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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

Indirect fluorometric detection techniques on thin layer chromatography and effect of ultrasound on gel electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yinfa, Ma.

Thin-layer chromatography (TLC) is a broadly applicable separation technique. It offers many advantages over high performance liquid chromatography (HPLC), such as easily adapted for two-dimensional separation, for whole-column'' detection and for handling multiple samples, etc. However, due to its draggy development of detection techniques comparing with HPLC, TLC has not received the attention it deserves. Therefore, exploring new detection techniques is very important to the development of TLC. It is the principal of this dissertation to present a new detection method for TLC -- indirect fluorometric detection method. This detection technique is universal sensitive, nondestructive, and simple. This will bemore » described in detail from Sections 1 through Section 5. Section 1 and 3 describe the indirect fluorometric detection of anions and nonelectrolytes in TLC. In Section 2, a detection method for cations based on fluorescence quenching of ethidium bromide is presented. In Section 4, a simple and interesting TLC experiment is designed, three different fluorescence detection principles are used for the determination of caffeine, saccharin and sodium benzoate in beverages. A laser-based indirect fluorometric detection technique in TLC is developed in Section 5. Section 6 is totally different from Sections 1 through 5. An ultrasonic effect on the separation of DNA fragments in agarose gel electrophoresis is investigated. 262 refs.« less

Ethanolic extraction, purification, and partial characterization of a fluorescent toxin from the coral reef crab, Lophozozymus pictor.

PubMed

Lau, C O; Tan, C H; Khoo, H E; Li, Q T; Yuen, R

1995-01-01

A purification procedure for Lophozozymus pictor toxin (LPTX) following ethanolic extraction of whole crab homogenate is described. The ethanol-extracted toxin (LPTX-E) had higher yield and specific activity than the hot aqueous-extracted one (LPTX-H). It was found that LPTX-E was fluorescent and cochromatographed with LPTX-H on two-dimensional thin-layer chromatography. Although LPTX-E, LPTX-H, and palytoxin (P. caribaeorum, PTX) had similar migration and retention times when analysed on high performance capillary electrophoresis and gel permeation-high performance liquid chromatography respectively, LPTX-E and LPTX-H were both fluorescent in contrast to PTX. In addition, LPTX-E had a different retention time compared with PTX when chromatographed on reversed phase high performance liquid chromatography in the solvent system 80% acetonitrile and 0.02 M Tris-HCl, pH 7.2, at a 4:1 ratio, respectively, indicating some differences in their chemical structures.

Room temperature rubbing for few-layer two-dimensional thin flakes directly on flexible polymer substrates

PubMed Central

Yu, Yan; Jiang, Shenglin; Zhou, Wenli; Miao, Xiangshui; Zeng, Yike; Zhang, Guangzu; Liu, Sisi

2013-01-01

The functional layers of few-layer two-dimensional (2-D) thin flakes on flexible polymers for stretchable applications have attracted much interest. However, most fabrication methods are “indirect” processes that require transfer steps. Moreover, previously reported “transfer-free” methods are only suitable for graphene and not for other few-layer 2-D thin flakes. Here, a friction based room temperature rubbing method is proposed for fabricating different types of few-layer 2-D thin flakes (graphene, hexagonal boron nitride (h-BN), molybdenum disulphide (MoS2), and tungsten disulphide (WS2)) on flexible polymer substrates. Commercial 2-D raw materials (graphite, h-BN, MoS2, and WS2) that contain thousands of atom layers were used. After several minutes, different types of few-layer 2-D thin flakes were fabricated directly on the flexible polymer substrates by rubbing procedures at room temperature and without any transfer step. These few-layer 2-D thin flakes strongly adhere to the flexible polymer substrates. This strong adhesion is beneficial for future applications. PMID:24045289

Frontally eluted components procedure with thin layer chromatography as a mode of sample preparation for high performance liquid chromatography quantitation of acetaminophen in biological matrix.

PubMed

Klimek-Turek, A; Sikora, M; Rybicki, M; Dzido, T H

2016-03-04

A new concept of using thin-layer chromatography to sample preparation for the quantitative determination of solute/s followed by instrumental techniques is presented Thin-layer chromatography (TLC) is used to completely separate acetaminophen and its internal standard from other components (matrix) and to form a single spot/zone containing them at the solvent front position (after the final stage of the thin-layer chromatogram development). The location of the analytes and internal standard in the solvent front zone allows their easy extraction followed by quantitation by HPLC. The exctraction procedure of the solute/s and internal standard can proceed from whole solute frontal zone or its part without lowering in accuracy of quantitative analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Thin Layer Chromatography (TLC) of Chlorophyll Pigments.

ERIC Educational Resources Information Center

Foote, Jerry

1984-01-01

Background information, list of materials needed, procedures used, and discussion of typical results are provided for an experiment on the thin layer chromatography of chlorophyll pigments. The experiment works well in high school, since the chemicals used are the same as those used in paper chromatography of plant pigments. (JN)

A Cost-Effective Two-Part Experiment for Teaching Introductory Organic Chemistry Techniques

ERIC Educational Resources Information Center

Sadek, Christopher M.; Brown, Brenna A.; Wan, Hayley

2011-01-01

This two-part laboratory experiment is designed to be a cost-effective method for teaching basic organic laboratory techniques (recrystallization, thin-layer chromatography, column chromatography, vacuum filtration, and melting point determination) to large classes of introductory organic chemistry students. Students are exposed to different…

Quantitative analysis of psilocybin and psilocin in psilocybe baeocystis (Singer and Smith) by high-performance liquid chromatography and by thin-layer chromatography.

PubMed

Beug, M W; Bigwood, J

1981-03-27

Rapid quantification of psilocybin and psilocin in extracts of wild mushrooms is accomplished by reversed-phase high-performance liquid chromatography with paired-ion reagents. Nine solvent systems and three solid supports are evaluated for their efficiency in separating psilocybin, psilocin and other components of crude mushroom extracts by thin-layer chromatography.

Critical Transitions in Thin Layer Turbulence

NASA Astrophysics Data System (ADS)

Benavides, Santiago; Alexakis, Alexandros

2017-11-01

We investigate a model of thin layer turbulence that follows the evolution of the two-dimensional motions u2 D (x , y) along the horizontal directions (x , y) coupled to a single Fourier mode along the vertical direction (z) of the form uq (x , y , z) = [vx (x , y) sin (qz) ,vy (x , y) sin (qz) ,vz (x , y) cos (qz) ] , reducing thus the system to two coupled, two-dimensional equations. Its reduced dimensionality allows a thorough investigation of the transition from a forward to an inverse cascade of energy as the thickness of the layer H = π / q is varied.Starting from a thick layer and reducing its thickness it is shown that two critical heights are met (i) one for which the forward unidirectional cascade (similar to three-dimensional turbulence) transitions to a bidirectional cascade transferring energy to both small and large scales and (ii) one for which the bidirectional cascade transitions to a unidirectional inverse cascade when the layer becomes very thin (similar to two-dimensional turbulence). The two critical heights are shown to have different properties close to criticality that we are able to analyze with numerical simulations for a wide range of Reynolds numbers and aspect ratios. This work was Granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01).

Genome sequencing-assisted identification and the first functional validation of N-acyl-homoserine-lactone synthases from the Sphingomonadaceae family

PubMed Central

Gan, Han Ming; Dailey, Lucas K.; Halliday, Nigel; Williams, Paul; Hudson, André O.

2016-01-01

Background Members of the genus Novosphingobium have been isolated from a variety of environmental niches. Although genomics analyses have suggested the presence of genes associated with quorum sensing signal production e.g., the N-acyl-homoserine lactone (AHL) synthase (luxI) homologs in various Novosphingobium species, to date, no luxI homologs have been experimentally validated. Methods In this study, we report the draft genome of the N-(AHL)-producing bacterium Novosphingobium subterraneum DSM 12447 and validate the functions of predicted luxI homologs from the bacterium through inducible heterologous expression in Agrobacterium tumefaciens strain NTL4. We developed a two-dimensional thin layer chromatography bioassay and used LC-ESI MS/MS analyses to separate, detect and identify the AHL signals produced by the N. subterraneum DSM 12447 strain. Results Three predicted luxI homologs were annotated to the locus tags NJ75_2841 (NovINsub1), NJ75_2498 (NovINsub2), and NJ75_4146 (NovINsub3). Inducible heterologous expression of each luxI homologs followed by LC-ESI MS/MS and two-dimensional reverse phase thin layer chromatography bioassays followed by bioluminescent ccd camera imaging indicate that the three LuxI homologs are able to produce a variety of medium-length AHL compounds. New insights into the LuxI phylogeny was also gleemed as inferred by Bayesian inference. Discussion This study significantly adds to our current understanding of quorum sensing in the genus Novosphingobium and provide the framework for future characterization of the phylogenetically interesting LuxI homologs from members of the genus Novosphingobium and more generally the family Sphingomonadaceae. PMID:27635318

High-performance thin layer chromatography to assess pharmaceutical product quality.

PubMed

Kaale, Eliangiringa; Manyanga, Vicky; Makori, Narsis; Jenkins, David; Michael Hope, Samuel; Layloff, Thomas

2014-06-01

To assess the sustainability, robustness and economic advantages of high-performance thin layer chromatography (HPTLC) for quality control of pharmaceutical products. We compared three laboratories where three lots of cotrimoxazole tablets were assessed using different techniques for quantifying the active ingredient. The average assay relative standard deviation for the three lots was 1.2 with a range of 0.65-2.0. High-performance thin layer chromatography assessments are yielding valid results suitable for assessing product quality. The local pharmaceutical manufacturer had evolved the capacity to produce very high quality products. © 2014 John Wiley & Sons Ltd.

Fabrication and Structural Characterization of an Ultrathin Film of a Two-Dimensional-Layered Metal-Organic Framework, {Fe(py)2[Ni(CN)4]} (py = pyridine).

PubMed

Sakaida, Shun; Haraguchi, Tomoyuki; Otsubo, Kazuya; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

2017-07-17

We report the fabrication and characterization of the first example of a tetracyanonickelate-based two-dimensional-layered metal-organic framework, {Fe(py) 2 Ni(CN) 4 } (py = pyridine), thin film. To fabricate a nanometer-sized thin film, we utilized the layer-by-layer method, whereby a substrate was alternately soaked in solutions of the structural components. Surface X-ray studies revealed that the fabricated film was crystalline with well-controlled growth directions both parallel and perpendicular to the substrate. In addition, lattice parameter analysis indicated that the crystal system is found to be close to higher symmetry by being downsized to a thin film.

Surface enhanced Raman scattering imaging of developed thin-layer chromatography plates.

PubMed

Freye, Chris E; Crane, Nichole A; Kirchner, Teresa B; Sepaniak, Michael J

2013-04-16

A method for hyphenating surface enhanced Raman scattering (SERS) and thin-layer chromatography (TLC) is presented that employs silver-polymer nanocomposites as an interface. Through the process of conformal blotting, analytes are transferred from TLC plates to nanocomposite films before being imaged via SERS. A procedure leading to maximum blotting efficiency was established by investigating various parameters such as time, pressure, and type and amount of blotting solvent. Additionally, limits of detection were established for test analytes malachite green isothiocyanate, 4-aminothiophenol, and Rhodamine 6G (Rh6G) ranging from 10(-7) to 10(-6) M. Band broadening due to blotting was minimal (∼10%) as examined by comparing the spatial extent of TLC-spotted Rh6G via fluorescence and then the SERS-based spot size on the nanocomposite after the blotting process. Finally, a separation of the test analytes was carried out on a TLC plate followed by blotting and the acquisition of distance × wavenumber × intensity three-dimensional TLC-SERS plots.

Quantitative thin-layer chromatography/mass spectrometry analysis of caffeine using a surface sampling probe electrospray ionization tandem mass spectrometry system.

PubMed

Ford, Michael J; Deibel, Michael A; Tomkins, Bruce A; Van Berkel, Gary J

2005-07-15

Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 mum/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methods determined from the calibration curve statistics were 0.20 ng injected (0.50 muL) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by approximately 8% or more) than the literature values.

Comparative chromatography of chloroplast pigment

NASA Technical Reports Server (NTRS)

Grandolfo, M.; Sherma, J.; Strain, H. H.

1969-01-01

Methods for isolation of low concentration pigments of the cocklebur species are described. The methods entail two step chromatography so that the different sorption properties of the various pigments in varying column parameters can be utilized. Columnar and thin layer methods are compared. Many conditions influence separability of the chloroplasts.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals

NASA Astrophysics Data System (ADS)

Carey, Benjamin J.; Ou, Jian Zhen; Clark, Rhiannon M.; Berean, Kyle J.; Zavabeti, Ali; Chesman, Anthony S. R.; Russo, Salvy P.; Lau, Desmond W. M.; Xu, Zai-Quan; Bao, Qiaoliang; Kevehei, Omid; Gibson, Brant C.; Dickey, Michael D.; Kaner, Richard B.; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-02-01

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (~1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals.

PubMed

Carey, Benjamin J; Ou, Jian Zhen; Clark, Rhiannon M; Berean, Kyle J; Zavabeti, Ali; Chesman, Anthony S R; Russo, Salvy P; Lau, Desmond W M; Xu, Zai-Quan; Bao, Qiaoliang; Kevehei, Omid; Gibson, Brant C; Dickey, Michael D; Kaner, Richard B; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-02-17

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (∼1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals

PubMed Central

Carey, Benjamin J.; Ou, Jian Zhen; Clark, Rhiannon M.; Berean, Kyle J.; Zavabeti, Ali; Chesman, Anthony S. R.; Russo, Salvy P.; Lau, Desmond W. M.; Xu, Zai-Quan; Bao, Qiaoliang; Kavehei, Omid; Gibson, Brant C.; Dickey, Michael D.; Kaner, Richard B.; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-01-01

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (∼1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes. PMID:28211538

The offline combination of thin-layer chromatography and high-performance liquid chromatography with diode array detection and micrOTOF-Q mass spectrometry for the separation and identification of spinochromes from sea urchin (Strongylocentrotus droebachiensis) shells.

PubMed

Shikov, Alexander N; Ossipov, Vladimir I; Martiskainen, Olli; Pozharitskaya, Olga N; Ivanova, Svetlana A; Makarov, Valery G

2011-12-16

Thin-layer chromatography (TLC) with off-line high-performance liquid chromatography coupled to diode array detection and micrOTOF-Q mass spectrometry (HPLC-DAD-MS) resulted in the successful fractionation, separation and identification of spinochrome pigments from sea urchin (Strongylocentrotus droebachiensis) shells. Two fractions of pigments were separated by TLC and eluted with methanol using a TLC-MS interface. HPLC-DAD-MS analysis of the fractions indicated the presence of six sea urchin pigments: spinochrome monomers B and D, three spinochrome dimers (anhydroethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin) and its isomer and ethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin)), and one pigment that was preliminary identified as a spinochrome dimer with the structural formula C(22)H(16)O(16). Copyright © 2011 Elsevier B.V. All rights reserved.

Bacterial Cell Wall Precursor Phosphatase Assays Using Thin-layer Chromatography (TLC) and High Pressure Liquid Chromatography (HPLC).

PubMed

Pazos, Manuel; Otten, Christian; Vollmer, Waldemar

2018-03-20

Peptidoglycan encases the bacterial cytoplasmic membrane to protect the cell from lysis due to the turgor. The final steps of peptidoglycan synthesis require a membrane-anchored substrate called lipid II, in which the peptidoglycan subunit is linked to the carrier lipid undecaprenol via a pyrophosphate moiety. Lipid II is the target of glycopeptide antibiotics and several antimicrobial peptides, and is degraded by 'attacking' enzymes involved in bacterial competition to induce lysis. Here we describe two protocols using thin-layer chromatography (TLC) and high pressure liquid chromatography (HPLC), respectively, to assay the digestion of lipid II by phosphatases such as Colicin M or the LXG toxin protein TelC from Streptococcus intermedius . The TLC method can also monitor the digestion of undecaprenyl (pyro)phosphate, whereas the HPLC method allows to separate the di-, mono- or unphosphorylated disaccharide pentapeptide products of lipid II.

Bacterial Cell Wall Precursor Phosphatase Assays Using Thin-layer Chromatography (TLC) and High Pressure Liquid Chromatography (HPLC)

PubMed Central

Pazos, Manuel; Otten, Christian; Vollmer, Waldemar

2018-01-01

Peptidoglycan encases the bacterial cytoplasmic membrane to protect the cell from lysis due to the turgor. The final steps of peptidoglycan synthesis require a membrane-anchored substrate called lipid II, in which the peptidoglycan subunit is linked to the carrier lipid undecaprenol via a pyrophosphate moiety. Lipid II is the target of glycopeptide antibiotics and several antimicrobial peptides, and is degraded by ‘attacking’ enzymes involved in bacterial competition to induce lysis. Here we describe two protocols using thin-layer chromatography (TLC) and high pressure liquid chromatography (HPLC), respectively, to assay the digestion of lipid II by phosphatases such as Colicin M or the LXG toxin protein TelC from Streptococcus intermedius. The TLC method can also monitor the digestion of undecaprenyl (pyro)phosphate, whereas the HPLC method allows to separate the di-, mono- or unphosphorylated disaccharide pentapeptide products of lipid II. PMID:29651453

What Factors Affect the Separation of Substances Using Thin-Layer Chromatography? An Undergraduate Experiment.

ERIC Educational Resources Information Center

Nash, John J.; Meyer, Jeanne A.; Everson, Barbara

2001-01-01

Rx values in thin-layer chromatography (TLC) depend strongly on the solvent saturation of the atmosphere above the liquid in the TLC developing chamber. Presents an experiment illustrating the potentially dramatic effects on TLC Rx values of not equilibrating the solvent atmosphere during development. (ASK)

A Thin Layer Chromatography Laboratory Experiment of Medical Importance

ERIC Educational Resources Information Center

Sharma, Loretta; Desai, Ankur; Sharma, Ajit

2006-01-01

A thin layer chromatography experiment of medical importance is described. The experiment involves extraction of lipids from simulated amniotic fluid samples followed by separation, detection, and scanning of the lecithin and sphingomyelin bands on TLC plates. The lecithin-to-sphingomyelin ratio is calculated. The clinical significance of this…

Analysis and Identification of Acid-Base Indicator Dyes by Thin-Layer Chromatography

ERIC Educational Resources Information Center

Clark, Daniel D.

2007-01-01

Thin-layer chromatography (TLC) is a very simple and effective technique that is used by chemists by different purposes, including the monitoring of the progress of a reaction. TLC can also be easily used for the analysis and identification of various acid-base indicator dyes.

In situ identification of high-performance thin-layer chromatography spots by fourier transform surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Koglin, Eckhardt; Kramer, Hella; Sawatski, Juergen; Lehner, Carolin; Hellman, Janice L.

1994-01-01

FT-SERS has been used to identify samples supported on high-performance thin-layer chromatography plates. The TLC plates were sprayed with colloidal silver solutions which resulted in enhancement of the FT-Raman scattering of these biologically and environmentally important compounds.

21 CFR 862.2270 - Thin-layer chromatography system for clinical use.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Thin-layer chromatography system for clinical use. 862.2270 Section 862.2270 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory...

21 CFR 862.2270 - Thin-layer chromatography system for clinical use.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Thin-layer chromatography system for clinical use. 862.2270 Section 862.2270 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory...

21 CFR 862.2270 - Thin-layer chromatography system for clinical use.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Thin-layer chromatography system for clinical use. 862.2270 Section 862.2270 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory...

Two-dimensional models for the optical response of thin films

NASA Astrophysics Data System (ADS)

Li, Yilei; Heinz, Tony F.

2018-04-01

In this work, we present a systematic study of 2D optical models for the response of thin layers of material under excitation by normally incident light. The treatment, within the framework of classical optics, analyzes a thin film supported by a semi-infinite substrate, with both the thin layer and the substrate assumed to exhibit local, isotropic linear response. Starting from the conventional three-dimensional (3D) slab model of the system, we derive a two-dimensional (2D) sheet model for the thin film in which the optical response is described by a sheet optical conductivity. We develop criteria for the applicability of this 2D sheet model for a layer with an optical thickness far smaller than the wavelength of the light. We examine in detail atomically thin semi-metallic and semiconductor van-der-Waals layers and ultrathin metal films as representative examples. Excellent agreement of the 2D sheet model with the 3D slab model is demonstrated over a broad spectral range from the radio frequency limit to the near ultraviolet. A linearized version of system response for the 2D model is also presented for the case where the influence of the optically thin layer is sufficiently weak. Analytical expressions for the applicability and accuracy of the different optical models are derived, and the appropriateness of the linearized treatment for the materials is considered. We discuss the advantages, as well as limitations, of these models for the purpose of deducing the optical response function of the thin layer from experiment. We generalize the theory to take into account in-plane anisotropy, layered thin film structures, and more general substrates. Implications of the 2D model for the transmission of light by the thin film and for the implementation of half- and totally absorbing layers are discussed.

Epitaxial Growth of Rhenium with Sputtering

DTIC Science & Technology

2016-05-06

corresponds to two atomic Re layers , considering that the c-axis lattice constant of the tri- atomic layered hcp Re unit cell is ~4.5 Å. Frequently, two...Å) corresponds to two Re atomic layers since the c-axis lattice constant of hcp Re, which is composed of three Re atomic layers , is ~4.5 Å...The growth starts in a three dimensional mode but transforms into two dimensional mode as the film gets thicker. With a thin (~2 nm) seed layer

Quantitative Thin-Layer Chromatography/Mass Spectrometry Analysis of Caffeine Using a Surface Sampling Probe Electrospray Ionization Tandem Mass Spectrometry System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ford, Michael J; Deibel, Michael A.; Tomkins, Bruce A

Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 {mu}m/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methodsmore » determined from the calibration curve statistics were 0.20 ng injected (0.50 {mu}L) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by 8% or more) than the literature values.« less

Thin-Layer Chromatography: The "Eyes" of the Organic Chemist

ERIC Educational Resources Information Center

Dickson, Hamilton; Kittredge, Kevin W.; Sarquis, Arlyne

2004-01-01

Thin-layer chromatography (TLC) methods are successfully used in many areas of research and development such as clinical medicine, forensic chemistry, biochemistry, and pharmaceutical analysis as TLC is relatively inexpensive and has found widespread application as an easy to use, reliable, and quick analytic tool. The usefulness of TLC in organic…

Phospholipids, Dietary Supplements, and Chicken Eggs: An Inquiry-Based Exercise Using Thin-Layer Chromatography

ERIC Educational Resources Information Center

Potteiger, Sara E.; Belanger, Julie M.

2015-01-01

This inquiry-based experiment is designed for organic or biochemistry undergraduate students to deduce the identity of phospholipids extracted from chicken eggs and dietary supplements. This is achieved using thin-layer chromatography (TLC) data, a series of guided questions of increasing complexity, and provided relative retention factor (Rf)…

Evaluating Mechanisms of Dihydroxylation by Thin-Layer Chromatography: A Microscale Experiment for Organic Chemistry

ERIC Educational Resources Information Center

Burlingham, Benjamin T.; Rettig, Joseph C.

2008-01-01

A microscale experiment is presented in which cyclohexene is dihydroxylated under three sets of conditions: epoxidation-hydrolysis, permanganate oxidation, and the Woodward dihydroxylation. The products of the reactions are determined by the use of thin-layer chromatography. Teams of students are presented with proposed mechanisms for each…

A Simple and Inexpensive Capillary Holder for Thin-Layer Chromatography

ERIC Educational Resources Information Center

Pintea, Beniamin-Nicolae V.

2011-01-01

Thin-layer chromatography (TLC) is a widely used method of qualitative analysis in organic synthesis, as it uniquely combines low cost, rapidity, simplicity, versatility, small quantities of sample and low detection limits. The simplest and most economical method for the application of samples onto TLC plates is by hand, using glass capillaries.…

Use of low volatility mobile phases in electroosmotic thin-layer chromatography.

PubMed

Berezkin, V G; Balushkin, A O; Tyaglov, B V; Litvin, E F

2005-08-19

A variant of electroosmotic thin-layer chromatography is suggested with the use of low volatility compounds as mobile phases aimed at drastically decreasing the evaporation of the mobile phase and improving the reproducibility of the method. The linear movement velocity of zones of separated compounds is experimentally shown to increase 2-12-fold in electroosmotic chromatography (compared to similar values in traditional TLC). The separation efficiency is also considerably increased.

[Polyphenol compounds from Hamamelis virginiana L].

PubMed

Kostálová, D; Misíková, E; Gáborová, G

2001-01-01

Two phenolic acids and two flavone aglycones were isolated from the aboveground part of Hamamelis virginiana L. and identified with the use of thin-layer chromatography, melting points, and spectroscopic methods as gallic acid, ethyl gallate, quercetin, and kaempferol.

Triangular Black Phosphorus Atomic Layers by Liquid Exfoliation.

PubMed

Seo, Soonjoo; Lee, Hyun Uk; Lee, Soon Chang; Kim, Yooseok; Kim, Hyeran; Bang, Junhyeok; Won, Jonghan; Kim, Youngjun; Park, Byoungnam; Lee, Jouhahn

2016-03-30

Few-layer black phosphorus (BP) is the most promising material among the two-dimensional materials due to its layered structure and the excellent semiconductor properties. Currently, thin BP atomic layers are obtained mostly by mechanical exfoliation of bulk BP, which limits applications in thin-film based electronics due to a scaling process. Here we report highly crystalline few-layer black phosphorus thin films produced by liquid exfoliation. We demonstrate that the liquid-exfoliated BP forms a triangular crystalline structure on SiO2/Si (001) and amorphous carbon. The highly crystalline BP layers are faceted with a preferred orientation of the (010) plane on the sharp edge, which is an energetically most favorable facet according to the density functional theory calculations. Our results can be useful in understanding the triangular BP structure for large-area applications in electronic devices using two-dimensional materials. The sensitivity and selectivity of liquid-exfoliated BP to gas vapor demonstrate great potential for practical applications as sensors.

Triangular Black Phosphorus Atomic Layers by Liquid Exfoliation

PubMed Central

Seo, Soonjoo; Lee, Hyun Uk; Lee, Soon Chang; Kim, Yooseok; Kim, Hyeran; Bang, Junhyeok; Won, Jonghan; Kim, Youngjun; Park, Byoungnam; Lee, Jouhahn

2016-01-01

Few-layer black phosphorus (BP) is the most promising material among the two-dimensional materials due to its layered structure and the excellent semiconductor properties. Currently, thin BP atomic layers are obtained mostly by mechanical exfoliation of bulk BP, which limits applications in thin-film based electronics due to a scaling process. Here we report highly crystalline few-layer black phosphorus thin films produced by liquid exfoliation. We demonstrate that the liquid-exfoliated BP forms a triangular crystalline structure on SiO2/Si (001) and amorphous carbon. The highly crystalline BP layers are faceted with a preferred orientation of the (010) plane on the sharp edge, which is an energetically most favorable facet according to the density functional theory calculations. Our results can be useful in understanding the triangular BP structure for large-area applications in electronic devices using two-dimensional materials. The sensitivity and selectivity of liquid-exfoliated BP to gas vapor demonstrate great potential for practical applications as sensors. PMID:27026070

Extraction of Nutraceuticals from Spirulina (Blue-Green Alga): A Bioorganic Chemistry Practice Using Thin-layer Chromatography

ERIC Educational Resources Information Center

Herrera Bravo de Laguna, Irma; Toledo Marante, Francisco J.; Luna-Freire, Kristerson R.; Mioso, Roberto

2015-01-01

Spirulina is a blue-green alga (cyanobacteria) with high nutritive value. This work provides an innovative and original approach to the consideration of a bioorganic chemistry practice, using Spirulina for the separation of phytochemicals with nutraceutical characteristics via thin-layer chromatography (TLC) plates. The aim is to bring together…

Analysis of Peppermint Leaf and Spearmint Leaf Extracts by Thin-Layer Chromatography

ERIC Educational Resources Information Center

Pelter, Libbie S. W.; Amico, Andrea; Gordon, Natalie; Martin, Chylah; Sandifer, Dessalyn; Pelter, Michael W.

2008-01-01

In this inquiry-based activity, the usefulness of thin-layer chromatography (TLC) to visualize the difference between spearmint and peppermint is explored. The experiment may be used in any class where TLC is discussed from high school to college. We have used this activity with science majors in an organic chemistry laboratory, with non-science…

Chromatography.

ERIC Educational Resources Information Center

Brantley, L. Reed, Sr.; Demanche, Edna L.; Klemm, E. Barbara; Kyselka, Will; Phillips, Edwin A.; Pottenger, Francis M.; Yamamoto, Karen N.; Young, Donald B.

This booklet presents some activities on chromatography. Directions for preparing leaf pigment extracts using alcohol are given, and paper chromatography and thin-layer chromatography are described as modifications of the basic principles of chromatography. (KHR)

Quantification of Quercetin and Rutin from Benincasa hispida Seeds and Carissa Congesta Roots by High-performance Thin Layer Chromatography and High-performance Liquid Chromatography.

PubMed

Doshi, Gaurav Mahesh; Une, Hemant Devidas

2016-01-01

In Indian Ayurvedic system, Benincasa hispida (BH) and Carissa congesta (CC) are well-known plants used for major and minor ailments. BH has been regarded as Kushmanda, whereas CC has been used in immune-related disorders of the human system. Quercetin and rutin identified from the vast plethora of plant extracts have proved to possess ethnopharmacological relevance. In present studies, we have determined quercetin and rutin in terms of percentage in BH seeds and CC roots by high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). After extraction and phytochemical screening, the extracts were subjected to quantification for the presence of quercetin and rutin by HPTLC and HPLC. HPTLC showed quercetin as 44.60, 27.13% and rutin as 32.00, 36.31% w/w, whereas HPLC revealed quercetin as 34.00, 35.00% and rutin as 21.99, 45.03% w/v in BH and CC extracts, respectively. The BH and CC extracts have elucidated peaks that were corresponding with standard peaks on undertaking chromatographic studies. Quercetin and rutin are isolated from BH seeds and CC roots by High Performance. Thin Layer Chromatography and High Performance Liquid Chromatography. HPTLC revealed presence of quercetin as 44.60, 27.13 % and rutin as 32.00, 36.31 % w/w. HPLC revealed presence of quercetin as 34.00, 35.00 % and rutin as 21.99, 45.03 % w/v. Abbreviation Used: HPTLC: High Performance Thin Layer Chromatography; HPLC: High Pressure Liquid Chromatography, UV: Ultraviolet, CC: Carissa congesta, BH: Benincasa hispida.

Quantitative Determination of Photosynthetic Pigments in Green Beans Using Thin-Layer Chromatography and a Flatbed Scanner as Densitometer

ERIC Educational Resources Information Center

Valverde, Juan; This, Herve; Vignolle, Marc

2007-01-01

A simple method for the quantitative determination of photosynthetic pigments extracted from green beans using thin-layer chromatography is proposed. Various extraction methods are compared, and it is shown how a simple flatbed scanner and free software for image processing can give a quantitative determination of pigments. (Contains 5 figures.)

Pharmacognostic Screening of Piper trichostachyon Fruits and its Comparative Analysis with Piper nigrum Using Chromatographic Techniques.

PubMed

Upadhya, Vinayak; Pai, Sandeep R; Ankad, Gireesh M; Hegde, Harsha V

2016-05-01

Piper trichostachyon is a wild, endemic Piper species from Western Ghats of India. The folklore healers of Belagavi region use this plant, similar to Piper nigrum. The present study investigates the comparison between P. nigrum and P. trichostachyon using pharmacognostic parameters. Pharmacognostic evaluation was carried out in terms of morphological, microscopic characters, and phytochemical analysis using standard methods. Comparative physicochemical analysis between P. trichostachyon and P. nigrum was also carried out through estimation of micro-macro nutrients, high-performance thin layer chromatography (HPTLC) investigation and using piperine as a marker compound for reversed phase-ultra flow liquid chromatographic (RP-UFLC) technique. P. trichostachyon grows in the forests, and the fruits are morphologically similar to P. nigrum fruits, so the name in Kannada "Kaadu Kalu menasu" (wild/forest black pepper). The microscopy revealed the presence of stone cells, starch grains, oil cells and globules, beaker cells, and yellowish brown pigment layer, parenchymatous cells. The presence of alkaloids, oil, and tannins were observed in P. trichostachyon fruits. The HPTLC studies visibly indicated differences among two species with 12 peaks and varied banding pattern. RP-UFLC results showed less amount of piperine in P. trichostachyon (0.05 ± 0.002 mg/g) than in P. nigrum (16.14 ± 0.807 mg/g). The study reports on pharmacognostic parameters of P. trichostachyon for the 1(st) time and will be useful for the identification and authentication. The comparative HPTLC and RP-UFLC studies resolve the differentiation impasse among two species. However, further biological efficacy studies are required to establish its use in traditional medicine. Piper trichostachyon grows in the forests, and the fruits are morphologically similar to Piper nigrum fruitsThe microscopy of P. trichostachyon revealed the presence of stone cells, starch grains, oil cells and globules, beaker cells and yellowish brown pigment layer, parenchymatous cellsThe high-performance thin layer chromatography studies visibly indicated differences among two species with varied banding patternReversed phase-ultra flow liquid chromatographic results showed less amount of piperine in P. trichostachyon than in P. nigrum. Abbreviation used: HPTLC: High Performance Thin Layer Chromatography, RP-UFLC: Reversed phase-ultra flow liquid chromatographic analysis, DST: Length of line, Maj: Length of large half axis for ellipse RDS - radius for circle, Rf: Retention Factor, TS: Transverse Section, TLC: Thin Layer Chromatography.

Approximate transient and long time limit solutions for the band broadening induced by the thin sidewall-layer in liquid chromatography columns.

PubMed

Broeckhoven, Ken; Desmet, Gert

2007-11-16

Using a combination of both analytical and numerical techniques, approximate analytical expressions have been established for the transient and long time limit band broadening, originating from the presence of a thin disturbed sidewall layer in liquid chromatography columns, including packed, monolithic as well as microfabricated columns. The established expressions can be used to compare the importance of a thin disturbed sidewall layer with that of other radial heterogeneity effects (such as transcolumn packing density variations due to the relief of packing stresses). The expressions are independent of the actual velocity profile inside the layer as long as the disturbed sidewall layer occupies less than 2.5% of the column width.

Reviews.

ERIC Educational Resources Information Center

Journal of Chemical Education, 1988

1988-01-01

Reviews three computer software packages for Apple II computers. Includes "Simulation of Hemoglobin Function,""Solution Equilibrium Problems," and "Thin-Layer Chromatography." Contains ratings of ease of use, subject matter content, pedagogic value, and student reaction according to two separate reviewers for each…

Quantification of Quercetin and Rutin from Benincasa hispida Seeds and Carissa Congesta Roots by High-performance Thin Layer Chromatography and High-performance Liquid Chromatography

PubMed Central

Doshi, Gaurav Mahesh; Une, Hemant Devidas

2016-01-01

Objective: In Indian Ayurvedic system, Benincasa hispida (BH) and Carissa congesta (CC) are well-known plants used for major and minor ailments. BH has been regarded as Kushmanda, whereas CC has been used in immune-related disorders of the human system. Quercetin and rutin identified from the vast plethora of plant extracts have proved to possess ethnopharmacological relevance. Materials and Methods: In present studies, we have determined quercetin and rutin in terms of percentage in BH seeds and CC roots by high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). After extraction and phytochemical screening, the extracts were subjected to quantification for the presence of quercetin and rutin by HPTLC and HPLC. Results: HPTLC showed quercetin as 44.60, 27.13% and rutin as 32.00, 36.31% w/w, whereas HPLC revealed quercetin as 34.00, 35.00% and rutin as 21.99, 45.03% w/v in BH and CC extracts, respectively. Conclusion: The BH and CC extracts have elucidated peaks that were corresponding with standard peaks on undertaking chromatographic studies. SUMMARY Quercetin and rutin are isolated from BH seeds and CC roots by High Performance. Thin Layer Chromatography and High Performance Liquid Chromatography. HPTLC revealed presence of quercetin as 44.60, 27.13 % and rutin as 32.00, 36.31 % w/w. HPLC revealed presence of quercetin as 34.00, 35.00 % and rutin as 21.99, 45.03 % w/v. Abbreviation Used: HPTLC: High Performance Thin Layer Chromatography; HPLC: High Pressure Liquid Chromatography, UV: Ultraviolet, CC: Carissa congesta, BH: Benincasa hispida PMID:26941534

Layer chromatography-bioassays directed screening and identification of antibacterial compounds from Scotch thistle.

PubMed

Móricz, Ágnes M; Krüzselyi, Dániel; Alberti, Ágnes; Darcsi, András; Horváth, Györgyi; Csontos, Péter; Béni, Szabolcs; Ott, Péter G

2017-11-17

The antibacterial profiling of Onopordum acanthium L. leaf extract and subsequent targeted identification of active compounds is demonstrated. Thin-layer chromatography (TLC) and off-line overpressured layer chromatography (OPLC) coupled with direct bioautography were utilized for investigation of the extract against eight bacterial strains including two plant and three human pathogens and a soil, a marine and a probiotic human gut bacteria. Antibacterial fractions obtaining infusion-transfusion OPLC were transferred to HPLC-MS/MS analysis that resulted in the characterization of three active compounds and two of them were identified as, linoleic and linolenic acid. OPLC method was adopted to preparative-scale flash chromatography for the isolation of the third active compound, which was identified after a further semi-preparative HPLC purification as the germacranolide sesquiterpene lactone onopordopicrin. Pure onopordopicrin exhibited antibacterial activity that was specified as minimal inhibitory concentration in the liquid phase as well. Copyright © 2017 Elsevier B.V. All rights reserved.

A simple analytical platform based on thin-layer chromatography coupled with paper-based analytical device for determination of total capsaicinoids in chilli samples.

PubMed

Dawan, Phanphruk; Satarpai, Thiphol; Tuchinda, Patoomratana; Shiowatana, Juwadee; Siripinyanond, Atitaya

2017-01-01

A new analytical platform based on the use of thin-layer chromatography (TLC) coupled with paper-based analytical device (PAD) was developed for the determination of total capsaicinoids in chilli samples. This newly developed TLC-PAD is simple and low-cost without any requirement of special instrument or skillful person. The analysis consisted of two steps, i.e., extraction of capsaicinoids from chilli samples by using ethanol as solvent and separation of capsaicinoids by thin-layer chromatography (TLC) and elution of capsaicinoids from the TLC plate with in situ colorimetric detection of capsaicinoids on the PAD. For colorimetric detection, Folin-Ciocalteu reagent was used to detect phenolic functional group of capsaicinoids yielding the blue color. The blue color on the PAD was imaged by a scanner followed by evaluation of its grayscale intensity value by ImageJ program. This newly developed TLC-PAD method provided a linear range from 50 to 1000mgL -1 capsaicinoids with the limit of detection as low as 50mgL -1 capsaicinoids. The proposed method was applied to determine capsaicinoids in dried chilli and seasoning powder samples and the results were in good agreement with those obtained by HPLC method. Copyright © 2016 Elsevier B.V. All rights reserved.

The reciprocal iso-inhibition volume concept: A procedure for the evaluation in effect-directed analysis with thin-layer chromatography - using the thin-layer chromatography-luminescent bacteria assay as an example.

PubMed

Schulz, Wolfgang; Weiss, Stefan C; Weber, Walter H; Winzenbacher, Rudi

2017-10-13

In effect-directed analysis (EDA) with high-performance thin-layer chromatography (HPTLC), the effect is often detected using images. Thus, an approach to create inhibition chromatograms from these images was developed using the example of the HPTLC- bioluminescence inhibition test. A comparison between the cuvette test and the HPTLC test shows that the test on the plate is significantly more sensitive. To describe the strength of the effect, the EC 50 value is determined from the dose-response relationship. However, the inhibiting compounds are generally unknown and thus their concentrations are also unknown. Therefore, instead of the concentration, the known application volumes are used. This enables the calculation of the application volume necessary to achieve 50% inhibition. Since the volume is inversely proportional to the concentration, the reciprocal value of the calculated volume is indicated and is referred to as the reciprocal iso-inhibition volume (RIV). Using this RIV-concept, it is now possible to compare inhibition bands within and between plates. The entire evaluation is described by the means of two samples from a contaminated site using the bioluminescence inhibition. Copyright © 2017 Elsevier B.V. All rights reserved.

Patch testing with thin-layer chromatograms of chamomile tea in patients allergic to sesquiterpene lactones.

PubMed

Lundh, Kerstin; Gruvberger, Birgitta; Möller, Halvor; Persson, Lena; Hindsén, Monica; Zimerson, Erik; Svensson, Ake; Bruze, Magnus

2007-10-01

Patients with contact allergy to sesquiterpene lactones (SLs) are usually hypersensitive to Asteraceae plant products such as herbal teas. The objective of this study was to show sensitizers in chamomile tea by patch testing with thin-layer chromatograms. Tea made from German chamomile was separated by thin-layer chromatography. Strips of the thin-layer chromatograms were used for patch testing SL-positive patients. 15 (43%) of 35 patients tested positively to 1 or more spots on the thin-layer chromatogram, with many individual reaction patterns. Patch testing with thin-layer chromatograms of German chamomile tea showed the presence of several allergens.

A reversed-phase compatible thin-layer chromatography autography for the detection of acetylcholinesterase inhibitors.

PubMed

Ramallo, I Ayelen; García, Paula; Furlan, Ricardo L E

2015-11-01

A dual readout autographic assay to detect acetylcholinesterase inhibitors present in complex matrices adsorbed on reversed-phase or normal-phase thin-layer chromatography plates is described. Enzyme gel entrapment with an amphiphilic copolymer was used for assay development. The effects of substrate and enzyme concentrations, pH, incubation time, and incubation temperature on the sensitivity and the detection limit of the assay were evaluated. Experimental design and response surface methodology were used to optimize conditions with a minimum number of experiments. The assay allowed the detection of 0.01% w/w of physostigmine in both a spiked Sonchus oleraceus L. extract chromatographed on normal phase and a spiked Pimenta racemosa (Mill.) J.W. Moore leaf essential oil chromatographed on reversed phase. Finally, the reversed-phase thin-layer chromatography assay was applied to reveal the presence of an inhibitor in the Cymbopogon citratus (DC.) Stapf essential oil. The developed assay is able to detect acetylcholinesterase inhibitors present in complex matrixes that were chromatographed in normal phase or reversed-phase thin-layer chromatography. The detection limit for physostigmine on both normal and reversed phase was of 1×10(-4) μg. The results can be read by a change in color and/or a change in fluorescence. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Limitations in the 2D description of the electromagnetic waves propagation in thin dielectric and magnetic layers

NASA Astrophysics Data System (ADS)

Radożycki, Tomasz; Bargieła, Piotr

2018-07-01

The propagation of electromagnetic waves trapped within dielectric and magnetic layers is considered. The description within the three-dimensional theory is compared to the simplified analysis in two dimensions. Two distinct media configurations of different topology are dealt with: a plane slab and a hollow cylinder. Choosing the appropriate values for the geometrical parameters (layer thickness, radius of the cylinder) and for the electromagnetic properties of the media one can trap exactly one mode corresponding to that obtained within the two-dimensional electromagnetism. However, the symmetry between electric and magnetic fields suggests, that the two versions of the simplified electromagnetism ought to be equally considered. Its usual form is incomplete to describe all modes. It is also found that there exists a domain of optimal values of parameters for which the 2D model works relatively correctly. However, in the case of a cylindrical surface we observe several differences which may be attributed to the curvature of the layer, and which exclude the propagation of evanescent modes. The two-dimensional electrodynamics, whichever form is used, turns out still too poor to describe the so-called 'hybrid modes' excited in a real layer. The obtained results can be essential for proper description of the propagating waves within thin layers for which 3D approach is not available due to mathematical complexity and reducing the layer to a lower dimensional structure seems the only possible option.

The polar lipids of Clostridium psychrophilum, an anaerobic psychrophile

PubMed Central

Guan, Ziqiang; Tian, Bing; Perfumo, Amedea; Goldfine, Howard

2013-01-01

We have examined the polar lipids of Clostridium psychrophilum, a recently characterized psychrophilic Clostridium isolated from an Antarctic microbial mat. Lipids were extracted from cells grown near the optimal growth temperature (+5 °C) and at −5 °C, and analyzed by two-dimensional thin layer chromatography and liquid chromatography coupled with mass spectrometry. The major phospholipids of this species are: cardiolipin, phosphatidylethanolamine, and phosphatidylglycerol. Phosphatidylserine and lyso-phosphatidylethanolamine were found as minor components. The most abundant glycolipids are a monoglycosyldiradylglycerol (MGDRG) and a diglycosyldiradylglycerol (DGDRG). The latter was only seen in cells grown at −5 °C. An ethanolamine-phosphate derivative of N-acetylglucosaminyldiradylglycerol was seen in cells grown at −5 °C and an ethanolamine-phosphate derivative of MGDRG was found in cells grown at +5 °C. All lipids were present in both the all acyl and plasmalogen (alk-1′-enyl acyl) forms with the exception of PS and MGDRG, which were predominantly in the diacyl form. The significance of lipid changes at the two growth temperatures is discussed. PMID:23454375

Phospholipid composition of cell-derived microparticles determined by one-dimensional high-performance thin-layer chromatography.

PubMed

Weerheim, A M; Kolb, A M; Sturk, A; Nieuwland, R

2002-03-15

Microparticles in the circulation activate the coagulation system and may activate the complement system via C-reactive protein upon conversion of membrane phospholipids by phospholipases. We developed a sensitive and reproducible method to determine the phospholipid composition of microparticles. Samples were applied to horizontal, one-dimensional high-performance thin-layer chromatography (HPTLC). Phospholipids were separated on HPTLC by chloroform:ethyl acetate:acetone:isopropanol:ethanol:methanol:water:acetic acid (30:6:6:6:16:28:6:2); visualized by charring with 7.5% Cu-acetate (w/v), 2.5% CuSO(4) (w/v), and 8% H(3)PO(4) (v/v) in water; and quantified by photodensitometric scanning. Erythrocyte membranes were used to validate the HPTLC system. Microparticles were isolated from plasma of healthy individuals (n = 10). On HPTLC, mixtures of (purified) phospholipids, i.e., lysophosphatidylcholine, phosphatidylcholine (PC), sphingomyelin (SM), lysophosphatidylserine, phosphatidylserine, lysophosphatidylethanolamine, phosphatidylethanolamine (PE), and phosphatidylinositol, could be separated and quantified. All phospholipids were detectable in erythrocyte ghosts, and their quantities fell within ranges reported earlier. Quantitation of phospholipids, including extraction, was highly reproducible (CV < 10%). Microparticles contained PC (59%), SM (20.6%), and PE (9.4%), with relatively minor (<5%) quantities of other phospholipids. HPTLC can be used to study the phospholipid composition of cell-derived microparticles and may also be a useful technique for the analysis of other samples that are available only in minor quantities. (C)2002 Elsevier Science (USA).

Effect-directed analysis via hyphenated high-performance thin-layer chromatography for bioanalytical profiling of sunflower leaves.

PubMed

Móricz, Ágnes M; Ott, Péter G; Yüce, Imanuel; Darcsi, András; Béni, Szabolcs; Morlock, Gertrud E

2018-01-19

High-performance thin-layer chromatography (HPTLC) coupled with effect-directed analysis was used for non-targeted screening of sunflower leaf extract for components exhibiting antioxidant, antibacterial and/or cholinesterase enzyme inhibitory effects. The active compounds were characterized by HPTLC-electrospray ionization-high resolution mass spectrometry (ESI-HRMS) and HPTLC-Direct Analysis in Real Time (DART)-MS/MS. The latter ambient ionization technique (less soft than ESI) resulted in oxidation and fragmentation products and characteristic fragment ions. NMR spectroscopy after targeted isolation via preparative normal phase flash chromatography and semi-preparative reversed phase high-performance liquid chromatography supported the identification of two diterpenes to be (-)-kaur-16-en-19-oic acid and 15-α-angeloyloxy-ent-kaur-16-en-19-oic acid. Both compounds found to be multi-potent as they inhibited acetylcholinesterase and butyrylcholinesterase and showed antibacterial effects against Gram-positive Bacillus subtilis and Gram-negative Aliivibrio fischeri bacteria. Kaurenoic acid was also active against the Gram-negative pepper pathogenic Xanthomonas euvesicatoria bacteria. Copyright © 2017 Elsevier B.V. All rights reserved.

Detection and determination of organophosphorus insecticides in tissues by thin-layer chromatography.

PubMed

Tewari, S N; Harpalani, S P

1977-01-11

The toxicological analysis of 12 common organophosphorus insecticides is described. Suitable methods for the extraction of organophosphorus insecticides from tissues are proposed. The detection, identification and estimation of these insecticides by thin-layer chromatography is described for 25 solvent systems and a series of chromogenic reagents. The distribution of insecticides in human body tissues in five cases of poisoning by ethyl parathion, malathion, dimethoate, sumithion and phosphamidon has also been studied.

Thin-layer chromatography and colorimetric analysis of multi-component explosive mixtures

DOEpatents

Pagoria, Philip F.; Mitchell, Alexander R.; Whipple, Richard E.; Carman, M. Leslie

2014-08-26

A thin-layer chromatography method for detection and identification of common military and peroxide explosives in samples includes the steps of provide a reverse-phase thin-layer chromatography plate; prepare the plate by marking spots on which to deposit the samples by touching the plate with a marker; spot one micro liter of a first standard onto one of the spots, spot one micro liter of a second standard onto another of the spots, and spot samples onto other of spots producing a spotted plate; add eluent to a developing chamber; add the spotted plate to the developing chamber; remove the spotted plate from the developing chamber producing a developed plate; place the developed plate in an ultraviolet light box; add a visualization agent to a dip tank; dip the developed plate in the dip tank and remove the developed plate quickly; and detect explosives by viewing said developed plate.

Low-Dimensional Nanomaterials as Active Layer Components in Thin-Film Photovoltaics

NASA Astrophysics Data System (ADS)

Shastry, Tejas Attreya

Thin-film photovoltaics offer the promise of cost-effective and scalable solar energy conversion, particularly for applications of semi-transparent solar cells where the poor absorption of commercially-available silicon is inadequate. Applications ranging from roof coatings that capture solar energy to semi-transparent windows that harvest the immense amount of incident sunlight on buildings could be realized with efficient and stable thin-film solar cells. However, the lifetime and efficiency of thin-film solar cells continue to trail their inorganic silicon counterparts. Low-dimensional nanomaterials, such as carbon nanotubes and two-dimensional metal dichalcogenides, have recently been explored as materials in thin-film solar cells due to their exceptional optoelectronic properties, solution-processability, and chemical inertness. Thus far, issues with the processing of these materials has held back their implementation in efficient photovoltaics. This dissertation reports processing advances that enable demonstrations of low-dimensional nanomaterials in thin-film solar cells. These low-dimensional photovoltaics show enhanced photovoltaic efficiency and environmental stability in comparison to previous devices, with a focus on semiconducting single-walled carbon nanotubes as an active layer component. The introduction summarizes recent advances in the processing of carbon nanotubes and their implementation through the thin-film photovoltaic architecture, as well as the use of two-dimensional metal dichalcogenides in photovoltaic applications and potential future directions for all-nanomaterial solar cells. The following chapter reports a study of the interaction between carbon nanotubes and surfactants that enables them to be sorted by electronic type via density gradient ultracentrifugation. These insights are utilized to construct of a broad distribution of carbon nanotubes that absorb throughout the solar spectrum. This polychiral distribution is then shown to result in record breaking performance in a carbon nanotube solar cell, and subsequent chapters study the mechanisms behind charge transfer in the polychiral carbon nanotube / fullerene solar cell. Further processing advances, chiral distribution tailoring, and solvent additives are shown to enable more uniform and larger area carbon nanotube solar cells while maintaining record-breaking performance. In order to increase overall photovoltaic performance of a carbon nanotube active layer solar cell, this dissertation also demonstrates a ternary polymer-carbon nanotube-small molecule photovoltaic with high efficiency and stability enabled by the nanomaterial. Finally, the use of the two-dimensional metal dichalcogenide molybdenum disulfide as a photovoltaic material is explored in an ultrathin solar cell with higher efficiency per thickness than leading organic and inorganic thin-film photovoltaics. Overall, this work demonstrates breakthroughs in utilizing low-dimensional nanomaterials as active layer components in photovoltaics and will inform ongoing research in making ultrathin, stable, efficient solar cells.

Pharmacognostic Screening of Piper trichostachyon Fruits and its Comparative Analysis with Piper nigrum Using Chromatographic Techniques

PubMed Central

Upadhya, Vinayak; Pai, Sandeep R.; Ankad, Gireesh M.; Hegde, Harsha V.

2016-01-01

Background: Piper trichostachyon is a wild, endemic Piper species from Western Ghats of India. The folklore healers of Belagavi region use this plant, similar to Piper nigrum. Aims: The present study investigates the comparison between P. nigrum and P. trichostachyon using pharmacognostic parameters. Materials and Methods: Pharmacognostic evaluation was carried out in terms of morphological, microscopic characters, and phytochemical analysis using standard methods. Comparative physicochemical analysis between P. trichostachyon and P. nigrum was also carried out through estimation of micro-macro nutrients, high-performance thin layer chromatography (HPTLC) investigation and using piperine as a marker compound for reversed phase-ultra flow liquid chromatographic (RP-UFLC) technique. Results: P. trichostachyon grows in the forests, and the fruits are morphologically similar to P. nigrum fruits, so the name in Kannada “Kaadu Kalu menasu” (wild/forest black pepper). The microscopy revealed the presence of stone cells, starch grains, oil cells and globules, beaker cells, and yellowish brown pigment layer, parenchymatous cells. The presence of alkaloids, oil, and tannins were observed in P. trichostachyon fruits. The HPTLC studies visibly indicated differences among two species with 12 peaks and varied banding pattern. RP-UFLC results showed less amount of piperine in P. trichostachyon (0.05 ± 0.002 mg/g) than in P. nigrum (16.14 ± 0.807 mg/g). Conclusion: The study reports on pharmacognostic parameters of P. trichostachyon for the 1st time and will be useful for the identification and authentication. The comparative HPTLC and RP-UFLC studies resolve the differentiation impasse among two species. However, further biological efficacy studies are required to establish its use in traditional medicine. SUMMARY Piper trichostachyon grows in the forests, and the fruits are morphologically similar to Piper nigrum fruitsThe microscopy of P. trichostachyon revealed the presence of stone cells, starch grains, oil cells and globules, beaker cells and yellowish brown pigment layer, parenchymatous cellsThe high-performance thin layer chromatography studies visibly indicated differences among two species with varied banding patternReversed phase-ultra flow liquid chromatographic results showed less amount of piperine in P. trichostachyon than in P. nigrum. Abbreviation used: HPTLC: High Performance Thin Layer Chromatography, RP-UFLC: Reversed phase-ultra flow liquid chromatographic analysis, DST: Length of line, Maj: Length of large half axis for ellipse RDS - radius for circle, Rf: Retention Factor, TS: Transverse Section, TLC: Thin Layer Chromatography. PMID:27279700

Formula Gives Better Contact-Resistance Values

NASA Technical Reports Server (NTRS)

Lieneweg, Udo; Hannaman, David J.

1988-01-01

Lateral currents in contact strips taken into account. Four-terminal test structures added to intergrated circuits to enable measurement of interfacial resistivities of contacts between thin conducting layers. Thin-film model simplified quasi-two-dimensional potential model that accounts adequately for complicated three-dimensional, nonuniform current densitites. Effects of nonuniformity caused by lateral current flow in strips summarized in equivalent resistance Rs and voltage Vs.

Thin-Layer Chromatography Experiments That Illustrate General Problems in Chromatography.

ERIC Educational Resources Information Center

Lederer, M.; Leipzig-Pagani, E.

1996-01-01

Describes experiments that illustrate a number of general principles such as pattern identification, displacement chromatography, and salting-out adsorption, plus an experiment that demonstrates that identification by chromatography alone is impossible. Illustrates that chromatography is still possible with quite simple means, notwithstanding the…

Extraction of nutraceuticals from Spirulina (blue-green alga): A bioorganic chemistry practice using thin-layer chromatography.

PubMed

Herrera Bravo de Laguna, Irma; Toledo Marante, Francisco J; Luna-Freire, Kristerson R; Mioso, Roberto

2015-01-01

Spirulina is a blue-green alga (cyanobacteria) with high nutritive value. This work provides an innovative and original approach to the consideration of a bioorganic chemistry practice, using Spirulina for the separation of phytochemicals with nutraceutical characteristics via thin-layer chromatography (TLC) plates. The aim is to bring together current research, theory, and practice, and always in accordance with pedagogical ideas. © 2015 The International Union of Biochemistry and Molecular Biology.

High performance thin layer chromatography fingerprint analysis of guava (Psidium guajava) leaves

NASA Astrophysics Data System (ADS)

Astuti, M.; Darusman, L. K.; Rafi, M.

2017-05-01

High-performance thin layer chromatography (HPTLC) fingerprint analysis is commonly used for quality control of medicinal plants in term of identification and authentication. In this study, we have been developed HPTLC fingerprint analysis for identification of guava (Psidium guajava) leaves raw material. A mixture of chloroform, acetone, and formic acid in the ratio 10:2:1 was used as the optimum mobile phase in HPTLC silica plate and with 13 bands were detected. As reference marker we chose gallic acid (Rf = 0.21) and catechin (Rf = 0.11). The two compound were detected as pale black bands at 366 nm after derivatization with sulfuric acid 10% v/v (in methanol) reagent. Validation of the method was met within validation criteria, so the developed method could be used for quality control of guava leaves.

Phospholipid and fatty acid compositions of Rhizobium leguminosarum biovar trifolii ANU843 in relation to flavone-activated pSym nod gene expression.

PubMed

Orgambide, G G; Huang, Z H; Gage, D A; Dazzo, F B

1993-11-01

The phospholipid and associated fatty acid compositions of the bacterial symbiont of clover, Rhizobium leguminosarum biovar trifolii wild-type ANU843, was analyzed by two-dimensional silica thin-layer chromatography, fast atom bombardment-mass spectrometry, flame-ionization detection gas-liquid chromatography and combined gas-liquid chromatography/mass spectrometry. The phospholipid composition included phosphatidylethanolamine (15%), N-methylphosphatidylethanolamine (47%), N,N-dimethylphosphatidylethanolamine (9%), phosphatidylglycerol (19%), cardiolipin (5%) and phosphatidylcholine (2%). Fatty acid composition included predominantly cis-11-octadecenoic acid, lower levels of cis-9-hexadecenoic acid, hexadecanoic acid, 11-methyl-11-octadecenoic acid, octadecanoic acid, 11,12-methyleneoctadecanoic acid, eicosanoic acid and traces of branched, and di- and triunsaturated fatty acids. The influence of expression of the "nodulation" genes encoding symbiotic functions on the composition of these membrane lipids was examined in wild-type cells grown with or without the flavone inducer, 4',7-dihydroxyflavone and in mutated cells lacking the entire symbiotic plasmid where these genes reside, or containing single transposon insertions in selected nodulation genes. No significant changes in phospholipid or associated fatty acid compositions were detected by the above methods of analysis.

High Performance Thin layer Chromatography: Densitometry Method for Determination of Rubraxanthone in the Stem Bark Extract of Garcinia cowa Roxb.

PubMed

Hamidi, Dachriyanus; Aulia, Hilyatul; Susanti, Meri

2017-01-01

Garcinia cowa is a medicinal plant widely grown in Southeast Asia and tropical countries. Various parts of this plant have been used in traditional folk medicine. The bark, latex, and root have been used as an antipyretic agent, while fruit and leaves have been used as an expectorant, for indigestion and improvement of blood circulation. This study aims to determine the concentration of rubraxanthone found in ethyl acetate extract of the stem bark of G. cowa by the high-performance thin-layer chromatography (HPTLC). HPTLC method was performed on precoated silica gel G 60 F254 plates using an HPTLC system with a developed mobile-phase system of chloroform: ethyl acetate: methanol: formic acid (86:6:3:5). A volume of 5 μL of standard and sample solutions was applied to the chromatographic plates. The plates were developed in saturated mode of twin trough chamber at room temperature. The method was validated based on linearity, accuracy, precision, limit of detection (LOD), limit of quantification (LOQ), and specificity. The spots were observed at ultraviolet 243 nm. The linearity of rubraxanthone was obtained between 52.5 and 157.5 ppm/spot. The LOD and LOQ were found to be 4.03 and 13.42 ppm/spot, respectively. The proposed method showed good linearity, precision, accuracy, and high sensitivity. Therefore, it may be applied for the quantification of rubraxanthone in ethyl acetate extract of the stem bark of G. cowa . High performance thin layer chromatography (HPTLC) method provides rapid qualitative and quantitative estimation of rubraxanthone as a marker com¬pound in G. cowa extract used for commercial productRubraxanthone found in ethyl acetate extracts of G. cowa was successfully quantified using HPTLC method. Abbreviations Used : TLC: Thin-layer chromatography, HPTLC: High-performance thin-layer chromatography, LOD: Limit of detection, LOQ: Limit of quantification, ICH: International Conference on Harmonization.

Determination of Absolute Configuration of Secondary Alcohols Using Thin-Layer Chromatography

PubMed Central

Wagner, Alexander J.; Rychnovsky, Scott D.

2013-01-01

A new implementation of the Competing Enantioselective Conversion (CEC) method was developed to qualitatively determine the absolute configuration of enantioenriched secondary alcohols using thin-layer chromatography. The entire process for the method requires approximately 60 min and utilizes micromole quantities of the secondary alcohol being tested. A number of synthetically relevant secondary alcohols are presented. Additionally, 1H NMR spectroscopy was conducted on all samples to provide evidence of reaction conversion that supports the qualitative method presented herein. PMID:23593963

Binding Assays for the Quantitative Detection of P. brevis Polyether Neurotoxins in Biological Samples and Antibodies as Therapeutic Aids for Polyether Marine Intoxication

DTIC Science & Technology

1987-12-01

editions are obsolete. -I Block 19 continued structure. Preliminary experiments involving conversion of the radio- immunoassay to a urease enzyme linked...the radioimmunoassay to a urease I enzyme linked form have been successful. DTIC GTAB Di tributioul AV~i~b~±~YCoded Avsi abi11i ntY___ tat Special...necessary prior to thin- layer chromatography. A preparative thin- layer chromatography step using silica gel plates (1000 u thickness) utilizes acetone

Thin-Layer and Paper Chromatography.

ERIC Educational Resources Information Center

Sherma, Joseph; Fried, Bernard

1984-01-01

Reviews literature on chromatography examining: books, reviews, student experiments; chromatographic systems, techniques, apparatus; detecting and identification of separated zones; preparative chromatography and radiochromatography; and applications related to specific materials (such as acids, alcohols, amino acids, antibiotics, enzymes, dyes,…

A numerical solution of the Navier-Stokes equations for chemically nonequilibrium, merged stagnation shock layers on spheres and two-dimensional cylinders in air

NASA Technical Reports Server (NTRS)

Johnston, K. D.; Hendricks, W. L.

1978-01-01

Results of solving the Navier-Stokes equations for chemically nonequilibrium, merged stagnation shock layers on spheres and two-dimensional cylinders are presented. The effects of wall catalysis and slip are also examined. The thin shock layer assumption is not made, and the thick viscous shock is allowed to develop within the computational domain. The results show good comparison with existing data. Due to the more pronounced merging of shock layer and boundary layer for the sphere, the heating rates for spheres become higher than those for cylinders as the altitude is increased.

In situ Silver Spot Preparation and on-Plate Surface-Enhanced Raman Scattering Detection in Thin Layer Chromatography Separation

NASA Astrophysics Data System (ADS)

Herman, K.; Mircescu, N. E.; Szabo, L.; Leopold, L. F.; Chiş, V.; Leopold, N.

2013-05-01

An improved approach for surface-enhanced Raman scattering (SERS) detection of mixture constituents after thin layer chromatography (TLC) separation is presented. A SERS active silver substrate was prepared under open air conditions, directly on the thin silica film by photo-reduction of silver nitrate, allowing the detection of binary mixtures of cresyl violet, bixine, crystal violet, and Cu(II) complex of 4-(2-pyridylazo)resorcinol. The recorded SERS spectrum provides a unique spectral fingerprint for each molecule; therefore the use of analyte standards is avoided, thus rendering the presented procedure advantageous compared to the conventional detection methodology in TLC.

Characterization of inositolphospholipids in Trypanosoma cruzi trypomastigote forms.

PubMed

Uhrig, M L; Couto, A S; Colli, W; de Lederkremer, R M

1996-05-20

In vivo labeling experiments with [3H]palmitic acid, [3H]inositol, and [3H]glucose allowed the identification of two main classes of inositolphospholipids (IPLs) from the trypomastigote stage of Trypanosoma cruzi. Purification of these compounds was achieved by ion-exchange chromatography, high performance liquid chromatography and thin layer chromatography. Specific phosphatidyl-inositol phospholipase C digestion, dephosphorylation and acid methanolysis showed a ceramide structure for the lower migrating IPL1. Palmitoyldihydrosphingosine and palmitoylsphingosine were detected by reverse-phase thin-layer chromatography. On the other hand, IPL2 showed to be a mixture of diacylglycero- and alkylacylglycero-phospholipids in a 1:1 ratio. After PI-PLC digestion, the lipids were separated by preparative TLC and individually analysed. The diacylglycerol contained mainly C18:0 fatty acid together with a low amount of C16:0. Hexadecylglycerol esterified with the C18:0 fatty acid was the only alkylacylglycerol detected. The C18:2 and C18:1 fatty acids, preponderant in the PI molecules of epimastigote forms, were not detected in trypomastigote forms. This is the first report on inositol phospholipids, putative precursors of lipid anchors in the infective stage of T. cruzi.

Universal Method for Creating Hierarchical Wrinkles on Thin-Film Surfaces.

PubMed

Jung, Woo-Bin; Cho, Kyeong Min; Lee, Won-Kyu; Odom, Teri W; Jung, Hee-Tae

2018-01-10

One of the most interesting topics in physical science and materials science is the creation of complex wrinkled structures on thin-film surfaces because of their several advantages of high surface area, localized strain, and stress tolerance. In this study, a significant step was taken toward solving limitations imposed by the fabrication of previous artificial wrinkles. A universal method for preparing hierarchical three-dimensional wrinkle structures of thin films on a multiple scale (e.g., nanometers to micrometers) by sequential wrinkling with different skin layers was developed. Notably, this method was not limited to specific materials, and it was applicable to fabricating hierarchical wrinkles on all of the thin-film surfaces tested thus far, including those of metals, two-dimensional and one-dimensional materials, and polymers. The hierarchical wrinkles with multiscale structures were prepared by sequential wrinkling, in which a sacrificial layer was used as the additional skin layer between sequences. For example, a hierarchical MoS 2 wrinkle exhibited highly enhanced catalytic behavior because of the superaerophobicity and effective surface area, which are related to topological effects. As the developed method can be adopted to a majority of thin films, it is thought to be a universal method for enhancing the physical properties of various materials.

Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

PubMed

Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

2016-07-06

Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

Sensitivity Enhancement of Transition Metal Dichalcogenides/Silicon Nanostructure-based Surface Plasmon Resonance Biosensor

PubMed Central

Ouyang, Qingling; Zeng, Shuwen; Jiang, Li; Hong, Liying; Xu, Gaixia; Dinh, Xuan-Quyen; Qian, Jun; He, Sailing; Qu, Junle; Coquet, Philippe; Yong, Ken-Tye

2016-01-01

In this work, we designed a sensitivity-enhanced surface plasmon resonance biosensor structure based on silicon nanosheet and two-dimensional transition metal dichalcogenides. This configuration contains six components: SF10 triangular prism, gold thin film, silicon nanosheet, two-dimensional MoS2/MoSe2/WS2/WSe2 (defined as MX2) layers, biomolecular analyte layer and sensing medium. The minimum reflectivity, sensitivity as well as the Full Width at Half Maximum of SPR curve are systematically examined by using Fresnel equations and the transfer matrix method in the visible and near infrared wavelength range (600 nm to 1024 nm). The variation of the minimum reflectivity and the change in resonance angle as the function of the number of MX2 layers are presented respectively. The results show that silicon nanosheet and MX2 layers can be served as effective light absorption medium. Under resonance conditions, the electrons in these additional dielectric layers can be transferred to the surface of gold thin film. All silicon-MX2 enhanced sensing models show much better performance than that of the conventional sensing scheme where pure Au thin film is used, the highest sensitivity can be achieved by employing 600 nm excitation light wavelength with 35 nm gold thin film and 7 nm thickness silicon nanosheet coated with monolayer WS2. PMID:27305974

Occurrence and in Vivo Biosynthesis of Indole-3-Butyric Acid in Corn (Zea mays L.) 1

PubMed Central

Ludwig-Müller, Jutta; Epstein, Ephraim

1991-01-01

Indole-3-butyric acid (IBA) was identified as an endogenous compound in leaves and roots of maize (Zea mays L.) var Inrakorn by thin layer chromatography, high-performance liquid chromatography, and gas chromatography-mass spectrometry. Its presence was also confirmed in the variety Hazera 224. Indole-3-acetic acid (IAA) was metabolized to IBA in vivo by seedlings of the two maize varieties. The reaction product was identified by thin layer chromatography, high performance liquid chromatography, and gas chromatography-mass spectrometry after incubating the corn seedlings with [14C]IAA and [13C6]IAA. The in vivo conversion of IAA to IBA and the characteristics of IBA formation in two different maize varieties of Zea mays L. (Hazera 224 and Inrakorn) were investigated. IBA-forming activity was examined in the roots, leaves, and coleoptiles of both maize varieties. Whereas in the variety Hazera 224, IBA was formed mostly in the leaves, in the variety Inrakorn, IBA synthesis was detected in the roots as well as in the leaves. A time course study of IBA formation showed that maximum activity was reached in Inrakorn after 1 hour and in Hazera after 2 hours. The pH optimum for the uptake of IAA was 6.0, and that for IBA formation was 7.0. The Km value for IBA formation was 17 micromolar for Inrakorn and 25 micromolar for Hazera 224. The results are discussed with respect to the possible functions of IBA in the plant. ImagesFigure 5 PMID:16668464

Combined thin layer chromatography and gas chromatography with mass spectrometric analysis of lipid classes and fatty acids in malnourished polar bears (Ursus maritimus) which swam to Iceland.

PubMed

Eibler, Dorothee; Krüger, Sabine; Skírnisson, Karl; Vetter, Walter

2017-03-01

Between 2008 and 2011, four polar bears (Ursus maritimus) from the Greenland population swam and/or drifted on ice to Iceland where they arrived in very poor body condition. Body fat resources in these animals were only between 0% and 10% of the body weight (usually 25%). Here we studied the lipid composition in different tissues (adipose tissue if available, liver, kidney and muscle). Lipid classes were determined by thin layer chromatography (TLC) and on-column gas chromatography with mass spectrometry (GC/MS). The fatty acid pattern of total lipids and free fatty acids was analyzed by GC/MS in selected ion monitoring (SIM) mode. Additionally, cholesteryl esters and native fatty acid methyl esters, initially detected as zones in thin layer chromatograms, were enriched by solid phase extraction and quantified by GC/MS. The ratio of free fatty acids to native fatty acid methyl esters could be correlated with the remained body lipids in the polar bears and thus may also serve as a marker for other starving animals or even for humans. Copyright © 2017 Elsevier B.V. All rights reserved.

Features of the rupture of free hanging liquid film under the action of a thermal load

NASA Astrophysics Data System (ADS)

Ovcharova, Alla S.

2011-10-01

We consider a deformation and a rupture of a thin liquid film which is hanging between two solid flat walls under the action of concentrated thermal load action. A two-dimensional model is applied to describe the motion of thin layers of viscous non-isothermal liquid under micro-gravity conditions. For flow simulation, two-dimensional Navier-Stokes equations are used. A computational analysis of the influence of thermal loads on the deformation and the rupture behavior of the thin freely hanging film is carried out. It is shown that the rupture of the thin film with generation of a droplet can occur under the thermal beam of specific width acting on the free surface of the film. The results of the model problem solutions are presented.

Quantitative determination of seven chemical constituents and chemo-type differentiation of chamomiles using high-performance thin-layer chromatography

USDA-ARS?s Scientific Manuscript database

Matricaria recutita L. (German Chamomile), Anthemis nobilis L. (Roman Chamomile) and Chrysanthemum morifolium Ramat are commonly used chamomiles. High performance thin layer chromatographic (HPTLC) method was developed for estimation of six flavonoids (rutin, luteolin-7-O-ß-glucoside, chamaemeloside...

Showing Its Colors. Thin-Layer Chromatographic Detection of Cannabinoid Metabolites.

ERIC Educational Resources Information Center

Bonicamp, Judith M.

1986-01-01

Describes a chemistry laboratory experiment in which thin-layer chromatography (TLC) is used to analyze urine specimens containing metabolites of the drug tetrahydro-cannabinol, which comes from the marijuana plant. The materials needed to conduct the experiment are listed, and the procedure and expected results are outlined. (TW)

Quantitative Caffeine Analysis Using a Surface Sampling Probe Electrospray Ionization Tandem Mass Spectrometry System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ford, Michael J; Deibel, Michael A.; Tomkins, Bruce A

Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 {mu}m/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methodsmore » determined from the calibration curve statistics were 0.20 ng injected (0.50 {mu}L) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by 8% or more) than the literature values.« less

Numerical simulation of steady supersonic flow. [spatial marching

NASA Technical Reports Server (NTRS)

Schiff, L. B.; Steger, J. L.

1981-01-01

A noniterative, implicit, space-marching, finite-difference algorithm was developed for the steady thin-layer Navier-Stokes equations in conservation-law form. The numerical algorithm is applicable to steady supersonic viscous flow over bodies of arbitrary shape. In addition, the same code can be used to compute supersonic inviscid flow or three-dimensional boundary layers. Computed results from two-dimensional and three-dimensional versions of the numerical algorithm are in good agreement with those obtained from more costly time-marching techniques.

Enhanced superconductivity in atomically thin TaS2

PubMed Central

Navarro-Moratalla, Efrén; Island, Joshua O.; Mañas-Valero, Samuel; Pinilla-Cienfuegos, Elena; Castellanos-Gomez, Andres; Quereda, Jorge; Rubio-Bollinger, Gabino; Chirolli, Luca; Silva-Guillén, Jose Angel; Agraït, Nicolás; Steele, Gary A.; Guinea, Francisco; van der Zant, Herre S. J.; Coronado, Eugenio

2016-01-01

The ability to exfoliate layered materials down to the single layer limit has presented the opportunity to understand how a gradual reduction in dimensionality affects the properties of bulk materials. Here we use this top–down approach to address the problem of superconductivity in the two-dimensional limit. The transport properties of electronic devices based on 2H tantalum disulfide flakes of different thicknesses are presented. We observe that superconductivity persists down to the thinnest layer investigated (3.5 nm), and interestingly, we find a pronounced enhancement in the critical temperature from 0.5 to 2.2 K as the layers are thinned down. In addition, we propose a tight-binding model, which allows us to attribute this phenomenon to an enhancement of the effective electron–phonon coupling constant. This work provides evidence that reducing the dimensionality can strengthen superconductivity as opposed to the weakening effect that has been reported in other 2D materials so far. PMID:26984768

Investigation of Boundary Layer Disturbances Caused by Periodic Heating of a Thin Ribbon

DTIC Science & Technology

1988-03-01

boundary layer. To obtain quantitative information about the development of these waves, they introduced a two-dimensional artificial disturbance into the...AF IT a. Thermo Systems Inc. (TSI) IFA-iO Intellegent Flow Analyzer Anemometry System b. TSI Model 1218-20 Hot Film Boundary Layer Probe c. Zenith Z

New technique for heterogeneous vapor-phase synthesis of nanostructured metal layers from low-dimensional volatile metal complexes

NASA Astrophysics Data System (ADS)

Badalyan, A. M.; Bakhturova, L. F.; Kaichev, V. V.; Polyakov, O. V.; Pchelyakov, O. P.; Smirnov, G. I.

2011-09-01

A new technique for depositing thin nanostructured layers on semiconductor and insulating substrates that is based on heterogeneous gas-phase synthesis from low-dimensional volatile metal complexes is suggested and tried out. Thin nanostructured copper layers are deposited on silicon and quartz substrates from low-dimensional formate complexes using a combined synthesis-mass transport process. It is found that copper in layers thus deposited is largely in a metal state (Cu0) and has the form of closely packed nanograins with a characteristic structure.

Non-enzymatic synthesis of the coenzymes, uridine diphosphate glucose and cytidine diphosphate choline, and other phosphorylated metabolic intermediates

NASA Technical Reports Server (NTRS)

Mar, A.; Dworkin, J.; Oro, J.

1987-01-01

Using urea and cyanamide, the two condensing agents considered to have been present on the primitive earth, uridine diphosphate glucose (UDPG), cytidine diphosphate choline (CDP-choline), glucose-1-phosphate (G1P), and glucose-6-phosphate (G6P) were synthesized under simulated prebiotic conditions. The reaction products were separated and identified using paper chromatography, thin layer chromatography, enzymatic analyses, and ion-pair reverse-phase high performance liquid chromatography. The possibility of nonenzymatic synthesis of metabolic intermediates on the primitive earth from simple precursors was thus demonstrated.

QUALITY ASSURANCE STUDY OF MARINE LIPID CLASS DETERMINATION USING CHROMAROD/IATROSCAN( REG. TRADEMARK) THIN-LAYER CHROMATOGRAPHY-FLAME IONIZATION DETECTOR

EPA Science Inventory

An Iatroscan thin-layer chromatorgraphy-flame ionization detector has been utilized to quantify lipid classes in marine samples. This method was evaluated relative to established quality assurance (QA) procedures used for the gas chromatographic analysis of PCBs. A method for ext...

Thin-layer chromatographic (TLC) separations and bioassays of plant extracts to identify antimicrobial compounds

USDA-ARS?s Scientific Manuscript database

A common screen for plant antimicrobial compounds consists of separating plant extracts by paper or thin-layer chromatography (PC or TLC), exposing the chromatograms to microbial suspensions (e.g. fungal spores in nutrient solution or bacteria in liquefied agar), allowing time for the microbes to gr...

[Analysis of pigments from Rhodotorula glutinis by Raman spectroscopy and thin layer chromatography].

PubMed

Yuan, Yu-feng; Tao, Zhan-hua; Wang, Xue; Li, Yong-qing; Liu, Jun-xian

2012-03-01

The pigments from Rhodotorula glutinis were separated by using thin layer chromatography, and the result showed that Rhodotorula glutinis cells could synthesize at least three kinds of pigments, which were beta-carotene, torulene, and torularhodin. The Raman spectra based on the three pigments were acquired, and original spectra were preprocessed by background elimination, baseline correction, and three-point-smoothing, then the averaged spectra from different pigments were investigated, and the result indicated that Raman shift which represents C-C bond was different, and the wave number of beta-carotene demonstrated the largest deviation, finally torulene and torularhodin in Rhodotorula glutinis had more content than beta-carotene. Quantitative analysis of Raman peak height ratio revealed that peak height ratio of pigments showed little difference, which could be used as parameters for further research on living cells, providing reference content of pigments. The above results suggest that Raman spectroscopy combined with thin layer chromatography can be applied to analyze pigments from Rhodotorula glutinis, provides abundant information about pigments, and serves as an effective method to study pigments.

Two-dimensional transition metal dichalcogenides as atomically thin semiconductors: opportunities and challenges.

PubMed

Duan, Xidong; Wang, Chen; Pan, Anlian; Yu, Ruqin; Duan, Xiangfeng

2015-12-21

The discovery of graphene has ignited intensive interest in two-dimensional layered materials (2DLMs). These 2DLMs represent a new class of nearly ideal 2D material systems for exploring fundamental chemistry and physics at the limit of single-atom thickness, and have the potential to open up totally new technological opportunities beyond the reach of existing materials. In general, there are a wide range of 2DLMs in which the atomic layers are weakly bonded together by van der Waals interactions and can be isolated into single or few-layer nanosheets. The van der Waals interactions between neighboring atomic layers could allow much more flexible integration of distinct materials to nearly arbitrarily combine and control different properties at the atomic scale. The transition metal dichalcogenides (TMDs) (e.g., MoS2, WSe2) represent a large family of layered materials, many of which exhibit tunable band gaps that can undergo a transition from an indirect band gap in bulk crystals to a direct band gap in monolayer nanosheets. These 2D-TMDs have thus emerged as an exciting class of atomically thin semiconductors for a new generation of electronic and optoelectronic devices. Recent studies have shown exciting potential of these atomically thin semiconductors, including the demonstration of atomically thin transistors, a new design of vertical transistors, as well as new types of optoelectronic devices such as tunable photovoltaic devices and light emitting devices. In parallel, there have also been considerable efforts in developing diverse synthetic approaches for the rational growth of various forms of 2D materials with precisely controlled chemical composition, physical dimension, and heterostructure interface. Here we review the recent efforts, progress, opportunities and challenges in exploring the layered TMDs as a new class of atomically thin semiconductors.

Chromatographic methods for determination of macrolide antibiotic residues in tissues and milk of food-producing animals.

PubMed

Moats, W A

1985-01-01

Tylosin, an antibiotic developed specifically for agricultural use, and erythromycin are the main macrolide antibiotics used in animal production. Two-dimensional thin layer chromatography has been used for detection of tylosin in poultry meat, eggs, and milk and for erythromycin in poultry meat. Detection limits reported are, for tylosin, 0.1 ppm in poultry meat, 0.05 ppm in egg, and 0.01 ppm in milk, and for erythromycin, 0.25 ppm in poultry meat. Liquid chromatography (LC) has also been used for determination of tylosin in milk, blood, and tissues of animals. Samples (milk, blood serum, or tissue homogenates in water or pH 2.2 buffer) were deproteinized with acetonitrile, tylosin was partitioned into methylene chloride, and the extracts were concentrated and dissolved in acetonitrile. Chromatography was done on a reverse phase end-capped C18 column using 0.002-0.005 M ammonium dihydrogen phosphate-acetonitrile-methanol (10 + 60 + 30-5 + 80 + 15). Solvent composition was varied with the type of sample analyzed. The method will detect 0.1 ppm tylosin in tissues and less in milk and blood serum. The LC method was more sensitive than microbiological assays for detection of tylosin in tissues of treated swine; recoveries of tylosin by the LC method were frequently several-fold higher.

Layer-by-layer assembly of two-dimensional materials into wafer-scale heterostructures

NASA Astrophysics Data System (ADS)

Kang, Kibum; Lee, Kan-Heng; Han, Yimo; Gao, Hui; Xie, Saien; Muller, David A.; Park, Jiwoong

2017-10-01

High-performance semiconductor films with vertical compositions that are designed to atomic-scale precision provide the foundation for modern integrated circuitry and novel materials discovery. One approach to realizing such films is sequential layer-by-layer assembly, whereby atomically thin two-dimensional building blocks are vertically stacked, and held together by van der Waals interactions. With this approach, graphene and transition-metal dichalcogenides--which represent one- and three-atom-thick two-dimensional building blocks, respectively--have been used to realize previously inaccessible heterostructures with interesting physical properties. However, no large-scale assembly method exists at present that maintains the intrinsic properties of these two-dimensional building blocks while producing pristine interlayer interfaces, thus limiting the layer-by-layer assembly method to small-scale proof-of-concept demonstrations. Here we report the generation of wafer-scale semiconductor films with a very high level of spatial uniformity and pristine interfaces. The vertical composition and properties of these films are designed at the atomic scale using layer-by-layer assembly of two-dimensional building blocks under vacuum. We fabricate several large-scale, high-quality heterostructure films and devices, including superlattice films with vertical compositions designed layer-by-layer, batch-fabricated tunnel device arrays with resistances that can be tuned over four orders of magnitude, band-engineered heterostructure tunnel diodes, and millimetre-scale ultrathin membranes and windows. The stacked films are detachable, suspendable and compatible with water or plastic surfaces, which will enable their integration with advanced optical and mechanical systems.

Layer-by-layer assembly of two-dimensional materials into wafer-scale heterostructures.

PubMed

Kang, Kibum; Lee, Kan-Heng; Han, Yimo; Gao, Hui; Xie, Saien; Muller, David A; Park, Jiwoong

2017-10-12

High-performance semiconductor films with vertical compositions that are designed to atomic-scale precision provide the foundation for modern integrated circuitry and novel materials discovery. One approach to realizing such films is sequential layer-by-layer assembly, whereby atomically thin two-dimensional building blocks are vertically stacked, and held together by van der Waals interactions. With this approach, graphene and transition-metal dichalcogenides-which represent one- and three-atom-thick two-dimensional building blocks, respectively-have been used to realize previously inaccessible heterostructures with interesting physical properties. However, no large-scale assembly method exists at present that maintains the intrinsic properties of these two-dimensional building blocks while producing pristine interlayer interfaces, thus limiting the layer-by-layer assembly method to small-scale proof-of-concept demonstrations. Here we report the generation of wafer-scale semiconductor films with a very high level of spatial uniformity and pristine interfaces. The vertical composition and properties of these films are designed at the atomic scale using layer-by-layer assembly of two-dimensional building blocks under vacuum. We fabricate several large-scale, high-quality heterostructure films and devices, including superlattice films with vertical compositions designed layer-by-layer, batch-fabricated tunnel device arrays with resistances that can be tuned over four orders of magnitude, band-engineered heterostructure tunnel diodes, and millimetre-scale ultrathin membranes and windows. The stacked films are detachable, suspendable and compatible with water or plastic surfaces, which will enable their integration with advanced optical and mechanical systems.

Yeast Metabolism of D-[U-14C]-Glucose: A Student Study of the Early Stages of Glycolysis.

ERIC Educational Resources Information Center

Taber, Richard L.; Harwood, Betty G.

1983-01-01

Describes an experiment which gives students experience with uncertainties encountered in studying metabolic pathways; handling/use of radioisotopes; application of thin layer chromatography; and liquid scintillation counting and fluorography as methods of detecting radioactivity. The experiment can be accomplished in two to three laboratory…

HPTLC detection of altitudinal variation of the potential antivenin stigmasterol in different populations of the tropical ethnic antidote Rauvolfia serpentina.

PubMed

Dey, Abhijit; Pandey, Devendra Kumar

2014-09-01

To determine the altitudinal variation of stigmasterol, a potential antivenin, in roots from seven populations of Rauvolfia serpentina (L). Benth. ex Kurz. (Apocynaceae) (R. serpentina), an important herb found in Indian subcontinent which has long been used in the treatment of snakebite, blood pressure and schizophrenia. Altitudinal variation of stigmasterol content in R. serpentina roots was analyzed by high performance thin layer chromatography. Chromatography was performed on silica gel 60 F254 thin layer chromatography plates with benzene-acetone 86:14 (v/v) as mobile phase. Densitometric analysis was done at λ=366 nm after derivatization with vanillin-10% (v/v) sulphuric acid alcohol reagent. The method was validated for precision and recovery. The present experiment demonstrates a simple, rapid, precise and sensitive high performance thin layer chromatography protocol for qualitative and quantitative determination of stigmasterol from different populations of R. serpentina. Results demonstrated that in root samples stigmasterol was present at Rf value of 0.44. This investigation demonstrates that stigmasterol content in R. serpentina roots varies in different altitudes. Popular ethnomedicinal use of this herb against snakebite may be contributed by the occurrence of stigmasterol in its roots. Copyright © 2014 Hainan Medical College. Published by Elsevier B.V. All rights reserved.

Comparison of the Effect of Horizontal Vibrations on Interfacial Waves in a Two-Layer System of Inviscid Liquids to Effective Gravity Inversion

NASA Astrophysics Data System (ADS)

Pimenova, Anastasiya V.; Goldobin, Denis S.; Lyubimova, Tatyana P.

2018-02-01

We study the waves at the interface between two thin horizontal layers of immiscible liquids subject to high-frequency tangential vibrations. Nonlinear governing equations are derived for the cases of two- and three-dimensional flows and arbitrary ratio of layer thicknesses. The derivation is performed within the framework of the long-wavelength approximation, which is relevant as the linear instability of a thin-layers system is long-wavelength. The dynamics of equations is integrable and the equations themselves can be compared to the Boussinesq equation for the gravity waves in shallow water, which allows one to compare the action of the vibrational field to the action of the gravity and its possible effective inversion.

Toxicity and physiological effect of quercetin on generalist herbivore, Spodoptera litura Fab. and a non-target earthworm Eisenia fetida Savigny

USDA-ARS?s Scientific Manuscript database

A novel flavonoid, quercetin, was isolated from Euphorbia hirta L., a medicinal plant using chromatography techniques including: Thin-layer chromatography, Column chromatography, Nuclear magnetic resonance spectroscopy. Toxicity to larval of Spodoptera litura analyze pupal weight, survival rate, fec...

A matrix dependent/algebraic multigrid approach for extruded meshes with applications to ice sheet modeling

DOE PAGES

Tuminaro, Raymond S.; Perego, Mauro; Tezaur, Irina Kalashnikova; ...

2016-10-06

A multigrid method is proposed that combines ideas from matrix dependent multigrid for structured grids and algebraic multigrid for unstructured grids. It targets problems where a three-dimensional mesh can be viewed as an extrusion of a two-dimensional, unstructured mesh in a third dimension. Our motivation comes from the modeling of thin structures via finite elements and, more specifically, the modeling of ice sheets. Extruded meshes are relatively common for thin structures and often give rise to anisotropic problems when the thin direction mesh spacing is much smaller than the broad direction mesh spacing. Within our approach, the first few multigridmore » hierarchy levels are obtained by applying matrix dependent multigrid to semicoarsen in a structured thin direction fashion. After sufficient structured coarsening, the resulting mesh contains only a single layer corresponding to a two-dimensional, unstructured mesh. Algebraic multigrid can then be employed in a standard manner to create further coarse levels, as the anisotropic phenomena is no longer present in the single layer problem. The overall approach remains fully algebraic, with the minor exception that some additional information is needed to determine the extruded direction. Furthermore, this facilitates integration of the solver with a variety of different extruded mesh applications.« less

Detection of mycoloylglycerol by thin-layer chromatography as a tool for the rapid inclusion of corynebacteria of clinical origin in the genus Corynebacterium.

PubMed

Yagüe, G; Segovia, M; Valero-Guillén, P L

2000-01-28

A chemotaxonomic study of some corynebacteria isolated from clinical samples revealed characteristic thin-layer chromatographic patterns for meso-diaminopimelic acid containing species included in the genera Corynebacterium, Dermabacter and Brevibacterium. Notably, a specific compound was consistently detected in mycolic acid containing species of the genus Corynebacterium. This compound was composed by glycerol and mycolic acids and structural analyses carried out by fast atom bombardment mass spectrometry in C. minutissimum confirmed its identification as mycoloylglycerol. The chain length of mycoloyl groups in this molecule ranged from 28 to 34 carbon atoms, being mono-, di- or triunsaturated. Detection of mycoloylglycerol by thin-layer chromatography may be thus useful for the rapid inclusion of a great variety of corynebacteria of clinical origin in the genus Corynebacterium in laboratories employing chromatographic techniques as an adjunct for the identification of these microorganisms.

A mechanism for hot-spot generation in a reactive two-dimensional sheared viscous layer

NASA Astrophysics Data System (ADS)

Timms, Robert; Purvis, Richard; Curtis, John P.

2018-05-01

A two-dimensional model for the non-uniform melting of a thin sheared viscous layer is developed. An asymptotic solution is presented for both a non-reactive and a reactive material. It is shown that the melt front is linearly stable to small perturbations in the non-reactive case, but becomes linearly unstable upon introduction of an Arrhenius source term to model the chemical reaction. Results demonstrate that non-uniform melting acts as a mechanism to generate hot spots that are found to be sufficient to reduce the time to ignition when compared with the corresponding one-dimensional model of melting.

GLC analysis of base composition of RNA and DNA hydrolysates

NASA Technical Reports Server (NTRS)

Lakings, D. B.; Gehreke, C. W.

1971-01-01

Various methods used for the analysis of the base composition of RNA and DNA hydrolysates are presented. The methods discussed are: (1) ion-exchange chromatography, (2) paper chromatography, (3) paper electrophoresis, (4) thin layer chromatography, (5) paper chromatography and time of flight mass spectrometry, and (6) gas-liquid chromatography. The equipment required and the conditions for obtaining the best results with each method are described.

Thin Layer Chromatography-Bioautography and Gas Chromatography-Mass Spectrometry of Antimicrobial Leaf Extracts from Philippine Piper betle L. against Multidrug-Resistant Bacteria.

PubMed

Valle, Demetrio L; Puzon, Juliana Janet M; Cabrera, Esperanza C; Rivera, Windell L

2016-01-01

This study isolated and identified the antimicrobial compounds of Philippine Piper betle L. leaf ethanol extracts by thin layer chromatography- (TLC-) bioautography and gas chromatography-mass spectrometry (GC-MS). Initially, TLC separation of the leaf ethanol extracts provided a maximum of eight compounds with R f values of 0.92, 0.86, 0.76, 0.53, 0.40, 0.25, 0.13, and 0.013, best visualized when inspected under UV 366 nm. Agar-overlay bioautography of the isolated compounds demonstrated two spots with R f values of 0.86 and 0.13 showing inhibitory activities against two Gram-positive multidrug-resistant (MDR) bacteria, namely, methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. The compound with an R f value of 0.86 also possessed inhibitory activity against Gram-negative MDR bacteria, namely, carbapenem-resistant Enterobacteriaceae-Klebsiella pneumoniae and metallo-β-lactamase-producing Acinetobacter baumannii. GC-MS was performed to identify the semivolatile and volatile compounds present in the leaf ethanol extracts. Six compounds were identified, four of which are new compounds that have not been mentioned in the medical literature. The chemical compounds isolated include ethyl diazoacetate, tris(trifluoromethyl)phosphine, heptafluorobutyrate, 3-fluoro-2-propynenitrite, 4-(2-propenyl)phenol, and eugenol. The results of this study could lead to the development of novel therapeutic agents capable of dealing with specific diseases that either have weakened reaction or are currently not responsive to existing drugs.

Thin Layer Chromatography-Bioautography and Gas Chromatography-Mass Spectrometry of Antimicrobial Leaf Extracts from Philippine Piper betle L. against Multidrug-Resistant Bacteria

PubMed Central

Valle, Demetrio L.; Puzon, Juliana Janet M.; Cabrera, Esperanza C.

2016-01-01

This study isolated and identified the antimicrobial compounds of Philippine Piper betle L. leaf ethanol extracts by thin layer chromatography- (TLC-) bioautography and gas chromatography-mass spectrometry (GC-MS). Initially, TLC separation of the leaf ethanol extracts provided a maximum of eight compounds with R f values of 0.92, 0.86, 0.76, 0.53, 0.40, 0.25, 0.13, and 0.013, best visualized when inspected under UV 366 nm. Agar-overlay bioautography of the isolated compounds demonstrated two spots with R f values of 0.86 and 0.13 showing inhibitory activities against two Gram-positive multidrug-resistant (MDR) bacteria, namely, methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. The compound with an R f value of 0.86 also possessed inhibitory activity against Gram-negative MDR bacteria, namely, carbapenem-resistant Enterobacteriaceae-Klebsiella pneumoniae and metallo-β-lactamase-producing Acinetobacter baumannii. GC-MS was performed to identify the semivolatile and volatile compounds present in the leaf ethanol extracts. Six compounds were identified, four of which are new compounds that have not been mentioned in the medical literature. The chemical compounds isolated include ethyl diazoacetate, tris(trifluoromethyl)phosphine, heptafluorobutyrate, 3-fluoro-2-propynenitrite, 4-(2-propenyl)phenol, and eugenol. The results of this study could lead to the development of novel therapeutic agents capable of dealing with specific diseases that either have weakened reaction or are currently not responsive to existing drugs. PMID:27478476

Ad-hoc surface-enhanced Raman spectroscopy methodologies for the detection of artist dyestuffs: thin layer chromatography-surface enhanced Raman spectroscopy and in situ on the fiber analysis.

PubMed

Brosseau, Christa L; Gambardella, Alessa; Casadio, Francesca; Grzywacz, Cecily M; Wouters, Jan; Van Duyne, Richard P

2009-04-15

Tailored ad-hoc methods must be developed for successful identification of minute amounts of natural dyes on works of art using Surface-Enhanced Raman Spectroscopy (SERS). This article details two of these successful approaches using silver film over nanosphere (AgFON) substrates and silica gel coupled with citrate-reduced Ag colloids. The latter substrate functions as the test system for the coupling of thin-layer chromatography and SERS (TLC-SERS), which has been used in the current research to separate and characterize a mixture of several artists' dyes. The poor limit of detection of TLC is overcome by coupling with SERS, and dyes which co-elute to nearly the same spot can be distinguished from each other. In addition, in situ extractionless non-hydrolysis SERS was used to analyze dyed reference fibers, as well as historical textile fibers. Colorants such as alizarin, purpurin, carminic acid, lac dye, crocin, and Cape jasmine were thus successfully identified.

Distribution of molecular weight in glyceride polymerizates or aggregates of them after contact with lunar grains

NASA Technical Reports Server (NTRS)

Asunmaa, S. K.; Haack, R.

1977-01-01

An attempt is made to report on experiments in which a molecular-weight increase was determined in thin layers of triglyceride-containing glycerides after thin-layer contact for two years with lunar topsoil grains at 25 C without any thermal activation. It is noted that solidification was observed on both dielectric grains and metal-rich areas and that changes in viscosity and molecular weights were first detected by solidification of surface layers. Gel permeation chromatography is described which detected a general shift of the Gaussian distribution of the molecular-weight data toward generally higher molecular weights as well as an increase in mean molecular weight. Reaction mechanisms are considered, and results of spectrographic analysis are cited which support the interpretations of the molecular-weight data.

Optimizing separations in online comprehensive two-dimensional liquid chromatography.

PubMed

Pirok, Bob W J; Gargano, Andrea F G; Schoenmakers, Peter J

2018-01-01

Online comprehensive two-dimensional liquid chromatography has become an attractive option for the analysis of complex nonvolatile samples found in various fields (e.g. environmental studies, food, life, and polymer sciences). Two-dimensional liquid chromatography complements the highly popular hyphenated systems that combine liquid chromatography with mass spectrometry. Two-dimensional liquid chromatography is also applied to the analysis of samples that are not compatible with mass spectrometry (e.g. high-molecular-weight polymers), providing important information on the distribution of the sample components along chemical dimensions (molecular weight, charge, lipophilicity, stereochemistry, etc.). Also, in comparison with conventional one-dimensional liquid chromatography, two-dimensional liquid chromatography provides a greater separation power (peak capacity). Because of the additional selectivity and higher peak capacity, the combination of two-dimensional liquid chromatography with mass spectrometry allows for simpler mixtures of compounds to be introduced in the ion source at any given time, improving quantitative analysis by reducing matrix effects. In this review, we summarize the rationale and principles of two-dimensional liquid chromatography experiments, describe advantages and disadvantages of combining different selectivities and discuss strategies to improve the quality of two-dimensional liquid chromatography separations. © 2017 The Authors. Journal of Separation Science published by WILEY-VCH Verlag GmbH & Co. KGaA.

Determination of Components in Beverages by Thin-Layer Chromatography.

ERIC Educational Resources Information Center

Ma, Yinfa; Yeung, Edward S.

1990-01-01

Described is a simple and interesting chromatography experiment using three different fluorescence detection principles for the determination of caffeine, saccharin and sodium benzoate in beverages. Experimental procedures and an analysis and discussion of the results are included. (CW)

Nanoscale pillar arrays for separations

DOE PAGES

Kirchner, Teresa; Strickhouser, Rachel; Hatab, Nahla; ...

2015-04-01

The work presented herein evaluates silicon nano-pillar arrays for use in planar chromatography. Electron beam lithography and metal thermal dewetting protocols were used to create nano-thin layer chromatography platforms. With these fabrication methods we are able to reduce the size of the characteristic features in a separation medium below that used in ultra-thin layer chromatography; i.e. pillar heights are 1-2μm and pillar diameters are typically in the 200- 400nm range. In addition to the intrinsic nanoscale aspects of the systems, it is shown they can be further functionalized with nanoporous layers and traditional stationary phases for chromatography; hence exhibit broad-rangingmore » lab-on-a-chip and point-of-care potential. Because of an inherent high permeability and very small effective mass transfer distance between pillars, chromatographic efficiency can be very high but is enhanced herein by stacking during development and focusing while drying, yielding plate heights in the nm range separated band volumes. Practical separations of fluorescent dyes, fluorescently derivatized amines, and anti-tumor drugs are illustrated.« less

Wake Management Strategies for Reduction of Turbomachinery Fan Noise

NASA Technical Reports Server (NTRS)

Waitz, Ian A.

1998-01-01

The primary objective of our work was to evaluate and test several wake management schemes for the reduction of turbomachinery fan noise. Throughout the course of this work we relied on several tools. These include 1) Two-dimensional steady boundary-layer and wake analyses using MISES (a thin-shear layer Navier-Stokes code), 2) Two-dimensional unsteady wake-stator interaction simulations using UNSFLO, 3) Three-dimensional, steady Navier-Stokes rotor simulations using NEWT, 4) Internal blade passage design using quasi-one-dimensional passage flow models developed at MIT, 5) Acoustic modeling using LINSUB, 6) Acoustic modeling using VO72, 7) Experiments in a low-speed cascade wind-tunnel, and 8) ADP fan rig tests in the MIT Blowdown Compressor.

Directional interlayer spin-valley transfer in two-dimensional heterostructures

DOE PAGES

Schaibley, John R.; Rivera, Pasqual; Yu, Hongyi; ...

2016-12-14

Van der Waals heterostructures formed by two different monolayer semiconductors have emerged as a promising platform for new optoelectronic and spin/valleytronic applications. In addition to its atomically thin nature, a two-dimensional semiconductor heterostructure is distinct from its three-dimensional counterparts due to the unique coupled spin-valley physics of its constituent monolayers. In this paper, we report the direct observation that an optically generated spin-valley polarization in one monolayer can be transferred between layers of a two-dimensional MoSe 2–WSe 2 heterostructure. Using non-degenerate optical circular dichroism spectroscopy, we show that charge transfer between two monolayers conserves spin-valley polarization and is only weaklymore » dependent on the twist angle between layers. Finally, our work points to a new spin-valley pumping scheme in nanoscale devices, provides a fundamental understanding of spin-valley transfer across the two-dimensional interface, and shows the potential use of two-dimensional semiconductors as a spin-valley generator in two-dimensional spin/valleytronic devices for storing and processing information.« less

Separation and purification of astaxanthin from Phaffia rhodozyma by preparative high-speed counter-current chromatography.

PubMed

Du, Xiping; Dong, Congcong; Wang, Kai; Jiang, Zedong; Chen, Yanhong; Yang, Yuanfan; Chen, Feng; Ni, Hui

2016-09-01

An effective high-speed counter-current chromatography (HSCCC) method was established for the preparative isolation and purification of astaxanthin from Phaffia rhodozyma. With a two-phase solvent system composed of n-hexane-acetone-ethanol-water (1:1:1:1, v/v/v/v), 100mg crude extract of P. rhodozyma was separated to yield 20.6mg of astaxanthin at 92.0% purity. By further one step silica gel column chromatography, the purity reached 99.0%. The chemical structure of astaxanthin was confirmed by thin layer chromatography (TLC), UV spectroscopy scanning, high performance liquid chromatography with a ZORBAX SB-C18 column and a Waters Nova-pak C18 column, and ESI/MS/MS. Copyright © 2016 Elsevier B.V. All rights reserved.

An Improved Method for the Extraction and Thin-Layer Chromatography of Chlorophyll A and B from Spinach

ERIC Educational Resources Information Center

Quach, Hao T.; Steeper, Robert L.; Griffin, William G.

2004-01-01

A simple and fast method, which resolves chlorophyll a and b from spinach leaves on analytical plates while minimizing the appearance of chlorophyll degradation products is shown. An improved mobile phase for the Thin-layer chromatographic analysis of spinach extract that allows for the complete resolution of the common plant pigments found in…

Ion Exchange and Thin Layer Chromatographic Separation and Identification of Amino Acids in a Mixture: An Experiment for General Chemistry and Biotechnology Laboratories

ERIC Educational Resources Information Center

Brunauer, Linda S.; Caslavka, Katelyn E.; Van Groningen, Karinne

2014-01-01

A multiday laboratory exercise is described that is suitable for first-year undergraduate chemistry, biochemistry, or biotechnology students. Students gain experience in performing chromatographic separations of biomolecules, in both a column and thin layer chromatography (TLC) format. Students chromatographically separate amino acids (AA) in an…

Standardisation of Gymnema sylvestre R.Br. by high-performance thin-layer chromatography: an improved method.

PubMed

Raju, Valivarthi S R; Kannababu, S; Subbaraju, Gottumukkala V

2006-01-01

An improved high-performance thin-layer chromatographic (HPTLC) method for the standardisation of Gymnema sylvestre is reported. The method involves the initial hydrolysis of gymnemic acids, the active ingredients, to a common aglycone followed by the quantitative estimation of gymnemagenin. The present method rectifies an error found in an HPTLC method reported recently.

Two-dimensional ferroelectric topological insulators in functionalized atomically thin bismuth layers

NASA Astrophysics Data System (ADS)

Kou, Liangzhi; Fu, Huixia; Ma, Yandong; Yan, Binghai; Liao, Ting; Du, Aijun; Chen, Changfeng

2018-02-01

We introduce a class of two-dimensional (2D) materials that possess coexisting ferroelectric and topologically insulating orders. Such ferroelectric topological insulators (FETIs) occur in noncentrosymmetric atomic layer structures with strong spin-orbit coupling (SOC). We showcase a prototype 2D FETI in an atomically thin bismuth layer functionalized by C H2OH , which exhibits a large ferroelectric polarization that is switchable by a ligand molecule rotation mechanism and a strong SOC that drives a band inversion leading to the topologically insulating state. An external electric field that switches the ferroelectric polarization also tunes the spin texture in the underlying atomic lattice. Moreover, the functionalized bismuth layer exhibits an additional quantum order driven by the valley splitting at the K and K' points in the Brillouin zone stemming from the symmetry breaking and strong SOC in the system, resulting in a remarkable state of matter with the simultaneous presence of the quantum spin Hall and quantum valley Hall effect. These phenomena are predicted to exist in other similarly constructed 2D FETIs, thereby offering a unique quantum material platform for discovering novel physics and exploring innovative applications.

Scanning tunneling spectroscopy study of the proximity effect in a disordered two-dimensional metal.

PubMed

Serrier-Garcia, L; Cuevas, J C; Cren, T; Brun, C; Cherkez, V; Debontridder, F; Fokin, D; Bergeret, F S; Roditchev, D

2013-04-12

The proximity effect between a superconductor and a highly diffusive two-dimensional metal is revealed in a scanning tunneling spectroscopy experiment. The in situ elaborated samples consist of superconducting single crystalline Pb islands interconnected by a nonsuperconducting atomically thin disordered Pb wetting layer. In the vicinity of each superconducting island the wetting layer acquires specific tunneling characteristics which reflect the interplay between the proximity-induced superconductivity and the inherent electron correlations of this ultimate diffusive two-dimensional metal. The observed spatial evolution of the tunneling spectra is accounted for theoretically by combining the Usadel equations with the theory of dynamical Coulomb blockade; the relevant length and energy scales are extracted and found in agreement with available experimental data.

Three-dimensional thin film for lithium-ion batteries and supercapacitors.

PubMed

Yang, Yang; Peng, Zhiwei; Wang, Gunuk; Ruan, Gedeng; Fan, Xiujun; Li, Lei; Fei, Huilong; Hauge, Robert H; Tour, James M

2014-07-22

Three-dimensional heterogeneously nanostructured thin-film electrodes were fabricated by using Ta2O5 nanotubes as a framework to support carbon-onion-coated Fe2O3 nanoparticles along the surface of the nanotubes. Carbon onion layers function as microelectrodes to separate the two different metal oxides and form a nanoscale 3-D sandwich structure. In this way, space-charge layers were formed at the phase boundaries, and it provides additional energy storage by charge separation. These 3-D nanostructured thin films deliver both excellent Li-ion battery properties (stabilized at 800 mAh cm(–3)) and supercapacitor (up to 18.2 mF cm(–2)) performance owing to the synergistic effects of the heterogeneous structure. Thus, Li-ion batteries and supercapacitors are successfully assembled into the same electrode, which is promising for next generation hybrid energy storage and delivery devices.

Topological characters in Fe (Te1 -xSex ) thin films

NASA Astrophysics Data System (ADS)

Wu, Xianxin; Qin, Shengshan; Liang, Yi; Fan, Heng; Hu, Jiangping

2016-03-01

We investigate topological properties in the Fe(Te,Se) thin films. We find that the single layer FeTe1 -xSex has nontrivial Z2 topological invariance which originates from the parity exchange at the Γ point of the Brillouin zone. The nontrivial topology is mainly controlled by the Te(Se) height. Adjusting the anion height, which can be realized as the function of lattice constants and x in FeTe1 -xSex , can drive a topological phase transition. In a bulk material, the two-dimensional Z2 topology invariance is extended to a strong three-dimensional one. In a thin film, we predict that the topological invariance oscillates with the number of layers. The results can also be applied to iron pnictides. Our research establishes FeTe1 -xSex as a unique system to integrate high-Tc superconductivity and topological properties in a single electronic structure.

Laser generated guided waves and finite element modeling for the thickness gauging of thin layers.

PubMed

Lefevre, F; Jenot, F; Ouaftouh, M; Duquennoy, M; Ourak, M

2010-03-01

In this paper, nondestructive testing has been performed on a thin gold layer deposited on a 2 in. silicon wafer. Guided waves were generated and studied using a laser ultrasonic setup and a two-dimensional fast Fourier transform technique was employed to obtain the dispersion curves. A gold layer thickness of 1.33 microm has been determined with a +/-5% margin of error using the shape of the two first propagating modes, assuming for the substrate and the layer an uncertainty on the elastic parameters of +/-2.5%. A finite element model has been implemented to validate the data post-treatment and the experimental results. A good agreement between the numerical simulation, the analytical modeling and the experimentations has been observed. This method was considered suitable for thickness layer higher than 0.7 microm.

The cellular lipids of Romboutsia.

PubMed

Guan, Ziqiang; Chen, Lingli; Gerritsen, Jacoline; Smidt, Hauke; Goldfine, Howard

2016-09-01

We have examined the lipids of three isolates, Romboutsia lituseburensis, Romboutsia ilealis, and Romboutsia sp. strain FRIFI, of the newly described genus Romboutsia by two-dimensional thin-layer chromatography (2D-TLC) and by liquid chromatography/mass spectrometry (LC/MS). We have found three phospholipids, phosphatidylglycerol (PG), cardiolipin and phosphatidic acid in all three species. A fourth phospholipid, lysyl-PG, was found in R. lituseburensis and strain FRIFI. Polyprenyl-phosphates were identified in the lipid extracts of all three species. Three glycolipids, mono-, di- and tri-hexosyldiacylglycerol, were common to all three species. An additional glycolipid, tetrahexosyl-diacylglycerol was identified in strain FRIFI. Acylated trihexosyldiacylglycerol and acyl-tetrahexosydiacylglycerol were also found in R. ilealis and strain FRIFI. Remarkably, no alk-1-enyl ether lipids (plasmalogens) were present in Romboutsia as distinct from bacteria of the related genus Clostridium in which these ether lipids are common. We have compared the lipidome of Romboutsia with that recently described for Clostridium difficile, which has plasmalogens, no lysyl-PG, and no tetrahexosyl-diacylglycerol. According to 16S rRNA gene sequencing, Romboutsia spp. and C. difficile are closely related (>95% sequence identity). Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of Four Major Saponins in Skin and Endosperm of Seeds of Horse Chestnut (Aesculus Hippocastanum L.) Using High Performance Liquid Chromatography with Positive Confirmation by Thin Layer Chromatography.

PubMed

Abudayeh, Zead Helmi Mahmoud; Al Azzam, Khaldun Mohammad; Naddaf, Ahmad; Karpiuk, Uliana Vladimirovna; Kislichenko, Viktoria Sergeevna

2015-11-01

To separate and quantify four major saponins in the extracts of the skin and the endosperm of seeds of horse chestnut (Aesculus hippocastanum L.) using ultrasonic solvent extraction followed by a high performance liquid chromatography-diode array detector (HPLC-DAD) with positive confirmation by thin layer chromatography (TLC). The saponins: escin Ia, escin Ib, isoescin Ia and isoescin Ib were extracted using ultrasonic extraction method. The optimized extraction conditions were: 70% methanol as extraction solvent, 80 °C as extraction temperature, and the extraction time was achieved in 4 hours. The HPLC conditions used: Zorbax SB-ODS-(150 mm × 2.1 mm, 3 μm) column, acetonitrile and 0.10% phosphoric acid solution (39:61 v/v) as mobile phase, flow rate was 0.5 mL min(-1) at 210 nm and 230 nm detection. The injection volume was 10 μL, and the separation was carried out isothermally at 30 °C in a heated chamber. The results indicated that the developed HPLC method is simple, sensitive and reliable. Moreover, the content of escins in seeds decreased by more than 30% in endosperm and by more than 40% in skin upon storage for two years. This assay can be readily utilized as a quality control method for horse chestnut and other related medicinal plants.

Computer simulation of ion beam analysis of laterally inhomogeneous materials

NASA Astrophysics Data System (ADS)

Mayer, M.

2016-03-01

The program STRUCTNRA for the simulation of ion beam analysis charged particle spectra from arbitrary two-dimensional distributions of materials is described. The code is validated by comparison to experimental backscattering data from a silicon grating on tantalum at different orientations and incident angles. Simulated spectra for several types of rough thin layers and a chessboard-like arrangement of materials as example for a multi-phase agglomerate material are presented. Ambiguities between back-scattering spectra from two-dimensional and one-dimensional sample structures are discussed.

Use of Pseudophase TLC in Teaching Laboratories.

ERIC Educational Resources Information Center

Armstrong, Daniel W.; And Others

1984-01-01

Suggests that pseudophase liquid chromatography, which uses aqueous surfactant solutions instead of organic solvents for the mobile phase, can be substituted for thin-layer chromatography in the introductory organic course. Outlines the method as it applies to common separations in the laboratory. (JN)

The determination and quantification of photosynthetic pigments by reverse phase high-performance liquid chromatography, thin-layer chromatography, and spectrophotometry.

PubMed

Pocock, Tessa; Król, Marianna; Huner, Norman P A

2004-01-01

Chorophylls and carotenoids are functionally important pigment molecules in photosynthetic organisms. Methods for the determination of chlorophylls a and b, beta-carotene, neoxanthin, and the pigments that are involved in photoprotective cycles such as the xanthophylls are discussed. These cycles involve the reversible de-epoxidation of violaxanthin into antheraxanthin and zeaxanthin, as well as the reversible de-epoxidation of lutein-5,6-epoxide into lutein. This chapter describes pigment extraction procedures from higher plants and green algae. Methods for the determination and quantification using high-performance liquid chromatograpy (HPLC) are described as well as methods for the separation and purification of pigments for use as standards using thin-layer chromatography (TLC). In addition, several spectrophotometric methods for the quantification of chlorophylls a and b are described.

Two-dimensional electron gas in tricolor oxide interfaces

NASA Astrophysics Data System (ADS)

Cao, Yanwei; Kareev, Michael; Liu, Xiaoran; Middey, Srimanta; Meyers, Derek; Tchakhalian, Jak

2014-03-01

Understanding and manipulating spin of electrons in nanometer scale is the main challenge of current spintronics, recent emergent two-dimensional electron gas in oxide interface provides a good platform to investigate the spin behavior by covering an insulating magnetic oxide layer. In this work, take titanates as an example, ultra-thin tricolor (tri-compound) titanate superlattices ([LaTiO3/SrTiO3/YTiO3]) were grown in a layer-by-layer way by pulsed laser deposition. High sample quality and their electronic structures were characterized by the combination of in-situ photoelectron and ex-situ structure and surface morphology probes. Temperature-dependent sheet resistance indicates the presence of metallic interfaces in both [LaTiO3 /SrTiO3 ] and all the tricolor structures, whereas a [YTiO3 /SrTiO3] bi-layer shows insulating behavior. The tricolor titanate superlattices provide an opportunity to induce tunable spin-polarization into the two-dimensional electron gas (2DEG) with Mott carriers.

One-Dimensional Model for the Ultrasonic Response of Resin-Filled Gaps in Automated Tape Layup Composites

NASA Technical Reports Server (NTRS)

Johnston, Patrick H.; Juarez, Peter D.

2017-01-01

Automated tow placement has become a widely used fabrication technique, especially for large aerospace structures. Robotic heads lay down strips (tows) of preimpregnated fiber along programmed paths. The intention is to lay adjacent tows abutted to one another, but sometimes a gap is left between a tow and the previously-placed tow. If a tow gap exists, it fills with resin during cure, forming a fiber-free volume. In immersion ultrasonic pulse-echo measurements of a cured laminate, the gap can be observed to produce a noticeable echo, without significantly attenuating the back-wall reflection of the laminate. To understand this behavior, we considered a one dimensional model of the composite laminate, with a thin layer having the ultrasonic sound speed and density of neat resin, sandwiched between two layers of material having the sound speed and density of fiber-reinforced composite and surrounded on both sides by water. Neglecting attenuation, we considered the transmission and reflection coefficients of each interface, as well as that of the thin resin layer. Using the initial water/composite reflection as a reference, we computed the relative magnitude of the back surface/water reflection in the presence and in the absence of a resin-only layer, as well as the relative magnitude of the reflection arising from a thin resin layer in composite. While the one-dimensional model did not fully match the measurements, it did qualitatively explain the observed behavior.

A validated high performance thin layer chromatography method for determination of yohimbine hydrochloride in pharmaceutical preparations

PubMed Central

Badr, Jihan M.

2013-01-01

Background: Yohimbine is an indole alkaloid used as a promising therapy for erectile dysfunction. A number of methods were reported for the analysis of yohimbine in the bark or in pharmaceutical preparations. Materials and Method: In the present work, a simple and sensitive high performance thin layer chromatographic method is developed for determination of yohimbine (occurring as yohimbine hydrochloride) in pharmaceutical preparations and validated according to International Conference of Harmonization (ICH) guidelines. The method employed thin layer chromatography aluminum sheets precoated with silica gel as the stationary phase and the mobile phase consisted of chloroform:methanol:ammonia (97:3:0.2), which gave compact bands of yohimbine hydrochloride. Results: Linear regression data for the calibration curves of standard yohimbine hydrochloride showed a good linear relationship over a concentration range of 80–1000 ng/spot with respect to the area and correlation coefficient (R2) was 0.9965. The method was evaluated regarding accuracy, precision, selectivity, and robustness. Limits of detection and quantitation were recorded as 5 and 40 ng/spot, respectively. The proposed method efficiently separated yohimbine hydrochloride from other components even in complex mixture containing powdered plants. The amount of yohimbine hydrochloride ranged from 2.3 to 5.2 mg/tablet or capsule in preparations containing the pure alkaloid, while it varied from zero (0) to 1.5–1.8 mg/capsule in dietary supplements containing powdered yohimbe bark. Conclusion: We concluded that this method employing high performance thin layer chromatography (HPTLC) in quantitative determination of yohimbine hydrochloride in pharmaceutical preparations is efficient, simple, accurate, and validated. PMID:23661986

A validated high performance thin layer chromatography method for determination of yohimbine hydrochloride in pharmaceutical preparations.

PubMed

Badr, Jihan M

2013-01-01

Yohimbine is an indole alkaloid used as a promising therapy for erectile dysfunction. A number of methods were reported for the analysis of yohimbine in the bark or in pharmaceutical preparations. In the present work, a simple and sensitive high performance thin layer chromatographic method is developed for determination of yohimbine (occurring as yohimbine hydrochloride) in pharmaceutical preparations and validated according to International Conference of Harmonization (ICH) guidelines. The method employed thin layer chromatography aluminum sheets precoated with silica gel as the stationary phase and the mobile phase consisted of chloroform:methanol:ammonia (97:3:0.2), which gave compact bands of yohimbine hydrochloride. Linear regression data for the calibration curves of standard yohimbine hydrochloride showed a good linear relationship over a concentration range of 80-1000 ng/spot with respect to the area and correlation coefficient (R(2)) was 0.9965. The method was evaluated regarding accuracy, precision, selectivity, and robustness. Limits of detection and quantitation were recorded as 5 and 40 ng/spot, respectively. The proposed method efficiently separated yohimbine hydrochloride from other components even in complex mixture containing powdered plants. The amount of yohimbine hydrochloride ranged from 2.3 to 5.2 mg/tablet or capsule in preparations containing the pure alkaloid, while it varied from zero (0) to 1.5-1.8 mg/capsule in dietary supplements containing powdered yohimbe bark. We concluded that this method employing high performance thin layer chromatography (HPTLC) in quantitative determination of yohimbine hydrochloride in pharmaceutical preparations is efficient, simple, accurate, and validated.

Identification of arsenobetaine in sole, lemon sole, flounder, dab, crab and shrimps by field desorption and fast atom bombardment mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luten, J.B.; Riekwel-Booy, G.; Greef, M.C.

1983-01-01

Organo-arsenic has been isolated from sole, lemon sole, flounder, dab, crab and shrimps by extraction or ion-exchange in combination with thin-layer chromatography. An alkaline digestion of the samples, followed by a reduction with sodiumborohydride leads to the formation of trimethylarsine. Field desorption mass spectrometry (FDMS) can be used to identify arsenobetaine in the isolates. Sufficient purification by thin-layer chromatography is found to be a prerequisite for the detection of a protonated molecular ion of arsenobetaine. If this situation is not met acid enchanced FDMS or Fast Atom Bombardment mass spectrometry in high resolution can be used successfully.

Congenital erythropoietic porphyria in an African hedgehog (Atelerix albiventris).

PubMed

Wolff, Carlos; Corradini, Paulina; Cortés, Galaxia

2005-06-01

A 6-mo-old, male African hedgehog (Atelerix albiventris) presented with a history of pink urine and demonstrating pink-colored teeth and mild hepatomegaly on examination. Urinalysis revealed no physical, chemical, or cellular abnormalities other than a pink color and fluorescence under ultraviolet light (UV). Also under UV, intense fluorescence of teeth, feet, and spines was noted. Porphyria was suspected. Spectrophotometric evaluation of urine showed extremely elevated levels of copro- and uroporphyrins. Analysis of the urine by thin-layer chromatography showed an abnormal pattern of excreted porphyrin intermediates. Urine high-performance thin-layer chromatography showed that excreted porphyrins were 90-95% of the type-I isomeric form, suggestive of congenital erythropoietic porphyria.

Chemical constituents of Phragmanthera austroarabica A. G. Mill and J. A. Nyberg with potent antioxidant activity

PubMed Central

Badr, Jihan M.

2015-01-01

Background: Phragmanthera austroarabica A.G. Mill. and J. A. Nyberg is a semi parasitic plant belonging to family Loranthaceae. It was collected from Saudi Arabia. It is widely used in folk medicine among the kingdom in treatment of various diseases including diabetes mellitus. Objective: The total alcoholic extract of P. austroarabica collected from Saudi Arabia was investigated for the chemical structure and prominent biological activity of the main constituents. Materials and Methods: Isolation of the active constituents was performed using different chromatographic techniques including column chromatography packed with silica or sephadex and preparative thin layer chromatography. The structures of the isolated compounds were established based on different spectroscopic data as mass spectrum, one-dimensional and two-dimensional nuclear magnetic resonance (correlation spectroscopy, heteronuclear single quantum coherence, and heteronuclear multiple-bond correlation). Results: Phytochemical investigation of the plant resulted in isolation of 12 compounds. The isolated compounds were identified as chrysophanic acid, emodin, chrysophanic acid-8-O-glucoside, emodin-8-O-glucoside, pectolinarigenin, quercetin, dillenetin-3-O-glucoside, catechin, catechin-4’-O-gallate, methyl gallate, lupeol and ursolic acid. All the isolated phenolic compounds revealed significant free radical scavenging activities when tested using 2,2-diphenyl-1-picrylhydrazyl reagent. Conclusion: The antioxidant activities of the isolated compounds can justify the use of P. austroarabica in traditional medicine for treatment of diabetes and verify its possible application as an antihyperglycemic drug. PMID:26692747

[Advance in study on zearalenone's toxicity and determination].

PubMed

He, Qing-Hua; Xu, Yang

2005-07-01

The article is intended to introduce the zearalenone's toxicity, determination methods and prevention. Zearalenone is one of the most widely distributed mycotoxins produces by Fusarium Species, it is harm to animals and human. And it can induce human liver cancer,carcinoma of tesis esophagus cancer. Now we use high-performance liquid chromatography, gas chromatography, thin layer chromatography, non-toxicity determinations to detect it.

Feasibility of correlating separation of ternary mixtures of neutral analytes via thin layer chromatography with supercritical fluid chromatography in support of green flash separations.

PubMed

Ashraf-Khorassani, M; Yan, Q; Akin, A; Riley, F; Aurigemma, C; Taylor, L T

2015-10-30

Method development for normal phase flash liquid chromatography traditionally employs preliminary screening using thin layer chromatography (TLC) with conventional solvents on bare silica. Extension to green flash chromatography via correlation of TLC migration results, with conventional polar/nonpolar liquid mixtures, and packed column supercritical fluid chromatography (SFC) retention times, via gradient elution on bare silica with a suite of carbon dioxide mobile phase modifiers, is reported. Feasibility of TLC/SFC correlation is individually described for eight ternary mixtures for a total of 24 neutral analytes. The experimental criteria for TLC/SFC correlation was assumed to be as follows: SFC/UV/MS retention (tR) increases among each of the three resolved mixture components; while, TLC migration (Rf) decreases among the same resolved mixture components. Successful correlation of TLC to SFC was observed for most of the polar organic solvents tested, with the best results observed via SFC on bare silica with methanol as the CO2 modifier and TLC on bare silica with a methanol/dichloromethane mixture. Copyright © 2015 Elsevier B.V. All rights reserved.

Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids.

PubMed

Yan, Yuanyuan; Wang, Xingguo; Liu, Yijun; Xiang, Jingying; Wang, Xiaosan; Zhang, Huijun; Yao, Yunping; Liu, Ruijie; Zou, Xiaoqiang; Huang, Jianhua; Jin, Qingzhe

2015-12-18

A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil. Copyright © 2015 Elsevier B.V. All rights reserved.

Preliminary Analysis of Lipids and Fatty Acids of Green Bacteria and Chloroflexus aurantiacus

PubMed Central

Kenyon, Christine N.; Gray, Alane M.

1974-01-01

The complex lipids and fatty acids of the seven type species of green bacteria and three strains of Chloroflexus aurantiacus were analyzed. The green bacteria contained lipids that behaved as cardiolipin and phosphatidylglycerol on thin-layer chromatography. They did not contain phosphatidylethanolamine or phosphatidylserine. Similarly, Chloroflexus contained lipids that behaved as phosphatidylglycerol and phosphatidylinositol on thin-layer chromatography and did not contain phosphatidylethanolamine or phosphatidylserine. The green bacteria contained glycolipids I and II of Constantopoulos and Bloch (monogalactosyldiglyceride and a galactose- and rhamnose-containing diglyceride). Chloroflexus exhibited galactose-containing glycolipids that behaved identically with the mono- and digalactosyldiglycerides of spinach on thin-layer chromatography, and each contained galactose as well as at least one other sugar. The fatty acids of both groups of bacteria consisted entirely of saturated and monounsaturated fatty acids. In the green bacteria, myristic, palmitic, and hexadecenoic acids predominated. In Chloroflexus, palmitic, stearic, and oleic acids predominated. The positions of the double bonds in the monounsaturated fatty acids of Chloroflexus indicated synthesis by the anaerobic pathway. The lipid analyses suggest a close relationship between the green bacteria and Chloroflexus and further suggest that these groups of photosynthetic bacteria are more closely related to the blue-green algae than are the purple bacteria. Images PMID:4421249

Analysis of chemical components of shiitake polysaccharides and its anti-fatigue effect under vibration.

PubMed

Li, Xiaoling; Zhang, Hongbo; Xu, Haibo

2009-11-01

The shiitake polysaccharides were obtained from shiitake mushroom. Four fractions were isolated from the polysaccharides using a Sephadex G-100 gel column. Chemical components of the two main fractions were determined by thin layer chromatography (TLC), and high performance liquid chromatography (HPLC). F1 was composed of rhamnose, glucose, and mannose. F3 was composed of xylose, mannose, arabinose and galactose. The obtained results still showed that administration of shiitake polysaccharides could improve muscle's comfortability of animals under a long period of vibration. The above findings might be applicable to studies of vibration ergonomics.

Thouless length and valley degeneracy factor of ZnMnO thin films with anisotropic, highly conductive surface layers

NASA Astrophysics Data System (ADS)

Vegesna, Sahitya V.; Bürger, Danilo; Patra, Rajkumar; Abendroth, Barbara; Skorupa, Ilona; Schmidt, Oliver G.; Schmidt, Heidemarie

2017-06-01

Isothermal magnetoresistance (MR) of n-type conducting Zn1-xMnxO thin films on a sapphire substrate with a Mn content of 5 at. % has been studied in in-plane and out-of-plane magnetic fields up to 6 T in the temperature range of 5 K to 300 K. During pulsed laser deposition of the ZnMnO thin films, we controlled the thickness and roughness of a highly conductive ZnMnO surface layer. The measured MR has been modeled with constant s-d exchange (0.2 eV in ZnMnO) and electron spin (S = 5/2 for Mn2+) for samples with a single two dimensional (2D) ZnMnO layer, a single three dimensional (3D) ZnMnO layer, or a 2D and 3D (2D + 3D) ZnMnO layer in parallel. The temperature dependence of modeled Thouless length LTh (LTh ˜ T-0.5) is in good agreement with the theory [Andrearczyk et al., Phys. Rev. B 72, 121309(R) (2005)]. The superimposed positive and negative MR model for ZnCoO thin films [Xu et al., Phys. Rev. B 76, 134417 (2007)] has been extended in order to account for the increase in the density of states close to the Fermi level of n-ZnMnO due to substitutional Mn2+ ions and their effect on the negative MR in ZnMnO.

Development and validation of High-performance Thin-layer Chromatography Method for Simultaneous Determination of Polyphenolic Compounds in Medicinal Plants.

PubMed

Jayachandran Nair, C V; Ahamad, Sayeed; Khan, Washim; Anjum, Varisha; Mathur, Rajani

2017-12-01

Quantitative standardization of plant-based products is challenging albeit essential to maintain their quality. This study aims to develop and validate high-performance thin-layer chromatography (HPTLC) method for the simultaneous determination of rutin (Ru), quercetin (Qu), and gallic acid (Ga) from Psidium guajava Linn. (PG) and Aegle marmelos (L.) Correa. (AM) and correlate with antioxidant activity. The stock solution (1 mg/mL) of standard Ru, Qu, and Ga in methanol: Water (1:1) was serially diluted and spotted (5 μL) on slica gel 60 F 254 thin-layer chromatography plates. Toluene: Ethyl acetate: Formic acid: Methanol (3:4:0.8:0.7, v/v/v) was selected as mobile phase for analysis at 254 nm. Hydroalcoholic (1:1) extracts of leaves of PG and AM were fractionated and similarly analyzed. Antioxidant activity was also determined using 2, 2-diphenyl-1-picrylhydrazyl assay. The developed method was robust and resolved Ru, Qu, and Ga at R f 0.08 ± 0.02, 0.76 ± 0.01, and 0.63 ± 0.02, respectively. The intra-day, interday precision, and interanalyst were <2% relative standard deviation. The limit of detection and limit of quantification for Ru, Qu, and Ga were 4.51, 4.2, 5.27, and 13.67, 12.73, 15.98 ng/spot, respectively. Antioxidant activity (Log 50% inhibition) of PG and AM was 4.947 ± 0.322 and 6.498 ± 0.295, respectively. The developed HPTLC method was rapid, accurate, precise, reproducible, and specific for the simultaneous estimation of Ru, Qu, and Ga. HPTLC method for simultaneous determination and quantification of Rutin, Quercetin and Gallic acid, is reported for quality control of herbal drugs. Abbreviations Used: A: Aqueous fraction; AM: Aegle marmelos L. Correa; B: Butanol fraction; C: Chloroform fraction; EA: Ethyl acetate fraction; Ga: Gallic acid; H: Hexane fraction; HA: Hydroalcoholic extract; HPTLC: High-performance thin-layer chromatography; PG: Psidium guajava ; Qu: Quercetin; Ru: Rutin.

Black phosphorus-based one-dimensional photonic crystals and microcavities.

PubMed

Kriegel, Ilka; Toffanin, Stefano; Scotognella, Francesco

2016-11-10

The latest achievements in the fabrication of thin layers of black phosphorus (BP), toward the technological breakthrough of a phosphorene atomically thin layer, are paving the way for their use in electronics, optics, and optoelectronics. In this work, we have simulated the optical properties of one-dimensional photonic structures, i.e., photonic crystals and microcavities, in which few-layer BP is one of the components. The insertion of the 5-nm black phosphorous layers leads to a photonic band gap in the photonic crystals and a cavity mode in the microcavity that is interesting for light manipulation and emission enhancement.

Synthesis and Degradation of Schiff Bases Containing Heterocyclic Pharmacophore

PubMed Central

Ledeţi, Ionuţ; Alexa, Anda; Bercean, Vasile; Vlase, Gabriela; Vlase, Titus; Şuta, Lenuţa-Maria; Fuliaş, Adriana

2015-01-01

This paper reports on the synthesis and characterization of two Schiff bases bearing 1,2,4-triazolic moieties, namely 4H-4-(2-hydroxy-benzylidene-amino)-5-benzyl-3-mercapto-1,2,4-triazole and 4H-4-(4-nitro-benzylidene-amino)-5-benzyl-3-mercapto-1,2,4-triazole using thin layer chromatography, melting interval, elemental analysis, spectroscopy and thermal stability studies. PMID:25590299

Laminated beams of isotropic or orthotropic materials subjected to temperature change

Treesearch

Shun Cheng; T. Gerhardt

1980-01-01

This paper considers laminated beams with layers of different isotropic or orthotropic materials fastened together by thin adhesives. The stresses that result from subjecting each component layer of the beam to different temperature or moisture stimuli which may also vary along the length of the beam, are calculated. Two-dimensional elasticity theory is used so that a...

Atom-Thin SnS2-xSex with Adjustable Compositions by Direct Liquid Exfoliation from Single Crystals.

PubMed

Yang, Zhanhai; Liang, Hui; Wang, Xusheng; Ma, Xinlei; Zhang, Tao; Yang, Yanlian; Xie, Liming; Chen, Dong; Long, Yujia; Chen, Jitao; Chang, Yunjie; Yan, Chunhua; Zhang, Xinxiang; Zhang, Xueji; Ge, Binghui; Ren, Zhian; Xue, Mianqi; Chen, Genfu

2016-01-26

Two-dimensional (2D) chalcogenide materials are fundamentally and technologically fascinating for their suitable band gap energy and carrier type relevant to their adjustable composition, structure, and dimensionality. Here, we demonstrate the exfoliation of single-crystal SnS2-xSex (SSS) with S/Se vacancies into an atom-thin layer by simple sonication in ethanol without additive. The introduction of vacancies at the S/Se site, the conflicting atomic radius of sulfur in selenium layers, and easy incorporation with an ethanol molecule lead to high ion accessibility; therefore, atom-thin SSS flakes can be effectively prepared by exfoliating the single crystal via sonication. The in situ pyrolysis of such materials can further adjust their compositions, representing tunable activation energy, band gap, and also tunable response to analytes of such materials. As the most basic and crucial step of the 2D material field, the successful synthesis of an uncontaminated and atom-thin sample will further push ahead the large-scale applications of 2D materials, including, but not limited to, electronics, sensing, catalysis, and energy storage fields.

The Catalyzed Substitution of CO by Isonitriles on (M(CO)6) (M=Cr, Mo, W).

ERIC Educational Resources Information Center

Albers, Michel O.; Singleton, Eric

1986-01-01

Describes experiments designed to: (1) familiarize students with inert atmosphere techniques; (2) teach monitoring reactions with thin-layer chromatography and infrared spectroscopy, isolation, and purification by crystallization and column chromatography; (3) estimate product purity spectroscopically; and (4) characterize reaction products by…

The impurity of radioiodinated triolein

PubMed Central

Kennedy, J. A.; Kinloch, J. D.

1964-01-01

Commercially supplied radioiodinated triolein has been shown by thin-layer chromatography and silicic acid column chromatography to contain impurities, consisting mainly of diglycerides and monoglycerides, but also a small amount of free fatty acid. The effect of these impurities on the radioiodinated triolein absorption test requires further investigation. Images PMID:14149942

Retention in porous layer pillar array planar separation platforms

DOE PAGES

Lincoln, Danielle R.; Lavrik, Nickolay V.; Kravchenko, Ivan I.; ...

2016-08-11

Here, this work presents the retention capabilities and surface area enhancement of highly ordered, high-aspect-ratio, open-platform, two-dimensional (2D) pillar arrays when coated with a thin layer of porous silicon oxide (PSO). Photolithographically prepared pillar arrays were coated with 50–250 nm of PSO via plasma-enhanced chemical vapor deposition and then functionalized with either octadecyltrichlorosilane or n-butyldimethylchlorosilane. Theoretical calculations indicate that a 50 nm layer of PSO increases the surface area of a pillar nearly 120-fold. Retention capabilities were tested by observing capillary-action-driven development under various conditions, as well as by running one-dimensional separations on varying thicknesses of PSO. Increasing the thicknessmore » of PSO on an array clearly resulted in greater retention of the analyte(s) in question in both experiments. In culmination, a two-dimensional separation of fluorescently derivatized amines was performed to further demonstrate the capabilities of these fabricated platforms.« less

Retention in porous layer pillar array planar separation platforms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lincoln, Danielle R.; Lavrik, Nickolay V.; Kravchenko, Ivan I.

Here, this work presents the retention capabilities and surface area enhancement of highly ordered, high-aspect-ratio, open-platform, two-dimensional (2D) pillar arrays when coated with a thin layer of porous silicon oxide (PSO). Photolithographically prepared pillar arrays were coated with 50–250 nm of PSO via plasma-enhanced chemical vapor deposition and then functionalized with either octadecyltrichlorosilane or n-butyldimethylchlorosilane. Theoretical calculations indicate that a 50 nm layer of PSO increases the surface area of a pillar nearly 120-fold. Retention capabilities were tested by observing capillary-action-driven development under various conditions, as well as by running one-dimensional separations on varying thicknesses of PSO. Increasing the thicknessmore » of PSO on an array clearly resulted in greater retention of the analyte(s) in question in both experiments. In culmination, a two-dimensional separation of fluorescently derivatized amines was performed to further demonstrate the capabilities of these fabricated platforms.« less

Atomically thin resonant tunnel diodes built from synthetic van der Waals heterostructures.

PubMed

Lin, Yu-Chuan; Ghosh, Ram Krishna; Addou, Rafik; Lu, Ning; Eichfeld, Sarah M; Zhu, Hui; Li, Ming-Yang; Peng, Xin; Kim, Moon J; Li, Lain-Jong; Wallace, Robert M; Datta, Suman; Robinson, Joshua A

2015-06-19

Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, atomically thin, multi-junction heterostructures by combining graphene with the monolayer transition-metal dichalcogenides: molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2). The realization of MoS2-WSe2-graphene and WSe2-MoS2-graphene heterostructures leads to resonant tunnelling in an atomically thin stack with spectrally narrow, room temperature negative differential resistance characteristics.

Determination of Four Major Saponins in Skin and Endosperm of Seeds of Horse Chestnut (Aesculus Hippocastanum L.) Using High Performance Liquid Chromatography with Positive Confirmation by Thin Layer Chromatography

PubMed Central

Abudayeh, Zead Helmi Mahmoud; Al Azzam, Khaldun Mohammad; Naddaf, Ahmad; Karpiuk, Uliana Vladimirovna; Kislichenko, Viktoria Sergeevna

2015-01-01

Purpose: To separate and quantify four major saponins in the extracts of the skin and the endosperm of seeds of horse chestnut (Aesculus hippocastanum L.) using ultrasonic solvent extraction followed by a high performance liquid chromatography-diode array detector (HPLC-DAD) with positive confirmation by thin layer chromatography (TLC). Methods: The saponins: escin Ia, escin Ib, isoescin Ia and isoescin Ib were extracted using ultrasonic extraction method. The optimized extraction conditions were: 70% methanol as extraction solvent, 80 °C as extraction temperature, and the extraction time was achieved in 4 hours. The HPLC conditions used: Zorbax SB-ODS-(150 mm × 2.1 mm, 3 μm) column, acetonitrile and 0.10% phosphoric acid solution (39:61 v/v) as mobile phase, flow rate was 0.5 mL min−1 at 210 nm and 230 nm detection. The injection volume was 10 μL, and the separation was carried out isothermally at 30 °C in a heated chamber. Results: The results indicated that the developed HPLC method is simple, sensitive and reliable. Moreover, the content of escins in seeds decreased by more than 30% in endosperm and by more than 40% in skin upon storage for two years. Conclusion: This assay can be readily utilized as a quality control method for horse chestnut and other related medicinal plants. PMID:26819933

Synthesis of the coenzymes adenosine diphosphate glucose, guanosine diphosphate glucose, and cytidine diphosphoethanolamine under primitive Earth conditions

NASA Technical Reports Server (NTRS)

Mar, A.; Oro, J.

1991-01-01

The nonenzymatic synthesis of the coenzymes adenosine diphosphate glucose (ADPG), guanosine diphosphate glucose (GDPG), and cytidine diphosphoethanolamine (CDP-ethanolamine) has been carried out under conditions considered to have been prevalent on the early Earth. The production of these compounds was performed by allowing simple precursor molecules to react under aqueous solutions, at moderate temperatures and short periods of time, with mediation by cyanamide or urea. These two condensing agents are considered to have been present in significant amounts on the primitive Earth and have been previously used in the nonenzymatic synthesis of several other important biochemical compounds. In our experiments, ADPG was obtained by heating glucose-1-phosphate (G1P) and ATP in the presence of cyanamide for 24 h at 70 degrees C. The reaction of G1P and GTP under the same conditions yielded GDPG. The cyanamide-mediated production of CDP-ethanolamine was carried out by reacting a mixture of ethanolamine phosphate and CTP for 24 h at 70 degrees C. The separation and identification of the reaction products was carried out by paper chromatography, thin-layer chromatography, high performance thin-layer chromatography, high performance liquid chromatography, both normal and reverse-phase, UV spectroscopy, enzymatic assays, and acid hydrolysis. Due to the mild conditions employed, and to the relative ease of these reactions, these studies offer a simple attractive system for the nonenzymatic synthesis of phosphorylated high-energy metabolic intermediates under conditions considered to have been prevalent on the ancient Earth.

Hand portable thin-layer chromatography system

DOEpatents

Haas, Jeffrey S.; Kelly, Fredrick R.; Bushman, John F.; Wiefel, Michael H.; Jensen, Wayne A.

2000-01-01

A hand portable, field-deployable thin-layer chromatography (TLC) unit and a hand portable, battery-operated unit for development, illumination, and data acquisition of the TLC plates contain many miniaturized features that permit a large number of samples to be processed efficiently. The TLC unit includes a solvent tank, a holder for TLC plates, and a variety of tool chambers for storing TLC plates, solvent, and pipettes. After processing in the TLC unit, a TLC plate is positioned in a collapsible illumination box, where the box and a CCD camera are optically aligned for optimal pixel resolution of the CCD images of the TLC plate. The TLC system includes an improved development chamber for chemical development of TLC plates that prevents solvent overflow.

Jasmonic acid-amino acid conjugation enzyme assays.

PubMed

Rowe, Martha L; Staswick, Paul E

2013-01-01

Jasmonic acid (JA) is activated for signaling by its conjugation to isoleucine (Ile) through an amide linkage. The Arabidopsis thaliana JASMONIC ACID RESISTANT1 (JAR1) enzyme carries out this Mg-ATP-dependent reaction in two steps, adenylation of the free carboxyl of JA, followed by condensation of the activated group to Ile. This chapter details the protocols used to detect and quantify the enzymatic activity obtained from a glutathione-S-transferase:JAR1 fusion protein produced in Escherichia coli, including an isotope exchange assay for the adenylation step and assays for the complete reaction that involve the high-performance liquid chromatography quantitation of adenosine monophosphate, a stoichiometric by-product of the reaction, and detection of the conjugation product by thin-layer chromatography or gas -chromatography/mass spectrometry.

Graphene enhanced surface plasmon resonance sensing based on Goos-Hänchen shift

NASA Astrophysics Data System (ADS)

Chen, Huifang; Tong, Jinguang; Wang, Yiqin; Jiang, Li

2018-03-01

A graphene/Ag structure is engineered as an enhanced platform for surface plasmon resonance sensing due to the high impermeability nature of graphene and the superior surface plasmon resonance performance of Ag. This structure is ultrasensitive to even tiny refractive index change of analytes based on Goos-Hänchen shift measurement compared to the traditional SPR sensor with bare Au film. The graphene/Ag configuration is consisted of five components, including BK7 glass slide, titanium thin film, silver thin film, two-dimensional graphene layers and biomolecular analyte layer. We have optimized the parameters of each layer and theoretically analyzed Goos-Hänchen shift of the plasmonic structure under surface plasmon resonance effect. The optimized graphene/Ag structure is monolayer graphene coated on Ag thin film with the thickness of 42 nm.

Mechanical properties of atomically thin boron nitride and the role of interlayer interactions

PubMed Central

Falin, Aleksey; Cai, Qiran; Santos, Elton J. G.; Scullion, Declan; Qian, Dong; Zhang, Rui; Yang, Zhi; Huang, Shaoming; Watanabe, Kenji; Taniguchi, Takashi; Barnett, Matthew R.; Chen, Ying; Ruoff, Rodney S.; Li, Lu Hua

2017-01-01

Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example, as mechanical reinforcements. PMID:28639613

Two dimensional simulation of patternable conducting polymer electrode based organic thin film transistor

NASA Astrophysics Data System (ADS)

Nair, Shiny; Kathiresan, M.; Mukundan, T.

2018-02-01

Device characteristics of organic thin film transistor (OTFT) fabricated with conducting polyaniline:polystyrene sulphonic acid (PANi-PSS) electrodes, patterned by the Parylene lift-off method are systematically analyzed by way of two dimensional numerical simulation. The device simulation was performed taking into account field-dependent mobility, low mobility layer at the electrode-semiconductor interface, trap distribution in pentacene film and trapped charge at the organic/insulator interface. The electrical characteristics of bottom contact thin film transistor with PANi-PSS electrodes and pentacene active material is superior to those with palladium electrodes due to a lower charge injection barrier. Contact resistance was extracted in both cases by the transfer line method (TLM). The extracted charge concentration and potential profile from the two dimensional numerical simulation was used to explain the observed electrical characteristics. The simulated device characteristics not only matched the experimental electrical characteristics, but also gave an insight on the charge injection, transport and trap properties of the OTFTs as a function of different electrode materials from the perspectives of transistor operation.

First-principles simulations of Graphene/Transition-metal-Dichalcogenides/Graphene Field-Effect Transistor

NASA Astrophysics Data System (ADS)

Li, Xiangguo; Wang, Yun-Peng; Zhang, X.-G.; Cheng, Hai-Ping

A prototype field-effect transistor (FET) with fascinating properties can be made by assembling graphene and two-dimensional insulating crystals into three-dimensional stacks with atomic layer precision. Transition metal dichalcogenides (TMDCs) such as WS2, MoS2 are good candidates for the atomically thin barrier between two layers of graphene in the vertical FET due to their sizable bandgaps. We investigate the electronic properties of the Graphene/TMDCs/Graphene sandwich structure using first-principles method. We find that the effective tunnel barrier height of the TMDC layers in contact with the graphene electrodes has a layer dependence and can be modulated by a gate voltage. Consequently a very high ON/OFF ratio can be achieved with appropriate number of TMDC layers and a suitable range of the gate voltage. The spin-orbit coupling in TMDC layers is also layer dependent but unaffected by the gate voltage. These properties can be important in future nanoelectronic device designs. DOE/BES-DE-FG02-02ER45995; NERSC.

Thin layer chromatography residue applicator sampler

DOEpatents

Nunes, Peter J [Danville, CA; Kelly, Fredrick R [Modesto, CA; Haas, Jeffrey S [San Ramon, CA; Andresen, Brian D [Livermore, CA

2007-07-24

A thin layer chromatograph residue applicator sampler. The residue applicator sampler provides for rapid analysis of samples containing high explosives, chemical warfare, and other analyses of interest under field conditions. This satisfied the need for a field-deployable, small, hand-held, all-in-one device for efficient sampling, sample dissolution, and sample application to an analytical technique. The residue applicator sampler includes a sampling sponge that is resistant to most chemicals and is fastened via a plastic handle in a hermetically sealed tube containing a known amount of solvent. Upon use, the wetted sponge is removed from the sealed tube and used as a swiping device across an environmental sample. The sponge is then replaced in the hermetically sealed tube where the sample remains contained and dissolved in the solvent. A small pipette tip is removably contained in the hermetically sealed tube. The sponge is removed and placed into the pipette tip where a squeezing-out of the dissolved sample from the sponge into the pipette tip results in a droplet captured in a vial for later instrumental analysis, or applied directly to a thin layer chromatography plate for immediate analysis.

Distribution and occurrence of polyisoprenoids in rambutan (Nephellium lappaceum)

NASA Astrophysics Data System (ADS)

Basyuni, M.; Wati, R.

2017-12-01

Rambutan (Nephellium lappaceum L., Sapindaceae) is a tropical plant having some biological activities. All parts of N. lappaceum either edible or non-edible part have shown some components beneficial to human health. Plant polyisoprenoids have been reported to have biological and pharmaceutical activities. Using a two-dimensional thin layer chromatography (2D-TLC), we analyzed composition and occurrence of polyisoprenoid alcohols (polyprenols and dolichols) in N. lappaceum consisting of leaves, roots, fruits, flowers, seeds, and rinds. The distribution of polyprenols and dolichols were detected and categorized into three types. Type-I, displaying a predominance of dolichols over polyprenols, was observed in the roots and flowers. Type-II, having the presence of both polyprenols and dolichols, was found in the fruits and seeds. Type-III, having the predominance of polyprenols over dolichols, was observed in the leaves. The diversity of polyisoprenoids in various tissues of N. lappaceum is the first report, suggested the chemotaxonomic importance of polyisoprenoids in this tropical fruit plant.

Separation of the Carotenoid Bixin from Annatto Seeds Using Thin-Layer and Column Chromatography

ERIC Educational Resources Information Center

McCullagh, James V.; Ramos, Nicholas

2008-01-01

In this experiment the carotenoid bixin is isolated from annatto ("Bixa orellana") seeds using column chromatography. The experiment has several key advantages over previous pigment separation experiments. First, unlike other experiments significant quantities of the carotenoid (typically 20 to 25 mg) can be isolated from small quantities of plant…

Purification of cardiolipin for surface pressure studies.

PubMed

Houle, A; Téchy, F; Aghion, J; Leblanc, R M

1982-03-01

Thin-layer chromatography and surface pressure-area isotherms of commercial bovine cardiolipins showed that the samples contained contaminants. They were purified by TLC and their purity was checked by chromatography and by their monolayer properties. The molecular area of cardiolipin and its purification yield depend upon the fatty acid composition, particularly the degree of unsaturation.

Purification and partial characterization of Flavotoxin A.

PubMed Central

Hu, W J; Zhang, G S; Chu, F S; Meng, H D; Meng, Z H

1984-01-01

A heat-resistant, low-molecular-weight toxin was isolated from semisolid potato dextrose agar medium after inoculation with Flavobacterium farinofermentans sp. nov., which was isolated from fermented corn meal that caused some outbreaks of food poisoning in China. The toxin was purified by solvent partition, Sephadex LH-20 gel filtration, and C-18 reversed-phase column chromatography. Thin-layer chromatography and high-pressure liquid chromatographic methods were developed for the identification and analysis of the toxin. The purified toxin exhibited a single spot in thin-layer chromatography and a single peak in high-pressure liquid chromatography and had adsorption maxima at 232 and 267 nm. Mass spectral analysis indicated a molecular weight of 169 with an experimental formula of C9H13O3. The 50% lethal dose of purified toxin in mice (oral) was less than 6.84 mg/kg, but greater than 0.68 mg/kg. Postmortem examination showed that the mice died of some type of neurological and cardiovascular system toxicity. The name Flavotoxin A is being assigned to the toxin. PMID:6391376

Pressurized planar electrochromatography, high-performance thin-layer chromatography and high-performance liquid chromatography--comparison of performance.

PubMed

Płocharz, Paweł; Klimek-Turek, Anna; Dzido, Tadeusz H

2010-07-16

Kinetic performance, measured by plate height, of High-Performance Thin-Layer Chromatography (HPTLC), High-Performance Liquid Chromatography (HPLC) and Pressurized Planar Electrochromatography (PPEC) was compared for the systems with adsorbent of the HPTLC RP18W plate from Merck as the stationary phase and the mobile phase composed of acetonitrile and buffer solution. The HPLC column was packed with the adsorbent, which was scrapped from the chromatographic plate mentioned. An additional HPLC column was also packed with adsorbent of 5 microm particle diameter, C18 type silica based (LiChrosorb RP-18 from Merck). The dependence of plate height of both HPLC and PPEC separating systems on flow velocity of the mobile phase and on migration distance of the mobile phase in TLC system was presented applying test solute (prednisolone succinate). The highest performance, amongst systems investigated, was obtained for the PPEC system. The separation efficiency of the systems investigated in the paper was additionally confirmed by the separation of test component mixture composed of six hormones. 2010 Elsevier B.V. All rights reserved.

Thin-layer chromatography with stationary phase gradient as a method for separation of water-soluble vitamins.

PubMed

Cimpoiu, Claudia; Hosu, Anamaria; Puscas, Anitta

2012-02-03

The group of hydrophilic vitamins play an important role in human health, and their lack or excess produces specific diseases. Therefore, the analysis of these compounds is indispensable for monitoring their content in pharmaceuticals and food in order to prevent some human diseases. TLC was successfully applied in the analysis of hydrophilic vitamins, but the most difficult problem in the simultaneous analysis of all these compounds is to find an optimum stationary phase-mobile phase system due to different chemical characteristics of analytes. Unfortunately structural analogues are difficult to separate in one chromatographic run, and this is the case in hydrophilic vitamins investigations. TLC gives the possibility to perform two-dimensional separations by using stationary phase gradient achieving the highest resolution by combining two systems with different selectivity. The goal of this work was to develop a method of analysis enabling separation of hydrophilic vitamins using TLC with adsorbent gradient. The developed method was used for identifying the water-soluble vitamins in alcoholic extracts of Hippophae rhamnoides and of Ribes nigrum. Copyright © 2011 Elsevier B.V. All rights reserved.

Cytotoxic activity of Cuphea aequipetala.

PubMed

Avila, Elisa Vega; Aguilar, Rafaela Tapia; Estrada, Manuel Jiménez; Ortega, Ma Luisa Villarreal; Ramos, Rubén Román

2004-01-01

Cuphea aequipetala (Lytraceae) is a perennial plant that has been used in Mexican traditional medicine to treat different types of tumors since prehispanic times. In the present work the cytotoxic potential of different fractions from acetone-water extract from the whole plant was investigated using a sulforhodamine B assay. Fractions were subjected to a bioscreening assay using several cell lines: HEp-2 (human larynx carcinoma), HCT-15 (human colon cancer) and DU-145 (human prostate carcinoma). Colchicine was used as positive control. Data are presented as the dose that inhibited 50.0% control growth (ED50). The cytotoxic activity is selective since the ED50 is different for the three cell lines employed. The highest activity was seen against the DU-145 cell line. "E" and PB1 fractions had the highest cytotoxic activities with ED50 values of 0.418 and 2.40 microg/ml respectively, on the DU-145 cell line. The "E" fraction was a yellow powder; it was methanol soluble and contained at least four separate components when separated by thin-layer chromatography. PB1 was a solid with metallic appearance; it was water soluble and its two dimensional chromatography showed 9 spots. These fractions have cytotoxic actives because their ED50 is less than 20 microg/ml and they will be further characterized.

Impact of comprehensive two-dimensional gas chromatography with mass spectrometry on food analysis.

PubMed

Tranchida, Peter Q; Purcaro, Giorgia; Maimone, Mariarosa; Mondello, Luigi

2016-01-01

Comprehensive two-dimensional gas chromatography with mass spectrometry has been on the separation-science scene for about 15 years. This three-dimensional method has made a great positive impact on various fields of research, and among these that related to food analysis is certainly at the forefront. The present critical review is based on the use of comprehensive two-dimensional gas chromatography with mass spectrometry in the untargeted (general qualitative profiling and fingerprinting) and targeted analysis of food volatiles; attention is focused not only on its potential in such applications, but also on how recent advances in comprehensive two-dimensional gas chromatography with mass spectrometry will potentially be important for food analysis. Additionally, emphasis is devoted to the many instances in which straightforward gas chromatography with mass spectrometry is a sufficiently-powerful analytical tool. Finally, possible future scenarios in the comprehensive two-dimensional gas chromatography with mass spectrometry food analysis field are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prediction of another semimetallic silicene allotrope with Dirac fermions

NASA Astrophysics Data System (ADS)

Wu, Haiping; Qian, Yan; Du, Zhengwei; Zhu, Renzhu; Kan, Erjun; Deng, Kaiming

2017-11-01

Materials with Dirac point are so amazing since the charge carriers are massless and have an effective speed of light. However, among the predicted two-dimensional silicon allotropes with Dirac point, no one has been directly proved by experiment. This fact motivates us to search for other two-dimensional silicon allotropes. As a result, another stable single atomic layer thin silicon allotrope is found with the help of CALYPSO code in this work. This silicene allotrope is composed of eight-membered rings linked by Si-Si bonds with buckling formation. The electronic calculation reveals that it behaves as a nodal line semimetal with the linear energy dispersion relation near the Fermi surface. Notably, the ab initio molecular dynamics simulations display that the original atomic configuration can be remained even at an extremely high temperature of 1000 K. Additionally, hydrogenation could induce a semimetal-semiconductor transition in this silicene allotrope. We hope this work can expand the family of single atomic layer thin silicon allotropes with special applications.

Spatiotemporal patterns in reaction-diffusion system and in a vibrated granular bed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swinney, H.L.; Lee, K.J.; McCormick, W.D.

Experiments on a quasi-two-dimensional reaction-diffusion system reveal transitions from a uniform state to stationary hexagonal, striped, and rhombic spatial patterns. For other reactor conditions lamellae and self-replicating spot patterns are observed. These patterns form in continuously fed thin gel reactors that can be maintained indefinitely in well-defined nonequilibrium states. Reaction-diffusion models with two chemical species yield patterns similar to those observed in the experiments. Pattern formation is also being examined in vertically oscillated thin granular layers (typically 3-30 particle diameters deep). For small acceleration amplitudes, a granular layer is flat, but above a well-defined critical acceleration amplitude, spatial patterns spontaneouslymore » form. Disordered time-dependent granular patterns are observed as well as regular patterns of squares, stripes, and hexagons. A one-dimensional model consisting of a completely inelastic ball colliding with a sinusoidally oscillating platform provides a semi-quantitative description of most of the observed bifurcations between the different spatiotemporal regimes.« less

From functional food to medicinal product: Systematic approach in analysis of polyphenolics from propolis and wine

PubMed Central

Medić-Šarić, Marica; Rastija, Vesna; Bojić, Mirza; Maleš, Željan

2009-01-01

In the last decade we have been working on standardization of propolis extract and determination of active constituents of wine those are rich in polyphenolics and have nutritional as well as therapeutic value. Here we are summarizing our results and providing overview on systematic approach how to analyse natural products rich in flavonoids and phenolic acids. Chromatographic methods (thin layer chromatography and high performance liquid chromatography) were used for identification, quantification, and characterization of individual flavonoid or phenolic acid. Total content of active constituents and antioxidant activity were determined by spectrophotometry. Pharmacokinetic parameters were determined by high performance liquid chromatography and using appropriate software. Quantitative structure-activity relationship study of antioxidant activity was conducted, as well as assessment of prolonged propolis supplementation on antioxidative status of organism. Thin layer chromatography-densitometry has been proven as quick and reliable method for standard analysis of propolis and wine; the best mobile phase being chloroform – methanol – formic acid (98–100%) in ratio 44 : 3.5 : 2.5 (v/v). Higher number of polyphenolics was determined by high performance liquid chromatography; 15 compared to 9 by thin layer chromatography. Interactions in situ with acetylsalicylic acid were detected with most of polyphenolics analysed. Plasma protein binding and blood-barrier penetration was greatest for flavone. The interactions with human serum albumin have been grater than 95% for all flavonoids analysed. The prolonged propolis consumption increased superoxide dismutase activity. The necessity of standardization of natural products and their registration as functional nutraceuticals demand easy, quick and inexpensive methods of analysis. In this work we provided overview of analytical part for polyphenolics that could be used as data for possible registration of final products either as functional food or medicinal product. This feature introduces the readers to the authors' research through a concise overview of the selected topic. Reference to important work from others in the field is included. PMID:19624827

Peptoid nanosheets as soluble, two-dimensional templates for calcium carbonate mineralization.

PubMed

Jun, Joo Myung V; Altoe, M Virginia P; Aloni, Shaul; Zuckermann, Ronald N

2015-06-25

Nacre-mimetic materials are of great interest, but difficult to synthesize, because they require the ordering of organic and inorganic materials on several length scales. Here we introduce peptoid nanosheets as a versatile two-dimensional platform to develop nacre mimetic materials. Free-floating zwitterionic nanosheets were mineralized with thin films of amorphous calcium carbonate (of 2-20 nm thickness) on their surface to produce planar nacre synthons. These can serve as tunable building blocks to produce layered brick and mortar nanoarchitectures.

All 2D, high mobility, flexible, transparent thin film transistor

DOEpatents

Das, Saptarshi; Sumant, Anirudha V.; Roelofs, Andreas

2017-01-17

A two-dimensional thin film transistor and a method for manufacturing a two-dimensional thin film transistor includes layering a semiconducting channel material on a substrate, providing a first electrode material on top of the semiconducting channel material, patterning a source metal electrode and a drain metal electrode at opposite ends of the semiconducting channel material from the first electrode material, opening a window between the source metal electrode and the drain metal electrode, removing the first electrode material from the window located above the semiconducting channel material providing a gate dielectric above the semiconducting channel material, and providing a top gate above the gate dielectric, the top gate formed from a second electrode material. The semiconducting channel material is made of tungsten diselenide, the first electrode material and the second electrode material are made of graphene, and the gate dielectric is made of hexagonal boron nitride.

Chromatographic Techniques for Rare Earth Elements Analysis

NASA Astrophysics Data System (ADS)

Chen, Beibei; He, Man; Zhang, Huashan; Jiang, Zucheng; Hu, Bin

2017-04-01

The present capability of rare earth element (REE) analysis has been achieved by the development of two instrumental techniques. The efficiency of spectroscopic methods was extraordinarily improved for the detection and determination of REE traces in various materials. On the other hand, the determination of REEs very often depends on the preconcentration and separation of REEs, and chromatographic techniques are very powerful tools for the separation of REEs. By coupling with sensitive detectors, many ambitious analytical tasks can be fulfilled. Liquid chromatography is the most widely used technique. Different combinations of stationary phases and mobile phases could be used in ion exchange chromatography, ion chromatography, ion-pair reverse-phase chromatography and some other techniques. The application of gas chromatography is limited because only volatile compounds of REEs can be separated. Thin-layer and paper chromatography are techniques that cannot be directly coupled with suitable detectors, which limit their applications. For special demands, separations can be performed by capillary electrophoresis, which has very high separation efficiency.

Atomically thin gallium layers from solid-melt exfoliation

PubMed Central

Kochat, Vidya; Samanta, Atanu; Zhang, Yuan; Bhowmick, Sanjit; Manimunda, Praveena; Asif, Syed Asif S.; Stender, Anthony S.; Vajtai, Robert; Singh, Abhishek K.; Tiwary, Chandra S.; Ajayan, Pulickel M.

2018-01-01

Among the large number of promising two-dimensional (2D) atomic layer crystals, true metallic layers are rare. Using combined theoretical and experimental approaches, we report on the stability and successful exfoliation of atomically thin “gallenene” sheets on a silicon substrate, which has two distinct atomic arrangements along crystallographic twin directions of the parent α-gallium. With a weak interface between solid and molten phases of gallium, a solid-melt interface exfoliation technique is developed to extract these layers. Phonon dispersion calculations show that gallenene can be stabilized with bulk gallium lattice parameters. The electronic band structure of gallenene shows a combination of partially filled Dirac cone and the nonlinear dispersive band near the Fermi level, suggesting that gallenene should behave as a metallic layer. Furthermore, it is observed that the strong interaction of gallenene with other 2D semiconductors induces semiconducting to metallic phase transitions in the latter, paving the way for using gallenene as promising metallic contacts in 2D devices. PMID:29536039

Fabrication of dielectric elastomer stack transducers (DEST) by liquid deposition modeling

NASA Astrophysics Data System (ADS)

Klug, Florian; Solano-Arana, Susana; Mößinger, Holger; Förster-Zügel, Florentine; Schlaak, Helmut F.

2017-04-01

Established fabrication methods for dielectric elastomer stack transducers (DEST) are mostly based on twodimensional thin-film technology. Because of this, DEST are based on simple two-dimensionally structured shapes. For certain applications, like valves or Braille displays, these structures are suited well enough. However, a more flexible fabrication method allows for more complex actuator designs, which would otherwise require extra processing steps. Fabrication methods with the possibility of three-dimensional structuring allow e.g. the integration of electrical connections, cavities, channels, sensor and other structural elements during the fabrication. This opens up new applications, as well as the opportunity for faster prototype production of individually designed DEST for a given application. In this work, a manufacturing system allowing three dimensional structuring is described. It enables the production of multilayer and three-dimensional structured DEST by liquid deposition modelling. The system is based on a custom made dual extruder, connected to a commercial threeaxis positioning system. It allows a computer controlled liquid deposition of two materials. After tuning the manufacturing parameters the production of thin layers with at thickness of less than 50 μm, as well as stacking electrode and dielectric materials is feasible. With this setup a first DEST with dielectric layer thickness less than 50 μm is build successfully and its performance is evaluated.

Atomically thin resonant tunnel diodes built from synthetic van der Waals heterostructures

PubMed Central

Lin, Yu-Chuan; Ghosh, Ram Krishna; Addou, Rafik; Lu, Ning; Eichfeld, Sarah M.; Zhu, Hui; Li, Ming-Yang; Peng, Xin; Kim, Moon J.; Li, Lain-Jong; Wallace, Robert M.; Datta, Suman; Robinson, Joshua A.

2015-01-01

Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, atomically thin, multi-junction heterostructures by combining graphene with the monolayer transition-metal dichalcogenides: molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2). The realization of MoS2–WSe2–graphene and WSe2–MoS2–graphene heterostructures leads to resonant tunnelling in an atomically thin stack with spectrally narrow, room temperature negative differential resistance characteristics. PMID:26088295

Isolation, Separation, and Identification of Synthetic Food Colors.

ERIC Educational Resources Information Center

Dixon, E. A.; Renyk, G.

1982-01-01

Describes a simple, inexpensive experiment for extraction of synthetic dyes permitted in foodstuffs, and their separation and identification using thin-layer chromatography and ultraviolet/visible spectroscopy. (Author/SK)

Pyrrolizidine Alkaloids: Testing for Toxic Constituents of Comfrey.

ERIC Educational Resources Information Center

Vollmer, John J.; And Others

1987-01-01

Discusses the possibilities of toxins present in medicinal herbs. Describes an experiment in which toxic constituents can be selectively detected by thin-layer chromatography and NMR spectroscopy. (TW)

Digitally enhanced thin layer chromatography: further development and some applications in isotopic chemistry.

PubMed

Manthorpe, Daniel P; Lockley, William J S

2013-09-01

Improvements to thin layer chromatography (TLC) analysis can be made easily and cheaply by the application of digital colour photography and image analysis. The combined technique, digitally enhanced TLC (DE-TLC), is applicable to the accurate quantification of analytes in mixtures, to reaction monitoring and to other typical uses of TLC. Examples are given of the application of digitally enhanced TLC to: the deuteromethylations of theophylline to [methyl-(2)H3]caffeine and of umbelliferone to [(2)H3]7-methoxycoumarin; the selection of tertiary amine bases in deuterodechlorination reactions; stoichiometry optimisation in the borodeuteride reduction of quinizarin (1,4-dihydroxyanthraquinone) and to the assessment of xanthophyll yields in Lepidium sativum seedlings grown in deuterated media. Copyright © 2013 John Wiley & Sons, Ltd.

Metallic atomically-thin layered silicon epitaxially grown on silicene/ZrB 2

DOE PAGES

Gill, Tobias G.; Fleurence, Antoine; Warner, Ben; ...

2017-02-17

We observe a new two-dimensional (2D) silicon crystal, using low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) and it's formed by depositing additional Si atoms onto spontaneously-formed epitaxial silicene on a ZrB 2 thin film. From scanning tunnelling spectroscopy (STS) studies, we find that this atomically-thin layered silicon has distinctly different electronic properties. Angle resolved photoelectron spectroscopy (ARPES) reveals that, in sharp contrast to epitaxial silicene, the layered silicon exhibits significantly enhanced density of states at the Fermi level resulting from newly formed metallic bands. Furthermore, the 2D growth of this material could allow for direct contacting tomore » the silicene surface and demonstrates the dramatic changes in electronic structure that can occur by the addition of even a single monolayer amount of material in 2D systems.« less

Perfect absorption in nanotextured thin films via Anderson-localized photon modes

NASA Astrophysics Data System (ADS)

Aeschlimann, Martin; Brixner, Tobias; Differt, Dominik; Heinzmann, Ulrich; Hensen, Matthias; Kramer, Christian; Lükermann, Florian; Melchior, Pascal; Pfeiffer, Walter; Piecuch, Martin; Schneider, Christian; Stiebig, Helmut; Strüber, Christian; Thielen, Philip

2015-10-01

The enhancement of light absorption in absorber layers is crucial in a number of applications, including photovoltaics and thermoelectrics. The efficient use of natural resources and physical constraints such as limited charge extraction in photovoltaic devices require thin but efficient absorbers. Among the many different strategies used, light diffraction and light localization at randomly nanotextured interfaces have been proposed to improve absorption. Although already exploited in commercial devices, the enhancement mechanism for devices with nanotextured interfaces is still subject to debate. Using coherent two-dimensional nanoscopy and coherent light scattering, we demonstrate the existence of localized photonic states in nanotextured amorphous silicon layers as used in commercial thin-film solar cells. Resonant absorption in these states accounts for the enhanced absorption in the long-wavelength cutoff region. Our observations establish that Anderson localization—that is, strong localization—is a highly efficient resonant absorption enhancement mechanism offering interesting opportunities for the design of efficient future absorber layers.

Localization of cellulose synthase in Acetobacter xylinum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bureau, T.E.

1987-01-01

The cytoplasmic and outer membranes of Acetobacter xylinum (ATCC 53582) were isolated by discontinuous sucrose density ultracentrifugation. Both lysozyme and trypsin were required for efficient crude membrane separation. Primary dehydrogenases and NADH oxidase were used as cytoplasmic membrane markers, and 2-keto-3-deoxy-octulosonic acid was used to identify the outer membranes. Cellulose synthetase activity was assayed as the conversion of radioactivity from UDP-(/sup 14/C)glucose into an alkali-insoluble ..beta..-1,4-D-(/sup 14/C)glucan. The cellulosic nature of the product was demonstrated by enzymatic hydrolysis followed by thin-layer chromatography, and by methylation analysis followed by thin-layer chromatography and gas chromatography-mass spectroscopy. X-ray diffraction analysis indicated that themore » in vitro product is cellulose II which is in contrast to the in vivo product, namely cellulose I. In addition, no microfibrillar morphology could be observed from negative stained and metal shadowed preparations of the in vitro product.« less

Hemolytic activity of Fusobacterium necrophorum culture supernatants due to presence of phospholipase A and lysophospholipase.

PubMed

Abe, P M; Kendall, C J; Stauffer, L R; Holland, J W

1979-01-01

Culture supernatants of Fusobacterium necrophorum demonstrated hemolytic activity. The hemolysin(s), which was partially purified by ammonium sulfate precipitation, was temperature-dependent and heat labile. The spectrum of hemolytic activity against various erythrocytes included rabbit, human, and dog erythrocytes. Goats, sheep, and bovine erythrocytes showed only trace hemolysis. According to results of thin-layer chromatography, the hemolysin hydrolyzed rabbit erythrocyte phosphatidyl choline, phosphatidyl ethanolamine, lysophosphatidyl choline, and bovine phosphatidyl choline. Hydrolysis of egg yolk phosphatidyl choline, bovine phosphatidyl ethanolamine, cholesterol, 1,2-dipalmitin, 1,3-dipalmitin, sphingomyelin, or triolein was not detected by thin layer chromatography. A more sensitive procedure utilizing gas-liquid chromatography revealed that, of the substrates tested, the following were bein hydrolyzed: bovine and egg yolk phosphatidyl choline, lysophosphatidyl choline, alpha-palmito-beta-eleoyl-L-alpha lecithin and alpha-oleoyl-betal-palmitoyl-L-alpha lecithin. Substrates which were weakly hydrolyzed were bovine phosphatidyl ethanolamine, DL-alpha-hosphatidyl ethanolamine dipalmitoyl, 1,2-dipalmitin, 1,3-dipalmitin, and triolein.

Generic instabilities in a fluid membrane coupled to a thin layer of ordered active polar fluid.

PubMed

Sarkar, Niladri; Basu, Abhik

2013-08-01

We develop an effective two-dimensional coarse-grained description for the coupled system of a planar fluid membrane anchored to a thin layer of polar ordered active fluid below. The macroscopic orientation of the active fluid layer is assumed to be perpendicular to the attached membrane. We demonstrate that activity or nonequilibrium drive of the active fluid makes such a system generically linearly unstable for either signature of a model parameter [Formula: see text] [Formula: see text] that characterises the strength of activity. Depending upon boundary conditions and within a range of the model parameters, underdamped propagating waves may be present in our model. We discuss the phenomenological significance of our results.

Separation of Caffeine from Beverages and Analysis Using Thin-Layer Chromatography and Gas Chromatography-Mass Spectrometry

ERIC Educational Resources Information Center

Torres y Torres, Janelle L.; Hiley, Shauna L.; Lorimor, Steven P.; Rhoad, Jonathan S.; Caldwell, Benjamin D.; Zweerink, Gerald L.; Ducey, Michael

2015-01-01

The Characterization and Analysis of a Product (CAP) project is used to introduce first-semester general chemistry students to chemical instrumentation through the analysis of caffeine-containing beverage products. Some examples of these products have included coffee, tea, and energy drinks. Students perform at least three instrumental experiments…

DOE Office of Scientific and Technical Information (OSTI.GOV)

L.P. Noskova

The products of the alkaline hydrolysis of wax isolated from brown coal from the Sergeevskoe deposit were studied using chromatography and IR and NMR spectroscopy. It was found that hydrocarbons, alcohols, acids, and a representative fraction of unsaponifiable esters were the constituents of wax. High-molecular-weight fatty alcohols and acids were identified as the constituents of wax with the use of thin-layer chromatography.

Turbine Engine Lubricant Reclamation.

DTIC Science & Technology

1983-06-01

results indicate no differences in additive/degradation product removal by varying the basic material level or between Ca(OH)2 and MgO. Data indicates...0H) 2 ɘ.09 .o difference in removal by changing Ca(OH) 2 treat- . ment level by HPLC and TLC. Thin Layer Chromatography Oil + adsorbents Oil + Ca(0H...2.1%) 0.17 3% by weight 0.17 4% by weight 0.16 No difference in removal by changing Ca(OH)2 treat- ment level by HPLC and TLC. Thin Layer

[Study on the ingredients of reserpine by TLC-FT-SERS].

PubMed

Wang, Y; Zi, F; Wang, Y; Zhao, Y; Zhang, X; Weng, S

1999-12-01

A new method for analysing the ingredients of reserpine by thin layer chromatography (TLC) and surface-enhanced Raman spectroscopy (SERS) is reported in this paper. The results show that the characteristic spectral bands of reserpine satuated at the thin layer with the amount of sample about 2 microg were obtained. The difference between SERS and solid spectra was found. An absorption model of reserpine and silver sol was proposed. This method can be used to analyse the chemical ingredients with high sensitivity.

Management of light absorption in extraordinary optical transmission based ultra-thin-film tandem solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashooq, Kishwar; Talukder, Muhammad Anisuzzaman, E-mail: anis@eee.buet.ac.bd

2016-05-21

Although ultra-thin-film solar cells can be attractive in reducing the cost, they suffer from low absorption as the thickness of the active layer is usually much smaller than the wavelength of incident light. Different nano-photonic techniques, including plasmonic structures, are being explored to increase the light absorption in ultra-thin-film solar cells. More than one layer of active materials with different energy bandgaps can be used in tandem to increase the light absorption as well. However, due to different amount of light absorption in different active layers, photo-generated currents in different active layers will not be the same. The current mismatchmore » between the tandem layers makes them ineffective in increasing the efficiency. In this work, we investigate the light absorption properties of tandem solar cells with two ultra-thin active layers working as two subcells and a metal layer with periodically perforated holes in-between the two subcells. While the metal layer helps to overcome the current mismatch, the periodic holes increase the absorption of incident light by helping extraordinary optical transmission of the incident light from the top to the bottom subcell, and by coupling the incident light to plasmonic and photonic modes within ultra-thin active layers. We extensively study the effects of the geometry of holes in the intermediate metal layer on the light absorption properties of tandem solar cells with ultra-thin active layers. We also study how different metals in the intermediate layer affect the light absorption; how the geometry of holes in the intermediate layer affects the absorption when the active layer materials are changed; and how the intermediate metal layer affects the collection of photo-generated electron-hole pairs at the terminals. We find that in a solar cell with 6,6-phenyl C61-butyric acid methyl ester top subcell and copper indium gallium selenide bottom subcell, if the periodic holes in the metal layer are square or polygon, total absorption remains approximately the same. However, the total absorption suffers significantly if the holes are triangle. The transmission spectra of incident light into the bottom subcell, and hence the absorption, change significantly for square and circle holes if the active materials change to cadmium selenide (CdSe) and cadmium telluride (CdTe) in the top and bottom subcells, respectively. Although the intermediate metal layer may induce electron-hole pair recombination due to surface defects, the short-circuit current density of an ultra-thin plasmonic solar cell with an intermediate metal layer with two-dimensional hole array is >9% of that of a structure without the intermediate metal layer.« less

Investigation of upwind, multigrid, multiblock numerical schemes for three dimensional flows. Volume 1: Runge-Kutta methods for a thin layer Navier-Stokes solver

NASA Technical Reports Server (NTRS)

Cannizzaro, Frank E.; Ash, Robert L.

1992-01-01

A state-of-the-art computer code has been developed that incorporates a modified Runge-Kutta time integration scheme, upwind numerical techniques, multigrid acceleration, and multi-block capabilities (RUMM). A three-dimensional thin-layer formulation of the Navier-Stokes equations is employed. For turbulent flow cases, the Baldwin-Lomax algebraic turbulence model is used. Two different upwind techniques are available: van Leer's flux-vector splitting and Roe's flux-difference splitting. Full approximation multi-grid plus implicit residual and corrector smoothing were implemented to enhance the rate of convergence. Multi-block capabilities were developed to provide geometric flexibility. This feature allows the developed computer code to accommodate any grid topology or grid configuration with multiple topologies. The results shown in this dissertation were chosen to validate the computer code and display its geometric flexibility, which is provided by the multi-block structure.

A liquid metal reaction environment for the room-temperature synthesis of atomically thin metal oxides

NASA Astrophysics Data System (ADS)

Zavabeti, Ali; Ou, Jian Zhen; Carey, Benjamin J.; Syed, Nitu; Orrell-Trigg, Rebecca; Mayes, Edwin L. H.; Xu, Chenglong; Kavehei, Omid; O'Mullane, Anthony P.; Kaner, Richard B.; Kalantar-zadeh, Kourosh; Daeneke, Torben

2017-10-01

Two-dimensional (2D) oxides have a wide variety of applications in electronics and other technologies. However, many oxides are not easy to synthesize as 2D materials through conventional methods. We used nontoxic eutectic gallium-based alloys as a reaction solvent and co-alloyed desired metals into the melt. On the basis of thermodynamic considerations, we predicted the composition of the self-limiting interfacial oxide. We isolated the surface oxide as a 2D layer, either on substrates or in suspension. This enabled us to produce extremely thin subnanometer layers of HfO2, Al2O3, and Gd2O3. The liquid metal-based reaction route can be used to create 2D materials that were previously inaccessible with preexisting methods. The work introduces room-temperature liquid metals as a reaction environment for the synthesis of oxide nanomaterials with low dimensionality.

Comparison of results for morphine urinalyses by radioimmunoassay and thin-layer chromatography in a narcotic clinic setting.

PubMed

Kokoski, R J; Jain, M

1975-03-01

Radioimmunoassay (RIA) and thin-layer chromatography (TLC) were compared for morphine detection in an actual narcotic clinic setting. A choice of urines from all those screened by TLC allowed a critical comparison as to actual use or non-use of narcotic drugs, rather than a sampling at random in which the question of possible false positives or negatives cannot be conclusively answered. Although RIA is more sensitive than TLC, its advantage is apparent only in those cases where urine specimens are difficult to obtain frequently regularly or where the use of morphine is suspected by the positive identification of quinine in urine that was morphine-negative by TLC. In a selected group of negative and positive specimens chosen without conscious bias, the two methods gave consistently similar results, indicating that the modified TLC method provided a few or no false positives or negatives if the negatives were from those cases that were not positive anytime up to 3-4 days before urine collection. We conclude that RIA can be of significant value as a supplement to a TLC screening program, without sacrificing the many advantages that TLC has to offer.

Thin layer chromatography-ion mobility spectrometry (TLC-IMS).

PubMed

Ilbeigi, Vahideh; Tabrizchi, Mahmoud

2015-01-06

Ion mobility spectrometry (IMS) is a fast and sensitive analytical method which operates at the atmospheric pressure. To enhance the capability of IMS for the analysis of mixtures, it is often used with preseparation techniques, such as GC or HPLC. Here, we report for the first time the coupling of the thin-layer chromatography and IMS. A variety of coupling schemes were tried that included direct electrospray from the TLC strip tip, indirect electrospray from a needle connected to the TLC strip, introducing the moving solvent into the injection port, and, the simplest way, offline introduction of scratched or cut pieces of strips into the IMS injection port. In this study a special solvent tank was designed and the TLC strip was mounted horizontally where the solvent would flow down. A very small funnel right below the TLC tip collected the solvent and transferred it to a needle via a capillary tubing. Using the TLC-ESI-IMS technique, acceptable separations were achieved for two component mixtures of morphine-papaverine and acridine-papaverine. A special injection port was designed to host the pieces cut off the TLC. The method was successfully used to identify each spot on the TLC by IMS in a few seconds.

Biotransformation of bromhexine by Cunninghamella elegans, C. echinulata and C. blakesleeana.

PubMed

Dube, Aman K; Kumar, Maushmi S

Fungi is a well-known model used to study drug metabolism and its production in in vitro condition. We aim to screen the most efficient strain of Cunninghamella sp. among C. elegans, C. echinulata and C. blakesleeana for bromhexine metabolites production. We characterized the metabolites produced using various analytical tools and compared them with mammalian metabolites in Rat liver microsomes (RLM). The metabolites were collected by two-stage fermentation of bromhexine with different strains of Cunninghamella sp. followed by extraction. Analysis was done by thin layer chromatography, high performance thin layer chromatography, Fourier transform infrared spectroscopy, high performance liquid chromatography and Liquid chromatography-mass spectrometry. The role of Cytochrome P3A4 (CYP3A4) enzymes in bromhexine metabolism was studied. Fungal incubates were spiked with reference standard - clarithromycin to confirm the role of CYP3A4 enzyme in bromhexine metabolism. Three metabolites appeared at 4.7, 5.5 and 6.4min retention time in HPLC. Metabolites produced by C. elegans and RLM were concluded to be similar based on their retention time, peak area and peak response of 30.05%, 21.06%, 1.34%, and 47.66% of three metabolites and bromhexine in HPLC. The role of CYP3A4 enzyme in metabolism of bromhexine and the presence of these enzymes in Cunninghamella species was confirmed due to absence of peaks at 4.7, 5.4 and 6.7min when RLM were incubated with a CYP3A4 enzyme inhibitor - clarithromycin. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Role of thin-layer chromatography in ascertaining Kashaya Rasa (astringent taste) in medicinal plants on the concept of Samana and Vichitra Pratyayarabdha principles of Ayurveda

PubMed Central

Kolhe, Rasika H.; Acharya, Rabinarayan; Shukla, Vinay J.

2014-01-01

Background: Pharmacodynamics, in Ayurveda has been described in terms of Rasadipanchaka. Rasa, on one side indicates the Bhautika composition of the drug and on the other side predicts the action. Different analytical techniques, pharmaceutical processes are being used in Ayurveda for the purpose of standardization of raw drugs. Aim: In this study an attempt has been made to apply chromatographic technique in determination of Kashaya (astringent) Rasa (taste). Materials and Methods: Two important Kashaya dominant drugs Kulattha (Dolichos biflorus Linn.) and Kanchanara (Bauhinia variegata Linn.), falling under Vichitra and Samana Pratyayarabdha category respectively, were subjected to physicochemical parameters and qualitative tests followed by High-Performance Thin-Layer Chromatography (HPTLC). In light of chromatographic fingerprinting; sample preparation protocol is modified to incorporate taste threshold in correlation. Column chromatography is used for first-level discrimination technique followed by HPTLC. Kashaya Rasa Dominant Zone (KsRDZ) was separated and subjected to TLC fingerprinting. The KsRDZ fraction was designated as Botanical Reference Material (BRM) in further analysis. Results: Ash value, Alcohol and water soluble extract value were more in B variegata as compared to D biflorus. Presence of tannin in both the samples was confirmed through qualitative test. The KsRDZ fraction separated at Rf 0.46 and 0.48 for Kulattha and Kanchanara respectively. Conclusion: The results showed that the planner chromatography technique seems very useful when BRM hypothesis was adjunct to method that explains the categorization according to traditional Rasa domain classification method. PMID:25558164

Chemometrics comparison of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry Daphnia magna metabolic profiles exposed to salinity.

PubMed

Parastar, Hadi; Garreta-Lara, Elba; Campos, Bruno; Barata, Carlos; Lacorte, Silvia; Tauler, Roma

2018-06-01

The performances of gas chromatography with mass spectrometry and of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry are examined through the comparison of Daphnia magna metabolic profiles. Gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with mass spectrometry were used to compare the concentration changes of metabolites under saline conditions. In this regard, a chemometric strategy based on wavelet compression and multivariate curve resolution-alternating least squares is used to compare the performances of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry for the untargeted metabolic profiling of Daphnia magna in control and salinity-exposed samples. Examination of the results confirmed the outperformance of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry over gas chromatography with mass spectrometry for the detection of metabolites in D. magna samples. The peak areas of multivariate curve resolution-alternating least squares resolved elution profiles in every sample analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry were arranged in a new data matrix that was then modeled by partial least squares discriminant analysis. The control and salt-exposed daphnids samples were discriminated and the most relevant metabolites were estimated using variable importance in projection and selectivity ratio values. Salinity de-regulated 18 metabolites from metabolic pathways involved in protein translation, transmembrane cell transport, carbon metabolism, secondary metabolism, glycolysis, and osmoregulation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thin-layer chromatographic determination of erythromycin and other macrolide antibiotics in livestock products.

PubMed

Petz, M; Solly, R; Lymburn, M; Clear, M H

1987-01-01

A method is described for determination of 4 macrolide antibiotics in livestock products. Erythromycin, tylosin, oleandomycin, and spiramycin were extracted from animal tissues, milk, and egg with acetonitrile at pH 8.5. Cleanup was done by adding sodium chloride and dichloromethane, evaporating the organic layer, and subsequent acid/base partitioning. After the antibiotics were separated by thin-layer chromatography (TLC), they were reacted with xanthydrol and could be detected as purple spots down to 0.02 mg/kg without interference by other commonly used therapeutic drugs (23 were tested). Anisaldehyde-sulfuric acid, cerium sulfate-molybdic acid, phosphomolybdic acid, and Dragendorff's reagent proved to be less sensitive as visualizing agents. For quantitation, TLC plates were scanned at 525 nm. Recoveries were between 71 and 96% for erythromycin and tylosin in liver, muscle, and egg at the 0.1-0.5 mg/kg level and 51% for erythromycin in milk at the 0.02 mg/kg level (coefficient of variation = 10-18%). Bioautography with Bacillus subtilis was used to confirm results, in addition to TLC analysis of derivatized antibiotics and liquid chromatography with electrochemical detection. Various derivatization procedures for erythromycin were investigated for improved ultra-violet or fluorescence detection in liquid chromatography.

Quantification of Quercetin Obtained from Allium cepa Lam. Leaves and its Effects on Streptozotocin-induced Diabetic Neuropathy.

PubMed

Dureshahwar, Khan; Mubashir, Mohammed; Une, Hemant Devidas

2017-01-01

Antioxidant potential has protective effects in diabetic neuropathy (DN); hence, the present study was designed with an objective to quantify quercetin from shade-dried leaves of Allium cepa Lam. and to study its effects on streptozotocin (STZ)-induced chronic DN. The shade-dried leaves of A. cepa Lam. were extracted with methanol and then fractionated using ethyl acetate (ACEA). The quantification of quercetin in ACEA was evaluated by high-performance thin layer chromatography (HPTLC). The STZ (40 mg/kg) was administered to Sprague-Dawley rats (180-250 g) maintained at normal housing conditions. The STZ was administered once a day for 3 consecutive days. The elevation in blood glucose was monitored for 3 weeks periodically using flavin adenine dinucleotide-glucose dehydrogenase method by Contour TS glucometer. Rats showing blood glucose above 250 mg/dl were selected for the study. Animals were divided into eight groups. ACEA (25, 50, and 100 mg/kg), quercetin (40 mg/kg), metformin (120 mg/kg), and gabapentin (100 mg/kg) were given orally once a day for 2 weeks. The blood glucose level was again measured at the end of treatment to assess DN. Thermal hyperalgesia, cold allodynia, motor incoordination, and neurotoxicity were studied initially and at the end of 2-week treatment. Biochemical parameters were also evaluated after 2-week drug treatment. The quercetin present in ACEA was 4.82% by HPTLC. All the ACEA treatment reduces blood glucose level at the end of the 2-week study and shows a significant neuroprotective effect in STZ-induced DN in the above experimental models. The quercetin present in ACEA proved protective effect in STZ-induced DN. High-performance thin layer chromatography reveals the presence of 4.82% quercetin in Allium cepa ethyl acetate. (ACEA). Its investigation against various diabetic neuropathy biomarkers has proved that ACEA has significant blood glucose reducing action shown neuroprotective action in thermal hyperalgesia, motor incoordination, and biochemical parameters. Abbreviations Used : HPTLC: High-performance thin layer chromatography, TLC: Thin layer chromatography, UV: Ultraviolet, ACEA: Allium cepa ethyl acetate, STZ: Streptozotocin, LDL: Low-density lipids, HDL: High-density lipids.

Two sensitizing oxidation products of p-phenylenediamine patch tested in patients allergic to p-phenylenediamine.

PubMed

Young, Ewa; Zimerson, Erik; Bruze, Magnus; Svedman, Cecilia

2016-02-01

The results from a previous study indicated the presence of several possible sensitizers formed during oxidation of the potent sensitizer p-phenylenediamine (PPD) to which PPD-sensitized patients might react, in various patterns. To extract and analyse a yellow spot from a thin-layer chromatogram with oxidized PPD, to which 6 of 14 (43%) PPD-positive patients had reacted in a previous study, in order to identify potential sensitizer(s) and to patch test this/these substance(s) in the 14 PPD-positive patients. The yellow spot was extracted from a thin-layer chromatogram of oxidized PPD, and two substances, suspected to be allergens, were identified by analysis with gas chromatography mass spectrometry (GCMS). The 14 PPD-positive patients, who had been previously tested with the thin-layer chromatogram of oxidized PPD, participated in the investigation, and were tested with dilutions of the two substances. GCMS analysis identified 4-nitroaniline and 4,4'-azodianiline in the yellow spot. Of the 14 PPD-positive test patients, 5 (36%) reacted to 4-nitroaniline and 9 (64%) reacted to 4,4'-azodianiline. The results show that 4-nitroaniline and 4,4'-azodianiline, formed during oxidation of PPD, are potent sensitizers. PPD-sensitized patients react to a high extent to concentrations equimolar to PPD of 4-nitroaniline and 4,4'-azodianiline. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Patterns of muscular strain in the embryonic heart wall.

PubMed

Damon, Brooke J; Rémond, Mathieu C; Bigelow, Michael R; Trusk, Thomas C; Xie, Wenjie; Perucchio, Renato; Sedmera, David; Denslow, Stewart; Thompson, Robert P

2009-06-01

The hypothesis that inner layers of contracting muscular tubes undergo greater strain than concentric outer layers was tested by numerical modeling and by confocal microscopy of strain within the wall of the early chick heart. We modeled the looped heart as a thin muscular shell surrounding an inner layer of sponge-like trabeculae by two methods: calculation within a two-dimensional three-variable lumped model and simulated expansion of a three-dimensional, four-layer mesh of finite elements. Analysis of both models, and correlative microscopy of chamber dimensions, sarcomere spacing, and membrane leaks, indicate a gradient of strain decreasing across the wall from highest strain along inner layers. Prediction of wall thickening during expansion was confirmed by ultrasonography of beating hearts. Degree of stretch determined by radial position may thus contribute to observed patterns of regional myocardial conditioning and slowed proliferation, as well as to the morphogenesis of ventricular trabeculae and conduction fascicles. Developmental Dynamics 238:1535-1546, 2009. (c) 2009 Wiley-Liss, Inc.

Onset of two-dimensional superconductivity in space charge doped few-layer molybdenum disulfide

NASA Astrophysics Data System (ADS)

Biscaras, Johan; Chen, Zhesheng; Paradisi, Andrea; Shukla, Abhay

2015-11-01

Atomically thin films of layered materials such as molybdenum disulfide (MoS2) are of growing interest for the study of phase transitions in two-dimensions through electrostatic doping. Electrostatic doping techniques giving access to high carrier densities are needed to achieve such phase transitions. Here we develop a method of electrostatic doping which allows us to reach a maximum n-doping density of 4 × 1014 cm-2 in few-layer MoS2 on glass substrates. With increasing carrier density we first induce an insulator to metal transition and subsequently an incomplete metal to superconductor transition in MoS2 with critical temperature ~10 K. Contrary to earlier reports, after the onset of superconductivity, the superconducting transition temperature does not depend on the carrier density. Our doping method and the results we obtain in MoS2 for samples as thin as bilayers indicates the potential of this approach.

Separation techniques: Chromatography

PubMed Central

Coskun, Ozlem

2016-01-01

Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis. Proteins can be purified based on characteristics such as size and shape, total charge, hydrophobic groups present on the surface, and binding capacity with the stationary phase. Four separation techniques based on molecular characteristics and interaction type use mechanisms of ion exchange, surface adsorption, partition, and size exclusion. Other chromatography techniques are based on the stationary bed, including column, thin layer, and paper chromatography. Column chromatography is one of the most common methods of protein purification. PMID:28058406

"Techniques for Teachers" Section

ERIC Educational Resources Information Center

Tait, A.

1972-01-01

A series of short articles describe a method of combined developing/fixing for monochrome film, techniques for thin layer chromatography, experiments with lasers, and safety precautions to be used with lasers in school laboratories. (AL)

An Undergraduate Thin-Layer Chromatography Experiment: Olfactory Delights

NASA Astrophysics Data System (ADS)

Lynch, Mary Anne; Gloffke, Wendy; Rauner, Richard A.

1995-12-01

Mixtures of flavors and fragrances were separated on silica gel sheets, employing toluene/ethyl acetate (90:10) as the solvent. Constituents were located using alkaline potassium permanganate and 2,4-dinitrophenylhydrazine.

37 CFR 1.84 - Standards for drawings.

Code of Federal Regulations, 2013 CFR

2013-07-01

... vivo imaging, thin layer chromatography plates, crystalline structures, and, in a design patent... oblique strokes, the space between strokes being chosen on the basis of the total area to be hatched. The...

37 CFR 1.84 - Standards for drawings.

Code of Federal Regulations, 2012 CFR

2012-07-01

... vivo imaging, thin layer chromatography plates, crystalline structures, and, in a design patent... oblique strokes, the space between strokes being chosen on the basis of the total area to be hatched. The...

37 CFR 1.84 - Standards for drawings.

Code of Federal Regulations, 2014 CFR

2014-07-01

... vivo imaging, thin layer chromatography plates, crystalline structures, and, in a design patent... oblique strokes, the space between strokes being chosen on the basis of the total area to be hatched. The...

Student Investigations Using Chromatography

ERIC Educational Resources Information Center

Witters, Weldon L.; Bush, Kenneth

1970-01-01

Three different problems are given for student investigation in determining amino acid compositions, floral pigments, and water soluble amino acids by using the techniques of Roll Chromotography, DISC Chromotography, Thin Layer, and Paper Chromotography. (BR)

Multi-Dimensional Damage Detection for Surfaces and Structures

NASA Technical Reports Server (NTRS)

Williams, Martha; Lewis, Mark; Roberson, Luke; Medelius, Pedro; Gibson, Tracy; Parks, Steen; Snyder, Sarah

2013-01-01

Current designs for inflatable or semi-rigidized structures for habitats and space applications use a multiple-layer construction, alternating thin layers with thicker, stronger layers, which produces a layered composite structure that is much better at resisting damage. Even though such composite structures or layered systems are robust, they can still be susceptible to penetration damage. The ability to detect damage to surfaces of inflatable or semi-rigid habitat structures is of great interest to NASA. Damage caused by impacts of foreign objects such as micrometeorites can rupture the shell of these structures, causing loss of critical hardware and/or the life of the crew. While not all impacts will have a catastrophic result, it will be very important to identify and locate areas of the exterior shell that have been damaged by impacts so that repairs (or other provisions) can be made to reduce the probability of shell wall rupture. This disclosure describes a system that will provide real-time data regarding the health of the inflatable shell or rigidized structures, and information related to the location and depth of impact damage. The innovation described here is a method of determining the size, location, and direction of damage in a multilayered structure. In the multi-dimensional damage detection system, layers of two-dimensional thin film detection layers are used to form a layered composite, with non-detection layers separating the detection layers. The non-detection layers may be either thicker or thinner than the detection layers. The thin-film damage detection layers are thin films of materials with a conductive grid or striped pattern. The conductive pattern may be applied by several methods, including printing, plating, sputtering, photolithography, and etching, and can include as many detection layers that are necessary for the structure construction or to afford the detection detail level required. The damage is detected using a detector or sensory system, which may include a time domain reflectometer, resistivity monitoring hardware, or other resistance-based systems. To begin, a layered composite consisting of thin-film damage detection layers separated by non-damage detection layers is fabricated. The damage detection layers are attached to a detector that provides details regarding the physical health of each detection layer individually. If damage occurs to any of the detection layers, a change in the electrical properties of the detection layers damaged occurs, and a response is generated. Real-time analysis of these responses will provide details regarding the depth, location, and size estimation of the damage. Multiple damages can be detected, and the extent (depth) of the damage can be used to generate prognostic information related to the expected lifetime of the layered composite system. The detection system can be fabricated very easily using off-the-shelf equipment, and the detection algorithms can be written and updated (as needed) to provide the level of detail needed based on the system being monitored. Connecting to the thin film detection layers is very easy as well. The truly unique feature of the system is its flexibility; the system can be designed to gather as much (or as little) information as the end user feels necessary. Individual detection layers can be turned on or off as necessary, and algorithms can be used to optimize performance. The system can be used to generate both diagnostic and prognostic information related to the health of layer composite structures, which will be essential if such systems are utilized for space exploration. The technology is also applicable to other in-situ health monitoring systems for structure integrity.

Probing Carrier Transport and Structure-Property Relationship of Highly Ordered Organic Semiconductors at the Two-Dimensional Limit.

PubMed

Zhang, Yuhan; Qiao, Jingsi; Gao, Si; Hu, Fengrui; He, Daowei; Wu, Bing; Yang, Ziyi; Xu, Bingchen; Li, Yun; Shi, Yi; Ji, Wei; Wang, Peng; Wang, Xiaoyong; Xiao, Min; Xu, Hangxun; Xu, Jian-Bin; Wang, Xinran

2016-01-08

One of the basic assumptions in organic field-effect transistors, the most fundamental device unit in organic electronics, is that charge transport occurs two dimensionally in the first few molecular layers near the dielectric interface. Although the mobility of bulk organic semiconductors has increased dramatically, direct probing of intrinsic charge transport in the two-dimensional limit has not been possible due to excessive disorders and traps in ultrathin organic thin films. Here, highly ordered single-crystalline mono- to tetralayer pentacene crystals are realized by van der Waals (vdW) epitaxy on hexagonal BN. We find that the charge transport is dominated by hopping in the first conductive layer, but transforms to bandlike in subsequent layers. Such an abrupt phase transition is attributed to strong modulation of the molecular packing by interfacial vdW interactions, as corroborated by quantitative structural characterization and density functional theory calculations. The structural modulation becomes negligible beyond the second conductive layer, leading to a mobility saturation thickness of only ∼3  nm. Highly ordered organic ultrathin films provide a platform for new physics and device structures (such as heterostructures and quantum wells) that are not possible in conventional bulk crystals.

Probing Carrier Transport and Structure-Property Relationship of Highly Ordered Organic Semiconductors at the Two-Dimensional Limit

NASA Astrophysics Data System (ADS)

Zhang, Yuhan; Qiao, Jingsi; Gao, Si; Hu, Fengrui; He, Daowei; Wu, Bing; Yang, Ziyi; Xu, Bingchen; Li, Yun; Shi, Yi; Ji, Wei; Wang, Peng; Wang, Xiaoyong; Xiao, Min; Xu, Hangxun; Xu, Jian-Bin; Wang, Xinran

2016-01-01

One of the basic assumptions in organic field-effect transistors, the most fundamental device unit in organic electronics, is that charge transport occurs two dimensionally in the first few molecular layers near the dielectric interface. Although the mobility of bulk organic semiconductors has increased dramatically, direct probing of intrinsic charge transport in the two-dimensional limit has not been possible due to excessive disorders and traps in ultrathin organic thin films. Here, highly ordered single-crystalline mono- to tetralayer pentacene crystals are realized by van der Waals (vdW) epitaxy on hexagonal BN. We find that the charge transport is dominated by hopping in the first conductive layer, but transforms to bandlike in subsequent layers. Such an abrupt phase transition is attributed to strong modulation of the molecular packing by interfacial vdW interactions, as corroborated by quantitative structural characterization and density functional theory calculations. The structural modulation becomes negligible beyond the second conductive layer, leading to a mobility saturation thickness of only ˜3 nm . Highly ordered organic ultrathin films provide a platform for new physics and device structures (such as heterostructures and quantum wells) that are not possible in conventional bulk crystals.

The analysis of carbohydrates in milk powder by a new "heart-cutting" two-dimensional liquid chromatography method.

PubMed

Ma, Jing; Hou, Xiaofang; Zhang, Bing; Wang, Yunan; He, Langchong

2014-03-01

In this study, a new"heart-cutting" two-dimensional liquid chromatography method for the simultaneous determination of carbohydrate contents in milk powder was presented. In this two dimensional liquid chromatography system, a Venusil XBP-C4 analysis column was used in the first dimension ((1)D) as a pre-separation column, a ZORBAX carbohydrates analysis column was used in the second dimension ((2)D) as a final-analysis column. The whole process was completed in less than 35min without a particular sample preparation procedure. The capability of the new two dimensional HPLC method was demonstrated in the determination of carbohydrates in various brands of milk powder samples. A conventional one dimensional chromatography method was also proposed. The two proposed methods were both validated in terms of linearity, limits of detection, accuracy and precision. The comparison between the results obtained with the two methods showed that the new and completely automated two dimensional liquid chromatography method is more suitable for milk powder sample because of its online cleanup effect involved. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

"Dry-column" chromatography of plant pigments

NASA Technical Reports Server (NTRS)

Woeller, F. H.; Lehwalt, M. F.; Oyama, V. I.

1973-01-01

Separation of plant pigments which can be accomplished on thin-layer silica plates with mixture of petroleum ether, halocarbon, acetone, and polar solvent can be readily translated into dry-column technique that yields reproducible chromatograms after elution in fashion of liquid chromatography with fluorimeter as detector. Best solvent system was found to be mixture of petroleum ether, dichloromethane, acetone, and ethyl acetate.

Combining surface enhanced Raman scattering (SERS) and high-performance thin-layer chromatography (HPTLC)

NASA Astrophysics Data System (ADS)

Koglin, E.

A new method for preparing SERS active surfaces using silver colloidal spheres deposited on HPTLC plates, used for thin-layer chromatography, is discussed in detail. The sensitivity of these activated HPTLC plates is so high that in-situ vibrational investigations of chromatogram spots are possible at the nanogram level. The HPTLC/SERS spectra of purine, benzoic acid and 1-nitro-pyrene adsorbed on silver colloidal activated silica gel plates are measured in the nanogram region. In addition we also report in this paper on the results of a feasibility study performed to evaluate the analytical potential of micro-Raman spectroscopy (triple monochromator, multichannel detection system) in SERS/HPTLC spot characterization. It permits the acquisition of Raman spectra from HPTLC spots down to 1 μm in size or other forms of microsamples approaching the picogram level in mass.

Photodiodes based in La0.7Sr0.3MnO3/single layer MoS2 hybrid vertical heterostructures

NASA Astrophysics Data System (ADS)

Niu, Yue; Frisenda, Riccardo; Svatek, Simon A.; Orfila, Gloria; Gallego, Fernando; Gant, Patricia; Agraït, Nicolás; Leon, Carlos; Rivera-Calzada, Alberto; Pérez De Lara, David; Santamaria, Jacobo; Castellanos-Gomez, Andres

2017-09-01

The fabrication of artificial materials by stacking of individual two-dimensional (2D) materials is amongst one of the most promising research avenues in the field of 2D materials. Moreover, this strategy to fabricate new man-made materials can be further extended by fabricating hybrid stacks between 2D materials and other functional materials with different dimensionality making the potential number of combinations almost infinite. Among all these possible combinations, mixing 2D materials with transition metal oxides can result especially useful because of the large amount of interesting physical phenomena displayed separately by these two material families. We present a hybrid device based on the stacking of a single layer MoS2 onto a lanthanum strontium manganite (La0.7Sr0.3MnO3) thin film, creating an atomically thin device. It shows a rectifying electrical transport with a ratio of 103, and a photovoltaic effect with V oc up to 0.4 V. The photodiode behaviour arises as a consequence of the different doping character of these two materials. This result paves the way towards combining the efforts of these two large materials science communities.

Mitigating leaks in membranes

DOEpatents

Karnik, Rohit N.; Bose, Suman; Boutilier, Michael S.H.; Hadjiconstantinou, Nicolas G.; Jain, Tarun Kumar; O'Hern, Sean C.; Laoui, Tahar; Atieh, Muataz A.; Jang, Doojoon

2018-02-27

Two-dimensional material based filters, their method of manufacture, and their use are disclosed. In one embodiment, a membrane may include an active layer including a plurality of defects and a deposited material associated with the plurality of defects may reduce flow therethrough. Additionally, a majority of the active layer may be free from the material. In another embodiment, a membrane may include a porous substrate and an atomic layer deposited material disposed on a surface of the porous substrate. The atomic layer deposited material may be less hydrophilic than the porous substrate and an atomically thin active layer may be disposed on the atomic layer deposited material.

Two-dimensional La2/3Sr4/3MnO4 Manganite Films Probed by Epitaxial Strain and Cation Ordering

NASA Astrophysics Data System (ADS)

Nelson-Cheeseman, Brittany; Santos, Tiffany; Bhattacharya, Anand

2010-03-01

Dimensionality is known to play a central role in the properties of strongly correlated systems. Here we investigate magnetism and transport in thin films of the Ruddlesden-Popper n=1 phase, La1-xSr1+xMnO4. Within this material, the MnO6-octahedra form two-dimensional perovskite sheets separated by an extra rocksalt layer. By fabricating high quality thin films with ozone-assisted molecular beam epitaxy, we study how the effects of epitaxial strain and intentional cation ordering, known as digital synthesis, influence the properties of this 2-dimensional manganite. For example, at the same Mn^3+:Mn^4+ ratio (2:1) as its fully spin-polarized 3D manganite counterpart, this two dimensional analog at x=1/3 only displays a spin glass phase below 20K in bulk. This is believed to result from a competition between superexchange and double exchange, as well as disordered Jahn-Teller distortions. However, in our films we find weak ferromagnetic order up to much higher temperatures in addition to a low temperature spin glass phase. We will discuss how strain and cation order effect the presence of this weak ferromagnetism.

Two-Dimensional Computational Model for Wave Rotor Flow Dynamics

NASA Technical Reports Server (NTRS)

Welch, Gerard E.

1996-01-01

A two-dimensional (theta,z) Navier-Stokes solver for multi-port wave rotor flow simulation is described. The finite-volume form of the unsteady thin-layer Navier-Stokes equations are integrated in time on multi-block grids that represent the stationary inlet and outlet ports and the moving rotor passages of the wave rotor. Computed results are compared with three-port wave rotor experimental data. The model is applied to predict the performance of a planned four-port wave rotor experiment. Two-dimensional flow features that reduce machine performance and influence rotor blade and duct wall thermal loads are identified. The performance impact of rounding the inlet port wall, to inhibit separation during passage gradual opening, is assessed.

Overview of online two-dimensional liquid chromatography based on cell membrane chromatography for screening target components from traditional Chinese medicines.

PubMed

Muhammad, Saqib; Han, Shengli; Xie, Xiaoyu; Wang, Sicen; Aziz, Muhammad Majid

2017-01-01

Cell membrane chromatography is a simple, specific, and time-saving technique for studying drug-receptor interactions, screening of active components from complex mixtures, and quality control of traditional Chinese medicines. However, the short column life, low sensitivity, low column efficiency (so cannot resolve satisfactorily mixture of compounds), low peak capacity, and inefficient in structure identification were bottleneck in its application. Combinations of cell membrane chromatography with multidimensional chromatography such as two-dimensional liquid chromatography and high sensitivity detectors like mass have significantly reduced many of the above-mentioned shortcomings. This paper provides an overview of the current advances in online two-dimensional-based cell membrane chromatography for screening target components from traditional Chinese medicines with particular emphasis on the instrumentation, preparation of cell membrane stationary phase, advantages, and disadvantages compared to alternative approaches. The last section of the review summarizes the applications of the online two-dimensional high-performance liquid chromatography based cell membrane chromatography reported since its emergence to date (2010-June 2016). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-performance thin-layer chromatography and three-dimensional image analysis for the determination of rutin in pharmaceutical preparations.

PubMed

Soponar, Florin; Moţ, Augustin C; Sârbu, Costel

2010-01-01

A novel HPTLC method was developed for fast and simple quantitative determination of rutin in pharmaceutical preparations. The proposed method combines the advantages of HPTLC with the comfort and the convenience of digital processing of images. For the separation of rutin, silica gel with attached amino groups was used as the stationary phase and ethyl acetate-formic acid-methanol-water (10 + 0.9 + 1.1 + 1.7, v/v/v/v) as the mobile phase. The chromatographic plate was sprayed with 2-aminoethyldiphenyl borate solution for visual detection of the spots. For the construction of a three-dimensional chromatogram, Melanie 7.0 software was used together with an HP flatbed scanner that allowed capture of the images on chromatographic plates. The calibration curve was linear within the range of 0.95-4.78 microg/spot with an r value of 0.9984. The RSD for six replicates at three concentration levels was less than 3%, while the recovery was between 97.28 and 103.27%. The proposed method was found to be simple, precise, sensitive, and accurate and has been applied for the determination of rutin in two commercial drugs. The results were compared with the results of other techniques that generate bidimensional chromatograms and validated by UV-Vis spectrophotometry.

Uni-dimensional double development HPTLC-densitometry method for simultaneous analysis of mangiferin and lupeol content in mango (Mangifera indica) pulp and peel during storage.

PubMed

Jyotshna; Srivastava, Pooja; Killadi, Bharti; Shanker, Karuna

2015-06-01

Mango (Mangifera indica) fruit is one of the important commercial fruit crops of India. Similar to other tropical fruits it is also highly perishable in nature. During storage/ripening, changes in its physico-chemical quality parameters viz. firmness, titrable acidity, total soluble solid content (TSSC), carotenoids content, and other biochemicals are inevitable. A uni-dimensional double-development high-performance thin-layer chromatography (UDDD-HPTLC) method was developed for the real-time monitoring of mangiferin and lupeol in mango pulp and peel during storage. The quantitative determination of both compounds of different classes was achieved by densitometric HPTLC method. Silica gel 60F254 HPTLC plates and two solvent systems viz. toluene/EtOAC/MeOH and EtOAC/MeOH, respectively were used for optimum separation and selective evaluation. Densitometric quantitation of mangiferin was performed at 390nm, while lupeol at 610nm after post chromatographic derivatization. Validated method was used to real-time monitoring of mangiferin and lupeol content during storage in four Indian cultivars, e.g. Bombay green (Bgreen), Dashehari, Langra, and Chausa. Significant correlations (p<0.05) between of acidity and TSSC with mangiferin and lupeol in pulp and peel during storage were also observed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hydrothermally formed three-dimensional nanoporous Ni(OH)2 thin-film supercapacitors.

PubMed

Yang, Yang; Li, Lei; Ruan, Gedeng; Fei, Huilong; Xiang, Changsheng; Fan, Xiujun; Tour, James M

2014-09-23

A three-dimensional nanoporous Ni(OH)2 thin-film was hydrothermally converted from an anodically formed porous layer of nickel fluoride/oxide. The nanoporous Ni(OH)2 thin-films can be used as additive-free electrodes for energy storage. The nanoporous layer delivers a high capacitance of 1765 F g(-1) under three electrode testing. After assembly with porous activated carbon in asymmetric supercapacitor configurations, the devices deliver superior supercapacitive performances with capacitance of 192 F g(-1), energy density of 68 Wh kg(-1), and power density of 44 kW kg(-1). The wide working potential window (up to 1.6 V in 6 M aq KOH) and stable cyclability (∼90% capacitance retention over 10,000 cycles) make the thin-film ideal for practical supercapacitor devices.

Experimental study of thermocapillary flows in a thin liquid layer with heat fluxes imposed on the free surface

NASA Technical Reports Server (NTRS)

Lai, Chun-Liang; Greenberg, Paul S.; Chai, An-Ti

1988-01-01

To study thermocapillary flows in a two-dimensional thin liquid layer with heat fluxes imposed on the free surface experimentally, a long tray configuration was employed to simulate the infinite layer. The surface temperature distribution due to thermocapillary convective for different flow regimes was measured and compared with theoretical predictions. A short tray configuration was also employed to study the end wall effects (insulating or conducting). The results show that for a strong convection flow with an insulating wall as the boundary the surface temperature distribution became quite uniform. Consequently, the thermocapillary driving force was greatly reduced. On the other hand, a strong fluid motion always existed adjacent to the conducting wall because of the large surface temperature gradient near the wall.

Determination of phytate in high molecular weight, charged organic matrices by two-dimensional size exclusion-ion chromatography

USDA-ARS?s Scientific Manuscript database

A two-dimensional chromatography method for analyzing anionic targets (specifically phytate) in complex matrices is described. Prior to quantification by anion exchange chromatography, the sample matrix was prepared by size exclusion chromatography, which removed the majority of matrix complexities....

Purification of flavonoids from licorice using an off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method.

PubMed

Fan, Yunpeng; Fu, Yanhui; Fu, Qing; Cai, Jianfeng; Xin, Huaxia; Dai, Mei; Jin, Yu

2016-07-01

An orthogonal (71.9%) off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method coupled with effective sample pretreatment was developed for separation and purification of flavonoids from licorice. Most of the nonflavonoids were firstly removed using a self-made Click TE-Cys (60 μm) solid-phase extraction. In the first dimension, an industrial grade preparative chromatography was employed to purify the crude flavonoids. Click TE-Cys (10 μm) was selected as the stationary phase that provided an excellent separation with high reproducibility. Ethyl acetate/ethanol was selected as the mobile phase owing to their excellent solubility for flavonoids. Flavonoids co-eluted in the first dimension were selected for further purification using reversed-phase liquid chromatography. Multiple compounds could be isolated from one normal-phase fraction and some compounds with bad resolution in one-dimensional liquid chromatography could be prepared in this two-dimensional system owing to the orthogonal separation. Moreover, this two-dimensional liquid chromatography method was beneficial for the preparation of relatively trace flavonoid compounds, which were enriched in the first dimension and further purified in the second dimension. Totally, 24 flavonoid compounds with high purity were obtained. The results demonstrated that the off-line two-dimensional liquid chromatography method was effective for the preparative separation and purification of flavonoids from licorice. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal and Magnetic Structures in Layered, Transition Metal Dihalides and Trihalides

DOE PAGES

McGuire, Michael A.

2017-04-27

Materials composed of two dimensional layers bonded to one another through weak van der Waals interactions often exhibit strongly anisotropic behaviors and can be cleaved into very thin specimens and sometimes into monolayer crystals. Interest in such materials is driven by the study of low dimensional physics and the design of functional heterostructures. Binary compounds with the compositions MX 2 and MX 3 where M is a metal cation and X is a halogen anion often form such structures. Magnetism can be incorporated by choosing a transition metal with a partially filled d-shell for M, enabling ferroic responses for enhancedmore » functionality. Here we give a brief overview of binary transition metal dihalides and trihalides, summarizing their crystallographic properties and long-range-ordered magnetic structures, focusing on those materials with layered crystal structures and partially filled d-shells required for combining low dimensionality and cleavability with magnetism.« less

Quantitative thin layer chromatographic multi-sulfonamide screening procedure.

PubMed

Thomas, M H; Soroka, K E; Thomas, S H

1983-07-01

In-situ optical scanning of fluorescamine derivatives on thin layer silica gel plates provides a rapid method for the determination of multiple sulfonamides at levels below 0.1 ppm. Sample preparation is minimal. Homogenized liver or muscle is extracted with ethyl acetate and then back-extracted into 0.2M glycine buffer. After pH adjustment, the extract is washed with hexane and extracted with methylene chloride. The organic phase is evaporated to dryness and reconstituted in methanol. Pre-adsorbent layer silica gel plates are used for chromatography. The method has been applied to residues of sulfamethazine, sulfadimethoxine, sulfathiazole, sulfaquinoxaline, and sulfabromomethazine in cattle, swine, turkey, and duck tissues.

A Tetrodotoxin-Producing Vibrio Strain, LM-1, from the Puffer Fish Fugu vermicularis radiatus

PubMed Central

Lee, Myoung-Ja; Jeong, Dong-Youn; Kim, Woo-Seong; Kim, Hyun-Dae; Kim, Cheorl-Ho; Park, Won-Whan; Park, Yong-Ha; Kim, Kyung-Sam; Kim, Hyung-Min; Kim, Dong-Soo

2000-01-01

Identification of tetrodotoxin (TTX) and its derivatives produced from a Vibrio strain in the intestine of the puffer fish Fugu vermicularis radiatus was performed by thin-layer chromatography, electrophoresis, high-performance liquid chromatography, and gas chromatography-mass spectrometry, together with a mouse bioassay for toxicity. It was demonstrated that the isolated bacterium produced TTX, 4-epi-TTX, and anhTTX during cultivation, suggesting that Vibrio strains are responsible for the toxification of the puffer fish. PMID:10742263

[A thin-layer chromatography method for determining the styrene metabolites mandelic and phenylglyoxylic acid in urine].

PubMed

Gartzke, J; Burck, D

1989-06-01

A thin-layer chromatographic method is described for the determination of mandelic and phenyglyoxillic acid on silicagel (Silufol UV 254) after extraction from urine of styrene exposed workers. The quantitative determination was performed after eluting the spots. Phenylglyoxilic acid was measured at 255 nm and mandelic acid by derivative spectroscopically estimation of the .CH(OH).COOH -chromophore at 217 nm or by a three-wavelength mode, respectively. The recovery in urine was 80-104% for phenylglyoxilic acid and 99-105% for mandelic acid.

Guest-Induced Two-Way Structural Transformation in a Layered Metal-Organic Framework Thin Film.

PubMed

Haraguchi, Tomoyuki; Otsubo, Kazuya; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

2016-12-28

Fabrication of thin films made of metal-organic frameworks (MOFs) has been intensively pursued for practical applications that use the structural response of MOFs. However, to date, only physisorption-induced structural response has been studied in these films. Chemisorption can be expected to provide a remarkable structural response because of the formation of bonds between guest molecules and reactive metal sites in host MOFs. Here, we report that chemisorption-induced two-way structural transformation in a nanometer-sized MOF thin film. We prepared a two-dimensional layered-type MOF Fe[Pt(CN) 4 ] thin film using a step-by-step approach. Although the as-synthesized film showed poor crystallinity, the dehydrated form of this thin film had a highly oriented crystalline nature (Film-D) as confirmed by synchrotron X-ray diffraction (XRD). Surprisingly, under water and pyridine vapors, Film-D showed chemisorption-induced dynamic structural transformations to Fe(L) 2 [Pt(CN) 4 ] thin films [L = H 2 O (Film-H), pyridine (Film-P)], where water and pyridine coordinated to the open Fe 2+ site. Dynamic structural transformations were also confirmed by in situ XRD, sorption measurement, and infrared reflection absorption spectroscopy. This is the first report of chemisorption-induced dynamic structural response in a MOF thin film, and it provides useful insights, which would lead to future practical applications of MOFs utilizing chemisorption-induced structural responses.

Microscale Synthesis and Analysis of a Dipeptide.

ERIC Educational Resources Information Center

Blatchly, Richard A.; And Others

1989-01-01

Described is a microscale chemistry laboratory in which a dipeptide is synthesized from its component amino acids and analyzed using chiral-phase thin-layer chromatography. Experimental procedures, and materials are discussed. Twelve references are listed. (CW)

An Introduction to Lipid Analysis in the Cell Biology Laboratory.

ERIC Educational Resources Information Center

Schuh, Timothy J.

2002-01-01

Explains a thin-layer chromatography (TLC) experiment that allows students to study complex mixtures of lipids using small volumes. Uses a water-soluble dye to stain lipids that is fast and safe. (YDS)

Aggregation, Deposition and Release of Graphene Oxide Nanomaterials in the Aquatic Environment

EPA Science Inventory

Graphene is an atomically thin two dimensional carbon-based nanomaterial that is composed of a single layer of sp2 – hybridized carbon atoms as found in graphite.1, 2 Usage of graphene-based nanomaterials is increasing rapidly and these materials are predicted to be the most abun...

Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics.

PubMed

Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

2014-10-08

Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT~0.9 GHz, fMAX~1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics.

Few layer epitaxial germanene: a novel two-dimensional Dirac material

NASA Astrophysics Data System (ADS)

Dávila, María Eugenia; Le Lay, Guy

2016-02-01

Monolayer germanene, a novel graphene-like germanium allotrope akin to silicene has been recently grown on metallic substrates. Lying directly on the metal surfaces the reconstructed atom-thin sheets are prone to lose the massless Dirac fermion character and unique associated physical properties of free standing germanene. Here, we show that few layer germanene, which we create by dry epitaxy on a gold template, possesses Dirac cones thanks to a reduced interaction. This finding established on synchrotron-radiation-based photoemission, scanning tunneling microscopy imaging and surface electron diffraction places few layer germanene among the rare two-dimensional Dirac materials. Since germanium is currently used in the mainstream Si-based electronics, perspectives of using germanene for scaling down beyond the 5 nm node appear very promising. Other fascinating properties seem at hand, typically the robust quantum spin Hall effect for applications in spintronics and the engineering of Floquet Majorana fermions by light for quantum computing.

Few layer epitaxial germanene: a novel two-dimensional Dirac material.

PubMed

Dávila, María Eugenia; Le Lay, Guy

2016-02-10

Monolayer germanene, a novel graphene-like germanium allotrope akin to silicene has been recently grown on metallic substrates. Lying directly on the metal surfaces the reconstructed atom-thin sheets are prone to lose the massless Dirac fermion character and unique associated physical properties of free standing germanene. Here, we show that few layer germanene, which we create by dry epitaxy on a gold template, possesses Dirac cones thanks to a reduced interaction. This finding established on synchrotron-radiation-based photoemission, scanning tunneling microscopy imaging and surface electron diffraction places few layer germanene among the rare two-dimensional Dirac materials. Since germanium is currently used in the mainstream Si-based electronics, perspectives of using germanene for scaling down beyond the 5 nm node appear very promising. Other fascinating properties seem at hand, typically the robust quantum spin Hall effect for applications in spintronics and the engineering of Floquet Majorana fermions by light for quantum computing.

Few layer epitaxial germanene: a novel two-dimensional Dirac material

PubMed Central

Dávila, María Eugenia; Le Lay, Guy

2016-01-01

Monolayer germanene, a novel graphene-like germanium allotrope akin to silicene has been recently grown on metallic substrates. Lying directly on the metal surfaces the reconstructed atom-thin sheets are prone to lose the massless Dirac fermion character and unique associated physical properties of free standing germanene. Here, we show that few layer germanene, which we create by dry epitaxy on a gold template, possesses Dirac cones thanks to a reduced interaction. This finding established on synchrotron-radiation-based photoemission, scanning tunneling microscopy imaging and surface electron diffraction places few layer germanene among the rare two-dimensional Dirac materials. Since germanium is currently used in the mainstream Si-based electronics, perspectives of using germanene for scaling down beyond the 5 nm node appear very promising. Other fascinating properties seem at hand, typically the robust quantum spin Hall effect for applications in spintronics and the engineering of Floquet Majorana fermions by light for quantum computing. PMID:26860590

Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics

PubMed Central

Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

2014-01-01

Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT ~ 0.9 GHz, fMAX ~ 1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics. PMID:25295573

The hard parts (trophi) of the rotifer mastax do contain chitin: evidence from studies on Brachionus plicatilis.

PubMed

Klusemann, J; Kleinow, W; Peters, W

1990-01-01

The jaws (trophi) of the rotifer Brachionus plicatilis are soluble in strong acids but are resistant to long treatments by strong alkali. They show the same buoyant density as chitin and also as the chitin-containing layers of rotifer egg-shells. The presence of chitin in these structures was confirmed using the following techniques: chitosan-tests, thin-layer chromatography of trophi-hydrolysates which revealed glucosamine, by dissolving trophi with chitinase and electron microscopic WGA/gold-labelling. The content of chitin in the trophi was estimated by two different methods to be approx. 64% (50-75%).

Transformers: Shape-Changing Space Systems Built with Robotic Textiles

NASA Technical Reports Server (NTRS)

Stoica, Adrian

2013-01-01

Prior approaches to transformer-like robots had only very limited success. They suffer from lack of reliability, ability to integrate large surfaces, and very modest change in overall shape. Robots can now be built from two-dimensional (2D) layers of robotic fabric. These transformers, a new kind of robotic space system, are dramatically different from current systems in at least two ways. First, the entire transformer is built from a single, thin sheet; a flexible layer of a robotic fabric (ro-fabric); or robotic textile (ro-textile). Second, the ro-textile layer is foldable to small volume and self-unfolding to adapt shape and function to mission phases.

Identification of Ginkgo biloba supplements adulteration using high performance thin layer chromatography and ultra high performance liquid chromatography-diode array detector-quadrupole time of flight-mass spectometry

USDA-ARS?s Scientific Manuscript database

Ginkgo biloba is one of the most widely sold herbal supplements and medicines in the world. Its popularity stems to have a positive effect on memory and the circulatory system in clinical studies. As ginkgo popularity increased, non-proprietary extracts were introduced claiming to have similar phyto...

Edge Delamination of Monolayer Transition Metal Dichalcogenides.

PubMed

Ly, Thuc Hue; Yun, Seok Joon; Thi, Quoc Huy; Zhao, Jiong

2017-07-25

Delamination of thin films from the supportive substrates is a critical issue within the thin film industry. The emergent two-dimensional, atomic layered materials, including transition metal dichalcogenides, are highly flexible; thus buckles and wrinkles can be easily generated and play vital roles in the corresponding physical properties. Here we introduce one kind of patterned buckling behavior caused by the delamination from a substrate initiated at the edges of the chemical vapor deposition synthesized monolayer transition metal dichalcogenides, led by thermal expansion mismatch. The atomic force microscopy and optical characterizations clearly showed the puckered structures associated with the strain, whereas the transmission electron microscopy revealed the special sawtooth-shaped edges, which break the geometrical symmetry for the buckling behavior of hexagonal samples. The condition of the edge delamination is in accordance with the fracture behavior of thin film interfaces. This edge delamination and buckling process is universal for most ultrathin two-dimensional materials, which requires more attention in various future applications.

Metastable Superconductivity in Two-Dimensional IrTe2 Crystals.

PubMed

Yoshida, Masaro; Kudo, Kazutaka; Nohara, Minoru; Iwasa, Yoshihiro

2018-05-09

Two-dimensional (2D) materials exhibit unusual physical and chemical properties that are attributed to the thinning-induced modification of their electronic band structure. Recently, reduced thickness was found to dramatically impact not only the static electronic structure, but also the dynamic ordering kinetics. The ordering kinetics of first-order phase transitions becomes significantly slowed with decreasing thickness, and metastable supercooled states can be realized by thinning alone. We therefore focus on layered iridium ditelluride (IrTe 2 ), a charge-ordering system that is transformed into a superconductor by suppressing its first-order transition. Here, we discovered a persistent superconducting zero-resistance state in mechanically exfoliated IrTe 2 thin flakes. The maximum superconducting critical temperature ( T c ) was identical to that which is chemically optimized, and the emergent superconductivity was revealed to have a metastable nature. The discovered robust metastable superconductivity suggests that 2D material is a new platform to induce, control, and functionalize metastable electronic states that are inaccessible in bulk crystals.

Controllable Growth of Large-Size Crystalline MoS2 and Resist-Free Transfer Assisted with a Cu Thin Film.

PubMed

Lin, Ziyuan; Zhao, Yuda; Zhou, Changjian; Zhong, Ren; Wang, Xinsheng; Tsang, Yuen Hong; Chai, Yang

2015-12-21

Two-dimensional MoS2 is a promising material for future nanoelectronics and optoelectronics. It has remained a great challenge to grow large-size crystalline and high surface coverage monolayer MoS2. In this work, we investigate the controllable growth of monolayer MoS2 evolving from triangular flakes to continuous thin films by optimizing the concentration of gaseous MoS2, which has been shown a both thermodynamic and kinetic growth factor. A single-crystal monolayer MoS2 larger than 300 μm was successfully grown by suppressing the nuclei density and supplying sufficient source. Furthermore, we present a facile process of transferring the centimeter scale MoS2 assisted with a copper thin film. Our results show the absence of observable residues or wrinkles after we transfer MoS2 from the growth substrates onto flat substrates using this technique, which can be further extended to transfer other two-dimensional layered materials.

Controllable Growth of Large-Size Crystalline MoS2 and Resist-Free Transfer Assisted with a Cu Thin Film

NASA Astrophysics Data System (ADS)

Lin, Ziyuan; Zhao, Yuda; Zhou, Changjian; Zhong, Ren; Wang, Xinsheng; Tsang, Yuen Hong; Chai, Yang

2015-12-01

Two-dimensional MoS2 is a promising material for future nanoelectronics and optoelectronics. It has remained a great challenge to grow large-size crystalline and high surface coverage monolayer MoS2. In this work, we investigate the controllable growth of monolayer MoS2 evolving from triangular flakes to continuous thin films by optimizing the concentration of gaseous MoS2, which has been shown a both thermodynamic and kinetic growth factor. A single-crystal monolayer MoS2 larger than 300 μm was successfully grown by suppressing the nuclei density and supplying sufficient source. Furthermore, we present a facile process of transferring the centimeter scale MoS2 assisted with a copper thin film. Our results show the absence of observable residues or wrinkles after we transfer MoS2 from the growth substrates onto flat substrates using this technique, which can be further extended to transfer other two-dimensional layered materials.

Optoelectronic transport properties in amorphous/crystalline silicon solar cell heterojunctions measured by frequency-domain photocarrier radiometry: multi-parameter measurement reliability and precision studies.

PubMed

Zhang, Y; Melnikov, A; Mandelis, A; Halliop, B; Kherani, N P; Zhu, R

2015-03-01

A theoretical one-dimensional two-layer linear photocarrier radiometry (PCR) model including the presence of effective interface carrier traps was used to evaluate the transport parameters of p-type hydrogenated amorphous silicon (a-Si:H) and n-type crystalline silicon (c-Si) passivated by an intrinsic hydrogenated amorphous silicon (i-layer) nanolayer. Several crystalline Si heterojunction structures were examined to investigate the influence of the i-layer thickness and the doping concentration of the a-Si:H layer. The experimental data of a series of heterojunction structures with intrinsic thin layers were fitted to PCR theory to gain insight into the transport properties of these devices. The quantitative multi-parameter results were studied with regard to measurement reliability (uniqueness) and precision using two independent computational best-fit programs. The considerable influence on the transport properties of the entire structure of two key parameters that can limit the performance of amorphous thin film solar cells, namely, the doping concentration of the a-Si:H layer and the i-layer thickness was demonstrated. It was shown that PCR can be applied to the non-destructive characterization of a-Si:H/c-Si heterojunction solar cells yielding reliable measurements of the key parameters.

Optoelectronic transport properties in amorphous/crystalline silicon solar cell heterojunctions measured by frequency-domain photocarrier radiometry: Multi-parameter measurement reliability and precision studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y.; Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094; Melnikov, A.

2015-03-15

A theoretical one-dimensional two-layer linear photocarrier radiometry (PCR) model including the presence of effective interface carrier traps was used to evaluate the transport parameters of p-type hydrogenated amorphous silicon (a-Si:H) and n-type crystalline silicon (c-Si) passivated by an intrinsic hydrogenated amorphous silicon (i-layer) nanolayer. Several crystalline Si heterojunction structures were examined to investigate the influence of the i-layer thickness and the doping concentration of the a-Si:H layer. The experimental data of a series of heterojunction structures with intrinsic thin layers were fitted to PCR theory to gain insight into the transport properties of these devices. The quantitative multi-parameter results weremore » studied with regard to measurement reliability (uniqueness) and precision using two independent computational best-fit programs. The considerable influence on the transport properties of the entire structure of two key parameters that can limit the performance of amorphous thin film solar cells, namely, the doping concentration of the a-Si:H layer and the i-layer thickness was demonstrated. It was shown that PCR can be applied to the non-destructive characterization of a-Si:H/c-Si heterojunction solar cells yielding reliable measurements of the key parameters.« less

The Effect of pH and Color Stability of Anthocyanin on Food Colorant

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Wulandari, L.; Wartono, M. W.; Munawaroh, H.; Ramelan, A. H.

2017-04-01

Anthocyanins are naturally occurring pigments of red and purple. Red anthocyanin pigments provide a strong and sharp and widely applied in various industries such as food coloring or drink. Anthocyanins isolated by maceration, extraction and thin layer chromatography (TLC). The extract has been obtained from the initial stages of maceration then separated into several fractions by chromatography to isolate fractions colored dark red. Identification of chemical compounds with TLC (Thin Layer Chromatography) is able to distinguish the fraction of anthocyanin produced. FTIR (Fourier Transform Infrared Spectroscopy) used to identification of the functional group of a compound. The UV-Vis absorption spectra have to produce maximum absorbance values that describe the intensity of anthocyanin spectra in different colors for different pH. Anthocyanins are more stable at low pH (acidic conditions) which gives a red pigment. Meanwhile, the higher the pH value of anthocyanin will provide color fading of the color blue. So as a food colorant, anthocyanin with a low pH or height pH has a significant effect on the food colorant.

The isolation and characterisation of jacalin [Artocarpus heterophyllus (jackfruit) lectin] based on its charge properties.

PubMed

Kabir, S

1995-02-01

Jackfruit extracts contain a protein termed jacalin which possesses diverse biological properties. A detailed analysis of its charge properties has been lacking. The present investigation was initiated to study isoelectric properties of jacalin in detail and to isolate a single isoform of jacalin. Jacalin was isolated from jackfruit extracts by affinity chromatography on immunoglobulin-A immobilised to Sepharose 4B. Various techniques such as ion-exchange chromatography, isoelectric focusing (IEF) on polyacrylamide gels and preparative liquid IEF with the Rotofor cell were used. When analysed by IEF on thin layer polyacrylamide gels, jacalin was resolved into 35 bands over a pH range of 5.0-8.5. Upon SDS-PAGE in the second dimension all these charge species gave rise to only two-bands at 12 and 15.4 kDa. The lectin was mostly eluted with 50 and 100 mM sodium chloride when jackfruit extracts were fractionated on an anion-exchange column of DEAE-cellulose. In a single 6 hour run by preparative IEF with the Rotofor cell in the pH range of 3-9.5, it has been possible to isolate pure jacalin fractions containing fewer number of charged isomers. A single jacalin isoform was isolated by subjecting a Rotofor fraction containing fewer charged species to preparative IEF on thin layer polyacrylamide gel and eluting the band of interest from the gel. The isolated jacalin isoform was biologically active as it agglutinated erythrocytes. The study reveals the complexity of jacalin as it exists as multiple charge isomers over a broad pH range. By performing preparative IEF in solution as well as in thin layer polyacrylamide gels, it was possible to isolate a single jacalin isoform with the retention of biological activity.

Characterization of E 471 food emulsifiers by high-performance thin-layer chromatography-fluorescence detection.

PubMed

Oellig, Claudia; Brändle, Klara; Schwack, Wolfgang

2018-07-13

Mono- and diacylglycerol (MAG and DAG) emulsifiers, also known as food additive E 471, are widely used to adjust techno-functional properties in various foods. Besides MAGs and DAGs, E 471 emulsifiers additionally comprise different amounts of triacylglycerols (TAGs) and free fatty acids (FFAs). MAGs, DAGs, TAGs and FFAs are generally determined by high-performance liquid chromatography (HPLC) or gas chromatography (GC) coupled to mass selective detection, analyzing the individual representatives of the lipid classes. In this work we present a rapid and sensitive method for the determination of MAGs, DAGs, TAGs and FFAs in E 471 emulsifiers by high-performance thin-layer chromatography with fluorescence detection (HPTLC-FLD), including a response factor system for quantitation. Samples were simply dissolved and diluted with t-butyl methyl ether before a two-fold development was performed on primuline pre-impregnated LiChrospher silica gel plates with diethyl ether and n-pentane/n-hexane/diethyl ether (52:20:28, v/v/v) as the mobile phases to 18 and 75 mm, respectively. For quantitation, the plate was scanned in the fluorescence mode at UV 366/>400 nm, when the cumulative signal for each lipid class was used. Calibration was done with 1,2-distearin and amounts of lipid classes were calculated with response factors and expressed as monostearin, distearin, tristearin and stearic acid. Limits of detection and quantitation were 1 and 4 ng/zone, respectively, for 1,2-distearin. Thus, the HPTLC-FLD approach represents a simple, rapid and convenient screening alternative to HPLC and GC analysis of the individual compounds. Visual detection additionally enables an easy characterization and the direct comparison of emulsifiers through the lipid class pattern, when utilized as a fingerprint. Copyright © 2018 Elsevier B.V. All rights reserved.

In-plane heterostructures of graphene and hexagonal boron nitride with controlled domain sizes

NASA Astrophysics Data System (ADS)

Liu, Zheng; Ma, Lulu; Shi, Gang; Zhou, Wu; Gong, Yongji; Lei, Sidong; Yang, Xuebei; Zhang, Jiangnan; Yu, Jingjiang; Hackenberg, Ken P.; Babakhani, Aydin; Idrobo, Juan-Carlos; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M.

2013-02-01

Graphene and hexagonal boron nitride (h-BN) have similar crystal structures with a lattice constant difference of only 2%. However, graphene is a zero-bandgap semiconductor with remarkably high carrier mobility at room temperature, whereas an atomically thin layer of h-BN is a dielectric with a wide bandgap of ~5.9 eV. Accordingly, if precise two-dimensional domains of graphene and h-BN can be seamlessly stitched together, hybrid atomic layers with interesting electronic applications could be created. Here, we show that planar graphene/h-BN heterostructures can be formed by growing graphene in lithographically patterned h-BN atomic layers. Our approach can create periodic arrangements of domains with size ranging from tens of nanometres to millimetres. The resulting graphene/h-BN atomic layers can be peeled off the growth substrate and transferred to various platforms including flexible substrates. We also show that the technique can be used to fabricate two-dimensional devices, such as a split closed-loop resonator that works as a bandpass filter.

Preparative separation of capsaicin and dihydrocapsaicin from Capsicum frutescens by high-speed counter-current chromatography.

PubMed

Peng, Aihua; Ye, Haoyu; Li, Xia; Chen, Lijuan

2009-09-01

Capsaicin and dihydrocapsaicin are two main bioactive components of Capsicum frutescens and are widely used as food additives and drugs in China and India. Due to their similarity in structures, isolation of capsaicin and dihydrocapsaicin with traditional methods such as silica gel column chromatography, normal-phase thin-layer chromatography (TLC) becomes difficult. This study involves separating capsaicin and dihydrocapsaicin with sufficient purity and recovery using high-speed counter-current chromatography (HSCCC) with a solvent system composed of n-hexane-ethyl acetate-methanol-water-acetic acid (20:20:20:20:2, v/v/v/v/v). Separation parameters such as sample volume, and sample concentration were first optimized on analytical HSCCC, and then scaled up to preparative HSCCC. 0.65 g capsaicin and 0.28 g dihydrocapsaicin were obtained from 1.2 g crude extract and their purities were 98.5 and 97.8%, respectively. The recoveries of the two compounds were 86.3 and 85.4%, respectively. The purity of the isolated compounds was analyzed by high-performance liquid chromatography (HPLC) and their structures were identified by (1)H nuclear magnetic resonance (NMR) and (13)C NMR analysis.

Lipophilicity Assessment of Ruthenium(II)-Arene Complexes by the Means of Reversed-Phase Thin-Layer Chromatography and DFT Calculations

PubMed Central

Shweshein, Khalil Salem A. M.; Andrić, Filip; Radoičić, Aleksandra; Gruden-Pavlović, Maja; Tešić, Živoslav; Milojković-Opsenica, Dušanka

2014-01-01

The lipophilicity of ten ruthenium(II)-arene complexes was assessed by reversed-phase thin-layer chromatography (RP-TLC) on octadecyl silica stationary phase. The binary solvent systems composed of water and acetonitrile were used as mobile phase in order to determine chromatographic descriptors for lipophilicity estimation. Octanol-water partition coefficient, logK OW, of tested complexes was experimentally determined using twenty-eight standard solutes which were analyzed under the same chromatographic conditions as target substances. In addition, ab initio density functional theory (DFT) computational approach was employed to calculate logK OW values from the differences in Gibbs' free solvation energies of the solute transfer from n-octanol to water. A good overall agreement between DFT calculated and experimentally determined logK OW values was established (R 2 = 0.8024–0.9658). PMID:24587761

Composite glycerol/graphite/aromatic acid matrices for thin-layer chromatography/matrix-assisted laser desorption/ionization mass spectrometry of heterocyclic compounds.

PubMed

Esparza, Cesar; Borisov, R S; Varlamov, A V; Zaikin, V G

2016-10-28

New composite matrices have been suggested for the analysis of mixtures of different synthetic organic compounds (N-containing heterocycles and erectile dysfunction drugs) by thin layer chromatography/matrix-assisted laser desorption ionization time-of-flight mass spectrometry (TLC/MALDI-TOF). Different mixtures of classical MALDI matrices and graphite particles dispersed in glycerol were used for the registration of MALDI mass spectra directly from TLC plates after analytes separation. In most of cases, the mass spectra possessed [M+H] + ions; however, for some analytes only [M+Na] + and [M+K] + ions were observed. These ions have been used to generate visualized TLC chromatograms. The described approach increases the desorption/ionization efficiencies of analytes separated by TLC, prevent spot blurring, simplifies and decrease time for sample preparation. Copyright © 2016 Elsevier B.V. All rights reserved.

Capillary-Force-Assisted Clean-Stamp Transfer of Two-Dimensional Materials.

PubMed

Ma, Xuezhi; Liu, Qiushi; Xu, Da; Zhu, Yangzhi; Kim, Sanggon; Cui, Yongtao; Zhong, Lanlan; Liu, Ming

2017-11-08

A simple and clean method of transferring two-dimensional (2D) materials plays a critical role in the fabrication of 2D electronics, particularly the heterostructure devices based on the artificial vertical stacking of various 2D crystals. Currently, clean transfer techniques rely on sacrificial layers or bulky crystal flakes (e.g., hexagonal boron nitride) to pick up the 2D materials. Here, we develop a capillary-force-assisted clean-stamp technique that uses a thin layer of evaporative liquid (e.g., water) as an instant glue to increase the adhesion energy between 2D crystals and polydimethylsiloxane (PDMS) for the pick-up step. After the liquid evaporates, the adhesion energy decreases, and the 2D crystal can be released. The thin liquid layer is condensed to the PDMS surface from its vapor phase, which ensures the low contamination level on the 2D materials and largely remains their chemical and electrical properties. Using this method, we prepared graphene-based transistors with low charge-neutral concentration (3 × 10 10 cm -2 ) and high carrier mobility (up to 48 820 cm 2 V -1 s -1 at room temperature) and heterostructure optoelectronics with high operation speed. Finally, a capillary-force model is developed to explain the experiment.

Two-dimensional X-ray diffraction and transmission electron microscopy study on the effect of magnetron sputtering atmosphere on GaN/SiC interface and gallium nitride thin film crystal structure

NASA Astrophysics Data System (ADS)

Shen, Huaxiang; Zhu, Guo-Zhen; Botton, Gianluigi A.; Kitai, Adrian

2015-03-01

The growth mechanisms of high quality GaN thin films on 6H-SiC by sputtering were investigated by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The XRD θ-2θ scans show that high quality ( 0002 ) oriented GaN was deposited on 6H-SiC by reactive magnetron sputtering. Pole figures obtained by 2D-XRD clarify that GaN thin films are dominated by ( 0002 ) oriented wurtzite GaN and { 111 } oriented zinc-blende GaN. A thin amorphous silicon oxide layer on SiC surfaces observed by STEM plays a critical role in terms of the orientation information transfer from the substrate to the GaN epilayer. The addition of H2 into Ar and/or N2 during sputtering can reduce the thickness of the amorphous layer. Moreover, adding 5% H2 into Ar can facilitate a phase transformation from amorphous to crystalline in the silicon oxide layer and eliminate the unwanted { 3 3 ¯ 02 } orientation in the GaN thin film. Fiber texture GaN thin films can be grown by adding 10% H2 into N2 due to the complex reaction between H2 and N2.

Comparison and characterization of soybean and sunflower lecithins used for chocolate production by high-performance thin-layer chromatography with fluorescence detection and electrospray mass spectrometry.

PubMed

Krüger, Stephanie; Bürmann, Laura; Morlock, Gertrud E

2015-03-25

The scarce availability of nongenetically modified soybeans on the world market represents a growing problem for food manufacturers. Hence, in this study the effects of substituting soybean with sunflower lecithin were investigated with regard to chocolate production. The glycerophospholipid pattern of the different lecithin samples was investigated by high-performance thin-layer chromatography fluorescence detection (HPTLC-FLD) and by HPTLC-positive ion electrospray ionization mass spectrometry (ESI(+)-MS) via the TLC-MS Interface and by scanning HPTLC-matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOFMS). Especially, the contents of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were of interest due to the influencing effects of these two glycerophospholipids on the rheological parameters of chocolate production. The lecithin substitution led to only slight differences in the rheological parameters of milk and dark chocolate. Limits of detection (LODs) and limits of quantification (LOQs) of seven glycerophospholipids were studied for three detection modes. Mean LODs ranged from 8 to 40 mg/kg for HPTLC-FLD and, using a single-quadrupole MS, from 10 to 280 mg/kg for HPTLC-ESI(+)-MS as well as from 15 to 310 mg/kg for HPTLC-FLD-ESI(+)-MS recorded after derivatization with the primuline reagent.

Formation of (4R)- and (4S)-4-hydroxyochratoxin A from ochratoxin A by liver microsomes from various species.

PubMed Central

Størmer, F C; Hansen, C E; Pedersen, J I; Hvistendahl, G; Aasen, A J

1981-01-01

Two metabolic products were formed from ochratoxin A by human, pig, and rat liver microsomal fractions in the presence of reduced nicotinamide adenine dinucleotide phosphate. They were isolated from the incubation mixture in the presence of pig liver microsomes by extraction, thin-layer chromatography, and high-pressure liquid chromatography Their structures are suggested to be (4R)- and (4S)-4-hydroxyochratoxin A on the basis of mass and nuclear magnetic resonance spectroscopy. Km and the maximum velocity for the formation of the two metabolites by human, pig, and rat microsomes were determined. Their formation was inhibited by carbon monoxide and metyrapone. The results indicate that the microsomal hydroxylation system is a cytochrome P-450 and that different species are involved in the formation of the two epimeric forms of 4-hydroxyochratoxin A. PMID:7316512

Integrated digital inverters based on two-dimensional anisotropic ReS₂ field-effect transistors

DOE PAGES

Liu, Erfu; Fu, Yajun; Wang, Yaojia; ...

2015-05-07

Semiconducting two-dimensional transition metal dichalcogenides are emerging as top candidates for post-silicon electronics. While most of them exhibit isotropic behaviour, lowering the lattice symmetry could induce anisotropic properties, which are both scientifically interesting and potentially useful. Here we present atomically thin rhenium disulfide (ReS₂) flakes with unique distorted 1T structure, which exhibit in-plane anisotropic properties. We fabricated monolayer and few-layer ReS₂ field-effect transistors, which exhibit competitive performance with large current on/off ratios (~10⁷) and low subthreshold swings (100 mV per decade). The observed anisotropic ratio along two principle axes reaches 3.1, which is the highest among all known two-dimensional semiconductingmore » materials. Furthermore, we successfully demonstrated an integrated digital inverter with good performance by utilizing two ReS₂ anisotropic field-effect transistors, suggesting the promising implementation of large-scale two-dimensional logic circuits. Our results underscore the unique properties of two-dimensional semiconducting materials with low crystal symmetry for future electronic applications.« less

Thin-layer chromatography coupled with high performance liquid chromatography for determining tetrabromobisphenol A/S and their derivatives in soils.

PubMed

Liu, Aifeng; Shen, Zhaoshuang; Tian, Yong; Shi, Rongguang; Liu, Yi; Zhao, Zongshan; Xian, Mo

2017-12-01

As brominated flame retardants (BFRs), tetrabromobisphenol A/S (TBBPA/S) and their derivatives have raised wide concerns owing to their widely usage, distributions and adverse effects on human health, thus monitoring these BFRs was urgently needed. In this study, a rapid and cost-effective method based on thin-layer chromatography (TLC) sample pre-treatment coupled with high performance liquid chromatography-diode array detector (HPLC-DAD) (UV=214nm) was developed for determining TBBPA/S and their derivatives in soils, including TBBPA, TBBPA bis(allyl ether) (TBBPA-BAE), TBBPA bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), TBBPS bis(allyl ether) (TBBPS-BAE) and TBBPS bis(2,3-dibromopropyl ether) (TBBPS-BDBPE). The method detection limits (MDLs) and the method quantification limits (MQLs) for these BFRs ranged from 0.023 to 0.087μgg -1 dw and 0.076-0.29μgg -1 dw, respectively. The recoveries were 41-108% and both RSD of repeatability and intermediate precision were less than 11%. The developed method presented good performance for analyzing natural soil samples collected from BFRs industrial park, suggesting its great application potential for monitoring environmental TBBPA/S and their derivatives. Copyright © 2017 Elsevier B.V. All rights reserved.

Waxes: A Forgotten Topic in Lipid Teaching.

ERIC Educational Resources Information Center

Dominguez, Eva; Heredia, Antonio

1998-01-01

Reviews the biological importance of the lipids categorized as waxes and describes some of the organic chemistry of these compounds. Presents a short laboratory exercise on the extraction of plant waxes and their analysis by thin layer chromatography. (Author/CCM)

Diffraction of a plane wave on two-dimensional conductive structures and a surface wave

NASA Astrophysics Data System (ADS)

Davidovich, Mikhael V.

2018-04-01

We consider the structures type of two-dimensional electron gas in the form of a thin conductive, in particular, graphene films described by tensor conductivity, which are isolated or located on the dielectric layers. The dispersion equation for hybrid modes, as well as scattering parameters. We show that free wave (eigenwaves) problem follow from the problem of diffraction when linking the amplitude of the current of the linear equations are unsolvable, i.e., the determinant of this system is zero. As a particular case the dispersion equation follow from the conditions of matching (with zero reflection coefficient).

CFL3D Contribution to the AIAA Supersonic Shock Boundary Layer Interaction Workshop

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.

2010-01-01

This paper documents the CFL3D contribution to the AIAA Supersonic Shock Boundary Layer Interaction Workshop, held in Orlando, Florida in January 2010. CFL3D is a Reynolds-averaged Navier-Stokes code. Four shock boundary layer interaction cases are computed using a one-equation turbulence model widely used for other aerodynamic problems of interest. Two of the cases have experimental data available at the workshop, and two of the cases do not. The effect of grid, flux scheme, and thin-layer approximation are investigated. Comparisons are made to the available experimental data. All four cases exhibit strong three-dimensional behavior in and near the interaction regions, resulting from influences of the tunnel side-walls.

Lipids from the nacreous and prismatic layers of two Pteriomorpha Mollusc shells

NASA Astrophysics Data System (ADS)

Farre, B.; Dauphin, Y.

2009-04-01

Mollusc shells are the best-known Ca-carbonate biominerals. They are commonly described as a mineralized two layered structure: an outer layer composed of calcite prismatic units, and an internal layer composed of tablets of aragonite: the nacreous layer. An external organic layer (periostracum) is present in most taxa. However, the most common structure in the Mollusc shell is the aragonite crossed lamellar layer, but aragonite prisms, calcite foliated layers and homogeneous layers have been also described by Boggild (1930) in all the Mollusc orders. Since, more detailed descriptions of Bivalve shells have been done (Taylor et al., 1969, 1973). Despite the nacroprismatic arrangement is rare, calcite prismatic and aragonite nacreous layers are the best studied because of their simple 3D structure and large units. Among these Molluscs, some Bivalve species composed of these two layers are of commercial interest, such as the pearl oyster, Pinctada margaritifera, cultivated in French Polynesia to produce black pearls. It is well established that Mollusc shells are composite structures of organic and inorganic components (Hatchett, 1799; Grégoire et al., 1955; Beedham, 1958; Simkiss, 1965; Mutvei, 1969; Cuif et al., 1980; Berman et al., 1993; Kobayashi and Samata, 2006). Numerous studies are concerned with the organic matrix of the shell. Organic components are commonly obtained after a strong or mild decalcification process. They are said to consist of both a soluble and insoluble fraction. The main part of studies is dedicated to the soluble components, and among them, proteins (Grégoire et al., 1955; Grégoire, 1961; Krampitz et al., 1976; Samata et al., 1980, 2004; Weiner, 1983; Miyamoto et al., 2006). Despite the pioneering work of Wada (1980) sugars are usually neglected despite their role in biomineralization. The third component of the organic matrix of calcareous biominerals is lipids. To date, there is a paucity of information concerning the presence, abundance and composition of these components in Mollusc shells. Goulletquer and Wolowicz (1989) have estimated that proteins represent 90% of the organic matrix of the shell, carbohydrates vary from 0.15 to 0.29%, while lipids vary from 0.8 to 2.9%. Fatty acids, cholesterol, phytadienes and ketones have been described in modern and fossil shells (Cobabe and Pratt, 1995). Using a procedure to extract intra- and intercrystalline organic matrices, Collins et al. (1995) have detected n-alkanes, n-alcohols, fatty acids and sterols in modern shells. It is suggested that the contents and ratios of these components are dependant on the environment and phylogeny. Lipids of the nacreous layer of Pinctada are diverse, with cholesterol, fatty acids, triglycerides and other unknown components (Rousseau et al., 2006). It has been established that the main part of the soluble organic matrices of the nacreous layer is composed of acidic proteins (Samata, 1988, 1990), whereas the prismatic layer of Pinna is mainly composed of acidic and sulphated polysaccharides (Dauphin, 2002; Dauphin et al., 2003). The amino acid compositions of the two layers are also different (Samata, 1990). Because the organic matrices extracted from the aragonite nacre and calcite prisms are the best known materials, the lipids extracted from the calcite prisms of Pinna nobilis and Pinctada margaritifera and the aragonite nacre of P. margaritifera have been chosen as test material for characterisation of the lipid fraction of molusk shells. The nacreous layer of Pinctada is thick,whereas its prismatic layer is thin, and the prisms display complex structures. On the opposite, the calcitic prismatic layer of Pinna is thick, with no intraprismatic membranes, and its nacreous layer is thin and present only in the oldest part of the shell. Moreover, these layers have a simple geometry so that some organic components (membranes, wall…) said to be insoluble, are clearly visible. Lipids were extracted from the calcite prismatic and aragonite nacreous layer of two mollusc shells thanks organic solvents. Two methods were used for the characterisation of the lipid obtaiened Fourier Tranform Infrared Spectrometry and thin layed chromatography. Fourier Transform Infrared Spectrometry shows that lipids are present in both samples, but they are not similar. Thin layer chromatography confirms that lipids are different in the two studied layers, so that it may be suggested they are species-dependant, but also structure-dependant. Although not yet deciphered, their role in biomineralization and fossilisation processes is probably important.

High performance thin layer chromatography (HPTLC) and high performance liquid chromatography (HPLC) for the qualitative and quantitative analysis of Calendula officinalis-advantages and limitations.

PubMed

Loescher, Christine M; Morton, David W; Razic, Slavica; Agatonovic-Kustrin, Snezana

2014-09-01

Chromatography techniques such as HPTLC and HPLC are commonly used to produce a chemical fingerprint of a plant to allow identification and quantify the main constituents within the plant. The aims of this study were to compare HPTLC and HPLC, for qualitative and quantitative analysis of the major constituents of Calendula officinalis and to investigate the effect of different extraction techniques on the C. officinalis extract composition from different parts of the plant. The results found HPTLC to be effective for qualitative analysis, however, HPLC was found to be more accurate for quantitative analysis. A combination of the two methods may be useful in a quality control setting as it would allow rapid qualitative analysis of herbal material while maintaining accurate quantification of extract composition. Copyright © 2014 Elsevier B.V. All rights reserved.

Infiltrating a thin or single-layer opal with an atomic vapour: Sub-Doppler signals and crystal optics

NASA Astrophysics Data System (ADS)

Moufarej, Elias; Maurin, Isabelle; Zabkov, Ilya; Laliotis, Athanasios; Ballin, Philippe; Klimov, Vasily; Bloch, Daniel

2014-10-01

Artificial thin glass opals can be infiltrated with a resonant alkali-metal vapour, providing novel types of hybrid systems. The reflection at the interface between the substrate and the opal yields a resonant signal, which exhibits sub-Doppler structures in linear spectroscopy for a range of oblique incidences. This result is suspected to originate in an effect of the three-dimensional confinement of the vapour in the opal interstices. It is here extended to a situation where the opal is limited to a few- or even a single-layer opal film, which is a kind of bidimensional grating. We have developed a flexible one-dimensional layered optical model, well suited for a Langmuir-Blodgett opal. Once extended to the case of a resonant infiltration, the model reproduces quick variations of the lineshape with incidence angle or polarization. Alternately, for an opal limited to a single layer of identical spheres, a three-dimensional numerical calculation was developed. It predicts crystalline anisotropy, which is demonstrated through diffraction on an empty opal made of a single layer of polystyrene spheres.

Onset of two-dimensional superconductivity in space charge doped few-layer molybdenum disulfide

PubMed Central

Biscaras, Johan; Chen, Zhesheng; Paradisi, Andrea; Shukla, Abhay

2015-01-01

Atomically thin films of layered materials such as molybdenum disulfide (MoS2) are of growing interest for the study of phase transitions in two-dimensions through electrostatic doping. Electrostatic doping techniques giving access to high carrier densities are needed to achieve such phase transitions. Here we develop a method of electrostatic doping which allows us to reach a maximum n-doping density of 4 × 1014 cm−2 in few-layer MoS2 on glass substrates. With increasing carrier density we first induce an insulator to metal transition and subsequently an incomplete metal to superconductor transition in MoS2 with critical temperature ≈10 K. Contrary to earlier reports, after the onset of superconductivity, the superconducting transition temperature does not depend on the carrier density. Our doping method and the results we obtain in MoS2 for samples as thin as bilayers indicates the potential of this approach. PMID:26525386

Thin-layer chromatographic technique for rapid detection of bacterial phospholipases.

PubMed

Legakis, N J; Papavassiliou, J

1975-11-01

Silica gel thin-layer chromatography was employed to detect lecithinase activity induced from bacterial resting cell preparations induced from bacterial resting cell preparations incubated at 37 C for 4 h in the presence of purified egg yolk lecithin. Bacillus subtilis, Bacillus cereus, Serratia marcescens, and Pseudomonas aeruginosa hydrolyzed lecithin with the formation of free fatty acids as the sole lipid-soluble product. In none of the Escherichia coli and Citrobacter freundii strains tested could lecithinase activity be detected. Four among eight strains of Enterobacter aerogenes and one among 12 strains of Proteus tested produced negligible amounts of free fatty acid.

Investigation of Second- and Third-Harmonic Generation in Few-Layer Gallium Selenide by Multiphoton Microscopy

PubMed Central

Karvonen, Lasse; Säynätjoki, Antti; Mehravar, Soroush; Rodriguez, Raul D.; Hartmann, Susanne; Zahn, Dietrich R. T.; Honkanen, Seppo; Norwood, Robert A.; Peyghambarian, N.; Kieu, Khanh; Lipsanen, Harri; Riikonen, Juha

2015-01-01

Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy. Both second- and third-harmonic generation from few-layer GaSe flakes were observed. Unexpectedly, even the peak at the wavelength of 390 nm, corresponding to the fourth-harmonic generation or the sum frequency generation from third-harmonic generation and pump light, was detected during the spectral measurements in thin GaSe flakes. PMID:25989113

Two-dimensional chromatography of complex polymers, 8. Separation of fatty alcohol ethoxylates simultaneously by end group and chain length.

PubMed

Raust, Jacques-Antoine; Bruell, Adele; Sinha, Pritish; Hiller, Wolf; Pasch, Harald

2010-09-01

A comprehensive two-dimensional liquid chromatography system was developed to precisely describe the molecular heterogeneity of fatty alcohol ethoxylates. The end-group functionality was analyzed by gradient HPLC while ethylene oxide oligomer distributions were characterized by liquid adsorption chromatography. A baseline separation of all functionality fractions irrespective of the ethylene oxide oligomer chain length was achieved on nonpolar X-Terra(®) C(18) with a methanol-water gradient, whereas an isocratic flow of isopropanol-water on a polar Chromolith(®) Si column gave a separation according to the oligomer chain length without interference of the end-group distribution. The combination of these two methods to conduct online two-dimensional liquid chromatography experiments resulted in a comprehensive two-dimensional picture on the molecular heterogeneity of the sample.

Self-surface charge exfoliation and electrostatically coordinated 2D hetero-layered hybrids

PubMed Central

Yang, Min-Quan; Xu, Yi-Jun; Lu, Wanheng; Zeng, Kaiyang; Zhu, Hai; Xu, Qing-Hua; Ho, Ghim Wei

2017-01-01

At present, the technological groundwork of atomically thin two-dimensional (2D) hetero-layered structures realized by successive thin film epitaxial growth is in principle constrained by lattice matching prerequisite as well as low yield and expensive production. Here, we artificially coordinate ultrathin 2D hetero-layered metal chalcogenides via a highly scalable self-surface charge exfoliation and electrostatic coupling approach. Specifically, bulk metal chalcogenides are spontaneously exfoliated into ultrathin layers in a surfactant/intercalator-free medium, followed by unconstrained electrostatic coupling with a dissimilar transition metal dichalcogenide, MoSe2, into scalable hetero-layered hybrids. Accordingly, surface and interfacial-dominated photocatalysis reactivity is used as an ideal testbed to verify the reliability of diverse 2D ultrathin hetero-layered materials that reveal high visible-light photoreactivity, efficient charge transfer and intimate contact interface for stable cycling and storage purposes. Such a synthetic approach renders independent thickness and composition control anticipated to advance the development of ‘design-and-build' 2D layered heterojunctions for large-scale exploration and applications. PMID:28146147

Thin-layer approximation and algebraic model for separated turbulent flows

NASA Technical Reports Server (NTRS)

Baldwin, B.; Lomax, H.

1978-01-01

An algebraic turbulence model for two- and three-dimensional separated flows is specified that avoids the necessity for finding the edge of the boundary layer. Properties of the model are determined and comparisons made with experiment for an incident shock on a flat plate, separated flow over a compression corner, and transonic flow over an airfoil. Separation and reattachment points from numerical Navier-Stokes solutions agree with experiment within one boundary-layer thickness. Use of law-of-the-wall boundary conditions does not alter the predictions significantly. Applications of the model to other cases are contained in companion papers.

Application of Rapid Prototyping and Wire Arc Spray to the Fabrication of Injection Mold Tools (MSFC Center Director's Discretionary Fund)

NASA Technical Reports Server (NTRS)

Cooper, K. G.

2000-01-01

Rapid prototyping (RP) is a layer-by-layer-based additive manufacturing process for constructing three-dimensional representations of a computer design from a wax, plastic, or similar material. Wire arc spray (WAS) is a metal spray forming technique, which deposits thin layers of metal onto a substrate or pattern. Marshall Space Flight Center currently has both capabilities in-house, and this project proposed merging the two processes into an innovative manufacturing technique, in which intermediate injection molding tool halves were to be fabricated with RP and WAS metal forming.

Uniaxially aligned electrospun cellulose acetate nanofibers for thin layer chromatographic screening of hydroquinone and retinoic acid adulterated in cosmetics.

PubMed

Tidjarat, Siripran; Winotapun, Weerapath; Opanasopit, Praneet; Ngawhirunpat, Tanasait; Rojanarata, Theerasak

2014-11-07

Uniaxially aligned cellulose acetate (CA) nanofibers were successfully fabricated by electrospinning and applied to use as stationary phase for thin layer chromatography. The control of alignment was achieved by using a drum collector rotating at a high speed of 6000 rpm. Spin time of 6h was used to produce the fiber thickness of about 10 μm which was adequate for good separation. Without any chemical modification after the electrospinning process, CA nanofibers could be readily devised for screening hydroquinone (HQ) and retinoic acid (RA) adulterated in cosmetics using the mobile phase consisting of 65:35:2.5 methanol/water/acetic acid. It was found that the separation run on the aligned nanofibers over a distance of 5 cm took less than 15 min which was two to three times faster than that on the non-aligned ones. On the aligned nanofibers, the masses of HQ and RA which could be visualized were 10 and 25 ng, respectively, which were two times lower than those on the non-aligned CA fibers and five times lower than those on conventional silica plates due to the appearance of darker and sharper of spots on the aligned nanofibers. Furthermore, the proposed method efficiently resolved HQ from RA and ingredients commonly found in cosmetic creams. Due to the satisfactory analytical performance, facile and inexpensive production process, uniaxially aligned electrospun CA nanofibers are promising alternative media for planar chromatography. Copyright © 2014 Elsevier B.V. All rights reserved.

Step-by-step fabrication of a highly oriented crystalline three-dimensional pillared-layer-type metal-organic framework thin film confirmed by synchrotron X-ray diffraction.

PubMed

Otsubo, Kazuya; Haraguchi, Tomoyuki; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

2012-06-13

Fabrication of a crystalline ordered thin film based on the porous metal-organic frameworks (MOFs) is one of the practical applications of the future functional nanomaterials. Here, we report the creation of a highly oriented three-dimensional (3-D) porous pillared-layer-type MOF thin film on a metal substrate using a step-by-step approach based on liquid-phase epitaxy. Synchrotron X-ray diffraction (XRD) study clearly indicates that the thin film is crystalline and its orientation is highly controlled in both horizontal and vertical directions relative to the substrate. This report provides the first confirmation of details of not only the crystallinity but also the orientation of 3-D MOF thin film using synchrotron XRD. Moreover, we also demonstrate its guest adsorption/desorption behavior by using in situ XRD measurements. The results presented here would promise useful insights for fabrication of MOF-based nanodevices in the future.

Isolation and characterization of bioactive components from Mirabilis jalapa L. radix

PubMed Central

Gogoi, Jyotchna; Nakhuru, Khonamai Sewa; Policegoudra, Rudragoud S.; Chattopadhyay, Pronobesh; Rai, Ashok Kumar; Veer, Vijay

2015-01-01

The present investigation was carried out to isolate and characterize bioactive components from Mirabilis jalapa L. radix (紫茉莉根 zǐ mò lì gēn). Thin-layer chromatography was used for the separation of spots from fractions of the crude extract. Separated spots were collected for identification of their activities. Free-radical scavenging activity was evaluated by spraying thin-layer chromatography plates (spotted with fractions) with 0.2% of 2,2-diphenyl-1-picrylhydrazyl solution. Activity against human pathogens such as Staphylococcus aureus and Candida albicans were determined using the agar diffusion method. Potential spots were subjected to infrared (IR) analysis and gas chromatography for characterization. Two spots (5F1 and 1F3) showed free-radical scavenging activity. The 1F3 spot was active against both S. aureus and C. albicans, whereas the 5F1 spot was active against S. aureus only. IR spectral analysis indicated that 5F1 spot to be a triterpenoid. Using IR spectral analysis and an IR library search, the 1F3 spot was identified to be a flavone, which may have a hydroxyl group in ring “A” of the flavone nucleus. Our results indicated that the 1F3 and 5F1 spots are potential free-radical scavengers. Both 1F3 and 5F1 exhibited antimicrobial activity. IR spectral analysis coupled with an IR library search indicated 1F3 and 5F1 to be a flavone and a triterpenoid, respectively. PMID:26870679

Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain

DOE PAGES

Zhang, Wenrui; Li, Mingtao; Chen, Aiping; ...

2016-06-13

Two-dimensional (2D) nanostructures emerge as one of leading topics in fundamental materials science and could enable next generation nanoelectronic devices. Beyond graphene and molybdenum disulphide, layered complex oxides are another large group of promising 2D candidates because of their strong interplay of intrinsic charge, spin, orbital and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials exhibiting new phenomena beyond their conventional form. Here we report the strain-driven self-assembly of Bismuth-based supercells (SC) with a 2D layered structure, and elucidate the fundamental growth mechanism with combined experimental tools and first-principles calculations.more » The study revealed that the new layered structures were formed by the strain-enabled self-assembled atomic layer stacking, i.e., alternative growth of Bi 2O 2 layer and [Fe 0.5Mn 0.5]O 6 layer. The strain-driven approach is further demonstrated in other SC candidate systems with promising room-temperature multiferroic properties. This well-integrated theoretical and experimental study inspired by the Materials Genome Initiatives opens up a new avenue in searching and designing novel 2D layered complex oxides with enormous promises.« less

Characterization of crude oil biomarkers using comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry.

PubMed

Mogollón, Noroska Gabriela Salazar; Prata, Paloma Santana; Dos Reis, Jadson Zeni; Neto, Eugênio Vaz Dos Santos; Augusto, Fabio

2016-09-01

Oil samples from Recôncavo basin (NE Brazil), previously analyzed by traditional techniques such as gas chromatography coupled to tandem mass spectrometry, were evaluated using comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry and comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry along with simplified methods of samples preparation to evaluate the differences and advantages of these analytical techniques to better understand the development of the organic matter in this basin without altering the normal distribution of the compounds in the samples. As a result, the geochemical parameters calculated by comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry described better the origin, maturity, and biodegradation of both samples probably by increased selectivity, resolution, and sensitivity inherent of the multidimensional technique. Additionally, the detection of the compounds such as, the C(14α-) homo-26-nor-17α-hopane series, diamoretanes, nor-spergulanes, C19 -C26 A-nor-steranes and 4α-methylsteranes resolved and detected by comprehensive two-dimensional gas chromatography coupled to tandem mass spectrometry were key to classify and differentiate these lacustrine samples according to their maturity and deposition conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Growth of quantum three-dimensional structure of InGaAs emitting at 1 μm applicable for a broadband near-infrared light source

NASA Astrophysics Data System (ADS)

Ozaki, Nobuhiko; Kanehira, Shingo; Hayashi, Yuma; Ohkouchi, Shunsuke; Ikeda, Naoki; Sugimoto, Yoshimasa; Hogg, Richard A.

2017-11-01

We obtained a high-intensity and broadband emission centered at 1 μm from InGaAs quantum three-dimensional (3D) structures grown on a GaAs substrate using molecular beam epitaxy. An InGaAs thin layer grown on GaAs with a thickness close to the critical layer thickness is normally affected by strain as a result of the lattice mismatch and introduced misfit dislocations. However, under certain growth conditions for the In concentration and growth temperature, the growth mode of the InGaAs layer can be transformed from two-dimensional to 3D growth. We found the optimal conditions to obtain a broadband emission from 3D structures with a high intensity and controlled center wavelength at 1 μm. This method offers an alternative approach for fabricating a broadband near-infrared light source for telecommunication and medical imaging systems such as for optical coherence tomography.

Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe 2: Enabling nanoscale direct write homo-junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stanford, Michael; Noh, Joo Hyon; Koehler, Michael R.

Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe 2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe 2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe 2more » thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe 2 is degraded more severely relative to electron transport after helium ion irradiation. Moreover, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe 2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.« less

Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe 2: Enabling nanoscale direct write homo-junctions

DOE PAGES

Stanford, Michael; Noh, Joo Hyon; Koehler, Michael R.; ...

2016-06-06

Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe 2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe 2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe 2more » thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe 2 is degraded more severely relative to electron transport after helium ion irradiation. Moreover, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe 2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.« less

Exciton Dynamics, Transport, and Annihilation in Atomically Thin Two-Dimensional Semiconductors.

PubMed

Yuan, Long; Wang, Ti; Zhu, Tong; Zhou, Mingwei; Huang, Libai

2017-07-20

Large binding energy and unique exciton fine structure make the transition metal dichalcogenides (TMDCs) an ideal platform to study exciton behaviors in two-dimensional (2D) systems. While excitons in these systems have been extensively researched, there currently lacks a consensus on mechanisms that control dynamics. In this Perspective, we discuss extrinsic and intrinsic factors in exciton dynamics, transport, and annihilation in 2D TMDCs. Intrinsically, dark and bright exciton energy splitting is likely to play a key role in modulating the dynamics. Extrinsically, defect scattering is prevalent in single-layer TMDCs, which leads to rapid picosecond decay and limits exciton transport. The exciton-exciton annihilation process in single-layer TMDCs is highly efficient, playing an important role in the nonradiative recombination rate in the high exciton density regime. Future challenges and opportunities to control exciton dynamics are discussed.

Projectile Motion on an Inclined Misty Surface: I. Capturing and Analysing the Trajectory

ERIC Educational Resources Information Center

Ho, S. Y.; Foong, S. K.; Lim, C. H.; Lim, C. C.; Lin, K.; Kuppan, L.

2009-01-01

Projectile motion is usually the first non-uniform two-dimensional motion that students will encounter in a pre-university physics course. In this article, we introduce a novel technique for capturing the trajectory of projectile motion on an inclined Perspex plane. This is achieved by coating the Perspex with a thin layer of fine water droplets…

Enhanced electron mobility at the two-dimensional metallic surface of BaSnO3 electric-double-layer transistor at low temperatures

NASA Astrophysics Data System (ADS)

Fujiwara, Kohei; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi

2017-05-01

Wide-bandgap oxides exhibiting high electron mobility hold promise for the development of useful electronic and optoelectronic devices as well as for basic research on two-dimensional electron transport phenomena. A perovskite-type tin oxide, BaSnO3, is currently one of such targets owing to distinctly high mobility at room temperature. The challenge to overcome towards the use of BaSnO3 thin films in applications is suppression of dislocation scattering, which is one of the dominant scattering origins for electron transport. Here, we show that the mobility of the BaSnO3 electric-double-layer transistor reaches 300 cm2 V-1 s-1 at 50 K. The improved mobility indicates that charged dislocation scattering is effectively screened by electrostatically doped high-density charge carriers. We also observed metallic conduction persisting down to 2 K, which is attributed to the transition to the degenerate semiconductor. The experimental verification of bulk-level mobility at the densely accumulated surface sheds more light on the importance of suppression of dislocation scattering by interface engineering in doped BaSnO3 thin films for transparent electrode applications.

Pressure induced metallization with absence of structural transition in layered molybdenum diselenide

PubMed Central

Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; Wang, Shibing; Lin, Yu; Zeng, Qiaoshi; Xu, Gang; Liu, Zhenxian; Solanki, G. K.; Patel, K. D.; Cui, Yi; Hwang, Harold Y.; Mao, Wendy L.

2015-01-01

Layered transition-metal dichalcogenides have emerged as exciting material systems with atomically thin geometries and unique electronic properties. Pressure is a powerful tool for continuously tuning their crystal and electronic structures away from the pristine states. Here, we systematically investigated the pressurized behavior of MoSe2 up to ∼60 GPa using multiple experimental techniques and ab-initio calculations. MoSe2 evolves from an anisotropic two-dimensional layered network to a three-dimensional structure without a structural transition, which is a complete contrast to MoS2. The role of the chalcogenide anions in stabilizing different layered patterns is underscored by our layer sliding calculations. MoSe2 possesses highly tunable transport properties under pressure, determined by the gradual narrowing of its band-gap followed by metallization. The continuous tuning of its electronic structure and band-gap in the range of visible light to infrared suggest possible energy-variable optoelectronics applications in pressurized transition-metal dichalcogenides. PMID:26088416

Pressure induced metallization with absence of structural transition in layered molybdenum diselenide

DOE PAGES

Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; ...

2015-06-19

Layered transition-metal dichalcogenides have emerged as exciting material systems with atomically thin geometries and unique electronic properties. Pressure is a powerful tool for continuously tuning their crystal and electronic structures away from the pristine states. Here, we systematically investigated the pressurized behavior of MoSe 2 up to ~60 GPa using multiple experimental techniques and ab-initio calculations. MoSe 2 evolves from an anisotropic two-dimensional layered network to a three-dimensional structure without a structural transition, which is a complete contrast to MoS 2. The role of the chalcogenide anions in stabilizing different layered patterns is underscored by our layer sliding calculations. MoSemore » 2 possesses highly tunable transport properties under pressure, determined by the gradual narrowing of its band-gap followed by metallization. The continuous tuning of its electronic structure and band-gap in the range of visible light to infrared suggest possible energy-variable optoelectronics applications in pressurized transition-metal dichalcogenides.« less

Cryo-mediated exfoliation and fracturing of layered materials into 2D quantum dots

PubMed Central

Wang, Yan; Liu, Yang; Zhang, Jianfang; Wu, Jingjie; Xu, Hui; Wen, Xiewen; Zhang, Xiang; Tiwary, Chandra Sekhar; Yang, Wei; Vajtai, Robert; Zhang, Yong; Chopra, Nitin; Odeh, Ihab Nizar; Wu, Yucheng; Ajayan, Pulickel M.

2017-01-01

Atomically thin quantum dots from layered materials promise new science and applications, but their scalable synthesis and separation have been challenging. We demonstrate a universal approach for the preparation of quantum dots from a series of materials, such as graphite, MoS2, WS2, h-BN, TiS2, NbS2, Bi2Se3, MoTe2, Sb2Te3, etc., using a cryo-mediated liquid-phase exfoliation and fracturing process. The method relies on liquid nitrogen pretreatment of bulk layered materials before exfoliation and breakdown into atomically thin two-dimensional quantum dots of few-nanometer lateral dimensions, exhibiting size-confined optical properties. This process is efficient for a variety of common solvents with a wide range of surface tension parameters and eliminates the use of surfactants, resulting in pristine quantum dots without surfactant covering or chemical modification. PMID:29250597

Sum-Frequency Generation from a Thin Cylindrical Layer

NASA Astrophysics Data System (ADS)

Shamyna, A. A.; Kapshai, V. N.

2018-01-01

In the Rayleigh-Gans-Debye approximation, we have solved the problem of the sum-frequency generation by two plane elliptically polarized electromagnetic waves from the surface of a dielectric particle of a cylindrical shape that is coated by a thin layer possessing nonlinear optical properties. The formulas that describe the sum-frequency field have been presented in the tensor and vector forms for the second-order nonlinear dielectric susceptibility tensor, which was chosen in the general form, containing chiral components. Expressions describing the sum-frequency field from the cylindrical particle ends have been obtained for the case of a nonlinear layer possessing chiral properties. Three-dimensional directivity patterns of the sum-frequency radiation have been analyzed for different combinations of parameters (angles of incidence, degrees of ellipticity, orientations of polarization ellipses, cylindrical particle dimensions). The mathematical properties of the spatial distribution functions of the sum-frequency field, which characterize the symmetry of directivity patterns, have been revealed.

Liquid Crystals in Chromatography

NASA Astrophysics Data System (ADS)

Witkiewicz, Zygfryd

The following sections are included: * INTRODUCTION * LIQUID CRYSTALS SUITABLE FOR GAS CHROMATOGRAPHY * Monomeric Liquid Crystal Stationary Phases * Polymeric Liquid Crystal Stationary Phases * Polymeric Liquid Crystal Stationary Phases * Conventional Analytical Columns * Capillary Columns * FACTORS AFFECTING THE CHROMATOGRAPHIC SEPARATIONS ON LIQUID CRYSTAL STATIONARY PHASES * Kind of Mesophase of the Liquid Crystal * Molecular Structure of the Liquid Crystals and of the Chromatographed Substances * Substrate on which the Liquid Crystal is Deposited * ANALYTICAL APPLICATIONS OF LIQUID CRYSTAL STATIONARY PHASES IN GAS CHROMATOGRAPHY * Separation of Isomers of Benzene and Naphthalene Derivatives * Separation of Alkane and Alkene Isomers * Separation of Mixtures of Benzene and Aliphatic Hydrocarbon Derivatives Containing Heteroatoms * Separation of Polynuclear Hydrocarbons * INVESTIGATION OF THE PROPERTIES OF LIQUID CRYSTALS BY GAS CHROMATOGRAPHY * APPLICATION OF LIQUID CRYSTALS IN LIQUID CHROMATOGRAPHY * Column Chromatography * Thin-Layer Chromatography * APPLICATION OF LIQUID CRYSTAL STATIONARY PHASES IN SUPERCRITICAL FLUID CHROMATOGRAPHY * FINAL REMARKS * References

Photovoltaic Effect in an Electrically Tunable van der Waals Heterojunction

PubMed Central

2014-01-01

Semiconductor heterostructures form the cornerstone of many electronic and optoelectronic devices and are traditionally fabricated using epitaxial growth techniques. More recently, heterostructures have also been obtained by vertical stacking of two-dimensional crystals, such as graphene and related two-dimensional materials. These layered designer materials are held together by van der Waals forces and contain atomically sharp interfaces. Here, we report on a type-II van der Waals heterojunction made of molybdenum disulfide and tungsten diselenide monolayers. The junction is electrically tunable, and under appropriate gate bias an atomically thin diode is realized. Upon optical illumination, charge transfer occurs across the planar interface and the device exhibits a photovoltaic effect. Advances in large-scale production of two-dimensional crystals could thus lead to a new photovoltaic solar technology. PMID:25057817

Filtrates and Residues: Chlorophyll Separation and Spectral Identification.

ERIC Educational Resources Information Center

Diehl-Jones, Susan M.

1984-01-01

Describes an experiment in which students become familiar with the organic chemistry extraction process, perform analyses by thin layer and column chromatography, and use the absorption spectrum (obtained from a spectrophotometer) for identification. List of materials needed and procedures used are provided. (JN)

Microscale Group Test for Carbonyl Compounds.

ERIC Educational Resources Information Center

Horak, V.; Klein, R. F. X.

1985-01-01

Procedures are provided for a test that (1) demonstrates principles of derivatization with 2,4-dinitrophenylhydrazine; (2) is a thin layer chromatography experiment that visually demonstrates separation of colored compounds of different polarities; and (3) introduces microscale experimentation to students in sophomore organic chemistry…

A Laboratory Exercise in the Determination of Carbohydrate Structures.

ERIC Educational Resources Information Center

White, Bernard J.; Robyt, John F.

1988-01-01

Describes an experiment in which students are given a naturally occurring oligosaccharide as an unknown and are asked to determine both its monosaccharide composition and its structure. Discusses methods and experimental techniques including thin layer chromatography and the use of enzymes. (CW)

Detection of Mannitol Formation by Bacteria

PubMed Central

Chalfan, Y.; Levy, R.; Mateles, R. I.

1975-01-01

A test is described by means of which formation of mannitol from fructose by lactic acid bacteria can be readily detected. The test is based on removal of interference of residual fructose by dehydration with hydrochloric acid followed by thin-layer chromatography. PMID:1101827

Stripping analysis of nanomolar perchlorate in drinking water with a voltammetric ion-selective electrode based on thin-layer liquid membrane.

PubMed

Kim, Yushin; Amemiya, Shigeru

2008-08-01

A highly sensitive analytical method is required for the assessment of nanomolar perchlorate contamination in drinking water as an emerging environmental problem. We developed the novel approach based on a voltammetric ion-selective electrode to enable the electrochemical detection of "redox-inactive" perchlorate at a nanomolar level without its electrolysis. The perchlorate-selective electrode is based on the submicrometer-thick plasticized poly(vinyl chloride) membrane spin-coated on the poly(3-octylthiophene)-modified gold electrode. The liquid membrane serves as the first thin-layer cell for ion-transfer stripping voltammetry to give low detection limits of 0.2-0.5 nM perchlorate in deionized water, commercial bottled water, and tap water under a rotating electrode configuration. The detection limits are not only much lower than the action limit (approximately 246 nM) set by the U.S. Environmental Protection Agency but also are comparable to the detection limits of the most sensitive analytical methods for detecting perchlorate, that is, ion chromatography coupled with a suppressed conductivity detector (0.55 nM) or electrospray ionization mass spectrometry (0.20-0.25 nM). The mass transfer of perchlorate in the thin-layer liquid membrane and aqueous sample as well as its transfer at the interface between the two phases were studied experimentally and theoretically to achieve the low detection limits. The advantages of ion-transfer stripping voltammetry with a thin-layer liquid membrane against traditional ion-selective potentiometry are demonstrated in terms of a detection limit, a response time, and selectivity.

Rapid identification of serotypes of Mycobacterium avium-M. intracellulare complex by using infected swine sera and reference antigenic glycolipids.

PubMed

Ikawa, H; Oka, S; Murakami, H; Hayashi, A; Yano, I

1989-11-01

The species of 136 strains of acid-fast bacteria isolated from swine with mycobacteriosis were identified by numerical taxonomy and chemotaxonomy on the basis of mycolic acid subclass composition as members of the Mycobacterium avium-M. intracellulare (MAI) complex. The isolates were further classified by using both thin-layer chromatography of the antigenic glycopeptidolipids (GPL) obtained from the bacteria by the method of Tsang et al. (A. Y. Tsang, I. Drupa, M. Goldberg, J. K. McClatchy, and P. J. Brennan, Int. J. Syst. Bacteriol. 33:285-292, 1983) and the seroagglutination test devised by W. B. Schaefer (Am. Rev. Respir. Dis. 92[Suppl.]:85-93, 1965). For the reference standard, purified antigenic GPL of serotypes 4, 8, and 9 were isolated and their structures were analyzed by negative fast-atom bombardment-mass spectrometry. The fast-atom bombardment-mass spectrometric spectra of the intact GPL antigens of serotypes 4, 8, and 9 agreed with the structures reported earlier by Brennan et al. (P. J. Brennan and M. B. Goren, J. Biol. Chem. 254:4205-4211, 1979; P. J. Brennan, G. O. Aspinall, and J. E. Nam Shin, J. Biol. Chem. 256:6817-6822, 1981). With these antigenic GPL, the thin-layer chromatographic behaviors of the alkali-stable lipids of the above-described isolates were examined. These MAI complex isolates fell into the serotype 8 (85 strains), 4 (33 strains), and 9 (7 strains) and untypeable (11 strains) categories. Furthermore, an enzyme-linked immunosorbent assay (ELISA) based on type-specific glycolipid antigens and infected swine sera was used to diagnose the serological types of the MAI complex isolates. Of 14 cases typed by both the seroagglutination reaction and thin-layer chromatography, 13 showed clear agreement with the ELISA results. The results demonstrated that ELISA using infected sera was especially useful, and it can be recommended on the basis of simplicity, sensitivity, and specificity as an adjunct to the seroaggulutination test and thin-layer chromatography for identification of mycobacteria belonging to the MAI complex.

Computation of turbulent flow in a thin liquid layer of fluid involving a hydraulic jump

NASA Technical Reports Server (NTRS)

Rahman, M. M.; Faghri, A.; Hankey, W. L.

1991-01-01

Numerically computed flow fields and free surface height distributions are presented for the flow of a thin layer of liquid adjacent to a solid horizontal surface that encounters a hydraulic jump. Two kinds of flow configurations are considered: two-dimensional plane flow and axisymmetric radial flow. The computations used a boundary-fitted moving grid method with a k-epsilon model for the closure of turbulence. The free surface height was determined by an optimization procedure which minimized the error in the pressure distribution on the free surface. It was also checked against an approximate procedure involving integration of the governing equations and use of the MacCormack predictor-corrector method. The computed film height also compared reasonably well with previous experiments. A region of recirculating flow was found to be present adjacent to the solid boundary near the location of the jump, which was caused by a rapid deceleration of the flow.

Lubricated immersed boundary method in two dimensions

NASA Astrophysics Data System (ADS)

Fai, Thomas G.; Rycroft, Chris H.

2018-03-01

Many biological examples of fluid-structure interaction, including the transit of red blood cells through the narrow slits in the spleen and the intracellular trafficking of vesicles into dendritic spines, involve the near-contact of elastic structures separated by thin layers of fluid. Motivated by such problems, we introduce an immersed boundary method that uses elements of lubrication theory to resolve thin fluid layers between immersed boundaries. We demonstrate 2nd-order accurate convergence for simple two-dimensional flows with known exact solutions to showcase the increased accuracy of this method compared to the standard immersed boundary method. Motivated by the phenomenon of wall-induced migration, we apply the lubricated immersed boundary method to simulate an elastic vesicle near a wall in shear flow. We also simulate the dynamics of a vesicle traveling through a narrow channel and observe the ability of the lubricated method to capture the vesicle motion on relatively coarse fluid grids.

Surface and Interface Engineering of Organometallic and Two Dimensional Semiconductor

NASA Astrophysics Data System (ADS)

Park, Jun Hong

For over half a century, inorganic Si and III-V materials have led the modern semiconductor industry, expanding to logic transistor and optoelectronic applications. However, these inorganic materials have faced two different fundamental limitations, flexibility for wearable applications and scaling limitation as logic transistors. As a result, the organic and two dimensional have been studied intentionally for various fields. In the present dissertation, three different studies will be presented with followed order; (1) the chemical response of organic semiconductor in NO2 exposure. (2) The surface and stability of WSe2 in ambient air. (3) Deposition of dielectric on two dimensional materials using organometallic seeding layer. The organic molecules rely on the van der Waals interaction during growth of thin films, contrast to covalent bond inorganic semiconductors. Therefore, the morphology and electronic property at surface of organic semiconductor in micro scale is more sensitive to change in gaseous conditions. In addition, metal phthalocyanine, which is one of organic semiconductor materials, change their electronic property as reaction with gaseous analytes, suggesting as potential chemical sensing platforms. In the present part, the growth behavior of metal phthalocyanine and surface response to gaseous condition will be elucidated using scanning tunneling microscopy (STM). In second part, the surface of layered transition metal dichalcogenides and their chemical response to exposure ambient air will be investigated, using STM. Layered transition metal dichalcogenides (TMDs) have attracted widespread attention in the scientific community for electronic device applications because improved electrostatic gate control and suppression of short channel leakage resulted from their atomic thin body. To fabricate the transistor based on TMDs, TMDs should be exposed to ambient conditions, while the effect of air exposure has not been understood fully. In this part, the effect of ambient air on TMDs will be investigated and partial oxidation of TMDs. In the last part, uniform deposition of dielectric layers on 2D materials will be presented, employing organic seedling layer. Although 2D materials have been expected as next generation semiconductor platform, direct deposition of dielectric is still challenging and induces leakage current commonly, because inertness of their surface resulted from absent of dangling bond. Here, metal phthalocyanine monolayer (ML) is employed as seedling layers and the growth of atomic layer deposition (ALD) dielectric is investigated in each step using STM.

Origin of vertical orientation in two-dimensional metal halide perovskites and its effect on photovoltaic performance.

PubMed

Chen, Alexander Z; Shiu, Michelle; Ma, Jennifer H; Alpert, Matthew R; Zhang, Depei; Foley, Benjamin J; Smilgies, Detlef-M; Lee, Seung-Hun; Choi, Joshua J

2018-04-06

Thin films based on two-dimensional metal halide perovskites have achieved exceptional performance and stability in numerous optoelectronic device applications. Simple solution processing of the 2D perovskite provides opportunities for manufacturing devices at drastically lower cost compared to current commercial technologies. A key to high device performance is to align the 2D perovskite layers, during the solution processing, vertical to the electrodes to achieve efficient charge transport. However, it is yet to be understood how the counter-intuitive vertical orientations of 2D perovskite layers on substrates can be obtained. Here we report a formation mechanism of such vertically orientated 2D perovskite in which the nucleation and growth arise from the liquid-air interface. As a consequence, choice of substrates can be liberal from polymers to metal oxides depending on targeted application. We also demonstrate control over the degree of preferential orientation of the 2D perovskite layers and its drastic impact on device performance.

Two-dimensional periodic structures in solid state laser resonator

NASA Astrophysics Data System (ADS)

Okulov, Alexey Y.

1991-07-01

Transverse effects in nonlinear optical devices are being widely investigated. Recently, synchronization of a laser set by means of the Talbot effect has been demonstrated experimentally. This paper considers a Talbot cavity formed by a solid-state amplifying laser separated from the output mirror by a free space interval. This approach involves the approximation of the nonlinear medium as a thin layer, within which the diffraction is negligible. The other part of a resonator is empty, and the wave field is transformed by the Fresnel-Kirchoff integral. As a result, the dynamics of the transverse (and temporal) structure is computed by a successively iterated nonlinear local map (one- or two-dimensional) and a linear nonlocal map (generally speaking, infinitely dimensional).

Chemotaxis and degradation of organophosphate compound by a novel moderately thermo-halo tolerant Pseudomonas sp. strain BUR11: evidence for possible existence of two pathways for degradation.

PubMed

Pailan, Santanu; Saha, Pradipta

2015-01-01

An organophosphate (OP) degrading chemotactic bacterial strain BUR11 isolated from an agricultural field was identified as a member of Pseudomonas genus on the basis of its 16S rRNA gene sequence. The strain could utilize parathion, chlorpyrifos and their major hydrolytic intermediates as sole source of carbon for its growth and exhibited positive chemotactic response towards most of them. Optimum concentration of parathion for its growth was recorded to be 200 ppm and 62% of which was degraded within 96 h at 37 °C. Growth studies indicated the strain to be moderately thermo-halo tolerant in nature. Investigation based on identification of intermediates of parathion degradation by thin layer chromatography (TLC), high performance liquid chromatography (HPLC), gas chromatography (GC) and liquid chromatography mass spectrometry (LC-MS/MS) provided evidence for possible existence of two pathways. The first pathway proceeds via 4-nitrophenol (4-NP) while the second proceeds through formation of 4-aminoparathion (4-APar), 4-aminophenol (4-AP) and parabenzoquinone (PBQ). This is the first report of chemotaxis towards organophosphate compound by a thermo-halo tolerant bacterium.

Chemotaxis and degradation of organophosphate compound by a novel moderately thermo-halo tolerant Pseudomonas sp. strain BUR11: evidence for possible existence of two pathways for degradation

PubMed Central

Pailan, Santanu

2015-01-01

An organophosphate (OP) degrading chemotactic bacterial strain BUR11 isolated from an agricultural field was identified as a member of Pseudomonas genus on the basis of its 16S rRNA gene sequence. The strain could utilize parathion, chlorpyrifos and their major hydrolytic intermediates as sole source of carbon for its growth and exhibited positive chemotactic response towards most of them. Optimum concentration of parathion for its growth was recorded to be 200 ppm and 62% of which was degraded within 96 h at 37 °C. Growth studies indicated the strain to be moderately thermo-halo tolerant in nature. Investigation based on identification of intermediates of parathion degradation by thin layer chromatography (TLC), high performance liquid chromatography (HPLC), gas chromatography (GC) and liquid chromatography mass spectrometry (LC-MS/MS) provided evidence for possible existence of two pathways. The first pathway proceeds via 4-nitrophenol (4-NP) while the second proceeds through formation of 4-aminoparathion (4-APar), 4-aminophenol (4-AP) and parabenzoquinone (PBQ). This is the first report of chemotaxis towards organophosphate compound by a thermo-halo tolerant bacterium. PMID:26587344

Effect of excimer laser annealing on a-InGaZnO thin-film transistors passivated by solution-processed hybrid passivation layers

NASA Astrophysics Data System (ADS)

Bermundo, Juan Paolo; Ishikawa, Yasuaki; Fujii, Mami N.; Nonaka, Toshiaki; Ishihara, Ryoichi; Ikenoue, Hiroshi; Uraoka, Yukiharu

2016-01-01

We demonstrate the use of excimer laser annealing (ELA) as a low temperature annealing alternative to anneal amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) passivated by a solution-processed hybrid passivation layer. Usually, a-IGZO is annealed using thermal annealing at high temperatures of up to 400 °C. As an alternative to high temperature thermal annealing, two types of ELA, XeCl (308 nm) and KrF (248 nm) ELA, are introduced. Both ELA types enhanced the electrical characteristics of a-IGZO TFTs leading to a mobility improvement of ~13 cm2 V-1 s-1 and small threshold voltage which varied from ~0-3 V. Furthermore, two-dimensional heat simulation using COMSOL Multiphysics was used to identify possible degradation sites, analyse laser heat localization, and confirm that the substrate temperature is below 50 °C. The two-dimensional heat simulation showed that the substrate temperature remained at very low temperatures, less than 30 °C, during ELA. This implies that any flexible material can be used as the substrate. These results demonstrate the large potential of ELA as a low temperature annealing alternative for already-passivated a-IGZO TFTs.

Bounded solutions in a T-shaped waveguide and the spectral properties of the Dirichlet ladder

NASA Astrophysics Data System (ADS)

Nazarov, S. A.

2014-08-01

The Dirichlet problem is considered on the junction of thin quantum waveguides (of thickness h ≪ 1) in the shape of an infinite two-dimensional ladder. Passage to the limit as h → +0 is discussed. It is shown that the asymptotically correct transmission conditions at nodes of the corresponding one-dimensional quantum graph are Dirichlet conditions rather than the conventional Kirchhoff transmission conditions. The result is obtained by analyzing bounded solutions of a problem in the T-shaped waveguide that the boundary layer phenomenon.

Instabilities and diffusion in a hydrodynamic model of a fluid membrane coupled to a thin active fluid layer.

PubMed

Sarkar, N; Basu, A

2012-11-01

We construct a coarse-grained effective two-dimensional (2d hydrodynamic theory as a theoretical model for a coupled system of a fluid membrane and a thin layer of a polar active fluid in its ordered state that is anchored to the membrane. We show that such a system is prone to generic instabilities through the interplay of nonequilibrium drive, polar order and membrane fluctuation. We use our model equations to calculate diffusion coefficients of an inclusion in the membrane and show that their values depend strongly on the system size, in contrast to their equilibrium values. Our work extends the work of S. Sankararaman and S. Ramaswamy (Phys. Rev. Lett., 102, 118107 (2009)) to a coupled system of a fluid membrane and an ordered active fluid layer. Our model is broadly inspired by and should be useful as a starting point for theoretical descriptions of the coupled dynamics of a cell membrane and a cortical actin layer anchored to it.

Emerging technology for transonic wind-tunnel-wall interference assessment and corrections

NASA Technical Reports Server (NTRS)

Newman, P. A.; Kemp, W. B., Jr.; Garriz, J. A.

1988-01-01

Several nonlinear transonic codes and a panel method code for wind tunnel/wall interference assessment and correction (WIAC) studies are reviewed. Contrasts between two- and three-dimensional transonic testing factors which affect WIAC procedures are illustrated with airfoil data from the NASA/Langley 0.3-meter transonic cyrogenic tunnel and Pathfinder I data. Also, three-dimensional transonic WIAC results for Mach number and angle-of-attack corrections to data from a relatively large 20 deg swept semispan wing in the solid wall NASA/Ames high Reynolds number Channel I are verified by three-dimensional thin-layer Navier-Stokes free-air solutions.

A target fibre study on seats in public houses.

PubMed

Kelly, E; Griffin, R M

1998-01-01

A target fibre survey was conducted to assess the random occurrence of a blue wool fibre on seats in public houses throughout the United Kingdom. Fibre tape lifts were taken from 80 seats. Four seats yielded matching fibres and five of these were found on one seat. A total of 292 fibres were identified; nine fibres proved indistinguishable from the target after comparison microscopy, microspectro-photometry and attempts at thin layer chromatography, and two of these fibres were still apparently indistinguishable after TLC analysis although only one dye component was visible.

Comprehensive two-dimensional liquid chromatography for polyphenol analysis in foodstuffs.

PubMed

Cacciola, Francesco; Farnetti, Sara; Dugo, Paola; Marriott, Philip John; Mondello, Luigi

2017-01-01

Polyphenols are a class of plant secondary metabolites that are recently drawing a special interest because of their broad spectrum of pharmacological effects. As they are characterized by an enormous structural variability, the identification of these molecules in food samples is a difficult task, and sometimes having only a limited number of commercially available reference materials is not of great help. One-dimensional liquid chromatography is the most widely applied analytical approach for their analysis. In particular, the hyphenation of liquid chromatography to mass spectrometry has come to play an influential role by allowing relatively fast tentative identification and accurate quantification of polyphenolic compounds at trace levels in vegetable media. However, when dealing with very complex real-world food samples, a single separation system often does not provide sufficient resolving power for attaining rewarding results. Comprehensive two-dimensional liquid chromatography is a technique of great analytical impact, since it offers much higher peak capacities than separations in a single dimension. In the present review, we describe applications in the field of comprehensive two-dimensional liquid chromatography for polyphenol analysis in real-world food samples. Comprehensive two-dimensional liquid chromatography applications to nonfood matrices fall outside the scope of the current report and will not be discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of γ-hydroxybutyrate in human urine samples by ion exclusion and ion exchange two-dimensional chromatography system.

PubMed

Liu, Junwei; Deng, Zhifen; Zhu, Zuoyi; Wang, Yong; Wang, Guoqing; Sun, Yu-An; Zhu, Yan

2017-12-15

A two-dimensional ion chromatography system was developed for the determination of γ-hydroxybutyrate (GHB) in human urine samples. Ion exclusion chromatography was used in the first dimensional separation for elimination of urine matrices and detection of GHB above 10mgL -1 , ion exchange chromatography was used in the second dimensional separation via column-switching technique for detection of GHB above 0.08mgL -1 . Under the optimized chromatographic conditions, the ion exclusion and ion exchange chromatography separation system exhibited satisfactory repeatability (RSD<3.1%, n=6) and good linearity in the range of 50-1000mgL -1 and 0.5-100mgL -1 , respectively. By this method, concentrations of GHB in the selected human urine samples were detected in the range of 0-1.57mgL -1 . The urine sample containing 0.89mgL -1 GHB was selected to evaluate the accuracy; the spiked recoveries of GHB were 95.9-102.8%. The results showed that the two-dimensional ion chromatography system was convenient and practical for the determination of GHB in human urine samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular Beam Epitaxy Growth and Characterization of Thin Layers of Semiconductor Tin

DTIC Science & Technology

2016-09-01

confirm that the thin layers of α-Sn are slightly strained, which supports theoretical prediction that α-Sn is a 3-D topological insulator (TI...topological insulator , single crystal 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF...its thickness, α-Sn is a 3-D or 2-D topological insulator (TI). Three-dimensional TIs are electronic materials that have a bulk bandgap and

Comparison of sampling methods for radiocarbon dating of carbonyls in air samples via accelerator mass spectrometry

NASA Astrophysics Data System (ADS)

Schindler, Matthias; Kretschmer, Wolfgang; Scharf, Andreas; Tschekalinskij, Alexander

2016-05-01

Three new methods to sample and prepare various carbonyl compounds for radiocarbon measurements were developed and tested. Two of these procedures utilized the Strecker synthetic method to form amino acids from carbonyl compounds with either sodium cyanide or trimethylsilyl cyanide. The third procedure used semicarbazide to form crystalline carbazones with the carbonyl compounds. The resulting amino acids and semicarbazones were then separated and purified using thin layer chromatography. The separated compounds were then combusted to CO2 and reduced to graphite to determine 14C content by accelerator mass spectrometry (AMS). All of these methods were also compared with the standard carbonyl compound sampling method wherein a compound is derivatized with 2,4-dinitrophenylhydrazine and then separated by high-performance liquid chromatography (HPLC).

Two-dimensionally grown single-crystal silicon nanosheets with tunable visible-light emissions.

PubMed

Kim, Sung Wook; Lee, Jaejun; Sung, Ji Ho; Seo, Dong-jae; Kim, Ilsoo; Jo, Moon-Ho; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

2014-07-22

Since the discovery of graphene, growth of two-dimensional (2D) nanomaterials has greatly attracted attention. However, spontaneous growth of atomic two-dimensional (2D) materials is limitedly permitted for several layered-structure crystals, such as graphene, MoS2, and h-BN, and otherwise it is notoriously difficult. Here we report the gas-phase 2D growth of silicon (Si), that is cubic in symmetry, via dendritic growth and an interdendritic filling mechanism and to form Si nanosheets (SiNSs) of 1 to 13 nm in thickness. Thin SiNSs show strong thickness-dependent photoluminescence in visible range including red, green, and blue (RGB) emissions with the associated band gap energies ranging from 1.6 to 3.2 eV; these emission energies were greater than those from Si quantum dots (SiQDs) of the similar sizes. We also demonstrated that electrically driven white, as well as blue, emission in a conventional organic light-emitting diode (OLED) geometry with the SiNS assembly as the active emitting layers. Tunable light emissions in visible range in our observations suggest practical implications for novel 2D Si nanophotonics.

Two-dimensional crystals: managing light for optoelectronics.

PubMed

Eda, Goki; Maier, Stefan A

2013-07-23

Semiconducting two-dimensional (2D) crystals such as MoS2 and WSe2 exhibit unusual optical properties that can be exploited for novel optoelectronics ranging from flexible photovoltaic cells to harmonic generation and electro-optical modulation devices. Rapid progress of the field, particularly in the growth area, is beginning to enable ways to implement 2D crystals into devices with tailored functionalities. For practical device performance, a key challenge is to maximize light-matter interactions in the material, which is inherently weak due to its atomically thin nature. Light management around the 2D layers with the use of plasmonic nanostructures can provide a compelling solution.

Quality improvements of ZnxCdyMg1-x-ySe layers grown on InP substrates by a thin ZnCdSe interfacial layer

NASA Astrophysics Data System (ADS)

Zeng, L.; Yang, B. X.; Tamargo, M. C.; Snoeks, E.; Zhao, L.

1998-03-01

The quality of lattice-matched ZnxCdyMg1-x-ySe epitaxial layers grown on (001) InP substrates with a III-V buffer layer has been improved by initially growing a ZnCdSe interfacial layer (50 Å) at low temperature. The widths of double crystal x-ray rocking curves for ZnxCdyMg1-x-ySe epilayers with band gaps as high as 3.05 eV were reduced to about 70 arcsec. The defect density evaluated from etch pit density and plan-view transmission electron microscopy measurements was reduced by two orders of magnitude, to 106-107cm-2. The photoluminescence band edge emission became more symmetric and slightly narrower. It is proposed that an initial two-dimensional growth mode has been achieved by incorporating such a lattice-matched ZnCdSe layer.

Chem Ed Compacts.

ERIC Educational Resources Information Center

Wolf, Walter A., Ed.

1978-01-01

Reported here are brief descriptions of a common grading and scaling formula for large multi-section courses, an ion exchange amino acid separation and thin layer chromatography identification experiment, a conservation of energy demonstration, a catalyst for synthesizing esters from fatty aids, and an inexpensive method for preparing platinum…

Isolation and Characterization of Phosphatidyl Choline from Spinach Leaves.

ERIC Educational Resources Information Center

Devor, Kenneth A.

1979-01-01

This inexpensive but informative experiment for undergraduate biochemistry students involves isolating phosphatidyl choline from spinach leaves. Emphasis is on introducing students to techniques of lipid extraction, separation of lipids, identification using thin layer chromatography, and identification of fatty acids. Three periods of three hours…

Qualitative and quantitative analysis of hyaluronan oligosaccharides with high performance thin layer chromatography using reagent-free derivatization on amino-modified silica and electrospray ionization-quadrupole time-of-flight mass spectrometry coupling on normal phase.

PubMed

Rothenhöfer, Martin; Scherübl, Rosmarie; Bernhardt, Günther; Heilmann, Jörg; Buschauer, Armin

2012-07-27

Purified oligomers of hyalobiuronic acid are indispensable tools to elucidate the physiological and pathophysiological role of hyaluronan degradation by various hyaluronidase isoenzymes. Therefore, we established and validated a novel sensitive, convenient, rapid, and cost-effective high performance thin layer chromatography (HPTLC) method for the qualitative and quantitative analysis of small saturated hyaluronan oligosaccharides consisting of 2-4 hyalobiuronic acid moieties. The use of amino-modified silica as stationary phase allows a simple reagent-free in situ derivatization by heating, resulting in a very low limit of detection (7-19 pmol per band, depending on the analyzed saturated oligosaccharide). By this derivatization procedure for the first time densitometric quantification of the analytes could be performed by HPTLC. The validated method showed a quantification limit of 37-71 pmol per band and was proven to be superior in comparison to conventional detection of hyaluronan oligosaccharides. The analytes were identified by hyphenation of normal phase planar chromatography to mass spectrometry (TLC-MS) using electrospray ionization. As an alternative to sequential techniques such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), the validated HPTLC quantification method can easily be automated and is applicable to the analysis of multiple samples in parallel. Copyright © 2012 Elsevier B.V. All rights reserved.

Thin layer chromatography coupled to paper spray ionization mass spectrometry for cocaine and its adulterants analysis.

PubMed

De Carvalho, Thays C; Tosato, Flavia; Souza, Lindamara M; Santos, Heloa; Merlo, Bianca B; Ortiz, Rafael S; Rodrigues, Rayza R T; Filgueiras, Paulo R; França, Hildegardo S; Augusti, Rodinei; Romão, Wanderson; Vaz, Boniek G

2016-05-01

Thin layer chromatography (TLC) is a simple and inexpensive type of chromatography that is extensively used in forensic laboratories for drugs of abuse analysis. In this work, TLC is optimized to analyze cocaine and its adulterants (caffeine, benzocaine, lidocaine and phenacetin) in which the sensitivity (visual determination of LOD from 0.5 to 14mgmL(-1)) and the selectivity (from the study of three different eluents: CHCl3:CH3OH:HCOOHglacial (75:20:5v%), (C2H5)2O:CHCl3 (50:50v%) and CH3OH:NH4OH (100:1.5v%)) were evaluated. Aiming to improve these figures of merit, the TLC spots were identified and quantified (linearity with R(2)>0.98) by the paper spray ionization mass spectrometry (PS-MS), reaching now lower LOD values (>1.0μgmL(-1)). The method developed in this work open up perspective of enhancing the reliability of traditional and routine TLC analysis employed in the criminal expertise units. Higher sensitivity, selectivity and rapidity can be provided in forensic reports, besides the possibility of quantitative analysis. Due to the great simplicity, the PS(+)-MS technique can also be coupled directly to other separation techniques such as the paper chromatography and can still be used in analyses of LSD blotter, documents and synthetic drugs. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Quantitative determination of triterpenes from Amphiptherygium adstringens by liquid chromatography and thin-layer chromatography and morphological analysis of cuachalalate preparations.

PubMed

Navarrete, Andres; Avula, Bharathi; Joshi, Vaishali C; Ji, Xiuhong; Hersh, Paul; Khan, Ikhlas A

2006-01-01

Amphiptherygium adstringens (Anacardiaceae/Julianaceae), local name "cuachalalate," is used in folk medicine for the treatment of cholelithiasis, fevers, fresh wounds, hypercholesterolemia, gastritis, gastric ulcers, and cancer of the gastrointestinal tract. The development of column high-performance liquid chromatography-photodiode array detector (LC-PDA) and high-performance thin-layer chromatography (HPTLC)-densitometry methods for the determination of masticadienonic acid and 3-hydroxymasticadienonic acid in cuachalalate preparations is described in this paper. Good separation of the compounds could be achieved by both methods. Either might be preparable depending on the requirements. The LC separation was performed on a Phenomenex Synergi MAX-RP 80A reversed-phase column operated at 40 degrees C with detection at 215 nm. The plant materials were extracted with methanol by sonication. The triterpenes present in the plant material and commercial extracts were separated with an acetonitrile-water reagent alcohol isocratic system. The limit of detection was 0.1-0.2 microg/mL. The relative standard deviation values for the determination of triterpenes in plant extracts were less than 1.00%. This is the first report of an analytical method developed for the quantitative analysis of triterpenes from Amphiptherygium adstringens by LC-PDA and HPTLC. The stem bark showed higher amounts of triterpenes, and low amounts in root and stem root. The microscopic description of the crude drug of cuachalalate was also provided.

Validation Thin Layer Chromatography for the Determination of Acetaminophen in Tablets and Comparison with a Pharmacopeial Method

PubMed Central

Pyka, Alina; Budzisz, Marika; Dołowy, Małgorzata

2013-01-01

Adsorption thin layer chromatography (NP-TLC) with densitometry has been established for the identification and the quantification of acetaminophen in three leading commercial products of pharmaceutical tablets coded as brand: P1 (Product no. 1), P2 (Product no. 2), and P3 (Product no. 3). Applied chromatographic conditions have separated acetaminophen from its related substances, namely, 4-aminophenol and and 4′-chloroacetanilide. UV densitometry was performed in absorbance mode at 248 nm. The presented method was validated by specificity, range, linearity, accuracy, precision, detection limit, quantitative limit, and robustness. The TLC-densitometric method was also compared with a pharmacopeial UV-spectrophotometric method for the assay of acetaminophen, and the results confirmed statistically that the NP-TLC-densitometric method can be used as a substitute method. It could be said that the validated NP-TLC-densitometric method is suitable for the routine analysis of acetaminophen in quantity control laboratories. PMID:24063006

Determination of cortisol in human plasma by thin-layer chromatography and fluorescence derivatization with isonicotinic acid hydrazide.

PubMed

Fenske, Martin

2008-01-01

The present work describes a specific and rapid determination of cortisol in human plasma. The method includes liquid-liquid extraction of plasma samples, thin-layer chromatography (TLC) of ethanolic extracts on aluminium foil-backed silica gel 60 TLC plates, derivatization of cortisol with isonicotinic acid hydrazide, and densitometric measurement of the fluorescence intensity of cortisol hydrazone. The fluorescence was linearly related to cortisol amounts; the correlation coefficients of standard curve plots were r>0.99. The coefficient of variation ranged between 2.8-7.9% (20 ng, within-assay/between assay variation) and 1.6-6.8% (80 ng, within-assay/between assay variation). The recovery of cortisol from plasma spiked with 21-deoxycortisol was 85%+/-4%. Cortisol concentration in the plasma was 66+/-32 ng/mL (mean+/-standard deviation, n=24). The advantage of this method is its simplicity to separate cortisol from other steroids by TLC, its specificity (formation of cortisol hydrazone), and the rapid quantitation of cortisol by densitometry.

Thin layer chromatography of p-aminophenol in urine after mixed exposure to aniline and toluene.

PubMed Central

Bieniek, G; Karmańska, K; Wilczok, T

1984-01-01

A simple method of evaluating p-aminophenol in the urine of people exposed simultaneously to aniline and toluene relies on separating p-aminophenol from hippuric acid and other physiological components of the urine by thin layer chromatography. The adsorbents and developing system have been thus fixed to make possible the separation of p-aminophenol from hippuric acid, urea, and creatinine and their quantitative determination. This method also makes possible the determination of p-aminophenol in urine in the presence of hippuric acid. Hippuric acid is a physiological component of urine and also the metabolite of toluene, so the determination of p-aminophenol is possible also after simultaneous exposure to both compounds: aniline and toluene. At the same time the concentrations of urea and creatinine as additional factors may be determined. The limit of detection of the method is: 5 micrograms/ml for p-aminophenol, 9 micrograms/ml for hippuric acid, 8 micrograms/ml for urea, and 6 micrograms/ml for creatinine. PMID:6722055

Ultra-thin layer chromatography and surface enhanced Raman spectroscopy on silver nanorod array substrates prepared by oblique angle deposition

NASA Astrophysics Data System (ADS)

Chen, Jing; Abell, Justin; Huang, Yao-wen; Zhao, Yiping

2012-06-01

We demonstrate the potential use of silver nanorod (AgNR) array substrates for on-chip separation and detection of chemical mixtures by ultra-thin layer chromatography (UTLC) and surface enhanced Raman spectroscopy (SERS). The capability of the AgNR substrates to separate different compounds in a mixture was explored using a mixture of the food colorant Brilliant Blue FCF and lactic acid, and the mixtures of Methylene Violet and BSA at various concentrations. After the UTLC process, spatially-resolved SERS spectra were collected along the mobile phase development direction and the intensities of specific SERS peaks from each component were used to generate chromatograms. The AgNR substrates demonstrate the capability of separating Brilliant Blue from lactic acid, as well as revealing the SERS signal of Methylene Violet from the massive BSA background after a simple UTLC step. This technique may have significant practical implications in actual detection of small molecules from complex food or clinical backgrounds.

Tuneable surface enhanced Raman spectroscopy hyphenated to chemically derivatized thin-layer chromatography plates for screening histamine in fish.

PubMed

Xie, Zhengjun; Wang, Yang; Chen, Yisheng; Xu, Xueming; Jin, Zhengyu; Ding, Yunlian; Yang, Na; Wu, Fengfeng

2017-09-01

Reliable screening of histamine in fish was of urgent importance for food safety. This work presented a highly selective surface enhanced Raman spectroscopy (SERS) method mediated by thin-layer chromatography (TLC), which was tailored for identification and quantitation of histamine. Following separation and derivatization with fluram, plates were assayed with SERS, jointly using silver nanoparticle and NaCl. The latter dramatically suppressed the masking effect caused by excessive fluram throughout the plate, thus offering clear baseline and intensive Raman fingerprints specific to the analyte. Under optimized conditions, the usability of this method was validated by identifying the structural fingerprints of both targeted and unknown compounds in fish samples. Meanwhile, the quantitative results of this method agreed with those by an HPLC method officially suggested by EU for histamine determination. Showing remarkable cost-efficiency and user-friendliness, this facile TLC-SERS method was indeed screening-oriented and may be more attractive to controlling laboratories of limited resource. Copyright © 2017 Elsevier Ltd. All rights reserved.

Portable thin layer chromatography for field detection of explosives and propellants

NASA Astrophysics Data System (ADS)

Satcher, Joe H.; Maienschein, Jon L.; Pagoria, Philip F.; Racoveanu, Ana; Carman, M. Leslie; Whipple, Richard E.; Reynolds, John G.

2012-06-01

A field deployable detection kit for explosives and propellants using thin layer chromatography (TLC) has been developed at Lawrence Livermore National Laboratory (LLNL). The chemistry of the kit has been modified to allow for field detection of propellants (through propellant stabilizers), military explosives, peroxide explosives, nitrates and inorganic oxidizer precursors. For many of these target analytes, the detection limit is in the μg to pg range. A new miniaturized, bench prototype, field portable TLC (Micro TLC) kit has also been developed for the detection and identification of common military explosives. It has been demonstrated in a laboratory environment and is ready for field-testing. The kit is comprised of a low cost set of commercially available components specifically assembled for rapid identification needed in the field and identifies the common military explosives: HMX, RDX, Tetryl, Explosive D or picric acid, and TNT all on one plate. Additional modifications of the Micro TLC system have been made with fluorescent organosilicon co-polymer coatings to detect a large suite of explosives.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, Tobias G.; Fleurence, Antoine; Warner, Ben

We observe a new two-dimensional (2D) silicon crystal, using low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) and it's formed by depositing additional Si atoms onto spontaneously-formed epitaxial silicene on a ZrB 2 thin film. From scanning tunnelling spectroscopy (STS) studies, we find that this atomically-thin layered silicon has distinctly different electronic properties. Angle resolved photoelectron spectroscopy (ARPES) reveals that, in sharp contrast to epitaxial silicene, the layered silicon exhibits significantly enhanced density of states at the Fermi level resulting from newly formed metallic bands. Furthermore, the 2D growth of this material could allow for direct contacting tomore » the silicene surface and demonstrates the dramatic changes in electronic structure that can occur by the addition of even a single monolayer amount of material in 2D systems.« less

Thin-layer chromatographic separation of conjugates of ursodeoxycholic acid from those of litho-, chenodeoxy-, deoxy-, and cholic acids.

PubMed

Batta, A K; Shefer, S; Salen, G

1981-05-01

Separation of the glycine and taurine conjugates of ursodeoxycholic acid from those of lithocholic acid, chenodeoxycholic acid, deoxycholic acid, and cholic acid by thin-layer chromatography is described. Thus, on running a silica gel G plate first in a solvent system of n-butanol-water 20:3 and then in a second solvent system of chloroform-isopropanol-acetic acid-water 30:20:4:1, all the above-mentioned conjugated bile acids are separated from one another. The application of this method to study the change in the biliary bile acid conjugation pattern in ursodeoxycholic acid-fed gallstone patients is described.

Column chromatography as a useful step in purification of diatom pigments.

PubMed

Tokarek, Wiktor; Listwan, Stanisław; Pagacz, Joanna; Leśniak, Piotr; Latowski, Dariusz

2016-01-01

Fucoxanthin, diadinoxanthin and diatoxanthin are carotenoids found in brown algae and most other heterokonts. These pigments are involved in photosynthetic and photoprotective reactions, and they have many potential health benefits. They can be extracted from diatom Phaeodactylum tricornutum by sonication, extraction with chloroform : methanol and preparative thin layer chromatography. We assessed the utility of an additional column chromatography step in purification of these pigments. This novel addition to the isolation protocol increased the purity of fucoxanthin and allowed for concentration of diadinoxanthin and diatoxanthin before HPLC separation. The enhanced protocol is useful for obtaining high purity pigments for biochemical studies.

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nole, Michael; Daigle, Hugh; Cook, Ann E.

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

DOE PAGES

Nole, Michael; Daigle, Hugh; Cook, Ann E.; ...

2017-02-01

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

Evaluation of ethanol vortex ELISA for detection of bovine tuberculosis in cattle and deer.

PubMed

Wadhwa, Ashutosh; Johonson, Rachel E; Eda, Keiko; Waters, W Ray; Palmer, Mitchell V; Bannantine, John P; Eda, Shigetoshi

2014-07-04

The use of serological assays for diagnosis of bovine tuberculosis (TB) has been intensively studied and use of specific antigens have aided in improving the diagnostic accuracy of the assays. In the present study, we report an in-house enzyme linked immunosorbent assay (ELISA), developed by using ethanol extract of Mycobacterium bovis (M. bovis). The assay, named (ethanol vortex ELISA [EVELISA]), was evaluated for detection of anti- M. bovis antibodies in the sera of cattle and white-tailed deer. By using the EVELISA, we tested sera obtained from two species of animals; cattle (n = 62 [uninfected, n = 40; naturally infected, n = 22]) and white-tailed deer (n = 41 [uninfected, n = 25; naturally infected, n = 7; experimentally infected, n = 9]). To detect species specific molecules, components in the ethanol extract were analyzed by thin layer chromatography and western blotting. Among the tested animals, 77.2% of infected cattle and 87.5% of infected deer tested positive for anti- M. bovis antibody. There were only minor false positive reactions (7.5% in cattle and 0% in deer) in uninfected animals. M. bovis -specific lipids and protein (MPB83) in the ethanol extract were detected by thin layer chromatography and western blotting, respectively. The results warrant further evaluation and validation of EVELISA for bovine TB diagnosis of traditional and alternative livestock as well as for free-ranging animal species.

Validation of lipolysis product extraction from aqueous/biological samples, separation and quantification by thin-layer chromatography with flame ionization detection analysis using O-cholesteryl ethylene glycol as a new internal standard.

PubMed

Cavalier, Jean-François; Lafont, Dominique; Boullanger, Paul; Houisse, David; Giallo, Jacqueline; Ballester, Jean-Michel; Carrière, Frédéric

2009-09-11

A general and easily accessible method for the extraction followed by the simultaneous separation and quantitative determination of triacylglycerols, diacylglycerols, monoacylglycerols and free fatty acids has been improved and optimized based on existing protocols using liquid-phase extraction and thin-layer chromatography coupled to flame ionization detection (TLC/FID Iatroscan). After lipid extraction in the presence of a suitable new synthetic internal standard, namely CholE1, a single elution step using n-heptane/diethyl ether/formic acid (55:45:1, v/v/v) was applied. This method was validated in line with international bioanalytical method validation guidelines using two different matrix systems: purified water and human gastro-intestinal fluid. Overall, the assay was found to have high levels of precision with coefficients of variation ranging from 1.48% to 11.0% and accuracy ranging from -13.3% to +5.79% RE. The confidence limits of the lipid mean recovery rates varied between 89.9% and 104%. This method is therefore highly suitable for quantifying the lipolysis products generated in vitro during the hydrolysis of various fats and oils by digestive lipases, as well as those collected from the gastro-intestinal tract in the course of human clinical studies on lipid digestion.

Application of 2-Trichloromethylbenzimidazole in Analytical Chemistry: A Highly Selective Chromogenic Reagent for Thin-Layer Chromatography and Some Other Analytical Uses

PubMed Central

Konopski, Leszek; Kiełczewska, Anna

2012-01-01

2-Trichloromethylbenzimidazole (TCMB) was used as a chromogenic reagent in organic or inorganic analysis, mainly in thin-layer chromatography (TLC). In reactions of TCMB with some heteroaromatic nitrogen containing compounds, such as azines, azoles and benzazoles, a formation of high colored products occurred. For azines, the chromogenic reaction was highly regioselective, since the both adjacent α-positions versus the nitrogen atom(s) must not be substituted. A TLC method of detection was developed. Thirty azines, azoles, and benzazoles were detected at the detection limit 10 ng to 1 μg. This method was also applied for detection of heteroaromatic pesticides, and the attempts to construct active and passive dosimeters for nicotine were made. In a prechromatographic reaction of aromatic o-diamines with methyl trichloroacetimidate, TCMB or its derivatives were formed in situ. Followed by TLC and visualization in pyridine vapors, this procedure was applied for detection of o-phenylenediamine derivatives. The reaction product of TCMB and pyridine (LI Complex) was identified and fully characterized. Two different reaction mechanisms: with electron deficient basic heteroaromatic compounds, like pyridine, and with more acidic compounds, for example, pyrrole, were discussed. In aqueous solutions, the LI Complex may be also used as a new indicator for complexometric, adsorption and acid-base titration of inorganic compounds. PMID:22567563

HPTLC and magnetochromatography of new complexes of carboxylates with transition metals or rare earth elements and their ligands - study of lipophilicity.

PubMed

Malinowska, Irena; Wronka, Agnieszka; Ferenc, Wiesława

2017-05-01

Nineteen new complexes of carboxylates with transition and rare elements as central ions and their ligands were characterized by chromatographic analyses. The parameter of relative lipophilicity (R M0 ) of the tested compounds was determined experimentally by the reversed-phase high-performance thin layer chromatography method with mixtures of various organic modifiers (acetonitrile, acetone, dioxane) and water as a mobile phase. The extrapolated R M0 values were compared with the logP values calculated from the molecular structures of tested solutes. Similarities between the lipophilicity indices were analysed by principal component analysis and linear regression. Thin-layer chromatography combined with a magnetic field has been proposed as a complementary method for determination of lipophilicity of the investigated compounds. The chromatograms in the field and outside it were developed simultaneously in two identical chromatographic chambers. One of them was placed in the external magnetic field of 0.4 T inductivity. We proved that chelation causes a drastic change in compound lipophilicity, but all complexes did not exhibit enhanced activity as compared with the parent ligand. Also in the magnetic field the retention of some complexes changed, which means that the presence of the field influences the physicochemical properties of the compounds and their interactions with the stationary phase. Copyright © 2016 John Wiley & Sons, Ltd.

A new solution chemical method to make low dimensional thermoelectric materials

NASA Astrophysics Data System (ADS)

Ding, Zhongfen

2001-11-01

Bismuth telluride and its alloys are currently the best thermoelectric materials known at room temperature and are therefore used for portable solid-state refrigeration. If the thermal electric figure of merit ZT could be improved by a factor of about 3, quiet and rugged solid-state devices could eventually replace conventional compressor based cooling systems. In order to test a theory that improved one-dimensional or two-dimensional materials could enhance ZT due to lower thermal conductivity, we are developing solution processing methods to make low dimensional materials. Bismuth telluride and its p-type and n-type alloys have layered structures consisting of 5 atom thick Te-Bi-Te-Bi-Te sheets, each sheet about 10 A thick. Lithium ions are intercalated into the layered materials using liquid ammonia. The lithium-intercalated materials are then exfoliated in water to form colloidal suspensions with narrow particle size distributions and are stable for more than 24 hours. The layers are then deposited on substrates, which after annealing at low temperatures, form highly c-axis oriented thin films. The exfoliated layers can potentially be restacked with other ions or layered materials in between the sheets to form novel structures. The restacked layers when treated with nitric acid and sonication form high yield nanorod structured materials. This new intercalation and exfoliation followed by sonication method could potentially be used for many other layered materials to make nanorod structured materials. The low dimensional materials are characterized by powder X-ray diffraction, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP) and dynamic light scattering.

Integrated digital inverters based on two-dimensional anisotropic ReS2 field-effect transistors

PubMed Central

Liu, Erfu; Fu, Yajun; Wang, Yaojia; Feng, Yanqing; Liu, Huimei; Wan, Xiangang; Zhou, Wei; Wang, Baigeng; Shao, Lubin; Ho, Ching-Hwa; Huang, Ying-Sheng; Cao, Zhengyi; Wang, Laiguo; Li, Aidong; Zeng, Junwen; Song, Fengqi; Wang, Xinran; Shi, Yi; Yuan, Hongtao; Hwang, Harold Y.; Cui, Yi; Miao, Feng; Xing, Dingyu

2015-01-01

Semiconducting two-dimensional transition metal dichalcogenides are emerging as top candidates for post-silicon electronics. While most of them exhibit isotropic behaviour, lowering the lattice symmetry could induce anisotropic properties, which are both scientifically interesting and potentially useful. Here we present atomically thin rhenium disulfide (ReS2) flakes with unique distorted 1T structure, which exhibit in-plane anisotropic properties. We fabricated monolayer and few-layer ReS2 field-effect transistors, which exhibit competitive performance with large current on/off ratios (∼107) and low subthreshold swings (100 mV per decade). The observed anisotropic ratio along two principle axes reaches 3.1, which is the highest among all known two-dimensional semiconducting materials. Furthermore, we successfully demonstrated an integrated digital inverter with good performance by utilizing two ReS2 anisotropic field-effect transistors, suggesting the promising implementation of large-scale two-dimensional logic circuits. Our results underscore the unique properties of two-dimensional semiconducting materials with low crystal symmetry for future electronic applications. PMID:25947630

Numerical simulation of three-dimensional transonic turbulent projectile aerodynamics by TVD schemes

NASA Technical Reports Server (NTRS)

Shiau, Nae-Haur; Hsu, Chen-Chi; Chyu, Wei-Jao

1989-01-01

The two-dimensional symmetric TVD scheme proposed by Yee has been extended to and investigated for three-dimensional thin-layer Navier-Stokes simulation of complex aerodynamic problems. An existing three-dimensional Navier-stokes code based on the beam and warming algorithm is modified to provide an option of using the TVD algorithm and the flow problem considered is a transonic turbulent flow past a projectile with sting at ten-degree angle of attack. Numerical experiments conducted for three flow cases, free-stream Mach numbers of 0.91, 0.96 and 1.20 show that the symmetric TVD algorithm can provide surface pressure distribution in excellent agreement with measured data; moreover, the rate of convergence to attain a steady state solution is about two times faster than the original beam and warming algorithm.

A model for thin layer formation by delayed particle settling at sharp density gradients

NASA Astrophysics Data System (ADS)

Prairie, Jennifer C.; White, Brian L.

2017-02-01

Thin layers - regions where plankton or particles accumulate vertically on scales of a few meters or less - are common in coastal waters, and have important implications for both trophic dynamics and carbon cycling. These features can form by a variety of biological and physical mechanisms, including localized growth, shear-thinning, and directed swimming. An additional mechanism may result in the formation of thin layers of marine aggregates, which have been shown to decrease their settling velocity when passing through sharp density gradients, a behavior termed delayed settling. Here, we apply a simple vertical advection-diffusion model to predict the properties of aggregate thin layers formed by this process. We assume a constant vertical flux of particles from the surface, which is parameterized by observations from laboratory experiments with marine aggregates. The formation, maintenance, and shape of the layers are described in relation to non-dimensional numbers that depend on environmental conditions and particle settling properties. In particular, model results demonstrate layer intensity and sharpness both increase with higher Péclet number (Pe), that is, under conditions with weaker mixing relative to layer formation. Similarly, more intense and sharper layers are found when the delayed settling behavior of aggregates is characterized by a lower velocity minimum. The model also predicts layers that are vertically asymmetric and highly "peaky" when compared with a Gaussian distribution, features often seen in thin layers in natural environments. Lastly, by comparing model predictions with observations of thin layers in the field, we are able to gain some insight into the applicability of delayed settling as a thin layer formation mechanism in different environmental conditions.

Isolation, purification, and identification of antialgal substances in green alga Ulva prolifera for antialgal activity against the common harmful red tide microalgae.

PubMed

Sun, Ying-ying; Wang, Hui; Guo, Gan-lin; Pu, Yin-fang; Yan, Bin-lun; Wang, Chang-hai

2016-01-01

Ten compounds (1~10) were successfully isolated from green algae Ulva prolifera through the combination of silica gel column chromatography, Sephadex LH-20 column chromatography and repeated preparative thin-layer chromatography. These ten compounds showed antialgal activity against red tide microalgae. Among them, compounds 3, 6, and 7 showed stronger antialgal activity against red tide microalgae. Furthermore, their structure was identified on the basis of spectroscopic data. There are three glycoglycerolipids: 1-O-octadecanoic acid-3-O-β-D-galactopyranosyl glycerol (2), 1-O-palmitoyl-3-O-β-D-galactopyranosyl glycerol (4), and 1-O-palmitoyl-2-O-oleoyl-3-O-β-D-galactopyranosyl glycerol (5); two monoglycerides: glycerol monopalmitate (1), 9-hexadecenoic acid, 2,3-dihydroxypropyl ester (3); two terpenoids: loliolide (6) and lsololiolide (7); one lipid-soluble pigments: zeaxanthin (8); one sterol: cholest-5-en-3-ol (9); and one alkaloid: pyrrolopiperazine-2,5-dione (10). These compounds were isolated from U. prolifera for the first time, and compounds 2, 3, 5, and 8 were isolated from marine macroalgae for the first time.

Three-dimensional atom probe tomography of oxide, anion, and alkanethiolate coatings on gold.

PubMed

Zhang, Yi; Hillier, Andrew C

2010-07-15

We have used three-dimensional atom probe tomography to analyze several nanometer-thick and monomolecular films on gold surfaces. High-purity gold wire was etched by electropolishing to create a sharp tip suitable for field evaporation with a radius of curvature of <100 nm. The near-surface region of a freshly etched gold tip was examined with the atom probe at subnanometer spatial resolution and with atom-level composition accuracy. A thin contaminant layer, primarily consisting of water and atmospheric gases, was observed on a fresh tip. This sample exhibited crystalline lattice spacings consistent with the interlayer spacing of {200} lattice planes of bulk gold. A thin oxide layer was created on the gold surface via plasma oxidation, and the thickness and composition of this layer was measured. Clear evidence of a nanometer-thick oxide layer was seen coating the gold tip, and the atomic composition of the oxide layer was consistent with the expected stoichiometry for gold oxide. Monomolecular anions layers of Br(-) and I(-) were created via adsorption from aqueous solutions onto the gold. Atom probe data verified the presence of the monomolecular anion layers on the gold surface, with ion density values consistent with literature values. A hexanethiolate monolayer was coated onto the gold tip, and atom probe analysis revealed a thin film whose ion fragments were consistent with the molecular composition of the monolayer and a surface coverage similar to that expected from literature. Details of the various coating compositions and structures are presented, along with discussion of the reconstruction issues associated with properly analyzing these thin-film systems.

Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries

NASA Technical Reports Server (NTRS)

Yushin, Gleb; Evanoff, Kara; Magasinski, Alexander

2012-01-01

Thin Si films coated on porous 3D particles composed of curved 2D graphene sheets have been synthesized utilizing techniques that allow for tunable properties. Since graphene exhibits specific surface area up to 100 times higher than carbon black or graphite, the deposition of the same mass of Si on graphene is much faster in comparison -- a factor which is important for practical applications. In addition, the distance between graphene layers is tunable and variation in the thickness of the deposited Si film is feasible. Both of these characteristics allow for optimization of the energy and power characteristics. Thicker films will allow higher capacity, but slower rate capabilities. Thinner films will allow more rapid charging, or higher power performance. In this innovation, uniform deposition of Si and C layers on high-surface area graphene produced granules with specific surface area (SSA) of 5 sq. m/g.

Artificial semiconductor/insulator superlattice channel structure for high-performance oxide thin-film transistors

PubMed Central

Ahn, Cheol Hyoun; Senthil, Karuppanan; Cho, Hyung Koun; Lee, Sang Yeol

2013-01-01

High-performance thin-film transistors (TFTs) are the fundamental building blocks in realizing the potential applications of the next-generation displays. Atomically controlled superlattice structures are expected to induce advanced electric and optical performance due to two-dimensional electron gas system, resulting in high-electron mobility transistors. Here, we have utilized a semiconductor/insulator superlattice channel structure comprising of ZnO/Al2O3 layers to realize high-performance TFTs. The TFT with ZnO (5 nm)/Al2O3 (3.6 nm) superlattice channel structure exhibited high field effect mobility of 27.8 cm2/Vs, and threshold voltage shift of only < 0.5 V under positive/negative gate bias stress test during 2 hours. These properties showed extremely improved TFT performance, compared to ZnO TFTs. The enhanced field effect mobility and stability obtained for the superlattice TFT devices were explained on the basis of layer-by-layer growth mode, improved crystalline nature of the channel layers, and passivation effect of Al2O3 layers. PMID:24061388

Deterministic strain-induced arrays of quantum emitters in a two-dimensional semiconductor

PubMed Central

Branny, Artur; Kumar, Santosh; Proux, Raphaël; Gerardot, Brian D

2017-01-01

An outstanding challenge in quantum photonics is scalability, which requires positioning of single quantum emitters in a deterministic fashion. Site positioning progress has been made in established platforms including defects in diamond and self-assembled quantum dots, albeit often with compromised coherence and optical quality. The emergence of single quantum emitters in layered transition metal dichalcogenide semiconductors offers new opportunities to construct a scalable quantum architecture. Here, using nanoscale strain engineering, we deterministically achieve a two-dimensional lattice of quantum emitters in an atomically thin semiconductor. We create point-like strain perturbations in mono- and bi-layer WSe2 which locally modify the band-gap, leading to efficient funnelling of excitons towards isolated strain-tuned quantum emitters that exhibit high-purity single photon emission. We achieve near unity emitter creation probability and a mean positioning accuracy of 120±32 nm, which may be improved with further optimization of the nanopillar dimensions. PMID:28530219

CO2-Assisted Conversion of Crystal Two-Dimensional Molybdenum Oxide to Amorphism with Plasmon Resonances.

PubMed

Liu, Wei; Xu, Qun

2018-04-20

Localized surface plasmon resonances (LSPRs) of ultra-thin two-dimensional (2D) nanomaterials opened a new regime in plasmonics in the last several years. 2D plasmonic materials are yet concentrated on the crystal structure, amorphous materials are hardly reported because of their limited preparation methods rather than undesired plasmonic properties. Taking molybdenum oxides as an example, herein, we elaborate the 2D amorphous plasmons prepared with the assistance of supercritical CO2. In brief, we examine the reported characteristic plasmonic properties of molybdenum oxides, and applications of supercritical CO2 in formations of 2D layer materials as well as introduced phase and disorder engineering based on our researchs. Furthermore, we propose our perspective on the development of 2D plasmons, especially for amorphous layer materials in the future. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pressure-Sensitive Paint: Effect of Substrate

PubMed Central

Quinn, Mark Kenneth; Yang, Leichao; Kontis, Konstantinos

2011-01-01

There are numerous ways in which pressure-sensitive paint can be applied to a surface. The choice of substrate and application method can greatly affect the results obtained. The current study examines the different methods of applying pressure-sensitive paint to a surface. One polymer-based and two porous substrates (anodized aluminum and thin-layer chromatography plates) are investigated and compared for luminescent output, pressure sensitivity, temperature sensitivity and photodegradation. Two luminophores [tris-Bathophenanthroline Ruthenium(II) Perchlorate and Platinum-tetrakis (pentafluorophenyl) Porphyrin] will also be compared in all three of the substrates. The results show the applicability of the different substrates and luminophores to different testing environments. PMID:22247685

Using a Microscale Approach to Rapidly Separate and Characterize Three Photosynthetic Pigment Species from Fern

ERIC Educational Resources Information Center

Ayudhya, Theppawut Israsena Na; Posey, Frederick T.; Tyus, Jessica C.; Dingra, Nin N.

2015-01-01

A rapid separation of three photosynthetic pigments (chlorophyll "a" and "b" and xanthophyll) from fern ("Polystichum acrostichoides") is described using microscale solvent extraction and traditional thin layer chromatography that minimizes use of harmful chemicals and lengthy procedures. The experiment introduces…

Smells Like Teen Shampoo

ERIC Educational Resources Information Center

Allan, Adrian

2017-01-01

Reform of the Scottish science curriculum for Higher Chemistry gave students the opportunity to experiment with essential oils and fragrances. With the support of a Royal Society Partnership Grant, the students learnt how to isolate and identify compounds in essential oils using microscale steam distillation and thin-layer chromatography. The…

Monogalactosyldiacylglycerols as host recognition cues for western corn rootworm larvae (Coleoptera: Chrysomelidae)

USDA-ARS?s Scientific Manuscript database

Monogalactosyldiacylglycerol (MGDG) was identified as a host recognition cue for larvae of the western corn rootworm Diabrotica virgifera virgifera LeConte. An active glycolipid fraction obtained from an extract of germinating maize roots was isolated with thin layer chromatography using a bioassay-...

Application of advanced computational codes in the design of an experiment for a supersonic throughflow fan rotor

NASA Technical Reports Server (NTRS)

Wood, Jerry R.; Schmidt, James F.; Steinke, Ronald J.; Chima, Rodrick V.; Kunik, William G.

1987-01-01

Increased emphasis on sustained supersonic or hypersonic cruise has revived interest in the supersonic throughflow fan as a possible component in advanced propulsion systems. Use of a fan that can operate with a supersonic inlet axial Mach number is attractive from the standpoint of reducing the inlet losses incurred in diffusing the flow from a supersonic flight Mach number to a subsonic one at the fan face. The design of the experiment using advanced computational codes to calculate the components required is described. The rotor was designed using existing turbomachinery design and analysis codes modified to handle fully supersonic axial flow through the rotor. A two-dimensional axisymmetric throughflow design code plus a blade element code were used to generate fan rotor velocity diagrams and blade shapes. A quasi-three-dimensional, thin shear layer Navier-Stokes code was used to assess the performance of the fan rotor blade shapes. The final design was stacked and checked for three-dimensional effects using a three-dimensional Euler code interactively coupled with a two-dimensional boundary layer code. The nozzle design in the expansion region was analyzed with a three-dimensional parabolized viscous code which corroborated the results from the Euler code. A translating supersonic diffuser was designed using these same codes.

Improvement of water resistance and dimensional stability of wood through titanium dioxide coating

Treesearch

Qingfeng Sun; Haipeng Yu; Yixing Liu; Jian Li; Yun Lu; John F. Hunt

2010-01-01

Moisture absorption and dimensional distortion are the major drawbacks of wood utilization as building material. In this study, poplar wood coated with a thin layer of titanium dioxide (TiO2) was prepared by the cosolvent-controlled hydrothermal method. Subsequently, its moisture absorption and dimensional stability were examined. Scanning...

Vapor-solid growth of one-dimensional layer-structured gallium sulfide nanostructures.

PubMed

Shen, Guozhen; Chen, Di; Chen, Po-Chiang; Zhou, Chongwu

2009-05-26

Gallium sulfide (GaS) is a wide direct bandgap semiconductor with uniform layered structure used in photoelectric devices, electrical sensors, and nonlinear optical applications. We report here the controlled synthesis of various high-quality one-dimensional GaS nanostructures (thin nanowires, nanobelts, and zigzag nanobelts) as well as other kinds of GaS products (microbelts, hexagonal microplates, and GaS/Ga(2)O(3) heterostructured nanobelts) via a simple vapor-solid method. The morphology and structures of the products can be easily controlled by substrate temperature and evaporation source. Optical properties of GaS thin nanowires and nanobelts were investigated and both show an emission band centered at 580 nm.

Quantitation of triacylglycerols in edible oils by off-line comprehensive two-dimensional liquid chromatography-atmospheric pressure chemical ionization mass spectrometry using a single column.

PubMed

Wei, Fang; Hu, Na; Lv, Xin; Dong, Xu-Yan; Chen, Hong

2015-07-24

In this investigation, off-line comprehensive two-dimensional liquid chromatography-atmospheric pressure chemical ionization mass spectrometry using a single column has been applied for the identification and quantification of triacylglycerols in edible oils. A novel mixed-mode phenyl-hexyl chromatographic column was employed in this off-line two-dimensional separation system. The phenyl-hexyl column combined the features of traditional C18 and silver-ion columns, which could provide hydrophobic interactions with triacylglycerols under acetonitrile conditions and can offer π-π interactions with triacylglycerols under methanol conditions. When compared with traditional off-line comprehensive two-dimensional liquid chromatography employing two different chromatographic columns (C18 and silver-ion column) and using elution solvents comprised of two phases (reversed-phase/normal-phase) for triacylglycerols separation, the novel off-line comprehensive two-dimensional liquid chromatography using a single column can be achieved by simply altering the mobile phase between acetonitrile and methanol, which exhibited a much higher selectivity for the separation of triacylglycerols with great efficiency and rapid speed. In addition, an approach based on the use of response factor with atmospheric pressure chemical ionization mass spectrometry has been developed for triacylglycerols quantification. Due to the differences between saturated and unsaturated acyl chains, the use of response factors significantly improves the quantitation of triacylglycerols. This two-dimensional liquid chromatography-mass spectrometry system was successfully applied for the profiling of triacylglycerols in soybean oils, peanut oils and lord oils. A total of 68 triacylglycerols including 40 triacylglycerols in soybean oils, 50 triacylglycerols in peanut oils and 44 triacylglycerols in lord oils have been identified and quantified. The liquid chromatography-mass spectrometry data were analyzed using principal component analysis. The results of the principal component analysis enabled a clear identification of different plant oils. By using this two-dimensional liquid chromatography-mass spectrometry system coupled with principal component analysis, adulterated soybean oils with 5% added lord oil and peanut oils with 5% added soybean oil can be clearly identified. Copyright © 2015 Elsevier B.V. All rights reserved.

One-dimensional conduction through supporting electrolytes: two-scale cathodic Debye layer.

PubMed

Almog, Yaniv; Yariv, Ehud

2011-10-01

Supporting-electrolyte solutions comprise chemically inert cations and anions, produced by salt dissolution, together with a reactive ionic species that may be consumed and generated on bounding ion-selective surfaces (e.g., electrodes or membranes). Upon application of an external voltage, a Faraday current is thereby established. It is natural to analyze this ternary-system process through a one-dimensional transport problem, employing the thin Debye-layer limit. Using a simple model of ideal ion-selective membranes, we have recently addressed this problem for moderate voltages [Yariv and Almog, Phys. Rev. Lett. 105, 176101 (2010)], predicting currents that scale as a fractional power of Debye thickness. We address herein the complementary problem of moderate currents. We employ matched asymptotic expansions, separately analyzing the two inner thin Debye layers adjacent to the ion-selective surfaces and the outer electroneutral region outside them. A straightforward calculation following comparable singular-perturbation analyses of binary systems is frustrated by the prediction of negative ionic concentrations near the cathode. Accompanying numerical simulations, performed for small values of Debye thickness, indicate a number unconventional features occurring at that region, such as inert-cation concentration amplification and electric-field intensification. The current-voltage correlation data of the electrochemical cell, obtained from compilation of these simulations, does not approach a limit as the Debye thickness vanishes. Resolution of these puzzles reveals a transformation of the asymptotic structure of the cathodic Debye layer. This reflects the emergence of an internal boundary layer, adjacent to the cathode, wherein field and concentration scaling differs from those of the Gouy-Chapman theory. The two-scale feature of the cathodic Debye layer is manifested through a logarithmic voltage scaling with Debye thickness. Accounting for this scaling, the complied current-voltage data collapses upon a single curve. This curve practically coincides with an asymptotically calculated universal current-voltage relation.

Reversible and nonvolatile ferroelectric control of two-dimensional electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films with a layered structure

NASA Astrophysics Data System (ADS)

Zhao, Xu-Wen; Gao, Guan-Yin; Yan, Jian-Min; Chen, Lei; Xu, Meng; Zhao, Wei-Yao; Xu, Zhi-Xue; Guo, Lei; Liu, Yu-Kuai; Li, Xiao-Guang; Wang, Yu; Zheng, Ren-Kui

2018-05-01

Copper-based ZrCuSiAs-type compounds of LnCuChO (Ln =Bi and lanthanides, Ch =S , Se, Te) with a layered crystal structure continuously attract worldwide attention in recent years. Although their high-temperature (T ≥ 300 K) electrical properties have been intensively studied, their low-temperature electronic transport properties are little known. In this paper, we report the integration of ZrCuSiAs-type copper oxyselenide thin films of B i0.94P b0.06CuSeO (BPCSO) with perovskite-type ferroelectric Pb (M g1 /3N b2 /3 ) O3-PbTi O3 (PMN-PT) single crystals in the form of ferroelectric field effect devices that allow us to control the electronic properties (e.g., carrier density, magnetoconductance, dephasing length, etc.) of BPCSO films in a reversible and nonvolatile manner by polarization switching at room temperature. Combining ferroelectric gating and magnetotransport measurements with the Hikami-Larkin-Nagaoka theory, we demonstrate two-dimensional (2D) electronic transport characteristics and weak antilocalization effect as well as strong carrier-density-mediated competition between weak antilocalization and weak localization in BPCSO films. Our results show that ferroelectric gating using PMN-PT provides an effective and convenient approach to probe the carrier-density-related 2D electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films.

Comparison of the phytochemical profiles of five native plant species in two different forest formations.

PubMed

Pilatti, D M; Fortes, A M T; Jorge, T C M; Boiago, N P

2018-06-14

The expression of chemical compounds by individual plants of the same species in different locations may be affected by abiotic factors resulting in differences in the production of allelopathic compounds. The objective of this study was to compare the phytochemical profiles of plant species from two different forest formations in the state of Paraná, Brazil. The forest formations were Seasonal Semideciduous Forest (SSF) and Lowland Ombrophilous Dense Forest (LODF), and the five study species were Jacaranda micrantha, Cecropia pachystachya, Mimosa bimucronata, Schinus terebinthifolius and Cedrela fissilis. Secondary metabolites were extracted by exhaustive extraction with methanol, and the crude extract was fractionated using column chromatography. The fractions were used to calculate the retention factor of the main compounds using thin layer chromatography and phytochemical tests. The classes of compounds identified were practically the same among the analyzed species, however, at different levels of concentration. The type of tannins found in S. terebinthifolius differed between the two forest formations.

Dual-gated MoS2/WSe2 van der Waals tunnel diodes and transistors.

PubMed

Roy, Tania; Tosun, Mahmut; Cao, Xi; Fang, Hui; Lien, Der-Hsien; Zhao, Peida; Chen, Yu-Ze; Chueh, Yu-Lun; Guo, Jing; Javey, Ali

2015-02-24

Two-dimensional layered semiconductors present a promising material platform for band-to-band-tunneling devices given their homogeneous band edge steepness due to their atomically flat thickness. Here, we experimentally demonstrate interlayer band-to-band tunneling in vertical MoS2/WSe2 van der Waals (vdW) heterostructures using a dual-gate device architecture. The electric potential and carrier concentration of MoS2 and WSe2 layers are independently controlled by the two symmetric gates. The same device can be gate modulated to behave as either an Esaki diode with negative differential resistance, a backward diode with large reverse bias tunneling current, or a forward rectifying diode with low reverse bias current. Notably, a high gate coupling efficiency of ∼80% is obtained for tuning the interlayer band alignments, arising from weak electrostatic screening by the atomically thin layers. This work presents an advance in the fundamental understanding of the interlayer coupling and electron tunneling in semiconductor vdW heterostructures with important implications toward the design of atomically thin tunnel transistors.

Electronic and Optical Properties of Two-Dimensional GaN from First-Principles.

PubMed

Sanders, Nocona; Bayerl, Dylan; Shi, Guangsha; Mengle, Kelsey A; Kioupakis, Emmanouil

2017-12-13

Gallium nitride (GaN) is an important commercial semiconductor for solid-state lighting applications. Atomically thin GaN, a recently synthesized two-dimensional material, is of particular interest because the extreme quantum confinement enables additional control of its light-emitting properties. We performed first-principles calculations based on density functional and many-body perturbation theory to investigate the electronic, optical, and excitonic properties of monolayer and bilayer two-dimensional (2D) GaN as a function of strain. Our results demonstrate that light emission from monolayer 2D GaN is blueshifted into the deep ultraviolet range, which is promising for sterilization and water-purification applications. Light emission from bilayer 2D GaN occurs at a similar wavelength to its bulk counterpart due to the cancellation of the effect of quantum confinement on the optical gap by the quantum-confined Stark shift. Polarized light emission at room temperature is possible via uniaxial in-plane strain, which is desirable for energy-efficient display applications. We compare the electronic and optical properties of freestanding two-dimensional GaN to atomically thin GaN wells embedded within AlN barriers in order to understand how the functional properties are influenced by the presence of barriers. Our results provide microscopic understanding of the electronic and optical characteristics of GaN at the few-layer regime.

Low emissivity Ag/Ta/glass multilayer thin films deposited by sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sun Ho; Lee, Kee Sun; Green Home Energy Technology Center, Cheonan City

Ta is deposited on a glass substrate as an interlayer for the two-dimensional growth of Ag thin films because Ta has good thermal stability and can induce a negative surface-energy change in Ag/glass. From the transmission electron microscopy results, we concluded that the Ag crystals in the bottom layer (seemingly on Ag/Ta) were flattened; this was rarely observed in the three-dimensional growth mode. Comparing Ag/Ta/glass with Ag/glass, we found that the Ta interlayer was effective in reducing both the resistance and the emissivity, accompanied by the relatively high transmittance in the visible region. In particular, Ag(9 nm)/Ta(1 nm)/glass film showedmore » 0.08 of the emissivity, including {approx}61% of the transmittance in the visible region (wavelength: 550 nm).« less

Amorphous and Crystalline Vanadium Oxides as High-Energy and High-Power Cathodes for Three-Dimensional Thin-Film Lithium Ion Batteries.

PubMed

Mattelaer, Felix; Geryl, Kobe; Rampelberg, Geert; Dendooven, Jolien; Detavernier, Christophe

2017-04-19

Flexible wearable electronics and on-chip energy storage for wireless sensors drive rechargeable batteries toward thin-film lithium ion batteries. To enable more charge storage on a given surface, higher energy density materials are required, while faster energy storage and release can be obtained by going to thinner films. Vanadium oxides have been examined as cathodes in classical and thin-film lithium ion batteries for decades, but amorphous vanadium oxide thin films have been mostly discarded. Here, we investigate the use of atomic layer deposition, which enables electrode deposition on complex three-dimensional (3D) battery architectures, to obtain both amorphous and crystalline VO 2 and V 2 O 5 , and we evaluate their thin-film cathode performance. Very high volumetric capacities are found, alongside excellent kinetics and good cycling stability. Better kinetics and higher volumetric capacities were observed for the amorphous vanadium oxides compared to their crystalline counterparts. The conformal deposition of these vanadium oxides on silicon micropillar structures is demonstrated. This study shows the promising potential of these atomic layer deposited vanadium oxides as cathodes for 3D all-solid-state thin-film lithium ion batteries.

Atomic Force Microscope Mediated Chromatography

NASA Technical Reports Server (NTRS)

Anderson, Mark S.

2013-01-01

The atomic force microscope (AFM) is used to inject a sample, provide shear-driven liquid flow over a functionalized substrate, and detect separated components. This is demonstrated using lipophilic dyes and normal phase chromatography. A significant reduction in both size and separation time scales is achieved with a 25-micron-length column scale, and one-second separation times. The approach has general applications to trace chemical and microfluidic analysis. The AFM is now a common tool for ultra-microscopy and nanotechnology. It has also been demonstrated to provide a number of microfluidic functions necessary for miniaturized chromatography. These include injection of sub-femtoliter samples, fluidic switching, and sheardriven pumping. The AFM probe tip can be used to selectively remove surface layers for subsequent microchemical analysis using infrared and tip-enhanced Raman spectroscopy. With its ability to image individual atoms, the AFM is a remarkably sensitive detector that can be used to detect separated components. These diverse functional components of microfluidic manipulation have been combined in this work to demonstrate AFM mediated chromatography. AFM mediated chromatography uses channel-less, shear-driven pumping. This is demonstrated with a thin, aluminum oxide substrate and a non-polar solvent system to separate a mixture of lipophilic dyes. In conventional chromatographic terms, this is analogous to thin-layer chromatography using normal phase alumina substrate with sheardriven pumping provided by the AFM tip-cantilever mechanism. The AFM detection of separated components is accomplished by exploiting the variation in the localized friction of the separated components. The AFM tip-cantilever provides the mechanism for producing shear-induced flows and rapid pumping. Shear-driven chromatography (SDC) is a relatively new concept that overcomes the speed and miniaturization limitations of conventional liquid chromatography. SDC is based on a sliding plate system, consisting of two flat surfaces, one of which has a recessed channel. A fluid flow is produced by axially sliding one plate past another, where the fluid has mechanical shear forces imposed at each point along the channel length. The shear-induced flow rates are very reproducible, and do not have pressure or voltage gradient limitations. SDC opens up a new range of enhanced separation kinetics by permitting the sample confinement with submicron dimensions. Small, highly confined liquid is advantageous for chromatographic separation because the separation rate is known to scale according to the square of the confined sample diameter. In addition, because shear-driven flows are not limited by fluid velocity, shear-driven liquid chromatography may provide up to 100,000 plate efficiency.

NMR of thin layers using a meanderline surface coil

DOEpatents

Cowgill, Donald F.

2001-01-01

A miniature meanderline sensor coil which extends the capabilities of nuclear magnetic resonance (NMR) to provide analysis of thin planar samples and surface layer geometries. The sensor coil allows standard NMR techniques to be used to examine thin planar (or curved) layers, extending NMRs utility to many problems of modern interest. This technique can be used to examine contact layers, non-destructively depth profile into films, or image multiple layers in a 3-dimensional sense. It lends itself to high resolution NMR techniques of magic angle spinning and thus can be used to examine the bonding and electronic structure in layered materials or to observe the chemistry associated with aging coatings. Coupling this sensor coil technology with an arrangement of small magnets will produce a penetrator probe for remote in-situ chemical analysis of groundwater or contaminant sediments. Alternatively, the sensor coil can be further miniaturized to provide sub-micron depth resolution within thin films or to orthoscopically examine living tissue. This thin-layer NMR technique using a stationary meanderline coil in a series-resonant circuit has been demonstrated and it has been determined that the flat meanderline geometry has about he same detection sensitivity as a solenoidal coil, but is specifically tailored to examine planar material layers, while avoiding signals from the bulk.

Degradation of 2,4,6-trinitrotoluene by P. aeruginosa and characterization of some metabolites.

PubMed

Mercimek, Hatice Aysun; Dincer, Sadik; Guzeldag, Gulcihan; Ozsavli, Aysenur; Matyar, Fatih; Arkut, Afet; Kayis, Fikret; Ozdenefe, Melis Sumengen

2015-03-01

Degradation of 2,4,6-trinitrotoluene (TNT), a nitroaromatic explosive found in the soil and ground water, was investigated using Pseudomonas aeruginosa in in vitro experiments . Biodegradable abilitiy of this bacteria was performed with 50 and 75 mg L (-1) TNT concentrations in a defined liquid medium for 96 h time period. Treatment of TNT in supernatant samples taken at 0, 6, 12, 24, 48, 72 and 96 h from agitated vessels was followed by reverse-phase high-performance liquid chromatography (HPLC). In cultures supplemented with 50 and 75 mgL (-1) TNT, after 96 h of incubation 46% and 59% reduction were detected respectively. Two metabolites as degradation intermediates with nitrite release into the medium, 2,4-dinitrotoluene (2,4-DNT) and 4-aminodinitrotoluene (4-ADNT), were elucidated by thin layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). These findings clearly indicate that Pseudomonas aeruginosa can be used in bioremediation of TNT contaminated sites.

Degradation of 2,4,6-trinitrotoluene by P. aeruginosa and characterization of some metabolites

PubMed Central

Mercimek, Hatice Aysun; Dincer, Sadik; Guzeldag, Gulcihan; Ozsavli, Aysenur; Matyar, Fatih; Arkut, Afet; Kayis, Fikret; Ozdenefe, Melis Sumengen

2015-01-01

Degradation of 2,4,6-trinitrotoluene (TNT), a nitroaromatic explosive found in the soil and ground water, was investigated using Pseudomonas aeruginosa in in vitro experiments . Biodegradable abilitiy of this bacteria was performed with 50 and 75 mg L −1 TNT concentrations in a defined liquid medium for 96 h time period. Treatment of TNT in supernatant samples taken at 0, 6, 12, 24, 48, 72 and 96 h from agitated vessels was followed by reverse-phase high-performance liquid chromatography (HPLC). In cultures supplemented with 50 and 75 mgL −1 TNT, after 96 h of incubation 46% and 59% reduction were detected respectively. Two metabolites as degradation intermediates with nitrite release into the medium, 2,4-dinitrotoluene (2,4-DNT) and 4-aminodinitrotoluene (4-ADNT), were elucidated by thin layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). These findings clearly indicate that Pseudomonas aeruginosa can be used in bioremediation of TNT contaminated sites. PMID:26221094

Production and structural analysis of the polysaccharide secreted by Trametes (Coriolus) versicolor ATCC 200801.

PubMed

Rau, Udo; Kuenz, Anja; Wray, Victor; Nimtz, Manfred; Wrenger, Julika; Cicek, Hasan

2009-01-01

Trametes versicolor ATCC 200801 secretes 4.1 g L(-1) of exopolysaccharide (EPS) when synthetic minimal medium and low-shear bioreactor cultivation technique are used. Structural and compositional analyses by thin layer chromatography, gas chromatography-mass spectrometry, electrospray ionization tandem mass spectrometry, and nuclear magnetic resonance spectroscopy yielded predominantly glucose and small amounts of galactose, mannose, arabinose, and xylose. The main EPS is composed of beta-1,3/beta-1,6-linked D-glucose molecules which is identical with Schizophyllan but does not possess a triple helical arrangement as secondary structure. Two molar mass fractions were detected by size exclusion chromatography yielding weight-average molecular weights of 4,100 and 2.6 kDa. Protein content varies between 2-3.6% (w/w). The exopolysaccharide is different in the nature of the glycosidic linkage, composition of monosaccharides, protein content, and weight-average molecular weight compared to the well-known polysaccharopeptide (PSP) and polysaccharopeptide Krestin (PSK).

Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

DOEpatents

Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.

1987-06-08

A field effect transistor comprises a semiconductor having a source, a drain, a channel and a gate in operational relationship. The semiconductor is a strained layer superlattice comprising alternating quantum well and barrier layers, the quantum well layers and barrier layers being selected from the group of layer pairs consisting of InGaAs/AlGaAs, InAs/InAlGaAs, and InAs/InAlAsP. The layer thicknesses of the quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice which has a superlattice conduction band energy level structure in k-vector space. The layer thicknesses of the quantum well layers are selected to provide a superlattice L/sub 2D/-valley which has a shape which is substantially more two-dimensional than that of said bulk L-valley. 2 figs.

Integrating Biology into the General Chemistry Laboratory: Fluorometric Analysis of Chlorophyll "a"

ERIC Educational Resources Information Center

Wesolowski, Meredith C.

2014-01-01

A laboratory experiment that introduces fluorometry of chlorophyll "a" at the general chemistry level is described. The use of thin-layer chromatography to isolate chlorophyll "a" from spirulina and leaf matter enables quantification of small amounts of chlorophyll "a" via fluorometry. Student results were reasonably…

Isolation and identification of nematode-antagonistic compounds from the fungus Aspergillus candidus

USDA-ARS?s Scientific Manuscript database

An isolate of the fungus Aspergillus candidus was tested for production of nematicidal compounds. Adults of the nematode Ditylenchus destructor were completely inactive after 24 hr exposure to soy medium in which A. candidus was cultured. Column, thin layer and preparative chromatographies, and spec...

7 CFR 868.90 - Fees for certain Federal inspection services.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Miscellaneous Processed Commodities: 2 (1) Additional Tests (cost per test, assessed in addition to the hourly rate): (i) Aflatoxin Test (Thin Layer Chromatography) 51.40 (ii) Falling Number 12.50 (iii) Aflatoxin Test Kit 7.50 Graded Commodities (Beans, Peas, Lentils, Hops, and Pulses): (1) Additional Tests—Unit...

Iron-Sulfur-Carbonyl and -Nitrosyl Complexes: A Laboratory Experiment.

ERIC Educational Resources Information Center

Glidewell, Christopher; And Others

1985-01-01

Background information, materials needed, procedures used, and typical results obtained, are provided for an experiment on iron-sulfur-carbonyl and -nitrosyl complexes. The experiment involved (1) use of inert atmospheric techniques and thin-layer and flexible-column chromatography and (2) interpretation of infrared, hydrogen and carbon-13 nuclear…

Materials Science and Device Physics of 2-Dimensional Semiconductors

NASA Astrophysics Data System (ADS)

Fang, Hui

Materials and device innovations are the keys to future technology revolution. For MOSFET scaling in particular, semiconductors with ultra-thin thickness on insulator platform is currently of great interest, due to the potential of integrating excellent channel materials with the industrially mature Si processing. Meanwhile, ultra-thin thickness also induces strong quantum confinement which in turn affect most of the material properties of these 2-dimensional (2-D) semiconductors, providing unprecedented opportunities for emerging technologies. In this thesis, multiple novel 2-D material systems are explored. Chapter one introduces the present challenges faced by MOSFET scaling. Chapter two covers the integration of ultrathin III V membranes with Si. Free standing ultrathin III-V is studied to enable high performance III-V on Si MOSFETs with strain engineering and alloying. Chapter three studies the light absorption in 2-D membranes. Experimental results and theoretical analysis reveal that light absorption in the 2-D quantum membranes is quantized into a fundamental physical constant, where we call it the quantum unit of light absorption, irrelevant of most of the material dependent parameters. Chapter four starts to focus on another 2-D system, atomic thin layered chalcogenides. Single and few layered chalcogenides are first explored as channel materials, with focuses in engineering the contacts for high performance MOSFETs. Contact treatment by molecular doping methods reveals that many layered chalcogenides other than MoS2 exhibit good transport properties at single layer limit. Finally, Chapter five investigated 2-D van der Waals heterostructures built from different single layer chalcogenides. The investigation in a WSe2/MoS2 hetero-bilayer shows a large Stokes like shift between photoluminescence peak and lowest absorption peak, as well as strong photoluminescence intensity, consistent with spatially indirect transition in a type II band alignment in this van der Waals heterostructure. This result enables new family of semiconductor heterostructures having tunable optoelectronic properties with customized composite layers and highlights the ability to build van der Waals semiconductor heterostructure lasers/LEDs.

Freestanding and Reactive Thin Films Fabricated by Covalent Layer-by-Layer Assembly and Subsequent Lift-Off of Azlactone-Containing Polymer Multilayers

PubMed Central

Buck, Maren E.

2010-01-01

We report an approach to the fabrication of freestanding and amine-reactive thin films that is based on the reactive layer-by-layer assembly and subsequent lift-off of azlactone-containing polymer multilayers. We demonstrate that covalently crosslinked multilayers fabricated using the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and a primary amine-containing polymer [poly(ethyleneimine) (PEI)] can be delaminated from planar glass and silicon surfaces by immersion in mildly acidic aqueous environments to yield flexible freestanding membranes. These freestanding membranes are robust and can withstand exposure to strong acid, strong base, or incubation in high ionic strength solutions that typically lead to the disruption and erosion of polymer multilayers assembled by reversible weak interactions (e.g., ‘polyelectrolyte multilayers’ assembled by electrostatic interactions or hydrogen bonding). We demonstrate further that these PEI/PVDMA assemblies contain residual reactive azlactone functionality that can be exploited to chemically modify the films (either directly after fabrication or after they have been lifted off of the substrates on which they were fabricated) using a variety of amine-functionalized small molecules. These freestanding membranes can also be transferred readily onto other objects (for example, onto the surfaces of planar substrates containing holes or pores) to fabricate suspended polymer membranes and other film-functionalized interfaces. In addition to planar, two-dimensional freestanding films, this approach can be used to fabricate and isolate three-dimensional freestanding membranes (e.g., curved films or tubes) by layer-by-layer assembly on, and subsequent lift-off from, the surfaces of topologically complex substrates (e.g., the curved ends of glass tubing, etc.). The results of this investigation, when combined, suggest the basis of methods for the fabrication of stable, chemically-reactive, and flexible polymer thin films and membranes of potential utility in a variety of fundamental and applied contexts. PMID:20857952

One dimensional metallic edges in atomically thin WSe2 induced by air exposure

NASA Astrophysics Data System (ADS)

Addou, Rafik; Smyth, Christopher M.; Noh, Ji-Young; Lin, Yu-Chuan; Pan, Yi; Eichfeld, Sarah M.; Fölsch, Stefan; Robinson, Joshua A.; Cho, Kyeongjae; Feenstra, Randall M.; Wallace, Robert M.

2018-04-01

Transition metal dichalcogenides are a unique class of layered two-dimensional (2D) crystals with extensive promising applications. Tuning the electronic properties of low-dimensional materials is vital for engineering new functionalities. Surface oxidation is of particular interest because it is a relatively simple method of functionalization. By means of scanning probe microscopy and x-ray photoelectron spectroscopy, we report the observation of metallic edges in atomically thin WSe2 monolayers grown by chemical vapor deposition on epitaxial graphene. Scanning tunneling microscopy shows structural details of WSe2 edges and scanning tunneling spectroscopy reveals the metallic nature of the oxidized edges. Photoemission demonstrates that the formation of metallic sub-stoichiometric tungsten oxide (WO2.7) is responsible for the high conductivity measured along the edges. Ab initio calculations validate the susceptibility of WSe2 nanoribbon edges to oxidation. The zigzag terminated edge exhibits metallic behavior prior the air-exposure and remains metallic after oxidation. Comprehending and exploiting this property opens a new opportunity for application in advanced electronic devices.

Recent progress in high-mobility thin-film transistors based on multilayer 2D materials

NASA Astrophysics Data System (ADS)

Hong, Young Ki; Liu, Na; Yin, Demin; Hong, Seongin; Kim, Dong Hak; Kim, Sunkook; Choi, Woong; Yoon, Youngki

2017-04-01

Two-dimensional (2D) layered semiconductors are emerging as promising candidates for next-generation thin-film electronics because of their high mobility, relatively large bandgap, low-power switching, and the availability of large-area growth methods. Thin-film transistors (TFTs) based on multilayer transition metal dichalcogenides or black phosphorus offer unique opportunities for next-generation electronic and optoelectronic devices. Here, we review recent progress in high-mobility transistors based on multilayer 2D semiconductors. We describe the theoretical background on characterizing methods of TFT performance and material properties, followed by their applications in flexible, transparent, and optoelectronic devices. Finally, we highlight some of the methods used in metal-semiconductor contacts, hybrid structures, heterostructures, and chemical doping to improve device performance.

Study of Separation and Identification of the Active Ingredients in Gardenia jasminoides Ellis Based on a Two-Dimensional Liquid Chromatography by Coupling Reversed Phase Liquid Chromatography and Hydrophilic Interaction Liquid Chromatography.

PubMed

Zhou, Xuan; Chen, Cen; Ye, Xiaolan; Song, Fenyun; Fan, Guorong; Wu, Fuhai

2017-01-01

In this paper, by coupling reversed phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC), a two-dimensional liquid chromatography system was developed for separation and identification of the active ingredients in Gardenia jasminoides Ellis (GJE). By applying the semi-preparative C18 column as the first dimension and the core-shell column as the second dimension, a total of 896 peaks of GJE were separated. Among the 896 peaks, 16 active ingredients including geniposide, gardenoside, gardoside, etc. were identified by mass spectrometry analysis. The results indicated that the proposed two-dimensional RPLC/HILIC system was an effective method for the analysis of GJE and might hold a high potential to become a useful tool for analysis of other complex mixtures. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Performance Characteristics of Plane-Wall Two-Dimensional Diffusers

NASA Technical Reports Server (NTRS)

Reid, Elliott G

1953-01-01

Experiments have been made at Stanford University to determine the performance characteristics of plane-wall, two-dimensional diffusers which were so proportioned as to insure reasonable approximation of two-dimensional flow. All of the diffusers had identical entrance cross sections and discharged directly into a large plenum chamber; the test program included wide variations of divergence angle and length. During all tests a dynamic pressure of 60 pounds per square foOt was maintained at the diffuser entrance and the boundary layer there was thin and fully turbulent. The most interesting flow characteristics observed were the occasional appearance of steady, unseparated, asymmetric flow - which was correlated with the boundary-layer coalescence - and the rapid deterioration of flow steadiness - which occurred as soon as the divergence angle for maximum static pressure recovery was exceeded. Pressure efficiency was found to be controlled almost exclusively by divergence angle, whereas static pressure recovery was markedly influenced by area ratio (or length) as well as divergence angle. Volumetric efficiency. diminished as area ratio increased, and at a greater rate with small lengths than with large ones. Large values of the static-pressure-recovery coefficient were attained only with long diffusers of large area ratio; under these conditions pressure efficiency was high and. volumetric efficiency low. Auxiliary tests with asymmetric diffusers demonstrated that longitudinal pressure gradient, rather than wall divergence angle, controlled flow separation. Others showed that the addition of even a short exit duct of uniform section augmented pressure recovery. Finally, it was found that the installation of a thin, central, longitudinal partition suppressed flow separation in short diffusers and thereby improved pressure recovery

Graphene/CdTe heterostructure solar cell and its enhancement with photo-induced doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Shisheng, E-mail: shishenglin@zju.edu.cn; Chen, Hongsheng; State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027

2015-11-09

We report a type of solar cell based on graphene/CdTe Schottky heterostructure, which can be improved by surface engineering as graphene is atomic thin. By coating a layer of ultrathin CdSe quantum dots onto graphene/CdTe heterostructure, the power conversion efficiency is increased from 2.08% to 3.10%. Photo-induced doping is mainly accounted for this enhancement, as evidenced by field effect transport, Raman, photoluminescence, and quantum efficiency measurements. This work demonstrates a feasible way of improving the performance of graphene/semiconductor heterostructure solar cells by combining one dimensional with two dimensional materials.

Numerical modeling of heat transfer during hydrogen absorption in thin double-layered annular ZrCo beds

NASA Astrophysics Data System (ADS)

Cui, Yehui; Zeng, Xiangguo; Kou, Huaqin; Ding, Jun; Wang, Fang

2018-06-01

In this work a three-dimensional (3D) hydrogen absorption model was proposed to study the heat transfer behavior in thin double-layered annular ZrCo beds. Numerical simulations were performed to investigate the effects of conversion layer thickness, thermal conductivity, cooling medium and its flow velocity on the efficiency of heat transfer. Results reveal that decreasing the layer thickness and improving the thermal conductivity enhance the ability of heat transfer. Compared with nitrogen and helium, water appears to be a better medium for cooling. In order to achieve the best efficiency of heat transfer, the flow velocity needs to be maximized.

Effect of growth temperature on the epitaxial growth of ZnO on GaN by ALD

NASA Astrophysics Data System (ADS)

Särkijärvi, Suvi; Sintonen, Sakari; Tuomisto, Filip; Bosund, Markus; Suihkonen, Sami; Lipsanen, Harri

2014-07-01

We report on the epitaxial growth of ZnO on GaN template by atomic layer deposition (ALD). Diethylzinc (DEZn) and water vapour (H2O) were used as precursors. The structure and the quality of the grown ZnO layers were studied with scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL) measurements and positron annihilation spectroscopy. The ZnO films were confirmed epitaxial, and the film quality was found to improve with increasing deposition temperature in the vicinity of the threshold temperature of two dimensional growth. We conclude that high quality ZnO thin films can be grown by ALD. Interestingly only separate Zn-vacancies were observed in the films, although ZnO thin films typically contain fairly high density of surface pits and vacancy clusters.

Dual-Code Solution Strategy for Chemically-Reacting Hypersonic Flows

NASA Technical Reports Server (NTRS)

Wood, William A.; Eberhardt, Scott

1995-01-01

A new procedure seeks to combine the thin-layer Navier-Stokes solver LAURA with the parabolized Navier-Stokes solver UPS for the aerothermodynamic solution of chemically-reacting air flow fields. The interface protocol is presented and the method is applied to two slender, blunted shapes. Both axisymmetric and three-dimensional solutions are included with surface pressure and heat transfer comparisons between the present method and previously published results. The case of Mach 25 flow over an axisymmetric six degree sphere-cone with a non-catalytic wall is considered to 100 nose radii. A stability bound on the marching step size was observed with this case and is attributed to chemistry effects resulting from the non-catalytic wall boundary condition. A second case with Mach 28 flow over a sphere-cone-cylinder-flare configuration is computed at both two and five degree angles of attack with a fully-catalytic wall. Surface pressures are seen to be within five percent with the present method compared to the baseline LAURA solution and heat transfers are within 10 percent. The effect of grid resolution is investigated in both the radial and streamwise directions. The procedure demonstrates significant, order of magnitude reductions in solution time and required memory for the three-dimensional case in comparison to an all thin-layer Navier-Stokes solution.

Ordered organic-organic multilayer growth

DOEpatents

Forrest, Stephen R.; Lunt, Richard R.

2016-04-05

An ordered multilayer crystalline organic thin film structure is formed by depositing at least two layers of thin film crystalline organic materials successively wherein the at least two thin film layers are selected to have their surface energies within .+-.50% of each other, and preferably within .+-.15% of each other, whereby every thin film layer within the multilayer crystalline organic thin film structure exhibit a quasi-epitaxial relationship with the adjacent crystalline organic thin film.

Ordered organic-organic multilayer growth

DOEpatents

Forrest, Stephen R; Lunt, Richard R

2015-01-13

An ordered multilayer crystalline organic thin film structure is formed by depositing at least two layers of thin film crystalline organic materials successively wherein the at least two thin film layers are selected to have their surface energies within .+-.50% of each other, and preferably within .+-.15% of each other, whereby every thin film layer within the multilayer crystalline organic thin film structure exhibit a quasi-epitaxial relationship with the adjacent crystalline organic thin film.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moradi, Afshin, E-mail: a.moradi@kut.ac.ir; Department of Nano Sciences, Institute for Studies in Theoretical Physics and Mathematics; Zangeneh, Hamid Reza

We develop an effective medium theory to obtain effective permittivity of a composite of two-dimensional (2D) aligned single-walled carbon nanotubes. Electronic excitations on each nanotube surface are modeled by an infinitesimally thin layer of a 2D electron gas represented by two interacting fluids, which takes into account different nature of the σ and π electrons. Calculations of both real and imaginary parts of the effective dielectric function of the system are presented, for different values of the filling factor and radius of carbon nanotubes.

Thin layer chromatographic method for the detection of uric acid: collaborative study.

PubMed

Thrasher, J J; Abadie, A

1978-07-01

A collaborative study has been completed on an improved method for the detection and confirmation of uric acid from bird and insect excreta. The proposed method involves the lithium carbonate solubilization of the suspect excreta material, followed by butanol-methanol-water-acetic acid thin layer chromatography, and trisodium phosphate-phosphotungstic acid color development. The collaborative tests resulted in 100% detection of uric acid standard at the 50 ng level and 75% detection at the 20-25 ng level. No false positives were reported during tests of compounds similar to uric acid. The proposed method has been adopted official first action; the present official final action method, 44.161, will be retained for screening purposes.

Screening, confirmation and quantification of boldenone sulfate in equine urine after administration of boldenone undecylenate (Equipoise).

PubMed

Weidolf, L O; Chichila, T M; Henion, J D

1988-12-09

Methods for screening by thin-layer chromatography, quantification by high-performance liquid chromatography with ultraviolet detection and confirmation by gas chromatography-mass spectrometry of boldenone sulfate in equine urine after administration of boldenone undecylenate (Equipoise) are presented. Sample work-up was done with C18 liquid-solid extraction followed by solvolytic cleavage of the sulfate ester. Confirmatory evidence of boldenone sulfate in equine urine was obtained from 2 h to 42 days following a therapeutic intramuscular dose of Equipoise. The use of 19-nortestosterone sulfate as the internal standard for quantification of boldenone sulfate is discussed.

Purification of lignans from Fructus Arctii using off-line two-dimensional supercritical fluid chromatography/reversed-phase liquid chromatography.

PubMed

Yang, Bichao; Xin, Huaxia; Wang, Feier; Cai, Jianfeng; Liu, Yanfang; Fu, Qing; Jin, Yu; Liang, Xinmiao

2017-08-01

As a common traditional Chinese medicine, Fructus Arctii has important clinical medical values. Its main components are lignans, which are difficult to separate and analyze because of the complex composition, similar chemical structures, and close properties. In this study, an off-line two-dimensional supercritical fluid chromatography/reversed-phase liquid chromatography method, as well as an effective sample pretreatment method based on hydrophilic interaction chromatography material, was developed to enrich the minor lignan fractions and obtain high-purity compounds. In total, 12 high-purity compounds were isolated from Fructus Arctii. Their structures were identified by using high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, which showed that all were lignans and that most of them were isomers. The results demonstrated the effective off-line two-dimensional supercritical fluid chromatography/reversed-phase liquid chromatography method for the purification of lignans from Fructus Arctii. The separation protocol established here will be beneficial for the separation of complex samples from other kinds of natural products. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jiandong; Neeway, James J.; Zhang, Yanyan

Glass particles with dimensions typically ranging from tens to hundreds of microns are often used in glass corrosion research in order to accelerate testing. Two-dimensional and three-dimensional nanoscale imaging techniques are badly needed to characterize the alteration layers at the surfaces of these corroded glass particles. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) can provide a lateral resolution as low as ~100 nm, and, compared to other imaging techniques, is sensitive to elements lighter than carbon. Here, we used ToF-SIMS to characterize the alteration layers of corroded international simple glass (ISG) particles. At most particle surfaces, we observed inhomogeneous or nomore » alteration layers, indicating that the thickness of the alterations layers may be too thin to be observable by ToF-SIMS imaging. Relatively thick (e.g., 1–10 µm) alteration layers were inhomogeneously distributed at a small portion of surfaces.Interestingly, some large-size (tens of microns) glass particles were fully altered. Above observations suggest that weak attachment and the defects on ISG particle surfaces play an important role in ISG glass corrosion.« less

Separation, identification and quantification of carotenoids and chlorophylls in dietary supplements containing Chlorella vulgaris and Spirulina platensis using High Performance Thin Layer Chromatography.

PubMed

Hynstova, Veronika; Sterbova, Dagmar; Klejdus, Borivoj; Hedbavny, Josef; Huska, Dalibor; Adam, Vojtech

2018-01-30

In this study, 14 commercial products (dietary supplements) containing alga Chlorella vulgaris and cyanobacteria Spirulina platensis, originated from China and Japan, were analysed. UV-vis spectrophotometric method was applied for rapid determination of chlorophylls, carotenoids and pheophytins; as degradation products of chlorophylls. High Performance Thin-Layer Chromatography (HPTLC) was used for effective separation of these compounds, and also Atomic Absorption Spectrometry for determination of heavy metals as indicator of environmental pollution. Based on the results obtained from UV-vis spectrophotometric determination of photosynthetic pigments (chlorophylls and carotenoids), it was confirmed that Chlorella vulgaris contains more of all these pigments compared to the cyanobacteria Spirulina platensis. The fastest mobility compound identified in Chlorella vulgaris and Spirulina platensis using HPTLC method was β-carotene. Spectral analysis and standard calibration curve method were used for identification and quantification of separated substances on Thin-Layer Chromatographic plate. Quantification of copper (Cu 2+ , at 324.7 nm) and zinc (Zn 2+ , at 213.9nm) was performed using Flame Atomic Absorption Spectrometry with air-acetylene flame atomization. Quantification of cadmium (Cd 2+ , at 228.8 nm), nickel (Ni 2+ , at 232.0nm) and lead (Pb 2+ , at 283.3nm) by Electrothermal Graphite Furnace Atomic Absorption Spectrometry; and quantification of mercury (Hg 2+ , at 254nm) by Cold Vapour Atomic Absorption Spectrometry. Copyright © 2017 Elsevier B.V. All rights reserved.

Resolution and isolation of enantiomers of (±)-isoxsuprine using thin silica gel layers impregnated with L-glutamic acid, comparison of separation of its diastereomers prepared with chiral derivatizing reagents having L-amino acids as chiral auxiliaries.

PubMed

Bhushan, Ravi; Nagar, Hariom

2015-03-01

Thin silica gel layers impregnated with optically pure l-glutamic acid were used for direct resolution of enantiomers of (±)-isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l-alanine, l-valine and S-benzyl-l-cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed-phase high-performance liquid chromatography on a C18 column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin-layer chromatography (TLC) on reversed phase (RP) C18 plates. Diastereomers prepared with enantiomerically pure (+)-isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)-isoxsuprine. The elution order in the experimental study of RP-TLC and RP-HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1-0.09 µg/mL in TLC while it was in the range of 22-23 pg/mL in HPLC and 11-13 ng/mL in RP-TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification. Copyright © 2014 John Wiley & Sons, Ltd.

Chromatographic and electrophoretic approaches in ink analysis.

PubMed

Zlotnick, J A; Smith, F P

1999-10-15

Inks are manufactured from a wide variety of substances that exhibit very different chemical behaviors. Inks designed for use in different writing instruments or printing methods have quite dissimilar components. Since the 1950s chromatographic and electrophoretic methods have played important roles in the analysis of inks, where compositional information may have bearing on the investigation of counterfeiting, fraud, forgery, and other crimes. Techniques such as paper chromatography and electrophoresis, thin-layer chromatography, high-performance liquid chromatography, gas chromatography, gel electrophoresis, and the relatively new technique of capillary electrophoresis have all been explored as possible avenues for the separation of components of inks. This paper reviews the components of different types of inks and applications of the above separation methods are reviewed.

Fluorescence And Alternative Methods In Urine Drug Testing

NASA Astrophysics Data System (ADS)

Jain, Naresh C.

1988-04-01

Drug abuse has become-one of the most compelling realities _ ot contemporary society. It has penetrated every segment ot our population: trom schools to sports and trom organized crime to board rooms . Drugs in tie w9rkplace allegedly cost government agencies and business millions ot dollars each year in increased absenteeism,. poor work performance, thefts,accidents andwastedtime. The President's Commission on Organized Crime and the federal government are in tavor ot urine drug testing. In fact many employers are now resorting to urine drug testing on current and prospective employees. This presep.tation discusses different laboratory methods used in urine drug.testing, including immunoassays, fluorescence polarization, thin layer chromatography, high pressure liquid chromatography, gas chromatography and gas-chromatography-mass spectrometry.

On steady two-dimensional Carreau fluid flow over a wedge in the presence of infinite shear rate viscosity

NASA Astrophysics Data System (ADS)

Khan, Masood; Sardar, Humara

2018-03-01

This paper investigates the steady two-dimensional flow over a moving/static wedge in a Carreau viscosity model with infinite shear rate viscosity. Additionally, heat transfer analysis is performed. Using suitable transformations, nonlinear partial differential equations are transformed into ordinary differential equations and solved numerically using the Runge-Kutta Fehlberg method coupled with the shooting technique. The effects of various physical parameters on the velocity and temperature distributions are displayed graphically and discussed qualitatively. A comparison with the earlier reported results has been made with an excellent agreement. It is important to note that the increasing values of the wedge angle parameter enhance the fluid velocity while the opposite trend is observed for the temperature field for both shear thinning and thickening fluids. Generally, our results reveal that the velocity and temperature distributions are marginally influenced by the viscosity ratio parameter. Further, it is noted that augmented values of viscosity ratio parameter thin the momentum and thermal boundary layer thickness in shear thickening fluid and reverse is true for shear thinning fluid. Moreover, it is noticed that the velocity in case of moving wedge is higher than static wedge.

Laminated and Two-Dimensional Carbon-Supported Microwave Absorbers Derived from MXenes.

PubMed

Han, Meikang; Yin, Xiaowei; Li, Xinliang; Anasori, Babak; Zhang, Litong; Cheng, Laifei; Gogotsi, Yury

2017-06-14

Microwave absorbers with layered structures that can provide abundant interfaces are highly desirable for enhancing electromagnetic absorbing capability and decreasing the thickness. The atomically thin layers of two-dimensional (2D) transition-metal carbides (MXenes) make them a convenient precursor for synthesis of other 2D and layered structures. Here, laminated carbon/TiO 2 hybrid materials composed of well-aligned 2D carbon sheets with embedded TiO 2 nanoparticles were synthesized and showed excellent microwave absorption. Disordered 2D carbon layers with an unusual structure were obtained by annealing multilayer Ti 3 C 2 MXene in a CO 2 atmosphere. The minimum reflection coefficient of laminated carbon/TiO 2 composites reaches -36 dB, and the effective absorption bandwidth ranges from 3.6 to 18 GHz with the tunable thickness from 1.7 to 5 mm. The effective absorption bandwidth covers the whole Ku band (12.4-18 GHz) when the thickness of carbon/TiO 2 /paraffin composite is 1.7 mm. This study is expected to pave the way to the synthesis of carbon-supported absorbing materials using a large family of 2D carbides.

Plasmon-induced optical switching of electrical conductivity in porous anodic aluminum oxide films encapsulated with silver nanoparticle arrays.

PubMed

Huang, Chen-Han; Lin, Hsing-Ying; Lau, Ben-Chao; Liu, Chih-Yi; Chui, Hsiang-Chen; Tzeng, Yonhua

2010-12-20

We report on plasmon induced optical switching of electrical conductivity in two-dimensional (2D) arrays of silver (Ag) nanoparticles encapsulated inside nanochannels of porous anodic aluminum oxide (AAO) films. The reversible switching of photoconductivity greatly enhanced by an array of closely spaced Ag nanoparticles which are isolated from each other and from the ambient by thin aluminum oxide barrier layers are attributed to the improved electron transport due to the localized surface plasmon resonance and coupling among Ag nanoparticles. The photoconductivity is proportional to the power, and strongly dependent on the wavelength of light illumination. With Ag nanoparticles being isolated from the ambient environments by a thin layer of aluminum oxide barrier layer of controlled thickness in nanometers to tens of nanometers, deterioration of silver nanoparticles caused by environments is minimized. The electrochemically fabricated nanostructured Ag/AAO is inexpensive and promising for applications to integrated plasmonic circuits and sensors.

Organic and inorganic–organic thin film structures by molecular layer deposition: A review

PubMed Central

Sundberg, Pia

2014-01-01

Summary The possibility to deposit purely organic and hybrid inorganic–organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic–organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

Electronic properties of moire superlattice bands in layered two dimensional materials

NASA Astrophysics Data System (ADS)

Jung, Jeil

2014-03-01

When atomically thin two-dimensional materials are layered they often form incommensurate non-crystalline structures that exhibit long period moiré patterns when examined by scanning probes. In this talk, I will present a theoretical method which can be used to derive an effective Hamiltonian for these twisted van der Waals heterostructures using input from ab initio calculations performed on short-period crystalline structures. I will argue that the effective Hamiltonian can quantitatively describe the electronic properties of these layered systems for arbitrary twist angle and lattice constants. Applying this method to the important cases of graphene on graphene and graphene on hexagonal-boron nitride, I will present a series of experimentally observable quantities that can be extracted from their electronic structure, including their density of states and local density of states as a function of twist angle, and compare with available experiments. Work done in collaboration with Allan MacDonald, Shaffique Adam, Arnaud Raoux, Zhenhua Qiao, and Ashley DaSilva; and supported by the Singapore National Research Foundation Fellowship NRF-NRFF2012-01.

Two-dimensional MoS2: A promising building block for biosensors.

PubMed

Gan, Xiaorong; Zhao, Huimin; Quan, Xie

2017-03-15

Recently, two-dimensional (2D) layered nanomaterials have trigged intensive interest due to the intriguing physicochemical properties that stem from a quantum size effect connected with their ultra-thin structure. In particular, 2D molybdenum disulfide (MoS 2 ), as an emerging class of stable inorganic graphene analogs with intrinsic finite bandgap, would possibly complement or even surpass graphene in electronics and optoelectronics fields. In this review, we first discuss the historical development of ultrathin 2D nanomaterials. Then, we are concerned with 2D MoS 2 including its structure-property relationships, synthesis methods, characterization for the layer thickness, and biosensor applications over the past five years. Thereinto, we are highlighting recent advances in 2D MoS 2 -based biosensors, especially emphasize the preparation of sensing elements, roles of 2D MoS 2 , and assay strategies. Finally, on the basis of the current achievements on 2D MoS 2 and other ultrathin layered nanomaterials, perspectives on the challenges and opportunities for the exploration of 2D MoS 2 -based biosensors are put forward. Copyright © 2016 Elsevier B.V. All rights reserved.

Effective permittivity of single-walled carbon nanotube composites: Two-fluid model

NASA Astrophysics Data System (ADS)

Moradi, Afshin; Zangeneh, Hamid Reza; Moghadam, Firoozeh Karimi

2015-12-01

We develop an effective medium theory to obtain effective permittivity of a composite of two-dimensional (2D) aligned single-walled carbon nanotubes. Electronic excitations on each nanotube surface are modeled by an infinitesimally thin layer of a 2D electron gas represented by two interacting fluids, which takes into account different nature of the σ and π electrons. Calculations of both real and imaginary parts of the effective dielectric function of the system are presented, for different values of the filling factor and radius of carbon nanotubes.

Mathematical modeling of a dynamic thin plate deformation in acoustoelasticity problems

NASA Astrophysics Data System (ADS)

Badriev, I. B.; Paimuhin, V. N.

2018-01-01

The coupled problem of planar acoustic wave propagation through a composite plate covered with a second damping layer with a large logarithmic decrement of oscillations is formulated. The aerohydrodynamic interaction of a plate with external acoustic environment is described by three-dimensional wave equations and the mechanical behavior of a two-layer plate by the classical Kirchhoff-Love model. An exact analytic solution of the problem is found for the case of hinged support of the edges of a plate. On the basis of this, the parameters of the covering damping layer were found, under which it is possible to achieve a practically complete damping of the plate vibration under resonant modes of its acoustic loading.

Thin film solar cell design based on photonic crystal and diffractive grating structures.

PubMed

Mutitu, James G; Shi, Shouyuan; Chen, Caihua; Creazzo, Timothy; Barnett, Allen; Honsberg, Christiana; Prather, Dennis W

2008-09-15

In this paper we present novel light trapping designs applied to multiple junction thin film solar cells. The new designs incorporate one dimensional photonic crystals as band pass filters that reflect short light wavelengths (400 - 867 nm) and transmit longer wavelengths(867 -1800 nm) at the interface between two adjacent cells. In addition, nano structured diffractive gratings that cut into the photonic crystal layers are incorporated to redirect incoming waves and hence increase the optical path length of light within the solar cells. Two designs based on the nano structured gratings that have been realized using the scattering matrix and particle swarm optimization methods are presented. We also show preliminary fabrication results of the proposed devices.

Metallic few-layered VS2 ultrathin nanosheets: high two-dimensional conductivity for in-plane supercapacitors.

PubMed

Feng, Jun; Sun, Xu; Wu, Changzheng; Peng, Lele; Lin, Chenwen; Hu, Shuanglin; Yang, Jinlong; Xie, Yi

2011-11-09

With the rapid development of portable electronics, such as e-paper and other flexible devices, practical power sources with ultrathin geometries become an important prerequisite, in which supercapacitors with in-plane configurations are recently emerging as a favorable and competitive candidate. As is known, electrode materials with two-dimensional (2D) permeable channels, high-conductivity structural scaffolds, and high specific surface areas are the indispensible requirements for the development of in-plane supercapacitors with superior performance, while it is difficult for the presently available inorganic materials to make the best in all aspects. In this sense, vanadium disulfide (VS(2)) presents an ideal material platform due to its synergic properties of metallic nature and exfoliative characteristic brought by the conducting S-V-S layers stacked up by weak van der Waals interlayer interactions, offering great potential as high-performance in-plane supercapacitor electrodes. Herein, we developed a unique ammonia-assisted strategy to exfoliate bulk VS(2) flakes into ultrathin VS(2) nanosheets stacked with less than five S-V-S single layers, representing a brand new two-dimensional material having metallic behavior aside from graphene. Moreover, highly conductive VS(2) thin films were successfully assembled for constructing the electrodes of in-plane supercapacitors. As is expected, a specific capacitance of 4760 μF/cm(2) was realized here in a 150 nm in-plane configuration, of which no obvious degradation was observed even after 1000 charge/discharge cycles, offering as a new in-plane supercapacitor with high performance based on quasi-two-dimensional materials.

Anti-enteric bacterial activity and phytochemical analysis of the seed kernel extract of Mangifera indica Linnaeus against Shigella dysenteriae (Shiga, corrig.) Castellani and Chalmers.

PubMed

Rajan, S; Thirunalasundari, T; Jeeva, S

2011-04-01

To evaluate the phytochemical and anti-bacterial efficacy of the seed kernel extract of Mangifera indica (M. indica) against the enteropathogen, Shigella dysenteriae (S. dysenteriae), isolated from the diarrhoeal stool specimens. The preliminary phytochemical screening was performed by the standard methods as described by Harborne. Cold extraction method was employed to extract the bioactive compounds from mango seed kernel. Disc diffusion method was adopted to screen antibacterial activity. Minimum inhibitory concentration (MIC) was evaluated by agar dilution method. The crude extracts were partially purified by thin layer chromatography (TLC) and the fractions were analyzed by high performance thin layer chromatography (HPTLC) to identify the bioactive compounds. Phytochemical scrutiny of M. indica indicated the presence of phytochemical constituents such as alkaloids, gums, flavanoids, phenols, saponins, steroids, tannins and xanthoproteins. Antibacterial activity was observed in two crude extracts and various fractions viz. hexane, benzene, chloroform, methanol and water. MIC of methanol fraction was found to be (95±11.8) μg/mL. MIC of other fractions ranged from 130-380 μg/mL. The present study confirmed that each crude extracts and fractions of M. indica have significant antimicrobial activity against the isolated pathogen S. dysenteriae. The antibacterial activity may be due to the phytochemical constituents of the mango seed kernel. The phytochemical tannin could be the reason for its antibacterial activity. Copyright © 2011 Hainan Medical College. Published by Elsevier B.V. All rights reserved.

Characterization of drug authenticity using thin-layer chromatography imaging with a mobile phone.

PubMed

Yu, Hojeong; Le, Huy M; Kaale, Eliangiringa; Long, Kenneth D; Layloff, Thomas; Lumetta, Steven S; Cunningham, Brian T

2016-06-05

Thin-layer chromatography (TLC) has a myriad of separation applications in chemistry, biology, and pharmacology due to its simplicity and low cost. While benchtop laboratory sample application and detection systems for TLC provide accurate quantitation of TLC spot positions and densities, there are many applications where inexpensive and portable instruments would greatly expand the applicability of the technology. In this work, we demonstrate identity verification and concentration determination of pharmaceutical compounds via TLC using a custom 3D-printed cradle that interfaces with an ordinary mobile phone. The cradle holds the mobile phone's internal, rear-facing camera in a fixed position relative to a UV lamp and a TLC plate that includes a phosphor in the stationary phase. Analysis of photographs thus reveals the locations and intensities of principal spots of UV--absorbing drugs. Automated image analysis software determines the center location and density of dark spots, which, using integrated calibration spots of known drug compounds and concentrations, can be used to determine if a drug has been diluted or substituted. Two independent image processing approaches have been developed that may be selected based upon the processing capabilities of the smartphone. Each approach is able to discern 5% drug concentration differences. Using single-component solutions of nevirapine, amodiaquine, and paracetamol that have been manually applied, the mobile phone-based detection instrument provides measurements that are equivalent to those obtained with a commercially available lab-based desktop TLC densitometer. Copyright © 2016 Elsevier B.V. All rights reserved.

Improved thin-layer chromatography bioautographic assay for the detection of actylcholinesterase inhibitors in plants.

PubMed

Yang, Zhong-Duo; Song, Zhu-Wen; Ren, Jin; Yang, Ming-Jun; Li, Shuo

2011-01-01

Thin-layer chromatography (TLC) bioautographic method is a simple and rapid method to screen acetylcholinesterase inhibitors from plant extracts. However, the high consumption of enzyme (6 U/mL) in current methods makes the procedure expensive, which is an obstacle to scientific research centers lacking funding. To develop a new low-cost TLC bioautographic method. A series of compounds, as substrates, were synthesised and their ability to be hydrolysed by acetylcholinesterase was evaluated by the HPLC method. 4-Methoxyphenyl acetate (14) was proved to be an appropriate substrate for TLC bioautographic assay. Therefore a new and cheap TLC bioautographic assay was set up. The mechanism of this new method is that the enzyme converts 4-methoxylphenyl acetate into 4-methoxyphenol, which reacts with a solution of potassium ferricyanide ([K₃(FeCN)₆]) and iron chloride hexahydrate (FeCl₃·6H₂O) to make an aquamarine blue coloured background on the TLC plates. Regions of the TLC plate which contain acetylcholinesterase inhibitors show up as light yellow spots against the background. The consumption of enzyme (1 U/mL) in the new method is low and the detection limit of two known acetylcholinesterase inhibitors, huperzine A (0.0001 μg) and physostigmine (0.001 μg), for this assay are close to published values. A low-cost TLC bioautographic method was developed, which will benefit research groups pursuing natural acetylcholinesterase inhibitors. Copyright © 2011 John Wiley & Sons, Ltd.

Identification of Novel Targets of the Human Cell Cycle Regulatory Protein Cdc34

DTIC Science & Technology

1999-07-01

centrifugal elutriation, with a purity of -80% as shown by micro - ethyl acetate and separated on thin-layer chromatography plates (Whatman, scopic...Spain. (2) Servicio Bioquimica, Hosp. La Paz. Madrid. ICER protein is elevated in mHR6b-/- (murine Rad6B) fibroblasts Spain. and in human cells

A Forensic Experiment: The Case of the Crime at the Cinema

ERIC Educational Resources Information Center

Valente Nabais, J. M.; Costa, Sara D.

2017-01-01

This paper reports an experimental activity where students have to carefully analyze the evidence collected at the crime scene, namely fibers and lipstick traces. The fibers are analyzed by infrared spectroscopy, solubility tests, and optical microscopy, while in turn the lipstick traces are investigated by thin layer chromatography. Students also…

Note on the chromatographic analyses of marine polyunsaturated fatty acids

USGS Publications Warehouse

Schultz, D.M.; Quinn, J.G.

1977-01-01

Gas-liquid chromatography was used to study the effects of saponification/methylation and thin-layer chromatographic isolation on the analyses of polyunsaturated fatty acids. Using selected procedures, the qualitative and quantitative distribution of these acids in marine organisms can be determined with a high degree of accuracy. ?? 1977 Springer-Verlag.

The Development of a Tool for Measuring Graduate Students' Topic Specific Pedagogical Content Knowledge of Thin Layer Chromatography

ERIC Educational Resources Information Center

Hale, L. V. A.; Lutter, J. C.; Shultz, G. V.

2016-01-01

Graduate students play a critical role in undergraduate education at doctorate granting institutions; but generally have minimal opportunity to develop teaching expertise. Furthermore, little is known about how graduate students develop teaching expertise in this context. We investigated the development of topic-specific pedagogical content…

A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence

ERIC Educational Resources Information Center

Grayson, Scott M.

2012-01-01

A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

Quantitation of Lipase Activity from a Bee: An Introductory Enzyme Experiment.

ERIC Educational Resources Information Center

Farley, Kathleen A.; Jones, Marjorie A.

1989-01-01

This four-hour experiment uses a bee as a source of the enzyme which is reacted with a radioactive substrate to determine the specific activity of the enzyme. Uses thin layer chromatography, visible spectrophotometry, and liquid scintillation spectrometry (if not available a Geiger-Muller counter can be substituted). (MVL)

Quantitative analysis of oxyresveratrol in different plant parts of Morus species and related Genera by HPTLC

USDA-ARS?s Scientific Manuscript database

Four aromatic compounds; oxyresveratrol (1), mulberroside A (2), cudraflavone C (3) and kuwanone J (4) were isolated from the stems of Morus rubra L. The quantitative determination of oxyresveratrol from M. rubra L., M. alba L. and related genera by high performance thin layer chromatography (HPTLC)...

Analysis of biodiesel and biodiesel-petrodiesel blends by high performance thin layer chromatography combined with easy ambient sonic-spray ionization mass spectrometry.

PubMed

Eberlin, Livia S; Abdelnur, Patricia V; Passero, Alan; de Sa, Gilberto F; Daroda, Romeu J; de Souza, Vanderlea; Eberlin, Marcos N

2009-08-01

High performance thin layer chromatography (HPTLC) combined with on-spot detection and characterization via easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is applied to the analysis of biodiesel (B100) and biodiesel-petrodiesel blends (BX). HPTLC provides chromatographic resolution of major components whereas EASI-MS allows on-spot characterization performed directly on the HPTLC surface at ambient conditions. Constituents (M) are detected by EASI-MS in a one component-one ion fashion as either [M + Na](+) or [M + H](+). For both B100 and BX samples, typical profiles of fatty acid methyl esters (FAME) detected as [FAME + Na](+) ions allow biodiesel typification. The spectrum of the petrodiesel spot displays a homologous series of protonated alkyl pyridines which are characteristic for petrofuels (natural markers). The spectrum for residual or admixture oil spots is characterized by sodiated triglycerides [TAG + Na](+). The application of HPTLC to analyze B100 and BX samples and its combination with EASI-MS for on-spot characterization and quality control is demonstrated.

Simultaneous Determination of Withanolide A and Bacoside A in Spansules by High-Performance Thin-Layer Chromatography

PubMed Central

Shinde, P B; Aragade, P D; Agrawal, M R; Deokate, U A; Khadabadi, S S

2011-01-01

The objective of this work was to develop and validate a simple, rapid, precise, and accurate high performance thin layer chromatography method for simultaneous determination of withanolide A and bacoside A in combined dosage form. The stationary phase used was silica gel G60F254. The mobile phase used was mixture of ethyl acetate: methanol: toluene: water (4:1:1:0.5 v/v/v/v). The detection of spots was carried out at 320 nm using absorbance reflectance mode. The method was validated in terms of linearity, accuracy, precision and specificity. The calibration curve was found to be linear between 200 to 800 ng/spot for withanolide A and 50 to 350 ng/spot for bacoside A. The limit of detection and limit of quantification for the withanolide A were found to be 3.05 and 10.06 ng/spot, respectively and for bacoside A 8.3 and 27.39 ng/spot, respectively. The proposed method can be successfully used to determine the drug content of marketed formulation. PMID:22303073

Simultaneous determination of withanolide a and bacoside a in spansules by high-performance thin-layer chromatography.

PubMed

Shinde, P B; Aragade, P D; Agrawal, M R; Deokate, U A; Khadabadi, S S

2011-03-01

The objective of this work was to develop and validate a simple, rapid, precise, and accurate high performance thin layer chromatography method for simultaneous determination of withanolide A and bacoside A in combined dosage form. The stationary phase used was silica gel G60F(254). The mobile phase used was mixture of ethyl acetate: methanol: toluene: water (4:1:1:0.5 v/v/v/v). The detection of spots was carried out at 320 nm using absorbance reflectance mode. The method was validated in terms of linearity, accuracy, precision and specificity. The calibration curve was found to be linear between 200 to 800 ng/spot for withanolide A and 50 to 350 ng/spot for bacoside A. The limit of detection and limit of quantification for the withanolide A were found to be 3.05 and 10.06 ng/spot, respectively and for bacoside A 8.3 and 27.39 ng/spot, respectively. The proposed method can be successfully used to determine the drug content of marketed formulation.

Flowing atmospheric pressure afterglow combined with laser ablation for direct analysis of compounds separated by thin-layer chromatography.

PubMed

Cegłowski, Michał; Smoluch, Marek; Reszke, Edward; Silberring, Jerzy; Schroeder, Grzegorz

2016-01-01

A thin-layer chromatography-mass spectrometry (TLC-MS) setup for characterization of low molecular weight compounds separated on standard TLC plates has been constructed. This new approach successfully combines TLC separation, laser ablation, and ionization using flowing atmospheric pressure afterglow (FAPA) source. For the laser ablation, a low-priced 445-nm continuous-wave diode laser pointer, with a power of 1 W, was used. The combination of the simple, low-budget laser pointer and the FAPA ion source has made this experimental arrangement broadly available, also for small laboratories. The approach was successfully applied for the characterization of low molecular weight compounds separated on TLC plates, such as a mixture of pyrazole derivatives, alkaloids (nicotine and sparteine), and an extract from a drug tablet consisting of paracetamol, propyphenazone, and caffeine. The laser pointer used was capable of ablating organic compounds without the need of application of any additional substances (matrices, staining, etc.) on the TLC spots. The detection limit of the proposed method was estimated to be 35 ng/cm(2) of a pyrazole derivative.

Comprehensive thin-layer chromatography mass spectrometry of flavanols from Juniperus communis L. and Punica granatum L.

PubMed

Smrke, Samo; Vovk, Irena

2013-05-10

The coupling of thin-layer chromatography with mass spectrometry (TLC-MS) for the analysis of monomeric flavanols and proanthocyanidins in samples presented as complex matrices has been studied. The elution conditions for TLC-MS were optimised and full scans were compared with selected reaction monitoring for the MS detection of compounds. The performance of silica gel and cellulose plates with different developing solvents in TLC-MS was assessed. Cellulose plates provided superior sensitivity while ionisation suppression was encountered with silica plates. The use of a HILIC guard column beyond the elution head was found to facilitate detection of monomer compounds on silica plates. A new comprehensive TLC×MS procedure for screening flavanols in the entire chromatogram was developed as an alternative to the use of 4-dimethylaminocinnamaldehyde to determine the locations of compounds on the plate. This new procedure was applied to detect flavanols in the peel of Punica granatum L. fruits and in seeds of Juniperus communis L., in which flavanols and proanthocyanidin dimers and trimers were detected for the first time. Copyright © 2013 Elsevier B.V. All rights reserved.

Secondary metabolite credentials of Evolvulus alsinoides by high performance thin layer chromatography (HPTLC)

PubMed Central

Gomathi, Duraisamy; Kalaiselvi, Manokaran; Ravikumar, Ganesan; Sophia, Dominic; Gopalakrishnan, Velliyur Kanniappan; Uma, Chandrasekar

2012-01-01

Plants and plant-based products are the bases of many modern pharmaceuticals that are current in use today for various diseases. The aim of the study was to investigate the biochemical constituents and high performance thin layer chromatography (HPTLC) finger printing of the ethanolic extract of Evolvulus alsinoides. Phytochemical screening was done by standard procedures and HPTLC method was also established to analyze alkaloids, flavonoids and phenolic compounds from the ethanolic extract of Evolvulus alsinoides. Preliminary phytochemical screening showed that ethanol extracted more secondary metabolites than other solvents. HPTLC fingerprinting analysis showed the presence of various alkaloids, flavonoids and phenols (quercetin) in the ethanolic extract. It can be concluded that Evolvulus alsinoides may serve as a source of potent antioxidants that may be used in the prevention of various diseases such as cancer, diabetes and cardiovascular diseases due to the presence of phenolic compounds. HPTLC finger print of Evolvulus alsinoides may be useful in the differentiation of the species from adulterants and act as a biochemical marker for this medicinally important plant in the pharmaceutical industry and plant systematic studies. PMID:23554763

On-chip ultra-thin layer chromatography and surface enhanced Raman spectroscopy.

PubMed

Chen, Jing; Abell, Justin; Huang, Yao-wen; Zhao, Yiping

2012-09-07

We demonstrate that silver nanorod (AgNR) array substrates can be used for on-chip separation and detection of chemical mixtures by combining ultra-thin layer chromatography (UTLC) and surface enhanced Raman spectroscopy (SERS). The UTLC-SERS plate consists of an AgNR array fabricated by oblique angle deposition. The capability of the AgNR substrates to separate the different compounds in a mixture was explored using a mixture of four dyes and a mixture of melamine and Rhodamine 6G at varied concentrations with different mobile phase solvents. After UTLC separation, spatially-resolved SERS spectra were collected along the mobile phase development direction and the intensities of specific SERS peaks from each component were used to generate chromatograms. The AgNR substrates demonstrate the potential for separating the test dyes with plate heights as low as 9.6 μm. The limits of detection are between 10(-5)-10(-6) M. Furthermore, we show that the coupling of UTLC with SERS improves the SERS detection specificity, as small amounts of target analytes can be separated from the interfering background components.

3D Band Diagram and Photoexcitation of 2D-3D Semiconductor Heterojunctions.

PubMed

Li, Bo; Shi, Gang; Lei, Sidong; He, Yongmin; Gao, Weilu; Gong, Yongji; Ye, Gonglan; Zhou, Wu; Keyshar, Kunttal; Hao, Ji; Dong, Pei; Ge, Liehui; Lou, Jun; Kono, Junichiro; Vajtai, Robert; Ajayan, Pulickel M

2015-09-09

The emergence of a rich variety of two-dimensional (2D) layered semiconductor materials has enabled the creation of atomically thin heterojunction devices. Junctions between atomically thin 2D layers and 3D bulk semiconductors can lead to junctions that are fundamentally electronically different from the covalently bonded conventional semiconductor junctions. Here we propose a new 3D band diagram for the heterojunction formed between n-type monolayer MoS2 and p-type Si, in which the conduction and valence band-edges of the MoS2 monolayer are drawn for both stacked and in-plane directions. This new band diagram helps visualize the flow of charge carriers inside the device in a 3D manner. Our detailed wavelength-dependent photocurrent measurements fully support the diagrams and unambiguously show that the band alignment is type I for this 2D-3D heterojunction. Photogenerated electron-hole pairs in the atomically thin monolayer are separated and driven by an external bias and control the "on/off" states of the junction photodetector device. Two photoresponse regimes with fast and slow relaxation are also revealed in time-resolved photocurrent measurements, suggesting the important role played by charge trap states.

van der Waals epitaxial two-dimensional CdSxSe(1-x) semiconductor alloys with tunable-composition and application to flexible optoelectronics.

PubMed

Xia, Jing; Zhao, Yun-Xuan; Wang, Lei; Li, Xuan-Ze; Gu, Yi-Yi; Cheng, Hua-Qiu; Meng, Xiang-Min

2017-09-21

Despite the substantial progress in the development of two-dimensional (2D) materials from conventional layered crystals, it still remains particularly challenging to produce high-quality 2D non-layered semiconductor alloys which may bring in some unique properties and new functions. In this work, the synthesis of well-oriented 2D non-layered CdS x Se (1-x) semiconductor alloy flakes with tunable compositions and optical properties is established. Structural analysis reveals that the 2D non-layered alloys follow an incommensurate van der Waals epitaxial growth pattern. Photoluminescence measurements show that the 2D alloys have composition-dependent direct bandgaps with the emission peak varying from 1.8 eV to 2.3 eV, coinciding well with the density functional theory calculations. Furthermore, photodetectors based on the CdS x Se (1-x) flakes exhibit a high photoresponsivity of 703 A W -1 with an external quantum efficiency of 1.94 × 10 3 and a response time of 39 ms. Flexible devices fabricated on a thin mica substrate display good mechanical stability upon repeated bending. This work suggests a facile and general method to produce high-quality 2D non-layered semiconductor alloys for next-generation optoelectronic devices.

Ferroelectric FET for nonvolatile memory application with two-dimensional MoSe2 channels

NASA Astrophysics Data System (ADS)

Wang, Xudong; Liu, Chunsen; Chen, Yan; Wu, Guangjian; Yan, Xiao; Huang, Hai; Wang, Peng; Tian, Bobo; Hong, Zhenchen; Wang, Yutao; Sun, Shuo; Shen, Hong; Lin, Tie; Hu, Weida; Tang, Minghua; Zhou, Peng; Wang, Jianlu; Sun, Jinglan; Meng, Xiangjian; Chu, Junhao; Li, Zheng

2017-06-01

Graphene and other two-dimensional materials have received considerable attention regarding their potential applications in nano-electronics. Here, we report top-gate nonvolatile memory field-effect transistors (FETs) with different layers of MoSe2 nanosheets channel gated by ferroelectric film. The conventional gate dielectric of FETs was replaced by a ferroelectric thin film that provides a ferroelectric polarization electric field, and therefore defined as an Fe-FET where the poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) was used as the gate dielectric. Among the devices with MoSe2 channels of different thicknesses, the device with a single layer of MoSe2 exhibited a large hysteresis of electronic transport with an over 105 write/erase ratio, and displayed excellent retention and endurance performance. The possible mechanism of the device’s good properties was qualitatively analyzed using band theory. Additionally, a comprehensive study comparing the memory properties of MoSe2 channels of different thicknesses is presented. Increasing the numbers of MoSe2 layers was found to cause a reduced memory window. However, MoSe2 thickness of 5 nm yielded a write/erase ratio of more than 103. The results indicate that, based on a Fe-FET structure, the combination of two-dimensional semiconductors and organic ferroelectric gate dielectrics shows good promise for future applications in nonvolatile ferroelectric memory.

Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

NASA Astrophysics Data System (ADS)

Klemm, Richard A.; Davis, Andrew E.; Wang, Qing X.; Yamamoto, Takashi; Cerkoney, Daniel P.; Reid, Candy; Koopman, Maximiliaan L.; Minami, Hidetoshi; Kashiwagi, Takanari; Rain, Joseph R.; Doty, Constance M.; Sedlack, Michael A.; Morales, Manuel A.; Watanabe, Chiharu; Tsujimoto, Manabu; Delfanazari, Kaveh; Kadowaki, Kazuo

2017-12-01

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C ∞v , C 4v , and C 3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

Emulsification properties of biosurfactant produced from Pseudomonas aeruginosa RB 28.

PubMed

Sifour, Mohamed; Al-Jilawi, Majid H; Aziz, Ghazi M

2007-04-15

Biosurfactant produced from P. aeruginosa RB 28 was extracted, purified and characterized. Thin layer chromatography results showed that the extract contained two different compounds. The identification of the nature of the two compounds showed that they were glycolipids and rhamnose was the sugar moiety in these glycolipids. It was concluded that these compounds were rhamnolipids. The production of biosurfactant was started at late log phase and reached its maximal level (2.7 g L(-1)) at the stationary phase. Study of some rhamnolipid properties showed that sunflower oil, heptadecane and paraffin were efficiently emulsified and emulsions formed with vegetable oils (olive oil, corn oil and sunflower oil) were more stable than emulsions formed with hydrocarbons.

Te Monolayer-Driven Spontaneous van der Waals Epitaxy of Two-dimensional Pnictogen Chalcogenide Film on Sapphire.

PubMed

Hwang, Jae-Yeol; Kim, Young-Min; Lee, Kyu Hyoung; Ohta, Hiromichi; Kim, Sung Wng

2017-10-11

Demands on high-quality layer structured two-dimensional (2D) thin films such as pnictogen chalcogenides and transition metal dichalcogenides are growing due to the findings of exotic physical properties and potentials for device applications. However, the difficulties in controlling epitaxial growth and the unclear understanding of van der Waals epitaxy (vdWE) for a 2D chalcogenide film on a three-dimensional (3D) substrate have been major obstacles for the further advances of 2D materials. Here, we exploit the spontaneous vdWE of a high-quality 2D chalcogenide (Bi 0.5 Sb 1.5 Te 3 ) film by the chalcogen-driven surface reconstruction of a conventional 3D sapphire substrate. It is verified that the in situ formation of a pseudomorphic Te atomic monolayer on the surface of sapphire, which results in a dangling bond-free surface, allows the spontaneous vdWE of 2D chalcogenide film. Since this route uses the natural surface reconstruction of sapphire with chalcogen under vacuum condition, it can be scalable and easily utilized for the developments of various 2D chalcogenide vdWE films through conventional thin-film fabrication technologies.

Towards Thermal Wavelength Scale Two- and Three-Dimensional Photonic Crystals

DTIC Science & Technology

2016-04-01

this now. We studied the anisotropic thermal conductivity of nanoscale graphite layers deposited by chemical vapor deposition on Ni substrates at...Braun, and David G. Cahill, “Thermal conductivity of graphite thin films grown by low temperature chemical vapor deposition on Ni (111),” submitted...that there is no degradation in the power factor. In the carbon work, we studied the deposited by chemical vapor deposition on Ni substrates at

Simple TLC-screening of acylglycerol levels in biodiesel as an alternative to GC determination.

PubMed

Fontana, J D; Zagonel, G; Vechiatto, W W; Costa, B J; Laurindo, J C; Fontana, R; Pelisson, L; Jorge, B H; Lanças, F M

2009-10-01

Thin layer chromatography (TLC) stained with hot acidic p-anisaldehyde, is an interesting, fast, and low-cost technique to monitor main lipid contaminants such as triacylglycerols, diacylglycerols, and monoacylglycerols in biodiesel. These acylglycerols are detectable by the proposed planar chromatographic method, provided the content of the contaminants exceeds the limits recommended by the international norms applicable to biodiesel quality/specification, namely 0.25% in mass for total combined glycerin. The TLC data are confirmed by gas chromatography of the methyl esters of soy oil.

Nanoscale imaging of alteration layers of corroded international simple glass particles using ToF-SIMS

DOE PAGES

Zhang, Jiandong; Neeway, James J.; Zhang, Yanyan; ...

2017-02-24

Glass particles with dimensions typically ranging from tens to hundreds of microns are often used in glass corrosion research in order to accelerate testing. Two-dimensional and three-dimensional nanoscale imaging techniques are badly needed to characterize the alteration layers at the surfaces of these corroded glass particles. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) can provide a lateral resolution as low as ~100 nm, and, compared to other imaging techniques, is sensitive to elements lighter than carbon. Here, we used ToF-SIMS to characterize the alteration layers of corroded international simple glass (ISG) particles. At most particle surfaces, we observed inhomogeneous or nomore » alteration layers, indicating that the thickness of the alterations layers may be too thin to be observable by ToF-SIMS imaging. Relatively thick (e.g., 1–10 µm) alteration layers were inhomogeneously distributed at a small portion of surfaces.Interestingly, some large-size (tens of microns) glass particles were fully altered. Above observations suggest that weak attachment and the defects on ISG particle surfaces play an important role in ISG glass corrosion.« less

Nanoscale imaging of alteration layers of corroded international simple glass particles using ToF-SIMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jiandong; Neeway, James J.; Zhang, Yanyan

Glass particles with dimensions typically ranging from tens to hundreds of microns are often used in glass corrosion research in order to accelerate testing. Two-dimensional and three-dimensional nanoscale imaging techniques are badly needed to characterize the alteration layers at the surfaces of these corroded glass particles. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) can provide a lateral resolution as low as ~100 nm, and, compared to other imaging techniques, is sensitive to elements lighter than carbon. In this work, we used ToF-SIMS to characterize the alteration layers of corroded international simple glass (ISG) particles. At most particle surfaces, inhomogeneous or nomore » alteration layers were observed, indicating that the thickness of the alterations layers may be too thin to be observable by ToF-SIMS imaging. Relatively thick (e.g., 1-10 microns) alteration layers were inhomogeneously distributed at a small portion of surfaces. More interestingly, some large-size (tens of microns) glass particles were fully altered. Above observations suggest that weak attachment and the defects on ISG particle surfaces play an important role in ISG glass corrosion.« less

Analysis of human plasma lipids by using comprehensive two-dimensional gas chromatography with dual detection and with the support of high-resolution time-of-flight mass spectrometry for structural elucidation.

PubMed

Salivo, Simona; Beccaria, Marco; Sullini, Giuseppe; Tranchida, Peter Q; Dugo, Paola; Mondello, Luigi

2015-01-01

The main focus of the present research is the analysis of the unsaponifiable lipid fraction of human plasma by using data derived from comprehensive two-dimensional gas chromatography with dual quadrupole mass spectrometry and flame ionization detection. This approach enabled us to attain both mass spectral information and analyte percentage data. Furthermore, gas chromatography coupled with high-resolution time-of-flight mass spectrometry was used to increase the reliability of identification of several unsaponifiable lipid constituents. The synergism between both the high-resolution gas chromatography and mass spectrometry processes enabled us to attain a more in-depth knowledge of the unsaponifiable fraction of human plasma. Additionally, information was attained on the fatty acid and triacylglycerol composition of the plasma samples, subjected to investigation by using comprehensive two-dimensional gas chromatography with dual quadrupole mass spectrometry and flame ionization detection and high-performance liquid chromatography with atmospheric pressure chemical ionization quadrupole mass spectrometry, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Blessing of dimensionality: mathematical foundations of the statistical physics of data.

PubMed

Gorban, A N; Tyukin, I Y

2018-04-28

The concentrations of measure phenomena were discovered as the mathematical background to statistical mechanics at the end of the nineteenth/beginning of the twentieth century and have been explored in mathematics ever since. At the beginning of the twenty-first century, it became clear that the proper utilization of these phenomena in machine learning might transform the curse of dimensionality into the blessing of dimensionality This paper summarizes recently discovered phenomena of measure concentration which drastically simplify some machine learning problems in high dimension, and allow us to correct legacy artificial intelligence systems. The classical concentration of measure theorems state that i.i.d. random points are concentrated in a thin layer near a surface (a sphere or equators of a sphere, an average or median-level set of energy or another Lipschitz function, etc.). The new stochastic separation theorems describe the thin structure of these thin layers: the random points are not only concentrated in a thin layer but are all linearly separable from the rest of the set, even for exponentially large random sets. The linear functionals for separation of points can be selected in the form of the linear Fisher's discriminant. All artificial intelligence systems make errors. Non-destructive correction requires separation of the situations (samples) with errors from the samples corresponding to correct behaviour by a simple and robust classifier. The stochastic separation theorems provide us with such classifiers and determine a non-iterative (one-shot) procedure for their construction.This article is part of the theme issue 'Hilbert's sixth problem'. © 2018 The Author(s).

Blessing of dimensionality: mathematical foundations of the statistical physics of data

NASA Astrophysics Data System (ADS)

Gorban, A. N.; Tyukin, I. Y.

2018-04-01

The concentrations of measure phenomena were discovered as the mathematical background to statistical mechanics at the end of the nineteenth/beginning of the twentieth century and have been explored in mathematics ever since. At the beginning of the twenty-first century, it became clear that the proper utilization of these phenomena in machine learning might transform the curse of dimensionality into the blessing of dimensionality. This paper summarizes recently discovered phenomena of measure concentration which drastically simplify some machine learning problems in high dimension, and allow us to correct legacy artificial intelligence systems. The classical concentration of measure theorems state that i.i.d. random points are concentrated in a thin layer near a surface (a sphere or equators of a sphere, an average or median-level set of energy or another Lipschitz function, etc.). The new stochastic separation theorems describe the thin structure of these thin layers: the random points are not only concentrated in a thin layer but are all linearly separable from the rest of the set, even for exponentially large random sets. The linear functionals for separation of points can be selected in the form of the linear Fisher's discriminant. All artificial intelligence systems make errors. Non-destructive correction requires separation of the situations (samples) with errors from the samples corresponding to correct behaviour by a simple and robust classifier. The stochastic separation theorems provide us with such classifiers and determine a non-iterative (one-shot) procedure for their construction. This article is part of the theme issue `Hilbert's sixth problem'.

Synthesis and evaluation of a maltose-bonded silica gel stationary phase for hydrophilic interaction chromatography and its application in Ginkgo Biloba extract separation in two-dimensional systems.

PubMed

Sheng, Qianying; Yang, Kaiya; Ke, Yanxiong; Liang, Xinmiao; Lan, Minbo

2016-09-01

Maltose covalently bonded to silica was prepared by using carbonyl diimidazole as a cross-linker and employed as a stationary phase for hydrophilic interaction liquid chromatography. The column efficiency and the effect of water content, buffer concentration, and pH value influenced on retention were investigated. The separation or enrichment selectivity was also studied with nucleosides, saccharides, amino acids, peptides, and glycopeptides. The results indicated that the stationary phase processed good separation efficiency and separation selectivity in hydrophilic interaction liquid chromatography mode. Moreover, a two-dimensional hydrophilic interaction liquid chromatography× reversed-phase liquid chromatography method with high orthogonality was developed to analyze the Ginkgo Biloba extract fractions. The development of this two-dimensional chromatographic system would be an effective tool for the separation of complex samples of different polarities and contents. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional Screening of Metagenome and Genome Libraries for Detection of Novel Flavonoid-Modifying Enzymes

PubMed Central

Rabausch, U.; Juergensen, J.; Ilmberger, N.; Böhnke, S.; Fischer, S.; Schubach, B.; Schulte, M.

2013-01-01

The functional detection of novel enzymes other than hydrolases from metagenomes is limited since only a very few reliable screening procedures are available that allow the rapid screening of large clone libraries. For the discovery of flavonoid-modifying enzymes in genome and metagenome clone libraries, we have developed a new screening system based on high-performance thin-layer chromatography (HPTLC). This metagenome extract thin-layer chromatography analysis (META) allows the rapid detection of glycosyltransferase (GT) and also other flavonoid-modifying activities. The developed screening method is highly sensitive, and an amount of 4 ng of modified flavonoid molecules can be detected. This novel technology was validated against a control library of 1,920 fosmid clones generated from a single Bacillus cereus isolate and then used to analyze more than 38,000 clones derived from two different metagenomic preparations. Thereby we identified two novel UDP glycosyltransferase (UGT) genes. The metagenome-derived gtfC gene encoded a 52-kDa protein, and the deduced amino acid sequence was weakly similar to sequences of putative UGTs from Fibrisoma and Dyadobacter. GtfC mediated the transfer of different hexose moieties and exhibited high activities on flavones, flavonols, flavanones, and stilbenes and also accepted isoflavones and chalcones. From the control library we identified a novel macroside glycosyltransferase (MGT) with a calculated molecular mass of 46 kDa. The deduced amino acid sequence was highly similar to sequences of MGTs from Bacillus thuringiensis. Recombinant MgtB transferred the sugar residue from UDP-glucose effectively to flavones, flavonols, isoflavones, and flavanones. Moreover, MgtB exhibited high activity on larger flavonoid molecules such as tiliroside. PMID:23686272

In Vitro Biosynthesis and Chemical Identification of UDP-N-acetyl-d-quinovosamine (UDP-d-QuiNAc)*

PubMed Central

Li, Tiezheng; Simonds, Laurie; Kovrigin, Evgenii L.; Noel, K. Dale

2014-01-01

N-acetyl-d-quinovosamine (2-acetamido-2,6-dideoxy-d-glucose, QuiNAc) occurs in the polysaccharide structures of many Gram-negative bacteria. In the biosynthesis of QuiNAc-containing polysaccharides, UDP-QuiNAc is the hypothetical donor of the QuiNAc residue. Biosynthesis of UDP-QuiNAc has been proposed to occur by 4,6-dehydration of UDP-N-acetyl-d-glucosamine (UDP-GlcNAc) to UDP-2-acetamido-2,6-dideoxy-d-xylo-4-hexulose followed by reduction of this 4-keto intermediate to UDP-QuiNAc. Several specific dehydratases are known to catalyze the first proposed step. A specific reductase for the last step has not been demonstrated in vitro, but previous mutant analysis suggested that Rhizobium etli gene wreQ might encode this reductase. Therefore, this gene was cloned and expressed in Escherichia coli, and the resulting His6-tagged WreQ protein was purified. It was tested for 4-reductase activity by adding it and NAD(P)H to reaction mixtures in which 4,6-dehydratase WbpM had acted on the precursor substrate UDP-GlcNAc. Thin layer chromatography of the nucleotide sugars in the mixture at various stages of the reaction showed that WbpM converted UDP-GlcNAc completely to what was shown to be its 4-keto-6-deoxy derivative by NMR and that addition of WreQ and NADH led to formation of a third compound. Combined gas chromatography-mass spectrometry analysis of acid hydrolysates of the final reaction mixture showed that a quinovosamine moiety had been synthesized after WreQ addition. The two-step reaction progress also was monitored in real time by NMR. The final UDP-sugar product after WreQ addition was purified and determined to be UDP-d-QuiNAc by one-dimensional and two-dimensional NMR experiments. These results confirmed that WreQ has UDP-2-acetamido-2,6-dideoxy-d-xylo-4-hexulose 4-reductase activity, completing a pathway for UDP-d-QuiNAc synthesis in vitro. PMID:24817117

[TLC-FT-SERS study on ingredients of Isrhynchophylline].

PubMed

Wang, Yuan; Wang, Song-ying; Zhao, Yi-xue; Ren, Gui-fen; Zi, Feng-lan

2002-02-01

A new method for analysing the ingredients of Isrhynchophylline in Uncaria Rhynchophylla Jacks by thin layer chromatography (TLC) and the surface-enhanced Raman spectroscopy (SERS) is reported in this paper. The results show that the characteristic spectra bands of Isrhynchophylline situated at the thin layer with the amount of sample about 2.5 micrograms were obtained. The difference between SERS and solid spectra was found. Great enhancement of the 1,615 cm-1 spectral band was abstained. Molecule was absorbed in surface silver sol by pi electrons in phenyl and by pair of electrons in N together. An absorption model of Isrhynchophylline and silver sol was proposed. This method can be used to analyse the chemical ingredients with high sensitivity.

Polycrystalline silicon thin-film transistors on quartz fiber

NASA Astrophysics Data System (ADS)

Sugawara, Yuta; Uraoka, Yukiharu; Yano, Hiroshi; Hatayama, Tomoaki; Fuyuki, Takashi; Nakamura, Toshihiro; Toda, Sadayuki; Koaizawa, Hisashi; Mimura, Akio; Suzuki, Kenkichi

2007-11-01

We demonstrate the fabrication of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) on a thin quartz fiber for the first time. The poly-Si used in the active layer of the TFTs was prepared by excimer laser annealing of an amorphous Si thin film deposited on the fiber. Top-gated TFTs were fabricated on the fiber, and a field effect mobility of 10cm2/Vs was obtained. The proposed TFTs on a thin quartz fiber, named fiber TFTs, have potential application in microelectronic devices using TFTs fabricated on one-dimensional substrates.

A shock-layer theory based on thirteen-moment equations and DSMC calculations of rarefied hypersonic flows

NASA Technical Reports Server (NTRS)

Cheng, H. K.; Wong, Eric Y.; Dogra, V. K.

1991-01-01

Grad's thirteen-moment equations are applied to the flow behind a bow shock under the formalism of a thin shock layer. Comparison of this version of the theory with Direct Simulation Monte Carlo calculations of flows about a flat plate at finite attack angle has lent support to the approach as a useful extension of the continuum model for studying translational nonequilibrium in the shock layer. This paper reassesses the physical basis and limitations of the development with additional calculations and comparisons. The streamline correlation principle, which allows transformation of the 13-moment based system to one based on the Navier-Stokes equations, is extended to a three-dimensional formulation. The development yields a strip theory for planar lifting surfaces at finite incidences. Examples reveal that the lift-to-drag ratio is little influenced by planform geometry and varies with altitudes according to a 'bridging function' determined by correlated two-dimensional calculations.

Three-dimensional blade coating of complex fluid

NASA Astrophysics Data System (ADS)

Singh, Vachitar; Grimaldi, Emma; Sauret, Alban; Dressaire, Emilie

2015-11-01

The application of a layer of non-newtonian fluid on a solid substrate is an important industrial problem involved in polymer or paint coatings, and an everyday life challenge when it comes to spreading peanut butter on a toast. Most experimental and theoretical work has focused on the two-dimensional situation, i.e. the scraping of a fixed blade on a moving substrate to turn a thick layer of liquid into a thin coat. However the spreading of a finite volume of non-newtonian fluid using a blade has received less attention, despite significant practical and fundamental implications. In this study, we investigate experimentally the spreading of a finite volume of a model non-newtonian fluid, carbopol, initially deposited against the fixed blade. As the substrate is translated at constant speed, we characterize the dynamics of spreading and the final shape of the coated layer. We measure and rationalize the influence of the liquid volume, the height and orientation of the blade, and the speed of the substrate on the spreading.

The rollup of a vortex layer near a wall

NASA Technical Reports Server (NTRS)

Jimenez, Javier; Orlandi, Paolo

1993-01-01

The behavior of an inviscid vortex layer of non-zero thickness near a wall is studied, both through direct numerical simulation of the two-dimensional vorticity equation at high Reynolds numbers, and using an approximate ordinary nonlinear integro-differential equation which is satisfied in the limit of a thin layer under long-wavelength perturbations. For appropriate initial conditions the layer rolls up and breaks into compact vortices which move along the wall at constant speed. Because of the effect of the wall, they correspond to equilibrium counter-rotating vortex dipoles. This breakup can be related to the disintegration of the initial conditions of the approximate nonlinear dispersive equation into solitary waves. The study is motivated by the formation of longitudinal vortices from vortex sheets in the wall region of a turbulent channel.

Miniature micromachined quadrupole mass spectrometer array and method of making the same

NASA Technical Reports Server (NTRS)

Chutjian, Ara (Inventor); Brennen, Reid A. (Inventor); Hecht, Michael (Inventor); Wiberg, Dean (Inventor); Orient, Otto (Inventor)

2001-01-01

The present invention provides a quadrupole mass spectrometer and an ion filter for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.

Miniature micromachined quadrupole mass spectrometer array and method of making the same

NASA Technical Reports Server (NTRS)

Fuerstenau, Stephen D. (Inventor); Yee, Karl Y. (Inventor); Chutjian, Ara (Inventor); Orient, Otto J. (Inventor); Rice, John T. (Inventor)

2002-01-01

The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.

Miniature micromachined quadrupole mass spectrometer array and method of making the same

NASA Technical Reports Server (NTRS)

Chutjian, Ara (Inventor); Rice, John T. (Inventor); Fuerstenau, Stephen D. (Inventor); Orient, Otto J. (Inventor); Yee, Karl Y. (Inventor)

2000-01-01

The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.

Miniature micromachined quadrupole mass spectrometer array and method of making the same

NASA Technical Reports Server (NTRS)

Yee, Karl Y. (Inventor); Fuerstenau, Stephen D. (Inventor); Orient, Otto J. (Inventor); Rice, John T. (Inventor); Chutjian, Ara (Inventor)

2001-01-01

The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.

Miniature micromachined quadrupole mass spectrometer array and method of making the same

NASA Technical Reports Server (NTRS)

Hecht, Michael (Inventor); Wiberg, Dean (Inventor); Orient, Otto (Inventor); Brennen, Reid A. (Inventor); Chutjian, Ara (Inventor)

2001-01-01

The present invention provides a quadrupole mass spectrometer and an ion filter for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and aligrnent for use in a final quadrupole mass spectrometer device.

Miniature micromachined quadrupole mass spectrometer array and method of making the same

NASA Technical Reports Server (NTRS)

Orient, Otto (Inventor); Wiberg, Dean (Inventor); Brennen, Reid A. (Inventor); Hecht, Michael (Inventor); Chutjian, Ara (Inventor)

2000-01-01

The present invention provides a quadrupole mass spectrometer and an ion filter for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.

Fabrication of amorphous IGZO thin film transistor using self-aligned imprint lithography with a sacrificial layer

NASA Astrophysics Data System (ADS)

Kim, Sung Jin; Kim, Hyung Tae; Choi, Jong Hoon; Chung, Ho Kyoon; Cho, Sung Min

2018-04-01

An amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistor (TFT) was fabricated by a self-aligned imprint lithography (SAIL) method with a sacrificial photoresist layer. The SAIL is a top-down method to fabricate a TFT using a three-dimensional multilayer etch mask having all pattern information for the TFT. The sacrificial layer was applied in the SAIL process for the purpose of removing the resin residues that were inevitably left when the etch mask was thinned by plasma etching. This work demonstrated that the a-IGZO TFT could be fabricated by the SAIL process with the sacrificial layer. Specifically, the simple fabrication process utilized in this study can be utilized for the TFT with a plasma-sensitive semiconductor such as the a-IGZO and further extended for the roll-to-roll TFT fabrication.

Elastic guided waves in a layered plate with rectangular cross section.

PubMed

Mukdadi, O M; Desai, Y M; Datta, S K; Shah, A H; Niklasson, A J

2002-11-01

Guided waves in a layered elastic plate of rectangular cross section (finite width and thickness) has been studied in this paper. A semianalytical finite element method in which the deformation of the cross section is modeled by two-dimensional finite elements and analytical representation of propagating waves along the length of the plate has been used. The method is applicable to arbitrary number of layers and general anisotropic material properties of each layer, and is similar to the stiffness method used earlier to study guided waves in a laminated composite plate of infinite width. Numerical results showing the effect of varying the width of the plate on the dispersion of guided waves are presented and are compared with those for an infinite plate. In addition, effect of thin anisotropic coating or interface layers on the guided waves is investigated.

Rapid, Bioassay-Guided Process for the Detection and Identification of Antibacterial Neem Oil Compounds.

PubMed

Krüzselyi, Dániel; Nagy, Róbert; Ott, Péter G; Móricz, Ágnes M

2016-08-01

Bioassay guidance was used along the whole process including method development, isolation and identification of antibacterial neem (Azadirachta indica) oil compounds. The biomonitoring was performed by direct bioautography (DB), a combination of thin-layer chromatography (TLC) and antimicrobial detection. DB of neem oil showed one antibacterial zone that was not UV-active; therefore, the TLC separation was improved under DB control. The chromatographic zone that exhibited activity against Bacillus subtilis, Xanthomonas euvesicatoria, Aliivibrio fischeri, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus was characterized by TLC reagents, indicating a lipophilic, fatty acid-like chemical feature. Two compounds were found and identified in the active zone by high-performance liquid chromatography-electrospray ionization mass spectrometry as linoleic and oleic acids. Both fatty acids inhibited B. subtilis, but A. fischeri was sensitive only against linoleic acid. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Isolation of bioactive allelochemicals from sunflower (variety Suncross-42) through fractionation-guided bioassays.

PubMed

Anjum, Tehmina; Bajwa, Rukhsana

2010-11-01

Plants are rich source of biologically active allelochemicals. However, natural product discovery is not an easy task. Many problems encountered during this laborious practice can be overcome through the modification of preliminary trials. Bioassay-directed isolation of active plant compounds can increase efficiency by eliminating many of the problems encountered. This strategy avoids unnecessary compounds, concentrating on potential components and thus reducing the cost and time required. In this study, a crude aqueous extract of sunflower leaves was fractionated through high performance liquid chromatography. The isolated fractions were checked against Chenopodium album and Rumex dentatus. The fraction found active against two selected weeds was re-fractionated, and the active components were checked for their composition. Thin layer chromatography isolated a range of phenolics, whereas the presence of bioactive terpenoids was confirmed through mass spectroscopy and nuclear magnetic resonance spectroscopy.

Chemical and biological comparison of the fruit extracts of Citrus wilsonii Tanaka and Citrus medica L.

PubMed

Zhao, Pan; Duan, Li; Guo, Long; Dou, Li-Li; Dong, Xin; Zhou, Ping; Li, Ping; Liu, E-Hu

2015-04-15

Citri Fructus (CF), the mature fruit of Citrus wilsonii Tanaka (CWT) or Citrus medica L. (CML), is an important citrus by-product with health promoting and nutritive properties. The present study compares the chemical and biological differences of CWT and CML. Thin layer chromatography and high performance liquid chromatography, coupled with quadrupole time-of-flight tandem mass spectrometry techniques, were employed to compare the chemical profiles of CWT and CML. A total of 25 compounds were identified and the results indicated that there were significant differences in chemical composition between the two CF species. The quantitative results obtained by HPLC coupled with diode array detector method demonstrated that naringin was present in the highest amounts in CWT, whilst nomilin was the most dominant constituent in CML. It was also found that CWT had significantly higher free radical-scavenging activity than CML. Copyright © 2014 Elsevier Ltd. All rights reserved.

Extremely efficient internal exciton dissociation through edge states in layered 2D perovskites

NASA Astrophysics Data System (ADS)

Blancon, J.-C.; Tsai, H.; Nie, W.; Stoumpos, C. C.; Pedesseau, L.; Katan, C.; Kepenekian, M.; Soe, C. M. M.; Appavoo, K.; Sfeir, M. Y.; Tretiak, S.; Ajayan, P. M.; Kanatzidis, M. G.; Even, J.; Crochet, J. J.; Mohite, A. D.

2017-03-01

Understanding and controlling charge and energy flow in state-of-the-art semiconductor quantum wells has enabled high-efficiency optoelectronic devices. Two-dimensional (2D) Ruddlesden-Popper perovskites are solution-processed quantum wells wherein the band gap can be tuned by varying the perovskite-layer thickness, which modulates the effective electron-hole confinement. We report that, counterintuitive to classical quantum-confined systems where photogenerated electrons and holes are strongly bound by Coulomb interactions or excitons, the photophysics of thin films made of Ruddlesden-Popper perovskites with a thickness exceeding two perovskite-crystal units (>1.3 nanometers) is dominated by lower-energy states associated with the local intrinsic electronic structure of the edges of the perovskite layers. These states provide a direct pathway for dissociating excitons into longer-lived free carriers that substantially improve the performance of optoelectronic devices.

Absence of effects of an in-plane magnetic field in a quasi-two-dimensional electron system

NASA Astrophysics Data System (ADS)

Brandt, F. T.; Sánchez-Monroy, J. A.

2018-03-01

The dynamics of a quasi-two-dimensional electron system (q2DES) in the presence of a tilted magnetic field is reconsidered employing the thin-layer method. We derive the effective equations for relativistic and nonrelativistic q2DESs. Through a perturbative expansion, we show that while the magnetic length is much greater than the confinement width, the in-plane magnetic field only affects the particle dynamics through the spin. Therefore, effects due to an in-plane magnetic vector potential reported previously in the literature for 2D quantum rings, 2D quantum dots and graphene are fictitious. In particular, the so-called pseudo chiral magnetic effect recently proposed in graphene is not realistic.

Solutions to Three-Dimensional Thin-Layer Navier-Stokes Equations in Rotating Coordinates for Flow Through Turbomachinery

NASA Technical Reports Server (NTRS)

Ghosh, Amrit Raj

1996-01-01

The viscous, Navier-Stokes solver for turbomachinery applications, MSUTC has been modified to include the rotating frame formulation. The three-dimensional thin-layer Navier-Stokes equations have been cast in a rotating Cartesian frame enabling the freezing of grid motion. This also allows the flow-field associated with an isolated rotor to be viewed as a steady-state problem. Consequently, local time stepping can be used to accelerate convergence. The formulation is validated by running NASA's Rotor 67 as the test case. results are compared between the rotating frame code and the absolute frame code. The use of the rotating frame approach greatly enhances the performance of the code with respect to savings in computing time, without degradation of the solution.

Modification of the optoelectronic properties of two-dimensional MoS2 crystals by ultraviolet-ozone treatment

NASA Astrophysics Data System (ADS)

Yang, Hae In; Park, Seonyoung; Choi, Woong

2018-06-01

We report the modification of the optoelectronic properties of mechanically-exfoliated single layer MoS2 by ultraviolet-ozone exposure. Photoluminescence emission of pristine MoS2 monotonically decreased and eventually quenched as ultraviolet-ozone exposure time increased from 0 to 10 min. The reduction of photoluminescence emission accompanied reduction of Raman modes, suggesting structural degradation in ultraviolet-ozone exposed MoS2. Analysis with X-ray photoelectron spectroscopy revealed that the formation of Ssbnd O and Mosbnd O bonding increases with ultraviolet-ozone exposure time. Measurement of electrical transport properties of MoS2 in a bottom-gate thin-film transistor configuration suggested the presence of insulating MoO3 after ultraviolet-ozone exposure. These results demonstrate that ultraviolet-ozone exposure can significantly influence the optoelectronic properties of single layer MoS2, providing important implications on the application of MoS2 and other two-dimensional materials into optoelectronic devices.

Self-assembled graphene hydrogel via a one-step hydrothermal process.

PubMed

Xu, Yuxi; Sheng, Kaixuan; Li, Chun; Shi, Gaoquan

2010-07-27

Self-assembly of two-dimensional graphene sheets is an important strategy for producing macroscopic graphene architectures for practical applications, such as thin films and layered paperlike materials. However, construction of graphene self-assembled macrostructures with three-dimensional networks has never been realized. In this paper, we prepared a self-assembled graphene hydrogel (SGH) via a convenient one-step hydrothermal method. The SGH is electrically conductive, mechanically strong, and thermally stable and exhibits a high specific capacitance. The high-performance SGH with inherent biocompatibility of carbon materials is attractive in the fields of biotechnology and electrochemistry, such as drug-delivery, tissue scaffolds, bionic nanocomposites, and supercapacitors.

Optical properties of bulk gallium nitride single crystals grown by chloride-hydride vapor-phase epitaxy

NASA Astrophysics Data System (ADS)

Agyekyan, V. F.; Borisov, E. V.; Serov, A. Yu.; Filosofov, N. G.

2017-12-01

A gallium nitride crystal 5 mm in thickness was grown by chloride-hydride vapor-phase epitaxy on a sapphire substrate, from which the crystal separated during cooling. At an early stage, a three-dimensional growth mode was implemented, followed by a switch to a two-dimensional mode. Spectra of exciton reflection, exciton luminescence, and Raman scattering are studied in several regions characteristic of the sample. Analysis of these spectra and comparison with previously obtained data for thin epitaxial GaN layers with a wide range of silicon doping enabled conclusions about the quality of the crystal lattice in these characteristic regions.

Cosmological applications of singular hypersurfaces in general relativity

NASA Astrophysics Data System (ADS)

Laguna-Castillo, Pablo

Three applications to cosmology of surface layers, based on Israel's formalism of singular hypersurfaces and thin shells in general relativity, are presented. Einstein's field equations are analyzed in the presence of a bubble nucleated in vacuum phase transitions within the context of the old inflationary universe scenario. The evolution of a bubble with vanishing surface energy density is studied. It is found that such bubbles lead to a worm-hole matching. Next, the observable four-dimensional universe is considered as a singular hypersurface of discontinuity embedded in a five-dimensional Kaluza-Klein cosmology. It is possible to rewrite the projected five-dimensional Einstein equations on the surface layer in a similar way to the four-dimensional Robertson-Walker cosmology equations. Next, a model is described for an infinite-length, straight U(1) cosmic string as a cylindrical, singular shell enclosing a region of false vacuum. A set of equations is introduced which are required to develop a three-dimensional computer code whose purpose is to study the process of intercommuting cosmic strings with the inclusion of gravitational effects. The outcome is evolution and constraint equations for the gravitational, scalar and gauge field of two initially separated, perpendicular, cosmic strings.

Quality control and in vitro antioxidant potential of Coriandrum sativum Linn.

PubMed Central

Singh, Mhaveer; Tamboli, E. T.; Kamal, Y. T.; Ahmad, Wasim; Ansari, S. H.; Ahmad, Sayeed

2015-01-01

Background: Coriandrum sativum Linn., commonly known as coriander, is a well-known spice and drug in India. It has various health-related benefits and used in various Unani formulations. In this present study, quality assessment of coriander fruits was carried out by studying anatomical characters, physicochemical tests, and chemoprofiling using high performance thin layer chromatography (HPTLC) and gas chromatography-mass spectroscopy (GC-MS) along with in vitro antioxidant potential. Materials and Methods: Standardization was carried out as per the pharmacopeial guidelines. Estimation of heavy metals, pesticides, and aflatoxins was carried out to ascertain the presence of any contaminant in the sample. Chemoprofiling was achieved by thin layer chromatography (TLC) by optimizing the mobile phase for different extracts. The most of the pharmacological activities of coriander are based on volatile oil constituents. Hence, GC-MS profiling was also carried out using hexane-soluble fraction of hydro-alcoholic extract. The total phenolic contents and in vitro antioxidant efficacy were determined using previously established methods. Results: The quality control and anatomical studies were very valuable for the identification whereas good antioxidant potential was observed when compared to ascorbic acid. The drug was found free of contaminant when analyzed for pesticides and aflatoxins whereas heavy metals were found under reported limits. Conclusion: The work embodied in this present research can be utilized for the identification and the quality control of the coriander fruit. PMID:26681883

Undergraduate Organic Experiment: Tetrazole Formation by Microwave Heated (3 + 2) Cycloaddition in Aqueous Solution

ERIC Educational Resources Information Center

DeFrancesco, Heather; Dudley, Joshua; Coca, Adiel

2018-01-01

An undergraduate experiment for the organic laboratory is described that utilizes microwave heating to prepare 5- substituted 1H-tetrazole derivatives through a (3 + 2) cycloaddition between aryl nitriles and sodium azide. The reaction mixture is analyzed by thin layer chromatography. The products are purified through an acid-base extraction and…

Detection of volatile spoilage metabolites in fermented cucumbers using nontargeted, comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS)

USDA-ARS?s Scientific Manuscript database

A nontargeted, comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS) method was developed for the analysis of fermented cucumber volatiles before and after anaerobic spoilage. Volatiles extracted by solid-phase microextraction were separated on a polyethyle...

Two-Dimensional Liquid Chromatography Analysis of Polystyrene/Polybutadiene Block Copolymers.

PubMed

Lee, Sanghoon; Choi, Heejae; Chang, Taihyun; Staal, Bastiaan

2018-05-15

A detailed characterization of a commercial polystyrene/polybutadiene block copolymer material (Styrolux) was carried out using two-dimensional liquid chromatography (2D-LC). The Styrolux is prepared by statistical linking reaction of two different polystyrene- block-polybutadienyl anion precursors with a multivalent linking agent. Therefore, it is a mixture of a number of branched block copolymers different in molecular weight, composition, and chain architecture. While individual LC analysis, including size exclusion chromatography, interaction chromatography, or liquid chromatography at critical condition, is not good enough to resolve all the polymer species, 2D-LC separations coupling two chromatography methods were able to resolve all polymer species present in the sample; at least 13 block copolymer species and a homopolystyrene blended. Four different 2D-LC analyses combining a different pair of two LC methods provide their characteristic separation results. The separation characteristics of the 2D-LC separations are compared to elucidate the elution characteristics of the block copolymer species.

Finite element stress analysis of idealized composite damage zones

NASA Technical Reports Server (NTRS)

Obrien, D.; Herakovich, C. T.

1978-01-01

A quasi three dimensional finite element stress analysis of idealized damage zones in composite laminates is presented. The damage zones consist of a long centered groove or cutout extending one or two layers in depth from both top and bottom surfaces of a thin composite laminate. Elastic results are presented for compressive loading of four and eight layer laminates. It is shown that a boundary layer exists near the cutout edge similar to that previously shown to exist along free edges. The cutout is shown to produce significant interlaminar stresses in the interior of the laminate away from free cutout edges. The interlaminar stresses are also shown to contribute to failure which is defined using the Tsai-Wu failure criteria.

Specific binding of Haemophilus influenzae to minor gangliosides of human respiratory epithelial cells.

PubMed Central

Fakih, M G; Murphy, T F; Pattoli, M A; Berenson, C S

1997-01-01

Gangliosides are sialylated glycosphingolipids that serve as receptors for various bacteria. To investigate endogenous gangliosides of human respiratory epithelial cells as potential receptors for Haemophilus influenzae, three strains, including nontypeable H. influenzae (NTHI) 1479, and isogenic fimbriated (f+) and nonfimbriated (f0) H. influenzae type b 770235, were 3H labeled and overlaid on two-dimensional thin-layer chromatography (TLC) plates containing either purified HEp-2 gangliosides or murine brain gangliosides. NTHI 1479 bound exclusively to two distinct minor ganglioside doublets, with mobilities near that of GM1. These minor gangliosides comprised only 14.2 and 9.4% of the total, respectively. NTHI 1479 also bound to a distinct ganglioside of human macrophages whose chromatographic mobilities closely resemble those of one of the NTHI-binding gangliosides of HEp-2 cells. H. influenzae type b 770235 f+ and f0 each bound to a different minor HEp-2 ganglioside doublet, with proportionately weaker affinity for a major ganglioside doublet. Remarkably, none of the three strains bound to any murine brain gangliosides. Moreover, when 80 to 90% of sialic acid residues were enzymatically removed from HEp-2 gangliosides, NTHI 1479 binding was proportionately impaired, compared with untreated controls. Our findings support a role for specific gangliosides of specific cells as receptors for H. influenzae strains. Our findings further demonstrate that individual minor gangliosides possess unique biological properties. PMID:9125549

Enhanced Laser-Driven Ion Acceleration by Superponderomotive Electrons Generated from Near-Critical-Density Plasma

NASA Astrophysics Data System (ADS)

Bin, J. H.; Yeung, M.; Gong, Z.; Wang, H. Y.; Kreuzer, C.; Zhou, M. L.; Streeter, M. J. V.; Foster, P. S.; Cousens, S.; Dromey, B.; Meyer-ter-Vehn, J.; Zepf, M.; Schreiber, J.

2018-02-01

We report on the experimental studies of laser driven ion acceleration from a double-layer target where a near-critical density target with a few-micron thickness is coated in front of a nanometer-thin diamondlike carbon foil. A significant enhancement of proton maximum energies from 12 to ˜30 MeV is observed when a relativistic laser pulse impinges on the double-layer target under linear polarization. We attributed the enhanced acceleration to superponderomotive electrons that were simultaneously measured in the experiments with energies far beyond the free-electron ponderomotive limit. Our interpretation is supported by two-dimensional simulation results.

Molecular beam epitaxial growth, transmittance and photoluminescence spectra of zinc-blende CdTe thin films with high-quality on perovskite SrTiO3 (1 1 1) substrates

NASA Astrophysics Data System (ADS)

Song, Kun; Zhu, Xuanting; Tang, Kai; Bai, W.; Zhu, Liangqing; Yang, Jing; Zhang, Yuanyuan; Tang, Xiaodong; Chu, Junhao

2018-03-01

High-crystalline quality CdTe thin films are grown on the largely lattice-mismatched SrTiO3 (STO) (1 1 1) substrates by molecular beam epitaxy. A transformation from a three dimensional regime to a two dimensional one is observed by the reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). The formation of an elastic deformation CdTe layer on STO (1 1 1), namely a pseudomorphic growth mode with a critical thickness of ∼40 nm, is supported by the RHEED, AFM and X-ray diffraction. Crystal structures and epitaxial relationships of CdTe epitaxial films on STO (1 1 1) are characterized by 2θ-ω scans and reciprocal space mapping. Two strong absorption peaks at the energies of ∼1.621 eV and ∼1.597 eV at 5 K are clearly observed for a ∼120 nm thick CdTe epitaxial film, which are proposed to be ascribed to the strained and unstrained epitaxial CdTe layers, respectively. Moreover, the presence of the exciton band while the absence of deep level defect states for the ∼120 nm thick CdTe film characterized by the temperature dependent photoluminescence spectra further supports the high-crystalline quality.

Exciton Rydberg series in mono- and few-layer WS2

NASA Astrophysics Data System (ADS)

Chernikov, Alexey; Berkelbach, Timothy C.; Hill, Heather M.; Rigosi, Albert; Li, Yilei; Aslan, Özgur B.; Hybertsen, Mark S.; Reichman, David R.; Heinz, Tony F.

2014-03-01

Considered a long-awaited semiconducting analogue to graphene, the family of atomically thin transition metal dichalcogenides (TMDs) attracted intense interest in the scientific community due to their remarkable physical properties resulting from the reduced dimensionality. A fundamental manifestation of the two-dimensional nature is a strong increase in the Coulomb interaction. The resulting formation of tightly bound excitons plays a crucial role for a majority of optical and transport phenomena. In our work, we investigate the excitons in atomically thin TMDs by optical micro-spectroscopy and apply a microscopic, ab-initio theoretical approach. We observe a full sequence of excited exciton states, i.e., the Rydberg series, in the monolayer WS2, identifying tightly bound excitons with energies exceeding 0.3 eV - almost an order of magnitude higher than in the corresponding, three-dimensional crystal. We also find significant deviations of the excitonic properties from the conventional hydrogenic physics - a direct evidence of a non-uniform dielectric environment. Finally, an excellent quantitative agreement is obtained between the experimental findings and the developed theoretical approach.

Functionalized graphene-Pt composites for fuel cells and photoelectrochemical cells

DOEpatents

Diankov, Georgi; An, Jihwan; Park, Joonsuk; Goldhaber, David J. K.; Prinz, Friedrich B.

2017-08-29

A method of growing crystals on two-dimensional layered material is provided that includes reversibly hydrogenating a two-dimensional layered material, using a controlled radio-frequency hydrogen plasma, depositing Pt atoms on the reversibly hydrogenated two-dimensional layered material, using Atomic Layer Deposition (ALD), where the reversibly hydrogenated two-dimensional layered material promotes loss of methyl groups in an ALD Pt precursor, and forming Pt-O on the reversibly hydrogenated two-dimensional layered material, using combustion by O.sub.2, where the Pt-O is used for subsequent Pt half-cycles of the ALD process, where growth of Pt crystals occurs.

A rapid phospholipase A2 bioassay using 14C-oleate-labelled E. coli bacterias.

PubMed

Meyer, T; von Wichert, P; Weins, D

1989-02-01

Two methods of phospholipase A2 determination using 14C-labelled E. coli bacterias as substrate were compared. One method works with a filter membrane for separation of cleaved 14C-oleate from remaining phospholipids, the other uses the well-known thin-layer chromatography for lipid analysis. Some features of human serum phospholipase A2 regarding pH and Ca2+ dependency were investigated. Possible sources of errors were discussed. It was shown that either method can differentiate between normal and pathologically elevated phospholipase A2 levels, but that the filter method is superior in terms of sensitivity and workload.

Preparative isolation of flavonoid glycosides from Sphaerophysa salsula using hydrophilic interaction solid-phase extraction coupled with two-dimensional preparative liquid chromatography.

PubMed

Jiao, Lijin; Tao, Yanduo; Wang, Weidong; Shao, Yun; Mei, Lijuan; Wang, Qilan; Dang, Jun

2017-10-01

An offline preparative two-dimensional reversed-phase liquid chromatography/hydrophilic interaction liquid chromatography coupled with hydrophilic interaction solid-phase extraction method was developed for the preparative isolation of flavonoid glycosides from a crude sample of Sphaerophysa salsula. First, the non-flavonoids were removed using an XAmide solid-phase extraction cartridge. Based on the separation results of three different chromatographic stationary phases, the first-dimensional preparation was performed on an XAqua C18 prep column, and 15 fractions were obtained from the 5.2 g target sample. Then, three representative fractions were selected for additional purification on an XAmide preparative column to further isolate the flavonoid glycosides. In all, eight flavonoid glycosides were isolated in purities over 97%. The results demonstrated that the two-dimensional liquid chromatography method used in this study was effective for the preparative separation of flavonoid glycosides from Sphaerophysa salsula. Additionally, this method showed great potential for the separation of flavonoid glycosides from other plant materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coexistence of Topological Edge State and Superconductivity in Bismuth Ultrathin Film.

PubMed

Sun, Hao-Hua; Wang, Mei-Xiao; Zhu, Fengfeng; Wang, Guan-Yong; Ma, Hai-Yang; Xu, Zhu-An; Liao, Qing; Lu, Yunhao; Gao, Chun-Lei; Li, Yao-Yi; Liu, Canhua; Qian, Dong; Guan, Dandan; Jia, Jin-Feng

2017-05-10

Ultrathin freestanding bismuth film is theoretically predicted to be one kind of two-dimensional topological insulators. Experimentally, the topological nature of bismuth strongly depends on the situations of the Bi films. Film thickness and interaction with the substrate often change the topological properties of Bi films. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy or spectroscopy and first-principle calculation, the properties of Bi(111) ultrathin film grown on the NbSe 2 superconducting substrate have been studied. We find the band structures of the ultrathin film is quasi-freestanding, and one-dimensional edge state exists on Bi(111) film as thin as three bilayers. Superconductivity is also detected on different layers of the film and the pairing potential exhibits an exponential decay with the layer thicknesses. Thus, the topological edge state can coexist with superconductivity, which makes the system a promising platform for exploring Majorana Fermions.

Planar edge Schottky barrier-tunneling transistors using epitaxial graphene/SiC junctions.

PubMed

Kunc, Jan; Hu, Yike; Palmer, James; Guo, Zelei; Hankinson, John; Gamal, Salah H; Berger, Claire; de Heer, Walt A

2014-09-10

A purely planar graphene/SiC field effect transistor is presented here. The horizontal current flow over one-dimensional tunneling barrier between planar graphene contact and coplanar two-dimensional SiC channel exhibits superior on/off ratio compared to conventional transistors employing vertical electron transport. Multilayer epitaxial graphene (MEG) grown on SiC(0001̅) was adopted as the transistor source and drain. The channel is formed by the accumulation layer at the interface of semi-insulating SiC and a surface silicate that forms after high vacuum high temperature annealing. Electronic bands between the graphene edge and SiC accumulation layer form a thin Schottky barrier, which is dominated by tunneling at low temperatures. A thermionic emission prevails over tunneling at high temperatures. We show that neglecting tunneling effectively causes the temperature dependence of the Schottky barrier height. The channel can support current densities up to 35 A/m.

Chiral separation and chemical profile of Dengzhan Shengmai by integrating comprehensive with multiple heart-cutting two-dimensional liquid chromatography coupled with quadrupole time-of-flight mass spectrometry.

PubMed

Sheng, Ning; Zheng, Hao; Xiao, Yao; Wang, Zhe; Li, Menglin; Zhang, Jinlan

2017-09-29

Chemical profile for Chinese medicine formulas composed of several herbs is always a challenge due to a big array of small molecules with high chemical diversity so much as isomers. The present paper develops a feasible strategy to characterize and identify complex chemical constituents of a four-herb traditional Chinese medicine formula, Denzhan Shenmai (DZSM) by integrating comprehensive two-dimensional liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC×LC-qTOF-MS) with multiple heart-cutting two-dimensional liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (MHC-qTOF-MS). DZSM was separated by C8×C18 HPLC column system for comprehensive two-dimensional liquid chromatography system and 283 compounds most of which belonged to phenolic acid, flavonoid, saponin and lignan families were characterized and identified within 75min. Some isomers and compounds at low level were analyzed on C8×Chiral HPLC column system for multiple heart-cutting two-dimensional liquid chromatography system with 1D and 2D optimized gradient elution program. These 1D cutting fractions were successively separated on 2D chiral chromatographic column under extended the 2D gradient elution time from 30s to 5.0min. 12 pairs of isomer compounds were separated with good resolution. The combination of LC×LC and MHC system provides a powerful technique for global chemical profiling of DZSM and provided feasible strategy for other complex systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Superconducting and Magnetic Properties of Vanadium/iron Superlattices.

NASA Astrophysics Data System (ADS)

Wong, Hong-Kuen

A novel ultrahigh vacuum evaporator was constructed for the preparation of superlattice samples. The thickness control was much better than an atomic plane. With this evaporator we prepared V/Fe superlattice samples on (0001) sapphire substrates with different thicknesses. All samples showed a good bcc(110) structure. Mossbauer experiments showed that the interface mixing extended a distance of about one atomic plane indicating an almost rectangular composition profile. Because of this we were able to prepare samples with layer thickness approaching one atomic plane. Even with ultrathin Fe layers, the samples are ferromagnetic, at least at lower temperatures. Superparamagnetism and spin glass states were not seen. In the absence of an external field, the magnetic moments lie close to the film plane. In addition to this shape anisotropy, there is some uniaxial anisotropy. No magnetic dead layers have been observed. The magnetic moments within the Fe layers vary little with the distance from the interfaces. At the interfaces the Fe moment is reduced and an antiparallel moment is induced on the vanadium atoms. It is observed that ultrathin Fe layers behave in a 2D fashion when isolated by sufficiently thick vanadium layers; however, on thinning the vanadium layers, a magnetic coupling between the Fe layers has been observed. We also studied the superconducting properties of V/Fe sandwiches and superlattices. In both cases, the Fe layer, a strong pair-breaker, suppresses the superconducting transition temperature consistent with the current knowledge of the magnetic proximity effect. For the sandwiches with thin (thick) vanadium layers, the temperature dependence of the upper critical fields is consistent with the simple theory for a 2D (3D) superconductor. For the superlattices, when the vanadium layer is on the order of the BCS coherence length and the Fe layer is only a few atomic planes thick, a 2D-3D crossover has been observed in the temperature dependence of the parallel upper critical field. This implies the coexistence of superconductivity and ferromagnetism. We observe three dimensional behavior for thinner Fe layers ((TURN)1 atomic plane) and two dimensional behavior for thicker Fe layers (greater than 10 atomic planes).

Characterization of synthetic dyes by comprehensive two-dimensional liquid chromatography combining ion-exchange chromatography and fast ion-pair reversed-phase chromatography.

PubMed

Pirok, Bob W J; Knip, Jitske; van Bommel, Maarten R; Schoenmakers, Peter J

2016-03-04

In the late 19th century, newly invented synthetic dyes rapidly replaced the natural dyes on the market. The characterization of mixtures of these so-called early synthetic dyes is complicated through the occurrence of many impurities and degradation products. Conventional one-dimensional liquid chromatography does not suffice to obtain fingerprints with sufficient resolution and baseline integrity. Comprehensive two-dimensional liquid chromatography (LC×LC) is employed in this study, with ion-exchange chromatography in the first dimension and fast ion-pair liquid chromatography in the second. Retention in the first dimension is largely determined by the number of charges, while the selection of a small ion-pair reagent (tetramethylammonium hydroxide) in the second dimension causes retention to be largely determined by the molecular structure of the dye. As a result, there is a high degree of orthogonality of the two dimensions, similar to the values typically encountered in GC×GC. The proposed LC×LC method shows a theroretical peak capacity of about 2000 in an analysis time of about three hours. Clear, informative fingerprints are obtained that open a way to a more efficient characterization of dyes used in objects of cultural heritage. Copyright © 2016 Elsevier B.V. All rights reserved.

Incorporation of leucine into phospholipids of Bacteroides thetaiotaomicron.

PubMed Central

Smith, R D; Salyers, A A

1981-01-01

L-[4,5-3H]- or L-[U-14C]leucine was incorporated by Bacteroides thetaiotaomicron into acid-precipitable material even when the bacteria were treated with concentrations of tetracycline high enough to prevent growth. Similar results were obtained when L-[2,3,4-3H]valine or L-[4,5-3H]isoleucine was used instead of leucine. In bacteria which had been treated with tetracycline, the acid-precipitable label was not solubilized by treatment with protease, lysozyme, or deoxyribonuclease. However, virtually all of the label was extractable with chloroform-methanol, indicating that the label had been incorporated into membrane lipids. Since L-[1-14C]leucine was not incorporated into lipids, leucine was probably decarboxylated before incorporation. When a chloroform extract from bacteria which had been labeled with both [32P]phosphate and [3H]leucine was resolved into component phospholipids by two-dimensional thin-layer chromatography, 3H was incorporated into all of the phospholipids. When these phospholipids were deacylated, the 3H from leucine was associated with released fatty acids rather than with the head groups. Thus, it appears that B. thetaiotaomicron can utilize leucine and similar amino acids not only by incorporating them into protein but also by incorporating portions of these amino acids into membrane phospholipids. PMID:7462155

Lipophilicity of some guaianolides isolated from two endemic subspecies of Amphoricarpos neumayeri (Asteraceae) from Montenegro.

PubMed

Atrrog, Abubaker A B; Natić, Maja; Tosti, Tomislav; Milojković-Opsenica, Dusanka; Dordević, Iris; Tesević, Vele; Jadranin, Milka; Milosavljević, Slobodan; Lazić, Milan; Radulović, Sinisa; Tesić, Zivoslav

2009-03-01

In this study 10 guaianolide-type sesquiterpene gamma-lactones named amphoricarpolides, isolated from the aerial parts of two endemic subspecies of Amphoricarpos neumayeri (ssp. neumayeri and ssp. murbeckii Bosnjak), were investigated by means of reversed-phase thin-layer chromatography. Methanol-water and tetrahydrofuran-water binary mixtures were used as mobile phase in order to determine lipophilicity parameters R (0) (M) and C(0). Some of the investigated compounds were screened for their cytotoxic activity against HeLa and B16 cells. Chromatographically obtained lipophilicity parameters were correlated with calculated logP values and IC(50) values. Principal component analysis identified the dominant pattern in the chromatographically obtained data. 2008 John Wiley & Sons, Ltd.

Thin metal nanostructures: synthesis, properties and applications

PubMed Central

Fan, Zhanxi; Huang, Xiao; Tan, Chaoliang

2015-01-01

Two-dimensional nanomaterials, especially graphene and single- or few-layer transition metal dichalcogenide nanosheets, have attracted great research interest in recent years due to their distinctive physical, chemical and electronic properties as well as their great potentials for a broad range of applications. Recently, great efforts have also been devoted to the controlled synthesis of thin nanostructures of metals, one of the most studied traditional materials, for various applications. In this minireview, we review the recent progress in the synthesis and applications of thin metal nanostructures with a focus on metal nanoplates and nanosheets. First of all, various methods for the synthesis of metal nanoplates and nanosheets are summarized. After a brief introduction of their properties, some applications of metal nanoplates and nanosheets, such as catalysis, surface enhanced Raman scattering (SERS), sensing and near-infrared photothermal therapy are described. PMID:28553459

Integrated circuits and logic operations based on single-layer MoS2.

PubMed

Radisavljevic, Branimir; Whitwick, Michael Brian; Kis, Andras

2011-12-27

Logic circuits and the ability to amplify electrical signals form the functional backbone of electronics along with the possibility to integrate multiple elements on the same chip. The miniaturization of electronic circuits is expected to reach fundamental limits in the near future. Two-dimensional materials such as single-layer MoS(2) represent the ultimate limit of miniaturization in the vertical dimension, are interesting as building blocks of low-power nanoelectronic devices, and are suitable for integration due to their planar geometry. Because they are less than 1 nm thin, 2D materials in transistors could also lead to reduced short channel effects and result in fabrication of smaller and more power-efficient transistors. Here, we report on the first integrated circuit based on a two-dimensional semiconductor MoS(2). Our integrated circuits are capable of operating as inverters, converting logical "1" into logical "0", with room-temperature voltage gain higher than 1, making them suitable for incorporation into digital circuits. We also show that electrical circuits composed of single-layer MoS(2) transistors are capable of performing the NOR logic operation, the basis from which all logical operations and full digital functionality can be deduced.

Tunable inversion symmetry in heterostructures of layered oxides

NASA Astrophysics Data System (ADS)

Rondinelli, James

Traditional approaches to create and control functional electronic materials have focused on new phases in previously unknown bulk minerals. More recently, interlayer physics has spawned interest in known materials in unexplored atomic scale geometries, especially in complex transition metal oxides (TMO), where heterostructures can be created on demand. In this talk, I show that although epitaxial strain routinely induces (enhances) electric polarizations, biaxial strain can also induce an unanticipated polar-to-nonpolar (P-NP) structural transition in (001) thin films of naturally layered An + 1Bn O3n+1 (n = 1 - ∞) oxides. Density functional theory calculations and a complete phenomenological model for Ca3Ti2O7 are used to show that the origin of the P-NP transition originates from the interplay of trilinear-related lattice mode interactions active in the layered oxides, and those interactions are directly strain tunable. Moreover these layered oxides exhibit a quasi-two dimensional phonon mode-an acoustic branch with quadratic dispersion, enabling unusual membrane effects such as tunable negative thermal expansion. I conclude by emphasizing that broken inversion symmetric structures offer a plentiful playground for realizing new functionalities in thin films, including new multiferroics from polar metals.

Cleanup procedure for water, soil, animal and plant extracts for the use of electron-capture detector in the gas chromatographic analysis of organophosphorus insecticide residues.

PubMed

Kadoum, A M

1968-07-01

A simple, aqueous acetonitrile partition cleanup method for analyses of some common organophosphorus insecticide residues is described. The procedure described is for cleanup and quantitative recovery of parathion, methyl parathion, diazinon, malathion and thimet from different extracts. Those insecticides in the purified extracts of ground water, grain, soil, plant and animal tissues can be detected quantitatively by gas chromatography with an electron capture-detector at 0.01 ppm. Cleanup is satisfactory for paper and thin-layer chromatography for further identification of individual insecticides in the extracts.

Analysis of arsenical metabolites in biological samples.

PubMed

Hernandez-Zavala, Araceli; Drobna, Zuzana; Styblo, Miroslav; Thomas, David J

2009-11-01

Quantitation of iAs and its methylated metabolites in biological samples provides dosimetric information needed to understand dose-response relations. Here, methods are described for separation of inorganic and mono-, di-, and trimethylated arsenicals by thin layer chromatography. This method has been extensively used to track the metabolism of the radionuclide [(73)As] in a variety of in vitro assay systems. In addition, a hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometric method is described for the quantitation of arsenicals in biological samples. This method uses pH-selective hydride generation to differentiate among arsenicals containing trivalent or pentavalent arsenic.

A One-Pot Synthesis of m-Terphenyls: A Guided Exploration of Reaction Chemistry, Chromatography, and Spectroscopy. A Miniproject for the Advanced Organic Chemistry Laboratory

NASA Astrophysics Data System (ADS)

Anam, Kishorekumar T.; Curtis, Michael P.; Irfan, Muhammad J.; Johnson, Michael P.; Royer, Andrew P.; Shahmohammadi, Kianor; Vinod, Thottumkara K.

2002-05-01

This four-week project-based laboratory exercise, developed for advanced organic chemistry students, involves a one-pot synthesis of m-terphenyls. Chemistry of aryl diazonium salts and Grignard reagents and reactivity of aryne intermediates toward nucleophilic reagents form the reaction chemistry basis for the project. The project exposes students to a number of important laboratory techniques (thin-layer chromatography, gas chromatography-mass spectrometry, and column chromatography) for monitoring reaction progress and product isolation. A variety of spectroscopic techniques, including IR, 1H NMR, 13C NMR, and attached proton test are used for product characterization. Students are also introduced to a useful empirical relationship to help predict (with considerable accuracy) the 13C chemical shift values of carbon atoms of substituted benzenes.