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Sample records for afm observations revealed

  1. Nanomechanics of Yeast Surfaces Revealed by AFM

    NASA Astrophysics Data System (ADS)

    Dague, Etienne; Beaussart, Audrey; Alsteens, David

    Despite the large and well-documented characterization of the microbial cell wall in terms of chemical composition, the determination of the mechanical properties of surface molecules in relation to their function remains a key challenge in cell biology.The emergence of powerful tools allowing molecular manipulations has already revolutionized our understanding of the surface properties of fungal cells. At the frontier between nanophysics and molecular biology, atomic force microscopy (AFM), and more specifically single-molecule force spectroscopy (SMFS), has strongly contributed to our current knowledge of the cell wall organization and nanomechanical properties. However, due to the complexity of the technique, measurements on live cells are still at their infancy.In this chapter, we describe the cell wall composition and recapitulate the principles of AFM as well as the main current methodologies used to perform AFM measurements on live cells, including sample immobilization and tip functionalization.The current status of the progress in probing nanomechanics of the yeast surface is illustrated through three recent breakthrough studies. Determination of the cell wall nanostructure and elasticity is presented through two examples: the mechanical response of mannoproteins from brewing yeasts and elasticity measurements on lacking polysaccharide mutant strains. Additionally, an elegant study on force-induced unfolding and clustering of adhesion proteins located at the cell surface is also presented.

  2. The AFM Observation of Single Polyethylene Molecules in Coiled State on Mica

    NASA Astrophysics Data System (ADS)

    Prokhorov, V. V.; Yaminsky, I. V.

    2003-12-01

    Single polyethylene molecules and their small aggregates have been deposited on mica from diluted solutions at elevated temperatures and visualized by AFM in coiled and crystalline states. Coils have two-dimensional conformations with both highly tangled sites and locally extended segments with a length much exceeding the persistent length in a solution. The length measurements of coils reveal a wide distribution with the length of a maximum much smaller than the length of fully stretched molecules, moreover the long coils have been observed indicating the existence of linear multimolecular aggregates. Two models have been considered for the explanation of the observed deficit in the coils length, correspondingly the model implying the substantial smoothing of a winding chain trajectory due to the lack of the AFM resolution and the model of locally extended surface conformations with the long intramolecular folds. The roots of the apparent negative AFM height contrast of coils have been discussed.

  3. AFM observation of monatomic step movements on NaCl(001) with the help of adsorbed water

    NASA Astrophysics Data System (ADS)

    Shindo, H.; Ohashi, M.; Baba, K.; Seo, A.

    1996-06-01

    AFM observation of cleaved NaCl(001) surface in air at room temperature revealed spontaneous motion of monatomic steps, depending on relative humidity, to minimize one-dimensional surface free energy. While step motion was recognized only at the parts having large positive curvature at 52% humidity, even straight steps moved at 57%. The motion was accelerated toward higher humidity. It is suggested that adsorbed water having 2-dimensional nature transports ions at the surface. By holding the AFM tip at one place, salt solution was collected beneath the tip by capillary action. Upon removal of the tip, the solution droplet turned into a bell-shaped hillock of salt as high as 78 nm. Although the hillocks gradually flattened spontaneously, the method has potential application in pattern formation.

  4. Structure and Dynamics of Four-way DNA Junctions Dynamics Revealed by Single-Molecule AFM

    NASA Astrophysics Data System (ADS)

    Lyubchenko, Yuri

    2004-03-01

    For-way DNA junctions (Holliday junctions) are critical intermediates for homologous, site-specific recombination, DNA repair and replication. A wealth of structural information is available for immobile four-way junctions. However, these data cannot give the answer on the mechanism of branch migration, the major property of the Holliday junction. Two models for the mechanism of branch migration were suggested. According to the early model of Alberts-Meselson-Sigal, exchanging DNA strands around the junction remain parallel during branch migration. Kinetic studies of branch migration suggest an alternative model in which the junction adopts an extended conformation. We tested these models using a Holliday junction undergoing branch migration. Note that it was the first time when the dynamics of the four-way DNA junction capable of branch migration had been analyzed. We applied time-lapse atomic force microscopy (single molecule dynamics AFM) to image directly loosely bound DNA at liquid-surface interface. These experiments show that mobile Holliday junctions adopt an unfolded conformation during branch migration. This conformation of the junction remains unchanged until strand separation. The data obtained support the model for branch migration having the extended conformation of the Holliday junction. The analysis of the Holliday junctions dynamics at conditions limiting branch migration revealed a broad movement of the arms suggesting that the range of mobility of these junctions is much wider than detected before. Further applications of the time-lapse AFM approach in attempt to resolve the subpopulations of the junctions conformers and the prospects for analyses of dynamics of complex biological systems will be discussed.

  5. Combined force spectroscopy, AFM and calorimetric studies to reveal the nanostructural organization of biomimetic membranes.

    PubMed

    Suárez-Germà, C; Morros, A; Montero, M T; Hernández-Borrell, J; Domènech, Ò

    2014-10-01

    In this work we studied a binary lipid matrix of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG), a composition that mimics the inner membrane of Escherichia coli. More specifically, liposomes with varying fractions of POPG were analysed by differential scanning calorimetry (DSC) and a binary phase diagram of the system was created. Additionally, we performed atomic force microscopy (AFM) imaging of supported lipid bilayers (SLBs) of similar compositions at different temperatures, in order to create a pseudo-binary phase diagram specific to this membrane model. AFM study of SLBs is of particular interest, as it is conceived as the most adequate technique not only for studying lipid bilayer systems but also for imaging and even nanomanipulating inserted membrane proteins. The construction of the above-mentioned phase diagram enabled us to grasp better the thermodynamics of the thermal lipid transition from a gel-like POPE:POPG phase system to a more fluid phase system. Finally, AFM force spectroscopy (FS) was used to determine the nanomechanics of these two lipid phases at 27°C and at different POPG fractions. The resulting data correlated with the specific composition of each phase was calculated from the AFM phase diagram obtained. All the experiments were done in the presence of 10 mM of Ca(2+), as this ion is commonly used when performing AFM with negatively charged phospholipids.

  6. AFM imaging reveals the tetrameric structure of the TRPC1 channel

    SciTech Connect

    Barrera, Nelson P.; Shaifta, Yasin; McFadzean, Ian; Ward, Jeremy P.T.; Henderson, Robert M.; Edwardson, J. Michael . E-mail: jme1000@cam.ac.uk

    2007-07-13

    We have determined the subunit stoichiometry of the transient receptor potential C1 (TRPC1) channel by imaging isolated channels using atomic force microscopy (AFM). A frequency distribution of the molecular volumes of individual channel particles had two peaks, at 170 and 720 nm{sup 3}, corresponding with the expected sizes of TRPC1 monomers and tetramers, respectively. Complexes were formed between TRPC1 channels and antibodies against a V5 epitope tag present on each subunit. The frequency distribution of angles between pairs of bound antibodies had two peaks, at 88{sup o} and 178{sup o}. This result again indicates that the channel assembles as a tetramer.

  7. Multiparametric AFM reveals turgor-responsive net-like peptidoglycan architecture in live streptococci

    NASA Astrophysics Data System (ADS)

    Saar Dover, Ron; Bitler, Arkady; Shimoni, Eyal; Trieu-Cuot, Patrick; Shai, Yechiel

    2015-05-01

    Cell-wall peptidoglycan (PG) of Gram-positive bacteria is a strong and elastic multi-layer designed to resist turgor pressure and determine the cell shape and growth. Despite its crucial role, its architecture remains largely unknown. Here using high-resolution multiparametric atomic force microscopy (AFM), we studied how the structure and elasticity of PG change when subjected to increasing turgor pressure in live Group B Streptococcus. We show a new net-like arrangement of PG, which stretches and stiffens following osmotic challenge. The same structure also exists in isogenic mutants lacking surface appendages. Cell aging does not alter the elasticity of the cell wall, yet destroys the net architecture and exposes single segmented strands with the same circumferential orientation as predicted for intact glycans. Together, we show a new functional PG architecture in live Gram-positive bacteria.

  8. AFM-TEM observations of effect of ``melt'' time on polytetrafluoroethylene morphology.

    NASA Astrophysics Data System (ADS)

    Kalish, J. P.; Williams, R. A.; Wang, J.; Geil, P. H.; Long, T.-C.; Xu, P.

    2006-03-01

    TEM observations of PTFE dispersion particles dispersed on glass and held at 350 C or above for various times indicates that individual, > 0.1 mm long molecules wander individually on the substrate and can, with time in the ``melt,'' aggregate and form either flat-on or on-edge, folded chain single crystals. If ``trapped'' by cooling before aggregation, on-edge, single molecule, single crystals can form. All on-edge crystals, both individually and as the shish of shish-kebabs, have a ``double-striation'' appearance, suggested to arise from nucleation of the Pt/C shadowing material, used for the TEM image, on the folds at the top edge of the crystals. AFM observations have confirmed these suggestions and, furthermore, indicate the nascent, rod-like dispersion particles of a ``nano-emulsion,'' with a volume corresponding to a single molecule, have faceted ends. Combined with the TEM and ED observations that the molecular axis is parallel with the rod axis, not only must chain-folding occur during polymerization but the chain folds must be staggered on the end surfaces. P. H. Geil, et al., Adv. Polym. Sci., 180, 89 (2005).

  9. Molecular shape and binding force of Mycoplasma mobile's leg protein Gli349 revealed by an AFM study

    SciTech Connect

    Lesoil, Charles; Nonaka, Takahiro; Sekiguchi, Hiroshi; Osada, Toshiya; Miyata, Makoto; Afrin, Rehana; Ikai, Atsushi

    2010-01-15

    Recent studies of the gliding bacteria Mycoplasma mobile have identified a family of proteins called the Gli family which was considered to be involved in this novel and yet fairly unknown motility system. The 349 kDa protein called Gli349 was successfully isolated and purified from the bacteria, and electron microscopy imaging and antibody experiments led to the hypothesis that it acts as the 'leg' of M. mobile, responsible for attachment to the substrate as well as for gliding motility. However, more precise evidence of the molecular shape and function of this protein was required to asses this theory any further. In this study, an atomic force microscope (AFM) was used both as an imaging and a force measurement device to provide new information about Gli349 and its role in gliding motility. AFM images of the protein were obtained revealing a complex structure with both rigid and flexible parts, consistent with previous electron micrographs of the protein. Single-molecular force spectroscopy experiments were also performed, revealing that Gli349 is able to specifically bind to sialyllactose molecules and withstand unbinding forces around 70 pN. These findings strongly support the idea that Gli349 is the 'leg' protein of M. mobile, responsible for binding and also most probably force generation during gliding motility.

  10. AFM/TIRF force clamp measurements of neurosecretory vesicle tethers reveal characteristic unfolding steps

    PubMed Central

    Harris, Mark C.; Cislo, Dillon; Lenz, Joan S.; Umbach, Christopher

    2017-01-01

    Although several proteins have been implicated in secretory vesicle tethering, the identity and mechanical properties of the components forming the physical vesicle-plasma membrane link remain unknown. Here we present the first experimental measurements of nanomechanical properties of secretory vesicle-plasma membrane tethers using combined AFM force clamp and TIRF microscopy on membrane sheets from PC12 cells expressing the vesicle marker ANF-eGFP. Application of pulling forces generated tether extensions composed of multiple steps with variable length. The frequency of short (<10 nm) tether extension events was markedly higher when a fluorescent vesicle was present at the cantilever tip and increased in the presence of GTPγS, indicating that these events reflect specifically the properties of vesicle-plasma membrane tethers. The magnitude of the short tether extension events is consistent with extension lengths expected from progressive unfolding of individual helices of the exocyst complex, supporting its direct role in forming the physical vesicle-plasma membrane link. PMID:28323853

  11. New insights into morphology of high performance BHJ photovoltaics revealed by high resolution AFM.

    PubMed

    Wang, Dong; Liu, Feng; Yagihashi, Noritoshi; Nakaya, Masafumi; Ferdous, Sunzida; Liang, Xiaobin; Muramatsu, Atsushi; Nakajima, Ken; Russell, Thomas P

    2014-10-08

    Direct imaging of the bulk heterojunction (BHJ) thin film morphology in polymer-based solar cells is essential to understand device function and optimize efficiency. The morphology of the BHJ active layer consists of bicontinuous domains of the donor and acceptor materials, having characteristic length scales of several tens of nanometers, that reduces charge recombination, enhances charge separation, and enables electron and hole transport to their respective electrodes. Direct imaging of the morphology from the molecular to macroscopic level, though, is lacking. Though transmission electron tomography provides a 3D, real-space image of the morphology, quantifying the structure is not possible. Here we used high-resolution atomic force microscopy (AFM) in the tapping and nanomechanical modes to investigate the BHJ active layer morphology that, when combined with Ar(+) etching, provided unique insights with unparalleled spatial resolution. PCBM was seen to form a network that interpenetrated into the fibrillar network of the hole-conducting polymer, both being imbedded in a mixture of the two components. The free surface was found to be enriched with polymer crystals having a "face-on" orientation and the morphology at the anode interface was markedly different.

  12. Observation of Spin-flop Transition in Antiferromagnetic Organic Molecular Conductors using AFM Micro-cantilever

    NASA Astrophysics Data System (ADS)

    Tokumoto, Madoka; Otsuka, Takeo; Kobayashi, Akiko

    2005-03-01

    A series of (BETS)2Fe1-xGaxCl1-yBry salts is a good candidate for a systematic study of π-d interaction between the conduction electrons and local magnetic moments in organic conductors. Some of them show antiferromagnetic ground state at low temperatures. A torque magnetometry is useful for precise determination of the easy axis as well as the spin-flop field. In this work we will report on the measurements of spin-flop transitions in antiferromagnetic organic molecular conductors including λ-(BETS)2FeCl4[1], using a commercial self-sensing piezo-resistive microcantilever for Atomic Force Microscopy (AFM) developed by Seiko Instruments Inc. We have succeeded in observation of spin-flop transitions of tiny single crystals including λ-(BETS)2FeCl4 as small as less than 1μg[2]. The results are consistent with the capacitive magnetic torque study[3]. [1] M. Tokumoto et al. Synth. Metals 86, 2161 (1997). [2] M. Tokumoto et al., ICMM2004, Polyhedron in press. [3] T. Sasaki et al., Synth. Metals 120, 759 (2001).

  13. Lower nanometer-scale size limit for the deformation of a metallic glass by shear transformations revealed by quantitative AFM indentation.

    PubMed

    Caron, Arnaud; Bennewitz, Roland

    2015-01-01

    We combine non-contact atomic force microscopy (AFM) imaging and AFM indentation in ultra-high vacuum to quantitatively and reproducibly determine the hardness and deformation mechanisms of Pt(111) and a Pt57.5Cu14.7Ni5.3P22.5 metallic glass with unprecedented spatial resolution. Our results on plastic deformation mechanisms of crystalline Pt(111) are consistent with the discrete mechanisms established for larger scales: Plasticity is mediated by dislocation gliding and no rate dependence is observed. For the metallic glass we have discovered that plastic deformation at the nanometer scale is not discrete but continuous and localized around the indenter, and does not exhibit rate dependence. This contrasts with the observation of serrated, rate-dependent flow of metallic glasses at larger scales. Our results reveal a lower size limit for metallic glasses below which shear transformation mechanisms are not activated by indentation. In the case of metallic glass, we conclude that the energy stored in the stressed volume during nanometer-scale indentation is insufficient to account for the interfacial energy of a shear band in the glassy matrix.

  14. Effects of fluoride treatment on phosphoric acid-etching in primary teeth: an AFM observation.

    PubMed

    Choi, Samjin; Rhee, Yeri; Park, Jeong-Hoon; Lee, Gi-Ja; Kim, Kyung-Sook; Park, Jae-Hong; Park, Young-Guk; Park, Hun-Kuk

    2010-07-01

    The aim of this study was to examine the effect of fluoride application on 37% phosphoric acid-etching by atomic force microscopy (AFM) in primary tooth samples based on a clinical protocol used in a pediatric dental hospital. Enamel samples were prepared from 36 exfoliated and non-carious primary teeth. Primary tooth samples were randomly assigned to one of the four groups based on the timing of acid-etching with 37% phosphoric acid after an acidulated phosphate fluoride (APF) pre-treatment. Group 1 received no fluoride application, Group 2 was pre-treated with fluoride and then received acid-etching 2 weeks later. One week separated the fluoride treatment and the acid-etching in Group 3, while Group 4 received acid-etching immediately after the fluoride treatment. The vestibular enamel surfaces of each primary tooth sample were scanned in air at a resolution of 512 x 512 pixels and a scan speed of 0.8 line/s. On the enamel surfaces of the primary teeth after APF pre-treatment, debris were observed although the teeth were smoother than they were prior to APF. As a result, it was concluded that APF treatment is responsible for decreased primary tooth surface roughness. The enamel surfaces etched for 20s showed that acid-etching was effective not only in removing scratches and debris, but also for evaluating enamel rod characteristics. Primary tooth enamel surfaces after etching showed minute structures caused by the decreased hydroxyapatite nanoparticle space, compared to those before etching. Also, acid-etching showed significantly increased roughness effects (p<0.0001, n=9). Finally, as more time elapsed after APF pre-treatment, the roughness was decreased to a lesser degree (p=0.005, n=9). We suggest that primary teeth etching 2 weeks after APF pre-treatment used clinically in pediatric hospitals may be effective to obtain properly etched enamel surfaces.

  15. Single Cell Wall Nonlinear Mechanics Revealed by a Multiscale Analysis of AFM Force-Indentation Curves.

    PubMed

    Digiuni, Simona; Berne-Dedieu, Annik; Martinez-Torres, Cristina; Szecsi, Judit; Bendahmane, Mohammed; Arneodo, Alain; Argoul, Françoise

    2015-05-05

    Individual plant cells are rather complex mechanical objects. Despite the fact that their wall mechanical strength may be weakened by comparison with their original tissue template, they nevertheless retain some generic properties of the mother tissue, namely the viscoelasticity and the shape of their walls, which are driven by their internal hydrostatic turgor pressure. This viscoelastic behavior, which affects the power-law response of these cells when indented by an atomic force cantilever with a pyramidal tip, is also very sensitive to the culture media. To our knowledge, we develop here an original analyzing method, based on a multiscale decomposition of force-indentation curves, that reveals and quantifies for the first time the nonlinearity of the mechanical response of living single plant cells upon mechanical deformation. Further comparing the nonlinear strain responses of these isolated cells in three different media, we reveal an alteration of their linear bending elastic regime in both hyper- and hypotonic conditions.

  16. Low and high cycle fatigue -- A continuum supported by AFM observations

    SciTech Connect

    Gerberich, W.W.; Harvey, S.E.; Kramer, D.E.; Hoehn, J.W.

    1998-09-01

    It is proposed that fatigue damage evolution is controlled by surface displacements and these can be accurately measured by atomic force microscopy (AFM). As these displacements can be followed throughout the history of a fatigued component, the fatigue process in general represents a continuum of behavior. In 10 and 200 {micro}m grain size titanium, AFM measurements demonstrate that the fraction of plasticity contributing to surface damage can be expressed as a single function over nearly five decades of cycles. Regarding this function, the effect of grain size appears to be small. In terms of damage accumulation rates, cyclic hardening parameters, and the threshold stress intensity, the proposed model represents a microstructurally-sensitive Manson-Coffin law for fatigue initiation. Coupling this with a more standard fracture mechanics approach for the latter stage of life allows a simple expression for life prediction. Over the range of 10{sup 3}--10{sup 6} cycles, this expression predicts fatigue life of titanium exposed to air and saline environments to first order.

  17. Reversible wetting of NaCl nanoparticles at relative humidities below deliquescence observed by environmental non-contact AFM

    SciTech Connect

    Bruzewicz, D.A.; Lewis, E.; Ocko, B. M.; McGraw, R. L.; Schwartz, S. E.

    2009-12-14

    The behavior of NaCl nanoparticles as a function of relative humidity (RH) was characterized by depositing particles on a prepared hydrophobic surface and measuring their height via non-contact environmental atomic force microscopy (AFM). Non-contact AFM allows greater sensitivity to changes in the size of particles than does contact AFM or scanning electron microscopy, and greater sensitivity to changes in shape than do mass-based techniques. Crystalline cubic NaCl nanoparticles with sides of 35 to 150 nm were found to reversibly take up water with increasing RH, and to form a liquid-like surface layer of thickness 2 to 4 nm at humidities well below the deliquescence point of 75.0% at 20°C. Measurable uptake begins at 70% RH. The maximum thickness of the layer increases with increasing RH for a given particle size and, for a given RH, increases with increasing particle size over the range studied. The liquid-like behavior of the layer is indicated by a reversible “rounding” at the tops of the particles, where the ratio of particle height to radius of curvature increases from zero (flat top) at 68% RH to 0.7 at 74% RH. These observations suggest that a reorganization of mass occurs on the solid NaCl nanoparticle, and hence that the behavior of NaCl aerosol nanoparticles at RH between 70 and 75% RH is more complex than an abrupt first-order phase transition. Theoretical treatments of the phase transition should therefore account for both the presence of a liquid-like layer prior to deliquescence, and the RH-dependent thickness of the layer.

  18. Tendon exhibits complex poroelastic behavior at the nanoscale as revealed by high-frequency AFM-based rheology.

    PubMed

    Connizzo, Brianne K; Grodzinsky, Alan J

    2017-03-21

    Tendons transmit load from muscle to bone by utilizing their unique static and viscoelastic tensile properties. These properties are highly dependent on the composition and structure of the tissue matrix, including the collagen I hierarchy, proteoglycans, and water. While the role of matrix constituents in the tensile response has been studied, their role in compression, particularly in matrix pressurization via regulation of fluid flow, is not well understood. Injured or diseased tendons and tendon regions that naturally experience compression are known to have alterations in glycosaminoglycan content, which could modulate fluid flow and ultimately mechanical function. While recent theoretical studies have predicted tendon mechanics using poroelastic theory, no experimental data have directly demonstrated such behavior. In this study, we use high-bandwidth AFM-based rheology to determine the dynamic response of tendons to compressive loading at the nanoscale and to determine the presence of poroelastic behavior. Tendons are found to have significant characteristic dynamic relaxation behavior occurring at both low and high frequencies. Classic poroelastic behavior is observed, although we hypothesize that the full dynamic response is caused by a combination of flow-dependent poroelasticity as well as flow-independent viscoelasticity. Tendons also demonstrate regional dependence in their dynamic response, particularly near the junction of tendon and bone, suggesting that the structural and compositional heterogeneity in tendon may be responsible for regional poroelastic behavior. Overall, these experiments provide the foundation for understanding fluid-flow-dependent poroelastic mechanics of tendon, and the methodology is valuable for assessing changes in tendon matrix compressive behavior at the nanoscale.

  19. AFM Imaging Reveals Topographic Diversity of Wild Type and Z Variant Polymers of Human α1-Proteinase Inhibitor

    PubMed Central

    Gaczynska, Maria; Karpowicz, Przemyslaw; Stuart, Christine E.; Norton, Malgorzata G.; Teckman, Jeffrey H.; Marszal, Ewa; Osmulski, Pawel A.

    2016-01-01

    α1-Proteinase inhibitor (antitrypsin) is a canonical example of the serpin family member that binds and inhibits serine proteases. The natural metastability of serpins is crucial to carry out structural rearrangements necessary for biological activity. However, the enhanced metastability of the mutant Z variant of antitrypsin, in addition to folding defect, may substantially contribute to its polymerization, a process leading to incurable serpinopathy. The metastability also impedes structural studies on the polymers. There are no crystal structures of Z monomer or any kind of polymers larger than engineered wild type (WT) trimer. Our understanding of polymerization mechanisms is based on biochemical data using in vitro generated WT oligomers and molecular simulations. Here we applied atomic force microscopy (AFM) to compare topography of monomers, in vitro formed WT oligomers, and Z type polymers isolated from transgenic mouse liver. We found the AFM images of monomers closely resembled an antitrypsin outer shell modeled after the crystal structure. We confirmed that the Z variant demonstrated higher spontaneous propensity to dimerize than WT monomers. We also detected an unexpectedly broad range of different types of polymers with periodicity and topography depending on the applied method of polymerization. Short linear oligomers of unit arrangement similar to the Z polymers were especially abundant in heat-treated WT preparations. Long linear polymers were a prominent and unique component of liver extracts. However, the liver preparations contained also multiple types of oligomers of topographies undistinguishable from those found in WT samples polymerized with heat, low pH or guanidine hydrochloride treatments. In conclusion, we established that AFM is an excellent technique to assess morphological diversity of antitrypsin polymers, which is important for etiology of serpinopathies. These data also support previous, but controversial models of in vivo

  20. AFM Imaging Reveals Topographic Diversity of Wild Type and Z Variant Polymers of Human α1-Proteinase Inhibitor

    DOE PAGES

    Gaczynska, Maria; Karpowicz, Przemyslaw; Stuart, Christine E.; ...

    2016-03-23

    α1-Proteinase inhibitor (antitrypsin) is a canonical example of the serpin family member that binds and inhibits serine proteases. The natural metastability of serpins is crucial to carry out structural rearrangements necessary for biological activity. However, the enhanced metastability of the mutant Z variant of antitrypsin, in addition to folding defect, may substantially contribute to its polymerization, a process leading to incurable serpinopathy. The metastability also impedes structural studies on the polymers. There are no crystal structures of Z monomer or any kind of polymers larger than engineered wild type (WT) trimer. Our understanding of polymerization mechanisms is based on biochemicalmore » data using in vitro generated WT oligomers and molecular simulations. Here we applied atomic force microscopy (AFM) to compare topography of monomers, in vitro formed WT oligomers, and Z type polymers isolated from transgenic mouse liver. We found the AFM images of monomers closely resembled an antitrypsin outer shell modeled after the crystal structure. We confirmed that the Z variant demonstrated higher spontaneous propensity to dimerize than WT monomers. We also detected an unexpectedly broad range of different types of polymers with periodicity and topography depending on the applied method of polymerization. Short linear oligomers of unit arrangement similar to the Z polymers were especially abundant in heat-treated WT preparations. Long linear polymers were a prominent and unique component of liver extracts. However, the liver preparations contained also multiple types of oligomers of topographies undistinguishable from those found inWT samples polymerized with heat, low pH or guanidine hydrochloride treatments. In conclusion, we established that AFM is an excellent technique to assess morphological diversity of antitrypsin polymers, which is important for etiology of serpinopathies. These data also support previous, but controversial models of in vivo

  1. AFM Imaging Reveals Topographic Diversity of Wild Type and Z Variant Polymers of Human α1-Proteinase Inhibitor

    SciTech Connect

    Gaczynska, Maria; Karpowicz, Przemyslaw; Stuart, Christine E.; Norton, Malgorzata G.; Teckman, Jeffrey H.; Marszal, Ewa; Osmulski, Pawel A.

    2016-03-23

    α1-Proteinase inhibitor (antitrypsin) is a canonical example of the serpin family member that binds and inhibits serine proteases. The natural metastability of serpins is crucial to carry out structural rearrangements necessary for biological activity. However, the enhanced metastability of the mutant Z variant of antitrypsin, in addition to folding defect, may substantially contribute to its polymerization, a process leading to incurable serpinopathy. The metastability also impedes structural studies on the polymers. There are no crystal structures of Z monomer or any kind of polymers larger than engineered wild type (WT) trimer. Our understanding of polymerization mechanisms is based on biochemical data using in vitro generated WT oligomers and molecular simulations. Here we applied atomic force microscopy (AFM) to compare topography of monomers, in vitro formed WT oligomers, and Z type polymers isolated from transgenic mouse liver. We found the AFM images of monomers closely resembled an antitrypsin outer shell modeled after the crystal structure. We confirmed that the Z variant demonstrated higher spontaneous propensity to dimerize than WT monomers. We also detected an unexpectedly broad range of different types of polymers with periodicity and topography depending on the applied method of polymerization. Short linear oligomers of unit arrangement similar to the Z polymers were especially abundant in heat-treated WT preparations. Long linear polymers were a prominent and unique component of liver extracts. However, the liver preparations contained also multiple types of oligomers of topographies undistinguishable from those found inWT samples polymerized with heat, low pH or guanidine hydrochloride treatments. In conclusion, we established that AFM is an excellent technique to assess morphological diversity of antitrypsin polymers, which is important for etiology of serpinopathies. These data also support previous, but controversial models of in

  2. In situ AFM observations of Ca-Mg carbonate crystallization catalyzed by dissolved sulfide: Implications for sedimentary dolomite formation

    NASA Astrophysics Data System (ADS)

    Zhang, Fangfu; Yan, Chao; Teng, H. Henry; Roden, Eric E.; Xu, Huifang

    2013-03-01

    It has been observed that the metabolism of sulfate-reducing bacteria can overcome the energy barrier to Mg2+ incorporation into growing Ca-Mg carbonates and enhance dolomite precipitation, although the role of SRB in dolomite formation is still under debate. In this study, we presented in situ AFM observations of Ca-Mg carbonate {1 0 4} surface growing from supersaturated solutions. Our data showed that not only can Mg2+ modify the morphology of the polygonal growth hillocks and impede step growth, but it can also inhibit 1-D step nucleation, resulting in the inability for spirals to continue their vertical growth. However, in the presence of dissolved sulfide, both the 1-D step nucleation and step growth which had been retarded by Mg2+ ions were significantly enhanced. For example, in the presence as low as 0.13 mM dissolved sulfide, the step velocity can be increased by more than 9 times compared to that in contact with solutions containing Mg2+ ions but no dissolved sulfide. The Ca-Mg carbonate growth hillock in contact with dissolved sulfide-bearing growth solutions eventually developed a micromosaic-like structure. Based on our observations, we propose that the overall catalytic effect of dissolved sulfide may be twofold, one to stabilize the critical nuclei during 1-D step nucleation by the adsorption of dissolved sulfide on Ca-Mg carbonate surfaces and two to facilitate the dehydration of surface Mg2+-water complexes during growth. We hypothesize that dissolved sulfide may adsorb on crystal faces through hydrogen bonding between the H in HS-/H2S and the O in calcite CO32- to weaken the rigid Mg2+ hydration shell, resulting in an elevated activation entropy for particle attachment and hence a larger kinetic coefficient for step growth. Together with previous studies on disorder dolomite precipitation induced by dissolved sulfide, we demonstrate the catalysis role of dissolved sulfide in sedimentary dolomite formation associate with SRB, which may shed new

  3. Germ direct observation by AFM under crystallization of self-organized assemblies of mono-protonated meso-tetraphenylporphine dimers

    NASA Astrophysics Data System (ADS)

    Udal'tsov, Alexander V.

    2016-08-01

    Assemblies consisting of mono-protonated meso-tetraphenylporphine dimers and water have been investigated by UV-vis spectroscopy in solution and atomic force microscopy (AFM) in thin layers. These assemblies self-organized into domains produce microcrystals in thin layer. Morphology of the microcrystals and characteristic features of crystallization germ on the top found by contact AFM indicate that surface tension of an aqueous layer on the domain generates the crystallization process. Estimations of the pressure producing the germ and bulk modulus (Bm) of microcrystals give 26.3±2.6 MPa and 3.72 GPa and Bm=12.7 GPa obtained for dried thin films. The former modulus is comparable with bulk modulus of water (2.174 GPa) that implies liquid crystals formation. Absorptions of longitudinal optical (LO) phonons with ћωLO=0.3761 and 0.3577 eV, which are arisen because of hole polaron moving through water, are found in the electronic spectra of the assemblies. The crystallization is suggested to occur due to Zundel cation (H5O2+) operation like the water-porphyrin matrix self-organization found earlier.

  4. [IR/UV spectroscopic analysis of gangliosides and their microstructures of polymeric aggregates observed by AFM technique].

    PubMed

    Wang, Hai-long; Sun, Run-guang; Zhang, Jing; Hao, Chang-chun

    2009-04-01

    Gangliosides, a kind of acid glycosphingolipid containing sialic acid, plays a very important physiological role in biomembrane as one of the important components of neurocyte membrane. They were extracted from bovine brain by the Folch method and purified by silica gel and DEAE-Sephadex A-25 column chromatograph. Their molecular functional groups and microstructures of polymeric aggregates were studied by infrared spectrum (IR), ultraviolet spectrum (UV) and atomic force microscope (AFM). The experimental results indicate that: 55.2 mg of Gls from 100 g of wet bovine brain had a certain purity, 62.84%. And their UV absorption spectra appeared at 195 nm, near to the results reported by other peoples. Compared with the IR spectra of sialic acid, the experimental results showed that the structures of the products had the units of sialic acid. In order to investigate the aggregate structures of ganglioside. AFM technique was applied in water, and the results showed that gangliosides can form spherical or ellipsoidal structures in water. It was determined that the size of polymeric aggregates of gangliosides varies between 55 and 380 nm, the average size is (148.9+/-66.7) nm; the height is between 1.0 and 5.0 nm, and the average height is (3.25+/-1.01) nm. The experimental results provide a theoretical and experimental basis for investigating biological activity and the exploitation and utilization of neural drugs.

  5. AFM Structural Characterization of Drinking Water Biofilm under Physiological Conditions

    EPA Science Inventory

    Due to the complexity of mixed culture drinking water biofilm, direct visual observation under in situ conditions has been challenging. In this study, atomic force microscopy (AFM) revealed the three dimensional morphology and arrangement of drinking water relevant biofilm in air...

  6. Nanoscale structural features determined by AFM for single virus particles

    NASA Astrophysics Data System (ADS)

    Chen, Shu-Wen W.; Odorico, Michael; Meillan, Matthieu; Vellutini, Luc; Teulon, Jean-Marie; Parot, Pierre; Bennetau, Bernard; Pellequer, Jean-Luc

    2013-10-01

    In this work, we propose ``single-image analysis'', as opposed to multi-image averaging, for extracting valuable information from AFM images of single bio-particles. This approach allows us to study molecular systems imaged by AFM under general circumstances without restrictions on their structural forms. As feature exhibition is a resolution correlation, we have performed AFM imaging on surfaces of tobacco mosaic virus (TMV) to demonstrate variations of structural patterns with probing resolution. Two AFM images were acquired with the same tip at different probing resolutions in terms of pixel width, i.e., 1.95 and 0.49 nm per pixel. For assessment, we have constructed an in silico topograph based on the three-dimensional crystal structure of TMV as a reference. The prominent artifacts observed in the AFM-determined shape of TMV were attributed to tip convolutions. The width of TMV rod was systematically overestimated by ~10 nm at both probing resolutions of AFM. Nevertheless, the effects of tip convolution were less severe in vertical orientation so that the estimated height of TMV by AFM imaging was in close agreement with the in silico X-ray topograph. Using dedicated image processing algorithms, we found that at low resolution (i.e., 1.95 nm per pixel), the extracted surface features of TMV can be interpreted as a partial or full helical repeat (three complete turns with ~7.0 nm in length), while individual protein subunits (~2.5 nm) were perceivable only at high resolution. The present study shows that the scales of revealed structural features in AFM images are subject to both probing resolution and processing algorithms for image analysis.

  7. Dimming titan revealed by the Cassini observations.

    PubMed

    Li, Liming

    2015-02-04

    Here we report the temporal variation of Titan's emitted energy with the Cassini/CIRS observations. In the northern hemisphere, the hemispheric-average emitted power decreased from 2007 to 2009 and increased from 2009 to 2012-13, which make the net change insignificant (0.1 ± 0.2%) during the period 2007-2013. The decrease from 2007 to 2009 is mainly due to the cooling around the stratospause, and the increase from 2009 to 2012-13 is probably related to temporal variation of atmospheric temperature around the tropopuase in the northern hemisphere. In the southern hemisphere, the emitted power continuously decreased by 5.0 ± 0.6% from 2.40 ± 0.01 W/m(2) in 2007 to 2.28 ± 0.01 in 2012-13, which is mainly related to Titan's seasonal variation. The asymmetry in the temporal variation between the two hemispheres results in the global-average emitted power decreasing by 2.5 ± 0.6% from 2.41 ± 0.01 W/m(2) in 2007 to 2.35 ± 0.01 W/m(2) in 2012-13. The solar constant at Titan decreased by ~13.0% in the same period 2007-2013, which is much stronger than the temporal variation of emitted power. The measurements of Titan's absorbed solar power are needed to determine the temporal variation of the global energy budget.

  8. Dimming Titan Revealed by the Cassini Observations

    NASA Astrophysics Data System (ADS)

    Li, Liming

    2015-02-01

    Here we report the temporal variation of Titan's emitted energy with the Cassini/CIRS observations. In the northern hemisphere, the hemispheric-average emitted power decreased from 2007 to 2009 and increased from 2009 to 2012-13, which make the net change insignificant (0.1 +/- 0.2%) during the period 2007-2013. The decrease from 2007 to 2009 is mainly due to the cooling around the stratospause, and the increase from 2009 to 2012-13 is probably related to temporal variation of atmospheric temperature around the tropopuase in the northern hemisphere. In the southern hemisphere, the emitted power continuously decreased by 5.0 +/- 0.6% from 2.40 +/- 0.01 W/m2 in 2007 to 2.28 +/- 0.01 in 2012-13, which is mainly related to Titan's seasonal variation. The asymmetry in the temporal variation between the two hemispheres results in the global-average emitted power decreasing by 2.5 +/- 0.6% from 2.41 +/- 0.01 W/m2 in 2007 to 2.35 +/- 0.01 W/m2 in 2012-13. The solar constant at Titan decreased by ~13.0% in the same period 2007-2013, which is much stronger than the temporal variation of emitted power. The measurements of Titan's absorbed solar power are needed to determine the temporal variation of the global energy budget.

  9. Dimming Titan Revealed by the Cassini Observations

    PubMed Central

    Li, Liming

    2015-01-01

    Here we report the temporal variation of Titan's emitted energy with the Cassini/CIRS observations. In the northern hemisphere, the hemispheric-average emitted power decreased from 2007 to 2009 and increased from 2009 to 2012–13, which make the net change insignificant (0.1 ± 0.2%) during the period 2007–2013. The decrease from 2007 to 2009 is mainly due to the cooling around the stratospause, and the increase from 2009 to 2012–13 is probably related to temporal variation of atmospheric temperature around the tropopuase in the northern hemisphere. In the southern hemisphere, the emitted power continuously decreased by 5.0 ± 0.6% from 2.40 ± 0.01 W/m2 in 2007 to 2.28 ± 0.01 in 2012–13, which is mainly related to Titan's seasonal variation. The asymmetry in the temporal variation between the two hemispheres results in the global-average emitted power decreasing by 2.5 ± 0.6% from 2.41 ± 0.01 W/m2 in 2007 to 2.35 ± 0.01 W/m2 in 2012–13. The solar constant at Titan decreased by ~13.0% in the same period 2007–2013, which is much stronger than the temporal variation of emitted power. The measurements of Titan's absorbed solar power are needed to determine the temporal variation of the global energy budget. PMID:25649341

  10. AFM observation of the surface morphology and impurity effects on orthorhombic hen egg-white lysozyme crystals

    NASA Astrophysics Data System (ADS)

    Matsuzuki, Y.; Kubota, T.; Liu, X. Y.; Ataka, M.; Takano, K. J.

    2002-07-01

    Cation-exchange high performance liquid chromatography at pH 6, developed originally to purify human lysozyme, was applied to hen egg-white lysozyme. We could remove at least three kinds of impurities from the commercial product. The impurities were considered to be modified lysozyme molecules, mostly based on N-terminal amino acid analyses. Atomic force microscopic observation was made on the crystals both from the purified and non-purified solutions. The (1 1 0) faces of the orthorhombic crystals grown at 40°C from the purified solution contained linear steps, while most of the linear edges became round and rugged on the crystals from non-purified solutions. A similar change in step morphology is known to occur on insulin crystals when two amino acids were mutated from the wild type. On the (0 1 0) face, elongated, round steps became rugged when crystals grew from non-purified solutions.

  11. AFM Structural Characterization of Drinking Water Biofilm ...

    EPA Pesticide Factsheets

    Due to the complexity of mixed culture drinking water biofilm, direct visual observation under in situ conditions has been challenging. In this study, atomic force microscopy (AFM) revealed the three dimensional morphology and arrangement of drinking water relevant biofilm in air and aqueous solution. Operating parameters were optimized to improve imaging of structural details for a mature biofilm in liquid. By using a soft cantilever (0.03 N/m) and slow scan rate (0.5 Hz), biofilm and individual bacterial cell’s structural topography were resolved and continuously imaged in liquid without loss of spatial resolution or sample damage. The developed methodology will allow future in situ investigations to temporally monitor mixed culture drinking water biofilm structural changes during disinfection treatments. Due to the complexity of mixed culture drinking water biofilm, direct visual observation under in situ conditions has been challenging. In this study, atomic force microscopy (AFM) revealed the three dimensional morphology and arrangement of drinking water relevant biofilm in air and aqueous solution. Operating parameters were optimized to improve imaging of structural details for a mature biofilm in liquid. By using a soft cantilever (0.03 N/m) and slow scan rate (0.5 Hz), biofilm and individual bacterial cell’s structural topography were resolved and continuously imaged in liquid without loss of spatial resolution or sample damage. The developed methodo

  12. Nanoscale Nucleosome Dynamics Assessed with Time-lapse AFM

    PubMed Central

    Lyubchenko, Yuri L.

    2013-01-01

    A fundamental challenge associated with chromosomal gene regulation is accessibility of DNA within nucleosomes. Recent studies performed by various techniques, including single-molecule approaches, led to the realization that nucleosomes are dynamic structures rather than static systems, as it was once believed. Direct data is required in order to understand the dynamics of nucleosomes more clearly and answer fundamental questions, including: What is the range of nucleosome dynamics? Does a non-ATP dependent unwrapping process of nucleosomes exist? What are the factors facilitating the large scale opening and unwrapping of nucleosomes? This review summarizes the results of nucleosome dynamics obtained with time-lapse AFM, including a high-speed version (HS-AFM) capable of visualizing molecular dynamics on the millisecond time scale. With HS-AFM, the dynamics of nucleosomes at a sub-second time scale was observed allowing one to visualize various pathways of nucleosome dynamics, such as sliding and unwrapping, including complete dissociation. Overall, these findings reveal new insights into the dynamics of nucleosomes and the novel mechanisms controlling spontaneous chromatin dynamics. PMID:24839467

  13. AFM characterization of nonwoven material functionalized by ZnO sputter coating

    SciTech Connect

    Deng Bingyao; Yan Xiong; Wei Qufu Gao Weidong

    2007-10-15

    Sputter coatings provide new approaches to the surface functionalization of textile materials. In this study, polyethylene terephthalate (PET) nonwoven material was used as a substrate for creating functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit functional zinc oxide (ZnO) nanostructures onto the nonwoven substrate. The evolution of the surface morphology of the fibers in the nonwoven web was examined using atomic force microscopy (AFM). The AFM observations revealed a significant difference in the morphology of the fibers before and after the sputter coating. The AFM images also indicated the effect of the sputtering conditions on the surface morphology of the fibers. The increase in the sputtering time led to the growth of the ZnO grains on the fiber surfaces. The higher pressure in the sputtering chamber could cause the formation of larger grains on the fiber surfaces. The higher power used also generated larger grains on the fiber surfaces.

  14. EVLA Observations of T Pyx Reveal Radio Brightening

    NASA Astrophysics Data System (ADS)

    Krauss, M. I.; Chomiuk, L.; Sokoloski, J. L.; Rupen, M. P.; Mioduszewski, A. J.; Roy, N.; O'Brien, T. J.; Bode, M. F.; Eyres, S. P. S.; Mukai, K.; Nelson, T.

    2011-10-01

    EVLA observations of T Pyx on 2011 September 17 and 24 show that it is now substantially brighter in the radio than previously reported (ATel #3318). This radio brightening follows a reported increase in X-ray flux and variability (ATel #3647). Our observed radio flux densities, covering a frequency range of 2 - 40 GHz, are reported below, including estimated 1σ errors. The spectrum can be characterized by a power-law with a spectral index of approximately α = 1.4 (where Sν ∝ να), suggesting an optically-thick thermal source of emission.

  15. A review of the application of atomic force microscopy (AFM) in food science and technology.

    PubMed

    Liu, Shaoyang; Wang, Yifen

    2011-01-01

    Atomic force microscopy (AFM) is a powerful nanoscale analysis technique used in food area. This versatile technique can be used to acquire high-resolution sample images and investigate local interactions in air or liquid surroundings. In this chapter, we explain the principles of AFM and review representative applications of AFM in gelatin, casein micelle, carrageenan, gellan gum, starch, and interface. We elucidate new knowledge revealed with AFM as well as ways to use AFM to obtain morphology and rheology information in different food fields.

  16. Raman and AFM study of gamma irradiated plastic bottle sheets

    NASA Astrophysics Data System (ADS)

    Ali, Yasir; Kumar, Vijay; Sonkawade, R. G.; Dhaliwal, A. S.

    2013-02-01

    In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV 60Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

  17. [Application of atomic force microscopy (AFM) in ophthalmology].

    PubMed

    Milka, Michał; Mróz, Iwona; Jastrzebska, Maria; Wrzalik, Roman; Dobrowolski, Dariusz; Roszkowska, Anna M; Moćko, Lucyna; Wylegała, Edward

    2012-01-01

    Atomic force microscopy (AFM) allows to examine surface of different biological objects in the nearly physiological conditions at the nanoscale. The purpose of this work is to present the history of introduction and the potential applications of the AFM in ophthalmology research and clinical practice. In 1986 Binnig built the AFM as a next generation of the scanning tunnelling microscope (STM). The functional principle of AFM is based on the measurement of the forces between atoms on the sample surface and the probe. As a result, the three-dimensional image of the surface with the resolution on the order of nanometres can be obtained. Yamamoto used as the first the AFM on a wide scale in ophthalmology. The first investigations used the AFM method to study structure of collagen fibres of the cornea and of the sclera. Our research involves the analysis of artificial intraocular lenses (IOLs). According to earlier investigations, e.g. Lombardo et al., the AFM was used to study only native IOLs. Contrary to the earlier investigations, we focused our measurements on lenses explanted from human eyes. The surface of such lenses is exposed to the influence of the intraocular aqueous environment, and to the related impacts of biochemical processes. We hereby present the preliminary results of our work in the form of AFM images depicting IOL surface at the nanoscale. The images allowed us to observe early stages of the dye deposit formation as well as local calcinosis. We believe that AFM is a very promising tool for studying the structure of IOL surface and that further observations will make it possible to explain the pathomechanism of artificial intraocular lens opacity formation.

  18. Structured Observations Reveal Slow HIV-1 CTL Escape

    PubMed Central

    Roberts, Hannah E.; Hurst, Jacob; Robinson, Nicola; Brown, Helen; Flanagan, Peter; Vass, Laura; Fidler, Sarah; Weber, Jonathan; Babiker, Abdel; Phillips, Rodney E.; McLean, Angela R.; Frater, John

    2015-01-01

    The existence of viral variants that escape from the selection pressures imposed by cytotoxic T-lymphocytes (CTLs) in HIV-1 infection is well documented, but it is unclear when they arise, with reported measures of the time to escape in individuals ranging from days to years. A study of participants enrolled in the SPARTAC (Short Pulse Anti-Retroviral Therapy at HIV Seroconversion) clinical trial allowed direct observation of the evolution of CTL escape variants in 125 adults with primary HIV-1 infection observed for up to three years. Patient HLA-type, longitudinal CD8+ T-cell responses measured by IFN-γ ELISpot and longitudinal HIV-1 gag, pol, and nef sequence data were used to study the timing and prevalence of CTL escape in the participants whilst untreated. Results showed that sequence variation within CTL epitopes at the first time point (within six months of the estimated date of seroconversion) was consistent with most mutations being transmitted in the infecting viral strain rather than with escape arising within the first few weeks of infection. Escape arose throughout the first three years of infection, but slowly and steadily. Approximately one third of patients did not drive any new escape in an HLA-restricted epitope in just under two years. Patients driving several escape mutations during these two years were rare and the median and modal numbers of new escape events in each patient were one and zero respectively. Survival analysis of time to escape found that possession of a protective HLA type significantly reduced time to first escape in a patient (p = 0.01), and epitopes escaped faster in the face of a measurable CD8+ ELISpot response (p = 0.001). However, even in an HLA matched host who mounted a measurable, specific, CD8+ response the average time before the targeted epitope evolved an escape mutation was longer than two years. PMID:25642847

  19. Eye movements reveal epistemic curiosity in human observers.

    PubMed

    Baranes, Adrien; Oudeyer, Pierre-Yves; Gottlieb, Jacqueline

    2015-12-01

    Saccadic (rapid) eye movements are primary means by which humans and non-human primates sample visual information. However, while saccadic decisions are intensively investigated in instrumental contexts where saccades guide subsequent actions, it is largely unknown how they may be influenced by curiosity - the intrinsic desire to learn. While saccades are sensitive to visual novelty and visual surprise, no study has examined their relation to epistemic curiosity - interest in symbolic, semantic information. To investigate this question, we tracked the eye movements of human observers while they read trivia questions and, after a brief delay, were visually given the answer. We show that higher curiosity was associated with earlier anticipatory orienting of gaze toward the answer location without changes in other metrics of saccades or fixations, and that these influences were distinct from those produced by variations in confidence and surprise. Across subjects, the enhancement of anticipatory gaze was correlated with measures of trait curiosity from personality questionnaires. Finally, a machine learning algorithm could predict curiosity in a cross-subject manner, relying primarily on statistical features of the gaze position before the answer onset and independently of covariations in confidence or surprise, suggesting potential practical applications for educational technologies, recommender systems and research in cognitive sciences. With this article, we provide full access to the annotated database allowing readers to reproduce the results. Epistemic curiosity produces specific effects on oculomotor anticipation that can be used to read out curiosity states.

  20. The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions

    SciTech Connect

    Famy, C.; Brough, A.R.; Taylor, H.F.W

    2003-09-01

    Scanning electron microscopy (SEM) microanalyses of the calcium-silicate-hydrate (C-S-H) gel in Portland cement pastes rarely represent single phases. Essential experimental requirements are summarised and new procedures for interpreting the data are described. These include, notably, plots of Si/Ca against other atom ratios, 3D plots to allow three such ratios to be correlated and solution of linear simultaneous equations to test and quantify hypotheses regarding the phases contributing to individual microanalyses. Application of these methods to the C-S-H gel of a 1-day-old mortar identified a phase with Al/Ca=0.67 and S/Ca=0.33, which we consider to be a highly substituted ettringite of probable composition C{sub 6}A{sub 2}S-bar{sub 2}H{sub 34} or {l_brace}Ca{sub 6}[Al(OH){sub 6}]{sub 2}{center_dot}24H{sub 2}O{r_brace}(SO{sub 4}){sub 2}[Al(OH){sub 4}]{sub 2}. If this is true for Portland cements in general, it might explain observed discrepancies between observed and calculated aluminate concentrations in the pore solution. The C-S-H gel of a similar mortar aged 600 days contained unsubstituted ettringite and an AFm phase with S/Ca=0.125.

  1. PREFACE: Non-contact AFM Non-contact AFM

    NASA Astrophysics Data System (ADS)

    Giessibl, Franz J.; Morita, Seizo

    2012-02-01

    This special issue is focussed on high resolution non-contact atomic force microscopy (AFM). Non-contact atomic force microscopy was established approximately 15 years ago as a tool to image conducting and insulating surfaces with atomic resolution. Since 1998, an annual international conference has taken place, and although the proceedings of these conferences are a useful source of information, several key developments warrant devoting a special issue to this subject. In the theoretic field, the possibility of supplementing established techniques such as scanning tunneling microscopy (STM) and Kelvin probe microscopy with atomically resolved force micrsoscopy poses many challenges in the calculation of contrast and contrast reversal. The surface science of insulators, self-assembled monolayers and adsorbates on insulators is a fruitful field for the application of non-contact AFM: several articles in this issue are devoted to these subjects. Atomic imaging and manipulation have been pioneered using STM, but because AFM allows the measurement of forces, AFM has had a profound impact in this field as well. Three-dimensional force spectroscopy has allowed many important insights into surface science. In this issue a combined 3D tunneling and force microscopy is introduced. Non-contact AFM typically uses frequency modulation to measure force gradients and was initially used mainly in a vacuum. As can be seen in this issue, frequency modulation is now also used in ambient conditions, allowing better spatial and force resolution. We thank all of the contributors for their time and efforts in making this special issue possible. We are also very grateful to the staff of IOP Publishing for handling the administrative aspects and for steering the refereeing process. Non-contact AFM contents Relation between the chemical force and the tunnelling current in atomic point contacts: a simple model Pavel Jelínek, Martin Ondrácek and Fernando Flores Theoretical simulation of

  2. AFM studies of the crystallization and habit modification of an excipient material, adipic acid.

    PubMed

    Keel, T R; Thompson, C; Davies, M C; Tendler, S J B; Roberts, C J

    2004-08-06

    Atomic force microscopy (AFM) has been used to investigate the (1 0 0) face of crystalline adipic acid, both in air and liquid environments. In air, surface reorganization occurred during scanning of the AFM probe, which has been investigated using single point force-distance analysis under a controlled relative humidity (RH) environment. We suggest such reorganization can be attributed to the influence of a network of water molecules bound to the hydrophilic (1 0 0) surface permitting local AFM tip-enhanced dissolution and reorganization of the solute. In situ imaging was also carried out on the crystals, revealing etch-pit formation during dissolution, and rapid growth at higher levels of supersaturation (sigma), both of which are direct consequences of the hydrophilic nature of the (1 0 0) face. Also presented here are nanoscale observations of the effect of octanoic acid, a structurally-related habit modifier, on crystalline adipic acid. Using AFM, we have been able to show that the presence of octanoic acid at low concentration has little observable affect on the development of the (1 0 0) face; however, as this concentration is increased, there are clear changes in step morphology and growth mode on the (1 0 0) face of the crystal. At a concentration of 1.26 mmol dm(-3) (a concentration corresponding to a molar ratio of approximately 1:175 octanoic acid:adipic acid), growth on the (1 0 0) face is inhibited, with in situ AFM imaging indicating this is a direct consequence of octanoic acid binding to the surface, and pinning the monomolecular growth steps.

  3. BOREAS AFM-6 Surface Meteorological Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Adminsitration/Environment Technology Laboratory (NOAA/ETL) collected surface meteorological data from 21 May to 20 Sep 1994 near the Southern Study Area-Old Jack Pine (SSA-OJP) tower site. The data are in tabular ASCII files. The surface meteorological data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  4. New insights into the mucoadhesion of pectins by AFM roughness parameters in combination with SPR.

    PubMed

    Joergensen, Lars; Klösgen, Beate; Simonsen, Adam Cohen; Borch, Jonas; Hagesaether, Ellen

    2011-06-15

    The object of this study was to assess the mucoadhesion of the three main commercially available types of pectin by atomic force microscopy (AFM) and surface Plasmon resonance (SPR). Polyacrylic acid and polyvinyl pyrrolidone were used as positive and negative control, respectively. Image analysis of the AFM scans revealed a significant change of roughness parameters when low-ester pectin was introduced to mica supported bovine submaxillarymucin, indicating a high mucoadhesion for this type of pectin. Only minor changes were observed with high-ester and amidated pectin. The same ranking order of adhesion affinity was confirmed by SPR. In conclusion, a high specific mucin interaction of pectin with a high charge density was demonstrated directly on a molecular scale without interference from the viscoelastic properties or the intra-molecular interactions between the polymer chains themselves, using two independent methods.

  5. AFM of biological complexes: what can we learn?

    PubMed Central

    Gaczynska, Maria; Osmulski, Pawel A.

    2009-01-01

    The term “biological complexes” broadly encompasses particles as diverse as multisubunit enzymes, viral capsids, transport cages, molecular nets, ribosomes, nucleosomes, biological membrane components and amyloids. The complexes represent a broad range of stability and composition. Atomic force microscopy offers a wealth of structural and functional data about such assemblies. For this review, we choose to comment on the significance of AFM to study various aspects of biology of selected nonmembrane protein assemblies. Such particles are large enough to reveal many structural details under the AFM probe. Importantly, the specific advantages of the method allow for gathering dynamic information about their formation, stability or allosteric structural changes critical for their function. Some of them have already found their way to nanomedical or nanotechnological applications. Here we present examples of studies where the AFM provided pioneering information about the biology of complexes, and examples of studies where the simplicity of the method is used toward the development of potential diagnostic applications. PMID:19802337

  6. Dispersion and Fixation of Adeno-Associated Virus with Glutaraldehyde for Afm Studies

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Wang, Xinyan; Yang, Haijun; Lü, Junhong

    Sample preparation is an important procedure for atomic force microscope (AFM) studies. However, flexible virus particles have a tendency to aggregate together and are easily compressed during sample preparation or by AFM tip that subsequently hamper studying of virus by AFM. Herein, low concentration chemical reagent of glutaraldehyde (2%, v/v) is pre-mixed in virus suspension that facilitates the dispersion and observation of recombinant serotype 2 adeno-associated virus particles deposited on mica surface with little deformation.

  7. AFM-Based Mechanical Nanomanipulation

    NASA Astrophysics Data System (ADS)

    Landolsi, Fakhreddine

    2011-12-01

    Advances in several research areas increase the need for more sophisticated fabrication techniques and better performing materials. Tackling this problem from a bottom-up perspective is currently an active field of research. The bottom-up fabrication procedure offers sub-nanometer accurate manipulation. At this time, candidates to achieve nanomanipulation include chemical (self-assembly), biotechnology methods (DNA-based), or using controllable physical forces (e.g. electrokinetic forces, mechanical forces). In this thesis, new methods and techniques for mechanical nanomanipulation using probe force interaction are developed. The considered probes are commonly used in Atomic Force Microscopes (AFMs) for high resolution imaging. AFM-based mechanical nanomanipulation will enable arranging nanoscale entities such as nanotubes and molecules in a precise and controlled manner to assemble and produce novel devices and systems at the nanoscale. The novelty of this research stems from the development of new modeling of the physics and mechanics of the tip interaction with nanoscale entities, coupled with the development of new smart cantilevers with multiple degrees of freedom. The gained knowledge from the conducted simulations and analysis is expected to enable true precision and repeatability of nanomanipulation tasks which is not feasible with existing methods and technologies.

  8. APOBEC3G Interacts with ssDNA by Two Modes: AFM Studies

    NASA Astrophysics Data System (ADS)

    Shlyakhtenko, Luda S.; Dutta, Samrat; Banga, Jaspreet; Li, Ming; Harris, Reuben S.; Lyubchenko, Yuri L.

    2015-10-01

    APOBEC3G (A3G) protein has antiviral activity against HIV and other pathogenic retroviruses. A3G has two domains: a catalytic C-terminal domain (CTD) that deaminates cytidine, and a N-terminal domain (NTD) that binds to ssDNA. Although abundant information exists about the biological activities of A3G protein, the interplay between sequence specific deaminase activity and A3G binding to ssDNA remains controversial. We used the topographic imaging and force spectroscopy modalities of Atomic Force Spectroscopy (AFM) to characterize the interaction of A3G protein with deaminase specific and nonspecific ssDNA substrates. AFM imaging demonstrated that A3G has elevated affinity for deaminase specific ssDNA than for nonspecific ssDNA. AFM force spectroscopy revealed two distinct binding modes by which A3G interacts with ssDNA. One mode requires sequence specificity, as demonstrated by stronger and more stable complexes with deaminase specific ssDNA than with nonspecific ssDNA. Overall these observations enforce prior studies suggesting that both domains of A3G contribute to the sequence specific binding of ssDNA.

  9. Optimization of phase contrast in bimodal amplitude modulation AFM

    PubMed Central

    Damircheli, Mehrnoosh; Payam, Amir F

    2015-01-01

    Summary Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes. PMID:26114079

  10. BOREAS AFM-6 Boundary Layer Height Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from National Oceanic and Atmospheric Adminsitration/Environment Technology Laboratory (NOAA/ETL) operated a 915-MHz wind/Radio Acoustic Sounding System (RASS) profiler system in the Southern Study Area (SSA) near the Old Jack Pine (OJP) site. This data set provides boundary layer height information over the site. The data were collected from 21 May 1994 to 20 Sep 1994 and are stored in tabular ASCII files. The boundary layer height data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  11. BOREAS AFM-06 Mean Wind Profile Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Administration/Environment Technology Laboratory (NOAA/ETL) operated a 915-MHz wind/Radio Acoustic Sounding System (RASS) profiler system in the Southern Study Area (SSA) near the Old Jack Pine (OJP) tower from 21 May 1994 to 20 Sep 1994. The data set provides wind profiles at 38 heights, containing the variables of wind speed; wind direction; and the u-, v-, and w-components of the total wind. The data are stored in tabular ASCII files. The mean wind profile data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  12. BOREAS AFM-06 Mean Temperature Profile Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Adminsitration/Environment Technology Laboratory (NOAA/ETL) operated a 915-MHz wind/Radio Acoustic Sounding System (RASS) profiler system in the Southern Study Area (SSA) near the Old Jack Pine (OJP) tower from 21 May 1994 to 20 Sep 1994. The data set provides temperature profiles at 15 heights, containing the variables of virtual temperature, vertical velocity, the speed of sound, and w-bar. The data are stored in tabular ASCII files. The mean temperature profile data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  13. Cryogenic AFM-STM for mesoscopic physics

    NASA Astrophysics Data System (ADS)

    Le Sueur, H.

    Electronic spectroscopy based on electron tunneling gives access to the electronic density of states (DOS) in conductive materials, and thus provides detailed information about their electronic properties. During this thesis work, we have developed a microscope in order to perform spatially resolved (10 nm) tunneling spectroscopy, with an unprecedented energy resolution (10 μeV), on individual nanocircuits. This machine combines an Atomic Force Microscope (AFM mode) together with a Scanning Tunneling Spectroscope (STS mode) and functions at very low temperatures (30 mK). In the AFM mode, the sample topography is recorded using a piezoelectric quartz tuning fork, which allows us to locate and image nanocircuits. Tunneling can then be performed on conductive areas of the circuit. With this microscope, we have measured the local DOS in a hybrid Superconductor-Normal metal-Superconductor (S-N-S) structure. In such circuit, the electronic properties of N and S are modified by the superconducting proximity effect. In particular, for short N wires, we have observed a minigap independent of position in the DOS of the N wire, as was previously predicted. Moreover, when varying the superconducting phase difference between the S electrodes, we have measured the modification of the minigap and its disappearance when the phase difference equals π. Our experimental results for the DOS, and its dependences (on phase, position, N length), are quantitatively accounted for by the quasiclassical theory of superconductivity. Some predictions of this theory are observed for the first time. La spectroscopie électronique basée sur l'effet tunnel donne accès à la densité d'états des électrons (DOS) dans les matériaux conducteurs, et renseigne ainsi en détail sur leurs propriétés électroniques. Au cours de cette thèse, nous avons développé un microscope permettant d'effectuer la spectroscopie tunnel résolue spatialement (10 nm) de nanocircuits individuels, avec une r

  14. Structural investigations on native collagen type I fibrils using AFM

    SciTech Connect

    Strasser, Stefan; Zink, Albert; Janko, Marek; Heckl, Wolfgang M.; Thalhammer, Stefan . E-mail: stefan.thalhammer@gsf.de

    2007-03-02

    This study was carried out to determine the elastic properties of single collagen type I fibrils with the use of atomic force microscopy (AFM). Native collagen fibrils were formed by self-assembly in vitro characterized with the AFM. To confirm the inner assembly of the collagen fibrils, the AFM was used as a microdissection tool. Native collagen type I fibrils were dissected and the inner core uncovered. To determine the elastic properties of collagen fibrils the tip of the AFM was used as a nanoindentor by recording force-displacement curves. Measurements were done on the outer shell and in the core of the fibril. The structural investigations revealed the banding of the shell also in the core of native collagen fibrils. Nanoindentation experiments showed the same Young's modulus on the shell as well as in the core of the investigated native collagen fibrils. In addition, the measurements indicate a higher adhesion in the core of the collagen fibrils compared to the shell.

  15. The importance of correcting for variable probe-sample interactions in AFM-IR spectroscopy: AFM-IR of dried bacteria on a polyurethane film.

    PubMed

    Barlow, Daniel E; Biffinger, Justin C; Cockrell-Zugell, Allison L; Lo, Michael; Kjoller, Kevin; Cook, Debra; Lee, Woo Kyung; Pehrsson, Pehr E; Crookes-Goodson, Wendy J; Hung, Chia-Suei; Nadeau, Lloyd J; Russell, John N

    2016-08-02

    AFM-IR is a combined atomic force microscopy-infrared spectroscopy method that shows promise for nanoscale chemical characterization of biological-materials interactions. In an effort to apply this method to quantitatively probe mechanisms of microbiologically induced polyurethane degradation, we have investigated monolayer clusters of ∼200 nm thick Pseudomonas protegens Pf-5 bacteria (Pf) on a 300 nm thick polyether-polyurethane (PU) film. Here, the impact of the different biological and polymer mechanical properties on the thermomechanical AFM-IR detection mechanism was first assessed without the additional complication of polymer degradation. AFM-IR spectra of Pf and PU were compared with FTIR and showed good agreement. Local AFM-IR spectra of Pf on PU (Pf-PU) exhibited bands from both constituents, showing that AFM-IR is sensitive to chemical composition both at and below the surface. One distinct difference in local AFM-IR spectra on Pf-PU was an anomalous ∼4× increase in IR peak intensities for the probe in contact with Pf versus PU. This was attributed to differences in probe-sample interactions. In particular, significantly higher cantilever damping was observed for probe contact with PU, with a ∼10× smaller Q factor. AFM-IR chemical mapping at single wavelengths was also affected. We demonstrate ratioing of mapping data for chemical analysis as a simple method to cancel the extreme effects of the variable probe-sample interactions.

  16. Microhardness, chemical etching, SEM, AFM and SHG studies of novel nonlinear optical crystal -L-threonine formate

    SciTech Connect

    Hanumantha Rao, Redrothu; Kalainathan, S.

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Microhardness studies of novel LTF crystal reported first time in the literature. Black-Right-Pointing-Pointer Surface studies are done by AFM, chemical etching and SEM. Black-Right-Pointing-Pointer From SHG studies, it is known that LTF is potential NLO crystal. -- Abstract: The crystal L-threonine formate, an organic NLO crystal was synthesized from aqueous solution by slow evaporation technique. The grown crystal surface has been analyzed by scanning electron microscopy (SEM), chemical etching and atomic force microscopy (AFM). SEM analysis reveals pyramidal shaped minute crystallites on the growth surface. The etching study indicates the occurrence of etch pit patterns like striations and step like pattern. The mechanical properties of LTF crystals were evaluated by mechanical testing which reveals certain mechanical characteristics like elastic stiffness constant (C{sub 11}) and young's modulus (E). The Vickers and Knoop microhardness studies have been carried out on LTF crystals over a range of 10-50 g. Hardness anisotropy has been observed in accordance with the orientation of the crystal. AFM image shows major hillock on growth surface. The second harmonic generation (SHG) efficiency has been tested by the Kurtz powder technique using Nd:YAG laser and found to be about 1.21 times in comparison with standard potassium dihydrogen phosphate (KDP) crystals.

  17. Arrangement of rotational domains of the (√31×√31) R±9° reconstruction of Al 2O 3( 0 0 0 1 ) revealed by non-contact AFM

    NASA Astrophysics Data System (ADS)

    Wang, J.; Howard, A.; Egdell, R. G.; Pethica, J. B.; Foord, J. S.

    2002-09-01

    Non-contact atomic force microscopy using a needle sensor with a phase shift feedback mechanism has been used to characterise Al 2O 3(0 0 0 1) surfaces prepared by annealing in 10 -4 mbar partial pressures of oxygen. The preparation procedure leads to flat terraces with lengths in excess of 1000 nm and widths of order 40 nm separated by c/6 steps. The unit cell of the (√31×√31) R±9° reconstruction is resolved, with a single rotational domain on each of the terraces. The 18° rotation between the domains is observed exclusively at step edges. The mechanism of imaging the (√31×√31) R±9° reconstruction is discussed.

  18. High aspect ratio AFM Probe processing by helium-ion-beam induced deposition.

    PubMed

    Onishi, Keiko; Guo, Hongxuan; Nagano, Syoko; Fujita, Daisuke

    2014-11-01

    A Scanning Helium Ion Microscope (SHIM) is a high resolution surface observation instrument similar to a Scanning Electron Microscope (SEM) since both instruments employ finely focused particle beams of ions or electrons [1]. The apparent difference is that SHIMs can be used not only for a sub-nanometer scale resolution microscopic research, but also for the applications of very fine fabrication and direct lithography of surfaces at the nanoscale dimensions. On the other hand, atomic force microscope (AFM) is another type of high resolution microscopy which can measure a three-dimensional surface morphology by tracing a fine probe with a sharp tip apex on a specimen's surface.In order to measure highly uneven and concavo-convex surfaces by AFM, the probe of a high aspect ratio with a sharp tip is much more necessary than the probe of a general quadrangular pyramid shape. In this paper we report the manufacture of the probe tip of the high aspect ratio by ion-beam induced gas deposition using a nanoscale helium ion beam of SHIM.Gas of platinum organic compound was injected into the sample surface neighborhood in the vacuum chamber of SHIM. The decomposition of the gas and the precipitation of the involved metal brought up a platinum nano-object in a pillar shape on the normal commercial AFM probe tip. A SHIM system (Carl Zeiss, Orion Plus) equipped with the gas injection system (OmniProbe, OmniGIS) was used for the research. While the vacuum being kept to work, we injected platinum organic compound ((CH3)3(CH3C5H4)Pt) into the sample neighborhood and irradiated the helium ion beam with the shape of a point on the apex of the AFM probe tip. It is found that we can control the length of the Pt nano-pillar by irradiation time of the helium ion beam. The AFM probe which brought up a Pt nano-pillar is shown in Figure 1. It is revealed that a high-aspect-ratio Pt nano-pillar of ∼40nm diameter and up to ∼2000 nm length can be grown. In addition, for possible heating

  19. SMA submillimeter observations of HL Tau: revealing a compact molecular outflow

    SciTech Connect

    Lumbreras, Alba M.; Zapata, Luis A.

    2014-04-01

    We present archival high angular resolution (∼2'') {sup 12}CO(3-2) line and continuum submillimeter observations of the young stellar object HL Tau made with the Submillimeter Array. The {sup 12}CO(3-2) line observations reveal the presence of a compact and wide opening angle bipolar outflow with a northeast to southwest orientation (P.A. = 50°) that is associated with the optical and infrared jet emanating from HL Tau with a similar orientation. On the other hand, the 850 μm continuum emission observations exhibit a strong and compact source in the position of HL Tau that has a spatial size of ∼200 × 70 AU with a P.A. = 145° and a dust mass of around 0.1 M {sub ☉}. These physical parameters are in agreement with values obtained recently from millimeter observations. This submillimeter source is therefore related to the disk surrounding HL Tau.

  20. AFM Manipulation of Viruses: Substrate Interactions and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Falvo, M. R.; Superfine, R.; Washburn, S.; Finch, M.; Taylor, R. M.; Chi, V.; Brooks, F. P.; Ferrari, F.; Samulski, R.

    1996-03-01

    Using an AFM tip as a manipulation tool, we have translated, rotated, and dissected individual Tobacco Mosaic Virus (TMV) and Adenovirus particles. We have implemented a teleoperation system which allows manual control of the relative tip-sample position while also allowing conventional AFM operation for imaging resulting structure. Using simple tip trajectories to bend the rod-shaped TMV, we observed a variety of resulting structures and mechanical failures. The distributed adhesive interaction between the virus and the sample surface, as well as the local tip-virus interaction affect the distortion in the shape of the virus. Experiments were performed in air as well as in liquid on graphite and Si substrates. The in-liquid experiments allow tuning of the environmental conditions, including osmolarity and pH, which are known to profoundly affect the virus structure. A continuum mechanical model relating mechanical properties to observations provides insight into the constraints for successful nondestructive manipulation.

  1. Nano Mechanical Machining Using AFM Probe

    NASA Astrophysics Data System (ADS)

    Mostofa, Md. Golam

    Complex miniaturized components with high form accuracy will play key roles in the future development of many products, as they provide portability, disposability, lower material consumption in production, low power consumption during operation, lower sample requirements for testing, and higher heat transfer due to their very high surface-to-volume ratio. Given the high market demand for such micro and nano featured components, different manufacturing methods have been developed for their fabrication. Some of the common technologies in micro/nano fabrication are photolithography, electron beam lithography, X-ray lithography and other semiconductor processing techniques. Although these methods are capable of fabricating micro/nano structures with a resolution of less than a few nanometers, some of the shortcomings associated with these methods, such as high production costs for customized products, limited material choices, necessitate the development of other fabricating techniques. Micro/nano mechanical machining, such an atomic force microscope (AFM) probe based nano fabrication, has, therefore, been used to overcome some the major restrictions of the traditional processes. This technique removes material from the workpiece by engaging micro/nano size cutting tool (i.e. AFM probe) and is applicable on a wider range of materials compared to the photolithographic process. In spite of the unique benefits of nano mechanical machining, there are also some challenges with this technique, since the scale is reduced, such as size effects, burr formations, chip adhesions, fragility of tools and tool wear. Moreover, AFM based machining does not have any rotational movement, which makes fabrication of 3D features more difficult. Thus, vibration-assisted machining is introduced into AFM probe based nano mechanical machining to overcome the limitations associated with the conventional AFM probe based scratching method. Vibration-assisted machining reduced the cutting forces

  2. BOREAS AFM-07 SRC Surface Meteorological Data

    NASA Technical Reports Server (NTRS)

    Osborne, Heather; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Young, Kim; Wittrock, Virginia; Shewchuck, Stan; Smith, David E. (Technical Monitor)

    2000-01-01

    The Saskatchewan Research Council (SRC) collected surface meteorological and radiation data from December 1993 until December 1996. The data set comprises Suite A (meteorological and energy balance measurements) and Suite B (diffuse solar and longwave measurements) components. Suite A measurements were taken at each of ten sites, and Suite B measurements were made at five of the Suite A sites. The data cover an approximate area of 500 km (North-South) by 1000 km (East-West) (a large portion of northern Manitoba and northern Saskatchewan). The measurement network was designed to provide researchers with a sufficient record of near-surface meteorological and radiation measurements. The data are provided in tabular ASCII files, and were collected by Aircraft Flux and Meteorology (AFM)-7. The surface meteorological and radiation data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  3. AFM nanoscale indentation in air of polymeric and hybrid materials with highly different stiffness

    NASA Astrophysics Data System (ADS)

    Suriano, Raffaella; Credi, Caterina; Levi, Marinella; Turri, Stefano

    2014-08-01

    In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol-gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force-distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry. AFM indentation tests show that the choice of the cantilever spring constant and of tip shape is crucially influenced by elastic properties of samples. When adhesion-dominated interactions occur between the tip and the surface of samples, force-displacement curves reveal that a suitable functionalization of AFM probes allows the control of such interactions and the extraction of Young' modulus from AFM curves that would be otherwise unfeasible. By applying different mathematical models depending on AFM probes and materials under investigation, the values of Young's modulus were obtained and compared to those measured by rheological and dynamic mechanical analysis or to literature data. Our results show that a wide range of elastic moduli (10 kPa-10 GPa) can be determined by AFM in good agreement with those measured by conventional macroscopic measurements.

  4. Morphological and Structural Changes on Human Dental Enamel After Er:YAG Laser Irradiation: AFM, SEM, and EDS Evaluation

    PubMed Central

    Rodríguez-Vilchis, Laura Emma; Olea-Mejìa, Oscar Fernando; Sánchez-Flores, Ignacio; Centeno-Pedraza, Claudia

    2011-01-01

    Abstract Objective: The purpose of this study was to evaluate, using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), the morphological and structural changes of the enamel after irradiation with the Er:YAG laser. Background data: A previous study showed that subablative Er:YAG laser irradiation produced undesirable morphological changes on the enamel surface, such as craters and cracks; however, the enamel acid resistance was not increased. Methods: Fifty-two samples of human enamel were divided into four groups (n = 13): Group I was the control (no laser irradiation), whereas Groups II, III, and IV were irradiated with the Er:YAG 100 mJ (12.7 J/cm2), 100 mJ (7.5 J/cm2), and 150 mJ (11 J/cm2), respectively, at 10 Hz with water spray. The morphological changes were observed by AFM and SEM. The weight percentages (wt%) of calcium (Ca), phosphorus (P), oxygen (O) and chlorine (Cl) were determined in the resultant craters and their periphery using EDS. Kruskal–Wallis and Mann–Whitney U tests were performed (p ≤ 0.05) to distinguish significant differences among the groups. Results: The AFM images showed cracks with depths between 250 nm and 750 nm for Groups II and IV, respectively, and the widths of these cracks were 5.37 μm and 2.58 μm. The interior of the cracks showed a rough surface. The SEM micrographs revealed morphological changes. Significant differences were detected in Ca, P, and Cl in the crater and its periphery. Conclusions: AFM observations showed triangular-shaped cracks, whereas craters and cracks were evident by SEM in all irradiated samples. It was not possible to establish a characteristic chemical pattern in the craters. PMID:21417912

  5. Anomalies in nanostructure size measurements by AFM

    NASA Astrophysics Data System (ADS)

    Mechler, Ádám; Kopniczky, Judit; Kokavecz, János; Hoel, Anders; Granqvist, Claes-Göran; Heszler, Peter

    2005-09-01

    Anomalies in atomic force microscopy (AFM) based size determination of nanoparticles were studied via comparative analysis of experiments and numerical calculations. Single tungsten oxide nanoparticles with a mean diameter of 3nm were deposited on mica and graphite substrates and were characterised by AFM. The size (height) of the nanoparticles, measured by tapping mode AFM, was found to be sensitive to the free amplitude of the oscillating tip, thus indicating that the images were not purely topographical. By comparing the experimental results to model calculations, we demonstrate that the dependence of the nanoparticle size on the oscillation amplitude of the tip is an inherent characteristic of the tapping mode AFM; it is also a function of physical properties such as elasticity and surface energy of the nanoparticle and the sample surface, and it depends on the radius of curvature of the tip. We show that good approximation of the real size can easily be obtained from plots of particle height vs free amplitude of the oscillating tip, although errors might persist for individual experiments. The results are valid for size (height) determination of any nanometer-sized objects imaged by tapping mode AFM.

  6. Nano-Bio-Mechanics of Neuroblastoma Cells Using AFM

    NASA Astrophysics Data System (ADS)

    Bastatas, Lyndon; Matthews, James; Kang, Min; Park, Soyeun

    2011-10-01

    We have conducted an in vitro study to determine the elastic moduli of neurobalstoma cell lines using atomic force microscopy. Using a panel of cell lines established from neuroblastoma patients at different stages of disease progress and treatment, we have investigated the differences in elastic moduli during a course of cancer progression and chemotherapy. The cells were grown on the hard substrates that are chemically functionalized to enhance adhesion. We have performed the AFM indentation experiments with different applied forces from the AFM probe. For the purpose of the comparison between cell lines, the indentations were performed only on cell centers. The obtained force-distance curves were analyzed using the Hertz model in order to extract the elastic moduli. We have found that the elastic moduli of human neuroblastoma cells significantly varied during the disease progression. We postulate that the observed difference might be affected by the treatment and chemotherapy.

  7. BOREAS AFM-5 Level-1 Upper Air Network Data

    NASA Technical Reports Server (NTRS)

    Barr, Alan; Hrynkiw, Charmaine; Newcomer, Jeffrey A. (Editor); Hall, Forrest G. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-5 team collected and processed data from the numerous radiosonde flights during the project. The goals of the AFM-05 team were to provide large-scale definition of the atmosphere by supplementing the existing Atmospheric Environment Service (AES) aerological network, both temporally and spatially. This data set includes basic upper-air parameters collected from the network of upper-air stations during the 1993, 1994, and 1996 field campaigns over the entire study region. The data are contained in tabular ASCII files. The level-1 upper-air network data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files also are available on a CD-ROM (see document number 20010000884).

  8. Quantitative nano-mechanics of biological cells with AFM

    NASA Astrophysics Data System (ADS)

    Sokolov, Igor

    2013-03-01

    The importance of study of living cells is hard to overestimate. Cell mechanics is a relatively young, yet not a well-developed area. Besides just a fundamental interest, large practical need has emerged to measure cell mechanics quantitatively. Recent studies revealed a significant correlation between stiffness of biological cells and various human diseases, such as cancer, malaria, arthritis, and even aging. However, really quantitative studies of mechanics of biological cells are virtually absent. It is not even clear if the cell, being a complex and heterogeneous object, can be described by the elastic modulus at all. Atomic force microscopy (AFM) is a natural instrument to study properties of cells in their native environments. Here we will demonstrate that quantitative measurements of elastic modulus of cells with AFM are possible. Specifically, we will show that the ``cell body'' (cell without ``brush'' surface layer, a non-elastic layer surrounding cells) typically demonstrates the response of a homogeneous elastic medium up to the deformation of 10-20%, but if and only if a) the cellular brush layer is taken into account, b) rather dull AFM probes are used. This will be justified with the help of the strong condition of elastic behavior of material: the elastic modulus is shown to be independent on the indentation depth. We will also demonstrate that an attempt either to ignore the brush layer or to use sharp AFM probes will result in the violation of the strong condition, which implies impossibility to use the concept of the elastic modulus to describe cell mechanics in such experiments. Examples of quantitative measurements of the Young's modulus of the cell body and the cell brush parameters will be given for various cells. Address when submitting: Clarkson University, Potsdam, NY 13699

  9. Nanoscale rippling on polymer surfaces induced by AFM manipulation

    PubMed Central

    2015-01-01

    Summary Nanoscale rippling induced by an atomic force microscope (AFM) tip can be observed after performing one or many scans over the same area on a range of materials, namely ionic salts, metals, and semiconductors. However, it is for the case of polymer films that this phenomenon has been widely explored and studied. Due to the possibility of varying and controlling various parameters, this phenomenon has recently gained a great interest for some technological applications. The advent of AFM cantilevers with integrated heaters has promoted further advances in the field. An alternative method to heating up the tip is based on solvent-assisted viscoplastic deformations, where the ripples develop upon the application of a relatively low force to a solvent-rich film. An ensemble of AFM-based procedures can thus produce nanoripples on polymeric surfaces quickly, efficiently, and with an unprecedented order and control. However, even if nanorippling has been observed in various distinct modes and many theoretical models have been since proposed, a full understanding of this phenomenon is still far from being achieved. This review aims at summarizing the current state of the art in the perspective of achieving control over the rippling process on polymers at a nanoscale level. PMID:26733086

  10. EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE BARNARD 5 STAR-FORMING CORE: EMBEDDED FILAMENTS REVEALED

    SciTech Connect

    Pineda, Jaime E.; Longmore, Steven; Goodman, Alyssa A.; Arce, Hector G.; Caselli, Paola; Corder, Stuartt

    2011-09-20

    We present {approx}6.'5 x 8' Expanded Very Large Array (EVLA) mosaic observations of the NH{sub 3} (1,1) emission in the Barnard 5 region in Perseus, with an angular resolution of 6''. This map covers the coherent region, where the dense gas presents subsonic non-thermal motions (as seen from single dish observations with the Green Bank Telescope, GBT). The combined EVLA and GBT observations reveal, for the first time, a striking filamentary structure (20'' wide or 5000 AU at the distance of Perseus) in this low-mass star-forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. The observed separation between the B5-IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The observed region displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions.

  11. AFM-based study of fullerenol (C60(OH)24)-induced changes of elasticity in living SMCC-7721 cells.

    PubMed

    Liu, Yang; Wang, Zuobin; Wang, Xinyue

    2015-05-01

    In this study, the alterations of the morphology and biomechanical properties of living SMCC-7721 cancer cells treated with fullerenol (C60(OH)24) for 24, 48, and 72h were investigated using an atomic force microscope (AFM). Comparative analyses show that the elastic moduli of the SMCC-7721 cells exposed to fullerenol decrease significantly with the increase of the treatment periods. Furthermore, in different phases of the treatment, a global decrease in elasticity is accompanied by cellular morphological changes, and the time-dependent effect of the fullerenol can be observed using AFM and optical microscope. In addition, as the treatment duration increases, the indentation force and depth penetrated into the cell membrane by the AFM tip are in a declining trend. The reduction in the stiffness of the cells exposed to fullerenol could be associated with the disruption of the cellular cytoskeleton network. The investigation indicates that the elastic modulus of single living cells can be a useful biomarker to evaluate the effects of fullerenol or other anticancer agents on the cells and reveal instructive information for cellular dynamic behaviors.

  12. Hydration states of AFm cement phases

    SciTech Connect

    Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Wadsö, Lars

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  13. Eddy-Kuroshio interaction processes revealed by mooring observations off Taiwan and Luzon

    NASA Astrophysics Data System (ADS)

    Tsai, Cheng-Ju; Andres, Magdalena; Jan, Sen; Mensah, Vigan; Sanford, Thomas B.; Lien, Ren-Chieh; Lee, Craig M.

    2015-10-01

    The influence and fate of westward propagating eddies that impinge on the Kuroshio were observed with pressure sensor-equipped inverted echo sounders (PIESs) deployed east of Taiwan and northeast of Luzon. Zero lag correlations between PIES-measured acoustic travel times and satellite-measured sea surface height anomalies (SSHa), which are normally negative, have lower magnitude toward the west, suggesting the eddy-influence is weakened across the Kuroshio. The observational data reveal that impinging eddies lead to seesaw-like SSHa and pycnocline depth changes across the Kuroshio east of Taiwan, whereas analogous responses are not found in the Kuroshio northeast of Luzon. Anticyclones intensify sea surface and pycnocline slopes across the Kuroshio, while cyclones weaken these slopes, particularly east of Taiwan. During the 6 month period of overlap between the two PIES arrays, only one anticyclone affected the pycnocline depth first at the array northeast of Luzon and 21 days later in the downstream Kuroshio east of Taiwan.

  14. Graphene MEMS: AFM probe performance improvement.

    PubMed

    Martin-Olmos, Cristina; Rasool, Haider Imad; Weiller, Bruce H; Gimzewski, James K

    2013-05-28

    We explore the feasibility of growing a continuous layer of graphene in prepatterned substrates, like an engineered silicon wafer, and we apply this as a mold for the fabrication of AFM probes. This fabrication method proves the fabrication of SU-8 devices coated with graphene in a full-wafer parallel technology and with high yield. It also demonstrates that graphene coating enhances the functionality of SU-8 probes, turning them conductive and more resistant to wear. Furthermore, it opens new experimental possibilities such as studying graphene-graphene interaction at the nanoscale with the precision of an AFM or the exploration of properties in nonplanar graphene layers.

  15. Undersea interplate coupling off the western Japan revealed by GPS-A observation

    NASA Astrophysics Data System (ADS)

    Yokota, Y.; Ishikawa, T.; Watanabe, S. I.; Tashiro, T.

    2015-12-01

    The recurring devastating earthquakes in the Nankai and Sagami Troughs subduction zone between the Philippine Sea plate and the continental plates (Eurasian and North American plates) have a potential to cause an extremely dangerous natural disaster in not-so-distant future. Many studies assumed the interplate coupling ratios using the onshore geodetic data only. However, the offshore region that has a potential to derive a devastating tsunami cannot be resolved enough due to the observation network that is biased to land area. The Hydrographic and Oceanographic Department of Japan (JHOD) have constructed the seafloor geodetic observation network on the seafloor surface using a GPS-acoustic combination technique (GPS-A) [e.g., Sato et al., 2011, Science] and observed seafloor crustal movements directly above the Nankai and Sagami Troughs subduction zones. We have set 17 sites off the western Japan to lead an undersea interplate coupling distribution. The observations around the Sagami Trough are consistent with the block motions presented by Nishimura [2011, Tectonophysics]. On the other hand, our seafloor geodetic observation network along the Nankai Trough revealed heterogeneity and complexity interplate coupling off the western Japan. The fast displacement rates observed in the eastern area indicate a strong interplate coupling around not only the future Tokai earthquake source region but also the Paleo-Zenisu ridge. Our observations in the westernmost area also suggest that the area off the Cape Ashizuri has a high-coupling ratio. The slow displacement rate observed in the shallower area than the 1946 Nankaido earthquake source region off the Cape Muroto-zaki reflects a weakening interplate coupling probably due to a subducting seamount. The observation in the westernmost area differs depending on the depth. The north deep area below Bungo-channel has a high-coupling ratio. The south shallow area has a low-coupling ratio. In these deep and shallow areas, VLFEs

  16. Nanomechanics of new materials — AFM and computer modelling studies of trichoptera silk

    NASA Astrophysics Data System (ADS)

    Strzelecki, Janusz; Strzelecka, Joanna; Mikulska, Karolina; Tszydel, Mariusz; Balter, Aleksander; Nowak, Wiesław

    2011-04-01

    Caddisfly (Trichopera) can glue diverse material underwater with a silk fiber. This makes it a particularly interesting subject for biomimetcs. Better understanding of silk composition and structure could lead to an adhesive capable to close bleeding wounds or to new biomaterials. However, while spiderweb or silkworm secretion is well researched, caddisfly silk is still poorly understood. Here we report a first nanomechanical analysis of H. Angustipennis caddisfly silk fiber. An Atomic Force Microscope (AFM) imaging shows dense 150 nm bumps on silk surface, which can be identified as one of features responsible for its outstanding adhesive properties. AFM force spectroscopy at the fiber surface showed, among others, characteristic saw like pattern. This pattern is attributed to sacrificial bond stretching and enhances energy dissipation in mechanical deformation. Similarities of some force curves observed on Tegenaria domestica spiderweb and caddisfly silk are also discussed. Steered Molecular Dynamics simulations revealed that the strength of short components of Fib-H HA species molecules, abundant in Trichoptera silk is critically dependent on calcium presence.

  17. Interlaboratory round robin on cantilever calibration for AFM force spectroscopy.

    PubMed

    te Riet, Joost; Katan, Allard J; Rankl, Christian; Stahl, Stefan W; van Buul, Arend M; Phang, In Yee; Gomez-Casado, Alberto; Schön, Peter; Gerritsen, Jan W; Cambi, Alessandra; Rowan, Alan E; Vancso, G Julius; Jonkheijm, Pascal; Huskens, Jurriaan; Oosterkamp, Tjerk H; Gaub, Hermann; Hinterdorfer, Peter; Figdor, Carl G; Speller, Sylvia

    2011-12-01

    Single-molecule force spectroscopy studies performed by Atomic Force Microscopes (AFMs) strongly rely on accurately determined cantilever spring constants. Hence, to calibrate cantilevers, a reliable calibration protocol is essential. Although the thermal noise method and the direct Sader method are frequently used for cantilever calibration, there is no consensus on the optimal calibration of soft and V-shaped cantilevers, especially those used in force spectroscopy. Therefore, in this study we aimed at establishing a commonly accepted approach to accurately calibrate compliant and V-shaped cantilevers. In a round robin experiment involving eight different laboratories we compared the thermal noise and the Sader method on ten commercial and custom-built AFMs. We found that spring constants of both rectangular and V-shaped cantilevers can accurately be determined with both methods, although the Sader method proved to be superior. Furthermore, we observed that simultaneous application of both methods on an AFM proved an accurate consistency check of the instrument and thus provides optimal and highly reproducible calibration. To illustrate the importance of optimal calibration, we show that for biological force spectroscopy studies, an erroneously calibrated cantilever can significantly affect the derived (bio)physical parameters. Taken together, our findings demonstrated that with the pre-established protocol described reliable spring constants can be obtained for different types of cantilevers.

  18. LET Spectrum Measurements In CR-39 PNTD With AFM

    SciTech Connect

    Johnson, C. E.; DeWitt, J. M.; Benton, E. R.; Yasuda, N.; Benton, E. V.

    2011-06-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range ({approx}<10 {mu}m) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching ({approx}<1 {mu}m) following by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features inherently present in the post-etch detector surface. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/{mu}m. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to 1 GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  19. LET Spectrum Measurements In CR-39 PNTD With AFM

    NASA Astrophysics Data System (ADS)

    Johnson, C. E.; DeWitt, J. M.; Benton, E. R.; Yasuda, N.; Benton, E. V.

    2011-06-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range (˜<10 μm) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching (˜<1 μm) following by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features inherently present in the post-etch detector surface. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/μm. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to 1 GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  20. LET spectrum measurements in Cr-39 PNTD with AFM

    SciTech Connect

    Johnson, Carl Edward; De Witt, Joel M; Benton, Eric R; Yasuda, Nakahiro; Benton, Eugene V

    2010-01-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range ({approx}< 10 {mu}m) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching ({approx}< 1 {mu}m) followed by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/{mu}m. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to I GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  1. Conductance of AFM Deformed Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Svizhenko, Alexei; Maiti, Amitesh; Anatram, M. P.; Biegel, Bryan (Technical Monitor)

    2002-01-01

    This viewgraph presentation provides information on the electrical conductivity of carbon nanotubes upon deformation by atomic force microscopy (AFM). The density of states and conductance were computed using four orbital tight-binding method with various parameterizations. Different chiralities develop bandgap that varies with chirality.

  2. Contact nanomechanical measurements with the AFM

    NASA Astrophysics Data System (ADS)

    Geisse, Nicholas

    2013-03-01

    The atomic force microscope (AFM) has found broad use in the biological sciences largely due to its ability to make measurements on unfixed and unstained samples under liquid. In addition to imaging at multiple spatial scales ranging from micro- to nanometer, AFMs are commonly used as nanomechanical probes. This is pertinent for cell biology, as it has been demonstrated that the geometrical and mechanical properties of the extracellular microenvironment are important in such processes as cancer, cardiovascular disease, muscular dystrophy, and even the control of cell life and death. Indeed, the ability to control and quantify these external geometrical and mechanical parameters arises as a key issue in the field. Because AFM can quantitatively measure the mechanical properties of various biological samples, novel insights to cell function and to cell-substrate interactions are now possible. As the application of AFM to these types of problems is widened, it is important to understand the performance envelope of the technique and its associated data analyses. This talk will discuss the important issues that must be considered when mechanical models are applied to real-world data. Examples of the effect of different model assumptions on our understanding of the measured material properties will be shown. Furthermore, specific examples of the importance of mechanical stimuli and the micromechanical environment to the structure and function of biological materials will be presented.

  3. Live-cell observation of cytosolic HIV-1 assembly onset reveals RNA-interacting Gag oligomers

    PubMed Central

    Hendrix, Jelle; Baumgärtel, Viola; Schrimpf, Waldemar; Ivanchenko, Sergey; Digman, Michelle A.; Gratton, Enrico; Kräusslich, Hans-Georg; Müller, Barbara

    2015-01-01

    Assembly of the Gag polyprotein into new viral particles in infected cells is a crucial step in the retroviral replication cycle. Currently, little is known about the onset of assembly in the cytosol. In this paper, we analyzed the cytosolic HIV-1 Gag fraction in real time in live cells using advanced fluctuation imaging methods and thereby provide detailed insights into the complex relationship between cytosolic Gag mobility, stoichiometry, and interactions. We show that Gag diffuses as a monomer on the subsecond timescale with severely reduced mobility. Reduction of mobility is associated with basic residues in its nucleocapsid (NC) domain, whereas capsid (CA) and matrix (MA) domains do not contribute significantly. Strikingly, another diffusive Gag species was observed on the seconds timescale that oligomerized in a concentration-dependent manner. Both NC- and CA-mediated interactions strongly assist this process. Our results reveal potential nucleation steps of cytosolic Gag fractions before membrane-assisted Gag assembly. PMID:26283800

  4. Spatial and Temporal Characteristics of Insulator Contaminations Revealed by Daily Observations of Equivalent Salt Deposit Density

    PubMed Central

    Ruan, Ling; Han, Ge; Zhu, Zhongmin; Zhang, Miao; Gong, Wei

    2015-01-01

    The accurate estimation of deposits adhering on insulators is of great significance to prevent pollution flashovers which cause huge costs worldwide. Researchers have developed sensors using different technologies to monitor insulator contamination on a fine time scale. However, there is lack of analysis of these data to reveal spatial and temporal characteristics of insulator contamination, and as a result the scheduling of periodical maintenance of power facilities is highly dependent on personal experience. Owing to the deployment of novel sensors, daily Equivalent Salt Deposit Density (ESDD) observations of over two years were collected and analyzed for the first time. Results from 16 sites distributed in four regions of Hubei demonstrated that spatial heterogeneity can be seen at both the fine and coarse geographical scales, suggesting that current polluted area maps are necessary but are not sufficient conditions to guide the maintenance of power facilities. Both the local emission and the regional air pollution condition exert evident influences on deposit accumulation. A relationship between ESDD and PM10 was revealed by using regression analysis, proving that air pollution exerts influence on pollution accumulations on insulators. Moreover, the seasonality of ESDD was discovered for the first time by means of time series analysis, which could help engineers select appropriate times to clean the contamination. Besides, the trend component shows that the ESDD increases in a negative exponential fashion with the accumulation date (ESDD = a − b × exp(−time)) at a long time scale in real environments. PMID:25643058

  5. Probing ternary solvent effect in high Voc polymer solar cells using advanced AFM techniques

    DOE PAGES

    Li, Chao; Soleman, Mikhael; Lorenzo, Josie; ...

    2016-01-25

    This work describes a simple method to develop a high Voc low band gap PSCs. In addition, two new atomic force microscopy (AFM)-based nanoscale characterization techniques to study the surface morphology and physical properties of the structured active layer are introduced. With the help of ternary solvent processing of the active layer and C60 buffer layer, a bulk heterojunction PSC with Voc more than 0.9 V and conversion efficiency 7.5% is developed. In order to understand the fundamental properties of the materials ruling the performance of the PSCs tested, AFM-based nanoscale characterization techniques including Pulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFMmore » (MSAFM) are introduced. Interestingly, MSAFM exhibits high sensitivity for direct visualization of the donor–acceptor phases in the active layer of the PSCs. Lastly, conductive-AFM (cAFM) studies reveal local variations in conductivity in the donor and acceptor phases as well as a significant increase in photocurrent in the PTB7:ICBA sample obtained with the ternary solvent processing.« less

  6. Energetic ion dynamics of the inner magnetosphere revealed in coordinated Cluster-Double Star observations

    NASA Astrophysics Data System (ADS)

    Dandouras, Iannis; Cao, Jinbin; Vallat, Claire

    2009-01-01

    Since early 2004 the Chinese spacecraft Tan Ce 1 (TC-1), first component of the Double Star (DSP) mission, has been on an equatorial elliptical orbit (13.4 R E apogee), allowing the study of the dynamics of the Earth's magnetosphere in conjunction with the four European Cluster spacecraft (19.6 R E apogee). The Cluster and Double Star spacecraft orbits are such that the spacecraft are almost in the same meridian, allowing conjugate studies. The four Cluster spacecraft highly eccentric polar orbit at 4 R E perigee permits them to sample the ring current, the radiation belts, and the outer plasmasphere from south to north, almost following the same magnetic flux tube (latitudinal profile), whereas TC-1, with its very low-perigee equatorial orbit, gives the plasma profile across L shells. Coordinated ion measurements provided by the Cluster Ion Spectrometry and Hot Ion Analyzer instruments onboard Cluster and TC-1, respectively, obtained during quiet conditions, disturbed geomagnetic conditions, and an intense storm, are used to analyze crossings of the plasmasphere and the ring current region. Multiple narrow ion energy bands (``nose-like'' structures) are simultaneously observed by both Cluster and TC-1. These observations reveal the large-scale character of these structures and pose a challenge for the simulation and modeling of the inner magnetosphere populations.

  7. Revealing the Volatile Abundances in Comet C/2012 F6 (Lemmon) From Ground-based Observations

    NASA Astrophysics Data System (ADS)

    Milam, Stefanie N.; Gicquel, A.; Cordiner, M. A.; Villanueva, G. L.; Remijan, A. J.; Biver, N.; Bockelee-Morvan, D.; Charnley, S. B.

    2013-10-01

    Comets are comprised of molecular ices that may be pristine interstellar remnants of Solar System formation, along with high-temperature crystalline silicate dust that is indicative of a more thermally varied history in the protosolar nebula [1]. Comparing abundances of cometary parent volatiles and isotopic fractionation ratios to those found in the interstellar medium, in disks around young stars, and between cometary families, is vital to understanding planetary system formation and the processing history experienced by organic matter in the so-called interstellar-comet connection. Recently, there have been complimentary observations from multiple facilities to try to unravel the chemical complexity of comets. We report spectral observations of C/2012 F6 (Lemmon) from the Arizona Radio Observatory’s Submillimeter Telescope and the Atacama Pathfinder Experiment. Multiple parent volatiles (e.g. HCN, CH3OH, CO) as well as a number of daughter products (e.g. CS) have been detected at multiple transitions from these facilities. Previous work has revealed a range of abundances of parent species (from “organics-poor” to “organics-rich”) with respect to water among comets [2,3,4], however the statistics are still poorly constrained and interpretations of the observed compositional diversity are uncertain. We will compare the molecular abundances of F6 to a broad range of comets from diverse dynamical families and chemical compositions, supporting our long-term effort of building a comet taxonomy based on composition. [1] Wooden 2008, SpSciRev., 138, 75. [2] DiSanti, M. A., & Mumma, M. J. (2008), Space Sci. Rev., 138, 127. [3] Mumma, M. J. and Charnley, S.B. (2011), ARA&A, 49, 471. [4] Crovisier, J. et al. (2009) Earth, Moon Planet, 105, 267.

  8. Detection of Pathogens Using AFM and SPR

    NASA Astrophysics Data System (ADS)

    Vaseashta, Ashok

    2005-03-01

    A priori detection of pathogens in food and water has become a subject of paramount importance. Several recent incidents have resulted in the government passing stringent regulations for tolerable amounts of contamination of food products. Identification and/or monitoring of bacterial contamination in food are critical. The conventional methods of pathogen detection require time-consuming steps to arrive disembark at meaningful measurement in a timely manner as the detection time exceeds the time in which perishable food recycles through the food chain distribution. The aim of this presentation is to outline surface plasmon resonance (SPR) and atomic force microscopy (AFM) as two methods for fast detect6ion of pathogens. Theoretical basis of SPR and experimental results of SPR and AFM on E. coli O157:H7 and prion are presented.

  9. Brain responses in humans reveal ideal observer-like sensitivity to complex acoustic patterns

    PubMed Central

    Pearce, Marcus T.; Griffiths, Timothy D.; Chait, Maria

    2016-01-01

    We use behavioral methods, magnetoencephalography, and functional MRI to investigate how human listeners discover temporal patterns and statistical regularities in complex sound sequences. Sensitivity to patterns is fundamental to sensory processing, in particular in the auditory system, because most auditory signals only have meaning as successions over time. Previous evidence suggests that the brain is tuned to the statistics of sensory stimulation. However, the process through which this arises has been elusive. We demonstrate that listeners are remarkably sensitive to the emergence of complex patterns within rapidly evolving sound sequences, performing on par with an ideal observer model. Brain responses reveal online processes of evidence accumulation—dynamic changes in tonic activity precisely correlate with the expected precision or predictability of ongoing auditory input—both in terms of deterministic (first-order) structure and the entropy of random sequences. Source analysis demonstrates an interaction between primary auditory cortex, hippocampus, and inferior frontal gyrus in the process of discovering the regularity within the ongoing sound sequence. The results are consistent with precision based predictive coding accounts of perceptual inference and provide compelling neurophysiological evidence of the brain's capacity to encode high-order temporal structure in sensory signals. PMID:26787854

  10. Characterizing Cell Mechanics with AFM and Microfluidics

    NASA Astrophysics Data System (ADS)

    Walter, N.; Micoulet, A.; Suresh, S.; Spatz, J. P.

    2007-03-01

    Cell mechanical properties and functionality are mainly determined by the cytoskeleton, besides the cell membrane, the nucleus and the cytosol, and depend on various parameters e.g. surface chemistry and rigidity, surface area and time available for cell spreading, nutrients and drugs provided in the culture medium. Human epithelial pancreatic and mammary cancer cells and their keratin intermediate filaments are the main focus of our work. We use Atomic Force Microscopy (AFM) to study cells adhering to substrates and Microfluidic Channels to probe cells in suspension, respectively. Local and global properties are extracted by varying AFM probe tip size and the available adhesion area for cells. Depth-sensing, instrumented indentation tests with AFM show a clear difference in contact stiffness for cells that are spread of controlled substrates and those that are loosely attached. Microfluidic Channels are utilized in parallel to evaluate cell deformation and ``flow resistance'', which are dependent on channel cross section, flow rate, cell nucleus size and the mechanical properties of cytoskeleton and membrane. The results from the study are used to provide some broad and quantitative assessments of the connections between cellular/subcellular mechanics and biochemical origins of disease states.

  11. Vibration signature analysis of AFM images

    SciTech Connect

    Joshi, G.A.; Fu, J.; Pandit, S.M.

    1995-12-31

    Vibration signature analysis has been commonly used for the machine condition monitoring and the control of errors. However, it has been rarely employed for the analysis of the precision instruments such as an atomic force microscope (AFM). In this work, an AFM was used to collect vibration data from a sample positioning stage under different suspension and support conditions. Certain structural characteristics of the sample positioning stage show up as a result of the vibration signature analysis of the surface height images measured using an AFM. It is important to understand these vibration characteristics in order to reduce vibrational uncertainty, improve the damping and structural design, and to eliminate the imaging imperfections. The choice of method applied for vibration analysis may affect the results. Two methods, the data dependent systems (DDS) analysis and the Welch`s periodogram averaging method were investigated for application to this problem. Both techniques provide smooth spectrum plots from the data. Welch`s periodogram provides a coarse resolution as limited by the number of samples and requires a choice of window to be decided subjectively by the user. The DDS analysis provides sharper spectral peaks at a much higher resolution and a much lower noise floor. A decomposition of the signal variance in terms of the frequencies is provided as well. The technique is based on an objective model adequacy criterion.

  12. Vertical wavenumber spectra of three-dimensional winds revealed by radiosonde observations at midlatitude

    NASA Astrophysics Data System (ADS)

    Zhang, Shao Dong; Huang, Chun Ming; Huang, Kai Ming; Zhang, Ye Hui; Gong, Yun; Gan, Quan

    2017-01-01

    By applying 12-year (1998-2009) radiosonde data over a midlatitude station, we studied the vertical wavenumber spectra of three-dimensional wind fluctuations. The horizontal wind spectra in the lower stratosphere coincide well with the well-known universal spectra, with mean spectral slopes of -2.91 ± 0.09 and -2.99 ± 0.09 for the zonal and meridional wind spectra, respectively, while the mean slopes in the troposphere are -2.64 ± 0.07 and -2.70 ± 0.06, respectively, which are systematically less negative than the canonical slope of -3. In both the troposphere and lower stratosphere, the spectral amplitudes (slopes) of the horizontal wind spectra are larger (less negative) in winter, and they are larger (less negative) in the troposphere than in the lower stratosphere. Moreover, we present the first statistical results of vertical wind fluctuation spectra, which revealed a very shallow spectral structure, with mean slopes of -0.58 ± 0.06 and -0.23 ± 0.05 in the troposphere and lower stratosphere, respectively. Such a shallow vertical wind fluctuation spectrum is considerably robust. Different from the horizontal wind spectrum, the slopes of the vertical wind spectra in both the troposphere and lower stratosphere are less negative in summer. The height variation of vertical wind spectrum amplitude is also different from that of the horizontal wind spectrum, with a larger amplitude in the lower stratosphere. These evident differences between the horizontal and vertical wind spectra strongly suggest they should obey different spectral laws. Quantitative comparisons with various theoretical models show that no existing spectral theories can comprehensively explain the observed three-dimensional wind spectra, indicating that the spectral features of atmospheric fluctuations are far from fully understood.

  13. Upper mantle structure of the Pacific and Philippine Sea plates revealed by seafloor seismic array observations

    NASA Astrophysics Data System (ADS)

    Isse, Takehi; Shiobara, Hajime; Suetsugu, Daisuke; Sugioka, Hiroko; Ito, Aki

    2016-04-01

    Seismic tomography studies have revealed the structure and dynamics of Earth's interior since the 1980s. However, the spatial resolution of the oceanic region is not good enough caused by sparse distribution of the seismic stations. The observations with broadband ocean-bottom seismographs (BBOBSs) since the 2000s enabled us to obtain seismic tomography models with higher spatial resolution. Our Japanese BBOBS group deployed more than 100 BBOBSs in the Pacific Ocean and obtained a high-resolution (300-500 km) three-dimensional shear wave velocity structure in the upper mantle beneath northwestern and south Pacific Ocean by using surface wave tomography technique. In the northwestern Pacific Ocean, where the Pacific plate subducts beneath the Philippine Sea plate, we found that the shear wave structure in the Philippine sea plate is well correlated with the seafloor age in the upper 120 km, three separate slow anomalies in the mantle wedge at depth shallower than 100 km beneath the Izu-Bonin-Mariana arc, which have a close relationship with the three groups of frontal and rear arc volcanoes having distinct Sr, Nd, and Pb isotope ratios, and that the Philippine Sea plate, which is a single plate, shows very large lateral variations in azimuthal and radial anisotropies compared with the Pacific plate. In the South Pacific Ocean, where midplate hotspots are concentrated, we found that the localized slow anomalies are found near hotspots in the upper mantle, estimated thickness of the lithosphere is about 90 km in average and is thinned by ~20 km in the vicinity of hotspots, which may represent thermal erosion due to mantle plumes.

  14. Non-contact AFM investigation of influence of freezing process on the surface structure of potato starch granule

    NASA Astrophysics Data System (ADS)

    Krok, F.; Szymońska, J.; Tomasik, P.; Szymoński, M.

    2000-04-01

    To assess the influence of the freezing process on the surface structure of a potato starch granule, a non-contact Atomic Force Microscopy (NC-AFM) investigation at ambient conditions has been undertaken. The observations were carried out for dried (oven-dried) and native (air-dried) starch. The obtained AFM images of the native starch granule surface demonstrated it as not uniformly smooth and having rough undulating appearance with layers of adsorbed water which could be removed by oven drying in 130°C. After freezing, the dried starch granule surface still consisted of nodules of about 100 nm in diameter. Significant changes in the granule surface appearance can be seen for dried starch samples frozen with some excess of water as well as for native starch samples frozen with its original water. Then the aggregation and polishing of the granules was observed and their surface revealed a microstructure with distinct ring-like protrusions of about 300 nm in diameter. Our observations tally with the amylopectine "blocket" starch granule structure model proposed in the literature and allowed to conclude that freezing may be a useful tool, among other methods, for modifying starch granule properties.

  15. Nanoscale thermal AFM of polymers: transient heat flow effects.

    PubMed

    Duvigneau, Joost; Schönherr, Holger; Vancso, G Julius

    2010-11-23

    Thermal transport around the nanoscale contact area between the heated atomic force microscopy (AFM) probe tip and the specimen under investigation is a central issue in scanning thermal microscopy (SThM). Polarized light microscopy and AFM imaging of the temperature-induced crystallization of poly(ethylene terephthalate) (PET) films in the region near the tip were used in this study to unveil the lateral heat transport. The radius of the observed lateral surface isotherm at 133 °C ranged from 2.2 ± 0.5 to 18.7 ± 0.5 μm for tip-polymer interface temperatures between 200 and 300 °C with contact times varying from 20 to 120 s, respectively. In addition, the heat transport into polymer films was assessed by measurements of the thermal expansion of poly(dimethyl siloxane) (PDMS) films with variable thickness on silicon supports. Our data showed that heat transport in the specimen normal (z) direction occurred to depths exceeding 1000 μm using representative non-steady-state SThM conditions (i.e., heating from 40 to 180 °C at a rate of 10 °C s(-1)). On the basis of the experimental results, a 1D steady-state model for heat transport was developed, which shows the temperature profile close to the tip-polymer contact. The model also indicates that ≤1% of the total power generated in the heater area, which is embedded in the cantilever end, is transported into the polymer through the tip-polymer contact interface. Our results complement recent efforts in the evaluation and improvement of existing theoretical models for thermal AFM, as well as advance further developments of SThM for nanoscale thermal materials characterization and/or manipulation via scanning thermal lithography (SThL).

  16. Fractal analysis of AFM images of the surface of Bowman's membrane of the human cornea.

    PubMed

    Ţălu, Ştefan; Stach, Sebastian; Sueiras, Vivian; Ziebarth, Noël Marysa

    2015-04-01

    The objective of this study is to further investigate the ultrastructural details of the surface of Bowman's membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman's membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution. Height and deflection images were acquired at multiple scan lengths using the MFP-3D AFM system software (Asylum Research, Santa Barbara, CA), based in IGOR Pro (WaveMetrics, Lake Oswego, OR). A novel approach, based on computational algorithms for fractal analysis of surfaces applied for AFM data, was utilized to analyze the surface structure. The surfaces revealed a fractal structure at the nanometer scale. The fractal dimension, D, provided quantitative values that characterize the scale properties of surface geometry. Detailed characterization of the surface topography was obtained using statistical parameters, in accordance with ISO 25178-2: 2012. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. The surface structure of Bowman's membrane of the human cornea is complex. The analyzed AFM images confirm a fractal nature of the surface, which is not taken into account by classical surface statistical parameters. Surface fractal dimension could be useful in ophthalmology to quantify corneal architectural changes associated with different disease states to further our understanding of disease evolution.

  17. Probing ternary solvent effect in high Voc polymer solar cells using advanced AFM techniques

    SciTech Connect

    Li, Chao; Soleman, Mikhael; Lorenzo, Josie; Dhasmana, Nitesh; Chantharasupawong, Panit; Ievlev, Anton; Gesquiere, Andre; Tetard, Laurene; Thomas, Jayan

    2016-01-25

    This work describes a simple method to develop a high Voc low band gap PSCs. In addition, two new atomic force microscopy (AFM)-based nanoscale characterization techniques to study the surface morphology and physical properties of the structured active layer are introduced. With the help of ternary solvent processing of the active layer and C60 buffer layer, a bulk heterojunction PSC with Voc more than 0.9 V and conversion efficiency 7.5% is developed. In order to understand the fundamental properties of the materials ruling the performance of the PSCs tested, AFM-based nanoscale characterization techniques including Pulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFM (MSAFM) are introduced. Interestingly, MSAFM exhibits high sensitivity for direct visualization of the donor–acceptor phases in the active layer of the PSCs. Lastly, conductive-AFM (cAFM) studies reveal local variations in conductivity in the donor and acceptor phases as well as a significant increase in photocurrent in the PTB7:ICBA sample obtained with the ternary solvent processing.

  18. Iron oxide mineral-water interface reactions studied by AFM

    SciTech Connect

    Hawley, M.E.; Rogers, P.S.Z.

    1994-07-01

    Natural iron mineral surfaces have been examined in air by atomic force (AFM) and scanning tunneling (STM) microscopies. A number of different surface features were found to be characteristic of the native surface. Even surfaces freshly exposed by crushing larger crystals were found to have a pebbly surface texture caused by the presence of thin coatings of what might be surface precipitates. This finding is interpreted as evidence for previous exposure to water, probably through an extensive network of microfractures. Surface reactions on the goethite crystals were studied by AFM at size resolutions ranging from microns to atomic resolution before, during, and after reaction with distilled water and 0.lN HCl. Immediate and extensive surface reconfiguration occurred on contact with water. In one case, after equilibration with water for 3 days, surface reprecipitation, etching and pitting were observed. Atomic resolution images taken under water were found to be disordered. The result of surface reaction was generally to increase the surface area substantially through the extension of surface platelet arrays, present prior to reaction. This work is being done in support of the site characterization project at Yucca Mountain.

  19. Visualization of internal structure of banana starch granule through AFM.

    PubMed

    Peroni-Okita, Fernanda H G; Gunning, A Patrick; Kirby, Andrew; Simão, Renata A; Soares, Claudinéia A; Cordenunsi, Beatriz R

    2015-09-05

    Atomic force microscopy (AFM) is a high resolution technique for studying the external and internal structures of starch granules. For this purpose granules were isolated from bananas and embedded in a non-penetrating resin. To achieve image contrast of the ultrastructure, the face of the cut blocks were wetted in steam and force modulation mode imaging was used. Images of starch from green bananas showed large variation of height across the granule due to a locational specific absorption of water and swelling of amorphous regions; the data reveal that the center of the granules are structurally different and have different viscoelastic properties. Images of starches from ripe bananas showed an even greater different level of organization: absence of growth rings around the hilum; the central region of the granule is richer in amylose; very porous surface with round shaped dark structures; the size of blocklets are larger than the green fruits.

  20. An AFM study of the chlorite-fluid interface. [Atomic Force Microscopy

    SciTech Connect

    Vrdoljak, G.A.; Henderson, G.S.; Fawcett, J.J. . Dept. of Geology)

    1992-01-01

    Chlorite is a ubiquitous mineral in many geologic environments and plays an important role in elemental adsorption and retention in soils. Chlorite has a 2:1 layer structure consisting of two tetrahedral sheets with an octahedral sheet between them (talc-like layer). The 2:1 layer is charge balanced and hydrogen-bonded by an interlayer of MgOH[sub 6] octahedra (brucite-like layer). The nature of chlorite's structure, its ease of imaging, and perfect 001 cleavage, make this mineral an ideal substrate for use in elemental adsorption studies in solution, with the AFM. The 001 cleavage plane of a 2b polytype with composition (Mg[sub 4.4]Fe[sub 0.6]Al[sub 1.0])[(Si[sub 2.9]Al[sub 1.1])]O[sub 10](OH)[sub g] has been imaged in air, water, and oil by atomic force microscopy. Dissolution features are observed in water, showing sub-micron features dissolving in real-time. Atomic resolution of both the talc-like and brucite-like layers has been obtained in air. However, only the tetrahedral sheet of the talc-like layer has been imaged at atomic resolution in oil and water, which may indicate a structural instability of the brucite-like surface in solution. Measurements of the unit-cell dimensions (a and b) for the talc-like layer in the three different media indicate a structural expansion of the mineral surface in solution. The a unit cell dimension expands by 7.4 [+-] 0.1% when in water; conversely, the b dimension varies greatly when in oil ([minus]10% to +20%), relative to air. The effects of these solution media on the structure of chlorite are revealed by characterization with the AFM. This information should prove useful in future studies of adsorption onto layer silicates.

  1. Sustained Classroom Observation: What Does It Reveal about Changing Teaching Practices?

    ERIC Educational Resources Information Center

    Lawson, Tony

    2011-01-01

    In the context of the tension between classroom observation as a form of empowerment and as an instrument of control, the partnership between three 16-19 colleges and a university School of Education in delivering a programme of sustained observation over eight years is explicated. Drawing on the literature about continuing professional…

  2. Direct AFM observations of impurity effects on a lysozyme crystal

    NASA Astrophysics Data System (ADS)

    Nakada, Toshitaka; Sazaki, Gen; Miyashita, Satoru; Durbin, Stephen D.; Komatsu, Hiroshi

    1999-01-01

    Impurity effects on the growth of tetragonal lysozyme crystals have been studied using in situ atomic force microscopy. Commercially available hen egg white lysozyme was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis with silver staining, and purified by re-crystallization and successive high pressure liquid chromatography. On the (1 1 0) crystal surface, there was no significant difference in morphology between crystals grown in commercial and in purified solutions. On the (1 0 1) surface, however, a large number of small particles were found when the crystal was grown in the commercial solution, while the surface grown in the purified solution was quite smooth. Among the typical residual impurities contained in commercial lysozyme, only covalently bound lysozyme dimer yielded such particles. From measurements of particle separation and an estimate of the critical nucleation size, we infer that the particles reduced the step velocity according to the mechanism described by Cabrera et al. [N. Cabrera, D.A. Vermilyea, in: R.H. Doremus et al. (Eds.), Growth and Perfection of Crystals, 1958, P. 393].

  3. FRAME (Force Review Automation Environment): MATLAB-based AFM data processor.

    PubMed

    Partola, Kostyantyn R; Lykotrafitis, George

    2016-05-03

    Data processing of force-displacement curves generated by atomic force microscopes (AFMs) for elastic moduli and unbinding event measurements is very time consuming and susceptible to user error or bias. There is an evident need for consistent, dependable, and easy-to-use AFM data processing software. We have developed an open-source software application, the force review automation environment (or FRAME), that provides users with an intuitive graphical user interface, automating data processing, and tools for expediting manual processing. We did not observe a significant difference between manually processed and automatically processed results from the same data sets.

  4. Custom AFM for X-ray beamlines: in situ biological investigations under physiological conditions

    PubMed Central

    Gumí-Audenis, B.; Carlà, F.; Vitorino, M. V.; Panzarella, A.; Porcar, L.; Boilot, M.; Guerber, S.; Bernard, P.; Rodrigues, M. S.; Sanz, F.; Giannotti, M. I.; Costa, L.

    2015-01-01

    A fast atomic force microscope (AFM) has been developed that can be installed as a sample holder for grazing-incidence X-ray experiments at solid/gas or solid/liquid interfaces. It allows a wide range of possible investigations, including soft and biological samples under physiological conditions (hydrated specimens). The structural information obtained using the X-rays is combined with the data gathered with the AFM (morphology and mechanical properties), providing a unique characterization of the specimen and its dynamics in situ during an experiment. In this work, lipid monolayers and bilayers in air or liquid environment have been investigated by means of AFM, both with imaging and force spectroscopy, and X-ray reflectivity. In addition, this combination allows the radiation damage induced by the beam on the sample to be studied, as has been observed on DOPC and DPPC supported lipid bilayers under physiological conditions. PMID:26524300

  5. An improved measurement of dsDNA elasticity using AFM

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi-Huong; Lee, Sang-Myung; Na, Kyounghwan; Yang, Sungwook; Kim, Jinseok; Yoon, Eui-Sung

    2010-02-01

    The mechanical properties of a small fragment (30 bp) of an individual double-stranded deoxyribonucleic acid (dsDNA) in water have been investigated by atomic force microscopy (AFM). We have stretched three systems including ssDNA, double-fixed dsDNA (one strand of the dsDNA molecules was biotinylated at the 3'-end and thiolated at the 5'-end, this was reversed for the other complementary strand) and single-fixed dsDNA (one strand of the dsDNA molecules was biotinylated at the 3'-end and thiolated at the 5'-end, whereas the other complementary strand was biotinylated at only the 5'-end). The achieved thiolation and biotinylation were to bind ds- or ssDNA to the gold surface and streptavidin-coated AFM tip, respectively. Analysis of the force versus displacement (F-D) curves from tip-DNA-substrate systems shows that the pull-off length (Lo) and stretch length (δ) from the double-fixed system were shorter than those observed in the ssDNA and the single-fixed system. The obtained stretch force (Fst) from the single-fixed dsDNA was much greater than that from the ssDNA even though it was about 10 pN greater than the one obtained in the double-fixed system. As a result, the Young's modulus of the double-fixed dsDNA was greater than that of the single-fixed dsDNA and the ssDNA. A more reliable stiffness of the dsDNA was observed via the double-fixed system, since there is no effect of the unpaired molecules during stretching, which always occurred in the single-fixed system. The unpaired molecules were also observed by comparing the stiffness of ssDNA and single-fixed dsDNA in which the end of one strand was left free.

  6. Dense Cloud Cores revealed by ALMA CO observations in the low metallicity dwarf galaxy WLM

    NASA Astrophysics Data System (ADS)

    Rubio, M.; Elmegreen, B.; Hunter, D.; Cortes, J.; Brinks, E.; Cigan, P.

    2017-03-01

    Understanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations, they are molecular with H2 the dominant species and CO the best available. When the abundances of carbon and oxygen are low compared to hydrogen, and the opacity from dust is also low, as in primeval galaxies and local dwarf irregular galaxies CO forms slowly and is easily destroyed, so it cannot accumulate inside dense clouds. Then we lose our ability to trace the gas in regions of star formation and we lose critical information on the temperatures, densities, and velocities of the material that collapses. I will report on high resolution observations with ALMA of CO clouds in the local group dwarf irregular galaxy WLM, which has a metallicity that is 13% of the solar value and 50% lower than the previous CO detection threshold and the properties derived of very small dense CO clouds mapped..

  7. Titan solar occultation observations reveal transit spectra of a hazy world.

    PubMed

    Robinson, Tyler D; Maltagliati, Luca; Marley, Mark S; Fortney, Jonathan J

    2014-06-24

    High-altitude clouds and hazes are integral to understanding exoplanet observations, and are proposed to explain observed featureless transit spectra. However, it is difficult to make inferences from these data because of the need to disentangle effects of gas absorption from haze extinction. Here, we turn to the quintessential hazy world, Titan, to clarify how high-altitude hazes influence transit spectra. We use solar occultation observations of Titan's atmosphere from the Visual and Infrared Mapping Spectrometer aboard National Aeronautics and Space Administration's (NASA) Cassini spacecraft to generate transit spectra. Data span 0.88-5 μm at a resolution of 12-18 nm, with uncertainties typically smaller than 1%. Our approach exploits symmetry between occultations and transits, producing transit radius spectra that inherently include the effects of haze multiple scattering, refraction, and gas absorption. We use a simple model of haze extinction to explore how Titan's haze affects its transit spectrum. Our spectra show strong methane-absorption features, and weaker features due to other gases. Most importantly, the data demonstrate that high-altitude hazes can severely limit the atmospheric depths probed by transit spectra, bounding observations to pressures smaller than 0.1-10 mbar, depending on wavelength. Unlike the usual assumption made when modeling and interpreting transit observations of potentially hazy worlds, the slope set by haze in our spectra is not flat, and creates a variation in transit height whose magnitude is comparable to those from the strongest gaseous-absorption features. These findings have important consequences for interpreting future exoplanet observations, including those from NASA's James Webb Space Telescope.

  8. Titan solar occultation observations reveal transit spectra of a hazy world

    PubMed Central

    Robinson, Tyler D.; Maltagliati, Luca; Marley, Mark S.; Fortney, Jonathan J.

    2014-01-01

    High-altitude clouds and hazes are integral to understanding exoplanet observations, and are proposed to explain observed featureless transit spectra. However, it is difficult to make inferences from these data because of the need to disentangle effects of gas absorption from haze extinction. Here, we turn to the quintessential hazy world, Titan, to clarify how high-altitude hazes influence transit spectra. We use solar occultation observations of Titan’s atmosphere from the Visual and Infrared Mapping Spectrometer aboard National Aeronautics and Space Administration’s (NASA) Cassini spacecraft to generate transit spectra. Data span 0.88–5 μm at a resolution of 12–18 nm, with uncertainties typically smaller than 1%. Our approach exploits symmetry between occultations and transits, producing transit radius spectra that inherently include the effects of haze multiple scattering, refraction, and gas absorption. We use a simple model of haze extinction to explore how Titan’s haze affects its transit spectrum. Our spectra show strong methane-absorption features, and weaker features due to other gases. Most importantly, the data demonstrate that high-altitude hazes can severely limit the atmospheric depths probed by transit spectra, bounding observations to pressures smaller than 0.1–10 mbar, depending on wavelength. Unlike the usual assumption made when modeling and interpreting transit observations of potentially hazy worlds, the slope set by haze in our spectra is not flat, and creates a variation in transit height whose magnitude is comparable to those from the strongest gaseous-absorption features. These findings have important consequences for interpreting future exoplanet observations, including those from NASA’s James Webb Space Telescope. PMID:24876272

  9. Observed bromodomain flexibility reveals histone peptide- and small molecule ligand-compatible forms of ATAD2.

    PubMed

    Poncet-Montange, Guillaume; Zhan, Yanai; Bardenhagen, Jennifer P; Petrocchi, Alessia; Leo, Elisabetta; Shi, Xi; Lee, Gilbert R; Leonard, Paul G; Geck Do, Mary K; Cardozo, Mario G; Andersen, Jannik N; Palmer, Wylie S; Jones, Philip; Ladbury, John E

    2015-03-01

    Preventing histone recognition by bromodomains emerges as an attractive therapeutic approach in cancer. Overexpression of ATAD2 (ATPase family AAA domain-containing 2 isoform A) in cancer cells is associated with poor prognosis making the bromodomain of ATAD2 a promising epigenetic therapeutic target. In the development of an in vitro assay and identification of small molecule ligands, we conducted structure-guided studies which revealed a conformationally flexible ATAD2 bromodomain. Structural studies on apo-, peptide-and small molecule-ATAD2 complexes (by co-crystallization) revealed that the bromodomain adopts a 'closed', histone-compatible conformation and a more 'open' ligand-compatible conformation of the binding site respectively. An unexpected conformational change of the conserved asparagine residue plays an important role in driving the peptide-binding conformation remodelling. We also identified dimethylisoxazole-containing ligands as ATAD2 binders which aided in the validation of the in vitro screen and in the analysis of these conformational studies.

  10. Spitzer Observations of OGLE-2015-BLG-1212 Reveal a New Path toward Breaking Strong Microlens Degeneracies

    NASA Astrophysics Data System (ADS)

    Bozza, V.; Shvartzvald, Y.; Udalski, A.; Calchi Novati, S.; Bond, I. A.; Han, C.; Hundertmark, M.; Poleski, R.; Pawlak, M.; Szymański, M. K.; Skowron, J.; Mróz, P.; Kozłowski, S.; Wyrzykowski, Ł.; Pietrukowicz, P.; Soszyński, I.; Ulaczyk, K.; OGLE Group; and; Beichman, C.; Bryden, G.; Carey, S.; Fausnaugh, M.; Gaudi, B. S.; Gould, A.; Henderson, C. B.; Pogge, R. W.; Wibking, B.; Yee, J. C.; Zhu, W.; Spitzer Team; Abe, F.; Asakura, Y.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Donachie, M.; Freeman, M.; Fukui, A.; Hirao, Y.; Inayama, K.; Itow, Y.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Nishioka, T.; Ohnishi, K.; Oyokawa, H.; Rattenbury, N.; Saito, To.; Sharan, A.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Wakiyama, Y.; Yonehara, A.; MOA Group; Choi, J.-Y.; Park, H.; Jung, Y. K.; Shin, I.-G.; Albrow, M. D.; Park, B.-G.; Kim, S.-L.; Lee, C.-U.; Cha, S.-M.; Kim, D.-J.; Lee, Y.; KMTNet Group; Dominik, M.; Jørgensen, U. G.; Andersen, M. I.; Bramich, D. M.; Burgdorf, M. J.; Ciceri, S.; D'Ago, G.; Evans, D. F.; Figuera Jaimes, R.; Gu, S.-H.; Hinse, T. C.; Kains, N.; Kerins, E.; Korhonen, H.; Kuffmeier, M.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Rasmussen, R. T.; Scarpetta, G.; Skottfelt, J.; Snodgrass, C.; Southworth, J.; Surdej, J.; Unda-Sanzana, E.; von Essen, C.; Wang, Y.-B.; Wertz, O.; MiNDSTEp; Maoz, D.; Friedmann, M.; Kaspi, S.; Wise Group

    2016-03-01

    Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively break a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive out of an initial set of 32 local minima in the parameter space. These models clearly indicate that the lens is a stellar binary system possibly located within the bulge of our Galaxy, ruling out the planetary alternative. We argue that several types of discrete degeneracies can be broken via such space-based parallax observations.

  11. Revealing "The Space Between": Creating an Observation Scale to Understand Infant Mental Health Reflective Supervision

    ERIC Educational Resources Information Center

    Watson, Christopher L.; Harrison, Mary E.; Hennes, Jill E.; Harris, Maren M.

    2016-01-01

    The Reflective Interaction Observation Scale (RIOS) describes and operationalizes the nature of the interactions between a supervisor and supervisee(s) during reflective supervision. Developed in collaboration among researchers and clinicians from the University of Minnesota, the Minnesota Association for Infant and Early Childhood Mental Health,…

  12. Hydrocarbons in phlogopite from Kasenyi kamafugitic rocks (SW Uganda): cross-correlated AFM, confocal microscopy and Raman imaging

    NASA Astrophysics Data System (ADS)

    Moro, Daniele; Valdrè, Giovanni; Mesto, Ernesto; Scordari, Fernando; Lacalamita, Maria; Ventura, Giancarlo Della; Bellatreccia, Fabio; Scirè, Salvatore; Schingaro, Emanuela

    2017-01-01

    This study presents a cross-correlated surface and near surface investigation of two phlogopite polytypes from Kasenyi kamafugitic rocks (SW Uganda) by means of advanced Atomic Force Microscopy (AFM), confocal microscopy and Raman micro-spectroscopy. AFM revealed comparable nanomorphology and electrostatic surface potential for the two mica polytypes. A widespread presence of nano-protrusions located on the mica flake surface was also observed, with an aspect ratio (maximum height/maximum width) from 0.01 to 0.09. Confocal microscopy showed these features to range from few nm to several μm in dimension, and shapes from perfectly circular to ellipsoidic and strongly elongated. Raman spectra collected across the bubbles showed an intense and convolute absorption in the range 3000–2800 cm‑1, associated with weaker bands at 1655, 1438 and 1297 cm‑1, indicating the presence of fluid inclusions consisting of aliphatic hydrocarbons, alkanes and cycloalkanes, with minor amounts of oxygenated compounds, such as carboxylic acids. High-resolution Raman images provided evidence that these hydrocarbons are confined within the bubbles. This work represents the first direct evidence that phlogopite, a common rock-forming mineral, may be a possible reservoir for hydrocarbons.

  13. Hydrocarbons in phlogopite from Kasenyi kamafugitic rocks (SW Uganda): cross-correlated AFM, confocal microscopy and Raman imaging.

    PubMed

    Moro, Daniele; Valdrè, Giovanni; Mesto, Ernesto; Scordari, Fernando; Lacalamita, Maria; Ventura, Giancarlo Della; Bellatreccia, Fabio; Scirè, Salvatore; Schingaro, Emanuela

    2017-01-18

    This study presents a cross-correlated surface and near surface investigation of two phlogopite polytypes from Kasenyi kamafugitic rocks (SW Uganda) by means of advanced Atomic Force Microscopy (AFM), confocal microscopy and Raman micro-spectroscopy. AFM revealed comparable nanomorphology and electrostatic surface potential for the two mica polytypes. A widespread presence of nano-protrusions located on the mica flake surface was also observed, with an aspect ratio (maximum height/maximum width) from 0.01 to 0.09. Confocal microscopy showed these features to range from few nm to several μm in dimension, and shapes from perfectly circular to ellipsoidic and strongly elongated. Raman spectra collected across the bubbles showed an intense and convolute absorption in the range 3000-2800 cm(-1), associated with weaker bands at 1655, 1438 and 1297 cm(-1), indicating the presence of fluid inclusions consisting of aliphatic hydrocarbons, alkanes and cycloalkanes, with minor amounts of oxygenated compounds, such as carboxylic acids. High-resolution Raman images provided evidence that these hydrocarbons are confined within the bubbles. This work represents the first direct evidence that phlogopite, a common rock-forming mineral, may be a possible reservoir for hydrocarbons.

  14. Hydrocarbons in phlogopite from Kasenyi kamafugitic rocks (SW Uganda): cross-correlated AFM, confocal microscopy and Raman imaging

    PubMed Central

    Moro, Daniele; Valdrè, Giovanni; Mesto, Ernesto; Scordari, Fernando; Lacalamita, Maria; Ventura, Giancarlo Della; Bellatreccia, Fabio; Scirè, Salvatore; Schingaro, Emanuela

    2017-01-01

    This study presents a cross-correlated surface and near surface investigation of two phlogopite polytypes from Kasenyi kamafugitic rocks (SW Uganda) by means of advanced Atomic Force Microscopy (AFM), confocal microscopy and Raman micro-spectroscopy. AFM revealed comparable nanomorphology and electrostatic surface potential for the two mica polytypes. A widespread presence of nano-protrusions located on the mica flake surface was also observed, with an aspect ratio (maximum height/maximum width) from 0.01 to 0.09. Confocal microscopy showed these features to range from few nm to several μm in dimension, and shapes from perfectly circular to ellipsoidic and strongly elongated. Raman spectra collected across the bubbles showed an intense and convolute absorption in the range 3000–2800 cm−1, associated with weaker bands at 1655, 1438 and 1297 cm−1, indicating the presence of fluid inclusions consisting of aliphatic hydrocarbons, alkanes and cycloalkanes, with minor amounts of oxygenated compounds, such as carboxylic acids. High-resolution Raman images provided evidence that these hydrocarbons are confined within the bubbles. This work represents the first direct evidence that phlogopite, a common rock-forming mineral, may be a possible reservoir for hydrocarbons. PMID:28098185

  15. Can observations inside the Solar System reveal the gravitational properties of the quantum vacuum?

    NASA Astrophysics Data System (ADS)

    Hajdukovic, Dragan Slavkov

    2013-02-01

    The understanding of the gravitational properties of the quantum vacuum might be the next scientific revolution. It was recently proposed that the quantum vacuum contains the virtual gravitational dipoles; we argue that this hypothesis might be tested within the Solar System. The key point is that the quantum vacuum ("enriched" with the gravitational dipoles) induces a retrograde precession of the perihelion. It is obvious that this phenomenon might eventually be revealed by more accurate studies of orbits of planets and orbits of the artificial Earth satellites. However, we suggest that potentially the best "laboratory" for the study of the gravitational properties of the quantum vacuum is the recently discovered dwarf planet Eris with its satellite named Dysnomia; the distance of nearly 100 AU from the Sun makes it the unique system in which the precession of the perihelion of Dysnomia (around Eris) is strongly dominated by the quantum vacuum.

  16. Mars surface diversity as revealed by the OMEGA/Mars Express observations.

    PubMed

    Bibring, Jean-Pierre; Langevin, Yves; Gendrin, Aline; Gondet, Brigitte; Poulet, François; Berthé, Michel; Soufflot, Alain; Arvidson, Ray; Mangold, Nicolas; Mustard, John; Drossart, P

    2005-03-11

    The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) investigation, on board the European Space Agency Mars Express mission, is mapping the surface composition of Mars at a 0.3- to 5-kilometer resolution by means of visible-near-infrared hyperspectral reflectance imagery. The data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy, offering key insights into the evolution of Mars. OMEGA has identified and mapped mafic iron-bearing silicates of both the northern and southern crust, localized concentrations of hydrated phyllosilicates and sulfates but no carbonates, and ices and frosts with a water-ice composition of the north polar perennial cap, as for the south cap, covered by a thin carbon dioxide-ice veneer.

  17. HII 2407: AN ECLIPSING BINARY REVEALED BY K2 OBSERVATIONS OF THE PLEIADES

    SciTech Connect

    David, Trevor J.; Hillenbrand, Lynne A.; Zhang, Celia; Riddle, Reed L.; Stauffer, John; Rebull, L. M.; Cody, Ann Marie; Conroy, Kyle; Stassun, Keivan G.; Pope, Benjamin; Aigrain, Suzanne; Gillen, Ed; Cameron, Andrew Collier; Barrado, David; Isaacson, Howard; Marcy, Geoffrey W.; Ziegler, Carl; Law, Nicholas M.; Baranec, Christoph

    2015-11-20

    The star HII 2407 is a member of the relatively young Pleiades star cluster and was previously discovered to be a single-lined spectroscopic binary. It is newly identified here within Kepler/K2 photometric time series data as an eclipsing binary system. Mutual fitting of the radial velocity and photometric data leads to an orbital solution and constraints on fundamental stellar parameters. While the primary has arrived on the main sequence, the secondary is still pre-main sequence and we compare our results for the M/M{sub ⊙} and R/R{sub ⊙} values with stellar evolutionary models. We also demonstrate that the system is likely to be tidally synchronized. Follow-up infrared spectroscopy is likely to reveal the lines of the secondary, allowing for dynamically measured masses and elevating the system to benchmark eclipsing binary status.

  18. Bimodal distribution of free tropospheric ozone over the tropical western Pacific revealed by airborne observations

    NASA Astrophysics Data System (ADS)

    Pan, L. L.; Honomichl, S. B.; Randel, W. J.; Apel, E. C.; Atlas, E. L.; Beaton, S. P.; Bresch, J. F.; Hornbrook, R.; Kinnison, D. E.; Lamarque, J.-F.; Saiz-Lopez, A.; Salawitch, R. J.; Weinheimer, A. J.

    2015-09-01

    A recent airborne field campaign over the remote western Pacific obtained the first intensive in situ ozone sampling over the warm pool region from oceanic surface to 15 km altitude (near 360 K potential temperature level). The new data set quantifies ozone in the tropical tropopause layer under significant influence of convective outflow. The analysis further reveals a bimodal distribution of free tropospheric ozone mixing ratio. A primary mode, narrowly distributed around 20 ppbv, dominates the troposphere from the surface to 15 km. A secondary mode, broadly distributed with a 60 ppbv modal value, is prominent between 3 and 8 km (320 K to 340 K potential temperature levels). The latter mode occurs as persistent layers of ozone-rich drier air and is characterized by relative humidity under 45%. Possible controlling mechanisms are discussed. These findings provide new insight into the physical interpretation of the "S"-shaped mean ozone profiles in the tropics.

  19. In-plane information from tapping mode AFM images

    NASA Astrophysics Data System (ADS)

    Marcus, Matthew

    2003-03-01

    Phase contrast in intermittent-contact atomic force microscopy is shown to reveal in-plane structural and mechanical properties of poly(diacetylene) monolayer films. This is surprising because measurements of in-plane properties typically require a contact mode of microscopy. Such measurements are possible because the tilt in the oscillating cantilever provides components of motion not just perpendicular to the surface, but also parallel to the sample surface. Lateral tip displacement is virtually universal in AFM, implying that any oscillating tip-AFM technique is sensitive to in-plane material properties. Although the tilt in the cantilever is small ( 10^o) it produces a component of motion that is 20% of the total tip displacement, and this motion accounts for 5-10% of dissipated energy through the tip-sample interaction[1]. The data is used in conjunction with a numerical model to extract in-plane material parameters. The effect of the cantilever tilt on phase measurements is directly verified through measurements on silicon samples tilted at a variety of angles with respect to the cantilever. The lateral tip displacement we make use of allows measurements of in-plane properties of soft samples such as polymer and biological samples. This work was done in collaboration with M. D'Amato, R.W. Carpick, and M.A. Eriksson, and was supported by the NSF CAREER and MRSEC programs and the Research Corporation. 1. M.S. Marcus, R.W. Carpick, D.Y. Sasaki, M.A. Eriksson, Phys. Rev. Lett. 88, 226103 (2002)

  20. BOREAS AFM-04 Twin Otter Aircraft Sounding Data

    NASA Technical Reports Server (NTRS)

    MacPherson, J. Ian; Desjardins, Raymond L.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-4 team used the National Research Council, Canada (NRC) Twin Otter aircraft to make sounding measurements through the boundary layer. These measurements included concentrations of carbon dioxide and ozone, atmospheric pressure, dry bulb temperature, potential temperature, dewpoint temperature, calculated mixing ratio, and wind speed and direction. Aircraft position, heading, and altitude were also recorded. Data were collected at both the Northern Study Area (NSA) and the Southern Study Area (SSA) in 1994 and 1996. These data are stored in tabular ASCII files. The Twin Otter aircraft sounding data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files also are available on a CD-ROM (see document number 20010000884).

  1. Hemispherical Nature of EUV Shocks Revealed by SOHO, STEREO, and SDO Observations

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Natchimuthuk; Nitta, N.; Akiyama, S.; Makela, P.; Yashiro, S.

    2011-01-01

    EUV wave transients associated with type II radio bursts are manifestation of CME-driven shocks in the solar corona. We use recent EUV wave observations from SOHO, STEREO, and SDO for a set of CMEs to show that the EUV transients have a spherical shape in the inner corona. We demonstrate this by showing that the radius of the EUV transient on the disk observed by one instrument is approximately equal to the height of the wave above the solar surface in an orthogonal view provided by another instrument. The study also shows that the CME-driven shocks often form very low in the corona at a heliocentric distance of 1.2 Rs, even smaller than the previous estimates from STEREO/CORl data (Gopalswamy et aI., 2009, Solar Phys. 259, 227). These results have important implications for the acceleration of solar energetic particles by CMEs

  2. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms.

    PubMed

    Rison, William; Krehbiel, Paul R; Stock, Michael G; Edens, Harald E; Shao, Xuan-Min; Thomas, Ronald J; Stanley, Mark A; Zhang, Yang

    2016-02-15

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. The breakdown is found to have a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.

  3. Direct observation of TALE protein dynamics reveals a two-state search mechanism

    PubMed Central

    Cuculis, Luke; Abil, Zhanar; Zhao, Huimin; Schroeder, Charles M.

    2015-01-01

    Transcription activator-like effector (TALE) proteins are a class of programmable DNA-binding proteins for which the fundamental mechanisms governing the search process are not fully understood. Here we use single-molecule techniques to directly observe TALE search dynamics along DNA templates. We find that TALE proteins are capable of rapid diffusion along DNA using a combination of sliding and hopping behaviour, which suggests that the TALE search process is governed in part by facilitated diffusion. We also observe that TALE proteins exhibit two distinct modes of action during the search process—a search state and a recognition state—facilitated by different subdomains in monomeric TALE proteins. Using TALE truncation mutants, we further demonstrate that the N-terminal region of TALEs is required for the initial non-specific binding and subsequent rapid search along DNA, whereas the central repeat domain is required for transitioning into the site-specific recognition state. PMID:26027871

  4. Direct observation of TALE protein dynamics reveals a two-state search mechanism

    NASA Astrophysics Data System (ADS)

    Cuculis, Luke; Abil, Zhanar; Zhao, Huimin; Schroeder, Charles M.

    2015-06-01

    Transcription activator-like effector (TALE) proteins are a class of programmable DNA-binding proteins for which the fundamental mechanisms governing the search process are not fully understood. Here we use single-molecule techniques to directly observe TALE search dynamics along DNA templates. We find that TALE proteins are capable of rapid diffusion along DNA using a combination of sliding and hopping behaviour, which suggests that the TALE search process is governed in part by facilitated diffusion. We also observe that TALE proteins exhibit two distinct modes of action during the search process--a search state and a recognition state--facilitated by different subdomains in monomeric TALE proteins. Using TALE truncation mutants, we further demonstrate that the N-terminal region of TALEs is required for the initial non-specific binding and subsequent rapid search along DNA, whereas the central repeat domain is required for transitioning into the site-specific recognition state.

  5. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

    SciTech Connect

    Rison, William; Krehbiel, Paul R.; Stock, Michael G.; Edens, Harald E.; Shao, Xuan-Min; Thomas, Ronald J.; Stanley, Mark A.; Zhang, Yang

    2016-02-15

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. We find that the breakdown has a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.

  6. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

    PubMed Central

    Rison, William; Krehbiel, Paul R.; Stock, Michael G.; Edens, Harald E.; Shao, Xuan-Min; Thomas, Ronald J.; Stanley, Mark A.; Zhang, Yang

    2016-01-01

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. The breakdown is found to have a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown. PMID:26876654

  7. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

    DOE PAGES

    Rison, William; Krehbiel, Paul R.; Stock, Michael G.; ...

    2016-02-15

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. We find that the breakdown has a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in naturemore » and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.« less

  8. Offshore seismicity in the western Marmara Sea, Turkey, revealed by ocean bottom observation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yojiro; Takahashi, Narumi; Citak, Seckin; Kalafat, Doǧan; Pinar, Ali; Gürbüz, Cemil; Kaneda, Yoshiyuki

    2015-04-01

    The North Anatolian Fault (NAF) extends 1600 km westward from a junction with the East Anatolian Fault at the Karliova Triple Junction in eastern Turkey, across northern Turkey and into the Aegean Sea, accommodating about 25 mm/yr of right-lateral motion between Anatolia and the Eurasian plate. Since 1939, devastating earthquakes with magnitude greater than seven ruptured NAF westward, starting from 1939 Erzincan (Ms=7.9) at the eastern Turkey and including the latest 1999 Izmit-Golcuk (Ms=7.7) and the Duzce (Ms=7.4) earthquakes in the Marmara region. Considering the fault segments ruptured by the May 24th, 2014 Northern Aegean earthquake (Mw=6.9), the only un-ruptured segments left behind the 1600 km long NAF locate beneath the Marmara Sea and those segments keep their mystery due to their underwater location. To consider the earthquake hazard and disaster mitigation, the detailed information about fault geometry and its stick-slip behavior beneath the western Marmara Sea is very important. Thus, we started to operate a series of ocean bottom seismographic (OBS) observations to estimate the fault geometry from microearthquake distribution. As a first step, we deployed 3 pop-up type OBSs on 20th of March 2014 as a trial observation, and recovered them on 18th of June 2014. Although one of the OBSs worked only 6 days from the start of the observation, other two OBSs functioned properly during the whole 3-month observation period. We first searched for the microearthquakes missing by the land seismic network and estimated their precious location by using the initial 6 days data, i.e., using all the temporary OBS stations. Although there are only 3 earthquakes listed on the Kandilli Observatory and Earthquake Research Institute (KOERI) catalogue, we could identify 41 earthquakes with more than 5 picking data of P and S first arrivals, and two-third of them located within the OBS network. We found the earthquake cluster along the main NAF and whose depth interval is 12

  9. Radio Observations Reveal a Smooth Circumstellar Environment Around the Extraordinary Type Ib Supernova 2012au

    NASA Astrophysics Data System (ADS)

    Kamble, Atish; Soderberg, Alicia M.; Chomiuk, Laura; Margutti, Raffaella; Medvedev, Mikhail; Milisavljevic, Dan; Chakraborti, Sayan; Chevalier, Roger; Chugai, Nikolai; Dittmann, Jason; Drout, Maria; Fransson, Claes; Nakar, Ehud; Sanders, Nathan

    2014-12-01

    We present extensive radio and X-ray observations of SN 2012au, an energetic, radio-luminous supernova of Type Ib that exhibits multi-wavelength properties bridging subsets of hydrogen-poor superluminous supernovae, hypernovae, and normal core-collapse supernovae. The observations closely follow models of synchrotron emission from a shock-heated circumburst medium that has a wind density profile (ρvpropr -2). We infer a sub-relativistic velocity for the shock wave v ≈ 0.2 c and a radius of r ≈ 1.4 × 1016cm at 25 days after the estimated date of explosion. For a wind velocity of 1000 km s-1, we determine the mass-loss rate of the progenitor to be \\dot{M} = 3.6 × 10-6 M⊙ yr-1, consistent with the estimates from X-ray observations. We estimate the total internal energy of the radio-emitting material to be E ≈ 1047 erg, which is intermediate to SN 1998bw and SN 2002ap. The evolution of the radio light curve of SN 2012au is in agreement with its interaction with a smoothly distributed circumburst medium and the absence of stellar shells ejected from previous outbursts out to r ≈ 1017 cm from the supernova site. We conclude that the bright radio emission from SN 2012au was not dissimilar from other core-collapse supernovae despite its extraordinary optical properties, and that the evolution of the SN 2012au progenitor star was relatively quiet, marked with a steady mass loss, during the final years preceding explosion.

  10. The peculiar mass-loss history of SN 2014C as revealed through AMI radio observations

    NASA Astrophysics Data System (ADS)

    Anderson, G. E.; Horesh, A.; Mooley, K. P.; Rushton, A. P.; Fender, R. P.; Staley, T. D.; Argo, M. K.; Beswick, R. J.; Hancock, P. J.; Pérez-Torres, M. A.; Perrott, Y. C.; Plotkin, R. M.; Pretorius, M. L.; Rumsey, C.; Titterington, D. J.

    2017-04-01

    We present a radio light curve of supernova (SN) 2014C taken with the Arcminute Microkelvin Imager (AMI) Large Array at 15.7 GHz. Optical observations presented by Milisavljevic et al. demonstrated that SN 2014C metamorphosed from a stripped-envelope Type Ib SN into a strongly interacting Type IIn SN within 1 yr. The AMI light curve clearly shows two distinct radio peaks, the second being a factor of 4 times more luminous than the first peak. This double bump morphology indicates two distinct phases of mass-loss from the progenitor star with the transition between density regimes occurring at 100-200 d. This reinforces the interpretation that SN 2014C exploded in a low-density region before encountering a dense hydrogen-rich shell of circumstellar material that was likely ejected by the progenitor prior to the explosion. The AMI flux measurements of the first light-curve bump are the only reported observations taken within ∼50 to ∼125 d post-explosion, before the blast-wave encountered the hydrogen shell. Simplistic synchrotron self-absorption and free-free absorption modelling suggest that some physical properties of SN 2014C are consistent with the properties of other Type Ibc and IIn SNe. However, our single frequency data does not allow us to distinguish between these two models, which implies that they are likely too simplistic to describe the complex environment surrounding this event. Lastly, we present the precise radio location of SN 2014C obtained with the electronic Multi-Element Remotely Linked Interferometer Network, which will be useful for future very long baseline interferometry observations of the SN.

  11. Radio observations reveal a smooth circumstellar environment around the extraordinary type Ib supernova 2012au

    SciTech Connect

    Kamble, Atish; Soderberg, Alicia M.; Margutti, Raffaella; Milisavljevic, Dan; Chakraborti, Sayan; Dittmann, Jason; Drout, Maria; Sanders, Nathan; Chomiuk, Laura; Medvedev, Mikhail; Chevalier, Roger; Chugai, Nikolai; Fransson, Claes; Nakar, Ehud

    2014-12-10

    We present extensive radio and X-ray observations of SN 2012au, an energetic, radio-luminous supernova of Type Ib that exhibits multi-wavelength properties bridging subsets of hydrogen-poor superluminous supernovae, hypernovae, and normal core-collapse supernovae. The observations closely follow models of synchrotron emission from a shock-heated circumburst medium that has a wind density profile (ρ∝r {sup –2}). We infer a sub-relativistic velocity for the shock wave v ≈ 0.2 c and a radius of r ≈ 1.4 × 10{sup 16}cm at 25 days after the estimated date of explosion. For a wind velocity of 1000 km s{sup –1}, we determine the mass-loss rate of the progenitor to be M-dot =3.6×10{sup −6} M{sub ⊙} yr{sup −1}, consistent with the estimates from X-ray observations. We estimate the total internal energy of the radio-emitting material to be E ≈ 10{sup 47} erg, which is intermediate to SN 1998bw and SN 2002ap. The evolution of the radio light curve of SN 2012au is in agreement with its interaction with a smoothly distributed circumburst medium and the absence of stellar shells ejected from previous outbursts out to r ≈ 10{sup 17} cm from the supernova site. We conclude that the bright radio emission from SN 2012au was not dissimilar from other core-collapse supernovae despite its extraordinary optical properties, and that the evolution of the SN 2012au progenitor star was relatively quiet, marked with a steady mass loss, during the final years preceding explosion.

  12. Mid-Cretaceous charred fossil flowers reveal direct observation of arthropod feeding strategies

    PubMed Central

    Hartkopf-Fröder, Christoph; Rust, Jes; Wappler, Torsten; Friis, Else Marie; Viehofen, Agnes

    2012-01-01

    Although plant–arthropod relationships underpin the dramatic rise in diversity and ecological dominance of flowering plants and their associated arthropods, direct observations of such interactions in the fossil record are rare, as these ephemeral moments are difficult to preserve. Three-dimensionally preserved charred remains of Chloranthistemon flowers from the Late Albian to Early Cenomanian of Germany preserve scales of mosquitoes and an oribatid mite with mouthparts inserted into the pollen sac. Mosquitoes, which today are frequent nectar feeders, and the mite were feeding on pollen at the time wildfire consumed the flowers. These findings document directly arthropod feeding strategies and their role in decomposition. PMID:21900310

  13. High Velocity Precessing Jet from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations

    NASA Astrophysics Data System (ADS)

    Yung, Bosco; Nakashima, J.; Imai, H.; Deguchi, S.; Diamond, P. J.; Kwok, S.

    2011-05-01

    We report the multi-epoch VLBA observations of 22.2GHz water maser emission associated with the "water fountain" star IRAS 18286-0959. The detected maser emission are distributed in the velocity range from -50km/s to 150km/s. The spatial distribution of over 70% of the identified maser features is found to be highly collimated along a spiral jet (namely, jet 1) extended from southeast to northwest direction, and the rest of the features appear to trace another spiral jet (jet 2) with a different orientation. The two jets form a "double-helix" pattern which lies across 200 milliarcseconds (mas). The maser features are reasonably fit by a model consisting of two precessing jets. The velocities of jet 1 and jet 2 are derived to be 138km/s and 99km/s, respectively. The precession period of jet 1 is about 56 years, and for jet 2 it is about 73 years. We propose that the appearance of two jets observed are the result of a single driving source with a significant proper motion. This research was supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region, China, the Seed Funding Programme for Basic Research of the University of Hong Kong, Grant-in-Aid for Young Scientists from the Ministry 9 of Education, Culture, Sports, Science, and Technology, and Grant-in-Aid for Scientific Research from Japan Society for Promotion Science.

  14. Micrometre-scale deformation observations reveal fundamental controls on geological rifting

    NASA Astrophysics Data System (ADS)

    Thun, Johannes; Lokmer, Ivan; Bean, Christopher J.; Eibl, Eva P. S.; Bergsson, Bergur H.; Braiden, Aoife

    2016-11-01

    Many of the world’s largest volcanic eruptions are associated with geological rifting where major fractures open at the Earth’s surface, yet fundamental controls on the near-surface response to the rifting process are lacking. New high resolution observations gleaned from seismometer data during the 2014 Bárðarbunga basaltic dyke intrusion in Iceland allow us unprecedented access to the associated graben formation process on both sub-second and micrometre scales. We find that what appears as quasi steady-state near-surface rifting on lower resolution GPS observation comprises discrete staccato-like deformation steps as the upper crust unzips through repetitive low magnitude (MW < 0) failures on fracture patches estimated between 300 m2 and 1200 m2 in size. Stress drops for these events are one to two orders of magnitude smaller than expected for tectonic earthquakes, demonstrating that the uppermost crust in the rift zone is exceptionally weak.

  15. Micrometre-scale deformation observations reveal fundamental controls on geological rifting

    PubMed Central

    Thun, Johannes; Lokmer, Ivan; Bean, Christopher J.; Eibl, Eva P. S.; Bergsson, Bergur H.; Braiden, Aoife

    2016-01-01

    Many of the world’s largest volcanic eruptions are associated with geological rifting where major fractures open at the Earth’s surface, yet fundamental controls on the near-surface response to the rifting process are lacking. New high resolution observations gleaned from seismometer data during the 2014 Bárðarbunga basaltic dyke intrusion in Iceland allow us unprecedented access to the associated graben formation process on both sub-second and micrometre scales. We find that what appears as quasi steady-state near-surface rifting on lower resolution GPS observation comprises discrete staccato-like deformation steps as the upper crust unzips through repetitive low magnitude (MW < 0) failures on fracture patches estimated between 300 m2 and 1200 m2 in size. Stress drops for these events are one to two orders of magnitude smaller than expected for tectonic earthquakes, demonstrating that the uppermost crust in the rift zone is exceptionally weak. PMID:27827417

  16. WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS

    SciTech Connect

    Flaherty, Kevin M.; Hughes, A. Meredith; Rosenfeld, Katherine A.; Andrews, Sean M.; Wilner, David J.; Chiang, Eugene; Kerzner, Skylar; Simon, Jacob B.

    2015-11-10

    Turbulence can transport angular momentum in protoplanetary disks and influence the growth and evolution of planets. With spatially and spectrally resolved molecular emission line measurements provided by (sub)millimeter interferometric observations, it is possible to directly measure non-thermal motions in the disk gas that can be attributed to this turbulence. We report a new constraint on the turbulence in the disk around HD 163296, a nearby young A star, determined from Atacama Large Millimeter/submillimeter Array Science Verification observations of four CO emission lines (the CO(3-2), CO(2-1), {sup 13}CO(2-1), and C{sup 18}O(2-1) transitions). The different optical depths for these lines permit probes of non-thermal line-widths at a range of physical conditions (temperature and density) and depths into the disk interior. We derive stringent limits on the non-thermal motions in the upper layers of the outer disk such that any contribution to the line-widths from turbulence is <3% of the local sound speed. These limits are approximately an order of magnitude lower than theoretical predictions for full-blown magnetohydrodynamic turbulence driven by the magnetorotational instability, potentially suggesting that this mechanism is less efficient in the outer (R ≳ 30 AU) disk than has been previously considered.

  17. Single-molecule RNA observation in vivo reveals dynamics of co-transcriptional splicing

    NASA Astrophysics Data System (ADS)

    Ferguson, M. L.; Coulon, A.; de Turris, V.; Palangat, M.; Chow, C. C.; Singer, R. H.; Larson, D. R.

    2013-03-01

    The synthesis of pre-mRNA and the splicing of that pre-mRNA to form completed transcripts requires coordination between two large multi-subunit complexes (the transcription elongation complex and the spliceosome). How this coordination occurs in vivo is unknown. Here we report the first experimental observation of transcription and splicing occurring at the same gene in living cells. By utilizing the PP7/MS2 fluorescent RNA reporter system, we can directly observe two distinct regions of the nascent RNA, allowing us to measure the rise and fall time of the intron and exon of a reporter gene stably integrated into a human cell line. The reporter gene consists of a beta globin gene where we have inserted a 24 RNA hairpin cassette into the intron/exon. Upon synthesis, the RNA hairpins are tightly bound by fluorescently-labeled PP7/MS2 bacteriophage coat proteins. After gene induction, a single locus of active transcription in the nucleus shows fluorescence intensity changes characteristic of the synthesis and excision of the intron/exon. Using fluctuation analysis, we determine the elongation rate to be 1.5 kb/min. From the temporal cross correlation function, we determine that splicing of this gene must be co-transcriptional with a splicing time of ~100 seconds before termination and a ~200 second pause at termination. We propose that dual-color RNA imaging may be extended to investigate other mechanisms of transcription, gene regulation, and RNA processing.

  18. Lunar crater ejecta: Physical properties revealed by radar and thermal infrared observations

    NASA Astrophysics Data System (ADS)

    Ghent, R. R.; Carter, L. M.; Bandfield, J. L.; Tai Udovicic, C. J.; Campbell, B. A.

    2016-07-01

    We investigate the physical properties, and changes through time, of lunar impact ejecta using radar and thermal infrared data. We use data from two instruments on the Lunar Reconnaissance Orbiter (LRO) - the Diviner thermal radiometer and the Miniature Radio Frequency (Mini-RF) radar instrument - together with Earth-based radar observations. We use this multiwavelength intercomparison to constrain block sizes and to distinguish surface from buried rocks in proximal ejecta deposits. We find that radar-detectable rocks buried within the upper meter of regolith can remain undisturbed by surface processes such as micrometeorite bombardment for >3 Gyr. We also investigate the thermophysical properties of radar-dark haloes, comprised of fine-grained, rock-poor ejecta distal to the blocky proximal ejecta. Using Diviner data, we confirm that the halo material is depleted in surface rocks, but show that it is otherwise thermophysically indistinct from background regolith. We also find that radar-dark haloes, like the blocky ejecta, remain visible in radar observations for craters with ages >3 Ga, indicating that regolith overturn processes cannot replenish their block populations on that timescale.

  19. An AFM study of calcite dissolution in concentrated electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Ruiz Agudo, E.; Putnis, C. V.; Putnis, A.; Rodriguez-Navarro, C.

    2009-04-01

    Calcite-solution interactions are of a paramount importance in a range of processes such as the removal of heavy metals, carbon dioxide sequestration, landscape modeling, weathering of building stone and biomineralization. Water in contact with minerals often carries significant amounts of solutes; additionally, their concentration may vary due to evaporation and condensation. It is well known that calcite dissolution is affected dramatically by the presence of such solutes. Here we present investigations on the dissolution of calcite in the presence of different electrolytes. Both bulk (batch reactors) experiments and nanoscale (in situ AFM) techniques are used to study the dissolution of calcite in a range of solutions containing alkaly cations balanced by halide anions. Previous works have indicated that the ionic strength has little influence in calcite dissolution rates measured from bulk experiments (Pokrovsky et al. 2005; Glendhill and Morse, 2004). Contrary to these results, our quantitative analyses of AFM observations show an enhancement of the calcite dissolution rate with increasing electrolyte concentration. Such an effect is concentration-dependent and it is most evident in concentrated solutions. AFM experiments have been carried out in a fluid cell using calcite cleavage surfaces in contact with solutions of simple salts of the alkaly metals and halides at different undersaturations with respect to calcite to try to specify the effect of the ionic strength on etch pit spreading rate and calcite dissolution rate. These results show that the presence of soluble salts may critically affect the weathering of carbonate rocks in nature as well as the decay of carbonate stone in built cultural heritage. References: Pokrosky, O.S.; Golubev, S.V.; Schott, J. Dissolution kinetics of calcite, dolomite and magnesite at 25°C and 0 to 50 atm pCO2. Chemical Geology, 2005, 217 (3-4) 239-255. Glendhill, D.K.; Morse, J.W. Dissolution kinetics of calcite in Na

  20. Source properties of microearthquakes revealed by near-source observation at SAFOD (Invited)

    NASA Astrophysics Data System (ADS)

    Imanishi, K.; Ellsworth, W. L.

    2010-12-01

    Near-source observation of earthquakes in deep boreholes and mines provides significant opportunities to enhance our understanding of the source properties of earthquakes. Short hypocentral distances and a high-Q environment make it possible to observe earthquake processes that cannot be seen in shallow boreholes or at the surface. The SAFOD Main Hole is a 3.2 km-deep inclined borehole that crosses the active traces of the San Andreas Fault. A 3-component 15 Hz GS-20DM geophone was deployed within the fault zone at depths between 2350 and 2750 m. Because of the close proximity to earthquake sources, we routinely observed earthquakes with Mw < 0 with high signal-to-noise ratio. Events were recorded at three different sampling rates (1000, 2000, and 4000 sps) depending on observation period (2005 - 2010). This study focuses on earthquakes with S-P time differences shorter than 0.5s, corresponding to hypocentral distance less than 3 km. Among more than 400 earthquakes, we selected 117 events classified into 35 clusters on the basis of waveform similarity at low frequencies. Selected events range in size from approximately Mw -3 to Mw 2. The dataset includes many events in three clusters that formed the SAFOD drilling target; San Francisco, Los Angeles and Hawaii named as their relative positions with respect to those cities. We determined source parameters by the Multi-Window Spectral Ratio (MWSR) method (Imanishi and Ellsworth, 2006). The key step in the method is to stack the ratios calculated from moving windows taken along the record starting with the direct waves. We confirmed that stacking better suppresses the random noise due to differences in path than single-window methods, producing a better estimate of the source spectral ratio. For Mw>-1, the calculated stress drops range between 0.1 and 100 MPa. These observations indicate that there is no breakdown in stress drop scaling for Mw>-1. The stacked spectral ratios show that corner frequencies of events for

  1. THE MAGNETIC STRUCTURE OF SOLAR PROMINENCE CAVITIES: NEW OBSERVATIONAL SIGNATURE REVEALED BY CORONAL MAGNETOMETRY

    SciTech Connect

    Bak-Steslicka, Urszula; Gibson, Sarah E.; Fan Yuhong; Bethge, Christian; Forland, Blake; Rachmeler, Laurel A.

    2013-06-20

    The Coronal Multi-Channel Polarimeter (CoMP) obtains daily full-Sun above-the-limb coronal observations in linear polarization, allowing, for the first time, a diagnostic of the coronal magnetic field direction in quiescent prominence cavities. We find that these cavities consistently possess a characteristic 'lagomorphic' signature in linear polarization indicating twist or shear extending up into the cavity above the neutral line. We demonstrate that such a signature may be explained by a magnetic flux-rope model, a topology with implications for solar eruptions. We find corroborating evidence for a flux-rope structure in the pattern of concentric rings within cavities seen in CoMP line-of-sight velocity.

  2. Unambiguous observation of blocked states reveals altered, blocker-induced, cardiac ryanodine receptor gating

    PubMed Central

    Mukherjee, Saptarshi; Thomas, N. Lowri; Williams, Alan J.

    2016-01-01

    The flow of ions through membrane channels is precisely regulated by gates. The architecture and function of these elements have been studied extensively, shedding light on the mechanisms underlying gating. Recent investigations have focused on ion occupancy of the channel’s selectivity filter and its ability to alter gating, with most studies involving prokaryotic K+ channels. Some studies used large quaternary ammonium blocker molecules to examine the effects of altered ionic flux on gating. However, the absence of blocking events that are visibly distinct from closing events in K+ channels makes unambiguous interpretation of data from single channel recordings difficult. In this study, the large K+ conductance of the RyR2 channel permits direct observation of blocking events as distinct subconductance states and for the first time demonstrates the differential effects of blocker molecules on channel gating. This experimental platform provides valuable insights into mechanisms of blocker-induced modulation of ion channel gating. PMID:27703263

  3. ULF wave power features in the topside ionosphere revealed by Swarm observations

    NASA Astrophysics Data System (ADS)

    Papadimitriou, Constantinos; Balasis, Georgios; Daglis, Ioannis A.

    2015-04-01

    Recently developed automated methods for deriving the characteristics of ultra low frequency (ULF) waves are applied to the Swarm datasets in order to retrieve, on an operational basis, new information about the near-Earth electromagnetic environment. Processing Swarm measurements with these methods helps to elucidate the processes influencing the generation and propagation of ULF waves, which in turn play a crucial role in magnetospheric dynamics. Here we present the first ULF wave observations by Swarm, obtained by applying our analysis tools to the latest months of the mission (i.e., after the constellation attained its final configuration) using scalar magnetic field data. We find that different local times (LTs) correspond to the maximum wave activity seen by the upper satellite and the lower pair of satellites. If these initial results were to be confirmed, it could imply significant spatial variability of ULF wave turbulence in the upper ionosphere.

  4. Ocean impact on decadal Atlantic climate variability revealed by sea-level observations

    NASA Astrophysics Data System (ADS)

    McCarthy, Gerard D.; Haigh, Ivan D.; Hirschi, Joël J.-M.; Grist, Jeremy P.; Smeed, David A.

    2015-05-01

    Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

  5. Ocean impact on decadal Atlantic climate variability revealed by sea-level observations.

    PubMed

    McCarthy, Gerard D; Haigh, Ivan D; Hirschi, Joël J-M; Grist, Jeremy P; Smeed, David A

    2015-05-28

    Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

  6. Ten years of satellite observations reveal highly variable sulphur dioxide emissions at Anatahan Volcano, Mariana Islands

    NASA Astrophysics Data System (ADS)

    McCormick, Brendan; Popp, Christoph; Andrews, Benjamin; Cottrell, Elizabeth

    2015-07-01

    Satellite remote sensing enables continuous multiyear observations of volcanic activity in remote settings. Anatahan (Mariana Islands) is a remote volcano in the western North Pacific. Available ground-based measurements of sulphur dioxide (SO2) gas emissions at Anatahan place it among thelargest volcanic SO2 sources worldwide. These ground-based measurements, however, are restricted to eruptive intervals. Anatahan's activity since 2003 has been dominated temporally by prolonged periods of quiescence. Using 10 years of satellite observations from OMI, AIRS, SCIAMACHY, and GOME-2, we report highly variable SO2 emissions within and between eruptive and quiescent intervals at Anatahan. We find close correspondence between levels of activity reported at the volcano and levels of SO2 emissions detected from space. Eruptive SO2 emission rates have a mean value of ˜6400 t d-1, but frequently are in excess of 20,000 t d-1. Conversely, SO2 emissions during quiescent intervals are below the detection limit of space-based sensors and therefore are not likely to exceed ˜300 t d-1. We show that while Anatahan occupies a quiescent state for 85% of the past 10 years, only ˜15% of total SO2 emissions over this interval occur during quiescence, with the remaining ˜85% released in short duration but intense syn-eruptive degassing. We propose that the integration of multiyear satellite data sets and activity histories are a powerful complement to targeted ground-based campaign measurements in better describing the long-term degassing behavior of remote volcanoes.

  7. Evidence of Viscoelastic Deformation following the 2011 Tohoku-oki Earthquake Revealed from Seafloor Geodetic Observation

    NASA Astrophysics Data System (ADS)

    Watanabe, S. I.; Sato, M.; Fujita, M.; Ishikawa, T.; Yokota, Y.; Ujihara, N.; Asada, A.

    2014-12-01

    The great Tohoku-oki earthquake (M9.0) occurred on 11th March, 2011 along the Japan Trench, off the Pacific coast of eastern Japan. The source region spreads over an area with a length of 500 km and a width of 200 km, almost all part of which is beneath the seafloor. We, the group of Japan Coast Guard (JCG), have continued repeated GPS-acoustic seafloor positioning after the Tohoku-oki earthquake at six seafloor sites in the offshore source region, the results of which are expected to provide information leading to better understandings of postseismic processes. In contrast to the coastal GNSS sites where trenchward-upward movements were reported, the offshore sites above the main rupture zone in the northern part of the source region exhibit landward displacements of tens of centimeters with significant subsidence from more than three years of repeated observations. At the sites above around the edge of the main rupture zone, smaller amount of trench-normal movements were found. Although the terrestrial movements were reasonably interpreted by afterslip beneath the coastal area, these offshore results are rather consistent with effects predicted from viscoelastic relaxation in the upper mantle, providing definitive evidence of its occurrence. On the other hand, a site in the southern part of the source region with relatively small coseismic slips shows not only trenchward movements with logarithmical decay with time but also significant subsidence, which imply superposition of effects from viscoelastic relaxation and afterslip. In this presentation, we report our latest observation results and discuss postseismic movements on the seafloor just above the source region for more than three years after the earthquake.

  8. Video Observations by Telepresence Reveal Two Types of Hydrothermal Venting on Kawio Barat Seamount

    NASA Astrophysics Data System (ADS)

    Butterfield, D. A.; Holden, J. F.; Shank, T. M.; Tunnicliffe, V.; Sherrin, J.; Herrera, S.; Baker, E. T.; Lovalvo, D.; Makarim, S.; Malik, M. A.; Wirasantosa, S.; Hammond, S. R.

    2010-12-01

    The INDEX-SATAL 2010 expedition began an international exploration of the seafloor in Indonesian waters using the methodology of telepresence, conducting EM302 multibeam mapping, water column CTD, and ROV high-definition video operations and sending data back to Exploration Command Centers in Indonesia and Seattle. Science observers in other locations in the US and Canada were engaged in real-time observations and interpretation of results. One mission goal was to locate hydrothermal or volcanic activity. Intense light scattering and redox potential measurements in the water column over Kawio Barat (KB)indicated a high level of hydrothermal activity, and direct video observations confirmed venting near the summit. None of the other volcanic features west of the Sangihe arc that were investigated during the mission had confirmed hydrothermal activity. ROV capabilities did not include physical sampling or temperature measurement, so our interpretation is based on visual comparison to other known sites. The steep western flank of KB from 2000 m depth to the summit (1850 m) has many areas of white and orange staining on exposed rocks, with some elemental sulfur, and broad areas covered with dark volcaniclastic sand, but no active venting was seen. KB has a summit ridge running WNW-ESE, with a major cross-cutting ridge on the western portion of the summit. Hydrothermal activity is concentrated near the eastern side of this intersection, on both the northern and southern sides of the summit ridge. Venting on the northern side of the summit ridge is characterized by intense white particle-rich fluids emanating directly from the rocky substrate with frozen flows of elemental sulfur down slope. This type of venting is visually very similar to the venting seen on NW Rota-1, an actively erupting volcano in the Mariana arc, and suggests that KB is actively releasing magmatic gases rich in sulfur dioxide to produce the elemental sulfur flows, inferred fine particulate sulfur

  9. XMM-Newton Observations of HESSJ1813-178 Reveal a Composite Supernova Remnant

    SciTech Connect

    Funk, S.; Hinton, J.A.; Moriguchi, Y.; Aharonian, F.A.; Fukui, Y.; Hofmann, W.; Horns, D.; Puehlhofer, G.; Reimer, O.; Rowell, G.; Terrier, R.; Vink, J.; Wagner, S.

    2006-11-27

    Aims--We present X-ray and {sup 12}CO(J=1-0) observations of the very-high-energy (VHE) {gamma}-ray source HESS J1813-178 with the aim of understanding the origin of the {gamma}-ray emission. Methods--High-angular resolution X-ray studies of the VHE {gamma}-ray emission region are performed using 18.6 ks of XMM-Newton data, taken on HESS J1813-178 in October 2005. Using this dataset we are able to undertake spectral and morphological studies of the X-ray emission object with greater precision than previous studies. NANTEN {sup 12}CO(J=1-0) data are used to search for correlations of the {gamma}-ray emission with molecular clouds which could act as target material for {gamma}-ray production in a hadronic scenario. Results--The NANTEN {sup 12}CO(J=1-0) observations show a giant molecular cloud of mass 2.5 x 10{sup 5} M{sub {circle_dot}} at a distance of 4 kpc in the vicinity of HESS J1813-178. Even though there is no direct positional coincidence, this giant cloud might have influenced the evolution of the {gamma}-ray source and its surroundings. The X-ray data show a highly absorbed (n{sub H} {approx} 1 x 10{sup 23} cm{sup -2}) non-thermal X-ray emitting object coincident with the previously known ASCA source AXJ1813-178 showing a compact core and an extended tail towards the north-east, located in the center of the radio shell-type Supernova remnant (SNR) G12.82-0.2. This central object shows morphological and spectral resemblance to a Pulsar Wind Nebula (PWN) and we therefore consider that this object is very likely to be a composite SNR. Nevertheless, we cannot distinguish between the scenarios in which the {gamma}-rays originate in the shell of the SNR and the one in which they originate in the central object. We discuss both scenarios in terms of a one-zone leptonic model and demonstrate, that in order to connect the core X-ray emission to the VHE {gamma}-ray emission electrons have to be accelerated to energies of at least 1 PeV. We conclude that if indeed the

  10. Dominance of Viscoelastic Relaxation after the 2011 Tohoku Earthquake Revealed By Seafloor GPS Observations

    NASA Astrophysics Data System (ADS)

    Sun, T.; Wang, K.; Hino, R.; Iinuma, T.; He, J.; Fujimoto, H.; Kido, M.; Osada, Y.; Hu, Y.

    2014-12-01

    Megathrust rupture is mostly offshore. Using land-based GPS data only, it is difficult to tell whether viscoelastic relaxation, when compared to afterslip, is important in driving post-seismic deformation immediately after the earthquake. GPS/acoustic observations, which measure the displacements of seafloor precision transponder arrays using sea surface platforms equipped with GPS antennas and acoustic transducers, were made by Japan Coast Guard and Tohoku University during and after the 2011 M 9 Tohoku earthquake. Five seafloor sites near the main rupture were reoccupied 4-10 times over the first two years after the earthquake and provide a unique opportunity to study the importance of viscoelastic relaxation. After the large coseismic seaward motion (up to ~ 31 m), the near-trench sites immediately reversed their direction to move landward, opposing the continuing seaward motion of all land sites. This landward motion (~ 30-50 cm over the first year) is faster than the plate convergence rate (8.3 cm/year) and therefore cannot be explained by the relocking of the subduction fault. Using numerical models with transient mantle rheology, we demonstrate that the fast landward motion is caused by viscoelastic relaxation of stresses induced by the asymmetric rupture of the thrust earthquake. For shallow megathrust events, the hanging wall has a lower stiffness and hence always exhibits larger coseismic seaward motion than the landward motion of the footwall. Greater tension is thus induced landward of the rupture area. As the mantle wedge undergoes viscoelastic relaxation, this tension in the upper plate drives the observed landward motion of the trench area. Tests on the effects of mantle rheology, coseismic slip distribution, and plate thickness suggest the wide presence of viscoelastic landward trench motion following large subduction earthquakes. This work indicates that afterslip models assuming a purely elastic Earth substantially overestimated or underestimated

  11. Preparation of DNA and nucleoprotein samples for AFM imaging

    PubMed Central

    Lyubchenko, Yuri L.

    2010-01-01

    Sample preparation techniques allowing reliable and reproducible imaging of DNA with various structures, topologies and complexes with proteins are reviewed. The major emphasis is given to methods utilizing chemical functionalization of mica, enabling preparation of the surfaces with required characteristics. The methods are illustrated by examples of imaging of different DNA structures. Special attention is given to the possibility of AFM to image the dynamics of DNA at the nanoscale. The capabilities of time-lapse AFM in aqueous solutions are illustrated by imaging of dynamic processes as transitions of local alternative structures (transition of DNA between H and B forms). The application of AFM to studies of protein-DNA complexes is illustrated by a few examples of imaging site-specific complexes, as well as such systems as chromatin. The time-lapse AFM studies of protein-DNA complexes including very recent advances with the use of high-speed AFM are reviewed. PMID:20864349

  12. Behavior of Solar Cycles 23 and 24 Revealed by Microwave Observations

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Yashiro, S.; Maekelae, P.; Michalek, G.; Shibasaki, K.; Hathaway, D. H.

    2012-01-01

    Using magnetic and microwave butterfly diagrams, we compare the behavior of solar polar regions to show that (1) the polar magnetic field and the microwave brightness temperature during solar minimum substantially diminished during the cycle 23/24 minimum compared to the 22/23 minimum. (2) The polar microwave brightness temperature (Tb) seems to be a good proxy for the underlying magnetic field strength (B). The analysis indicates a relationship, B = 0.0067Tb - 70, where B is in G and Tb in K. (3) Both the brightness temperature and the magnetic field strength show north-south asymmetry most of the time except for a short period during the maximum phase. (4) The rush-to-the-pole phenomenon observed in the prominence eruption (PE) activity seems to be complete in the northern hemisphere as of 2012 March. (5) The decline of the microwave brightness temperature in the north polar region to the quiet-Sun levels and the sustained PE activity poleward of 60degN suggest that solar maximum conditions have arrived at the northern hemisphere. The southern hemisphere continues to exhibit conditions corresponding to the rise phase of solar cycle 24. Key words: Sun: chromosphere Sun: coronal mass ejections (CMEs) Sun: filaments, prominences Sun: photosphere Sun: radio radiation Sun: surface magnetism

  13. BEHAVIOR OF SOLAR CYCLES 23 AND 24 REVEALED BY MICROWAVE OBSERVATIONS

    SciTech Connect

    Gopalswamy, N.; Yashiro, S.; Maekelae, P.; Michalek, G.; Shibasaki, K.; Hathaway, D. H.

    2012-05-10

    Using magnetic and microwave butterfly diagrams, we compare the behavior of solar polar regions to show that (1) the polar magnetic field and the microwave brightness temperature during solar minimum substantially diminished during the cycle 23/24 minimum compared to the 22/23 minimum. (2) The polar microwave brightness temperature (Tb) seems to be a good proxy for the underlying magnetic field strength (B). The analysis indicates a relationship, B = 0.0067Tb - 70, where B is in G and Tb in K. (3) Both the brightness temperature and the magnetic field strength show north-south asymmetry most of the time except for a short period during the maximum phase. (4) The rush-to-the-pole phenomenon observed in the prominence eruption (PE) activity seems to be complete in the northern hemisphere as of 2012 March. (5) The decline of the microwave brightness temperature in the north polar region to the quiet-Sun levels and the sustained PE activity poleward of 60{sup o}N suggest that solar maximum conditions have arrived at the northern hemisphere. The southern hemisphere continues to exhibit conditions corresponding to the rise phase of solar cycle 24.

  14. Acoustic Observation of Living Organisms Reveals the Upper Limit of the Oxygen Minimum Zone

    PubMed Central

    Bertrand, Arnaud; Ballón, Michael; Chaigneau, Alexis

    2010-01-01

    Background Oxygen minimum zones (OMZs) are expanding in the World Ocean as a result of climate change and direct anthropogenic influence. OMZ expansion greatly affects biogeochemical processes and marine life, especially by constraining the vertical habitat of most marine organisms. Currently, monitoring the variability of the upper limit of the OMZs relies on time intensive sampling protocols, causing poor spatial resolution. Methodology/Principal Findings Using routine underwater acoustic observations of the vertical distribution of marine organisms, we propose a new method that allows determination of the upper limit of the OMZ with a high precision. Applied in the eastern South-Pacific, this original sampling technique provides high-resolution information on the depth of the upper OMZ allowing documentation of mesoscale and submesoscale features (e.g., eddies and filaments) that structure the upper ocean and the marine ecosystems. We also use this information to estimate the habitable volume for the world's most exploited fish, the Peruvian anchovy (Engraulis ringens). Conclusions/Significance This opportunistic method could be implemented on any vessel geared with multi-frequency echosounders to perform comprehensive high-resolution monitoring of the upper limit of the OMZ. Our approach is a novel way of studying the impact of physical processes on marine life and extracting valid information about the pelagic habitat and its spatial structure, a crucial aspect of Ecosystem-based Fisheries Management in the current context of climate change. PMID:20442791

  15. Direct observations of ice seasonality reveal changes in climate over the past 320–570 years

    PubMed Central

    Sharma, Sapna; Magnuson, John J.; Batt, Ryan D.; Winslow, Luke A.; Korhonen, Johanna; Aono, Yasuyuki

    2016-01-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality. PMID:27113125

  16. Direct observations of ice seasonality reveal changes in climate over the past 320–570 years

    NASA Astrophysics Data System (ADS)

    Sharma, Sapna; Magnuson, John J.; Batt, Ryan D.; Winslow, Luke A.; Korhonen, Johanna; Aono, Yasuyuki

    2016-04-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality.

  17. Direct observations of ice seasonality reveal changes in climate over the past 320–570 years

    USGS Publications Warehouse

    Sharma, Sapna; Magnuson, John J.; Batt, Ryan D; Winslow, Luke; Korhonen, Johanna; Yasuyuki Aono,

    2016-01-01

    Lake and river ice seasonality (dates of ice freeze and breakup) responds sensitively to climatic change and variability. We analyzed climate-related changes using direct human observations of ice freeze dates (1443–2014) for Lake Suwa, Japan, and of ice breakup dates (1693–2013) for Torne River, Finland. We found a rich array of changes in ice seasonality of two inland waters from geographically distant regions: namely a shift towards later ice formation for Suwa and earlier spring melt for Torne, increasing frequencies of years with warm extremes, changing inter-annual variability, waning of dominant inter-decadal quasi-periodic dynamics, and stronger correlations of ice seasonality with atmospheric CO2 concentration and air temperature after the start of the Industrial Revolution. Although local factors, including human population growth, land use change, and water management influence Suwa and Torne, the general patterns of ice seasonality are similar for both systems, suggesting that global processes including climate change and variability are driving the long-term changes in ice seasonality.

  18. Offshore seismicity in the western Marmara Sea, Turkey, revealed by ocean bottom observation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yojiro; Takahashi, Narumi; Citak, Seckin; Kalafat, Doğan; Pinar, Ali; Gurbuz, Cemil; Kaneda, Yoshiyuki

    2015-09-01

    The faults' geometry and their seismic activity beneath the Marmara Sea have been under debate for a couple of decades. We used data recorded by three ocean bottom seismographs (OBSs) over a period of 3 months in 2014 to investigate the relationship of fault geometry to microseismicity under the western Marmara Sea in Turkey. We detected a seismic swarm at 13 to 20 km depth beneath the main Marmara fault (MMF), and the maximum depth of seismogenic zone was 25 km within the OBS observation area. These results provided evidence that the dip of the MMF is almost vertical and that the seismogenic zone in this region extends into the lower crust. Our analysis of past seismicity indicated that the seismic swarm we recorded is the most recent of an episodic series of seismic activity with an average recurrence interval of 2-3 years. The repetitive seismicity indicates that the MMF beneath the western Marmara Sea is coupled and that some of the accumulated strain is released every 2 to 3 years. Our study shows that OBS data can provide useful information about seismicity along the MMF, but more extensive studies using more OBSs deployed over a wider area are needed to fully understand the fault geometry and stick-slip behavior of faults under the Marmara Sea.

  19. Radial distribution of compressive waves in the solar corona revealed by Akatsuki radio occultation observations

    SciTech Connect

    Miyamoto, Mayu; Imamura, Takeshi; Ando, Hiroki; Toda, Tomoaki; Nakamura, Masato; Tokumaru, Munetoshi; Shiota, Daikou; Isobe, Hiroaki; Asai, Ayumi; Häusler, Bernd; Pätzold, Martin; Nabatov, Alexander

    2014-12-10

    Radial variations of the amplitude and the energy flux of compressive waves in the solar corona were explored for the first time using a spacecraft radio occultation technique. By applying wavelet analysis to the frequency time series taken at heliocentric distances of 1.5-20.5 R{sub S} (solar radii), quasi-periodic density disturbances were detected at almost all distances. The period ranges from 100 to 2000 s. The amplitude of the fractional density fluctuation increases with distance and reaches ∼30% around 5 R{sub S} , implying that nonlinearity of the wave field is potentially important. We further estimate the wave energy flux on the assumption that the observed periodical fluctuations are manifestations of acoustic waves. The energy flux increases with distance below ∼6 R{sub S} and seems to saturate above this height, suggesting that the acoustic waves do not propagate from the low corona but are generated in the extended corona, probably through nonlinear dissipation of Alfvén waves. The compressive waves should eventually dissipate through shock generation to heat the corona.

  20. AFM tip effect on a thin liquid film.

    PubMed

    Ledesma-Alonso, R; Legendre, D; Tordjeman, Ph

    2013-06-25

    We study the interaction between an AFM probe and a liquid film deposited over a flat substrate. We investigate the effects of the physical and geometrical parameters, with a special focus on the film thickness E, the probe radius R, and the distance D between the probe and the free surface. Deformation profiles have been calculated from the numerical simulations of the Young-Laplace equation by taking into account the probe/liquid and the liquid/substrate interactions, characterized by the Hamaker constants, Hpl and Hls. We demonstrate that the deformation of a shallow film is determined by a particular characteristic length λF = (2πγE(4)/Hls)(1/2), resulting from the balance between the capillary force (γ is the surface tension) and the van der Waals liquid/substrate attraction. For the case of a bulk liquid, the extent of the interface deformation is simply controlled by the capillary length λC = (γ/Δρg)(1/2). These trends point out two asymptotic regimes, which in turn are bounded by two characteristic film thicknesses Eg = (Hls/2πΔρg)(1/4) and Eγ = (R(2)Hls/2πγ)(1/4). For E > Eg, the bulk behavior is recovered, and for E < Eγ, we show the existence of a particular shallow film regime in which a localized tip effect is observed. This tip effect is characterized by the small magnitude of the deformation and an important restriction of its radial extent λF localized below the probe. In addition, we have found that the film thickness has a significant effect on the threshold separation distance Dmin below which the irreversible jump-to-contact process occurs: Dmin is probe radius-dependent for the bulk whereas it is film-thickness-dependent for shallow films. These results have an important impact on the optimal AFM scanning conditions.

  1. GOODS-Herschel: ultra-deep XMM-Newton observations reveal AGN/star-formation connection

    NASA Astrophysics Data System (ADS)

    Rovilos, E.; Comastri, A.; Gilli, R.; Georgantopoulos, I.; Ranalli, P.; Vignali, C.; Lusso, E.; Cappelluti, N.; Zamorani, G.; Elbaz, D.; Dickinson, M.; Hwang, H. S.; Charmandaris, V.; Ivison, R. J.; Merloni, A.; Daddi, E.; Carrera, F. J.; Brandt, W. N.; Mullaney, J. R.; Scott, D.; Alexander, D. M.; Del Moro, A.; Morrison, G.; Murphy, E. J.; Altieri, B.; Aussel, H.; Dannerbauer, H.; Kartaltepe, J.; Leiton, R.; Magdis, G.; Magnelli, B.; Popesso, P.; Valtchanov, I.

    2012-10-01

    Models of galaxy evolution assume some connection between the AGN and star formation activity in galaxies. We use the multi-wavelength information of the CDFS to assess this issue. We select the AGNs from the 3 Ms XMM-Newton survey and measure the star-formation rates of their hosts using data that probe rest-frame wavelengths longward of 20 μm, predominantly from deep 100 μm and 160 μm Herschel observations, but also from Spitzer-MIPS-70 μm. Star-formation rates are obtained from spectral energy distribution fits, identifying and subtracting an AGN component. Our sample consists of sources in the z ≈ 0.5-4 redshift range, with star-formation rates SFR ≈ 101-103 M⊙ yr-1 and stellar masses M⋆ ≈ 1010-1011.5 M⊙. We divide the star-formation rates by the stellar masses of the hosts to derive specific star-formation rates (sSFR) and find evidence for a positive correlation between the AGN activity (proxied by the X-ray luminosity) and the sSFR for themost active systems with X-ray luminosities exceeding Lx ≃ 1043 erg s-1 and redshifts z ≳ 1. We do not find evidence for such a correlation for lower luminosity systems or those at lower redshifts, consistent with previous studies. We do not find any correlation between the SFR (or the sSFR) and the X-ray absorption derived from high-quality XMM-Newton spectra either, showing that the absorption is likely to be linked to the nuclear region rather than the host, while the star-formation is not nuclear. Comparing the sSFR of the hosts to the characteristic sSFR of star-forming galaxies at the same redshift (the so-called "main sequence") we find that the AGNs reside mostly in main-sequence and starburst hosts, reflecting the AGN-sSFR connection; however the infrared selection might bias this result. Limiting our analysis to the highest X-ray luminosity AGNs (X-ray QSOs with Lx > 1044 erg s-1), we find that the highest-redshift QSOs (with z ≳ 2) reside predominantly in starburst hosts, with an average s

  2. Hydration effects on gypsum dissolution revealed by in situ nanoscale atomic force microscopy observations

    NASA Astrophysics Data System (ADS)

    Burgos-Cara, A.; Putnis, C. V.; Rodriguez-Navarro, C.; Ruiz-Agudo, E.

    2016-04-01

    Recent work has suggested that the rates of mineral dissolution in aqueous solutions are dependent on the kinetics of dehydration of the ions building the crystal. Dehydration kinetics will be ultimately determined by the competition between ion-water and water-water interactions, which can be significantly modified by the presence of background ions in solution. At low ionic strength, the effect of electrolytes on ion-water (electrostatic) interactions will dominate (Kowacz et al., 2007). By performing macroscopic and in situ, microscopic (atomic force microscopy) dissolution experiments, the effect of background electrolytes on the dissolution kinetics of gypsum (CaSO4·2H2O) {0 1 0} cleavage surfaces is tested at constant, low ionic strength (IS = 0.05) and undersaturation (saturation index, SI = -0.045). Dissolution rates are systematically lower in the presence of 1:1 background electrolytes than in an electrolyte-free solution, regardless of the nature of the electrolyte tested. We hypothesize that stabilization of the hydration shell of calcium by the presence of background ions can explain this result, based on the observed correlations in dissolution rates with the ionic surface tension increment of the background ion in solution. Stabilization of the cation hydration shell should favor dissolution. However, in the case of strongly hydrated ions such as Ca2+, this has a direct entropic effect that reduces the overall ΔG of the system, so that dissolution is energetically less favorable. Overall, these results provide new evidence that supports cation dehydration being the rate-controlling step for gypsum dissolution, as proposed for other minerals such as barite, dolomite and calcite.

  3. Jupiter's Deep Cloud Structure Revealed Using Keck Observations of Spectrally Resolved Line Shapes

    NASA Technical Reports Server (NTRS)

    Bjoraker, G. L.; Wong, M.H.; de Pater, I.; Adamkovics, M.

    2015-01-01

    Technique: We present a method to determine the pressure at which significant cloud opacity is present between 2 and 6 bars on Jupiter. We use: a) the strength of a Fraunhofer absorption line in a zone to determine the ratio of reflected sunlight to thermal emission, and b) pressure- broadened line profiles of deuterated methane (CH3D) at 4.66 meters to determine the location of clouds. We use radiative transfer models to constrain the altitude region of both the solar and thermal components of Jupiter's 5-meter spectrum. Results: For nearly all latitudes on Jupiter the thermal component is large enough to constrain the deep cloud structure even when upper clouds are present. We find that Hot Spots, belts, and high latitudes have broader line profiles than do zones. Radiative transfer models show that Hot Spots in the North and South Equatorial Belts (NEB, SEB) typically do not have opaque clouds at pressures greater than 2 bars. The South Tropical Zone (STZ) at 32 degrees South has an opaque cloud top between 4 and 5 bars. From thermochemical models this must be a water cloud. We measured the variation of the equivalent width of CH3D with latitude for comparison with Jupiter's belt-zone structure. We also constrained the vertical profile of H2O in an SEB Hot Spot and in the STZ. The Hot Spot is very dry for a probability less than 4.5 bars and then follows the H2O profile observed by the Galileo Probe. The STZ has a saturated H2O profile above its cloud top between 4 and 5 bars.

  4. CHARACTERIZING THE YOUNGEST HERSCHEL-DETECTED PROTOSTARS. I. ENVELOPE STRUCTURE REVEALED BY CARMA DUST CONTINUUM OBSERVATIONS

    SciTech Connect

    Tobin, John J.; Stutz, Amelia M.; Henning, Thomas; Ragan, Sarah E.; Megeath, S. Thomas; Fischer, William J.; Ali, Babar; Stanke, Thomas; Manoj, P.; Calvet, Nuria; Hartmann, Lee

    2015-01-10

    We present Combined Array for Research in Millimeter-wave Astronomy 2.9 mm dust continuum emission observations of a sample of 14 Herschel-detected Class 0 protostars in the Orion A and B molecular clouds, drawn from the PACS Bright Red Sources (PBRS) sample. These objects are characterized by very red 24-70 μm colors and prominent submillimeter emission, suggesting that they are very young Class 0 protostars embedded in dense envelopes. We detect all of the PBRS in 2.9 mm continuum emission and emission from four protostars and one starless core in the fields toward the PBRS; we also report one new PBRS source. The ratio of 2.9 mm luminosity to bolometric luminosity is higher by a factor of ∼5 on average, compared to other well-studied protostars in the Perseus and Ophiuchus clouds. The 2.9 mm visibility amplitudes for 6 of the 14 PBRS are very flat as a function of uv distance, with more than 50% of the source emission arising from radii <1500 AU. These flat visibility amplitudes are most consistent with spherically symmetric envelope density profiles with ρ ∝ R {sup –2.5}. Alternatively, there could be a massive unresolved structure like a disk or a high-density inner envelope departing from a smooth power law. The large amount of mass on scales <1500 AU (implying high average central densities) leads us to suggest that that the PBRS with flat visibility amplitude profiles are the youngest PBRS and may be undergoing a brief phase of high mass infall/accretion and are possibly among the youngest Class 0 protostars. The PBRS with more rapidly declining visibility amplitudes still have large envelope masses, but could be slightly more evolved.

  5. Formation of hierarchical molecular assemblies from poly(oxypropylene)-segmented amido acids under AFM tapping.

    PubMed

    Lin, Jiang-Jen; Tsai, Wei-Cheng; Wang, Chi-He

    2007-04-10

    Molecular self-aligning of amphiphilic molecules into bundles with a constant width of 7-13 nm was observed under tapping-mode atomic force microscopy (TM-AFM). The requisite amphiphile, a poly(oxypropylene)-trimellitic amido acid sodium salt, is constituted of a symmetric amido acid structure with potential noncovalent forces of ionic charges, hydrogen bonds, pi-pi aromatic stacking, and hydrophobic interactions for intermolecular interaction. The amphiphiles are able to self-align into orderly hierarchical assemblies after simply being dissolved in water and dried under spin-coated evaporation. Under the TM-AFM tapping process, the bundles increased their length from an initial 20 to 600 nm. A sequential TM-AFM scanning and interval heating process was designed to probe the morphological transformations from the molecular bundles to lengthy strips (nearly micrometer scale) and to columns (with 5-7 nm spacing between the parallel strips). The formation of hierarchical arrays via molecular stretching, aligning, and connecting to each other was simultaneously observed and accelerated under the TM-AFM vibration energy. The molecular self-alignment caused by vibrations is envisioned to be a potential methodology for manipulating molecules into assembled templates, sensors, and optoelectronic devices.

  6. Manufacturing process of nanofluidics using afm probe

    NASA Astrophysics Data System (ADS)

    Karingula, Varun Kumar

    A new process for fabricating a nano fluidic device that can be used in medical application is developed and demonstrated. Nano channels are fabricated using a nano tip in indentation mode on AFM (Atomic Force Microscopy). The nano channels are integrated between the micro channels and act as a filter to separate biomolecules. Nano channels of 4 to7 m in length, 80nm in width, and at varying depths from 100nm to 850 nm allow the resulting device to separate selected groups of lysosomes and other viruses. Sharply developed vertical micro channels are produced from a deep reaction ion etching followed by deposition of different materials, such as gold and polymers, on the top surface, allowing the study of alternative ways of manufacturing a nanofluidic device. PDMS (Polydimethylsiloxane) bonding is performed to close the top surface of the device. An experimental setup is used to test and validate the device by pouring fluid through the channels. A detailed cost evaluation is conducted to compare the economical merits of the proposed process. It is shown that there is a 47:7% manufacturing time savings and a 60:6% manufacturing cost savings.

  7. Microrheology using a custom-made AFM

    NASA Astrophysics Data System (ADS)

    Kosgodagan Acharige, Sebastien; Benzaquen, Michael; Steinberger, Audrey

    In the past few years, a new method was developed to measure local properties of liquids (X. Xiong et al., Phys. Rev. E 80, 2009). This method consists of gluing a micron-sized glass fiber at the tip of an AFM cantilever and probing the liquid with it. In ENS Lyon, this method was perfected (C. Devailly et al., EPL, 106 5, 2014) with the help of an interferometer developped in the same laboratory (L. Bellon et al., Opt. Commun. 207 49, 2002 and P. Paolino et al., Rev. Sci. Instrum. 84, 2013), which background noise can reach 10-14 m /√{ Hz } . This method allows us to measure a wide range of viscosities (1 mPa . s to 500 mPa . s) of transparent and opaque fluids using a small sample volume ( 5 mL). In this presentation, I will briefly describe the interferometer developped in ENS Lyon, then explain precisely the microrheology measurements and then compare the experimental results to a model developped by M. Benzaquen. This work is supported financially by the ANR project NANOFLUIDYN (Grant Number ANR-13-BS10-0009).

  8. An AFM-based pit-measuring method for indirect measurements of cell-surface membrane vesicles

    SciTech Connect

    Zhang, Xiaojun; Chen, Yuan; Chen, Yong

    2014-03-28

    Highlights: • Air drying induced the transformation of cell-surface membrane vesicles into pits. • An AFM-based pit-measuring method was developed to measure cell-surface vesicles. • Our method detected at least two populations of cell-surface membrane vesicles. - Abstract: Circulating membrane vesicles, which are shed from many cell types, have multiple functions and have been correlated with many diseases. Although circulating membrane vesicles have been extensively characterized, the status of cell-surface membrane vesicles prior to their release is less understood due to the lack of effective measurement methods. Recently, as a powerful, micro- or nano-scale imaging tool, atomic force microscopy (AFM) has been applied in measuring circulating membrane vesicles. However, it seems very difficult for AFM to directly image/identify and measure cell-bound membrane vesicles due to the similarity of surface morphology between membrane vesicles and cell surfaces. Therefore, until now no AFM studies on cell-surface membrane vesicles have been reported. In this study, we found that air drying can induce the transformation of most cell-surface membrane vesicles into pits that are more readily detectable by AFM. Based on this, we developed an AFM-based pit-measuring method and, for the first time, used AFM to indirectly measure cell-surface membrane vesicles on cultured endothelial cells. Using this approach, we observed and quantitatively measured at least two populations of cell-surface membrane vesicles, a nanoscale population (<500 nm in diameter peaking at ∼250 nm) and a microscale population (from 500 nm to ∼2 μm peaking at ∼0.8 μm), whereas confocal microscopy only detected the microscale population. The AFM-based pit-measuring method is potentially useful for studying cell-surface membrane vesicles and for investigating the mechanisms of membrane vesicle formation/release.

  9. AFM imaging of fenestrated liver sinusoidal endothelial cells.

    PubMed

    Braet, F; Wisse, E

    2012-12-01

    Each microscope with its dedicated sample preparation technique provides the investigator with a specific set of data giving an instrument-determined (or restricted) insight into the structure and function of a tissue, a cell or parts thereof. Stepwise improvements in existing techniques, both instrumental and preparative, can sometimes cross barriers in resolution and image quality. Of course, investigators get really excited when completely new principles of microscopy and imaging are offered in promising new instruments, such as the AFM. The present paper summarizes a first phase of studies on the thin endothelial cells of the liver. It describes the preparation-dependent differences in AFM imaging of these cells after isolation. Special point of interest concerned the dynamics of the fenestrae, thought to filter lipid-carrying particles during their transport from the blood to the liver cells. It also describes the attempts to image the details of these cells when alive in cell cultures. It explains what physical conditions, mainly contributed to the scanning stylus, are thought to play a part in the limitations in imaging these cells. The AFM also offers promising specifications to those interested in cell surface details, such as membrane-associated structures, receptors, coated pits, cellular junctions and molecular aggregations or domains. The AFM also offers nano-manipulation possibilities, strengths and elasticity measurements, force interactions, affinity measurements, stiffness and other physical aspects of membranes and cytoskeleton. The potential for molecular approaches is there. New developments in cantilever construction and computer software promise to bring real time video imaging to the AFM. Home made accessories for the first generation of AFM are now commodities in commercial instruments and make the life of the AFM microscopist easier. Also, the combination of different microscopies, such as AFM and TEM, or AFM and SEM find their way to the

  10. The diversity and structure of marine protists in the coastal waters of China revealed by morphological observation and 454 pyrosequencing

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Song, Shuqun; Chen, Tiantian; Li, Caiwen

    2017-04-01

    Pyrosequencing of the 18S rRNA gene has been widely adopted to study the eukaryotic diversity in various types of environments, and has an advantage over traditional morphology methods in exploring unknown microbial communities. To comprehensively assess the diversity and community composition of marine protists in the coastal waters of China, we applied both morphological observations and high-throughput sequencing of the V2 and V3 regions of 18S rDNA simultaneously to analyze samples collected from the surface layer of the Yellow and East China Seas. Dinoflagellates, diatoms and ciliates were the three dominant protistan groups as revealed by the two methods. Diatoms were the first dominant protistan group in the microscopic observations, with Skeletonema mainly distributed in the nearshore eutrophic waters and Chaetoceros in higher temperature and higher pH waters. The mixotrophic dinoflagellates, Gymnodinium and Gyrodinium, were more competitive in the oligotrophic waters. The pyrosequencing method revealed an extensive diversity of dinoflagellates. Chaetoceros was the only dominant diatom group in the pyrosequencing dataset. Gyrodinium represented the most abundant reads and dominated the offshore oligotrophic protistan community as they were in the microscopic observations. The dominance of parasitic dinoflagellates in the pyrosequencing dataset, which were overlooked in the morphological observations, indicates more attention should be paid to explore the potential role of this group. Both methods provide coherent clustering of samples. Nutrient levels, salinity and pH were the main factors influencing the distribution of protists. This study demonstrates that different primer pairs used in the pyrosequencing will indicate different protistan community structures. A suitable marker may reveal more comprehensive composition of protists and provide valuable information on environmental drivers.

  11. High-speed AFM of human chromosomes in liquid

    NASA Astrophysics Data System (ADS)

    Picco, L. M.; Dunton, P. G.; Ulcinas, A.; Engledew, D. J.; Hoshi, O.; Ushiki, T.; Miles, M. J.

    2008-09-01

    Further developments of the previously reported high-speed contact-mode AFM are described. The technique is applied to the imaging of human chromosomes at video rate both in air and in water. These are the largest structures to have been imaged with high-speed AFM and the first imaging in liquid to be reported. A possible mechanism that allows such high-speed contact-mode imaging without significant damage to the sample is discussed in the context of the velocity dependence of the measured lateral force on the AFM tip.

  12. Effect of chain lengths of PEO-PPO-PEO on small unilamellar liposome morphology and stability: an AFM investigation.

    PubMed

    Liang, Xuemei; Mao, Guangzhao; Ng, K Y Simon

    2005-05-01

    The morphology and stability of small unilamellar egg yolk phosphatidylcholine (EggPC) liposomes modified with the Pluronic copolymer (poly (oxyethylene)-poly (oxypropylene)-poly (oxyethylene) (PEO-PPO-PEO)) with different compositions on mica surface have been investigated using atomic force microscopy. Morphology studies reveal significant morphological changes of liposomes upon incorporating the Pluronic copolymer. Bilayers are observed for Pluronic with small hydrophilic (PEO) chain lengths such as L81 [(PEO)2(PPO)40(PEO)2] and L121 [(PEO)4(PPO)60(PEO)4]; bilayer and vesicle coexistence is observed for P85 [(PEO)26(PPO)39.5(PEO)26] and F87 [(PEO)61.1(PPO)39.7(PEO)61.1]; and stable vesicles are observed for F88 [(PEO)103.5(PPO)39.2(PEO)103.5], F127 [(PEO)100(PPO)65(PEO)100], and F108 [(PEO)132.6(PPO)50.3(PEO)132.6]. The micromechanical properties of Pluronic-modified EggPC vesicles were studied by analyzing AFM approaching force curve. The bending modulus (k(c)) of the Pluronic-modified EggPC vesicles increased several-fold compared with that of the pure EggPC vesicles. The significant difference is due to the enhanced rigidity of the EggPC vesicles as a result of the incorporation of PPO molecules and PEO chains. Based on the analysis of onset point by AFM and diameters of vesicles by light scattering, it was concluded that the favorable model to describe the polymer-bilayer interaction is the membrane-spanning model.

  13. BOREAS AFM-12 1-km AVHRR Seasonal Land Cover Classification

    NASA Technical Reports Server (NTRS)

    Steyaert, Lou; Hall, Forrest G.; Newcomer, Jeffrey A. (Editor); Knapp, David E. (Editor); Loveland, Thomas R.; Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-12 team's efforts focused on regional scale Surface Vegetation and Atmosphere (SVAT) modeling to improve parameterization of the heterogeneous BOREAS landscape for use in larger scale Global Circulation Models (GCMs). This regional land cover data set was developed as part of a multitemporal one-kilometer Advanced Very High Resolution Radiometer (AVHRR) land cover analysis approach that was used as the basis for regional land cover mapping, fire disturbance-regeneration, and multiresolution land cover scaling studies in the boreal forest ecosystem of central Canada. This land cover classification was derived by using regional field observations from ground and low-level aircraft transits to analyze spectral-temporal clusters that were derived from an unsupervised cluster analysis of monthly Normalized Difference Vegetation Index (NDVI) image composites (April-September 1992). This regional data set was developed for use by BOREAS investigators, especially those involved in simulation modeling, remote sensing algorithm development, and aircraft flux studies. Based on regional field data verification, this multitemporal one-kilometer AVHRR land cover mapping approach was effective in characterizing the biome-level land cover structure, embedded spatially heterogeneous landscape patterns, and other types of key land cover information of interest to BOREAS modelers.The land cover mosaics in this classification include: (1) wet conifer mosaic (low, medium, and high tree stand density), (2) mixed coniferous-deciduous forest (80% coniferous, codominant, and 80% deciduous), (3) recent visible bum, vegetation regeneration, or rock outcrops-bare ground-sparsely vegetated slow regeneration bum (four classes), (4) open water and grassland marshes, and (5) general agricultural land use/ grasslands (three classes). This land cover mapping approach did not detect small subpixel-scale landscape

  14. Comparative quantification and statistical analysis of η′ and η precipitates in aluminum alloy AA7075-T651 by TEM and AFM

    SciTech Connect

    Garcia-Garcia, Adrian Luis Dominguez-Lopez, Ivan Lopez-Jimenez, Luis Barceinas-Sanchez, J.D. Oscar

    2014-01-15

    Quantification of nanometric precipitates in metallic alloys has been traditionally performed using transmission electron microscopy, which is nominally a low throughput technique. This work presents a comparative study of quantification of η′ and η precipitates in aluminum alloy AA7075-T651 using transmission electron microscopy (TEM) and non-contact atomic force microscopy (AFM). AFM quantification was compared with 2-D stereological results reported elsewhere. Also, a method was developed, using specialized software, to characterize nanometric size precipitates observed in dark-field TEM micrographs. Statistical analysis of the quantification results from both measurement techniques supports the use of AFM for precipitate characterization. Once the precipitate stoichiometry has been determined by appropriate analytical techniques like TEM, as it is the case for η′ and η in AA7075-T651, the relative ease with which specimens are prepared for AFM analysis could be advantageous in product and process development, and quality control, where a large number of samples are expected for analysis on a regular basis. - Highlights: • Nanometric MgZn{sub 2} precipitates in AA7075-T651 were characterized using AFM and TEM. • Phase-contrast AFM was used to differentiate metal matrix from MgZn{sub 2} precipitates. • TEM and AFM micrographs were analyzed using commercially available software. • AFM image analysis and TEM 2-D stereology render statistically equivalent results.

  15. Introduction to atomic force microscopy (AFM) in biology.

    PubMed

    Goldsbury, Claire S; Scheuring, Simon; Kreplak, Laurent

    2009-11-01

    The atomic force microscope (AFM) has the unique capability of imaging biological samples with molecular resolution in buffer solution. In addition to providing topographical images of surfaces with nanometer- to angstrom-scale resolution, forces between single molecules and mechanical properties of biological samples can be investigated from the nanoscale to the microscale. Importantly, the measurements are made in buffer solutions, allowing biological samples to "stay alive" within a physiological-like environment while temporal changes in structure are measured-e.g., before and after addition of chemical reagents. These qualities distinguish AFM from conventional imaging techniques of comparable resolution, e.g., electron microscopy (EM). This unit provides an introduction to AFM on biological systems and describes specific examples of AFM on proteins, cells, and tissues. The physical principles of the technique and methodological aspects of its practical use and applications are also described.

  16. AFM AND XPS Characterization of Zinc-Aluminum Alloy Coatings with Attention to Surface Dross and Flow Lines

    NASA Astrophysics Data System (ADS)

    Harding, Felipe A.; Alarcon, Nelson A.; Toledo, Pedro G.

    Surfaces of various zinc-aluminum alloy (Zn-Al) coated steel samples are studied with attention to foreign surface dross by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS/ESCA). AFM topographic maps of zinc-aluminum alloy surfaces free of dross reveal the perfect nanoscale details of two kinds of dendrites: branched and globular. In all magnifications the dendrites appear smooth and, in general, very clean. XPS analysis of the extreme surface of a Zn-Al sample reveals Al, Zn, Si and O as the main components. The XPS results show no segregation or separation of phases other than those indicated by the ternary Al-Zn-Si diagram. For surfaces of Zn-Al plagued with impurities, high resolution AFM topographic maps reveal three situations: (1) areas with well-defined dendrites, relatively free of dross; (2) areas with small, millimeter-sized black spots known as dross; and (3) areas with large black stains, known as flow lines. Dendrite deformation and dross accumulation increase notably in the neighborhood, apparently clean to the naked eye, of dross or flow lines. XPS results of areas with dross and flow lines indicate unacceptable high concentration of Si and important Si phase separation. These results, in the light of AFM work, reveal that dross and flow lines are a consequence of a high local concentration of Si from high melting point silica and silicate impurities in the Zn-Al alloy source.

  17. Molecular dynamics study on the mechanism of AFM-based nanoscratching process with water-layer lubrication

    NASA Astrophysics Data System (ADS)

    Ren, Jiaqi; Zhao, Jinsheng; Dong, Zeguang; Liu, Pinkuan

    2015-08-01

    The atomic force microscopy (AFM) based direct nanoscratching has been thoroughly studied but the mechanism of nanoscratching with water-layer lubrication is yet to be well understood. In current study, three-dimensional molecular dynamics (MD) simulations are conducted to evaluate the effects of the water-layer lubrication on the AFM-based nanoscratching process on monocrystalline copper. Comparisons of workpiece deformation, scratching forces, and friction coefficients are made between the water-lubricated and dry scratching under various thickness of water layer, scratching depth and scratching velocity. Simulation results reveal that the water layer has positive impact on the surface quality and significant influence on the scratching forces (normal forces and tangential forces). The friction coefficients of the tip in water-lubricated nanoscratching are significantly bigger than those in the dry process. Our simulation results shed lights on a promising AFM-based nanofabrication method, which can assist to get nanoscale surface morphologies with higher quality than traditional approaches.

  18. Complex mean circulation over the inner shelf south of Martha's Vineyard revealed by observations and a high-resolution model

    USGS Publications Warehouse

    Ganju, Neil K.; Lentz, Steven J.; Kirincich, Anthony R.; Farrar, J. Thomas

    2011-01-01

    Inner-shelf circulation is governed by the interaction between tides, baroclinic forcing, winds, waves, and frictional losses; the mean circulation ultimately governs exchange between the coast and ocean. In some cases, oscillatory tidal currents interact with bathymetric features to generate a tidally rectified flow. Recent observational and modeling efforts in an overlapping domain centered on the Martha's Vineyard Coastal Observatory (MVCO) provided an opportunity to investigate the spatial and temporal complexity of circulation on the inner shelf. ADCP and surface radar observations revealed a mean circulation pattern that was highly variable in the alongshore and cross-shore directions. Nested modeling incrementally improved representation of the mean circulation as grid resolution increased and indicated tidal rectification as the generation mechanism of a counter-clockwise gyre near the MVCO. The loss of model skill with decreasing resolution is attributed to insufficient representation of the bathymetric gradients (Δh/h), which is important for representing nonlinear interactions between currents and bathymetry. The modeled momentum balance was characterized by large spatial variability of the pressure gradient and horizontal advection terms over short distances, suggesting that observed inner-shelf momentum balances may be confounded. Given the available observational and modeling data, this work defines the spatially variable mean circulation and its formation mechanism—tidal rectification—and illustrates the importance of model resolution for resolving circulation and constituent exchange near the coast. The results of this study have implications for future observational and modeling studies near the MVCO and other inner-shelf locations with alongshore bathymetric variability.

  19. BOREAS AFM-03-NCAR Electra 1994 Aircraft Sounding Data

    NASA Technical Reports Server (NTRS)

    Lenschow, Donald H.; Oncley, Steven P.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-3 team used the National Center for Atmospheric Research's (NCAR) Electra aircraft to make sounding measurements to study the planetary boundary layer using in situ and remote-sensing measurements. Measurements were made of wind speed and direction, air pressure and temperature, potential temperature, dewpoint, mixing ratio of H, O, CO, concentration, and ozone concentration. Twenty-five research missions were flown over the Northern Study Area (NSA), Southern Study Area (SSA), and the transect during BOREAS Intensive Field Campaigns (IFCs) 1, 2, and 3 during 1994. All missions had from four to ten soundings through the top of the planetary boundary layer. This sounding data set contains all of the in situ vertical profiles through the boundary layer top that were made (with the exception of 'porpoise' maneuvers). Data were recorded in one-second time intervals. These data are stored in tabular ASCII files. The NCAR Electra 1994 aircraft sounding data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  20. A phase 1 study of the bispecific anti-CD30/CD16A antibody construct AFM13 in patients with relapsed or refractory Hodgkin lymphoma

    PubMed Central

    Rothe, Achim; Sasse, Stephanie; Topp, Max S.; Eichenauer, Dennis A.; Hummel, Horst; Reiners, Katrin S.; Dietlein, Markus; Kuhnert, Georg; Kessler, Joerg; Buerkle, Carolin; Ravic, Miroslav; Knackmuss, Stefan; Marschner, Jens-Peter; Pogge von Strandmann, Elke; Borchmann, Peter

    2015-01-01

    AFM13 is a bispecific, tetravalent chimeric antibody construct (TandAb) designed for the treatment of CD30-expressing malignancies. AFM13 recruits natural killer (NK) cells via binding to CD16A as immune effector cells. In this phase 1 dose-escalation study, 28 patients with heavily pretreated relapsed or refractory Hodgkin lymphoma received AFM13 at doses of 0.01 to 7 mg/kg body weight. Primary objectives were safety and tolerability. Secondary objectives included pharmacokinetics, antitumor activity, and pharmacodynamics. Adverse events were generally mild to moderate. The maximum tolerated dose was not reached. Pharmacokinetics assessment revealed a half-life of up to 19 hours. Three of 26 evaluable patients achieved partial remission (11.5%) and 13 patients achieved stable disease (50%), with an overall disease control rate of 61.5%. AFM13 was also active in brentuximab vedotin–refractory patients. In 13 patients who received doses of ≥1.5 mg/kg AFM13, the overall response rate was 23% and the disease control rate was 77%. AFM13 treatment resulted in a significant NK-cell activation and a decrease of soluble CD30 in peripheral blood. In conclusion, AFM13 represents a well-tolerated, safe, and active targeted immunotherapy of Hodgkin lymphoma. A phase 2 study is currently planned to optimize the dosing schedule in order to further improve the therapeutic efficacy. This phase 1 study was registered at www.clinicaltrials.gov as #NCT01221571. PMID:25887777

  1. Meteoroid Fragmentation as Revealed in Head- and Trail-Echoes Observed with the Arecibo UHF and VHF Radars

    NASA Technical Reports Server (NTRS)

    Mathews, J. D.; Malhorta, A.

    2011-01-01

    We report recent 46.8/430 MHz (VHF/UHF) radar meteor observations at Arecibo Observatory (AO) that reveal many previously unreported features in the radar meteor return - including flare-trails at both UHF and VHF - that are consistent with meteoroid fragmentation. Signature features of fragmentation include strong intra-pulse and pulse-to-pulse fading as the result of interference between or among multiple meteor head-echo returns and between head-echo and impulsive flare or "point" trail-echoes. That strong interference fading occurs implies that these scatterers exhibit well defined phase centers and are thus small compared with the wavelength. These results are consistent with and offer advances beyond a long history of optical and radar meteoroid fragmentation studies. Further, at AO, fragmenting and flare events are found to be a large fraction of the total events even though these meteoroids are likely the smallest observed by the major radars. Fragmentation is found to be a major though not dominate component of the meteors observed at other HPLA radars that are sensitive to larger meteoroids.

  2. Tip in-light on: Advantages, challenges, and applications of combining AFM and Raman microscopy on biological samples.

    PubMed

    Prats-Mateu, Batirtze; Gierlinger, Notburga

    2017-01-01

    Scanning probe microscopies and spectroscopies, especially AFM and Confocal Raman microscopy are powerful tools to characterize biological materials. They are both non-destructive methods and reveal mechanical and chemical properties on the micro and nano-scale. In the last years the interest for increasing the lateral resolution of optical and spectral images has driven the development of new technologies that overcome the diffraction limit of light. The combination of AFM and Raman reaches resolutions of about 50-150 nm in near-field Raman and 1.7-50 nm in tip enhanced Raman spectroscopy (TERS) and both give a molecular information of the sample and the topography of the scanned surface. In this review, the mentioned approaches are introduced, the main advantages and problems for application on biological samples discussed and some examples for successful experiments given. Finally the potential of colocated AFM and Raman measurements is shown on a case study of cellulose-lignin films: the topography structures revealed by AFM can be related to a certain chemistry by the colocated Raman scan and additionally the mechanical properties be revealed by using the digital pulsed force mode. Microsc. Res. Tech. 80:30-40, 2017. © 2016 Wiley Periodicals, Inc.

  3. Tip in–light on: Advantages, challenges, and applications of combining AFM and Raman microscopy on biological samples

    PubMed Central

    Gierlinger, Notburga

    2016-01-01

    Abstract Scanning probe microscopies and spectroscopies, especially AFM and Confocal Raman microscopy are powerful tools to characterize biological materials. They are both non‐destructive methods and reveal mechanical and chemical properties on the micro and nano‐scale. In the last years the interest for increasing the lateral resolution of optical and spectral images has driven the development of new technologies that overcome the diffraction limit of light. The combination of AFM and Raman reaches resolutions of about 50–150 nm in near‐field Raman and 1.7–50 nm in tip enhanced Raman spectroscopy (TERS) and both give a molecular information of the sample and the topography of the scanned surface. In this review, the mentioned approaches are introduced, the main advantages and problems for application on biological samples discussed and some examples for successful experiments given. Finally the potential of colocated AFM and Raman measurements is shown on a case study of cellulose‐lignin films: the topography structures revealed by AFM can be related to a certain chemistry by the colocated Raman scan and additionally the mechanical properties be revealed by using the digital pulsed force mode. Microsc. Res. Tech. 80:30–40, 2017. © 2016 Wiley Periodicals, Inc. PMID:27514318

  4. Geometry and Characteristics of the Heliosheath Revealed in the First Five Years of Interstellar Boundary Explorer Observations

    NASA Astrophysics Data System (ADS)

    Zirnstein, E. J.; Funsten, H. O.; Heerikhuisen, J.; McComas, D. J.; Schwadron, N. A.; Zank, G. P.

    2016-07-01

    We investigate and interpret the geometry and characteristics of the inner heliosheath (IHS) plasma and their impact on the heliotail structure as observed in energetic neutral atom (ENA) maps acquired during the first 5 yr of Interstellar Boundary Explorer (IBEX) observations. In particular, IBEX observations of the heliotail reveal distinct, localized emission features (lobes) that provide a rich set of information about the properties and evolution of the heliosheath plasma downstream of the termination shock (TS). We analyze the geometry of the heliotail lobes and find that the plane intersecting the port and starboard heliotail lobe centers is ˜6° from the solar equatorial plane, and the plane intersecting the north and south heliotail lobe centers is ˜90° from the solar equatorial plane, both indicating strong correlation with the fast-slow solar wind asymmetry, and thus reflecting the structure of the IHS flow around the Sun. We also analyze the key parameters and processes that form and shape the port and starboard lobes, which are distinctly different from the north and south lobes. By comparing IBEX ENA observations with results from a simplistic flow model of the heliosphere and a multicomponent description for pickup ions (PUIs) in the IHS, we find that the port and starboard lobe formation is driven by a thin IHS, large nose-tail asymmetry of the distance to the TS (and consequently, a large nose-tail asymmetry of the relative abundance of PUIs at the TS) and the energy-dependent removal of PUIs by charge exchange in the IHS.

  5. Low tip damage AFM technique development for nano structures characterization

    NASA Astrophysics Data System (ADS)

    Liu, Biao; Wang, Charles C.; Huang, Po-Fu; Uritsky, Yuri

    2010-06-01

    Ambient dynamic mode (tapping mode or intermittent-contact mode) AFM imaging has been used extensively for the characterization of the topography of nano structures. However, the results are beset with artifacts, because hard tapping of the AFM tip on sample surface usually causes premature tip damage. Through careful study of the cantilever amplitude and phase signals as functions of tip-to-sample distance, principle of non-contact AFM operation was discovered to enable high resolution and low tip damage AFM image acquisition [1, 2]. However, current study discovers that the conventional way of acquiring amplitude and phase versus distance curves gives erroneous non-contact operating range, because the tip gets damaged during the data acquisition process. A new technique is developed to reliably map the operating parameters of an intact tip that ensures the AFM be operated with the correct non-contact settings. Two examples are given to illustrate the successful applications of this new technique. The first example involves the size characterization of polystyrene latex (PSL) nano particles used for light scattering tool calibration. The second example is the development of robust recipes for the measurement of the depth of phase-shift mask trenches.

  6. Characterization of the polycaprolactone melt crystallization: complementary optical microscopy, DSC, and AFM studies.

    PubMed

    Speranza, V; Sorrentino, A; De Santis, F; Pantani, R

    2014-01-01

    The first stages of the crystallization of polycaprolactone (PCL) were studied using several techniques. The crystallization exotherms measured by differential scanning calorimetry (DSC) were analyzed and compared with results obtained by polarized optical microscopy (POM), rheology, and atomic force microscope (AFM). The experimental results suggest a strong influence of the observation scale. In particular, the AFM, even if limited on time scale, appears to be the most sensitive technique to detect the first stages of crystallization. On the contrary, at least in the case analysed in this work, rheology appears to be the least sensitive technique. DSC and POM provide closer results. This suggests that the definition of induction time in the polymer crystallization is a vague concept that, in any case, requires the definition of the technique used for its characterization.

  7. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-01

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M2 provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of ‑25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches ‑60.7 × 10‑6/K over T = 231–338 K and 0.6 × 10‑6/K over T = 175–231 K during cooling.

  8. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition.

    PubMed

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-30

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M(2) provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of -25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches -60.7 × 10(-6)/K over T = 231-338 K and 0.6 × 10(-6)/K over T = 175-231 K during cooling.

  9. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition

    PubMed Central

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-01

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M2 provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of −25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches −60.7 × 10−6/K over T = 231–338 K and 0.6 × 10−6/K over T = 175–231 K during cooling. PMID:28134355

  10. Enzymatic nanolithography of FRET peptide layer using V8 protease-immobilized AFM probe.

    PubMed

    Nakamura, Chikashi; Miyamoto, Chie; Obataya, Ikuo; Takeda, Seiji; Yabuta, Masayuki; Miyake, Jun

    2007-04-15

    In our study, a method based on Enzymatic nanolithography was successfully performed in a buffered solution using Staphylococcal serine V8 protease and AFM. To estimate the lithographing activity of the protease immobilized on the AFM tip to peptides immobilized on a substrate, we designed fluorescence resonance energy transfer (FRET) peptides as reporter peptides that showed enzymatic action specific to the V8 protease. When the protease digested the reporter peptide a quencher residue was released from the peptide and resulted in the appearance of fluorescence. In the designed 9-mer peptides, TAMRA functioned as a good quencher for FAM. When the fluorescence resonance energy transfer peptides immobilized on a glass substrate were hydrolyzed by V8 protease at the C-terminal of glutamic acid, fluorescence of a reporter dye was observed because of the release of a quencher from the substrate. After contacting and lateral scanning of the protease-immobilized AFM tip to the reporter peptide layer, a fluorescent area was observed by imaging using total internal refection fluorescence microscopy (TIRFM). The increment of fluorescence intensity of the digested peptide indicates the performance of lithography. Lithographing rates increased in inverse relation to scanning rates of the probe. The maximum limit of the scanning rate, i.e., that was too fast to permit cutting of the peptide on the substrate, and the lithographing performance are discussed in this study.

  11. Population genetic structure and direct observations reveal sex-reversed patterns of dispersal in a cooperative bird

    PubMed Central

    Harrison, Xavier A; York, Jennifer E; Young, Andrew J

    2014-01-01

    Sex-biased dispersal is pervasive and has diverse evolutionary implications, but the fundamental drivers of dispersal sex biases remain unresolved. This is due in part to limited diversity within taxonomic groups in the direction of dispersal sex biases, which leaves hypothesis testing critically dependent upon identifying rare reversals of taxonomic norms. Here, we use a combination of observational and genetic data to demonstrate a rare reversal of the avian sex bias in dispersal in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). Direct observations revealed that (i) natal philopatry was rare, with both sexes typically dispersing locally to breed, and (ii), unusually for birds, males bred at significantly greater distances from their natal group than females. Population genetic analyses confirmed these patterns, as (i) corrected Assignment index (AIc), FST tests and isolation-by-distance metrics were all indicative of longer dispersal distances among males than females, and (ii) spatial autocorrelation analysis indicated stronger within-group genetic structure among females than males. Examining the spatial scale of extra-group mating highlighted that the resulting ‘sperm dispersal’ could have acted in concert with individual dispersal to generate these genetic patterns, but gamete dispersal alone cannot account entirely for the sex differences in genetic structure observed. That leading hypotheses for the evolution of dispersal sex biases cannot readily account for these sex-reversed patterns of dispersal in white-browed sparrow weavers highlights the continued need for attention to alternative explanations for this enigmatic phenomenon. We highlight the potential importance of sex differences in the distances over which dispersal opportunities can be detected. PMID:25346189

  12. Fractal properties of macrophage membrane studied by AFM.

    PubMed

    Bitler, A; Dover, R; Shai, Y

    2012-12-01

    Complexity of cell membrane poses difficulties to quantify corresponding morphology changes during cell proliferation and damage. We suggest using fractal dimension of the cell membrane to quantify its complexity and track changes produced by various treatments. Glutaraldehyde fixed mouse RAW 264.7 macrophage membranes were chosen as model system and imaged in PeakForce QNM (quantitative nanomechanics) mode of AFM (atomic force microscope). The morphology of the membranes was characterized by fractal dimension. The parameter was calculated for set of AFM images by three different methods. The same calculations were done for the AFM images of macrophages treated with colchicine, an inhibitor of the microtubule polymerization, and microtubule stabilizing agent taxol. We conclude that fractal dimension can be additional and useful parameter to characterize the cell membrane complexity and track the morphology changes produced by different treatments.

  13. Sub-diffraction nano manipulation using STED AFM.

    PubMed

    Chacko, Jenu Varghese; Canale, Claudio; Harke, Benjamin; Diaspro, Alberto

    2013-01-01

    In the last two decades, nano manipulation has been recognized as a potential tool of scientific interest especially in nanotechnology and nano-robotics. Contemporary optical microscopy (super resolution) techniques have also reached the nanometer scale resolution to visualize this and hence a combination of super resolution aided nano manipulation ineluctably gives a new perspective to the scenario. Here we demonstrate how specificity and rapid determination of structures provided by stimulated emission depletion (STED) microscope can aid another microscopic tool with capability of mechanical manoeuvring, like an atomic force microscope (AFM) to get topological information or to target nano scaled materials. We also give proof of principle on how high-resolution real time visualization can improve nano manipulation capability within a dense sample, and how STED-AFM is an optimal combination for this job. With these evidences, this article points to future precise nano dissections and maybe even to a nano-snooker game with an AFM tip and fluorospheres.

  14. Mounting of Escherichia coli spheroplasts for AFM imaging.

    SciTech Connect

    Sullivan, Claretta J; Morrell-Falvey, Jennifer L; Allison, David P; Doktycz, Mitchel John

    2005-11-01

    The cytoplasmic membrane of Escherichia coli (E. coli) is the location of numerous, chemically specific transporters and recognition elements. Investigation of this membrane in vivo by atomic force microscopy (AFM) requires removal of the cell wall and stable immobilization of the spheroplast. AFM images demonstrate that spheroplasts can be secured with warm gelatin applied to the mica substrate just before the addition of a spheroplast suspension. The resulting preparation can be repeatedly imaged by AFM over the course of several hours. Confocal fluorescence imaging confirms the association of the spheroplasts with the gelatin layer. Gelatin molecules are known to reorder into a network after heating. Entrapment within this gelatin network is believed to be responsible for the immobilization of spheroplasts on mica.

  15. The Emergence of AFM Applications to Cell Biology: How new technologies are facilitating investigation of human cells in health and disease at the nanoscale.

    PubMed

    Yang, Ruiguo; Xi, Ning; Fung, Carmen Kar Man; Seiffert-Sinha, Kristina; Lai, King Wai Chiu; Sinha, Animesh A

    2011-01-01

    Atomic Force Microscopy (AFM) based nanorobotics has been used for building nano devices in semiconductors for almost a decade. Leveraging the unparallel precision localization capabilities of this technology, high resolution imaging and mechanical property characterization is now increasingly being performed in biological settings. AFM also offers the prospect for handling and manipulating biological materials at nanometer scale. It has unique advantages over other methods, permitting experiments in the liquid phase where physiological conditions can be maintained. Taking advantage of these properties, our group has visualized membrane and cytoskeletal structures of live cells by controlling the interaction force of the AFM tip with cellular components at the nN or sub-nN range. Cell stiffness changes were observed by statistically analyzing the Young's modulus values of human keratinocytes before and after specific antibody treatment. Furthermore, we used the AFM cantilever as a robotic arm for mechanical pushing, pulling and cutting to perform nanoscale manipulations of cell-associated structures. AFM guided nano-dissection, or nanosurgery was enacted on the cell in order to sever intermediate filaments connecting neighboring keratinocytes via sub 100 nm resolution cuts. Finally, we have used a functionalized AFM tip to probe cell surface receptors to obtain binding force measurements. This technique formed the basis for Single Molecule Force Spectroscopy (SMFS). In addition to enhancing our basic understanding of dynamic signaling events in cell biology, these advancements in AFM based biomedical investigations can be expected to facilitate the search for biomarkers related to disease diagnosis progress and treatment.

  16. Surface morphology changes of lignin filled natural rubber latex films investigated using AFM in relation to tensile strengths

    NASA Astrophysics Data System (ADS)

    Asrul, M.; Othman, M.; Zakaria, M.

    2015-07-01

    The paper describes the preparation of lignin filled natural rubber latex composite and the consequential changes in tensile strength observed with varying lignin loading. The changes in tensile strength were shown to be associated with the changes in surface morphology as investigated via AFM. From the AFM analysis it can be inferred that lignin filled rubber latex film which exhibited an increase in tensile strength also demonstrated better phase homogeneity with lowest surface roughness value in comparison to the rest of the lignin filled rubber latex films analysed.

  17. Mapping individual cosmid DNAs by direct AFM imaging.

    PubMed

    Allison, D P; Kerper, P S; Doktycz, M J; Thundat, T; Modrich, P; Larimer, F W; Johnson, D K; Hoyt, P R; Mucenski, M L; Warmack, R J

    1997-05-01

    Individual cosmid clones have been restriction mapped by directly imaging, with the atomic force microscope (AFM), a mutant EcoRI endonuclease site-specifically bound to DNA. Images and data are presented that locate six restriction sites, predicted from gel electrophoresis, on a 35-kb cosmid isolated from mouse chromosome 7. Measured distances between endonuclease molecules bound to lambda DNA, when compared to known values, demonstrate the accuracy of AFM mapping to better than 1%. These results may be extended to identify other important site-specific protein-DNA interactions, such as transcription factor and mismatch repair enzyme binding, difficult to resolve by current techniques.

  18. BOREAS AFM-04 Twin Otter Aircraft Flux Data

    NASA Technical Reports Server (NTRS)

    MacPherson, J. Ian; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Desjardins, Raymond L.; Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-5 team collected and processed data from the numerous radiosonde flights during the project. The goals of the AFM-05 team were to provide large-scale definition of the atmosphere by supplementing the existing AES aerological network, both temporally and spatially. This data set includes basic upper-air parameters collected from the network of upper-air stations during the 1993, 1994, and 1996 field campaigns over the entire study region. The data are contained in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  19. Determining surface properties with bimodal and multimodal AFM.

    PubMed

    Forchheimer, D; Borysov, Stanislav S; Platz, D; Haviland, David B

    2014-12-05

    Conventional dynamic atomic force microscopy (AFM) can be extended to bimodal and multimodal AFM in which the cantilever is simultaneously excited at two or more resonance frequencies. Such excitation schemes result in one additional amplitude and phase images for each driven resonance, and potentially convey more information about the surface under investigation. Here we present a theoretical basis for using this information to approximate the parameters of a tip-surface interaction model. The theory is verified by simulations with added noise corresponding to room-temperature measurements.

  20. GPIM AF-M315E Propulsion System

    NASA Technical Reports Server (NTRS)

    Spores, Ronald A.; Masse, Robert; Kimbrel, Scott; McLean, Chris

    2014-01-01

    The NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) Technology Demonstration Mission (TDM) will demonstrate an operational AF-M315E green propellant propulsion system. Aerojet-Rocketdyne is responsible for the development of the propulsion system payload. This paper statuses the propulsion system module development, including thruster design and system design; Initial test results for the 1N engineering model thruster are presented. The culmination of this program will be high-performance, green AF-M315E propulsion system technology at TRL 7+, with components demonstrated to TRL 9, ready for direct infusion to a wide range of applications for the space user community.

  1. HIGH-RESOLUTION CO OBSERVATION OF THE CARBON STAR CIT 6 REVEALING THE SPIRAL STRUCTURE AND A NASCENT BIPOLAR OUTFLOW

    SciTech Connect

    Kim, Hyosun; Liu, Sheng-Yuan; Hirano, Naomi; Zhao-Geisler, Ronny; Trejo, Alfonso; Yen, Hsi-Wei; Taam, Ronald E.; Kemper, Francisca; Kim, Jongsoo; Byun, Do-Young; Liu, Tie

    2015-11-20

    CIT 6 is a carbon star in the transitional phase from the asymptotic giant branch (AGB) to the protoplanetary nebulae (pPNs). Observational evidences of two point sources in the optical, circumstellar arc segments in an HC{sub 3}N line emission, and a bipolar nebula in near-infrared provide strong support for the presence of a binary companion. Hence, CIT 6 is very attractive for studying the role of companions in the AGB–pPN transition. We have carried out high-resolution {sup 12}CO J = 2–1 and {sup 13}CO J = 2–1 observations of CIT 6 with the Submillimeter Array combined with the Submillimeter Telescope (single-dish) data. The {sup 12}CO channel maps reveal a spiral-shell pattern connecting the HC{sub 3}N segments in a continuous form and an asymmetric outflow corresponding to the near-infrared bipolar nebula. Rotation of the {sup 12}CO channel peak position may be related to the inner spiral winding and/or the bipolar outflow. An eccentric orbit binary is suggested for the presence of an anisotropic mass loss to the west and a double spiral pattern. The lack of interarm emission to the west may indicate a feature corresponding to the periastron passage of a highly eccentric orbit of the binary. Spatially averaged radial and spectral profiles of {sup 12}CO J = 2–1 and {sup 13}CO J = 2–1 are compared with simple spherical radiative transfer models, suggesting a change of {sup 12}CO/{sup 13}CO abundance ratio from ∼30 to ∼50 inward in the CSE of CIT 6. The millimeter continuum emission is decomposed into extended dust thermal emission (spectral index ∼ −2.4) and compact emission from radio photosphere (spectral index ∼ −2.0)

  2. High-resolution CO Observation of the Carbon Star CIT 6 Revealing the Spiral Structure and a Nascent Bipolar Outflow

    NASA Astrophysics Data System (ADS)

    Kim, Hyosun; Liu, Sheng-Yuan; Hirano, Naomi; Zhao-Geisler, Ronny; Trejo, Alfonso; Yen, Hsi-Wei; Taam, Ronald E.; Kemper, Francisca; Kim, Jongsoo; Byun, Do-Young; Liu, Tie

    2015-11-01

    CIT 6 is a carbon star in the transitional phase from the asymptotic giant branch (AGB) to the protoplanetary nebulae (pPNs). Observational evidences of two point sources in the optical, circumstellar arc segments in an HC3N line emission, and a bipolar nebula in near-infrared provide strong support for the presence of a binary companion. Hence, CIT 6 is very attractive for studying the role of companions in the AGB-pPN transition. We have carried out high-resolution 12CO J = 2-1 and 13CO J = 2-1 observations of CIT 6 with the Submillimeter Array combined with the Submillimeter Telescope (single-dish) data. The 12CO channel maps reveal a spiral-shell pattern connecting the HC3N segments in a continuous form and an asymmetric outflow corresponding to the near-infrared bipolar nebula. Rotation of the 12CO channel peak position may be related to the inner spiral winding and/or the bipolar outflow. An eccentric orbit binary is suggested for the presence of an anisotropic mass loss to the west and a double spiral pattern. The lack of interarm emission to the west may indicate a feature corresponding to the periastron passage of a highly eccentric orbit of the binary. Spatially averaged radial and spectral profiles of 12CO J = 2-1 and 13CO J = 2-1 are compared with simple spherical radiative transfer models, suggesting a change of 12CO/13CO abundance ratio from ˜30 to ˜50 inward in the CSE of CIT 6. The millimeter continuum emission is decomposed into extended dust thermal emission (spectral index ˜ -2.4) and compact emission from radio photosphere (spectral index ˜ -2.0).

  3. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM).

    PubMed

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen

    2016-01-21

    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and per-protonated monolayers, i.e., DPPC-d75/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

  4. Single molecule detection of PARP1 and PARP2 interaction with DNA strand breaks and their poly(ADP-ribosyl)ation using high-resolution AFM imaging

    PubMed Central

    Sukhanova, Maria V.; Abrakhi, Sanae; Joshi, Vandana; Pastre, David; Kutuzov, Mikhail M.; Anarbaev, Rashid O.; Curmi, Patrick A.; Hamon, Loic; Lavrik, Olga I.

    2016-01-01

    PARP1 and PARP2 are implicated in the synthesis of poly(ADP-ribose) (PAR) after detection of DNA damage. The specificity of PARP1 and PARP2 interaction with long DNA fragments containing single- and/or double-strand breaks (SSBs and DSBs) have been studied using atomic force microscopy (AFM) imaging in combination with biochemical approaches. Our data show that PARP1 localizes mainly on DNA breaks and exhibits a slight preference for nicks over DSBs, although the protein has a moderately high affinity for undamaged DNA. In contrast to PARP1, PARP2 is mainly detected at a single DNA nick site, exhibiting a low level of binding to undamaged DNA and DSBs. The enhancement of binding affinity of PARP2 for DNA containing a single nick was also observed using fluorescence titration. AFM studies reveal that activation of both PARPs leads to the synthesis of highly branched PAR whose size depends strongly on the presence of SSBs and DSBs for PARP1 and of SSBs for PARP2. The initial affinity between the PARP1, PARP2 and the DNA damaged site appears to influence both the size of the PAR synthesized and the time of residence of PARylated PARP1 and PARP2 on DNA damages. PMID:26673720

  5. Deep-water feeding and behavioral plasticity in Manta birostris revealed by archival tags and submersible observations.

    PubMed

    Stewart, Joshua D; Hoyos-Padilla, Edgar Mauricio; Kumli, Katherine R; Rubin, Robert D

    2016-10-01

    Foraging drives many fundamental aspects of ecology, and an understanding of foraging behavior aids in the conservation of threatened species by identifying critical habitats and spatial patterns relevant to management. The world's largest ray, the oceanic manta (Manta birostris) is poorly studied and threatened globally by targeted fisheries and incidental capture. Very little information is available on the natural history, ecology and behavior of the species, complicating management efforts. This study provides the first data on the diving behavior of the species based on data returned from six tagged individuals, and an opportunistic observation from a submersible of a manta foraging at depth. Pop-off archival satellite tags deployed on mantas at the Revillagigedo Archipelago, Mexico recorded seasonal shifts in diving behavior, likely related to changes in the location and availability of zooplankton prey. Across seasons, mantas spent a large proportion of their time centered around the upper limit of the thermocline, where zooplankton often aggregate. Tag data reveal a gradual activity shift from surface waters to 100-150m across the tagging period, possibly indicating a change in foraging behavior from targeting surface-associated zooplankton to vertical migrators. The depth ranges accessed by mantas in this study carry variable bycatch risks from different fishing gear types. Consequently, region-specific data on diving behavior can help inform local management strategies that reduce or mitigate bycatch of this vulnerable species.

  6. A low-cost AFM setup with an interferometer for undergraduates and secondary-school students

    NASA Astrophysics Data System (ADS)

    Bergmann, Antje; Feigl, Daniela; Kuhn, David; Schaupp, Manuel; Quast, Günter; Busch, Kurt; Eichner, Ludwig; Schumacher, Jens

    2013-07-01

    Atomic force microscopy (AFM) is an important tool in nanotechnology. This method makes it possible to observe nanoscopic surfaces beyond the resolution of light microscopy. In order to provide undergraduate and secondary-school students with insights into this world, we have developed a very robust low-cost AFM setup with a Fabry-Perot interferometer as a detecting device. This setup is designed to be operated almost completely manually and its simplicity gives access to a profound understanding of the working principle. Our AFM is operated in a constant height mode, i.e. the topography of the sample surface is represented directly by the deflection of the cantilever. Thus, the measuring procedure can be understood even by secondary-school students; furthermore, it is the method with the lowest cost, totalling not more than 10-15 k Euros. Nevertheless, we are able to examine a large variety of sample topographies such as CD and DVD surfaces, IC structures, blood cells, butterfly wings or moth eyes. Furthermore, force-distance curves can be recorded and the tensile moduli of some materials can be evaluated. We present our setup in detail and describe its working principles. In addition, we show various experiments which have already been performed by students.

  7. Topographical and electrical study of contact and intermittent contact mode InP AFM lithography

    NASA Astrophysics Data System (ADS)

    Tranvouez, E.; Budau, P.; Bremond, G.

    2006-01-01

    In order to fabricate nanoscale oxide patterns on an InP(001) surface, local anodization by atomic force microscopy (AFM) contact and intermittent contact modes has been performed. Contact mode results are similar to those obtained with the local anodization of silicon, and mainly limited by the effect of space charge that occurs during the oxide growth. The existence of this space charge associated with the poor dielectric quality of the obtained oxide has been verified by performing scanning capacitance microscopy (SCM) measurements. Results for oxidation using intermittent AFM contact mode associated with a modulated voltage are more specific. For a more than two decade variation of probe velocity (0.01-5 µm s-1), the AFM oxidation introduces no significant changes in the oxide pattern. Experiments on the influence of oxidation time give rise to two regimes. First, for times shorter than 100 ms, a high growth rate is found. Second, for oxidation times longer than 100 ms, we observe an oxide height saturation and a significant decrease of lateral growth rate. These results provide a way to easily control the oxide shape. The space charge neutralization in this mode has also been investigated by SCM. The interesting results for intermittent contact oxidation confirm the capability of this technique to modify a nanoscale InP surface.

  8. High-speed AFM images of thermal motion provide stiffness map of interfacial membrane protein moieties.

    PubMed

    Preiner, Johannes; Horner, Andreas; Karner, Andreas; Ollinger, Nicole; Siligan, Christine; Pohl, Peter; Hinterdorfer, Peter

    2015-01-14

    The flexibilities of extracellular loops determine ligand binding and activation of membrane receptors. Arising from fluctuations in inter- and intraproteinaceous interactions, flexibility manifests in thermal motion. Here we demonstrate that quantitative flexibility values can be extracted from directly imaging the thermal motion of membrane protein moieties using high-speed atomic force microscopy (HS-AFM). Stiffness maps of the main periplasmic loops of single reconstituted water channels (AqpZ, GlpF) revealed the spatial and temporal organization of loop-stabilizing intraproteinaceous H-bonds and salt bridges.

  9. High-Speed AFM Images of Thermal Motion Provide Stiffness Map of Interfacial Membrane Protein Moieties

    PubMed Central

    2014-01-01

    The flexibilities of extracellular loops determine ligand binding and activation of membrane receptors. Arising from fluctuations in inter- and intraproteinaceous interactions, flexibility manifests in thermal motion. Here we demonstrate that quantitative flexibility values can be extracted from directly imaging the thermal motion of membrane protein moieties using high-speed atomic force microscopy (HS-AFM). Stiffness maps of the main periplasmic loops of single reconstituted water channels (AqpZ, GlpF) revealed the spatial and temporal organization of loop-stabilizing intraproteinaceous H-bonds and salt bridges. PMID:25516527

  10. New developments at PTB in 3D-AFM with tapping and torsion AFM mode and vector approach probing strategy

    NASA Astrophysics Data System (ADS)

    Dai, G.; Hässler-Grohne, W.; Hüser, D.; Wolff, H.; Fluegge, J.; Bosse, H.

    2011-06-01

    A new 3D-AFM for true 3D measurements of nano structures has been developed at Physikalisch Technische-Bundesanstalt, the national metrology institute of Germany. In its configuration, two piezo actuators are applied to drive the AFM cantilever near its vertical and torsional resonant frequencies. In such a way, the AFM tip can probe the surface with a vertical and/or a lateral oscillation, offering high 3D probing sensitivity. For enhancing measurement flexibility as well as reducing tip wear, a so called "vector approach probing" (VAP) method has been applied. The sample is measured point by point using this method. At each probing point, the tip is approached towards the surface in its normal direction until the desired tip-sample interaction is detected and then immediately withdrawn from the surface. Preliminary experimental results show promising performance of the developed system. The measurement of a line structure of 800 nm height employing a super sharp AFM tip is performed, showing a repeatability of its 3D profiles of better than 1 nm (p-v). A single crystal critical dimension reference material (SCCDRM) having features with almost vertical sidewall is measured using a flared AFM tip. Results show that the feature has averaged left and right sidewall angles of 88.64° and 88.67deg;, respectively. However, the feature width non-uniformity may reach 10 nm within the measurement range of 1 μm. The standard deviation of the averaged middle CD values of 7 repeated measurements reaches 0.35 nm. In addition, an investigation of long term measurement stability is performed on a PTB photomask. The results shows that the 3D-AFM has a drift rate of about 0.00033 nm per line, which confirms the high measurement stability and the very low tip wear.

  11. AFM-IR: Technology and Applications in Nanoscale Infrared Spectroscopy and Chemical Imaging.

    PubMed

    Dazzi, Alexandre; Prater, Craig B

    2016-12-13

    Atomic force microscopy-based infrared spectroscopy (AFM-IR) is a rapidly emerging technique that provides chemical analysis and compositional mapping with spatial resolution far below conventional optical diffraction limits. AFM-IR works by using the tip of an AFM probe to locally detect thermal expansion in a sample resulting from absorption of infrared radiation. AFM-IR thus can provide the spatial resolution of AFM in combination with the chemical analysis and compositional imaging capabilities of infrared spectroscopy. This article briefly reviews the development and underlying technology of AFM-IR, including recent advances, and then surveys a wide range of applications and investigations using AFM-IR. AFM-IR applications that will be discussed include those in polymers, life sciences, photonics, solar cells, semiconductors, pharmaceuticals, and cultural heritage. In the Supporting Information , the authors provide a theoretical section that reviews the physics underlying the AFM-IR measurement and detection mechanisms.

  12. AFM imaging of natural optical structures

    NASA Astrophysics Data System (ADS)

    Dallaeva, Dinara; Tománek, Pavel; Prokopyeva, Elena; Kaspar, Pavel; Grmela, Lubomír.; Škarvada, Pavel

    2015-01-01

    The colors of some living organisms assosiated with the surface structure. Irridesence butterfly wings is an example of such coloration. Optical effects such as interference, diffraction, polarization are responsible for physical colors appearance. Alongside with amazing beauty this structure represent interest for design of optical devices. Here we report the results of morphology investigation by atomic force microscopy. The difference in surface structure of black and blue wings areas is clearly observed. It explains the angle dependence of the wing blue color, since these micrometer and sub-micrometer quasiperiodical structures could control the light propagation, absorption and reflection.

  13. 3D Color Digital Elevation Map of AFM Sample

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This color image is a three dimensional (3D) view of a digital elevation map of a sample collected by NASA's Phoenix Mars Lander's Atomic Force Microscope (AFM).

    The image shows four round pits, only 5 microns in depth, that were micromachined into the silicon substrate, which is the background plane shown in red. This image has been processed to reflect the levelness of the substrate.

    A Martian particle only one micrometer, or one millionth of a meter, across is held in the upper left pit.

    The rounded particle shown at the highest magnification ever seen from another world is a particle of the dust that cloaks Mars. Such dust particles color the Martian sky pink, feed storms that regularly envelop the planet and produce Mars' distinctive red soil.

    The particle was part of a sample informally called 'Sorceress' delivered to the AFM on the 38th Martian day, or sol, of the mission (July 2, 2008). The AFM is part of Phoenix's microscopic station called MECA, or the Microscopy, Electrochemistry, and Conductivity Analyzer.

    The AFM was developed by a Swiss-led consortium, with Imperial College London producing the silicon substrate that holds sampled particles.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  14. Probing the Double Layer: Effect of Image Forces on AFM

    PubMed Central

    Sachs, Frederick

    2006-01-01

    Force probes such as AFM tips or laser trap latex beads have a dielectric constant much less than that of the water that they displace. Thus when a probe approaches a charged surface under water it will be repelled simply based upon the image forces, and these can be of nN magnitude. PMID:16714346

  15. Cantilever's behavior in the AC mode of an AFM

    SciTech Connect

    Nunes, V.B.; Zanette, S.I.; Caride, A.O.; Prioli, R.; Rivas, A.M.F

    2003-03-15

    In this paper, a model with a small number of parameters is used to simulate the motion of a cantilever in the AC mode of an atomic force microscope (AFM). The results elucidate the transition dependence-from noncontact to tapping operating mode-on the height of the contamination layer and on the stiffness of the sample.

  16. The Vertical Distribution of Buried Volatiles at the Moon revealed by Thermal and Epithermal Neutron Fluxes from LEND Observations

    NASA Astrophysics Data System (ADS)

    Chin, G.; Sagdeev, R.; Su, J. J.; Murray, J.; Livengood, T. A.

    2015-12-01

    Determining the quantity and vertical distribution of volatile species on and below the surface of planetary bodies is vital to understand the primordial chemical inventory and subsequent evolution of planets. Volatiles may provide resources to support future human exploration. This is particularly true for the Moon, which is well observed by many methods from ground-based, lunar orbit, and in situ, and is an accessible destination or way station for human exploration. We present Geant4 models of relative fluxes of Fast, Epithermal, and Thermal neutron emission generated in a planetary regolith by galactic cosmic rays to reveal the first 1-2 meters vertical structure of embedded hydrogen or water. Varying ratios of Thermal versus Epithermal, low-energy-Epithermal versus high-energy-Epithermal, and Thermal versus Fast neutron emissions are diagnostics of the depth in which hydrogen/water layers are buried within the top 1-2 meters of the regolith. In addition, we apply model calculations to Lunar Exploration Neutron Detector (LEND) thermal and epithermal data, acquired on the Lunar Reconnaissance Orbiter (LRO), in specific regions of the Moon to retrieve the vertical distribution of buried ice from the remote sensing information. GEANT4 is a set of particle physics transport simulation codes that exploits object-oriented software methods to deliver a comprehensive and flexible toolkit that is modular and extensible, based on a free open-source development model. GEANT4 has become a standard tool to simulate applications as diverse as particle telescope and detector response, space radiation shielding and optimization, total ionizing dose in spacecraft components, and biological effects of radiation.

  17. Scanning hall probe microscopy (SHPM) using quartz crystal AFM feedback.

    PubMed

    Dede, M; Urkmen, K; Girişen, O; Atabak, M; Oral, A; Farrer, I; Ritchie, D

    2008-02-01

    Scanning Hall Probe Microscopy (SHPM) is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of approximately 50 nm and 7 mG/Hz(1/2) at room temperature. In the SHPM technique, scanning tunneling microscope (STM) or atomic force microscope (AFM) feedback is used to keep the Hall sensor in close proximity of the sample surface. However, STM tracking SHPM requires conductive samples; therefore the insulating substrates have to be coated with a thin layer of gold. This constraint can be eliminated with the AFM feedback using sophisticated Hall probes that are integrated with AFM cantilevers. However it is very difficult to micro fabricate these sensors. In this work, we have eliminated the difficulty in the cantilever-Hall probe integration process, just by gluing a Hall Probe chip to a quartz crystal tuning fork force sensor. The Hall sensor chip is simply glued at the end of a 32.768 kHz or 100 kHz Quartz crystal, which is used as force sensor. An LT-SHPM system is used to scan the samples. The sensor assembly is dithered at the resonance frequency using a digital Phase Locked Loop circuit and frequency shifts are used for AFM tracking. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. Magnetic domains and topography of an Iron Garnet thin film crystal, NdFeB demagnetised magnet and hard disk samples are presented at room temperature. The performance is found to be comparable with the SHPM using STM feedback.

  18. A tetravalent bispecific TandAb (CD19/CD3), AFM11, efficiently recruits T cells for the potent lysis of CD19+ tumor cells

    PubMed Central

    Reusch, Uwe; Duell, Johannes; Ellwanger, Kristina; Herbrecht, Carmen; Knackmuss, Stefan HJ; Fucek, Ivica; Eser, Markus; McAleese, Fionnuala; Molkenthin, Vera; Le Gall, Fabrice; Topp, Max; Little, Melvyn; Zhukovsky, Eugene A

    2015-01-01

    To harness the potent tumor-killing capacity of T cells for the treatment of CD19+ malignancies, we constructed AFM11, a humanized tetravalent bispecific CD19/CD3 tandem diabody (TandAb) consisting solely of Fv domains. The molecule exhibits good manufacturability and stability properties. AFM11 has 2 binding sites for CD3 and 2 for CD19, an antigen that is expressed from early B cell development through differentiation into plasma cells, and is an attractive alternative to CD20 as a target for the development of therapeutic antibodies to treat B cell malignancies. Comparison of the binding and cytotoxicity of AFM11 with those of a tandem scFv bispecific T cell engager (BiTE) molecule targeting the same antigens revealed that AFM11 elicited more potent in vitro B cell lysis. Though possessing high affinity to CD3, the TandAb mediates serial-killing of CD19+ cells with little dependence of potency or efficacy upon effector:target ratio, unlike the BiTE. The advantage of the TandAb over the BiTE was most pronounced at lower effector:target ratios. AFM11 mediated strictly target-dependent T cell activation evidenced by CD25 and CD69 induction, proliferation, and cytokine release, notwithstanding bivalent CD3 engagement. In a NOD/scid xenograft model, AFM11 induced dose-dependent growth inhibition of Raji tumors in vivo, and radiolabeled TandAb exhibited excellent localization to tumor but not to normal tissue. After intravenous administration in mice, half-life ranged from 18.4 to 22.9 h. In a human ex vivo B-cell chronic lymphocytic leukemia study, AFM11 exhibited substantial cytotoxic activity in an autologous setting. Thus, AFM11 may represent a promising therapeutic for treatment of CD19+ malignancies with an advantageous safety risk profile and anticipated dosing regimen. PMID:25875246

  19. A tetravalent bispecific TandAb (CD19/CD3), AFM11, efficiently recruits T cells for the potent lysis of CD19(+) tumor cells.

    PubMed

    Reusch, Uwe; Duell, Johannes; Ellwanger, Kristina; Herbrecht, Carmen; Knackmuss, Stefan Hj; Fucek, Ivica; Eser, Markus; McAleese, Fionnuala; Molkenthin, Vera; Gall, Fabrice Le; Topp, Max; Little, Melvyn; Zhukovsky, Eugene A

    2015-01-01

    To harness the potent tumor-killing capacity of T cells for the treatment of CD19(+) malignancies, we constructed AFM11, a humanized tetravalent bispecific CD19/CD3 tandem diabody (TandAb) consisting solely of Fv domains. The molecule exhibits good manufacturability and stability properties. AFM11 has 2 binding sites for CD3 and 2 for CD19, an antigen that is expressed from early B cell development through differentiation into plasma cells, and is an attractive alternative to CD20 as a target for the development of therapeutic antibodies to treat B cell malignancies. Comparison of the binding and cytotoxicity of AFM11 with those of a tandem scFv bispecific T cell engager (BiTE) molecule targeting the same antigens revealed that AFM11 elicited more potent in vitro B cell lysis. Though possessing high affinity to CD3, the TandAb mediates serial-killing of CD19(+) cells with little dependence of potency or efficacy upon effector:target ratio, unlike the BiTE. The advantage of the TandAb over the BiTE was most pronounced at lower effector:target ratios. AFM11 mediated strictly target-dependent T cell activation evidenced by CD25 and CD69 induction, proliferation, and cytokine release, notwithstanding bivalent CD3 engagement. In a NOD/scid xenograft model, AFM11 induced dose-dependent growth inhibition of Raji tumors in vivo, and radiolabeled TandAb exhibited excellent localization to tumor but not to normal tissue. After intravenous administration in mice, half-life ranged from 18.4 to 22.9 h. In a human ex vivo B-cell chronic lymphocytic leukemia study, AFM11 exhibited substantial cytotoxic activity in an autologous setting. Thus, AFM11 may represent a promising therapeutic for treatment of CD19(+) malignancies with an advantageous safety risk profile and anticipated dosing regimen.

  20. Vibrational CD (VCD) and atomic force microscopy (AFM) study of DNA interaction with Cr3+ ions: VCD and AFM evidence of DNA condensation.

    PubMed

    Andrushchenko, V; Leonenko, Z; Cramb, D; van de Sande, H; Wieser, H

    The interaction of natural calf thymus DNA with Cr(3+) ions was studied at room temperature by means of vibrational CD (VCD) and infrared absorption (ir) spectroscopy, and atomic force microscopy (AFM). Cr(3+) ion binding mainly to N(7) (G) and to phosphate groups was demonstrated. Psi-type VCD spectra resembling electronic CD (ECD) spectra, which appear during psi-type DNA condensation, were observed. These spectra are characterized mainly by an anomalous, severalfold increase of VCD intensity. Such anomalous VCD spectra were assigned to DNA condensation with formation of large and dense particles of a size comparable to the wavelength of the probing ir beam and possessing large-scale helicity. Atomic force microscopy confirmed DNA condensation by Cr(3+) ions and the formation of tight DNA particles responsible for the psi-type VCD spectra. Upon increasing the Cr(3+) ion concentration the shape of the condensates changed from loose flower-like structures to highly packed dense spheres. No DNA denaturation was seen even at the highest concentration of Cr(3+) ions studied. The secondary structure of DNA remained in a B-form before and after the condensation. VCD and ir as well as AFM proved to be an effective combination for investigating DNA condensation. In addition to the ability of VCD to determine DNA condensation, VCD and ir can in the same experiment provide unambiguous information about the secondary structure of DNA contained in the condensed particles.

  1. Structure, cell wall elasticity and polysaccharide properties of living yeast cells, as probed by AFM

    NASA Astrophysics Data System (ADS)

    Alsteens, David; Dupres, Vincent; McEvoy, Kevin; Wildling, Linda; Gruber, Hermann J.; Dufrêne, Yves F.

    2008-09-01

    Although the chemical composition of yeast cell walls is known, the organization, assembly, and interactions of the various macromolecules remain poorly understood. Here, we used in situ atomic force microscopy (AFM) in three different modes to probe the ultrastructure, cell wall elasticity and polymer properties of two brewing yeast strains, i.e. Saccharomyces carlsbergensis and S. cerevisiae. Topographic images of the two strains revealed smooth and homogeneous cell surfaces, and the presence of circular bud scars on dividing cells. Nanomechanical measurements demonstrated that the cell wall elasticity of S. carlsbergensis is homogeneous. By contrast, the bud scar of S. cerevisiae was found to be stiffer than the cell wall, presumably due to the accumulation of chitin. Notably, single molecule force spectroscopy with lectin-modified tips revealed major differences in polysaccharide properties of the two strains. Polysaccharides were clearly more extended on S. cerevisiae, suggesting that not only oligosaccharides, but also polypeptide chains of the mannoproteins were stretched. Consistent with earlier cell surface analyses, these findings may explain the very different aggregation properties of the two organisms. This study demonstrates the power of using multiple complementary AFM modalities for probing the organization and interactions of the various macromolecules of microbial cell walls.

  2. Observation

    ERIC Educational Resources Information Center

    Helfrich, Shannon

    2016-01-01

    Helfrich addresses two perspectives from which to think about observation in the classroom: that of the teacher observing her classroom, her group, and its needs, and that of the outside observer coming into the classroom. Offering advice from her own experience, she encourages and defends both. Do not be afraid of the disruption of outside…

  3. Observations

    ERIC Educational Resources Information Center

    Joosten, Albert Max

    2016-01-01

    Joosten begins his article by telling us that love and knowledge together are the foundation for our work with children. This combination is at the heart of our observation. With this as the foundation, he goes on to offer practical advice to aid our practice of observation. He offers a "List of Objects of Observation" to help guide our…

  4. Revealing Amphiphilic Nanodornains of Anti-Biofouling Polymer Coatings

    SciTech Connect

    Amadei, CA; Yang, R; Chiesa, M; Gleason, KK; Santos, S

    2014-04-09

    Undesired bacterial adhesion and biofilm formation on wetted surfaces leads to significant economic and environmental costs in various industries. Amphiphilic coatings with molecular hydrophilic and hydrophobic patches can mitigate such biofouling effectively in an environmentally friendly manner. The coatings are synthesized by copolymerizing (Hydroxyethyl)methacrylate and perfluorodecylacrylate via initiated chemical vapor deposition (iCVD). In previous studies, the size of the patches was estimated to be similar to 1.4-1.75 nm by fitting protein adsorption data to a theoretical model. However, no direct observations of the molecular heterogeneity exist and therefore the origin of the fouling resistance of amphiphilic coatings remains unclear. Here, the amphiphilic nature is investigated by amplitude modulation atomic force microscopy (AM-AFM). High-resolution images obtained by penetrating and oscillating the AFM tip under the naturally present water layer with sub-nanometer amplitudes reveal, for the first time, the existence of amphiphilic nanodomains (1-2 nm(2)). Compositional heterogeneity at the nanoscale is further corroborated by a statistical analysis on the data obtained with dynamic AM-AFM force spectroscopy. Variations in the long range attractive forces, responsible for water affinity, are also identified. These nanoscopic results on the polymers wettability are also confirmed by contact angle measurements (i.e., static and dynamic). The unprecedented ability to visualize the amphiphilic nanodomains as well as sub-nanometer crystalline structures provides strong evidence for the existence of previously postulated nanostructures, and sheds light on the underlying antifouling mechanism of amphiphilic chemistry.

  5. Automated assembly of holder chips to AFM probes

    NASA Astrophysics Data System (ADS)

    Reinhart, Gunther; Jacob, Dirk; Fouchier, Marc

    2001-10-01

    At the Belgian institute IMEC techniques for the production of electrically conductive atomic force microscope (AFM) probes are developed. To facilitate handling of the fragile probes, holder chips are required. The assembly of such holder chips, which can be split up into the application of solder paste, the positioning of the holder chip and the soldering of the chip, is a crucial manufacturing step, that, until now, was performed manually for economic reasons. With the help of a modular micro assembly tool, developed by the Institute for Machine Tools and Industrial Management (iwb) of the Technische Universitaet Muenchen, an economical automated assembly of the holder chips was developed. Thanks to our integrated sensor technology, even the automated assembly onto the extremely fragile membranes of moulded AFM probes was possible. In particular, the dispensing process of the solder paste onto the membranes was improved by the integration of a non-contact sensor for the needle clearance.

  6. Leading Change: Transitioning the AFMS into a High Reliability Organization

    DTIC Science & Technology

    2016-02-16

    AIR WAR COLLEGE AIR UNIVERSITY LEADING CHANGE: TRANSITIONING THE AFMS INTO A HIGH RELIABILTY ORGANIZATION by Robert K. Bogart...academic research paper are those of the author and do not reflect the official policy or position of the US government, the Department of Defense, or Air ...University. In accordance with Air Force Instruction 51-303, it is not copyrighted, but is the property of the United States government. iii

  7. Investigation of biopolymer networks by means of AFM

    NASA Astrophysics Data System (ADS)

    Keresztes, Z.; Rigó, T.; Telegdi, J.; Kálmán, E.

    Natural hydrogel alginate was investigated by means of atomic force microscopy (AFM) to gain microscale information on the morphological and rheological properties of the biopolymer network cross-linked by various cations. Local rheological properties of the gels measured by force spectroscopy gave correlation between increasing ion selectivity and increasing polymer elasticity. Adhesive forces acting between the surface of the gel and the probe, and also the intrinsic rheological properties of bulk polymers affect the microscopical image formation.

  8. Adiabatic Compression Sensitivity of AF-M315E

    DTIC Science & Technology

    2015-07-01

    the development of green rocket propellants . The Air Force Research Laboratory’s (AFRL) monopropellant, AF-M315E, has been selected for...art rocket fuels and propellants . A known quantity of liquid propellant is placed in a metal U-tube and held isothermally in a preheated mixture of... Propellant Infusion Mission (GPIM) program. As the propulsion system developed by Aerojet- Rocketdyne for this propellant advances in maturity, studies

  9. Biophysical properties of cardiomyocyte surface explored by multiparametric AFM.

    PubMed

    Smolyakov, Georges; Cauquil, Marie; Severac, Childerick; Lachaize, Véronique; Guilbeau-Frugier, Céline; Sénard, Jean-Michel; Galés, Céline; Dague, Etienne

    2017-03-02

    PeakForce Quantitative Nanomechanical Mapping (PeakForce QNM) multiparametric AFM mode was adapted to qualitative and quantitative study of the lateral membrane of cardiomyocytes (CMs), extending this powerful mode to the study of soft cells. On living CM, PeakForce QNM depicted the crests and hollows periodic alternation of cell surface architecture previously described using AFM Force Volume (FV) mode. PeakForce QNM analysis provided better resolution in terms of pixel number compared to FV mode and reduced acquisition time, thus limiting the consequences of spontaneous living adult CM dedifferentiation once isolated from the cardiac tissue. PeakForce QNM mode on fixed CMs clearly visualized subsarcolemmal mitochondria (SSM) and their loss following formamide treatment, concomitant with the interfibrillar mitochondria climbing up and forming heaps at the cell surface. Interestingly, formamide-promoted SSM loss allowed visualization of the sarcomeric apparatus ultrastructure below the plasma membrane. High PeakForce QNM resolution led to better contrasted mechanical maps than FV mode and provided correlation between adhesion, dissipation, mechanical and topographical maps. Modified hydrophobic AFM tip enhanced contrast on adhesion and dissipation maps and suggested that CM surface crests and hollows exhibit distinct chemical properties. Finally, two-dimensional Fast Fourier Transform to objectively quantify AFM maps allowed characterization of periodicity of both sarcomeric Z-line and M-band. Overall, this study validated PeakForce QNM as a valuable and innovative mode for the exploration of living and fixed CMs. In the future, it could be applied to depict cell membrane architectural, mechanical and chemical defects as well as sarcomeric abnormalities associated with cardiac diseases.

  10. Near-Field Spectroscopy with Nanoparticles Deposited by AFM

    NASA Technical Reports Server (NTRS)

    Anderson, Mark S.

    2008-01-01

    An alternative approach to apertureless near-field optical spectroscopy involving an atomic-force microscope (AFM) entails less complexity of equipment than does a prior approach. The alternative approach has been demonstrated to be applicable to apertureless near-field optical spectroscopy of the type using an AFM and surface enhanced Raman scattering (SERS), and is expected to be equally applicable in cases in which infrared or fluorescence spectroscopy is used. Apertureless near-field optical spectroscopy is a means of performing spatially resolved analyses of chemical compositions of surface regions of nanostructured materials. In apertureless near-field spectroscopy, it is common practice to utilize nanostructured probe tips or nanoparticles (usually of gold) having shapes and dimensions chosen to exploit plasmon resonances so as to increase spectroscopic-signal strengths. To implement the particular prior approach to which the present approach is an alternative, it is necessary to integrate a Raman spectrometer with an AFM and to utilize a special SERS-active probe tip. The resulting instrumentation system is complex, and the tasks of designing and constructing the system and using the system to acquire spectro-chemical information from nanometer-scale regions on a surface are correspondingly demanding.

  11. Tissue section AFM: In situ ultrastructural imaging of native biomolecules

    PubMed Central

    Graham, Helen K.; Hodson, Nigel W.; Hoyland, Judith A.; Millward-Sadler, Sarah J.; Garrod, David; Scothern, Anthea; Griffiths, Christopher E.M.; Watson, Rachel E.B.; Cox, Thomas R.; Erler, Janine T.; Trafford, Andrew W.; Sherratt, Michael J.

    2010-01-01

    Conventional approaches for ultrastructural high-resolution imaging of biological specimens induce profound changes in bio-molecular structures. By combining tissue cryo-sectioning with non-destructive atomic force microscopy (AFM) imaging we have developed a methodology that may be applied by the non-specialist to both preserve and visualize bio-molecular structures (in particular extracellular matrix assemblies) in situ. This tissue section AFM technique is capable of: i) resolving nm–µm scale features of intra- and extracellular structures in tissue cryo-sections; ii) imaging the same tissue region before and after experimental interventions; iii) combining ultrastructural imaging with complimentary microscopical and micromechanical methods. Here, we employ this technique to: i) visualize the macro-molecular structures of unstained and unfixed fibrillar collagens (in skin, cartilage and intervertebral disc), elastic fibres (in aorta and lung), desmosomes (in nasal epithelium) and mitochondria (in heart); ii) quantify the ultrastructural effects of sequential collagenase digestion on a single elastic fibre; iii) correlate optical (auto fluorescent) with ultrastructural (AFM) images of aortic elastic lamellae. PMID:20144712

  12. Observation

    ERIC Educational Resources Information Center

    Kripalani, Lakshmi A.

    2016-01-01

    The adult who is inexperienced in the art of observation may, even with the best intentions, react to a child's behavior in a way that hinders instead of helping the child's development. Kripalani outlines the need for training and practice in observation in order to "understand the needs of the children and...to understand how to remove…

  13. Conductive area ratio of multiblock copolymer electrolyte membranes evaluated by e-AFM and its impact on fuel cell performance

    NASA Astrophysics Data System (ADS)

    Takimoto, Naohiko; Takamuku, Shogo; Abe, Mitsutaka; Ohira, Akihiro; Lee, Hae-Seung; McGrath, James E.

    The correlation between membrane surface morphology and fuel cell performance was investigated using a series of hydrophilic-hydrophobic multiblock copolymers based on poly(arylene ether sulfone) with different block lengths. The proton conductive regions on the membrane surface were successfully observed by using electrochemical atomic force microscopy (e-AFM). The results revealed a strong dependence of the hydrophilic/hydrophobic microphase-separated structure on the block length. The conductive area ratio (CAR) estimated from the proton conduction image decreased as the block length increased, and it was found to be closely connected with cell resistance that determines fuel cell performance. The well-defined phase-separated structure of multiblock copolymers can improve proton conductivity without any undesirable increments in water uptake or swelling, but in some instances, it affects the interfacial connection with the catalyst layer, resulting in lower fuel cell performance. The results of this study suggest the necessity for further improvement of the membrane morphology by optimizing both the casting conditions and the molecular design of the block sequences.

  14. The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations

    DTIC Science & Technology

    2010-06-28

    the crucial interface between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Lyα line at 1216Å. In...chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly line at 1216 A. In Two Flights, VAULT succeeded in...first solar imaging space missions that this so-called temperature transition region (TR) between the chromosphere and the corona , is also where the

  15. Structural changes of polysulfone membrane use for hemodialysis in the consecutive regime: nanometric analysis by AFM

    NASA Astrophysics Data System (ADS)

    Batina, Nikola; Acosta García, Ma. Cristina; Avalos Pérez, Angélica; Alberto Ramírez, Mario; Franco, Martha; Pérez Gravas, Héctor; Cadena Méndez, Miguel

    2013-08-01

    Nowadays, the hemodialytic treatment of patients with either acute or chronic renal failure has been improved by promoting biocompatibility in the use of new materials and improve membrane surface characteristics. Low and high flux polysulfone membranes (PM) used in dialysis and ultra filtration have been studied in order to understand the geometry and surface chemistry of the pores at inner (nanometric) and outer (micrometric) membrane parts. The surface changes of polysulfone cartridge membrane (PM) during different number of consecutive reuse trials: after 1st, 10th and 23th times of use. The morphology of the hollow fibers surfaces was studied by means of the atomic force microscopy (AFM) imaging and the surface roughness analysis. The roughness of both inner and outer part of PM surface increases with numbers of reuse trails. Thus, small and medium size pores were wiped out when the number of uses changed from zero to 23 on the outer surface. The pore density decreases. The inner part of membrane shows some nanometric size deformation in forms of new openings and raptures. The AFM analysis show differences in the PM morphology at the nanometric level, not previously revealed, which could be important in the evaluation of the PM.

  16. Investigation of the influence of UV irradiation on collagen thin films by AFM imaging.

    PubMed

    Stylianou, Andreas; Yova, Dido; Alexandratou, Eleni

    2014-12-01

    Collagen is the major fibrous extracellular matrix protein and due to its unique properties, it has been widely used as biomaterial, scaffold and cell-substrate. The aim of the paper was to use Atomic Force Microscopy (AFM) in order to investigate well-characterized collagen thin films after ultraviolet light (UV) irradiation. The films were also used as in vitro culturing substrates in order to investigate the UV-induced alterations to fibroblasts. A special attention was given in the alteration on collagen D-periodicity. For short irradiation times, spectroscopy (fluorescence/absorption) studies demonstrated that photodegradation took place and AFM imaging showed alterations in surface roughness. Also, it was highlighted that UV-irradiation had different effects when it was applied on collagen solution than on films. Concerning fibroblast culturing, it was shown that fibroblast behavior was affected after UV irradiation of both collagen solution and films. Furthermore, after a long irradiation time, collagen fibrils were deformed revealing that collagen fibrils are consisting of multiple shells and D-periodicity occurred on both outer and inner shells. The clarification of the effects of UV light on collagen and the induced modifications of cell behavior on UV-irradiated collagen-based surfaces will contribute to the better understanding of cell-matrix interactions in the nanoscale and will assist in the appropriate use of UV light for sterilizing and photo-cross-linking applications.

  17. AFM Studies of Salt Concentration Effects on the (110) Surface Structure of Tetragonal Lysozyme Crystals

    NASA Technical Reports Server (NTRS)

    Pusey, Marc Lee; Gorti, Sridhar; Forsythe, Elizabeth; Konnert, John

    2002-01-01

    Previous high resolution AFM studies of the (110) surface of tetragonal chicken egg white lysozyme crystals had shown that only one of two possible molecular surfaces is present, those constituting the completed 43 helices. These suggested that the crystal growth process was by the solution-phase assembly of the growth units, which then attach to the surface. However, the best fit for the imaged surfaces, vs. those predicted based upon the bulk crystallographic coordinates, were obtained when the packing about the 43 helices was "tightened up", while maintaining the underlying crystallographic unit cell spacing. This results in a widening of the gap between adjacent helices, and the top- most layer(s) may no longer be in contact. We postulated that the tightened packing about the helices is a result of the high salt concentrations in the bulk solution, used to crystallize the protein, driving hydrophobic interactions. Once the crystal surface is sufficiently buried by subsequent growth layers the ratio of salt to protein molecules decreases and the helices relax to their bulk crystallographic coordinates. The crystal surface helix structure is thus a reflection of the solution structure, and the tightness of the packing about the 43 helices would be a function of the bulk salt concentration. AFM images of the (110) surface of tetragonal lysozyme crystals grown under low (2%) and high (5%) NaCl concentrations reveal differences in the packing about the 43 helices consistent with the above proposal.

  18. Molecular-level insights of early-stage prion protein aggregation on mica and gold surface determined by AFM imaging and molecular simulation.

    PubMed

    Lou, Zhichao; Wang, Bin; Guo, Cunlan; Wang, Kun; Zhang, Haiqian; Xu, Bingqian

    2015-11-01

    By in situ time-lapse AFM, we investigated early-stage aggregates of PrP formed at low concentration (100 ng/mL) on mica and Au(111) surfaces in acetate buffer (pH 4.5). Remarkably different PrP assemblies were observed. Oligomeric structures of PrP aggregates were observed on mica surface, which was in sharp contrast to the multi-layer PrP aggregates yielding parallel linear patterns observed Au(111) surface. Combining molecular dynamics and docking simulations, PrP monomers, dimers and trimers were revealed as the basic units of the observed aggregates. Besides, the mechanisms of the observed PrP aggregations and the corresponding molecular-substrate and intermolecular interactions were suggested. These interactions involved gold-sulfur interaction, electrostatic interaction, hydrophobic interaction, and hydrogen binding interaction. In contrast, the PrP aggregates observed in pH 7.2 PBS buffer demonstrated similar large ball-like structures on both mica and Au(111) surfaces. The results indicate that the pH of a solution and the surface of the system can have strong effects on supramolecular assemblies of prion proteins. This study provides in-depth understanding on the structural and mechanistic nature of PrP aggregation, and can be used to study the aggregation mechanisms of other proteins with similar misfolding properties.

  19. Unspecific membrane protein-lipid recognition: combination of AFM imaging, force spectroscopy, DSC and FRET measurements.

    PubMed

    Borrell, Jordi H; Montero, M Teresa; Morros, Antoni; Domènech, Òscar

    2015-11-01

    In this work, we will describe in quantitative terms the unspecific recognition between lactose permease (LacY) of Escherichia coli, a polytopic model membrane protein, and one of the main components of the inner membrane of this bacterium. Supported lipid bilayers of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) (3:1, mol/mol) in the presence of Ca(2+) display lateral phase segregation that can be distinguished by atomic force microscopy (AFM) as well as force spectroscopy. LacY shows preference for fluid (Lα) phases when it is reconstituted in POPE : POPG (3:1, mol/mol) proteoliposomes at a lipid-to-protein ratio of 40. When the lipid-to-protein ratio is decreased down to 0.5, two domains can be distinguished by AFM. While the upper domain is formed by self-segregated units of LacY, the lower domain is constituted only by phospholipids in gel (Lβ) phase. On the one hand, classical differential scanning calorimetry (DSC) measurements evidenced the segregation of a population of phospholipids and point to the existence of a boundary region at the lipid-protein interface. On the other hand, Förster Resonance Energy Transfer (FRET) measurements in solution evidenced that POPE is selectively recognized by LacY. A binary pseudophase diagram of POPE : POPG built from AFM observations enables to calculate the composition of the fluid phase where LacY is inserted. These results are consistent with a model where POPE constitutes the main component of the lipid-LacY interface segregated from the fluid bulk phase where POPG predominates.

  20. Comparative AFM nanoscratching tests in air of bulk copper and electrogenerated cuprous oxide films

    NASA Astrophysics Data System (ADS)

    Chaal, Lila; Debiemme-Chouvy, Catherine; Deslouis, Claude; Maurin, Georges; Pailleret, Alain; Saidani, Boualem

    2011-01-01

    The normal and lateral spring constants of rectangular silicon AFM cantilevers bearing pyramidal silicon tips were accurately calibrated using a procedure that takes into account their tilt compared to horizontal orientation and their trapezoidal cross section. Such systems were used to carry out nanoscratching tests in air on technical substrates presenting a moderate roughness (RMS ≈ 40 nm) and made either from bulk copper or from cuprous oxide thin films electrogenerated on copper. The various events occurring during these nanoscratching procedures were characterized in details. In particular, the features of the scars appearing on the scratched zones and SEM observations of the AFM tips used during the nanoscratching procedures are described and exploited to establish a better understanding of the effects of the nanoscratching procedures on the targeted samples. In the case of electrodeposited Cu 2O films, these effects are discussed with the help of chemical and structural characterizations using XPS and XRD studies. All this set of information is used i) to describe the history of the nanoscratching tests and ii) to compare mechanical resistance of bulk copper and electrogenerated Cu 2O thin films using these nanoscratching tests carried out in air. The wear mechanism occurring during nanoscratching tests is discussed for both kinds of samples and compared with the one observed during erosion in erosion-corrosion tests.

  1. Insights Into Precipitation Processes As Revealed By Profiling Radar, Disdrometer and Aircraft Observations During The MC3E Campaign.

    NASA Astrophysics Data System (ADS)

    Giangrande, S. E.; Toto, T.; Mishra, S.; Ryzhkov, A.; Bansemer, A.; Kumjian, M.

    2014-12-01

    The Midlatitude Continental Convective Clouds Experiment (MC3E) was a collaborative campaign led by the National Aeronautic and Space Administration's (NASA's) Global Precipitation Measurement (GPM) mission and the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program. This campaign was held at the DOE ARM Southern Great Plains (SGP) Central Facility (CF) in north-central Oklahoma, with the programs joining forces to deploy an extensive array of airborne, radiosonde and ground-based instrumentation towards an unprecedented set of deep convective environment and cloud property observations. An overarching motivation was to capitalize on the wealth of aircraft observations and new multi-frequency dual-polarization radars to provide insights for improving the treatments of cloud processes in convective models. This study considers a coupled aircraft, radar and surface disdrometer approach for identifying key cloud processes and linking those to possible radar-based microphysical fingerprints and/or cloud properties. Our emphasis is on the MC3E observations collected during aircraft spirals over the column of the ARM CF. We focus on those spirals associated with radar 'bright band' signatures and Doppler spectral anomalies observed within trailing stratifrom precipitation. Two cases are highlighted, one following a weaker convective event, and one following a stronger squall line. For each event, we investigate the usefulness of radar to inform on processes including aggregation and riming as viewed by the vertically-pointing ARM wind profiler (915 MHz) and cloud radar Doppler spectral observations (35 GHz). Matching dual-polarization radar signatures from nearby cm-wavelength radar are also consulted for complementary insights. For one event, the successive Citation II aircraft spirals through the melting layer and associated ground observations indicate a fortunate capture of the transition from a region of riming to one favoring aggregation

  2. In-situ atomic force microscopy observation revealing gel-like plasticity on a metallic glass surface

    NASA Astrophysics Data System (ADS)

    Lu, Y. M.; Zeng, J. F.; Huang, J. C.; Kuan, S. Y.; Nieh, T. G.; Wang, W. H.; Pan, M. X.; Liu, C. T.; Yang, Y.

    2017-03-01

    It has been decade-long and enduring efforts to decipher the structural mechanism of plasticity in metallic glasses; however, it still remains a challenge to directly reveal the structural change, if any, that precedes; and dominant plastics flow in them. Here, by using the dynamic atomic force microscope as an "imaging" as well as a "forcing" tool, we unfold a real-time sequence of structural evolution occurring on the surface of an Au-Si thin film metallic glass. In sharp contrast to the common notion that plasticity comes along with mechanical softening in bulk metallic glasses, our experimental results directly reveal three types of nano-sized surface regions, which undergo plasticity but exhibit different characters of structural evolution following the local plasticity events, including stochastic structural rearrangement, unusual local relaxation and rejuvenation. As such, yielding on the metallic-glass surface manifests as a dynamic equilibrium between local relaxation and rejuvenation as opposed to shear instability in bulk metallic-glasses. Our finding demonstrates that plasticity on the metallic glass surface of Au-Si metallic glass bears much resemblance to that of the colloidal gels, of which nonlinear rheology rather than shear instability governs the constitutive behavior of plasticity.

  3. Equatorial spread F initiation and growth from satellite traces as revealed from conjugate point observations in Brazil

    NASA Astrophysics Data System (ADS)

    Abdu, M. A.; Kherani, E. A.; Batista, I. S.; Reinisch, B. W.; Sobral, J. H. A.

    2014-01-01

    better understanding of the precursor conditions for the instability growth is very important for identifying the causes of day-to-day variability in the equatorial spread F (ESF)/plasma bubble irregularity development. We investigate here the satellite trace (S-trace) in the ionograms, a precursor to the postsunset ESF occurrence, as observed by Digisondes operated at an equatorial and two magnetic conjugate sites in Brazil during a 66 day observational campaign (Conjugate Point Equatorial Experiment 2002). The satellite traces first occur at the equatorial site, and sequentially, after a variable delay of approximately 20 to 50 min, they are observed nearly simultaneously over the two conjugate sites. The evening prereversal enhancement in the zonal electric field/vertical drift is found to control its development. Using a three-dimensional simulation code based on collisional interchange instability mechanism, it is shown that the observed S-trace occurrence sequence is fully consistent with the instability initiation over the equator with the field-aligned plasma depletion vertical growth marked by latitudinal expansion of its extremities to conjugate locations. The delay in the S-trace occurrence at the conjugate sites (a measure of the nonlinear growth of the instability for plasma depletion) is controlled also by field line parallel (meridional) neutral wind. The relationship between the S-trace and the large-scale wave structure in the F layer, another widely known characterization of the precursor condition for the ESF development, is also clarified.

  4. Lateral Tip Control Effects in CD-AFM Metrology: The Large Tip Limit.

    PubMed

    Dixson, Ronald G; Orji, Ndubuisi G; Goldband, Ryan S

    2016-01-25

    Sidewall sensing in critical dimension atomic force microscopes (CD-AFMs) usually involves continuous lateral dithering of the tip or the use of a control algorithm and fast response piezo actuator to position the tip in a manner that resembles touch-triggering of coordinate measuring machine (CMM) probes. All methods of tip position control, however, induce an effective tip width that may deviate from the actual geometrical tip width. Understanding the influence and dependence of the effective tip width on the dither settings and lateral stiffness of the tip can improve the measurement accuracy and uncertainty estimation for CD-AFM measurements. Since CD-AFM typically uses tips that range from 15 nm to 850 nm in geometrical width, the behavior of effective tip width throughout this range should be understood. The National Institute of Standards and Technology (NIST) has been investigating the dependence of effective tip width on the dither settings and lateral stiffness of the tip, as well as the possibility of material effects due to sample composition. For tip widths of 130 nm and lower, which also have lower lateral stiffness, the response of the effective tip width to lateral dither is greater than for larger tips. However, we have concluded that these effects will not generally result in a residual bias, provided that the tip calibration and sample measurement are performed under the same conditions. To validate that our prior conclusions about the dependence of effective tip width on lateral stiffness are valid for large CD-tips, we recently performed experiments using a very large non-CD tip with an etched plateau of approximately 2 μm width. The effective lateral stiffness of these tips is at least 20 times greater than typical CD-AFM tips, and these results supported our prior conclusions about the expected behavior for larger tips. The bottom-line importance of these latest observations is that we can now reasonably conclude that a dither slope of 3 nm

  5. Solvent-mediated repair and patterning of surfaces by AFM

    SciTech Connect

    Elhadj, S; Chernov, A; De Yoreo, J

    2007-10-30

    A tip-based approach to shaping surfaces of soluble materials with nanometer-scale control is reported. The proposed method can be used, for example, to eliminate defects and inhomogeneities in surface shape, repair mechanical or laser-induced damage to surfaces, or perform 3D lithography on the length scale of an AFM tip. The phenomenon that enables smoothing and repair of surfaces is based on the transport of material from regions of high- to low-curvature within the solution meniscus formed in a solvent-containing atmosphere between the surface in question and an AFM tip scanned over the surface. Using in situ AFM measurements of the kinetics of surface remodeling on KDP (KH{sub 2}PO{sub 4}) crystals in humid air, we show that redistribution of solute material during relaxation of grooves and mounds is driven by a reduction in surface free energy as described by the Gibbs-Thomson law. We find that the perturbation from a flat interface evolves according to the diffusion equation where the effective diffusivity is determined by the product of the surface stiffness and the step kinetic coefficient. We also show that, surprisingly, if the tip is instead scanned over or kept stationary above an atomically flat area of the surface, a convex structure is formed with a diameter that is controlled by the dimensions of the meniscus, indicating that the presence of the tip and meniscus reduces the substrate chemical potential beneath that of the free surface. This allows one to create nanometer-scale 3D structures of arbitrary shape without the removal of substrate material or the use of extrinsic masks or chemical compounds. Potential applications of these tip-based phenomena are discussed.

  6. Image Analysis and Length Estimation of Biomolecules Using AFM

    PubMed Central

    Sundstrom, Andrew; Cirrone, Silvio; Paxia, Salvatore; Hsueh, Carlin; Kjolby, Rachel; Gimzewski, James K.; Reed, Jason; Mishra, Bud

    2014-01-01

    There are many examples of problems in pattern analysis for which it is often possible to obtain systematic characterizations, if in addition a small number of useful features or parameters of the image are known a priori or can be estimated reasonably well. Often, the relevant features of a particular pattern analysis problem are easy to enumerate, as when statistical structures of the patterns are well understood from the knowledge of the domain. We study a problem from molecular image analysis, where such a domain-dependent understanding may be lacking to some degree and the features must be inferred via machine-learning techniques. In this paper, we propose a rigorous, fully automated technique for this problem. We are motivated by an application of atomic force microscopy (AFM) image processing needed to solve a central problem in molecular biology, aimed at obtaining the complete transcription profile of a single cell, a snapshot that shows which genes are being expressed and to what degree. Reed et al. (“Single molecule transcription profiling with AFM,” Nanotechnology, vol. 18, no. 4, 2007) showed that the transcription profiling problem reduces to making high-precision measurements of biomolecule backbone lengths, correct to within 20–25 bp (6–7.5 nm). Here, we present an image processing and length estimation pipeline using AFM that comes close to achieving these measurement tolerances. In particular, we develop a biased length estimator on trained coefficients of a simple linear regression model, biweighted by a Beaton–Tukey function, whose feature universe is constrained by James–Stein shrinkage to avoid overfitting. In terms of extensibility and addressing the model selection problem, this formulation subsumes the models we studied. PMID:22759526

  7. The underlying relationships between the observed practices as revealed by an exploratory factor analysis of equip ratings

    NASA Astrophysics Data System (ADS)

    Nettles, Jenesta Rae

    The Electronic Quality of Inquiry Protocol (EQUIP) is an instrument to measure the amount and quality of inquiry instruction of science and mathematics classrooms. The EQUIP rubric includes detailed descriptions for the inquiry practices that it measures. This study analyzed a large dataset of Texas science teacher observations using a discriminant factor analysis and exploratory factor analysis. The discriminant factor analysis found the inquiry instruction practices of primary (1st-5th grade) science teachers and secondary (6th-12th grade) science teachers to differ greatly, with primary science teachers using inquiry practices more often than secondary science teachers. Based on this information the primary and secondary datasets were analyzed separately with the exploratory factor analysis. The resulting factors indicate a variety of differences in the observed practices. The results also, suggest that discourse practices play a divergent but influential role for both datasets. Potential implications for professional development and future research are discussed.

  8. Deep Chandra Observations of NGC 1404: Cluster Plasma Physics Revealed by an Infalling Early-type Galaxy

    NASA Astrophysics Data System (ADS)

    Su, Yuanyuan; Kraft, Ralph P.; Roediger, Elke; Nulsen, Paul; Forman, William R.; Churazov, Eugene; Randall, Scott W.; Jones, Christine; Machacek, Marie E.

    2017-01-01

    The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot be achieved on Earth. NGC 1404 is a bright elliptical galaxy that is being gas stripped as it falls through the ICM of the Fornax Cluster. We use the new Chandra X-ray observations of NGC 1404 to study ICM microphysics. The interstellar medium of NGC 1404 is characterized by a sharp leading edge, 8 kpc from the Galaxy center, and a short downstream gaseous tail. Contact discontinuities are resolved on unprecedented spatial scales (0.″5 = 45 pc) due to the combination of the proximity of NGC 1404, the superb spatial resolution of Chandra, and the very deep (670 ks) exposure. At the leading edge, we observe sub-kiloparsec-scale eddies generated by Kelvin–Helmholtz instability (KHI) and put an upper limit of 5% Spitzer on the isotropic viscosity of the hot cluster plasma. We also observe mixing between the hot cluster gas and the cooler galaxy gas in the downstream stripped tail, which provides further evidence of a low viscosity plasma. The assumed ordered magnetic fields in the ICM ought to be smaller than 5 μG to allow KHI to develop. The lack of an evident magnetic draping layer just outside the contact edge is consistent with such an upper limit.

  9. Deep-sea in situ observations of gonatid squid and their prey reveal high occurrence of cannibalism

    NASA Astrophysics Data System (ADS)

    Hoving, H. J. T.; Robison, B. H.

    2016-10-01

    In situ observations are rarely applied in food web studies of deep-sea organisms. Using deep-sea observations obtained by remotely operated vehicles in the Monterey Submarine Canyon, we examined the prey choices of more than 100 individual squids of the genus Gonatus. Off the California coast, these squids are abundant, semelparous (one reproductive cycle) oceanic predators but their diet has remained virtually unknown. Gonatus onyx and Gonatus berryi were observed to feed on mesopelagic fishes (in particular the myctophid Stenobrachius leucopsarus) as often as on squids but inter-specific differences in feeding were apparent. Gonatids were the most common squid prey and while cannibalism occurred in both species it was particularly high in Gonatus onyx (42% of all prey items). Typically, the size of prey was similar to the size of the predator but the squids were also seen to take much larger prey. Postjuvenile gonatids are opportunistic predators that consume nektonic members of the meso-and bathypelagic communities, including their own species. Such voracious feeding is likely necessary to support the high energetic demands associated with the single reproductive event; and for females the long brooding period during which they must depend on stored resources.

  10. Optical fiber fluorescence spectroscopy for detecting AFM1 in milk

    NASA Astrophysics Data System (ADS)

    Mignani, A. G.; Cucci, C.; Ciaccheri, L.; Dall'Asta, C.; Galaverna, G.; Dossena, A.; Marchelli, R.

    2008-04-01

    Fluorescence spectroscopy carried out by means of optical fibers was used for the rapid screening of M1 aflatoxin in milk, enabling the detection of concentrations up to the legal limit, which is 50 ppt. A compact fluorometric device equipped with a LED source, a miniaturized spectrometer, and optical fibers for illumination/detection of the measuring micro-cell was tested for measuring threshold values of AFM1 in pre-treated milk samples. Multivariate processing of the spectral data made it possible to obtain a preliminary screening at the earlier stages of the industrial process, as well as to discard contaminated milk stocks before their inclusion in the production chain.

  11. High-speed AFM probe with micromachined membrane tip

    NASA Astrophysics Data System (ADS)

    Kim, Byungki; Kwak, Byung Hyung; Jamil, Faize

    2008-08-01

    This paper presents a micromachined silicon membrane type AFM tip designed to move nearly 1µm by electrostatic force. Since the tip can be vibrated in small amplitude with AC voltage input and can be displaced up to 1μm by DC voltage input, an additional piezo actuator is not required for scanning of submicron features. The micromachined membrane tips are designed to have 100 kHz ~ 1 MHz resonant frequency. Displacement of the membrane tip is measured by an optical interferometer using a micromachined diffraction grating on a quartz wafer which is positioned behind the membrane tip.

  12. Theoretical modelling of AFM for bimetallic tip-substrate interactions

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1991-01-01

    Recently, a new technique for calculating the defect energetics of alloys based on Equivalent Crystal Theory was developed. This new technique successfully predicts the bulk properties for binary alloys as well as segregation energies in the dilute limit. The authors apply this limit for the calculation of energy and force as a function of separation of an atomic force microscope (AFM) tip and substrate. The study was done for different combinations of tip and sample materials. The validity of the universality discovered for the same metal interfaces is examined for the case of different metal interactions.

  13. The Advancing State of AF-M315E Technology

    NASA Technical Reports Server (NTRS)

    Masse, Robert; Spores, Ronald A.; McLean, Chris

    2014-01-01

    The culmination of twenty years of applied research in hydroxyl ammonium nitrate (HAN)-based monopropellants, the NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) will achieve the first on-orbit demonstration of an operational AF-M315E green propellant propulsion system by the end of 2015. Following an contextual overview of the completed flight design of the GPIM propellant storage and feed system, results of first operation of a flight-representative heavyweight 20-N engineering model thruster (to be conducted in mid-2014) are presented with performance comparisons to prior lab model (heavyweight) test articles.

  14. Examination of Humidity Effects on Measured Thickness and Interfacial Phenomena of Exfoliated Graphene on SiO2 via AC-AFM

    NASA Astrophysics Data System (ADS)

    Jinkins, Katherine; Camacho, Jorge; Farina, Lee; Wu, Yan

    2015-03-01

    Tapping (AC) mode Atomic Force Microscopy (AFM) is commonly used to determine the thickness of graphene samples. However, AFM measurements have been shown to be sensitive to environmental conditions such as adsorbed water, in turn dependent on relative humidity (RH). In the present study, AC-AFM is used to measure the thickness and loss tangent of exfoliated graphene on silicon dioxide (SiO2) as RH is increased from 10% to 80%. We show that the measured thickness of graphene is dependent on RH. Loss tangent is an AFM imaging technique that interprets the phase information as a relationship between the stored and dissipated energy in the tip-sample interaction. This study demonstrates the loss tangent of the graphene and oxide regions are both affected by humidity, with generally higher loss tangent for graphene than SiO2. As RH increases, we observe the loss tangent of both materials approaches the same value. We hypothesize that there is a layer of water trapped between the graphene and SiO2 substrate to explain this observation. Using this interpretation, the loss tangent images also indicate movement and change in this trapped water layer as RH increases, which impacts the measured thickness of graphene using AC-AFM.

  15. AFM review study on pox viruses and living cells.

    PubMed

    Ohnesorge, F M; Hörber, J K; Häberle, W; Czerny, C P; Smith, D P; Binnig, G

    1997-10-01

    Single living cells were studied in growth medium by atomic force microscopy at a high--down to one image frame per second--imaging rate over time periods of many hours, stably producing hundreds of consecutive scans with a lateral resolution of approximately 30-40 nm. The cell was held by a micropipette mounted onto the scanner-piezo as shown in Häberle, W., J. K. H. Hörber, and G. Binnig. 1991. Force microscopy on living cells. J. Vac. Sci. Technol. B9:1210-0000. To initiate specific processes on the cell surface the cells had been infected with pox viruses as reported earlier and, most likely, the liberation of a progeny virion by the still-living cell was observed, hence confirming and supporting earlier results (Häberle, W., J. K. H. Hörber, F. Ohnesorge, D. P. E. Smith, and G. Binnig. 1992. In situ investigations of single living cells infected by viruses. Ultramicroscopy. 42-44:1161-0000; Hörber, J. K. H., W. Häberle, F. Ohnesorge, G. Binnig, H. G. Liebich, C. P. Czerny, H. Mahnel, and A. Mayr. 1992. Investigation of living cells in the nanometer regime with the atomic force microscope. Scanning Microscopy. 6:919-930). Furthermore, the pox viruses used were characterized separately by AFM in an aqueous environment down to the molecular level. Quasi-ordered structural details were resolved on a scale of a few nm where, however, image distortions and artifacts due to multiple tip effects are probably involved--just as in very high resolution (<15-20 nm) images on the cells. Although in a very preliminary manner, initial studies on the mechanical resonance properties of a single living (noninfected) cell, held by the micropipette, have been performed. In particular, frequency response spectra were recorded that indicate elastic properties and enough stiffness of these cells to make the demonstrated rapid scanning of the imaging tip plausible. Measurements of this kind, especially if they can be proven to be cell-type specific, may perhaps have a large

  16. Activated FcgammaRII and signalling molecules revealed in rafts by ultra-structural observations of plasma-membrane sheets.

    PubMed

    Strzelecka-Kiliszek, Agnieszka; Korzeniowski, Marek; Kwiatkowska, Katarzyna; Mrozińska, Kazimiera; Sobota, Andrzej

    2004-01-01

    To reveal topography of FcgammaRII components of the receptor-signalling complex, large plasma-membrane sheets were obtained by cell cleavage and analysed by immuno-electron microscopy. Non-activated FcgammaRII was dispersed in the plane of the plasma membrane and only rarely was localized in the proximity of Lyn, an Src family tyrosine kinase, and CD55, a glycosylphosphatidylinositol-anchored protein. After FcgammaRII activation by cross-linking with antibodies, clusters of an electron-dense material acquiring about 86% of FcgammaRII and reaching up to 300 nm in diameter were formed within 5 min. These structures also accommodated about 85% of Lyn and 63% of CD55 labels that were located in close vicinity of gold particles attributed to the cross-linked FcgammaRII . The electron-dense structures were also abundant in tyrosine phosphorylated proteins. At their margins PIP2 was preferentially located. Based on a concentration of Lyn, CD55 and activated FcgammaRII , the electron-dense structures seem to reflect coalescent membrane rafts.

  17. Persistent inelastic deformation in central Japan revealed by GPS observation before and after the Tohoku-oki earthquake

    NASA Astrophysics Data System (ADS)

    Meneses-Gutierrez, Angela; Sagiya, Takeshi

    2016-09-01

    We analyze strain rate distribution in central-northeastern Japan based on continuous GPS data before and after the occurrence of the Great Tohoku earthquake (Mw 9.0) on March 11th, 2011, focusing on the far-field response in the Niigata Kobe Tectonic Zone (NKTZ), an E-W contraction region along the Japan seacoast of central Japan. Wavelength decomposition of the strain rate on the E-W direction, calculated from GPS data, indicates that the long-wavelength pattern changed from preseismic E-W contraction to postseismic E-W extension, representing elastic response to plate interaction at the Japan Trench. However, the short wavelength patterns reveal a persistent localized contraction zone around northern NKTZ before and after the Tohoku-oki earthquake. The persistent localized deformation pattern can be reproduced by an aseismic slip on a fault cutting the lower crust and a part of the upper crust. These results demonstrate that an inelastic process plays an essential role in the deformation of the Japan island arc.

  18. Post-eruptive volcanic dome evolution as revealed by deformation and microgravity observations at Usu volcano (Hokkaido, Japan)

    NASA Astrophysics Data System (ADS)

    Jousset, Philippe; Okada, Hiromu

    1999-04-01

    Usu volcano (Hokkaido, Japan) is a dacitic volcano, known for its high production rate of lava domes and crypto-domes. It is thus a good target to study processes of volcanic dome evolution (upheaval and/or relaxation). We carried out repeated GPS and microgravity surveys on the three most recent domes of Mt. Usu (1910: Meiji Shinzan; 1943-1945: Showa-Shinzan and 1977-1982: Usu-Shinzan). The repeat period was 1 to 2 months and extended from October 1996 to June 1997. We also compare new data with results from former studies. More than 20 years after the start of Usu-Shinzan dome growth, there is still subsidence at a maximum rate of about 7 to 8 cm/year. The reasons for this subsidence are discussed. Repeated gravity surveys revealed an increase of gravity on the domes (about 60±10 microgal/year for Usu-Shinzan, about 15 microgal at Showa-Shinzan and 10 to 20 microgal for Meiji-shinzan); this gravity increase exceeds that expected due to subsidence. We discuss and interpret the excess gravity change in terms of a density increase in the edifice, caused by a combination of processes (contraction of the edifice, water level change, devesiculisation, cooling and magma intrusion). Quantification of these processes at Usu volcano may help to understand the processes of evolution at domes on other volcanoes such as Merapi (Indonesia), Unzen (Japan) or Montserrat (West Indies).

  19. The Emergence of AFM Applications to Cell Biology: How new technologies are facilitating investigation of human cells in health and disease at the nanoscale

    PubMed Central

    Yang, Ruiguo; Xi, Ning; Fung, Carmen Kar Man; Seiffert-Sinha, Kristina; Lai, King Wai Chiu; Sinha, Animesh A.

    2013-01-01

    Atomic Force Microscopy (AFM) based nanorobotics has been used for building nano devices in semiconductors for almost a decade. Leveraging the unparallel precision localization capabilities of this technology, high resolution imaging and mechanical property characterization is now increasingly being performed in biological settings. AFM also offers the prospect for handling and manipulating biological materials at nanometer scale. It has unique advantages over other methods, permitting experiments in the liquid phase where physiological conditions can be maintained. Taking advantage of these properties, our group has visualized membrane and cytoskeletal structures of live cells by controlling the interaction force of the AFM tip with cellular components at the nN or sub-nN range. Cell stiffness changes were observed by statistically analyzing the Young’s modulus values of human keratinocytes before and after specific antibody treatment. Furthermore, we used the AFM cantilever as a robotic arm for mechanical pushing, pulling and cutting to perform nanoscale manipulations of cell-associated structures. AFM guided nano-dissection, or nanosurgery was enacted on the cell in order to sever intermediate filaments connecting neighboring keratinocytes via sub 100 nm resolution cuts. Finally, we have used a functionalized AFM tip to probe cell surface receptors to obtain binding force measurements. This technique formed the basis for Single Molecule Force Spectroscopy (SMFS). In addition to enhancing our basic understanding of dynamic signaling events in cell biology, these advancements in AFM based biomedical investigations can be expected to facilitate the search for biomarkers related to disease diagnosis progress and treatment. PMID:24416719

  20. Kaposiform hemangioendothelioma complicated by Kasabach-Merritt phenomenon: ultrastructural observation and immunohistochemistry staining reveal the trapping of blood components.

    PubMed

    Yuan, Si-Ming; Hong, Zhi-Jian; Chen, Hai-Ni; Shen, Wei-Min; Zhou, Xiao-Jun

    2013-12-01

    Kaposiform hemangioendothelioma (KHE), a borderline tumor of endothelial origin, is associated with Kasabach-Merritt phenomenon, characterized by profound thrombocytopenia and consumptive coagulopathy resulting from the localized intravascular coagulation (LIC) in the tumor. Previous studies have suggested that the trapping of blood components, including platelets, may underlie the LIC in KHE. However, more evidence is needed to support this hypothesis. In this study, one case of a Chinese infant with a KHE in the left arm was complicated by Kasabach-Merritt phenomenon. The tumor was partially resected and the sample was used for ultrastructural observation and immunohistochemistry staining of Glut-1. Ultrastructural observation found the trapping of erythrocytes, platelets, macrophages, and lymphocytes in the slit-like channels of the tumor nodules, and phagocytic vesicles in the cytoplasm of neoplastic cells. Immunohistochemistry staining further showed numerous Glut-1(+) erythrocytes in the channels. In conclusion, our results provided compelling morphological evidence of the trapping of blood components in KHE, which may interpret the LIC in the tumor and subsequent consumptive coagulopathy.

  1. Revealing the broad iron Kα line in Cygnus X-1 through simultaneous XMM-Newton, RXTE, and INTEGRAL observations

    NASA Astrophysics Data System (ADS)

    Duro, Refiz; Dauser, Thomas; Grinberg, Victoria; Miškovičová, Ivica; Rodriguez, Jérôme; Tomsick, John; Hanke, Manfred; Pottschmidt, Katja; Nowak, Michael A.; Kreykenbohm, Sonja; Cadolle Bel, Marion; Bodaghee, Arash; Lohfink, Anne; Reynolds, Christopher S.; Kendziorra, Eckhard; Kirsch, Marcus G. F.; Staubert, Rüdiger; Wilms, Jörn

    2016-05-01

    We report on the analysis of the broad Fe Kα line feature of Cyg X-1 in the spectra of four simultaneous hard intermediate state observations made with the X-ray Multiple Mirror mission (XMM-Newton), the Rossi X-ray Timing Explorer (RXTE), and the International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The high quality of the XMM-Newton data taken in the Modified Timing Mode of the EPIC-pn camera provides a great opportunity to investigate the broadened Fe Kα reflection line at 6.4 keV with a very high signal to noise ratio. The 4-500 keV energy range is used to constrain the underlying continuum and the reflection at higher energies. We first investigate the data by applying a phenomenological model that consists of the sum of an exponentially cutoff power law and relativistically smeared reflection. Additionally, we apply a more physical approach and model the irradiation of the accretion disk directly from the lamp post geometry. All four observations show consistent values for the black hole parameters with a spin of a ~ 0.9, in agreement with recent measurements from reflection and disk continuum fitting. The inclination is found to be i ~ 30°, consistent with the orbital inclination and different from inclination measurements made during the soft state, which show a higher inclination. We speculate that the difference between the inclination measurements is due to changes in the inner region of the accretion disk.

  2. Direct observation of single stationary-phase bacteria reveals a surprisingly long period of constant protein production activity

    PubMed Central

    Gefen, Orit; Fridman, Ofer; Ronin, Irine; Balaban, Nathalie Q.

    2014-01-01

    Exponentially growing bacteria are rarely found in the wild, as microorganisms tend to spend most of their lifetime at stationary phase. Despite this general prevalence of stationary-phase bacteria, they are as yet poorly characterized. Our goal was to quantitatively study this phase by direct observation of single bacteria as they enter into stationary phase and by monitoring their activity over several days during growth arrest. For this purpose, we devised an experimental procedure for starving single Escherichia coli bacteria in microfluidic devices and measured their activity by monitoring the production rate of fluorescent proteins. When amino acids were the sole carbon source, the production rate decreased by an order of magnitude upon entry into stationary phase. We found that, even while growth-arrested, bacteria continued to produce proteins at a surprisingly constant rate over several days. Our identification of this newly observed period of constant activity in nongrowing cells, designated as constant activity stationary phase, makes possible the conduction of assays that require constant protein expression over time, and are therefore difficult to perform under exponential growth conditions. Moreover, we show that exogenous protein expression bears no fitness cost on the regrowth of the population when starvation ends. Further characterization of constant activity stationary phase—a phase where nongrowing bacteria can be quantitatively studied over several days in a reproducible manner—should contribute to a better understanding of this ubiquitous but overlooked physiological state of bacteria in nature. PMID:24344288

  3. Satellite observations reveal little inter-annual variability in the radiant flux from the Mount Erebus lava lake

    NASA Astrophysics Data System (ADS)

    Wright, Robert; Pilger, Eric

    2008-11-01

    Satellite remote sensing represents a mature technology for long-term monitoring of volcanic activity at Mount Erebus, either independently or as a complement to field instrumentation. Observations made on 4290 discrete occasions over a six year period by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) indicate that the radiant flux from the volcano's summit crater (and by inference, the lava lake contained therein), while variable on the time scale of days to weeks, has varied little on an inter-annual basis over this period. The average radiant flux from the lake during this time was 15 MW, with a maximum flux of 100 MW. Such heat flux time-series have been shown to act as a reliable proxy for general levels of activity at erupting volcanoes around the world, particularly when these time-series are of a long duration. The apparent stability of Erebus' power output is in marked contrast to fluxes observed at three other terrestrial volcanoes, Erta 'Ale (Ethiopia), Nyiragongo (Democratic Republic of Congo) and Ambrym (Vanuatu), which, while also hosting active lava lakes, all exhibit much greater variability in radiant flux over the same period of time. The results presented in this paper are confluent with those obtained from geochemical considerations of the Erebus' degassing regime, and confirm that remarkably stable open-system volcanism appears to be characteristic of this long-active volcano.

  4. GAS INFLOW AND OUTFLOW HISTORIES IN DISK GALAXIES AS REVEALED FROM OBSERVATIONS OF DISTANT STAR-FORMING GALAXIES

    SciTech Connect

    Toyouchi, Daisuke; Chiba, Masashi

    2015-09-01

    We investigate gas inflow and outflow histories in Milky Way-like disk galaxies, to get new insights into the baryonic processes in galaxy formation and evolution. For this purpose, we solve the equations for the evolution of the surface mass densities of gas and metals at each radius in a galactic disk, based on the observed structural properties of distant star-forming galaxies, including the redshift evolution of their stellar mass distribution, their scaling relation between the mass of baryonic components, star formation rate (SFR), and chemical abundance, as well as the supposed evolution of their radial metallicity gradients (RMGs). We find that the efficiency of gas inflow for a given SFR decreases with time and that the inflow rate is always nearly proportional to the SFR. For gas outflow, although its efficiency for a given SFR is a decreasing function of time, similar to gas inflow, the outflow rate is not necessarily proportional to the SFR and the relation between the outflow rate and SFR strongly depends on the evolution of the adopted RMG. We also find that the results on the outflow rate can be reproduced in the framework of a momentum-driven (energy-driven) wind mechanism if the RMG is steepening (flattening) with time. Therefore if the well-measured RMGs and their evolution for Milky Way-like galaxies are obtained from future observations, then our results will be useful to constrain the main driving mechanism for their galactic outflows.

  5. Adsorption Studies with AFM of Human Plasma Fibrinogen on Silicon Surfaces

    NASA Astrophysics Data System (ADS)

    Gause, Sheena; Kong, Wendy; Rowe

    2007-11-01

    Fibrinogen (FGN) plays an important role in the clotting of blood. Human plasma fibrinogen (HPF) is a protein that readily adsorbs on biomaterial surfaces. The purpose of this experiment was to use the Atomic Force Microscope to study the adsorption of HPF molecules or FGN onto several silicon surfaces with different orientations and resistivities. The size of the FGN molecules found to be somewhat different of Si(111), (100) and (110) were compared to the size of the FGN molecules in solution (45 nm in length, the end dynodes measures to be 6.5 nm in diameter, and the middle dynode measures to be 5 nm in diameter. For this study, the CPR (Thermo-microscope) Atomic Force Microscope (AFM) was used to observe the amount of fibrinogen molecules adsorbed by Si (111) with a resistance of .0281-.0261 φ cm, Si (111) with a resistance of 1 φ cm, Si (100), and Si (110) surfaces. In finding any single fibrinogen molecules, the appropriate image scans and measurements were taken. After collection and analysis of the data, it was found from AFM that the fibrinogen molecules found on Si (110) mostly resembled fibrinogen molecules found in solution. The other images showed that the fibrinogen molecules adsorbed on Silicon substrates is significantly greater (˜10-20 %) than those in solution.

  6. Possible enhancements of AFM spin-fluctuations in high-TC cuprates

    NASA Astrophysics Data System (ADS)

    Jarlborg, Thomas

    2009-03-01

    Ab-initio band calculations for high-TC cuprates, together with modelling based of a free electron like band, show a strong interaction between anti-ferromagnetic (AFM) spin waves and periodic lattice distortions as for phonons, even though this type of spin-phonon coupling (SPC) is underestimated in calculations using the local density approximation. The SPC has a direct influence on the properties of the HTC cuprates and it can explain many observations. The strongest effects are seen for modulated waves in the CuO bond direction, and a band gap is formed near the X,Y points, but unusal band dispersion (like ``waterfalls'') might also be induced below the Fermi energy (EF) in the diagonal direction. The band results are used to propose different ways of increasing AFM spin-fluctuations locally, and to have a higher density-of-states (DOS) at EF. Static potential modulations, via periodic distribution of dopants or lattice distortions, can be tuned to increase the DOS. This opens for possibilities to enhance coupling for spin fluctuations (λsf) and superconductivity. The exchange enhancement is in general increased near a surface, which suggests a tendency towards static spin configurations. The sensivity of the band results to corrections of the local density potential are discussed.

  7. Cantilever energy effects on bimodal AFM: phase and amplitude contrast of multicomponent samples

    NASA Astrophysics Data System (ADS)

    Chakraborty, Ishita; Yablon, Dalia G.

    2013-11-01

    Bimodal atomic force microscopy (AFM) is a recently developed technique of dynamic AFM where a higher eigenmode of the cantilever is simultaneously excited along with the fundamental eigenmode. The effects of different operating parameters while imaging an impact copolymer blend of polypropylene (PP) and ethylene-propylene (E-P) rubber in bimodal mode are explored through experiments and numerical simulations. The higher mode amplitude and phase contrasts between the two components of the sample reverse at different points as the free amplitude of the higher eigenmode is increased. Three different regimes are identified experimentally depending on the relative contrast between the PP and the E-P rubber. It is observed that the kinetic energy and free air drive input energy of the two cantilever eigenmodes play a role in determining the regimes of operation. Numerical simulations conducted with appropriate tip-sample interaction forces support the experimental results. An understanding of these regimes and the associated cantilever dynamics will guide a rational approach towards selecting appropriate operating parameters.

  8. Cantilever energy effects on bimodal AFM: phase and amplitude contrast of multicomponent samples.

    PubMed

    Chakraborty, Ishita; Yablon, Dalia G

    2013-11-29

    Bimodal atomic force microscopy (AFM) is a recently developed technique of dynamic AFM where a higher eigenmode of the cantilever is simultaneously excited along with the fundamental eigenmode. The effects of different operating parameters while imaging an impact copolymer blend of polypropylene (PP) and ethylene-propylene (E-P) rubber in bimodal mode are explored through experiments and numerical simulations. The higher mode amplitude and phase contrasts between the two components of the sample reverse at different points as the free amplitude of the higher eigenmode is increased. Three different regimes are identified experimentally depending on the relative contrast between the PP and the E-P rubber. It is observed that the kinetic energy and free air drive input energy of the two cantilever eigenmodes play a role in determining the regimes of operation. Numerical simulations conducted with appropriate tip-sample interaction forces support the experimental results. An understanding of these regimes and the associated cantilever dynamics will guide a rational approach towards selecting appropriate operating parameters.

  9. Combining AFM and Acoustic Probes to Reveal Changes in the Elastic Stiffness Tensor of Living Cells

    PubMed Central

    Nijenhuis, Nadja; Zhao, Xuegen; Carisey, Alex; Ballestrem, Christoph; Derby, Brian

    2014-01-01

    Knowledge of how the elastic stiffness of a cell affects its communication with its environment is of fundamental importance for the understanding of tissue integrity in health and disease. For stiffness measurements, it has been customary to quote a single parameter quantity, e.g., Young’s modulus, rather than the minimum of two terms of the stiffness tensor required by elasticity theory. In this study, we use two independent methods (acoustic microscopy and atomic force microscopy nanoindentation) to characterize the elastic properties of a cell and thus determine two independent elastic constants. This allows us to explore in detail how the mechanical properties of cells change in response to signaling pathways that are known to regulate the cell’s cytoskeleton. In particular, we demonstrate that altering the tensioning of actin filaments in NIH3T3 cells has a strong influence on the cell's shear modulus but leaves its bulk modulus unchanged. In contrast, altering the polymerization state of actin filaments influences bulk and shear modulus in a similar manner. In addition, we can use the data to directly determine the Poisson ratio of a cell and show that in all cases studied, it is less than, but very close to, 0.5 in value. PMID:25296302

  10. Experimental and observational evidence reveals that predators in natural environments do not regulate their prey: They are passengers, not drivers

    NASA Astrophysics Data System (ADS)

    White, T. C. R.

    2013-11-01

    Among both ecologists and the wider community there is a tacit assumption that predators regulate populations of their prey. But there is evidence from a wide taxonomic and geographic range of studies that predators that are adapted to co-evolved prey generally do not regulate their prey. This is because predators either cannot reproduce as fast as their prey and/or are inefficient hunters unable to catch enough prey to sustain maximum reproduction. The greater capacity of herbivores to breed successfully is, however, normally restricted by a lack of enough food of sufficient quality to support reproduction. But whenever this shortage is alleviated by a large pulse of food, herbivores increase their numbers to outbreak levels. Their predators are unable to contain this increase, but their numbers, too, surge in response to this increase in food. Eventually both their populations will crash once the food supply runs out, first for the herbivores and then for the predators. Then an “over-run” of predators will further depress the already declining prey population, appearing to be controlling its abundance. This latter phenomenon has led many ecologists to conclude that predators are regulating the numbers of their prey. However, it is the same process that is revealed during outbreaks that limits populations of both predator and prey in “normal” times, although this is usually not readily apparent. Nevertheless, as all the diverse cases discussed here attest, the abundance of predators and their co-evolved prey are both limited by their food: the predators are passengers, not drivers.

  11. RADIO AND X-RAY OBSERVATIONS OF THE TYPE Ic SN 2007gr REVEAL AN ORDINARY, NON-RELATIVISTIC EXPLOSION

    SciTech Connect

    Soderberg, A. M.; Brunthaler, A.; Nakar, E.; Chevalier, R. A.; Bietenholz, M. F.

    2010-12-10

    We present extensive radio and X-ray observations of the nearby Type Ic SN 2007gr in NGC 1058 obtained with the Very Large Array (VLA) and the Chandra X-ray Observatory and spanning 5 to 150 days after explosion. Through our detailed modeling of these data, we estimate the properties of the blast wave and the circumstellar environment. We find evidence for a freely expanding and non-relativistic explosion with an average blast wave velocity, v-bar {approx}0.2c, and a total internal energy for the radio emitting material of E {approx} 2 x 10{sup 46} erg assuming equipartition of energy between electrons and magnetic fields ({epsilon}{sub e} = {epsilon}{sub B} = 0.1). The temporal and spectral evolution of the radio emission points to a stellar wind-blown environment shaped by a steady progenitor mass loss rate of M-dot {approx}6x10{sup -7} M{sub sun} yr{sup -1} (wind velocity, v{sub w} = 10{sup 3} km s{sup -1}). These parameters are fully consistent with those inferred for other SNe Ibc and are in line with the expectations for an ordinary, homologous SN explosion. Our results are at odds with those of Paragi et al. who recently reported evidence for a relativistic blast wave in SN 2007gr based on their claim that the radio emission was resolved away in a low signal-to-noise Very Long Baseline Interferometry (VLBI) observation. Here we show that the exotic physical scenarios required to explain the claimed relativistic velocity-extreme departures from equipartition and/or a highly collimated outflow-are excluded by our detailed VLA radio observations. Moreover, we present an independent analysis of the VLBI data and propose that a modest loss of phase coherence provides a more natural explanation for the apparent flux density loss which is evident on both short and long baselines. We conclude that SN 2007gr is an ordinary Type Ibc supernova.

  12. UV laser ablation of intraocular lenses: SEM and AFM microscopy examination of the biomaterial surface

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Asproudis, I.; Tsoutsi, D.; Bacharis, C.; Moutsouris, K.; Makropoulou, M.; Serafetinides, A. A.

    2010-02-01

    Several new materials and patterns are studied for the formation and etching of intraocular lenses (IOLs), in order to improve their optical properties, to reduce the diffractive aberrations and to decrease the incidence of posterior capsular opacification. The aim of this study is to investigate the use of UV ( λ = 266 nm) laser pulses to ablate the intraocular lenses materials, and thus to provide an alternative to conventional surface shaping techniques for IOLs fabrication. Ablation experiments were conducted using various polymer substrates of hydrophobic acrylic IOLs and PMMA IOLs. We investigated the ablation efficiency and the morphology of the ablated area by imaging the surface modification with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The morphological appearance of IOL samples reveals the effect of a photochemical and photothermal ablation mechanism.

  13. [AFM study on microtopography of NOM and newly formed hydrous manganese dioxide adsorbed on mica].

    PubMed

    Guo, Jin; Ma, Jun; Shi, Xue-hua

    2006-05-01

    With the methods of mica adsorbing, the microtopography of the newly formed hydrous manganese dioxide was perfectly captured. The tapping mode AFM study results revealed that the newly formed hydrous manganese dioxide possesses a perforated sheet (with a thickness of 0-1.75 nm) as well as some spheric particle structures compared with the hydrous manganese dioxide with 2 h aging time, which demonstrated that the newly formed hydrous manganese dioxide have a large surface area and adsorption capacity. When 1 mmol/L newly formed hydrous manganese dioxide was added, the microtopography of NOM molecules shifted from loosely dispersed pancake shape (with adsorption height of 5-8.5 nm) to densely dispersed and uniform spheric structure. NOM was prone to adsorb on the surface of the newly formed hydrous manganese dioxide, which provided a valid proof for the coagulation-aid mechanism of permanganate preoxidation.

  14. Hubble Space Telescope/NICMOS Observations of I Zw 18: A Population of Old Asymptotic Giant Branch Stars Revealed.

    PubMed

    Östlin

    2000-06-01

    I present the first results from a Hubble Space Telescope/NICMOS imaging study of the most metal-poor blue compact dwarf galaxy, I Zw 18. The near-infrared color-magnitude diagram (CMD) is dominated by two populations, one 10-20 Myr population of red supergiants and one 0.1-5 Gyr population of asymptotic giant branch stars. Stars older than 1 Gyr are required to explain the observed CMD at the adopted distance of 12.6 Mpc, showing that I Zw 18 is not a young galaxy. The results hold also if the distance to I Zw 18 is significantly larger. This rules out the possibility that I Zw 18 is a truly young galaxy formed recently in the local universe.

  15. The Radial Distribution of H2 and CO in TW Hya as Revealed by Resolved ALMA Observations of CO Isotopologues

    NASA Astrophysics Data System (ADS)

    Schwarz, Kamber R.; Bergin, Edwin A.; Cleeves, L. Ilsedore; Blake, Geoffrey A.; Zhang, Ke; Öberg, Karin I.; van Dishoeck, Ewine F.; Qi, Chunhua

    2016-06-01

    CO is widely used as a tracer of molecular gas. However, there is now mounting evidence that gas phase carbon is depleted in the disk around TW Hya. Previous efforts to quantify this depletion have been hampered by uncertainties regarding the radial thermal structure in the disk. Here we present resolved ALMA observations of 13CO 3-2, C18O 3-2, 13CO 6-5, and C18O 6-5 emission in TW Hya, which allow us to derive radial gas temperature and gas surface density profiles, as well as map the CO abundance as a function of radius. These observations provide a measurement of the surface CO snowline at ˜30 AU and show evidence for an outer ring of CO emission centered at 53 AU, a feature previously seen only in less abundant species. Further, the derived CO gas temperature profile constrains the freeze out temperature of CO in the warm molecular layer to \\lt 21 K. Combined with the previous detection of HD 1-0, these data constrain the surface density of the warm H2 gas in the inner ˜30 AU such that {{{Σ }}}{warm{gas}}={4.7}-2.9+3.0 {{g}} {{cm}}-2{(R/10{au})}-1/2. We find that CO is depleted by two orders of magnitude from R=10{--}60 {{AU}}, with the small amount of CO returning to the gas phase inside the surface CO snowline insufficient to explain the overall depletion. Finally, this new data is used in conjunction with previous modeling of the TW Hya disk to constrain the midplane CO snowline to 17-23 AU.

  16. The circumbinary dusty disk of upsilon Sgr revealed by mid-IR interferometric observations with the VLTI/MIDI

    NASA Astrophysics Data System (ADS)

    Bonneau, D.; Netolický, M.; Chesneau, O.; Harmanec, P.; Koubský, P.; Mourard, D.; Stee, P.

    2008-11-01

    The first mid-IR interferometric observations of a hydrogen-deficient binary star, υ Sgr, were carried out using the MIDI/VLTI instrument between April 2007 and May 2008. The dusty circumbinary envelope is resolved in the N band (8-13.5 μ m), and has a typical size of 20 x 14 mas. The calibrated fringe visibilities, the mid-IR spectrum and the SED were fitted using models computed with the radiative transfer code MC3D using several mixtures of carbon and silicate dust, in order to determine the geometry and chemical composition of the envelope. The best model we obtain is a geometrically thin and dense disk with an inner radius of R_{in} ≃ 6.0AU and a scale height h_{100} ≃ 3.5 AU. The inclination of the disk is i ≃ 50° and its position angle is PA ≃ 80°. The chemical composition of the dust is approximatelya ratio of 60% of carbon dust and 40% of silicate dust. We constrained for the first time the geometry and the chemistry of the circumbinary dusty envelope of υ Sgr. It is now clear that the components of υ Sgr are massive stars (> 10 M_⊙) and the results are compatible with evolutionary scenario proposed by Delgado & Thomas (1981) of a binary with massive components experiencing several phases of important mass transfer leading to the hydrogen-deficient primary star. However, complementary spectro-interferometric observations in the near infrared and the visible are mandatory to investigate the complex structure of the inner circumstellar environment and directly resolve the stellar components of the υ Sgr system.

  17. SU-8 hollow cantilevers for AFM cell adhesion studies

    NASA Astrophysics Data System (ADS)

    Martinez, Vincent; Behr, Pascal; Drechsler, Ute; Polesel-Maris, Jérôme; Potthoff, Eva; Vörös, Janos; Zambelli, Tomaso

    2016-05-01

    A novel fabrication method was established to produce flexible, transparent, and robust tipless hollow atomic force microscopy (AFM) cantilevers made entirely from SU-8. Channels of 3 μm thickness and several millimeters length were integrated into 12 μm thick and 40 μm wide cantilevers. Connected to a pressure controller, the devices showed high sealing performance with no leakage up to 6 bars. Changing the cantilever lengths from 100 μm to 500 μm among the same wafer allowed the targeting of various spring constants ranging from 0.5 to 80 N m-1 within a single fabrication run. These hollow polymeric AFM cantilevers were operated in the optical beam deflection configuration. To demonstrate the performance of the device, single-cell force spectroscopy experiments were performed with a single probe detaching in a serial protocol more than 100 Saccharomyces cerevisiae yeast cells from plain glass and glass coated with polydopamine while measuring adhesion forces in the sub-nanoNewton range. SU-8 now offers a new alternative to conventional silicon-based hollow cantilevers with more flexibility in terms of complex geometric design and surface chemistry modification.

  18. AFM analysis of bleaching effects on dental enamel microtopography

    NASA Astrophysics Data System (ADS)

    Pedreira de Freitas, Ana Carolina; Espejo, Luciana Cardoso; Botta, Sergio Brossi; Teixeira, Fernanda de Sa; Luz, Maria Aparecida A. Cerqueira; Garone-Netto, Narciso; Matos, Adriana Bona; Salvadori, Maria Cecilia Barbosa da Silveira

    2010-02-01

    The purpose of this in vitro study was to test a new methodology to evaluate the effects of 35% hydrogen peroxide agent on the microtopography of sound enamel using an atomic force microscope (AFM). The buccal sound surfaces of three extracted human lower incisors were used, without polishing the surfaces to maintain them with natural morphology. These unpolished surfaces were subjected to bleaching procedure with 35% hydrogen peroxide that consisted of 4 applications of the bleaching agent on enamel surfaces for 10 min each application. Surface images were obtained in a 15 μm × 15 μm area using an AFM. The roughness (Ra and RMS) and the power spectral density (PSD) were obtained before and after the bleaching treatment. As results we could inquire that the PSD analyses were very suitable to identifying the morphological changes on the surfaces, while the Ra and RMS parameters were insufficient to represent the morphological alterations promoted by bleaching procedure on enamel. The morphological wavelength in the range of visible light spectrum (380-750 nm) was analyzed, showing a considerable increase of the PSD with the bleaching treatment.

  19. Pathogen identification using peptide nanotube biosensors and impedance AFM

    NASA Astrophysics Data System (ADS)

    Maccuspie, Robert I.

    Pathogen identification at highly sensitive levels is crucial to meet urgent needs in fighting the spread of disease or detecting bioterrorism events. Toward that end, a new method for biosensing utilizing fluorescent antibody nanotubes is proposed. Fundamental studies on the self-assembly of these peptide nanotubes are performed, as are applications of aligning these nanotubes on surfaces. As biosensors, these nanotubes incorporate recognition units with antibodies at their ends and fluorescent signaling units at their sidewalls. When viral pathogens were mixed with these antibody nanotubes in solution, the nanotubes rapidly aggregated around the viruses. The size of the aggregates increased as the concentration of viruses increased, as detected by flow cytometry on the order of attomolar concentrations by changes in fluorescence and light scattering intensities. This enabled determination of the concentrations of viruses at trace levels (102 to 106 pfu/mL) within 30 minutes from the receipt of samples to the final quantitative data analysis, as demonstrated on Adenovirus, Herpes Simplex Virus, Influenza, and Vaccinia virus. As another separate approach, impedance AFM is used to study the electrical properties of individual viruses and nanoparticles used as model systems. The design, development, and implementation of the impedance AFM for an Asylum Research platform is described, as well as its application towards studying the impedance of individual nanoparticles as a model system for understanding the fundamental science of how the life cycle of a virus affects its electrical properties. In combination, these approaches fill a pressing need to quantify viruses both rapidly and sensitively.

  20. Structure of the Circumnuclear Region of Seyfert 2 Galaxies Revealed by RXTE Hard X-Ray Observations of NGC 4945

    NASA Technical Reports Server (NTRS)

    Madejski, G.; Zycki, P.; Done, C.; Valinia, A.; Blanco, P.; Rothschild, R.; Turek, B.

    2000-01-01

    NGC 4945 is one of the brightest Se.yfert galaxies on the sky at 100 keV, but is completely absorbed below 10 keV, implying an optical depth of the absorber to electron scattering of a few; its absorption column is probably the largest which still allows a direct view of the nucleus at hard X-ray energies. Our observations of it with the Rossi X-ray Timing Explorer (RXTE) satellite confirm the large absorption, which for a simple phenomenological fit using an absorber with Solar abundances implies a column of 4.5(sup 0.4, sub -0.4) x 10(exp 24) /sq cm. Using a a more realistic scenario (requiring Monte Carlo modeling of the scattering), we infer the optical depth to Thomson scattering of approximately 2.4. If such a scattering medium were to subtend a large solid angle from the nucleus, it should smear out any intrinsic hard X-ray variability on time scales shorter than the light travel time through it. The rapid (with a time scale of approximately a day) hard X-ray variability of NGC 4945 we observed with the RXTE implies that the bulk of the extreme absorption in this object does not originate in a parsec-size, geometrically thick molecular torus. Limits on the amount of scattered flux require that the optically thick material on parsec scales must be rather geometrically thin, subtending a half-angle < 10 deg. This is only marginally consistent with the recent determinations of the obscuring column in hard X-rays, where only a quarter of Seyfert 2s have columns which are optically thick, and presents a problem in accounting for the Cosmic X-ray Background primarily with AGN possessing the geometry as that inferred by us. The small solid angle of the obscuring material, together with the black hole mass (of approximately 1.4 x 10(exp 6) solar mass) from megamaser measurements. allows a robust determination of the source luminosity, which in turn implies that the source radiates at approximately 10% of the Eddington limit.

  1. SN 2010jl: Optical to hard X-ray observations reveal an explosion embedded in a ten solar mass cocoon

    SciTech Connect

    Ofek, Eran O.; Gal-Yam, Avishay; Arcavi, Iair; Zoglauer, Andreas; Boggs, Steven E.; Barriére, Nicolas M.; Reynolds, Stephen P.; Fryer, Chris L.; Even, Wesley; Harrison, Fiona A.; Kulkarni, Shrinivas R.; Bellm, Eric; Grefenstette, Brian; Cenko, S. Bradley; Bloom, Joshua S.; Filippenko, Alexei V.; Christensen, Finn; Craig, William W.; Hailey, Charles J.; Laher, Russ; and others

    2014-01-20

    Some supernovae (SNe) may be powered by the interaction of the SN ejecta with a large amount of circumstellar matter (CSM). However, quantitative estimates of the CSM mass around such SNe are missing when the CSM material is optically thick. Specifically, current estimators are sensitive to uncertainties regarding the CSM density profile and the ejecta velocity. Here we outline a method to measure the mass of the optically thick CSM around such SNe. We present new visible-light and X-ray observations of SN 2010jl (PTF 10aaxf), including the first detection of an SN in the hard X-ray band using NuSTAR. The total radiated luminosity of SN 2010jl is extreme—at least 9 × 10{sup 50} erg. By modeling the visible-light data, we robustly show that the mass of the circumstellar material within ∼10{sup 16} cm of the progenitor of SN 2010jl was in excess of 10 M {sub ☉}. This mass was likely ejected tens of years prior to the SN explosion. Our modeling suggests that the shock velocity during shock breakout was ∼6000 km s{sup –1}, decelerating to ∼2600 km s{sup –1} about 2 yr after maximum light. Furthermore, our late-time NuSTAR and XMM spectra of the SN presumably provide the first direct measurement of SN shock velocity 2 yr after the SN maximum light—measured to be in the range of 2000-4500 km s{sup –1} if the ions and electrons are in equilibrium, and ≳ 2000 km s{sup –1} if they are not in equilibrium. This measurement is in agreement with the shock velocity predicted by our modeling of the visible-light data. Our observations also show that the average radial density distribution of the CSM roughly follows an r {sup –2} law. A possible explanation for the ≳ 10 M {sub ☉} of CSM and the wind-like profile is that they are the result of multiple pulsational pair instability events prior to the SN explosion, separated from each other by years.

  2. Predictive Factors for Anastomotic Leakage After Colorectal Surgery: Study Protocol for a Prospective Observational Study (REVEAL Study)

    PubMed Central

    Bosmans, Joanna WAM; Kartal, Serdar; Lubbers, Tim; Sosef, Meindert; Slooter, Gerrit D; Stoot, Jan H; van Schooten, Frederik-Jan; Bouvy, Nicole D; Derikx, Joep PM

    2016-01-01

    Background Anastomotic leakage (AL) remains the most important complication following colorectal surgery, and is associated with high morbidity and mortality rates. Previous research has focused on identifying risk factors and potential biomarkers for AL, but the sensitivity of these tests remains poor. Objective This prospective multicenter observational study aims at combining multiple parameters to establish a diagnostic algorithm for colorectal AL. Methods This study aims to include 588 patients undergoing surgery for colorectal carcinoma. Patients will be eligible for inclusion when surgery includes the construction of a colorectal anastomosis. Patient characteristics will be collected upon consented inclusion, and buccal swabs, breath, stool, and blood samples will be obtained prior to surgery. These samples will allow for the collection of information regarding patients’ inflammatory status, genetic predisposition, and intestinal microbiota. Additionally, breath and blood samples will be taken postoperatively and patients will be strictly observed during their in-hospital stay, and the period shortly thereafter. Results This study has been open for inclusion since August 2015. Conclusions An estimated 8-10% of patients will develop AL following surgery, and they will be compared to non-leakage patients. The objectives of this study are twofold. The primary aim is to establish and validate a diagnostic algorithm for the pre-operative prediction of the risk of AL development using a combination of inflammatory, immune-related, and genetic parameters. Previously established risk factors and novel parameters will be incorporated into this algorithm, which will aid in the recognition of patients who are at risk for AL. Based on these results, recommendations can be made regarding the construction of an anastomosis or deviating stoma, and possible preventive strategies. Furthermore, we aim to develop a new algorithm for the post-operative diagnosis of AL at an

  3. HIGH VELOCITY PRECESSING JETS FROM THE WATER FOUNTAIN IRAS 18286-0959 REVEALED BY VERY LONG BASELINE ARRAY OBSERVATIONS

    SciTech Connect

    Yung, Bosco H. K.; Nakashima, Jun-ichi; Kwok, Sun; Imai, Hiroshi; Deguchi, Shuji; Diamond, Philip J.

    2011-11-10

    We report the results of multi-epoch Very Long Baseline Array observations of the 22.2 GHz H{sub 2}O maser emission associated with the 'water fountain' IRAS 18286-0959. We suggest that this object is the second example of a highly collimated bipolar precessing outflow traced by H{sub 2}O maser emission, the other is W 43A. The detected H{sub 2}O emission peaks are distributed over a velocity range from -50 km s{sup -1} to 150 km s{sup -1}. The spatial distribution of over 70% of the identified maser features is found to be highly collimated along a spiral jet (jet 1) extended southeast to northwest; the remaining features appear to trace another spiral jet (jet 2) with a different orientation. The two jets form a 'double-helix' pattern which lies across {approx}200 mas. The maser distribution is reasonably fit by a model consisting of two bipolar precessing jets. The three-dimensional velocities of jet 1 and jet 2 are derived to be 138 km s{sup -1} and 99 km s{sup -1}, respectively. The precession period of jet 1 is about 56 years. For jet 2, three possible models are tested and they give different values for the kinematic parameters. We propose that the appearance of two jets is the result of a single driving source with significant proper motion.

  4. A scalable algorithm to order and annotate continuous observations reveals the metastable states visited by dynamical systems

    NASA Astrophysics Data System (ADS)

    Blöchliger, Nicolas; Vitalis, Andreas; Caflisch, Amedeo

    2013-11-01

    Advances in IT infrastructure have enabled the generation and storage of very large data sets describing complex systems continuously in time. These can derive from both simulations and measurements. Analysis of such data requires the availability of scalable algorithms. In this contribution, we propose a scalable algorithm that partitions instantaneous observations (snapshots) of a complex system into kinetically distinct sets (termed basins). To do so, we use a combination of ordering snapshots employing the method's only essential parameter, i.e., a definition of pairwise distance, and annotating the resultant sequence, the so-called progress index, in different ways. Specifically, we propose a combination of cut-based and structural annotations with the former responsible for the kinetic grouping and the latter for diagnostics and interpretation. The method is applied to an illustrative test case, and the scaling of an approximate version is demonstrated to be O(NlogN) with N being the number of snapshots. Two real-world data sets from river hydrology measurements and protein folding simulations are then used to highlight the utility of the method in finding basins for complex systems. Both limitations and benefits of the approach are discussed along with routes for future research.

  5. In situ observations of the basal angiosperm Amborella trichopoda reveal a long fruiting cycle overlapping two annual flowering periods.

    PubMed

    Fourcade, Fanny; Pouteau, Robin; Jaffré, Tanguy; Marmey, Philippe

    2015-09-01

    Amborella trichopoda is the sole living angiosperm species belonging to the sister lineage of all other extant flowering plants. In the last decade, the species has been the focus of many phylogenetic, genomic and reproductive biology studies, bringing new highlights regarding the evolution of flowering plants. However, little attention has been paid to in situ A. trichopoda populations, particularly to their fruiting cycle. In this study, an A. trichopoda population was observed during three annual flowering cycles. Individuals and branches were labeled in order to monitor the fruiting cycle precisely, from the flowering stage until the abscission of the fruit. Fruit exocarp was green during the first 9 months following flowering, turned red when the next flowering started a year later then remained on the branch during another year, between fruit ripping and abscission. Presence of fruits with two stages of maturity on shrubs was always noticed. Germination tests showed that seeds acquired their germination capacity 1 year after flowering, when fruits changed color. A. trichopoda's fruiting cycle is a long process overlapping two annual flowering periods. These results introduce a new model for flowering and fruiting cycles. The availability of mature seeds on shrubs for more than 1 year is likely to maximize opportunities to be dispersed, thus promoting the survival of this basal angiosperm.

  6. Atmosphere-Ionosphere Response to the M9 Tohoku Earthquake Revealed by Joined Satellite and Ground Observations. Preliminary Results

    NASA Technical Reports Server (NTRS)

    Ouzounov, Dimitar; Pulinets, Sergey; Romanov, Alexey; Tsybulya, Konstantin; Davidenko, Dimitri; Kafatos, Menas; Taylor, Patrick

    2011-01-01

    The recent M9 Tohoku Japan earthquake of March 11, 2011 was the largest recorded earthquake ever to hit this nation. We retrospectively analyzed the temporal and spatial variations of four different physical parameters - outgoing long wave radiation (OLR), GPS/TEC, Low-Earth orbit tomography and critical frequency foF2. These changes characterize the state of the atmosphere and ionosphere several days before the onset of this earthquake. Our first results show that on March 8th a rapid increase of emitted infrared radiation was observed from the satellite data and an anomaly developed near the epicenter. The GPS/TEC data indicate an increase and variation in electron density reaching a maximum value on March 8. Starting on this day in the lower ionospheric there was also confirmed an abnormal TEC variation over the epicenter. From March 3-11 a large increase in electron concentration was recorded at all four Japanese ground based ionosondes, which return to normal after the main earthquake. We found a positive correlation between the atmospheric and ionospheric anomalies and the Tohoku earthquake. This study may lead to a better understanding of the response of the atmosphere/ionosphere to the Great Tohoku earthquake.

  7. Substantial Underestimation of Post-Harvest Burning Emissions in the North China Plain Revealed by Multi-Species Space Observations.

    PubMed

    Stavrakou, T; Müller, J-F; Bauwens, M; De Smedt, I; Lerot, C; Van Roozendael, M; Coheur, P-F; Clerbaux, C; Boersma, K F; van der A, R; Song, Y

    2016-08-31

    The large-scale burning of crop residues in the North China Plain (NCP), one of the most densely populated world regions, was recently recognized to cause severe air pollution and harmful health effects. A reliable quantification of the magnitude of these fires is needed to assess regional air quality. Here, we use an eight-year record (2005-2012) of formaldehyde measurements from space to constrain the emissions of volatile organic compounds (VOCs) in this region. Using inverse modelling, we derive that satellite-based post-harvest burning fluxes are, on average, at least a factor of 2 higher than state-of-the-art bottom-up statistical estimates, although with significant interannual variability. Crop burning is calculated to cause important increases in surface ozone (+7%) and fine aerosol concentrations (+18%) in the North China Plain in June. The impact of crop fires is also found in satellite observations of other species, glyoxal, nitrogen dioxide and methanol, and we show that those measurements validate the magnitude of the top-down fluxes. Our study indicates that the top-down crop burning fluxes of VOCs in June exceed by almost a factor of 2 the combined emissions from other anthropogenic activities in this region, underscoring the need for targeted actions towards changes in agricultural management practices.

  8. Substantial Underestimation of Post-Harvest Burning Emissions in the North China Plain Revealed by Multi-Species Space Observations

    NASA Astrophysics Data System (ADS)

    Stavrakou, T.; Müller, J.-F.; Bauwens, M.; de Smedt, I.; Lerot, C.; van Roozendael, M.; Coheur, P.-F.; Clerbaux, C.; Boersma, K. F.; van der A, R.; Song, Y.

    2016-08-01

    The large-scale burning of crop residues in the North China Plain (NCP), one of the most densely populated world regions, was recently recognized to cause severe air pollution and harmful health effects. A reliable quantification of the magnitude of these fires is needed to assess regional air quality. Here, we use an eight-year record (2005–2012) of formaldehyde measurements from space to constrain the emissions of volatile organic compounds (VOCs) in this region. Using inverse modelling, we derive that satellite-based post-harvest burning fluxes are, on average, at least a factor of 2 higher than state-of-the-art bottom-up statistical estimates, although with significant interannual variability. Crop burning is calculated to cause important increases in surface ozone (+7%) and fine aerosol concentrations (+18%) in the North China Plain in June. The impact of crop fires is also found in satellite observations of other species, glyoxal, nitrogen dioxide and methanol, and we show that those measurements validate the magnitude of the top-down fluxes. Our study indicates that the top-down crop burning fluxes of VOCs in June exceed by almost a factor of 2 the combined emissions from other anthropogenic activities in this region, underscoring the need for targeted actions towards changes in agricultural management practices.

  9. The 2011 outburst of recurrent nova T PYX: Radio observations reveal the ejecta mass and hint at complex mass loss

    SciTech Connect

    Nelson, Thomas; Chomiuk, Laura; Roy, Nirupam; Krauss, Miriam I.; Mioduszewski, Amy J.; Rupen, Michael P.; Sokoloski, J. L.; Weston, Jennifer; Mukai, Koji

    2014-04-10

    Despite being the prototype of its class, T Pyx is arguably the most unusual and poorly understood recurrent nova. Here, we use radio observations from the Karl G. Jansky Very Large Array to trace the evolution of the ejecta over the course of the 2011 outburst of T Pyx. The radio emission is broadly consistent with thermal emission from the nova ejecta. However, the radio flux began rising surprisingly late in the outburst, indicating that the bulk of the radio-emitting material was either very cold, or expanding very slowly, for the first ∼50 days of the outburst. Considering a plausible range of volume filling factors and geometries for the ejecta, we find that the high peak flux densities of the radio emission require a massive ejection of (1-30) × 10{sup –5} M {sub ☉}. This ejecta mass is much higher than the values normally associated with recurrent novae, and is more consistent with a nova on a white dwarf well below the Chandrasekhar limit.

  10. Substantial Underestimation of Post-Harvest Burning Emissions in the North China Plain Revealed by Multi-Species Space Observations

    PubMed Central

    Stavrakou, T.; Müller, J.-F.; Bauwens, M.; De Smedt, I.; Lerot, C.; Van Roozendael, M.; Coheur, P.-F.; Clerbaux, C.; Boersma, K. F.; van der A, R.; Song, Y.

    2016-01-01

    The large-scale burning of crop residues in the North China Plain (NCP), one of the most densely populated world regions, was recently recognized to cause severe air pollution and harmful health effects. A reliable quantification of the magnitude of these fires is needed to assess regional air quality. Here, we use an eight-year record (2005–2012) of formaldehyde measurements from space to constrain the emissions of volatile organic compounds (VOCs) in this region. Using inverse modelling, we derive that satellite-based post-harvest burning fluxes are, on average, at least a factor of 2 higher than state-of-the-art bottom-up statistical estimates, although with significant interannual variability. Crop burning is calculated to cause important increases in surface ozone (+7%) and fine aerosol concentrations (+18%) in the North China Plain in June. The impact of crop fires is also found in satellite observations of other species, glyoxal, nitrogen dioxide and methanol, and we show that those measurements validate the magnitude of the top-down fluxes. Our study indicates that the top-down crop burning fluxes of VOCs in June exceed by almost a factor of 2 the combined emissions from other anthropogenic activities in this region, underscoring the need for targeted actions towards changes in agricultural management practices. PMID:27577535

  11. Regional modeling reveals summer precipitation trend signals over the European Alps consistent with trends observed in recent decades

    NASA Astrophysics Data System (ADS)

    Giorgi, Filippo; Torma, Csaba; Coppola, Erika

    2015-04-01

    We analyze an ensemble of high resolution regional climate model (RCM) projections for the 21st century (RCP8.5 scenario) over the European Alps from the EURO-CORDEX and MED-CORDEX experiments. We find that, while the driving global models project a reduction in future summer precipitation over the region, the RCM ensemble project an increase in precipitation over the highest elevations of the Alpine chain. This positive precipitation change signal is associated with an increase of convective precipitation driven by increased potential instability induced by high elevation surface heating. An analysis of observed summer precipitation trends over the region during the historical period 1975-2004 shows a precipitation trend signal consistent with the late 21st century RCM projections and with the RCM-simulated late 20th century trends. These multiple lines of evidence challenge the picture of a decreasing summer precipitation change signal over the Alps found in most GCM projections and point to the added value of high resolution RCMs in providing future climate information over mountainous regions.

  12. Non-reciprocal directional dichroism in the AFM phase of BiFeO3 at THz frequencies

    NASA Astrophysics Data System (ADS)

    Nagel, Urmas; Rõõm, T.; Farkas, D.; Szaller, D.; Bordács, S.; Kézsmárki, I.; Engelkamp, H.; Ozaki, Y.; Tomiaki, Y.; Ito, T.; Fishman, Randy S.

    We did THz absorption spectroscopy of BiFeO3 single crystals in the AFM phase, where the spin cycloid is destroyed in magnetic fields between 18 T and 32 T in Voigt geometry at 1.6 K. If B0 ∥ [ 1 1 0 ] , we see strong directional dichroism (DD) of absorption of the magnon mode with light propagating along the direction of the ferroelectric polarization k ∥ P ∥ [ 111 ] and eω ∥ [ 1 1 0 ] , bω ∥ [ 1 1 2 ] . The sign of DD can be reversed (i) by reversing the direction of B0 or (ii) by flipping the sample, thus reversing the propagation direction of light. The observed effect is caused by the strong magneto-electric coupling in the collinear AFM phase. Research sponsored by the Estonian Ministry of Education and Research (IUT23-3).

  13. Crustal Deformation During the 2011 Volanic Crisis of El Hierro, Canary Islands, Revealed by Continuous GPS Observation

    NASA Astrophysics Data System (ADS)

    Sagiya, T.; Barrancos Martinez, J.; Calvo, D.; Padron, E.; Hernandez, G. H.; Hernández, P. A.; Perez Rodriguez, N.; Suárez, J. M. P.

    2012-04-01

    Seismo-volcnic activity of El Hierro started in the middle of July of 2011 and resulted in the active submarine eruption after October 12 south off La Restinga, the southern tip of the island. We have been operating one continuous GPS site on the island since 2004. Responding to the activity, we quickly installed 5 more GPS sites. Including another site operated by the Canary Islands Cartograhical Service (GRAFCAN) for a cartographic purpose, we have been monitoring 7 GPS sites equipped with dual-frequency receivers. We present the result of our crustal deformation monitoring and the magmatic activity inferred from the deformation data. In accordance with the deformation pattern, we divide the volcanic activity in 2011 into 4 stages. The first stage is from the middle of July to middle of September, during which steady magmatic inflation is estimated at the center of the island. The inflated volume of the first stage is estimated to be about 1.3 X 107 m3 at the depth of about 5km. The second stage, which continued until the first submarine eruption on October 12, is characterized by the accelerated deformation due to the upward as well as southward migration of magma. Additional inflation of about 2.1 X 107 m3 occurred in the depth range of 1-2km. The third stage continued for about 3 weeks after the first submarine eruption. During this stage, submarine eruption continues while no significant surface deformation is observed. It is considered magma supply from a deeper magma chamber continued during this 3 weeks period. Therefore, the total inflation volume during the first two stages gives the minimum estimate for the total magma volume. Since the beginning of November 2011, many GPS sites started subsiding. However, this deflation pattern is quite different from those in the shallow inflation stages. Horizontal deformation during this 4th stage is not significant, implying that deflation is occurring below the moho.

  14. Two crystal structures of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis reveal protein–ligand interactions including a structural basis for observed antifolate resistance

    SciTech Connect

    Anderson, Amy C.

    2005-03-01

    An analysis of the protein–ligand interactions in two crystal structures of DHFR-TS from C. hominis reveals a possible structural basis for observed antifolate resistance in C. hominis DHFR. A comparison with the structure of human DHFR reveals residue substitutions that may be exploited for the design of species-selective inhibitors. Cryptosporidium hominis is a protozoan parasite that causes acute gastrointestinal illness. There are no effective therapies for cryptosporidiosis, highlighting the need for new drug-lead discovery. An analysis of the protein–ligand interactions in two crystal structures of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from C. hominis, determined at 2.8 and 2.87 Å resolution, reveals that the interactions of residues Ile29, Thr58 and Cys113 in the active site of C. hominis DHFR provide a possible structural basis for the observed antifolate resistance. A comparison with the structure of human DHFR reveals active-site differences that may be exploited for the design of species-selective inhibitors.

  15. The Sea of Japan and Its Unique Chemistry Revealed by Time-Series Observations over the Last 30 Years

    NASA Astrophysics Data System (ADS)

    Gamo, T.; Nakayama, N.; Takahata, N.; Sano, Y.; Zhang, J.; Yamazaki, E.; Taniyasu, S.; Yamashita, N.

    2014-02-01

    Chemical tracers in seawater, as well as physical parameters such as temperature and salinity, have been measured to better characterize the dynamics of water convection and its spatiotemporal changes in the Sea of Japan (also called the Japan Sea), a semi-closed, hyperoxic marginal sea (maximum depth: ˜3,800 m) in the northwestern corner of the Pacific Ocean. Repeated conductivity, temperature, and depth (CTD) observations and measurements of dissolved oxygen, for more than 30 years, have confirmed that the bottom layer of the Japan Sea, with a thickness of ˜1 km below the boundary at a depth of ˜2,500 m, is characterized by vertical homogeneity with fluctuations of potential temperature and dissolved oxygen of <0.001°C and <0.5 μmol kg-1, respectively. The timescale of the abyssal circulation in the Japan Sea has been estimated to be 100-300 years, using 14C and other chemical tracers. Stable isotope analyses for dissolved He, O2 and CH4 have given us information on their unique geochemical cycles in the Japan Sea. Profiles of the short-lived radioisotope 222Rn just above the sea bottom have brought new insights into the short-term lateral water movement with a timescale of several days in the Japan Sea bottom water. It is of special concern that the gradual deoxygenation and warming of the bottom water over the last 30 years have resulted in an ˜10% decrease in dissolved oxygen and ˜0.04°C increase in potential temperature, suggesting a change of the deep convection system in the Japan Sea. The temporal changes in the vertical profiles of tritium from 1984 to 1998 have suggested a shift of the abyssal circulation pattern from a ``total (overall) convection mode" to a ``shallow (partial) convection mode". It is likely that the global warming since the last century has hindered the formation of dense surface seawater and its ability to sink down to the bottom, isolating the bottom layer from the deep convection loop that is indispensable as the source of

  16. Intrinsically High-Q Dynamic AFM Imaging in Liquid with a Significantly Extended Needle Tip

    PubMed Central

    Minary-Jolandan, Majid; Tajik, Arash; Wang, Ning; Yu, Min-Feng

    2012-01-01

    Atomic force microscope (AFM) probe with a long and rigid needle tip was fabricated and studied for high Q factor dynamic (tapping mode) AFM imaging of samples submersed in liquid. The extended needle tip over a regular commercially-available tapping mode AFM cantilever was sufficiently long to keep the AFM cantilever from submersed in liquid, which significantly minimized the hydrodynamic damping involved in dynamic AFM imaging of samples in liquid. Dynamic AFM imaging of samples in liquid at an intrinsic Q factor of over 100 and an operation frequency of over 200 kHz was demonstrated. The method has the potential to be extended to acquire viscoelastic materials properties and provide truly gentle imaging of soft biological samples in physiological environments. PMID:22595833

  17. Device level 3D characterization using PeakForce AFM

    NASA Astrophysics Data System (ADS)

    Timoney, Padraig; Zhang, Xiaoxiao; Vaid, Alok; Hand, Sean; Osborne, Jason; Milligan, Eric; Feinstein, Adam

    2016-03-01

    Traditional metrology solutions face a range of challenges at the 1X node such as three dimensional (3D) measurement capabilities, shrinking overlay and critical dimension (CD) error budgets driven by multi-patterning and via in trench CD measurements. With advent of advanced technology nodes and 3D processing, an increasing need is emerging for in-die metrology including across-structure and structure-to-structure characterization. A myriad of work has emerged in the past few years intending to address these challenges from various aspects; in-die OCD with reduced spot size and tilt beam on traditional critical dimension scanning electron microscopy (CDSEM) for height measurements. This paper explores the latest capability offered by PeakForceTM Tapping Atomic Force Microscopy (PFT-AFM). The use of traditional harmonic tapping mode for scanning high aspect ratio, and complex "3D" wafer structures, results in limited depth probing capability as well as excessive tip wear. These limitations arise due to the large tip-sample interaction volume in such confined spaces. PeakForce Tapping eliminates these limitations through direct real time control of the tip-sample interaction contact force. The ability of PeakForce to measure, and respond directly to tip- sample interaction forces results in more detailed feature resolution, reduced tip wear, and improved depth capability. In this work, the PFT-AFM tool was applied for multiple applications, including the 14nm fin and replacement metal gate (RMG) applications outlined below. Results from DOE wafers, detailed measurement precision studies and correlation to reference metrology are presented for validation of this methodology. With the fin application, precision of 0.3nm is demonstrated by measuring 5 dies with 10 consecutive runs. Capability to resolve within-die and localized within-macro height variation is also demonstrated. Results obtained from the fin measurements support the increasing trend that measurements

  18. Acquisition of a Modular, Multi-laser, Raman-AFM Instrument for Multdisciplinary Research

    DTIC Science & Technology

    2015-04-28

    vapor deposition on copper foils. The four lasers range from the blue to 785 nm and provides a unique handle to determine excitation dependence of...Acquisition of a Modular, Multi- laser , Raman- AFM Instrument for Multdisciplinary Research A four- laser , confocal Raman/Atomic Force Scanning... laser , Raman-AFM Instrument for Multdisciplinary Research Report Title A four- laser , confocal Raman/Atomic Force Scanning microscope (Raman-AFM

  19. Formation of sensor array on the AFM chip surface by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Shumov, I. D.; Kanashenko, S. L.; Ziborov, V. S.; Ivanov, Yu D.; Archakov, A. I.; Pleshakova, T. O.

    2017-01-01

    Development of atomic force microscopy (AFM)-based nanotechnological approaches to highly sensitive detection of proteins is a perspective direction in biomedical research. These approaches use AFM chips to concentrate the target proteins from the test solution volume (buffer solution, diluted biological fluid) onto the chip surface for their subsequent registration on the chip surface by AFM. Atomic force microscope is a molecular detector that enables protein detection at ultra-low (subfemtomolar) concentrations in single-molecule counting mode. Due to extremely high sensitivity of AFM, its application for multiplexed protein detection is of great interest for use in proteomics and diagnostic applications. In this study, AFM chips containing an array of sensor areas have been fabricated. Magnetron sputtering of chromium and tungsten nanolayers has been used to form optically visible metallic marks on the AFM chip surface to provide necessary precision of AFM probe positioning against each sensor area for scanning. It has been demonstrated that the marks formed by magnetron sputtering of Cr and W are stable on the surface of the AFM chips during the following activation and intensive washing of this surface. The results obtained in our present study allow application of the developed chips for multiplexed protein analysis by AFM.

  20. Bubble colloidal AFM probes formed from ultrasonically generated bubbles.

    PubMed

    Vakarelski, Ivan U; Lee, Judy; Dagastine, Raymond R; Chan, Derek Y C; Stevens, Geoffrey W; Grieser, Franz

    2008-02-05

    Here we introduce a simple and effective experimental approach to measuring the interaction forces between two small bubbles (approximately 80-140 microm) in aqueous solution during controlled collisions on the scale of micrometers to nanometers. The colloidal probe technique using atomic force microscopy (AFM) was extended to measure interaction forces between a cantilever-attached bubble and surface-attached bubbles of various sizes. By using an ultrasonic source, we generated numerous small bubbles on a mildly hydrophobic surface of a glass slide. A single bubble picked up with a strongly hydrophobized V-shaped cantilever was used as the colloidal probe. Sample force measurements were used to evaluate the pure water bubble cleanliness and the general consistency of the measurements.

  1. AFM, SEM and TEM Studies on Porous Anodic Alumina

    PubMed Central

    2010-01-01

    Porous anodic alumina (PAA) has been intensively studied in past decade due to its applications for fabricating nanostructured materials. Since PAA’s pore diameter, thickness and shape vary too much, a systematical study on the methods of morphology characterization is meaningful and essential for its proper development and utilization. In this paper, we present detailed AFM, SEM and TEM studies on PAA and its evolvements with abundant microstructures, and discuss the advantages and disadvantages of each method. The sample preparation, testing skills and morphology analysis are discussed, especially on the differentiation during characterizing complex cross-sections and ultrasmall nanopores. The versatility of PAAs is also demonstrated by the diversity of PAAs’ microstructure. PMID:20672104

  2. AFM, SEM and TEM Studies on Porous Anodic Alumina

    NASA Astrophysics Data System (ADS)

    Zhu, Yuan Yuan; Ding, Gu Qiao; Ding, Jian Ning; Yuan, Ning Yi

    2010-04-01

    Porous anodic alumina (PAA) has been intensively studied in past decade due to its applications for fabricating nanostructured materials. Since PAA’s pore diameter, thickness and shape vary too much, a systematical study on the methods of morphology characterization is meaningful and essential for its proper development and utilization. In this paper, we present detailed AFM, SEM and TEM studies on PAA and its evolvements with abundant microstructures, and discuss the advantages and disadvantages of each method. The sample preparation, testing skills and morphology analysis are discussed, especially on the differentiation during characterizing complex cross-sections and ultrasmall nanopores. The versatility of PAAs is also demonstrated by the diversity of PAAs’ microstructure.

  3. SPR and AFM study of engineered biomolecule immobilisation techniques.

    PubMed

    Craig, Ian; McLaughlin, James A

    2006-01-01

    A comparative study into two novel and diverse schemes designed to improve immobilization of biomolecules for biosensing purposes is presented. In the first method a silicon rich matrix is created using PECVD. The second method involves creating nano-patterns on the sensor surface to create a large number of surface discontinuities to which the proteins will bind preferentially. The basic theory of SPR is provided to show the importance of the surface sensitive nature of this optical transduction technique. The present work suggests that both may prove both for SPR and other biosensing applications. Of the two schemes proposed, the results for nano-patterning seem to suggest that it is promoting better surface attachment of biomolecules. The results of SPR and AFM studies are presented that have shown that each of these schemes promotes improved binding of various proteins.

  4. An Expressive Bodily Movement Repertoire for Marimba Performance, Revealed through Observers' Laban Effort-Shape Analyses, and Allied Musical Features: Two Case Studies.

    PubMed

    Broughton, Mary C; Davidson, Jane W

    2016-01-01

    Musicians' expressive bodily movements can influence observers' perception of performance. Furthermore, individual differences in observers' music and motor expertise can shape how they perceive and respond to music performance. However, few studies have investigated the bodily movements that different observers of music performance perceive as expressive, in order to understand how they might relate to the music being produced, and the particular instrument type. In this paper, we focus on marimba performance through two case studies-one solo and one collaborative context. This study aims to investigate the existence of a core repertoire of marimba performance expressive bodily movements, identify key music-related features associated with the core repertoire, and explore how observers' perception of expressive bodily movements might vary according to individual differences in their music and motor expertise. Of the six professional musicians who observed and analyzed the marimba performances, three were percussionists and experienced marimba players. Following training, observers implemented the Laban effort-shape movement analysis system to analyze marimba players' bodily movements that they perceived as expressive in audio-visual recordings of performance. Observations that were agreed by all participants as being the same type of action at the same location in the performance recording were examined in each case study, then across the two studies. A small repertoire of bodily movements emerged that the observers perceived as being expressive. Movements were primarily allied to elements of the music structure, technique, and expressive interpretation, however, these elements appeared to be interactive. A type of body sway movement and more localized sound generating actions were perceived as expressive. These movements co-occurred and also appeared separately. Individual participant data revealed slightly more variety in the types and locations of actions

  5. An Expressive Bodily Movement Repertoire for Marimba Performance, Revealed through Observers' Laban Effort-Shape Analyses, and Allied Musical Features: Two Case Studies

    PubMed Central

    Broughton, Mary C.; Davidson, Jane W.

    2016-01-01

    Musicians' expressive bodily movements can influence observers' perception of performance. Furthermore, individual differences in observers' music and motor expertise can shape how they perceive and respond to music performance. However, few studies have investigated the bodily movements that different observers of music performance perceive as expressive, in order to understand how they might relate to the music being produced, and the particular instrument type. In this paper, we focus on marimba performance through two case studies—one solo and one collaborative context. This study aims to investigate the existence of a core repertoire of marimba performance expressive bodily movements, identify key music-related features associated with the core repertoire, and explore how observers' perception of expressive bodily movements might vary according to individual differences in their music and motor expertise. Of the six professional musicians who observed and analyzed the marimba performances, three were percussionists and experienced marimba players. Following training, observers implemented the Laban effort-shape movement analysis system to analyze marimba players' bodily movements that they perceived as expressive in audio-visual recordings of performance. Observations that were agreed by all participants as being the same type of action at the same location in the performance recording were examined in each case study, then across the two studies. A small repertoire of bodily movements emerged that the observers perceived as being expressive. Movements were primarily allied to elements of the music structure, technique, and expressive interpretation, however, these elements appeared to be interactive. A type of body sway movement and more localized sound generating actions were perceived as expressive. These movements co-occurred and also appeared separately. Individual participant data revealed slightly more variety in the types and locations of actions

  6. Revealing the topography of cellular membrane domains by combined atomic force microscopy/fluorescence imaging.

    PubMed

    Frankel, D J; Pfeiffer, J R; Surviladze, Z; Johnson, A E; Oliver, J M; Wilson, B S; Burns, A R

    2006-04-01

    Simultaneous atomic force microscopy (AFM) and confocal fluorescence imaging were used to observe in aqueous buffer the three-dimensional landscape of the inner surface of membrane sheets stripped from fixed tumor mast cells. The AFM images reveal prominent, irregularly shaped raised domains that label with fluorescent markers for both resting and activated immunoglobin E receptors (FcepsilonRI), as well as with cholera toxin-aggregated GM1 and clathrin. The latter suggests that coated pits bud from these regions. These features are interspersed with flatter regions of membrane and are frequently surrounded and interconnected by cytoskeletal assemblies. The raised domains shrink in height by approximately 50% when cholesterol is extracted with methyl-beta-cyclodextrin. Based on composition, the raised domains seen by AFM correspond to the cholesterol-enriched dark patches observed in transmission electron microscopy (TEM). These patches were previously identified as sites of signaling and endocytosis based on their localization of activated FcepsilonRI, at least 10 associated signaling molecules, and the presence of clathrin-coated pits. Overall the data suggest that signaling and endocytosis occur in mast cells from raised membrane regions that depend on cholesterol for their integrity and may be organized in specific relationship with the cortical cytoskeleton.

  7. AFM and SEM study of the effects of etching on IPS-Empress 2 TM dental ceramic

    NASA Astrophysics Data System (ADS)

    Luo, X.-P.; Silikas, N.; Allaf, M.; Wilson, N. H. F.; Watts, D. C.

    2001-10-01

    The aim of this study was to investigate the effects of increasing etching time on the surface of the new dental material, IPS-Empress 2 TM glass ceramic. Twenty one IPS-Empress 2 TM glass ceramic samples were made from IPS-Empress 2 TM ingots through lost-wax, hot-pressed ceramic fabrication technology. All samples were highly polished and cleaned ultrasonically for 5 min in acetone before and after etching with 9.6% hydrofluoric acid gel. The etching times were 0, 10, 20, 30, 60, 90 and 120 s respectively. Microstructure was analysed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to evaluate the surface roughness and topography. Observations with SEM showed that etching with hydrofluoric acid resulted in preferential dissolution of glass matrix, and that partially supported crystals within the glass matrix were lost with increasing etching time. AFM measurements indicated that etching increased the surface roughness of the glass-ceramic. A simple least-squares linear regression was used to establish a relationship between surface roughness parameters ( Ra, RMS), and etching time, for which r2>0.94. This study demonstrates the benefits of combining two microscopic methods for a better understanding of the surface. SEM showed the mode of action of hydrofluoric acid on the ceramic and AFM provided valuable data regarding the extent of surface degradation relative to etching time.

  8. BOREAS AFM-6 NOAA/ETL 35 GHz Cloud/Turbulence Radar GIF Images

    NASA Technical Reports Server (NTRS)

    Martner, Brooks E.; Newcomer, Jeffrey A. (Editor); Hall, Forrest G.; Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Administration/Environment Technology Laboratory (NOAA/ETL) operated a 35-GHz cloud-sensing radar in the Northern Study Area (NSA) near the Old Jack Pine (OJP) tower from 16 Jul 1994 to 08 Aug 1994. This data set contains a time series of GIF images that show the structure of the lower atmosphere. The NOAA/ETL 35-GHz cloud/turbulence radar GIF images are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  9. Measurement of a CD and sidewall angle artifact with two-dimensional CD AFM metrology

    NASA Astrophysics Data System (ADS)

    Dixson, Ronald G.; Sullivan, Neal T.; Schneir, Jason; McWaid, Thomas H.; Tsai, Vincent W.; Prochazka, Jerry; Young, Michael

    1996-05-01

    Despite the widespread acceptance of SEM metrology in semiconductor manufacturing, there is no SEM CD standard currently available. Producing such a standard is challenging because SEM CD measurements are not only a function of the linewidth, but also dependent on the line material, sidewall roughness, sidewall angle, line height, substrate material, and the proximity of other objects. As the presence of AFM metrology in semiconductor manufacturing increases, the history of SEM CD metrology raises a number of questions about the prospect of AFM CD artifacts. Is an AFM CD artifact possible? What role would it play in the manufacturing environment? Although AFM has some important advantages over SEM, such as relative insensitivity to material differences, the throughput and reliability of most AFM instruments is not yet at the level necessary to support in-line CD metrology requirements. What, then, is the most useful relationship between AFM and SEM metrology? As a means of addressing some of these questions, we have measured the CD and sidewall angle of 1.2 micrometer oxy-nitride line on Si using three different techniques: optical microscopy (with modeling), AFM, and cross sectional TEM. Systematic errors in the AFM angle measurements were reduced by using a rotational averaging technique that we describe. We found good agreement with uncertainties below 30 nm (2 sigma) for the CD measurement and 1.0 degrees (2 sigma) for the sidewall angles. Based upon these results we suggest a measurement procedure which will yield useful AFM CD artifacts. We consider the possibility that AFMs, especially when used with suitable CD artifacts, can effectively support SEM CD metrology. This synergistic relationship between the AFM and SEM represents an emerging paradigm that has also been suggested by a number of others.

  10. Mechanical properties of in situ demineralised human enamel measured by AFM nanoindentation

    NASA Astrophysics Data System (ADS)

    Finke, Manuela; Hughes, Julie A.; Parker, David M.; Jandt, Klaus D.

    2001-10-01

    Diet-induced demineralisation is one of the key factors in surface changes of tooth enamel, with soft drinks being a significant etiological agent. The first step in this dissolution process is characterised by a change in the mechanical properties of the enamel and a roughening of the surface. The objective of this pilot study was to measure early stages of in situ induced hardness changes of polished human enamel surfaces with high accuracy using a nanoindenter attached to an atomic force microscope (AFM). Human unerupted third molars were cleaned, sterilised with sodium hypochlorite, sectioned and embedded in epoxy resin. The outer enamel surface was polished and the samples partly covered with a tape, allowing a 2-mm-wide zone to be exposed to the oral environment. Samples were fitted in an intra-oral appliance, which was worn from 9 a.m. to 5 p.m. for one day. During this time the volunteer sipped 250 ml of a drink over 10 min periods at 9.00, 11.00, 13.00 and 15.00 h. Three different drinks, mineral water, orange juice and the prototype of a blackcurrant drink with low demineralisation potential were used in this study. At the end of the experiment the samples were detached from the appliance, the tape removed and the surfaces chemically cleaned. The surface hardness and reduced Young's modulus of the exposed and unexposed areas of each sample were determined. In addition, high resolution topographical AFM images were obtained. This study shows that by determining the hardness and reduced Young's modulus, the difference in demineralisation caused by the drinks can be detected and quantified before statistically significant changes in surface topography could be observed with the AFM. The maximum decrease in surface hardness and Young's modulus occurred in the samples exposed to orange juice, followed by those exposed to the blackcurrant drink, while exposure to water led to the same values as unexposed areas. A one-way ANOVA showed a statistically significant

  11. High-resolution, terrestrial radar velocity observations and model results reveal a strong bed at stable, tidewater Rink Isbræ, West Greenland

    NASA Astrophysics Data System (ADS)

    Bartholomaus, T. C.; Walker, R. T.; Stearns, L. A.; Fahnestock, M. A.; Cassotto, R.; Catania, G. A.; Felikson, D.; Fried, M.; Sutherland, D.; Nash, J. D.; Shroyer, E.

    2015-12-01

    At tidewater Rink Isbræ, on the central west coast of Greenland, satellite observations reveal that glacier velocities and terminus positions have remained stable, while the lowest 25 km have thinned 30 m since 1985. Over this same time period, other tidewater glaciers in central west Greenland have retreated, thinned and accelerated. Here we present field observations and model results to show that the flow of Rink Isbræ is resisted by unusually high basal shear stresses. Terrestrial radar interferometry (TRI) observations over 9 days in summer 2014 demonstrate weak velocity response to 4 km wide, full thickness calving events. Velocities at the terminus change by +/- 10% in response to rising and falling tides within a partial-width, 2.5-km-long floating ice tongue; however these tidal perturbations damp out within 2 km of the grounding line. Inversions for basal shear stress and force balance analyses together show that basal shear stresses in excess of 300 kPa support the majority of the driving stress at thick, steep Rink Isbræ. These observational and modeling results tell a consistent story in which a strong bed may limit the unstable tidewater glacier retreats observed elsewhere. Rink Isbræ has an erosion resistant quartzite bed with low fracture density. We hypothesize that this geology may play a major role in the bed strength.

  12. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction.

    PubMed

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-07-25

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation.

  13. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction

    NASA Astrophysics Data System (ADS)

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-07-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation.

  14. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction

    PubMed Central

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-01-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation. PMID:27452115

  15. Proceedings of the 2010 AFMS Medical Research Symposium. Volume 5. Nursing Track: Abstracts and Presentations

    DTIC Science & Technology

    2011-03-15

    will include hematocrit, hemoglobin , mean corpuscle volume, iron , total iron binding capacity, Ferritin , and soluble transferring receptor. The...Iraq/Afghanistan ........ 2  Iron Status of Deployed Military Members...2010 AFMS Medical Research Symposium Volume 5 Nursing 8 Proceedings of the 2010 AFMS Medical Research Symposium Volume 5 Nursing 9 Iron

  16. BOREAS AFM-2 Wyoming King Air 1994 Aircraft Sounding Data

    NASA Technical Reports Server (NTRS)

    Kelly, Robert D.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-2 team used the University of Wyoming King Air aircraft during IFCs 1, 2, and 3 in 1994 to collected pass-by-pass fluxes (and many other statistics) for the large number of level (constant altitude), straight-line passes used in a variety of flight patterns over the SSA and NSA and areas along the transect between these study areas. The data described here form a second set, namely soundings that were incorporated into nearly every research flight by the King Air in 1994. These soundings generally went from near the surface to above the inversion layer. Most were flown immediately after takeoff or immediately after finishing the last flux pattern of that particular day's flights. The parameters that were measured include wind direction, wind speed, west wind component (u), south wind component (v), static pressure, air dry bulb temperature, potential temperature, dewpoint, temperature, water vapor mixing ratio, and CO2 concentration. Data on the aircraft's location, attitude, and altitude during data collection are also provided. These data are stored in tabular ASCH files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  17. Study of the influence of the acrylic acid plasma parameters on silicon and polyurethane substrates using XPS and AFM

    NASA Astrophysics Data System (ADS)

    Vilani, C.; Weibel, D. E.; Zamora, R. R. M.; Habert, A. C.; Achete, C. A.

    2007-10-01

    XPS and AFM have been used to investigate surface modifications produced by acrylic acid (AA) vapor plasma treatment of silicon (Si)(1 0 0) substrates and polyurethanes (PUs) membranes. XPS analyses of Si and PUs treated substrates at low plasma power (5-20 W) revealed the formation of a thin film on the surfaces, which chemically resembles the poly(acrylic acid) film conventionally synthesised. No signal of the Si substrate could be seen under these low plasma power applications on silicon. However, when the plasma power is higher than 30 W one can clearly see XPS silicon signatures. AFM measurements of silicon substrates treated with AA plasma at low power (5-20 W) showed the formation of a thin polymer film of about 220-55 nm thickness. Further, applications of high plasma power (30-100 W) displayed a marked difference from low plasma modifications and it was found sputtering of the silicon substrate. Pervaporation results of AA plasma treated PUs membranes revealed that the selectivity for the separation of methanol from methyl- t-butyl ether is higher at 100 W and 1 min treatment time, than the other conditions studied. This last finding is discussed concerning the surface modifications produced on plasma treated silicon substrates and PU membranes.

  18. Tip Characterization Method using Multi-feature Characterizer for CD-AFM

    PubMed Central

    Orji, Ndubuisi G.; Itoh, Hiroshi; Wang, Chumei; Dixson, Ronald G.; Walecki, Peter S.; Schmidt, Sebastian W.; Irmer, Bernd

    2016-01-01

    In atomic force microscopy (AFM) metrology, the tip is a key source of uncertainty. Images taken with an AFM show a change in feature width and shape that depends on tip geometry. This geometric dilation is more pronounced when measuring features with high aspect ratios, and makes it difficult to obtain absolute dimensions. In order to accurately measure nanoscale features using an AFM, the tip dimensions should be known with a high degree of precision. We evaluate a new AFM tip characterizer, and apply it to critical dimension AFM (CD-AFM) tips used for high aspect ratio features. The characterizer is made up of comb-shaped lines and spaces, and includes a series of gratings that could be used as an integrated nanoscale length reference. We also demonstrate a simulation method that could be used to specify what range of tip sizes and shapes the characterizer can measure. Our experiments show that for non re-entrant features, the results obtained with this characterizer are consistent to 1 nm with the results obtained by using widely accepted but slower methods that are common practice in CD-AFM metrology. A validation of the integrated length standard using displacement interferometry indicates a uniformity of better than 0.75%, suggesting that the sample could be used as highly accurate and SI traceable lateral scale for the whole evaluation process. PMID:26720439

  19. Revealing Interactions between Human Resources, Quality of Life and Environmental Changes within Socially-oriented Observations : Results from the IPY PPS Arctic Project in the Russian North

    NASA Astrophysics Data System (ADS)

    Vlasova, Tatiana

    2010-05-01

    Socially-oriented Observations (SOO) in the Russian North have been carried out within multidisciplinary IPY PPS Arctic project under the leadership of Norway and supported by the Research Council of Norway as well as Russian Academy of Sciences. The main objective of SOO is to increase knowledge and observation of changes in quality of life conditions (state of natural environment including climate and biota, safe drinking water and foods, well-being, employment, social relations, access to health care and high quality education, etc.) and - to reveal trends in human capital and capacities (health, demography, education, creativity, spiritual-cultural characteristics and diversity, participation in decision making, etc.). SOO have been carried out in industrial cities as well as sparsely populated rural and nature protection areas in observation sites situated in different bioms (from coastal tundra to southern taiga zone) of Murmansk, Arkhangelsk Oblast and Republic of Komi. SOO were conducted according to the international protocol included in PPS Arctic Manual. SOO approaches based both on local people's perceptions and statistics help to identify main issues and targets for life quality, human capital and environment improvement and thus to distinguish leading SOO indicators for further monitoring. SOO have revealed close interaction between human resources, quality of life and environmental changes. Negative changes in human capital (depopulation, increasing unemployment, aging, declining physical and mental health, quality of education, loss of traditional knowledge, marginalization etc.), despite peoples' high creativity and optimism are becoming the major driving force effecting both the quality of life and the state of environment and overall sustainability. Human induced disturbances such as uncontrolled forests cuttings and poaching are increasing. Observed rapid changes in climate and biota (ice and permafrost melting, tundra shrubs getting taller and

  20. XPS and AFM Study of GaAs Surface Treatment

    SciTech Connect

    Contreras-Guerrero, R.; Wallace, R. M.; Aguirre-Francisco, S.; Herrera-Gomez, A.; Lopez-Lopez, M.

    2008-11-13

    Obtaining smooth and atomically clean surfaces is an important step in the preparation of a surface for device manufacturing. In this work different processes are evaluated for cleaning a GaAs surface. A good surface cleaning treatment is that which provides a high level of uniformity and controllability of the surface. Different techniques are useful as cleaning treatments depending on the growth process to be used. The goal is to remove the oxygen and carbon contaminants and then form a thin oxide film to protect the surface, which is easy to remove later with thermal desorption mechanism like molecular beam epitaxy (MBE) with minimal impact to the surface. In this study, atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to characterize the structure of the surface, the composition, as well as detect oxygen and carbon contaminant on the GaAs surface. This study consists in two parts. The first part the surface was subjected to different chemical treatments. The chemical solutions were: (a)H{sub 2}SO{sub 4}:H{sub 2}O{sub 2}:H{sub 2}O(4:1:100), (b) HCl: H{sub 2}O(1:3), (c)NH{sub 4}OH 29%. The treatments (a) and (b) reduced the oxygen on the surface. Treatment (c) reduces carbon contamination. In the second part we made MOS devices on the surfaces treated. They were characterized by CV and IV electrical measurements. They show frequency dispersion.

  1. AF-M315E Propulsion System Advances and Improvements

    NASA Technical Reports Server (NTRS)

    Masse, Robert K.; Allen, May; Driscoll, Elizabeth; Spores, Ronald A.; Arrington, Lynn A.; Schneider, Steven J.; Vasek, Thomas E.

    2016-01-01

    Even as for the GR-1 awaits its first on-orbit demonstration on the planned 2017 launch of NASA's Green Propulsion Infusion Mission (GPIM) program, ongoing efforts continue to advance the technical state-of-the-art through improvements in the performance, life capability, and affordability of both Aerojet Rocketdyne's 1-N-class GR-1 and 20-N-class GR-22 green monopropellant thrusters. Hot-fire testing of a design upgrade of the GR-22 thruster successfully demonstrated resolution of a life-limiting thermo-structural issue encountered during prototype testing on the GPIM program, yielding both an approximately 2x increase in demonstrating life capability, as well as fundamental insights relating to how ionic liquid thrusters operate, thruster scaling, and operational factors affecting catalyst bed life. Further, a number of producibility improvements, related to both materials and processes and promising up to 50% unit cost reduction, have been identified through a comprehensive Design for Manufacturing and Assembly (DFMA) assessment activity recently completed at Aerojet Rocketdyne. Focused specifically on the GR-1 but applicable to the common-core architecture of both thrusters, ongoing laboratory (heavyweight) thruster testing being conducted under a Space Act Agreement at NASA Glenn Research Center has already validated a number of these proposed manufacturability upgrades, additionally achieving a greater than 40% increase in thruster life. In parallel with technical advancements relevant to conventional large spacecraft, a joint effort between NASA and Aerojet Rocketdyne is underway to prepare 1-U CubeSat AF-M315E propulsion module for first flight demonstration in 2018.

  2. Contrast mechanisms on nanoscale subsurface imaging in ultrasonic AFM: scattering of ultrasonic waves and contact stiffness of the tip-sample.

    PubMed

    Sharahi, Hossein Jiryaei; Shekhawat, Gajendra; Dravid, Vinayak; Park, Simon; Egberts, Philip; Kim, Seonghwan

    2017-02-09

    Ultrasonic atomic force microscopy (AFM) and its associated derivatives are nondestructive techniques that can elucidate subsurface nanoscale structures and properties. Despite the usefulness of these techniques, the physical contrast mechanisms responsible for the reported subsurface features observed in ultrasonic AFM are not well defined. In this study, we present a comprehensive model combining ultrasonic wave scattering and tip-sample contact stiffness to better reproduce the experimentally measured phase variations over subsurface features in two model systems. These model systems represent the two extreme sample types typically imaged by ultrasonic AFM, one being a hard material and the other a soft polymeric material. The theoretical analysis presented and associated comparisons with experimental results suggest that the image contrast depends on the combination of two contrast mechanisms: the perturbation of the scattered ultrasonic waves and the local variation of the contact stiffness at the tip-sample contact. The results of this study open up a new door for the depth estimation of buried nanoscale features into hard (engineering structures) and soft (polymers and biological structures) materials, and eventually lead to non-invasive, high-resolution 3D nano-tomography by ultrasonic AFM.

  3. The formation of liquid bridge in different operating modes of AFM

    NASA Astrophysics Data System (ADS)

    Wei, Zheng; Sun, Yan; Ding, WenXuan; Wang, ZaiRan

    2016-09-01

    The liquid bridge is one of the principal factors that cause artifacts in ambient-pressure atomic force microscope (AFM) images. Additionally, it is the main component of the adhesion force in ambient conditions. To understand the AFM imaging mechanism and the sample characteristics, it is essential to study the liquid bridge. This study interprets the physical mechanism involved in liquid bridge formation, which is composed of three different physical processes: the squeezing process, capillary condensation, and liquid film flow. We discuss the contributions of these three mechanisms to the volume and the capillary force of the liquid bridge in different AFM operation modes.

  4. Wetting properties of AFM probes by means of contact angle measurement

    NASA Astrophysics Data System (ADS)

    Tao, Zhenhua; Bhushan, Bharat

    2006-09-01

    An atomic force microscopy (AFM) based technique was developed to measure the wetting properties of probe tips. By advancing and receding the AFM tip across the water surface, the meniscus force between the tip and the liquid was measured at the tip-water separation. The water contact angle was determined from the meniscus force. The obtained contact angle results were compared with that by the sessile drop method. It was found that the AFM based technique provided higher contact angle values than the sessile drop method. The mechanisms responsible for the difference are discussed.

  5. AFM imaging of ligand binding to platelet integrin alphaIIbbeta3 receptors reconstituted into planar lipid bilayers.

    PubMed

    Hussain, Mohammad A; Agnihotri, Aashiish; Siedlecki, Christopher A

    2005-07-19

    The platelet integrin alphaIIbbeta3 plays a key role in platelet adhesion, activation, and aggregation at the subendothelium and at protein-coated synthetic biomaterials. In this study, interactions between alphaIIbbeta3 and both protein and peptide ligands for the receptor were imaged under physiological conditions by high-resolution atomic force microscopy (AFM). To directly image the ligand-receptor interactions, alphaIIbbeta3 receptors were reconstituted into a supported lipid bilayer formed on a mica surface in the AFM fluid cell assembly and subsequently activated with Mn2+. Fibrinogen, the natural protein ligand for the integrin, as well as a nanogold-labeled peptide ligand (an RGD-containing heptamer) were infused into the AFM fluid cell, incubated with the reconstituted and activated receptors, and imaged under buffer. Height images illustrating topographical features showed the integrin reconstituted in the bilayer. Fibrinogen molecules binding to the receptors were easily observed in the height images, with fibrinogen showing its characteristic trinodular structure and occasionally bridging integrin receptors. Fibrinogen was observed to bind to integrins at the D-domain consistent with the location of the gamma-chain dodecapeptide, while fibrinogen bridging integrins bound to receptors on opposite sides of the protein consistent with a 2-fold axis of symmetry. Peptide ligands were not visible in height images; however, phase images that map the mechanical properties detected the nanogold labels and demonstrated the presence of peptide ligands bound to the receptors. The results demonstrate the ability of this high-resolution microscopy technique to directly visualize single ligand/receptor interactions in a dynamic and physiologically relevant environment, and establish a framework for future fundamental studies of single protein/receptor interactions during normal pathological processes as well as biomaterial surface-induced thrombosis.

  6. In situ observation of fluoride-ion-induced hydroxyapatite collagen detachment on bone fracture surfaces by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kindt, J. H.; Thurner, P. J.; Lauer, M. E.; Bosma, B. L.; Schitter, G.; Fantner, G. E.; Izumi, M.; Weaver, J. C.; Morse, D. E.; Hansma, P. K.

    2007-04-01

    The topography of freshly fractured bovine and human bone surfaces was determined by the use of atomic force microscopy (AFM). Fracture surfaces from both kinds of samples exhibited complex landscapes formed by hydroxyapatite mineral platelets with lateral dimensions ranging from ~90 nm × 60 nm to ~20 nm × 20 nm. Novel AFM techniques were used to study these fracture surfaces during various chemical treatments. Significant topographical changes were observed following exposure to aqueous solutions of ethylenediaminetetraacetic acid (EDTA) or highly concentrated sodium fluoride (NaF). Both treatments resulted in the apparent loss of the hydroxyapatite mineral platelets on a timescale of a few seconds. Collagen fibrils situated beneath the overlying mineral platelets were clearly exposed and could be resolved with high spatial resolution in the acquired AFM images. Time-dependent mass loss experiments revealed that the applied agents (NaF or EDTA) had very different resulting effects. Despite the fact that the two treatments exhibited nearly identical results following examination by AFM, bulk bone samples treated with EDTA exhibited a ~70% mass loss after 72 h, whereas for the NaF-treated samples, the mass loss was only of the order of ~10%. These results support those obtained from previous mechanical testing experiments, suggesting that enhanced formation of superficial fluoroapatite dramatically weakens the protein-hydroxyapatite interfaces. Additionally, we discovered that treatment with aqueous solutions of NaF resulted in the effective extraction of noncollagenous proteins from bone powder.

  7. The phase transformation of methane caused by pressure change during its rise from the seafloor revealed by video observation and acoustic reflection data

    NASA Astrophysics Data System (ADS)

    Aoyama, C.

    2013-12-01

    Acoustic reflection depending on physical property differences among solid of methane hydrates and methane gas bubbles from seafloor and sea water.By sending ultrasonic waves from the transducer of an echo sounder or a sonar system through the water and measuring the echo of the back-scatterings from the methane hydrates or bubbles,it is possible that a visualized image of the methane plumes is displayed on the display of an echo sounder or a sonar system.Estimates of the amount of the methane plumes are extremely important for the global environment as part of the carbon cycle.The observations were carried out at Umitaka Spur and Joetsu knoll in the Sea of Japan every year since 2004. There are many methane plumes in the same ocean area. Thus, we investigate minutely about methane plumes in this study.In order to recognize estimates of the methane plumes, we observed the image of methane plumes using a remotely operated submarine vehicle (Hyper Dolphin, of the Japan Agency of Marine-Earth Science and Technology (JAMSTEC)), and captured the methane bubble using a funnel.We observe the images of the methane plumes seeping points on the seafloor taken by a high-definition camera loaded in the vehicle, measure the surfacing velocity of the gushed methane plumes, and compute the surfacing velocity of the gas and solid substance using a theoretical formula.The observation was carried out at Umitaka Spur in the Japan Sea. The depth was 1000 m and the seawater temperature was 0.3 C°.From 3 seeping points, we gathered 300ml of methane in 643 seconds in the funnel with an opening of 20 cm in diameter.If it is assumed that the seeping points are equally scattered in the area, the seeping volume per unit area is 5.4×104cm3 per hour, which is 4.7×102m3 per year.The experiment in the ocean revealed the followings.The methane hydrate particles that are seeping out from seafloor are solid substances just above the seafloor.In the studied ocean area, 7.7×104m3 of methane

  8. Probing Cytoskeletal Structures by Coupling Optical Superresolution and AFM Techniques for a Correlative Approach

    PubMed Central

    Chacko, Jenu Varghese; Zanacchi, Francesca Cella; Diaspro, Alberto

    2013-01-01

    In this article, we describe and show the application of some of the most advanced fluorescence superresolution techniques, STED AFM and STORM AFM microscopy towards imaging of cytoskeletal structures, such as microtubule filaments. Mechanical and structural properties can play a relevant role in the investigation of cytoskeletal structures of interest, such as microtubules, that provide support to the cell structure. In fact, the mechanical properties, such as the local stiffness and the elasticity, can be investigated by AFM force spectroscopy with tens of nanometers resolution. Force curves can be analyzed in order to obtain the local elasticity (and the Young's modulus calculation by fitting the force curves from every pixel of interest), and the combination with STED/STORM microscopy integrates the measurement with high specificity and yields superresolution structural information. This hybrid modality of superresolution-AFM working is a clear example of correlative multimodal microscopy. PMID:24027190

  9. Nanogap based graphene coated AFM tips with high spatial resolution, conductivity and durability.

    PubMed

    Lanza, Mario; Gao, Teng; Yin, Zixuan; Zhang, Yanfeng; Liu, Zhongfan; Tong, Yuzhen; Shen, Ziyong; Duan, Huiling

    2013-11-21

    After one decade of analyzing the intrinsic properties of graphene, interest into the development of graphene-based devices and micro electromechanical systems is increasing. Here, we fabricate graphene-coated atomic force microscope tips by growing the graphene on copper foil and transferring it onto the apex of a commercially available AFM tip. The resulting tip exhibits surprising enhanced resolution in nanoscale electrical measurements. By means of topographic AFM maps and statistical analyses we determine that this superior performance may be related to the presence of a nanogap between the graphene and the tip apex, which reduces the tip radius and tip-sample contact area. In addition, the graphene-coated tips show a low tip-sample interaction, high conductivity and long life times. The novel fabrication-friendly tip could improve the quality and reliability of AFM experiments, while reducing the cost of AFM-based research.

  10. Adiabatic Compression Sensitivity of AF-M315E (Briefing Charts)

    DTIC Science & Technology

    2015-07-27

    dynamic response • Waterhammer effect Distribution A: Approved for public release; distribution unlimited Hydroxyethylhydrazinium Nitrate ...Hydroxylammonium Nitrate (HEHN) (HAN) [ ]-NO3 + [ ]HOCH2CH2N2H4 [ ]-+[ ]NH3OH NO3 AF-M315E

  11. Quantitative Measurements of Elastic Properties with Ultrasonic-Based AFM and Conventional Techniques

    NASA Astrophysics Data System (ADS)

    Hurley, D. C.

    A prime motivation for the original development of ultrasonic-based AFM methods was to enable measurements of elastic properties with nanoscale spatial resolution. In this chapter, we discuss the quantitative measurement of elastic modulus with ultrasonic-based AFM methods and compare it to measurement by more conventional or established techniques. First, we present the basic principles of modulus measurement with methods that involve contact resonance spectroscopy, such as atomic force acoustic microscopy (AFAM) and ultrasonic AFM (U-AFM). Fundamental concepts of modulus measurement with more established approaches, especially instrumented (nano-) indentation (NI) and surface acoustic wave spectroscopy (SAWS), are then discussed. We consider the relative strengths and limitations of various approaches, for example measurement accuracy, spatial resolution, and applicability to different materials. Example results for specific material systems are given with an emphasis on studies involving direct intercomparison of different techniques. Finally, current research in this area and opportunities for future work are described.

  12. Direct electrochemical and AFM detection of amyloid-β peptide aggregation on basal plane HOPG

    NASA Astrophysics Data System (ADS)

    Lopes, Paula; Xu, Meng; Zhang, Min; Zhou, Ting; Yang, Yanlian; Wang, Chen; Ferapontova, Elena E.

    2014-06-01

    Amyloidogenesis is associated with more than 30 human diseases, including Alzheimer's which is related to aggregation of β-amyloid peptide (Aβ). Here, consecutive stages of Aβ42 aggregation and amyloid fibril formation were followed electrochemically via oxidation of tyrosines in Aβ42 adsorbed on the basal plane graphite electrode and directly correlated with Aβ42 morphological changes observed by atomic force microscopy of the same substrate. The results offer new tools for analysis of mechanisms of Aβ aggregation.Amyloidogenesis is associated with more than 30 human diseases, including Alzheimer's which is related to aggregation of β-amyloid peptide (Aβ). Here, consecutive stages of Aβ42 aggregation and amyloid fibril formation were followed electrochemically via oxidation of tyrosines in Aβ42 adsorbed on the basal plane graphite electrode and directly correlated with Aβ42 morphological changes observed by atomic force microscopy of the same substrate. The results offer new tools for analysis of mechanisms of Aβ aggregation. Electronic supplementary information (ESI) available: Experimental details: procedures for Aβ42 aggregation and electrode modification, DPV/AFM measurements and analysis. See DOI: 10.1039/c4nr02413c

  13. AFM characterization of spin coated carboxylated polystyrene nanospheres/xyloglucan layers on mica and silicon.

    PubMed

    Lubambo, Adriana F; Lucyszyn, Neoli; Petzhold, Cesar L; Sierakowski, Maria-R; Schreiner, Wido H; Saul, Cyro K

    2013-03-01

    Self-assembled nano-arrays have a potential application as solid-phase diagnostics in many biomedical devices. The easiness of its production is directly connected to manufacture cost reduction. In this work, we present self-assembled structures starting from spin coated thin films of carboxylated polystyrene (PSC) and xyloglucan (XG) mixtures on both mica and silicon substrates. AFM images showed PSC nanospheres on top of a homogeneous layer of XG, for both substrates. The average nanosphere diameter fluctuated for a constant speed and it was likely to be independent of the component proportions on the mixture within a range of 30-50% (v/v) PSC. It was also observed that the largest diameters were found at the center of the sample and the smallest at the border. The detected nanospheres were also more numerous at the border. This behavior presents a similarity to spin coated colloidal dispersions. We observed that the average nanosphere diameter on mica substrates was bigger than the nanosphere diameters obtained on top of silicon substrates, under the same conditions. This result seems to be possibly connected to different mixture-surface interactions.

  14. Inhibition of cold rolled steel corrosion by Tween-20 in sulfuric acid: weight loss, electrochemical and AFM approaches.

    PubMed

    Mu, Guannan; Li, Xianghong

    2005-09-01

    The inhibiting action of a nonionic surfactant of Tween-20 on the corrosion of cold rolled steel (CRS) in 0.5-7.0 M sulfuric acid (H(2)SO(4)) was studied by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the surface conditions. The results show that inhibition efficiency increases with the inhibitor concentration, while it decreases with the sulfuric acid concentration. The adsorption of inhibitor on the cold rolled steel surface obeys the Langmuir adsorption isotherm equation. Effect of immersion time was studied and discussed. The effect of temperature on the corrosion behavior of cold rolled steel was also studied at four temperatures ranging from 30 to 60 degrees C, the thermodynamic parameters such as adsorption heat, adsorption free energy, and adsorption entropy were calculated. The results revealed that the adsorption was physisorption mechanism. A kinetic study of cold rolled steel in uninhibited and inhibited acid was also discussed. The kinetic parameters such as apparent activation energy, pre-exponential factor, rate constant, and reaction constant were calculated for the reactions of corrosion. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic models. Polarization curves show that Tween-20 is a cathodic-type inhibitor in sulfuric acid. The results obtained from weight loss and potentiodynamic polarization are in good agreement, and the Tween-20 inhibition action could also be evidenced by surface AFM images.

  15. The morphological and biomechanical changes of keratocytes cultured on modified p (HEMA-MMA) hydrogel studied by AFM.

    PubMed

    Yan, Tuo; Sun, Rong; Deng, Hua; Tan, Baihua; Ao, Ningjian

    2009-01-01

    The poor integration with host cornea tissue and the low mechanical properties of pHEMA hydrogel for artificial cornea remains a difficult problem to solve. A modified pHEMA hydrogel, MMA copolymerized and type-I collagen and bFGF immobilized, was previously prepared in an attempt to solve the problems. In this study, the cytotoxicity of Col/bFGF-p (HEMA-MMA) and p (HEMA-MMA) was studied by cell adhesion assay and atomic force microscopy (AFM). The results of cell adhesion assay show that the attachment of keratocytes on the modified membrane is much higher than that of the unmodified membrane. This indicates that the material after modification have better cell-material interaction. The AFM images reveal that the morphology of keratocytes cultured on different substrate is obviously different. The cell cultured on modified membrane presented a completely elongated and spindle-shape morphology. The force-distance indicates that the biomechanical of keratocytes changes significantly after culturing on different substrates. The adhesion force (2328+/-523 pN) and Young's modulus (0.51+/-0.125 kPa) of the cell cultured on modified membrane are much higher, and the stiffness (0.08+/-0.022 mN/m) is lower than those of the cell cultured on unmodified membrane. These results show that the cytotoxicity of Col/bFGF-p (HEMA-MMA) for keratocytes is much improved.

  16. The effect of low-temperature plasma on bacteria as observed by repeated AFM imaging

    NASA Astrophysics Data System (ADS)

    Pompl, René; Jamitzky, Ferdinand; Shimizu, Tetsuji; Steffes, Bernd; Bunk, Wolfram; Schmidt, Hans-Ulrich; Georgi, Matthias; Ramrath, Katrin; Stolz, Wilhelm; Stark, Robert W.; Urayama, Takuya; Fujii, Shuitsu; Eugen Morfill, Gregor

    2009-11-01

    Research on low-temperature atmospheric plasma sources (LTAPS) has grown strongly over the last few years, in part driven by possible medical 'in vivo' applications. LTAPS offer new technology for medicine and biomedical engineering. Important application examples include in situ production of reactive molecules and ions, delivery at the molecular level, contact-free and self-sterilizing devices. An important issue is the efficient bactericidal effect of LTAPS, which has already been studied widely in vitro. In spite of the many investigations, details of the plasma effect on bacteria are still largely unknown. To contribute to a better understanding of the sterilization process, we investigated the morphological changes of bacteria using atomic force microscopy before and after plasma treatment at high resolution. We examined both gram-positive and gram-negative bacteria at different plasma exposure times. Additionally, the effect of UV radiation as one agent in the plasma was investigated separately. Our results suggest that several sterilizing mechanisms exist and they proceed at different timescales.

  17. In-Situ atomic force microscopic observation of ion beam bombarded plant cell envelopes

    NASA Astrophysics Data System (ADS)

    Sangyuenyongpipat, S.; Yu, L. D.; Brown, I. G.; Seprom, C.; Vilaithong, T.

    2007-04-01

    A program in ion beam bioengineering has been established at Chiang Mai University (CMU), Thailand, and ion beam induced transfer of plasmid DNA molecules into bacterial cells (Escherichia coli) has been demonstrated. However, a good understanding of the fundamental physical processes involved is lacking. In parallel work, onion skin cells have been bombarded with Ar+ ions at energy 25 keV and fluence1-2 × 1015 ions/cm2, revealing the formation of microcrater-like structures on the cell wall that could serve as channels for the transfer of large macromolecules into the cell interior. An in-situ atomic force microscope (AFM) system has been designed and installed in the CMU bio-implantation facility as a tool for the observation of these microcraters during ion beam bombardment. Here we describe some of the features of the in-situ AFM and outline some of the related work.

  18. In situ observation of electrolyte-concentration-dependent solid electrolyte interphase on graphite in dimethyl sulfoxide.

    PubMed

    Liu, Xing-Rui; Wang, Lin; Wan, Li-Jun; Wang, Dong

    2015-05-13

    High lithium salt concentration strategy has been recently reported to be an effective method to enable various organic solvents as electrolyte of Li-ion batteries. Here, we utilize in situ atomic force microscopy (AFM) to investigate the interfacial morphology on the graphite electrode in dimethyl sulfoxide (DMSO)-based electrolyte of various concentrations. The significant differences in interfacial features of the graphite in electrolytes of different concentrations are revealed. In the concentrated electrolyte, stable films form primarily at the step edges and defects on the graphite surface after initial electrochemical cycling. On the other hand, in the dilute electrolyte, DMSO-solvated lithium ions constantly intercalate into graphite layers, and serious decomposition of solvent accompanied by structural deterioration of the graphite surface is observed. The in situ AFM results provide direct evidence for the concentration-dependent interface reactions between graphite electrode and DMSO-based electrolyte.

  19. Investigation of mussel adhesive protein adsorption on polystyrene and poly(octadecyl methacrylate) using angle dependent XPS, ATR-FTIR, and AFM

    SciTech Connect

    Baty, A.M.; Suci, P.A.; Tyler, B.J.; Geesey, G.G.

    1996-02-10

    Despite many years of research effort, the molecular interactions that are responsible for microbial adhesion and fouling of surfaces remain obscure. An understanding of these interactions would contribute to the development of surfaces that resist colonization of microorganisms. The irreversible adsorption of mussel adhesive proteins (MAP) from the marine mussel Mytilus edulis has been investigated on polystyrene (PS) and poly(octadecyl methacrylate) (POMA) surfaces using angle resolved X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrometry, and atomic force microscopy (AFM). Angle resolved XPS was used to quantify the elemental composition with depth of the upper 90 {angstrom} of the surface, and AFM was used to obtain the surface topography. The adsorption pattern of MAP, revealed by AFM images, is distinctly different on the two polymer surfaces and suggests that the substratum influences protein adhesion. The depth profiles of MAP, obtained from angle resolved XPS, show differences in nitrogen composition with depth for MAP adsorbed to PS and POMA. Infrared spectra of hydrated adsorbed MAP revealed significant differences in the amide III region and in two bands which may originate from residues in the tandemly repeated sequences of MAP. This data demonstrates that the chemistry of the polymer film that is present at the protein-polymer interface can influence protein-protein and protein-surface interactions.

  20. Leveraging Air Force Medical Service (AFMS) Senior Leadership Corps Diversity to Improve Efficiency

    DTIC Science & Technology

    2013-04-01

    commanders and AFMS senior leadership; • Set a single PME standard for AFMS officers; • Shift provider billets to patient care roles and establish...single PME standard, and by realigning human resources to increase clinical currency, medical readiness and resource efficiency. Some structural...organizational entity. Like running a surgical service or a medical service. . . . It’s much bigger than that, because you’re dealing with finance and

  1. Surface Microstructure of Mo(C)N Coatings Investigated by AFM

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T.; Zubar, T.; Chizhik, S.; Gilewicz, A.; Lupicka, O.; Warcholinski, B.

    2016-12-01

    MoCN coatings have been formed by cathodic arc evaporation using the mixture of acetylene and nitrogen and pure molybdenum target. The surface structure, in conjunction with x-ray data, was analyzed by atomic force microscopy (AFM). The AFM results show differently shaped grain forms on the surface of coatings investigated. The increase in carbon in chemical coatings composition results in the reduction in surface grain size and the increase in roughness of the coatings.

  2. Attaching single biomolecules selectively to the apex of AFM tips for measuring specific interactions.

    PubMed

    Gu, Jianhua; Xiao, Zhongdang; Yam, Chi-Ming; Qin, Guoting; Deluge, Maxence; Boutet, Sabine; Cai, Chengzhi

    2005-11-01

    We present a general approach for preparing well-defined AFM tips for probing single target molecules. We demonstrated that carboxylic acid groups could be generated by electrochemical oxidation selectively at the apex of an AFM tip that is coated with a monolayer of oligo(ethylene glycol) derivatives for resisting nonspecific interactions. These carboxylic acid groups were used as handles to tether only one ligand molecule, such as biotin, to the tip apex for measurement of specific interactions with biomolecules.

  3. Using XAFS, EDAX and AFM in comparative study of various natural and synthetic emeralds

    NASA Astrophysics Data System (ADS)

    Parikh, P.; Saini, N. L.; Dalela, S.; Bhardwaj, D. M.; Fernandes, S.; Gupta, R. P.; Garg, K. B.

    2003-01-01

    We have performed XAFS, EDAX and AFM studies on some natural and synthetic emeralds. While the XAFS results yield information on changes in the valence of the Cr ion and the n-n distance the AFM is used to determine the areal atomic density on surface of the crystals. It is a pilot study to explore if the three techniques can offer a possible way of distinguishing between the natural and synthetic emeralds and the results are promising.

  4. Ultra-large scale AFM of lipid droplet arrays: investigating the ink transfer volume in dip pen nanolithography.

    PubMed

    Förste, Alexander; Pfirrmann, Marco; Sachs, Johannes; Gröger, Roland; Walheim, Stefan; Brinkmann, Falko; Hirtz, Michael; Fuchs, Harald; Schimmel, Thomas

    2015-05-01

    There are only few quantitative studies commenting on the writing process in dip-pen nanolithography with lipids. Lipids are important carrier ink molecules for the delivery of bio-functional patters in bio-nanotechnology. In order to better understand and control the writing process, more information on the transfer of lipid material from the tip to the substrate is needed. The dependence of the transferred ink volume on the dwell time of the tip on the substrate was investigated by topography measurements with an atomic force microscope (AFM) that is characterized by an ultra-large scan range of 800 × 800 μm(2). For this purpose arrays of dots of the phospholipid1,2-dioleoyl-sn-glycero-3-phosphocholine were written onto planar glass substrates and the resulting pattern was imaged by large scan area AFM. Two writing regimes were identified, characterized of either a steady decline or a constant ink volume transfer per dot feature. For the steady state ink transfer, a linear relationship between the dwell time and the dot volume was determined, which is characterized by a flow rate of about 16 femtoliters per second. A dependence of the ink transport from the length of pauses before and in between writing the structures was observed and should be taken into account during pattern design when aiming at best writing homogeneity. The ultra-large scan range of the utilized AFM allowed for a simultaneous study of the entire preparation area of almost 1 mm(2), yielding good statistic results.

  5. Dual role of Cu²⁺ ions on the aggregation and degradation of soluble Aβ oligomers and protofibrils investigated by fluorescence spectroscopy and AFM.

    PubMed

    García, Silvia; Cuscó, Cristina; Brissos, Rosa F; Torrents, Ester; Caubet, Amparo; Gamez, Patrick

    2012-11-01

    The neuropathological character of copper(II) ions (Cu(2+)) upon interaction with soluble human amyloid-β(1-42) that subsequently generates senile plaques and/or reactive oxygen species (ROS) is considered as one of the very important features of Alzheimer's disease. The present study carried out by using fluorescence spectroscopy and atomic-force microscopy (AFM) indeed confirms the dual role played by Cu(2+), namely as mediator of protein aggregation and as generator of ROS leading to irreversible protein alteration, which most likely involve two distinct copper-binding sites. The AFM investigations clearly evidence the copper-induced aggregation of Aβ oligomers and protofibrils, while comparative fluorescence measurements with copper and zinc reveals the crucial involvement of redox-active copper in the generation of Aβ-cross-linked structures.

  6. Slow Narrow Spectral Width E Region Echoes Observed During the March 17-2015 Storm and What They Reveal About the Disturbed Ionosphere.

    NASA Astrophysics Data System (ADS)

    St-Maurice, J. P.; Chau, J. L.

    2015-12-01

    As auroral-type disturbances moved equatorward during the March 17-2015 storm, coherent E region echoes were observed simultaneously with three radar links separated by 40 km each in the east-west direction in northern Germany. One radar operated at 36.2, and the other two at 32.55 MHz. One of the latter operated in a bistatic configuration. On each radar site five separate antennas were used to locate the echoes using interferometry. The unique configuration provided an unsurpassed opportunity to study the origin and evolution of ionospheric structures in a wide field of view during a strong storm. A most noticeable feature was that over a few time intervals, several minutes in duration each, very narrow spectra were observed, with Doppler shifts roughly 1/2 the ion-acoustic speed (often called "type III" echoes in the past). The inferred location indicated that the echoes came from below 100 km altitude. Echoes moving at the nominal ion-acoustic speed came from higher up and/or different flow angles. In one particularly clear instance the "Type III" echo region came from a region 50 to 75 km in extent drifting at roughly 1.5 km/s, while moving at some small (but non-zero) flow angle with respect to the line-of-sight. In view of the observations, a reevaluation of existing theories indicates that the echoes cannot be related to ion cyclotron waves. Instead, their low altitude and flow angle dependence reveal that they are the by-product of the ion Pedersen instability, which has been investigated by a few groups in relation to a non-isothermal treatment of the Farley-Buneman instability. In our present treatment of the problem, nonlinear effects are invoked to compute the final Doppler shift of the resulting structures. We find that the stronger the electric field is, the closer the region of slow echoes has to be to the ExB direction. In our most dramatic example of Type III structures, the size of the echo region pointed to a region of high energy precipitation

  7. fMRI Adaptation between Action Observation and Action Execution Reveals Cortical Areas with Mirror Neuron Properties in Human BA 44/45

    PubMed Central

    de la Rosa, Stephan; Schillinger, Frieder L.; Bülthoff, Heinrich H.; Schultz, Johannes; Uludag, Kamil

    2016-01-01

    Mirror neurons (MNs) are considered to be the supporting neural mechanism for action understanding. MNs have been identified in monkey’s area F5. The identification of MNs in the human homolog of monkeys’ area F5 Broadmann Area 44/45 (BA 44/45) has been proven methodologically difficult. Cross-modal functional MRI (fMRI) adaptation studies supporting the existence of MNs restricted their analysis to a priori candidate regions, whereas studies that failed to find evidence used non-object-directed (NDA) actions. We tackled these limitations by using object-directed actions (ODAs) differing only in terms of their object directedness in combination with a cross-modal adaptation paradigm and a whole-brain analysis. Additionally, we tested voxels’ blood oxygenation level-dependent (BOLD) response patterns for several properties previously reported as typical MN response properties. Our results revealed 52 voxels in left inferior frontal gyrus (IFG; particularly BA 44/45), which respond to both motor and visual stimulation and exhibit cross-modal adaptation between the execution and observation of the same action. These results demonstrate that part of human IFG, specifically BA 44/45, has BOLD response characteristics very similar to monkey’s area F5. PMID:26973496

  8. Comparative studies of thin film growth on aluminium by AFM, TEM and GDOES characterization

    NASA Astrophysics Data System (ADS)

    Qi, Jiantao; Thompson, George E.

    2016-07-01

    In this present study, comparative studies of trivalent chromium conversion coating formation, associated with aluminium dissolution process, have been investigated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and glow-discharge optical emission spectroscopy (GDOES). High-resolution electron micrographs revealed the evident and uniform coating initiation on the whole surface after conversion treatment for only 30 s, although a network of metal ridges was created by HF etching pre-treatment. In terms of conversion treatment process on electropolished aluminium, constant kinetics of coating growth, ∼0.30 ± 0.2 nm/s, were found after the prolonged conversion treatment for 600 s. The availability of electrolyte anions for coating deposition determined the growth process. Simultaneously, a proceeding process of aluminium dissolution during conversion treatment, of ∼0.11 ± 0.02 nm/s, was found for the first time, indicating constant kinetics of anodic reactions. The distinct process of aluminium consumption was assigned with loss of corrosion protection of the deposited coating material as evidenced in the electrochemical impedance spectroscopy. Based on the present data, a new mechanism of coating growth on aluminium was proposed, and it consisted of an activation period (0-30 s), a linear growth period (0.30 nm/s, up for 600 s) and limited growth period (0.17 nm/s, 600-1200 s). In addition, the air-drying post-treatment and a high-vacuum environment in the microscope revealed a coating shrinkage, especially in the coatings after conversion treatments for longer time.

  9. Surface deformation associated with the 2015 Mw 8.3 Illapel earthquake revealed by satellite-based geodetic observations and its implications for the seismic cycle

    NASA Astrophysics Data System (ADS)

    Feng, Wanpeng; Samsonov, Sergey; Tian, Yunfeng; Qiu, Qiang; Li, Peng; Zhang, Yong; Deng, Zhiguo; Omari, Khalid

    2017-02-01

    In this study, we present inter-, co- and post-seismic displacements observed in the 2015 Illapel earthquake area by Global Positioning System (GPS) and Synthetic Aperture Radar Interferometry (InSAR). RADARSAT-2, ALOS-2 and Sentinel-1A interferograms capture the co- and post-seismic displacements due to the Illapel earthquake. Based on a layered Earth structure, we modeled both co- and post-seismic faulting behaviors on the subduction interface of central Chile. The best-fit model shows that the coseismic rupture broke a 200 km × 200 km area with a maximum slip of 10 m at a depth of 20 km. Two distinct slip centers, likely controlled by local ramp-flat structure, are revealed. The total coseismic geodetic moment is 2.76 ×1021 N m, equivalent to a moment magnitude 8.3. The accumulated afterslip in the first two months after the mainshock is observed on both sides of the coseismic rupture zone with both ascending and descending Sentinel-1A interferograms. A limited overlap zone between co- and post-seismic slip models can be observed, suggesting partitioning of the frictional properties within the Illapel earthquake rupture zone. The total afterslip releases ∼ 5.0 ×1020 N m geodetic moment, which is equivalent to an earthquake of Mw 7.7. The 2010 Mw 8.8 Maule earthquake that occurred ∼400 km away from the Illapel earthquake epicenter could have exerted certain effects on the seismic cycle of the Illapel earthquake area. The seismic records from 2000 to 2015 imply that the rate of annual seismic moment release in the Illapel earthquake area dropped from 0.4 to 0.2 ×1019 N m /yr after the Maule earthquake. Based on the forward modeling with the best-fit slip models determined in this study, we reproduce the local surface displacements before, during and after the Illapel earthquake. A rough deformation cycle, 105 ± 29 yr, calculated by using the coseismic displacements and interseismic rate is basically identical with the revisit interval of M8 events in the

  10. Application of Electron Backscattered Diffraction (EBSD) and Atomic Force Microscopy (AFM) to Determine Texture, Microtexture, and Grain Boundary Energies in Ceramics

    SciTech Connect

    Glass, S.J.; Rohrer, G.S.; Saylor, D.M.; Vedula, V.R.

    1999-05-19

    Crystallographic orientations in alumina (Al203) and magnesium aluminate spinel (MgAl204) were obtained using electron backscattered diffraction (EBSD) patterns. The texture and mesotexture (grain boundary misorientations) were random and no special boundaries were observed. The relative grain boundary energies were determined by thermal groove geometries using atomic force microscopy (AFM) to identify relationships between the grain boundary energies and misorientations.

  11. Interaction force measurement between E. coli cells and nanoparticles immobilized surfaces by using AFM

    SciTech Connect

    Zhang, Wen; Chen, Yongsheng

    2011-01-01

    To better understand environmental behaviors of nanoparticles (NPs), we used the atomic force microscopy (AFM) to measure interaction forces between E. coli cells and NPs immobilized on surfaces in an aqueous environment. The results showed that adhesion force strength was significantly influenced by particle size for both hematite ( -Fe2 O3 ) and corundum ( -Al2 O3 ) NPs whereas the effect on the repulsive force was not observed. The adhesion force decreased from 6.3 0.7 nN to 0.8 0.4 nN as hematite NPs increased from 26 nm to 98 nm in diameter. Corundum NPs exhibited a similar dependence of adhesion force on particle size. The Johnson Kendall Roberts (JKR) model was employed to estimate the contact area between E. coli cells and NPs, and based on the JKR model a new model that considers local effective contact area was developed. The prediction of the new model matched the size dependence of adhesion force in experimental results. Size effects on adhesion forces may originate from the difference in local effective contact areas as supported by our model. These findings provide fundamental information for interpreting the environmental behaviors and biological interactions of NPs, which barely have been addressed.

  12. BOREAS AFM-1 NOAA/ATDD Long-EZ Aircraft Flux data Over the SSA

    NASA Technical Reports Server (NTRS)

    Crawford, Timothy L.; Baldocchi, Dennis; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Gunter, Laureen; Dumas, Ed; Smith, David E. (Technical Monitor)

    2000-01-01

    This data set contains measurements from the Airborne Flux and Meteorology (AFM)-1 National Oceanographic and Atmospheric Administration/Atmospheric Turbulence and Diffusion Division (NOAA/ATDD) Long-EZ Aircraft collected during the 1994 Intensive Field Campaigns (IFCs) at the southern study area (SSA). These measurements were made from various instruments mounted on the aircraft. The data that were collected include aircraft altitude, wind direction, wind speed, air temperature, potential temperature, water mixing ratio, U and V components of wind velocity, static pressure, surface radiative temperature, downwelling and upwelling total radiation, downwelling and upwelling longwave radiation, net radiation, downwelling and upwelling photosynthectically active radiation (PAR), greenness index, CO2 concentration, O3 concentration, and CH4 concentration. There are also various columns that indicate the standard deviation, skewness, kurtosis, and trend of some of these data. The data are stored in tabular ASCII files. The NOAA/ATDD Long-EZ aircraft flux data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  13. Sequence-controlled RNA self-processing: computational design, biochemical analysis, and visualization by AFM.

    PubMed

    Petkovic, Sonja; Badelt, Stefan; Block, Stephan; Flamm, Christoph; Delcea, Mihaela; Hofacker, Ivo; Müller, Sabine

    2015-07-01

    Reversible chemistry allowing for assembly and disassembly of molecular entities is important for biological self-organization. Thus, ribozymes that support both cleavage and formation of phosphodiester bonds may have contributed to the emergence of functional diversity and increasing complexity of regulatory RNAs in early life. We have previously engineered a variant of the hairpin ribozyme that shows how ribozymes may have circularized or extended their own length by forming concatemers. Using the Vienna RNA package, we now optimized this hairpin ribozyme variant and selected four different RNA sequences that were expected to circularize more efficiently or form longer concatemers upon transcription. (Two-dimensional) PAGE analysis confirms that (i) all four selected ribozymes are catalytically active and (ii) high yields of cyclic species are obtained. AFM imaging in combination with RNA structure prediction enabled us to calculate the distributions of monomers and self-concatenated dimers and trimers. Our results show that computationally optimized molecules do form reasonable amounts of trimers, which has not been observed for the original system so far, and we demonstrate that the combination of theoretical prediction, biochemical and physical analysis is a promising approach toward accurate prediction of ribozyme behavior and design of ribozymes with predefined functions.

  14. Sequence-controlled RNA self-processing: computational design, biochemical analysis, and visualization by AFM

    PubMed Central

    Petkovic, Sonja; Badelt, Stefan; Flamm, Christoph; Delcea, Mihaela

    2015-01-01

    Reversible chemistry allowing for assembly and disassembly of molecular entities is important for biological self-organization. Thus, ribozymes that support both cleavage and formation of phosphodiester bonds may have contributed to the emergence of functional diversity and increasing complexity of regulatory RNAs in early life. We have previously engineered a variant of the hairpin ribozyme that shows how ribozymes may have circularized or extended their own length by forming concatemers. Using the Vienna RNA package, we now optimized this hairpin ribozyme variant and selected four different RNA sequences that were expected to circularize more efficiently or form longer concatemers upon transcription. (Two-dimensional) PAGE analysis confirms that (i) all four selected ribozymes are catalytically active and (ii) high yields of cyclic species are obtained. AFM imaging in combination with RNA structure prediction enabled us to calculate the distributions of monomers and self-concatenated dimers and trimers. Our results show that computationally optimized molecules do form reasonable amounts of trimers, which has not been observed for the original system so far, and we demonstrate that the combination of theoretical prediction, biochemical and physical analysis is a promising approach toward accurate prediction of ribozyme behavior and design of ribozymes with predefined functions. PMID:25999318

  15. BOREAS AFM-08 ECMWF Hourly Surface and Upper Air Data for the SSA and NSA

    NASA Technical Reports Server (NTRS)

    Viterbo, Pedro; Betts, Alan; Hall, Forrest G. (Editor); Newcomer, Jeffrey A.; Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-8 team focused on modeling efforts to improve the understanding of the diurnal evolution of the convective boundary layer over the boreal forest. This data set contains hourly data from the European Center for for Medium-Range Weather Forecasts (ECMWF) operational model from below the surface to the top of the atmosphere, including the model fluxes at the surface. Spatially, the data cover a pair of the points that enclose the rawinsonde sites at Candle Lake, Saskatchewan, in the Southern Study Area (SSA) and Thompson, Manitoba, in the Northern Study Area (NSA). Temporally, the data include the two time periods of 13 May 1994 to 30 Sept 1994 and 01 Mar 1996 to 31 Mar 1997. The data are stored in tabular ASCII files. The number of records in the upper air data files may exceed 20,000, causing a problem for some software packages. The ECMWF hourly surface and upper air data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  16. Measuring the viscoelastic creep of soft samples by step response AFM.

    PubMed

    Yango, Achu; Schäpe, Jens; Rianna, Carmela; Doschke, Holger; Radmacher, Manfred

    2016-10-12

    We have measured the creep response of soft gels and cells after applying a step in loading force with atomic force microscopy (AFM). By analysing the creep response data using the standard linear solid model, we can quantify the viscous and elastic properties of these soft samples independently. Cells, in comparison with gels of similar softness, are much more viscous, as has been qualitatively observed in conventional force curve data before. Here, we quantify the spring constant and the viscous damping coefficient from the creep response data. We propose two different modes for applying a force step: (1) indirectly by increasing the sample height or (2) directly by employing magnetic cantilevers. Both lead to similar results, whereas the latter seems to be better defined since it resembles closely a constant strain mode. The former is easier to implement in most instruments, and thus may be preferable from a practical point of view. Creep analysis by step response is much more appropriate to analyse the viscoelastic response of soft samples like cells than the usually used force curve analysis.

  17. Mechanical properties of complex biological systems using AFM-based force spectroscopy

    NASA Astrophysics Data System (ADS)

    Graham, John Stephen

    An atomic force microscope (AFM) was designed and built to study the mechanical properties of small collagen fibrils and the plasma membrane of living cells. Collagen is a major component of bone, skin and connective tissues, and is abundant in the extracellular matrix (ECM). Because of its abundance, an understanding of how disease affects collagen mechanics is crucial in disease prevention efforts. Two levels of type I collagen structure were investigated, subfibrils (on the order of 1 mum in length) and longer fibrils. Comparisons were made between measurements of wild-type (wt) collagen and collagen from the mouse model of osteogenesis imperfecta (OI). Significant differences between OI and wt collagen were observed, primarily that intermolecular bonds in OI collagen fibrils are weaker than in wt, or not ruptured, as in the case of OI subfibrils. As cells interact with collagen in the ECM, the mechanical properties of the plasma membrane are also of great interest. Membrane tethers were extracted from living cells under varied conditions in order to assess the contributions of membrane-associated macromolecules such as the actin cytoskeleton and the glycocalyx, and intracellular signaling. Tether extraction force was found to be sensitive to all of these altered conditions, suggesting that tether extraction may be used to monitor various cellular processes.

  18. STM/AFM studies of the evolution of morphology of electroplated Ni/W alloys

    NASA Astrophysics Data System (ADS)

    Zhu, L.; Younes, O.; Ashkenasy, N.; Shacham-Diamand, Y.; Gileadi, E.

    2002-11-01

    The surface morphology evolution of Ni/W alloys was studied, as a function of the alloy composition. Using the modified plating baths developed in our laboratory recently, electroplated Ni/W alloys with different W content, in the range of 7-67 atom percent (a/o), can be obtained. This was found to lead to different structures, ranging from polycrystalline fcc-Ni type structure to amorphous, followed by orthorhombic with increasing W content in the alloy. Powder XRD was studied to determine the crystal structures. Ex situ STM, AFM and SEM were used to study in detail the surface morphologies of the different alloys, and their evolution with increasing W content. The important findings are that a mixture of two crystalline forms can give rise to an amorphous structure. Hillocks that are usually a characteristic of epitaxial growth can also exist in the amorphous alloys. Oriented scratches caused by stress can also be formed. Up to 20 a/o of W is deposited in the alloys in crystalline form, with the fcc-Ni type structure. Between 20 and about 40 a/o an amorphous structure is observed, and above that an orthorhombic crystal structure is seen, which is characteristic of the NiW binary alloy. Careful choice of the composition of the plating bath allowed us to deposit an alloy containing 67 a/o W, which corresponds to the composition NiW 2.

  19. A rapid and automated relocation method of an AFM probe for high-resolution imaging.

    PubMed

    Zhou, Peilin; Yu, Haibo; Shi, Jialin; Jiao, Niandong; Wang, Zhidong; Wang, Yuechao; Liu, Lianqing

    2016-09-30

    The atomic force microscope (AFM) is one of the most powerful tools for high-resolution imaging and high-precision positioning for nanomanipulation. The selection of the scanning area of the AFM depends on the use of the optical microscope. However, the resolution of an optical microscope is generally no larger than 200 nm owing to wavelength limitations of visible light. Taking into consideration the two determinants of relocation-relative angular rotation and positional offset between the AFM probe and nano target-it is therefore extremely challenging to precisely relocate the AFM probe to the initial scan/manipulation area for the same nano target after the AFM probe has been replaced, or after the sample has been moved. In this paper, we investigate a rapid automated relocation method for the nano target of an AFM using a coordinate transformation. The relocation process is both simple and rapid; moreover, multiple nano targets can be relocated by only identifying a pair of reference points. It possesses a centimeter-scale location range and nano-scale precision. The main advantages of this method are that it overcomes the limitations associated with the resolution of optical microscopes, and that it is label-free on the target areas, which means that it does not require the use of special artificial markers on the target sample areas. Relocation experiments using nanospheres, DNA, SWCNTs, and nano patterns amply demonstrate the practicality and efficiency of the proposed method, which provides technical support for mass nanomanipulation and detection based on AFM for multiple nano targets that are widely distributed in a large area.

  20. Development of a 3D-AFM for true 3D measurements of nanostructures

    NASA Astrophysics Data System (ADS)

    Dai, Gaoliang; Häßler-Grohne, Wolfgang; Hüser, Dorothee; Wolff, Helmut; Danzebrink, Hans-Ulrich; Koenders, Ludger; Bosse, Harald

    2011-09-01

    The development of advanced lithography requires highly accurate 3D metrology methods for small line structures of both wafers and photomasks. Development of a new 3D atomic force microscopy (3D-AFM) with vertical and torsional oscillation modes is introduced in this paper. In its configuration, the AFM probe is oscillated using two piezo actuators driven at vertical and torsional resonance frequencies of the cantilever. In such a way, the AFM tip can probe the surface with a vertical and a lateral oscillation, offering high 3D probing sensitivity. In addition, a so-called vector approach probing (VAP) method has been applied. The sample is measured point-by-point using this method. At each probing point, the tip is approached towards the surface until the desired tip-sample interaction is detected and then immediately withdrawn from the surface. Compared to conventional AFMs, where the tip is kept continuously in interaction with the surface, the tip-sample interaction time using the VAP method is greatly reduced and consequently the tip wear is reduced. Preliminary experimental results show promising performance of the developed system. A measurement of a line structure of 800 nm height employing a super sharp AFM tip could be performed with a repeatability of its 3D profiles of better than 1 nm (p-v). A line structure of a Physikalisch-Technische Bundesanstalt photomask with a nominal width of 300 nm has been measured using a flared tip AFM probe. The repeatability of the middle CD values reaches 0.28 nm (1σ). A long-term stability investigation shows that the 3D-AFM has a high stability of better than 1 nm within 197 measurements taken over 30 h, which also confirms the very low tip wear.

  1. Adsorption of modified dextrins to a hydrophobic surface: QCM-D studies, AFM imaging, and dynamic contact angle measurements.

    PubMed

    Sedeva, Iliana G; Fetzer, Renate; Fornasiero, Daniel; Ralston, John; Beattie, David A

    2010-05-15

    The adsorption of three dextrin-based polymers, regular wheat dextrin (Dextrin TY), phenyl succinate dextrin (PS Dextrin), and styrene oxide dextrin (SO Dextrin) on a model hydrophobic surface, consisting of a mixed alkanethiol layer on gold, has been characterized using the quartz crystal microbalance with dissipation monitoring (QCM-D). The three polymers exhibited varying affinities and capacity for adsorption on the hydrophobic substrate. Atomic force microscope (AFM) imaging of the polymer layers indicates that all three polymers fully cover the surface. The effect of the three polymers on the static contact angle of the surface was studied using captive bubble contact angle measurements. The three polymers were seen to reduce the receding contact angle by similar amounts (approximately 14°) in spite of having varying adsorbed amounts and differences in adsorbed layer water content. Although no differences were observed in the ability of the polymers to reduce the static contact angle, measurements of the dynamic contact angle between a rising air bubble and the polymer covered substrate yielded stark differences between the polymers, with one polymer (SO Dextrin) slowing the dewetting by an order of magnitude more than the other two polymers. The differences in dewetting behavior correlate with the adsorbed layer characteristics determined by QCM-D and AFM. The role of the dynamic and static contact angle in the performance of a polymer as depressant is discussed.

  2. The in situ characterization and structuring of electrografted polyphenylene films on silicon surfaces. An AFM and XPS study.

    PubMed

    Ghorbal, Achraf; Grisotto, Federico; Laudé, Marion; Charlier, Julienne; Palacin, Serge

    2008-12-15

    An atomic force microscope was used so as to structure by nanofriction films of polynitrophenylene electrografted on substrates of n-type silicon (100) with the native oxide on the top of the surface. AFM measurements of thin films thickness have been carried out in the electrolytic solution for different applied potentials during the electrografting. This investigation allows (i) to determine the relationship between the applied potential and the final thickness of electrografted polyphenylene films and (ii) to specify how the thin layers grow. XPS analysis confirmed the AFM observations on (i) the effective shaving of the grafted polymer chains under mechanical stress and (ii) the existence of a potential threshold for electrografting a polyphenylene film on silicon oxide surfaces. The presence of a residual film in the rubbed zone was attributed to stronger interactions between the first electrografted layer and the native oxide of silicon (through Si-C or/and Si-O-C bonds) than those insuring the cohesion of the multilayer (C-C and C-N bonds).

  3. Characterization of microscale wear in a ploysilicon-based MEMS device using AFM and PEEM-NEXAFS spectromicroscopy.

    SciTech Connect

    Grierson, D. S.; Konicek, A. R.; Wabiszewski, G. E.; Sumant, A. V.; de Boer, M. P.; Corwin, A. D.; Carpick, R. W.

    2009-12-01

    Mechanisms of microscale wear in silicon-based microelectromechanical systems (MEMS) are elucidated by studying a polysilicon nanotractor, a device specifically designed to conduct friction and wear tests under controlled conditions. Photoelectron emission microscopy (PEEM) was combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM) to quantitatively probe chemical changes and structural modification, respectively, in the wear track of the nanotractor. The ability of PEEM-NEXAFS to spatially map chemical variations in the near-surface region of samples at high lateral spatial resolution is unparalleled and therefore ideally suited for this study. The results show that it is possible to detect microscopic chemical changes using PEEM-NEXAFS, specifically, oxidation at the sliding interface of a MEMS device. We observe that wear induces oxidation of the polysilicon at the immediate contact interface, and the spectra are consistent with those from amorphous SiO{sub 2}. The oxidation is correlated with gouging and debris build-up in the wear track, as measured by AFM and scanning electron microscopy (SEM).

  4. Bioassay and Scanning Electron Microscopic Observations Reveal High Virulence of Entomopathogenic Fungus, Beauveria bassiana, on the Onion Maggot (Diptera: Anthomyiidae) Adults.

    PubMed

    Zhang, Hui; Wu, Shengyong; Xing, Zhenlong; Wang, Xiaoqing; Lei, Zhongren

    2016-12-01

    When flies were dipped in 1 × 10(8) conidia/ml conidia suspensions and then kept in the incubator (22 ± 1 °C, 70 ± 5% RH), scanning electron microscope observations revealed that, at 2 h, the majority of adhering Beauveria bassiana conidia were attached to either the wing surface or the interstitial area between the macrochaetae on the thorax and abdomen of the onion maggot adults. Germ tubes were being produced and had oriented toward the cuticle by 18 h. Penetration of the insect cuticle had occurred by 36 h, and by 48 h, germ tubes had completely penetrated the cuticle. Fungal mycelia had emerged from the insect body and were proliferating after 72 h. The superficial area and structure of the wings and macrochaetae may facilitate the attachment of conidia and enable effective penetration. The susceptibility of adults to 12 isolates, at a concentration of 1 × 10(7) conidia/ml, was tested in laboratory experiments. Eight of the more potent strains caused in excess of 85% adult mortality 8 d post inoculation, while the median lethal time (LT50) of these strains was <6 d. The virulence of the more effective strains was further tested, and the median lethal concentrations (LC50) were calculated by exposing adults to doses ranging from 10(3)-10(7) conidia/ml. The lowest LC50 value, found in the isolate XJWLMQ-32, for the adults was 3.87 × 10(3) conidia/ml. These results demonstrate that some B. bassiana strains are highly virulent to onion maggot adults and should be considered as potential biocontrol agents against the adult flies.

  5. New Observations Reveal How the Martian Residual South Polar Cap Develops Quasi-Circular Pits, Heart-Shaped Pits, Troughs, and Moats

    NASA Astrophysics Data System (ADS)

    Buhler, Peter Benjamin; Ingersoll, Andrew P.; Ehlmann, Bethany; Fassett, Caleb; Head, James W.

    2016-10-01

    The martian residual south polar cap (RSPC) is a ~1-10 m thick deposit of CO2 ice perched on the much larger H2O ice cap. Because it is the only known CO2 reservoir annually exchanging with the predominantly-CO2 martian atmosphere, understanding its evolution is important to understanding the modern martian climate. The 8 x 105 m2 RSPC is perennial and characterized by mesas dissected by quasi-circular pits, heart-shaped pits, linear troughs and ridges, and moats (a low, CO2-free boundary surrounding a mesa wholly contained within another mesa) that evolve at meter-scales each year [1,2]. However, the underlying processes leading to the development of these landforms have not yet been described. Using repeat-coverage HiRISE (25-50 cm/px) imagery, we observe previously undescribed features on the RSPC, which reveal the processes leading to the emergence of its meter-to-kilometer-scale morphology. We observe dark fans emanating from the sides of RSPC mesas and widespread fracturing and collapse of the upper surface of mesas, which we interpret as evidence for sublimation in the interiors of mesas. On relatively smooth areas of the RSPC, even small relief (~10 cm) collapses generate surface roughness, which concentrates sunlight and enhances sublimation, leading to the development of steep, eroding scarps. Typically, CO2 deposition during the winter then smooths terrain and creates gently sloping scarps (although uneven CO2 deposition can also create steep scarps). A collapse that drops down, such that it is entirely bounded by a steep scarp, develops into a quasi-circular pit. However, when a portion of the collapsing area remains attached to the upper surface, the perimeter is partially bounded by a steep scarp and partially bounded by a gently sloping ramp, which develops into either a heart-shaped pit, linear trough, or moat, depending on the local interplay between deposition and erosion. Finally, we use the spatial distribution of pits in order to determine the

  6. AFM1 in Milk: Physical, Biological, and Prophylactic Methods to Mitigate Contamination

    PubMed Central

    Giovati, Laura; Magliani, Walter; Ciociola, Tecla; Santinoli, Claudia; Conti, Stefania; Polonelli, Luciano

    2015-01-01

    Aflatoxins (AFs) are toxic, carcinogenic, immunosuppressive secondary metabolites produced by some Aspergillus species which colonize crops, including many dietary staple foods and feed components. AFB1 is the prevalent and most toxic among AFs. In the liver, it is biotransformed into AFM1, which is then excreted into the milk of lactating mammals, including dairy animals. AFM1 has been shown to be cause of both acute and chronic toxicoses. The presence of AFM1 in milk and dairy products represents a worldwide concern since even small amounts of this metabolite may be of importance as long-term exposure is concerned. Contamination of milk may be mitigated either directly, decreasing the AFM1 content in contaminated milk, or indirectly, decreasing AFB1 contamination in the feed of dairy animals. Current strategies for AFM1 mitigation include good agricultural practices in pre-harvest and post-harvest management of feed crops (including storage) and physical or chemical decontamination of feed and milk. However, no single strategy offers a complete solution to the issue. PMID:26512694

  7. AFM as an analysis tool for high-capacity sulfur cathodes for Li–S batteries

    PubMed Central

    Sörgel, Seniz; Costa, Rémi; Carlé, Linus; Galm, Ines; Cañas, Natalia; Pascucci, Brigitta; Friedrich, K Andreas

    2013-01-01

    Summary In this work, material-sensitive atomic force microscopy (AFM) techniques were used to analyse the cathodes of lithium–sulfur batteries. A comparison of their nanoscale electrical, electrochemical, and morphological properties was performed with samples prepared by either suspension-spraying or doctor-blade coating with different binders. Morphological studies of the cathodes before and after the electrochemical tests were performed by using AFM and scanning electron microscopy (SEM). The cathodes that contained polyvinylidene fluoride (PVDF) and were prepared by spray-coating exhibited a superior stability of the morphology and the electric network associated with the capacity and cycling stability of these batteries. A reduction of the conductive area determined by conductive AFM was found to correlate to the battery capacity loss for all cathodes. X-ray diffraction (XRD) measurements of Li2S exposed to ambient air showed that insulating Li2S hydrolyses to insulating LiOH. This validates the significance of electrical ex-situ AFM analysis after cycling. Conductive tapping mode AFM indicated the existence of large carbon-coated sulfur particles. Based on the analytical findings, the first results of an optimized cathode showed a much improved discharge capacity of 800 mA·g(sulfur)−1 after 43 cycles. PMID:24205455

  8. Mutant AFM 2 of Alcaligenes faecalis for phenol biodegradation using He-Ne laser irradiation.

    PubMed

    Jiang, Yan; Wen, Jianping; Caiyin, Qinggele; Lin, Liangcai; Hu, Zongding

    2006-11-01

    He-Ne laser technology was utilized in this study to investigate the response of Alcaligenes faecalis to laser stimulation. The irradiation experiments were conducted by the adjustment of the output power from 5 to 25 mW and the exposure time from 5 to 25 min. The results showed that the survival rate changed regularly with the variety of irradiation dose, and high positive mutation frequency was determined by both the energy density and the output power. The mutant strain AFM 2 was obtained. Phenol biodegradation assay demonstrated that AFM 2 possessed a more prominent phenol-degrading potential than its parent strain, which presumably attributed to the improvements of phenol hydroxylase and catechol 1,2-dioxygenase activities. The phenol of 2000 mgl(-1) was completely degraded by AFM 2 within 85.5h at 30 degrees C. In addition, the cell growth and phenol degradation kinetics of the mutant strain AFM 2 and its parent strain in batch cultures were also investigated at the wide initial phenol concentration ranging from 0 to 2000 mgl(-1) by Haldane model. The results of these experiments further demonstrated that the mutant strain AFM 2 possessed a higher capacity to resist phenol.

  9. Accelerated design and quality control of impact modifiers for plastics through atomic force microscopy (AFM) analysis

    NASA Astrophysics Data System (ADS)

    Moeller, Gunter

    2011-03-01

    Standard polymer resins are often too brittle or do not meet other mechanical property requirements for typical polymer applications. To achieve desired properties it is common to disperse so called ``impact modifiers'', which are spherical latex particles with diameters of much less than one micrometer, into the pure resin. Understanding and control of the entire process from latex particle formation to subsequent dispersion into polymer resins are necessary to accelerate the development of new materials that meet specific application requirements. In this work AFM imaging and nanoindentation techniques in combination with AFM-based spectroscopic techniques were applied to assess latex formation and dispersion. The size and size distribution of the latex particles can be measured based on AFM amplitude modulation images. AFM phase images provide information about the chemical homogeneity of individual particles. Nanoindentation may be used to estimate their elastic and viscoelastic properties. Proprietary creep and nanoscale Dynamic Mechanical Analysis (DMA) tests that we have developed were used to measure these mechanical properties. The small size of dispersed latex inclusions requires local mechanical and spectroscopic analysis techniques with high lateral and spatial resolution. We applied the CRAVE AFM method, developed at NIST, to perform mechanical analysis of individual latex inclusions and compared results with those obtained using nanoscale DMA. NanoIR, developed by Anasys Inc., and principal component confocal Raman were used for spectroscopic analysis and results from both techniques compared.

  10. Enabling accurate gate profile control with inline 3D-AFM

    NASA Astrophysics Data System (ADS)

    Bao, Tianming; Lopez, Andrew; Dawson, Dean

    2009-05-01

    The logic and memory semiconductor device technology strives to follow the aggressive ITRS roadmap. The ITRS calls for increased 3D metrology to meet the demand for tighter process control at 45nm and 32nm nodes. In particular, gate engineering has advanced to a level where conventional metrology by CD-SEM and optical scatterometry (OCD) faces fundamental limitations without involvement of 3D atomic force microscope (3D-AFM or CD-AFM). This paper reports recent progress in 3D-AFM to address the metrology need to control gate dimension in MOSFET transistor formation. 3D-AFM metrology measures the gate electrode at post-etch with the lowest measurement uncertainty for critical gate geometry, including linewidth, sidewall profile, sidewall angle (SWA), line width roughness (LWR), and line edge roughness (LER). 3D-AFM enables accurate gate profile control in three types of metrology applications: reference metrology to validate CD-SEM and OCD, inline depth or 3D monitoring, or replacing TEM for 3D characterization for engineering analysis.

  11. Quantitating membrane bleb stiffness using AFM force spectroscopy and an optical sideview setup.

    PubMed

    Gonnermann, Carina; Huang, Chaolie; Becker, Sarah F; Stamov, Dimitar R; Wedlich, Doris; Kashef, Jubin; Franz, Clemens M

    2015-03-01

    AFM-based force spectroscopy in combination with optical microscopy is a powerful tool for investigating cell mechanics and adhesion on the single cell level. However, standard setups featuring an AFM mounted on an inverted light microscope only provide a bottom view of cell and AFM cantilever but cannot visualize vertical cell shape changes, for instance occurring during motile membrane blebbing. Here, we have integrated a mirror-based sideview system to monitor cell shape changes resulting from motile bleb behavior of Xenopus cranial neural crest (CNC) cells during AFM elasticity and adhesion measurements. Using the sideview setup, we quantitatively investigate mechanical changes associated with bleb formation and compared cell elasticity values recorded during membrane bleb and non-bleb events. Bleb protrusions displayed significantly lower stiffness compared to the non-blebbing membrane in the same cell. Bleb stiffness values were comparable to values obtained from blebbistatin-treated cells, consistent with the absence of a functional actomyosin network in bleb protrusions. Furthermore, we show that membrane blebs forming within the cell-cell contact zone have a detrimental effect on cell-cell adhesion forces, suggesting that mechanical changes associated with bleb protrusions promote cell-cell detachment or prevent adhesion reinforcement. Incorporating a sideview setup into an AFM platform therefore provides a new tool to correlate changes in cell morphology with results from force spectroscopy experiments.

  12. Noise in NC-AFM measurements with significant tip–sample interaction

    PubMed Central

    Lübbe, Jannis; Temmen, Matthias

    2016-01-01

    The frequency shift noise in non-contact atomic force microscopy (NC-AFM) imaging and spectroscopy consists of thermal noise and detection system noise with an additional contribution from amplitude noise if there are significant tip–sample interactions. The total noise power spectral density D Δ f(f m) is, however, not just the sum of these noise contributions. Instead its magnitude and spectral characteristics are determined by the strongly non-linear tip–sample interaction, by the coupling between the amplitude and tip–sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL) detector used for frequency demodulation. Here, we measure D Δ f(f m) for various NC-AFM parameter settings representing realistic measurement conditions and compare experimental data to simulations based on a model of the NC-AFM system that includes the tip–sample interaction. The good agreement between predicted and measured noise spectra confirms that the model covers the relevant noise contributions and interactions. Results yield a general understanding of noise generation and propagation in the NC-AFM and provide a quantitative prediction of noise for given experimental parameters. We derive strategies for noise-optimised imaging and spectroscopy and outline a full optimisation procedure for the instrumentation and control loops. PMID:28144538

  13. Morphology of Vapor-Deposited Ice at Low Temperatures by Atomic Force Microscopy (AFM)

    NASA Astrophysics Data System (ADS)

    Fain, , Jr.; Donev, J. M. K.; Tait, B. R. Long, Jr.; Yu, Q.

    2002-03-01

    The morphology of multilayer films of ice on various substrates is measured by AFM as a function of vapor-deposition and annealing temperatures below 150K. The films are deposited in-situ in UHV from an effusive doser at 67 degrees from the surface normal. For depositions near 100K on clean Au(111), previous measurements by Donev et al. using needle-sensor AFM indicate that 3-D clustering starts near 120K for initially flat thin films of amorphous solid water (ASW). For depositions below 85K on clean Au(111), preliminary measurements using non-contact AFM (nc-AFM) indicate that clustering does not occur during annealing until bulk diffusion becomes operative at T>140K. Deposition at glancing angle at the lower temperatures is known to increase porosity and is also expected to decrease the number of crystalline nuclei in the ASW. For depositions near 100K on mica that had been annealed in UHV, preliminary measurements using ncAFM show clustering near 120K. Supported by U. W. Nanotechnology Fellowship (J.M.K.D.), Mary Gates Fellowship (B. R. L.), and M. J. Murdock Charitable Trust.

  14. Effect of AFM probe geometry on visco-hyperelastic characterization of soft materials

    NASA Astrophysics Data System (ADS)

    Boccaccio, Antonio; Lamberti, Luciano; Papi, Massimiliano; De Spirito, Marco; Pappalettere, Carmine

    2015-08-01

    Atomic force microscopy (AFM) nanoindentation is very suited for nano- and microscale mechanical characterization of soft materials. Although the structural response of polymeric networks that form soft matter depends on viscous effects caused by the relative slippage of polymeric chains, the usual assumption made in the AFM-based characterization is that the specimen behaves as a purely elastic material and viscous forces are negligible. However, for each geometric configuration of the AFM tip, there will be a limit indentation rate above which viscous effects must be taken into account to correctly determine mechanical properties. A parametric finite element study conducted on 12 geometric configurations of a blunt cone AFM tip (overall, the study included about 200 finite element analyses) allowed us to determine the limit indentation rate for each configuration. The selected tip dimensions cover commercially available products and account for changes in tip geometry caused by serial measurements. Nanoindentation rates cover typical experimental conditions set in AFM bio-measurements on soft matter. Viscous effects appear to be more significant in the case of sharper tips. This implies that, if quantitative data on sample viscosity are not available, using a rounded indenter and carrying out experiments below the limit indentation rate will allow errors in the determination of mechanical properties to be minimized.

  15. The ReactorAFM: Non-contact atomic force microscope operating under high-pressure and high-temperature catalytic conditions

    SciTech Connect

    Roobol, S. B.; Cañas-Ventura, M. E.; Bergman, M.; Spronsen, M. A. van; Onderwaater, W. G.; Tuijn, P. C. van der; Koehler, R.; Frenken, J. W. M.; Ofitserov, A.; Baarle, G. J. C. van

    2015-03-15

    An Atomic Force Microscope (AFM) has been integrated in a miniature high-pressure flow reactor for in-situ observations of heterogeneous catalytic reactions under conditions similar to those of industrial processes. The AFM can image model catalysts such as those consisting of metal nanoparticles on flat oxide supports in a gas atmosphere up to 6 bar and at a temperature up to 600 K, while the catalytic activity can be measured using mass spectrometry. The high-pressure reactor is placed inside an Ultrahigh Vacuum (UHV) system to supplement it with standard UHV sample preparation and characterization techniques. To demonstrate that this instrument successfully bridges both the pressure gap and the materials gap, images have been recorded of supported palladium nanoparticles catalyzing the oxidation of carbon monoxide under high-pressure, high-temperature conditions.

  16. Effect of tetramethylammonium hydroxide/isopropyl alcohol wet etching on geometry and surface roughness of silicon nanowires fabricated by AFM lithography

    PubMed Central

    Yusoh, Siti Noorhaniah

    2016-01-01

    Summary The optimization of etchant parameters in wet etching plays an important role in the fabrication of semiconductor devices. Wet etching of tetramethylammonium hydroxide (TMAH)/isopropyl alcohol (IPA) on silicon nanowires fabricated by AFM lithography is studied herein. TMAH (25 wt %) with different IPA concentrations (0, 10, 20, and 30 vol %) and etching time durations (30, 40, and 50 s) were investigated. The relationships between etching depth and width, and etching rate and surface roughness of silicon nanowires were characterized in detail using atomic force microscopy (AFM). The obtained results indicate that increased IPA concentration in TMAH produced greater width of the silicon nanowires with a smooth surface. It was also observed that the use of a longer etching time causes more unmasked silicon layers to be removed. Importantly, throughout this study, wet etching with optimized parameters can be applied in the design of the devices with excellent performance for many applications. PMID:27826521

  17. Crystallographic order and decomposition of [MnIII6CrIII]3+ single-molecule magnets deposited in submonolayers and monolayers on HOPG studied by means of molecular resolved atomic force microscopy (AFM) and Kelvin probe force microscopy in UHV

    PubMed Central

    2014-01-01

    Monolayers and submonolayers of [Mn III 6 Cr III ] 3+ single-molecule magnets (SMMs) adsorbed on highly oriented pyrolytic graphite (HOPG) using the droplet technique characterized by non-contact atomic force microscopy (nc-AFM) as well as by Kelvin probe force microscopy (KPFM) show island-like structures with heights resembling the height of the molecule. Furthermore, islands were found which revealed ordered 1D as well as 2D structures with periods close to the width of the SMMs. Along this, islands which show half the heights of intact SMMs were observed which are evidences for a decomposing process of the molecules during the preparation. Finally, models for the structure of the ordered SMM adsorbates are proposed to explain the observations. PMID:24495692

  18. Lipid asymmetry in DLPC/DSPC supported lipid bilayers, a combined AFM and fluorescence microscopy study

    SciTech Connect

    Lin, W; Blanchette, C D; Ratto, T V; Longo, M L

    2005-06-20

    A fundamental attribute of cell membranes is transmembrane asymmetry, specifically the formation of ordered phase domains in one leaflet that are compositionally different from the opposing leaflet of the bilayer. Using model membrane systems, many previous studies have demonstrated the formation of ordered phase domains that display complete transmembrane symmetry but there have been few reports on the more biologically relevant asymmetric membrane structures. Here we report on a combined atomic force microscopy (AFM) and fluorescence microscopy study whereby we observe three different states of transmembrane symmetry in phase-separated supported bilayers formed by vesicle fusion. We find that if the leaflets differ in gel-phase area fraction, then the smaller domains in one leaflet are in registry with the larger domains in the other leaflet and the system is dynamic. In a presumed lipid flip-flop process similar to Ostwald Ripening, the smaller domains in one leaflet erode away while the large domains in the other leaflet grow until complete compositional asymmetry is reached and remains stable. We have quantified this evolution and determined that the lipid flip-flop event happens most frequently at the interface between symmetric and asymmetric DSPC domains. If both leaflets have nearly identical area fraction of gel-phase, gel-phase domains are in registry and are static in comparison to the first state. The stability of these three DSPC domain distributions, the degree of registry observed, and the domain immobility have direct biological significance with regards to maintenance of lipid asymmetry in living cell membranes, communication between inner leaflet and outer leaflet, membrane adhesion, and raft mobility.

  19. Using AFM Force Curves to Explore Properties of Elastomers

    ERIC Educational Resources Information Center

    Ferguson, Megan A.; Kozlowski, Joseph J.

    2013-01-01

    polydimethylsiloxane (PDMS) elastomers. Force curves are used to quantify the stiffness of elastomers prepared with different base-to-curing agent ratios. Trends in observed spring constants of the…

  20. DNA-duplex linker for AFM-SELEX of DNA aptamer against human serum albumin.

    PubMed

    Takenaka, Musashi; Okumura, Yuzo; Amino, Tomokazu; Miyachi, Yusuke; Ogino, Chiaki; Kondo, Akihiko

    2017-02-15

    DNA-duplex interactions in thymines and adenins are used as a linker for the novel methodology of Atomic Force Microscope-Systematic Evolution of Ligands by EXpotential enrichment (AFM-SELEX). This study used the hydrogen bonds in 10 mer of both thymines (T10) and adenines (A10). Initially, the interactive force in T10-A10 was measured by AFM, which returned an average interactive force of approximately 350pN. Based on this result, DNA aptamers against human serum albumin could be selected in the 4th round, and 15 different clones could be sequenced. The lowest dissociation constant of the selected aptamer was identified via surface plasmon resonance, and it proved to be identical to that of the commercial aptamer. Therefore, specific hydrogen bonds in DNA can be useful linkers for AFM-SELEX.

  1. In situ nanomanipulators as a tool to separate individual tobermorite crystals for AFM studies.

    PubMed

    Yang, Tianhe; Holzer, Lorenz; Kägi, Ralf; Winnefeld, Frank; Keller, Bruno

    2007-10-01

    Atomic force microscopy (AFM) studies of cementitious materials are limited, mainly due to the lack of appropriate sample preparation techniques. In porous autoclaved aerated concrete (AAC), calcium silicate hydrate (C-S-H) is produced in its crystalline form, tobermorite. The crystals are lath-like with a length of several micrometers. In this work, we demonstrate the application of nanomanipulators to separate an individual tobermorite crystal from the bulk AAC for subsequent AFM investigations. The nanomanipulators are operated directly in an environmental scanning electron microscope (ESEM). We studied the interaction between moisture and the tobermorite surface under controlled relative humidity (RH). The results of topography and adhesion force measurements with AFM suggest that the surface of tobermorite is hydrophobic, which contrasts the macroscopic material properties (e.g. moisture transport in capillary pores).

  2. Imaging and force measurement of LDL and HDL by AFM in air and liquid

    PubMed Central

    Gan, Chaoye; Ao, Meiying; Liu, Zhanghua; Chen, Yong

    2015-01-01

    The size and biomechanical properties of lipoproteins are tightly correlated with their structures/functions. While atomic force microscopy (AFM) has been used to image lipoproteins the force measurement of these nano-sized particles is missing. We detected that the sizes of LDL and HDL in liquid are close to the commonly known values. The Young’s modulus of LDL or HDL is ∼0.4 GPa which is similar to that of some viral capsids or nanovesicles but greatly larger than that of various liposomes. The adhesive force of LDL or HDL is small (∼200 pN). The comparison of AFM detection in air and liquid was also performed which is currently lacking. Our data may provide useful information for better understanding and AFM detection of lipoproteins. PMID:25893163

  3. AFM study of forces between silica, silicon nitride and polyurethane pads.

    PubMed

    Sokolov, Igor; Ong, Quy K; Shodiev, Hasan; Chechik, Nina; James, David; Oliver, Mike

    2006-08-15

    Interaction of silica and silicon nitride with polyurethane surfaces is rather poorly studied despite being of great interest for modern semiconductor industry, e.g., for chemical-mechanical planarization (CMP) processes. Here we show the results from the application of the atomic force microscopy (AFM) technique to study the forces between silica or silicon nitride (AFM tips) and polyurethane surfaces in aqueous solutions of different acidity. The polyurethane surface potentials are derived from the measured AFM data. The obtained potentials are in rather good agreement with measurements of zeta-potentials using the streaming-potentials method. Another important parameter, adhesion, is also measured. While the surface potentials of silica are well known, there are ambiguous results on the potentials of silicon nitride that is naturally oxidized. Deriving the surface potential of the naturally oxidized silicon nitride from our measurements, we show that it is not oxidized to silica despite some earlier published expectations.

  4. Imaging and force measurement of LDL and HDL by AFM in air and liquid.

    PubMed

    Gan, Chaoye; Ao, Meiying; Liu, Zhanghua; Chen, Yong

    2015-01-01

    The size and biomechanical properties of lipoproteins are tightly correlated with their structures/functions. While atomic force microscopy (AFM) has been used to image lipoproteins the force measurement of these nano-sized particles is missing. We detected that the sizes of LDL and HDL in liquid are close to the commonly known values. The Young's modulus of LDL or HDL is ∼0.4 GPa which is similar to that of some viral capsids or nanovesicles but greatly larger than that of various liposomes. The adhesive force of LDL or HDL is small (∼200 pN). The comparison of AFM detection in air and liquid was also performed which is currently lacking. Our data may provide useful information for better understanding and AFM detection of lipoproteins.

  5. Multiparametric high-resolution imaging of native proteins by force-distance curve-based AFM.

    PubMed

    Pfreundschuh, Moritz; Martinez-Martin, David; Mulvihill, Estefania; Wegmann, Susanne; Muller, Daniel J

    2014-05-01

    A current challenge in the life sciences is to understand how the properties of individual molecular machines adjust in order to meet the functional requirements of the cell. Recent developments in force-distance (FD) curve-based atomic force microscopy (FD-based AFM) enable researchers to combine sub-nanometer imaging with quantitative mapping of physical, chemical and biological properties. Here we present a protocol to apply FD-based AFM to the multiparametric imaging of native proteins under physiological conditions. We describe procedures for experimental FD-based AFM setup, high-resolution imaging of proteins in the native unperturbed state with simultaneous quantitative mapping of multiple parameters, and data interpretation and analysis. The protocol, which can be completed in 1-3 d, enables researchers to image proteins and protein complexes in the native unperturbed state and to simultaneously map their biophysical and biochemical properties at sub-nanometer resolution.

  6. Cell volume increase in murine MC3T3-E1 pre-osteoblasts attaching onto biocompatible tantalum observed by magnetic AC mode atomic force microscopy.

    PubMed

    Andersen, L Klembt; Contera, S Antoranz; Justesen, J; Duch, M; Hansen, O; Chevallier, J; Foss, M; Pedersen, F S; Besenbacher, F

    2005-12-02

    Magnetic AC mode (MACmode) atomic force microscopy (AFM) was used to study murine (mouse) MC3T3-E1 preosteoblastic cells attached to biocompatible tantalum substrates. Cell volumes of attached cells derived from AFM images were compared to volumes of detached cells in suspension measured by the Coulter sizing technique. An increase of approximately 50% in cell volume was observed when the cells attached to planar tantalum substrates and developed a flattened structure including lamellipodia. We address thoroughly the issues general to the AFM determination of absolute cell volumes, and compare our magnetic AC mode AFM measurements to hitherto reported cell volume determinations by contact mode AFM.

  7. An Evaluation of the Impacts of AF-M315E Propulsion Systems for Varied Mission Applications

    NASA Technical Reports Server (NTRS)

    Deans, Matthew C.; Oleson, Steven R.; Fittje, James; Colozza, Anthony; Packard, Tom; Gyekenyesi, John; McLean, Christopher H.; Spores, Ronald A.

    2015-01-01

    The purpose of the AF-M315E COMPASS study is to identify near-term (3-5 years) and long term (5 years +) opportunities for infusion, specifically the thruster and associated component technologies being developed as part of the GPIM project. Develop design reference missions which show the advantages of the AF-M315E green propulsion system. Utilize a combination of past COMPASS designs and selected new designs to demonstrate AF-M315E advantages. Use the COMPASS process to show the puts and takes of using AF-M315E at the integrated system level.

  8. Absorption Spectroscopy and Imaging from the Visible through Mid-IR with 20 nm Resolution Using AFM probes

    NASA Astrophysics Data System (ADS)

    Centrone, Andrea

    2015-03-01

    Correlated nanoscale composition and optical property maps are important to engineer nanomaterials in applications ranging from photovoltaics to sensing and therapeutics. Wavelengths (λs) from the visible to near-IR probe electronic transitions in materials, providing information regarding band gap and defects while light in mid-IR probes vibrational transitions and provide chemical composition. However, light diffraction limits the lateral resolution of conventional micro-spectroscopic techniques to approximately λ/2, which is insufficient to image nanomaterials. Additionally, the λ-dependent resolution impedes direct comparison of spectral maps from different spectral ranges. Photo Thermal Induced Resonance (PTIR) is a novel technique that circumvents light diffraction by employing an AFM tip as a local detector for measuring light absorption with λ-independent nanoscale resolution. Our PTIR setup combines an AFM microscope with three lasers providing λ-tunability from 500 nm to 16000 nm continuously. The AFM tip transduces locally the sample thermal expansion induced by light absorption into large cantilever oscillations. Local absorption spectra (electronic or vibrational) and maps are obtained recording the amplitude of the tip deflection as a function of λ and position, respectively. The working principles of the PTIR technique will be described first, and nano-patterned polymer samples will be used to evaluate its lateral resolution, sensitivity and linearity. Results show that the PTIR signal intensity is proportional to the local absorbed energy suggesting applicability of this technique for quantitative chemical analysis at nanoscale, at least for thin (less than 1000 nm thick) samples. Additionally, a λ-independent resolution as high as 20 nm is demonstrated across the whole spectral range. In the second part of the talk, PTIR will be applied to image the dark plasmonic resonance of gold Asymmetric Split Ring Resonators (A-SRRs) in the mid

  9. Studying post-etching silicon crystal defects on 300mm wafer by automatic defect review AFM

    NASA Astrophysics Data System (ADS)

    Zandiatashbar, Ardavan; Taylor, Patrick A.; Kim, Byong; Yoo, Young-kook; Lee, Keibock; Jo, Ahjin; Lee, Ju Suk; Cho, Sang-Joon; Park, Sang-il

    2016-03-01

    Single crystal silicon wafers are the fundamental elements of semiconductor manufacturing industry. The wafers produced by Czochralski (CZ) process are very high quality single crystalline materials with known defects that are formed during the crystal growth or modified by further processing. While defects can be unfavorable for yield for some manufactured electrical devices, a group of defects like oxide precipitates can have both positive and negative impacts on the final device. The spatial distribution of these defects may be found by scattering techniques. However, due to limitations of scattering (i.e. light wavelength), many crystal defects are either poorly classified or not detected. Therefore a high throughput and accurate characterization of their shape and dimension is essential for reviewing the defects and proper classification. While scanning electron microscopy (SEM) can provide high resolution twodimensional images, atomic force microscopy (AFM) is essential for obtaining three-dimensional information of the defects of interest (DOI) as it is known to provide the highest vertical resolution among all techniques [1]. However AFM's low throughput, limited tip life, and laborious efforts for locating the DOI have been the limitations of this technique for defect review for 300 mm wafers. To address these limitations of AFM, automatic defect review AFM has been introduced recently [2], and is utilized in this work for studying DOI on 300 mm silicon wafer. In this work, we carefully etched a 300 mm silicon wafer with a gaseous acid in a reducing atmosphere at a temperature and for a sufficient duration to decorate and grow the crystal defects to a size capable of being detected as light scattering defects [3]. The etched defects form a shallow structure and their distribution and relative size are inspected by laser light scattering (LLS). However, several groups of defects couldn't be properly sized by the LLS due to the very shallow depth and low

  10. WGA-QD probe-based AFM detects WGA-binding sites on cell surface and WGA-induced rigidity alternation

    SciTech Connect

    Wang Xiaoping; He Dongmei; Cai Jiye Chen Tongsheng; Zou Feiyan; Li Yalan; Wu Yangzhe; Chen, Zheng W.; Chen Yong

    2009-02-06

    A strategy involving the conjugation of fluorescent quantum dot (QD) with wheat germ agglutinin (WGA) acting as fluorescent and topographic probes prior to cell surface staining is developed for fluorescence microscopy and atomic force microscopy (AFM). This strategy provided at least two advantages: (a) an amplified fluorescence of WGA-QD aggregates, strongly resistant to photobleaching, ensures repeated/real-time observations of the probe-labeled cells by fluorescence microscopy; (b) the enlarged size of WGA-QD probe makes it possible for labeled WGA to be distinguished from other membrane proteins by AFM. Here, the random distribution of WGA-binding sites on non-crosslinked cells and the uneven or polarized reorganization due to WGA-induced crosslinking on cell surfaces were studied using AFM-detectable WGA-QD probe. Moreover, we developed a method to rapidly detect the WGA-induced rigidity alternation of the whole cells, which is efficient and has the potentiality of being developed to a useful tool in clinical diagnosis.

  11. Mechano-chemical manipulation of Sn chains on Si(1 0 0) by NC-AFM.

    PubMed

    Sweetman, A; Lekkas, I; Moriarty, P

    2017-02-22

    We investigate the atomic structure of Sn dimer chains grown on the Si(1 0 0) surface using non-contact atomic force microscopy (NC-AFM) at cryogenic temperatures. We find that similar to the native Si(1 0 0) dimer structure, the ground state of the Sn dimer structure is buckled at low temperature. At 5 K we show that the buckling state of the Sn dimers may be controllably, and reversibly, manipulated with atomic precision by close approach of the tip, without modification of the underlying substrate buckling structure. At intermediate cryogenic temperatures we observe changes in the configuration of the dimer chains in the region where the tip-sample interaction is very weak, suggesting that the energy barrier to transit between configurations is sufficiently small to be surmounted at 78 K.

  12. Mechano-chemical manipulation of Sn chains on Si(1 0 0) by NC-AFM

    NASA Astrophysics Data System (ADS)

    Sweetman, A.; Lekkas, I.; Moriarty, P.

    2017-02-01

    We investigate the atomic structure of Sn dimer chains grown on the Si(1 0 0) surface using non-contact atomic force microscopy (NC-AFM) at cryogenic temperatures. We find that similar to the native Si(1 0 0) dimer structure, the ground state of the Sn dimer structure is buckled at low temperature. At 5 K we show that the buckling state of the Sn dimers may be controllably, and reversibly, manipulated with atomic precision by close approach of the tip, without modification of the underlying substrate buckling structure. At intermediate cryogenic temperatures we observe changes in the configuration of the dimer chains in the region where the tip-sample interaction is very weak, suggesting that the energy barrier to transit between configurations is sufficiently small to be surmounted at 78 K.

  13. X-AFm stabilization as a mechanism of bypassing conversion phenomena in calcium aluminate cements

    SciTech Connect

    Falzone, Gabriel; Balonis, Magdalena; Sant, Gaurav

    2015-06-15

    Phase conversion phenomena are often observed in calcium aluminate cements (CACs), when the water-rich hydrates (e.g., CAH{sub 10}, C{sub 2}AH{sub 8}) formed at early ages, at temperatures ≤ 30 °C, expel water in time to form more compact, less water-rich structures (C{sub 3}AH{sub 6}). The phase conversions follow a path regulated by the thermodynamic stabilities (solubilities) of phases. Based on this premise, it is proposed that conversion phenomena in CACs can be bypassed by provoking the precipitation of phases more preferred than those typically encountered along the conversion pathway. Therefore, X-AFm formation (where in this case, X = NO{sub 3}{sup −}) triggered by the sequential addition of calcium nitrate (Ca(NO{sub 3}){sub 2} = CN) additives is identified as a new means of bypassing conversion. A multi-method approach comprising X-ray diffraction (XRD), thermal analytics, and evaluations of the compressive strength is applied to correlate phase balances and properties of CAC systems cured at 25 °C and 45 °C. The results highlight the absence of the C{sub 3}AH{sub 6} phase across all systems and the curing conditions considered, with enhanced strengths being noted, when sufficient quantities of CN are added. The experimental outcomes are supported by insights gained from thermodynamic calculations which highlight thermodynamic selectivity as a means of regulating and controlling the evolutions of solid phase balances using inorganic salts in CACs, and more generally in cementing material systems.

  14. Combination of ToF-SIMS imaging and AFM to study the early stages of corrosion in Al-Cu thin films

    SciTech Connect

    Seyeux, A.; Missert, Nancy; Frankel, Gerald; Unocic, Kinga A; Klein, L. H.; Galtayries, A.; Marcus, P

    2011-01-01

    The pitting corrosion of Al-Cu thin film alloys was investigated using samples that were heat treated in air to form through-thickness Al2Cu particles within an Al-0.5%Cu matrix. Time-of-Flight SIMS (ToF-SIMS) analysis revealed Cu-rich regions 250 - 800 nm in lateral extent near the metal/oxide interface. Following exposure that generated pitting corrosion, secondary electron, secondary ion, and AFM images showed pits with size and density similar to those of the Cu-rich regions. The role of the Cu-rich regions is addressed.

  15. Accuracy of diagnostic heat and moisture budgets using SESAME-79 field data as revealed by observing system simulation experiments. [Severe Environmental Storm and Mesoscale Experiment

    NASA Technical Reports Server (NTRS)

    Kuo, Y.-H.; Anthes, R. A.

    1984-01-01

    Observing system simulation experiments are used to investigate the accuracy of diagnostic heat and moisture budgets which employ the AVE-SESAME 1979 data. The time-including, four-dimensional data set of a mesoscale model is used to simulate rawinsonde observations from AVE-SESAME 1979. The 5 C/day (heat budget) and 2 g/kg per day (moisture budget) magnitudes of error obtained indicate difficulties in the diagnosis of the heating rate in weak convective systems. The influences exerted by observational frequency, objective analysis, observational density, vertical interpolation, and observational errors on the budget are also studied, and it is found that the temporal and spatial resolution of the SESAME regional network is marginal for diagnosing convective effects on a horizontal time scale of 550 x 550 km.

  16. Investigation of Molecular Interactions between AFM-Tip and Thiol Films

    NASA Astrophysics Data System (ADS)

    Touhami, Ahmed; Moore, Justin; Lee, T. Randall

    Among various self-assembly processes, the formation of a self-assembled monolayer (SAM) is one of the most elegant ways for making an organic film with specific surface properties. Recently, much effort has been devoted in using AFM-based single-molecule force spectroscopy (SMFS) to understanding the formation of alkanethiol SAMs on gold surfaces. Investigating the factors that affect the AFM tip-SAMs interactions is necessary to clarify the controversial results of these studies. Here, we investigated the interactions between bare AFM-tips and several SAMs thiols-gold surfaces under controlled humidity conditions. Our results demonstrate that the Tip-SAM interactions can be used to precisely determine the length of the thiol chains, the adhesion force between thiols head groups and the AFM tip, and the strength of the thiol-gold contact. Our findings on the dynamics and the structure of the SAMs of alkanethiols on gold are useful for detail understanding of the thermodynamics, kinetics and mechanisms of SAM technology assembly. NSF.

  17. AFM tip characterization by using FFT filtered images of step structures.

    PubMed

    Yan, Yongda; Xue, Bo; Hu, Zhenjiang; Zhao, Xuesen

    2016-01-01

    The measurement resolution of an atomic force microscope (AFM) is largely dependent on the radius of the tip. Meanwhile, when using AFM to study nanoscale surface properties, the value of the tip radius is needed in calculations. As such, estimation of the tip radius is important for analyzing results taken using an AFM. In this study, a geometrical model created by scanning a step structure with an AFM tip was developed. The tip was assumed to have a hemispherical cone shape. Profiles simulated by tips with different scanning radii were calculated by fast Fourier transform (FFT). By analyzing the influence of tip radius variation on the spectra of simulated profiles, it was found that low-frequency harmonics were more susceptible, and that the relationship between the tip radius and the low-frequency harmonic amplitude of the step structure varied monotonically. Based on this regularity, we developed a new method to characterize the radius of the hemispherical tip. The tip radii estimated with this approach were comparable to the results obtained using scanning electron microscope imaging and blind reconstruction methods.

  18. Single-Molecule Studies of Integrins by AFM-Based Force Spectroscopy on Living Cells

    NASA Astrophysics Data System (ADS)

    Eibl, Robert H.

    The characterization of cell adhesion between two living cells at the single-molecule level, i.e., between one adhesion receptor and its counter-receptor, appears to be an experimental challenge. Atomic force microscopy (AFM) can be used in its force spectroscopy mode to determine unbinding forces of a single pair of adhesion receptors, even with a living cell as a probe. This chapter provides an overview of AFM force measurements of the integrin family of cell adhesion receptors and their ligands. A focus is given to major integrins expressed on leukocytes, such as lymphocyte function-associated antigen 1 (LFA-1) and very late antigen 4 (VLA-4). These receptors are crucial for leukocyte trafficking in health and disease. LFA-1 and VLA-1 can be activated within the bloodstream from a low-affinity to a high-affinity receptor by chemokines in order to adhere strongly to the vessel wall before the receptor-bearing leukocytes extravasate. The experimental considerations needed to provide near-physiological conditions for a living cell and to be able to measure adequate forces at the single-molecule level are discussed in detail. AFM technology has been developed into a modern and extremely sensitive tool in biomedical research. It appears now that AFM force spectroscopy could enter, within a few years, medical applications in diagnosis and therapy of cancer and autoimmune diseases.

  19. Combined AFM nano-machining and reactive ion etching to fabricate high aspect ratio structures.

    PubMed

    Peng, Ping; Shi, Tielin; Liao, Guanglan; Tang, Zirong

    2010-11-01

    In this paper, a new combined method of sub-micron high aspect ratio structure fabrication is developed which can be used for production of nano imprint template. The process includes atomic force microscope (AFM) scratch nano-machining and reactive ion etching (RIE) fabrication. First, 40 nm aluminum film was deposited on the silicon substrate by magnetron sputtering, and then sub-micron grooves were fabricated on the aluminum film by nano scratch using AFM diamond tip. As aluminum film is a good mask for etching silicon, high aspect ratio structures were finally fabricated by RIE process. The fabricated structures were studied by SEM, which shows that the grooves are about 400 nm in width and 5 microm in depth. To obtain sub-micron scale groove structures on the aluminum film, experiments of nanomachining on aluminum films under various machining conditions were conducted. The depths of the grooves fabricated using different scratch loads were also studied by the AFM. The result shows that the material properties of the film/substrate are elastic-plastic following nearly a bilinear law with isotropic strain hardening. Combined AFM nanomachining and RIE process provides a relative lower cost nano fabrication technique than traditional e-beam lithography, and it has a good prospect in nano imprint template fabrication.

  20. Fracture Mechanics Testing of Titanium 6AL-4V in AF-M315E

    NASA Technical Reports Server (NTRS)

    Sampson, J. W.; Martinez, J.; McLean, C.

    2016-01-01

    The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant on orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent processing flaws will not cause failure during the design life of the tank. Material property inputs for this analysis require testing to determine the stress intensity factor for environment-assisted cracking (KEAC) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched, or SE(B), specimens representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to AF-M315E at 50 C for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor for environment-assisted cracking of the Ti 6Al-4V forged tank material was found to be at least 22 ksivin and at least 31 ksivin for the weld material when exposed to AF-M315E monopropellant.

  1. [AFM-based technologies as the way towards the reverse Avogadro number].

    PubMed

    Pleshakova, T O; Shumov, I D; Ivanov, Yu D; Malsagova, K A; Kaysheva, A L; Archakov, A I

    2015-01-01

    Achievement of the concentration detection limit for proteins at the level of the reverse Avogadro number determines the modern development of proteomics. In this review, the possibility of approximating the reverse Avogadro number by using nanotechnological methods (AFM-based fishing with mechanical and electrical stimulation, nanowire detectors, and other methods) are discussed. The ability of AFM to detect, count, visualize and characterize physico-chemical properties of proteins at concentrations up to 10(-17)-10(-18) M is demonstrated. The combination of AFM-fishing with mass-spectrometry allows the identification of proteins not only in pure solutions, but also in multi-component biological fluids (serum). The possibilities to improve the biospecific fishing efficiency by use of SOMAmers in both AFM and nanowire systems are discussed. The paper also provides criteria for evaluation of the sensitivity of fishing-based detection systems. The fishing efficiency depending on the detection system parameters is estimated. The practical implementation of protein fishing depending on the ratio of the sample solution volume and the surface of the detection system is discussed. The advantages and disadvantages of today's promising nanotechnological protein detection methods implemented on the basis of these schemes.

  2. First-principles AFM image simulation with frozen density embedding theory

    NASA Astrophysics Data System (ADS)

    Sakai, Yuki; Lee, Alex J.; Chelikowsky, James R.

    We present efficient first-principles method of non-contact atomic force microscopy (nc-AFM). Ordinary nc-AFM simulations based on density functional theory (DFT) require exhaustive computational cost because it involves thousands of total energy calculations. Regarding the sample as a fixed external potential can reduce the computational cost, and we adopt frozen density embedding theory (FDET) for this purpose. Simulated nc-AFM images with FDET using a carbon monoxide tip well reproduces the full DFT images of benzene, pentacene, and graphene, although optimized tip-sample distances and interaction energies in FDET are underestimated and overestimated, respectively. The FDET-based simulation method is promising for AFM image simulation of surfaces and two-dimensional materials. This work was supported by U.S. DOE under Grant No. DE-FG02-06ER46286 and Award No. DE-SC0008877, and by Welch Foundation under Grant F-1837. Computational resources are provided by NERSC and TACC.

  3. High-speed AFM for 1x node metrology and inspection: Does it damage the features?

    NASA Astrophysics Data System (ADS)

    Sadeghian, Hamed; van den Dool, Teun C.; Uziel, Yoram; Bar Or, Ron

    2015-03-01

    This paper aims at unraveling the mystery of damage in high speed AFMs for 1X node and below. With the device dimensions moving towards the 1X node and below, the semiconductor industry is rapidly approaching the point where existing metrology, inspection and review tools face huge challenges in terms of resolution, the ability to resolve 3D, and throughput. In this paper, we critically asses the important issue of damage in high speed AFM for metrology and inspection of semiconductor wafers. The issues of damage in four major scanning modes (contact mode, tapping mode, non-contact mode, and peak force tapping mode) are described to show which modes are suitable for which applications and which conditions are damaging. The effects of all important scanning parameters on resulting damage are taken into account for materials such as silicon, photoresists and low K materials. Finally, we recommend appropriate scanning parameters and conditions for several use cases (FinFET, patterned photoresist, HAR structures) that avoid exceeding a critical contact stress such that sample damage is minimized. In conclusion, we show using our theoretical analysis that selecting parameters that exceed the target contact stress, indeed leads to significant damage. This method provides AFM users for metrology with a better understanding of contact stresses and enables selection of AFM cantilevers and experimental parameters that prevent sample damage.

  4. Implications of the contact radius to line step (CRLS) ratio in AFM for nanotribology measurements.

    PubMed

    Helt, James M; Batteas, James D

    2006-07-04

    Investigating the mechanisms of defect generation and growth at surfaces on the nanometer scale typically requires high-resolution tools such as the atomic force microscope (AFM). To accurately assess the kinetics and activation parameters of defect production over a wide range of loads (F(z)), the AFM data should be properly conditioned. Generally, AFM wear trials are performed over an area defined by the length of the slow (L(sscan)) and fast scan axes. The ratio of L(sscan) to image resolution (res, lines per image) becomes an important experimental parameter in AFM wear trials because it defines the magnitude of the line step (LS = L(sscan)/res), the distance the AFM tip steps along the slow scan axis. Comparing the contact radius (a) to the line step (LS) indicates that the overlap of successive scans will result unless the contact radius-line step ratio (CRLS) is < or =(1)/(2). If this relationship is not considered, then the scan history (e.g., contact frequency) associated with a single scan is not equivalent at different loads owing to the scaling of contact radius with load (a proportional variant F(z)(1/3)). Here, we present a model in conjunction with empirical wear tests on muscovite mica to evaluate the effects of scan overlap on surface wear. Using the Hertz contact mechanics definition of a, the CRLS model shows that scan overlap pervades AFM wear trials even under low loads. Such findings indicate that simply counting the number of scans (N(scans)) in an experiment underestimates the full history conveyed to the surface by the tip and translates into an error in the actual extent to which a region on the surface is contacted. Utilizing the CRLS method described here provides an approach to account for image scan history accurately and to predict the extent of surface wear. This general model also has implications for any AFM measurement where one wishes to correlate scan-dependent history to image properties as well as feature resolution in scanned

  5. Versatile method for AFM-tip functionalization with biomolecules: fishing a ligand by means of an in situ click reaction.

    PubMed

    Kumar, Rakesh; Ramakrishna, Shivaprakash N; Naik, Vikrant V; Chu, Zonglin; Drew, Michael E; Spencer, Nicholas D; Yamakoshi, Yoko

    2015-04-21

    A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions.

  6. Insights into riming and aggregation processes as revealed by aircraft, radar, and disdrometer observations for a 27 April 2011 widespread precipitation event: Insights into Riming and Aggregation

    SciTech Connect

    Giangrande, Scott E.; Toto, Tami; Bansemer, Aaron; Kumjian, Matthew R.; Mishra, Subhashree

    2016-05-19

    Our study presents aircraft spiral ascent and descent observations intercepting a transition to riming processes during widespread stratiform precipitation. The sequence is documented using collocated scanning and profiling radar, including longer-wavelength dual polarization measurements and shorter-wavelength Doppler spectra. Riming regions are supported using aircraft measurements recording elevated liquid water concentrations, spherical particle shapes, and saturation with respect to water. Profiling cloud radar observations indicate riming regions during the event as having increasing particle fall speeds, rapid time-height changes, and bimodalities in Doppler spectra. These particular riming signatures are coupled to scanning dual polarization radar observations of higher differential reflectivity (ZDR) aloft. Moreover, reduced melting layer enhancements and delayed radar bright-band signatures in the column are also observed during riming periods, most notably with the profiling radar observations. The bimodal cloud radar Doppler spectra captured near riming zones indicate two time-height spectral ice peaks, one rimed particle peak, and one peak associated with pristine ice needle generation and/or growth between -4°C and -7°C also sampled by aircraft probes. We observe this pristine needle population near the rimed particle region which gives a partial explanation for the enhanced ZDR. The riming signatures aloft and radar measurements within the melting level are weakly lag correlated (r~0.6) with smaller median drop sizes at the surface, as compared with later times when aggregation of larger particle sizes was believed dominant.

  7. Insights into riming and aggregation processes as revealed by aircraft, radar, and disdrometer observations for a 27 April 2011 widespread precipitation event: Insights into Riming and Aggregation

    DOE PAGES

    Giangrande, Scott E.; Toto, Tami; Bansemer, Aaron; ...

    2016-05-19

    Our study presents aircraft spiral ascent and descent observations intercepting a transition to riming processes during widespread stratiform precipitation. The sequence is documented using collocated scanning and profiling radar, including longer-wavelength dual polarization measurements and shorter-wavelength Doppler spectra. Riming regions are supported using aircraft measurements recording elevated liquid water concentrations, spherical particle shapes, and saturation with respect to water. Profiling cloud radar observations indicate riming regions during the event as having increasing particle fall speeds, rapid time-height changes, and bimodalities in Doppler spectra. These particular riming signatures are coupled to scanning dual polarization radar observations of higher differential reflectivity (ZDR)more » aloft. Moreover, reduced melting layer enhancements and delayed radar bright-band signatures in the column are also observed during riming periods, most notably with the profiling radar observations. The bimodal cloud radar Doppler spectra captured near riming zones indicate two time-height spectral ice peaks, one rimed particle peak, and one peak associated with pristine ice needle generation and/or growth between -4°C and -7°C also sampled by aircraft probes. We observe this pristine needle population near the rimed particle region which gives a partial explanation for the enhanced ZDR. The riming signatures aloft and radar measurements within the melting level are weakly lag correlated (r~0.6) with smaller median drop sizes at the surface, as compared with later times when aggregation of larger particle sizes was believed dominant.« less

  8. Immunoactive two-dimensional self-assembly of monoclonal antibodies in aqueous solution revealed by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Ido, Shinichiro; Kimiya, Hirokazu; Kobayashi, Kei; Kominami, Hiroaki; Matsushige, Kazumi; Yamada, Hirofumi

    2014-03-01

    The conformational flexibility of antibodies in solution directly affects their immune function. Namely, the flexible hinge regions of immunoglobulin G (IgG) antibodies are essential in epitope-specific antigen recognition and biological effector function. The antibody structure, which is strongly related to its functions, has been partially revealed by electron microscopy and X-ray crystallography, but only under non-physiological conditions. Here we observed monoclonal IgG antibodies in aqueous solution by high-resolution frequency modulation atomic force microscopy (FM-AFM). We found that monoclonal antibodies self-assemble into hexamers, which form two-dimensional crystals in aqueous solution. Furthermore, by directly observing antibody-antigen interactions using FM-AFM, we revealed that IgG molecules in the crystal retain immunoactivity. As the self-assembled monolayer crystal of antibodies retains immunoactivity at a neutral pH and is functionally stable at a wide range of pH and temperature, the antibody crystal is applicable to new biotechnological platforms for biosensors or bioassays.

  9. High throughput nanofabrication of silicon nanowire and carbon nanotube tips on AFM probes by stencil-deposited catalysts.

    PubMed

    Engstrom, Daniel S; Savu, Veronica; Zhu, Xueni; Bu, Ian Y Y; Milne, William I; Brugger, Juergen; Boggild, Peter

    2011-04-13

    A new and versatile technique for the wafer scale nanofabrication of silicon nanowire (SiNW) and multiwalled carbon nanotube (MWNT) tips on atomic force microscope (AFM) probes is presented. Catalyst material for the SiNW and MWNT growth was deposited on prefabricated AFM probes using aligned wafer scale nanostencil lithography. Individual vertical SiNWs were grown epitaxially by a catalytic vapor-liquid-solid (VLS) process and MWNTs were grown by a plasma-enhanced chemical vapor (PECVD) process on the AFM probes. The AFM probes were tested for imaging micrometers-deep trenches, where they demonstrated a significantly better performance than commercial high aspect ratio tips. Our method demonstrates a reliable and cost-efficient route toward wafer scale manufacturing of SiNW and MWNT AFM probes.

  10. Investigation of growth rate dispersion in lactose crystallisation by AFM

    NASA Astrophysics Data System (ADS)

    Dincer, T. D.; Ogden, M. I.; Parkinson, G. M.

    2014-09-01

    α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (0 1 0) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (0 1 0) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (0 1 0) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.

  11. AFM force spectroscopy reveals how subtle structural differences affect the interaction strength between Candida albicans and DC-SIGN.

    PubMed

    te Riet, Joost; Reinieren-Beeren, Inge; Figdor, Carl G; Cambi, Alessandra

    2015-11-01

    The fungus Candida albicans is the most common cause of mycotic infections in immunocompromised hosts. Little is known about the initial interactions between Candida and immune cell receptors, such as the C-type lectin dendritic cell-specific intracellular cell adhesion molecule-3 (ICAM-3)-grabbing non-integrin (DC-SIGN), because a detailed characterization at the structural level is lacking. DC-SIGN recognizes specific Candida-associated molecular patterns, that is, mannan structures present in the cell wall of Candida. The molecular recognition mechanism is however poorly understood. We postulated that small differences in mannan-branching may result in considerable differences in the binding affinity. Here, we exploit atomic force microscope-based dynamic force spectroscopy with single Candida cells to gain better insight in the carbohydrate recognition capacity of DC-SIGN. We demonstrate that slight differences in the N-mannan structure of Candida, that is, the absence or presence of a phosphomannan side chain, results in differences in the recognition by DC-SIGN as follows: (i) it contributes to the compliance of the outer cell wall of Candida, and (ii) its presence results in a higher binding energy of 1.6 kB T. The single-bond affinity of tetrameric DC-SIGN for wild-type C. albicans is ~10.7 kB T and a dissociation constant kD of 23 μM, which is relatively strong compared with other carbohydrate-protein interactions described in the literature. In conclusion, this study shows that DC-SIGN specifically recognizes mannan patterns on C. albicans with high affinity. Knowledge on the binding pocket of DC-SIGN and its pathogenic ligands will lead to a better understanding of how fungal-associated carbohydrate structures are recognized by receptors of the immune system and can ultimately contribute to the development of new anti-fungal drugs.

  12. Interlayer formation of diamond-like carbon coatings on industrial polyethylene: Thickness dependent surface characterization by SEM, AFM and NEXAFS

    NASA Astrophysics Data System (ADS)

    Fischer, Christian B.; Rohrbeck, Magdalena; Wehner, Stefan; Richter, Matthias; Schmeißer, Dieter

    2013-04-01

    The coating of materials with diamond-like carbon (DLC) is a very common way to change and improve their basic characteristics. Although DLC is used on several substrates, the chemical and physical properties throughout the coating process on plastics are yet sparsely investigated. Two types of protective coatings one sp3-enriched (robust, r-type) and one with more sp2-centers (flexible, f-type) have been realized on polyethylene by PECVD deposition. SEM and AFM analysis of coated samples of DLC types revealed diverse surface topographies on different scales and images appeared even differently smoothed by the carbonaceous deposits. Grains of both DLC types are platelet-shaped and nearly double in size for the robust type indicating fundamental differences in the epitaxial DLC growth. NEXAFS spectroscopy showed significant details of carbon centers in chemically different neighborhood displaying a characteristic fingerprint behavior. Comparison of deposition models revealed a mechanism of interlayer formation which is discussed in detail. Interlayer formation is clearly the appropriate explanation of the process for the current carbon deposition between these two unequal materials. An improved understanding of hard DLC and soft polyethylene assembly is given in the presented work.

  13. The First Simultaneous Microlensing Observations by Two Space Telescopes: Spitzer and Swift Reveal a Brown Dwarf in Event OGLE-2015-BLG-1319

    NASA Astrophysics Data System (ADS)

    Shvartzvald, Y.; Li, Z.; Udalski, A.; Gould, A.; Sumi, T.; Street, R. A.; Calchi Novati, S.; Hundertmark, M.; Bozza, V.; Beichman, C.; Bryden, G.; Carey, S.; Drummond, J.; Fausnaugh, M.; Gaudi, B. S.; Henderson, C. B.; Tan, T. G.; Wibking, B.; Pogge, R. W.; Yee, J. C.; Zhu, W.; (Spitzer Team; Tsapras, Y.; Bachelet, E.; Dominik, M.; Bramich, D. M.; Cassan, A.; Figuera Jaimes, R.; Horne, K.; Ranc, C.; Schmidt, R.; Snodgrass, C.; Wambsganss, J.; Steele, I. A.; Menzies, J.; Mao, S.; (RoboNet; Poleski, R.; Pawlak, M.; Szymański, M. K.; Skowron, J.; Mróz, P.; Kozłowski, S.; Wyrzykowski, Ł.; Pietrukowicz, P.; Soszyński, I.; Ulaczyk, K.; (OGLE Group; Abe, F.; Asakura, Y.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Bond, I. A.; Freeman, M.; Hirao, Y.; Itow, Y.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Fukui, A.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Nishioka, T.; Ohnishi, K.; Oyokawa, H.; Rattenbury, N. J.; Saito, To.; Sharan, A.; Sullivan, D. J.; Suzuki, D.; Tristram, P. J.; Yonehara, A.; (MOA Group; Jørgensen, U. G.; Burgdorf, M. J.; Ciceri, S.; D'Ago, G.; Evans, D. F.; Hinse, T. C.; Kains, N.; Kerins, E.; Korhonen, H.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Scarpetta, G.; Skottfelt, J.; Southworth, J.; Peixinho, N.; Verma, P.; (MiNDSTEp; Sbarufatti, B.; Kennea, J. A.; Gehrels, N.; (Swift

    2016-11-01

    Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the “microlens parallax.” We report the discovery of a 30-65M J brown dwarf orbiting a K dwarf in the microlensing event OGLE-2015-BLG-1319. The system is located at a distance of ˜5 kpc toward the Galactic Bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing a measurement of the physical properties. However, the event is still subject to an eight-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either ˜0.25 au or ˜45 au. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that though Swift could not measure the microlens parallax with respect to ground-based observations for this event, it can be important for other events. Specifically, it is important for detecting nearby brown dwarfs and free-floating planets in high magnification events.

  14. New AFM Techniques for Investigating Molecular Growth Mechanisms of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Konnert, John H.; Pusey, Marc L.

    1998-01-01

    Atomic Force Microscopy (AFM) has emerged as a powerful technique for investigating protein crystal growth. Earlier AFM studies were among the first to demonstrate that these crystals grew by dislocation and 2D nucleation growth mechanisms [1]. These investigations were restricted to the micron range where only surface features, such as dislocation hillocks and 2D islands are visible. Most AFM instruments can scan at higher resolutions and have the potential to resolve individual protein molecules at nanometer ranges. Such scans are essential for determining the molecular packing arrangements on crystal faces and for probing the growth process at the molecular level. However, at this resolution the AFM tip influences the image produced, with the resulting image being a convolution of the tip shape and the surface morphology [2]. In most studies this problem is resolved by deconvoluting the image to obtain the true surface morphology. Although deconvolution routines work reasonably well for simple one- dimensional shapes, for complex surfaces this approach does not produce accurate results. In this study we devised a new approach which takes advantage of the precise molecular order of crystal surfaces, combined with the knowledge of individual molecular shapes from the crystallographic data of the protein and the AFM tip shape. This information is used to construct expected theoretical AFM images by convoluting the tip shape with the constructed crystal surface shape for a given surface packing arrangement. By comparing the images from actual AFM scans with the constructed ones for different possible surface packing arrangements, the correct packing arrangement can be conclusively determined. This approach was used in this study to determine the correct one from two possible packing arrangements on (I 10) faces of tetragonal lysozyme crystals. Another novel AFM technique was also devised to measure the dimension of individual growth units of the crystal faces

  15. AFM stiffness nanotomography of normal, metaplastic and dysplastic human esophageal cells

    NASA Astrophysics Data System (ADS)

    Fuhrmann, A.; Staunton, J. R.; Nandakumar, V.; Banyai, N.; Davies, P. C. W.; Ros, R.

    2011-02-01

    The mechanical stiffness of individual cells is important in tissue homeostasis, cell growth, division and motility, and the epithelial-mesenchymal transition in the initiation of cancer. In this work, a normal squamous cell line (EPC2) and metaplastic (CP-A) as well as dysplastic (CP-D) Barrett's Esophagus columnar cell lines are studied as a model of pre-neoplastic progression in the human esophagus. We used the combination of an atomic force microscope (AFM) with a scanning confocal fluorescence lifetime imaging microscope to study the mechanical properties of single adherent cells. Sixty four force indentation curves were taken over the nucleus of each cell in an 8 × 8 grid pattern. Analyzing the force indentation curves, indentation depth-dependent Young's moduli were found for all cell lines. Stiffness tomograms demonstrate distinct differences between the mechanical properties of the studied cell lines. Comparing the stiffness for indentation forces of 1 nN, most probable Young's moduli were calculated to 4.7 kPa for EPC2 (n = 18 cells), 3.1 kPa for CP-A (n = 10) and 2.6 kPa for CP-D (n = 19). We also tested the influence of nuclei and nucleoli staining organic dyes on the mechanical properties of the cells. For stained EPC2 cells (n = 5), significant stiffening was found (9.9 kPa), while CP-A cells (n = 5) showed no clear trend (2.9 kPa) and a slight softening was observed (2.1 kPa) in the case of CP-D cells (n = 16). Some force-indentation curves show non-monotonic discontinuities with segments of negative slope, resembling a sawtooth pattern. We found the incidence of these 'breakthrough events' to be highest in the dysplastic CP-D cells, intermediate in the metaplastic CP-A cells and lowest in the normal EPC2 cells. This observation suggests that the microscopic explanation for the increased compliance of cancerous and pre-cancerous cells may lie in their susceptibility to 'crumble and yield' rather than their ability to 'bend and flex'.

  16. Defective etioplasts observed in variegation mutants may reveal the light-independent regulation of white/yellow sectors of Arabidopsis leaves.

    PubMed

    Wu, Wenjuan; Elsheery, Nabil; Wei, Qing; Zhang, Lingang; Huang, Jirong

    2011-11-01

    Leaf variegation resulting from nuclear gene mutations has been used as a model system to elucidate the molecular mechanisms of chloroplast development. Since most variegation genes also function in photosynthesis, it remains unknown whether their roles in photosynthesis and chloroplast development are distinct. Here, using the variegation mutant thylakoid formation1 (thf1) we show that variegation formation is light independent. It was found that slow and uneven chloroplast development in thf1 can be attributed to defects in etioplast development in darkness. Ultrastructural analysis showed the coexistence of plastids with or without prolamellar bodies (PLB) in cells of thf1, but not of WT. Although THF1 mutation leads to significant decreases in the levels of Pchlide and Pchllide oxidoreductase (POR) expression, genetic and 5-aminolevulinic acid (ALA)-feeding analysis did not reveal Pchlide or POR to be critical factors for etioplast formation in thf1. Northern blot analysis showed that plastid gene expression is dramatically reduced in thf1 compared with that in WT, particularly in the dark. Our results also indicate that chlorophyll biosynthesis and expression of plastidic genes are coordinately suppressed in thf1. Based on these results, we propose a model to explain leaf variegation formation from the plastid development perspective.

  17. Aflatoxin M1 Concentration in Various Dairy Products: Evidence for Biologically Reduced Amount of AFM1 in Yoghurt

    PubMed Central

    RAHIMIRAD, Amir; MAALEKINEJAD, Hassan; OSTADI, Araz; YEGANEH, Samal; FAHIMI, Samira

    2014-01-01

    Abstract Background Aflatoxin M1 (AFM1), a carcinogenic substance is found in milk and dairy products. The effect of season and type of dairy products on AFMi level in northern Iran was investigated in this study. Methods Three hundred samples (each season 75 samples) including raw and pasteurized milk, yoghurt, cheese, and cream samples were collected from three distinct milk producing farms. The samples were subjected to chemical and solid phase extractions and were analyzed by using HPLC technique. Recovery percentages, limit of detection and limit of quantification values were determined. Results Seventy percent and 98% were the minimum and maximum recoveries for cheese and raw milk, respectively and 0.021 and 0.063 ppb were the limit of detection and limit of quantification values for AFM1. We found that in autumn and winter the highest level (0.121 ppb) of AFM1 in cheese and cream samples and failed to detect any AFM1 in spring samples. Interestingly, our data showed that the yoghurt samples had the lowest level of AFM1 in all seasons. Conclusion There are significant differences between the AFM1 levels in dairy products in various seasons and also various types of products, suggesting spring and summer yoghurt samples as the safest products from AFM1 level point of view. PMID:25927044

  18. XMM-Newton Observations Reveal the X-ray Counterpart of the Very-high-energy gamma-ray Source HESS J1640-465

    SciTech Connect

    Funk, S.; Hinton, J.A.; Puhlhofer, G.; Aharonian, F.A.; Hofmann, W.; Reimer, O.; Wagner, S.; Funk, S.; Hinton, J.A.; Puehlhofer, G.; Aharonian, F.A.; Hofmann, W.; Reimer, O.; Wagner, S.

    2007-03-05

    We present X-ray observations of the as of yet unidentified very high-energy (VHE) {gamma}-ray source HESS J1640-465 with the aim of establishing a counterpart of this source in the keV energy range, and identifying the mechanism responsible for the VHE emission. The 21.8 ksec XMM-Newton observation of HESS J1640-465 in September 2005 represents a significant improvement in sensitivity and angular resolution over previous ASCA studies in this region. These new data show a hard-spectrum X-ray emitting object at the centroid of the H.E.S.S. source, within the shell of the radio Supernova Remnant (SNR) G338.3-0.0. This object is consistent with the position and flux previously measured by both ASCA and Swift-XRT but is now shown to be significantly extended. We argue that this object is very likely the counterpart to HESS J1640-465 and that both objects may represent the Pulsar Wind Nebula of an as of yet undiscovered pulsar associated with G338.3-0.0.

  19. Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies

    NASA Astrophysics Data System (ADS)

    Rolffs, R.; Schilke, P.; Comito, C.; Bergin, E. A.; van der Tak, F. F. S.; Lis, D. C.; Qin, S.-L.; Menten, K. M.; Güsten, R.; Bell, T. A.; Blake, G. A.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Crockett, N. R.; Daniel, F.; Dubernet, M.-L.; Emprechtinger, M.; Encrenaz, P.; Gerin, M.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Gupta, H.; Herbst, E.; Joblin, C.; Johnstone, D.; Langer, W. D.; Latter, W. D.; Lord, S. D.; Maret, S.; Martin, P. G.; Melnick, G. J.; Morris, P.; Müller, H. S. P.; Murphy, J. A.; Ossenkopf, V.; Pearson, J. C.; Pérault, M.; Phillips, T. G.; Plume, R.; Schlemmer, S.; Stutzki, J.; Trappe, N.; Vastel, C.; Wang, S.; Yorke, H. W.; Yu, S.; Zmuidzinas, J.; Diez-Gonzalez, M. C.; Bachiller, R.; Martin-Pintado, J.; Baechtold, W.; Olberg, M.; Nordh, L. H.; Gill, J. J.; Chattopadhyay, G.

    2010-10-01

    Aims: To investigate the accretion and feedback processes in massive star formation, we analyze the shapes of emission lines from hot molecular cores, whose asymmetries trace infall and expansion motions. Methods: The high-mass star forming region SgrB2(M) was observed with Herschel/HIFI (HEXOS key project) in various lines of HCN and its isotopologues, complemented by APEX data. The observations are compared to spherically symmetric, centrally heated models with density power-law gradient and different velocity fields (infall or infall+expansion), using the radiative transfer code RATRAN. Results: The HCN line profiles are asymmetric, with the emission peak shifting from blue to red with increasing J and decreasing line opacity (HCN to H13CN). This is most evident in the HCN 12-11 line at 1062 GHz. These line shapes are reproduced by a model whose velocity field changes from infall in the outer part to expansion in the inner part. Conclusions: The qualitative reproduction of the HCN lines suggests that infall dominates in the colder, outer regions, but expansion dominates in the warmer, inner regions. We are thus witnessing the onset of feedback in massive star formation, starting to reverse the infall and finally disrupting the whole molecular cloud. To obtain our result, the THz lines uniquely covered by HIFI were critically important. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  20. Study of relaxation and transport processes by means of AFM based dielectric spectroscopy

    SciTech Connect

    Miccio, Luis A.

    2014-05-15

    Since its birth a few years ago, dielectric spectroscopy studies based on atomic force microscopy (AFM) have gained a growing interest. Not only the frequency and temperature ranges have become broader since then but also the kind of processes that can be studied by means of this approach. In this work we analyze the most adequate experimental setup for the study of several dielectric processes with a spatial resolution of a few nanometers by using force mode AFM based dielectric spectroscopy. Proof of concept experiments were performed on PS/PVAc blends and PMMA homopolymer films, for temperatures ranging from 300 to 400 K. Charge transport processes were also studied by this approach. The obtained results were analyzed in terms of cantilever stray contribution, film thickness and relaxation strength. We found that the method sensitivity is strongly coupled with the film thickness and the relaxation strength, and that it is possible to control it by using an adequate experimental setup.

  1. Confocal Raman spectroscopy and AFM for evaluation of sidewalls in type II superlattice FPAs

    NASA Astrophysics Data System (ADS)

    Rotter, T. J.; Busani, T.; Rathi, P.; Jaeckel, F.; Reyes, P. A.; Malloy, K. J.; Ukhanov, A. A.; Plis, E.; Krishna, S.; Jaime-Vasquez, M.; Baril, N. F.; Benson, J. D.; Tenne, D. A.

    2015-06-01

    We propose to utilize confocal Raman spectroscopy combined with high resolution atomic force microscopy (AFM) for nondestructive characterisation of the sidewalls of etched and passivated small pixel (24 μm×24 μm) focal plane arrays (FPA) fabricated using LW/LWIR InAs/GaSb type-II strained layer superlattice (T2SL) detector material. Special high aspect ratio Si and GaAs AFM probes, with tip length of 13 μm and tip aperture less than 7°, allow characterisation of the sidewall morphology. Confocal microscopy enables imaging of the sidewall profile through optical sectioning. Raman spectra measured on etched T2SL FPA single pixels enable us to quantify the non-uniformity of the mesa delineation process.

  2. Atom probe, AFM, and STM studies on vacuum-fired stainless steels.

    PubMed

    Stupnik, A; Frank, P; Leisch, M

    2009-04-01

    The surface morphology of grades 304L and 316LN stainless steels, after low-temperature bake-out process and vacuum annealing, has been studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). The local elemental composition on the surface before and after thermal treatment has been investigated by atom probe (AP) depth profiling measurements. After vacuum annealing, AFM and STM show significant changes in the surface structure and topology. Recrystallization and surface reconstruction is less pronounced on the 316LN stainless steel. AP depth profiling analyses result in noticeable nickel enrichment on the surface of grade 304L samples. Since hydrogen recombination is almost controlled by surface structure and composition, a strong influence on the outgassing behaviour by the particular surface microstructure can be deduced.

  3. AFM investigation and optical band gap study of chemically deposited PbS thin films

    NASA Astrophysics Data System (ADS)

    Zaman, S.; Mansoor, M.; Abubakar; Asim, M. M.

    2016-08-01

    The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

  4. Development of a novel nanoindentation technique by utilizing a dual-probe AFM system

    PubMed Central

    Sahin, Ferat; Yablon, Dalia

    2015-01-01

    Summary A novel instrumentation approach to nanoindentation is described that exhibits improved resolution and depth sensing. The approach is based on a multi-probe scanning probe microscopy (SPM) tool that utilizes tuning-fork based probes for both indentation and depth sensing. Unlike nanoindentation experiments performed with conventional AFM systems using beam-bounce technology, this technique incorporates a second probe system with an ultra-high resolution for depth sensing. The additional second probe measures only the vertical movement of the straight indenter attached to a tuning-fork probe with a high spring constant and it can also be used for AFM scanning to obtain an accurate profiling. Nanoindentation results are demonstrated on silicon, fused silica, and Corning Eagle Glass. The results show that this new approach is viable in terms of accurately characterizing mechanical properties of materials through nanoindentation with high accuracy, and it opens doors to many other exciting applications in the field of nanomechanical characterization. PMID:26665072

  5. Nano-Electrochemistry and Nano-Electrografting with an Original Combined AFM-SECM

    PubMed Central

    Ghorbal, Achraf; Grisotto, Federico; Charlier, Julienne; Palacin, Serge; Goyer, Cédric; Demaille, Christophe; Ben Brahim, Ammar

    2013-01-01

    This study demonstrates the advantages of the combination between atomic force microscopy and scanning electrochemical microscopy. The combined technique can perform nano-electrochemical measurements onto agarose surface and nano-electrografting of non-conducting polymers onto conducting surfaces. This work was achieved by manufacturing an original Atomic Force Microscopy-Scanning ElectroChemical Microscopy (AFM-SECM) electrode. The capabilities of the AFM-SECM-electrode were tested with the nano-electrografting of vinylic monomers initiated by aryl diazonium salts. Nano-electrochemical and technical processes were thoroughly described, so as to allow experiments reproducing. A plausible explanation of chemical and electrochemical mechanisms, leading to the nano-grafting process, was reported. This combined technique represents the first step towards improved nano-processes for the nano-electrografting.

  6. Exploring electron transport through organic monolayers using conductive tip AFM techniques

    NASA Astrophysics Data System (ADS)

    Scaini, Denis; Castronovo, Matteo; Dell'Angela, Martina; Hudej, Robert; Casalis, Loredana; Scoles, Giacinto

    2006-03-01

    We follow an alternative approach to the study of Metal-molecule-Metal junctions that uses a combination of two atomic force microscopy (AFM) techniques. We use Nanografting to build a nanopatch of the molecules of interest and a second made of a reference molecule into a hosting self assembled monolayer (SAM) typically made of alkanethiols. After the tip is changed to a conductive one CT-AFM is used to characterized the whole system recording, at the same time, the system topography. Some of the advantages of this approach are the possibility to build and study a wide range of different M-m-M junctions and the in-situ control of the quality of the monolayers and patches. Results will be presented on saturated and unsaturated thiols self-assembled and nanografted on Au(111) surfaces. The results will be compared with those obtained by Liang and Scoles at Princeton using similar techniques.

  7. BOREAS AFM-5 Level-2 Upper Air Network Standard Pressure Level Data

    NASA Technical Reports Server (NTRS)

    Barr, Alan; Hrynkiw, Charmaine; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-5 team collected and processed data from the numerous radiosonde flights during the project. The goals of the AFM-05 team were to provide large-scale definition of the atmosphere by supplementing the existing AES aerological network, both temporally and spatially. This data set includes basic upper-air parameters interpolated at 0.5 kiloPascal increments of atmospheric pressure from data collected from the network of upper-air stations during the 1993, 1994, and 1996 field campaigns over the entire study region. The data are contained in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  8. Dynamics of a disturbed sessile drop measured by atomic force microscopy (AFM).

    PubMed

    McGuiggan, Patricia M; Grave, Daniel A; Wallace, Jay S; Cheng, Shengfeng; Prosperetti, Andrea; Robbins, Mark O

    2011-10-04

    A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (<100 nm) oscillations are readily measured with AFM. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

  9. Molecular Dynamic Simulations of Interaction of an AFM Probe with the Surface of an SCN Sample

    NASA Technical Reports Server (NTRS)

    Bune, Adris; Kaukler, William; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Molecular dynamic (MD) simulations is conducted in order to estimate forces of probe-substrate interaction in the Atomic Force Microscope (AFM). First a review of available molecular dynamic techniques is given. Implementation of MD simulation is based on an object-oriented code developed at the University of Delft. Modeling of the sample material - succinonitrile (SCN) - is based on the Lennard-Jones potentials. For the polystyrene probe an atomic interaction potential is used. Due to object-oriented structure of the code modification of an atomic interaction potential is straight forward. Calculation of melting temperature is used for validation of the code and of the interaction potentials. Various fitting parameters of the probe-substrate interaction potentials are considered, as potentials fitted to certain properties and temperature ranges may not be reliable for the others. This research provides theoretical foundation for an interpretation of actual measurements of an interaction forces using AFM.

  10. Accurate and precise calibration of AFM cantilever spring constants using laser Doppler vibrometry.

    PubMed

    Gates, Richard S; Pratt, Jon R

    2012-09-21

    Accurate cantilever spring constants are important in atomic force microscopy both in control of sensitive imaging and to provide correct nanomechanical property measurements. Conventional atomic force microscope (AFM) spring constant calibration techniques are usually performed in an AFM. They rely on significant handling and often require touching the cantilever probe tip to a surface to calibrate the optical lever sensitivity of the configuration. This can damage the tip. The thermal calibration technique developed for laser Doppler vibrometry (LDV) can be used to calibrate cantilevers without handling or touching the tip to a surface. Both flexural and torsional spring constants can be measured. Using both Euler-Bernoulli modeling and an SI traceable electrostatic force balance technique as a comparison we demonstrate that the LDV thermal technique is capable of providing rapid calibrations with a combination of ease, accuracy and precision beyond anything previously available.

  11. AFM fishing nanotechnology is the way to reverse the Avogadro number in proteomics.

    PubMed

    Archakov, Alexander Ivanovich; Ivanov, Yurii Dmitrievich; Lisitsa, Andrey Valerevich; Zgoda, Victor Gavrilovich

    2007-01-01

    Future development of proteomics may be hindered by limitations in the concentration sensitivity of widespread technological approaches. The concentration sensitivity limit (CSL) of currently used approaches, like 2-DE/LC separation coupled with MS detection, etc., varies from 10(-9) to 10(-12) M. Therefore, proteomic technologies enable detection of up to 20% of the protein species present in the plasma. New technologies, like atomic force microscopy (AFM molecular detector), enable the counting of single molecules, whereas biospecific fishing can be used to capture these molecules from the biomaterial. At the same time, fishing also has thermodynamic limitations due to the reversibility of the binding. In cases where the fishing becomes irreversible, its combination with an AFM detector enables the registration of single protein molecules, and that opens up a way to lower the CSL down to the reverse Avogadro number.

  12. Influence of Fluid Cell Design on the Frequency Response of AFM Microcantilevers in Liquid Media

    PubMed Central

    Motamedi, Ramin; Wood-Adams, Paula M.

    2008-01-01

    A study of the frequency response of AFM microcantilevers in liquid media contained in a commercial fluid cell is presented. Such systems exhibit complicated dynamics which are often not well described by available theories. Their dynamic behavior has a direct effect on the use of the AFM in dynamic mode while imaging in liquid or while extracting the rheological properties of the fluid. We explore the issues related to the design of the cantilever holder/fluid cell and propose an approach for evaluating, minimizing and recognizing the ultimate limitations of commercial cantilever holders. A technique for estimating the frequency response spectrum of the fluid cell itself from experimental data is presented. This spectrum can then be used to evaluate whether or not the fluid cell is suited for the desired purpose. PMID:27873849

  13. Mechanism of high-resolution STM, AFM and IETS-STM imaging with functionalized tips

    NASA Astrophysics Data System (ADS)

    Temirov, R.; Hapala, P.; Tautz, F. S.; Jelinek, P.

    2015-03-01

    High-resolution AFM and STM with functionalized tips is well established, but a detailed understanding of the image mechanism is still missing. Moreover, recently this family of imaging techniques has been complemented by a method based on inelastic electron tunneling spectroscopy. Here we present a comprehensive mechanical and transport simulation model that explains essentially all image features in functionalized tip STM, AFM and IETS-STM. Important aspects of the mechanism are: (i) Images are dominantly determined by Pauli repulsion, (ii) in STM and IETS STM this force signal is transduced into an elastic or inelastic conductance signal, (iii) probe particle relaxation leads to image sharpening, (iv) the apparent imaging of hydrogen bonds can be explained by a relaxation effect, and (v) electrostatic forces may also influence the image contrast.

  14. Searching events in AFM force-extension curves: A wavelet approach.

    PubMed

    Benítez, R; Bolós, V J

    2017-01-01

    An algorithm, based on the wavelet scalogram energy, for automatically detecting events in force-extension AFM force spectroscopy experiments is introduced. The events to be detected are characterized by a discontinuity in the signal. It is shown how the wavelet scalogram energy has different decay rates at different points depending on the degree of regularity of the signal, showing faster decay rates at regular points and slower rates at singular points (jumps). It is shown that these differences produce peaks in the scalogram energy plot at the event points. Finally, the algorithm is illustrated in a tether analysis experiment by using it for the detection of events in the AFM force-extension curves susceptible to being considered tethers. Microsc. Res. Tech. 80:153-159, 2017. © 2016 Wiley Periodicals, Inc.

  15. Characterization of the specific interaction between the DNA aptamer sgc8c and protein tyrosine kinase-7 receptors at the surface of T-cells by biosensing AFM.

    PubMed

    Leitner, Michael; Poturnayova, Alexandra; Lamprecht, Constanze; Weich, Sabine; Snejdarkova, Maja; Karpisova, Ivana; Hianik, Tibor; Ebner, Andreas

    2017-04-01

    We studied the interaction of the specific DNA aptamer sgc8c immobilized at the AFM tip with its corresponding receptor, the protein tyrosine kinase-7 (PTK7) embedded in the membrane of acute lymphoblastic leukemia (ALL) cells (Jurkat T-cells). Performing single molecule force spectroscopy (SMFS) experiments, we showed that the aptamer sgc8c bound with high probability (38.3 ± 7.48%) and high specificity to PTK7, as demonstrated by receptor blocking experiments and through comparison with the binding behavior of a nonspecific aptamer. The determined kinetic off-rate (koff = 5.16 s(-1)) indicates low dissociation of the sgc8c-PTK7 complex. In addition to the pulling force experiments, simultaneous topography and recognition imaging (TREC) experiments using AFM tips functionalized with sgc8c aptamers were realized on the outer regions surface of surface-immobilized Jurkat cells for the first time. This allowed determination of the distribution of PTK7 without any labeling and at near physiological conditions. As a result, we could show a homogeneous distribution of PTK7 molecules on the outer regions of ALL cells with a surface density of 325 ± 12 PTK7 receptors (or small receptor clusters) per μm(2). Graphical Abstract The specific interaction of the DNA aptamer sgc8c and protein tyrosine kinase-7 (PTK7) on acute lymphoblastic leukemia (ALL) cells was characterized. AFM based single molecule force spectroscopy (SMFS) yielded a kinetic off-rate of 5.16 s(-1) of the complex. Simultaneous topography and recognition imaging (TREC) revealed a PTK7 density of 325 ± 12 molecules or clusters per μm(2) in the cell membrane.

  16. U.S. Army Training and Testing Area Carrying Capacity (ATTACC) for Munitions (AFM)

    DTIC Science & Technology

    2006-11-01

    days. The RUSLE dataset delivered with the AFM model is defined below and in Appendix E. The Adapted RUSLE is defined as A=R*K* LS *C*P where: A...hr [hundreds of ft-tons]-1 in.-1) LS = slope length and steepness factor (dimensionless) C = cover and management factor (dimensionless) P...erosion index unit under standardized conditions. Higher K factor values indicate more easily erodible soils. • LS Factor. The rate of soil

  17. Study of mechanical behavior of AFM silicon tips under mechanical load

    NASA Astrophysics Data System (ADS)

    Kopycinska-Mueller, M.; Gluch, J.; Köhler, B.

    2016-11-01

    In this paper we address critical issues concerning calibration of AFM based methods used for nanoscale mechanical characterization of materials. It has been shown that calibration approaches based on macroscopic models for contact mechanics may yield excellent results in terms of the indentation modulus of the sample, but fail to provide a comprehensive and actual information concerning the tip-sample contact radius or the mechanical properties of the tip. Explanations for the severely reduced indentation modulus of the tip included the inadequacies of the models used for calculations of the tip-sample contact stiffness, discrepancies in the actual and ideal shape of the tip, presence of the amorphous silicon phase within the silicon tip, as well as negligence of the actual size of the stress field created in the tip during elastic interactions. To clarify these issues, we investigated the influence of the mechanical load applied to four AFM silicon tips on their crystalline state by exposing them to systematically increasing loads, evaluating the character of the tip-sample interactions via the load-unload stiffness curves, and assessing the state of the tips from HR-TEM images. The results presented in this paper were obtained in a series of relatively simple and basic atomic force acoustic microscopy (AFAM) experiments. The novel combination of TEM imaging of the AFM tips with the analysis of the load-unload stiffness curves gave us a detailed insight into their mechanical behavior under load conditions. We were able to identify the limits for the elastic interactions, as well as the hallmarks for phase transformation and dislocation formation and movement. The comparison of the physical dimensions of the AFM tips, geometry parameters determined from the values of the contact stiffness, and the information on the crystalline state of the tips allowed us a better understanding of the nanoscale contact.

  18. Observation of strain-controlled electronic modulations revealed by Fermi surface superstructures in strongly correlated LaNiO3 films

    NASA Astrophysics Data System (ADS)

    Yoo, Hyangkeun; Hyun, Seungill; Moreschini, Luca; Kim, Hyeong-Do; Chang, Youngjun; Sohn, Changhee; Jeong, Dawoon; Sinn, Soobin; Kim, Yongsu; Bostwick, Aaron; Rotenberg, Eli; Shim, Jihoon; Noh, Taewon

    2014-03-01

    Control over the electronic properties of strongly correlated electron systems can be achieved by exploiting the misfit strain that exists in epitaxial films on lattice mismatched substrates. Here, we report a systematic investigation of electronic structures in strongly correlated LaNiO3 films under different strain states, using in situ angle-resolved photoemission spectroscopy and the dynamical mean field theory. LaNiO3 film shows a change of a Fermi surface (FS) topology, driven by interplay between strong electron-electron correlations and misfit strain effects. Additionally, different from compressive strain case, a FS with tensile strain has a large flat region to induce strong FS nesting. As a result, different FS superstructures are observed in the compressive and tensile strain cases, and their origins are attributed to charge disproportionation and spin density waves, respectively. The more details will be discussed in the presentation.

  19. The Mysterious Origins of Solar Flares: New observations are beginning to reveal what triggers these hughes explosions of the sun's atmosphere

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.

    2006-01-01

    Solar flares can release the energy equivalent of billions of atomic bombs in the span of just a few minutes. These explosions give off a burst of x-rays and charged particles, some of which may later hit Earth, endangering satellites and causing power outages. The sun's tumultuous magnetic fields provide the fuel of flares. The sudden release of energy in a flare results from a process called reconnection, whereby oppositely directed magnetic field lines come together and partially annihilate each other. Although theoretical studies of magnetic reconnection on the sun have been carried out for decades, only recently have space probes uncovered observational evidence for this phenomenon. The telltale signs include pointed magnetic loops located below the spot where magnetic reconnection is taking place.

  20. Trophic relationships on a fucoid shore in south-western Iceland as revealed by stable isotope analyses, laboratory experiments, field observations and gut analyses

    NASA Astrophysics Data System (ADS)

    Steinarsdóttir, M. B.; Ingólfsson, A.; Ólafsson, E.

    2009-04-01

    Rocky shores in the North Atlantic are known for their zonation patterns of both algae and animals, which can be expected to greatly affect food availability to consumers at different height levels on the shore. We tested the hypothesis that consumers would feed on the most abundant suitable food source in their surroundings. In total 36 species/taxa of common primary producers and consumers were sampled for stable isotope analyses from a sheltered fucoid shore at Hvassahraun in south-western Iceland. A selection of these species was also collected seasonally and from different height levels. Feeding experiments, field observations and gut analyses were also conducted. Our results were in good overall agreement with pre-existing knowledge of trophic relationships in the rocky intertidal. Consumers often appeared to be assimilating carbon and nitrogen from the most common diet in their immediate surroundings. The predator Nucella lapillus was thus feeding on different prey at different height levels in accordance with different densities of prey species. When tested in the laboratory, individuals taken from low on the shore would ignore the gastropod Littorina obtusata, uncommon at that height level, even when starved, while individuals from mid-shore readily ate the gastropod. This indicated that some kind of learned behaviour was involved. There were, however, important exceptions, most noteworthy the relatively small contribution to herbivores, both slow moving (the gastropod L. obtusata) and fast moving (the isopod Idotea granulosa and the amphipod Gammarus obtusatus) of the dominant alga at this site, Ascophyllum nodosum. The recent colonizer Fucus serratus seemed to be favoured. Selective feeding was indicated both by isotope signatures as well as by results of feeding experiments. Seasonal migrations of both slow and fast moving species could partly explain patterns observed.

  1. GEOMETRIC AND KINEMATIC STRUCTURE OF THE OUTFLOW/ENVELOPE SYSTEM OF L1527 REVEALED BY SUBARCSECOND-RESOLUTION OBSERVATION OF CS

    SciTech Connect

    Oya, Yoko; López-Sepulcre, Ana; Watanabe, Yoshimasa; Yamamoto, Satoshi; Sakai, Nami; Lefloch, Bertrand; Ceccarelli, Cecilia

    2015-10-10

    Subarcsecond-resolution images of the rotational line emissions of CS and c-C{sub 3}H{sub 2} obtained toward the low-mass protostar IRAS 04368+2557 in L1527 with the Atacama Large Millimeter/submillimeter Array are investigated to constrain the orientation of the outflow/envelope system. The distribution of CS consists of an envelope component extending from north to south and a faint butterfly shaped outflow component. The kinematic structure of the envelope is well reproduced by a simple ballistic model of an infalling rotating envelope. Although the envelope has a nearly edge-on configuration, we find that the western side of the envelope faces the observer. This configuration is opposite to the direction of the large-scale (∼10{sup 4} AU) outflow suggested previously from the {sup 12}CO (J = 3–2) observation, and to the morphology of infrared reflection near the protostar (∼200 AU). The latter discrepancy could originate from high extinction by the outflow cavity of the western side, or may indicate that the outflow axis is not parallel to the rotation axis of the envelope. Position–velocity diagrams show the accelerated outflow cavity wall, and its kinematic structure in the 2000 AU scale is explained by a standard parabolic model with the inclination angle derived from the analysis of the envelope. The different orientation of the outflow between the small and large scale implies a possibility of precession of the outflow axis. The shape and the velocity of the outflow in the vicinity of the protostar are compared with those of other protostars.

  2. XMM-NEWTON OBSERVATIONS REVEAL VERY HIGH X-RAY LUMINOSITY FROM THE CARBON-RICH WOLF-RAYET STAR WR 48a

    SciTech Connect

    Zhekov, Svetozar A.; Gagne, Marc; Skinner, Stephen L. E-mail: mgagne@wcupa.edu

    2011-01-20

    We present XMM-Newton observations of the dusty Wolf-Rayet (W-R) star WR 48a. This is the first detection of this object in X-rays. The XMM-Newton EPIC spectra are heavily absorbed and the presence of numerous strong emission lines indicates a thermal origin of the WR 48a X-ray emission, with dominant temperature components at kT{sub cool} {approx} 1 keV and kT{sub hot} {approx} 3 keV, the hotter component dominating the observed flux. No significant X-ray variability was detected on timescales {<=}1 day. Although the distance to WR 48a is uncertain, if it is physically associated with Open clusters Danks 1 and 2 at d {approx}4 kpc, then the resultant X-ray luminosity L{sub X}{approx} 10{sup 35} erg s{sup -1} makes it the most X-ray luminous W-R star in the Galaxy detected so far, after the black hole candidate Cyg X-3. We assume the following scenarios as the most likely explanation for the X-ray properties of WR 48a: (1) colliding stellar winds in a wide WR+O binary system, or in a hierarchical triple system with non-degenerate stellar components and (2) accretion shocks from the WR 48a wind onto a close companion (possibly a neutron star). More specific information about WR 48a and its wind properties will be needed to distinguish between the above possibilities.

  3. Accurate, explicit formulae for higher harmonic force spectroscopy by frequency modulation-AFM.

    PubMed

    Kuchuk, Kfir; Sivan, Uri

    2015-01-01

    The nonlinear interaction between an AFM tip and a sample gives rise to oscillations of the cantilever at integral multiples (harmonics) of the fundamental resonance frequency. The higher order harmonics have long been recognized to hold invaluable information on short range interactions but their utilization has thus far been relatively limited due to theoretical and experimental complexities. In particular, existing approximations of the interaction force in terms of higher harmonic amplitudes generally require simultaneous measurements of multiple harmonics to achieve satisfactory accuracy. In the present letter we address the mathematical challenge and derive accurate, explicit formulae for both conservative and dissipative forces in terms of an arbitrary single harmonic. Additionally, we show that in frequency modulation-AFM (FM-AFM) each harmonic carries complete information on the force, obviating the need for multi-harmonic analysis. Finally, we show that higher harmonics may indeed be used to reconstruct short range forces more accurately than the fundamental harmonic when the oscillation amplitude is small compared with the interaction range.

  4. Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample

    NASA Astrophysics Data System (ADS)

    Guo, Shifeng; Zhu, Xiaoying; Jańczewski, Dominik; Lee, Serina Siew Chen; He, Tao; Teo, Serena Lay Ming; Vancso, G. Julius

    2016-09-01

    Protein charge at various pH and isoelectric point (pI) values is important in understanding protein function. However, often only trace amounts of unknown proteins are available and pI measurements cannot be obtained using conventional methods. Here, we show a method based on the atomic force microscope (AFM) to determine pI using minute quantities of proteins. The protein of interest is immobilized on AFM colloidal probes and the adhesion force of the protein is measured against a positively and a negatively charged substrate made by layer-by-layer deposition of polyelectrolytes. From the AFM force-distance curves, pI values with an estimated accuracy of ±0.25 were obtained for bovine serum albumin, myoglobin, fibrinogen and ribonuclease A over a range of 4.7-9.8. Using this method, we show that the pI of the ‘footprint’ of the temporary adhesive proteins secreted by the barnacle cyprid larvae of Amphibalanus amphitrite is in the range 9.6-9.7.

  5. Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample.

    PubMed

    Guo, Shifeng; Zhu, Xiaoying; Jańczewski, Dominik; Lee, Serina Siew Chen; He, Tao; Teo, Serena Lay Ming; Vancso, G Julius

    2016-09-01

    Protein charge at various pH and isoelectric point (pI) values is important in understanding protein function. However, often only trace amounts of unknown proteins are available and pI measurements cannot be obtained using conventional methods. Here, we show a method based on the atomic force microscope (AFM) to determine pI using minute quantities of proteins. The protein of interest is immobilized on AFM colloidal probes and the adhesion force of the protein is measured against a positively and a negatively charged substrate made by layer-by-layer deposition of polyelectrolytes. From the AFM force-distance curves, pI values with an estimated accuracy of ±0.25 were obtained for bovine serum albumin, myoglobin, fibrinogen and ribonuclease A over a range of 4.7-9.8. Using this method, we show that the pI of the 'footprint' of the temporary adhesive proteins secreted by the barnacle cyprid larvae of Amphibalanus amphitrite is in the range 9.6-9.7.

  6. Single-cycle-PLL detection for real-time FM-AFM applications.

    PubMed

    Schlecker, Benedikt; Dukic, Maja; Erickson, Blake; Ortmanns, Maurits; Fantner, Georg; Anders, Jens

    2014-04-01

    In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilever's resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.

  7. Bacterial adhesion to protein-coated surfaces: An AFM and QCM-D study

    NASA Astrophysics Data System (ADS)

    Strauss, Joshua; Liu, Yatao; Camesano, Terri A.

    2009-09-01

    Bacterial adhesion to biomaterials, mineral surfaces, or other industrial surfaces is strongly controlled by the way bacteria interact with protein layers or organic matter and other biomolecules that coat the materials. Despite this knowledge, many studies of bacterial adhesion are performed under clean conditions, instead of in the presence of proteins or organic molecules. We chose fetal bovine serum (FBS) as a model protein, and prepared FBS films on quartz crystals. The thickness of the FBS layer was characterized using atomic force microscopy (AFM) imaging under liquid and quartz crystal microbalance with dissipation (QCM-D). Next, we characterized how the model biomaterial surface would interact with the nocosomial pathogen Staphylococcus epidermidis. An AFM probe was coated with S. epidermidis cells and used to probe a gold slide that had been coated with FBS or another protein, fibronectin (FN). These experiments show that AFM and QCM-D can be used in complementary ways to study the complex interactions between bacteria, proteins, and surfaces.

  8. AFM and pulsed laser ablation methods for Cultural Heritage: application to archeometric analysis of stone artifacts

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Veltri, S.; Stranges, F.; Bonanno, A.; Xu, F.; Antici, P.

    2015-09-01

    In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface's roughness is evaluated from very small artifact's fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

  9. AFM-based quantification of conformational changes in DNA caused by reactive oxygen species.

    PubMed

    Berg, Florian; Wilken, Janine; Helm, Christiane A; Block, Stephan

    2015-01-08

    Radical induced modification of DNA plays an important role in many pathological pathways like cancer development, aging, etc. In this work, we quantify radical-induced DNA damage that causes transitions from double to single stranded DNA using atomic force microscopy (AFM). The plasmid pBR322 is attacked by free hydroxyl radicals that are produced by Fenton's reaction; the strength of the radical attack is controlled via the ratio of hydroxyl radical molecules to DNA base pairs. The extent of DNA modification is assessed by AFM tapping mode (TM) imaging of the plasmids (after adsorption onto PAH-functionalized mica) in air. As single stranded DNA chains (height ∼2 Å) are much smaller than intact DNA strands (∼5 Å), their fraction can be quantified based on the height distribution, which allows a simplified data analysis in comparison to similar AFM-based approaches. It is found that the amount of damaged DNA strands increases with increasing strength of radical attack, and decreases if ROS scavengers like sodium acetate are added. Competition curves are calculated for the interaction of hydroxyl radicals with DNA and sodium acetate, which finally allows calculation of relative rate constants for the respective reactions.

  10. Fabrication of nanochannels with ladder nanostructure at the bottom using AFM nanoscratching method

    PubMed Central

    2014-01-01

    This letter presents a novel atomic force microscopy (AFM)-based nanomanufacturing method combining the tip scanning with the high-precision stage movement to fabricate nanochannels with ladder nanostructure at the bottom by continuous scanning with a fixed scan size. Different structures can be obtained according to the matching relation of the tip feeding velocity and the precision stage moving velocity. This relationship was first studied in detail to achieve nanochannels with different ladder nanostructures at the bottom. Machining experiments were then performed to fabricate nanochannels on an aluminum alloy surface to demonstrate the capability of this AFM-based fabrication method presented in this study. Results show that the feed value and the tip orientation in the removing action play important roles in this method which has a significant effect on the machined surfaces. Finally, the capacity of this method to fabricate a large-scale nanochannel was also demonstrated. This method has the potential to advance the existing AFM tip-based nanomanufacturing technique of the formation these complex structures by increasing the removal speed, simplifying the processing procedure and achieving the large-scale nanofabrication. PMID:24940171

  11. EEMD based pitch evaluation method for accurate grating measurement by AFM

    NASA Astrophysics Data System (ADS)

    Li, Changsheng; Yang, Shuming; Wang, Chenying; Jiang, Zhuangde

    2016-09-01

    The pitch measurement and AFM calibration precision are significantly influenced by the grating pitch evaluation method. This paper presents the ensemble empirical mode decomposition (EEMD) based pitch evaluation method to relieve the accuracy deterioration caused by high and low frequency components of scanning profile during pitch evaluation. The simulation analysis shows that the application of EEMD can improve the pitch accuracy of the FFT-FT algorithm. The pitch error is small when the iteration number of the FFT-FT algorithms was 8. The AFM measurement of the 500 nm-pitch one-dimensional grating shows that the EEMD based pitch evaluation method could improve the pitch precision, especially the grating line position precision, and greatly expand the applicability of the gravity center algorithm when particles and impression marks were distributed on the sample surface. The measurement indicates that the nonlinearity was stable, and the nonlinearity of x axis and forward scanning was much smaller than their counterpart. Finally, a detailed pitch measurement uncertainty evaluation model suitable for commercial AFMs was demonstrated and a pitch uncertainty in the sub-nanometer range was achieved. The pitch uncertainty was reduced about 10% by EEMD.

  12. On the determination of elastic moduli of cells by AFM based indentation

    PubMed Central

    Ding, Yue; Xu, Guang-Kui; Wang, Gang-Feng

    2017-01-01

    The atomic force microscopy (AFM) has been widely used to measure the mechanical properties of biological cells through indentations. In most of existing studies, the cell is supposed to be linear elastic within the small strain regime when analyzing the AFM indentation data. However, in experimental situations, the roles of large deformation and surface tension of cells should be taken into consideration. Here, we use the neo-Hookean model to describe the hyperelastic behavior of cells and investigate the influence of surface tension through finite element simulations. At large deformation, a correction factor, depending on the geometric ratio of indenter radius to cell radius, is introduced to modify the force-indent depth relation of classical Hertzian model. Moreover, when the indent depth is comparable with an intrinsic length defined as the ratio of surface tension to elastic modulus, the surface tension evidently affects the indentation response, indicating an overestimation of elastic modulus by the Hertzian model. The dimensionless-analysis-based theoretical predictions, which include both large deformation and surface tension, are in good agreement with our finite element simulation data. This study provides a novel method to more accurately measure the mechanical properties of biological cells and soft materials in AFM indentation experiments. PMID:28368053

  13. Investigation of surface changes of nanoparticles using TM-AFM phase imaging.

    PubMed

    Dong, Rong; Yu, Liya E

    2003-06-15

    Tapping-mode AFM (TM-AFM) phase imaging was utilized to characterize the surface changes of nanosize particles, in regard to the effects of different amounts of condensed water and organic coatings on particle surfaces. Model nanoparticles were continuously examined under various relative humidity (RH) levels by concurrently obtaining both topographic and phase images. The condensed water appeared to soften particle surfaces and to increase tip-sample attractive interaction over relatively stiff surfaces, which were shown with dark phase contrasts and negative phase shift values in phase images. Under high RH, a massive amount of water gave the particles a droplet-like surface, which reversed the original negative phase shifts to positive values with bright contrasts. Glutaric-acid coatings provided a compliant surface with high viscosity resulting in a dark phase contrast, whereas water droplets containing relatively low viscosity gave a bright phase contrast and positive phase shift. Overall, our results show that it is essential to describe the physical properties of a sample surface as solid, soft, or droplet-like material in order to derive a meaningful understanding of the surface changes of nanosize particles based on TM-AFM phase images. In contrast to other phase imaging studies, this work clearly correlates continuous surface changes with phase images, demonstrating a promising approach to characterize environmental nanoparticles.

  14. A novel dog-bone oscillating AFM probe with thermal actuation and piezoresistive detection.

    PubMed

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-10-31

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments.

  15. A Novel Dog-Bone Oscillating AFM Probe with Thermal Actuation and Piezoresistive Detection †

    PubMed Central

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-01-01

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments. PMID:25365463

  16. A study of water droplet between an AFM tip and a substrate using dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Pal, Souvik; Lan, Chuanjin; Li, Zhen; Hirleman, E. Daniel; Ma, Yanbao

    2014-11-01

    Formation of a water droplet between a sharp AFM tip and a substrate due to capillary condensation affects the tip-substrate interaction. As a consequence, AFM measurements lose precision and often produce incorrect sample topology. Understanding the physics of liquid bridges is also important in the field of Dip-pen nanolithography (DPN). Significant research is being carried out to understand the mechanics of the formation of the liquid bridge and its dependence of surface properties, ambient conditions etc. The in-between length scale, i.e., mesoscale (~100 nm) associated with this phenomenon presents a steep challenge for experimental measurements. In addition, molecular dynamics (MD) can be computationally prohibitive to model the entire system, especially over microseconds to seconds. Theoretical analysis using Young Laplace equation has so far provided some qualitative insights only. We study this system using Dissipative Particle Dynamics (DPD) which is a simulation technique suitable for describing mesoscopic hydrodynamic behavior of fluids. In this work, we carry out simulations to improve understanding of the process of formation of the meniscus, the mechanics of manipulation and control of its shape, and better estimation of capillary forces. The knowledge gained through our study will help in correcting the AFM measurements affected by capillary condensation. Moreover, it will improve understanding of more accurate droplet manipulation in DPN.

  17. Graphene Nanopore Support System for Simultaneous High-Resolution AFM Imaging and Conductance Measurements

    PubMed Central

    2015-01-01

    Accurately defining the nanoporous structure and sensing the ionic flow across nanoscale pores in thin films and membranes has a wide range of applications, including characterization of biological ion channels and receptors, DNA sequencing, molecule separation by nanoparticle films, sensing by block co-polymers films, and catalysis through metal–organic frameworks. Ionic conductance through nanopores is often regulated by their 3D structures, a relationship that can be accurately determined only by their simultaneous measurements. However, defining their structure–function relationships directly by any existing techniques is still not possible. Atomic force microscopy (AFM) can image the structures of these pores at high resolution in an aqueous environment, and electrophysiological techniques can measure ion flow through individual nanoscale pores. Combining these techniques is limited by the lack of nanoscale interfaces. We have designed a graphene-based single-nanopore support (∼5 nm thick with ∼20 nm pore diameter) and have integrated AFM imaging and ionic conductance recording using our newly designed double-chamber recording system to study an overlaid thin film. The functionality of this integrated system is demonstrated by electrical recording (<10 pS conductance) of suspended lipid bilayers spanning a nanopore and simultaneous AFM imaging of the bilayer. PMID:24581087

  18. Fracture Growth Testing of Titanium 6AL-4V in AF-M315E

    NASA Technical Reports Server (NTRS)

    Sampson, Jeffrey W.; Martinez, Jonathan; McLean, Christopher

    2015-01-01

    The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant in orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent flaws will not cause failure during the design life. Material property inputs for this analysis require testing to determine the stress intensity factor for environmentally-assisted cracking (K (sub EAC)) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched specimens SE(B) representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to the monopropellant at 50 degrees Centigrade for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor of the Ti 6Al-4V forged tank material when exposed to AF-M315E monopropellant was found to be at least 22.0 kilopounds per square inch. The stress intensity factor of the weld material was at least 31.3 kilopounds per square inch.

  19. Advantages and limitations of OM, SEM, TEM and AFM in the study of ancient decorated pottery

    NASA Astrophysics Data System (ADS)

    Arenas-Alatorre, J.; Silva-Velazquez, Y.; Alva Medina, A.; Rivera, M.

    2010-03-01

    This paper presents results from the study of two fragments of pre-Hispanic pottery, decorated with red pigment, using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM). Capabilities and limitations of these techniques in the analysis of archaeological material are highlighted with special emphasis on TEM, AFM and MFM due to their contribution in the study of the pigment layer at micro and nano scale. The analyzed samples come from the archaeological sites of El Tajin and Xochicalco, both in Mexico. Results of conventional TEM and HRTEM analysis of the red pigment showed nanometric Fe2O3 particles in both samples but different particle shape and size distributions: specimen from El Tajin presented irregular particles between 50-100 nm while that from Xochicalco exhibited semispherical shapes in the 3-25 nm range. AFM images showed the topography of the pigments, which are related to the texture of their surface and thus to the production process. Finally, MFM showed different contrast regions suggesting the presence of ferromagnetic elements forming clusters and domain orientations on the color layer.

  20. Robust deposition of lambda DNA on mica for imaging by AFM in air.

    PubMed

    Cervantes, Nancy Anabel Gerling; Gutiérrez-Medina, Braulio

    2014-01-01

    Long DNA molecules remain difficult to image by atomic force microscopy (AFM) because of their tendency to entanglement and spontaneous formation of networks. We present a comparison of two different DNA deposition methods operating at room temperature and humidity conditions, aimed at reproducible imaging of isolated and relaxed λ DNA conformations by AFM in air. We first demonstrate that a standard deposition procedure, consisting in adsorption of DNA in the presence of divalent cations followed by washing and air-drying steps, yields a coexistence of different types of λ DNA networks with a only a few isolated DNA chains. In contrast, deposition using a spin-coating-based technique results in reproducible coverage of a significant fraction of the substrate area by isolated and relaxed λ DNA molecules, with the added benefit of a reduction in the effect of a residual layer that normally embeds DNA strands and leads to an apparent DNA height closer to the expected value. Furthermore, we show that deposition by spin-coating is also well-suited to visualize DNA-protein complexes. These results indicate that spin-coating is a simple, powerful alternative for reproducible sample preparation for AFM imaging.

  1. Multilayer silicon rich oxy-nitride films characterization by SIMS, VASE and AFM

    NASA Astrophysics Data System (ADS)

    Barozzi, M.; Vanzetti, L.; Iacob, E.; Bersani, M.; Anderle, M.; Pucker, G.; Kompocholis, C.; Ghulinyan, M.; Bellutti, P.

    2008-03-01

    In this work secondary ion mass spectrometry (SIMS), variable angle spectroscopy ellipsometry (VASE) and atomic force microscopy (AFM) are used to investigate the structure, composition and morphology of multilayer SRON films. Three/four SRON sequential layers were deposited on silicon wafers by PECVD and silicon, nitrogen and oxygen content was varied by changing the N2O/SiH4 ratio. The total thickness of the resulting SRON stack is about 50nm. SIMS analyses of NCs+, OCs+, SiCs+, in MCs+ methodology are performed by a Cameca SC-ultra instrument. Depth profiles are obtained at 500eV of primary beam impact energy with sample rotation. An approximate method to obtain silicon concentration is used. Total layer thickness are obtained from both SIMS and VASE measurements. In addition, we compare the thickness of the single layers obtained from VASE with the SIMS depth profiles. A detailed analysis of films morphology is obtained by AFM. The SRON stack is sputtered by SIMS until a certain layer is exposed, which is then analyzed by AFM. The sputtered layers are then etched in HF solution to better resolve the exposed nano-crystals.

  2. On the determination of elastic moduli of cells by AFM based indentation.

    PubMed

    Ding, Yue; Xu, Guang-Kui; Wang, Gang-Feng

    2017-04-03

    The atomic force microscopy (AFM) has been widely used to measure the mechanical properties of biological cells through indentations. In most of existing studies, the cell is supposed to be linear elastic within the small strain regime when analyzing the AFM indentation data. However, in experimental situations, the roles of large deformation and surface tension of cells should be taken into consideration. Here, we use the neo-Hookean model to describe the hyperelastic behavior of cells and investigate the influence of surface tension through finite element simulations. At large deformation, a correction factor, depending on the geometric ratio of indenter radius to cell radius, is introduced to modify the force-indent depth relation of classical Hertzian model. Moreover, when the indent depth is comparable with an intrinsic length defined as the ratio of surface tension to elastic modulus, the surface tension evidently affects the indentation response, indicating an overestimation of elastic modulus by the Hertzian model. The dimensionless-analysis-based theoretical predictions, which include both large deformation and surface tension, are in good agreement with our finite element simulation data. This study provides a novel method to more accurately measure the mechanical properties of biological cells and soft materials in AFM indentation experiments.

  3. Non--Cubic Symmetry of the Electronic Response in AFM Late Transition--Metal Oxides.

    NASA Astrophysics Data System (ADS)

    Posternak, M.; Baldereschi, A.; Massidda, S.; Resta, R.

    1998-03-01

    The late transition--metal monoxides (MnO, FeO, CoO, NiO) have the rocksalt structure in their paramagnetic phase, while below the Neel temperature a weak structural distortion accompanies an AFM ordering of type II. Therefore, it is generally assumed that most nonmagnetic (i.e. spin--integrated) crystalline properties are essentially cubic: we give here convincing evidence of the contrary. We focus on the half--filled d shell oxide MnO as the most suitable case study, on which we perform accurate ab--initio, all--electron calculations, within different one--particle schemes. In order to study the symmetry lowering due to AFM ordering, we assume an ideal cubic geometry throughout. The calculated TO frequencies and Born effective charge tensor do not have cubic symmetry. The standard LSD severely exaggerates the deviations from cubic symmetry, confirming its unreliability for calculating properties of insulating AFM oxides, while a model self--energy correction scheme(S. Massidda et al.), Phys. Rev. B 55, 13494 (1997). reduces considerably the anisotropy. We also explain the origin and the magnitude of this effect in terms of the mixed charge--transfer/Mott--Hubbard character of MnO.

  4. Brain tumor classification using AFM in combination with data mining techniques.

    PubMed

    Huml, Marlene; Silye, René; Zauner, Gerald; Hutterer, Stephan; Schilcher, Kurt

    2013-01-01

    Although classification of astrocytic tumors is standardized by the WHO grading system, which is mainly based on microscopy-derived, histomorphological features, there is great interobserver variability. The main causes are thought to be the complexity of morphological details varying from tumor to tumor and from patient to patient, variations in the technical histopathological procedures like staining protocols, and finally the individual experience of the diagnosing pathologist. Thus, to raise astrocytoma grading to a more objective standard, this paper proposes a methodology based on atomic force microscopy (AFM) derived images made from histopathological samples in combination with data mining techniques. By comparing AFM images with corresponding light microscopy images of the same area, the progressive formation of cavities due to cell necrosis was identified as a typical morphological marker for a computer-assisted analysis. Using genetic programming as a tool for feature analysis, a best model was created that achieved 94.74% classification accuracy in distinguishing grade II tumors from grade IV ones. While utilizing modern image analysis techniques, AFM may become an important tool in astrocytic tumor diagnosis. By this way patients suffering from grade II tumors are identified unambiguously, having a less risk for malignant transformation. They would benefit from early adjuvant therapies.

  5. SN 2010j1: Optical to Hard X-Ray Observations Reveal an Explosion Embedded in a Ten Solar Mass Cocoon

    NASA Technical Reports Server (NTRS)

    Ofek, Eran; Zoglauer, Andreas; Boggs, Steven E.; Barriere, Nicolas M.; Reynolds, Stephen P.; Fryer, Chris L.; Harrison, Fiona A.; Cenko, S. Bradley; Kulkarni, Shrinivas R.; Zhang, William W.; Kulkarni, Shrinivas R.; Gal-Yam, Avishay; Arcavi, Iair; Bellm, Eric; Bloom, Joshua S.; Christensen, Finn; Craig, William W.; Even, Wesley; Filippenko, Alexei V.; Grefenstette, Brian; Hailey, Charles J.; Laher, Russ; Madsen, Kristin; Nakar, Ehud; Nugent, Peter E.; Stern, Daniel; Sullivan, Mark; Surace, Jason; Zhang, William W.

    2014-01-01

    Some supernovae (SNe) may be powered by the interaction of the SN ejecta with a large amount of circumstellar matter (CSM). However, quantitative estimates of the CSM mass around such SNe are missing when the CSM material is optically thick. Specifically, current estimators are sensitive to uncertainties regarding the CSM density profile and the ejecta velocity. Here we outline a method to measure the mass of the optically thick CSM around such SNe. We present new visible-light and X-ray observations of SN 2010jl (PTF 10aaxf), including the first detection of an SN in the hard X-ray band using NuSTAR. The total radiated luminosity of SN 2010jl is extreme atleast 9 1050 erg. By modeling the visible-light data, we robustly show that the mass of the circumstellar material within 1016 cm of the progenitor of SN 2010jl was in excess of 10M_. This mass was likely ejected tens of years prior to the SN explosion. Our modeling suggests that the shock velocity during shock breakout was 6000 km s1, decelerating to 2600 km s1 about 2 yr after maximum light. Furthermore, our late-time NuSTAR and XMM spectra of the SN presumably provide the first direct measurement of SN shock velocity 2 yr after the SN maximum light measured to be in the range of 2000-4500 km s1 if the ions and electrons are in equilibrium, and_2000 km s1 if they are not in equilibrium. This measurement is in agreement with the shock velocity predicted by our modeling of the visible-light data. Our observations also show that the average radial density distribution of the CSM roughly follows an r2 law. A possible explanation for the _10M_ of CSM and the wind-like profile is that they are the result of multiple pulsational pair instability events prior to the SN explosion, separated from each other by years.

  6. Tropospheric ozone enhancements during the Indonesian Forest Fire Events in 1994 and in 1997 as revealed by ground-based observations

    NASA Astrophysics Data System (ADS)

    Fujiwara, M.; Kita, K.; Kawakami, S.; Ogawa, T.; Komala, N.; Saraspriya, S.; Suripto, A.

    Pronounced enhancements of total and tropospheric ozone were observed with the Brewer spectrophotometer and ozonesondes at Watukosek (7.5°S, 112.6°E), Indonesia in 1994 and in 1997 when extensive forest fires were reported in Indonesia. The integrated tropospheric ozone increased from 20 DU to 40 DU in October 1994 and to 55 DU in October 1997. On October 13, 1994, most ozone mixing ratios were more than 50 ppbv throughout the troposphere and exceeded 80 ppbv at some altitudes. On October 22, 1997, the concentrations were more than 50 ppbv throughout the troposphere and exceeded 100 ppbv at several altitudes. The coincidences of the ozone enhancements with the forest fires suggest the photochemical production of tropospheric ozone due to its precursors emitted from the fires for both cases. The years of 1994 and 1997 correspond to El Niño events when convective activity becomes low in Indonesia. Thus, in this region, it is likely that pronounced enhancements of tropospheric ozone associated with extensive forest fires due to sparse precipitation may take place with a period of a few years coinciding with El Niño events. This is in a marked contrast to the situation in South America and Africa where large-scale biomass burnings occur every year.

  7. AFM study of the effects of laser surface remelting on the morphology of Al-Fe aerospace alloys

    SciTech Connect

    Pariona, Moises Meza; Teleginski, Viviane; Santos, Kelly dos; Leandro Ribeiro dos Santos, Everton; Aparecida de Oliveira Camargo de Lima, Angela; Riva, Rudimar

    2012-12-15

    Laser beam welding has recently been incorporated into the fabrication process of aircraft and automobile structures. Surface roughness is an important parameter of product quality that strongly affects the performance of mechanical parts, as well as production costs. This parameter influences the mechanical properties such as fatigue behavior, corrosion resistance, creep life, etc., and other functional characteristics such as friction, wear, light reflection, heat transmission, lubrification, electrical conductivity, etc. The effects of laser surface remelting (LSR) on the morphology of Al-Fe aerospace alloys were examined before and after surface treatments, using optical microscopy (OM), scanning electron microscopy (SEM), low-angle X-ray diffraction (LA-XRD), atomic force microscopy (AFM), microhardness measurements (Vickers hardness), and cyclic voltammetry. This analysis was performed on both laser-treated and untreated sanded surfaces, revealing significant differences. The LA-XRD analysis revealed the presence of alumina, simple metals and metastable intermetallic phases, which considerably improved the microhardness of laser-remelted surfaces. The morphology produced by laser surface remelting enhanced the microstructure of the Al-Fe alloys by reducing their roughness and increasing their hardness. The treated surfaces showed passivity and stability characteristics in the electrolytic medium employed in this study. - Highlights: Black-Right-Pointing-Pointer The samples laser-treated and untreated showed significant differences. Black-Right-Pointing-Pointer The La-XRD revealed the presence of alumina in Al-1.5 wt.% Fe. Black-Right-Pointing-Pointer The laser-treated reducing the roughness and increasing the hardness. Black-Right-Pointing-Pointer The laser-treated surfaces showed characteristic passive in the electrolytic medium. Black-Right-Pointing-Pointer The laser-treated is a promising technique for applications technological.

  8. Mars Atmospheric CO2 Condensation Above the North and South Poles as Revealed by Radio Occultation, Climate Sounder, and Laser Ranging Observations

    NASA Technical Reports Server (NTRS)

    Hu, Renyu; Cahoy, Kerri; Zuber, Maria T.

    2012-01-01

    We study the condensation of CO2 in Mars atmosphere using temperature profilesretrieved from radio occultation measurements from Mars Global Surveyor (MGS) as wellas the climate sounding instrument onboard the Mars Reconnaissance Orbiter (MRO),and detection of reflective clouds by the MGS Mars Orbiter Laser Altimeter (MOLA). Wefind 11 events in 1999 where MGS temperature profiles indicate CO2 condensation andMOLA simultaneously detects reflective clouds. We thus provide causal evidence thatMOLA non-ground returns are associated with CO2 condensation, which strongly indicatestheir nature being CO2 clouds. The MGS and MRO temperature profiles together revealthe seasonal expansion and shrinking of the area and the vertical extent of atmosphericsaturation. The occurrence rate of atmospheric saturation is maximized at high latitudes inthe middle of winter. The atmospheric saturation in the northern polar region exhibits moreintense seasonal variation than in the southern polar region. In particular, a shrinking ofsaturation area and thickness from LS 270 to 300 in 2007 is found; this is probablyrelated to a planet-encircling dust storm. Furthermore, we integrate the condensation areaand the condensation occurrence rate to estimate cumulative masses of CO2 condensatesdeposited onto the northern and southern seasonal polar caps. The precipitation flux isapproximated by the particle settling flux which is estimated using the impulse responses ofMOLA filter channels. With our approach, the total atmospheric condensation mass canbe estimated from these observational data sets with average particle size as the onlyfree parameter. By comparison with the seasonal polar cap masses inferred from thetime-varying gravity of Mars, our estimates indicate that the average condensate particleradius is 822 mm in the northern hemisphere and 413 mm in the southern hemisphere.Our multi-instrument data analysis provides new constraints on modeling the global climateof Mars.

  9. VLT/SINFONI Observations of SPITZER/MIPSGAL 24 μm Circumstellar Shells: Revealing the Natures of Their Central Sources

    NASA Astrophysics Data System (ADS)

    Silva, K. M.; Flagey, N.; Noriega-Crespo, A.; Carey, S.; Ingallinera, A.

    2017-03-01

    We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared H- and K-band spectra of potential central stars within the inner 8″-by-8″ regions of 55 MIPSGAL “bubbles” (MBs), sub-arcminute circumstellar shells discovered in the mid-IR survey of the Galactic plane with Spitzer/MIPS. At magnitudes brighter than 15, we detect a total of 230 stars in the K band and 179 stars in the H band. We spectrally identify 145 stars in all but three MBs, with average magnitudes of 13.8 and 12.7 respectively, using spectral libraries and previous studies of near-IR stellar spectra. We also use tabulated intrinsic stellar magnitudes and colors to derive distances and extinction values, and to better constrain the classifications of the stars. We reliably identify the central sources for 21 of the 55 MBs, which we classify as follows: one Wolf–Rayet, three luminous blue variable candidates, four early-type (O to F), and 15 late-type (G to M) stars. The 21 central sources are, on average, one magnitude fainter than these in the most recent study of MBs, and we notice a significant drop in the fraction of massive star candidates. For the 34 remaining MBs in our sample, we are unable to identify the central sources due to confusion, low spectroscopic signal-to-noise ratio, and/or lack of detections in the images near the centers of the bubbles. We discuss how our findings compare with previous studies and support the trend, for the most part, between the shells’ morphologies in the mid-IR and central sources spectral types.

  10. Integrin-Specific Mechanoresponses to Compression and Extension Probed by Cylindrical Flat-Ended AFM Tips in Lung Cells

    PubMed Central

    Acerbi, Irene; Luque, Tomás; Giménez, Alícia; Puig, Marta; Reguart, Noemi; Farré, Ramon; Navajas, Daniel; Alcaraz, Jordi

    2012-01-01

    Cells from lung and other tissues are subjected to forces of opposing directions that are largely transmitted through integrin-mediated adhesions. How cells respond to force bidirectionality remains ill defined. To address this question, we nanofabricated flat-ended cylindrical Atomic Force Microscopy (AFM) tips with ∼1 µm2 cross-section area. Tips were uncoated or coated with either integrin-specific (RGD) or non-specific (RGE/BSA) molecules, brought into contact with lung epithelial cells or fibroblasts for 30 s to form focal adhesion precursors, and used to probe cell resistance to deformation in compression and extension. We found that cell resistance to compression was globally higher than to extension regardless of the tip coating. In contrast, both tip-cell adhesion strength and resistance to compression and extension were the highest when probed at integrin-specific adhesions. These integrin-specific mechanoresponses required an intact actin cytoskeleton, and were dependent on tyrosine phosphatases and Ca2+ signaling. Cell asymmetric mechanoresponse to compression and extension remained after 5 minutes of tip-cell adhesion, revealing that asymmetric resistance to force directionality is an intrinsic property of lung cells, as in most soft tissues. Our findings provide new insights on how lung cells probe the mechanochemical properties of the microenvironment, an important process for migration, repair and tissue homeostasis. PMID:22384196

  11. An NC-AFM and KPFM study of the adsorption of a triphenylene derivative on KBr(001)

    PubMed Central

    Hinaut, Antoine; Pujol, Adeline; Chaumeton, Florian; Martrou, David; Gourdon, André

    2012-01-01

    Summary The adsorption on KBr(001) of a specially designed molecule, consisting of a flat aromatic triphenylene core equipped with six flexible propyl chains ending with polar cyano groups, is investigated by using atomic force microscopy in the noncontact mode (NC-AFM) coupled to Kelvin probe force microscopy (KPFM) in ultrahigh vacuum at room temperature. Two types of monolayers are identified, one in which the molecules lie flat on the surface (MLh) and another in which they stand approximately upright (MLv). The Kelvin voltage on these two structures is negatively shifted relative to that of the clean KBr surface, revealing the presence of surface dipoles with a component pointing along the normal to the surface. These findings are interpreted with the help of numerical simulations. It is shown that the surface–molecule interaction is dominated by the electrostatic interaction of the cyano groups with the K+ ions of the substrate. The molecule is strongly adsorbed in the MLh structure with an adsorption energy of 1.8 eV. In the MLv layer, the molecules form π-stacked rows aligned along the polar directions of the KBr surface. In these rows, the molecules are less strongly bound to the substrate, but the structure is stabilized by the strong intermolecular interaction due to π-stacking. PMID:22496995

  12. AFM/MFM hybrid nanocharacterization of martensitic transformation and degradation for Fe-Pd shape memory alloy

    NASA Astrophysics Data System (ADS)

    Suzuki, Takayuki; Nagatani, Kohei; Hirano, Kazumi; Teramoto, Tokuo; Taya, Minoru

    2003-07-01

    Martensitic transformation and degradation characteristics for Fe-Pd ferromagnetic shape memory alloy were investigated by the developed AFM (Atomic Force Microscope)/MFM (Magnetic Force Microscope) hybrid nano-characterization technique. In AFM martensitic transformation was detected by the changes of surface topography of martensite plates. In MFM martensitic transformation was detected by the changes of magnetic domain structures. This technique has an advantage that martensitic transformation characteristics such as martensitic transformation temperature and reverse transformation temperature can be measured at microscopic and nanoscopic small area. Degradation characteristics of martensitic transformation under cyclic loading were also detected by the changes of AFM and MFM images. In AFM images surface topography of martensite plates became flat and in MFM images the morphology of magnetic domain structures became unfocused under cyclic loading. Then it was found that the hybrid nano-characterization was very high sensitive technique to evaluate degradation for Fe-Pd ferromagnetic shape memory alloy.

  13. Two-Dimensional Measurement of n+-p Asymmetrical Junctions in Multicrystalline Silicon Solar Cells Using AFM-Based Electrical Techniques with Nanometer Resolution: Preprint

    SciTech Connect

    Jiang, C. S.; Moutinho, H. R.; Li, J. V.; Al-Jassim, M. M.; Heath, J. T.

    2011-07-01

    Lateral inhomogeneities of modern solar cells demand direct electrical imaging with nanometer resolution. We show that atomic force microscopy (AFM)-based electrical techniques provide unique junction characterizations, giving a two-dimensional determination of junction locations. Two AFM-based techniques, scanning capacitance microscopy/spectroscopy (SCM/SCS) and scanning Kelvin probe force microscopy (SKPFM), were significantly improved and applied to the junction characterizations of multicrystalline silicon (mc-Si) cells. The SCS spectra were taken pixel by pixel by precisely controlling the tip positions in the junction area. The spectra reveal distinctive features that depend closely on the position relative to the electrical junction, which allows us to indentify the electrical junction location. In addition, SKPFM directly probes the built-in potential over the junction area modified by the surface band bending, which allows us to deduce the metallurgical junction location by identifying a peak of the electric field. Our results demonstrate resolutions of 10-40 nm, depending on the techniques (SCS or SKPFM). These direct electrical measurements with nanometer resolution and intrinsic two-dimensional capability are well suited for investigating the junction distribution of solar cells with lateral inhomogeneities.

  14. The model of amyloid aggregation of Escherichia coli RNA polymerase σ70 subunit based on AFM data and in vitro assays.

    PubMed

    Koroleva, Olga N; Dubrovin, Evgeniy V; Khodak, Yu A; Kuzmina, Natalia V; Yaminsky, Igor V; Drutsa, Valeriy L

    2013-07-01

    To propose a model for recently described amyloid aggregation of E.coli RNA polymerase σ(70) subunit, we have investigated the role of its N-terminal region. For this purpose, three mutant variants of protein with deletions Δ1-73, Δ1-100 and Δ74-100 were constructed and studied in a series of in vitro assays and using atomic force microscopy (AFM). Specifically, all RNA polymerase holoenzymes, reconstituted with the use of mutant σ subunits, have shown reduced affinity for promoter-containing DNA and reduced activity in run-off transcription experiments (compared to that of WT species), thus substantiating the modern concept on the modulatory role of N-terminus in formation of open complex and transcription initiation. The ability of mutant proteins to form amyloid-like structures has been investigated using AFM, which revealed the increased propensity of mutant proteins to form rodlike aggregates with the effect being more pronounced for the mutant with the deletion Δ1-73 (10 fold increase). σ(70) subunit aggregation ability has shown complex dependence on the ionic surrounding, which we explain by Debye screening effect and the change of the internal state of the protein. Basing on the obtained data, we propose the model of amyloid fibril formation by σ(70) subunit, implying the involvement of N-terminal region according to the domain swapping mechanism.

  15. XPS, UV-vis spectroscopy and AFM studies on removal mechanisms of Si-face SiC wafer chemical mechanical polishing (CMP)

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Pan, Guoshun; Shi, Xiaolei; Xu, Li; Zou, Chunli; Gong, Hua; Luo, Guihai

    2014-10-01

    Chemical mechanical polishing (CMP) removal mechanisms of on-axis Si-face SiC wafer have been investigated through X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) spectroscopy and atomic force microscopy (AFM). XPS results indicate that silicon oxide is formed on Si-face surface polished by the slurry including oxidant H2O2, but not that after immersing in H2O2 solution. UV-vis spectroscopy curves prove that •OH hydroxyl radical could be generated only under CMP polishing by the slurry including H2O2 and abrasive, so as to promote oxidation of Si-face to realize the effective removal; meanwhile, alkali KOH during CMP could induce the production of more radicals to improve the removal. On the other side, ultra-smooth polished surface with atomic step structure morphology and extremely low Ra of about 0.06 nm (through AFM) is obtained using the developed slurry with silica nanoparticle abrasive. Through investigating the variations of the atomic step morphology on the surface polished by different slurries, it's reveals that CMP removal mechanism involves a simultaneous process of surface chemical reaction and nanoparticle atomic scale abrasion.

  16. Modeling AFM-induced PEVK extension and the reversible unfolding of Ig/FNIII domains in single and multiple titin molecules.

    PubMed

    Zhang, B; Evans, J S

    2001-02-01

    Molecular elasticity is associated with a select number of polypeptides and proteins, such as titin, Lustrin A, silk fibroin, and spider silk dragline protein. In the case of titin, the globular (Ig) and non-globular (PEVK) regions act as extensible springs under stretch; however, their unfolding behavior and force extension characteristics are different. Using our time-dependent macroscopic method for simulating AFM-induced titin Ig domain unfolding and refolding, we simulate the extension and relaxation of hypothetical titin chains containing Ig domains and a PEVK region. Two different models are explored: 1) a series-linked WLC expression that treats the PEVK region as a distinct entropic spring, and 2) a summation of N single WLC expressions that simulates the extension and release of a discrete number of parallel titin chains containing constant or variable amounts of PEVK. In addition to these simulations, we also modeled the extension of a hypothetical PEVK domain using a linear Hooke's spring model to account for "enthalpic" contributions to PEVK elasticity. We find that the modified WLC simulations feature chain length compensation, Ig domain unfolding/refolding, and force-extension behavior that more closely approximate AFM, laser tweezer, and immunolocalization experimental data. In addition, our simulations reveal the following: 1) PEVK extension overlaps with the onset of Ig domain unfolding, and 2) variations in PEVK content within a titin chain ensemble lead to elastic diversity within that ensemble.

  17. Modeling AFM-induced PEVK extension and the reversible unfolding of Ig/FNIII domains in single and multiple titin molecules.

    PubMed Central

    Zhang, B; Evans, J S

    2001-01-01

    Molecular elasticity is associated with a select number of polypeptides and proteins, such as titin, Lustrin A, silk fibroin, and spider silk dragline protein. In the case of titin, the globular (Ig) and non-globular (PEVK) regions act as extensible springs under stretch; however, their unfolding behavior and force extension characteristics are different. Using our time-dependent macroscopic method for simulating AFM-induced titin Ig domain unfolding and refolding, we simulate the extension and relaxation of hypothetical titin chains containing Ig domains and a PEVK region. Two different models are explored: 1) a series-linked WLC expression that treats the PEVK region as a distinct entropic spring, and 2) a summation of N single WLC expressions that simulates the extension and release of a discrete number of parallel titin chains containing constant or variable amounts of PEVK. In addition to these simulations, we also modeled the extension of a hypothetical PEVK domain using a linear Hooke's spring model to account for "enthalpic" contributions to PEVK elasticity. We find that the modified WLC simulations feature chain length compensation, Ig domain unfolding/refolding, and force-extension behavior that more closely approximate AFM, laser tweezer, and immunolocalization experimental data. In addition, our simulations reveal the following: 1) PEVK extension overlaps with the onset of Ig domain unfolding, and 2) variations in PEVK content within a titin chain ensemble lead to elastic diversity within that ensemble. PMID:11159428

  18. Versatile method for AFM-tip functionalization with biomolecules: fishing a ligand by means of an in situ click reaction

    NASA Astrophysics Data System (ADS)

    Kumar, Rakesh; Ramakrishna, Shivaprakash N.; Naik, Vikrant V.; Chu, Zonglin; Drew, Michael E.; Spencer, Nicholas D.; Yamakoshi, Yoko

    2015-04-01

    A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions.A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions. Electronic supplementary information (ESI) available: Experimental details with synthesis and characterization of compounds. Procedures for modifications of Au surfaces and AFM tips. AFM images and full PM-IRRAS spectra of modified surfaces. Detailed procedure for QCM measurement. A table showing ligand-receptor interaction probability. NMR, IR and MS charts. See DOI: 10.1039/c5nr01495f

  19. Applications of AFM in semiconductor R&D and manufacturing at 45 nm technology node and beyond

    NASA Astrophysics Data System (ADS)

    Lee, Moon-Keun; Shin, Minjung; Bao, Tianming; Song, Chul-Gi; Dawson, Dean; Ihm, Dong-Chul; Ukraintsev, Vladimir

    2009-03-01

    Continuing demand for high performance microelectronic products propelled integrated circuit technology into 45 nm node and beyond. The shrinking device feature geometry created unprecedented challenges for dimension metrology in semiconductor manufacturing and research and development. Automated atomic force microscope (AFM) has been used to meet the challenge and characterize narrower lines, trenches and holes at 45nm technology node and beyond. AFM is indispensable metrology techniques capable of non-destructive full three-dimensional imaging, surface morphology characterization and accurate critical dimension (CD) measurements. While all available dimensional metrology techniques approach their limits, AFM continues to provide reliable information for development and control of processes in memory, logic, photomask, image sensor and data storage manufacturing. In this paper we review up-todate applications of automated AFM in every mentioned above semiconductor industry sector. To demonstrate benefits of AFM at 45 nm node and beyond we compare capability of automated AFM with established in-line and off-line metrologies like critical dimension scanning electron microscopy (CDSEM), optical scatterometry (OCD) and transmission electronic microscopy (TEM).

  20. Studying Chemical Reactions, One Bond at a Time, with Single Molecule AFM Techniques

    NASA Astrophysics Data System (ADS)

    Fernandez, Julio M.

    2008-03-01

    atomic force microscopy (AFM) techniques, as shown here, can probe dynamic rearrangements within an enzyme's active site which cannot be resolved with any other current structural biological technique. Furthermore, our work at the single bond level directly demonstrates that thiol/disulfide exchange in proteins is a force-dependent chemical reaction. Our findings suggest that mechanical force plays a role in disulfide reduction in vivo, a property which has never been explored by traditional biochemistry. 1.-Wiita, A.P., Ainavarapu, S.R.K., Huang, H.H. and Julio M. Fernandez (2006) Force-dependent chemical kinetics of disulfide bond reduction observed with single molecule techniques. Proc Natl Acad Sci U S A. 103(19):7222-7 2.-Wiita, A.P., Perez-Jimenez, R., Walther, K.A., Gräter, F. Berne, B.J., Holmgren, A., Sanchez-Ruiz, J.M., and Fernandez, J.M. (2007) Probing the chemistry of thioredoxin catalysis with force. Nature, 450:124-7.

  1. Revealing the hidden structural phases of FeRh

    NASA Astrophysics Data System (ADS)

    Kim, Jinwoong; Ramesh, R.; Kioussis, Nicholas

    2016-11-01

    Ab initio electronic structure calculations reveal that tetragonal distortion has a dramatic effect on the relative stability of the various magnetic structures (C-, A-, G-, A'-AFM, and FM) of FeRh giving rise to a wide range of novel stable/metastable structures and magnetic phase transitions between these states. We predict that the cubic G-AFM structure, which was believed thus far to be the ground state, is metastable and that the tetragonally expanded G-AFM is the stable structure. The low energy barrier separating these states suggests phase coexistence at room temperature. We propose an A'-AFM phase to be the global ground state among all magnetic phases which arises from the strain-induced tuning of the exchange interactions. The results elucidate the underlying mechanism for the recent experimental findings of electric-field control of magnetic phase transition driven via tetragonal strain. The magnetic phase transitions open interesting prospects for exploiting strain engineering for the next-generation memory devices.

  2. Characterization of Pebax angioplasty balloon surfaces with AFM, SEM, TEM, and SAXS.

    PubMed

    Warner, Jacob A; Forsyth, Bruce; Zhou, Fang; Myers, Jason; Frethem, Chris; Haugstad, Greg

    2016-04-01

    In the medical device industry, angioplasty balloons have been widely used in the less invasive treatment of heart disease by expanding and relieving clogged structures in various arterial segments. However, new applications using thin coatings on the balloon surface have been explored to enhance therapeutic value in the delivery of pharmaceuticals (drug-elution) or control thermal energy output (RF ablation). In this study, angioplasty balloon materials comprised of poly(ether-block-amide) (Pebax) were investigated via atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS) to characterize physical properties at the balloon surface that may affect coating adhesion. The soft segment of this Pebax 1074 material is polyethylene oxide (PEO) and the hard segment is nylon-12. The morphology of the hard segments of this block co-polymer are found via AFM stiffness measurements to be (40 ± 20) nm by (300 ± 150) nm and are oriented parallel to the surface of the balloon. SAXS measurements found the lamellar spacing to be (18.5 ± 0.5) nm, and demonstrate a preferential orientation in agreement with TEM and AFM measurements. Fixation of this balloon in resin, followed by cryo-sectioning is shown to provide a novel manner in which to investigate surface characteristics on the balloon such as material or coating thickness as well as uniformity in comparison to the bulk structure. These outputs were deemed critical to improve overall balloon processing such as molding and surface treatment options for robust designs toward better procedural outcomes targeting new therapeutic areas.

  3. Measurement of Cationic and Intracellular Modulation of Integrin Binding Affinity by AFM-Based Nanorobot

    PubMed Central

    Patterson, Kevin C.; Yang, Ruiguo; Zeng, Bixi; Song, Bo; Wang, Shouye; Xi, Ning; Basson, Marc D.

    2013-01-01

    Integrins are dynamic transmembrane cation-dependent heterodimers that both anchor cells in position and transduce signals into and out of cells. We used an atomic force microscope (AFM)-based nanorobotic system to measure integrin-binding forces in intact human intestinal epithelial Caco-2 cells. The AFM-based nanorobot enables human-directed, high-accuracy probe positioning and site-specific investigations. Functionalizing the AFM probe with an arginine-glycine-aspartate (RGD)-containing sequence (consensus binding sequence for integrins) allowed us to detect a series of peptide-cell membrane interactions with a median binding force of 115.1 ± 4.9 pN that were not detected in control interactions. Chelating divalent cations from the culture medium abolished these interactions, as did inhibiting intracellular focal adhesion kinase (FAK) using Y15. Adding 1 mM Mg2+ to the medium caused a rightward shift in the force-binding curve. Adding 1 mM Ca2+ virtually abolished the RGD-membrane specific interactions and blocked the Mg2+ effects. Cell adhesion assays demonstrated parallel effects of divalent cations and the FAK inhibitor on cell adhesion. These results demonstrate direct modulation of integrin-binding affinity by both divalent cations and intracellular signal inhibition. Additionally, three binding states (nonspecific, specific inactivated, and specific activated) were delineated from affinity measurements. Although other research has assumed that this process of integrin conformational change causes altered ligand binding, in this work we directly measured these three states in individual integrins in a physiologically based study. PMID:23823222

  4. Measurement of cationic and intracellular modulation of integrin binding affinity by AFM-based nanorobot.

    PubMed

    Patterson, Kevin C; Yang, Ruiguo; Zeng, Bixi; Song, Bo; Wang, Shouye; Xi, Ning; Basson, Marc D

    2013-07-02

    Integrins are dynamic transmembrane cation-dependent heterodimers that both anchor cells in position and transduce signals into and out of cells. We used an atomic force microscope (AFM)-based nanorobotic system to measure integrin-binding forces in intact human intestinal epithelial Caco-2 cells. The AFM-based nanorobot enables human-directed, high-accuracy probe positioning and site-specific investigations. Functionalizing the AFM probe with an arginine-glycine-aspartate (RGD)-containing sequence (consensus binding sequence for integrins) allowed us to detect a series of peptide-cell membrane interactions with a median binding force of 115.1 ± 4.9 pN that were not detected in control interactions. Chelating divalent cations from the culture medium abolished these interactions, as did inhibiting intracellular focal adhesion kinase (FAK) using Y15. Adding 1 mM Mg(2+) to the medium caused a rightward shift in the force-binding curve. Adding 1 mM Ca(2+) virtually abolished the RGD-membrane specific interactions and blocked the Mg(2+) effects. Cell adhesion assays demonstrated parallel effects of divalent cations and the FAK inhibitor on cell adhesion. These results demonstrate direct modulation of integrin-binding affinity by both divalent cations and intracellular signal inhibition. Additionally, three binding states (nonspecific, specific inactivated, and specific activated) were delineated from affinity measurements. Although other research has assumed that this process of integrin conformational change causes altered ligand binding, in this work we directly measured these three states in individual integrins in a physiologically based study.

  5. Fabrication and characterization of mesoscale protein patterns using atomic