Chemical Modification of Boron-Doped Diamond Electrodes for Applications to Biosensors and Biosensing.

Science.gov (United States)

Svítková, Jana; Ignat, Teodora; Švorc, Ľubomír; Labuda, Ján; Barek, Jiří

2016-05-03

Boron-doped diamond (BDD) is a prospective electrode material that possesses many exceptional properties including wide potential window, low noise, low and stable background current, chemical and mechanical stability, good biocompatibility, and last but not least exceptional resistance to passivation. These characteristics extend its usability in various areas of electrochemistry as evidenced by increasing number of published articles over the past two decades. The idea of chemically modifying BDD electrodes with molecular species attached to the surface for the purpose of creating a rational design has found promising applications in the past few years. BDD electrodes have appeared to be excellent substrate materials for various chemical modifications and subsequent application to biosensors and biosensing. Hence, this article presents modification strategies that have extended applications of BDD electrodes in electroanalytical chemistry. Different methods and steps of surface modification of this electrode material for biosensing and construction of biosensors are discussed.

Surface chemical modification for exceptional wear life of MEMS materials

Directory of Open Access Journals (Sweden)

R. Arvind Singh

2011-12-01

Full Text Available Micro-Electro-Mechanical-Systems (MEMS are built at micro/nano-scales. At these scales, the interfacial forces are extremely strong. These forces adversely affect the smooth operation and cause wear resulting in the drastic reduction in wear life (useful operating lifetime of actuator-based devices. In this paper, we present a surface chemical modification method that reduces friction and significantly extends the wear life of the two most popular MEMS structural materials namely, silicon and SU-8 polymer. The method includes surface chemical treatment using ethanolamine-sodium phosphate buffer, followed by coating of perfluoropolyether (PFPE nanolubricant on (i silicon coated with SU-8 thin films (500 nm and (ii MEMS process treated SU-8 thick films (50 μm. After the surface chemical modification, it was observed that the steady-state coefficient of friction of the materials reduced by 4 to 5 times and simultaneously their wear durability increased by more than three orders of magnitude (> 1000 times. The significant reduction in the friction coefficients is due to the lubrication effect of PFPE nanolubricant, while the exceptional increase in their wear life is attributed to the bonding between the -OH functional group of ethanolamine treated SU-8 thin/thick films and the -OH functional group of PFPE. The surface chemical modification method acts as a common route to enhance the performance of both silicon and SU-8 polymer. It is time-effective (process time ≤ 11 min, cost-effective and can be readily integrated into MEMS fabrication/assembly processes. It can also work for any kind of structural material from which the miniaturized devices are/can be made.

Chemical Modification of Waste Cotton Linters for Oil Spill Cleanup Application

Science.gov (United States)

Chattopadhyay, Debapriya; Umrigar, Keval

2017-12-01

The possibility of use of waste cotton linters as oil sorbents by chemical modification such as acetylation and cyanoethylation was studied. The acetylation process was carried out in presence of acetic anhydride using either H2SO4 or HClO4 as catalyst. The acetylation treatment time was 30, 60 and 120 min and treatment temperature was room temperature, 50 and 70 °C. For cyanoethylation, the waste cotton linters were pre-treated with 2, 5 and 10% NaOH. The treatment temperature for cyanoethylation was room temperature, 50 and 70 °C and treatment time was 30, 60 and 120 min. Both the chemical modification processes were optimized on the basis of oil absorption capacity of the chemically modified cotton fibre with the help of MATLAB software. The modified samples were tested for its oleophilicity in terms of oil absorption capacity, oil retention capacity, oil recovery capacity, reusability of sample and water uptake and buoyancy as oil sorbent. Chemically modified fibres were characterized by Fourier transform infra red spectrophotometer, scanning electron microscope and degree of substitutions.

Aqueous polymer emulsions by chemical modifications of thermosetting alternating polyketones

NARCIS (Netherlands)

Zhang, Youchun; Broekhuis, A. A.; Picchioni, F.

2007-01-01

Aqueous polymer emulsions were prepared by chemical modifications of thermosetting alternating polyketones in a one-pot reaction. Polymeric amines derived from the polyketones can act as polymeric surfactants for the self-emulsification of polyketones. The stability and structure of the emulsions

Thermal stability of Trichoderma reesei c30 cellulase and aspergillus niger; -glucosidase after ph and chemical modification

Energy Technology Data Exchange (ETDEWEB)

Woodward, J.; Whaley, K.S.; Zachry, G.S.; Wohlpart, D.L.

1981-01-01

Treatment of Trichoderma reesei C30 cellulase at pH 10.0 for 1 h at room temperature increased its pH and thermal stability. Chemical modification of the free epsilon-amino groups of cellulase at pH 10.0 resulted in no further increase in stability. Such chemical modification, however, decreased the thermal stability of the cellulose-cellulase complex. On the contrary, the chemical modification of Aspergillus niger glucosidase with glutaraldehyde at pH 8.0 increased the thermal stability of this enzyme.

Chemical modification of jute fibers for the production of green-composites

Energy Technology Data Exchange (ETDEWEB)

Corrales, F. [Group Lepamap, Department of Chemical Engineering, University of Girona, Girona 17071 (Spain)]. E-mail: farners.corrales@udg.es; Vilaseca, F. [Group Lepamap, Department of Chemical Engineering, University of Girona, Girona 17071 (Spain); Llop, M. [Group Lepamap, Department of Chemical Engineering, University of Girona, Girona 17071 (Spain); Girones, J. [Group Lepamap, Department of Chemical Engineering, University of Girona, Girona 17071 (Spain); Mendez, J.A. [Group Lepamap, Department of Chemical Engineering, University of Girona, Girona 17071 (Spain); Mutje, P. [Group Lepamap, Department of Chemical Engineering, University of Girona, Girona 17071 (Spain)

2007-06-18

Natural fiber reinforced composites is an emerging area in polymer science. Fibers derived from annual plants are considered a potential substitute for non-renewable synthetic fibers like glass and carbon fibers. The hydrophilic nature of natural fibers affects negatively its adhesion to hydrophobic polymeric matrices. To improve the compatibility between both components a surface modification has been proposed. The aim of the study is the chemical modification of jute fibers using a fatty acid derivate (oleoyl chloride) to confer hydrophobicity and resistance to biofibers. This reaction was applied in swelling and non-swelling solvents, pyridine and dichloromethane, respectively. The formation of ester groups, resulting from the reaction of oleoyl chloride with hydroxyl group of cellulose were studied by elemental analysis (EA) and Fourier Transform infrared spectroscopy (FTIR). The characterization methods applied has proved the chemical interaction between the cellulosic material and the coupling agent. The extent of the reactions evaluated by elemental analysis was calculated using two ratios. Finally electron microscopy was applied to evaluate the surface changes of cellulose fibers after modification process.

Direct chemical modification and voltammetric detection of glycans in glycoproteins

Czech Academy of Sciences Publication Activity Database

Trefulka, Mojmír; Paleček, Emil

2014-01-01

Roč. 48, NOV2014 (2014), s. 52-55 ISSN 1388-2481 R&D Projects: GA ČR(CZ) GAP301/11/2055 Institutional support: RVO:68081707 Keywords : Glycoproteins * Chemical modification * Os(VI)L complexes Subject RIV: BO - Biophysics Impact factor: 4.847, year: 2014

Chemical synthesis of membrane proteins by the removable backbone modification method.

Science.gov (United States)

Tang, Shan; Zuo, Chao; Huang, Dong-Liang; Cai, Xiao-Ying; Zhang, Long-Hua; Tian, Chang-Lin; Zheng, Ji-Shen; Liu, Lei

2017-12-01

Chemical synthesis can produce membrane proteins bearing specifically designed modifications (e.g., phosphorylation, isotope labeling) that are difficult to obtain through recombinant protein expression approaches. The resulting homogeneously modified synthetic membrane proteins are valuable tools for many advanced biochemical and biophysical studies. This protocol describes the chemical synthesis of membrane proteins by condensation of transmembrane peptide segments through native chemical ligation. To avoid common problems encountered due to the poor solubility of transmembrane peptides in almost any solvent, we describe an effective procedure for the chemical synthesis of membrane proteins through the removable-backbone modification (RBM) strategy. Two key steps of this protocol are: (i) installation of solubilizing Arg4-tagged RBM groups into the transmembrane peptides at any primary amino acid through Fmoc (9-fluorenylmethyloxycarbonyl) solid-phase peptide synthesis and (ii) native ligation of the full-length sequence, followed by removal of the RBM tags by TFA (trifluoroacetic acid) cocktails to afford the native protein. The installation of RBM groups is achieved by using 4-methoxy-5-nitrosalicyladehyde by reduction amination to incorporate an activated O-to-N acyl transfer auxiliary. The Arg4-tag-modified membrane-spanning peptide segments behave like water-soluble peptides to facilitate their purification, ligation and mass characterization.

Glycan Reader is improved to recognize most sugar types and chemical modifications in the Protein Data Bank.

Science.gov (United States)

Park, Sang-Jun; Lee, Jumin; Patel, Dhilon S; Ma, Hongjing; Lee, Hui Sun; Jo, Sunhwan; Im, Wonpil

2017-10-01

Glycans play a central role in many essential biological processes. Glycan Reader was originally developed to simplify the reading of Protein Data Bank (PDB) files containing glycans through the automatic detection and annotation of sugars and glycosidic linkages between sugar units and to proteins, all based on atomic coordinates and connectivity information. Carbohydrates can have various chemical modifications at different positions, making their chemical space much diverse. Unfortunately, current PDB files do not provide exact annotations for most carbohydrate derivatives and more than 50% of PDB glycan chains have at least one carbohydrate derivative that could not be correctly recognized by the original Glycan Reader. Glycan Reader has been improved and now identifies most sugar types and chemical modifications (including various glycolipids) in the PDB, and both PDB and PDBx/mmCIF formats are supported. CHARMM-GUI Glycan Reader is updated to generate the simulation system and input of various glycoconjugates with most sugar types and chemical modifications. It also offers a new functionality to edit the glycan structures through addition/deletion/modification of glycosylation types, sugar types, chemical modifications, glycosidic linkages, and anomeric states. The simulation system and input files can be used for CHARMM, NAMD, GROMACS, AMBER, GENESIS, LAMMPS, Desmond, OpenMM, and CHARMM/OpenMM. Glycan Fragment Database in GlycanStructure.Org is also updated to provide an intuitive glycan sequence search tool for complex glycan structures with various chemical modifications in the PDB. http://www.charmm-gui.org/input/glycan and http://www.glycanstructure.org. wonpil@lehigh.edu. Supplementary data are available at Bioinformatics online. © The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Marine Derived Polysaccharides for Biomedical Applications: Chemical Modification Approaches

Directory of Open Access Journals (Sweden)

Paola Laurienzo

2008-09-01

Full Text Available Polysaccharide-based biomaterials are an emerging class in several biomedical fields such as tissue regeneration, particularly for cartilage, drug delivery devices and gelentrapment systems for the immobilization of cells. Important properties of the polysaccharides include controllable biological activity, biodegradability, and their ability to form hydrogels. Most of the polysaccharides used derive from natural sources; particularly, alginate and chitin, two polysaccharides which have an extensive history of use in medicine, pharmacy and basic sciences, and can be easily extracted from marine plants (algae kelp and crab shells, respectively. The recent rediscovery of poly-saccharidebased materials is also attributable to new synthetic routes for their chemical modification, with the aim of promoting new biological activities and/or to modify the final properties of the biomaterials for specific purposes. These synthetic strategies also involve the combination of polysaccharides with other polymers. A review of the more recent research in the field of chemical modification of alginate, chitin and its derivative chitosan is presented. Moreover, we report as case studies the results of our recent work concerning various different approaches and applications of polysaccharide-based biomaterials, such as the realization of novel composites based on calcium sulphate blended with alginate and with a chemically modified chitosan, the synthesis of novel alginate-poly(ethylene glycol copolymers and the development of a family of materials based on alginate and acrylic polymers of potential interest as drug delivery systems.

Chemical modifications of polymer films induced by high energy heavy ions

International Nuclear Information System (INIS)

Zhu Zhiyong; Sun Youmei; Liu Changlong; Liu Jie; Jin Yunfan

2002-01-01

Polymer films including polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) were irradiated at room temperature with ions of 35 MeV/u 40 Ar, 25 MeV/u 84 Kr, 15.1 MeV/u 136 Xe and 11.4 MeV/u 238 U to fluences ranging from 9x10 9 to 5.5x10 12 ions/cm 2 . The radiation-induced chemical changes of the materials were investigated by Fourier-transform infrared (FTIR) and ultraviolet/visible spectroscopies. It is found that the absorbance in the ultraviolet and visible range induced by all irradiations follows a linear relationship with fluence. The radiation-induced absorbance normalized to one particle increases slowly with increasing of electronic energy loss below about 8 keV/nm followed by a sharp increase up to about 15 keV/nm above which saturation is reached. FTIR measurements reveal that the materials suffer serious degradation through bond breaking. The absorbance of the typical infrared bands decays exponentially with increase of ion fluence and the bond-disruption cross-section shows a sigmoid variation with electronic energy loss. In PET loss of crystallinity is attributed to the configuration transformation of the ethylene glycol residue from trans into the gauche. Alkyne end groups are induced in all the materials above certain electronic energy loss threshold, which is found to be about 0.8 keV/nm for PS and 0.4 keV/nm for PC. The production cross-section of alkyne end group increases with increasing of electronic energy loss and shows saturation at high electronic energy loss values. It is concluded that not only the physical processes but also the chemical processes of the energy deposition determine the modification of polymer

Chemically Patterned Inverse Opal Created by a Selective Photolysis Modification Process.

Science.gov (United States)

Tian, Tian; Gao, Ning; Gu, Chen; Li, Jian; Wang, Hui; Lan, Yue; Yin, Xianpeng; Li, Guangtao

2015-09-02

Anisotropic photonic crystal materials have long been pursued for their broad applications. A novel method for creating chemically patterned inverse opals is proposed here. The patterning technique is based on selective photolysis of a photolabile polymer together with postmodification on released amine groups. The patterning method allows regioselective modification within an inverse opal structure, taking advantage of selective chemical reaction. Moreover, combined with the unique signal self-reporting feature of the photonic crystal, the fabricated structure is capable of various applications, including gradient photonic bandgap and dynamic chemical patterns. The proposed method provides the ability to extend the structural and chemical complexity of the photonic crystal, as well as its potential applications.

Discovery of a Chemical Modification by Citric Acid in a Recombinant Monoclonal Antibody

Science.gov (United States)

2015-01-01

Recombinant therapeutic monoclonal antibodies exhibit a high degree of heterogeneity that can arise from various post-translational modifications. The formulation for a protein product is to maintain a specific pH and to minimize further modifications. Generally Recognized as Safe (GRAS), citric acid is commonly used for formulation to maintain a pH at a range between 3 and 6 and is generally considered chemically inert. However, as we reported herein, citric acid covalently modified a recombinant monoclonal antibody (IgG1) in a phosphate/citrate-buffered formulation at pH 5.2 and led to the formation of so-called “acidic species” that showed mass increases of 174 and 156 Da, respectively. Peptide mapping revealed that the modification occurred at the N-terminus of the light chain. Three additional antibodies also showed the same modification but displayed different susceptibilities of the N-termini of the light chain, heavy chain, or both. Thus, ostensibly unreactive excipients under certain conditions may increase heterogeneity and acidic species in formulated recombinant monoclonal antibodies. By analogy, other molecules (e.g., succinic acid) with two or more carboxylic acid groups and capable of forming an anhydride may exhibit similar reactivities. Altogether, our findings again reminded us that it is prudent to consider formulations as a potential source for chemical modifications and product heterogeneity. PMID:25136741

Thermal stability of Trichoderma reesei C30 cellulase and Aspergillus niger. beta. -glucosidase after pH and chemical modification

Energy Technology Data Exchange (ETDEWEB)

Woodward, J.; Whaley, K.S.; Zachry, G.S.; Wohlpart, D.L.

1981-01-01

Treatment of Trichoderma reesei C30 cellulase at pH 10.0 for 1 h at room temperature increased its pH and thermal stability. Chemical modification of the free epsilon-amino groups of cellulase at pH 10.0 resulted in no further increase in stability. Such chemical modification, however, decreased the thermal stability of the cellulose-cellulase complex. On the contrary, the chemical modification of Aspergillus niger ..beta..-glucosidase with glutaraldehyde at pH 8.0 increased the thermal stability of this enzyme.

No-threshold dose-response curves for nongenotoxic chemicals: Findings and applications for risk assessment

International Nuclear Information System (INIS)

Sheehan, Daniel M.

2006-01-01

We tested the hypothesis that no threshold exists when estradiol acts through the same mechanism as an active endogenous estrogen. A Michaelis-Menten (MM) equation accounting for response saturation, background effects, and endogenous estrogen level fit a turtle sex-reversal data set with no threshold and estimated the endogenous dose. Additionally, 31 diverse literature dose-response data sets were analyzed by adding a term for nonhormonal background; good fits were obtained but endogenous dose estimations were not significant due to low resolving power. No thresholds were observed. Data sets were plotted using a normalized MM equation; all 178 data points were accommodated on a single graph. Response rates from ∼1% to >95% were well fit. The findings contradict the threshold assumption and low-dose safety. Calculating risk and assuming additivity of effects from multiple chemicals acting through the same mechanism rather than assuming a safe dose for nonthresholded curves is appropriate

Conductivity enhancement via chemical modification of chitosan based green polymer electrolyte

International Nuclear Information System (INIS)

Mobarak, N.N.; Ahmad, A.; Abdullah, M.P.; Ramli, N.; Rahman, M.Y.A.

2013-01-01

The potential of carboxymethyl chitosan as a green polymer electrolyte has been explored. Chitosan produced from partial deacetylation of chitin was reacted with monochloroacetic acid to form carboxymethyl chitosan. A green polymer electrolyte based chitosan and carboxymethyl chitosan was prepared by solution-casting technique. The powder and films were characterized by reflection Fourier transform infrared (ATR-FTIR) spectroscopy, 1 H nuclear magnetic resonance, elemental analysis and X-ray diffraction, electrochemical impedance spectroscopy, and scanning electron microscopy. The shift of wavenumber that represents hydroxyl and amine stretching confirmed the polymer solvent complex formation. The XRD spectra results show that chemical modification of chitosan has improved amorphous properties of chitosan. The ionic conductivity was found to increase by two magnitudes higher with the chemical modification of chitosan. The highest conductivity achieved was 3.6 × 10 −6 S cm −1 for carboxymethyl chitosan at room temperature and 3.7 × 10 −4 S cm −1 at 60 °C

Soft X-ray induced chemical modification of polysaccharides in vascular plant cell walls

International Nuclear Information System (INIS)

Cody, George D.; Brandes, Jay; Jacobsen, Chris; Wirick, Susan

2009-01-01

Scanning transmission X-ray microscopy and micro carbon X-ray Absorption Near Edge Spectroscopy (C-XANES) can provide quantitative information regarding the distribution of the biopolymers cellulose, hemicellulose, and lignin in vascular plant cell walls. In the case of angiosperms, flowering plants, C-XANES may also be able to distinguish variations in lignin monomer distributions throughout the cell wall. Polysaccharides are susceptible to soft X-ray irradiation induced chemical transformations that may complicate spectral analysis. The stability of a model polysaccharide, cellulose acetate, to variable doses of soft X-rays under conditions optimized for high quality C-XANES spectroscopy was investigated. The primary chemical effect of soft X-ray irradiation on cellulose acetate involves mass loss coincident with de-acetylation. A lesser amount of vinyl ketone formation also occurs. Reduction in irradiation dose via defocusing does enable high quality pristine spectra to be obtained. Radiation induced chemical modification studies of oak cell wall reveals that cellulose and hemicellulose are less labile to chemical modification than cellulose acetate. Strategies for obtaining pristine C-XANES spectra of polysaccharides are presented.

Concatenation of electrochemical grafting with chemical or electrochemical modification for preparing electrodes with specific surface functionality

International Nuclear Information System (INIS)

Verma, Pallavi; Maire, Pascal; Novak, Petr

2011-01-01

Surface modified electrodes are used in electro-analysis, electro-catalysis, sensors, biomedical applications, etc. and could also be used in batteries. The properties of modified electrodes are determined by the surface functionality. Therefore, the steps involved in the surface modification of the electrodes to obtain specific functionality are of prime importance. We illustrate here bridging of two routes of surface modifications namely electrochemical grafting, and chemical or electrochemical reduction. First, by electrochemical grafting an organic moiety is covalently immobilized on the surface. Then, either by chemical or by electrochemical route the terminal functional group of the grafted moiety is transformed. Using the former route we prepared lithium alkyl carbonate (-O(CH 2 ) 3 OCO 2 Li) modified carbon with potential applications in batteries, and employing the latter we prepared phenyl hydroxyl amine (-C 6 H 4 NHOH) modified carbon which may find application in biosensors. Benzyl alcohol (-C 6 H 4 CH 2 OH) modified carbon was prepared by both chemical as well as electrochemical route. We report combinations of conjugating the two steps of surface modifications and show how the optimal route of terminal functional group modification depends on the chemical nature of the moiety attached to the surface in the electrochemical grafting step.

Concatenation of electrochemical grafting with chemical or electrochemical modification for preparing electrodes with specific surface functionality

Energy Technology Data Exchange (ETDEWEB)

Verma, Pallavi; Maire, Pascal [Paul Scherrer Institut, Electrochemistry Laboratory, Section Electrochemical Energy Storage, CH-5232 Villigen PSI (Switzerland); Novak, Petr, E-mail: petr.novak@psi.c [Paul Scherrer Institut, Electrochemistry Laboratory, Section Electrochemical Energy Storage, CH-5232 Villigen PSI (Switzerland)

2011-04-01

Surface modified electrodes are used in electro-analysis, electro-catalysis, sensors, biomedical applications, etc. and could also be used in batteries. The properties of modified electrodes are determined by the surface functionality. Therefore, the steps involved in the surface modification of the electrodes to obtain specific functionality are of prime importance. We illustrate here bridging of two routes of surface modifications namely electrochemical grafting, and chemical or electrochemical reduction. First, by electrochemical grafting an organic moiety is covalently immobilized on the surface. Then, either by chemical or by electrochemical route the terminal functional group of the grafted moiety is transformed. Using the former route we prepared lithium alkyl carbonate (-O(CH{sub 2}){sub 3}OCO{sub 2}Li) modified carbon with potential applications in batteries, and employing the latter we prepared phenyl hydroxyl amine (-C{sub 6}H{sub 4}NHOH) modified carbon which may find application in biosensors. Benzyl alcohol (-C{sub 6}H{sub 4}CH{sub 2}OH) modified carbon was prepared by both chemical as well as electrochemical route. We report combinations of conjugating the two steps of surface modifications and show how the optimal route of terminal functional group modification depends on the chemical nature of the moiety attached to the surface in the electrochemical grafting step.

[Chemical modification of allergen leading to changes in its epitopic activity].

Science.gov (United States)

Babakhin, A A; Gushchin, I S; Andreev, S M; Petrukhina, A I; Viler, A V; Stokinger, B; Nolte, G; Dubuske, L M; Khaitov, R M; Petrpv, R V

1999-01-01

Modification of a model allergen ovalbumin (OA) with succinylation led to a decrease of its allergenicity measured by passive cutaneous anaphylaxis reaction, RAST inhibition assay and basophil histamine release. Modified OA stimulated OA-specific T-cell hybrid 3DO-548 to produce IL-2 at the same level as in case of non-modified OA. Modified OA did not induce anti-OA IgE, but did induce anti-OA IgG antibodies. This approach to chemical modification of allergen-selective blockade of B-cell epitopes while not affecting T-cell epitopes suggests new opportunities in creation of safe and effective allergovaccines.

Chemical modification of arginine residues in the lactose repressor

International Nuclear Information System (INIS)

Whitson, P.A.; Matthews, K.S.

1987-01-01

The lactose repressor protein was chemically modified with 2,3-butanedione and phenylglyoxal. Arginine reaction was quantitated by either amino aced analysis or incorporation of 14 C-labeled phenylglyoxal. Inducer binding activity was unaffected by the modification of arginine residues, while both operator and nonspecific DNA binding activities were diminished, although to differing degrees. The correlation of the decrease in DNA binding activities with the modification of ∼ 1-2 equiv of arginine per monomer suggests increased reactivity of a functionally essential residue(s). For both reagents, operator DNA binding activity was protected by the presence of calf thymus DNA, and the extent of reaction with phenylglyoxal was simultaneously diminished. This protection presumably results from steric restriction of reagent access to an arginine(s) that is (are) essential for DNA binding interactions. These experiments suggest that there is (are) an essential reactive arginine(s) critical for repressor binding to DNA

Bentonite chemical modification for use in industrial effluents

International Nuclear Information System (INIS)

Laranjeira, E.; Pinto, M.R.O.; Rodrigues, D.P.; Costa, B.P.; Guimaraes, P.L.F.

2010-01-01

The present work aims at synthesizing organoclays using a layered silicate of regional importance, bentonite clay, for the treatment of industrial effluents. The choice of clay to be organophilized was based on cation exchange capacity (CEC). Bentonite with higher CTC was called AN 35 (92 meq/100 g), and therefore was the one that suffered the chemical modification with salt cetyl trimethyl ammonium Cetremide, provided by Vetec.The unmodified and modified clays were characterized by FTIR and XDR. The data obtained through the characterizations confirmed the acquisition of bentonite organoclay thus suggesting its subsequent application in the treatment of industrial effluents. (author)

Chemical modification of DNA: Molecular specificity studied by tandem mass spectrometry and liquid chromatography

International Nuclear Information System (INIS)

Chang, Ching-jer; Cooks, R.G.; Chae, Whi-Gun; Wood, J.M.

1989-01-01

Chemical modifications of DNA in vitro could be directly studied by C-13 NMR and P-31 NMR, which eliminated all degradation and separation processes. The prospects of utilized the NMR method in the in vitro experiments are limited because of the inherent low sensitivity of NMR and low level of DNA modification. We have developed a reverse-phase ion-paired HPLC method to study DNA modifications by methylating agents. The structural specificity of HPLC is significantly enhanced by conjunction with the specificity of enzymic transformations. The HPLC studies have also revealed the limitation of HPLC method for simultaneous determination of many minor modified nucleosides. This problem has been overcome by tandem mass spectrometry. In conjunction with the resolving power of HPLC in separating isomers, desorption chemical ionization tandem mass spectrometry has been utilized in the determination of the modified nucleosides at the picomole level using stable-isotope labeled compounds as internal references

Chemical Modification of Uniform Soils and Soils with High/Low Plasticity Index

OpenAIRE

Li, Xuanchi; Tao, Fei; Bobet, Antonio

2015-01-01

Lime and/or cement are used to treat weak subgrade soils during construction of highways. These chemicals are mixed with the soil to improve its workability, compactability and engineering properties. INDOT (Indiana Department of Transportation) has been using chemical modification of native soils for the past 20 years. In fact, 90% of current subgrade is treated, typically with quick lime, lime byproducts or cement. For pavement design, it is customary to not include any improvement of the s...

Redirecting adenovirus tropism by genetic, chemical, and mechanical modification of the adenovirus surface for cancer gene therapy.

Science.gov (United States)

Yoon, A-Rum; Hong, Jinwoo; Kim, Sung Wan; Yun, Chae-Ok

2016-06-01

Despite remarkable advancements, clinical evaluations of adenovirus (Ad)-mediated cancer gene therapies have highlighted the need for improved delivery and targeting. Genetic modification of Ad capsid proteins has been extensively attempted. Although genetic modification enhances the therapeutic potential of Ad, it is difficult to successfully incorporate extraneous moieties into the capsid and the engineering process is laborious. Recently, chemical modification of the Ad surface with nanomaterials and targeting moieties has been found to enhance Ad internalization into the target by both passive and active mechanisms. Alternatively, external stimulus-mediated targeting can result in selective accumulation of Ad in the tumor and prevent dissemination of Ad into surrounding nontarget tissues. In the present review, we discuss various genetic, chemical, and mechanical engineering strategies for overcoming the challenges that hinder the therapeutic efficacy of Ad-based approaches. Surface modification of Ad by genetic, chemical, or mechanical engineering strategies enables Ad to overcome the shortcomings of conventional Ad and enhances delivery efficiency through distinct and unique mechanisms that unmodified Ad cannot mimic. However, although the therapeutic potential of Ad-mediated gene therapy has been enhanced by various surface modification strategies, each strategy still possesses innate limitations that must be addressed, requiring innovative ideas and designs.

The behavior of various chemical forms of nickel in graphite furnace atomic absorption spectrometry under different chemical modification approaches

International Nuclear Information System (INIS)

Kowalewska, Zofia

2012-01-01

Various organic and inorganic Ni forms were investigated using graphite furnace atomic absorption spectrometry. Experiments without chemical modification showed a wide range of characteristic mass values for Ni (from 6.7 to 29 pg) and the importance of interaction with graphite. With the aim of achieving signal unification of organic Ni forms, different ways of chemical modification were tested. Some rules that govern the behavior of Ni were found and confirmed a significant role of the organic component of the analyte molecule in the analytical process. The application of air as an internal furnace gas in the pyrolysis phase and the Pd modifier injected with the sample solution improved the signal of porphyrins, while the application of iodine and methyltrioctylammonium chloride was required for organic compounds containing oxygen-bound Ni atoms. The Ni signal was strongly diminished when an aqueous solution containing hydrochloric acid was measured with the Pd modifier injected over the sample. Using the developed analytical methods, the range of characteristic mass values for various Ni forms totally dissolved in organic or aqueous solution was 6.5–7.9 pg. - Highlights: ► Some rules that govern behavior of organic Ni forms during GFAAS analysis were found. ► Interaction with graphite can significantly influence evaporation of porphyrins. ► Determination of Ni in form of porphyrins needs Pd organic modifier and air ashing. ► Determination of Ni in O-bound organic compounds needs pretreatment with I2+MTOACl. ► Chemical modification for GFAAS determination of Ni in HCl-containing solution.

Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

International Nuclear Information System (INIS)

Gonzalez, G.; Krishnan, B.; Avellaneda, D.; Castillo, G. Alan; Das Roy, T.K.; Shaji, S.

2011-01-01

Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G. Alan; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

2011-08-31

Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

Chemical surface reactions by click chemistry: coumarin dye modification of 11-bromoundecyltrichlorosilane monolayers

International Nuclear Information System (INIS)

Haensch, Claudia; Hoeppener, Stephanie; Schubert, Ulrich S

2008-01-01

The functionalization of surfaces and the ability to tailor their properties with desired physico-chemical functions is an important field of research with a broad spectrum of applications. These applications range from the modification of wetting properties, over the alteration of optical properties, to the fabrication of molecular electronic devices. In each of these fields, it is of specific importance to be able to control the quality of the layers with high precision. The present study demonstrates an approach that utilizes the 1,3-dipolar cycloaddition of terminal acetylenes to prepare triazole-terminated monolayers on different substrates. The characterization of the precursor monolayers, the optimization of the chemical surface reactions as well as the clicking of a fluorescent dye molecule on such azide-terminated monolayers was carried out. A coumarin 343 derivative was utilized to discuss the aspects of the functionalization approach. Based on this approach, a number of potential surface reactions, facilitated via the acetylene-substituted functional molecules, for a broad range of applications is at hand, thus leading to numerous possibilities where surface modifications are concerned. These modifications can be applied on non-structured surfaces of silicon or glass or can be used on structured surfaces. Various possibilities are discussed

Differential reconstructed gene interaction networks for deriving toxicity threshold in chemical risk assessment.

Science.gov (United States)

Yang, Yi; Maxwell, Andrew; Zhang, Xiaowei; Wang, Nan; Perkins, Edward J; Zhang, Chaoyang; Gong, Ping

2013-01-01

Pathway alterations reflected as changes in gene expression regulation and gene interaction can result from cellular exposure to toxicants. Such information is often used to elucidate toxicological modes of action. From a risk assessment perspective, alterations in biological pathways are a rich resource for setting toxicant thresholds, which may be more sensitive and mechanism-informed than traditional toxicity endpoints. Here we developed a novel differential networks (DNs) approach to connect pathway perturbation with toxicity threshold setting. Our DNs approach consists of 6 steps: time-series gene expression data collection, identification of altered genes, gene interaction network reconstruction, differential edge inference, mapping of genes with differential edges to pathways, and establishment of causal relationships between chemical concentration and perturbed pathways. A one-sample Gaussian process model and a linear regression model were used to identify genes that exhibited significant profile changes across an entire time course and between treatments, respectively. Interaction networks of differentially expressed (DE) genes were reconstructed for different treatments using a state space model and then compared to infer differential edges/interactions. DE genes possessing differential edges were mapped to biological pathways in databases such as KEGG pathways. Using the DNs approach, we analyzed a time-series Escherichia coli live cell gene expression dataset consisting of 4 treatments (control, 10, 100, 1000 mg/L naphthenic acids, NAs) and 18 time points. Through comparison of reconstructed networks and construction of differential networks, 80 genes were identified as DE genes with a significant number of differential edges, and 22 KEGG pathways were altered in a concentration-dependent manner. Some of these pathways were perturbed to a degree as high as 70% even at the lowest exposure concentration, implying a high sensitivity of our DNs approach

Association of Odor Thresholds and Responses in Cerebral Blood Flow of the Prefrontal Area during Olfactory Stimulation in Patients with Multiple Chemical Sensitivity.

Directory of Open Access Journals (Sweden)

Kenichi Azuma

Full Text Available Multiple chemical sensitivity (MCS is a disorder characterized by nonspecific and recurrent symptoms from various organ systems associated with exposure to low levels of chemicals. Patients with MCS process odors differently than controls do. Previously, we suggested that this odor processing was associated with increased regional cerebral blood flow (rCBF in the prefrontal area during olfactory stimulation using near-infrared spectroscopic (NIRS imaging. The aim of this study was to investigate the association of odor thresholds and changes in rCBF during olfactory stimulation at odor threshold levels in patients with MCS. We investigated changes in the prefrontal area using NIRS imaging and a T&T olfactometer during olfactory stimulation with two different odorants (sweet and fecal at three concentrations (zero, odor recognition threshold, and normal perceived odor level in 10 patients with MCS and six controls. The T&T olfactometer threshold test and subjective assessment of irritating and hedonic odors were also performed. The results indicated that the scores for both unpleasant and pungent odors were significantly higher for those for sweet odors at the normal perceived level in patients with MCS than in controls. The brain responses at the recognition threshold (fecal odor and normal perceived levels (sweet and fecal odors were stronger in patients with MCS than in controls. However, significant differences in the odor detection and recognition thresholds and odor intensity score between the two groups were not observed. These brain responses may involve cognitive and memory processing systems during past exposure to chemicals. Further research regarding the cognitive features of sensory perception and memory due to past exposure to chemicals and their associations with MCS symptoms is needed.

Physico-chemical modifications of plastics by ionization

International Nuclear Information System (INIS)

Rouif, S.

2002-01-01

The industrial use of ionizing radiations (beta and gamma), initially for the sterilization of medico-surgical instruments and for the preservation of food products, has led to the development of the chemistry of polymers under radiations. Ionizing radiations can initiate chemical reactions (chain cutting, poly-additions, polymerization etc..) thanks to the formation of free radicals. The main applications concerns the degradation of plastics, the reticulation of plastics and of woods impregnated with resin, and the grafting of polymers. The processing of plastic materials was initially performed with low energy electron accelerators (0.1 to 3 MeV), allowing only surface treatments, while recent high energy accelerators (10 MeV) and gamma facilities allow the treatment in depth of materials (from few cm to 1 m). This article describes the industrial treatments performed with such high energy facilities: 1 - action of ionizing radiations on plastic materials: different types of ionizing radiations, action of beta and gamma radiations, chemical changes induced by beta and gamma radiations; 2 - reticulation of plastic materials submitted to beta and gamma radiations: radio-'reticulable' polymers and reticulation co-agents, modification of the properties of reticulated plastic materials under beta and gamma radiations; 3 - industrial aspects of reticulation under beta and gamma radiation: industrial irradiation facilities, dosimetry and radio-reticulation control, applications; 4 - conclusion. (J.S.)

Influence of major-groove chemical modifications of DNA on transcription by bacterial RNA polymerases.

Science.gov (United States)

Raindlová, Veronika; Janoušková, Martina; Slavíčková, Michaela; Perlíková, Pavla; Boháčová, Soňa; Milisavljevič, Nemanja; Šanderová, Hana; Benda, Martin; Barvík, Ivan; Krásný, Libor; Hocek, Michal

2016-04-20

DNA templates containing a set of base modifications in the major groove (5-substituted pyrimidines or 7-substituted 7-deazapurines bearing H, methyl, vinyl, ethynyl or phenyl groups) were prepared by PCR using the corresponding base-modified 2'-deoxyribonucleoside triphosphates (dNTPs). The modified templates were used in an in vitro transcription assay using RNA polymerase from Bacillus subtilis and Escherichia coli Some modified nucleobases bearing smaller modifications (H, Me in 7-deazapurines) were perfectly tolerated by both enzymes, whereas bulky modifications (Ph at any nucleobase) and, surprisingly, uracil blocked transcription. Some middle-sized modifications (vinyl or ethynyl) were partly tolerated mostly by the E. colienzyme. In all cases where the transcription proceeded, full length RNA product with correct sequence was obtained indicating that the modifications of the template are not mutagenic and the inhibition is probably at the stage of initiation. The results are promising for the development of bioorthogonal reactions for artificial chemical switching of the transcription. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Plant Sterols: Chemical and Enzymatic Structural Modifications and Effects on Their Cholesterol-Lowering Activity.

Science.gov (United States)

He, Wen-Sen; Zhu, Hanyue; Chen, Zhen-Yu

2018-03-28

Plant sterols have attracted increasing attention due to their excellent cholesterol-lowering activity. However, free plant sterols have some characteristics of low oil solubility, water insolubility, high melting point, and low bioavailability, which greatly limit their application in foods. Numerous studies have been undertaken to modify their chemical structures to improve their chemical and physical properties in meeting the needs of various applications. The present review is to summarize the literature and update the progress on structural modifications of plant sterols in the following aspects: (i) synthesis of plant sterol esters by esterification and transesterification with hydrophobic fatty acids and triacylglycerols to improve their oil solubility, (ii) synthesis of plant sterol derivatives by coupling with various hydrophilic moieties to enhance their water solubility, and (iii) mechanisms by which plant sterols reduce plasma cholesterol and the effect of structural modifications on plasma cholesterol-lowering activity of plant sterols.

Damage Mechanisms In Polymers Upon NIR Femtosecond Pulse Laser Irradiation: Sub-Threshold Processes And Their Implications For Laser Safety Applications

International Nuclear Information System (INIS)

Bonse, Joern; Krueger, Joerg; Solis, Javier; Spielmann, Christian; Lippert, Thomas

2010-01-01

This contribution investigates laser-induced damage of thin film and bulk polymer samples, with the focus on physical processes occurring close to the damage threshold. In-situ real-time reflectivity (RTR) measurements with picosecond (ps) and nanosecond (ns) temporal resolution were performed on thin polymer films on a timescale up to a few microseconds (μs). A model for polymer thin film damage is presented, indicating that irreversible chemical modification processes take place already below the fluence threshold for macroscopic damage. On dye-doped bulk polymer filters (as used for laser goggles), transmission studies using fs-and ps-laser pulses reveal the optical saturation behavior of the material and its relation to the threshold of permanent damage. Implications of the sub-threshold processes for laser safety applications will be discussed for thin film and bulk polymer damage.

Silica aerogel threshold Cherenkov counters for the JLab Hall A spectrometers: improvements and proposed modifications

CERN Document Server

Lagamba, L; Colilli, S; Crateri, R; De Leo, R; Frullani, S; Garibaldi, F; Giuliani, F; Gricia, M; Iodice, M; Iommi, R; Leone, A; Lucentini, M; Mostarda, A; Nappi, E; Perrino, R; Pierangeli, L; Santavenere, F; Urciuoli, G M

2001-01-01

Recently approved experiments at Jefferson Lab Hall A require a clean kaon identification in a large electron, pion, and proton background environment. To this end, improved performance is required of the silica aerogel threshold Cherenkov counters installed in the focal plane of the two Hall A spectrometers. In this paper we propose two strategies to improve the performance of the Cherenkov counters which presently use a hydrophilic aerogel radiator, and convey Cherenkov photons towards the photomultipliers by means of mirrors with a parabolic shape in one direction and flat in the other. The first strategy is aerogel baking. In the second strategy we propose a modification of the counter geometry by replacing the mirrors with a planar diffusing surface and by displacing in a different way the photomultipliers. Tests at CERN with a 5 GeV/c multiparticle beam revealed that both the strategies are able to increase significantly the number of the detected Cherenkov photons and, therefore, the detector performan...

The influence of chemical methods (acid modification) on elephant foot yam flour to improve physical and chemical quality on processed food

Science.gov (United States)

Paramita, Octavianti; Wahyuningsih, Ansori, Muhammad

2018-03-01

This study was aimed at improving the physicochemical quality of elephant foot yam flour in Gunungpati, Semarang by acid modification. The utilization of elephant foot yam flour in several processed food was also discussed in this study. The flour of the experimental result discussed in this study was expected to become a reference for the manufacturers of elephant foot yam flour and its processed food in Gunungpati. This study modified the elephant foot yam flour using acid modification method. The physical and chemical quality of each elephant foot yam flour of the experimental result sample were assessed using proximate analysis. The resulting tuber flour weighed 50 grams and the soaked in acid solution with various concentrations 5 %, 10 % and 15 % with soaking duration 30, 60 and 90 minutes at temperature 35 °C. The resulting suspension was washed 3 times, filtered and then dried by cabinet dryer using 46 °C for 2 days. The dried flour was sifted with a 80 mesh sieve. Chemical test was conducted after elephant foot yam was acid modification to determine changes in the quality flour: test levels of protein, fat, crude fiber content, moisture content, ash content and starch content. In addition, color tests and granular test on elephant foot yam flour were also conducted. The acid modification as chemical treatment on elephant foot yam flour in this study was able to change the functional properties of elephant foot yam flour towards a better processing characterized by a brighter color (L = 80, a = 8 and b = 12), the hydrolysis of polysaccharides flour into shorter chain (flour content decreased to 72%), the expansion of granules in elephant foot yam resulting in a process - ready flour, and better monolayer water content of 11%. The content of protein and fiber on the elephant foot yam flour also can be maintained at a level of 8% and 1.9% levels.

Patterns of development of unspecific reaction of cells and modification of chemical protection

International Nuclear Information System (INIS)

Veksler, A.M.; Korystov, Yu.N.; Kublik, L.N.; Ehjdus, L.Kh.

1980-01-01

A study was made of a correlation between radioprotective efficiency of different chemical agents (weak electrolytes) and conditions of treatment. It was demonstrated that the pattern of changes in the protection efficiency, with modification thereof, is similar to that of the development of unspecific reaction and determined by the intracellular concentration of the chemical agents, which, in turn, is function of physicochemical parameters of the substance and pH gradient between cell and medium. With similar intracellular concentration, caffeine-benzoate, thioglicolic acid and caffeine proved to be equally effective, while the protective effect of cysteamine was appreciably higher

Areal variation and chemical modification of weathered shale infiltration characteristics

International Nuclear Information System (INIS)

Luxmoore, R.J.; Spalding, B.P.; Munro, I.M.

1981-01-01

Spatial variability of infiltration into a weathered shale subsoil was evaluated at a site proximal to one used for shallow land burial of low-level radioactive waste at Oak Ridge National Laboratory. Double-ring infiltometers were installed at 48 locations on a 2- by 2-m grid after the removal of 1 to 2 m of soil (Litz-Sequoia association, Typic Hapludults). Infiltration rates were measured before and during the 0- to 20- and 239- to 259-day periods following treatment with solutions of NaOH, KOH, NaF, NaAlO 2 , and Na 2 SiO 3 at rates of 151 equivalents/m 2 . None of these chemical treatments significantly altered infiltration rate, indicating that chemical modification of soil exchange properties may be achieved without inducing hydrologic disturbance in these subsoils. A semivariogram analysis of infiltration data showed that areal variability was random; any spatial patterning must therefore occur at a smaller scale than 2 m

Modification of chemical reactivity of enzymatic hydrolysis lignin by ultrasound treatment in dilute alkaline solutions.

Science.gov (United States)

Ma, Zhuoming; Li, Shujun; Fang, Guizhen; Patil, Nikhil; Yan, Ning

2016-12-01

In this study, we have explored various ultrasound treatment conditions for structural modification of enzymatic hydrolysis lignin (EHL) for enhanced chemical reactivity. The key structural modifications were characterized by using a combination of analytical methods, including, Fourier Transform-Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance ( 1 H NMR), Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and Folin-Ciocalteu (F-C) method. Chemical reactivity of the modified EHL samples was determined by both 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity and their reactivity towards formaldehyde. It was observed that the modified EHL had a higher phenolic hydroxyl group content, a lower molecular weight, a higher reactivity towards formaldehyde, and a greater antioxidant property. The higher reactivity demonstrated by the samples after treatment suggesting that ultrasound is a promising method for modifying enzymatic hydrolysis lignin for value-added applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Engineering specific chemical modification sites into a collagen-like protein from Streptococcus pyogenes.

Science.gov (United States)

Stoichevska, Violet; Peng, Yong Y; Vashi, Aditya V; Werkmeister, Jerome A; Dumsday, Geoff J; Ramshaw, John A M

2017-03-01

Recombinant bacterial collagens provide a new opportunity for safe biomedical materials. They are readily expressed in Escherichia coli in good yield and can be readily purified by simple approaches. However, recombinant proteins are limited in that direct secondary modification during expression is generally not easily achieved. Thus, inclusion of unusual amino acids, cyclic peptides, sugars, lipids, and other complex functions generally needs to be achieved chemically after synthesis and extraction. In the present study, we have illustrated that bacterial collagens that have had their sequences modified to include cysteine residue(s), which are not normally present in bacterial collagen-like sequences, enable a range of specific chemical modification reactions to be produced. Various model reactions were shown to be effective for modifying the collagens. The ability to include alkyne (or azide) functions allows the extensive range of substitutions that are available via "click" chemistry to be accessed. When bifunctional reagents were used, some crosslinking occurred to give higher molecular weight polymeric proteins, but gels were not formed. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 806-813, 2017. © 2016 Wiley Periodicals, Inc.

Effects of chemical modifications on photophysics and exciton dynamics on {pi}-conjugation attenuated and metal-chelated photoconducting polymers

Energy Technology Data Exchange (ETDEWEB)

Chen, L. X.; Jager, W. J. H.; Gosztola, D. J.; Niemczyk, M. P.; Wasielewski, M. R.

2000-03-11

Effects of two types of chemical modifications on photoconducting polymers consisting of polyphenylenevinylene (PPV) derivatives are studied by static and ultrafast transient optical spectroscopy as well as semi-empirical ZINDO calculations. The first type of modification inserts 2,2{prime}-bipyridyl-5-vinylene units (bpy V) in the PPV backbone, and the second type involves metal-chelation with the bpy sites. Photoluminescence and exciton dynamics of polymers 1 and 2 with PV:bpyV ratios of 1 and 3 were examined in solution, and compared to those of the homopolymer, poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV). Similar studies were carried out for several metal-chelated polymers. These results can be explained by changes in {pi}-conjugation throughout the polymer backbone. The attenuation in {pi}-conjugation by the chemical modifications transforms a conducting polymer from one-dimensional semiconductor to molecular aggregates.

Expanding the Bioactive Chemical Space of Anthrabenzoxocinones through Engineering the Highly Promiscuous Biosynthetic Modification Steps.

Science.gov (United States)

Mei, Xianyi; Yan, Xiaoli; Zhang, Hui; Yu, Mingjia; Shen, Guangqing; Zhou, Linjun; Deng, Zixin; Lei, Chun; Qu, Xudong

2018-01-19

Anthrabenzoxocinones (ABXs) including (-)-ABXs and (+)-ABXs are a group of bacterial FabF-specific inhibitors with potent antimicrobial activity of resistant strains. Optimization of their chemical structures is a promising method to develop potent antibiotics. Through biosynthetic investigation, we herein identified and characterized two highly promiscuous enzymes involved in the (-)-ABX structural modification. The promiscuous halogenase and methyltransferase can respectively introduce halogen-modifications into various positions of the ABX scaffolds and methylation to highly diverse substrates. Manipulation of their activity in both of the (-)-ABXs and (+)-ABXs biosyntheses led to the generation of 14 novel ABX analogues of both enantiomers. Bioactivity assessment revealed that a few of the analogues showed significantly improved antimicrobial activity, with the C3-hydroxyl and chlorine substitutions critical for their activity. This study enormously expands the bioactive chemical space of the ABX family and FabF-specific inhibitors. The disclosed broad-selective biosynthetic machineries and structure-activity relationship provide a solid basis for further generation of potent antimicrobial agents.

ReportSites - A Computational Method to Extract Positional and Physico- Chemical Information from Large-Scale Proteomic Post-Translational Modification Datasets

DEFF Research Database (Denmark)

Edwards, Alistair; Edwards, Gregory; Larsen, Martin Røssel

2012-01-01

-translational modification data sets, wherein patterns of sequence surrounding processed sites may reveal more about the functional and structural requirements of the modification and the biochemical processes that regulate them. Results: We developed Report Sites using a test set of phosphoproteomic data from rat......-chemical environment (local pI and hydrophobicity). These were then also compared to corresponding values extracted from the full database to allow comparison of phosphorylation trends. Conclusions: Report Sites enabled physico-chemical aspects of protein phosphorylation to be deciphered in a test set of eleven...... thousand phospho sites. Basic properties of modified proteins, such as site location in the context of the complete protein, were also documented. This program can be easily adapted to any post-translational modification (or, indeed, to any defined amino acid sequence), or expanded to include more...

Baryon-antibaryon threshold and ω-baryonium mixing

International Nuclear Information System (INIS)

Gavai, R.V.

1981-01-01

It is shown that in any dual-topological-unitarization model of ω-baryonium (B) mixing at the cylinder level, in which the production of baryon-antibaryon (bb-bar) pairs can take place only above a certain threshold energy, the phenomenologically relevant ω and B trajectories do not mix below bb-bar threshold. However, their couplings to external particles do get modified. The ω-B mixing angle theta/sub omegahyphenB/, which characterizes these coupling modification effects below bb-bar threshold at t = 0, is estimated in some models. These estimates are found to agree reasonably well with the existing phenomenological bound on theta/sub omegahyphenB/

Effects of electron-transfer chemical modification on the electrical characteristics of graphene

International Nuclear Information System (INIS)

Fan Xiaoyan; Tanigaki, Katsumi; Nouchi, Ryo; Yin Lichang

2010-01-01

Because of the large reactivity of single layer graphene to electron-transfer chemistries, 4-nitrobenzene diazonium tetrafluoroborate is employed to modify the electrical properties of graphene field-effect transistors. After modification, the transfer characteristics of chemically modified graphene show a reduction in the minimum conductivity, electron-hole mobility asymmetry, a decrease in the electron/hole mobility, and a positive shift of the charge neutrality point with broadening of the minimum conductivity region. These phenomena are attributed to a dediazoniation reaction and the adsorbates on the graphene surface.

Effects of electron-transfer chemical modification on the electrical characteristics of graphene

Energy Technology Data Exchange (ETDEWEB)

Fan Xiaoyan; Tanigaki, Katsumi [Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Nouchi, Ryo [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8578 (Japan); Yin Lichang, E-mail: nouchi@sspns.phys.tohoku.ac.jp [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

2010-11-26

Because of the large reactivity of single layer graphene to electron-transfer chemistries, 4-nitrobenzene diazonium tetrafluoroborate is employed to modify the electrical properties of graphene field-effect transistors. After modification, the transfer characteristics of chemically modified graphene show a reduction in the minimum conductivity, electron-hole mobility asymmetry, a decrease in the electron/hole mobility, and a positive shift of the charge neutrality point with broadening of the minimum conductivity region. These phenomena are attributed to a dediazoniation reaction and the adsorbates on the graphene surface.

Chemical modification of b-lactoglobulin by quinones

Directory of Open Access Journals (Sweden)

DUSAN SLADIC

2003-05-01

Full Text Available The avarone/avarol quinone/hydroquinone couple, as well as their derivatives show considerable antitumor activity. In this work, covalent modifications of b-lactoglobulin, isolated from cow milk, by avarone, its model compound 2-tert-butyl-1,4-benzoquinone, and several of their alkylthio derivatives were studied. The techniques applied for assaying the modifications were: UV/VIS spectrophotometry, SDS PAGE and isoelectrofocusing. The results of the SDS PAGE suggest that polymerisation of the protein occurs. The shift of the pI of the protein upon modification toward lower values indicates that lysine amino groups are the principal site of the reaction of b-lactoglobulin with the quinones.

Ultrastructural demonstration of chemical modification of melanogenesis in hairless mouse skin

International Nuclear Information System (INIS)

Nishimura, M.; Gellin, G.A.; Hoshino, S.; Epstein, J.H.; Epstein, W.L.; Fukuyama, K.

1982-01-01

We investigated chemical and physical modifications of the genetically determined ultrastructure of melanosomes. The flank skin of hairless mice was treated with ultraviolet energy (UV) shorter than 320 nm or with a combination of a photosensitizer and UV (PUVA treatment). All melanosomes in the induced melanocytes and those in resident melanocytes in the ear skin showed eumelanogenesis, although the degree of melanin deposition differed considerably according to the induction process. Eumelanogenesis was most advanced in the resident melanocytes while PUVA-induced melanocytes showed more immature premelanosomes. We then topically applied 4-tertiary butyl catechol on the skin. The depigmenting agent caused an appearance of pheomelanosomes. The alteration in melanogenesis was seen most distinctly in premelanosomes of the PUVA-induced cells. Altered ultrastructure was also observed in matured melanosomes; this change was most apparent in the resident melanocytes. These findings indicate that cells with eumelanogenesis may undergo pheomelanogenesis. The present study demonstrated effects of chemicals on genetically determined function of melanocytes by quantitative analysis of melanosome ultrastructure

Thresholds of Toxicological Concern - Setting a threshold for testing below which there is little concern.

Science.gov (United States)

Hartung, Thomas

2017-01-01

Low dose, low risk; very low dose, no real risk. Setting a pragmatic threshold below which concerns become negligible is the purpose of thresholds of toxicological concern (TTC). The idea is that such threshold values do not need to be established for each and every chemical based on experimental data, but that by analyzing the distribution of lowest or no-effect doses of many chemicals, a TTC can be defined - typically using the 5th percentile of this distribution and lowering it by an uncertainty factor of, e.g., 100. In doing so, TTC aims to compare exposure information (dose) with a threshold below which any hazard manifestation is very unlikely to occur. The history and current developments of this concept are reviewed and the application of TTC for different regulated products and their hazards is discussed. TTC lends itself as a pragmatic filter to deprioritize testing needs whenever real-life exposures are much lower than levels where hazard manifestation would be expected, a situation that is called "negligible exposure" in the REACH legislation, though the TTC concept has not been fully incorporated in its implementation (yet). Other areas and regulations - especially in the food sector and for pharmaceutical impurities - are more proactive. Large, curated databases on toxic effects of chemicals provide us with the opportunity to set TTC for many hazards and substance classes and thus offer a precautionary second tier for risk assessments if hazard cannot be excluded. This allows focusing testing efforts better on relevant exposures to chemicals.

Improving lead adsorption through chemical modification of wheat straw by lactic acid

Science.gov (United States)

Mu, Ruimin; Wang, Minxiang; Bu, Qingwei; Liu, Dong; Zhao, Yanli

2018-01-01

This work describes the creation of a new cellulosic material derived from wheat straw modified by lactic acid for adsorption of lead in aqueous solution, called 0.3LANS (the concentration of the lactic acid were 0.3mol/L). Batch experiments were conducted to study the effects of initial pH value, contact time, adsorbent dose, initial concentration and temperature. Fourier transform infrared (FTIR), Elemental analysis, BET surface area and Scanning electron micrographs (SEM) analysis were used to investigate the chemical modification. Adsorption isotherm models namely, Langmuir, Freundlich were used to analyse the equilibrium data, and the Langmuir isotherm model provided the best correlation, means that the adsorption was chemical monolayer adsorption and the adsorption capacity qm was increased with increasing temperature, and reached 51.49mg/g for 0.3LANS at 35°C, showing adsorption was exothermic.

40 CFR 68.115 - Threshold determination.

Science.gov (United States)

2010-07-01

... (CONTINUED) CHEMICAL ACCIDENT PREVENTION PROVISIONS Regulated Substances for Accidental Release Prevention... process exceeds the threshold. (b) For the purposes of determining whether more than a threshold quantity... portion of the process is less than 10 millimeters of mercury (mm Hg), the amount of the substance in the...

Compositional threshold for Nuclear Waste Glass Durability

International Nuclear Information System (INIS)

Kruger, Albert A.; Farooqi, Rahmatullah; Hrma, Pavel R.

2013-01-01

Within the composition space of glasses, a distinct threshold appears to exist that separates 'good' glasses, i.e., those which are sufficiently durable, from 'bad' glasses of a low durability. The objective of our research is to clarify the origin of this threshold by exploring the relationship between glass composition, glass structure and chemical durability around the threshold region

Laser-assisted modification of polystyrene surfaces for cell culture applications

International Nuclear Information System (INIS)

Pfleging, Wilhelm; Bruns, Michael; Welle, Alexander; Wilson, Sandra

2007-01-01

Laser-assisted patterning and modification of polystyrene (PS) was investigated with respect to applications in micro-fluidics and cell culture. For this purpose the wettability, the adsorption of proteins and the adhesion of animal cells were investigated as function of laser- and processing parameters. The change of surface chemistry was characterized by X-ray photoelectron spectroscopy. The local formation of chemical structures suitable for improved cell adhesion was realized on PS surfaces by UV laser irradiation. Above and below the laser ablation threshold two different mechanisms affecting cell adhesion were detected. In the first case the debris deposited on and along laser irradiated areas was responsible for improved cell adhesion, while in the second case a photolytic activation of the polymer surface including a subsequent oxidization in oxygen or ambient air is leading to a highly localized alteration of protein adsorption from cell culture media and finally to increased cell adhesion. Laser modifications of PS using suitable exposure doses and an appropriate choice of the processing gas (helium or oxygen) enabled a highly localized control of wetting. The dynamic advancing contact angle could be adjusted between 2 o and 150 o . The hydrophilic and hydrophobic behaviour are caused by chemical and topographical surface changes

Chemical modification of hybrid nanostructures (POSS for application as lubricant

Directory of Open Access Journals (Sweden)

Caroline Luvison

2014-08-01

Full Text Available Polyhedral oligomeric silsesquioxanes (POSS are hybrid structures type RSiO15n, with n organic groups R. These molecules can be easily functionalized by simply changing the chemical constitution of the organic groups. In this work, chemical modification of POSS-NH2 was performed by amidation reaction with butyric acid at elevated temperature, 160°C. The formation of the amide group is evinced by the appearance of NH angular deformation band at 1540 cm-1 in the FTIR spectra. Approximately 40% of the amino groups reacted, according to titration results. The formation of the amide groups resulted in a shift of the glass transition temperature (Tg from -36.9°C to -25.6°C for the modified-POSS sample. Both POSS-NH2 and modified-POSS samples exhibited similar thermal degradation pattern. Analysis of the pairs distribution function (PDF has determined that the hybrid nanoparticles are separated by a periodic distance of approximately 1.32 nm. POSS-NH2 and modified-POSS exhibit newtonian behavior, which will range from 10-1 s-1 and 1000 s-1. The viscosity decreased with increasing temperature, a typical behavior of liquid lubricants.

Acceptance threshold hypothesis is supported by chemical similarity of cuticular hydrocarbons in a stingless bee, Melipona asilvai.

Science.gov (United States)

Nascimento, D L; Nascimento, F S

2012-11-01

The ability to discriminate nestmates from non-nestmates in insect societies is essential to protect colonies from conspecific invaders. The acceptance threshold hypothesis predicts that organisms whose recognition systems classify recipients without errors should optimize the balance between acceptance and rejection. In this process, cuticular hydrocarbons play an important role as cues of recognition in social insects. The aims of this study were to determine whether guards exhibit a restrictive level of rejection towards chemically distinct individuals, becoming more permissive during the encounters with either nestmate or non-nestmate individuals bearing chemically similar profiles. The study demonstrates that Melipona asilvai (Hymenoptera: Apidae: Meliponini) guards exhibit a flexible system of nestmate recognition according to the degree of chemical similarity between the incoming forager and its own cuticular hydrocarbons profile. Guards became less restrictive in their acceptance rates when they encounter non-nestmates with highly similar chemical profiles, which they probably mistake for nestmates, hence broadening their acceptance level.

Bioaccumulation and chemical modification of Tc by soil bacteria

International Nuclear Information System (INIS)

Henrot, J.

1989-01-01

Bioaccumulation and chemical modification of pertechnetate (TcO 4 -) by aerobically and anaerobically grown soil bacteria and by pure cultures of sulfate-reducing bacteria (Desulfovibrio sp.) were studied to gain insight on the possible mechanisms by which bacteria can affect the solubility of Tc in soil. Aerobically grown bacteria had no apparent effect on TcO 4 -; they did not accumulate Tc nor modify its chemical form. Anaerobically grown bacteria exhibited high bioaccumulation and reduced TcO 4 -, enabling its association with organics of the growth medium. Reduction was a metabolic process and not merely the result of reducing conditions in the growth medium. Association of Tc with bacterial polysaccharides was observed only in cultures of anaerobic bacteria. Sulfate-reducing bacteria efficiently removed Tc from solution and promoted its association with organics. Up to 70% of the total Tc in the growth medium was bioaccumulated and/or precipitated. The remaining Tc in soluble form was entirely associated with organics. Pertechnetate was not reduced by the same mechanism as dissimilatory sulfate reduction, but rather by some reducing agent released in the growth medium. A calculation of the amount of Tc that could be associated with the bacterial biomass present in soil demonstrates that high concentration ratios in cultures do not necessarily imply that bioaccumulation is an important mechanism for long-term retention of Tc in soil

Soil-release behaviour of polyester fabrics after chemical modification with polyethylene glycol

Science.gov (United States)

Miranda, T. M. R.; Santos, J.; Soares, G. M. B.

2017-10-01

The fibres cleanability depends, among other characteristics, on their hydrophilicity. Hydrophilic fibres are easy-wash materials but hydrophobic fibres are difficult to clean due to their higher water-repellent surfaces. This type of surfaces, like polyester (PET), produce an accumulation of electrostatic charges, which favors adsorption and retention of dirt. Thus, the polyester soil-release properties can be increased by finishing processes that improve fiber hydrophilicity. In present study, PET fabric modification was described by using poly(ethylene glycol) (PEG) and N,N´-dimethylol-4,5-dihydroxyethylene urea (DMDHEU) chemically modified resin. Briefly, the modification process was carried out in two steps, one to hydrolyse the polyester and create hydroxyl and carboxylic acid groups on the surface and other to crosslink the PEG chains. The resulting materials were characterized by contact angle, DSC and FTIR-ATR methods. Additionally, the soil release behavior and the mechanical properties of modified PET were evaluated. For the best process conditions, the treated PET presented 0° contact angle, grade 5 stain release and acceptable mechanical performance.

Altering protein surface charge with chemical modification modulates protein–gold nanoparticle aggregation

International Nuclear Information System (INIS)

Jamison, Jennifer A.; Bryant, Erika L.; Kadali, Shyam B.; Wong, Michael S.; Colvin, Vicki L.; Matthews, Kathleen S.; Calabretta, Michelle K.

2011-01-01

Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein–AuNP assembly or influence the formation of the protein “corona,” modification of the protein surface as a mechanism to modulate protein–AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteins—lysozyme with high isoelectric point (pI) and established interactions with AuNP; α-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein–AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein–NP solutions and other properties due to aggregate formation. Above the expected pI, however, protein–AuNP interaction is minimal, and both components remain isolated, presumably because both species are negatively charged. These data demonstrate that protein modification provides a powerful tool for modulating whether nanoparticle–protein interactions result in material aggregation. The results also underscore that naturally occurring protein modifications found in vivo may be critical in defining nanoparticle–protein corona compositions.

Topological surface states of Bi{sub 2}Te{sub 2}Se are robust against surface chemical modification

Energy Technology Data Exchange (ETDEWEB)

Thomas, Conor R.; Sahasrabudhe, Girija; Kushwaha, Satya Kumar; Cava, Robert J.; Schwartz, Jeffrey [Department of Chemistry, Princeton University, Princeton, NJ (United States); Xiong, Jun [Department of Physics, Princeton University, Princeton, NJ (United States)

2014-12-01

The robustness of the Dirac-like electronic states on the surfaces of topological insulators (TIs) during materials process-ing is a prerequisite for their eventual device application. Here, the (001) cleavage surfaces of crystals of the topological insulator Bi{sub 2}Te{sub 2}Se (BTS) were subjected to several surface chemical modification procedures that are common for electronic materials. Through measurement of Shubnikov-de Hass (SdH) oscillations, which are the most sensitive measure of their quality, the surface states of the treated surfaces were compared to those of pristine BTS that had been exposed to ambient conditions. In each case - surface oxidation, deposition of thin layers of Ti or Zr oxides, or chemical modification of the surface oxides - the robustness of the topological surface electronic states was demonstrated by noting only very small changes in the frequency and amplitude of the SdH oscillations. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Comparison of some effects of modification of a polylactide surface layer by chemical, plasma, and laser methods

Science.gov (United States)

Moraczewski, Krzysztof; Rytlewski, Piotr; Malinowski, Rafał; Żenkiewicz, Marian

2015-08-01

The article presents the results of studies and comparison of selected properties of the modified PLA surface layer. The modification was carried out with three methods. In the chemical method, a 0.25 M solution of sodium hydroxide in water and ethanol was utilized. In the plasma method, a 50 W generator was used, which produced plasma in the air atmosphere under reduced pressure. In the laser method, a pulsed ArF excimer laser with fluency of 60 mJ/cm2 was applied. Polylactide samples were examined by using the following techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and X-ray photoelectron spectroscopy (XPS). Images of surfaces of the modified samples were recorded, contact angles were measured, and surface free energy was calculated. Qualitative and quantitative analyses of chemical composition of the PLA surface layer were performed as well. Based on the survey it was found that the best modification results are obtained using the plasma method.

Effect of chemical modifications of cellulose on the activity of a cellulase from Aspergillus niger

Energy Technology Data Exchange (ETDEWEB)

Boyer, R.F.; Redmond, M.A.

1983-05-01

Five chemically modified forms of cellulose were prepared, characterized, and tested as substrates for a homogeneous glucanohydrolase from A. niger. The relative order of reactivity at pH 4.0 was DEAE = PEI more than benzyl DEAE more than cellulose more than P more than CM. This indicates that positively charged cellulose substrates are more susceptible to hydrolysis by the cellulase. This observation strengthens an earlier proposal that carboxyl groups on the enzyme are involved in substrate binding and catalytic action. Chemical modification is suggested as a method to increase the rate of enzymatic hydrolysis of cellulose, a process now in the commercial development stage. (Refs. 27).

A Chemical-Adsorption Strategy to Enhance the Reaction Kinetics of Lithium-Rich Layered Cathodes via Double-Shell Surface Modification.

Science.gov (United States)

Guo, Lichao; Li, Jiajun; Cao, Tingting; Wang, Huayu; Zhao, Naiqin; He, Fang; Shi, Chunsheng; He, Chunnian; Liu, Enzuo

2016-09-21

Sluggish surface reaction kinetics hinders the power density of Li-ion battery. Thus, various surface modification techniques have been applied to enhance the electronic/ionic transfer kinetics. However, it is challenging to obtain a continuous and uniform surface modification layer on the prime particles with structure integration at the interface. Instead of classic physical-adsorption/deposition techniques, we propose a novel chemical-adsorption strategy to synthesize double-shell modified lithium-rich layered cathodes with enhanced mass transfer kinetics. On the basis of experimental measurement and first-principles calculation, MoO2S2 ions are proved to joint the layered phase via chemical bonding. Specifically, the Mo-O or Mo-S bonds can flexibly rotate to bond with the cations in the layered phase, leading to the good compatibility between the thiomolybdate adsorption layer and layered cathode. Followed by annealing treatment, the lithium-excess-spinel inner shell forms under the thiomolybdate adsorption layer and functions as favorable pathways for lithium and electron. Meanwhile, the nanothick MoO3-x(SO4)x outer shell protects the transition metal from dissolution and restrains electrolyte decomposition. The double-shell modified sample delivers an enhanced discharge capacity almost twice as much as that of the unmodified one at 1 A g(-1) after 100 cycles, demonstrating the superiority of the surface modification based on chemical adsorption.

Effect of chemical modification on reduction and sorptive properties of chars from hydropyrolysis of coal

Energy Technology Data Exchange (ETDEWEB)

Stanczyk, K.; Miga, K.; Fabis, G.; Jastrzab, K. [Polskiej Akademii Nauk, Gliwice (Poland)

1998-01-01

Hydropyrolysis of bituminous coal and lignite as way of synthesis of adsorbents has been applied. Chemical modification of chars based on simultaneous carbonization of coal and plastics containing sulfur and nitrogen has been carried out. It was stated that modified chars exhibit better reduction and sorptive properties than non-modified and that modified adsorbents made of lignite exceed commercial ones. 7 refs., 4 figs., 3 tabs.

Comparison the performance of different catalysts in chemical modification of Poplar wood with Glutaraldehyde

Directory of Open Access Journals (Sweden)

ندا اسماعیلی

2016-12-01

Full Text Available In this study, the effect of different catalysts on chemical modification of poplar wood and physical properties of the resulting product was evaluated. 12.5% HCl and water soluble salts containing ZnCl2, CaCl2, AlCl3, MgCl2 (based on the weight of glutaraldehyde and 1% Al2O3, SiO2 and ZnO nano particles (based on the weight of glutaraldehyde were used. After heating in oven for 48 hour, modification with glutaraldehyde and MgCl2, ZnO nano particles, SiO2, Al2O3, ZnCl2, AlCl3, CaCl2 and HCl as catalysts were resulted to 14.5, 12.57, 10.62, 8.69, 8.51, 7.19, 5.97 and 5.41 % weight gain respectively. After 24h soaking in water, the physical properties of modified specimens, such as water absorption, volume swelling and ASE were measured. The highest and lowest bulking were calculated for Mgcl2 and Hcl catalysts with 6.98 and 2.37% respectively. The modification in presence of Mgcl2 catalyst was shown highest increase of density with average of 0.55 g/cm3. The highest and lowest water absorption was measured 79.61 and 45.32% in the modification with HCl and MgCl catalysts. Hcl with acidic quality, can break ether bonds in hemiacetal and even acetal structure. Modification with MgCl2 was shown best result in comparison with other catalysts. It is likely that the formation a complex of magnesium with oxygen, could resulted to activate carbonyl groups in glutaraldehyde and created the crosslink.

Chemical modifications of Au/SiO2 template substrates for patterned biofunctional surfaces.

Science.gov (United States)

Briand, Elisabeth; Humblot, Vincent; Landoulsi, Jessem; Petronis, Sarunas; Pradier, Claire-Marie; Kasemo, Bengt; Svedhem, Sofia

2011-01-18

The aim of this work was to create patterned surfaces for localized and specific biochemical recognition. For this purpose, we have developed a protocol for orthogonal and material-selective surface modifications of microfabricated patterned surfaces composed of SiO(2) areas (100 μm diameter) surrounded by Au. The SiO(2) spots were chemically modified by a sequence of reactions (silanization using an amine-terminated silane (APTES), followed by amine coupling of a biotin analogue and biospecific recognition) to achieve efficient immobilization of streptavidin in a functional form. The surrounding Au was rendered inert to protein adsorption by modification by HS(CH(2))(10)CONH(CH(2))(2)(OCH(2)CH(2))(7)OH (thiol-OEG). The surface modification protocol was developed by testing separately homogeneous SiO(2) and Au surfaces, to obtain the two following results: (i) SiO(2) surfaces which allowed the grafting of streptavidin, and subsequent immobilization of biotinylated antibodies, and (ii) Au surfaces showing almost no affinity for the same streptavidin and antibody solutions. The surface interactions were monitored by quartz crystal microbalance with dissipation monitoring (QCM-D), and chemical analyses were performed by polarization modulation-reflexion absorption infrared spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS) to assess the validity of the initial orthogonal assembly of APTES and thiol-OEG. Eventually, microscopy imaging of the modified Au/SiO(2) patterned substrates validated the specific binding of streptavidin on the SiO(2)/APTES areas, as well as the subsequent binding of biotinylated anti-rIgG and further detection of fluorescent rIgG on the functionalized SiO(2) areas. These results demonstrate a successful protocol for the preparation of patterned biofunctional surfaces, based on microfabricated Au/SiO(2) templates and supported by careful surface analysis. The strong immobilization of the biomolecules resulting from the described

Evaluation of the chemical modifications in petroleum asphalt cement with the addition of polypropylene

International Nuclear Information System (INIS)

Marcondes, C.P.; Sales, M.J.A.; Resck, I.S.; Farias, M.M.; Souza, M.V.R.

2010-01-01

Studies show that the common distress mode in the Brazilian highway network are fatigue cracks and plastic deformation, which are associated with the type of material used in the pavement layers, structural project, excessive traffic load and weathering. To minimize these defects, research on modifiers such as polymers, added to asphalt binders have been developed to provide physical, chemical and rheological improvement. This paper investigates chemical modifications of the binders with the addition of PP by FTIR, NMR and DSC. FTIR spectra of pure and modified binder showed no differences in absorption. NMR analysis showed no strong chemical bonds between the binder and PP. DSC curve of PP showed a melting temperature of 160 deg C (ΔH = 94J/g) and the pure binder presented an endothermic transition between 20 and 40 deg C (ΔH = 2J/g). In the DSC curves of mixtures, these transitions are not significant, indicating possible interactions between asphalt binder and PP. (author)

DNA modification by alkylating compounds

Energy Technology Data Exchange (ETDEWEB)

Kruglyakova, E.E.

1985-09-01

Results are given for research on the physico-chemical properties of alkylating compounds - nitroso alkyl ureas (NAU) which possess a broad spectrum of biological activity, such as mutagenic, carcinogenic, and anti-tumor action that is due to the alkylation and carbamoylation of DNA as well as other cellular components. Identified chemical products of NAU interaction with DNA and its components are cited. Structural conversions of a DNA macromolecule resulting from its chemical modification are examined. NAU are used to discuss possible biological consequences of DNA modification. 148 references.

Effect of different chemical modification of carbon nanotubes for the oxygen reduction reaction in alkaline media

International Nuclear Information System (INIS)

Dumitru, Anca; Mamlouk, M.; Scott, K.

2014-01-01

The electrochemical reduction of oxygen on chemically modified multi-walled carbon nanotubes (CNTs) electrodes in 1 M KOH solution has been studied using the rotating ring disc electrode (RDE). The surface modification of CNTs has been estimated by XPS and Raman spectroscopy. The effect of different oxygen functionalities on the surface of carbon nanotube for the oxygen reduction reaction (ORR) is considered in terms of the number of electrons (n) involved. Electrochemical studies indicate that in the case of the modification of CNTs with citric acid and diazonium salts the n values were close to two in the measured potential range, and the electrochemical reduction is limited to the production of peroxide as the final product. In the case of the modification of carbon nanotubes with peroxymonosulphuric acid, in the measured potential range, the n value is close to 4 indicating the four-electron pathway for the ORR. By correlating ORR measurements with the XPS analysis, we propose that the increase in electrocatalytic activity towards the ORR, for CNT can be attributed to the increase in C-O groups on the surface of CNTs after modification with peroxymonosulphuric acid

Radiation modification of swollen and chemically modified cellulose

International Nuclear Information System (INIS)

Borsa, J.; Toth, T.

2002-01-01

Complete text of publication follows. Biodegradable hydrogel was produced by radiation-induced crosslinking of water soluble carboxymethyl cellulose. Mobility of the molecular chain was found to play an important role in the crosslinking reaction. In this work the role of cellulose chains' mobility in radiation-induced reactions of fibrous cellulose was studied. Mobility of chains was improved by swelling (in sodium hydroxide and tetramethylammonium hydroxide) and chemical modification (substitution of about 3 % of hydroxyl groups with carboxymethyl groups), respectively. All samples were neutralized after the treatments. Accessibility of cellulose characterized by water adsorption and retention was significantly improved by the treatments in the following order: sodium hydroxide < tetramethylammonium hydroxide < carboxymethylation. Less fibrillar structure of modified fibers was observed by electron microscope. Samples were irradiated in wet form in open air (10 kGy). Untreated sample coated with soluble CMC was also irradiated. Degree of polymerization, FTIR spectra, and water sorption of samples before and after irradiation are presented. Amount of water adsorbed on samples decreased after irradiation. It can be considered the consequence of crosslinks, which might improve the crease recovery ability of cotton fabric. High accessibility improved degradation rather than crosslinking of cellulose chains

High-resolution study of photoinduced modification in fused silica produced by a tightly focused femtosecond laser beam in the presence of aberrations

International Nuclear Information System (INIS)

Hnatovsky, C.; Taylor, R.S.; Simova, E.; Bhardwaj, V.R.; Rayner, D.M.; Corkum, P.B.

2005-01-01

An ultrahigh-resolution (20 nm) technique of selective chemical etching and atomic force microscopy has been used to study the photoinduced modification in fused silica produced at various depths by tightly focused femtosecond laser radiation affected by spherical aberration. We demonstrate that shapes of the irradiated zones near the threshold for modification can be predicted by taking proper account of spherical aberration caused by the refractive index mismatched air-silica interface. We establish a depth dependence of the pulse energy required to initiate modification and characterize the relationship between numerical aperture of the writing lens and practically achievable writing depth. We also show that spatial characteristics of the laser-modified zones can be controlled by a specially designed focusing system which allows correction for a variable amount of spherical aberration

Comparison of some effects of modification of a polylactide surface layer by chemical, plasma, and laser methods

Energy Technology Data Exchange (ETDEWEB)

Moraczewski, Krzysztof, E-mail: kmm@ukw.edu.pl [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Rytlewski, Piotr [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Malinowski, Rafał [Institute for Engineering of Polymer Materials and Dyes, ul. M. Skłodowskiej–Curie 55, 87-100 Toruń (Poland); Żenkiewicz, Marian [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland)

2015-08-15

Highlights: • We modified polylactide surface layer with chemical, plasma or laser methods. • We tested selected properties and surface structure of modified samples. • We stated that the plasma treatment appears to be the most beneficial. - Abstract: The article presents the results of studies and comparison of selected properties of the modified PLA surface layer. The modification was carried out with three methods. In the chemical method, a 0.25 M solution of sodium hydroxide in water and ethanol was utilized. In the plasma method, a 50 W generator was used, which produced plasma in the air atmosphere under reduced pressure. In the laser method, a pulsed ArF excimer laser with fluency of 60 mJ/cm{sup 2} was applied. Polylactide samples were examined by using the following techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and X-ray photoelectron spectroscopy (XPS). Images of surfaces of the modified samples were recorded, contact angles were measured, and surface free energy was calculated. Qualitative and quantitative analyses of chemical composition of the PLA surface layer were performed as well. Based on the survey it was found that the best modification results are obtained using the plasma method.

Particle Distribution Modification by Low Amplitude Modes

International Nuclear Information System (INIS)

White, R.B.; Gorelenkov, N.; Heidbrink, W.W.; Van Zeeland, M.A.

2009-01-01

Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

The use of new, aqueous chemical wood modifications to improve the durability of wood-plastic composites

Science.gov (United States)

Rebecca E. Ibach; Craig M. Clemons; George C. Chen

2017-01-01

The wood flour used in wood-plastic composites (WPCs) can biologically deteriorate and thus the overall mechanical performance of WPCs decrease when exposed to moisture and fungal decay. Protecting the wood flour by chemical modification can improve the durability of the wood in a nontoxic way so it is not harmful to the environment. WPCs were made with modified wood...

EFFECT OF CHEMICAL MODIFICATION AND HOT-PRESS DRYING ON POPLAR WOOD

Directory of Open Access Journals (Sweden)

Guo-Feng Wu

2010-11-01

Full Text Available Urea-formaldehyde prepolymer and hot-press drying were used to improve the properties of poplar wood. The wood was impregnated with the prepolymer using a pulse-dipping machine. The impregnated timbers were compressed and dried by a multilayer hot-press drying kiln. The drying rate was more rapid during the chemical modification and hot-press drying than conventional kiln-drying. In addition, the properties of timber were also enhanced obviously. When the compression rate was 28.6%, the basic density, oven dry density and air-dried density of modified wood improved 22%, 71%, and 70%, respectively. The bending strength and compressive strength parallel to grain increased 60% and 40%. The water uptake of treated wood was significantly decreased compared with the untreated wood. The FTIR analysis successfully showed that the intensity of hydroxyl and carbonyl absorption peaks decreased significantly, which was attributed to a reaction of the NHCH2OH of urea-formaldehyde prepolymer with the wood carboxyl (C=O and hydroxyl (-OH groups. The XRD results indicated that the degree of crystallinity increased from 35.09% to 36.91%. The morphologic models of chemical within wood were discovered by SEM.

Studies on chemical modification of cold agglutinin from the snail Achatina fulica.

Science.gov (United States)

Sarkar, M; Mitra, D; Sen, A K

1987-01-01

The cold agglutinin isolated from the albumin gland of the snail Achatina fulica was modified with various chemical reagents in order to detect the amino acids and/or carbohydrate residues present in its carbohydrate-binding sites. Treatment with reagents considered specific for modification of lysine, arginine and tryptophan residues of the cold agglutinin did not affect the carbohydrate-binding activity of the agglutinin. Modification of tyrosine residues showed some change. However, modification with carbodiimide followed by alpha-aminobutyric acid methyl ester causes almost complete loss of its binding activity, indicating the involvement of aspartic acid and glutamic acid in its carbohydrate-binding activity. The carbohydrate residues of the cold agglutinin were removed by beta-elimination reaction, indicating that the sugars are O-glycosidically linked to protein part of the molecule. Removal of galactose residues from the cold agglutinin by the action of beta-galactosidase indicated that the galactose molecules are beta-linked. These carbohydrate-modified glycoproteins showed a marked change in agglutination property, i.e. they agglutinated rabbit erythrocytes at both 10 degrees C and 25 degrees C, indicating that the galactose residues of the glycoprotein play an important role in the cold-agglutination property of the glycoprotein. The c.d. data showed the presence of an almost identical type of random-coil conformation in the native cold agglutinin at 10 degrees C and in the carbohydrate-modified glycoprotein at 10 degrees C and 25 degrees C. This particular random-coil conformation is essential for carbohydrate-binding property of the agglutinin. Images Fig. 1. PMID:3118867

Chemical modifications and stability of diamond nanoparticles resolved by infrared spectroscopy and Kelvin force microscopy

Czech Academy of Sciences Publication Activity Database

Kozak, Halyna; Remeš, Zdeněk; Houdková, Jana; Stehlík, Štěpán; Kromka, Alexander; Rezek, Bohuslav

2013-01-01

Roč. 15, č. 4 (2013), "1568-1"-"1568-9" ISSN 1388-0764 R&D Projects: GA ČR GAP108/12/0910; GA ČR GPP205/12/P331; GA MŠk LH12186 Institutional support: RVO:68378271 Keywords : diamond nanoparticles * chemical modification * GAR-FTIR * AFM * KFM * XPS Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.278, year: 2013 http://link.springer.com/article/10.1007%2Fs11051-013-1568-7

Chemical mechanisms of histone lysine and arginine modifications

OpenAIRE

Smith, Brian C.; Denu, John M.

2008-01-01

Histone lysine and arginine residues are subject to a wide array of post-translational modifications including methylation, citrullination, acetylation, ubiquitination, and sumoylation. The combinatorial action of these modifications regulates critical DNA processes including replication, repair, and transcription. In addition, enzymes that modify histone lysine and arginine residues have been correlated with a variety of human diseases including arthritis, cancer, heart disease, diabetes, an...

Control of peptide nanotube diameter by chemical modifications of an aromatic residue involved in a single close contact

Science.gov (United States)

Tarabout, Christophe; Roux, Stéphane; Gobeaux, Frédéric; Fay, Nicolas; Pouget, Emilie; Meriadec, Cristelle; Ligeti, Melinda; Thomas, Daniel; IJsselstijn, Maarten; Besselievre, François; Buisson, David-Alexandre; Verbavatz, Jean-Marc; Petitjean, Michel; Valéry, Céline; Perrin, Lionel; Rousseau, Bernard; Artzner, Franck; Paternostre, Maité; Cintrat, Jean-Christophe

2011-01-01

Supramolecular self-assembly is an attractive pathway for bottom-up synthesis of novel nanomaterials. In particular, this approach allows the spontaneous formation of structures of well-defined shapes and monodisperse characteristic sizes. Because nanotechnology mainly relies on size-dependent physical phenomena, the control of monodispersity is required, but the possibility of tuning the size is also essential. For self-assembling systems, shape, size, and monodispersity are mainly settled by the chemical structure of the building block. Attempts to change the size notably by chemical modification usually end up with the loss of self-assembly. Here, we generated a library of 17 peptides forming nanotubes of monodisperse diameter ranging from 10 to 36 nm. A structural model taking into account close contacts explains how a modification of a few Å of a single aromatic residue induces a fourfold increase in nanotube diameter. The application of such a strategy is demonstrated by the formation of silica nanotubes of various diameters. PMID:21518895

The effect of chemical modification on the physico-chemical characteristics of halloysite: FTIR, XRF, and XRD studies

Science.gov (United States)

Szczepanik, Beata; Słomkiewicz, Piotr; Garnuszek, Magdalena; Czech, Kamil; Banaś, Dariusz; Kubala-Kukuś, Aldona; Stabrawa, Ilona

2015-03-01

The effect of chemical modification of halloysite from a Polish strip mine "Dunino" on the chemical composition and structure of this clay mineral was studied using infrared spectroscopy (ATR FT-IR), wavelength dispersive X-ray fluorescence (WDXRF), and X-ray powder diffraction (XRPD) methods. The results obtained by the WDXRF technique confirm that the content of silica and alumina was the highest for bleached halloysite samples and the lowest for acid-treated halloysite. A higher content of Fe2O3 in comparison to halloysite samples coming from other countries was observed for raw halloysite samples. XRPD diffraction pattern obtained for raw halloysite confirmed the presence of halloysite, kaolinite, hematite, and calcite minerals in the sample. Bleaching the halloysite removes (or significantly reduces) the content of other minerals present in the raw halloysite. The FT-IR spectra of the studied halloysite samples show in the 3700-3600 cm-1 region well-defined hydroxyl stretching bands characteristic for the kaolin-group minerals and bands associated with the vibrations of the aluminium-silicon skeleton in the 1400-1000 cm-1 region. Modifying halloysite with 4-chloro-aniline causes successive incorporation of amine into the BH sample.

Chemical modification of glass surface with a monolayer of nonchromophoric and chromophoric methacrylate terpolymer

Energy Technology Data Exchange (ETDEWEB)

Janik, Ryszard [Department of Polymer Engineering and Technology, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Kucharski, Stanislaw, E-mail: stanislaw.kucharski@pwr.wroc.pl [Department of Polymer Engineering and Technology, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Sobolewska, Anna [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Barille, Regis [Institut des Sciences et Techniques Moleculaires d' Angers ' Moltech Anjou' , CNRS UMR 6200, 49045 Angers (France)

2010-11-15

The methacrylate terpolymers, a nonchromophoric and chromophoric one, containing 2-hydroxyethyl groups were reacted with 3-isocyanatopropyltriethoxysilane to obtain reactive polymers able to form covalent bonding with -SiOH groups of the glass surface via triethoxysilane group condensation. Chemical modification of the Corning 2949 glass plates treated in this way resulted in increase of wetting angle from 11{sup o} to ca. 70-73{sup o}. Determination of ellipsometric parameters revealed low value of the substrate refractive index as compared with that of bulk Corning 2949 glass suggesting roughness of the surface. The AFM image of the bare glass surface and that modified with terpolymer monolayer confirmed this phenomenon. Modification of the glass with the terpolymer monolayer made it possible to create the substrate surface well suited for deposition of familiar chromophore film by spin-coating. The chromophore polymer film deposited onto the modified glass surface was found to be resistant to come unstuck in aqueous solution.

Threshold guidance update

International Nuclear Information System (INIS)

Wickham, L.E.

1986-01-01

The Department of Energy (DOE) is developing the concept of threshold quantities for use in determining which waste materials must be handled as radioactive waste and which may be disposed of as nonradioactive waste at its sites. Waste above this concentration level would be managed as radioactive or mixed waste (if hazardous chemicals are present); waste below this level would be handled as sanitary waste. Last years' activities (1984) included the development of a threshold guidance dose, the development of threshold concentrations corresponding to the guidance dose, the development of supporting documentation, review by a technical peer review committee, and review by the DOE community. As a result of the comments, areas have been identified for more extensive analysis, including an alternative basis for selection of the guidance dose and the development of quality assurance guidelines. Development of quality assurance guidelines will provide a reasonable basis for determining that a given waste stream qualifies as a threshold waste stream and can then be the basis for a more extensive cost-benefit analysis. The threshold guidance and supporting documentation will be revised, based on the comments received. The revised documents will be provided to DOE by early November. DOE-HQ has indicated that the revised documents will be available for review by DOE field offices and their contractors

Summary of DOE threshold limits efforts

International Nuclear Information System (INIS)

Wickham, L.E.; Smith, C.F.; Cohen, J.J.

1987-01-01

The Department of Energy (DOE) has been developing the concept of threshold quantities for use in determining which waste materials may be disposed of as nonradioactive waste in DOE sanitary landfills. Waste above a threshold level could be managed as radioactive or mixed waste (if hazardous chemicals are present); waste below this level would be handled as sanitary waste. After extensive review of a draft threshold guidance document in 1985, a second draft threshold background document was produced in March 1986. The second draft included a preliminary cost-benefit analysis and quality assurance considerations. The review of the second draft has been completed. Final changes to be incorporated include an in-depth cost-benefit analysis of two example sites and recommendations of how to further pursue (i.e. employ) the concept of threshold quantities within the DOE. 3 references

Modification of electrical pain threshold by voluntary breathing-controlled electrical stimulation (BreEStim in healthy subjects.

Directory of Open Access Journals (Sweden)

Shengai Li

Full Text Available BACKGROUND: Pain has a distinct sensory and affective (i.e., unpleasantness component. BreEStim, during which electrical stimulation is delivered during voluntary breathing, has been shown to selectively reduce the affective component of post-amputation phantom pain. The objective was to examine whether BreEStim increases pain threshold such that subjects could have improved tolerance of sensation of painful stimuli. METHODS: Eleven pain-free healthy subjects (7 males, 4 females participated in the study. All subjects received BreEStim (100 stimuli and conventional electrical stimulation (EStim, 100 stimuli to two acupuncture points (Neiguan and Weiguan of the dominant hand in a random order. The two different treatments were provided at least three days apart. Painful, but tolerable electrical stimuli were delivered randomly during EStim, but were triggered by effortful inhalation during BreEStim. Measurements of tactile sensation threshold, electrical sensation and electrical pain thresholds, thermal (cold sensation, warm sensation, cold pain and heat pain thresholds were recorded from the thenar eminence of both hands. These measurements were taken pre-intervention and 10-min post-intervention. RESULTS: There was no difference in the pre-intervention baseline measurement of all thresholds between BreEStim and EStim. The electrical pain threshold significantly increased after BreEStim (27.5±6.7% for the dominant hand and 28.5±10.8% for the non-dominant hand, respectively. The electrical pain threshold significantly decreased after EStim (9.1±2.8% for the dominant hand and 10.2±4.6% for the non-dominant hand, respectively (F[1, 10] = 30.992, p = .00024. There was no statistically significant change in other thresholds after BreEStim and EStim. The intensity of electrical stimuli was progressively increased, but no difference was found between BreEStim and EStim. CONCLUSION: Voluntary breathing controlled electrical stimulation

Application of radiation technology in starch modification

International Nuclear Information System (INIS)

Chen Huiyuan; Peng Zhigang; Ding Zhongmin; Lu Jiajiu

2007-01-01

In order to commercialize the radiation modification of starch, corn starch was irradiated with different dose of 60 Co gamma radiations. Some basic physical and chemical properties of the resulted modified starch paste were measured with emphasis on the viscosity stability and tensile strength. The results indicate that irradiation of corn starch with a dose of 4-10 kGy can decrease its viscosity to 5-14 mPa·s, and the tensile strength can meet the standard set up for textile paste. In comparison with chemical modification for starch, radiation modification is simpler in technology, more convenient in operation, more stable in modification quality, and easier to control. The mechanism of radiation modification of starch was also discussed. (authors)

Novel approach for classifying chemicals according to skin sensitizing potency by non-radioisotopic modification of the local lymph node assay.

Science.gov (United States)

Takeyoshi, Masahiro; Iida, Kenji; Shiraishi, Keiji; Hoshuyama, Satsuki

2005-01-01

The murine local lymph node assay (LLNA) is currently recognized as a stand-alone sensitization test for determining the sensitizing potential of chemicals, and it has the advantage of yielding a quantitative endpoint that can be used to predict the sensitization potency of chemicals. The EC3 has been proposed as a parameter for classifying chemicals according to the sensitization potency. We previously developed a non-radioisotopic endpoint for the LLNA based on 5-bromo-2'-deoxyuridine (BrdU) incorporation (non-RI LLNA), and we are proposing a new procedure to predict the sensitization potency of chemicals based on comparisons with known human contact allergens. Nine chemicals (i.e. diphencyclopropenone, p-phenylenediamine, glutaraldehyde, cinnamicaldehyde, citral, eugenol, isopropyl myristate, propyleneglycol and hexane) categorized as human contact allergen classes 1-5 were tested by the non-RI LLNA with the following reference allergens: 2,4-dinitrochlorobenzene (DNCB) as a class 1 human contact allergen, isoeugenol as a class 2 human contact allergen and alpha-hexylcinnamic aldehyde (HCA) as a class 3 human contact allergen. Consequently, nine test chemicals were almost assigned to their correct allergen class. The results suggested that the new procedure for non-RI LLNA can provide correct sensitization potency data. Sensitization potency data are useful for evaluating the sensitization risk to humans of exposure to new chemical products. Accordingly, this approach would be an effective modification of LLNA with regard to its experimental design. Moreover, this procedure can be applied also to the standard LLNA with radioisotopes and to other modifications of the LLNA. Copyright 2005 John Wiley & Sons, Ltd.

In-medium Modifications of Hadron Masses and Chemical Freeze-out in Ultra-relativistic Heavy-ion Collisions

International Nuclear Information System (INIS)

Florkowski, W.; Broniowski, W.

1999-10-01

We confront the hypothesis of chemical freeze-out in ultra-relativistic heavy-ion collisions with the hypothesis of large modifications of hadron masses in nuclear medium. We find that the thermal-model predictions for the ratios of particle multiplicities are sensitive to the values of in-medium hadronic masses. In particular, the π + /p ratio decreases by 35% when the masses of all hadrons (except for pseudo-Goldstone bosons) are scaled down by 30%. (author)

Chemical modification and characterization of quaternized polysulfones.

CSIR Research Space (South Africa)

Nonjola, P

2008-12-01

Full Text Available Synthesis and characterization of anion-exchange membranes (AEMs) using polysulfones is described. The modification process of polysulfones involves two steps: Firstly, by introducing chloromethyl groups followed by quaternization reaction...

Higgs-boson production and decay close to thresholds

International Nuclear Information System (INIS)

Kniehl, B.A.; Palisoc, C.P.; Sirlin, A.; New York Univ., NY

2000-07-01

At one loop in the conventional on-mass-shell renormalization scheme, the production and decay rates of the Higgs boson H exhibit singularities proportional to (2M V -M) -1/2 as the Higgs-boson mass M approaches from below the pair-production threshold of a vector boson V with mass M V . This problem is of phenomenological interest because the values 2M W and 2M Z , corresponding to the W- and Z-boson thresholds, lie within the M range presently favoured by electroweak precision data. We demonstrate how these threshold singularities are eliminated when the definitions of mass and total decay width of the Higgs boson are based on the complex-valued pole of its propagator. We illustrate the phenomenological implications of this modification for the partial width of the H → W + W - decay. (orig.)

Higgs-boson production and decay close to thresholds

International Nuclear Information System (INIS)

Kniehl, Bernd A.; Palisoc, Caesar P.; Sirlin, Alberto

2000-01-01

At one loop in the conventional on-mass-shell renormalization scheme, the production and decay rates of the Higgs-boson H exhibit singularities proportional to (2M V -M) -1/2 as the Higgs-boson mass M approaches from below the pair-production threshold of a vector boson V with mass M V . This problem is of phenomenological interest because the values 2M W and 2M Z , corresponding to the W- and Z-boson thresholds, lie within the M range presently favoured by electroweak precision data. We demonstrate how these threshold singularities are eliminated when the definitions of mass and total decay width of the Higgs-boson are based on the complex-valued pole of its propagator. We illustrate the phenomenological implications of this modification for the partial width of the H→W + W - decay

Chemical Modification of Semiconductor Surfaces for Molecular Electronics.

Science.gov (United States)

Vilan, Ayelet; Cahen, David

2017-03-08

Inserting molecular monolayers within metal/semiconductor interfaces provides one of the most powerful expressions of how minute chemical modifications can affect electronic devices. This topic also has direct importance for technology as it can help improve the efficiency of a variety of electronic devices such as solar cells, LEDs, sensors, and possible future bioelectronic ones. The review covers the main aspects of using chemistry to control the various aspects of interface electrostatics, such as passivation of interface states and alignment of energy levels by intrinsic molecular polarization, as well as charge rearrangement with the adjacent metal and semiconducting contacts. One of the greatest merits of molecular monolayers is their capability to form excellent thin dielectrics, yielding rich and unique current-voltage characteristics for transport across metal/molecular monolayer/semiconductor interfaces. We explain the interplay between the monolayer as tunneling barrier on the one hand, and the electrostatic barrier within the semiconductor, due to its space-charge region, on the other hand, as well as how different monolayer chemistries control each of these barriers. Practical tools to experimentally identify these two barriers and distinguish between them are given, followed by a short look to the future. This review is accompanied by another one, concerning the formation of large-area molecular junctions and charge transport that is dominated solely by molecules.

Femtosecond laser damage threshold and nonlinear characterization in bulk transparent SiC materials

International Nuclear Information System (INIS)

DesAutels, G. Logan; Finet, Marc; Ristich, Scott; Whitaker, Matt; Brewer, Chris; Juhl, Shane; Walker, Mark; Powers, Peter

2008-01-01

Semi-insulating and conducting SiC crystalline transparent substrates were studied after being processed by femtosecond (fs) laser radiation (780 nm at 160 fs). Z-scan and damage threshold experiments were performed on both SiC bulk materials to determine each sample's nonlinear and threshold parameters. 'Damage' in this text refers to an index of refraction modification as observed visually under an optical microscope. In addition, a study was performed to understand the damage threshold as a function of numerical aperture. Presented here for the first time, to the best of our knowledge, are the damage threshold, nonlinear index of refraction, and nonlinear absorption measured values

Sequence-engineered mRNA Without Chemical Nucleoside Modifications Enables an Effective Protein Therapy in Large Animals

OpenAIRE

Thess, Andreas; Grund, Stefanie; Mui, Barbara L; Hope, Michael J; Baumhof, Patrick; Fotin-Mleczek, Mariola; Schlake, Thomas

2015-01-01

Being a transient carrier of genetic information, mRNA could be a versatile, flexible, and safe means for protein therapies. While recent findings highlight the enormous therapeutic potential of mRNA, evidence that mRNA-based protein therapies are feasible beyond small animals such as mice is still lacking. Previous studies imply that mRNA therapeutics require chemical nucleoside modifications to obtain sufficient protein expression and avoid activation of the innate immune system. Here we sh...

Perceptual thresholds for detecting modifications applied to the acoustical properties of a violin.

Science.gov (United States)

Fritz, Claudia; Cross, Ian; Moore, Brian C J; Woodhouse, Jim

2007-12-01

This study is the first step in the psychoacoustic exploration of perceptual differences between the sounds of different violins. A method was used which enabled the same performance to be replayed on different "virtual violins," so that the relationships between acoustical characteristics of violins and perceived qualities could be explored. Recordings of real performances were made using a bridge-mounted force transducer, giving an accurate representation of the signal from the violin string. These were then played through filters corresponding to the admittance curves of different violins. Initially, limits of listener performance in detecting changes in acoustical characteristics were characterized. These consisted of shifts in frequency or increases in amplitude of single modes or frequency bands that have been proposed previously to be significant in the perception of violin sound quality. Thresholds were significantly lower for musically trained than for nontrained subjects but were not significantly affected by the violin used as a baseline. Thresholds for the musicians typically ranged from 3 to 6 dB for amplitude changes and 1.5%-20% for frequency changes. Interpretation of the results using excitation patterns showed that thresholds for the best subjects were quite well predicted by a multichannel model based on optimal processing.

Chemical modification of flax reinforced polypropylene composites

CSIR Research Space (South Africa)

Jacob John, Maya

2009-04-01

Full Text Available This paper presents an experimental study on the static and dynamic mechanical properties of nonwoven based flax fibre reinforced polypropylene composites. The effect of zein modification on flax fibres is also reported. Flax nonwovens were treated...

Nanofibrillated Cellulose Surface Modification: A Review

Directory of Open Access Journals (Sweden)

Julien Bras

2013-05-01

Full Text Available Interest in nanofibrillated cellulose (NFC has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bionanocomposites or in paper thanks to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. It is worth noting that chemical surface modification of this material can be a key factor to achieve a better compatibility with matrices. In order to increase the compatibility in different matrices or to add new functions, surface chemical modification of NFC appears to be the prior choice to conserve its intrinsic nanofibre properties. In this review, the authors have proposed for the first time an overview of all chemical grafting strategies used to date on nanofibrillated cellulose with focus on surface modification such as physical adsorption, molecular grafting or polymer grafting.

Influence of Chemical Surface Modification of Woven Fabrics on Ballistic and Stab Protection of Multilayer Packets

Directory of Open Access Journals (Sweden)

Diana GRINEVIČIŪTĖ

2014-06-01

Full Text Available In order to achieve enhanced protective and wear (flexibility, less bulkiness properties of ballistic and stab protecting panels the investigation of chemical surface modification of woven p-aramid fabrics was performed applying different chemical composition shear thickening fluid (STF which improves friction inside fabric structure. For the chemical treatment silicic acid and acrylic dispersion water solutions were used and influence of their different concentrations on panels’ protective properties were investigated. Results of ballistic tests of multilayer protective panel have revealed that shear thickening effect was negligible when shooting at high energy range (E > 440 J. Determination of stab resistance of p-aramid panels has shown that different chemical composition of STFs had different influence on protective properties of the panels. Application of low concentrations of silicic acid determined higher stab resistance values comparing to higher concentrations of acrylic dispersion water solutions. At this stage of research stab tests results as ballistic ones determined that STF application for multilayer p-aramid fabrics protective panels is more efficient at low strike energy levels. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.3138

Chemical modification of wood

Science.gov (United States)

Roger M. Rowell

2007-01-01

After millions of years of evolution, wood was designed to perform in a wet environment, and nature is programmed to recycle it, in a timely way, back to the basic building blocks of carbon dioxide and water through biological, thermal, aqueous, photochemical, chemical, and mechanical degradation. The properties of wood are, for the most part, a result of the chemistry...

The influence of thresholds on the risk assessment of carcinogens in food.

Science.gov (United States)

Pratt, Iona; Barlow, Susan; Kleiner, Juliane; Larsen, John Christian

2009-08-01

The risks from exposure to chemical contaminants in food must be scientifically assessed, in order to safeguard the health of consumers. Risk assessment of chemical contaminants that are both genotoxic and carcinogenic presents particular difficulties, since the effects of such substances are normally regarded as being without a threshold. No safe level can therefore be defined, and this has implications for both risk management and risk communication. Risk management of these substances in food has traditionally involved application of the ALARA (As Low as Reasonably Achievable) principle, however ALARA does not enable risk managers to assess the urgency and extent of the risk reduction measures needed. A more refined approach is needed, and several such approaches have been developed. Low-dose linear extrapolation from animal carcinogenicity studies or epidemiological studies to estimate risks for humans at low exposure levels has been applied by a number of regulatory bodies, while more recently the Margin of Exposure (MOE) approach has been applied by both the European Food Safety Authority and the Joint FAO/WHO Expert Committee on Food Additives. A further approach is the Threshold of Toxicological Concern (TTC), which establishes exposure thresholds for chemicals present in food, dependent on structure. Recent experimental evidence that genotoxic responses may be thresholded has significant implications for the risk assessment of chemicals that are both genotoxic and carcinogenic. In relation to existing approaches such as linear extrapolation, MOE and TTC, the existence of a threshold reduces the uncertainties inherent in such methodology and improves confidence in the risk assessment. However, for the foreseeable future, regulatory decisions based on the concept of thresholds for genotoxic carcinogens are likely to be taken case-by-case, based on convincing data on the Mode of Action indicating that the rate limiting variable for the development of cancer

Mechanistic understanding of the cysteine capping modifications of antibodies enables selective chemical engineering in live mammalian cells.

Science.gov (United States)

Zhong, Xiaotian; He, Tao; Prashad, Amar S; Wang, Wenge; Cohen, Justin; Ferguson, Darren; Tam, Amy S; Sousa, Eric; Lin, Laura; Tchistiakova, Lioudmila; Gatto, Scott; D'Antona, Aaron; Luan, Yen-Tung; Ma, Weijun; Zollner, Richard; Zhou, Jing; Arve, Bo; Somers, Will; Kriz, Ronald

2017-04-20

Protein modifications by intricate cellular machineries often redesign the structure and function of existing proteins to impact biological networks. Disulfide bond formation between cysteine (Cys) pairs is one of the most common modifications found in extracellularly-destined proteins, key to maintaining protein structure. Unpaired surface cysteines on secreted mammalian proteins are also frequently found disulfide-bonded with free Cys or glutathione (GSH) in circulation or culture, the mechanism for which remains unknown. Here we report that these so-called Cys-capping modifications take place outside mammalian cells, not in the endoplasmic reticulum (ER) where oxidoreductase-mediated protein disulfide formation occurs. Unpaired surface cysteines of extracellularly-arrived proteins such as antibodies are uncapped upon secretion before undergoing disulfide exchange with cystine or oxidized GSH in culture medium. This observation has led to a feasible way to selectively modify the nucleophilic thiol side-chain of cell-surface or extracellular proteins in live mammalian cells, by applying electrophiles with a chemical handle directly into culture medium. These findings provide potentially an effective approach for improving therapeutic conjugates and probing biological systems. Copyright © 2017 Elsevier B.V. All rights reserved.

The Sensory Difference Threshold of Menthol Odor in Flavored Tobacco Determined by Combining Sensory and Chemical Analysis.

Science.gov (United States)

Krüsemann, Erna J Z; Cremers, Johannes W J M; Visser, Wouter F; Punter, Pieter H; Talhout, Reinskje

2017-03-01

Cigarettes are an often-used consumer product, and flavor is an important determinant of their product appeal. Cigarettes with strong nontobacco flavors are popular among young people, and may facilitate smoking initiation. Discriminating flavors in tobacco is important for regulation purposes, for instance to set upper limits to the levels of important flavor additives. We provide a simple and fast method to determine the human odor difference threshold for flavor additives in a tobacco matrix, using a combination of chemical and sensory analysis. For an example, the human difference threshold for menthol odor, one of the most frequently used tobacco flavors, was determined. A consumer panel consisting of 20 women compared different concentrations of menthol-flavored tobacco to unflavored cigarette tobacco using the 2-alternative forced choice method. Components contributing to menthol odor were quantified using headspace GC-MS. The sensory difference threshold of menthol odor corresponded to a mixture of 43 (37-50)% menthol-flavored tobacco, containing 1.8 (1.6-2.1) mg menthol, 2.7 (2.3-3.1) µg menthone, and 1.0 (0.9-1.2) µg neomenthyl acetate per gram of tobacco. Such a method is important in the context of the European Tobacco Product Directive, and the US Food and Drug Administration Tobacco Control Act, that both prohibit cigarettes and roll-your-own tobacco with a characterizing flavor other than tobacco. Our method can also be adapted for matrices other than tobacco, such as food. © The Author 2016. Published by Oxford University Press.

Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.

Science.gov (United States)

Martin, S C; Minus, M B; Ball, Z T

2016-01-01

Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications. © 2016 Elsevier Inc. All rights reserved.

Improved Bat Algorithm Applied to Multilevel Image Thresholding

Directory of Open Access Journals (Sweden)

Adis Alihodzic

2014-01-01

Full Text Available Multilevel image thresholding is a very important image processing technique that is used as a basis for image segmentation and further higher level processing. However, the required computational time for exhaustive search grows exponentially with the number of desired thresholds. Swarm intelligence metaheuristics are well known as successful and efficient optimization methods for intractable problems. In this paper, we adjusted one of the latest swarm intelligence algorithms, the bat algorithm, for the multilevel image thresholding problem. The results of testing on standard benchmark images show that the bat algorithm is comparable with other state-of-the-art algorithms. We improved standard bat algorithm, where our modifications add some elements from the differential evolution and from the artificial bee colony algorithm. Our new proposed improved bat algorithm proved to be better than five other state-of-the-art algorithms, improving quality of results in all cases and significantly improving convergence speed.

Surface modification of porous poly(tetrafluoraethylene) film by a simple chemical oxidation treatment

International Nuclear Information System (INIS)

Wang Shifang; Li Juan; Suo Jinping; Luo Tianzhi

2010-01-01

A simple, inexpensive and environmental chemical treatment process, i.e., treating porous poly(tetrafluoroethylene) (PTFE) films by a mixture of potassium permanganate solution and nitric acid, was proposed to improve the hydrophilicity of PTFE. To evaluate the effectiveness of this strong oxidation treatment, contact angle measurement was performed. The effects of treatment time and temperature on the contact angle of PTFE were studied as well. The results showed that the chemical modification decreased contact angle of as-received PTFE film from 133 ± 3 deg. to 30 ± 4 deg. treated at 100 deg. C for 3 h, effectively converting the hydrophobic PTFE to a hydrophilic PTFE matrix. The changes in chemical structure, surface compositions and crystal structure of PTFE were examined by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), respectively. It was found that the F/C atomic ratio decreased from untreated 1.65-0.10 treated by the mixture at 100 deg. C for 3 h. Hydrophilic groups such as carbonyl (C=O) and hydroxyl (-OH) were introduced on the surface of PTFE after treatment. Furthermore, hydrophilic compounds K 0.27 MnO 2 .0.54H 2 O was absorbed on the surface of porous PTFE film. Both the introduction of hydrophilic groups and absorption of hydrophilic compounds contribute to the significantly decreased contact angle of PTFE.

Surface modification of porous poly(tetrafluoraethylene) film by a simple chemical oxidation treatment

Energy Technology Data Exchange (ETDEWEB)

Wang Shifang; Li Juan [State Key Laboratory of Mould Technology, Department of Materials Science and Engineering, Huazhong University of Science and Technology, Luo-Yu Road 1037, Wuhan, Hubei 430074 (China); Suo Jinping, E-mail: jpsuo@yahoo.com.cn [State Key Laboratory of Mould Technology, Department of Materials Science and Engineering, Huazhong University of Science and Technology, Luo-Yu Road 1037, Wuhan, Hubei 430074 (China); Luo Tianzhi [State Key Laboratory of Mould Technology, Department of Materials Science and Engineering, Huazhong University of Science and Technology, Luo-Yu Road 1037, Wuhan, Hubei 430074 (China)

2010-01-15

A simple, inexpensive and environmental chemical treatment process, i.e., treating porous poly(tetrafluoroethylene) (PTFE) films by a mixture of potassium permanganate solution and nitric acid, was proposed to improve the hydrophilicity of PTFE. To evaluate the effectiveness of this strong oxidation treatment, contact angle measurement was performed. The effects of treatment time and temperature on the contact angle of PTFE were studied as well. The results showed that the chemical modification decreased contact angle of as-received PTFE film from 133 {+-} 3 deg. to 30 {+-} 4 deg. treated at 100 deg. C for 3 h, effectively converting the hydrophobic PTFE to a hydrophilic PTFE matrix. The changes in chemical structure, surface compositions and crystal structure of PTFE were examined by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), respectively. It was found that the F/C atomic ratio decreased from untreated 1.65-0.10 treated by the mixture at 100 deg. C for 3 h. Hydrophilic groups such as carbonyl (C=O) and hydroxyl (-OH) were introduced on the surface of PTFE after treatment. Furthermore, hydrophilic compounds K{sub 0.27}MnO{sub 2}.0.54H{sub 2}O was absorbed on the surface of porous PTFE film. Both the introduction of hydrophilic groups and absorption of hydrophilic compounds contribute to the significantly decreased contact angle of PTFE.

Chemical modification of magnetite nanoparticles and preparation of acrylic-base magnetic nanocomposite particles via miniemulsion polymerization

Energy Technology Data Exchange (ETDEWEB)

Mahdieh, Athar; Mahdavian, Ali Reza, E-mail: a.mahdavian@ippi.ac.ir; Salehi-Mobarakeh, Hamid

2017-03-15

Nowadays, magnetic nanocomposite particles have attracted many interests because of their versatile applications. A new method for chemical modification of Fe{sub 3}O{sub 4} nanoparticles with polymerizable groups is presented here. After synthesis of Fe{sub 3}O{sub 4} nanoparticles by co-precipitation method, they were modified sequentially with 3-aminopropyl triethoxysilane (APTES), acryloyl chloride (AC) and benzoyl chloride (BC) and all were characterized by FTIR, XRD, SEM and TGA analyses. Then the modified magnetite nanoparticles with unsaturated acrylic groups were copolymerized with methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA) through miniemulsion polymerization. Although several reports exist on preparation of magnetite-base polymer particles, but the efficiency of magnetite encapsulationwith reasonable content and obtaining final stable latexes with limited aggregation ofFe{sub 3}O{sub 4} are still important issues. These were considered here by controlling reaction parameters. Hence, a seriesofmagneticnanocomposites latex particlescontaining different amounts of Fe{sub 3}O{sub 4} nanoparticles (0–10 wt%) were prepared with core-shell morphology and diameter below 200 nm and were characterized by FT-IR, DSC and TGA analyses. Their morphology and size distribution were studied by SEM, TEM and DLS analyses too. Magnetic properties of all products were also measuredby VSM analysis and the results revealed almost superparamagnetic properties for the obtained nanocomposite particles. - Highlights: • Chemical modification of magnetite nanoparticles. • Encapsulation of modified magnetite with acrylic copolymer. • Superparamagnetic Fe3O4/polyacrylic nanocomposite particles.

Ultralow energy ion beam surface modification of low density polyethylene.

Science.gov (United States)

Shenton, Martyn J; Bradley, James W; van den Berg, Jaap A; Armour, David G; Stevens, Gary C

2005-12-01

Ultralow energy Ar+ and O+ ion beam irradiation of low density polyethylene has been carried out under controlled dose and monoenergetic conditions. XPS of Ar+-treated surfaces exposed to ambient atmosphere show that the bombardment of 50 eV Ar+ ions at a total dose of 10(16) cm(-2) gives rise to very reactive surfaces with oxygen incorporation at about 50% of the species present in the upper surface layer. Using pure O+ beam irradiation, comparatively low O incorporation is achieved without exposure to atmosphere (approximately 13% O in the upper surface). However, if the surface is activated by Ar+ pretreatment, then large oxygen contents can be achieved under subsequent O+ irradiation (up to 48% O). The results show that for very low energy (20 eV) oxygen ions there is a dose threshold of about 5 x 10(15) cm(-2) before surface oxygen incorporation is observed. It appears that, for both Ar+ and O+ ions in this regime, the degree of surface modification is only very weakly dependent on the ion energy. The results suggest that in the nonequilibrium plasma treatment of polymers, where the ion flux is typically 10(18) m(-2) s(-1), low energy ions (<50 eV) may be responsible for surface chemical modification.

Use of Threshold of Toxicological Concern (TTC) with High Throughput Exposure Predictions as a Risk-Based Screening Approach to Prioritize More Than Seven Thousand Chemicals (ASCCT)

Science.gov (United States)

Here, we present results of an approach for risk-based prioritization using the Threshold of Toxicological Concern (TTC) combined with high-throughput exposure (HTE) modelling. We started with 7968 chemicals with calculated population median oral daily intakes characterized by an...

Radiation modification of glass fiber - reinforced plastics

International Nuclear Information System (INIS)

Allayarov, S.R.; Smirnov, Yu.N.; Lesnichaya, V.A.; Ol'khov, Yu.A.; Belov, G.P.; Dixon, D.A.; Kispert, L.D.

2007-01-01

Modification of glass fiber - reinforced plastics (GFRPs) by gamma-irradiation has been researched to receipt of polymeric composite materials. They were produced by the film - technology method and the cheapest thermoplastics (polythene, polyamide were used as polymeric matrixes for their manufacture. GFRPs were irradiated with Co 60 gamma-rays from a Gammatok-100 source in air and in vacuum. The strength properties of GFRPs and initial polymeric matrixes were investigated before and after radiolysis. Molecular - topological structure of the polymeric matrixes were tested by the method of thermomechanical spectroscopy. The strength properties of GFRPs depend on a parity of speeds of structural (physical) and chemical modification of the polymeric matrixes. These two processes proceed simultaneously. The structural modification includes physical transformation of polymers at preservation of their chemical structure. Covalent bonds between various macromolecules or between macromolecules and surface of fiberglasses are formed at the chemical modification of polymeric matrixes induced by radiation. Action of ionizing radiation on the used polymeric matrix results to its structurization (polythene) or to destruction (polyamide). Increasing of durability of GFRPs containing polythene is caused by formation of the optimum molecular topological structure of the polymeric matrix. (authors)

Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Primo, Gastón A.; Alvarez Igarzabal, Cecilia I. [IMBIV (CONICET), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Edificio de Ciencias II, Ciudad Universitaria, Córdoba X5000HUA (Argentina); Pino, Gustavo A.; Ferrero, Juan C. [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina); Rossa, Maximiliano, E-mail: mrossa@fcq.unc.edu.ar [INFIQC (CONICET), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, and Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Córdoba X5000IUS (Argentina)

2016-04-30

Graphical abstract: - Highlights: • Laser-induced surface modification of crosslinked hydrophilic co-polymers by ns pulses. • Formation of ablation craters observed under most of the single-pulse experimental conditions. • UV laser foaming of dried hydrogel samples resulting from single- and multiple-pulse experiments. • Threshold values of the incident laser fluence reported for the observed surface modifications. • Lower threshold fluences for acrylate-based, compared to acrylamide-based hydrogels. - Abstract: This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

The surface modification of polystyrene

International Nuclear Information System (INIS)

Tremlett, C.

2000-03-01

Polymers have ideal bulk properties for many applications. However, adhesion to many polymers is poor without surface pretreatment. This can result, for example, in peeling paint and printing, adhesive joint failure and bio-incompatibility. In applications such as painting, printing, adhesive bonding and biocompatibility, various cleaning or surface chemical modifications may be employed. A commodity polymer where pretreatment is sometimes needed is polystyrene. This project investigated, in detail, the effects of a novel method of modification namely mediated electrochemical oxidation (MEO), as a mode of surface modification on polystyrene and a comparison was made with other polymers. The resulting modification was investigated using a range of surface analysis techniques to obtain complementary information. These included, X-ray photoelectron spectroscopy, contact angles, static secondary ion mass spectrometry, atomic force microscopy, chemical derivatization, scanning electron microscopy, attenuated total reflection Fourier Transform infrared spectroscopy and composite lap shear joint testing. It has been shown that MEO modifies the surface of polystyrene introduced oxygen mainly as hydroxyl groups, and a small number of carbonyl groups, that are positioned only on the backbone hydrocarbon chain. This modification improved adhesion, was stable and samples could be stored in aqueous media. The resulting hydroxylation was further derivatized using an amino acid to provide a specialised surface. This was very different from the multiple oxygen functionalities introduced in the comparison studies by UV/ozone and plasma treatments. (author)

MODIFICATION OF SURFACE KONDENSITSIONNYH AEROSOLS WELDING AND METALLURGICHESKIH PRODUCTIONS

Directory of Open Access Journals (Sweden)

A. A. Ennan

2016-04-01

Full Text Available Chemical modification of surface kondensitsionnyh aerosols (KA which formation when heat treatment metals (process of weld, foundry processes with application chlorosilanes are suggested. Adsorbtion vapor of water on modification powders KA decreases and changes in varies from modifier and conditions modification are setted.

The effects of high electronic energy loss on the chemical modification of polyimide

CERN Document Server

SunYouMei; Jin Yun Fan; Liu Chang Long; LiuJie; Wang Zhi Guang; Zhang Qi; Zhu Zhi Yong

2002-01-01

In order to observe the role of electronic energy loss (dE/dX) sub e on chemical modification of polyimide (PI), the multi-layer stacks (corresponding to different dE/dX) were irradiated by different swift heavy ions (1.37 GeV Ar sup 4 sup 0 , 1.98 GeV Kr sup 8 sup 4 , 1.755 GeV Xe sup 1 sup 3 sup 6 and 2.636 GeV U sup 2 sup 3 sup 8) under vacuum and room temperature. The chemical changes of modified PI films were studied by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) absorption spectroscopy. The degradation of PI was investigated in the fluence range from 1x10 sup 1 sup 0 to 5.5x10 sup 1 sup 2 ions/cm sup 2 and different electronic energy loss from 0.77 to 11.5 keV/nm. The FTIR results show the absorbance of the typical function group decrease exponentially as a function of fluence. The alkyne end group was found after irradiation and its formation radii were 5.6 and 5.9 nm corresponding to 8.8 and 11.5 keV/nm Xe irradiation respectively. UV/Vis analysis indicates the radiation induced...

2008 Toxic Chemical Release Inventory 2008 Toxic Chemical Release Inventory Community Right-to-Know Act of 1986, Title III, Section 313

Energy Technology Data Exchange (ETDEWEB)

Ecology and Air Quality Group

2009-10-01

For reporting year 2008, Los Alamos National Laboratory (LANL) submitted a Form R report for lead as required under the Emergency Planning and Community Right-to- Know Act (EPCRA) Section 313. No other EPCRA Section 313 chemicals were used in 2008 above the reportable thresholds. This document was prepared to provide a description of the evaluation of EPCRA Section 313 chemical use and threshold determinations for LANL for calendar year 2008, as well as to provide background information about data included on the Form R reports. Section 313 of EPCRA specifically requires facilities to submit a Toxic Chemical Release Inventory Report (Form R) to the U.S. Environmental Protection Agency (EPA) and state agencies if the owners and operators manufacture, process, or otherwise use any of the listed toxic chemicals above listed threshold quantities. EPA compiles this data in the Toxic Release Inventory database. Form R reports for each chemical over threshold quantities must be submitted on or before July 1 each year and must cover activities that occurred at the facility during the previous year. In 1999, EPA promulgated a final rule on persistent bioaccumulative toxics (PBTs). This rule added several chemicals to the EPCRA Section 313 list of toxic chemicals and established lower reporting thresholds for these and other PBT chemicals that were already reportable. These lower thresholds became applicable in reporting year 2000. In 2001, EPA expanded the PBT rule to include a lower reporting threshold for lead and lead compounds. Facilities that manufacture, process, or otherwise use more than 100 lb of lead or lead compounds must submit a Form R.

Chemical modification of Art v 1, a major mugwort pollen allergen, by cis-aconitylation and citraconylation

Directory of Open Access Journals (Sweden)

DRAGANA STANIĆ

2009-04-01

Full Text Available Art v 1 is the major allergen of mugwort (Artemisia vulgaris pollen, a significant cause of hay fever all over Europe. Specific immunotherapy is the only treatment modality for allergic disease. Application of modified allergens makes the treatment safer and more efficient. In this work, two out of three (citraconic anhydride, cis-aconitic anhydride, 2,3-dimethylmaleic anhydride tested anhydrides were proven to be suitable for chemical modifications of allergens. Art v 1 was modified by cis-aconitylation and citraconylation in order to obtain derivatives of Art v 1 that may be suitable for further immunological testing. Acylation of Art v 1 gave derivatives (caaArt v 1 and citArt v 1 with about 80 % modified amino groups. The derivatives were in the monomeric form and had dramatically reduced pI values. Both derivatives were relatively stable at neutral pH values, while the acyl groups undergo hydrolysis under acidic conditions. Modification of allergens by cis-aconitylation and citraconylation could be a new tool for obtaining allergoids.

Modification of mesoporous silica SBA-15 with different organic molecules to gain chemical sensors: a review

Directory of Open Access Journals (Sweden)

Negar Lashgari

2016-01-01

Full Text Available The recognition of the biologically and environmentally important ions is of great interest in the field of chemical sensors in recent years. The fluorescent sensors as a powerful optical analytical technique for the detection of low level of various analytes such as anions and metal cations have been progressively developed due to the simplicity, cost effective, and selectivity for monitoring specific analytes in various systems. Organic-inorganic hybrid nanomaterials have important advantages as solid chemosensors and various innovative hybrid materials modified by fluorescence molecules were recently prepared. On the other hand, the homogeneous porosity and large surface area of mesoporous silica make it a promising inorganic support. SBA-15 as a two-dimensional hexagonal mesoporous silica material with stable structure, thick walls, tunable pore size, and high specific surface area is a valuable substrate for modification with different organic chelating groups. This review highlights the fluorescent chemosensors for ionic species based on modification of the mesoporous silica SBA-15 with different organic molecules, which have been recently developed from our laboratory.

A hybrid flower pollination algorithm based modified randomized location for multi-threshold medical image segmentation.

Science.gov (United States)

Wang, Rui; Zhou, Yongquan; Zhao, Chengyan; Wu, Haizhou

2015-01-01

Multi-threshold image segmentation is a powerful image processing technique that is used for the preprocessing of pattern recognition and computer vision. However, traditional multilevel thresholding methods are computationally expensive because they involve exhaustively searching the optimal thresholds to optimize the objective functions. To overcome this drawback, this paper proposes a flower pollination algorithm with a randomized location modification. The proposed algorithm is used to find optimal threshold values for maximizing Otsu's objective functions with regard to eight medical grayscale images. When benchmarked against other state-of-the-art evolutionary algorithms, the new algorithm proves itself to be robust and effective through numerical experimental results including Otsu's objective values and standard deviations.

Chemical modifications of antisense morpholino oligomers enhance their efficacy against Ebola virus infection.

Science.gov (United States)

Swenson, Dana L; Warfield, Kelly L; Warren, Travis K; Lovejoy, Candace; Hassinger, Jed N; Ruthel, Gordon; Blouch, Robert E; Moulton, Hong M; Weller, Dwight D; Iversen, Patrick L; Bavari, Sina

2009-05-01

Phosphorodiamidate morpholino oligomers (PMOs) are uncharged nucleic acid-like molecules designed to inactivate the expression of specific genes via the antisense-based steric hindrance of mRNA translation. PMOs have been successful at knocking out viral gene expression and replication in the case of acute viral infections in animal models and have been well tolerated in human clinical trials. We propose that antisense PMOs represent a promising class of therapeutic agents that may be useful for combating filoviral infections. We have previously shown that mice treated with a PMO whose sequence is complementary to a region spanning the start codon of VP24 mRNA were protected against lethal Ebola virus challenge. In the present study, we report on the abilities of two additional VP24-specific PMOs to reduce the cell-free translation of a VP24 reporter, to inhibit the in vitro replication of Ebola virus, and to protect mice against lethal challenge when the PMOs are delivered prior to infection. Additionally, structure-activity relationship evaluations were conducted to assess the enhancement of antiviral efficacy associated with PMO chemical modifications that included conjugation with peptides of various lengths and compositions, positioning of conjugated peptides to either the 5' or the 3' terminus, and the conferring of charge modifications by the addition of piperazine moieties. Conjugation with arginine-rich peptides greatly enhanced the antiviral efficacy of VP24-specific PMOs in infected cells and mice during lethal Ebola virus challenge.

The chemical modification and characterization of polypropylene membrane with environment response by in-situ chlorinating graft copolymerization

Science.gov (United States)

Zhang, Yue; Liu, Jiankai; Hu, Wenjie; Feng, Ying; Zhao, Jiruo

2017-08-01

In this study, a novel chemical surface modification method of polyolefin membranes is applied following the in-situ chlorinating graft copolymerization (ISCGC). Polypropylene (PP)/methyl methacrylate (MMA) system was used as an example. A unique structure was formed by the modification process on the original membrane surface and the product exhibited an environmental response. Chlorine free radicals were generated using ultraviolet and heat and were used to capture the hydrogen in the polymer chains on the substrate surface. The formed macromolecular radicals could react with MMA over 2 h to achieve a high coverage ratio polymer on the PP membrane surface. The graft copolymers were characterized using FTIR, 1H-NMR, DSC, and XPS, which all proved the feasibility of chemically modifying the PP membrane surface by ISCGC. The surface morphology of the grafted PP membrane was characterized using SEM and AFM. The results showed that the grafted product presents a uniform, neat, and dense mastoid structure with an average thickness of 4.44 μm, which was expected to be similar to the brush-like surface structure. The contact angle and AFM tests indicated that the product surface is responsive to solvent and pH. The experimental results showed that the PP membrane surface structure can be reconstructed using ISCGC, a method that can be used for environment-responsive polymer materials. Moreover, the product has the characteristics of polymer interfacial brush.

Chemical modification of clay from the state of vermiculite Paraiba for use in nanocomposites of thermoset matrices

International Nuclear Information System (INIS)

Freitas, W.A.; Alves, T.S.; Barbosa, R.

2011-01-01

Vermiculite is a hydrated aluminosilicate of magnesium, iron and aluminum flake shape, formed by stacking cells 2:1 and feature high cation exchange capacity. In the present study was performed the treatment of an expanded vermiculite clay from Paraiba state with surfactant agent, in order to make it organophilic and allow its use in thermoset matrix nanocomposites. The natural clay and organophilizated one were characterized by X-Ray Diffraction (XRD), by Fourier Transform Infra-Red spectroscopy (FTIR) and swelling of Foster's swelling. The results indicated a change in the chemical composition of clay, related to the presence of characteristic groups of the salt in the clay and an increase of up to 124% in the basal interlayer distance. The chemical modification of the clay was efficient, indicating the possibility to apply the clay in polymeric nanocomposites. (author)

Evaluation of electrode surface modification techniques for the development of chemical sensors

International Nuclear Information System (INIS)

Galiatsatos, C.

1988-01-01

This thesis covers several aspects of electrode surface modification techniques. The successful application of gamma-radiation to create polymer-coated electrodes, where the polymers can be ion exchangers and consequently of great analytical interest by themselves (such as the polymer poly(diallyl) dimethyl ammonium chloride) or where some other neutral polymers can function as convenient matrices for the introduction of biomolecules and/or other electrochemically interesting species is reported. This is demonstrated by using the neutral polymer poly(vinyl alcohol) (PVAL) as a matrix for immobilization of the enzyme glucose oxidase and the mediator methyl viologen. The effect of γ-radiation on PVAL is discussed, as well as swelling properties of the irradiated polymers and specific characteristics of the created chemical sensors. Results of an experiment where the various kinds of interactions between the ion-exchange polymer Nafion and some positively charged species are explored are reported, and a model system for competition (methyl viologen vs. ruthenium hexaamine) which increases significantly our understanding of the interaction is mentioned. The effect of γ-radiation on Nafion and its ion-exchange compabilities is discussed also. A system of conduction polymers primarily polypyrrole, used as a detector of electroinactive anions due to their doping-undergoing in the film is discussed. Preliminary results on a new method that involves chemical cross-linking of a triisocyane molecule with -OH containing polymers in the presence of enzymes are reported

A novel fabrication method of carbon electrodes using 3D printing and chemical modification process.

Science.gov (United States)

Tian, Pan; Chen, Chaoyang; Hu, Jie; Qi, Jin; Wang, Qianghua; Chen, Jimmy Ching-Ming; Cavanaugh, John; Peng, Yinghong; Cheng, Mark Ming-Cheng

2017-11-23

Three-dimensional (3D) printing is an emerging technique in the field of biomedical engineering and electronics. This paper presents a novel biofabrication method of implantable carbon electrodes with several advantages including fast prototyping, patient-specific and miniaturization without expensive cleanroom. The method combines stereolithography in additive manufacturing and chemical modification processes to fabricate electrically conductive carbon electrodes. The stereolithography allows the structures to be 3D printed with very fine resolution and desired shapes. The resin is then chemically modified to carbon using pyrolysis to enhance electrochemical performance. The electrochemical characteristics of 3D printing carbon electrodes are assessed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The specific capacitance of 3D printing carbon electrodes is much higher than the same sized platinum (Pt) electrode. In-vivo electromyography (EMG) recording, 3D printing carbon electrodes exhibit much higher signal-to-noise ratio (40.63 ± 7.73) than Pt electrodes (14.26 ± 6.83). The proposed biofabrication method is envisioned to enable 3D printing in many emerging applications in biomedical engineering and electronics.

Effects of aluminium surface morphology and chemical modification on wettability

Energy Technology Data Exchange (ETDEWEB)

Rahimi, M., E-mail: mar@sbi.aau.dk [Department of Energy and Environment, Danish Building Research Institute, Aalborg University, A.C. Meyers Vænge 15, 2450 København SV (Denmark); Fojan, P.; Gurevich, L. [Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4, DK-9220 Aalborg East (Denmark); Afshari, A. [Department of Energy and Environment, Danish Building Research Institute, Aalborg University, A.C. Meyers Vænge 15, 2450 København SV (Denmark)

2014-03-01

Highlights: • Successful surface modification procedures on aluminium samples were performed involving formation of the layer of hydrophilic hyperbranched polyethyleneglycol (PEG) via in situ polymerization, molecular vapour deposition of a monolayer of fluorinated silane, and a combination of those. • The groups of surfaces with hydrophobic behavior were found to follow the Wenzel model. • A transition from Cassie–Baxter's to Wenzel's regime was observed due to changing of the surface roughness upon mechanical polishing in aluminium samples. - Abstract: Aluminium alloys are some of the predominant metals in industrial applications such as production of heat exchangers, heat pumps. They have high heat conductivity coupled with a low specific weight. In cold working conditions, there is a risk of frost formation on the surface of aluminium in the presence of water vapour, which can lead to the deterioration of equipment performance. This work addresses the methods of surface modification of aluminium and their effect of the underlying surface morphology and wettability, which are the important parameters for frost formation. Three groups of real-life aluminium surfaces of different morphology: unpolished aluminium, polished aluminium, and aluminium foil, were subjected to surface modification procedures which involved the formation of a layer of hydrophilic hyperbranched polyethyleneglycol via in situ polymerization, molecular vapour deposition of a monolayer of fluorinated silane, and a combination of those. The effect of these surface modification techniques on roughness and wettability of the aluminium surfaces was elucidated by ellipsometry, contact angle measurements and atomic force microscopy. We demonstrated that by employing different types of surface modifications the contact angle of water droplets on aluminium samples can be varied from 12° to more than 120°. A crossover from Cassie–Baxter to Wenzel regime upon changing the surface

Modification of foxtail millet starch by combining physical, chemical and enzymatic methods.

Science.gov (United States)

Dey, Ashim; Sit, Nandan

2017-02-01

Modification of foxtail millet starch was carried out by heat moisture treatment (HT), acid hydrolysis (AH), enzymatic treatment (EH), Ultrasound treatment (UT) and their combinations. A total of 15 modified starches were prepared by combining the various methods and properties were compared with native starch. The solubilities of the starches modified by HT were found to decrease whereas for other single modifications it increased. It also increased with number of modifications applied. The swelling power decreased for all the modified starches and a decrease in swelling power was observed with increase in number of modifications. Freeze-thaw stability improved for starches modified by single physical modifications i.e. HT and UT. Decrease in viscosities was observed for the modified starches and was particularly affected by AH. The pasting temperature was found to increase for those modified starches where HT was carried out. The modified starches gave softer gels. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of aluminium surface morphology and chemical modification on wettability

DEFF Research Database (Denmark)

Rahimi, Maral; Fojan, Peter; Gurevich, Leonid

2014-01-01

-life aluminium surfaces of different morphology: unpolished aluminium, polished aluminium, and aluminium foil, were subjected to surface modification procedures which involved the formation of a layer of hydrophilic hyperbranched polyethyleneglycol via in situ polymerization, molecular vapour deposition...... of a monolayer of fluorinated silane, and a combination of those. The effect of these surface modification techniques on roughness and wettability of the aluminium surfaces was elucidated by ellipsometry, contact angle measurements and atomic force microscopy. We demonstrated that by employing different types...

Chemical modifications of therapeutic proteins induced by residual ethylene oxide.

Science.gov (United States)

Chen, Louise; Sloey, Christopher; Zhang, Zhongqi; Bondarenko, Pavel V; Kim, Hyojin; Ren, Da; Kanapuram, Sekhar

2015-02-01

Ethylene oxide (EtO) is widely used in sterilization of drug product primary containers and medical devices. The impact of residual EtO on protein therapeutics is of significant interest in the biopharmaceutical industry. The potential for EtO to modify individual amino acids in proteins has been previously reported. However, specific identification of EtO adducts in proteins and the effect of residual EtO on the stability of therapeutic proteins has not been reported to date. This paper describes studies of residual EtO with two therapeutic proteins, a PEGylated form of the recombinant human granulocyte colony-stimulating factor (Peg-GCSF) and recombinant human erythropoietin (EPO) formulated with human serum albumin (HSA). Peg-GCSF was filled in an EtO sterilized delivery device and incubated at accelerated stress conditions. Glu-C peptide mapping and LC-MS analyses revealed residual EtO reacted with Peg-GCSF and resulted in EtO modifications at two methionine residues (Met-127 and Met-138). In addition, tryptic peptide mapping and LC-MS analyses revealed residual EtO in plastic vials reacted with HSA in EPO formulation at Met-328 and Cys-34. This paper details the work conducted to understand the effects of residual EtO on the chemical stability of protein therapeutics. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Threshold of toxicological concern values for non-genotoxic effects in industrial chemicals: re-evaluation of the Cramer classification.

Science.gov (United States)

Kalkhof, H; Herzler, M; Stahlmann, R; Gundert-Remy, U

2012-01-01

The TTC concept employs available data from animal testing to derive a distribution of NOAELs. Taking a probabilistic view, the 5th percentile of the distribution is taken as a threshold value for toxicity. In this paper, we use 824 NOAELs from repeated dose toxicity studies of industrial chemicals to re-evaluate the currently employed TTC values, which have been derived for substances grouped according to the Cramer scheme (Cramer et al. in Food Cosm Toxicol 16:255-276, 1978) by Munro et al. (Food Chem Toxicol 34:829-867, 1996) and refined by Kroes and Kozianowski (Toxicol Lett 127:43-46, 2002), Kroes et al. 2000. In our data set, consisting of 756 NOAELs from 28-day repeated dose testing and 57 NOAELs from 90-days repeated dose testing, the experimental NOAEL had to be extrapolated to chronic TTC using regulatory accepted extrapolation factors. The TTC values derived from our data set were higher than the currently used TTC values confirming the safety of the latter. We analysed the prediction of the Cramer classification by comparing the classification by this tool with the guidance values for classification according to the Globally Harmonised System of classification and labelling of the United Nations (GHS). Nearly 90% of the chemicals were in Cramer class 3 and assumed as highly toxic compared to 22% according to the GHS. The Cramer classification does underestimate the toxicity of chemicals only in 4.6% of the cases. Hence, from a regulatory perspective, the Cramer classification scheme might be applied as it overestimates hazard of a chemical.

DOE approach to threshold quantities

International Nuclear Information System (INIS)

Wickham, L.E.; Kluk, A.F.; Department of Energy, Washington, DC)

1985-01-01

The Department of Energy (DOE) is developing the concept of threshold quantities for use in determining which waste materials must be handled as radioactive waste and which may be disposed of as nonradioactive waste at its sites. Waste above this concentration level would be managed as radioactive or mixed waste (if hazardous chemicals are present); waste below this level would be handled as sanitary waste. Ideally, the threshold must be set high enough to significantly reduce the amount of waste requiring special handling. It must also be low enough so that waste at the threshold quantity poses a very small health risk and multiple exposures to such waste would still constitute a small health risk. It should also be practical to segregate waste above or below the threshold quantity using available instrumentation. Guidance is being prepared to aid DOE sites in establishing threshold quantity values based on pathways analysis using site-specific parameters (waste stream characteristics, maximum exposed individual, population considerations, and site specific parameters such as rainfall, etc.). A guidance dose of between 0.001 to 1.0 mSv/y (0.1 to 100 mrem/y) was recommended with 0.3 mSv/y (30 mrem/y) selected as the guidance dose upon which to base calculations. Several tasks were identified, beginning with the selection of a suitable pathway model for relating dose to the concentration of radioactivity in the waste. Threshold concentrations corresponding to the guidance dose were determined for waste disposal sites at a selected humid and arid site. Finally, cost-benefit considerations at the example sites were addressed. The results of the various tasks are summarized and the relationship of this effort with related developments at other agencies discussed

Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

Energy Technology Data Exchange (ETDEWEB)

Abdullah, Mohd Zamri, E-mail: zamriab@petronas.com.my; Ismail, Siti Salwa [Chemical Engineering Department, Universiti Teknologi PETRONAS, 31750 Bandar Seri Iskandar, Perak (Malaysia)

2015-07-22

The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.

Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

International Nuclear Information System (INIS)

Abdullah, Mohd Zamri; Ismail, Siti Salwa

2015-01-01

The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature

76 FR 65769 - Airport Improvement Program: Modifications to Benefit Cost Analysis (BCA) Threshold

Science.gov (United States)

2011-10-24

... have risen faster than the general rate of inflation. Since we were unable to locate construction cost... enables us to best respond. B. Modifications to Policy The previous AIP grant policy, issued June 24, 1997... established a docket and invited airport sponsors and other interested parties to comment on the BCA...

Surface modification of protein enhances encapsulation in chitosan nanoparticles

Science.gov (United States)

Koyani, Rina D.; Andrade, Mariana; Quester, Katrin; Gaytán, Paul; Huerta-Saquero, Alejandro; Vazquez-Duhalt, Rafael

2018-04-01

Chitosan nanoparticles have a huge potential as nanocarriers for environmental and biomedical purposes. Protein encapsulation in nano-sized chitosan provides protection against inactivation, proteolysis, and other alterations due to environmental conditions, as well as the possibility to be targeted to specific tissues by ligand functionalization. In this work, we demonstrate that the chemical modification of the protein surface enhances the protein loading in chitosan nanocarriers. Encapsulation of green fluorescent protein and the cytochrome P450 was studied. The increase of electrostatic interactions between the free amino groups of chitosan and the increased number of free carboxylic groups in the protein surface enhance the protein loading, protein retention, and, thus, the enzymatic activity of chitosan nanoparticles. The chemical modification of protein surface with malonic acid moieties reduced drastically the protein isoelectric point increasing the protein interaction with the polycationic biomaterial and chitosan. The chemical modification of protein does not alter the morphology of chitosan nanoparticles that showed an average diameter of 18 nm, spheroidal in shape, and smooth surfaced. The strategy of chemical modification of protein surface, shown here, is a simple and efficient technique to enhance the protein loading in chitosan nanoparticles. This technique could be used for other nanoparticles based on polycationic or polyanionic materials. The increase of protein loading improves, doubtless, the performance of protein-loaded chitosan nanoparticles for biotechnological and biomedical applications.

Use of hydrostatic pressure for modulation of protein chemical modification and enzymatic selectivity.

Science.gov (United States)

Makarov, Alexey A; Helmy, Roy; Joyce, Leo; Reibarkh, Mikhail; Maust, Mathew; Ren, Sumei; Mergelsberg, Ingrid; Welch, Christopher J

2016-05-11

Using hydrostatic pressure to induce protein conformational changes can be a powerful tool for altering the availability of protein reactive sites and for changing the selectivity of enzymatic reactions. Using a pressure apparatus, it has been demonstrated that hydrostatic pressure can be used to modulate the reactivity of lysine residues of the protein ubiquitin with a water-soluble amine-specific homobifunctional coupling agent. Fewer reactive lysine residues were observed when the reaction was carried out under elevated pressure of 3 kbar, consistent with a pressure-induced conformational change of ubiquitin that results in fewer exposed lysine residues. Additionally, modulation of the stereoselectivity of an enzymatic transamination reaction was observed at elevated hydrostatic pressure. In one case, the minor diasteromeric product formed at atmospheric pressure became the major product at elevated pressure. Such pressure-induced alterations of protein reactivity may provide an important new tool for enzymatic reactions and the chemical modification of proteins.

Surface modification on PMMA : PVDF polyblend: hardening under ...

Indian Academy of Sciences (India)

Unknown

Keywords. Polyblend; surface modification; microhardness; hardening; plasticization; segmental mobility. 1. Introduction. Polymeric materials have a specific feature of stability towards various aggressive chemical environments, which depends on a multiplicity of factors like structure and nature of the polymers and chemical ...

SS-mPEG chemical modification of recombinant phospholipase C for enhanced thermal stability and catalytic efficiency.

Science.gov (United States)

Fang, Xian; Wang, Xueting; Li, Guiling; Zeng, Jun; Li, Jian; Liu, Jingwen

2018-05-01

PEGylation is one of the most promising and extensively studied strategies for improving the properties of proteins as well as enzymic physical and thermal stability. Phospholipase C, hydrolyzing the phospholipids offers tremendous applications in diverse fields. However, the poor thermal stability and higher cost of production have restricted its industrial application. This study focused on improving the stabilization of recombinant PLC by chemical modification with methoxypolyethylene glycol-Succinimidyl Succinate (SS-mPEG, MW 5000). PLC gene from isolate Bacillus cereus HSL3 was fused with SUMO, a novel small ubiquitin-related modifier expression vector and over expressed in Escherichia coli. The soluble fraction of SUMO-PLC reached 80% of the total recombinant protein. The enzyme exhibited maximum catalytic activity at 80 °C and was relatively thermostable at 40-70 °C. It showed extensive substrate specificity pattern and marked activity toward phosphatidylcholine, which made it a typical non-specific PLC for industrial purpose. SS-mPEG-PLC complex exhibited an enhanced thermal stability at 70-80 °C and the catalytic efficiency (K cat /K m ) had increased by 3.03 folds compared with free PLC. CD spectrum of SS-mPEG-PLC indicated a possible enzyme aggregation after chemical modification, which contributed to the higher thermostability of SS-mPEG-PLC. The increase of antiparallel β sheets in secondary structure also made it more stable than parallel β sheets. The presence of SS-mPEG chains on the enzyme molecule surface somewhat changed the binding rate of the substrates, leading to a significant improvement in catalytic efficiency. This study provided an insight into the addition of SS-mPEG for enhancing the industrial applications of phospholipase C at higher temperature. Copyright © 2018 Elsevier B.V. All rights reserved.

Sequence-engineered mRNA Without Chemical Nucleoside Modifications Enables an Effective Protein Therapy in Large Animals

Science.gov (United States)

Thess, Andreas; Grund, Stefanie; Mui, Barbara L; Hope, Michael J; Baumhof, Patrick; Fotin-Mleczek, Mariola; Schlake, Thomas

2015-01-01

Being a transient carrier of genetic information, mRNA could be a versatile, flexible, and safe means for protein therapies. While recent findings highlight the enormous therapeutic potential of mRNA, evidence that mRNA-based protein therapies are feasible beyond small animals such as mice is still lacking. Previous studies imply that mRNA therapeutics require chemical nucleoside modifications to obtain sufficient protein expression and avoid activation of the innate immune system. Here we show that chemically unmodified mRNA can achieve those goals as well by applying sequence-engineered molecules. Using erythropoietin (EPO) driven production of red blood cells as the biological model, engineered Epo mRNA elicited meaningful physiological responses from mice to nonhuman primates. Even in pigs of about 20 kg in weight, a single adequate dose of engineered mRNA encapsulated in lipid nanoparticles (LNPs) induced high systemic Epo levels and strong physiological effects. Our results demonstrate that sequence-engineered mRNA has the potential to revolutionize human protein therapies. PMID:26050989

Modification and characterization of microcrystalline cellulose with succinic anhydride

International Nuclear Information System (INIS)

Santos, Clecio M.R.; Santos, Douglas C.; Freitas, Gizele B.; Cardoso, Giselia

2011-01-01

Cellulose is a natural polymer, non-toxic, biodegradable and renewable source. With increasing global attention to environmental problems, the chemical modification of cellulose has been evaluated with increasing applicability in various industrial sectors. The cellulose can be chemical modified through the hydroxyl present in their molecules. This paper aims to present the main results in the modification of microcrystalline cellulose. The sample was pure and modified chemically and morphologically characterized by absorption spectroscopy in the infrared (IR) and showed the band in the 1551cm -1 characterization modification made, X-ray diffraction (XRD) where it was observed that the change led to a reduction significant crystallinity, and determination of average pore radius through the analyzer porosity and surface area resulting in values of 6.97 angstrom for pure sample and 8.62 angstrom for the modified. In addition to these tests we determined the average degree of substitution finding the value of 1.67. (author)

In vitro study of morphological and chemical modification threshold of bovine dental enamel irradiated by the holmium laser

International Nuclear Information System (INIS)

Eduardo, Patricia Lerro de Paula

2001-01-01

The aim of this study is to investigate the Ho:YLF laser effects on the dental enamel surface with regards to its morphology, thermal variations during its irradiation in the pulp chamber and its increased resistance to demineralization through quantitative analysis of calcium and phosphorous atoms reactive concentrations in samples. Twenty samples of bovine enamel were used and divided in four groups: control - acidulated phosphate fluoride (APF) application followed by demineralization treatment with lactic acid; irradiation with Ho:YLF laser (100 J/cm 2 ) followed by APF topic application and demineralization treatment with lactic acid; irradiation with Ho:YLF laser (350 J/cm 2 ) followed by APF topic application and demineralization treatment with lactic acid: and irradiation with Ho:YLF laser ( 450 J/cm 2 ) followed by APF topic application and demineralization treatment with lactic acid. Ali samples were quantified according to their calcium and phosphorous atoms relative concentrations before and after the treatments above. X-Ray fluorescence spectrochemical analysis and scanning electron microscopy were carried out. It was observed an increase on the calcium and phosphorous atoms concentration ratio and therefore the enamel demineralization reduction as a result of the lactic acid treatment in the samples irradiated with the holmium laser followed by the APF application. In order to evaluate the feasibility of this study for clinical purposes, morphological changes caused by the holmium laser irradiation were analyzed. Such modifications were characterized by melted and re-solidified regions of the enamel with consequent changes on its permeability and solubility. Temperature changes of ten human pre-molars teeth irradiated with 350 J/cm 2 and 450 J/cm 2 were also monitored in the pulp chamber in real time. Temperature increases over 4,20 C did not occur. The results obtained from this study along with the results from previous researches developed at

Modification of poly(styrene-block-butadiene-block-styrene) [SBS] with phosphorus containing fire retardants

DEFF Research Database (Denmark)

Chernyy, Sergey; Ullah, Saif; Jomaas, Grunde

2015-01-01

An elaborate survey of the chemical modification methods for endowing highly flammable SBS with increased fire resistant properties by means of chemical modification of the polymer backbone with phosphorus containing fire retardant species is presented. Optimal conditions for free radical addition...

Chemical modification and pH dependence of kinetic parameters to identify functional groups in a glucosyltransferase from Strep. Mutans

International Nuclear Information System (INIS)

Bell, J.E.; Leone, A.; Bell, E.T.

1986-01-01

A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of 14 C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5 must be protonated to maximize substrate binding. From plots of V/sub max/ vs pH two groups, with pKa's of 4.5 and 5.5 were indicated. The results suggest the involvement of either two carboxyl groups (one protonated, one unprotonated in the native enzyme) or a carboxyl group (unprotonated) and some other protonated group such as histidine, cysteine. Chemical modification studies showed that Diethylyrocarbonate (histidine specific) had no effect on enzyme activity while modification with p-phydroxy-mercuribenzoate or iodoacetic acid (sulfhydryl reactive) and carbodimide reagents (carboxyl specific) resulted in almost complete inactivation. Activity loss was dependent upon time of incubation and reagent concentration. The disaccharide lylose, (shown to be an inhibitor of the enzyme with similar affinity to sucrose) offers no protection against modification by the sulfhydryl reactive reagents

Compressively sampled MR image reconstruction using generalized thresholding iterative algorithm

Science.gov (United States)

Elahi, Sana; kaleem, Muhammad; Omer, Hammad

2018-01-01

Compressed sensing (CS) is an emerging area of interest in Magnetic Resonance Imaging (MRI). CS is used for the reconstruction of the images from a very limited number of samples in k-space. This significantly reduces the MRI data acquisition time. One important requirement for signal recovery in CS is the use of an appropriate non-linear reconstruction algorithm. It is a challenging task to choose a reconstruction algorithm that would accurately reconstruct the MR images from the under-sampled k-space data. Various algorithms have been used to solve the system of non-linear equations for better image quality and reconstruction speed in CS. In the recent past, iterative soft thresholding algorithm (ISTA) has been introduced in CS-MRI. This algorithm directly cancels the incoherent artifacts produced because of the undersampling in k -space. This paper introduces an improved iterative algorithm based on p -thresholding technique for CS-MRI image reconstruction. The use of p -thresholding function promotes sparsity in the image which is a key factor for CS based image reconstruction. The p -thresholding based iterative algorithm is a modification of ISTA, and minimizes non-convex functions. It has been shown that the proposed p -thresholding iterative algorithm can be used effectively to recover fully sampled image from the under-sampled data in MRI. The performance of the proposed method is verified using simulated and actual MRI data taken at St. Mary's Hospital, London. The quality of the reconstructed images is measured in terms of peak signal-to-noise ratio (PSNR), artifact power (AP), and structural similarity index measure (SSIM). The proposed approach shows improved performance when compared to other iterative algorithms based on log thresholding, soft thresholding and hard thresholding techniques at different reduction factors.

Novel method for chemical modification and patterning of the SU-8 photoresist

DEFF Research Database (Denmark)

Blagoi, Gabriela; Keller, Stephan Urs; Boisen, Anja

2007-01-01

the wetting behaviour of SU-8. The resolution limit of the AQ photopatterning method was 20 μm when using an uncollimated light source. AQ modification followed by a reaction with amino groups of Alexa-647 cadaverine and a Biotin-amino derivative proved possible modification and patterning of polymeric...

Ultrahigh Error Threshold for Surface Codes with Biased Noise

Science.gov (United States)

Tuckett, David K.; Bartlett, Stephen D.; Flammia, Steven T.

2018-02-01

We show that a simple modification of the surface code can exhibit an enormous gain in the error correction threshold for a noise model in which Pauli Z errors occur more frequently than X or Y errors. Such biased noise, where dephasing dominates, is ubiquitous in many quantum architectures. In the limit of pure dephasing noise we find a threshold of 43.7(1)% using a tensor network decoder proposed by Bravyi, Suchara, and Vargo. The threshold remains surprisingly large in the regime of realistic noise bias ratios, for example 28.2(2)% at a bias of 10. The performance is, in fact, at or near the hashing bound for all values of the bias. The modified surface code still uses only weight-4 stabilizers on a square lattice, but merely requires measuring products of Y instead of Z around the faces, as this doubles the number of useful syndrome bits associated with the dominant Z errors. Our results demonstrate that large efficiency gains can be found by appropriately tailoring codes and decoders to realistic noise models, even under the locality constraints of topological codes.

A study of chemical modifications of a Nafion membrane by incorporation of different room temperature ionic liquids

Energy Technology Data Exchange (ETDEWEB)

Martinez de Yuso, M.V.; Rodriguez-Castellon, E. [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Malaga (Spain); Neves, L.A.; Coelhoso, I.M.; Crespo, J.G. [REQUIMTE/CQFB, Departamento de Quimica, Universidade Nova de Lisboa, Caparica (Portugal); Benavente, J. [Departamento de Fisica Aplicada I, Facultad de Ciencias, Universidad de Malaga (Spain)

2012-08-15

Surface and bulk chemical changes in a Nafion membrane as a result of room temperature ionic liquids (RTILs) incorporation were determined by X-ray photoelectron spectroscopy (XPS) and elemental analysis, respectively. RTILs with different physicochemical properties were selected. Two imidazolium based RTIL-cations (1-octyl-3-methylimidazolium and 1-butyl-3-methylimidazolium) were used to detect the effect of cation size on membrane modification, while the effect of the RTIL hydrophilic/hydrophobic character was also considered by choosing different anions. Angle resolved XPS measurements (ARXPS) were carried out varying the angle of analysis between 15 and 75 to get elemental information on the Nafion/RTIL-modified membranes interactions for a deepness of around 10 nm. Moreover, changes in the RTIL-modified membranes associated to thermal effect were also considered by analyzing the samples after their heating at 120 C for 24 h. Agreement between both chemical techniques, bulk and destructive elemental analysis and surface and non-destructive XPS, were obtained. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Threshold effects on renormalization group running of neutrino parameters in the low-scale seesaw model

International Nuclear Information System (INIS)

Bergstroem, Johannes; Ohlsson, Tommy; Zhang He

2011-01-01

We show that, in the low-scale type-I seesaw model, renormalization group running of neutrino parameters may lead to significant modifications of the leptonic mixing angles in view of so-called seesaw threshold effects. Especially, we derive analytical formulas for radiative corrections to neutrino parameters in crossing the different seesaw thresholds, and show that there may exist enhancement factors efficiently boosting the renormalization group running of the leptonic mixing angles. We find that, as a result of the seesaw threshold corrections to the leptonic mixing angles, various flavor symmetric mixing patterns (e.g., bi-maximal and tri-bimaximal mixing patterns) can be easily accommodated at relatively low energy scales, which is well within the reach of running and forthcoming experiments (e.g., the LHC).

Performance of new thresholds of the Glasgow Blatchford score in managing patients with upper gastrointestinal bleeding.

Science.gov (United States)

Laursen, Stig B; Dalton, Harry R; Murray, Iain A; Michell, Nick; Johnston, Matt R; Schultz, Michael; Hansen, Jane M; Schaffalitzky de Muckadell, Ove B; Blatchford, Oliver; Stanley, Adrian J

2015-01-01

Upper gastrointestinal hemorrhage (UGIH) is a common cause of hospital admission. The Glasgow Blatchford score (GBS) is an accurate determinant of patients' risk for hospital-based intervention or death. Patients with a GBS of 0 are at low risk for poor outcome and could be managed as outpatients. Some investigators therefore have proposed extending the definition of low-risk patients by using a higher GBS cut-off value, possibly with an age adjustment. We compared 3 thresholds of the GBS and 2 age-adjusted modifications to identify the optimal cut-off value or modification. We performed an observational study of 2305 consecutive patients presenting with UGIH at 4 centers (Scotland, England, Denmark, and New Zealand). The performance of each threshold and modification was evaluated based on sensitivity and specificity analyses, the proportion of low-risk patients identified, and outcomes of patients classified as low risk. There were differences in age (P = .0001), need for intervention (P 97%). The GBS at cut-off values of ≤1 and ≤2, and both modifications, identified low-risk patients with higher levels of specificity (40%-49%) than the GBS with a cut-off value of 0 (22% specificity; P < .001). The GBS at a cut-off value of ≤2 had the highest specificity, but 3% of patients classified as low-risk patients had adverse outcomes. All GBS cut-off values, and score modifications, had low levels of specificity when tested in New Zealand (2.5%-11%). A GBS cut-off value of ≤1 and both GBS modifications identify almost twice as many low-risk patients with UGIH as a GBS at a cut-off value of 0. Implementing a protocol for outpatient management, based on one of these scores, could reduce hospital admissions by 15% to 20%. Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.

Post-Translational Modifications of TRP Channels

Directory of Open Access Journals (Sweden)

Olaf Voolstra

2014-04-01

Full Text Available Transient receptor potential (TRP channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.

A probabilistic generative model for quantification of DNA modifications enables analysis of demethylation pathways.

Science.gov (United States)

Äijö, Tarmo; Huang, Yun; Mannerström, Henrik; Chavez, Lukas; Tsagaratou, Ageliki; Rao, Anjana; Lähdesmäki, Harri

2016-03-14

We present a generative model, Lux, to quantify DNA methylation modifications from any combination of bisulfite sequencing approaches, including reduced, oxidative, TET-assisted, chemical-modification assisted, and methylase-assisted bisulfite sequencing data. Lux models all cytosine modifications (C, 5mC, 5hmC, 5fC, and 5caC) simultaneously together with experimental parameters, including bisulfite conversion and oxidation efficiencies, as well as various chemical labeling and protection steps. We show that Lux improves the quantification and comparison of cytosine modification levels and that Lux can process any oxidized methylcytosine sequencing data sets to quantify all cytosine modifications. Analysis of targeted data from Tet2-knockdown embryonic stem cells and T cells during development demonstrates DNA modification quantification at unprecedented detail, quantifies active demethylation pathways and reveals 5hmC localization in putative regulatory regions.

Applications of molecules as high-resolution, high-sensitivity threshold electron detectors

International Nuclear Information System (INIS)

Chutjian, A.

1991-01-01

The goal of the work under the contract entitled ''Applications of Molecules as High-Resolution, High-Sensitivity Threshold Electron Detectors'' (DoE IAA No. DE-AI01-83ER13093 Mod. A006) was to explore the electron attachment properties of a variety of molecules at electron energies not accessible by other experimental techniques. As a result of this work, not only was a large body of basic data measured on attachment cross sections and rate constants; but also extensive theoretical calculations were carried out to verify the underlying phenomenon of s-wave attachment. Important outgrowths of this week were also realized in other areas of research. The basic data have applications in fields such as combustion, soot reduction, rocket-exhaust modification, threshold photoelectron spectroscopy, and trace species detection

TEXTILE SURFACE MODIFICATION BY PYHSICAL VAPOR DEPOSITION – (REVIEW

Directory of Open Access Journals (Sweden)

YUCE Ismail

2017-05-01

Full Text Available Textile products are used in various branches of the industry from automotive to space products. Textiles produced for industrial use are generally referred to as technical textiles. Technical textiles are nowadays applied to several areas including transportation, medicine, agriculture, protection, sports, packaging, civil engineering and industry. There are rapid developments in the types of materials used in technical textiles. Therefore, modification and functionalization of textile surfaces is becoming more crucial. The improvements of the properties such as anti-bacterial properties, fire resistivity, UV radiation resistance, electrical conductivity, self cleaning, and super hydrophobic, is getting more concern with respect to developments in textile engineering. The properties of textile surfaces are closely related to the fiber structure, the differences in the polymer composition, the fiber mixture ratio, and the physical and chemical processes applied. Textile surface modifications can be examined in four groups under the name mechanical, chemical, burning and plasma. Surface modifications are made to improve the functionality of textile products. Textile surface modifications affect the properties of the products such as softness, adhesion and wettability. The purpose of this work is to reveal varieties of vapor deposition modifications to improve functionality. For this purpose, the pyhsical vapor deposition methods, their affects on textile products and their end-uses will be reviewed.

Influence of the Chemical Structure on Odor Qualities and Odor Thresholds of Halogenated Guaiacol-Derived Odorants

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Florian Juhlke

2017-12-01

Full Text Available Chlorinated guaiacol derivatives are found in waste water of pulp mills using chlorine in the bleaching process of wood pulp. They can also be detected in fish tissue, possibly causing off-odors. To date, there is no systematic investigation on the odor properties of halogenated guaiacol derivatives. To close this gap, odor thresholds in air and odor qualities of 14 compounds were determined by gas chromatography-olfactometry. Overall, the investigated compounds elicited smells that are characteristic for guaiacol, namely smoky, sweet, vanilla-like, but also medicinal and plaster-like. Their odor thresholds in air were, however, very low, ranging from 0.00072 to 23 ng/Lair. The lowest thresholds were found for 5-chloro- and 5-bromoguaiacol, followed by 4,5-dichloro- and 6-chloroguaiacol. Moreover, some inter-individual differences in odor threshold values could be observed, with the highest variations having been recorded for the individual values of 5-iodo- and 4-bromoguaiacol.

Influence of the chemical structure on odor qualities and odor thresholds of halogenated guaiacol-derived odorants

Science.gov (United States)

Juhlke, Florian; Lorber, Katja; Wagenstaller, Maria; Buettner, Andrea

2017-12-01

Chlorinated guaiacol derivatives are found in waste water of pulp mills using chlorine in the bleaching process of wood pulp. They can also be detected in fish tissue, possibly causing off-odors. To date, there is no systematic investigation on the odor properties of halogenated guaiacol derivatives. To close this gap, odor thresholds in air and odor qualities of 14 compounds were determined by gas chromatography-olfactometry. Overall, the investigated compounds elicited smells that are characteristic for guaiacol, namely smoky, sweet, vanilla-like, but also medicinal and plaster-like. Their odor thresholds in air were, however, very low, ranging from 0.00072 to 23 ng/Lair. The lowest thresholds were found for 5-chloro- and 5-bromoguaiacol, followed by 4,5-dichloro- and 6-chloroguaiacol. Moreover, some inter-individual differences in odor threshold values could be observed, with the highest variations having been recorded for the individual values of 5-iodo- and 4-bromoguaiacol.

Chemical synthesis on SU-8

DEFF Research Database (Denmark)

Qvortrup, Katrine; Taveras, Kennedy; Thastrup, Ole

2011-01-01

In this paper we describe a highly effective surface modification of SU-8 microparticles, the attachment of appropriate linkers for solid-supported synthesis, and the successful chemical modification of these particles via controlled multi-step organic synthesis leading to molecules attached...

In-situ kinetics of modifications induced by swift heavy ions in Al2O3: Colour centre formation, structural modification and amorphization

International Nuclear Information System (INIS)

Grygiel, C.; Moisy, F.; Sall, M.; Lebius, H.; Balanzat, E.; Madi, T.; Been, T.; Marie, D.; Monnet, I.

2017-01-01

This paper details in-situ studies of modifications induced by swift heavy ion irradiation in α-Al2O3. This complex behaviour is intermediary between the behaviour of amorphizable and non-amorphizable materials, respectively. A unique combination of irradiation experiments was performed at the IRRSUD beam line of the GANIL facility, with three different characterisation techniques: in-situ UV–Vis absorption, in-situ grazing incidence X-Ray diffraction and ex-situ transmission electron microscopy. This allows a complete study of point defects, and by depth profile of structural and microstructural modifications created on the trajectory of the incident ion. The α-Al2O3 crystals have been irradiated by 92 MeV Xenon and 74 MeV Krypton ions, the irradiation conditions have been chosen rather similar with an energy range where the ratio between electronic and nuclear stopping power changes dramatically as function of depth penetration. The main contribution of electronic excitation, above the threshold for track formation, is present beneath the surface to finally get almost only elastic collisions at the end of the projected range. Amorphization kinetics by the overlapping of multiple ion tracks is observed. In the crystalline matrix, long range strains, unit-cell swelling, local microstrain, domain size decrease, disordering of oxygen sublattice as well as colour centre formation are found. This study highlights the relationship between ion energy losses into a material and its response. While amorphization requires electronic stopping values above a certain threshold, point defects are predominantly induced by elastic collisions, while some structural modifications of the crystalline matrix, such as unit-cell swelling, are due to contribution of both electronic and nuclear processes.

Study on the ablation threshold induced by pulsed lasers at different wavelengths

International Nuclear Information System (INIS)

Torrisi, L.; Borrielli, A.; Margarone, D.

2007-01-01

A study of the effects induced by pulsed laser ablation on different materials as a function of the laser wavelength is presented. In particular the ablation at low laser fluence, of the order of 10 8 -10 10 W/cm 2 with ns pulse width, is investigated experimentally on different metals, semiconductors and polymers. Two theoretical models, explain the experimental results about the fluence threshold value measurements, as depending on the laser wavelength are discussed. The photothermal process is valid for the estimation of the threshold fluence for IR and visible radiation, both inducing thermal heating in metals and semiconductors through the photon-free electron energy transfer. This model is not valid for polymers. The photochemical process is valid for the estimation of the threshold fluence for UV radiation, which photon energy is higher with respect to the chemical binding energy. This radiation induces chemical bond breaking in insulators and scission and cross linking effects can be produced. This last model is not valid for metals and semiconductors

Modification of surfaces and surface layers by non equilibrium processes

International Nuclear Information System (INIS)

Beamson, G.; Brennan, W.J.; Clark, D.T.; Howard, J.

1988-01-01

Plasmas are examples of non-equilibrium phenomena which are being used increasingly for the synthesis and modification of materials impossible by conventional routes. This paper introduces methods available by describing the construction and characteristics of some equipment used for the production of different types of plasmas and other non-equilibrium phenomena. This includes high energy ion beams. The special features, advantages and disadvantages of the techniques will be described. There are a multitude of potential application relevant to electronic, metallic, ceramic, and polymeric materials. However, scale-up from the laboratory to production equipment depends on establishing a better understanding of both the physics and chemistry of plasma as well as plasma-solid interactions. Examples are given of how such an understanding can be gained. The chemical analysis of polymer surfaces undergoing modification by inert gas, hydrogen or oxygen plasmas is shown to give physical information regarding the relative roles of diffusion of active species, and direct and radiative energy transfer from the plasma. Surface modification by plasma depositing a new material onto an existing substrate is discussed with particular reference to the deposition of amorphous carbon films. Applications of the unique properties of these films are outlined together with our current understanding of these properties based on chemical and physical methods of analysis of both the films and the plasmas producing them. Finally, surface modification by ion beams is briefly illustrated using examples from the electronics and metals industries where the modification has had a largely physical rather than chemical effect on the starting material. (orig.)

Versatile Chemical Derivatizations to Design Glycol Chitosan-Based Drug Carriers

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Sung Eun Kim

2017-10-01

Full Text Available Glycol chitosan (GC and its derivatives have been extensively investigated as safe and effective drug delivery carriers because of their unique physiochemical and biological properties. The reactive functional groups such as the amine and hydroxyl groups on the GC backbone allow for easy chemical modification with various chemical compounds (e.g., hydrophobic molecules, crosslinkers, and acid-sensitive and labile molecules, and the versatility in chemical modifications enables production of a wide range of GC-based drug carriers. This review summarizes the versatile chemical modification methods that can be used to design GC-based drug carriers and describes their recent applications in disease therapy.

Role of low density lipoprotein in the activation of plasma lysolecithin acyltransferase activity. Effect of chemical and enzymatic modifications of the lipoprotein on enzyme activity.

Science.gov (United States)

Subbaiah, P V; Chen, C H; Bagdade, J D; Albers, J J

1985-01-01

The effect of various chemical and enzymatic modifications of low density lipoprotein (LDL) on its ability to activate the isolated human plasma lysolecithin acyltransferase (LAT) was studied. Removal of all lipids from LDL resulted in the complete loss of LAT activation. Removal of only neutral lipids by extraction with heptane retained up to 50% of the original activity, which was not increased further by reconstitution of the LDL with the extracted lipids. Hydrolysis of the diacylphosphoglycerides of the LDL with phospholipases resulted in complete loss of LAT activation which was partially restored by the addition of egg lecithin. Hydrolysis of more than 4% of LDL protein by trypsin led to a linear decrease in activity with complete loss of activity occurring when about 25% of the LDL protein is hydrolyzed. Modification of the arginine groups of LDL reversibly inhibited the activation of LAT. Modification of lysine residues of LDL by acetylation, acetoacetylation or succinylation also abolished its ability to activate lysolecithin acylation.

Threshold quantum cryptography

International Nuclear Information System (INIS)

Tokunaga, Yuuki; Okamoto, Tatsuaki; Imoto, Nobuyuki

2005-01-01

We present the concept of threshold collaborative unitary transformation or threshold quantum cryptography, which is a kind of quantum version of threshold cryptography. Threshold quantum cryptography states that classical shared secrets are distributed to several parties and a subset of them, whose number is greater than a threshold, collaborates to compute a quantum cryptographic function, while keeping each share secretly inside each party. The shared secrets are reusable if no cheating is detected. As a concrete example of this concept, we show a distributed protocol (with threshold) of conjugate coding

Influence of the chemical modification and content of the clay on the mechanical properties of polypropylene and national bentonite composites

International Nuclear Information System (INIS)

Libano, Elaine V.D.G.; Pacheco, Elen B.A.V.; Visconte, Leila L.Y.

2011-01-01

The polypropylene/national clay composite was prepared by melt intercalation in a counter-rotating twin screw extruder, using bentonite as filler either in the natural (BENT) form or modified with the ammonium salt, cetyltrimethylammonium chloride (BENT-org). The clay was used in 1, 3 and 5%w. The influence of the modification and content of clay on the mechanical properties of this system was analysed. The analyses of infrared spectroscopy (FTIR) and X-ray diffraction (XRD) showed that clay organophilization did occur. The tensile modulus and the tensile strength at the yield point were not affected by chemical modification (BENT and BENT-org) or clay content. On the other hand, it was evidenced that the elongation at the yield point decreased with the addition of BENT and BENT-org to polypropylene. According to the thermogravimetric results, it was evidenced that the incorporation of clay into polypropylene improved thermal stability of the polymer in the composites with 5%w of BENT and 3 and 5%w of BENT-org. (author)

Study on the surface chemical properties of UV excimer laser irradiated polyamide by XPS, ToF-SIMS and CFM

International Nuclear Information System (INIS)

Yip, Joanne; Chan, Kwong; Sin, Kwan Moon; Lau, Kai Shui

2002-01-01

Polyamide (nylon 6) was irradiated by a pulsed ultraviolet (UV) excimer laser with a fluence below its ablation threshold. Chemical modifications on laser treated nylon were studied by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (Tof-SIMS) and chemical force microscopy (CFM). XPS study provides information about changes in chemical composition and the chemical-state of atom types on the fiber surface. The high sensitivity of ToF-SIMS to the topmost layers was used to detect crosslinking after the laser treatment. Gold-coated AFM tips modified with -COOH terminated self-assembled alkanethiol monolayers (SAMs) were used to measure adhesion forces on the untreated and laser treated samples. XPS results revealed that the irradiated samples have higher oxygen content than prior to laser irradiation. Tof-SIMS analysis illustrated that carbonyl groups in nylon 6 decrease significantly but hydroxyl groups increase after low-fluence laser irradiation. The adhesion force measurements by CFM showed spatial distribution of hydroxyl groups on nylon 6 after the laser treatment

Photoproduction of {omega} mesons on nuclei near the production threshold

Energy Technology Data Exchange (ETDEWEB)

Nanova, M.; Friedrich, S.; Metag, V.; Thiel, M.; Gregor, R.; Kotulla, M.; Lugert, S.; Novotny, R.; Pant, L.M.; Pfeiffer, M.; Roy, A.; Schadmand, S.; Trnka, D.; Varma, R. [Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Weil, J.; Mosel, U. [Universitaet Giessen, Institut fuer Theoretische Physik I, Giessen (Germany); Anton, G.; Bogendoerfer, R.; Hoessl, J.; Suft, G. [Universitaet Erlangen, Physikalisches Institut, Erlangen (Germany); Bacelar, J.C.S.; Castelijns, R.; Loehner, H.; Messchendorp, J.G.; Shende, S. [Kernfysisch Versneller Institut, Groningen (Netherlands); Bartholomy, O.; Crede, V.; Ehmanns, A.; Essig, K.; Fabry, I.; Fuchs, M.; Funke, C.; Gutz, E.; Hoeffgen, S.; Hoffmeister, P.; Horn, I.; Junkersfeld, J.; Kalinowsky, H.; Klempt, E.; Lotz, J.; Pee, H. van; Schmidt, C.; Szczepanek, T.; Thoma, U.; Walther, D.; Weinheimer, C.; Wendel, C. [Helmholtz-Institut fuer Strahlen- und Kernphysik Universitaet Bonn, Bonn (Germany); Bayadilov, D. [Helmholtz-Institut fuer Strahlen- und Kernphysik Universitaet Bonn, Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Beloglazov, Y.A.; Gridnev, A.B.; Lopatin, I.V.; Radkov, A.; Sumachev, V.V. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Dutz, H.; Elsner, D.; Ewald, R.; Gothe, R.; Klein, Frank; Klein, Friedrich; Konrad, M.; Menze, D.; Morales, C.; Ostrick, M.; Schmieden, H.; Schoch, B.; Suele, A. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Jaegle, I.; Krusche, B.; Mertens, T. [Universitaet Basel, Physikalisches Institut, Basel (Switzerland); Kopf, B. [Institut fuer Kern- und Teilchenphysik, TU Dresden, Dresden (Germany); Universitaet Bochum, Physikalisches Institut, Bochum (Germany); Langheinrich, J. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Universitaet Bochum, Physikalisches Institut, Bochum (Germany)

2011-02-15

The photoproduction of {omega} mesons on LH{sub 2}, C and Nb has been measured for incident photon energies from 900 to 1300MeV using the CB/TAPS detector at ELSA. The {omega} lineshape does not show any significant difference between the LH{sub 2} and the Nb targets. The experiment was motivated by transport calculations that predicted a sensitivity of the {omega} lineshape to in-medium modifications near the production threshold on a free nucleon of E{sub {gamma}}{sup lab}=1109 MeV. A comparison with recent calculations is given. (orig.)

Enzymatic modification of starch

DEFF Research Database (Denmark)

Jensen, Susanne Langgård

In the food industry approaches for using bioengineering are investigated as alternatives to conventional chemical and physical starch modification techniques in development of starches with specific properties. Enzyme-assisted post-harvest modification is an interesting approach to this, since...... it is considered a clean and energy saving technology. This thesis aimed to investigate the effect of using reaction conditions, simulating an industrial process, for enzymatic treatment of starch with branching enzyme (BE) from Rhodothermus obamensis. Thus treatements were conducted at 70°C using very high...... substrate concentration (30-40% dry matter (DM)) and high enzyme activity (750-2250 BE units (BEU)/g sample). Starches from various botanical sources, representing a broad range of properties, were used as substrates. The effects of the used conditions on the BE-reaction were evaluated by characterization...

Supramolecular engineering through temperature-induced chemical modification of 2H-tetraphenylporphyrin on Ag(111): flat phenyl conformation and possible dehydrogenation reactions.

Science.gov (United States)

Di Santo, Giovanni; Blankenburg, Stephan; Castellarin-Cudia, Carla; Fanetti, Mattia; Borghetti, Patrizia; Sangaletti, Luigi; Floreano, Luca; Verdini, Alberto; Magnano, Elena; Bondino, Federica; Pignedoli, Carlo A; Nguyen, Manh-Thuong; Gaspari, Roberto; Passerone, Daniele; Goldoni, Andrea

2011-12-16

Scratching the surface: Formation of a monolayer of 2H-tetraphenylporphyrins (2H-TPP) on Ag(111), either by sublimation of a multilayer in the range 525-600 K or by annealing (at the same temperature) a monolayer deposited at room temperature, induces a chemical modification of the molecules. Rotation of the phenyl rings into a flat conformation is observed and tentatively explained, by using DFT calculations, as a peculiar reaction due to molecular dehydrogenation. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Disorder-induced modification of the transmission of light through two-dimensional photonic crystals

International Nuclear Information System (INIS)

Beggs, D M; Kaliteevski, M A; Abram, R A; Cassagne, D; Albert, J P

2005-01-01

Disordered two-dimensional photonic crystals with a complete photonic band-gap have been investigated. Transmission and reflection spectra have been modelled for both ballistic and scattered light. The density of states and electromagnetic field profiles of disorder-induced localized states have also been calculated, for various levels of disorder. It is found that there is a threshold-like behaviour in the amount of disorder. Below the threshold, it is seen that there is a vanishing probability of disorder-induced localized states being introduced into the centre of the photonic band-gap, but that edge-states narrow the band-gap. Above the threshold, there is a non-zero probability of disorder-induced localized states throughout the photonic band-gap, and the modification of the transmission and reflection spectra due to disorder rapidly increases with increasing disorder

Fast surface modification by microwave assisted click reactions on silicon substrates

NARCIS (Netherlands)

Haensch, C.; Erdmenger, T.; Fijten, M.W.M.; Höppener, S.; Schubert, U.S.

2009-01-01

Microwave irradiation has been used for the chemical modification of functional monolayers on silicon surfaces. The thermal and chemical stability of these layers was tested under microwave irradiation to investigate the possibility to use this alternative heating process for the surface

Measuring Input Thresholds on an Existing Board

Science.gov (United States)

Kuperman, Igor; Gutrich, Daniel G.; Berkun, Andrew C.

2011-01-01

temperatures to show that the interface had voltage margin under all worst case conditions. Gate input thresholds are normally measured at the manufacturer when the device is on a chip tester. A key function of this machine was duplicated on an existing flight board with no modifications to the nets to be tested, with the exception of changes in the FPGA program.

Microwave plasma induced surface modification of diamond-like carbon films

Science.gov (United States)

Rao Polaki, Shyamala; Kumar, Niranjan; Gopala Krishna, Nanda; Madapu, Kishore; Kamruddin, Mohamed; Dash, Sitaram; Tyagi, Ashok Kumar

2017-12-01

Tailoring the surface of diamond-like carbon (DLC) film is technically relevant for altering the physical and chemical properties, desirable for useful applications. A physically smooth and sp3 dominated DLC film with tetrahedral coordination was prepared by plasma-enhanced chemical vapor deposition technique. The surface of the DLC film was exposed to hydrogen, oxygen and nitrogen plasma for physical and chemical modifications. The surface modification was based on the concept of adsorption-desorption of plasma species and surface entities of films. Energetic chemical species of microwave plasma are adsorbed, leading to desorbtion of the surface carbon atoms due to energy and momentum exchange. The interaction of such reactive species with DLC films enhanced the roughness, surface defects and dangling bonds of carbon atoms. Adsorbed hydrogen, oxygen and nitrogen formed a covalent network while saturating the dangling carbon bonds around the tetrahedral sp3 valency. The modified surface chemical affinity depends upon the charge carriers and electron covalency of the adsorbed atoms. The contact angle of chemically reconstructed surface increases when a water droplet interacts either through hydrogen or van dear Waals bonding. These weak interactions influenced the wetting property of the DLC surface to a great extent.

Characterisation of waste derived biochar added biocomposites: chemical and thermal modifications

Energy Technology Data Exchange (ETDEWEB)

Das, Oisik [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Sarmah, Ajit K., E-mail: a.sarmah@auckland.ac.nz [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Zujovic, Zoran [School of Chemical Sciences, University of Auckland, Auckland 1142 (New Zealand); Bhattacharyya, Debes [Centre for Advanced Composite Materials, Department of Mechanical Engineering, University of Auckland, Auckland 1142 (New Zealand)

2016-04-15

A step towards sustainability was taken by incorporating waste based pyrolysed biochar in wood and polypropylene biocomposites. The effect of biochar particles on the chemistry and thermal makeup of the composites was determined by characterising them through an array of characterisation techniques such as 3D optical profiling, X-ray diffraction, transmission electron microscopy, electron spin/nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. It was observed that addition of biochar increased the presence of free radicals in the composite while also improving its thermal conductivity. Biochar particles did not interfere with the melting behaviour of polymer in the thermal regime. However, wood and biochar acted as nucleation agents consequently increasing the crystallisation temperature. The crystal structure of polypropylene was not disrupted by biochar inclusion in composite. Transmission electron microscopy images illustrated the aggregated nature of the biochar particles at higher loading levels. Nuclear magnetic resonance studies revealed the aromatic nature of biochar and the broadening of peak intensities of composites with increasing biochar levels due to its amorphous nature and presence of free radicals. Thus, this insight into the chemical and thermal modification of biochar added composites would allow effective engineering to optimise their properties while simultaneously utilising wastes. - Highlights: • Waste derived biochars were used to make polymer based biocomposites. • Composites were characterised by NMR, ESR, DSC, XRD, TEM etc. • Biochar increased the thermal conductivity of composites. • Biochar did not disrupt the crystal structure of polypropylene. • NMR revealed aromatic nature of biochar in composites.

Characterisation of waste derived biochar added biocomposites: chemical and thermal modifications

International Nuclear Information System (INIS)

Das, Oisik; Sarmah, Ajit K.; Zujovic, Zoran; Bhattacharyya, Debes

2016-01-01

A step towards sustainability was taken by incorporating waste based pyrolysed biochar in wood and polypropylene biocomposites. The effect of biochar particles on the chemistry and thermal makeup of the composites was determined by characterising them through an array of characterisation techniques such as 3D optical profiling, X-ray diffraction, transmission electron microscopy, electron spin/nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. It was observed that addition of biochar increased the presence of free radicals in the composite while also improving its thermal conductivity. Biochar particles did not interfere with the melting behaviour of polymer in the thermal regime. However, wood and biochar acted as nucleation agents consequently increasing the crystallisation temperature. The crystal structure of polypropylene was not disrupted by biochar inclusion in composite. Transmission electron microscopy images illustrated the aggregated nature of the biochar particles at higher loading levels. Nuclear magnetic resonance studies revealed the aromatic nature of biochar and the broadening of peak intensities of composites with increasing biochar levels due to its amorphous nature and presence of free radicals. Thus, this insight into the chemical and thermal modification of biochar added composites would allow effective engineering to optimise their properties while simultaneously utilising wastes. - Highlights: • Waste derived biochars were used to make polymer based biocomposites. • Composites were characterised by NMR, ESR, DSC, XRD, TEM etc. • Biochar increased the thermal conductivity of composites. • Biochar did not disrupt the crystal structure of polypropylene. • NMR revealed aromatic nature of biochar in composites.

Chemical modification with phthalic anhydride and chitosan: Viable options for the stabilization of raw starch digesting amylase from Aspergillus carbonarius.

Science.gov (United States)

Nwagu, Tochukwu Nwamaka; Okolo, Bartholomew; Aoyagi, Hideki; Yoshida, Shigeki

2017-06-01

The raw starch digesting type of amylase (RSDA) presents greater opportunities for process efficiency at cheaper cost and shorter time compared to regular amylases. Chemical modification is a simple and rapid method toward their stabilization for a wider application. RSDA from Aspergillus carbonarius was modified with either phthalic anhydride (PA) or chitosan. Activity retention was 87.3% for PA-modified and 80.9% for chitosan-modified RSDA. Optimum pH shifted from 5 to 7 after PA-modification. Optimum temperature changed from 30°C (native) to 30-40°C and 60°C for PA-modified and chitosan-modified, respectively. Activation energy (kJmol -1 ) for hydrolysis was 13.5, 12.7, and 10.2 while the activation energy for thermal denaturation was 32.8, 80.3, 81.9 for free, PA-modified and chitosan-modified, respectively. The specificity constants (V max /K m ) were 73.2 for PA-modified, 63.1 for chitosan-modified and 77.1 for native RSDA. The half-life (h) of the RSDA at 80°C was increased from 6.1 to 25.7 for the PA-modified and 138.6 for the chitosan derivative. Modification also led to increase in D value, activation enthalpy and Gibbs free energy of enzyme deactivation. Fluorescence spectra showed that center of spectral mass decreased for the PA-modified RSDA but increased for chitosan modified RSDA. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of surface halide modification of nitrile butadiene rubber

Science.gov (United States)

Sukhareva, K. V.; Mikhailov, I. A.; Andriasyan, Yu O.; Mastalygina, E. E.; Popov, A. A.

2017-12-01

The investigation is devoted to the novel technology of surface halide modification of rubber samples based on nitrile butadiene rubber (NBR). 1,1,2-trifluoro-1,2,2-trichlorethane was used as halide modifier. The developed technology is characterized by production stages reduction to one by means of treating the rubber compound with a halide modifier. The surface halide modification of compounds based on nitrile butadiene rubber (NBR) was determined to result in increase of resistance to thermal oxidation and aggressive media. The conducted research revealed the influence of modification time on chemical resistance and physical-mechanical properties of rubbers under investigation.

Rapid Estimation of Gustatory Sensitivity Thresholds with SIAM and QUEST

Directory of Open Access Journals (Sweden)

Richard Höchenberger

2017-06-01

Full Text Available Adaptive methods provide quick and reliable estimates of sensory sensitivity. Yet, these procedures are typically developed for and applied to the non-chemical senses only, i.e., to vision, audition, and somatosensation. The relatively long inter-stimulus-intervals in gustatory studies, which are required to minimize adaptation and habituation, call for time-efficient threshold estimations. We therefore tested the suitability of two adaptive yes-no methods based on SIAM and QUEST for rapid estimation of taste sensitivity by comparing test-retest reliability for sucrose, citric acid, sodium chloride, and quinine hydrochloride thresholds. We show that taste thresholds can be obtained in a time efficient manner with both methods (within only 6.5 min on average using QUEST and ~9.5 min using SIAM. QUEST yielded higher test-retest correlations than SIAM in three of the four tastants. Either method allows for taste threshold estimation with low strain on participants, rendering them particularly advantageous for use in subjects with limited attentional or mnemonic capacities, and for time-constrained applications during cohort studies or in the testing of patients and children.

Physical- chemical changes in irradiated sodium alginate algimar

International Nuclear Information System (INIS)

Rapado Paneque, Manuel; Alazanes, Sonia; Sainz Vidal, Dianelys; Wandrey, Christine

2003-01-01

The effect of gamma radiation on the physical-chemical properties of sodium alginate Algimar has been investigated. dilution viscometric, densitometry FTIR spectroscopy served to identify modifications. Decreasing intrinsic, viscosities clearly revealed chain cleavage for both solid alginate indicate that chain degradation occurs without significant change of the chemical structure, The obtained results have practical implication change of the chemical structure. The obtained results have practical implication in the field of radiation modification and sterilization of sodium alginate used for microcapsule formation

Effect of infrared radiation on the threshold behavior of scattering (and decay) processes

International Nuclear Information System (INIS)

Mohanty, A.K.; Rosenberg, L.; Spruch, L.

1988-01-01

An analysis is given of the effect of radiative corrections on the threshold behavior of the cross section for the inelastic scattering of a light charged particle by a neutral composite system. Explicit results are obtained for a model problem where the target consists of a proton and antiproton bound under their mutual Coulomb interaction and excited to a 2p state from its 1s ground state by electron impact, but the conclusions drawn are applicable, qualitatively, to a wide range of problems. It is found that when the energy resolution Δepsilon-c of the electron detector is small compared with the kinetic energy K' of the electron in the final state, the more careful treatment given here, which properly accounts for the rapid variation of the cross section for scattering energies near threshold, leads to only small modifications in the standard form of the radiative correction factor δ. For sufficiently high resolution in energy of a (high-energy) incident beam, the modification could be significant if Δepsilon-c is comparable with K'. The above considerations are applicable not only to scattering cross sections but to endpoints of the energy spectrum of the charged particle in a decay process in which only one charged particle is emitted

Controlled modification of biomolecules by ultrashort laser pulses in polar liquids

DEFF Research Database (Denmark)

Gruzdev, Vitaly; Korkin, Dmitry; Mooney, Brian P.

2017-01-01

Targeted chemical modification of peptides and proteins by laser pulses in a biologically relevant environment, i.e. aqueous solvent at room temperature, allows for accurate control of biological processes. However, the traditional laser methods of control of chemical reactions are applicable onl...

Thresholds for Coral Bleaching: Are Synergistic Factors and Shifting Thresholds Changing the Landscape for Management? (Invited)

Science.gov (United States)

Eakin, C.; Donner, S. D.; Logan, C. A.; Gledhill, D. K.; Liu, G.; Heron, S. F.; Christensen, T.; Rauenzahn, J.; Morgan, J.; Parker, B. A.; Hoegh-Guldberg, O.; Skirving, W. J.; Strong, A. E.

2010-12-01

As carbon dioxide rises in the atmosphere, climate change and ocean acidification are modifying important physical and chemical parameters in the oceans with resulting impacts on coral reef ecosystems. Rising CO2 is warming the world’s oceans and causing corals to bleach, with both alarming frequency and severity. The frequent return of stressful temperatures has already resulted in major damage to many of the world’s coral reefs and is expected to continue in the foreseeable future. Warmer oceans also have contributed to a rise in coral infectious diseases. Both bleaching and infectious disease can result in coral mortality and threaten one of the most diverse ecosystems on Earth and the important ecosystem services they provide. Additionally, ocean acidification from rising CO2 is reducing the availability of carbonate ions needed by corals to build their skeletons and perhaps depressing the threshold for bleaching. While thresholds vary among species and locations, it is clear that corals around the world are already experiencing anomalous temperatures that are too high, too often, and that warming is exceeding the rate at which corals can adapt. This is despite a complex adaptive capacity that involves both the coral host and the zooxanthellae, including changes in the relative abundance of the latter in their coral hosts. The safe upper limit for atmospheric CO2 is probably somewhere below 350ppm, a level we passed decades ago, and for temperature is a sustained global temperature increase of less than 1.5°C above pre-industrial levels. How much can corals acclimate and/or adapt to the unprecedented fast changing environmental conditions? Any change in the threshold for coral bleaching as the result of acclimation and/or adaption may help corals to survive in the future but adaptation to one stress may be maladaptive to another. There also is evidence that ocean acidification and nutrient enrichment modify this threshold. What do shifting thresholds mean

Protein covalent modification by biologically active quinones

Directory of Open Access Journals (Sweden)

MIROSLAV J. GASIC

2004-11-01

Full Text Available The avarone/avarol quinone/hydroquinone couple shows considerable antitumor activity. In this work, covalent modification of b-lactoglobulin by avarone and its derivatives as well as by the synthetic steroidal quinone 2,5(10-estradiene-1,4,17-trione and its derivatives were studied. The techniques for studying chemical modification of b-lactoglobulin by quinones were: UV/Vis spectrophotometry, SDS PAGE and isoelectrofocusing. SDS PAGE results suggest that polymerization of the protein occurs. It could be seen that the protein of 18 kD gives the bands of 20 kD, 36 kD, 40 kD, 45 kD, 64 kD and 128 kD depending on modification agent. The shift of the pI of the protein (5.4 upon modification toward lower values (from pI 5.0 to 5.3 indicated that lysine amino groups are the principal site of the reaction of b-lactoglobulin with the quinones.

CARA Risk Assessment Thresholds

Science.gov (United States)

Hejduk, M. D.

2016-01-01

Warning remediation threshold (Red threshold): Pc level at which warnings are issued, and active remediation considered and usually executed. Analysis threshold (Green to Yellow threshold): Pc level at which analysis of event is indicated, including seeking additional information if warranted. Post-remediation threshold: Pc level to which remediation maneuvers are sized in order to achieve event remediation and obviate any need for immediate follow-up maneuvers. Maneuver screening threshold: Pc compliance level for routine maneuver screenings (more demanding than regular Red threshold due to additional maneuver uncertainty).

Diazo Compounds: Versatile Tools for Chemical Biology.

Science.gov (United States)

Mix, Kalie A; Aronoff, Matthew R; Raines, Ronald T

2016-12-16

Diazo groups have broad and tunable reactivity. That and other attributes endow diazo compounds with the potential to be valuable reagents for chemical biologists. The presence of diazo groups in natural products underscores their metabolic stability and anticipates their utility in a biological context. The chemoselectivity of diazo groups, even in the presence of azido groups, presents many opportunities. Already, diazo compounds have served as chemical probes and elicited novel modifications of proteins and nucleic acids. Here, we review advances that have facilitated the chemical synthesis of diazo compounds, and we highlight applications of diazo compounds in the detection and modification of biomolecules.

Radiation modification of materials

International Nuclear Information System (INIS)

Pikaev, A.K.

1987-01-01

Industrial and radiation chemical processes of material modification based on cross-linking of polymers as a result of radiation are considered. Among them are production of cables and rods with irradiated modified insulation, production of hardened and thermo-shrinkaging polymer products (films, tubes, fashioned products), production of radiation cross-linked polyethylene foam, technology of radiation vulcanization of elastomers. Attention is paid to radiation plants on the basis of γ-sources and electron acceleratos as well as to radiation conditions

Negative thermal expansion in functional materials: controllable thermal expansion by chemical modifications.

Science.gov (United States)

Chen, Jun; Hu, Lei; Deng, Jinxia; Xing, Xianran

2015-06-07

Negative thermal expansion (NTE) is an intriguing physical property of solids, which is a consequence of a complex interplay among the lattice, phonons, and electrons. Interestingly, a large number of NTE materials have been found in various types of functional materials. In the last two decades good progress has been achieved to discover new phenomena and mechanisms of NTE. In the present review article, NTE is reviewed in functional materials of ferroelectrics, magnetics, multiferroics, superconductors, temperature-induced electron configuration change and so on. Zero thermal expansion (ZTE) of functional materials is emphasized due to the importance for practical applications. The NTE functional materials present a general physical picture to reveal a strong coupling role between physical properties and NTE. There is a general nature of NTE for both ferroelectrics and magnetics, in which NTE is determined by either ferroelectric order or magnetic one. In NTE functional materials, a multi-way to control thermal expansion can be established through the coupling roles of ferroelectricity-NTE, magnetism-NTE, change of electron configuration-NTE, open-framework-NTE, and so on. Chemical modification has been proved to be an effective method to control thermal expansion. Finally, challenges and questions are discussed for the development of NTE materials. There remains a challenge to discover a "perfect" NTE material for each specific application for chemists. The future studies on NTE functional materials will definitely promote the development of NTE materials.

Cobalt surface modification during γ-Fe2O3 nanoparticle synthesis by chemical-induced transition

International Nuclear Information System (INIS)

Li, Junming; Li, Jian; Chen, Longlong; Lin, Yueqiang; Liu, Xiaodong; Gong, Xiaomin; Li, Decai

2015-01-01

In the chemical-induced transition of FeCl 2 solution, the FeOOH/Mg(OH) 2 precursor was transformed into spinel structured γ-Fe 2 O 3 crystallites, coated with a FeCl 3 ·6H 2 O layer. CoCl 2 surface modified γ-Fe 2 O 3 nanoparticles were prepared by adding Co(NO 3 ) 2 during the synthesis. CoFe 2 O 4 modified γ-Fe 2 O 3 nanoparticles were prepared by adding NaOH during the surface modification with Co(NO 3 ) 2 . The CoFe 2 O 4 layer grew epitaxially on the γ-Fe 2 O 3 crystallite to form a composite crystallite, which was coated by CoCl 2 ·6H 2 O. The composite could not be distinguished using X-ray diffraction or transmission electron microscopy, since CoFe 2 O 4 and γ-Fe 2 O 3 possess similar spinel structures and lattice constants. X-ray photoelectron spectroscopy was used to distinguish them. The saturation magnetization and coercivity of the spinel structured γ-Fe 2 O 3 -based nanoparticles were related to the grain size. - Highlights: • γ-Fe 2 O 3 nanoparticles were synthesized by chemical induced transition. • CoCl 2 modified nanoparticles were prepared by additional Co(NO 3 ) 2 during synthesization. • CoFe 2 O 4 modified nanoparticles were prepared by additional Co(NO 3 ) 2 and NaOH. • The magnetism of the nanoparticles is related to the grain size

Modification of Polymer Materials by Ion Bombardment: Case Studies

International Nuclear Information System (INIS)

Bielinski, D. M.; Jagielski, J.; Lipinski, P.; Pieczynska, D.; Ostaszewska, U.; Piatkowska, A.

2009-01-01

The paper discusses possibility of application of ion beam bombardment for modification of polymers. Changes to composition, structure and morphology of the surface layer produced by the treatment and their influence on engineering and functional properties of wide range of polymer materials are presented. Special attention has been devoted to modification of tribological properties. Ion bombardment results in significant reduction of friction, which can be explained by increase of hardness and wettability of polymer materials. Hard but thin enough skin does not result in cracking but improves their abrasion resistance. Contrary to conventional chemical treatment ion beam bombardment works even for polymers hardly susceptible to modification like silicone rubber or polyolefines.

Chemical modifications of liquid natural rubber

Science.gov (United States)

Azhar, Nur Hanis Adila; Rasid, Hamizah Md; Yusoff, Siti Fairus M.

2016-11-01

Liquid natural rubber (LNR) was synthesized via photosentisized degradation of natural rubber (NR). LNR was modified into epoxidized liquid natural rubber (LENR) and hydroxylated liquid natural rubber (LNR-OH) using Na2WO4/CH3COOH/H2O2 catalytic system. Chemical structures of LNR and modified LNRs were characterized using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and 1H Nuclear Magnetic Resonance (NMR) spectroscopies. Integration of 1H NMR was used to calculate the epoxy content (%) of LENR. 1H NMR detected the formation of LNR-OH after prolonged heating and increased of catalyst in oxidation reaction.

Fifty-Year Trends in the Chemical Industry: What Do They Mean for Chemical Education?

Science.gov (United States)

Tolman, Chadwick A.; Parshall, George W.

1999-01-01

Describes major changes that have occurred in the chemical industry over the last 50 years including trends in the development of products and processes, changes in chemical manufacturing, the globalization of business, and modifications of research laboratory practices. Discusses implications for chemistry education and predictions for future…

Use of modern methods of fibre surface modification to obtain the multifunctional properties of textile materials

Directory of Open Access Journals (Sweden)

Jocić Dragan

2003-01-01

Full Text Available The modern textile fibre treatments aim to obtain the required level of beneficial effect while attempting to confine the modification to the fibre surface. Recently, much attention has been focused on different physical methods of fibre surface modification, cold plasma treatment being considered as very useful. Moreover, there are efficient chemical methods available, such as peroxide, biopolymer and enzyme treatment. Some interesting combinations of these physical and chemical surface modification methods as means to modify fibre surface topography and thus controlling the surface-related properties of the fibre are presented in this paper. The properties obtained are discussed on the basis of the physico-chemical changes in the surface layer of the fibre, being assessed by wettability and contact angle measurements, as well as by FTIR-ATR and XPS analysis. The SEM and AFM technique are used to assess the changes in the fibre surface topography and to correlate these changes to the effectiveness, uniformity and severity of the textile fibre surface modification treatments.

BIOCHAR MODIFICATION, THERMAL STABILITY AND TOXICITY OF PRODUCTS MODIFICATION

Directory of Open Access Journals (Sweden)

Romana FRIEDRICHOVÁ

2017-12-01

Full Text Available Biochar is a product obtained from processing of waste biomass. The main application of biochar is in soil and environment remediation. Some new applications of this carbonaceous material take advantage of its adsorption capacity use it as a heterogeneous catalyst for energy storage and conversion etc. This contribution describes thermal stability of the original biochar. It discusses biochar modified by chemical and physical methods including a new compound of biochar-graphene oxide. The purpose of the modifications is to increase its active surface to introduce active functional groups into the carbon structure of biochar in relation to fire safety and toxicity of those products.

Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

Science.gov (United States)

Reis, Rackel; Dumée, Ludovic F.; Tardy, Blaise L.; Dagastine, Raymond; Orbell, John D.; Schutz, Jürg A.; Duke, Mikel C.

2016-01-01

Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties. PMID:27363670

Surface chemical reactions probed with scanning force microscopy

NARCIS (Netherlands)

Werts, M.P L; van der Vegte, E.W.; Hadziioannou, G

1997-01-01

In this letter we report the study of surface chemical reactions with scanning force microscopy (SFM) with chemical specificity. Using chemically modified SFM probes, we can determine the local surface reaction conversion during a chemical surface modification. The adhesion forces between a

siRNAmod: A database of experimentally validated chemically modified siRNAs.

Science.gov (United States)

Dar, Showkat Ahmad; Thakur, Anamika; Qureshi, Abid; Kumar, Manoj

2016-01-28

Small interfering RNA (siRNA) technology has vast potential for functional genomics and development of therapeutics. However, it faces many obstacles predominantly instability of siRNAs due to nuclease digestion and subsequently biologically short half-life. Chemical modifications in siRNAs provide means to overcome these shortcomings and improve their stability and potency. Despite enormous utility bioinformatics resource of these chemically modified siRNAs (cm-siRNAs) is lacking. Therefore, we have developed siRNAmod, a specialized databank for chemically modified siRNAs. Currently, our repository contains a total of 4894 chemically modified-siRNA sequences, comprising 128 unique chemical modifications on different positions with various permutations and combinations. It incorporates important information on siRNA sequence, chemical modification, their number and respective position, structure, simplified molecular input line entry system canonical (SMILES), efficacy of modified siRNA, target gene, cell line, experimental methods, reference etc. It is developed and hosted using Linux Apache MySQL PHP (LAMP) software bundle. Standard user-friendly browse, search facility and analysis tools are also integrated. It would assist in understanding the effect of chemical modifications and further development of stable and efficacious siRNAs for research as well as therapeutics. siRNAmod is freely available at: http://crdd.osdd.net/servers/sirnamod.

Identification of Maillard reaction induced chemical modifications on Ara h 1

Science.gov (United States)

The Maillard reaction is a non-enzymatic glycation reaction between proteins and reducing sugars that can modify nut allergens during thermal processing. These modifications can alter the structural and immunological properties of these allergens, and may result in increased IgE binding. Here, we ...

Structural modifications of spinels under radiation

International Nuclear Information System (INIS)

Quentin, A.

2010-12-01

This work is devoted to the study of spinel structure materials under radiation. For that purpose, samples of polycrystalline ZnAl 2 O 4 and monocrystalline MgAl 2 O 4 were irradiated by different heavy ions with different energies. Samples of ZnAl 2 O 4 were studied par electron transmission microscopy, and by grazing incidence X-Ray diffraction and Rietveld analysis. Samples of MgAl 2 O 4 were studied by optical spectroscopy. Most of the results concern amorphization and crystalline structure modification of ZnAl 2 O 4 especially the inversion. We were able to determine a stopping power threshold for amorphization, between 11 keV/nm and 12 keV/nm, and also the amorphization process, which is a multiple impacts process. We studied the evolution of the amorphous phase by TEM and showed a nano-patterning phenomenon. Concerning the inversion, we determined that it did happen by a single impact process, and the saturation value did not reach the random cation distribution value. Inversion and amorphization have different, but close, stopping power threshold. However, amorphization seems to be conditioned by a pre-damage of the material which consists in inversion. (author)

Theory of threshold phenomena

International Nuclear Information System (INIS)

Hategan, Cornel

2002-01-01

Theory of Threshold Phenomena in Quantum Scattering is developed in terms of Reduced Scattering Matrix. Relationships of different types of threshold anomalies both to nuclear reaction mechanisms and to nuclear reaction models are established. Magnitude of threshold effect is related to spectroscopic factor of zero-energy neutron state. The Theory of Threshold Phenomena, based on Reduced Scattering Matrix, does establish relationships between different types of threshold effects and nuclear reaction mechanisms: the cusp and non-resonant potential scattering, s-wave threshold anomaly and compound nucleus resonant scattering, p-wave anomaly and quasi-resonant scattering. A threshold anomaly related to resonant or quasi resonant scattering is enhanced provided the neutron threshold state has large spectroscopic amplitude. The Theory contains, as limit cases, Cusp Theories and also results of different nuclear reactions models as Charge Exchange, Weak Coupling, Bohr and Hauser-Feshbach models. (author)

Integrating real-time subsurface hydrologic monitoring with empirical rainfall thresholds to improve landslide early warning

Science.gov (United States)

Mirus, Benjamin B.; Becker, Rachel E.; Baum, Rex L.; Smith, Joel B.

2018-01-01

Early warning for rainfall-induced shallow landsliding can help reduce fatalities and economic losses. Although these commonly occurring landslides are typically triggered by subsurface hydrological processes, most early warning criteria rely exclusively on empirical rainfall thresholds and other indirect proxies for subsurface wetness. We explore the utility of explicitly accounting for antecedent wetness by integrating real-time subsurface hydrologic measurements into landslide early warning criteria. Our efforts build on previous progress with rainfall thresholds, monitoring, and numerical modeling along the landslide-prone railway corridor between Everett and Seattle, Washington, USA. We propose a modification to a previously established recent versus antecedent (RA) cumulative rainfall thresholds by replacing the antecedent 15-day rainfall component with an average saturation observed over the same timeframe. We calculate this antecedent saturation with real-time telemetered measurements from five volumetric water content probes installed in the shallow subsurface within a steep vegetated hillslope. Our hybrid rainfall versus saturation (RS) threshold still relies on the same recent 3-day rainfall component as the existing RA thresholds, to facilitate ready integration with quantitative precipitation forecasts. During the 2015–2017 monitoring period, this RS hybrid approach has an increase of true positives and a decrease of false positives and false negatives relative to the previous RA rainfall-only thresholds. We also demonstrate that alternative hybrid threshold formats could be even more accurate, which suggests that further development and testing during future landslide seasons is needed. The positive results confirm that accounting for antecedent wetness conditions with direct subsurface hydrologic measurements can improve thresholds for alert systems and early warning of rainfall-induced shallow landsliding.

THRESHOLD OF SIGNIFICANCE IN STRESS MANAGEMENT

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Elena RUSE

2015-12-01

Full Text Available Stress management is the individual's ability to handle any situation, external conditions, to match the demands of the external environment. The researchers revealed several stages in the stress response. A first phase was called ‘‘alert reaction'' or ‘‘immediate reaction to stress‘‘, phase in which there are physiological modifications and manifestations that occur under psychological aspect. Adaptation phase is the phase in which the reactions from the first phase diminishes or disappears. Exhaustion phase is related to the diversity of stress factors and time and may exceed the resources of the human body to adapt. Influencing factors may be: limited, cognitive, perceptual, and a priori. But there is a threshold of significance in stress management. Once the reaction to external stimuli occurs, awareness is needed. The capability effect occurs, any side effect goes away and comes out the ''I AM'' effect.

Soy protein modification: A review

Directory of Open Access Journals (Sweden)

Barać Miroljub B.

2004-01-01

Full Text Available Soy protein products such as flour, concentrates and isolates are used in food formulation because of their functionality, nutritional value and low cost. To obtain their optimal nutritive and functional properties as well as desirable flavor different treatments are used. Soybean proteins can be modified by physical, chemical and enzymatic treatments. Different thermal treatments are most commonly used, while the most appropriate way of modifying soy proteins from the standpoint of safety is their limited proteolysis. These treatments cause physical and chemical changes that affect their functional properties. This review discusses three principal methods used for modification of soy protein products, their effects on dominant soy protein properties and some biologically active compounds.

Laser surface modification of PEEK

Energy Technology Data Exchange (ETDEWEB)

Riveiro, A., E-mail: ariveiro@uvigo.es [Applied Physics Department, University of Vigo ETSII, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Centro Universitario de la Defensa, Escuela Naval Militar, Plaza de Espana 2, 36920 Marin (Spain); Soto, R.; Comesana, R.; Boutinguiza, M.; Val, J. del; Quintero, F.; Lusquinos, F.; Pou, J. [Applied Physics Department, University of Vigo ETSII, Lagoas-Marcosende, 9, Vigo 36310 (Spain)

2012-09-15

Highlights: Black-Right-Pointing-Pointer Role of laser irradiation wavelength on the surface modification of PEEK (polyether-ether-ketone) was investigated. Black-Right-Pointing-Pointer Adequate processing conditions to improve wettability, roughness, and cell adhesion characteristics are determined. Black-Right-Pointing-Pointer A design of experiments (DOE) methodology was performed. Black-Right-Pointing-Pointer UV (355 nm) radiation is the most promising laser radiation for improving the adhesive surface properties of PEEK. - Abstract: Polyether-ether-ketone (PEEK) is a synthetic thermoplastic polymer with excellent mechanical and chemical properties, which make it attractive for the field of reconstructive surgery. Nevertheless, this material has a poor interfacial biocompatibility due to its large chemical stability which induces poor adhesive bonding properties. The possibilities of enhancing the PEEK adhesive properties by laser treatments have been explored in the past. This paper presents a systematic approach to discern the role of laser irradiation wavelength on the surface modification of PEEK under three laser wavelengths ({lambda} = 1064, 532, and 355 nm) with the aim to determine the most adequate processing conditions to increase the roughness and wettability, the main parameters affecting cell adhesion characteristics of implants. Overall results show that the ultraviolet ({lambda} = 355 nm) laser radiation is the most suitable one to enhance surface wettability of PEEK.

Electron beam modification of vanadium dioxide oscillators

Energy Technology Data Exchange (ETDEWEB)

Belyaev, Maksim; Velichko, Andrey; Putrolaynen, Vadim; Perminov, Valentin; Pergament, Alexander [Petrozavodsk State University, Petrozavodsk (Russian Federation)

2017-03-15

The paper presents the results of a study of electron-beam modification (EBM) of VO{sub 2}-switch I-V curve threshold parameters and the self-oscillation frequency of a circuit containing such a switching device. EBM in vacuum is reversible and the parameters are restored when exposed to air at pressure of 150 Pa. At EBM with a dose of 3 C cm{sup -2}, the voltages of switching-on (V{sub th}) and off (V{sub h}), as well as the OFF-state resistance R{sub off}, decrease down to 50% of the initial values, and the oscillation frequency increases by 30% at a dose of 0.7 C cm{sup -2}. Features of physics of EBM of an oscillator are outlined considering the contribution of the metal and semiconductor phases of the switching channel. Controlled modification allows EBM forming of switches with preset parameters. Also, it might be used in artificial oscillatory neural networks for pattern recognition based on frequency shift keying. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Plasma assisted surface coating/modification processes: An emerging technology

Science.gov (United States)

Spalvins, T.

1986-01-01

A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation). These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

Plasma assisted surface coating/modification processes - An emerging technology

Science.gov (United States)

Spalvins, T.

1987-01-01

A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation. These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

Experience of secondary cooling system modification at fast breeder reactor MONJU

International Nuclear Information System (INIS)

Ito, Keisuke; Nakatsuji, M.; Matsuno, Hiroki; Matsui, K.; Tone, T.

2007-01-01

The prototype fast breeder reactor MONJU has been shut down since the secondary sodium leak accident which occurred in December 1995. After the accident, the investigation of its cause and the comprehensive review were performed and the various counter measures against the sodium leak were also discussed. The main modification works of MONJU started in September 2005. The work should adopt suitable methods to treat sodium, since MONJU uses chemically active sodium as a coolant. Considering the chemical activity of sodium, MONJU learned the modification methods from the experimental fast reactor JOYO and precedent plants of overseas and adopted plastic bags when the sodium boundary is opened, management of oxygen concentration in the plastic bags, a slightly positive control of the cover gas pressure, compress cut by the roll cutters to prevent the entry of the chips, etc.. Owing to introduction of these methods, the modification works have proceeded almost on schedule without troubles. (author)

Particles near threshold

International Nuclear Information System (INIS)

Bhattacharya, T.; Willenbrock, S.

1993-01-01

We propose returning to the definition of the width of a particle in terms of the pole in the particle's propagator. Away from thresholds, this definition of width is equivalent to the standard perturbative definition, up to next-to-leading order; however, near a threshold, the two definitions differ significantly. The width as defined by the pole position provides more information in the threshold region than the standard perturbative definition and, in contrast with the perturbative definition, does not vanish when a two-particle s-wave threshold is approached from below

High pain sensitivity is distinct from high susceptibility to non-painful sensory input at threshold level.

Science.gov (United States)

Hummel, Thomas; Springborn, Maria; Croy, Ilona; Kaiser, Jochen; Lötsch, Jörn

2011-04-01

Individuals may differ considerably in their sensitivity towards various painful stimuli supporting the notion of a person as stoical or complaining about pain. Molecular and functional imaging research provides support that this may extend also to other sensory qualities. Whether a person can be characterized as possessing a generally high or low sensory acuity is unknown. This was therefore assessed with thresholds to painful and non-painful stimuli, with a focus on chemical stimuli that besides pain may evoke clearly non-painful sensations such as taste or smell. In 36 healthy men and 78 women (ages 18 to 52 years), pain thresholds to chemo-somatosensory (intranasal gaseous CO(2)) and electrical stimuli (cutaneous stimulation) were significantly correlated (ρ(2)=0.2268, psensory qualities, i.e., for the rose-like odor phenyl ethyl alcohol and gustatory thresholds for sour (citric acid) and salty (NaCl). Similarly, pain clusters showed no differences in thresholds to other stimuli. Moreover, no clustering was obtained for thresholds to both painful and non-painful stimuli together. Thus, individuals could not be characterized as highly sensitive (or insensitive) to all chemical stimuli no matter of evoking pain. This suggests that pain is primarily a singular sensory perception distinct from others such as olfaction or taste. Copyright © 2011 Elsevier B.V. All rights reserved.

Influence of Polylactide Modification with Blowing Agents on Selected Mechanical Properties

Directory of Open Access Journals (Sweden)

Aneta Tor-Świątek

2017-12-01

Full Text Available Article presents research of modification of PLA with four types of chemical blowing agents with a different decomposition characteristic. The modification was done both cellular extrusion and injection molding processes. Obtained results shows that dosing blowing agents have the influence on mechanical properties and structure morphology of PLA. The differences in obtained results are also visible and significant between cellular processes.

Threshold anomaly in the elastic scattering of 6He on 209Bi

International Nuclear Information System (INIS)

Garcia, A. R.; Padron, I.; Lubian, J.; Gomes, P. R. S.; Lacerda, T.; Garcia, V. N.; Gomez-Camacho, A.; Aguilera, E. F.

2009-01-01

The energy dependence of the optical potential for the elastic scattering of 6 He on 209 Bi at near and subbarrier energies is studied. Elastic angular distributions and the reaction cross section were simultaneously fitted by performing some modifications in the ECIS code. A phenomenological optical model potential with the Woods-Saxon form was used. There are signatures that the so called breakup threshold anomaly (BTA) is present in this system having a halo projectile 6 He, as it had been found earlier for systems involving stable weakly bound nuclei. (Author)

Chitosan Modification and Pharmaceutical/Biomedical Applications

Directory of Open Access Journals (Sweden)

Jiali Zhang

2010-06-01

Full Text Available Chitosan has received much attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine. Our recent efforts focused on the chemical and biological modification of chitosan in order to increase its solubility in aqueous solutions and absorbability in the in vivo system, thus for a better use of chitosan. This review summarizes chitosan modification and its pharmaceutical/biomedical applications based on our achievements as well as the domestic and overseas developments: (1 enzymatic preparation of low molecular weight chitosans/chitooligosaccharides with their hypocholesterolemic and immuno-modulating effects; (2 the effects of chitin, chitosan and their derivatives on blood hemostasis; and (3 synthesis of a non-toxic ion ligand—D-Glucosaminic acid from Oxidation of D-Glucosamine for cancer and diabetes therapy.

Estudo da modificação química de polidienos do tipo SBR e BR Study of chemical modification of SBR and BR polydiene

Directory of Open Access Journals (Sweden)

Tatiana L. A. C. Rocha

2004-12-01

Full Text Available A utilização de modificações químicas de polidienos comerciais tem sido estudada como um meio alternativo à síntese de novos polímeros, para otimização das propriedades finais destes materiais através da introdução de diferentes grupamentos reativos na cadeia polimérica. A modificação química pode ser feita através de diferentes métodos, os quais podem ser realizados tanto em solução como em massa, onde podem ser destacadas as reações de epoxidação, sulfonação, maleinização, carboxilação, etc. Neste trabalho foi estudado o método de epoxidação de borrachas do tipo SBR e BR. Foi possível observar que mesmo pequenos graus de modificação química causam mudanças marcantes nas propriedades finais dos polímeros, como determinado para a temperatura de transição vítrea.Chemical modification of polydiene has been studied as an alternative route to obtain modified polymers with improved final properties. This improvement is due to the introduction of different kinds of reactive groups into a polymer chain, and it can be done in solution as well as in bulk. The chemical modification can be carried out by different methods such as epoxidation, maleination, carboxylation, sulfonation etc. In this work we show that in the epoxidation of SBR and BR even a small degree of modification can change the final properties of the polymer, as it occurred for the glass transition temperature.

Vapor phase modification of sol-gel derived titania (TiO{sub 2}) surfaces

Energy Technology Data Exchange (ETDEWEB)

Piwonski, Ireneusz [University of Lodz, Department of Chemical Technology and Environmental Protection, Pomorska 163, 90-236 Lodz (Poland)]. E-mail: irek@uni.lodz.pl; Ilik, Aneta [University of Lodz, Department of Chemical Technology and Environmental Protection, Pomorska 163, 90-236 Lodz (Poland)

2006-12-30

Chemical vapor deposition (CVD) method was used in titania surface modification. Titania layers were obtained in sol-gel process and prepared as thin films on silicon wafers in dip-coating method. In order to define the influence of modification on titania surface properties (e.g., friction), various types of fluoroalkylsilanes were used. The effectiveness of the modification was monitored by FT-IR spectroscopy. The topography and frictional measurements were investigated with the use of atomic force microscopy (AFM)

Chemical display of pyrimidine bases flipped out by modification-dependent restriction endonucleases of MspJI and PvuRts1I families.

Directory of Open Access Journals (Sweden)

Evelina Zagorskaitė

Full Text Available The epigenetic DNA modifications 5-methylcytosine (5mC and 5-hydroxymethylcytosine (5hmC in eukaryotes are recognized either in the context of double-stranded DNA (e.g., by the methyl-CpG binding domain of MeCP2, or in the flipped-out state (e.g., by the SRA domain of UHRF1. The SRA-like domains and the base-flipping mechanism for 5(hmC recognition are also shared by the recently discovered prokaryotic modification-dependent endonucleases of the MspJI and PvuRts1I families. Since the mechanism of modified cytosine recognition by many potential eukaryotic and prokaryotic 5(hmC "readers" is still unknown, a fast solution based method for the detection of extrahelical 5(hmC would be very useful. In the present study we tested base-flipping by MspJI- and PvuRts1I-like restriction enzymes using several solution-based methods, including fluorescence measurements of the cytosine analog pyrrolocytosine and chemical modification of extrahelical pyrimidines with chloroacetaldehyde and KMnO4. We find that only KMnO4 proved an efficient probe for the positive display of flipped out pyrimidines, albeit the method required either non-physiological pH (4.3 or a substitution of the target cytosine with thymine. Our results imply that DNA recognition mechanism of 5(hmC binding proteins should be tested using a combination of all available methods, as the lack of a positive signal in some assays does not exclude the base flipping mechanism.

Chemical modifications and applications of alternating aliphatic polyketones

NARCIS (Netherlands)

Zhang, Youchun

2008-01-01

Alternating aliphatic polyketones, produced by co- and terpolymerization of carbon monoxide and olefins (mixtures of ethylene and propylene) using palladium-based homogeneous catalysis represent a very promising class of polymers for a wide range of applications. Besides many interesting chemical

Application of xenon difluoride for surface modification of polymers

International Nuclear Information System (INIS)

Barsamyan, G.B.; Belokonov, K.V.; Vargasova, N.A.; Sokolov, V.B.; Chaivanov, B.B.; Zubov, V.P.

1994-01-01

Chemical interaction between xenon difluoride (XeF 2 ) and polymeric materials was investigated. It was shown that the reaction occurs on the surface of solid polymer layer and brings to chemical modification of the surface properties of the polymer leaving the bulk properties unchanged. The results of various analysis of the fluorinated samples (IR, FTIR-ATR, ESCA, bulk analysis etc) are presented. The mechanism of reaction is proposed. 12 refs.; 13 figs

Chemical Etching, AFM, Laser Damage Threshold, and Nonlinear Optical Studies of Potential Nonlinear Optical Crystal: Bis (L-Glutamine Potassium Nitrate

Directory of Open Access Journals (Sweden)

Redrothu Hanumantharao

2013-01-01

Full Text Available A novel semiorganic nonlinear optical crystal bis (L-glutamine potassium nitrate (BGPN grown by slow evaporation technique at ambient temperature. The grown crystal surface has been analyzed by chemical etching and atomic force microscopy (AFM studies. Amplitude parameters like area roughness, roughness average, valley height, valley depth, peak height, and peak valley height were measured successfully from AFM studies. Etching studies were carried out by various solvents like water, methanol and ethanol. The etching study indicates the occurrence of different types of etch pit patterns like striations and steplike pattern. The laser damage threshold energy has been measured by irradiating laser beam using a Q-switched Nd: YAG laser (1064 nm. Second harmonic generation (SHG studies have been performed by famous Kurtz powder technique with reference to standard potassium dihydrogen phosphate single crystals (KDP. It is found from this technique that SHG efficiency of BGPN is in comparison to that of standard KDP crystals.

Chemical-modification studies of a unique sialic acid-binding lectin from the snail Achatina fulica. Involvement of tryptophan and histidine residues in biological activity.

Science.gov (United States)

Basu, S; Mandal, C; Allen, A K

1988-01-01

A unique sialic acid-binding lectin, achatininH (ATNH) was purified in single step from the haemolymph of the snail Achatina fulica by affinity chromatography on sheep submaxillary-gland mucin coupled to Sepharose 4B. The homogeneity was checked by alkaline gel electrophoresis, immunodiffusion and immunoelectrophoresis. Amino acid analysis showed that the lectin has a fairly high content of acidic amino acid residues (22% of the total). About 1.3% of the residues are half-cystine. The glycoprotein contains 21% carbohydrate. The unusually high content of xylose (6%) and fucose (2.7%) in this snail lectin is quite interesting. The protein was subjected to various chemical modifications in order to detect the amino acid residues and carbohydrate residues present in its binding sites. Modification of tyrosine and arginine residues did not affect the binding activity of ATNH; however, modification of tryptophan and histidine residues led to a complete loss of its biological activity. A marked decrease in the fluorescence emission was found as the tryptophan residues of ATNH were modified. The c.d. data showed the presence of an identical type of conformation in the native and modified agglutinin. The modification of lysine and carboxy residues partially diminished the biological activity. The activity was completely lost after a beta-elimination reaction, indicating that the sugars are O-glycosidically linked to the glycoprotein's protein moiety. This result confirms that the carbohydrate moiety also plays an important role in the agglutination property of this lectin. Images Fig. 3. PMID:3140796

Music effect on pain threshold evaluated with current perception threshold

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

AIM: Music relieves anxiety and psychotic tension. This effect of music is applied to surgical operation in the hospital and dental office. It is still unclear whether this music effect is only limited to the psychological aspect but not to the physical aspect or whether its music effect is influenced by the mood or emotion of audience. To elucidate these issues, we evaluated the music effect on pain threshold by current perception threshold (CPT) and profile of mood states (POMC) test. METHODS: Healthy 30 subjects (12 men, 18 women, 25-49 years old, mean age 34.9) were tested. (1)After POMC test, all subjects were evaluated pain threshold with CPT by Neurometer (Radionics, USA) under 6 conditions, silence, listening to the slow tempo classic music, nursery music, hard rock music, classic paino music and relaxation music with 30 seconds interval. (2)After Stroop color word test as the stresser, pain threshold was evaluated with CPT under 2 conditions, silence and listening to the slow tempo classic music. RESULTS: Under litening to the music, CPT sores increased, especially 2 000 Hz level related with compression, warm and pain sensation. Type of music, preference of music and stress also affected CPT score. CONCLUSION: The present study demonstrated that the concentration on the music raise the pain threshold and that stress and mood influence the music effect on pain threshold.

Stability studies of plasma modification effects of polylactide and polycaprolactone surface layers

Energy Technology Data Exchange (ETDEWEB)

Moraczewski, Krzysztof, E-mail: kmm@ukw.edu.pl [Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Stepczyńska, Magdalena [Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Malinowski, Rafał [Institute for Engineering of Polymer Materials and Dyes, Marii Skłodowskiej-Curie 55, 87‐100 Toruń (Poland); Rytlewski, Piotr; Jagodziński, Bartłomiej; Żenkiewicz, Marian [Kazimierz Wielki University, Chodkiewicza 30, 85-064 Bydgoszcz (Poland)

2016-07-30

Highlights: • Plasma modification affects surface roughness, wettability and surface energy. • Polylactide and polycaprolactone aging causes decay of the modification effects. • Changes in the surface characteristic and wettability deterioration were observed. • The decay occurs due to migration of low molecular weight molecules to the surface. • Plasma modification effect lasts longer in the case of polycaprolactone. - Abstract: The article presents results of research on the stability of oxygen plasma modification effects of polylactide and polycaprolactone surface layers. The modified samples were aged for three, six or nine weeks. The studies were carried out using scanning electron microscopy, goniometry and Fourier transform infrared spectroscopy. Studies have shown that the plasma modification has significant impact on the geometric structure and chemical composition of the surface, wettability and surface energy of tested polymers. The modification effects are not permanent. It has been observed that over time the effects of plasma modification fade. Studies have shown that modifying effect lasts longer in the case of polycaprolactone.

Surface modification and characterization Collaborative Research Center at ORNL

International Nuclear Information System (INIS)

1986-01-01

The Surface Modification and Characterization Collaborative Research Center (SMAC/CRC) is a unique facility for the alteration and characterization of the near-surface properties of materials. The SMAC/CRC facility is equipped with particle accelerators and high-powered lasers which can be used to improve the physical, electrical, and/or chemical properties of solids and to create unique new materials not possible to obtain with conventional ''equilibrium'' processing techniques. Surface modification is achieved using such techniques as ion implantation doping, ion beam mixing, laser mixing, ion deposition, and laser annealing

Chemical modification of antifungal polyene macrolide antibiotics

International Nuclear Information System (INIS)

Solovieva, S E; Olsufyeva, E N; Preobrazhenskaya, M N

2011-01-01

The review summarizes advances in the methods for the synthesis of polyene antibiotics (amphotericin B, partricin A, etc.) and investigations of the structure-activity relationship made in the last 15 years. State-of-the-art approaches based on the combination of the chemical synthesis and genetic engineering are considered. Emphasis is given to the design of semisynthetic antifungal agents against chemotherapy-resistant pathogens having the highest therapeutic indices. Recent results of research on the mechanisms of action of polyenes are outlined.

Mapping of Complete Set of Ribose and Base Modifications of Yeast rRNA by RP-HPLC and Mung Bean Nuclease Assay.

Directory of Open Access Journals (Sweden)

Jun Yang

Full Text Available Ribosomes are large ribonucleoprotein complexes that are fundamental for protein synthesis. Ribosomes are ribozymes because their catalytic functions such as peptidyl transferase and peptidyl-tRNA hydrolysis depend on the rRNA. rRNA is a heterogeneous biopolymer comprising of at least 112 chemically modified residues that are believed to expand its topological potential. In the present study, we established a comprehensive modification profile of Saccharomyces cerevisiae's 18S and 25S rRNA using a high resolution Reversed-Phase High Performance Liquid Chromatography (RP-HPLC. A combination of mung bean nuclease assay, rDNA point mutants and snoRNA deletions allowed us to systematically map all ribose and base modifications on both rRNAs to a single nucleotide resolution. We also calculated approximate molar levels for each modification using their UV (254nm molar response factors, showing sub-stoichiometric amount of modifications at certain residues. The chemical nature, their precise location and identification of partial modification will facilitate understanding the precise role of these chemical modifications, and provide further evidence for ribosome heterogeneity in eukaryotes.

Shock modification and chemistry and planetary geologic processes

International Nuclear Information System (INIS)

Boslough, M.S.

1991-01-01

This paper brings the rapid advances on shock processing of materials to the attention of Earth scientists, and to put these advances in the context of planetary geologic processes. Most of the recent research in this area has been directed at materials modification an synthesis, and the information gained has direct relevance to shock effects in nature. Research on various types of shock modification and chemistry in both naturally and experimentally shocked rocks and minerals is reviewed, and where appropriate their significance to planetary processes is indicated. As a case study, the surface of Mars is suggested as a place where conditions are optimal for shock processing to be a dominant factor. The various mechanisms of shock modification, activation, synthesis and decomposition are all proposed as major contributors to the evolution of chemical, mineralogical, and physical properties of the Martian regolith

Surface modification of polyester biomaterials for tissue engineering

International Nuclear Information System (INIS)

Jiao Yanpeng; Cui Fuzhai

2007-01-01

Surfaces play an important role in a biological system for most biological reactions occurring at surfaces and interfaces. The development of biomaterials for tissue engineering is to create perfect surfaces which can provoke specific cellular responses and direct new tissue regeneration. The improvement in biocompatibility of biomaterials for tissue engineering by directed surface modification is an important contribution to biomaterials development. Among many biomaterials used for tissue engineering, polyesters have been well documented for their excellent biodegradability, biocompatibility and nontoxicity. However, poor hydrophilicity and the lack of natural recognition sites on the surface of polyesters have greatly limited their further application in the tissue engineering field. Therefore, how to introduce functional groups or molecules to polyester surfaces, which ideally adjust cell/tissue biological functions, becomes more and more important. In this review, recent advances in polyester surface modification and their applications are reviewed. The development of new technologies or methods used to modify polyester surfaces for developing their biocompatibility is introduced. The results of polyester surface modifications by surface morphological modification, surface chemical group/charge modification, surface biomacromolecule modification and so on are reported in detail. Modified surface properties of polyesters directly related to in vitro/vivo biological performances are presented as well, such as protein adsorption, cell attachment and growth and tissue response. Lastly, the prospect of polyester surface modification is discussed, especially the current conception of biomimetic and molecular recognition. (topical review)

Identification and Interrogation of Combinatorial Histone Modifications

Directory of Open Access Journals (Sweden)

Kelly R Karch

2013-12-01

Full Text Available Histone proteins are dynamically modified to mediate a variety of cellular processes including gene transcription, DNA damage repair, and apoptosis. Regulation of these processes occurs through the recruitment of non-histone proteins to chromatin by specific combinations of histone post-translational modifications (PTMs. Mass spectrometry has emerged as an essential tool to discover and quantify histone PTMs both within and between samples in an unbiased manner. Developments in mass spectrometry that allow for characterization of large histone peptides or intact protein has made it possible to determine which modifications occur simultaneously on a single histone polypeptide. A variety of techniques from biochemistry, biophysics, and chemical biology have been employed to determine the biological relevance of discovered combinatorial codes. This review first describes advancements in the field of mass spectrometry that have facilitated histone PTM analysis and then covers notable approaches to probe the biological relevance of these modifications in their nucleosomal context.

Cell signaling, post-translational protein modifications and NMR spectroscopy

International Nuclear Information System (INIS)

Theillet, Francois-Xavier; Smet-Nocca, Caroline; Liokatis, Stamatios; Thongwichian, Rossukon; Kosten, Jonas; Yoon, Mi-Kyung; Kriwacki, Richard W.; Landrieu, Isabelle; Lippens, Guy; Selenko, Philipp

2012-01-01

Post-translationally modified proteins make up the majority of the proteome and establish, to a large part, the impressive level of functional diversity in higher, multi-cellular organisms. Most eukaryotic post-translational protein modifications (PTMs) denote reversible, covalent additions of small chemical entities such as phosphate-, acyl-, alkyl- and glycosyl-groups onto selected subsets of modifiable amino acids. In turn, these modifications induce highly specific changes in the chemical environments of individual protein residues, which are readily detected by high-resolution NMR spectroscopy. In the following, we provide a concise compendium of NMR characteristics of the main types of eukaryotic PTMs: serine, threonine, tyrosine and histidine phosphorylation, lysine acetylation, lysine and arginine methylation, and serine, threonine O-glycosylation. We further delineate the previously uncharacterized NMR properties of lysine propionylation, butyrylation, succinylation, malonylation and crotonylation, which, altogether, define an initial reference frame for comprehensive PTM studies by high-resolution NMR spectroscopy.

Differential reconstructed gene interaction networks for deriving toxicity threshold in chemical risk assessment

OpenAIRE

Yang, Yi; Maxwell, Andrew; Zhang, Xiaowei; Wang, Nan; Perkins, Edward J; Zhang, Chaoyang; Gong, Ping

2013-01-01

Background Pathway alterations reflected as changes in gene expression regulation and gene interaction can result from cellular exposure to toxicants. Such information is often used to elucidate toxicological modes of action. From a risk assessment perspective, alterations in biological pathways are a rich resource for setting toxicant thresholds, which may be more sensitive and mechanism-informed than traditional toxicity endpoints. Here we developed a novel differential networks (DNs) appro...

Critical role of surface chemical modifications induced by length shortening on multi-walled carbon nanotubes-induced toxicity

Directory of Open Access Journals (Sweden)

Bussy Cyrill

2012-11-01

Full Text Available Abstract Given the increasing use of carbon nanotubes (CNT in composite materials and their possible expansion to new areas such as nanomedicine which will both lead to higher human exposure, a better understanding of their potential to cause adverse effects on human health is needed. Like other nanomaterials, the biological reactivity and toxicity of CNT were shown to depend on various physicochemical characteristics, and length has been suggested to play a critical role. We therefore designed a comprehensive study that aimed at comparing the effects on murine macrophages of two samples of multi-walled CNT (MWCNT specifically synthesized following a similar production process (aerosol-assisted CVD, and used a soft ultrasonic treatment in water to modify the length of one of them. We showed that modification of the length of MWCNT leads, unavoidably, to accompanying structural (i.e. defects and chemical (i.e. oxidation modifications that affect both surface and residual catalyst iron nanoparticle content of CNT. The biological response of murine macrophages to the two different MWCNT samples was evaluated in terms of cell viability, pro-inflammatory cytokines secretion and oxidative stress. We showed that structural defects and oxidation both induced by the length reduction process are at least as responsible as the length reduction itself for the enhanced pro-inflammatory and pro-oxidative response observed with short (oxidized compared to long (pristine MWCNT. In conclusion, our results stress that surface properties should be considered, alongside the length, as essential parameters in CNT-induced inflammation, especially when dealing with a safe design of CNT, for application in nanomedicine for example.

Surface Modification of Polymer Substrates for Biomedical Applications

Directory of Open Access Journals (Sweden)

Oldřich Neděla

2017-09-01

Full Text Available While polymers are widely utilized materials in the biomedical industry, they are rarely used in an unmodified state. Some kind of a surface treatment is often necessary to achieve properties suitable for specific applications. There are multiple methods of surface treatment, each with their own pros and cons, such as plasma and laser treatment, UV lamp modification, etching, grafting, metallization, ion sputtering and others. An appropriate treatment can change the physico-chemical properties of the surface of a polymer in a way that makes it attractive for a variety of biological compounds, or, on the contrary, makes the polymer exhibit antibacterial or cytotoxic properties, thus making the polymer usable in a variety of biomedical applications. This review examines four popular methods of polymer surface modification: laser treatment, ion implantation, plasma treatment and nanoparticle grafting. Surface treatment-induced changes of the physico-chemical properties, morphology, chemical composition and biocompatibility of a variety of polymer substrates are studied. Relevant biological methods are used to determine the influence of various surface treatments and grafting processes on the biocompatibility of the new surfaces—mammalian cell adhesion and proliferation is studied as well as other potential applications of the surface-treated polymer substrates in the biomedical industry.

Chemical and morphological modifications of single layer graphene submitted to annealing in water vapor

Science.gov (United States)

Rolim, Guilherme Koszeniewski; Corrêa, Silma Alberton; Galves, Lauren Aranha; Lopes, João Marcelo J.; Soares, Gabriel Vieira; Radtke, Cláudio

2018-01-01

Modifications of single layer graphene transferred to SiO2/Si substrates resulting from annealing in water vapor were investigated. Near edge X-ray absorption fine structure spectroscopy evidenced graphene puckering between 400 and 500 °C. Synchrotron radiation based X-ray photoelectron spectroscopy showed variation of sp2 and sp3C bonding configurations specially in this same temperature range. Moreover, oxygen related functionalities are formed as a result of water vapor annealing. Based on these results and complementary Raman and nuclear reaction analysis, one distinguishes three different regimes of water interaction with graphene concerning modifications of the graphene layer. In the low temperature range (200-400 °C), no prominent modification of graphene itself is observed. At higher temperatures (400-500 °C), to accommodate newly formed oxygen functionalities, the flat and continuous sp2 bonding network of graphene is disrupted, giving rise to a puckered layer. For 600 °C and above, shrinking of graphene domains and a higher doping level take place.

Ion beam-induced topographical and chemical modification on the poly(styrene-co-allyl alcohol) and its effect on the molecular interaction between the modified surface and liquid crystals

International Nuclear Information System (INIS)

Jeong, Hae-Chang; Park, Hong-Gyu; Lee, Ju Hwan; Jang, Sang Bok; Oh, Byeong-Yun; Seo, Dae-Shik

2016-01-01

We demonstrated uniform liquid crystal (LC) alignment on ion beam (IB)-irradiated poly(styrene-co-allyl alcohol) by modifying the chemical bonding on the surface. An IB-irradiated copolymer was used for the alignment layer. We used physico-chemical analysis to determine the IB-irradiated surface modification and LC alignment mechanism on the surface. During IB treatment on poly(styrene-co-allyl alcohol), IB irradiation induces breaking of chemical bonds on the surface to give rise to new bonds with oxygen atoms. This causes a strong Van der Waals interaction between LCs and the modified surface, thereby resulting in uniform LC alignment. The results of contact angle (CA) studies of the copolymer support the chemical bonding changes that were investigated by XPS. We achieved uniform homogeneous LC alignment and obtained stable electro-optical performance by controlling the IB energy. Therefore, the LC cells with IB-irradiated poly(styrene-co-allyl alcohol) exhibited a good potential for alternative alignment of layers in LC applications.

Ion beam-induced topographical and chemical modification on the poly(styrene-co-allyl alcohol) and its effect on the molecular interaction between the modified surface and liquid crystals

Energy Technology Data Exchange (ETDEWEB)

Jeong, Hae-Chang [Information Display Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Park, Hong-Gyu [School of Electrical, Electronic & Control Engineering, Changwon National University, 20 Changwondaehak-ro, Uichang-gu, Changwon-si, Gyeongsangnam-do, 51140 (Korea, Republic of); Lee, Ju Hwan; Jang, Sang Bok [Information Display Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Oh, Byeong-Yun [ZeSHTech Co., Ltd., Business Incubator, Gwangju Institute of Science and Technology, 123, Cheomdangwagi-ro, Buk-gu, Gwangju, 500-712 (Korea, Republic of); Seo, Dae-Shik, E-mail: dsseo@yonsei.ac.kr [Information Display Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of)

2016-10-01

We demonstrated uniform liquid crystal (LC) alignment on ion beam (IB)-irradiated poly(styrene-co-allyl alcohol) by modifying the chemical bonding on the surface. An IB-irradiated copolymer was used for the alignment layer. We used physico-chemical analysis to determine the IB-irradiated surface modification and LC alignment mechanism on the surface. During IB treatment on poly(styrene-co-allyl alcohol), IB irradiation induces breaking of chemical bonds on the surface to give rise to new bonds with oxygen atoms. This causes a strong Van der Waals interaction between LCs and the modified surface, thereby resulting in uniform LC alignment. The results of contact angle (CA) studies of the copolymer support the chemical bonding changes that were investigated by XPS. We achieved uniform homogeneous LC alignment and obtained stable electro-optical performance by controlling the IB energy. Therefore, the LC cells with IB-irradiated poly(styrene-co-allyl alcohol) exhibited a good potential for alternative alignment of layers in LC applications.

Accelerated differentiation of osteoblast cells on polycaprolactone scaffolds driven by a combined effect of protein coating and plasma modification

Energy Technology Data Exchange (ETDEWEB)

Yildirim, Eda D; Gueceri, Selcuk; Sun, Wei [Department of Mechanical Engineering and Mechanics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Besunder, Robyn; Allen, Fred [Drexel University, School of Biomedical Engineering Science and Health System, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Pappas, Daphne, E-mail: edy22@drexel.ed [Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States)

2010-03-15

A combined effect of protein coating and plasma modification on the quality of the osteoblast-scaffold interaction was investigated. Three-dimensional polycaprolactone (PCL) scaffolds were manufactured by the precision extrusion deposition (PED) system. The structural, physical, chemical and biological cues were introduced to the surface through providing 3D structure, coating with adhesive protein fibronectin and modifying the surface with oxygen-based plasma. The changes in the surface properties of PCL after those modifications were examined by contact angle goniometry, surface energy calculation, surface chemistry analysis (XPS) and surface topography measurements (AFM). The effects of modification techniques on osteoblast short-term and long-term functions were examined by cell adhesion, proliferation assays and differentiation markers, namely alkaline phosphatase activity (ALP) and osteocalcin secretion. The results suggested that the physical and chemical cues introduced by plasma modification might be sufficient for improved cell adhesion, but for accelerated osteoblast differentiation the synergetic effects of structural, physical, chemical and biological cues should be introduced to the PCL surface.

A methodology for determining environmental threshold quantities for substances covered by CEPA's Environmental Emergency Regulation

International Nuclear Information System (INIS)

Ketcheson, K.; Shrives, J.

2005-01-01

Sections 199 and 200 of the Canadian Environmental Protection Act (CEPA) 1999 oblige persons who own or manage specified toxic and hazardous substances to develop and implement environmental emergency plans. This paper discussed the methodology for determining how a chemical is assessed for recommending an environmental emergency plan. For Section 199, once substances are declared toxic, each chemical is assessed to determine whether it requires a plan or not. For Section 200, any chemical can be added under the E2 regulations, as long as it can be ascertained that the substance is toxic according to the following criteria: it has an immediate or long-term harmful effect on the environment or its biological diversity; it constitutes a danger to the environment on which human life depends; and/or it constitutes a danger in Canada to human life or health. An overview of the risk evaluation framework was provided, including details of the pre-assessment filter. Summaries of trigger criteria were presented, as well as environmental hazard ratings and details of persistence of organic chemicals in the environment and bioaccumulation. Aquatic toxicity and ingestion toxicity details were also provided. Human hazard ratings included carcinogenicity, inhalation toxicity, dermal toxicity, rabbit and rat toxicity and corrosion and skin irritation ratings. Issues concerning vapour cloud explosions were examined. A reactivity table was presented with hazard descriptions. European Union Threshold quantities were examined, as well as a list of comparisons of selected substances of CEPA with the European Union. It was concluded that the Environmental Emergency Branch (EEB) has created environmental thresholds by first examining how other countries have protected the environment. Substance thresholds for the United States have focused on protecting humans, while Europe has established threshold quantities that work for their countries. The EEB has selected classification tables

Integrated pest management: theoretical insights from a threshold policy

Energy Technology Data Exchange (ETDEWEB)

Costa, Michel I. da Silveira [Laboratorio Nacional de Computacao Cientifica (LNCC), Petropolis, RJ (Brazil)], e-mail: michel@lncc.br; Faria, Lucas del B. [Universidade Federal de Lavras, MG (Brazil). Dept. de Biologia. Setor de Ecologia], e-mail: lucasdbf@gmail.com

2010-01-15

An Integrated Pest Management is formulated as a threshold policy. It is shown that when this strategy is applied to a food web consisting of generalist, specialist predators and endemic and pest prey, the dynamics can be stable and useful from the pest control point of view, despite the dynamical complexities inherent to the application of biocontrol only. In addition, pesticide toxicity depends rather on the species intrinsic parameters than on the chemical agent concentration. (author)

Chemical changes in PMMA as a function of depth due to proton beam irradiation

International Nuclear Information System (INIS)

Szilasi, S.Z.; Huszank, R.; Szikra, D.; Vaczi, T.; Rajta, I.; Nagy, I.

2011-01-01

Highlights: → Chemical changes were investigated as a function of depth in proton irradiated PMMA → The depth profile of numerous functional groups was determined along the depth → The degree of chemical modification strongly depends on the LET of protons → At low-fluences the zone of maximal modification is restricted to the Bragg peak → At higher fluences the zone of max. modification extends towards the sample surface. - Abstract: In this work we determined depth profiles of the chemical change in PMMA irradiated with 2 MeV protons by infrared spectroscopic and micro-Raman measurements. The measurements were carried out on 10 μm thin stacked foil samples using an infrared spectrometer in universal attenuated total reflectance (UATR) and transmission modes; while the thick samples were analyzed with a confocal micro-Raman spectrometer. The depth profiles of the changes formed due to the various delivered fluences were compared to each other. The measurements show the strong dependence of the degree of modification on the energy transfer from the decelerating protons. Depth profiles reveal that at the fluences applied in this work the entire irradiated volume suffered some chemical modifications. In case of low-fluence samples the zone of maximal modification is restricted only to the Bragg peak, but with increasing fluences the region of maximal modification extends towards the sample surface.

Surface charging, discharging and chemical modification at a sliding contact

DEFF Research Database (Denmark)

Singh, Shailendra Vikram; Kusano, Yukihiro; Morgen, Per

2012-01-01

Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X...... are also able to comment on the behavior and the charge decay time in the ambient air-like condition, once the sliding contact is discontinued. XPS analysis showed a marginal deoxidation effect on the polyester disks due to the charging and discharging of the surfaces. Moreover, these XPS results clearly...

On the controlling parameters for fatigue-crack threshold at low homologous temperatures

International Nuclear Information System (INIS)

Yu, W.; Gerberich, W.W.

1983-01-01

Fatigue crack propagation phenomena near the threshold stress intensity level ΔK /SUB TH/ , has been a vigorously studied topic in recent years. Near threshold the crack propagates rather slowly, thus giving enough time for various physical and chemical reactions to take place. Room air, which is the most commonly encountered environment, can still supply various ingredients such as oxygen, water vapor (and thus hydrogen) to support these reactions. Much effort had been directed toward the environmental aspects of near threshold fatigue crack growth. By conducting tests under vacuum, Suresh and coworkers found that the crack propagation rate in a 2-1/4 Cr-1Mo steel was higher in vacuum than in air. An oxide induced closure, which served to reduce the effective stress intensity at the crack tip, seems to furnish a good explanation. Neumann and coworkers proposed that during the fatigue process, extrusion-intrusion pairs can develop as a consequence of reversed slip around the crack tip when the crack was propagated near threshold stress intensity. Beevers demonstrated that fatigue fracture surfaces contact each other during unloading even under tension-tension cycling. Kanninen and Atkinson also reached the conclusion that the compressive stress acting at the crack tip due to residual plasticity can induce closure. Microstructural effects have also been cited as important factors in near threshold crack growth. It is generally accepted that coarser grains have a beneficial effect on the resistance to the near threshold crack propagation

Chemical modification of birch allergen extract leads to a reduction in allergenicity as well as immunogenicity.

Science.gov (United States)

Würtzen, Peter Adler; Lund, Lise; Lund, Gitte; Holm, Jens; Millner, Anders; Henmar, Helene

2007-01-01

In Europe, specific immunotherapy is currently conducted with vaccines containing allergen preparations based on intact extracts. In addition to this, chemically modified allergen extracts (allergoids) are used for specific allergy treatment. Reduced allergenicity and thereby reduced risk of side effects in combination with retained ability to activate T cells and induce protective allergen-specific antibody responses has been claimed for allergoids. In the current study, we compared intact allergen extracts and allergoids with respect to allergenicity and immunogenicity. The immunological response to birch allergen extract, alum-adsorbed extract, birch allergoid and alum-adsorbed allergoid was investigated in vitro in human basophil histamine release assay and by stimulation of human allergen-specific T cell lines. In vivo, Bet v 1-specific IgG titers in mice were determined after repetitive immunizations. In all patients tested (n = 8), allergoid stimulations led to reduced histamine release compared to the intact allergen extract. However, the allergoid preparations were not recognized by Bet v 1-specific T cell lines (n = 7), which responded strongly to the intact allergen extract. Mouse immunizations showed a clearly reduced IgG induction by allergoids and a strongly potentiating effect of the alum adjuvant. Optimal IgG titers were obtained after 3 immunizations with intact allergen extracts, while 5 immunizations were needed to obtain maximal response to the allergoid. The reduced histamine release observed for allergoid preparations may be at the expense of immunological efficacy because the chemical modifications lead to a clear reduction in T cell activation and the ability to induce allergen-specific IgG antibody responses. Copyright 2007 S. Karger AG, Basel.

Natural background levels and threshold values of chemical species in three large-scale groundwater bodies in Northern Italy

International Nuclear Information System (INIS)

Molinari, Antonio; Guadagnini, Laura; Marcaccio, Marco; Guadagnini, Alberto

2012-01-01

We analyze natural background levels (NBLs) and threshold values (TVs) of spatially distributed chemical species (NH 4 , B and As) which may be a potential pressure and concern in three large scale alluvial and fluvio-deltaic aquifers at different depths of the Apennines and Po river plains in Emilia–Romagna, Northern Italy. Our results are based on statistical methodologies designed to separate the natural and anthropogenic contributions in monitored concentrations by modeling the empirical distribution of the detected concentration with a mixture of probability density functions. Available chemical observations are taken over a 20 years period and are associated with different depths and cover planar investigation scales of the order of hundreds of kilometers. High concentration values detected for NH 4 and B appear to be related to high natural background levels. Due to interaction with the host rock in different geochemical environments we observed that concentration vary in time and space (including in depth) consistently with the hydrogeochemical features and the occurrence of natural attenuation mechanisms in the analyzed reservoirs. Conversely, estimated As NBLs are not consistent with the conceptual model of the hydrogeochemical behavior of the systems analyzed and experimental evidences of As content in aquifer cores. This is due to the inability of these techniques to incorporate the complex dynamics of the processes associated with the specific hydrogeochemical setting. Statistical analyses performed upon aggregating the concentration data according to different time observation windows allow identifying temporal dynamics of NBLs and TVs of target compounds within the observation time frame. Our results highlight the benefit of a dynamic monitoring process and analysis of well demarcated groundwater bodies to update the associated NBLs as a function of the temporal dependence of natural processes occurring in the subsurface. Monitoring protocols could

The scientific basis for the establishment of threshold levels and dose response relationships of carcinogenesis

International Nuclear Information System (INIS)

1975-01-01

The International Atomic Energy Agency hosted a two day Symposium from 2-3 December 1974 at its Headquarters, organized by the 'International Academy for Environmental Safety and the Forum fur Wissenschaft, Wirtschaft und Politik' on the subject 'Scientific Basis for the Establishment of Threshold. Levels and Dose Response Relationships of Carcinogenesis'. Following an introductory paper by the Radiation Biology Section of the Agency on 'Radiation Carcinogenesis - Dose Response Relationship, Threshold and Risk Estimates', a series of papers dealt with this problem in chemical carcinogenesis.It was suggested that more experiments should be done using non-human primates for tests of carcinogens, especially chemicals. Preliminary experiments using monkeys with a potent carcinogen - nitrosoamine - indicate that there could possibly be a dose where no effect can be observed during the 5 year period of study. It was also pointed out that the overall cost/benefit and risk/ benefit relationships should be taken into consideration in determining limits for chemicals which are potentially carcinogenic but are used routinely by the public and industries; these considerations have been weighed in setting exposure limits for radiation

Chemical shift homology in proteins

International Nuclear Information System (INIS)

Potts, Barbara C.M.; Chazin, Walter J.

1998-01-01

The degree of chemical shift similarity for homologous proteins has been determined from a chemical shift database of over 50 proteins representing a variety of families and folds, and spanning a wide range of sequence homologies. After sequence alignment, the similarity of the secondary chemical shifts of C α protons was examined as a function of amino acid sequence identity for 37 pairs of structurally homologous proteins. A correlation between sequence identity and secondary chemical shift rmsd was observed. Important insights are provided by examining the sequence identity of homologous proteins versus percentage of secondary chemical shifts that fall within 0.1 and 0.3 ppm thresholds. These results begin to establish practical guidelines for the extent of chemical shift similarity to expect among structurally homologous proteins

Definition of the Nature and Hapten Threshold of the β-Lactam Antigen Required for T Cell Activation In Vitro and in Patients.

Science.gov (United States)

Meng, Xiaoli; Al-Attar, Zaid; Yaseen, Fiazia S; Jenkins, Rosalind; Earnshaw, Caroline; Whitaker, Paul; Peckham, Daniel; French, Neil S; Naisbitt, Dean J; Park, B Kevin

2017-06-01

Covalent modification of protein by drugs may disrupt self-tolerance, leading to lymphocyte activation. Until now, determination of the threshold required for this process has not been possible. Therefore, we performed quantitative mass spectrometric analyses to define the epitopes formed in tolerant and hypersensitive patients taking the β-lactam antibiotic piperacillin and the threshold required for T cell activation. A hydrolyzed piperacillin hapten was detected on four lysine residues of human serum albumin (HSA) isolated from tolerant patients. The level of modified Lys 541 ranged from 2.6 to 4.8%. Analysis of plasma from hypersensitive patients revealed the same pattern and levels of modification 1-10 d after the commencement of therapy. Piperacillin-responsive skin-homing CD4 + clones expressing an array of Vβ receptors were activated in a dose-, time-, and processing-dependent manner; analysis of incubation medium revealed that 2.6% of Lys 541 in HSA was modified when T cells were activated. Piperacillin-HSA conjugates that had levels and epitopes identical to those detected in patients were shown to selectively stimulate additional CD4 + clones, which expressed a more restricted Vβ repertoire. To conclude, the levels of piperacillin-HSA modification that activated T cells are equivalent to the ones formed in hypersensitive and tolerant patients, which indicates that threshold levels of drug Ag are formed in all patients. Thus, the propensity to develop hypersensitivity is dependent on other factors, such as the presence of T cells within an individual's repertoire that can be activated with the β-lactam hapten and/or an imbalance in immune regulation. Copyright © 2017 by The American Association of Immunologists, Inc.

Tyrosine residues modification studied by MALDI-TOF mass spectrometry

International Nuclear Information System (INIS)

Santrucek, Jiri; Strohalm, Martin; Kadlcik, Vojtech; Hynek, Radovan; Kodicek, Milan

2004-01-01

Amino acid residue-specific reactivity in proteins is of great current interest in structural biology as it provides information about solvent accessibility and reactivity of the residue and, consequently, about protein structure and possible interactions. In the work presented tyrosine residues of three model proteins with known spatial structure are modified with two tyrosine-specific reagents: tetranitromethane and iodine. Modified proteins were specifically digested by proteases and the mass of resulting peptide fragments was determined using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Our results show that there are only small differences in the extent of tyrosine residues modification by tetranitromethane and iodine. However, data dealing with accessibility of reactive residues obtained by chemical modifications are not completely identical with those obtained by nuclear magnetic resonance and X-ray crystallography. These interesting discrepancies can be caused by local molecular dynamics and/or by specific chemical structure of the residues surrounding

A chemical specialty semantic network for the Unified Medical Language System

Directory of Open Access Journals (Sweden)

Morrey C

2012-05-01

Full Text Available Abstract Background Terms representing chemical concepts found the Unified Medical Language System (UMLS are used to derive an expanded semantic network with mutually exclusive semantic types. The UMLS Semantic Network (SN is composed of a collection of broad categories called semantic types (STs that are assigned to concepts. Within the UMLS’s coverage of the chemical domain, we find a great deal of concepts being assigned more than one ST. This leads to the situation where the extent of a given ST may contain concepts elaborating variegated semantics. A methodology for expanding the chemical subhierarchy of the SN into a finer-grained categorization of mutually exclusive types with semantically uniform extents is presented. We call this network a Chemical Specialty Semantic Network (CSSN. A CSSN is derived automatically from the existing chemical STs and their assignments. The methodology incorporates a threshold value governing the minimum size of a type’s extent needed for inclusion in the CSSN. Thus, different CSSNs can be created by choosing different threshold values based on varying requirements. Results A complete CSSN is derived using a threshold value of 300 and having 68 STs. It is used effectively to provide high-level categorizations for a random sample of compounds from the “Chemical Entities of Biological Interest” (ChEBI ontology. The effect on the size of the CSSN using various threshold parameter values between one and 500 is shown. Conclusions The methodology has several potential applications, including its use to derive a pre-coordinated guide for ST assignments to new UMLS chemical concepts, as a tool for auditing existing concepts, inter-terminology mapping, and to serve as an upper-level network for ChEBI.

Modification of inorganic surface with 1-alkenes and 1-alkynes

NARCIS (Netherlands)

Maat, ter J.

2012-01-01

Surface modification is important because it allows the tuning of surface properties, thereby enabling new applications of a material. It can change physical properties such as wettability and friction, but can also introduce chemical functionalities and binding specificity. Several techniques

Hybrid membrane using polyethersulfone-modification of multiwalled carbon nanotubes with silane agent to enhance high performance oxygen separation

Directory of Open Access Journals (Sweden)

Tutuk Djoko Kusworo

2014-04-01

Full Text Available Mixed matrix membrane comprising carbon nanotubes embedded in polymer matrix have become one of the emerging technologies. This study was investigated in order to study the effect of silane agent modification towards carbon nanotubes (CNT surface at different concentration on oxygen enrichment performances of asymmetric mixed matrix membrane. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using Dynasylan Ameo (DA silane agent to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Sieve-in-a-cage’ morphology observed shows the poor adhesion between polymer and unmodified CNT. The gas separation performance of the asymmetric flat sheet mixed matrix membranes with modified CNT were relatively higher compared to the unmodified CNT. Hence, coated hollow fiber mixed matrix membrane with chemical modification on CNT surface using (3-aminopropyl-triethoxy methyl silane agent can potentially enhance the gas separation performance of O2 and N2.

Response-only modal identification using random decrement algorithm with time-varying threshold level

International Nuclear Information System (INIS)

Lin, Chang Sheng; Tseng, Tse Chuan

2014-01-01

Modal Identification from response data only is studied for structural systems under nonstationary ambient vibration. The topic of this paper is the estimation of modal parameters from nonstationary ambient vibration data by applying the random decrement algorithm with time-varying threshold level. In the conventional random decrement algorithm, the threshold level for evaluating random dec signatures is defined as the standard deviation value of response data of the reference channel. The distortion of random dec signatures may be, however, induced by the error involved in noise from the original response data in practice. To improve the accuracy of identification, a modification of the sampling procedure in random decrement algorithm is proposed for modal-parameter identification from the nonstationary ambient response data. The time-varying threshold level is presented for the acquisition of available sample time history to perform averaging analysis, and defined as the temporal root-mean-square function of structural response, which can appropriately describe a wide variety of nonstationary behaviors in reality, such as the time-varying amplitude (variance) of a nonstationary process in a seismic record. Numerical simulations confirm the validity and robustness of the proposed modal-identification method from nonstationary ambient response data under noisy conditions.

Characterization of the audiologic thresholds in workers of funeral urns

Directory of Open Access Journals (Sweden)

Pereira, José Roberto

2009-09-01

Full Text Available Introduction: The industrial technological advance has brought benefits and a series of implications that may commit the worker's health and life quality. The exposure to physical, chemical agents and organizational stressors contribute for the increase of work accidents risks. The noise, taken as the most frequent physical agent in the work environment, may cause auditory alterations called Noise-Induced Hearing Loss that affect the communication and life quality of the workers. Objective: To research the auditory health of employees in a funeral urns factory. Method: 90 workers took part in this study, aged between 16 and 52 years, exposed to sound pressure levels equal or higher than 85 dBNPS, vibration and/or chemical agents in the work environment. We carried out a specific interview and Threshold Tonal Audiometry. Results: This study identified altered audiometry results in 13.33% the right ear and 16.67% in the left ear and the age also influenced these auditory thresholds. Conclusion: The accomplishment of a workers' health surveillance program with all people involved is critical and will contribute for the human resources formation, in the management to proceed with actions as well as those by the proper workers being careful of their health.

40 CFR 136.6 - Method modifications and analytical requirements.

Science.gov (United States)

2010-07-01

... modifications and analytical requirements. (a) Definitions of terms used in this section. (1) Analyst means the..., oil and grease, total suspended solids, total phenolics, turbidity, chemical oxygen demand, and.... Except as set forth in paragraph (b)(3) of this section, an analyst may modify an approved test procedure...

Rapid End-Group Modification of Polysaccharides for Biomaterial Applications in Regenerative Medicine.

Science.gov (United States)

Bondalapati, Somasekhar; Ruvinov, Emil; Kryukov, Olga; Cohen, Smadar; Brik, Ashraf

2014-09-15

Polysaccharides have emerged as important functional materials because of their unique properties such as biocompatibility, biodegradability, and availability of reactive sites for chemical modifications to optimize their properties. The overwhelming majority of the methods to modify polysaccharides employ random chemical modifications, which often improve certain properties while compromising others. On the other hand, the employed methods for selective modifications often require excess of coupling partners, long reaction times and are limited in their scope and wide applicability. To circumvent these drawbacks, aniline-catalyzed oxime formation is developed for selective modification of a variety of polysaccharides through their reducing end. Notably, it is found that for efficient oxime formation, different conditions are required depending on the composition of the specific polysaccharide. It is also shown how our strategy can be applied to improve the physical and functional properties of alginate hydrogels, which are widely used in tissue engineering and regenerative medicine applications. While the randomly and selectively modified alginate exhibits similar viscoelastic properties, the latter forms significantly more stable hydrogel and superior cell adhesive and functional properties. Our results show that the developed conjugation reaction is robust and should open new opportunities for preparing polysaccharide-based functional materials with unique properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Genetic engineering and chemical conjugation of potato virus X.

Science.gov (United States)

Lee, Karin L; Uhde-Holzem, Kerstin; Fischer, Rainer; Commandeur, Ulrich; Steinmetz, Nicole F

2014-01-01

Here we report the genetic engineering and chemical modification of potato virus X (PVX) for the presentation of various peptides, proteins, and fluorescent dyes, or other chemical modifiers. Three different ways of genetic engineering are described and by these means, peptides are successfully expressed not only when the foot and mouth disease virus (FMDV) 2A sequence or a flexible glycine-serine linker is included, but also when the peptide is fused directly to the PVX coat protein. When larger proteins or unfavorable peptide sequences are presented, a partial fusion via the FMDV 2A sequence is preferable. When these PVX chimeras retain the ability to assemble into viral particles and are thus able to infect plants systemically, they can be utilized to inoculate susceptible plants for isolation of sufficient amounts of virus particles for subsequent chemical modification. Chemical modification is required for the display of nonbiological ligands such as fluorophores, polymers, and small drug compounds. We present three methods of chemical bioconjugation. For direct conjugation of small chemical modifiers to solvent exposed lysines, N-hydroxysuccinimide chemistry can be applied. Bio-orthogonal reactions such as copper-catalyzed azide-alkyne cycloaddition or hydrazone ligation are alternatives to achieve more efficient conjugation (e.g., when working with high molecular weight or insoluble ligands). Furthermore, hydrazone ligation offers an attractive route for the introduction of pH-cleavable cargos (e.g., therapeutic molecules).

Threshold Signature Schemes Application

Directory of Open Access Journals (Sweden)

Anastasiya Victorovna Beresneva

2015-10-01

Full Text Available This work is devoted to an investigation of threshold signature schemes. The systematization of the threshold signature schemes was done, cryptographic constructions based on interpolation Lagrange polynomial, elliptic curves and bilinear pairings were examined. Different methods of generation and verification of threshold signatures were explored, the availability of practical usage of threshold schemes in mobile agents, Internet banking and e-currency was shown. The topics of further investigation were given and it could reduce a level of counterfeit electronic documents signed by a group of users.

Chemical modification of protein a chromatography ligands with polyethylene glycol. II: Effects on resin robustness and process selectivity.

Science.gov (United States)

Weinberg, Justin; Zhang, Shaojie; Kirkby, Allison; Shachar, Enosh; Carta, Giorgio; Przybycien, Todd

2018-04-20

We have proposed chemical modification of Protein A (ProA) chromatography ligands with polyethylene glycol (PEGylation) as a strategy to increase the resin selectivity and robustness by providing the ligand with a steric repulsion barrier against non-specific binding. Here, we report on robustness and selectivity benefits for Repligen CaptivA PriMAB resin with ligands modified with 5.2 kDa and 21.5 kDa PEG chains, respectively. PEGylation of ProA ligands allowed the resin to retain a higher percentage of static binding capacity relative to the unmodified resin upon digestion with chymotrypsin, a representative serine protease. The level of protection against digestion was independent of the PEG molecular weight or modification extent for the PEGylation chemistry used. Additionally, PEGylation of the ligands was found to decrease the level of non-specific binding of fluorescently labeled bovine serum albumin (BSA) aggregates to the surface of the resin particles as visualized via confocal laser scanning microscopy (CLSM). The level of aggregate binding decreased as the PEG molecular weight increased, but increasing the extent of modification with 5.2 kDa PEG chains had no effect. Further examination of resin particles via CLSM confirmed that the PEG chains on the modified ligands were capable of blocking the "hitchhiking" association of BSA, a mock contaminant, to an adsorbed mAb that is prone to BSA binding. Ligands modified with 21.5 kDa PEG chains were effective at blocking the association, while ligands modified with 5.2 kDa PEG chains were not. Finally, ligands with 21.5 kDa PEG chains increased the selectivity of the resin against host cell proteins (HCPs) produced by Chinese Hamster Ovary (CHO) cells by up to 37% during purification of a monoclonal antibody (mAb) from harvested cell culture fluid (HCCF) using a standard ProA chromatography protocol. The combined work suggests that PEGylating ProA chromatography media is a viable pathway for

Thresholds in radiobiology

International Nuclear Information System (INIS)

Katz, R.; Hofmann, W.

1982-01-01

Interpretations of biological radiation effects frequently use the word 'threshold'. The meaning of this word is explored together with its relationship to the fundamental character of radiation effects and to the question of perception. It is emphasised that although the existence of either a dose or an LET threshold can never be settled by experimental radiobiological investigations, it may be argued on fundamental statistical grounds that for all statistical processes, and especially where the number of observed events is small, the concept of a threshold is logically invalid. (U.K.)

Encoded libraries of chemically modified peptides.

Science.gov (United States)

Heinis, Christian; Winter, Greg

2015-06-01

The use of powerful technologies for generating and screening DNA-encoded protein libraries has helped drive the development of proteins as pharmaceutical ligands. However the development of peptides as pharmaceutical ligands has been more limited. Although encoded peptide libraries are typically several orders of magnitude larger than classical chemical libraries, can be more readily screened, and can give rise to higher affinity ligands, their use as pharmaceutical ligands is limited by their intrinsic properties. Two of the intrinsic limitations include the rotational flexibility of the peptide backbone and the limited number (20) of natural amino acids. However these limitations can be overcome by use of chemical modification. For example, the libraries can be modified to introduce topological constraints such as cyclization linkers, or to introduce new chemical entities such as small molecule ligands, fluorophores and photo-switchable compounds. This article reviews the chemistry involved, the properties of the peptide ligands, and the new opportunities offered by chemical modification of DNA-encoded peptide libraries. Copyright © 2015. Published by Elsevier Ltd.

Polymeric membranes: surface modification for minimizing (bio)colloidal fouling.

Science.gov (United States)

Kochkodan, Victor; Johnson, Daniel J; Hilal, Nidal

2014-04-01

This paper presents an overview on recent developments in surface modification of polymer membranes for reduction of their fouling with biocolloids and organic colloids in pressure driven membrane processes. First, colloidal interactions such as London-van der Waals, electrical, hydration, hydrophobic, steric forces and membrane surface properties such as hydrophilicity, charge and surface roughness, which affect membrane fouling, have been discussed and the main goals of the membrane surface modification for fouling reduction have been outlined. Thereafter the recent studies on reduction of (bio)colloidal of polymer membranes using ultraviolet/redox initiated surface grafting, physical coating/adsorption of a protective layer on the membrane surface, chemical reactions or surface modification of polymer membranes with nanoparticles as well as using of advanced atomic force microscopy to characterize (bio)colloidal fouling have been critically summarized. Copyright © 2013 Elsevier B.V. All rights reserved.

Quantitative proteomic characterization of redox-dependent post-translational modifications on protein cysteines

Energy Technology Data Exchange (ETDEWEB)

Duan, Jicheng; Gaffrey, Matthew J.; Qian, Wei-Jun

2017-01-01

Protein cysteine thiols play a crucial role in redox signaling, regulation of enzymatic activity and protein function, and maintaining redox homeostasis in living systems. The unique chemical reactivity of thiol groups makes cysteine susceptible to oxidative modifications by reactive oxygen and nitrogen species to form a broad array of reversible and irreversible protein post-translational modifications (PTMs). The reversible modifications in particular are one of the major components of redox signaling and are involved in regulation of various cellular processes under physiological and pathological conditions. The biological significance of these redox PTMs in health and diseases has been increasingly recognized. Herein, we review the recent advances of quantitative proteomic approaches for investigating redox PTMs in complex biological systems, including the general considerations of sample processing, various chemical or affinity enrichment strategies, and quantitative approaches. We also highlight a number of redox proteomic approaches that enable effective profiling of redox PTMs for addressing specific biological questions. Although some technological limitations remain, redox proteomics is paving the way towards a better understanding of redox signaling and regulation in human health and diseases.

2002 Toxic Chemical Release Inventory Report for the Emergency Planning and Community Right-to-Know Act of 1986, Title III, Section 313

International Nuclear Information System (INIS)

Stockton, M.

2003-01-01

For reporting year 2002, Los Alamos National Laboratory (LANL or the Laboratory) submitted Form R reports for lead compounds and mercury as required under the Emergency Planning and Community Right-to-Know Act (EPCRA), Section 313. No other EPCRA Section 313 chemicals were used in 2002 above the reportable thresholds. This document was prepared to provide a description of the evaluation of EPCRA Section 313 chemical usage and threshold determinations for LANL for calendar year 2002 as well as provide background information about the data included on the Form R reports. Section 313 of EPCRA specifically requires facilities to submit a Toxic Chemical Release Inventory report (Form R) to the U.S. Environmental Protection Agency (EPA) and state agencies if the owners and operators manufacture, process, or otherwise use any of the listed toxic chemicals above listed threshold quantities. EPA compiles this data in the Toxic Release Inventory database. Form R reports for each chemical over threshold quantities must be submitted on or before July 1 each year and must cover activities that occurred at the facility during the previous year. In 1999 EPA promulgated a final rule on Persistent Bioaccumulative Toxics (PBTs). This rule added several chemicals to the EPCRA Section 313 list of toxic chemicals and established lower reporting thresholds for these and other PBT chemicals that were already reportable under EPCRA Section 313. These lower thresholds became applicable in reporting year 2000. In 2001, EPA expanded the PBT rule to include a lower reporting threshold for lead and lead compounds. Facilities that manufacture, process, or otherwise use more than 100 lb of lead or lead compounds must submit a Form R

2006 Toxic Chemical Release Inventory Report for the Emergency Planning and Community Right-to-Know Act of 1986, Title III, Section 313

Energy Technology Data Exchange (ETDEWEB)

Ecology and Air Quality Group (ENV-EAQ)

2007-12-12

For reporting year 2006, Los Alamos National Laboratory (LANL or the Laboratory) submitted Form R reports for lead as required under the Emergency Planning and Community Right-to-Know Act (EPCRA) Section 313. No other EPCRA Section 313 chemicals were used in 2006 above the reportable thresholds. This document was prepared to provide a description of the evaluation of EPCRA Section 313 chemical use and threshold determinations for LANL for calendar year 2006, as well as to provide background information about data included on the Form R reports. Section 313 of EPCRA specifically requires facilities to submit a Toxic Chemical Release Inventory Report (Form R) to the U.S. Environmental Protection Agency (EPA) and state agencies if the owners and operators manufacture, process, or otherwise use any of the listed toxic chemicals above listed threshold quantities. EPA compiles this data in the Toxic Release Inventory database. Form R reports for each chemical over threshold quantities must be submitted on or before July 1 each year and must cover activities that occurred at the facility during the previous year. In 1999, EPA promulgated a final rule on persistent bioaccumulative toxics (PBTs). This rule added several chemicals to the EPCRA Section 313 list of toxic chemicals and established lower reporting thresholds for these and other PBT chemicals that were already reportable. These lower thresholds became applicable in reporting year 2000. In 2001, EPA expanded the PBT rule to include a lower reporting threshold for lead and lead compounds. Facilities that manufacture, process, or otherwise use more than 100 lb of lead or lead compounds must submit a Form R.

Chemical Modification of Activated Carbon and Its Application for Solid Phase Extraction of Copper(II and Iron(III Ions

Directory of Open Access Journals (Sweden)

M. Ghaedi

2014-06-01

Full Text Available Powder activated carbon surface (AC was grinded and modified and altered procedure thorough a facile and easy chemical reaction to appearance of 2-((3silylpropylimino1-methyl phenol (AC- (SPIMP. Subsequently, this novel sorbent efficiently applied for the extraction and preconcentration of some metal ions from real samples. Preliminary the influences of variables such as pH, amounts of reagents and porous AC, eluting solution conditions (type and concentrations, sample volume and influence of interference of many ions on the analytes recoveries was studied and optimized. This new sorbents property including pore size, pore volume and surface properties was evaluated and monitored by BET, while structure and homogeneously of sorbent was identified by SEM. The surface modification was traced by FT-IR as powerful and strong identification techniques. The proposed sorbent has high surface area(>1317.1346 m2 g-1 and small pore size(

Surface modification by vacuum annealing for field emission from heavily phosphorus-doped homoepitaxial (1 1 1) diamond

International Nuclear Information System (INIS)

Yamada, Takatoshi; Nebel, Christoph E.; Somu, Kumaragurubaran; Shikata, Shin-ichi

2008-01-01

The relationship between field emission properties and C 1s core level shifts of heavily phosphorus-doped homoepitaxial (1 1 1) diamond is investigated as a function of annealing temperature in order to optimize surface carbon bonding configurations for device applications. A low field emission threshold voltage is observed from surfaces annealed at 800 deg. C for hydrogen-plasma treated surface, while a low field emission threshold voltage of wet-chemical oxidized surface is observed after annealing at 900 deg. C. The C 1s core level by X-ray photoelectron spectroscopy (XPS) showed a shoulder peak at 1 eV below the main peak over 800 and 900 deg. C annealing temperature for hydrogen-plasma treated and wet-chemical oxidized surfaces, respectively. When the shoulder peak intensity is less than 10% of the main peak intensity, lower threshold voltages are observed. This is due to the carbon-reconstruction which gives rise to a small positive electron affinity. By increasing annealing temperature, the shoulder peak ratios also increase, which indicates that a surface graphitization takes place. This leads to higher threshold voltages

Chiral reagents in glycosylation and modification of carbohydrates.

Science.gov (United States)

Wang, Hao-Yuan; Blaszczyk, Stephanie A; Xiao, Guozhi; Tang, Weiping

2018-02-05

Carbohydrates play a significant role in numerous biological events, and the chemical synthesis of carbohydrates is vital for further studies to understand their various biological functions. Due to the structural complexity of carbohydrates, the stereoselective formation of glycosidic linkages and the site-selective modification of hydroxyl groups are very challenging and at the same time extremely important. In recent years, the rapid development of chiral reagents including both chiral auxiliaries and chiral catalysts has significantly improved the stereoselectivity for glycosylation reactions and the site-selectivity for the modification of carbohydrates. These new tools will greatly facilitate the efficient synthesis of oligosaccharides, polysaccharides, and glycoconjugates. In this tutorial review, we will summarize these advances and highlight the most recent examples.

Shifts in the relationship between motor unit recruitment thresholds versus derecruitment thresholds during fatigue.

Science.gov (United States)

Stock, Matt S; Mota, Jacob A

2017-12-01

Muscle fatigue is associated with diminished twitch force amplitude. We examined changes in the motor unit recruitment versus derecruitment threshold relationship during fatigue. Nine men (mean age = 26 years) performed repeated isometric contractions at 50% maximal voluntary contraction (MVC) knee extensor force until exhaustion. Surface electromyographic signals were detected from the vastus lateralis, and were decomposed into their constituent motor unit action potential trains. Motor unit recruitment and derecruitment thresholds and firing rates at recruitment and derecruitment were evaluated at the beginning, middle, and end of the protocol. On average, 15 motor units were studied per contraction. For the initial contraction, three subjects showed greater recruitment thresholds than derecruitment thresholds for all motor units. Five subjects showed greater recruitment thresholds than derecruitment thresholds for only low-threshold motor units at the beginning, with a mean cross-over of 31.6% MVC. As the muscle fatigued, many motor units were derecruited at progressively higher forces. In turn, decreased slopes and increased y-intercepts were observed. These shifts were complemented by increased firing rates at derecruitment relative to recruitment. As the vastus lateralis fatigued, the central nervous system's compensatory adjustments resulted in a shift of the regression line of the recruitment versus derecruitment threshold relationship. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Effect of chemical modification on behavior of various organic vanadium forms during analysis by electrothermal atomic absorption spectrometry

International Nuclear Information System (INIS)

Kowalewska, Zofia

2007-01-01

The behavior of various organic V forms dissolved in xylene during analysis by electrothermal atomic absorption spectrometry (ETAAS) was compared. The investigated analyte forms included compounds with vanadium at the oxidation state III, IV or V, as well as N, O or S atoms in molecules. Another group consisted of petroleum products containing naturally-occurring V species. Although the characteristic mass determined under different analytical conditions was in the very wide range from 11 up to 55 pg, some rules of V behavior were found. In the case of porphyrins and petroleum products, the application of Pd as a chemical modifier (xylene solution of Pd(II) acetylacetonate) seemed to be crucial. It was shown that Pd must be introduced to a furnace together with a sample. Pd injected and thermally pretreated before the sample injection was less effective for porphyrins and the petroleum products, but it increased signals of V compounds containing O as donor atom. The iodine pretreatment followed by the methyltrioctylammonium chloride (MTOACl) pretreatment was advantageous for these V forms. The air ashing in a graphite tube appeared to be important to improve decomposition of the petroleum products. No significant influence of the V oxidation state on the analytical signal was observed. The behavior of V contained in two Conostan oil standards, the single-element and the S21 multielement standard, was different in many situations. Probably, the joint action of other elements is responsible for this effect. In general, chemical modification was applied in the work for two reasons: to reduce the V volatility (in some cases losses at about 300 deg. C were observed) and to enhance the atomization efficiency. For routine analysis air ashing, modification by Pd introduced into the furnace together with the sample solution and petroleum products with known V content as standard is recommended. Using this procedure the characteristic mass varied from 16 to 19 pg for

Surface Modification of α-Fe Metal Particles by Chemical Surface Coating

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

The structure of α-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms.

Chemical modification of nanocellulose with canola oil fatty acid methyl ester

Science.gov (United States)

Liqing Wei; Umesh P. Agarwal; Kolby C. Hirth; Laurent M. Matuana; Ronald C. Sabo; Nicole M. Stark

2017-01-01

Cellulose nanocrystals (CNCs), produced from dissolving wood pulp, were chemically functionalized by transesterification with canola oil fatty acid methyl ester (CME). CME performs as both the reaction reagent and solvent. Transesterified CNC (CNCFE) was characterized for their chemical structure, morphology, crystalline structure, thermal stability, and hydrophobicity...

Threshold factorization redux

Science.gov (United States)

Chay, Junegone; Kim, Chul

2018-05-01

We reanalyze the factorization theorems for the Drell-Yan process and for deep inelastic scattering near threshold, as constructed in the framework of the soft-collinear effective theory (SCET), from a new, consistent perspective. In order to formulate the factorization near threshold in SCET, we should include an additional degree of freedom with small energy, collinear to the beam direction. The corresponding collinear-soft mode is included to describe the parton distribution function (PDF) near threshold. The soft function is modified by subtracting the contribution of the collinear-soft modes in order to avoid double counting on the overlap region. As a result, the proper soft function becomes infrared finite, and all the factorized parts are free of rapidity divergence. Furthermore, the separation of the relevant scales in each factorized part becomes manifest. We apply the same idea to the dihadron production in e+e- annihilation near threshold, and show that the resultant soft function is also free of infrared and rapidity divergences.

Comparison between intensity- duration thresholds and cumulative rainfall thresholds for the forecasting of landslide

Science.gov (United States)

Lagomarsino, Daniela; Rosi, Ascanio; Rossi, Guglielmo; Segoni, Samuele; Catani, Filippo

2014-05-01

This work makes a quantitative comparison between the results of landslide forecasting obtained using two different rainfall threshold models, one using intensity-duration thresholds and the other based on cumulative rainfall thresholds in an area of northern Tuscany of 116 km2. The first methodology identifies rainfall intensity-duration thresholds by means a software called MaCumBA (Massive CUMulative Brisk Analyzer) that analyzes rain-gauge records, extracts the intensities (I) and durations (D) of the rainstorms associated with the initiation of landslides, plots these values on a diagram, and identifies thresholds that define the lower bounds of the I-D values. A back analysis using data from past events can be used to identify the threshold conditions associated with the least amount of false alarms. The second method (SIGMA) is based on the hypothesis that anomalous or extreme values of rainfall are responsible for landslide triggering: the statistical distribution of the rainfall series is analyzed, and multiples of the standard deviation (σ) are used as thresholds to discriminate between ordinary and extraordinary rainfall events. The name of the model, SIGMA, reflects the central role of the standard deviations in the proposed methodology. The definition of intensity-duration rainfall thresholds requires the combined use of rainfall measurements and an inventory of dated landslides, whereas SIGMA model can be implemented using only rainfall data. These two methodologies were applied in an area of 116 km2 where a database of 1200 landslides was available for the period 2000-2012. The results obtained are compared and discussed. Although several examples of visual comparisons between different intensity-duration rainfall thresholds are reported in the international literature, a quantitative comparison between thresholds obtained in the same area using different techniques and approaches is a relatively undebated research topic.

Chemical Emergency Preparedness and Prevention Advisory: Ammonia

Science.gov (United States)

This advisory recommends ways Local Emergency Planning Committees (LEPCs) and chemical facilities can minimize risks from this extremely hazardous substance, especially when present in excess of its 500 pounds threshold planning quantity.

Barley lipid transfer protein, LTP1, contains a new type of lipid-like post-translational modification

DEFF Research Database (Denmark)

Lindorff-Larsen, Kresten; Lerche, Mathilde H.; Poulsen, Flemming Martin

2001-01-01

in which an aspartic acid in LTP1 is bound to the modification through what most likely is an ester bond. The chemical structure of the modification has been characterized by means of two-dimensional homo- and heteronuclear nuclear magnetic resonance spectroscopy as well as mass spectrometry and is found...

Experimental investigation on the threshold chloride concentration for corrosion initiation in reinforced concrete structures

International Nuclear Information System (INIS)

Byung Hwan Oh; Seung Yup Jang

2005-01-01

The corrosion of steel reinforcements in concrete is of great importance in the view of safety and durability of reinforced concrete structures. This study is focused on the corrosion behavior of steel bars induced by internal chlorides in concrete. The main objective of this study is to determine the threshold chloride concentration causing depassivation and active corrosion of steel reinforcement in concrete. To examine the threshold concentration of chloride ion, the half-cell potential, the chemical composition of extracted pore solutions of concrete and the extent of corroded area of the specimens were measured. Major test variables include the added amount of chlorides in concrete, type of binder, and water-to-binder ratios. From the present comprehensive test results, the factors influencing threshold chloride concentration are investigated, and the rational ranges of threshold chloride concentration causing active corrosion of steels are proposed. The present study provides the realistic chloride limit for corrosion initiation of reinforced concrete structures, which can be used efficiently in the future technical specification. (authors)

Chemical inventory control program for mixed and hazardous waste facilities at SRS

International Nuclear Information System (INIS)

Ades, M.J.; Vincent, A.M. III.

1997-01-01

Mixed Waste (MW) and Hazardous Waste (HW) are being stored at the Savannah River Site (SRS) pending onsite and/or offsite treatment and disposal. The inventory control for these wastes has recently been brought under Technical Safety Requirements (TSR) in accordance with DOE Order 5480.22. With the TSRs was the question of the degree of rigor with which the inventory is to be tracked, considering that the variety of chemicals present, or that could be present, numbers in the hundreds. This paper describes the graded approach program to track Solid Waste (SW) inventories relative to TSRs. The approach uses a ratio of the maximum anticipated chemical inventory to the permissible inventory in accordance with Emergency Response Planning Guideline (ERPG) limits for on- and off-site receptors. A specific threshold ratio can then be determined. The chemicals above this threshold ratio are to be included in the chemical inventory control program. The chemicals that fall below the threshold ratio are managed in accordance with existing practice per State and RCRA hazardous materials requirements. Additionally, the facilities are managed in accordance with process safety management principles, specifically using process hazards analyses, which provides safety assurance for even the small quantities that may be excluded from the formal inventory control program. The method yields a practical approach to chemical inventory control, while maintaining appropriate chemical safety margins. The resulting number of specific chemicals that require inclusion in a rigorous inventory control program is greatly reduced by about 80%, thereby resulting in significant reduction in chemical data management while preserving appropriate safety margins

Detection thresholds of macaque otolith afferents.

Science.gov (United States)

Yu, Xiong-Jie; Dickman, J David; Angelaki, Dora E

2012-06-13

The vestibular system is our sixth sense and is important for spatial perception functions, yet the sensory detection and discrimination properties of vestibular neurons remain relatively unexplored. Here we have used signal detection theory to measure detection thresholds of otolith afferents using 1 Hz linear accelerations delivered along three cardinal axes. Direction detection thresholds were measured by comparing mean firing rates centered on response peak and trough (full-cycle thresholds) or by comparing peak/trough firing rates with spontaneous activity (half-cycle thresholds). Thresholds were similar for utricular and saccular afferents, as well as for lateral, fore/aft, and vertical motion directions. When computed along the preferred direction, full-cycle direction detection thresholds were 7.54 and 3.01 cm/s(2) for regular and irregular firing otolith afferents, respectively. Half-cycle thresholds were approximately double, with excitatory thresholds being half as large as inhibitory thresholds. The variability in threshold among afferents was directly related to neuronal gain and did not depend on spike count variance. The exact threshold values depended on both the time window used for spike count analysis and the filtering method used to calculate mean firing rate, although differences between regular and irregular afferent thresholds were independent of analysis parameters. The fact that minimum thresholds measured in macaque otolith afferents are of the same order of magnitude as human behavioral thresholds suggests that the vestibular periphery might determine the limit on our ability to detect or discriminate small differences in head movement, with little noise added during downstream processing.

Carbon deposition thresholds on nickel-based solid oxide fuel cell anodes II. Steam:carbon ratio and current density

Science.gov (United States)

Kuhn, J.; Kesler, O.

2015-03-01

For the second part of a two part publication, coking thresholds with respect to molar steam:carbon ratio (SC) and current density in nickel-based solid oxide fuel cells were determined. Anode-supported button cell samples were exposed to 2-component and 5-component gas mixtures with 1 ≤ SC ≤ 2 and zero fuel utilization for 10 h, followed by measurement of the resulting carbon mass. The effect of current density was explored by measuring carbon mass under conditions known to be prone to coking while increasing the current density until the cell was carbon-free. The SC coking thresholds were measured to be ∼1.04 and ∼1.18 at 600 and 700 °C, respectively. Current density experiments validated the thresholds measured with respect to fuel utilization and steam:carbon ratio. Coking thresholds at 600 °C could be predicted with thermodynamic equilibrium calculations when the Gibbs free energy of carbon was appropriately modified. Here, the Gibbs free energy of carbon on nickel-based anode support cermets was measured to be -6.91 ± 0.08 kJ mol-1. The results of this two part publication show that thermodynamic equilibrium calculations with appropriate modification to the Gibbs free energy of solid-phase carbon can be used to predict coking thresholds on nickel-based anodes at 600-700 °C.

Artificial Specific Binders Directly Recovered from Chemically Modified Nucleic Acid Libraries

Directory of Open Access Journals (Sweden)

Yuuya Kasahara

2012-01-01

Full Text Available Specific binders comprised of nucleic acids, that is, RNA/DNA aptamers, are attractive functional biopolymers owing to their potential broad application in medicine, food hygiene, environmental analysis, and biological research. Despite the large number of reports on selection of natural DNA/RNA aptamers, there are not many examples of direct screening of chemically modified nucleic acid aptamers. This is because of (i the inferior efficiency and accuracy of polymerase reactions involving transcription/reverse-transcription of modified nucleotides compared with those of natural nucleotides, (ii technical difficulties and additional time and effort required when using modified nucleic acid libraries, and (iii ambiguous efficacies of chemical modifications in binding properties until recently; in contrast, the effects of chemical modifications on biostability are well studied using various nucleotide analogs. Although reports on the direct screening of a modified nucleic acid library remain in the minority, chemical modifications would be essential when further functional expansion of nucleic acid aptamers, in particular for medical and biological uses, is considered. This paper focuses on enzymatic production of chemically modified nucleic acids and their application to random screenings. In addition, recent advances and possible future research are also described.

Artificial specific binders directly recovered from chemically modified nucleic acid libraries.

Science.gov (United States)

Kasahara, Yuuya; Kuwahara, Masayasu

2012-01-01

Specific binders comprised of nucleic acids, that is, RNA/DNA aptamers, are attractive functional biopolymers owing to their potential broad application in medicine, food hygiene, environmental analysis, and biological research. Despite the large number of reports on selection of natural DNA/RNA aptamers, there are not many examples of direct screening of chemically modified nucleic acid aptamers. This is because of (i) the inferior efficiency and accuracy of polymerase reactions involving transcription/reverse-transcription of modified nucleotides compared with those of natural nucleotides, (ii) technical difficulties and additional time and effort required when using modified nucleic acid libraries, and (iii) ambiguous efficacies of chemical modifications in binding properties until recently; in contrast, the effects of chemical modifications on biostability are well studied using various nucleotide analogs. Although reports on the direct screening of a modified nucleic acid library remain in the minority, chemical modifications would be essential when further functional expansion of nucleic acid aptamers, in particular for medical and biological uses, is considered. This paper focuses on enzymatic production of chemically modified nucleic acids and their application to random screenings. In addition, recent advances and possible future research are also described.

Mechanical properties of chemically modified portuguese pinewood

OpenAIRE

Lopes, Duarte B; Mai, Carsten; Militz, Holger

2014-01-01

To turn wood into a construction material with enhanced properties, many methods of chemical modification have been developed in the last few decades. In this work, mechanical properties of pine wood were chemically modified, compared and evaluated. Maritime pine wood (Pinus pinaster) was modified with four chemical processes: 1,3-dimethylol-4,5- dihydroxyethyleneurea, N-methylol melamine formaldehyde, tetra-alkoxysilane and wax. The following mechanical properties were assessed experiment...

Sensing the intruder: a quantitative threshold for recognition cues perception in honeybees

Science.gov (United States)

Cappa, Federico; Bruschini, Claudia; Cipollini, Maria; Pieraccini, Giuseppe; Cervo, Rita

2014-02-01

The ability to discriminate among nestmates and non-nestmate is essential to defend social insect colonies from intruders. Over the years, nestmate recognition has been extensively studied in the honeybee Apis mellifera; nevertheless, the quantitative perceptual aspects at the basis of the recognition system represent an unexplored subject in this species. To test the existence of a cuticular hydrocarbons' quantitative perception threshold for nestmate recognition cues, we conducted behavioural assays by presenting different amounts of a foreign forager's chemical profile to honeybees at the entrance of their colonies. We found an increase in the explorative and aggressive responses as the amount of cues increased based on a threshold mechanism, highlighting the importance of the quantitative perceptual features for the recognition processes in A. mellifera.

Surface modification of titanium and titanium alloys by ion implantation.

Science.gov (United States)

Rautray, Tapash R; Narayanan, R; Kwon, Tae-Yub; Kim, Kyo-Han

2010-05-01

Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, to improve the biological, chemical, and mechanical properties, surface modification is often performed. In view of this, the current review casts new light on surface modification of titanium and titanium alloys by ion beam implantation. (c) 2010 Wiley Periodicals, Inc.

Identifying community thresholds for lotic benthic diatoms in response to human disturbance.

Science.gov (United States)

Tang, Tao; Tang, Ting; Tan, Lu; Gu, Yuan; Jiang, Wanxiang; Cai, Qinghua

2017-06-23

Although human disturbance indirectly influences lotic assemblages through modifying physical and chemical conditions, identifying thresholds of human disturbance would provide direct evidence for preventing anthropogenic degradation of biological conditions. In the present study, we used data obtained from tributaries of the Three Gorges Reservoir in China to detect effects of human disturbance on streams and to identify disturbance thresholds for benthic diatoms. Diatom species composition was significantly affected by three in-stream stressors including TP, TN and pH. Diatoms were also influenced by watershed % farmland and natural environmental variables. Considering three in-stream stressors, TP was positively influenced by % farmland and % impervious surface area (ISA). In contrast, TN and pH were principally affected by natural environmental variables. Among measured natural environmental variables, average annual air temperature, average annual precipitation, and topsoil % CaCO 3 , % gravel, and total exchangeable bases had significant effects on study streams. When effects of natural variables were accounted for, substantial compositional changes in diatoms occurred when farmland or ISA land use exceeded 25% or 0.3%, respectively. Our study demonstrated the rationale for identifying thresholds of human disturbance for lotic assemblages and addressed the importance of accounting for effects of natural factors for accurate disturbance thresholds.

Natural background levels and threshold values of chemical species in three large-scale groundwater bodies in Northern Italy

Energy Technology Data Exchange (ETDEWEB)

Molinari, Antonio, E-mail: ant.molinari2002@libero.it [Politecnico di Milano, Dipartimento di Ingegneria Idraulica, Ambientale, Infrastrutture Viarie e Rilevamento, Piazza L. Da Vinci, 32-20133 Milano (Italy); Guadagnini, Laura [Politecnico di Milano, Dipartimento di Ingegneria Idraulica, Ambientale, Infrastrutture Viarie e Rilevamento, Piazza L. Da Vinci, 32-20133 Milano (Italy); Marcaccio, Marco [ARPA Emilia-Romagna, Direzione Tecnica, Largo Caduti del Lavoro, 6-40122 Bologna (Italy); Guadagnini, Alberto [Politecnico di Milano, Dipartimento di Ingegneria Idraulica, Ambientale, Infrastrutture Viarie e Rilevamento, Piazza L. Da Vinci, 32-20133 Milano (Italy)

2012-05-15

We analyze natural background levels (NBLs) and threshold values (TVs) of spatially distributed chemical species (NH{sub 4}, B and As) which may be a potential pressure and concern in three large scale alluvial and fluvio-deltaic aquifers at different depths of the Apennines and Po river plains in Emilia-Romagna, Northern Italy. Our results are based on statistical methodologies designed to separate the natural and anthropogenic contributions in monitored concentrations by modeling the empirical distribution of the detected concentration with a mixture of probability density functions. Available chemical observations are taken over a 20 years period and are associated with different depths and cover planar investigation scales of the order of hundreds of kilometers. High concentration values detected for NH{sub 4} and B appear to be related to high natural background levels. Due to interaction with the host rock in different geochemical environments we observed that concentration vary in time and space (including in depth) consistently with the hydrogeochemical features and the occurrence of natural attenuation mechanisms in the analyzed reservoirs. Conversely, estimated As NBLs are not consistent with the conceptual model of the hydrogeochemical behavior of the systems analyzed and experimental evidences of As content in aquifer cores. This is due to the inability of these techniques to incorporate the complex dynamics of the processes associated with the specific hydrogeochemical setting. Statistical analyses performed upon aggregating the concentration data according to different time observation windows allow identifying temporal dynamics of NBLs and TVs of target compounds within the observation time frame. Our results highlight the benefit of a dynamic monitoring process and analysis of well demarcated groundwater bodies to update the associated NBLs as a function of the temporal dependence of natural processes occurring in the subsurface. Monitoring

Evaluation of the chemical modifications in petroleum asphalt cement with the addition of polypropylene; Avaliacao das modificacoes quimicas no cimento asfaltico de petroleo com a adicao de polipropileno

Energy Technology Data Exchange (ETDEWEB)

Marcondes, C.P.; Sales, M.J.A.; Resck, I.S., E-mail: mjsales@unb.b [Universidade de Brasilia (LabPol/UnB), DF (Brazil). Inst. de Quimica. Lab. de Pesquisa em Polimeros; Farias, M.M.; Souza, M.V.R. [Universidade de Brasilia (UnB), DF (Brazil). Dept. de Engenharia Civil e Ambiental

2010-07-01

Studies show that the common distress mode in the Brazilian highway network are fatigue cracks and plastic deformation, which are associated with the type of material used in the pavement layers, structural project, excessive traffic load and weathering. To minimize these defects, research on modifiers such as polymers, added to asphalt binders have been developed to provide physical, chemical and rheological improvement. This paper investigates chemical modifications of the binders with the addition of PP by FTIR, NMR and DSC. FTIR spectra of pure and modified binder showed no differences in absorption. NMR analysis showed no strong chemical bonds between the binder and PP. DSC curve of PP showed a melting temperature of 160 deg C ({Delta}H = 94J/g) and the pure binder presented an endothermic transition between 20 and 40 deg C ({Delta}H = 2J/g). In the DSC curves of mixtures, these transitions are not significant, indicating possible interactions between asphalt binder and PP. (author)

Design and Control of Chemical Grouting : Volume 3 - Engineering Practice

Science.gov (United States)

1983-04-01

Recent improvements in the engineering practice of chemical grouting have provided increased confidence in this method of ground modification. Designers can significantly improve the success of chemical grouting by defining their grouting program obj...

Probing Chromatin-modifying Enzymes with Chemical Tools

KAUST Repository

Fischle, Wolfgang

2016-02-04

Chromatin is the universal template of genetic information in all eukaryotic organisms. Chemical modifications of the DNA-packaging histone proteins and the DNA bases are crucial signaling events in directing the use and readout of eukaryotic genomes. The enzymes that install and remove these chromatin modifications as well as the proteins that bind these marks govern information that goes beyond the sequence of DNA. Therefore, these so-called epigenetic regulators are intensively studied and represent promising drug targets in modern medicine. We summarize and discuss recent advances in the field of chemical biology that have provided chromatin research with sophisticated tools for investigating the composition, activity, and target sites of chromatin modifying enzymes and reader proteins.

Catalytic modification of cellulose and hemicellulose - Sugarefine

Energy Technology Data Exchange (ETDEWEB)

Repo, T. [Helsinki Univ. (Finland),Laboratory of Inorganic Chemistry], email: timo.repo@helsinki.fi

2012-07-01

The main goal of the project is to develop catalytic methods for the modification of lignocellulose-based saccharides in the biorefineries. The products of these reactions could be used for example as biofuel components, raw materials for the chemical industry, solvents and precursors for biopolymers. The catalyst development aims at creating efficient, selective and green catalytic methods for profitable use in biorefineries. The project is divided in three work packages: In WP1 (Catalytic dehydration of cellulose) the aim is at developing non-toxic, efficient methods for the catalytic dehydration of cellulose the target molecule being here 5-hydroxymethylfurfural (5-HMF). 5-HMF is an interesting platform chemical for the production of fuel additives, solvents and polymers. In WP2 (Catalytic reduction), the objective of the catalytic reduction studies is to produce commercially interesting monofunctional chemicals, such as 1-butanol or 2-methyltetrahydrofuran (2-MeTHF). In WP3 (Catalytic oxidation), the research focuses on developing a green and efficient oxidation method for producing acids. Whereas acetic and formic acids are bulk chemicals, diacids such as glucaric and xylaric acids are valuable specialty chemicals for detergent, polymer and food production.

Chemical characterization of the acid alteration of diesel fuel: Non-targeted analysis by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry with tile-based Fisher ratio and combinatorial threshold determination

Energy Technology Data Exchange (ETDEWEB)

Parsons, Brendon A.; Pinkerton, David K.; Wright, Bob W.; Synovec, Robert E.

2016-04-01

The illicit chemical alteration of petroleum fuels is of scientific interest, particularly to regulatory agencies which set fuel specifications, or excises based on those specifications. One type of alteration is the reaction of diesel fuel with concentrated sulfuric acid. Such reactions are known to subtly alter the chemical composition of the fuel, particularly the aromatic species native to the fuel. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC–TOFMS) is ideally suited for the analysis of diesel fuel, but may provide the analyst with an overwhelming amount of data, particularly in sample-class comparison experiments comprised of many samples. The tile-based Fisher-ratio (F-ratio) method reduces the abundance of data in a GC × GC–TOFMS experiment to only the peaks which significantly distinguish the unaltered and acid altered sample classes. Three samples of diesel fuel from different filling stations were each altered to discover chemical features, i.e., analyte peaks, which were consistently changed by the acid reaction. Using different fuels prioritizes the discovery of features which are likely to be robust to the variation present between fuel samples and which will consequently be useful in determining whether an unknown sample has been acid altered. The subsequent analysis confirmed that aromatic species are removed by the acid alteration, with the degree of removal consistent with predicted reactivity toward electrophilic aromatic sulfonation. Additionally, we observed that alkenes and alkynes were also removed from the fuel, and that sulfur dioxide or compounds that degrade to sulfur dioxide are generated by the acid alteration. In addition to applying the previously reported tile-based F-ratio method, this report also expands null distribution analysis to algorithmically determine an F-ratio threshold to confidently select only the features which are sufficiently class-distinguishing. When

Site-selective protein-modification chemistry for basic biology and drug development.

Science.gov (United States)

Krall, Nikolaus; da Cruz, Filipa P; Boutureira, Omar; Bernardes, Gonçalo J L

2016-02-01

Nature has produced intricate machinery to covalently diversify the structure of proteins after their synthesis in the ribosome. In an attempt to mimic nature, chemists have developed a large set of reactions that enable post-expression modification of proteins at pre-determined sites. These reactions are now used to selectively install particular modifications on proteins for many biological and therapeutic applications. For example, they provide an opportunity to install post-translational modifications on proteins to determine their exact biological roles. Labelling of proteins in live cells with fluorescent dyes allows protein uptake and intracellular trafficking to be tracked and also enables physiological parameters to be measured optically. Through the conjugation of potent cytotoxicants to antibodies, novel anti-cancer drugs with improved efficacy and reduced side effects may be obtained. In this Perspective, we highlight the most exciting current and future applications of chemical site-selective protein modification and consider which hurdles still need to be overcome for more widespread use.

Intermediate structure and threshold phenomena

International Nuclear Information System (INIS)

Hategan, Cornel

2004-01-01

The Intermediate Structure, evidenced through microstructures of the neutron strength function, is reflected in open reaction channels as fluctuations in excitation function of nuclear threshold effects. The intermediate state supporting both neutron strength function and nuclear threshold effect is a micro-giant neutron threshold state. (author)

Modification of polyetherurethane for biomedical application by radiation-induced grafting. I. Grafting procedure, determination of mechanical properties, and chemical modification of grafted films

International Nuclear Information System (INIS)

Jansen, B.; Ellinghorst, G.

1985-01-01

Radiation grafting of monomers onto suitable trunk polymers is a useful tool for tailoring new polymers for special purposes. This technique has been used in the past for the development of biocompatible materials, e.g., by grafting hydrogels onto mechanically stable polymers. In this first part of our work, the radiation grafting of hydrophilic or reactive monomers onto a polyetherurethane film using the pre-swelling technique is described. Following this technique the trunk polymer was swollen in the monomer before irradiation. As monomers 2-hydroxyethyl methacrylate (HEMA), 2,3-epoxypropyl methacrylate (GMA), 2,3-dihydroxypropyl methacrylate (GOMA), and acrylamide (AAm) were used. The kinetics of the grafting reactions were examined, and the distribution of the graft component inside the trunk polymer was investigated by means of infrared (IR) spectroscopy. Surface-grafted as well as bulk- and surface-grafted products could be obtained. The mechanical behavior of the grafted films--especially in the water-swollen state--was examined and compared with that of the pure trunk polymer. In nearly all cases it was found that the tensile strength sigma B and the elongation at break epsilon R decreases as the grafting yield increases. Modification of GMA- and AAm-grafted films via chemical reactions was performed to create new functional groups of biomedical interest. In this manner a diol structure, a carboxylic acid structure, and a sulfonic acid group could be introduced in the grafted polymer. The water uptake of such modified films is increased markedly when compared with that of the unmodified samples

Structure and Modification of Electrode Materials for Protein Electrochemistry.

Science.gov (United States)

Jeuken, Lars J C

The interactions between proteins and electrode surfaces are of fundamental importance in bioelectrochemistry, including photobioelectrochemistry. In order to optimise the interaction between electrode and redox protein, either the electrode or the protein can be engineered, with the former being the most adopted approach. This tutorial review provides a basic description of the most commonly used electrode materials in bioelectrochemistry and discusses approaches to modify these surfaces. Carbon, gold and transparent electrodes (e.g. indium tin oxide) are covered, while approaches to form meso- and macroporous structured electrodes are also described. Electrode modifications include the chemical modification with (self-assembled) monolayers and the use of conducting polymers in which the protein is imbedded. The proteins themselves can either be in solution, electrostatically adsorbed on the surface or covalently bound to the electrode. Drawbacks and benefits of each material and its modifications are discussed. Where examples exist of applications in photobioelectrochemistry, these are highlighted.

Chemical modification as a probe of the topography and reactivity of horse-spleen apoferritin

International Nuclear Information System (INIS)

Wetz, K.; Crichton, R.R.; Louvain Univ.

1976-01-01

In apoferritin, but not in ferritin, 1.0 +- 0.1 cysteine residue per subunit can be modified. In ferritin 3.3 +- 0.3 lysine residues and 7.1 +- 0.7 carboxyl groups per subunit can be modified, whilst the corresponding values for apoferritin are 4.4 +- 0.4 lysine residues and 11.0 +- 0.4 carboxyl groups per subunit. Modification of lysine residues with maleic anhydride and of carboxyl groups with glycineamide in apoferritin which has been dissociated and denatured in guanidine hydrochloride leads to the introduction of 9.1 +- 0.5 maleyl groups per subunit and 22.0 +- 0.9 glycineamide residues per subunit. Whereas unmodified apoferritin subunit can be reassociated from guanidine hydrochloride to apoferritin monomer, the ability of maleylated apoferritin to reassociate is impaired. Apoferritin in which all the carboxyl group have been blocked with glycineamide cannot be reassociated to apoferritin and exists in solution as stable subunits. The modification of one cysteine residue per subunit, of 3 or 4 lysine per subunit or of 7 carboxyl groups per subunit has no effect on the catalytic activity of apoferritin. In contrast, the modification of 11 carboxyl groups per subunit completely abolishes the catalytic properties of the protein. We conclude that one or more carboxyl groups are essential for the catalytic activity of horse spleen apoferritin. (orig.) [de

Nuclear threshold effects and neutron strength function

International Nuclear Information System (INIS)

Hategan, Cornel; Comisel, Horia

2003-01-01

One proves that a Nuclear Threshold Effect is dependent, via Neutron Strength Function, on Spectroscopy of Ancestral Neutron Threshold State. The magnitude of the Nuclear Threshold Effect is proportional to the Neutron Strength Function. Evidence for relation of Nuclear Threshold Effects to Neutron Strength Functions is obtained from Isotopic Threshold Effect and Deuteron Stripping Threshold Anomaly. The empirical and computational analysis of the Isotopic Threshold Effect and of the Deuteron Stripping Threshold Anomaly demonstrate their close relationship to Neutron Strength Functions. It was established that the Nuclear Threshold Effects depend, in addition to genuine Nuclear Reaction Mechanisms, on Spectroscopy of (Ancestral) Neutron Threshold State. The magnitude of the effect is proportional to the Neutron Strength Function, in their dependence on mass number. This result constitutes also a proof that the origins of these threshold effects are Neutron Single Particle States at zero energy. (author)

Enzymatic Modification of Plant Cell Wall Polysaccharides

DEFF Research Database (Denmark)

Øbro, Jens; Hayashi, Takahisa; Mikkelsen, Jørn Dalgaard

2011-01-01

Plant cell walls are intricate structures with remarkable properties, widely used in almost every aspect of our life. Cell walls consist largely of complex polysaccharides and there is often a need for chemical and biochemical processing before industrial use. There is an increasing demand...... for sustainable processes that replace chemical treatments with white biotechnology. Plants can contribute significantly to this sustainable process by producing plant or microbialenzymes in planta that are necessary for plant cell wall modification or total degradation. This will give rise to superior food...... fibres, hydrocolloids, paper,textile, animal feeds or biofuels. Classical microbial-based fermentation systems could in the future face serious competition from plant-based expression systems for enzyme production. Plant expressed enzymes can either be targeted to specific cellular compartments...

Reduced chemical warfare agent sorption in polyurethane-painted surfaces via plasma-enhanced chemical vapor deposition of perfluoroalkanes.

Science.gov (United States)

Gordon, Wesley O; Peterson, Gregory W; Durke, Erin M

2015-04-01

Perfluoralkalation via plasma chemical vapor deposition has been used to improve hydrophobicity of surfaces. We have investigated this technique to improve the resistance of commercial polyurethane coatings to chemicals, such as chemical warfare agents. The reported results indicate the surface treatment minimizes the spread of agent droplets and the sorption of agent into the coating. The improvement in resistance is likely due to reduction of the coating's surface free energy via fluorine incorporation, but may also have contributing effects from surface morphology changes. The data indicates that plasma-based surface modifications may have utility in improving chemical resistance of commercial coatings.

A biological basis for the linear non-threshold dose-response relationship for low-level carcinogen exposure

International Nuclear Information System (INIS)

Albert, R.E.

1981-01-01

This chapter examines low-level dose-response relationships in terms of the two-stage mouse tumorigenesis model. Analyzes the feasibility of the linear non-threshold dose-response model which was first adopted for use in the assessment of cancer risks from ionizing radiation and more recently from chemical carcinogens. Finds that both the interaction of B(a)P with epidermal DNA of the mouse skin and the dose-response relationship for the initiation stage of mouse skin tumorigenesis showed a linear non-threshold dose-response relationship. Concludes that low level exposure to environmental carcinogens has a linear non-threshold dose-response relationship with the carcinogen acting as an initiator and the promoting action being supplied by the factors that are responsible for the background cancer rate in the target tissue

Chemical modification of fibers and fabrics with high-energy radiation

International Nuclear Information System (INIS)

Stannett, V.; Walsh, W.K.; Bittencourt, E.; Liepins, R.; Surles, J.R.

1977-01-01

Some fundamental considerations related to the radiation modification of fibers and fabrics are discussed. Experiments are described on the radiation ''grafting'' of various phosphorus- and bromine-containing vinyl monomers to polyester, cotton, and their blends to impart flame resistance. It was found that the flame retardancy was more efficient when the grafted polymer was located inside the fiber. The efficiency of the bromine containing polymers was found to be related to the bromine/aliphatic hydrogen ratio and to the thermal stability of the polymers. Experiments are also described illustrating the successful use of radiation processing with a number of vinyl monomers and oligomers to impart water sorbancy, for the bonding of nonwoven fabrics for fabric coating, and for the binding of pigment prints. 11 tables, 18 figures

Variable threshold algorithm for division of labor analyzed as a dynamical system.

Science.gov (United States)

Castillo-Cagigal, Manuel; Matallanas, Eduardo; Navarro, Iñaki; Caamaño-Martín, Estefanía; Monasterio-Huelin, Félix; Gutiérrez, Álvaro

2014-12-01

Division of labor is a widely studied aspect of colony behavior of social insects. Division of labor models indicate how individuals distribute themselves in order to perform different tasks simultaneously. However, models that study division of labor from a dynamical system point of view cannot be found in the literature. In this paper, we define a division of labor model as a discrete-time dynamical system, in order to study the equilibrium points and their properties related to convergence and stability. By making use of this analytical model, an adaptive algorithm based on division of labor can be designed to satisfy dynamic criteria. In this way, we have designed and tested an algorithm that varies the response thresholds in order to modify the dynamic behavior of the system. This behavior modification allows the system to adapt to specific environmental and collective situations, making the algorithm a good candidate for distributed control applications. The variable threshold algorithm is based on specialization mechanisms. It is able to achieve an asymptotically stable behavior of the system in different environments and independently of the number of individuals. The algorithm has been successfully tested under several initial conditions and number of individuals.

Process safety management for highly hazardous chemicals

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-02-01

Purpose of this document is to assist US DOE contractors who work with threshold quantities of highly hazardous chemicals (HHCs), flammable liquids or gases, or explosives in successfully implementing the requirements of OSHA Rule for Process Safety Management of Highly Hazardous Chemicals (29 CFR 1910.119). Purpose of this rule is to prevent releases of HHCs that have the potential to cause catastrophic fires, explosions, or toxic exposures.

Modification of Food Systems by Ultrasound

Directory of Open Access Journals (Sweden)

L. M. Carrillo-Lopez

2017-01-01

Full Text Available This review describes the mechanism, operation, and recent potential applications of ultrasound in various food systems, as well as the physical and chemical effects of ultrasound treatments on the conservation and modification of different groups of food. Acoustic energy has been recognized as an emerging technology with great potential for applications in the food industry. The phenomenon of acoustic cavitation, which modifies the physical, chemical, and functional properties of food, can be used to improve existing processes and to develop new ones. The combination of ultrasonic energy with a sanitizing agent can improve the effect of microbial reduction in foods and, thereby, their quality. Finally, it is concluded that the use of ultrasound in food is a very promising area of research; however, more research is still needed before applying this technology in a wider range of industrial sectors.

Cobalt surface modification during γ-Fe{sub 2}O{sub 3} nanoparticle synthesis by chemical-induced transition

Energy Technology Data Exchange (ETDEWEB)

Li, Junming [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Li, Jian, E-mail: aizhong@swu.edu.cn [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Chen, Longlong; Lin, Yueqiang; Liu, Xiaodong; Gong, Xiaomin [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Li, Decai [School of Mechanical and Control Engineering, Beijing Jiaotong University, Beijing 100044 (China)

2015-02-01

In the chemical-induced transition of FeCl{sub 2} solution, the FeOOH/Mg(OH){sub 2} precursor was transformed into spinel structured γ-Fe{sub 2}O{sub 3} crystallites, coated with a FeCl{sub 3}·6H{sub 2}O layer. CoCl{sub 2} surface modified γ-Fe{sub 2}O{sub 3} nanoparticles were prepared by adding Co(NO{sub 3}){sub 2} during the synthesis. CoFe{sub 2}O{sub 4} modified γ-Fe{sub 2}O{sub 3} nanoparticles were prepared by adding NaOH during the surface modification with Co(NO{sub 3}){sub 2}. The CoFe{sub 2}O{sub 4} layer grew epitaxially on the γ-Fe{sub 2}O{sub 3} crystallite to form a composite crystallite, which was coated by CoCl{sub 2}·6H{sub 2}O. The composite could not be distinguished using X-ray diffraction or transmission electron microscopy, since CoFe{sub 2}O{sub 4} and γ-Fe{sub 2}O{sub 3} possess similar spinel structures and lattice constants. X-ray photoelectron spectroscopy was used to distinguish them. The saturation magnetization and coercivity of the spinel structured γ-Fe{sub 2}O{sub 3}-based nanoparticles were related to the grain size. - Highlights: • γ-Fe{sub 2}O{sub 3} nanoparticles were synthesized by chemical induced transition. • CoCl{sub 2} modified nanoparticles were prepared by additional Co(NO{sub 3}){sub 2} during synthesization. • CoFe{sub 2}O{sub 4} modified nanoparticles were prepared by additional Co(NO{sub 3}){sub 2} and NaOH. • The magnetism of the nanoparticles is related to the grain size.

Enzymatic modification of phospholipids forfunctional applications and human nutrition

DEFF Research Database (Denmark)

Guo, Zheng; Vikbjerg, Anders / Falk; Xu, Xuebing

2005-01-01

analogs based on the latest understanding of pivotal role of phospholipids in manifold biological processes, exploration of remarkable application potentials of phospholipids in meliorating human health, as well as development of new chemical and biotechnological approaches applied to the modification...... design. This will of course provide fundamental bases also for the development of enzymatic technology to produce structured or modified phospholipids....

A New Wavelet Threshold Function and Denoising Application

Directory of Open Access Journals (Sweden)

Lu Jing-yi

2016-01-01

Full Text Available In order to improve the effects of denoising, this paper introduces the basic principles of wavelet threshold denoising and traditional structures threshold functions. Meanwhile, it proposes wavelet threshold function and fixed threshold formula which are both improved here. First, this paper studies the problems existing in the traditional wavelet threshold functions and introduces the adjustment factors to construct the new threshold function basis on soft threshold function. Then, it studies the fixed threshold and introduces the logarithmic function of layer number of wavelet decomposition to design the new fixed threshold formula. Finally, this paper uses hard threshold, soft threshold, Garrote threshold, and improved threshold function to denoise different signals. And the paper also calculates signal-to-noise (SNR and mean square errors (MSE of the hard threshold functions, soft thresholding functions, Garrote threshold functions, and the improved threshold function after denoising. Theoretical analysis and experimental results showed that the proposed approach could improve soft threshold functions with constant deviation and hard threshold with discontinuous function problems. The proposed approach could improve the different decomposition scales that adopt the same threshold value to deal with the noise problems, also effectively filter the noise in the signals, and improve the SNR and reduce the MSE of output signals.

Surface modification of cyclomatrix polyphosphazene microsphere by thiol-ene chemistry and lectin recognition

International Nuclear Information System (INIS)

Chen, Chen; Zhu, Xue-yan; Gao, Qiao-ling; Fang, Fei; Huang, Xiao-jun

2016-01-01

Graphical abstract: A new synthetic route leading to polyphosphazene cyclomatrix microsphere with various functional groups has achieved via thiol-ene click modification. Herein, hexacholorocyclophosphazene (HCCP) crosslinked with bisphenol-S and 4,4′-diallyl bisphenol-S to generate broadly dispersed microspheres. Thiol-ene modification under UV irradiation not only presented high efficiency and flexibility for post-functionalization, but also imposed no harm on global morphology and crosslinked skeleton of such microspheres. - Highlights: • Functional polyphosphazene microspheres with high chemical flexibility were synthesized by thiol-ene modification. • Polyphosphazene microspheres possessed high thermal stability. • Glycosylated polyphosphazene microspheres showed affinity to lectin Con-A, which inferred potential application in biomedicine. - Abstract: A new synthetic route leading to functional polyphosphazene cyclomatrix microsphere has been developed via thiol-ene click modification. Hexacholorocyclophosphazene (HCCP) was crosslinked with both bisphenol-S and 4,4′-diallyl bisphenol-S to obtain vinyl polyphosphazene microspheres (VPZM) in order to ensure high crosslinking degree and introduce vinyl moieties. Compared to the microspheres obtained by HCCP and bisphenol-S, the size of VPZM was broadly dispersed from 400 nm to 1.40 μm. Thiol-ene click reactions were carried out to attach functional groups, such as glucosyl, carboxyl, ester and dodecyl groups onto polyphosphazene microspheres, which demonstrated no change in morphology and size after modification. Solid state NMR (SSNMR) and Fourier transform infrared spectoscopy (FT-IR) results showed that the vinyl moieties were introduced in the period of crosslinking and functionalization was also successful via click reactions. Moreover, the microspheres presented a little difference in thermal properties after modification. Concanavalin A (Con-A) fluorescent adsorption was also observed for

Surface modification of cyclomatrix polyphosphazene microsphere by thiol-ene chemistry and lectin recognition

Energy Technology Data Exchange (ETDEWEB)

Chen, Chen; Zhu, Xue-yan; Gao, Qiao-ling; Fang, Fei; Huang, Xiao-jun, E-mail: hxjzxh@zju.edu.cn

2016-11-30

Graphical abstract: A new synthetic route leading to polyphosphazene cyclomatrix microsphere with various functional groups has achieved via thiol-ene click modification. Herein, hexacholorocyclophosphazene (HCCP) crosslinked with bisphenol-S and 4,4′-diallyl bisphenol-S to generate broadly dispersed microspheres. Thiol-ene modification under UV irradiation not only presented high efficiency and flexibility for post-functionalization, but also imposed no harm on global morphology and crosslinked skeleton of such microspheres. - Highlights: • Functional polyphosphazene microspheres with high chemical flexibility were synthesized by thiol-ene modification. • Polyphosphazene microspheres possessed high thermal stability. • Glycosylated polyphosphazene microspheres showed affinity to lectin Con-A, which inferred potential application in biomedicine. - Abstract: A new synthetic route leading to functional polyphosphazene cyclomatrix microsphere has been developed via thiol-ene click modification. Hexacholorocyclophosphazene (HCCP) was crosslinked with both bisphenol-S and 4,4′-diallyl bisphenol-S to obtain vinyl polyphosphazene microspheres (VPZM) in order to ensure high crosslinking degree and introduce vinyl moieties. Compared to the microspheres obtained by HCCP and bisphenol-S, the size of VPZM was broadly dispersed from 400 nm to 1.40 μm. Thiol-ene click reactions were carried out to attach functional groups, such as glucosyl, carboxyl, ester and dodecyl groups onto polyphosphazene microspheres, which demonstrated no change in morphology and size after modification. Solid state NMR (SSNMR) and Fourier transform infrared spectoscopy (FT-IR) results showed that the vinyl moieties were introduced in the period of crosslinking and functionalization was also successful via click reactions. Moreover, the microspheres presented a little difference in thermal properties after modification. Concanavalin A (Con-A) fluorescent adsorption was also observed for

Performance of New Thresholds of the Glasgow Blatchford Score in Managing Patients With Upper Gastrointestinal Bleeding

DEFF Research Database (Denmark)

Laursen, Stig B; Dalton, Harry R; Murray, Iain A

2015-01-01

BACKGROUND & AIMS: Upper gastrointestinal hemorrhage (UGIH) is a common cause of hospital admission. The Glasgow Blatchford score (GBS) is an accurate determinant of patients' risk for hospital-based intervention or death. Patients with a GBS of 0 are at low risk for poor outcome and could....... METHODS: We performed an observational study of 2305 consecutive patients presenting with UGIH at 4 centers (Scotland, England, Denmark, and New Zealand). The performance of each threshold and modification was evaluated based on sensitivity and specificity analyses, the proportion of low-risk patients...

Variable elimination in post-translational modification reaction networks with mass-action kinetics

DEFF Research Database (Denmark)

Feliu, Elisenda; Wiuf, Carsten

2013-01-01

We define a subclass of chemical reaction networks called post-translational modification systems. Important biological examples of such systems include MAPK cascades and two-component systems which are well-studied experimentally as well as theoretically. The steady states of such a system...

Environmental chemical exposures and human epigenetics

Science.gov (United States)

Hou, Lifang; Zhang, Xiao; Wang, Dong; Baccarelli, Andrea

2012-01-01

Every year more than 13 million deaths worldwide are due to environmental pollutants, and approximately 24% of diseases are caused by environmental exposures that might be averted through preventive measures. Rapidly growing evidence has linked environmental pollutants with epigenetic variations, including changes in DNA methylation, histone modifications and microRNAs. Environ mental chemicals and epigenetic changes All of these mechanisms are likely to play important roles in disease aetiology, and their modifications due to environmental pollutants might provide further understanding of disease aetiology, as well as biomarkers reflecting exposures to environmental pollutants and/or predicting the risk of future disease. We summarize the findings on epigenetic alterations related to environmental chemical exposures, and propose mechanisms of action by means of which the exposures may cause such epigenetic changes. We discuss opportunities, challenges and future directions for future epidemiology research in environmental epigenomics. Future investigations are needed to solve methodological and practical challenges, including uncertainties about stability over time of epigenomic changes induced by the environment, tissue specificity of epigenetic alterations, validation of laboratory methods, and adaptation of bioinformatic and biostatistical methods to high-throughput epigenomics. In addition, there are numerous reports of epigenetic modifications arising following exposure to environmental toxicants, but most have not been directly linked to disease endpoints. To complete our discussion, we also briefly summarize the diseases that have been linked to environmental chemicals-related epigenetic changes. PMID:22253299

Modification of the surface energy in isovalent nano-oxides prepared by chemical synthesis

International Nuclear Information System (INIS)

Miagava, J.; Gouvea, D.

2011-01-01

The phase stability of the nano-oxides depends on the bulk energy but it also depends on the surface energy. The difference of surface energy of the rutile and anatase phases result in a change of phase stability: TiO_2 without additives is stable as anatase when particles have nanometric size and a high specific surface area whereas rutile is stable when particles are larger. But this stability can be modified through the use of additives. Different studies demonstrate that additives segregate on the particle surface modifying the surface energy. In this work (1-X)TiO_2-XSnO_2 powders were synthesized by the polymeric precursor method with concentrations of 0 ≤ X ≤ 1. The specific surface area measurements demonstrate that the modification of the composition change the specific surface areas and it reaches a maximum at X = 0.005. The Raman spectroscopy demonstrates that a modification on the stability of the TiO_2 polymorphs occurs and the phase rutile is stabilized when SnO_2 is added to the nano powders.(author)

Membrane technology: in the chemical industry

National Research Council Canada - National Science Library

Nunes, S. P; Peinemann, K. V

2001-01-01

... terephthalate) 15 22 23 32 37 5 5.1 5.2 5.3 5.4 Surface Modification of Membranes Chemical Oxidation 39 Plasma Treatment 40 Classical Organic Reactions 41 Polymer Grafting 41 39VI Contents 6 6.1 ...

Structural modifications under reactive atmosphere of cobalt catalysts; Modifications structurales sous atmospheres reactionnelles de catalyseurs a base de cobalt

Energy Technology Data Exchange (ETDEWEB)

Ducreux, O.

1999-11-23

The purpose of this work was to develop in situ methods under reactive dynamic conditions (XRD and Fourier transform infrared spectroscopy) to describe the active phase structure in order to understand Fischer-Tropsch catalyst behaviour and improve the natural gas conversion process performance. Experiments were designed to correlate structural modifications with catalytic results. The effect of ruthenium used as a promoter has also been studied. The impregnation process increases cobalt-support interaction. The presence of ruthenium promoter reduces this effect. Interactions between Co{sub 3}O{sub 4} oxide and support play an important role in the reducibility of cobalt and in the resulting metal structure. This in turn strongly influences the catalytic behaviour. Our results show a close correlation between structure modification and reactivity in the systems studied. Cobalt metal and CO can react to form a carbide Co{sub 2}C under conditions close to those of the Fischer-Tropsch synthesis. This carbide formation seems to be related to a deactivation process. The presence of interstitial carbon formed by dissociation of CO is proposed as a key to understanding the mechanism of the Fischer-Tropsch reaction. A specific catalyst activation treatment was developed to increase the catalytic activity. This work permits correlation of materials structure with their chemical properties and demonstrates the contribution of in situ physico-chemical characterisation methods to describe solids under reactive atmosphere. (author)

Rayleigh-type parametric chemical oscillation

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Shyamolina; Ray, Deb Shankar, E-mail: pcdsr@iacs.res.in [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

2015-09-28

We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

Rayleigh-type parametric chemical oscillation.

Science.gov (United States)

Ghosh, Shyamolina; Ray, Deb Shankar

2015-09-28

We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

Threshold behavior in electron-atom scattering

International Nuclear Information System (INIS)

Sadeghpour, H.R.; Greene, C.H.

1996-01-01

Ever since the classic work of Wannier in 1953, the process of treating two threshold electrons in the continuum of a positively charged ion has been an active field of study. The authors have developed a treatment motivated by the physics below the double ionization threshold. By modeling the double ionization as a series of Landau-Zener transitions, they obtain an analytical formulation of the absolute threshold probability which has a leading power law behavior, akin to Wannier's law. Some of the noteworthy aspects of this derivation are that the derivation can be conveniently continued below threshold giving rise to a open-quotes cuspclose quotes at threshold, and that on both sides of the threshold, absolute values of the cross sections are obtained

Enhanced understanding of the relationship between chemical modification and mechanical properties of wood

Science.gov (United States)

Charles R. Frihart; Daniel J. Yelle; John Ralph; Robert J. Moon; Donald S. Stone; Joseph E. Jakes

2008-01-01

Chemical additions to wood often change its bulk properties, which can be determined using conventional macroscopic mechanical tests. However, the controlling interactions between chemicals and wood take place at and below the scale of individual cells and cell walls. To better understand the effects of chemical additions to wood, we have adapted and extended two...

Chemical modification of graphene aerogels for electrochemical capacitor applications.

Science.gov (United States)

Hong, Jin-Yong; Wie, Jeong Jae; Xu, Yu; Park, Ho Seok

2015-12-14

Graphene aerogel is a relatively new type of aerogel that is ideal for energy storage applications because of its large surface area, high electrical conductivity and good chemical stability. Also, three dimensional interconnected macropores offer many advantages such as low density, fast ion and mass transfer, and easy access to storage sites. Such features allow graphene aerogels to be intensively applied for electrochemical capacitor applications. Despite the growing interest in graphene aerogel-based electrochemical capacitors, however, the graphene aerogels still suffer from their low capacitive performances and high fragility. Both relatively low capacitance and brittleness of physically crosslinked graphene aerogels remain a critical challenge. Until now, a number of alternative attempts have been devoted to overcome these shortcomings. In this perspective, we summarize the recent research progress towards the development of advanced graphene aerogel-based electrochemical capacitors according to the different approaches (e.g. porosity, composition and structure controls). Then, the recently proposed chemical strategies to improve the capacitive performances and mechanical durability of graphene aerogels for practical applications are highlighted. Finally, the current challenges and perspectives in this emerging material are also discussed.

2001 Toxic Chemical Release Inventory Emergency Planning and Community Right to Know Act SEC 313

International Nuclear Information System (INIS)

ZALOUDEK, D.E.

2002-01-01

Pursuant to section 313 of the Emergency Planning and Community Right-To-Know Act of 1986 (EPCRA), and Executive Order 13148, Greening the Government Through Leadership in Environmental Management, the US Department of Energy has prepared and submitted a Toxic Chemical Release Inventory for the Hanford Site covering activities performed during calendar year 2001. EPCRA Section 313 requires facilities that manufacture, process, or otherwise use listed toxic chemicals in quantities exceeding established threshold levels to report total annual releases of those chemicals. During calendar year 2001, Hanford Site activities resulted in one chemical used in amounts exceeding an activity threshold. Accordingly, the Hanford Site 2001 Toxic Chemical Release Inventory, DOE/RL-2002-37, includes total annual amount of lead released to the environment, transferred to offsite locations, and otherwise managed as waste

Multifunctional surface modification of silk fabric via graphene oxide repeatedly coating and chemical reduction method

Science.gov (United States)

Cao, Jiliang; Wang, Chaoxia

2017-05-01

Multifunctional silk fabrics with electrical conductive, anti-ultraviolet and water repellent were successfully prepared by surface modification with graphene oxide (GO). The yellow-brown GO deposited on the surface of silk fabric was converted into graphitic black reduced graphene (RGO) by sodium hydrosulfite. The surface properties of silk fabrics were changed by repeatedly RGO coating process, which have been proved by SEM and XPS. The SEM results showed that the RGO sheets were successive form a continuously thin film on the surface of silk fabrics, and the deposition of GO or RGO also can be proved by XPS. The electrical conductivity was tested by electrical surface resistance value of the silk fabric, the surface resistance decreased with increasing of RGO surface modification times, and a low surface resistance value reached to 3.24 KΩ cm-1 after 9 times of modification, indicating the silk obtained excellent conductivity. The UPF value of one time GO modification silk fabric (silk-1RGO) was enhanced significantly to 24.45 in comparison to 10.40 of original silk. The contact angle of RGO coating silk samples was all above of 120°. The durability of RGO coated silk fabrics was tested by laundering. The electrical surface resistance of silk-4RGO (65.74 KΩ cm-1), silk-6RGO (15.54 KΩ cm-1) and silk-8RGO (3.86 KΩ cm-1) fabrics was up to 86.82, 22.30 and 6.57 KΩ cm-1 after 10 times of standard washing, respectively. The UPF value, contact angle and color differences of RGO modified silk fabric slightly changed before and after 10 times of standard washing. Therefore, the washing fastness of electric conduction, anti-ultraviolet and water repellent multifunctional silk fabrics was excellent.

Chemical modification of protein A chromatography ligands with polyethylene glycol. I: Effects on IgG adsorption equilibrium, kinetics, and transport.

Science.gov (United States)

Weinberg, Justin; Zhang, Shaojie; Crews, Gillian; Carta, Giorgio; Przybycien, Todd

2018-04-20

Chemical modification of Protein A (ProA) chromatography ligands with polyethylene glycol (PEGylation) has been proposed as a strategy to increase the process selectivity and resin robustness by providing the ligand with a steric repulsion barrier against non-specific binding. This article comprises a comprehensive study of IgG adsorption and transport in Repligen CaptivA PriMAB resin with PEGylated ProA ligands that are modified using 5.2 and 21.5 kDa PEG chains. We studied the impact of the molecular weight of the PEG as well as the extent of PEGylation for the 5.2 kDa PEG modification. In all cases, PEGylation of ProA ligands decreases the resin average pore size, particle porosity, and static binding capacity for IgG proportional to the volume of conjugated PEG in the resin. Resin batch uptake experiments conducted in bulk via a stirred-tank system and with individual resin particles under confocal laser scanning microscopy suggests that PEGylation introduces heterogeneity into IgG binding kinetics: a fraction of the IgG binding sites are transformed from typical fast association kinetic behavior to slow kinetic behavior. pH gradient elution experiments of an IgG molecule on the modified resins show an increase in IgG elution pH for all modified resins, implying a decrease in IgG-ProA binding affinity on modification. Despite losses in static binding capacity for all resins with PEGylated ligands, the loss of dynamic binding capacity at 10% breakthrough (DBC 10% ) ranged more broadly from almost 0-47% depending on the PEG molecular weight and the extent of PEGylation. Minimal losses in DBC 10% were observed with a low extent of PEGylation with a smaller molecular weight PEG, while higher losses were observed at higher extents of PEGylation and with higher molecular weight PEG due to decreased static binding capacity and increased mass transfer resistance. This work provides insight into the practical implications for resin performance if PEGylation is

Double Photoionization Near Threshold

Science.gov (United States)

Wehlitz, Ralf

2007-01-01

The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

Research Progress of Optical Fabrication and Surface-Microstructure Modification of SiC

Directory of Open Access Journals (Sweden)

Fang Jiang

2012-01-01

Full Text Available SiC has become the best candidate material for space mirror and optical devices due to a series of favorable physical and chemical properties. Fine surface optical quality with the surface roughness (RMS less than 1 nm is necessary for fine optical application. However, various defects are present in SiC ceramics, and it is very difficult to polish SiC ceramic matrix with the 1 nm RMS. Surface modification of SiC ceramics must be done on the SiC substrate. Four kinds of surface-modification routes including the hot pressed glass, the C/SiC clapping, SiC clapping, and Si clapping on SiC surface have been reported and reviewed here. The methods of surface modification, the mechanism of preparation, and the disadvantages and advantages are focused on in this paper. In our view, PVD Si is the best choice for surface modification of SiC mirror.

2004 Toxic Chemical Release Inventory Report for the Emergency Planning and Community Right-to-Know Act of 1986, Title III, Section 313

Energy Technology Data Exchange (ETDEWEB)

M. Stockton

2006-01-15

Section 313 of Emergency Planning and Community Right-to-Know Act (EPCRA) specifically requires facilities to submit a Toxic Chemical Release Inventory Report (Form R) to the U.S. Environmental Protection Agency (EPA) and state agencies if the owners and operators manufacture, process, or otherwise use any of the listed toxic chemicals above listed threshold quantities. EPA compiles this data in the Toxic Release Inventory database. Form R reports for each chemical over threshold quantities must be submitted on or before July 1 each year and must cover activities that occurred at the facility during the previous year. For reporting year 2004, Los Alamos National Laboratory (LANL or the Laboratory) submitted Form R reports for lead compounds, nitric acid, and nitrate compounds as required under the EPCRA Section 313. No other EPCRA Section 313 chemicals were used in 2004 above the reportable thresholds. This document provides a description of the evaluation of EPCRA Section 313 chemical use and threshold determinations for LANL for calendar year 2004, as well as background information about data included on the Form R reports.

Multiphoton microscopy guides neurotrophin modification with poly(ethylene glycol) to enhance interstitial diffusion

Science.gov (United States)

Stroh, Mark; Zipfel, Warren R.; Williams, Rebecca M.; Ma, Shu Chin; Webb, Watt W.; Saltzman, W. Mark

2004-07-01

Brain-derived neurotrophic factor (BDNF) is a promising therapeutic agent for the treatment of neurodegenerative diseases. However, the limited distribution of this molecule after administration into the brain tissue considerably hampers its efficacy. Here, we show how multiphoton microscopy of fluorescently tagged BDNF in brain-tissue slices provides a useful and rapid screening method for examining the diffusion of large molecules in tissues, and for studying the effects of chemical modifications-for example, conjugating with polyethylene glycol (PEG)-on the diffusion constant. This single variable, obtained by monitoring short-term diffusion in real time, can be effectively used for rational drug design. In this study on fluorescently tagged BDNF and BDNF-PEG, we identify slow diffusion as a major contributing factor to the limited penetration of BDNF, and demonstrate how chemical modification can be used to overcome this barrier.

Enzyme-Catalyzed Modifications of Polysaccharides and Poly(ethylene glycol

Directory of Open Access Journals (Sweden)

H. N. Cheng

2012-06-01

Full Text Available Polysaccharides are used extensively in various industrial applications, such as food, adhesives, coatings, construction, paper, pharmaceuticals, and personal care. Many polysaccharide structures need to be modified in order to improve their end-use properties; this is mostly done through chemical reactions. In the past 20 years many enzyme-catalyzed modifications have been developed to supplement chemical derivatization methods. Typical reactions include enzymatic oxidation, ester formation, amidation, glycosylation, and molecular weight reduction. These reactions are reviewed in this paper, with emphasis placed on the work done by the authors. The polymers covered in this review include cellulosic derivatives, starch, guar, pectin, and poly(ethylene glycol.

Reactive modification of polyesters and their blends

Science.gov (United States)

Wan, Chen

2004-12-01

As part of a broader research effort to investigate the chemical modification of polyesters by reactive processing a low molecular weight (MW) unsaturated polyester (UP) and a higher MW saturated polyester, polyethylene terephthalate (PET), alone or blended with polypropylene (PP) were melt processed in a batch mixer and continuous twin screw extruders. Modification was monitored by on-line rheology and the products were characterized primarily by off-line rheology, morphology and thermal analysis. Efforts were made to establish processing/property relationships and provide an insight of the accompanying structural changes. The overall response of the reactively modified systems was found to be strongly dependent on the component characteristics, blend composition, type and concentrations of reactive additives and processing conditions. The work concluded that UP can be effectively modified through reactive melt processing. Its melt viscosity and MW can be increased through chemical reactions between organic peroxides (POX) and chain unsaturation or between MgO and carboxyl/hydroxyl end groups. Reactive blending of PP/UP blends through peroxide modification gave finer and more uniform morphology than unreacted blends and at a given PP/UP weight ratio more thermoplastic elastomers-like rheological behavior. This is due to the continuously decreasing viscosity ratio of PP/UP towards unity by the competing reactions between POX and the blend components and formation of PP-UP copolymers which serve as in-situ compatibilizers to promote better interfacial adhesion. Kinetics of the competing reactions were analyzed through a developed model. In addition to POX concentration and mixing efficiency, rheology and morphology of UP/PP bends were significantly affected by the addition of inorganic and organic coagents. Addition of coagents such as a difunctional maleimide, MgO and/or an anhydride functionalized PP during reactive blending offers effective means for tailoring

Effect of chemical treatment on thermal properties of fibers from pineapple

International Nuclear Information System (INIS)

Fernandes, Rafael I.M.; Mulinari, Daniella R.; Carvalho, Kelly C.C.; Conejo, Luiza dos Santos; Voorwald, Herman J.C.; Cioffi, Maria Odila H.

2009-01-01

In this work the effect of the chemical modification of natural fibres from of pineapple fibres with alkaline solution was studied. After modification the in nature and modified fibres were analyzed by XRD diffractometry and thermogravimetry with objective to evaluate influence chemical treatment in surface and in the thermal properties fibres. With the obtained results it was possible to verify an increase of 10.4 % in the crystallinity index of fibres beyond the increase around 4.5% in the degradation temperature, what it indicates an increase in the stability thermal of the fibres. (author)

Investigation of electrophysical properties of allotropic modifications of carbon in the range of temperatures 140-400 K

Science.gov (United States)

Goshev, A. A.; Eseev, M. K.; Volkov, A. S.; Lyah, N. L.

2017-09-01

The paper presents the results of the investigation of allotropic modifications of carbon (coal, graphite, fullerenes, CNTs. Dependences of conductivity on the field frequency in the temperature range 140-400 K are presented. The characteristic features associated with the structure and types of hybridization are revealed. Calculation of the activation energy of carriers was performed. As well article presents experimental study of electrical properties of polymeric composites, reinforced different types of allotropic modifications of carbon (CNTs, graphite, fullerenes, coal) in alternating electrical field in frequency band from 0.01 Hz to 10 MHz. The threshold of percolation of polymer composites with various types of additives and their influence for conduction properties was estimated.

Chemical modification of HTPB for application as polymeric additives for diesel fuel. 1 - phenyl ethers; Modificacao quimicado PBLH para aplicacao como aditivos polimericos para oleo diesel. 1. eteres fenilicos

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Agne R.; Prezibella, Alysson M.; Ferraz, Fernando A.; Soldi, Rafael A.; Oliveira, Angelo R.S.; Cesar-Oliveira, Maria Aparecida F. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Quimica. Lab. de Polimeros Sinteticos

2007-07-01

The petroleum industry faces several problems related to the crystallization of paraffins, in petroleum and its derivatives, with the reduction of the service temperature. To solve this problem polymeric additives are used, of which the esters have been enough studied in several areas of the world, except in Brazil. In this work, this class of pour point depressant additives it was obtained through the chemical modification of Hydroxyl Terminate Polybutadiene (HTPB) that present a hydrocarbon chemical structure containing one double bound in each repetitive unit and hydroxyl groups of the primary and secondary allylic types - functional groups potentially reactive. The obtained products were characterized by Fourier transformed infrared spectroscopy and nuclear magnetic resonance, and they are being tested as additive for the pour point reduction of a diesel oil samples (REPAR-PETROBRAS). (author)

Factors modifying sensitivity to carcinogens and the problem of threshold in carcinogenesis

International Nuclear Information System (INIS)

Anisimov, V.N.

1983-01-01

Maximum allowable concentrations of chemical carcinogens and dose rates of ionizing radiation have been under extensive study both experimentally and epidemiologically. The problem of the carcinogenic hazards of low-level radiation is a very difficult one: in epidemiological studies it is hard to take into account the many factors (e.g. diseases, diet, genetic peculiarities) that may affect sensitivity to radiation; in experimental studies it is hard to extrapolate with accuracy from one species to another or from the individual threshold to that of the whole population. Age, enzyme activity, sex, and DNA repair capability also modify sensitivity to radiation; when factors such as these are better understood it is expected that epidemiological studies will give a solution that allows estimation of the carcinogenic risk from low-level radiation and hence establishment of a threshold dose. (author)

ASTM Data Banks and Chemical Information Sources

Science.gov (United States)

Batik, Albert; Hale, Eleanor

1972-01-01

Among the data described are infrared indexes, mass spectral data, chromatographic data, X-ray emmission data, odor and taste threshold data, and thermodynamics data. This paper provides the chemical documentarian a complete reference source to a wide variety of analytical data. (Author/NH)

Determination of copper binding in Pseudomonas putida CZ1 by chemical modifications and X-ray absorption spectroscopy.

Science.gov (United States)

Chen, XinCai; Shi, JiYan; Chen, YingXu; Xu, XiangHua; Chen, LiTao; Wang, Hui; Hu, TianDou

2007-03-01

Previously performed studies have shown that Pseudomonas putida CZ1 biomass can bind an appreciable amount of Cu(II) and Zn(II) ions from aqueous solutions. The mechanisms of Cu- and Zn-binding by P. putida CZ1 were ascertained by chemical modifications of the biomass followed by Fourier transform infrared and X-ray absorption spectroscopic analyses of the living or nonliving cells. A dramatic decrease in Cu(II)- and Zn(II)-binding resulted after acidic methanol esterification of the nonliving cells, indicating that carboxyl functional groups play an important role in the binding of metal to the biomaterial. X-ray absorption spectroscopy was used to determine the speciation of Cu ions bound by living and nonliving cells, as well as to elucidate which functional groups were involved in binding of the Cu ions. The X-ray absorption near-edge structure spectra analysis showed that the majority of the Cu was bound in both samples as Cu(II). The fitting results of Cu K-edge extended X-ray absorption fine structure spectra showed that N/O ligands dominated in living and nonliving cells. Therefore, by combining different techniques, our results indicate that carboxyl functional groups are the major ligands responsible for the metal binding in P. putida CZ1.

Chemical bonding modifications of tetrahedral amorphous carbon and nitrogenated tetrahedral amorphous carbon films induced by rapid thermal annealing

International Nuclear Information System (INIS)

McCann, R.; Roy, S.S.; Papakonstantinou, P.; Bain, M.F.; Gamble, H.S.; McLaughlin, J.A.

2005-01-01

Tetrahedral amorphous carbon (ta-C) and nitrogenated tetrahedral amorphous carbon films (ta-CN x ), deposited by double bend off plane Filtered Vacuum Cathodic Arc were annealed up to 1000 deg. C in flowing argon for 2 min. Modifications on the chemical bonding structure of the rapidly annealed films, as a function of temperature, were investigated by NEXAFS, X-ray photoelectron and Raman spectroscopies. The interpretation of these spectra is discussed. The results demonstrate that the structure of undoped ta-C films prepared at floating potential with an arc current of 80 A remains stable up to 900 deg. C, whereas that of ta-CN x containing 12 at.% nitrogen is stable up to 700 deg. C. At higher temperatures, all the spectra indicated the predominant formation of graphitic carbon. Through NEXAFS studies, we clearly observed three π* resonance peaks at the ' N K edge structure. The origin of these three peaks is not well established in the literature. However our temperature-dependant study ascertained that the first peak originates from C=N bonds and the third peak originates from the incorporation of nitrogen into the graphite like domains

Modification of optical and electrical properties of chemical bath deposited SnS using O{sub 2} plasma treatments

Energy Technology Data Exchange (ETDEWEB)

Gómez, A. [Facultad de Ciencias, Universidad Autónoma del Estado de México, Estado de México, México (Mexico); Martínez, H., E-mail: hm@fis.unam.mx [Instituto de Ciencias Fisicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico); Calixto-Rodríguez, M. [Centro de Investigación en Energía, Universidad Autónoma del Estado de México, Estado de México, México (Mexico); Avellaneda, D. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, México (Mexico); Reyes, P.G. [Facultad de Ciencias, Universidad Autónoma del Estado de México, Estado de México, México (Mexico); Flores, O. [Instituto de Ciencias Fisicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico)

2013-06-15

In this paper, we report modifications of structural and optical, electrical properties that occur in tin sulphide (SnS) treated in O{sub 2} plasma. The SnS thin films were deposited by chemical bath deposition technique. The samples were treated in an O{sub 2} plasma discharge at 3 Torr of pressure discharge, a discharge voltage of 2.5 kV and 20 mA of discharge current. The prepared and treated thin films were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The photoconductivity and electrical effects of SnS have been studied. The SnS thin films had an orthorhombic crystalline structure. With the plasma treatment the optical gap and electrical properties of the SnS films changed from 1.61 to 1.84 eV, for 3.9 × 10{sup 5} to 10.42 Ω cm, respectively. These changes can be attributed to an increase in electron density, percolation effects due to porosity, surface degradation/etching that is an increase in surface roughness, where some structural changes related to crystallinity occurs like a high grain size as revealed by SEM images.

Abstracts Book of 41. Scientific Assembly of Polish Chemical Society and Association of Engineers and Technicians of Chemical Industry

International Nuclear Information System (INIS)

1998-01-01

Scientific Assembly of Polish Chemical Society and Association of Engineers and Technicians of Chemical Industry is the most important scientific forum of Polish Chemists. The state of the art in many basic, fundamental and applied investigations has been presented and discussed. The following scientific sessions and microsymposia have been proposed: theoretical chemistry; molecular interactions; metal compounds - chemical, physical, electronic and biological aspects; catalysis and surface physico-chemistry; polymers - radiochemistry, modifications, physics and analytical methods; organic and bioorganic chemistry; physico-chemistry of condensed matter; chemical metallurgy; environmental protection; inorganic technology; chemistry and technology of coal; radiation chemistry; analytical chemistry; chemical engineering; young scientists forum; chemical didactics; petrochemistry; energetic materials; membranes and membrane processes; medical chemistry

Thresholds for HLB vector control in infected commercial citrus and compatibility with biological control

OpenAIRE

Monzo, C.; Hendricks, K.; Roberts, P.; Stansly, P. A.

2014-01-01

Control of the HLB vector, Diaphorina citri Kuwayama, is considered a basic component for management this disease, even in a high HLB incidence scenario. Such control is mostly chemically oriented. However, over use of insecticides would increase costs and be incompatible with biological control. Establishment of economic thresholds for psyllid control under different price scenarios could optimize returns on investment.

Printing-assisted surface modifications of patterned ultrafiltration membranes

International Nuclear Information System (INIS)

Wardrip, Nathaniel C.; Dsouza, Melissa; Urgun-Demirtas, Meltem; Snyder, Seth W.

2016-01-01

Understanding and restricting microbial surface attachment will enhance wastewater treatment with membranes. We report a maskless lithographic patterning technique for the generation of patterned polymer coatings on ultrafiltration membranes. Polyethylene glycol, zwitterionic, or negatively charged hydrophilic polymer compositions in parallel- or perpendicular-striped patterns with respect to feed flow were evaluated using wastewater. Membrane fouling was dependent on the orientation and chemical composition of the coatings. Modifications reduced alpha diversity in the attached microbial community (Shannon indices decreased from 2.63 to 1.89) which nevertheless increased with filtration time. Sphingomonas species, which condition membrane surfaces and facilitate cellular adhesion, were depleted in all modified membranes. Microbial community structure was significantly different between control, different patterns, and different chemistries. Lastly, this study broadens the tools for surface modification of membranes with polymer coatings and for understanding and optimization of antifouling surfaces.

Surface modification and functionalization of metal and metal oxide nanoparticles by organic ligands

NARCIS (Netherlands)

Neouze, M.A.; Schubert, U.S.

2008-01-01

Metal or metal oxide nanoparticles possess unique features compared to equivalent larger-scale materials. For applications, it is often necessary to stabilize or functionalize such nanoparticles. Thus, modification of the surface of nanoparticles is an important chemical challenge. In this survey,

Chemical characterization of the acid alteration of diesel fuel: Non-targeted analysis by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry with tile-based Fisher ratio and combinatorial threshold determination.

Science.gov (United States)

Parsons, Brendon A; Pinkerton, David K; Wright, Bob W; Synovec, Robert E

2016-04-01

The illicit chemical alteration of petroleum fuels is of keen interest, particularly to regulatory agencies that set fuel specifications, or taxes/credits based on those specifications. One type of alteration is the reaction of diesel fuel with concentrated sulfuric acid. Such reactions are known to subtly alter the chemical composition of the fuel, particularly the aromatic species native to the fuel. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) is well suited for the analysis of diesel fuel, but may provide the analyst with an overwhelming amount of data, particularly in sample-class comparison experiments comprised of many samples. Tile-based Fisher-ratio (F-ratio) analysis reduces the abundance of data in a GC×GC-TOFMS experiment to only the peaks which significantly distinguish the unaltered and acid altered sample classes. Three samples of diesel fuel from differently branded filling stations were each altered to discover chemical features, i.e., analyte peaks, which were consistently changed by the acid reaction. Using different fuels prioritizes the discovery of features likely to be robust to the variation present between fuel samples and may consequently be useful in determining whether an unknown sample has been acid altered. The subsequent analysis confirmed that aromatic species are removed by the acid alteration, with the degree of removal consistent with predicted reactivity toward electrophilic aromatic sulfonation. Additionally, we observed that alkenes and alkynes were also removed from the fuel, and that sulfur dioxide or compounds that degrade to sulfur dioxide are generated by the acid alteration. In addition to applying the previously reported tile-based F-ratio method, this report also expands null distribution analysis to algorithmically determine an F-ratio threshold to confidently select only the features which are sufficiently class-distinguishing. When applied to the acid

Modeling chemical and topological disorder in irradiation-amorphized silicon carbide

International Nuclear Information System (INIS)

Yuan Xianglong; Hobbs, Linn W.

2002-01-01

In order to explore the relationship of chemical disorder to topological disorder during irradiation-induced amorphization of silicon carbide, a topological analysis of homonuclear bond distribution, atom coordination number and network ring size distribution has been carried out for imposed simulated disorder, equilibrated with molecular dynamics (MD) procedures utilizing a Tersoff potential. Starting configurations included random atom positions, β-SiC coordinates chemically disordered over a range of chemical disorder parameters and atom coordinates generated from earlier MD simulations of embedded collision cascades. For random starting positions in embedded simulations, the MD refinement converged to an average Si coordination of 4.3 and an average of 1.4 Si-Si and 1.0 C-C bonds per Si and C site respectively. A chemical disorder threshold was observed (χ≡N C-C /N Si-C >0.3-0.4), below which range MD equilibration resulted in crystalline behavior at all temperatures and above which a glass transition was observed. It was thus concluded that amorphization is driven by a critical concentration of homonuclear bonds. About 80% of the density change at amorphization was attributable to threshold chemical disorder, while significant topological changes occurred only for larger values of the chemical disorder parameter

Influence of soy protein’s structural modifications on their microencapsulation properties: a-tocopherol microparticles preparation

OpenAIRE

Nesterenko, Alla; Alric, Isabelle; Silvestre, Françoise; Durrieu, Vanessa

2012-01-01

Enzymatic and chemical modifications of soy protein isolate (SPI) were studied in order to improve SPI properties for their use as wall material for a-tocopherol microencapsulation by spray-drying. The structural modifications of SPI by enzymatic hydrolysis and/or N-acylation were carried out in aqueous media without any use of organic solvent neither surfactant. Emulsions from aqueous solutions of native or modified SPI and hydrophobic a-tocopherol, were prepared and spray-dri...

Small-threshold behaviour of two-loop self-energy diagrams: two-particle thresholds

International Nuclear Information System (INIS)

Berends, F.A.; Davydychev, A.I.; Moskovskij Gosudarstvennyj Univ., Moscow; Smirnov, V.A.; Moskovskij Gosudarstvennyj Univ., Moscow

1996-01-01

The behaviour of two-loop two-point diagrams at non-zero thresholds corresponding to two-particle cuts is analyzed. The masses involved in a cut and the external momentum are assumed to be small as compared to some of the other masses of the diagram. By employing general formulae of asymptotic expansions of Feynman diagrams in momenta and masses, we construct an algorithm to derive analytic approximations to the diagrams. In such a way, we calculate several first coefficients of the expansion. Since no conditions on relative values of the small masses and the external momentum are imposed, the threshold irregularities are described analytically. Numerical examples, using diagrams occurring in the standard model, illustrate the convergence of the expansion below the first large threshold. (orig.)

Nanoscale surface modification for enhanced biosensing a journey toward better glucose monitoring

CERN Document Server

Zhang, Guigen

2015-01-01

This book gives a comprehensive overview of electrochemical-based biosensors and their crucial components. Practical examples are given throughout the text to illustrate how the performance of electrochemical-based biosensors can be improved by nanoscale surface modification and how an optimal design can be achieved. All essential aspects of biosensors are considered, including electrode functionalization, efficiency of the mass transport of reactive species, and long term durability and functionality of the sensor. This book also: ·       Explains how the performance of an electrochemical-based biosensor can be improved by nanoscale surface modification ·       Gives readers the tools to evaluate and improve the performance of a biosensor with a multidisciplinary approach that considers electrical, electrostatic, electrochemical, chemical, and biochemical events ·       Links the performance of a sensor to the various governing physical and chemical principles so readers can fully unders...

Plasma immersion ion implantation for the efficient surface modification of medical materials

International Nuclear Information System (INIS)

Slabodchikov, Vladimir A.; Borisov, Dmitry P.; Kuznetsov, Vladimir M.

2015-01-01

The paper reports on a new method of plasma immersion ion implantation for the surface modification of medical materials using the example of nickel-titanium (NiTi) alloys much used for manufacturing medical implants. The chemical composition and surface properties of NiTi alloys doped with silicon by conventional ion implantation and by the proposed plasma immersion method are compared. It is shown that the new plasma immersion method is more efficient than conventional ion beam treatment and provides Si implantation into NiTi surface layers through a depth of a hundred nanometers at low bias voltages (400 V) and temperatures (≤150°C) of the substrate. The research results suggest that the chemical composition and surface properties of materials required for medicine, e.g., NiTi alloys, can be successfully attained through modification by the proposed method of plasma immersion ion implantation and by other methods based on the proposed vacuum equipment without using any conventional ion beam treatment

Chemically Modified Polyvinyl Chloride for Removal of Thionine Dye (Lauth’s Violet

Directory of Open Access Journals (Sweden)

Helena Ma A. M. M. S. Ali

2017-11-01

Full Text Available The chemical modification of hydrophobic polymer matrices is an alternative way to elchange their surface properties. The introduction of sulfonic groups in the polymer changes the surface properties such as adhesion, wettability, catalytic ability, and adsorption capacity. This work describes the production and application of chemically modified polyvinyl chloride (PVC as adsorbent for dyes removal. Chemical modification of PVC was evaluated by infrared spectroscopy and elemental analysis, which indicated the presence of sulfonic groups on PVC. The chemically modified PVC (PVCDS showed an ion exchange capacity of 1.03 mmol−1, and efficiently removed the thionine dye (Lauth’s violet from aqueous solutions, reaching equilibrium in 30 min. The adsorption kinetics was better adjusted for a pseudo second order model. This result indicates that the adsorption of thionine onto PVCDS occurs by chemisorption. Among the models for the state of equilibrium, SIPS and Langmuir exhibited the best fit to the experimental results and PVCDS showed high adsorption capacities (370 mg−1. Thus, it is assumed that the system presents homogeneous characteristics to the distribution of active sites. The modification promoted the formation of surface characteristics favorable to the dye adsorption by the polymer.

Modification of biomolecules and combined actions by radiation

International Nuclear Information System (INIS)

Kim, Jin Kyu; Lee, J. W.; Kim, J. H.; Choi, J. I.; Song, B. S.; Kim, J. K.; Park, J. H.; Lee, Y. J.; Ryu, S. H.; Sung, N. Y.; Cha, M. K.; Nam, J. Y.; Park, J. Y.; Cho, E. R.; Ryu, T. H.

2011-12-01

Advanced Radiation Technology Institute is a government-supported institute for radiation research and application. It has focused on development of fundamentals for radiation applications based on the existing radiation technology, and on enhancement of biological effectiveness of radiation through theoretical approach to the combined actions of radiation with another factor. Application of radiation technology together with the existing technologies to enhance the physical, chemical, biological characteristics through modification of biomolecules resulted in creation of de novo materials of scientific and industrial values. A theoretical model for combined action of radiation with another physico-chemical factor has been established. Conclusively the results of this study can provide scientific bases for maximizing the efficacy of ionizing radiation in relation to industrial applications

Response of algal metrics to nutrients and physical factors and identification of nutrient thresholds in agricultural streams

Science.gov (United States)

Black, R.W.; Moran, P.W.; Frankforter, J.D.

2011-01-01

Many streams within the United States are impaired due to nutrient enrichment, particularly in agricultural settings. The present study examines the response of benthic algal communities in agricultural and minimally disturbed sites from across the western United States to a suite of environmental factors, including nutrients, collected at multiple scales. The first objective was to identify the relative importance of nutrients, habitat and watershed features, and macroinvertebrate trophic structure to explain algal metrics derived from deposition and erosion habitats. The second objective was to determine if thresholds in total nitrogen (TN) and total phosphorus (TP) related to algal metrics could be identified and how these thresholds varied across metrics and habitats. Nutrient concentrations within the agricultural areas were elevated and greater than published threshold values. All algal metrics examined responded to nutrients as hypothesized. Although nutrients typically were the most important variables in explaining the variation in each of the algal metrics, environmental factors operating at multiple scales also were important. Calculated thresholds for TN or TP based on the algal metrics generated from samples collected from erosion and deposition habitats were not significantly different. Little variability in threshold values for each metric for TN and TP was observed. The consistency of the threshold values measured across multiple metrics and habitats suggest that the thresholds identified in this study are ecologically relevant. Additional work to characterize the relationship between algal metrics, physical and chemical features, and nuisance algal growth would be of benefit to the development of nutrient thresholds and criteria. ?? 2010 The Author(s).

Chemoproteomics Reveals Chemical Diversity and Dynamics of 4-Oxo-2-nonenal Modifications in Cells.

Science.gov (United States)

Sun, Rui; Fu, Ling; Liu, Keke; Tian, Caiping; Yang, Yong; Tallman, Keri A; Porter, Ned A; Liebler, Daniel C; Yang, Jing

2017-10-01

4-Oxo-2-nonenal (ONE) derived from lipid peroxidation modifies nucleophiles and transduces redox signaling by its reactions with proteins. However, the molecular interactions between ONE and complex proteomes and their dynamics in situ remain largely unknown. Here we describe a quantitative chemoproteomic analysis of protein adduction by ONE in cells, in which the cellular target profile of ONE is mimicked by its alkynyl surrogate. The analyses reveal four types of ONE-derived modifications in cells, including ketoamide and Schiff-base adducts to lysine, Michael adducts to cysteine, and a novel pyrrole adduct to cysteine. ONE-derived adducts co-localize and exhibit crosstalk with many histone marks and redox sensitive sites. All four types of modifications derived from ONE can be reversed site-specifically in cells. Taken together, our study provides much-needed mechanistic insights into the cellular signaling and potential toxicities associated with this important lipid derived electrophile. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Identification of ecological thresholds from variations in phytoplankton communities among lakes: contribution to the definition of environmental standards.

Science.gov (United States)

Roubeix, Vincent; Danis, Pierre-Alain; Feret, Thibaut; Baudoin, Jean-Marc

2016-04-01

In aquatic ecosystems, the identification of ecological thresholds may be useful for managers as it can help to diagnose ecosystem health and to identify key levers to enable the success of preservation and restoration measures. A recent statistical method, gradient forest, based on random forests, was used to detect thresholds of phytoplankton community change in lakes along different environmental gradients. It performs exploratory analyses of multivariate biological and environmental data to estimate the location and importance of community thresholds along gradients. The method was applied to a data set of 224 French lakes which were characterized by 29 environmental variables and the mean abundances of 196 phytoplankton species. Results showed the high importance of geographic variables for the prediction of species abundances at the scale of the study. A second analysis was performed on a subset of lakes defined by geographic thresholds and presenting a higher biological homogeneity. Community thresholds were identified for the most important physico-chemical variables including water transparency, total phosphorus, ammonia, nitrates, and dissolved organic carbon. Gradient forest appeared as a powerful method at a first exploratory step, to detect ecological thresholds at large spatial scale. The thresholds that were identified here must be reinforced by the separate analysis of other aquatic communities and may be used then to set protective environmental standards after consideration of natural variability among lakes.

Surface modification by preparation of buffer zone in glow-discharge plasma

International Nuclear Information System (INIS)

Cho, D.L.

1986-01-01

Reactive species, energetic particles, and uv radiation in the plasma created by a glow discharge strongly interact with solid surfaces under the influence of the plasma. As a result of the strong interaction, various physical and chemical reactions, unique and advantageous for the surface modification of solid materials, occur on the solid surfaces. The surface modification is carried out through formation of a thin buffering layer on the solid surface. The preparation of a buffer zone on solid surfaces for surface modification is described. Two kinds of a buffer zone are prepared by plasma polymerization, or simultaneous sputter deposition of electrode material with plasma polymerization: a transitional buffer zone and a graded buffer zone. Important factors for preparation of the buffer zone (pre-conditioning of a substrate surface, thin-film deposition, post-treatment of the film, magnetron discharge, energy input, geometry of a substrate and a plasma) are discussed

Modification of alumina matrices through chemical etching and electroless deposition of nano-Au array for amperometric sensing

Directory of Open Access Journals (Sweden)

Valinčius Gintaras

2007-01-01

Full Text Available AbstractSimple nanoporous alumina matrix modification procedure, in which the electrically highly insulating alumina barrier layer at the bottom of the pores is replaced with the conductive layer of the gold beds, was described. This modification makes possible the direct electron exchange between the underlying aluminum support and the redox species encapsulated in the alumina pores, thus, providing the generic platform for the nanoporous alumina sensors (biosensors with the direct amperometric signal readout fabrication.

Hyper-arousal decreases human visual thresholds.

Directory of Open Access Journals (Sweden)

Adam J Woods

Full Text Available Arousal has long been known to influence behavior and serves as an underlying component of cognition and consciousness. However, the consequences of hyper-arousal for visual perception remain unclear. The present study evaluates the impact of hyper-arousal on two aspects of visual sensitivity: visual stereoacuity and contrast thresholds. Sixty-eight participants participated in two experiments. Thirty-four participants were randomly divided into two groups in each experiment: Arousal Stimulation or Sham Control. The Arousal Stimulation group underwent a 50-second cold pressor stimulation (immersing the foot in 0-2° C water, a technique known to increase arousal. In contrast, the Sham Control group immersed their foot in room temperature water. Stereoacuity thresholds (Experiment 1 and contrast thresholds (Experiment 2 were measured before and after stimulation. The Arousal Stimulation groups demonstrated significantly lower stereoacuity and contrast thresholds following cold pressor stimulation, whereas the Sham Control groups showed no difference in thresholds. These results provide the first evidence that hyper-arousal from sensory stimulation can lower visual thresholds. Hyper-arousal's ability to decrease visual thresholds has important implications for survival, sports, and everyday life.

1998 Toxic Chemical Release Inventory Report for the Emergency Planning and Community Right-to-Know Act of 1986, Title III

International Nuclear Information System (INIS)

Stockton, Marjorie B.

1999-01-01

The Emergency Planning and Community Right-to-Know Act (EPCRA) of 1986 [also known as the Superfund Amendment and Reauthorization Act (SARA), Title III], as modified by Executive Order 12856, requires that all federal facilities evaluate the need to submit an annual Toxic Chemical Release Inventory report as prescribed in Title III, Section 313 of this Act. This annual report is due every July for the preceding calendar year. Owners and operators who manufacture, process, or otherwise use certain toxic chemicals above listed threshold quantities are required to report their toxic chemical releases to all environmental mediums (air, water, soil, etc.). At Los Alamos National Laboratory (LANL), no EPCRA Section 313 chemicals were used in 1998 above the reportable threshold limits of 10,000 lb or 25,000 lb. Therefore LANL was not required to submit any Toxic Chemical Release Inventory reports (Form Rs) for 1998. This document was prepared to provide a detailed description of the evaluation on chemical usage and EPCRA Section 313 threshold determinations for LANL for 1998

A numerical study of threshold states

International Nuclear Information System (INIS)

Ata, M.S.; Grama, C.; Grama, N.; Hategan, C.

1979-01-01

There are some experimental evidences of charged particle threshold states. On the statistical background of levels, some simple structures were observed in excitation spectrum. They occur near the coulombian threshold and have a large reduced width for the decay in the threshold channel. These states were identified as charged cluster threshold states. Such threshold states were observed in sup(15,16,17,18)O, sup(18,19)F, sup(19,20)Ne, sup(24)Mg, sup(32)S. The types of clusters involved were d, t, 3 He, α and even 12 C. They were observed in heavy-ions transfer reactions in the residual nucleus as strong excited levels. The charged particle threshold states occur as simple structures at high excitation energy. They could be interesting both from nuclear structure as well as nuclear reaction mechanism point of view. They could be excited as simple structures both in compound and residual nucleus. (author)

Conceptions of nuclear threshold status

International Nuclear Information System (INIS)

Quester, G.H.

1991-01-01

This paper reviews some alternative definitions of nuclear threshold status. Each of them is important, and major analytical confusions would result if one sense of the term is mistaken for another. The motives for nations entering into such threshold status are a blend of civilian and military gains, and of national interests versus parochial or bureaucratic interests. A portion of the rationale for threshold status emerges inevitably from the pursuit of economic goals, and another portion is made more attraction by the derives of the domestic political process. Yet the impact on international security cannot be dismissed, especially where conflicts among the states remain real. Among the military or national security motives are basic deterrence, psychological warfare, war-fighting and, more generally, national prestige. In the end, as the threshold phenomenon is assayed for lessons concerning the role of nuclear weapons more generally in international relations and security, one might conclude that threshold status and outright proliferation coverage to a degree in the motives for all of the states involved and in the advantages attained. As this paper has illustrated, nuclear threshold status is more subtle and more ambiguous than outright proliferation, and it takes considerable time to sort out the complexities. Yet the world has now had a substantial amount of time to deal with this ambiguous status, and this may tempt more states to exploit it

Threshold-Voltage Shifts in Organic Transistors Due to Self-Assembled Monolayers at the Dielectric: Evidence for Electronic Coupling and Dipolar Effects.

Science.gov (United States)

Aghamohammadi, Mahdieh; Rödel, Reinhold; Zschieschang, Ute; Ocal, Carmen; Boschker, Hans; Weitz, R Thomas; Barrena, Esther; Klauk, Hagen

2015-10-21

The mechanisms behind the threshold-voltage shift in organic transistors due to functionalizing of the gate dielectric with self-assembled monolayers (SAMs) are still under debate. We address the mechanisms by which SAMs determine the threshold voltage, by analyzing whether the threshold voltage depends on the gate-dielectric capacitance. We have investigated transistors based on five oxide thicknesses and two SAMs with rather diverse chemical properties, using the benchmark organic semiconductor dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene. Unlike several previous studies, we have found that the dependence of the threshold voltage on the gate-dielectric capacitance is completely different for the two SAMs. In transistors with an alkyl SAM, the threshold voltage does not depend on the gate-dielectric capacitance and is determined mainly by the dipolar character of the SAM, whereas in transistors with a fluoroalkyl SAM the threshold voltages exhibit a linear dependence on the inverse of the gate-dielectric capacitance. Kelvin probe force microscopy measurements indicate this behavior is attributed to an electronic coupling between the fluoroalkyl SAM and the organic semiconductor.

Chemical modification, antioxidant and α-amylase inhibitory activities of corn silk polysaccharides.

Science.gov (United States)

Chen, Shuhan; Chen, Haixia; Tian, Jingge; Wang, Yanwei; Xing, Lisha; Wang, Jia

2013-10-15

Water-soluble corn silk polysaccharides (CSPS) were chemically modified to obtain their sulfated, acetylated and carboxymethylated derivatives. Chemical characterization and bioactivities of CSPS and its derivatives were comparatively investigated by chemical methods, gas chromatography, gel filtration chromatography, scanning electron microscope, infrared spectroscopy and circular dichroism spectroscopy, scavenging DPPH free radical assay, scavenging hydroxyl radical assay, ferric reducing power assay, lipid peroxidation inhibition assay and α-amylase activity inhibitory assay, respectively. Among the three derivatives, carboxylmethylated polysaccharide (C-CSPS) demonstrated higher solubility, narrower molecular weight distribution, lower intrinsic viscosity, a hyperbranched conformation, significantly higher antioxidant and α-amylase inhibitory abilities compared with the native polysaccharide and other derivatives. C-CSPS might be used as a novel nutraceutical agent for human consumption. Copyright © 2013 Elsevier Ltd. All rights reserved.

Synthesis and thermal behaviour of pauflerite, β-VOSO4, and its α-modification

International Nuclear Information System (INIS)

Paufler, Peter; Filatov, Stanislav K.; Krzhizhanovskaya, Maria G.; Bubnova, Rimma S.; Russian Academy of Sciences, St. Peterburg

2014-01-01

Powder α-VOSO 4 was prepared by dehydration of VOSO 4 . 3H 2 O. β-VOSO 4 was synthesized by boiling of V 2 O 5 in H 2 SO 4 . Thermal behaviour of VOSO 4 . 3H 2 O, α- and β-VOSO 4 modifications is studied by high-temperature powder X-ray diffraction and thermal analysis, including two-step dehydration of VOSO 4 . 3H 2 O, formation of α-VOSO 4 , thermal expansion and decomposition of both modifications into V 2 O 5 . Higher anisotropy of thermal expansion of the tetragonal α-modification α c = 39(2) . 10 -6 K -1 along the vanadyl ion and α a = 2.4(6) . 10 -6 K -1 in the perpendicular direction comparing to the orthorhombic β-modification (α a = 20.2(7), α b = 2.8(8), α c = 17.8(4) . 10 -6 K -1 ) is explained from a crystal chemical point of view.

Ammonia modification for flotation separation of polycarbonate and polystyrene waste plastics.

Science.gov (United States)

Wang, Chong-Qing; Wang, Hui; Gu, Guo-Hua; Lin, Qing-Quan; Zhang, Ling-Ling; Huang, Luo-Luo; Zhao, Jun-Yao

2016-05-01

A promising method, ammonia modification, was developed for flotation separation of polycarbonate (PC) and polystyrene (PS) waste plastics. Ammonia modification has little effect on flotation behavior of PS, while it changes significantly that of PC. The PC recovery in the floated product drops from 100% to 3.17% when modification time is 13min and then rises to 100% after longer modification. The mechanism of ammonia modification was studied by contact angle, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements. Contact angle of PC indicates the decline of PC recovery in the floated product is ascribed to an increase in surface wettability. FT-IR and XPS spectra suggest that ammonia modification causes chemical reactions occurred on PC surface. Flotation behavior of ammonia-modified PC and PS was investigated with respect to flotation time, frother concentration and particle sizes. Flotation separation of PC and PS waste plastics was conducted based on the flotation behavior of single plastic. PC and PS mixtures with different particle sizes are separated efficiently, implying that the technology possesses superior applicability to particle sizes of plastics. The purity of PS and PC is up to 99.53% and 98.21%, respectively, and the recovery of PS and PC is larger than 92.06%. A reliable, cheap and effective process is proposed for separation of PC and PS waste plastics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Enzymatic Modification of Sphingomyelin

DEFF Research Database (Denmark)

Due to its major role in maintaining the water-retaining properties of the epidermis, ceramide is of great commercial potential in cosmetic and pharmaceuticals such as hair and skin care products. Currently, chemical synthesis of ceramide is a costly process, and developments of alternative cost......-efficient, high yield production methods are of great interest. In the present study, the potential of producing ceramide through the enzymatic hydrolysis of sphingomyelin have been studied. sphingomyelin is a ubiquitous membrane-lipid and rich in dairy products or by-products. It has been verified...... that sphingomyelin modification gives a feasible approach to the potential production of ceramide. The reaction system has been improved through system evaluation and the optimization of several important factors, and phospholipase C from Clostridium perfringens shows higher activity towards the hydrolysis reaction...

Student’s mental model, misconceptions, troublesome knowledge, and threshold concept on thermochemistry with DToM-POE

Science.gov (United States)

Wiji, W.; Mulyani, S.

2018-05-01

The purpose of this study is to obtain a profile of students' mental models, misconceptions, troublesome knowledge, and threshold concept on thermochemistry. The subjects in this study were 35 students. The method used in this research was descriptive method with instruments Diagnostic Test of Mental Model - Prediction, Observation, and Explanation (DToM-POE). The results showed that the students' ability to predict, observe, and explain ΔH of neutralization reaction of NaOH with HCl was still lacking. Most students tended to memorize chemical concepts related to symbolic level and they did not understand the meaning of the symbols used. Furthermore, most students were unable to connect the results of observations at the macroscopic level with the symbolic level to determine ΔH of neutralization reaction of NaOH with HCl. Then, most students tended to give an explanation by a net ionic equation or a chemical reaction equation at the symbolic level when explaining ΔH of neutralization reaction at the submicroscopic level. In addition, there are seven misconceptions, three troublesome knowledges, and three threshold concepts held by students on thermochemistry.

Threshold Concepts in Finance: Student Perspectives

Science.gov (United States)

Hoadley, Susan; Kyng, Tim; Tickle, Leonie; Wood, Leigh N.

2015-01-01

Finance threshold concepts are the essential conceptual knowledge that underpin well-developed financial capabilities and are central to the mastery of finance. In this paper we investigate threshold concepts in finance from the point of view of students, by establishing the extent to which students are aware of threshold concepts identified by…

Thresholding magnetic resonance images of human brain

Institute of Scientific and Technical Information of China (English)

Qing-mao HU; Wieslaw L NOWINSKI

2005-01-01

In this paper, methods are proposed and validated to determine low and high thresholds to segment out gray matter and white matter for MR images of different pulse sequences of human brain. First, a two-dimensional reference image is determined to represent the intensity characteristics of the original three-dimensional data. Then a region of interest of the reference image is determined where brain tissues are present. The non-supervised fuzzy c-means clustering is employed to determine: the threshold for obtaining head mask, the low threshold for T2-weighted and PD-weighted images, and the high threshold for T1-weighted, SPGR and FLAIR images. Supervised range-constrained thresholding is employed to determine the low threshold for T1-weighted, SPGR and FLAIR images. Thresholding based on pairs of boundary pixels is proposed to determine the high threshold for T2- and PD-weighted images. Quantification against public data sets with various noise and inhomogeneity levels shows that the proposed methods can yield segmentation robust to noise and intensity inhomogeneity. Qualitatively the proposed methods work well with real clinical data.

Future needs and recommendations in the development of species sensitivity distributions: Estimating toxicity thresholds for aquatic ecological communities and assessing impacts of chemical exposures.

Science.gov (United States)

Belanger, Scott; Barron, Mace; Craig, Peter; Dyer, Scott; Galay-Burgos, Malyka; Hamer, Mick; Marshall, Stuart; Posthuma, Leo; Raimondo, Sandy; Whitehouse, Paul

2017-07-01

A species sensitivity distribution (SSD) is a probability model of the variation of species sensitivities to a stressor, in particular chemical exposure. The SSD approach has been used as a decision support tool in environmental protection and management since the 1980s, and the ecotoxicological, statistical, and regulatory basis and applications continue to evolve. This article summarizes the findings of a 2014 workshop held by the European Centre for Toxicology and Ecotoxicology of Chemicals and the UK Environment Agency in Amsterdam, The Netherlands, on the ecological relevance, statistical basis, and regulatory applications of SSDs. An array of research recommendations categorized under the topical areas of use of SSDs, ecological considerations, guideline considerations, method development and validation, toxicity data, mechanistic understanding, and uncertainty were identified and prioritized. A rationale for the most critical research needs identified in the workshop is provided. The workshop reviewed the technical basis and historical development and application of SSDs, described approaches to estimating generic and scenario-specific SSD-based thresholds, evaluated utility and application of SSDs as diagnostic tools, and presented new statistical approaches to formulate SSDs. Collectively, these address many of the research needs to expand and improve their application. The highest priority work, from a pragmatic regulatory point of view, is to develop a guidance of best practices that could act as a basis for global harmonization and discussions regarding the SSD methodology and tools. Integr Environ Assess Manag 2017;13:664-674. © 2016 SETAC. © 2016 SETAC.

Near threshold fatigue testing

Science.gov (United States)

Freeman, D. C.; Strum, M. J.

1993-01-01

Measurement of the near-threshold fatigue crack growth rate (FCGR) behavior provides a basis for the design and evaluation of components subjected to high cycle fatigue. Typically, the near-threshold fatigue regime describes crack growth rates below approximately 10(exp -5) mm/cycle (4 x 10(exp -7) inch/cycle). One such evaluation was recently performed for the binary alloy U-6Nb. The procedures developed for this evaluation are described in detail to provide a general test method for near-threshold FCGR testing. In particular, techniques for high-resolution measurements of crack length performed in-situ through a direct current, potential drop (DCPD) apparatus, and a method which eliminates crack closure effects through the use of loading cycles with constant maximum stress intensity are described.

Genotoxic thresholds, DNA repair, and susceptibility in human populations

International Nuclear Information System (INIS)

Jenkins, Gareth J.S.; Zair, Zoulikha; Johnson, George E.; Doak, Shareen H.

2010-01-01

It has been long assumed that DNA damage is induced in a linear manner with respect to the dose of a direct acting genotoxin. Thus, it is implied that direct acting genotoxic agents induce DNA damage at even the lowest of concentrations and that no 'safe' dose range exists. The linear (non-threshold) paradigm has led to the one-hit model being developed. This 'one hit' scenario can be interpreted such that a single DNA damaging event in a cell has the capability to induce a single point mutation in that cell which could (if positioned in a key growth controlling gene) lead to increased proliferation, leading ultimately to the formation of a tumour. There are many groups (including our own) who, for a decade or more, have argued, that low dose exposures to direct acting genotoxins may be tolerated by cells through homeostatic mechanisms such as DNA repair. This argument stems from the existence of evolutionary adaptive mechanisms that allow organisms to adapt to low levels of exogenous sources of genotoxins. We have been particularly interested in the genotoxic effects of known mutagens at low dose exposures in human cells and have identified for the first time, in vitro genotoxic thresholds for several mutagenic alkylating agents (Doak et al., 2007). Our working hypothesis is that DNA repair is primarily responsible for these thresholded effects at low doses by removing low levels of DNA damage but becoming saturated at higher doses. We are currently assessing the roles of base excision repair (BER) and methylguanine-DNA methyltransferase (MGMT) for roles in the identified thresholds (Doak et al., 2008). This research area is currently important as it assesses whether 'safe' exposure levels to mutagenic chemicals can exist and allows risk assessment using appropriate safety factors to define such exposure levels. Given human variation, the mechanistic basis for genotoxic thresholds (e.g. DNA repair) has to be well defined in order that susceptible individuals are

Kinetic, spectroscopic and chemical modification study of iron release from transferrin; iron(III) complexation to adenosine triphosphate

International Nuclear Information System (INIS)

Thompson, C.P.

1985-01-01

Amino acids other than those that serve as ligands have been found to influence the chemical properties of transferrin iron. The catalytic ability of pyrophosphate to mediate transferrin iron release to a terminal acceptor is largely quenched by modification non-liganded histine groups on the protein. The first order rate constants of iron release for several partially histidine modified protein samples were measured. A statistical method was employed to establish that one non-liganded histidine per metal binding domain was responsible for the reduction in rate constant. These results imply that the iron mediated chelator, pyrophosphate, binds directly to a histidine residue on the protein during the iron release process. EPR spectroscopic results are consistent with this interpretation. Kinetic and amino acid sequence studies of ovotransferrin and lactoferrin, in addition to human serum transferrin, have allowed the tentative assignment of His-207 in the N-terminal domain and His-535 in the C-terminal domain as the groups responsible for the reduction in rate of iron release. The above concepts have been extended to lysine modified transferrin. Complexation of iron(II) to adenosine triphosphate (ATP) was also studied to gain insight into the nature of iron-ATP species present at physiological pH. 31 P NMR spectra are observed when ATP is presented in large excess

Development of Short-term Molecular Thresholds to Predict Long-term Mouse Liver Tumor Outcomes: Phthalate Case StudyTo be

Science.gov (United States)

Molecular Thresholds for Early Key Events in Liver Tumorgensis: PhthalateCase StudyTriangleShort-term changes in molecular profiles are a central component of strategies to model health effects of environmental chemicals such as phthalates, for which there is widespread human exp...

Encoding of Fundamental Chemical Entities of Organic Reactivity Interest using chemical ontology and XML.

Science.gov (United States)

Durairaj, Vijayasarathi; Punnaivanam, Sankar

2015-09-01

Fundamental chemical entities are identified in the context of organic reactivity and classified as appropriate concept classes namely ElectronEntity, AtomEntity, AtomGroupEntity, FunctionalGroupEntity and MolecularEntity. The entity classes and their subclasses are organized into a chemical ontology named "ChemEnt" for the purpose of assertion, restriction and modification of properties through entity relations. Individual instances of entity classes are defined and encoded as a library of chemical entities in XML. The instances of entity classes are distinguished with a unique notation and identification values in order to map them with the ontology definitions. A model GUI named Entity Table is created to view graphical representations of all the entity instances. The detection of chemical entities in chemical structures is achieved through suitable algorithms. The possibility of asserting properties to the entities at different levels and the mechanism of property flow within the hierarchical entity levels is outlined. Copyright © 2015 Elsevier Inc. All rights reserved.

At-Risk-of-Poverty Threshold

Directory of Open Access Journals (Sweden)

Táňa Dvornáková

2012-06-01

Full Text Available European Statistics on Income and Living Conditions (EU-SILC is a survey on households’ living conditions. The main aim of the survey is to get long-term comparable data on social and economic situation of households. Data collected in the survey are used mainly in connection with the evaluation of income poverty and determinationof at-risk-of-poverty rate. This article deals with the calculation of the at risk-of-poverty threshold based on data from EU-SILC 2009. The main task is to compare two approaches to the computation of at riskof-poverty threshold. The first approach is based on the calculation of the threshold for each country separately,while the second one is based on the calculation of the threshold for all states together. The introduction summarizes common attributes in the calculation of the at-risk-of-poverty threshold, such as disposable household income, equivalised household income. Further, different approaches to both calculations are introduced andadvantages and disadvantages of these approaches are stated. Finally, the at-risk-of-poverty rate calculation is described and comparison of the at-risk-of-poverty rates based on these two different approaches is made.

Modifications of radiation detection response of PADC track detectors by photons

CERN Document Server

Sinha, D

1998-01-01

Photon induced modifications in polyalyldiglycol carbonate (PADC) track detectors have been studied in the dose range of 10 sup 1 -10 sup 6 Gy. It was found that some of the properties like bulk-etch rate, track-etch rate got enhanced at the dose of 10 sup 6 Gy. Activation energy for bulk-etching has been determined for different gamma doses. In order to correlate the high etch rate with the chemical modifications, UV-Vis, IR and ESR studies were carried out. These studies clearly give the indication that radiation damage results into radical formation through bond cleavage. TGA study was performed for understanding the thermal resistance of this detector. The results are presented and discussed.

1997 toxic chemical release inventory. Emergency Planning and Community Right-To-Know Act, Section 313

International Nuclear Information System (INIS)

Zaloudek, D.E.

1998-01-01

Two listed toxic chemicals were used at the Hanford Site above established activity thresholds: phosphoric acid and chlorine. Because total combined quantities of chlorine released, disposed, treated, recovered through recycle operations, co-combusted for energy recovery, and transferred to off-site locations for the purpose of recycle, energy recovery, treatment, and/or disposal, amounted to less than 500 pounds, the Hanford Site qualified for the alternate one million pound threshold for chlorine. Accordingly, this Toxic Chemical Release Inventory includes a Form A for chlorine, and a Form B for phosphoric acid

Chemical Modification Effect on the Mechanical Properties of Coir Fiber

Directory of Open Access Journals (Sweden)

Samia Sultana Mir

2012-04-01

Full Text Available Natural fiber has a vital role as a reinforcing agent due to its renewable, low cost, biodegradable, less abrasive and eco-friendly nature. Whereas synthetic fibers like glass, boron, carbon, metallic, ceramic and inorganic fibers are expensive and not eco-friendly. Coir is one of the natural fibers easily available in Bangladesh and cheap. It is derived from the husk of the coconut (Cocos nucifera. Coir has one of the highest concentrations of lignin, which makes it stronger. In recent years, wide range of research has been carried out on fiber reinforced polymer composites [4-13].The aim of the present research is to characterize brown single coir fiber for manufacturing polymer composites reinforced with characterized fibers. Adhesion between the fiber and polymer is one of factors affecting the strength of manufactured composites. In order to increase the adhesion, the coir fiber was chemically treated separately in single stage (with Cr₂(SO₄3•12(H₂O and double stages (with CrSO₄ and NaHCO₃. Both the raw and treated fibers were characterized by tensile testing, Fourier transform infrared (FTIR spectroscopic analysis, scanning electron microscopic analysis. The result showed that the Young’s modulus increased, while tensile strength and strain to failure decreased with increase in span length. Tensile properties of chemically treated coir fiber was found higher than raw coir fiber, while the double stage treated coir fiber had better mechanical properties compared to the single stage treated coir fiber. Scanning electron micrographs showed rougher surface in case of the raw coir fiber. The surface was found clean and smooth in case of the treated coir fiber. Thus the performance of coir fiber composites in industrial application can be improved by chemical treatment.

Vacuum-based surface modification of organic and metallic substrates

Science.gov (United States)

Torres, Jessica

Surface physico-chemical properties play an important role in the development and performance of materials in different applications. Consequently, understanding the chemical and physical processes involved during surface modification strategies is of great scientific and technological importance. This dissertation presents results from the surface modification of polymers, organic films and metallic substrates with reactive species, with the intent of simulating important modification processes and elucidating surface property changes of materials under different environments. The reactions of thermally evaporated copper and titanium with halogenated polytetrafluoroethylene (PTFE) and polyvinyl chloride (PVC) are used to contrast the interaction of metals with polymers. Results indicate that reactive metallization is thermodynamically favored when the metal-halogen bond strength is greater than the carbon-halogen bond strength. X-ray post-metallization treatment results in an increase in metal-halide bond formation due to the production of volatile halogen species in the polymer that react with the metallic overlayer. The reactions of atomic oxygen (AO) and atomic chlorine with polyethylene (PE) and self-assembled monolayers (SAMs) films were followed to ascertain the role of radical species during plasma-induced polymer surface modification. The reactions of AO with X-ray modified SAMs are initially the dominated by the incorporation of new oxygen containing functionality at the vacuum/film interface, leading to the production of volatile carbon containing species such as CO2 that erodes the hydrocarbon film. The reaction of atomic chlorine species with hydrocarbon SAMs, reveals that chlorination introduces C-Cl and C-Cl2 functionalities without erosion. A comparison of the reactions of AO and atomic chlorine with PE reveal a maximum incorporation of the corresponding C-O and C-Cl functionalities at the polymer surface. A novel method to prepare phosphorous

Novel Fabrication of Biodegradable Superabsorbent Microspheres with Diffusion Barrier through Thermo-Chemical Modification and Their Potential Agriculture Applications for Water Holding and Sustained Release of Fertilizer.

Science.gov (United States)

Feng, Diejing; Bai, Bo; Wang, Honglun; Suo, Yourui

2017-07-26

Synergistic utilization of water and fertilizer has vital contribution to the modern production of agriculture. This work reports on a simple and facile strategy to prepare biodegradable yeast/sodium alginate/poly(vinyl alcohol) superabsorbent microspheres with a diffusion barrier merit by thermo-chemical modification route. The integrated performances, including water absorbency, water retention, water evaporation ratio, leaching loss control, sustained-release behaviors, and degradation in soil, were systematically investigated. The results revealed that the modified microspheres were a triumphant water and fertilizer manager to effectively hold water and control the unexpected leakage of fertilizer for sustained release. Therefore, this work provides a promising approach to ameliorate the utilization efficiency of water and fertilizer in potential agriculture applications.

Parton distributions with threshold resummation

CERN Document Server

Bonvini, Marco; Rojo, Juan; Rottoli, Luca; Ubiali, Maria; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Hartland, Nathan P.

2015-01-01

We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on the NNPDF3.0 analysis, are extracted from deep-inelastic scattering, Drell-Yan, and top quark pair production data, for which resummed calculations can be consistently used. We find that, close to threshold, the inclusion of resummed PDFs can partially compensate the enhancement in resummed matrix elements, leading to resummed hadronic cross-sections closer to the fixed-order calculation. On the other hand, far from threshold, resummed PDFs reduce to their fixed-order counterparts. Our results demonstrate the need for a consistent use of resummed PDFs in resummed calculations.

Effect of threshold quantization in opportunistic splitting algorithm

KAUST Repository

Nam, Haewoon

2011-12-01

This paper discusses algorithms to find the optimal threshold and also investigates the impact of threshold quantization on the scheduling outage performance of the opportunistic splitting scheduling algorithm. Since this algorithm aims at finding the user with the highest channel quality within the minimal number of mini-slots by adjusting the threshold every mini-slot, optimizing the threshold is of paramount importance. Hence, in this paper we first discuss how to compute the optimal threshold along with two tight approximations for the optimal threshold. Closed-form expressions are provided for those approximations for simple calculations. Then, we consider linear quantization of the threshold to take the limited number of bits for signaling messages in practical systems into consideration. Due to the limited granularity for the quantized threshold value, an irreducible scheduling outage floor is observed. The numerical results show that the two approximations offer lower scheduling outage probability floors compared to the conventional algorithm when the threshold is quantized. © 2006 IEEE.

Chemical derivatization to enhance chemical/oxidative stability of resorcinol-formaldehyde resin

Energy Technology Data Exchange (ETDEWEB)

Hubler, T.L. [Pacific Northwest National Lab., Richland, WA (United States)

1997-10-01

The goal of this task is to develop modified resorcinol-formaldehyde (R-F) resin to improve the chemical/oxidative stability of the resin. R-F resin is a regenerable organic ion-exchange resin that is selective for cesium ion in highly alkaline, high ionic-strength solutions. R-F resin tends to undergo chemical degradation, reducing its ability to remove cesium ion from waste solutions; the mechanistic details of these decomposition reactions are currently unknown. The approach used for this task is chemical modification of the resin structure, particularly the resorcinol ring unit of the polymer resin. This approach is based on prior characterization studies conducted at Pacific Northwest National Laboratory (PNNL) that indicated the facile chemical degradation of the resin is oxidation of the resorcinol ring to the para-quinone structure, with subsequent loss of ion-exchange sites for cesium ion. R-F resin represents an important alternative to current radiocesium remediation technology for tank wastes at both the Hanford and Savannah River sites, particularly if regenerable resins are needed.

ArF laser surface modification of polyethersulfone film: Effect of laser fluence in improving surface biocompatibility

International Nuclear Information System (INIS)

Pazokian, H.; Jelvani, S.; Mollabashi, M.; Barzin, J.; Azizabadi Farahani, G.

2011-01-01

ArF laser treatment of polyethersulfone (PES) films was performed to improve biocompatibility of surfaces. For this purpose, the threshold fluence for laser ablation of PES was obtained from experimental measurements and then samples were irradiated at 2 separate ranges of fluences, i.e. below and above the ablation threshold. In order to investigate the physico-chemical changes, the modified surfaces were characterized by attenuated total reflectance (ATR) infrared spectroscopy and contact-angle measurements. The biocompatibility of the treated samples in comparison to those untreated was examined in vitro using a platelet adhesion test. The number of adhered platelets was obtained using the lactate dehydrogenase (LDH) method. For surfaces irradiated below the ablation threshold, a high reduction in the number of the adhered platelets was observed; while this number increased in samples treated at the fluence above the ablation threshold. The change in platelet adhesion was attributed to the change in chemistry and roughness of the irradiated surfaces.

In-situ modification, regeneration, and application of keratin biopolymer for arsenic removal

Energy Technology Data Exchange (ETDEWEB)

Khosa, Muhammad A.; Ullah, Aman, E-mail: amanullah@ualberta.ca

2014-08-15

Graphical abstract: - Highlights: • In-situ chemical modification of keratin based material was carried out. • Characterization techniques such as SEM, FTIR, XRD, and DSC were employed. • TGA data was elaborated for its complete thermal and kinetic study. • Sorption of As(III) using modified material was experimentally studied. • Thermodynamics and Isotherm study was made for elucidation of adsorption data. - Abstract: Chemical modification of chicken feathers (CF) and their subsequent role in arsenic removal from water is presented in this paper. The ground CF were chemically treated with four selective dopants such as poly (ethylene glycol) (PEG) diglycidyl ether, poly (N-isopropylacrylamide) (PNIPAM), allyl alcohol (AA) and TrisilanolCyclohexyl POSS. After modification, the solubilized keratin was regenerated by precipitation at acidic pH. The structural changes and properties of modified biopolymer were compared with untreated CF and confirmed by different characterization techniques such as SEM, FTIR, XRD, and DSC. The TGA data was used to discuss thermal decomposition and kinetic behavior of modified biopolymer exhaustively. The modified biopolymers were further investigated as biosorbents for their application in As(III) removal from water. The AA and POSS supported biosorbents executed high removal capacity for As(III) up to 11.5 × 10{sup −2}and 11.0 × 10{sup −2} mg/g from 100 ml arsenic polluted water solution respectively. Thermodynamic parameters such as ΔG{sup 0}, ΔH{sup 0}, ΔS{sup 0} were also evaluated with the finding that overall sorption process was endothermic and spontaneous in nature. Based on linear and non-linear regression analysis, Freundlich Isotherm model showed good fit for obtained sorption data apart from high linear regression values supporting Langmuir isotherm model in sorption of As(III)

A tandem regression-outlier analysis of a ligand cellular system for key structural modifications around ligand binding.

Science.gov (United States)

Lin, Ying-Ting

2013-04-30

A tandem technique of hard equipment is often used for the chemical analysis of a single cell to first isolate and then detect the wanted identities. The first part is the separation of wanted chemicals from the bulk of a cell; the second part is the actual detection of the important identities. To identify the key structural modifications around ligand binding, the present study aims to develop a counterpart of tandem technique for cheminformatics. A statistical regression and its outliers act as a computational technique for separation. A PPARγ (peroxisome proliferator-activated receptor gamma) agonist cellular system was subjected to such an investigation. Results show that this tandem regression-outlier analysis, or the prioritization of the context equations tagged with features of the outliers, is an effective regression technique of cheminformatics to detect key structural modifications, as well as their tendency of impact to ligand binding. The key structural modifications around ligand binding are effectively extracted or characterized out of cellular reactions. This is because molecular binding is the paramount factor in such ligand cellular system and key structural modifications around ligand binding are expected to create outliers. Therefore, such outliers can be captured by this tandem regression-outlier analysis.

Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

Directory of Open Access Journals (Sweden)

M. Opiela

2012-04-01

Full Text Available The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermo- mechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%, phosphorus (from 0.006 to 0.008% and oxygen (6 ppm. The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17m2. The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of non- metallic inclusions during hot-working.

Electron beam induced modification of grafted polyamides

International Nuclear Information System (INIS)

Timus, D.M.; Brasoveanu, M.M.; Bradley, D.A.; Popov, A.M.

1998-01-01

It is well known that irradiation, when applied on its own or in combination with other physical and chemical treatments, can manifest in radiation damage to materials. Radiation processing technology focuses upon producing favourable modification of materials through use of relatively high dose and dose rates. Current interest is in modifying the thermal and electrical properties of textured polymers in an effort to improve safety and wear comfort of clothing. No less important is the production of textiles which are safe to use, both in homes and offices. Present investigations provide additional data in support of findings which show that polyamides, a particular class of textured polymer, are amenable to radiation processing. Accelerated electron beam irradiation of sheets of polyamide fibre results in induced grafting of acrylic and methacrylic acids. The degree of grafting is critically dependent upon irradiation dose and the extent of monomers dilution. Of particular importance is the high correlation which is found between degree of grafting and a decrease in the softening rate of the modified polyamide. A systematic modification of electrical conductivity is also observed. (author)

Acoustic sensors for the control of liquid-solid interface evolution and chemical reactivity

International Nuclear Information System (INIS)

Ferrandis, J.Y.; Tingry, S.; Attal, J.; Seta, P.

2006-01-01

Less classical than far-field acoustic investigations of solid materials and/or solid-liquid interfaces, near-field acoustic properties of an acoustic solid wave guide (tip), thin enough at its termination to present an external diameter smaller than the excitation acoustic wave wavelength, is shown to be able to probe interface properties. As a result of that, these near-field acoustic probes can play the role of chemical sensors, if chemical modifications or chemical reactions are concerned at their surface. In that context, a chemical sensor was realized by electrochemical deposition of an electron-conducting polymer (polypyrrole-biotin) on a metal tip, followed by enzyme attachment by molecular recognition process involving the biotin-avidin-specific interaction. Results from near-field acoustic showed that the enzyme modification of the polymer layer can be detected by this new acoustic sensor

Experience of secondary cooling system modification at prototype fast breeder reactor MONJU (Translated document)

International Nuclear Information System (INIS)

Kisohara, Naoyuki; Sakamoto, Yoshihiko

2010-09-01

The prototype fast breeder reactor MONJU has been shut down since the secondary sodium leak accident that occurred in December 1995. After the accident, an investigation into the cause and a comprehensive safety review of the plant were conducted, and various countermeasures for sodium leak were examined. Modification work commenced in September 2005. Since sodium, a chemically active material, is used as coolant in MONJU, the modification work required work methods suitable for the handling of sodium. From this perspective, the use of a plastic bag when opening the sodium boundary, oxygen concentration control in a plastic bag, slightly-positive pressure control of cover gas in the systems, pressing and cutting with a roller cutter to prevent the incorporation of metal fillings, etc. were adopted, with careful consideration given to experience and findings from previous modification work at the experimental fast reactor JOYO and plants abroad. Owing to these work methods, the modification work proceeded close to schedule without incident. (author)

Log canonical thresholds of smooth Fano threefolds

International Nuclear Information System (INIS)

Cheltsov, Ivan A; Shramov, Konstantin A

2008-01-01

The complex singularity exponent is a local invariant of a holomorphic function determined by the integrability of fractional powers of the function. The log canonical thresholds of effective Q-divisors on normal algebraic varieties are algebraic counterparts of complex singularity exponents. For a Fano variety, these invariants have global analogues. In the former case, it is the so-called α-invariant of Tian; in the latter case, it is the global log canonical threshold of the Fano variety, which is the infimum of log canonical thresholds of all effective Q-divisors numerically equivalent to the anticanonical divisor. An appendix to this paper contains a proof that the global log canonical threshold of a smooth Fano variety coincides with its α-invariant of Tian. The purpose of the paper is to compute the global log canonical thresholds of smooth Fano threefolds (altogether, there are 105 deformation families of such threefolds). The global log canonical thresholds are computed for every smooth threefold in 64 deformation families, and the global log canonical thresholds are computed for a general threefold in 20 deformation families. Some bounds for the global log canonical thresholds are computed for 14 deformation families. Appendix A is due to J.-P. Demailly.

Estimation of risks by chemicals produced during laser pyrolysis of tissues

Science.gov (United States)

Weber, Lothar W.; Spleiss, Martin

1995-01-01

Use of laser systems in minimal invasive surgery results in formation of laser aerosol with volatile organic compounds of possible health risk. By use of currently identified chemical substances an overview on possibly associated risks to human health is given. The class of the different identified alkylnitriles seem to be a laser specific toxicological problem. Other groups of chemicals belong to the Maillard reaction type, the fatty acid pyrolysis type, or even the thermally activated chemolysis. In relation to the available different threshold limit values the possible exposure ranges of identified substances are discussed. A rough estimation results in an exposure range of less than 1/100 for almost all substances with given human threshold limit values without regard of possible interactions. For most identified alkylnitriles, alkenes, and heterocycles no threshold limit values are given for lack of, until now, practical purposes. Pyrolysis of anaesthetized organs with isoflurane gave no hints for additional pyrolysis products by fragment interactions with resulting VOCs. Measurements of pyrolysis gases resulted in detection of small amounts of NO additionally with NO2 formation at plasma status.

Response of genioglossus muscle to increasing chemical drive in sleeping obstructive apnea patients.

Science.gov (United States)

Loewen, Andrea H S; Ostrowski, Michele; Laprairie, John; Maturino, Frances; Hanly, Patrick J; Younes, Magdy

2011-08-01

Subjects with a collapsible upper airway must activate their pharyngeal dilators sufficiently in response to increasing chemical drive if they are to maintain airway patency without arousal from sleep. Little is known about the response of pharyngeal dilators to increasing chemical drive in these subjects. We wished to determine, in obstructive apnea patients, the response of the genioglossus to increasing chemical drive and the contribution of mechanoreceptor feedback to this response. Physiological study. University-based sleep laboratory. 20 patients with obstructive apnea. Genioglossus activity was monitored during overnight polysomnography on optimal continuous positive airway pressure (CPAP). Intermittently, inspired gases were altered to produce different levels of ventilatory stimulation. CPAP was then briefly reduced to 1.0 cm H(2)O (dial-down), inducing an obstruction. Without mechanoreceptor feedback (i.e., on CPAP) the increase in genioglossus activity as ventilation increased from 6.1 ± 1.4 to 16.1 ± 4.8 L/min was modest (ΔTonic activity 0.3% ± 0.5%maximum; ΔPhasic activity 1.7% ± 3.4%maximum). Genioglossus activity increased immediately upon dial-down, reflecting mechanoreceptor feedback, but only when ventilation before dial-down exceeded a threshold value. This threshold varied among patients and, once surpassed, genioglossus activity increased briskly with further increases in chemical drive (1.1% ± 0.84%GG(MAX) per L/min increase in V(E)). In sleeping obstructive apnea patients: (1) Mechanoreceptor feedback is responsible for most of the genioglossus response to chemical drive. (2) Mechanoreceptor feedback is effective only above a threshold chemical drive, which varies greatly among patients. These findings account in part for the highly variable relation between pharyngeal mechanical abnormalities and apnea severity.

Experimental Study on Modification of Concrete with Asphalt Admixture

Science.gov (United States)

Bołtryk, Michał; Małaszkiewicz, Dorota; Pawluczuk, Edyta

2017-10-01

Durability of engineering structures made of cement concrete with high compressive strength is a very vital issue, especially when they are exposed to different aggressive environments and dynamic loads. Concrete resistance to weathering actions and chemical attack can be improved by combined chemical and mechanical modification of concrete microstructure. Asphalt admixture in the form of asphalt paste (AP) was used for chemical modification of cement composite microstructure. Concrete structure was formed using special technology of compaction. A stand for vibro-vibropressing with regulated vibrator force and pressing force was developed. The following properties of the modified concrete were tested: compressive strength, water absorption, freeze-thaw resistance, scaling resistance in the presence of de-icing agents, chloride migration, resistance to CO2 and corrosion in aggressive solutions. Corrosion resistance was tested alternately in 1.8% solutions of NH4Cl, MgSO4, (NH2)2CO and CaCl2, which were altered every 7 days; the experiment lasted 9.5 months. Optimum compaction parameters in semi-industrial conditions were determined: ratio between piston stress (Qp ) and external top vibrator force (Po ) in the range 0.4÷-0.5 external top vibrator force 4 kN. High strength concretes with compressive strength fcm = 60÷70 MPa, very low water absorption (barrier formed in pores of cement hydrates against dioxide and chloride ions. Concrete specimens containing AP 4% c.m. and consolidated by vibro-vibropressing method proved to be practically resistant to highly corrosive environment. Vibro-vibropressing compaction technology of concrete modified with AP can be applied in prefabrication plants to produce elements for road, bridge and hydraulic engineering constructions.

Conformational impact of structural modifications in 2-fluorocyclohexanone

Directory of Open Access Journals (Sweden)

Francisco A. Martins

2017-08-01

Full Text Available 2-Haloketones are building blocks that combine physical, chemical and biological features of materials and bioactive compounds, while organic fluorine plays a fundamental role in the design of performance organic molecules. Since these features are dependent on the three-dimensional chemical structure of a molecule, simple structural modifications can affect its conformational stability and, consequently, the corresponding physicochemical/biological property of interest. In this work, structural changes in 2-fluorocyclohexanone were theoretically studied with the aim at finding intramolecular interactions that induce the conformational equilibrium towards the axial or equatorial conformer. The interactions evaluated were hydrogen bonding, hyperconjugation, electrostatic and steric effects. While the gauche effect, originated from hyperconjugative interactions, does not appear to cause some preferences for the axial conformation of organofluorine heterocycles, more classical effects indeed rule the conformational equilibrium of the compounds. Spectroscopic parameters (NMR chemical shifts and coupling constants, which can be useful to determine the stereochemistry and the interactions operating in the series of 2-fluorocyclohexanone derivatives, were also calculated.

Surface modification and characterization for dispersion stability of inorganic nanometer-scaled particles in liquid media

International Nuclear Information System (INIS)

Kamiya, Hidehiro; Iijima, Motoyuki

2010-01-01

Inorganic nanoparticles are indispensable for science and technology as materials, pigments and cosmetics products. Improving the dispersion stability of nanoparticles in various liquids is essential for those applications. In this review, we discuss why it is difficult to control the stability of nanoparticles in liquids. We also overview the role of surface interaction between nanoparticles in their dispersion and characterization, e.g. by colloid probe atomic force microscopy (CP-AFM). Two types of surface modification concepts, post-synthesis and in situ modification, were investigated in many previous studies. Here, we focus on post-synthesis modification using adsorption of various kinds of polymer dispersants and surfactants on the particle surface, as well as surface chemical reactions of silane coupling agents. We discuss CP-AFM as a technique to analyze the surface interaction between nanoparticles and the effect of surface modification on the nanoparticle dispersion in liquids. (topical review)

Surface modification and characterization for dispersion stability of inorganic nanometer-scaled particles in liquid media

Directory of Open Access Journals (Sweden)

Hidehiro Kamiya and Motoyuki Iijima

2010-01-01

Full Text Available Inorganic nanoparticles are indispensable for science and technology as materials, pigments and cosmetics products. Improving the dispersion stability of nanoparticles in various liquids is essential for those applications. In this review, we discuss why it is difficult to control the stability of nanoparticles in liquids. We also overview the role of surface interaction between nanoparticles in their dispersion and characterization, e.g. by colloid probe atomic force microscopy (CP-AFM. Two types of surface modification concepts, post-synthesis and in situ modification, were investigated in many previous studies. Here, we focus on post-synthesis modification using adsorption of various kinds of polymer dispersants and surfactants on the particle surface, as well as surface chemical reactions of silane coupling agents. We discuss CP-AFM as a technique to analyze the surface interaction between nanoparticles and the effect of surface modification on the nanoparticle dispersion in liquids.

On the Electrodeposition of Ca-P Coatings on Nitinol Alloy: A Comparison Between Different Surface Modification Methods

Science.gov (United States)

Etminanfar, M. R.; Khalil-Allafi, J.

2016-02-01

In this study, a combination of surface modification process and the electrochemical deposition of Ca-P coatings was used for the modification of the Nitinol shape memory alloy. DSC, SEM, GIB-XRD, FT-Raman, XPS, and FTIR measurements were performed for the characterization of the samples. Results indicated that chemical etching and boiling of the samples in distilled water formed TiO film on the surface. After the chemical modification, subsequent aging of the sample, at 470 °C for 30 min, converted the oxide film to a stable structure of titanium dioxide. In that case, the treated substrate indicated a superelastic behavior. At the same electrochemical condition, the treated substrate revealed more stable and uniform Ca-P coatings in comparison with the abraded Nitinol substrate. This difference was attributed to the presence of hydroxyl groups on the titanium dioxide surface. Also, after soaking the sample in SBF, the needle-like coating on the treated substrate was completely covered with the hydroxyapatite phase which shows a good bioactivity of the coating.

Threshold Concepts and Information Literacy

Science.gov (United States)

Townsend, Lori; Brunetti, Korey; Hofer, Amy R.

2011-01-01

What do we teach when we teach information literacy in higher education? This paper describes a pedagogical approach to information literacy that helps instructors focus content around transformative learning thresholds. The threshold concept framework holds promise for librarians because it grounds the instructor in the big ideas and underlying…

Influence of arousal threshold and depth of sleep on respiratory stability in man: analysis using a mathematical model.

Science.gov (United States)

Longobardo, G S; Evangelisti, C J; Cherniack, N S

2009-12-01

We examined the effect of arousals (shifts from sleep to wakefulness) on breathing during sleep using a mathematical model. The model consisted of a description of the fluid dynamics and mechanical properties of the upper airways and lungs, as well as a controller sensitive to arterial and brain changes in CO(2), changes in arterial oxygen, and a neural input, alertness. The body was divided into multiple gas store compartments connected by the circulation. Cardiac output was constant, and cerebral blood flows were sensitive to changes in O(2) and CO(2) levels. Arousal was considered to occur instantaneously when afferent respiratory chemical and neural stimulation reached a threshold value, while sleep occurred when stimulation fell below that value. In the case of rigid and nearly incompressible upper airways, lowering arousal threshold decreased the stability of breathing and led to the occurrence of repeated apnoeas. In more compressible upper airways, to maintain stability, increasing arousal thresholds and decreasing elasticity were linked approximately linearly, until at low elastances arousal thresholds had no effect on stability. Increased controller gain promoted instability. The architecture of apnoeas during unstable sleep changed with the arousal threshold and decreases in elasticity. With rigid airways, apnoeas were central. With lower elastances, apnoeas were mixed even with higher arousal thresholds. With very low elastances and still higher arousal thresholds, sleep consisted totally of obstructed apnoeas. Cycle lengths shortened as the sleep architecture changed from mixed apnoeas to total obstruction. Deeper sleep also tended to promote instability by increasing plant gain. These instabilities could be countered by arousal threshold increases which were tied to deeper sleep or accumulated aroused time, or by decreased controller gains.

A Threshold Continuum for Aeolian Sand Transport

Science.gov (United States)

Swann, C.; Ewing, R. C.; Sherman, D. J.

2015-12-01

The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.

Chemical process control using Mat lab

International Nuclear Information System (INIS)

Kang, Sin Chun; Kim, Raeh Yeon; Kim, Yang Su; Oh, Min; Yeo, Yeong Gu; Jung, Yeon Su

2001-07-01

This book is about chemical process control, which includes the basis of process control with conception, function, composition of system and summary, change of laplace and linearization, modeling of chemical process, transfer function and block diagram, the first dynamic property of process, the second dynamic property of process, the dynamic property of combined process, control structure of feedback on component of control system, the dynamic property of feedback control loop, stability of closed loop control structure, expression of process, modification and composition of controller, analysis of vibration response and adjustment controller using vibration response.

Cellular uptake and cytotoxic potential of respirable bentonite particles with different quartz contents and chemical modifications in human lung fibroblasts

Energy Technology Data Exchange (ETDEWEB)

Geh, Stefan; Rettenmeier, Albert W.; Dopp, Elke [University Hospital, Institute of Hygiene and Occupational Medicine, Essen (Germany); Yuecel, Raif [University Hospital, Institute of Cell Biology (Cancer Research), Essen (Germany); Duffin, Rodger [Institute of Environmental Health Research (IUF), Duesseldorf (Germany); University of Edinburgh, ELEGI COLT Lab, Scotland (United Kingdom); Albrecht, Catrin; Borm, Paul J.A. [Institute of Environmental Health Research (IUF), Duesseldorf (Germany); Armbruster, Lorenz [Verein fuer Technische Sicherheit und Umweltschutz e.V., Gotha (Germany); Raulf-Heimsoth, Monika; Bruening, Thomas [Research Institute for Occupational Medicine of the Institutions for Statutory Accident Insurance and Prevention (BGFA), Bochum (Germany); Hoffmann, Eik [University of Rostock, Institute of Biology, Department of Cell Biology and Biosystems Technology, Rostock (Germany)

2006-02-01

Considering the biological reactivity of pure quartz in lung cells, there is a strong interest to clarify the cellular effects of respirable siliceous dusts, like bentonites. In the present study, we investigated the cellular uptake and the cytotoxic potential of bentonite particles (Oe< 10 {mu}m) with an {alpha}-quartz content of up to 6% and different chemical modifications (activation: alkaline, acidic, organic) in human lung fibroblasts (IMR90). Additionally, the ability of the particles to induce apoptosis in IMR90-cells and the hemolytic activity was tested. All bentonite samples were tested for endotoxins with the in vitro-Pyrogen test and were found to be negative. Cellular uptake of particles by IMR90-cells was studied by transmission electron microscopy (TEM). Cytotoxicity was analyzed in IMR90-cells by determination of viable cells using flow cytometry and by measuring of the cell respiratory activity. Induced apoptotic cells were detected by AnnexinV/Propidiumiodide-staining and gel electrophoresis. Our results demonstrate that activated bentonite particles are better taken up by IMR90-cells than untreated (native) bentonite particles. Also, activated bentonite particles with a quartz content of 5-6% were more cytotoxic than untreated bentonites or bentonites with a quartz content lower than 4%. The bentonite samples induced necrotic as well as apoptotic cell death. In general, bentonites showed a high membrane-damaging potential shown as hemolytic activity in human erythrocytes. We conclude that cellular effects of bentonite particles in human lung cells are enhanced after chemical treatment of the particles. The cytotoxic potential of the different bentonites is primarily characterized by a strong lysis of the cell membrane. (orig.)

Analysis of the interaction of phytoestrogens and synthetic chemicals: An in vitro/in vivo comparison

International Nuclear Information System (INIS)

Charles, Grantley D.; Gennings, Chris; Tornesi, Belen; Kan, H. Lynn; Zacharewski, Timothy R.; Bhaskar Gollapudi, B.; Carney, Edward W.

2007-01-01

In the evaluation of chemical mixture toxicity, it is desirable to develop an evaluation paradigm which incorporates some critical attributes of real world exposures, particularly low dose levels, larger numbers of chemicals, and chemicals from synthetic and natural sources. This study evaluated the impact of low level exposure to a mixture of six synthetic chemicals (SC) under conditions of co-exposure to various levels of plant-derived phytoestrogen (PE) compounds. Estrogenic activity was evaluated using an in vitro human estrogen receptor (ER) transcriptional activation assay and an in vivo immature rat uterotrophic assay. Initially, dose-response curves were characterized for each of the six SCs (methoxyclor, o,p-DDT, octylphenol, bisphenol A, β-hexachlorocyclohexane, 2,3-bis(4-hydroxyphenyl)-propionitrile) in each of the assays. The six SCs were then combined at equipotent ratios and tested at 5-6 dose levels spanning from very low, sub-threshold levels, to a dose in which every chemical in the mixture was at its individual estrogenic response threshold. The SC mixtures also were tested in the absence or presence of 5-6 different levels of PEs, for a total of 36 (in vitro) or 25 (in vivo) treatment groups. Both in vitro and in vivo, low concentrations of the SC mixture failed to increase estrogenic responses relative to those induced by PEs alone. However, significant increases in response occurred when each chemical in the SC mixture was near or above its individual response threshold. In vitro, interactions between high-doses of SCs and PEs were greater than additive, whereas mixtures of SCs in the absence of PEs interacted in a less than additive fashion. In vivo, the SC and PE mixture responses were consistent with additivity. These data illustrate a novel approach for incorporating key attributes of real world exposures in chemical mixture toxicity assessments, and suggest that chemical mixture toxicity is likely to be of concern only when the mixture

Strong dependence of ultracold chemical rates on electric dipole moments

International Nuclear Information System (INIS)

Quemener, Goulven; Bohn, John L.

2010-01-01

We use the quantum threshold laws combined with a classical capture model to provide an analytical estimate of the chemical quenching cross sections and rate coefficients of two colliding particles at ultralow temperatures. We apply this quantum threshold model (QT model) to indistinguishable fermionic polar molecules in an electric field. At ultracold temperatures and in weak electric fields, the cross sections and rate coefficients depend only weakly on the electric dipole moment d induced by the electric field. In stronger electric fields, the quenching processes scale as d 4(L+(1/2)) where L>0 is the orbital angular-momentum quantum number between the two colliding particles. For p-wave collisions (L=1) of indistinguishable fermionic polar molecules at ultracold temperatures, the quenching rate thus scales as d 6 . We also apply this model to pure two-dimensional collisions and find that chemical rates vanish as d -4 for ultracold indistinguishable fermions. This model provides a quick and intuitive way to estimate chemical rate coefficients of reactions occuring with high probability.

Iran: the next nuclear threshold state?

OpenAIRE

Maurer, Christopher L.

2014-01-01

Approved for public release; distribution is unlimited A nuclear threshold state is one that could quickly operationalize its peaceful nuclear program into one capable of producing a nuclear weapon. This thesis compares two known threshold states, Japan and Brazil, with Iran to determine if the Islamic Republic could also be labeled a threshold state. Furthermore, it highlights the implications such a status could have on U.S. nonproliferation policy. Although Iran's nuclear program is mir...

External field threshold for the unlocking of magnetic islands in the presence of resistive Wall effects and toroidal mode coupling

International Nuclear Information System (INIS)

Coelho, R.; Lazzaro, E.

2000-01-01

The unlocking of static resistive tearing modes by rotating external magnetic perturbations such as those which may arise from the natural tokamak error-field is discussed. For a single mode the balance between the accelerating torque imparted by the error-field and the braking torque due to the interaction of the mode with the wall sets a threshold for the error-field current [H. P. Furth et al. Phys. Fluids 6, 459 (1963)], below which the mode frequency will not lock to the error-field frequency. If the mode resonant with the error-field is coupled to another mode with a rational surface located elsewhere in the plasma, the unlocking process is more elaborated and substantial modifications to the current threshold are expected. The present analysis may contribute to the explanation of some mode unlocking events in tokamak discharges with a non negligible error-field. (orig.)

Hydrometeorological threshold conditions for debris flow initiation in Norway

Directory of Open Access Journals (Sweden)

N. K. Meyer

2012-10-01

Full Text Available Debris flows, triggered by extreme precipitation events and rapid snow melt, cause considerable damage to the Norwegian infrastructure every year. To define intensity-duration (ID thresholds for debris flow initiation critical water supply conditions arising from intensive rainfall or snow melt were assessed on the basis of daily hydro-meteorological information for 502 documented debris flow events. Two threshold types were computed: one based on absolute ID relationships and one using ID relationships normalized by the local precipitation day normal (PDN. For each threshold type, minimum, medium and maximum threshold values were defined by fitting power law curves along the 10th, 50th and 90th percentiles of the data population. Depending on the duration of the event, the absolute threshold intensities needed for debris flow initiation vary between 15 and 107 mm day⁻¹. Since the PDN changes locally, the normalized thresholds show spatial variations. Depending on location, duration and threshold level, the normalized threshold intensities vary between 6 and 250 mm day⁻¹. The thresholds obtained were used for a frequency analysis of over-threshold events giving an estimation of the exceedance probability and thus potential for debris flow events in different parts of Norway. The absolute thresholds are most often exceeded along the west coast, while the normalized thresholds are most frequently exceeded on the west-facing slopes of the Norwegian mountain ranges. The minimum thresholds derived in this study are in the range of other thresholds obtained for regions with a climate comparable to Norway. Statistics reveal that the normalized threshold is more reliable than the absolute threshold as the former shows no spatial clustering of debris flows related to water supply events captured by the threshold.

Recent advances in synthesis and surface modification of superparamagnetic iron oxide nanoparticles with silica

Energy Technology Data Exchange (ETDEWEB)

Sodipo, Bashiru Kayode, E-mail: bashirsodipo@gmail.com [School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia); Nano-Biotechnology Research and Innovation (NanoBRI), Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia); Aziz, Azlan Abdul [School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia); Nano-Biotechnology Research and Innovation (NanoBRI), Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia)

2016-10-15

Research on synthesis of superparamagnetic iron oxide nanoparticles (SPION) and its surface modification for biomedical applications is of intense interest. Due to superparamagnetic property of SPION, the nanoparticles have large magnetic susceptibility, single magnetic domain and controllable magnetic behaviour. However, owing to easy agglomeration of SPION, surface modification of the magnetic particles with biocompatible materials such as silica nanoparticle has gained much attention in the last decade. In this review, we present recent advances in synthesis of SPION and various routes of producing silica coated SPION. - Highlights: • We present recent advances in synthesis of SPION and various routes of producing silica coated SPION • The synthetic routes of producing SPION can be classified into three: physical, chemical and biological methods. • The chemical method is the most cited method of producing SPION and it sub-classified into liquid and gas phase. • The techniques of producing silica coated SPION is grouped into seeded and non-seeded methods.

Recent advances in synthesis and surface modification of superparamagnetic iron oxide nanoparticles with silica

International Nuclear Information System (INIS)

Sodipo, Bashiru Kayode; Aziz, Azlan Abdul

2016-01-01

Research on synthesis of superparamagnetic iron oxide nanoparticles (SPION) and its surface modification for biomedical applications is of intense interest. Due to superparamagnetic property of SPION, the nanoparticles have large magnetic susceptibility, single magnetic domain and controllable magnetic behaviour. However, owing to easy agglomeration of SPION, surface modification of the magnetic particles with biocompatible materials such as silica nanoparticle has gained much attention in the last decade. In this review, we present recent advances in synthesis of SPION and various routes of producing silica coated SPION. - Highlights: • We present recent advances in synthesis of SPION and various routes of producing silica coated SPION • The synthetic routes of producing SPION can be classified into three: physical, chemical and biological methods. • The chemical method is the most cited method of producing SPION and it sub-classified into liquid and gas phase. • The techniques of producing silica coated SPION is grouped into seeded and non-seeded methods.

Integration of community structure data reveals observable effects below sediment guideline thresholds in a large estuary

KAUST Repository

Tremblay, Louis A.

2017-04-07

The sustainable management of estuarine and coastal ecosystems requires robust frameworks due to the presence of multiple physical and chemical stressors. In this study, we assessed whether ecological health decline, based on community structure composition changes along a pollution gradient, occurred at levels below guideline threshold values for copper, zinc and lead. Canonical analysis of principal coordinates (CAP) was used to characterise benthic communities along a metal contamination gradient. The analysis revealed changes in benthic community distribution at levels below the individual guideline values for the three metals. These results suggest that field-based measures of ecological health analysed with multivariate tools can provide additional information to single metal guideline threshold values to monitor large systems exposed to multiple stressors.

Chemical modification of chitosan in the absence of solvent for diclofenac sodium removal: pH and kinetics studies

Energy Technology Data Exchange (ETDEWEB)

Pereira, Kerlaine Alexandre Araujo; Osorio, Luizangela Reis; Silva, Marcos Pereira; Silva Filho, Edson Cavalcanti da, E-mail: edsonfilho@ufpi.edu.br [Universidade Federal do Piaui (UFPI/CCN), Teresina, PI (Brazil). Centro de Ciencias da Natureza. Lab. Interdisciplinar de Materiais Avancados; Sousa, Kaline Soares [Universidade Federal da Paraiba (UFPB/CCEN), Joao Pessoa, PB (Brazil). Centro de Ciencias Exatas e da Natureza. Dept. de Quimica

2014-08-15

Chitosan was modified with acetylacetone and ethylenediamine in the absence of solvent. The new biopolymer obtained from the modification was characterized by elemental analysis and NMR 13C and applied in the removal of diclofenac sodium aqueous solution varying the pH and time. Through elemental analysis was possible to verify a decreasing in C/N relation after reaction with acetylacetone and an increasing after modification with ethylenediamine. From NMR analysis was verified the appearance of peaks around 160-210 ppm in both materials due to free carbonyl groups in the first step of the modification, besides the formation of imine bonds. The adsorption tests showed that the highest value occurred at pH 4 and from the results of the kinetic study was found that maximum adsorption occurred within 45 minutes and experimental data adjusted better to linear adjustment, following pseudo second-order model. The results show a material efficient in the removal of emerging pollutants. (author)

3-(3-amino-3-carboxypropyl)-5,6-Dihydrouridine is one of two novel post-transcriptional modifications in tRNA^Lys(UUU) from Trypanosoma brucei

DEFF Research Database (Denmark)

Krog, Jesper Schak; Español, Yaiza; Giessing, Anders M B

2011-01-01

tRNA is the most heavily modified of all RNA types, with typically 10-20% of the residues being post-transcriptionally altered. Unravelling the modification pattern of a tRNA is a challenging task; there are 92 currently known tRNA modifications [1], many of which are chemically similar. Furtherm......tRNA is the most heavily modified of all RNA types, with typically 10-20% of the residues being post-transcriptionally altered. Unravelling the modification pattern of a tRNA is a challenging task; there are 92 currently known tRNA modifications [1], many of which are chemically similar...... of the unmodified tRNA revealed the modified residues. The modifications were further characterized at the nucleoside level by chromatographic retention time and fragmentation pattern upon higher-order tandem MS. Phylogenetic comparison with modifications in tRNA(Lys) from other organisms was used through......: a minor fraction with the previously described 2-methylthio-N(6) -threonylcarbamoyl-modification, and a major fraction with A37 being modified by a 294.0-Da moiety. The latter product is the largest adenosine modification reported so far, and we discuss its nature and origin....

Biomass as feedstock for chemicals and energy on the threshold of the 21st. century

International Nuclear Information System (INIS)

Cunningham, R.E.

1993-01-01

A historical background is first given in which the role of biomass is described in relation to its competition with fossil biomass for the production of chemicals and energy. Occurrences of reserves from both sources are then compared. Petrochemical and biomass routes are then analyzed in terms of their relative competitive advantages. The oleochemical and biotechnology cases are analyzed in more detail as examples of biomass utilization. Latin American examples of industrial manufacturing of biomass derived chemicals are then provided. Alcochemicals are analyzed in detail as well as essential oils and other chemicals. Finally, references are made to regional Latin American initiatives regarding biomass and the objectives, organization and nature of the initiative are presented

Identifying the nature of surface chemical modification for directed self-assembly of block copolymers

Directory of Open Access Journals (Sweden)

Laura Evangelio

2017-09-01

Full Text Available In recent years, block copolymer lithography has emerged as a viable alternative technology for advanced lithography. In chemical-epitaxy-directed self-assembly, the interfacial energy between the substrate and each block copolymer domain plays a key role on the final ordering. Here, we focus on the experimental characterization of the chemical interactions that occur at the interface built between different chemical guiding patterns and the domains of the block copolymers. We have chosen hard X-ray high kinetic energy photoelectron spectroscopy as an exploration technique because it provides information on the electronic structure of buried interfaces. The outcome of the characterization sheds light onto key aspects of directed self-assembly: grafted brush layer, chemical pattern creation and brush/block co-polymer interface.

11 CFR 9036.1 - Threshold submission.

Science.gov (United States)

2010-01-01

... credit or debit card, including one made over the Internet, the candidate shall provide sufficient... section shall not count toward the threshold amount. (c) Threshold certification by Commission. (1) After...

Effect of pH on the chemical modification of quercetin and structurally related flavonoids characterized by optical (UV-visible and Raman) spectroscopy.

Science.gov (United States)

Jurasekova, Z; Domingo, C; Garcia-Ramos, J V; Sanchez-Cortes, S

2014-07-07

In this work we report the study of the chemical modifications undergone by flavonoids, especially by quercetin (QUC), under alkaline conditions by UV-visible absorption, Raman and surface-enhanced Raman scattering (SERS) spectroscopy, the study was performed in aqueous solution and also on Ag nanoparticles (AgNPs). Several processes are involved in the effect of alkaline pH both in solution and on AgNPs: autoxidation affecting mainly the C-ring of the molecule and giving rise to the molecular fragmentation leading to simpler molecular products, and/or the dimerization and further polymerization leading to species with a higher molecular weight. In addition, there exists a clear structure-instability correlation concerning mainly particular groups in the molecule: the C3-OH group in the C-ring, the catechol moiety in the B-ring and the C2=C3 bond also existing in the C-ring. QUC possesses all these groups and exhibits high instability in alkaline solution. The SERS spectra registered at different pH revealed a change in the dimerization protocol of QUC going from the A- and C-rings-like-condensation to B-ring-like-condensation. Increasing the knowledge of the chemical properties of these compounds and determining the structure-activity relationship under specific environmental factors allow us to improve their beneficial properties for health as well as the preservation of Cultural Heritage objects, for example, by preventing their degradation.

Pseudoxylallemycins A-F, cyclic tetrapeptides with rare allenyl modifications isolated from Pseudoxylaria sp. X802

DEFF Research Database (Denmark)

Guo, Huijuan; Kreuzenbeck, Nina B.; Otani, Saria

2016-01-01

. Pseudoxylallemycins B-D (2-4) possess a rare and chemically accessible allene moiety amenable for synthetic modifications, and derivatives A-D showed antimicrobial activity against Gram-negative human-pathogenic Pseudomonas aeruginosa and antiproliferative activity against human umbilical vein endothelial cells and K...

Causes of genome instability: the effect of low dose chemical exposures in modern society

Science.gov (United States)

Langie, Sabine A.S.; Koppen, Gudrun; Desaulniers, Daniel; Al-Mulla, Fahd; Al-Temaimi, Rabeah; Amedei, Amedeo; Azqueta, Amaya; Bisson, William H.; Brown, Dustin; Brunborg, Gunnar; Charles, Amelia K.; Chen, Tao; Colacci, Annamaria; Darroudi, Firouz; Forte, Stefano; Gonzalez, Laetitia; Hamid, Roslida A.; Knudsen, Lisbeth E.; Leyns, Luc; Lopez de Cerain Salsamendi, Adela; Memeo, Lorenzo; Mondello, Chiara; Mothersill, Carmel; Olsen, Ann-Karin; Pavanello, Sofia; Raju, Jayadev; Rojas, Emilio; Roy, Rabindra; Ryan, Elizabeth; Ostrosky-Wegman, Patricia; Salem, Hosni K.; Scovassi, Ivana; Singh, Neetu; Vaccari, Monica; Van Schooten, Frederik J.; Valverde, Mahara; Woodrick, Jordan; Zhang, Luoping; van Larebeke, Nik; Kirsch-Volders, Micheline; Collins, Andrew R.

2015-01-01

Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome’s integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling, telomere length), acrylamide (DNA repair, chromosome segregation), bisphenol A (epigenetic modification, DNA damage signaling, mitochondrial function, chromosome segregation), benomyl (chromosome segregation), quinones (epigenetic modification) and nano-sized particles (epigenetic pathways, mitochondrial function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make scientists aware of the increasing need to unravel the underlying mechanisms via which chemicals at low doses can induce genome instability and thus promote carcinogenesis. PMID:26106144

High-frequency (8 to 16 kHz) reference thresholds and intrasubject threshold variability relative to ototoxicity criteria using a Sennheiser HDA 200 earphone.

Science.gov (United States)

Frank, T

2001-04-01

The first purpose of this study was to determine high-frequency (8 to 16 kHz) thresholds for standardizing reference equivalent threshold sound pressure levels (RETSPLs) for a Sennheiser HDA 200 earphone. The second and perhaps more important purpose of this study was to determine whether repeated high-frequency thresholds using a Sennheiser HDA 200 earphone had a lower intrasubject threshold variability than the ASHA 1994 significant threshold shift criteria for ototoxicity. High-frequency thresholds (8 to 16 kHz) were obtained for 100 (50 male, 50 female) normally hearing (0.25 to 8 kHz) young adults (mean age of 21.2 yr) in four separate test sessions using a Sennheiser HDA 200 earphone. The mean and median high-frequency thresholds were similar for each test session and increased as frequency increased. At each frequency, the high-frequency thresholds were not significantly (p > 0.05) different for gender, test ear, or test session. The median thresholds at each frequency were similar to the 1998 interim ISO RETSPLs; however, large standard deviations and wide threshold distributions indicated very high intersubject threshold variability, especially at 14 and 16 kHz. Threshold repeatability was determined by finding the threshold differences between each possible test session comparison (N = 6). About 98% of all of the threshold differences were within a clinically acceptable range of +/-10 dB from 8 to 14 kHz. The threshold differences between each subject's second, third, and fourth minus their first test session were also found to determine whether intrasubject threshold variability was less than the ASHA 1994 criteria for determining a significant threshold shift due to ototoxicity. The results indicated a false-positive rate of 0% for a threshold shift > or = 20 dB at any frequency and a false-positive rate of 2% for a threshold shift >10 dB at two consecutive frequencies. This study verified that the output of high-frequency audiometers at 0 dB HL using

Thermotactile perception thresholds measurement conditions.

Science.gov (United States)

Maeda, Setsuo; Sakakibara, Hisataka

2002-10-01

The purpose of this paper is to investigate the effects of posture, push force and rate of temperature change on thermotactile thresholds and to clarify suitable measuring conditions for Japanese people. Thermotactile (warm and cold) thresholds on the right middle finger were measured with an HVLab thermal aesthesiometer. Subjects were eight healthy male Japanese students. The effects of posture in measurement were examined in the posture of a straight hand and forearm placed on a support, the same posture without a support, and the fingers and hand flexed at the wrist with the elbow placed on a desk. The finger push force applied to the applicator of the thermal aesthesiometer was controlled at a 0.5, 1.0, 2.0 and 3.0 N. The applicator temperature was changed to 0.5, 1.0, 1.5, 2.0 and 2.5 degrees C/s. After each measurement, subjects were asked about comfort under the measuring conditions. Three series of experiments were conducted on different days to evaluate repeatability. Repeated measures ANOVA showed that warm thresholds were affected by the push force and the rate of temperature change and that cold thresholds were influenced by posture and push force. The comfort assessment indicated that the measurement posture of a straight hand and forearm laid on a support was the most comfortable for the subjects. Relatively high repeatability was obtained under measurement conditions of a 1 degrees C/s temperature change rate and a 0.5 N push force. Measurement posture, push force and rate of temperature change can affect the thermal threshold. Judging from the repeatability, a push force of 0.5 N and a temperature change of 1.0 degrees C/s in the posture with the straight hand and forearm laid on a support are recommended for warm and cold threshold measurements.

Doubler system quench detection threshold

International Nuclear Information System (INIS)

Kuepke, K.; Kuchnir, M.; Martin, P.

1983-01-01

The experimental study leading to the determination of the sensitivity needed for protecting the Fermilab Doubler from damage during quenches is presented. The quench voltage thresholds involved were obtained from measurements made on Doubler cable of resistance x temperature and voltage x time during quenches under several currents and from data collected during operation of the Doubler Quench Protection System as implemented in the B-12 string of 20 magnets. At 4kA, a quench voltage threshold in excess of 5.OV will limit the peak Doubler cable temperature to 452K for quenches originating in the magnet coils whereas a threshold of 0.5V is required for quenches originating outside of coils

Laser-Based Surface Modification of Microstructure for Carbon Fiber-Reinforced Plastics

Science.gov (United States)

Yang, Wenfeng; Sun, Ting; Cao, Yu; Li, Shaolong; Liu, Chang; Tang, Qingru

2018-05-01

Bonding repair is a powerful feature of carbon fiber-reinforced plastics (CFRP). Based on the theory of interface bonding, the interface adhesion strength and reliability of the CFRP structure will be directly affected by the microscopic features of the CFRP surface, including the microstructure, physical, and chemical characteristics. In this paper, laser-based surface modification was compared to Peel-ply, grinding, and polishing to comparatively evaluate the surface microstructure of CFRP. The surface microstructure, morphology, fiber damage, height and space parameters were investigated by scanning electron microscopy (SEM) and laser confocal microscopy (LCM). Relative to the conventional grinding process, laser modification of the CFRP surface can result in more uniform resin removal and better processing control and repeatability. This decreases the adverse impact of surface fiber fractures and secondary damage. The surface properties were significantly optimized, which has been reflected such things as the obvious improvement of surface roughness, microstructure uniformity, and actual area. The improved surface microstructure based on laser modification is more conducive to interface bonding of CFRP structure repair. This can enhance the interfacial adhesion strength and reliability of repair.

Surge-Resistant Nanocomposite Enameled Wire Using Silica Nanoparticles with Binary Chemical Compositions on the Surface

Directory of Open Access Journals (Sweden)

Jeseung Yoo

2015-01-01

Full Text Available We developed polyesterimide (PEI nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was confirmed by optical observation and viscosity measurement. The glass transition temperature of the silica-PEI nanocomposite increased with the silica content. The silica-dispersed PEI varnish was then used for enameled wire fabrication. The silica-PEI nanocomposite enameled wire exhibited a much longer lifetime compared to that of neat PEI enameled wire in partial discharge conditions.

Covalent modification of graphene and graphite using diazonium chemistry: tunable grafting and nanomanipulation.

Science.gov (United States)

Greenwood, John; Phan, Thanh Hai; Fujita, Yasuhiko; Li, Zhi; Ivasenko, Oleksandr; Vanderlinden, Willem; Van Gorp, Hans; Frederickx, Wout; Lu, Gang; Tahara, Kazukuni; Tobe, Yoshito; Uji-I, Hiroshi; Mertens, Stijn F L; De Feyter, Steven

2015-05-26

We shine light on the covalent modification of graphite and graphene substrates using diazonium chemistry under ambient conditions. We report on the nature of the chemical modification of these graphitic substrates, the relation between molecular structure and film morphology, and the impact of the covalent modification on the properties of the substrates, as revealed by local microscopy and spectroscopy techniques and electrochemistry. By careful selection of the reagents and optimizing reaction conditions, a high density of covalently grafted molecules is obtained, a result that is demonstrated in an unprecedented way by scanning tunneling microscopy (STM) under ambient conditions. With nanomanipulation, i.e., nanoshaving using STM, surface structuring and functionalization at the nanoscale is achieved. This manipulation leads to the removal of the covalently anchored molecules, regenerating pristine sp(2) hybridized graphene or graphite patches, as proven by space-resolved Raman microscopy and molecular self-assembly studies.

Reaction thresholds in doubly special relativity

International Nuclear Information System (INIS)

Heyman, Daniel; Major, Seth; Hinteleitner, Franz

2004-01-01

Two theories of special relativity with an additional invariant scale, 'doubly special relativity', are tested with calculations of particle process kinematics. Using the Judes-Visser modified conservation laws, thresholds are studied in both theories. In contrast with some linear approximations, which allow for particle processes forbidden in special relativity, both the Amelino-Camelia and Magueijo-Smolin frameworks allow no additional processes. To first order, the Amelino-Camelia framework thresholds are lowered and the Magueijo-Smolin framework thresholds may be raised or lowered

C-5 Propynyl Modifications Enhance the Mechanical Stability of DNA.

Science.gov (United States)

Aschenbrenner, Daniela; Baumann, Fabian; Milles, Lukas F; Pippig, Diana A; Gaub, Hermann E

2015-07-20

Increased thermal or mechanical stability of DNA duplexes is desired for many applications in nanotechnology or -medicine where DNA is used as a programmable building block. Modifications of pyrimidine bases are known to enhance thermal stability and have the advantage of standard base-pairing and easy integration during chemical DNA synthesis. Through single-molecule force spectroscopy experiments with atomic force microscopy and the molecular force assay we investigated the effect of pyrimidines harboring C-5 propynyl modifications on the mechanical stability of double-stranded DNA. Utilizing these complementary techniques, we show that propynyl bases significantly increase the mechanical stability if the DNA is annealed at high temperature. In contrast, modified DNA complexes formed at room temperature and short incubation times display the same stability as non-modified DNA duplexes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Chemical Sciences; Volume 129; Issue 11. Preparation, characterization, and post-synthetic ... The results revealed that MCM-22 has a layered sphere, doughnut like morphology and after modification, swollen and broken sphere was observed. Physicochemical analysis revealed that the ...

Durable chemical sensors based on field-effect transistors

NARCIS (Netherlands)

Reinhoudt, David

1995-01-01

The design of durable chemical sensors based on field-effect transistors (FETs) is described. After modification of an ion-sensitive FET (ISFET) with a polysiloxane membrane matrix, it is possible to attach all electroactive components covalently. Preliminary results of measurements with a

Site-specific chemical modification of antibody fragments using traceless cleavable linkers.

Science.gov (United States)

Bernardes, Gonçalo J L; Steiner, Martina; Hartmann, Isabelle; Neri, Dario; Casi, Giulio

2013-11-01

Antibody-drug conjugates (ADCs) are promising agents for the selective delivery of cytotoxic drugs to specific cells (for example, tumors). In this protocol, we describe two strategies for the precise modification at engineered C- or N-terminal cysteines of antibodies in IgG, diabody and small immunoprotein (SIP) formats that yield homogenous ADCs. In this protocol, cemadotin derivatives are used as model drugs, as these agents have a potent cytotoxic activity and are easy to synthesize. However, other drugs with similar functional groups could be considered. In the first approach, a cemadotin derivative containing a sulfhydryl group results in a mixed disulfide linkage. In the second approach, a cemadotin derivative containing an aldehyde group is joined via a thiazolidine linkage. The procedures outlined are robust, enabling the preparation of ADCs with a defined number of drugs per antibody in a time frame between 7 and 24 h.

Simulating Quantitative Cellular Responses Using Asynchronous Threshold Boolean Network Ensembles

Directory of Open Access Journals (Sweden)

Shah Imran

2011-07-01

Full Text Available Abstract Background With increasing knowledge about the potential mechanisms underlying cellular functions, it is becoming feasible to predict the response of biological systems to genetic and environmental perturbations. Due to the lack of homogeneity in living tissues it is difficult to estimate the physiological effect of chemicals, including potential toxicity. Here we investigate a biologically motivated model for estimating tissue level responses by aggregating the behavior of a cell population. We assume that the molecular state of individual cells is independently governed by discrete non-deterministic signaling mechanisms. This results in noisy but highly reproducible aggregate level responses that are consistent with experimental data. Results We developed an asynchronous threshold Boolean network simulation algorithm to model signal transduction in a single cell, and then used an ensemble of these models to estimate the aggregate response across a cell population. Using published data, we derived a putative crosstalk network involving growth factors and cytokines - i.e., Epidermal Growth Factor, Insulin, Insulin like Growth Factor Type 1, and Tumor Necrosis Factor α - to describe early signaling events in cell proliferation signal transduction. Reproducibility of the modeling technique across ensembles of Boolean networks representing cell populations is investigated. Furthermore, we compare our simulation results to experimental observations of hepatocytes reported in the literature. Conclusion A systematic analysis of the results following differential stimulation of this model by growth factors and cytokines suggests that: (a using Boolean network ensembles with asynchronous updating provides biologically plausible noisy individual cellular responses with reproducible mean behavior for large cell populations, and (b with sufficient data our model can estimate the response to different concentrations of extracellular ligands. Our

Gas-discharge plasma processes for surface modification and conversion of chemical substances. Application for fuel cells

Energy Technology Data Exchange (ETDEWEB)

Schroeder, K.; Meyer, D.; Rohland, B.; Heintze, M.; Zahn, R.J.; Hannemann, M.; Meusinger, J.; Ohl, A. [Institute of Non-Thermal Plasma Physics, Greifswald (Germany)]|[Gesellschaft fuer Angewandte Technik mbH Greifswald (Germany)]|[GAPC, Adam Opel AG, IPC, Ruesselsheim (Germany)

2001-07-01

The potential of plasma processes towards hydrogen and fuel cell technology will be demonstrated by two examples with preliminary results: 1. plasma modification of polymer electrolyte membranes for direct methanol fuel cells, and 2. plasma supported steam reforming.

Control of wettability of hydrogenated amorphous carbon thin films by laser-assisted micro- and nanostructuring

International Nuclear Information System (INIS)

Pfleging, Wilhelm; Kohler, Robert; Torge, Maika; Trouillet, Vanessa; Danneil, Friederike; Stueber, Michael

2011-01-01

A flexible and rapid surface functionalization of amorphous carbon films shows a great potential for various application fields such as biological surfaces and tribological systems. For this purpose, the combination of thin film deposition and subsequent laser material processing was investigated. Amorphous carbon layers doped with hydrogen were deposited on silicon wafers by reactive direct-current magnetron sputtering. Films with three different hydrogen contents were synthesized. Subsequent to the thin film deposition process, UV laser material processing at wavelengths of 193 nm or 248 nm was performed with respect to chemical surface modification and surface structuring on micro- and nanometer scale. Depending on structure size and laser-induced chemical surface modification the adjustment of the surface energy and wetting behaviour in a broad range from hydrophobic to hydrophilic was possible. The chemical modification and the ablation mechanisms near the ablation threshold were strongly influenced by the hydrogen content in amorphous carbon thin films. Structural and chemical information of the as-deposited and modified films was obtained by Raman spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements.

Selectivity on-target of bromodomain chemical probes by structure-guided medicinal chemistry and chemical biology.

Science.gov (United States)

Galdeano, Carles; Ciulli, Alessio

2016-09-01

Targeting epigenetic proteins is a rapidly growing area for medicinal chemistry and drug discovery. Recent years have seen an explosion of interest in developing small molecules binding to bromodomains, the readers of acetyl-lysine modifications. A plethora of co-crystal structures has motivated focused fragment-based design and optimization programs within both industry and academia. These efforts have yielded several compounds entering the clinic, and many more are increasingly being used as chemical probes to interrogate bromodomain biology. High selectivity of chemical probes is necessary to ensure biological activity is due to an on-target effect. Here, we review the state-of-the-art of bromodomain-targeting compounds, focusing on the structural basis for their on-target selectivity or lack thereof. We also highlight chemical biology approaches to enhance on-target selectivity.

Low-level toxicity of chemicals: No acceptable levels?

Directory of Open Access Journals (Sweden)

Bruce P Lanphear

2017-12-01

Full Text Available Over the past 3 decades, in a series of studies on some of the most extensively studied toxic chemicals and pollutants, scientists have found that the amount of toxic chemical linked with the development of a disease or death-which is central to determining "safe" or "hazardous" levels-is proportionately greater at the lowest dose or levels of exposure. These results, which are contrary to the way the United States Environmental Protection Agency (EPA and other regulatory agencies assess the risk of chemicals, indicate that we have underestimated the impact of toxic chemicals on death and disease. If widely disseminated chemicals and pollutants-like radon, lead, airborne particles, asbestos, tobacco, and benzene-do not exhibit a threshold and are proportionately more toxic at the lowest levels of exposure, we will need to achieve near-zero exposures to protect public health.

Enhancing the functionality of cotton fabric by physical and chemical pre-treatments: A comparative study.

Science.gov (United States)

Gargoubi, Sondes; Tolouei, Ranna; Chevallier, Pascale; Levesque, Lucie; Ladhari, Neji; Boudokhane, Chedly; Mantovani, Diego

2016-08-20

Recently, antimicrobial and decontaminating textiles, such as cotton a natural carbohydrate polymer, are generating more attention. Plant materials used for natural dyes are expected to impart biofunctional properties and high added valued functional textiles. In the current study, surface modification of cotton to maximize the dye amount on the surface has been investigated. Physical modification using nitrogen-hydrogen plasma, chemical modification using chitosan and chemical modification using dopamine as biopolymers imparting amino groups were explored. Furthermore, dye exhaustion of curcumin, as a natural functional dye has been studied. Dye stability tests were also performed after fabric washing using hospital washing protocol to predict the durability of the functionalizations. The results demonstrated that cotton surfaces treated with dopamine exhibit a high level of dye uptake (78%) and a good washing fastness. The use of non-toxic and natural additives during cotton finishing process could give the opportunity of cradle to cradle design for antimicrobial textile industries. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optimizing Systems of Threshold Detection Sensors

National Research Council Canada - National Science Library

Banschbach, David C

2008-01-01

.... Below the threshold all signals are ignored. We develop a mathematical model for setting individual sensor thresholds to obtain optimal probability of detecting a significant event, given a limit on the total number of false positives allowed...

Chemical modification of bitumen heavy ends and their non-fuel uses

Energy Technology Data Exchange (ETDEWEB)

Moschopedis, S.E.; Speight, J.G.

1976-01-01

Bitumen asphaltenes undergo a variety of simple chemical conversions. For example, asphaltenes can be oxidized, sulfonated, sulfomethylated, halogenated, and phosphorylated. The net result is the introduction of functional entities into the asphaltene structure which confers interesting properties on the products for which a variety of uses are proposed.

Identifying Threshold Concepts for Information Literacy: A Delphi Study

Directory of Open Access Journals (Sweden)

Lori Townsend

2016-06-01

Full Text Available This study used the Delphi method to engage expert practitioners on the topic of threshold concepts for information literacy. A panel of experts considered two questions. First, is the threshold concept approach useful for information literacy instruction? The panel unanimously agreed that the threshold concept approach holds potential for information literacy instruction. Second, what are the threshold concepts for information literacy instruction? The panel proposed and discussed over fifty potential threshold concepts, finally settling on six information literacy threshold concepts.

Tungstate-induced color-pattern modifications of butterfly wings are independent of stress response and ecdysteroid effect.

Science.gov (United States)

Otaki, Joji M; Ogasawara, Tsuyoshi; Yamamoto, Haruhiko

2005-06-01

Systemic injections of sodium tungstate, a protein-tyrosine phosphatase (PTPase) inhibitor, to pupae immediately after pupation have been shown to efficiently produce characteristic color-pattern modifications on the wings of many species of butterflies. Here we demonstrated that the tungstate-induced modification pattern was entirely different from other chemically-induced ones in a species of nymphalid butterfly Junonia (Precis) orithya. In this species, the systemic injections of tungstate produced characteristic expansion of black area and shrinkage of white area together with the move of parafocal elements toward the wing base. Overall, pattern boundaries became obscure. In contrast, an entirely different modification pattern, overall darkening of wings, was observed by the injections of stress-inducing chemicals, thapsigargin, ionomycin, or geldanamycin, to pupae under the rearing conditions for the adult summer form. On the ventral wings, this darkening was due to an increase of the proportion of peppered dark scales, which was reminiscent of the natural fall form of this species. Under the same rearing conditions, the injections of ecdysteroid, which is a well-known hormone being responsible for the seasonal polyphenism of nymphalid butterflies, yielded overall expansion of orange area especially around eyespots. Taken together, we conclude that the tungstate-induced modifications are clearly distinguishable from those of stress response and ecdysteroid effect. This conclusion then suggests that the putative PTPase signaling pathway that is sensitive to tungstate uniquely contributes to the wing-wide color-pattern development in butterflies.

Study of a spherical gaseous detector for research of rare events at low energy threshold

International Nuclear Information System (INIS)

Dastgheibi-Fard, Ali

2014-01-01

The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of a particle detector, with a broad range of applications. Its main features include a very low energy threshold which is independent of the volume (due to its very low capacitance), a good energy resolution, robustness and a single detection readout channel. SEDINE, a low background detector installed at the underground site of Laboratoire Souterrain de Modane is currently being operated and aims at measuring events at a very low energy threshold, around 40 eV. The sensitivity for the rare events detection at low energy is correlated to the detector background and to the decreasing the level of energy threshold, which was the main point of this thesis. A major effort has been devoted to the operating of the experimental detector. Several detection parameters were optimized: the electric field homogeneity in the sphere, keeping clear of sparks, the electronic noise level and the leak rate of the detector. The detector is optimized for operation with a high pressure stable gain. The modification of the shield, cleanings of the detector and the addition of an anti-Radon tent have significantly reduced the background of SEDINE. Progress has increased the sensitivity of the detector at low energy up to a value comparable to the results other underground research experiences for the low mass WIMPs. We will present the results with a measured background in the region of keV, which has allowed us to show a competitive figure of exclusion for the production of light dark matter. (author) [fr

Multiuser switched diversity scheduling systems with per-user threshold

KAUST Repository

Nam, Haewoon

2010-05-01

A multiuser switched diversity scheduling scheme with per-user feedback threshold is proposed and analyzed in this paper. The conventional multiuser switched diversity scheduling scheme uses a single feedback threshold for every user, where the threshold is a function of the average signal-to-noise ratios (SNRs) of the users as well as the number of users involved in the scheduling process. The proposed scheme, however, constructs a sequence of feedback thresholds instead of a single feedback threshold such that each user compares its channel quality with the corresponding feedback threshold in the sequence. Numerical and simulation results show that thanks to the flexibility of threshold selection, where a potentially different threshold can be used for each user, the proposed scheme provides a higher system capacity than that for the conventional scheme. © 2006 IEEE.

Isotope dependence of chemical erosion of carbon

International Nuclear Information System (INIS)

Reinhold, C.O.; Krstic, P.S.; Stuart, S.J.; Zhang, H.; Harris, P.R.; Meyer, F.W.

2010-01-01

We study the chemical erosion of hydrogen-supersaturated carbon due to bombardment by hydrogen isotopes H, D, and T at energies of 1-30 eV using classical molecular dynamics simulations. The chemical structure at the hydrogen-saturated interface (the distribution of terminal hydrocarbon moieties, in particular) shows a weak dependence on the mass of the impinging atoms. However, the sputtering yields increase considerably with increasing projectile mass. We analyze the threshold energies of chemical sputtering reaction channels and show that they are nearly mass independent, as expected from elementary bond-breaking chemical reactions involving hydrocarbons. Chemical sputtering yields for D impact are compared with new experimental data. Good agreement is found for small hydrocarbons but the simulations overestimate the production of large hydrocarbons for energies larger than 15 eV. We present a thorough analysis of the dependence of our simulations on the parameters of the bombardment schemes and discuss open questions and possible avenues for development.

Proton-Conducting Sulfonated Ionomers by Chemical Modification and Atom Transfer Radical Polymerization

DEFF Research Database (Denmark)

Nielsen, Mads Møller

The cornerstone in this dissertation is made up by three individual assessments of the diversity in the macromolecular landscape that can be obtained by applying relatively few efficient chemical tools. The intention is to gain deeper knowledge on the chemical tuning of proton exchange membranes...... of hydrocarbon macromolecular architectures, PSU with postsulfonated polystyrene (PS) grafts are investigated. Here, IEC is controlled through the degree of substitution, the graft length and DS. The grafting is performed with atom transfer radical polymerization (ATRP). The third assessment is dedicated...... of control by ATRP and click chemistry enables a wide selection of polymer structures with the handles: degree of substitution (DS), polymerization and sulfonation, and blending....

Posttranslational Modifications and the Immunogenicity of Biotherapeutics

Directory of Open Access Journals (Sweden)

Roy Jefferis

2016-01-01

Full Text Available Whilst the amino acid sequence of a protein is determined by its gene sequence, the final structure and function are determined by posttranslational modifications (PTMs, including quality control (QC in the endoplasmic reticulum (ER and during passage through the Golgi apparatus. These processes are species and cell specific and challenge the biopharmaceutical industry when developing a production platform for the generation of recombinant biologic therapeutics. Proteins and glycoproteins are also subject to chemical modifications (CMs both in vivo and in vitro. The individual is naturally tolerant to molecular forms of self-molecules but nonself variants can provoke an immune response with the generation of anti-drug antibodies (ADA; aggregated forms can exhibit enhanced immunogenicity and QC procedures are developed to avoid or remove them. Monoclonal antibody therapeutics (mAbs are a special case because their purpose is to bind the target, with the formation of immune complexes (ICs, a particular form of aggregate. Such ICs may be removed by phagocytic cells that have antigen presenting capacity. These considerations may frustrate the possibility of ameliorating the immunogenicity of mAbs by rigorous exclusion of aggregates from drug product. Alternate strategies for inducing immunosuppression or tolerance are discussed.

Effect of radiation-induced modification in fluoroelastomer

International Nuclear Information System (INIS)

Zen, Heloisa Augusto; Lugao, Ademar Benevolo

2013-01-01

Polymers exposed to ionizing irradiation, even at low doses, often undergo structural changes accompanied by molecular crosslinking and chain scission (degradation) reactions. The general effect of the radiation on polymers is determined by the ratio of crosslinking to chain scission events. This ratio depends on parameters such as chemical structure, physical state, radicals stability and mobility, irradiation rate and irradiation atmosphere. The radiation process is a large used technique to promote modification in their structures to apply them in different areas and is well known for its merits and potential in modifying the chemical and the physical properties of polymeric materials without cause drastic changes in their inherent properties, depend on the dose irradiated. In this study was used fluoroelastomer with 70% - fluor that having excellent thermal, chemical and mechanical properties. Vulcanized and non-vulcanized samples of this material were submitted to gamma radiation under air atmosphere in order to observe the effect of atmosphere in the polymer matrix. The irradiated doses were 5, 10 and 20kGy, at room temperature. The characterization was made by scanning electron microscope (SEM), infrared spectroscopy using attenuate reflectance (ATR-IR) and X-ray diffraction. The results demonstrated which was expected, the degradation reactions were observed. (author)

Effect of surface modification on carbon fiber and its reinforced phenolic matrix composite

Energy Technology Data Exchange (ETDEWEB)

Yuan Hua [Key Laboratory for Liquid phase chemical oxidation Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Carbon Fibre Engineering Research Center, Faculty of Materials Science, Shandong University, Jinan 250061 (China); Wang Chengguo, E-mail: sduwangchg@gmail.com [Carbon Fibre Engineering Research Center, Faculty of Materials Science, Shandong University, Jinan 250061 (China); Zhang Shan; Lin Xue [Carbon Fibre Engineering Research Center, Faculty of Materials Science, Shandong University, Jinan 250061 (China)

2012-10-15

Highlights: Black-Right-Pointing-Pointer We used very simple and effective modification method to treat PAN-based carbon fiber by liquid oxidation and coupling agent. Black-Right-Pointing-Pointer Carbon fiber surface functional groups were analyzed by LRS and XPS. Black-Right-Pointing-Pointer Proper treatment of carbon fiber can prove an effective way to increase composite's performance. Black-Right-Pointing-Pointer Carbon fiber surface modifications by oxidation and APS could strengthen fiber activity and enlarge surface area as well as its roughness. - Abstract: In this work, polyacrylonitrile (PAN)-based carbon fiber were chemically modified with H{sub 2}SO{sub 4}, KClO{sub 3} and silane coupling agent ({gamma}-aminopropyltriethoxysilane, APS), and carbon fiber reinforced phenolic matrix composites were prepared. The structural and surface characteristics of the carbon fiber were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), laser Raman scattering (LRS) and Fourier transform infrared spectroscopy (FTIR). Single fiber mechanical properties, specific surface area, composite impact properties and interfacial shear strength (ILSS) were researched to indicate the effects of surface modification on fibers and the interaction between modified fiber surface and phenolic matrix. The results showed that carbon fiber surface modification by oxidation and APS can strengthen fiber surface chemical activity and enlarge the fiber surface area as well as its roughness. When carbon fiber (CF) is oxidized treatment, the oxygen content as well as the O/C ratio will be obviously increased. Oxygen functional groups increase with oxidation time increasing. Carbon fiber treated with APS will make C-O-R content increase and O-C=O content decrease due to surface reaction. Proper treatment of carbon fiber with acid and silane coupling agent prove an effective way to increase the interfacial adhesion and improve the mechanical and outdoor

Effect of surface modification on carbon fiber and its reinforced phenolic matrix composite

International Nuclear Information System (INIS)

Yuan Hua; Wang Chengguo; Zhang Shan; Lin Xue

2012-01-01

Highlights: ► We used very simple and effective modification method to treat PAN-based carbon fiber by liquid oxidation and coupling agent. ► Carbon fiber surface functional groups were analyzed by LRS and XPS. ► Proper treatment of carbon fiber can prove an effective way to increase composite's performance. ► Carbon fiber surface modifications by oxidation and APS could strengthen fiber activity and enlarge surface area as well as its roughness. - Abstract: In this work, polyacrylonitrile (PAN)-based carbon fiber were chemically modified with H 2 SO 4 , KClO 3 and silane coupling agent (γ-aminopropyltriethoxysilane, APS), and carbon fiber reinforced phenolic matrix composites were prepared. The structural and surface characteristics of the carbon fiber were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), laser Raman scattering (LRS) and Fourier transform infrared spectroscopy (FTIR). Single fiber mechanical properties, specific surface area, composite impact properties and interfacial shear strength (ILSS) were researched to indicate the effects of surface modification on fibers and the interaction between modified fiber surface and phenolic matrix. The results showed that carbon fiber surface modification by oxidation and APS can strengthen fiber surface chemical activity and enlarge the fiber surface area as well as its roughness. When carbon fiber (CF) is oxidized treatment, the oxygen content as well as the O/C ratio will be obviously increased. Oxygen functional groups increase with oxidation time increasing. Carbon fiber treated with APS will make C-O-R content increase and O-C=O content decrease due to surface reaction. Proper treatment of carbon fiber with acid and silane coupling agent prove an effective way to increase the interfacial adhesion and improve the mechanical and outdoor performance of the resulting fiber/resin composites.

Pain thresholds, supra-threshold pain and lidocaine sensitivity in patients with erythromelalgia, including the I848Tmutation in NaV 1.7.

Science.gov (United States)

Helås, T; Sagafos, D; Kleggetveit, I P; Quiding, H; Jönsson, B; Segerdahl, M; Zhang, Z; Salter, H; Schmelz, M; Jørum, E

2017-09-01

Nociceptive thresholds and supra-threshold pain ratings as well as their reduction upon local injection with lidocaine were compared between healthy subjects and patients with erythromelalgia (EM). Lidocaine (0.25, 0.50, 1.0 or 10 mg/mL) or placebo (saline) was injected intradermally in non-painful areas of the lower arm, in a randomized, double-blind manner, to test the effect on dynamic and static mechanical sensitivity, mechanical pain sensitivity, thermal thresholds and supra-threshold heat pain sensitivity. Heat pain thresholds and pain ratings to supra-threshold heat stimulation did not differ between EM-patients (n = 27) and controls (n = 25), neither did the dose-response curves for lidocaine. Only the subgroup of EM-patients with mutations in sodium channel subunits Na V 1.7, 1.8 or 1.9 (n = 8) had increased lidocaine sensitivity for supra-threshold heat stimuli, contrasting lower sensitivity to strong mechanical stimuli. This pattern was particularly clear in the two patients carrying the Na V 1.7 I848T mutations in whom lidocaine's hyperalgesic effect on mechanical pain sensitivity contrasted more effective heat analgesia. Heat pain thresholds are not sensitized in EM patients, even in those with gain-of-function mutations in Na V 1.7. Differential lidocaine sensitivity was overt only for noxious stimuli in the supra-threshold range suggesting that sensitized supra-threshold encoding is important for the clinical pain phenotype in EM in addition to lower activation threshold. Intracutaneous lidocaine dose-dependently blocked nociceptive sensations, but we did not identify EM patients with particular high lidocaine sensitivity that could have provided valuable therapeutic guidance. Acute pain thresholds and supra-threshold heat pain in controls and patients with erythromelalgia do not differ and have the same lidocaine sensitivity. Acute heat pain thresholds even in EM patients with the Na V 1.7 I848T mutation are normal and only nociceptor

A new green methodology for surface modification of diatomite filler in elastomers

Energy Technology Data Exchange (ETDEWEB)

Lamastra, F.R. [Italian Interuniversity Consortium on Materials Science and Technology (INSTM), Research Unit Roma Tor Vergata, Via del Politecnico 1, 00133, Rome (Italy); Mori, S.; Cherubini, V. [Italian Interuniversity Consortium on Materials Science and Technology (INSTM), Research Unit Roma Tor Vergata, Via del Politecnico 1, 00133, Rome (Italy); Department of Enterprise Engineering, University of Rome ' Tor Vergata' , Via del Politecnico 1, 00133, Rome (Italy); Scarselli, M. [Department of Physics, University of Rome ' Tor Vergata' , Via della Ricerca Scientifica 1, 00133, Rome (Italy); Nanni, F., E-mail: fnanni@ing.uniroma2.it [Italian Interuniversity Consortium on Materials Science and Technology (INSTM), Research Unit Roma Tor Vergata, Via del Politecnico 1, 00133, Rome (Italy); Department of Enterprise Engineering, University of Rome ' Tor Vergata' , Via del Politecnico 1, 00133, Rome (Italy)

2017-06-15

In this work a new, simple and green protocol to introduce a limited content of silanol groups on the surface of an hydrophobic diatomite, in order to be slightly hydrophilic and susceptible to be silanized by bifunctional, sulfur-containing organosilanes for rubber applications, is proposed. The chemical modification was carried out at 85 °C in a solution of H{sub 2}O:NaOH:H{sub 2}O{sub 2}. The modified diatomite was then silanized with bis(triethoxysilylpropyl) disulfide by a procedure that does not involve toxic solvent. Morphological features and elemental composition of diatomite were investigated by Field emission scanning electron microscopy coupled with Energy dispersive X-ray spectroscopy. The surface modification and silanization process were assessed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Diatomite was composed by micrometric frustules from different diatom species with pore size ranging from 25 nm to 1 μm. The spectroscopic characterizations confirmed the surface modification of diatomite with some silanols that acted as sites for silanization reaction. The silanized diatomite and the untreated one were used as filler in unvulcanized solvent-cast SBR films in order to verify that the modification does not negatively affect the polymer/filler interface and as consequence the mechanical properties. Mechanical properties of the realized samples were assessed by uniaxial tensile tests. Films filled with 10 wt% of diatomite (untreated or silanized) showed an increase of Elastic Modulus about of 50% and a decrease of the strain at break with respect to SBR samples, while the tensile strength was not significantly affected by the diatomite addition. SEM images of fracture surfaces of tested specimens showed a fine dispersion of both untreated and silanized diatomite in the polymeric matrix and the achieving of a good interfacial adhesion SBR/fillers. The silanized diatomite, as it is potentially able to bind

A new green methodology for surface modification of diatomite filler in elastomers

International Nuclear Information System (INIS)

Lamastra, F.R.; Mori, S.; Cherubini, V.; Scarselli, M.; Nanni, F.

2017-01-01

In this work a new, simple and green protocol to introduce a limited content of silanol groups on the surface of an hydrophobic diatomite, in order to be slightly hydrophilic and susceptible to be silanized by bifunctional, sulfur-containing organosilanes for rubber applications, is proposed. The chemical modification was carried out at 85 °C in a solution of H_2O:NaOH:H_2O_2. The modified diatomite was then silanized with bis(triethoxysilylpropyl) disulfide by a procedure that does not involve toxic solvent. Morphological features and elemental composition of diatomite were investigated by Field emission scanning electron microscopy coupled with Energy dispersive X-ray spectroscopy. The surface modification and silanization process were assessed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Diatomite was composed by micrometric frustules from different diatom species with pore size ranging from 25 nm to 1 μm. The spectroscopic characterizations confirmed the surface modification of diatomite with some silanols that acted as sites for silanization reaction. The silanized diatomite and the untreated one were used as filler in unvulcanized solvent-cast SBR films in order to verify that the modification does not negatively affect the polymer/filler interface and as consequence the mechanical properties. Mechanical properties of the realized samples were assessed by uniaxial tensile tests. Films filled with 10 wt% of diatomite (untreated or silanized) showed an increase of Elastic Modulus about of 50% and a decrease of the strain at break with respect to SBR samples, while the tensile strength was not significantly affected by the diatomite addition. SEM images of fracture surfaces of tested specimens showed a fine dispersion of both untreated and silanized diatomite in the polymeric matrix and the achieving of a good interfacial adhesion SBR/fillers. The silanized diatomite, as it is potentially able to bind chemically to

When do price thresholds matter in retail categories?

OpenAIRE

Pauwels, Koen; Srinivasan, Shuba; Franses, Philip Hans

2007-01-01

textabstractMarketing literature has long recognized that brand price elasticity need not be monotonic and symmetric, but has yet to provide generalizable market-level insights on threshold-based price elasticity, asymmetric thresholds, and the sign and magnitude of elasticity transitions. This paper introduces smooth transition regression models to study threshold-based price elasticity of the top 4 brands across 20 fast-moving consumer good categories. Threshold-based price elasticity is fo...

Chemical treatment of the intra-canal dentin surface: a new approach to modify dentin hydrophobicity

Directory of Open Access Journals (Sweden)

Cesar GAITAN-FONSECA

2013-01-01

Full Text Available Objective This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS. Material and Methods An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA. The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT. Results and Conclusions Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system.

High-order above-threshold dissociation of molecules

Science.gov (United States)

Lu, Peifen; Wang, Junping; Li, Hui; Lin, Kang; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Zhang, Wenbin; Ma, Junyang; Li, Hanxiao; Zeng, Heping; He, Feng; Wu, Jian

2018-03-01

Electrons bound to atoms or molecules can simultaneously absorb multiple photons via the above-threshold ionization featured with discrete peaks in the photoelectron spectrum on account of the quantized nature of the light energy. Analogously, the above-threshold dissociation of molecules has been proposed to address the multiple-photon energy deposition in the nuclei of molecules. In this case, nuclear energy spectra consisting of photon-energy spaced peaks exceeding the binding energy of the molecular bond are predicted. Although the observation of such phenomena is difficult, this scenario is nevertheless logical and is based on the fundamental laws. Here, we report conclusive experimental observation of high-order above-threshold dissociation of H2 in strong laser fields where the tunneling-ionized electron transfers the absorbed multiphoton energy, which is above the ionization threshold to the nuclei via the field-driven inelastic rescattering. Our results provide an unambiguous evidence that the electron and nuclei of a molecule as a whole absorb multiple photons, and thus above-threshold ionization and above-threshold dissociation must appear simultaneously, which is the cornerstone of the nowadays strong-field molecular physics.

Automated backbone assignment of labeled proteins using the threshold accepting algorithm

International Nuclear Information System (INIS)

Leutner, Michael; Gschwind, Ruth M.; Liermann, Jens; Schwarz, Christian; Gemmecker, Gerd; Kessler, Horst

1998-01-01

The sequential assignment of backbone resonances is the first step in the structure determination of proteins by heteronuclear NMR. For larger proteins, an assignment strategy based on proton side-chain information is no longer suitable for the use in an automated procedure. Our program PASTA (Protein ASsignment by Threshold Accepting) is therefore designed to partially or fully automate the sequential assignment of proteins, based on the analysis of NMR backbone resonances plus C β information. In order to overcome the problems caused by peak overlap and missing signals in an automated assignment process, PASTA uses threshold accepting, a combinatorial optimization strategy, which is superior to simulated annealing due to generally faster convergence and better solutions. The reliability of this algorithm is shown by reproducing the complete sequential backbone assignment of several proteins from published NMR data. The robustness of the algorithm against misassigned signals, noise, spectral overlap and missing peaks is shown by repeating the assignment with reduced sequential information and increased chemical shift tolerances. The performance of the program on real data is finally demonstrated with automatically picked peak lists of human nonpancreatic synovial phospholipase A 2 , a protein with 124 residues

Thresholds in Xeric Hydrology and Biogeochemistry

Science.gov (United States)

Meixner, T.; Brooks, P. D.; Simpson, S. C.; Soto, C. D.; Yuan, F.; Turner, D.; Richter, H.

2011-12-01

Due to water limitation, thresholds in hydrologic and biogeochemical processes are common in arid and semi-arid systems. Some of these thresholds such as those focused on rainfall runoff relationships have been well studied. However to gain a full picture of the role that thresholds play in driving the hydrology and biogeochemistry of xeric systems a full view of the entire array of processes at work is needed. Here a walk through the landscape of xeric systems will be conducted illustrating the powerful role of hydrologic thresholds on xeric system biogeochemistry. To understand xeric hydro-biogeochemistry two key ideas need to be focused on. First, it is important to start from a framework of reaction and transport. Second an understanding of the temporal and spatial components of thresholds that have a large impact on hydrologic and biogeochemical fluxes needs to be offered. In the uplands themselves episodic rewetting and drying of soils permits accelerated biogeochemical processing but also more gradual drainage of water through the subsurface than expected in simple conceptions of biogeochemical processes. Hydrologic thresholds (water content above hygroscopic) results in a stop start nutrient spiral of material across the landscape since runoff connecting uplands to xeric perennial riparian is episodic and often only transports materials a short distance (100's of m). This episodic movement results in important and counter-intuitive nutrient inputs to riparian zones but also significant processing and uptake of nutrients. The floods that transport these biogeochemicals also result in significant input to riparian groundwater and may be key to sustaining these critical ecosystems. Importantly the flood driven recharge process itself is a threshold process dependent on flood characteristics (floods greater than 100 cubic meters per second) and antecedent conditions (losing to near neutral gradients). Floods also appear to influence where arid and semi