; Catalán, Nuria; Bravo, Andrea G.; Buck, Moritz; Colom-Montero, William; Mustonen, Kristiina; Pierson, Don; Yang, Yang; Raposeiro, Pedro M.; Gonçalves, Vítor; Antoniou, Maria G.; Tsiarta, Nikoletta; McCarthy, Valerie; Perello, Victor C.; Feldmann, Tõnu; Laas, Alo; Panksep, Kristel; Tuvikene, Lea; Gagala, Ilona; Mankiewicz-Boczek, Joana; Yağcı, Meral Apaydın; Çınar, Şakir; Çapkın, Kadir; Yağcı, Abdulkadir; Cesur, Mehmet; Bilgin, Fuat; Bulut, Cafer; Uysal, Rahmi; Obertegger, Ulrike; Boscaini, Adriano; Flaim, Giovanna; Salmaso, Nico; Cerasino, Leonardo; Richardson, Jessica; Visser, Petra M.; Verspagen, Jolanda M. H.; Karan, Tünay; Soylu, Elif Neyran; Maraşlıoğlu, Faruk; Napiórkowska-Krzebietke, Agnieszka; Ochocka, Agnieszka; Pasztaleniec, Agnieszka; Antão-Geraldes, Ana M.; Vasconcelos, Vitor; Morais, João; Vale, Micaela; Köker, Latife; Akçaalan, Reyhan; Albay, Meriç; Špoljarić Maronić, Dubravka; Stević, Filip; Žuna Pfeiffer, Tanja; Fonvielle, Jeremy; Straile, Dietmar; Rothhaupt, Karl-Otto; Hansson, Lars-Anders; Urrutia-Cordero, Pablo; Bláha, Luděk; Geriš, Rodan; Fránková, Markéta; Koçer, Mehmet Ali Turan; Alp, Mehmet Tahir; Remec-Rekar, Spela; Elersek, Tina; Triantis, Theodoros; Zervou, Sevasti-Kiriaki; Hiskia, Anastasia; Haande, Sigrid; Skjelbred, Birger; Madrecka, Beata; Nemova, Hana; Drastichova, Iveta; Chomova, Lucia; Edwards, Christine; Sevindik, Tuğba Ongun; Tunca, Hatice; Önem, Burçin; Aleksovski, Boris; Krstić, Svetislav; Vucelić, Itana Bokan; Nawrocka, Lidia; Salmi, Pauliina; Machado-Vieira, Danielle; de Oliveira, Alinne Gurjão; Delgado-Martín, Jordi; García, David; Cereijo, Jose Luís; Gomà, Joan; Trapote, Mari Carmen; Vegas-Vilarrúbia, Teresa; Obrador, Biel; Grabowska, Magdalena; Karpowicz, Maciej; Chmura, Damian; Úbeda, Bárbara; Gálvez, José Ángel; Özen, Arda; Christoffersen, Kirsten Seestern; Warming, Trine Perlt; Kobos, Justyna; Mazur-Marzec, Hanna; Pérez-Martínez, Carmen; Ramos-Rodríguez, Eloísa; Arvola, Lauri; Alcaraz-Párraga, Pablo; Toporowska, Magdalena; Pawlik-Skowronska, Barbara; Niedźwiecki, Michał; Pęczuła, Wojciech; Leira, Manel; Hernández, Armand; Moreno-Ostos, Enrique; Blanco, José María; Rodríguez, Valeriano; Montes-Pérez, Jorge Juan; Palomino, Roberto L.; Rodríguez-Pérez, Estela; Carballeira, Rafael; Camacho, Antonio; Picazo, Antonio; Rochera, Carlos; Santamans, Anna C.; Ferriol, Carmen; Romo, Susana; Soria, Juan Miguel; Dunalska, Julita; Sieńska, Justyna; Szymański, Daniel; Kruk, Marek; Kostrzewska-Szlakowska, Iwona; Jasser, Iwona; Žutinić, Petar; Gligora Udovič, Marija; Plenković-Moraj, Anđelka; Frąk, Magdalena; Bańkowska-Sobczak, Agnieszka; Wasilewicz, Michał; Özkan, Korhan; Maliaka, Valentini; Kangro, Kersti; Grossart, Hans-Peter; Paerl, Hans W.; Carey, Cayelan C.; Ibelings, Bas W.

    2018-04-13

    Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.

  12. Botulinum toxin for treatment of glandular hypersecretory disorders.

    LENUS (Irish Health Repository)

    Laing, T A

    2012-02-03

    SUMMARY: The use of botulinum toxin to treat disorders of the salivary glands is increasing in popularity in recent years. Recent reports of the use of botulinum toxin in glandular hypersecretion suggest overall favourable results with minimal side-effects. However, few randomised clinical trials means that data are limited with respect to candidate suitability, treatment dosages, frequency and duration of treatment. We report a selection of such cases from our own department managed with botulinum toxin and review the current data on use of the toxin to treat salivary gland disorders such as Frey\\'s syndrome, excessive salivation (sialorrhoea), focal and general hyperhidrosis, excessive lacrimation and chronic rhinitis.

  13. Gene therapy for carcinoma of the breast: Genetic toxins

    International Nuclear Information System (INIS)

    Vassaux, Georges; Lemoine, Nick R

    2000-01-01

    Gene therapy was initially envisaged as a potential treatment for genetically inherited, monogenic disorders. The applications of gene therapy have now become wider, however, and include cardiovascular diseases, vaccination and cancers in which conventional therapies have failed. With regard to oncology, various gene therapy approaches have been developed. Among them, the use of genetic toxins to kill cancer cells selectively is emerging. Two different types of genetic toxins have been developed so far: the metabolic toxins and the dominant-negative class of toxins. This review describes these two different approaches, and discusses their potential applications in cancer gene therapy

  14. Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

    Directory of Open Access Journals (Sweden)

    Evanthia Mantzouki

    2018-04-01

    Full Text Available Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins. Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a and cytotoxins (e.g., cylindrospermopsin due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.

  15. Dysport: pharmacological properties and factors that influence toxin action.

    Science.gov (United States)

    Pickett, Andy

    2009-10-01

    The pharmacological properties of Dysport that influence toxin action are reviewed and compared with other botulinum toxin products. In particular, the subject of diffusion is examined and discussed based upon the evidence that currently exists, both from laboratory studies and from clinical data. Diffusion of botulinum toxin products is not related to the size of the toxin complex in the product since the complex dissociates under physiological conditions, releasing the naked neurotoxin to act. The active neurotoxin in Type A products is the same and therefore diffusion is equal when equal doses are administered.

  16. Emergence of Escherichia coli encoding Shiga toxin 2f in human Shiga toxin-producing E-coli (STEC) infections in the Netherlands, January 2008 to December 2011

    NARCIS (Netherlands)

    Friesema, I.; van der Zwaluw, K.; Schuurman, T.; Kooistra-Smid, M.; Franz, E.; van Duynhoven, Y.; van Pelt, W.

    2014-01-01

    The Shiga toxins of Shiga toxin-producing Escherichia coli (STEC) can be divided into Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) with several sub-variants. Variant Stx(2f) is one of the latest described, but has been rarely associated with symptomatic human infections. In the enhanced STEC

  17. Botulinum toxin for treatment of restrictive strabismus.

    Science.gov (United States)

    Merino, Pilar S; Vera, Rebeca E; Mariñas, Laura G; Gómez de Liaño, Pilar S; Escribano, Jose V

    To study the types of acquired restrictive strabismus treated in a tertiary hospital and the outcome of treatment with botulinum toxin. We performed a 10-year retrospective study of patients with restrictive strabismus aged ≥18 years who were treated with botulinum toxin. Treatment was considered successful if the final vertical deviation was ≤5 PD, horizontal deviation ≤10 PD, with no head turn or diplopia. We included 27 cases (mean age, 61.9 years). Horizontal strabismus was diagnosed in 11.1%, vertical in 51.9%, and mixed in 37%. Strabismus was secondary to cataract surgery in 6 cases, high myopia in 6, orbital fractures in 5, retinal surgery in 5, Graves ophthalmopathy in 4, and repair of conjunctival injury in 1 case. Diplopia was diagnosed in all patients, head turn in 33.3%. The initial deviation was 14 PD (range, 2-40), the mean number of injections per patient was 1.6 (range, 1-3), and the mean dose was 9.5 IU (range, 2.5-22.5). At the end of follow-up, diplopia was recorded in 59.3%, head turn in 18.5%, surgical treatment in 51.9%, and need for prism glasses in 14.8%. Outcome was successful in 37% of patients (4 high myopia, 3 orbital fractures, 2 post-surgical retinal detachment, and 1 post-cataract surgery). Mean follow-up was 3±1.8 years. Vertical deviation was observed in half of the sample. The most frequent deviation was secondary to cataract surgery and high myopia. Treatment with botulinum toxin was successful in one-third of the patients at the end of follow-up. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

  18. Ultrasound-guided botulinum toxin injections

    Directory of Open Access Journals (Sweden)

    S. E. Khatkova

    2016-01-01

    Full Text Available One of the key conditions for achieving the desirable result during botulinum toxin therapy for muscular dystonia, spasticity, and other diseases accompanied by spasm, pain, and autonomic dysfunction (dystonias, spasticity, etc. is the proper administration of the agent into the muscles directly involved in the pathological process. The exact entry of botulinum toxin into the target muscles is essential for successful and safe treatment because its injection into a normal muscle may cause side effects. The most common errors are the incorrect depth and incorrect direction of a needle on insertion. Therefore, the exact injection of the agent particularly into the shallow and deep muscles is a difficult task even for an experienced specialist and requires the use of controlling methods.The European Consensus on Botulinum Toxin Therapy points out that various injection techniques are needed for the better identification of necessary muscles. However, there are currently no reports on the clear advantage of any technique. In our country, injections using palpation and anatomical landmarks have been widely used in routine practice so far; electromyographic monitoring and electrostimulation have been less frequently applied. In recent years, the new method ultrasound-guided injection has continued to grow more popular. This effective, accessible, and easy-to-use method makes it possible to manage a real-time injection process and to ensure the exact entry of the agent into the muscle. This paper is dedicated to a comparative analysis of different injection methods and to a description of the ultrasound-guided technique and its advantages over others. 

  19. Prevention, control and detection of Fusarial toxins

    Directory of Open Access Journals (Sweden)

    Nešić Ksenija D.

    2013-01-01

    Full Text Available The past couple of decades have provided considerable details on fungi and the toxins that they produce, as well on the mechanism of toxin action, toxicity and effects on animal and human health. But, since they are natural contaminants, their presence is often inevitable. Fusaria are widespread in all cereal-growing territories of the world, but they are especially common in our geographic area. Therefore, special attention is paid to the prevention and control, and also to the improvement of methods for their detection. Although all collected data were critical for understanding this worldwide problem, managing the impact of these toxins on the feed and food safety is still great practical challenge. There are a number of approaches that can be taken to minimize mycotoxin contamination in this chain: prevention of fungal growth and thus mycotoxin formation, strategies to reduce or eliminate mycotoxins from contaminated feedstuffs or diverting the contaminated products to low risk uses. A control program for mycotoxins from field to table should in­volve the criteria of an HACCP (Hazard Analysis Critical Control Points approach. It requires an understanding of the important aspects of the interactions of the toxigenic fungi with crop plants, the on-farm production and harvest methods for crops, the production of livestock using grains and processed feeds, including diagnostic capabilities for mycotoxicoses, and all the way to the development of processed foods for human consumption, as well as understanding the marketing and trade channels including storage and delivery of foods to the consumer’s table. A good testing protocol for mycotoxins is necessary to manage all of the control points and in order to be able to ensure a food supply free of toxic levels of mycotoxins for the consumer. [Projekat Ministarstva nauke Republike Srbije, br. III 46009

  20. Binding of Diphtheria Toxin to Phospholipids in Liposomes

    Science.gov (United States)

    Alving, Carl R.; Iglewski, Barbara H.; Urban, Katharine A.; Moss, Joel; Richards, Roberta L.; Sadoff, Jerald C.

    1980-04-01

    Diphtheria toxin bound to the phosphate portion of some, but not all, phospholipids in liposomes. Liposomes consisting of dimyristoyl phosphatidylcholine and cholesterol did not bind toxin. Addition of 20 mol% (compared to dimyristoyl phosphatidylcholine) of dipalmitoyl phosphatidic acid, dicetyl phosphate, phosphatidylinositol phosphate, cardiolipin, or phosphatidylserine in the liposomes resulted in substantial binding of toxin. Inclusion of phosphatidylinositol in dimyristol phosphatidylcholine / cholesterol liposomes did not result in toxin binding. The calcium salt of dipalmitoyl phosphatidic acid was more effective than the sodium salt, and the highest level of binding occurred with liposomes consisting only of dipalmitoyl phosphatidic acid (calcium salt) and cholesterol. Binding of toxin to liposomes was dependent on pH, and the pattern of pH dependence varied with liposomes having different compositions. Incubation of diphtheria toxin with liposomes containing dicetyl phosphate resulted in maximal binding at pH 3.6, whereas binding to liposomes containing phosphatidylinositol phosphate was maximal above pH 7. Toxin did not bind to liposomes containing 20 mol% of a free fatty acid (palmitic acid) or a sulfated lipid (3-sulfogalactosylceramide). Toxin binding to dicetyl phosphate or phosphatidylinositol phosphate was inhibited by UTP, ATP, phosphocholine, or p-nitrophenyl phosphate, but not by uracil. We conclude that (a) diphtheria toxin binds specifically to the phosphate portion of certain phospholipids, (b) binding to phospholipids in liposomes is dependent on pH, but is not due only to electrostatic interaction, and (c) binding may be strongly influenced by the composition of adjacent phospholipids that do not bind toxin. We propose that a minor membrane phospholipid (such as phosphatidylinositol phosphate or phosphatidic acid), or that some other phosphorylated membrane molecule (such as a phosphoprotein) may be important in the initial binding of

  1. Uptake and bioaccumulation of Cry toxins by an aphidophagous predator

    International Nuclear Information System (INIS)

    Paula, Débora P.; Andow, David A.

    2016-01-01

    Uptake of Cry toxins by insect natural enemies has rarely been considered and bioaccumulation has not yet been demonstrated. Uptake can be demonstrated by the continued presence of Cry toxin after exposure has stopped and gut contents eliminated. Bioaccumulation can be demonstrated by showing uptake and that the concentration of Cry toxin in the natural enemy exceeds that in its food. We exposed larvae of the aphidophagous predator, Harmonia axyridis, to Cry1Ac and Cry1F through uniform and constant tritrophic exposure via an aphid, Myzus persicae, and looked for toxin presence in the pupae. We repeated the experiment using only Cry1F and tested newly emerged adults. Both Cry toxins were detected in pupae, and Cry1F was detected in recently emerged, unfed adults. Cry1Ac was present 2.05 times and Cry1F 3.09 times higher in predator pupae than in the aphid prey. Uptake and bioaccumulation in the third trophic level might increase the persistence of Cry toxins in the food web and mediate new exposure routes to natural enemies. - Highlights: • Uptake and bioaccumulation of two Cry toxins by a larval coccinellid was tested. • Uptake was demonstrated by presence of the toxins in pupae and adults. • Bioaccumulation was shown by higher toxin concentration in pupae than prey. • Cry1Ac was present 2.05× and Cry1F 3.09× higher in predator pupae than prey. • This might increase persistence of Cry toxins in food webs with new exposure routes. - Immatures of the predaceous coccinellid Harmonia axyridis can uptake and bioaccumulate Cry toxins delivered via their aphid prey.

  2. The value of exfoliative cytology in the diagnostic of oral mucosa changes in diabetes mellitus.

    Science.gov (United States)

    Mirescu, Ştefan Claudiu; Păiş, Rodica; Stănoiu, Bogdan Petre; Di Natale, Luca; Şovrea, Alina Simona

    2016-01-01

    In this study, we performed microscopic qualitative analyses of the oral epithelium cytological smears in potential early phase of diabetes and in type 1 and 2 diabetic patients versus a healthy control group. The cytological assessment of the oral changes was realized on superficial and profound smears, from jugal and ventral tongue mucosa and it was based on the comparison between three staining methods [Papanicolaou, APT (polychrome tannin blue)-Dragan and Hematoxylin-Eosin (HE)]. Cytological changes of oral cells population were correlated with the type, duration and complications of diabetes. Oral flora was also evaluated. Irrespective the staining used, we found a clear dividing line between the control group and the real diabetic patients. In all diabetes cases (independently of the type of smear, harvest site, clinical form of disorder and present complications), cells presented alterations both at the level of cytoplasm and nucleus. Dyschromasia, cytolysis, different degrees of fatty degenerescence, binucleated cells, hyperchromasia, nuclear enlargement with modified nuclear÷cytoplasmic ratio, were the most frequent findings. There were no discrepancies in the cellular aspects of type 1 or 2 diabetic patients' smears or between the control group and the potential prediabetic status patients. Findings were interpreted as oral epithelium reactive changes induced by the disease. We concluded that exfoliative cytology alone is of low value as a diagnostic and prognostic tool in the diagnosis of diabetes mellitus (DM); it detects the reactive changes induced by the disease, but it makes no differences between DM types or degree of severity and does not allow by qualitative analysis alone to detect abnormalities in early diabetes.

  3. Solvent exfoliated graphene for reinforcement of PMMA composites prepared by in situ polymerization

    International Nuclear Information System (INIS)

    Wang, Jialiang; Shi, Zixing; Ge, Yu; Wang, Yan; Fan, Jinchen; Yin, Jie

    2012-01-01

    Graphene (GP)-based polymer nanocomposites have attracted considerable scientific attention due to its pronounced improvement in mechanical, thermal and electrical properties compared with pure polymers. However, the preparation of well-dispersed and high-quality GP reinforced polymer composites remains a challenge. In this paper, a simple and facile approach for preparation of poly(methyl methacrylate) (PMMA) functionalized GP (GPMMA) via in situ free radical polymerization is reported. Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS), Raman, transmission electron microscope (TEM) and thermogravimetric analysis (TGA) are used to confirm the successful grafting of PMMA chains onto the GP sheets. Composite films are prepared by incorporating different amounts of GPMMA into the PMMA matrix through solution-casting method. Compared with pure PMMA, PMMA/GPMMA composites show simultaneously improved Young's modulus, tensile stress, elongation at break and thermal stability by addition of only 0.5 wt% GPMMA. The excellent reinforcement is attributed to good dispersion of high-quality GPMMA and strong interfacial adhesion between GPMMA and PMMA matrix as evidenced by scanning electron microscope (SEM) images of the fracture surfaces. Consequently, this simple protocol has great potential in the preparation of various high-performance polymer composites. Highlights: ► Functionalization of solvent exfoliated graphene by in situ polymerization. ► A simple and scalable method for preparing high-quality graphene. ► Functionalized graphene can be well-dispersed and have a strong interfacial adhesion with the polymer matrix. ► The nanocomposites exhibit a remarkable improvement of thermal and mechanical properties.

  4. Reinforcement of poly ether sulphones (PES) with exfoliated graphene oxide for aerospace applications

    International Nuclear Information System (INIS)

    Balasubramanian, K

    2012-01-01

    Composite materials have been used for aerospace for some time now and have gained virtually 100% acceptance as the materials of choice. Speciality polymers like poly ether sulphones (PES), poly ether ether ketones(PEEK), poly ether imides (PEI) are highly preferred materials as plastic matrix due to their superior temperature performance, excellent wear and friction resistance, excellent dimensional accuracy, high tensile strength, high modulus, precise machinability and chemical resistance. In recent years nanoadditives like single and multiwall carbon nanotubes, graphenes and graphene oxides(GO) are finding huge market potential in aerospace and automobile industries. But manufacture related factors such as particle/ matrix interphases, surface activation, mixing process, particle agglomeration, particle size and shape may lead to different property effects. In this research GO/PES composites were prepared by high shear melt blending technique. GO monolayers were exfoliated from natural graphite flake and dispersed homogeneously in PES matrix for the GO content ranging between 0.5 to 2.0 volume percentage with a high shear twin screw batch mixer. These melt blended nanocomposites were injection moulded for mechanical property validation of tensile strength, flexural modulus and impact resistance. Addition of 0.5 volume percentage of GO enhanced the tensile strength and flexural modulus by 40% and 90% respectively. The results show that addition of GO to PES increase mechanical properties due to the formation of continuous network, good dispersion and strong interfacial interactions. The strong interfacial interactions were accounted for the increase in glass transition temperature. Also there was a significant improvement in the impact resistance of the PES/ GO nanocomposite. The injection moulded samples were tested for stealth performance by measuring the electromagnetic shielding property.

  5. Peripheral Nerve Regeneration by Secretomes of Stem Cells from Human Exfoliated Deciduous Teeth.

    Science.gov (United States)

    Sugimura-Wakayama, Yukiko; Katagiri, Wataru; Osugi, Masashi; Kawai, Takamasa; Ogata, Kenichi; Sakaguchi, Kohei; Hibi, Hideharu

    2015-11-15

    Peripheral nerve regeneration across nerve gaps is often suboptimal, with poor functional recovery. Stem cell transplantation-based regenerative therapy is a promising approach for axon regeneration and functional recovery of peripheral nerve injury; however, the mechanisms remain controversial and unclear. Recent studies suggest that transplanted stem cells promote tissue regeneration through a paracrine mechanism. We investigated the effects of conditioned media derived from stem cells from human exfoliated deciduous teeth (SHED-CM) on peripheral nerve regeneration. In vitro, SHED-CM-treated Schwann cells exhibited significantly increased proliferation, migration, and the expression of neuron-, extracellular matrix (ECM)-, and angiogenesis-related genes. SHED-CM stimulated neuritogenesis of dorsal root ganglia and increased cell viability. Similarly, SHED-CM enhanced tube formation in an angiogenesis assay. In vivo, a 10-mm rat sciatic nerve gap model was bridged by silicon conduits containing SHED-CM or serum-free Dulbecco's modified Eagle's medium. Light and electron microscopy confirmed that the number of myelinated axons and axon-to-fiber ratio (G-ratio) were significantly higher in the SHED-CM group at 12 weeks after nerve transection surgery. The sciatic functional index (SFI) and gastrocnemius (target muscle) wet weight ratio demonstrated functional recovery. Increased compound muscle action potentials and increased SFI in the SHED-CM group suggested sciatic nerve reinnervation of the target muscle and improved functional recovery. We also observed reduced muscle atrophy in the SHED-CM group. Thus, SHEDs may secrete various trophic factors that enhance peripheral nerve regeneration through multiple mechanisms. SHED-CM may therefore provide a novel therapy that creates a more desirable extracellular microenvironment for peripheral nerve regeneration.

  6. Efficient synthesis of graphene oxide and the mechanisms of oxidation and exfoliation

    Science.gov (United States)

    Yuan, Rui; Yuan, Jing; Wu, Yanping; Chen, Lei; Zhou, Huidi; Chen, Jianmin

    2017-09-01

    An efficient method for the preparation of graphene oxide (GO) was descried through inducing the ultrasonic in the rate-determining step of oxidation processes. Both the transformation procedures and the detailed molecular behavior of parent graphene (PG), partially oxidized graphene (PGO) and GO in H2SO4 and aqueous solution were investigated by molecular dynamic simulation (MD) combining with experiments. The results obtained from MD simulation show that the addition of KMnO4 truly marked the beginning of the reaction which carried out from the border of PG flakes to the centre. This oxidation procedure was the rate-determining step and mainly contained three steps: the boundary carbon atoms oxidized, the distance of the corresponding interlayer enlarged and the oxidizing agent diffused into the unoxidized region, the processes was repeated until oxidized completely. So, the introducing ultrasonic in this section can accelerate not only the exfoliation of layers but also the diffusion of oxidizer and finally raises the oxidation efficiency dramatically. To further clarify these simulation results, the GO was prepared by the method mentioned above. The analyses results for the X-ray diffraction (XRD), Raman spectra and X-ray photoelectron spectroscopy (XPS) of the resulting GO show that the ultrasonic method could perfectly shortens the oxidation time from 12 h to 3 h and forms the higher degree of oxidation products with more carboxylic acid groups on its edges. Thus, this study provides a better understanding of the transformation procedures of graphite and proposes an efficient way to produce GOs suitable for various chemical modifications.

  7. A multi-staining chip using hydrophobic valves for exfoliative cytology in cancer

    Science.gov (United States)

    Lee, Tae Hee; Bu, Jiyoon; Moon, Jung Eun; Kim, Young Jun; Kang, Yoon-Tae; Cho, Young-Ho; Kim, In Sik

    2017-07-01

    Exfoliative cytology is a highly established technique for the diagnosis of tumors. Various microfluidic devices have been developed to minimize the sample numbers by conjugating multiple antibodies in a single sample. However, the previous multi-staining devices require complex control lines and valves operated by external power sources, to deliver multiple antibodies separately for a single sample. In addition, most of these devices are composed of hydrophobic materials, causing unreliable results due to the non-specific binding of antibodies. Here, we present a multi-staining chip using hydrophobic valves, which is formed by the partial treatment of 2-hydroxyethyl methacrylate (HEMA). Our chip consists of a circular chamber, divided into six equal fan-shaped regions. Switchable injection ports are located at the center of the chamber and at the middle of the arc of each fan-shaped zone. Thus, our device is beneficial for minimizing the control lines, since pre-treatment solutions flow from the center to outer ports, while six different antibodies are introduced oppositely from the outer ports. Furthermore, hydrophobic narrow channels, connecting the central region and each of the six fan-shaped zones, are closed by capillary effect, thus preventing the fluidic mixing without external power sources. Meanwhile, HEMA treatment on the exterior region results in hydrophobic-to-hydrophilic transition and prevents the non-specific binding of antibodies. For the application, we measured the expression of six different antibodies in a single sample using our device. The expression levels of each antibody highly matched the conventional immunocytochemistry results. Our device enables cancer screening with a small number of antibodies for a single sample.

  8. Conductive composites of tapioca based bioplastic and electrochemical-mechanical liquid exfoliation (emle) graphene

    Science.gov (United States)

    Amri, A.; Rahmana, H.; Utami, S. P.; Iriyanti, R. S.; Jiang, Z. T.; Rahman, M. M.

    2018-04-01

    The conductive composites of tapioca based bioplastic and the electrochemical- mechanical liquid exfoliation (EMLE) graphene have been successfully synthesized via the solution intercalation method for conductive bioplastic applications. The synthesized EMLE graphene quality, the mechanical properties, the functional group interactions and the conductivity of bioplastic composites, respectively, were analyzed using Raman spectroscopy, Universal Testing Machine (UTM) via ASTM D882-92, Fourier Transform Infrared (FTIR) spectroscopy, Multitester via Four Probe Method. Raman spectroscopy analyses revealed that the graphene used is multi layer graphene (~ 3-10 layer) with deffects and minor impurity of graphene oxide (EMLE graphene). The tensile strength and the Young’s modulus increased with the increasing of the EMLE graphene content in the composites, while the elongation decreased. The bioplastic synthesized using the 9% EMLE graphene content and the mixing time of 50 minutes exhibited the best mechanical properties with the tensile strength of 4.116 Mpa, the Young’s modulus of 75.476 Mpa, and the elongation of 5.453%. The FTIR spectra indicated that there was a good interactions of EMLE graphene in the bioplastic matrix due to the hydrophylic properties and the secondary bonds between the EMLE graphene and the starch and glycerol plasticizer. The higher amount of graphene added, the higher conductivity of bioplastic would be, and vice versa for the resistivity. The best electrical properties of 1.57 x10‑1/ohm.cm (conductivity) and 6.34 ohm.cm (resistivity) was reached by the bioplastic synthesized with addition of 9% EMLE graphene and 50 minutes stirring time. EMLE Graphene is the promissing filler for further development of Tapioca based conductive bioplastics.

  9. A multi-staining chip using hydrophobic valves for exfoliative cytology in cancer

    International Nuclear Information System (INIS)

    Lee, Tae Hee; Bu, Jiyoon; Kim, Young Jun; Kang, Yoon-Tae; Cho, Young-Ho; Moon, Jung Eun; Kim, In Sik

    2017-01-01

    Exfoliative cytology is a highly established technique for the diagnosis of tumors. Various microfluidic devices have been developed to minimize the sample numbers by conjugating multiple antibodies in a single sample. However, the previous multi-staining devices require complex control lines and valves operated by external power sources, to deliver multiple antibodies separately for a single sample. In addition, most of these devices are composed of hydrophobic materials, causing unreliable results due to the non-specific binding of antibodies. Here, we present a multi-staining chip using hydrophobic valves, which is formed by the partial treatment of 2-hydroxyethyl methacrylate (HEMA). Our chip consists of a circular chamber, divided into six equal fan-shaped regions. Switchable injection ports are located at the center of the chamber and at the middle of the arc of each fan-shaped zone. Thus, our device is beneficial for minimizing the control lines, since pre-treatment solutions flow from the center to outer ports, while six different antibodies are introduced oppositely from the outer ports. Furthermore, hydrophobic narrow channels, connecting the central region and each of the six fan-shaped zones, are closed by capillary effect, thus preventing the fluidic mixing without external power sources. Meanwhile, HEMA treatment on the exterior region results in hydrophobic-to-hydrophilic transition and prevents the non-specific binding of antibodies. For the application, we measured the expression of six different antibodies in a single sample using our device. The expression levels of each antibody highly matched the conventional immunocytochemistry results. Our device enables cancer screening with a small number of antibodies for a single sample. (paper)

  10. Property Analysis of Exfoliated Graphite Nanoplatelets Modified Asphalt Model Using Molecular Dynamics (MD Method

    Directory of Open Access Journals (Sweden)

    Hui Yao

    2017-01-01

    Full Text Available This Molecular Dynamics (MD simulation paper presents a physical property comparison study between exfoliated graphite nanoplatelets (xGNP modified and control asphalt models, including density, glass transition temperature, viscosity and thermal conductivity. The three-component control asphalt model consists of asphaltenes, aromatics, and saturates based on previous references. The xGNP asphalt model was built by incorporating an xGNP and control asphalt model and controlling mass ratios to represent the laboratory prepared samples. The Amber Cornell Extension Force Field (ACEFF was used with assigned molecular electro-static potential (ESP charge from NWChem analysis. After optimization and ensemble relaxation, the properties of the control and xGNP modified asphalt models were computed and analyzed using the MD method. The MD simulated results have a similar trend as the test results. The property analysis showed that: (1 the density of the xGNP modified model is higher than that of the control model; (2 the glass transition temperature of the xGNP modified model is closer to the laboratory data of the Strategic Highway Research Program (SHRP asphalt binders than that of the control model; (3 the viscosities of the xGNP modified model at different temperatures are higher than those of the control model, and it coincides with the trend in the laboratory data; (4 the thermal conductivities of the xGNP modified asphalt model are higher than those of the control asphalt model at different temperatures, and it is consistent with the trend in the laboratory data.

  11. Unsatisfactory exfoliative anal cytology samples, 15-year experience with histologic, cytologic, and molecular follow-up.

    Science.gov (United States)

    Khattab, Ruba; McMeekin, Emily; Taege, Alan J; Hekman, James M; Brainard, Jennifer A; Underwood, Dawn; Procop, Gary W; Sturgis, Charles D

    2018-02-01

    The incidence of anal carcinoma has risen in recent decades. Exfoliative cytology screening of selected high risk patients is performed in many centers. Unsatisfactory cytology results are frustrating to patients, clinicians, and laboratorians. The aim of this study is to ascertain outcomes of patients with non-diagnostic anal cytology. A retrospective review of anal cytology testing performed at the Cleveland Clinic between 01/01/2001 and 12/31/2015 was performed. All cases were received as liquid-based samples and processed as ThinPreps (Hologic, Marlborough, MA). Co-testing for HR-HPV DNA was performed using Hybrid Capture 2® (Qiagen, Germantown, MD) in the majority of patients. Of 1,276 ThinPrep anal cytology samples, 130 (10%) were deemed unsatisfactory. 77% of patients were HIV positive. 85% were males. Of the unsatisfactory cases, 116 (89%) were co-tested for HR-HPV DNA. Of those, 40 patients (34%) had a simultaneous positive HR-HPV DNA. Adequate follow up cytology within a one year and a two year period revealed that 18/130 (14%) and 26/130 (20%) of patients had ASC or SIL respectively. Histologic follow-up within one and two years showed 3 patients (2%) and 8 patients (6%) with HSIL or worse. High risk patients with unsatisfactory anal cytology are not "negative". At least one-third proved to be concomitantly HR-HPV DNA positive with one-fifth showing subsequent cytologic squamous abnormalities and with more than 5% being diagnosed with a high grade intraepithelial lesion within two years. Prompt repeat cytology and/or HR-HPV DNA is recommended for high risk patients with non-diagnostic cytology. © 2017 Wiley Periodicals, Inc.

  12. Molybdenum oxide nanosheets prepared by an anodizing-exfoliation process and observation of photochromic properties

    Energy Technology Data Exchange (ETDEWEB)

    Ranjba, M., E-mail: ranjbar@cc.iut.ac.ir; Delalat, F.; Salamati, H.

    2017-02-28

    Highlights: • Blue molybdenum oxide nanosheets are prepared by a facile anodizing method. • PdCl{sub 2} solution is able to decolorize the nanosheets from blue to colorless. • The colorless colloids show a strong photochromic effect under UV laser irradiation. - Abstract: Anodizing-exfoliation of molybdenum foil was performed in 0.02 M HCl electrolyte at 30 V. In this process, the electrolyte rapidly turned into a blue colloidal solution of molybdenum oxide nanosheets with fragmented edges observed on transmission electron microscope (TEM). X-ray Diffraction (XRD) pattern of particles was free of peak while annealing at a temperature range of 100–500 °C led to formation of monoclinic (for T < 300 °C) and orthorhombic (for T > 300 °C) phases of MoO{sub 3}. Moreover, addition of PdCl{sub 2} (0.2 g/l) salt solution caused a spontaneous bleaching of the initial blue colloid. Annealing of powders extracted from these bleached solutions with different PdCl{sub 2} concentrations at 500 °C led to a preferential growth of (0k0) orientation. X-ray photoelectron spectroscopy (XPS) revealed that the blue nanosheets solution contains mainly Mo{sup 5+} with slightly Mo{sup 6+} oxidation states and each of annealing or salt bleaching procedures can entirely convert Mo{sup 5+} to Mo{sup 6+}. When the bleached solutions was exposed to KrF laser beam (λ = 248 nm) a strong photochromic coloration with a deep blue color was occurred. Regardless of Pd:Mo ratio, the primary and laser irradiated solutions showed analogues optical absorption bands in the 1–3 nm photon energy range while the photochromic process led to a broader absorption band.

  13. Dielectric response, functionality and energy storage in epoxy nanocomposites: Barium titanate vs exfoliated graphite nanoplatelets

    International Nuclear Information System (INIS)

    Patsidis, A.C.; Kalaitzidou, K.; Psarras, G.C.

    2012-01-01

    Barium titanate/epoxy and exfoliated graphite nanoplatelets/epoxy nanocomposites were prepared and studied varying the filler content. Morphological characteristics were examined via scanning electron microscopy, while structural changes occurring in barium titanate as a function of temperature were investigated by means of X-ray diffraction. Broadband dielectric spectroscopy was employed for determining the dielectric response of the prepared systems. Based on the conducted analysis it was found that three relaxation processes are present in the spectra of the examined materials. From the slower to the faster one, these are interfacial polarization, glass to rubber transition of the polymer matrix, and rearrangement of polar side groups of the polymer chain. Systems' functionality and energy storing efficiency were assessed in terms of dielectric reinforcing function. Finally, the energy density of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites. -- Graphical abstract: Systems' functionality, electrical relaxations and energy storing efficiency were assessed in terms of dielectric permittivity, electric modulus and dielectric reinforcing function (G). Further, the energy density (U) of all systems was evaluated. Composite systems with embedded graphite nanoplatelets exhibit higher energy storing efficiency, while thermally induced structural changes in ferroelectric particles provide functional behavior to barium titanate composites. Highlights: ► Relaxation phenomena were found to be present in all studied systems. ► Two processes emanate from the polymer matrix (α-mode and β-mode). ► Systems' electrical heterogeneity gives rise to interfacial polarization. ► BaTiO 3 /epoxy composites exhibit functional behavior due to structural changes. ► x

  14. Immunomodulatory Role of Stem Cell from Human Exfoliated Deciduous Teeth on Periodontal Regeneration.

    Science.gov (United States)

    Gao, Xianling; Shen, Zongshan; Guan, Meiliang; Huang, Qiting; Chen, Lingling; Qin, Wei; Ge, Xiaohu; Chen, Haijia; Xiao, Yin; Lin, Zhengmei

    2018-03-20

    Periodontitis is initiated by the infection of periodontal bacteria and subsequent tissue inflammation due to immunoreaction, eventually leading to periodontal apparatus loss. Stem cells from human exfoliated deciduous teeth (SHEDs) have exhibited beneficial characteristics in dental tissue regeneration. However, the immunomodulatory functions of SHEDs have not been elucidated in the context of periodontitis treatment. In this study, we investigated the potential immunomodulatory effects of SHEDs on experimental periodontitis and demonstrated that multi-dose delivery of SHEDs led to periodontal tissue regeneration. SHEDs and monocytes/macrophages were cocultured in transwell systems and SHEDs were found to be capable of promoting monocyte/macrophages conversion to CD206+ M2-like phenotype. Bioluminescence imaging (BLI) was employed to assess the survival and distribution of SHEDs after delivery in periodontal tissues in an induced periodontitis model, and BLI revealed that SHEDs survived for approximately 7 days in periodontal tissues with little tissue diffusion. Then, multi-dose SHEDs delivery was applied to treat periodontitis at 7-day intervals. Results showed that muti-dose SHEDs altered the cytokine expression profile in gingival crevicular fluid, reduced gum bleeding, increased new attachment of periodontal ligament and decreased osteoclast differentiation. Micro-computed tomography analysis showed SHEDs administration significantly increased periodontal regeneration and alveolar bone volume, and decreased distance of cementoenamel junction to alveolar bone crest (CEJ-ABC). Furthermore, an increase in the number of CD206+ M2 macrophages was observed in periodontal tissues following the delivery of SHEDs, which aligned well with the promoted conversion to CD206+ M2-like cells from monocytes/macrophages in vitro after stimulation by SHEDs. This study demonstrated in a rat periodontitis model that local delivery of SHEDs attributed to the induction of M2

  15. Isolation of Shiga toxin-producing Escherichia coli harboring variant Shiga toxin genes from seafood

    Directory of Open Access Journals (Sweden)

    Sreepriya Prakasan

    2018-03-01

    Full Text Available Background and Aim: Shiga toxin-producing Escherichia coli (STEC are important pathogens of global significance. STEC are responsible for numerous food-borne outbreaks worldwide and their presence in food is a potential health hazard. The objective of the present study was to determine the incidence of STEC in fresh seafood in Mumbai, India, and to characterize STEC with respect to their virulence determinants. Materials and Methods: A total of 368 E. coli were isolated from 39 fresh seafood samples (18 finfish and 21 shellfish using culture-based methods. The isolates were screened by polymerase chain reaction (PCR for the genes commonly associated with STEC. The variant Shiga toxin genes were confirmed by Southern blotting and hybridization followed by DNA sequencing. Results: One or more Shiga toxins genes were detected in 61 isolates. Of 39 samples analyzed, 10 (25.64% samples harbored STEC. Other virulence genes, namely, eaeA (coding for an intimin and hlyA (hemolysin A were detected in 43 and 15 seafood isolates, respectively. The variant stx1 genes from 6 isolates were sequenced, five of which were found to be stx1d variants, while one sequence varied considerably from known stx1 sequences. Southern hybridization and DNA sequence analysis suggested putative Shiga toxin variant genes (stx2 in at least 3 other isolates. Conclusion: The results of this study showed the occurrence of STEC in seafood harboring one or more Shiga toxin genes. The detection of STEC by PCR may be hampered due to the presence of variant genes such as the stx1d in STEC. This is the first report of stx1d gene in STEC isolated from Indian seafood.

  16. Two-stage preparation of magnetic sorbent based on exfoliated graphite with ferrite phases for sorption of oil and liquid hydrocarbons from the water surface

    Science.gov (United States)

    Pavlova, Julia A.; Ivanov, Andrei V.; Maksimova, Natalia V.; Pokholok, Konstantin V.; Vasiliev, Alexander V.; Malakho, Artem P.; Avdeev, Victor V.

    2018-05-01

    Due to the macropore structure and the hydrophobic properties, exfoliated graphite (EG) is considered as a perspective sorbent for oil and liquid hydrocarbons from the water surface. However, there is the problem of EG collection from the water surface. One of the solutions is the modification of EG by a magnetic compound and the collection of EG with sorbed oil using the magnetic field. In this work, the method of the two-stage preparation of exfoliated graphite with ferrite phases is proposed. This method includes the impregnation of expandable graphite in the mixed solution of iron (III) chloride and cobalt (II) or nickel (II) nitrate in the first stage and the thermal exfoliation of impregnated expandable graphite with the formation of exfoliated graphite containing cobalt and nickel ferrites in the second stage. Such two-stage method makes it possible to obtain the sorbent based on EG modified by ferrimagnetic phases with high sorption capacity toward oil (up to 45-51 g/g) and high saturation magnetization (up to 42 emu/g). On the other hand, this method allows to produce the magnetic sorbent in a short period of time (up to 10 s) during which the thermal exfoliation is carried out in the air atmosphere.

  17. 76 FR 78215 - Possession, Use, and Transfer of Select Agents and Toxins; Biennial Review; Proposed Rule

    Science.gov (United States)

    2011-12-16

    ... agents and toxins list; whether minimum standards for personnel reliability, physical and cyber security... toxins list; (3) whether minimum standards for personnel reliability, physical and cyber security should...

  18. Shiga Toxin (Stx) Gene Detection and Verotoxigenic Potentials of ...

    African Journals Online (AJOL)

    DR-AMADI

    Nigerian Journal of Basic and Applied Science (June, 2016), 24(1): 98-105 .... dangerous pathogenic shiga- toxin producing E. coli from the food product. Consequent .... Table 3: Vero Toxin Analysis of non – 0157 E. coli Isolates From Nono Sold in Nigeria. City .... receptors in their plasma membranes and will detect all ...

  19. EFFECT OF MARINE TOXINS ON THERMOREGULATION IN MICE.

    Science.gov (United States)

    Marine algal toxins are extremely toxic and can represent a major health problem to humans and animals. Temperature regulation is one of many processes to be affected by exposure to these toxins. Mice and rats become markedly hypothermic when subjected to acute exposure to the ma...

  20. Clostridial Binary Toxins: Iota and C2 Family Portraits

    Science.gov (United States)

    Stiles, Bradley G.; Wigelsworth, Darran J.; Popoff, Michel R.; Barth, Holger

    2011-01-01

    There are many pathogenic Clostridium species with diverse virulence factors that include protein toxins. Some of these bacteria, such as C. botulinum, C. difficile, C. perfringens, and C. spiroforme, cause enteric problems in animals as well as humans. These often fatal diseases can partly be attributed to binary protein toxins that follow a classic AB paradigm. Within a targeted cell, all clostridial binary toxins destroy filamentous actin via mono-ADP-ribosylation of globular actin by the A component. However, much less is known about B component binding to cell-surface receptors. These toxins share sequence homology amongst themselves and with those produced by another Gram-positive, spore-forming bacterium also commonly associated with soil and disease: Bacillus anthracis. This review focuses upon the iota and C2 families of clostridial binary toxins and includes: (1) basics of the bacterial source; (2) toxin biochemistry; (3) sophisticated cellular uptake machinery; and (4) host–cell responses following toxin-mediated disruption of the cytoskeleton. In summary, these protein toxins aid diverse enteric species within the genus Clostridium. PMID:22919577

  1. Cellular Uptake of the Clostridium perfringens Binary Iota-Toxin

    Science.gov (United States)

    Blöcker, Dagmar; Behlke, Joachim; Aktories, Klaus; Barth, Holger

    2001-01-01

    The binary iota-toxin is produced by Clostridium perfringens type E strains and consists of two separate proteins, the binding component iota b (98 kDa) and an actin-ADP-ribosylating enzyme component iota a (47 kDa). Iota b binds to the cell surface receptor and mediates the translocation of iota a into the cytosol. Here we studied the cellular uptake of iota-toxin into Vero cells. Bafilomycin A1, but not brefeldin A or nocodazole, inhibited the cytotoxic effects of iota-toxin, indicating that toxin is translocated from an endosomal compartment into the cytoplasm. Acidification (pH ≤ 5.0) of the extracellular medium enabled iota a to directly enter the cytosol in the presence of iota b. Activation by chymotrypsin induced oligomerization of iota b in solution. An average mass of 530 ± 28 kDa for oligomers was determined by analytical ultracentrifugation, indicating heptamer formation. The entry of iota-toxin into polarized CaCo-2 cells was studied by measuring the decrease in transepithelial resistance after toxin treatment. Iota-toxin led to a significant decrease in resistance when it was applied to the basolateral surface of the cells but not following application to the apical surface, indicating a polarized localization of the iota-toxin receptor. PMID:11292715

  2. Oxidative Stress in Shiga Toxin Production by Enterohemorrhagic Escherichia coli

    Directory of Open Access Journals (Sweden)

    Katarzyna Licznerska

    2016-01-01

    Full Text Available Virulence of enterohemorrhagic Escherichia coli (EHEC strains depends on production of Shiga toxins. These toxins are encoded in genomes of lambdoid bacteriophages (Shiga toxin-converting phages, present in EHEC cells as prophages. The genes coding for Shiga toxins are silent in lysogenic bacteria, and prophage induction is necessary for their efficient expression and toxin production. Under laboratory conditions, treatment with UV light or antibiotics interfering with DNA replication are commonly used to induce lambdoid prophages. Since such conditions are unlikely to occur in human intestine, various research groups searched for other factors or agents that might induce Shiga toxin-converting prophages. Among other conditions, it was reported that treatment with H2O2 caused induction of these prophages, though with efficiency significantly lower relative to UV-irradiation or mitomycin C treatment. A molecular mechanism of this phenomenon has been proposed. It appears that the oxidative stress represents natural conditions provoking induction of Shiga toxin-converting prophages as a consequence of H2O2 excretion by either neutrophils in infected humans or protist predators outside human body. Finally, the recently proposed biological role of Shiga toxin production is described in this paper, and the “bacterial altruism” and “Trojan Horse” hypotheses, which are connected to the oxidative stress, are discussed.

  3. Short Toxin-like Proteins Abound in Cnidaria Genomes

    Directory of Open Access Journals (Sweden)

    Michal Linial

    2012-11-01

    Full Text Available Cnidaria is a rich phylum that includes thousands of marine species. In this study, we focused on Anthozoa and Hydrozoa that are represented by the Nematostella vectensis (Sea anemone and Hydra magnipapillata genomes. We present a method for ranking the toxin-like candidates from complete proteomes of Cnidaria. Toxin-like functions were revealed using ClanTox, a statistical machine-learning predictor trained on ion channel inhibitors from venomous animals. Fundamental features that were emphasized in training ClanTox include cysteines and their spacing along the sequences. Among the 83,000 proteins derived from Cnidaria representatives, we found 170 candidates that fulfill the properties of toxin-like-proteins, the vast majority of which were previously unrecognized as toxins. An additional 394 short proteins exhibit characteristics of toxin-like proteins at a moderate degree of confidence. Remarkably, only 11% of the predicted toxin-like proteins were previously classified as toxins. Based on our prediction methodology and manual annotation, we inferred functions for over 400 of these proteins. Such functions include protease inhibitors, membrane pore formation, ion channel blockers and metal binding proteins. Many of the proteins belong to small families of paralogs. We conclude that the evolutionary expansion of toxin-like proteins in Cnidaria contributes to their fitness in the complex environment of the aquatic ecosystem.

  4. Physiological effect of the toxin from Xanthomonas retroflexus on ...

    African Journals Online (AJOL)

    Physiological effect of the toxin from Xanthomonas retroflexus on redroot pigweed (Amaranthus retroflexus). Z Sun, M Li, J Chen, Y Li. Abstract. A new toxin from Xanthomonas retroflexus could cause a series of physiological responses on seedlings of redroot pigweed. The experimental results revealed that respiratory ratio ...

  5. Treatment of anismus in intractable constipation with botulinum A toxin.

    Science.gov (United States)

    Hallan, R I; Williams, N S; Melling, J; Waldron, D J; Womack, N R; Morrison, J F

    1988-09-24

    In seven patients with anismus the striated sphincter muscle complex was selectively weakened by local injection of Clostridium botulinum type A toxin. Symptom scores improved significantly and correlated with a significant reduction in the maximum voluntary and canal squeeze pressure and a significant increase in the anorectal angle on straining. Botulinum A toxin seems to be promising treatment for some patients with anismus.

  6. T-2 toxin Analysis in Poultry and Cattle Feedstuff.

    Science.gov (United States)

    Gholampour Azizi, Issa; Azarmi, Masumeh; Danesh Pouya, Naser; Rouhi, Samaneh

    2014-05-01

    T-2 toxin is a mycotoxin that is produced by the Fusarium fungi. Consumption of food and feed contaminated with T-2 toxin causes diseases in humans and animals. In this study T-2 toxin was analyzed in poultry and cattle feedstuff in cities of Mazandaran province (Babol, Sari, Chalus), Northern Iran. In this study, 90 samples were analyzed for T-2 toxin contamination by the ELISA method. Out of 60 concentrate and bagasse samples collected from various cities of Mazandaran province, 11.7% and 3.3% were contaminated with T-2 toxin at concentrations > 25 and 50 µg/kg, respectively. For mixed poultry diets, while 10% of the 30 analyzed samples were contaminated with > 25 µg/kg, none of the tested samples contained T-2 toxin at levels > 50 µg/kg. The results obtained from this study show that poultry and cattle feedstuff can be contaminated with different amounts of T-2 toxin in different conditions and locations. Feedstuff that are contaminated by this toxin cause different diseases in animals; thus, potential transfer of mycotoxins to edible by-products from animals fed mycotoxin-contaminated feeds drives the need to routinely monitor mycotoxins in animal feeds and their components. This is the basis on which effective management of mycotoxins and their effects can be implemented.

  7. Retrograde transport of protein toxins through the Golgi apparatus

    DEFF Research Database (Denmark)

    Sandvig, Kirsten; Skotland, Tore; van Deurs, Bo

    2013-01-01

    at the cell surface, and they are endocytosed both by clathrin-dependent and clathrin-independent mechanisms. Sorting to the Golgi and retrograde transport to the endoplasmic reticulum (ER) are common to these toxins, but the exact mechanisms turn out to be toxin and cell-type dependent. In the ER...

  8. Short inventory of EU legislation on plant toxins in food

    NARCIS (Netherlands)

    Nijs, de M.; Noordam, M.Y.; Mol, H.G.J.

    2017-01-01

    Plant toxins, secondary metabolites that are not essential for the survival of the organism itself but are toxic to human health, are produced by many plants. Plant toxins can be present as inherent metabolites in daily foods such as potatoes, herbs and spices or in herbal preparations. Plant

  9. 9 CFR 121.3 - VS select agents and toxins.

    Science.gov (United States)

    2010-01-01

    ... genetically modified. (d) VS select agents or toxins that meet any of the following criteria are excluded from... AGRICULTURE VIRUSES, SERUMS, TOXINS, AND ANALOGOUS PRODUCTS; ORGANISMS AND VECTORS POSSESSION, USE, AND... recombinant organisms: (1) Nucleic acids that can produce infectious forms of any of the select agent viruses...

  10. Solid-phase synthesis of polyamine toxin analogues

    DEFF Research Database (Denmark)

    Kromann, Hasse; Krikstolaityte, Sonata; Andersen, Anne J

    2002-01-01

    The wasp toxin philanthotoxin-433 (PhTX-433) is a nonselective and noncompetitive antagonist of ionotropic receptors, such as ionotropic glutamate receptors and nicotinic acetylcholine receptors. Polyamine toxins are extensively used for the characterization of subtypes of ionotropic glutamate re...

  11. Guidelines for safe handling of toxins. Technical report

    Energy Technology Data Exchange (ETDEWEB)

    Szilagyi, M.

    1995-11-01

    Toxins are highly toxic chemicals which cause illness through all routes of entry into the body. This technical note has been prepared to ensure that preparation, handling, and disposal of toxins does not constitute a greater occupational hazard than is necessary. It includes hazards that may be encountered and the precautions that should be taken against such hazards.

  12. Recent advances in the medicinal chemistry of polyamine toxins

    DEFF Research Database (Denmark)

    Strømgaard, K; Andersen, K; Krogsgaard-Larsen, P

    2001-01-01

    This review describes the recent developments in the field of polyamine toxins, with focus on structure activity relationship investigations, including studies of importance of the polyamine moiety for biological activity, photolabeling studies using polyamine toxins as templates, as well as use ...

  13. The resurgence of botulinum toxin injection for strabismus in children.

    Science.gov (United States)

    Mahan, Marielle; Engel, J Mark

    2017-09-01

    The present review discusses recent advances in the use of botulinum toxin for the management of strabismus in children. Botulinum toxin injection produces similar results compared to surgery for certain subtypes of strabismus, especially acute onset esotropia. It may be more effective in many subtypes of esotropia where surgery has been less reliable, including partially accommodative esotropia, esotropia associated with cerebral palsy, and thyroid eye disease. Small retrospective studies have demonstrated the efficacy of botulinum toxin in the treatment of many types of pediatric strabismus, providing some guidance for clinicians to determine which patients would benefit most from this intervention. Although administration of botulinum toxin is generally accepted as a reasonable option in select cases, many strabismus surgeons have not fully embraced the treatment, in part because of perceived disadvantages compared to surgery and difficulty in identifying subsets with the highest potential for therapeutic success. A recent study compared the administration of botulinum toxin in children with acute-onset esotropia to surgical correction and found botulinum toxin had a statistically equal success rate, but with the advantage of significantly less time under general anesthesia. In addition, botulinum toxin has been recently tried in patients with partially accommodative esotropia, esotropia associated with cerebral palsy, cyclic esotropia, and in patients with thyroid eye disease. The present review will discuss current clinical recommendations based on recent studies on the use of botulinum toxin in children with strabismus.

  14. Effect of Cryphonectria parasitica toxin on lipid peroxidation and ...

    African Journals Online (AJOL)

    In order to clarify the responses of different chestnut cultivars to Cp-toxin stress, the effect of Cp-toxin from Cryphonectria parasitica (Murr.) Barr on Castanea mollissima Blume, especially on its cell structure, was examined. Chestnut shoots of both resistant (Beiyu No. 2) and susceptible (Hongguang) cultivars were treated ...

  15. Enhanced sporulation and toxin production by a mutant derivative of ...

    African Journals Online (AJOL)

    fatima

    total proteins determined with the toxin producing organism. All values are the ... synthesis specific yield was the ratio of δ-endo-toxin (mg L-1) divided by .... corresponding to 31.8 mg. 108 spore. −1 delta-endotoxins, it became apparent that ...

  16. Cryopreserved Dental Pulp Tissues of Exfoliated Deciduous Teeth Is a Feasible Stem Cell Resource for Regenerative Medicine

    Science.gov (United States)

    Yamaza, Haruyoshi; Akiyama, Kentaro; Hoshino, Yoshihiro; Song, Guangtai; Kukita, Toshio; Nonaka, Kazuaki; Shi, Songtao; Yamaza, Takayoshi

    2012-01-01

    Human exfoliated deciduous teeth have been considered to be a promising source for regenerative therapy because they contain unique postnatal stem cells from human exfoliated deciduous teeth (SHED) with self-renewal capacity, multipotency and immunomodulatory function. However preservation technique of deciduous teeth has not been developed. This study aimed to evaluate that cryopreserved dental pulp tissues of human exfoliated deciduous teeth is a retrievable and practical SHED source for cell-based therapy. SHED isolated from the cryopreserved deciduous pulp tissues for over 2 years (25–30 months) (SHED-Cryo) owned similar stem cell properties including clonogenicity, self-renew, stem cell marker expression, multipotency, in vivo tissue regenerative capacity and in vitro immunomodulatory function to SHED isolated from the fresh tissues (SHED-Fresh). To examine the therapeutic efficacy of SHED-Cryo on immune diseases, SHED-Cryo were intravenously transplanted into systemic lupus erythematosus (SLE) model MRL/lpr mice. Systemic SHED-Cryo-transplantation improved SLE-like disorders including short lifespan, elevated autoantibody levels and nephritis-like renal dysfunction. SHED-Cryo amended increased interleukin 17-secreting helper T cells in MRL/lpr mice systemically and locally. SHED-Cryo-transplantation was also able to recover osteoporosis bone reduction in long bones of MRL/lpr mice. Furthermore, SHED-Cryo-mediated tissue engineering induced bone regeneration in critical calvarial bone-defect sites of immunocompromised mice. The therapeutic efficacy of SHED-Cryo transplantation on immune and skeletal disorders was similar to that of SHED-Fresh. These data suggest that cryopreservation of dental pulp tissues of deciduous teeth provide a suitable and desirable approach for stem cell-based immune therapy and tissue engineering in regenerative medicine. PMID:23251621

  17. Clinical, histopathological and immunological characteristics of exfoliative cutaneous lupus erythematosus in 25 German short-haired pointers.

    Science.gov (United States)

    Bryden, Sharon L; White, Stephen D; Dunston, Stanley M; Burrows, Amanda K; Olivry, Thierry

    2005-08-01

    Clinical, histopathological and immunological features of exfoliative cutaneous lupus erythematosus, an uncommon generalized exfoliative dermatitis occurring exclusively in German short-haired pointers, were characterized in 25 dogs. The disease affects young adult dogs and its familial incidence strongly suggests a hereditary origin. Lesions were characterized by scaling and alopecia affecting 100 (25/25) and 76% (19/25) of dogs, respectively. Follicular casts were present in 28% (7/25) of dogs. The muzzle, pinnae and dorsum were typically affected. Generalized skin lesions were described in 52% (13/25) of dogs. Systemic signs of pain and lameness affected several dogs. Anaemia and thrombocytopenia were detected in several dogs with a more severe clinical phenotype. The most common histopathological features were hyperkeratosis and a lymphocytic interface dermatitis. Direct immunostaining revealed IgG deposition in the epidermal and follicular basement membrane of 100 (19/19) and 41% (7/17) of dogs, respectively. Circulating antifollicular and antisebaceous gland IgG antibodies were demonstrated by indirect immunostaining in 57% (4/7) of dogs. This disease usually responds poorly to immunosuppressive therapy and it has a guarded prognosis. Where outcome was recorded, 85% (10/12) of dogs were euthanased due to either a failure to respond to, or complications associated with, immunomodulatory therapy. Two affected dogs are in remission and maintained on immunomodulatory dosages of prednisolone. This study demonstrates the existence of a cellular and humoral immune response directed against the epidermal basement membrane of dogs with exfoliative cutaneous lupus erythematosus. Additional studies are required to further characterize the immunological pathogenesis of this disease.

  18. The Biochemical Toxin Arsenal from Ant Venoms

    Directory of Open Access Journals (Sweden)

    Axel Touchard

    2016-01-01

    Full Text Available Ants (Formicidae represent a taxonomically diverse group of hymenopterans with over 13,000 extant species, the majority of which inject or spray secretions from a venom gland. The evolutionary success of ants is mostly due to their unique eusociality that has permitted them to develop complex collaborative strategies, partly involving their venom secretions, to defend their nest against predators, microbial pathogens, ant competitors, and to hunt prey. Activities of ant venom include paralytic, cytolytic, haemolytic, allergenic, pro-inflammatory, insecticidal, antimicrobial, and pain-producing pharmacologic activities, while non-toxic functions include roles in chemical communication involving trail and sex pheromones, deterrents, and aggregators. While these diverse activities in ant venoms have until now been largely understudied due to the small venom yield from ants, modern analytical and venomic techniques are beginning to reveal the diversity of toxin structure and function. As such, ant venoms are distinct from other venomous animals, not only rich in linear, dimeric and disulfide-bonded peptides and bioactive proteins, but also other volatile and non-volatile compounds such as alkaloids and hydrocarbons. The present review details the unique structures and pharmacologies of known ant venom proteinaceous and alkaloidal toxins and their potential as a source of novel bioinsecticides and therapeutic agents.

  19. Cardiovascular-Active Venom Toxins: An Overview.

    Science.gov (United States)

    Rebello Horta, Carolina Campolina; Chatzaki, Maria; Rezende, Bruno Almeida; Magalhães, Bárbara de Freitas; Duarte, Clara Guerra; Felicori, Liza Figueiredo; Ribeiro Oliveira-Mendes, Bárbara Bruna; do Carmo, Anderson Oliveira; Chávez-Olórtegui, Carlos; Kalapothakis, Evanguedes

    2016-01-01

    Animal venoms are a mixture of bioactive compounds produced as weapons and used primarily to immobilize and kill preys. As a result of the high potency and specificity for various physiological targets, many toxins from animal venoms have emerged as possible drugs for the medication of diverse disorders, including cardiovascular diseases. Captopril, which inhibits the angiotensin-converting enzyme (ACE), was the first successful venom-based drug and a notable example of rational drug design. Since captopril was developed, many studies have discovered novel bradykinin-potentiating peptides (BPPs) with actions on the cardiovascular system. Natriuretic peptides (NPs) have also been found in animal venoms and used as template to design new drugs with applications in cardiovascular diseases. Among the anti-arrhythmic peptides, GsMTx-4 was discovered to be a toxin that selectively inhibits the stretch-activated cation channels (SACs), which are involved in atrial fibrillation. The present review describes the main components isolated from animal venoms that act on the cardiovascular system and presents a brief summary of venomous animals and their venom apparatuses.

  20. The Biochemical Toxin Arsenal from Ant Venoms

    Science.gov (United States)

    Touchard, Axel; Aili, Samira R.; Fox, Eduardo Gonçalves Paterson; Escoubas, Pierre; Orivel, Jérôme; Nicholson, Graham M.; Dejean, Alain

    2016-01-01

    Ants (Formicidae) represent a taxonomically diverse group of hymenopterans with over 13,000 extant species, the majority of which inject or spray secretions from a venom gland. The evolutionary success of ants is mostly due to their unique eusociality that has permitted them to develop complex collaborative strategies, partly involving their venom secretions, to defend their nest against predators, microbial pathogens, ant competitors, and to hunt prey. Activities of ant venom include paralytic, cytolytic, haemolytic, allergenic, pro-inflammatory, insecticidal, antimicrobial, and pain-producing pharmacologic activities, while non-toxic functions include roles in chemical communication involving trail and sex pheromones, deterrents, and aggregators. While these diverse activities in ant venoms have until now been largely understudied due to the small venom yield from ants, modern analytical and venomic techniques are beginning to reveal the diversity of toxin structure and function. As such, ant venoms are distinct from other venomous animals, not only rich in linear, dimeric and disulfide-bonded peptides and bioactive proteins, but also other volatile and non-volatile compounds such as alkaloids and hydrocarbons. The present review details the unique structures and pharmacologies of known ant venom proteinaceous and alkaloidal toxins and their potential as a source of novel bioinsecticides and therapeutic agents. PMID:26805882

  1. Lactobacillus bulgaricus mutants decompose uremic toxins.

    Science.gov (United States)

    Bai, Yun-Huan; Jiang, Ya-Fen; Jiang, Yun-Sheng

    2014-06-01

    We aim to obtain a probiotic strain from Lactobacillus bulgaricus by testing its capability to decompose uremic toxins to provide new intestinal bacteria for the treatment of chronic renal failure. Original L. bulgaricus was cultured with the serum of uremic patients and then mutated by physical (ultraviolet) and chemical (diethyl sulfate) methods repeatedly. Using creatinine decomposition rate as an observed index, we selected the best strains which decreased the most concentration of the creatinine. We then tested its ability to decompose urea, uric acid, serum phosphate, parathyroid hormone, and homocysteine and its genetic stability. After inductive and mutagenic treatment, DUC3-17 was selected. Its decomposition rate of creatinine, urea nitrogen, uric acid, phosphorus, parathyroid hormone, and homocysteine were 17.23%, 36.02%, 9.84%, 15.73%, 78.26%, and 12.69%, respectively. The degrading capacity was sustained over five generations. After directional induction and compound mutation, L. bulgaricus has greater capacity to decompose uremic toxins, with a stable inheritance.

  2. [Botulinum toxin and rejuvenation of the eye].

    Science.gov (United States)

    Volpei, Ch; Miniconi, M-J; Brunner, C I; Besins, T; Braccini, F

    2013-01-01

    Treatments with botulinum toxin in the forehead and periorbital areas may induce disappointing or even paradoxical results. Our study, focused on this area aimed at refining injection techniques by analyzing muscular balances and comparing the effect according to injection doses and topography. This experimental study has been carried out in the form of 2 session workshops, with volunteers duly informed of the study contents and giving their informed consent. It was conducted by physicians and surgeons members of SAMCEP* (Société Avancée de Médecine et Chirurgie Esthétique et Plastique). The botulinum toxin was onabotulinumtoxin A. Results were evaluated 15 days after treatment, in regard to global eyebrow position, eyebrow head and tail position; muscle interactions; lines above the eyebrow. Eleven case reports and their results are shown and discussed. Our study underlines two important insights: muscle balances and "border areas", between orbicularis oculi and corrugator, key features for eyebrow head, and between frontalis and orbicularis oculifor eyebrow tail.

  3. Prokaryotic adenylate cyclase toxin stimulates anterior pituitary cells in culture

    International Nuclear Information System (INIS)

    Cronin, M.J.; Evans, W.S.; Rogol, A.D.; Weiss, A.A.; Thorner, M.O.; Orth, D.N.; Nicholson, W.E.; Yasumoto, T.; Hewlett, E.L.

    1986-01-01

    Bordetella pertussis synthesis a variety of virulence factors including a calmodulin-dependent adenylate cyclase (AC) toxin. Treatment of anterior pituitary cells with this AC toxin resulted in an increase in cellular cAMP levels that was associated with accelerated exocytosis of growth hormone (GH), prolactin, adrenocorticotropic hormone (ACTH), and luteinizing hormone (LH). The kinetics of release of these hormones, however, were markedly different; GH and prolactin were rapidly released, while LH and ACTH secretion was more gradually elevated. Neither dopamine agonists nor somatostatin changes the ability of AC toxin to generate cAMP (up to 2 h). Low concentrations of AC toxin amplified the secretory response to hypophysiotrophic hormones. The authors conclude that bacterial AC toxin can rapidly elevate cAMP levels in anterior pituitary cells and that it is the response that explains the subsequent acceleration of hormone release

  4. Milling technological experiments to reduce Fusarium toxin contamination in wheat

    Directory of Open Access Journals (Sweden)

    Véha A.

    2015-01-01

    Full Text Available We examine 4 different DON-toxin-containing (0.74 - 1.15 - 1.19 - 2.14 mg/kg winter wheat samples: they were debranned and undebranned, and we investigated the flour’s and the by-products’ (coarse, fine bran toxin content changes. SATAKE lab-debranner was used for debranning and BRABENDER lab-mill for the milling process. Without debranning, two sample flours were above the DON toxin limit (0.75 mg/kg, which are waste. By minimum debranning (and minimum debranning mass loss; 6-8%, our experience with whole flour is that the multi-stage debranning measurement significantly reduces the content of the flour’s DON toxin, while the milling by-products, only after careful consideration and DON toxin measurements, may be produced for public consumption and for feeding.

  5. Botulinum toxin in the treatment of vocal fold nodules.

    Science.gov (United States)

    Allen, Jacqui E; Belafsky, Peter C

    2009-12-01

    Promising new techniques in the management of vocal fold nodules have been developed in the past 2 years. Simultaneously, the therapeutic use of botulinum toxin has rapidly expanded. This review explores the use of botulinum toxin in treatment of vocal nodules and summarizes current therapeutic concepts. New microsurgical instruments and techniques, refinements in laser technology, radiosurgical excision and steroid intralesional injections are all promising new techniques in the management of vocal nodules. Botulinum toxin-induced 'voice rest' is a new technique we have employed in patients with recalcitrant nodules. Successful resolution of nodules is possible with this technique, without the risk of vocal fold scarring inherent in dissection/excision techniques. Botulinum toxin usage is exponentially increasing, and large-scale, long-term studies demonstrate its safety profile. Targeted vocal fold temporary paralysis induced by botulinum toxin injection is a new, well tolerated and efficacious treatment in patients with persistent vocal fold nodules.

  6. Treatment of Gastrointestinal Sphincters Spasms with Botulinum Toxin A

    Directory of Open Access Journals (Sweden)

    Giuseppe Brisinda

    2015-05-01

    Full Text Available Botulinum toxin A inhibits neuromuscular transmission. It has become a drug with many indications. The range of clinical applications has grown to encompass several neurological and non-neurological conditions. One of the most recent achievements in the field is the observation that botulinum toxin A provides benefit in diseases of the gastrointestinal tract. Although toxin blocks cholinergic nerve endings in the autonomic nervous system, it has also been shown that it does not block non-adrenergic non-cholinergic responses mediated by nitric oxide. This has promoted further interest in using botulinum toxin A as a treatment for overactive smooth muscles and sphincters. The introduction of this therapy has made the treatment of several clinical conditions easier, in the outpatient setting, at a lower cost and without permanent complications. This review presents current data on the use of botulinum toxin A in the treatment of pathological conditions of the gastrointestinal tract.

  7. Preparation and applications of mechanically exfoliated single-layer and multilayer MoS₂ and WSe₂ nanosheets.

    Science.gov (United States)

    Li, Hai; Wu, Jumiati; Yin, Zongyou; Zhang, Hua

    2014-04-15

    Although great progress has been achieved in the study of graphene, the small current ON/OFF ratio in graphene-based field-effect transistors (FETs) limits its application in the fields of conventional transistors or logic circuits for low-power electronic switching. Recently, layered transition metal dichalcogenide (TMD) materials, especially MoS2, have attracted increasing attention. In contrast to its bulk material with an indirect band gap, a single-layer (1L) MoS2 nanosheet is a semiconductor with a direct band gap of ~1.8 eV, which makes it a promising candidate for optoelectronic applications due to the enhancement of photoluminescence and high current ON/OFF ratio. Compared with TMD nanosheets prepared by chemical vapor deposition and liquid exfoliation, mechanically exfoliated ones possess pristine, clean, and high-quality structures, which are suitable for the fundamental study and potential applications based on their intrinsic thickness-dependent properties. In this Account, we summarize our recent research on the preparation, characterization, and applications of 1L and multilayer MoS2 and WSe2 nanosheets produced by mechanical exfoliation. During the preparation of nanosheets, we proposed a simple optical identification method to distinguish 1L and multilayer MoS2 and WSe2 nanosheets on a Si substrate coated with 90 and 300 nm SiO2. In addition, we used Raman spectroscopy to characterize mechanically exfoliated 1L and multilayer WSe2 nanosheets. For the first time, a new Raman peak at 308 cm(-1) was observed in the spectra of WSe2 nanosheets except for the 1L WSe2 nanosheet. Importantly, we found that the 1L WSe2 nanosheet is very sensitive to the laser power during characterization. The high power laser-induced local oxidation of WSe2 nanosheets and single crystals was monitored by Raman spectroscopy and atomic force microscopy (AFM). Hexagonal and monoclinic structured WO3 thin films were obtained from the local oxidization of single- to triple

  8. Probing edge-activated resonant Raman scattering from mechanically exfoliated 2D MoO3 nanolayers

    International Nuclear Information System (INIS)

    Yano, Taka-aki; Yoshida, Keisuke; Hayashi, Tomohiro; Hara, Masahiko; Hayamizu, Yuhei; Ohuchi, Fumio

    2015-01-01

    We report spatially resolved vibrational analysis of mechanically exfoliated single-crystalline α-MoO 3 nanolayers. Raman scattering from α-MoO 3 was enhanced predominantly at the outside edges of the nanolayers. The enhanced Raman scattering at the edges was attributed primarily to the enhanced resonant Raman effect caused by a high density of oxygen vacancies localized at the edges. The localized vacancy sites corresponded to a non-stoichiometric phase of MoO 3 , which would provide reactive sites with high catalytic activity. (paper)

  9. Botulinum Toxin and Muscle Atrophy: A Wanted or Unwanted Effect.

    Science.gov (United States)

    Durand, Paul D; Couto, Rafael A; Isakov, Raymond; Yoo, Donald B; Azizzadeh, Babak; Guyuron, Bahman; Zins, James E

    2016-04-01

    While the facial rejuvenating effect of botulinum toxin type A is well known and widespread, its use in body and facial contouring is less common. We first describe its use for deliberate muscle volume reduction, and then document instances of unanticipated and undesirable muscle atrophy. Finally, we investigate the potential long-term adverse effects of botulinum toxin-induced muscle atrophy. Although the use of botulinum toxin type A in the cosmetic patient has been extensively studied, there are several questions yet to be addressed. Does prolonged botulinum toxin treatment increase its duration of action? What is the mechanism of muscle atrophy and what is the cause of its reversibility once treatment has stopped? We proceed to examine how prolonged chemodenervation with botulinum toxin can increase its duration of effect and potentially contribute to muscle atrophy. Instances of inadvertent botulinum toxin-induced atrophy are also described. These include the "hourglass deformity" secondary to botulinum toxin type A treatment for migraine headaches, and a patient with atrophy of multiple facial muscles from injections for hemifacial spasm. Numerous reports demonstrate that muscle atrophy after botulinum toxin type A treatment occurs and is both reversible and temporary, with current literature supporting the notion that repeated chemodenervation with botulinum toxin likely responsible for both therapeutic and incidental temporary muscle atrophy. Furthermore, duration of response may be increased with subsequent treatments, thus minimizing frequency of reinjection. Practitioners should be aware of the temporary and reversible effect of botulinum toxin-induced muscle atrophy and be prepared to reassure patients on this matter. © 2016 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com.

  10. Influence of the stirring time on the exfoliation of the Cloisite 30 B clay in PVC composite: structural characterization by XRD

    International Nuclear Information System (INIS)

    Cabral, Andreia M.V.; Rodrigues, Meiry G.F.

    2009-01-01

    This study aims to evaluate the influence of the stirring time on the exfoliation efficiency of the montmorillonite clay in PVC composites, prepared by the polymerization 'in situ' process. The work was performed in 2 steps. In first stage: tests of expansion with Cloisite 30B clay in MVC, which was used to assess the degree of expansion in MVC of each of them at different stirring times: 2, 4 and 6 h. After stirring, each system was kept in observation for 3 days to evaluate the changes in the decanted volume of the clay in the reactor. Second stage: the Influence of the stirring time for the clay exfoliation. Cloisite 30B clay was used to compare the influence of the stirring time for exfoliation and characterized by X-ray diffraction (XRD). (author)

  11. pH triggered superior selective adsorption and separation of both cationic and anionic dyes and photocatalytic activity on a fully exfoliated titanate layer-natural polymer based nanocomposite.

    Science.gov (United States)

    Sarkar, Amit Kumar; Saha, Arka; Panda, Asit Baran; Pal, Sagar

    2015-11-18

    A fully exfoliated titanate layer-natural polymer amylopectin based nanocomposite, with pH responsive superior selective adsorption, separation of both cationic (MB: 599 mg g(-1) at pH 9) and anionic (MO: 558 mg g(-1) at pH 3) dyes and photodegradation properties, has been realized through simultaneous in situ layered titanate formation, exfoliation and polymerization.

  12. Comparison on exfoliated graphene nano-sheets and triturated graphite nano-particles for mode-locking the Erbium-doped fibre lasers

    Science.gov (United States)

    Yang, Chun-Yu; Lin, Yung-Hsiang; Wu, Chung-Lun; Cheng, Chih-Hsien; Tsai, Din-Ping; Lin, Gong-Ru

    2018-06-01

    Comparisons on exfoliated graphene nano-sheets and triturated graphite nano-particles for mode-locking the Erbium-doped fiber lasers (EDFLs) are performed. As opposed to the graphite nano-particles obtained by physically triturating the graphite foil, the tri-layer graphene nano-sheets is obtained by electrochemically exfoliating the graphite foil. To precisely control the size dispersion and the layer number of the exfoliated graphene nano-sheet, both the bias of electrochemical exfoliation and the speed of centrifugation are optimized. Under a threshold exfoliation bias of 3 volts and a centrifugation at 1000 rpm, graphene nano-sheets with an average diameter of 100  ±  40 nm can be obtained. The graphene nano-sheets with an area density of 15 #/µm2 are directly imprinted onto the end-face of a single-mode fiber made patchcord connector inside the EDFL cavity. Such electrochemically exfoliated graphene nano-sheets show comparable saturable absorption with standard single-graphene and perform the self-amplitude modulation better than physically triturated graphite nano-particles. The linear transmittance and modulation depth of the inserted graphene nano-sheets are 92.5% and 53%, respectively. Under the operation with a power gain of 21.5 dB, the EDFL can be passively mode-locked to deliver a pulsewidth of 454.5 fs with a spectral linewidth of 5.6 nm. The time-bandwidth product of 0.31 is close to the transform limit. The Kelly sideband frequency spacing of 1.34 THz is used to calculate the chirp coefficient as  ‑0.0015.

  13. SVM-based prediction of propeptide cleavage sites in spider toxins identifies toxin innovation in an Australian tarantula.

    Directory of Open Access Journals (Sweden)

    Emily S W Wong

    Full Text Available Spider neurotoxins are commonly used as pharmacological tools and are a popular source of novel compounds with therapeutic and agrochemical potential. Since venom peptides are inherently toxic, the host spider must employ strategies to avoid adverse effects prior to venom use. It is partly for this reason that most spider toxins encode a protective proregion that upon enzymatic cleavage is excised from the mature peptide. In order to identify the mature toxin sequence directly from toxin transcripts, without resorting to protein sequencing, the propeptide cleavage site in the toxin precursor must be predicted bioinformatically. We evaluated different machine learning strategies (support vector machines, hidden Markov model and decision tree and developed an algorithm (SpiderP for prediction of propeptide cleavage sites in spider toxins. Our strategy uses a support vector machine (SVM framework that combines both local and global sequence information. Our method is superior or comparable to current tools for prediction of propeptide sequences in spider toxins. Evaluation of the SVM method on an independent test set of known toxin sequences yielded 96% sensitivity and 100% specificity. Furthermore, we sequenced five novel peptides (not used to train the final predictor from the venom of the Australian tarantula Selenotypus plumipes to test the accuracy of the predictor and found 80% sensitivity and 99.6% 8-mer specificity. Finally, we used the predictor together with homology information to predict and characterize seven groups of novel toxins from the deeply sequenced venom gland transcriptome of S. plumipes, which revealed structural complexity and innovations in the evolution of the toxins. The precursor prediction tool (SpiderP is freely available on ArachnoServer (http://www.arachnoserver.org/spiderP.html, a web portal to a comprehensive relational database of spider toxins. All training data, test data, and scripts used are available from

  14. Botulinum toxin injection in laryngeal dyspnea.

    Science.gov (United States)

    Woisard, Virginie; Liu, Xuelai; Bes, Marie Christine Arné; Simonetta-Moreau, Marion

    2017-02-01

    Data, regarding the use of botulinum toxin (BT-A) in laryngeal dyspnea, are scarce, coming from some cases reports in the literature, including Vocal fold paralysis, laryngeal dystonia, vocal cord dysfunction also called paradoxical motion of the vocal fold (PMVF), and post-neuroleptic laryngeal dyskinesia. There is no consensus regarding the muscles and the doses to inject. The aim of this study is to present a retrospective review of patients treated in our ENT Department by BT-A injection in this indication. This study is a retrospective study describing patients who underwent an injection of botulinum toxin for laryngeal dyspnea in the ENT Department from 2005 to 2015 years. The inclusion criteria were a dyspnea associated with a laryngeal dysfunction, confirmed by flexible fiberoptic nasopharyngolaryngoscopy. Information concerning the causes of the dyspnea, the botulinum toxin BT-A injections procedure, post-injection follow-up, and respiratory outcome were collected for all patients included. In the group of 13 patients included, the main cause identified as principal factor linked with the short breath was: a bilateral VF paralysis (Patel et al., Otolaryngol Head Neck Surg 130:686-689, 7), laryngeal dystonia (Balkissoon and Kenn, Semin Respir Crit Care Med 33:595-605, 2), Anxiety syndrome associated with unilateral vocal fold paralysis or asthma (Marcinow et al., Laryngoscope 124:1425-1430, 3), and an isolated asthma (Zwirner et al., Eur Arch Otorhinolaryngol 254:242-245, 1). Nine out of the thirteen patients were improved by the injections. A BT-A-induced stable benefit for four patients led them to stop the injections in the follow-up. Good outcome was observed in five other patients (main cause: bilateral VP paralysis), allowing a progressive lengthening of the delay between BT-A injections. Four patients did not report a positive risk/benefit ratio after BT-A injections; two of them (with bilateral VF paralysis), because of respiratory side effects and

  15. Comparison of ocular response analyzer parameters in primary open angle glaucoma and exfoliative glaucoma patients

    Directory of Open Access Journals (Sweden)

    Emrullah Beyazyildiz

    2014-01-01

    Full Text Available Aim: We sought to identify differences in the following measures of the ocular response analyser (ORA between primary open angle glaucoma (POAG and exfoliative glaucoma (EXG patients: Corneal hysteresis (CH, corneal resistance factor (CRF, corneal-compensated intraocular pressure (IOPcc and Goldmann-correlated intraocular pressure (IOPg. We also sought to relate these ORA measures with central corneal thickness (CCT. Materials and Methods: This cross-sectional study was conducted on a total of 162 individuals (46 EXG patients, 66 POAG patients and 50 healthy subjects without any ocular and systemic disease. ORA measurements were performed, and a minimum of three readings were obtained from each test subject. Groups were compared according to their ORA parameters. Results: The mean CH levels of the EXG, POAG and healthy subjects were 7.6 ± 2.1, 9.1 ± 1.9 and 9.6 ± 1.7 mmHg, respectively. CH was significantly lower in the EXG patients compared to the other groups (P < 0.001.The mean CRF levels of the EXG, POAG and healthy subjects were 9.0 ± 2.0, 10.1 ± 1.7 and 9.8 ± 1.8mmHg, respectively. CRF levels in the eyes of the EXG patients were significantly lower compared to those of either the POAG patients (P = 0.005 or the healthy subjects (P = 0.03, but there was no significant difference in CRF levels between the POAG patients and the healthy subjects (P = 0.59. There was a significant positive correlation between CH and CCT in the EXG patients and healthy subjects (P < 0.001, but this correlation was not present in the POAG patients (P = 0.70. Conclusions: In this study, CH and CRF were found to be significantly reduced in the eyes of EXG patients compared to both the POAG patients and healthy subjects. Reduced CH in EXG patients might result in decreased support of peripapillary scleral structure and increased damage to the optic nerve during IOP increase.

  16. Liquid-phase exfoliated graphene as highly-sensitive sensor for simultaneous determination of endocrine disruptors: Diethylstilbestrol and estradiol

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Lintong; Cheng, Qin [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Chen, Danchao; Ma, Ming [Ningbo Entry-exit Inspection and Quarantine Bureau of China, Ningbo 315012 (China); Wu, Kangbing, E-mail: kbwu@hust.edu.cn [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-02-11

    Graphical abstract: - Highlights: • A novel electrochemical sensor was developed for diethylstilbestrol and estradiol. • Graphene prepared by solvent exfoliation greatly enhances the detection sensitivity. • The newly-developed method has promising application and the accuracy is good. - Abstract: It is quite important to develop convenient and rapid analytical methods for trace levels of endocrine disruptors because they heavily affect health and reproduction of humans and animals. Herein, graphene was easily prepared via one-step exfoliation using N-methyl-2-pyrrolidone as solvent, and then used to construct an electrochemical sensor for highly-sensitive detection of diethylstilbestrol (DES) and estradiol (E2). On the surface of prepared graphene film, two independent and greatly-increased oxidation waves were observed at 0.28 V and 0.49 V for DES and E2. The remarkable signal enlargements indicated that the detection sensitivity was improved significantly. The influences of pH value, amount of graphene and accumulation time on the oxidation signals of DES and E2 were discussed. As a result, a highly-sensitive and rapid electrochemical method was newly developed for simultaneous detection of DES and E2. The values of detection limit were evaluated to be 10.87 nM and 4.9 nM for DES and E2. Additionally, this new method was successfully used in lake water samples and the accuracy was satisfactory.

  17. Exfoliation Corrosion and Pitting Corrosion and Their Role in Fatigue Predictive Modeling: State-of-the-Art Review

    Directory of Open Access Journals (Sweden)

    David W. Hoeppner

    2012-01-01

    Full Text Available Intergranular attack (IG and exfoliation corrosion (EC have a detrimental impact on the structural integrity of aircraft structures of all types. Understanding the mechanisms and methods for dealing with these processes and with corrosion in general has been and is critical to the safety of critical components of aircraft. Discussion of cases where IG attack and exfoliation caused issues in structural integrity in aircraft in operational fleets is presented herein along with a much more detailed presentation of the issues involved in dealing with corrosion of aircraft. Issues of corrosion and fatigue related to the structural integrity of aging aircraft are introduced herein. Mechanisms of pitting nucleation are discussed which include adsorption-induced, ion migration-penetration, and chemicomechanical film breakdown theories. In addition, pitting corrosion (PC fatigue models are presented as well as a critical assessment of their application to aircraft structures and materials. Finally environmental effects on short crack behavior of materials are discussed, and a compilation of definitions related to corrosion and fatigue are presented.

  18. Graphene nanosheets preparation using magnetic nanoparticle assisted liquid phase exfoliation of graphite: The coupled effect of ultrasound and wedging nanoparticles.

    Science.gov (United States)

    Hadi, Alireza; Zahirifar, Jafar; Karimi-Sabet, Javad; Dastbaz, Abolfazl

    2018-06-01

    This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic Fe 3 O 4 nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of Fe 3 O 4 particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of Fe 3 O 4 particle separation from graphene solution which arises from the magnetic nature of Fe 3 O 4 nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, Fe 3 O 4 nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Raman Spectroscopic Study of As-Deposited and Exfoliated Defected Graphene Grown on (001 Si Substrates by CVD

    Directory of Open Access Journals (Sweden)

    T. I. Milenov

    2017-01-01

    Full Text Available We present here results on a Raman spectroscopic study of the deposited defected graphene on Si substrates by chemical vapor deposition (thermal decomposition of acetone. The graphene films are not deposited on the (001 Si substrate directly but on two types of interlayers of mixed phases unintentionally deposited on the substrates: а diamond-like carbon (designated here as DLC and amorphous carbon (designated here as αC are dominated ones. The performed thorough Raman spectroscopic study of as-deposited as well as exfoliated specimens by two different techniques using different excitation wavelengths (488, 514, and 613 nm as well as polarized Raman spectroscopy establishes that the composition of the designated DLC layers varies with depth: the initial layers on the Si substrate consist of DLC, nanodiamond species, and C70 fullerenes while the upper ones are dominated by DLC with an occasional presence of C70 fullerenes. The αC interlayer is dominated by turbostratic graphite and contains a larger quantity of C70 than the DLC-designated interlayers. The results of polarized and unpolarized Raman spectroscopic studies of as-grown and exfoliated graphene films tend to assume that single- to three-layered defected graphene is deposited on the interlayers. It can be concluded that the observed slight upshift of the 2D band as well as the broadening of 2D band should be related to the strain and doping.

  20. Laser induced self-propagating reduction and exfoliation of graphite oxide as an electrode material for supercapacitors

    International Nuclear Information System (INIS)

    Wang, Dewei; Min, Yonggang; Yu, Youhai; Peng, Bo

    2014-01-01

    Graphical abstract: - Highlights: • Few layers graphene was obtained by laser induced self-propagating reduction. • The process is ultrafast without assistance of any high temperate/vacuum environment. • The as-prepared graphene exhibits excellent electrochemical performance. • The superior capacitive behavior is owing to its unique structures. - Abstract: Focused laser beam induced self-propagating reaction has been developed for fabrication of graphene rapidly and efficiently through simultaneous reduction and exfoliation of graphite oxide (GO) process. This chemical-free approach can realize the reduction and exfoliation at room temperature without assistance of any high temperature/vacuum environment. We found that the small sized spot can trigger an ultrafast and highly thermal transferred process by self-propagating reaction at ambient conditions. Benefiting from its high surface area and unique structure, the laser induced self-propagating reaction reduced graphene (LIG) shows excellent capacitive performance. Considering that the cost-effective and feasible process, this facile technique presented here will not only provide a promising method for production of graphene on an industrial scale, but also put forward the application graphene materials in energy storage and conversion